Search NASA⌕ Search

SEARCH · Search NASA

Results for “TITANIUM OXIDES”

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.

At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

High throughput embryonic zebrafish test with automated dechorionation to evaluate nanomaterial toxicity

Engineered nanomaterials pose occupational health and environmental concerns as they possess unique physical and chemical properties that can contribute to toxicity. High throughput toxicity screening methods are needed to address the increasing number of nanomaterials in production. Here we used a zebrafish photomotor response (PMR) test to evaluate a set of fifteen nanomaterials with military relevance. Automated dechorionation of zebrafish embryos was used to enhance nanomaterials bioavailability. Optimal PMR activity in zebrafish embryos was found at 30–31 hours post-fertilization (hpf). Behavioral and toxicological responses were measured at 30 and 120 hpf; behavioral responses were found for thirteen of the fifteen nanomaterials and acute toxicity (LC50) levels for nine of the fifteen nanomaterials below the maximum test concentration of 500 μg/ml. Physico-chemical characterization of the nanomaterials detected endotoxin and bacterial contamination in two of the tested samples, which may have contributed to observed toxicity and reinforces the need for physical and chemical characterization of nanomaterials use in toxicity testing. The zebrafish PMR test, together with automated dechorionation, provides an initial rapid assessment of the behavioral effects and toxicity of engineered nanomaterials that can be followed up by physico-chemical characterization if toxicity is detected, reducing the amount of time and monetary constraints of physico-chemical testing.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Controlled exposure of CuO thin films through corrosion-protecting, ALD-deposited TiO 2 overlayers

Ultra-thin film coatings are used to protect semiconductor photoelectrodes from the harsh chemical environments common to photoelectrochemical energy conversion. These layers add contact transfer resistance to the interface that can result in a reduction of photoelectrochemical energy conversion efficiency of the photoelectrode. Here, we describe the concept of a partial protection layer, which allows for direct chemical access to a small fraction of the semiconductor underlayer for further functionalization by an electrocatalyst. The rest of the interface remains protected by a stable, inert protection layer. CuO is used as a model system for this scheme. Atomic layer deposition (ALD)-prepared TiO 2 layers on CuO thin films prepared from electrodeposited Cu 2 O allow for the control of interfacial morphology to intentionally expose the CuO underlayer. The ALD-TiO 2 overlayer shrinks during crystallization, while Cu 2 O in the underlayer expands during oxidation. As a result, the TiO 2 protection layer cracks to expose the oxidized underlying CuO layer, which can be controlled by preceding thermal oxidation. Furthermore, this work demonstrates a potentially promising strategy for the parallel optimization of photoelectrochemical interfaces for chemical stability and high performance.

14 SOLAR ENERGY↗
NASA NTRS1966

Stress corrosion

This article recounts briefly some of the more critical stress-corrosion failures that have been experienced at Marshall Space Flight Center and the corrective action taken. Some of the recent stress corrosion studies are described and preliminary results tabulated. Specific problems described are the H-1 Engine LOX dome, the pneumatic line fitting sleeve problems and the more recent problem with wave springs used on MF-flared tube fittings. The use of nitric oxide in preventing stress-corrosion failures in titanium tanks is also discussed.

HIGH STRENGTH ALLOY↗
NASA NTRS1973

Improved diffusion welding and roll welding of titanium alloys

Auto-vacuum cleaning technique was applied to titanium parts prior to welding. This provides oxide-free welding surfaces. Diffusion welding can be accomplished in as little as five minutes of hot pressing. Roll welding can be accomplished with only ten percent deformation.

Holko, K. H.↗
NASA NTRS1980

Non-noble catalysts and catalyst supports for phosphoric acid fuel cells

Tungsten carbide, which is known to be active for hydrogen oxidation and CO tolerant has a hexagonal structure. Titanium carbide is inactive and has a cubic structure. Four different samples of the cubic alloys Wx-1TixC were prepared and found to be active and CO tolerant. These alloys are of interest as possible phosphoric acid fuel cell catalysts. They also are of interest as opportunities to study the activity of W in a different crystalline environment and to correlate the activities of the surface sites with surface composition.

