FCC (Fe55Ni45)1−xCx supersaturated solid solution was prepared in a wide concentration range (0?x?0.9) by mechanical alloying of nanocrystalline Fe55Ni45 with graphite. The lattice constant of Fe55Ni45 increases linearly with increasing carbon content up to x=0.25. At the same time, it is found that the magnetic moment per metal atom (Fe, Ni) decreases linearly with increasing carbon content for 0?x?0.25 with a slope of 1.2 μB/at. For high carbon content, x?0.5, it is observed that the decrease of lattice constant and increase of moment per metal atom (Fe, Ni) with increasing C content, indicates that the dissolution of carbon is hindered by the high-volume fraction of graphite in the initial powder mixture. The complete amorphization of x=0.5 does not occur after the extended ball milling. The alloying effect of carbon on the magnetization is compared with other metalloid B, P, and Si in Fe- and Ni-based binary system. 相似文献
Nanocrystalline Fe75Si25 powders were prepared by mechanical alloying in a planetary ball mill. The evolution of the microstructure and magnetic properties during the milling process were studied by X-ray diffraction, scanning electron microscope and vibrating sample magnetometer measurements. The evolution of non-equilibrium solid solution Fe (Si) during milling was accompanied by refinement of crystallite size down to 10 nm and the introduction of high density of dislocations of the order of 1017 m−2. During the milling process, Fe sites get substituted by Si. This structural change and the resulting disorder are reflected in the lattice parameters and average magnetic moment of the powders milled for various time periods. A progressive increase of coercivity was also observed with increasing milling time. The increase of coercivity could be attributed to the introduction of dislocations and reduction of powder particle size as a function of milling time. 相似文献
Monodisperse Cu2O nanocubes are synthesized by reducing freshly prepared Cu(OH)2 with N2H4·H2O in water at room temperature. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show that most of these nanocubes are uniform in size, with the average edge length of ∼500 nm. Selected area electron diffraction (SAED) investigation reveals that these nanocubes are single crystalline. Further, Cu2O nanoboxes are obtained by etching Cu2O nanocubes with acetic acid solution at room temperature. The nanoboxes retain the size and external morphology of the nanocubes. 相似文献
The sol-gel method has been applied for the synthesis of a series of acid metal-carbon xerogels (with M = V, Cr, Mo and Ni) by polymerisation of resorcinol with formaldehyde in the presence of metallic precursors. A blank sample was also prepared without any metal addition. The xerogels were heated in nitrogen at 1000 °C to obtain the pyrolysed products. The samples were characterised by different techniques such as thermal-mass spectrometry analysis, gas physisorption, and mercury porosimetry. In addition, the acid character of the pyrolysed products was tested by the Claisen-Schmidt condensation between benzaldehyde and acetophenone for the formation of chalcones. 相似文献
The crystallization process of mechanically alloyed Fe75Zr25 metallic glasses is investigated by means of both thermo‐magnetization and in situ neutron powder thermo‐diffraction experiments in the temperature range 300–1073 K. It was found that the crystallization takes place in a two‐step process, involving firstly the appearance of metastable Fe and Fe2Zr crystalline phases between 880 K and 980 K, and a subsequent polymorphic transformation into Fe3Zr above 980 K. These findings explain the anomalous magnetization vs. temperature behaviour on heating–cooling cycles.
