Increase In Additive Concentration Research Articles

Effect of BaO/WO3 on the Microwave Loss Quality of Ba(Mg1/3Ta2/3)O3

Effects of BaO/WO3 ratio on the loss quality of complex perovskite Ba(Mg1/3Ta2/3)O3 were investigated as a function of the amount of (1-y)BaO-yWO3 (y=0.56, 0.8) from 0.3 wt.% to 7.0 wt.% at 10 GHz. The specimens with 1.5 wt.% of y=0.56 and/or with 1.0 wt.% of y=0.8 showed a maximum value of loss quality, respectively, and then decreased with an increase of additive content. The increase of loss quality with (1-y)BaO-yWO3, is resulted that the W6+ ions substitution of Ta5+ ions is enhanced the B-site ordering of Ba(Mg1/3Ta2/3)O3. The dielectric constant and temperature coefficient of resonant frequency (TCF) were decreased slightly with additives, which are due to the increase of BaWO4 phase as a secondary phase. The effects of additives on the intrinsic microwave losses of the specimens were investigated by the infrared reflectivity spectra from 50 to 4000 cm-1.

Investigations on the mechanism of aqueous solubility increase caused by some hydrotropes

The effects of nicotinamide, sodium p-toluenesulfonate and tetrapropyl and tetrabutyl ammonium bromides on the cloud points of non-ionic surfactant solutions and on the solubility of an apolar dye were determined. They all revealed a continuous effect of increased solubility as the additive concentration increases. Surface tension and heats of dilution were also measured for these solutions and the results support the view of a continuous hydrotrope self-association, which is then proposed as a key process to their ability of increasing aqueous solubility of apolar compounds.

Micellar Growth in Presence of Alcohols and Amines: A Viscometric Study

Viscosity measurements have been made to study the effect of alcohols (C3-C8OH) and amines (C4−C8NH2) on the micellar growth of 0.2 M cetylpyridinium chloride in the presence and absence of 0.1 M potassium chloride (KCl). The studies have been performed in aqueous solutions between 25 and 40 °C at intervals of 5 deg. The presence of 0.1 M KCl or organic additive of lower chain length (C3OH, C4OH, or C4NH2) singly or jointly has little effect on the viscosity of micellar solutions. As the chain length of the additive increases, the viscosity increases with the increase of additive concentration, the magnitude being substantial in presence of 0.1 M KCl. However, for equal chain lengths, the effect was greater for n-alcohols. In few cases, viscosity shows a peaked behavior when the concentration of the additive was increased beyond the maximum viscosity value. Increased effectiveness of additives in the presence of added salt was discussed in light of electrostatic and hydrophobic forces operating in the solution which are always responsible for growth processes. Changes of the effective Mitchell−Ninham parameter of the surfactant in the presence of various additives were related to viscosity behavior of the solution. Temperature dependence of the viscosity was used to compute the free energy of activation, ΔG*, for the viscous flow.

High-field ZnO-based varistors

The role of principal additives is investigated in an attempt to obtain high-threshold-field ZnO-based varistors in the traditional way. In the order of effect level, these are Sb2O3, Co3O4, Cr2O3 and MnO2. In the range of 0.5-5 mol%, the increase of additive content decreases the average ZnO grain size. As a result, the number of grains per unit thickness increases, which gives rise to the threshold field. The value of barrier voltage vb calculated from experimental data is about 1.4-2 V. The potential barrier height determined from the temperature dependence of the current-voltage characteristics is 0.3-0.5 eV. The abnormally large vb of a sample doped with 8 mol% Sb2O3 is quantitatively interpreted by the influence of the spinel phase through the energy-band-bending effect caused by the Bi2O3-rich phase and the hypothesis of a 'preferential path' of the current.

Refractory compound enriched T42 high-speed steels by liquid phase sintering

The aim of this work was to develop a composite based on T42 hss containing TiC/TiN for cutting applications. Green pellets were consolidated through liquid phase sintering and nearly full dense composites (98% of theoretical density) were optimally heat treated to peak hardness after tempering. Mechanical property, cutting ability testing and microstructural analysis were done to evaluate the products. The optimum sintering temperatre increased with the increase in additive content. Composites containing 4 mass% TiC possessed the best combination of properties which is attributed to better bonding of these particles. The results have been discussed within the framework of supersolids liquid phase sintering.

