Showing papers by "Central Glass and Ceramic Research Institute published in 1989"
TL;DR: In this paper, the absorption and luminescence spectra for interconfigurational 3d10 ↔3d94s transitions of Cu+ ions in a glass of near-pure silica have been studied.
117 citations
TL;DR: In this paper, high-Tc superconductor wire and sheet were fabricated by electrophoretic deposition of super-conductor powders on silver-metal substrates followed by an appropriate sintering schedule.
Abstract: High-Tc superconductor wire and sheet were fabricated by electrophoretic deposition of superconductor powders on silver-metal substrates followed by an appropriate sintering schedule. The technique has some promise for technological applications.
40 citations
TL;DR: Etude de la preparation d'un revetement antireflechissant a 3 couches d'epaisseur 1,2 μm sur un verre optique crown de borosilicate a partir de sols polymeriques.
Abstract: Etude de la preparation d'un revetement antireflechissant a 3 couches (SiO 2 -TiO 2 /ZnO 2 /SiO 2 ) d'epaisseur 1,2 μm sur un verre optique crown de borosilicate a partir de sols polymeriques
33 citations
TL;DR: In this paper, the electrical resistance, Meissner signal, magnetoresistance and Hall coefficient of Bi1.75Pb0.25Sr2Ca2Cu3Ox and Bi 1.5Pb 0.5Sr 2C2C3Ox have been measured.
Abstract: The electrical resistance, Meissner signal, magnetoresistance and Hall coefficient of Bi1.75Pb0.25Sr2Ca2Cu3Ox and Bi1.5Pb0.5Sr2Ca2Cu3Ox (nominal compositions) have been measured. Resistance of the Bi1.75Pb0.25 sample becomes zero for T≤106 K while the Bi1.5Pb0.5 sample shows a 65% drop in the resistance around 106 K and TR = 0c ≈ 73 K. Powder X-ray diffraction analysis reveals that the major phase in the Bi1.75Pb0.25 sample is the high-Tc phase and in the Bi1.5 Pb0.5 sample the low-Tc phase. The Hall coefficients (RH) of both samples are positive with R−1H> linear in temperature. The temperature dependence of RH is stronger in the Bi1.75Pb0.25 sample than in the Bi1.5Pb0.5 sample. The carrier concentration determined R−1H for the Bi1.75Pb0.25 and the Bi1.5Pb0.5 samples at 300 K are 1.59 × 1021 cm−3 and 3.66 × 1021 cm−3, respectively. The excess conductivity of both samples is analyzed using the Aslamazov-Larkin expression. The critical exponent λ obtained for the Bi1.75Pb0.25 sample is 0.78 and that for the Bi1.5Pb0.5 sample, in the temperature region where the high-Tc phase contributes only, is 0.77.
31 citations
TL;DR: In this article, a multilayer, wavelength-selective reflecting coatings were prepared by alternate stackings of amorphous zirconia and silica by the sol-gel spinning technique; alkoxide derived, polymeric sols were used.
Abstract: Multilayer, wavelength-selective reflecting coatings were prepared by alternate stackings of amorphous zirconia and silica by the sol-gel spinning technique; alkoxide-derived, polymeric sols were used. A detuned, i.e. non-λ/4 stacking system was applied. The spectrum showed a transmission minimum (∼ 4%) at a wavelength of 430 nm, with a bandwidth of 72.5 nm after deposition of the 17th layer.
28 citations
TL;DR: In this article, the decay times of the emitting state of Cu+ ions have been compared with the value calculated from the UV absorption in the case of two Cu+-containing glasses.
24 citations
TL;DR: In this article, the excess conductivity in a magnetic field perpendicular to the current direction was determined using the linear extrapolation method and Anderson-Zou formula for the TI-system and the Bi-system.
