Conformational equilibrium of tetraethylammonium ion (Et4N+) in alcohols (methanol, ethanol, n-propanol) has been investigated by Raman spectroscopy as functions of concentration, pressure and temperature. The difference in the partial molar volume (ΔVtg.tg→tt.tt) between the trans-gauche.trans-gauche (tg.tg) and trans-trans.trans-trans (tt.tt) conformers of Et4N+ ion has been calculated from the pressure dependence of the relative Raman intensity ratio between the conformers. ΔVtg.tg→tt.tt is found to be negative throughout the studied concentration region. The value of ΔVtg.tg→tt.tt is the smallest in the methanol solution. The difference in the partial molar enthalpy (ΔHtg.tg→tt.tt) is also estimated from the temperature dependence of the relative Raman intensity. From these results, we discuss the close relationship between the conformational change and the solvation structure.
A microreactor for the catalysis of gas-liquid reactions was designed and fabricated. The microreactor consists of a concentric inner column and an outer cylinder. The interstitial space between these components is a channel for the liquid. The column is made of a porous material, so that gas can be fed to the channel by passing it through the column to the column surface, where micro-bubbles are emitted that can efficiently contact and react with the liquid. The column is made of commercially available graphite, machined by lathe to 18mm in diameter and 67mm long. The cylinder is made of SUS304 stainless steel, bored to 18.1mm in diameter, resulting in an effective channel gap of approximately 50μm when the components are fitted together. After machining of the graphite column, a catalyst was fixed to the column. The ratio of the specific surface area of the catalyst to the volume of the mixture becomes very large, due to the gas-liquid mixture flow in the 50μm channel. As a model reaction, the hydrogenation of nitrobenzene to aniline was carried out using a nickel catalyst, and catalysis performance was tested for deposition using sputtering, electroplating and electroless plating methods. The following results were obtained : (1) In a conventional autoclave system, which serves as the benchmark for batch methods, the aniline produced is further converted to undesired organic products, due to successive hydrogenation. However, compared with the performance of the conventional reactor, such side reactions can be significantly suppressed using the proposed microreactor, because the product is readily discharged and the residence time is steadily and adequately controlled. (2) Deactivation of the catalyst was observed for continuous operation. The most likely cause is that polymers formed during the reaction are adsorbed on the catalyst surface, thus reducing activity. All catalysts exhibited the same initial conversion ; however, the lifespan of the catalyst was dependent on the method of deposition, and followed the order: sputtering>electroplating>electroless plating. This is similar to the deactivation behavior observed for a palladium catalyst with the hydrogenation reaction using a falling film microreactor. Therefore, it is necessary to develop a catalyst deposition method suitable for the microreactor in order to achieve long-term operation.
Two different types of the high-temperature high-pressure reactor systems with one-line or two-line flow paths have been developed to examine the hydrothermal syntheses of metal nanoparticles. For the two-line reactor system, two kinds of reaction solutions could be quickly mixed at the Y-shaped junction inside the reactor under high-temperature high-pressure conditions. The aqueous solutions containing 1.5mM silver nitrate, 30 wt% polyvinylpyrrolidone and three different kinds of reducing agents (trisodium citrate, ethanol or acetone) were reacted at T = 200-350°C and P = 40MPa by the one-line reactor system. The finest silver nanoparticles with average diameter of about 15nm were obtained when trisodium citrate was used as the reducing agent. The bimetallic nanoparticles composed of silver and platinum have been synthesized with the one-line reactor system by using the mixed solution of silver nitrate and dihydrogen hexachloroplatinate (IV) as the starting material. The optical absorption spectra of the obtained bimetallic nanoparticles in the aqueous solutions indicated the spontaneous formation of the platinum-core silver-shell structure. It was demonstrated that smaller Ag nanoparticles with narrower size distribution could be synthesized when the two-line reactor system was used instead of the one-line reactor system under nearly identical experimental conditions.
The influence of thermoplastic deformation on the mechanical properties of Zr60Cu25Al10Ni5 bulk metallic glass (BMG) at room temperature was studied experimentally. The strength of this BMG at room temperature after thermoplastic deformation can be decreased with deformation under a hot condition, even if the thermal condition does not exceed the specific TTT curve of this material and does not induce crystallization with embrittlement. It is supposed that the crystallization is caused not only by thermal condition but also by plastic deformation, and induces the decrease in the strength and embrittlement. Therefore the increase in the thermoplastic strain tends to promote the crystallization, and decrease the fracture stress at room temperature. However, it is confirmed experimentally that a high strain rate and low temperature is effective to avoid the decrease in the fracture stress at room temperature although the thermoplastic strain increases.
