Ni 2B Research Articles

A study of mechanism of nickel interferences in hydride generation atomic absorption spectrometric determination of arsenic and antimony

Studies have been carried out to clarify the mechanism of nickel interferences in the hydride generation atomic absorption spectrometric determination of arsenic and antimony. The most serious nickel interferences are observed when nickel/nickel boride nanoparticles are produced during NaBH 4 reduction. In this study these particles have been observed to have diameters of less than 40 nm and sorb As(III), As(V) and Sb(III) species rather than arsine and stibine generated as so far assumed. Bulk chemical composition and surface structure of these nanoparticles were studied and it was found that if the NaBH 4 reduction is carried out while passing nitrogen through the solution the black nanoparticles were composed of Ni 2B and, if the reduction is carried out under air the black nanoparticles were found to consist of Ni 3B or possibly a mixture of Ni(0) and Ni 2B. Surface analysis studies with scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray photoelectron spectrometry and X-ray diffraction analysis have shown that the particles have amorphous structure consisting of Ni(0), Ni 2B, Ni 3B and Ni(OH) 2. However, sorption studies have shown that Ni(0) and Ni(OH) 2 do not sorb the analyte ions and arsine and stibine significantly.

Fabrication of nickel boride-coated carbon nanotube films by electrophoresis and electroless deposition for electrochemical hydrogen storage

Network-like carbon nanotube (CNT) films free of polymer binder were deposited directly onto a stainless steel substrate by electrophoresis. Results of experiments indicated that a CNT film with duplex surface treatment (nitric acid etching and nickel boride coating) provides satisfactory electrochemical hydrogen storage. Nitric acid treatment increased the hydrogen storage capacity of the CNT film due to the opening of CNTs, the formation of micropores in the CNT surface, and the improvement of surface wettability. Coating the CNT film with nickel boride (Ni 2B) greatly improved the electrochemical activity of the film and consequently increased the hydrogen storage capacity. The optimal amount of nickel boride coating on the CNT film was found to be about 45 wt%. Smaller amounts of nickel boride cannot provide enough electrochemical activity. Excessive nickel boride, on the other hand, leads to a decrease in the number of active sites on CNTs that are available for hydrogen storage.

Elastic and thermodynamic properties of the Ni–B system studied by first-principles calculations and experimental measurements

The elastic and thermodynamic properties of NiB, Ni 2B, Ni 3B, orthorhombic Ni 4B 3(O–Ni 4B 3), monoclinic Ni 4B 3(M–Ni 4B 3), and Ni 23B 6, are calculated via first-principles method for the Ni–B system. The ground state energies, the full sets of elastic constants and the associated macroscopic elastic parameters of these Ni–B alloys are computed for the first time. Taking contributions from lattice vibrations and thermally excited electrons into account, thermodynamic properties at finite temperatures are then predicted. In addition, we measure the molar heat capacity at constant pressure for NiB and compare the results with the theoretical predictions. Various calculations demonstrate that the first-principles calculation can be used to clarify the diverse experimental data, and provide reliable thermodynamic data.

Effects of aging on stress-induced martensitic transformation in ductile Cu–Al–Mn-based shape memory alloys

Effects of aging at 473–573 K on stress-induced martensitic transformation for textured Cu 71.9Al 16.6Mn 9.3Ni 2B 0.2 and random-textured Cu 72.1Al 16.9Mn 10.5Co 0.5 shape memory alloy (SMA) wires with a large relative grain size d/ D = 6 were investigated by cyclic tensile testing at room temperature, where d and D indicate mean grain size and wire diameter, respectively. The random-textured Cu 72.1Al 16.9Mn 10.5Co 0.5 wire cannot be uniformly deformed and the ductility is drastically reduced by aging treatment. On the other hand, in the textured Cu 71.9Al 16.6Mn 9.3Ni 2B 0.2 SMA wire, the critical stress for martensitic transformation σ t and the tensile strength σ f are increased by aging without the associated loss of superelasticity (SE). Even in textured wire with a high σ t of over 750 MPa, an excellent SE strain of about 6% can be obtained due to the formation of a fine bainite phase. Moreover, it was confirmed by in situ observation that stress-induced martensite plates grow, accompanying distortion of the bainite plates.

