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02124 Dielectric relaxation and calorimetric measurements of glass transition in the glass-forming dihydroxyl alcohols
72 Refractones/ceramics
12
REFRACTORIES/ CERAMICS Properties, production,
00/02118
applications
A thermotropic biaxial nematic liquid crystal
Chandrasekhar. S. C~trr. .‘?~,i. 199X. 75. (IO). 1042-1046. The calorimetric and optical studies on the mesophasea of 1.4’.(pterphenyl)-bis[2,3.4tri(dodecyloxy)benzal]imine are described. It has been revealed by differential scanning calorimetric analysis that there is a second, much weaker transition just below the usual isotropic-nematlc point. Optical observations indicate that these transitions represent the isotropicuniaxial nematic transition and at a slightly lower temperature the uniaxialbiaxial nematic transition. Also presented are the measurements of the temperature variation of the biaxial angle in the biaxial nematic phase.
00/02119 A transient method study of nonequilibrium effects in a sintering process Bohac, V. High Tuup. - High Prc~\,~w~~~. 199X. 30. (6). 651-654. Glass powders were wintered in order to prepare borosilicate glass (E-glass) samples of various bulk densities. The transient method was used to investigate the samples at room temperature and the data produced provides information on the specific heat, thermal diffusivity, and thermal conduction. The sintering process changes arrangements in the particle contact-surface region. The local deformations influence the anharmonicity of the structure that is responsible for the anharmonic contribution to the specific heat. The anharmonicity promotes the phonon-phonon interaction due to which the thermal diffusivity falls. 00/02120 Application of DTA in silicate industry Zhang, M. Bali YU Tmgc,i. 1998, 26. (4). 38-42. (In Chinese) The application of differential thermal analysis (DTA) in the silicate industry, which encompasses glass and cement, is reviewed in thih paper. The emphasis is on optimization of raw materials and energy-saving technologies based on DTA.
00/02121 Change of compressibility at the glass transition and Prlgogine-Defay ratio in ZrTlCuNiBe alloys Samwer, K. Ph~,.s. Rrl,. Lerr.. 1999. 82. (3). 580-583. An evaluation of changes in compressibility at the glass transition T, ,is presented. The analysis uses data from pressure experiments in the liquid and the glassy state of the ZrTiCuNiBe bulk metallic glass forming system. An increase of T, with pressure of 3.6 K/GPa is derived via the enthalpy recovery method. Comparing the changes of the compressibility, the specific heat capacity and the thermal expansion coefficient at T,. a Prigogine-Defay ratio in metallic systems is estimated for the first time. For the present alloy the ratio is approximately 2.4 and is comparable with documented non-metallic glass forming systems.
00/02122 Characterization of Ge-Bi-S glass by thermal, electrical, switching and optical measurements Sedeek, K. J. Mtrrc~r. .Sci.. 1998. 33. (18). 462 l-4626. A study of the synthesized GeZ2.sBi7S7,1.5 glassy system is presented. Differential thermal analysis data indicate the retention in the gasquenched sample of two amorphous phases. Thermal evaporation of the The synthesized ingot gives films with Ge_,,) ,-Bih.sS7: 5 as components. values of the activation energy and the pre-exponential factor calculated from the d.c. electric conduction above 53°C suggest that carrier conduction occurred between extended states in these films. An investigation is also carried out into the I-V characteristics in the off-state and the switching phenomenon. For the studied film, a memory switch with a threshold voltage that decreases with temperature is detected. Optical parameters such as absorption coefficient, optical gap and refractive index are also detected. Comparison with binary Ge-S glass reveals that the addition of Bi introduces additional absorbing states at band edges.
00/02123
Crystallization kinetics of Ge,Sb~o.,S60 glasses
Pamukchieva, V. Ph!,.r. Chem. G/o.~se.r, 1998. 39, (6), 328-331. This paper reports on and discusses the results of differential scanning calorimetry at different heating rates on Ge,Sb~,&,~, glasses. From the variation of heating rate (0). glass transition temperature (T,), crystallization temp. (Jc) peak temperature of crystallization (Tp), enthalpy of crystallization (=H,) and effective activation energy for crystallization (E,) are evaluated and their composition dependencies assessed. From the results it was discovered that the crystallization of Ge)lSbJ,ISh,, glasses occurs with a mixed mechanism.
