Fuji Funabiki

Ligand field modification around Cu2+ ions in sodium borate glass by codoping.

Understanding the effect of codoping on the properties of photonic glasses is important for improving their properties. The effect of codoping on the ligand field around Cu(2+) ions in a sodium borate glass is examined using optical absorption spectroscopy, continuous-wave electron paramagnetic resonance, and three-pulse electron-spin-echo envelope-modulation. Glass with a composition of 0.1CuO·5Na(2)O·95B(2)O(3) was codoped with 2 mol % of Al(3+), Si(4+), P(5+), Zr(4+), or La(3+) oxide. Three codoping effects are found: strengthening the ligand field, as observed for Zr-codoping, which induces a large blue shift of the optical absorption peak of Cu(2+); weakening the ligand field, as observed for P-codoping, which causes a red shift of the Cu(2+) absorption peak; and almost no effect on the ligand field, which is observed for Al-, Si-, and La-codoping. Coordination structure models based on local charge neutrality are proposed for the codoped glasses. The mechanism of the codoping effect is revealed by elucidating the local structure around Cu(2+).

Electrical conductivity of Ag+/Na+ ion-exchanged titanosilicate glasses

Abstract The Ag 2 O–TiO 2 –SiO 2 glasses were prepared by Ag + /Na + ion-exchange method from Na 2 O–TiO 2 –SiO 2 glasses at 380–450 °C below their glass transition temperatures ( T g ), and their electrical conductivities were investigated as functions of TiO 2 content and the ion-exchange ratio (Ag/(Ag+Na)). In a series of glasses 20R 2 O· x TiO 2 ·(80− x )SiO 2 with x =10, 20, 30 and 40 in mol%, the electrical conductivities at 200 °C of the fully ion-exchanged glasses of R=Ag were in the order of 10 −5 or 10 −4 S cm −1 and were 1 or 2 orders of magnitude higher than those of the initial glasses of R=Na. The glass of x =30 exhibited the highest increase of conductivity from 3.8×10 −7 to 1.3×10 −4 S cm −1 at 200 °C by Ag + /Na + ion exchange among them. When the ion-exchange ratio was changed in 20R 2 O·30TiO 2 ·50SiO 2 system, the electrical conductivity at 200 °C exhibited a minimum value of 7.6×10 −8 S cm −1 around Ag/(Ag+Na)=0.3 and increased steeply in the region of Ag/(Ag+Na)=0.5–1.0. When the ion-exchange temperature was changed from 450 to 400 °C, the conductivity of the ion-exchanged glass of x =30 decreased. The infrared spectroscopy measurement revealed that the ion-exchange temperature of 450 °C induced a structural change in the glass of x =30. The T g of the fully ion-exchanged glass of x =30 was 498 °C. It was suggested that the incorporated silver ions changed the average coordination number of titanium ions to form higher ion-conducting pathway and resulted in high conductivity in the titanosilicate glasses.

Characteristic Coordination Structure around Nd Ions in Sol–Gel-Derived Nd–Al-Codoped Silica Glasses

Al codoping can improve the poor solubility of rare-earth ions in silica glasses. However, the mechanism is not well understood. The coordination structure around Nd ions in sol-gel-derived Nd-Al-codoped silica glasses with different Al content was investigated by optical and pulsed electron paramagnetic resonance spectroscopies. Both tetrahedral AlO4 and octahedral AlO6 units were observed around Nd ions as ligands. The average total number of these two types of ligands for each Nd(3+) ion was ∼ 2 irrespective of Al content and was larger by 1-2 orders of magnitude than that calculated for a uniform distribution of codopant ions (∼ 0.08-0.25). With increasing Al content, AlO4 units disappeared and AlO6 units became dominant. The preferential coordination of AlOx (x = 4, 6) units to Nd ions enabled the amount of Al necessary to dissolve Nd ions uniformly in silica glass at a relatively low temperature of 1150-1200 °C to be minimized, and the conversion of AlO4 units to AlO6 units around Nd ions caused the asymmetry of the crystal field at the Nd sites to increase and the site-to-site distribution to decrease.

