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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Adhesion and wear resistance of materials

Recent studies into the nature of bonding at the interface between two solids in contact or a solid and deposited film have provided a better understanding of those properties important to the adhesive wear resistance of materials. Analytical and experimental progress are reviewed. For simple metal systems the adhesive bond forces are related to electronic wave function overlap. With metals in contact with nonmetals, molecular-orbital energy, and density of states, respectively can provide insight into adhesion and wear. Experimental results are presented which correlate adhesive forces measured between solids and the electronic surface structures. Orientation, surface reconstruction, surface segregation, adsorption are all shown to influence adhesive interfacial strength. The interrelationship between adhesion and the wear of the various materials as well as the life of coatings applied to substrates are discussed. Metallic systems addressed include simple metals and alloys and these materials in contact with themselves, both oxide and nonoxide ceramics, diamond, polymers, and inorganic coating compounds, h as diamondlike carbon.

Buckley, D. H.↗
DOE OSTI2025

Interlayer Design for Halide Electrolytes in All‐Solid‐State Lithium Metal Batteries

Abstract All‐solid‐state lithium‐metal batteries (ASSLMBs) are promising for transportation electrification due to their superior safety and high energy density. Lithium halide electrolytes provide excellent processing flexibility, high ionic conductivity, and anodic stability (>4.1 V), making them highly compatible with high‐voltage cathodes, surpassing sulfide electrolytes (<2.1 V). Nevertheless, halide electrolytes suffer from low cathodic stability and form an electronically conductive interphase with lithium, resulting in a critical current density (CCD) of nearly zero. Herein, Li 3 YbCl 6 electrolytes are synthesized that are kinetically stable with lithium by forming an electronic insulating solid electrolyte interphase. Guided by critical overpotential criteria, a PI 3 interlayer is designed that transforms into Li 6 PI 3 upon contact with lithium, substantially reducing the interfacial resistance of Li 3 YbCl 6 against lithium to 34 Ω and achieving a high critical overpotential of 114 mV. By substituting Yb with Lu, Li 3 LuCl 6 electrolytes with Li 6 PI 3 interlayers reach a CCD of 1.0 mA cm −2 at a capacity of 1.0 mAh cm −2 , comparable to sulfide electrolytes but with higher oxidation stability. Additionally, Li 6 PI 3 enables stable cycling of Li//Li cells with Li 3 LuCl 6 electrolytes at 0.5 mA cm −2 for 400 cycles and maintains 86.5% capacity in Li//LiCoO 2 cells after 220 cycles at 30 °C, paving the way for high‐performance ASSLMBs.

Chemistry↗
DOE OSTI2022

Vertical gradient freeze growth of detector grade CdZnTeSe single crystals

Here, we report the growth of detector grade Cd 0.9 Zn 0.1 Te 0.97 Se 0.03 (CZTS) single crystals, a recently discovered quaternary semiconductor for room temperature radiation detection, by a vertical gradient freeze (VGF) method. VGF is a comparatively low-temperature growth method and avoids relative motion between the heater and the ampoule containing the precursor materials which minimizes any thermal drift or temperature fluctuations. As a result, CZTS single crystals with superior charge transport properties has been obtained. Growth of detector-grade CZTS single crystals using VGF method has not been reported yet. X-ray spectroscopy based elemental analysis showed that the grown crystals demonstrated the desired stoichiometry required for high resolution radiation detection. Planar detectors fabricated by deposition of gold contacts (~0.07 cm 2 ) demonstrated high bulk resistivity ~10 10 Ω-cm and a very low leakage current density of 2.8 × 10 –8 A/cm 2 at a bias of 100 V when measured at room temperature. The detectors showed excellent radiation response with 100 % charge collection efficiency when exposed to 5486 keV alpha particles. The electron mobility-lifetime (μτ) product was measured to be 3 × 10 –3 cm 2 /V using a single polarity Hecht analysis which is at par with the recently reported values measured in CZTS grown using conventional Bridgman or travelling heater method. The electron mobility has been calculated to be 964 cm 2 V –1 s –1 using a time-of-flight (TOF) method, a substantial improvement over that obtained from conventionally grown CZTS single crystals.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Macroscale superlubricity by a sacrificial carbon nanotube coating

