The effec ts of mat erial plasticity and local slip on the sliding inception of asperity are studied in the present work.Firstly,a semi-analytical solution is derived under the full-stick condition to analyze the effe...The effec ts of mat erial plasticity and local slip on the sliding inception of asperity are studied in the present work.Firstly,a semi-analytical solution is derived under the full-stick condition to analyze the effect of material plasticity on sliding friction.Then,a friction model with contact stiffness criterion is proposed to study the cases from partial-slip condition to full-stick condition.Finite element simulations with the provided model are used to present the friction map.The friction coefficient of full-s tick interface converges at a st able value,approxima tely 0.3.Plasticity saturation appears as the normalized contact interference u*is larger than 3.A transition mechanism from slip-dominated to yield-dominated takes place in the sliding process.The simulation results are compared with the semi-analytical solution.展开更多
Results of inelastic neutron scattering experinients and ab initio molecular dynamics simulations for GeTe 一 the parent compound of phase-change materials are reported. The inelastic neutron spectra of GeTe powder sa...Results of inelastic neutron scattering experinients and ab initio molecular dynamics simulations for GeTe 一 the parent compound of phase-change materials are reported. The inelastic neutron spectra of GeTe powder samples have been determined in the temperature range extending from 300 to 700 K. The phonon peaks undergo thermal shifts resulting from anharmonic effects being weaker for acoustic than optic modes. A small concentration of free charge carries arising from the presence of Ge-vacancies was found not to affect significantly the neutron weighted phonon densities of states of GeTe. The spectral pattern changes qualitatively across the structural phase transition, but the local structure of GeTe remains hardly affected, as confirmed by the analysis of temperature dependence of the pairdistribution function obtained from ab initio molecular dynamics investigations. The present theoretical studies support in a wide extent our experimental observations and also those provided by local probe methods.展开更多
We have synthesized and investigated physical properties of two new quaternary compounds Gd2CoAl4T2 (T = Si, Ge) single crystals, which are isostructural to Tb2NiAl4Ge2 and Er2CoAl4Ge2. The most important structural f...We have synthesized and investigated physical properties of two new quaternary compounds Gd2CoAl4T2 (T = Si, Ge) single crystals, which are isostructural to Tb2NiAl4Ge2 and Er2CoAl4Ge2. The most important structural feature of these materials is the anti-CaF2-type CoAl4T2 slabs. These materials show metallic behavior below 300 K and there is a long-range antiferromagnetic (AFM) transition appearing at 20 and 27 K for GdCoAl4Ge2 and Gd2CoAl4Si2, respectively. Resistivity and heat capacity measurements also confirm these bulk AFM transitions. Further analysis indicates that this long-range antiferromagnetism should result from the magnetic interaction between local moments of Gd^3+ ions.展开更多
基金the National Natural Science Foundation of China(Grant Nos.11772334,11432014,11672301)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB22040501)the State Key Laboratory of Structural Analysis for Industrial Equipment(DUT Grant No.GZ15116).
文摘The effec ts of mat erial plasticity and local slip on the sliding inception of asperity are studied in the present work.Firstly,a semi-analytical solution is derived under the full-stick condition to analyze the effect of material plasticity on sliding friction.Then,a friction model with contact stiffness criterion is proposed to study the cases from partial-slip condition to full-stick condition.Finite element simulations with the provided model are used to present the friction map.The friction coefficient of full-s tick interface converges at a st able value,approxima tely 0.3.Plasticity saturation appears as the normalized contact interference u*is larger than 3.A transition mechanism from slip-dominated to yield-dominated takes place in the sliding process.The simulation results are compared with the semi-analytical solution.
文摘Results of inelastic neutron scattering experinients and ab initio molecular dynamics simulations for GeTe 一 the parent compound of phase-change materials are reported. The inelastic neutron spectra of GeTe powder samples have been determined in the temperature range extending from 300 to 700 K. The phonon peaks undergo thermal shifts resulting from anharmonic effects being weaker for acoustic than optic modes. A small concentration of free charge carries arising from the presence of Ge-vacancies was found not to affect significantly the neutron weighted phonon densities of states of GeTe. The spectral pattern changes qualitatively across the structural phase transition, but the local structure of GeTe remains hardly affected, as confirmed by the analysis of temperature dependence of the pairdistribution function obtained from ab initio molecular dynamics investigations. The present theoretical studies support in a wide extent our experimental observations and also those provided by local probe methods.
基金the National Natural Science Foundation of China (Grant Nos. 11574394, 11774423, 11822412, and 51608273)the Fundamental Research Funds for the Central Universities (Grant No. 2017RC20)+3 种基金the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (No. 16KJB560008)the Young Researcher Program Nanjing Forestry University of China (No. CX2016023)Key Laboratory of Advanced Building Materials of Anhui Province of China (No. JZCL201603KF)State Key Laboratory of High Performance Civil Engineering Materials of China (No. 2016CEM004).
文摘We have synthesized and investigated physical properties of two new quaternary compounds Gd2CoAl4T2 (T = Si, Ge) single crystals, which are isostructural to Tb2NiAl4Ge2 and Er2CoAl4Ge2. The most important structural feature of these materials is the anti-CaF2-type CoAl4T2 slabs. These materials show metallic behavior below 300 K and there is a long-range antiferromagnetic (AFM) transition appearing at 20 and 27 K for GdCoAl4Ge2 and Gd2CoAl4Si2, respectively. Resistivity and heat capacity measurements also confirm these bulk AFM transitions. Further analysis indicates that this long-range antiferromagnetism should result from the magnetic interaction between local moments of Gd^3+ ions.
