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1.
Chromium aluminum nitride (Cr1−xAlxN) coatings were deposited onto AISI H13 steel and silicon substrates by r.f. reactive magnetron co-sputtering in (Ar/N2) gas mixture from chromium and aluminum targets. Properties of deposited Cr1−xAlxN coatings such as compositional, structural, morphological, electrochemical, mechanical and tribological, were investigated as functions of aluminum content. X-ray diffraction patterns of Cr1−xAlxN coatings with different atomic concentrations of aluminum (0.51 < x < 0.69) showed the presence and evolution of (1 1 1), (2 0 0), and (1 0 2) crystallographic orientations associated to the Cr1−xAlxN cubic and w-AlN phases, respectively. The rate of corrosion of the steel coated with Cr1−xAlxN varied with the applied power; however, always being clearly lower when compared to the uncoated substrate. The behavior of the protective effect of the Cr1−xAlxN coatings is based on the substitution of Cr for Al, when the power applied to the aluminum target increases. The mechanical properties were also sensitive to the power applied, leading to a maximum in hardness and a reduced elastic modulus of 30 and 303 GPa at 350 W and a monotonic decrease to 11 and 212 GPa at 450 W, respectively. Finally, the friction coefficient measured by pin-on disk revealed values between 0.45 and 0.70 in humid atmosphere.  相似文献   

2.
Amorphous Ge1−xCrx thin films are deposited on (1 0 0)Si by using a thermal evaporator. Amorphous phase is obtained when Cr concentration is lower than 30.7 at%. The electrical resistivities are 1.89×10−3–0.96×102 Ω cm at 300 K, and decrease with Cr concentration. The Ge1−xCrx thin films are p-type. The hole concentrations are 5×1016–7×1021 cm−3 at 300 K, and increase with Cr concentration. Magnetizations are 7.60–1.57 emu/cm3 at 5 K in the applied field of 2 T. The magnetizations decrease with Cr concentration and temperature. Magnetization characteristics show that the Ge1−xCrx thin films are paramagnetic.  相似文献   

3.
In order to gain better insight into the origin of the observed differences between Fe3−xCrxAl and Fe3−xCrxSi, alloys of Fe3−xCrxAl0.5Si0.5 (x=0, 0.125, 0.250, 0.375 and 0.5) were prepared and studied by means of X-ray and neutron diffraction as well as by magnetization measurements. Electronic structure calculations of these alloys have been performed by means of TB-LMTO-ASA method. It was expected, and experimentally verified, that the presence of silicon and aluminum atoms in 1:1 proportion will result in the independence of the lattice parameter on the iron/chromium concentration. All samples have been proved to be a single phase of the DO3-type of structure. Theoretical and experimental results indicate that chromium atoms locate preferentially in B sublattice. Cr magnetic moments are oriented antiparallel to Fe magnetic moments. Neutron measurements show a linear dependence of the magnetic moments of Fe(A,C), Fe(B) and Cr(B) as a function of Cr concentration. However the calculated total magnetic moment decreases faster with chromium content than indicated by the experiment.  相似文献   

4.
CrNx films were deposited on stainless steel and Si (1 1 1) substrates via medium frequency magnetron sputtering in a N2 + Ar mixed atmosphere. The influence of N2 content on the deposition rate, composition, microstructure, mechanical and tribological properties of the as-deposited films was investigated by means of the X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), nanoindentation and tribometer testing. It was found that the N atomic concentration increased and the phase transformed from a mixture of Cr2N + Cr(N) to single-phase Cr2N, and then Cr2N + CrN to pure CrN phase with the increase of N2 content. The Cr 2p3/2 and N 1s of XPS spectra also confirmed the evolution of phase. Accordingly, all films exhibited a typical columnar structure which lies in the zone T of Thornton Model. The mixed Cr2N and Cr(N) phases showed low hardness and high friction coefficient. Cr2N possessed higher hardness than CrN while CrN exhibited lower friction coefficient.  相似文献   

5.
Single-phase BiFe1 − xCrxO3 (x=0, 0.05 and 0.1) compounds are synthesized by a sol-gel process. The lattice parameters decrease and the magnetizations increase with the Cr content. Moreover, the magnetoelectric coupling between magnetic order and ferroelectric order at room temperature was enhanced.  相似文献   

