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Segregation of solute atoms in ZrC grain boundaries and their effects on grain boundary strengths

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Journal of Materials Science & Technology 2022年第6期101卷 234-241页

作者： Fu-Zhi Dai Yinjie Sun Yixiao Ren Huimin XIANG Yanchun Zhou Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China

ZrC is a promising candidate for the application in ultra-high temperature regime due to its unique combination of excellent properties,such as high melting point,good chemical inertness and high temperature stability.The rapid decrease of strength at high temperatures,however,is one of the obstacles that impedes its practical services.Strengthening of grain boundaries by solute segregation is believed to be an effective way to improve its high temperature performance.Therefore,the segregation tendency of ten solid solute atoms,including Sc,Ti,V,Cr,Y,Nb,Mo,Hf,Ta,W,in Zr C grain boundaries,and the strengthening/weakening effects on grain boundaries due to segregation are investigated by first-principles calculations.The segregation tendency is found dominated by the size effect,which is confirmed by both a qualitative analysis and a quantitative approach based on support vector regression.It means that big atoms tend to segregate to grain boundary sites with local expansions,while small atoms tend to segregate to grain boundary sites with local compressions.Simulations on stress-strain responses indicate that segregation of small atoms(Ti,V,Cr,Nb,Ta,Mo,W)can usually improve grain boundary strengths by inducing compression strains to grain boundaries,even though there is also an exception.In contrast,segregation of Sc and Y will soften grain boundaries.The results reveal that strengthening of grain boundaries by solute segregation is a valuable avenue to enhance high temperature mechanical properties of ZrC,providing guidelines for further design of ZrC based materials.

关键词： ZrC Grain boundary Segregation Strength First-principles calculation Machine learning

Beyond two-dimension: One-and zero-dimensional halide perovskites as new-generation passivators for high-performance perovskite solar cells

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能源化学:英文版 2023年第8期83卷 189-208,I0007页

作者： Yuanyuan Zhao Huimin XIANG Ran Ran Wei Zhou Wei Wang Zongping Shao State Key Laboratory of Materials-Oriented Chemical Engineering College of Chemical EngineeringNanjing Tech UniversityNanjing 210009JiangsuChina WA School of Mines:Minerals Energy and Chemical EngineeringCurtin UniversityPerthWA 6845Australia

Perovskite solar cells(PSCs) as a rising star in the photovoltaic field have received rapidly increasing attention recently due to the boosting power conversion efficiencies(PCEs) from 3.8% to 25.7% in the last13 years. Nevertheless, the conventional PSCs with three-dimensional(3D) halide perovskites as light absorbers suffer from inferior PCEs and poor durability under sunlight, high-temperature and humid conditions due to the high defect amount and structural instability of 3D perovskites, respectively. To tackle these crucial issues, lower-dimensional halide perovskites including zero-dimensional(0D), onedimensional(1D), and two-dimensional(2D) perovskites have been employed as efficient passivators to boost the PCEs and durability of 3D-PSCs due to the high structural stability and superior resistance against moisture, heat and sunlight. Therefore, in order to achieve better understanding about the advantages and superiorities of combining low-dimensional perovskites with their 3D counterparts in improving the PCEs and durability of 3D-PSCs, the recent advances in the development and fabrication of mixeddimensional PSCs with 1D/0D perovskites as passivators are summarized and discussed in the review.The superiority of 1D/0D perovskites as passivators over 2D counterparts, the passivation mechanism and the methods of 1D/0D perovskites are also presented and discussed. Furthermore, the rules to choose1D/0D perovskites or relevant spacer cations are also emphasized. On this basis, several specific strategies to design and fabricate mixed-dimensional PSCs with 1D/0D perovskites are presented and discussed.Finally, the crucial challenges and future research directions of mixed-dimensional PSCs with 1D/0D perovskites as passivators are also proposed and discussed. This review will provide some useful insights for the future development of high-efficiency and durable mixed-dimensional PSCs.

