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precursor chemistry towards highly efficient and phase-stable red emitting CsPbI_(3) perovskite nanocrystals

Nano Research 2022年第1期15卷 644-652页

作者： Dejian Chen Decai Huang Mingwei Yang Kunyuan Xu Jie Hu Sisi Liang Haomiao Zhu CAS Key Laboratory of Design and Assembly of Functional Nanostructures and Fujian Key Laboratory of NanomaterialsFujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002China Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials Xiamen Institute of Rare Earth MaterialsHaixi InstituteChinese Academy of SciencesXiamen 361021China

All-inorganic cesium lead halide perovskite nanocrystals(CsPbX_(3),X=Cl,Br,I)have attracted considerable scientific and technological interest due to their precise bandgap tunability,high color purity and efficient ***,their poor stability in harsh conditions such as moisture,ultraviolet(UV)light irradiation and high temperature,is a major obstacle for their further commercial ***,by simply using a new type of precursor,namely“HPbX_(3)”(X=Cl,Br,I),we can achieve the coordination equilibrium for Pb precursors during reaction and obtain high-quality perovskite nanocrystals with tremendously enhanced luminous efficiency and chemical stability based on hot-injection *** prepared a-CsPbb nanocrystals exhibit an extremely high photoluminescence quantum yield of 96%and keep stable in air for more than two months without any post-synthesis ***,stability evaluations under UV light irradiation,water or thermal impact are also performed and the results show substantially improved stability of these nanocrystals as compared with the samples prepared using traditional Pbl_(2) as *** temperature-dependent(10-300 K)steady and transient spectral analysis combined with compositional measurements,it is revealed that the lower structural defect density,which is guaranteed by abundant halogen when using HPbX3 as precursor,is the most important reason for such performance enhancement.

关键词： perovskite nanocrystals CsPbX_(3) precursor stability vacancy defect

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Low-agglomerated yttria nanopowders via decomposition of sulfate-doped precursor with transient morphology

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Journal of Rare Earths 2014年第4期32卷 320-325页

作者： R.P.Yavetskiy D.Yu.Kosyanov V.N.Baumer A.G.Doroshenko A.I.Fedorov N.A.Matveevskaya A.V.Tolmachev O.M.Vovk Institute for Single Crystals of NAS of Ukraine State Scientific Institution"Institute for Single Crystals"of NAS of Ukraine

The fabrication peculiarities of low-agglomerated yttria （Y2O3） nanopowders via thermal decomposition of sulfate-doped precursor with transient morphology were studied. It was determined that Y2（OH）5（NO3）x（CO2）y（SO4）z·nH2O （n=1-2） crystalline precursor underwent fragmentation and decomposition into isolated quasi-spherical Y2O3 particles upon calcination. Effect was con-nected with minimizing the free energy of the plate-like crystallites via reducing the contact surface until to the moment of spheroidi-zation and attainment of isolation that occurred atТ=1100 °С. Residual sulfate ions slowed down the surface diffusion during heat treatment thus retaining quasy-spherical morphology and low aggregation degree of Y2O3 nanopowders. Sulfate-doped yttria nanopowders with medium particle size of 53±13 nm possessed improved sinterability in comparison with undoped ones arising from finer particle size, narrower particle distribution and lower agglomeration degree.

关键词： precursor transient morphology sulfate-ions yttria nanopowders particle size sinterability rare earths

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Intrinsic effects of precursor functional groups on the Na storage performance in carbon anodes

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Nano Research 2023年第11期16卷 12579-12586页

作者： Xiaohan Tang Fei Xie Yaxiang Lu Zhao Chen Xiangfei Li Hong Li Xuejie Huang Liquan Chen Yuanjiang Pan Yong-Sheng Hu Department of Chemistry Zhejiang UniversityHangzhou 310027China Key Laboratory for Renewable Energy Beijing Key Laboratory for New Energy Materials and DevicesBeijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing 100190China Huairou Division Institute of PhysicsChinese Academy of SciencesBeijing 101400China Yangtze River Delta Physics Research Center Co. Ltd.Liyang 213300China College of Materials Science and Optoelectronic Technology University of Chinese Academy of SciencesBeijing 100049China

