Abstract: Evaporation of a thin layer of a polar liquid (water) having a free surface and located on a solid substrate is investigated. A surfactant is solved in the liquid film. The surface tension is a linear function of the surface concentration of the surfactant. The surface energy of the solid-liquid interface is a nonmonotonic function of the layer thickness and is the sum of the Van der Waals interaction and the specific interaction of the double electric layer on the interface. The effect of the solvable surfactant on the dynamics of the propagation of the evaporation front in the thin liquid film is analyzed in the long-wave approximation in the system of Navier-Stokes equations.
Abstract: Silicene is a two-dimensional (2D) allotrope of silicon known to have a lower thermal conductivity than graphene; thus, more suitable for thermoelectric applications. This paper investigates the effect of hydrogenation on the thermal conductivity of silicene nanoribbon (SiNR) using equilibrium molecular dynamics (EMD) simulations. The simulations were carried out in Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) using a modified Tersoff potential that considers both Si-Si and Si-H interactions. The thermal conductivity of fully hydrogenated silicene nanoribbon (H-SiNR), also known as silicane nanoribbon, was found to be higher than that of pristine SiNR in all the temperatures and dimensions considered here. This anomalous enhancement in the thermal conductivity is similar to that found in hydrogenated silicon nanowires (H-SiNWs). A mechanism for this anomalous effect has been proposed relating the hydrogenation of SiNR with the stiffening and increase of the acoustic out-of-plane flexural (ZA) phonon modes. Also, for both SiNR and H-SiNR, the thermal conductivities generally increase as the dimensions are increased while they generally decrease as the temperatures are increased, in agreement to other reports.
Abstract: TiO2 coated mica (TiO2/Mica) as solar reflective pigment was prepared under hydrothermal treatment. Dispersed TiO2 nanosol, having an average particle size of about 25-30nm, was coated on mica flake by the difference between the surface charge of the particles at pH 2 and then calcined at 850°C to stabilize the coated layer on mica. The CIE color coordinate and total solar reflectance (TSR) properties of these pigments were investigated in relation to thickness variation of TiO2 layer coated on mica having various lateral sizes. Dense and uniform TiO2 layers were tightly coated on the surfaces on mica substrates. Isolation-heat paints were prepared with 20wt% pigments fully dispersed in acryl-urethane resin and several additives to coat the film uniformly. Thermal property of these films, recorded by an isolation-heat measuring system, was observed for the relationship of TSR value according to the thickness of TiO2 layer and mica’s lateral size, compared to TiO2 itself.
Abstract: The copper phthalocyanine thin films were deposited on quartz and Si/SiO2 substrates at different substrate temperatures. The morphologies, structures and optical properties of CuPc films were characterized by scanning electron microscopy, X-ray diffra ction and UV-Visible spectroscopy. The polymorph of alpha–CuPc was observed in films deposited at temperature ranging from 20°C to 145°C. The transmission and absorption spectra of CuPc films deposited at different temperatures are presented.
Abstract: A model based on the k.p perturbation theory to compute the energy bands in a CdTe/PbTe superlattice structure is developed. The model uses the dispersion relations for the heavy hole, light hole and the split off bands to compute the effective bandgap in a CdTe/PbTe superlattice structure. Given a certain thickness of the layers composing the superlattice the model computes the effective bandgap. This model will be used towards understanding the relationship between film thickness and optical bandgaps in a CdTe/PbTe superlattice. The end goal is to tailor the optical bandgap of a CdTe/PbTe superlattice to result in maximum efficiency when used in a solar cell.
Abstract: In this paper, we analyze the temperature effect on the performance of photovoltaic cells using a virtual wafer fabrication TCAD Silvaco. As is often done, the previous work on this solar cell involved optimizing it at 300 K, even though operating temperatures are typically higher. Therefore, for this article, we model the InGaP/GaAs heterojunction solar cell from 275 °K to 375° K in 25°K increments while varying their thicknesses and doping levels, as well as varying the molar fraction of InAlAsP, AlGaAs and InGaP. We chose to vary these design parameters to observe their effect on performance and suggest a better design for operating at higher temperatures.
Abstract: In this paper, a new-type electro-optical sensor based on the total-internal reflections theory in heterodyne interferometry is proposed. The sensor is designed as a semi-circle shape. It is made of BK7 glass with the refractive index of 1.51509. And the end surface of the sensor is designed as a micro-mirror. The phase difference between s-and p-polarizations at the output of the optical fiber sensor can be obtained when a heterodyne optical source is launched into the electro-optical sensor at a suitable incident angle. By numerical calculation, the resolution of the system by using the intensity method can reach refractive index unit (RIU) in the measurement range of. The electro-optical sensor could be valuable for chemical, biological and biochemical sensing. It is with some advantages, such as, high resolution and stability, high sensitivity and real-time measurement.
Abstract: TiO2 nanosize particles have attracted significant interest of materials scientists and physicists due to their special properties and have attained a great importance in several technological applications such as photocatalysis, sensors, solar cells and memory devices. TiO2 nanoparticles can be produced by a variety of techniques ranging from simple chemical to mechanical to vacuum methods, including many variants of physical and chemical vapour deposition techniques. In the present research work we report the synthesis of TiO2 nanoparticles by Sol-Gel technique. The characterization of particles was carried out by XRD and SEM techniques. The importance and applications of these nanoparticles for solar cells are also discussed in this work. Recently, the importance of tailored particles has been recognized in a number of applications such as solar cells and photonic crystals. Among the many metal oxides and their inorganic-organic hybrid materials used for the above applications, one of the most important and complex in this regard is titanium dioxide (titania). In this study, the processing parameters in an alkoxide free sol-gel synthesis of anatase titania nanoparticles were investigated. Factors affecting the sol-gel process include the reactivity of inorganic titanium salt, calcinations temperature, the influence of varying stirrer speeds on the formation of anatase particles, and the nature of hydrolytic solvent and peptisation reagent. By varying these processing parameters, materials with different microstructure and surface chemistry can be obtained.
Abstract: The effect of asymmetric rolling with cone-shaped rolls on ultra-fine grain evolution was investigated. To do this, low-carbon steel containing 0.15 % C (mass fraction) billet (h|b|l = 10|45|100 mm3) with the initial average grain size of 60 μm was deformed up to the thickness of 5mm in cone-shaped rolls with diameters ratio of 1.5, as well as in cylindrical rolls. Rolling was conducted at three different temperatures: 900 °C, 1000 °C and 1100 °C. Four passes of asymmetric rolling in cone-shaped rolls were given to gain thickness of 5 mm with total reduction of 61,7 %. It has been shown that during asymmetric rolling in cone-shaped rolls at low temperature of 900 °C grain size is smaller (0.092 μm – at the surface layer and 0.112 μm – at the middle layer) than that of 1000 °C and 1100 °C. Tensile properties of asymmetrically rolled specimen were much higher (580 MPa) in comparison to symmetrically rolled one (486 MPa).
Abstract: This article discusses the calculation of the apparent activation energy (CuMoO4 + C) on the DTA curve, to study and optimize the time-temperature synthesis mode, in particular the activation energy. Activation energy allows us to investigate the elementary act of chemical interaction. Thus, we propose to use this method to calculate Eact interaction processes (CuMoO4 + C) in the solid phase synthesis occurring during the reinforcement. The research results are checked by thermodynamic calculations. The results obtained allow us to trace the energy quantity expended to start the reaction.