Molar Increase Research Articles

Remarkable change of structural, optical, photoluminescence and electrical properties of chemically prepared nanocrystalline films of PbS with concentration of triethanolamine (TEA)

Although triethanolamine (TEA) is widely used as complexing agent in the preparation of nanocrystalline PbS thin film by chemical bath deposition method, not enough studies have been reported on how its concentration affects various properties of the films. In the present work, we studied the effect of concentration of TEA on structural, morphological, optical, photoluminescence and electrical conduction properties of the films. We observed that with the increase of molar concentration of TEA—the crystallinity deteriorates with reduced crystallite size and increased strain and dislocation density; the densities of the films have been reduced; the films become non stoichiometric; optically these become more transparent but less reflecting showing prominent blue shift in the optical band gap which increased with the concentration of TEA; the width of the localized states in the band gap has been increased. The refractive index and extinction coefficient of the films are observed to be wavelength dispersive. The refractive index decreases with the increase of TEA complexation. In the NIR region, the extinction coefficient also decreases as concentration of TEA increases. The real and imaginary parts of dielectric constant replicates the refractive index and extinction coefficient curves respectively against wavelength. The PL spectra reveal conduction band to valence band transition with reduced intensity at higher molarity of TEA. The current–voltage measurement shows that the conductivity decreases considerably with the increase of TEA concentration. Our measurement estimated the crystallite size in the range of 29–37.49 nm, strain ~10−3, dislocation density ~1011 cm−2, band gap 0.8–1.55 eV, bandtail width 0.27–0.57 eV, the refractive index 2.3–5.8 and conductivity 0.0011–0.20 (Ωcm)−1.

Influence of molar concentration on triethanolamine (TEA) added tin sulfide (SnS) thin films by SILAR method

In the present work, thin films of Tin Sulphide (SnS) with TEA are deposited on glass substrate at room temperature by successive ionic layer adsorption and reaction method for solar cell application. The structural, topographical, morphalogical and optical properties of triethanolamine doped tin sulphide thin films are analyzed by X-ray diffraction, SEM, AFM, FTIR and UV–Vis analysis. The X-ray diffraction studies confirm that the deposited SnS films are amorphous and polycrystalline structure. From the SEM micrographs, it is clear that the film possesses almost smooth surface although some particles have distributed on the film because of the increasing concentration. The AFM image indicates that these coatings cover the surface of the substrate completely. A well ordered stair case structure of the SnS thin films are spread over the surface. Various functional groups present in the developed thin film are investigated by FT-IR analysis. The band gap energy decreases with increase in molar concentration as observed by UV–Vis studies and also it shows that the band gap decreases with the increasing particle size.

Molar Concentration Effects on the Optical and Structural Properties of Nanostructural SnO<sub>2</sub> Thin Films

Thin films of nanostructured SnO2 with different molariteswere prepared by chemical spray pyrolysis technique. XRD analysis reveals that all the films were tetragonal polycrystalline with a preferred orientation along (110) plane. AFM measurements indicate that the value of the grain size for 0.05 M, 0.1 M and 0.15 M were 111nm, 78 nm and 58 nm respectively. SEM micrograph proved the existence of small cracks on the film surface, EDS confirmed the composition percentage ratio of Sn and O­2 and no trace of impurities could be detected. PL spectra gives the indication about optical energy gap and the effect of concentration on it which appeared as a blue shift. The transmittance was studied for the deposited thin films, identifying that the transmittance decreases by the increase in molarity. The value of the optical energy gap of the deposited thin films was increased upon increasing molar concentration due o quantum confinement effect. The Urbach energy was also studied, their values decrease as the molar concentration increase.

Molar Concentration Effects on the Optical and Structural Properties of Nanostructural SnO<sub>2</sub> Thin Films

Thin films of nanostructured SnO2 with different molariteswere prepared by chemical spray pyrolysis technique. XRD analysis reveals that all the films were tetragonal polycrystalline with a preferred orientation along (110) plane. AFM measurements indicate that the value of the grain size for 0.05 M, 0.1 M and 0.15 M were 111nm, 78 nm and 58 nm respectively. SEM micrograph proved the existence of small cracks on the film surface, EDS confirmed the composition percentage ratio of Sn and O­2 and no trace of impurities could be detected. PL spectra gives the indication about optical energy gap and the effect of concentration on it which appeared as a blue shift. The transmittance was studied for the deposited thin films, identifying that the transmittance decreases by the increase in molarity. The value of the optical energy gap of the deposited thin films was increased upon increasing molar concentration due o quantum confinement effect. The Urbach energy was also studied, their values decrease as the molar concentration increase.

