The Manufacturing Process And Properties Of Porous Cordierite Ceramics By Additive Manufacturing

Porous cordierite ceramics have been widely used in various industrial fields such as catalyst carriers, filters, thermal insulations due to its low thermal expansion coefficient and high resistance to thermal shock. At present, porous cordierite ceramics are generally manufactured by model shaping technology. Simple structure such as straight-though hole can only be made due to limitations of model shaping technology, and porous ceramics with three-dimensional or gradient pores are still difficult to be manufactured.Additive manufacturing(AM), based on the principle of layer-wise forming, has advantages of needing no part-specefic tools and fixtures, and capability of building components with complex geometry. Therefore, additive manufacturing process of porous cordierite ceramics is studied in this article, including three dimensional printing and selective laser sintering. Using additive manufacturing to fabricate ceramic green parts and then using high temperature sintering to obtain the final porous ceramic parts with high porosity and complex geometrical structures.The effects of material composition, AM/high temperature sintering process parameters on microstructures, phase composition, mechnical properties, thermal expansion coefficient(CET), dimensional error, and porosity of porous ceramic parts were studied by SEM, X-ray diffraction,compressive strength tester, thermal dilatometer, and Archimedes methods. The main results are summarized as follows:(1) On the aspect of manufacturing cordierite/PVA porous ceramic parts by three dimensional printing, the process parameters were decided as grayscale 100%, and overlap ratio 50%. The SEM results showed that the interconnecting micro-hole network structures in whole part and nanopores at grain boundaries were observed. The XRD results showed that cordierite phase was obtained in gren parts and final parts after high temperature sintering. The results of mechnical property showed that the green parts had ductility, when the strain was 36%, the compressive strength arrived at 8.58 MPa, and the ductility disappeared after high temperature sintering. Compressive strength was increasing with the increase of sintering temperature. When the sintering temperature was 1425 ?, the compressive strength of final parts was 7.32 MPa, and the porosity was 59%. The dimensional error was different at diameter direction and height direction. The average dimensional error of height direction exceeded 5%, and the average error of diameter direction was about 2.3%. the results of porosity showed that the porosity of green parts was decreasing with the increase of the PVA content before sintering and increasing with the increase of the PVA content after sintering.(2) On the aspect of manufacturing cordierite/resin E12 porous ceramic parts by selective laser sintering, the optimized process parameters were determined as laser power(15 W), scanning speed(1500 mm/s), scanning space(150 ?m), layer thickness(150 ?m). The SEM results showed that powders with larger range of particle size distribution was beneficial to form binding neck of ceramic, thus improving the compressive strength. The XRD results showed that cordierite phase was obtained below 1400 ?, and cordierite phase decomposed into Mg O phase under 1450 ?. The results of mechanical property, porosity, and CET showed that when the sintering temperature was 1375 ?, the compressive strength was 8.92 MPa, the porosity was 59%, and the CET was 1.87 ×10-6/?(800 ?).(3) On the aspect of manufacturing cordierite/carbon fiber-resin E12 porous ceramic parts by selective laser sintering, the process parameters were optimized by orthogonal experiment method, and the parameters were determined as laser power(11 W), scanning speed(3000 mm/s), scanning space(120 ?m), layer thickness(150 ?m). Adding carbon fiber could enlarge the process parameters window effectively, and porous ceramic green parts were fabricated successfully under lower laser power and higher scanning speed, thus improving the accuracy. The SEM results showed that carbon fiber still existed below 1375 ?, and then disappeared with increasing temperature. The XRD results showed that cordierite phase was obtained in gren parts and final parts after high temperature sintering. The results of mechanical property, porosity, and CET showed that green parts with carbon fiber presented ductility, when the strain was 50%, the compressive strength was 2.3 MPa, and its ductility disappeared after high temperature sintering. When the sintering temperature is 1425 ?, the compressive strength was 5.48 MPa, the porosity was 62.26%, and the CET under 1400 ? was 1.87 ×10-6/?(800 ?).Finally, based on the above study, porous cordierite ceramic parts with three dimensional pores, which were difficult to be fabricated by conventional model shaping technology, were manufactured by optimized process parameters. This article provides a foundation for improving the properties of porous cordierite ceramic parts by structural design, thus promoting further applicaions of AM technology in porous ceramics industry.