No abstract

A new atomization process, plasma atomization (P.A.), has been developed to produce fine, spherical powders. Unlike conventional high-pressure atomizers, P.A. utilizes multiple nontransferred direct-current arc plasmas to accelerate the atomization gas. In the P.A. process, metal wires are fed into the apex of the multiple plasmas, where they melt and are atomized in a single step. This process offers the unique ability to produce spherical powders of reactive metals with a typical average particle size of 40 pm.

A thermal plasma process is described for the synthesis of fullerenes via the dissociation of hydrocarbons. The plasma reactor is equipped with a nontransferred dc plasma torch which was used to dissociate hydrocarbons. The hydrocarbons investigated include CH4, C2H2, CBrF3, CCl2F2, and C2Cl4. The best results are obtained with C2Cl4. The collection temperature of the fullerene soot in the process was found to play a critical role in the collection rate of fullerenes.

Phenomena occurring on the surface o/'a thoriated tungsten cathode operating in a trans.ferred-arc reactor were investigated. The efjeets of cathode geomet o, (pointedtip vs. fiat-tip)

The vacuum-plasma-spraying technique presented in this article is suited to produce aluminum-matrix composites with a low coefficient of thermal expansion reinforced with fine ceramic particles, resulting in a uniform particle dispersion and bulk porosity of less than 1.5% in the as-sprayed condition. Plastic deformation of the plates followed by annealing resulted in significant increases in ultimate tensile strength, hardness, and elongation.