共查询到20条相似文献,搜索用时 15 毫秒
1.
R.K. Jain Ankur Jain Shivani Agarwal N.P. Lalla V. Ganesan D.M. Phase I.P. Jain 《Journal of Alloys and Compounds》2007,430(1-2):165-169
The effect of partial substitution of Ni by Cr in CeNi5 intermetallic compound has been studied by pressure–composition isotherm measurements for different temperatures. The samples were prepared of high purity materials using the standard arc melting technique in argon atmosphere. The structure and the elemental composition of different alloys have been investigated by means of XRD, SEM and EDX techniques. The unit cell volume of the alloy was found to increase with increasing Cr content. In order to calculate the hydrogen storage capacity pressure–composition isotherm has been investigated for CeNi5−xCrx (x = 1, 2) alloys in the temperature and pressure ranges of 293 ≤ T ≤ 333 K and 0.5 ≤ P ≤ 35 bar, respectively. The P–C–T isotherm for different alloys clearly shows the presence of three regions , + β and β. The enthalpy and entropy for the systems has also been calculated using Van’t Hoff plot. The variation of enthalpy and entropy with hydrogen content has also been studied. 相似文献
2.
This paper reports the results of the electrical conductivity measurements for KCaH3−xFx series with (x = 1, 1.5, 2, 2.5) in the temperature range 298–503 K.The activation energy of the electrical conductivity for the studied compounds depends on hydrogen amount and Reau's criteria. Differential thermal analysis curves were measured in the same temperature range 298–503 K.Possible correspondence between preferential order given by X-ray diffraction, thermal behaviour and electrical properties are discussed. 相似文献
3.
Single crystals of the spinel solid solutions ZnCr2−xAlxSe4 with x = 0.15 and 0.23 were grown and studied by X-ray diffraction and macroscopic magnetic measurements. The solubility of Al3+ ions in the parent compound ZnCr2Se4 is very limited and only weakly substituted single crystals can be obtained. The spinel structure is hardly modified by this admixture and regular cation distribution is preserved. Alike ZnCr2Se4, the two compounds investigated order antiferromagnetically at low temperatures. Both the Néel temperatures and the paramagnetic Curie temperatures are similar to that reported for the parent selenide. Also the effective magnetic moments are close to that of ZnCr2Se4 and compatible with trivalent Cr ions. In contrast, the saturation magnetic moments measured above the metamagnetic phase transitions in strong magnetic fields and calculated per one Cr atom, appear to be strongly affected by the Al-substitution, being rapidly suppressed with rising Al-content. 相似文献
4.
Kohta Asano Kouji Sakaki Xiangfeng Liu Etsuo Akiba 《Journal of Alloys and Compounds》2009,482(1-2):L18-L21
CaLi2−xMgx (0 ≤ x ≤ 2) which has the C14-type Laves phase structure has been successfully synthesized and hydrogenated. The C14-type Laves phase structure was kept after hydrogenation of CaLi2−xMgx (x = 0.2, 0.5, 1). After hydrogenation of CaLi2 and CaMg2, the Laves phase disappeared. The CaH2 and LiH phases were formed from CaLi2 and the CaH2 and Mg phases from CaMg2, respectively. CaLi2−xMgx (0 < x < 2) ternary alloys formed stable hydride phases with the C14-type Laves phase structure in contrast to CaLi2 and CaMg2 binary alloys. 相似文献
5.
Yang-huan Zhang Xiao-ying Han Bao-wei Li Hui-ping Ren Xiao-ping Dong Xin-lin Wang 《Journal of Alloys and Compounds》2008,450(1-2):208-214
The electrode alloys Mg2−xZrxNi (x = 0, 0.15, 0.3, 0.45 and 0.6) were prepared by mechanical alloying (MA). Mg in the alloy was partially substituted with Zr in order to improve the electrochemical characteristics of the Mg2Ni-type alloy. The microstructures and the electrochemical characteristics of the experimental alloys were measured systemically. The effects of substituting Mg with Zr and MA technique on the microstructures and electrochemical performances of the alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the substitution of Zr is favourable for the formation of an amorphous phase. For a fixed milling time, the amorphous phase in the alloy grows with increasing Zr content. The electrochemical measurement indicates that the substitution of Zr can dramatically enhance the discharge capacity with preferable cycle stability, and it markedly improves the discharge voltage characteristic of the alloys. For x ≤ 0.3, the discharge capacity of the alloys monotonically increases with milling time. But for x > 0.3, it has a maximum value with the change of milling time. 相似文献
6.
