Search

Failures of bushing caused by corrosive sulfur has gradually appeared in recent years. Apart from copper and sulfur, certain amount of aluminum was also found both in oil and paper after disassembling. The corrosion mechanism of the aluminum foil and its effect on oil-paper insulation were unknown. In this study, series of sulfur corrosion experiments were taken to investigate the sulfur corrosion of aluminum foil. The results showed the aluminum foil could certainly be corroded in oil containing corrosive sulfur (DBDS). Thermal products of insulting paper triggered the corrosion by removing the alumina film on the surface. Then, the contact corrosion occurred between aluminum and DBDS. In addition, the mechanisms of corrosion products generation both in oil and on paper were studied. The corrosion products in oil was DBDS-Al(3,4) and that on paper was RCOOAln. It caused the decrease of electrical properties of oil-paper. Particularly, the dielectric loss of oil and paper were dramatically enhanced.

Made available in DSpace on 2018-12-11T17:37:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-11-05 A simple, fast, low-cost, portable, and eco-friendly method using a spot test on a paper platform, together with diffuse reflectance spectroscopy, was developed and validated for the quantification of aluminum hydrochloride, a potential neurotoxic agent, in antiperspirant samples. The determination of aluminum hydrochloride was performed at a wavelength of 615 nm, by measuring consumption of the purple colorimetric reagent Alizarin S, due to reaction with aluminum. The linear range was from 10.0 to 125.0 mg L−1 and could be described by the equation: AR = 0.4479 − 0.002543 CAl (R = 0.999). The limits of detection (LOD) and quantification (LOQ) were 3.06 and 10.2 mg L−1, respectively. The method was specific, accurate, and repeatable, with relative standard deviation (RSD)

Inorganic fillers are usually used in papermaking industry to reduce production costs and enhance paper optical properties. As an attempt to improve fillers application in papermaking, carboxymethyl cellulose (CMC) and poly aluminum chloride (PAC) were used to encapsulate precipitated calcium carbonate (PCC) filler and modify its surfaces. In the first step, the optimum conditions for filler treatment (i.e. pH, CMC and PAC contents) were obtained. Through the second step, different amounts of CMC-encapsulated PCC were added to fiber suspension and some hand-sheets were made. Then, the effect of modified filler addition in different levels of 20, 25, and 35% on mechanical and optical properties of paper was investigated. The PAC dosage was found to be a critical factor for effective encapsulation of PCC fillers by carboxymethyl cellulose. When the dosages of CMC and PAC were 4% and 0.8% (based on the dry weight of PCC), respectively, filler modification caused to improve significantly the retention by more than twice. Strength properties of the hand-sheets fabricated with the CMC/PAC-modified PCC were also found to be significantly better than those obtained with the unmodified PCC at similar levels of filler content. In addition, the brightness and opacity of the filled papers at 30% addition of CMC-modified fillers were strikingly enhanced to 88,45 and 77%, respectively. SEM observations of the filled papers also demonstrated that CMC-encapsulated filler particles were clustered and retained efficiently onto the fiber network. The present method for modification of PCC may provide an alternative approach to increase the filler amount in the paper structure by alleviating filler drawbacks.

A simple field method for determination of fluoride in drinking water using handmade fluoride reagent paper impregnated by aluminium quinalizarin complex was developed. Fluoride reacts with the impregnated reagent paper to release the free ligand with new colour, orange different from that of the complex. The change in the colour, which is proportional to the amount of fluoride, was measured by the Arsenator. The functionality of the Arsenator which is based on a photometric measurement of spot on the reagent paper is expanded to analyse fluoride. The method allows a reliable determination of fluoride in the range 0.0–2.0 mg L−1. Further spectrophotometric determinations of fluoride showed that Beer’s law is obeyed in the range of 0.3–5.0 mg L−1 at 553 nm. Sensitivity, detection limit, quantitation limit, and the percentage recovery of 1.5 mg L−1 fluoride were found to be 0.117 μg mL−1, 0.1 mg L−1, 0.3 mg L−1, and 101.2 respectively.