Superlubricity, i.e., coefficient of friction (COF) below 0.01, was earlier limited to microscale in controlled environments in the earlier literature and more recently realized for macroscale sliding of ceramic or carbon surfaces lubricated by water or other polar fluids. However, there is lack of report of superlubricity for the most common bearing system, i.e., steel-steel contact in non-polar oil lubrication. Here, in this work, we present ultra-low COF of 0.001–0.007 by using a sacrificial coating composed of vertically-aligned carbon nanotubes (CNTs) for macroscale steel-steel sliding under minimum quantity lubrication (MQL) of a polyalphaolefin (PAO) oil in the ambient environment. Raman spectroscopy and electron microscopy analyses detected graphene-containing tribofilms on both the steel surfaces, which was produced by the fractured CNT flakes and metallic wear debris during running-in. The in situ formed graphene-graphene contact interface presumably possesses a low shear resistance leading to superlubricity. The presence of oil, despite as little as one droplet, has proven to be crucial. Such a superlubricity performance has shown good sustainability in extended testing of more than 500,000 cycles and strong ability of accommodating changes in sliding conditions. Results here demonstrate feasibility with fundamental insights for achieving ambient environment macroscale superlubricity.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Mechanical and electrical changes in electrochemically active polyimide binders for Li-ion batteries

Polyimide binders are often used in electrodes made with silicon for lithium-ion batteries for their mechanical strength and adhesion, which help mitigate mechanical issues associated with large volumetric expansion. These binders can be electrochemically active, but it is difficult to characterize what physical and chemical changes occur due to a composite electrode with multiple components and processes at play. Here, in this work, we study electrodes consisting only of polyimide binder and conductive carbon, using scanning probe-based techniques—contact resonance, force volume, and scanning spreading resistance microscopy—along with cryo-scanning transmission electron microscopy, electron energy loss spectroscopy, and energy dispersive X-ray spectroscopy. We show that lithium becomes trapped in the binder during cycling and results in large initial capacity losses, the formation of dendrite-like features, column-like domains of significantly increased mechanical modulus, and a slight increase in electronic resistivity.

25 ENERGY STORAGE↗
DOE OSTI2020

Control of passivation and compensation in Mg-doped GaN by defect quasi Fermi level control

A defect quasi Fermi level (dQFL) control process based on above bandgap illumination was applied to control H and V N -complexes, which are the main contributors to the passivation and self-compensation, respectively, in Mg:GaN grown via metalorganic chemical vapor deposition. Secondary ion mass spectrometry measurements confirmed that the total Mg incorporation was unaffected by the process. However, the total H concentration was reduced to similar levels obtained by post-growth thermal activation prior to any annealing treatment. Similarly, the 2.8 eV emission in the photoluminescence spectra, attributed to compensating V N and its complexes, was reduced for the dQFL-process samples. After thermal activation and Ni/Au contact deposition, Hall effect measurements revealed lower resistivities (increased mobilities and free hole concentrations) for dQFL-grown samples with Mg doping concentrations above and below 2 × 10 19 cm -3 . All these results demonstrate that the dQFL process can effectively reduce the H-passivation and self-compensation of the Mg:GaN films.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Aging of Limestones and Silane–Siloxane-Based Protective Hydrophobics: The Impact of Heating–Cooling and Freeze–Thaw Cycles

Stones are traditionally used in construction and architectural applications as building elements due to their aesthetic and technical/structural performance. Like other environmental factors (rain, humidity, moisture, salt presence, biological activity, etc.), heating–cooling and freeze–thaw cycles significantly threaten the longevity of stone materials. Hence, considering the socio-economic and cultural value of stones, preventive actions such as hydrophobic coatings are applied to prevent or mitigate damage. The scope of this study is the performance assessment of limestones with different characteristics and the efficiency of various commercial silane/siloxane-based hydrophobic coatings when exposed to thermal variation and freeze–thaw. For that purpose, the standards EN 14066:2013 (determination of resistance to aging by thermal shock) and EN 12371:2010 (determination of frost resistance) were followed. Open porosity and static contact angles were estimated to assess the stone durability and water protection capabilities of the hydrophobics. Additionally, sound speed propagation velocity, quality of building material index, elastic modulus and flexural strength were measured to evaluate the variation of mechanical properties. Static contact angle revealed that the coatings maintained an efficient level of hydrophobicity even after thermal-shock and freeze–thaw weathering tests. The study also revealed a critical interaction between freeze–thaw cycles, hydrophobic coatings and structural integrity of the stones, mostly on more porous ones. When they are subjected to harsh environmental conditions, untreated porous limestones keep structural cohesion, allowing for the natural absorption and release of water during freezing and thawing. On the contrary, when limestones are treated, the hydrophobic coatings can moderately obstruct the water release due to the partial saturation of the porous framework by the products. It also probably resulted from the different mechanical behavior between the inner matrix and layer of stone coated, resulting in a premature breakout and mechanical damage of the stone.

Lisci, Carla (ORCID:000000032179130X)↗
NASA NTRS1964

Elastomers bonded to metal surfaces seal electrochemical cells

A leakproof seal secondary cell containing alkaline electrolytes was developed by bonding an alkali-resistant elastomer, such as neoprene, to metal contact surfaces. Test results of several different elastomers strongly indicate the feasibility of this sealing method.

