Research & Technical Programmes

Development of Ceramic Honeycombs

Looking at the vast application potential by the virtue of its unique configuration of Ceramic Honeycombs, centre has initiated the activity on extrusion processing of ceramic honeycombs and succeeded in producing a wide range of Shapes, Configurations, Compositions catering a variety of innovative Technologies/Products and Applications.

Range of Honeycombs Extruded at ARCI and Extrusion process

Technology Development Programmes based on Honeycombs

Ceramic Honeycomb based Air Heaters

In the area of honeycomb-based technologies, energy efficient air heater is one of the most innovative developments. The development initiated jointly by ARCI and a private entrepreneur was based on the innovative idea of weaving the heating elements through honeycomb channels and channelizing the airflow over the heating elements for energy efficient heating. As the honeycombs are required to withstand thermal shock and exposure to high temperatures while operation, a cordierite-based formulation, which can be incite reaction sintered from indigenous raw materials was developed. Further, depending on the volume of air flow, pressure drop and space requirements for heating elements within the channels, honeycomb dies which can extrude honeycombs with varying open frontal area were fabricated for optimum selections.

Honeycombs thus developed were supplied to the entrepreneur for the development of a weaving system based on their expertise. Weaved thermocombs were subjected to extensive trials where the concept was proved to possess the advantages of high thermal efficiency, channelized flow of air for maximum Heat Transfer, Compact Design, Low Thermal Inertia and Prolonged Life.

A joint Indian patent was granted vide IP No 200787 and the entrepreneur has also filed PCT for their innovative products. Further, as per the agreement the technology of honeycomb manufacturing developed at ARCI has successfully been transferred. Based on the expertise gained in producing thermocomb heaters the entrepreneur was granted a project under Techno Entrepreneur Promotion Programme (TEPP) of TIFAC, New Delhi to develop and demonstrate various prototypes.

Honeycomb Air-Heaters

Ceramic Honeycombs for Molten Metal Filters

Honeycomb based molten metal filters are another interesting development. The concept of molten metal filtration using ceramic filters is well practiced as an effective way to reduce the process scrap that results from unwanted inclusions in the finished castings. Molten metal filtration, pose a unique set of Thermal, Mechanical and Design Challenges. The filters thus developed, cater to high temperature (>1450°C) application requirements using zirconia-spinel formulations and cordierite mullite filters for low temperature melts. The technology is being transferred to an industry and supplied samples are presently undergone successful trials at various foundries.

Zirconia and Cordierite - Mullite Filters and the Filters after Trial

Ceramic Honeycombs for Thermal Management

Honeycomb based thermal management is another area the centre is working on with an innovative concept under SERC scheme. The thermal conduction () of a honeycomb can be represented as shown in the figure and can be defined as = s + g + c + r where s Conduction through the solids, g Conduction through the gas, c Convection within the cells r Radiation through the cell walls and across the cell voids. The contribution of heat transmission by conduction is the combined effect of the product of thermal conductivity of solid, s and its volume fraction (*/s) plus the conductivity of air, air and its volume fraction in the honeycomb (1-*/s). Honeycomb panels designed are also shown below.

Ceramic Honeycombs for Solid Oxide Fuel Cell (SOFC)

Nickel oxide and Zirconia based honeycombs Produced and which are being coated by electrophoretic deposition for SOFC applications.

Project Team on Cellular Ceramics (Dr Roy Johnson, Mr B. P. Saha)

Ceramic Crucibles for Carbon and Sulphur Analysis

High thermal shock and slag erosion resistant crucible for carbon and sulphur analysis is another development, which the centre has undertaken and developed at par with imported crucibles. Technology has been transferred to a private industry and is in commercial production. Typical test results along with the crucibles are shown below.

Project Team (Dr Roy Johnson, Mr B. P. Saha)

Development of Spinel Grain for Refractory Applications

Refractory ceramics is another area this centre has been involved with in the last few years. Magnesium Aluminate Spinel developed by double stage sintering process is transferred to a private industry that established a 25 crore project with a production capacity of 6,000 MT/annum.

