凝结时空精华,铸就序构材料,力促大尺寸功能晶体新发展

中国科学技术协会发布的2021年重大科学问题、工程技术难题和产业技术问题,将“如何突破大尺寸晶体材料的制备理论和技术”列为首要问题,位居十个对科学发展具有导向作用的前沿科学问题之首。这不仅对于进一步激发功能晶体材料领域研究人员的好奇心和自由探索热情,引领科技创新趋势和科研攻关方向,服务国家科技创新发展具有重要意义,而且将引导功能晶体材料领域广大科技工作者围绕问题开展原创性、引领性的科技攻关,为加快建设科技强国作出更大贡献,以优异成绩丰富中国式现代化内涵。大尺寸晶体材料在矿物学领域自然天成,常常令材料科技工作者感到震惊。例如,在所有已获认证的晶体中,最大尺寸的晶体是来自马达加斯加共和国的绿柱石,长18 m,直径3.5 m,体积约为143 m^(3),质量约为380 t。追溯矿物的形成过程,人们不难发现形成大尺寸晶体在时空上的基本要求是时间长、空间大。因此,道法自然,生长大尺寸功能材料装备的研制与晶体生长动力学研究是两个关键自由度。由于晶体生长动力学与热力学互为函数,晶体生长的宏观行为不但在多尺度水平上受到结晶学结构对称性、组成元素间键合行为、晶体缺陷等多种物理化学因素制约,而且在多层次上受到生长装备塑造的生长环境的影响。随着数值模拟计算、SolidWorks和COMSOL多物理场仿真软件,以及结晶固液界面形态可视化技术、装备自动化升级和多种原位检测技术的广泛应用,可利用电子背散射衍射和中子衍射等检测手段,从多维度、多尺度表征晶体的色心、局域配位结构、位错和晶界缺陷。开展晶体生长动力学与热力学研究可以依赖越来越丰富的精确数据。基于对“零缺陷”功能晶体的发展需求,大尺寸人工晶体总体上呈现从传统的单温区向多温区、传统的单加热体向多加热体耦合方向发展,更多深入系统的研究成果将会越来越振奋人心。

稀土改性锂基氧化物固态电解质研究现状与展望

全固态锂电池具有能量密度高和安全性好等优点,成为新能源领域的研究热点。固态电解质作为全固态锂电池的核心部分,决定了电池的能量密度、循环稳定性以及安全性等。其中,氧化物固态电解质因离子电导率高、电化学窗口宽、力学性能优异而备受青睐,所涉及的研究体系主要包括石榴石型、NASICON型以及钙钛矿型固态电解质。然而,烧结温度高、室温离子电导率低、结构不稳定使其难以满足实际应用。本文概述了石榴石型、NASICON型以及钙钛矿型氧化物固态电解质近年的研究现状和存在的问题;总结了具有大离子半径、高价态、低电负性、可变配位数和4f5d电子结构的稀土离子在改性氧化物固态电解质时起到的增加致密度、提高离子电导率以及稳定高离子导电晶相的作用;分析了当前稀土改性氧化物固态电解质面临的主要科学问题和技术瓶颈;最后,对未来稀土改性氧化物固态电解质发展方向进行了展望。

基于图卷积神经网络的电力系统暂态稳定评估

随着新能源高渗透、特高压输电互联及电网数字化智能化等新兴技术的高速发展,电力系统结构变得更加复杂,因此对电力系统的安全稳定运行工作提出了更高要求。基于此,给出一种以图卷积神经网络模型为基础的暂态稳定分析方法,将短时模拟与神经网络预测相结合,减少暂态稳定分析所需周期,该方法适用于多种仿真分析场景。同时,将图卷积神经网络代理模型与遗传算法相结合,快速稳定地完成针对预想故障集的暂态稳定中预防控制优化策略的求解。与传统暂态稳定分析方法相比,提出的方法所需运行时间短、效率高。基于IEEE-30和IEEE-39节点系统的测试结果验证了所提方法的适用性、高效性和优越性。

Perspective for OER electrocatalysts:Lattice engineering of clay-like frameworks with near-surface cluster active sites

Near-surface cluster active centers(NSCAC)are pivotal functional units in the catalysis of oxygen evolution reaction(OER),which exceeds the limitations imposed by the diverse coordination environments experienced in atomic and molecular active centers,thereby serving as an exceptional medium for exploring the dynamic catalytic processes of metal active sites[1,2].In the OER,the NSCAC primarily consist of the catalytic site and the first neighboring coordinating atoms.The investigation of NSCAC surpasses the exclusive reliance on the electron state regulation mechanism at the atomic level.

