David W. Skelly

High-temperature refractory metal-intermetallic composites

In this article, toughness, oxidation, and rupture behaviors of present-generation refractory metal-intermetallic composites are compared to the performance requisites necessary to make these materials a competitive choice for the jet engine turbine environment of the future.

Ion implantation of cobalt-tungsten carbide tools for machining titanium

Abstract Cobalt-base tungsten carbide cutting tools were implanted with Cl, F, Br, I, S, In, Ga and Sn to dose levels of 2 × 10 16 ions cm −2 to 5 × 10 17 ions cm −2 . Both untreated and implanted tools were tested in turning against a log of Ti-6Al-4V alloy at a cutting speed of 300 f.p.m. Each test was carried out for 1 min and the uniform flank wear was measured, whereupon the tool was tested for a further 1 min. Testing continued in this fashion until the uniform flank wear approached or exceeded 0.02″. The distribution of the implanted elements was determined by secondary ion mass spectrometry. In general, doses of 1 × 10 17 ions cm −2 increased tool life by a factor of two in the case of the chlorine and indium implants. Other implant elements were less effective in increasing tool life against the titanium alloy.

Mechanical properties of an in situ synthesized Nb/Nb3Al layered composite

Abstract A layered metal/intermetallic, consisting of Nb and Nb3Al, has been synthesized using a high rate magnetron sputtering technique. The microstructure and various mechanical properties have been explored. It is demonstrated that the Nb phase contributes substantially to the toughness, through plastic dissipation, combined with frictional sliding at contacting surfaces. However, the toughness is suboptimal, because of the small layer thickness, which limits the width of the plastic zone. The tensile strength is also relatively low, because of growth defects. Some concepts for improving the strength and fracture resistance by tailoring the constituent and interface properties are suggested.

Electron sensitive resists derived from vinylether-maleic anhydride copolymers

A series of polymers derived from vinylether-maleic anhydride copolymers were prepared and their electron sensitivities measured. One of the most sensitive polymers prepared was the allyl half-ester of an octadecylvinylether maleic anhydride copolymer (VL-100). This material was stable, formed excellent films, and was insensitive to UV and visible light with λ > 2000 Å. The sensitivity to electron irradiation was found to be 4 × 10-8C/cm2at 9 keV compared to 5 × 10-7for KTFR under identical conditions. The evaluation of this material as an electron resist as well as sensitivity data for numerous derivatives is reported.

Spectroscopic Evidence for the Formation of I3− in Silver Iodide at High Pressures

The presence of an absorption maximum at 360 mμ indicates the formation of I3− in the fcc phase of AgI at approximately 4 kbar. The concentration of I3− is pressure dependent above 4 kbar and falls to zero somewhere below the transition to the new phase at approximately 100 kbar. A mechanism is proposed to explain the presence (in the fcc structure) and subsequent disappearance of I3−.