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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Surface characterization and failure analysis of thermally aged, polyimide bonded titanium

This study of high temperature stable adhesive systems using 6Al-4V titanium adherends found that certain adhesive/adherends exhibit a change from cohesive to adhesive failure mode during long term 450 F thermal aging. Lap-shear specimens which exhibited adhesive failures were subjected to failure analysis using scanning transmission electron microscopy (STEM) and surface analysis techniques. Data is presented which supports the conclusion of interfacial failures for these samples.

Peters, P. D.↗
NASA NTRS1977

The use of analytical surface tools in the fundamental study of wear

Various techniques and surface tools available for the study of the atomic nature of the wear of materials are reviewed These include chemical etching, x-ray diffraction, electron diffraction, scanning electron microscopy, low-energy electron diffraction, Auger emission spectroscopy analysis, electron spectroscopy for chemical analysis, field ion microscopy, and the atom probe. Properties of the surface and wear surface regions which affect wear, such as surface energy, crystal structure, crystallographic orientation, mode of dislocation behavior, and cohesive binding, are discussed. A number of mechanisms involved in the generation of wear particles are identified with the aid of the aforementioned tools.

Buckley, D. H.↗
NASA NTRS1977

The use of analytical surface tools in the fundamental study of wear

This paper reviews the various techniques and surface tools available for the study of the atomic nature of the wear of materials. These include chemical etching, X-ray diffraction, electron diffraction, scanning electron microscopy, low-energy electron diffraction, Auger emission spectroscopy analysis, electron spectroscopy for chemical analysis, field ion microscopy, and the atom probe. Properties of the surface and wear surface regions which effect wear such as surface energy, crystal structure, crystallographic orientation, mode of dislocation behavior, and cohesive binding are discussed. A number of mechanisms involved in the generation of wear particles are identified with the aid of the aforementioned tools.

Buckley, D. H.↗
NASA NTRS2017

Characterization of Biological Fallout Particles of Cleanrooms to Measure Spacecraft Cleanliness

NASA cleanrooms are humidity, temperature-regulated, and particle contaminant-controlled environments used for spacecraft assembly. Microorganisms, which are crucial contaminants shed from humans and transported through the environment, can adapt to the oligotrophic cleanroom conditions. These biogenic particles need to be identified to extend our knowledge of biological contamination for future NASA mission use. Here, we devised an aluminum coupon with polycarbonate filter setup to collect fallout particles from an ISO 5 and an ISO 7 cleanroom. We demonstrated the presence of microbial particles, as standalone entities and associated with inert particles in cleanroom environments. The contamination was confirmed as biogenic in virtue of estimating the elemental composition of individual and aggregated particles using an epifluorescence and Field Emission Scanning Electron Microscopy (FESEM) coupled with an energy dispersive X-ray analysis (EDX). Epifluorescence microscopy showed that the particles were stained less (25%) with SYTO 9 and more (75%) with propidium iodide, suggesting that the suspected biogenic particles are membrane-compromised. Remarkably, biological particles such as bacteria and fungal spores/hyphae were observed at sizes ranging from 2 to 70 µm, with abundant C and O elemental signatures and essential tracers (Na, Mg, K, Ca and Cl). Inert particles (2 to 500 µm) that were characterized included compositions such as silica (SiO2), aluminosilicates (Al, Si), and carbonaceous fibers. Furthermore, we designed and illustrated a unique correlative epifluorescence and FE-SEM method to strengthen this approach by acquiring the same biogenic particles in the same filter coupon for a one-to-one comparison. Interestingly, the SYTO 9 stained particles showed abundant C and O elemental signature implying that they are viable microbial particles. Constant evaluation of cleanroom biological and inert particles will help to characterize biological contamination for future NASA missions (e.g. Mars 2020).

