Micrometer-sized,irregularly shaped Ti particles(0.5wt%and 1.0wt%)were mixed with an Al-Si-Mg-Zr matrix powder,and a novel Ti-modified Al-Si-Mg-Zr aluminum alloy was subsequently fabricated via laser-powder bed fusion...Micrometer-sized,irregularly shaped Ti particles(0.5wt%and 1.0wt%)were mixed with an Al-Si-Mg-Zr matrix powder,and a novel Ti-modified Al-Si-Mg-Zr aluminum alloy was subsequently fabricated via laser-powder bed fusion(L-PBF).The results demonstrated that the introduction of Ti particles promoted the formation of near-fully equiaxed grains in the alloy owing to the strong grain refinement of the primary(Al,Si)3(Ti,Zr)nanoparticles.Furthermore,the presence of(Al,Si)3(Ti,Zr)nanoparticles inhibited the decomposition of Si-rich cell boundaries and the precipitation of Si nanoparticles in theα-Al cells.The ultimate tensile strength(UTS),yield strength(YS),and elongation of the asbuilt 0.5wt%Ti(0.5Ti)alloy were(468±11),(350±1)MPa,and(10.0±1.4)%,respectively,which are comparable to those of the L-PBF Al-Si-Mg-Zr matrix alloy and significantly higher than those of traditional L-PBF Al-Si-Mg alloys.After direct aging treatment at 150°C,the precipitation of secondary nanoparticles notably enhanced the strength of the 0.5Ti alloy.Specifically,the 0.5Ti alloy achieved a maximum UTS of(479±11)MPa and YS of(376±10)MPa.At 250°C,the YS of the L-PBF Ti/Al-Si-Mg-Zr alloy was higher than that of the L-PBF Al-Si-Mg-Zr matrix alloy due to the retention of Si-rich cell boundaries,indicating a higher thermal stability.As the aging temperature was increased to 300°C,the dissolution of Si-rich cell boundaries,desolvation of solid-solution elements,and coarsening of nanoprecipitates led to a decrease in the UTS and YS of the alloy to below 300 and 200 MPa,respectively.However,the elongation increased significantly.展开更多
Mesoporous molecular sieves possessing high mesopore volumes and large specific surface areas were prepared and characterized by means of XRD, low temperature N_2 adsorption-desorption measurements, FT IR, Raman, UV...Mesoporous molecular sieves possessing high mesopore volumes and large specific surface areas were prepared and characterized by means of XRD, low temperature N_2 adsorption-desorption measurements, FT IR, Raman, UV-visible diffuse reflectance and XPS spectroscopy. The materials contain both framework and extra-framework Ti centers which exhibit selective oxidation catalytic activity and photocatalytic activity respectively. The catalysis of selective oxidation was studied with the hydroxylation of benzene with hydrogen peroxide and photochemical activity was studied by the yields of ·OH and H_2O_2, respectively.展开更多
The Ti-modified sepiolite （Ti-Sep）-supported Mn-Cu mixed oxide （yMn5Cu/Ti-Sep） catalysts were synthesized using the co-precipitation method. The materials were characterized by the X-ray diffraction scanning elect...The Ti-modified sepiolite （Ti-Sep）-supported Mn-Cu mixed oxide （yMn5Cu/Ti-Sep） catalysts were synthesized using the co-precipitation method. The materials were characterized by the X-ray diffraction scanning electron microscope, N2 adsorption-desorption, H2-TPR, O2-TPD, and XPS techniques, and their catalytic activities for CO oxidation were evaluated. It was found that the catalytic activities ofyMn5Cu/Ti-Sep were higher than those of 5Cu/Ti-Sep and 30Mn/Ti-Sep, and the Mn/Cu molar ratio had a distinct influence on catalytic activity of the sample. Among the yMn5Cu/Ti- Sep samples, the 30Mn5Cu/Ti-Sep catalyst showed the best activity （which also outperformed the 30Mn5Cu/Sep catalyst）, giving the highest reaction rate of 0.875 × 10^- 3 mmol· g^-1· s^-1 and the lowest T50%and T100% of 56℃ and 86℃, respectively. Moreover, the 30Mn5Cu/Ti-Sep possessed the best low-temperature reducibility, the lowest 02 desorption temperature, and the highest surface Mn3＋/ Mn4＋ atomic ratio. It is concluded that factors, such as the strong interaction between the copper or manganese oxides and the Ti-Sep support, good low-temperature reducibility, and good mobility of ehemisorbed oxygen species, were responsible for the excellent catalytic activity of 30Mn5Cu/Ti-Sep.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52001140 and 52475361).
