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1.
The difference of annealing behaviors of vacancy-oxygen complex (VO) in varied dose neutron irradiated Czochralski silicon: (S1 5×10 17 n/cm 3 and S2 1.07×10 19 n/cm 3) were studied. The results show that the VO is one of the main defects formed in neutron irradiated Czochralski silicon (CZ-Si). In this defect, oxygen atom shares a vacancy, it is bonded to two silicon neighbors. Annealed at 200 °C, divacancies are trapped by interstitial oxygen(O i) to form V 2O (840 cm −1). With the decrease of the 829 cm −1 (VO) three infrared absorption bands at 825 cm −1 (V 2O 2), 834 cm −1 (V 2O 3) and 840 cm −1 (V 2O) will rise after annealed at temperature range of 200–500 °C. After annealed at 450–500 °C the main absorption bands in S1 sample are 834 cm −1, 825 cm −1 and 889 cm −1 (VO 2), in S2 is 825 cm −1. Annealing of A-center in varied neutron irradiated CZ-Si is suggested to consist of two processes. The first is due to trapping of VO by O i in low dose neutron irradiated CZ-Si (S1) and the second is due to capture the wandering vacancy by VO, etc, in high dose neutron irradiated CZ-Si (S2), the VO 2 plays an important role in the annealing of A-center. With the increase of the irradiation dose, the annealing behavior of A-center is changed. 相似文献
2.
Glasses of the SiO 2–Al 2O 3–BaO–MgO and SiO 2–Al 2O 3–ZrO 2–CaO–Na 2O systems were synthesized in the perspective to apply them as sealants in SOFC at operating temperatures of 700–900 °C. Thermal properties of the chosen glass compositions and their compatibility with the SOFC materials (YSZ-electrolyte and alloy-interconnector Crofer22APU, 15×25T) were investigated by means of synchronic thermal analysis and high-temperature dilatometry. The elemental analysis was performed by atomic emission spectroscopy. The average values of the temperature coefficients of the linear extension are 10.0×10 −6 °C −1 for glass 45%SiO 2– 15%Al 2O 3–25%BaO–15%MgO and 9.5×10 −6 °C −1 for glass 60%SiO 2–10%Al 2O 3–10%ZrO 2–5%CaO–15%Na 2O. The gluing microstructure in YSZ/glass/Crofer22APU was studied by scanning electron microscopy. The crystallization process of silicate phases was revealed to occur in the SiO 2–Al 2O 3–BaO–MgO glass. The analysis of the crystallization products was performed by Raman spectroscopy and X-ray diffraction. Glassy ceramics was proved to possess better parameters in comparison with amorphous glass to be used as a sealant in electrochemical sensors and oxygen sensors. The SiO 2–Al 2O 3–ZrO 2–CaO–Na 2O low-temperature amorphous glass can be applied in SOFC. 相似文献
3.
The chemical composition of metal/oxide (M/O)-interfaces was studied for an internally oxidized Ag–1at.%Mg-alloy with small MgO nanoprecipitates in a dilute Ag matrix. This composition was varied by exposing the sample to oxygen ( p(O 2) = 2 × 10 4 Pa), hydrogen ( p(H 2) = 10 5 Pa) or vacuum ( p<10 −4 Pa). By means of small angle neutron scattering (SANS) we were able to show that hydrogen segregates at the internal Ag/MgO-interfaces. The average hydrogen occupancy at the Ag/MgO-phase boundary can be determined to be ΘH=(7.1±0.5)×10 14 H/cm 2. In addition it could be shown that for each segregated hydrogen atom one Ag atom is displaced from the M/O-interface. The amount of hydrogen at the interfaces is in agreement with a model of structural vacancies at densely packed interface planes. To the best of our knowledge these are the first SANS-measurements that provide information about the segregation of hydrogen and deuterium at internal interfaces. 相似文献
4.
