Mossbauer study of hydrogen diffused in iron and steels
Mossbauer effect study of hydrogen adsorption onto metal surface by cathodic charging
METAL SURFACE↗
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Reflectance and Mossbauer spectroscopy of ferrihydrite-montmorillonite assemblages as Mars soil analog materials
Spectroscopic analyses show that Fe(3+)-doped smectites prepared in the laboratory exhibit important similarities to the soils on Mars. Ferrihydrite has been identified as the interlayer ferric component in Fe(3+)-doped smectites by a low quadrupole splitting and magnetic field strength of approximately 48 tesla in Mossbauer spectra measured at 4.2 K, as well as a crystal field transition at 0.92 micrometer. Ferrihydrite in these smectites explains features in the visible-near infrared region that resemble the energies and band strengths of features in reflectance spectra observed for several bright regions on Mars. Clay silicates have met resistance in the past as Mars soil analogs because terrestrial clay silicates exhibit prominent hydrous spectral features at 1.4, 1.9, and 2.2 micrometers; and these are observed weakly, if at all, in reflectance spectra of Mars. However, several mechanisms can weaken or compress these features, including desiccation under low-humidity conditions. The hydration properties of the interlayer cations also effect band strengths, such that a ferrihydrite-bearing smectite in the Martian environment would exhibit a 1.9 micrometers H2O absorption that is even weaker than the 2.2 micrometers structural OH absorption. Mixing experiments demonstrate that infrared spectral features of clays can be significantly suppressed and that the reflectance can be significantly darkened by mixing with only a few percent of a strongly absorbing opaque material. Therefore, the absolute reflectance of a soil on Mars may be disproportionately sensitive to a minor component. For this reason, the shape and position of spectral features and the chemical composition of potential analogs are of utmost importance in assessing the composition of the soil on Mars. Given the remarkable similarity between visible-infrared reflectance spectra of soils in bright regions on Mars and Fe(3+)-doped montmorillonites, coupled with recent observations of smectites in SNC meteorites and a weak 2.2 micrometers absorption in some Mars soils, ferrihydrite-bearing smectites warrant serious consideration as a Mars soil analog.
NASA Discipline Exobiology↗
Mineralogy at Gusev Crater from the Mossbauer spectrometer on the Spirit Rover
Mossbauer spectra measured on Mars by the Spirit rover during the primary mission are characterized by two ferrous iron doublets (olivine and probably pyroxene) and a ferric iron doublet (tentatively associated to nanophase ferric iron oxide). Two sextets resulting from nonstoichiometric magnetite are also present, except for a coating on the rock Mazatzal, where a hematite-like sextet is present. Greater proportions of ferric-bearing phases are associated with undisturbed soils and rock surfaces as compared to fresh rock surfaces exposed by grinding. The ubiquitous presence of olivine in soil suggests that physical rather than chemical weathering processes currently dominate at Gusev crater.
Minerals↗
Vibration analysis utilizing Mossbauer effect
Measuring instrument analyzes mechanical vibrations in transducers at amplitudes in the range of a few to 100 angstroms. This instrument utilizes the Mossbauer effect, the phenomenon of the recoil-free emission and resonant absorption of nuclear gamma rays in solids.
Roughton, N. A.↗
The use of the Mossbauer effect and laser interferometry to determine extremely small amplitudes for vibration measurements and calibration
Using Mossbauer effect and laser interferometry to determine extremely small amplitudes for vibration measurements and calibration of scale models
Lackner, H. G.↗
Small amplitude vibration calibration using the Mossbauer effect.
Design criteria and operational properties of small amplitude vibration calibration capabilities using Mossbauer effect
Netusil, W. F.↗
Mossbauer-effect data-collection system
Automated data collection system which uses a small, general-purpose digital computer provides data acquisition from, and minor control of, four Mossbauer-effect experiments. This system is economical with no loss of versatility to the experimenter and is useful in handling large volumes of data from research experiments.
Aschenbrenner, R. A.↗
Mossbauer vibration calibration systems evaluated
Mossbauer effect vibration calibrator measures the velocity of high frequency, low amplitude vibration at various velocity and frequency ranges. It contains a highly precise calibrations standard unit and a vibration measuring system and may be applied to ultrafine testing and calibrating prezoelectric shakers, and vibration transducers.
Hobbs, J. V.↗
A study of sensitization in types 304 and 304L stainless steels using Mossbauer spectroscopy.
Stainless steel sensitization analyzed using Mossbauer spectroscopy and X ray diffraction, noting ferromagnetic phase
Albritton, O. W.↗
A versatile Mossbauer spectrometer and its applications in vibration measurement
A Fe-57 Mossbauer spectrometer, equally efficient in transmission and reflection geometries, is described. The radiation detector consists of a 1.524- by 5.08 by 5.08-cm rectangular NaI(Tl) crystal with a hole 1.524 cm in diameter. The front and back faces of the crystal are covered with beryllium windows 0.0127 cm thick and 3.81 cm in diameter. The energy of the radiation accepted for counting ranges from 6.3 keV conversion X-rays to the 14.4 keV reemitted gamma rays. The spectrometer was used to measure various types of low frequency (10 Hz) and low amplitude (0.254 mm) periodic motion of steel specimens.
