8-9th August, 2008 School of Materials Science & Nanotechnology,Jadavpur University
Ceramic Nano Materials – Synthesis and Applications
N. Bandyopadhyay, P. Halder, Ms. D. Bhattacharya and S.Maitra
Govt. College of Engineering and Ceramic Technology
73, A. C. Banerjee Lane
Kolkata-700010
By definition, nano ceramic materials include different oxide and non-oxide ceramic materials, silicates, hard metals and composites. Among these some materials like tungsten carbide are already in use. For some materials like, ZrO2, TiO2, ZnO etc already mass production of the powders have been started. For some materials like Si3N4 , Y2O3, CeO2, BN, SiC etc , powders haven been developed in different laboratories, basic researches are still continuing and early applications have been started. For some materials like AlN, TiN, MgAl2O4, YBa2Cu3O7-x, ZrO2-Y2O3, ZrO2-MgO etc, powders are commercially available. In general, Nanocrystalline materials exhibit increased strength/hardness, enhanced diffusivity, improved ductility/ toughness, reduced density, reduced elastic modulus, higher electrical resistance, increased specific heat, higher thermal expansion coefficient, lower thermal conductivity, and superior soft magnetic properties in comparison to conventional coarse-grained materials. Since nanocrystalline materials contain a very large fraction of atoms at the grain boundaries, the numerous interfaces provide a high density of short-circuit diffusion paths.
The enhanced diffusivity can have a significant effect on mechanical properties such as creep and superplasticity, and ability to efficiently dope nanocrystalline materials with impurities at relatively low temperatures. The increased diffusivity leads to increased solid solubility limits and increased sinterability of nanocrystalline powders.
The methods commonly employed to synthesize these materials include both the top-down approach (breaking up larger microparticles by external forces) and the bottom-up approach (by chemical route). The latter is more effective since it provides a substantially wider spectrum of possibilities. Furthermore, by chemical bottom-up high purity narrow size products can be obtained impurities introduced by comminution steps are prevented. The chemical synthesis routes can be further divided into liquid-solid transformations (e. g. sol-gel processing, co-precipitation, micro emulsion routes, electrochemical deposition or decomposition of liquid precursors) and gas-
solid transformations (e. g. inert gas condensation, plasma processing, laser ablation or flame pyrolysis). Generally, the latter yield less agglomerated nanoparticles.
The main present challenge in the synthesis of nano particles is their up-scaling from lab scale to standard production Although nano-ceramic products are already in the market (ceramics made of oxide nanomaterials, light filter substances, effect pigments, coatings, data storage layers, etc.), most areas of nanotechnology are still in the basic research stage. But it is expected that the applications of nanoceramics in the fields of optics, precision engineering, analytics, chemistry, automotive and mechanical engineering, materials management and medical engineering, pharmaceutics and biology will be increasing in the near future.
In this paper a comprehensive review on the successful synthesis process of different nanoceramics and their applications in new areas has been made.
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[e-mail of corresponding author: bandyopadhyay_n @rediffmail.com]
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