The oxidation of chromium at 300 °C was investigated in situ by ToF -SIMS for three different oxygen pressures ( \(P_{{{\text{O}}_{2} }} = 2.0 \times 10^{ - 7}\), 6.0 × 10 ?7 and 2.0 × 10 ?6 mbar). Sequential exposure to the 18O isotopic tracer was performed to reveal the governing transport mechanism in the oxide film. The evolution of the oxide thickness was monitored. Volatilization of Cr 2O 3 was evidenced. A model was used to describe the kinetics resulting from the measurements. Both the parabolic and volatilization constants showed a dependence on oxygen partial pressure like \(P_{{{\text{O}}_{2} }}^{ - 1/n}\), with n = 1.9 ± 0.1, indicating a defect structure mainly consisting of oxygen vacancies. The re-oxidation in 18O 2 shows a growth of the oxide layer at the metal/oxide interface, demonstrating an oxidation process governed by anionic transport via oxygen vacancies. The diffusion coefficient of oxygen in the oxide was determined by fitting the ToF -SIMS depth profiles. It is 2.0 × 10 ?18 cm 2 s ?1. 相似文献
5.
Density functional theory and Boltzmann theory calculations of the electronic and thermoelectric properties of Mg 2Si subjected to isotropic strains have been performed. The electrical conductivity, the Seebeck coefficient and the power factor have been evaluated at two temperatures (300 K and 900 K) and two charge carrier concentrations (10 18 cm −3 and 1.2 × 10 20 cm −3 electrons and holes). Up to 3% of both compressive and tensile strains have been applied to the material. From our results, we can highlight that a significant improvement of both the Seebeck coefficient ( S) and the power factor (PF) is obtained at low temperature and moderate n-doping. The increase in S and PF amounts to 40% and 100%, respectively, compared to the unstrained Mg 2Si. 相似文献
6.
Aluminium was implanted into iron at different doses between 1 × 10 14 and 1.5 × 10 17 atm cm ?2. Oxidation tests were carried out in oxygen during 100–120 h in the temperature range 720–1020 K. Doses of 5 × 10 16 atm cm ?2 had to be achieved to observe a notable inhibition of the oxidation process. In these conditions, the formation of two ternary oxides was detected but the spinel phase Fe Al 2O 4 seemed to be responsible for the observed blocking effect. 相似文献
7.
Tetra-substituted tetra-2,3-[5,6-(9,10-phenanthro)pyrazino]porphyrazinino copper(II) complexes (AzaPhc, 5a–d) have been prepared via complexation of mono-substituted 5,6- (9,10-phenanthro)-2,3-dicyanopyrazines with copper(I) chloride. Their nonlinear optical properties have been studied by the Z-scan measurements at 532 nm. We found that their effective nonlinear refractive indices n2eff (ranging from −4.6×10 −10 to −10.0×10 −10 e.s.u.) are about two to four times larger than the octa-substituted phthalocyaninine complex, and their triplet excited-state absorption cross sections σexτ (ranging from 8.2×10 −19 to 9.8×10 −19 cm 2) are about an order less than the phthalocyanine compound. The one-photon excitation and the heating effect have been applied to interpret our experimental results. 相似文献
8.
An amorphous Bi 4Ti 3O 12 phase was formed when films were grown at <400 °C while Bi 2Ti 2O 7 and Bi 2Ti 4O 11 transient phases were developed when films were grown at 400–500 and 600 °C, respectively. A homogeneous Bi 4Ti 3O 12 crystalline phase was formed in the film grown at 700 °C. The high leakage current density (5 × 10 ?7 A cm ?2 at 0.2 MV cm ?1) of the film grown at 300 °C under 100 mTorr oxygen partial pressure (OPP) decreased to 2 × 10 ?8 A cm ?2 for the film grown at 200 mTorr OPP, due to the decreased number of intrinsic oxygen vacancies. However, when OPP exceeded 200 mTorr, the electrical properties were deteriorated due to the formation of oxygen interstitial ions. Mn-doping at a suitable level improved the electrical properties of the films by producing extrinsic oxygen vacancies that reduced the number of intrinsic oxygen vacancies. Schottky emission was suggested as the leakage current mechanism of the Bi 4Ti 3O 12 film. 相似文献
9.
