Functional Areas: Beyond the Synthesis of Nano-Particles Masahiro YOSHIMURA
Promotion Center for Global Materials Research, Dept of Mater.,Sci. and Eng., National Cheng Kung University, Tainan,Taiwan: firstname.lastname@example.org
Prof. Emeritus. Tokyo Institute of Technology, Japan :email@example.com
Keywords: Soft process,Ceramic,Synthesis,Particle,Film,Pattern,Solution As well as organic and/or bio- materials, advanced inorganic(ceramic) materials have been used in wide area of applications like structural, mechanical, chemical, electrical, electronic, optical, photonic, biological, medical, etc. They have generally been fabricated by so-called high-technology, where high temperature, high pressure, vacuum, molecule, atom, ion, plasma, etc. have been used for their fabrications, because inorganic materials are difficult in shape forming and fixing due to their intrinsic rigidity and brittleness. Even though nano-sized particles of inorganic materials could be synthesized by low-energetic route, i.e.”soft chemistry” or “green chemistry”, their shape forming and fixing cost energetically and environmentally.
We have challenged to fabricate those advanced inorganic materials with desired shape/size/location,etc. directly in low energetic ways using aqueous solutions since 1989 when we found a method to fabricate BaTiO3 film on Ti substrate in a Ba(OH)2 solution by Hydrothermal Electrochemical[HEC] method at low temperatures of 60-200 C. We proposed in 1995 an innovative concept and technology, “Soft Processing” or “Soft Solution Processing,” which aims low energetic (=environmentally benign) fabrication of shaped, sized, located, and oriented inorganic materials in/from solutions. It can be regarded as one of bio-inspired processing, green processing, or eco-processing.1,2) When we have activated/stimulated interfacial reactions locally and/or moved the reaction point dynamically, we can get patterned ceramic films directly in solution without any firing, masking or etching. They can be called Direct Patterning methods which differ from previous patterning methods consisting of multi-step processes. The notable feature of Direct Patterning is that each reactant reacts directly on site, at the interface with the substrate. Therefore, the chemical driving force of the reaction, A+B=AB, can be utilized not only for synthesis but also for crystallization and/or consolidation of the compound AB. It is rather contrasting to general patterning methods where thermal driving force of firing is mostly used for the consolidation of the particles.3)
We have developed the Direct Patterning of CdS, PbS and CaWO4 on papers by Ink-Jet Reaction method and LiCoO2 by electrochemically activated interfacial reactions.3) Furthermore, we have succeeded to fabricate BaTiO3 patterns on Ti by a laser beam scanning and carbon patterns on Si by a needle electrode scanning directly in solutions.4) Recent success in TiO2 and CeO2 patterns by Ink-Jet Deposition, where nano-particles are nucleated and grown successively on the surface of substrate thus become dense even below 300 C3) will be presented.
1)MRS Bulletin,25,Sept. issue 2000, special issue for Soft Processing of Advanced Inorganic Materials ,Guest Editor:M. Yoshimura and J. Livage.
2)Yoshimura, M., J. Mater. Sci.,41 ,1299-1306 (2006), 432085-2103(2008).
3)Yoshimura, M. and Gallage R., Solid State Electrochem., 12[7/8]775-782(2008).
4) Watanabe,T., Yoshimura, M. ,Thin Solid Film, 515, 2696-2699 (2006), Carbon, 44, 799-802 (2006). 5)Wu,J-J.,Liao,W-P.,Yoshimura,M. Nano Energy,On-line July 11,2013 .