Cobalt oxide thin films prepared by NSP technique: Impact of molar concentration on the structural, optical, morphological and electrical properties

Cubic cobalt oxide (Co3O4) thin films are deposited using cobalt chloride hexahydrate as precursor by nebulizer spray pyrolysis technique with different molar concentrations. The structural, optical, morphological and electrical properties are investigated. X-ray diffraction (XRD) analysis shows the polycrystalline nature of the films with cubic structure having preferential orientation through (220) plane. The maximum crystallite size is found to be ∼21nm. The optical bandgap energy of the film is decreased with the increase of molar concentration. The obtained maximum bandgap energy values are 2.88 and 1.56eV for the films prepared at 0.025M. High-resolution scanning electron microscope illustrates the overgrown crystals like structure and coalescence of grains. The electrical conductivity of the films increases with the increase of molar concentration.

An investigation on the tuning effect of glucose-capping on the size and bandgap of CuO nanoparticles

We report herein the synthesis of CuO nanoparticles with varying concentrations of the organic modifier glucose as capping agent by the facile and versatile sol–gel route. The microstructure, surface morphology with composition, optical and transport properties of the nanoparticles thus produced were analyzed using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Electron Diffraction X-ray Analysis (EDAX), Fourier Transform Infrared Spectroscopy (FTIR), UV–Visible Spectroscopy (UV–Vis) and photoconductivity techniques. XRD analysis showed that the crystallite size of the nanoparticles as calculated by the Scherrer’s formula tends to decrease with increase in the molar concentration of capping agent. SEM results revealed that with increase in the molar concentration of the capping agent CuO nanopowder tends to become more homogeneous and thus well prevented the agglomeration of the nanoparticles. Also the particle size was observed to decline with increasing capping agent concentration. Band gap calculations made employing the Tauc’s plot method indicate a consistent increase in the band gap with increase in concentration of capping agent corresponding to the reduction in particle size. The impact of the capping agent on the vibration pattern of CuO nanoparticles is evident from the FTIR spectra. The photoconductivity of the CuO nanoparticles showed a decrease in the dark and photo current values with the increase in molar concentration of the capping agent which could be attributed to the increase in the optical band gap. Thus the particle size and hence the band gap of nanoparticles could be tuned effectively by altering the concentration of the capping agent.

Sequential Modular Simulation of Hydrodynamics and Reaction Kinetics in a Biomass Bubbling Fluidized-Bed Gasifier Using Aspen Plus

A sequential modular simulation (SMS) approach was used to simulate hydrodynamics and detailed kinetics of a fluidized-bed biomass gasifier in Aspen Plus. The kinetics of tar cracking reactions was taken into account in the simulation. The effects of operating conditions including temperature, equivalence ratio (ER), and steam-to-biomass ratio (SBR) on the composition and the lower heating value (LHV) of the effluent gas were studied and compared with experimental data. The model predictions well agreed with the experimental data. The increase of the bed temperature significantly decreased the tar content and increased the hydrogen content of the product gas. At ER = 0.3, the increase of the temperature from 973 K to 1123 K resulted in the increase of H2 molar concentration in the product gas from 7.6% to 11.3% and CO molar concentration from 13.1% to 17.0%. At a temperature of 1073 K, the optimum ER value was 0.3 and the increase in ER from 0.2 to up to 0.3 increased the amount of fuel gases but further increases in ER shifted the system kinetics toward the combustion regime. At 1073 K and ER = 0.3, with an increase in SBR from 0 to 1.0, H2 and CO2 concentrations increased from 9.3% and 13.3% to 10.8% and 14.7%, respectively, and CO concentration decreased from 15.8% to 12.9%. The analysis showed the SMS model with four stages gives the most satisfactory predictions, via comparison with the experimental data.

