Preparation Of Nano-structure Oxide Powder By DC Arc Plasma And Sintered By Spark Plasma Sintering Technique

Pulse electric current sintering is an advanced technology for materials synthesis and one of effective methods for preparation nano-structure ceramic. But the sintering mechanism is different with traditional sintering method. The sintering phenomena of oxide nano-powders have been investigated in this paper.ZrO2(6%Y2O3)(YSZ) nano-powders were perpared by DC non-transferred arc plasma systems. Based on the TEM and XRD analysis results of powde, the particle size of TSZ was about 20nm with high purity more than 98.7%. Using metal for reaction material, SnO2 and TiO2 nano-powders were obtained through DC transferred arc plasma with purity more than 98% and average size of particle being l00nm and 60nm, in the same time the particle size could be adjusted according to the cooling medium. The power ofreactor pressure of gas were the important technologic parameters to affecting the purity and size of powders.XRD analysis at different depth of ZrO2 sintered body indicates that it has trace to be bombarded by high-energy particles at top surface, this results are the evidence for the existence of pulse electric field. The periodicity fluctuating has been produced by pulse magnetic field so that there are periodic high temperature region exists in sintered body, it results in the symmetrical crack in sintered body of ZrO2.The sintered temperature was one of key parameters to the relative density and grain size. The analysis of microstructure of samples showed that the grain of TiO2 were very small under 700℃, the distance of grain became small with temperature increasing, the rate and size of pore was decreasing. The relative density of sample at 900℃ was 97% and the grain size of sintered body was about 200nm. When the temperature exceeded 1100℃, the grain size of body grew up several times(>2 m).The speed of sintered was faster with smaller size of particls than larger size, there were more pore in the corresponding sample so as to having lower relative density. Higher pressure contributed to the exhausting of pore and relative density. The sintered body of TiO2 whose particles had been mixed with liquor had a higher relative density(98.6%) than the body without liquor(96.4%). Although the sintered pressure could reduce the affection of pore, but the affection of molding system shoud not be ignored to relative density.Low heating rate and high sintered pressure were profitably for reducingthe rate of pore so as to increase the relative density of sintered body. With the same sintered conditions, the relative density of sintered body was 98.7% at 25MPa sintered pressure and it was 91.4% at 12MPa. Reducing heating rate enhanced the density of sample. The density was more than 98% and had finest microstructure with a heating rate of 100癈/min, it was 94.8% at 300癈/min heating rate. On the other hand longer sintered time could cause the grain size of sample increasing.