A series of boron suboxide films with hardness higher than 40 GPa was prepared and characterized. The correlation between OB ratio and mechanical properties, both hardness and elastic modulus were analyzed. Our studies on beta r-B, B2O3, surface oxidation of betar-B, and B6O illustrate that an XPS peak shift can be caused by a change in chemical state and bonding configuration. The shifts of B 1s peaks provide some good evidence to substantiate this conventional wisdom of XPS. We have applied this concept to enrich our XPS studies of boron and BxO y, and indeed found an intriguing variety of surface and interfacial physical conditions of those samples. / In our study, three boron nitride (BN) samples, the c-BN, h-BN and a-BN were prepared to serve as the standard specimens. And also, a series of thick BN films with different cubic phase content were prepared using a dual-ion beam assisted deposition (DIBAD) system. A quantitative method to measure the various phases content in BN film by the deconvolution of the energy loss features of N 1s signal was established. The feasibility of this method was proved by comparing the results with the results from FT-IR. To our understanding, this method has never been reported. / Many mechanical applications constantly demand superhard materials. Commonly a material is qualified as "superhard" when its microhardness exceeds 40 GPa. Therefore, great efforts have been made to search for other materials with high hardness in the past several decades. In the design of superhard materials, boron is a peculiar element/constituent. c-BN that possesses the zinc-blende structure shows numerous highly desirable mechanical properties, especially the high hardness and chemical inertness. Boron often exhibits three-center two-electron bonds in addition to the common two-center two-electron bonds. This overall bonding configuration must be very effective as shown by the high hardness of solid boron at 35 GPa. When impurities with more valence electrons than boron are added to pure boron, the overall mechanical strength can be further enhanced. By incorporation of oxygen, a family of hard boron suboxide compounds is thereby formed such as B6O. / Zheng Bin. / "August 2005." / Adviser: Chan Man Chor. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6427. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_343730 |
| Date | January 2005 |
| Contributors | Zheng, Bin, Chinese University of Hong Kong Graduate School. Division of Chemistry. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (ix, 142 p. : ill.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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