Showing papers in "Silicon in 2017"

Effect of Fiber Orientation and Stacking Sequence on Mechanical and Thermal Characteristics of Banana-Kenaf Hybrid Epoxy Composite

Abstract: The usage of hybrid natural composites has surged in almost all fields of engineering due to their advantage of possessing high strength to weight ratio and biodegradability. This paper deals with the fabrication and investigation of mechanical and thermal properties of banana-kenaf glass fiber reinforced epoxy composite which is relatively a newer hybrid composite. In this study, the composite is fabricated by a hand layup process with different fiber orientations and also with different volume fractions. The composites are prepared with five different proportions of banana-kenaf fibers. Various mechanical and thermal tests are conducted and the result shows that the hybrid composite in which fibers are arranged at 450 inclination has better properties than the others. Also, failure morphology analysis is done using a Scanning Electron Microscope (SEM) through which the internal structures of the tested specimen are analysed.

Synthesis, Characterization and In Vitro Biological Evaluation of Sol-gel Derived Sr-containing Nano Bioactive Glass

Abstract: In this study, bioactive glass of the type SiO2–CaO–SrO–P2O5 was obtained by the sol-gel processing method and the effects of SrO/CaO substitution on the in vitro biological properties of the synthesized glasses were evaluated. The obtained bioactive glasses were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), differentioal scanning caloremetry (DSC) and Brunauer, Emmett and Teller (BET) analyses. The effects of various glass compositions on proliferation and differentiation of osteoblastic cells were also evaluated. The results showed that incorporation of Sr in the obtained glass network did not result in any structural alteration due to the similar role of SrO compared with that of CaO. In vitro experiments with human osteosarcoma cell lines (MG-63) indicated that bioactive glass incorporating 5 mol % in the composition revealed optimal cell proliferation and alkaline phosphatase (ALP) activity. Our results ascertained this material to be non-toxic and compatible for the proposed work in segmental defects in the rabbit model in vivo.

The Effects of the Application of Foliar Sprays with Stabilized Silicic Acid: An Overview of the Results From 2003-2014

Abstract: The silicic acid agro technology (SAAT) is the application of stabilized silicic acid on the plant. SAAT can be used as a foliar spray or as a soil amendment. The foliar application of (stabilized) silicic acid induces significantly better results for growth, yield and quality parameters compared to ‘traditional’ silica soil fertilizers and foliar sprays with silicates. Foliar silicic acid is only effective at very low dose rates during the vegetative stage and should be regarded as a biostimulant (‘plant growth promoter’). As well as its effectiveness, it is safe, eco-friendly and cost-effective.

Effect of MoO 3 Content on Structural, Thermal, Mechanical and Optical Properties of (B 2 O 3 -SiO 2 -Bi 2 O 3 -Na 2 O-Fe 2 O 3 ) Glass System

Abstract: The glass system 40B2O3–20SiO2–9Na2O–1Fe2O3–(30-x)Bi2O3–xMoO3, x = (0, 5, 10, 12.5 and 15 mol%) was prepared and analyzed by using X-ray diffraction, IR spectroscopy, density, differential thermal analysis (DTA), optical properties and mechanical properties. The structural variations due to the increase of the MoO4 at the expense of the BiO3 structural unit increase the ultrasonic velocity and the elastic moduli along with a decrease of the density. The increase of the glass transition temperature, T g, according to DTA confirmed this behavior. The values of the optical band gap E g and refractive index have been determined and it was found that these parameters are sensitive to the increase of MoO3 content.

Investigation of Methane and Carbon Dioxide Gases Permeability Through PEBAX/PEG/ZnO Nanoparticle Mixed Matrix Membrane

Abstract: This paper presents a new kind of mixed matrix membrane using polyethylene glycol (PEG) as organic filler. In this mix, PEG and ZnO nanoparticles (as inorganic modifier) were added to a PEBAX polymer matrix at different concentration to study their effects on the morphology, permeability and selectivity of the membrane. To characterize the chemical structure of samples FTIR and for morphological characterization, XRD and SEM were employed. The permeability of pure gases CO2 and CH4 in PEBAX, and PEBAX/PEG/ZnO with different ZnO and PEG contents were determined by the constant pressure-variable volume method. Also influences of temperature and pressure on permeation properties of these membranes were studied. The results were indicative of an increase in gas permeability and enhancement which for neat PEBAX membrane, CO2/CH4 permeability of 44.6 and 2.193 Barrer and selectivity of 20.39 were obtained. The permeability of PEBAX/PEG (40 wt.%)/ZnO (4 wt.%) membrane was enhanced to 94.49 Barrer for CO2 and 3.933 for CH4. The selectivity of PEBAX/ZnO(4 wt.%) improved to 31.58 for the CO2/CH4 gas pair.

