L0159 – Viscosity of Ba–B–Si–Al–O glass measured by indentation creep test at operating temperature of IT-SOFC
Viscosity of a specific Ba–B–Si–Al–O glass used for intermediate-temperature solid oxide fuel cell was measured using indentation creep tests. Responses of shear strain to corresponding shear stress at the operating temperature of solid oxide fuel cell were analyzed, and the results revealed that the glass system
possesses Newtonian flow behavior at 600–630 °C. In addition, the stress exponent and the activation energy for viscous flow at different temperatures and stresses were also determined. Finally, the absolute-rate theory was adopted to describe the viscous flow for the glass. The results were compared with other glass systems.
L0129 – Some studies on the phase formation and kinetics in TiO2 containing lithium aluminum silicate glasses nucleated by P2O5
Lithium aluminum silicate (LAS) glasses of compositions (wt%) 10.6Li2O–71.7SiO2–7.1Al2O3–4.9K2O–3.2B2O3–1.25P2O5–1.25TiO2 were prepared by the melt quench technique. Crystallization kinetics was investigated by the method of Kissinger and Augis–Bennett using differential thermal analysis (DTA). Based on the DTA data, glass ceramics were prepared by single-, two-, and three-step heat treatment schedules. The interdependence of different phases formed, microstructure, thermal expansion coefficient (TEC) and microhardness (MH) was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-mechanical analysis (TMA), and microhardness (MH) measurements. Crystallization kinetics revealed that Li2SiO3 is the kinetically favored phase with activation energy of 91.10 kJ/mol. An Avrami exponent of n = 3.33 indicated the dominance of bulk crystallization. Based upon the formation of phases, it was observed that the two-stage heat treatment results in highest TEC glass ceramics. The single-step heat treatment yielded glass ceramics with the highest MH.
L0128 – Preparation and studies of some thermal, mechanical and optical properties of xAl2O3(1 – x)NaPO3 glass system
Sodium aluminophosphate glasses having compositions of xAl2O3(1 – x)NaPO3 (x = 0×05–0×2) were prepared using conventional melt-quench technique. Density, glass transition temperature, microhardness (MH), thermal expansion coefficient (TEC) and transmission characteristics were measured as a function of alumina content for different samples. They were found to depend on O/P ratio with pronounced changes taking place for O/P ratio ³ 3×5. Density, glass transition temperature and microhardness were found to increase up to 15 mol% of alumina and then they showed a decreasing trend. Thermal expansion coefficient decreased continuously with alumina content. Optical gaps for different glass samples as measured from
transmission characteristics were found to be in the range 3×13–3×51 eV. It initially decreased with alumina content up to 15 mol% and then increased. The behaviour was explained on the basis of change in the average aluminum coordination number from six Al(6) to four Al(4) (i.e. Al(OP)6/Al(OP)4 ratio) along with the changes in polyhedra linkages in the glass network due to change in O/P ratio.
L0016 – Effect of alumina concentration on thermal and structural properties of MAS glass and glass-ceramics
Magnesium aluminum silicate (MAS) glass samples with different concentrations of alumina (7.58 to 14.71 mol%) were prepared by melt and quench-technique. Total Mg content in the form of MgF2+MgO was kept constant at 25 mol%. MAS glass was converted into glass-ceramics by controlled heat treatment at around 950°C. Crystalline phases present in different samples were identified by powder X-ray diffraction technique. Dilatometry technique was used to measure the thermal expansion coefficient and glass transition temperature. Scanning electron microscopy (SEM) was employed to study the microstructure of the glass-ceramic sample. It is seen from X-ray diffraction studies that at low Al2O3 concentrations (up to 10.5 mol%) both MgSiO3 and fluorophlogopite phases are present and at higher Al2O3 concentrations of 12.3 and 14.7 mol%, fluorophlogopite and magnesium silicate (Mg2SiO4), respectively are found as major crystalline phases. The average thermal expansion co-efficient (avg) of the glass samples decreases systematically from 9.8 to 5.5 x 10^(-6)°C-1 and the glass transition temperature (T g) increases from 610.1 to 675°C with increase in alumina content. However, in glass-ceramic samples the avg varies in somewhat complex manner from 6.8 to 7.9 x 10^(-6)°C-1 with variation of Al2O3 content. This was thought to be due to the presence of different crystalline phases, their relative concentration and microstructure.
L0014 – Thermal properties and structural aspects of PbO-SiO2-B2O3 glasses
L0013 – Thermal expansion properties of some sealing and related glasses and glass ceramics
E0338 – Silica doped bismuth lead oxyfluoride glass ionic conductors
Doping of bismuth lead oxyfluorides by silica (30 at.%) makes it possible to stabilize a large vitreous domain. The presented study relates to the stability of the vitreous phase and the variation of conductivity versus temperature, as well as composition. DTA heating analyses evidenced the temperature of vitreous transition followed by the material recrystallization. The crystallized phase was identified by high temperature Guinier Lenné pattern. The best conductivity, about 3 × 10? 3 Scm? 1 at 220 °C, was obtained for the fluorine richest material.
E0337 – Thermal and optical investigation of EuF3-doped lead fluorogermanate glasses
Europium-doped lead germanate and lead fluorogermanate glasses are studied by using differential thermal analysis, X-ray diffraction, photoluminescence and fluorescence lifetimes measurements of the 5Dj, j = 0, 1, 2 levels. PbF2 addition increases the thermal stability of the lead germanate glass, while Eu3+ ions promote the crystallization of ?-PbF2:Eu3+ nano-crystals embedded in a glassy matrix. In the lead fluorogermanate glasses, Eu3+ ions exhibit a strong affinity for F? ions although oxygen ions are much more numerous. It appears that luminescence concentration quenching is not important, while cross relaxation is very efficient in the glasses. The results allow to propose for these glasses a molecular model in which small fluorine rich island, incorporating the Eu3+ ions in low symmetry sites, are separated from each other by chains of germanate (GeO4)4? ions linked together.
E0335 – Physical properties and MAS-NMR studies of titanium phosphate-based glasses
In this study, for a series phosphate-based glasses ((P2O5)0.45(CaO)0.3(Na2O)0.25?x(TiO2)x, 0 ? x ? 0.15), their degradation, ion release, surface and thermal properties have been determined. The results show that adding TiO2 was associated with a significant increase in density and glass transition temperature, but a decrease in degradation rate and ion release. 31P solid-state magic-angle-spinning nuclear magnetic resonance (MAS-NMR) showed that the local structure of the glasses changes with increasing TiO2 content. As TiO2 is incorporated into the glass, the phosphate connectivity increases as Q1 units transform to Q2, confirming that an increase in the nominal TiO2 content correlates unequivocally with an increase in glass stability. As reported for titania–silica gels, Ti4+ is clearly adopting a network former role in these phosphate-based glasses. 23Na MAS-NMR results corroborate this phenomenon with a marked upfield trend of the 23Na isotropic chemical shift suggesting that the local Na–O bond distances are decreasing within a more condensed glass network upon increased incorporation of TiO2.
E0334 – Laser cladding of bioactive glass coatings
Laser cladding by powder injection has been used to produce bioactive glass coatings on titanium alloy (Ti6Al4V) substrates. Bioactive glass compositions alternative to 45S5 Bioglass® were demonstrated to exhibit a gradual wetting angle–temperature evolution and therefore a more homogeneous deposition of the coating over the substrate was achieved. Among the different compositions studied, the S520 bioactive glass showed smoother wetting angle–temperature behavior and was successfully used as precursor material to produce bioactive coatings. Coatings processed using a Nd:YAG laser presented calcium silicate crystallization at the surface, with a uniform composition along the coating cross-section, and no significant dilution of the titanium alloy was observed. These coatings maintain similar bioactivity to that of the precursor material as demonstrated by immersion in simulated body fluid.
E0333 – Investigations of the non-isothermal crystallization of CaF2 nanoparticles in Sm-doped oxy-fluoride glasses
Oxyfluoride glass samples in the system SiO2–Al2O3–CaF2–SmF3 were produced by using the melt-quenched technique and the kinetics of non-isothermal crystallization of CaF2 nano-crystals has been investigated. Differential thermal analysis (DTA) has shown an exothermic peak at about 700 °C which was assigned to the CaF2 nano-crystals precipitation within the glass matrix as was identified by X-ray diffraction (XRD) analysis of the annealed glass samples. It was shown the Ozawa model is most suitable for describing the behaviour of non-isothermal crystallization of CaF2 nano-crystals within the glass matrix. The mean value of the Avrami exponent was found 1.16 which indicates the diffusion-controlled growth process of nano-particles in the glass system with zero nucleation rate as the single operative mechanism; the activation energy of the crystallization is Ed = 379 ± 25 kJ/mol (3.93 ± 0.26 eV). The activation energy of the nano-crystals growth was computed within the same model and agrees very well with the activation energy of the crystallization.
E0331 – Processing and Properties of Eu3+-Doped Transparent YAG (Y3Al5O12) Nanoglass–Ceramics
An Eu3+-doped novel mother glass in the K2O–SiO2–Y2O3–Al2O3 (KSYA) system was prepared by the melt-quench technique. The transparent Y3Al5O12 (YAG) glass–ceramics were derived from this glass by a controlled crystallization process. The formation of YAG crystal phase, size and morphology with the progression of heat treatment was examined by X-ray diffraction (XRD), transmission electron microscopy, field-emission scanning electron microscopy, and Fourier transformed infrared reflectance spectroscopy. The crystallite sizes obtained from XRD are found to increase with heat-treatment time and vary in the range of 35–45 nm. The photoluminescence spectra of Eu3+ ions exhibit emission transitions of 5D0?7Fj (j=0, 1, 2, 3, and 4) and its excitation spectra show a charge transfer band around 280 nm. From these emissions, the site symmetry in the vicinity of Eu3+ ions has been found to be Cs or lower than Cs in the nanoglass–ceramics. Absorption and fluorescence spectra reveal that the Eu3+ ions are entering into the YAG nanocrystals of the glass–ceramics. The present study indicates that the incorporation of Eu3+ ions into the YAG crystal lattice enhance the fluorescence performance of the nanoglass–ceramics. We believe that this work would generate new avenues in the exploration of YAG nanoglass–ceramics in particular and other glass–ceramics of very high-temperature melting crystals in general.
E0326 – Diopside -Mg orthosilicate and diopside -Ba disilicate glass-ceramics for sealing applications in SOFC: Sintering and chemical interactions studies
Diopside (CaMgSi2O6) based glasses compositions containing magnesium orthosilicate or barium aluminosilicates phases have been appraised for sealing applications in solid oxide fuel cells (SOFCs) and other solid-electrolyte devices. The sintering behavior and crystalline phase evolution of glass powders has been investigated under isothermal and non-isothermal conditions in the SOFC operating temperature range (800–900 °C). All the glass compositions exhibited two-stage shrinkage behavior resulting in well sintered and mechanically strong glass–ceramics with Augite as the primary crystalline phase. The appropriate coefficient of thermal expansion (CTE), long term thermal stability (300 h at 900 °C), high electrical resistivity, good adhesion and minimal reactivity with SOFC components makes the investigated glass–ceramics potential candidates for further experimentation as SOFC sealants.
E0323 – Effect of iron oxide addition on structural properties of calcium silico phosphate glass/glass-ceramics
Glasses with nominal composition 34SiO2–(45 ? x) CaO–16 P2O5–4.5 MgO–0.5 CaF2–x Fe2O3 (where x = 5, 10, 15, 20 wt.%) have been synthesized by melt quench technique. These have been investigated for structural features by using Fourier transform infra-red (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Results have shown an increase in fraction of non?bridging oxygen in glasses with an increase in iron oxide content up to 15 wt.% and subsequently decreases with further increase in iron oxide content to 20 wt.%. These effects are originated by the incorporation of Fe2O3 into the silica network. Iron oxide behaves as a network modifier at low concentration and stabilizes the glass network at higher content. The glass-ceramics exhibit an increase in the formation of magnetite phase with an increase in iron oxide. The glass phase in the glass-ceramics matrix, controls the surface dissolution, which in turn decides the response of the material in-vitro. The glass-ceramics with 15 wt.% iron oxide has shown optimum response in simulated body fluid.
