Characterization of Directionally Solidified B<SUB>4</SUB>C-SiC Composites Prepared by a Floating Zone Method

Abstract

Directionally solidified B 4 C-SiC composites were prepared by a Floating Zone method. The lamellar texture was observed at 53 mol%SiC. The c-axis of B 4 C phase was tilted 20 • to the growth direction. The (102) plane and [121] direction of the B 4 C phase were parallel to the (311) plane and [121] direction of the SiC phase, respectively. The thermal conductivity of the composite parallel to the growth direction (κ ) was about twice as great as that of monolithic B 4 C. The anisotropy of electrical conductivity and thermal conductivity were explained by a mixing law using the values of B 4 C and SiC. The mass gain due to oxidation was about 1/3 to 1/5 less than that of monolithic B 4 C at 1023 K. The surface perpendicular to the growth direction showed slightly better oxidation resistance than that parallel to the growth direction. The microhardness of the composite was almost the same as that of B 4 C.

Preparation of Directionally Solidified B<SUB>4</SUB>C&ndash;TiB<SUB>2</SUB>&ndash;SiC Ternary Eutectic Composites by a Floating Zone Method and Their Properties

“…It was reported that B 4 C-TiB 2 and B 4 C-SiC were binary eutectic systems whose eutectic compositions were 75B 4 C-25TiB 2 , 23) 80B 4 C-20TiB 2 18) and 70B 4 C-30SiC to 47B 4 C-53SiC (mol%). 10,13,24) We have found that TiB 2 -SiC was a binary eutectic system. The detailed results will be reported elsewhere.…”

“…The planes perpendicular to the growth direction (growth plane) were B 4 C(104) (hexagonal), TiB 2 (100) (hexagonal) and SiC(111) (cubic, type) in the B 4 C-TiB 2 -SiC ternary eutectic composite, respectively. Binary eutectic point [13] Ternary eutectic composition TiB 2 +T Binary eutectic point [21] Binary eutectic point Figure 7 shows the indenter load dependence of Vickers micro hardness of the B 4 C-TiB 2 -SiC composites for the ternary eutectic composition (51.2B 4 C-8.1TiB 2 -40.7SiC (mol%)), and B 4 C, TiB 2 and SiC excess compositions. The hardness of B 4 C-TiB 2 -SiC composites increased with decreasing the indenter load.…”

“…Figure 9 shows the temperature dependence of electrical conductivity for the B 4 C-TiB 2 -SiC composites and compared with the reference values of B 4 C, TiB 2 and SiC together with the B 4 C-TiB 2 and B 4 C-SiC eutectic composites. 13,21) The electrical conductivity of B 4 C-TiB 2 -SiC composite slightly decreased with increasing temperature. The electrical conductivity of B 4 C-TiB 2 -SiC composite was much higher than that of B 4 C, SiC and B 4 C-SiC eutectic composite, and increased with the increase of the content of TiB 2 because the higher electrical conductivity of TiB 2 than those of B 4 C and SiC.…”

“…Silicon carbide (SiC) is also a hard and wear resistant material having high oxidation resistance and excellent thermal shock resistance. [10][11][12] We have prepared B 4 C-SiC eutectic composites by a floating zone (FZ) method, and reported significantly higher oxidation resistance than that of B 4 C. 13) Titanium diboride (TiB 2 ) can be a useful additive material to improve the performance of B 4 C because of its high electrical conductivity, thermal conductivity and hardness. [14][15][16][17][18][19][20] We have reported the characteristics and microstructure of B 4 C-TiB 2 eutectic composites.…”

Preparation of TiC-TiB<SUB>2</SUB>-SiC Ternary Eutectic Composites by Arc-Melting and Their Characterizations

“…Some promising results have been reported for the B 4 C-SiC, B 4 C-TiB 2 and B 4 CTiB 2 -SiC eutectic composites. [18][19][20] However, the study on the TiC-TiB 2 -SiC eutectic composite has not been reported. In this study, the TiC-TiB 2 -SiC ternary composites were prepared by arc-melting, and the microstructure, hardness, thermal conductivity and electrical conductivity were investigated.…”