Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： The formation of amorphous phase has been investigated in U-Co system over a wide range of compositions, namely, UxCo100-x (x=50~87.5) by mean of melt-spinning. Phase identification for the arc-melted ingots and rapidly quenched alloys, and the thermal stability of the amorphous phases thus formed have been examined by XRD and DSC, respectively. The component phases in the ingot alloys were structurally the same as those presented in U-Co phase diagram, but were associated with a certain compositional metastability. Rapid quenching experiment revealed that the ease of formation of amorphous phase occurred within the composition range of 58.5≤x≤78, and amorphous phase was most readily formed in the vicinity of U66.7Co33.3 composition. The dynamical crystallization temperatures of the amorphous phases were determined to be 534~550 K at a DSC heating rate of 20 K/min, and the highest reduced crystallization temperature (relative to the liquidus temperature) as calculated to be 0.535, and moreover, the exothermal enthalpies of crystallization were determined to be in a range of 4.8~8.5 kJ/mol. Upon room temperature electrochemical polarization in a 50×10- 6 Cl- electrolyte, these amorphous alloys exhibited corrosion potentials as high as about -50 mV, being much more positive than that of depleted uranium. In these amorphous alloys, it has also been found that the rust resistance performance appears to be parallel to the ease of amorphous phase formation.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： Nanoparticles of carbon encapsulated nickel (Ni@C NPs) were in-situ synthesized by direct current arc-discharge plasma method through evaporating pure Ni in methane atmosphere. Transmission electron microscopy observation revealed that the nanoparticles (Ni@C NPs) exhibited an encapsulation structure with Ni metal as core and carbon 3-5 nm in thickness as shell. The BET surface area of the prepared Ni@C NPs is 38.82 m2穏-1 according to N2 adsorption-desorption isotherm. Surface modification with hydrogen peroxide was carried to graft oxygen-containing groups on carbon, which can improve the wettability and hydrophilicity of the Ni@C NPs. Then the effect of contact time, adsorption time and pH values on the adsorption of methylene blue was systematically investigated with the surface modified Ni@C NPs as adsorbent. The adsorption kinetics was analyzed with pseudo-first-order and pseudo-second-order models and the adsorption isotherm of methylene blue onto Ni@C NPs was fitted by Langmuir and Freundlich models. In addition, the result of recycling experiments for 5 cycles showed that a recovery rate 69.4% for the adsorbent could be reached. Furthermore, results of trial separation of Ni@C NPs by applied magnetic fields show that the magnetic field assisted separation technology is efficient means for the recycling and reuse of this adsorbent.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-18 Cooperative journals: 《材料研究学报》
Abstract： Fe-nanoparticles (NPs)/ carbon fibers (CF)/epoxy resin (EP) based composites were designed and fabricated. The microwave absorbers Fe-NPs were prepared by the direct current (DC) arcdischarge plasma method and modified with silane coupling agent KH550. The reflection losses of composites were measured in the frequency range of 2-18 GHz and the effects of Fe-NPs, CF and the geometry feature of test plates on the microwave absorbing properties were investigated. Results show that reflection loss peaks appear at low frequency and the microwave absorbing properties are enhanced due to the addition of CF. With the increasing mass fraction of Fe-NPs the microwave dissipation increases and the reflection loss peaks move towards the low frequency. The concentration gradient of Fe-NPs in EP matrix was caused by gravity during the preparation process and it causes reflection loss differences between the two surfaces of a plate, which is beneficial for microwave to enter the composite plate and be absorbed by properly setting the plate.
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