Sherfey, J. M.↗
NASA NTRS1978

Carbon fiber study. A compilation of an intergovernmental committee study

Carbon fibers have opened a wealth of new structural engineering and consumer product opportunities. The potential benefits are higher strength, and lighter weight military and commercial products, which portend energy savings and increases safety. Unfortunately, these benefits are not realized without risk. Inadvertent fiber release, during manufacture or by destruction of the resin binder in fire, is the major hazard associated with composites. The carbon (or graphite) fibers are finer than human hair and if released into the air, they can be easily transported by winds or currents. In contact with electrical devices, they can create resistive loading, short circuits, and arcing, resulting in stoppages or destruction. Their health impact is not fully known and requires careful research and analysis before any firm conclusions can be reached; however, based upon current available information, they are primarily an irritant to the eyes and skin, like fiberglass, rather than carcinogenic or destructive to lung tissue. Major manufacturers are aware of the unique problems associated with these materials and have successfully applied controls to avoid the inplant problems.

Source record↗
NASA NTRS1979

Wide-temperature-spectrum self-lubricating coatings prepared by plasma spraying

Self-lubricating, multicomponent coatings, which lubricate over a wide range of operating conditions, are described. The coatings were successfully applied by plasma-spraying mixed powders onto superalloy substrates. They were evaluated in friction and wear experiments, and in sliding contact bearing tests. These coatings are wear resistant by virtue of their self lubricating characteristics rather than because of extreme hardness; a further benefit is low friction. Experiments with simple pin on disk sliding specimens and oscillating plain cylindrical bearing tests were performed to evaluate the tribological properties of the coatings. It was shown that coatings of nichrome, glass and calcium fluoride are self-lubricating from about 500 to 900 C, but give high friction at the lower temperatures. The addition of silver to the coating composition improved the low temperature bearing properties and resulted in coatings which are self-lubricating from cryogenic temperatures to at least 870 C; they are therefore, wide temperature spectrum, self-lubricating compositions.

Sliney, H. E.↗
NASA NTRS1979

Wide-temperature-spectrum self-lubricating coatings prepared by plasma spraying

Self-lubricating, multicomponent coatings, which lubricate over a wide range of operating conditions, are described. The coatings have been successfully applied by plasma-spraying mixed powders onto superalloy substrates. They have been evaluated in friction and wear experiments, and in sliding contact bearing tests. These coatings are wear resistant by virtue of their self-lubricating characteristics rather than because of extreme hardness; a further benefit is low friction. Experiments with simple pin on disk sliding specimens and oscillating plain cylindrical bearing tests were performed to evaluate the tribological properties of the coatings. It was shown that coatings of nichrome, glass and calcium fluoride are self-lubricating from about 500 to 900 C, but give high friction at the lower temperatures. The addition of silver to the coating composition improved the low temperature bearing properties and resulted in coatings which are self-lubricating from cryogenic temperatures to at least 870 C; they are therefore 'wide temperature spectrum,' self-lubricating compositions.

Sliney, H. E.↗
NASA NTRS1980

Method of making bearing material

A composite material is described which will provide low friction surfaces for materials in rolling or sliding contact and is self lubricating and oxidation resistant up to and in excess of about 930 C. The composite is comprised of a metal component which lends strength and elasticity to the structure, a fluoride salt component which provides lubrication and, lastly, a glass component which not only provides oxidation protection to the metal but may also enhance the lubrication qualities of the composite.

Sliney, H. E.↗
NASA NTRS1987

Measuring Thicknesses of Wastewater Films

Sensor determines when thickness of film of electrically conductive wastewater on rotating evaporator drum exceeds preset value. Sensor simple electrical probe that makes contact with liquid surface. Made of materials resistant to chemicals in liquid. Mounted on shaft in rotating cylinder, liquid-thickness sensor extends toward cylinder wall so tip almost touches. Sensor body accommodates probe measuring temperature of evaporated water in cylinder.

Schubert, F. H.↗
NASA NTRS1992

Noncontact Measurement Of Critical Current In Superconductor

Critical current measured indirectly via flux-compression technique. Magnetic flux compressed into gap between superconductive hollow cylinder and superconductive rod when rod inserted in hole in cylinder. Hall-effect probe measures flux density before and after compression. Method does not involve any electrical contact with superconductor. Therefore, does not cause resistive heating and consequent premature loss of superconductivity.

