Glazing of 3D-Printed Silica to Reduce Surface Roughness and Permeability

Abstract

The advantages that 3D printing brings to the development and production of customized structures make it suitable for use in the space industry, since spacecraft components are rarely produced in large series. This work explores the use of stereolithography printing of a silica resin for microfluidic applications, in particular small-scale microthrusters, where an impermeable high-temperature material with a smooth surface is required. The printing accuracy, firing shrinkage, surface roughness and permeability of 3D-printed ceramic samples were investigated. Furthermore, glazing of the ceramic material with a stoneware glaze was performed and evaluated with respect to its effect on surface roughness and gas permeability. Open microchannels with diameter down to 250 µm were obtained. However, the accuracy was poor. Surface roughness (Sa) of the unglazed material was between 2.4 and 20 µm in green state and 4.2-16 µm after firing, depending on the layer thickness and printing angle of the sample. Half of the unglazed samples were permeable, owing to porous areas at the interfaces between the printed layers. Two glazing methods were investigated: dip coating and airbrushing. For the latter, two amounts of coatings were explored. Dip coating and airbrushing with the larger amount of coatings resulted in uniform and smooth glaze layers. The smoothest surfaces, with Sa less than 0.2 µm, were obtained using airbrushing. Glazing made all samples impermeable, no matter the method used. Finally, the potential of the material in the suggested application was demonstrated through operation of a printed and glazed microthruster nozzle.