E0322 – The role of strontium and potassium on crystallization and bioactivity of Na2O–CaO–P2O5–SiO2 glasses
The effect of SrO/CaO and K2O/Na2O replacements on the crystallization process of glasses based on Na2O–CaO–P2O5–SiO2 system was investigated. The glasses were thermally treated through controlled heat treatment regimes to obtain glass ceramic materials. Combeite Na2Ca2Si3O9, sodium calcium silicate Na2Ca3Si6O16, wollastonite solid solution, and whitlockite Ca3(PO4)2 were identified as major crystalline phases in the prepared thermally treated glasses. No potassium and strontium-containing phases could be detected in the glass–ceramics; potassium seems to be accommodated in the wollastonite structure, while strontium might be incorporated in the sodium calcium silicate structure.
The surface reactivity of the prepared glass–ceramic specimens was also studied in vitro in Kokobo's simulated body fluid (SBF). EDAX, SEM, inductively coupled plasma ICP, and FTIR were used to examine the formation of apatite layer's surface and characterize the glass ceramic surface and SBF compositional changes. A decrease in the bioactivity of the glass ceramic was observed as Na2O was replaced by K2O. Strontium together with calcium ions in the apatite layer formed was detected with SrO/CaO replacement.
The role played by the glass oxide constituents in determining the crystallization and bioactivity behaviour of the prepared thermally treated glasses was discussed.
E0321 – Performance investigation of Li2O–Al2O3–4SiO2 based glass–ceramics with B2O3, Na3AlF6 and Na2O fluxes
Influence of single fluxes (10 wt.% B2O3), bi-component fluxes (4 wt.% B2O3 + 6 wt.% Na3AlF6), and complex fluxes (4 wt.% B2O3 + 4 wt.% Na3AlF6 + 2 wt.% Na2O) on the thermal kinetic parameters, microstructure, flexural strength and coefficient of thermal expansion (CTE) of Li2O–Al2O3–4SiO2 (LAS) glass–ceramics was investigated through differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscope (SEM). The results showed that complex fluxes could efficiently decrease transition temperature (Tg) and crystallization temperature (Tp), and accelerate the formation of needle-like ?-spodumene crystals which benefit high flexural strength. The homogeneous LAS glass–ceramic (sample C3) which has a high strength of 132.4 MPa and low CTE (100–650 °C) of 2.74 × 10? 6/°C is obtained by doping of the initial LAS glass by complex fluxes of 4 wt.% B2O3, 4 wt.% Na3AlF6, and 2 wt.% Na2O, nucleating at 630 °C/120 min and then crystallized at 780 °C/120 min. It is worthy of further investigation as a bonder of diamond composite material due to its outstanding prosperities.
E0319 – Study of glasses/glass-ceramics in the SrOeZnOeSiO2 system as high temperature sealant for SOFC applications
Glasses having composition (in wt.%) 51SrO-9ZnO-(40?x)SiO2 (SZS), where x represents the additives like B2O3, Al2O3, V2O5, and Cr2O3, were prepared by melt-quench method and transformed into glass-ceramics by controlled crystallization based on differential thermal analysis (DTA) data. Glasses and glass-ceramics were characterized using dilatometry, X-ray diffraction (XRD), microhardness, and Raman spectroscopy. XRD revealed that glass-ceramics are composed of mainly Sr2ZnSi2O7 and SrSiO3 crystalline phases along with residual glassy phase. Raman spectroscopy showed that main constitutes of the glass network are the Q1 and Q2 silicate structural units. With the addition of B2O3 and other additives silicate glass network depolymerizes and concentration of Q1 structural units increases at the expense of Q2 units. Formation of phases during crystallization depends on the presence of different silicate structural units in the glass matrix. B2O3 goes into the glass network as triangular (BO3) borate structural units and at higher concentration of B2O3, only a part of the B2O3 forms tetragonal (BO4) structural units. Investigated glasses and glass-ceramics have thermal expansion coefficient (TEC) in the range of 105–120 × 10?7/°C which matches with TEC of other cell components. B2O3 containing SZS glasses show good adhesion/bonding with YSZ and Crofer 22 APU. Elemental line scans indicate that interdiffusion of Fe, Cr and Si across interface is responsible for good bonding with Crofer 22 APU and interdiffusion of Sr, Si, Y and Zr is responsible for good bonding with YSZ.
E0316 – Investigation of crystallization kinetic of SrO-La2O3-Al2O3-B2O3-SiO2 glass and its suitability for SOFC sealant
Strontium-lanthanum-aluminoborosilicate (SrO-La2O3-Al2O3-B2O3-SiO2) (SLABS) glass was prepared for sealant material in planar Solid Oxide Fuel Cells (pSOFC). Differential Thermal Analysis of the glass showed the formation of two crystalline phases, first one 807 C and the second phase at 1021 C. Crystallization kinetic of the first crystalline phase was investigated by differential thermal analysis (DTA) and using the JMA-kinetic model.
The activation energy for crystallization was calculated to be 114.04 kJ/mol with frequency factor 5.9 x 103. Coefficient of Thermal Expansion (CTE) of the glass was measured to be 9.72x 10- 6/ C. Optical band gap of the glass was measured to be 3.07 eV. Conductivity measured by Impedance spectroscopy found to be 5.68x 10-7 S cm-1 at 600 C and it increased with temperature to 2.68x 10-6 S cm-1 at 800 C. Activation energy for electrical conduction was measured to be 66.12 kJ/mol. Wetting behavior of the glass on a ferritic steel substrate was investigated under hot stage microscopy. It showed initial deformation
temperature (IDT) 754 C, softening temperature (ST) 840 C, hemispherical temperature (HT) 1108 C and flow temperature (FT) 1279 C.
E0315 – Physical and thermal behaviour of Sr–La–Al–B–Si based SOFC glass sealants as function of SrO content and B2O3/SiO2 ratio in the matrix
A series of SOFC glass sealants with composition SrO (x), La2O3 (15), Al2O3 (15), B2O3 (40 ? x), and SiO2 (30) [x = 10, 15, 20, 25 and 30] (wt.%) [SLABS] are investigated for their structure property correlations at different compositions. Quantitative Fourier transform infrared spectroscopy shows structural rigidity with increasing SrO content, as demonstrate by an increase in the Si–O–Si/O–Si–O bending and B–O–B stretching frequencies. The role of SrO as a modifier dominates the control of the structure and behaviour of glasses compared with the effect of network formers, i.e., the B2O3/SiO2 ratio. Consequent to the structural changes, increasing substitution of B2O3 by SrO the glasses causes increases in the density, glass transition temperature and dilatometric softening point. On the other hand, the crystallization temperatures show a decreasing trend and the coefficient of thermal expansion increases with increase in substitution.
E0309 – Enhancement of cells proliferation and control of bioactivity of strontium doped glass
Bioactivity and chemical reactivity of bioactive glass offer the ability to bond for soft and hard biological tissues. In this work, synthesis was carried out by using melting and rapid quenching. Strontium was introduced as trace element at different contents in the glass matrix, according to its concentration in the bone matrix. This chemical element presents a high interest in the bone metabolism activity. Investigations were conducted on the surface of biomaterials by using in vitro assay after immersion in SBF. Several physico-chemical methods such as SEM, FTIR, NMR, ICP-OES and MTT test were employed to highlight the effects of the Sr. The in vitro experiments showed that after soaking in SBF, the behaviour of pure glass is different compared to glass doped with Sr. NMR analyses showed in the 29Si MAS-NMR that glass matrix undergoes some changes after in vitro assays particularly the emergence of new components attributed to Q3(OH). The presence of Sr slowed down the bioactivity of glass after immersion in SBF. The non toxic character of compounds was confirmed. Introduction of Sr at 0.1 wt % induce an enhancement of cells at about 14.3%.
E0306 – Influence of strontium on structure, sintering and biodegradation behaviour of CaO–MgO–SrO–SiO2–P2O5–CaF2 glasses
The present study investigates the influence of SrO on structure, apatite-forming ability, physico-chemical degradation and sintering behaviour of melt-quenched bioactive glasses with the composition (mol.%): (36.07 ? x) CaO–xSrO–19.24MgO–5.61P2O5–38.49SiO2–0.59CaF2, where x varies between 0 and 10. The detailed structural analysis of the glasses is made by infrared spectroscopy and magic angle spinning–nuclear magnetic resonance spectroscopy. Silicon is predominantly present as Q2 (Si) species, while phosphorus is found as orthophosphate in all the investigated glasses. The apatite-forming ability of glasses is investigated by immersion of glass powders in simulated body fluid for time durations varying between 1 h and 7 days. While increasing the Sr2+/Ca2+ ratio in the glasses does not affect their structure significantly, their apatite-forming ability is decreased considerably. Further, physico-chemical degradation of glasses is studied in accordance with ISO 10993-14 “Biological evaluation of medical devices – Part 14: Identification and quantification of degradation products from ceramics” in Tris–HCl and citric acid buffer, and the possible implications of the ion release profiles from the glasses in different solutions are discussed. The addition of strontium to the glasses leads to a sevenfold decrease in chemical degradation of glasses in Tris–HCl. The sintering of glass powders renders glass ceramics (GCs) with varying degrees of crystallinity and good flexural strength (98–131 MPa), where the mechanical properties depend on the nature and amount of crystalline phases present in the GCs.
E0303 – The effect of P2O5 on the structure, sintering and sealing properties of barium calcium aluminum boro-silicate (BCABS) glasses
The effect of P2O5 incorporation on the sintering, flow and crystallization characteristics of BCABS glasses of composition (mol%) 35BaO–15CaO–5Al2O3–(37 ? x)SiO2–8B2O3–xP2O5 (0 ? x ?5) is investigated. It is observed that addition of P2O5, removes cations (Ba2+ and Ca2+) from the silicate network, resulting in an increase in polymerization. This is reflected by a reduction in TEC and an increase in sealing temperature. In addition, the removal of cations for charge compensation causes a change in major crystalline phases formed, from BaSiO3 to Ba(Al2Si2O8). In addition, beyond 3 mol% P2O5, crystallization of phosphate phases is evident. Based upon the flow temperature, glasses with 0, 1 and 2 mol% P2O5 are selected for sealing. In these glasses, conversion of Cr to Cr2O3 is observed, yielding improved adhesion. However, the 2 mol% P2O5 glass showed an increased crystallization tendency, resulting in incomplete sintering. Therefore, 1 mol% P2O5 seems a good compromise for sealing with improved adhesion
E0301 – Compositional effects on the properties of high nitrogen content alkaline-earth silicon oxynitride glasses, AE = Mg, Ca, Sr, Ba
A series of alkaline-earth element containing high nitrogen content oxynitride glasses (AESiON), with AE = Mg, Ca, Sr, Ba, were prepared in order to investigate the compositional effects on the physical properties of the alkaline-earth element. The physical properties were found to change linearly with the concentration of AE elements. The density of the glasses increases substantially with an increase in the AE atomic mass and slightly with an increase in nitrogen ratio. Ba containing glasses shows the value of density 4.16 g/cm3. Glass transition temperatures are found to be higher for Mg glasses, ca. 1020 °C, in comparison with Ba glasses, ca. 895 °C. The hardness of Mg containing glasses shows high values, up to 12.2 GPa and decreases for Ca, Sr and Ba containing glasses. Ba, containing glasses shows high values of refractive index in comparison with the Sr, Ca and Mg containing glasses.
E0297 – Characteristic free volume change of bulk metallic glasses
The free volume change ?Vf(T) of bulk metallic glasses (BMGs) relative to a hypothesized amorphous reference state was measured using the thermal dilatation method. The characteristic free volume change, i.e., the free volume released in structural relaxation ?Vf-sr, was identified quantitatively from the ?Vf(T) curve. For a Fe-based BMG, it was found that ?Vf-sr increases with decreases in the sample diameter and heating rate. ?Vf-sr measured under the same sample diameter and heating rate conditions allowed the convenient comparison of different BMGs. The comparison revealed that the glass-forming ability (GFA) enhancement of each of two Pd-, Mg-, Cu-, Zr-, Ti-, and Fe-based BMGs can be sensitively reflected in the decrease in ?Vf-sr and the narrowing of the difference between the peak temperature of the thermal expansion coefficient and the end temperature of the glass transition process. In addition, for these twelve typical BMGs, there is a good linear relationship between ?Vf-sr and LogDc2 or LogDc, where Dc is the critical diameter. ?Vf-sr is thus sensitive to and has a close correlation with GFA. Furthermore, the ?Vf-sr measurement results are in good agreement with the free volume change measured with the specific heat capacity, room temperature density, and positron annihilation lifetime methods. In the study of the relationship between the structure and properties of BMGs, ?Vf-sr thus plays an important role given its comparability and convenience.