文摘Micrometer-sized,irregularly shaped Ti particles(0.5wt%and 1.0wt%)were mixed with an Al-Si-Mg-Zr matrix powder,and a novel Ti-modified Al-Si-Mg-Zr aluminum alloy was subsequently fabricated via laser-powder bed fusion(L-PBF).The results demonstrated that the introduction of Ti particles promoted the formation of near-fully equiaxed grains in the alloy owing to the strong grain refinement of the primary(Al,Si)3(Ti,Zr)nanoparticles.Furthermore,the presence of(Al,Si)3(Ti,Zr)nanoparticles inhibited the decomposition of Si-rich cell boundaries and the precipitation of Si nanoparticles in theα-Al cells.The ultimate tensile strength(UTS),yield strength(YS),and elongation of the asbuilt 0.5wt%Ti(0.5Ti)alloy were(468±11),(350±1)MPa,and(10.0±1.4)%,respectively,which are comparable to those of the L-PBF Al-Si-Mg-Zr matrix alloy and significantly higher than those of traditional L-PBF Al-Si-Mg alloys.After direct aging treatment at 150°C,the precipitation of secondary nanoparticles notably enhanced the strength of the 0.5Ti alloy.Specifically,the 0.5Ti alloy achieved a maximum UTS of(479±11)MPa and YS of(376±10)MPa.At 250°C,the YS of the L-PBF Ti/Al-Si-Mg-Zr alloy was higher than that of the L-PBF Al-Si-Mg-Zr matrix alloy due to the retention of Si-rich cell boundaries,indicating a higher thermal stability.As the aging temperature was increased to 300°C,the dissolution of Si-rich cell boundaries,desolvation of solid-solution elements,and coarsening of nanoprecipitates led to a decrease in the UTS and YS of the alloy to below 300 and 200 MPa,respectively.However,the elongation increased significantly.
基金Supported by the State Major Basic Research Project of China(No. 2 0 0 0 0 4 80 0 9) and the National Natural ScienceFoundation of China(No. 2 0 1730 0 3)
文摘Mesoporous molecular sieves possessing high mesopore volumes and large specific surface areas were prepared and characterized by means of XRD, low temperature N_2 adsorption-desorption measurements, FT IR, Raman, UV-visible diffuse reflectance and XPS spectroscopy. The materials contain both framework and extra-framework Ti centers which exhibit selective oxidation catalytic activity and photocatalytic activity respectively. The catalysis of selective oxidation was studied with the hydroxylation of benzene with hydrogen peroxide and photochemical activity was studied by the yields of ·OH and H_2O_2, respectively.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant Nos. 21277008 and 20777005） and Natural Science Foundation of Beijing （No. 8082008）.
文摘The Ti-modified sepiolite （Ti-Sep）-supported Mn-Cu mixed oxide （yMn5Cu/Ti-Sep） catalysts were synthesized using the co-precipitation method. The materials were characterized by the X-ray diffraction scanning electron microscope, N2 adsorption-desorption, H2-TPR, O2-TPD, and XPS techniques, and their catalytic activities for CO oxidation were evaluated. It was found that the catalytic activities ofyMn5Cu/Ti-Sep were higher than those of 5Cu/Ti-Sep and 30Mn/Ti-Sep, and the Mn/Cu molar ratio had a distinct influence on catalytic activity of the sample. Among the yMn5Cu/Ti- Sep samples, the 30Mn5Cu/Ti-Sep catalyst showed the best activity （which also outperformed the 30Mn5Cu/Sep catalyst）, giving the highest reaction rate of 0.875 × 10^- 3 mmol· g^-1· s^-1 and the lowest T50%and T100% of 56℃ and 86℃, respectively. Moreover, the 30Mn5Cu/Ti-Sep possessed the best low-temperature reducibility, the lowest 02 desorption temperature, and the highest surface Mn3＋/ Mn4＋ atomic ratio. It is concluded that factors, such as the strong interaction between the copper or manganese oxides and the Ti-Sep support, good low-temperature reducibility, and good mobility of ehemisorbed oxygen species, were responsible for the excellent catalytic activity of 30Mn5Cu/Ti-Sep.
