Characterization of nanodiamonds for metamaterial applications

Several different types of nanodiamonds were characterized in order to find the best sample to be used in further experiments with metamaterials. In this work we present the results of optical analysis of aqueous suspensions containing nanodiamonds, SEM analysis of diamond particles dispersed on silicon substrates and measurements of photoluminescence from defects in nanodiamonds.     

Photochromic properties of modified nanodiamonds

A functionalization of the surface of detonation nanodiamonds by photochromic spirocompounds from the classes of spiropyrans and spirooxazines has been carried out for the first time. A comparative study of the interaction of nanodiamonds with positive and negative potential is performed by the spectral–kinetic method, which shows the possibility of surface modification by only functionalized molecules of spirocompounds with the formation of surface proton complexes. This is confirmed by the hypsochromic shift of the absorption bands of the photoinduced merocyanine forms of adsorbed molecules of spirocompounds and by the decrease of the speed of their dark relaxation to the initial state in the presence of nanodiamonds with a negative potential.     

Electron emission properties of detonation nanodiamonds

This paper summarizes the results of systematic studies of field electron emission from detonation nanodiamond coatings corresponding to nanodiamond powders of different modifications. The role of the chemical composition of the surface of detonation nanodiamond particles in field emission mechanisms is discussed. Field emission-related electronic properties of single diamond nanodots are studied using tight-binding calculations and continuum electrostatic simulations.     

石墨烯的结构、性能及潜在应用

石墨烯是一种二维零带隙半金属材料,近年来受到学术界和工业界的广泛关注。文章将石墨烯合成方法分为固、液、气三类并分别加以讨论,介绍了石墨烯的结构和缺陷特征及其电、光、热、力学等性能。石墨烯的应用研究主要集中在电学、力学、选择性分离膜、基底和生长衬底等方面。     

Synthesis, characterization, and applications of shaped single crystals

In this paper we shall review techniques for the growth of single crystal, mostly of insulating material, which are shaped during the growth process. In particular, we shall focus on the growth of single-crystal fibers of optically activated materials; the emphasis will be placed on the so-called Laser Heated Pedestal Growth (LHPG) method of pulling crystalline fibers. LHPG offers a number of logistical advantages which can be exploited as a tool for materials research. Progress in the synthesis of materials using LHPG is described, as are spectroscopic techniques which are employed in characterizing the optical and physical properties of the crystal fibers obtained by this method. Fiz. Tverd. Tela (St. Petersburg) 41, 770–773 (May 1999) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

Electrophysical properties of carbon nanocomposites based on nanodiamonds irradiated with fast neutrons

The electrophysical properties of nanoporous carbon composites consisting of a nanometer-sized pyrolytic carbon matrix and nanodiamonds have been analyzed. It has been shown that the power-law dependence of the electrical resistivity on the thickness of the pyrolytic carbon layer D on a log-log scale has an inflection for D = 1 Å. It has been found that the temperature dependence of the electrical resistivity of the nanocomposite is described by an exponential function with an exponent of 1/4 for both unirradiated samples and samples irradiated with fast neutrons. This is characteristic of variable-range hopping conductivity in the case of strong localization in systems with semiconductor conductivity in the presence of a local disorder. With an increase in the neutron fluence, the electrical resistivity of the studied material changes very significantly (by several hundred percent) and nonmonotonically. This result is associated with the transformation of the structure of the graphite-like matrix and with possible graphite-diamond phase transitions.     

Silicon nanoparticles: Preparation,properties, and applications

Silicon nanoparticles have attracted great attention in the past decades because of their intriguing physical properties,active surface state, distinctive photoluminescence and biocompatibility. In this review, we present some of the recent progress in preparation methodologies and surface functionalization approaches of silicon nanoparticles. Further, their promising applications in the fields of energy and electronic engineering are introduced.     

Fabrication,properties, and applications of flexible magnetic films

Flexible magnetic devices, i.e., magnetic devices fabricated on flexible substrates, are very attractive in applications such as detection of magnetic field in an arbitrary surface, non-contact actuators, and microwave devices, due to their stretchable, biocompatible, light-weight, portable, and low cost properties. Flexible magnetic films are essential for the realization of various functionalities of flexible magnetic devices. To give a comprehensive understanding for flexible magnetic films and related devices, recent advances in the study of flexible magnetic films are reviewed, including fabrication methods, magnetic and transport properties of flexible magnetic films, and their applications in magnetic sensors, actuators, and microwave devices. Our aim is to foster a comprehensive understanding of these films and devices. Three typical methods have been introduced to prepare the flexible magnetic films, by deposition of magnetic films on flexible substrates, by a transfer and bonding approach or by including and then removing sacrificial layers. Stretching or bending the magnetic films is a good way to apply mechanical strain to them, so that magnetic anisotropy, exchange bias, coercivity, and magnetoresistance can be effectively manipulated. Finally, a series of examples is shown to demonstrate the great potential of flexible magnetic films for future applications.     

