In this paper, silicon nitride (Si3N4) ceramics by aligning α-Si3N4 whiskers were prepared via tape casting, hot-press sintering technique using Y2O3 and MgO as sintering additives. Aligned α-Si3N4 whiskers were rea...
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In this paper, silicon nitride (Si3N4) ceramics by aligning α-Si3N4 whiskers were prepared via tape casting, hot-press sintering technique using Y2O3 and MgO as sintering additives. Aligned α-Si3N4 whiskers were realized by modifying the tape casting technique. After tape casting, Si3N4 tape with good flexibility and uniform pores can be obtained. Microstructures of the tape, green body and sintered sample were observed by SEM images. The results show α-Si3N4 whiskers in Si3N4 tape and green body were aligned preferentially along the tape casting direction. Si3N4 ceramics with aligned elongated grains are developed by hot-press sintering technique based on the reaction between Si3N4 and the sintering additives which lead to the liquid phase.
A new kind of functionally graded materials (FGM) with density gradient has come to show great potentials as flier-plates for creating quasi-isotropic compression waves. In order to meet the demand of lower density in...
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A new kind of functionally graded materials (FGM) with density gradient has come to show great potentials as flier-plates for creating quasi-isotropic compression waves. In order to meet the demand of lower density in the front face and wider density range for such flier-plate, Mg with a density of 1.74g/cm3 and W of 19.3g/cm3 are selected to make Mg-W system density graded materials, Mg-W alloys with various mass fractions of Mg and W were sintered by spark plasma sintering (SPS) technique at low temperatures, and the processing of densification is mainly investigated. It is found that, up to 92wt%W, the Mg-W alloys can be fully densified at 873K due to the conglutination of Mg particles. The Mg-W alloys still exist as a mechanical mixture of Mg and W. Finally, the Mg-W density graded materials with a density change from 1.74g/cm3 to 10.55g/cm3 have been successfully prepared.
In the present study, BaTi2O5 thin films were epitaxially grown on MgO (100) substrate by pulsed laser deposition, and the microstructure of the films was investigated. The b-axis oriented BaTi 2O5 thin film was obtai...
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ISBN:
(纸本)9788880800842
In the present study, BaTi2O5 thin films were epitaxially grown on MgO (100) substrate by pulsed laser deposition, and the microstructure of the films was investigated. The b-axis oriented BaTi 2O5 thin film was obtained at the optimum substrate temperature (Tsub = 973 K) and oxygen partial pressure (PO2 = 12.5 Pa). The as-deposited film was epitaxially grown on MgO (100), exhibiting a dense and rectangularly crossed granular texture. The epitaxial relationship between the film and substrate was BaTi2O5 (020) [100] // MgO (100) [001] and BaTi2O5 (020) [100] // MgO (100) [010].
A material in the system W/W-Cu/Cu with a density gradient, which has an important application in dynamic high pressure physics, was prepared by one-step hot-press sintering. W-Cu composite interlayers were produced f...
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ISBN:
(纸本)9788880800842
A material in the system W/W-Cu/Cu with a density gradient, which has an important application in dynamic high pressure physics, was prepared by one-step hot-press sintering. W-Cu composite interlayers were produced from W and Cu powders with Zn (2wt%) as the sintering aid. With increasing the sintering temperature, the relative density of W-Cu composites increased, reaching a higher value (>96%) at 850°C. Then by inserting three W-Cu composite interlayers between the tungsten and copper alloy plates followed by one-step hot-press at 850°C-20MPa-60min, a wholly dense W/W-Cu/Cu system functionally graded material was obtained, which had a large density range from 8.9 to 17.25g/cm3.
The influences of mass concentration of nickel chloride hexahydrate, sodium borohydride, ethylenediamine, pH value, bath temperature on deposition rate were studied with orthogonal experiments by a series of pre-treat...
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The influences of mass concentration of nickel chloride hexahydrate, sodium borohydride, ethylenediamine, pH value, bath temperature on deposition rate were studied with orthogonal experiments by a series of pre-treatments on micro-diamond particle, and the optimized parameters were obtained. Both the morphology and the composition of original diamond and the diamond with Ni-B coating were analyzed by SEM and XRD respectively. The SEM image shows that the spherical Ni-B particle is coated upon diamond. XRD pattern shows that the coating compositions are Ni and Ni2B.
