用微波多端口技术测量粉末状材料复电磁参数

介绍了测量双端口网络散射参数的微波多端口技术,提出了测量粉末状物质复电磁参数的级联网络分解法,并指出了与测试方法相关的端面相位修正措施。给出了四种典型粉末状物质的测试结果。

级联网络分解法在材料电磁参数测量中的应用

介绍了一种由三级级联网络构成的取样器,论述了分式线性变换级联网络分解法,并利用奇偶模法计算被测材料的复电磁参数.该方法适用于糊状及粉末状材料电磁参数的测量.给出了多种材料测量实例和数据,并根据不同测量对象的特征,讨论了一些值得重视的误差因素和修正方法.

聚乳酸/磷酸钙复合微球的制备

采用O/W乳液溶剂挥发法,制备粉末状聚乳酸/磷酸钙状微球。讨论搅拌速度、搅拌时间等因素对微球的影响。实验结果表明:最佳的制备条件为搅拌速度800 r/min,搅拌时间3 h,油水相体积比1∶100,聚乳酸的质量浓度30 g/L。

Deformation behaviors and processing maps of CNTs/Al alloy composite fabricated by flake powder metallurgy

Deformation behaviors of CNTs/Al alloy composite fabricated by the method of flake powder metallurgy were investigated by hot compression tests, which were performed in the temperature range of 300?550 °C and strain rate range of 0.001? 10 s?1 with Gleeble?3500 thermal simulator system. Processing maps of the CNTs/Al alloy at different strains were calculated to study the optimum processing domain. Microstructures before and after hot compressions were characterized by electron backscattered diffraction (EBSD) method. Stress?strain curves indicate that the flow stress increases with the increase of strain rate and the decrease of temperature. The processing maps of the CNTs/Al alloy at different strains show that the optimum processing domain is 500?550 °C, 10 s?1 for hot working. EBSD analysis demonstrates that fully dynamic recrystallization occurs in the optimum processing domain (high strainrate 10 s?1), whereas the main soften mechanism is dynamic recovery at low strain rate (0.001 s?1).

Hot deformation and processing maps of Al_2O_3/Al composites fabricated by flake powder metallurgy

The deformation behaviors of Al2O3/Al composites were investigated by compressive tests conducted at temperature of 300-450 °C and strain rates of 0.001-1.0 s-1 with Gleeble-1500 D thermal simulator system. The results show that the flow stress increases with increasing strain rate and decreasing temperature. The hyperbolic sine constitutive equation can describe the flow stress behavior of Al2O3/Al composites, and the deformation activation energy and constitutive equations were calculated. The processing maps of Al2O3/Al-2 μm and Al2O3/Al-1 μm composites at strain of 0.6 were obtained and the optimum processing domains are in ranges of 300-330 °C, 0.007-0.03 s-1 and 335-360 °C, 0.015-0.06 s-1 for hot working, respectively. The instability zones of flow behavior can also be recognized by the maps.

钐铁氮磁体的抗氧化技术

精密机械上采用的粘结磁体主要是钕铁硼磁体,但其性能很难再提高,因而磁体厂家将目光转向了钐铁氮磁体。 由大阪大学足立吟也教授、町田宪一副教授等组成的研究小组成功地实现了钐铁氮磁体的高性能化。