二维 Mo2CTx MXene 的制备及其应用研究进展

MXene 是一类新兴的二维层状过渡金属碳化物、 氮化物或碳氮化物. 二维 Mo2CTx MXene 是 MXene 家族中的重要成员, 它是通过选择性刻蚀前驱体 Mo2Ga2C 中的Ga 原子层而得到. 由于其独特的片层结构、丰富且可控的表面官能团、高比表面积、优异的金属热导率、高的导电性、 良好的机械稳定性等使其在储能、 光催化、 光电和超导等领域具有巨大的应用前景. 本文综述了二维 Mo2CTx MXene 材料的制备方法以及最新的应用进展, 进一步激发对 Mo2CTx MXene 材料更深入的研究.     

二维量子片及其光学研究进展

以石墨烯为代表的二维材料因其独特的结构和优异性能而受到广泛关注。随着二维材料在无限小的方向不断发展,二维(材料)量子片逐渐引起人们极大的兴趣。二维量子片不仅保留了二维材料的本征特性,而且表现出量子限域和突出的边缘效应,为二维材料的潜在应用带来全新机遇。本文详细介绍了二维量子片的基本概念,制备现状与光学性能的研究进展,特别强调了二维量子片本征、普适和规模制备的实现及其重大意义。此外,重点关注了二维量子片的光致发光特性以及在非线性光学、固态发光器件等领域的应用。最后,分析了二维量子片的发展趋势以及面临的主要挑战。     

“薄膜即是界面，界面即是薄膜”：二维有机半导体晶体的研究进展

自首次于聚乙炔发现导电现象以来,具有共轭结构的有机半导体材料赖其种类丰富多样、 制备工艺简捷低耗、以及优异的机械柔性等特点,在“后硅时代”中有望以先进光电子设备展现 其广阔前景,因而多年来备受学界和产业界的瞩目。如何进一步阐明有机半导体中结构和性能之 间的关系,探索电荷载流子微观动力学行为,构筑高性能、新功能的有机光电子器件,是当下有 机电子学领域的前沿核心问题,也是保证其持续发展的基石。近年来,二维有机半导体晶体材料 在秉持高度有序的分子排列与极低的杂质缺陷浓度等优点的同时,更是以“薄膜即是界面、界面 即是薄膜”为一帜,克服传统体材料在研究与应用中的瓶颈,为揭示材料构性关系及其中基本物 理过程提供了良好的平台,也是实现多样化的新型有机光电子器件的理想材料,有望为微纳电子 领域带来新一轮变革。本文从二维有机半导体晶体的制备工艺、电荷载流子微观动力学行为,再 到新型器件的光电功能应用等方面,综述了最新研究进展,做出总结和展望,并提出目前面临的 挑战及未来研究方向,旨在为进一步深入理论研究,结合有机材料与先进技术,推动有机电子学 的发展提供有益帮助。     

单元素二维原子晶体材料研究进展

非碳元素构成的二维单质原子晶体材料,具有与石墨烯相似的单层结构和物理性质,对它们的研究有望发掘一些崭新的性能及相关的应用,是当前凝聚态物理及新材料等相关领域的重要研究方向之一。文章详细介绍了近几年发展起来的单一元素所形成的二维原子晶体材料,分别对其结构、物性、应用前景等方面的研究进展进行了综述介绍。     

室温稳定的二维铁电材料：CuInS2P6 及其异质结构

二维铁电材料有助于实现半导体性质与非易失存储特性在微纳尺度上的有机结合，在高集成化电子器件、光电器件、能量收集、及机电耦合系统等领域展现出巨大的应用潜力。二维铁电材料的层状结构，保证了原子层间的可剥离性，为从理论和实验上探索超薄极限下的铁电性质提供理想的研究平台。考虑到二维磁性研究的低温瓶颈，二维铁电材料为实现铁性功能材料的高温器件化与实用化提供了新途径。在本文中，我们介绍了一种室温稳定的二维铁电材料：铜铟硫代磷酸盐(CuInP2S6)。该材料体系的科学内涵和应用前景，引发了新的研究热潮。在本文中，关于其较高的铁电居里转变温度、显著的压电响应、巨大的负纵向压电系数、可调谐的四重势阱铁电特性、以及基于该材料及其异质结构的器件研究，均有所涉及。我们还简要介绍了几种过渡金属硫代磷酸盐化合物材料体系(M^IM^IIIP2(S/Se)6)中的其他代表性材料。最后，我们关于二维铁电材料研究的未来发展方向进行了讨论。     

