For a decade, solution-processed functional materials and various printing technologies have attracted increasingly the significant interest in realizing low-cost flexible electronics. In this study, Cu nanoparticles are synthesized via the chemical reduction of Cu ions under inert atmosphere. To prevent interparticle agglomeration and surface oxidation, oleic acid is incorporated as a surface capping molecule and hydrazine is used as a reducing agent. To endow water-compatibility, the surface of synthesized Cu nanoparticles is modified by a mixture of carboxyl-terminated anionic polyelectrolyte and polyoxylethylene oleylamine ether. For reducing the surface tension and the evaporation rate of aqueous Cu nanoparticle inks, the solvent composition of Cu nanoparticle ink is designed as DI water:2-methoxy ethanol:glycerol:ethylene glycol = 50:20:5:25 wt%. The effects of poly(styrene-co-maleic acid) as an adhesion promoter(AP) on rheology of aqueous Cu nanoparticle inks and adhesion of Cu pattern printed on polyimid films are investigated. The 40 wt% aqueous Cu nanoparticle inks with 0.5 wt% of Poly(styrene-co-maleic acid) show the “Newtonian flow” and has a low viscosity under 10 mPa·S, which is applicable to inkjet printing. The Cu patterns with a linewidth of 50~60 μm are successfully fabricated. With the addition of Poly(styrene-co-maleic acid), the adhesion of printed Cu patterns on polyimid films is superior to those of patterns prepared from Poly(styrene-comaleic acid)-free inks. The resistivities of Cu films are measured to be 10~15 μΩ·cm at annealing temperature of 300 ˚C.

Nanostructured carbon materials have been found to have applications in fuel cell electrodes, field emitters, electronic devices, sensors and electromagnetic absorbers, etc. Especially, the CNF (carbon nanofiber) can be expected to play an important role in catalyst supporters for fuel cell electrodes and chemical reactions. In this study, we synthesized CNF from a liquid phase carbon source by a solvothermal method. In addition, we studied the parameters for the preparation of CNF by controlling heating and cooling rates, synthesis temperature and time. We characterized the CNF by SEM/TEM, XRD, Raman spectroscopy and EDS. We found that the heating and cooling rate have strong effects on the CNF formation and growth. We were able to prepare the best CNF at the heating rate of 10˚/min, at 450˚ for 60 minutes, and at the cooling rate of 4˚/min. As a result of Raman spectra, we found that the sample showed two characteristic Raman bands at ~1350cm-1 (D band) and ~1600cm-1 (G band). The G band indicates the original graphite feature, but the D band has been explained as a disorder feature of the carbon structure. The diameter and length of the CNF was about 15~20nm, and over 1μ, respectively.