Removal of Impurities from Metallurgical Grade Silicon During Ga-Si Solvent Refining

Abstract: Purification of metallurgical grade silicon (MG-Si), using gallium as the impurity getter has been investigated. The technique involves growing Si dendrites from an alloy of MG-Si with Ga, followed by their separation by acid leaching. The morphologies of impurity phases in the MG-Si and the Ga-Si alloy were investigated during the solvent refining process. Effective segregation ratios of B and P in the Ga-Si system were calculated. Most metallic impurities formed silicides, such as Si-Fe-Ga-Mn or Si-Fe-Ga impurity phases, which segregated to the grain boundaries of Si or into the Ga phase during the Ga-Si solvent refining process. After purification, the refined Si is plate-like with crystallographic orientation, and the removal fraction of B and P was 83.28 % and 14.84 % respectively when the Si proportion was 25 % in the Ga-Si alloy. The segregation ratios of B and P were determined to be 0.15 and 0.83 when the solid fraction of Si was 0.25. The effective removal of B and P by a solidification refining process with a Ga-Si melt is clarified.

Experimental Investigations and Multi-response Optimization of Silicon Dioxide (Quartz) Machining in Magnetic Field Assisted TW-ECSM Process

Abstract: Travelling wire electrochemical spark machining (TW-ECSM) has the potential for the machining of advanced non-conducting materials like glass, quartz, silicon nitride, various composites and ceramics. In the present work, experimental investigations have been conducted on the magnetic field assisted travelling wire electrochemical spark machining (TW-ECSM) process. In this technique, a magnetic field has been introduced in the TW-ECSM process in order to improve the machining performance in terms of improved material removal rate (MRR) and reduced surface roughness (Ra) of non-conducting materials. Material removal rate (MRR) and surface roughness (Ra) were selected as the responses during the experimentation. The experimental results revealed that the magnetic field assisted approach gives reduced values of Ra and increased MRR when compared to the TW-ECSM process. The minimum and maximum values of surface roughness and MRR were found to be 7.42 µm and 0.19 mg/min with magnetic field assisted TW-WCSM process respectively. The optimization function has been developed to minimize Ra and maximize MRR for obtaining the optimum process parameters.

Study of Porous Silicon Prepared Using Metal-Induced Etching (MIE): a Comparison with Laser-Induced Etching (LIE)

Abstract: Porous silicon (p-Si), prepared by two routes (metal induced etching (MIE) and laser induced etching (LIE)) have been studied by comparing the observed surface morphologies using SEM. A uniformly distributed smaller (submicron sized) pores are formed when MIE technique is used because the pore formation is driven by uniformly distributed metal (silver in present case) nanoparticles, deposited prior to the porosification step. Whereas in p-Si, prepared by LIE technique, wider pores with some variation in pore size as compared to MIE technique is observed because a laser having gaussian profile of intensity is used for porosification. Uniformly distribute well-aligned Si nanowires are observed in samples prepared by MIE method as seen using cross-sectional SEM imaging. A single photoluminescence (PL) peak at 1.96 eV corresponding to red emission at room temperature is observed which reveals that the Si nanowires, present in p-Si prepared by MIE, show quantum confinement effect. The single PL peak confirms the presence of uniform sized nanowires in MIE samples. These vertically aligned Si nanowires can be used for field emission application.

Tribological Behavior of Al-SiC Metal Matrix Composite Under Dry, Aqueous and Alkaline Medium

Abstract: The present study considers friction and wear behavior of aluminum matrix composites reinforced with SiC particles under three different working environments, viz., dry condition, aqueous medium and alkaline medium. The experiments are conducted with a pin-on-disk tribotester where the composite specimen slides against an alumina disk under the application of varying normal load and sliding speed. It is observed that wear increases with increase in applied load and sliding speed for all three working environments and the maximum wear occurs in the case of the alkaline medium followed by the aqueous medium and the dry condition. In general, the friction coefficient decreases with increase in applied normal load. The microstructure analysis of the worn sliding surface is done with the help of a scanning electron microscope and energy dispersive X-ray analysis. It is seen that the wear mechanism in dry condition is dominated by adhesive and abrasive wear while both mechanical and corrosive wear occur in corrosive environments.

