The structure and some electro-physical properties of TlSbS2 films

The 1m thick films of TlSbS₂ were obtained by thermal evaporation in vacuum. It has been shown that, depending on the conditions of preparation and annealing, amorphous or polycrystalline and grain-oriented layers of TlSbS₂ can be obtained. The electro-physical parameters of the films (electrical conductivity, thermoelectromotive force, and width of the forbidden band) and their changes in the transition from amorphous to crystalline were studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedehii, Fizika, Vol. 16, No. 9, pp. 37–40, 1973.The authors wish to thank S. A. Dembovskii, Dr. Chem. Sc., for supplying TlSbS₂ monocrystals.     

The influence of temperature on the optical properties of gold nanoparticles

The optical properties of gold nanoparticles in a transparent matrix are studied at temperatures from 300 to 1000 K within the spectral range from 450 nm to 1.5 μm. It is shown that, in the case of small nanoparticles and short wavelengths in the plasmon resonance band, an increase in temperature leads to a decrease in the absorption efficiency factor. The light absorption efficiency factor of gold nanoparticles with a radius exceeding 40 nm increases with increasing temperature in the entire spectral range studied. The single scattering efficiency factor always decreases with increasing temperature. The effects observed are related to a change in the refractive indices of gold and the matrix with comparable contributions. It is shown that results of calculations agree qualitatively with available experimental data. The results are necessary to optimize the composition of the actuators, including gold nanoparticles, in the transparent matrices.     

The effect of oxygen-plasma treatment on Kevlar fibers and the properties of Kevlar fibers/bismaleimide composites

The effect of oxygen-plasma treatment for Kevlar fibers on the interfacial adhesion and typical macro-properties of Kevlar fiber/bismaleimide composites was intensively studied. It is found that oxygen-plasma treatment significantly affects the interfacial adhesion by changing the chemistry and morphology of the surfaces of the fibers, and thus leading to improved interlaminar shear strength, water resistance and dielectric properties of the composites. However, the improvement is closely related to the treatment power and time. The best condition for treating Kevlar fiber is 70 W for 5 min. Oxygen-plasma treatment provides an effective technique for overcoming the poor interfacial adhesion of Kevlar fiber based composites, and thus showing great potential in fabricating high performance copper clad laminates.     

The influence of temperature and dynamic quenching on the properties of 3-hydroxyflavone excited states

The influence of temperature and dynamic quenching on the properties of excited states of the normal and tautomeric 3-hydoxyflavone forms was studied. The stationary two-band fluorescence spectra of this luminophore in acetonitrile were recorded and analyzed. The spectra were observed under excitation by electromagnetic radiation in the region of the S ₁ absorption band over the temperature range 20–80°C. TEMPO was used as a quencher of the excited state. Heating caused temperature quenching of luminescence, and the tautomer formed via the excited state of the normal form of the luminophore was quenched more strongly both in pure solvent and in the presence of the quencher. An analysis of two-band fluorescence parameters led us to conclude that solution heating over the temperature range studied increased the rate of proton transfer by 1.25 times. The introduction of the quencher also accelerated proton transfer by 1.16–1.25 times as the temperature increased from room temperature to 80°C.     

The influence of perchloric acid on the spectral and luminescent properties of cyclopalladated complexes

The influence of perchloric acid in ethanol on the spectral and luminescent characteristics of cyclopalladated amine complexes with 4-phenylpyrimidine, 1,7-phenanthroline, and coumarin-6 is studied. A protonation mechanism is proposed.     

Investigation of thermal influence on the bandgap properties of liquid-crystal photonic crystal fibers

We have analyzed the thermal influence on the bandgap properties of liquid-crystal photonic crystal fibers. The bandgap parameters which affect the transmission conditions have been investigated. It is observed that the photonic bandgap can be thermally tuned, i.e. the red or blue shift of the bandgap results from the temperature dependence of the refractive index of the liquid crystal. For the planar alignment of liquid-crystal filled cladding, the ordinary refractive index plays a major role in determining the bandgap properties; the extraordinary refractive index comes into influence while the ordinary refractive index is relatively constant of temperature. The analyses agree well with the experiments results.     

