Mohini Saxena

Plant Fiber — Industrial Waste Reinforced Polymer Composites as a Potential Wood Substitute Material

This investigation deals with the property characterization and utilization of abundantly available and renewable resources of plant fibers such as jute and sisal. These plant fibers along with industrial wastes (fly ash and red mud) have been used for synthesizing value added composite materials. Relevant engineering properties such as physical and mechanical, resistance to abrasive wear, weathering and fire, etc., of the plant fiber reinforced polymer matrix composites so synthesized were characterized. The characteristics of conventional wood and other commercially available potential candidate building materials were also compared to assess the application potential of the newly developed materials vis-a-vis their conventional counterparts. The study reveals that the developed polymer—natural fiber—industrial (inorganic) waste composites attain far superior mechanical properties and resistance to abrasive wear, fire, water absorption, weathering, and chemical attack, as compared to their conventional counterparts such as wood, medium density fibre (MDF) boards, particle board, etc. The versatile material system so developed has potential for wood substitute applications like door shutters, flooring tiles, roofing sheets, partitions, etc., and is envisaged to significantly contribute towards forest conservation and environmental protection. The study strongly suggests that the newly developed plant fiber and/or industrial waste reinforced polymer composite materials are quite capable to serve as a potential cost and energy effective, technologically viable, and attractive substitute to the conventionally used wood and other identical materials. The study gains significance from the fact that earlier investigators have focussed their attention mainly towards exploring the use of chopped (sisal), and textile (jute) composites for different engineering applications including building while the present study examines the suitability of abundantly available natural fibers such as sisal and jute in the presence of otherwise harmful industrial wastes like red mud and fly ash for synthesizing polymer-based composites. This is followed by assessing the potential of the developed composite materials as a cost and energy effective wood substitute for building applications.

Corrosion behaviour of squeeze-cast aluminium alloy-silicon carbide composites

The corrosion behaviour of squeeze-cast Al alloy (LM11) separately dispersed with 10 vol% SiC fibres and SiC particles was investigated in 3% aqueous NaCl solution by general corrosion as well as potentiodynamic polarization techniques. Erosion-corrosion tests were also performed on the specimens in the solution. The base alloy was also subjected to identical tests to examine the influence of the presence of SiC in the matrix. The base alloy showed a lower corrosion rate than the composites. Furthermore, the alloy containing SiC fibres showed a higher corrosion rate than the one with SiC particle dispersion. Erosioncorrosion tests indicated that the rate of material loss followed a trend similar to that in other corrosion tests. The material loss was significantly higher in the case of erosion-corrosion tests. In addition to pitting and attack at the CuAl2 precipitate-Al interface in the matrix, dispersoid-matrix interfacial attack by the corrosion medium was also observed in the case of composites. On the other hand, erosion-corrosion revealed occasional partial removal of the dispersoid due to the impingement of the electrolyte. The tendency of the dispersoid removal by the impinging electrolyte was predominantly more in the case of the composites dispersed with SiC fibres. Results are explained in terms of the interfacial bonding as well as the shape of the dispersoid.

Corrosion characteristics of cast aluminum alloy—3 wt% graphite particulate composites in different environments

The corrosion behaviour of cast aluminum alloy (LM 13)—3 wt% graphite particulate composite has been investigated in oil and marine environments by a weight loss method. The room temperature corrosion behaviour of this composite has also been studied by potentiodynamic polarization measurements in sea water. Results have shown that in a marine environment, the rate of corrosion of particulate composite is higher than the base alloy and aluminum. The high corrosion rate of particulate composite in marine environment is possibly due to the graphite particles being cathodic relative to the matrix thus leading to galvanic corrosion in the presence of an electrolyte. However, this particulate composite did not show any sign of corrosion in the engine oil SAE-40 (fresh and used) at 150°C, indicating that it can safely be used in this environment.

Erosion and corrosion characteristics of an aluminium alloy-alumina fibre composite

Abstract The present paper describes the erosion-corrosion behaviour of an aluminium alloy (BS: LM 5) and its composite containing 10 vol.% alumina fibres. Tests were performed in 3% NaCl solution with and without sand particles (10 wt.%) using the rotating sample method. Salt immersion and potentiodynamic polarization studies of the specimens were also carried out in 3% NaCl solution. Both the tests showed increased weight loss with test duration. The composite suffered from more material loss than the base alloy. The erosion-corrosion test revealed a significantly higher extent of weight loss in the specimens as compared to the immersion test in an identical electrolyte (3% NaCl). Corrosion of the samples proceeded by the breaking-off of the oxide layer followed by nucleation of micropits and crater formation. Further, the composite suffered from additional attack by the electrolyte at the dispersoid-matrix interfaces. The potentiodynamic study indicated only a nominal shift in the corrosion potential of the composite, while a considerable increase in the corrosion current density of the base alloy was observed due to the incorporation of Al 2 O 3 fibres. The presence of the alumina fibres in the matrix alloy increased the susceptibility of the composite towards pitting (at the fibre-matrix interface). In erosion-corrosion tests, weight loss of the samples was accelerated by the impingement of the electrolyte at corroded sites leading to easy removal of corrosion products from the surface. The presence of sand particles in the electrolyte further accelerated the process of material removal due to rapid formation of pits and craters and (partial) removal of alumina fibres from the surface. Four stages of erosion-corrosion, namely (1) incubation period, (2) accelerated erosion-corrosion, (3) deceleration period and (4) steady state material loss, were observed during the erosion-corrosion tests.

