SEARCH · Engineering Papers
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
3D printing of cadmium sulfur selenide quantum dot functionalized materials compatible with fused deposition modeling type processes and applications.
Highlights: • All coarse aggregates and steel fibres were surrounded by the binder. • X-ray diffraction is useful for explaining the increase in compressive strength with increasing temperature. • Rosenhahnite and/or quartz Dauphiné-twinned phases improved the compressive strength. • Polypropylene fibres prevented spalling and preserved the compressive strength. • Concrete with steel and polypropylene fibres did not exhibit spalling at 300 °C. Concrete with two types of steel fibres and a polypropylene fibre prevented spalling and preserved the compressive strength at 300 °C, which makes these concretes suitable for long-term applications up to 300 °C, such as for steam collectors or thermal energy storage systems. The compressive strength behaviour of three types of ultra-high-performance fibre-reinforced concrete manufactured with the same matrix was investigated. For this purpose, a complete characterisation of all the raw materials and the three types of fibres used was performed. The morphology of all concrete mixtures at room temperature was analysed using scanning electron microscopy–energy-dispersive X-ray spectroscopy. From the results, it was ascertained that the steel fibres and coarse siliceous aggregates were not in contact (being separated by ≥3.41 μm) and were surrounded by the binder (of ≥1 μm in thickness) for all the mixtures studied. Rosenhahnite and/or quartz Dauphiné-twinned phases improved the compressive strength (as determined by X-ray diffraction).
We report an investigation of the electrical and material characteristics of Ni on an n-type GeSn film under thermal annealing. The current-voltage traces measured with the transmission line method are linear for a wide range of annealing temperatures. The specific contact resistivity was found to decrease with increasing annealing temperature, followed by an increase as the annealing temperature further increased, with a minimum value at an annealing temperature of 350 °C. The material characteristics at the interface layer were measured by energy-dispersive spectrometer, showing that an atomic ratio of (Ni)/(GeSn) = 1:1 yields the lowest specific contact resistivity.
Large improvements in the performance of thermoelectric materials have come from designing materials with reduced thermal conductivity. Yet as the thermal conductivity of some materials now approaches their amorphous limit, it is unclear if microstructure engineering can further improve thermoelectric performance in these cases. In this contribution, we use large data sets to examine 300 compositions in 11 families of thermoelectric materials and present a type of plot that quickly reveals the maximum possible zT that can be achieved by reducing the thermal conductivity. This plot allows researchers to quickly distinguish materials where the thermal conductivity has been optimized from those where improvement can be made. Moreover, through these large data sets we examine structure-property relationships to identify methods that decrease thermal conductivity and improve thermoelectric performance. We validate, with the data, that increasing (i) the volume of a unit cell and/or (ii) the number of atoms in the unit cell decreases the thermal conductivity of many classes of materials, without changing the electrical resistivity.
Here, this paper presents a comprehensive review of existing research examining the effects of supplementary cementitious materials on age-dependent concrete properties with the most profound implications for precast concrete production. The review covers the physical and chemical properties of selected types of supplementary cementitious materials, concrete mixture proportions, concrete curing methods, testing procedures, and test results related to the fresh properties and strengths of a range of concrete mixtures. Although the use of supplementary cementitious materials in precast concrete products is common, the detailed information provided in this paper may facilitate more widespread use of these materials to enhance concrete properties and comply with sustainability initiatives.
Promising candidate designs currently being considered for the management of spacecraft solid waste and waste-water materials were assessed. The candidate processes were: (1) the radioisotope thermal energy evaporation/incinerator process; (2) the dry incineration process; and (3) the wet oxidation process. The types of spacecraft waste materials that were included in the base-line computational input to the candidate systems were feces, urine residues, trash and waste-water concentrates. The performance characteristics and system requirements for each candidate process to handle this input and produce the specified acceptable output (i.e., potable water, a storable dry ash, and vapor phase products that can be handled by a spacecraft atmosphere control system) were estimated and compared. Recommendations are presented.
Compressive failure mechanisms in quasi-isotropic graphite/epoxy laminates were characterized for both unnotched and notched specimens and also following damage by impact. Two types of fibers (Thornel 300 and 700) and four resin systems (Narmco 5208, American Cyanamid BP907, and Union Carbide 4901/MDA and 4901/mPDA) were studied. For all material combinations, failure of unnotched specimens was initiated by kinking of fibers in the 0-degree plies. A major difference was observed, however, in the mode of failure propagation after the 0-degree ply failure. The strength of quasi-isotropic laminates in general increased with increasing resin tensile modulus. The laminates made with Thornel 700 fibers exhibited slightly lower compressive strengths than did the laminates made with Thornel 300 fibers. The notch sensitivity as measured by the hole strength was lowest for the BP907 resin and highest for the 5208 resin. For the materials studied, however, the type of fiber had no effect on the notch sensitivity.