Study of the Effect of Incorporation of CdS Nanoparticles on the Porous Silicon Photodetector

Abstract: In this study, the influence of embedding cadmium sulfide nanoparticles, synthesised by a chemical method, on the performance of porous silicon matrix photodetectors was investigated. An anodization technique was used to fabricate porous silicon photodetectors at 16 mA/cm2 for 10 min.The characteristics of porous silicon and CdS nanoparticles were investigated by using x-ray diffraction XRD, atomic force microscopy AFM, scanning electron microscopy SEM, and energy dispersive x-ray EDX. Dark and illuminated current-voltage I-V characteristics and spectral responsivity of photodetectors were investigated before and after the incorporation of CdS nanoparticles. Considerable improvement was noticed in responsivity of the porous silicon photodetector after incorporating the CdS nanoparticles into the silicon matrix.

Extensive Investigation Into Field Based Responses to a Silica Fertiliser

Abstract: Silicon (Si) is a beneficial plant nutrient and yield responses to its application have been frequently demonstrated in Si-accumulator crops such as rice and sugarcane. Increased yields are the result of simultaneous increases in plant tolerance to a wide range of stresses, yet the actual stress experienced by crops in the field is poorly quantified and understood today. The purpose of this paper is to provide results from extensive, replicated field trials in diverse regions, across different crops and seasons with the same Si fertiliser and to demonstrate the value of this fertiliser as a source of silicon. In the replicated field trial program, amorphous silica was applied to all the crops and the Si availability of the soils is quantified using a CaCl2 extractant. The applied silica results in yield increases of up to 35 %. There is a variability in yield responses that cannot be explained by initial Si soil availability, rates of application, varietal or soil differences and must be attributed, at least in part, to stress experienced by the plant in different seasons or environmental conditions. Aspects that require future research include a better quantification of the availability of Si in the soil and a greater understanding of the effects of stresses experienced by crops in the field. This research would allow improved recommendations of Si fertiliser applications in standard crop practices.

Effect of Tool Rotational and Al2O3 Powder in Electro Discharge Machining Characteristics of NiTi-60 Shape Memory Alloy

Abstract: Nickel titanium is an intelligent alloy which are used in optical devices, thermal sensors, actuators, medical equipment and aerospace, because memory shape property, high strength, good creep and fatigue resistance. This alloy has features like the response to electrical stimulation, thermal, magnetic and mechanical stimulation. According to hardness and mechanical properties of this alloy, one of the ways it is used for machining, is EDM. EDM is one of the machining of precision and complex parts methods which material removal rate, tool wear rate, surface roughness and thickness of the recast layer one is very important in it. In this study the effect of current, voltage, pulse on time, pulse off time, tool rotational, Al2O3 powder, material removal rates, tool wear rate and surface roughness are examined. The results show that using Al2O3 powder and tool rotational along with increasing current intensity, pulse on time and voltage, increases the material removal rate. Rotation of the tool create a centrifugal force and Al2O3 powder increases the gap and the material removal rate. Rotation of the tool prevents spreading of the plasma channel and Al2O3 powder fills gap between tool and workpiece, decrease kinetic energy of ions and reduced tool wear rate. By adding powder Al2O3, rotation of the tool, reducing current intensity, voltage and time pulse, sparks get smaller and will have less penetration and surface roughness reduces.

