Effect Of Impurity Concentration Research Articles

Effect of impurity content on structure of living water

In order to study the influence of impurities content on the water structure, Raman spectra and degrees of depolarization of different living water are measured by Raman spectroscopy, the relationship between the depolarization ratio and the impurity content in drinking water was obtained by the utilisation of computer deconvolution for the stretching vibration peak. The results showed that the intensity of different bending vibration is almost the same, and the intensity of the stretching vibration reflects different content of impurities in water. Depolarization calculation of water molecules showed that the stretching vibration is stronger than the bending vibration. The interaction of impurity ions and water molecules enhances the vibration rate of water molecules, making the symmetry of stretching vibration reduced, and leading to increased depolarization ratio. Therefore, the impurities content can be determined from the relative intensity of Raman characteristic peaks and the degrees of depolarization.

Impurity concentration effects on the structures, ductile and electronic properties of Zr-doped gamma-TiAl alloys

This investigation aims at the Zr-doping in -TiAl alloy systems in which Ti (or Al) atoms are partly replaced and the impurity concentrations are 1/54, 1/36, 1/24 and 1/16 (molar ratio), respectively. The structural, energy, plastic and electronic properties of the alloys are calculated and studied by using the first-principles method based on the density functional theory and other physical theory. From geometry optimization results it is shown that doping with Zr can change the structural symmetry of the -TiAl systems. These results also suggest that the cubic degree of Zr-doped -TiAl alloys can be increased due to the Zr-substitution. For instance, the cubic degrees of Ti12Al11Zr and Ti18Al17Zr systems are enhanced distinctly, which are positive for improving the mechanical properties of the alloys. The average formation energies obtained indicate that the Ti atom replaced by Zr can slightly decrease the formation energy of the system (0.003 eV/atom); while Zr substituting the Al atom can increase the formation energies of the systems (0.07 eV/atom). Accordingly, when Zr atoms are introduced in the -TiAl system, they tend to substitute Ti atoms, and can also substitute Al atoms with a certain possibility. Thus, various Zr-doped -TiAl regions can be produced in the system. The integral effects are of significance for improving the performance of the -TiAl based alloys by means of Zr-doping method. Comparing the axial ratios of Zr-doped -TiAl systems with that of pure -TiAl system, we find that Zr substituting Al atom can reduce the axial ratio of the Zr-doped alloys, which is responsible for the ductility of the materials. It should be mentioned that when the impurity concentration is in the range of 1.85 at%-6.25 at%, the doping effect will be most distinct and the axial ratio of the alloys is close to unity. It is expected that the Ti12Al11Zr system has a good ductility for its axial ratio equals to 1.007. The band structures of Zr-doped -TiAl systems show that they all have metallic conductivities. After Zr atom substitutes the Al atom in the -TiAl system, the intensity of covalent bond between Zr atom and its nearest neighbour Ti atoms in Ti12Al11Zr system reduces evidently and the bond length increases (0.032 ), which is indicated by the obtained overlap population (decrease by 0.21) and the densities of states in the Zr-doped and pure -TiAl systems. These results in the decrease of average intensity of Ti-Al(Zr) bonds and the increase of metallic bonds in Ti12Al11Zr system, which is an important factor for improving the ductility of -TiAl based alloys.

The Effect of Impurity Concentration and Cr Content on the Passive Oxide Films in Ferritic Stainless Steels

The properties of passive oxides on three steels consisting of 11%Cr, 18%Cr, and 30%Cr-2%Mo were studied in acidic sulfate solution by the Mott-Schottky relation for semiconducting properties, potential modulation reflectance (PMR) spectroscopy for light absorption properties, X-ray photoelectron spectroscopy (XPS) for composition estimation, and Fe3+/ Fe2+ redox current measurement for properties of electron transfer. The influence of the impurity concentration in the steels was also studied. The donor density in n-type semiconducting passive oxides as estimated from the Mott-Schottky plot decreased with a higher Cr content and with a lower impurity concentration. Cr enrichment occurred in the passive oxide and, for example, for 30Cr-2Mo steels, the ratio of Cr ions to total metallic ions in the passive oxide was approximately 70 wt%. The light absorption edge of the passive oxide measured by PMR was approximately 2.4 eV, irrespective of the Cr content and impurity concentration. The redox current on the passive oxide was much inhibited compared with that on the Pt electrode. The redox current decreased in a similar manner as the donor density. The inhibition of the redox current was assumed to be due to the space charge layer in the n-type semiconducting passive oxide.

