The hot deformation behavior of Al-Zn-Mg-0.25Sc-Zr alloy and its microstructural evolution were investigated by isothermal axisymmetric hot compression tests at temperatures from 340 to 500°C and strain rates ranging from 0.001 to 10 s -1 .The steady flow stress increased with increasing the strain rate or decreasing the deformation temperature,which can be described by a hyperbolic-sine constitutive equation with the deformation activation energy of 150.25 kJ/mol.The tendency of dynamic recrystallization enhanced at high deforming temperatures and low strain rates,which corresponded to low Z values.With decreasing Z value,the main softening mechanism of the alloy transformed from dynamic recovery to dynamic recrystallization, correspondingly,the subgrain size increased and the dislocation density decreased.
利用可再生电力将二氧化碳转化为高附加值产品的电催化二氧化碳还原反应(CO_(2)RR)是一项具有革命性潜力的技术,因而备受关注.其中,一氧化碳被视为CO_(2)RR中最具经济效益的产物之一,可直接利用费托合成工艺将其用于合成醛、酮、烃类等产品.酞菁钴(CoPc)作为单位点催化剂,因其高原子利用率和高催化选择性能,在二氧化碳转化为一氧化碳过程中具有很大优势.然而,CoPc无法为CO_(2)RR中的质子化过程提供足够质子,导致其在工业大电流密度下的效率较低.因此,探索一种能够解决CO_(2)RR中质子供给不足问题的高效电催化剂对于提升CO_(2)RR的性能至关重要.本文设计了具有增强质子供给作用的缺陷碳纳米管(d-CNT),将其作为导电载体分散CoPc,用于制备CoPc/d-CNT电催化剂.通过引入富缺陷的碳纳米管(d-CNT),加速水解离进而增加CO_(2)RR的质子供给量.X射线光电子能谱、X射线吸收近边光谱和扩展X射线吸收精细结构谱结果表明,CoPc/d-CNT成功合成,同时保留了CoPc完整的Co-N4配位结构.透射电镜、粉末X射线衍射谱和拉曼光谱共同表明,d-CNT表面缺陷相对于商用CNT明显增加.动力学实验和原位衰减全反射表面增强红外吸收光谱研究表明,含大量缺陷的d-CNT具有加速水解离的能力,显著提高了二氧化碳还原反应过程中的质子供给,从而促进了CoPc_上CO_(2)活化生成*COOH.同时,密度泛函理论计算结果表明,d-CNT表面缺陷位点上从吸附水(*H2O)到质子水(H3O+)的吉布斯自由能为0.74 eV,远低于CNT(超过2 eV),表明d-CNT促进了水解过程和质子传递,再次证实了d-CNT降低了水分子解离的势垒.通过实验和理论的共同验证,阐明了d-CNT中的缺陷能够促进水解离,改善CO_(2)RR反应过程中质子供给,增强CoPc高效催化CO_(2)RR的能力.因此,CoPc/d-CNT混合材料表现出较好的催化性能.在电流密度为500 mA cm^(-2)的流动电池中,CoPc/d-CNT�
Al-5.8Mg-0.4Mn-0.25Sc-0.1Zr （mass fraction, %） alloys were prepared by water chilling copper mould ingot metallurgy processing which was protected by active flux. The recrystallization temperature and nucleation mechanism of the alloy were studied by means of hardness tests, observations of optical microscopy and transmission electron microscopy. The results show that the anti-crystallization ability can be significantly improved by adding minor Sc and Zr into Al-Mg-Mn alloy. This can be proved by a much higher recrystalliztion temperature （450 ~C） than Al-Mg-Mn alloy without Sc and Zr （150 ℃）. The main reason of the great increase of recrystallization temperature can be attributed to the strong pinning effect of highly disperseded Al3（Sc,Zr） particles on dislocations and sub-grain boundaries. The recrystallizing process reveals itself the nucleation mechanism of the alloy involving not only the sub-grain coalescence but also the sub-grain growth.