Application of In-Flight Melting Technology by RF Induction Thermal Plasmas to Glass Production

An innovative in-flight glass melting technology with induced thermal plasmas was developed for the purpose of energy conservation and environmental protection. Two-dimensional modeling was used to simulate the thermofluid fields in the plasma torch. The in-flight melting behavior of glass raw material was investigated by various analysis methods. Results showed that the plasma temperature was up to 10000 K with a maximum velocity over 30 m/s, which made it possible to melt the granulated glass raw material within milliseconds. The carbonates in the raw material decomposed completely and the compounds in the raw material attainted 100% vitrification during the in-flight time from the nozzle exit to substrate. The particle melting process is similar to the unreacted-core shrinking model.

Local structure around rare-earth ions in B2O3 glass at high pressure

Melt quenching of B2O3 with less than 25 mol. % rare-earth oxide (RE2O3) at ambient pressure results in a milky white glass because of liquid-liquid phase separation into B2O3 and RE2O3·3B2O phases. In contrast, we have found that melt quenching under GPa-order pressure realizes a transparent RE-doped B2O3 glass. This study investigates the local structure around the RE ions in the B2O3 glass prepared at 3 GPa using optical measurements and electron-spin-echo envelope modulation spectroscopy. It is shown that the RE-rich microparticles disappear and the RE ions are isolated from each other in a highly symmetric crystal field formed by triangular and tetrahedral boron units. This result is consistent with that extrapolated from the data for RE-doped sodium borate glasses.

In-flight melting of granulated powders by 12-phase AC arc discharge for glass production

Current glass melting technology, based on the Siemens furnace developed in 1860s, has evolved in response to manufacturing requirement. However few revolutionary changes to the basic technology have occurred. Glass production is still one of the most energy intensive industries, because the conventional method used for glass melting is air-fuel firing, which is inefficient, energy-intensive and time-consuming. With increased energy issue and global warming, it is urgent to develop a new technology to save energy and reduce emissions for glassmaking. In view of high temperatures of thermal plasmas, an innovative in-flight glass melting technology with an induction plasma, a multiphase AC arc, and an oxygen burner was developed. In this study, characteristics of the treated powders by a 12-phase AC arc during their flight time were investigated. The reagents for alkali-free glass was mixed and prepared into granulated powders with the grain size of 20-80 mum by spray dry method. The granulated powders were injected into a 12-phase AC arc for the in-flight treatment. The stable 12- phase AC arc discharge with 100 mm in diameter was obtained at the power of 46 kW. The vitrification, morphology, size distribution, and composition of the treated powders were characterized to evaluate the melting characteristics. Results show that the melted particles are spherical with a smooth surface and compact structure. Higher vitrification and decomposition degrees of raw material as well as higher volatilization of B2O3 are attributed to larger heat transferred to per particle under smaller flow rate of carrier gas and lower feed rate of granulated powders. The properties of glass powders were strongly dependent on the feed rate and the carrier gas flow rate. The high decomposition and vitrification degrees, which are achieved in milliseconds, shorten the melting and fining times of glass considerably. Our results indicate that the proposed in-flight melting technology is a promising method for use in the glass industry.

Laser interference deposition of silver nanoparticles on glass

A couple of glass plates sandwiching the molten AgNO3-KNO3 mixture at the temperature of 250°C was irradiated by pulsed Nd:YAG laser with a wavelength of 1.06μm. The irradiation induced the color of transparent yellow and orange in the glasses with the irradiation time because of the deposition of silver nanoparticles. In the observations using FE-SEM and AFM, periodically aligned structures, stripes and circles, formed by silver nanoparticles were observed in the irradiated area. The stripes had the interval of 600-700nm, and the circles had the diameters more than 40μm, the latter of which were considered to be due to the Newtons ring interference of laser on bubbles in the molten salt. On the other hand, in the experiment of two-beam irradiation, we obtained strictly aligned stripes pattern with a periodic interval of 2.6μm and a height of 50nm on the glass surface. The observed interval gave a good agreement with the theoretical length that was calculated from the wavelength and the inter-crossing angle of the coherent lasers. Moreover, the stripes pattern showed the Bragg diffraction of visible light from violet to red. From these, it was found that the laser deposition method united with light interference was useful to prepare periodic pattern of nanoparticles on a transparent substrate.