Showing papers on "Nickel boride published in 2007"

Properties of Core−Shell Ni−Au Nanoparticles Synthesized through a Redox-Transmetalation Method in Reverse Microemulsion

Abstract: Core−shell Ni−Au nanoparticles were chemically synthesized through a redox-transmetalation method in reverse microemulsion. The powder X-ray diffraction patterns revealed the presence of crystalline gold and nickel and the absence of any nickel oxides, nickel boride or other byproducts. The core−shell structure could be clearly observed by the transmission electron microscope. In addition, the Ni cores and the gold shells were further verified by the high-resolution transmission electron microscope and the Z-contrast image. The diameter of the nanoparticles ranged from 15 to 30 nm, with 5−10 nm core diameters and 5−10 nm shell thickness. The UV−visible absorption spectra of these nanoparticles showed a red shift (relative to pure gold nanoparticles), also in agreement with the gold shell morphology. For magnetic properties, the zero-field-cooled and field-cooled temperature dependence of the magnetization indicated the blocking temperature was at 16 K. The magnetization curves carried out at 5 K showed th...

Catalytic properties of bimetallic NiCoB nanoalloy catalysts for hydrogenation of p-chloronitrobenzene

Abstract: Nanosized NiCoB amorphous alloy catalysts with Co/Ni ratios varying from 0 to 3 were prepared by chemical reduction of nickel acetate and cobalt acetate with sodium borohydride in methanolic solution at room temperature under N2 gas with vigorous stirring The catalysts were characterized by nitrogen sorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and X-ray photoelectron spectroscopy (XPS) NiCoB catalysts were tested for liquid-phase hydrogenation of p-chloronitrobenzene (p-CNB) The liquid-phase hydrogenation of p-CNB was carried out at 12 MPa hydrogen pressure, 373 K reaction temperature, methanol as reaction medium, 500 rpm stirring speed, 02 M p-CNB and 2 mmol Ni catalysts The molar ratios of Co/Ni in the starting materials affected the concentrations of boron bounded to the nickel and cobalt metals, resulting in the change of surface area, electronic structures of the metals and catalytic activities of the catalysts Nickel is enriched on the surface Doping Co in NiB decreased the particle size and increased the stability of the NiCoB amorphous alloys Doping Co in NiB increased the boron content, which in turn increased the electron density of Ni The sample NiCoB(1:01) (the value in the bracket is the Ni:Co ratio in bulk) had the highest surface area of 235 m2/g and the smallest particle size TEM micrographs show that Co can reduce the particle size of NiB catalyst DSC patterns demonstrated that the addition of cobalt suppressed the growth of crystalline structure of NiB Adding small amount of cobalt to the NiB catalyst increased the surface area and reaction activity, but decreased the selectivity for the desired product, p-chloroaniline (p-CAN) However, overdosed cobalt had an opposite effect on Ni catalyst, ie, reduced the reaction activity and increased the selectivity for p-CAN The Co-dopant could weaken the extent of electron donation from the Ni atoms to the aromatic ring in p-CAN, which would further suppress the hydrodechlorination of p-CAN The selectivity for p-CAN was also a function of conversion of p-CNB Based on the electron transfer between elemental nickel and boron, NiCoB(1:01) had the most d-band electrons and the highest activities in hydrogenation of nitro group and dechlorination The results can be interpreted by the electronegativity of the functional groups

Controlled Synthesis of Supported Nickel Boride Catalyst Using Electroless Plating

Abstract: The supported nickel boride (Ni−B/MgO) catalysts have been synthesized using electroless plating method. The effects of reaction parameters including the molar ratios of the starting materials, pH value of the plating solution, and the additives have been systematically studied. The catalysts have been characterized by various techniques such as inductively coupled plasma atomic emission spectrometry, high-resolution transmission electron microscopy, scanning electron microscopy, and chemisorption of hydrogen. The hydrogenating properties were evaluated using the liquid-phase hydrogenation of sulfolene and acetophenone. We found that (1) the size, compositions, and load of porous Ni−B nanoparticles depended on the starting ratio of ethylenediamine/Ni2+ and pH value; (2) the addition of stabilizer to plating solution resulted in changing from a porous Ni−B particle to a solid one, (3) the surface properties of supported Ni−B catalysts depended on their sizes, loading, and compositions, and (4) the hydrogen...

Effect of nickel boride additive on simultaneous densification and phase decomposition of TiB2–WB2 solid solutions by pressureless sintering using induction heating

Abstract: Short time process of simultaneous densification and phase decomposition of TiB 2 –WB 2 solid solutions by pressureless sintering using induction heating has been investigated. The products were obtained by sintering of mixture powder compacts of (Ti,W)B 2 with nickel and boron (Ni/B = 3/1) varying between 0 and 7.5 wt.%. It was found that the presence of nickel boride as an additive markedly enhances the kinetics of the subsequent densification and decomposition from the (Ti,W)B 2 single phase to the two phases of (Ti,W)B 2 and (W,Ti)B 2 . The sintered products were evaluated using X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy analysis. In an addition of 7.5 wt.%, the product with a relative density of 91% is produced by induction heating for only 600 s. The mechanical properties of the product, which improved by densification and decomposition of (Ti,W)B 2 , is also presented.

7,11-diaryl-2,4-diazaspiro〔5.5〕undecane-1,5,9-triones: a new series of spiroheterocycles

Abstract: A novel two step synthesis of 7,11 -diaryl-2,4-diazaspiro[5.5]undecane-1,5,9-triones has been reported based on double Michael addition of 2-thiobarbiturates or N,N'-diaryl-2-thiobarbiturates with dibenzalacetones followed by reductive desulfurization with nickel boride.

Inhibitor of lead-induced stress corrosion cracking comprising nickel boride in secondary side of steam generator tubes in nuclear power plants and inhibition method using the same

Abstract: This invention relates to an inhibitor of lead-induced stress corrosion cracking including nickel boride in the secondary side of steam generator tubes in nuclear power plants and an inhibition method using the same, and more particularly, to an inhibitor of lead-induced stress corrosion cracking, in which nickel boride is added to secondary side cooling water of the steam generator in an amount of 0.2˜6 g/l, and to an inhibition method using the same. According to this invention, when the inhibitor of lead-induced stress corrosion cracking is added to the secondary side of the steam generator tube in nuclear power plants, stress corrosion cracking of the tubes, which occurs in the lead-containing neutral or caustic solution, and a crack growth rate are decreased, thus increasing elongation. Further, a stress corrosion cracking ratio is decreased, and therefore the stress corrosion cracking resistance of metal or alloy can be improved. Therefore, nickel boride can be usefully used as an inhibitor of lead-induced stress corrosion cracking of the steam generator tubes in nuclear power plants.

Stereoselective Debromination and Selective Reduction of vic‐Dibromides with Nickel Boride.

Abstract: A simple procedure is reported for the stereoselective debromination of vic-dibromides with nickel boride at ambient temperature. Debromination with concomitant reduction of vic-dibromides to give ...

A Novel Two‐Step Synthesis of 3,4‐Dihydro‐4‐oxo‐5H‐pyrano[2,3‐d]pyrimidines.

Abstract: A novel two step synthesis of 5,7-diaryl-3,4-dihydro-4-oxo-5H-pyrano[2,3-d]pyrimidines has been reported based on condensation of 2-thiobarbiturates with chalcones followed by reductive desulfurization of 5,7-diaryl-1,2,3,4-tetrahydro-4-oxo-2-thioxo-5H-pyrano[2,3-d]pyrimidines with nickel boride.