Engineering Powders for Ceramic 3-D Printing

Abstract

The powder processing problems that control the performance of ceramic forming methods also apply to 3-D printing. Binder jet printing requires well flowing powders to form smooth powder beds, however, powders that flow well typically lack the surface area required for sintering. Granulating fine powders facilitates flow and sintering but also increases binder usage and shrinkage which is not a viable solution. in this work, a powder was engineered for 3-D printing that potentially solves the powder flow and shrinkage problems and sinters. Granules with a bimodal distribution consisting of 70% 5 μm particles and 30% 0.5 μm particles were produced. The granules were then mixed in a 10:1 size ratio (80% coarse granules, 20% fine particles). This approach solved the powder flow problem and produced high packed bed densities but only marginally sintered. Incorporating a glass frit as the fine particle fraction maintained particle flow and packing while facilitating sintering. Packing data obtained through tapping and vibration indicated that powders containing fine particles experience a "packing transition" region between 30-300 cycles. This transition exhibited significant packing density increases and does not appear to have been discussed in the literature. Packing efficiency through vibration suggests there is an optimal frequency for most efficient compaction. Conversely, there may be an optimal frequency that facilitates particle movement but does not induce improved compaction.