Dependence Of Physical Properties Research Articles

Pressure action on ductility and optoelectronic properties of non-toxic AGeBr[formula omitted] (A = Cs, K, Na, Rb) perovskites

We performed first-principles calculations base on generalized gradient approximation(GGA) in the framework of density functional theory (DFT) to examine the effect of pressure on the structural, mechanical, electronic and optical properties of non-toxic AGeBr3 perovskites (A = Cs, K, Na, Rb) for applications in photovoltaic and optoelectronic devices. The dependence of physical properties is evaluated for several pressure values ranging from 0 GPa to 10 GPa. The determined lattice parameters show agreement with previous values and decrease with the applied pressure. All considered materials show semiconductor behavior with direct bandgap (R ⟶ R) at atmospheric pressure. The hybrid functionals HSE and PBE0 have been used to determine accurate values for bandgaps. A very good agreement was found with available experimental values. The calculated bandgap values were found to be 2.129 [2.608] for CsGeBr3, 2.065 [2.481] for KGeBr3, 2.032 [2.397] for NaGeBr3 and 2.089 [2.530] for RbGeBr3, at the HSE [PBE0] level of theory. However, as the applied pressure increases, a reduction in the bandgap is observed, leading to semiconductor to metallic transition. The materials similarly show improved optical properties under pressure with high absorption coefficients in the visible and ultraviolet regions. In addition, the ductility and stability of the considered materials were found also to improve under hydrostatic pressure, which makes them suitable for incorporation into thin films for high performance optoelectronic devices application.

Toward In Silico Design of Highly Tunable Liquid Crystal Elastomers

In this work, a two-component acrylate liquid crystal elastomer, with varying composition and templating phase, is synthesized in the laboratory and investigated in parallel using atomistic molecular dynamics simulations. The anisotropic nature of both the mono- and bifunctional acrylates used in this study enables a large tunability in the compositional range while still retaining liquid crystalline properties in the final elastomer. The use of simulations allows important evaluation and comparison of physical properties such as glass transition temperature, nematic to isotropic phase transition temperature, and order parameter. The dependence of physical properties (glass transition, nematic to isotropic transition, order parameter, coefficient of thermal expansion, and mechanical properties) is established as a function of chemical composition, showing a high degree of tunability. Interestingly, the templating phase (nematic or isotropic) is also shown to impact the subsequent elastomer properties, with excellent agreement shown here between experiments and simulations. The in silico approach to polymerization, coupled with excellent comparison with the experimental system, represents a new methodology for the targeted design of liquid crystal elastomers with specific physical properties.

Correlation between glass transition effect and structural changes in multicomponent iron phosphate-silicate glasses

Iron phosphate-silicate glasses from P2O5–SiO2–K2O–MgO–CaO–Fe2O3 system were subjected to the thermal and spectroscopic studies in order to gain information about their structure and thermal behavior in the range of glass transition effect. Research includes results obtained via DSC, MIR and DRIFT spectroscopy. Designated values of glass transition temperature and specific heat change slightly increases with Fe2O3 incorporation. Spectra collected during thermal treatment of glasses containing 2 and 30 mol% Fe2O3 exhibited various changes. Fe2O3 addition affected the glass structure by its reinforcement and led to its preservation during thermal treatment. The connection between density, molar volume, oxygen packing density and the chemical composition’s alteration were also established because of the direct dependence of physical properties and the structure. Obtained results supported thermal and spectroscopic studies. Conducted research is considered as a contribution to the knowledge about the family of iron phosphate glasses, which are known from their interesting properties and widely used applications.

Flash boiling explosion model of dimethyl ether (DME)/n-pentane bi-component droplet under gasoline engine conditions

The flash boiling explosion model that integrates the sub-processes of the boiling period, including the homogeneous nucleation sub-model, the bubble growth sub-model and the boiling explosion sub-model, is proposed to investigate the evaporation and explosion characteristics of a superheated bi-component droplet under gasoline engine conditions. The bubble point pressure is discussed based on the Wilson approach. The dependence of physical properties on the temperature and the concentration is considered. A comprehensive bubble growth model is developed to predict the bubble growth and evaporation of the DME/n-pentane droplet with different mixing ratios. Two criteria in parallel are employed to predict the time of boiling explosion. The result shows that a larger DME mixing ratio and higher liquid temperature can decrease the duration of the surface tension controlled stage, expedite the bubble growth, and consequently shorten the boiling explosion time. A higher DME proportion can improve the evaporation rate of DME, meanwhile, the peak value of the evaporation rate is shifted to an earlier moment at a fixed droplet temperature. Furthermore, the boiling explosion time map illustrates the appropriate region of the temperature and the mass fraction of DME for the flash boiling explosion.

