Titanium with gradient nano-to-micron scale grains from surface to matrix was fabricated by surface mechanical grinding treatment(SMGT) at room temperature.The SMGT-treated titanium shows higher strength than that of ...Titanium with gradient nano-to-micron scale grains from surface to matrix was fabricated by surface mechanical grinding treatment(SMGT) at room temperature.The SMGT-treated titanium shows higher strength than that of as-received one,but moderate ductility between those of ultra-fine grained(UFG) and coarse-grained titanium.Tensile stress-strain curves of SMGT-treated titanium show double strain hardening regimes.The strain hardening rate(dσ/dε) decreases with increasing strain in tensile deformation.The high strain hardening rate at initial yielding is attributed to nano-to-micron-grained surface layer.The low strain hardening rate at large plastic strain regime primarily results from coarse-grained matrix.The SMGT-treated titanium shows a ductile fracture mode with a large number of dimples.The small size of dimples in the treated surface layer is due to the combination of the high strength and strain hardening exponent.The difference between dimple size in nano-to-micron-grained surface layer and coarse-grained matrix is discussed in terms of plastic zone size at the tip of crack in the SMGT-treated titanium.展开更多
Ultrasonic treatment and hydrothermal method were applied in the traditional homogeneous precipitation for nano-TiO_2 preparation, which was used as carrier material for the production of honeycomb selective catalytic...Ultrasonic treatment and hydrothermal method were applied in the traditional homogeneous precipitation for nano-TiO_2 preparation, which was used as carrier material for the production of honeycomb selective catalytic reduction(SCR) catalyst. The influence rules of the two improved methods on characterization of TiO_2 samples, denitration activity and mechanical strength of honeycomb SCR catalyst samples were mainly focused on. The results indicate that the specific surface area, particle size and uniformity of TiO_2 samples are significantly improved by both of the ultrasonic and hydrothermal treatments compared with the traditional homogeneous precipitation. Also, the denitration activities of catalyst samples are enhanced by the two improved methods(the NO_x reduction ratio increases from 88.89% to 95.45% by ultrasonic homogeneous precipitation process, and to 94.12% by hydrothermal homogeneous precipitation process). On the other hand, because of good spherical shape and high particle distribution of TiO_2 sample from hydrothermal homogeneous precipitation process, the corresponding honeycomb catalyst samples get the best mechanical strength, which is even higher than that of the reference sample from commercial nano-TiO_2. So, it is concluded that the hydrothermal homogeneous precipitation can be a feasible and effective preparation method of TiO_2 carrier for the honeycomb SCR catalyst production.展开更多
We investigate the unconventional Landau levels of ultracold fermionic atoms on the two-dimensionalhoneycomb optical lattice subjected to an effective magnetic field,which is created with optical means.In the presence...We investigate the unconventional Landau levels of ultracold fermionic atoms on the two-dimensionalhoneycomb optical lattice subjected to an effective magnetic field,which is created with optical means.In the presenceof the effective magnetic field,the energy spectrum of the unconventional Landau levels is calculated.Furthermore,wepropose to detect the unconventional Landau levels with Bragg scattering techniques.展开更多
Vacancies are prevalent and versatile in solid-state physics and materials science.The role of vacancies in strongly correlated materials,however,remains uncultivated until now.Here,we report the discovery of an unpre...Vacancies are prevalent and versatile in solid-state physics and materials science.The role of vacancies in strongly correlated materials,however,remains uncultivated until now.Here,we report the discovery of an unprecedented vacancy state forming an extended buckled-honeycomb-vacancy(BHV)ordering in Ir16Sb18.Superconductivity emerges by suppressing the BHV ordering through squeezing of extra Ir atoms into the vacancies or isovalent Rh substitution.The phase diagram on vacancy ordering reveals the superconductivity competes with the BHV ordering.Further theoretical calculations suggest that this ordering originates from a synergistic effect of the vacancy formation energy and Fermi surface nesting with a wave vector of(1/3,1/3,0).The buckled structure breaks the crystal inversion symmetry and can mostly suppress the density of states near the Fermi level.The peculiarities of BHV ordering highlight the importance of"correlated vacancies"and may serve as a paradigm for exploring other non-trivial excitations and quantum criticality.展开更多
基金Project(2014CB644003)supported by the National Basic Research Program of ChinaProject(51321003)supported by the National Natural Science Foundation of ChinaProject(B06025)supported by"111"Project of China
文摘Titanium with gradient nano-to-micron scale grains from surface to matrix was fabricated by surface mechanical grinding treatment(SMGT) at room temperature.The SMGT-treated titanium shows higher strength than that of as-received one,but moderate ductility between those of ultra-fine grained(UFG) and coarse-grained titanium.Tensile stress-strain curves of SMGT-treated titanium show double strain hardening regimes.The strain hardening rate(dσ/dε) decreases with increasing strain in tensile deformation.The high strain hardening rate at initial yielding is attributed to nano-to-micron-grained surface layer.The low strain hardening rate at large plastic strain regime primarily results from coarse-grained matrix.The SMGT-treated titanium shows a ductile fracture mode with a large number of dimples.The small size of dimples in the treated surface layer is due to the combination of the high strength and strain hardening exponent.The difference between dimple size in nano-to-micron-grained surface layer and coarse-grained matrix is discussed in terms of plastic zone size at the tip of crack in the SMGT-treated titanium.