Compressive failure mechanisms in quasi-isotropic graphite/epoxy laminates were characterized for both unnotched and notched specimens and also following damage by impact. Two types of fibers (Thornel 300 and 700) and four resin systems (Narmco 5208, American Cyanamid BP907, and Union Carbide 4901/MDA and 4901/mPDA) were studied. For all material combinations, failure of unnotched specimens was initiated by kinking of fibers in the 0-degree plies. A major difference was observed, however, in the mode of failure propagation after the 0-degree ply failure. The strength of quasi-isotropic laminates in general increased with increasing resin tensile modulus. The laminates made with Thornel 700 fibers exhibited slightly lower compressive strengths than did the laminates made with Thornel 300 fibers. The notch sensitivity as measured by the hole strength was lowest for the BP907 resin and highest for the 5208 resin. For the materials studied, however, the type of fiber had no effect on the notch sensitivity.
Despite of the permanent progress of technique and finding of the new, modern materials that successfully replace metals, steel continues to play an important role in the technical practice. The tendency is to discover the new alloys with better mechanical and technological characteristics, compared to conventional and standard types of steels. High-alloyed Cr–Mo steel, with a high content of Vanadium is the new type of wear resistant material, with high hardness and satisfactory impact and fracture toughness. During the solidification process Vanadium, as a strong carbide forming element, creates a network of M{sub 7}C{sub 3} type carbide grains around the metal matrix, while in the matrix, the finely dispersed V{sub 6}C{sub 5} type carbides are formed. In this paper, the chemical composition and morphology have been studied of carbides and the other phases present in the metal matrix in 1.4 wt % C, 12 wt % Cr, 1.0 wt % Mo steels with additions up to 3.0 wt % V. Experimental results indicate that Vanadium affects the solidification process in high Chromium steel. Vanadium is distributed between eutectic M{sub 7}C{sub 3} carbide and the matrix, but its content in carbides is considerably higher. Vanadium changed the microstructure parameters of phases present in the structure of alloys, including volume fraction, size and morphology.
A microextraction sampling system coupled to a quadrupole inductively coupled plasma-mass spectrometer (ICP-MS) was utilized to spatially discern uranium particles, isotopically, on a cellulose-based swipe material ( i.e. , J-type swipe).
Near-infrared reflectance spectra have been acquired (1) for Moses Rock diatreme in SE Utah using an airborne imaging spectrometer (AIS) and (2) for small areas in and around the large lunar impact crater Copernicus using a spectrometer on earth-based telescopes. The high spectral resolution and precision of these data allow several mineral components of surface material to be identified and analyzed in a spatial context. The derived mineralogical information is used to address specific geological problems. For the terrestrial study the distribution of the measured abundance of mantle derived ultramafic microbreccia across Moses Rock dike indicates that flow stabilized into a few channels during the violent eruption. For the lunar study the variety of rock types identified in crustal material of deep-seated origin is distinct from the dominant rock types sampled from the upper lunar crust and suggests a complex crustal evolution.
Caliper-type brakes simulation experiments were conducted on seven different carbon-graphite material formulations against a steel disk material and against a carbon-graphite disk material. The effects of binder level, boron carbide (B4C) additions, graphite fiber additions, and graphite cloth reinforcement on friction and wear behavior were investigated. Reductions in binder level and additions of B4C each resulted in increased wear. The wear rate was not affected by the addition of graphite fibers. Transition to severe wear and high friction was observed in the case of graphite-cloth-reinforced carbon sliding against a disk of similar composition. This transition was related to the disruption of a continuous graphite shear film that must form on the sliding surfaces if low wear is to occur. The exposure of the fiber structure of the cloth constituent is believed to play a role in the shear film disruption.
Results of structural, magnetic, and Mössbauer studies of quasi ordered alloys Fe{sub 65}Al{sub 35−} {sub x}M{sub x} (M{sub x} = Ga, B; x = 0, 5 at %) are presented. The magnetic state of examined structurally–single-phase alloys at low temperatures is interpreted from the viewpoint of magnetic phase separation. An explanation is proposed for the observed behavior of magnetic characteristics of Fe{sub 65}Al{sub 35} and Fe{sub 65}Al{sub 30}Ga{sub 5} in the framework of the model of two magnetic phases, a ferromagnetic-type one and a spin density wave. The boron-doped alloy Fe{sub 65}Al{sub 30}B{sub 5} is shown to demonstrate behavior that is typical of materials with the ferromagnetic type of ordering.
