XPS study of carbon nitride films deposited by hot filament chemical vapor deposition using carbon filament

Amorphous carbon nitride, a-CN_x, thin films were deposited by hot filament CVD using a carbon filament with dc negative bias voltage on the substrate. The effects of the negative bias and the filament components on the binding structure of the films are investigated by XPS. The composition ratio of graphite to amorphous carbon in the filaments affects the bonding structure of carbon and nitrogen in the films, although the nitrogen content in the films is almost same as 0.1. The nitrogen content in the films changes from 0.1 to 0.3 as the negative bias changes from 0 to − 300 V.     

Excess Solute Carbon and Tetragonality in As-Quenched Fe-1Mn-C (C:0.07 to 0.8 Mass Pct) Martensite

The carbon distribution behavior and crystal structure of as-quenched martensite in Fe-1Mn-C (C: 0.07 to 0.8 mass pct) steels were quantitatively investigated by atom probe tomography (APT) and X-ray diffraction with Rietveld analysis. APT revealed that the martensite steels contained quantities of carbon in solid solution far beyond its solubility in body-centered cubic (bcc)-Fe in all the alloys investigated; the carbon atoms were non-homogeneously distributed as carbides or aggregates on dislocations due to autotempering. Tetragonality was observed in the steels with interstitial solute carbon concentrations in the range of 0.1 to 0.7 mass pct, but was not evident below 0.1 mass pct. The appearance and disappearance of tetragonality in the low-carbon steels may be explained by the disordered bcc ? ordered body-centered tetragonal (bct) mechanism, considering the partial tetragonality due to the heterogeneity of the interstitial solute carbon distribution. The existence of tetragonality in the autotempered low-carbon steels can alternatively be understood by a mechanism based on the kinetic decrease of tetragonality during cooling, where the microscopic strain release is the rate-controlling process. The excess carbon solubility in the autotempered low- and medium-carbon martensite is due to the existence of tetragonal distortions, owing to the slow kinetics of the tetragonality decrease during cooling.

     

Experimental Study of the Viscous Pump with a Helical Channel Rotor： Torsion Effect of the Channel

The viscous pump, which has a rotor with a helical square channel, is studied experimentally. The non-dimensional channel curvature is taken to be about 0.1. Three types of torsion of the channel are made to investigate the torsion effect on the flow characteristics. We measure the flux through the channel at a constant rotor speed by changing the pressures at the entrance and exit of the pump. We also observe the secondary flow at a crosssection of the channel. Some of the results obtained are shown as follows： The friction factor along the channel to get the same flux is large for large channel torsion at a constant rotation, and becomes small when the favorable rotation of the rotor to the flow is applied. As for the secondary flow in a cross-section, there appear several types of vortex. When there is no rotation, the secondary flow is almost a symmetric two-vortex type for small flux as is the ordinary Dean vortex, but it changes to a four-vortex type when the flux is large. The secondary flow becomes asymmetric as the rotation is applied. We have unsteady flow patterns at large flux and rotation.     

Crystal Orientation and Transport Properties of a 633-nm-Diameter Bismuth Nanowire

The crystal orientation and resistivity of a bismuth nanowire (diameter 633 nm, length 1.91 mm) encased in quartz were measured. The nanowire surface was irradiated with a high-intensity, collimated x-ray beam through the quartz template, and several Laue spots were observed with no streak patterns. Therefore, we concluded that the nanowire was a single crystal. The crystal orientation could be determined by measuring the relationship between the Laue spot distribution and the location of the nanowire fixed by a goniometer. The direction along the wire length was strongly directed toward the bisectrix axis of bismuth. The temperature dependence of the nanowire resistivity was measured; the resistivity at 300 K was 1.40 μΩ m, which is somewhat greater than that of the bulk sample due to the lower mobility of the nanowire. The temperature coefficient of resistivity was positive in the temperature range from 300 K to 165 K, and it became negative below 165 K. The temperature dependence can be modeled by accounting for the limited electron mean free path in the bismuth nanowire based on the crystal orientation determined by the Laue measurements.     

Two‐Dimensional Orientation in Bi4Ti3O12 Prepared Using Platelet Particles and a Magnetic Field

Tailoring the crystallographic orientation in piezoelectric ceramics is very useful for improving their properties. Orientation in ceramics can be controlled by templated grain growth, hot forging, etc. We have focused on using a strong magnetic field for the crystallographic orientation even in diamagnetic ceramics. In a previous study, although only a one‐directional orientation could be controlled by these methods, it was difficult to control the multi‐axis orientation in the ceramics. In this study, we demonstrated that alignments of the c‐axis and the <100> axis in Bi₄Ti₃O₁₂ piezoelectric ceramics were controlled by using a strong magnetic field as well as platelet particles. We also estimated the degree of orientation by an electron back scattering diffraction analysis. When the magnetic field was applied to the platelet particles, appropriately 80% of the grains were aligned with the tilt angle made by the c‐axis and the vertical direction less than 10° and 73% of grains were oriented with the angle between the <100> axis and the magnetic field less than 10°.     