Analytical Dependence of the Ignition Dynamics Parameters on the Low-Z Impurity Concentration

Abstract In this paper, thermonuclear burning of the deuterium-tritium (D/T) plasma of an inertial confinement fusion (ICF) target is studied in the presence of low-Z impurities (lithium, beryllium, and carbon) with arbitrary concentrations. The effect of impurities produced due to the mixing of the thermonuclear fuel with the material of the structural elements of the target during its compression on the process of target burning is studied. Also, the effect of impurity concentration on the plasma ignition parameters such as ignition temperature, confinement parameter ρR, and ignition energy are discussed. The models are constructed for an isobaric and an isochoric plasma for the case in which the burning is initiated in the central heated region of the target and then propagated into the surrounding relatively cold fuel. In ICF spherical implosions of the D/T fuel, the ignition parameters as ignition temperature and parameter ρR in the hot spot are approximately 7 - 10 keV and 0.2 - 0.4 g cm-2 respectively, and these values are increased by the presence of impurities.

A Current–Voltage Model for Graphene Electrolyte-Gated Field-Effect Transistors

This paper presents a model for graphene electrolyte-gated field-effect transistors (EGFETs) that incorporates the effects of the graphene-electrolyte interface and quantum capacitance of graphene. The model is validated using experimental data collected from fabricated graphene EGFETs and is employed to extract device parameters such as mobility, minimum carrier concentration, interface capacitance, contact resistance, and effective charged impurity concentration. The proposed graphene EGFET model accurately determines a number of properties necessary for circuit design, such as current-voltage characteristics, transconductance, output resistance, and intrinsic gain. The model can also be used to optimize the design of EGFETs. For example, simulated and experimental results show that avoiding the practice of partial channel passivation enhances the transconductance of graphene EGFETs.

Advancement in the photocatalytic properties of TiO2 by vanadium and yttrium codoping: Effect of impurity concentration on the photocatalytic activity

In this work, we report the synthesis and characterization of vanadium (V)–yttrium (Y) codoped TiO2 photocatalyst for photocatalytic degradation of aqueous pollutants. Nano-sized crystalline (V, Y) codoped TiO2 samples with different V concentrations were synthesized by hydrothermal method without post calcination. A redshift of optical absorption is found in all codoped samples describing the modification of the band structure. A nonlinear increase in the optical absorption edge of V, Y codoped TiO2 was observed with increasing V doping concentration. Spectroscopic investigations show that the doping occurs in the form of substitution for lattice sites. V, Y codoped TiO2 exhibits great enhancement in the photocatalytic response compared to pure TiO2 and it is attributed to the visible light absorption and effective utilization of the photogenerated carriers. The sample with 0.2% V, Y codoped TiO2 demonstrated the best photocatalytic behavior compared to the other synthesized samples.

Effect of Impurity Concentration on Magnetic Properties of SnO2 Nanoparticle

Effect of Impurity Concentration on Magnetic Properties of SnO2 Nanoparticle

Effects of strontium and aluminum impurities on optical properties of iron sulfide (FeS2) thin films

Chemical bath deposited iron sulfide (FeS2) thin films were grown at room temperature (26 o C) on glass substrates and the effects of impurity concentrations of strontium (Sr, 0.02-0.04M) and aluminum (Al, 0.02-0.04M) on the optical properties of the FeS2 thin films were investigated using a spectrophotometer in the UV-VIS region. The highest transmittance of 70% occurred for 0.04M Al impurities and 27% for 0.02M of Sr impurities as compared to 18% for un-doped iron sulfide thin films, while the reflectance exhibited varying peak values at 550 nm and 650 nm wavelengths for all concentrations of both impurities. Other optical properties obtained from the spectrophotometer data using appropriate relations showed a corresponding low absorbance of 0.2 for 0.04M Al impurity and fairly high absorbance of 0.6 for 0.02M of Sr impurity. A significant increase in the energy band gap occurred from 1.9 - 2.2eV for Strontium impurity concentrations and 2.0 - 3.8eV for Al impurity concentrations with the highest of 3.8eV at 0.04 Al doping. The effects of Sr and Al dopants on the extinction coefficient and refractive index of the thin films are also reported in this paper.

