Shigeru Fujino

Fabrication of fine α-alumina powders by thermal decomposition of ammonium aluminum carbonate hydroxide (AACH)

In this paper, the phase transformations that occur during the thermal decomposition of ammonium aluminum carbonate hydroxide (AACH) into α-Al 2 O 3 have been studied. Amorphous, γ-, and θ-Al 2 O 3 were identified as intermediate products. A time-temperature-transformation (TTT) diagram for thermal decomposition in air was determined. The critical particle size of θ-Al 2 O 3 in the θ→α phase transformation is ∼30 nm; the size does not depend on the firing atmosphere. However, the atmosphere affects the grain size distribution of the final α-Al 2 O 3 particles. Powders with an average grain size of 60 nm were obtained by firing in vacuum or hydrogen.

Refractive index and material dispersions of multi-component oxide glasses

Abstract Refractive index dispersion curves in the wavelength region of 0.40 to 5.03 μm are presented for multi-component oxide glass systems: borate, silicate, aluminate, germanate, tellurite, antimonate and heavy metal gallate. The material dispersion was determined using the refractive index data. Reflection spectra in the ultraviolet and infrared regions were measured to investigate the effects of electronic transitions and lattice vibrations on the material dispersion. Thallium tellurite, thallium antimonate and lead gallate glasses exhibit zero material dispersion wavelengths (ZMDWs) over 2.4 μm. The factors affecting the ZMDW are discussed.

Density, viscosity and surface tension of 50RO–50P2O5 (R: Mg, Ca, Sr, Ba, and Zn) glass melts

Abstract The density, surface tension and viscosity of the 50RO–50P2O5 (R: Mg, Ca, Sr, Ba and Zn) glass melts have been measured over the range, 1073–1623 K. The effects of R cations on these properties have been investigated. The density of the melt was found to increase in the order, R: Mg Ca Zn Sr Ba, with increasing molar weight of cation. The surface tension in the temperature range of 1373–1473 K increased approximately with cation in the order, R: Zn Ba Mg Ca Sr. The viscosity and the negative, temperature coefficient of surface tension increased in the order, R: Ba Sr Ca Zn Mg. All melts exhibited negative temperature coefficients of surface tension. The effect of Mg and Zn cations on the properties were different to that for Ba, Sr, and Ca cations and this is discussed using bulk glass data published in a previous report. The features of Mg and Zn metaphosphate glass melts, that is high values of viscosity, and temperature coefficient of surface tension, are related to the small Oxygen Coordination Number of the cations (=4) when compared with those of Ca, Sr, Ba metaphosphate glass melts.

Preparation and properties of SnO–SnCl2–P2O5 glass

Abstract The glass forming region in the ternary system SnO–SnCl 2 –P 2 O 5 has been determined. Glass transition temperature ( T g ), dilatomeric softening temperature ( T s ) of the glass, and the viscosity of the liquids in the binary SnO–P 2 O 5 and SnCl 2 –P 2 O 5 systems were measured. Compositional dependencies of these properties have been investigated. The T g and T s of the glasses and the viscosity of liquids for the SnO–P 2 O 5 glasses increase linearly with increasing SnO content in a range of 40–60 mol% SnO. The substitution of chlorine for oxygen by increasing the SnCl 2 /SnO ratio results in a decrease of T g and T s of the glasses and the viscosity of the liquids. The T g and T s of the glasses and the viscosity of the liquids of the SnCl 2 –P 2 O 5 system increase between 40 and 60 mol% SnCl 2 , are a maximum at about 60 mol% SnCl 2 , and then decrease with further addition. The SnCl 2 –P 2 O 5 systems had a decreasing viscosity, which is not observed in the SnO–P 2 O 5 and SnF 2 –P 2 O 5 systems. The 70SnCl 2 –30P 2 O 5 glass, having a viscosity between 0.4 and 10 Pa s in a temperature range of 500–600 K, would be useful in a practical application for sealing glasses.