Israelsson, Ulf E.↗
NASA NTRS1992

Noise in Josepson effect mixers and the RSJ model

Josephson effect mixers have previously been observed to display 'excess' noise both in experiments with point contacts and in numerical simulations using the resistively shunted junction (RSJ) model. This excess noise causes the mixer noise temperature to be a factor of typically 20-100 times the physical temperature of the device. Previously, this excess was ascribed to conversion from unwanted sidebands of the local oscillator and Josephson frequencies and their harmonics. Our numerical modeling of the RSJ equations has led to a new understanding of the excess noise, which is simply due to the intrinsic Josephson oscillations of the device. In addition, we have extended the modeling to include the previously ignored case of finite device capacitance (i.e. RSJ capacitance parameter beta(sub c) does not equal 0, which is more realistic for lithographically defined Josephson such as shunted tunnel junctions or SNS bridges. For some cases, this yields an improvement of a factor of two in noise temperature from the zero capacitance models. We will discuss the device parameters which optimize the mixer performance for frequencies approaching the characteristic frequency of the device, which is given by the Josephson frequency at the I(sub c)R(sub n) voltage (nu = 2eI(sub c)R(sub n)/h). These modeling results predict good conversion efficiency and a noise temperature within a factor of a few of the physical temperature. Experiments are in progress to determine the accuracy of this modeling using a waveguide mixer at 100 GHz with optimized, resistively shunted Nb tunnel junctions. If the modeling results are valid, they are particularly encouraging for mixers in the submillimeter regime, given the possibility of obtaining non-hysteretic Josephson devices with I(sub c)R(sub n) products in excess of a millivolt, using for instance, high-T(sub c) SNS bridges. We discuss the modifications to the classical RSJ model which are necessary in the quantum regime (h nu greater than kT), and conclude the Josephson mixers may attain noise temperatures less than ten times the quantum limit at high frequencies.

Schoelkopf, R.↗
NASA NTRS1996

Two Electrical Switching Phenomena In A Silver-Filled Epoxy

Two distinct electrical switching phenomena observed in experiments on commercial silver-filled epoxy: Depending on geometry of epoxy layer or strip and of metal electrical contacts, either transition from "off" (high-resistance) state at low applied electric field to "on" (low-resistance) state at high applied electric field; or transition from "on" (low resistance) at low applied electric field to "off" (high resistance) at high applied electric field. Improved understanding of phenomena leads to design of new and improved surge arrestors.

Javadi, Hamid↗
DOE OSTI2024

Low cost switching circuit for van der Pauw resistivity and Hall measurements at various temperatures

The electrical characterization of materials, particularly superconductors, semiconductors, and those undergoing metal-insulator transitions (MITs), relies significantly on resistivity and Hall measurements as a function of temperature. The van der Pauw four-point probe method is commonly used for such measurements, which involves resistance measurements for different circuit configurations connected to sample contacts. However, repeating these measurements at different temperatures is challenging and time consuming. Here, this study introduces a novel approach utilizing a switching circuit controlled by an Arduino device and a LabVIEW program to automate resistance measurements for different electrical configurations. The effectiveness of this setup was demonstrated by testing V 2 O 3 thin film samples deposited on Al 2 O 3 (001) substrates using DC magnetron sputtering. The MIT temperature of the sample was 115 K during heating and 100 K during cooling. The sample exhibited p-type charge carriers with a Hall coefficient of 1.3 ± 0.1 x 10 -4 cm 3 /C and Hall mobility of 1.7 x 10 -1 cm 2 /V∙s, which is consistent with findings from other studies employing commercial equipment.

36 MATERIALS SCIENCE↗
NASA NTRS2009

Intermetallic Nickel-Titanium Alloys for Oil-Lubricated Bearing Applications

An intermetallic nickel-titanium alloy, NITINOL 60 (60NiTi), containing 60 wt% nickel and 40 wt% titanium, is shown to be a promising candidate material for oil-lubricated rolling and sliding contact applications such as bearings and gears. NiTi alloys are well known and normally exploited for their shape memory behavior. When properly processed, however, NITINOL 60 exhibits excellent dimensional stability and useful structural properties. Processed via high temperature, high-pressure powder metallurgy techniques or other means, NITINOL 60 offers a broad combination of physical properties that make it unique among bearing materials. NITINOL 60 is hard, electrically conductive, highly corrosion resistant, less dense than steel, readily machined prior to final heat treatment, nongalling and nonmagnetic. No other bearing alloy, metallic or ceramic encompasses all of these attributes. Further, NITINOL 60 has shown remarkable tribological performance when compared to other aerospace bearing alloys under oil-lubricated conditions. Spiral orbit tribometer (SOT) tests were conducted in vacuum using NITINOL 60 balls loaded between rotating 440C stainless steel disks, lubricated with synthetic hydrocarbon oil. Under conditions considered representative of precision bearings, the performance (life and friction) equaled or exceeded that observed with silicon nitride or titanium carbide coated 440C bearing balls. Based upon this preliminary data, it appears that NITINOL 60, despite its high titanium content, is a promising candidate alloy for advanced mechanical systems requiring superior and intrinsic corrosion resistance, electrical conductivity and nonmagnetic behavior under lubricated contacting conditions.

DellaCorte, C.↗