Separation of sulfonate and sulfate surfactants by capillary electrophoresis: effect of buffer cation

The separation of alkanesulfonate (RSO 3 - ) and alkyl sultate (ROSO 2 - ) surfactants by capillary electrophoresis (CE) is dependent on the butter cation and its concentration. Divalent cations increased migration time and resolution to a greater extent than that of monovalent cations. As the cation additive concentration increases, anion surfactant migration time increases. The effect is due to a change in electroosmotic flora which occurs because of cation exchange between the cation additive and the weakly acidic silanol surface of the silica capillary wall

Effects of chlorine based gettering on the electrical properties of rapid thermal oxidation/nitridation dielectric films

Dielectric films have been grown on single-crystalline silicon substrates with the thickness ranging from 100 to 180 Å at various gas and temperature conditions by using a rapid thermal processing that included an independent nitridation step. The film characteristics and their dependence on the additive contents of the hydrogen chloride gas and the processing time have been studied. The additive concentration of the hydrogen chloride gas in the oxidizing atmosphere were changed from 0% to 8%. By the addition of the hydrogen chloride gas, the oxidation rates and the initial oxide thickness were significantly increased, but after sequential nitridation processes the thickness of the films was nevertheless a little bit varied within 10 Å. The effective refractive index of the dielectric films were slightly changed with the additive contents of hydrogen chloride gas, and increased rapidly after nitridation process. All the samples of the dielectric films show the increased breakdown voltages and decreased average breakdown strength in proportion to the additive contents of the hydrogen chloride gas, as a result of the increment of the initial oxide thickness. In the nitridation of silicon dioxide films, the dielectric constant was increased by the addition of the hydrogen chloride gas. The accumulation capacitance was increased after nitridation of silicon oxide film which formed in the hydrogen chloride gas free atmosphere, due to the increased dielectric constants of the rapid thermal nitridation films as well as the actual change in the film thickness. But, after nitridation of hydrogen chloride gas processed oxide, the flatband voltages shift monotonically toward negative voltages, however the maximum capacitance value was decreased with the increase of additive concentration of the hydrochloric gas.

Studies in additive grinding of minerals

The effects of solid and liquid additives on a dry grinding process were studied at four additive concentrations and two grinding times, using a laboratory vibration ball mill with calcite as the feed material, under selected milling conditions. Among the additives used, the fatty acids are the most effective followed by alcohols, other organic solvents and inorganic salts. The experimental results show that the fineness of the product increases to a maximum and then decreases with an increase in additive concentration. Statistical correlations show that the increase in surface tension and dipole moment and also decrease in viscosity and density of the liquid additives can enhance the grinding process. Based on experimental results and correlations, it is concluded that the physico-chemical properties of the additive influence the cohesive interactions among the particles and in turn the breakage mechanisms for a better grinding environment.

Dynamic surface effect on boiling of aqueous surfactant solutions

Boiling of aqueous surfactant solutions is known to be drastically different from that of pure water. The experimental results showed that a small amount of surfactant additive makes the nucleate boiling heat transfer coefficient, h b, considerably higher, and that there is an optimum additive concentration for higher heat fluxes. Beyond this optimum point, further increase in additive concentration makes h b lower. In this work, the effect of surfactant additive on boiling is attributed to the departure from equilibrium surface tension which is produced by extension of the vapor-liquid interface during growth and coalescence of vapor bubbles in the vicinity of boiling surface. The surface tension of a surfactant solution is higher than the static value because the surfactant component cannot diffuse to the adsorbed layer promptly. This dynamic surface effect can be expressed by the Y (≡c(dσ/dc) 2) value which is shown to be a representation of the elasticity of an adsorbed film as well. The similarity between the increment of h b due to the addition of surfactant and the Y curves indicates that the dynamic surface effect may play an important role in the boiling process of aqueous surfactant solutions.

