Function Of Zinc Concentration Research Articles

Influence of Zn in the CdS Crystal Lattice and Its Impact over the Catalytic Activity in the H2 Production

Solid solutions ZnxCd1−xS were compared by coprecipitation and sonochemistry methods, where x = 0.2 . This rate is the one that presents the best photocatalytic activity and the best performance for the production of hydrogen from a water source, according to our previous results. The influence of the synthesis method on the morphology and its electronic properties of the CdS and Zn0.2Cd0.8S systems was investigated, as well as the effect of the incorporation of Zn in the crystal lattice and its effect on the production of hydrogen from the division of water. X-ray diffraction characterization confirmed the formation of a solid solution corresponding to a face-centered cubic crystalline phase with preferential growth of (111), (220), and (311) planes and hierarchical morphology according to SEM and TEM microscopy, formed by aggregated nanoparticles of ZnxCd1−xS compound. The crystallite size decreased with the Zn incorporation in the crystal lattice from 8.61 nm by a coprecipitation method to 4.37 nm when the synthesis was assisted with sonochemistry, and the crystallite sizes range from 7.92 nm to 3.80 nm for the case of CdS pure. Other characterization techniques were also used, such as photoluminescence (PL), Raman microscopy, and N2 adsorption and desorption. The PL results show tunability of band edge emission as a function of zinc concentration in the Zn0.2Cd0.8S nanoparticles. For the water splitting to hydrogen production, the separation of the charge carriers promoted by the incorporation of Zn in addition to the shallow trap emissions generated defects in the catalyst structure; such processes are important factors found which increased with the sonochemical method, as well as the potential matched positions.

Oxygen Availability in ZnxCe1–xO2 Nanocrystallites as a Function of Zinc Concentration

Oxygen Availability in Zn_<i>x</i>Ce_1–<i>x</i>O₂ Nanocrystallites as a Function of Zinc Concentration

The effect of zinc concentration upon electronic structure, optical and dielectric properties of Cd1− xZnxTe alloy: TB-mBJ investigation

In this paper, the structural, electronic, optical, and dielectric properties of Cd1-xZnxTe alloy are reported using (FP-LAPW) method based on DFT, within GGA, LDA approximations, and Tran–Blaha-modified Becke–Johnson (TB-mBJ) exchange potential. Energy gaps, dielectric function, refractive index, static dielectric constant, and the reflection coefficient have been determined and their variation as a function of zinc concentration has been analyzed and discussed. All studied parameters are found to vary nonlinearly with Zn concentration ongoing from CdTe (x = 0) to ZnTe (x = 1). The direct Γ- Γ, W–W, L-L and indirect Γ- W and Γ- L bands gaps are determined. The results will be of practical use to the community of crystal growers, semiconductor challenges, and new alloys designers.

Tribological performance and microstructural evolution of \u03b1-brass alloys as a function of zinc concentration

Tailoring a material’s properties for low friction and little wear in a strategic fashion is a long-standing goal of materials tribology. Plastic deformation plays a major role when metals are employed in a sliding contact; therefore, the effects of stacking fault energy and mode of dislocation glide need to be elucidated. Here, we investigated how a decrease in the stacking fault energy affects friction, wear, and the ensuing sub-surface microstructure evolution. Brass samples with increasing zinc concentrations of 5, 15, and 36 wt% were tested in non-lubricated sphere-on-plate contacts with a reciprocating linear tribometer against Si3N4 spheres. Increasing the sliding distance from 0.5 (single trace) to 5,000 reciprocating cycles covered different stages in the lifetime of a sliding contact. Comparing the results among the three alloys revealed a profound effect of the zinc concentration on the tribological behavior. CuZn15 and CuZn36 showed similar friction and wear results, whereas CuZn5 had a roughly 60% higher friction coefficient (COF) than the other two alloys. CuZn15 and CuZn36 had a much smaller wear rate than CuZn5. Wavy dislocation motion in CuZn5 and CuZn15 allowed for dislocation self-organization into a horizontal line about 150 nm beneath the contact after a single trace of the sphere. This feature was absent in CuZn36 where owing to planar dislocation slip band-like features under a 45° angle to the surface were identified. These results hold the promise to help guide the future development of alloys tailored for specific tribological applications.

