Thermal lensing of laser beams in optically transmitting materials

Detailed numerical computations of thermal lensing in optically transmitting materials are carried out. The time evolution of the transmitted beam intensity, revealing defocusing and degradation effects, is displayed for a variety of materials, under a variety of geometrical configurations and operating conditions. While the degradation is monotonic with increasing time or incident power for materials with small induced birefringence, it may display an oscillatory character when birefringence effects are large. From the intensity degradation, criteria are formulated for rating optical performance of materials under transient and steady-state conditions. Ratings are obtained for a variety of transmitting materials at 10.6 μm. As a class, ionic materials are found to substantially outperform semiconductors and glasses at 10.6 μm.     

Thermal expansion of SOFC materials

A short overview is given for the thermal expansion of solid oxide fuel cell materials. The thermomechanical compatibility of state-of-the-art materials is compared with alternative, new materials. With these alternatives a better adjustment of the thermal expansion coefficients of the various fuel cell components is possible and fuel cells based on the newly developed materials are proposed.     

Topological insulators in ternary compounds with a honeycomb lattice

We investigate a new class of ternary materials such as LiAuSe and KHgSb with a honeycomb structure in Au-Se and Hg-Sb layers. We demonstrate the band inversion in these materials similar to HgTe, which is a strong precondition for existence of the topological surface states. In contrast with graphene, these materials exhibit strong spin-orbit coupling and a small direct band gap at the Γ point. Since these materials are centrosymmetric, it is straightforward to determine the parity of their wave functions, and hence their topological character. Surprisingly, the compound with strong spin-orbit coupling (KHgSb) is trivial, whereas LiAuSe is found to be a topological insulator.     

A Review of Research Trends in Microwave Processing of Metal-Based Materials and Opportunities in Microwave Metal Casting

Microwave processing of materials has emerged as a new method for processing of a variety of materials in the recent years. Microwaves have been used effectively with significant advantages, particularly in food processing and chemical synthesis. They are also found to be efficient for processing polymers, ceramics, polymeric composites, and ceramic composites. The physics of interaction of microwaves with characteristically different materials is not yet explored well; consequently, there are challenges in microwave processing of metal-based materials. Industrial processing of bulk metal is yet to be popular in spite of the fact that the feasibility of metal powder sintering was demonstrated a few decades ago. This article provides a summary of fundamental aspects of microwave processing of metal-based materials and their interaction with metallic materials. The processing challenges have been surveyed; developments in terms of techniques and tooling have been analyzed. Possible effects of microwave processing on metallic materials, in particular metal powders, bulk metals, bulk metal-metal powder systems, and sheet metals have been presented. Future research aspects of microwave processing of metallic materials with reference to metal casting have been identified.     

凝聚态物理学与材料研究的前沿问题

讨论了凝聚态物理学在当代材料研究的前沿问题中所起的作用，首先对，于那些基本物理学业已能晓的常规材料，极好的机会在于设计并制备出微结构和纳米结构，其次，对于具有强关联电子特征的复杂材料，虽则其物理学尚在探索之中，已有迹象表明这将是新材料的“富矿区”，再次，关于有机及聚合物材料，物理学正在向这领域延拓，在设计和制备分子和超分子结构方面，将会提供许多新的可能性。     

微波吸收法研究ZnO光电子衰减过程

微波吸收无接触测量技术可以用于半导体粉体材料、微晶材料等研究光生载流子衰减过程。本文采用微波吸收法在室温下分别测量了ZnO纳米材料和微晶材料的光电子衰减过程。发现在紫外激光短脉冲激发下,两种材料的导带光电子寿命有很大的差异,ZnO微晶粉体材料的光电子寿命为50ns,而ZnO纳米材料的光电子寿命仅为10ns。分析认为纳米ZnO的光电子寿命缩短是由于纳米ZnO晶体的表面积远远大于体材料的表面积,纳米材料的表面形成了大量的缺陷能级,加速了光电子的表面复合,缩短了光电子的寿命。纳米材料内部缺陷增多和量子限域效应同样会缩短光电子的寿命。     