Microstructure analysis of boronized pure nickel using boronizing powders with SiC as diluent

In this study, boronizing of 99.9% pure nickel was performed by means of a powder-pack method using Commercial LSB-II powders (that contained SiC) at 850, 900 and 950 °C for 2, 4, 6 and 8 h, respectively. The coated samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and hardness tests. The presence of boride (Ni 2B) and silicide (Ni 5Si 2, Ni 2Si) phases, formed on the surface of boronized pure nickel, were confirmed by X-ray diffraction analysis. The Ni 3Si phase was found when pure nickel was boronized at 850 °C for 2 h. Depending on boronizing time and temperature, the thickness of coating layer ranged from 36 to 237 μm. The hardness values were 832 HV 0.01 for the silicide layer, 984 HV 0.01 for boride layer, and 139 HV 0.01 for the Ni substrate.

Microstructure and property investigation of paste boronized pure nickel and Nimonic 90 superalloy

In the present work, pure nickel (99.5%) and a Ni-superalloy (Nimonic 90) have been boronized by a self-protective paste, and the effect of the boronizing parameters on the phase constituents (type and morphology) has been investigated. For the Nimonic 90 alloy, the experimental results showed that the employed temperature and time have no evident effect on the phase constituents of the boride layers, i.e., CrB and Ni 2B. By contrast, the growth of CrB was substantially influenced by the temperature and time, as was also the microhardness of the boride layer. Based on these observations, optimum temperature and holding time were determined for boronizing of Nimonic 90. For both pure Ni and Nimonic 90, the surface microhardness of the two materials was significantly raised after boronizing, i.e., from 100 HV 0.1 to 1100 HV 0.1 and from 400 HV 0.1 to 2500 HV 0.1 for the two alloys, respectively. In addition, seawater corrosion tests indicated that the corrosion resistance of the boronized pure nickel was slightly improved, while the corrosion resistance of boronized Nimonic 90 was somewhat reduced.

An investigation on boriding kinetics of AISI 316 stainless steel

Boronizing was performed by using a solid medium of Ekabor powders at 1073, 1148 and 1223 K for 2, 4 and 8 h. After boronizing, the major dominant phase was found to be Fe 2B and the minors were CrB and Ni 2B. Boride coating resulted in smooth and dense feature confirmed by optical and SEM. The thickness of boride layer varied from 7 to 87 μm depending on the process time and temperature. Boride layer has a hardness of over 1700 HVN, while the substrate's hardness was about 180 HVN. The growth kinetics of boride layer was found to obey a parabolic rate demonstrating a solid diffusion limited process. The kinetic rates for different process times were plotted by using Arrhenius equation. From this measurement, the activation energy of boride growth for this study was determined as 199 kJ/mol. In addition, the possibility of predicting the iso-thickness of boride layer variation was studied and an empirical relationship between process parameters and boride layer thickness was established. EDS studies showed that Cr concentrated in the coating layer and Ni and Fe concentrated in the substrate.

Nanocrystalline Ni–B coating surface strengthening pure copper

An electroless deposition technique is used to synthesize nanocrystalline Ni–B coating in strengthening the surface of pure copper. The microstructure and some properties of Ni–B coating are studied. It is practicable to coat a uniform and continuous nanocrystalline Ni–B hardening layer on copper surface by this technique, Ni 2B and Ni 3B are formed in the Ni–B coated layer during heat treatment, and the average grain size of nanocrystalline Ni–B coating is about 42–65 nm and properties of the prepared copper alloys are also improved.