Experimental Study of Surfactant Effects on Pool Boiling Heat Transfer

In the first part of this work, nucleate boiling of aqueous solutions of sodium lauryl sulfate (SLS) over relatively wide ranges of concentration and heat flux was carried out in a pool boiling apparatus. The experimental results show that a small amount of surface active additive makes the nucleate boiling heat transfer coefficient h considerably higher, and that there is an optimum additive concentration for higher heat fluxes. Beyond this optimum point, further increase in additive concentration makes h lower. In the second part of this work, nucleate boiling heat transfer rate for n-propanol-water binary mixtures with various amounts of sodium lauryl sulfate were measured in the same pool boiling apparatus. The importance of the mass diffusion effect, which is caused by preferential evaporation of the more volatile component at the vapor-liquid interface on the boiling of the binary mixture, has been confirmed. However, it is shown that the effect exerted by the addition of a surfactant dominates over the mass diffusion effect in dilute binary mixtures.

Effect of Impurities on the Etching of Sodium Chloride Crystals

AbstractThe results of a study of the effect of HgCl2, ZnCl2, PbCl2 and CaCl2 on the surface micro‐morphology and kinetics of etching of {100} planes of NaCl crystals in methanol and ethanol are described and discussed. It was found that addition of an impurity to the solvent leads to the formation of contrasting dislocation etch pits, and that the overall dissolution rate in a solvent decreases with an increase in additive concentration. In the case of HgCl2 impurity added to methanol terraced etch pits are observed, but their terracing behaviour diminishes with the increasing impurity concentration.

Residual stresses in optical fiber preforms

AbstractThe optical fiber consisting mainly of quartz glass comprises a number of different kinds of glass having different constituents. Therefore, as is widely known, there are residual stresses left in the optical fiber preforms and the fiber itself which are caused by the difference of thermal expansion coefficients. To clarify the effect of the residual stress on the optical performances of the optical fiber, a measurement was carried out on the residual stresses of the optical fiber preforms and the fiber in a vertical plane normal to the longitudinal axis by means of optoelastic effect. Then the variation due to different thermal hysteresis and dimensions, influence of GeO2 addition concentration in the core and the effect of different refractive index were studied. As a result, it was revealed that the thermal hysteresis during drawing almost did not influence the residual stress distribution. The residual stress increased depending on the increase of additive concentration and its tendency agreed well qualitatively with a theoretical forecast. The residual stresses had such an influence on the refraction index decrease that with respect to the quadratic distribution of 1% relative refractive index difference between core and clad, the refractive index decreased by approximately 3.9 × 10‐4, Also, it was made obvious that the effect of residual stresses could not be disregarded for more precise refractive index control.

A new class of acid corrosion inhibitors: 2-Hydroxy-3-(2-undecyl, pentadecyl or heptadecyl amido-ethylamino) propane-1-tri-ethyl ammonium hydroxides

The inhibition of the corrosion of low carbon steel in 0.5M HCl by three compounds of a new class of cationic surfactants was studied, using the gasometric method, in the temperature range 19–60°C. More than 98% inhibition was achieved with an inhibitor concentration as low as 10 −4M. Inhibition by the three surfactants increased with the increase of additive concentration. It was not greatly affected by temperature. The apparent activation energy of the corrosion process in the absence and presence of the cationic surfactants was computed. Electrocapillary curves at a dropping mercury electrode were constructed for various concentrations of the different additives. These revealed that the three compounds are strongly adsorbed both on the anodic and cathodic sides of the electrocapillary curve maximum. † Faculty of Pharmacy, Pharmaceutical Chemistry Department, University of Alexandria. ‡ Faculty of Engineering, Chemical Engineering Department, University of Alexandria.

A new class of acid corrosion inhibitors: 2-hydroxy-3-(2-undecyl, pentadecyl or heptadecyl amido-ethylamino) propane-1-tri-ethyl ammonium hydroxides

The inhibition of the corrosion of low carbon steel in 0.5M HCl by three compounds of a new class of cationic surfactants was studied, using the gasometric method, in the temperature range 19–60°C. More than 98% inhibition was achieved with an inhibitor concentration as low as 10 −4M. Inhibition by the three surfactants increased with the increase of additive concentration. It was not greatly affected by temperature. The apparent activation energy of the corrosion process in the absence and presence of the cationic surfactants was computed. Electrocapillary curves at a dropping mercury electrode were constructed for various concentrations of the different additives. These revealed that the three compounds are strongly adsorbed both on the anodic and cathodic sides of the electrocapillary curve maximum.

