Additive Manufacturing of Ceramic Products Based on Millimeter-Wave Heating

Abstract Additive manufacturing of ceramic articles making use of concentrated energy flows attracts the research interest worldwide. While the application of laser beams faces serious problems associated with high temperature of sintering and low thermal conductivity of ceramics, layer-by-layer sintering by focused millimeter-wave radiation appears to be a promising method of additive manufacturing. This paper describes the studies of fast millimeter-wave sintering of yttria-stabilized zirconia and hydroxyapatite ceramics. Coefficients of the millimeter-wave absorption have been determined in broad frequency and temperature ranges. Rapid sintering of compacted ceramics samples was accomplished using volumetric microwave heating in a work chamber of a 24 GHz / 5 kW gyrotron system. In addition, using a 263 GHz / 1 kW cwgyrotron millimeter-wave source and a purposely designed electrodynamic focusing structure, radiation intensities of up to 20 kW/cm2could be achieved, which was sufficient for fast localized heating of ceramic layers to the solidification temperature. The results of a study of the microstructure and mechanical properties of the sintered ceramics are presented.</jats:p

Microwave assisted synthesis of barium zirconium titanate nanopowders

This article is closed access.The paper reports the synthesis, structural and high frequency dielectric properties of Ba(Zr x Ti1−x )O3,BZT, nanopowders where x = 0, 0.1, 0.2, 0.3. These powders were synthesized using both microwave assisted and conventional heating, with the former requiring lower temperature and shorter times compared to the latter, viz., 700 °C for 30 min versus 900 °C for 5 h. The synthesized nanopowders were characterized using X-ray diffraction, micro-Raman spectroscopy, transmission electron microscopy, BET surface area analysis, differential scanning calorimetry and high frequency dielectric measurements. All the microwave synthesized BZT compositions were found to have well crystallized, finer nanoparticles with less agglomeration and higher dielectric permittivity compared to the conventionally prepared powders. The rapidity and less demanding processing conditions associated with the microwave assisted method augers well for the general applicability of the technique for the production of nanocrystalline powders