Characterization and thermodynamic study of ultra-fine particle of Ni-B amorphous alloy

Ultra-fine particle of Ni-B amorphous alloy was prepared by chemical reduction of Ni2+ with NaBH4 and characterized with TEM and XRD. The heat capacity and thermal stability were measured with a high-precision automatic adiabatic calorimeter and DTA. The upper limit of applied temperature of the substance was found to be 684 K for use as catalyst. (C) 1999 Elsevier Science B.V. All rights reserved.

Fe 和(Ga,Cr)As 薄膜的分子束外延生长及磁学性质

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-04-28T14:23:05Z No. of bitstreams: 1 鲁军_博士论文.pdf: 4237580 bytes, checksum: 3a1a5f0ea10b0895d92e102e4cdcf5d0 (MD5)

Fe对Pt-Fe/C催化剂电催化氧还原反应活性的影响

制备了用作直接甲醇燃料电池的碳载Pt-Fe(Pt-Fe/C)阴极催化剂,X射线能量色散谱(EDX)、X射线衍射谱和电化学测量的结果表明,在Pt-Fe/C催化剂中,Fe以3种形式存在.质量分数大约为20%的Fe进入Pt的晶格,形成Pt-Fe合金,质量分数大约为80%的Fe没有进入Pt的晶格而以Fe和Fe2O3的形式单独存在.该催化剂经酸处理后,非合金化Fe和Fe2O3被溶解,而使Pt-Fe/C催化剂的电化学活性比表面积要比未经酸处理前的增加约30%左右,导致Pt-Fe/C催化剂对氧还原的电催化活性优于未经酸处理前的Pt-Fe/C催化剂.研究结果表明,Pt-Fe/C催化剂的电化学活性比表面积对氧还原的电催化活性起重要的作用,另外,只有与Pt形成合金的Fe能提高Pt对氧还原的电催化活性,而非合金化的Fe对Pt催化剂对氧还原的电催化活性基本没有影响.

Assembly of the transition metal substituted polyoxometalates ZnW11M(H2O)O-39(n-) (M = Mn, Cu, Fe, Co, Cr, Ni, Zn) on 4-aminobenzoic acid modified glassy carbon electrode and their electrochemical study

Through layer-by-layer assembly, a series of undecatungstozincates monosubstituted by first-row transition metals, ZnW11M(H2O)O-39(n-) (M=Cr, Mn, Fe, Co, Ni, Cu. or Zn) were first successfully immobilized on a 4-aminobenzoic acid modified glassy carbon electrode surface. The electrochemical behaviors of these polyoxometalates were investigated. They exhibit some special properties in the films different from those in homogeneous aqueous solution. The Cu-centered reaction mechanism in the ZnW11Cu multilayer film was described. The electrocatalytic behaviors of these multilayer film electrodes to the reduction of H2O2 and BrO3- were comparatively studied.

植烟土壤有效态微量元素的空间变异及分布特征

以辽宁昌图烟区为例,采用GIS和地统计学相结合的方法,研究了县级区域植烟土壤有效态微量元素的空间变异及分布特征。结果表明:土壤有效态Fe、Mn、Cu、Zn、B、Mo含量的空间变异函数分别为高斯、高斯、球状、指数、指数、指数模型。其中,有效态Cu、Zn、B具有中等的空间相关性,其变异受母质、地形、土壤类型等结构因素和施肥、管理水平等随机因素的共同影响;有效态Fe、Mn、Mo的空间相关性微弱,其变异受随机因素影响较大。点克里格(Kriging)法插值图显示,Fe、Mn、Cu、Zn、B、Mo有效含量均总体呈现南高北低的分布趋势,其中Cu、Zn、B的分布格局相对更加复杂,在北部烟区表现为从西南向东北逐渐增加,在南部烟区表现为自中偏北部向四周逐渐降低。

