Sinterability of Silicon Carbide and Boron Carbide under Single-Mode Microwave Fields
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JMEPEG https://doi.org/10.1007/s11665-020-04895-7
Sinterability of Silicon Carbide and Boron Carbide under Single-Mode Microwave Fields Selva Vennila Raju, Michael Kornecki, and Raymond E. Brennan (Submitted November 7, 2019; in revised form May 19, 2020) The feasibility of processing silicon carbide (SiC) and boron carbide (B4C) using a 2.45 GHz single-mode microwave system has been investigated. In order to determine the appropriate sintering conditions, samples were processed under various electric/magnetic (E/H) field ratios. Proportional 50% E/H-field ratios and 100% H-field conditions resulted in higher sample temperatures up to 1500 °C under equivalent microwave power. Sinterability was improved by adding B4C and carbon to SiC, but limited to a thin outer layer of the pellet. While partial densification was observed under all conditions, isolated regions of full densification in microwave-processed B4C samples were observed under 100% H-field mode. Microstructural analysis of microwave-processed SiC with and without additives indicated non-uniform sintering, while B4C showed evidence of relatively homogeneous microstructures. Keywords
carbides, microstructure, microwave processing, x-ray diffraction
1. Introduction Ultrafast sintering techniques such as microwave and flash sintering have gained interest in ceramic industries for their potential to significantly reduce processing temperatures and times, while influencing microstructural control and phase behavior (Ref 1-3). Microwave processing has led to rapid sintering of ceramics, metals, and ceramic–metal composites at drastically reduced temperatures compared to conventional sintering techniques. Processing times have been reduced from hours to minutes, while sintering temperatures have been lowered by several hundreds of degrees, yielding dense materials with finer grain structures. By avoiding the extreme conditions typically required to process advanced ceramic materials, energy savings and cost reductions have also been realized (Ref 3-7). Microwave susceptors, or absorbers, have also been introduced to improve coupling with microwave fields and enhance the heating response of selected samples. Carbon, for example, has been utilized as an excellent microwave susceptor (Ref 8-10), as it has demonstrated improvement in sinterability. Two ceramic systems that have been explored using microwave sintering include SiC and B4C, which are critical for use in protective systems that require low density and high This article is an invited paper selected from presentations at the ‘‘11th International Symposium on Green and Sustainable Technologies for Materials Manufacturing and Processing,’’ held during Materials Science & Technology (MS&TÕ19), September 29–October 3, 2019, in Portland, OR, and has been expanded from the original presentation. Selva Vennila Raju, Oak Ridge Associated Universities, Belcamp, MD; Michael Kornecki, SURVICE Engineering, Belcamp, MD; and Raymond E. Brennan, CCDC Army Research Laboratory, Aberdeen, MD. Contact e-mail: raymond.e.brennan.civ@ma
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