Tzu-Wei Huang Yee-Shin Chang Guo-Ju Chen Yen-Hwei Chang 《Journal of Alloys and Compounds》2007,430(1-2):205-211
The La1−xKxCo1−xNbxO3 system was performed by conventional solid state reaction technique using metal oxides. By DSC analysis, the activation energy of crystallization of the powders with x = 0.3 is 388.4 kJ/mol. The crystal structure of the compound reveals a transition from rhombohedral to cubic, and then to orthorhombic structure as the amount of the potassium niobate (KNbO3) increases. It is found that the structure of the samples with x < 0.3 is similar to that of lanthanum cobaltate (LaCoO3), while at the compositions with 0.7 ≥ x ≥ 0.3, the structure transforms to cubic. Finally, with x ≥ 0.7, the structures were similar to that of KNbO3. According to the results of selected-area-diffraction (SAD) patterns and X-ray diffraction (XRD) identifications, the lattice parameters were calculated. The direction of superlattice structure along [2 1 0] was found for x = 0.5 as identified from SAD patterns. The dielectric constants were measured with cubic structure. Dielectric constant (K) decreases with increasing x. 相似文献
7.
The effect of Al content on the glass formation and mechanical properties was studied for (Cu50Zr50)100−xAlx (x = 0, 4, 5, 7) bulk metallic glasses. The crystallization temperatures of fully amorphous Cu50Zr50, Cu48Zr48Al4, Cu47.5Zr47.5Al5 and Cu46.5Zr46.5Al7 as-cast rods are 724 K, 753 K, 758 K and 782 K, respectively. The mechanical properties were investigated under compression at room temperature. As-cast Cu46.5Zr46.5Al7 shows the highest yield strength (1867 MPa), whereas Cu47.5Zr47.5Al5 shows the largest fracture strain of 11.2%. The fracture surfaces of the compressed samples were investigated by scanning electron microscopy and their morphology has been correlated with the compressive plasticity. 相似文献
8.
The oxidation in 1 atm of pure oxygen of Ni–Cr–Al alloys with a constant aluminum content of 7 at.% and containing 5, 10 and 15 at.% Cr was studied at 900 and 1000 °C and compared to the behavior of the corresponding binary Ni–Al alloy (Ni–7Al). A dense external scale of NiO overlying a zone of internal oxide precipitates formed on Ni–7Al and Ni–5Cr–7Al at both temperatures. Conversely, an external Al2O3 layer formed on Ni–10Cr–7Al at both temperatures and on Ni–15Cr–7Al at 900 °C, while the scales grown initially on Ni–15Cr–7Al at 1000 °C were more complex, but eventually developed an innermost protective alumina layer. Thus, the addition of sufficient chromium levels to Ni–7Al produced a classical third-element effect, inducing the transition between internal and external oxidation of aluminum. This effect is interpreted on the basis of an extension to ternary alloys of a criterion first proposed by Wagner for the transition between internal and external oxidation of the most reactive component in binary alloys. 相似文献
9.
Spinel LiGaxMn2−xO4 (0 ≤ x ≤ 0.05) cathode materials with phase-pure particles and nano-sized distribution were synthesized by sol–gel method using triethanolamine as the chelating agent. The effects of heat treatment on the physicochemical properties of the spinel LiGaxMn2−xO4 powders were examined with thermogravimetric and differential thermal analysis (TG/DTA), powder X-ray diffraction (XRD) and scanning electron micrograph (SEM). The LiGaxMn2−xO4 (0 ≤ x ≤ 0.05) electrodes were characterized electrochemically by charge/discharge experiments under a current rate of 0.5C at 55 °C. Although the Ga-doped spinel electrode showed smaller initial discharge capacity, it exhibited better cycling performance than the undoped-LiMn2O4 electrode. The dQ/dV versus potential plots at 55 °C revealed that the improvement in cycling performance of the Ga-doped spinel electrode is attributed to stabilization of the spinel structure by the presence of gallium ion. 相似文献
10.
