Correlation between barrier heights and ideality factors of H-terminated Sn/p-Si(1 0 0) Schottky barrier diodes

Schottky barrier diodes (SBDs) were prepared by evaporation on H-terminated p-Si(1 0 0) surfaces. The Si(1 0 0)-H surfaces were obtained by wet chemical etching in diluted hydrofluoric acid. The current–voltage (I–V) characteristics of real SBDs are described by using two fitting parameters that are the effective barrier height (EBH) and ideality factor n. They were determined from I–V characteristics of SBDs (30 diodes) fabricated under experimentally identical conditions. The obtained values of EBHs varied from 0.729 to 0.749 eV, and the values of ideality factors varied from 1.083 to 1.119. The results showed that both parameters of SBDs differ from one diode to another even if they are identically prepared. The EBH distributions were fitted by two Gaussian distribution functions, and their mean values were found to be 0.739 ± 0.003 eV and 0.733 ± 0.001 eV, respectively. The homogeneous barrier height of SBDs was found to be 0.770 eV from the linear relationship between EBHs () and ideality factors (n).     

Processing and characterisation of 2-D woven metal fibre-reinforced multilayer silica matrix composites using electrophoretic deposition and pressure filtration

A novel, cost-effective and rapid processing route including electrophoretic deposition (EPD) and pressure filtration (PF) has been developed for the fabrication of 2-D woven metallic fibre mat reinforced multilayer silica matrix composites. Commercially available silica sol containing ultrafine ceramic particles (15 nm) was used as the matrix whilst 2-D woven metal stainless steel 316L fibre mat was used as the metal reinforcement to produce a composite having 2-D isotropic properties. The colloidal silica sol was modified with boria and boehmite in order to produce a silica matrix which could be sintered at 900°C (the maximum use temperature for the particular fibre architecture employed), and with densification taking place before crystallisation. An in-situ electrophoretic deposition (EPD) cell capable of measuring the weight gain in real time during deposition was designed. This technique enabled the woven fibre inter/intra tow regions to be infiltrated with the ultrafine silica particles in a very short time (2 min). Green bodies made from electrophoretically deposited fibre mats were further consolidated using pressure filtration. The EPD parameters were optimised in terms of time, voltage and deposition thickness as well as deposit formation rate. Microstructural observation indicated that the composites produced were dense and of high microstructural homogeneity.     

Mathematical modeling of multiple-effect evaporators and energy economy

In this study, a mathematical model was developed for multiple-effect evaporators. These evaporators have cocurrent, countercurrent and parallel flow operation options. Each operation was investigated with and without pre-heaters. The effect of pre-heating on evaporation process was investigated from the point of energy economy. A sugar factory's data was used with the applied models as a case study. The results obtained for pre-heated and non-pre-heated situations were compared with each other. The maximum COP is found as 3.33 for countercurrent operation with pre-heating. The minimum COP is 2.57 for parallel flow operation without pre-heating.     

Permalloy-coated tungsten probe for magnetic manipulation of micro droplets

In this work, we present the magnetic manipulation of biocompatible droplets using a probe-based approach. First, we describe a simple method to develop magnetic probes that are capable of delivering localized magnetic fields, which is important for precise manipulation. The fabrication of magnetic probes involves controlled electroplating of permalloy (Ni₈₀Fe₂₀) on commercially available tungsten needles with tip radii as small as 0.5 μm. Experimental validation of probe functionality was achieved by characterizing the magnetic response of the probe with a highly sensitive scanning Hall probe system. The magnetic probe was then employed in manipulating biocompatible alginate micro droplets with encapsulated magnetic particles. The synthesis of the droplets was carried out in-house and droplets of different sizes and magnetic particle concentrations were obtained for use in manipulation experiments. Multiple experiments were done to demonstrate the efficacy of the developed probe in manipulating droplets, which is crucial for constructing droplet-based microfluidic systems.     

Use of nano-scale double-gate MOSFETs in low-power tunable current mode analog circuits

Use of independently-driven nano-scale double gate (DG) MOSFETs for low-power analog circuits is emphasized and illustrated. In independent drive configuration, the top gate response of DG-MOSFETs can be altered by application of a control voltage on the bottom gate. We show that this could be a powerful method to conveniently tune the response of conventional CMOS analog circuits especially for current-mode design. Several examples of such circuits, including current mirrors, a differential current amplifier and differential integrators are illustrated and their performance gauged using TCAD simulations. The topologies and biasing schemes explored here show how the nano-scale DG-MOSFETs may pave way for efficient, mismatch-tolerant and smaller circuits with tunable characteristics.     

