Story of the Week  
Novel Ceramics
 

The last few decades have seen sustained global efforts directed towards the development of new materials with improved and novel properties. Structural ceramics are one of the classes of new generation materials, which have generated immense interest in the materials community. They are deemed to replace some of the existing materials in various demanding applications viz. high temperature structural applications, heavy duty wear applications, machining applications, applications in space shuttles and rocket engines and lately in biomedical applications. The high hardness, elastic modulus, strength retention at high temperature, coupled with chemical inertness as well as biocompatibility of most ceramic materials is the driving force behind their increasing applications.

Dr. Basu's research is focused on the development and characterization of such new generation materials. His contributions are largely on the understanding of the toughening mechanisms and the development of novel composites. The notable among them is the development of ZrB2/TiB2 reinforced ceramics based on relatively tougher zirconia. Apart from zirconia, extensive research is being carried out related to the processing and characterization of difficult to sinter titanium-diboride/WC-based materials with suitable ceramic sinter-additives. Extremely high hardness (>20 GPa i.e. three times harder than fully hardened structural steels) along with moderate fracture toughness (~5 MPa m1/2 ) is achieved with TiB2 -MoSi2 and WC-ZrO2 materials. Relatively tougher ceramics based on Ti3 SiC2 and SiAlON also form a part of the ongoing research in the laboratory for advanced ceramics.

One of the major motivations for the development of structural ceramics is the tribological application, which involves critical study of the friction and wear behavior. The characteristic high hardness and strength of ceramic materials make them potential candidate for use in heavy duty wear parts. The coefficient of friction, mechanisms of material removal and optimization of composition to improve the wear behavior form the major areas of study in our laboratory. For example, the friction and wear related failure significantly limit the life of bearings, used in space shuttle main engine. Till to date, research in this direction was limited mainly due to the unavailability of high-speed tribometers suitable for testing under cryogenic conditions. Recently, a new high-speed tribometer has been designed and installed at IIT-Kanpur, India, for tribological testing at high speeds (up to 36,000 rpm) in cryogenic environment. Such a testing facility has enabled us to investigate the fundamental deformation and fracture mechanisms of brittle materials in cryogenic environment. A recent research collaboration with ISRO scientists has been initiated in the field of cryo-tribology, and high speed sliding wear tests (upto 36000 rpm) has been conducted on martensitic steel (SUS440C, AISI304L) as well as on brittle materials like alumina, yttria-stabilised zirconia etc.

The subject of nanomaterials has also attracted attention of researchers enormously in laboratory for Advanced Ceramics. In collaborative work with scientists from Seoul National University, South Korea, a novel processing technique i.e Spark plasma sintering, has been used to develop various nanoceramic materials like 3Y-TZP, ZrO2/ZrB2, and WC-ZrO2 nanocomposites. The property evaluation demonstrated much better wear resistance of the novel ceramic composites. It has been found that WC/ZrO2 nanocomposite has the potential of replacing conventional WC/Co cermets in various applications.

Biomaterials' is another field of our recent interest. We are now engaged in developing different materials viz. bioinert ceramics, like stabilized zirconia, bioactive ceramics like Hydroxyapatite/Calcium Phosphate based composite. In our research, novel composite composition (HA-based) has been formulated and such materials have been obtained with optimal density using advanced sintering route, like microwave sintering. In collaboration with scientists from Biological and Bioscience Engineering (BSBE), IIT-Kanpur, we have been able to demonstrate that the newly developed bio-ceramic composites have good cell adhesion properties. Our future research will strive towards the development of ceramic-polymer biocomposite as well as HAP-based coatings.

Professor Bikramjit Basu
Department of Materials and Metallurgical Engineering
    Email: bikram@iitk.ac.in

More information about the activities of Professor Bikramjit Basu and Laboratory for Advanced Ceramics can be found at http://www.iitk.ac.in/ceramiclab and http://home.iitk.ac.in/~bikram

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