Abstract: The excess conductivity (Δσ) in Tl1Ca3Ba1Cu3Oχ and Bi1Ca3Sr1Cu2Oχ (nominal compositions) is determined using the linear extrapolation method and Anderson-Zou formula. Δσ for the TI-system shows a 2-dimensional character and is well described by the Aslamazov-Larkin (A-L) contribution for a layered superconductor. The interlayer coupling for the TI-system is found to be very small. The excess conductivity in a magnetic field perpendicular to the current direction Δσ⊥(H), for T≤Tc and H≥62; Hc2 shows a 3-dimensional character. Similar behavior is also observed in the Bi-system.
22 citations
TL;DR: In this paper, the authors studied the creep behavior of silicon nitride with three different sintering aids and determined the stress exponents and activation energies in addition to the creep rates.
14 citations
TL;DR: In this article, the cubic ZrO2 was stabilized at room temperature by the addition of AIN and the lattice spacing of the cubic phase gradually expanded up to 20 mol% AIN.
Abstract: Cubic ZrO2 is stabilized at room temperature by the addition of AIN. The percentage of c-ZrO2 in the mixture of c-ZrO2 and m-ZrO2 increases linearly with the addition of up to 20 mol% AIN and decreases thereafter. Stabilization becomes complete at 50 mol% AIN. The lattice spacing of the cubic phase gradually expands up to 20 mol% AIN. A displacement reaction ZrO2+ AIN → ZrN+Al2O3 occurs above 20 mol% AIN and is completed at 50 mol% AIN.
11 citations
TL;DR: In this paper, the superconductivity, antiferromagnetic, Hall coefficient and thermoelectric power of a single-band Hubbard model with strong on-site correlation have been studied using mean-field approximations.
Abstract: The superconductivity, antiferromagnetism, Hall coefficient and thermoelectric power of a system described by a single-band Hubbard model with strong on-site correlation have been studied using mean-field approximations. In one approach, the strong correlation reduces the bandwidth, the band remains half-filled for n =1 (one electron per site) and the chemical potential lies at the centre of the band. This approach describes the antiferromagnetic transition satisfactorily but not the electronic transport properties. The other approach follows the Hubbard method in which for n ⩽1 and strong correlation only the states of the lower Hubbard subband are occupied. This approach can describe superconductivity in the region of hole concentration in which high-temperature superconductivity has been observed in the oxide systems and also explains the Hall coefficient and thermoelectric power. Comparison of the theoretical results with the observed superconductivity and the thermoelectric power of the high- T c systems suggests that the effective bandwidths in these systems are small.
10 citations
TL;DR: In this article, a glass-ceramic coating of composition RO-R′2O-Al2O3-SiO2 (R = Ca, Mg; R′ = Na, K, Li), with TiO2 and P2O5 as nucleation agents, has been applied on steel samples and their performances studied.
TL;DR: The Hall coefficient has been measured in Bi-Sr-Ca-Cu-O andTl-Ba- Ca- Cu-O systems as a function of temperature and the behavior is opposite in nature to that observed in theLa/sub 2/minus//ital x//Sr/sub /ital X//CuO/sub 4/ andYBa/ sub 2/Cu/sub 3/O/ sub 7/minus/1 systems.
Abstract: The Hall coefficient ${R}_{H}$ has been measured in Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O systems as a function of temperature. In all the systems ${R}_{H}^{\mathrm{\ensuremath{-}}1}$ varies linearly with temperature. ${T}_{c}$ decreases as the filling factor \ensuremath{
u} (${n}_{H}$ normalized to Cu ions present in the unit cell) increases in the Bi and Tl systems. This behavior is opposite in nature to that observed in the ${\mathrm{La}}_{2\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Sr}}_{\mathrm{x}}$${\mathrm{CuO}}_{4}$ and ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{x}}$ systems.
TL;DR: In this article, a mechanism based on the Marangoni effect appears to be the cause of the tendency of Y1Ba2Cu3O7−x superconductors to melt along the container wall or any solid surface.
TL;DR: On discute de la cause de l'exotherme a 980 o C and de la composition de la phase spinelle a 980 O C dans la transformation de kaolinite en mullite.
