Nickel-based composite coatings containing ceramic particles as the distributed phase have been widely used in aerospace and automotive industries. In the present work, a Ni-composite coating containing nanosized monoclinic zirconia (ZrO2) powder is prepared by solution combustion (SC) method. The SC method is modified to get phase pure white zirconia powder by using the mixture of fuels approach. Since the synthesized powder contained agglomerated particles, the powder is ball milled and dispersed in a nickel sulphamate bath. The Ni and Ni-ZrO2 coatings are electrodeposited at 0.75 A/dm2 for 6 h. The Ni-ZrO2 composite coating exhibits a microhardness of 750 KHN(50 gf) as against 270 KHN(50 gF) observed for plain Ni coating. The Ni-ZrO2 coating exhibits improved corrosion resistance and wear resistance compared to plain nickel coating as confirmed by potentiodynamic polarization and continuous salt spray tests. The as-deposited hydrophobic Ni-ZrO2 coating transforms to superhydrophobic upon depositing a thin layer of fluoroalkyl silane on the coating. Thus, the synthesized zirconia particles when incorporated in the Ni matrix impart multifunctional properties to the electrodeposited Ni coating.
Copper sulphides (Cu2-xS) based chalcogenide materials have received voluminous consideration for supercapacitive energy storage with unique semiconducting properties, nontoxicity and extensive earth abudancy. The existence of Cu2-xS in discrete crystal geometries and morphology liberalizes opportunities to tune them for desired performances. Consequently, the understanding of the phase and morphology dependency on performances can be pivotal in building novel designs for enhanced power and energy delivery. Herein an in-depth recent literature investigation into the synthesis of diverse phases and morphologies of Cu2-xS nano/ microstructures and their super capacitive behaviours has been reported. Given the potent of Cu2-xS as highly efficient supercapacitive electrode as low cost material and their extensive deployment it is imperative to profoundly highlight the recent advances in Cu2-xS based electrode materials directed towards supercapacitive energy storage.
Hydrogels have established their utility in the field of biomedical science and technology including drug delivery and tissue engineering, among other applications. Crosslinking density critically affects the resultant physical property of the hydrogels. Here, we have successfully synthesized carboxymethylchitosan (CMC) and oxidized alginate (AA) from chitosan and sodium alginate, respectively. CMC and AA were used to fabricate CMC-AA-single network (CMC-AA-SNH) and CMC-AA-double network (CMC-AA-DNH) hydrogels. Crosslinking of CMC-AA-SNH was done by dynamic covalent bonding, that is, imine bond formation, whereas CMC-AA-DNH was crosslinked via covalent imine bond and Ca2+ mediated ionic interactions. Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR) studies were employed to characterize the components of the hydrogels. Effect of dual crosslinking over the single crosslinked hydrogel was extensively analyzed by rheological studies. Scanning electron microscopy revealed that the CMC-AA-DNH was more densely packed with interconnected structure than CMC-AA-SNH. Swelling study demonstrated that the degree of swelling of CMC-AA-DNH was significantly less than CMC-AA-SNH due to more crosslinking density. Compressive mechanical test of the hydrogels further indicated that CMC-AA-DNH exhibits fracture stress of 79.5 kPa. These results indicate how the physical and mechanical properties of a polymeric hydrogel system can be tuned through control of crosslinking, which have important implications for the use of these gels for biomedical applications.
Photoelectrochemical water splitting process for solar hydrogen production has attained great consideration due to acceptance of hydrogen as a sustainable and environmentally friendly energy carrier. The key functional components of a PEC cell are the semiconductor electrode and semiconductorelectrolyte interfacial junction. The semiconductor-electrolyte interface, the other crucial functional unit of PEC cell is rarely investigated. The nature of the charge carrier’s movement at the semiconductor/electrolyte interface is fundamental for the optimization of semiconductor electrode performance for efficient hydrogen generation. To understand the above processes at the interface, various techniques are being used to investigate the electrochemical reactions and photocatalytic response of a stable photoelectrode. In this review, the charge transfer kinetics and various methods used to investigate the e /h+ transfer processes at the semiconductor/electrolyte interface are reviewed and discussed.
