Aluminum Intermetallic Compound Research Articles

Creating a Coating from a Titanium–Aluminum Intermetallic Compound By the Cold Spray Technology

Results of experimental and numerical investigations of the process of creating coatings from a titanium–aluminum intermetallic compound by using an additive method are presented. It is demonstrated that the process of intermetallic compound formation is limited by the rate of titanium dissolution and diffusion in the aluminum melt. The proposed method can be applied for hardening titanium plate surfaces for their exploitation at high temperatures and pressures.

Method for Semi-Automated Measurement and Statistical Evaluation of Iron Aluminum Intermetallic Compound Layer Thickness and Morphology

In the present study, a semi-automated method for the measurement of intermetallic compound layer thicknesses is introduced. Based on backscattered electron contrast images of the bond zones that feature a sufficient contrast between the substrates and the intermetallic compound layer, every line of pixels perpendicular to the bond zone is analyzed. This provides the opportunity to evaluate the distribution of the measured single thicknesses to describe the layer morphology quantitatively. It is shown that it is possible to identify several morphological features by employing certain statistical values. Commonly used measurement methods are compared to the results of the proposed method to show its applicability.

Conversion of ferrous compounds in a flameless combustion wave of hexogen-based systems filled with iron formate and other additives

The thermal decomposition of the energetic component and chemical reactions occurring at elevated temperatures in a flameless combustion wave of systems based on hexogen (filled with iron(II) formate and polyisocyanurate binding agent) afford a mixture of iron oxides and iron nitride as nanosized particles. The purposeful change in the ratio of the indicated basis components can provide individual Fe2O3, Fe3O4, or FeO in the conversion products. Additives of anthracene and hydroquinone to the initial composition can result in the formation of predominantly iron carbide in the products, whereas mainly iron nitrides are formed upon the addition of guanidine nitrate or 5-aminotetrazole. The addition of aluminum hydride components to the initial mixture results in the reduction of iron to the zero-valence state in the form of iron—aluminum intermetallic compounds.

Effective and Environmentally Friendly Nickel Coating on the Magnesium Alloy

The low density and good mechanical properties make magnesium and its alloys attractive construction materials in the electronics, automotive, and aerospace industry, together with application in medicine due to their biocompatibility. Magnesium AZ91D alloy is an alloy with a high content of aluminum, whose mechanical properties overshadow the low corrosion resistance caused by the composition of the alloy and the existence of two phases: α magnesium matrix and β magnesium aluminum intermetallic compound. To improve the corrosion resistance, it is necessary to find an effective protection method for the alloy surface. Knowing and predicting electrochemical processes is an essential for the design and optimization of protective coatings on magnesium and its alloys. In this work, the formations of nickel protective coatings on the magnesium AZ91D alloy surface by electrodeposition and chemical deposition, are presented. For this purpose, environmentally friendly electrolytes were used. The corrosion resistance of the protected alloy was determined in chloride medium using appropriate electrochemical techniques. Characterization of the surface was performed with highly sophisticated surface-analytical methods.

Nickel–Aluminum Intermetallic Compounds as Highly Selective and Stable Catalysts for the Hydrogenation of Naphthalene to Tetralin

AbstractSelective hydrogenation of naphthalene to tetralin was conducted by using Ni–Al intermetallic compounds (IMCs) prepared by a chemical synthetic route. Ni–Al IMC catalysts achieved a lasting high conversion with 100 % selectivity up to 125 h. During the synthesis process, the Ni–Al IMCs underwent the following phase transformation as a function of the content of the Al source (LiAlH4): Ni(cubic)→Ni3Al(tetragonal)→NiAl(cubic)→Ni2Al3(hexagonal). In the selective hydrogenation of naphthalene, the catalytic activity of NiAl was much higher than that of metallic Ni and other Ni–Al IMCs (Ni3Al and Ni2Al3). The results can be understood by a combination of site isolation and alteration of the electronic structure by chemical bonding. Ni atoms are scattered and spatially isolated by Al atoms, which in turn resists carbon deposition. The findings provide a useful approach to tailor the catalytic properties of transition metals by formation of IMCs, which could be applicable in heterogeneous catalysis.

