The superconductivity of two-dimensional(2D)materials has extremely important research significance.To date,superconducting transition temperatures(T_(c))of 2D superconductors are still far from practical applications...The superconductivity of two-dimensional(2D)materials has extremely important research significance.To date,superconducting transition temperatures(T_(c))of 2D superconductors are still far from practical applications.Previously,2D MXene Mo_(2)N has been successfully synthesized[Urbankowski et al.Nanoscale 917722,(2017)].We systematically investigate the effects of carbonization and further hydrogenation on the stability,electronic property and superconductivity of 1T-and 2H-M_(2)N(M=Mo,W)based on first-principles calculations.The results show that the 1T-M_(2)N and 2H-M_(2)N(M=Mo,W)are all dynamically and thermodynamically stable after carbonization and further hydrogenation.After carbonization,Tc’s of 1T-M_(2)NC_(2)(M=Mo,W)are all increased,while Tc’s of 2H-M_(2)NC_(2)(M=Mo,W)are all decreased.By further hydrogenation,the Tc’s of 1T-and 2H-M_(2)NC2H2are all increased.Among all of these structures,Tcof 1T-Mo_(2)NC_(2)H_(2)is the highest one,reaching 42.7 K,and the corresponding electron-phonon coupling strengthλis 2.27.Therefore,hydrogenation is an effective method to modulate Tc’s of 2D M_(2)NC_(2)(M=Mo,W)materials.展开更多
用金相显微镜、定量金相、扫描电镜(SEM)、能谱分析(EDX)及 X 射线衍射(XRD)研究了 0%,4%,6%Ta(质量分数) 3 种成分的低 Cr 高 W 铸造镍基高温合金铸态及热暴露后的显微组织,结果表明:Ta 是强 MC 碳化物形成元素,它形成 MC 碳化物的倾...用金相显微镜、定量金相、扫描电镜(SEM)、能谱分析(EDX)及 X 射线衍射(XRD)研究了 0%,4%,6%Ta(质量分数) 3 种成分的低 Cr 高 W 铸造镍基高温合金铸态及热暴露后的显微组织,结果表明:Ta 是强 MC 碳化物形成元素,它形成 MC 碳化物的倾向低于 Nb、高于 Ti,当合金中 Ta 的原子百分含量超过 Nb 3 倍时,Ta 在 MC 碳化物中的原子百分含量超过 Nb。Ta 是强γ′形成元素,它促进共晶γ′的形成,在合金成分中以等量原子百分含量的 Ta 代替 Al 不会改变合金的共晶γ′数量。在高 W 铸造高温合金中 M6C 是比 MC 更加稳定的碳化物,Ta 的加入不能抑制 1 100℃,500 h 长时热暴露后 MC 完全转变为粒状或片状 M6C。MC 分解时释放的碳还促使α(W,Mo)+C→M6C 反应。对 Ni-1.5Cr-10Co-16W-2Mo-5Al-1Ti-1Nb 基础成分合金,其最佳的含 Ta 量为 4% (质量分数),而且含碳量应低于 0.07%(质量分数)。展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12074213,11574108,and 12104253)the Major Basic Program of Natural Science Foundation of Shandong Province(Grant No.ZR2021ZD01)+3 种基金the Natural Science Foundation of Shandong Provincial(Grant No.ZR2023MA082)the Project of Introduction and Cultivation for Young Innovative Talents in Colleges and Universities of Shandong Provincethe Texas Center for Superconductivity at University of Houstonthe Robert A.Welch Foundation(Grant No.E-1146)。
文摘The superconductivity of two-dimensional(2D)materials has extremely important research significance.To date,superconducting transition temperatures(T_(c))of 2D superconductors are still far from practical applications.Previously,2D MXene Mo_(2)N has been successfully synthesized[Urbankowski et al.Nanoscale 917722,(2017)].We systematically investigate the effects of carbonization and further hydrogenation on the stability,electronic property and superconductivity of 1T-and 2H-M_(2)N(M=Mo,W)based on first-principles calculations.The results show that the 1T-M_(2)N and 2H-M_(2)N(M=Mo,W)are all dynamically and thermodynamically stable after carbonization and further hydrogenation.After carbonization,Tc’s of 1T-M_(2)NC_(2)(M=Mo,W)are all increased,while Tc’s of 2H-M_(2)NC_(2)(M=Mo,W)are all decreased.By further hydrogenation,the Tc’s of 1T-and 2H-M_(2)NC2H2are all increased.Among all of these structures,Tcof 1T-Mo_(2)NC_(2)H_(2)is the highest one,reaching 42.7 K,and the corresponding electron-phonon coupling strengthλis 2.27.Therefore,hydrogenation is an effective method to modulate Tc’s of 2D M_(2)NC_(2)(M=Mo,W)materials.
文摘用金相显微镜、定量金相、扫描电镜(SEM)、能谱分析(EDX)及 X 射线衍射(XRD)研究了 0%,4%,6%Ta(质量分数) 3 种成分的低 Cr 高 W 铸造镍基高温合金铸态及热暴露后的显微组织,结果表明:Ta 是强 MC 碳化物形成元素,它形成 MC 碳化物的倾向低于 Nb、高于 Ti,当合金中 Ta 的原子百分含量超过 Nb 3 倍时,Ta 在 MC 碳化物中的原子百分含量超过 Nb。Ta 是强γ′形成元素,它促进共晶γ′的形成,在合金成分中以等量原子百分含量的 Ta 代替 Al 不会改变合金的共晶γ′数量。在高 W 铸造高温合金中 M6C 是比 MC 更加稳定的碳化物,Ta 的加入不能抑制 1 100℃,500 h 长时热暴露后 MC 完全转变为粒状或片状 M6C。MC 分解时释放的碳还促使α(W,Mo)+C→M6C 反应。对 Ni-1.5Cr-10Co-16W-2Mo-5Al-1Ti-1Nb 基础成分合金,其最佳的含 Ta 量为 4% (质量分数),而且含碳量应低于 0.07%(质量分数)。