完美无瑕是人工晶体永恒的追求

人工晶体是晶格结构完整、有序度高、性能独特的一类功能材料,是信息技术、激光技术、高端制造、先进医疗装备、航空航天、国防安全等高科技领域发展的关键基础材料。人工晶体的物理化学性质和功能特性是由其周期性微观结构所决定的。位错、晶界、杂质等因素引起的晶格缺陷可在不同的维度与尺度上影响晶体的均匀性与完整性,是制约晶体功能特性提升的根本原因。当前,面向国家重大工程和先进制造业的重大需求,“四极”(极大尺寸、极低缺陷、极限性能、极端应用)成为人工晶体领域高质量发展的主要趋势。

Design considerations for re-functionalizing electrocatalytic materials

Electrocatalytic materials are a critical bottleneck for the development of new energy economics.This review summarizes the unique physicochemical properties of topological,magnetic,and rare earth materials and their applications in the functionalization of electrocatalysts.Topological materials have unique band structures and geometric structures,and the interface difference in charge transport structures can give rise to topological insulators,topological superconductors,and Dirac metals.Magnetic materials possess distinctive electron spin-splitting configurations,and varying spin strengths induce disparate impacts on the intermediate equilibrium adsorption capability.Rare earth materials have unique f-electron roaming properties,broad atomic radius,and f-orbital configurations,which typically confer notable advantages in oxygen reduction reactions.Furthermore,the catalytic performance exhibits significant differences under an external alternating electric,thermal,and magnetic field.These new materials show great potential in the re-functionalization of electrocatalytic materials and are expected to lead the development of the next generation of emerging energy materials.

Rare earth and transitional metal colloidal supercapacitors

The search of electrode materials with high electrochemical activity is one of key solutions to actualize both high energy density and high power density in a supercapacitor. Recently, we have developed one novel kind of rare earth and transitional metal colloidal supercapacitors, which can deliver higher specific capacitance than electrical double-layer capacitors(EDLC) and traditional pseudocapacitors. The electrode materials in colloidal supercapacitors are in-situ formed electroactive colloids, which were transformed from commercial rare earth and transitional metal salts in alkaline electrolyte by chemical and electrochemical assisted coprecipitation. In these colloidal supercapacitors, multiple-electron Faradaic redox reactions can be utilized, which can deliver ultrahigh specific capacitance often larger than one-electron capacitance. Multiple-valence metal cations used in our designed colloidal supercapacitors mainly include Ce3+, Yb3+, Er3+, Fe3+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Sn2+ and Sn4+. The colloidal supercapacitors can be served as the promising next-generation high performance supercapacitors.

4f chemistry towards rare earth materials science and engineering

The big challenge in rare earth （RE） resource utilization is to effectively manage their balanced use and advanced applica- tions of 17 elements （Sc, Y and La-Lu） [ 1,2]. As a family, RE materials possess outstanding optical, electronic, and mag- netic properties owing to the unique valence electron structure of RE elements, especially the 4felectrons [3]. With in- creasing demands of modern applications, the development of novel RE materials becomes an unceasing topic. The application window of RE materials is mainly targeted by two aspects, the high-end utilization and balanced utilization of RE resources. In order to add value to RE resources,

Pulling growth technique towards rare earth single crystals

Pulling growth technique serves as a popular method to grow congruent melting single crystals with multiscale sizes ranging from micrometers to centimeters.In order to obtain high quality single crystals,the crystal constituents would be arranged at the lattice sites by precisely controlling the crystal growth process.Growing interface is the position where the phase transition of crystal constituents occurs during pulling growth process.The precise control of energy at the growing interface becomes a key technique in pulling growth.In this work,we review some recent advances of pulling technique towards rare earth single crystal growth.In Czochralski pulling growth,the optimized growth parameters were designed for rare earth ions doped Y_3Al_5O_(12)and Ce:(Lu_(1-x)Y_x)_2Si O_5on the basis of anisotropic chemical bonding and isotropic mass transfer calculations at the growing interface.The fast growth of high quality rare earth single crystals is realized by controlling crystallization thermodynamics and kinetics in different size zones.On the other hand,the micro pulling down technique can be used for high throughput screening novel rare earth optical crystals.The growth interface control is realized by improving the crucible bottom and temperature field,which favors the growth of rare earth crystal fibers.The rare earth laser crystal fiber can serve as another kind of laser gain medium between conventional bulk single crystal and glass fiber.The future work on pulling technique might focus on the mass production of rare earth single crystals with extreme size and with the size near that of devices.

