Effect of Particle Size and Phase Composition of Titanium Dioxide Nanoparticles on the Photocatalytic Properties

Titanium dioxide (TiO₂) nanoparticles were prepared by the oxidation of titanium tetrachloride (TiCl₄) in a diffusion flame reactor. The average diameter of particles was 15–30 nm and mass fraction of anatase ranged from 40% to 80%. Effects of particle size and phase composition of those TiO₂ nanoparticles on photocatalytic properties such as decomposition of methylene blue, bacteria and ammonia gas were investigated. The degree of decomposition of methylene blue by the TiO₂ nanoparticles under the illumination of the black light was directly proportional to the anatase mass fraction, but inversely to the particle size. The decomposition of bacteria and ammonia gas by the TiO₂ nanoparticles under the illumination of the fluorescent light showed the same trend as in the case of the methylene blue.     

Enhancement of Mechanical Stability of Silicon Macrospecimens Containing Hierarchically-Structured Porous Silicon

Russian Physics Journal - The paper presents the research findings in the field of mechanical stability of single-crystal silicon macrospecimens containing hierarchically-structured porous silicon....     

Influence of Iron Alloying on the Properties of Vanadium Dioxide

Russian Physics Journal - Results of investigations of the x-ray structural parameters of the crystal lattice and their temperature dependences in the vicinities of the metal-dielectric phase...     

The Influence of Structure and Phase Composition of Titanium Alloy on Superplastic Deformation

Russian Physics Journal - The paper presents research into the behavior of high-temperature plastic deformation of titanium alloy Ti–4.74 wt.% Al–5.57 wt.% Mo–5.04 wt.% V alloy...     

Effect of the Dose of Irradiation by Fast Neutrons on the Optical Properties of Vitreous Silicon Dioxide

The influence of neutron irradiation on some parameters of vitreous silicon dioxide was investigated by optical, dielectric, and x-ray spectroscopy. The laws governing the change in the spectral characteristics, structure parameters, polarizability, and refractive index of vitreous silicon dioxide in a wide range of fluences of fast neutrons are determined. It is assumed that the revealed species of the corresponding dose dependences of some characteristics are caused by the radiation-stimulated change in the structure of the substance. The effect of large doses is considered.     

相态对冰水混合云微观特性反演的影响研究

当云层的温度在－40℃~0℃之间时, 云层中会存在冰和水两种相态的云滴, 其散射特性与纯水云以及纯冰云特性有较大差异, 因此遥感反演混合相云层的微观和宏观物理特性具有重要的意义。本文采用冰水双层球模型模拟了冰水混合云中的云滴, 利用Mie理论计算了纯水、纯冰和冰水颗粒的单次散射特性, 分析了单次散射相函数, 不对称因子, 单次散射反照率等随着有效半径、相态、内外半径比等的变化特性。利用离散纵标法(DISORT)计算了水云和冰云对0.75 μm、2.16 μm和3.3 μm的双向反射函数, 讨论了利用纯水滴和纯冰滴反演冰水混合云滴的误差。分析结果表明, 利用0.75 μm和2.16 μm的太阳光反演冰水混合云的光学厚度和有效半径时, 光学厚度误差较大, 有效半径误差较小; 结合0.75 μm和3.3 μm的太阳光反演冰水混合云的光学厚度和有效半径时, 光学厚度误差较小, 有效半径误差较大, 其会高估其有效半径; 另外结合0.75 μm和3.3 μm这两个波长的反射函数反演冰水云的冰水混合比更为有效。     

In插入层对硅衬底外延InN晶体质量和光学特性的影响

在Si(111)衬底上分别预沉积0,0.1,0.5,1 nm厚度的In插入层后,采用等离子辅助分子束外延法制备了纤锌矿结构的InN材料,结合X射线衍射(XRD)、扫描电子显微镜(SEM)、吸收谱及光致发光谱研究了不同厚度的In插入层对外延InN晶体质量和光学特性的影响。XRD和SEM的测试结果表明,在Si衬底上预沉积0.5 nm厚的In插入层有利于改善外延InN材料的形貌,提高材料的晶体质量。吸收谱和光致发光谱测试表明,0.5 nm厚In插入层对应的InN样品吸收边蓝移程度最小,光致发射谱半峰宽最窄,并且有最高的带边辐射复合发光效率。可见,引入适当厚度的InN插入层可以改善Si衬底上外延InN材料的晶体质量和光学特性。     