Influence of precursor molar concentration on the structural, morphological, optical and electrical properties of PbS thin films deposited by spray pyrolysis technique using perfume atomizer

PbS thin films were deposited onto glass substrates at 400°C using lead nitrate and thiourea as sources of Pb and S respectively. The molar concentration of precursor salts (both cationic and anionic) was varied as 0.025, 0.05, 0.075 and 0.1 keeping S/Pb ratio equal to 1. The structural studies reveal that the S:Pb concentration has a strong influence on the microstructural characteristics of the sprayed PbS films. The films were adherent to the substrate and well crystallized according to orthorhombic structure with the preferential orientation making a transition from (004) plane to (413) plane when S:Pb molar concentration increases. All the films have high optical transmittance>70%. The optical band gap values are found to be in the range of 2.44 – 2.55eV. The refractive index dispersion of the films obeys the single oscillator model. Electrical resistivity of all the films was found to be in the order of 102Ωcm. PbS films fabricated by this simplified technique are found to be good in structural, optical and electrical properties which are desirable for window layers in solar cell applications.

Effect of Alkali-Acid-Heat Chemical Surface Treatment on Electron Beam Melted Porous Titanium and Its Apatite Forming Ability.

Advanced additive manufacturing techniques such as electron beam melting (EBM), can produce highly porous structures that resemble the mechanical properties and structure of native bone. However, for orthopaedic applications, such as joint prostheses or bone substitution, the surface must also be bio-functionalized to promote bone growth. In the current work, EBM porous Ti6Al4V alloy was exposed to an alkali acid heat (AlAcH) treatment to bio-functionalize the surface of the porous structure. Various molar concentrations (3, 5, 10M) and immersion times (6, 24 h) of the alkali treatment were used to determine optimal parameters. The apatite forming ability of the samples was evaluated using simulated body fluid (SBF) immersion testing. The micro-topography and surface chemistry of AlAcH treated samples were evaluated before and after SBF testing using scanning electron microscopy and energy dispersive X-ray spectroscopy. The AlAcH treatment successfully modified the topographical and chemical characteristics of EBM porous titanium surface creating nano-topographical features ranging from 200–300 nm in size with a titania layer ideal for apatite formation. After 1 and 3 week immersion in SBF, there was no Ca or P present on the surface of as manufactured porous titanium while both elements were present on all AlAcH treated samples except those exposed to 3M, 6 h alkali treatment. An increase in molar concentration and/or immersion time of alkali treatment resulted in an increase in the number of nano-topographical features per unit area as well as the amount of titania on the surface.

Resistance to Electrochemical Corrosion of Extruded Magnesium Alloy AZ31

The purpose of the study was evaluation of electrochemical corrosion resistance of extruded magnesium alloy AZ31. Corrosion tests were performed in NaCl solutions featuring chloride ions concentration from 0.01 to 2 M NaCl. Potentiodynamic tests enabled to register anodic polarisation curves. Immersion tests were performed in NaCl solution and time 1-5 days. Electrochemical impedance spectroscopy (EIS) was used to evaluate phenomena that take place on the surface of the tested alloy. Impedance spectra of the system were made in the tests, and obtained measurement data was matched to the equivalent system. The results of all performed tests prove explicitly deterioration of corrosion properties of extruded magnesium alloy AZ31 with the increase of molar concentration of NaCl solution. Options of magnesium alloy AZ31 application in aircraft and automotive industry are connected with the need for application of protective layers on elements made of the tested alloy.

ULTRASONIC INVESTIGATION OF BIO-LIQUID MIXTURES OF METHANOL WITH CINNAMALDEHYDE BY INTERFEROMETRIC METHOD OPERATED IN THE FREQUENCY RANGE 1 MHZ-10 MHZ

