Naoshi Ozawa

Effect of seed crystal and composition of solution on the formation of TiO2 thin film from aqueous solution

Abstract TiO 2 thin film can be formed from aqueous solution at ordinary temperature and ordinary pressure by using hydrolysis reaction of titanium fluoro-complex. In this study, effect of seed crystal and composition of solution on the formation of TiO 2 thin film was investigated. The amount of deposited TiO 2 increased with increasing both (NH 4 ) 2 TiF 6 and B 2 O 3 concentrations. Crystallinity of TiO 2 increased with decrease of (NH 4 ) 2 TiF 6 concentration for short soaking period. Addition of suitable amount of seed crystal enhanced the formation of TiO 2 thin film particularly for low (NH 4 ) 2 TiF 6 concentration and short soaking period.

Micro pattern formation of ceramic thin film by synthesis from aqueous solution using resist pattern as a mold

Abstract Fabrication of micro patterns of ceramic films was made by ceramic thin film synthesis reaction from aqueous solution using resist pattern as a mold. This method was applied to the formation of micro patterns of titanium dioxide and apatite. Minute patterns such as blocks, lines, geometrical figures and characters were well formed. The minimum line width of the micro pattern was 1 μm for titanium dioxide thin films and 2 μm for apatite thin films. This method is promising for fabricating micro patterns of ceramic thin films.

Charge-Discharge Cycle Behavior of MgAl2 O 4-Doped LiMn2 O 4 Cathode Material for Lithium-Ion Secondary Battery

MgAl 2 O 4 -doped LiMn 2 O 4 spinels, (LiMn 2 O 4 ) 1 - x (MgAl 2 O 4 ) x (x = 0, 0.02, 0.05, 0.10), were synthesized and the cycle performance as cathode material for lithium-ion secondary battery was investigated. Doping with MgAl 2 O 4 improved the cycle performance of LiMn 2 O 4 spinel. For (LiMn 2 O 4 ) 0 . 9 5 (MgAl 2 O 4 ) 0 . 0 5 the capacity fading was markedly suppressed compared to nondoped LiMn 2 O 4 . It is considered that stable Mg-O-Al bonds dispersed into the LiMn 2 O 4 matrix stabilized the whole crystal lattice through the common oxygen arrangement between MgAl 2 O 4 spinel and LiMn 2 O 4 spinel and inhibited the deterioration of the crystal structure due to the repetition of lithium insertion and deinsertion, resulting in the improvement of cycle performance.

Development of a Bioactive Alumina-based Composite by Electrophoretic Deposition

Alumina is excellent biomaterial and used in hip prostheses, dental implants and so on. Wollastonite particles were deposited in the pores of foamed alumina by electrophoretic deposition. Apatite was formed both inside the pores and on the surface of the compos ite of foamed alumina and wollastonite by soaking in a simulated body fluid. It is indicated that the deposited wollastonite particles induced the apatite formation. It is considered that novel alum ina-based composite with both excellent mechanical properties and high bioactivity was developed. Introduction Alumina is excellent biomaterial with good biocompatibility, high cor rosion resistance, high wear resistance and high strength and used in hip prostheses, dental implants and so on. If bioactivity is imparted to alumina, the range of its application as a biomaterial will be largely extended. Wollastonite (CaO SiO2) has high apatite-forming ability [1]. But it is difficult to ut ilize wollastonite independently for a biomaterial, because of its poor sinterability. Electrophoretic deposition (EPD) offers an advantage as a method for ceramic processing, because the process is simple, no expensive apparatus is required, and substrate s, even those with wide areas and/or complicated shapes, are available. Conventionally, EPD was possibl e only on conductive substrates such as metals. Recently, we have invented a method for depositing cer amic particles on a porous insulating ceramic substrate by EPD [2]. When a porous substrate i arranged on a metal electrode in a suspension of ceramic particles and voltage is appli ed, the particles migrate to and deposit inside the pores of substrate due to the attractive force of th electric field coming through the pores. In the present study, wollastonite particles were deposited in the por es of foamed alumina by EPD and apatite-forming ability was investigated for the obtained wollastonitedeposited foamed alumina in a simulated body fluid. Methods A foamed alumina (Toshiba Ceramics Co., Ltd., Tokyo, Japan), 10 x 20 x 2 mm 3 in size, was used as the substrate. Wollastonite was synthesized by sintering a mixtur e of CaCO3 and SiO2 at 1500°C for 5 h. The wollastonite was crushed with a laboratory planetary-type bal l mill (Model P7, Fritsch Co., idarOberstein, Germany) and particles ~0.3 m in average diameter were obtained. The wollastonite particles were suspended in acetone with iodine added. The concentration of w llastonite particles was 5 g dm. Stainless plate was used as the anode and aluminum foil was used a s th c thode. The electrodes and the substrate were immersed in the suspension. The anode and cathode were placed in parallel and the foamed alumina substrate was set in tight contac t wi h the cathode. The distance between the electrodes was 10 mm. EPD was performed at constant vol ge of 1000 V with stirring the suspension for 20 min. Thus the composite of foamed alumina and wollastoni te was obtained. Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 67-70 doi:10.4028/www.scientific.net/KEM.240-242.67

