Characterisation of Ceramic-Coated 316LN Stainless Steel Exposed to High-Temperature Thermite Melt and Molten Sodium

Currently, stainless steel grade 316LN is the material of construction widely used for core catcher of sodium-cooled fast reactors. Design philosophy for core catcher demands its capability to withstand corium loading from whole core melt accidents. Towards this, two ceramic coatings were investigated for its application as a layer of sacrificial material on the top of core catcher to enhance its capability. Plasma-sprayed thermal barrier layer of alumina and partially stabilised zirconia (PSZ) with an intermediate bond coat of NiCrAlY are selected as candidate material and deposited over 316LN SS substrates and were tested for their suitability as thermal barrier layer for core catcher. Coated specimens were exposed to high-temperature thermite melt to simulate impingement of molten corium. Sodium compatibility of alumina and PSZ coatings were also investigated by exposing samples to molten sodium at 400 °C for 500 h. The surface morphology of high-temperature thermite melt-exposed samples and sodium-exposed samples was examined using scanning electron microscope. Phase identification of the exposed samples was carried out by x-ray diffraction technique. Observation from sodium exposure tests indicated that alumina coating offers better protection compared to PSZ coating. However, PSZ coating provided better protection against high-temperature melt exposure, as confirmed during thermite melt exposure test.     

TG/DTA-based techniques for the determination of equilibrium vapour pressures of N,N′-propylenebis(2,4-pentanedion-iminoato)nickel(II) for CVD applications

The Schiff’s base complexes of nickel(II) prepared by condensing 1,2-diaminopropane (pn), 1,3-diaminopropane (trien), 1,4-diaminobutane (tren) or 1,2-diaminobenzene (opdn) with 2,4-pentanedione (acac) in a 1:2 mole ratio followed by chelation with nickel(II) were examined for their volatility/decomposition behaviour for CVD applications. Among the complexes screened, only one complex namely N,N′-propylenebis (2,4-pentanedion-iminoato) nickel(II) (designated as [Ni(acac)₂pn], Ni′) exhibited a single stepped volatilisation commencing from above its melting point (T_o) of 431.9 K and ending up with nil residue at about 570 K. Fast Atom Bombardment Mass Spectrometry was employed to determine the molecular mass of the vapour species to be 295 in accordance with the molecular mass for the monomeric Ni(C₁₃H₂₀O₂N₂). The equilibrium vapour pressure (p_e) of Ni′ over the range of 434–498 K was determined to be log p_e/Pa = 13.771 (±0.574)–4925.4 (±258.2) K/T by employing a TG-based transpiration technique, which yielded a value of 94.3±5.0 kJ mol⁻¹ for its standard enthalpy of vapourisation . The DTA-based melting point depression (T_o–T) studies were carried out on four mixtures of Ni′ (as a volatile solvent) with bis(2,4-pentanedionato)nickel(II) (designated as Ni(acac)₂ or Ni″) as the non-volatile solute. The dependence of log X_Ni′ against 1/T(K) for the four mixtures with the solvent mole fraction X_Ni′ = 0.910, 0.897, 0.881 or 0.849 exhibited near constant slope leading to an average value of 19.4±1.6 kJ mol⁻¹ for the standard enthalpy of fusion . Combining and , a value of 113.7 ± 6.6 kJ mol⁻¹ for standard enthalpy of sublimation was derived to facilitate the estimation of vapour pressures for solid/vapour equilibrium below the melting point.     

Aligned carbon nanotube-polymer hybrid architectures for diverse flexible electronic applications

We present the fabrication and electrical characterization of a flexible hybrid composite structure using aligned multiwall carbon nanotube arrays in a poly(dimethylsiloxane) (PDMS) matrix. Using lithographically patterned nanotube arrays, one can make these structures at any length scale from submicrometer levels to bulk quantities. The PDMS matrix undergoes excellent conformal filling within the dense nanotube network, giving rise to extremely flexible conducting structures with unique electromechanical properties. We demonstrate its robustness against high stress conditions, under which the composite is found to retain its conducting nature. We also demonstrate that these structures can be utilized directly as flexible field-emission devices. Our devices show some of the best field-enhancement factors and turn-on electric fields reported so far.     

Radiation degradation in the mechanical properties of Polyetheretherketone–alumina composites

Polyetheretherketone (PEEK) is extensively employed in corrosive and radiation environments. To improve the radiation tolerance of PEEK in the presence of high energetic radiation, PEEK was reinforced with micron sized alumina powder (5–25% by weight) and PEEK–alumina composite sheets fabricated were irradiated to 10 MGy. Mechanical properties of the irradiated composites revealed significant reduction in the degradation of PEEK with addition of alumina as the polymer reinforced with ceramic additives is expected to increase the interface area of the constituents in the system resulting in an improvement in the performance of the reinforced material.     

Effect of Deposition Time on Structural,Morphological and Optical Properties of PVA Capped SnS Films Grown by CBD Process

Semiconductors - In this study, the effect of deposition time on physical properties of tin monosulphide films capped by polyvinyl alcohol was investigated. Chemical bath deposition technique was...     

Wear and tribocorrosion behaviour of 304L stainless steel welds

The influence of the microstructures of the base metal and weld metals on the wear and tribocorrosion properties of 304L stainless steel (SS) welds prepared by Manual Gas Tungsten Arc Welding (M-GTAW) and Activated Flux Gas Tungsten Arc Welding (A-GTAW) processes are reported. Increase in sliding speed increased both friction forces as well as wear rate. Higher hardness in M-GTAW weld metal resulted in increased wear resistance than A-GTAW weld metal and base metal. The inferior wear resistance of the base metal was due to the strain hardening behaviour under sliding condition. The polarization curves showed increase in passive current density under sliding condition. The applied potential was found to influence the tribocorrosion resistance of the material. Under tribocorrosion condition, the total material loss was higher in base metal followed by A-GTAW weld metal and M-GTAW weld metal. Characterization of worn surface by SEM indicated a mixed wear mechanism of abrasive and adhesive wear. The worn surface appeared relatively smoother in nitric acid medium than in dry condition. The influence of microstructure affecting the hardness, wear and tribocorrosion resistance of the base metal and weld metals of 304L SS is discussed.