Development of biodegradable conductive cotton yarns by in-situ polymerisation of pyrrole

Cotton yarns were modified with pyrrole in the presence of ferric chloride following a dip-nip-dry technique. Treatment of cotton with 23.4% aqueous pyrrole followed by treatment with 40.6% aqueous ferric chloride and subsequent drying in atmospheric air produced balanced improvements in the properties of the yarn such as conductivity, tensile strength and extensibility. Among the three types of yarns such as ring spun, rotor spun and friction spun considered for such treatment, ring spun yarn performed best in respect of conductivity and retention of strength. Examination of surface morphology of yarns by scanning electron microscopy revealed a common discontinuity in the growth of polypyrrole along the length of the yarns spun using friction spinning and rotor spinning systems. Such discontinuity was caused by the wrapper fibres. Ring spun yarn, on the other hand, allowed a continuous spiral growth and deposition of polypyrrole in the inter-fibre space and on the surface of the yarn. Study of pyrrole modified ring spun yarn in a typical photoluminescence system indicated photoluminescence property of such pyrrole-treated cotton yarn.     

Stability and Durability Study of Nano Pt Coated Titanium for Electrode Application

The present work involves development of noble metal nanoparticle coated Ti based electrode for application in severe corrosive environments. The etched Ti substrate was coated with noble metal nanoparticle via a seed mediated hydrothermal reduction method. Advanced surface characterization techniques elucidated that this two step synthesis method generated a uniform and highly dispersed nanoparticle coating on Ti which is essential for application in severe corrosive medium. The enhanced activity for methanol electro-oxidation compared to polycrystalline Pt proved the excellent electrocatalytic activity of as synthesized Pt nanoparticles coated Ti electrode. The adhesion strength of the coating on the Ti substrate was found to be excellent with a rank of 5A as per ASTM standard. The long term durability of Pt nanoparticles coated big cylindrical Ti mesh with 164 cm² surface area was tested by employing it as anode for electro-oxidation of Ce in 11.5 M nitric acid under an applied operational current density of 9 mA/cm² for 1000 h. Only 1 V increment was observed even after 1000 h confirming the excellent durability of this electrode. SEM and elemental mapping of the surface of coated electrode after 1000 h exposure in severe corrosive nitric acid further confirmed uniform dispersion of Pt on the surface and absence of delamination.     

Corrosion and Passive Film Formation Studies on Modified 9Cr–1Mo Steel in Different Sodium Hydroxide Concentrations at Room Temperature and in Boiling Condition

Studies were carried out on modified 9Cr–1Mo steel to understand its corrosion as well as passive film characteristics in caustic environment. Potentiodynamic anodic polarization studies were carried out in 1–8 M sodium hydroxide solutions at room temperature (RT) and in boiling conditions. The specimens were passivated at 0.0 V(SCE) for 1 h in 3 and 8 M sodium hydroxide solutions at RT as well as in boiling condition. Laser Raman spectroscopic (LRS) analysis was carried out to examine the nature of oxides/hydroxides formed on the surface of the specimens. Corrosion rates increased by one order of magnitude whereas passive current density increased by almost two orders of magnitude in boiling solution compared to the RT values. Appearance of only maghemite (γ-Fe₂O₃) peaks in passivated steel in 3 M sodium hydroxide solution at RT compared to that in the 8 M sodium hydroxide solution, which showed Fe(OH)₂, maghemite, magnetite, goethite (α-FeOOH) and CrO(OH), Cr₂O₃ peaks, indicated corrosion attack on the outer layer of the passive film. The passivated steel specimens in 3 and 8 M boiling solutions showed maghemite, magnetite, goethite, hematite (α-Fe₂O₃) (only in 8 M) and extremely weak peaks of Cr(OH)₃ and Cr₂O₅. These observations indicated dissolution of the outermost part of the passive film with superficial attack on the inner part of the passive film exposing Cr oxide/hydroxides in boiling 3 M solution. However, passivated steel in 8 M solution showed molybdenum oxides, apart from the other iron and chromium oxides/oxyhydroxides. The scanning electron microscopic (SEM) studies on the morphology of the corrosion products along with LRS analysis/characterization confirmed these observations. These results showed increased corrosion attack during passivation with increase in concentration of alkali and temperature.     

