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An iron carbonyl-mediated Ostwald-ripening-like growth mechanism of an FexCy active phase in Fischer–Tropsch synthesis is firstly revealed by in situ mass-spectrometric and theoretical analysis.

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Carbon-encapsulated nanonickel particles were prepared by heating nickel acetate highly dispersed in cured phenolic resin at 673 K in N 2 . The metallic nickel cores were about 50s80 nm in diameter, completely encapsulated with carbon shells about 10 nm thick. No byproduct, such as carbides, carbon rods, and carbon fibers, were formed in the samples prepared this way. The carbon shells prevented the metallic nickel cores from oxidation by air at high temperatures. The metallic cores remained even after the encapsulated particles were treated with 6 M hydrochloric acid solution for 24 h. The surface of the encapsulated particles was originally hydrophobic due to the hydrophobic property of the carbon shells formed under the high carbonization temperature. The treatment of the encapsulated particles with O 3 at room temperature generated substantial amounts of carboxylic groups on the outer surface of carbon shells, leading to the hydrophilic surface of the encapsulated nanonickel particles.

A 10 mm narrow gap TC4 titanium alloy welded joint by laser welding with filler wire was obtained by different welding heat inputs. The microstructures of the welded joint were analyzed by OM, SEM, XRD and EBSD. The mechanical properties of the welded joint were analyzed by microhardness test and tensile test. The results show that with the increase of laser welding heat input, the average grain size and width of the equiaxed crystal zone in the center of the weld increases, the grain angle in the columnar crystal zone gradually tends to be perpendicular to the center of the weld, and the width of the heat affected zone (HAZ) increases without obvious grain coarsening. The HAZ of the welded joint is softened, and its microhardness value is lower than that of the weld and the base metal. The tensile strength of the welded joint is slightly higher than those of the base metal, but the elongation after fracture is less than that of the base metal, and it decreases with the increase of laser welding heat input.