Zinc Adsorption Properties of Alginate-SBA-15 Nanocomposite

Assessment of adsorption zinc (II) ions from aqueous solution using alginate-SBA-15 sorbent nanocomposite was investigated as a function of zinc concentration, solution pH, and contact time. For that purpose, the alginate-SBA-15 nanocomposite adsorbent was prepared through encapsulation method by immobilization mesoporous SBA-15 into a polymeric matrix. Identification of functional groups and surface morphology of the obtained nanocomposite was carried out by X-Ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and nitrogen porosimetry experiments. Sorption performance of the alginate-SBA-15 adsorbent during batch experiments was studied. A mathematically explanation of adsorption process using kinetics and isotherm models was also performed. Kinetic study was revealed that the pseudo second-order model has good agreement with the experimental results than the pseudo first-order model. Therefore, it indicates that the concentration of both alginate-SBA-15 and zinc metal ions are involved in the rate determining step of the sorption process. The qmax value for zinc (II) ions adsorption onto alginate-SBA-15 was found 46.3 mg g-1. According to thermodynamic analysis, physisorption and the endothermic of the sorption process nature of Zn(II) ions onto alginate-SBA-15 nanocomposite was revealed.

Novel zinc alginate hydrogels prepared by internal setting method with intrinsic antibacterial activity

In this paper, a controlled gelation of alginate was performed for the first time using ZnCO3 and GDL. Uniform and transparent gels were obtained and investigated as potential wound dressings. Homogeneity, water content, swelling capability, water evaporation rate, stability in normal saline solution, mechanical properties and antibacterial activity were assessed as a function of zinc concentration. Gelation rate increased at increasing zinc content, while a decrease in water uptake and an improvement of stability were found. Release of zinc in physiological environments showed that concentration of zinc released in solution lies below the cytotoxicity level. Hydrogels showed antimicrobial activity against Escherichia coli. The hydrogel with highest zinc content was stabilized with calcium by immersion in a calcium chloride solution. The resulting hydrogel preserved homogeneity and antibacterial activity. Furthermore, it showed even an improvement of stability and mechanical properties, which makes it suitable as long-lasting wound dressing.

Structural, Electrical and Dielectric Properties of Nanocrystalline Mg-Zn Ferrites

The nanocrystalline Mg-Zn ferrites having general formula Mg1-xZnxFe2O4 (x=0, 0.1, 0.2, 0.3, 0.4, 0. 5) were prepared by WOWS sol-gel route. All prepared samples were sintered at 700°C for 2 h. X-ray powder diffraction (XRD) technique was used to investigate structural properties of the samples. The crystal structure was found to be spinel. The crystallite size, lattice parameters and porosity of samples were calculated by XRD data analysis as function of zinc concentration. The crystallite size for each sample was calculated using the Scherrer formula considering the most intense (3 1 1) peak and the range obtained was 34-68 nm. The dielectric constant (ε), dielectric loss tangent () and AC electrical conductivity of nanocrystalline Mg-Zn ferrites are investigated as a function of frequency. The dielectric constant (ε), dielectric loss tangent () increased with increase of Zn concentration. All the electrical properties are explained in accordance with MaxwellWagner model and Koops phenomenological theory.

