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The Industrial Plasma

The commissioning of the Aditya Tokamak in 1989 and its transition to a phase of routine operation was a good time for me to sit back and reflect on what to do next. The prospects for fusion appeared bleak, primarily because of the international events of the early 90s, especially the Gulf War leading to oil price stabilization. Plasma physicists all over the world were exploring novel opportunities to apply their knowledge to fields beyond the conventional.

With a predilection to build devices trusting intuition more than engineering rigour, the ADITYA tokamak demanded too much discipline for comfort. An old obsession with finding immediate practical use of my knowledge of plasma physics was also churning in my mind, opportunistically sensing the dissatisfaction with the years spent in the straitjacket of Aditya. The itch to try something novel, after spending close to two decades building plasma experiments, relativistic electron beam devices and ADITYA was also a powerful driver for change.

Using plasmas for near-term industrial applications appeared to be very timely. The rich experimental knowledge base created over two decades of producing and manipulating plasmas to support research at the Physical Research Laboratory and the Institute for Plasma Research was a substantial capital. This also reflected the prevailing perspective that the plasma science offers unique and novel opportunities in high-energy density and high value-added material processing. Despite criticisms that this was a deviation from the original charter of the institute, the Director, Prof. Kaw wholeheartedly supported pursuing this path. This was in complete conformity with his belief that any interesting idea should be pursued with full vigour.

Plasma assisted manufacturing exploits plasma as an industrial tool. Plasma can respond to external electromagnetic energy fields and transport energy. The fluid properties are enhanced by the particles setting up internal self-consistent electric and magnetic fields, resulting in collective effects like flows, waves, instabilities and self-organization. Each specie may have independent energy distribution, not necessarily in equilibrium with other species. The internal energy is composed of thermal, electric, magnetic and radiation fields, whose relative magnitudes allow the plasma state to exist in an extended, multi-dimensional parameter space. 

Plasma processing was surging internationally with the realization that the fourth state of matter offers unique opportunities in material processing. Properties like high chemical reactivity, microscopic electric fields, sheaths, radiation and particle flux mediate plasma processing. Plasma-based manufacturing integrates the plasma-material interaction phenomena with the manufacturing process. The technology adds value to conventional materials and makes new types of materials and processing techniques possible. The characteristics of both the equilibrium and non-equilibrium plasmas can be exploited for commercial uses. Comparable stature of international and indigenous capability in this field was a rare opportunity for leadership in an emerging field.

The IPR Council gave a favourable nod to the idea of pursuing plasmas for profit. I remember particularly the support given by Prof. S. Ramaseshan and Dr. P. K. Iyengar. There were no pre-existing models of similar activity in basic research organizations in India. So, the business plan evolved and matured along with our learning curve. The programme had to be industry-driven to make it agile and responsive to rapid changes and focused on a few thrust areas where immediate impact would be possible. Financial self-reliance was a goal from the beginning.

The Plasma Processing Programme had some unique features not encountered in basic research. The necessity for it to be relevant to industry, the fact that it can make or lose money in its commercial exploitation, the contractor-client relationship with industries etc. are some examples. It was the first time in India that a basic research institute ventured into a commercial application programme. So, there were no rules from earlier experience. Predhiman was a willing sounding board on issues of managing an activity like this. He played a crucial role in ensuring that the learning process was sound, and the rules conformed to good principles of management.

The first foray was into plasma nitriding because of the interest shown by several industries. This is a process in which Nitrogen is incorporated into the steel matrix to increase hardness. Along with Chitra Natarajan, I looked at the specifications of the state-of-the-art systems. We then took a conscious decision not to build them, but to start an accelerated trek through the various phases of its development. So, we started with conventional DC glow discharges stabilized with external ballast resistors. Later on, we incorporated pulsed DC. The first prototype was a cold wall furnace with only plasma heating. Heat shields were added to minimize heat loss. By allowing an insulated liner to reach elevated temperatures, we increased thermal efficiency and temperature uniformity. By actively heating the vacuum vessel or the liner with a heating element, we obtain the auxiliary heated hot wall reactor. Heating of the workpiece is obtained by the combination of plasma heating and radiation and convection heating by the wall. During this time, we also added automation and computer control to build state-of-the-art systems.

It is easy to fall into a false sense of confidence of knowing the technology of plasma nitriding when you see the familiar glow around an industrial component. The technology is in the unglamorous details. I had prepared a long list of questions for which we needed credible answers before we could say that we have mastered nitriding technology. How exactly do we distribute the workpieces so that temperature is uniform or how we can control the microstructure are two of such questions.

Plasma Nitriding became the first technology to be transferred to industry. In addition to this, we set up a job-shop to do nitriding of high value component like plastic dyes etc on a commercial basis.

Work on many other applications like thermal plasma processing of zircon sands, anodic vacuum arcs, plasma ion implantation etc. followed this. The zircon dissociation was our first foray into thermal plasmas and plasma torches.

Plasma processing got a big boost when it became part of the Surface Engineering initiative of the Department of Science and Technology when Prof. P. Rama Rao was the Secretary, DST. This programme opened up collaboration with German Institutions. I was a member of a delegation which visited the Fraunhoffer Institutes to set up programmes of institutional collaboration. We got partnered with the Technical University of Clausthall and the Nuclear Institute in Dresden on plasma ion implantation, which involved visits and exchange of research personnel. In addition to providing commercial scale implantation service to industries, we were able to sell a pulsed high voltage system for plasma ion implantation to the Technical University.

I felt an urge to communicate the excitement of all this new knowledge to industries. The first issue of the Plasma Processing Update came out in 1994. The early issues were written almost entirely by me. With time, came new enthusiasts from among the new staff. The fact that it has survived all these years is a true indication of the passion of the practitioners of plasma processing in their work and their commitment to engage with the industry.

I also started planning to write a book discussing the versatility of the plasma state of matter as an enabling tool for industrial, manufacturing, environmental and engineering applications. Conceived as an introduction to the technology, practice and the commercial aspects of plasma-enabled material processing and manufacturing, the book was meant for the agents of change in the present day society; students, professionals, entrepreneurs. The book, titled “Plasma Sciences and the Creation of Wealth” was published in 2005 by McGraw-Hill, India.

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