Low thermal expansion and low thermal expansion anisotropy ceramic of Sr0.5Zr2(PO4)3 system

A low thermal expansion ceramic with a very low thermal expansion anisotropy was synthesized from the Sr_0.5Zr₂(PO₄)₃ system. The sintering was promoted by addition of MgO, and the solgel technique also improved the sinterability. The thermal expansion of the crystal was lowered by substituting Nb⁵⁺ for Zr⁴⁺ and 1/2Sr²⁺ pairs, becoming near-zero for Sr_0.25Nb_0.5Zr_1.5(PO₄)₃. All dense ceramics in this system had a strength of about 80 MPa, and did not suffer microcracking even in the coarse-grained polycrystalline ceramics, owing to the very low thermal expansion anisotropy of the crystals.     

Tuning the optical bandgap of multi-walled carbon nanotube-modified zinc silicate glass-ceramic composites

Novel glass-ceramic composites with optical bandgap tunability were synthesised. Zinc silicate powder (ZS) was mixed with multi-walled carbon nanotubes (MWCNTs) at various mass fractions (0, 1, 2, and 3 wt %), followed by argon sintering. X-ray diffraction (XRD) analysis revealed the structural change from an amorphous ZS phase to a crystalline willemite phase (Zn₂SiO₄) by adding MWCNTs, and the largest crystallite size was obtained for ZS with 2.0 wt% MWCNTs. Although the agglomeration of ZS and MWCNTs was observed by field emission scanning electron microscopy (FESEM), there was no chemical interaction between ZS and MWCNTs as confirmed by Fourier transform infrared spectroscopy (FTIR). MWCNTs enhanced the crystallisation, which led to the green emission of Zn₂SiO₄ blue-shifting from 572 nm to 557 nm. The narrowed optical bandgap of Zn₂SiO₄ was attributed to the MWCNT-induced exciton localised between the valence band and conduction band of Zn₂SiO₄. The bandgap tuning effect of MWCNTs potentially paved new ways to mass fabricate zinc silicate-based semiconductors with desirable optical bandgap energy E_g, which significantly benefits the sensor and laser-related industry.     

Performance and quality analysis of Mo-Si multilayers formed by ion-beam and magnetron sputtering for extreme ultraviolet lithography

Mo-Si multilayer structures were grown by ion-beam and magnetron sputtering to make high-performance mask blanks for practical use in extreme-ultraviolet (EUV) lithography. For ion-beam sputtering, the effect of using Ar or Xe as the sputtering gas, and the impact of the acceleration voltage of Ar or Xe ions on the EUV reflectivity of multilayers were evaluated. In the wavelength range of 12.5-14.5 nm, the peak EUV reflectivity was 60-63% for 40 Mo-Si bilayers grown by ion-beam sputtering, and 62-65% for those grown by magnetron sputtering. Transmission electron microscopy images of Mo-Si multilayers revealed interface layers between the Mo and Si layers. They were found to be composed of a mixture of Mo and Si and to be formed during sputtering. They had a thickness of 1.5-2.0 nm for the deposition sequence Mo-on-Si, and 0.5-1.0 nm for Si-on-Mo. In addition, they were 20-30% thicker for ion-beam sputtering than for magnetron sputtering. Calculations of the EUV reflectivity spectrum for 40 Mo-Si bilayers indicate that interface layer thickness plays a crucial role in determining the EUV performance of multilayers. Finally, an ion-implantation model was found to provide a better explanation of the mechanism of interface layer formation than a thermal-interdiffusion model.     

Real-time imaging of single-molecule fluorescence with a zero-mode waveguide for the analysis of protein-protein interaction

Real-time imaging of single-molecule fluorescence with a zero-mode waveguide (ZMW) was achieved. With modification of the ZMW geometry, the signal-to-background ratio is twice that obtainable with a conventional ZMW. The improved signal-to-background ratio makes it possible to visualize individual binding-release events between chaperonin GroEL and cochaperonin GroES at a concentration of 5 microM. Two rate constants representing two-timer kinetics in the release of GroES from GroEL were measured with the ZMW, and the measurements agreed well with those made with a total internal reflection fluorescence microscopy. These results indicate that the novel ZMW makes feasible the direct observation of protein-protein interaction at an intracellular concentration in real time.     

