Decrease In Ni Content Research Articles

Cysteine 295 indirectly affects Ni coordination of carbon monoxide dehydrogenase-II C-cluster

A unique [Ni–Fe–S] cluster (C-cluster) constitutes the active center of Ni-containing carbon monoxide dehydrogenases (CODHs). His261, which coordinates one of the Fe atoms with Cys295, is suggested to be the only residue required for Ni coordination in the C-cluster. To evaluate the role of Cys295, we constructed CODH-II variants. Ala substitution for the Cys295 substitution resulted in the decrease of Ni content and didn’t result in major change of Fe content. In addition, the substitution had no effect on the ability to assemble a full complement of [Fe–S] clusters. This strongly suggests Cys295 indirectly and His261 together affect Ni-coordination in the C-cluster.

Electronic structure and optical properties of TbNi5−xCux

In this paper we present theoretical investigation of optical conductivity for intermetallic TbNi_{5-x}Cu_x series. In the frame of LSDA+U calculations electronic structure for x=0,1,2 and on top of that optical conductivities were calculated. Disorder effects of Ni for Cu substitution on a level of LSDA+U densities of states (DOS) were taken into account via averaging over all possible Cu ion positions for given doping level x. Gradual suppression and loosing of structure of optical conductivity at 2 eV together with simultaneous intensity growth at 4 eV correspond to increase of Cu and decrease of Ni content. As reported before [Knyazev et al., Optics and Spectroscopy 104, 360 (2008)] plasma frequency has non monotonic doping behaviour with maximum at x=1. This behaviour is explained as competition between lowering of total density of states on the Fermi level N(E_F) and growing of number of carriers. Our theoretical results agree well with variety of recent experiments.

Magnetic characterization of nickel-rich NiFe nanowires grown by pulsed electrodeposition

Nickel-rich NiFe nanowires with well-controlled diameters and compositions are fabricated in various porous alumina templates by using a pulsed electrochemical deposition technique. The average pore diameter of the templates is tuned either by coating the pore walls with thin silica layers using an atomic layer deposition (ALD) technique or by applying a chemical pore widening process. The composition of the alloy is controlled by varying the frequency of the deposition pulse. The coercivity of the nanowire array is influenced by its texture and the amount of iron content in the alloy. The effective field and the saturation magnetization are found to be reinforced with the decrease in Ni content. A distinct enhancement of the axial coercivity and squareness of permalloy, Ni80Fe20, nanowire array are obtained by decreasing the average nanowire diameter. The processes of magnetization reversal in Ni80Fe20 nanowire array are investigated. The temperature dependence of Ni80Fe20 nanowires coercivity is interpreted in accordance with magnetization fluctuation over a single energy barrier.

Phase transition and mechanical properties of constraint-aged Ni–Mn–Ga–Ti magnetic shape memory alloy

Ni–Mn–Ga Heusler-type ferromagnetic shape memory alloys are attractive materials for micro-actuator, but the relatively poor ductility and low strength of Ni–Mn–Ga alloys have triggered a great deal of interest. In this study, we attempt to introduce some ductile second phase in the alloy by partially substituting Ti for Ga and constraint aging treatment. The results show that the martensitic transformation temperature first decreases and then increases slightly with the increasing of constraint-aging temperature, which can be attributed to the decrease of Ni content in the matrix and strengthening effect of the second particles. It is found that the amount of the Ni-rich precipitates by constraint-aged samples is more and the size of the second phase particle is smaller than that of the free-aged samples. The compressive stress and ductility can be significantly improved by the constraint-aging treatment, and the maximum compressive stress for constraint-aging alloy is about 1400 MPa, which is the highest value up to date compared with the 400 MPa in solution-treated Ni–Mn–Ga–Ti alloy and about 900 MPa in Ni–Mn–Ga–Ti alloy free-aged at 1073 K for 3 h. Scanning electron microscopy observations of fracture surfaces confirm that the Ni-rich second phase play a key role in improving the compression stress and ductility of Ni–Mn–Ga–Ti alloy.