27Al pulsed nuclear magnetic resonance study of CeAl2

The magnetic properties and the electronic structures of a rare-earth aluminum intermetallic compound CeAl2 are investigated by magnetic susceptibility measurements and 27Al pulsed nuclear magnetic resonance (NMR) techniques. The magnetic susceptibility is strongly temperature-dependent, following a Curie–Weiss law down to ∼12 K, and shows an antiferromagnetic transition at 4 K. The 27Al NMR spectra show a typical powder pattern for a nuclear spin I of 5/2 with the second-order nuclear quadrupole interaction at high temperature and an additional large dipolar broadening between the 4f electron spins of cerium and the 27Al nuclear spins at low temperature. The 27Al NMR Knight shift follows the same temperature dependence as the magnetic susceptibility, suggesting that the 27Al NMR Knight shift originates from the transferred hyperfine field of the Ce 4f electron spins with the hyperfine coupling constant of A = +5.7 kOe/μB. The spin-lattice relaxation rate 1/T1 is roughly proportional to temperature, as with most non-magnetic metals at high temperature, and then strongly temperature-dependent, increasing rapidly with a peak near the antiferromagnetic transition temperature and decreasing at lower temperature. The temperature dependence of the Korringa ratio K, however, suggests that the antiferromagnetic spin fluctuation signature, which is an enhancement in the Korringa ratio, is washed out owing to the geometrical cancellation of Ce 4f fluctuations at the Al sites.

Evaluation of Ni–Ni 3Al(5 wt.%)–Al(3 wt.%) as an anode electrode for molten carbonate fuel cell : Part I: Creep and sintering resistance

To develop an anode electrode of molten carbonate fuel cell (MCFC) that has higher creep and sintering resistance and more stable reactivity than the traditional anode electrode, the five kinds of nickel anode electrodes such as Ni–Al(5), Ni–Cr(10), Ni–Ni 3Al(7), Ni–Ni 3Al(5)–Cr(5) and Ni–Ni 3Al(5)–Al(3) (number in parenthesis means the weight percent of its component) were prepared and their performance were investigated under the same conditions of MCFC operation. In part I of our study, their relative creep and sintering resistance were compared. The Ni–Ni 3Al(5)–Al(3) anode electrode was the most resistant against the sintering and its porosity was kept over 60% even at 1000 °C. And its porosity decrease and thickness shrinkage by creep were the least among the five kinds of anode electrodes. Thus, the effects of the aluminum and nickel–aluminum intermetallic compound (Ni 3Al) addition to nickel as the dispersant strengthening and the solid solution strengthening agents were confirmed by comparative tests for sintering and creep resistance of five kinds of anode electrodes. Besides these results, we could also know that the creep of anode electrode for MCFC mostly proceeded within 60 h from the start of operation irrespective of the kinds of anode electrodes. And in part II of paper, for more information about the wetting ability and cell performances of these five kinds of anode electrodes, the measurement of wetting ability and unit cell operations were carried out.

Electronic Properties of Gold—Aluminum Intermetallic Compounds.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Crystal structure, phase stability, and electronic structure of Ti-Al intermetallics: Ti3Al.

The structural phase stability and electronic properties of the intermetallic compound ${\mathrm{TiAl}}_{3}$ are investigated with use of the self-consistent all-electron total-energy linear muffin-tin orbitals band-structure method within the local-density-functional approximation. The calculated equilibrium volumes have a Wigner-Seitz radius of 2.92 a.u. for the D${0}_{22}$ and D${0}_{19}$ structures, and 2.91 a.u. for the L${1}_{2}$ structure, showing the expected consistency in the volume among the different structures. The calculated value also agrees with experiment for the D${0}_{22}$ structure to within 2%. The calculated heats of formation are 0.42, 0.37, and 0.28 eV/atom for the D${0}_{22}$, L${1}_{2}$, and D${0}_{19}$ lattices, respectively. The D${0}_{22}$ structure is calculated to be the most stable phase, as observed experimentally. The calculated bulk moduli are 1.2, 1.5, and 1.1 Mbar for D${0}_{22}$, L${1}_{2}$, and D${0}_{19}$, respectively. Among the three structures, the density of states at the Fermi energy, N(${\mathit{E}}_{\mathit{F}}$), is lowest in D${0}_{22}$ and so is consistent with the inverse relation between N(${\mathit{E}}_{\mathit{F}}$) and stability found for other aluminum intermetallic compounds.

Crystal structure, phase stability, and electronic structure of Ti-Al intermetallics: TiAl3.

The structural phase stability and electronic properties of the intermetallic compound ${\mathrm{TiAl}}_{3}$ are investigated with use of the self-consistent all-electron total-energy linear muffin-tin orbitals band-structure method within the local-density-functional approximation. The calculated equilibrium volumes have a Wigner-Seitz radius of 2.92 a.u. for the D${0}_{22}$ and D${0}_{19}$ structures, and 2.91 a.u. for the L${1}_{2}$ structure, showing the expected consistency in the volume among the different structures. The calculated value also agrees with experiment for the D${0}_{22}$ structure to within 2%. The calculated heats of formation are 0.42, 0.37, and 0.28 eV/atom for the D${0}_{22}$, L${1}_{2}$, and D${0}_{19}$ lattices, respectively. The D${0}_{22}$ structure is calculated to be the most stable phase, as observed experimentally. The calculated bulk moduli are 1.2, 1.5, and 1.1 Mbar for D${0}_{22}$, L${1}_{2}$, and D${0}_{19}$, respectively. Among the three structures, the density of states at the Fermi energy, N(${\mathit{E}}_{\mathit{F}}$), is lowest in D${0}_{22}$ and so is consistent with the inverse relation between N(${\mathit{E}}_{\mathit{F}}$) and stability found for other aluminum intermetallic compounds.

