Passivity characteristics on Ni(Cr)(Fe)SiB glassy alloys in phosphate solution

AbstractPassivity characteristics of three nickel-metalloids glassy alloys (Ni92.3Si4.5B32, Ni82.3Cr7Fe3Si4.5B3.2 and Ni75.5Cr13Fe4.2Si4.5B2.8) and the immersion time effect on the corrosion resistance were carried out by AC and DC electrochemical methods and SEM and XPS analyses. The study also focused on the effect of H3PO4 concentration and its role on the corrosion rate, passivation ability of nickel base glassy alloys surface. The present investigation revealed (i) corrosion resistance of Cr-free alloy shows pseudo passivity at all examined H3PO4 concentrations, (ii) high corrosion resistance of Cr contains alloys due to the formation of protective layer of chromium oxyhydroxide on the surface which acts as a diffusion barrier against alloy dissolution, (iii) the negative resistance observed in the case Ni75.5Cr13Fe4.2Si4.5B2.8 alloy revealed the sudden transition of metal/solution interface from a state of active dissolution to the passive state

Pickering emulsions stabilized by coloured organic pigment particles

The possibility of stabilizing emulsions of water and non-polar alkane with pure, coloured organic pigment particles is explored. Seven pigment types each possessing a primary colour of the rainbow were selected. Their solubility in water or heptane was determined using a spectrophotometric method and their surface energies were derived from the contact angles of probe liquids on compressed disks of the particles. As expected, most of the pigments are relatively hydrophobic but pigment orange is quite hydrophilic. At equal volumes of oil and water, preferred emulsions were water-in-oil (w/o) for six pigment types and oil-in-water (o/w) for pigment orange. The emulsion type is in line with calculated contact angles of the particles at the oil–water interface being either side of 90°. Their stability to coalescence increases with particle concentration. Emulsions are shown to undergo limited coalescence from which the coverage of drop interfaces by particles has been determined. In a few cases, close-packed primary particles are visible around emulsion droplets. At constant particle concentration, the influence of the volume fraction of water (ϕw) on emulsions was also studied. For the most hydrophilic pigment orange, emulsions are o/w at all ϕw, whereas they are w/o for the most hydrophobic pigments (red, yellow, green and blue). For pigments of intermediate hydrophobicity however (indigo and violet), catastrophic phase inversion becomes possible with emulsions inverting from w/o to o/w upon increasing ϕw. For the first time, we link the pigment surface energy to the propensity of emulsions to phase invert transitionally or catastrophically.

On the use of nanocellulose as reinforcement in polymer matrix composites

AbstractNanocellulose is often being regarded as the next generation renewable reinforcement for the production of high performance biocomposites. This feature article reviews the various nanocellulose reinforced polymer composites reported in literature and discusses the potential of nanocellulose as reinforcement for the production of renewable high performance polymer nanocomposites. The theoretical and experimentally determined tensile properties of nanocellulose are also reviewed. In addition to this, the reinforcing ability of BC and NFC is juxtaposed. In order to analyse the various cellulose-reinforced polymer nanocomposites reported in literature, Cox–Krenchel and rule-of-mixture models have been used to elucidate the potential of nanocellulose in composite applications. There may be potential for improvement since the tensile modulus and strength of most cellulose nanocomposites reported in literature scale linearly with the tensile modulus and strength of the cellulose nanopaper structures. Better dispersion of individual cellulose nanofibres in the polymer matrix may improve composite properties

Modelling the Latex Spreading on Clay

In this manuscript a model was proposed in order to predict the extent of the latex spreading on clay pigment. The results from Scan Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) were used to evaluate the predicted results. A good agreement of the predicted results was found. Keywords: Latex, clay, coalescence, XPS, SEM Paper coatings generally consist of a pigment, a binder, and some additives. Their main objectives are to improve the optical and printing properties of paper. For many years, most of the research effort devoted to the subject of paper coating has been aimed at establishing relationships between the various coating process parameters (e.g. color composition and rheology, method of application, substrate properties, and finishing conditions) and the properties of the coated paper. While differences in the performance of coated papers have been attributed to structural differences, relatively little was known about the development or consolidation of coating structure and the binder-pigment interaction process. In order to avoid complications, researchers have made many attempts to understand only the latex film formation The effect of binder-pigment interactions was investigated with AFM in paint coatings In our earlier work [4] the evolution of surface structure and chemistry and the surface energy of wet-coalesced clay-latex coatings were followed. It was found that latex spreading rather than "binder migration" was responsible for the high styrene-butadiene (SB) area percent at the final stage of consolidation at the surface. Even at PVC as low as 40%, XPS results indicate that the surface is still heterogeneous and not covered totally with latex. Drying in the presence of water (wet coalescing) was compared to drying in the absence of water (sintering) for clay-latex coatings In this work a model is proposed for predicting the extent of latex spreading on clay pigment. The results from SEM and XPS were used to evaluate the predicted results. Experimental part Materials and methods The coatings were based on kaolin pigment (Premier ECC International) and SB latex binder (GENCORP Performance Chemicals Co.). Two carboxylated SB latices with low Tg (-3 o C) and high Tg (50 o C) were used. The Tg of the latex has been changed by altering the S:B weight percentage during emulsion polymerization. The higher the styrene content, the higher the carbon contents. Acrylic acid at the same level with both latices, was used as a monomeric acid. Very slight difference in C:O ratio between the two latex was reported. The C/O ratio of the low and the high Tg latex are 51.28/1 and 51.7/1, respectively. The surfactant used in these latices was sodium laurel sulfate. Both latices have a density of 1.02 g/ cm 3 , and they were supplied as emulsions, also they had the same level of carboxylation and similar particle sizes. The level of (internal) polymer cross linking changed by altering the level of chain transfer agent during emulsion polymerization. As provided by the manufacturer, the physical properties of the two SB latices are given below (table 1). The supplied particle size by the manufacturer was measured by Hydrodynamic Differential Fractionated (HDF). However, when SEM was used to examine the latex particle size, a smaller size was obtained. SB latex particle size was measured over a line of packed particles of high Tg latex after drying. SB particle size was obtained as 0.133 μm only. In order to prepare the coating layer, The clay pigment was first dispersed in water at 75% solids by weight, using 0.03 parts sodium polyacrylate (Dipex N-40) per hundred parts of pigments (pph). The dispersant amount of 0.03 pph was used because at this level a minimum in the measured viscosity of the clay suspension was observed, which is an indication of best pigment dispersion. The pH of clay suspension was adjusted between 8-9 with NH 4 OH. Later, coatings at 80% Pigment Volume Concentration (PVC) was prepared by mixing the clay and latex under a good agitation. In order to achieve smooth and applicable coatings the coating colors were further diluted to 60% solids by weight. The coating colors were applied with a lab coater (K303) on a non-absorbent polyester film (Mylar). The la