(1-x)(K0.44Na0.52Li0.04)(Nb 0.84Ta0.10Sb0.06)O3-xSrTiO 3 (KNNT-ST) lead free piezoelectric ceramics have been synthesized by a solid state reaction method. The effect of SrTiO3 content on the piezoelectric properties,...
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(1-x)(K0.44Na0.52Li0.04)(Nb 0.84Ta0.10Sb0.06)O3-xSrTiO 3 (KNNT-ST) lead free piezoelectric ceramics have been synthesized by a solid state reaction method. The effect of SrTiO3 content on the piezoelectric properties, sintering behavior and microstructure of (1-x) KNNT-x ST ceramics was investigated. The experimental results showed that the addition of SrTiO3 can restrain the volatilization of Na ions and K ions and improve relative density of the samples. A morphotropic phase boundary between orthorhombic and tetragonal phases is found in the composition range of 0.03
Based on the nitridation reaction of aluminum with boron nitride (BN), aluminum nitride (AlN) matrix composites were fabricated by reaction synthesis technique. The effect of the amount of Al on the microstructure and...
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Based on the nitridation reaction of aluminum with boron nitride (BN), aluminum nitride (AlN) matrix composites were fabricated by reaction synthesis technique. The effect of the amount of Al on the microstructure and properties was investigated. The bending strength, thermal conductivity and dielectric constant increase with the content of aluminum. A heat-treatment schedule was performed to investigate the effect of the microstructure on the properties. The results showed that the heat-treatment leads to the grain growth and thermal conductivity increase with the grain growth.
Effect of adding up to 5wt% CaF2 on the densification and microstructural development of hot pressed aluminum nitride (AlN) was investigated. SEM investigation showed that the grain size of the sintered sample decreas...
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Effect of adding up to 5wt% CaF2 on the densification and microstructural development of hot pressed aluminum nitride (AlN) was investigated. SEM investigation showed that the grain size of the sintered sample decreases with the increasing content of CaF2. Secondary-phase evolution paths converge from CA6 to CA phase above 1650°C TEM micrographs showed that formed secondary phases could evaporate from sintered bodies at higher temperatures in the carbon-containing nitrogen atmosphere and the residuals were mainly distributed at triple grain junctions, keeping direct connections of AlN grains. Translucnet AlN ceramics were prepared using CaF 2 additive sintered at 1850°C for 5 h.
In this work, Fe and Si powders were used to fabricate 6.5% Si silicon steel. The mixing powder was rolled into strip and then treated at 900°C in Ar. Sn was added into the mixing powder to investigate the effect...
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In this work, Fe and Si powders were used to fabricate 6.5% Si silicon steel. The mixing powder was rolled into strip and then treated at 900°C in Ar. Sn was added into the mixing powder to investigate the effect of Sn on the sintering. The density, composition, and structure were examined. The results show that Fe almost does not react with Si at 900°C But with the addition of Sn, Fe reacts with Si to produce Fe3Si at 900°C Increasing the amount of Sn accelerates this reaction. When the amount of Sn addition is excessive, there will leave many pores in the alloy because the reaction rate is too fast to shrink. The proper amount of Sn addition can decrease the sintering temperature and shorten the sintering time.
Polycrystalline alumina was prepared at high temperature and high pressure from combustion reaction plus mechanical pressure. The defect structure in the sintered alumina was investigated by transmission electron micr...
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Polycrystalline alumina was prepared at high temperature and high pressure from combustion reaction plus mechanical pressure. The defect structure in the sintered alumina was investigated by transmission electron microscopy and a regular hexagonal dislocation network was found. Diffraction contrast technique revealed that the regular hexagonal network on the (0001) plane was composed of three dislocations with Burgers vectors: 1/3[12¯10], 1/3[2¯110] and 1/3[112¯0]. The formation process of dislocation network was discussed.
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