Mcalister, A. J.↗
NASA NTRS1990

Intelligent processing of intermetallic composite consolidation

Intermetallic composites based upon titanium aluminide matrices and silicon carbide of aluminum oxide fibers are emerging candidates for future hypersonic vehicle airframes and engines. To tailor the properties of these 'engineered' materials for specific application, to increase process yield, and to reduce costs, 'intelligent processing of materials' (IPM) control strategies are being explored for their processing. Recent progress is evaluated in the development of predictive process models, advanced sensors and control methodologies (the components of the IPM approach) for the critical near net-shape consolidation process step of continuous fiber reinforced intermetallic composite manufacture.

Wadley, H. N. G.↗
NASA NTRS2005

Brazing of Stainless Steels to Yttria Stabilized Zirconia (YSZ) Using Silver -Base Brazes

Three silver-base brazes containing either noble metal palladium (Palcusil-10 and Palcusil-15) or active metal titanium (Ticusil) were evaluated for high-temperature oxidation resistance, and their effectiveness in joining yttria stabilized zirconia (YSZ) to a corrosion-resistant ferritic stainless steel. Thermogravimetric analysis (TGA), and optical- and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS) were used to evaluate the braze oxidation behavior and the structure and chemistry of the YSZ/braze/steel joints. The effect of the braze type and processing conditions on the interfacial microstructure and composition of the joint regions is discussed with reference to the chemical changes that occur at the interface. It was found that chemical interdiffusion of the constituents of YSZ, steel and the brazes led to compositional changes and/or interface reconstruction, and metallurgically sound joints.

Singh, Mrityunjay↗
NASA NTRS1998

Two-Phase (TiAl+TiCrAl) Coating Alloys for Titanium Aluminides

A coating for protecting titanium aluminide alloys, including the TiAl gamma + Ti3Al (alpha(sub 2)) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C. is disclosed. This protective coating consists essentially of titanium, aluminum. and chromium in the following approximate atomic ratio: Ti(41.5-34.5)Al(49-53)Cr(9.5-12.5)

Brady, Michael P.↗
NASA NTRS1973

Environmental protection to 922K (1200 F) for titanium alloys

Evaluations are presented of potential coating systems for protection of titanium alloys from hot-salt stress-corrosion up to temperatures of 755 K (900 F) and from oxidation embrittlement up to temperature of 922 K (1200 F). Diffusion type coatings containing Si, Al, Cr, Ni or Fe as single coating elements or in various combinations were evaluated for oxidation protection, hot-salt stress-corrosion (HSSC) resistance, effects on tensile properties, fatigue properties, erosion resistance and ballistic impact resistance on an alpha and beta phase titanium alloy (Ti-6Al-2Sn-4Zr-2Mo). All of the coatings investigated demonstrated excellent oxidation protectiveness, but none of the coatings provided protection from hot-salt stress-corrosion. Experimental results indicated that both the aluminide and silicide types of coatings actually decreased the HSSC resistance of the substrate alloy. The types of coatings which have typically been used for oxidation protection of refractory metals and nickel base superalloys are not suitable for titanium alloys because they increase the susceptibility to hot-salt stress-corrosion, and that entirely new coating concepts must be developed for titanium alloy protection in advanced turbine engines.

Groves, M. T.↗
NASA NTRS1951

Elevated Temperature Properties of Titanium Carbide Base Ceramals Containing Nickel or Iron

Elevated-temperature properties of titanium carbide base ceramals containing nickel or iron were determined in oxidation, modulus of rupture, tensile strength, and thermal-shock resistance. These materials followed the general growth law and exhibited two stages in oxidation. The following tensile strengths were found at 2000 degrees F: 13.3 weight percent nickel, 16, 150 pounds per square inch; 11.8 weight percent iron, 12,500 pounds per square inch; unalloyed titanium carbide, 16,450 pounds per square inch. Nickel or iron additions to titanium carbide improved the thermal-shock resistance, nickel more. The path of fracture in tensile and thermal-shock specimens was found to progress approximately 50 percent intergranularly and 50 percent transgranularly.