This work illustrates the importance as well as major challenges related to the development of malleable metallic Au thin film micropattern on soft elastomeric film and then presents a fabrication technique to overcome these challenges for developing reliable, flexible electronic sensors and circuits. A self-assembled molecular adhesive layer has been introduced between the polydimethylsiloxane (PDMS) and the thin metal film to increase the adhesion and then analyzed the multilayer structure. The contact angle measurement showed that the introduction (3-mercaptopropyl) trimethoxysilane (MPTMS) molecular adhesive layer increases the hydrophilicity of the PDMS film for a more extended period and Au film on MPTMS coated PDMS shows superior film quality. The random buckles formed on the thin Au film have been successively manipulated using controlled heating after micropatterning. The SEM analysis of the Au thin film confirmed that the deposited film is granular and filled with nanogaps. The electrical characterization of the deposited showed that the sheet resistance of the metal thin is higher compared to the Au thin film on Si surface. This investigation is beneficial for realizing reliable, flexible electronic devices and circuits on soft polymer.
Epoxy coatings are the most used industrial coating system. While corrosion resistance through the barrier performance of the coating is well tested, the addition of multifunctionality is the new research objective. The responsiveness of the epoxy coating to the mechanical damage will not only add to its barrier performance but also delay the corrosion of the underlying metal. Such responsiveness of the coating is desired to manage the maintenance schedule. Various methods tested to add the “self-healing” attribute to the epoxy coatings are discussed. Surface modification to add hydrophobic character to the epoxy coating is also another functionality for value addition and is useful in many applications. For marine applications, fouling resistance is very important. Attempts made to develop anti-fouling epoxy coating are also reviewed. The brief review, giving a broad overview of the research trend, is intended to give a way forward in the development of the epoxy coating.
In international market, the price of precious metals is increasing rapidly due to increase in its demand. Limited natural resources, stringent environmental regulations and generation of huge amount of e-waste containing precious metals (Au, Ag, Pd, Pt) compels to develop feasible technology to recover metals from waste and save the environment from other hazardous substances present in such wastes. Present paper is focused on the recycling of precious metals (Au, Pd) from the printed circuit boards (PCBs) of e-waste. PCBs were de-soldered to separate the integrated circuits (ICs) and separated ICs were pulverized to get fine powder. The pulverized ICs were analysed and found to contain ∼0.8% Au, 0.01% Pd, 12% Cu along with plastics and ceramics. Leaching was carried out using nitric acid to dissolve Cu and Pd, leaving Au in the leached residue. Solvent extraction studies were carried out using 0.5% LIX84IC at low pH to selectively extract Pd leaving Cu in the raffinate. Further, using cementation/evaporation techniques, metal/salt of Cu and Pd were produced. The process developed is environment friendly and acts in accordancewith stringent environmental policy.
Residue (zinc dross) generated during galvanization of steel contains about >80 wt% zinc metal. In present paper, zinc powder is produced from zinc dross in an alkaline medium by electrolysis using zinc dross as a consumable anode. In an electrolytic cell various parameters such as current density, current efficiency, voltage and concentration of electrolyte etc. have been optimized. The electrolytic cell was operated at room temperature using 16 g/L Zn, 200 g/L NaOH at current density of 5 A/dm2. The current efficiency was found to be 90% and the purity of zinc powder is 99.5%. This process offers single step recovery of zinc in the form of powder from galvanizing waste.
The demand of composites is significantly increased in the 21st century which resulted in evolution of modern industries. The conventional monolithic metals and alloys in most of the applications are being replaced with the metal matrix composites (MMCs). The need of MMCs has been essential for the enhancement of properties or reduction of the cost of the manufacturing. In this era of light weight and high strength materials, the MMCs which are currently being used rapidly are Aluminummetal matrix composites (AMCs). The AMCs are not only successful in increasing the properties but also in reducing the cost of manufacturing sometime. The properties for which AMCs are found suitable for various applications are high specific strength, wear resistance, controlled coefficient of thermal expansion, corrosion resistance, good hardness, Ballistic resistance, and neutron absorbing capability with respect tomonolithic metal. In some AMCs these properties can even be maintained at elevated temperatures. This paper represents an overview of AMCs, their applications, strengthening mechanisms and processing techniques used to fabricate AMCs.
