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Glass-ceramics manufactured from cullet and crystallizable glass at high soft-point by sintering process
12 Refractories/ceramics
(properties, production, applications)
00100554 Finite strain behavior of poly(ethylene terephthalate) above the glass transition temperature Llana, P. G. and Boyce, M. C. Polymer, 1999, 40, (24), 6729-6751. The strain rate and temperature dependencies of the stress-strain behaviour of PET under large strain deformation was studied experimentally. The investigation was conducted over a range in strain rates (-0.005 to -2.0 s- ) and temperatures (90-105°C) in both uniaxial and plane-strain compression. The increase in crystallinity content with varying strain rate and temperature and for the two different states of strain that developed as a result of these deformation conditions was investigated using Differential Scanning Calorimetry (DSC). Wide-Angle X-ray Diffraction (WAXD) measurements were used to study the nature and evolution of the crystallography textures. The stress-strain behaviour is found to exhibit four characteristic features: (1) a relatively high initial stiffness, (2) followed by a rollover in the stress-strain curve to flow behaviour, (3) followed by an increase in stress with continuing strain, (4) followed by a dramatic increase in stress with strain at very large strains. Temperature, the state of strain and the strain rate are the determining factors of the four characteristic features. DSC and WAXD measurements on deformed specimens indicated an increase in crystallinity with increasing strain rate and decreasing deformation temperature under both uniaxial and planestrain conditions. The WAXD measurements also revealed that the preferential crystallography texture that develops is consistent with the molecular orientation which forms with the different states of strain.
00100555 Formation of graduated layers at the surface, of ceramics and steels in a high-enthalpy gas stream Frolov, Cr. A. et al. Powder Meiall. Met. Ceram., 1999, 37, (II-12), 626631. It was established experimentally that the failure rate for quartz glassceramics with fusion in a high-enthalpy gas stream depends markedly on the thermal conductivity of the surface layer, which may be reduced by excluding the radiation component of heat transfer through the alloying of material with chromium oxide.
00100556 Glass transition temperatures of butyl acrylatemethvl methacnflate cooolvmers Fernandez-Garcia,.M. et al.‘J. iolym. Sci., Part B: Polym. Phys., 1999, 37, (l7), 2512-2520. Differential scanning calorimtery (DSC) was used to measure the glass transition temperaiures (Ts) dr butyl acrylate-Me methacrylate copolymers obtained by free-radical polymerization in 3 and 5 mol/l benzene solution. The values obtained were correlated using Johnston’s equation with inter-intramolecular copolymer structure. Using the data calculated with copolymer prepared at low conversion, theoretical predictions were made of the variation of glass transition temperature with copolymer conversion.
00100557 Glass-ceramics manufactured from cullet and crystallizable glass at high soft-point by sintering process Wang, Z. Q. et al. Dalian Qinggongye Xueyuan Xuebao, 1999, 18, (2), 91-95. (In Chinese) Differential thermal analysis, X-ray diffraction, and scanning electron microscope analysis, are used to study the manufacture of glassceramics from spent cullet and crystallizable glass by the sintering process. Some properties such as chemical durability and microhardness are investigated. The results demonstrate that the proper addition of crystallizable glass can improve the sintering and crystallization ability and some other properties.
00/038:
High temperature internal friction of engineering
Yagi, T. er al. Mater. Technol. (Tokyo), 1999, 17, (5), 189-194. (In Japanese) The torsional vibration method was used to measure the influences of temperature on the internal friction of SIC, SisN4, Mullite and ZrOz. The relaxation peaks were observed for all the ceramics. In Sic, two relaxation peaks caused by the diffusion of boron and the diffusion of boron and carbon appeared at 363 K and 798 K respectively. In SisN4, Mullite, and ZrOz the relaxation peaks appeared at 1178 K, 1253 K and 423 K respectively. From the Arrhenius plots its activation energy and relaxation time were 425 V/mol, 170 kJ/mol, and 84.0 kJ/mol, 1.5 x 10-21 seconds, 1.2 x lo-’ seconds, and 4.8 x lo-l3 seconds, respectively. The relaxation peaks of SisN4 and Mullite were caused by the diffusion of oxide atoms at the grain boundary. In ZrOz it was caused by two factors. At following high temperatures, a conspicuous increase of the internal friction probably based on plastic flow of the grain boundary was observed for SisN4, Mullite, and ZrOz. Its activation energy was 63.3-202 kJ/mol.
