Recent advances in anisotropic two-dimensional materials and device applications

Two-dimensional(2D)materials,such as transition metal dichalcogenides(TMDs),black phosphorus(BP),MXene and borophene,have aroused extensive attention since the discovery of graphene in 2004.They have wide range of applications in many research fields,such as optoelectronic devices,energy storage,catalysis,owing to their striking physical and chemical properties.Among them,anisotropic 2D material is one kind of 2D materials that possess different properties along different directions caused by the intrinsic anisotropic atoms5 arrangement of the 2D materials,mainly including BP,borophene,low-symmetry TMDs(ReSe2 and ReSa)and group IV monochalcogenides(SnS,SnSe,GeS,and GeSe).Recently,a series of new devices has been fabricated based on these anisotropic 2D materials.In this review,we start from a brief introduction of the classifications,crystal structures,preparation techniques,stability,as well as the strategy to discriminate the anisotropic characteristics of 2D materials.Then,the recent advanced applications including electronic devices,optoelectronic devices,thermoelectric devices and nanomechanical devices based on the anisotropic 2D materials both in experiment and theory have been summarized.Finally,the current challenges and prospects in device designs,integration,mechanical analysis,and micro-/nano-fabrication techniques related to anisotropic 2D materials have been discussed.This review is aimed to give a generalized knowledge of anisotropic 2D materials and their current devices applications,and thus inspiring the exploration and development of other kinds of new anisotropic 2D materials and various novel device applications.     

Density functional methods as computational tools in materials design

Summary This article gives a brief overview of density functional theory and discusses two specific implementations: a numerical localized basis approach (DMol) and the pseudopotential plane-wave method. Characteristic examples include Cu, clusters, CO and NO dissociation on copper surfaces, Li-, K-, and O-endohedral fullerenes, tris-quaternary ammonium cations as zeolite template, and oxygen defects in bulk SiO₂. The calculations reveal the energetically favorable structures (estimated to be within ± 0.02 Å of experiment), the energetics of geometric changes, and the electronic structures underlying the bonding mechanisms. A characteristic DMo1 calculation on a 128-node nCUBE 2 parallel computer shows a speedup of about 107 over a single processor. A plane-wave calculation on a unit cell with 64 silicon atoms using 1024 nCUBE 2 processors runs about five times faster than on a single-processor CRAY YMP.     

Recent advances in thermoelectric materials

Thermoelectric materials are crucial in renewable energy conversion technologies to solve the global energy crisis. They have been proven to be suitable for high-end technological applications such as missiles and spacecraft. The thermoelectric performance of devices depends primarily on the type of materials used and their properties such as their Seebeck coefficient, electrical conductivity, thermal conductivity, and thermal stability. Classic inorganic materials have become important due to their enhanced thermoelectric responses compared with organic materials. In this review, we focus on the physical and chemical properties of various thermoelectric materials. Newly emerging materials such as carbon nanomaterials, electronically conducting polymers, and their nanocomposites are also briefly discussed. Strategies for improving the thermoelectric performance of materials are proposed, along with an insight into semiconductor physics. Approaches such as nanostructuring, nanocomposites, and doping are found to enhance thermoelectric responses by simultaneously tuning various properties within a material. A recent trend in thermoelectric research shows that high-performance thermoelectric materials such as inorganic materials and carbon nanomaterials/electronically conducting polymer nanocomposites may be suitable for power generation and energy sustainability in the near future.     

Recent advances and remaining challenges of nanostructured materials for hydrogen storage applications

The rapid and extensive development of advanced nanostructures and nanotechnologies has driven a correspondingly rapid growth of research that presents enormous potential for fulfilling the practical requirements of solid state hydrogen storage applications. This article reviews the most recent progress in the development of nanostructured materials for hydrogen storage technology, demonstrating that nanostructures provide a pronounced benefit to applications involving molecular hydrogen storage, chemical hydrogen storage, and as supports for the nanoconfinement of various hydrides. To further optimize hydrogen storage performance, we emphasize the desirability of exploring and developing nanoporous materials with ultrahigh surface areas and the advantageous incorporation of metals and functionalities, nanostructured hydrides with excellent mechanic stabilities and rigid main construction, and nanostructured supports comprised of lightweight components and enhanced hydride loading capacities. In addition to highlighting the conspicuous advantages of nanostructured materials in the field of hydrogen storage, we also discuss the remaining challenges and the directions of emerging research for these materials.     

