Self-propagating high-temperature synthesis of advanced ceramics MoSi2–HfB2–MoB

This study focuses on the investigation of the macrokinetic features of SHS (combustion synthesis) of elemental mixtures Mo–Hf–Si–B, in particular the mechanisms of structure and phase formation in the combustion front as well as the structure and properties of consolidated ceramics. Two routes for the fabrication of the composite SHS powder in system MoSi₂–HfB₂–MoB were used: (1) synthesis using Mo–Si–B and Hf–B mixtures followed by mixing of the combustion products and (2) synthesis using the four-component Mo–Hf–Si–B mixture. Dense ceramic samples with a homogeneous structure and low residual porosity (0.8–3.6%) were prepared by hot pressing of SHS powders. Although the particles size distribution and phase composition of SHS powders are similar for both synthesis routes, the structure and properties of both the composite SHS powders and hot-pressed ceramics differ considerably. Synthesis using the four-component Mo–Hf–Si–B mixture allows one to produce hierarchically ordered nanocomposite material with improved mechanical properties: hardness up to 17.6?GPa and fracture toughness up to 7.16?MPa?m^1/2.     

用压下法测定混有不同量未燃煤粉的高炉渣流动性

用压下法测定了混有不同量未燃煤粉的高炉渣的流动性．结果表明：活塞压下量的变化规律与炉渣粘度相关．压下量随温度升高而升高，随混入渣中未燃煤粉量的增加而降低．压下量增加，流动性变好．活塞压下量的变化可以定性判断混有不同量未燃煤粉高炉渣的流动性。     

烧结助剂对自增韧Si3N4陶瓷显微结构和性能的影响

研究了烧结助剂质量分数及比例对热压自增韧Si3N4 陶瓷显微结构和力学性能的影响。结果表明 :材料室温抗弯强度和断裂韧性均在烧结助剂的质量分数为 15 %时达到峰值 ,其中 5 %Y2 O3 10 %La2 O3 85 %Si3N4 体系的抗弯强度达 911.3MPa,断裂韧性达10 .0 2MPa·m1 /2 。同时 ,分析了材料显微结构与力学性能的关系 ,发现自增韧Si3N4 陶瓷中 β-Si3N4 柱状晶直径的双峰分布特征对材料力学性能的提高起着很重要的作用     

PVC生产中的二次水回收工艺改造

介绍了在PVC生产过程中产生的蒸汽冷凝水、压滤水、废自来水、母液水的回收和综合利用的情况。工艺改进后,青岛海晶化工集团有限公司12万t/a PVC装置可节水67万t/a,节约资金204万元/a。     

Effect of Microstructural Control on Thermoelectric Properties of Hot-Pressed Aluminum-Doped Zinc Oxide

The thermal conductivity of polycrystalline Al-doped ZnO was controlled through the fabrication of nanostructured polycrystalline materials, by hot-pressing nanosized Zn_{1– x} Al _x O ( x = 0.01, 0.02) particles, which were synthesized by a coprecipitation and spray-drying method. This process resulted in an improved thermoelectric power factor because of the nanosized Zn_0.99Al_0.01O particles of the polycrystalline products. The thermal conductivity also was decreased as a result of the formation of nanocrystalline Zn_0.99Al_0.01O.     

高含水率杨木单板室温胶合的脲醛树脂胶研究

在实验室条件下 ,以传统脲醛树脂胶的生产工艺为基础 ,加用氨基取代羧酸类化合物。新配方制得脲醛树脂胶 ,用DSC分析了树脂固化反应热过程 ,对含水率在 12 % -2 0 %杨木单板进行了室温胶合研究     

一种双向火焰雷管的研制及应用

为解决某切割器原设计切刀不能可靠切断钛合金拉杆问题,在不改变切割器各项性能指标和结构尺寸条件下,研制了一种只装点火药和起爆药的双向火焰雷管,装填于电点火器与切刀末端之间,这种双向火焰雷管具有双向点火和起爆的功能,解决了推动切刀力量不足问题．     

Pressureless low temperature sintering of nanocrystalline zirconia ceramics via dry powder processing

Pressureless sintering approaches provide a simple avenue to manufacture dense ceramic parts with minimal processing equipment, but current pressureless sintering techniques have yet to demonstrate capabilities of producing dense ceramics while maintaining sub-50 nm grain sizes. Nanocrystalline yttria stablized zirconia ceramics were process from 4 mol% yttria stablized zirconia (4YSZ) nanopowders with a crystallite size of 7.5 nm using dry cold isostatic pressing (CIP) where powders are dried immediately prior to green compact formation and CIP vacuum bagging. It is shown that CIP pressures >75 000 psi (517 MPa) effectively remove pores larger than 100 nm and that pressureless sintering occurs at reduced temperatures for green densities ≥50%. Though the sintering kinetics are shown to be similar to other zirconia nanopowder sintering studies, the small initial crystallize size and reduced sintering temperature allowed densities as high as 97.2%, while retaining a ceramic grain size at or below 40 nm. Produced nanocrystalline 4YSZ ceramics with a grain size of 30.3 nm and a density of 96.3% had Vicker's hardnesses as high as 14.2 GPa and Vicker's indentation fracture resistance of 3.43 MPa·, demonstrating that simple processing approaches can be refined to fabricate nanocrystalline ceramics while maintaining high hardness and indentation fracture resistance.     

T型ECAP变形纯铝微观组织与力学性能研究

在室温下对工业纯铝进行T型等通道挤压变形(T-ECAP),研究了挤压速度(5、12、60、120、180mm/min)和挤压道次(1道次、2道次、4道次)对纯铝微观组织与力学性能的影响.结果表明:不同挤压速度下,1道次挤压变形可以将晶粒细化到1μm以下,但是微观组织存在不均匀性;随着挤压道次的增加,晶粒逐渐细化,4道次时晶粒大小为350nm.在试样的纵向中心位置,显微硬度呈现“两端高,中间低”的漏斗状分布;随着挤压道次的增加,漏斗状的硬度分布逐渐减弱,4道次挤压变形后,硬度逐渐趋于均匀.挤压速度180mm/min时,拉伸强度呈现反常的Hall-Petch关系.随着挤压道次的增加,伸长率逐渐增大,2道次挤压变形后,拉伸强度趋于平稳.