基金Project(201031)supported by the Environmental Protection Scientific Research of Jiangsu Province,ChinaProject(BE2010184)supported by the Technology Support Program of Jiangsu Province-Industrial Parts,China
文摘Ultrasonic treatment and hydrothermal method were applied in the traditional homogeneous precipitation for nano-TiO_2 preparation, which was used as carrier material for the production of honeycomb selective catalytic reduction(SCR) catalyst. The influence rules of the two improved methods on characterization of TiO_2 samples, denitration activity and mechanical strength of honeycomb SCR catalyst samples were mainly focused on. The results indicate that the specific surface area, particle size and uniformity of TiO_2 samples are significantly improved by both of the ultrasonic and hydrothermal treatments compared with the traditional homogeneous precipitation. Also, the denitration activities of catalyst samples are enhanced by the two improved methods(the NO_x reduction ratio increases from 88.89% to 95.45% by ultrasonic homogeneous precipitation process, and to 94.12% by hydrothermal homogeneous precipitation process). On the other hand, because of good spherical shape and high particle distribution of TiO_2 sample from hydrothermal homogeneous precipitation process, the corresponding honeycomb catalyst samples get the best mechanical strength, which is even higher than that of the reference sample from commercial nano-TiO_2. So, it is concluded that the hydrothermal homogeneous precipitation can be a feasible and effective preparation method of TiO_2 carrier for the honeycomb SCR catalyst production.
基金Supported by the Teaching and Research Foundation for the Outstanding Young Faculty of Southeast University
文摘We investigate the unconventional Landau levels of ultracold fermionic atoms on the two-dimensionalhoneycomb optical lattice subjected to an effective magnetic field,which is created with optical means.In the presenceof the effective magnetic field,the energy spectrum of the unconventional Landau levels is calculated.Furthermore,wepropose to detect the unconventional Landau levels with Bragg scattering techniques.
基金support by the National Key Research and Development Program of China(2018YFA0704300)the National Natural Science Foundation of China(U1932217 and 11974246)+4 种基金the Natural Science Foundation of Shanghai(19ZR1477300)supported by MEXT Element Strategy Initiative to form Core Research Centerpartially supported by ChEM,SPST of ShanghaiTech University(02161943)Analytical Instrumentation Center(SPST-AIC10112914),SPST of ShanghaiTech Universitysupported by the National Natural Science Foundation of China(11888101)。
文摘Vacancies are prevalent and versatile in solid-state physics and materials science.The role of vacancies in strongly correlated materials,however,remains uncultivated until now.Here,we report the discovery of an unprecedented vacancy state forming an extended buckled-honeycomb-vacancy(BHV)ordering in Ir16Sb18.Superconductivity emerges by suppressing the BHV ordering through squeezing of extra Ir atoms into the vacancies or isovalent Rh substitution.The phase diagram on vacancy ordering reveals the superconductivity competes with the BHV ordering.Further theoretical calculations suggest that this ordering originates from a synergistic effect of the vacancy formation energy and Fermi surface nesting with a wave vector of(1/3,1/3,0).The buckled structure breaks the crystal inversion symmetry and can mostly suppress the density of states near the Fermi level.The peculiarities of BHV ordering highlight the importance of"correlated vacancies"and may serve as a paradigm for exploring other non-trivial excitations and quantum criticality.