靶材料面密度用β射线测量的定标问题

 惯性约束聚变靶材料面密度及其均匀性分布可以通过β射线束透射法进行测量,要完成这一测量,需首先用一系列面密度已知、组成成分与待测材料相同的标准材料对测量装置进行刻度。针对惯性约束聚变靶材料一类还处于研制阶段的新材料的密度测量,提出了用成分相近的材料作为替代标准进行刻度的方法,并用蒙特卡罗方法模拟计算了不同能量电子穿过不同材料的透射率,得到了这种刻度方法对测量结果带来的误差大小,用纸作标准测量CH泡沫靶材料的误差只有百分之几,这一误差在实际测量中可以由蒙特卡罗模拟方法得到修正。该刻度方法解决了惯性约束聚变靶材料一类新材料面密度用β透射法测量中的定标问题。     

Young’s moduli and Poisson’s ratios of curvilinear anisotropic hexagonal and rhombohedral nanotubes. Nanotubes-auxetics

The study of materials with unusual mechanical properties has attracts a lot of attention in view of new possibilities for their application. One of these properties is negative Poisson’s ratio which is commonly found in crystalline materials (materials with linear anisotropy). However, until now the capabilities of negative Poisson’s ratios in tubular crystals (materials with curvilinear anisotropy), e.g., in today’s popular nanotubes, have not been studied.     

Two-dimensional materials: Emerging toolkit for construction of ultrathin high-efficiency microwave shield and absorber

Two-dimensional (2D) materials generally have unusual physical and chemical properties owing to the confined electro-strong interaction in a plane and can exhibit obvious anisotropy and a significant quantum-confinement effect, thus showing great promise in many fields. Some 2D materials, such as graphene and MXenes, have recently exhibited extraordinary electromagnetic-wave shielding and absorbing performance, which is attributed to their special electrical behavior, large specific surface area, and low mass density. Compared with traditional microwave attenuating materials, 2D materials have several obvious inherent advantages. First, similar to other nanomaterials, 2D materials have a very large specific surface area and can provide numerous interfaces for the enhanced interfacial polarization as well as the reflection and scattering of electromagnetic waves. Second, 2D materials have a particular 2D morphology with ultrasmall thickness, which is not only beneficial for the penetration and dissipation of electromagnetic waves through the 2D nanosheets, giving rise to multiple reflections and the dissipation of electromagnetic energy, but is also conducive to the design and fabrication of various well-defined structures, such as layer-by-layer assemblies, core–shell particles, and porous foam, for broadband attenuation of electromagnetic waves. Third, owing to their good processability, 2D materials can be integrated into various multifunctional composites for multimode attenuation of electromagnetic energy. In addition to behaving as microwave reflectors and absorbers, 2D materials can act as impedance regulators and provide structural support for good impedance matching and setup of the optimal structure. Numerous studies indicate that 2D materials are among the most promising microwave attenuation materials. In view of the rapid development and enormous advancement of 2D materials in shielding and absorbing electromagnetic wave, there is a strong need to summarize the recent research results in this field for presenting a comprehensive view and providing helpful suggestions for future development.     

Light–matter interaction of 2D materials:Physics and device applications

In the last decade, the rise of two-dimensional(2D) materials has attracted a tremendous amount of interest for the entire field of photonics and opto-electronics. The mechanism of light–matter interaction in 2D materials challenges the knowledge of materials physics, which drives the rapid development of materials synthesis and device applications. 2D materials coupled with plasmonic effects show impressive optical characteristics, involving efficient charge transfer, plasmonic hot electrons doping, enhanced light-emitting, and ultrasensitive photodetection. Here, we briefly review the recent remarkable progress of 2D materials, mainly on graphene and transition metal dichalcogenides, focusing on their tunable optical properties and improved opto-electronic devices with plasmonic effects. The mechanism of plasmon enhanced light–matter interaction in 2D materials is elaborated in detail, and the state-of-the-art of device applications is comprehensively described. In the future, the field of 2D materials holds great promise as an important platform for materials science and opto-electronic engineering, enabling an emerging interdisciplinary research field spanning from clean energy to information technology.     

Some remarks regarding electrodynamics of materials with negative refraction

In the following article some electrodynamical problems of materials with negative refraction are considered. In contrast to the usual case when the index of refraction is positive, for these sorts of materials many laws and equations must be recorded differently. Special note is taken of the fact that most of the books and textbooks are written with the so-called “nonmagnetic approach”, which is only valid for nonmagnetic materials (μ = 1). This approach is undoubtedly unfit for material with a negative index of refraction.It is shown that materials with simultaneously negative dielectric and magnetic permeabilities undoubtedly must possess the frequency dispersion. Correlation is brought between phase and group velocities for these sorts of materials.The question is considered in detail about the so-called “overcoming of the diffraction limit” by means of plates from materials with a negative factor of refraction. It is shown that this effect is indeed reduced to the problem of matching between source and receiver of radiation. Such matching is possible by spreading the so-called evanescent modes, for which a diffraction limit does not exist. These modes fade within a distance of the order of the wavelength, and only at such a distance is the transfer of picture details that are smaller than the wavelength possible.     

