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Revealing the crystallization process and realizing uniform 1.8 eV MA-based wide-bandgap mixed-halide perovskites via solution engineering

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Nano Research 2019年第5期12卷 1033-1039页

作者： Yue-Min Xie Chunqing Ma Xiuwen Xu Menglin Li Yuhui Ma Jing Wang Hrisheekesh Thachoth Chandran Chun-Sing Lee Sai-Wing Tsang Department of Materials Science and Engineering City University of Hong KongHong Kong SARChina City University of Hong Kong Shenzhen Research Institute Shenzhen 518057China Center of Super-Diamond and Advanced Films (COSDAF) City University of Hong KongHong Kong SARChina

Wide-bandgap perovskites are recently drawing tremendous attention in the community for high-efficiency all-perovskite tandem solar cells.However,the formamidinium (FA^+) and methylammonium (MA^+) based wide-bandgap mixed halide perovskites suffered from high density of traps and pin-holes,respectively.Fundamental understanding on the crystallization and film formation processes are keys to overcome those challenges but not yet clearly understood.In this study,an in-situ photoluminescence technique was used to investigate the perovskite crystallization during the thermal annealing process.It is found that the crystallization of a mixed halide perovskite with bromide (Br^-) and iodine (I^-) ions following the Ostward ripening crystal growth.Interestingly,it is found that the initial nucleation reaction is quickly completed in the first few seconds,however,leaving the small crystals with inhomogeneous composition.The different aggregation affinities of such inhomogeneous small crystals provoke the formation of pin-holes during the thermal annealing process.By engineering the precursor solution to control the nucleation rate,the chemical composition of the small crystals has become homogenous.Uniform pin-hole free high Br-composited wide-bandgap MA0.9Cs0.1Pb(I0.6Br0.4)3 perovskite films with bandgap energy of 1.8 eV have been realized.The corresponding photovoltaic devices have achieved an encouraging device efficiency of 15.1% with superb photostability.

关键词： in-situ photoluminance wide-bandgap perovskite pin-holes solution engineering

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Postbuckling analysis of functionally graded graphene platelet-reinforced polymer composite cylindrical shells using an analytical solution approach

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Applied Mathematics and Mechanics(English Edition) 2019年第7期40卷 1001-1016页

作者： S. BLOORIYAN R. ANSARI A. DARVIZEH R. GHOLAMI H. ROUHI Department of Mechanical Engineering University of Guilan Rasht 41635-3756 Iran Department of Mechanical Engineering Lahijan Branch Islamic Azad University Lahijan 44169-39515Iran Department of Engineering Science Faculty of Technology and Engineering University of Guilan Rudsar-Vajargah 44891-63157 Iran

An analytical approach is proposed to study the postbuckling of circular cylindrical shells subject to axial compression and lateral pressure made of functionally graded graphene platelet-reinforced polymer composite (FG-GPL-RPC). The governing equations are obtained in the context of the classical Donnell shell theory by the von K′arm′an nonlinear relations. Then, based on the Ritz energy method, an analytical solution approach is used to trace the nonlinear postbuckling path of the shell. The effects of several parameters such as the weight fraction of the graphene platelet (GPL), the geometrical properties, and distribution patterns of the GPL on the postbuckling characteristics of the FG-GPL-RPC shell are analyzed.

关键词： cylindrical shell nanocomposite graphene platelet (GPL) postbuckling analytical solution

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Periodic solution and Ergodic Stationary Distribution of Stochastic SIRI Epidemic Systems with Nonlinear Perturbations

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Journal of Systems Science & Complexity 2019年第4期32卷 1104-1124页

作者： ZHANG Weiwei MENG Xinzhu DONG Yulin College of Electrical Engineering and Automation Shandong University of Science and TechnologyQingdao 266590China College of Mathematics and Systems Science Shandong University of Science and TechnologyQingdao 266590China State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology Shandong University of Science and TechnologyQingdao 266590China

This paper formulates two stochastic nonautonomous SIRI epidemic systems with nonlinear perturbations.The main aim of this study is to investigate stochastic dynamics of the two SIRI epidemic systems and obtain their thresholds.For the nonautonomous stochastic SIRI epidemic system with white noise,the authors provide analytic results regarding the stochastic boundedness,stochastic permanence and persistence in mean.Moreover,the authors prove that the system has at least one nontrivial positive T-periodic solution by using Lyapunov function and Hasminskii’s theory.For the system with Markov conversion,the authors establish sufficient conditions for positive recurrence and existence of ergodic stationary distribution.In addition,sufficient conditions for the extinction of disease are obtained.Finally,numerical simulations are introduced to illustrate the main results.