Shock-wave sintering of nanodiamonds

A two-stage technology of compaction of ultrafine-dispersed diamonds (UDDs) is developed and successfully applied for ampoule-free sintering of dense UDD granules in lead under a pressure of up to 100 GPa. Standard strength tests of polycrystals (fractions 80/63, 125/80) thus obtained showed a wide spread in strength (from grade AS4 to AS80), which is indicative of highly inhomogeneous sintering conditions. A single-crystal diamond is obtained for the first time by using shock-wave compaction; the crystal is a transparent twinned octahedron 0.6 mm in size with an impurity content of less than 0.05%. This result is unexpected and encourages us to believe that this method can be used to manufacture jewellery-grade diamonds (larger than 2 mm in size). The pressure and temperature conditions of sintering are analyzed.     

Surface chemistry of nanodiamonds

The experimental data available in the literature and the results obtained by the author in research into the structure of nanodiamonds and the physicochemical and chemical properties of their surface are generalized. An account is given of the problems concerning the chemical state and modification of the nanodiamond surface in gaseous and liquid media and the infiuence of modification on the sorption and catalytic properties of nanodiamonds, their compactibility, and sintering. The similarity and difference in the behavior of nanodiamonds and diamond macrocrystals in oxidation processes are discussed. The activation energies of oxidation of nanodiamonds by different reagents are determined in the absence and presence of catalysts.     

Structure, properties and applications of thin Fe--Al layers

Fe-Al alloys show interesting physical properties and offer some special industrial applications. There are phase transitions combined with changes in the magnetic behaviour. Another interesting fact is the excellent oxidation and corrosion resistance of iron aluminides even at high temperatures. Thin Fe-Al layers can be produced in different ways. Ion beam methods are able to produce surface layers on bulk material modifying the initial properties completely. The properties depend strongly on the phase structure induced by the preparation process. 57-Fe Mössbauer spectroscopy, and in the case of surface layers conversion electron Mössbauer spectroscopy, is very suitable to identify this phase structure. In the present work, it is described for Al implanted Fe layers. Depending on implantation dose and energy both magnetic and non-magnetic phases can be produced. Due to the inhomogeneous distribution of Al in the Fe target a layer structure of different phases can be created. Moreover, due to double implantation an Fe-Si-Al alloy can be prepared.     

Synthesis,structure, and properties of BIFENBVOX

Solid solutions Bi₄V_2-x Fe _x/2Nb _x/2O_11-δ (х?=?0.05–1.0) and Bi₄V_2-х-y Fe _x Nb _y O_11–δ (with fixed x or y?=?0.2 and variable х or y?=?0.2–0.5 with step 0.1) were synthesized by the standard ceramic technology in the temperature range 773–1113 K and by mechanochemical activation method using Bi₂O₃, V₂O₅ Fe₂O₃, and Nb₂O₅ oxides as initial compounds. The formation of solid solutions was studied. Ranges of stability and temperature values of phase transitions for different polymorphous modifications were defined using dylatometric and thermo gravimetric studies. The morphology and the local chemical composition of the ceramic samples were studied. Samples with concentration of dopants x?>?0.3 contain two phases; both major and impurity phases are solid solutions of the BIFENBVOX type although the dopants atoms distribution between them is random. The thermal expansion coefficients (TEC) were measured. The electrical conductivity of ceramic samples was investigated in a wide range of temperatures. The highest conductivity values among the studied solid solutions are observed for the sample with a small amount of dopants x?=?0.25.     

Processing, properties and some novel applications of magnetic nanoparticles

Magnetic nanoparticles have been prepared by various soft chemical methods including self-assembly. The bare or surface-modified particles find applications in areas such as hyperthermia treatment of cancer and magnetic field-assisted radioactive chemical separation. We present here some of the salient features of processing of nanostructured magnetic materials of different sizes and shapes, their properties and some possible applications. The materials studied included metals, metal-ceramic composites, and ferrites.     

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.     

Fabrication, properties, and applications of porous metals with directional pores

Lotus-type porous metals with aligned long cylindrical pores are fabricated by unidirectional solidification from the melt with a dissolved gas such as hydrogen, nitrogen, or oxygen. The gas atoms can be dissolved into the melt via a pressurized gas atmosphere or thermal decomposition of gaseous compounds. Three types of solidification techniques have been developed: mold casting, continuous zone melting, and continuous casting techniques. The last method is superior from the viewpoint of mass production of lotus metals. The observed anisotropic behaviors of the mechanical properties, sound absorption, and thermal conductivity are inherent to the anisotropic porous structure. In particular, the remarkable anisotropy in the mechanical strength is attributed to the stress concentration around the pores aligned perpendicular to the loading direction. Heat sinks are a promising application of lotus metals due to the high cooling performance with a large heat transfer.     

Preparation,properties, and applications of laser-prepared intercalated structures in nanoelectronics

Experimental investigation of the structure and electrical properties of layered gallium selenide and indium selenide crystals laser-intercalated by copper and gallium is discussed.