Results for “electron microscope” — Page 50

NASA NTRS1979

A theory of local and global processes which affect solar wind electrons. 2: Experimental support

The microscopic characteristics of the Coulomb cross section show that there are three natural subpopulations for plasma electrons: the subthermals with local kinetic energy E kT sub c; the transthermals with kT sub c E 7 kT sub c and the extrathermals E 7 kT sub c. Data from three experimental groups on three different spacecraft in the interplanetary medium over a radial range are presented to support the five interrelations projected between solar wind electron properties and changes in the interplanetary medium: (1) subthermals respond primarily to local changes (compression and rarefactions) in stream dynamics; (2) the extrathermal fraction of the ambient electron density should be anti-correlated with the asymptotic bulk speed; (3) the extrathermal "temperature" should be anti-correlated with the local wind speed at 1 AU; (4) the heat flux carried by electrons should be anti-correlated with the local bulk speed; and (5) the extrathermal differential 'temperature' should be nearly independent of radius within 1 AU.

Scudder, J. D.↗

NASA NTRS2005

Automatic Focus Adjustment of a Microscope

AUTOFOCUS is a computer program for use in a control system that automatically adjusts the position of an instrument arm that carries a microscope equipped with an electronic camera. In the original intended application of AUTOFOCUS, the imaging microscope would be carried by an exploratory robotic vehicle on a remote planet, but AUTOFOCUS could also be adapted to similar applications on Earth. Initially control software other than AUTOFOCUS brings the microscope to a position above a target to be imaged. Then the instrument arm is moved to lower the microscope toward the target: nominally, the target is approached from a starting distance of 3 cm in 10 steps of 3 mm each. After each step, the image in the camera is subjected to a wavelet transform, which is used to evaluate the texture in the image at multiple scales to determine whether and by how much the microscope is approaching focus. A focus measure is derived from the transform and used to guide the arm to bring the microscope to the focal height. When the analysis reveals that the microscope is in focus, image data are recorded and transmitted.

Huntsberger, Terrance↗

NASA NTRS1974

Random walk theory applied to electron avalanche formation

Use of microscopic detail in random walk theory describing the initial formations of a large number of avalanches shows that concomitant electron transport coefficients quickly relax to equilibrium values. This enables the use of random walks having step sizes and probabilities based only on local electric field strengths and densities. A self-consistent avalanche solution which accounts for collective long range Coulomb interactions as well as short range elastic and inelastic collisions between electrons and background atoms is demonstrated for helium. Avalanche growth retardation followed by an abrupt growth augmentation as time proceeds is shown to be associated with the formation of regions of charge density extrema near the avalanche axis and within the axial distance covered by the electron swarm.

Englert, G. W.↗

NASA NTRSDate not supplied

Variable Pressure - Scanning Electron Microscopy (VP-SEM)

Variable Pressure (or Environmental) Scanning Electron Microscopy (VP-SEM) combined with Energy Dispersive X-ray Spectroscopy (EDS) is one of the most powerful methods for characterizing the sub-micron topography and chemical composition of uncoated samples. Terrestrially, VP-SEM is extensively used to non-destructively study geologic and manufactured materials with high spatial resolution (tens of nanometers) and large depth-of-field. An SEM offers a geologist a first survey of microscopic mineral phases via secondary electron imaging (SEI), which provides a topographic look at a sample, as well as backscattered electron (BEI) imaging, which contrasts the phases present based on their geochemistry (atomic number). A VP-SEM utilizes a gas in the sample chamber as a charge dissipation and signal amplification method, allowing analysis of a sample without preparation in the form of a conductive coating. A miniaturized VP-SEM operating in-situ on a lander or rover would be able to use the CO2-rich Martian atmosphere (e.g., Nier et al., 1976; Williams 2016) as an imaging medium for this purpose. Adaptation of a VP-SEM for in-situ Mars surface studies will provide a new imaging capability (via SEI) that is at least an order of magnitude higher resolution than the Mars Hand Lens Imager (MAHLI) on the Mars Science Laboratory (Williams et al., 2015), and equal to or better than the achieved resolution of the Atomic Force Microscope on the Phoenix Mars lander (Pike et al., 2011). In addition, the MVP-SEM is capable of BSI and simultaneous chemical analysis of the imaged region. In this sense, the MVP-SEM can be regarded as an instrument suite that will provide a new set of information not achievable by any other instrument. The Miniaturized Variable Pressure Scanning Electron Microscope (MVP-SEM) was designed, built, and benchtop tested by a team at NASA’s Marshall Space Flight Center and Jet Propulsion Laboratory (JPL), Jacobs Space Exploration Group, Applied Physics Technologies, Inc. (AP-Tech), and Creare LLC, working with a team of technical and science collaborators. Benchtop testing was successful, proving concept feasibility. To date, the MVP-SEM has achieved an imaging resolution of <100 nm in the lab, and with continued optimization, even better performance (~50 nm resolution) is possible. Use in-situ on the lunar or other planetary surfaces would require some redesign to optimize instrument performance, but such an instrument would be equally useful.