Ultrasonic absorption study of binary liquid mixtures of cinnamaldehyde with polar solvent methanol and their binary liquid mixture were carried out at 298 K in the frequency range 1MHz-10MHz and at five different temperatures 293 K, 298 K, 303 K, 308 K and 313 K for 7 MHz over the entire range of composition. The observed ultrasonic absorption (α/f 2 obs), classical absorption (α/f 2 class), excess absorption (α/f 2 excess) and the ratio of the observed ultrasonic absorption (α/f 2 obs) and classical absorption (α/f 2 class) in the temperature range 293 K, 298 K, 303 K, 308 K and 313 K and at 7 MHz over the entire range of composition and their variation with compositions were studied. In this binary system it is observed that ultrasonic absorption is higher than the classical absorption. It is a characteristic feature of this binary liquid mixture. The thermo acoustical parameters acoustic impedance (Z), molecular weight (M), molar volume (V), molar sound velocity (R), molar compressibility (W), Vander Waal’s constant (b), internal pressure (πi), viscosity (η), intermolecular radius (ro), relaxation time (τ), adiabatic compressibility (βa), free volume (Vf), isothermal compressibility (βi) , intermolecular free length (Lf ),etc were computed for the all the binary systems from ultrasonic velocities, densities and viscosities at 303 K and at frequency 7 MHz. Comparison of experimental ultrasonic velocity and it’s theoretically calculated values by Junjie’s relation, Impedance dependence relation and Nomoto’s relation were studied. The increase in ultrasonic absorption with increase in molar concentration is due to the possible structural relaxation process in this binary system. These structural relaxation processes play very important role in the study of molecular and structural properties of the component molecules in binary liquid mixture.

Evaporation-induced flows inside a confined droplet of diluted saline solution.

Flow patterns inside a droplet of diluted aqueous NaCl solution confined by two flat substrates under natural evaporation were investigated both experimentally and numerically. We focused on natural convection-driven flows inside confined droplets at high Rayleigh numbers (i.e., the ratio of buoyancy to diffusion, Ra), where the convection of solutes is strongly dominant, compared to diffusion. The evaporated water at the free surface of the droplet builds up a concentration gradient inside the solution, which induces the Rayleigh convection flow. Three-dimensional trajectories of tracer particles in the droplet were tracked, and axisymmetric flow motions induced by the Rayleigh convection were experimentally measured by using a digital in-line holographic microscopy technique. In addition, the effects of the confined droplet's aspect ratio and the liquid's molar concentration on the evaporation-induced flows were investigated. The convection velocity is found to be increased as molar concentration increases, because Rayleigh convection becomes significant at high the molar concentration is high (i.e. high Ra). Our numerical simulation based on the Boussinesq approximation fairly well predicted the velocity profiles of evaporating confined droplets at low concentrations. Consequently, evaporation kinetics inside the confined droplets can be controlled with varying droplet's aspect ratio and the liquid's molar concentration, which provides helpful information for the design of biochemical microplating with limited resources and for tuning self-assembly micro/nanoparticle clusters.

Structural, Optical and Photoluminescence Study of Nanocrystalline SnO2 Thin Films Deposited by Spray Pyrolysis

Undoped SnO2 thin films prepared by spray pyrolysis method reveal polycrystalline nature with prominent peaks along (110), (101) and (211) planes. All the films are nanocrystalline with particle size lying in the range of 3·14–8·6 nm calculated by DS formula. Orientation along plane (200) decreases continuously as molar concentration of SnO2 increases. Dislocation density along plane (110) also decreases as molar concentration increases except 0·4 M SnO2 thin film. Scanning electron microscopy image of the films contain jelly structures along with agglomerated clusters of particles. SnO2 synthesized successfully, which confirms by Fourier transform infra-red spectroscopy. The optical transmittance spectra of 0·2 M SnO2 thin film shows transmittance about 50–60% transmission in visible and near infrared region with a sharp cut off in the ultraviolet region. The transmission decreases in visible and near infrared region as molar concentration increases. Broad UV emission at 398 nm is observed in photoluminescence spectra of the films along with a blue emission, when excited at 250 nm wavelength. Emission intensity randomly changed as SnO2 molar concentration increases. When excited at 320 nm, one UV and two visible peaks appeared at 385, 460 and 485 nm, respectively.