Shape and aspect ratio analysis of anisotropic magnetic nanochains based on TEM micrographs

Due to advances in electron microscopy and to the development of novel nanoparticle structures with different morphologies and the dependence of physical properties on the nanoparticle morphology, there is a need for a more precise analysis of nanoparticle structure and morphology. That should provide a simple and unambiguous comparison of nanoparticles‘ shapes and of material properties that depend on the shape, which has been lacking thus far. Here we study nanochains consisting of silica-coated iron oxide (maghemite, γ-Fe2O3) nanoparticle clusters covered by an additional layer of silica (core-shell structure). We have developed an algorithm for image segmentation and a quantitative analysis of nanochain shape from real TEM images. To that end we used two distinct measures of circularity and elongation measure (the aspect ratio measure). We show that the relative position and the area of the links, as well as the links‘ shape lead to significant differences in the measured aspect ratio of the entire nanochain (substantially influence the elongation of nanochains). We have also analyzed the core-shell structures in nanochains, and computed the shell's share in the overall area of observed nanochains. A Matlab code was developed and used for the computation of the elongation measure of shapes appearing in electron microscopy images. Here we have investigated magnetic properties of synthetic nanochains, that revealed superparamagnetic behavior at room temperature (SPION) with the possibility of tuning the magnetization values (approx. from 19 to 46 emu/g). We have compared of magnetization M(H) curves of the anisotropic nanochains and of isotropic nanoparticle (nanochain links), with the conclusion that the nanochains have a higher magnetic susceptibility, which fact can be understood as a consequence of their anisotropic shapes. The nanochains may be applied in biomedicine and magnetic separation, due to their morphology and magnetic properties.

Microwave heating of liquid at the forced flow around a flat plate under the conditions of non-stationary radiation-convection heat transfer

A class of nonlinear problems of non-stationary radiation-convective heat transfer under the conditions of microwave action with a small depth of penetration is considered in a forced laminar flow of liquid around a flat plane. The solutions to these problems are obtained using the effective asymptotic procedures at the successive stages of nonstationary and stationary radiation-convective heat transfer on the heat-radiating horizontal plane. The non-stationary and stationary stages of solution are matched using the “longitudinal coordinate-time” characteristic. The solutions constructed on such principles correlate reliably with the exact ones at the limiting values of such parameters as a small and large intensity of external thermal impact, small and large times, etc. The error of solutions does not exceed 1–7 %. As the plate is removed from the leading edge of the plate due to heat radiation, convective heat transfer degenerates from values characteristic of the boundary condition of the second kind to the values characteristic of the boundary condition of the first kind. A strong effect on the nature of variations of the surface temperature and Nusselt number of the complex parameter of microwave and thermal radiation is noted. An important advantage of the developed method for solving this class of external problems is that even before complex calculations it is possible to perform an exhaustive analysis of the fundamental laws of the processes under study. Despite a number of initial simplifications, the latter do not significantly affect the accuracy of results, guaranteeing reliable quantitative information. The developed method can also be extended to the regimes of forced convection with linear dependence of physical properties on temperature using transformation of A.A. Dorodnitsyn. To confirm adequacy of the constructed mathematical model, stationary radiation-convective heat transfer under the forced flow around a flat plate was studied experimentally. The results of comparison of the theoretical and experimental data show that they are in a good agreement. This again confirms the effectiveness of the developed method for constructing theoretical solutions to the nonlinear problems of forced convection using the asymptotic procedures.

Amorphous Copper-Based Alloys: Structure, Technology and Properties

The scientific interest in amorphous and nanocrystalline materials is associated with the expectation of different structural and size effects on the properties of solids, as applied attention due to the possibility of fundamental changes in the properties of polycrystalline materials. Numerous experimental studies indicate the following regularities: the higher the degree of equilibrium of the melt prior to crystallization is, the better quality has a solid metal. In industrial conditions the equilibrium state of the melt is achieved by the technology for heat treatment of the melt. The scientific rationale for this technology is the results of studying the temperature and time dependence of physical properties. The present work describes the analysis of the physical properties of liquid amorphous solder, conducted heat treatment of the melt and the study of the samples mechanical properties in the solid state. Amorphous ribbons obtained by the technology for melt heat treatment, ceteris paribus withstand higher loads in tension, exhibit better ductility and are characterized by high stability of the results. This fact confirms a more uniform material structure.

Measuring the Thermo-Technical Parameters of Autoclaved Aerated Concrete

Bulk density and moisture content are factors that significantly affect the physical properties of autoclaved aerated concrete (AAC) including thermal conductivity and other thermo-technical characteristics. This article shows the results of measurements of compressive strength, capillary absorption, water absorption and porosity of AAC (ash on fluidized fly ash) at different bulk density and also the results of thermal conductivity of AAC at different bulk density and variable moisture content of the material. The thermo-technical properties were measured using the Isomet 2104, a portable measuring device. Acquired results demonstrate dependence of physical properties including thermal conductivity of AAC on bulk density and moisture content. The reliability and accuracy of the method of measuring was also shown.