Microstructure and in vitro Bioactivity of Silicon-Substituted Hydroxyapatite

Abstract: Silicon-substituted hydroxyapatite has shown superior biological performance compared to its stoichiometric counterpart both in vitro and in vivo. In the present study, single-phase silicon-substituted hydroxyapatite was successfully synthesized by the precipitation method. Chemical composition, crystalline phase, microstructure, and morphology of the materials were characterized by XRF, XRD, FT-IR, solid-state NMR and SEM. The results showed that hydroxyapatite kept its original structure with silicon up to a level of 0.9 wt%. The precipitation method was proved to be an efficient way to synthesize single-phase silicon-substituted hydroxyapatite. Solid-state NMR combined with other techniques gave direct evidence for the isomorphous substitution of PO43- by SiO44- in the hydroxyapatite structure. Silicon-substituted hydroxyapatite showed better bioactivity than stoichiometric hydroxyapatite in the in vitro bioactivity experiment. The higher the silicon content in the hydroxyapatite structure, the better the in vitro bioactivity. The enhanced bioactivity of silicon-substituted hydroxyapatite over pure hydroxyapatite has been attributed to the effect of silicate ions in accelerating dissolution.

Silicone Hydrophobicity and Oleophilicity

Abstract: Polydimethylsiloxane (PDMS), the most familiar silicone polymer, is a very water repellent material. Its hydrophobicity is not markedly less than many fluorine containing polymers. The original purpose of introducing fluorine into silicones in the form of polymethyltrifluoropropylsiloxane (PMTFPS) was not to seek enhanced water repellency but to provide improved resistance to organic oils and solvents. Because of the two methyl groups on each silicon atom in PDMS, the resultant oleophilicity is a considerable drawback in applications involving exposure to hydrocarbon fluids and oils. In this article we survey the contact angles with water and n-hexadecane of these polymers and related, more highly fluorinated fluorosilicones, being the simplest measure of their hydrophobicity and oleophilicity, respectively. These contact angle values provide quantitative insight into commercially valuable aspects of silicone surface science.

Temperature and Pressure Dependence of Elastic Constants and Related Parameters for InP Semiconductor

Abstract: Based on the empirical pseudo-potential method (EPM), the symmetric and anti-symmetric pseudo-potential form factors have been adjusted to match the calculated energy gaps of InP with the corresponding experimental values. The adjusted symmetrical and anti-symmetrical form factors at G(1,1,1) have been used to calculate the polarity of the considered material. The elastic constants C 11, C 12 and C 44 of InP have been obtained. The knowledge of these constants helps us to determine their related elastic parameters such as bulk (Bu), shear (Cs) and Young’s (Y0) moduli. Other important parameters such as Poisson’s ratio (σ ), linear compressibility (C0 ), Cauchy ratio (Ca) , Born ratio (B0), isotropy factor (A ), bond stretching (α ), bond binding force (β ) and internal strain parameter (ζ ) for InP have also been calculated. The variation of all studied quantities with temperature and pressure has been investigated. Our results show a good agreement with the available experimental data. Most of our data may be taken as references especially for high values of temperature and pressure.

Sputtered AZO Thin Films for TCO and Back Reflector Applications in Improving the Efficiency of Thin Film a-Si:H Solar Cells

Abstract: We report the properties of Al doped ZnO (AZO) thin films on glass substrates and its effect on the efficiency of amorphous silicon (a-Si:H) solar cells as the back reflector. Oriented AZO thin films were grown using DC magnetron sputtering by varying Ar gas flow rates. The influence of Ar flow rate on the structural, electrical and optical properties of AZO thin films suitable for transparent conducting oxide (TCO) and back reflector applications was investigated. The (a-Si:H) solar cells, with and without AZO back reflector, were fabricated on FTO coated glass substrates using the PECVD technique. The solar cells were tested using a Sun simulator under AM 1.5 condition. Enhancement in current density from 12.46 to 14.24 mA/cm2 with the AZO back reflector was observed, thereby increasing the efficiency of the solar cell from 6.38 to 7.82 %, respectively.

3-Aminopropyltriethoxysilane-Assisted Si@SiO2/CNTs Hybrid Microspheres as Superior Anode Materials for Li-ion Batteries

Abstract: A silicon based composite (Si@SiO2/CNTs) with outstanding electrochemistry performance has been easily synthesized using a spray drying method; The composite microsphere is mainly made up of carbon nanotubes and the prepared nano silicon particles. With the help of a silane coupling agent, carbon nanotubes tightly intertwined with nano silicon particles and formed microspheres together. On the surface of the prepared nano silicon particles, a layer of oxide film plays a role as a barrier to reduce the rupture of the particles during the lithium intercalation/extraction process. In addition, the added twisted carbon nanotubes can help to maintain the conductive network, thus stabilizing the electrode working environment during the lithium intercalation/extraction process. As a superior anode material, an initial specific discharge capacity of approximately 2846.9 mAh g−1 with a coulombic efficiency of 86 % and a reversible specific capacity of 2035.9 mAh g−1 after 100 cycles at a constant density of 500 mA g−1 are obtained.