二维材料的转移方法

二维材料及其异质结在电子学、光电子学等领域具有潜在应用,是延续摩尔定律的候选电子材料.二维材料的转移对于物性测量与器件构筑至关重要.本文综述了一些具有代表性的转移方法,详细介绍了各个方法的操作步骤,并基于转移后样品表面清洁程度、转移所需时间以及操作难易等方面对各个转移方法进行了对比归纳.经典干、湿法转移技术是进行物理堆...     

Strained 2D Layered Materials and Heterojunctions

2D layered materials and heterojunctions with excellent ductility and controllable atomic‐layer thicknesses have shown promise for use in advanced electronics and optical functional devices. Tailoring of nanoscale configurations and physical properties is essential and required for bespoke fabrication of advanced devices based on 2D materials. Due to the high strain tolerance of 2D layered materials, strain engineering is an effective method to tune their behaviors of electrons and phonons. A wide variety of 2D materials are available with tunable bandgaps from interface coupling effects, making 2D layered heterojunctions a versatile platform for understanding fundamental physical issues. Most physical properties and functional applications can be tailored by applying strain to 2D layered materials and heterostructures to realize a scheduled target in carrier concentration, mobility, and barrier height. Herein, the latest research on the roles of strain in modulating the physical properties of 2D layered materials and heterojunctions is introduced, focusing on the physical properties behind strain modulation in 2D materials. Understanding and manipulating strain in 2D layered materials and heterojunctions is important and beneficial for creating tunable electronic and optoelectronic constructions with advanced components, including functional flexible and wearable devices.     

Broad-band apochromatic retarders: choice of materials

Apochromatic retarders can be constructed by using a combination of three plates of different birefringent materials with properly chosen thicknesses. However, when dealing with a broad wavelength range, their performance depends very much on the materials chosen. A procedure is presented for optimizing the choice of materials for such a broad-band retarder.     

Modern microwave magnetic materials: Recent advances and trends

In recent years, a large variety of microwave magnetic materials has been developed, with different compositions, shapes, and fabrication processes. The physics of the dynamic magnetic responses of these materials is very rich, due to the interplay between the intrinsic magnetic properties of the materials, the domain structure, and dynamic shape effects. These materials are associated to a variety of applications, some of them well-established, for direct interaction with rf waves; others corresponding to etablished uses of magnetic materials, but at higher speeds or higher frequencies; and some in association with hot topics in the magnetic or rf communities including metamaterials, nanoscale structures, and nonlinear devices.     

Omnidirectional reflection in one-dimensional ternary photonic crystals and photonic heterostructures

Designing dielectric systems to create omnidirectional band gaps (OBGs) is an attractive topic in the field of photonic band gap (PBG) structures. In this Letter, we propose a new approach to create OBGs by ternary photonic heterostructures (TPHs) composed of three kinds of materials with different refractive indices and obtain the formulae of the structures of TPHs, i.e., those of the thicknesses of materials and the number of sub-ternary photonic crystals. It may provide a powerful technique for designing the structures being able to produce OBGs by use of usual materials, lowcost materials, and materials with low refractive indices, etc.     

纳米微晶材料的结构和性质

纳米微晶材料是纳米量级晶粒所构成的多晶物质,其晶界区域中存在与长程有序晶态和短程有序非晶态结构不相同的“气体状”的结构。本文讨论了纳米微晶材料的制备方法、结构特点和奇异性质及其在材料科学中的应用。     

Physics towards next generation Li secondary batteries materials: A short review from computational materials design perspective

The physics that associated with the performance of lithium secondary batteries (LSB) are reviewed. The key physical problems in LSB include the electronic conduction mechanism, kinetics and thermodynamics of lithium ion migration, electrode/ electrolyte surface/interface, structural (phase) and thermodynamics stability of the electrode materials, physics of intercalation and deintercalation. The relationship between the physical/chemical nature of the LSB materials and the batteries performance is summarized and discussed. A general thread of computational materials design for LSB materials is emphasized concerning all the discussed physics problems. In order to fasten the progress of the new materials discovery and design for the next generation LSB, the Materials Genome Initiative (MGI) for LSB materials is a promising strategy and the related requirements are highlighted.