The Effect of Pressure in Producing Ultrafine Powder Compacts from Zirconium Dioxide Doped with Bismuth Oxide on Compaction Efficiency and Mechanical Properties of the Sintered Ceramics Under Conditions of High-Temperature Sintering

Russian Physics Journal -     

The Influence of the Cobalt Content on the Strength Properties of Tungsten Carbide Ceramics under Dynamic Loads

Based on the registration and analysis of the full wave profiles, the Hugoniot elastic limit and spall strength of ceramics based on tungsten carbide with different cobalt content are measured. We also study the influence of the cobalt content on the mechanical characteristics of tungsten carbide such as hardness, fracture strength, Young’s modulus, shear modulus, and sound velocity. It is shown that in the process of spalling, the failure stresses grow and the dynamic elastic limit decreases almost linearly within the scatter of their values with growing cobalt content; moreover, the value of the Hugoniot elastic limit is abruptly practically halved as the cobalt content grows from 0 to 2 wt %.     

The Influence of Particles Interaction in Low-Temperature Plasma on its Composition and Optical Properties

A model theory of the influence of particles interaction in plasma on its composition and optical properties is developed. The interaction of charged particles in plasma reduces the ionization energy of atoms and ions. The action of internal microfields in plasma on atoms and ions reduces the statistical weight of electron levels which affects the populations of excited states. The latter effect leads to an effective cutoff of partition functions and determines the behaviour of optical properties of plasma (of absorption coefficient and emissivity) at increased number densities of charged particles. The formulas are obtained for calculation of the continuous and discrete spectrum in plasma taking into account the particles interaction. A non-monotonic dependence of optical plasma density upon number density of charged particles is quantitatively explained. A satisfactory agreement is obtained with a large number of experimental data some of which were considered to be contradictory. The method developed can be used for calculations in the field of atomic spectroscopy and low-temperature plasma physics including increased densities of charged particles. The use of the formulas obtained in plasma diagnostics will enable one to avoid considerable errors.     

Grain Boundary Phase Transitions and their Influence on Properties of Polycrystals

Grain boundary (GB) phase transitions can change drastically the properties of polycrystals. The GB wetting phase transition can occur in the two-phase area of the bulk phase diagram where the liquid (L) and solid (S) phases are in equlibrium. Above the temperature of the GB wetting phase transition a GB cannot exist in equlibrium contact with the liquid phase. The experimental data on GB wetting phase transitions in numerous systems are analysed. The GB wetting tie-line can continue in the one-phase area of the bulk phase diagram as a GB solidus line. This line represents the GB premelting or prewetting phase transitions. The GB properties change drastically when GB solidus line is crossed by a change in the temperature or concentration. The experimental data on GB segregation, energy, mobility and diffusivity obtained in various systems both in polycrystals and bicrystals are analysed. In case if two solid phases are in equilibrium, the GB “solid state wetting” can occur. In this case the layer of the solid phase 2 has to substitute GBs in the solid phase 1. Such GB phase transition occurs if the energy of two interphase boundaries is lower than the GB energy in the phase 1.     

Influence of Mechanical Stretching on Adsorption Properties of Nitrogen-Doped Graphene

This paper presents the results of quantum chemical modeling of chemisorption of atomic hydrogen and epoxy, carboxyl, and hydroxyl functional groups on nitrogen-doped graphene. It is shown that the substitutional nitrogen atom does not bind to adsorbing groups directly, but significantly increases the adsorption activity of neighboring carbon atoms. Mechanical stretching of doped graphene reduces the adsorption energy of all the aforementioned radicals. This reduction is significantly greater for the epoxy group than for the other functional groups. The results obtained confirm that, upon a sufficient stretching of a nitrogen-doped graphene sheet, the dissociation of molecular hydrogen and oxygen with subsequent precipitation of the resulting radicals onto graphene can be energetically favorable.

     

Thermal Stability of the Structure and Phase Composition of Titanium Treated with Compression Plasma Flows

The results of studying the structure and phase composition of the surface layer of commercial pure VT1-0 titanium treated with compression plasma flows in nitrogen atmosphere and annealed in the temperature range of 400–900°C for 1 h are presented. Using the X-ray diffraction method, the α-Ti(O) solid solution is found to form in the titanium surface layer at 500°C, without pretreatment with plasma, and to transform into the titanium oxide TiO₂ (rutile) phase at 600°C. Pretreatment of titanium with compression plasma flows promotes the formation of α-Ti(N) solid solution decreasing the rate of surface oxidation and increasing the initial temperature of rutile formation to 700°C, which indicates enhancement of the thermal stability of this structure.     