Apatite Formation on Polymers Coated with Titania Synthesized from an Aqueous Solution

Titania thin film was formed on organic polymers such as polystyr ene, poly(ethylene terephthalate), polyamide 66, poly(methyl methacrylate), polyethylene and polyethersulfone, by a hydrolysis reaction of titanium fluoro-complex in an aqueous solution. The s ubstrates were soaked in an aqueous solution with ion concentrations nearly 1.5 times those of human blood plasma and apatite was formed on the titania coated polymer substrates. Bioactive mat erials with various mechanical properties can be developed by the present method. Introduction Recently, we have developed a method to form titania thin film by a hy drolysis reaction of titanium-fluoro complex in an aqueous solution [1]. The reaction formula is as follows. TiF6 2+ 2H2O TiO2 + 6F + 4H (1) BO3 3+ 4F + 6H BF4 + 3H2O (2) It is considered that the chemical equilibrium between hexafluorotit ana e ion and titania holds as in reaction (1). When borate ion is added, fluoride ion is consumed by reaction (2), then the chemical equilibrium in reaction (1) shifts from left to right to increase fluoride ions, resulting in the formation of titania. This method offers an advantage, because no vacuum, high temper ature, or expensive apparatus are required, and substrates, even those with wide areas and/ or complicated shapes, are available. Previously, we presented that the titania thin film form ed on titanium metal and glass substrates by this method has an apatite-forming ability [2]. When t itania thin film is formed on wide variety of materials, especially low heat resistant materi als such as organic polymers, by using this method, and has an apatite-forming ability, bioactive materials wit h various mechanical properties can be developed. In the present study, titania thin film was formed on va rious kinds of organic polymers by the hydrolysis reaction of titanium fluoro-complex in an a queous solution and the apatite-forming ability was investigated. Methods Polystyrene (PS), poly(ethylene terephthalate) (PET), polyamide 66 (PA), poly(methyl methacrylate) (PMMA), polyethylene (PE) and polyethersulfone (PESF), 10 x 10 x 1 mm 3 in size, were used as the substrates. A PET fabric was also used as the substrate. The subs trates were treated with 5 mol ·dm NaOH at room temperature for 10 min or with UV irradiation, 253.7 nm in wavelength, for 24 h to increase the hydrophilicity of the surface. The substrates were s oak d in suspension of anatase-type titania nano particles as seed crystals for 20 min. The substrate s wer soaked in a mixed solution of Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 71-74 doi:10.4028/www.scientific.net/KEM.240-242.71

Micropatterning of Apatite by Using CaO-SiO2 Based Glass Powder Dispersed Solution

Combination of biomimetic method and transcription of resist pattern wa s made to form apatite micropattern. A resist pattern printed substrate was sus pended in CaO-SiO 2 based glass (CaO 44.7, SiO2 34.0, P2O5 16.2, MgO 4.6, CaF 2 0.5 mass%) powder dispersed simulated body fluid (SBF) with ion concentration nearly equal to human blood plasma, and then soaked in SB F. Apatite nuclei were seeded on whole the surface of the substrate. Next the resis t material was dissolved off with the apatite nuclei just formed on it. Then, the substrate was soaked in SBF to grow the r emaining nuclei. As the result, an apatite micropattern transcribing the resist pattern was obtained. This method is promising for producing multifunctional materials having bioaffinity

Twin Roll Casting of Aluminium Alloy ADC12, A3003, A7075

This paper describes a vertical type twin roll strip casting process for producing aluminum alloy strip of ADC12, A3003 and A7075. Twin roll casting process is able to produce a strip from molten metal directly. Thus this process has a possibility to reduce total cost of sheet making comparing to conventional rolling process. Aluminum alloy ADC12 is a casting material that is used for die casting. A3003 is known as a wrought aluminum alloy for aluminum can body sheet. The A3003 sheet is generally produced by rolling, so it is effective for reducing a process cost to produce the strip by twin roll casting process. Aluminum alloy A7075 has high tensile strength, and it is known as a material for aerospace application. The sheet is manufactured in small quantities comparing to the other sheet aluminum alloy. It is supposed that the demand of high tensile strength aluminum sheet such as A7075 is going to increase for weight saving of structural material. In this study, twin roll casting experiment was performed to produce these three aluminum alloy strip in same experimental conditions. Castability, surface conditions and strip thickness were estimated. It was possible to cast these aluminum alloy strip.

Direct Molten Metal Rolling of Aluminum Alloy A3003

This paper describes a production process for aluminum alloy sheet metal. Direct molten metal rolling, in other words strip casting process for aluminum alloy A3003 sheet was operated. Strip casting process is able to produce the metal sheet from molten metal directly. Thus this process has possibility of improving the productivity of sheet because of shortening operation of rolling. In this study, experimental device was designed for direct molten metal rolling. Aluminum alloy A3003 was chosen. A3003 is for aluminum can body, and the sheet required the high productivity. The effect of roll speed on the produced strip surface and strip thickness was investigated. Roll speed were 1, 2 and 3 m/min. It was possible to produce A3003 strip by direct rolling at the conditions of roll speed 3 m/min, pouring temperature 700 °C, solidification length 15 mm and nozzle exit width 15 mm. Obtained strip surface was flatten and had a metallic luster.