The base handsheets were prepared from a pulp suspension containing either aluminum sulfate (alum) or polydiallyldimethylammonium chloride (PDADMAC), followed by being soaked in the chloroform solution of stearic and palmitic acids (SPA), which were brominated, or non-brominated, at the α-carbon positions adjacent to respective carbonyl groups. No sizing effect was observed in the absence of alum or PDADMAC, and thus these additives that form anchor sites for size components were indispensable for sizing appearance. Besides, extremely different sizing responses were found, strongly depending on the combinations of fatty acids and additives. Alum-treated handsheets showed good sizing effects by dipping them in an SPA⁄chloroform solution; however sizing with 2-brominated SPA (Br-SPA) had no contribution to sizing appearance. By contrast, PDADMAC-handsheets sized with Br-SPA exhibited high sizing degrees, although there was no sizing effect in the case of using non-brominated, original SPA. Highly sensitive sizing responses would provide a new insight to elucidate paper sizing mechanisms.

Carbon fiber papers supported Ag catalysts (Ag/CFP) with different coverage of electro-active site are prepared by electrochemical deposition and used as binder free cathodes in primary aluminum-air (Al-air) battery. Scanning Electron Microscopy and X-ray Diffraction studies are carried out to characterize the as-prepared Ag/CFP air cathodes. Oxygen reduction reaction (ORR) activities on these air cathodes in alkaline solutions are systematic studied. A newly designed aluminum-air cell is used to further determine the cathodes performance under real operation condition and during the test, the Ag/CFP electrodes show outstanding catalytic activity for ORR in concentrated alkaline electrolyte, and no obvious activity degradation is observed after long-time discharge. The electrochemical test results display the dependence of coverage of the electro-active Ag on the catalytic performance of the air cathodes. The resulting primary Al-air battery made from the best-performing cathode shows an impressive discharge peak power density, outperforming that of using commercial nano-manganese catalyst air electrodes.

The aging behavior of transformer insulation Kraft paper aged in a natural ester oil, recently developed from palm kernel oil, is compared to the behavior of paper samples aged in mineral insulating oil. This study aimed to investigate the effect of the natural ester oil on the aging of cellulose insulation paper if used as an alternative insulating fluid in transformers. Thermally upgraded insulation paper was aged in both insulating fluids together with strips of galvanized steel, copper and aluminium to represent the transformer, under nitrogen pressure in a sealed mild steel pressure vessel for 150 degC for 28, 56, and 84 days. The degradation after aging was assessed using tensile strength and breakdown strength measurements of the paper. The paper samples impregnated with natural ester fluid exhibited similar behavior before and after aging, with an approximately 5% reduction in tensile strength after 28 days of ageing. Two sets of response were obtained for paper samples aged in mineral insulating oil under the same ageing conditions; the paper closer to the copper strips had a faster degradation rate (~35% reduction). The natural ester fluid retarded the aging of the Kraft paper. The characteristic breakdown strength of natural ester impregnated paper was found to be, on the average, 42% better than that of mineral oil impregnated paper.

The fabrication process of anodic aluminium oxide (AAO) on a paper-based substrate is challenging because the use of a highly economical, conformable and ecological substrate. This process is based on a simple, cost-effective, self-ordering anodization of aluminium, which yields a vertically aligned and a highly ordered nanoporous structure. The manufacturing process on a flexible substrate with the use of phosphoric acid is described, and a capacitive sensor produced on this layer is investigated versus the humidity concentration and the frequency. The AAO morphology and the structure obtained were analysed, and the electrical properties of the sensing layer were investigated, using a 4192A LF network analyser in a climatic chamber. The surface conduction mechanism and the effect of humidity on the dielectric properties of a porous anodic aluminium oxide are discussed.