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1.
Summary Improved methods for Al 2O 3 metallization by Cu are described. Good adhesion between Cu and Al 2O 3 substrate depends on the formation of chemical bonds between the substrate and the metallic layer. The temperature needed for the formation of a CuAl 2O 4 spinel interface is reduced from 1050°C to 900°C by the addition of various oxides. The adhesion between the CuAl 2O 4 interface and deposited Cu is stronger then the tensile strength of pure Cu. Plasma techniques for the formation of a Cu containing interface are also described. Bombardment of a Cu film with Xe + ions in a rf-glow discharge implants Cu atoms into the substrate to a depth of 5 nm, as determined by SIMS depth profiling. Methods for reduction of the CuAl 2O 4 surface for subsequent metallization are also presented. 相似文献
2.
Magnesium alloys are the basis for the creation of light and ultra‐light alloys. They have attracted attention as potential materials for the accumulation and storage of hydrogen, as well as electrode materials in metal‐hydride and magnesium‐ion batteries. The search for new metal hydrides has involved magnesium alloys with rare‐earth transition metals and doped by p‐ or s‐elements. The synthesis and characterization of a new quaternary carbide, namely dimagnesium lithium aluminium carbide, Mg 1.52Li 0.24Al 0.24C 0.86, belonging to the family of hexagonal close‐packed (hcp) structures, are reported. The title compound crystallizes with hexagonal symmetry (space group Pm2), where two sites with m2 symmetry and one site with 3 m. symmetry are occupied by an Mg/Li statistical mixture (in Wyckoff position 1 a), an Mg/Al statistical mixture (in position 1 d) and C atoms (2 i). The cuboctahedral coordination is typical for Mg/Li and Mg/Al, and the C atom is enclosed in an octahedron. Electronic structure calculations were used for elucidation of the ability of lithium or aluminium to substitute magnesium, and evaluation of the nature of the bonding between atoms. The presence of carbon in the carbide phase improves the corrosion resistance of the Mg 1.52Li 0.24Al 0.24C 0.86 alloy compared to the ternary Mg 1.52Li 0.24Al 0.24 alloy and Mg. 相似文献
3.
The interface microstructure, formation of diffusion bonded joint and regulation of atom diffusion were studied by means of
scanning electron microscope (SEM), energy dispersion spectroscopy (EDS) and electron probe microanalyser (EPMA). The experimental
results indicated that an obvious interfacial transition zone was formed between Mg and Al, and there are three intermetallic
layers Mg 17Al 12, MgAl and Mg 2Al 3 in this zone. Diffusion activation energy of Mg and Al in the above layers was lower than that in the Mg and Al base metals.
The thickness ( x) of each layer can be expressed as x
2 = 4.14exp(−28780/ RT)( t− t
0), x
2 = 31.4exp(−25550/ RT)( t− t
0) and x
2 = 0.6exp(−22600/ RT)( t− t
0) corresponding to Mg 17Al 12, MgAl and Mg 2Al 3 with heating temperature ( T) and holding time ( t). 相似文献
4.
The new ternary lithium copper aluminide Li 8Cu 12+xAl 6−x ( x = 1.16) crystallizes in the P6 3/ mmc space group with six independent atom positions of site symmetries m. (Al/Cu mixture), m2 (Li atoms), 3 m. (Al/Cu mixture and Li atoms) and . m. (Cu atoms). The compound is a derivative of the K 7Cs 6 binary structure type and is related to the binary MgZn 2 Laves phase and the LiCuAl 2, MgCu 1.07Al 0.93 and Mg(Cu 1−xAl x) 2 ( x = 0.465) ternary Laves phases. The coordination polyhedra of the atoms in this structure are icosahedra (Cu atoms), slightly distorted icosahedra and bicapped hexagonal antiprisms (Al/Cu statistical mixture), and Frank–Kasper and distorted Frank–Kasper polyhedra (Li atoms). All interatomic distances indicate metallic type bonding. 相似文献
5.