Fabrication of transparent silica glass by powder sintering

Abstract Transparent silica glasses were obtained by sintering a green compact (fabricated by slip-casting methods for high-purity silica glass powder) in diverse atmospheres. The relationships between sintering atmosphere and sintering temperature that result in transparent, sintered silica glass were shown. The results indicate that there are four forming phases for each sintering atmosphere and temperature: (1) nontransparent glass resulting from an overabundance of pores (2) crystal, such as cristobalite or β-quartz, (3) moganite, and (4) transparent glass. Optimum sintering temperature for fabricating transparent silica glass was above 1673 K in a high-vacuum (10–4 Pa: p(O2) = 10–14) atmosphere. We investigate the fabrication of transparent and hydroxyl-free silica glass by a powder-sintered method. After studying the effect of sintering schedule on residual [OH–] concentration for transparent, sintered silica glasses, we sintered a green compact prepared by silica powders with a mean particle size of 1.6 µm, first heating it to 1523 K for dehydration and then to 1873 K for densification. This typical fabricated condition resulted in a transparent, sintered silica glass with <1 ppm [OH–] concentration.

Pr3+-doped fluoro-oxide lithium glass as scintillator for nuclear fusion diagnostics

Experimental results are presented on the neutron scintillating properties of a custom-designed Pr3+ (praseodymium)-doped lithium (Li) glass. Luminescence was observed at 278 nm wavelength, originating from the 5d-4f transition. Time-resolved measurements yielded about 20 ns decay times for ultraviolet and x-ray excitation while much faster decay times of about 6 ns were observed for alpha particle and neutron excitation. Actual time-of-flight data in laser fusion experiments at the GEKKO XII facility of the Institute of Laser Engineering, Osaka University reveal that it can clearly discriminate fusion neutrons from the much stronger x-rays signals. This material can promise improved accuracy in future scattered neutron diagnostics.

Material dispersion and its compositional parameter of oxide glasses

Abstract Refractive indexes of oxide glasses: silica, borate, silicate, aluminate, germanate, tellurite, antimonate and heavy metal gallate are measured in the wavelength range of 0.40–5.03 μm. The zero material dispersion wavelength (ZMDW) was determined using the refractive index data. To predict the ZMDW, we calculated the molecular electronic polarizability, α i , of oxide glasses using the Lorentz-Lorenz equation. An empirical equation between ZMDW and α i was obtained, from which the ZMDW from the compositional parameter, α i can be calculated.

Reconstruction of cartilage tissue using scaffold-free organoid culture technique.

We applied the scaffold-free culture method to chondrocytes and attempted to reconstitute articular cartilage grafts. Primary rat costal chondrocytes were immobilized into hollow fibers by centrifugation at a density of 3 x 10(8) cells/cm(3) to induce the formation of cylindrical-shaped multicellular aggregates (organoids) and cultured for one month. The organoids were evaluated by histological and gene expression analyses. Chondrocytes formed cylindrical organoids in hollow fibers (HFs). Histochemical analysis revealed the accumulation of a cartilage extracellular matrix (collagen and proteoglycan) around cells in the lumen of HFs with culture time, forming a low-cellular-density tissue similar to native cartilage by day 28. Furthermore, in contrast to that in traditional monolayer culture, the organoid maintained the gene expression of the cartilage extracellular matrix (type II collagen, aggrecan) for one month of culture. In conclusion, our organoid formation method was effective in producing a cartilage-like tissue. This result suggests that the technique may be applicable to the development of an articular cartilage graft.

Custom-Designed Fast-Response Praseodymium-Doped Lithium 6 Fluoro-Oxide Glass Scintillator With Enhanced Cross-Section for Scattered Neutron Originated From Inertial Confinement Fusion

Scintillation properties of Pr3+-doped 20Al(PO3)3-80 LiF glasses melted in N2 were investigated to seek a candidate for a scattered neutron scintillator in nuclear fusion diagnostics. The fluorescence lifetime of the sample with 217 nm ultraviolet femtosecond pulse excitation was measured to be 19.5 ns. More importantly, the fluorescence lifetime with alpha particles from 241Am radioisotope excitation was determined to be 6.7 ns. Based on our material design strategy, we have successfully developed the fast response time praseodymium-doped 6Li glass scintillator for scattered neutron diagnostics.

Down-scattered neutron imaging detector for areal density measurement of inertial confinement fusion

A custom developed (6)Li glass scintillator (APLF80+3Pr) for down-scattered neutron diagnostics in inertial confinement fusion experiments is presented. (6)Li provides an enhanced sensitivity for down-scattered neutrons in DD fusion and its experimentally observed 5-6 ns response time fulfills the requirement for down-scattered neutron detectors. A time-of-flight detector operating in the current mode using the APLF80+3Pr was designed and its feasibility observing down-scattered neutrons was demonstrated. Furthermore, a prototype design for a down-scattered neutron imaging detector was also demonstrated. This material promises viability as a future down-scattered neutron detector for the National Ignition Facility.