Hardfacing is a surface modification technique mostly utilized for the deposition of superior and hard materials on the surface of a substrate with the help of some suitable welding process. This technique is commonly used for improving the desirable surface characteristics, for example, erosion resistance, corrosion resistance, etc. of several engineering parts. In the present investigation, three different types of Fe-C-Cr based hardfacing alloys were deposited on the surface of ASTM A36 steel by using manual metal arc welding process in order to enhance its wear resistance. Sliding wear behavior of bare ASTM A36 steel specimens and hardfaced ASTM A36 steel samples were studied on a pin-on-disc wear tester. It was observed that the sliding wear behavior and performance of all the hardfaced specimens was found to be better than that of the bare ASTM A36 steel samples. The effect of the different hardfacings on the wear characteristics, behavior, performance and the extent of wear on ASTM A36 steel were thoroughly examined. The effect of varying the percentage composition of chromium from 23% to 33% and carbon from 3.5% to 4.5% in the different Fe-C-Cr based hardfacing electrodes on the resultant microstructure as well as the wear behavior of the deposited layers was studied. The comparison of cumulative wear rate (in Bowden) of all the hardfaced specimens with that of the bare ASTM A36 samples exhibited a considerable advancement in the wear resistance imparted by Fe-C-Cr based hardfacings over the ASTM A36 steel.
Compression tests were performed on Gleeble 3800 Thermo-Mechanical Simulator to study the flow properties of rotor grade steel 28CrMoNiV59. Compression specimens were deformed at a constant strain rate of 10-3 s-1. The temperature range during tests was between room temperature and 1000°C with an interval of 100°C. When the normalized flow stress was plotted as a function of temperature, it exhibited three different regions. In regions I and III flow stress decreases with increase in temperature but the same increases with temperature in region II. Microstructural changes and work hardening behaviour have been studied for the deformed specimen. Furthermore, TEM analysis was also done for the samples of these three different regions (I, II & III). Strain hardening rate as a function of the normalized flow stresses decreases at larger strain and become negligible at higher temperature.
Uni-axial hot compression tests were conducted at different temperatures(1173-1423 K) and at strain rates of 0.1, 1, 10 and 100/s using Thermo-mechanical Simulator (Gleeble-3500C System) on a 2.7% Si electrical steel to understand the hot workability issues associated with this steel during hot rolling. The flow curves obtained revealed dynamic recovery as the predominant softening mechanism at majority of hot deformation conditions except at lower temperature and high strain rate where work hardening was observed. However, the work hardening was not very prominent due to ferrite structure throughout the hot deformation temperature range established by Thermo-Calc software. Small amount of cementite (pearlite) transformed from austenite along prior ferrite grain was observed due to presence of carbon in excess of 0.02. Strain rate sensitivity varied within a narrow range of 0.18 - 0.21 with rising tendency with an increase in temperature.
Toxicity of industrial effluent is mainly due to the presence of heavy metals like Zn, Cd, Cr, Pb, As, etc. The treatment of these effluents will not only reduce environmental pollution but also conserve the natural resources. Present paper reports selective extraction and separation of zinc and chromium from the electroplating effluent (~15 g/L Zn and ~30 g/L Cr) using solvent extraction technique. Initial studies were carried out from synthetic solution containing Zn (1.78 g/L) and Cr (3.6 g/L) using 10% DE2PHA diluted with kerosene. Various process parameters viz. effect of pH, time, O/A ratio, loading capacity, etc. were studied and optimized. 98.17% Zn gets extracted in 5 min at equilibrium pH 2.5 maintaining O/A ratio 1. 10% H SO was used for stripping 2 4 the loaded organic. The optimum condition for extraction was validated with the original electroplating effluent supplied by M/s Sinha Electrochemical Plant, Jamshedpur, India. Complete extraction of Zn from the original effluent takes place in 5 min at an equilibrium pH 2.5 and phase ratio (O/A) 1, leaving 99% Cr in the raffinate. From the pure solution obtained, metal or salt could be produced by evaporation,precipitation, electrowinning, crystallization, etc.
The double-time thermal Green function method with the symmetric and antisymmetric decoupling scheme and modified pseudospin model proposed by Li and Qin for squaric acid have been used in present study to discuss the effect of electric field on some dielectric properties. Expressions for shift, width, soft mode frequency, dielectric constant, loss and transition temperature have been evaluated. By fitting model values of physical quantities in the theoretical expressions thermal dependence of antiferroelectric mode frequency, dielectric constant and loss have been calculated in presence of electric field in the vicinity of transition temperature. Theoretical results are similar to other antiferroelectric crystals.