Abstract: On discute de la cause de l'exotherme a 980 o C et de la composition de la phase spinelle a 980 o C dans la transformation de kaolinite en mullite
TL;DR: In this paper, the synthesis of dense sintered sialon with external additives selected from the system Y2O3-AIN-SiO2 was reported, and the highest density (3.21 g/cm3) was achieved at 1750°C at 90 min of sintering with 5 wt% additive.
Abstract: The synthesis of dense sintered sialon with external additives selected from the system Y2O3–AIN–SiO2 is reported. The highest density (3.21 g/cm3) was achieved at 1750°C at 90 min of sintering with 5 wt% additive. The degree of sialon substitution increased with the amount of liquid; the YSiO2N crystalline phase formed concurrently. Strength degradation occurred above 1000°C. The fracture toughness of the material sintered with a lower amount of sintering aid remained relatively unchanged to 1200°C. The material with more additive exhibited decreased toughness above 1000°C.
TL;DR: In this paper, Zirconia-mullite composites were prepared byin situ reaction between zircon and alumina, and almost vitrified bodies were obtained by sintering at 1465-1535°C.
Abstract: Zirconia-mullite composites were prepared byin situ reaction between zircon and alumina. Stabilizers like yttria and magnesium carbonate were used. Almost vitrified bodies were obtained by sintering at 1465–1535°C. Flexural strength increased on annealing at 1040°C.
TL;DR: Conditions de preparation a partir de ZrOCl 2 and de H 2 SO 4 en solution aqueuse. Analyse thermique et examen des cristaux par microscopie electronique.
Abstract: Conditions de preparation a partir de ZrOCl 2 et de H 2 SO 4 en solution aqueuse. Analyse thermique et examen des cristaux par microscopie electronique
20 Dec 1989-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, strength, Young's modulus and fracture toughness data in the temperature range 30-1400°C were presented for reaction-bonded silicon nitride and its particulate composites with SiC (5−20 vol%).
Abstract: Strength, Young's modulus and fracture toughness data in the temperature range 30–1400°C are presented for reaction-bonded silicon nitride and its particulate composites with SiC (5–20 vol.%), BN (10 vol.%) and TiC (5 vol.%). The composites of Si3N4 with SiC showed the best mechanical properties of the three types of composites. The toughening mechanism and interdependence of various mechanical properties for these composites are discussed.
TL;DR: In this article, electrical resistance, magnetoresistance, Meissner effect, magnetisation and 205Tl Knight shift have been measured in the Tl1Ca3Ba1Cu3Ox (nominal composition) compound.
Abstract: Electrical resistance, magnetoresistance, Meissner effect, magnetisation and 205Tl Knight shift have been measured in the Tl1Ca3Ba1Cu3Ox (nominal composition) compound. Resistance becomes zero below 120 K, Meissner signal appears at 122 K, the lower critical field at 77 K is found to be 290 Oe in this system. Magnetoresistance starts rising at about 126 K. The Knight shift of 205Tl in the system is found to be positive, its value at room temperature is 0.25%. The shift decreases below 130 K. From the value of the Knight shift and Pauli paramagnetic susceptibility the hyperfine coupling constant a(s) is determined as ∽0.025– 0.030 cm-1.
TL;DR: In this article, the strength of hot pressed silicon nitride at room and high temperatures has been analyzed in terms of a modification of the Weibull flaw distribution function, giving an upper and lower strength limit and characterised by two shape parameters.
TL;DR: In this paper, the critical current density of Bi-Sr-Ca-Cu-O superconductors of 1112 nominal composition can be improved appreciably by giving them a flash heat treatment at 1050°C for 5 minutes followed by sintering at 860°c for 18 hours.
TL;DR: In this article, the authors measured flexural strength, fracture toughness and creep of silicon nitride samples at 1700-1800°C with liquids in the ternary system MgO, AlN, SiO 2, and SiO 3 N 4 of 98% theoretical density.