Effects of vacuum conditions on the oxygen content and microstructure of Mo layers used with Cu gate lines as thin-film transistor-liquid crystal display diffusion barriers were investigated. Mo was deposited using ion-beam sputtering at 1.0 × 10 ?5 and 7.0 × 10 ?7 Torr. The Mo layer oxygen content and the microstructure and changes in chemical composition of the Cu/Mo/SiO 2/Si layer during annealing were examined. The Mo layer microstructure was influenced by oxygen; increasing concentration increased the energy required for secondary grain growth. Growth was suppressed at high oxygen levels. Therefore, diffusion barrier performance is enhanced by finer Mo layer grain sizes. 相似文献
10.
Silicide coatings including MoSi 2 and Si-MoSi 2 were prepared on molybdenum substrates by electrodeposition in NaCl-KCl-NaF-K 2SiF 6 molten salt. The experimental was conducted under different cathodic current densities at the temperature of 1073 K. The effect of the current density on the microstructure, phase composition, cross-section morphologies and elemental distribution of the as-prepared coatings were investigated by means of SEM, XRD and EDX. The results revealed that the type of the silicide coatings was strongly dependent on the current density and the relevant deposition mechanism was discussed. Besides, the electrochemical behavior of silicon ion in the chloride-fluoride molten salts was also studied using cyclic voltammetry and chronopotentiometry to reveal the electroreduction mechanism. The reduction of Si(IV) to Si was proved to be a quasi-reversible or irreversible diffusion-controlled single-step reaction and the diffusion coefficient of Si(IV) calculated from chronopotentiograms was (1.28 ± 0.25) × 10 −5 cm 2·s −1. 相似文献
11.
The fracture energy of TiN/SiO 2 interfaces, prepared as part of multi-layer structures by conventional thin-film device processing, has been measured using a residually stressed, micro-strip decohesion test. Both the decohesion energy and the decohesion velocity, at fixed strain energy release rate, are found to be affected by the presence of moisture and are functions of relative humidity. A threshold strain energy release rate for interface decohesion in the presence of moisture is determined. Also, the diffusivity of moisture along the TiN/SiO 2 interface, at room temperature, is determined to be (6±2)×10 −13 cm 2/s from sequential images of the 2D concentration profiles formed by dynamic secondary ion mass spectroscopy (SIMS). Evidence is presented indicating that the TiN/SiO 2 interface is weakened by in-diffusion of moisture ahead of the advancing decohesion front. 相似文献
12.
We systematically studied the passivation process of 6082 aluminium alloy under the bending stress situation by combining electrochemical measurement techniques with three-point bending stress fixture designed by our lab, and then examined the microstructures of corroded specimens to analyze electrochemical corrosion mechanism in 1.5% NaCl solution. The results show that secondary Mg 2Si phase acts as the anodic electrode, leading to the self-corrosion of Mg 2Si phase. As a result, the spots of self-corroded Mg 2Si phase within grains act as initial pitting corrosion site, combined with tiny, massive precipitated Mg 2Si particles at the grain boundaries and bending stress, leading to the failure of surface of the 6082 aluminium alloy. The corrosion current density increases from 3.422 × 10 −7 to 13.77 × 10 −7 A/cm 2 when bending stress level was increased from 0% up to 100% of yield stress. Passive film formation process occurred between polarization potential area of −1.05 and −0.65 V. Sectional microstructural investigations show that the corrosion starts penetrating vertically into the material before it develops corrosion paths extending parallel to the surface, leading to massive stress-induced corrosion cracks. The maximum corrosion depth increases from ∼24 μm on specimen without any stress applied to 85 μm when bending stress of 100% yield strength is applied. 相似文献
13.
