Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “INTERMETALLIC COMPOUNDS”

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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Prediction of superconducting iron–bismuth intermetallic compounds at high pressure

The synthesis of materials in high-pressure experiments has recently attracted increasing attention, especially since the discovery of record breaking superconducting temperatures in the sulfur–hydrogen and other hydrogen-rich systems. Commonly, the initial precursor in a high pressure experiment contains constituent elements that are known to form compounds at ambient conditions, however the discovery of high-pressure phases in systems immiscible under ambient conditions poses an additional materials design challenge. We performed an extensive multi component ab initio structural search in the immiscible Fe–Bi system at high pressure and report on the surprising discovery of two stable compounds at pressures above ≈36 GPa, FeBi 2 and FeBi 3 . According to our predictions, FeBi 2 is a metal at the border of magnetism with a conventional electron–phonon mediated superconducting transition temperature of T c = 1.3 K at 40 GPa.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Structure and magnetism of new rare-earth-free intermetallic compounds: Fe 3+x Co 3-x Ti 2 (0 ≤ x ≤ 3)

Here, we report the fabrication of a set of new rare-earth-free magnetic compounds, which form the Fe 3 Co 3 Ti 2 -type hexagonal structure with P-6m2 symmetry. Neutron powder diffraction shows a significant Fe/Co anti-site mixing in the Fe 3 Co 3 Ti 2 structure, which has a strong effect on the magnetocrystalline anisotropy as revealed by first-principle calculations. Increasing substitution of Fe atoms for Co in the Fe 3 Co 3 Ti 2 lattice leads to the formation of Fe 4 Co 2 Ti 2 , Fe 5 CoTi, and Fe 6 Ti 2 with significantly improved permanent-magnet properties. A high magnetic anisotropy (13.0 Mergs/cm 3 ) and saturation magnetic polarization (11.4 kG) are achieved at 10 K by altering the atomic arrangements and decreasing Fe/Co occupancy disorder.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Superconductivity in the intermetallic compound Zr 5 Al 4

Polycrystalline Zr 5 Al 4 was synthesized using the arc-melting method. Powder X-ray diffraction confirms the previously reported crystal structure of the Ti 5 Ga 4 -type ( P 6 3 / mcm ) with lattice parameters: a = 8.4312(6) Å, and c = 5.7752(8) Å. Electrical resistivity and low-temperature magnetic susceptibility measurements indicate that Zr 5 Al 4 exhibits superconducting behavior below 2K. The normalized heat capacity jump at T c = 1.82 K, Δ C/γT c = 1.50, confirms the bulk superconductivity. The Sommerfeld coefficient γ = 28.5 mJ mol -1 K -2 and the Debye temperature Θ D = 320 K were obtained by fitting the low-temperature heat capacity data. The electron-phonon coupling strength λ el-ph = 0.49 and estimated upper critical field μ 0 H c2 (0) = 1.09 T (dirty limit) suggest that Zr 5 Al 4 is a weakly coupled type-II superconductor. Finally, first-principles calculations show the presence of a van Hove singularity near the Fermi energy.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Microstructure study of the rare-earth intermetallic compounds R 5 (Si x Ge 1-x ) 4 and R 5 (Si x Ge 1-x ) 3

The unique combination of magnetic properties and structural transitions exhibited by many members of the R 5 (Si x Ge 1-x ) 4 family (R = rare earths, 0 ≤ x ≤ 1) presents numerous opportunities for these materials in advanced energy transformation applications. Past research has proven that the crystal structure and magnetic ordering of the R 5 (Si x Ge 1-x ) 4 compounds can be altered by temperature, magnetic field, pressure and the Si/Ge ratio. Results of this thesis study on the crystal structure of the Er 5 Si 4 compound have for the first time shown that the application of mechanical forces (i.e. shear stress introduced during the mechanical grinding) can also result in a structural transition from Gd 5 Si 4 -type orthorhombic to Gd 5 Si 2 Ge 2 -type monoclinic. This structural transition is reversible, moving in the opposite direction when the material is subjected to low-temperature annealing at 500 °C.

36 MATERIALS SCIENCE↗
NASA NTRS1967

Theoretical studies on the relationship between the thermionic work functions of refractory-metal intermetallic compounds and their electronic and crystal structures Final summary report

The Group VIA-Re binary systems are characterized by the presence of several intermediate phases. The u phase is present in all of the systems, but the a-Mn phases occur in only the Mo-Re and W-Re systems. The occurrence of these intermediate phases appears to be governed largely by electronic factors and is predictable on the basis of electron/atom ratio. The thermionic work functions of the intermediate phase materials were experimentally determined. function and the screening of the outermost electrons in the Group VIA metals was found. A correlation between the work As might be expected for purely metallic substances, the work functions were relatively high, in the range 4. 5 to 5. 0 eV, and in each case were bracketed by the work functions of the pure constituents. A discontinuous change in the average work function with composition is proposed, based on a thermodynamical treatment of the electron vapor.