The performance of heteronuclear clusters [Al XO 3] + ( X=Al, AlO 4, AlMg 2O 2, AlZnO, AlAu 2, Mg, Y, VO, NbO, TaO) in activating methane has been explored by a combination of high–level quantum calculations with reported and supplementary gas-phase experiments. With different dopants in [Al XO 3] +, the mechanism, reactivity and selectivity towards methane activation varies accordingly. The classic HAT competes with PCET, depending on the composition of intramolecular interactions. Although the existence of terminal oxygen radical is beneficial for classic HAT, the Al t−C interaction in the [Al XO 3] + clusters as enhanced by the strongly electronegative doping groups ( X=Al, AlZnO, Mg, Zn, VO, NbO, TaO) favors the PCET process, facilitating C−H bond breaking. In addition, with different dopants, the destiny of the split methyl group varies accordingly. While strong interaction between Al t and CH 3 results in the formation of the Al t−C bond, dopants with variable valance may promote the formation of deep-oxidation products like formaldehyde. It has been discussed in detail how to regulate the activity and selectivity of the active center of the catalyst via rational doping. 相似文献
6.
Cu–Al spinel oxide, which contains a small portion of the CuO phase, has been successfully used in methanol steam reforming (MSR) without prereduction. The omission of prereduction not only avoids the copper sintering prior to the catalytic reaction, but also slows down the copper‐sintering rate in MSR. During this process, the CuO phase can initiate MSR at a lower temperature, and CuAl 2O 4 releases active copper gradually. The catalyst CA2.5‐900, calcined at 900 °C with n(Al)/ n(Cu)=2.5, has a higher CuAl 2O 4 content, higher BET surface area, and smaller CuAl 2O 4 crystal size. Its activity first increases and then decreases during MSR. Furthermore, both fresh and regenerated CA2.5‐900 showed better catalytic performance than the commercial Cu–Zn–Al catalyst. 相似文献
7.
Single crystals of diterbium dinickel trimagnesium, Tb 2Ni 2Mg 3, were synthesized from the elements by induction melting. The novel compound crystallizes in the space group Cmmm with one Mg atom of site symmetry mmm and the Tb, Ni and other Mg atom in m2 m positions. This ternary compound represents a new structure type that is derived from Ru 3Al 2B 2 by way of Wyckoff site distribution. The two‐layer structure of Tb 2Ni 2Mg 3 is a new representative of a homologous linear structure series of general formula R′ k+nX2nR′′ 2m+k based on structural fragments of the α‐Fe, CsCl and AlB 2 structure types. The Tb atoms in the structure are enclosed in 17‐vertex polyhedra, while rhombododecahedra and distorted rhombododecahedra surround the Mg atoms, and equatorially tricapped trigonal prisms form around the Ni atoms. All interatomic distances indicate metallic type bonding. 相似文献
8.
The title compound, lithium aluminium silicide (15/3/6), crystallizes in the hexagonal centrosymmetric space group P6 3/ m. The three‐dimensional structure of this ternary compound may be depicted as two interpenetrating lattices, namely a graphite‐like Li 3Al 3Si 6 layer and a distorted diamond‐like lithium lattice. As is commonly found for LiAl alloys, the Li and Al atoms are found to share some crystallographic sites. The diamond‐like lattice is built up of Li cations, and the graphite‐like anionic layer is composed of Si, Al and Li atoms in which Si and Al are covalently bonded [Si—Al = 2.4672 (4) Å]. 相似文献
9.
Silicon oxide-coated lithium aluminum layered double hydroxide (Li xAl 2-LDH@SiO 2) nanocrystals (NCs) are investigated to selectively separate lithium cations in aqueous lithium resources. We directly synthesized Li xAl 2-LDH NC arrays by oxidation of aluminum foil substrate under a urea and lithium solution. Various lithium salts, including Cl −, CO 32−, NO 3−, and SO 42−, were applied in aqueous solution to confirm the anion effect on the captured and released lithium quantity of the Li xAl 2-LDH NCs. In a 5% solution of sulfate ions mix with lithium chloride, the Li xAl 2-LDH NCs separated a larger quantity of lithium than in other anion conditions. To enhance regeneration stability and lithium selectivity, thin layers of SiO 2 were coated onto the Li xAl 2-LDH nanostructure arrays for inhibition of nanostructure destruction after desorption of lithium cations in hot water. The Li xAl 2-LDH@SiO 2 nanostructures showed enhanced properties for lithium adsorption, including increase of stable regeneration cycles from three to five cycles, and they showed high lithium selectivity in the Mg 2+, Na +, and K + cation mixed aqueous resource. Our nanostructured LDH lithium adsorbents would provide a facile and efficient application for cost-efficient and large-scale lithium production. 相似文献
10.
