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Effect of anodizing time on the multiscale porous structure of the inner wall of the microchannel produced in a titanium alloy body has been investigated. The microchannel was produced by a powder-metallurgical process in which a titanium-powder compact containing thin aluminum wire was sintered at a temperature above the melting point of aluminum. During sintering, microscopic infiltration of molten aluminum into the porosity of the compacted titanium powder and subsequent diffusion of aluminum into the titanium powder particles brought about the formation of a microchannel lined with Ti–Al alloy layer in the sintered body. The inner walls of the microchannels with uniform composition, Ti–18.0(±1.8)mol%Al, were provided for anodizing experiments. When the anodizing time was in the range from 1.8 to 28.8 ks, the structure of the anodic oxide film was nanotube array. Each specimen had a microchannel of several hundred micrometers in diameter, inner wall asperity of several ten micrometers in size, and nanotube array structure of the anodic oxide film. In the specimen anodized for 59.6 ks, on the other hand, the nanotube array had changed to a different structure resembling that of nanoporous metals produced by dealloying.

歯列矯正用ワイヤとして用いられるNi-Ti合金は，超弾性の性質を持ち，大気中でTiO_2を主成分とする薄く安定な酸化被膜を表面に生成するため，極めて良好な耐食性を示す。しかし，う蝕予防薬などに含まれるフッ化物からF^-イオンが生成し，H^+イオンと結合してHF分子が形成されると，酸化被膜の溶解が起こる。特に，強い酸性環境では酸化被膜の溶解が促進し，下地合金からTiとNiが溶出する。溶出したNiによる有害作用として，細胞毒性，アレルギー，発癌性などが知られており，Ni溶出を減少することが強く望まれる。本研究の目的は，市販のNi-Ti矯正用ワイヤを酸性またはアルカリ性電解液中にて陽極酸化し，それら試料をF^-イオン含有の酸性溶液中に浸漬し，陽極酸化による表面改質の効果，つまり，Ni溶出量の減少を確認することである。市販のNi-Ti矯正用ワイヤを長さ20mmに切断し，試料とした。陽極酸化は，0.008mol/L H_2SO_4または0.030mol/L NaOHを電解液として用い，室温にて，直流10Vで，300秒間通電して行った。溶出試験は，入手のままと陽極酸化した試料を1,000ppmのNaFを含むpH 3.6またはpH 4.4の腐食溶液中に，37℃で，１時間浸漬して行った。腐食溶液中に溶出したTiとNiは，誘導結合プラズマ質量分析装置（ICP-MS）を用いて定量した。溶出試験前後の各試料の酸化被膜の厚さと組成は，X線光電子分光法（XPS）を用い，デプスプロファイルにより検討した。陽極酸化時の電流密度は，どちらの電解液を用いた場合も，平均値は1.3mA/mm^2であった。各試料の酸化被膜厚さは，入手のまま：4.0±0.5nm，H_2SO_4中で陽極酸化：33.3±1.5nm，NaOH中で陽極酸化：8.3±0.8nmであった。また，陽極酸化によって生成した酸化被膜の主成分は，TiO_2であった。各試料からのNi溶出量は以下のようになった。pH 3.6の腐食溶液への浸漬では，入手のまま：24.3±1.3μg/cm^2，H_2SO_4中で陽極酸化：19.1±1.7μg/cm^2, NaOH中で陽極酸化：26.7±0.1μg/cm^2であった。また，pH 4.4の腐食溶液への浸漬では，入手のまま：6.5±0.7μg/cm^2，H_2SO_4 中で陽極酸化：2.7±1.4μg/cm^2，NaOH中で陽極酸化：7.6±0.5μg/cm^2であった。すなわち，H_2SO_4中で陽極酸化した試料は，NaOHを用いた場合よりも，酸化被膜が厚く生成され，その結果，pH 4.4では，Ni溶出量は入手のままの場合の約40％に減少した。これらの結果，陽極酸化を適切に行えば，HF分子の存在する腐食溶液中でも，Ni-Ti矯正用ワイヤからのNi溶出量を少なくできることが確認された。, Ni-Ti alloy used as an orthodontic arch wire has super-elasticity and shows excellent corrosion resistance due to the thin oxide layer of TiO_2 formed in the atmosphere. However, dissolution of the oxide layer occurs when HF molecule is formed from H^+ ion and F^- ion which is contained in dental caries prophylactics. In particular, an oxide layer breaks in strong acidic environment and as a result both Ti and Ni elute from the alloy. As adverse effect by the dissolved Ni, cytotoxicity, allergy, and carcinogenicity are known, and accordingly decrease of the amount of Ni dissolution is strongly desired. The aim of this study is to confirm decrease of the amount of Ni dissolution by the surface treatment of anodic oxidation. Therefore, the electrochemical treatment of the commercial Ni-Ti orthodontic wires in acid or alkaline electrolyte was carried out and dissolution test of treated wires was done in acid solution containing F^- ion. Commercially available Ni-Ti orthodontic wires were cut into the pieces of 20 mm in length as specimens. In an aqueous solution of 0.008 mol/L H_2SO_4 or 0.030 mol/L NaOH as electrolyte, the anodic oxidation of the specimens was carried out for 300 s at applied voltage of 10 VDC at room temperature. Each specimen, as received, anodized in H_2SO_4 or anodized in NaOH, was dipped at 37℃ for 1 hour into one of two corrosive solutions, pH 3.6 or pH 4.4, which contained 1,000 ppm of NaF. The inductively-coupled plasma mass spectrometer (ICP-MS) was used to determine the amounts of Ti and Ni that were eluted from the specimens into the corrosive solutions. Before and after the dissolution tests, the chemical composition of oxide films and thickness of them were estimated from the depth profiles performed by the X-ray photoelectron spectroscopy (XPS). The mean values of current density at anodizing treatment were 1.3 mA/mm^2 regardless of the electrolyte. Each thickness of oxide films was as follows; 4.0±0.5 nm (as received), 33.3±1.5 nm (anodized in H_2SO_4), and 8.3±0.8 nm (anodized in NaOH). The main component of the oxide films generated by anodic oxidation was TiO_2. In the case of the solution of pH 3.6, each amount of Ni dissolution was as follows; 24.3±1.3 μg/cm^2 (as received), 19.1±1.7 μg/cm^2 (anodized in H_2SO_4), and 26.7 ±0.1 μg/cm^2 (anodized in NaOH). In the case of the solution of pH 4.4, each was as follows; 6.5±0.7 μg/cm^2 (as received), 2.7±1.4 μg/cm^2 (anodized in H_2SO_4), and 7.6±0.5 μg/cm^2 (anodized in NaOH). As for the specimen anodized in H_2SO_4, an oxide layer was generated thicker than that of the specimen anodized in NaOH. As a result, the amount of Ni dissolution decreased to about 40 % of that of as received specimen in the solution of pH 4.4. The amount of Ni dissolution from Ni-Ti orthodontic wires reduced when we properly performed anodic oxidation even if containing considerably amount of HF in the solution.

