Papers by Author: Li Xue Yu

Abstract: Mullite-corundum multiphase ceramic materials were prepared at 1400°C for 2h with bauxite chamotte and clay clinker as raw material (size<74 μm), molded at pressure of 50 MPa. Effect of raw materials composition on sintering and themal shock resistance of composite were researched by measurements of apparent porosity, bending strength，thermal shock resistance and thermal expansion rates, and analysed by XRD and SEM. The results showed that the best weigh percentage of raw materials with better sintering and themal shock resistance are bauxite chamotte 50 wt%, clay clinker 50wt% for mullite-corundum multiphase ceramic materials. The test results for high temperature gas cleaning dust removal technology development and the application of the composite ceramic material has important application value.

Abstract: Zirconyl chloride was used as zirconium source and fused silica particles were used as main raw material. First of all, the composite powders were prepared by wet chemical synthesis using ammonia as the precipitator and polyethylene glycol as the dispersant. Then, fused silica nanozirconia composite ceramic containing nanometer particle zirconia with different contents (5%, 15%, 25% and 35%) were fabricated in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1 h. The bulk density and bending strength were measured, microstructure was observed by SEM. The result indicated bulk density and bending strength of composite ceramic increase and microstructure becomes denser with content of zirconia increasing. Bulk density of composite ceramic increases and bending strength which reaches maximum at 1350°C firstly increases then decreases with the increase of sintering temperature. Both high sintering temperature and nanozirconia possessing high energy interface can improve the composite ceramic sintering.

Abstract: In order to improve the hydration resistance of MgO-Al-C bricks, Fe₂O₃ was chosen as an additive according to thermodynamic calculations. MgO-Al-C refractories were prepared by using Si, Fe₂O₃ or both as additives. The effects of additives on the hydration resistance of specimens were investigated. XRD was conducted to determine the phase composition. The results showed that the hydration resistance of MgO-Al-C bricks would be slightly bettered with addition of only Si. However, it was helpful when Fe₂O₃ was added along with Si. The mechanism is that Fe₂O₃ could decompose to give off oxygen during heating, which could promote the oxidation of Al powder and inhibit the formation of Al₄C₃ and AlN.

Abstract: The effects of different deflocculants, fume silica, reactive micro-alumina powder and high alumina cement on the flowability of corundum based self-flowing castables were investigated using brown corundum as the main starting materials. The behavior of the castables was evaluated according to the self-flow value of the castables. The results showed that the best self-flow characteristics of corundum based self-flowing castables is obtained using sodium hexametaphosphate as deflocculant, suitable amount of alumina micropowder, fume silica, and high alumina cement as binders. The resultant castables were successfully used in the bottom of a refining ladle with capacity of 80 tons. The service life could match that of well blocks and meet the production requirements.

Abstract: Fused quartz powder (d₅₀=19μm) was used as raw material, and nano-Nd₂O₃ was used as additive with dosages of 1% (in mass, similarly hereinafter), 2% and 3%. The effects of nano-Nd₂O₃ on crystallization and sintering behavior of the materials at various temperatures (1300 °C/1h, 1350 °C /1h and 1400°C /1h) were studied by measurements of apparent porosity, bending strength and thermal expansion ratios (RT~1200°C), and analyses of XRD and SEM. The results of XRD and thermal expansion ratios analysis showed that 3% nano-Nd₂O₃ additive had excellent effect on inhibiting crystallization of the samples sintered at 1350 °C and 1400°C. The results showed that the samples sintered at various temperatures with 3% nano-Nd2O3 had the lowest apparent porosity and more compact microstructure. This indicated that 3% nano-Nd₂O₃ had better effect on facilitating sintering of fused quartz materials.

Abstract: Silicon carbide with diffierent granularity and three grain composition was used as raw material. Silicon carbide refractory material was prepared in oxidizing atmosphere at 1400 °C, 1450 °C and 1500 °C for 3 h. Performence of samples were researched by measurements of apparent porosity, bulk density, bending strength at room temperature, thermal shock resistance and thermal expansion rate, and analyzed by SEM. The results showed that samples sintered at 1400 °C have low thermal expansion rate and apparent porosity, high bending strength and bulk density, good thermal shock resistance, compact texture as well. It can be deduced that (1.0-0.5mm) / (0.5-0.1mm) / (45μm) / (5μm) = 50 / 17/ 20/ 13 is the best grain composition to improve integrated performance of silicon carbide refractory material.

