|
|
|
Expertise |
|
 Synthesis of nano materials by sol-gel, microemulsion, reverse microemulsion, deposition precipitation, coprecipitation and photoreduction methods |
|
|
| |
We have prepared nano metal capped on various supports, nano oxides, mesoporous, solid acids and pillared materials by sol-gel, microemulsion, reverse microemulsion, deposition precipitation, coprecipitation and photoreduction methods.
|
|
|
|
|
Characterisation of the materials by low temperature nitrogen adsorption /desorption method, UV-Visible DRS, TPD/TPR/TPO, FTIR, Thermal analysis, TEM, SEM |
|
|
| |
The surface and textural characterisation of the materials are performed by XRD, low angle XRD, BET surface area, pore size, pore volume, pore diameter by low temperature nitrogen adsorption/desorption, acid sites and redox sites by TPD/TPR/TPO UV-Visible DRS, FTIR, SEM, TEM, Thermal Analysis.
|
|
|
|
|
Stabilization of colloids/nano particle in aqueous/ non-aqueous medium |
|
|
We have developed & patented technique to stabilize particulate materials of wide range of size in aqueous/non-aqueous medium. The techniques are applicable to wide variety of organic/inorganic particulate materials including ceramics, clays, metals, paints, pigments etc.
We have successfully demonstrated preparation of stable, homogeneous, and highly loaded slurry of AD90 ( patented formulation of M/s Carborundum Universal, Hosur, TN ) based on Alumina.
|
|
|
|
|
Direct consolidation of ceramic suspension( Gelcasting / Bio-gelcasting) |
|
|
| |
Gelcasting, a direct consolidation technique, uses gelling of cast slurry to form green bodies by in-situ polymerization. In recent years the process has gained significant interest around the world because of its ability to produce tailor-made final microstructure by judicious control of suspension characteristics. The process is versatile and allows forming near net shape bodies. We have developed know-how for gelcasting of dense, porous, thin and thick oxide/non-oxide bodies using synthetic/biological gelling/fugitive agents.
We have successfully prepared porous hydroxyapatite bodies with 75 % total porosity with pores of 100 – 300 micron and dense alumina bodies with more than 98% of theoretical density.
|
|
|
|
|
Electrophoretic deposition of particulate material |
|
|
| |
Electrophoretic deposition is a colloidal processing method in which the charged particles dispersed in a liquid medium are attracted and deposited onto a conductive and oppositely charged electrode on application of a DC electric field. The technique with a wide range of novel applications in the processing of advanced ceramic materials and coatings, has recently gained increasing interest both in academia and industrial sector not only because of the high versatility of its use with different materials and their combinations but also because of its cost-effectiveness requiring simple apparatus, short formation time, little restriction in the shape of deposition substrate and suitability for mass production. In addition, there is no requirement of binder burnout because the green coating contains little or no organics. In particular, EPD offers easy control of the thickness and morphology of the deposited films through simple adjustment of the deposition time and applied potential. The principal driving force for electrophoretic deposition is the electric force exerted on charged particles on application of an electric field. The rate of electrophoretic deposition depends primarily on the charges on the particles, the electrophoretic mobility of the particles in the solvent, and the applied electric field.
Schematics of electrophoretic deposition process
(a) Cathodic EPD
(b) Anodic EPD
We are utilizing the EPD technique to deposit submicron and nano-size particles from aqueous and non-aqueous suspension on a variety of electrically conducting substrates. We are studying the influence of primary particle properties as well as their secondary properties like surface charge in a liquid medium in addition to the process parameters for obtaining thin as well as thick films of Al2O3 on conducting substrates like steel, carbon, graphite etc. We have developed technique to prepare free-standing films of YSZ, thin and dense YSZ film on NiO and lanthanum strontium manganite [ La 0.85 Sr 0.15 MnO 3 (LSM) ] substrates as well as electrophoretic deposition on non-conducting NiO-YSZ composite substrates and other materials for wide range of applications such as solid oxide fuel cells, oxidation resistant coatings, multilayer composites and hybrid materials, laminates/layered ceramics etc. Work is also initiated on electrophoretic deposition of hydroxyapatite (HAp) on metal implants for biomedical applications, luminescent materials for field emission display (FED) applications, mixed ionic and electronics conductor (MIEC) materials on porous substrates for gas separation sensors etc. Presently our thrust has also been initiated towards template assisted electrophoretic deposition for preparation of 2-D as well as 3-D ordered nanostructured array for functional materials. Such ordered arrays of nanoparticles have attracted much attention because of their application as building blocks in many potential nanodevices and smart materials such as data storage media, photonic crystals, electronics, sensors (gas sensors, biosensors etc), catalysts, etching masks and many other advanced ceramic fields. We are contemplating to use templates made from block-copolymer films. Block copolymers consist of two or more polymer chains connected with covalent bonds. Most pairs of polymers are immiscible and blends of polymer tend to phase separate. But block polymers, when subjected to selective chemical etching or UV light treatment, the constituent polymers are unable to phase separate at macroscopic length scales and instead spontaneously form ordered structures at molecular scale. We are trying to incorporate nanoparticles into these ordered domains by electrophoretic deposition for making ordered arrays of desirable nanostructures.
|
|
|
|
|
Rheology of ceramic suspension |
|
|
| |
Particulate suspension ( slurry) is a non-newtonian fluid and rheological properties of the slurry are very important in controlling the flowability of the suspension. In many of engineering applications, we need to have slurry with > 40vol% solid loading. In general, high solid slurry displays several characteristics such as colloidal instability, excessively high viscosity, difficulty in adding additional powder, and dilatancy etc. Rhoelogical measurements then become an important tool to determine the visco-elastic properties. The following curve demonstrate flow curve behaviour of alumina slurry with different amount of additive addition.
