作者机构：
[Wang, Mingyang; He, Debing; Wang, Liang] College of Science, Hunan Agricultural University Changsha Hunan 410128 People's Republic of China wangliang0329@hunau.edu.cn;[Bi, Wenbo] Graduate School of China Academy of Engineering Physics Beijing 100193 People's Republic of China biwenbo23@gscaep.ac.cn
通讯机构：
[Bi, Wenbo] G;[He, Debing] C;Graduate School of China Academy of Engineering Physics, Beijing 100193, People's Republic of China<&wdkj&>College of Science, Hunan Agricultural University, Changsha, Hunan 410128, People's Republic of China
摘要：
Consolidating nanopowder metals via impact loading is a potentially significant method for synthesizing and processing bulk nanocrystalline materials. However, until now, the microstructural features, plastic deformation during consolidation, and corresponding mechanisms have been seldom revealed. Using molecular dynamics (MD) simulations, we have studied the plastic deformation, densification, spallation, and micro-jetting in nanopowder titanium (np-Ti) during shock. Upon impact, np-Ti undergoes a transition from heterogeneous plasticity, including basal stacking faults (SFs) and {101̄2} twinning, to homogeneous disordering, as the impact velocity increases. Then the nanopowder structure evolves into a bulk nanostructure after the final densification, contributed by pore collapse. The subsequent detwinning arises during the release and tension stage, conducing to a partial structural recovery. When the impact velocity u(p) ≥ 1.0 km s(-1), the spallation is following, prompted via GB-sliding and disordering. Upon shock impact, it also facilitates micro-jetting owing to the presence of nanopores, contributing to the pressure gradient and transverse velocity gradient.
作者：
Bi, W. B.;Wang, Y. F.;Zhang, X. M.;Deng, L.;Tang, J. F.;...
期刊：
Journal of Applied Physics,2023年133(6):065103 ISSN：0021-8979
作者机构：
[Bi, W. B.; Zhang, X. M.; Wang, Y. F.; Deng, L.; Tang, J. F.; Wang, L.] Hunan Agr Univ, Coll Sci, Changsha 410128, Peoples R China.;[Zhao, F.] Chengdu Univ, Inst Adv Study, Chengdu 610106, Peoples R China.;[Zhao, F.] Chengdu Univ, Inst Adv Mat Deformat & Damage Multiscale, Chengdu 610106, Sichuan, Peoples R China.;[Wang, L.] Peac Inst Multiscale Sci, Chengdu 610207, Sichuan, Peoples R China.
摘要：
We systematically study the low cycle fatigue behavior and its dependence of specific surface area ( zeta) for nanoporous copper (NPC) under ultrahigh strain rate ( gamma asymptotic to 10 (9) s (- 1)) cyclic shear loading by conducting large-scale molecular dynamic simulation and small-angle x-ray scattering analysis. With an increase in zeta, NPC undergoes a transition from the first excellent anti-fatigue property ( zeta < 1.24 nm - 1) to the subsequent easy-to-fatigue capacity ( zeta >= 1.24 nm( - 1)). Two different mechanisms are governing fatigue: (i) smooth nucleation and propagation of dislocations for the former and (ii) nanopore compaction/coalescence for the latter by prohibiting the activities of dislocations. For NPC with zeta = 0.42 nm (- 1), fatigue contributes to a surprising superelasticity, prompted by the entanglements and reversed disentanglements of longer dislocations. Surface reconstruction contributes to the fatigue tolerance of NPC by facilitating local surface roughening and the emission of dislocation slips, and it becomes more pronounced with decreasing zeta.
