다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

인공고관절의 세라믹 볼 헤드의 기계적 안정성 평가를 위한 3 차원 유한요소 해석

Materials Science and Technology

Nowadays, application of nanocrystalline nickel-tungsten (Ni-W) alloys is receiving a great interest because they are an efficient replacement for hard chromium coatings owing to their premium hardness, wear, and corrosion properties. Moreover, heat-treated nanocrystalline Ni-W alloys demonstrate proper mechanical properties as well as thermal stability at high temperatures. The current paper reviews different aspects of electrodeposition, microstructure, corrosion, oxidation, wear, and mechanical properties Ni-W alloys and nano/micro composites. Besides, heat treatment effects on properties and thermal stability of these alloys are also reviewed.

Ni-W electrodeposited coatings: Characterization, properties and applications

Journal of Materials Processing Technology: Preface

Studies were conducted using the double zincate method on the surface morphologies of aluminum substrates at each stage from pretreatment to electroless nickel plating, on the structure of immersion zinc-iron deposits and on the initial deposition process of electroless nickel plating on aluminum. A large number of zinc crystals about 1μm in diameter were deposited by displacement plating after the first zincate stage, and island-like protuberances were observed on the aluminum surface after stripping of the zinc crystals. It was confirmed that zinc crystals were formed on the tops of the protuberances prior to the flat aluminum surface during the second zincate displacement reaction.The zinc crystal formed in both the first and second zincate processes contained about 1wt% of iron.The structure of the initial electroless nickel deposition layer was studied by TEM of cross sections prepared by ultramicrotomy. The presence on the zinc crystal surface of a layer that appeared to be pure nickel, acting as a center of autocatalytic reaction was confirmed.

Relationship between Pretreatment and Initial Deposition in Electroless Nickel Plating on Aluminum Substrate

The double-zincate processing of aluminum in three different zincate solutions was examined to evaluate the effect of solution composition. Higher concentrations of NaOH and ZnO in zincate solution dissolve both the Al oxide layer and Al substrate more rapidly. This leads to faster Zn deposition. In a solution containing Fe3+ions, Fe codeposition resulted in the growth of rather small, nonhexagonal Zn particles during the first zincate process. In the second zincate process, a stratiform Zn layer grows to cover the Al substrate in a zincate solution without Fe3+ions. Granular Zn is deposited due to Zn growth suppressed laterally by the codeposition of Fe in a solution containing Fe3+ions. Such granular Zn deposition provides a sufficient anchor effect for subsequent electroless Ni plating.

Effect of Solution Composition on Double Zincate Process of Aluminum

Sojiro Kirihara, Yashushi Umeda, Katsuhiko Tashiro, Hideo Honma and Osamu Takai 1 Department of Industrial Chemistry, College of Engineering, Kanto Gakuin University (1-50-1、Mutsuurahigasi,Kanazawa,Yokohama,Kanagawa ,Japan, 236-8501) 2 Kanto Gakuin University Materials and Surface Engineering Research Institute (1-1-1、Hukuura,Kanazawa,Yokohama,Kanagawa,Japan, 236-0004) 3 ERG. Co.,ltd (250-6 Uda, Tomioka, Gunma, Japan, 370-2451) * Corresponding author: s-kirihara@k-erg.co.jp

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Development of Ni-W alloy plating as a substitution of hard chromium plating

ABS resin has been widely applied as a plating substrate for plastics in applications such as the parts of vehicles and electrical devices. Hexavalent chromium has been applied as an etchant of plating on ABS resin. However, it is required to eliminate hexavalent chromium from the pretreatment process, since the prohibition of these treatments was determined by the EU directive on the End of Life Vehicles (ELV) from July, 2007. Therefore, alternative etching without hexavalent chromium has been investigated by using ultra violet irradiation (UV) and titanium oxide (TiO2) as a photocatalyst. We already achieved adhesion with the strength of about 1.0kNm−1 between ABS resin and deposited metal without hexavalent chromic acid etching. In this study, the mechanism of adhesion strength improvement with photocatalysts has been investigated using ABS specimens and rubber related ABS resin. As the results, the 1,2-polybutadiene distributed in the AS matrix was preferentially reformed and induced hydrophilicity on the reformed surface with the remaining network structure by cross-linking. In addition, we found that the reformed layer was composed a few μm thick and the catalyst penetrated into 30-40nm from the surface. It was concluded that the good adhesion strength between the deposited metal and resin was derived from the nano-anchor effect by the deposition of metal from the inside of 30-40nm of reformed resin.

Surface Reforming of ABS Resin Using TiO2 under UV Light Irradiation

ABS樹脂は, 最も身近な素材であり, 自動車や家電部品に幅広く使われている。一般的に, ABS樹脂および析出金属間の密着強度を改善するために, H2SO4およびCrO3を含有するエッチング溶液を使用する。また, その手法は工業的に40年以上行われている。近年, 環境汚染の問題はWEEE/RoHS指令に代表されるように, 世界的に重要なテーマとなっている。特に, 自動車における防錆表面処理技術は, EUのELV指令の環: 境負荷物質削減の大きな課題となっている。これらの規制により関係する部品は, 2007年7月以降, EU域内に6価クロムの使用が禁止となる。したがって, 有害物質を使用しない代替技術に変更が迫られている。われわれは, 光触媒である酸化チタンを利用したクロム酸を含まないエッチング代替処理に着目した。TiO2共存下において紫外線照射を行うことで, ABS樹脂表面が改質されることを見出した。この表面改質により, 無電解NiPめっき膜とABS樹脂との密着性が改善されることを確認した。さらに, 最適な条件下で, 約1kgf/cmの密着強度が得られた。

Katsuhiko Tashiro

Papers

Relationship between Pretreatment and Initial Deposition in Electroless Nickel Plating on Aluminum Substrate

Effect of Solution Composition on Double Zincate Process of Aluminum

Development of Ni-W alloy plating as a substitution of hard chromium plating

Surface Reforming of ABS Resin Using TiO2 under UV Light Irradiation

New Chromium Free Pretreatment Method for Plating on ABS Resin Using TiO2 under UV Light Irradiation