Malli Mohan, Ganesh Babu↗
NASA NTRS2019

Achieving Improved Reliability with Failure Analysis

Reliability is the ability of a product to properly function, within specified performance limits, for a specified period of time, under the life cycle application conditions. Failure analysis is a vital tool in the effort to ensure reliability of electronic products and systems throughout their product lifecycle. Today, organizations involved in activities within the electronics supply chain are facing new challenges, not just from complex assembly styles, harsher lifecycle environments, and sophisticated supply chains, but also from customers who are demanding a quicker turn-around. Unfortunately, root cause failure analysis is often performed incompletely, leading to a poor understanding of failure mechanisms and causes and, customer dissatisfaction due to recurring failures. The PDC (Professional Development Course) starts with an introduction to reliability concepts, physics of failure and an overview of failure mechanisms that affect PCBs (Printed Circuit Boards), PCBAs (Printed Circuit Board Assembly) and components. The PDC then dives into root cause hypothesizing techniques (Pareto, FMEA (Failure Modes and Effects Analysis), fishbone (Cause-And-Effect Diagram), FTA (Fault Tree Analysis)), non-destructive and destructive analysis and, materials characterization will be discussed. Numerous failure analysis case studies will be used to illustrate the techniques and analysis principles to arrive at the root cause(s) of field failures on printed circuit boards, active components, and assemblies. What Attendees will Learn: Topics include: Overview of Reliability Concepts Failure mechanisms of electronic products Root cause analysis Failure analysis techniques -Non-destructive techniques (optical, CSAM (Confocal Scanning Electron Microscopy) etc.) -Destructive analysis (DPA (Destructive Physical Analysis), Decap (Decapsulation), FIB (Focused Ion Beam) etc.) -Materials characterization (XRF (X-Ray Fluorescence) , EDS (Error Detection Sequential), TMA/DSC (Thermal Mechanical Analysis/Differential Scanning Calorimetry) etc.)

PCB quality↗
NASA NTRS2004

Soot Nanostructure: Using Fringe Analysis Software on High Resolution Transmission Electron Microscopy of Carbon Soot

Using high resolution transmission electron images of carbon nanotubes and carbon particles, we are able to use image analysis program to determine several carbon fringe properties, including length, separation, curvature and orientation. Results are shown in the form of histograms for each of those quantities. The combination of those measurements can give a better indication of the graphic structure within nanotubes and particles of carbon and can distinguish carbons based upon fringe properties. Carbon with longer, straighter and closer spaced fringes are considered graphite, while amorphous carbon contain shorter, less structured fringes.

King, James D.↗
NASA NTRS2004

A parametric study of single-wall carbon nanotube growth by laser ablation

Results of a parametric study of carbon nanotube production by the double-pulse laser oven process are presented. The effect of various operating parameters on the production of single-wall carbon nanotubes (SWCNTs) is estimated by characterizing the nanotube material using analytical techniques, including scanning electron microscopy, transmission electron microscopy, thermo gravimetric analysis and Raman spectroscopy. The study included changing the sequence of the laser pulses, laser energy, pulse separation, type of buffer gas used, operating pressure, flow rate, inner tube diameter, as well as its material, and oven temperature. It was found that the material quality and quantity improve with deviation from normal operation parameters such as laser energy density higher than 1.5 J/cm2, pressure lower than 67 kPa, and flow rates higher than 100 sccm. Use of helium produced mainly small diameter tubes and a lower yield. The diameter of SWCNTs decreases with decreasing oven temperature and lower flow rates.

Nanotubes, Carbon/chemistry↗
NASA NTRS2015

The THS Experiment: Simulating Titans Atmospheric Chemistry at Low Temperature (200K)

