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Beta-SiC/SiO2 core-shell nanowires were obtained in a mullite boat after the reaction between silicon nanopowder and CH4 gas at 1623 K (1350°C), without adding metal catalysts from outside. The as-grown nanowires were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, scanning TEM, and infrared-ray spectroscopy.The results showed that the typical nanowires consisted of single crystalline β -phase SiC core of 50-70 nm in diameter and a uniform wrapping layer of low crystallinity SiO2 of ~15 nm in thickness, and their lengths were up to several tens of micrometers. The nanowires axes lay along the [111] direction of β -SiC. Oxygen from the experimental setup or the raw powder should be a key factor to synthesize the core/shell nanowires.

High-yield SiC/SiO2 core-shell nanowires were synthesized without adding metal catalysts from outside through a simple thermal evaporation of silicon powders during decomposition of methane gas. The influence of three parameters, size of Si raw powder (50 nm and 5 μ m), reaction temperature (1573, 1623 and 1673 K), and soaking time (1, 3 and 6 h), was investigated.The typical synthesized nanowires from different conditions possess the diameter of no thicker than 100 nm with several tens micrometers in length. It was addressed that the condition using the smaller size Si powder, which contained the highest amount of oxygen, at higher temperature lead to more complete reaction to obtain a large quantity of nanowires. The synthesized nanowires at higher reaction temperature and longer soaking time possessed larger core than those nanowires prepared at lower reaction temperature and shorter soaking time. Oxidation of larger size Si powder improved yield of nanowires. Based on these results, it was suggested that the typical nanowires should be grown via the oxide-assisted growth mechanism.

No abstract

The paper is focused on the influence of alternative fillers on rubber compounds properties. Three different types of powder fillers, drinking water treatment sludge (DWTS), perlite and calcium carbonate, were mixed into rubber compound mixtures. The mixtures were composed of STR20, EPDM, zinc oxide, steric acid, paraffin wax, 2-mercaptobenzothiazole (MBT), sulphur, Wingstay L, and filler. The mixtures were mixed in a Kneader type mixer at temperature of 70°C and then continuously mixed using a two-roll mill at temperature of 70°C. The relationships between type and the amount of filler versus properties of rubber compounds were demonstrated. The results showed that tensile and elongation at break of rubber compounds gradually decreased with increasing the amount of filler. Rubber compounds filled with small particle size filler possessed higher tensile strength and elongation at break than those filled with large particle size filler. Values of DIN abrasion loss of rubber compounds prepared under proper mixing condition were not more than 300 mm3. Under appropriate condition, the rubber compounds with DWTS, perlite and calcium carbonate provided sufficiently high shore A hardness (not less than 50 Shore A hardness). Finally, alternative fillers such as DWTS and perlite were expected to replace calcium carbonate in normal formula.