Fabrication of cellular NiTi intermetallic compounds
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Fabrication of cellular NiTi intermetallic compounds Bing-Yun Li, Li-Jian Rong, and Yi-Yi Li Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110015, People’s Republic of China
V.E. Gjunter V.D. Kuznetsov Siberian Physical Technical Institute, Tomsk, 634050, Russia (Received 10 August 1999; accepted 1 November 1999)
Self-propagating high-temperature synthesis (SHS) has been successfully developed for the fabrication of cellular NiTi intermetallic compounds, which have an open cellular structure with about 60 vol% porosity and more than 95% open-porosity ratio. The SHS reactions lead to the formation of TiNi, Ti2Ni, Ni3Ti, and Ni4Ti3 intermetallics. The SHS process can be controlled by regulating the preheating temperature, which has effects on the phase amount and the shape as well as macrodistribution of pores in the products.
There is a growing need for fabrication of artificial hard-tissue replacements. The biomaterials industry worldwide has an annual turnover of $2.3 billion in the field of hard-tissue repair and replacement (total of $12 billion). There is currently an increasing growth rate of 7–12% per annum for biomaterials in clinical applications.1 Several nonmetallic materials have been proposed as candidates for artificial bones and/or teeth, but none has found wide applications. Due to their low reliability, especially in wet environments, materials such as hydroxyapatite-based biomaterials cannot presently be used for heavy load-bearing applications (like artificial bones or teeth).2 Metals have been widely used for major load-bearing applications. There are, however, various problems related to normal metallic materials in the human body due to physical properties, corrosion, wear, and/or negative tissue reaction.3 Appropriate hard-tissue replacement implants should achieve a match of mechanical behavior with the tissue to be replaced.4 It is almost certain that cellular materials permit the simultaneous optimization of stiffness, strength, and overall weight in a given application. Cellular materials are naturally load-bearing materials; for example, nature often uses cellular materials such as wood, bone, and coral as load-bearing materials. Recently, cellular NiTi intermetallic compound has been acknowledged as a most promising biomaterial for use as artificial bones or teeth roots because of its special pseudoelasticity, which can accommodate the deformation behavior of hard tissue, and its attractive combination of properties such as excellent mechanical properties, good corrosion resistance, biocompatibility, and shape-memory effect.5–6 Moreover, its cellular structure allows the ingrowth of bone tissue and is favorable for the fixation of the im10
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J. Mater. Res., Vol. 15, No. 1, Jan 2000 Downloaded: 27 Jan 2015
plant as well as the transport of body fluids. In addition, by obtaining different porosity and pore sizes through controlling the synthesis conditions, it is easy to adjust the mechanic
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