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[Display omitted] • Solvothermal treatment on flake Cu-Ag powder was performed. • Anti-oxidation performance of powder was investigated. • The treatment significantly enhanced the oxidation resistance of powder. • This was ascribed to the reaction between Cu matrix and sodium formate solution. • A [Cu(μ.HCOO)(OH) 2 ] 2 layer was generated on the surface of powders during treatment. Cu-Ag flake powders demonstrate strong potential applying as the conductive phase in conductive polymer composite due to the good combination properties of electrical conductivity and anti-oxidation performance. In this study, the influence of solvothermal treatment in sodium formate on the surface microstructure and anti-oxidation performance of flake Cu-Ag powder was investigated systematically. The results indicated that solvothermal treatment at 200℃ for at least 16 h significantly enhanced the oxidation resistance of the aged Cu-5Ag flake powder in air, which was ascribed to the reaction between Cu matrix and sodium formate solution to create a [Cu(μ.HCOO)(OH) 2 ] 2 layer on the surface of powders and precipitated Ag along GBs during aging treatment. During the oxidation process, the [Cu(μ.HCOO)(OH) 2 ] 2 formed on the surface of flake powders provided cathodic protection to Cu atoms, and the precipitated Ag along GBs blocked the diffusion channels of Cu and O atoms, which resulted in exceptionally high anti-oxidation performance up to 283℃ of Cu-Ag flake powders. [ABSTRACT FROM AUTHOR]

• Characteristics of various PREP powders were investigated by CT. • Higher powder fluidity at low rotation speed than high rotation speed. • Fraction of hollow particle is dependent on particle size. • Alloy type plays a key role on hollow particle fraction. Flowability, particle size distribution and particle inner pore features for powders of Ti-6Al-4V, 316-steel, and Co-29Cr-6Mo alloys produced by plasma rotating electrode process (PREP) at various rotation speeds are analyzed by using scanning electron microscopy (SEM) and synchrotron X-ray computed tomography (CT). The results show that powder flowability is related to particle size distribution, surface morphology and dynamic friction coefficient of the alloy itself. This results in the higher powder flowability at low rotation speed than that at high rotation speed. Average particle size is roughly proportional to the square root of the reciprocal of rotation speed. In addition, particle size has an important effect on the particle porosity and the number faction of hollow powder in coarse powder is obviously larger than that in fine powder. Meanwhile, the alloy composition also plays a key role on porosity due to the various surface tension of alloys. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ag precipitation in particle surface is dependent on size at low temperature. • Ag precipitation was independent on particle size at high temperature. • Ag diffusion at low temperature is dominated by surface and GB diffusion. • Ag network in particle surface improve the oxidation resistance of powders. Ag precipitation and the resultant oxidation behavior of Cu-5wt.%Ag powder of various particle sizes were investigated. During low-temperature aging (250 ℃), Ag precipitation along grain boundaries (GBs) in particle surface is closely dependent on particle size. The depth of Ag precipitation-free area (Ag-PFA) are 0 μm, 1.17 μm and 2.78 μm for S, M and L samples, respectively. While for high-temperature aging (550 ℃), the Ag precipitation was independent on particle size. This is ascribed to that Ag diffusion in particles at low temperature is dominated by both surface diffusion and GB diffusion, while at the higher temperature, the volume diffusion also becomes dominant. The formation of a continuous 3D-Ag network along GBs in particle surface can significantly improve the oxidation resistance of powders. [ABSTRACT FROM AUTHOR]

[Display omitted] • Flake Cu-5Ag powder was prepared by ball milling. • Aging is effective to enhance oxidation resistance of powder. • Ag precipitated along grain boundaries and in the interior of grains after aging. • Ag hindered the inward diffusion of O through the defects during oxidation. In this study, flake Cu-5Ag alloy powder with mean diameter-thickness ratio (D / T) higher than 110 were successively prepared by ball milling. Effect of milling time on the morphology and D / T of flake powder was investigated in detail. The subsequent aging treatment at 400 ℃ was proved to be effective in enhancing the oxidation resistance of flake Cu-5Ag powder. After oxidation at 300℃ for 10 min, the oxygen content in the surface of aged Cu-5Ag flake powder was reduced by approximately 50 % compared to the as-milled Cu-5Ag flake powder. The aging enhanced the precipitation of Ag phase along the grain boundaries and in the interior of grains, which could act as hindrances to the preferential inward diffusion of oxygen along the defects during oxidation. [ABSTRACT FROM AUTHOR]