Standard Gibbs energy of formation of Mo3Te4 by emf measurements

The emf of the galvanic cells Pt, Mo, MoO₂¦8 YSZ¦‘FeO’, Fe, Pt (I) and Pt, Fe,‘FeO’ ¦8 YSZ¦MoO₂, Mo₃Te₄, MoTe₂(), C, Pt (II) were measured over the temperature ranges 837 to 1151 K and 775 to 1196 K, respectively, using 8 mass% yttria-stabilized zirconia (8 YSZ) as the solid electrolyte. From the emf values, the partial molar Gibbs energy of solution of molybdenum in Mo₃Te₄/MoTe₂(), was found to be

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. Using the literature data for the Gibbs energy of formation of MoTe₂(). the expression ΔG°_f(Mo₃Te_4,s) ± 5.97 (kj/mol) = −253.58 + 0.09214T(K) was derived for the range 775 to 1196 K. A third-law analysis yielded a value of −209 ± 10 kJ/mol for ΔH°_f.298^o of Mo₃Te₄(s).     

Development and Control of Bacterial Biofilms on Dairy Processing Membranes

Membrane fouling is a major operational problem that leads to reduced membrane performance and premature replacement of membranes. Bacterial biofilms developed on reverse osmosis membranes can cause severe flux declines during whey processing. Various types of biological, physical, and chemical factors regulate the formation of biofilms. Extracellular polymeric substances produced by constitutive microflora provide an effective barrier for the embedded cells. Cultural and microscopic techniques also revealed the presence of biofilms with attached bacterial cells on membrane surfaces. Presence of biofilms, despite regular cleaning processes, reflects ineffectiveness of cleaning agents. Cleaning efficiency depends upon factors such as pH of the cleaning agent, temperature, pressure, cleaning agent dose, optimum cleaning time, and cross‐flow velocity during cleaning. Among different cleaning agents, surfactants help to prevent bacterial attachment to surfaces by reducing the surface tension of water and interfacial tension between the layers. Enzymes mixed with surfactants and chelating agents can be used to penetrate the biofilm matrix formed by microbes. Recent studies have shown the role of quorum‐sensing‐based cell‐to‐cell signaling, which provides communication within bacterial cells to form a mature biofilm, and also the role of applying quorum inhibitors to prevent biofilm formation. Major cleaning applications are also summarized in Table 1 .     

Molten Salt Corrosion Resistance of Yttria Stabilized Zirconia Coating with Silicon Carbide Interlayer on High Density Graphite

The high temperature corrosion behaviour of yttria stabilized zirconia (YSZ) coated high density graphite (HDG) with and without SiC interlayer was evaluated in LiCl–KCl molten salt at 600 °C. The YSZ coated HDG samples without interlayer were tested for 50, 250, 1000 and 2000 h and the YSZ coated HDG samples with SiC interlayer were studied for 50, 500, 2000 and 3500 h durations. Characterisation of the corrosion tested samples revealed no delamination or failure of the YSZ coating in both the cases, and insignificant weight gain was observed in all the tested samples in the molten salt. The lamellar morphology of the plasma spray coating was intact even after exposure to molten salt for long duration, implying no corrosion attack of the coating and HDG in the molten salt. SEM cross-section examination confirmed neither coating degradation, nor penetration of molten salt into the HDG substrate. X-ray diffraction and Laser Raman spectroscopic analyses ascertained that no phase change occurred in YSZ after the long exposure in molten salt. Present study confirmed the phase stability and durability of YSZ coating in providing corrosion resistance and protection to HDG for high-temperature molten salt applications.     

Evaluation of Thermal Spray Alumina Coatings on Nickel Electrode Connector for Reprocessing Applications

Electro-oxidative dissolution of the spent mixed oxide nuclear fuels with high plutonium content from prototype fast breeder reactor need to be carried out in boiling 11.5 M HNO₃. Nickel electrode connectors employed in the electrolyser of the dissolver should possess good corrosion resistance as well as good electrical conductivity. Alumina coating deposited on Ni by plasma spraying was evaluated by electrochemical polarization and impedance experiments in 11.5 M HNO₃ at room temperature. In order to improve corrosion resistance, alumina coating relatively denser than plasma spray coating was deposited over Ni by detonation gun (D-gun) spray coating. This alumina coating exhibited a high insulation resistance and the weight loss of alumina coated Ni disc was only 3% compared to 29% for bare Ni disc sample when exposed to the vapour of 11.5 M boiling HNO₃ for 12 h. However, coating delamination observed at the alumina/bond coat interface was attributed to the penetration of HNO₃ vapour through the pores in the coating. Since alumina coating deposited by D-gun technique over Ni was also found to offer only short-term protection against corrosion due to HNO₃ vapour, monolithic dense alumina sleeve fabricated through powder metallurgy route was recommended instead of coating, for better corrosion protection in HNO₃ vapour compared to thermal spray coating.