Analytical model for thermal lensing and spherical aberration in diode side-pumped Nd:YAG laser rod having Gaussian pump profile

In this paper, according to the temperature and strain distribution obtained by considering the Gaussian pump profile and dependence of physical properties on temperature, we derive an analytical model for refractive index variations of the diode side-pumped Nd:YAG laser rod. Then we evaluate this model by numerical solution and our maximum relative errors are 5% and 10% for variations caused by thermo–optical and thermo–mechanical effects; respectively. Finally, we present an analytical model for calculating the focal length of the thermal lens and spherical aberration. This model is evaluated by experimental results.

Effect of temperature dependence of physical properties of fluid on flow and evaporation of film with concurrent gas flow in a microchannel

Effect of temperature dependence of physical properties of fluid on flow and evaporation of film with concurrent gas flow in a microchannel

Transport and Thermodynamic Studies of Stripe and Checkerboard Ordering in Layered Nickel Oxides R2−xSrxNiO4 (R = La and Nd)

We have investigated the Sr-doped layered nickelates Nd2−xSrxNiO4 and La2−xSrxNiO4 to elucidate qualitative differences between the stripe-type and checkerboard (CB)-type charge/spin ordered phases. From electrical resistivity, specific heat, magnetic susceptibility and inelastic neutron-scattering measurements, we construct a revised phase diagram around the border of the stripe and CB phases in Nd2−xSrxNiO4, and show the marked difference in the hole-concentration dependence of physical properties between two phases. These results strongly indicate that the CB order is not a simple structural limit of the stripe order.

Effect of Composition on the Physical Properties of (TlInSe2)1-х (TlGaTe2)х Solid Solutions

ABSTRACTWe carried out thermodynamic study of the TlInSe2-TlGaTe2 system based on the data of physicochemical analysis. Based on thermodynamic analysis and concentration dependence of physical properties, it was found that there is anion-cation substitution in TlInSe2-TlGaTe2 system. Continuous series of (TlInSe2)1-x (TlGaTe2)x solid solutions is forming throughout entire concentration range. We determined dielectric characteristics of samples, their frequency dispersion and nature of dielectric losses. The results demonstrate that the dielectric dispersion in the studied crystals TlInSe2 and (TlInSe2)0.5(TlGaTe2)0.5 has a relaxation nature. Hyperbolic decline of loss tangent with increasing frequency from 50 kHz to 35 MHz indicates the loss of pass-through conduction in (TlInSe2)1-x(TlGaTe2)x solid solutions.

Time-Temperature Treatment of the Iron Melt

The temperature dependence of physical properties of iron and their temperature peculiarities curves have been investigated. The influence of the time-temperature treatment (TTT) on the efficacy of the modification of iron including durable have been also determined.

Titanium Hafnium Oxide Alloy Films by a Novel Sub-Atomic Layer Sputtering Process for High Index and Graded Index Applications

ABSTRACTWe studied physical properties of titanium hafnium oxide (TixHf1-xO2) alloy thin films deposited by pulsed DC reactive magnetron sputtering with AC substrate bias. Thin films of two end oxides, hafnium oxides (HfO2) and titanium oxides (TiO2), and their alloys TixHf1-xO2 with a range of compositions deposited with and without the substrate bias were compared to study the dependence of physical properties of the thin films on the substrate bias. Structural, chemical and optical properties of the thin films were analyzed to assess inter-relationship among these properties. Thin films deposited with the AC substrate bias consistently show much higher refractive index and significantly lower optical extinction coefficient than those of thin films deposited without the substrate bias suggesting that characteristic microstructures developed in these thin films are responsible for the differences in the optical properties.

Symmetry analysis and self-similar forms of fluid flow and heat-mass transfer in turbulent boundary layer flow of a nanofluid

Heat, momentum, and mass transport in turbulent boundary layer nanofluid flow over a flat plate were investigated. Boundary layer equations were reduced to self-similar forms and solved numerically. The Lie group technique, which is based on the symmetry properties of governing equations, was used to derive self-similar forms of these equations. Turbulent viscosity was predicted using the mixing-length model. Also, dependences of physical properties (viscosity, thermal conductivity, and diffusion coefficients) on the nanofluid concentration and temperature were accounted for. Influences of different dimensionless parameters and nanoparticle concentration on the velocity and temperature profiles, as well as on the relative Nusselt number and skin-friction coefficient, were investigated.

