A novel technology to prepare styrene-butadiene rubber (SBR)/carbon nanotubes (CNTs) composites was developed by means of combining a spray drying method and a subsequent mechanical mixing process. The cross-linking degrees of the vulcanized composites increased gradually with the additive CNTs contents. Comparing with those of the pure SBR composites, the mechanical properties such as tensile strength, tear strength and hardness of the composites filled with CNTs at certain contents were dramatically improved almost by 600%, 250% and 70% respectively. The fabrication of the CNTs filled SBR composites by combination of the spray drying method and subsequent mechanical mixing process was effective for enhancing the reinforcement effects of CNTs in rubbers. The novel technology can also open a new route for the modification and reinforcement on the nanocomposites with large amount of CNTs.

Abstract The yield asymmetry between compression and tension of magnesium alloy Mg-3Al-1Zn (AZ31) with different grain sizes and textures has been studied by tensile and compressive testing of as-cast, as-extruded and equal channel angular pressed (ECAPed) specimens. The significant yield asymmetry (the ratio of yield strength between compression and tension σyc/σyt is ~0.44) was found in as-extruded specimens and the corresponding microstructure evolution during deformation revealed that tensile twinning is the underlying reason for the large yield asymmetry. Strong texture and grain size are influential factors for large yield asymmetry. The separate contributions of grain size and texture on yield asymmetry were investigated.

Silicon carbide (SiC) is a Ⅳ-Ⅳ compound semiconductor material with a wide band gap. Semiconductor electronic devices and circuits made from SiC are presently developed for high-temperature, high-power, and high-radiation conditions in which conventional semiconductors can not be adequately performed. In this paper, SiH4 and C2H2 were used to synthesize SiC nano-whiskers. Metal Ni was the catalyst. SiC nano-whiskers were grown by vapor-liquid-solid mechanism. The effects of the H2 flow rate, growth temperature, catalyst thickness and growth pressure to grow SiC nano-whiskers were studied. 3C-SiC thin film and nano-tips can be synthesized by controlling the growth conditions.

The uniaxial ratcheting behaviors of several metals with different crystal structures or values of fault energy were observed by the stress-controlled cyclic tests at room temperature. The prescribed metals included 316L stainless steel, pure copper, pure aluminum, and ordinary 20 carbon steel. The effects of applied mean stress, stress amplitude and stress ratio on the uniaxial ratcheting were also investigated. The observations show that different crystal structures or values of fault energy result in more or less different ratcheting behaviors for the prescribed metals. The different ratcheting behaviors are partially caused by the variation of dislocation mobility.

The machinability tests were conducted by using a YD-21 dynamometer on a CA6161A lathe. The experiments, conducted to determine the effect of free-cutting additives on machining characteristics of austenitic stainless steels, are presented. The results have shown that machinable inclusions were composed of MnS and CuO, and they might be also Ti4C2S2. The presence of Bi in the inclusion was detected by the atom map and electro-probe microanalysis (EPMA), which might be the most important factor to improve the machinability of austenitic stainless steels. The cutting forces for steel B were lower than those of steel A at various cutting speeds; the abrasion depth of the flank of the tool for steel B was less than that of the steel A in the case of the same cutting conditions. The machinability of austenitic stainless steel was visibly improved by adding free-cutting additives, such as sulfur, copper and bismuth, etc. Ultimate tensile, yield strength, and total elongation values of the free cutting austenitic stainless steel reach a satisfactory effect due to the addition of these free-cutting additives.