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1.
Phase equilibria in the Al–Cu–Fe system alloyed with 5% Cr were studied. Based on the data of X-ray powder diffraction analysis, electron microscopy, and differential thermal analysis, the effect of temperature on i ? d phase transitions in alloys Al 65Cu 25Fe 5Cr 5 and Al 70Cu 20Fe 5Cr 5. In the Al–Cu–Fe–Cr system, multiphase structures were detected; these structures are mixtures of quasi-crystalline and approximant phases, the contents and morphologies of which depend on the composition of the initial mixture and the crystallization rate. 相似文献
2.
Subsolidus phase relations in the CuO x-TiO 2-Nb 2O 5 system were determined at 935 °C. The phase diagram contains one new phase, Cu 3.21Ti 1.16Nb 2.63O 12 (CTNO) and one rutile-structured solid solution series, Ti 1−3xCu xNb 2xO 2: 0< x<0.2335 (35). The crystal structure of CTNO is similar to that of CaCu 3Ti 4O 12 (CCTO) with square planar Cu 2+ but with A site vacancies and a disordered mixture of Cu +, Ti 4+ and Nb 5+ on the octahedral sites. It is a modest semiconductor with relative permittivity ∼63 and displays non-Arrhenius conductivity behavior that is essentially temperature-independent at the lowest temperatures. 相似文献
3.
The influence of additions of 2, 4, 6, 8, 10 and 12 mass% Ag on the thermal behavior of the Cu–8 mass% Al alloy was studied
using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX)
and X-ray diffractometry (XRD). The results indicate that the presence of silver introduces new thermal events, due to the
formation of a silver-rich phase and, for additions of 10 and 12 mass% Ag, it is possible to verify the formation of the γ 1 phase (Cu 9Al 4) and the metastable transitions which are only observed in alloys with a minimum of 9 mass% Al.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
In this work three alloys, Fe 74Nb 6B 20,
Fe 64Ni 10Nb 6B 20
and Fe 54Ni 20Nb 6B 20,
were obtained by mechanical alloying to analyze the influence of Ni content
on Fe–Nb–B alloy formation. Structural analysis by X-ray diffraction
(XRD) confirms that partial substitution of Fe by Ni favours the formation
during milling of a more disordered structure. Furthermore, thermal stability
study was performed by differential scanning calorimetry (DSC) because thermally
induced structural changes can affect soft magnetic behaviour. After 40 h
of milling time, all DSC curves show several exothermic effects on heating
associated to structural relaxation and crystallization. All alloys present
a crystallization process with associated activation energy values ranged
between 238 and 265 kJ mol –1 related to the
crystalline growth of the bcc-Fe rich phase. In alloys with Ni, a second crystallization
process appears at temperatures over 500°C with activation energies 397
(10% Ni alloy) and 385 kJ mol –1 (20% Ni alloy)
probably associated to the nucleation and crystalline growth of a new phase. 相似文献
5.
The crystallization behavior of amorphous Fe–Cr–B–Si alloys in the presence of Ni and Nb elements was the goal of this study. In this regard, four different amorphous–nanocrystalline Fe 40Cr 20Si 15B 15M 10 (M=Fe, Nb, Ni, Ni 0.5Nb 0.5) alloys were prepared using mechanical alloying technique up to 20 h. Based on the achieved results, in contrast to Fe 50Cr 20Si 15B 15 alloy, the amorphous phase can be successfully prepared in the presence of Ni and Nb in composition. Although the crystallization mechanism of prepared amorphous phase in different alloys was the same, the Fe 40Cr 20Si 15B 15Nb 10 alloy showed higher thermal stability in comparison with other samples. The crystallization activation energy of this amorphous alloy was estimated about 410 kJ mol ?1 which was much higher than Fe 40Cr 20Si 15B 15Ni 10 (195.5 kJ mol ?1) and Fe 40Cr 20Si 15B 15Ni 5Nb 5 (360 kJ mol ?1) samples. The calculated values of Avrami exponent (1.5 < n < 2.2) indicated that the crystallization process in different alloying systems is the same and to be governed by a three-dimensional diffusion-controlled growth. 相似文献
6.
This work firstly discovered that the Ni 60Nb 15Zr 5Ti 15Ta 5 metallic glass exhibits high corrosion resistance in boiling 6 N HNO 3 solutions with and without Cr 6+ ions, which may be of great potential for nuclear fuel reprocessing applications. The high corrosion resistance of the alloy is due to the formation of the passive film composed exclusively of Nb 5+ and Ta 5+ cations after immersion in the solution without Cr 6+ ions, and Nb 5+, Ta 5+ and Cr 3+ cations after immersion in the solution with Cr 6+ ions. 相似文献
7.
