EPR-atomic scale experimental stress analysis
Electron paramagnetic resonance atomic scale stress analysis of high polymer fibers and rubber, measuring chain scission and bond rupture for different loading histories
Devries, K. L.↗
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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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A micro-macro correlation of ozone-induced fracture in rubber
Molecular bond rupture and strain energy release rates correlation during ozone cracking of rubber from electron paramagnetic resonance and stress elongation measurements
Devries, K. L.↗
Magnetic susceptibility of vanadium carbide
Single crystal vanadium carbide magnetic susceptibility decrease with increasing carbon content attributed to orbital paramagnetism
Bloom, D. W.↗
The practical use of magnetic cooling
Paramagnetic cycles for low temperature superconducting magnet cooling, discussing refrigerator, cryogenic pumps, regenerators and adjustable heat source and sink
Brown, G. V.↗
Magnetostriction, thermal expansion, and phase transitions in CsMnCl3.2H2O
Magnetostriction in antiferromagnetic, spin flopped and paramagnetic phases of hydrated cesium manganese trichloride, studying volume changes and thermal expansion near phase transition
Aron, P. R.↗
Chemical alterations resulting from proton irradiation of the lunar surface
Proton irradiation damage on lunar surface, considering solar wind sputtering, reduction, chemical bond breakage and electron paramagnetic resonance
Dreschhoff, G.↗
ESR studies of hydrogen trapped in alkali halides by proton irradiation
Trapped hydrogen atoms detection in proton irradiated KCl and NaCl single crystals at 77 K, using electron paramagnetic resonance spectroscopy
Virmani, Y. P.↗
Low temperature scale for a 1 to 20 degree Kelvin region
New temperature scale, accurate to better than plus or minus 0.001 Kelvin over low temperature region, is based on National Bureau of Standards 1955 platinum resistance thermometer scale and utilizes precise susceptibility measurements on two paramagnetic salts.
Cetas, T. C.↗
A dual-beam actinic light source for photosynthesis research
Simulation of photosynthetic process in plants is accomplished by using two separate and identical optical channels that provide independently adjustable wavelengths (filters), shutter sequencing, and control intensity of illumination. In addition to experiments using electron paramagnetic resonance spectroscopy, system may be applicable to other types of research in photosynthetic field.
Margozzi, A. P.↗
Induction plasma calcining of pigment particles for thermal control coatings
Induction plasma heating techniques were studied for calcining zinc orthotitanate particles for use in thermal control coatings. Previous studies indicated that the optimum calcining temperature is between 1400 and 1750 C. An intermediate temperature (1670 C) was chosen as a reference point for running a temperature series at the reference point and 220 C on both sides. The effect of varying chamber temperature on the reflectance spectra, before and after vacuum UV irradiation, is presented. The correlation between Zn2Ti04 paramagnetic resonance activity and its susceptibility to vacuum UV damage is discussed.
Farley, E. P.↗
Magnetism, dimensional changes, and magnetic transitions in hydrated cesium manganese chloride
Dimensional changes (strain) along the three principal crystal axes of the antiferromagnet CsMnCl3-2H2O are studied as a function of magnetic field and temperature in the antiferromagnetic, spin flopped, and paramagnetic phases. Changes in dimensions through the phase transitions between the magnetic states are examined. By applying the molecular field model and utilizing all available information, magnetic properties of CsMnCl3-2H2O are determined. The possible usefulness of this material in a magnetic refrigeration cycle is evaluated.
Woollam, J. A.↗
Design and testing of a magnetic suspension and damping system for a space telescope
The basic equations of motion are derived for a two dimensional, three degree of freedom simulation of a space telescope coupled to a spacecraft by means of a magnetic suspension and isolation system. The system consists of paramagnetic or ferromagnetic discs confined to the magnetic field between two Helmholtz coils. Damping is introduced by varying the magnetic field in proportion to a velocity signal derived from the telescope. The equations of motion are nonlinear, similar in behavior to the one-dimensional Van der Pol equation. The computer simulation was verified by testing a 264-kilogram air bearing platform which simulates the telescope in a frictionless environment. The simulation demonstrated effective isolation capabilities for disturbance frequencies above resonance. Damping in the system improved the response near resonance and prevented the build-up of large oscillatory amplitudes.
