High vacuum tribology of polycrystalline diamond coatings

Polycrystalline diamond coatings have been grown on unpolished side of Si(100) wafers by hot filament chemical vapour deposition process. The morphology of the grown coatings has been varied from cauliflower morphology to faceted morphology by manipulation of the growth temperature from 700°C to 900°C and methane gas concentration from 3% to 1·5%. It is found that the coefficient of friction of the coatings under high vacuum of 133·32×10^?7 Pa (10^?7 torr) with nanocrystalline grains can be manipulated to 0·35 to enhance tribological behaviour of bare Si substrates.     

Template-free synthesis of flower-shaped zero-valent iron nanoparticle: Role of hydroxyl group in controlling morphology and nitrate reduction

Well-dispersed single phasic flower-like zero valent iron nanoparticles have been synthesized under aerobic conditions using a facile approach without the addition of any additives or templates. The role of hydroxyl groups of polyhydroxy alcohols in controlling surface morphology of nanoparticles has been thoroughly investigated. The obtained nanoparticles have been characterized by TEM, FE-SEM, XRD and BET surface area analyzer. Electron microscopy analyses reveal that the solvent plays a pivotal role in determining the morphology of the particles. With increase in viscosity of the solvent, formations of ‘petal-like’ structures, which are joined at the center are formed. The nitrate removal efficiency of the iron nanoparticles synthesized in different solvents has been studied and it is seen that the “flower-like” iron nanoparticles were most active in the removal of nitrate. Experiments have been done by varying (i) nitrate concentrations, (ii) nanoparticle dose, and (iii) type of nanoparticles. The results conclude that highest removal efficiency (～100%) was achieved when the nanoparticle dose was 2.88 g/L, even for high nitrate concentrations up to 400 mg/L. The major highlight of this work is the fact that even though the nanoparticles synthesized in glycerol-water mixture have larger size in comparison to the other nanoparticles, still they remove the nitrates with highest efficiency.”     

Indus Water Treaty: the Negotiating Process

ABSTRACT

For many arid and semiarid countries, international water bodies are the only new additional sources of water that could be economically developed to meet their ever increasing water requirements. Agreements between cobasin countries are necessary if such sources are to be developed promptly and properly. While some attempt is now being made to develop laws of nonnavigable uses of international watercourses, regrettably not enough attention has been paid thus far to review the negotiating processes that have led to successful water treaties. The present paper is an analysis of the negotiating process that resulted in the Indus River Treaty between India and Pakistan.     

Leak-before-break analysis of Prototype Fast Breeder Reactor main vessel

In Prototype Fast Breeder Reactor, the core is immersed in a sodium pool contained within the main vessel (MV). There is an argon cover gas space over the sodium. Top Shield supports the control plug which houses important components such as Control and Safety Rod Driving Mechanism. A core support structure welded to the bottom of MV carries the Grid plate which in turn supports the fuel subassemblies. MV is a cylindrical shell with a bottom dished end and supported at the top. Double ended guillotine rupture of MV will lead to downward movement of the core, which is in effect equivalent to withdrawal of control and safety rod and thus causing a series safety concern. It is essential to demonstrate Leak Before Break (LBB) argument for MV. LBB argument is justified if leak detection is ensured with adequate margin on critical crack length corresponding to failure by tearing instability. The material of construction of MV is SS316 LN. Towards assuring the justification of LBB argument, an isolated 5 mm deep X 200 mm long semi elliptical flaw is taken as the initial flaw and analysed under fatigue loading. A through wall crack in the argon space can be detected by sampling the nitrogen in the annular space between MV and safety vessel surrounding it. Accordingly the detectable crack length is arrived at. The critical crack length is obtained considering stable tearing. More details of the analysis and justification of LBB argument as per RCC-MR Appendix A16 are presented in the paper.     

Electrospinning formaldehyde‐crosslinked zein solutions

In order to develop zein fibers with improved physical properties and solvent resistance, formaldehyde was used as a crosslinking reagent before spinning. The crosslinking reaction was carried out in either acetic acid or ethanolic HCl where the amount of crosslinking reagent was between 1 and 6%. Reactions were carried out at various times and temperatures. When carried out in acetic acid, the maximum amount of formaldehyde that could be used was 1.5% as gelation occurred at higher levels. In ethanolic HCl, 6% formaldehyde could be incorporated into zein. All solutions were successfully electrospun, producing predominantly ribbon and round fibers; the morphology was strongly dependent on solvent and spinning solids. The formaldehyde‐crosslinked zein fabrics had double the tensile strength of control fabrics. SDS‐PAGE analysis clearly showed crosslinking had occurred. Electrospun fabrics from all formaldehyde‐treated zein solutions required an additional heating step in order to be resistant to dissolution in acetic acid, a known very good solvent for zein. Copyright © 2011 Society of Chemical Industry     

Synthesis of visible light-active nanostructured TiOx (x < 2) photocatalysts in a flame aerosol reactor

Titanium dioxide is a wide band gap (3.2 eV) semiconductor which is photo-active when irradiated with UV light. For wider scale use of TiO₂ as a photocatalyst, its activity needs to be extended to the visible light region (constituting 45% of total incident solar energy). A diffusion flame aerosol reactor (FLAR) with an oxygen lean environment in the particle formation zone has been used to synthesize oxygen deficient titanium suboxide (TiO_x with x < 2) nanoparticles. Using a standard-based electron energy loss spectroscopy (EELS) technique, the non-stoichiometry (x in TiO_x) in the flame synthesized particles has been quantified with high accuracy (uncertainty less than 3%). Under an oxygen lean environment in the particle formation zone, the non-stoichiometry in the TiO_x particles is a function of the flame temperature. The value of x in the flame synthesized TiO_x nanoparticles is in the range of 1.88 < x < 1.94. Diffuse reflectance spectra confirmed that the oxygen deficient TiO_x particles absorbed visible light. Visible light activity of the TiO_x particles is demonstrated by photocatalytic degradation of methyl orange solution under visible light illumination.     

Experimental and FE analysis of submerged arc weld induced residual stress and angular deformation of single and double sided fillet welded joint

Submerged arc welding is well-known for its very high deposition rate and thus the capability to join very high thickness metal pieces in large structural applications. Fillet joints are mostly used in structural applications which can be extensively seen in shipbuilding, bridge construction, house buildings, automobile or any other large structures. Thermal stresses generates in a fusion welded joint due to high temperature gradient, which is the cause of the residual stresses upon cooling followed by the angular deformation and failure of the welded structure. As an effect of the thermal gradient, the induced longitudinal, transverse residual stress & angular distortion can vary in single sided and double sided submerged arc welded fillet joints, during designing & manufacturing welded structures which should be taken into account. The main objective of this paper is to quantify the amount of residual stresses and angular deformation in a fillet welding joint. An elasto-plastic thermomechanical model has been developed for predicting residual stresses. A comparison of the residual stress and angular deformation between single and double sided fillet weld joint has been made. The simulation results reveal that the amount of residual stress present in the single sided fillet weld is more and unbalanced in both side of the center of weld line compared to the double sided fillet weld and the predicted results have been matched with the experiments as well as published literatures.