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 & Mach number. The organization has 5817 authors who have published 9157 publications receiving 292559 citations. The organization is also known as: Wright-Patterson AFB & FFO.

Donor-π-Acceptor Conjugated Copolymers for Photovoltaic Applications: Tuning the Open-Circuit Voltage by Adjusting the Donor/Acceptor Ratio

Abstract: A class of new conjugated copolymers containing a donor (thiophene)−acceptor (2-pyran-4-ylidene-malononitrile) was synthesized via Stille coupling polymerization. The resulting copolymers were characterized by 1H NMR, elemental analysis, GPC, TGA, and DSC. UV−vis spectra indicated that the increase in the content of the thiophene units increased the interaction between the polymer main chains to cause a red-shift in the optical absorbance. Cyclic voltammetry was used to estimate the energy levels of the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) and the band gap (Eg) of the copolymers. The basic electronic structures of the copolymers were also studied by DFT calculations with the GGA/B3LYP function. Both the experimental and the calculated results indicated an increase in the HOMO energy level with increasing the content of thiophene units, whereas the corresponding change in the LUMO energy level was much smaller. Polymer photovoltaic cells of a bulk het...

Cold‐Pressing and Low‐Temperature Sintering of Alkoxy‐Derived PLZT

Abstract: Multiorganometallic compounds were used to prepare high-purity submicron-size lead lanthanum zirconate-titanate (PLZT) powders which can be consolidated at low sintering temperatures to high-density piezoelectric and electrooptic ceramic bodies. Simultaneous hydrolytic decomposition of lead isoamyloxide, lanthanum isopropoxide, and zirconium and titanium tertiary amyloxides produced quaternary titanate powders with particle sizes of 75 to 300 A and analyzed purity of 99.92%; the major contaminant was Na from an intermediate reaction product. Homogeneity and stoichiometry of the powders before and after processing were demonstrated by electron microscopy and chemical analysis. High-temperature X-ray diffraction indicated an amorphous material up to ∼600°C, where the crystalline phase was first observed. Powders prepared in this manner sintered to high-density fine-grained transparent bodies with uniform microstructure. The experimental results suggest that less rigorous consolidation methods are required with high-purity homogeneous precursor materials with fine particle size.

Analysis of the Rail Shear Test-Applications and Limitations

Abstract: A detailed theoretical and experimental analysis of the rail shear test is presented. A Fourier series solution is obtained for the stresses in an idealized rail shear specimen. The theoretical results are quali tatively verified on fiber reinforced rubber composites. Rail shear data on the modulus and strength of current high-modulus rein forced composites is compared to predicted values obtained from lamination theory. Results show that, despite definite limitations, the rail shear test can be useful in the determination of the in-plane shear properties of a laminated composite.

Mechanical Properties of Fine‐Grained Substoichiomebic Titanium Carbide

Abstract: An attempt was made to lower the ductile-to-brittle transition temperature (DBTT) of polycrystalline TiC and to prevent the premature intergranular fracture noted in stoichiometric Tic at high temperatures by producing four substoichiometric compositions chosen from the single-phase TiC phase field. Each desired composition was prepared by blending and vacuum hot-pressing the appropriate mixture of Ti powder and stoichiometric TiC powder. Each billet was characterized for density, hardness, lattice parameter, and microstructure. The actual bulk compositions were determined by averaging electron probe microanalysis data collected randomly from a polished section of each billet. Specimens cut from the billets were strength-tested in four-point bending from room temperature to 1400°C and in compression from room temperature to 1200°C. A qualitative determination of the material's ductility was obtained from a load vs deflection plot and by optical microscopy of polished surfaces after deformation. Both the hardness and strength dropped with decreasing C/Ti atom ratios. Billets produced at the lower C/Ti atom ratios showed a significant deviation from linearity of the load/ deflection curve at temperatures as low as 1200°C in bending, with little or no drop in strength, and as low as 600°C in compression.