Papers by Keyword: Carbonthermal Reduction

Abstract: Zirconium diboride (ZrB₂) powders were synthesized by sol-gel carbonthermal reduction method using zirconium oxychloride (ZrOCl₂·8H₂O), boric acid (H₃BO₃), source (C₁₂H₂₂O₁₁) and citrate (as chelation agent). The Zirconium diboride precursors were calcined at 1600¡æ for 2h, 3h and 4h under argon atmosphere. The precursors and sintered samples were characterized by TG-DSC, XRD and SEM. Results revealed that the ZrB₂ powders prepared at 1600°C for 4h exhibited quasi-tabular morphology with a small average crystalline size about 20μ. With respect to the conventional solid state method, the Sol-gel method route guaranteed a faster, easier and energy-saving process for obtaining nanopowders.

Abstract: 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.

Abstract: A new environment friendly method to synthesize sialon composites using fly ash with high content of Al2O3 by carbon-thermal reduction-nitridation was presented. The results showed that sintering temperature and the pressure of N2 gas are in favor of the nitrification synthesis of Sialon composites. When Samples wear buried in silicon powder and sintered at 1400°C under N2 atmosphere, Sialon (Si4Al2O2N6) had been synthesized.