The corrosion behaviors of Ti 40Zr 25Ni 12 -xNb xCu 3Be 20 ( x = 0, 4, 8, and 12 at.%) alloys in 0.5 mol/L H 2SO 4 solution were studied, aiming to establish the relationship between Nb content and corrosion resistance. The addition of Nb element gives rise to a clear microstructural evolution, from a completely amorphous structure for the alloys without Nb and with 4% Nb alloys to an amorphous/crystalline composite structure for the alloys with 8% and 12% Nb. The alloy with higher Nb content exhibits better corrosion resistance, which can be attributed to the formation of Ti 4 +-, Zr 4 +-, and Nb 5 +-enriched highly protective surface film in corrosive solutions. 相似文献
8.
A Contribution on Ternary Oxides of the AMO 4-Type (A = Ti 3+, Cr 3+; M = Nb 5+, Ta 5+ ) CrNbO 4, CrTaO 4, TiNbO 4, and TiTaO 4 were prepared by CO 2-laser technique. X-ray single crystal investigations show a random distribution of the metal ions in Rutil type structure, space group D–P4 2/mnm. Calculations of the free energy of reaction between Ti 2O 3 and Nb 2O 5 show higher stability of TiO 2 beside NbO 2. In TiNbO 4 both metals exhibit the oxidation state +4. 相似文献
9.
The superiority of NiMnSn alloy on NiMnGa alloy is far ahead in term of some physical characteristics, and therefore, the development of this alloy group is very important. In this work, Ni50Mn45−xSn5Crx magnetic shape memory alloys were produced for x = 0, 4, 6, 10 and 12. Thermal analysis was performed on produced alloys in a wide range (200–1000 °C) by using differential scanning calorimetry, thermogravimetric and differential thermal analysis. According to the thermal analysis results, the austenite ↔ martensite transformation temperatures of the NiMnSn alloy decreased with increasing chromium content. Furthermore, the increase in the chromium ratio caused single-phase transformation due to the multiple phase transformation that was observed in the NiMnSn alloy. In addition, the crystal structure and microstructure analyses of the alloys were determined by using X-ray diffraction and scanning electron microscopy–energy-dispersive X-ray spectroscopy. In all cases, martensite and gamma phase were encountered and the gamma phase ratio was found to be increased by chromium addition. The magnetization characteristics were studied by using physical properties measurement systems device, and it was found that the alloys have a considerably small response to magnetic flux. 相似文献
10.
Amorphous to crystalline transformation in Cu 60Ti 40 alloy has been studied under conditions of constant heating rate experiments, using XRD and DSC. In the high temperature XRD experiment, the transformation has been monitored continuously as the integrated X-ray intensity corresponding to a chosen reflection from one of the two crystalline products forming at close by temperatures. Differentiation of the curve thus obtained gives the transformation rate curve which passes through a maximum. From the peak shift with heating rate, the activation energy for the formation of Cu 3Ti 2 crystalline phase has been obtained. The results have been compared with those obtained by DSC. 相似文献
11.
Alloy formation is ubiquitous in inorganic materials science, and it strongly depends on the similarity between the alloyed atoms. Since molecules have widely different shapes, sizes and bonding properties, it is highly challenging to make alloyed molecular crystals. Here we report the generation of homogenous molecular alloys of organic light emitting diode materials that leads to tuning in their bandgaps and fluorescence emission. Tris(8-hydroxyquinolinato)aluminium (Alq 3) and its Ga, In and Cr analogues (Gaq 3, Inq 3, and Crq 3) form homogeneous mixed crystal phases thereby resulting in binary, ternary and even quaternary molecular alloys. The M xM′ (1−x)q 3 alloy crystals are investigated using X-ray diffraction, energy dispersive X-ray spectroscopy and Raman spectroscopy on single crystal samples, and photoluminescence properties are measured on the exact same single crystal specimens. The different series of alloys exhibit distinct trends in their optical bandgaps compared with their parent crystals. In the Al xGa (1−x)q 3 alloys the emission wavelengths lie in between those of the parent crystals, while the Al xIn (1−x)q 3 and Ga xIn (1−x)q 3 alloys have red shifts. Intriguingly, efficient fluorescence quenching is observed for the M xCr (1−x)q 3 alloys (M = Al, Ga) revealing the effect of paramagnetic molecular doping, and corroborating the molecular scale phase homogeneity.Multicomponent molecular alloy crystals exhibit intriguing effects of tuning and quenching in their photoluminescence, suggesting ‘alloy-crystal engineering’ as a useful design strategy for molecular functional materials. 相似文献
12.