In Titan's atmosphere, composed mainly of N2 (95-98%) and CH4 (2-5%), a complex chemistry occurs at low temperature, and leads to the production of heavy organic molecules and subsequently solid aerosols. Here, we used the Titan Haze Simulation (THS) experiment, an experimental setup developed at the NASA Ames COSmIC simulation facility to study Titan's atmospheric chemistry at low temperature. In the THS, the chemistry is simulated by plasma in the stream of a supersonic expansion. With this unique design, the gas is cooled to Titan-like temperature ( approximately 150K) before inducing the chemistry by plasma, and remains at low temperature in the plasma discharge (approximately 200K). Different N2-CH4-based gas mixtures can be injected in the plasma, with or without the addition of heavier precursors present as trace elements on Titan, in order to monitor the evolution of the chemical growth. Both the gas- and solid phase products resulting from the plasma-induced chemistry can be monitored and analyzed using a combination of complementary in situ and ex situ diagnostics. A recent mass spectrometry[1] study of the gas phase has demonstrated that the THS is a unique tool to probe the first and intermediate steps of Titan's atmospheric chemistry at Titan-like temperature. In particular, the mass spectra obtained in a N2-CH4-C2H2-C6H6 mixture are relevant for comparison to Cassini's CAPS-IBS instrument. The results of a complementary study of the solid phase are consistent with the chemical growth evolution observed in the gas phase. Grains and aggregates form in the gas phase and can be jet deposited on various substrates for ex situ analysis. Scanning Electron Microscopy images show that more complex mixtures produce larger aggregates. A mass spectrometry analysis of the solid phase has detected the presence of aminoacetonitrile, a precursor of glycine, in the THS aerosols. X-ray Absorption Near Edge Structure (XANES) measurements also show the presence of imine and nitrile functional groups, showing evidence of nitrogen chemistry. These complementary studies show the high potential of THS to better understand Titan's chemistry and the origin of aerosol formation.

Laboratory↗
NASA NTRS1974

A study of the effects of solid phase reactions on the thermal degradation and ballistic properties of solid propellants

The thermal stability of perchlorate composite propellants was studied at 135 and 170 C. The experimental efforts were concentrated on determining the importance of heterogeneous oxidizer-fuel reactions in the thermal degradation process. The experimental approach used to elucidate the mechanisms by which the oxidizer fuel composites thermally degrade was divided into two parts: (1) keeping the fuel constant and varying the nature of the oxidizers, and (2) holding the oxidizer constant and varying the fuel components. The fuel component primarily utilized in the first phase was polyethylene. Oxidizers included KClO4, KClO3, NH4ClO4 and NH4ClO4 doped with materials such as chlorate, phosphate and arsenate. In the second phase the oxidizer used was primarily NH4ClO4 while the fuels included saturated and unsaturated polybutadiene prepolymers and a series of bonding agents. Techniques employed in the current study include thermogravimetric measurements, differential thermal analysis, infrared, mass spectrometry, electron microscopy, and appropriate wet chemical analysis.

Schmidt, W. G.↗
NASA NTRS2004

Robust Joining Technology for Solid Oxide Fuel Cells Applications

Recently there has been a great deal of interest in research development and commercialization of solid oxide fuel cells (SOFCs). Joining and sealing are critical issues that will need to be addressed before SOFCs can truly perform as expected. Ceramics and metals can be difficult to join together, especially when the joint must withstand up to 900 C operating temperature of the SOFCs. The goal of the present study is to find the most suitable braze material for joining of yttria stabilized zirconia (YSZ) to stainless steel. A number of commercially available braze materials TiCuSil, TiCuNi, Copper-ABA, Gold-ABA and Gold-ABA-V have been evaluated. The oxidation behavior of the braze materials and steel substrates in air was also examined through thermogravimetric analysis. The microstructure and composition of the brazed regions have been examined by optical and scanning electron microscopy and eDS analysis. Effect of braze composition and processing conditions on the interfacial microstructure and composition of the joint regions will be presented.

Shpargel, Tarah P.↗
NASA NTRS2005

Brazing of Stainless Steels to Yttria Stabilized Zirconia (YSZ) for Solid Oxide Fuel Cells

Recently, there has been a great deal of interest in research, development, and commercialization of solid oxide fuel cells. Joining and sealing are critical issues that will need to be addressed before SOFC's can truly perform as expected. Ceramics and metals can be difficult to join together, especially when the joint must withstand up to 900 C operating temperature of the SOFC's. The goal of the present study is to find the most suitable braze material for joining of yttria stabilized zirconia (YSZ) to stainless steels. A number of commercially available braze materials TiCuSil, TiCuNi, Copper-ABA, Gold-ABA, and Gold-ABA-V have been evaluated. The oxidation behavior of the braze materials and steel substrates in air was also examined through thermogravimetric analysis. The microstructure and composition of the brazed regions have been examined by optical and scanning electron microscopy and EDS analysis. Effect of braze composition and processing conditions on the interfacial microstructure and composition of the joint regions will be presented.

