Zincated Nanoclay Polymer Composites (ZNCPCs): Synthesis,Characterization, Biodegradation and Controlled Release Behaviour in Soil

Novel zincated nanoclay polymer composites (ZNCPCs) with variable percentage of commercial bentonite and nanobentonite (8%, 10% and 12% of monomer for each case) were synthesized. Polyacrylic acid-Polyacrylamide copolymer was synthesized using N, N-Methylene bisacrylamide as crosslinker and ammonium persulfate as initiator. Clays as well as ZNCPCs were characterized by XRD, SEM, TEM and FTIR. 12% nanoclay containing formulation showed slowest release rate. ZNCPCs containing 8% clay recorded highest Zn content as well as highest equilibrium water absorbency. Biodegradation study revealed that Aspergillus spp was more effective as compared with Trichoderma spp in degradation of ZNCPCs.     

Binding of the phenothiazinium dye methylene blue with single stranded polyriboadenylic acid

The binding of the phenothiazinium dye methylene blue to single stranded poly(riboadenylic acid) was investigated by spectroscopic and calorimetric techniques. The binding was cooperative and the affinity was of the order of 10⁶ M⁻¹ at 100 mM [Na⁺] as determined from absorbance, fluorescence and calorimetric studies. Ferrocyanide quenching studies showed intercalative binding of methylene blue to poly(riboadenylic acid). The binding perturbed the circular dichroism spectrum of poly(riboadenylic acid) with concomitant formation of prominent exciton split type of extrinsic CD bands in the 550-700 nm region. The interaction involved a single binding mode with a 1:2 binding stoichiometry. The binding affinity increased with [Na⁺] ion concentration in the range 10-200 mM [Na⁺]. Dye binding induced self-assembled duplex formation in poly(riboadenylic acid). The biological utility of the dye methylene blue in probing nucleic acid structure is revealed from these studies.     

Removal of Poly Aromatic Hydrocarbons (PAHs) from Water: Effect of Nano and Modified Nano-clays as a Flocculation Aid and Adsorbent in Coagulation-flocculation Process

Water treatment process involving simultaneous action of adsorption on different nano and organo-modified nano-clays followed by coagulation-flocculation by alum and poly aluminium chloride (PAC) has been evaluated for the removal of PAHs (naphthalene, acenaphthalene, phenanthrene, fluoranthene, anthracene, and pyrene) from water. When clay minerals along with alum and PAC were used for treatment, 37.4–100.0% removal of PAHs was observed compared to 20–38% removal using normal water treatment process with either alum or alum + PAC. The effectiveness of clay minerals for removal of PAHs followed the order (P < 0.05): halloysitenano-clay (HN-clay) < normal bentonite (NB-clay) < hydrophilic nano-bentonite (HNB-clay) < nano-montmorillonite modified with dimethyl dialkyl amine (DMDA-M-clay) ≈ nano-montmorillonite modified with octadecylamine and aminopropyltriethoxysilane (ODAAPS-M-clay) ≈ nano-montmorillonite modified with octadecylamine (ODA-M-clay) in combination with alum + PAC. The modified treatment process (alum + PAC + clay minerals), where water was initially treated with clays followed by normal process of coagulation (alum + PAC), was found to be the most effective method with maximum removal for ODAAPS-M-clay (97.7–100.0%) which is at par wih ODA-M (97.0–100.0%), and DMDA-M-clay (94.8–100%). The removal of PAHs varied in the order: naphthalene ≈ acenaphthalene > anthracene ≈ pyrene > phenanthrene > fluoranthrene. The treatment combination having the maximum removal capacity was also used eficiently for the removal of PAHs from natural and fortified natural water. This article demonstrated adsorption-coagulation integrated system has the potential to remediate PAHs polluted water.     

Characterization of Laser Remelted Plasma-Sprayed Mo Coating on AISI 1020 Steel

Plasma-sprayed molybdenum (Mo) coating was deposited on an AISI 1020 steel substrate. Laser remelting was used to eliminate the open pores and microcracks of the plasma-sprayed molybdenum coating. The quantitative investigation of porosity was carried out with the help of Biovis image analysis software. The microhardness was measured using a Vickers indenter. The influence of laser remelting on the wear volume loss of plasma-sprayed Mo was estimated by using a pin-on-disc wear test rig. The worn surface was characterized by scanning electron microscopy. The experimental results demonstrate that the porosity of the coating was decreased and microhardness was improved by laser remelting. The laser remelted plasma-sprayed Mo coating exhibits better wear resistance compared to the untreated plasma-sprayed Mo coating. It is concluded that laser remelting is a potential treatment for the plasma-sprayed coating. In this study, the laser remelted plasma-sprayed Mo coating exhibited of lowest porosity, higher hardness and better wear resistance.     

Wire Electro Discharge Machining Performance of TiNiCu Shape Memory Alloy

The study presents the effect of Wire Electro Discharge Machining (WEDM) system parameters on the Material Removal Rate (MRR), surface roughness and surface morphology of Ti ₅₀Ni ₄₅Cu ₅ SMA developed using vacuum arc melting. The WEDM parameters such as pulse on time, peak current, pulse off time and table feed were selected as control factors over MRR and surface roughness. The results reveal that the surface roughness and MRR increases with increased peak current, pulse on time and table feed but decreases slightly with pulse off time. Higher MRR was attained at 5Amps peak current and 70 μm/s table feed. Better surface roughness was obtained for a combination of lower pulse on time, peak current and table feed with high pulse off time. Surface defects such as recast layer, craters, micro–cracks, pockmarks and voids were found on the machined surface. The globule of appendages formed around the craters and the intensity of the crater was evident for the higher surface roughness with an increase in peak current and pulse-on time during WEDM.     

Enhancing the localised corrosion resistance of 316L stainless steel via FBR-CVD chromising treatment

The resistance of stainless steels to localised corrosion can be adversely affected by environmental and metallurgical heterogeneities existed in complex industrial infrastructures such as seawater desalination plants exposed to aggressive evnironments. It is therefore critical to enhance the localised corrosion resistance and understand the corrosion behaviour of stainless steels in complex and aggressive industrial environmental conditions. In this work, the localised corrosion resistance of chromised stainless steel 316L (SS316L) in simulated seawater desalination systems has been investigated by electrochemical and surface analytical techniques. It has been found that chromising processes have improved the localised corrosion resistance of SS316L by reducing its susceptibility to pitting, crevice, and welding zone corrosion in simulated seawater desalination environments. This increased corrosion resistance has been explained by electrochemical polarisation studies and surface analysis showing that the chromising treatment at 1050°C resulted in a continuous and stable chromium-enriched layer on the SS316L surface.