Theoretical studies have been carried out to examine hydrogen storage in some binary transition metal alloys which include titanium as one of the alloying elements. Quantum mechanical calculations at the Extended Hückel level of approximation have been performed on numerous clusters of compositions Ti 18Ni 18, Ti 18Ni 18H, Ti 18Ni 18H 12, Ti 24Ni 12, Ti 24Ni 12H, Ti 24Ni 12Hi 12, Ti 16Cu 16, Ti 16Cu 16H, Ti 24Cu 2, Ti 16Fe 16, Ti 16Fe 16H 9, and Ti 16Fe 16H 32, to yield information on energetics, densities of states, charge distributions, and the effects of hydrogenation on these properties. In addition, ab initio calculations at the split valence level of approximation have been performed on several smaller clusters. The hydrogens have been shown to acquire a partially anionic character in all cases. Another conclusion is that the preference of H for certain types of sites (for example the tetrahedral Ti 4 sites in crystalline TiCu) is more likely to be related not to the intrinsically greater stability of a hydrogen atom located in such a site, but to more general topological and electronic considerations. Qualitative concepts related to the classification, spatial distribution, and sizes and shapes of hole sites which could become occupied by hydrogen atoms, have been shown to correlate with hydrogen storage capacity for crystalline materials. These qualitative concepts have been extended to amorphous materials and corroborate the observations that under optimized conditions amorphous alloys can be found with better reversible hydrogen storage properties than the crystalline or microcrystalline systems. Distorted tetrahedral and octahedral holes have been examined in detail, and parameters (volume, area, tetrahedrality, and octahedrality) have been introduced to describe their sizes and shapes. An algorithmic surveying technique has been introduced, and shown to provide useful information about the limiting amounts of hydrogen uptake.Camille and Henry Dreyfus teacher-scholar 相似文献
13.
Magnetic Properties of Ti 3?xM xO 5 Phases (M = V 3+, Cr 3+, Nb 4+) The magnetic properties of Ti 3?xV xO 5, Ti 3?xCr xO 5, and Ti 3?xNb xO 5 phases are reported. In the case of V 3+ and Cr 3+ the magnetic leaping-temperature decreases, however Nb 4+ shift the phase-transition towards higher temperatures. All samples show a “memory-effect” in magnetic properties, i. e. the results of heating- and cooling-cycles are higher susceptibilities of the α-phase of Ti 3O 5. Endowed Ti 3O 5 phases show for the α- and β-Ti 3?xM xO 5 til the leap Curie-Weiss characteristic in 1/ X vs. temperature measurements. Exception is β-Ti 3?xNb xO 5, its susceptibility is independend of the temperature up to x ? 0.3. 相似文献
14.
The Cu-Bi-Se system was studied using DTA, X-ray powder diffraction, and electromotive force (e.m.f.) measurements in (−)
Cu (solid)|Cu 4RbCl 3I 2 (solid)|(Cu in alloy) (solid) (+) concentration cells in the range 300–430 K. Polythermal sections and a 300-K isothermal
section of the phase diagram are constructed, as well as a liquidus surface projection. The existence of ternary compounds
CuBi 3Se 5, CuBiSe 2, and Cu 3BiSe 3 is verified, and phase fields involving them are established. Primary separation fields and the types and coordinates of
invariant and monovariant equilibria are determined. E.m.f. data were used to calculate partial molar functions $
(\Delta \bar G,\Delta \bar H,\Delta \bar S)
$
(\Delta \bar G,\Delta \bar H,\Delta \bar S)
of copper in alloys and the standard thermodynamic functions of formation and entropies of the ternary compounds and the
end-member (Cu 9BiSe 6) of solid solutions based on the low-temperature Cu 2Se phase. 相似文献
15.
The Cu—Tl—S system was studied by the EMF method with Cu 4RbCl 3I 2 solid Cu +-conducting electrolyte within the temperature range from 300 to 390 K. The earlier plotted solid-phase equilibrium diagram of this system was confirmed, the partial copper molar functions $ (\Delta \bar G,\Delta \bar H,\Delta \bar S) $ ) in alloys and standard thermodynamic formation functions and standard entropies of CuTlS 2, CuTlS, Cu 3TlS 2, and Cu 9TlS 5 ternary compounds were calculated. The derived results demonstrated an opportunity of thermodynamic studies of copper-containing ternary systems of this modification by EMF method even if they contain a less noble component than copper. 相似文献
17.