Variable Pressure Scanning Electron Microscopy↗

NASA NTRSDate not supplied

Miniature Variable Pressure - Scanning Electron Microscopy (MVP-SEM)

Variable Pressure (or Environmental) Scanning Electron Microscopy (VP-SEM) combined with Energy Dispersive X-ray Spectroscopy (EDS) is one of the most powerful methods for characterizing the sub-micron topography and chemical composition of uncoated samples. Terrestrially, VP-SEM is extensively used to non-destructively study geologic and manufactured materials with high spatial resolution (tens of nanometers) and large depth-of-field. An SEM offers a geologist a first survey of microscopic mineral phases via secondary electron imaging (SEI), which provides a topographic look at a sample, as well as backscattered electron (BEI) imaging, which contrasts the phases present based on their geochemistry (atomic number). A VP-SEM utilizes a gas in the sample chamber as a charge dissipation and signal amplification method, allowing analysis of a sample without preparation in the form of a conductive coating. A miniaturized VP-SEM operating in-situ on a lander or rover would be able to use the CO2-rich Martian atmosphere (e.g., Nier et al., 1976; Williams 2016) as an imaging medium for this purpose. Adaptation of a VP-SEM for in-situ Mars surface studies will provide a new imaging capability (via SEI) that is at least an order of magnitude higher resolution than the Mars Hand Lens Imager (MAHLI) on the Mars Science Laboratory (Williams et al., 2015), and equal to or better than the achieved resolution of the Atomic Force Microscope on the Phoenix Mars lander (Pike et al., 2011). In addition, the MVP-SEM is capable of BSI and simultaneous chemical analysis of the imaged region. In this sense, the MVP-SEM can be regarded as an instrument suite that will provide a new set of information not achievable by any other instrument. The Miniaturized Variable Pressure Scanning Electron Microscope (MVP-SEM) was designed, built, and benchtop tested by a team at NASA’s Marshall Space Flight Center and Jet Propulsion Laboratory (JPL), Jacobs Space Exploration Group, Applied Physics Technologies, Inc. (AP-Tech), and Creare LLC, working with a team of technical and science collaborators. Benchtop testing was successful, proving concept feasibility. To date, the MVP-SEM has achieved an imaging resolution of <100 nm in the lab, and with continued optimization, even better performance (~50 nm resolution) is possible. Use in-situ on the lunar or other planetary surfaces would require some redesign to optimize instrument performance, but such an instrument would be equally useful.

Variable Pressure Scanning Electron Microscopy↗

NASA NTRS1970

Elevated temperature instability of Stellite 6B

Metallographic and chemical analysis by X-ray diffraction, microscopic examination, and electron microprobes of elevated temperature instability effects on Stellite 6B

Bleil, H. E.↗

NASA NTRS1976

Mineralogy and petrology of complex breccia 14063,14

Breccia 14063,14 is a complex, probably pre-Imbrian, unmetamorphosed breccia dominated almost entirely by mineral clasts. Electron-probe and microscope examination showed at least four distinct lithologies in a centimeter-sized thin-section. Examination of each lithology showed or suggested the following contributing rock types or mineralogies: (1) dunite with minor chromite, very high-Mg ilmenite and bronzite; (2) spinel troctolite with olivine and Mg-Al spinel; (3) high-Ti mare-like basalt with high-Mg ilmenite and coarse pyroxene; (4) low-KREEP noritic breccia; (5) anorthosite; (6) very Ni-rich Fe metal.

Steele, I. M.↗

NASA NTRS1977

Research directed toward improved echelles for the ultraviolet

Low frequency gratings obtainable with present technology, can meet the grating-efficiency design goals for potential space telescope spectrographs. Gratings made with changes in the three specific parameters: the ruling tool profile, the coating material, and the lubricants used during the ruling process were compared. A series of coatings and test gratings were fabricated and were examined for surface smoothness with a Nomarski differential interference microscope and an electron microsocope. Photomicrographs were obtained to show the difference in smoothness of the various coatings and rulings. Efficiency measurements were made for those test rulings that showed good groove characteristics: smoothness, proper ruling depth, and absence of defects (e.g., streaks, feathered edges and rough sides). Higher grating efficiency should be correlated with the degree of smoothness of both the coating and the grating groove.

