F E A T U R E A R T I C L E Current understanding and future research directions at the onset of the next century of sintering science and technology Rajendra K. Bordia1 | Suk-Joong L. Kang2,3 | Eugene A. Olevsky4 1Department of Materials Science and Engineering, Clemson University, Clemson, South Carolina 2Korea Institute of Ceramic Engineering and Technology (KICET), Jinju, Korea 3Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea 4 Departmentof Mechanical Engineering, San Diego State University, San Diego, California Correspondence Rajendra K. Bordia, Department of Materials Science and Engineering, Clemson University, Clemson, SC Email: rbordia@clemson.edu Funding information US National Science Foundation Division of Civil and Mechanical Systems and Manufacturing Innovations NSF, Grant/ Award Number: CMMI 1502392, CMMI 1234114 Abstract Sintering and accompanying microstructural evolution is inarguably the most important step in the processing of ceramics and hard metals. In this process, an ensemble of particles is converted into a coherent object of controlled density and microstructure at an elevated temperature (but below the melting point) due to the thermodynamic tendency of the particle system to decrease its total surface and interfacial energy. Building on a long development history as a major tech- nological process, sintering remains among the most viable methods of fabricat- ing novel ceramics, including high surface area structures, nanopowder-based systems, and tailored structural and functional materials. Developing new and perfecting existing sintering techniques is crucial to meet ever-growing demand for a broad range of technologically significant systems including, for example, fuel and solar cell components, electronic packages and elements for computers and wireless devices, ceramic and metal-based bioimplants, thermoelectric materi- als, materials for thermal management, and materials for extreme environments. In this study, the current state of the science and technology of sintering is pre- sented. This study is, however, not a comprehensive review of this extremely broad field. Furthermore, it only focuses on the sintering of ceramics. The funda- mentals of sintering, including the thermodynamics and kinetics for solid-state- and liquid-phase-sintered systems are described. This study summarizes that the sintering of amorphous ceramics (glasses) is well understood and there is excel- lent agreement between theory and experiments. For crystalline materials, atten- tion is drawn to the effect of the grain boundary and interface structure on sintering and microstructural evolution, areas that are expected to be significant for future studies. Considerable emphasis is placed on the topics of current research, including the sintering of composites, multilayered systems, microstruc- ture-based models, multiscale models, sintering under external stresses, and inno- vative and novel sintering approaches, such as field-assisted sintering. This study includes the status of these subfields, the outstanding challenges and opportuni- ties, and the outlook of progress in sintering research. Throughout the manu- script, we highlight the important lessons learned from sintering fundamentals and their implementation in practice. - -- -- - -- -- - -- -- - -- -- -- - -- -- - -- -- - -- -- - -- -- - -- -- - -- -- - -- -- - -- -- -- - -- -- - -- -- - -- -- - -- -- - -- -- - -- -- - -- -- - -- -- -- - -- -- - -- -- - -- -- - -- -- - -- -- - -- -- - -- -- -- - -- -- - -- -- - -- -- - -- -- - -- This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. © 2017 The Authors. Journal of the American Ceramic Society published by Wiley Periodicals, Inc. on behalf of American Ceramic Society (ACERS) Received: 22 February 2017 | Accepted: 6 March 2017 DOI: 10.1111/jace.14919 2314 | wileyonlinelibrary.com/journal/jace J Am Ceram Soc. 2017 100:2314–2352.
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