Protection Glass Eyewear Against a YAG Laser Based on a Bandpass Absorption Filter

Abstract: In this article, copper zinc phosphate glass doped with 5 % barium oxide has an amazing optical property due to its application as bandpass filters. Typically, the glass conventional casting with chemical composition 42P2O5–(14- x)Na2O–39ZnO–5BaO–xCu2O where (x = 2, 4, 6, 8 and 10) was formed. The density was measured using the conventional Archimedes method and the molar volume was calculated. The change of glass structure was investigated using X-ray diffraction analysis (XRD). Distinctly, the results revealed that no crystal growth in all glass systems was observed. The density of glass samples was increased whereas the molar volume was decreased with increasing copper content. The absorption, transmission and reflection were measured and some other optical properties were calculated like UV cut-off, and IR cut-off. For instance, the visible cut-off started from 462 to 532 nm while the IR bonds were initiated at 630 to 1200 nm with 6 to 10 % Cu2O concentration.

Investigation on TG n-FinFET Parameters by Varying Channel Doping Concentration and Gate Length

Abstract: In this paper, a 3D process of a nanometric n-channel fin field-effect transistor (FinFET) is discussed and the impact of variations of the fin parameter, the gate work function, and doping concentration on device characteristics are studied using the ATLAS Silvaco device simulator. Simulation results for various gate lengths are reported and analyzed. As the quantum effects are pronounced in nanoscale devices, we have included these effects in our study and simulation. We have then compared the achieved results to classical simulations to assess their performance limits. Finally, a comparison of our results with recently published data is presented to confirm our study.

Preparation and Characterization of Precipitated Silica using Sodium Silicate Prepared from Saudi Arabian Desert Sand

Abstract: The present study reveals a cost benefit process in an open system for utilizing desert sand for preparing sodium silicate or precipitated silica. A simple alkali fusion method has been developed to prepare sodium silicate directly from sand and finally pure precipitated silica by acid precipitation. The reaction weight ratio of alkali to sand reaction parameters are studied for optimizing the silica yield. About 80% pure precipitated silica has been prepared in an open system at 150 °C within 45 min. Wet chemical methods, FTIR, TG-DTA, XRD and SEM techniques are used to characterize the silica prepared from sand available in Saudi Arabian deserts. In the XRD pattern, the peak corresponding to silica was obtained at the diffraction angle of 21.8 ° and it was found to be amorphous in nature.

The Characteristic Parameters of Ni/n-6H-SiC Devices Over a Wide Measurement Temperature Range

Abstract: Ni/n-type 6H-SiC/Ni Schottky barrier diodes (SBDs) have been prepared by the DC magnetron sputtering deposition technique. Their current-voltage characteristics (I-V) have been measured in the measurement temperature range of 40-400 K with steps of 20 K under dark conditions. The barrier height (BH) values from the temperature-dependent forward and reverse bias I-V characteristics by different methods coincide with each other which indicates the elimination of the polarity between the Si and C ions. The ideality factor value remains almost unchanged in the 160-400 K range, and below 160 K, it has the values of 1.57 at 140 K, and 3.82 at 60 K. The BH has the values of 0.79 eV at 400 K, and 0.71 eV at 300 K. The decrease in the BH is due to the fact that the current will preferentially flow through the lowest BH with decreasing temperature due to barrier inhomogeneity. The value of 0.71 eV at 300 K is in close agreement with the values of 0.65 and 0.83 eV reported from the forward bias I-V characteristics for the Ni /n-type 6H-SiC in the literature. Thus, it has been concluded that the reduced barrier devices are promising for applications in devices operating at cryogenic temperatures as infrared detectors, sensors in thermal imaging and small signal zero-bias rectifiers and microwave mixers.