期刊：
Chemical Engineering Journal,2023年452:139313 ISSN：1385-8947
通讯作者：
Zou, Rui(zourui@mail2.sysu.edu.cn)
作者机构：
[Cao, Lu-Yu; Guo, Xiao-Xuan; Liu, Bo-Mei; Huang, Lin; Wang, Jing] Sun Yat Sen Univ, Sch Chem, State Key Lab Optoelect Mat & Technol, Minist Educ,Key Lab Bioinorgan & Synthet Chem, Guangzhou 510275, Peoples R China.;[Zou, Rui] Sun Yat Sen Univ, Affiliated Hosp 3, Dept Nucl Med, 600 Tianhe Rd, Guangzhou 510630, Peoples R China.;[Zhou, Zhi] Hunan Agr Univ, Coll Sci, Hunan Opt Agr Engn Technol Res Ctr, Changsha, Hunan, Peoples R China.
通讯机构：
[Rui Zou] D;[Zhi Zhou] C;[Jing Wang] M;Department of Nuclear Medicine, The Third Affiliated Hospital of Sun Yat-Sen University, 600 Tianhe Road, Guangzhou 510630, China<&wdkj&>College of Science, Hunan Optical Agriculture Engineering Technology Research Center, Hunan Agricultural University, Changsha City, Hunan 10128, China<&wdkj&>Ministry of Education Key Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
关键词：
Ni;NIR spectroscopy;NIR-II luminescence;Phosphor-converted LED
作者机构：
[Liu, Bo-Mei; Huang, Lin; Wang, Jing] Sun Yat Sen Univ, Sch Mat Sci & Engn, Guangzhou 510275, Peoples R China.;[Gu, Si-Min; Wang, Jing] Sun Yat Sen Univ, Sch Chem, State Key Lab Optoelectron Mat & Technol, Minist Educ,Key Lab Bioinorgan & Synthet Chem, Guangzhou 510275, Peoples R China.;[Zhou, Rong-Fu] Foshan Univ, Sch Environm & Chem Engn, Foshan 528225, Peoples R China.;[Zhou, Zhi] Hunan Agr Univ, Coll Sci, Hunan Optic Agr Engn Technol Res Ctr, Changsha 10128, Hunan, Peoples R China.;[Ma, Chong-Geng] Chongqing Univ Posts & Telecommunicat, Sch Optoelectron Engn CQUPT BUL Innovat Inst, Chongqing 400065, Peoples R China.
通讯机构：
[Rui Zou] D;[Jing Wang] S;School of Materials Science and Engineering, Sun Yat-Sen University, Guangzhou 510275, China<&wdkj&>Ministry of Education Key Laboratory of Bioinorganic and Synthetic Chemistry, State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China<&wdkj&>Department of Nuclear Medicine, The Third Affiliated Hospital of Sun Yat-Sen University, 600 Tianhe Road, Guangzhou 510630, China
摘要：
An effective and reliable Finnis-Sinclair (FS) type potential is developed for large-scale molecular dynamics (MD) simulations of plasticity and phase transition of magnesium (Mg) single crystals under high-pressure shock loading. The shock-wave profiles exhibit a split elastic-inelastic wave in the [0001](HCP) shock orientation and a three-wave structure in the [10-10](HCP) and [-12-10](HCP) directions, namely, an elastic precursor, a followed plastic front, and a phase-transition front. The shock Hugoniot of the particle velocity (U (p)) vs the shock velocity (U (s)) of Mg single crystals in three shock directions under low shock strength reveals apparent anisotropy, which vanishes with increasing shock strength. For the [0001](HCP) shock direction, the amorphization caused by strong atomic strain plays an important role in the phase transition and allows for the phase transition from an isotropic stressed state to the product phase. The reorientation in the shock directions [10-10](HCP) and [-12-10](HCP), as the primary plasticity deformation, leads to the compressed hexagonal close-packed (HCP) phase and reduces the phase-transition threshold pressure. The phase-transition pathway in the shock direction [0001](HCP) includes a preferential contraction strain along the [0001](HCP) direction, a tension along [-12-10](HCP) direction, an effective contraction and shear along the [10-10](HCP) direction. For the [10-10](HCP) and [-12-10](HCP) shock directions, the phase-transition pathway consists of two steps: a reorientation and the subsequent transition from the reorientation hexagonal close-packed phase (RHCP) to the body-centered cubic (BCC). The orientation relationships between HCP and BCC are (0001)(HCP) ⟨-12-10⟩(HCP) // {110}(BCC) ⟨001⟩(BCC). Due to different slipping directions during the phase transition, three variants of the product phase are observed in the shocked samples, accompanied by three kinds of typical coherent twin-grain boundaries between the variants. The results indicate that the highly concentrated shear stress leads to the crystal lattice instability in the elastic precursor, and the plasticity or the phase transition relaxed the shear stress.