The oxygen-containing functional groups in disordered carbon anodes have been widely reported to influence the Na storage ***,the effect of original oxygen-containing groups in the precursors on the final structures and electrochemical performance is rarely ***,we used the anthraquinone derivatives with different oxygen-containing functional groups as precursors to make the disordered carbon anodes for Na-ion batteries(NIBs).Through comprehensive structural and electrochemical analyses,we found that the different types of functional groups in carbon precursors directly affect the cross-linking process during *** original precursors containing enough inter-chain oxygen or oxygen-containing functional groups with unsaturated bonds unattached to the ring are beneficial for the oxygen atoms to remain or cross-link in structure to result in more C–O–C group,forming nanovoids and disordered structure,which then determine the high performance of the carbon anodes in *** work highlights the importance of the type/content of functional groups in precursor and provides guidance for the future design of carbon anodes in NIBs from the perspective of precursor selection.

关键词： disordered carbon precursor oxygen-contained functional group Na-ion batteries

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Effects of precursor moisture and inert N_2 atmosphere calcinations on structure and properties of alumina modified CeZrLaNd mixed oxides

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Journal of Rare Earths 2019年第6期37卷 609-616页

作者： Meisheng Cui Zhizhe Zhai Hao Wang Yongke Hou Yongqi Zhang Xiaowei Huang National Engineering Research Center for Rare Earth Materials General Research Institute for Nonferrous Metals Grirem Advanced Materials Co. Ltd.

CeO_2-ZrO_2 mixed oxides are widely used in the three-way catalysts due to their unique reversible oxygen storage and release capacity. Large surface area, high oxygen storage capacity and good thermal stability of cerium zirconium mixed oxides are the key properties for the automotive catalysts so as to meet the strict emission regulations. In this work, alumina modified CeZrLaNd mixed oxides were prepared by a co-precipitation method. The effects of moisture in precursor and inert N2 atmosphere during calcinations on the structure and properties were investigated by Brunauer-Emmett-Teller(BET) surface area measurements, X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), hydrogen temperature-programmed reduction(H_2-TPR), oxygen storage capacity(OSC), Raman spectroscopy, and X-ray photoelectron spectroscopy(XPS). The results show that the moisture in precursor during calcinations increases the crystal grain size of the cerium zirconium mixed oxides, improving the thermal stability. And the aged surface area of sample after being calcined at1000 ℃ for 4 h reaches 68.8 m^2/g(5.7% increase compared with the common sample). The inert N2 atmosphere endows a great pore-enlarging effect, which leads to high fresh surface area of 148.9 m2/g(13.5% increase compared with the common sample) and big pore volume of 0.5705 mL/g. The redox and oxygen storage capacity are also improved by inert N2 atmosphere with high OSC value of 241.06μmolO_2/g(41.3% increase compared with the common calcination), due to the abundant formation of the crystal defects and oxygen vacancies.

关键词： precursor moisture Inert N2 atmosphere Calcinations Alumina modified CeZrLaNd mixed oxides Rare earths

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Synthesis of vanadium and chromium carbides(V_8C_7–Cr_3C_2) nanocomposite via an in situ precursor method

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Rare Metals 2015年第7期34卷 498-504页

作者： Zhi-Wei Zhao Wen-Meng Hu Hong-Juan Zheng Fei-Xiao Chen College of Materials Science and Engineering Henan University of Technology

In situ synthesis method was used to prepare V8C7–*** vanadate, ammonium dichromate and nanometer carbon black were used as raw *** products were characterized by X-ray diffractometry(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), thermogravimetric and differential scanning calorimetry(TGDSC) and X-ray photoelectron spectroscopy(XPS) *** results show that V8C7–Cr3C2nanocomposite with an average crystallite size of 25.4 nm can be synthesized at 1200 °C for 1 *** synthesis temperature required by the method is at least 200 °C lower than that required by the conventional approaches for preparing vanadium and chromium *** powders show good dispersion and are mainly composed of spherical or nearly spherical particles with a mean diameter of about 30 *** weight loss ratio of the precursor throughout the reaction process reaches 58 wt%.Three exothermic peaks and four endothermic peaks occur during the *** surface of the specimen is mainly composed of V, Cr, C and O elements.