Effects of Neutron Flux on the Temperature Dependency of Permittivity of 3C-SiC Nanoparticles

Abstract: In the present work, the real and imaginary parts of permittivity of cubic modification silicon carbide (3C-SiC) nanoparticles are investigated before and after neutron irradiation. The real and imaginary parts of permittivity for the samples were studied in 0.1 Hz–2.5 MHz frequency and 100 K–400 K temperature ranges. The samples were continuously irradiated by neutron flux (2x10 13 n ⋅cm −2 s −1) up to 20 hours. The real and imaginary parts of permittivity were comparatively studied before and after irradiation. Neutron irradiation effects were studied with comparative analysis of non-irradiated samples. The increase in polarization was observed as a result of the increase in the impact period of neutron flux. All the mechanisms of the observed effects are given in the work.

Synthesis of Microcrystalline Wollastonite Bioceramics and Evolution of Bioactivity

Abstract: Alpha and beta wollastonite can serve as alternative low-cost bioceramics for bone repair and drug delivery. However, it has been challenging to develop energy-saving, facile and rapid synthetic methodologies for bioactive wollastonite phases. The aim of this work was the rapid preparation and characterization of bioactive α- and β-wollastonite powders by a coprecipitation method and their in-vitro bioactivity evaluation in the SBF solution. The results revealed that heating of the reactant solution at 100 ∘C for 2 h before sintering induced rapid formation of pure α- and β-wollastonite powders with agglomerated particles size in the range 2–7 μm. In-vitro bioactivity testing showed that the prepared α- and β-Wollastonite powders exhibit excellent bioactivity performance. Therefore, this method is promising for preparing bioactive wollastonite structures for medical applications such as bone substitutes and drug carriers.

Tribological and Microstructure Examination of Environmental Waste (Marble Dust) Filled Silicon Bronze Alloy for Wear Resistant Applications

Abstract: In the present work, marble dust particulate filled silicon bronze (SiBr) alloy composites were fabricated in five different weight percentages (0 wt.%, 2.5 wt.%, 5 wt.%, 7.5 wt.% and 10 wt.% of MD). The main focus of this work was to study their physical and dry sliding wear behavior for rolling elements. The void contents of the particulate filled alloy composites decreased with the increase in marble dust content in the composites up to 7.5 wt.% of marble dust (MD). Similarly, the hardness of the filled composites showed an increasing trend with the increase in hard marble dust content in the alloy composites i.e. 119.25 Hv to 181.5 Hv for 0 wt.% to 7.5 wt.% addition of MD particulates. However, both the void content and hardness showed inferior properties in higher weight percentages of marble dust content. The Taguchi design of experimental (L 25 orthogonal array) technique was implemented to find out the dry specific wear rate of the unfilled and marble dust filled SiBr alloy composites. A scanning electron microscopy (SEM) study was performed to study the wear mechanism of the worn composites along with atomic force microscopic (AFM) analysis to predict the surface profile of the worn particulate filled alloy composites.

Structural and Optical Characterization of Chemically Deposited PbS Thin Films

Abstract: PbS thin films were deposited on glass substrates by a chemical bath deposition method. The effect of varying the film thickness on the structural and optical properties has been investigated. XRD analysis reveals the crystallinity of the deposited PbS films with (200) preferred crystal orientation. Increasing the film thickness enhances the crystallinity of the films as well as decreases the strain and dislocation density. The surface morphology features were dramatically changed from small spherical grains to bead-like shape. The absence of impurities in the deposited films was confirmed by energy dispersive x-ray spectrometry (EDX) measurements. The optical constants of the deposited films were calculated and a small decrease in the band gap energy was observed with increasing the film thickness.

Temperature Stability and Photocatalytic Activity of Nanocrystalline Cristobalite Powders with Cu Dopant

Abstract: The SiO2 nanoparticles doped by 10 % mol Cu were prepared via a sol-gel method under process control. The effects of doping and calcination temperature on the structural and photo-catalytic properties of SiO2 nanopowders have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis absorption spectroscopy. Cristobalite and tridymite crystalline phases were found at a calcinations temperature range of 900∼1200 °C and amorphous phase was formed at a temperature of 800 °C for doped SiO2. The photocatalyst activity was evaluated by photocatalytic degradation kinetics of aqueous methyl orange (MO) under visible radiation. The results show that the photocatalytic activity of the 10 % mol Cu doped SiO2 nanopowders have a larger degradation efficiency than pure SiO2 under visible light at 900 °C temperature.