Hydrothermal synthesis of pseudocubic BaTiO3 nanoparticles using TiO2 nanofibers: Study on photocatalytic and dielectric properties

In this study, TiO₂ nanofibers were fabricated via the electrospinning method followed by air annealing. Then, Ti-requirement in the conventional hydrothermal synthesis of BaTiO₃ stoichiometry was supplied by using these nanofibers. The microstructural and compositional properties of BaTiO₃ nanoparticles were studied using SEM, TEM, XRD, XPS, and Raman spectroscopy. The structural analysis showed that the cubic symmetry was the dominant one in the BaTiO₃ nanoparticles, whereas Raman spectroscopy indicated the coexistence of cubic symmetry with the tetragonal polymorph. The nanoparticles displayed higher photocatalytic reactivity under UV-A light compared to visible irradiation during decomposition of methylene blue dye and reached 24.2% and 18.8% degradation, respectively, after 1 hour. Furthermore, the dielectric properties were investigated using sintered compacts of these nanoparticles. Among the employed temperatures for sintering, the highest relative density (90%) and dielectric constant (2165 at 1 MHz) were obtained at 1250°C and 5 hours. This study revealed that the electrospun TiO₂ nanofiber precursor can successfully be used for the production of nanoscale barium titanate particles suitable for various applications.     

The false positive effect of residue of sulphur sources on dithiocarbamate analysis based on CS2 measurement

Turkey plays an important role in the international trade of apricots as it has the largest production rate in the world. Since the sulphurisation process is allowed to be used for different products, the effect of residual sulphur and its compounds (which can be found in products as pesticide residues or additive residues) on the positive detection of carbon disulphide (CS₂) still creates a big challenge in international trade. Therefore, the main objective of the present study was to investigate the effects of residues of sulphur or sulphur compounds on dithiocarbamate analysis methods based on CS₂ measurement. In this study, apricots were chosen since they contain sulphur residues as a result of the sulphurisation process. Sulphur dioxide and dithiocarbamate analyses were conducted on dried apricots prepared with the sulphurisation process (SA) and without the sulphurisation process (NSA); analysis was by two different accredited laboratories. No of pesticide was applied to either SA or NSA samples. Although some of the NSA samples had <LOQ values, approximately 70 ± 32 mg/kg SO₂ and 0.061 ± 0.021 mg/kg dithiocarbamate were detected for NSA samples. On the other hand, for the SA sample group, 927–2915 mg/kg of SO₂ and 0.265–0.825 mg/kg of dithiocarbamate were detected. Furthermore, a strong correlation between residual sulphur and dithiocarbamate values was observed. This study showed that the analysis method based on CS₂ measurement may lead to false positive results for dithiocarbamates when residues of sulphur or sulphur compounds are found in products as pesticide or additive residues. Therefore, residual sulphur compounds as a result of the sulphurisation process (which is not considered during the evaluation of products) must be taken into account during the evaluation of products for dithiocarbamates.     

Progress in modification of sunflower oil to expand its industrial value

Increasing the sunflower seed oil content as well as improving its quality makes it compatible for industrial demands. This is an important breeding objective of sunflower which increases its market value and ensures high returns for the producers. The present review focuses on determining the progress of improving sunflower seed oil content and modifying its quality by empirical and advanced molecular breeding methods. It is known that the sunflower oil content and quality have been altered through empirical selection methods and mutation breeding programmes in various parts of the world. Further improvement in seed oil content and its components (such as phytosterols, tocopherols and modified fatty acid profile) has been slowed down due to low genetic variation in elite germplasm and complex of hereditary traits. Introgression from wild species can be carried out to modify the fatty acids profile and tocopherol contents with linkage drags. Different transgenes introduced through biotechnological methods may produce novel long‐chain fatty acids within sunflower oil. Bio‐engineering of sunflower oil could allow it to be used in diverse industrial products such as bio‐diesel or bio‐plastics. These results showed that past and current trends of modifying sunflower oil quality are essential for its further expansion as an oilseed crop. © 2017 Society of Chemical Industry