We have studied photovoltaic cells using sexithiophene in (ITO/6T/Al) structure, and we have measured the action spectrum obtained by illumination through the aluminum side which is compared to the measured absorption spectrum. Two models were used to interpret this experiment: the Ghosh model using the carriers diffusion property in the bulk, and the kinetic model describing the dynamic behavior of the charge carriers in the device. The confrontation of these models with the experimental spectra allows us to reach the diffusion length of electron–hole pair L=2×10 −6 cm. We also give the mobility of carriers ( μn≈1.5×10 −4 cm 2/V s, and μp≈1.5×10 −5 cm 2/V s) and their diffusion coefficients ( Dn≈4×10 −6 cm 2/s, and Dp≈4×10 −7 cm 2/s). 相似文献
14.
This paper investigates the effect of nitrogen ion implantation on surface structure as well as resistance against tantalum corrosion. Bulk Ta surface was implanted with 30?keV nitrogen ions at a temperature of 100°C with doses between 1?×?10 17 and 1?×?10 18?ions/cm 2. The implanted samples were characterised by atomic force microscopy, X-ray diffraction analyses and the corrosion test to identify structural, compositional and electrochemical changes at various doses. The experimental results indicate the formation of hexagonal tantalum nitride (TaN 0.43), in addition to the fact that by increasing the ion dose, nitrogen atoms occupy more interstitial spaces in the target crystal, a case which can significantly improve corrosion resistance. The maximum extent in the improvement of the micro hardness was 75% and the reduction in the corrosion current was 83%. According to scanning electronic microscopy and corrosion results, in the dose of 1?×?10 18?ions/cm 2 the highest corrosion resistance was received against the H 2SO 4 corroding media. 相似文献
15.
Chromium, a p-type dopant, has been incorporated into silicon carbide by laser doping. Secondary ion mass spectrometric data revealed enhanced solid solubility (2.29 × 10 19 cm −3 in 6H–SiC and 1.42 × 19 19 cm −3 in 4H–SiC), exceeding the equilibrium limit (3 × 10 17 cm −3 in 6H–SiC above 2500 °C). The roughness, surface chemistry and crystalline integrity of the doped sample were examined by optical interferometry, energy dispersive X-ray spectrometry and transmission electron microscopy, respectively, and showed no crystalline disorder due to laser heating. Deep-level transient spectroscopy confirmed Cr as a deep-level acceptor with activation energies Ev + 0.80 eV in 4H–SiC and Ev + 0.45 eV in 6H–SiC. The Hall effect measurements showed that the hole concentration (1.942 × 10 19 cm −3) is almost twice the average Cr concentration (1 × 10 19 cm −3), confirming that almost all of the Cr atoms were completely activated to the double acceptor state by the laser-doping process without requiring any additional annealing step. 相似文献
16.
The coefficients of thermal expansion (CTE) of the W 5Si 3 and T 2 phases of the W–Si–B system were determined using high-temperature X-ray diffraction in the 298–1273 K temperature interval. Alloys with nominal compositions 62.5W37.5Si (at%) and 58W21Si21B (at%) were prepared from high-purity materials through arc melting followed by heat treatment at 2073 K for 12 h under argon atmosphere. The highly different thermal expansion coefficients of W 5Si 3 along the a (5.0 × 10 −6 K −1) and c (16.3 × 10 −6 K −1) axes lead to a high thermal expansion anisotropy ( αc/ αa ≅ 3.3). On the other hand, the T 2-phase exhibits similar thermal expansion coefficients along the a (6.9 × 10 −6 K −1) and c (7.6 × 10 −6 K −1) axes, indicating a behavior close to isotropic ( αc/ αa ≅ 1.1). 相似文献
17.
We report the epitaxial growth of Ni 2MnGa thin films on MgO(100) substrate deposited at elevated temperature using direct current magnetron sputtering. The structural and texture analysis of as-deposited film reveal the (010) crystallographic orientation with seven modulated martensite phase and an epitaxial relationship of Ni 2MnGa(010){101} || MgO(001){110} between the film and the substrate. The crystal quality of the films was analysed by performing symmetric and asymmetric rocking curve measurements and dislocation density for screw and edge dislocations is determined to be 6 × 10 9 cm −2 and 3.45 × 10 10 cm −2, respectively. The presence of micro-twins at an angle of 45° with respect to growth direction and seven modulated nano-twins formed by adaptive modulation has been observed with transmission electron microscopy investigations. The magnetic measurements indicates magnetic field induced reorientation of martensitic variants, strong magneto-crystalline anisotropy and a very high saturation magnetization (I S) of 61 emu g −1 in the film. 相似文献
18.