Effect of phase transition and particle size on thermoluminescence characteristics of nanocrystalline K2Ca2(SO4)3:Cu+ phosphor

Abstract A new K 2 Ca 2 (SO 4 ) 3 :Cu + nanocrystalline TLD phosphor was prepared by chemical coprecipitation method using calcium chloride, potassium chloride and ammonium sulphate as reactants and copper chloride (Cu 2 Cl 2 , as impurity) in the presence of ethanol. The samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Differential thermal and thermogravimetric analysis (DT-TGA) techniques. XRD and DTA data show that there is a phase transformation from orthorhombic to cubic occurring at around 550 K. The effects of impurity concentration, annealing temperature and γ rays dose on TL characteristics of the material have been studied. Different glow curves have been theoretically deconvoluted using computerized glow curve deconvolution (CGCD method) into simple glow peaks to determine their trapping parameters. The results show that different phases existing in the material on annealing might have reorganized the electron-traps (energy levels) and hole-traps (luminescence centers) and are responsible for changing glow curve structures. This is very important to know as any change in the glow curve structure would cause errors in estimation of doses of high-energy radiations and also may lose its reusability. The photoluminescence (PL) studies show that there are no redox reactions (Cu + Cu 2+ ) taking place and Cu remains in its Cu + form after annealing and even after irradiation.

Effect of Impurity Content on Elastic Modulus and Poisson Ratio of Salt Rock

The basic features of salt rock in China are as follows: thickness single layer, more layered distribution and impurities and others. The unstable mechanical parameters are caused by the different types and content of minerals in natural salt rock. Elastic modulus and Poisson ratio of natural samples from certain northern area in China which are compressed under different confining pressure is then analysed with the impurity content to get the relationship between them. Comparing the experimental values with the predicted calculated by Mori-Tanaka method, a linear estimation formula is proposed for the prediction of mechanical parameters suitable for practical engineering applications in this area.

The effect of impurity level on ultrafine-grained microstructures and their stability in low stacking fault energy silver

The effect of impurity content on the evolution of microstructure in low stacking fault energy silver processed by severe plastic deformation (SPD) was studied. The SPD-processing was carried out on 4N5 and 4N purity Ag samples by equal-channel angular pressing (ECAP) up to 16 passes. It was found that, although the minimum grain size and the maximum dislocation density were not affected by the different impurity atom content, there is a lower degree of twinning in the less pure material for high number of passes. The small increase of impurity level from 4N5 to 4N in Ag resulted in a significantly better thermal stability at room temperature for the ultrafine-grained microstructures obtained by ECAP.

Simulation of high conversion efficiency and open-circuit voltages of α-si/poly-silicon solar cell

The P+ {\alpha}-Si /N+ polycrystalline solar cell is molded using the AMPS-1D device simulator to explore the new high efficiency thin film poly-silicon solar cell. In order to analyze the characteristics of this device and the thickness of N+ poly-silicon, we consider the impurity concentration in the N+ poly-silicon layer and the work function of transparent conductive oxide (TCO) in front contact in the calculation. The thickness of N+ poly-silicon has little impact on the device when the thickness varies from 20 {\mu}m to 300 {\mu}m. The effects of impurity concentration in polycrystalline are analyzed. The conclusion is drawn that the open-circuit voltage (Voc) of P+ {\alpha}-Si /N+ polycrystalline solar cell is very high, reaching 752 mV, and the conversion efficiency reaches 9.44%. Therefore, based on the above optimum parameters the study on the device formed by P+ {\alpha}-Si/N+ poly-silicon is significant in exploring the high efficiency poly-silicon solar cell.

Micrograin Superplasticity: Characteristics and Utilization.

Micrograin Superplasticity refers to the ability of fine-grained materials (1 µm < d < 10 μm, where d is the grain size) to exhibit extensive neck-free elongations during deformation at elevated temperatures. Over the past three decades, good progress has been made in rationalizing this phenomenon. The present paper provides a brief review on this progress in several areas that have been related to: (a) the mechanical characteristics of micrograin superplasticity and their origin; (b) the effect of impurity content and type on deformation behavior, boundary sliding, and cavitation during superplastic deformation;

Dissociation and Diffusion of Hydrogen on the Mg(0001) Surface: Catalytic Effect of V and Ni Double Substitution

To understand the effect of impurity concentration in hydrogen dissociation and diffusion, an extensive first-principles investigation has been performed over doubly substituted Mg surface and the ...