Resistance to Electrochemical Corrosion of Extruded Magnesium Alloy AZ61

The purpose of the study was the evaluation of the electrochemical corrosion resistance of extruded magnesium alloy AZ61 in solutions with concentration of 0.012 M NaCl. Resistance to electrochemical corrosion was evaluated on the ground of registered anodic polarisation curves by means of potentiodynamic method. Immersion tests were performed in NaCl solution and time periods of 1-6 days. Scanning microscopy was used to obtain images of the alloy microstructure after immersion tests. Electrochemical impedance spectroscopy was used to evaluate phenomena that take place on the surface of the tested alloy. The results of all performed tests prove explicitly deterioration of corrosion properties of magnesium alloy AZ31 with the increase of molar concentration of NaCl solution. It was found that irrespective of molar concentration of NaCl solution, pitting corrosion can be detected on the surface of the tested alloy. Test results prove that it is necessary to apply protective layers on elements made of the tested alloy.

Effect of zinc nitrate concentration on structural and optical properties of ZnO thin films deposited by Spray Plasma device

ZnO thin films were deposited on glass substrate at 200°C by Spray Plasma device using an aqueous solution of zinc nitrate. In this technique, the energy required for chemical transformations of precursors to zinc oxide is provided by plasma electrons rather than heat transfer. The effect of solution concentration on the structural and optical properties of the deposited films was investigated. X-ray diffraction results show that nanostructured polycrystalline films are formed with the typical wurtzite structure. The c-axis orientation growth depends highly on the initial concentration of precursor. Williamson–Hall calculations, atomic force and transmission electron microscopy images show an increase of grain size with an increase in molar concentration from 0.1 to 0.4M. The transmittance decreases from 85 to 50% with an increase of the molar concentration.

The impacts of water stress on phloem transport in Douglas-fir trees

Despite the critical role that phloem plays in a number of plant functional processes and the potential impact of water stress on phloem structural and phloem sap compositional characteristics, little research has been done to examine how water stress influences phloem transport. The objectives of this study were to develop a more accurate understanding of how water stress affects phloem transport in trees, both in terms of the short-term impacts of water stress on phloem sap composition and the longer-term impacts on sieve cell anatomical characteristics. Phloem sieve cell conductivity (kp) was evaluated along a gradient of tree height and xylem water potential in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees in order to evaluate the influence of water stress on phloem transport capacity. The Hagen-Poiseuille equation was used with measurements of sieve cell anatomical characteristics, water content of phloem sap, non-structural carbohydrate content of phloem sap and shoot water potential (Ψl) to evaluate impacts of water stress on kp. Based on regression analysis, for each 1 MPa decrease in mean midday Ψl, sieve cell lumen radius decreased by 2.63 µm MPa(-1). Although there was no significant trend in sucrose content with decreasing Ψl, glucose and fructose content increased significantly with water stress and sieve cell relative water content decreased by 13.5% MPa(-1), leading to a significant increase in sugar molar concentration of 0.46 mol l(-1) MPa(-1) and a significant increase in viscosity of 0.27 mPa s MPa(-1). Modeled kp was significantly influenced both by trends in viscosity as well as by water stress-related trends in sieve cell anatomy.

Integration of stable carbon isotope, microbial community, dissolved hydrogen gas, and 2HH2O tracer data to assess bioaugmentation for chlorinated ethene degradation in fractured rocks

An in situ bioaugmentation (BA) experiment was conducted to understand processes controlling microbial dechlorination of trichloroethene (TCE) in groundwater at the Naval Air Warfare Center (NAWC), West Trenton, NJ. In the BA experiment, an electron donor (emulsified vegetable oil and sodium lactate) and a chloro-respiring microbial consortium were injected into a well in fractured mudstone of Triassic age. Water enriched in ²H was also injected as a tracer of the BA solution, to monitor advective transport processes. The changes in concentration and the δ¹³C of TCE, cis-dichloroethene (cis-DCE), and vinyl chloride (VC); the δ²H of water; changes in the abundance of the microbial communities; and the concentration of dissolved H₂ gas compared to pre- test conditions, provided multiple lines of evidence that enhanced biodegradation occurred in the injection well and in two downgradient wells. For those wells where the biodegradation was stimulated intensively, the sum of the molar chlorinated ethene (CE) concentrations in post-BA water was higher than that of the sum of the pre-BA background molar CE concentrations. The concentration ratios of TCE/(cis-DCE+VC) indicated that the increase in molar CE concentration may result from additional TCE mobilized from the rock matrix in response to the oil injection or due to desorption/diffusion. The stable carbon isotope mass-balance calculations show that the weighted average ¹³C isotope of the CEs was enriched for around a year compared to the background value in a two year monitoring period, an effective indication that dechlorination of VC was occurring. Insights gained from this study can be applied to efforts to use BA in other fractured rock systems. The study demonstrates that a BA approach can substantially enhance in situ bioremediation not only in fractures connected to the injection well, but also in the rock matrix around the well due to processes such as diffusion and desorption. Because the effect of the BA was intensive only in wells where an amendment was distributed during injection, it is necessary to adequately distribute the amendments throughout the fractured rock to achieve substantial bioremediation. The slowdown in BA effect after a year is due to some extend to the decrease abundant of appropriate microbes, but more likely the decreased concentration of electron donor.