We describe nanofabrication processes developed for the fabrication of InAs/AIGaSb heterostructures using atomic-force-microscope (AFM) oxidation and applications to the fabrication of nanoscale devices such as single-electron transistors. Oxidation processes were developed for GaSb, GaSb/AlSb, and InAs layers. We demonstrate that our AFM oxidation processes are simple and useful by showing each fabrication process and corresponding device structure and characteristics.

[Abstract] Micrometer-scale patterning of a sol-gel derived TiO2 film was formed on a titanium plate using photo-irradiation patterning.The patterned TiO2 on a micrometer scale, which had nearly the same design as the TiO2 gel film, was formed at pulsed-current density by anodic oxidation in an alkaline bath under spark discharge., Copyright (c) 2009 社団法人一般社団法人 表面技術協会

[Abstract] Hydroxyapatite fine particles (HAp) were loaded on an anodized titanium plate in an alkaline electrolytic bath under spark discharge. Bioactivity was investigated by immersion of the materials into the simulated body fluid for a predetermined period. Bioactivity was remarkably improved by loading of HAp on the anodized titanium surface., Copyright (c) 2009 社団法人一般社団法人 表面技術協会, KUDO, Kohki

The combination of hot dipping in molten aluminum and the subsequent anodic oxidation to dense Al2O3 films was studied to prepare an oxidation-resistant coating on niobium surface. By immersing Nb into a molten Al bath, granular NbAl3 was precipitated and improved the coherency of the film to the substrate. Amorphous Al2O3 was formed by anodic oxidation of the Al layer and crystallized to corrosion resistant α-Al2O3 by the subsequent heat treatment. The Nb substrate after this combined treatment did not form any niobium oxides even after heating in air for 64.8 ks at 1073 K, and the oxygen increment in the Nb bulk was suppressed below 400 mass ppm.

The effect of microelectrical current on internal remodeling and anodic oxidation in long tubular bone was examined using femurs of 24 adult mongrel dogs. To minimize anodic oxidation, obtaining effective stimulation, a generator with pulse current of charge recovery type was made. The femur of dog was stimulated for four weeks by various waveform current, i.e., pulse current of charge recovery type, 1 Hz 10 uA; pulse current, 1 Hz, 10 uA; direct current, 10 uA; and alternating rectangular pulse, 1 Hz, 10 uA. The effect was evaluated by histomorphometric parameters in terms of number of resorption cavities (Ar), number of osteons with osteoid seam (osAf) and area of bone resorption around the electrode. The following results were obtained. 1. A significant increase of internal remodeling of bone was noted in the femur as stimulated by pulse current of charge recovery type as compared with the nonstimulated femur. 2. The smallest area of bone resorption was shown in a portion around anode of pulse current of charge recovery type pulse, which occurred less anodic oxidation, and larger area was also observed in order of pulse current and direct current. No significant difference of the area of bone resorption was shown among portions around cathode and anode of pulse current of charge recovery type stimulation and electrodes of alternating rectangular pulse. 3. Using pulse current of charge recovery type the internal remodeling of bone around cathode of femur, in which both cathode and anode were inserted, showed a more increase than that around cathode, which was inserted only in femur, and anode was placed in subcutaneous tissue of the thigh. 4. The internal remodeling around cathode of pulse curret of charge recovery type pulse stimulation showed a significant increase than that around the electrode of alternating rectangular pulse stimulation.