Characteristics Variation of Coal Combustion Residues in an Indian Ash Pond

Coal-fired power plants all over the world are cited as one of the major sources that generate huge quantities of coal combustion residues (CCRs) as solid wastes. Most frequently CCRs are collected through electrostatic precipitators, mixed with bottom ash by hydraulic systems and deposited in ash ponds. The quality of the CCRs at different locations in one of the ash ponds in Central India was evaluated to understand the variation in characteristics with a view to effective utilization. Results revealed that the presence of fine particles (< 50 μm) increased with increasing distance from the ash slurry inlet zone in the ash pond. Wide variations in the bulk density (800-980 kg m-3), porosity (45-57%) and water-holding capacity (57.5-75.7%) of CCRs were recorded. With increasing distance the pH of the CCRs decreased (from 9.0 to 8.2) and electrical conductivity increased (from 0.25 to 0.65 dS m-1). The presence of almost all the heavy metals in CCRs exhibited an increase with distance from the ash slurry discharge zone due to the increase in surface area (from 0.1038 to 2.3076 m2 g-1) of CCRs particles. The present paper describes the variation of characteristics of CCRs deposited in the ash pond and their potential applications.

Corrosion characteristics of aluminium alloy graphite particulate composite in various environments

The present study was aimed at understanding the response of 2014 Al alloy dispersed with graphite particles in various corrosive environments. Marine (sodium chloride) as well as acidic media were selected for the purpose with a view to widen the range of utility of the composite for applications where such environments may be encountered. Studies were also extended to characterize the corrosion resistance of the composite in fresh as well as used lubricating oils to explore the possibilities of using it in bearing, bushing and such other applications. The corrosion behaviour of the base alloy processed under identical conditions was also examined in the above media to see the influence of graphite addition in the alloy. In order to assess the role of the matrix microstructure, the composite as well as the base alloy was subjected to corrosion in heat-treated as well as-cast conditions. It was observed that the specimens suffered from the maximum rate of corrosion in acid, while sodium chloride produced the minimum corrosion rate. Oil in both used and fresh conditions revealed a negligibly small extent of corrosion. The composite was found to show a higher rate of corrosion than the base alloy under identical test conditions. This was attributed to the dispersoid/matrix interfacial corrosion in the case of the graphitic aluminium alloy. Heat treatment of the composite and the base alloy was found to lower the rate of corrosion in the environments tested. Microstructural modifications of the matrix and possible relief of residual stresses were thought to be responsible for the lower rate of corrosion in the heat-treated condition.

BSL-based coatings for bamboo protection

Bhilawanut shell liquid is a natural product, and because of its phenolic nature it undergoes reactions similar to those of phenol. Surface coatings based on BSL were prepared from formaldehyde, styrene, hexamine, and epichlorohydrin for the protection of bamboo surfaces. BSL-based coatings were applied on bamboo and the performance of these coatings was evaluated by accelerated and chemical resistance tests. It was observed that these coatings can be used for the protection of bamboo from corrosive environments.

Corrosion behaviour of sintered 6061 aluminium alloy-graphite particle composites

The corrosion behaviour of sintered 6061 aluminium alloy and its composite dispersed with 7.0 vol% graphite particles is described. Techniques, namely immersion, tafel and impedance, were employed to study the corrosion behaviour. Immersion tests were performed in different media, namely HCl, NaCl and lubricating oil (used and fresh) while tafel and impedance tests were performed in 0.1 N HCl and 3% NaCl solution. Corrosion behaviour was monitored by measuring the weight change in immersion studies and corrosion current, icorr, in tafel and impedance tests. The values of corrosion potential, Ecorr, and icorr were calculated from the tafel plots obtained at a scanning rate of 1 mV s−1. In impedance study, icorr was calculated from the value of polarization resistance, Rp, obtained from the Nyquist plot; the latter was obtained by merging the lock-in and FFT plots. Aluminium alloy and its composite suffered from corrosion in HCl and NaCl. However, the extent of severity was greater in the case of HCl. The icorr values obtained by the impedance method also revealed a similar trend. The higher corrosion rate of the alloy and composites in HCl was due to the dissolution of the thin oxide (protective) film in the solution. The decreased corrosion rate of the composite and the base alloy in NaCl was attributed to the formation of stable corrosion product, Al (OH)3, on the surface, which prevented further attack on the surface of the specimen. There was practically no evidence of corrosion attack on the alloy and the composite surface in used and fresh lubricating oil.

INTERFACIAL PHENOMENA OF PLANT MATERIALS AND INDUSTRIAL WASTE COMPOSITES FOR DEVELOPMENT OF NEW MATERIALS FOR HOUSING

The development of new cost effective plant based Building Materials including industrial wastes have been highlighted. Physical-mechanical properties of sisal fibre, ipomoea reeds, redmud, flyash cement/polymer/mud based composites for Rural and Urban housing were determined including study of interfacial phenomena leading to surface coatings of fibres/reeds thereby improving their performance and environmental resistance in the matrices. Key words: Fibres, Reeds, Coatings, Housing Material