00102124 Dielectric relaxation and calorimetric measurements of glass transition in the glass-forming dlhydroxyl alcohols Park. I. S. J. P/IV.\.
Sock. Jpm.
1998. 67. (12). 4131-4138.
(properiies,production.applications)
The dielectric and thermal properties were studied in hoth liquid and \upercoolcd liquid states. in order to study the molecular weight dependence of the o-relaxation and glass transttions of intermediate glass-forming materials. Propylene glycol (PG) and its five oligomers (poly-propylene glycol. PPG). which have the similar chemical structure but different molecular weights 76-4000 gimol, were studied paying attention to their fragility and co-operativity. using modulate differential scanning calorimetry at IO mHz and broadband dielectric spectroscopy in the frequency range from IO MHz to IO GHz. The fragility of PG and PPGs trom the dielectric and thermal measurements was analysed and compared using both the intermolecular co-operativity model and the Adam-Gibbs model. The Vogel-Fulcher energy and minimum configurational entropy were evaluated for PG and PPGs using the comparison method. Their values were related to the density of -OH end group and its intermolecular hydrogen honding. Wtth increasing molecular weight the strength parameter decreased indicating that PG monomer liquid is stronger than PPG liquids. The domain size at T,. which was introduced by the Matsuoka’s co-oprrativity model, was -5 to 5 for PG and PPGs, increasing with molecular weight. 00/02125 Effect of La203 on Li*O-A1203-Si02 glass-ceramics Deng. Z. Bolf )‘I, 7tr~,qci. 1998. 26. (4). 5-10. 60. (In Chinese) Differntial thermal analysis, X-ray diffraction and scanning electron microscopy were used to study the effects of rare earth oxide LazOI on melting and crystallization property. crystal phase and microstructure. and coefficient of thermal expansion of Li,O-AIZOi-Si02 glass-ceramics. The results demonstrate that a small amount of L.a20J increased viscosity of the glass melt and melting temperatures. The crystalization temperature of the glass was increased by ahout 20 C and 5 C compared with those of the same component glass-ceramics without LazO+ LaZOJ didn’t go into crystal phase of the glass-ceramics and it existed in glass phase. Main crystal phase of the glass-ceramics was .l-spodumene when La103 content was low (0.02 mol) and main crystal phase was same as that of the glass-ceramics without La,Oi content was high and the main crystal phase was Lil).hAl,1.6Si~.~Oh. With increasing La*03 content in the glass-ceramics, the coefficient of thermal expansion (CTE) decreased. The CTE was reduced by approximately 33% when LazOI content increased to 0.1% (mole fraction).
00102128 Glass and production by flotation and magnetic separation technology Teodoreacu. E. I~~~~orc~tiorr.\,Mivcr. C‘rrtrl Pro: ot s PUIC~. Irrr. Mirtw Prouw. sw1p.. 7//i. 1998. 379 343. Presented in this paper is glass sand productIon using gravitational. volumetric and centrifugal sizing, flotation and magnetic separation operations. The main vitrifying oxide is SiOz! thus the glass industry uses significant quantities of sand. Besides the SlO: content. the quality of a sand depends on the contaminant content. The iron. chrome, vanadium and titanium oxides are undesired owing to their colouring action. An undesirable reducing medium can be created during the melting process. if a coal substance is present in the glass sand. By completing the sand processing technology with the flotation and magnetic separation phases, from a common quartz sand, a quality raw material was obtained for the production of household white glass. glass for lighting fittings and semicrystal glass.
