کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
188601 459663 2012 7 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
The chemistry and structure of nickel–tungsten coatings obtained by pulse galvanostatic electrodeposition
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی مهندسی شیمی (عمومی)
پیش نمایش صفحه اول مقاله
The chemistry and structure of nickel–tungsten coatings obtained by pulse galvanostatic electrodeposition
چکیده انگلیسی

A detailed characterization of electrodeposited NiW coatings prepared by pulse electrodeposition on steel and copper substrates is presented. The coatings were obtained at high current pulse frequency and show high microhardness and absence of brittleness. The surface of the coating consists of nanometer sized crystals forming a cauliflower-like structure protected by a mixture of nickel and tungsten oxides. The cauliflower structure is preserved into the bulk coating that exhibits an average composition ≈70 at% Ni30 at% W. Different phases are observed in the bulk structure: a W-rich amorphous phase (≈40%) and Ni-rich crystalline phases (≈60%). The crystalline phases consist of crystalline domains ≈7 nm in size of Ni(W) (fcc) solid solution (12 at% W content) and a minor Ni4W component (less than 10%). The amorphous phase exhibits a less compact NiW structure where some amount of C could also be present. Oxidized W species cannot be detected in the bulk coating, thus discarding the presence of significant amounts of tungsten carbide, tungstates or citrate–tungsten complexes. Our results shed light on controversial points related to the chemical composition and demonstrate the complex structure of this system.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Electrochimica Acta - Volume 72, 30 June 2012, Pages 87–93
نویسندگان
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