T.S.R.Ch. Murthy

Synthesis and consolidation of boron carbide: a review

Abstract Boron carbide is a strategic material, finding applications in nuclear industry, armour for personnel and vehicle safety, rocket propellant, etc. Its high hardness makes it suitable for grinding and cutting tools, ceramic bearing, wire drawing dies, etc. Boron carbide is commercially produced either by carbothermic reduction of boric acid in electric furnaces or by magnesiothermy in presence of carbon. Since many specialty applications of boron carbide require dense bodies, its densification is of great importance. Hot pressing and hot isostatic pressing are the main processes employed for densification. In the recent past, various researchers have made attempts to improve the existing methods and also invent new processes for synthesis and consolidation of boron carbide. All the techniques on synthesis and consolidation of boron carbide are discussed in detail and critically reviewed.

Mechanical properties of HfB2 reinforced B4C matrix ceramics processed by in situ reaction of B4C, HfO2 and CNT

Boron carbide and its composites find a wide range of applications such as armour material, p-type semiconductor in electronic industries, as a neutron detectors and absorbers in nuclear industry and as a thermo-electric device for space applications, due to their unique physical, thermal and thermo-electric properties. This work discusses about the development of B4C-HfB2 ceramic-ceramic composites. Nearly full dense B4C-HfB2 ceramic composites were fabricated by in situ processing using B4C, HfO2 and CNT, as starting materials. The effect of HfO2 and CNT content on microstructure and mechanical properties of B4C composite has been investigated. Additions of 2.5–30 wt% HfO2 and 0.2–2.5 wt% CNT resulted in improvement in density and fracture toughness of the material. On increasing the additive contents, the fracture toughness of the composite increased more than twice that of monolithic B4C, whereas hardness decreased by about 12 %. Elastic Modulus of the composites was measured to be in the range of 570–625 GPa. Crack deflection observed in the composites was found to be the major toughening mechanism due to the existence of residual thermal stress. The maximum value of hardness, fracture toughness and elastic modulus were 36 GPa, 6.6 MPa m1/2, and 625 GPa, respectively.

Impression creep behaviour of TiB2 particles reinforced steel matrix composites

ABSTRACT Impression creep behaviour of the powder metallurgy processed steel matrix composites was investigated under constant stress at different temperatures in the range of 873–973 K. By using the power-law relationship, the estimated activation energy for unreinforced steel was found to be 149 kJ mol−1 and steel reinforced with 2 and 4 vol.-% TiB2 was found to be 298 and 338 kJ mol−1, respectively indicating better creep resistance of the reinforced steel matrix composites. Dislocation creep is the dominant creep mechanism based on the calculated values of stress exponent and activation energy. Hence, this method can be used to assess the potential of steel matrix composites for use as structural materials for high-temperature application.