A5068679442- Surface Modification and Superhydrophobicity
- Planetary Science and Exploration
- Laser Material Processing Techniques
- Space Exploration and Technology
- Particle Dynamics in Fluid Flows
- Adhesion, Friction, and Surface Interactions
- Silicone and Siloxane Chemistry
- Icing and De-icing Technologies
- Plant Surface Properties and Treatments
- Mechanical Behavior of Composites
- Smart Materials for Construction
- Synthesis and properties of polymers
- Fluid Dynamics and Turbulent Flows
- Epoxy Resin Curing Processes
- Tribology and Wear Analysis
- Marine Biology and Environmental Chemistry
- Photochromic and Fluorescence Chemistry
- Aerosol Filtration and Electrostatic Precipitation
- Gas Dynamics and Kinetic Theory
- Combustion and flame dynamics
- Electronic Packaging and Soldering Technologies
- Engineering and Material Science Research
- Fluid Dynamics and Heat Transfer
- Force Microscopy Techniques and Applications
- Astro and Planetary Science
Langley Research Center
2016-2025
National Aeronautics and Space Administration
2023
National Institute of Aerospace
2010
Virginia Commonwealth University
2004-2006
Rowan University
2006
Virginia Tech
2004
Absolute rate constants and Arrhenius parameters for hydrogen abstractions (from carbon) by the t-butoxyl radical (tBuO·) are reported several hydrocarbons tertiary amines in solution. Combined with data already literature, an analysis of all available reveals that most tBuO· entropy controlled (i.e., TΔS⧧ > ΔH⧧, solution at room temperature). For substrates C−H bond dissociation energies (BDEs) 92 kcal/mol, activation energy abstraction decreases decreasing BDE accord Evans−Polanyi...
Merocyanine (MC) isomers that are formed after absorption of a UV photon by 1',3'-dihydro-1',3'-3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2',2'-(2H)-indole] were studied. Several, predominantly TTC and TTT, merocyanine present in toluene solution ("T" "C" indicate trans cis conformations the C−C bonds methine bridge). Excitation MC visible band (at 490, 550, 630 nm) with 100 fs laser pulses was used to study excited-state dynamics. Internal conversion on picosecond time scale found be...
Adhesive bonding offers many advantages over mechanical fastening, but requires certification before it can be incorporated in primary structures for commercial aviation without disbond-arrestment features or redundant load paths. Surface preparation is widely recognized as the key step to producing robust and predictable adhesive bonds. by laser ablation provides an alternative expensive, hazardous, polluting, less precise practices used currently such chemical-dip, manual abrasion grit...
Low surface energy copoly(imide siloxane)s were generated via condensation polymerization reactions. The materials characterized spectroscopically, thermally, mechanically, and contact angle goniometry. decrease in tensile modulus opaque appearance of siloxane) films indicated phase segregation the bulk. Preferential partitioning siloxane moieties was verified by X-ray photoelectron spectroscopy (XPS) increased advancing water values (theta(A)). Pristine surfaces typically exhibited theta(A)...
A piezoelectric sensor with a floating element was developed for direct measurement of flow induced shear stress. The designed to detect the pure stress while suppressing effect normal generated from vortex lift-up by applying opposite poling vectors elements. During calibration stage, prototyped showed high sensitivity (91.3 ± 2.1 pC/Pa) due coefficients (
Novel copoly(imide siloxane)s were synthesized from commercially available aminopropyl terminated siloxane oligomers, aromatic dianhydrides, and diamines. This synthetic approach produced copolymers with well-defined blocks linked imide units in a random fashion. The copoly(amide acid)s characterized by solution viscosity subsequently used to cast thin films followed thermal imidization an inert atmosphere. Thin using contact angle goniometry, attenuated total reflection Fourier transform...
Transient absorption spectroscopy was used to investigate the dynamics of photochromic indolinobenzospiropyran reaction in toluene solution and phosphatidylcholine bilayers (1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)). After excitation with UV light, colorless (R/S)-2-(3',3'-dimethyl-6-nitro-3'H-spiro[chromene-2,2'-indol]-1'-yl)ethanol derivatives are converted colored merocyanine...
Particulate contamination is of concern in a variety environments. This issue especially important confined spaces with highly controlled atmospheres such as space exploration vehicles involved extraterrestrial surface missions. Lunar dust was significant challenge for the Apollo astronauts and will be greater longer duration, future Passive mitigation strategies, those not requiring external energy, may decrease some these concerns, have been investigated this work. A myriad approaches to...
Polystyrene latex sphere particles are widely used to seed flows for velocimetry techniques such as Particle Image Velocimetry (PIV) and Laser Doppler (LDV). These may be doped with fluorescent dyes that signals spectrally shifted from the incident laser wavelength detected via Induced Fluorescence (LIF). An attractive application of LIF signal is achieving in presence strong interference scatter, opening up new research possibilities very near solid surfaces or at liquid/gas interfaces....
Abstract Through a novel laser ablative patterning (LAP) process, the present work reported increase in wetting contact angle of two ceramic materials, boron carbide (B 4 C) and molybdenum aluminum boride (MoAlB). The LAP technique employed picosecond pulses to form crosshatch pattern with micropillars on surfaces. behavior both surfaces was successfully transitioned from hydrophilic ( θ < 90°) hydrophobic > 90°), which related Wenzel Cassie–Baxter mechanisms. Parameters such as...
The free volume properties of phospholipid bilayers have been determined using a new assay that applies the photochromic and solvatochromic merocyanines. orientation embedding depth merocyanines in bilayer are controlled substitution on merocyanine indole moiety. changes at aqueous interface (region 1), headgroup 2), aliphatic interior 3) compared by analyzing rate constants for ring-closing reaction. Free variations during Pβ'(gel) ↔ Lα(liquid) phase transition observed region 1, accordance...