Potentiodynamic Tests of Magnesium Alloy AZ31 with Lithium Additive

The purpose of the study is to assess electrochemical corrosion resistance of magnesium alloy AZ31 with additives of 4.5, 7.5 and 15 % lithium in NaCl solutions. Corrosion tests were performed in solutions with concentration 0.01 2 M NaCl with application of electrochemical testing system VoltaLab®PGP201. Resistance to electrochemical corrosion was evaluated on the ground of registered anodic polarisation curves by means of potentiodynamic method. Results of performed tests show unequivocally deterioration of corrosion characteristics of the alloy together with increase of molar concentration of NaCl solution. As chloride ions concentration increases, decrease of corrosion potential and polarisation resistance, as well as increase of corrosion current density are observed. Deterioration of corrosion characteristics of AZ31 alloy was shown with the increase of lithium content. It must be highlighted that irrespective of molar concentration of NaCl solution, there is also presence of pitting corrosion in the tested alloy. It proves that magnesium alloy AZ31-Li is not resistant to that type of corrosion. Test results prove that it is necessary to apply protective films on elements made of magnesium alloy with lithium additive.

Gastropod shell as a precursor for the synthesis of binary alkali-earth and transition metal oxide for Cr(VI) Abstraction from Aqua System

The synergies of binary metal oxides, habitual in natural system, in sequestrating metal ions were the premise on the synthesis of binary alkali earth and transition metal oxides (ATM) for possible environmental remediation. Gastropod shell (GS) was used as a precursor for alkali earth metal generation in the perspective of wastes recycling and cost minimization in material synthesis. ATM of different combination ratios of Ca: Fe, were synthesized and characterized (XRD, SEM, EDAX, TGA and PZC) and the potential for Cr(VI) attenuation in aqua system was appraised. The Langmuir sorption capacities (mg/g) of the ATM (112.36–117.65) were higher than that of the respective metal ion constituents (101.01–105.26). Kinetic modeling showed that the pseudo second order gave the best description of the process. pH had nominal effect on the extent of Cr(VI) sorption while the magnitude of Cr(VI) sorbed reduced with increase in molar concentrations of anions and ionic strength. The spent ATM stability, determined via the toxicity characteristic leaching procedure (TCLP), was higher in acidic medium than the alkaline medium. SEM and EDAX elucidation, confirmed the presence of Cr(VI) on the sorbent while the formation of complexes of Cr ions with metal-O functional groups was confirmed via FTIR analysis.

Chemical Precipitation Synthesis of Ferric Chloride Doped Zinc Sulphide Nanoparticles andtheir Characterization Studies

Nanoparticles of Ferric Chloride doped ZnS has been synthesized by simple chemical precipitation method and characterized by XRD, SEM, UV-Vis analysis, Differential Thermal Analysis, Thermo Gravimetric Analysis and Differential Scanning Calorimetry. XRD patterns of the samples reveal particle size, specific surface area and the formation of cubic structure. The SEM images show that the cauliflower likes structure. Optical band gap values have been obtained from UV-Vis absorption spectra. It has also been found that energy band gap (Eg) increases with the increase in molar concentration of reactant solution. Thermal analysis measurement of the prepared sample shows that the thermal stability of pure ZnS is decreased due to increase in Ferric Chloride concentration. Undoped ZnS is more thermal stable when compared to FeCl3 doped ZnS.