Novel confinement combustion method of nanosized WC/C for efficient electrocatalytic oxygen reduction

Nanosized tungsten carbide(WC)/carbon(C)catalyst was synthesized via a novel ultra-rapid confinement combustion synthesis method.The amount of activated carbon(AC)plays an important role in the morphology and structure,controlling both the precursor and final powder.The WC particles synthesized inside the pores of the AC had been 10-20 nm because of the confinement of the pore structure and the large specific surface area of AC.When used for oxygen reduction performance,the half-wave potential was−0.24 V,and the electron transfer number was 3.45,indicating the main reaction process was the transfer of four electrons.The detailed electrocatalytic performance and underlying mechanism were investigated in this work.Our study provides a novel approach for the design of catalysts with new compositions and new structures,which are significant for promoting the commercialization of fuel cells.

钨铜梯度材料热震过程中显微组织及热性能

针对目前W-Cu功能梯度材料(FGM)在长期热震循环过程中的稳定性缺乏相应研究的问题,以化学镀W-10wt%Cu复合粉体和Cu粉为原料,通过叠层压制和常压气氛烧结的工艺制备了W-10wt%Cu/W-20wt%Cu/W-30wt%Cu层状梯度材料。在600℃、800℃、1000℃温度下进行热震试验,对试样在不同热震温度、热震次数下的显微组织和热学性能变化进行了研究。试验结果表明,随着热震温度升高,渗出至试样各梯度层表面的Cu逐渐增加。当热震温度达到1000℃时,试样各梯度层表面出现大量Cu聚集成片的现象,同时在W-20wt%Cu/W-30wt%Cu界面处发现了界面裂纹。随着热震次数的提高,在W-10Cu层中,Cu逐渐渗出表面并在内部留下微孔。此外,W-Cu FGM的热导率随热震次数的增加而减小,在1000℃经过200次热震后,室温热导率由200.54 W·(m·K)^(−1)降至159.23 W·(m·K)^(−1),降低了20.60%。该结果揭示了热震循环中裂纹形成与显微组织变化的耦合失效机制,明确了W-Cu FGM安全服役的范围。