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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Nanomanufacturing: Nano-Structured Materials Made Layer-by-Layer

Large-scale, high-throughput production of nano-structured materials (i.e. nanomanufacturing) is a strategic area in manufacturing, with markets projected to exceed $\$$1T by 2015. Nanomanufacturing is still in its infancy; process/product developments are costly and only touch on potential opportunities enabled by growing nanoscience discoveries. The greatest promise for high-volume manufacturing lies in age-old coating and imprinting operations. For materials with tailored nm-scale structure, imprinting/embossing must be achieved at high speeds (roll-to-roll) and/or over large areas (batch operation) with feature sizes less than 100 nm. Dispersion coatings with nanoparticles can also tailor structure through self- or directed-assembly. Layering films structured with these processes have tremendous potential for efficient manufacturing of microelectronics, photovoltaics and other topical nano-structured devices. This project is designed to perform the requisite R and D to bring Sandia's technology base in computational mechanics to bear on this scale-up problem. Project focus is enforced by addressing a promising imprinting process currently being commercialized.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A Comparison of the Solubility Products of Layered Me(II)–Al(III) Hydroxides Based on Sorption Studies with Ni(II), Zn(II), Co(II), Fe(II), and Mn(II)

The precipitation of mixed metal–aluminum-layered double hydroxides (Me(II)–Al(III)-LDH)) may be an important control of the solubility of Mn(II), Fe(II), Ni(II), Zn(II), and Co(II) in soils, but assessment of this process is hindered by a lack of thermodynamic data. Here, we determined the solubility products (Ksp) of the Me(II)–Al(III)-LDHs formed by these metals based on long-term Me(II)–γAl2O3 sorption studies complemented with X-ray absorption spectroscopy (XAS) measurements. The LDH phases had the chemical formula Me(II)2/3Al1/3(OH)2Cl1/3. Solubility products were derived as Ksp = (Me2+)aq2/3(Al3+)aq1/3(OH−)aq2(Cl−)aq1/3, where brackets represent aqueous activity values determined from the equilibrium solution chemistry of the sorption samples. The Ksps are metal-dependent, with values increasing by two orders of magnitude in the order Ni(II) < Zn(II) < Co(II) < Fe(II) < Mn(II). Comparison to the solubility of β-Me(OH)2 suggests considerable thermodynamic preference of Me(II)–Al(III)-LDH over β-Me(OH)2 in soil environments and reveals a linear relation between the log-transformed Ksp values of Me(II)–Al(III)-LDH and β-Me(OH)2. Solubility plots suggest that Ni(II)–, Zn(II)–, and Co(II)–Al(III)-LDH may form in metal-polluted soils. Fe(II)–Al(III)-LDH may occur in riparian soils undergoing reduction, but precipitation of Mn(II)–Al(III)-LDH appears unlikely as it requires [Mn2+]aq much higher than commonly encountered in reducing soils. Additional thermodynamic and field studies are needed to further assess the importance of Me(II)–Al(III)-LDHs in soils and related geochemical systems.

Bhattacharya, Lasita↗
NASA NTRS1975

Application of a general boundary layer analysis to turbulent boundary layers subjected to strong favorable pressure gradients

Theoretical predictions of turbulent boundary layer development under the influence of strong favorable pressure gradients made using a finite-difference calculation procedure are compared to experimental data. Comparisons are presented for low speed flows with and without wall heat transfer as well as for supersonic flows with adiabatic walls. The turbulence model used is governed by an integral form of the turbulence kinetic energy equation and the results are compared with predictions made using a conventional equilibrium turbulence model based upon Prandtl's mixing length, a Clauser-type eddy viscosity model used by Cebecci and Mosinskis, and a two-equation turbulence energy model of Launder and Jones.

Kreskovsky, J. P.↗
NASA NTRS1987

The measurement of boundary layers on a compressor blade in cascade. II - Suction surface boundary layers

A one-component laser Doppler velocimeter (LDV) has been used to measure the two-dimensional, periodic flow field about a double circular arc, compressor blade in cascade. Eleven boundary layer profiles were taken on both the pressure and suction surfaces of the blade, and two were taken in the near wake. In this part of the study, the LDV system is described and the suction surface flow field is documented. The suction surface profiles appear to separate both at the leading edge and again somewhat beyond midchord; the leading edge separation apparently reattaches by 2.6 percent chord.

