Study On The Synthesis Of Nano-carbide Materials By Sol-Gel Precursor Method

Carbide materials were used in many applications because of their high melting point, high hardness and strength, high wear resistance, low thermal expansion cofficient, excellent resistance to oxidation and corrosion. Preparation of nano-carbide materials has become an important part of modern ceramic research. Sol-gel and carbothermal method were used to synthesize SiC and TiC nano-materials, the influence factors of the synthesis process were studied.To begin with, high surface area silicon carbide was synthesized using citric acid as the pore forming agent by the tetraethoxysilane(TEOS) sol-gel and carbothermal method.BET,TG,XRD and SEM were carried out to characterize the properties of the specimens. The results show that, the optimal technics of gel synthesis was control the mole ratio of H2O to TEOS at 6~7, the volume ratio of solvent to TEOS at 4~6, and the surface area of product derived from sample added with CA varied from 13 to 61 m2g- 1, and its value can be controlled with the mole ratio of CA to TEOS; the pores remained after pyrolysis of CA was the key reason to obtain high surface area SiC.When the mole ratio of CA to TEOS was 0.8,the dry gel react at 1500℃for 2h,the product could get high surface area,and the average particle size was 100nm.Furthermore, Titanium carbide powder of nanometer was synthesized by the sol-gel and carbothermal method. First, the precursor was prepared using Ti(OBu)4 and phenolic resin as the raw materials, ethylene glycol,acetic acid and nitric acid as the solvent, chelating reagent and catalyzer separately; then,the precurser was heated to high temperature in flowing argon atmosphere to get TiC particles. The factor influence the gel time was discussed, the precurser and product were characterized by TG, XRD and SEM.The result show that translucent red-brown gel of shortest gel time was obtained when the pH value of the solution was 2-3, the mole ratio of acetic acid to Ti(OBu)4 was 2.5,the mole ratio of H2O to Ti(OBu)4 was 6, and the volume ratio of solvent to Ti(OBu)4 was 4. While XRD and SEM demonstrate that the product, formed at 1400℃for 1 h in flowing argon atmosphere was TiC, which was obtained through a series of lower oxidation of TiO2, with smooth surface, fine particle size, and the average size of the product was 100-300nm.