Centre for Non-Oxide Ceramics (CNOC)
Gel casting is a near net shape colloidal processing technique for ceramics which can be adapted to develop ceramic products having various size and shapes. This technique offers advantages of machining intricate shape ceramic parts in green condition. It is possible to tailor the properties of ceramics in terms of density, mechanical properties by tailoring the composition and processing parameters. ARCI has developed SiC, Si3N4 and SiAlON products in prototype scale with the help of gel casting process and successfully sintered the products without any warpage or defect.
- Near-net processing of complex shapes.
- Green machining
- Scalable to large size.
- Cost effective.
- Non-oxide based crucibles for metallurgical industry.
- Electromagnetic windows.
- Cellular SiC product for solar receiver applications.
- Up-scaling is in progress for large size products.
Ready-to-press silicon carbide (RTP SiC) granules is being produced using spray drying or spray freeze drying technique through an intermediate aqueous processing route. This method is capable of producing different size spherical shaped granules with narrow size distribution and free flow properties. As the granules are produced from uniformly dispersed aqueous slurries of SiC powder, hence wide range of additives can be accommodated in the formulation of the RTP granules. This process is beneficial to manufacture the feedstock for producing green SiC compacts with high density and defect free homogenous microstructure. The sintered products thus produced exhibit superior properties than conventionally produced SiC.
- Cost effective technique to produce RTP SiC granules.
- Flexibility to incorporate either solid-state or liquid-phase sintering additives in the formulation of RTP granules.
- Control on granule size with narrow distribution
- The process can be adopted for manufacturing various oxide or non-oxide ceramics.
- Feedstock for manufacturing of SiC components
- RTP granules processed in the laboratory scale
- Scaling up the process is in progress
Major Patents / Publications
- P. Barick, B. P. Saha, S. V. Joshi and R. Mitra, Spray-freeze-dried nano-crystalline SiC containing granules: processing, compaction behaviour and sintering, J. Euro. Ceram. Soc., 36 (2016), 3863-3877
Silicon carbide (SiC) is one of the most attractive ceramic materials because of its excellent mechanical properties such as high strength, moderate toughness, and high wear and oxidation resistance, and strength retention at elevated temperature. ARCI has the expertise to manufacture SiC parts with various size and shapes by pressureless sintering using solid-state or liquid phase sintering additives and also by hot pressing technique. SiC parts of complex geometry can also be manufactured through machining at the green stage using 5-axis CNC machine. Dimensional accuracy can also be achieved on sintered SiC parts by final shaping with the help of sophisticated ultrasonic machining.
- Tuneable density and other thermo-mechanical properties.
- Flexibility in producing SiC parts incorporating solid-state or liquid phase sintering additives.
- Capable to produce SiC components up to 750 mm diameter.
- SiC parts with critical can be manufactured.
- Mechanical seals particularly for corrosive environment.
- Impact and abrasion resistance parts.
- Light-weight structural parts for aerospace applications.
- Impact and wear resistant parts.
- The technology has been validated for production of SiC parts by pressureless sintering and available for technology transfer.
Theoretically dense SiC processed by chemical vapour deposition (CVD) exhibits superior physical, mechanical, thermal and optical properties with excellent wear, abrasion and chemical corrosion resistance. The properties of CVD SiC coating can be tailored by control of various parameters including reactor design, process temperature, pressure, reactants composition and flow geometry. ARCI has established a CVD system for coating of large size components (up to 1.0 m meter) by thermal deposition of methyl-trichlorosilane (MTS) in excess of hydrogen. High density CVD SiC coating on various substrates with different geometries have been produced. It has been demonstrated that the CVD SiC coating can be polished up to the RMS surface roughness < 1 nm. ARCI also has the capability to produce self-standing CVD SiC parts.
- State-of-the art CVD SiC coating facility.
- The processes technology has been established
- SiC coating on different size and shapes can be produced.
- CVD SiC coating can be polished to very high surface finish.
- Reflectors for high energy laser and synchrotron radiation.
- Wear and corrosion resistant coatings
- Reflectors for concentrated solar power (CSP) applications
- Solar collectors and concentrators for astronomical telescopes.
- Solar collectors and concentrators for astronomical telescopes.
Cellular SiC ceramics are used as volumetric absorber in the generation of large amounts of electricity by concentrated solar power (CSP) technology because of their unique advantages of excellent mechanical, thermal, high temperature oxidation resistance and solar radiation absorption properties. SiC foam and honeycombs in CSP application can effectively absorbs the solar radiation and transfer the absorbed energy in terms of heat to the working fluid (usually air) which generates steam for spinning turbines in electricity generation. The operating temperature of working fluid can be increased to 1000°C or above by use of SiC based volumetric receivers. Presently, ARCI is actively pursuing R&D for development SiC honeycombs and foams with tuneable properties suiting for volumetric receiver.
- Capable of handling working fluid temperature up to 1200°C and high thermal conductivity.
- Tuneable permeability and mechanical properties due to the various foam configuration.
- Excellent optical properties (high absorptivity and moderate emissivity).
- Cost effective aqueous processing and scalable technology.
- Volumetric solar receiver.
- Hot gas and molten metal filters.
- Light-weight substrates for optical applications.
- Molten metal filters.
- Preliminary R&D shows encouraging results and laboratory scale samples are produced for properties evaluation.
SiC tubes have emerged as potential candidate material in the area of concentrated solar power generation, heat exchangers for recovery of heat from industrial waste, fuel cladding in nuclear reactors because of superior thermos-mechanical properties, high thermal conductivity, resistance to chemical attack and nuclear radiation. ARCI has developed the process for producing SiC tube by extrusion as well as cold iso-static pressing technique followed by sintering.
- Extrusion press is capable of producing long tubes of different diameter and wall thickness.
- High production rate.
- Process flexibility to produce dense and porous SiC tubes.
- Tubular solar receiver in CSP technology.
- Heat exchanger.
- Nuclear fuel cladding tubes.
- Support tubes in membrane separation.
- SiC tubes produced by both extrusion and cold-isostatic pressing have been produced and properties tubes are being evaluated.