Morphology and carbon content of WC-6%Co nanosized composite powders prepared using glucose as carbon source

Pure WC-6%Co nanosized composite powders were synthesized via a low-temperature method.The effects of carbon source on microstructure characteristic of composite powders were investigated,and the effects of heat-treatment parameter on carbon content of composite powders were also discussed.The results of SEM and XRD revealed that the carbon decomposing from glucose was more active than carbon black.Therefore,WC-Co nanosized composite powders could be synthesized at 900°C for 1 h under a hydrogen atmosphere.The individual WC grains were bonded together into a long strip under the action of cobalt.The results of carbon analysis revealed that the total carbon content decreased with the increase of the temperature in the range of 800-1000°C.Moreover,the total carbon content and the compounded carbon increased with the increase of the flow rate of H2 in the range of 1.1-1.9 m3/h.

Attaining synergetic equilibrium of electrical conductivity and tensile strength in GQDs@GN/Cu composites through multi-scale intragranular and intergranular reinforcements

The configuration and quality of reinforcements, as well as the robustness of interfacial bonding,holding a critical significance in determining the concurrence between electrical conductivity and mechanical strength in metal matrix composites. In this study, citric acid was employed as the precursor for synthesizing multiscale carbon nanomaterials(graphene quantum dots and graphene, abbreviated as GQDs and GN). The GQDs@GN/Cu composites were fabricated through a segmented ball milling process in conjunction with subsequent spark plasma sintering(SPS). The intragranular GQDs and intergranular GQDs@GN had synergistically reinforced Cu composites through Orowan strengthening, load transfer strengthening and refinement strengthening. Furthermore,the robust interface bonding between GQDs@GN and Cu effectively mitigated interfacial impedance stemming from electron-boundary scattering. The yield strength and ultimate tensile strength of the GQDs@GN/Cu composites were recorded as 270 and 314 MPa, respectively, representing an improvement of 92 and 28% over pure Cu, while maintaining electrical conductivity at a level comparable to that of pure Cu. This study advances the understanding of the possibility of realizing a synergistic compatibility between electrical conductivity and mechanical strength in Cu composites.

Effect of Y_(2)O_(3)doping on preparation ultrafine/nano-tungsten powder and refinement mechanism

In this study,ultrafine/nano W-Y_(2)O_(3)composite powders were synthesized by spray drying,roasting and two-step hydrogen reduction using ammonium metatungstate and yttrium nitrate as raw materials.The mechanism of the influence of Y_(2)O_(3)on the growth of WO_(2.72)and the particle refinement of tungsten powder is discussed.The effect of Y_(2)O_(3)particles on the reduction behavior of tungsten powder was investigated using scanning electron microscopy to study the near surface morphology and X-ray diffraction for phase ID(composition)and crystal structural changes for the reduced powders at each step.The results show that the doping of 0.3 wt.%Y_(2)O_(3)can significantly increase the aspect ratio of WO_(2.72)in the first step of hydrogen reduction.Moreover,Y_(2)O_(3)can effectively inhibit the growth of tungsten particles in the hydrogen reduction process.Therefore,The Y_(2)O_(3)-doped tungsten powders have finer particles and a narrower particle size distribution range than the undoped powders.The average particle diameter of 0.3 wt.%Y_(2)O_(3)doping tungsten powder was in the range of 90-120 nm.