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.

Carbon nanotube-MoS2 composites as solid lubricants.

Abstract: Solid lubricants (SLs) characterized by low coefficients of friction (μ) and wear rates (w) drastically improve the life span of instruments that undergo extreme frictional wear. However, the performance of SLs such as sputtered or nanoparticulate molybdenum disulfide (MoS2), tungsten disulfide (WS2), or graphite deteriorates heavily under extreme operational conditions such as elevated temperatures and high humidity. Here, we present our preliminary results, which demonstrate that composites of carbon nanotubes (CNTs) and MoS2 produced by electrodeposition of MoS2 on vertically aligned CNT films have low μ (∼0.03) and w (∼10−13 mm3/N·mm) even at 300 °C, which are about 2 orders of magnitude better than those of nanoparticulate MoS2-based coatings. The high load-bearing capacity of CNTs provides a strong enduring support to MoS2 nanoclusters and is responsible for their ultralow w. The incorporation of these composites in liquid lubricants reduces the friction coefficient of the liquid lubricants by ∼15%....

Hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering for high-speed gas-phase thermometry

Abstract: We demonstrate hybrid femtosecond/picosecond (fs/ps) coherent anti-Stokes Raman scattering for high-speed thermometry in unsteady high-temperature flames, including successful comparisons with a time- and frequency-resolved theoretical model. After excitation of the N(2) vibrational manifold with 100 fs broadband pump and Stokes beams, the Raman coherence is probed using a frequency-narrowed 2.5 ps probe beam that is time delayed to suppress the nonresonant background by 2 orders of magnitude. Experimental spectra were obtained at 500 Hz in steady and pulsed H(2)-air flames and exhibit a temperature precision of 2.2% and an accuracy of 3.3% up to 2400 K. Strategies for real-time gas-phase thermometry in high-temperature flames are also discussed, along with implications for kilohertz-rate measurements in practical combustion systems.

Assessment of metal nanoparticle agglomeration, uptake, and interaction using high-illuminating system

Abstract: In the present study, an ultrahigh-resolution system was applied as a simple and convenient technique to characterize the extent of metal nanoparticle agglomeration in solution and to visualize nanoparticle agglomeration, uptake, and surface interaction in three cell phenotypes under normal culture conditions. The experimental results demonstrated that silver (25, 80, 130 nm); aluminum (80 nm); and manganese (40 nm) particles and agglomerates were effectively internalized by rat liver cells (BRL 3A), rat alveolar macrophages (MACs), and rat neuroendocrine cells (PC-12). Individual and agglomerated nanoparticles were observed within the cells and agglomerates were observed on the cell surface membranes. The particles were initially dispersed in aqueous or physiological balanced salt solutions and agglomeration was observed using the Ultra Resolution Imaging (URI) system. Different methods, such as sonication and addition of surfactant (0.1% sodium dodecyl sulfate [SDS]) reduced agglomeration. Due to effects of SDS itself on cell viability, the surfactant could not be directly applied during cell exposure. Therefore, following addition of 0.1% SDS, the particles were washed twice with ultrapure water, which reduced agglomeration even further. Reducing the agglomeration of the nanoparticles is important for studying their uptake and in applications that benefit from individual nanoparticles such as diagnostics. In summary, this study demonstrates a simple technique to characterize the extent of nanoparticle agglomeration in solution and visualize nanoparticle (40 nm and larger) uptake and interaction with cells. Additionally, an example application of nanoparticle labeling onto the surface and neurite extensions of murine neuroblastoma cells (N2A) is presented as a potential imaging tool.

Self-consistent modeling of the flow behavior of wrought alpha/beta titanium alloys under isothermal and nonisothermal hot-working conditions

Abstract: A self-consistent model was applied to predict the plastic flow behavior during hot working of alpha/beta titanium alloys with wrought (equiaxed alpha) microstructures as a function of the flow behavior and volume fractions of the individual phases. For this purpose, constitutive relations that incorporated composition-dependent strength coefficients were determined for the alpha and beta phases. With these constitutive relations and measurements of the specific compositions and volume fractions of the two phases at hot-working temperatures, the flow stress dependence on temperature under nominally isothermal conditions and the (average) strain rates in the individual phases were predicted for Ti-6Al-4V. The effect of temperature transients during hot deformation on the flow stress under nonisothermal (conventional) forging conditions and under nominally isothermal, high strain-rate conditions was also established using the self-consistent modeling approach. In these instances, the effect of a rapid temperature drop or rise, respectively, on the retention of a metastable microstructure was quantified. The predicted flow behaviors showed good agreement with experimental measurements.