Studies of thermal stability of nanocrystalline SnO2, ZrO2, and SiC for semiconductor and thermocatalytic gas sensors

The thermal stability of synthesized and commercial SnO2, ZrO2, and SiC nanopowders is compared. The crystallite growth rate during the isothermal annealing of the materials at 700°C for 30 h is evaluated. The crystallites’ average size was determined by X-ray phase analysis (using the Scherrer method). The effect of impurity content on the kinetics of crystallite growth is studied for the synthesized SnO2 and ZrO2. Semiconductor and thermocatalytic sensors, based on the synthesized and commercial materials, are manufactured. The long-term stability of the sensors’ signal is compared with the thermal stability of the nanopowders.

Effects of Impurity Content on the Sintering Characteristics of Plasma-Sprayed Zirconia

Yttria-stabilized zirconia powders, containing different levels of SiO2 and Al2O3, have been plasma sprayed onto metallic substrates. The coatings were detached from their substrates and a dilatometer was used to monitor the dimensional changes they exhibited during prolonged heat treatments. It was found that specimens containing higher levels of silica and alumina exhibited higher rates of linear contraction, in both in-plane and through-thickness directions. The in-plane stiffness and the through-thickness thermal conductivity were also measured after different heat treatments and these were found to increase at a greater rate for specimens with higher impurity (silica and alumina) levels. Changes in the pore architecture during heat treatments were studied using Mercury Intrusion Porosimetry (MIP). Fine scale porosity (<_50 nm) was found to be sharply reduced even by relatively short heat treatments. This is correlated with improvements in inter-splat bonding and partial healing of intra-splat microcracks, which are responsible for the observed changes in stiffness and conductivity, as well as the dimensional changes.

Effect of the quality of microsilica on the flow properties of cement slurry and characteristics of low-cement refractory concrete on a chamotte filler

The effect of impurity content in different grades of microsilica (MS) on the physicomechanical characteristics of a low-cement refractory concrete based on a chamotte filler is considered. The high content of impurities in MS degrades the flow properties of cement slurry and the respective concrete slurry. It is shown that as ambient temperature grows to 30°C, the impurities in MS increase the cement slurry thickness and impede the placement of refractory concrete in summer period. If low-quality MS is used in concrete, an increased crack formation is observed under the cyclic high-temperature effect.

TL and PL in BaSr(SO4)2:Eu mixed sulphate

AbstractA highly sensitive thermoluminescent (TL) phosphor based on BaSr(SO4)2:Eu has been developed. The phosphor was recrystallized from H2SO4 solution by evaporation. Photoluminescence studies of this mixed‐sulphate phosphor show that Eu is incorporated in the host in its divalent (emission at 383 nm) as well as trivalent (emissions at 575 and 731 nm) form due to 4f65d → 8S7/2 and 5D0 → 7Fj transitions, respectively. The intensity of the 383 nm band increases with increasing irradiation, while that of the 731 nm band decreases, showing Eu3+ → Eu2+ conversion. The TL glow curve of the BaSr(SO4)2:Eu material shows a single peak at 470 K along with a small shoulder at around 428 K. The relative intensities of these peaks are found to vary with γ‐ray exposure. The TL sensitivity of the mixed‐sulphate phosphor is nearly 2.5, 7 and 1.2 times higher than those of BaSO4:Eu, SrSO4:Eu and CaSO4:Dy phosphors, respectively. The annealing temperature and the impurity concentration effects are also studied. (© 2006 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Using Image Analysis to Look into the Effect of Impurity Concentration in NaCl Crystallization

This paper presents and describes a methodology for morphology assessment, crystal particle classification and quantification of the complexity level of a crystal or a population of crystals. It further describes the application of such methodology to the study of the influence of MgCl 2 in the crystallization of NaCl, namely on crystal size and morphology. Image analysis techniques are combined with discriminant factorial analysis leading to results that allow the computation of the complexity of crystals through a new parameter, the agglomeration degree of crystals. With this methodology it has been possible to distinguish automatically among three different classes of crystals, and within each class as per their complexity. Agreement between manual and automated classification measured in terms of a performance index is 90% on average. The effect of supersaturation and impurity concentration on the type, amount and complexity level of the agglomerates was further determined.

Silicon crystal growth from the melt: Analysis from atomic and macro scales

AbstractThe effect of impurity concentration on thermal conductivity of natural and isotope silicon by using equilibrium molecular dynamics simulation is investigated. It was found that the concentrations of the impurities such as boron, phosphor and arsene play an important role in the propagation of phonons in silicon crystals. It was also clarified that a mass difference of impurities and host crystals results in degradation of thermal conductivity of silicon. (© 2005 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)