激光作用下的铝管热参数的变化对温度场的影响

用有限元方法数值模拟了脉冲激光作用于铝管时所产生的温升情况。比较了物理参数随温度变化和不随温度变化两种情况下的温度场的区别,分别给出了两种情况下的温度随角向的分布曲线。结果表明:物理参数随温度的变化对整个瞬态温度场的影响很大,为在热弹条件下在激光激发管状材料时的超声导波的研究提供了定量的基础。     

The influence of annealing temperature on the structure,morphologies and optical properties of ZnO nanoparticles

ZnO nanoparticles (NPs) have been successfully synthesized by the simple solution method at low temperature. The effects of annealing temperature on the structure and optical properties of ZnO NPs were investigated in detail by X-ray diffraction, transmission electron microscopy (TEM), ultraviolet–visible (UV–vis) spectroscopy and photoluminescence (PL) measurements. As the annealing temperature was increased above 180 ^°C the particles morphology evolved from spherical to hexagonal shape, indicating that the average particle size increased from 11 nm to 87 nm. The UV-vis and PL spectra showed a red-shift from 3.62 to 3.33 eV when the annealing temperature was increased.     

Optical properties of Yb-doped fibers and fiber lasers at high temperature

Recent advances in power scaling of Yb^+ 3-doped fiber lasers to the kilowatt level suggest a need to examine the performance of Yb^+ 3-doped silica at temperatures well above ambient. We report experimental results for the absorption coefficient, emission cross-section, fluorescence lifetime, and slope efficiency of a Yb³⁺-doped large mode area (LMA) silica fiber for temperatures spanning 23 °C-977 °C. To the best of our knowledge these are the highest temperatures to date for which these optical properties have been measured. We find a sharp reduction in the energy storing capability and lasing performance of Yb^+ 3:SiO₂ above 500 °C that coincides with the onset of non-radiative transitions in the excited state manifold (thermal quenching). As the temperature increases from room temperature to 977 °C, absorption in the 1020-1120 nm operating band increases monotonically, concurrent with a reduction in absorption at the 920-nm and 977-nm pumping bands. Conversely, the spectral weight of the emission cross-section shifts from transitions above 1010 nm to those below, with the exception of the 977-nm emission band.     

The influence of annealing temperature on the slip plane activity and optical properties of nanostructured ZnO films

The zinc oxide films were prepared by the sol-gel method on the ordinary glass substrates. The activity of slip systems were evaluated by X-ray diffraction line broadening analysis using convolution multiple whole profile (CMWP) fitting procedures. It was found that in all temperatures the 〈a〉 type dislocations is dominating and its fraction increases with the rise of annealing temperature in the range of 350-600 °C. The investigation on the optical properties of films showed that the optical band gap energy increases linearly with the annealing temperature and crystallite size but decreases with the lattice strain.     

The influence of optical properties of shallow shelf seas on temperature structure and acoustic propagation

The penetration of solar radiation below the sea surface is not always taken into account in numerical ocean models, even though its influence on the temperature (and therefore sound speed), structure of the water column can be significant, especially in shallow shelf seas where water turbidity tends to be high. Variations in sound speed structure have a consequent effect on the propagation of sound underwater which, in turn, influences the performance of sonar systems. A double exponential parameterization for the penetration of solar radiation with depth was implemented in an N × 1D turbulence closure model of the UK shelf seas. The model was run along a section through the Celtic Sea Front, with sets of optical extinction coefficients representing different water clarities, for one month to simulate the generation of the front, and the results were compared with a control model run in which all solar radiation was absorbed in the surface layer. Temperature structure and sound propagation were only affected by changes to the optical parameterization on the stratified side of the front, where consequent variations in acoustic propagation loss of up to 10 dB relative to the control were simulated using an acoustic model. Changes in propagation loss were greatest for acoustic sources placed in the stratified water above the thermocline. Similar changes to the optical parameterization made on the well-mixed side of the front had no discernible effect.     