56
Fuel and Energy Abstracts
January 2001
00/00559 Kinetic study on formation of bulk glass state Zr52.5Nil4.BAlloCu17.~Ti5alloy
He, G. et al. Trans. Nonferrous Met. Sot. China, 1999, 9, (2), 273-271. Melt injection was used to prepare an alloy sample with a 6 mm diameter. Differential scanning calorimetry (DSC) and differential thermal analysis (DTA) were used to detect and analyse its thermal properties. The critical cooling rate for glass formation in the alloy was evaluated to be 13.4, 19.0 and 32.6 KS from the empirical model and the kinetic model of glass formability respectively by using the DTA and DSC data. The real cooling rate in centre of wedge-shaped samples was estimated by testing the glass state area on the longitudinal cross sectional structure of the wedge-shaped samples. A discussion is also included on the key factors that affect crystallization and growth.
00100560 Kinetics and mechanism of crystallization of borophosphate glasses of the ZnO-B203-P205 system Mosner, P. Koudelka, L. Sci. Pap. Univ. Pardubice. Ser. A, 1998,4, 1585. Borophosphate glasses of the ZnO-BzOs-PzOs system were prepared by cooling the melt from 1230°C. Differential scanning calorimetry and X-ray diffraction were used to study their crystallization. The crystallization occurs primarily at 600-800°C giving at least two crystallization phases with BP04 as one of the products. The kinetics of the crystallization of borophosphate glass 58.3ZnO-8.3BzOs-33.4PzOs can be described using the Sestak-Berggren model, while that of 50ZnO50BzOs is better described by the Johnson-Mehl Avrami model. The analysis of the shape and position of the crystallization peak for different sizes of glass powders resulted in the conclusion that surface crystallization prevails for the borophosphate glass, while for the borate glass surface crystallization dominates only when the particle size is smaller 300 pm, however, in the bulk glass, internal crystallization prevails.
00/00561 Kinetics of perlite glasses degassing. TG and DSC analysis. Bagdassarov, N. et al. Glass Sci. Technol. (Frankfurt 1 Main), 1999, 12, (9), 277-290. Described in this report is the simultaneous thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC) of the kinetics of dehydration of natural water-bearing perlite glass. Thermal balance was used to perform the dehydration profiling of natural perlite samples from Eastern Rhodopes (Bulgaria) and a pitchstone form the Eastern Transbaikal region (Russia). Initial water content in samples varied between 4.0-6.5wt% HzO. In pitchstone TG and differential thermogravimetric analysis signals indicate two degassing maxima at 220 and 290”. The peaks in the DTG signal mimic those in DSC signal. Perlitic water is driven out smoothly under heating over a wide range of temperatures from 140-700” up to the glass transition temperature (Ts). The glass transition temperature was detected independently from viscosity measurement using a micropenetration method. In slowly cooled perlites DTG and DSC signals have one distinct peak which extends from 140-850”. In fast cooled perlites DTG and DSC signals often exhibit two distinct peaks at ~200-450 and 600-700”. The temperature range of DTG and DSC peaks is wider than in slowly cooled perlites. The enthalpy effect of perlite glass dehydration at 200300” has the enthalpy value of 55-75 kJ/mol, which is much larger than the enthalpy value (30-25 kJ/mol) of water evaporation at these temperatures. Finally, there may be an association between the additional thermal effect of perlite dehydration and the water desorption reaction and water vapour expansion in microcracks.
00/00562 Lime-alumina-silica vitreous ceramic processing incorporating wollastonite Bryden, R. H. Caley, W. F. Br. Ceram. Trans, 1999, 98, (3), 127-132. High processing costs and the reputation of unpredictable reliability have caused improvements in mechanical and physical properties of advanced ceramics to be undermined. One potential technique to address this situation is to use a naturally occurring mineral to develop new ceramic microstructures using a simple processing technique. The system chosen for potential development was an alumina ceramic modified using 20 wt% wollastonite (CaSiOs) -Green body production was carried out by wet processing optimized by rheological measurements. The best conditions were found to be a pH of 3 using 1500 ppm BETZ 1190 (a cationic polyelectrolyte dispersant) processed at ~0.35 volume fraction of solids in a water based suspension. Thermal analysis revealed that the optimum sintering procedure involved vitreous composite sintering for 15 minutes at 1500°C followed by an air quench. This glass ceramic was then devitrified using a heat treatment at 1032°C (4 hours) followed by 4 hours at 1200°C. The final material of 68 wt% alumina, with anorthite and gehlenite, had a high indentation toughness (6.2 MPa ml’*) and an improved thermal expansion coefficient. In conclusion, the new material should prove to be attractive as a low cost material for anti-abrasion applications under high temperature conditions.