In this work wüstite nanoparticles have been prepared via high-energy ball milling, using high-purity hematite (Fe2O3) and iron (Fe) powders as the starting materials. In order to get a single-phase wüstite different mole ratios of (Fe/Fe2O3) were milled, using a planetary mill. X-ray diffraction studies of the as-milled powders show that a single-phase wüstite was formed for a mole ratio of 0.6. Lattice parameter of the wüstite was obtained from XRD data, by which a value of 0.072 was obtained for x in Fe1−xO. A mean crystallite size of 13±1 nm was calculated for the single-phase wüstite, using Scherrer's formula. The morphology of the powders was also checked by TEM. Variations of pressure and temperature in the vial were recorded with respect to the milling time, using a GTM unit. Hysteresis loops of the as-milled powders at 5 K and room temperature have been obtained by SQUID and by VSM systems, respectively. The loops show non-zero coercivity, in contrast to the bulk wüstite. The observed magnetizations can be explained by a model based on the spinel-type defect clusters in non-stoichiometry wüstite. 相似文献
The nature of the NOx species produced during the adsorption of NO at room temperature and during its coadsorption with oxygen on LaMnAl11O19 sample with magnetoplumbite structure obtained by a sol-gel process has been investigated by means of in situ FT-IR spectroscopy. The adsorption of NO leads to formation of anionic nitrosyls and/or cis-hyponitrite ions and reveals the presence of coordinatively unsaturated Mn3+ ions. Upon NO/O2 adsorption at room temperature various nitro-nitrato structures are observed. The nitro-nitrato species produced with the participation of electrophilic oxygen species decompose at 350 °C directly to N2 and O2. No NO decomposition is observed in absence of molecular oxygen. The adsorbed nitro-nitrato species are inert towards the interaction with methane and block the active sites (Mn3+ ions) for its oxidation. Noticeable oxidation of the methane on the NOx−-precovered sample is observed at temperatures higher than 350 °C due to the liberation of the active sites as a result of decomposition of the surface nitro-nitrato species. Mechanism explaining the promoting effect of the molecular oxygen in the NO decomposition is proposed. 相似文献
Indium tin oxide nanoparticles prepared by co-precipitation were re-dispersed in benzyl alcohol and modified successfully with titanium dioxide using titanium tetrachloride as precursor. The morphologies and the re-dispersing processes of both the initial and modified indium tin oxide nanoparticles were investigated, respectively. The photocatalytic properties of the modified nanoparticles were compared with commercial P25 photocatalyst. It was found that (i) the average diameter of the initial indium tin oxide nanoparticles was 10.7 nm and that of the surface-modified nanoparticles was 14.5 nm; (ii) the optimal ultrasonication time was 10.0 min and 8.0 min for the initial and surface-modified ITO nanoparticles, respectively; (iii) the modified particles possessed a higher photocatalytic activity than commercial P25 photocatalyst in the photodegradation of rhodamine B in aqueous medium at pH 5.00; (iv) the pH of the medium markedly influences the photodegradation efficiency. 相似文献
The effects of Si doping on the structural and electrical properties of Ge2Sb2Te5 film are studied in detail. Electrical properties and thermal stability can be improved by doping small amount of Si in the Ge2Sb2Te5 film. The addition of Si in the Ge2Sb2Te5 film results in the increase of both crystallization temperature and phase-transition temperature from face-centered cubic (fcc) phase to hexagonal (hex) phase, however, decreases the melting point slightly. The crystallization activation energy reaches a maximum at 4.1 at.% and then decreases with increasing dopant concentration. The electrical conduction activation energy increases with the dopant concentration, which may be attributed to the increase of strong covalent bonds in the film. The resistivity of Ge2Sb2Te5 film shows a significant increase with Si doping. When doping 11.8 at.% of Si in the film, the resistivity after 460 °C annealing increases from 1 to 11 mΩ cm compared to the undoped Ge2Sb2Te5 film. Current-voltage (I-V) characteristics show Si doping may increase the dynamic resistance, which is helpful to writing current reduction of phase-change random access memory. 相似文献
The current–voltage characteristics and photoresponse of mesa structured {111}‐oriented homoepitaxial CVD diamond p(i)n‐junctions with different intrinsic layer thickness are investigated. When a sufficiently thick intrinsic layer is present, a rectification ratio of 108 at ±10 V could be obtained. Good rectifying diodes show a high photoresponse ratio between 210 nm (above bandgap) and 500 nm (below bandgap), making them suitable for UV detection purposes. The results are compared with similar measurements carried out on polycrystalline CVD diamond pn‐junctions.
Ba0.6Sr0.4TiO3 (BST) bulk ceramic synthesized by solid state reaction was used as target for thin films grown by pulsed laser deposition
(PLD) and radiofrequency beam assisted PLD (RF-PLD). The X-ray diffraction patterns indicate that the films exhibit a polycrystalline
cubic structure with a distorted unit cell. Scanning Electron Microscopy investigations showed a columnar microstructure with
size of spherical grains up to 150 nm. The capacitance–voltage (C–V) characteristics of the BST films were performed by applying
a DC voltage up to 5 V. A value of 280 for dielectric constant and 12.5% electrical tunability of the BST capacitor have been
measured at room temperature. 相似文献
ZrOxNy thin films have been prepared by radio frequency magnetron sputtering at various substrate temperatures. The effect of substrate temperature on structural, optical properties and energy-band alignments of as-deposited ZrOxNy thin films are investigated. Atomic force microscopy results indicate the decreased root-mean-square (rms) values with substrate temperature. Fourier transform infrared spectroscopy spectra indicate that an interfacial layer has been formed between Si substrate and ZrOxNy thin films during deposition. X-ray photoelectron spectroscopy and spectroscopy ellipsometry (SE) results indicate the increased nitrogen incorporation in ZrOxNy thin films and therefore, the decreased optical band gap (Eg) values as a result of the increased valence-band maximum and lowered conduction-band minimum. 相似文献