Abstract: Silicon nitride was pressureless sintered at 1700–1800°C with liquids in the ternary system MgOAlNSiO 2 ; liquids rich in nitrogen and high MgO content sintered readily; Si 3 N 4 of 98% theoretical density was obtained. Heat treatments of the samples were carried out to crystallise the grain boundary phase. Hightemperature flexural strength, fracture toughness and creep of the samples were measured. Increase in nitrogen content with constant MgO:SiO 2 ratio produced products with better thermomechanical properties. Superior products were obtained with high nitrogen and low MgO content in the sintering liquid due to a slower sintering rate and acicular grain growth. The best product had a flexural strength (4-point bending test, 40-20 mm) of 490 MPa and fracture toughness of 6·1 MPam 1 2 . The creep strain rate and stress of a sample sintered with a liquid with a high MgO content were 1·0 × 10 −5 h −1 (at 1200°C) and 100 MPa, respectively.
TL;DR: In this article, a spectrophotometric method was developed for the determination of trace amounts of silica in barium titanate and zirconia ceramics based on the formation of molybdosilicic acid, its preconcentration on polyurethane foam, elution in acetone (acetone: HCl = 99:1) and reduction to molybdenum blue form.
Abstract: A spectrophotometric method has been developed for the determination of trace amounts of silica in barium titanate and zirconia ceramics based on the formation of molybdosilicic acid, its preconcentration on polyurethane foam, elution in acetone (acetone: HCl = 99:1) and reduction to molybdenum blue form. The method is applicable up to 2 μg Si/ml. The minimum that was detected by this method was 5.0 ng Si/ml. The method yielded agreeable results.
TL;DR: In this paper, reaction sintering of zircon and mullite at relatively low temperatures was used to construct zirco-mullite ceramics, and the strength of the composites was found to have improved by annealing.
Abstract: Zirco-mullite ceramics have been prepared by reaction sintering of zircon and mullite at relatively low temperatures. The strength of the composites was found to have improved by annealing.
TL;DR: In this article, the synthesis of dense sintered sialon with external additives selected from the system Y2O3-AIN-SiO2 was reported, and the highest density (3.21 g/cm3) was achieved at 1750°C at 90 min of sintering with 5 wt% additive.
Abstract: The synthesis of dense sintered sialon with external additives selected from the system Y2O3–AIN–SiO2 is reported. The highest density (3.21 g/cm3) was achieved at 1750°C at 90 min of sintering with 5 wt% additive. The degree of sialon substitution increased with the amount of liquid; the YSiO2N crystalline phase formed concurrently. Strength degradation occurred above 1000°C. The fracture toughness of the material sintered with a lower amount of sintering aid remained relatively unchanged to 1200°C. The material with more additive exhibited decreased toughness above 1000°C.
TL;DR: In this paper, a chip was designed to replace 28 standard integrated circuits on the subscriber module of a 8508 A microprocessor-based PAX system, which was fabricated using silicon gate NMOS process developed at CEERI.
Abstract: This chip was design basically to replace 28 standard integrated circuits on the subscriber module of a 8088 A microprocessor-based PAX system. The circuit was fabricated using silicon gate NMOS process developed at CEERI. The threshold voltages were controlled by ion-implantations and tested on the test structures on wafer after fabrication. The minimum feature size is 6 micron and the chip containing about 500 components is of 3.35 × 3.35 mm size. The circuit chip was bonded and encapsulated in 44 lead ceramic chip carrier. The packaged chips passing all the set specifications were put in the system and found to work satisfactorily.
TL;DR: In this paper, the effect of powder preparation on the mechanical properties of partially stabilized zirconia has been studied and it has been observed that fracture toughness, transverse rupture strength, microhardness etc improved with the improvement in the powder preparation method.
Abstract: The effect of method of powder preparation on the mechanical properties of partially stabilized zirconia has been studied. Zirconia powder doped with 3 mol% of yttria was prepared by three different methods, viz. mechanical method, modified mechanical method and co-precipitation method. It has been observed that fracture toughness, transverse rupture strength, microhardness etc improved with the improvement in the powder preparation method.