Surface strengthening pure copper by Ni-B coating

An electroless deposition technique is used in strengthening the surface of pure copper. The microstructure, the effect of chemical composition of the coating bath on Ni-B deposition rate and some properties of Ni-B coating are studied. It is practicable to coat a uniform and continuous Ni-B hardening layer on copper surface by this technique. The coating rate is controlled mainly by the concentration of NiCl 2, KBH 4, NaOH, Pb(NO 3) 2 and H 2NCH 2CH 2NH 2. The phase structure of Ni-B coating is a nickel—supersaturated solid solution, and Ni 2B and Ni 3B are formed in the Ni-B coated layer during heat treatment where the microhardness of the coating is improved. The Ni-B coating has a little effect on the specific resistance of the pure copper.

Formation and characterization of borohydride reduced electroless nickel deposits

The present work aims to study the formation of electroless Ni-B deposits and evaluation of their characteristic properties. An alkaline bath having nickel chloride as the source of nickel and borohydride as the reducing agent was used to prepare the electroless Ni-B deposits. The influence of variation in bath constituents as well as operating conditions on the plating rate, and, the nickel and boron content, of the resultant Ni-B deposits were studied. Selected deposits were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), evolved gas analysis (EGA), vibrating sample magnetometer (VSM) and transmission electron microscope (TEM), respectively, for assessing the phase content, phase transformation behaviour, liberation of hydrogen during crystallization, saturation magnetic moment and micro-structural features. The corrosion resistance of Ni-B deposits, in 3.5% sodium chloride solution, both in as-plated and heat-treated (450 °C/1 h) conditions, was also evaluated by potentiostatic polarization and electrochemical impedance studies. XRD patterns reveal that Ni-B deposits of the present study are amorphous in as-plated condition and undergo phase transformation to crystalline nickel and nickel borides upon heat-treatment. DSC traces exhibit two exothermic peaks at 306 and 427 °C, corresponding to the phase transformation of amorphous Ni-B to crystalline nickel and Ni 3B phases and the transformation of a higher phase compound to Ni 3B and Ni 2B, respectively. TEM microstructures and EGA strongly support the occurrence of phase transitions at 306 and 427 °C. Electroless Ni-B deposits demonstrate a moderate corrosion resistance in 3.5% sodium chloride solution. The extent of corrosion resistance offered by electroless Ni-B deposits is relatively less compared to electroless Ni-9 wt.% P deposit.

Stereoselective reduction of arteannuin B and its chemical transformations

Absolute stereochemistry of dihydroarteannuin B 5 obtained by the reduction of arteannuin B 3 with Ni 2B, NaBH 4 or CdCl 2–Mg–MeOH–H 2O has been established by 2D NMR and single crystal X-ray diffraction studies. Some experiments aimed at the synthesis of dihydrodeoxyarteannuin B [C-4, 5 double bond isomer of 11 ] are also discussed.

Thermally sprayed Ni(Cr)–TiB 2 coatings using powder produced by self-propagating high temperature synthesis: microstructure and abrasive wear behaviour

High velocity oxy-fuel (HVOF) thermal spraying was used to deposit Ni(Cr)–TiB 2 cermet coatings onto steel substrates from a feedstock powder produced by a self-propagating high-temperature synthesis (SHS) reaction. The powder and coating microstructures were investigated by scanning electron microscopy and X-ray diffraction (XRD), whilst dry sand rubber wheel abrasive wear and microhardness tests were performed on the coatings. The SHS reacted powder was found to comprise principally 1–5 μm sized TiB 2 in a crystalline, Ni-based solid solution matrix, with approximately 60 vol.% TiB 2 and 40 vol.% metallic binder. XRD revealed the presence of only around 2% of the following phases: TiB, Ni 2B, NiTi, TiO. The reacted compact was crushed, ground and classified into a powder of size range (+8 to −38) μm for thermal spraying. The HVOF sprayed deposits had layered, splat-like morphologies typical of thermally sprayed cermets. The coating microstructure consisted primarily of TiB 2 in the Ni-rich binder phase but the boride fraction was reduced compared to that of the feedstock powder as a result of TiB 2 dissolution in the molten alloy during spraying. XRD analysis of the coating indicated that the binder solidified to, in part, an amorphous/nanocrystalline structure with ∼2% of Ti-containing oxide phases also present. The TiB, Ni 2B and NiTi phases were not detected in the coating. Under the wear conditions employed, angular alumina generated significantly higher wear rates than the rounded silica abradent, and the wear mechanism changed from microcutting with alumina to pull-out with silica. The wear coefficients obtained with the coating were significantly reduced compared with those of mild steel, in the case of alumina abrasive a factor of four reduction. Additionally, a significant improvement in wear resistance was also found when compared to HVOF-sprayed chromium carbide–nickel/chromium cermet coatings produced from commercially available powders.

