Daniel M. Makowiecki

Low temperature reactive bonding

OF THE DISCLOSURE A joining technique that requires no external heat source and generates very little heat in the joining technique. It involves the reaction of thin multilayered films deposited on faying surfaces to create a stable compound that functions as an intermediate or braze material in order to create a high strength bond. While high temperatures are reached in the reaction of the multilayer film, very little heat is generated because the films are very thin. It is essentially a room temperature joining process.

Evaluation of B4C as an Ablator Material for NIF Capsules

AbstractBoron carbide (B4C) is examined as a potential fuel container and ablator for implosion capsules on the National Ignition Facility (NIF). A capsule of pure B4C encasing a layer of solid DT implodes stably and ignites with anticipated NIF x-ray drives, producing 18 MJ of energy. Thin films of B4C were found to be resistant to oxidation and modestly transmitting in the infrared (IR), possibly enabling IR fuel characterization and enhancement for thin permeation barriers but not for full-thickness capsules. Polystyrene mandrels 0.5 mm in diameter were successfully coated with 0.15–2.0 µm of B4C. Thicknesses estimated from optical density agreed well with those measured by scanning electron microscopy (SEM). The B4C microstructure was columnar but finer than for Be made at the same conditions. B4C is a very strong material, with a fiber tensile strength capable of holding NIF fill pressures at room temperature, but it is also very brittle, and microscopic flaws or grain structure may limit the noncryo...

Surface-defect formation in graphite targets during magnetron sputtering

Magnetron sputtering of graphite targets is frequently marred by the formation of topographic defects. The defects are either soft with a furry appearance or hard with a stalagmite appearance. The soft defects are often found on top of the hard ones, implying a close connection in formation sequence between the two types of defects. The formation mechanism of the hard defects is related to the presence on the surface of low sputtering‐yield impurities or other types of lattice imperfections, which suppress the erosion induced locally by sputtering, and to porosity‐induced asperities. The emergence of the soft defects is ascribed to a growth phenomenon involving redeposition of carbon from debris and possibly generated in a chemical vapor deposition (CVD) process. The gradual coverage of the target surface by defects causes a steady decrease of the sputtering rate of carbon. Also, the breakup of the soft defects promotes nodular defects in the subsequent growth of the carbon film, thus severely degrading t...