In case of Gelcasting process, where in-situ gelation has been used to consolidate the body, measurement of storage modulus gives the gelling behaviour of the slurry. Adjacent figure shows that how storage modulus of alumina slurry respond when different additives and foam were present in the slurry ordered arrays of desirable nanostructures.
|
|
|
|
|
Solid Oxide Fuel Cell (SOFC) by electrophoretic deposition |
|
|
| |
Fuel cells, an electrochemical device which converts chemical energy directly into electrical energy without involving the conventional combustion step, is now been widely seen as the future energy systems for electricity generation to meet the huge gap in energy demand and supply in the country. Amongest the several type of fuel cells, the solid oxide fuel cells (SOFCs) have attracted great attention because of their high energy conversion efficiency, clean power generation, reliability, modularity, fuel adaptability ( capability to run on existing fossil fuels such as natural gas), noise free, excellent long term stability and the versatile nature of the technology for direct conversion of chemical energy to electrical energy.
In general, an SOFC consists of stacks made of single fuel cells in series. A single cell in turn comprises of a solid electrolyte layer with an oxidizer electrode (cathode) on one side of the electrolyte and a fuel electrode (anode) on the other side. The electrodes are required to be porous, or at least permeable to oxidizer at the cathode and fuel at the anode, while the electrolyte layer is required to be dense/gas-tight so as to prevent leakage of gas across the layer. One of the most critical aspect in development of solid oxide fuel cells is the preparation of thin and dense electrolyte layer. The conventional ultra-high vacuum (UHV) methods including the physical vapour deposition (PVD) such as sputtering, pulsed laser deposition, molecular beam epitaxy (MBE), chemical vapour deposition (CVD) or electrochemical vapour deposition (EVD) methods ordinarily require sophisticated and expensive equipment making them either undesirable or impracticable for implementation in manufacturing environment. They are also plagued by high processing temperatures and limitations on the materials from which the support anode is made. Hence, improved method for forming the dense electrolyte and porous electrode are needed.
We are employing the electrophoretic deposition (EPD), for deposition of thin films of YSZ on NiO and NiO-YSZ composite substrates. The YSZ films are densified subsequently by co-sintering the bi-layer at high temperatures. The NiO and NiO-YSZ substrates are made either by uniaxial dry pressing or by tapecasting. The cathode material, mainly La 0.85 Sr 0.15 MnO 3 (LSM), is then deposited on the YSZ film by slurry painting. A planar SOFC prepared in this manner has exhibited an open circuit voltage (OCV) of about 1.0 V and a peak power density of more than 600 mW/cm 2 at 850 oC when tested using H2 as fuel. Recently we have started working on development of honeycomb fuel cells by electrophoretic deposition. The scope of the work involve preparation of monolithic honeycomb structures of anode and electrolyte materials by extrusion. Deposition of requisite electrode/electrolyte material of desired thickness and microstructure in the honeycomb channels will be made by electrophoretic deposition.
|
|
|
|
|
Preparation of sub-micron and nano powders by combustion synthesis |
|
|
| |
We have perfected a simple and inexpensive route for preparation of a variety of nanopowders by combustion synthesis called Glycine nitrate process (GNP). In this method the starting precursors is the nitrate salts of the desired materials which is dissolved in distilled water. Stoichiometric amount of glycine is dissolved in the same solution and shaken vigorously for complete solubilisation of the constituents. The solution contained in a beaker is then subjected to rapid heating on a hot plate to evaporate the liquid. Towards the end of evaporation a spontaneous flame develops and its burns vigorously for 1-5 seconds. The resultant ash is then subjected to calcinations at higher temperatures to eliminate any residual carbon in it.
(a) vigorous combustion .
(b) beaker containing product ash after completion of reaction.
|
|
|
|
|
Surface film pressure characterization of surfactants by Langmuir –Blodgett technique |
|
|
| |
Longmuir-Blodgett technique is one of the most promising techniques for preparing insoluble thin films as it enables the precise control of the monolayer thickness, homogeneous deposition of monolayer over large areas, possibility to make multilayer structures with varying layer composition etc. Langmuir developed the fundamental methodology to measure the properties of insoluble monolayer as a function of their surface concentration, leading to the determination of molecular dimensions.
Using LB equipment a technique has been developed for characterizing and predicting the performance of flotation collectors based on property-performance relationship between collector performance and surface film pressure. The experimental data are presented for oxide minerals (iron oxide). Collectors chosen are those which are tested for flotation performance, namely oleic acid (found most effective in the present case) and tallamine (least effective). It became apparent during the course of this investigation that the more effective collector causes greater reduction in surface film pressure compared to the less effective one, which is most desirable for an effective collector. Therefore, the study of physical characteristics of collectors prior to flotation can be useful in flotation and selection of suitable collectors. The results obtained demonstrate the usefulness of the surface film pressure measurements in selection of flotation collectors for optimum performance. This approach not only gives quantitative measure for choosing most effective collector but additional data supporting the disjoining pressure mechanism of flotation.
|
|
|
|
|
Development of eco-friendly catalyst for fine chemical synthesis, environmental pollution abatement and water splitting for hydrogen production. |
|
|
| |
The materials are evaluated for nitration, esterification, alkylation, acylation, oxybromination, isomerisation, hydroxylation of aromatic/aliphatic compounds, photodegradation of organic/inorganic pollutants, decomposition of volatile organic compounds( VOCs), low temperature CO oxidation and water splitting for hydrogen production.
|
|
|
| |
|
|
|
| |
|
|
|
|
|
|
|
