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51.
The emerging discipline of biomolecular computation in the US 总被引:2,自引:0,他引:2
52.
C. Persson C.L. Dong L. Vayssieres T. Schmitt R. Ahuja C.L. Chang J.-H. Guo 《Microelectronics Journal》2006,37(8):686-689
The electronic structures of ZnO nanoparticles and microrod arrays are studied by O 1s X-ray absorption spectroscopy (XAS) and O Kα X-ray emission spectroscopy (XES). We show that the present LDA+USIC calculation approach is suitable to correct the LDA self-interaction error of the cation d-states. The atomic eigenstates of 3d in zinc and 2p in oxygen are energetically close, which induces strong Zn-3d-O-2p hybridization. This anomalous valence band cation-d-anion-p hybridization is affected when the localization of the Zn 3d-states is taken into account. Experimentally, the XES spectra show energy dependence in the spectral shape revealing selected excitations to the Zn 3d, 4s and 4p states, hybridized with O 2p states. Strong anisotropic effects are observed for the highly oriented ZnO rods, but not for the isotropic spherical nanoparticles. The nanostructured ZnO has primarily bulk XAS and XES properties. 相似文献
53.
Highly aluminium doped barium and strontium ferrite nanoparticles prepared by citrate auto-combustion synthesis 总被引:2,自引:0,他引:2
Aluminium doped barium and strontium hexaferrite nanoparticles BaAlxFe(12−x)O19 and SrAlxFe(12−x)O19 were synthesised via a sol-gel route using citric acid to complex the ions followed by an auto-combustion reaction. This method shows promise for the synthesis of complex ferrite powders with small particle size. It was found that around half of the iron could be substituted for aluminium in the barium ferrite with structure retention, whereas strontium aluminium ferrites could be produced with any aluminium content including total substitution of the iron. All synthesised materials consisted of particles smaller than 1 μm, which is the size of a single magnetic domain, and various doping levels were achieved with the final elemental composition being within the bounds of experimental error. The materials show structural and morphological changes as they move from iron to aluminium ferrites. Such materials may be promising for imaging applications. 相似文献
54.
The solid-solid interactions between nanosized pure and NiO-substituted ferric and titanium(IV) oxides have been investigated using XRD technique and microstructure studies, also magnetic properties were studied using vibrating samples magnetometer (VSM). The amounts of substituting Ni2+ were x = 0, 0.2, 0.4, 0.6, 0.8 and 1 mole. A mixture equimolar proportions of finely powdered Fe2O3 and TiO2 were mixed with NiO, ball milled, compressed at 250 kg/cm2 and fired at 1200 °C for 4 h.The obtained results showed that with substituting Ni2+ concentration x = 0 only Fe2TiO5 phase is present (∼80 nm) which showed a very small saturation magnetic flux density (Bs), remnant magnetic flux density (Br) and the maximum energy product (BH)max. By the addition of x = 0.2 NiO, new phases were observed NiTiO3 and NiFe2O4 of crystallite sizes 160 and 110 nm, respectively. By the increase of substituting Ni2+ concentration the NiTiO3 and NiFe2O4 phases increased on the expense of Fe2TiO5 up to x = 0.4, then the increase in substituting Ni2+ concentration led to a decrease in Fe2TiO5 and NiTiO3 while NiFe2O4 increases which results in a great improvement of magnetic properties.All samples exhibit a catalytic activity towards H2O2 decomposition and the values of rate constant increase with increasing amount of Ni2+ substituting. The most acidic active sites are shown by specimens substituted with x = 0 this concludes that H2O2 decomposition is not favored on acidic active sites. 相似文献
55.
《Current Opinion in Solid State & Materials Science》2016,20(6):371-373
The low Z metals Fe, Co, Ni, Cu and Zn are Earth abundant, i.e. inexpensive, and their sulfides are of low toxicity. This makes them appealing candidates for materials applications requiring semiconductors or, in the case of CoS2, a metal since they can potentially be produced in large quantities and low cost. Though of great potential little work has explored how subtractive methods can be used to form nanostructured and/or porous structures in, e.g. FeS2, CoS2, NiS, Cu2S and ZnS. 相似文献
56.
