Grain-Boundary Resistivity of Stabilized Zirconia Films

The influence of grain-boundary density on the resistivity of grains and grain boundaries in stabilized zirconia films, made by a modified doctor blade method using Al₂O₃ as a sintering agent, was investigated at 300° to 500°C. Only cubic zirconia was detected by X-ray diffraction. However, electron probe microanalysis showed that the Al concentration was preferentially enriched near grain boundaries. The resistance per square centimeter of grain-boundary surface decreased with increasing grain-boundary density in the range 170 to 310 cm^-1 .     

Measurement of effective atomic numbers using energy-resolved computed tomography

For ion radiation therapy, the measurement of effective atomic numbers, Z_eff, is necessary to know the material distribution in a human body; the range of ions entering the human body is influenced by the material distribution along their paths. Z_eff, however, cannot be measured at hospitals because monochromatic X-rays with different energies are necessary and are used only at synchrotron facilities. To make Z_eff measurements at hand, we propose energy-resolved computed tomography (CT) using a “transXend detector”. By assigning two narrow energy ranges in the unfolding process of the data obtained by the transXend detector, Z_eff for acrylic and aluminum can be estimated by energy-resolved CT. The estimated Z_eff are compared with those obtained by dual-energy and monochromatic X-ray CT.     

Effect of pore size of self-organized honeycomb-patterned polymer films on spreading, focal adhesion, proliferation, and function of endothelial cells

The design of nano- and microstructures based on self-organization is a key area of research in the search for new materials, and it has a variety of potential applications in tissue engineering scaffolds. We have reported a honeycomb-patterned polymer film (honeycomb film) with highly regular pores that is formed by self-organization. This study describes the behavior of vascular endothelial cells (ECs) on honeycomb films with four different pore sizes (5, 9, 12, and 16 microm) as well as on a flat film. We examined the influence of the honeycomb pattern and pore size on cell behavior. The changes in cell morphologies, actin filaments, vinculin clusters, cell proliferation, and secreted extracellular matrix (ECM) (fibronectin, laminin, type IV collagen, and elastin) production profiles were observed by using optical, fluorescence, and scanning electron microscopy. The ECs that adhered to the flat film showed an elongated morphology with random orientation; the actin filaments and focal adhesions were not conspicuous. On the other hand, the ECs on the honeycomb films exhibited greater spreading and flattening; the degree of spreading of the ECs increased with an increase in the pore size. The actin filaments and focal adhesions appeared conspicuous, and the focal adhesions localized along the edge of the honeycomb pores were distributed over the entire projected cell area. The honeycomb film with a pore size of 5 microm showed the highest cell proliferation and ECM production profiles. These results suggest that the honeycomb film is a suitable material for designing a new vascular device.     

The method for surface functionalization of single-walled carbon nanotubes with fuming nitric acid

Surface functionalization of single-walled carbon nanotubes (SWCNTs) was carried out using fuming nitric acid as a NO₂ radical source. The surface double bonds of the SWCNTs reacted with the NO₂ radicals at 10–90 °C under sonication, and following treatment with aqueous NaOH yielded modified carbon nanotubes with high affinity for polar solvents such as dimethylformamide. The structure of the product was characterized using Fourier transform-infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis, and atomic force microscopy. FT-IR and XPS spectra revealed the product has OH groups (3400, 1200 cm⁻¹), which was expected due to the addition of NO₂ radicals to the surface double bonds and subsequent substitution with OH groups. C_1s curve fitting analysis of the XPS spectra was used to quantitatively determine the different functional groups on the surface, and the amount of COOH groups was found to be increased from 2.8% to 9.3% due to progressive oxidation by increasing the reaction temperature from 10 to 90 °C.     

A new method for disclosing internal phenomena in a distillation column by use of material-utilization diagram

Graphical representation of separation performance and the exergy loss of all subprocesses in a distillation column on material-utilization diagram (MUD) are demonstrated to disclose behaviors of distillation columns. The diagram displays flowrates of liquid and gas on abscissa and logarithm of mole fractions, ln x and ln y, on ordinate. By using this diagram, separation performance, i.e., concentrations of light component in the distillate and of heavy component in the bottoms, can be elucidated. This diagram is also useful for qualifying and quantifying the exergy loss in a distillation column, since the four kinds of exergy losses, i.e., losses due to mixing in liquid phase, due to mixing in vapor phase, and due to evaporation of light components and condensation of heavy components through phase change, can be displayed compactly in a single figure. The effect of the change in feed flowrate is also demonstrated.     

Enhancement of pool boiling heat transfer in water and ethanol/water mixtures (effect of surface‐active agent)

The surface tension of alcohol/water mixtures has been measured over the whole fraction range and then it has been measured when a surface‐active agent was added into the mixtures. The effect of the concentration of alcohol and the surface‐ active agent on surface tension was experimentally clarified, in order to gain base data related to enhancement of the heat transfer coefficient in the mixtures and water. The experiment was also carried out to enhance the boiling heat transfer coefficients of water and alcohol/water mixtures on a horizontal heated fine wire at a pressure of 0.1 MPa by adding a surface‐active agent into the tested liquid. The results show, the coefficients were enhanced in lower alcohol concentration (C ≦ 0.5) and low heat flux range which occur just after the onset of boiling. It was also found that the enhancement effect by the surfactant disappears in concentrations over 1000 ppm. Finally, we demonstrated that the surface tension remarkably affects the heat transfer coefficients in nucleate pool boiling. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(4): 229–244, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20010     

Atomic force microscopy and Raman spectroscopy study of the early stages of carbon nanowall growth by dc plasma-enhanced chemical vapor deposition

The early stage of carbon nanowall (CNW) growth on Si substrate by dc plasma-enhanced chemical vapor deposition (PECVD) was investigated by means of atomic force microscopy and Raman spectroscopy. First nanodiamond particles with highly defective graphene layers are shown to be formed over the substrate. Subsequently nanographite grains are formed on the nanodiamond film. The density of nanographite grains increases with increasing deposition time, and they coalesce to form a continuous graphite film. Finally CNWs are shown to grow vertically on the graphite film. Such understanding of the interface layers between the substrate and CNWs will be useful for not only the growth control but also device applications.     

Investigation of particle reduction and its transport mechanism in UHF-ECR dielectric etching system

Control of particle transport was investigated by using a UHF-ECR etching apparatus with a laser particle monitor. The particles, which float at a plasma-sheath boundary, fall on a wafer when the plasma is turned off. These floating particles can be removed from the region above the wafer by changing the plasma distribution. We measured the distribution of the rotational temperature of nitrogen molecules across the wafer to investigate the effect of the thermophoretic force. We found that mechanisms of particle transport in directions parallel to the wafer surface can be explained by the balance between thermophoretic and gas viscous forces.