XRD and TEM study of high pressure treated single-walled carbon nanotubes and C60-peapods

In situ synchrotron X-ray diffraction measurements of single-walled carbon nanotube and C₆₀-peapod samples under high pressures up to 13 GPa and at high temperature were carried out. Anisotropical shrinkages of their bundle two-dimensional lattices by compression at room temperature were observed. It was found that the lattices recover original forms reversibly upon pressure release. It was also found that irreversible phase transformations occur by raising temperature at the highest pressure. The high pressure and high temperature treated samples were examined by X-ray diffraction, transmission electron microscope, and Raman measurements. It was indicated by transmission electron microscope observation that hexagonal diamond is able to be synthesized by high pressure and high temperature treatment of C₆₀-peapods.     

Current‐Induced Nucleation and Annihilation of Magnetic Skyrmions at Room Temperature in a Chiral Magnet

A magnetic skyrmion is a nanometer‐scale magnetic vortex carrying an integer topological charge. Skyrmions show a promise for potential application in low‐power‐consumption and high‐density memory devices. To promote their use in applications, it is attempted to control the existence of skyrmions using low electric currents at room temperature (RT). This study presents real‐space observations for the current‐induced formation and annihilation of a skyrmion lattice (SkL) as well as isolated skyrmions in a microdevice composed of a thin chiral magnet Co₈Zn₉Mn₃ with a Curie temperature, T _C ≈ 325 K, above RT. It is found that the critical current for the manipulation of Bloch‐type skyrmions is on the order of 10⁸ A m^?2, approximately three orders of magnitude lower than that needed for the creation and drive of ferromagnetic (FM) domain walls in thin FM films. The in situ real‐space imaging also demonstrates the dynamical topological transition from a helical or conical structure to a SkL induced by the flow of DC current, thus paving the way for the electrical control of magnetic skyrmions.     

An investigation of cavity growth in a superplastic aluminum alloy processed by ECAP

Quantitative measurements were taken to evaluate the significance of cavitation in the tensile testing of a superplastic spray-cast Al-7034 alloy processed by equal-channel angular pressing (ECAP). Samples were processed by ECAP and then tested in tension at 673 K using strain rates from 10⁻³ to 10⁻¹ s⁻¹. For comparison purposes, similar tensile testing was conducted also on samples without ECAP processing. Inspection of polished sections after tensile testing revealed extensive internal cavitation in all samples. Measurements were taken to provide detailed information on the sizes and shapes of the cavities and these measurements were analyzed to determine the dominant cavity growth mechanisms. The results demonstrate the importance of superplastic diffusion growth in ultrafine-grained materials processed by ECAP.     

Suppression of pH effect on the electrochemical deformation in polyaniline film

pH effect on the electrochemical deformation of freestanding polyaniline (PANi) film was investigated by means of electrochemomechanical deformation (ECMD) measurement. The maximum anodic expansion was found in PANi at around pH = 1.5 in aqueous acid consisted of HCl and NaCl. The deformation vs. redox charge (D−Q) plots revealed the critical differences in the deformation characteristics below and above pH = 1.5. The similar pH dependences were also observed in other acidic media. Against these results, we investigated the surface coating effect of PANi film on deformation behaviors. It was revealed that the PPy coating on PANi film successfully reduced the pH dependence of the PANi/PPy film deformation. The results indicate that the buffer layer coated on the PANi film surface decreases the ion concentration effects on the PANi deformation. The result indicates the extensive usage of PANi actuator in wide pH aqueous media.     

Anisotropic thermal conductivity of three-layer laminated carbon-graphite composites from carbonized wood

Composites with characteristics of anisotropic thermal conductivity for thermal management in Solar Power Satellite (SPS), to discharge the heat that was generated when solar energy was not converted to electricity, were developed by alternating layers of laminated graphite and carbonized wood. The effects of the weight fraction of carbonized wood, particle size, interlayer interfaces, and environment temperature on the thermal conductivity and the ratio of thermal conductivity between horizontal and vertical directions (H/V ratio) to the plain surface of samples were discussed. The thermal conductivities of carbon–graphite (C/G) composites were measured using the laser flash method. Laminated C/G composites improved the anisotropic thermal conductivity. The highest H/V ratio of 10.17 was obtained at 10 wt% of carbonized wood. Particle size and interlayer interfaces were found to affect the anisotropic thermal conductivity. The thermal conductivity of C/G composites increased with increasing temperature from 25 °C to 150 °C.     

Technologies to improve photo-sensitivity and reduce VOD shuttervoltage for CCD image sensors

New technologies to increase the photo-sensitivity and reduce the shutter voltage of the vertical over-flow-drain (VOD) have been developed for CCD image sensors. The photo-sensitivity was increased 40% by forming an anti-reflection film over the photodiode and reducing the thickness of the p⁺-layer formed at the photodiode surface. The VOD shutter voltage was reduced from 31 to 18 V by using an epitaxially grown substrate with double impurity concentration layers     

Characteristics of VHF excited hydrogen plasmas using a ladder-shaped electrode

A VHF excited hydrogen plasma was produced with a ladder-shaped electrode whose excitation frequency ranged up to 100 MHz for gas pressures of 40–200 mTorr and the plasma parameters were measured with a Langmuir probe. When the excitation frequency was increased, the electron density increased and the electron temperature decreased. The pressure dependence of the electron temperature at excitation frequencies of 65 and 100 MHz was different from the usual relationship: the electron temperature tended to increase with increasing pressure.     

Discrete–variational Xα calculations of graphite and alkali–metal graphite intercalation compounds

First-principles molecular orbital calculations using discrete–variational (DV)-Xα method are carried out on the model clusters of graphite and alkali–metal graphite intercalation compounds MC_x(M=Li, Na, K, Rb, and Cs). Results of the calculations are used so as to simulate the experimentally observed near-edge X-ray-absorption fine-structures (XANES) and ultraviolet photoelectron spectra. For the clusters of graphite and KC_x, the calculated partial electronic densities of states (PDOSs) are in good agreement with the experimental C K-edge and K K-edge XANES spectra, respectively. Furthermore, the accordance between the calculated DOSs and the observed UPS spectra of graphite and RbC_x is also satisfactory. It is shown that the Fermi level is pushed up into the conduction band of graphite by doping alkali metals.     

High-Index-Layer Coating on a Lensed Fiber Endface for Enhanced Focusing Power

A new scheme for lensed fibers with a high focusing power is proposed. The new lensed fiber has a high-index layer coated (HILC) on a convex-shaped endface of a single-mode fiber (SMF). Numerical investigation shows that, by coating a 10-mum-thick film with refractive index of 3.7, the lensed fiber can contract the beam diameter of the propagating mode from 10.4 mum at the wavelength of 1.55 mum, to 1.2 mum. The enhanced focusing effect of the lensed fiber has been confirmed experimentally by coating an a-Si:H film on the lensed endface. The measured focused spot diameter was as small as 1.6 mum, much the same as the wavelength.