Semi-dry press forming using ceramics granules with plasticity due to large amount of water was attempted. The granules with a fair amount of water were prepared using a stirring granulator and compared with the spray-dried granules generally used for press forming. In order to investigate the compaction behavior of the granules, press forming was carried out under various pressures. The relative density of a compacted body increased with increasing water content of the granules. The pressure dependence of the relative density of the powder compact was small in the case of the high water content granules. The granules containing large amount of water had a loose agglomerate structure, so they were easily deformed and crushed at low pressure. On the other hand, dry granules were hardly deformed because of their rigid agglomerate structure. Therefore, the volume change of the granules containing much water during pressing was larger than that of the dry granules, resulting in high relative densities of powder compacts at low pressure. Moreover, in the case of wet granules, the firing shrinkage of the powder compact was independent of forming pressure and homogeneous sintered bodies were obtained even at low forming pressure.
Asbestos is typically disposed of as hazardous waste in limited managed landfill sites. Recently, it has been difficult to secure the landfill and the cost soaring of disposing the waste has been watched with misgiving. In this research, hydrothermal treatments were studied as a method to decompose asbestos and recycle to zeolite, because the method was considered to enable the cost reduction and zero-emission for disposal of asbestos. Chrysotile, a kind of asbestos was found to be decomposed by a hydrothermal treatment ; 175°C-24h-14N NaOH soln. Other asbestos were decomposed by the method under similar conditions. Real composite materials including asbestos were confirmed to be decomposed by the hydrothermal method. Zeolite was synthesized from asbestos waste by 2nd hydrothermal treatment with Al(OH)3 after 1st decomposition process.
Oxygen storage capacity (OSC) of ceria (CeO2) is the important property of recent automotive exhaust catalysts. Alumina-supported ceria catalyst is useful for removal of carbon monoxide, hydrocarbons, and nitrogen oxides under dynamic condition. In this work, temperature programmed reduction and OSC of 10-50mol%v-Al2O3 catalysts were compared with their morphology. The OSC per CeO2 decreases with the added amount of CeO2 to Al2O3 because the crystallite size of ceria increased. The OSC per surface area of CeO2 was enhanced by alumina support.
ZrO2/SiC composite ceramics were sintered and subjected to three-point bending. A surface crack of 100μm in diameter was made on each specimen. We studied crack-healing behavior. The main conclusions are as follows. (1) ZrO2/SiC composite ceramics could heal a crack. Then the best healing condition is 800°C × 30h in air. (2) A crack was healed even at 600°C, which was a very low temperature compared with other ceramics. (3) The ZrO2/Y2O3/SiC system ceramics caused an extensive corrosion at over 1000°C. (4) Healing temperature and the minimum -time to heal were in the good proportional relation on the Arrhenius diagram at 600–800°C.
The fabrication of Au3+ containing 3-dimensional ordered PS-TiO2 has been accomplished by the Liquid Phase Deposition (LPD) method using polystyrene (PS) colloidal crystal as template. The interstitial spaces of template were completely filled with deposited oxide by the LPD. After calcination, template was completely removed simultaneously Au3+ was reduced to Au, and well-ordered 3D macro porous Au nano-particles dispersed TiO2 was formed. The obtained Au-TiO2 inverse opal was characterized by SEM, TEM, XRD, and VIS spectroscopy.
In order to extend the potential application of the staining, which has been used only for coloring glasses, we have investigated the Cs-staining as a new staining technique other than Ag and Cu-staining. At first, we prepared new Cs-stains consisting of Cs2SO4-Na2SO4, Cs2SO4-CsCl mixed salts, or CsNO3. The Cs-staining was carried out at 500∼600°Cfor 12∼96 hours using commercially available borosilicate (BK7®) and soda-lime silicate (B270®) glasses as substrates. Elemental analyses and X-ray microanalyses showed that Cs+ ions were incorporated into the surface area of the glass substrates. The refractive indices measured by a prism coupling method at 633nm increased by 0.01 to 0.02. The measurements also indicated that the light was propagated in the stained area showing that the waveguides were successfully formed.
High-strength and ultra low-permeability concrete (HSULPC) is a strong candidate for a radioactive waste package containing transuranic radionuclides (TRU waste) for geological disposal. The information and knowledge of the time-dependent fracturing of HSULPC and surrounding rock mass are essential to assess the long-term stability of such underground repositories. Here we measured crack velocity in andesite and HSULPC both in air and water to examine slow crack growth (subcritical crack growth) by Double-Torsion method. In air, the crack velocity in andesite increased when the temperature increased. On the other hand, the temperature had little effect on the crack velocity in HSULPC in air. In water, the crack velocity increased when the temperature was higher for both andesite and HSULPC. By using the experimental results of subcritical crack growth, the long-term strength was estimated based on the model of a single crack subjected to tension in an infinite plate. It was shown that the long-term strength of HSULPC was higher than that of andesite. When the temperature increased, the long-term strength of andesite both in air and water and that of HSULPC in water decreased. The long-term strength in water was smaller than that in air for both materials. It is concluded that water remarkably affects subcritical crack growth and the long-term strength in these materials.