单元素类石墨烯二维拓扑材料的研究进展

除了石墨烯外,很多主族元素也可以形成类似石墨烯的稳定单层结构,并且具有丰富的物理化学性质及广阔的应用前景.其中在物理学中最引人注目的是理论预言在这些材料中预言存在的二维拓扑物性.单元素类石墨烯二维材料已经经历了十余年的研究进程,目前已经理论发现和实验制备出了若干新型二维拓扑材料,成为当前凝聚态物理和新材料领域重要研究方向之一.在这篇评述中,我们将详细介绍这一领域的研究历程、研究思路,以及最新研究进展,并对其进一步的研究方向做出展望.     

褶皱状蜂窝结构的单层二维材料研究进展

以石墨烯为代表的二维材料具有新颖的物理特性和潜在的应用前景.但石墨烯的零带隙限制了它在半导体器件中的应用,寻找新的半导体型替代材料成为当前的一个研究热点.作为黑磷的单层,磷烯具有褶皱状蜂窝结构.它具有可调直接带隙、高载流子迁移率和面内各向异性等独特的性质,引起了人们的广泛关注.磷烯的发现开辟了Ⅴ族二维单层材料的研究领域.本文首先着重介绍具有黑磷结构的五种单元素二维材料(氮、磷、砷、锑和铋)的结构、合成和物理性质.其次,讨论了一些类黑磷结构的二元二维材料,包括Ⅳ-Ⅵ族化合物、Ⅴ-Ⅴ族化合物.这些材料具有独特的晶体对称性,通过改变结构以及维度可以实现对性质的调控.最后指出了一些当前需要解决的问题,并对这些二维半导体材料未来可能的应用前景进行了展望.     

MXene与溶剂界面电子振动耦合现象的直接观测（英文）

作为一种新型的二维材料,MXene凭借其各种优异的物理化学性质已受到极为广泛的关注,例如其具有极其出色的光热转换效率.然而,人们对MXene的光热转换机制仍然知之甚少.本文通过结合飞秒可见和中红外瞬态吸收光谱技术,对分散在各种溶剂中MXene(Ti_3C_2T_x)纳米片内的电子能量耗散动力学进行了系统的研究.结果表明,MXene的激发态寿命在很大程度上取决于周围的溶剂环境.在MXene被超快激光泵浦后,可以直接观察到MXene纳米片与相邻溶剂分子之间的界面电子振动耦合现象.这些结果表明界面相互作用在MXene的超快能量传输动力学中起着关键的作用.这一发现可为二维体系光转换性能的改进提供了一条潜在可行的途径.     

面向硅基光电子混合集成的二维材料探测器

二维材料因其独特的结构和优异的电子和光电性能,为硅基光电子集成器件提供了新的发展机遇。近年来,面向硅基光电子混合集成的二维材料探测器已被广泛研究。本文梳理了构建光电探测器的几种二维材料基本特性及其探测机制,回顾了基于二维材料的硅光子集成光电探测器研究进展,总结了其器件结构和主要性能指标。最后,讨论了进一步提升硅光子集成二维材料光电探测器性能的策略,包括大规模二维材料集成器件的制备、器件结构与金属接触界面的优化以及新兴二维材料光电探测器的探索,以期推动二维材料在硅基光电子混合集成探测器领域的商业化应用。     