E0293 – Alkali-free bioactive glasses for bone tissue engineering: A preliminary investigation
An alkali-free series of bioactive glasses has been designed and developed in the glass system CaO-MgO-SiO(2)-P(2)O(5)-CaF(2) along the diopside (CaMgSi(2)O(6))-fluorapatite (Ca(5)(PO(4))(3)F)-tricalcium phosphate (3CaO·P(2)O(5)) join. The silicate network in all the investigated glasses is predominantly coordinated in Q(2) (Si) units, while phosphorus tends to remain in an orthophosphate (Q(0)) environment. The in vitro bioactivity analysis of glasses has been made by immersion of glass powders in simulated body fluid (SBF) while chemical degradation has been studied in Tris-HCl in accordance with ISO-10993-14. Some of the investigated glasses exhibit hydroxyapatite formation on their surface within 1-12 h of their immersion in SBF solution. The sintering and crystallization kinetics of glasses has been investigated by differential thermal analysis and hot-stage microscopy, respectively while the crystalline phase evolution in resultant glass-ceramics has been studied in the temperature range of 800-900°C using powder X-ray diffraction and scanning electron microscopy. The alkaline phosphatase activity and osteogenic differentiation for glasses have been studied in vitro on sintered glass powder compacts using rat bone marrow mesenchymal stem cells. The as-designed glasses are ideal candidates for their potential applications in bone tissue engineering in the form of bioactive glasses as well as glass/glass-ceramic scaffolds
E0292 – Crystallization kinetics, stability and glass forming ability of iron phosphate and cesium loaded iron phosphate glasses
The activation energy of crystallization of iron phosphate glass (IPG) as a function of the fraction of crystallization was evaluated by Kissinger–Akahira–Sunose isoconversional method utilizing crystallization curves obtained from differential thermal analysis (DTA). The crystallization products were identified by using X-ray diffraction technique. Similar crystallization kinetic studies were carried out on IPG loaded with 5.5 mol% Cs2O. The glass stability and glass forming ability of IPG and various cesium loaded IPG were also estimated in terms of the characteristic temperatures obtained from DTA. The characteristic temperatures include glass transition, crystallization and liquidus temperature. The glass forming ability is correlated with the evaluated critical cooling rate of the glasses
E0291 – Structural and thermal characterization of CaO–MgO–SiO2–P2O5–CaF2 glasses
The influence of varying the CaO/MgO ratio on the structure and thermal properties of CaO–MgO–SiO2–P2O5–CaF2 glasses was studied in a series of eight glass compositions in the glass forming region of diopside (CaMgSi2O6)–fluorapatite [Ca5(PO4)3F]–wollastonite (CaSiO3) ternary system. The melt-quenched glasses were characterized for their structure by infrared spectroscopy (FTIR) and magic angle spinning (MAS)-nuclear magnetic resonance (NMR) spectroscopy. Silicon is predominantly present as Q2 (Si) species, while phosphorus tends to coordinate in orthophosphate environment. The sintering and crystallization parameters of the glasses were obtained from differential thermal analysis (DTA) while crystalline phase fractions in the sintered glass–ceramics were analyzed by X-ray diffraction adjoined with Rietveld refinement. Diopside, fluorapatite, wollastonite and pseudowollastonite crystallized as the main crystalline phases in all the glass–ceramics with their content varying with respect to variation in CaO/MgO ratio in glasses. The implications of structure and sintering behaviour of glasses on their bioactivity were discussed.
E0287 – Investigations of the non-isothermal crystallization of Bi4Ge3O12 (2:3) glasses
Amorphous Bi4Ge3O12 glass samples were produced by melt quenching procedure stating with Bi4Ge3O12 (BGO) powder, obtained by solid state reaction between oxides. The kinetics of non-isothermal crystallization of BGO nano-crystals has been investigated. Differential Thermal Analysis (DTA) can give the main parameters of crystallization with an exothermic peak from 813 K to 851 K depending on the heating rate, which was assigned to the crystallization of cubic BGO in the amorphous matrix and compared with the X-Ray Diffraction (XRD) patterns. The nano-crystal dimensions were calculated from the XRD patterns by using the Debye–Scherrer method and were compared with Transmission Electron Microscopy (TEM) images. It was shown that the Ozawa model is most suitable for describing the behavior of non-isothermal crystallization of BGO nano-crystals within the glass matrix. Experimental results suggest a disk-shape type growth mechanism for the Bi4Ge3O12 nano-crystallites. The Flynn–Wall–Ozawa method has shown that the average activated energy value is 385 ± 14 kJ/mol which was computed within the same model and agrees very well with the activation energy of the crystallization.
E0286 – The microstructure of erbium–ytterbium co-doped oxyfluoride glass–ceramic optical fibers
Oxyfluoride transparent glass–ceramics combine some features of glasses (easier shaping or lower than single crystals cost of fabrication) and some advantages of rare-earth doped single crystals (narrow absorption/emission lines and longer lifetimes of luminescent levels). Since the material seems to be promising candidate for efficient fiber amplifiers, the manufacturing as well as structural and optical examination of the oxyfluoride glass–ceramic fibers doped with rare-earth ions seems to be a serious challenge. In the first stage oxyfluoride glasses of the following compositions 48SiO2–11Al2O3–7Na2CO3–10CaO–10PbO–11PbF2–3ErF3 and 48SiO2–11Al2O3–7Na2CO3–10CaO–10PbO–10PbF2–3YbF3–1ErF3 (in molar%) were fabricated from high purity commercial chemicals (Sigma–Aldrich). The fabricated glass preforms were drawn into glass fibers using the mini-tower. Finally, the transparent Er3+ doped and Er3+/Yb3+ co-doped oxyfluoride glass–ceramic fibers were obtained by controlled heat treatment of glass fibers. The preceding differential thermal analysis (DTA) studies allowed estimating both the fiber drawing temperature and the controlled crystallization temperature of glass fibers. X-ray diffraction examination (XRD) at each stage of the glass–ceramic fibers fabrication confirmed the undesirable crystallization of preforms and glass fibers has been avoided. The fibers shown their mixed amorphous–crystalline microstructure with nano-crystals of size even below 10 nm distributed in the glassy host. The crystal structure of the grown nano-crystals has been determined by XRD and confirmed by electron diffraction (SAED). Results obtained by both techniques seem to be compatible: Er3FO10Si3 (monoclinic; ICSD 92512), Pb5Al3F19 (triclinic; ICSD 91325) and Er4F2O11Si3 (triclinic; ICSD 51510) against to initially expected PbF2 crystals
E0285 – Effects of addition of nitrogen on bioglass properties and structure
Bioglasses have been developed for use in surgery because of their ability to form a hydroxy-carbonate apatite (HCA) layer on their surface which facilitates bonding to natural bone. However, they do not have sufficient strength for use in load-bearing situations and therefore improving their mechanical properties would allow their use in more robust applications. The purpose of this work was to study the effects of nitrogen addition on the physical and mechanical properties and the structure of oxynitride bioglasses based on the system Na2O–CaO–SiO2–Si3N4. The density, glass transition temperature, hardness and elastic modulus were measured and observed to increase linearly with nitrogen content. These increases are consistent with the incorporation of N into the glass structure in three-fold coordination with silicon which results in extra cross-linking of the glass network. The characterization of these oxynitride bioglasses using solid state nuclear magnetic resonance 29Si MAS NMR and infrared spectroscopy have shown firstly that all the N atoms are bonded to Si atoms and secondly that this increase in rigidity of the glass network can be explained by the formation of SiO3N, SiO2N2 tetrahedra and Q4 units with extra bridging anions at the expense of Q3 units. The oxynitride bioglasses in simulated body fluid form a hydroxy-carbonate apatite (HCA) layer on their surfaces showing that bioactivity is retained
E0284 – Crystallization characteristics of La2O3-containing glasses for glass ionomer cement
Glasses with general formula 4.5SiO2 ? 3Al2O3 ? 1.5P2O5?(2.5 ? x)CaO ? xLa2O3 ? 2.5CaF2 (x = 0.0–1.0) for glass ionomer cement have been prepared by conventional melting and water quenching. The influence of substitution of La2O3 for CaO on glass transition temperature (Tg), setting time and crystallization was studied. An increase in La2O3/CaO ratio shifted Tg to higher temperature. Fluorapatite (Ca5(PO4)3F), mullite (3Al2O3 ? 2SiO2), lanthanum aluminum silicate solid solution, and anorthite (CaO ? Al2O3 ? 2SiO2) were identified by XRD in the heat-treated materials; then, their formation was dependent on glass composition and heat-treatment temperature. After heat-treating at 750 °C with glass samples of La2O3/CaO = 0, 0.25 (molar ratio), only fluorapatite phase was precipitated; however, anorthite was additionally formed at 950 and 1050 °C. With further increasing La2O3/CaO ratio and/or heat-treatment temperature, lanthanum aluminum silicate solid solution existed as the major phase
E0283 – The role of K2O on sintering and crystallization of glass powder compacts in the Li2O–K2O–Al2O3–SiO2 system
The effects of K2O content on sintering and crystallization of glass powder compacts in the Li2O–K2O–Al2O3–SiO2 system were investigated. Glasses featuring SiO2/Li2O molar ratios of 2.69–3.13, far beyond the lithium disilicate (LD-Li2Si2O5) stoichiometry, were produced by conventional melt-quenching technique. The sintering and crystallization behaviour of glass powders was explored using hot stage microscopy (HSM), scanning electron microscopy (SEM), differential thermal (DTA) and X-ray diffraction (XRD) analyses. Increasing K2O content at the expense of SiO2 was shown to lower the temperature of maximum shrinkage, eventually resulting in early densification of the glass-powder compacts. Lithium metasilicate was the main crystalline phase formed upon heat treating the glass powders with higher amounts of K2O. In contrast, lithium disilicate predominantly crystallized from the compositions with lower K2O contents resulting in strong glass–ceramics with high chemical and electrical resistance. The total content of K2O should be kept below 4.63 mol% for obtaining LD-based glass–ceramics.
E0282 – Effect of K2O on structure–property relationships and phase transformations in Li2O–SiO2 glasses
Glass compositions with formula (71.78 ? x)SiO2–2.63Al2O3–(2.63 + x)K2O–23.7Li2O (mol.%, x = 0–10) and SiO2/Li2O molar ratios far beyond that of stoichiometric lithium disilicate (Li2Si2O5) were prepared by conventional melt-quenching technique to investigate the influence of K2O content on structural transformations and devitrification behaviour of glasses in the Li2O–SiO2 system. The scanning electron microscopy (SEM) examination of as cast non-annealed glasses revealed the presence of nanosized droplets in glassy matrices suggesting occurrence of liquid–liquid phase separation. An overall trend towards depolymerization of the silicate glass network with increasing K2O content was demonstrated by employing magic angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopy. The distribution of structural units in the experimental glasses was estimated using 29Si MAS-NMR spectroscopy suggesting the appearance of Q2, enhancement of Q3 and diminishing of Q4 groups with increasing K2O contents. X-ray diffraction (XRD) and differential thermal analysis (DTA) were used to assess the influence of K2O on devitrification process and formation of lithium disilicate (Li2Si2O5) and/or lithium metasilicate (Li2SiO3) crystalline phases.
The crystallisation kinetics of experimental glasses in 3 different systems: (A) Li2O–SiO2, (B) Li2O–Al2O3–SiO2 and (C) Li2O–K2O–Al2O3–SiO2 were studied under non-isothermal conditions. The DTA results revealed a stronger tendency to crystallisation of binary compositions in comparison to the ternary and quaternary compositions comprising Al2O3 and K2O which present the lower crystallisation, i.e. the crystallisation propensity follows the trend A[B[C. The devitrification process in theLi2O–SiO2 andLi2O–Al2O3–SiO2 systems began earlier and the rate was higher in comparison to that of glasses in the quaternary Li2O–K2O–Al2O3–SiO2 system. Thus, addition of Al2O3 and K2O to glasses of Li2O–SiO2 system was demonstrated to promote glass stability against crystallisation. However, the activation energy for crystallisation was shown to depend also on the SiO2/Li2O ratio with the binary systemshowing a decreasing trendwith increasingSiO2/Li2O ratio,while the opposite tendencywas being observed for compositions with added Al2O3 and K2O.