The gas‐phase ligand‐exchange reactions between Cu(II) and Ni(II) complexes containing the acetylacetonate (acac), hexafluoroacetylacetonate (hfac), and trifluorotrimethylacetylacetonate (tftm) ligands were investigated using a triple quadrupole mass spectrometer. The gas‐phase mixed‐ligand products of [Cu(acac)(tftm)] +, [Ni(acac)(tftm)] +, [Cu(hfac)(tftm)] +, and [Ni(hfac)(tftm)] + were formed following the co‐sublimation of either homo‐metal or hetero‐metal precursors. The gas‐phase formation of [Cu(acac)(tftm)] +, [Cu(hfac)(tftm)] +, [Ni(acac)(tftm)] +, and [Ni(hfac)(tftm)] + complexes is reported herein for the first time. The corresponding fragmentation patterns of these species along with those of Cu(tftm) 2 and Ni(tftm) 2 are also presented. Mass‐selected ion‐neutral reactions were investigated. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
11.
Phase transitions in MgAl 2O 4 were examined at 21-27 GPa and 1400-2500 °C using a multianvil apparatus. A mixture of MgO and Al 2O 3 corundum that are high-pressure dissociation products of MgAl 2O 4 spinel combines into calcium-ferrite type MgAl 2O 4 at 26-27 GPa and 1400-2000 °C. At temperature above 2000 °C at pressure below 25.5 GPa, a mixture of Al 2O 3 corundum and a new phase with Mg 2Al 2O 5 composition is stable. The transition boundary between the two fields has a strongly negative pressure-temperature slope. Structure analysis and Rietveld refinement on the basis of the powder X-ray diffraction profile of the Mg 2Al 2O 5 phase indicated that the phase represented a new structure type with orthorhombic symmetry ( Pbam), and the lattice parameters were determined as a=9.3710(6) Å, b=12.1952(6) Å, c=2.7916(2) Å, V=319.03(3) Å 3, Z=4. The structure consists of edge-sharing and corner-sharing (Mg, Al)O 6 octahedra, and contains chains of edge-sharing octahedra running along the c-axis. A part of Mg atoms are accommodated in six-coordinated trigonal prism sites in tunnels surrounded by the chains of edge-sharing (Mg, Al)O 6 octahedra. The structure is related with that of ludwigite (Mg, Fe 2+) 2(Fe 3+, Al)(BO 3)O 2. The molar volume of the Mg 2Al 2O 5 phase is smaller by 0.18% than sum of molar volumes of 2MgO and Al 2O 3 corundum. High-pressure dissociation to the mixture of corundum-type phase and the phase with ludwigite-related structure has been found only in MgAl 2O 4 among various A 2+B 3+2O 4 compounds. 相似文献
12.
The yet unknown intermetallic phase La 5Al 3Ni 2 was obtained by partially crystallizing amorphous La 50Al 25Ni 25 at 550 K (further heating above 600 K leads to irreversible disappearance of this phase), and its crystal structure was determined from X‐ray powder diffraction data. The crystal structure of the La 5Al 3Ni 2 phase constitutes a new structure type ( Cmcm, a = 14.231Å, b = 6.914Å, c = 10.460Å, oC40) and is built from [Al 3Ni 2] chains surrounded by La atoms. In the ternary system La‐Al‐Ni La 5Al 3Ni 2 is located on the section La 50Al 50−nNi n (0 ≤ n ≤ 50) with the binary compounds LaAl and LaNi as end members. Strikingly, also the crystal structures of the end members can be conceived as chain structures with Al and Ni chains surrounded by La, respectively. 相似文献
13.
