Tian Ying Xiong

Preparation of bioactive titania films on titanium metal via anodic oxidation.

OBJECTIVESnTo research the crystal structure and surface morphology of anodic films on titanium metal in different electrolytes under various electrochemical conditions and investigate the effect of the crystal structure of the oxide films on apatite-forming ability in simulated body fluid (SBF).nnnMETHODSnTitanium oxide films were prepared using an anodic oxidation method on the surface of titanium metal in four different electrolytes: sulfuric acid, acetic acid, phosphoric acid and sodium sulfate solutions with different voltages for 1 min at room temperature.nnnRESULTSnAnodic films that consisted of rutile and/or anatase phases with porous structures were formed on titanium metal after anodizing in H(2)SO(4) and Na(2)SO(4) electrolytes, while amorphous titania films were produced after anodizing in CH(3)COOH and H(3)PO(4) electrolytes. Titanium metal with the anatase and/or rutile crystal structure films showed excellent apatite-forming ability and produced a compact apatite layer covering all the surface of titanium after soaking in SBF for 7d, but titanium metal with amorphous titania layers was not able to induce apatite formation.nnnSIGNIFICANCEnThe resultant apatite layer formed on titanium metal in SBF could enhance the bonding strength between living tissue and the implant. Anodic oxidation is believed to be an effective method for preparing bioactive titanium metal as an artificial bone substitute even under load-bearing conditions.

Effect of Surface Morphology and Crystal Structure on Bioactivity of Titania Films Formed on Titanium Metal via Anodic Oxidation in Sulfuric Acid Solution

tyxiong@imr.ac.cn Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan Department of Ceramic Engineering, School of Advanced Materials Engineering, Yonsei University 134 Shinchon-dong, Seodaemun-gu, Seoul 120-749, Korea Research Institute for Science and Technology, Chubu University, 1200 Matsumoto-cho, Kasugai-shi, Aichi 487-8501, Japan Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan

Photocatalytic Properties of TiO2 Coatings Prepared by Cold Spray Process

Cold spray process offers an oxidation-free atmosphere. It is usually used for TiO2 coatings used in photocatalytic applications to purify a given medium. Cold sprayed coatings with spray dried powder and evaporated powder were compared. Investigation of properties using SEM, XRD, roughness test were performed. SEM and XRD data were found to be very similar, however, variations were found for the surface roughness. Nano-sized powders were used in this investigation, therefore the coatings achieved were very thin in comparison to those from conventional powders, also they showed high uniformity.benzene removal from air by means of photoelectrocatalytic reaction was achived.

Microstructures and Microhardness of SNCed Medium Carbon Low Alloy Steels

Nanostructured layers were fabricated on the surface of 0.4C-1.0Cr and 1.0C-1.5Cr low alloy steels by using an ultrasonic particulate peening (USPP) technique. The microstructures and mechanical properties of the nanocrystallized layers were characterized by means of transmission electron microscopy, and nano-indentation test. Results showed that the average grain size in the surface nanocrystallized layer of 0.4C-1.0Cr and 1.0C-1.5Cr low alloy steel was about 5nm and 10nm, respectively. The nano-indentation hardnesses of the surface nanocrystallized layer were enhanced significantly and reach upwards of 8.0 GPa and 12.5 GPa, respectively.

Structure of Porous Copper Fabricated by Unidirectional Solidification under Pressurized Hydrogen

Porous copper with elongated cylindrical pores were fabricated by a unidirectional solidification method in a mixture of hydrogen and argon with high pressures. The porous copper with longitudinal pores and radial pores were compared on structure. The effect of both hydrogen pressure and argon pressure on structure of the porous copper including pore size, pore density, and porosity was investigated. The reason for the effect is explained.

Enhanced Photocatalytic Activities of Ta2O5 and Nitrogen Co-Doped TiO2 under Visible Light Irradiation

Tantalum dioxide and nitrogen co-doped titanium dioxide nanopowders, denoted as (Ta2O5, N) co-doped TiO2, were fabricated by a high-energy ball miller using TiO2, Ta2O5 and urea as raw materials. Experiments on the photocatalytic activities of the (Ta2O5, N) co-doped TiO2 were carried out in the form of photodegradation of methylene blue (MB) in aqueous solution under visible light irradiation. Enhanced photocatalytic activities were observed for the (Ta2O5, N) co-doped TiO2 than commercial Degussa P25. Besides, physical, chemical and optical properties, including XRD, DRS, and XPS were detected to analyze the origins for the enhanced photocatalytic activities of the prepared samples.

Thermal Stability of 40Cr Steel with Surface Nanocrystallization

Surface Nanocrystallization(SNC) is a new method of fabricating nanostructured materials while thermal stability is an important problem for the application of nanostructured materials. A nanostructured layer was fabricated on the surface of 40Cr steel by Supersonic Particles Bombarding method, and the variation of microstructure and microhardness of nanostructured layer was studied. Nanostructured surface layer showed high thermal stability.

Study of Corrosion Resistance of Anodized Ti6Al4V in SBF

A layer of amorphous thick anodic oxide film was formed on Ti6Al4V substrate after anodization, and its thickness achieved 30-40µm. After immersion in SBF, anodized sample and substrate indicated different corrosion resistance. According to icorr, Rp and Ecorr, the concerned experimental results of potentiodynamic polarization curves, the anodic oxide film provided effective corrosion protection, which could be attributed to its relatively uniform, smooth, compact and intact microstructure. And the results of total immersion test also proved the protective role of the anodic film.

A Brief Review on TiO2 Coating Deposited by Cold Spraying

TiO2 is a promising photocatalyst with great potential for environment purification and energy conversion. TiO2 coatings have more advantages over powders in practical use. Cold spraying is an ideal technique to fabricate TiO2 coatings because of its low heat input compared with thermal sparing which may induce undesirable phase transformation from anatase to rutile. The paper will give a short introduction on recent development of TiO2 coatings by cold spraying. Then, the factors affecting the quality of coating should be analyzed. And finally, the bonding mechanism of cold sprayed TiO2 coating on metal substrates will also be proposed.

Porosity Measurement of Porous Copper by Unidirectional Solidification

Generally, there are two ways available for porosity measurement of porous metals. One is by calculating density ratio of a porous metal and a corresponding non-porous metal, called as relative density method. The other is by counting the percentage of pores on cross section of a porous metal, called as image analysis method. In this work, both methods were employed for lotus-type porous copper on porosity measurement. The effects of several parameters in both methods on porosity values of the porous copper are reported and discussed. The relative density method is recommended as porosity by this method is more reliable for the porous copper.