Abstract. Aluminum nitride(AlN) powders were synthesized by carbonthermal reduction of Ammonium aluminum carbonate hydroxide(AACH). The AACH were prepared from ammonium alum and ammonium hydrogen carbonate by precipitation method and AACH adhere to carbon black during precipitation. The precursor has a high reaction activity (near 100% of nitridation ratio after heated in flow nitrogen at 1400°C, 2h). After carbon remove in muffle furnace at 700 °C, white color Aluminum nitride (AlN) powder attained and mean size is 100 nm. The specific surface area of the powders decreased with increasing of concentration of ammonium alum and ammonium hydrogen carbonate, which range from 22 m2/g to 7 m2/g, particle size vary from 58 to 120 nm. Phase presents in the products during heating in flowed nitrogen were observed by X-ray diffraction. The -Al2O3 formed when the precursor heated to 1200°C, AlN was founded at 1300°C and the reaction ended at 1400°C, the reaction temperature and annealing time were much lower than nitridate the mixture of Al2O3 and carbon black. Particle size was increased when reaction temperature increased from 1400°C to 1550°C.
The fabrication of porous diamond preforms is a key step for obtain diamond/metal copposites with high proporties by liquid infiltration. In order to prepare porous diamond preforms with high strength and excellent compatibility with liquid metal. The diamond metallization should be treated first usually.In this paper, the microstructure, composition, phase structure and bond strength of tungsten coating on diamond surface by using salt-bath method were observed and analyzed experimentally including scanning electron microscope (SEM), energy spectrometer analysis (EDS), X-ray diffraction (XRD). The results show that tungsten start to react with carbon atoms on the surface of diamond at 1100°C while a dense and completely covered coating can be obtained at the temperature of 1150°C with 10-120 minutes dwell time. With this process, the layer on diamond surface can be regulated in the range of 1.18 to 3.24μm. The phase structure of coating from outside to inside is W, W2C and WC phase, respectively. Thermal shock experiments also show that the coatings on diamond surface have excellent bond strength as well as high temperature resistance.
AlN powders were synthesized by carbothermal reduction method using a combustion synthesis precursor derived from aluminum nitrate (oxidizer), glucose (carbon source), and urea (fuel) mixed solution. Effects of carbon source content on the combustion temperature of solutions, the particle size and morphology of the precursors and the synthesized AlN were studied in detail. The results indicated that a regular variation in the particle size and morphology of precursors had been observed with the increasing molar ratio of glucose to aluminum nitrate (C/Al). The products prepared with (C/Al=8–12), calcined at 1500 oC for 2 h, could have completed the nitridation reaction, while the nitridation products prepared with (C/Al=4 and 16) are opposite. The nitridation products prepared with (C/Al=8–12), calcined at 1500 oC for 2 h, are comprised of well-distributed spherical particles of AlN with the average size ranging from 50 to 80 nm.
The CuS flower-like superstructures were selectively and facilely synthesized by a hydrothermal method at 120 °C. The EDS, SEM, HRTEM and FFT results show that the CuS superstore has a well-defined uniform 3-dimensional flower-like morphology. These superstructures have sizes of about 500 nm and are built from several intersectional nanoplates, which have a mean length of about 500 nm and an average thickness of about 50 nm. Optical absorption spectrum of the CuS superstructure shows it has good absorption in the near-IR region and the band gap is 2.08 eV.
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