Influence Of Different Additives Research Articles

Impedance Spectroscopy of Nonactive Metal Electrodes at Low Potentials in Propylene Carbonate Solutions: A Comparison to Studies of Li Electrodes

Surface films formed on nonactive metals (nickel, gold, and silver) in propylene carbonate solutions were investigated using impedance spectroscopy. The salts used included , , , and , and the impact of their concentration on the properties of the surface films was explored. In addition, the influence of the presence of additives such as, , and in solutions and the potential of formation on the properties of these surface films was rigorously studied. Using simple methods and simulation programs, it was possible to separate the time constants of the impedance spectra, relate them to different parts of the metal‐solution interface, and to calculate the thickness of these surface films from the interfacial capacitances. Following variations of the thickness calculated for the surface films formed in the different systems as a function of applied potential and solution composition, it was possible to study the stability of the surface films, their dissolution rates and the influence of different additives on their stability. For a few systems, ex situ Fourier transform infrared spectroscopy (external reflectance mode) was also applied. The results thus obtained were correlated to previous studies of Li electrodes in the same solutions.

Influence of additives on the sensing properties of screen-printed SnO 2 gas sensors

The responses of semiconductor gas sensors are affected by the changes in charge carrier density related to the surface combustion reaction arising from the interaction with dopants, impurities and catalysts. The present paper investigates the modification of the gas sensing properties of screen-printed tin dioxide based devices due to the influence of different additives on the electrical conductivity mechanism. The effects of aluminium silicate and Pd as catalyst are explored together with the addition of a glass layer as coverage.

The influence of different additions on portland cement hydration heat

This paper presents the results obtained using the Langavant Calorimeter method on portland cements with different addition materials that are commonly used in the manufacture of commercial cements. The effects of these materials on the hydration heat with respect to a control cement were studied. The first hours show that most of the additions, which present highet activity at early stages, increase the hydration heat of their mixed cements in relation to the control cement. The use of pozzolans reduces the heat given off by the cements during hydration. However, the reactions of the pozzolanic materials with the lime also produce heat and the decrease should not be proportional to the level of clinker substitution in the mixed cements.

Influence of different additives on the reaction between hydrated lime and sulfur dioxide

AbstractFive commercial calcium hydroxides were tested in a fixed‐bed reactor for SO2 removal at bag‐filter conditions. Small amounts of different additives (fly ash, NaOH, NaCl and CaCl2) were added to the commercial Ca(OH)2 which showed the greatest reactivity respect to SO2 (by a drying process). Fly ash performance was negative whereas the rest of additives enhanced the desulfurization power of the Ca(OH)2, specially NaOH (due to its basic and deliquescent character) and CaCl2 (by its delilquescence). CaCl2 has been the best additive tested at the used experimental conditions.

Human alpha-1-antitrypsin subtyping by hybrid isoelectric focusing in miniaturized polyacrylamide gel.

The polymorphism of alpha-1-antitrypsin (PI) has been studied by hybrid isoelectric focusing in miniaturized immobilized pH gradient gels, with an interelectrode distance of 55 mm, in two narrow ranges of pH 4.35-4.75 and 4.35-4.55), following rehydration with pH 4.2-4.9 carrier ampholytes. The use of the separator N-(2-acetamido)-2-aminoethanesulfonic acid (ACES) in combination with carrier ampholytes for gel rehydration has been shown to enhance PI band sharpness. The influence of different additives (sucrose, sorbitol and glycerol) on the PI band pattern has also been evaluated. Glycerol has been shown to be responsible for the change in the relative mobility of the M3 band. The analysis of the minor M-7 isoprotein zone by hybrid isoelectric focusing followed by silver staining has permitted a more reliable classification of PIM subtypes. A population study carried out with 164 unrelated individuals living in Spain is also presented.

Are proton NMR observations supportive of the osmotic model of cement hydration?

Abstract The complex chemical and physical processes occurring in hydrating cement pastes are not fully understood. The properties of cement setting and the influence of different additives are encompassed by the delayed nucleation and the protective layer theories. Each of these two theories is supported by several different experimental observations. In order to resolve this question further, the proton nuclear magnetic resonance (NMR) data of the hydrating cement pastes are analysed and discussed. This analysis shows that NMR data favour the osmotic model of cement setting.

Influence of additives on the thermostability of glucose oxidase

The influence of different additives (polyhydric alcohols, polyethylene glycol, and salts) on the thermostability of glucose oxidase at 60°C has been studied in aqueous medium. The results obtained show a stabilizing effect in the presence of polyhydric alcohols (ethylene glycol, glycerol, erythritol, xylitol, and sorbitol) and for most of the polyethylene glycol used. The influence of the monovalent ions on glucose oxidase thermostability can be correlated to the lyotropic series of Hofmeister. The thermal denaturation of glucose oxidase has been performed in a 97% deuterium water medium. In this medium, the enzyme was more stable and its half-life 2.6-fold higher than in normal water.

Revert and direct Liesegang phenomenon of silver iodide: Factors influencing the transition point

The experimental conditions for obtaining the revert type followed by the direct Liesegang rings of silver iodide in agar gel columns have been reported. The existing theories of Ostwald, Mathur, Shinohara, and Ross have been critically reviewed. A new theory based on the DLVO theory of stability of colloids has been proposed to explain the mechanism of revert and direct Liesegang phenomenon and the transition of revert to direct type. This theory takes into account the surface potential, the zeta potential, the zero point of charge and the reversal of charge of the sol particles. The factors influencing the transition point have been reported. The concentration and pH of the gel have a pronounced effect on the transition of revert to direct. The influence of different additives has been discussed. All the observations have been explained on the basis of the proposed theory.

Medium-pressure liquid chromatography of platinum metal ions on Spheron DEAE

Spheron DEAE (modified macroreticular hydroxyethylmethacrylate-ethylenedimethacrylate copolymer) was used for chromatographic separation and determination of Rh(III), Pd(II), and Pt(IV) in chloride medium. The most suitable composition of the mobile phase was looked for by studying the influence of hydrochloric acid concentration on the capacity ratios of the metal ions mentioned and on their resolution, as well as the influence of different additions to the mobile phase on the decrease of the high Pt(IV) retention. Using the photometric (UV) detection, the linear dependence was found up to following concentrations: Rh 200 mg l-1, Pd 2 g l-1, Pt 500 mg l-1. The detection limit was 23 ng Rh, 62 ng Pd and 96 ng Pt in 7 μl sample injected.The reproducibility of the determination was (as relative standard deviation for n = 3) 1-4%, relative error 0.7-7%.

Fragmentation and isomerization of [(CH3)2CHCHCH3]+ ions in gas-phase radiolysis

A study has been made of the influence of different additives on the radiolysis of gaseous mixtures of hydrogen, 3-methyl-but-1-ene and oxygen. In these systems the [(CH3)2CHCHCH3]+ ion is formed by proton transfer from the XH+ ion to the olefin. For X = H2 the secondary pentyl ion is formed with sufficient internal energy to decompose, producing mainly ethylene. When X is CO2, CH4, N2O or CO the secondary pentyl ion partially isomerizes into the tertiary pentyl ion. This isomerization has been investigated in the mixture of xenon, methane, 3-methyl-but-1-ene and nitric oxide between –10 and + 110°C. If it is assumed that the rate of isomerization (internal hydride-ion displacement) is a function only of the temperature, the measured activation energy of the process [(CH3)2CHCHCH3]+→[(CH3)2CCH2CH3]+ is Ea= 8.8 ± 0.4 kJ mol–1(2.1 ± 0.1 kcal mol–1 or 0.092 ± 0.005 eV).