A low energy N 2 ? ion beam impinged on a α-Al 2O 3(0001) single crystal surface in the range of fluence 5×10 15/cm 2?1×10 18/cm 2 at room temperature. After ion bombardment, chemical bonding on the modified sapphire surface was investigated by x-ray photoelectron spectroscopy. Below a fluence of 1×10 15/cm 2, only a non-bonded N1s peak at the binding energy 398.7 eV was found, but further irradiation up to 2×10 17/cm 2 induced Al?O?N bonding at around 403 eV. The occurrence of Al?N bonding was identified at ion fluence higher than 5×10 17/cm 2 at 396.6 eV. II–VI ZnO thin films were grown on an untreated/ion-beam-induced sapphire surface by pulsed laser deposition (PLD) for the investigation of the modified-substrate effect on photoluminescence. The ZnO films grown on modified sapphire containing Al?O?N bonding only, and both Al?O?N and Al?N bonding showed a significant reduction of the peak related to deep-level defects in photoluminescence. These results are explained in terms of the formation of Al?N?O and Al?O?N layers and relaxation of the interfacial strain between Al 2O 3 and ZnO. 相似文献
19.
In recent years, the coating prepared by laser cladding has attracted much attention in the field of wear research. In this work, AlCrFeNiMo0.5Six (x=0, 0.5, 1.0, 1.5, 2.0) high-entropy alloy coatings were designed and prepared on Q235 steel by laser cladding. The effect of Si content on microstructure, microhardness and wear resistance of the coatings was studied in detail. The results indicate that the AlCrFeNiMo0.5Six high-entropy alloy coatings show an excellent bonding between substrate and the cladding layer. The AlCrFeNiMo0.5Six coatings are composed of nano-precipitated phase with BCC structure and matrix with ordered B2 structure. With the addition of Si, the white phase (Cr, Mo)3Si with cubic structure appears in the interdendritic, and the morphology of the coating (x=2.0) transforms into lamellar eutectic-like structures. The addition of Si enhances the microhardness and significantly improves the wear resistance of the coatings. As x increases from 0 to 2.0, the average hardness of the cladding zone increases from 632 HV to 835 HV, and the wear rate decreases from 1.64×10−5 mm3·(N·m)−1 to 5.13×10−6 mm3·(N·m)−1. When x≥1.5, the decreasing trend of the wear rate gradually slows down. The wear rates of Si1.5 and Si2.0 coatings are 5.85×10−6 mm3·(N·m)−1 and 5.13×10−6 mm3·(N·m)−1, respectively, which is an order of magnitude lower than that of Q235 steel. 相似文献
20.
Electrical and magnetic properties of two new radicalion salts of BEDT-TTF (BEDT-TTF is bis(ethylenedithio)-tetrathiafulvalene) are reported. (BEDT-TTF) 2[Au III(i-mnt) 2] (i-mnt is 1,1-dithio-2,2-dicyano-ethylene) is a semiconductor, σ r.t. = 2.0 × 10 −1−5.5 × 10 −2 S cm −1 with a temperature dependent activation energy (0.14–19 eV). The powder magnetic susceptibility (10–300 K) has been fitted according to a uniform antiferromagnetic ( S = 1/2) Heisenberg model by using the experimental g value of 2.0067 and a magnetic exchange constant J/kB of −110 K. (BEDT-TTF) 2 [BiBr 4] shows similar electrical and magnetic behaviour with σ r.t. = 5 × 10 −2 S cm −1 on a powdered sample and J/kB = − 79 K. At low temperature impurities are responsible for the Curie-like behaviour. 相似文献
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