Ockman, N. J.↗
Development of space stable thermal control coatings for use on large space vehicles
The evaluation and environmental testing of zinc orthotitanate pigments for use as space stable thermal control coatings on large space vehicles are discussed. Electron paramagnetic resonance spectra of the pigments and their precursor compounds are examined. A continuing study of the spectral intensity of mercury-argon and mercury-xenon sources in reported. Results of long term environmental testing of commercially available, strippable, protective coatings are discussed.
Gilligan, J. E.↗
Fracture Behavior in Nylon 6 Fibers
Electron paramagnetic resonance (EPR) techniques are used to determine the number of free radicals produced during deformation leading to fracture of nylon 6 fibers. A reaction rate molecular model is proposed to explain some of the deformation and bond rupture behavior leading to fracture. High-strength polymer fibers are assumed to consist of a sandwich structure of disordered and ordered regions along the fiber axis. In the disordered or critical flaw regions, tie chains connecting the ordered or crystalline block regions are assumed to have a statistical distribution in length. These chains are, therefore, subjected to different stresses. The effective length distribution was determined by EPR. The probability of bond rupture was assumed to be controlled by reaction-rate theory with a stress-aided activation energy and behavior of various loadings determined by numerical techniques. The model is successfully correlated with experimental stress, strain, and bond rupture results for creep, constant rate loadings, cyclic stress, stress relaxation and step strain tests at room temperature.
Lloyd, B. A.↗
Nuclear magnetic resonance of Al-27 in topaz, Al2SiO4/F, OH/2.
The Al-27 nuclear quadrupolar coupling constant and asymmetry parameter (eta) in topaz have been determined to be 1.67 (plus or minus 0.03) MHz and 0.38 plus or minus 0.05, respectively. These values and the orientations of the principal axes are consistent with the Fe(3+) paramagnetic resonance data and with the symmetry of the AlO4F2 octahedron.
Tsang, T.↗
Concerning the production of free radicals in proteins by ultraviolet light.
The response to UV light of several solid proteins and model compounds has been studied in vacuum and at low temperature, using electron paramagnetic resonance techniques. The results indicate that the details of amino acid composition and sequence, and the tertiary structure of a protein are important in determining both the rate of, and the mechanism for, the production of free radicals, and in determining the conditions under which sulfur-type radicals can be produced. The results presented are related to enzyme inactivation and to the UV stability of proteins generally.
Androes, G. M.↗
Internal motion and its pressure dependence in FeSiF6+6/H2O/.
Both wideline and pulsed NMR techniques were used to examine the internal motion in FeSiF6+6(H2O). Corrections of second moments for bulk paramagnetic effects were essential. At room temperature and pressure, the fluorine-fluorine contribution to the 19F second moment is 0.38 (plus or minus 0.06) G2, and indicates rapid orientation of the SiF6(--) group. Analysis of the second moment within the transition region allows calculation of an activation volume which is 2.4 (plus or minus 0.4) % of the molar volume. The application of pressure slows the internal motion such that the rigid lattice values of the 19F second moment are obtained above 50 kbar.
Vaughan, R. W.↗
Lower critical field measurements in NbN bulk and thin films.
Low-field magnetization measurements were made at 4.2 K on thin-film and bulk NbN samples by using a vibrating-sample Foner magnetometer with a 50-kG superconducting solenoid. Values of the lower and upper critical fields are calculated, using magnetization curves as the basis. The significance of the Pauli spin paramagnetism and spin-orbit scattering in these materials is discussed.
Mathur, M. P.↗