Yang-Huan Zhang Bao-Wei Li Hui-Ping Ren Ying Cai Xiao-Ping Dong Xin-Lin Wang 《Journal of Alloys and Compounds》2008,458(1-2):340-345
In order to improve the cycle stability of La–Mg–Ni system (PuNi3-type) hydrogen storage alloy, Ni in the alloy was partly substituted by Fe, Mn and Al, and the electrode alloys La0.7Mg0.3Ni2.55−xCo0.45Mx (M = Fe, Mn, Al; x = 0, 0.1) were prepared by casting and rapid quenching. The effects of the substitution of Fe, Mn and Al for Ni and rapid quenching on the microstructures and electrochemical properties of the alloys were investigated in detail. The results obtained by XRD, SEM and TEM indicate that element substitution has no influence on the phase compositions of the alloys, but it changes the phase abundances of the alloys. Particularly, the substitution of Al and Mn obviously raises the amount of the LaNi2 phase. The substitution of Al and Fe leads to a significant refinement of the as-quenched alloy's grains. The substitution of Al strongly restrains the formation of an amorphous in the as-quenched alloy, but the substitution of Fe is quite helpful for the formation of an amorphous phase. The effects of the substitution of Fe, Mn and Al on the cycle stabilities of the as-cast and quenched alloys are different. The positive influence of the substitution elements on the cycle stabilities of the as-cast alloys is in proper order Al > Fe > Mn, and for as-quenched alloys, the order is Fe > Al > Mn. Rapid quenching engenders an inappreciable influence on the phase composition, but it markedly enhances the cycle stabilities of the alloys. 相似文献
11.
Zhenyu Zhang Zhenyuan Jia Dongming Guo Hang Gao Renke Kang 《Surface & coatings technology》2008,202(16):3897-3902
A series of LaxCeyO1 − x − y films (x = 0–0.54, y = 0–0.58) with thickness of 35–45 nm was deposited by unbalanced magnetron sputtering. High-resolution transmission electron microscope observation shows that La0.24Ce0.34O0.42 film has polycrystalline structure. La2O3 and CeO2 are formed within the LaxCeyO1 − x − y films confirmed by the X-ray diffraction and X-ray photoelectron microscopy. The friction coefficient and residual compressive stress of five kinds of three-element compound films exhibit symmetric distribution with the relative equilibrium of La and Ce atomic concentration within the films. The critical load of all deposited films is between 28 and 33 mN. The friction coefficient of two kinds of rare earth complex oxide films is in the range of 0.08–0.09, which is lower than that of only one kind of rare earth oxide films, and the friction mechanism is discussed. 相似文献
12.
Ruiqi Zhao Xishu Wang Juzhou Tao Xiaojing Yang Hui Ma Xinhua Zhao 《Journal of Alloys and Compounds》2009,470(1-2):379-382
Cubic Zr1−xYbxWMoO8−x/2 (x = 0–0.05) ceramic was first fabricated by a polymorphous precursor transition method. X-ray diffraction experiment indicates that samples with x ≤ 0.05 are single phase solid solution. The measured bulk density, microstructure, maximal compression strength and Young's modulus are obviously sensitive to Yb substitution level, while none of such sensitivity was found for the lattice parameters, negative thermal expansion coefficients and Vickers hardness. Drilling tests on Zr0.96Yb0.04WMoO7.98 ceramic indicate good machinability, which is often required for quality and shape control in engineering applications. 相似文献
13.
Y. Yin T. Kakeshita M.S. Choi T. Fukuda T.D. Xia 《Journal of Alloys and Compounds》2008,464(1-2):422-428
Phase transformation of solid solution (Ti–50Ni)1−xCx (x = 0.1, 0.5 at.%) alloys have been studied by using differential scanning calorimetry, physical property measurement system and optical microscope. The transformation temperature decreases due to the existence of titanium carbide (TiC) particles compared with that of near-equiatomic Ti–Ni shape memory alloy. The resistivity vs. temperature curves show hysteresis. Thermoelastic martensitic transformation occurred in two alloys despite the difference in TiC content. Nevertheless, the resistivity results show different martensitic transformation routes. A one-step B2 → B19′ transformation occurred in the low TiC content alloy and an R transformation appeared in another alloy, suggesting that the martensitic transformation routes depended on the TiC content. The cumulative effect of the TiC particles causes the local stress field and lattice distortion to restrain the transformation of the B19′. On the other hand, the TiC content has an effect on the temperature coefficient of electrical resistivity (TCR) of alloys. The Ti–Ni–0.5C alloy shows a negative TCR in the range 100–300 K during which transformation occurs. Another alloy shows the opposite result. The cause of the negative TCR is briefly discussed. 相似文献
14.