Catalysts active in ammonia oxidation have been obtained by the substitution of transition metal (Mn, Fe, Co, Ni, and Cu) ions for Mg ions in the cordierite structure 2MgO · 2Al 2O 3 · 5SiO 2 at 1100°C. Their phase composition, texture, and activity depend on the type and amount of introduced transition metal oxide. The Mn- and Cu-containing catalysts, which consist of substituted cordierites 2(Mg 1 ? x M x )O · 2Al 2O 3 · 5SiO 2 and Mn 2O 3 or CuO crystallites located on their surface, are most active in ammonia oxidation. The catalysts are characterized by a small specific surface area and have large pores, whose total volume is small. The Fe-containing catalysts consist of the Fe-substituted cordierite phase and particles of an iron oxide phase. These particles are mostly located in internal pores of the catalysts and are, therefore, hardly accessible to ammonia molecules. The introduction of Co or Ni oxide leads to the formation of a low-active spinel phase rather than the cordierite phase. 相似文献
14.
Summary For the isolation of the intermetallic compounds Al 2Cu, Al 12Mg 17, Al 3Fe, Al 9Co 2 and Al 3Ni in their binary alloys a new method is proposed: Sample alloy particles are placed in a flask with a methanolic solution of benzoic acid (20% wt.), oxine (5% wt.), chloroform (20% vol.) and sodium hydroxide (0.02% wt.). After sufficient time of agitation, the intermetallic compounds remain quantitatively in the solution.
Isolierung der intermetallischen Verbindungen Al2Cu, Al12Mg17, Al3Fe, Al9Co2 und Al3Ni aus binären Aluminiumlegierungen mit Hilfe eines organischen Lösungsmittels Zusammenfassung Zur Isolierung der intermetallischen Verbindungen aus den entsprechenden binären Legierungen wird die Probe mehrere Stunden bis Tage unter Rühren mit einer methanolischen Lösung von Benzoesäure (20%), Oxin (5%), Chloroform (20%) und Natriumhydroxid (0,02%) behandelt. Hierbei wird die Matrix aufgelöst und die intermetallischen Verbindungen bleiben zurück. 相似文献
15.
Changes in crystallographic, electrical, and thermal properties of CuCr 2O 4 spinel were investigated by replacing Cu with Mg, i.e., Cu 1?xMg xCr 2O 4, and Cr with Al, i.e., CuCr 2?xAl xO 4. The tetragonal distortion in CuCr 2O 4 disappeared with 60% replacement of Cu by Mg ( x = 0.6) or 50% replacement of Cr by Al ( x = 1.0). The temperature variation of electrical resistivity for all the tetragonal samples was similar to that of CuCr 2O 4. The first order, diffusionless phase transition was manifest in the hysteresis loops of log ? vs plots. The resistivity and activation energy for conduction changed sharply near the phase transition composition. With the replacement of Cr by Al, the conduction in CuCr 2O 4 was found to change from p type to n type. The low thermal stability of the spinel was found to be due to a high concentration of tetrahedral Cu 2+ ions (>80%) and compressed tetragonal distortion which strains the spinel lattice. This strain is removed by replacing either Cu with Mg or Cr with Al, whereby the spinel becomes stable. 相似文献
16.
Aluminum–magnesium alloys, fabricated by bi-directional rotation ball milling, were used as a kind of promising solid fuel in “reactive material” that can be ignited by impact to release a large quantity of heats. Different percentages of Mg were added to Al to yield Al 90%–Mg 10% and Al 70%–Mg 30% alloys in order to probe the effect of Mg content on the microstructure and thermal reactivity of Al–Mg alloys. Structural characterization revealed that a nanometer-scale structure was formed and oxidation of as-fabricated alloy powders was faint. Moreover, as the Mg percentage increased, the particle size of alloy decreased with increasing brittleness of Al–Mg. TGA/DSC curves of the [Al 70%–Mg 30%]–O 2 system exhibited an intense exothermic peak before melting with reaction heat of 2478 J g ?1 and its weight increase reached 90.16% of its theoretical value, which contrasted clearly with 181.2 J g ?1 and 75.35% of [Al 90%–Mg 10%]–O 2 system, respectively. In addition, other than [Al 90%–Mg 10%]–Fe 2O 3 system, the [Al 70%–Mg 30%]–Fe 2O 3 system exhibited a considerable solid–solid reaction and a low activation energy. Finally, target penetration experiments were conducted and the results confirmed that a projectile composed of [Al 70%–Mg 30%]–Fe 2O 3 displayed a more complete ignition of target than that of Al–Fe 2O 3 formulation. 相似文献
17.