India is a very important global player in the casting sector not only of cast iron but also of non-ferrous sector such as brass and bell metal. Melting furnaces of these are mainly coke based. There is also a growing awareness of pollution control levels in the country in recent times and this is a perceived as a threat to the existence of these small scale foundries including melting unit for casting for brass and bell metals scattered in various parts of the country. Attempt has been made to carry out research and development work on developing various modules eco-friendly furnaces concerning melting and of brass and bell metal casting/ product. This paper also discusses technoeconomical aspect of the mentioned coke based and coke less furnaces concerning brass and bell metal product.
Rail is the most important constituent of the track structure and plays a very vital role in the reliability of railway system as a whole. Quality of rail steel with reference to its chemical composition has been a matter of prime importance for the manufacturers as well as Railways. Sulphur is a detrimental element in rails since it causes hot shortness during rolling, centerline segregation during casting, poor weldability for the rails etc. To improve quality of rails, a substantially low range of sulphur < 0.015% (Railway's specified norms <0.03%) has been targeted in Bhilai Steel Plant by adequate sulphur control measures in steelmaking process. A two stage desulphurisation treatment is now employed in which the blast furnace hot metal is first treated by co-injection of Mg and CaC reagents, and subsequent treatment with a 2 synthetic slag former (CaO-Al O ) added to the ladle during tapping from the Basic 2 3 Oxygen furnace. Improvement in the internal quality of the cast bloom has been established by introduction of Electro Magnetic Stirring. The centerline segregation is minimized vis-a-vis the properties of the cast product and rails improved by the successful implementation of step by step control measures.
Foam-filled thin-walled structures have drawn considerable attention and been widely applied in automotive and aerospace industries for their significant advantages in a high energy absorption and light weight.Recently the application of foam filled square tube in automobile industries has taken hike because of crashworthiness characteristic of foams.In the present study, energy absorption capacity of the empty (aluminum and mild steel) and foam in-filled (various aluminum alloys) square tubes have been numerically evaluated under car hitting condition.The finite element method (FEM) is applied in modeling the empty and foam-filled square tubes.The results show that the foam-filled square tubes have outstanding energy absorption characteristics under all the conditions considered.Based on the study results, best combination of materials in shell column wall and in-filled foam has been recommended.
Three different Silanes were identified which are suitable for coating the copper alloy condenser tubes as Silane-I, Silane-II and Silane-III. These silanes are dissolved in Isopropanol/Methanol solvent and the PH is suitably adjusted with Glacial Acetic acid. The silane solutions of specified concentrations are then coated on the copper alloy samples and then dried. Then the coated samples are evaluated by electrochemical techniques like Tafel polarisation, Impedance technique etc in Sodium chloride solution. The corrosion resistances observed in all the cases without and with Silane coating are reported. Silane II worked more efficiently on all the three alloys. The impedance values also confirmed this.
The changing lifestyle and urbanization has led to increasing rate of consumption of electronic goods. The estimated life of such goods is 3–5 years and waste generated from such discarded products are e-waste. Generation of e-waste is growing exponentially in the developing countries. Increasing market penetration, large replacement market and high obsolescence rate make e-waste one of the fastest growing stream of wastes in developing countries. The developed countries on the other hand find it convenient and economical to export to India rather than taking any trouble to process the e-waste to generate any wealth from it. In India the main source of e-waste are manufacturers, government agencies, public and private companies and household etc. Such e-waste are dumped at sites and results in deposition in river beads, reservoir, landfills where toxic chemicals can reach out to water bodies contaminating the drinking water. This e-waste can affect the wild life also,. Moreover in the times to come there will be severe space problems to dump such e-waste. It is, therefore, the need of the hour to have an eco-friendly e-waste disposal where approach should be scientific supported by strong technological cost-effective process and Government regulations. The paper highlights the definition of e-waste; current system of generation, collection and disposal of e-waste; its impact on environment; e-waste recycling technologies used by formal as well as informal sectors in India vis-a-vis internationally; available regulations in India and other countries; recommended action plans to mitigate the problem.