Recent advances in germanium nanocrystals: Synthesis,optical properties and applications

Germanium nanocrystals (Ge NCs) have recently attracted renewed scientific interest as environmentally friendlier alternatives to classical II–VI and IV–VI QDs containing toxic elements such as Hg, Cd and Pb. Importantly, Ge NCs are nontoxic, biocompatible, and electrochemically stable. An essential requirement is the ability to prepare Ge NCs with narrow size distributions and well characterized surface chemistry, as these define many of their photophysical properties. However, a thorough discussion on these criteria has not been achieved to date. Here, size, surface control, and mechanisms for light emission in Ge NCs are discussed and their exciting recent applications are highlighted. The beneficial properties of Ge NCs suggest that this material can improve the performance of numerous devices like solar cells, photodetectors, and lithium ion batteries.     

Knowledge-based methods and smart algorithms in computational mechanics

Effective methods leading to automated, computer-based solution of complex engineering design problems are studied in this paper. In particular, methods of automation of the finite element analyses are of primary interest here. These include algorithmic approaches, based on error estimation, adaptivity and smart algorithms, as well as heuristic approaches based on methods of knowledge engineering. A computational environment, which interactively couples h-p adaptive finite element methods with object-oriented programming and expert system tools, is presented. Several examples illustrate the merit and potential of the approaches studied here.     

Recent advances in ZnO materials and devices

Wurtzitic ZnO is a wide-bandgap (3.437 eV at 2 K) semiconductor which has many applications, such as piezoelectric transducers, varistors, phosphors, and transparent conducting films. Most of these applications require only polycrystalline material; however, recent successes in producing large-area single crystals have opened up the possibility of producing blue and UV light emitters, and high-temperature, high-power transistors. The main advantages of ZnO as a light emitter are its large exciton binding energy (60 meV), and the existence of well-developed bulk and epitaxial growth processes; for electronic applications, its attractiveness lies in having high breakdown strength and high saturation velocity. Optical UV lasing, at both low and high temperatures, has already been demonstrated, although efficient electrical lasing must await the further development of good, p-type material. ZnO is also much more resistant to radiation damage than are other common semiconductor materials, such as Si, GaAs, CdS, and even GaN; thus, it should be useful for space applications.     

Recent advances in MXenes: From fundamentals to applications

The family of MAX phases and their derivative MXenes are continuously growing in terms of both crystalline and composition varieties. In the last couple of years, several breakthroughs have been achieved that boosted the synthesis of novel MAX phases with ordered double transition metals and, consequently, the synthesis of novel MXenes with a higher chemical diversity and structural complexity, rarely seen in other families of two-dimensional (2D) materials. Considering the various elemental composition possibilities, surface functional tunability, various magnetic orders, and large spin–orbit coupling, MXenes can truly be considered as multifunctional materials that can be used to realize highly correlated phenomena. In addition, owing to their large surface area, hydrophilicity, adsorption ability, and high surface reactivity, MXenes have attracted attention for many applications, e.g., catalysts, ion batteries, gas storage media, and sensors. Given the fast progress of MXene-based science and technology, it is timely to update our current knowledge on various properties and possible applications. Since many theoretical predictions remain to be experimentally proven, here we mainly emphasize the physics and chemistry that can be observed in MXenes and discuss how these properties can be tuned or used for different applications.     

Recent advances in iron-based superconductors toward applications

Iron with a large magnetic moment was widely believed to be harmful to the emergence of superconductivity because of the competition between the static ordering of electron spins and the dynamic formation of electron pairs (Cooper pairs). Thus, the discovery of a high critical temperature (T_c) iron-based superconductor (IBSC) in 2008 was accepted with surprise in the condensed matter community and rekindled extensive study globally. IBSCs have since grown to become a new class of high-T_c superconductors next to the high-T_c cuprates discovered in 1986. The rapid research progress in the science and technology of IBSCs over the past decade has resulted in the accumulation of a vast amount of knowledge on IBSC materials, mechanisms, properties, and applications with the publication of more than several tens of thousands of papers. This article reviews recent progress in the technical applications (bulk magnets, thin films, and wires) of IBSCs in addition to their fundamental material characteristics. Highlights of their applications include high-field bulk magnets workable at 15–25 K, thin films with high critical current density (J_c) > 1 MA/cm² at ～10 T and 4 K, and an average J_c of 1.3 × 10⁴ A/cm² at 10 T and 4 K achieved for a 100-m-class-length wire. These achievements are based on the intrinsically advantageous properties of IBSCs such as the higher crystallographic symmetry of the superconducting phase, higher critical magnetic field, and larger critical grain boundary angle to maintain high J_c. These properties also make IBSCs promising for applications using high magnetic fields.     