REFRACTORY METAL↗
NASA NTRS1995

Investigation of Strain Aging in the Ordered Intermetallic Compound beta-NiAl

The phenomenon of strain aging has been investigated in polycrystalline and single crystal NiAl alloys at temperatures between 300 and 1200 K. Static strain aging studies revealed that after annealing at 1100 K for 7200 s (i.e., 2h) followed by furnace cooling, high purity, nitrogen-doped and titanium-doped polycrystalline alloys exhibited continuous yielding, while conventional-purity and carbon-doped alloys exhibited distinct yield points and Luders strains. Prestraining by hydrostatic pressurization removed the yield points, but they could be reintroduced by further annealing treatments. Yield points could be reintroduced more rapidly if the specimens were prestrained uniaxially rather than hydrostatically, owing to the arrangement of dislocations into cell structures during uniaxial deformation. The time dependence of the strain aging events followed at t(exp 2/3) relationship suggesting that the yield points observed in polycrystalline NiAl were the result of the pinning of mobile dislocations by interstitials, specifically carbon. Between 700 and 800 K, yield stress plateaus, yield stress transients upon a ten-fold increase in strain rate, work hardening peaks, and dips in the strain rate sensitivity (SRS) have been observed in conventional-purity and carbon-doped polycrystals. In single crystals, similar behavior was observed; in conventional-purity single crystals, however, the strain rate sensitivity became negative resulting in serrated yielding, whereas, the strain rate sensitivity stayed positive in high purity and in molybdenum-doped NiAl. These observations are indicative of dynamic strain aging (DSA) and are discussed in terms of conventional strain aging theories. The impact of these phenomena on the composition-structure-property relations are discerned. Finally, a good correlation has been demonstrated between the properties of NiAl alloys and a recently developed model for strain aging in metals and alloys developed by Reed-Hill et al.

Weaver, Mark Lovell↗
NASA NTRS2012

Processing Issues for Preliminary Melts of the Intermetallic Compound 60-NITINOL

The effect of various high temperature heat treatments and cooling rates on the hardness of cast 60-NITINOL (60wt%Ni- 40wt%Ti) was studied. The hardness ranged from approximately 33 HRC for annealed specimens to 63 HRC for water quenched specimens. Aging did not have a further effect on the hardness of the heat-treated and quenched material. The issue of material contamination and its possible effect on quench cracking during heat treatment above 1000 C was explored. The Charpy impact energy of the material was found to be relatively low (ranging from 0.4 to 1.0 J) and comparable to that of cast magnesium. Selection of service environments and applications for this material based on these findings should consider the processing route by which it was produced.

Stanford, Malcolm K.↗
NASA NTRS2012

Addressing Machining Issues for the Intermetallic Compound 60-NITINOL

60-NITINOL (60 wt.% Ni - 40 wt.% Ti) is being studied as a material for advanced aerospace components. Frequent wire breakage during electrical-discharge machining of this material was investigated. The studied material was fabricated from hot isostatically pressed 60-NITINOL powder obtained through a commercial source. Bulk chemical analysis of the material showed that the composition was nominal but had relatively high levels of certain impurities, including Al and O. It was later determined that Al2O3 particles had contaminated the material during the hot isostatic pressing procedure and that these particles were the most likely cause of the wire breakage. The results of this investigation highlight the importance of material cleanliness to its further implementation.

Stanford, Malcolm K.↗
NASA NTRS2020

Creepy (not KREEPy) Gold-Indium Intermetallic Compounds on Secondary Ion Mass Spectrometry Samples

A series of Secondary Ion Mass Spectrometry (SIMS) sessions to measure hydrogen (H) in Martian meteorite minerals was completed using the Cameca 6f SIMS and NanoSIMS 50L at Arizona State University (ASU). During these sessions, a “creeping” phenomenon has occurred, where the edges of samples pressed in indium are covered by a metal alloy. We summarize these observations herein, present a collection of preliminary data, and discuss explanations and concerns for future SIMS work. We conclude the report with a research plan for further study.