Singh, J. J.↗
Analysis of Mossbauer Fe-57 absorption in an F.C.C. Fe-Co-V alloy
Mossbauer Fe-57 absorption spectra of superparamagnetic F.C.C. Fe sub .34 Co sub .52 V sub 14 (Vicalloy II) have been analyzed using a cluster model and magnetic resonance relaxation theory. The number and magnetic moment of the clusters were determined from magnetization data. A least squares fit to the spectrum at 4.2 K gives sub Hhyp = 175. kG, substantially greater than the value 55 kG inferred just from the observed broadening of the single line spectrum. From this broadening an estimate of 40 kG is obtained for the width of the distribution in Hhyp at 4.2 K arising from compositional fluctuations sub and small cluster effects.
Bambakidis, G.↗
Mossbauer spectroscopic study of Luna 16 lunar regolith
Samples of bulk fractions of lunar regolith from the surface layer A and the deep layer V were measured by Mossbauer spectroscopy with the FE57 nucleus. Metallic iron, ilmenite, olivine, pyroxene (mainly augite), and glasses were found. The iron distribution by mineral phases indicates that Luna 16 regolith differs from Apollo 11 regolith by a lower ilmenite content and a greater amount of olivine, and differs from Apollo 12 regolith by somewhat more olivine. No appreciable amount of iron was found in the trivalent state.
Malysheva, T. V.↗
Mossbauer analysis of Luna 16 lunar surface material
Samples of Apollo 11 lunar surface material were studied by the Mossbauer effect. Owing to the small number of other resonant isotopes, all measurements were made with Fe-57 nuclei. The principal constituents of the material were as follows: Iron containing silicates (olivine, pyroxene, and so on), ilmenite (FeTiO3), and metallic iron.
Nady, D. L.↗
Feasibility of Mossbauer survey meter for hydrocarbon and mineral reserves
The feasibility of developing a Mossbauer survey meter for geophysical prospecting was investigated. Various critical requirements that will have to be met by the source and absorber crystals in such an instrument were identified. It was concluded that a survey meter based on (Rh-103 resonance (40 kev) yields Rh-103) isomeric transition is feasible and should be developed.
Singh, J. J.↗
Mossbauer effect studies in iron containing nonmagnetic impurities
Mossbauer parameters of dilute quaternary (Fe-XYZ) alloys where X, Y, Z, are Al, Ge, and La, respectively were studied. A comparison between the computed and the observed values indicates that changes in effective hyperfine field, outer peak widths and the isomer shift predicted on the basis of binary alloys of the individual impurities are equal, within experimental errors, to those obtained in quaternary (Fe-XYZ) alloys. The effects of simultaneously present dilute impurities are shown to be additive, independent of their respective electronic configurations.
Singh, J. J.↗
Mossbauer spectroscopy of iron in the Luna 20 regolith
Results of the Mossbauer effect measurements on Fe-57 in the average sample of the Luna 20 regolith, and their comparison with similar measurements of the Luna 16 samples are presented. Room temperature measurements of the nonmagnetic as well as magnetic components of the spectra were performed. By careful least-squares analysis, six quadrupole doublets in the inner parts of spectra were resolved. According to their splittings, they were interpreted as four types of iron in silicates (olivine, two inequivalent pyroxene sites, and a glassy fraction) and two types of nonmagnetic iron-titanium oxides (ilmenite and a spinel). Velocity-window measurements, were used to determine the average nickel content of (2.01 plus or minus 0.84) wt. %. These results are discussed in terms of distribution of iron among different phases. In comparison with the Luna 16 sample, the Luna 20 sample contains more olivine and less ilmenite as well as metal with a slightly higher nickel content.
Zemcik, T.↗
A computer program for analyzing unresolved Mossbauer hyperfine spectra
The program for analyzing unresolved Mossbauer hyperfine spectra was written in FORTRAN 4 language for the Control Data CYBER 170 series digital computer system with network operating system 1.1. With the present dimensions, the program requires approximately 36,000 octal locations of core storage. A typical case involving two innermost coordination shells in which the amplitudes and the peak positions of all three components were estimated in 25 iterations requires 30 seconds on CYBER 173. The program was applied to determine the effects of various near neighbor impurity shells on hyperfine fields in dilute FeAl alloys.
Schiess, J. R.↗
Mossbauer study of FeSi2 and FeSe thin films
Structural studies of FeSi2 and FeSe thin films have been conducted via Mossbauer spectroscopy as continuation of earlier investigation of FeTe films. Results discuss structures of bulk and thin-film FeSi2 and bulk and thin-film FeSe.
Aggarwal, K.↗