PLASMA PROCESSING UPDATE

A newsletter from the

Facilitation Centre for Industrial Plasma Technologies

Institute for Plasma Research

Issue 48 January - April 2005

Contents

Editor's Note

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Surface Modification of Angora Wool to Improve Processing

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Prototype Glow Discharge Systems for Universities

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Calcination of Calcium Carbonate

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Plasma Diagnostics of Hall thrusters

Editor's note

Angora fibre is considered one of the world’s finest luxury fibre. It is extremely warm, soft, and silky to touch, and is the lightest natural fibre known. However its smooth surface doesn’t permit easy weaving of fabrics. This characteristic of the wool sans the use of machines for spinning and weaving, and is spun only on hand driven ‘takli’ (spindle). Further, due to its fibrosity, it is extremely difficult to weave a fabric with 100% Angora wool. Plasma etching was tried at FCIPT, to modify the surface of this wool, so that the micro-roughness generated on the surface would increase the friction and cohesion between the fibres. Mr. M.K. Garg elaborates on the techniques adopted for the successful demonstration of the concept.

Plasma Nitriding is a surface hardening technique using glow discharge plasma. FCIPT has pioneered this area and generated a vast data on ‘nitriding of different steels’. Of late, the institute has developed low cost prototype plasma nitriding reactors, especially for universities and colleges, in an endeavour to give a thrust to the basic research in the field of ‘glow discharge plasma applications’. We hope that the universities make full use of this opportunity. Mrs. Alphonsa Joseph explains in detail.

Lime (the Oxide of Calcium) is one of the important ceramic materials. However it is not available in its native form. It is extracted from limestone i.e. Calcium Carbonate, by heating it to a temperature of the order of 1000° C, generally in a rotary kiln. The fuel requirements of these kilns impose certain restrictions on the location of the plant etc. Thermal plasma, known for its high temperatures and reaction rates, was successfully tried out to calcine the limestone, at FCIPT. An in-flight plasma reactor was used for the purpose. Mr. Satyaprasad presents further details.

Hall thruster is a type of ion thruster in which the propellant is accelerated by an electric field in a plasma discharge with a radial magnetic field, to generate the thrust. These thrusters are used for spacecraft propulsion like orbit raising, on-orbit manoeuvres, and de-orbit functions. They use the ‘Hall effect’ to trap the electrons and these trapped electrons are used for ionizing the fresh propellant, leading to higher ionization efficiency in the discharge chamber. A Memorandum Of Understanding was signed between FCIPT and ISRO to develop diagnostics for studying the plasma properties of ISAC thruster. FCIPT has developed a thruster, in-house, for studying the plasma characteristics and the details of the thruster and some of the results obtained are presented by Mr. Mukesh Ranjan.

Alphonsa Joseph

Editorial Assistance: A. Satyaprasad

Facilitation Centre for Industrial Plasma Technologies

The Institute for Plasma Research (IPR) is exclusively devoted to research in plasma science, technology and applications. India’s first high temperature plasma device `Aditya Tokamak’, built at IPR, produces plasmas at 5 million degrees temperature - comparable to that of the sun.  An advanced fusion device with superconducting magnets, capable of steady state operation is under fabrication. IPR is also active on a broad front of fundamental studies. It has engineering groups skilled in technologies of Superconducting Magnetics, Ultra High Vacuum, Pulsed Power, Microwave and RF, Computer-based Control and Data Acquisition, theory and computer simulation complement experimental programmes.

The Facilitation Centre for Industrial Plasma Technologies (FCIPT) links the Institute with the Indian industries and commercially exploits the IPR knowledgebase. FCIPT interacts closely with entrepreneurs through the phases of development, incubation, demonstration and delivery of technologies. Complete package of a broad spectrum of plasma-based industrial technologies and facilitation services is offered.

Some of the recent FCIPT achievements are: plasma nitriding of industrial components to increase wear resistance and hardness, coating of quartz-like films on brassware to inhibit oxidation and tarnishing, ceramic synthesis and processing, plasma ion implantation and ion plating for surface engineering, thermal plasma technologies for smelting of minerals and waste treatment etc.

The Centre has process development laboratories, jobshops and material characterisation facilities. The process development laboratory exploits the areas of expertise in plasma and other allied fields of the institute in developing new plasma based technologies for the industry. The jobshop executes job work for surface and material treatment on an industrial scale to promote the acceptance of plasma based technologies and to generate techno-commercial data relevant to entrepreneurs. The advanced instruments in the material characterisation facility are open to users from industry, research establishments and universities.

This newsletter is designed to help you keep abreast with the developments in the important field of plasma assisted manufacturing and  to look for new industrial opportunities. We would be  very happy to have you write to us on ways of improving this service or visit us for further discussions.

Please visit our website: http://www.plasmaindia.com

Surface Modification of Angora Fibre to Improve Processing

The Angora fibre is the wool obtained from the hair of a special breed of rabbits – known as Angora rabbits. This wool is known for its extreme warmth, and lightweight. It is eight times warmer than the sheep’s wool and is the lightest natural fibre known. Angora fibre production is the third largest animal fibre industry in the world after wool and mohair. China dominates, the world Angora fibre trade, producing approximately 90% of the world Angora fibre. In India these rabbits are reared in Pittoragarh in Uttaranchal. The Angora wool is generally blended with superfine wool, mohair, silk, and alpaca to produce fashion garments. However, because of its smooth surface, it is found to be slippery to spin and requires a lot of twist to hold it firmly in the yarn. These limitations can be eliminated if the surface of the fibre is modified, so that its grip would be improved, and the fibre loss is reduced. FCIPT has put some effort using cold plasma technology to improve the surface properties of the angora wool.

Cold plasmas improve fibre surface properties without affecting its bulk properties. The plasma treatment on the surface of Angora fibre helps in increasing micro-roughness and polar groups at the surface that improve cohesion between the fibres. The entire plasma process is done in an environment friendly manner. In our experiments, we have used two types of cold plasmas 1) a glow discharge plasma at atmospheric pressure and 2) a sub-atmospheric pressure RF plasma, to modify the surface of the Angora fibre. The atmospheric pressure glow discharge was generated at 10-20 KHz frequency whereas the RF low pressure glow discharge was produced using 13.56 MHz frequency power source. However the experimental set-up was same for generating both the plasmas. The schematic of experimental set up is shown in Figure1.