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Sakka Yoshio,Saito Sho,Honda Atsushi,Suzuki Tohru S.,Moriyoshi Yusuke 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
We have demonstrated that textured nanocomposites can be fabricated by slip casting followed by partial oxidation. reaction sintering of mixed suspensions of and SiC powders in a high magnetic field. The sintered density was changed by the degree of oxidation at 1200C and 1300C. The degree of orientation of alumina in the nanocomposite was examined on the basis of the X-ray diffraction patterns and scanning electron micrographs. It is confirmed that aluminaoriented nanocomposites were fabricated. The three-point bending strength at room temperature was observed for the nanocomposites.
Synthesis and Properties of Multimetal Oxide Nanopowders via Nano-explosive Technique
Vasylkiv Oleg,Sakka Yoshio,Skorokhod Valeriy 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
We demonstrate the methodology of engineering the multi-component ceramic nanopowder with precise morphology by nanoblast calcinations decomposition of preliminary engineered nanoreactors. Multiple explosions of just melted embedded into preliminary engineered nanoreactors break apart the agglomerates due to the highly energetic impacts of the blast waves. Also, the solid-solubility of one component into the other is enhanced by the extremely high local temperature generated during each nano-explosion in surrounding area. This methodology was applied for production of agglomeratefree nano-aggregates of with an average size of 42 nm and nanopowder with an average aggregate size of 83 nm.
Bend Deformation Behavior of Silicon Carbide Reticulated Porous Ceramics
Zhu Xinwen,Sakka Yoshio,Tan Shouhong,Jiang Dongliang 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
The deformation behavior under three-point bend test was found to depend on the loading uniformity and the macrostructure for SiC reticulated porous ceramics (RPCs). However, this dependence of loading uniformity is alleviated by improved macrostructure with fewer flaws and clogged pores. Even, this dependence becomes less important as the struts become thicker and stronger. The bend result of RPCs with highly uniform macrostructure is in excellent agreement with the GA (Gibson and Ashby) model, but the one with un-uniform macrostructure deviates from the GA model, suggesting that the macrostructure plays an important role in deformation behavior of RPCs under bend.
Aqueous Processing of Textured Silicon Nitride Ceramics by Slip Casting in a Strong Magnetic Field
Zhu Xinwen,Uchikoshi Tetsuo,Sakka Yoshio 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
This work will report a highly textured β-Si3N4 ceramic by aqueous slip casting in a magnetic field and subsequent pressureless sintering, Effects of the sintering aids, polymer dispersant, pH and stirring time on the stability of the Si3N4 slurries were studied. The textured β-Si3N4 with 97 % relative density could be obtained by slip casting in a magnetic field of 12 T and subsequent sintering at 1800 oC for 1 h. The textured microstructure is featured by the alignment of c-axis of β-Si3N4 crystals perpendicular to the magnetic field, and the Lotgering orientation factor, f, is determined to be 0.8.
Di, Weihua,Li, Jie,Shirahata, Naoto,Sakka, Yoshio,Willinger, Marc-Georg,Pinna, Nicola Royal Society of Chemistry 2011 Nanoscale Vol.3 No.3
<P>Luminescent TbPO<SUB>4</SUB> nanoparticles were synthesized <I>via</I> a citric-acid-mediated hydrothermal route. Eu<SUP>3+</SUP> doping of TbPO<SUB>4</SUB> enables an efficient Tb<SUP>3+</SUP>-to-Eu<SUP>3+</SUP> energy transfer, leading to a four-fold increase of the absolute emission quantum yield (QY), compared to that of undoped TbPO<SUB>4</SUB>. To check the potential of biological use, we conducted <I>in vitro</I> biological experiments on human cervical carcinoma HeLa cells incubated with TbPO<SUB>4</SUB>:Eu nanoparticles. TbPO<SUB>4</SUB>:Eu nanoparticles can be successfully internalized into the cells, and they show bright intracellular luminescence and very low cytotoxicity. Photoluminescence intensity dependence upon time demonstrates that Eu<SUP>3+</SUP>-doped TbPO<SUB>4</SUB> nanoparticles are highly resistant to photobleaching. Our present work represents a demonstration of the use of rare-earth-based nanocrystals as a biological labeling agent because they combine several advantages including high emission quantum yield, long luminescence lifetime, low cytotoxicity and high photostability.</P> <P>Graphic Abstract</P><P>Highly luminescent TbPO<SUB>4</SUB> nanoparticles are obtained upon Eu<SUP>3+</SUP> doping due to an efficient Tb<SUP>3+</SUP>-to-Eu<SUP>3+</SUP> energy transfer. The biological experiments performed using HeLa cells demonstrate that our nanoparticles can be successfully internalized into the cells, and show bright intracellular luminescence, low cytotoxicity and high photostability. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0nr00673d'> </P>
Fabrication of Alumina Free-standing Objects by Electrophoretic Deposition
Uchikoshi Tetsuo,Furumi Seiichi,Suzuki Tohru S.,Sakka Yoshio 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
The coating of conductive polypyrrole (Ppy) on nonconductive ceramic substrates was performed by polymerization of pyrrole (Py) in an aqueous solution. The Ppy film was characterized by scanning electron microscopy and conductivity measurements. Electrophoretic deposition of bimodal alumina suspension prepared with a phosphate ester was performed using Ppy film as a cathode. Fabrication of alumina ceramics with irregular shapes or complicated patterns were also attempted by sintering the deposits together with the Ppy coated substrates in air.
Development of the Micro Metal Balloon Using Sirasu-balloons as a Core Material
Uezono Tsuyoshi,Sodeyama Ken-ichi,Onomae Hiroshi,Sakka Yoshio 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Recently the Marangoni convention is supposed to be an important phenomenon that significantly affects the solidification. For understanding the Marangoni convection mechanism, visualizing the convention phenomenon of molten tin with ultrasonic has been conducted. This paper reports developing a tracer material of micro metal balloon that is used in the molten system. We have succeeded in coating the surface of Shirasu-ballons with nickel by plating process. The obtained metal balloon is spherical and some characterizations were conducted.
Bending Strength of Textured Alumina Prepared by Slip Casting in a Strong Magnetic Field
Suzuki Tohru S.,Uchikoshi Tetsuo,Morita Koji,Hirage Keijiro,Sakka Yoshio 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
The mechanical properties of ceramics materials can be tailored by designing their microstructures. We have reported that development of texture can be controlled by slip casting in a strong magnetic field followed by heating even for diamagnetic ceramics such as alumina. A strong magnetic field of 12T was applied to the suspension indcuding alumina powder to rotate each particle during slip casting. The sintering was conducted at the desired temperature in air without a magnetic field. C-axis of alumina was parallel to the magnetic field. Bending strength of textured alumina depended on the direction of oriented microstructure.