No abstract

As part of an effort to determine the feasibility of carbothermic reduction of alumina in plasmas, spatial distributions of temperature, velocity and species in the plume of an argon radio-frequency plasma with alumina and carbon additions were estimated using a two dimensional theoretical model of the flow field and a thermochemical model based on equilibrium conditions. Experimentally determined boundary conditions were input to the models. Using a 30 kW inductively coupled plasma, experimental measurements were made to allow comparison with predictions. A practical process for carbothermic reduction will require prevention of back reactions, either by separation of the aluminum species or by some kind of quenching of the process. The significance of the experimental results and comparisons with predictions are discussed.

Inertial confinement by heavy ion beams is the most promizing approach to future generation of electrical energy. Activities in Europe concentrate at present on some key issues, the generation of intense heavy ion beams and the interaction of these beams with matter. After the completion of a systems study and some work on fundamental issues like ion stopping in fully ionized dense plasma, during the last decade, two aspects characterize the directions of future research: (1) The heavy ion synchrotron and cooler ring facility SIS/ESR at GSI is being commissioned these days and will allow a number of new experiments in the fields of high intensity beam dynamics and beam target interaction. With this facility beam instabilities at high space charge density can be investigated and dense plasmas can be produced u p to temperatures of several tens of electron volts. (2) New accelerator scenarios based on non-Liouvillean techniques, which allow current multiplication without increasing the phase space volume, are being investigated and may greatly influence the situation of heavy ion drivers. Plasma processing has t h e advantages o f h i g h l y e f f i c i e n t d e s t r u c t i o n ; smaller throughput, r e a c t o r , and a u x i l i a r y equipment; lower c a p i t a l costs; p o r t a b i l i t y ; h i g h l y s t a b i l i z e d waste forms; f a s t s t a r t u p and shutdown; closed system design; and c o m p e t i t i v e processing c o s t f o r mixed wastes. major disadvantages are r e l a t i v e l y h i g h energy costs; t h e assumption t h a t energy cost i s t h e o v e r r i d i n g economic f a c t o r ; l i m i t e d R&D funding t o develop t h e plasma engineering science (e.g., compared t o combustion science); and l i m i t e d experience of engineering f i r m s w i t h plasma processing systems. and a u x i l i a r y h e a t i n g methods. advantages f o r c e r t a i n types o f m a t e r i a l s and d e s i r e d products, b u t as i n combustion, s u f f i c i e n t time, temperature, and turbulence (mixing) are r e q u i r e d t o perform the d e s t r u c t i o n and recombination i n t o d e s i r a b l e products. The engineering science aspects o f these methods w i l l be discussed i n some d e t a i l as r e g a r d i n g gas phase r e a c t i o n s , s l a g chemistry, and f i n a l waste form c h a r a c t e r i s t i c s . Present plasma processing science p a r a l l e l s t h e e a r l y days o f combustion science. To o b t a i n e f f i c i e n t plasma processing methods, research i s r e q u i r e d i n : 1. Plasma processing science regarding e l e c t r i c a l , thermodynamic, t r a n s p o r t , chemical r e a c t i v i t y , and p h y s i c a l p r o p e r t i e s 2. Plasma process energy t r a n s f e r t o enhance energy e f f i c i e n c y 3 . Plasma process chemical r e a c t i o n s t o enhance d e s t r u c t i o n e f f i c i e n c y 4 . Plasma process electromagnetic e f f e c t s t o reduce energy losses, enhance mixing, and promote se1 e c t i v e chemical r e ...

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This article focuses on direct extrusion processing where metal powders undergo plastic deformation, usually at an elevated temperature, to produce a densified and elongated form having structural integrity. It provides information on the basic powder extrusion processes and the mechanics of extrusion. The article also examines specific extrusion practices for the production of wrought material from powder stock and provides examples of materials processed by powder extrusion.