专用粉末涂料和涂装发展的新展望

新型专用粉末涂料以其涂膜超薄型化、低温固化和高耐候性等优势,并以预裁割坯料新工艺代替预涂装卷材工艺的新特点,将成为粉末涂料新的增长点。还提出了若干建议和意见。     

Effect of thermal insulation on microstructural homogeneity and onset temperature of flash sintered materials

The present work aimed to reduce the microstructure heterogeneity inherent to flash sintering by using alumina blankets as a thermal insulator around ZnO cylindrical samples during the sintering process, under different electric field conditions. Thermal insulation significantly reduced the flash onset temperature and the grain size heterogeneity. For higher electric fields, a temperature reduction as high as 480 °C was observed, which also led to lower densification. These findings were discussed in terms of changes in the heat loss dynamics coupled with the adsorbed water retention, both promoted by the applied thermal insulation. A model to estimate the temperature at stage III of flash sintering was proposed. The final temperature reached with thermal insulation did not differ significantly from the ones without it. Thus, thermal insulation could represent an alternative route to flash sinter materials with lower furnace temperatures with energy savings up to 78 % and a more homogeneous microstructure.     

Effect of binder-phase modification and Cr3C2 addition on properties of WC-IOC0 cemented carbide

For production of fine-grained and corrosion-resistant tungsten carbide (WC) based cemented carbides, addition of chromium carbide (Cr₃3C₂) in small amounts is standard practice. No systematic study, however, has been made of the effects of large additions (maximum 6 wt % ) of Cr₃C₂ as a substitute for tungsten carbide. This study focuses on the effect of hard-phase substitution by C₃C₂ in WC-1OCo cemented carbide. An attempt is also made to modify the binder metal cobalt by partial or complete substitution of nickel. Specimens were prepared using the standard liquid-phase sintering process and were tested for sintered porosity, mechanical properties, corrosion resistance, and microstructural parameters. Results confirm the findings of earlier workers regarding grain refinement and improvement of mechanical properties upon the addition of small amounts (<2 wt%) of Cr₃C₂. Modification of the binder phase improves indentation fracture toughness and corrosion resistance. Addition of Cr₃C₂ independent of the binder type improves corrosion resistance.     

影响结晶化玻璃板材质量因素的分析

研究了烧结法生产结晶化玻璃装饰板材中的气孔、翘板及炸裂产生的原因以及解决的方法。     

Sintering and Electronic Conducting Properties of Lao.7Ca0.3CrO3 Perovskite Synthesized by a Glycine-nitrate Process

La0.7 Ca0.3 CrO3 powder consisting of superfine and uniform particles （ 100-200 nm ） were synthesized using a glycine-nitrate process （ GNP ）. The sintering and electronic conducting properties of La0.7 Ca0.3 CrO3 were invetigated in the sintering temperature range of 1 200-1 450 ℃. The desired morphology of the powder significantly improved its sinterability. La0.7 Ca0.3 CrO3 ceramics sintered at 1 250-1 450 ℃ show high relative densities above 95 % . The ceramics sintered at 1 250-1 400 ℃ have very similar electronic conduct- ing properties, providing electronic conductivities around 55 Ω^-1 cm^-1 at a measuring temperature of 800 ℃ . Further increasing the sintering temperature to 1450 ℃ led to an apparent degradation of electronic conducting properties. This research demonstrates the advantage of the GNP in producing La0.7 Ca0.3 CrO3 with respect to the enhanced sintering properties and superior electronic conducting properties.     

Nd-Fe-B磁体烧结致密化过程的研究

定量描述了Nd-Fe-B磁体的烧结致密化过程, 分析了有效稀土含量、合金粉末粒度与烧结致密化过程的关系, 讨论了Nd-Fe-B磁体烧结过程的致密化机制. Nd-Fe-B磁体烧结致密化过程可分为3个阶段, 即致密化过程迅速进行阶段、缓慢进行阶段、相对稳定阶段;随着烧结温度的上升, 第一阶段表现得更为突出, 第二阶段对应的烧结时间区段大大缩短. 有效稀土含量的提高、合金粉末粒度的减小显著促进Nd-Fe-B磁体烧结致密化过程. 主相颗粒重排以及主相颗粒长大与形状适位性变化是Nd-Fe-B磁体烧结过程的两类主要致密化机制, 而且后者对于Nd-Fe-B烧结磁体实现完全致密化起着决定性的作用.