Effect Of Alumina Concentration Research Articles

Effect of Alumina Concentration on Morphology, Wear, and Corrosion: Electroless Ni-W-P/Al2O3 Composite Coatings on Aluminum Surfaces

Effect of Alumina Concentration on Morphology, Wear, and Corrosion: Electroless Ni-W-P/Al2O3 Composite Coatings on Aluminum Surfaces

Evaluation of alumina nanoparticles concentration and stirring rate on wear and corrosion behavior of nanocomposite PEO coating on AZ31 magnesium alloy

The effect of electrolyte stirring rate and concentration of nanoparticles on alumina nanoparticles absorption in the coating fabricated by plasma electrolytic oxidation on magnesium substrate was investigated. Microstructure, corrosion resistance and wear behavior of the nanocomposite coating were analyzed by scanning electron microscopy (SEM), potentiodynamic polarization and electrochemical impedance spectroscopy, and pin-on-disk tests, respectively. The results showed that the highest amount of nanoparticle absorption happened at the stirring rate of 100rpm, and decreased at higher stirring rates because of the high turbulence of the electrolyte, which washes the nanoparticles away from the surface of the anode. The effect of alumina concentration in the electrolyte on the alumina nanoparticles' absorption was also analyzed, and the results indicated that by increasing the concentration of nanoparticles in the electrolyte, the absorption of nanoparticles increased up to 30g/L, and then reached the saturated level. Also the best corrosion resistance the lowest wear rate was obtained in the stirring rate of 100rpm at a concentration of 30g/L of alumina nanoparticles.

How deposition parameters affect corrosion behavior of TiO2-Al2O3 nanocomposite coatings

Titania-Alumina coatings were grown on titanium substrates by Eectrophoretic Enhanced Micro Arc Oxidation (EEMAO) technique in electrolytes containing various concentrations of alumina nanoparticles. The effect of concentration of alumina on surface morphology, phase composition, microhardness, and corrosion behavior was investigated at different voltages. It was found that the impact of alumina concentration on microstructure actually depends on the voltage and its effects gets more conspicuous at intermediate and high voltages. A finer morphology was obtained at higher concentrations of alumina at a constant voltage. The coatings mainly consisted of anatase and rutile. Tialite was observed at 450V and 3gl−1 alumina. The formation kinetics and thermodynamics of the tialite phase was studied. In all voltages, samples prepared in an alumina-rich electrolyte showed a higher surface hardness. The nanocomposite coatings exhibited an enhanced corrosion resistance compared to the titanium substrates where the effect of alumina concentration became more tangible when the voltage exceeded a critical value (350V). At 450V, the polarization resistance of the sample prepared in alumina-rich electrolytes was higher by 3 orders of magnitude compared to the coating prepared in the electrolyte containing 1gl−1 alumina. A processing-microstructure-properties correlation is established.

Cyanate ester–alumina nanoparticle suspensions: Effect of alumina concentration on viscosity and cure behavior

AbstractThe effect of alumina nanoparticles on the viscosity and curing behavior of a bisphenol E cyanate ester monomer suspension was investigated by rheometry and differential scanning calorimetry. The viscosity was found to increase with solids content and was fit well by the Mooney equation. Cure experiments indicate that alumina particles catalyze the curing of the suspensions. The viscosity reduction achieved at high particle loadings by the addition of benzoic acid was also investigated by nuclear magnetic resonance. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Strength and Notch Sensitivity of Porous‐Matrix Oxide Composites

The effects of matrix strength on the notched and unnotched tensile properties of a family of porous‐matrix oxide composites are examined both experimentally and theoretically. Experiments are performed on three composites, distinguished from one another by the amount of binding alumina within the matrix. Increases in alumina concentration produce elevations in unnotched tensile and shear strengths, but the benefits are offset by an increase in notch sensitivity. The degree of notch sensitivity is rationalized on the basis of a model that accounts for interactions between notch tip tensile and shear bands. The model predictions are cast in terms of the ratio of the notch length to a characteristic bridging length scale. These results, in turn, form the basis for a simple analytical formula for notched strength, accounting for effects of elastic anisotropy and finite sample size. The utility of this formula in predicting notched strength is assessed. Issues associated with bridging law shapes and bridging length scales are addressed. The effect of alumina concentration on notch sensitivity is discussed in terms of its influence on the bridging length scale, dictated by the interplay between the unnotched tensile strength, the longitudinal Young's modulus, the degree of in‐plane elastic anisotropy, and the fracture energy. The net result is a decreasing bridging length scale and hence increasing notch sensitivity as the matrix is strengthened with alumina.

Effect of alumina concentration on thermal and structural properties of mas glass and glass-ceramics

Effect of alumina concentration on thermal and structural properties of mas glass and glass-ceramics

Effect of alumina concentration on thermal and structural properties of mas glass and glass-ceramics

Magnesium aluminum silicate (MAS) glass samples with different concentrations of alumina (7.58 to 14.71 mol%) were prepared by melt and quench-technique. Total Mg content in the form of MgF2+MgO was kept constant at 25 mol%. MAS glass was converted into glass-ceramics by controlled heat treatment at around 950°C. Crystalline phases present in different samples were identified by powder X-ray diffraction technique. Dilatometry technique was used to measure the thermal expansion coefficient and glass transition temperature. Scanning electron microscopy (SEM) was employed to study the microstructure of the glass-ceramic sample. It is seen from X-ray diffraction studies that at low Al2O3 concentrations (up to 10.5 mol%) both MgSiO3 and fluorophlogopite phases are present and at higher Al2O3 concentrations of 12.3 and 14.7 mol%, fluorophlogopite and magnesium silicate (Mg2SiO4), respectively are found as major crystalline phases. The average thermal expansion co-efficient (αavg) of the glass samples decreases systematically from 9.8 to 5.5·10−6 °C−1 and the glass transition temperature (Tg) increases from 610.1 to 675°C with increase in alumina content. However, in glass-ceramic samples the αavg varies in somewhat complex manner from 6.8 to 7.9·10−6 °C−1 with variation of Al2O3 content. This was thought to be due to the presence of different crystalline phases, their relative concentration and microstructure.

Effect of alumina concentration on the incipience of the anode effect in aluminium electrolysis

The cause of the incipience of the anode effect in alumina reduction cells has long been a controversial issue. The most plausible interpretations are (i) an insufficient release of the gaseous phase from underneath the anode surface together with the action of diminished wettability and (ii) the depletion of oxygen-containing ions at the anode surface to result in the limiting current condition. It is shown by means of a mathematical model that each of these effects may be active. The predominant mechanism depends on the operational conditions. Theoretical results are compared with experimental data.

Effect of alumina concentration on the thermal diffusivity of dental porcelain

The importance of the thermal diffusivity of restorative dental materials is well established. The laser flash method first described by Parker et al. (1961) is widely used to determine the diffusivity of industrial materials but has not hitherto been reported in the study of dental materials. The effect of the crystalline alumina content of dental porcelains has been investigated using this technique which permits rapid and accurate measurement. Values of 1·45 mm 2/s and 0·66 mm 2/s were determined for a commercial aluminous core porcelain and a dentine porcelain respectively. Mixtures of core and dentine powders exhibited intermediate levels. Increasing the alumina content resulted in increased diffusivity. The highest value was determined for a new high strength aluminous core porcelain which yielded a diffusivity of 1·74 mm 2/s. This material was found to contain an increased concentration of alumina particles.