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Structural and magnetic properties of Ni doped titanate nanotubes synthesized by hydrothermal method
여준한,Wolfgang M. Sigmund 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.1
A new method, hydrothermal method, to synthesize Ni doped rutile TiO2 nanotube (TNT) powders is introduced. This method is more scalable than ones used before. Interestingly, our Ni doped TNTs’ structures show different characteristics and properties than ones fabricated by other methods. We report these resulting structural and magnetic properties here. Ni doped nanotubes contained H2Ti2O5H2O doped with trivalent Ni. The layered structures had six nm inner and ten nm outer diameters, aspect ratios of seven, and exhibited ferromagnetism at room temperature (undoped nanotubes were diamagnetic). Contrary to earlier versions of Ni doped TNTs, we found that trivalent Ni atoms substituted H+ in the nanotubes and thus interacted with titanate’s 3d electrons to produce ferromagnetic activity. This opens the possibility to achieve ferromagnetic activity in TNTs in a new way.
여준한,Wolfgang M. Sigmund 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.1
Titanate nanotube powders with high specific surface area for hydrogen storage were synthesized by alkaline hydrothermal treatment of a TiO2 powder at 150 o C for 48 hrs. With controlling contents of H2O and Na+ in synthesized titanate powders, via ion-exchanging and drying processes, their hydrogen uptake characteristics were evaluated. The titanate nanotube powders showed an increase in the specific surface area with the decreases in Na+ content by the ion-exchanging process and in H2O content by drying processes, but in reverse an decrease in that with severe ion-exchanging or over-drying at high temperature. Their hydrogen uptake increased with decreasing H2O contents in the powders with appropriate Na+ content only under no changing in the particle shape. Therefore, the powders with controlled H2O and Na+ contents had high hydrogen uptake of 2.21 wt% at 90 atm due to proper support of Na+ for interlayer distance in multi-walled tube typed titanate particle.
Effect of liquid media on nanoparticles synthesized of nickel oxide by pulsed laser ablation
강석현,Tian Yi Liu,최봉근,여준한,심광보 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.2
Since nano science and technology has been developed at the end of the 20st century, the key technical issues is how to get alarge number of high purity nano materials which were precisely controlled on the morphology, size and structure, andimprove the dispersion and stability of nano materials. Among the numerous methods, laser as an advanced technology hasgot more and more attention. And the introduction of liquid medium makes the laser ablation process become more complex. This work presents the characteristics of nano-sized magnetic material. Focus on the application and preparation of NiOnanoparticles. By using liquid phase pulsed laser ablation method, NiO nanoparticles have been made in different liquidmedia. The comparison of the effect of different liquid medium on composition, size and shape, and process mechanism of thepreparation by this method were discussed. In addition, because of the magnetic properties of the NiO nanoparticles obtained,it can be better applied in many fields. This unique method of liquid phase pulsed laser ablation, is expected to obtain newnano structure and material, show better physical and chemical properties of material.