Shpargel, Tarah P.↗
NASA NTRS1988

Growth of diamond by RF plasma-assisted chemical vapor deposition

A system has been designed and constructed to produce diamond particles by inductively coupled radio-frequency, plasma-assisted chemical vapor deposition. This is a low-pressure, low-temperature process used in an attempt to deposit diamond on substrates of glass, quartz, silicon, nickel, and boron nitride. Several deposition parameters have been varied including substrate temperature, gas concentration, gas pressure, total gas flow rate, RF input power, and deposition time. Analytical methods employed to determine composition and structure of the deposits include scanning electron microscopy, absorption spectroscopy, scanning Auger microprobe spectroscopy, and Raman spectroscopy. Analysis indicates that particles having a thin graphite surface, as well as diamond particles with no surface coatings, have been deposited. Deposits on quartz have exhibited optical bandgaps as high as 4.5 eV. Scanning electron microscopy analysis shows that particles are deposited on a pedestal which Auger spectroscopy indicates to be graphite. This is a phenomenon that has not been previously reported in the literature.

Meyer, Duane E.↗
NASA NTRS1993

Internal strain analysis of ceramics using scanning laser acoustic microscopy

Quantitative studies of material behavior characteristics are essential for predicting the functionality of a material under its operating conditions. A nonintrusive methodology for measuring the in situ strain of small dimeter (to 11 microns) ceramic fibers under uniaxial tensile loading and the local internal strains of ceramics and ceramic composites under flexural loading is introduced. The strain measurements and experimentally observed mechanical behavior are analyzed in terms of the microstructural development and fracture behavior of each test specimen evaluated. Measurement and analysis of Nicalon silicon carbide (SiC) fiber (15 microns diameter) indicate that the mean elastic modulus of the individual fiber is 185.3 GPa. Deviations observed in the experimentally determined elastic modulus values between specimens were attributed to microstructural variations which occur during processing. Corresponding variations in the fracture surface morphology were also observed. The observed local mechanical behavior of a lithium alumino-silicate (LAS) glass ceramic, a LAS/SiC monofilament composite, and a calcium alumino-silicate (CAS)/SiC fully reinforced composite exhibits nonlinearities and apparent hysteresis due to the subcritical mechanical loading. Local hysteresis in the LAS matrices coincided with the occurrence of multiple fracture initiation sites, localized microcracking, and secondary cracking. The observed microcracking phenomenon was attributed to stress relaxation of residual stresses developed during processing, and local interaction of the crack front with the microstructure. The relaxation strain and stress predicted on apparent mechanical hysteresis effects were defined and correlated with the magnitude of the measured fracture stress for each specimen studied. This quantitative correlation indicated a repeatable measure of the stress at which matrix microcracking occurred for stress relief of each material system. Stress relaxation occurred prior to the onset of steady state cracking conditions. The relaxation stress occurred at 18.5 percent of the fracture stress in LAS and 11.0 percent of the yield stress in CAS/SiC. The relaxation stress ratio was dependent upon the dominant fracture mode of the LAS/SiC specimens. Relaxation stress ratios greater than 0.30 were observed for specimens which fractured due to shear at the fiber matrix interface; specimens which fracture due to tensile cracking had relaxation stress ratios less than 0.30. The stress relaxation ratio appeared to be a specific characteristic of the glass ceramic material. The measured stress relaxation for LAS indicated a measure of the inherent residual stresses in the material due to processing and suggested localized toughening mechanisms for brittle material structures.