Microstructure changes in two phase β+ γ Co-Ni-Al ferromagnetic shape memory alloys in relation to Al/Co ratio

The microstructure of Co 35+x - Ni 40-x - Al 25 (x = 0, 2.5, 5.0) ferromagnetic shape memory alloys annealed at 1200°C and water quenched has been investigated by optical (OM) and analytical transmission electron microscopy (TEM). The microstructure consists of elongated grains of martensite and 7 phase. Annealing twins were found frequently in the 7 phase. The volume fraction of γ phase has been determined to be about 40%. TEM observations show twinned L1 0 martensite with {111}-type twinning plane and tetragonality c/a = 0.85 in all investigated alloys. Determination of the composition of β phase, allows to calculate Al/Co and e/a ratio in the range 7.68-8.40 in correlation with its Ms temperatures between 66 and 167 °C, respectively. An increase in the Al/Co ratio together with a decrease of Ni content in β phase causes a decrease of the e/a ratio, which promotes a decrease of martensitic transformation temperatures.

WC–TiC–Ni cemented carbide with enhanced properties

In the paper, the effect of Ni content, WC grain size and Mo2C addition on WC–6.25 wt%TiC–9.3 wt%Ni cemented carbide were investigated to improve the properties of Ni-bonded cemented carbides. The results show that the decrease of Ni content will result in the decrease of transverse rupture strength and increase of hardness; with the decrease of WC particle size, hardness increases due to the refinement of WC grains, however, the transverse rupture strength decrease due to the decrease of Ni binder thickness; Mo2C proves to be an effective grain growth inhibitor. With the increase of Mo2C content, the WC grains are refined and the hardness and transverse rupture strength are improved. Generally, when the Ni content is decreased to 8.4 wt%, 13.45 μm WC is used and 1.2 wt% Mo2C is added, a higher hardness and transverse rupture strength of 90.6 HRA and 1900 MPa can be achieved. The results obtained in this study extend the knowledge on Ni-bonded cemented carbide.

Sol–gel preparation and characterization of Ni–YSZ cermet electrode

Optimizing both the internal gelation (IGP) and EDTA (ethylene-diamine-tetra-acetic acid) complexes-gel reduction process (CGRP) was carried out for manufacturing Ni–YSZ (yttria-stabilized zirconia) cermet as the membrane electrode. For the IGP, we found the adequate additive amounts of gelling agent and stabilizer such as HMTA (hexamethylenetetramine) and urea for the starting solution, so that precursor gels containing Ni content of 45–61.3 mol% were successfully synthesized. However, the sample prepared via IGP did not show the electronic conductivity but ionic one, although NiO in the samples was completely reduced to Ni. This might be caused by a decrease of Ni content during sintering at high temperature. On the other hand, for EDTA CGRP, precursor gels were successfully synthesized by controlling pH value in the preparation of soluble complexes. In addition, the sample synthesized via EDTA CGRP showed the electronic conductivity for Ni content of 60 mol%.

Surface characterization of the Zn–Ni–Al 2O 3 nanocomposite coating fabricated under ultrasound condition

Zn–Ni–Al 2O 3 nanocomposite coating, which was fabricated by eletrodeposition technique with the aid of ultrasound, was investigated by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis and X-ray photoelectron spectroscopy (XPS). The results reveal that 7.2 wt.% nano-alumina particles uniformly dispersed in the matrix of the composite coating. The XPS analyses demonstrate that the outermost layer of Zn–Ni–Al 2O 3 coating was composed of nano-alumina and Zn(OH) 2, while the transition layer between the outermost layer and the Zn–Ni matrix consisted of nano-alumina, metallic Zn, ZnO and metallic Ni. In order to investigate the influences of ultrasonic agitation and the incorporation of nano-alumina on the composition and surface structure of Zn–Ni matrix, the comparison studies of Zn–Ni–Al 2O 3 nanocomposite coating with Zn–Ni coatings fabricated with and without ultrasound were conducted. The results indicate that ultrasonic agitation resulted in a decrease of Ni content in the Zn–Ni matrix and an increase of the thickness of surface oxide layer; while the incorporation of nano-α-Al 2O 3 increased the Ni content in the Zn–Ni matrix.