(properties, production, applications)
00100554 Finite strain behavior of poly(ethylene terephthalate) above the glass transition temperature Llana, P. G. and Boyce, M. C. Polymer, 1999, 40, (24), 6729-6751. The strain rate and temperature dependencies of the stress-strain behaviour of PET under large strain deformation was studied experimentally. The investigation was conducted over a range in strain rates (-0.005 to -2.0 s- ) and temperatures (90-105°C) in both uniaxial and plane-strain compression. The increase in crystallinity content with varying strain rate and temperature and for the two different states of strain that developed as a result of these deformation conditions was investigated using Differential Scanning Calorimetry (DSC). Wide-Angle X-ray Diffraction (WAXD) measurements were used to study the nature and evolution of the crystallography textures. The stress-strain behaviour is found to exhibit four characteristic features: (1) a relatively high initial stiffness, (2) followed by a rollover in the stress-strain curve to flow behaviour, (3) followed by an increase in stress with continuing strain, (4) followed by a dramatic increase in stress with strain at very large strains. Temperature, the state of strain and the strain rate are the determining factors of the four characteristic features. DSC and WAXD measurements on deformed specimens indicated an increase in crystallinity with increasing strain rate and decreasing deformation temperature under both uniaxial and planestrain conditions. The WAXD measurements also revealed that the preferential crystallography texture that develops is consistent with the molecular orientation which forms with the different states of strain.
00100555 Formation of graduated layers at the surface, of ceramics and steels in a high-enthalpy gas stream Frolov, Cr. A. et al. Powder Meiall. Met. Ceram., 1999, 37, (II-12), 626631. It was established experimentally that the failure rate for quartz glassceramics with fusion in a high-enthalpy gas stream depends markedly on the thermal conductivity of the surface layer, which may be reduced by excluding the radiation component of heat transfer through the alloying of material with chromium oxide.
00100556 Glass transition temperatures of butyl acrylatemethvl methacnflate cooolvmers Fernandez-Garcia,.M. et al.‘J. iolym. Sci., Part B: Polym. Phys., 1999, 37, (l7), 2512-2520. Differential scanning calorimtery (DSC) was used to measure the glass transition temperaiures (Ts) dr butyl acrylate-Me methacrylate copolymers obtained by free-radical polymerization in 3 and 5 mol/l benzene solution. The values obtained were correlated using Johnston’s equation with inter-intramolecular copolymer structure. Using the data calculated with copolymer prepared at low conversion, theoretical predictions were made of the variation of glass transition temperature with copolymer conversion.
00100557 Glass-ceramics manufactured from cullet and crystallizable glass at high soft-point by sintering process Wang, Z. Q. et al. Dalian Qinggongye Xueyuan Xuebao, 1999, 18, (2), 91-95. (In Chinese) Differential thermal analysis, X-ray diffraction, and scanning electron microscope analysis, are used to study the manufacture of glassceramics from spent cullet and crystallizable glass by the sintering process. Some properties such as chemical durability and microhardness are investigated. The results demonstrate that the proper addition of crystallizable glass can improve the sintering and crystallization ability and some other properties.
00/038:
High temperature internal friction of engineering
Yagi, T. er al. Mater. Technol. (Tokyo), 1999, 17, (5), 189-194. (In Japanese) The torsional vibration method was used to measure the influences of temperature on the internal friction of SIC, SisN4, Mullite and ZrOz. The relaxation peaks were observed for all the ceramics. In Sic, two relaxation peaks caused by the diffusion of boron and the diffusion of boron and carbon appeared at 363 K and 798 K respectively. In SisN4, Mullite, and ZrOz the relaxation peaks appeared at 1178 K, 1253 K and 423 K respectively. From the Arrhenius plots its activation energy and relaxation time were 425 V/mol, 170 kJ/mol, and 84.0 kJ/mol, 1.5 x 10-21 seconds, 1.2 x lo-’ seconds, and 4.8 x lo-l3 seconds, respectively. The relaxation peaks of SisN4 and Mullite were caused by the diffusion of oxide atoms at the grain boundary. In ZrOz it was caused by two factors. At following high temperatures, a conspicuous increase of the internal friction probably based on plastic flow of the grain boundary was observed for SisN4, Mullite, and ZrOz. Its activation energy was 63.3-202 kJ/mol.
