Masayoshi Sadakata

Absolute emission current density of O− from 12CaO⋅7Al2O3 crystal

Strong and high purity O− negative ion emission has been observed from a synthesized crystal 12CaO⋅7Al2O3 surface. A μA/cm2-level O− emission from this material has been achieved at the surface temperature of 800 °C and the extraction field over 1000 V/cm, which is about three orders of magnitude higher than the current density emitted from the Y2O3-stabilized ZrO2 electrolyte surface. The strong emissivity of this material, as well as easy and economical fabrication, may provide a useful tool to generate the O− negative ion, which is expected to be one of the most important radicals for chemical syntheses and material modifications.

Alkali Soil Reclamation with Flue Gas Desulfurization Gypsum in China and Assessment of Metal Content in Corn Grains

Flue gas desulfurization gypsum (FGDG), the by-product of wet and semi-dry desulfurization processes, has been used as an alkali soil amendment in China. We evaluated the change in soil properties, agricultural production and the safety of FGDG as a soil amendment. As a result, soil pH and ESP (exchangeable sodium percentage) decreased and corn production increased in FGDG-treated plots. The metal (B, Cr, Mn, Ni, Cu, As, Cd, Pb) contents in soil, FGDG, and corn grains were quantified by ICP-MS. Consequently, the contents of almost all metals in FGDG were lower than in soil. Moreover, the contents of almost all of the metals in the corn grains in the FGDG-treated plots were almost the same or lower than those in the control plot. Statistical analysis indicated that there was no effect of gypsum application on the metal content in the corn grains. Almost all of the metal contents were lower than the standard values set by FAO/WHO for human intake. The results showed that the FGDG from wet and semi-dry FGD processes is suitable as an alkali soil amendment.

Crack-free porous YSZ membrane via controlled synthesis of zirconia sol

Abstract Sol-gel processing is one of the most powerful tool to synthesize inorganic thin membranes. Several membranes, such as alumina, silica, titania, etc., have been prepared so far. The key in the sol-gel process is how to conquer cracking in the drying stage. We approach this problem in view of the control of sol-gel chemistry. The particulate zirconia sol is a useful precursor to synthesize nanostructured yttria stabilized zirconia (YSZ) at low temperature, but we could not prepare a crack-free film on a porous support due to its mechanical fragileness. Polymeric sol containing linear chains of zirconium and oxygen was synthesized via controlled hydrolysis and condensation of zirconium n -butoxide using triethanolamine (TEA, 2,2′,2″-nitrilotriethanol) as a chelating agent. Polymeric sol is useful to remove cracking, but the film formation property on a porous support is so poor since most of the sol is sucked into the support and no gel layer is formed on the top. By mixing two sols, we successfully balance the film formation property and the mechanical strength to cracking. Thus, crack-free porous YSZ thin membrane with a few-tens of nanometers pores are successfully prepared. The nanostructure is still stable after the post-calcination at 1173 K.

Gas permeation of porous organic/inorganic hybrid membranes

Selective gas permeation of porous organic/inorganic hybrid membranes via sol-gel route and its thermal stability are described. Separation performance of the hybrid membrane was improved compared with porous membranes governed by the Knudsen flow, and gas permeability was still much higher than that through nonporous membranes. Additionally, it was shown that these membranes were applicable at higher temperatures than organic membranes.SEM observation demonstrated that the thin membrane was crack-free. Nitrogen physisorption isotherms showed the pore size was in the range of nanometers. Gas permeability through this membrane including phenyl group was in the range of 10−8 [cc(STP) cm/(cm2 s cmHg)] at 25°C. The ratios of O2/N2 and CO2/N2 were 1.5 and 6.0, respectively, showing the permeation was not governed by the Knudsen flow. The permeability decreased as the temperature increased. Furthermore, the specific affinity between gas molecules and surface was observed not only in the permeation data of the hybrid membranes but in the physisorption data. These results suggested that the gas permeation through the hybrid membrane was governed by the surface flow mechanism.Thermal analysis indicated that these functional groups were still stable at higher temperatures. The phenyl group especially remained undamaged even at 400°C.