关键词： Nanocomposite Carbides precursor In situ synthesis

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Carbon-fiber-reinforced silicon carbide composites prepared by precursor pyrolysis-hot pressing

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中国有色金属学会会刊：英文版 1999年第4期9卷 778-784页

作者：何新波张新明张长瑞周新贵周安郴 Cent S Univ Dept Mat Sci & Engn Changsha 410083 Peoples R China Natl Univ Def Technol Dept Mat Engn & Appl Chem Changsha 410073 Peoples R China

The Cf/SiC composites were prepared by precursor conversion-hot pressing sintering with AIN and Y2Os as additives. The effects of sintering temperature and additives on the microstructures and properties of the composites were investigated. The composite sintered at as low as 1 75O℃ already showed higher density and better mechanical properties, which was mainly attributed to the liquid-phase-sintering and the formation of the AIN-SiC solid solution. With increasing the sintering temperature to 1 800 ℃, the flexural strength and fracture toughness of the composite were substantially improved up to 691. 6 MPa and 2O. 7 MPa’ m1/2 respectively in spite of the slightly elevated density, and the composite exhibited "tough" failure. Despite the improved density, the composite sintered at 1 85O℃ displayed brittle failure, which mainly attributed to the strongly bonded fiber/matrix interface and the degradation of the properties of the fibers.

关键词： precursor pyrolysis-hot pressing C_f/SiC composites sintering temperature

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Effects of the properties of Mg(OH)_(2)precursor on the hydrothermal synthesis of magnesium oxysulfate whiskers

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Particuology 2024年第9期92卷 13-23页

作者： Thanayos Boonrit Mei Yang Guangwen Chen Dalian Institute of Chemical Physics Chinese Academy of SciencesDalian116023China University of Chinese Academy of Sciences Beijing100049China

Magnesium oxysulfate(MOS)whiskers are commonly synthesized through a dissolution-precipitation mechanism,wherein Mg(OH)_(2)dissolves to form Mg(OH)_(6)^(4−),followed by reactions with SO_(4)^(2−)and H_(2)O to yield MOS ***,the impact of Mg(OH)_(2)precursor properties on the formation process of MOS whiskers has been insufficiently explored,and sector-like and needle-like morphologies were both observed in previous *** this study,we systematically investigated how the properties of Mg(OH)_(2)precursors influenced the crystalline structure and morphology of MOS *** various experimental conditions,MgSO_(4)·5Mg(OH)_(2)·2H_(2)O(152MOS)whiskers were consistently obtained,regardless of Mg(OH)_(2)morphology and *** size of Mg(OH)_(2)emerged as a critical factor in shaping the morphology of 152MOS ***-sized Mg(OH)_(2)(≤106±37 nm)favored the formation of sector-like whiskers,while larger-sized Mg(OH)_(2)(≥206±98 nm)encouraged the development of needle-like *** distinction was attributed to the slower dissolution rate exhibited by larger-sized Mg(OH)_(2),maintaining a smaller number of 152MOS nuclei and promoting the growth of needle-like whiskers instead of the aggregation of 152MOS nuclei into sector-like *** addition,the effects of the molar ratio of Mg^(2+)to SO_(4)^(2−)and hydrothermal temperature were also *** average length and diameter of the needle-like whiskers prepared with Mg(OH)_(2)of 331±145 nm under optimized conditions were 77±32 and 0.39±0.10μm,*** study presented an effective strategy for controlling the morphology of 152MOS whiskers.

关键词： Magnesium oxysulfate whiskers Morphology control precursor Microreactor

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ZrC-ZrB_2-SiC ceramic nanocomposites derived from a novel single-source precursor with high ceramic yield

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Journal of Advanced Ceramics 2019年第1期8卷 112-120页

作者： Zhaoju YU Xuan LV Shuyi LAI Le YANG Wenjing LEI Xingang LUAN Ralf RIEDEL College of Materials Key Laboratory of High Performance Ceramic Fibers (Xiamen University) Ministry of Education College of Materials Fujian Key Laboratory of Advanced Materials (Xiamen University) College of Materials Science and Engineering Huaqiao University Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical University Technische Universit?t Darmstadt Institut für Materialwissenschaft

For the first time, ZrC-ZrB_2-SiC ceramic nanocomposites were successfully prepared by a single-source-precursor route, with allylhydridopolycarbosilane(AHPCS),triethylamine borane(TEAB),and bis(cyclopentadienyl) zirconium dichloride(Cp_2 ZrCl_2) as starting materials. The polymer-to-ceramic transformation and thermal behavior of obtained single-source precursor were characterized by means of Fourier transform infrared spectroscopy(FT-IR) and thermal gravimetric analysis(TGA). The results show that the precursor possesses a high ceramic yield about 85% at 1000 ℃.The phase composition and microstructure of formed ZrC-ZrB_2-SiC ceramics were investigated by means of X-ray diffraction(XRD) and high resolution transmission electron microscopy(HRTEM).Meanwhile, the weight loss and chemical composition of the resultant ZrC-ZrB_2-SiC nanocomposites were investigated after annealing at high temperature up to 1800 ℃. High temperature behavior with respect to decomposition as well as crystallization shows a promising high temperature stability of the formed ZrC-ZrB_2-SiC nanocomposites.