Abstract: Silicon carbide with diffierent granularity was used as raw material, quartz, silica fume, aluminum powder or alumina was used as additive with dosages of 1% (in mass, similarly hereinafter), 3% and 5%. Silicon carbide refractory material was prepared in oxidizing atmosphere at 1400 °C for 3 h. Performence of samples were researched by measurements of apparent porosity, bulk density, bending strength at room temperature, thermal shock resistance and thermal expansion rate, and analyzed by SEM. The results showed that samples added silica fume have low thermal expansion rate and apparent porosity, high bending strength and bulk density, good thermal shock resistance, compact texture as well. It can be deduced that 5% silica fume plays the excellent role to improve integrated performance of silicon carbide refractory material.

Abstract: Fused quartz granule (d50=10μm) was used as raw material, and Al₂O₃-AlN (1:1, in mass) was used as additive with dosages of 1 wt%, 2 wt% and 3 wt%. The crystallization characteristics of fused quartz ceramic fabricated in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1h has been investigated by thermal expansion ratio and XRD. The results showed that the crystallization characteristics were markedly improved by 1 wt% AI₂O₃-AIN compound additive. 1 wt% Al2O3-AIN had obvious effect on inhibiting crystallization of the samples sintered at various temperatures. The apparent porosity, bending strength and SEM of the samples were also examined. The results showed that the samples with 1 wt% AI₂O₃-AIN had the lowest apparent porosity among the samples containing Al₂O₃-AlN, the highest bending strength, and the sample AA1 sintered at 1350°C had more compact microstructure, which indicated that 1 wt% Al₂O₃-AlN was conducive to sintering of fused quartz ceramic materials. It can be deduced that the 1 wt% Al₂O₃-AIN compound additive plays the excellent role on inhibiting crystallization and promoting sintering of fused quartz ceramic materials.

Abstract: Zr(Ca)-Al-O-N composites were prepared with ZrO₂(Ca) (i.e Ca-PSZ, d₅₀ < 10 μm) and Al powder (d₅₀ =7.5 μm, 29 μm, and 62 μm) as raw materials by in situ reaction sintering in N₂ atmosphere at 1600 °C. Phase constiturion of the composites was affirmed by XRD and SEM-EDS, and effect of grain size and content of Al powder on sintering performance of the composites was investigated, and oxidation characteristic of the composites were analysed by measure increasing weight of oxidation. The results showed that major phases of the composites composed of (t+c)-ZrO₂, ZrN, ZrAl₃O₃N and CaAl₁₂O₁₉, and Al powder of 5 wt% - 7 wt% d₅₀ =7.5 μm and 3 wt% - 5 wt% d₅₀ =29 μm were suitable for preparation of the composites and bendiing strength of its samples sintered at 1600 °C had 60-90MPa. In atmosphere, oxidation onset temperature of Zr(Ca)-Al-O-N composites were approximately 550 °C, and the end temperature of its oxidening were approximately 950 °C. Treating with antioxidation is a key for application of Zr(Ca)-Al-O-N composites.

Abstract: Fused quartz granules (d₅₀=19 μm) were used as raw material, and Gd₂O₃-Nd₂O₃ (1:1, in mass) was used as additive with dosages of 1% (in mass, similarly hereinafter), 2% and 3%. Fused quartz ceramic materials were fabricated in reduction atmosphere at 1300 °C, 1350 °C and 1400 °C for 1 h. The apparent porosity, bending strength and thermal expansion ratios of the samples were examined and the samples were further analysed by means of XRD and SEM. The results showed that the sample sintered at each temperature with 3% Gd₂O₃-Nd₂O₃ had the lowest apparent porosity, the highest bending strength and more compact microstructure. This indicated that 3% Gd₂O₃-Nd₂O₃ was helpful to sintering of fused quartz ceramic materials. The results of XRD and thermal expansion ratio analysis showed that 3% Gd₂O₃-Nd₂O₃ compound additive had better effect on inhibiting crystallization of the samples sintered at 1300 °C and 1350 °C, but had a little effect on inhibiting crystallization of the sample sintered at 1400 °C.