56
Fuel and Energy Abstracts
January 2001
00/00559 Kinetic study on formation of bulk glass state Zr52.5Nil4.BAlloCu17.~Ti5alloy
He, G. et al. Trans. Nonferrous Met. Sot. China, 1999, 9, (2), 273-271. Melt injection was used to prepare an alloy sample with a 6 mm diameter. Differential scanning calorimetry (DSC) and differential thermal analysis (DTA) were used to detect and analyse its thermal properties. The critical cooling rate for glass formation in the alloy was evaluated to be 13.4, 19.0 and 32.6 KS from the empirical model and the kinetic model of glass formability respectively by using the DTA and DSC data. The real cooling rate in centre of wedge-shaped samples was estimated by testing the glass state area on the longitudinal cross sectional structure of the wedge-shaped samples. A discussion is also included on the key factors that affect crystallization and growth.
00100560 Kinetics and mechanism of crystallization of borophosphate glasses of the ZnO-B203-P205 system Mosner, P. Koudelka, L. Sci. Pap. Univ. Pardubice. Ser. A, 1998,4, 1585. Borophosphate glasses of the ZnO-BzOs-PzOs system were prepared by cooling the melt from 1230°C. Differential scanning calorimetry and X-ray diffraction were used to study their crystallization. The crystallization occurs primarily at 600-800°C giving at least two crystallization phases with BP04 as one of the products. The kinetics of the crystallization of borophosphate glass 58.3ZnO-8.3BzOs-33.4PzOs can be described using the Sestak-Berggren model, while that of 50ZnO50BzOs is better described by the Johnson-Mehl Avrami model. The analysis of the shape and position of the crystallization peak for different sizes of glass powders resulted in the conclusion that surface crystallization prevails for the borophosphate glass, while for the borate glass surface crystallization dominates only when the particle size is smaller 300 pm, however, in the bulk glass, internal crystallization prevails.
00/00561 Kinetics of perlite glasses degassing. TG and DSC analysis. Bagdassarov, N. et al. Glass Sci. Technol. (Frankfurt 1 Main), 1999, 12, (9), 277-290. Described in this report is the simultaneous thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC) of the kinetics of dehydration of natural water-bearing perlite glass. Thermal balance was used to perform the dehydration profiling of natural perlite samples from Eastern Rhodopes (Bulgaria) and a pitchstone form the Eastern Transbaikal region (Russia). Initial water content in samples varied between 4.0-6.5wt% HzO. In pitchstone TG and differential thermogravimetric analysis signals indicate two degassing maxima at 220 and 290”. The peaks in the DTG signal mimic those in DSC signal. Perlitic water is driven out smoothly under heating over a wide range of temperatures from 140-700” up to the glass transition temperature (Ts). The glass transition temperature was detected independently from viscosity measurement using a micropenetration method. In slowly cooled perlites DTG and DSC signals have one distinct peak which extends from 140-850”. In fast cooled perlites DTG and DSC signals often exhibit two distinct peaks at ~200-450 and 600-700”. The temperature range of DTG and DSC peaks is wider than in slowly cooled perlites. The enthalpy effect of perlite glass dehydration at 200300” has the enthalpy value of 55-75 kJ/mol, which is much larger than the enthalpy value (30-25 kJ/mol) of water evaporation at these temperatures. Finally, there may be an association between the additional thermal effect of perlite dehydration and the water desorption reaction and water vapour expansion in microcracks.
00/00562 Lime-alumina-silica vitreous ceramic processing incorporating wollastonite Bryden, R. H. Caley, W. F. Br. Ceram. Trans, 1999, 98, (3), 127-132. High processing costs and the reputation of unpredictable reliability have caused improvements in mechanical and physical properties of advanced ceramics to be undermined. One potential technique to address this situation is to use a naturally occurring mineral to develop new ceramic microstructures using a simple processing technique. The system chosen for potential development was an alumina ceramic modified using 20 wt% wollastonite (CaSiOs) -Green body production was carried out by wet processing optimized by rheological measurements. The best conditions were found to be a pH of 3 using 1500 ppm BETZ 1190 (a cationic polyelectrolyte dispersant) processed at ~0.35 volume fraction of solids in a water based suspension. Thermal analysis revealed that the optimum sintering procedure involved vitreous composite sintering for 15 minutes at 1500°C followed by an air quench. This glass ceramic was then devitrified using a heat treatment at 1032°C (4 hours) followed by 4 hours at 1200°C. The final material of 68 wt% alumina, with anorthite and gehlenite, had a high indentation toughness (6.2 MPa ml’*) and an improved thermal expansion coefficient. In conclusion, the new material should prove to be attractive as a low cost material for anti-abrasion applications under high temperature conditions.