6.
Cr1−xAlxC films were deposited on high-speed steel by RF reactive magnetron sputtering. In this study, we aimed to identify the effect of the Al content on the properties of Cr1−xAlxC films. We found that Cr1−xAlxC films exhibited a fine columnar grain microstructure with some special characteristics, such as high hardness of Hv 1426, a low friction coefficient of 0.29, and a large contact angle of 90° for x = 0.18. Furthermore, an increase in Al content resulted in a decrease in film hardness and an increase in contact angle. Moreover, on annealing at 923 K, the mechanical properties of the films improved and a dense protective film of complex Cr2O3 and Al2O3 oxides was formed on the surface for better wear resistance, which will ultimately increase the lifetime of the high-speed steel substrate.  相似文献   

7.
Blue phosphors Ca1 − xAl2O4: xEu2+ were prepared by high temperature solid-state method. Their structure, morphology and luminescent properties were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and fluorescence spectroscopy. The effect of different amounts of fluxing agent H3BO3 on structure, morphology and luminescent properties of blue phosphors Ca1 − xAl2O4: xEu2+ luminous intensity caused by different amount of H3BO3 was also investigated. The amount of H3BO3 doped Ca1 − xAl2O4: xEu2+ in optimal luminous intensity had been determined. The results showed that both the excitation and emission spectra of samples were all broad bands, and that the peak of emission spectra was near 442 nm, which was corresponding to the 4f65d → 4f7 transition of Eu2+ illuminating blue light. Ca1 − xAl2O4: xEu2+ (x = 3.5 mol%) could be gained with good morphology and the best luminous intensity when H3BO3 mass ratio was 0.5 wt%.  相似文献   

8.
We report an investigation of the nature of room-temperature ferromagnetism enhancement in Ce1−xCrxO2−δ nanoparticles (0.00≤x≤0.05), synthesized by a sol–gel-based method. Energy-dispersed X-ray spectrometry (EDS) analysis was used to estimate the dopant concentrations. The average crystallite sizes and particle size were estimated by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. Both studies showed a gradual decrease in the size of the crystallites and particles for x>0.01. Cr can substitute for Ce in the crystal lattice, and the Raman measurements indicated that structural defects in the samples increased as a function of the Cr content in the CeO2 crystal lattice. The surface topography, examined by scanning electron microscopy (SEM), showed that the undoped sample has a porous and loosely organized structure, whereas the Cr-doped samples exhibited a dense and compact structure. Magnetic measurements of the Ce1−xCrxO2−δ samples at 27 oC showed a maximum remanent magnetization value of 0.01 emu/g for x=0.05. The nature and enhancement of room-temperature ferromagnetism was interpreted by taking into account the exchange interaction between Cr3+ ions and oxygen vacancies in CeO2.  相似文献   

9.
Infrared, Raman, electron absorption, excitation and emission spectra were measured for RbCrxAl1−x(MoO4)2 and CsCrxAl1−x(MoO4)2 crystals (x=0-2%) at the temperatures ranging from 7 to 300 K. A very rich vibronic structure of the emission band was explained and assigned to the respective vibrational modes. One Cr3+ center characterized by 2.35 ms lifetimes for rubidium derivative and 1.3 ms for cesium one at 7 K for the 2E→4A2 transition was identified for both crystals. The local structure of the Cr3+ surrounding is discussed in terms of the spectroscopic results and the crystal field parameters are derived for both materials.  相似文献   

10.
Sr-doped and Sr-free La1 − xSrxMn1 − yCryO3 ± δ (LSMC, x(Sr) = 0-0.2, y(Cr) = 0.4-0.6) perovskite-type oxides were synthesized and evaluated as single phase anodes for use in intermediate temperature solid oxide fuel cell applications. Their thermo-chemical and chemical stabilities were investigated in hydrogen at high temperatures and correlated with their oxygen non-stoichiometry (3 ± δ), determined by permanganate titration. The catalytic activity towards hydrogen oxidation was examined as a function of oxide sintering time, operating temperature, and the Sr and Cr contents, using a Pt mesh current collector. While all of the perovskite oxides studied here showed some irreversible performance degradation with time under both open circuit and anodically polarized conditions, La0.9Sr0.1Mn0.6Cr0.4O3.03 (LSMC9164), sintered at 1200 °C for 10 h, was found to be the most catalytically active and also the most stable.  相似文献   