O.L. Sologub L.P. Salamakha H. Noël T. Roisnel A.P. Gonalves 《Journal of Alloys and Compounds》2008,450(1-2):215-221
A new compound CePt2+xSb2−y (x = 0.125, y = 0.25) was synthesized by arc-melting of the elements. The chemical and structural characterizations were carried out at room temperature on as-cast samples using X-ray diffractometry, metallographic analysis and EDS-microanalysis. According to the results of X-ray single crystal diffraction this antimonide crystallizes in I4cm space group (no. 108), Z = 32, ρ = 12.19 Mg/m3, μ = 89.05 mm−1 (a = 12.5386(3) Å, c = 21.4692(6) Å (crystal I) and a = 12.5455(2) Å, c = 21.4791(5) Å (crystal II)). The structure and composition were confirmed by powder X-ray diffraction (a = 12.4901(2) Å, c = 21.3620(4) Å) and EDS-microanalysis respectively. Isotypic compounds were observed with La and Pr from X-ray powder diffraction of as-cast alloys at room temperature (a = 12.6266(4) Å, c = 21.4589(6) Å for LaPt2+xSb2−y and a = 12.5184(5) Å, c = 21.4178(7) Å for PrPt2+xSb2−y). The CePt2+xSb2−y structure is derived from CaBe2Ge2 (a = 2a0 − 2b0, b = 2a0 + 2b0, c = 2c0) and comprises a new atomic arrangement with both vacancy on 4(b) pyramidal site and substitution of antimony atoms (X) by platinum (B) in the B–XX–B layers (referring to the subcell structure) forming two B––1/2B1/2XX–3/4B and two X–BB–X layers per cell. The structure of CePt2+xSb2−y is compared with those reported before for URh1.6As1.9 and CeNi1.91As1.94. 相似文献
15.
Yang-Huan Zhang Bao-Wei Li Hui-Ping Ren Zhong-Wang Wu Xiao-Ping Dong Xin-Lin Wang 《Journal of Alloys and Compounds》2008,460(1-2):414-420
In order to improve the cycle stability of the La–Mg–Ni system PuNi3-type hydrogen storage electrode alloys, Ni in the alloy was partially substituted by Fe. The La0.7Mg0.3Co0.45Ni2.55−xFex (x = 0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of the substitution of Fe for Ni on the structures and electrochemical performances of the as-cast and quenched alloys were investigated in detail. The results of the electrochemical measurement indicate that the substitution of Fe for Ni obviously decreases the discharge capacity, high rate discharge capability (HRD) and discharge potential of the as-cast and quenched alloys, but it significantly improves their cycle stabilities, and its positive impact on the cycle life of as-quenched alloy is much more significant than on that of the as-cast one. The microstructure of the alloys analyzed by XRD, SEM and TEM show that the as-cast and quenched alloys have a multiphase structure which is composed of two major phases (La, Mg)Ni3 and LaNi5 as well as a residual phase LaNi2. The substitution of Fe for Ni helps the formation of a like amorphous structure in the as-quenched alloy. With the increase of Fe content, the grain sizes of the as-quenched alloys significantly reduce, and the lattice constants and cell volumes of the alloys obviously increase. 相似文献
16.