关键词： Perovskite solar cells Mixed-dimensional Passivators Stability Power conversion efficiency

Sodium fluoride sacrificing layer concept enables high-efficiency and stable methylammonium lead iodide perovskite solar cells

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Journal of Materials Science & Technology 2022年第18期113卷 138-146页

作者： Huimin XIANG Pengyun Liu Wei Wang Ran Ran Wei Zhou Zongping Shao College of Chemical Engineering State Key Laboratory of Materials-Oriented Chemical EngineeringNanjing Tech UniversityNanjing 210009China WA School of Mines:Minerals Energy and Chemical Engineering(WASM-MECE)Curtin UniversityPerthWA 6845Australia

As next-generation photovoltaic devices,methylammonium lead iodide(MAPbI_(3))-based organic-inorganic halide perovskite solar cells(PSCs)have received considerable attention because of their cost effectiveness and high efficiency.However,their practical applications are retarded due to severe instability under moisture,thermal and sunlight conditions,which are closely related to the insufficient perovskite film quality and high photocatalytic activity of defective TiO_(2) electron-transporting layer(ETL)to accelerate the perovskite decomposition.Herein,remarkably enhanced power conversion efficiency(PCE)and stability of MAPbI_(3)-based PSCs is reached through the use of a new sodium fluoride(NaF)sacrificing layer,which,introduced between the perovskite layer and ETL,is sacrificed during cell fabrication by penetrating into the perovskite layer,improving the perovskite film quality,while partial NaF is incorporated into the mesoporous TiO_(2) ETL during NaF layer fabrication to passivate TiO_(2) and construct a well-matched energy level alignment.As a result,the optimized PSC generates a high PCE of 20.9%,which is 17%higher than that of the pristine cell(17.9%),and outstanding performance stability due to remarkably enhanced moisture,thermal and sunlight stability.This study highlights a simple and effective approach to boost the PCE and durability of MAPbI 3-based PSCs simultaneously,accelerating the commercialization of this technology.

关键词： Perovskite solar cells Sodium fluoride sacrificing layer Defect passivation Stability

Y_5Si_3C and Y_3Si_2C_2: Theoretically predicted MAX phase like damage tolerant ceramics and promising interphase materials for SiC_f/SiC composites

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Journal of Materials Science & Technology 2019年第3期35卷 313-322页

作者： Yanchun Zhou Huimin XIANG Fu-Zhi Dai Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials & Processing Technology

Researching for interphase materials that can protect SiC fibers from oxygen and water vapor attacks has become one of the most important issues for the applications of SiC_f/SiC composites in high-temperature combustion environment. However, such kinds of interphase materials are not available yet. Herein,we report theoretically predicted properties of two promising interphase materials Y_5Si_3 C and Y_3Si_2C_2.Although crystallizing in different structures, they share the common features of layered structure,anisotropic chemical bonding, anisotropic electrical and mechanical properties, and low shear deformation resistance. The bulk moduli for Y_5Si_3C and Y_3Si_2C_2 are 78 and 93 GPa, respectively; while their shear moduli are 52 and 50GPa, respectively. The maximum to minimum Young's modulus ratios are1.44 for Y_5Si_3C and 3.27 for Y_3Si_2C_2. Based on the low shear deformation resistance and low Pugh's ratios(G/B = 0.666 forY_5Si_3C and 0.537 for Y_3Si_2C_2; G: shear modulus; B: bulk modulus), they are predicted as damage tolerant and soft ceramics with predicted Vickers hardness of 9.6 and 6.9 GPa, respectively.The cleavage plane and possible slip systems are(000 l) and(0001)[1120] and(1010)[0001] forY_5Si_3C,and those for Y_3Si_2C_2 are {h00} and(010)[101]. Since the oxidation products are water-vapor resistant Y2 Si2 O7, Y2 SiO5 and/or Y_2 O_3 upon oxidation, and the volume expansions are ca 140% and ca 26% for Y_5Si_3C and Y_3Si_2C_2, they are expected to seal the interfacial cracks in SiC_f/SiC composites. The unique combination of easy cleavage, low shear deformation resistance, volume expansions upon oxidation, and the resistance of the oxidation products to water vapor attack warrant them promising as interphase materials of SiC_f/SiC composites for water-vapor laden environment applications.

关键词： Y5Si3C Y3Si2C2 Interphase material Damage tolerant ceramics Electronic structure

An effective planting model to decrease cadmium accumulation in rice grains and plants:Intercropping rice with wetland plants

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Pedosphere 2023年第2期33卷 355-364页

作者： Huimin XIANG Ni LAN Fugang WANG Benliang ZHAO Hui WEI Jiaen ZHANG Guangdong Provincial Key Laboratory of Eco-Circular Agriculture South China Agricultural UniversityGuangzhou 510642(China) Key Laboratory of Agro-Environment in the Tropics Ministry of AgricultureCollege of Natural Resources and EnvironmentSouth China Agricultural UniversityGuangzhou 510642(China) Guangdong Engineering Research Center for Modern Eco-Agriculture and Circular Agriculture Guangzhou 510642(China) Key Laboratory of Agroecology and Rural Environment of Guangdong Regular Higher Education Institutions South China Agricultural UniversityGuangzhou 510642(China)