Slag-cement concretes that contain complex antifreeze additives and require no heating

Investigations were made of slag-portland-cement concretes that harden in subzero temperatures of from -5 to -25 deg. C and require no heating. M 300 slag portland cement, 2 groups of slag binders - grades 300 and 400 respectively, 5-20 mm crushed granite and fine-grained sand were investigated. Calcium nitrate, calcium-nitrite-nitrate, and calcium- nitrate-chloride served as antifreeze additives that accelerated the hardening process. The test results indicate that slag-portland-cement concretes without additives acquire virtually no strength when frozen when subsequently cured for 60 days under normal conditions, the strength of concretes frozen at -5 deg C is approximately 80% of the design strength. Failure of the concrete surface was noted in a number of cases. For slag- portland-cement concretes with antifreeze additives and slag-binder concretes containing chemical activators, a post-freeze strength ranging from 20-50% and 10-35% respectively of the design strength is acquired. The post-thaw hardening rate does not exhibit a well-defined dependence on the freezing point nor on the type of antifreeze additives used. It was noted that an increase in additive concentration contributes to a gain in concrete strength both on curing while frozen, and in the process of continued curing under normal conditions. Comments are also made on the optimum percentage of additives, frost-resistance tests, strength properties, the utility of the slag binders, sulfate resistance, and the corrosive action of antifreeze additives.

Measurement of interfacial and surface tensions in polymer systems

AbstractPrincen's modification of Vonnegut's rotating drop procedure for measuring inter‐facial tension between low viscosity liquids has been adapted for use with pairs of liquid polymers with viscosities up to 5000 poise. Extrapolation to infinite time of results obtained with 10–20 min of rotation provided steady state data as indicated by its corre‐spondence with results reported from other techniques. An adaptation of this procedure was also found useful for determining surface tension values of molten polymers at temperatures up to 290°C. Reductions of 60–70% in interfacial tension between viscous samples of a polydimethylsiloxane and a copolyether were accomplished by addition of 1–2% of amphi‐pathic or polar compounds such as polydimethylsiloxane‐polyoxyethylene copolymers and carboxyl‐substituted polydimethylsiloxanes. A linear reduction in interfacial tension with a logarithmic increase of additive concentration was noted.

Effect of the method of making modifying additions on the properties of oxide catalysts

1. A study was made of the catalytic and adsorptive properties of magnesium oxide samples containing additions of stennic oxide introduced in quantities of 0.01–6.4% by various methods: by application to prepared magnesium oxide via organic and inorganic tin compounds, and by coprecipitation. 2. It was shown that the introduction of stannic oxide into magnesium oxide by impregnation with tetraphenyl tin or stannic chloride results in a modification of the action of the magnesium oxide catalyst in the decomposition of hydrogen peroxide.The main effect is already brought about by the very smallest additions of stannic oxide. As the temperature of the catalytic process is lowered from 90' to. 5% the modification curves change is form, becoming flattened out. 3. The dependence on stannic oxide content of the activity of catalysts prepared by the coprecipitation of magnesium and tin salts is expressed by a curve having a minimum and a maximum. Minimum catalytic activity corresponds to a stannic oxide content of 0.02% and maximum activity to a stannic oxide content of 1%. 4. It was shown that the introduction of stannic oxide into magnesium oxide by impregnation with tetraphenyl we showed previously-results in a marked change in the adsorptive properties of the catalyst. When stannic oxide is introduced into prepared magnesium oxide. the adsorptivity and specific surface of the sample Increases with increase in additive content. When stannic oxide is introduced into magnesium oxide by coptecipitation, the adsorptivity and specific surface of the products are almost unaffected by increase in additive content 5. On the basis of a comparison of the catalytic and adsorptive properties of the catalysts studied, we have advanced the hypothesis that the ways in which additions of stannic oxide are incorporated into magnesium oxide are of two different types and that the manner in which the additions act depends on the method by which they are introduced into the catalyst.