Magnetic and dielectric studies of nanocrystalline zinc substituted Cu–Mn ferrites

Ferrites with the general formula Cu 1− x Zn x FeMnO 4 (where 0≤ x≤1) were prepared through a citrate gel auto-combustion route. Structural characterizations carried out by X-ray diffraction reveal that the lattice constant increases with increase in zinc content. Transmission electron microscopic measurements confirm the nanoscale nature of the particles. Room temperature saturation magnetization was measured as a function of zinc concentration. The saturation magnetization increases up to x=0.25 and then decreases as zinc concentration increases. Dielectric permittivity, dielectric loss tangent, ac conductivity and complex dielectric impedance were studied in the frequency range 20 Hz–1 MHz. The results indicated a usual dielectric dispersion due to the Maxwell–Wagner type of interfacial polarization. Dielectric loss showed similar behavior as dielectric permittivity. The ac conductivity increased linearly with frequency. Complex impedance spectroscopic studies confirmed that conduction in the samples is via grain boundaries. In general, substitution of zinc plays an important role in changing the structural, electrical and magnetic properties of these ferrites.

Structural, magnetic and electrical properties of NiCuZn ferrites prepared by microwave sintering method suitable for MLCI applications

Polycrystalline NiCuZn soft ferrites with stoichiometric iron were prepared by a novel microwave sintering method. The powders were calcined, compacted and sintered at 950 °C for 30 min in a microwave sintering furnace. X-ray diffraction patterns confirm the formation of single phase cubic spinel structure. The grain size was estimated using SEM micrographs. The lattice constant is found to increase with increase in zinc concentration. The sintered ferrites have been investigated for their physical, magnetic and electrical properties such as bulk density, X-ray density, porosity, anisotropy constant, initial permeability, saturation magnetization, DC resistivity, dielectric constant and dielectric loss as a function of zinc concentration. Permeability, saturation magnetization, dielectric constant and dielectric loss were found to increase while DC resistivity was found to decrease with the replacement of Zn with Ni. The present series of ferrites are found to posses properties that are suitable for the core materials in multilayer chip inductors.

Dual control of cytosolic metals by lysosomal transporters in lobster hepatopancreas

This study describes the membrane transport mechanisms used by lobster (Homarus americanus) hepatopancreatic epithelial lysosomes to accumulate and sequester heavy metals from the cytosol, and thereby aid in the regulation of these ions entering the animal from dietary constituents. The present investigation extends previous work describing lysosomal metal uptake by cation exchange with protons and suggests that a second, parallel, lysosomal transport process involving metal-thiol conjugates may work in conjunction with the cation antiporter to control cytoplasmic metal concentrations. Transport of (65)Zn(2+) by lysosomal membrane vesicles (LMV) incubated in 1 mmol l(-1) glutathione (GSH) was not significantly different from metal transport in the absence of the tripeptide. However, preloading LMV with 1 mmol l(-1) alpha-ketoglutarate (AKG), and then incubating in a medium containing 1 mmol l(-1) GSH, more than doubled metal uptake, compared with vesicles equilibrated with chloride or possessing an outwardly directed chloride gradient. Kinetic analysis of lysosomal (65)Zn(2+) influx as a function of zinc concentration, in vesicles containing 1 mmol l(-1) AKG and incubated in 1 mmol l(-1) GSH, revealed the presence of a sigmoidal, low affinity, high capacity carrier process transporting the metal into the organelle. These data indicated the possible presence of an organic anion exchanger in lobster lysosomal membranes. Western blot analysis of LMV with a rabbit anti-rat OAT1 antibody showed the presence of an orthologous OAT1-like protein (approximate molecular mass of 80 kDa) signal from these membranes. These results, and those published previously, suggest the occurrence of two metal transporters on hepatopancreatic membranes, a high affinity, low capacity cation antiporter and a low affinity, high capacity organic anion exchanger. Together these two systems have the potential to regulate cytoplasmic metals over a wide concentration range.

Response of cultured tomato cells subjected to excess zinc: role of cell wall in zinc compartmentation

The aim of this preliminary study was to evaluate the role of the cell wall in Zn accumulation and tolerance by tomato suspension-cultured cells. Growth parameters, Zn distribution and accumulation by tomato cells were determined in function of zinc concentration. A particular attention was paid to the variations of the total cell wall material (cell wall carbohydrates, proteins, and exopolymers) in relation to extracellular levels of Zn. Cells treated with 0.5–5 mM Zn showed typical symptoms of heavy metal toxicity as testified by various growth parameters. Fresh and dry weights as well as total cell volume per vial decreased with increasing Zn concentration in the culture medium. Concurrently, the cell wall biomass increased, as well as the Zn amount retained by cell wall polymers. Cell wall appeared to assume important roles in Zn fixation and could therefore limit Zn influx into the cell. Our results also suggested that zinc fixation by cell wall was not only due to an increase in cell wall biomass but also to an improvement of its binding capacity.

