Investigation of field emission properties of nanorods formed on nanostructured laminated films

The origin of field emission of nano-crystalline diamond/carbon nanowall (ND/CNW) films prepared by DC plasma CVD has been investigated by macroscopic field emission measurements and SEM observation. We found that there is correlation between the field enhancement factors estimated from Fowler-Nordheim plots and shape parameters of the highest nanorods of ND/CNW films deposited at various deposition times. In addition, it was found that emission site densities were almost independent to the deposition time although the deposition time changed the total nanorod densities by over a factor of ten. We concluded that the origin of field emission of ND/CNW films derives from a part of the highest nanorods which mainly grow during CNW deposition.     

Hetero-epitaxial growth of zinc electrodeposits on low-carbon steel sheets

Crystallographic aspects of the electrodeposition of zinc on low-carbon steel sheets have been examined with particular emphasis on the hetero-epitaxy. The hetero-epitaxial growth of zinc crystals largely depends on the surface condition of the ferrite substrate and occurs even at a current density as high as 2 A cm^–2 by reducing the surface oxidation layer. The surface roughness of the substrate induces local disturbance in hetero-epitaxial growth. The orientation relationship between zinc crystals and the ferrite substrate can be interpreted in terms of the minimum misfit atomic arrangements between both phases.     

Viscosities of molten alkali-metal bromides and iodides

Viscosities of molten alkali-metal bromides and iodides, whose reported values are scattered, have been measured by the use of a capillary viscometer made of quartz which is newly designed to obtain a high precision. The viscometer consists of the quartz capillary with a funnel of the suspended level type, and the melt is sealed in it under vacuum. The total error in the measurement is estimated to be within 0.7% at high temperatures. Viscosities of all the alkalimetal bromides and iodides show similar values at a constant temperature. Viscous flow behaviors of all the alkali-metal halides are discussed based on the activation energy and the hard sphere model. The apparent activation energy increases with an increase in the melting temperature of the salt. The viscosity of the alkali-metal halide melt at the melting temperature increases as the ratio of hard sphere volume to hole volume calculated from the surface tension.     

Preparation of uniform titania nanocoating on ZnS-based phosphors by a sol–gel process

A sol–gel process has been developed to coat micron-sized ZnS:Cu,Au,Al phosphors with a smooth and uniform layer of amorphous titania having nanosize thickness. The titania nanocoating is based on the hydrolysis and condensation of titanium tetrabutoxide Ti(OBu)₄. Acetylacetone was used to decrease the reactivity of Ti(OBu)₄. The experimental variables such as water concentration, the amount of ZnS particles, and reaction time were investigated. The thickness of the titania nanocoating was homogeneous and can easily be controlled from 20 to 54 nm by adjusting the experimental variables. The as-prepared titania nanocoating was amorphous phase and could be crystallized to anatase phase upon heating at 500 °C in Ar atmosphere.     

Optimization for removal of ruthenium from nitric acid solution by volatilizing with electrochemical oxidation

Ruthenium is a major fission product element among the platinum group elements (PGEs) in high-level liquid waste (HLLW). Ru tetra-oxide, RuO₄, has high vapor pressure, which is high enough to be run off from its solution even at room temperature. Electrochemical oxidation method, to oxidize nitrosyl ruthenium to the tetra-oxide and then to remove ruthenium from liquid phase to gas phase, was studied to separate Ru from the HLLW. The advantage of this method requires neither additional reagents nor adjustment its valency before the oxidation and disadvantage is necessity of long time for oxidation. In order to improve oxidation rate, we carried out the experiments to clarify the effects following fundamental conditions to the electrochemical oxidation, which are (a) electrolyte temperature, (b) presence of promoter elements, (c) evaporation or reflux of condensed phase, and (d) using or not using of diaphragm at counter electrode. We found the fast oxidation conditions as follows: (1) higher temperature; 95°C, (2) Ce coexistence; 3000 ppm; and (3) usage of a diaphragm for counter electrode. However, evaporation or reflux conditions did not directly affect the electrochemical oxidation efficiency.     

Solution-processed organic crystals for field-effect transistor arrays with smooth semiconductor/dielectric interface on paper substrates

Large surface roughness is a major obstacle for electronic systems fabricated on paper substrates. Here, a mixture solution of organic semiconductor and polymer dielectric was spin-coated on paper substrate with a patterned wettability. This spin-coating process produced organic crystals and a very smooth semiconductor/dielectric interface with a low trap density in well-confined patterns. Despite the large roughness of the paper substrate, the fabricated transistor arrays exhibited high performance with a field-effect mobility reaching 1.3 cm²/V s and an on/off ratio of 10⁸. The presented results offer a simple fabrication method for the current rapidly developing technology of paper electronics.