Centre for Ceramic Processing (CCP)
Initiated activities on porous burner based energy efficient heating systems and successfully stabilized the flame using ceramic foams.
Successfully stabilized alumina based advanced ceramic slurry for pressure casting application and grinding balls upto 50mm diameter were cast and sintered. The samples achieved >99% of TD as shown in the figure.
High temperature oxide based ceramic tubes with engineered porosity and pore size distribution was developed through addition of pore formers. Extrusion process developed to shape tube up to 300mm length and 80mm diameter with 5-7mm wall thickness for thermal management applications.
Magnesium aluminate spinel based scaffolds are processed and being evaluated for the biocompatibility with INMAS (DRDO). Initial results are found encouraging.
Honeycomb-shaped Solid Oxide Fuel Cell (HCSOFC) design is considered to be one of the innovative concepts for the miniaturization of cell size because of its monolithic structural advantages. The major difficulty in exploiting the Solid Oxide Fuel Cells (SOFC) commercially is the long start up time for which various cell configurations are proposed to arrive at practical solutions. HCSOFC is one of the most promising designs among the proposed configurations due to their low relative densities and inherent high geometrical and active surface areas. In the present study, Ni- 8YSZ honeycombs fabricated by the extrusion process were coated with Zirconia Electrolyte and Lanthanum Strontium Manganate (LSM) cathode. Honeycomb structures due to its unique monolithic structures, maximum heat capacity per unit weight by the virtue of its low relative densities and high surface to volume ratio in comparison to the solid counter parts permits rapid heat transfer leading to quick start up times and reduced thermal gradients contributing towards better efficiencies. Thus honeycomb based structures due to their unique configuration and in combination with the flexibility in processing can be explored for the development of novel and compact designs of solid oxide fuel cells with enhanced performance.
Transparent ceramics, a new class of advanced functional materials, find diverse applications in strategic and civilian sectors owing to the unique combination of mechanical and transmission properties. The prerequisites for obtaining transparency in combination with superior mechanical properties are to achieve the microstructural tailoring and a density close to near theoretical (99.95%) values. The Centre's expertise in shaping and sintering have made it possible to tailor the Physico-chemical and microstructural properties of a wide range of advanced ceramics to achieve desirable optical transparency. The transparent ceramic systems, which are explored currently, include transparent polycrystalline sub micron alumina (Al2O3), aluminium oxynitride (AlON), spinel (MgAl2O4) and zinc sulphide (ZnS) ceramics. The Centre is also capable of shaping transparent ceramics into complex shapes including honeycomb structures and high luminous discharge lamp envelops.
Current and potential applications of ceramic honeycombs ranges from high surface area supports for heterogeneous catalysis especially for environmental control, biotechnology and biomedical applications, molten metal filtration, gas particulate filtration, acoustic transfer in ceramic surface burners, energy conservation and heat transfer, solar radiation conversion, aerospace etc. The Centre has involved in the development of a variety of honeycomb based technologies and products. Out of the various honeycomb based technologies developed at ARCI energy efficient air heaters is one of the most interesting developments based on the innovative idea which, utilizes honeycombs fabricated out of cheap insulating ceramic material for channelizing the airflow over the heating elements weaved through the channels in collaboration with M/s. Sowbal Aerothermics, Hyderabad. Honeycomb based molten metal filters is another interesting development, which caters high temperature melts (>1450oC) using zirconia: spinel and low temperatures through cordierite mullite filters. Low expanding cordierite based honeycombs for pollution control, zirconia based honeycombs for thermal management and cordierite: mullite honeycombs for mechanical shock attenuation are some of the other interesting areas being developed at this Centre.
Colloidal shaping technique involves the consolidation of well dispersed slurries which offers the advantage of near net shaping especially for complex shaped ceramic bodies. Conventional slip casting is proven for centauries for ceramic forming which employs Plaster of Paris moulds and the casting is carried out under atmospheric pressure. However, recent developments in durable polymer mold not only offer the possibility of casting under controlled pressure but also the mechanization of the process. Additionally, the process provides high efficiency, reduced water content of the cast, better green strength and complex shaping capability with respect to hollow and solid articles. Pressure casting is presently well established in the traditional ceramic processing nevertheless in the area of advanced ceramics attempts have resulted in limited success. Unlike traditional clay based ceramics, advanced ceramics pose improper alignment of particles and mechanical interlocking resulting in serious problems while de-molding. The Centre is therefore exploring the possibility of pressure casting of advanced ceramics for fabrication of complex shapes.