The effect of impact angle on craters formed by hypervelocity particles

The Space Power Institute (SPI) at Auburn University has conducted experiments on the effects of impact angle on crater morphology and impactor residue retention for hypervelocity impacts. Copper target plates were set at angles of 30 deg, 45 deg, 60 deg, and 75 deg from the particle flight path. For the 30 deg and 45 deg impacts, in the velocity regime greater than 8 km s(exp -1) the resultant craters are almost identical to normal incidence impacts. The only difference found was in the apparent distribution of particle residue within the crater, and further research is needed to verify this. The 60 deg and 75 deg impacts showed marked differences in crater symmetry, crater lip shape, and particle residue distribution in the same velocity regime. Impactor residue shock fractionation effects have been quantified in first-order. It is concluded that a combination of analysis techniques can yield further information on impact velocity, direction, and angle of incidence

Low-Temperature Activity and PdO-PdOx Transition in Methane Combustion by a PdO-PdOx/γ-Al2O3 Catalyst

The search to discover a suitable catalyst for complete combustion of methane at low temperature continues to be an active area of research. We prepared a 5 wt % PdO-PdOx/γ-Al2O3 catalyst by a modified Vortex-assisted Incipient Wetness Method. X-ray Photoelectron Spectroscopy showed that the original catalyst contained PdO (38%) and PdOx (62%) on the surface and indicated that PdOx originated from the interaction of PdO with the support. Scanning Transmission Electron Microscopy confirmed the catalyst had an average particle size of 10 nm and was well-dispersed in the support. The catalyst exhibited exceptional low-temperature activities with 90–94% methane conversion at 300–320 °C. The catalyst was active and stable after several catalytic runs with no signs of deactivation by steam in this narrow temperature range. However, the conversion decreased in the temperature range 325–400 °C. The surface composition changed to some extent after the reaction at 325 °C. A tentative mechanism proposes PdOx (Pd native oxide) as the active phase and migration of oxide ions from the support to PdO and then to PdOx during the catalytic oxidation. The high methane conversion at low temperature is attributed to the vortex method providing better dispersion, and to catalyst–support interaction producing the active phase of PdOx

Low-temperature activity and PdO-PdO\u3csub\u3ex\u3c/sub\u3e transition in methane combustion by a PdO-PdO\u3csub\u3ex\u3c/sub\u3e/γ-AL\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e catalyst

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. The search to discover a suitable catalyst for complete combustion of methane at low temperature continues to be an active area of research. We prepared a 5 wt % PdO-PdOx/γ-Al2O3 catalyst by a modified Vortex-assisted Incipient Wetness Method. X-ray Photoelectron Spectroscopy showed that the original catalyst contained PdO (38%) and PdOx (62%) on the surface and indicated that PdOx originated from the interaction of PdO with the support. Scanning Transmission Electron Microscopy confirmed the catalyst had an average particle size of 10 nm and was well-dispersed in the support. The catalyst exhibited exceptional low-temperature activities with 90–94% methane conversion at 300–320 °C. The catalyst was active and stable after several catalytic runs with no signs of deactivation by steam in this narrow temperature range. However, the conversion decreased in the temperature range 325–400 °C. The surface composition changed to some extent after the reaction at 325 °C. A tentative mechanism proposes PdOx (Pd native oxide) as the active phase and migration of oxide ions from the support to PdO and then to PdOx during the catalytic oxidation. The high methane conversion at low temperature is attributed to the vortex method providing better dispersion, and to catalyst–support interaction producing the active phase of PdOx

High rate ECR etching of III-V nitride materials

The III-V nitride compound semiconductors are attracting considerable attention for blue and ultraviolet light emitting diodes (LEDs) and lasers as well as high temperature electronics due to their wide band gaps and high dielectric constants. The recent progress observed in the growth of these materials has not been matched by progress in processing techniques to fabricate more highly sophisticated devices. Patterning these materials has been especially difficult due to the relatively inert chemical nature of the group-III nitrides. The authors review dry etch techniques which have been used to pattern these materials including electron cyclotron resonance (ECR), reactive ion etch (RIE), and chemically assisted ion beam etching (CAIBE). ECR etch rates greater than 3,800 {angstrom}/min for InN, 3,500 {angstrom}/min for GaN, and 1,170 A/min for AlN are reported. Etch anisotropy, surface morphology, and near-surface stoichiometry will be discussed