The Influence of Thermal Properties Anisotropy on Subtractive Laser Processing of B4C/h-BN Composites

Abstract

This work concerns boron carbide matrix composites with the addition of hexagonal boron nitride particles (h-BN) as a solid lubricate. The composite materials were hot-pressed and analysed in terms of phase, structure, and microstructure changes in relation to the h-BN content. The uniaxial pressure applied during the manufacturing process allowed the orientation of single h-BN particles and its agglomerates in perpendicular direction to the pressing axis. The anisotropy of heat transfer and thermal expansion coefficient (CTE) and density changes in relation to temperature are discussed. Thermal diffusivity and conductivity were measured in relation to the material direction by the laser flash analysis method (LFA). In this paper, understanding the heat flow and CTE changes allowed explaining the results of investigated subtractive laser processes of the manufactured composites. The laser ablation process was conducted on B4C/h-BN composites in parallel and perpendicular direction to each other. It was done in a continuous work (CW) mode at 50 W with a 40 µm spot and 3 mm/s beam travel speed. The influence of h-BN particles and their orientation on thermal properties is discussed. The effect of laser processing on B4C/h-BN composites was also discussed in relation to the material surface roughness measured with a confocal microscope, microstructure observations, density, and thermal properties changes in relation to the material direction.

Design and optimisation of a laboratory scale microwave furnace for heating titanomagnetite ironsand

“…The specific type of BN used in this research was hot-pressed hexagonal Boron Nitride produced by Innovacera, pictured in Figure 2.6. The temperature dependent thermal conductivity and heat capacity of BN is taken from [50], and data for the emittance of BN was obtained from [51]. A fibreboard was chosen over loose fibre insulation due to the high mechanical stability and uniformity of the fibreboard material, which ensured high experimental repeatability.…”

Design and optimisation of a laboratory scale microwave furnace for heating titanomagnetite ironsand

“…The specific type of BN used in this research was hot-pressed hexagonal Boron Nitride produced by Innovacera, pictured in Figure 2.6. The temperature dependent thermal conductivity and heat capacity of BN is taken from [50], and data for the emittance of BN was obtained from [51]. A fibreboard was chosen over loose fibre insulation due to the high mechanical stability and uniformity of the fibreboard material, which ensured high experimental repeatability.…”