Prediction of the Thermal Conductivity of Beds Which Contain Polymer Coated Metal Particles

Structural parts of ceramics or metals can, in principle, be made by laser sintering polymer coated ceramic or metal powders, followed by conventional methods for removing the binder and sintering in ovens. Understanding the laser sintering of coated materials requires knowledge of the behavior of beds containing composite particles. Many correlations for predicting the effective thermal conductivity of a bed of solid particles exist in literature, but little work has been done on beds of coated particles. We coated lead shots(high conductivity) with a styrene acrylic acid copolymer (low conductivity) to study the effect of coating thickness on the thermal conductivity. The thermal conductivity ofthe coated particle·hed was found to •drop rapidly in the beginning·· and then level off with increasing coating thickness. We also developed an equation that yields the equivalent conductivity of a coated spherical particle subjected to axial heat flow. The predicted results with the experimental measurements of bed conductivity obtained by an unsteady state method.