无机陶瓷膜应用过程研究的进展

从无机膜的微观结构、膜材料表面性质、应用体系的性质以及操作参数对膜分离性能的影响进行了综述与分析，认为不同因素对膜过滤性能影响规律的研究是进行膜和膜过程优化设计的基础，通过建立面向应用过程的膜材料设计的理论框架，有可能实现膜材料设计与过程工艺参数的协同优化，从而达到降低浓差极化和膜污染、提高膜过程综合效益的目的．     

Recent advances in electron imaging, image interpretation and applications: environmental scanning electron microscopy

One of the latest developments in electron microscopy is the environmental scanning electron microscope (ESEM), which enables soft, moist and/or electrically insulating materials to be viewed without pre-treatment, unlike conventional scanning electron microscopy, in which specimens must be solid, dry and usually electrically conductive. Such an advance has significant implications for studies of the 'native' surfaces of specimens including rocks and minerals, polymers, biological tissues and cells, food and pharmaceutical products, precious artefacts and forensic material, for example. Previous types of electron microscopes made scientists think carefully about the physics of electron-beam interactions with specimens and, hence, the interpretation of images. We now face additional factors influencing the emission and detection of electron signals, unique to the imaging of specimens in the partial vacuum of an ESEM. Just as importantly, we must consider the thermodynamic and kinetic stability of specimens, as appropriate, and explore the possibilities for new applications, particularly those of a dynamic nature. This paper briefly describes some of the issues involved and reviews the current state of understanding.     

Novel metal-hydride materials and technologies: Recent advances and further prospects

We present the review of joint works between the Physicomechanical Institute of the Ukrainian Academy of Sciences and the University of Birmingham on investigations of fundamental and applied aspects of the development of new intermetallic hydrides carried out in 1992–1997. Most attention is paid to the results of the following investigations: first experimental observations of the appearance of “anomalously bound” hydrogen in NdFeB permanent magnets during their brittle fracture in hydrogen environments; the use of hydrogen vibrodecrepitation in the synthesis of materials with advanced properties; new advanced hydrogen absorbers, their structure and magnetic properties; the application of the hydrogenation-disproportionation-desorption-recombination process to alloys of rare-earth metals and zirconium as hydrogen storages and permanent-magnet materials. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. School of Metallurgy and Materials, University of Birmingham, UK. Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 33, No. 4, pp. 39–52, July–August, 1997.     

Recent advances in methods for measuring the dynamic response of geological materials to 100 GPA

Modeling certain classes of hypervelocity impact events requires laboratory materials data for benchmarking purposes. These data include Hugoniot states, release paths and strength. Two classes of impact techniques have been employed for measuring equation-of-state properties for rocks and rock simulants. These techniques both use velocity interferometer diagnostics. One, employing a sample-in-projectile geometry, provides high-precision Hugoniot data and continuous release trajectories for dry or water-saturated materials. The majority of the present experiments have been performed with this geometry. The other, employing a sample-in-target geometry, provides loading path and Hugoniot data as well as limited release data. Materials studied by these two techniques have included a variety of tuffs, rhyolites, carbonates, grouts and an epoxy-alumina mixture. Uncertainties in the results from these techniques have been estimated by analyzing the effects of errors in observables and ancillary material properties.     

Recent advances in 2 : 17 and 3 : 29 permanent magnet materials

The structural and magnetic properties of 2 : 17 compounds, their nitrides and carbides and the recent development of the novel 3 : 29 compounds are discussed.     

Recent advances in anode materials for potassium-ion batteries: A review

Potassium-ion batteries (PIBs) are appealing alternatives to conventional lithium-ion batteries (LIBs) because of their wide potential window, fast ionic conductivity in the electrolyte, and reduced cost. However, PIBs suffer from sluggish K⁺ reaction kinetics in electrode materials, large volume expansion of electroactive materials, and the unstable solid electrolyte interphase. Various strategies, especially in terms of electrode design, have been proposed to address these issues. In this review, the recent progress on advanced anode materials of PIBs is systematically discussed, ranging from the design principles, and nanoscale fabrication and engineering to the structure-performance relationship. Finally, the remaining limitations, potential solutions, and possible research directions for the development of PIBs towards practical applications are presented. This review will provide new insights into the lab development and real-world applications of PIBs.

     

Recent advances in gel materials with special wettability: a review

Journal of Materials Science - The special wettable gel material solves the problem that the rigid solid surface with special wettability does not perform well in the face of flexibility...     

酶的膜固定化及其应用的研究进展

酶的膜固定化作为一种重要的生物技术已经得到了广泛的应用．文章在总结传统的酶膜固定化方法的基础上，对这一领域新的进展，如光、辐射等物理技术的应用、定点固定化技术以及多酶系统共固定等作了相应的综述．此外，还对酶膜生物反应器，尤其是其在对外消旋混合物手性拆分以及污水处理方面的应用作了简要的介绍．