The influence of immersion and contact ultrasound treatment on selected properties of the apple tissue

Ultrasound (US) treatment is considered to be one of the most promising non-thermal technology used in the food processing. The food-related applications of this technique are linked to the analytical and technological purposes. The ultrasound waves in the food can cause the formation of micro-channels due to the systematic and alternating compression and decompression of the material (so called “sponge effect”). Additionally, in liquids the ultrasound application can cause the cavitation which can modify the food properties as well. Hence, due to its mechanism, the ultrasound treatment can also improve the extraction of pigments, aromas or antioxidants from the food matrices.     

The influence of γ radiation on the electrical properties of triglycinsulphate in a temperature autostabilization regime

The influence ofγ ⁶⁰ Co radiation on some of the electrical properties of single crystals of triglycinsulphate irradiated under various conditions was studied with special emphasis on the temperature autostabilization regime. The smallest changes in these properties occur with crystals whose temperature during irradiation is kept above the Curie temperature and which are at the same time exposed to the effects of a strong alternating electric field, and with crystals which are kept in the temperature autostabilization regime during irradiation. The changes caused by irradiation can be partly eliminated by additionally bringing the crystals into the autostabilization regime (renovation).     

温度对吡啶离子液体性质影响的分子动力学模拟研究

运用分子动力学模拟方法研究了温度对三种吡啶离子液体[BPy][BF4]、[HPy][BF4]、[OPy][BF4]热力学性质的影响, 得到了每个体系的密度、自扩散系数、电导率和黏度等. 研究结果表明: 随着温度升高, 同一种离子液体的密度减小, 阴阳离子的自扩散系数明显增大, 电导率升高, 而黏度降低. 在同一温度下, 随着阳离子上烷基链的增长, 离子液体的密度减小, 但热力学性质的变化规律并不完全同步. 烷基链长最短的[BPy][BF4]的自扩散系数和电导率在每个温度下均为最大, 而黏度最小; 但烷基碳链更长的[OPy][BF4]和[HPy][BF4]的各种性质相差不大,甚至当温度大于323K时, 烷基链较长的[OPy][BF4]的自扩散系数比[HPy][BF4]的大.     

温度对吡啶离子液体性质影响的分子动力学模拟研究

运用分子动力学模拟方法研究了温度对三种吡啶离子液体[BPy][BF_4]、[HPy][BF_4]、[OPy][BF_4]热力学性质的影响,得到了每个体系的密度、自扩散系数、电导率和黏度等.研究结果表明:随着温度升高,同一种离子液体的密度减小,阴阳离子的自扩散系数明显增大,电导率升高,而黏度降低.在同一温度下,随着阳离子上烷基链的增长,离子液体的密度减小,但热力学性质的变化规律并不完全同步.烷基链长最短的[BPy][BF_4]的自扩散系数和电导率在每个温度下均为最大,而黏度最小;但烷基碳链更长的[OPy][BF_4]和[HPy][BF_4]的各种性质相差不大,甚至当温度大于323 K时,烷基链较长的[OPy][BF_4]的自扩散系数比[HPy][BF_4]的大.     

The influence of the substrate temperature on the photovoltaic properties of spray-deposited CdS:In thin films

Polycrystalline and highly transparent CdS:In thin films were produced by the spray pyrolysis (SP) technique at different substrate temperatures ranging from 350 to 490 °C on glass substrates. The effect of the substrate temperature on the photovoltaic properties of the films was investigated by studying the transmittance measurements, X-ray diffraction (XRD) patterns, scanning electron microscope (SEM) observations and the I-V plots. The transmittance measurements were used to estimate the band gap energy by the linear fit of (αhν)² versus hν. The band gap energy was found to be slightly increasing with the substrate temperature. XRD diffractograms show that a phase transition from the cubic to the hexagonal phase occurs by increasing the substrate temperature, beside more orientation of crystal growth. Also they show that complex cadmium compounds are still present till T_s ≈ 460 °C after which they practically disappear. From the linear I-V plots the resistivity was estimated and found to be strongly decreasing with the substrate temperature.     