Kent, Renee M.↗
NASA NTRS1972

Use of LEED, Auger emission spectroscopy and field ion microscopy in microstructural studies

Surface research tools such as LEED, Auger emission spectroscopy analysis, and field ion microscopy are discussed. Examples of their use in studying adhesion, friction, wear, and lubrication presented. These tools have provided considerable insight into the basic nature of solid surface interactions. The transfer of metals from one surface to another at the atomic level has been observed and studied with each of these devices. The field ion microscope has been used to study polymer-metal interactions and Auger analysis to study the mechanism of polymer adhesion to metals. LEED and Auger analysis have identified surface segregation of alloying elements and indicated the influence of these elements in metallic adhesion. LEED and Auger analysis have assisted in adsorption studies in determining the structural arrangement and quantity of adsorbed species present in making an understanding of the influence of these species on adhesion possible. These devices are assisting in the furtherance of understanding of the fundamental mechanism involved in the adhesion, friction, wear, and lubrication processes.

Ferrante, J.↗
NASA NTRS1993

Thin film processing of photorefractive BaTiO3

During the period covered by this report, October 11, 1991 through October 10, 1992, the research has progressed in a number of different areas. The sol-gel technique was initially studied and experimentally evaluated for depositing films of BaTiO3. The difficulties with the precursors and the poor quality of the films deposited lead to the investigation of pulsed laser deposition as an alternative approach. The development of the pulsed laser deposition technique has resulted in continuous improvements to the quality of deposited films of BaTiO3. The initial depositions of BaTiO3 resulted in amorphous films, however, as the pulsed laser deposition technique continued to evolve, films were deposited in the polycrystalline state, then the textured polycrystalline state, and most recently heteroepitaxial films have also been successfully deposited on cubic (100) oriented SrTiO3 substrates. A technique for poling samples at room temperature and in air is also undergoing development with some very preliminary but positive results. The analytical techniques, which include x-ray diffraction, ferroelectric analysis, UV-Vis spectrophotometry, scanning electron microscopy with x-ray compositional analysis, optical and polarized light microscopy, and surface profilometry have been enhanced to allow for more detailed evaluation of the samples. In the area of optical characterization, a pulsed Nd:YAG laser has been incorporated into the experimental configuration. Now data can also be acquired within various temporal domains resulting in more detailed information on the optical response of the samples and on their photorefractive sensitivity. The recent establishment of collaborative efforts with two departments at Johns Hopkins University and the Army Research Lab at Fort Belvoir has also produced preliminary results using the metallo-organic decomposition technique as an alternative method for thin film processing of BaTiO3. RF and DC sputtering is another film deposition approach that should be initiated in the near future. Other techniques for optical characterization, which may even allow for intragrannular (within single grains) investigations, are also being considered.

Schuster, Paul R.↗
NASA NTRS1972

Scanning electron microscopy, non-dispersive X-ray analysis and electron microprobe studies of lunar soil, rocks and microbreccia

Silicate glass of composition similar to brown lunar glass was reduced with carbon and hydrogen. The typical complex iron sulfide and metallic iron mound formed by reduction with carbon is zoned. Its interior is metallic iron or a mixture of iron sulfide and metallic iron. The outer layer is pure metallic iron which is generally discontinuous, but the surface of the mound next to the silicate host is iron sulfide. This type of mound commonly has a waist of metallic iron and a void beneath it. The silicate surface of the void is covered with droplets or stringers of iron sulfide. The complex iron sulfide and metallic iron mounds formed by reduction with hydrogen generally are zoned. The outer layer is iron sulfide or a mixture of iron sulfide and metallic iron but the interior is metallic iron and iron sulfide, and the mound material next to the silicate host is iron sulfide. On the surface of some complex mounds, globules of silicate material are present. In one example, the globules consist of particles of aluminum oxide surrounded by silicate material. In turn, the margin of the globules is surrounded by iron sulfide. Dimples are present and surface of the dimples is covered by dendritic sheaths of iron sulfide and isolated metallic iron globules.

Carter, J. L.↗