Calculated phase diagram of the Ni–Mo–B ternary system

The phase diagram of the Ni–Mo–B ternary system in the region of less than 50 mol%B was constructed by thermodynamic calculation. We found three ternary eutectic points and three ternary peritecto-eutectic points as follows: E 1: L(1365 K, 71.5 mol%Ni–6.0 mol%Mo–22.5 mol%B)=(Ni)+Ni 3B+NiMo 2B 2. E 2: L(1355 K, 62.5 mol%Ni–2.5 mol%Mo–30.5 mol%B)=Ni 3B+Ni 2B+NiMo 2B 2. E 3: L(1445 K, 42.0 mol%Ni–30.6 mol%Mo–10.3 mol%B)=(Ni)+NiMo+NiMo 2B 2. P 1: L(1812 K, 34.9 mol%Ni–42.3 mol%Mo–22.8 mol%B)+MoB=Mo 2B+NiMo 2B 2. P 2: L(1633 K, 42.3 mol%Ni–40.4 mol%Mo–17.3 mol%B)+Mo=Mo 2B+NiMo 2B 2. P 3: L(1478 K, 53.5 mol%Ni–33.7 mol%Mo–12.8 mol%B)+Mo=NiMo+NiMo 2B 2. The calculated phase diagram is expected to be useful for the development of new Ni-based heat-, corrosion- or wear-resistance alloys.

The characterization of borided 99.5% purity nickel

A series of experiments were performed to evaluate some properties of borided 99.5% purity nickel. Boronizing was carried out in a solid media consisting of Ekabor powders at 950°C for 2, 4, and 8 h, respectively. Data on intermetallic silicides and borides (Ni 5Si 2, Ni 2B) that formed on the surface of nickel substrate during boronizing were confirmed by a classical metallographic technique and X-ray diffraction (XRD) analysis. It was observed that the predominant phase in the coating layer was a silicide. It is probable that the formation of the nickel silicide layer was due to silicon in the boronizing powder. The hardness of silicides was measured by using a Vickers indenter with a load of 0.5 N. The microhardness of silicides formed on the surface of the nickel substrate reached up to 805 HV. Metallographic studies revealed that the silicide layer has an equiaxed granular morphology, whereas the boride layer formed had a needle-shaped structure. Depending on process temperature and boronizing time the thickness of coating layers ranged from 123 to 281 μm. The thickness of silicide and boride layers depended strongly on the processing time at 950°C. The longer boronizing time resulted in the thicker surface layer. The distribution of alloying elements from the surface to the interior was determined using energy dispersive X-ray spectroscopy (EDS).