Source record↗

NASA NTRS1977

Metallic phases in the Luna 24 soil samples

The metal and sulfide phases in the Luna 24 soil samples were studied with the optical microscope and the electron microprobe. The compositions of the metal particles fall into three groups based on their Ni and Co contents: (1) Samples of meteoritic composition which have undergone metamorphism on the lunar surface. (2) Samples of submeteoritic, low Ni and low Co contents, including most of the metal particles observed. These particles are contained in glass and agglutinate particles and were probably formed by the mixing of meteoritic metal with lunar metal produced by the reduction of silicates during shock-impact. (3) Samples of high-CO content probably formed by mixing of meteoritic material with high-Co metal from the mare basalt or by fractional crystallization from a metal silicate melt. The sulfide minerals were also studied. These are almost pure FeS, and crystallized from a late stage liquid in the mare basalt. Three high-Ni sulfides were also found in the glass phase of agglutinates.

Friel, J. J.↗

NASA NTRS1979

The petrology and chemistry of basaltic fragments from the Apollo 11 soil - I

A study of basaltic fragments from the Apollo 11 bulk sample using instrumental neutron activation analysis, the petrographic microscope, and the electron microprobe is presented. The fragments include Group A, B2, and B3 basalts, of which two of the Group A samples are vitrophyres with bulk compositions similar to the crystalline high-K rocks which crystallized under different physical conditions and represent a second high-K cooling unit. The B2 samples relate to each other through ilmenite fractionation, and the B3 samples relate through olivine fractionation; it is concluded that the B2 samples have an anomalously high La/K ratio and may have generated in the same source region as the Group D basalts.

Beaty, D. W.↗

NASA NTRS1979

Carbon fiber modification

The effect of several chemical treatments on the electrical and mechanical properties of carbon fibers was investigated with an optimum goal of increasing the electrical resistivity by a factor of 1000 without appreciably changing the mechanical properties. It was possible to effect resistivity increases from 10 to 50 percent without adversely affecting the tensile strength or Young's modulus for T-300 and C-6000 PAN fibers by treatments with either AlCl3 or nitric acid mixtures. Larger increases in the resistivity were produced with pitch fibers treated with nitric acid mixtures. This treatment also produced a partial decomposition of the pitch fiber and deterioration of the mechanical properties. The rationale behind the approch was to immobilize the conductivity producing pi electrons in the microscopic aromatic structure of the carbon fibers without destroying the strength producing sigma bonds. The investigations indicate that certain chemical treatments can produce such results, but the total reduction in the electrical conductivity which was achieved was not large enough to impact on problems which might arise from the high conductivities of the fibers.

Thompson, T. E.↗

NASA NTRS1982

Plastic deformation and wear process at a surface during unlubricated sliding

The plastic deformation and wear of a 304 stainless steel surface sliding against an aluminum oxide rider with a spherical surface (the radius of curvature: 1.3 cm) were observed by using scanning electron and optical microscopes. Experiments were conducted in a vacuum of one million Pa and in an environment of fifty thousandth Pa of chlorine gas at 25 C. The load was 500 grams and the sliding velocity was 0.5 centimeter per second. The deformed surface layer which accumulates and develops successively is left behind the rider, and step shaped proturbances are developed even after single pass sliding under both environmental conditions. A fully developed surface layer is gradually torn off leaving a characteristic pattern. The mechanism for tearing away of the surface layer from the contact area and sliding track contour is explained assuming the simplified process of material removal based on the adhesion theory for the wear of materials.

Yamamoto, T.↗

NASA NTRS1982

SEM, optical, and Moessbauer studies of submicrometer chromite in Allende

New scanning electron and optical microscope results are presented showing that sub-micrometer chromite is abundant along healed cracks and grain boundaries in Allende chondrule olivine. Some wider healed cracks also contain pentlandite and euhedral Ni3Fe grains. Also reported are Moessbauer measurements on Allende HF-HCl residues confirming a high Fe(+++)/Fe(++) ratio.