关键词： Extinction and stochastic permanence Markov chain periodic solution stationary distribution and ergodicity stochastic SIRI epidemic model

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Microstructure of Al-Si-Mg alloy with Zr/Hf additions during solidification and solution treatment

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Rare Metals 2019年第11期38卷 1033-1042页

作者： Hui-Lan Huang Zhi-Hong Jia Yuan Xing Xue-Li Wang Qing Liu College of Materials Science and Engineering Chongqing University

In this study,the morphology,composition and evolution of intermetallics in Al-7Si-0.3Mg,Al-7Si-0.3Mg-0.47Hf,Al-7Si-0.3Mg-0.16 Zr and Al-7Si-0.3Mg-0.14Zr-0.44Hf alloys were characterized by optical microscope(OM),scanning electron microscope(SEM)with energy-dispersive spectrometer(EDS) and transmission electron microscope(TEM).The AlSiZr,AlSiHf and AlSiZrHf phases are formed with additions of Zr and/or Hf in base alloy during solidification,especially the AlZrHf primary particles.The three-dimensional morphology of the AlZrHf particle evolves from 10-polyhedron-like to compressed cube-like during solidification.The new AlZrHf phase experiences partial dissolution after solution treatment,while the others remain in the initial morphology.High Si contents lead to form thermally stable Zr/Hfrich precipitates in Zr/Hf-containing alloys during solution treatment,especially the nanobelt-like Si2Zr,Si2Hf and Si2(Zr,Hf) precipitates.Particular orientation relationships and the growth mechanism are identified.The finding of the work broadens the elevated temperature application of Al-Si-Mg in modern automotive aluminum engine.

关键词： Al-Si-Mg cast alloy Primary phase solution treatment Precipitate Orientation relationships

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Precipitation of spherical boehmite from concentrated sodium aluminate solution by adding gibbsite as seed

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International Journal of Minerals,Metallurgy and Materials 2017年第8期24卷 954-963页

作者： Gui-hua Liu Zheng Li Xiao-bin Li Tian-gui Qi Zhi-hong Peng Qiu-sheng Zhou School of Metallurgy and Environment Central South University

The precipitation of spherical boehmite was studied by surface energy calculations, measurements of precipitation ratios, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The surface energy calculation results show that the(001) and(112) planes of gibbsite surfaces are remarkably stable because of their low surface energies. In addition, the(010) plane of boehmite grows preferentially during precipitation because of its low surface energy. Thus, we propose a method to precipitate spherical boehmite from a supersaturated sodium aluminate solution by adding gibbsite as seed in a heterogeneous system. In this method, gibbsite acts as the preliminary seed and saturation modifier. The results show that the fine boehmite first nucleates on the(001) and(112) planes of gibbsite and then grows vertically on the(001) and(112) basal planes of gibbsite via self-assembly, thereby forming spherical boehmite. Simultaneously, gibbsite is dissolved into the aluminate solution to maintain the saturation for the precipitation of boehmite. The precipitation ratio fluctuates(forming an M-shaped curve) because of gibbsite dissolution and boehmite precipitation. The mechanism of boehmite precipitation was further discussed on the basis of the differences in surface energy and solubility between gibbsite and boehmite. This study provides an environmentally friendly and economical method to prepare specific boehmite in a heterogeneous system.

关键词： precipitation sodium aluminate solution morphology boehmite gibbsite surface energy

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Skin layer of A380 aluminium alloy die castings and its blistering during solution treatment

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Journal of Materials Science & Technology 2019年第9期35卷 1906-1916页

作者： Zihao Yuan Zhipeng Guo S.M.Xionga School of Materials Science and Engineering Tsinghua UniversityBeijing100084China State Key Laboratory of Automobile Safety and Energy Tsinghua UniversityBeijing100084China

Skin layer is a characteristic microstructure of aluminium die castings, which would effect the surface blistering during solution treatment. In this study, the microstructures of skin layer were investigated by the methods of optical microscope (OM), scanning electron microscope (SEM) and electron probe microanalyzer (EPMA). High resolution X-ray CT was used to compare the skin layer with normal surface before and after solution treatment. With the aid of computational fluid dynamics (CFD), the formation mechanism of the skin layer was discussed based on microstructure distribution, solute segregation, porosity distribution and surface blistering. The results suggested that the skin layer is related to a succession of complex processes before the filling process finished. Pore clusters or laminar defects would be formed in skin layers during solution treatm ent and cause severe surface blistering.

关键词： Skin layer Die castings solution treatment Blistering

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Highly efficient and selective photocatalytic dehydrogenation of benzyl alcohol for simultaneous hydrogen and benzaldehyde production over Ni-decorated Zn_(0.5)Cd_(0.5)S solid solution

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Journal of Energy Chemistry 2019年第3期28卷 71-77页

作者： Lei Zhang Daochuan Jiang Rana Muhammad Irfan Shan Tang Xin Chen Pingwu Du Hefei National Laboratory of Physical Science at the Microscale CAS Key Laboratory of Materials for Energy Conversion Department of Materials Science and Engineering iChEM (Collaborative Innovation Center of Chemistry for Energy Materials) University of Science and Technology of China (USTC)

Photocatalytic conversion of solar energy into hydrogen and high value-added fine chemicals has attracted increasing attention. Herein, we demonstrate an efficient photocatalytic system for simultaneous hydrogen evolution and benzaldehyde production by dehydrogenation of benzyl alcohol over Nidecorated Zn_(0.5)Cd_(0.5)S solid solution under visible light. The photocatalytic system shows an excellent hydrogen production rate of 666.3 μmol h^(-1) with high stability. The optimal apparent quantum yield of52.5% is obtained at 420 nm. This noble-metal-free photocatalytic system displays much higher activity than pure Zn_(0.5)Cd_(0.5)S and Pt-loaded Zn_(0.5)Cd_(0.5)S solid solution. Further studies reveal that the metallic Ni nanocrystals play an important role in accelerating the separation of photogenerated charge carriers and the subsequent cleavage of α-C–H bond during dehydrogenation of benzyl alcohol.