MATERIALS - TEMPERATURES, HIGH↗
DOE OSTI2022

Interaction mechanism of transition metal phthalocyanines on transition metal nitride supports

Here, we investigated the electronic interactions between transition metal phthalocyanine (TMPc’s) on a refractory transition metal nitride support, specifically copper phthalocyanine (CuPc) on titanium nitride (TiN). X-ray Photoelectron Spectroscopy (XPS) results suggest a presence of a few nanometer native oxide layer on the surface of the TiN nanoparticles, which consists of TiN, TiO 2 , and Titanium oxynitrides (Ti x O y N z ). A TiNCuPc nanocomposite was synthesized via a simple mixing method due to the strong binding between CuPc and TiN confirmed by density functional theory (DFT) calculations. Both XPS data and DFT calculations revealed an electron transfer from TiN substrate to CuPc molecule. The nature of charge transfer is not influenced by the presence of an oxide layer on the surface of TiN. Substantial deviations are however found between photoelectron emission microscopy (PEEM) measured work function for TiN (4.68 eV) and theoretically calculated work function for pristine stoichiometric TiN (2.63 eV). This behavior is attributed to the presence of an oxide layer on the TiN surface. TiNCuPc composite system has a work function value between those of TiN and CuPc. Our studies open up an opportunity to apply a new class of materials based on transition metal phthalocyanine/transition metal nitride composites to catalysis and optoelectronic devices.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Surface Treatment

A simple surface treatment process is provided which offers a high performance surface for a variety of applications at low cost. This novel surface treatment, which is particularly useful for Ti-6Al-4V alloys, is achieved by forming oxides on the surface with a two-step chemical process and without mechanical abrasion. First, after solvent degreasing, sulfuric acid is used to generate a fresh titanium surface. Next, an alkaline perborate solution is used to form an oxide on the surface. This acid-followed-by-base treatment is cost effective and relatively safe to use in commercial applications. In addition, it is chromium-free, and has been successfully used with a sol-gel coating to afford a strong adhesive bond that exhibits excellent durability after the bonded specimens have been subjected to a harsh 72 hour water boil immersion. Phenylethynyl containing adhesives were used to evaluate this surface treatment with a novel coupling agent containing both trialkoxysilane and phenylethynyl groups. 8 Claims, 16 Drawing Sheets

Park, Cheol↗
DOE OSTI2025

Supported Single‐Atom Manganese Catalysts for the Trimerization of Ethylene

Selective ethylene oligomerization via oxidative cyclization, forming metallacyclic intermediates, is typically catalyzed by molecular titanium and chromium complexes to produce butenes, hexenes, or octenes, depending on the supporting ligand framework. However, this mechanism requires significant electron density at the metal active site and is not known to be generalizable to other first-row transition metals. In this work, we computationally investigate the electronic modulation of five transition metals (Mn, Fe, Co, Ni, and Cu) supported on titania (TiO₂) through reductive lithium intercalation to promote selective oligomerization via oxidative cyclization, using density functional theory (DFT). Our findings predict that Mn/LiTiO₂ exhibits high catalytic activity due to the exergonic nature of oxidative cyclization with two ethylene molecules. Additionally, lithium titanate (LiTiO₂) supports enhance catalytic performance compared to TiO₂. Experimental validation confirms that Mn/LiTiO₂ achieves higher conversion rates and improved selectivity toward hexene (C₄:C₆ = 1:2.6). The enhanced activity is attributed to lithiation, which alters the electronic environment around Mn active sites. Mechanistic studies reveal that the formation of a seven-membered ring, a key intermediate for hexene formation, is more favorable on LiTiO₂ than TiO₂. This work provides the first evidence of Mn catalyzing selective ethylene oligomerization via oxidative cyclization in either homogeneous or heterogeneous catalysis.