Deutsch, Steven↗
NASA NTRS1989

The effects of forcing on a single stream shear layer and its parent boundary layer

The detailed response of a large single-stream shear layer to a sinusoidal forcing at x = 0 is quantitatively defined. Phase-averaged data are used to characterize the increased disturbance convection velocity and a width measure of the disturbance field. These findings are consistent with and complement those of Fiedler and Mensing (1985).

Haw, R. C.↗
NASA NTRS1990

Critical-layer nonlinearity in the resonance growth of three-dimensional waves in boundary layers

The nonlinear interactions of a triad of initially linear stability waves are addressed. The triad consisted of a single two-dimensional mode at a given frequency and two oblique modes with equal and opposite spanwise wave numbers. The oblique waves were at half the frequency and streamwise wave number of the two-dimensional mode. Attention was focused on the boundary-layer transition at low frequencies and high Reynolds numbers. A five-zoned structure and low-frequency scaling were used to derive the nonlinear-interaction equations. The initial nonlinear development of the waves was analyzed; the results indicated that the two-dimensional wave behaves according to linear theory. Nonlinear interactions caused exponential-of-an-exponential growth of the oblique modes. This resonant amplification of the subharmonic depended on the initial amplitude of the two-dimensional wave and on the initial phase angle between the two-dimensional wave and the oblique waves. The resonant growth of the oblique modes was more pronounced at lower frequencies than at higher frequencies. The results are in good agreement with experimental results and offer explanations of the observed process.

Mankbadi, Reda R.↗
NASA NTRS1999

Layered double hydroxide stability. 2. Formation of Cr(III)-containing layered double hydroxides directly from solution

Solutions containing divalent metal [M(II) = Mg2+, Zn2+, Co2+, Ni2+, Mn2+] chlorides and CrCl3 6H2O were titrated with NaOH to yield, for M(II) = Zn, Co, and Ni, hydrotalcite-like layered double hydroxides (LDHs), [[M(II)]1-z[Cr(III)]z(OH)2][Cl]z yH2O, in a single step, without intermediate formation of chromium hydroxide. Analysis of the resultant titration curves yields solubility constants for these compounds. These are in the order Zn < Ni approximately Co, with a clear preference for formation of the phase with z = 1/3. With Mg2+ as chloride, titration gives a mixture of Cr(OH)3 and Mg(OH)2, but the metal sulfates give Mg2Cr(OH)6 1/2(SO4) by a two-step process. Titrimetric and spectroscopic evidence suggests short-range cation order in the one-step LDH systems.

Non-NASA Center↗
NASA NTRS1999

Layered double hydroxide stability. 1. Relative stabilities of layered double hydroxides and their simple counterparts

Solutions containing di- and trivalent metal chlorides [M(II) = Mg2+, Zn2+, Co2+, Ni2+, Mn2+; M(III) = Al3+, Fe3+] were titrated with NaOH to yield hydrotalcite-like layered double hydroxides (LDH), [[M(II)]1-x[M(III)]x(OH)2][Cl]x yH2O, by way of M(III) hydroxide/hydrous oxide intermediates. Analysis of the resultant titration curves yields nominal solubility constants for the LDH. The corresponding LDH stabilities are in the order Mg < Mn < Co approximately Ni < Zn for M(II) and Al < Fe for M(III). The stability of LDH relative to the separate metal hydroxides/hydrous oxides is discussed.

Non-NASA Center↗
NASA NTRS2005

Influence of a fat layer on the near infrared spectra of human muscle: quantitative analysis based on two-layered Monte Carlo simulations and phantom experiments

The influence of fat thickness on the diffuse reflectance spectra of muscle in the near infrared (NIR) region is studied by Monte Carlo simulations of a two-layer structure and with phantom experiments. A polynomial relationship was established between the fat thickness and the detected diffuse reflectance. The influence of a range of optical coefficients (absorption and reduced scattering) for fat and muscle over the known range of human physiological values was also investigated. Subject-to-subject variation in the fat optical coefficients and thickness can be ignored if the fat thickness is less than 5 mm. A method was proposed to correct the fat thickness influence. c2005 Optical Society of America.

NASA Discipline Life Sciences Technologies↗
DOE OSTI2013

Low-dislocation-density epitatial layers grown by defect filtering by self-assembled layers of spheres

A method for growing low-dislocation-density material atop a layer of the material with an initially higher dislocation density using a monolayer of spheroidal particles to bend and redirect or directly block vertically propagating threading dislocations, thereby enabling growth and coalescence to form a very-low-dislocation-density surface of the material, and the structures made by this method.

36 MATERIALS SCIENCE↗