Chromatic Classification of Ouargla (Algeria) Dunes Sand: Determination of Main Compositions and Color Causes, by Using XRD, FTIR and XRF

Abstract: In the present work, a manually chromatic classification of Ouargla dunes sand has been carried out. According to its visual color, eight chromatic types of sand have been obtained: transparent (yellow, orange and red), and opaque (white, milky, gray, black and red). According to the main chemical compositions of sand, both XRD and FTIR have divided the chromatically sorted sand into three groups: quartzite (transparent samples), calcareous (milky, gray and black opaque samples) and calcareous quartzite (white and red opaque samples), without possibility of distinguishing between the sorted samples. FTIR spectroscopy has shown all functional groups and vibration modes in these samples. XRF spectroscopy has shown that sand grain colors are closely related to the main compositions as well as the impurities. It has also been shown that transparent samples contain more than 92 % of quartz (SiO 2). The redness of transparent samples is proportional to iron (Fe) impurities. It has also been shown that milky, gray and black opaque samples contain more than 55 % of calcium oxide (CaO). The milky color is due to magnesium (Mg) and sulfur (S), whereas the blackness is due to iron (Fe) and manganese (Mn). Both white and red opaque samples contain approximately equal concentrations of quartz and calcite, whilst the redness refers to the high concentration of iron (Fe), whereas the whiteness is due to the presence of magnesium (Mg).

First-Principles Insights of CO Adsorption Characteristics on Ge and In Substituted Silicene Nanosheet

Abstract: The structural stability, electronic properties and CO adsorption properties of pristine, Ge substituted and In substituted silicene nanosheet are studied using density functional theory. The pristine silicene is found to be more stable than the impurity substituted silicene. The electronic properties such as density of states and band gap are studied for pristine and Ge substituted silicene nanosheet. The favorable adsorption site of the CO molecule on the silicene nanosheet is identified. The adsorption characteristics of the CO molecule on silicene nanostructures are studied in terms of adsorption energy, Mulliken population, electron density, HOMO-LUMO gap, density of states spectrum and average energy gap variation. The adsorption energy, Mulliken charge transfer and average energy gap show a significant variation for the pristine and Ge substituted silicene nanosheet rather than the In substituted silicene nanosheet. From the observations, the adsorption characteristics of CO on pristine and Ge substituted silicene are found to be more favorable.

Influence of Thermally Assisted Machining Parameters on the Machinability of Inconel 718 Superalloy

Abstract: The present study describes the effect of thermally assisted machining (TAM) parameters on the cutting force, tool wear and surface integrity characteristics (surface roughness, surface topography, and microhardness) of Inconel 718. An inexpensive flame heating technique using oxy-acetylene flame is used to heat the workpiece material. The TAM parameters such as cutting speed, feed rate, depth of cut, and workpiece temperature were selected as process parameters over cutting force, tool wear and surface integrity characteristics.The experimental results reveal that the cutting forces and surface roughness decrease with increases in cutting speed and workpiece temperature, while the workpiece temperature increases as tool wear decreases. The tool wear mechanisms observed were abrasive, adhesive, diffusion and notch wear. The XRD results of thermally assisted machining reveal that neither phase change nor broadening of the peaks were observed at different machining conditions.

Thermodynamic Estimation of Silicon Tetrachloride to Trichlorosilane by a Low Temperature Hydrogenation Technique

Abstract: The chemical reactions in the SiCl4-Si-H2 system using a low temperature hydrogenation technique related to the Siemens process were studied based on thermodynamics. The diagrams of standard Gibbs free energy of formation and equilibrium constants for seven reactions used as a function of temperature in this system were calculated and plotted for a temperature range of 473 K to 1073 K. It showed that the lower the temperature, the larger the conversion ratio of SiCl4. The equilibrium composition of gaseous species in the SiCl4-Si-H2 system with different initial SiCl4/H2 ratio and systematic pressure was calculated and the corresponding conversion ratio of SiCl4 was obtained. The conversion ratio was improved by increasing the initial ratio of H2 in raw materials and the systematic pressure but was reduced with the increase of temperature. The conversion ratio of SiCl4 reached 0.41 with an initial SiCl4/H2 ratio of 1/5 and a systematic pressure of 5 MPa at 473 K.