Oxidation behavior of CVI,MSI and CVI+MSI C/SiC composites

The oxidation behavior of chemical vapor infiltration(CVI),molten silicon infiltration(MSI)and CVI+MSI C/SiC composites at 500-1 400℃was studied.The oxidation below 900℃increased successively for CVI,CVI+MSI and MSI composites.However,the oxidation of CVI composite above 1 000 ℃was much faster thanthat of MSI and CVI+MSI composites. As active carbon atoms produced by siliconization of fibers during MSI process were oxidized first and decreased initial oxidation temperature.The initial oxidation temperature of MSI,MSI+CVI and CVI composites was 526,552 and 710℃,respectively.New active carbon atoms were generated due to the breaking of 2D molecular chains during oxidation,so the activation energy of three C/SiC composites was decreased gradually at 500-800℃with oxidation process,exhibiting a self-catalytic characteristic.

Erosion-corrosion investigation of high chromium cast irons using newly designed jet type tester

A jet type erosion-corrosion tester was developed for the erosion-corrosion investigation of high-chromium cast irons. During tests the size and the shape of particles in the slurry can be maintained stable. The jet velocity and attack angle can be accurately controlled. The repeatability and ranking consistency of the test results are satisfactory. The test parameters can be adjusted in a wide range, so that the tester can simulate various practical working conditions. Electrochemical test data can be automatically collected and processed. Dynamic polarization curves can be obtained during erosion-corrosion test, which can be used to study the dynamic corrosion characteristics.Two high chromium cast irons were studied in hot concentrated alkaline slurry. The results show that the erosioncorrosion mass loss rate and dynamic corrosion rate of 295Cr26 iron is lower than that of 185Cr13 under the conditions similar to alumyte processing. The mechanism of erosion-corrosion of 295Cr26 and 185Cr13 was studied by using the tester. The interaction between erosion and corrosion was also quantitatively evaluated.

Synthesis of tetramethyl ammonium hydroxide by cell diaphragm electrolytic method

Under the conditions of tetramethyl ammonia chloride (TMAC) used as starting material, Ti-based Dimensionally Stable Anode (DSA), stainless steel used as cathode and Nafion 900 cation membrane as cell diaphragm, this paper studies the synthesis of tetramethyl ammonium hydroxide (TMAH) by cell diaphragm electrolytic method, examining not only the effects of current density, concentration of starting material and cell temperature, on the product purity and current efficiency, but also the effects of electrolyte circulation rate on the service life of Ti-based DSA. The experiment puts forward an optimum processing condition, and experimental findings show that preparing TMAH by using this technique can obtain a current efficiency 74.7% and get product with a purity greater than 99.9%.

Characteristic Investigation of Nano-Crystal Hydrogen Storage Alloys

A Ml (NiCoMnA1)5 hydrogen storage alloys was prepared by double-roller rapid quenching.Its microstructure, electrochemically and kinetic characteristic were studied.A uniform crystal phase with CaCu5 structure could be detected by XRD analyses, whose average grain size is 30 ～ 50 nm and the ratio of c/a of nano-crystal hydrogen storage alloy is larger.The hydrogen absorption/desertion p - C isotherms of alloy show that its fiat-performance is perfect and the magnetic stagnant effect is very little.An simulate cell is used for electrochemical measurement.Electrode is 10C, the capacity decreasing rate via the 450 cycles at 7C is less than 20%.

X-RAY STUDY ON TITANIUM NITRIDE FILMS DEPOSITED BY VCAD METHOD

TiN films deposited by the VCAD method at the substrate of stainless steel and superhigh speed tool steels are uniform and dense.Their colour,orientation and lattice parameter depend on deposited condition The lattice structure of deposited film,the change of the lattice parameter and its preferred orientation were studied by the XRD method,different behaviours of TiNx film were analysed.The lattice parameter of TiNx films is increased with the nitrogen content and The colour of TiNx film is strongly related to the content of Nitrogen also.The change of preferred orientation depends mainly on the Bias.

Low-temperature growth of stoichiometric aluminum nitride films prepared by magnetic-filtered cathodic arc ion plating

A1N films were prepared on Si（100） and quartz glass substrates with high deposition rate of 30 nm-min-I at the temperature of below 85 ℃ by the magnetic-filtered cathodic arc ion plating （FCAIP） method. The as-deposited A1N films show very smooth surface and almost no macrodroplets. The films are in amorphous state, and the formation of A1N is confirmed by Nls and A12p X-ray photoelectron spectroscopy （XPS）. The XPS depth profile analysis shows that oxygen is mainly absorbed on the A1N surface. The A1N film has A1 and N concentrations close to the stoichiometric ratio with a small amount of A1203. The prepared A1N films are highly transparent over the wave- length range of 210-990 nm. The optical transmission spectrum reveals the bandgap of 6.1 eV. The present technique provides a good approach to prepare large-scale A1N films with controlled structure and good optical properties at low temperature.