Cadmium(Cd)pollution affects plant growth and poses a serious threat to food safety and human health.Cadmium-contaminated rice is assumed to be the main source of Cd exposure to humans,with grave health risks.Phytoremediation is an efficient,cost-effective,and eco-friendly approach to minimize Cd accumulation in rice.However,research on the effect of rice intercropping with wetland plants that exhibit great capacity for phytoremediation in decreasing Cd concentrations in paddies is limited.A pot experiment in greenhouse was conducted to evaluate the effect of rice intercropping with two wetland plants(Pontederia cordata and Canna indica)under different soil Cd levels(0,1,10,and 25 mg kg^(-1))on rice growth and Cd accumulation and translocation.The results showed that rice intercropping with the two wetland plants significantly improved plant height,tiller,and biomass of rice,but reduced Cd bioconcentration factors(BCFs)and Cd concentrations in rice and wetland plants.Compared with rice monocropping,the BCF in rice grain under 25 mg kg^(-1)soil Cd level significantly decreased by 54.39%and 59.65%in the systems of rice intercropping with C.indica and P.cordata,respectively.In addition,intercropping inhibited the increase in BCFs in rice and wetland plants under increasing soil Cd levels.In conclusion,the systems of rice intercropping with P.cordata and C.indica can be considered two new and effective approaches for ameliorating Cd pollution in paddies,as well as minimizing Cd accumulation in rice and improving food safety.Of the two intercropping systems,rice intercropping with P.cordata performed better than intercropping with C.indica.

关键词： bioconcentration factor Cd pollution Cd translocation phytoremediation transfer factor

Theoretical investigation on the stability, mechanical and thermal properties of the newly discovered MAB phase Cr4AlB4

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Journal of Materials Science & Technology 2020年第4期39卷 161-166页

作者： Fu-Zhi Dai Haiming Zhang Huimin XIANG Yanchun Zhou Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing100076China School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing100044China

The nanolaminated MAB phases have attracted great research interests in recent years due to their similarities to MAX phases,which display both metallic and ceramic-like properties.In the present work,a newly discovered MAB phase Cr4AlB4 was investigated by first principles calculations.Energy evaluations indicate that Cr4AlB4 can be synthetized in Al lean condition,which can further transform to Cr2AlB2 in Al rich condition.The full set of elastic properties and their dependences on temperature,ideal strengths under different tensile and shear deformations,and thermal expansions of Cr4AlB4 were predicted.The results reveal that the properties of Cr4AlB4 are dominated by the layered crystal structure and weak bonding nature between Al and Cr2B2 layers,including low elastic stiffness and large thermal expansion along[010]direction(the stacking direction of Al and Cr2B2 layers),low shear resistances in(010)plane,and preferentially cleavage along and/or shear in(010)plane.Therefore,it suggests that Cr4AlB4 displays similar mechanical properties to MAX phases,including readily machinable,thermal shock resistant,and damage tolerant.In combination with the fact that Cr,Al and B all can form dense oxides to protect the material from further oxidation,Cr4AlB4 is regarded as a promising high temperature ceramic.

关键词： MAB phase Cr4AlB4 First-principles Mechanical properties Thermal properties

Grain boundary segregation induced strong UHTCs at elevated temperatures:A universal mechanism from conventional UHTCs to high entropy UHTCs

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Journal of Materials Science & Technology 2022年第28期123卷 26-33页

作者： Fu-Zhi Dai Bo Wen Yinjie Sun Yixiao Ren Huimin XIANG Yanchun Zhou Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China DP Technology Beijing 100044China

Ultra-high temperature ceramics(UHTCs)exhibit a unique combination of excellent properties,including ultra-high melting point,excellent chemical stability,and good oxidation resistance,which make them promising candidates for aerospace and nuclear applications.However,the degradation of hightemperature strength is one of the main limitations for their ultra-high temperature applications.Thus,searching for mechanisms that can help to develop high-performance UHTCs with good high-temperature mechanical properties is urgently needed.To achieve this goal,grain boundary segregation of a series of carbides,including conventional,medium entropy,and high entropy transition metal carbides,i.e.,Zr_(0.95)W_(0.05)C,TiZrHfC_(3),ZrHfNbTaC_(4),TiZrHfNbTaC_(5),were studied by atomistic simulations with a fitted Deep Potential(DP),and the effects of segregation on grain boundary strength were emphasized.For all the studied carbides,grain boundary segregations are realized,which are dominated by the atomic size effect.In addition,tensile simulations indicate that grain boundaries(GBs)will usually be strengthened due to segregation.Our simulation results reveal that grain boundary segregation may be a universal mechanism in enhancing the high-temperature strength of both conventional UHTCs and medium/high entropy UHTCs,since GBs play a key role in controlling the fracture of UHTCs at elevated temperatures.

