Study of grains in boron carbide and its composite sintered by spark plasma sintering
Liew, Jia Qi
Date of Issue2016-03-30
School of Materials Science and Engineering
Among the ceramic materials, boron carbide (B4C) is a leading candidate for ballistic applications, especially for light armour, since it possesses higher hardness and lower density compared to other ceramics. For ceramics, it is desirable to obtain an ultra-fine grained dense microstructures; an absence of pores and small grains generally correlates to having superior mechanical properties, such as higher hardness and higher fracture toughness. Spark plasma sintering (SPS) is a novel sintering technique that has been proven to be very effective in controlling the growth of grains of a material during densification. In the last two decades, considerable efforts have been undertaken to improve B4C sinterability and mechanical properties, through the manipulation of sintering conditions and the addition of additives. Although sintering additives have been used to facilitate the densification of B4C, they often result in grain growth, hence a reduction in hardness. In this research, the grains of spark plasma sintered B4C and the behaviour of grains upon the addition of Titanium Diboride (TiB2) and Boron were studied. Densification of B4C was also discussed concurrently with grain growth as it is equally important in affecting the mechanical properties of B4C. Grain growth was observed when pure B4C was spark plasma sintered at 1850oC. The particle size of the initial powder used seems to be a key factor in creating fully dense and fine-grained samples. Although grain growth was observed, the grain size of dense B4C (>95%) was averaged to 1.846 µm, one of the lowest compared to literature. On addition of TiB2, B4C particles of varying size and shapes tend to agglomerate throughout the microstructure. Although a dense microstructure could not be achieved, it was found that TiB2 could be a possible grain inhibitor by suppressing grain growth of B4C through the pinning effect of the secondary phase, keeping the grain size of B4C as low as 1.456µm. However, the role of boron in B4C was not conclusive, as the composition of boron in B4C composite was too low to be able to have any effect on the microstructure.
Final Year Project (FYP)
Nanyang Technological University