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During the past decade, interest in transition metal nitrides has grown considerably. Nitrides of various elements play an important role in industry, science, and technology for their interesting and useful resilient properties. For example, many transition metal nitrides based on titanium, boron, and nitrogen have stimulated commercial interest because of their extreme hardness, wear and corrosion resistance, and thermal and electrical properties. All of these features are enhanced by the resulting structures and the large degree of covalency exhibited by the transition metal-nitride bonds. Coatings of select nitrides may particularly influence physico-chemical properties in critical surface and interface regions. This article attempts to present a brief overview on transition metal-nitride research for advancement in reliable machine part manufacturing.

Some candidate fusion materials such as nickelbase alloys and graphites were studied, because of their importance as first wall components in CTR devices. Polycrystalline samples of Inconel 600, Inconel 625, Nimonic alloy PE 16, nuclear grade graphite ATJ and pyrolytic graphite were investigated. Results for surface damage and topography, blistering, flaking, ion erosion and sputtering yields are reported for irradiations with low energy He/sup +/ ions (5-12 keV) at room temperature, using total ion doses up to 2 x 10/sup 19/ ions cm/sup -2/. SEM, TEM and AES analyses were used to identify surface damage, structure and compositional changes after irradiation. Comparative studies of the ion erosion yield of nickel-base alloys, as measured by the step-height technique, were made. Total sputtering yields were determined dynamically for sputtered films of these alloys using a quartz crystal microbalance. The yields were studied as a function of ion dose, energy and surface roughness.

0.5 and 2 kev Kr+ ions were injected into polycrystalline tungsten. The gas-loaded target was then bombarded with Ar+ ions with energies between 0.1 and 4 kev and the rate of release of Kr and the fraction of Kr released after a given Ar+ ion dose were measured. Effective gas sputtering coefficients were then deduced and a comparison of the form of their variation with Ar+ ion energy with the known variation of the sputtering coefficient of tungsten suggests that the gas release is not conditioned wholly by target erosion. It is believed that some of the gas release is a result of localized heating effects which occur near the point of ion impact (thermal spikes) and cause an enhancement of thermally induced gas desorption.

This communication describes a versatile apparatus for the production of thin polycrystalline metallic films under conditions of high purity. The apparatus includes facilities for film preparation by evaporation and cathodic sputtering and for ion bombardment of the films under the same conditions of purity as obtained during preparation. The films can also be annealed before and after ion bombardment, although at this stage of the programme these facilities have not been fully used. Electrical conductivity measurements of the films can be made in situ and some preliminary data on the effects of ion bombardment on the electrical conductivity of thin metallic films are reported.

Energetic argon ions were injected into thin films (100–500 Å) of Ag, Au, Ti, and W, and changes in the electrical resistance of the films were observed. Three stages in the resistance change/ion dose relation were observed. The first at low ion doses, where the resistance falls, is believed to be a result of removal of contaminant gas from the surface. The next stage at higher ion doses, where the resistance increases to a quasi-constant value, is believed to be associated with damage production at and near the film surface. At still higher ion doses, the resistance increases to infinity as a result of sputtering of the film.

A description of an ion bombardment unit is given. Ions of energies between 3 and 15 kev are supplied by a high frequency ion source with post-acceleration. The object chamber can accommodate up to twelve specimens at a time, and a low power microscope is provided for the observation of the specimen changes during the bombardment.

The change in electrical resistance of thin Ag, Au, Ti, and W films was studied following energetic A+ ion bombardment. There is an initial reduction in film resistance (for all materials) during bombardment, which is attributed to removal of surface contaminant gas. The resistance then increases to a quasiequilibrium value, which is believed to be due to introduction of radiation damage to the films, and finally the resistance increases rapidly as the films sputter and thin.