Ultraprecision Silicon Carbide Polishing Researchers Win Rudolf Kingslake Medal

Three researchers from PLA University of Science and Technology and two from the Research Center for Ultraprecision Science and Technology of Osaka University are recipients of the annual Rudolf Kingslake Medal and Prize. The award is presented annually to the most noteworthy original paper published in Optical Engineering, by SPIE, the international society for optics and photonics.

Xinmin Shen, Qunzhang Tu, Guoliang Jiang, Hui Deng, and Kazuya Yamamura are the authors of the winning paper, “Mechanism analysis on finishing of reaction-sintered silicon carbide by combination of water vapor plasma oxidation and ceria slurry polishing.” It was published in the May 2015 issue of the journal. The award will be presented at an awards banquet on 31 August during SPIE Optics + Photonics in San Diego.

Reaction-sintered silicon carbide (RS-SiC) has robust mechanical, chemical, and thermal properties, making it ideal for applications in space telescope systems and as ceramic material used for molds of glass lenses. Some of these properties include a low thermal expansion coefficient, high thermal conductivity, high radiation resistance, high specific stiffness, and impressive bending strength.

Due to the compound’s high level of hardness and chemical inertness, researchers have run into a few challenges including the removal of RS-SiC post-application, which is very difficult using traditional mechanical and chemical techniques.

Smoothing and finishing of a RS-SiC surface has also proved to be a difficult task. The most promising and effective method so far involves a two-step process of water vapor plasma surface oxidation for 90 minutes shown in the paper’s Fig. 3 (a), followed by 40 minutes of ceria slurry polishing on the oxidized layer shown in (b) [below]. Once an ultra-smooth surface has been achieved, the compound can be further developed and/or promoted for application in the fields of optics and ceramics.

The proposed technique is "a low-cost, efficient, and simple process, and the oxide layer is easy to machine, which can be an attractive technique for the machining of RS-SiC, RB-SiC, HP-SiC, and other SiC products by further development," say the authors.

The material is challenging to fabricate due to its high hardness, chemical durability, and grain structure, saidOptical Engineering associate editor Jessica DeGroote Nelson. "The approach described by the authors combines precise chemical and mechanical processes utilizing plasma etching and cerium oxide polishing to provide ultrasmooth surfaces on RB-SiC," she said.

DeGroote Nelson also noted that this unique material removal approach may also prove beneficial on other types of SiC in the future.

Xinmin Shen is a lecturer at PLA University of Science and Technology. He received his BS, MS, and PhD degrees in mechanical engineering from National University of Defense Technology (NUDT) and did additional studies at Osaka University. He is the author of more than 20 papers. His current research focuses on the ultraprecision machining of optical components.

Kazuya Yamamura is an associate professor at Osaka University, where he received his PhD degree in engineering. His research area is development of unconventional ultraprecision manufacturing process and its application, such as figuring, finishing, functionalization, utilizing reactive plasma or electrochemical process.

Deng Hui obtained his PhD degree in precision engineering from Osaka University. He is now a scientist of Singapore Institute of Manufacturing Technology. His research is focusing on hybrid machining using atmospheric pressure plasma.

Michael Eismann, Chief Scientist, Sensors Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, is editor-in-chief of Optical Engineering. The journal is published in print and digitally by SPIE in the SPIE Digital Library, which contains more than 430,000 articles from SPIE journals, proceedings, and books, with approximately 18,000 new research papers added each year.