采用XRD、FESEM-EDS、ICP及EIS等方法研究了Ti 0.17Zr 0.08V 0.34Nb 0.01Cr 0.1Ni 0.3氢化物电极合金微观结构和电化学性能。X射线衍射分析表明:该合金由体心立方结构(bcc)的V基固溶体主相和少量六方结构的C14型Laves相组成;FESEM及EDS分析表明:V基固溶体主相形成树枝晶,C14型Laves相呈网格状围绕着树枝晶的晶界,元素在两相中的分布呈现镜像关系。电化学性能测试结果表明:该合金的氢化物电极在303~343 K较宽的温度区间内,表现出较高的电化学容量,在303 K和343 K时,电化学容量分别为337.0 mAh·g -1和327.9 mAh·g -1。在303 K循环100周后,容量为282.7 mAh·g -1。ICP分析结果表明,氢化物电极在充放电循环过程中,V及Zr元素向KOH电解质中的溶出较为严重。EIS研究表明,金属氢化物电极表面电化学反应的电荷转移电阻(R T)随循环次数的增加而增加,相应的交换电流密度则随循环次数的增加而降低。氢化物电极循环过程中RT的增大以及V和Zr元素的溶解,可能是导致电极容量衰减的主要原因。 相似文献
18.
The review collates the results of studies on the chemical dispersion and phase transformations of Ti, Zr, and Y alloys with iron and nickel during the reaction with ammonia at a pressure of 0.6—0.8 MPa in the temperature range of 100—500 °C in the presence of NH 4Cl as the activator. Promising working materials for metal hydride hydrogen storage, including alloys (Ti 90Mg 10, Y 67Fe 33, and Ti 67Fe 33) and intermetallics (Ti 2Ni, Zr 2Ni, Zr 3Al 2, ZrV 2), are considered. At 150—250 °C, the mentioned intermetallics absorb considerable amounts of hydrogen with conservation of the initial metallic lattice and formation of the highly dispersed hydrides Ti 2NiH 3.3, Zr 2NiH 4.7, Zr 3Al 2H 1.1, and ZrV 2H 2.2. The phase transformations taking place on heating of the intermetallics from 250 to 500 °C, resulting in mixtures of intermetallic hydridonitrides and metal nitrides, are elucidated. The transformation products of the Ti 90Mg 10, Y 67Fe 33, and Ti 67Fe 33 alloys in ammonia atmosphere in the temperature range of 100—500 °C are established. 相似文献
19.
Al 0.10Ti 0.30V 0.25Zr 0.10Nb 0.25 was prepared to evaluate the effect of 10% aluminum into the previously reported quaternary alloy, Ti 0.325V 0.275Zr 0.125Nb 0.275. The as-cast quinary alloy formed a single-phase body centered cubic solid solution and transformed into a body centered tetragonal after hydrogenation. The alloy had a storage capacity of 1.6 H/M (2.6 wt.%) with fast absorption kinetics at room temperature, reaching full capacity within the first 10 min. The major improvements of Al addition (10%) were related to the desorption and cycling properties of the material. The temperature for hydrogen release was significantly decreased by around 100 °C, and the quinary alloy showed superior cycling stability and higher reversible storage capacity than its quaternary counterpart, 94% and 85% of their respective initial capacity, after 20 hydrogenation cycles without phase decomposition. 相似文献
20.
Reduction of the titanium-niobium oxides follows a common pattern. TiO 2 is eliminated, to form a new phase richer in titanium than the original compound, and Nb(iv) replaces Ti(iv) in the original block structure, which is thereby enriched in niobium. With TiNb 2O 7, the second phase is a TiO 2NbO 2 solid solution, with the rutile structure, initially with a high titanium content, in equilibrium with a solid solution of composition Me3O 7, isostructural with TiNb 2O 7. At log pO2 (atm) about ?9.0 this reaches the limiting composition Ti 0.72Nb 2.28O 7, in equilibrium with Ti 0.56Nb 0.44O 2. The Me3O 7 block structure then transforms into the Me12O 29 block structure (Ti 2Nb 10O 29Nb 12O 29 solid solution), which rapidly increases in niobium content as reduction continues. Reduction of Ti 2Nb 10O 29 at oxygen fugacities above log pO2 (atm) = ?9.0 forms the Me3O 7 phase as the titanium-rich phase. At log pO2 = ?9.0, and a composition about Ti 1.6Nb 10.4O 29, the rutile solid solution takes over as second phase. The niobium/titanium ratio in both phases rises as reduction proceeds, and the last vestiges of the Me12O 29 phase, in equilibrium with the final product, Ti 0.17Nb 0.67O 2, are almost denuded of titanium. 相似文献
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