Study of gypsum formation for appropriate dry desulfurization process of flue gas

Abstract The mechanism of gypsum formation during dry desulfurization process of flue gas by calcium oxide was investigated in order to demonstrate any possible increase in the ratio of gypsum among the reaction products in the temperature range from 300 to 600°C. Infrared spectroscopic results indicated that both CaSO 4 and CaSO 3 existed in the products of the reaction between CaO and SO 2 in this temperature range. It was observed that SO 2 could react with CaSO 3 even at a temperature lower than 480°C. The reaction processes could be outlined as follows: CaO first reacted with SO 2 to form CaSO 3 , and then CaSO 3 continually reacted with SO 2 to produce CaSO 4 . One kind of CaO·Al 2 O 3 absorbent was prepared to study the effect of Al 2 O 3 on the reaction of SO 2 +CaO+O 2 . The results indicated that the main reaction product was CaSO 4 and that the formation of CaSO 3 was suppressed. The initial reaction rate and the apparent activation energy of the reaction between SO 2 and CaO by using pure CaO and the prepared absorbent were measured. Results showed that the reaction rate was increased apparently and the apparent activation energies were different with the existence of Al 2 O 3 . It was concluded that CaO·Al 2 O 3 was the active material on the desulfurization reaction.

Early stages of MFI film formation

Abstract The early stages of MFI (Si-ZSM-5) film formation on a quartz substrate are observed in nanometer scale by a field emission scanning electron microscope, and the crystallization mechanism is discussed. The change in the morphology, the number and the size of particles formed on a substrate surface are carefully studied in the course of the synthesis. Our results indicate that a gel layer, most probably consisting of silica/tetrapropylammonium composites, is formed at first. Then there are two crystallization routes, In one route, spherical composites are formed, enlarged, and aggregated, followed by crystallization. In the other route, the crystallization starts within the gel layer, and the crystals grow out of the gel layer. The effect of the aging process on the crystallization is also studied.

One-step synthesis of phenol by O- and OH- emission material

A novel approach to the direct synthesis of phenol from benzene was obtained with high benzene conversion (30%) and phenol selectivity (approximately 90%) by using a microporous material [Ca24Al28O64]4+.4O-(C12A7-O-) as catalyst with oxygen and water; active O- and OH- anions are proposed to play important roles in the formation of phenol by hydroxylating the aromatic ring of benzene.

Substitution of H− for O− and H− emissions of 12CaO∙7Al2O3

By using an anion-exchanging method, about 90% of the O− anions in the C12A7‐O− microporous crystal ([Ca24Al28O64]4+∙4O−) have been substituted primarily by the H− anions, leading to the successful formation of a new H− emission material, C12A7‐H−([Ca24Al28O64]4+∙4H−). A sustainable and stable emission of H−, in a current density of μA∕cm2 level, has been obtained by supplying H2 and electrons on the backside of the C12A7‐H− sample. The emission features of C12A7‐H−, including temperature and field effects, have been investigated. It is expected that the present material could be practically used as an H− anion generator.

Electric Field Emission of High Density O − Ions from 12CaO ⋅ 7Al2 O 3 Engineered to Incorporate Oxygen Radicals

We succeeded in extracting intense O - ion beam by applying dc voltage to a microporous crystal 12CaO.7Al 2 O 3 (C12A7) engineered to incorporate extremely large amounts of O - (1.3 X 10 2 0 cm - 3 ) and O 2 - (2.7 X 10 2 0 cm - 3 ) in crystallographic cages. The O - ion beam is monochromatic and the current density (∼2 μA/cm 2 ) is higher by three orders of magnitude than the maximum value recorded for yttrium-stabilized ZrO 2 (YSZ). A surface metal electrode, essential for the YSZ to dissociate a drifted O 2 - in the bulk into an O - and an electron on the surface, is not needed for the C12A7. The presence of extremely large concentrations of O - and O - 2 ions and fast oxygen-ion-conductive nature of C12A7 allow extraction of O - ions directly from the surface.

Emission of O- Radical Anions from a Solid Electrolyte Surface into the Gas Phase

We have observed the emission of O- radical anions from a solid electrolyte surface. A simple experimental apparatus was designed to incorporate a gap between a YSZ (yttria stabilized zirconia) anode and a stainless steel space electrode. By applying a DC voltage of 100 V across the gap, O- radical anions and electrons were produced which could be detected using a quadrupole mass spectrometer. Recently, Greber et al.. reported the observation of O- radical anion emission from a cesium-coated surface when the surface was exposed to thermal oxygen molecules. However, this method cannot maintain O- emission without adsorbed oxygen molecules. In the present work, the possibility of obtaining continuous emission of O- from a YSZ surface was examined.