Microstructural Development of TiB 2 Ion Implanted with 1 Mev Nickel
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MICROSTRUCTURAL DEVELOPMENT OF TiB 2 ION IMPLANTED WITH 1 MEV NICKEL* P. S. SKLAD, P. ANGELINI, M. B. LEWIS, AND C. J. McHARGUE Metals and Ceramics Division Oak Ridge National Laboratory, Post Office Box X, Oak Ridge, TN 37831 ABSTRACT An Analytical Electron Microscopy (AEM) investigation of polycrystalline TiB 2 implanted with 1 MeV Ni+ to 1 x 2 1021 ions/m has shown that the implanted region remained crystalline and showed no evidence of precipitation. A region containing tangled dislocations extended from the implanted surface to -500 nm. Between -500 and 750 nm, the microstructure was more complicated and could be indicative The maximum of a high density of 5 to 10 nm diam defects. nickel concentration determined by energy dispersive spectroscopy (EDS) occurred at -450 nm, slightly deeper than the calculated depth of 390 nm. Observations after in situ annealing revealed cavities and nickel-rich precipitates. Radiation damage models are invoked to explain the microstructures observed. INTRODUCTION It is well known that many of the properties of ceramics are controlled by the condition of the specimen surface. For example, fracture toughness can be improved with the application of compressive surface stresses, oxidation resistance may depend critically on the presence of a protective surface layer, and wear resistance may be enhanced by improving the response of the surfaces to contact stresses. Surface modification techniques which have been successfully applied to a number of metals and semiconductors in recent years, offer the potential for overcoming some of the surface related limitations on the use of ceramics. Specific applications include structural materials in advanced energy conversion systems where high operating temperatures and highly reactive environments may be encountered. The research emphasis at ORNL is on A12 03 implanted with Cr, Zr, Ti, Ni, and Fe, SiC implanted with Cr and Zr, and TiB 2 implanted with Ni and Zr. The present study is concerned with the microstructure produced by The experimental program includes not implanting TiB 2 with 1 MeV Ni+ ions. only characterization of the as-implanted microstructure but also studies of the stability of the microstructure during exposure to elevated temperatures with the purpose of determining the mechanisms by which these microstructures are altered. In this respect, comparison of the experimental observations with predictions of radiation damage models of microstructural development has been useful. Such information is important to the development of surface modified ceramics for use in elevated temperature applications and will form a basis on which ion implantation techniques may be used to successfully tailor surface characteristics of this class of materials.
*Research sponsored by the Division of Materials Sciences,
U.S. Department
of Energy under contract W-7405-eng-26 with the Union Carbide Corporation.
Mat.
Res. Soc. Symp. Proc. Vol.
27 (1984) oElsevier Science Publishing Co.,
Inc.
408
MATERIALS AND PROCEDURES Specimens of TiB 2
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