Electrochemical energy storage applications of “pristine” graphene produced by non-oxidative routes

Graphene is a promising material as both active components and additives in electrochemical energy storage devices. The properties of graphene strongly depend on the fabrication methods. The applications of reduced graphene oxide as electrode materials have been well studied and reviewed, but the using of "pristine" graphene as electrode material for energy storage is still a new topic. In this paper, we review state-of-the-art progress in the fabrication of "pristine" graphene by different methods and the electrochemical performance of graphene-based electrodes. The achievements in this area will be summarized and compared with the graphene oxide route in terms of cost, scalability, material properties and performances, and the challenges in these methods will be discussed as well.

Multisize and multiweight effects in materials science and engineering

Materials mainly refer to the matters with a certain composition,structure,and property,which can be formed by natural mineralization or artificial manufacture and are widely used in various specific fields,therefore,materials serve as the substance basis for human survival and development [1].

Perspective on multiple degrees of freedom in crystal materials

Degrees of freedom describe the freedom of variables or values to vary within a specific material system.Research on functional crystalline materials generally involves their preparation and growth to large-sized crystals,as well as the exploration of structure-property relationships[1,2].With the continuous research on the applications of functional crystalline materials in quantum science and technology.

Chemical bonding in micro-pulling down process: High throughput single crystal growth

The micro-pulling down (MPD) method is a high-efficiency crystal growth technique from melt, which has been invented by French scientist Ricard in 1975 [1] and developed by Japanese scientist Fukuda since 1992 [2] and French scientist Lebbou in 2000s [3]. Appropriate configuration of a die at the crucible bottom and the proper selection of temperature gradient allow the crystal shape control during growth of crystals with the cross section of 0.1–10 mm without mechanical and thermal stresses [2]. MPD growth method is an economical and quick single crystal growth technique, which may be used for high throughput screening novel rare earth optical crystals [4,5].

In-situ micro-spectroscopy technique for chemical bonding during nucleation: A transition from soft bond to stiff bond

In-situ technique has been widely used in recent years since the advent of high-resolution spectroscopy systems, which stimulates us to probe into the time-dependent, dynamic behaviors and relevant mechanisms during a series of physical processes [1]. Especially, in-situ analysis presents a unique real-time glimpse into the fascinating physical phenomena [2], which are very important to develop the materials for subsequent applications.

Perspective on perovskite materials as X-ray detectors

X-ray imaging plays an important role in medical applications[1].Two available strategies are currently employed for X-ray detection,direct conversion and indirect conversion method(Figure 1).In the direct method,X-ray photons are converted by the active layer into electrical signals.

Preface

Nowadays each country in the world has been facing great challenges of energy, which is especially clear in China due to strong demands from economy development. Fortunately, much work has been successfully done and shown that electrical energy storage may be one of key strategies to deal with these challenges. Electrochemical energy storage is such a huge topic that we cannot use limited space to summarize all big progresses in core scientific disciplines, comment on all aspects of research status, but we try to show representative advances and give possible suggestions for future work.

Bandgap tunable preparation of GaS nanosheets and their application in photoelectrochemical photodetectors

Bandgap engineering of two-dimensional(2D)materials is essential for the design of photoelectrochemical(PEC)devices.Gallium(II)sulfide(GaS),a layered semiconductor material with a direct bandgap of approximately 3.05 eV,has recently gained extensive attention owing to its unique photoresponse property.However,its bandgap tunability relative to the number of layers has not been experimentally confirmed;thus,the effect of bandgap on the photoresponse has not been explored yet.Herein,fewlayered GaS nanosheets(Ns)are prepared using a simple liquid-phase exfoliation(LPE)approach.After centrifuging at different speeds,GaS Ns with defined layers are obtained,which enable verification of the tunable bandgap from 2.02 to 3.15 eV.When applied as a PEC-type photodetector,the responsivity of the photodetector is 4.77 mA W^(−1)and 33.7μA W^(−1)under bias voltages of 0.6 and 0 V,respectively.Theoretical models of the electronic structure suggest that a reduction in the number of layers,leading to a decrease of the effective mass at the valence band maximum(VBM),can enhance the carrier mobility of GaS Ns.This results in high photocurrents and indicates that 2D GaS Ns are ideal materials for future high-performance optoelectronic systems.

Perspective on rare earth crystals

Rare earth crystals represent our society utilization of rare earth resources via crystallization engineering strategies.Rare earth crystals include more than 30 types of functional and structural crystals,with more than 30 kinds of inorganic or metal compounds.Multiscale nature of rare earth crystals was proposed.