Independent Reinforced Soil Structure with Pile Foundation—Piled Geo-Wall: An Experimental Study on the Application to Seismic Measure for Embankment—

Our aim in this study was to achieve an independent reinforced soil structure with pile foundation that can be applied to such structures as earth retaining walls and countermeasures against the collapse of embankments or rockfall impact built on narrow construction sites, such as on slopes. In order to confirm the effectiveness of the application of pile foundation to reinforced soil structures by geogrid for improvement of the lateral resistance of the structure and to investigate the interaction between pile and reinforced soil structure, a dynamic centrifuge model test (25 G) was carried out. Two geogrid reinforced soil, one with piles and one without, were used in a countermeasure to reduce the deformation of a road embankment built on a slope in the event of an earthquake, and the effectiveness of the pile foundation to the reinforced soil structure was considered with regard to it affected the road surface. The details and the results of the dynamic centrifuge model test, as well as the interaction between pile and reinforced soil structure are described, and the effectiveness of the application of pile foundation to reinforced soil structure is discussed in this paper.     

Interfacial interaction and mechanical properties of chitin whisker–poly(vinyl alcohol) gel‐spun nanocomposite fibers

Nanocomposite fibers were prepared from chitin whiskers (ChWs) as the reinforcing phase and poly(vinyl alcohol) (PVA) as the matrix. Colloidal suspensions of ChWs, obtained by acid hydrolysis of chitin from crab shell, were thoroughly mixed with aqueous PVA. The homogeneous PVA–ChW suspensions were gel‐spun into a methanol coagulating bath. Wide‐angle X‐ray diffraction patterns evidenced the orientation of ChWs along the fiber axis. From differential scanning calorimetry, the crystallinity of the PVA component was found to increase with ChW loading due to the possible dragging of PVA chains adhering to ChWs during vertical extrusion. The non‐isothermal crystallization peak of PVA was observed to shift to lower temperature with ChW loading indicating interfacial interactions between PVA and ChW. Further interaction between PVA and ChW was evidenced by the shifting of the Fourier transform infrared bands of PVA to lower wavenumber and the dynamic tan δ peak, corresponding to α‐relaxation of PVA, shifting to higher temperature. The interaction of ChWs with the matrix PVA yielded a significant enhancement in the mechanical properties of the nanocomposites. Copyright © 2012 Society of Chemical Industry     

A New Simple Model of Direct Spectral Irradiance with Easily Observable Atmospheric Parameters

Direct irradiance and direct spectral irradiance were measured for 16 months along with other basic atmospheric parameters. The direct irradiance changed smoothly on a clear day and fluctuated on a fair day. Then, we considered the possibility of a new, simple model of direct spectral irradiance expressed with fewer atmospheric parameters and applicable for even fair days. This new model, called DISPEC, can calculate the direct spectral irradiance from basic atmospheric parameters for wavelengths >400 nm. In DISPEC, the ozone absorption was ignored and the thin cloud effect was taken into account as a new parameter, which was considered to be proportional to the direct irradiance, instead of aerosol parameters. The performance of DISPEC was then compared with that of a well‐known model of SPCTRAL2. Although the calculation results by SPCTRAL2 exhibited considerable error, especially in visible wavelength range on a fair day, those calculated using DISPEC showed good agreement with observed data on both clear and fair days. © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Real-time PCR detection of adenoviruses, polyomaviruses, and torque teno viruses in river water in Japan

The prevalence of DNA viruses in water from the Tamagawa River, Japan was quantitatively surveyed for 6 months, from April to September 2003. A total of 18 river water samples were subjected to virus concentration method using an electronegative membrane, followed by DNA extraction and direct quantitative real-time polymerase chain reaction (qPCR) for DNA viruses. Adenoviruses of serotypes 40 and 41 were detected most frequently in the river water samples tested (61.1%), at a concentration ranging from 3.16 × 10³ to 1.38 × 10⁵ copies/l, followed by JC polyomaviruses (11.1%) and torque teno viruses (5.6%). No sample was positive for BK polyomaviruses. In addition, for selective detection of virus particles, adenoviruses 40 and 41 were tested with qPCR combined with an immunomagnetic separation technique; they were detected in only 16.7% of the samples, showing a concentration ranging from 7.42 × 10² to 4.24 × 10⁴ copies/l. This study is significant since it is the first study to demonstrate the prevalence of polyomaviruses in water samples in Japan and to use immunomagnetic separation qPCR to detect adenovirus particles in aquatic environments.