00/02127 Glass-forming tendency and stability of aqueous solutions of diethylformamide and dimethylformamide Baudot, A. and Boutron. P. C~~~ohir~Ir~,~,r.199X. 37. (3). IX7 ~199. Calorimetry has been used to study the tendency of glass formation on cooling and the stability of the wholly amorphous state on warming of aqueous solutions of diethylformamlde and N,N-dimethylformamide (DMF). It has been observed that with diethylformamide, only ice formation occurs, except on warming at the lowest rate of 2S”/min, where occasionally a hydrate forms also. The hydrate was observed up to I0’/min with 50% diethylformamide. With However. for dimethyl-formamide, hydrates form even at high warming rates. The last hydrate melts at -47.7’ For the tendency to form glass on cooling and for the stability of the wholly amorphous state on warming, these two compounds. at concentrations of 40, 45, or S(lCh (wt!wt.) in water. are more efficient than glycerol and levo-2.3-hutanediol. and ethylene glycol, hut lezs than I .2-propanediol on warming. The glass transition of They are comparable to DMSO aqueous solutions of diethylformamide Increases and then decreases with the dlethylformamide concentration in water. in contrast to other cryoprotectants. for which it always increases or decreases.
Kyanite from Minas Gerais, Brazil: characterization for use in ceramic materials
00/02128
Brandao. P. R. G. and Mendes, L. C. //~~~rtrrt~~!r.\ Mijtcr. Con/ Prows.r.. Proc~. 1171. Miwr. Pwc~c.~.t. Sj,mp 7111. 1998. 295 300. Samples were taken from a residual deposit of kyanite ore located in Central Minas Gerais State, Brazil and were subjected to characterization and beneficiation research. to decide if they h;tdthe potential to be used in ceramic materials. The original composition was Al203 42.6. SiOz $1.3, and Fez07 3.5 wt%;. Quartz. hematite, mica. and rutile. were the main gangue minerals, as inclusions in kyanite phenorrystals. as well as fine graphite. Gihhsite and goethite occurred as lateritic crust around the kyanite centimeter-size mass. A combination of scrub washing, attrition milling and high intensity magnetic separation were used to produce the concentrations. Removal of most of the crust lowered the Fe?O, content
Fuel and Energy Abstracts
July 2000
235
12
REFRACTORIES/ CERAMICS Properties, production,
00/02118
applications
A thermotropic biaxial nematic liquid crystal
Chandrasekhar. S. C~trr. .‘?~,i. 199X. 75. (IO). 1042-1046. The calorimetric and optical studies on the mesophasea of 1.4’.(pterphenyl)-bis[2,3.4tri(dodecyloxy)benzal]imine are described. It has been revealed by differential scanning calorimetric analysis that there is a second, much weaker transition just below the usual isotropic-nematlc point. Optical observations indicate that these transitions represent the isotropicuniaxial nematic transition and at a slightly lower temperature the uniaxialbiaxial nematic transition. Also presented are the measurements of the temperature variation of the biaxial angle in the biaxial nematic phase.
00/02119 A transient method study of nonequilibrium effects in a sintering process Bohac, V. High Tuup. - High Prc~\,~w~~~. 199X. 30. (6). 651-654. Glass powders were wintered in order to prepare borosilicate glass (E-glass) samples of various bulk densities. The transient method was used to investigate the samples at room temperature and the data produced provides information on the specific heat, thermal diffusivity, and thermal conduction. The sintering process changes arrangements in the particle contact-surface region. The local deformations influence the anharmonicity of the structure that is responsible for the anharmonic contribution to the specific heat. The anharmonicity promotes the phonon-phonon interaction due to which the thermal diffusivity falls. 00/02120 Application of DTA in silicate industry Zhang, M. Bali YU Tmgc,i. 1998, 26. (4). 38-42. (In Chinese) The application of differential thermal analysis (DTA) in the silicate industry, which encompasses glass and cement, is reviewed in thih paper. The emphasis is on optimization of raw materials and energy-saving technologies based on DTA.
