Preparation and characteristics of gelcast RBSC–B₄C composite

Abstract

The preparation and mechanical properties of silicon infiltrated SiC-B 4 C composite were studied in the present work. Gelcasting process was adopted to obtain green bodies with uniformity and compaction. The gelation behaviour of the slurry was controlled by introducing the polymerisation inhibitor mixture and the gelation reaction was delayed to about 10 min with increasing B 4 C content from 20 to 40%. Mechanical properties of the SiC-B 4 C sintered samples were tested and the results showed that increasing B 4 C content led to an increase in bending strength, fracture toughness and hardness. Microstructure investigation revealed that the SiC-B 4 C composites showed less content of free silicon and finer grains comparing to RBSC ceramics.

Investigation of Microstructural Features and Mechanical Characteristics of the Pressureless Sintered B4C/C(Graphite) Composites and the B4C-SiC-Si Composites Fabricated by the Silicon Infiltration Process

“…The EDS spectroscopic analysis depicted that the silicon infiltrated composites were composed primarily of boron, silicon, and carbon, thereby demonstrating that the composites obtained following silicon infiltration comprised boron carbide and silicon carbide along with some content of silicon. It can therefore be assumed that the liquid silicon infiltrated into the interior of the composite and produce silicon carbide upon reaction with boron carbide, according to the following reaction equations [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ]: 5 Si + 3 B 4 C = 3 SiC + 2 SiB 6 2 Si + B 4 C = SiC + SiB 4 …”

“…The liquid silicon underwent a chemical reaction with graphite producing silicon carbide as shown by the following chemical reactions [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ]: Si + C = SiC …”

“…During the silicon infiltration, the liquid silicon infiltrated into the interior of the composite’s specimens, and subsequently reacted chemically with boron carbide producing silicon carbide according to the following chemical reactions [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 ]: 5 Si + 3 B 4 C = 3 SiC + 2 SiB 6 ; 2 Si + B 4 C = SiC + SiB 4 . …”

“…Following liquid silicon infiltration, the boron carbide and graphite react with the liquid silicon, producing silicon carbide [11][12][13][14][15][16][17][18][19][20]. Because the pressureless sintered B 4 C/C(graphite) composites have a porosity of about 25-38%, the liquid silicon could be conveniently infiltrated into the interior of the composites [11][12][13][14][15][16][17][18][19][20], subsequently reacting with B 4 C and graphite to produce the silicon carbide [20][21][22][23][24][25][26][27][28][29][30]. While the boron carbide reacted only partially [30][31][32][33][34][35][36][37][38][39][40], the graphite reacted completely with silicon producing silicon carbide [40][41][42][43][44]…”

Influence of Phenolic Resin Impregnation on the Properties of Reaction‐Bonded Silicon Carbide

“…It is widely acknowledged that, homogeneous microstructure and small particle size will be favorable to improve the mechanical properties of the RBSC. Generally, wet forming processes are more practicable for preparing green preforms with uniform microstructure and composition distribution than the dry pressing method . The RBSC with high mechanical strength reported in literatures were always prepared by wet‐processing methods …”