Synthesis, characterization and comparison of sediment electro-codeposited nickel-micro and nano SiC composites

Nickel-silicon carbide composites were produced using 1 μm and 50 nm size powders from a conventional Watt's bath using tetra methyl ammonium hydroxide as the surfactant. Sediment codeposition technique with horizontal electrodes was used. The effect of silicon carbide concentration and bath operating parameters on the volume percents and deposition rates of coatings obtained with the two different particles was studied. Substantial improvements in mechanical properties such as hardness, wear resistance, scratch resistance and roughness were obtained with the nanocomposite material, as compared with composites containing microsized particles.     

Performance evaluation of PVdF gel polymer electrolytes

A series of gel polymer electrolytes containing PVdF as homo polymer, a mixture of 1:1 Ethylene Carbonate (EC) : Propylene Carbonate (PC) as plasticizer and lithium-bistrifluoromethane sulphone imide [imide — LiN (CF₃SO₂)₂] has been developed. Amounts of polymer (PVdF), plasticizer and the imide lithium salt have been varied as a function of their weight ratio composition in this regard. Dimensionally stable films possessing appreciable room temperature conductivity values have been obtained with respect to certain weight ratio compositions. However, conductivity data have been recorded at different possible temperatures, i.e., from 20 °C to 65 °C. XRD and DSC studies were carried out to characterize the polymer films for better amorphicity and reduced glass transition temperature, respectively. The electrochemical interface stability of the PVdF based gel polymer electrolytes over a range of storage period (24 h – 10 days) have been investigated using A.C. impedance studies. Test cells containing Li/gel polymer electrolyte (GPE)/Li have been subjected to undergo 50 charge-discharge cycles in order to understand the electrochemical performance behaviour of the dimensionally stable films of superior conductivity. The observed capacity fade of less than 20% even after 50 cycles is in favour of the electrochemical stability of the gel polymer electrolyte containing 27.5% PVdF −67.5 % EC+PC −5% imide salt. Cyclic voltammetry studies establish the possibility of a reversible intercalation — deintercalation process involving Li⁺ ions through the gel polymer electrolyte.     

Synthesis of Amines by Reduction of Imines with the MCl2/NaBH4 (M = Co,Ni) System

A simple method for the synthesis of amines by the reduction of imines, anils and enamines, including some chiral substrates, with the MCl₂/NaBH₄/CH₃OH reagent (M = Co, Ni) in 64–82% yields is described.     

Ruthenium(II) complexes containing bidentate Schiff bases and their antifungal activity

The reactions of ruthenium(II) complexes, [RuHCl(CO)(PPh₃)₂(B)] [B = PPh₃, pyridine (py) or piperidine (pip)], with bidentate Schiff base ligands derived by condensing salicylaldehyde with aniline, o-, m- or p-toluidine have been carried out. The products were characterised by analytical, i.r., electronic, ¹H-n.m.r. and ³¹P-n.m.r. spectral studies and are formulated as [RuCl(CO)(L)(PPh₃)(B)] (L = Schiff base anion; B = PPh₃, py or pip). An octahedral structure has been tentatively proposed for the new complexes. The Schiff bases and the new complexes were tested in vitro to evaluate their activity against the fungus Aspergillus flavus.     

Regio- and diastereoselective synthesis of anticancer spirooxindoles derived from tryptophan and histidine via three-component 1,3-dipolar cycloadditions in an ionic liquid

A small library of novel hybrid spiroheterocycles containing spirooxindole, pyrrolidine and indole/imidazole moieties were synthesized with complete regio- and diastereoselectively in good to excellent yields from a three-component process starting from a series of variously substituted (E)-(2-nitrovinyl)benzenes, indoline-2,3-dione derivatives and l-tryptophan or l-histidine in an ionic liquid. The key step of this transformation is a 1,3-dipolar cycloaddition reaction involving a rare class of in situ-generated azomethine ylides derived from aromatic amino acids. The compounds thus synthesized were evaluated for their anticancer activity and were shown to inhibit the proliferation of FaDu cells, a human epithelial cell line isolated from a squamous cell carcinoma of the hypopharynx, via apoptotic cell death.     

Inhibitive properties of a phosphonate-based formulation for corrosion control of carbon steel

The aim of the present work was to study the corrosion inhibition of carbon steel using a ternary formulation. This new ternary inhibitor formulation, viz., 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), with zinc ions and silicate ions was used to protect carbon steel from corrosion in a low-chloride environment. The gravimetric studies showed that 96 % inhibition efficiency was achieved with the ternary system consisting of 50 ppm PBTC, 50 ppm Zn²⁺ ions, and 10 ppm silicate ions. Out of 0.310 mmol of Zn²⁺ ions, 0.218 mmol was diffused from the bulk of the solution to the metal surface, as revealed from the studies of the solutions by atomic absorption spectroscopy (AAS). Electrochemical methods (potentiostatic polarization and electrochemical impedance spectroscopy) and surface characterization techniques [Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), and atomic force microscopy (AFM)] were used to ascertain the nature of the protective film and for explaining the mechanistic aspects of corrosion inhibition.     

A simple,direct synthesis of Na2Fe(CO)4

Summary Reduction of anhydrous FeCl₃ in THF with sodium naphthalenide under a CO atmosphere at room temperature leads directly to Na₂Fe(CO)₄, which on reaction with alkyl bromides gives the corresponding aldehydes, ketones and carboxylic acids under appropriate conditions.     

Measurement of Orthogonal Stress Gradients Due to Impact Load on a Transparent Sheet using Digital Gradient Sensing Method

A full-field optical method called Digital Gradient Sensing (DGS) for measuring stress gradients due to an impact load on a planar transparent sheet is presented. The technique is based on the elasto-optic effect exhibited by transparent solids due to an imposed stress field causing angular deflections of light rays quantified using 2D digital image correlation method. The measured angular deflections are proportional to the in-plane gradients of stresses under plane stress conditions. The method is relatively simple to implement and is capable of measuring stress gradients in two orthogonal directions simultaneously. The feasibility of this method to study material failure/damage is demonstrated on transparent planar sheets of PMMA subjected to both quasi-static and dynamic line load acting on an edge. In the latter case, ultra high-speed digital photography is used to perform time-resolved measurements. The quasi-static measurements are successfully compared with those based on the Flamant solution for a line-load acting on a half-space in regions where plane stress conditions prevail. The dynamic measurements, prior to material failure, are also successfully compared with finite element computations. The measured stress gradients near the impact point after damage initiation are also presented and failure behavior is discussed.