00/02121 Change of compressibility at the glass transition and Prlgogine-Defay ratio in ZrTlCuNiBe alloys Samwer, K. Ph~,.s. Rrl,. Lerr.. 1999. 82. (3). 580-583. An evaluation of changes in compressibility at the glass transition T, ,is presented. The analysis uses data from pressure experiments in the liquid and the glassy state of the ZrTiCuNiBe bulk metallic glass forming system. An increase of T, with pressure of 3.6 K/GPa is derived via the enthalpy recovery method. Comparing the changes of the compressibility, the specific heat capacity and the thermal expansion coefficient at T,. a Prigogine-Defay ratio in metallic systems is estimated for the first time. For the present alloy the ratio is approximately 2.4 and is comparable with documented non-metallic glass forming systems.
00/02122 Characterization of Ge-Bi-S glass by thermal, electrical, switching and optical measurements Sedeek, K. J. Mtrrc~r. .Sci.. 1998. 33. (18). 462 l-4626. A study of the synthesized GeZ2.sBi7S7,1.5 glassy system is presented. Differential thermal analysis data indicate the retention in the gasquenched sample of two amorphous phases. Thermal evaporation of the The synthesized ingot gives films with Ge_,,) ,-Bih.sS7: 5 as components. values of the activation energy and the pre-exponential factor calculated from the d.c. electric conduction above 53°C suggest that carrier conduction occurred between extended states in these films. An investigation is also carried out into the I-V characteristics in the off-state and the switching phenomenon. For the studied film, a memory switch with a threshold voltage that decreases with temperature is detected. Optical parameters such as absorption coefficient, optical gap and refractive index are also detected. Comparison with binary Ge-S glass reveals that the addition of Bi introduces additional absorbing states at band edges.
00/02123
Crystallization kinetics of Ge,Sb~o.,S60 glasses
Pamukchieva, V. Ph!,.r. Chem. G/o.~se.r, 1998. 39, (6), 328-331. This paper reports on and discusses the results of differential scanning calorimetry at different heating rates on Ge,Sb~,&,~, glasses. From the variation of heating rate (0). glass transition temperature (T,), crystallization temp. (Jc) peak temperature of crystallization (Tp), enthalpy of crystallization (=H,) and effective activation energy for crystallization (E,) are evaluated and their composition dependencies assessed. From the results it was discovered that the crystallization of Ge)lSbJ,ISh,, glasses occurs with a mixed mechanism.
00102124 Dielectric relaxation and calorimetric measurements of glass transition in the glass-forming dlhydroxyl alcohols Park. I. S. J. P/IV.\.
Sock. Jpm.
1998. 67. (12). 4131-4138.
(properiies,production.applications)
The dielectric and thermal properties were studied in hoth liquid and \upercoolcd liquid states. in order to study the molecular weight dependence of the o-relaxation and glass transttions of intermediate glass-forming materials. Propylene glycol (PG) and its five oligomers (poly-propylene glycol. PPG). which have the similar chemical structure but different molecular weights 76-4000 gimol, were studied paying attention to their fragility and co-operativity. using modulate differential scanning calorimetry at IO mHz and broadband dielectric spectroscopy in the frequency range from IO MHz to IO GHz. The fragility of PG and PPGs trom the dielectric and thermal measurements was analysed and compared using both the intermolecular co-operativity model and the Adam-Gibbs model. The Vogel-Fulcher energy and minimum configurational entropy were evaluated for PG and PPGs using the comparison method. Their values were related to the density of -OH end group and its intermolecular hydrogen honding. Wtth increasing molecular weight the strength parameter decreased indicating that PG monomer liquid is stronger than PPG liquids. The domain size at T,. which was introduced by the Matsuoka’s co-oprrativity model, was -5 to 5 for PG and PPGs, increasing with molecular weight. 00/02125 Effect of La203 on Li*O-A1203-Si02 glass-ceramics Deng. Z. Bolf )‘I, 7tr~,qci. 1998. 26. (4). 5-10. 60. (In Chinese) Differntial thermal analysis, X-ray diffraction and scanning electron microscopy were used to study the effects of rare earth oxide LazOI on melting and crystallization property. crystal phase and microstructure. and coefficient of thermal expansion of Li,O-AIZOi-Si02 glass-ceramics. The results demonstrate that a small amount of L.a20J increased viscosity of the glass melt and melting temperatures. The crystalization temperature of the glass was increased by ahout 20 C and 5 C compared with those of the same component glass-ceramics without LazO+ LaZOJ didn’t go into crystal phase of the glass-ceramics and it existed in glass phase. Main crystal phase of the glass-ceramics was .l-spodumene when La103 content was low (0.02 mol) and main crystal phase was same as that of the glass-ceramics without La,Oi content was high and the main crystal phase was Lil).hAl,1.6Si~.~Oh. With increasing La*03 content in the glass-ceramics, the coefficient of thermal expansion (CTE) decreased. The CTE was reduced by approximately 33% when LazOI content increased to 0.1% (mole fraction).