NASA missions and space exploration rely on strong, ultra lightweight materials. Such materials are needed for building up past and present space vehicles such as the Sojourner Rover (1997) or the two MERs (2003), but also for a number of components and/or systems including thermal insulators, Solar Sails, Rigid Aeroshells, and Ballutes. The purpose of my internship here at Glenn Research Center is to make dual purpose materials; materials that in addition to being lightweight have electronic, photophysical and magnetic properties and, therefore, act as electronic components and sensors as well as structural components. One type of ultra lightweight material of great interest is aerogels, which have densities ranging from 0.003 g/cc to 0.8 g/cc . However, aerogels are extremely fragile and, as a result, have limited practical applications. Recently, Glenn Research Center has developed a process of nano-casting polymers onto the inorganic network of silica-based aerogels increasing the strength 300 fold while only increasing the density 3 fold. By combining the process of nano-casting polymers with inorganic oxide networks other than silica, we are actively pursuing lightweight dual purpose materials. To date, thirty different inorganic oxide aerogels have been prepared using either standard sol-gel chemistry or a non-alkoxide method involving metal chloride precursors and an epoxide; epichlorohydrin, propylene oxide or trimethylene oxide, as proton scavengers. More importantly, preliminary investigations show that the residual surface hydroxyl groups on each of these inorganic oxide aerogels can be successfully crosslinked with urethane. In addition to characterizing physical and mechanical properties such as density, strength and flexibility, each of these metal oxide aerogels are being characterized for thermal and electronic conductivity and magnetic and optical properties.
Covetic materials have been claimed to be new types of metal matrix nano-composite materials. These materials are formed from face-centered-cubic metals which are alleged to be super-saturated with up to ~ 10 wt pct of activated nano-carbon. The focus of this study was to characterize the chemical composition of copper covetic materials of varying nano-carbon concentrations, and characterize the thermal properties of these materials in order to determine if these materials exhibit enhanced material properties.
The study examines twenty-nine different concrete mix designs with varying constituents to improve thermal performance for energy storage at elevated temperatures up to 420 °C. Effects of variables including the type and volumetric percentage of coarse and fine aggregates, the type and replacement content of supplemental cementitious materials, water-to-cement ratio, the type and quantity of steel fiber reinforcement, and the inclusion of iron oxide powder are experimentally investigated by measuring the mechanical and thermal properties of each mix, with the overall goal of enhancing thermal performance and mitigating mechanical degradation for thermal energy storage (TES) applications. It is found that the use of siliceous aggregate with a high volumetric percentage produces the highest improvement (23 %–37 % at elevated temperatures) of concrete thermal conductivity, while silica fume replacement of Type I cement provides the highest improvement (4 %–8 % at elevated temperatures) of concrete specific heat. To simulate the operation of a TES system, thermal cycling was conducted to examine the change in concrete properties as a function of repetitive heating (during and after 50 total cycles to 420 °C). Based on the results of testing, concrete mix designs with high aggregate percentages (up to 72 % by volume), siliceous coarse aggregate, silica fume replacement of Type I cement (15 % by weight), and steel fiber reinforcement (up to 2 % by volume) facilitate enhanced TES performance by providing consistent thermal conductivity of ~2.2 W/m·K and specific heat of ~3.2 MJ/m 3 ·K under cyclic high temperature exposure.
Lightweight components are increasingly used in different industrial sectors such as transportation, energy generation and automotive. This growing field includes different types of CFRP-structures, hybrid materials and glued components showing - compared to their pure metallic counterparts- a significant more complicated structure in terms of internal interfaces and anisotropy of material parameters. In this work we present the use of matrix phased array to increase the amount of obtained information to enhance the inspection quality. We used different types of carbon materials such as 6 mm thick uni- and bidirectional prepreg specimens containing impact damages. The latter were introduced with different energy levels ranging from 1.3 to 7.2 J. By scanning a 2.25 MHz matrix array with 6 × 10 elements above the prepreg surface and using different angels of incidence a complete 3D-image was generated which allows the detection of defects as small as 1mm in a depth of 4 mm. A comparison with conventional approaches show that the signal-to-noise ratio can be highly increased. This enables us to visualize the region of damage within the impact zone, clearly showing the cone-like damage distribution along increasing material depth. The detection quality allows the estimation of the opening angles of the cone shaped damage, which can be used for further evaluation and quantitation of energy dependent impact damages.
Modern techniques for detection of covert nuclear ma-terial requires some combination of real time measurement and/or sampling of the material. More common is real time measure-ment of the ionizing emission caused by radioactive decay or through the materials measured in response to external interroga-tion radiation. One can expose the suspect material with various radiation types, including high energy photons such as x rays or with larger particles such as neutrons and muons, to obtain images or measure nuclear reactions induced in the material. Stand-off detection using imaging modalities similar to those in the medical field can be accomplished, or simple collimated detec-tors can be used to localize radioactive materials. In all such cases, the common feature is that some or all of the nuclear materials have to be present for the measurement, which makes sense; as one might ask, “How you can measure something that is not there?” The current work and results show how to do exactly that: characterize nuclear materials after they have been removed from an area leaving no chemical trace. This new approach is demon-strated to be fully capable of providing both previous source spa-tial distribution and emission energy grouping. The technique uses magnetic resonance for organic insulators and/or lumines-cence techniques on ubiquitous refractory materials similar in theory to the way the nuclear industry carries out worker person-nel dosimetry. Spatial information is obtained by acquiring gridded samples for dosimetric measurements, while energy infor-mation comes through dose depth profile results that are func-tions of the incident radiation energies.