氮化硼改善BaTiO_3基高温热敏陶瓷耐压特性的研究

研究了掺杂BN对改善高温PTC热敏陶瓷耐压特性的影响。实验结果表明,BN的加入促进了产品在达到最大电阻后电阻的稳定性,大幅提高了PTC陶瓷的耐电压强度,同时降低了其烧成温度,弱化了保温时间对敏感陶瓷常温电阻率的影响,提高了PTC的性能。     

多孔Si3N4/BN复相陶瓷的常压烧结制备

以微米级Si3N4和h-BN粉末为原料,Yb2O3-Al2O3-Y2O3为烧结助剂,采用常压烧结工艺制备了BN体积含量为25%的多孔Si3N4/25%h-BN复相陶瓷。研究了Yb2O3添加量对Si3N4/25%BN复相陶瓷力学性能的影响,通过X射线衍射和扫描电子显微镜分析了复相陶瓷的物相组成和显微结构。结果表明:随着Yb2O3添加量增加,制备的Si3N4/25%BN复相陶瓷的气孔率逐渐增大,收缩率变小,相对密度减小。Yb2O3添加量为2%(质量分数)时,Si3N4/25%BN复相陶瓷的气孔率为15.1%,相对密度为72.8%;当Yb2O3添加量提高至15%时复相陶瓷的气孔率增加至32.1%,相对密度则降至60.3%。同时随着Yb2O3添加量增加,复相陶瓷的室温抗弯强度先增大后减小,Yb2O3含量为4%时,室温抗弯强度呈现最大值,可达264.3MPa。     

乙烯装置碳三加氢反应系统安全运行措施的探讨与改进

文章对乙烯装置碳三加氢反应系统的使用条件进行了介绍和分析,提出了保护碳三加氢催化剂的有效措施,并对下一步装置技术改造提出了自己的建议,阐述了碳三加氢系统安全运行的改进措施。     

球槽曲面电解加工流场设计及试验研究

球槽曲面是一种球形轮廓扫掠曲线所形成的包络曲面,该曲面所构成的零件驱动轴和螺杆常应用于盘式制动器,可采用电解加工实现高效加工.采用数值分析方法研究了两种电解液流动方式的三种方案对流场的影响,得出电解液侧向短流程方案的流场均匀性较好,并进行了电解加工试验验证.其次,采用数值分析方法研究了导流结构参数、电解液入口压力和压力对流场的影响,并选择最优参数进行了电解加工试验验证.最后,选择不同极间电压与进给速度进行球槽曲面电解加工试验,得知极间电压与平衡间隙成正比、进给速度与平衡间隙成反比,尽量小的极间电压与高进给速度,可得到较好的工艺稳定性.     

CdS nanocrystallites prepared by chemical and physical templates

In this work, a convenient method combining physical and chemical templates is presented to obtain a regular arrangement of CdS nanocrystallites. Poly (ethylene oxide) (PEO) is used to control the crystallite sizes as a chemical template and Si-based anodic aluminum oxide (AAO) act as a physical template to form an ordered arrangement of nanocrystallites. TEM images and SEAD patterns reveal that the CdS/PEO composite deposited into the nanopores of the Si-based AAO films is in a tube shape. In UV/Vis spectra, the absorption onsets of the CdS nanocrystallites shift to a shorter wavelength with decreasing Cd²⁺ concentration in PEO. The corresponding photoluminescence (PL) peaks are all located at about 630 nm due to the sulfur vacancies, while their intensities increase with the increasing mol ratio of Cd²⁺/PEO. This method will provide more choices to prepare optoelectronic materials.     

微乳状液体系应用研究进展

综述了微乳状液体系在医药、化学化工等领域的应用研究现状。着重介绍了微乳超声造影剂和微乳燃料等。     

不规则空间曲面零件的CAD放样及应用

通过对不规则空间曲面零件产品的结构特点、难点及加工工艺进行分析,采用CAD放样方法对零件进行了放样,得出了放样图。并根据此图找到了此种零件的成形方法,解决了复杂零件成形困难的难题,实现了不规则空间曲面零件新的成形方法。     

Microstructure and corrosion resistance of 304 stainless steel electroslag strip cladding

The 304 stainless steel strips were deposited one layer on carbon steel base metal by electroslag strip cladding(ESC) and submerged arc cladding(SAC),respectively.The solidification microstructure of ESC metal was analyzed by the optical microscopy,scanning electron microscope and energy dispersive spectroscopy.The corrosion resistance studies of strip cladding metals were carried out in 10%oxalic acid electrolytic etching test.The results showed that the cladding metal obtained by ESC presented low content of C,high content of Cr and enough alloying element of Ni in the chemical composition.The transition zone of ESC with small width was almost parallel with the base metal,leading to a lower dilution.There are three types of solidification modes(A→AF→FA) occurred in the ESC metal due to the decrease of cooling rate and degree of dilution from the transition zone to the top of ESC metal.As a result,the microstructure of ESC metal exhibited mainly austenite with a small amount offerrite,contributing to achievement of better corrosion resistance.     

带极电渣堆焊奥氏体不锈钢耐晶间腐蚀性能

用带极电渣堆焊和带极埋弧堆焊2种方法堆焊了Cr-Ni不锈钢,研究了这两种方法和焊接速度对堆焊层金属显微组织及耐晶间腐蚀性能的影响。显微组织观察表明,带极电渣堆焊和带极埋弧堆焊层的显微组织都为奥氏体+δ铁素体。带极电渣堆焊层金属中δ铁素体随着焊速的提高而增多,含量由6。8%增加到20.4%,带极埋弧堆焊金属中的δ铁素体含量比带极电渣堆焊的高,达到了23.6%;电化学动电位再活化试验结果表明,焊接速度8m/h的带极电渣堆焊层金属的再活化率仅为3.22%,耐晶间腐蚀的性能最佳,焊速快慢或焊接方法改变都将使带极电渣堆焊层金属的再活化率升高,耐晶间腐蚀性能下降。10%草酸溶液电解浸蚀试验的结果与EPR曲线结果一致。     

绝缘陶瓷往复走丝线切割加工放电状态检测方法

绝缘陶瓷材料在工程中应用广泛,但由于其脆硬性,用普通方法很难加工.通过辅助电极利用往复走丝电火花线切割的方法对绝缘陶瓷氮化硅作了加工实验研究,并用普通金属与电阻串联的方法进行了仿绝缘陶瓷氮化硅加工实验研究.对实验数据进行了分析,根据导电层对维持电压的影响情况,将导电层分为良、中、差3个等级, 并设计出一种专门用于绝缘陶瓷碳化硅往复走丝线切割加工放电状态检测的方法,能区分出3种处于不同导电层等级状况下的正常放电、空载以及短路等5种放电状态.