二维范德瓦尔斯异质结构的制备与物性研究

二维范德瓦尔斯材料(可简称二维材料)已发展成为备受瞩目的材料大家族,而由其衍生的二维范德瓦尔斯异质结构的集成、性能及应用是现今凝聚态物理和材料科学领域的研究热点之一.二维范德瓦尔斯异质结构为探索丰富多彩的物理效应和新奇的物理现象,以及构建新型的自旋电子学器件提供了灵活而广阔的平台.本文从二维材料的转移技术着手,介绍二维范德瓦尔斯异质结构的构筑、性能及应用.首先,依据湿法转移和干法转移的分类,详细介绍二维范德瓦尔斯异质结构的制备技术,内容包括转移技术的通用设备、常用转移方法的具体操作步骤、三维操纵二维材料的方法、异质界面清洁.随后介绍二维范德瓦尔斯异质结构的性能和应用,重点介绍二维磁性范德瓦尔斯异质结构,并列举在二维范德瓦尔斯磁隧道结和摩尔超晶格领域的应用.因此,二维材料转移技术的发展和优化将进一步助力二维范德瓦尔斯异质结构在基础科学研究和实际应用上取得突破性的成果.     

Ab initio studies of polarization and piezoelectricity in vinylidene fluoride and BN-based polymers

Highly piezoelectric and pyroelectric phases of boron-nitrogen-based polymers have been designed from first principles. They offer excellent electrical and structural properties, with up to 100% improvement in the piezoelectic response and an enhanced thermal stability with respect to polyvinylidene fluoride (PVDF). Since methods for their synthesis are readily available, these polymers are extremely promising for numerous technological applications, rivaling the properties of ferroelectric ceramics and superseding PVDF-based materials in high-performance devices.     

Recent advances in MXene: Preparation,properties, and applications

Owing to the exceptional properties of graphene, intensive studies have been carried out on novel two-dimensional (2D) materials. In the past several years, an elegant exfoliation approach has been used to successfully create a new family of 2D transition metal carbides, nitrides, and carbonitrides, termed MXene, from layered MAX phases. More recently, some unique properties of MXene have been discovered leading to proposals of potential applications. In this review, we summarize the latest progress in development of MXene from both a theoretical and experimental view, with emphasis on the possible applications.     

Density Functional Theory Study of Mn+1AXn Phases: A Review

M_n+1AX_n phases (MAX phases for short with M: transition metal, A: A group elements, X: C or N, and n = 1–3) have attracted considerable attention due to the unique combination of the ceramic- and metal-like properties. The density functional theory (DFT) has emerged as a powerful theoretical approach that complements experimental testing and serves as a predictive tool in the identification and characterization of MAX phases. After the beginning with a brief introduction of the MAX phase and DFT, we review the DFT study on this class of materials, including crystal structure, electronic structure, point defects, lattice dynamics, and related properties, phase stability, compressibility, and elastic properties. Comparison between the theoretical values and available experimental ones shows that they are in decent agreement for most part, especially in the lattice constants, elastic properties, and compressibility. This article is concluded with an outlook of future research on DFT study of MAX phases, major challenges to be met and possible solutions in some cases.     

Technology of PLZT ceramics microfibers for multiferroics composites

Compactness and large energy conversion capacity are the main reasons of development of sophisticated ceramics materials in microfibers form, which are prepared for high-speed multiferroic systems and devices. These multifunctional composite applications are owing to coupling of electrical and magnetic properties, as well as additional thermal and mechanical properties. So that, they are suitable for magnetic sensors, electrically tunable non-linear transducers, and non-volatile memories. In our experiment, the thin fibers ceramics have been produced using special environmental chamber where the high temperature sintering can be protected by controlling such parameters as temperature and sintering atmosphere. Consequently, for these purposes structural and physical properties, preparation and thermal synthesis of micrometer sized lead lanthanum zirconate titanate (PLZT) fibers were investigated thoroughly. Since the phase transition properties of PLZT fibers differ much, the production process of fibers suffers from lack of proper high temperature control. Consequently, our experiments should help to eliminate this drawback, so that various technological conditions, parameters, and subsequent sintering atmosphere with different mixtures of PbO and ZrO were experimentally tested. Final conclusions include comparative analysis of obtained PLZT fibers ferroelectric phase transition properties to specific sintering atmosphere.     

Comparative spectroscopic investigation of Yb-doped YAG, YSAG and YLaO3 transparent ceramics

Transparent Yb doped YAG, YSAG and YaLaO3 ceramics are fabricated by using the co-precipitation method. The spectral properties and thermal parameters of these Yb doped cubic phase transparent ceramics are compared, and their different and potential applications are also analysed. The absorption cross-section and the emission cross-section of these ceramics are measured and calculated. The essential properties of these materials especially for the rep-rated pulsed high-energy diode-pumped solid-state lasers are investigated. The results show that Yb doped YAG, YSAG and YaLaO3 are all suitable materials used for diode-pumped solid-state lasers.     