Thermal Stability of the Microstructure and Mechanical Properties of the Ferritic-Martensitic Steel EK-181

Russian Physics Journal - Thermal stability of the microstructure and high-temperature mechanical properties of the low-activate 12% Cr ferritic-martensitic steel EK-181 are studied at temperatures...     

Empirical Molecular Dynamics Modeling of Silicon and Silicon Dioxide: A Review

A number of computational methods have been developed over the last 40 years to simulate the behavior of solid materials with small dimensions. On the macro-scale, Finite Element analysis calculates mechanical stress on micron-sized cantilevers and motors. On the atomic level, newer ab initio methods compute nuclear and electronic behavior of hundred atom models with unprecedented rigor. By implementing the laws of classic mechanics, empirical Molecular Dynamics (MD) programs help bridge these two computational extremes. MD identifies nonelectronic, particle motion for large 100,000 atom cells with good success. MD derives both equilibrium and nonequilibrium properties for many complex condensed regimes; quantitatively (and qualitatively) reaffirms empirical data; aids discovery of new materials processing techniques, and helps predict unknown physical phenomena often only observable under extreme environmental settings. One material of great technical importance to the semiconductor industry is silicon (Si). This element and its oxide (SiO2) play key roles in Complementary Metal-Oxide Semiconductor (CMOS) integrated circuits and in Silicon on Insulator (SOI) technology. Thousands of publications of the structure and function of Si and SiO₂ fill the literature. Hundreds of these employ Molecular Dynamics. Herein, we describe the MD process; its particular application to these two materials; explore past research and propose possible directions for future work. While no review can fully comprehend or thoroughly evaluate the entire bibliographic mass, this report provides a starting point for researchers interested in the field. It attempts to uncomplicate the oft-complex mathematics and physics frequently associated with the subject. Little prior knowledge of classic Molecular Dynamics is needed. Although most information is taken directly from MD-related theory, results from experimental or non-MD-related work are occasionally added to help fill in gaps. Finally, because details of every simulation and experiment cited herein cannot be made, the reader is encouraged to refer to specific bibliographic references whenever necessary.     

Influence of Iodine-Containing Solutions on the Condition of a Porous Silicon Surface and Its Photoluminescent Properties

The influence of surface treatment of porous silicon in iodine-containing solutions on its photoluminescent properties has been investigated. The porous silicon samples were prepared by anodizing in HF-based electrolytes and placed in fluoride-hydrogen solutions with the addition of iodine immediately after their formation. The surface condition was controlled by IR Fourier spectroscopy methods in the 400–4000-cm^–1 range. It has been established that the result of the porous silicon treatment in iodine-containing solutions is a decrease in the intensity of Si–H _x -bonds without the appearance of additional vibrations in the range under investigation. At the same time, such a treatment substantially affects the spectrum and intensity of porous silicon photoluminescence and increases its stability in subsequent storage. The possible reasons for the revealed phenomena are discussed.     

Features of the Elastic Properties of HTSC Ceramics in the Transition Zone to the Superconducting Phase

Acoustical Physics - The article presents the results of studies of the elastic properties of the YBa2Cu3O(7 –x) high-temperature superconducting ceramic in the vicinity of the phase...     

Influence of Radio-Frequecy Power on Structural and Electrical Properties of Sputtered Hafnium Dioxide Thin Films

Hafnium dioxide （HfO2） thin films are prepared by rf magnetron sputtering. The influences of rf power on the structure, chemical states and electrical properties of the thin films were investigated through x-ray diffraction, x-ray photoelectron spectroscopy, capacitance-voltage and leakage current density-voltage measurement and UV-VIS spectrophotometry. The results show that the HfO2 thin films have a mixed structure of amorphous and polycrystalline phases. With increasing rf power, the crystallinity is enhanced and the crystallite size of the thin films is increased. The oxidation of Hf atoms is improved with increasing rf power for the HfO2 thin films. The flat band shift, oxide charge density and leakage current density of the thin films all decrease as the rf power increases from 50 to 110 W, and then increase as the rf power is increased to 140 W. The band gap energy is smaller for the thin film deposited at 110 W.