Housley, R. M.↗

NASA NTRS1983

Plastic deformation and wear process at a surface during unlubricated sliding

The plastic deformation and wear of a 304 stainless steel surface sliding against an aluminum oxide rider with a spherical surface (the radius of curvature: 1.3 cm) were observed by using scanning electron and optical microscopes. Experiments were conducted in a vacuum of one million Pa and in an environment of fifty thousandth Pa of chlorine gas at 25 C. The load was 500 grams and the sliding velocity was 0.5 centimeter per second. The deformed surface layer which accumulates and develops successively is left behind the rider, and step shaped proturbances are developed even after single pass sliding under both environmental conditions. A fully developed surface layer is gradually torn off leaving a characteristic pattern. The mechanism for tearing away of the surface layer from the contact area and sliding track contour is explained assuming the simplified process of material removal based on the adhesion theory for the wear of materials. Previously announced in STAR as N82-32735

Yamamoto, T.↗

NASA NTRS1984

Extreme incompatibility of Pb during the crystallization of magmatic iron meteorites

The partitioning behavior of Pb in the three-phase system metal-troilite-sulfide liquid was investigated. Microscopic examination and electron microprobe analysis of a polished section showed three phases--Fe metal, troilite and an Fe-S-Pb-O metallic liquid. The Pb concentration of the metallic liquid was 1.4 wt.%; the Pb contents of both the troilite and the Fe metal were below the detection limit of the electron probe. To better define the Pb concentrations of the solid phases, the same sample was analyzed for Pb and Fe using the M.I.T., Harvard and Brown ion microprobe. Even at this level of precision, some conclusions and speculations are possible: (1) The D(Pb) (troilite/metallic liquid) is low (.01 to .001) and, contrary to expectation, troilite, like metal, excludes Pb very effectively during the crystallization of metallic liquids; (2) Pb in iron meteorites is conceivably concentrated in trace phases which are less susceptible to contamination than metal and troilite; and (3) taken at face value D(Pb)(metal/troilite) is 0.1, but given the Pb and Fe ion yields from simple endmember phases (Fe, FeS, Pb, PbS), this D is more likely to be 0.05 to 0.03.

Jones, J. H.↗

NASA NTRS1988

Constraints on the origin of Archean trondhjemites based on phase relationships of Nuk gneiss with H2O at 15 kbar

Constraints on the origin of Archean trondhemites were investigated by studying the T-X(H2O) phase relationships, as a function of water content, of the trondhjemitic Nuk gneiss (the principal component of the second phase of Archean igneous activity in the Godthab region, Greenland) with water at 15-kbar pressure. High-pressure experiments were completed in a piston-cylinder apparatus wih samples enclosed in gold capsules, and phase assemblages exposed on polished surfaces of run products and analyzed using optical microscope, SEM, and electron microprobe. The data obtained were found to be consistent with the multistage development model for the Archean crust in Finland, developed by Jahn et al. (1984), which calls for at least three stages of crustal development.

Johnston, A. Dana↗

NASA NTRS2006

Tin Whiskers: A History of Documented Electrical System Failures

This viewgraph presentation reviews the history of tin and other metal whiskers, and the damage they have caused equipment. There are pictures of whiskers on various pieces of electronic equipment, and microscopic views of whiskers. There is also a chart with information on the documented failures associated with metal whiskers. There are also examples of on-orbit failures believed to be caused by whiskers.

Leidecker, Henning↗

NASA NTRSDate not supplied

Bosch Carbon Catalyst Regeneration in Water II: Analysis of Bosch Catalyst Beads Throughout the Initial Regeneration Process

Catalyst integrity is an important factor in reactor longevity since it changes the effectiveness of a reaction. A Carbon Formation Reactor (CFR), used within Series Bosch (S-Bosch), utilizes an iron alloy catalyst to convert carbon monoxide and hydrogen into water and solid carbon. The catalyst promotes the formation of carbon to such an extent that pressure-causing clogs form within the reactor and reaction sites on the catalyst become limited. To remove carbon from both the reactor and the surface of the iron alloy catalyst, a technique was developed that utilizes water, an In-Situ Resource Utilization (ISRU) Resource, and agitation to regenerate the reactor. To ascertain catalyst integrity throughout this regenerative process, sample catalyst beads were taken before and after the carbon formation reaction, and then after the regeneration process. Additionally, wastewater from the regeneration process was sampled. The sampled beads and wastewater were observed under a Scanning Electron Microscopy (SEM) microscope and the beads were chemically etched to determine if the catalyst had degraded at any point during this process, and if catalyst was lost. Minimal catalyst degradation was observed after carbon formation in the CFR.

regeneration↗