Microstructural Features in Multicore Cu–Nb Composites

The study is devoted to heavily drawn multicore Cu–18Nb composites of cylindrical and rectangular shapes. The composites were fabricated by the melt-and-deform method, namely, 600 in situ rods of Cu–18%Nb alloy were assembled in a copper shell and cold-drawn to a diameter of 15.4 mm (e = 10.2) and then rolled into a rectangular shape the size of 3 × 5.8 mm (e = 12.5). The specimens were analyzed from the viewpoints of their microstructure, microhardness, and thermal stability. The methods of SEM, TEM, X-ray analysis, and microhardness measurements were applied. It is demonstrated that, at higher strain, the fiber texture <110>Nb <111>Cu DD (drawing direction), characteristic of this material, becomes sharper. The distortions of niobium lattice can be observed, namely, the {110} Nb interplanar distance is broadened in longitudinal direction of specimens and compacted in transverse sections. The copper matrix lattice is distorted as well, though its distortions are much less pronounced due to its recrystallization. Evolution of microstructure under annealing consists mainly in the coagulation of ribbon-like Nb filaments and in the vanishing of lattice distortions. The structural changes in Nb filaments start at 300–400 °С, then develop actively at 600 °С and cause considerable decrease of strength at 700–800 °С.

Increasing the Adherence of Metallic Copper to the Surface of Titanium Hydride

Studies have been carried out to increase the adhesive interaction between a titanium hydride substrate and a copper coating. An additional layer containing chemically active groups was created on the surface of the spherical titanium hydride by chemisorption modification. This paper discusses the results of scanning electron microscopy (SEM) using energy-dispersive X-ray spectroscopic mapping of coatings obtained on spherical granules of titanium hydride before and after adsorption modification. The mechanism of interaction of the surface of spherical granules of titanium hydride and titanium sulfate salt is proposed. It is shown that the creation of a chemisorbed layer of hydroxotitanyl and the subsequent electrodeposition of metallic copper contribute to the formation of a multilayer shell of a titanium–copper coating on the surface of spherical titanium hydride granules (≡Ti-O-Cu-) with a high adhesive interaction. Results have been given for an experimental study of the thermal stability of the initial spherical granules of titanium hydride and granules coated with a multilayer titanium-copper shell.

Study of a highly porous composite material based on an aluminum matrix with an ordered cellular structure formed by hollow copper-graphite spherical granules

The structure and properties of a highly porous cellular composite material based on a framework of hollow spherical granules with a thin copper-graphite coating impregnated with an aluminum alloy have been investigated. Highly porous composite composite casting with molten form, filled with expanded polystyrene spherical granules with a thin copper-graphite layer applied to their surface. When the polymer core of the granules burns out in the casting, a highly porous cellular composite material is formed with an aluminum matrix filled with spherical pores ∅ 4 – 8 mm, adjoining the metal matrices through a thin (300 – 500 μm) copper shell. The density of the porous composite material obtained in this way is 1.67 g/cm3. In order to fill the space between the granules with aluminum melt, their surfaces were coated with a thin layer of titanium, molybdenum, or chromium borides, which positively affected the strength characteristics of the composite material as a whole. Estimated calculation of the shock absorber index of a new highly porous structural material based on aluminum matrices with a cellular structure made of spherical hollow granules regularly distributed over the volume proved the prospects of its subsequent use as an absorber of shock energy in shock-absorbing devices.

Spent Fuel Leaching in the Presence of Corroding Iron

ABSTRACTThe Swedish spent nuclear fuel canister design KBS-3 consists of a cylindrical copper shell surrounding an iron insert that holds the spent fuel. Like in most other canister designs the mass of iron constitutes the majority of the canister weight. In order for groundwater to access the spent fuel in a future repository the copper shell must fail and iron corrosion occur. Spent nuclear fuel dissolution will therefor likely proceed under conditions of simultaneous anoxic iron corrosion. The iron corrosion can likely suppress the spent fuel release by creation of strongly reducing conditions from Fe(II) formation and the generation of large quantities of hydrogen. Redox sensitive radionuclides may either be reductively precipitated by dissolved Fe(II) or from interaction with iron corrosion products such a magnetite or green rusts. The generated hydrogen (up to several MPa) may also inhibit the spent nuclear fuel dissolution at the surface of the fuel via the so called hydrogen effect. In order to probe these effects an autoclave experiment was performed in which a basket with PWR spent nuclear fuel (burnup ∼43 MWd/kgU) was suspended in an autoclave containing a simplified groundwater (10 mM NaCl, 2 mM NaHCO3) with iron powder. The autoclave was sparged and pressurized with argon. Following an initial rise in radionuclide concentrations from dissolution of pre-oxidised phases the U concentration dropped to 3x10-9 M within 76 days, in-line with the solubility of amorphous UO2, expected to form under reducing conditions. Any Cs and Sr release also ceased within 223 days indicating complete transition from dissolution of pre-oxidized phases and instant release fractions to conditions with inhibition of the dissolution of the fuel matrix. Gas phase analysis and pressure monitoring showed a steady build-up of hydrogen at a rate higher than what could be attributed to radiolysis, reaching hydrogen partial pressures of several hundred kPa. The results indicate continuous corrosion of iron, with magnetite as the dominating iron corrosion product.

Preparation and Optical Properties of PS @Au-Cu Core-Shell Nano Composite

An appropriate low-cost uncomplicated chemical method has been used to obtain the optical properties in the production of plasmon by manufacturing nanomaterial's consisting of dielectric core and a shell that grows on its surface . This core consists of the polystyrene PS and a gold – copper shell. The synthesis was made in two steps . In the first step PS core was fabricated , then coated by a shell consisting of Au –Cu particles . The shell shape differs according to the change in the amount of molar concentrations of Cu, and H2O2. It is found that variation of this materials amount gives us absorbance measurements (Localised Surface Plasmon Resonance, LSPR) that increase proportionally with changing quantities directly, where the size of core is constant.And the peak position in blue shift high energy then changes to red shift low energy . This change depends on the size and shape of particles. The same case applies for the transmittance of its change with the change of this material. The nano shell was characterized by using Scanning electron microscopy,SEM and UV –vis spectroscopy by varying the amount of Cu and H2O2.