A Review of Advanced Composite and Nanostructured Coatings by Solid-State Cold Spraying Process

Cold spraying (CS) has been widely explored over the last decade due to its low process temperature and limited thermal effect on spray materials. As a solid-state process, the inherent deficiencies of traditional thermal spraying such as oxidation, decomposition, and grain growth are avoided. This article summarizes the research work on the fabrication of composites and nanostructured coatings by the promising CS process. After a brief introduction to CS and its deposition mechanisms, the preparation methods of spray powders are classified. Different methods are appropriate for particles of various properties, and the tendency is to design composite powders by combined methods in order to create coatings with specified properties. Then, the co-deposition mechanism of composite particles as well as research findings on metal–metal, metal–ceramic, and metal–intermetallic composite coatings are reviewed concerning the deposition characteristics, microstructure and its relation to properties. Moreover, CS has been used to deposit a variety of nanostructured materials, including metals, metal–ceramic composites, and even ceramics, retaining their nanocrystalline nature in the coating without grain growth or phase transformation. Finally, the potential applications of CS and issues to be addressed in coating deposition are discussed.     

Quantum transport in topological semimetals under magnetic fields (II)

Research about two-dimensional (2D) materials is growing exponentially across various scientific and engineering disciplines due to the wealth of unusual physical phenomena that occur when charge transport is confined to a plane. The applications of 2D materials are highly affected by the electrical properties of these materials, including current distribution, surface potential, dielectric response, conductivity, permittivity, and piezoelectric response. Hence, it is very crucial to characterize these properties at the nanoscale. The Atomic Force Microscopy (AFM)-based techniques are powerful tools that can simultaneously characterize morphology and electrical properties of 2D materials with high spatial resolution, thus being more and more extensively used in this research field. Here, the principles of these AFM techniques are reviewed in detail. After that, their representative applications are further demonstrated in the local characterization of various 2D materials’ electrical properties.

     

Alumina-zirconium ceramics synthesis by selective laser sintering/melting

In the present paper, porous refractory ceramics synthesized by selective laser sintering/melting from a mixture of zirconium dioxide, aluminum and/or alumina powders are subjected to optical metallography and X-ray analysis to study their microstructure and phase composition depending on the laser processing parameters. It is shown that high-speed laser sintering in air yields ceramics with dense structure and a uniform distribution of the stabilizing phases. The obtained ceramic-matrix composites may be used as thermal and electrical insulators and wear resistant coating in solid oxide fuel cells, crucibles, heating elements, medical tools. The possibility to reinforce refractory ceramics by laser synthesis is shown on the example of tetragonal dioxide of zirconium with hardened micro-inclusion of Al₂O₃. By applying finely dispersed Y₂O₃ powder inclusions, the type of the ceramic structure is significantly changed.     

Structural phase transitions and elastic properties of zirconia

The structural phase transformations in various phases (monoclinic, ortho I, ortho II, and tetragonal) of zirconia (ZrO₂) have been investigated using an effective interionic interaction potential. The cohesive energy, the equation of state, and the elastic properties of these phases have also been studied and found to reproduce well the experimentally observed data for almost all the phases of zirconia ceramics.     

高温压电材料、器件与应用

作为重要的功能材料,压电材料已经在国民经济的多个领域里有着重要应用.随着现代工业的快速发展,特别是新能源、交通和国防工业的高速发展,功能材料的应用已经从常规使用转向极端环境下的服役.本文综述了具有高居里点的压电材料,包括钙钛矿型压电陶瓷、铋层状结构氧化物压电陶瓷、钨青铜结构压电陶瓷以及非铁电压电单晶等;介绍了其晶体结构特征和高温压电性能、最新研究进展,并列举了一系列的高温压电器件和应用,包括高温压电探测器、传感器、换能器和驱动器等.另外,本文总结了高温压电材料的热点研究问题,并展望了今后的发展方向.