Silica and titania nanoparticles were individually coated with ultrathin alumina films using atomic layer deposition (ALD) in a fluidized bed reactor. The effect of the coating on interparticle forces was studied. Coated particles showed increased interactions which impacted their flowability. This behavior was attributed to modifications of the Hamaker coefficient and the size of nanoparticles. Stronger interparticle forces translated into a larger mean aggregate size during fluidization, which increased the minimum fluidization velocity. A lower bed expansion was observed for coated particles due to enhanced interparticle forces that increased the cohesive strength of the bed. Increased cohesiveness of coated powders was also determined through angle of repose and Hausner index measurements. The dispersability of nanopowders was studied through sedimentation and z-potential analysis. The optimum dispersion conditions and isoelectric point of nanoparticle suspensions changed due to the surface modification. A novel atomic force microscope (AFM) technique was used to directly measure interactions between nanoparticles dispersed on a flat substrate and the tip of an AFM cantilever. Both Van der Waals and electrostatic interactions were detected during these measurements. Long and short range interactions were modified by the surface coating. 相似文献
57.
Vertically aligned Fe arrays have been self-assembled on anodic aluminum oxide templates by evaporation. The rims of the pores, which act as obstacles to the stacking of atoms, prevent them from forming continuous films. By controlling the Fe nominal thicknesses (τn) from 400 to 5 nm, the morphology is changed from continuous film to isolated arrays, leading to the change of the predominant magnetization reversal from domain wall motion to spin rotation. For samples with τn < 59 nm, isolated, rather than interconnected, morphology is formed. In this range, the coercivity shows a spectacular change for τn = 47 nm, with an array diameter of about 52 nm, achieving a maximum of about 38 kA/m. The critical dimension of single-domain array is therefore determined. The magnetostatic and exchange interactions are reduced due to the thermal fluctuation, and the magnetization leaves from the in-plane direction to be randomly distributed in 3-D, for τn < 27 nm. 相似文献
58.
Through an electrostatics-induced adsorption effect, nickel ions were found to be preferentially adsorbed onto the surface of colloidal particles at template top during the template-mediated electrodeposition process for preparing macroporous structures. This phenomenon results in the preferential reduction and growth of nickel on colloid surface on the template top, instead of filling into the channels among the colloids. After removing the template, an egg-shell-roofed macroporous nickel, consisting of macroporous film covered with monolayer of hollow spheres, can be created. 相似文献
59.
The Ge quantum dots on anodized nanometer porous silicon layers are prepared by area preferential nucleation at a low temperature of 720°C. The porous silicon was formed by anodic conversion of p-type (1 0 0)-oriented crystalline silicon in hydrofluoric acid diluted by alcohol. Clear phonon-resolved PL, as a NP transition and its TA phonon replica, was observed from the Ge dots at the temperature of 10 K. We attributed the very large blue-shift in energy of the PL peak to the quantum size effect in Ge dots. The present technique is a potential low-cost method for producing quantum dot arrays. 相似文献
60.
Gregor Schinkel Immo Garrn Benjamin Frank Ulrich Gernert Helmut Schubert Reinhard Schomcker 《Materials Chemistry and Physics》2008,111(2-3):570-577
The engineering aspects of the preparation of nanostructured alumina ceramic precursors by alcoholate hydrolysis using microemulsions as reaction media are investigated here. The precipitate was subjected to several treatment steps. Although the properties of the primary precipitated powders are independent of the chemical or reaction engineering parameters of the precipitation procedure, the structure of treated powders and sintered, dense ceramics strongly depends on thermal and mechanical handling like crystallization or grinding of the alumina ceramic precursor. Strong differences are manifested in relative densities and sintering kinetics and can be observed by SEM analysis. 相似文献