The achievement of chemical diversity and performance regulation of MAX phases primarily relies on solid solution approaches.However,the reported A-site solid solution is undervalued due to their expected chemical dis...The achievement of chemical diversity and performance regulation of MAX phases primarily relies on solid solution approaches.However,the reported A-site solid solution is undervalued due to their expected chemical disorder and compliance with Vegard’s law,as well as discontinuous composition and poor purity.Herein,we synthesized high-purity Ti_(2)(Sn_(x)Al_(1−x))C(x=0–1)solid solution by the feasible pressureless sintering,enabling us to investigate their property evolution upon the A-site composition.The formation mechanism of Ti_(2)(Sn_(x)Al_(1−x))C was revealed by thermal analysis,and crystal parameters were determined by Rietveld refinement of X-ray diffraction(XRD).The lattice constant(a)adheres to Vegard’s law,while the lattice constant(c)and internal free parameter(zM)have noticeable deviations from the law,which is caused by the significant nonlinear distortion of Ti_(6)C octahedron as Al atoms are substituted by Sn atoms.Also,the deviation also results in nonlinear changes in their physicochemical properties,which means that the solid solution often exhibits better performance than end members,such as hardness,electrical conductivity,and corrosion resistance.This work offers insights into the deviation from Vegard’s law observed in the A-site solid solution and indicates that the solid solution with enhanced performance may be obtained by tuning the A-site composition.展开更多
A series of diphenyl-sulfide （Ph2S）-immobilized Pd/C catalysts （Pd-Ph2Scx）/C） were prepared using the wetness-impregnation and immobilization method. Pd-Ph2S（x）/C catalysts employed for the hydro- genation of o...A series of diphenyl-sulfide （Ph2S）-immobilized Pd/C catalysts （Pd-Ph2Scx）/C） were prepared using the wetness-impregnation and immobilization method. Pd-Ph2S（x）/C catalysts employed for the hydro- genation of o-chloronitrobenzene showed very high selectivity. The structure of Pd-Ph2Scx）/C with different molar ratio of ligand （x-values） was characterized by XPS and TG-DSC-MS. The results suggest a ＂saturated＂ surface ratio of Ph2S/Pd （about 0.3） was formed on the Pd-Ph2S（x）[C catalysts surface. The Ph2S immobilized on the Pd particle is quite stable, and the desorption of Ph2S or dissociative loss of phenyl group was only found at temperatures above 500 K. The possible catalytic mechanism of the Pd-Ph2S（x）/C catalyst was also discussed.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(No.52171033)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX22_0247).
文摘The achievement of chemical diversity and performance regulation of MAX phases primarily relies on solid solution approaches.However,the reported A-site solid solution is undervalued due to their expected chemical disorder and compliance with Vegard’s law,as well as discontinuous composition and poor purity.Herein,we synthesized high-purity Ti_(2)(Sn_(x)Al_(1−x))C(x=0–1)solid solution by the feasible pressureless sintering,enabling us to investigate their property evolution upon the A-site composition.The formation mechanism of Ti_(2)(Sn_(x)Al_(1−x))C was revealed by thermal analysis,and crystal parameters were determined by Rietveld refinement of X-ray diffraction(XRD).The lattice constant(a)adheres to Vegard’s law,while the lattice constant(c)and internal free parameter(zM)have noticeable deviations from the law,which is caused by the significant nonlinear distortion of Ti_(6)C octahedron as Al atoms are substituted by Sn atoms.Also,the deviation also results in nonlinear changes in their physicochemical properties,which means that the solid solution often exhibits better performance than end members,such as hardness,electrical conductivity,and corrosion resistance.This work offers insights into the deviation from Vegard’s law observed in the A-site solid solution and indicates that the solid solution with enhanced performance may be obtained by tuning the A-site composition.
基金supported by National Natural Science Foundation of China(No.NSFC-20976164)National Basic Research Program of China(973 Program)(No.2011 CB710800)
文摘A series of diphenyl-sulfide （Ph2S）-immobilized Pd/C catalysts （Pd-Ph2Scx）/C） were prepared using the wetness-impregnation and immobilization method. Pd-Ph2S（x）/C catalysts employed for the hydro- genation of o-chloronitrobenzene showed very high selectivity. The structure of Pd-Ph2Scx）/C with different molar ratio of ligand （x-values） was characterized by XPS and TG-DSC-MS. The results suggest a ＂saturated＂ surface ratio of Ph2S/Pd （about 0.3） was formed on the Pd-Ph2S（x）[C catalysts surface. The Ph2S immobilized on the Pd particle is quite stable, and the desorption of Ph2S or dissociative loss of phenyl group was only found at temperatures above 500 K. The possible catalytic mechanism of the Pd-Ph2S（x）/C catalyst was also discussed.