Mechanism of plastic deformation of Mn-added TiAl L 10 -type intermetallic compound

Titanium aluminum intermetallic compound is a possible candidate for a high-temperature structural material, except for a problem of lack of room-temperature ductility. Recently, this problem was found to be overcome possibly by the addition of Mn, but this mechanism has not been fully understood yet. In order to understand the fundamental mechanism of the ductility improvement by Mn addition, microanalyses have been carried out. The results are as follows. Twin structures in a TiAl intermetallic compound in the as-cast state can be climinated by high-temperature annealing, while those in Mn-added TiAl are thermally more stable and exist even after annealing for 86.4 ks at 1273 K. The reason for this thermal stabilization of twin structures is considered to be due to the pinning effect of twin dislocations by Mn addition. The enhancement of twin deformation in TiAl by Mn addition is regarded to be caused by two factors. One is the stabilization of twin partial dislocations, becoming the nucleation sites for twin formation. The other is the decrease in stacking fault energy, which makes twin deformation energetically easier.

アルミニウム金属間化合物の電気化学的性質とアルミニウム合金の腐食形態の関係

アルミニウム金属間化合物の電気化学的性質とアルミニウム合金の腐食形態の関係

Aluminum Ion Plating of Uranium–Molybdenum Alloy Fast-Burst Reactor Elements

Ion plating of thin (<0.002 in.) aluminum coatings on fast-burst reactor parts fabricated from uranium–10% molybdenum alloy was evaluated as a method of protecting the alloy from oxidation and as a means of containing the fission products. A number of core rings were plated with nickel while other rings were ion-plated with aluminum so that a comparison between the two coatings could be made. During the ion plating of aluminum and subsequent heat treatment, certain uranium–aluminum intermetallic compounds (UAl2, UAl3, and UAl4) were formed. During the process of testing to destruction, these rings encountered fissions in excess of 1017 and temperatures in excess of 700°C during which the nickel plating spalled severely while the aluminum and the uranium–aluminum intermetallics remained adherent to the alloy.

Nuclear Quadrupole Coupling and Crystal-Field Effects in the Cubic Intermetallic Compounds ErAl3, TmAl3, and YbAl3

The presence of a large nuclear quadrupole coupling of the Al nucleus, as measured with NMR, in the cubic rare-earth aluminum intermetallic compounds $\ensuremath{\beta}$-Er${\mathrm{Al}}_{3}$, Tm${\mathrm{Al}}_{3}$, and Yb${\mathrm{Al}}_{3}$ indicates that the net charges at the rare-earth and aluminum sites differ by as much as 3 to 4 unit charges. Data on the magnetic susceptibility and this result have been used to analyze crystal-field effects in Tm${\mathrm{Al}}_{3}$. The ground state appears to be a nonmagnetic doublet ${\ensuremath{\Gamma}}_{3}$, the next higher level being the triplet ${\ensuremath{\Gamma}}_{5}^{(1)}$ at a distance of 45\ifmmode^\circ\else\textdegree\fi{}K. In addition, from the Knight shift, exchange constants between conduction electrons and $4f$ electrons have been derived to be ${\mathcal{I}}_{\mathrm{sf}}=\ensuremath{-}0.24$ eV.

The Effect of Valence and Coordination on K Series Diagram and Nondiagram Lines of Magnesium, Aluminum, and Silicon*

AbstractWavelengths and intensities are reported for the K series of magnesium, aluminum, and silicon, using primary excitation. Included in the tabulation for magnesium and aluminum are the diagram lines α1α2 and β and the nondiagram lines α', α3, α4, α5, and α6. Data are given for the Si K spectral lines α1α2, β, α3, and α4, Spectra are shown and line positions and intensities are detailed using both metal and oxide as the X-ray source. Significant differences are seen between metal and oxide spectra especially in wavelength and shape of Kβ, and large changes are noted in the intensities of some satellite lines. Spectra from a number of aluminum intermetallic compounds are discussed, including line positions, satellite line ratios, and line shape. It is shown that the spectra fall into three predictable groups; good conductors; poorer conductors; and semiconductors and insulators. Structurally similar compounds give similar spectra. For instance, line positions, shapes, and intensities are nearly identical for NbAl3 and TaAl3. It is not possible to correlate spectra with aluminum coordination number, and previous work using Kα, where secondary excitation was used, could not be reproduced using primary excitation. Possible reasons for this disagreement are discussed.