Synthesis of zeolite from steel slag and its application as a support of nano-sized TiO2 photocatalyst

Steel slag, commercial waste material containing silica and alumina which are the chemical components elements of zeolite, was used as a source for synthesis of FAU zeolite (Y-zeolite, X-zeolite). Through acid-treatment to remove CaO species from steel slag and hydrothermal treatment, well-crystallized Na type FAU zeolite was obtained. Furthermore the synthesized FAU zeolite was applied as a support of photocatalyst. It was found that hydrophobic surface property of zeolite enhances photocatalytic activity for decomposition of organic pollutants and the zeolite synthesized from steel slag would be applicable as promising support of TiO₂ photocatalyst.     

Portable application of thermal plasma and arc discharge for waste treatment,thermal spraying and surface treatment

Thermal plasma and arc discharge have numerous useful characteristics related to their high temperature and intense radiation. Many applications have been developed. Recently, a portable twin‐torch plasma arc furnace for waste treatment, thermal spraying torches, steam plasma torches, and surface treatment of low‐pressure arc was developed. This paper describes the recent development of a portable application of thermal plasma and arc discharge. The portable device can treat wastes and perform thermal spraying and surface treatments on site. This technology is expected to become more attractive. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Rocket‐triggered lightning current waveforms in winter and investigation of extra‐fast current change

Since 1986, the authors have been taking part in triggered lightning experiments in winter, at Okushishiku, Ishikawa, for the purpose of observing the entire lightning current waveforms with coaxial shunt resistors and an electro‐optical measuring system. Extra‐fast current changes of the order of 1,000 kA/μs were recognized by sharp pulse records superposed on the positive current waveform obtained by a shunt resistor of relatively high residual inductance. This was not the case with a resistor of lower inductance. Furthermore, a positive lightning current waveform which looks like the composite result of bi‐polar discharges has been observed by an advanced measuring system of high performance. This paper deals with these current‐related topics of triggered lightning discharges, which will be analyzed hereafter in detail. © 1999 Scripta Technica, Electr Eng Jpn, 128(2): 18–23, 1999     

Structure Change of Ca2SiO4 Solid Solutions with Ba Concentration

A series of Ba-bearing Ca₂SiO₄ solid solutions (C₂S( ss )), (Ba _x Ca_{1− x} )₂SiO₄ with 0.075 x 0.30, were prepared and examined by X-ray and electron beam diffraction. They are all made up of orthorhombic domains 120° different in orientation around the common c axis of the former α phase. The C₂S solid solution with x = 0.075 shows a superstructure incommensurate along the a axis with λ (modulation wavelength) = 3.5 and commensurate along the c axis with Δ= 3. With x = 0.15, modulation is observed only along the a axis and Δ= 3.4. No evidence of superstructure is found with x = 0.24; the space group and cell dimensions are comparable with those of pure α '_H-C₂S. The C₂S( ss ) with x = 0.30 gives a superlattice with the cell-edge length of 3 b . All the C₂S( ss ), when reheated at 1000°C for 24 h, produced lamellae of the trigonal phase T nearly in parallel with (001) of the host α '_L phase. The crystallographic orientation between the two phases is

This indicates that the above Ba-bearing C₂S( ss ) phases occur as precursors to the thermodynamically more stable two-phase mixtures.     

Statistical treatment of scalar transfer in isotropic turbulence

It has recently been known that local high-gradient regions of an advected scalar, such as temperature or mass contaminant, in a turbulent state of fluid form thin sheets, randomly oriented and moving around with turbulent motion. Here is presented a joint multifractal model for velocity and scalar dissipations in isotropic turbulence which can predict the statistical distributions of the worms, vorticity-concentrated regions, as well as the above-described scalar-gradient sheets. This model allows us to derive turbulent diffusion coefficient in isotropic turbulence scaled by Reynolds number and Prandtl number, which predominates far over molecular diffusion coefficient.