가스 분무법으로 제조된 NixFe100-x(x=40~50) 퍼멀로이 분말 및 압분 코아의 자기적 특성

가슨 분무법으로 제조한 High-Flux형 <TEX>$Ni_{x}Fe_{100-x}$</TEX>(x=40~50, wt.%) 퍼멀로이 분말 및 압분 코아의 자기적 특성을 조사하였다. 포화자화는 45%Ni조성에서 최대 값을 보이며 이보다 보 함량이 낮아지면 인바 효과의 작용에 의해 급격하게 감소하였다. 압분 코아의 투자율은 Ni 농도가 낮아지면 현저히 증가하는 바 이는 자기변형의 감소에 기인하는 것으로 사료되었으며, 자심손실은 Ni=45%에서 가장 낮은 값을 나타내었다. Ni농도가 50%에서 45%로 낮아짐에 따라 자심손실이 감소하는 주원인은 전기 비저항의 증대에 따른 와전류 손실의 감소에 있는 것으로 생각되었다. Ni=45% 분말 합금으로 만든 압분 코아는 Ni=50%의 경우보다 더 우수한 투자율의 주파수 의존성, 큰 Q 값, 그리고 더 나은 직류 바이어스 특성을 나타내어 상용 High-Flux 코아(50%Ni-50%Fe)에 비해 더 좋은 압분 자심 재료가 될 수 있음을 확인하였다. We investigated the magnetic properties of High Flux-type <TEX>$Ni_{x}Fe_{100-x}$</TEX>(x=40∼50, wt.％) permalloy powders and dust cores. The powder was prepared by conventional gas atomization in mass production scale. At the composition of <TEX>$Ni_{x}Fe_{55}$</TEX>, saturation magnetization was maximum. In case of lower Ni content than X=45, the <TEX>$M_{s}$</TEX>, decreased largely with the decrease in Ni content, which is due to the invar effect. The permeability of compressed powder cores increased with the decrease in Ni content, which was considered to be due to the decrease in the magnetostriction. In addition, the dust core with Ni=45％ showed the lowest core loss because of the increase in electrical resistivity leading to the low eddy current loss. From the better frequency dependence of permeability, larger Q value and superior DC bias characteristics of Ni=45％ than those of Ni=50％ core, it was confirmed that the 45％Ni-55％Fe powder alloy was better material for the dust core than commercial High Flux core materials.

Preparation and properties of TiC-Ni cermets using Ni-plated TiC

TiC powders were coated with Ni by a chemical plating technique and the pressed compacts sintered at 1623K. The density of the sintered bodies was 98–99%. Compared with mechanically-mixed powder, Ni-plated TiC powders gave a more uniform microstructure in which TiC particles were well dispersed in the Ni matrix. The cermets exhibited ductile fracture for TiC-70 vol.% Ni and brittle fracture for TiC-30 vol.% Ni. The flexural strength was improved by the homogeneous dispersion of TiC. The thermal expansion coefficient increased with a decrease in Ni content, following a nearly linear law of mixtures on the basis of volume fractions of pure TiC and Ni.

The effect of Cu addition on the structure and mechanical properties of AlNiM (M  Ce or Nd) amorphous alloys containing nanoscale f.c.c.-Al particles

The crystallized structure and mechanical strength of amorphous Al 87Ni 7Cu 3Ce 3 and Al 87Ni 7Cu 3Nd 3 alloys were examined with the aim of clarifying the effect of the replacement of Ni by Cu. These amorphous alloys crystalline via a two-stage process: Al + amorphous phase and Al + compounds. The replacement extends the temperature region in which the Al phase precipitates, causing a decrease in particle size from 10 to 3 nm. These changes are presumably due to the following two factors: (1) the difficulty of growth of Al particles resulting from the necessity of redistribution of Cu at the amorphous-Al interface, and (2) an increase in the nucleation sites of the Al phase resulting from the apparent increase in Al content due to the decrease in Ni content as well as to the addition of Cu which is soluble in the Al phase. The homogeneous dispersion of the smaller Al particles causes a more significant increase in σ f and H v compared with the amorphous single phase, and the highest σ f and H v are 1460 MPa and 480 respectively, for the AlNiCuNd alloy annealed for 60 s at 436 K. It is thus concluded that the replacement of Ni by Cu in AlNiLn (Ln  Ce or Nd) alloys is effective in increasing σ f through refinement of the Al particle size.