关键词： polymer derived ceramics single-source precursor ceramic nanocomposite

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The macroscopic mechanisms and associated atmospheric precursor environmental capacities that lead to secondary fine particle pollution

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Science China Earth Sciences 2019年第12期62卷 2069-2082页

作者： Dahai XU Junming CHEN State Key Laboratory of Severe Weather and Key Laboratory of Atmospheric Chemistry of China Meteorological Administration Chinese Academy of Meteorological Sciences

This paper establishes the kinetic equations in atmospheric chemistry that describe the macroscopic mechanisms of secondary fine particle pollution generated by precursors during atmospheric *** dynamic and static solutions of these equations can be applied to calculate quantitative relationships between the concentration ratio of precursors and secondary fine particles as well as the physical clearance power of the atmosphere,chemical reaction rate,and the scale of a contaminated *** dynamic solution presented here therefore corresponds with a theoretical formula for calculating the overall rate constant for the oxidation reaction of reducing pollutants in the actual atmosphere based on their local concentrations and meteorological monitoring *** addition,the static solution presented in this paper reveals the functional relationship between the concentration of secondary fine particles and precursor emission rate as well as atmospheric self-purification *** result can be applied to determine the atmospheric environmental capacity of a *** records collected over the last 40 years from 378 weather stations in China's Mainland as well as the spatiotemporal distribution sequence of overall oxidation reaction rates from precursors show that when the reference concentration limit of secondary fine particles is100μmol m-3,the atmospheric environmental capacity of total precursors canbe calculated as 24890×1010 mol ***,when the annual average concentration limit of given fine particles is 35μg m-3 and the ratio of sulfate and nitrate to 30%and 20%of the total amount of fine particles,the capacities of SO2,NOx and NH3 are 1255,1344,and 832(1010g yr-1),*** clearance density of precursors for different return periods across China's Mainland under above conditions are also provided in this study.

关键词： Atmospheric chemical kinetic equations precursor of secondary fine particle Overall oxidation reaction rate Atmospheric self-purification power Atmospheric environmental capacity Clearance density Return period

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Thermophysical properties of solution precursor plasma-sprayed La2Ce2O7 thermal barrier coatings

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Rare Metals 2019年第7期38卷 689-694页

作者： Bei-Bei Feng Yi Wang Qiang Jia Wei Huang Hong-Li Suo Wen Ma School of Materials Science and Engineering Beijing University of Technology Beijing 100022 China The Key Laboratory of Advanced Functional Materials Ministry of Education of China Beijing University of Technology Beijing 100022 China School of Materials Science and Engineering Inner Mongolia University of Technology Huhhot 010051. China

La2Ce2O7 (LCO) is a promising candidate for thermal barrier coatings (TBCs) due to that it provides better thermal insulation than yttria-stabilized zirconia (YSZ) does. In this work, a TBC LCO was produced by solution precursor plasma spraying (SPPS). After the solution precursors were prepared and the spraying parameters were optimized, the thermophysical properties and thermal shock performance of the coatings were tested. It was found that the SPPS coating with segmentation crack density of 6 mm^-1 had the porosities of about 33.5% at spray distances of 35 mm. The thermal conductivity of the SPPS coatings is 0.50-0.75 W·m^-1·K^-1, much lower than that of the atmospheric plasma spraying (APS) coatings (0.85-1.25 W·m^-1·K^-1). The thermal shock performance of the SPPS coatings reached 60 cycles, much better than the APS coatings. This improvement is due to the segmentation cracks in the coatings, which can improve strain tolerance and effectively relieve internal stress. This study provides reference significance for further research on thermal barrier coatings.

关键词： La2Ce2O7 Solution precursor plasma spraying Thermal conductivity Segmentation cracks

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