E0268 – Processing, characterisation, and biocompatibility of zinc modified metaphosphate based glasses for biomedical applications
Bulk and structural properties of zinc oxide (0 up to 20 mol%) containing phosphate glasses, developed for biomedical applications, were investigated throughout this study using differential thermal analysis (DTA), differential scanning calorimetry, X-ray powder diffraction and 31P and 23Na MAS NMR. Surface wettability and MG63 viability were also considered for surface characterisation of these glasses. The results indicated that incorporation of zinc oxide as a dopant into phosphate glasses produced a significant increase in density; however,
the thermal properties presented in glass transition, and melting temperatures were reduced. NaZn(PO3)3 was detected in the X-Ray Powder Diffraction Analysis (XRD) trace of zinc containing glasses, and the proportion of this phase increased with increasing zinc oxide content. NaCa(PO3)3 as a second main phase and CaP2O6 in minor amounts were also detected. The 31P and 23Na MAS NMR results suggested that the relative abundances of the Q1 and Q2 phosphorus sites, and the local sodium environment were unaffected as CaO was replaced by ZnO in this system. The replacement of CaO with ZnO did seem to have the effect of increasing the local disorder of the Q2 metaphosphate chains, but less so for the Q1 chain-terminating sites which were already relatively disordered due to the proximity of modifying cations. Glasses with zinc oxide less than 5 mol% showed higher surface wettability, while those with 5 up to 20 mol% showed comparable wettability as zinc oxide free glasses. Regardless of the high hydrophilicity and surface reactivity of these zinc oxide containing glasses, they had lower biocompatibility, in particular 10–20 mol% ZnO, compared to both zinc free glasses and Thermanox1. This may be associated with the release of significant amount of Zn2+ enough to be toxic to MG63.
E0260 – New solid-state glass electrodes by using zinc oxide thin films as interface layer
Novel glass electrodes for the determination of cations with reversible internal solid contact are introduced. They are based on a semiconducting zinc oxide layer with a maximum thickness of 1 ?m in contact with ion selective glasses on one side and with a metal layer on the other side. The metal oxide layer is thereby generated either by ultrasonic spray pyrolysis from zinc acetate solution, by electrochemical deposition from zinc nitrate solution or by spin coating from a dispersion of ZnO in an organic binder. A following activation in a palladiumchloride solution
allows the chemical reductive deposition of NiP as electronic conductor. Dipping-type and flow through electrodes as well as planar glass electrodes in thick film technology fabricated in the above-mentioned method are described. In this case gold electrodes are applied by screen printing on isolated steel substrates. The zinc oxide layers, created in different manners,
are covered afterwards with cation selective glasses in thick film technology. They cause a stabilisation of the half-cell potentials of the all solid state indicator electrodes proved by suitable measurements.
E0251 – Thermal analysis and in vitro bioactivity of bioactive glass–alumina composites
Bioactive glass–alumina composite (BA) pellets were fabricated in the range 95/5–60/40 wt.% respectively and were heat-treated under a specific thermal treatment up to 950 °C. Control
(unheated) and heat-treated pellets were immersed in Simulated Body Fluid (SBF) for bioactivity testing. All pellets before and after immersion in SBF were studied by Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM-EDS) and X-ray Diffraction (XRD) analysis. All composite pellets presented bioactive response. On the surface of the heat-treated pellets the development of a rich biological hydroxyapatite (HAp) layer was delayed for one day, compared to the respective control pellets. Independent of the proportion of the two components, all composites of each group (control and heat-treated) presented the same bioactive response as a function of immersion time in SBF. It was found that by the applied methodology, Al2O3 can be successfully applied in bioactive glass composites without obstructing their bioactive response
E0248 – A hazardous waste from secondary aluminium metallurgy as a new raw material for calcium aluminate glasses
A solid waste coming from the secondary aluminium industry was successfully vitrified in the ternary CaO–Al2O3–SiO2 system at 1500 ?C. This waste is a complex material which is considered hazardous because of its behaviour in the presence of water or moisture. In these conditions, the dust can generate gases such as H2, NH3, CH4, H2S, along with heat and potential aluminothermy. Only silica sand and calcium carbonate were added as external raw materials to complete the glasses formula. Different nominal compositions of glasses, with Al2O3 ranging between 20% and 54%, were studied to determine the glass forming area. The glasses obtained allow the immobilisation of up to 75% of waste in a multicomponent
oxide system in which all the components of the waste are incorporated. The microhardness Hv values varied between 6.05 and 6.62 GPa and the linear thermal expansion coefficient, ?, varied between (62 and 139)×10?7 K?1. Several glasses showed a high hydrolytic resistance in deionised water at 98 ?C.
E0244 – Strontium oxide doped quaternary glasses: effect on structure, degradation and cytocompatibility
This preliminary study focuses on the effect of adding SrO to a Ti-containing quaternary phosphate glass system denoted by P2O5–Na2O–CaO–TiO2. The following four different glass compositions were manufactured: 0.5P2O5–0.17Na2O–0.03TiO2–(0.3-x)CaO–xSrO where x = 0, 0.01, 0.03 and 0.05. Structural characterisation revealed glass transition temperatures in the range 427–437°C and the presence of sodium calcium phosphate as the dominant phase in all the glasses. Degradation and ion release studies conducted over a 15-day period revealed
that the Sr-containing glasses showed significantly higher degradation and ion release rates than the Sr-free glass. Cytocompatibility studies performed over a 7-day period using MG63 cells showed that the addition of 5 mol% SrO yielded glasses with cell viability nearly equivalent to that observed for quaternary TiO2 glasses.
E0238 – Crystallization and dielectric and optical properties of borate glasses (1 ? x)Na2B4O7 + xNb2O5
The crystallization and dielectric and optical properties of glasses (1 ? x)Na2B4O7 + xNb2O5, where x = 0.15–0.35, have been studied. The formation of structural entities based on NbO6 octahedra in the glass has been detected by Raman spectroscopy. In the thermally poled glass, a layer with nonlinear optical properties is formed under the anode surface. The nonlinear optical properties of the poled sample have been studied by the second harmonic generation method using laser radiation. The nonlinear optical coefficient d 33 for the poled glass with the maximal content of niobia is 0.1 pm/V.
E0235 – Development and characterization of glass-ceramic sealants in the (CaO-Al2O3-SiO2-B2O3) system for Solid Oxide Electrolyzer Cells
The efficiency of glass-ceramic sealants plays a crucial role in Solid Oxide Electrolyzer Cell performance and durability. In order to develop suitable sealants, operating around 800 °C, two parent glass compositions, CAS1B and CAS2B, from the CaO-Al2O3-SiO2-B2O3 system were prepared and explored. The thermal and physicochemical properties of the glass ceramics and their crystallization behavior were investigated by HSM, DTA and XRD analyses. The microstructure and chemical compositions of the crystalline phases were investigated by microprobe analysis. Bonding characteristic as well as chemical interactions of the parent glass with yttria-stabilized zirconia (YSZ) electrolyte and ferritic steel-based interconnect (Crofer!) were also investigated. The preliminary results revealed the superiority of CAS2B glass for sealing application in SOECs. The effect of minor additions of V2O5, K2O and TiO2 on the thermal properties was also studied and again demonstrated the advantages of the CAS2B glass composition. Examining the influence of heat treatment on the seal behavior showed that the choice of the heating rate is a compromise between delaying the crystallization process and delaying the viscosity drop. The thermal Expansion Coefficients (TEC) obtained for the selected glass ceramic are within the desired range after the heat treatment of crystallization. The crystallization kinetic parameters of the selected glass composition were also determined under non-isothermal conditions by means of differential thermal analysis (DTA) and using the formal theory of transformations for heterogeneous nucleation.
E0229 – The effect of TiO2 and P2O5 on densification behavior and properties of Anortite-Diopside glass-ceramic substrates
In this work the synthesis of anorthite-diopside glass-ceramics (GCs) was carried out via sintering and crystallization of glass powder compacts in the temperature interval 800°C and 950°C. Glass powder compacts with mean particle size of 2 ?m were prepared. The effects of adding TiO2 and P2O5 on the sintering behavior of glass powder compacts and on the properties of resultant glass-ceramics were studied. Mechanical, thermal, chemical and dielectric properties of sintered GCs were investigated with the aim to evaluate the potential of the GCs as substrate materials for microelectronics applications.
E0228 – Electrical properties of some Y2O3 and/or Fe2O3-containing lithium silicate glasses and glass-ceramics
The ac electrical properties of some lithium silicate glasses and glass-ceramics containing varying proportions of Y2O3 and/or Fe2O3 were measured to investigate their electronic hopping mechanism. There is a clear variation of these properties with composition. The obtained results were related to the concentration and role of Y2O3 and/or Fe2O3 in the lithium silicate glass structure. In crystalline solids the electrical properties data obtained were correlated to the type and content of the mineral phases formed as indicated by X-ray diffraction analysis (XRD).
The conductivity, dielectric constant and dielectric loss of the studied glasses were studied using the frequency response in the interval 30 Hz–100 KHz and the effect of compositional changes on the measured properties was investigated. The measurements revealed that the electrical responses of the samples were different and complex. The addition of Y2O3 generally, decreased the ac conductivity, dielectric constant and dielectric losses of the lithium silicate glasses. The addition of Fe2O3 in Y2O3-containing glasses increases the conductivity, while, the dielectric constant and dielectric losses were found to be decreased. However, the addition of Fe2O3 instead of Y2O3 led to decrease the ac conductivity and increased their dielectric
constant and dielectric losses. The obtained data were argued to the internal structure of the lithium silicate glass and the nature or role-played by weakness or rigidity of the structure of the sample. Lithium disilicate-Li2Si2O5, lithium metasilicate-Li2-SiO3, two forms of yttrium silicate Y2Si2O7 & Y2SiO5, iron yttrium oxide-YFeO3, lithium iron silicate-LiFeSi2O6 and
a-quartz phases were mostly developed in the crystallized glasses. The conductivity of the crystalline materials was found to be relatively lower than those of the glass. At low frequency, as the Y2O3 content increased the ac conductivity, dielectric constant and dielectric loss data of the glass-ceramics decreased. However, the addition of Fe2O3 to the Y2O3 containing glass-ceramic led to increase the conductivity. The addition of high content of Fe2O3 instead of Y2O3 in the glass ceramic led to increase the ac conductivity.
E0227 – In vivo behavior of bioactive phosphate glass-ceramics from the system P2O5–Na2O–CaO containing TiO2
Soda lime phosphate bioglass-ceramics with incorporation of small additions of TiO2 were prepared in the metaphosphate and pyrophosphate region, using an appropriate two-step heat treatment of controlled crystallization defined by differential thermal analysis results. Identification and quantification of crystalline phases precipitated from the soda lime phosphate glasses were performed using X-ray diffraction analysis. Calcium pyrophosphate (b-Ca2P2O7), sodium metaphosphate (NaPO3), calcium metaphosphate (b-Ca(PO3)2), sodium pyrophosphate (Na4P2O7), sodium calcium phosphate (Na4Ca(PO3)6) and sodium titanium phosphate (Na5Ti(PO4)3) phases were detected in the prepared glass-ceramics. The degradation of the prepared glass-ceramics were carried out for different periods of time in simulated body fluid at 37 °C using granules in the range of (0.300–0.600 mm). The released ions were estimated by
atomic absorption spectroscopy and the surface textures were measured by scanning electron microscopy. Evaluation of in vivo bioactivity of the prepared glass-ceramics was carried through implanting the samples in the rabbit femurs. The results showed that the addition of 0.5 TiO2 mol% enhanced the bioactivity while further increase of the TiO2 content decreased the bioactivity. The effect of titanium dioxide on the bioactivity was interpreted on the basis of its action on the crystallization process of the glass-ceramics.
E0226 – Development and bioactivity evaluation of bioglasses with low Na2O content based on the system Na2O–CaO–MgO–P2O5–SiO2
Osteoconductive bioglasses, free of K2O and Al2O3 and with content of Na2O lower than 10 mol%, were designed based on the ratio (SiO2 + MgO)/(P2O5 + CaO + Na2O) in the system Na2O–CaO–MgO–P2O5–SiO2. The developed glasses have shown a strong potential for the formation of hydroxycarbonated apatite (HCA) in vitro. The particles of HCA aggregates tend to be of finer size with increasing the ratio of (SiO2 + MgO)/(CaO + P2O5 + Na2O) in the glass chemical composition indicating significant bioactivity. Critical size bone defects created in the femurs of albino adult female rats, and grafted with the glass particles for 12 weeks post implantation, were completely healed by filling with mineralized bone matrix without infection showing a strong potential for new bone formation in vivo. Osteoblasts and osteocytes were observed close to the surface of the granular implants with active areas of bone deposition, resorption and
remodelling. The bioglass with lowest (SiO2 + MgO)/(CaO + P2O5 + Na2O) ratio has shown the highest bioactivity while the bioglass with the highest (SiO2 + MgO)/(CaO + P2O5 + Na2O) has shown the lowest bioactivity. The newly formed bone in vivo has shown a similar structure to that of the original bone as indicated by the histology and microstructural results. In addition, Ca/P molar ratio of the newly formed bone was found to be (~1.67), which is similar to that of the original bone.