11.
The exchange interactions (JBB and JAB are the intra and the inter-sublattice exchange interactions between neighbouring spins, respectively) are obtained by using the general expressions of canting angle and critical temperature obtained by mean field theory of Li0.5Fe2.5−2xAlxCrxO4. The expression of magnetic energy of Li0.5Fe2.5−2xAlxCrxO4 is obtained for different spin configurations and dilution x. The saturation magnetisation of Li0.5Fe2.5-2xAlxCrxO4 is obtained with different values of dilution x. The magnetic phase diagram of Li0.5Fe2.5-2xAlxCrxO4 materials is obtained by high temperature series expansions (HTSEs). The critical exponent associated with the magnetic susceptibility of Li0.5Fe2.5−2xAlxCrxO4 is deduced.  相似文献   

12.
In this report, we fabricated a series of Fe3−xCrxO4(0≦x≦2) films by plasma-oxygen-assisted molecular beam epitaxy (MBE) and did structural and electrical characterizations of these films. These films show textured single phase quality and the lattice parameters are consistent with those of the bulk at low Cr composition (x<0.9). However, the lattice parameters show severe deviation from the bulk value in the intermediate region of 0.9≦x≦1.5 and no diffraction can be resolved at x∼2. These discrepancies may be attributed to the cation distributions and the instability of spinal structure as Cr concentration becomes dominant. The resistivity presents a typical Arrhenius temperature dependence with ρ=ρ0 exp (Ep/kBT) indicating that the transport is due to a hopping mechanism. The prefactor ρ0 increases in Fe3−xCrxO4, at smaller x but tends to level out for x>1, suggesting that Cr3+ ions may start to replace Fe3+ ions at the A site in the high x region. The activation energy of electrical hopping gradually increases at low Cr concentration but abruptly rises to ∼110 meV at x>0.9, suggesting a crossover from electron-hopping mediated transport to a thermally activated band gap excitation.  相似文献   

13.
Melt-spun ribbons of Co64Fe4Ni2B19−xSi8Cr3Alx (x=0, 1 and 2) alloy at wheel speed of 25 m/s and Co64Fe4Ni2B19−xSi8Cr3Al1 alloy at different wheel speeds (25, 30, 35 and 40 m/s) have been prepared and investigated for structural and magnetic properties and magnetoimpedance effect. Based on the results obtained, it was shown that replacement of B by Al can improve the magnetoimpedance ratio (MIR) and the highest value of MIR (191%) was observed for the sample with XAl=1 at wheel speed of 25 m/s. Further, it was seen that the higher quenching wheel speed gives rise to a higher coercivity and lower magnetic permeability/MIR value.  相似文献   

14.
The influence of the substitution of manganese by boron on the crystal structure and magnetic properties of Ni2Mn1−xBxGa Heusler alloys with 0?x?0.5 has been investigated using X-ray diffraction, thermal expansion, resistivity, and magnetization measurements. The samples with concentrations x<0.25 were found to be of single phase and belonged to the cubic L21 crystal structure at room temperature. Crystal cell parameters of the alloys decreased from 5.830 to 5.825 Å with increasing boron concentration (x) from 0 to 0.25. The alloys were ferromagnetically ordered at 5 K and the saturation magnetization decreased with increasing boron concentration. The ferromagnetic ordering and structural transition temperatures for 0?x?0.3 have been observed and the phase (xT) diagram of the Ni2Mn1−xBxGa system was constructed. The phase (xT) diagram indicates that the ground state of Ni2Mn1−xBxGa alloys belongs to ferromagnetic martensitic, premartensitic, and austenitic phases in x?0.12, 0.12<x?0.18, and 0.18<x?0.3, respectively. The relative influence of cell parameters and electron concentrations on the phase diagram is discussed.  相似文献   

15.
The effect of Cr100−xTix underlayer on orderd-L10 FePt films was investigated. A low-temperature ordering of FePt films could be attained through changing the Ti content of Cr100−xTix underlayer. The ordering temperature of the 30 nm FePt film grown on 20 nm Cr90Ti10 underlayer was reduced to 250 °C which is practical manufacture process temperature. An in-plane coercivity was very high to 6000 Oe and a ratio of remnant magnetization (Mr) to saturation magnetization (Ms) was as large as 0.85. This result indicates that the coercivity obtained at 250 °C by the effect of CrTi underlayer is significantly higher than those obtained at 250-275 °C by the effect of underlayers in other conventional studies. The prominent improvement of the magnetic properties of ordered FePt thin films at low temperature of 250 °C could be understood with considering the strain-induced ordering phase transformation associated with lattice mismatch between Cr underlayer and FePt magnetic layer due to an addition of Ti content.  相似文献   