E. V. Voronina E. P. Elsukov S. K. Godovikov A. V. Korolev A. E. Elsukova 《The Physics of Metals and Metallography》2010,109(5):417-426
Results of M?ssbauer and magnetic studies of partially ordered alloys Fe100 − x
Al
x
(25 < x < 35 at %) are discussed depending on the temperature and applied magnetic field. Two variants of the interpretation of the
temperature behavior of magnetization and average hyperfine magnetic field at 57Fe nuclei in the model of a collinear magnet with magnetic inhomogeneities of a nanometer range are suggested. In the first
variant, the existence of clusters with magnetic moments oriented parallel and antiparallel to the total magnetization is
assumed. Temperature anomalies, such as the nonmonotonic dependence of magnetization and hyperfine magnetic field in the temperature
range of 100–200 K, are explained at a qualitative level by the stabilization of relaxation phenomena in clusters due to Stoner-type
spin excitations. The second variant is based on the assumption of a change in the orientation of spins antiparallel to the
magnetization with increasing temperature. 相似文献
17.
Copper–zinc ferrites bearing chemical formula Cu1−xZnxFe2O4 for x ranging from 0.0 to 1.0 with the step increment of 0.2 were prepared by the standard solid-state technique. The variation of Zn substitution has a significant effect on the structural, electrical and magnetic properties. Lattice parameters ‘a’ increased from 8.370 to 8.520 Å. Dielectric constant decreased up to 311 with the increase in frequency from 80 Hz to 1 MHz at room temperature. All the samples follow the Maxwell–Wagner's interfacial polarization. Saturation magnetization, magnetic moment and Yafet–Kittel angles were also determined. The possible reasons responsible for the change in density related, electrical and magnetic properties with the increase in Zn concentration are undertaken. 相似文献
18.
The structural, electrical transport and magnetic properties have been studied for compounds: La1−xSrxFe1−xMnxO3 (0.3 ≤ x ≤ 0.7). The lattice parameter, a, first decreases with x, and followed by an increase when Sr2+ and Mn4+ was continuously doped. The cell parameters, b and c, slightly decrease with coupled substitution of Sr2+ for La3+ and Mn4+ for Fe3+. In the paramagnetic temperature range, formation of magnetic clusters is suggested; the sizes of clusters decrease with x up to 0.5, following that they increase sharply with continuing doping. The electrical behaviors of all specimens demonstrate insulators and the electrical resistivity increases with content of Mn4+ and Sr2+ ions doped. A variable range hopping model is suitable to describe electrical transport process for the compounds at low temperature. At high temperature the electrical transport process can be described by bipolaron model for all compounds. 相似文献
19.
S. El Khiraoui M. Sajieddine M. Vergnat M. Sahlaoui Ph. Bauer M. Mabrouki 《Journal of Alloys and Compounds》2007,440(1-2):43-45
Single phase (Fe1−xNix)4N compounds (0.2 ≤ x ≤ 0.6) have been synthesized by reactive evaporation and investigated by X-ray diffraction and Mössbauer spectrometry. The lattice parameters of the nitrides decrease from 3.796 to 3.774 Å with increasing Ni concentration. The fitting results of Mössbauer spectra indicate that the average hyperfine field have the same changing tendency with lattice parameter and the nickel atoms have a tendency to be located at the corner site. 相似文献
20.
G. Jaeger I. Endler K. Bartsch M. Heilmaier A. Leonhardt 《Surface & coatings technology》2002,150(2-3):282-289
Recently, modified surface treatment methods for cutting tools were developed combining a heat treatment and a subsequent hard coating (duplex treatment). As a consequence, the wear resistance has been improved considerably. As fatigue is an important failure mechanism during application, the present paper focuses on the improvement of the fatigue behavior by an optimization of heat treatment and hard coating. The problem is approached in two steps: first, the fatigue behavior of high-speed tool steel S6-5-2 is investigated, surface-treated with different plasma heat treatments (plasma nitriding and -carbonitriding). The results on bending fatigue testing indicate the superiority of plasma nitriding compared with both plasma carbonitriding and untreated substrate. Hence, in a second step the plasma nitrided tool steel is coated with PACVD hard coatings of the system Ti-Al-C-N and the fatigue behavior of these hard coating steel compounds is investigated. Obviously, the type and stoichiometry of the hard coating influence the fatigue behavior of the compound. For TiCxN1−x films, the fatigue strength increases with increasing carbon content, whereas for Ti1−xAlxN-films, the fatigue strength decreases with increasing Al content. While for an optimized hard coating the fatigue behavior of the compound is superior to hardened non-nitrided steel, no significant improvement was found as compared with plasma nitrided steel. 相似文献