This review paper summarizes early Mössbauer and DTA studies of different oxide glasses containing small amounts of iron (III) or tin (IV) as the probe. A lot of valuable information of the atomic level has been obtained about the role of nonbridging oxygen (NBO), network former (NWF), network modifier (NWM), local network structure, glass transition, structural relaxation, crystallization, etc. Introduction of alkali oxide into iron (III)-containing oxide glass causes a marked decrease in glass transition temperature (Tg) amounting to 100 °C and a concordant decrease in quadrupole splitting (Δ) of FeIII, which reflects decreased distortion of NWF–oxygen polyhedra and formation of NBO. By contrast, introduction of non-alkali oxide into oxide glass causes an increase in Tg amounting to more than 100 °C and a concordant increase in Δ, reflecting increased distortion of NWF–oxygen polyhedra in highly cross-linked network. These experimental results led to a discovery of “Tg-Δ rule”, which was consistent with the “conformer model” proposed for polymers by Matsuoka and Quan. Debye temperatures (θD) obtained by low-temperature Mössbauer measurements proved to be useful to determine short- and long-range structures of glass and glass ceramics. Isothermal annealing of vanadate glasses at temperatures higher than Tg or crystallization temperature (Tc) causes a “tunable” decrease in DC-resistivity from the order of MΩ cm to Ω cm. Introduction of metal oxide with a narrow bandgap (Eg) is highly effective to increase the conductivity after the annealing. It was proved that “structural relaxation” of NWF–oxygen polyhedra and resultant decrease in the activation energy (Ea) for conduction are responsible for the improved conductivity. Heat treatment of IR-transmitting aluminate, gallate, and tellurite glasses at temperatures higher than Tg or Tc revealed that crystallization was triggered by the cleavage of NWF–oxygen bonds. These findings will contribute to the development of functional glass and glass ceramics such as smart glass and eco-friendly glass.
Monoacylglycerols (MAG) are impurities present in biodiesel as a result of incomplete reactions. MAG often solidify in biodiesel even at room temperature because of their high melting points. This worsens the cold-flow properties such as the cloud point and pour point. We hypothesized that several types of MAG solidify simultaneously; therefore, we performed differential scanning calorimetry of binary mixtures of MAG to elucidate their interactions during solidification. Three thermodynamic formulas were then applied to the experimental results: (1) non-solid-solution, (2) solid-solution, and (3) compound formation models. Binary mixtures of MAG showed complicated liquidus curves with multiple upward convex shapes, with which only the compound formation model fitted well. This model was applied to multicomponent mixtures that consisted of MAG and fatty acid methyl esters (FAME) as surrogate biodiesel fuels. We confirmed that the model still worked well. The results show that the compound formation model has good potential for predicting the cold-flow properties of biodiesel. 相似文献
Discovery of novel phosphors is extremely important to target the ever change of the solid state lighting technology. In this paper, we present a high-speed way to discover new phosphors, namely single-particle-diagnosis approach. This approach is based on investigating the crystal structure and luminescence of a tiny single crystal, without the necessity of the growth of large-size single crystals or the preparation of single phase powder samples. The concept of the approach and some new nitride phosphors explored by this approach are shown in this paper. 相似文献
It is thought that the adjustment of intraspecific aggression is an essential factor in the development of a social structure. To understand the natural laws for organizing the social structure, we focus on the fighting behavior of crickets, Gryllus bimaculatus, and investigate the neuronal mechanisms to adjust aggressiveness associated with a neuromodulatory biological amine: serotonin (5-HT).In this paper, we present a working theory of a neurophysiological mechanism based on the past biological studies on the 5-HT hypothesis, and a mathematical model of the mechanism. We analyzed this model and concluded that this neurophysiological mechanism makes the forgetting process slower. Next, we fitted our theoretical forgetting curve to an experimental curve and estimated the parameters of our model. These estimated values were in agreement with common belief in biological science. 相似文献
The real vacuum vessel (VV) manufacturing of JT-60SA has started since November 2009 at Toshiba. Prior to starting manufacturing, fundamental welding R&Ds had been performed by three stages. In the first stage, primary tests for screening welding method were performed. In the second stage, the trial welding for 1 m-long straight and curved double shell samples were conducted. The dependences of welding quality and distortion on the welding conditions, such as arc voltage and current, setting accuracy, welding sequence, and the shape of grooves were studied. In addition, welding condition with low heat input was explored. In the last stage, fabrication sequence was confirmed and established by the trial manufacturing of the 20° upper half mock-up [1]. This paper presents the R&D results obtained in the first and second stages. 相似文献
Site-controlled InAs nano dots were successfully fabricated by a STMBE system (in situ scanning tunneling microscopy during
molecular beam epitaxy growth) at substrate temperatures from 50 to 430°C. After 1.5 ML of the InAs wetting layer (WL) growth
by ordinal Stranski–Krastanov dot fabrication procedures, we applied voltage at particular sites on the InAs WL, creating
the site where In atoms, which were migrating on the WL, favored to congregate. At 240°C, InAs nano dots (width: 20–40 nm,
height: 1.5–2.0 nm) were fabricated. At 430°C, InAs nano dots (width: 16–20 nm, height: 0.75–1.5 nm) were also fabricated.
However, these dots were remained at least 40 s and collapsed less than 1000 s. Then, we fabricated InAs nano dots (width:
24–150 nm, height: 2.8–28 nm) at 300°C under In and As4 irradiations. These were not collapsed and considered to high crystalline dots. 相似文献
The exacting quality required of hemispherical heavy-walled steel castings, used in nuclear power applications, has been remarkably improved by the adoption of a newly developed metal-mould process. This technique is dependent on the use of a metal core. The optimum conditions for solidification were determined by the finite element analytical method. The appropriate wall-thickness of the chill elements was also investigated using data based on actual experience. The core was designed in such a manner that the surface carried a series of concave “dimples” in the manner of a golf-ball, the pattern being intended to prevent the formation of cracks, generated on the casting surface when in contact with a metal mould. Stresses caused by solidification shrinkage were reduced by splitting the core. In the event, the casting structure conformed well to the results of the solidification analysis. Radiographic examination revealed a high level of soundness, with no trace of internal defects. No anisotropy was detected in mechanical properties. It is shown that this process is being currently employed in the manufacture of actual products. 相似文献