Kim, Yu Lim [Argonne National Laboratory (ANL), Ar↗
NASA NTRS1999

Monte Carlo Simulation of Nanoparticle Encapsulation in Flames

Gas-phase combustion (flame) synthesis has been an essential industrial process for producing large quantities of powder materials such as carbon black, titanium dioxide, and silicon dioxide. Flames typically produce simple oxides, with carbon black being the noted exception because the oxides of carbon are gaseous and are easily separated from the particulate matter that is formed during fuel pyrolysis. Furthermore, the powders produced in flames are usually agglomerated, nanometer-sized particles (nanoparticles). This composition and morphology is acceptable for many applications. However, the present interest in nanoparticles for advanced materials application has led to efforts to employ flames for the synthesis of unagglomerated nanoparticles (2 to 100 nm) of metals and non-oxide ceramics. Sodium-halide chemistry has proven to be viable for producing metals and non-oxide ceramics in flames. Materials that have been produced to date include Si (Calcote and Felder, 1993), TiN, TiB2, TiC, TiSi2, SiC, B4C (Glassman et al, 1993) Al, W, Ti, TiB2, AlN, and W-Ti and Al-AlN composites (DuFaux and Axelbaum, 1995, Axelbaum et al 1996,1997). Many more materials are possible. The main challenge that faces application of flame synthesis for advanced materials is overcoming formation of agglomerates in flames (Brezinsky, 1997). The high temperatures and high number densities in the flame environment favor the formation of agglomerates. Agglomerates must be avoided for many reasons. For example, when nanopowders are consolidated, agglomerates have a deleterious effect on compaction density, leading to voids in the final part. Efforts to avoid agglomeration in flames without substantially reducing particle number density and, consequently, production rate, have had limited success. Another critical challenge that faces all synthesis routes for nanopowders is ensuring that the powders are high purity and that the process is scaleable. Though the containerless, high temperature environment of a flame is excellent for producing high-purity simple compounds, ultrafine metals and non-oxide ceramic powders are inherently reactive in the presence of oxygen and/or moisture. Thus, the handling of these powders after synthesis poses a challenging problem. Impurities acquired during handling of nanoparticles have plagued the advancement of nanostructured materials technology.

Sun, Z.↗
DOE OSTI2020

Solvent effects on the heterogeneous growth of TiO 2 nanostructure arrays by solvothermal synthesis

One-dimensional titanium dioxide (TiO 2 ) nanostructure arrays (nanoarrays) are important metal oxide nanomaterials that can be synthesized via facile solvothermal methods. The properties of the organic solvents can impose significant effects on the microstructures and properties of the final products. However, the discussions were limited to the homogeneously nucleated TiO 2 nanomaterials in free-standing powder form, while the solvent effects are less understood during the heterogeneous growth of TiO 2 nanoarrays on a substrate surface. In this work, six organic compounds, namely 2-butanone, n-decane, n-hexane, toluene, ethylene glycol and ethanol, were selected as the solvents for the solvothermal synthesis of TiO 2 nanoarrays on the cordierite monolithic substrates. Special attentions are paid to the morphology, crystallinity, specific surface area, and porosity of the samples. The heterogeneous growth of TiO 2 nanoarrays on substrate surfaces is found to favor the solvents with moderate dielectric constants, which can be partially dissolved in the aqueous solution and modulate the reaction rate during the solvothermal synthesis. Organic solvents with low dielectric constants may result in a complete separation between the precursors and aqueous solution, and therefore slow down the overall reaction, causing the insufficient growth of the nanoarrays. The TiO 2 nanoarrays are obtained with optimum morphology from the combination of 2-butanone and titanium (IV) butoxide as solvent and precusor, respectively, with a high specific surface area up to 56 m 2 /g including cordierite substrate given a micron thickness. When loaded with Pt catalyst, the TiO 2 nanoarray-based monolithic catalysts show excellent low-temperature catalytic activity and hydrothermal stability for the CO and hydrocarbon oxidation under the simulated exhausted conditions. This article shall shed light on a better understanding of the growth mechanism and rational design of TiO 2 nanoarrays for high-performance catalytic converters.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Iraq/Afghanistan war lung injury reflects burn pits exposure