The effect of zinc concentration on vacancies jump rate, diffusion coefficient and jump length in Cu–Zn ferrite

Samples with the chemical formula Cu 1− x Zn x Fe 2O 4 ( x=0.2, 0.4, 0.6, 0.8 and 1) were prepared by the standard ceramic method. The dielectric constant and dielectric loss tangent were studied as a function of vacancy jump rate. The results show that the dielectric constant and dielectric loss tangent decrease with increasing vacancy jump rate. In addition, the electron jump length in the octahedral sites was studied as a function of zinc concentration. The increase in jump length with Zn concentration has been attributed to the substitution of Fe +3 for Zn 2+ at the A-sites, which increases the B–B interaction. The increase of diffusion coefficient with increasing Zn concentration was reinforced by the increase of jump rate.

Studies on solution – growth thin films of CdS : Zn for photovoltaic application

Structural, optical, and electrical properties of thin films of CdS : Zn prepared by the solution – growth technique are reported as a function of zinc concentration. CdS are window layers influencing the photovoltaic response of CIS solar cells. The zinc doping concentration was varied from 0.05 to 0.5 wt %, zinc doping apparently increase the band gap and lowers the resistivity. All beneficial optical properties of chemically deposited CdS thin films for application as window material in heterojunction optoelectronic devices are retained. Heat treatment in air at 400 °C for 1h modify crystalline structure, optical, and electrical properties of solution growth deposited CdS : Zn films.

Studies on solution – growth thin films of CdS : Zn for photovoltaic application

Structural, optical, and electrical properties of thin films of CdS : Zn prepared by the solution – growth technique are reported as a function of zinc concentration. CdS are window layers influencing the photovoltaic response of CIS solar cells. The zinc doping concentration was varied from 0.05 to 0.5 wt %, zinc doping apparently increase the band gap and lowers the resistivity. All beneficial optical properties of chemically deposited CdS thin films for application as window material in heterojunction optoelectronic devices are retained. Heat treatment in air at 400 °C for 1h modify crystalline structure, optical, and electrical properties of solution growth deposited CdS : Zn films.

The diffusion coefficient of vacancies and jump length of electrons in zinc doped manganese ferrite

Samples of mixed ferrite Mn 1− x Zn x Fe 2O 4 ( x = 0.0, 0.1, 0.3, 0.5 and 0.7) have been prepared by the usual ceramic technique. X-ray diffraction patterns confirmed the spinel cubic structure for the samples. The jump length of electrons in the octahedral sites and electrical conductivity were studied as a function of zinc concentration. The increase of the jump length with Zn concentration is attributed to the substitution of Fe 3+ for Zn 2+ at the A sites which increase the B-B interaction. The increase of the diffusion coefficient and jump rate of vacancies with increasing Zn concentration expedite densification of the samples during sintering.

Quasi-particle tunneling in zinc doped yttrium barium copper oxide

Point contact junctions of AlAl 2O 3YBa 2Cu 3-xZn xO 7-y (where x = 0.025, 0.05 and 0.1) were made in order to study quasi-particle tunneling at 4.2 K. Such studies are expected to yield information on the superconducting energy gap parameter, Δ, as a function of zinc concentration, x. Zinc doping brings down the temperature of zero resistance, T C. In these specimens, symmetric conductance curves with a fairly large conductance overshoot were obtained. The tunneling curves obtained at different spots on the same sample showed peaks at nearly the same values of the applied voltage. Multiple peaks were observed in the conductance curves. It was seen that the separation of the symmetrically situated inner peaks decreased systematically as the concentration of zinc was increased. This shows that Δ decreases with decreasing T C. 2Δ k BT C approaches the BCS weak coupling limit as T C decreases with increasing zinc concentration.

