Carbon-coated Non-magnetic Iron Oxide Particles for the Substrate of Multi-layered Magnetic Recording Media

Non-magnetic particles with finer size (less than 200 nm), higher dispersibility, higher blackness and lower electrical resistance are required to produce better multi-layered magnetic tape media which have non-magnetic substrate using non-magnetic sub-layer materials. A special method to prepare acicular hematite particles, whose cross-sectional diameter is about 150 nm, coated with carbon black using a surface modification agent is reported in this paper. Transmission electron microscopy photographs of carbon-coated hematite particles indicate that all of the carbon black is firmly bound to the surface in a distinct layer. The thickness of carbon-coating layer was about 1 to 2 nm if 15% by weight of carbon black is coated onto the particle surface.Non-magnetic substrates for multi-layered magnetic recording media prepared using the carbon-coated particles exhibit improvements in both light transparency and electrical resistance. A decrease in transparency of about 30% as well as a reduction in the electrical resistance of about 1.5 orders of magnitude relative to conventionally prepared substrates was achieved. The surface smoothness and the viscosity were also improved because the dispersibility of these particles in non-magnetic lacquer became better than that of the physical mixture of uncoated hematite particles and carbon black.     

On the Dual Mode of Aldol Cyclization of Bicyclo-[4.3.1] Decane-3,8-Dione: A Novel,Efficient Entry into the Isotwistanone System

Isotwistanones have been highlighted since their use in the sesquiterpene syntheses.¹ Begley and coworkers reported a new access to this system via the postulated aldol cyclization of bicyclo [4.3.1]decane-2, 7-dione.² We have found another novel path of a similar mode.     

Experimental investigation of nanoparticle dispersion by beads milling with centrifugal bead separation

A new type of beads mill for dispersing nanoparticles into liquids has been developed. The bead mill utilizes centrifugation to separate beads from nanoparticle suspensions and allows for the use of small sized beads (i.e. 15-30 microm in diameter). The performance of the beads mill in dispersing a suspension of titanium dioxide nanoparticle with 15 nm primary particles was evaluated experimentally. Dynamic light scattering was used to measure titania particle size distributions over time during the milling process, and bead sizes in the 15-100 microm range were used. It was found that larger beads (50-100 microm) were not capable of fully dispersing nanoparticles, and particles reagglomerated after long milling times. Smaller beads (15-30 microm) were capable of dispersing nanoparticles, and a sharp peak around 15 nm in the titania size distribution was visible when smaller beads were used. Because nanoparticle collisions with smaller beads have lower impact energy, it was found by X-ray diffraction and transmission electron microscopy that changes in nanoparticle crystallinity and morphology are minimized when smaller beads are used. Furthermore, inductively-coupled plasma spectroscopy was used to determine the level of bead contamination in the nanoparticle suspension during milling, and it was found that smaller beads are less likely to fragment and contaminate nanoparticle suspensions. The new type of beads mill is capable of effectively dispersing nanoparticle suspensions and will be extremely useful in future nanoparticle research.     

Scale effects on flexural wave propagation in nanoplate embedded in elastic matrix with initial stress

In this paper, the small-scale effects on the flexural wave in the nanoplate are studied. Based on the nonlocal continuum theory, the equation of wave motion is derived and the dispersion relation is presented. Numerical simulations are performed to investigate the influences of the scale coefficient, the surrounding elastic matrix and the initial stress on the wave propagation properties. The results show that the nonlocal model provides an appropriate method to investigate the characteristics of the flexural wave in the nanoplate. Furthermore, the direction and amplitude of the biaxial load, the stiffness of the shearing layer and the Winkler foundation can change the wave properties, significantly.     

Excitons in optical spectra of boron-nitride (BN) nanotubes

Exciton effects are studied in single-wall boron-nitride nanotubes. The Coulomb interaction dependence of the band gap, the optical gap, and the binding energy of excitons are discussed. The optical gap of the (5,0) nanotube is about 6 eV at the on-site interaction U=2t with the hopping integral t=1.1 eV. The binding energy of the exciton is 0.50 eV for these parameters. This energy agrees well with that of other theoretical investigations. We find that the energy gap and the binding energy are almost independent of the geometries of nanotubes. This novel property is in contrast with that of the carbon nanotubes, which show metallic and semiconducting properties depending on the chiralities.     

Effect of initial stress on Love waves in a piezoelectric structure carrying a functionally graded material layer

The effect of initial stress on the propagation behavior of Love waves in a piezoelectric half-space of polarized ceramics carrying a functionally graded material (FGM) layer is analytically investigated in this paper from the three-dimensional equations of linear piezoelectricity. The analytical solutions are obtained for the dispersion relations of Love wave propagating in this kind of structure with initial stress for both electrical open case and electrical short case, respectively. One numerical example is given to graphically illustrate the effect of initial stress on dispersive curve, phase velocity and electromechanical coupling factor of the Love wave propagation. The results reported here are meaningful for the design of surface acoustic wave (SAW) devices with high performance.     

Focus on Research in Nanoparticle in Asia

Journal of Nanoparticle Research -     

Filtration efficiency of a fibrous filter for nanoparticles

The filtration efficiency for nanoparticles down to 1 nm in size through glass fibrous filters was measured using an improved PSM-CNC system. In addition, the effects of relative humidity and particle charge were investigated for various nanoparticle diameters. The results show that the filtration efficiencies were independent of humidity and affected by particle charge in the case of particles below 100 nm in size. For particles smaller than 2 nm, the particle penetrations increased with decreasing particle size. These results suggest that the thermal rebound phenomena would be operative for nanoparticles with diameters below 2 nm, even though it would depend on the states of both the particles and the filter media. These results are particularly important for experimental investigations of the behavior of nanoparticles on a filter.     

A super coupling of radiation field and excitons confined in spatially periodic structure

By means of the microscopic nonlocal response theory, we analyze the mode structure of the coupled system of radiation and periodically confined excitons in multiple thin films. It is clarified how the spatially separated excitons which are coupled with each other via radiation share the radiative shift and width depending on the period and thickness of the excitonic active layers, and on their quantum number of confined levels. These results show the possibility that the very large radiative width can be realized by setting up the period and thickness of the excitonic active layers at appropriate values, which leads to very fast radiative decay beyond the saturated value of the giant oscillator strength effect.