Magnetic properties of the quaternary intermetallic compounds RNiBC (R=Ho, Dy, Tb, Gd, Dy 1− xGd x)

The structural, resistive (2 K< T<300 K) and magnetic properties (2 K< T<300 K, H<80 kOe) of RNiBC ( R=Ho, Dy, Tb, Gd, Dy 1− x Gd x [ x=0.25, 0.5, 0.75]) were investigated and compared with the structurally related RNi 2B 2C series. The crystal structure is LuNiBC-type (space group P4/nmm) wherein the unit-cell a-axis parameter and volume increase linearly with the R 3+ ionic radius as expected from the lanthanide contraction. On the other hand the c-parameter, different from that of RNi 2B 2C, show a quasi-constant R-dependency. For T>2 K, none of the studied RNiBC is superconducting. The R 3+ free-ion magnetism is observed for T>100 K, however, due to crystal field effects, a considerable reduction in the saturated R 3+ magnetic moments (Gd 3+ is an exception) is observed at low T. Furthermore, their magnetic critical temperatures, T C, do not show a strict scaling with the de Gennes factor as expected for localized RKKY-coupled 4f-moments: in RNiBC de Gennes scaling is satisfied for R=Er, Ho and Dy but violated for R=Tb, Gd and Dy 1− x Gd x while, in contrast, T C for RNi 2B 2C follows reasonably this scaling. Such a trend in the R-dependency of T C and of the c-parameter in RNiBC will be discussed in terms of the characteristic stacking-pattern of their RC and Ni 2B 2 sheets.

Investigation on the microstructure of spray coating

Thermal spraying has been used in industry for many years to improve the properties of the surface of a workpiece such as its mechanical and electrical properties and its corrosion resistance. Most of the literature on spray coating has reported spraying techniques, and the properties of the coatings, the literature on microstructure investigation still being weak. In this paper the authors lay emphasis on the microstructure of the coating layer, and the constituents of the phases and their distribution within the coating. By observations using the transmission electron microscope and electron diffraction pattern analysis, two solid solutions (γ and NiCr), and some compounds (M 23C 6, Ni 2B, CrB, Cr 6Ni 16Si 7) have been found in the coating layer.

Anharmonic excitations in high Tc materials

Some chains of atoms in YBa 2Cu 3O 7, Y 2Ba 4Cu 6O 13 and La 2CuO 4 behave as quasi-one-dimensional structures in which anharmonic self-focusing breathers can propagate. Such breathers have no threshold energy and are created in response to perturbations of the lattice by charge movement and in charge self-trapping. The creation and directionally selective propagation of such breathers occurs whatever the charge pairing mechanism. The presence of quasi-one-dimensional chains appears to be a necessary structural condition for high T c behaviour in the layered family based on (Ni 2B 2).

A new coupling reaction of alkyl iodides with α,β-unsaturated esters using Ni 2B(cat.)-BER in methanol

Alkyl iodides can be coupled with α,β-unsaturated esters using Ni 2B(0.05–0.2 eq)-BER(3 eq) in methanol at room temperature. Products (68–95%) are conveniently isolated, simply filtering the resin and evaporating the excess enoates and methanol.

An excellent nickel boride catalyst for the cis-selective semihydrogenation of acetylenes

Internal alkynes were hydrogenated quantitatively to the corresponding cis-alkenes over nickel boride (Ni 2B), prepared on borohydride exchange resin (BER) in methanol under hydrogen atmosphere. Further hydrogenation was very slow under the reaction conditions, and pure cis-alkenes were conveniently isolated in excellent yields. Hydroxy and ester functional groups did not interfere with the semihydrogenation.

Neutron powder diffraction study of the 12 K superconductor La 3Ni 2B 2N 3− x

The structure of superconducting La 3Ni 2B 2N 3− x has been investigated by neutron powder diffraction methods at room temperature. The compound crystallizes with the symmetry of space group I4/mmm (No. 139) and lattice parameters a = 3.72512(5) and c = 20.5172(4)Å. The structure is layered and is made of (LaN) (LaN) (LaN) blocks with the rock-salt configuration alternating along the c-axis with Ni 2B 2 blocks having a fluorite-type arrangement of the atoms. The nitrogen site located on the central layer of the rock-salt block is only 90% occupied, yielding stoichiometry La 3Ni 2B 2N 2.9. Layers are connected to each other along the c-axis by La N, B N and Ni B bonds, while the connections within the layers are provided by La N and Ni Ni bonds.