Dudley, J. M.↗
DOE OSTI2019

High hardness, high elasticity intermetallic compounds for mechanical components

One or more substitutional elements may be used to reduce the solution treatment temperature and required quench rates for hardening of 60-NITINOL. The advantages of modified NITINOL include that less energy is consumed during the heat treatment process, the material is subjected to less thermal distortion, and less machining is required. Modified NITINOL may have adequate hardness for bearing applications and may display highly elastic behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Steering the methanol steam reforming reactivity of intermetallic Cu–In compounds by redox activation: stability vs . formation of an intermetallic compound–oxide interface

To compare the inherent methanol steam reforming properties of intermetallic compounds and a corresponding intermetallic compound–oxide interface, we selected the Cu–In system as a model to correlate the stability limits, self-activation and redox activation properties with the catalytic performance. Three distinct intermetallic Cu–In compounds – Cu 7 In 3 , Cu 2 In and Cu 11 In 9 – were studied both in an untreated and redox-activated state resulting from alternating oxidation–reduction cycles. The stability of all studied intermetallic compounds during methanol steam reforming (MSR) operation is essentially independent of the initial stoichiometry and all accordingly resist substantial structural changes. The inherent activity under batch MSR conditions is highest for Cu 2 In, corroborating the results of a Cu 2 In/In 2 O 3 sample accessed through reactive metal–support interaction. Under flow MSR operation, Cu 7 In 3 displays considerable deactivation, while Cu 2 In and Cu 11 In 9 feature stable performance at simultaneously high CO 2 selectivity. Here, the missing significant self-activation is most evident in the operando thermogravimetric experiments, where no oxidation is detected for any of the intermetallic compounds. In situ X-ray diffraction allowed us to monitor the partial decomposition and redox activation of the Cu–In intermetallic compounds into Cu 0.9 In 0.1 /In 2 O 3 (from Cu 7 In 3 ), Cu 7 In 3 /In 2 O 3 (from Cu 2 In) and Cu 7 In 3 /Cu 0.9 In 0.1 /In 2 O 3 (from Cu 11 In 9 ) interfaces with superior MSR performance compared to the untreated samples. Although the catalytic profiles appear surprisingly similar, the latter interface with the highest indium content exhibits the least deactivation, which we explain by formation of stabilizing In 2 O 3 patches under MSR conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Deformation and fracture characteristics of Al6092/SiC/17.5p metal matrix composite sheets due to heat treatments

Highlights: • Al{sub 2}Cu, Al{sub 4}Cu{sub 2}Mg{sub 8}Si{sub 7} and MgAl{sub 2} precipitations are formed between Al-matrix and SiC particle interface after T6-treatement • O-condition annealing decrease Al{sub 2}Cu intermetallic compound and increase elongation to fracture • 6092Al/SiCp composite at O-condition annealing is more sensitive to strain rate than the one heat treated by T6-treatment • Dimple density in the fracture surface of Al/SiCp composite varies as a function of heat treatment and strain rate - Abstract: In metal matrix composite (MMC) materials, the reaction between the metal matrix and reinforcement particles could change the composition of the matrix and the interface and lead to interfacial compounds. These intermetallic compounds may have either a deleterious effect to the mechanical properties or beneficial effect in enhancing the toughness and ductility of the composite. An aluminium 6092 alloy with 17.5% volume fraction silicon carbide (SiC) particles sheet manufactured by means of powder metallurgical method, heat treated to T6 condition, is used to obtain a fundamental understanding of the heat treatment effect on the fracture mechanism, the microstructural changes and the interface between the Al-matrix and SiC particles. Changes in the microstructure of the Al/SiCp and the topography of the fracture are investigated using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) to characterize the precipitate and intermetallic compounds formed at the Al/Sic interface. X-ray diffraction (XRD) is utilized to characterize the phase formation and to give confidence in the results of TEM and EDS. Tensile tests with different strain rates (8 × 10{sup −5}, 8 × 10{sup −4}, 8 × 10{sup −3}, 8 × 10{sup −2} and 0.16 s{sup −1}) were carried out to study the toughness and to find a correlation between the strain rate and heat treatment. Under T6 condition, the results show that the mechanical property of this MMC is less ductile due to the formation of precipitations as a result of either the interaction between the Al and SiCp or from hardening precipitation treatment, e.g. Al{sub 2}Cu, Al{sub 4}Cu{sub 2}Mg{sub 8}Si{sub 7} and MgAl{sub 2}. O-condition annealing can reduce the detrimental effect of the intermetallic compounds in the interface region and improve the toughness and ductility of the material by decreasing the intermetallic compound (Al{sub 2}Cu). However, the Al/SiC sheet treated with O-condition annealing is more sensitive to the strain rate than the one treated with T6.

36 MATERIALS SCIENCE↗