Papers by Keyword: Nickel Powder

Abstract: The authors investigated the mechanical mixing and compacting briquettes of nickel powder (particle size 30...75 μm) and nanopowder modifier SiC+Si₃N₄ (particle size 70...100 nanometers), obtained by the azide technology SHS. The mixtures containing 5%, 10%, 15%, 20% of the modifier were investigated. Mechanical mixing was carried out during 60 minutes in planetary mill «Pulverizette-5». Some physic-technological properties of the obtained powder mixtures, such as, particle size distribution, density, bulk weight and flowability, are determined. The powder compositions' pressing was carried out on hydraulic press PSU-50 with pressure 65...700 MPa. Nanopowder ligature briquettes of 18.2 mm diameter, height to 4.2 mm, weighing 5 grams, with relative density 70...89% and porosity 11...30%, intended for subsequent input in aluminum melt with the aim of modification are obtained.

Abstract: Compacting after pressing and sintering of briquettes made from an aluminum powder with an average particle size from 50 to 150 microns, the specific surface area S_sp=0.26 m²/g and a nickel powder with an average particle size from 25 to 100 microns, the specific surface area S_sp= 0.03 m²/g has been investigated. Pressing load varied from 15 to 25 MPa for the aluminum powder and from 20 to 45 MPa for the nickel powder. Sintering of aluminum powder briquettes was carried out at temperatures (0.5-0.83) of melting temperature, (0.3-0.46) of melting temperature from the nickel powder. It is shown that the application of high pressure, low temperatures and short time makes it possible to receive pseudo-ligatures from an aluminum powder with porosity about 32% and a nickel powder with porosity about 30%.

Abstract: Use Cr15 high chrome steel as base, WC particles as reinforcing particles, and adopting casting-infiltration method, a kind of quite steel-base surface wear-resistant material was prepared. The effect of Alloy powder for WC/steel base surface composite structure and interface was tested by OM, SEM and EDS. The results showed that after adding nickel powder into the composite layer, martensite, austenite, pearlite and eutectic carbide distributed in the matrix; after adding tungsten iron powder into the composite layer, more martensite distributed in the matrix; after adding molybdenum iron powder into the composite layer, martensite, austenite, pearlite and carbide distributed in the matrix. If the base material was high chrome (Cr15) and adds molybdenum iron powder in the composite layer, composite layer interface transition is good, more WC particles and irregular small carbide particles in composite layer.

Abstract: A novel method via electroless silver coating on nickel powders was reported., which introduced reduction reaction using hydrazine as the reducing agent, had some advantages such as inhibiting the substitution reaction and reducing consumption of nickel powders. In the process of dispersion, PVP acted as the dispersant and prevented the nickel powders from agglomerating.The Zeta potential of slurry which determined the dispersibility and the reaction condition was tested.The investigation shows that the grain size of Ag-Ni bimetallic powders is similar to the nickel powders, bimetallic powders possesses fine dispersibility and a continuous silver film is formed on the surface of nickel powders by two-times coating. Morphology of Ag-Ni bimetallic powders, composition of the coated-surface are respectively characterized by SEM and EDX.

Abstract: The shape memory polymer (SMP) materials are able to change these shape in response to external stimulus such as stress, temperature, solvent, PH, magnetic, electricity or light. The above-mentioned methods are only to recover initial shape of the deformed SMP, could not give the SMP predeformation. In this paper, magnetic field gives the shape memory polymer composite (SMPC) pre-deformation was studied, through on and off of magnetic field the two-way activation of SMPC was achieved. Shape memory effect of shape memory composite in magnetic field was studied. The SMPC was filled by nickel powder, and the nickel powder was treated by silane coupling agent. The Tg of shape memory composite was measured by dynamic mechanical analyzer. The surface element of treated nickel powder was analysized with XPS. The results indicated that the shape of composite filled by untreated nickel powder did not change in the magnetic field, while the composite filled by treated nickel powder was drawn in the magnetic field. The tensile stretch was decrease with the increase of nickel powder content in the shape memory composite. The addition of silane coupling agent onto nickel powder surface was helpful for the dispersion of nickel in polymer.

Abstract: Fine nickel powders have been prepared by chemical reduction between nickel acetate and alcohol under solvothermal conditions. The effect of adding surfactant and varying solvent on the particle size of the as-synthesized nickel powders have been explored. SEM, XRD and TG were employed to characterize the size, morphology, crystalline structure and the thermal stability of the as-synthesized nickel powders. It is revealed that the FCC-structured nickel powders are of uniform spherical shape with good crystallinity and thermal stability. Typically, nickel powders with an average size of 300 nm were obtained at 200°C for 8 h using 0.04 mol/L solution of Ni(CH3COO)2·4H2O in n-butyl alcohol under solvothermal conditions.

Abstract: Nickel powders were synthesized by the reduction of hydrazine of nickel salts from diethanolamine (DEA) solution, and the morphological characteristics of nickel powders were investigated with various process conditions such as the addition of hydrazine, reaction temperature, the composition of mixed solvents. The addition of hydrazine in DEA solution largely affected the size control of nickel powders. Under N2H4/Ni2+molar ratio= 1.5 and 2.0 conditions, spherical nickel powders in the submicron range were obtained owing to higher the reduction rate. An increase of temperature increased the size of nickel particles. At 220°C for 40min, the nickel powders were composed of polyhedral particles with a high crystalline in the submicron range. The mixed volume ratio of TEA to DEA solvent improved the inhibition of agglomerate between particles.

Abstract: Nickel powders were prepared by the reduction of hydrazine of Ni(OH)2 reactant slurries from non-aqueous media. The morphological characteristics of nickel powders were investigated under various processing conditions. Nickel powders were characterized by using scanning electron microscope (SEM), X-ray diffractometer (XRD), thermal gravitational analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The size of nickel powders was increased as the reaction temperature and time increased because of the thermal agglomeration of nuclei and/or increased growth rate. The surface of nickel powders composed of both Ni and Ni(OH)2 was oxidized in the temperature range of 400-600°C.