Project Team (Dr Roy Johnson, Mr B. P. Saha and Dr I. Ganesh)

Development of Wear Resistant Alumina Tiles

Wear resistant alumina tiles developed using indigenously available low-cost raw materials have exhibited excellent wear properties in dry/wet conditions. The tiles with the optimised composition are sintered through liquid phase sintering. The technology is patented and is ready for transfer.

Project Team (Dr Roy Johnson, Mr B. P. Saha)

Nanopowder Synthesis by Spray Pyrolysis

In the area of nanoceramics, centre has recently set-up a facility based on spray pyrolysis presently optimized to produce doped zinc oxide and lanthanum strontium manganese for lightning arrestors and Solid Oxide Fuel Cell Applications. Typical powder characteristics of the powder produced and classified by the vortex are shown in Figure.

Phase Pure LSM; SEM showing Particle Size; Spray Pyrolyser Water Evaporation Capacity - 7 kg/hr

Centre has also acquired a nano powder granulation facility with aqueous and organic medium leading to engineered granule morphology depending on the applications. Surface modified granules are characterized for their flow behavior and are further compacted to a green density > 50% TD for sintering studies.

Dense Alumina Granules; Hollow Alumoxane Granules; Spray Drier

Project Team (Dr Roy Johnson, Dr Y. S. Rao and Mr P. Ramavath)

Rate Controlled Sintering of Ultra Fine Powders

Grain growth associated with sintering of ultra fine nano powders poses serious problem for the development of structural ceramics with improved mechanical properties. On addressing this critical issue through the non-conventional techniques, Rate Controlled Sintering (RCS) is now being looked upon as a viable process to control the grain growth. RCS methodology basically involves a careful choice of the sintering schedule that controls the massive structural change during the various stages of sintering which is essential to accomplish the twin objectives of full densification and sub micrometer sintered grain sizes. The mechanism involves extension of pore closure through the application of extremely low shrinkage rates at the final densification regime where there is logarithmic dependence of densification with shrinkage rate. The feedback established between the shrinkage rate and instantaneous temperature facilitates the derivation of a temperature-time path best suited to achieve the twin objectives.

Nanosized zirconia powders, surface modified using Trioxodecanoic acid having an average particle size of 30 nm (ZP4, INM Germany), were ground, sieved and compacted to discs using PVA as binder. The samples were first subjected to dilatometry at different heating rates and the RCS protocol was derived from the shrinkage curve thus obtained. Fig below shows the microstructure obtained on zirconia samples sintered under RCS conditions. The average sintered grain size is less than 100nm, which is normally not achievable for conventional sintering methods.

Project Team (Dr Roy Johnson and Dr U. S. Hareesh)

Development of Calcium Aluminate Cements

On refractory ceramics, the Centre is working on monolithic castable materials such as calcium aluminate cements and dense mullite aggregates. Furnace coats based on zircon is also being developed at ARCI. These technology developments undertaken for a private entrepreneur is expected to be transferred shortly.

Project Team (Dr Roy Johnson, Dr Y. S. Rao and Dr U. S. Hareesh)

Transparent Ceramics

The Centre is also working in the area of transparent ceramics based on sintered submicron Polycrystalline Alumina, Aluminium Oxynitride and Zinc Sulphide. Attempts are being made to produce transparent ZnS through chemical vapour deposition and alumina and aluminum oxy nitride ceramics through HIPing.

Project Team (Dr Roy Johnson, Dr U. S. Hareesh, R. Senthil Kumar, P. Ramavath and P. Biswas)

Gel Casting

Centre also developed expertise in the area of gel casting of alumina ceramics looking at the capability to produce complex shapes. Crack free samples of alumina with micro hardness up to 23 GPa have been successfully produced at the centre.

Project Team (Dr Roy Johnson, Dr U. S. Hareesh, P. Biswas and R. Senthil Kumar)

Development of Zirconia, Zirconia Toughened Alumina

In the area of Zirconia, Zirconia Toughened Alumina and alumina the centre has developed the products such as spacers, Ingots and hydrocyclones, wear resistant tiles as per the requirements from the user industries. Centre is presently receives recurring orders for mass supply of these components which is taken up from time to time by this centre.

Project Team (Dr Roy Johnson, Mr B. P. Saha)