关键词： Photocatalysis Benzyl alcohol oxidation Hydrogen production Nickel Solid solution Charge separation

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Enhancements of Passive Film and Pitting Resistance in Chloride solution for 316LX Austenitic Stainless Steel After Sn Alloying

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Acta Metallurgica Sinica(English Letters) 2019年第1期32卷 98-106页

作者： Yuan-Yuan Yang Yuan-Yuan Liu Man-Lang Cheng Nian-Wei Dai Min Sun Jin Li Yi-Ming Jiang Department of Materials Science Fudan University

In the present work, the electrochemical behavior and properties of the passive film of a new Sn-alloyed 316 LX austenitic stainless steel were investigated. With the increase in Sn content in 316 LX austenitic stainless steel from 0 to 0.21%, the critical pitting temperature value increased from 32.6 to 38.8 °C, and the pitting potential increased from 0.252 V_(SCE) to 0.317 V_(SCE). Electrochemical impedance spectroscopy results showed that the corrosion resistance of passive film rose with the increase in Sn content, indicating a more stable passive film. The Mott–Schottky measurement revealed an n-type passive film with a decreased carrier concentration on the 316 LX austenitic stainless steel surface. The Cr, Sn^(2+) and Sn^(4+)(SnO, SnOHCl or SnO_2) enrichments were observed in the passive layer by X-ray photoelectron spectroscopy. The enrichment of Sn and Cr in the passive film can account for the enhanced pitting resistance of 316 LX austenitic stainless steel in chloride solution.

关键词： Austenitic stainless steel Sn alloying Pitting Chloride solution

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Synthesis and characterization of the nanostructured solid solution with extended solubility of graphite in nickel by mechanical alloying

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International Journal of Minerals,Metallurgy and Materials 2019年第8期26卷 1031-1037页

作者： Nitika Kundan Biswajit Parida Anup Kumar Keshri Prathvi Raj Soni Department of Metallurgical and Materials Engineering Malaviya National Institute of TechnologyJaipurRajasthan 302017India Department of Materials Science and Engineering Indian Institute of Technology PatnaBihar 801106India

In the present work,mechanical alloying of a powder mixture of nickel and graphite(up to 15wt%)was carried out in an attrition mill under a nitrogen atmosphere.The as-milled powders were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),and transmission electron microscopy(TEM).The 15wt%graphite dissolved into the nickel(exceeding the negligible solid solubility in the nickel–carbon system),thereby forming a supersaturated solid solution of graphite in a nickel matrix.The dissolved graphite occupied interstitial positions along the dislocation edges and at the grain-boundary regions.A three-step graphite dissolution mechanism has been proposed.The associated changes in the nickel lattice,such as changes in the crystallite size(62 to 43 nm),lattice strain(0.12%to 0.3%),and lattice parameter(0.3533 to 0.3586 nm),which led to the formation of the supersaturated solid solution,were also evaluated and discussed.

关键词： Ni-C system mechanical alloying supersaturated solid solution nanostructured powder

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Corrosion behavior of pure aluminum in FeCl_3 solution

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Transactions of Nonferrous Metals Society of China 2006年第6期7卷 1460-1466页

作者：屈钧娥郭兴蓬王海人黄金营 School of Chemistry and Material Science Hubei University Department of Chemistry Huazhong University of Science and Technology Postdoctoral Station of Technical Institute of Physics and Chemistry Chinese Academy of Sciences

The corrosion behavior of pure aluminum in FeCl3 solution was investigated mainly by in-situ AFM(Atomic Force Microscopy).The results of combined researches of AFM,SEM(Scanning Electron Microscopy)and EDAX(Energy Dispersive Analysis of X-ray)show that in addition to uniform attack,pitting corrosion takes place also on pure aluminum surface in FeCl3 solution at open-circuit potential,and impurity elements Fe and Cu are found enriched in corrosion product.In-situ AFM was also used to examine the initiation and development of pitting corrosion of pure aluminum induced by potentiodynamic sweep,and the repassivation of an active pit is observed.AFM tip scratching technique was used to produce a physical defect on metal surface,which is traced by in-situ AFM and it is found that the defect is likely to be preferentially attacked and evolve to pitting corrosion.

关键词： pure aluminum pitting corrosion FeCl3 solution AFM uniform attack

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