Coherent potential approximation for randomly diluted uniaxial antiferromagnets : Application to Mn1−xZnxF2

A recently proposed CPA theory (Tahir-Kheli et al), for treating randomly diluted antiferromagnets with uniaxial anisotropy is revised. It is shown that such a procedure, which ignores dynamical effects occasioned by fluctuations in the local anisotropy field, leads to unphysical results beyond certain critical concentrations at which the theory breaks down. A study of the weakness, the relevance and validity of this theory is presented. The theory is expected to be relevant only when applied to systems with relatively small anisotropy. In fact, owing to its simplicity, within its range of validity, we apply a such CPA to analyse the behaviour of the zero-field antiferromagnetic resonance in the mixed system of manganese and zinc fluorides as function of zinc concentration. Our results are compared with those from several recent experiments and a very good agreement is found. Moreover, the general features and complexity of an alternative CPA formalism which takes into account dynamical effects of fluctuations in both exchange and anisotropy fields, are also briefly discussed.

Luminescence of zinc doped solution grown gallium arsenide

Crystals of gallium arsenide with zinc in solid solution were grown with seeds and by self nucleation, using a solution growth technique. Crystals were obtained from liquidus compositions along several isotherms in the GaAs primary phase field of the GaAsZn system. Photoluminescence measurements were performed at 20°K, 77°K and 300°K. The variation in intensity of the most intense peak has been studied as a function of zinc concentration in the solid, temperature of crystal growth, and in a more limited way, arsenic pressure. The luminescence intensity, I, attains a maximum at a hole concentration p = p m ; p m ≈3×10 18 holes/cm 3 at 77°K and 2 ×10 19 holes/cm 3 at room temperature. For p < p m , I measured at 300°K falls linearly with p for GaAs grown at its melting point, but is nearly constant for solution-grown GaAs. This different intensity dependence on doping is attributed to nonradiative minority carrier lifetimes which do not vary with hole concentration in the crystals grown near the melting point. In this case recombination is assumed to be controlled by quenched-in lattice defects. In crystals grown from low-temperature solutions the nearly constant intensity can be attributed to a carrier lifetime that increases linearly with 1/ p. For p > p m , I drops sharply with increasing p.

Square‐Loop Ferrites for Logic Application

The effects of composition, post sintering, and operating temperature in a square‐loop ferrite system of interest for performing logic functions in digital telemetry applications are described. Ceramic processing methods used in preparing the multiaperture ferrite cores for this study are also described. Magnetic hysteresis loop characteristics of squareness ratio (Ra), magnetic induction switched (δBm), critical switching field (Hc, and maximum permeability (μm,) are reported as a function of zinc concentration in the system Mg0.5‐tMn0.8ZnxFe1.7O4abc. These characteristics are also investigated as a function of the post‐sintering treatments of air quenching and nitrogen annealing for the composition Mgo.35Zn0.15 Isel Essentially identical results are obtained for both the air‐quenching and the nitrogen‐annealing treatments. Significant hysteresis loop characteristics are shown at various operating temperatures in the range −78° to + 100°C.

The critical shear stress in α-brass as a function of zinc concentration and temperature

Single-crystal tensile specimens of α-brass of various compositions up to 30 at. per cent Zn were pulled at four temperatures (4.2, 78, 195 and 297°K) to measure the critical shear stress. The ratios of the critical shear stress at each of the lower temperatures to that at 297°K show a sharp increase from unity for 0% zinc (measured by previous workers) to a plateau at about 7% and then another rise starting at about 20% zinc. A significant result is that for small percentages of zinc (up to about 4%) the critical shear stress at 4.2°K is actually lower than that at 78°K. An explanation of this anomaly is offered in terms of jog formation in the dislocations during their movement prior to yielding of the specimen.