Microstructure Study Of Laser Welding Cast Nickel-Based Superalloy K418

Experiments of laser welding cast nickel-based superalloy K418 were conducted. Microstructure of the welded seam was characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectrometer (EDS). Mechanical properties of the welded seam were evaluated by microhardness. The corresponding mechanisms were discussed in detail. Results show that the laser welded seam have non-equilibrium solidified microstructures consisting of Cr-Ni-Fe-C austenite solid solution dendrites as the dominant and some fine and dispersed Ni-3(Al,Ti) gamma' phase as well as little amount of MC needle carbides and particles enriched in Nb, Ti and Mo distributed in the interdendritic regions, cracks originated from the liquation of the low melting points eutectics in the HAZ grain boundary are observed, the average microhardness of the welded seam and HAZ is higher than that of the base metal due to alloy elements' redistribution of the strengthening phase gamma'. (C) 2008 Elsevier B.V. All rights reserved.

Development And Characterization Of Composite Ni-Cr-C-Caf2 Laser Cladding On Gamma-Tial Intermetallic Alloy

A process of laser cladding Ni-CF-C-CaF2 mixed powders to form a multifunctional composite coatingd on gamma-TiAl substrate was carried out. The microstructure of the coating was examined using XRD, SEM and EDS. The coating has a unique microstructure consisting of primary dendrite or short-stick TiC and block Al4C3 carbides reinforcement as well as fine isolated spherical CaF2 solid lubrication particles uniformly dispersed in the NiCrAlTi (gamma) matrix. The average microhardness of the composite coatings is approximately HV 650 and it is 2-factor greater than that of the TiAl substrate. (C) 2008 Elsevier B.V. All rights reserved.

Theoretical investigation on the phase stability of Nd2Fe14B and site preference of V, Cr, Mn, Zr and Nb

The stability of the excellent permanent magnetic compound Nd2Fe14B and substitution of Fe in the compound by V, Cr, Mn, Zr and Nb are investigated by using interatomic pair potentials which are converted from lattice-inversion method. Calculation shows that the substitution always makes the cell volume larger, and the increase of the volume is almost linear with substituent concentration. The calculated cohesive energy shows that the preferential order of substitution of Fe is Nb, V, Cr, Mn, Zr. Nevertheless, all the five substituting elements should most preferentially replace Fe in the j(2)' site, which has the greatest space among all six Fe sites. (C) 2005 Elsevier B.V. All rights reserved.

Effects of reaction conditions on the selective oxidation of propane to acrylic acid on Mo-V-Te-Nb oxides

An effective Mo-1 V(0.3)Te(0.23)Nb(0.12)Ox catalysts for the selective oxidation of propane to acrylic acid was successfully prepared by using rotavap method. The catalyst was characterized by XRD and shown to contain (V0.07Mo0.93)(5)O-14, (Nb0.09Mo0.91)O-2.8,3MoO(2)(.)Nb(2)O(5), Mo5TeO16 and/or TeMo4O13, Te4Nb2O13 and a new TeMO (TeVMoO or TeVNbMoO; M = Mo, V and Nb) crystalline phase as the major phase. Regardless of the intrinsic catalytic characteristics of the catalyst, the external reaction conditions would have strong effects on the catalytic performance for propane oxidation. So in this paper, the effects of reaction conditions were investigated and discussed, including temperature, space velocity, V(air)/V(C3H8) ratio and V(steam)/V(C3H8) ratio. A stability test was also carried out on Mo1V0.3Te0.23Nb0.12Ox catalyst. The experimental run was performed during 100 h under the optimized reaction conditions. During the 100 h of operation, propane conversion and acrylic acid selectivity remained at about 59 and 64%, respectively. (C) 2004 Elsevier B.V. All rights reserved.

Low temperature specific heat and thermal stability of Fe-B ultrafine amorphous alloy particles

Fe-B ultrafine amorphous alloy particles (UFAAP) were prepared by chemical reduction of Fe3+ with NaBHO4 and confirmed to be ultrafine amorphous particles by transmission electron microscopy and X-ray diffraction. The specific heat of the sample was measured by a high precision adiabatic calorimeter, and a differential scanning calorimeter was used for thermal stability analysis. A topological structure of Fe-B atoms is proposed to explain two crystallization peaks and a melting peak observed at T=600, 868 and 1645 K, respectively.