E0223 – Use of spent pot linings from primary aluminium production as raw materials for the production of opal glasses
The use of the carbonaceous fraction of spent pot linings (SPL) from primary aluminium electrolytic cells as a raw material for the production of opal glasses is evaluated. The SPL was heat treated and mixed with limestone to eliminate carbon and to minimise fluorine volatilisation. This material was then mixed with other glass formers, melted, and quenched to produce a glass. The cyanide which forms part of the SPL was thermally decomposed and some of the fluorine is incorporated into the glass matrix. The final material contains small crystals of fluorspar, which are responsible for light scattering and the opacity of the material, dispersed in an amorphous phase. The crystalline phase was identified by x-ray diffraction and its morphology was observed by scanning electron microscopy
E0221 – Effect of TiO2 addition on the crystallization and tribological properties of MgO–CaO–SiO2–P2O5–F glasses
The kinetic parameters including the activation energy for crystallization (E), the Avrami parameter (n) and frequency factor (?) of a glass in the MgO–CaO–SiO2–P2O5–F system were studied using non-isothermal differential thermal analysis (DTA) with regard to small amount of TiO2 additions. It has been shown that the role of TiO2 changes from a glass network former to a glass network modifier with increasing TiO2 content in this system. The kinetic parameters of the crystallizing phases, apatite and wollastonite, indicated changes accompanied with TiO2 additions, implying that the TiO2 is an effective nucleating agent for promoting the crystallization of apatite and wollastonite. The most effective addition is of about 4 wt% TiO2 in this system. The wear rate and friction coefficient decreased from 1.8 ± 0.1 to 0.9 ± 0.2 and 0.87 to 0.77, respectively, when 4 wt% TiO2 was incorporated to the base glass
E0213 – Crystallization study of Na–Gd phosphate glass using non-isothermal DTA
Na–Gd phosphate glasses doped with Ce3+ are intensively studied due to their high intensity radioluminescence. Crystallization kinetics of glass with nominal composition of NaGd(PO3)4 was investigated using non-isothermal DTA at heating rates between 10 and 115 K min–1 and evaluated by the Kissinger and Ozawa peak methods. The activation energy for crystallization was determined for heating rates lower than 72 Kmin–1 as 789.91 and 802.77 kJmol–1 by using the Kissinger and Ozawamethods, respectively. Formation of nuclei, their dimensions and movement of the crystallization front were observed using isothermal optical thermomicroscopy
E0212 – Effect of Na2O/K2O substitution on thermophysical properties of PbO based phosphate glasses
PbO based phosphate glasses having composition 40P2O5 12Al2O3 6B2O3 9PbO xNa2O (33–x)K2O (x=0–33) [F=Na/(Na+K)] have been prepared using conventional melt quench technique. Density, morphology, thermal expansion coefficient ( ) and glass transition temperature (Tg) were studied as a function of Na/(Na+K) ratio. Formation of transparent, bubble free and clear glass was observed up to x=18 mol%. Density was found to vary from 2.70 to 3.69 g cm–3. The significant changes were noticed in external morphologies at temperatures corresponding to softening, half ball and melting points under high temperature microscope for three compositions (x=0, 10 and 15 mol%). These glasses recorded the softening and half ball temperatures in the range 454–470°C and 523–576°C respectively and melting temperatures agree well with DTA studies within the experimental limits. Glass transition temperature showed a broad maxima while thermal expansion coefficient (TEC) a broad minima around Na/(Na+K)=0.54. This behaviour is explained on the basis of bond formation/phase separation.
E0072 – Evolution thermique d’un gel de borosilicate de plomb.
B3296 – Properties, crystallization mechanism and microstructure of lithium disilicate glass–ceramic
In this study, lithium disilicate glass–ceramic in the TiO2–ZrO2–Li2O–CaO–Al2O3–SiO2 system was investigated for dentistry applications by incorporation of P2O5 and Nb2O5 as nucleation agent. The influence of the particles size (nano and submicron size) and nucleating agents on the crystalline phases, microstructure, crystallization mechanism and mechanical properties were investigated. Our data indicated that in ceramic glass with nano and submicron P2O5, the main crystalline phase was lithium disilicate. The results also showed that change of P2O5 particle’s size had significant effect on the crystalline phases and microstructure. By replacement of submicron P2O5 with submicron Nb2O5, crystallization mechanism was changed from volume to surface crystallization. Due to the nature of crystalline phases as well as the directional crystallization and coarsening, many cracks were observed in the samples containing submicron Nb2O5. The composition of base glass was changed and nano Nb2O5 was added. As a result of these changes, the crystallization mechanism was altered.
B3293 – Modification of magnetic and magnetocaloric properties of Dy–Co–Al bulk metallic glass introduced by hydrogen
Dy53.8Co17.3Al28.9 bulk metallic glass with a diameter of 3 mm exhibits spin-glass behavior and large coercivity and remanence. Hydrogenation of Dy53.8Co17.3Al28.9 suppresses the magnetic transition temperature and removes coercivity and remanence because of the expansion of average interatomic distance. The advantage of large magnetic entropy changes (17.5 and 9.5 J/kg?K for the field changes from 0 to 50, and from 0 to 20 kOe, respectively) without any hysteresis loss makes Dy53.8Co17.3Al28.9 H170.6 alloy a promising magnetic refrigerant
B3261 – Glass formation in the Nb–Si binary system
Nb81.3Si18.7 ribbons were prepared by rapid quenching of the liquid on a rotating copper wheel using various values of rotating speed. It was found that the melt spun ribbons consisted of an amorphous matrix; however the critical cooling rate for the formation of fully amorphous ribbons was achieved at rather high values of wheel speed. Crystallization occurs upon annealing above 971 K. The Vickers hardness of the amorphous ribbons was found to be 915 HV, an unusually high value for a binary alloy. The atomic structure of the amorphous Nb–Si alloy was studied using real space pair distribution (PDF)/radial distribution functions (RDF) derived from high precision X-ray diffraction data acquired with high-energy, monochromatic synchrotron light in transmission.
B3260 – Structural role of Zr4+ as a nucleating agent in a MgO–Al2O3–SiO2 glass-ceramics: A combined XAS and HRTEM approach
The environment around Zr4+ is studied at the Zr K-edge in a MgO–Al2O3–SiO2 glass-ceramics heat treated along its very first crystallization steps. The heat treatments were calibrated by differential scanning calorimetry. ZrO2 acts as a nucleating agent, adding a nucleation/crystallization event around 920 °C, less than 100 °C above the glass transition temperature (830 °C) and below the massive crystallization of the parent-glass (~ 1015 °C). It also lowers crystallization temperatures of the matrix as compared with a Zr-free sample. High-resolution transmission electron microscopy imaging allows an unambiguous attribution to tetragonal ZrO2 for, at least, some of the very first detectable crystallites. Zr K-edge extended X ray absorption fine structure analysis shows a peculiar surrounding around Zr4+ in the parent glass, composed of Si (Mg,Al) and Zr sites linked by edge sharing. This indicates direct linkages between Zr sites, pre-existing in the glass structure that play a key role for promoting nucleation. This analysis is in agreement with only a small part of Zr4+ evolving during the first steps of nucleation toward the formation of few nano-crystals of tetragonal (ZrO2).
B3250 – Crystallisation mechanism of a multicomponent lithium alumino-silicate glass
A base glass of composition 3.5 Li2O?0.15 Na2O?0.2 K2O?1.15 MgO?0.8 BaO?1.5 ZnO?20 Al2O3?67.2 SiO2?2.6 TiO2?1.7 ZrO2?1.2 As2O3 (in wt.%), melted and provided by SCHOTT AG (Mainz), was used to study the crystallisation mechanism of lithium alumino-silicate glass employing X-ray diffraction combined with neutron diffraction and non-isothermal differential scanning calorimetry (DSC). A high-quartz solid solution of LiAlSi2O6 with nanoscaled crystals forms at 750 °C. Quantitative Rietveld refinement of samples annealed at 750 °C for 8 h determined a crystallised fraction of around 59 wt.%. The room temperature crystallised phase adopts an ordered, ?-eucryptite-like structure (2 × 2 × 2 cell) with Li ordered in the structural channels. The Avrami parameter (n ? 4), calculated from DSC data using different theoretical approaches, indicates that bulk crystallisation occurs and that the number of nuclei increases during annealing. The activation energy of the crystallisation is 531 ± 20 kJ mol?1.
B3248 – Diffusion mechanism of Zr-based metallic glass during oxidation under dry air
Oxidation kinetics of a Zr55Cu30Al10Ni5 bulk metallic glass (BMG) and its crystalline counterpart were studied under dry artificial air at 673 K for long oxidation duration by thermogravimetry analysis (TGA). Oxidation kinetics was observed to follow a parabolic-rate law for the crystalline counterpart and a three-stage behaviour for the BMG. The ionic diffusion mechanism was investigated by using a two-stage oxidation treatment (16O2 oxidation and then 18O2 oxidation). The evident solute penetration zone and ion diffusion characteristic through the oxide scale were determined by Cs+ secondary ion mass spectrometry (SIMS) depth profile. The results of ion evolution indicated that the oxide grew under concurrent inward oxygen and outward Zr diffusions in short-term stage of the BMG oxidation; and the oxidation kinetics was controlled mainly by outward Cu and inward O diffusions in the case of long-term oxidation process.
B3244 – Nucleation and crystallisation kinetics of a Na-fluorrichterite based glass by differential scanning calorimetry (DSC)
The present paper shows the results of a nucleation and crystallisation study of a Na-fluorrichterite glass carried out by dynamic scanning calorimetry (DSC). The kinetic study was performed using different procedures (Kissinger, Matusita–Sakka and Kissinger–Akahira–Sunose (KAS) methods), and the Avrami parameter was determined from the Ozawa and Malek approximations and the Malek equation. The results have indicated the coexistence of surface and bulk crystallisation in the devitrification process of the studied glass. The kinetic study has shown that the activation energy of the crystallisation process is over 400 kJ/mol and that the mechanism proposed is a Johnson–Mehl–Avrami mechanism with n equal to 3, which implies that the crystallisation develops through the three-dimensional growth of crystals. The study of the variation of the activation energy with crystallisation using the KAS method has shown that the crystallisation process undergoes a multiple step mechanism, where the main part of the whole process corresponds to the three-dimensional growth of crystals. The mechanism proposed was confirmed by applying the Pérez-Maqueda et al. criterion.
B3243 – Structural and physico-chemical characterization of some soda lime zinc alumino-silicate glasses
The physico-chemical characterization of the 15Na2O-20CaO-5Al2O3-(60-x)SiO2-xZnO glasses (where x stands for 0, 4, 7 and 10 wt.%), designed as Z(0/ 4 / 7/ 10) and obtained by quenching method, has been carried out by DSC measurements, leaching tests and electrical conductivity measurements in the corresponding melts. Fitted multi-component DSC exotherms of crystallization are discussed in terms of the structural modifications derived from the X-ray measurements and room temperature Raman spectra. Combeite, Na2Ca2Si3O9, was identified as the low-temperature phase crystallized in all glasses under discussion while wollastonite (CaSiO3) was separated as main crystalline phase from the Z4, Z7 and Z10 glasses treated at 800 °C for 20 h. Zn-containing compounds, gahnite (ZnAl2O4) and Ca1.94Zn0.43Al1.25Si1.38O7, were crystallized at 924 °C for a 20 h span in the Z10 glass. The lowest Q3 population, 44.18%, responsible for network connectivity is derived by fitting the Raman spectrum of the Z10 glass. According to the unequal behavior of the Z10 glass as regarding leaching data as well as electrical conductivity measurements of the corresponding melts, the 7% ZnO represents the threshold from where higher degree of network depolymerization and presence of both four- and six-folded zinc atoms are met in these glasses.
