Synthesis of a Metallic Ceramic -Ti 3 SiC 2 by PDS Process and its Properties
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Synthesis of a Metallic Ceramic -Ti3SiC2 by PDS Process and its Properties ZhengMing Sun, Hitoshi Hashimoto, ZheFeng Zhang, SongLang Yang, Toshihiko Abe National Institute of Advanced Industrial Science and Technology (AIST Tohoku) 4-2-1 Nigatake, Miyagino, Sendai 983-8551, Japan ([email protected]) ABSTRACT Powder mixtures of Ti/Si/C, Ti/SiC/C, Ti/Si/TiC, Ti/SiC/TiC and Ti/TiSi2/TiC were used for the synthesis of Ti3SiC2 by using a pulse discharge sintering (PDS) process. The Ti/Si/TiC powder was found to be the best among the five powder mixtures for the Ti3SiC2 synthesis. The highest content of Ti3SiC2 can be improved to about 99wt% at the sintering temperature of 1300°C for 15 minutes. The relative density of all the synthesized samples is higher than 98-99% at the sintering temperature above 1275°C. The nearly single phase Ti3SiC2 was found to show plastic deformation at room temperature and a good machinability. Both electrical and thermal conductivity were found to be more than two times of the value of a control pure Ti sample. The high-temperature mechanical tests confirmed that the Ti3SiC2 samples synthesized by the PDS process displayed a comparable performance with those fabricated by the other techniques.
INTRODUCTION Recently, Barsoum [1] summarized the fabrication and characterization of ternary compound Ti3SiC2, which is like a metal showing good electrical and thermal conductivity, machinability, low hardness and good thermal-shock resistance, and it is also like a ceramic being elastically rigid, oxidation resistant and stable to at least 1700°C. The early synthesis of Ti3SiC2 was carried out by Jeitschko and Nowotny [2] via chemical reaction in 1967, followed by Goto and Hirai [3] through CVD method in 1987. Barsoum et al. [4, 5] successfully synthesized this material with high Ti3SiC2 content (about 98 vol%) through hot-isostatic pressing (HIP) method from Ti/SiC/C mixtures. Besides, there are some other successful examples from Ti/Si/C and Ti/Si/TiC mixtures through the HIP technique or other methods [e.g. 6-8]. However, the sintering processes available were often conducted at relatively high temperature (1400-1600°C) for long time. Recently, an innovative technique for rapid sintering, i.e. pulse discharge sintering (PDS), was developed for sintering ceramics and intermetallic materials [9]. However, up to now, this new technique was seldom applied to the synthesis of Ti3SiC2. The main purpose of the present research is to apply the PDS technique on the rapid fabrication of Ti3SiC2 samples by using different starting powder mixtures at relatively low temperature. Furthermore, the deformation at room temperature, machinability, thermal conductivity, electrical conductivity as well as high-temperature mechanical properties were examined.
EXPERIMENTAL PROCEDURES There are five possible reaction paths in total for the synthesis of Ti3SiC2, that is, (A) Ti+Si+C → Ti3SiC2, (B) Ti+SiC+C → Ti3SiC2, (C) Ti+Si+TiC → Ti3SiC2, (D) Ti+SiC+TiC →
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Ti3SiC2 , (E) Ti+TiSi2+TiC → Ti3SiC2. T
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