16.
The phosphors in the system Y3−xAl5-yO12:xCe3+,yCr3+ were synthesized by solid-state reactions and their photoluminescence properties were investigated. These phosphors have absorption in the visible light region and give luminescence in the far-red region (∼688 nm), which are suitable for the application in the device of luminescent solar concentrator (LSC). In these phosphors, Ce3+ located at Y3+ site can effectively transfer its absorbed energy to Cr3+ at Al3+ site.  相似文献   

17.
We report the effects of Al doping on the structure, magnetic properties, and magnetocaloric effect of antiperovskite compounds Ga1−xAlxCMn3 (0≤x≤0.15). Partial substitutions of Al for Ga enhance the Curie temperature (from 250 K for x=0.0 to 312 K for x=0.15) and the saturation magnetization. On increasing the doping level x, the maximum values of the magnetic entropy change (−ΔSM) decreases while the temperature span of ΔSM vs. T plot broadens. Furthermore, the relative cooling power (RCP) is also studied. For 20 kOe, the RCP value tends to saturate at a high doping level (for x=0.12, 119 J/kg at 296 K). However, at 45 kOe, the RCP value increases quickly with increasing x (for x=0.15, 293 J/kg at 312 K). Considering the relatively large RCP and inexpensive raw materials, Ga1−xAlxCMn3 may be alternative candidates for room-temperature magnetic refrigeration.  相似文献   

18.
We have investigated the electronic and magnetic properties of the doped Heusler alloys Co2Cr1−xVxAl(x=0, 0.25, 0.5, 0.75, 1) using first-principles density functional theory within the generalized gradient approximation (GGA) scheme. The calculated results reveal that with increasing V content the lattice parameter slightly increases; both cohesive energy and bulk modulus increase with increasing x. The magnetic moment of the Co(Cr) sites increases with V doping; the total spin moment of these compounds linearly decreases. We also have performed the electronic structure calculations for Co2Cr1−xVxAl with positional disorder of Co-Y(Cr,V)-type and Al-Y(Cr,V)-type. It is found that formation of Al-Y-type disorder in Co2Cr1−xVxAl alloys is more favorable than that of Co-Y-type disorder. Furthermore, we found that Co2Cr1−xVxAl of the L21-type structure have a half-metallic character. And the stability of L21 structure will enhance, however, the Curie temperature decreases as the V concentration increases. The disorder between Cr(V) and Al does not significantly reduce the spin polarization of the alloys Co2Cr1−xVxAl.  相似文献   

19.
Sn1−xMnxO2 (x=0.01-0.05) thin films were synthesized on quartz substrate using an inexpensive ultrasonic spray pyrolysis technique. The influence of doping concentration and substrate temperature on structural and magnetic properties of Sn1−xMnxO2 thin films was systematically investigated. X-ray diffraction (XRD) studies of these films reflect that the Mn3+ ions have substituted Sn4+ ions without changing the tetragonal rutile structure of pure SnO2. A linear increase in c-axis lattice constant has been observed with corresponding increase in Mn concentration. No impurity phase was detected in XRD patterns even after doping 5 at% of Mn. A systematic change in magnetic behavior from ferromagnetic to paramagnetic was observed with increase in substrate temperature from 500 to 700 °C for Sn1−xMnxO2 (x=0.01) films. Magnetic studies reveal room-temperature ferromagnetism (RTFM) with 3.61×10−4 emu saturation magnetization and 92 Oe coercivity in case of Sn1−xMnxO2 (x=0.01) films deposited at 500 °C. However, paramagnetic behavior was observed for the films deposited at a higher substrate temperature of 700 °C. The presence of room-temperature ferromagnetism in these films was observed to have an intrinsic origin and could be obtained by controlling the substrate temperature and Mn doping concentration.  相似文献   

20.
The first-principles full-potential linearized augmented plane-wave method within the generalized gradient approximation for the exchange-correlation functional is used to investigate the structural, electronic and magnetic properties of Zn1−xCrxSe (x=0.25, 0.5, 0.75 and 1.0). We find that Zn1−xCrxSe exhibits a half-metallic characteristic, and the ferromagnetic state is more favourable in energy than the antiferromagnetic state. The calculated total magnetic moment of Zn1−xCrxSe per Cr atom is 4.00 μB, which mainly arises from the Cr atom with a little contribution from the Se and Zn atoms. Furthermore, the robustness of half-metallicity with respect to the variation of lattice constants of Zn1−xCrxSe is discussed.  相似文献   

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