Effect of processing method on microstructure,electrical conductivity and electromagnetic wave interference (EMI) shielding performance of carbon nanofiber filled thermoplastic polyurethane composites

In this study, effect of processing method on microstructure formation and related electrical conductivity and electromagnetic interference shielding effectiveness of carbon nanofiber (CNF) filled thermoplastic polyurethane (TPU) composites, prepared via three different processing techniques; (i) melt compounding (MC) in a twin screw extruder, (ii) simple solution mixing (SM) on a magnetic stirrer, and (iii) solution mixing with sonication (SM-U) were investigated. It was found that the electrical conductivity values of samples decreased in the order of SM > SM-U > MC for a particular amount of CNF. The electromagnetic test results showed that the samples prepared with SM and SM-U methods yielded higher total shielding effectiveness (SE_T) values than those prepared with MC. SE_T values of samples including of 20 phr of CNF prepared with MC, SM-U and SM methods were varied in the range of 10–30 dB, 20–60 dB and 20–80 dB, respectively within a frequency range of 1–12 GHz.     

提高选钼技术经济指标的探讨

介绍了德兴铜矿提高铜钼混合精矿用品位的几项科研成果以及在生产中应用情况。采用充氮新工艺、充填式浮选柱新设备的试验结果表明不仅能提高铜钼分选指标而且可显著降低生产成本。     

氰化工艺过程中金属存量计算方法探讨

为搞好金属平衡，减少理论与实际差值，依据某黄金矿山氰化工艺流程特点，对脱药用单层浓密切、漫出槽、三层洗涤浓密机三个作业中的金属存量的计算方法进行了探讨。     

鲍店煤矿供电安全监测及管理系统的开发

兖矿集团鲍店煤矿应用ＡＵＴＯＣＡＤ、网络技术对分散的供电系统进行改造,实现了采区变电所电网状态及绝缘监测。在地面建立机电管理网,将地面３５ｋＶ 微机监测纳入矿ＷＩＮＤＯＷＳＮＴ 网络,实现了全矿井上下变电所的微机监测和管理,并对井下在线监测做了有益的探索。     

电子轨道衡转向架计量控制程序的应用

本文论述了转向架计量电子轨道的数据处理过程.对车皮过衡速度、车型判断、重量计算、采集数据的存贮给出了实现方法.此程序适用于绝大多数四轴车以转向架方式过衡.     

Effect of ultrafine grain refinement on hydrogen embrittlement of metastable austenitic stainless steel

Micro-tensile tests were performed on high-pressure-torsion-processed specimens of type 304 steel with grain sizes in the range of 0.1–0.5 μm to clarify the effect of ultrafine grain refinement on the hydrogen embrittlement (HE) of metastable austenitic steel. The ultrafine-grained (UFG) specimens with average grain sizes < ～0.4 μm exhibited a limited uniform elongation followed by a steady-stress regime in the stress–strain curves, which was attributed to a martensitic transformation. A high yield stress and a moderate elongation to failure were attained for the UFG specimens with an average grain size of ～0.5 μm in the uncharged state. Hall–Petch relationships well hold between the yield stress and the average grain size for each uncharged and hydrogen-charged specimen. Hydrogen charging increased the friction stress by 40% but did not change the Hall–Petch coefficient. Hydrogen-induced ductility loss was mitigated by ultrafine grain refinement. Ductility loss due to hydrogen charging manifested in the local deformation after a martensitic transformation. This indicates that hydrogen does not significantly affect the martensitic transformation, but shortens the subsequent local deformation process.     

Contents of eight harmful elements in baby toys and their migration tests

Levels of eight harmful elements, i.e., antimony, arsenic, barium, cadmium, chromium, lead, mercury and selenium, were investigated in 45 baby toys and 10 paints, which were mainly made of polyvinyl chloride. All samples contained barium at levels of 0.3-3,700 mg/kg, several samples contained cadmium (0.2-26 mg/kg), chromium (0.5-280 mg/kg) and lead (1.5-1,300 mg/kg), and one sample contained antimony (5.3 mg/kg). They might have been used as colorants of the toy materials and paints. They were then evaluated using the migration test of ISO 8124-3, in which samples were ground up, and then soaked in 0.07 mol/L HCl at 37 degrees C for two hours. Barium, cadmium, chromium and lead migrated from some of the samples, but at levels lower than the migration limits required by ISO 8124-3. Compared with the Japanese official method, the ISO method resulted in higher migration, but there are significant differences in the migration limits, test method, and so on between them. Further investigation is needed in this area.     

Strain-induced structural transformation of a silver nanowire

We have investigated the structural characteristics of the experimentally observed phase transition of a silver nanowire into a tube under tensile strain. In the simulations, atoms are allowed to interact via a model potential extracted from the modified embedded atom method. Our calculations demonstrate that the formation of the hollow structure is governed by the nature of the applied strain, the length of the wire, and the initial cross-sectional shape. The results further offer insights into the atomistic nature of this specific structural transformation into a nanotube with the smallest possible cross-section.     

Effect of High-Pressure Torsion Processing and Annealing on Hydrogen Embrittlement of Type 304 Metastable Austenitic Stainless Steel

The effect of high-pressure torsion (HPT) and annealing on hydrogen embrittlement (HE) of a type 304 stainless steel was studied by metallographic characterization and tensile test after hydrogen gas charging. A volume fraction of ~78 pct of the austenite transformed to α′ martensite by the HPT processing at an equivalent strain of ~30. Annealing the HPT-processed specimen at a temperature of 873 K (600 °C) for 0.5 hours decreased the α′ martensite to ~31 pct with the average grain size reduced to ~0.43 μm through the reverse austenitic transformation. Hydrogen charge into the HPT-processed and the HPT+annealed specimens in the hydrogen content of ~10 to 20 ppm led to no severe HE but appeared in the solution-treated specimen. Especially the 873 K (600 °C) annealed specimen had the ~1.4 GPa tensile strength and the ~50 pct reduction of area (RA) despite the hydrogenation.     

基于智能传感器的矿井水文监测系统的设计

基于智能传感器的应用,设计了一种矿井水文监测系统。该系统集智能水压传感器等于一体,同时具有体积小、成本低、可靠性好、响应速度快和智能化程度高等优点。可以对多种水文参数进行监控,同时将数据、文字、图形和图像等与多媒体有机结合,以提高信息的准确率。