关键词： UHTCs High entropy ceramics Grain boundary segregation High-temperature strength Machine learning potential

Achieving ultra-broadband electromagnetic wave absorption in high-entropy transition metal carbides (HE TMCs)

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Journal of Advanced Ceramics 2022年第4期11卷 545-555页

作者： Weiming ZHANG Huimin XIANG Fu-Zhi DAI Biao ZHAO Shijiang WU Yanchun ZHOU Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China Henan Key Laboratory of Aeronautical Materials and Application Technology School of Material Science and EngineeringZhengzhou University of AeronauticsZhengzhou 450046China Zibo Firststar New Material Incorporated Co. Ltd.Zibo 255000China

Electronic devices pervade everyday life,which has triggered severe electromagnetic(EM)wave pollution.To face this challenge,developing EM wave absorbers with ultra-broadband absorption capacity is critically required.Currently,nano-composite construction has been widely utilized to realize impedance match and broadband absorption.However,complex experimental procedures,limited thermal stability,and interior oxidation resistance are still unneglectable issues.Therefore,it is appealing to realize ultra-broadband EM wave absorption in single-phase materials with good stability.Aiming at this target,two high-entropy transition metal carbides(HE TMCs)including(Zr,Hf,Nb,Ta)C(HE TMC-2)and(Cr,Zr,Hf,Nb,Ta)C(HE TMC-3)are designed and synthesized,of which the microwave absorption performance is investigated in comparison with previously reported(Ti,Zr,Hf,Nb,Ta)C(HE TMC-1).Due to the synergistic effects of dielectric and magnetic losses,HE TMC-2 and HE TMC-3 exhibit better impedance match and wider effective absorption bandwidth(EAB).In specific,the exclusion of Ti element in HE TMC-2 endows it optimal minimum reflection loss(RL_(min))and EAB of−41.7 dB(2.11 mm,10.52 GHz)and 3.5 GHz(at 3.0 mm),respectively.Remarkably,the incorporation of Cr element in HE TMC-3 significantly improves the impedance match,thus realizing EAB of 10.5,9.2,and 13.9 GHz at 2,3,and 4 mm,respectively.The significance of this study lays on realizing ultra-broadband capacity in HE TMC-3(Cr,Zr,Hf,Nb,Ta),demonstrating the effectiveness of high-entropy component design in tailoring the impedance match.

关键词： transition metal carbide(TMC) high-entropy ceramics electromagnetic(EM)wave absorption dielectric and magnetic loss coupling ultra-broadband absorption

Theoretical Investigation on Mechanical and Thermal Properties of a Promising Thermal Barrier Material:Yb_3Al_5O_(12)

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Journal of Materials Science & Technology 2014年第7期30卷 631-638页

作者： Yanchun Zhou Huimin XIANG Zhihai Feng Science and Technology of Advanced Functional Composite Laboratory Aerospace Research Institute of Materials and Processing Technology

An investigation on the mechanical and thermal properties of Yb3Al5O12 is conducted by a combination of first- principles calculations and chemical bond theory calculation. Density functional theory （DFT） computations were performed for the structural, mechanical, and thermal properties, and the results are confirmed by chemical bond theory. Based on the calculated equilibrium crystal structure, heterogeneous bonding nature is revealed. The full set of elastic constants and mechanical properties of Yb3Al5O12 are presented for the first time. The thermal expansion coefficient of Yb3Al5O12 is calculated to be 7.5 × 10^-6 K-1 by chemical bond theory. In addition, the minimum thermal conductivity of Yb3Al5O12 is estimated to be 1.22 W m-t K-1, and the origin of such low thermal conductivity is discussed. Our theoretical results highlight the potential of Yb3Al5O12 as a prospective thermal barrier coating material.

关键词： Thermal barrier coating Ytterbium aluminum garnet First principles calculations Chemical bond theory