Hard-coupled model of local direct resistance heating of thin sheets

A monolithic model of local direct resistance heating of thin sheets is presented. The model respects all material nonlinearities of the system such as the temperature dependences of physical properties of individual parts of the system. Numerical computations are performed by a finite element method of higher order of accuracy and realized by our own codes Hermes2D and Agros2D. The methodology is illustrated by a typical example, whose results are discussed.

Self-similar analysis of fluid flow and heat-mass transfer of nanofluids in boundary layer

Processes of heat, momentum, and concentration transport in a boundary layer of a nanofluid near a flat wall were studied. The study was performed by means of numerical analysis of boundary layer equations in a self-similar form. Self-similar forms of these equations were obtained based on symmetry properties (Lie groups). In doing so, dependence of physical properties (viscosity, thermal conductivity, and diffusion coefficient) on concentration of nanofluids and temperature were taken into account. Effects of concentration of the nano-particles on velocity and temperature profiles, as well as on the relative Nusselt numbers and skin-friction coefficients, were elucidated.

Compositional dependence of physical properties of ternary Se–Te–Bi alloys

Bulk samples of (Se100− x Bi x )90Te10 (x = 0, 0.5, 1, 1.5, 2, 2.5 and 3 at%) system were prepared using the melt quenching technique. The amorphous nature of bulk samples was confirmed using X-ray diffraction. The compositional variation in physical properties, namely density ρ, molar volume V m, compactness δ, average coordination number m, average number of constraints N con, number of lone pair electrons L, bond energy, average heat of atomization H s, mean bond energy ⟨E⟩ and glass transition temperature T g of the system have been studied. The mean bond energy has been calculated using the chemical bond approach (CBA). The glass transition temperature was calculated using the Tichy–Ticha method and was found to increase with Bi content. The mean bond energy was found to be proportional to the glass transition temperature. Average coordination number, average number of constraints, mean bond energy and density increase, whereas the average heat of atomization decreases with increasing Bi content in Se–Te alloys. The energies of the various possible bonds have also been determined.

Polyurethanes from benzene polyols synthesized from vegetable oils: Dependence of physical properties on structure

AbstractAsymmetric and symmetric aromatic triol isomers were synthesized from erucic acid. The pure asymmetric and symmetric triols were crosslinked with MDI into their corresponding polyurethane sheets. The physico‐chemical properties of these polyurethanes were studied by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis coupled with Fourier transform infrared (TGA‐FTIR) spectroscopy, and tensile analysis. The A‐PU and S‐PU demonstrated differences in their glass transition temperatures (Tg) and crosslinking densities. The difference inTgof these polyurethanes could be explained by the differences in crosslinking densities, which could be related to the increase in steric hindrance, to the crosslinking MDI molecules, between adjacent hydroxyl groups of the asymmetric triol monomers. Overall, it was found that both polyurethanes had similar mechanical and thermal properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Physical and morphological properties ofz~ 3 Lyman break galaxies: dependence on Lyαline emission

<i>Aims. <i/>We investigate the physical and morphological properties of Lyman break galaxies (LBGs) at redshift ~2.5 to ~3.5, to determine if and how they depend on the nature and strength of the Ly<i>α<i/> emission.<i>Methods. <i/>We selected U-dropout galaxies from the <i>z<i/>-detected GOODS-MUSIC catalog by adapting the classical Lyman break criteria on the GOODS filter set. We kept only those galaxies with spectroscopic confirmation, mainly from VIMOS and FORS public observations. Using the full multi-wavelength 14-bands information (U to IRAC), we determined the physical properties of the galaxies through a standard spectral energy distribution fitting procedure with the updated Charlot & Bruzual (2009) templates. We also added other relevant observations of the GOODS field, i.e. the 24 <i>μ<i/>m observations from Spitzer/MIPS and the 2 MSec Chandra X-ray observations. Finally, using non parametric diagnostics (Gini, Concentration, Asymmetry, <i>M<i/><sub>20<sub/> and ellipticity), we characterized the rest-frame UV morphologies of the galaxies. We then analyzed how these physical and morphological properties correlate with the presence of the Ly<i>α<i/> emission line in the optical spectra.<i>Results. <i/>We find that unlike at higher redshift, the dependence of physical properties on the Ly<i>α<i/> line is milder: galaxies without Ly<i>α<i/> in emission tend to be more massive and dustier than the rest of the sample, but all other parameters, ages, star formation rates (SFR), X-ray emission and UV morphology do not depend strongly on the presence of the Ly<i>α<i/> emission. A simple scenario where all LBGs have intrinsically high Ly<i>α<i/> emission, but where the dust and neutral hydrogen content (which shapes the final appearance of the Ly<i>α<i/>) depend on the mass of the galaxies, is able to reproduce the majority of the observed properties at . Some modification might be needed to account for the observed evolution of these properties with cosmic epoch, which is also discussed.