In-situ synthesis of Si 3 N 4 /TiN nanocomposite powders in cryogenic solution
- PDF / 3,359,584 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 41 Downloads / 218 Views
1056-HH11-29
In-situ synthesis of Si3N4/TiN nanocomposite powders in cryogenic solution Mei YANG, Mingli Lü, and Hongmin ZHU School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing, 100083, China, People's Republic of ABSTRACT A new method of Si3N4/TiN nanocomposite powders through reaction at low temperatures was proposed and tested. The reduction of titanium chloride and silicon chloride by sodium was conducted in liquid ammonia at the temperature range of -40 ~-50 , and titanium nitride and silicon nitride nanopowders were obtained. Based on these reactions, in-situ coating and co-precipitation were conducted. The TiN nano-particles deposited on the surface of Si3N4 particles as the nuclei in the in-situ coating and in the co-precipitation two or more source of ions were reduced uniformly in the liquid ammonia. Si3N4/TiN nanocomposite powders were prepared by both the routes and were characterized with X-ray diffraction, transmission electron microscopy. The effects of in-situ treatment and the particle size on the morphology of the composite were discussed.
℃ ℃
Keywords: in situ; titanium nitride, silicon nitride, nanocomposite powders, ammonia. INTRODUCTION Nitrides have many excellent characteristics, such as high melting point, compressive strength, good thermal stability and strong corrosion resistance [1]. However, those nitrides are very hard to be prepared at low temperatures. Usually corresponding metals or oxides are used as source material and react with nitrogen or ammonia gas for several hours or longer at high [2-5] . Therefore, it is difficult to avoid the growth of temperature, for example, 700 -1200 produced powders and hard to obtain nitride nanopowders. Liquid ammonia can dissolve alkali and alkaline earth metals over a wide range of concentration and forming a powerful reducing agent [6-8]. At same time, during the reaction, the solvent ammonia also provide nitrogen source. Importantly, liquid ammonia is often used at cryogenic solution because of its low boiling point (just -33.5 [6]. Liquid condition and low reaction temperature is helpful to improve the uniform distribution of ion and limit the growth of the product powders. In this paper, titanium nitride and silicon nitride nanopowders were obtained via reduction by sodium in liquid ammonia at the temperature range of -40 ~-50 , and based on these reactions, Si3N4/TiN nanocomposite powders were prepared by in-situ coating and in-situ co-precipitation.
℃
℃
℃)
℃ ℃
EXPERIMENT Analytical grade titanium chloride (TiCl4), silicon chloride (SiCl4) and commercial silicon nitride (Si3N4) were used as the source materials and metal sodium was as reduction agent. The synthesis process is described in fig.1.The starting materials (Si3N4 and TiCl4 for in-
situ coating and SiCl4 and TiCl4 for co-precipitation) were fed into one of double-chamber flask and Na was put into another one in the proportion of TiN volume in a glove box. In order to keep the effect of the in-situ process, full mixing
Data Loading...