Influence of temperature on dispersion properties of photonic crystal fibers infiltrated with water

Temperature change of the water infiltrated PCF is an interesting and practical method for a dynamical fine tuning of dispersion in active dispersion shift compensating systems. In this paper we present a numerical study on the influence of the temperature of infiltrated water on the dispersion and modal characteristics of photonic crystal fiber. We study regular hexagonal lattice photonic crystal fibers with various geometrical parameters using finite element method.     

The influence of substrate temperature and annealing on the properties of pulsed laser-deposited YIG films on fused quartz substrate

Yttrium iron garnet (YIG) thin films were deposited on fused quartz substrate at different substrate temperatures (T_s) varying from room temperature (RT) to 850 °C using pulsed laser deposition (PLD) technique. All the films in the as-deposited state were X-ray amorphous and non-magnetic at RT. The film deposited at RT after annealing at temperatures T_a?700 °C showed both X-ray peaks and the magnetic order. The films deposited at higher T_s (500–850 °C) and then annealed at 700 °C resulted in better-quality films with higher 4πM_s value. The highest value of magnetization was for the sample deposited at 850 °C and annealed at 700 °C, which is 68% of the bulk 4πM_s value.     

Effect of tungsten film on electro-physical properties of silicon after annealing at 1100°C

We investigated changes in the bulk electro-physical properties of crucibleless silicon after repeated annealing at 1100°C both with and without a tungsten film on the surface. We observed much less change in the resistivity of samples with tungsten films than in those with no films. We observed a significant (about a factor of 10) reduction in the photoresponse decay time, and an increase in the spectral band in which there is a photocurrent as compared with the uncoated samples. The photoconductivity as a function of temperature exhibits a power-law dependence, with β₁=(1.75±0.06) and β₂=(0.20±0.03) for coated and uncoated samples. The change in the relaxation time of the stationary photoconductivity of coated samples is a nonmonotonic function of the intensity of the uniform illumination. Engineering Physics Institute, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 42–46, May, 1996.     

The properties of free polymer surfaces and their influence on the glass transition temperature of thin polystyrene films

We present a detailed study of free polymer surfaces and their effects on the measured glass transition temperature (T_g) of thin polystyrene (PS) films. Direct measurements of the near-surface properties of PS films are made by monitoring the embedding of 10 and 20 nm diameter gold spheres into the surface of spin-cast PS films. At a temperature T = 378K( > T_g), the embedding of the spheres is driven by geometrical considerations arising from the wetting of the gold spheres by the PS. At temperatures below T_g ( 363K < T < 370K), both sets of spheres embed 3-4 nm into the PS films and stop. These studies suggest that a liquid-like surface layer exists in glassy PS films and also provide an estimate for the lower bound of the thickness of this layer of 3-4 nm. This qualitative idea is supported by a series of calculations based upon a previously developed theoretical model for the indentation of nanoscale spheres into linear viscoelastic materials. Comparing data with simulations shows that this surface layer has properties similar to those of a bulk sample of PS having a temperature of 374 K. Ellipsometric measurements of the T_g are also performed on thin spin-cast PS films with thicknesses in the range 8nm < h < 290nm. Measurements are performed on thin PS films that have been capped by thermally evaporating 5 nm thick metal (Au and Al) capping layers on top of the polymer. The measured T_g values (as well as polymer metal interface structure) in such samples depend on the metal used as the capping layer, and cast doubt on the general validity of using evaporative deposition to cover the free surface. We also prepared films that were capped by a new non-evaporative procedure. These films were shown to have a T_g that is the same as that of bulk PS (370±1 K) for all film thicknesses measured (> 7 nm). The subsequent removal of the metal layer from these films was shown to restore a thickness-dependent T_g in these samples that was essentially the same as that observed for uncapped PS films. An estimate of the thickness of the liquid-like surface layer was also extracted from the ellipsometry measurements and was found to be 5±1 nm. The combined ellipsometry and embedding studies provide strong evidence for the existence of a liquid-like surface layer in thin glassy PS films. They show that the presence of the free surface is an important parameter in determining the existence of T_g reductions in thin PS films.