Wright-Patterson Air Force Base

About: Wright-Patterson Air Force Base is a other organization based out in Wright-Patterson AFB, Ohio, United States. It is known for research contribution in the topics: Laser & Microstructure. The organization has 5817 authors who have published 9157 publications receiving 292559 citations. The organization is also known as: Wright-Patterson AFB & FFO.

Effectiveness of Monazite Coatings in Oxide/Oxide Composites after Long-Term Exposure at High Temperature

Abstract: The effectiveness of monazite (LaPO4) in providing an oxidation-resistant weak fiber/matrix interface was evaluated in a fiber roving/thin coating/ceramic-matrix composite with >20% fiber volume fraction. Nextel™ 610/monazite/alumina composites were fabricated and tensile tested after isothermal exposures of up to 1000 h. Some strength loss was seen after short-term exposures (1100°–1200°C/5–250 h); however, no further loss was observed after 1000 h at 1200°C. Conversely, control samples containing uncoated fiber displayed >70% strength losses after only 5 h at 1200°C. Fiber pullout was seen in monazite-containing samples even after 1000 h at 1200°C. Debonding was predominantly in the coating or at either the fiber/coating or coating/matrix interface. Push-out testing confirmed the weakness of the monazite coating interface.

Wet Chemical Digital Etching of GaAs at Room Temperature

Abstract: A new room temperature wet chemical digital etching technique for GaAs is presented which uses hydrogen peroxide and an acid in a two‐step etching process to remove GaAs in approximately 15 A increments. In the first step, GaAs is oxidized by 30% hydrogen peroxide to form an oxide layer that is diffusion limited to a thickness of 14 to 17 A for time periods from 15 to 120 s. The second step removes this oxide layer with an acid that does not attack unoxidized GaAs. These steps are repeated in succession until the desired etch depth is obtained. Experimental results are presented for this digital etching technique demonstrating the etch rate and process invariability with respect to hydrogen peroxide and acid exposure times.

A Theory of Situation Assessment : Implications for Measuring Situation Awareness

Abstract: Measures of pilot situation awareness (SA) are needed in order to know whether new concepts in display design help pilots keep track of rapidly changing tactical situations. In order to measure SA,...

Tribological properties of adaptive nanocomposite coatings made of yttria stabilized zirconia and gold

Abstract: Composite coating architectures where hard nanocrystalline grains are embedded in an amorphous matrix provide considerable improvement in hardness, toughness, wear resistance, and environmental adaptation. Using this concept, nanocrystalline yttria stabilized zirconia (YSZ) was embedded in an amorphous YSZ/Au matrix to address problems with YSZ ceramics in sliding wear. The coatings were produced by a hybrid of laser ablation of YSZ and magnetron sputtering of Au. Coating composition and microstructure were investigated using a number of analytical techniques, and correlated with results of sliding friction tests at 25 and 500°C. In situ transmission electron microscope imaging of microstructure evolution during a temperature cycling from 25 to 500°C was performed to explain changes in tribological properties. In comparison to YSZ ceramic, YSZ/Au coatings were tougher, formed less wear debris, and reduced friction coefficients from 1.0 to 0.3–0.4 at 25°C and to 0.2 at heating to 500°C. Improvements in tribological properties were related to the microstructure adaptive changes at elevated temperatures and formation of lubricating Au transfer films.

Friction and wear of diamond and diamondlike carbon coatings

Abstract: Reciprocating sliding friction experiments were conducted with a natural diamond flat, diamond films, and low- and high-density diamondlike carbon (DLC) films in contact with pin specimens of natural diamond and silicon nitride (Si 3 N 4 ) both in humid air and in dry nitrogen. The results indicated that for natural diamond pin contacts the diamond films and the natural diamond flat were not susceptible to moisture but that moisture could increase both the coefficients of friction and wear factors of the DLC films. The coefficients of friction and wear factors of the diamond films were generally similar to those of the natural diamond flat both in humid air and in dry nitrogen. In dry nitrogen the coefficients of friction of the high-density DLC films in contact with pin specimens of both diamond and Si 3 N 4 were generally low (about 0.02) and similar to those of the natural diamond flat and the diamond films. The wear factors of the materials in contact with both natural diamond and Si 3 N 4 were generally in the ascending order of natural diamond flat, diamond film, high-density DLC film, and low-density DLC film. Moisture in the environment increased the coefficients of friction for Si 3 N 4 pins in contact with all the materials (natural diamond flat, diamond films, and DLC films). This increase in friction is due to the silicon oxides film produced on the surface of Si 3 N 4 pins in humid air.