B3200 – Thermal stability of a low Tg phosphate glass investigated by DSC, XRD and solid state NMR
The thermal stability of a low Tg phosphate glass (Tg = 339 °C), formulated in the ZnO–Na2O–P2O5 system, is investigated in this contribution by Differential Scanning Calorimetry (DSC), X-Ray diffraction (XRD) and solid state Nuclear Magnetic Resonance (NMR). DSC measurement indicates a very important Tx ? Tg value (197 °C) for the investigated composition compared to other low Tg phosphate glasses found in literature. XRD and 1D 31P solid state NMR were used to monitor the isothermal crystallization process occurring at 60 °C above Tg (400 °C). The mixture of phases formed after crystallization cannot be identified by XRD but 2D MAS-NMR experiment provides valuable information about the composition and the structure of the unknown sample.
B3199 – On the dependence of the properties of glasses on cooling and heating rates I. Entropy, entropy production, and glass transition temperature
The glass transition is theoretically described in terms of a generic non-equilibrium thermodynamics approach employing De Donder's structural order parameter method, appropriate expressions for the relaxation behavior of glass-forming systems and a simplified but qualitative correct model of glass-forming melts with one order parameter related to the free volume of the system. Employing this approach the behavior of a variety of thermodynamic quantities describing glass-forming systems in vitrification and devitrification processes is interpreted theoretically. The present paper is devoted to the computation of the entropy, the entropy production and the glass transition temperature in dependence on the cooling and heating rates, varying latter parameter in a broad interval. A comparison with experimental results is given and some further consequences and possible extensions are discussed briefly.
B3195 – Thermal analysis and in vitro bioactivity of bioactive glass–alumina composites
Bioactive glass–alumina composite (BA) pellets were fabricated in the range 95/5–60/40 wt.% respectively and were heat-treated under a specific thermal treatment up to 950 °C. Control (unheated) and heat-treated pellets were immersed in Simulated Body Fluid (SBF) for bioactivity testing. All pellets before and after immersion in SBF were studied by Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM-EDS) and X-ray Diffraction (XRD) analysis. All composite pellets presented bioactive response. On the surface of the heat-treated pellets the development of a rich biological hydroxyapatite (HAp) layer was delayed for one day, compared to the respective control pellets. Independent of the proportion of the two components, all composites of each group (control and heat-treated) presented the same bioactive response as a function of immersion time in SBF. It was found that by the applied methodology, Al2O3 can be successfully applied in bioactive glass composites without obstructing their bioactive response.
B3191 – Optical and spectroscopic properties of germanotellurite glasses
In this work, new glass compositions in the TeO2–GeO2–Nb2O5–K2O system have been prepared and studied. The germanotellurite glasses were prepared by melt-quenching and their density, refractive index and characteristic temperatures have been determined. The structure of these glasses has been studied by infrared and Raman spectroscopies.
The progressive replacement of TeO2 by GeO2 led to an increase of the glass transition and crystallisation temperatures of the glasses and a simultaneous decrease of their density and refractive index. Typical density and refractive index values of these glasses ranged from 4.98 to 3.85 g cm? 3 and 2.08 to 1.79, respectively, with increasing GeO2 content. The infrared spectra are dominated by a band ~ 640 cm? 1 in the tellurite glass and ~ 800 cm? 1 in the germanate glass. The Raman spectra of the germanotellurite glasses present an intense boson peak between ~ 34 and 47 cm? 1, together with high frequency peaks at ~ 670 cm? 1 and ~ 470 cm? 1 for high tellurite and high germanate glass compositions, respectively. The vibrational spectra of these germanotellurite glasses indicate that the glass network consists basically of TeO4 and [TeO3]/[TeO3 + 1] units, mixed with GeO4 and NbO6 polyhedra
B3177 – High-temperature X-ray analysis of phase evolution in Sr-doped zinc-silicate glasses
Bone grafts are required in many clinical situations. Autografts are the traditional gold standard for treating conditions requiring bone grafts. However autografts have inherent drawbacks such as donor site morbidity, pain and increased operative time. An alternative for autografts are synthetic grafts. A series of strontium doped zinc silicate glasses were developed which were investigated using high temperature X-ray diffraction (HT-XRD) in order to establish phase transformations, which occur up to the first crystallization temperature, (Tp1), thus identifying the composition–structure relationships which arise during this thermal processing. In analysing BT110 it was observed that all glass material crystallised into 4 phases including strontium zinc silicate, sodium calcium silicate, calcium silicate and strontium silicate, leaving no residual glass phase. BT111 and BT112 were shown to contain a residual glassy phase alongside for BT111, sodium zinc silicate, larnite and silicon oxide and for BT112 strontium silicate, calcium silicate, sodium silicate and silicon oxide. In the case of BT111 the residual glass phase appears to be rich in strontium. The residual glass phase being Sr enriched with respect to the glass-ceramic may offer increased release of Sr2+ from the material; important for the regulation of osteoblastic and osteoclastic activity. BT113 crystallized to form strontium silicate, sodium silicate, and strontium zinc silicate. BT114 crystallized to form strontium silicate and sodium silicate. The biocompatibility of phases formed in BT113 and BT114 is as yet unknown. Further knowledge will be generated by later work examining the biocompatibility of these phases identified in this research. However, on the basis of these results, the materials (BT110–BT112) exhibit potential as a bone graft substitutes, whilst BT113–BT114 give rise to phases with unknown biocompatibility and so warrant further investigation.
B3176 – Sol–gel synthesis of a new composition of bioactive glass in the quaternary system SiO2–CaO–Na2O–P2O5. Comparison with melting method
New sol–gel experimental conditions were tested to prepare a new SiO2-based bioactive glass with high Na2O content. The aim of this work is to investigate the real influence of the synthesis route (sol–gel versus melting) on the glass intrinsic properties and then, later, on the glass behavior and particularly on bioactivity. The obtained glass and its melt derived counterpart were characterized from structural and morphological (porosity, specific surface area) point of view. It could be noticed that the synthesis mode has no significant influence on glass structure. Conversely, the synthesis mode greatly influences the glass texture. The sol–gel derived glass exhibits a greatly higher specific surface area and pore volume than melt derived glass. This parameter may be a key factor of glass bioactivity.
B3175 – Transparent phosphosilicate glasses containing crystals formed during cooling of melts
Effect of P2O5–SiO2 substitution on spontaneous crystallization of SiO2–Al2O3–P2O5–Na2O–MgO melts during cooling was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and rotation viscometry. Results show that addition of P2O5 leads to amorphous phase separation (APS), i.e., phosphate- and silicate-rich phases. It is due to the tendency of Mg2+ to form [MgO4] linking with [SiO4]. Molar substitution of P2O5 for SiO2 enhances the network polymerization of silicate-rich phase in the melts, and thereby the spontaneous crystallization of cubic Na2MgSiO4 is also enhanced during cooling of the melts. In addition, the sizes of the local crystalline and separated glassy domains are smaller than the wavelength of the visible light, and this leads to the transparency of the obtained glasses containing crystals
B3148 – Physicochemical properties of Cs borosilicate glasses containing CaO
A series of Cs-borosilicate glasses of general formula (mol%): 17.5Na2O–2.5Cs2O–45SiO2–(35-x)B2O3–xCaO, where x varies from 0 to 10, were prepared by conventional melt quenching technique. Physicochemical properties like glass transition temperature, extent of volatilization loss of Cs and chemical durability of these glasses have been investigated in detail. Based on the Tg values obtained from DSC studies, it is confirmed that the glass network remains unaffected with increase in CaO content in the glass at the expense of B2O3. Cs loss as function of duration of heating revealed that the Cs evaporation follows diffusion controlled mechanism and the extent of loss increases with the increase of CaO incorporation in glass. Chemical durability of the glasses has been found to improve significantly with in the increase of CaO content in glass and this has been attributed to the formation of Ca and Si rich layer at the outer surface of the glass, as inferred from SEM with EDX analysis.
B3034 – Majority charge carrier reversal and its effect on thermal and electron transport in xV2O5–(1?x) As2O3 glasses
DC resistivity, thermopower and optical absorption of xV2O5–(1?x) As2O3 (0.58?x?0.93) glasses have been studied as a function of composition. The transport mechanism in these glasses has been identified to be a combination of hopping of small polarons between V4+ and V5+ sites and small bipolarons between As3+ and As5+ sites respectively. Electrical conductivity is found to be more of a function of vanadium content than arsenic concentration in the glasses, indicating that the contribution of bipolarons to the conductivity is negligible. Thermopower has also been found to be sensitive to the composition of the glasses. At lowvanadiumconcentrations, the thermopower is negative,which exhibits a sign reversal as vanadiumconcentration is increased (at x=0.7). An important feature of these glasses is that the thermopower is not a function of [V5+]/[V4+] ratio, as is normally observed in vanadate glasses, and such a phenomenon suggests that the arsenic ions (bipolarons) in these glasses contribute to the thermal transport phenomena in a significant way.
B3033 – Multi-scale structuration of glasses: Observations of phase separation and nanoscale heterogeneities in glasses by Z-contrast scanning electron transmission microscopy
Chemical fluctuations are probed in glasses obtained with different thermal histories using scanning transmission electron microscopy in high angle annular dark field mode. Direct imaging of the glass structure is obtained at the sub-nanometer scale with Z-contrast. Macroscopic glass-in-glass separation is probed in a slowly quenched melt where chemical resolution allows the determination of the regions associated with Zr/Zn atoms. In a quickly cooled glass, exempt of macroscopic phase separation, a segregation of Zr/Zn atoms is still evidenced but on a different length scale, suggesting either the beginnings of glass separation or intrinsic features of the glass structure. Glass inhomogeneities must be taken into account to have a quantitative
evaluation of nucleation processes. These “nano”-heterogeneities can be associated with the nucleation of zirconia phases, giving important clues to understand the nucleation pathways and the structural role of nucleating agents in aluminosilicate glasses.
B3032 – Mixed transition-ion effect in the glass system: Fe2O3-MnO-TeO2
In earlier studies on phosphate and tellurite glasses containing vanadium and iron oxides, non-linear variation of physical properties as functions of the ratios of the transition ions (V/V+Fe) were observed. The most striking effect was observed with electrical conductivity, where a 3 orders of magnitude reduction in conductivity was observed at a V/V+Fe ratio of ~0.4. The effect was termed Mixed Transition-ion Effect or MTE. In phosphate glasses, however, MTE was not observed when one of the transition ions was manganese. It was concluded that Mn does not contribute to conduction in these glasses. In the present study, we demonstrate a mixed transition ion effect in tellurite glasses containing MnO and Fe2O3 (xFe2O3(0.2?x) MnO0.8TeO2
with x varying from 0 to 0.2). A maximum in the property at an intermediate composition (x=8.5 mol%), was observed in DC resistivity, activation energy, molar volume etc. Mossbauer and optical absorption (UV–VIS–NIR) measurements were performed on these glasses and the transport mechanism has been identified to be hopping of small polarons between Fe3+ (Mn3+) and Fe2+ (Mn2+) sites.
B2921 – Crystal/glass phase change in K1 xRbxSb5S8 (x = 0.25, 0.50, 0.75) studied through thermal analysis techniques
K1 xRbxSb5S8 (x = 0.25, 0.5, 0.75) is a well-defined single-phase system that undergoes a reversible phase change. We determined the activation energy of glass transition and crystallization, respectively, for the three compositions using the Kissinger and Ozawa–Flynn–Wall equations. The results have shown that for K0.25Rb0.75Sb5S8 the crystallization mechanism could be interpreted in terms of a single-step reaction. For the other two compositions the glass-to-crystal transformation is a process of increasing mechanistic complexity with time and it involves simultaneously several different nucleation and growth events. The slope of the lines in the Avrami plots was observed to be independent of heating rate for K0.25Rb0.75Sb5S8 and the mean value of the activation energy was found to be 262 ± 6 kJ/mol. For the other two compositions, the slope varies with the heating rate. In the K0.25Rb0.75Sb5S8 glasses, bulk nucleation with threedimensional crystal growth appears to dominate the phase-change process.