This descriptive case series retrospectively reviewed medical records from thirty-one previously healthy, war-fighting veterans who self-reported exposure to airborne hazards while serving in Iraq and Afghanistan between 2003 and the present. They all noted new-onset dyspnea, which began during deployment or as a military contractor. Twenty-one subjects underwent non-invasive pulmonary diagnostic testing, including maximum expiratory pressure (MEP) and impulse oscillometry (IOS). In addition, five soldiers received a lung biopsy; tissue results were compared to a previously published sample from a soldier in our Iraq Afghanistan War Lung Injury database and others in our database with similar exposures, including burn pits. We also reviewed civilian control samples (5) from the Stony Brook University database. Military personnel were referred to our International Center of Excellence in Deployment Health and Medical Geosciences, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell under the auspices of Northwell IRB: 17-0140-FIMR Feinstein Institution for Medical Research “Clinicopathologic characteristics of Iraq Afghanistan War Lung Injury.” We retrospectively examined medical records, including exposure data, radiologic imaging, and non-invasive pulmonary function testing (MGC Diagnostic Platinum Elite Plethysmograph) using the American Thoracic Society (ATS) standard interpretation based on Morgan et al., and for a limited cohort, biopsy data. Lung tissue, when available, was examined for carbonaceous particles, polycyclic aromatic hydrocarbons (Raman spectroscopy), metals, titanium connected to iron (Brookhaven National Laboratory, National Synchrotron Light Source II, Beamline 5-ID), oxidized metals, combustion temperature, inflammatory cell accumulation and fibrosis, neutrophil extracellular traps, Sirius red, Prussian Blue, as well as polarizable crystals/particulate matter/dust. Among twenty-one previously healthy, deployable soldiers with non-invasive pulmonary diagnostic tests, post-deployment, all had severely decreased MEP values, averaging 42% predicted. These same patients concurrently demonstrated abnormal airways reactance (X5Hz) and peripheral/distal airways resistance (D5–D20%) via IOS, averaging – 1369% and 23% predicted, respectively. These tests support the concept of airways hyperresponsiveness and distal airways narrowing, respectively. Among the five soldiers biopsied, all had constrictive bronchiolitis. We detected the presence of polycyclic aromatic hydrocarbons (PAH)—which are products of incomplete combustion—in the lung tissue of all five warfighters. All also had detectable titanium and iron in the lungs. Metals were all oxidized, supporting the concept of inhaling burned metals. Combustion temperature was consistent with that of burned petrol rather than higher temperatures noted with cigarettes. All were nonsmokers. Neutrophil extracellular traps were reported in two biopsies. Compared to our prior biopsies in our Middle East deployment database, these histopathologic results are similar, since all database biopsies have constrictive bronchiolitis, one has lung fibrosis with titanium bound to iron in fixed mathematical ratios of 1:7 and demonstrated polarizable crystals. These results, particularly constrictive bronchiolitis and polarizable crystals, support the prior data of King et al. (N. Engl. J. Med. 365:222–230, 2011) Soldiers in this cohort deployed to Iraq and Afghanistan since 2003, with exposure to airborne hazards, including sandstorms, burn pits, and improvised explosive devices, are at high risk for developing chronic clinical respiratory problems, including: (1) reduction in respiratory muscle strength; (2) airways hyperresponsiveness; and (3) distal airway narrowing, which may be associated with histopathologic evidence of lung damage, reflecting inhalation of burned particles from burn pits along with particulate matter/dust. Non-invasive pulmonary diagnostic tests are a predictor of burn pit-induced lung injury

36 MATERIALS SCIENCE↗
NASA NTRS2005

Mechanical Behavior of Gamma-Met PX under Uniaxial Loading at Elevated Temperatures and High Strain Rates

Gamma titanium aluminides have received considerable attention over the last decade. These alloys are known to have low density, good high temperature strength retention and good oxidation and corrosion resistance. However, poor ductility and low fracture toughness have been the key limiting factors in the full utilization of these alloys. More recently, a new generation of gamma titanium aluminide alloys, commonly referred to as Gamma-met PX, has been developed by GKSS, Germany. These alloys have been observed to have superior strength and better oxidation resistance at elevated temperatures when compared with conventional gamma titanium aluminides. The present paper discusses results of a study to understand the uniaxial mechanical behavior in both compression and tension of Gamma-Met PX at elevated temperatures and high strain rates. The compression and tensile tests are conducted using a modified split-Hopkinson bar apparatus at test temperatures ranging from room temperature to 900 C and strain rates of up to 3500/s. Under uniaxial compression, in the temperature range from room to 600 C, the flow stress is observed to be nearly independent of test temperature. However, at temperatures higher than 600 C thermal softening is observed at all strain rates with the rate of thermal softening increasing dramatically between 800 C and 900 C. The room temperature tensile tests show negligible strain-rate dependence on both yield stress and flow stress. With an increase in test temperature from room to 900 C the material shows a drop in both yield and flow stress at all levels of plastic strain. However, the measured flow stress is still higher when compared to nickel based super-alloys and other gamma titanium aluminides under similar test conditions. Also, no anomaly in yield stress is observed up to 900 C.

Shazly, Mostafa↗