00102128 Glass and production by flotation and magnetic separation technology Teodoreacu. E. I~~~~orc~tiorr.\,Mivcr. C‘rrtrl Pro: ot s PUIC~. Irrr. Mirtw Prouw. sw1p.. 7//i. 1998. 379 343. Presented in this paper is glass sand productIon using gravitational. volumetric and centrifugal sizing, flotation and magnetic separation operations. The main vitrifying oxide is SiOz! thus the glass industry uses significant quantities of sand. Besides the SlO: content. the quality of a sand depends on the contaminant content. The iron. chrome, vanadium and titanium oxides are undesired owing to their colouring action. An undesirable reducing medium can be created during the melting process. if a coal substance is present in the glass sand. By completing the sand processing technology with the flotation and magnetic separation phases, from a common quartz sand, a quality raw material was obtained for the production of household white glass. glass for lighting fittings and semicrystal glass.
00/02127 Glass-forming tendency and stability of aqueous solutions of diethylformamide and dimethylformamide Baudot, A. and Boutron. P. C~~~ohir~Ir~,~,r.199X. 37. (3). IX7 ~199. Calorimetry has been used to study the tendency of glass formation on cooling and the stability of the wholly amorphous state on warming of aqueous solutions of diethylformamlde and N,N-dimethylformamide (DMF). It has been observed that with diethylformamide, only ice formation occurs, except on warming at the lowest rate of 2S”/min, where occasionally a hydrate forms also. The hydrate was observed up to I0’/min with 50% diethylformamide. With However. for dimethyl-formamide, hydrates form even at high warming rates. The last hydrate melts at -47.7’ For the tendency to form glass on cooling and for the stability of the wholly amorphous state on warming, these two compounds. at concentrations of 40, 45, or S(lCh (wt!wt.) in water. are more efficient than glycerol and levo-2.3-hutanediol. and ethylene glycol, hut lezs than I .2-propanediol on warming. The glass transition of They are comparable to DMSO aqueous solutions of diethylformamide Increases and then decreases with the dlethylformamide concentration in water. in contrast to other cryoprotectants. for which it always increases or decreases.
Kyanite from Minas Gerais, Brazil: characterization for use in ceramic materials
00/02128
Brandao. P. R. G. and Mendes, L. C. //~~~rtrrt~~!r.\ Mijtcr. Con/ Prows.r.. Proc~. 1171. Miwr. Pwc~c.~.t. Sj,mp 7111. 1998. 295 300. Samples were taken from a residual deposit of kyanite ore located in Central Minas Gerais State, Brazil and were subjected to characterization and beneficiation research. to decide if they h;tdthe potential to be used in ceramic materials. The original composition was Al203 42.6. SiOz $1.3, and Fez07 3.5 wt%;. Quartz. hematite, mica. and rutile. were the main gangue minerals, as inclusions in kyanite phenorrystals. as well as fine graphite. Gihhsite and goethite occurred as lateritic crust around the kyanite centimeter-size mass. A combination of scrub washing, attrition milling and high intensity magnetic separation were used to produce the concentrations. Removal of most of the crust lowered the Fe?O, content
Fuel and Energy Abstracts
July 2000
235