B2828 – Synthesis, crystal structure and ferroelectric properties of SrBi2Nb2O9 embedded in a 50 % Li2B4O7 glass matrix
Transparent glass sample [50Li2B4O7–50(SrO–Bi2O3–Nb2O5)] (mol%) was prepared by the melt-quenching technique. The glassy nature of the as-prepared sample was established by Differential scanning calorimetry (DSC). Ferroelectric SrBi2Nb2O9 (SBN) embedded in a 50 % Li2B4O7 glass matrix was produced by heat-treating the as-prepared sample at 874 K (HT874) for 6 h. The X-ray structural analysis showed that SrBi2Nb2O9 crystallizes in the orthorhombic (A21am) with a = 5.5104, b05.5096 and c = 25.0794 Å. Infrared spectroscopy studies corroborate the observation of SrBi2Nb2O9 phase formation. The dielectric properties have been studied in the frequency range of 120 Hz to 100 kHz at various temperatures (300–815 K).
The high frequency dielectric constant "?'r" shows a peak at Tc (743 K). The exponent n(T) and the coefficient A(T) in the Jonscher’s expression were found to be minimum and maximum respectively at the Curie temperature (Tc). AC conductivity measurements for present sample were reported.
B2708 – The residual configurational entropy below the glass transition: Determination for two commercial optical glasses
Essentially from differential scanning calorimetry and viscosimetry, the residual configurational entropy below the glass transition is determined for two linearly cooled commercial optical glasses, K7TM and NLaK12TM from SCHOTT. The procedure is according to the conventional understanding of glass entropy and the conventional description of the configurational state by a distribution of fictive temperatures. For a cooling rate of 10 K/min, the residual entropy values found below the glass transition are 0.146 J/(g K) for K7TM and 0.148 J/(g K) for N-LaK12TM. The result is discussed comparing with both the lower limit for the residual entropy resulting from the reversibly exchanged heat ( ? dq/T, ‘Clausius limit’) and the upper limit given by the configurational entropy of an equilibrium liquid with the same fictive temperature. The difference between the residual entropy and its lower limit is equal to the entropy generation
due to the fall-out from equilibrium during linear cooling. The difference between the residual entropy and its upper limit is the driving force of the crossover- (or Kovacs-) effect. It turns out that the difference between the residual entropy and the Clausius limit is very small. The values found amount to less than 0.0001 J/(g K) for both glasses. Therefore, this difference can be neglected concerning the extrapolation of the Adam–Gibbs relation to low temperatures.
B2632 – Thermal analyses to assess diffusion kinetics in the nano-sized interspaces between the growing crystals of a glass ceramics
According to a hypothesis by Rüssel and coworkers, the absence of Ostwald ripening during isothermal crystallization of lithium aluminosilicate (LAS) and other glass ceramics indicates the existence of a kinetic hindrance of atomic reorganization in the interstitial spaces between the crystals. Methods of Thermal Analysis (Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA)) which are sensitive to the local atomic rearrangements in the interstitial spaces (including viscous flow) are applied to find support for the idea of kinetic hindrance and the formation of a core shell structure acting as diffusion barrier. Both the DSC-measured calorimetric glass transition and the DMA-measured viscoelastic properties indicate an increase in the time constants of atomic rearrangements and diffusion by at least two orders of magnitude during ceramization. This fits to the above idea. Based on these findings, thermo analytic studies have been performed in order to find out how Ostwald ripening may be provoked.
B2062 – Kinetics of iron redox reactions in silicate liquids: A high-temperature X-ray absorption and Raman spectroscopy study
The oxidation kinetics of a Fe-bearing supercooled liquid of the system SiO2-CaO-MgO-Na2O-FeO has been determined
near the glass transition range by X-ray absorption near edge structure (XANES) and Raman spectroscopies. Both
techniques yield room-temperature iron redox ratios in accord with wet chemical, Mössbauer and electron microprobe
analyses. Similar oxidation kinetics have also been observed with both methods. At constant temperature, the kinetics obey
an exponential law with a characteristic time that follows an Arrhenian temperature dependence. As redox changes are too
fast to be accounted for in terms of diffusion of either ionic or molecular oxygen, these results lend further support to the
idea that the rate-limiting factor for oxidation near the glass transition is diffusion of network-modifying cations along
with a flux of electron holes.
B2000 – Fe-based bulk metallic glasses with Y addition
This paper aims to study the role of residual vacuum during sample preparation and of quenching rate on glass formation in
Fe(50-x)Cr15Mo14YxC15B6 (x = 0, 2) alloys. The equilibrium phase mixture has been clarified for both alloys, combining X-ray diffraction (XRD)
and scanning electron microscopy (SEM) measurements. The beneficial effects of minor addition of Y on the glass formation are evidenced. A
high residual vacuum during sample preparation promotes glass formation. Glass transition temperature for amorphous sample containing 2 at.%
Y is 881K and the onset crystallization temperature is 904 K. The melting behavior for both as-cast alloys were measured with high temperature
differential scanning calorimeter (HTDSC). Melting starts at 1384 K, ends at 1506 and 1470K as liquidus temperatures for Fe50Cr15Mo14C15B6
and Fe48Cr15Mo14Y2C15B6 alloys, respectively. The addition of Y leads to a melting behavior of as-cast sample close to eutectic, which enhances
B1917 – Effect of bismuth oxide on the thermal stability and Judd-Ofelt parameters of Er3+/Yb3+ co-doped aluminophosphate glasses
The Er3+/Yb3+ co-doped glasses with compositions of xBi2O3-(65-x)P2O5-4Yb2O3-
11Al2O3-5BaO-15Na2O(where x =0, 2.5, 5, 7.5 and 10 mol%) were prepared using the
normal melt quench technique. The optical absorption spectra of the glasses were
recorded in the wavelength range 300-1700nm. The effect of Bi2O3 content on the
thermal stability and absorption spectra of glasses was investigated. In addition, the
Judd-Ofelt parameters and oscillator strengths were calculated by employing
Judd-Ofelt theory. It was observed that the positions of the fundamental absorption
edge and cut-off wavelength shifted towards red as the content of Bi2O3 increased.
However, there were no red shifts found both in the peak wavelength and in the center
of mass wavelength of all absorption bands with Bi2O3 content increasing. The results
of Judd-Ofelt theory analysis showed that Judd-Ofelt parameters ?t (t = 2, 4, 6)
changed sharply when Bi2O3 concentration exceeded 5mol%. The variation trends of
experimental oscillator strength were similar with those of Judd-Ofelt parameters as function of Bi2O3 concentrations. Moreover, Differential scanning calorimetry
experiments showed that the increases of Bi2O3 content weakened the network
structure and then lowered the thermal stability of the glasses. The spontaneous
emission probability Arad, branching ratio beta and the radiative lifetime Trad were also
calculated and analyzed. The stimulated emission cross-section of Er3+ was calculated
according to the McCumber theory. It was found that the stimulated emission
cross-section of Er3+ was monotonically increases with Bi2O3 content increasing.
B1892 – Effect of water on the heat capacity of polymerized aluminosilicate glasses and melts
The effect of water on heat capacity has been determined for four series of hydrated synthetic aluminosilicate glasses and supercooled
liquids close to albite, phonolite, trachyte, and leucogranite compositions. Heat capacities were measured at atmospheric pressure by
differential scanning calorimetry for water contents between 0 and 4.9 wt % from 300 K to about 100 K above the glass transition temperature
(Tg). The partial molar heat capacity of water in polymerized aluminosilicate glasses, which can be considered as independent of
composition, is CpH2O = - 122,319 + 341,631 x 10^(-3) T + 63,4426 x 10^5/T^2 (J/mol K). In liquids containing at least 1 wt % H2O, the partial
molar heat capacity of water is about 85 J/mol K. From speciation data, the effects of water as hydroxyl groups and as molecular
water have tentatively been estimated, with partial molar heat capacities of 153 ± 18 and 41 ± 14 J/mol K, respectively. In all cases,
water strongly increases the configurational heat capacity at Tg and exerts a marked depressing effect on Tg, in close agreement with
the results of viscosity experiments on the same series of glasses. Consistent with the Adam and Gibbs theory of relaxation processes,
the departure of the viscosity of hydrous melts from Arrhenian variations correlates with the magnitude of configurational heat
B1862 – Detailed study of the crystallization behaviour of the metallic glass Fe75Si9B16
The crystallization behaviour of the metallic glass Fe75Si9B16 was studied by means of transmission electron microscopy (TEM), differential
scanning calorimetry (DSC) and magnetic measurements. A detailed interpretation of the results led to some interesting conclusions. The
material is crystallised in three distinguished steps. During the first step, iron crystallises in two different forms, i.e. pure iron spherulites
and Fe(Si) dendrites. High resolution TEM reveals some short-ranged order iron cluster which explains the two morphologies. The primary
crystallization follows a homogeneous nucleation and diffusion-controlled three-dimensional growth. The other two steps (i.e. the eutectic
crystallization of bcc Fe(Si) and bct Fe3B plus the separation of Fe3B into bcc Fe(Si) and bct Fe2B and the independent crystallization of
the bct Fe2B from the amorphous matrix), as one peak in the DSC measurements, follow a homogenous nucleation and interface reaction
controlled three-dimensional growth. Finally, a satisfactory coincidence of the DSC and magnetic curves was achieved, something which has
to be emphasised, as it is being described for the first time.
B1271 – Heat capacities of TiO2-bearing silicate liquids : evidence for anomalous changes in configurational entropy with temperature
The heat capacities of several TiO2-bearing silicate glasses and liquids containing Cs2O, Rb2O, Na2O, K2O, CaO, MgO, or BaO have been measured to 1100 K using a differential scanning calorimeter and to 1800 K using a Setaram HT-1500 calorimeter in step-scanning mode. The results for liquids of M2O-TiO2-2SiO2 composition (M - Na, K, Cs) are compared to those for liquids of M2O-3SiO2 composition. The presence of TiO2 has a profound influence on the heat capacity of simple three-component silicate liquids over the temperature range 900-1300 K. Specifically, replacement of Si4+ by Ti4+ leads to doubling of the magnitude of the jump in Cp at the glass transion (Tg); this is followed by a progressive decrease in liquid Cp for over 400 K, until Cp eventually becomes constant and similar to that in Ti-free systems. The large heat capacity step at Tg in the TiO2-bearing melts suggests significant configurational rearrangements in the liquid that are not available to TiO2-free silicates. In addition, these "extra" configurational changes apparently saturate as temperature increases, implying the completion of whatever process is responsible for them, or the attainment of a random distribution of structural states. Above 1400 K, however, where the heat capacities of TiO2-bearing and TiO2-free alkali silicate liquids are similar, their configurational entropies differ by 3.5 J/g.f.w.-K. The larger configurational entropy of the TiO2-bearing alkali silicate liquids relative to the TiO2-free liquids is energetically equivalent to raising the liquid temperature by more than 300 degrees. This result clearly demonstrates the energetic magnitude of the configurational changes apparent in the supercooled liquid region and their impact on the thermodynamic properties of the stable liquid. Consideration of both density measurements on liquids and spectroscopic data on quenched glasses (from the literature) suggests that the anomalous configurational rearrangements may involve the breakdown of alkali and alkaline earth titanate complexes and changes in Ti4+ coordination.
B1270 – Scanning calorimetric measurements of heat capacity during incongruent melting of diopside
Scanning calorimetric measurements (in step-scan mode) using a Setaram HT1500 calorimeter
were performed on initially crystalline diopside (CaMgSi206) between 1403 and
1762 K and provide a direct measurement of heat capacity. Incongruent melting begins
approximately 59 K below the melting point reported previously of 1665 K. Backscattered
electron imaging confirms that the starting crystalline sample is a single phase at a resolution
of 2: 1 ~m. The diopside is stoichiometric to ::!:2%(resolution of electron microprobe
analysis). The observed incongruency, which has been noted previously, is therefore intrinsic
to pure CaMgSi206 and not related to the presence of other phases or to deviations
in the CalMg ratio from unity. The first 20% of melting occurs over an interval of 44 K
and the remaining 80% within 15 K. Measurements of heat capacity of crystalline and
liquid diopside (outside the melting interval) scatter within 5 and 12%, respectively, of
the accepted literature values. The integrated heat contents, in both the crystalline and
liquid regions, are within 0.3% of reported values. The enthalpy offusion is 137.7 kllmol,
in excellent agreement with previous determinations (Stebbins et aI., 1983; Richet and
Bottinga, 1984; Ziegler and Navrotsky, 1986). Continuous scanning measurements during
cooling of diopside liquid at different rates produce a large heat effect at temperatures well
below the melting point reported previously. This heat effect can be correlated with the
simultaneous crystallization of a clinopyroxene solid solution and wollastonite. Scanning
measurements at a constant cooling rate of 10 K/h were repeated three times under identical
conditions; each time the observed heat effect, indicating crystallization, took place
at a different temperature (1576, 1534, and 1566 K). These observations are in general
agreement with the kinetic crystallization study of Kirkpatrick et ai. (1981), although
metastable crystallization of forsterite was not detected in our cooling experiments.
