Nanophase ceramics materials

An innovative strategy to enhanee the mechanieal properties of biodegradable polymers is the ineorporation of nanomaterials as fillers within polymer matrices. With the appropriate modifications to facilitate dispersion into polymers and to enhance interactions with the snrronnding matrix, nanocomposites have demonstrated improved mechanical properties compared with unfilled polymers or polymers loaded with larger, micrometersized particles. A few studies have also shown enhanced cell function when bone cells are cultured on nanophase ceramic materials. 

Thomas J. Webster, Nanophase Ceramics The Future Orthopedic and Dental Implant Material Yu-Ming Lin, Mildred S. Dresselhaus, and Jackie Y. Ying, Fabrication, Structure, and Transport Properties if Nanowires... 

Burggraaf, A. J., K. Keizer and B. A. van Hassel. 1989a. Nanophase ceramics, membranes and ion implanted layers. Paper read at S.I.C. Mat. 88-Nato ASl, Surfaces and interfaces of ceramic materials, 4-16 September 1988, lie d 01eron. 

NANOPHASE CERAMICS THE FUTURE ORTHOPEDIC AND DENTAL IMPLANT MATERIAL... 

Fig. 12. Schematic deformation properties of nanophase ceramics. For ceramics, decreasing the grain size into the nanometer regime corresponds to an increase in grain boundary sliding, resulting in increased ductility of these materials. (Adapted and redrawn from Siegel, 1994.)...

As the disciplines of cell-tissue engineering and nanophase material science develop and mature, the preceding design criteria will be expanded and refined. Undoubtedly, nanophase ceramics have great potential to become the next generation of choice proactive biomaterials for innovative biotechnology and biomedical applications that could have profound clinical impact. 

Metallic nanopartides were deposited on ceramic and polymeric partides using ultrasound radiation. A few papers report also on the deposition of nanomaterials produced sonochemically on flat surfaces. Our attention will be devoted to spheres. In a typical reaction, commerdally available spheres of ceramic materials or polymers were introduced into a sonication bath and sonicated with the precursor of the metallic nanopartides. In the first report Ramesh et al. [43] employed the Sto-ber method [44] for the preparation of 250 nm silica spheres. These spheres were introduced into a sonication bath containing a decalin solution of Ni(CO)4. The as-deposited amorphous clusters transform to polyciystalline, nanophasic, fee nickel on heating in an inert atmosphere of argon at a temperature of 400 °C. Nitrogen adsorption measurements showed that the amorphous nickel with a high surface area undergoes a loss in surface area on crystallization. 

The synthesis of nanophase ceramics is one of these concepts, it allows micro-porous ceramic materials with ceramic grains in the nanometer range to be obtained. Research in the field of nanophase materials is very active. A number of results on the control of microstructure and temperature stability of metal oxide ceramics can be applied to membrane preparation. Works carried out on non-oxide ceramics such as silicon carbide, silicon oxinitride or aluminum nitride should be regarded in order to extend the domain of available membrane materials. 

These membranes are achievable using the concept of nanophase ceramics. According to literature, this new class of materials can result from the emphasis of some new ceramic processes, such as the condensation of gaseous atomic clusters [30] or the sol-gel process [31]. This last method, which has been successfully applied to ultrafiltration membranes, was used recently to prepare ceramic nanofilters. Nanophase materials deal both with the nanometer-sized particle and with the nanometer pore size aspects. The nanopore aspect is central to membrane technologies because of the need for selective separation processes at the molecular level. 

To understand the importance of nanostructures in microsieving membranes, the basic structure of nanophased ceramics must be briefly described. Because the particles are extremely small, one to a few tens of nanometers, an important fraction of the atoms is found in or very near the interface between grains, as reported in Table 2 [32]. Figure 11 is a schematic representation of a nanophase material. One can see that individual grains in the 5 nm range induce a biphasic material with an interfacial phase between the grains and a residual nanoporosity, evidenced by positron lifetime spectroscopy [33]. Transmission electron microscopy is also a well-adapted technique for nanoscale structure characterization, as illustrated later. 

Concerning membranes, new separation capabilities are expected for these materials. The molecular sieving effect caused by connected nanopores can be applied to the separation of molecules with molecular weights smaller than 1000. The key properties of such membranes are based on the preponderant effect of activated diffusion in nanopores, however. This phase transport phenomenon derives from the nanophased ceramic concept and classes these membranes among those materials expected to be crucial in the areas of modem technology, such as environmental protection, biotechnology, and the production of effect chemical. 

Webster TJ. Nanophase ceramics the future orthopedic and dental implant material. In Advances in chemical engineering, vol. 27. New York Academic Press 2001. p. 125-66. 

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