The ultralight hypoeutectic α-phase Mg–4.5Li–1.5Al alloy and hypereutectic β-phase Mg–12Li–1.5Al alloy in as-cast state were fabricated and subjected to modification by 0.2 mass% TiB and 0.2 mass% Sr grain modifiers. The crystallisation sequence of Mg–Li–Al alloys has been investigated in detail by using thermal-derivative analysis and microstructural observations. The presented work includes the effects of grain refiners on grain size and microstructure and thermal events registered during crystallisation of ultralight Mg–Li–Al alloys by recording and analysis of the temperature vs time, i.e. as TN, Tα, Tβ, Tη(LiAl) and TSOL. Microstructure and phase observation has been done by light microscope, X-ray diffraction and energy dispersive X-ray spectroscopy. The changes of characteristic temperature points for phase transformation are studied in detail. Due to the addition of 0.2 mass% TiB and 0.2 mass% Sr, the grain structure of the alloy was refined, and mechanical properties were improved. When a TiB and Sr added simultaneously, the average grain size of the analysed alloys strongly decreases. When the TiB or Sr content was severally added, a low effect of improvements of mechanical properties was observed. With the TiB and Sr content, the liquidus and solidus decrease gradually. 相似文献
18.
The new ternary lithium copper aluminide, Li 12Cu 16+xAl 26−x ( x = 3.2), dodecalithium nonadecacopper tricosaaluminide, crystallizes in a new structure type with space group P4/ mbm. Among nine independent atomic positions, two Al (one of which is statistically disordered with Cu) and three Li atoms have point symmetry m.2 m, two statistically disordered Al/Cu atoms are in m.. sites, one Al atom is in a 4/ m.. site and one Cu atom occupies a general site. The framework of Li 12Cu 16+xAl 26−x consists of pseudo‐Frank–Kasper polyhedra enclosing channels of hexagonal prisms occupied by Li atoms. The crystallochemical peculiarity of this new structure type is discussed in relation to the derivatives from Laves phases (LiCuAl 2 and Li 8Cu 12+xAl 6−x) and to the well known CaCu 5 structure. 相似文献
19.
The paper presents the conductometric data on solutions of Mg(ClO 4) 2 and Ni(ClO 4) 2 in acetonitrile over the temperature ranges 5–55°C for Mg(ClO 4) 2 and 25–75°C for Ni(ClO 4) 2. The extended Lee-Wheaton equation for unsymmetrical electrolytes was used to determine the limiting equivalent conductivities of the Mg 2+, Ni 2+, and ClO 4 ? ions and first-step ionic association constants with the formation of [KtClO 4] + ion pairs. Lower ionic association constants for Ni(ClO 4) 2 compared with Mg(ClO 4) 2 were a consequence of stronger non-Coulomb repulsion in the formation of [KtClO 4] + ion pairs because of the formation of a firmer solvation shell by the nickel compared with magnesium cation. The structure-dynamic parameter of ionic solvation was estimated. It was found that spatial-time correlations in the nearest environment of ions increased in the series ClO 4 ? > Mg 2+ > Ni 2+. 相似文献
20.
The study of non-hydrolytic reactions for the synthesis of Mg x Al 2(1?x)Ti (1+x)O 5 solid solution with x = 0.6 is reported. The reagents chosen were Al(O sBu) 3, Ti(O iPr) 4, TiCl 4 and Mg(NO 3) 2·6H 2O in toluene. The reactions were followed using 13C Nuclear Magnetic Resonance (NMR) spectroscopy. Sol-gel synthesized powders were calcined in air at 300, 500, 1000, and 1200°C for 1 h. The powders were analysed by X-Ray Diffraction (XRD) demonstrating the formation of a Mg 0.6Al 0.8Ti 1.6O 5 phase in samples treated at the higher calcination temperature. 相似文献
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