B0847 – Etude de la transformation d’un gel en verre borosilicate de sodium par analyse thermique et microscopie électronique. Application à la synthèse de nano-cristallites de CdS
B0815 – Thermomechanical analysis (TMA) correlated to differential scanning calorimetry (DSC) for ageing study of some metallic glasses
To characterize the ageing of some metallic glasses, a correlated study of the differential
scanning calorimetry method (DSC) and of the thermomechanical analysis (TMA) emphasizes
the specificity of the latter. We analyzed metallic glasses which have been produced
either by chemical methods or by melt spinning techniques. Using TMA and DSC, we have
established that the relaxation of metallic glasses is strongly dependent on treatment applied:
either thermal or mechanical history. Conversely, we do not observe large differences
between DSC and TMA analysis for the crystallisation. From experimental data, we try to
modelize the behaviour of this type of materials under operating conditions.
B0564 – Détermination de la capacité calorifique de quelques verres oxyazotes
Six oxygenated and oxynitrided glasses in the Ca--Si- AI---O--N system were prepared
from pure lime, silica, alumina and aluminium nitride. Their enthalpies were measured by drop
enthalpimetry with a Calvet calorimeter in a 100-1000° temperature range including glass
transitions Tg. Their heat capacity Cp in glassy and liquid states were deduced by derivation. The
C, variations at Tg were calculated. The glass transition temperature were checked by differential
B0527 – DSC investigation of caesium borate glasses
The Thermodynamic properties of XCs2O.(1-X)B2O3. ( X - molar fraction of CS2O, O < X < 0.4) glasses and crystals at 200-1100 K were DSC studied. The coincidence of heat capacity of stable and metastable melts of the same composition was observed. The variation of heat capacity per mol.with composition is connected with nonmonotonous change of the glass and crystal structure with increasing content of Cs2O.
B0506 – Kalorimetrische untersuchung der kinetischen parameter im glastransformations-bereich bei gläsern im system diopsid-anorthit-albit und bei einem NBS-710-standardglas
B0412 – An attempt to assess the long term crystallization rate of nuclear waste glasses
B0382 – An attempt to assess the long term crystallization rate of nuclear waste glasses
A2368 – Autonomic Self-Repairing Glassy Materials
A new process that enables glassy materials to self-repair from mechanical damage is presented in this paper. Contrary to intrinsic self-healing, which involves overheating to enable crack healing by glass softening, this process is based on an extrinsic effect produced by vanadium boride (VB) particles dispersed within the glass matrix. Self-repair is obtained through the oxidation of VB particles, and thus without the need to increase the operating temperature. The VB healing agent is selected for its capacity to oxidize at a lower temperature than the softening point of the glass. Thermogravimetric analyses indeed show that VB oxidation is rapid and occurs below the glass transition temperature. Solid-state nuclear magnetic resonance spectroscopy indicates that VB is oxidized into V2O5 and B2O3, which enable the local formation of glass. The autonomic self-healing effect is demonstrated by an in situ experiment visualized using an environmental scanning electron microscope. It is shown that a crack could be healed by the VB oxidation products.
A2098 – Influence of Y2O3 on the structure and properties of calcium magnesium aluminosilicate glasses
Glasses were prepared whose composition is defined by the formula: 25CaO20MgOxY2O3(9–x) Al2O346SiO2 mol.% (0 < x > 3). To investigate the relation between the structural change and compositional variation by introducing Y2O3 instead of Al2O3, the glasses were analyzed by Fourier transform Infrared (FT-IR) analysis and differential thermal analysis (DTA). The density, molar volume, hardness and the chemical durability were measured and calculated. The FTIR spectra were recorded in the spectral range from 400 to 4000 cm?1 and showed significant depolymerization of silicate groups and hence resulting in a net decrease of local symmetry. Introducing yttrium in the glasses increases both glass transition (Tg) and softening (Ts) temperatures. The obtained Vicker’s microhardness, the density values and the chemical stability data were increased by addition Y2O3 instead of Al2O3 in the glasses. The resulting data were greatly correlated to the role played by the cations present in the glass structure.
A1834 – Thermolysis of fibreglass polyester composite and reutilisation of the glass fibre residue to obtain a glass–ceramic material
This study reports the feasibility of reusing glass fibre waste resulting from the thermolysis of polyester fibreglass (PFG) to produce a glass–ceramic material. PFG was treated at 550 °C for 3 h in a 9.6 dm3 thermolytic reactor. This process yielded a solid residue (?68 wt%), an oil (?24 wt%) and a gas (?8 wt%). The oil was mainly composed of aromatic (?84%) and oxygenated compounds (?16%) and had a fairly high gross calorific value (?34 MJ kg?1). The major PFG degradation products were styrene, toluene, ethylbenzene, amethyl styrene, 3butynyl benzene, benzoic acid and 1,2benzenedicarboxylic acid anhydride. The gas contained basically CO2 and CO; the hydrocarbon content was below 10 vol%. The higher gross calorific value of the gas was low (26 MJ Nm?3). The solid residue (97 wt% fibreglass, 3 wt% char) was converted into a glass–ceramic material. For this, a mixture consisting of 95 wt% of this solid residue and 5%
Na2O was melted at 1450 °C to obtain a glass frit. A powder glass sample (<63 mm) was then sintered and crystallized at 1013 °C, leading to the formation of a glass–ceramic material composed of wollastonite and plagioclase s.s. with possible building applications
A1774 – Development of UV transparent nanostructured sol–gel materials at low/moderate temperature and study of their physical properties
Sol–gel glass samples are prepared at 60 °C and are treated by various solvents as rinse and dip treatments. Comparative study of treated samples in various solvents is carried out by measuring Optical Transmission, Bulk Density, Mechanical Strength and Porosity. Nitrogen adsorption/desorption studies of these samples were performed at 77 K and shows that the size of the pores to be about 2.0 nm. Various instrumental techniques used for analysis are FTIR, XRD, SEM, and TGA-DTA. The untreated samples take long time to dry up and show moderate transmission in near UV and UV region which is much enhanced by rinse and dip treatments. The dipped glass samples using distilled water (DW) were found to have 36% porosity. Methanol (MeOH) dipped glass samples have good mechanical strength. From various physical properties these nanostructured glass samples can be useful as silica gel host matrices for solid state dye lasers and many other applications.
A1753 – Synthesis of Fullerene-Containing Sol-Gel Glasses
Macroscopically homogeneous and visually transparent fullerene-containing glasses are fabricated from sol-gel mixtures of aminated C60 derivatives and tetraethyl orthosilicate (TEOS) through physical blending and chemical reaction. The aminated fullerenes are synthesized by the amination reactions of C60 with 6-amino-1-hexanol, cyclohexylamine, 2-(2-aminoethoxy)ethanol, and 3-aminopropyltriethoxysilane at 100?C under nitrogen. The amination products are purified by filtration, precipitation, and column chromatography and are
isolated in good to excellent yields (32–82%). Characterization by NMR, MS, and TGA analyses reveals that the aminated fullerenes possess molecular structures HxC60[NH(CH2)6OH]x (1; ¯x=7), HxC60(NH-cyclo-C6H11)x(2; ¯x=11), HxC60[NH(CH2CH2O)2H]x (3; ¯x=11), and HxC60[NH(CH2)3Si(OCH2CH3)3]x (4; ¯x=4). All the aminated fullerenes except 2 are completely soluble in aqueous alcoholic solutions of TEOS and can be incorporated into silica gel networks by sol-gel process in the absence or presence of drying-control chemical additives, giving
crack-free monoliths of large sizes (up to ?60 mm). Electronic absorption spectrum of the fullerene glass continuously red shifts with an increase in the C60 content, suggesting the formation of fullerene nanoclusters in the sol-gel process. The fullerene glasses are thermally and optically stable, resisting continuous attack of strong laser pulses of 532 nm for a prolonged period of time without losing their optical limiting power.
A1599 – Manufacturing and replication of glass pyramidal micro-structures by using the injection moulding process
The aim of this work is to perform experimental investigations related to the different injection moulding conditions required for the proper replication of glass structures. The paper investigates the thermal and rheological characterisations of the feedstock. This study demonstrates that the structured shapes could be successfully injected in the structured metallic mould with pyramidal shapes, with suitable forming parameters. After sintering, the experiment results confirm that the components exhibit anisotropic shrinkage in range from 10 to 20 %.
A1330 – Synthesis of lithium aluminosilicate glass and glass-ceramics from spodumene material
The synthesis of lithium aluminosilicate glasses and glass-ceramics from spodumene material was investigated. Basing on the general
formula Li(2-2(x+y))MgxZnyAl(2-m)BmSizO(2z+4), 40 mol% of the Li2O was replaced with 20 mol% of MgO and 20 mol% of ZnO, and 40 mol%
of Al2O3 with B2O3. BaO was also introduced for improving glass melting behaviour. 2 and 5 wt.% TiO2 was used as nucleation agent. In
the TiO2-containing glasses, virgilite was primarily crystallized. The degree of crystallinity was considerably improved at 900°C. Virgilite
was transformed into crystals of spodumene solid solutions embedded in a glass matrix, while Zn-gahnite formed a second crystalline phase.
Rutile was crystallized in the glasses containing 5 wt.% TiO2. The thermal expansion coefficient for the 2% and the 5 wt.% TiO2-containing
glass-ceramics was 6.39 x 10-7 and 17.1 x 10-7 K-1, respectively (70-300°C).
A0736 – Mixed alkali effect in Li and Na aluminophosphate glasses: influence of the cation environment
This paper deals with the variation of the mixed alkali effect (MAE) in Li and Na aluminophosphate glasses. The general system
investigated is: 0.46 [xNa2O(1 x)Li2O], 0.54 [ yAl2O3(1 y)P2O5], with x varying between 0 and 1 to probe the MAE, and y between 0 and
0.08 to modify the cation environment and to try to understand how the amorphous host affects the ionic motions. We show that the dc
conductivity minimum characteristic of the MAE effect decreases and almost disappears as Al2O3 is added to mixed phosphate glasses. On
another hand, the dc conductivity of the single alkali glasses is almost not affected by Al2O3 addition. Dielectric relaxation characteristics
also change with the Al2O3 concentration in mixed glasses and not in single ones. On another hand, the mixed alkali peak measured using
mechanical relaxation appears to be almost not affected by the presence of Al2O3. This decoupling between the mechanical and dielectric
relaxation processes appears to Tthrough into questionr the proposal that the mechanical relaxation in mixed alkali glasses accounts for sites
reconfiguration to adapt to the different cations.
A0516 – Influence of particle size on the crystallization process and the bioactive behavior of a bioactive glass system
Bioactive glasses have attracted considerable interest in recent years, due to their technological application, especially in biomaterials research. Differential scanning calorimetry (DSC) has been used in the study of the crystallization mechanism in the SiO2-Na2O-CaO-P2O5 glass system, as a function of particle size. The curve of the bulk glass presents a slightly asymmetric crystallization peak that could be deconvoluted into two separate peaks, their separation being followed in the form of powder glasses. Also, a shift of the crystallization peaks to lower temperatures was observed with the decrease of the particle size. FTIR studies - that are confirmed by XRD measurements - proved that the different peaks could be attributed to different crystallization mechanisms. Moreover, it is presented the bioactive behavior of the specific glass as a function of particle size. The study of bioactivity is performed through the process of its immersion in simulated human blood plasma (simulated body fluid, SBF) and the subsequent examination of the development of carbonate-containing hydroxyapatite layer on the surface of the particles. The bioactive response is improved with the increase of the particle size of powders up to 80 ?m and remains almost unchanged for further increase, following the specific surface to volume ratio decrease.
A0347 – Characterization of polyphosphate glasses preparation using CRTA.
We used CRTA for the study of both the elaboration and characterization of several polyphosphate glasses. We show that controlled transformation rate thermal analysis is able to remove a systematic error present in classical thermal analysis, in the study of the precursor of the phosphate glass. We show too that in CRTA, water release in the phosphate glasses can take place by diffusion phenomena at low temperature and that it is not due to the crystallization. These two examples illustrate some interests of this inverse method in the study of the decomposition of inorganic compounds with water release.
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