作者机构：
[Jonathan R.Adsetts; 杨柳青; 丁志峰; Darshil Patel; Kenneth Chu; Brian L.Pagenkopf; 张丛洋] Department of Chemistry, Western University;湖南农业大学化学与材料科学学院;凯莱英医药集团(天津)股份有限公司北京分公司;[覃晓丽] Department of Chemistry, Western University<&wdkj&>湖南农业大学化学与材料科学学院;[王鑫] Department of Chemistry, Western University<&wdkj&>凯莱英医药集团(天津)股份有限公司北京分公司
期刊：
International Journal of Plasticity,2022年155:103329 ISSN：0749-6419
通讯作者：
Fei Gao<&wdkj&>Huiqiu Deng
作者机构：
[Guo, Long; Hu, Wangyu; Liu, Beibei; Wang, Kun] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Peoples R China.;[Xiao, Shifang; Chen, Yangchun; Deng, Huiqiu; Guo, Long] Hunan Univ, Sch Phys & Elect, Changsha 410082, Peoples R China.;[Wang, Liang] Hunan Agr Univ, Coll Sci, Changsha 410128, Peoples R China.;[Gao, Ning] Shandong Univ, Inst Frontier & Interdisciplinar Sci, Qingdao 266237, Shandong, Peoples R China.;[Gao, Fei] Univ Michigan, Dept Nucl Engn & Radiol Sci, Ann Arbor, MI 48109 USA.
通讯机构：
[Fei Gao] D;[Huiqiu Deng] S;School of Physics and Electronics, Hunan University, Changsha 410082, China<&wdkj&>Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Michigan 48109, United States
摘要：
Nowadays, due to uncontrolled synthesis and lack of more direct and systematic evidences, the photoluminescence origin of "zero-dimensional" Cs4PbI6 remains great controversy and the luminescence cannot be controlled. Here we propose a controllable dissolution-recrystallization method to synthesize "emissive" and "non-emissive" Cs4PbI6 nanocrystals (NCs) respectively. Through comparing "emissive" and "non-emissive" Cs4PbI6 NCs, it is clearly proved that the visible emission in "emissive" Cs4PbI6 NCs comes from embedded CsPbI3 quantum dots (QDs). It is found for CsPbI3@Cs4PbI6 nanocomposites, methyl acetate (MeAC) and cyclohexane play an important role in dissolution and recrystallization respectively to obtain Cs4PbI6 matrix and CsPbI3 cores. Benefiting from this two-step method, the as-synthesized CsPbI3@Cs4PbI6 nanocomposites with CsPbI3 QDs uniformly distributed in Cs4PbI6 matrix are bright with photoluminescence quantum yield (PLQY) up to 71.4% and exhibit improved stability than CsPbI3 NCs. Moreover, utilizing its formation mechanism, the size of embedded CsPbI3 QDs can be controlled by reasonable designing the "dissolution" process, so that the luminescence of this CsPbI3@Cs4PbI6 nanocomposites can be adjusted in a wide range from green to red (554-630 nm). Our finding not only provides a novel method for synthesizing tunable "emissive" Cs4PbI6 NCs, but also makes clear the photoluminescence origin of "emissive" Cs4PbI6.
作者机构：
[Deng, HuiQiu; Wen, ShuLong] Hunan Univ, Sch Phys & Elect, Changsha 410082, Peoples R China.;[Zhang, XingMing] Hunan Agr Univ, Coll Sci, Changsha 410128, Peoples R China.;[Pan, Min] Southwest Jiao Tong Univ, Superconduct & New Energy R&D Ctr, Key Lab Adv Technol Mat, Minist Educ, Chengdu 610031, Peoples R China.
通讯机构：
[HuiQiu Deng; Min Pan] S;School of Physics and Electronics, Hunan University, Changsha 410082, People’s Republic of China<&wdkj&>Superconductivity and New Energy R&D Center, Key Laboratory of Advanced Technology of Materials (Ministry of Education), Southwest Jiao Tong University, Chengdu 610031, People’s Republic of China
通讯机构：
[Wang, YM ] H;Hunan Agr Univ, Dept Appl Math, Changsha 410128, Peoples R China.
关键词：
Julia sets;Buried component;Singular perturbations;Cantor set of circles
摘要：
Let f be a hyperbolic rational map with degree
$$d\ge 2$$
whose Julia set is connected. We give an elementary approach to prove that there exists a rational map g with degree
$$\le 7d-2$$
such that g contains a buried Julia component which is homeomorphic to the Julia set of f.
期刊：
Journal of Materials Chemistry C,2022年10(22):8797-8805 ISSN：2050-7526
通讯作者：
Bo-Mei Liu<&wdkj&>Jing Wang
作者机构：
[Zheng, Zhi-Hang; Liu, Bo-Mei; Wang, Jing] Sun Yat Sen Univ, State Key Lab Optoelect Mat & Technol, Sch Mat Sci & Engn, Minist Educ,Sch Chem,Key Lab Bioinorgan & Synthet, Guangzhou 510275, Guangdong, Peoples R China.;[Zhou, Zhi] Hunan Agr Univ, Hunan Opt Agr Engn Technol Res Ctr, Coll Sci, Changsha 10128, Hunan, Peoples R China.;[Ma, Chong-Geng] Chongqing Univ Posts & Telecommun, CQUPT BUL Innovat Inst, 2 Chongwen Rd, Chongqing 400065, Peoples R China.
通讯机构：
[Bo-Mei Liu; Jing Wang] M;Ministry of Education Key Laboratory of Bioinorganic and Synthetic Chemistry State Key Laboratory of Optoelectronic Materials and Technologies School of Chemistry, School of Materials Science and Engineering Sun Yat-Sen University, Guangzhou 510275, China
摘要：
Cr3+-activated broadband near-infrared (NIR) emitting phosphors have attracted more attention worldwide as they are strongly expected to be promising light convertors for phosphor-converted NIR light sources for NIR spectroscopy and imaging technologies. Unfortunately, few works have reported the co-existence of multi-valence Cr ions and its negative effects on the luminescence efficiency of the Cr3+ ion in NIR emitting phosphors. Herein, we systematically investigated and prove the existence of Cr6+ ions in novel LiInO2:Cr3+ NIR emitting phosphors based on optical absorption, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and inductive coupled plasma (ICP) measurements. The competitive absorption of Cr6+ ions is found to be the main reason for greatly limiting the high luminescence efficiency of Cr3+ ions in NIR emitting phosphors. More importantly, we proposed a generic post-treatment strategy to eliminate the Cr6+ ions in Cr3+-activated NIR emitting phosphors by simply soaking the phosphors in deionized water or dilute acid. For LiInO2:Cr, the ICP data show 82.7% of Cr ions present in a valence of +6 in LiInO2 and they were finally washed out, which consequently enhances its NIR emission intensity by 72.6% and increases its quantum efficiency by 21.3% from 14.8% to 36.1%. More interestingly, the as-proposed post-treatment strategy is highly versatile and successfully applied to other well-known Cr3+-activated NIR-emitting phosphors reported previously. Our findings suggest that this simple and generic post-treatment strategy can open up new avenues for developing highly efficient Cr3+-activated broadband NIR-emitting phosphors.
