Analytical TEM study on structural changes of Au particles on cerium oxide using a heating holder

The structure changes of Au nano-particles supported on CeO₂ were observed by using an analytical transmission electron microscope (TEM) with a specimen heating holder. The disintegration and growth of Au particles on CeO₂ were successfully observed in the atomic scale. In situ observation of Au particles at elevated temperature reveals that the Au particles on CeO₂ grow by Ostwald ripening process through surface diffusion. Iridium particles on CeO₂ were also observed during the heating process for comparison. The growth mode of Au particles is quite different from that of Ir.     

Design and Synthesis of Chiral Zn2+ Complexes Mimicking Natural Aldolases for Catalytic C–C Bond Forming Reactions in Aqueous Solution

Extending carbon frameworks via a series of C–C bond forming reactions is essential for the synthesis of natural products, pharmaceutically active compounds, active agrochemical ingredients, and a variety of functional materials. The application of stereoselective C–C bond forming reactions to the one-pot synthesis of biorelevant compounds is now emerging as a challenging and powerful strategy for improving the efficiency of a chemical reaction, in which some of the reactants are subjected to successive chemical reactions in just one reactor. However, organic reactions are generally conducted in organic solvents, as many organic molecules, reagents, and intermediates are not stable or soluble in water. In contrast, enzymatic reactions in living systems proceed in aqueous solvents, as most of enzymes generally function only within a narrow range of temperature and pH and are not so stable in less polar organic environments, which makes it difficult to conduct chemoenzymatic reactions in organic solvents. In this review, we describe the design and synthesis of chiral metal complexes with Zn²⁺ ions as a catalytic factor that mimic aldolases in stereoselective C–C bond forming reactions, especially for enantioselective aldol reactions. Their application to chemoenzymatic reactions in aqueous solution is also presented.     

Structure and performance of cationic assembly dispersed in amphoteric surfactants solution as a shampoo for hair damaged by coloring

In recent years, hair coloring gains popularity as a trend of consumer's hair care. This coloring frequently damages hair. In response to this, a new shampoo-base was developed for repairing hair damaged by coloring. The new shampoo-base was prepared by dispersing cationic assembly in a solution of amphoteric surfactants. The mixture of behenyl trimethyl ammonium chloride (C22TAC) and behenyl alcohol (C22OH) was applied as the cationic assembly, which are dispersed in amido propyl betaine laurate (LPB) solution. LPB, which behaves as an amphoteric surfactant, was used as the wash-base. It was verified from the results on the measurements of DSC, calorimeter polarization, cryo-SEM and X-ray diffraction that the cationic assembly has a crystalline structure in the LPB solution. The new shampoo-base was highly efficient to change the color-damaged hair from hydrophilic to hydrophobic. The friction level of the hair washed with the new shampoo-base recovered to the same state as that of healthy hair. The exfoliation of cuticle was reduced after washing with the new shampoo-base.     

SELECTIVE REMOVAL OF CESIUM FROM HIGHLY CONCENTRATED SODIUM NITRATE NEUTRAL SOLUTIONS BY POTASSIUM NICKEL HEXACYANOFERRATE(II)-LOADED SILICA GELS

ABSTRACT

Potassium nickel hexacyanoferrate(II) (KNiFC)-loaded silica gels were prepared by successive impregnation of macro pores with Ni(NO₃)₂, and K₄Fe(CN)₆ solutions. The KNiFC precipitates uniformly dispersed in the matrix of silica gel, and the loading percentage of KNiFC increased with the number impregnation cycles. The uptake of Cs⁺ on KNiFC-loaded silica gels (SLFC) attained equilibrium within 2 d, and relatively large distribution coefficients of Cs⁺, K_d,cs, above 10⁴ cm³/g, were obtained even in the presence of 5 M NaNO₃. The ion exchange of K⁺ Cs⁺ in SLFC followed a Langmuir-type isotherm and the maximum uptake amount of Cs⁺ was estimated to be 0.305 mmol/g. The breakthrough curve of Cs⁺ through a column packed with SLFC exhibited a favorable S-shaped profile. This exchanger proved to be effective for the selective removal of radioactive cesium from neutral waste solutions containing highly concentrated NaNO₃.     

Incorporation limit of MoO3 in sodium borosilicate glasses

Optimizing the concentration of molybdenum incorporated in a borosilicate glass matrix is essential in the vitrification of high-level radioactive waste. However, the incorporation limit of MoO₃ in fundamental borosilicate systems has been rarely correlated with the local structure of the molybdenum cations. This study investigates the variations in the incorporation limit of MoO₃ in ternary sodium borosilicate glass upon varying the B₂O₃/(SiO₂ + B₂O₃) ratio (i.e., B)_. The incorporation limit of MoO₃ was less than 3 mol% in the low-B region (B < 0.7), where molybdenum cations mainly existed as [MoO₄]²⁻. However, when B was higher than 0.85, the incorporation limit was higher than 6 mol%, and the Raman spectra indicated the presence of octahedrally coordinated molybdenum cations, essential to stabilize the Mo–O–Mo linkage. The variation in the local structure of molybdenum cations can be explained by the available amount of non-framework cations compensating for the negative charge near [MoO₄]²⁻. These results allow the development of glass compositions with a high incorporation limit of MoO₃ simply by controlling the local structure near the molybdenum cations.     

Biobased thermosetting resins composed of terpene and bismaleimide

Prepolymers prepared by reactions of 1,1′‐(methylenedi‐4,1‐phenylene)bismaleimide (BMI) with myrcene (Myr) and limonene (Lim) in 1,3‐dimethyl‐2‐imidazolidinone (DMI) at 150°C were compressed at 250°C to produce crosslinked Myr/BMI [molar ratio = 2:2–2:5 (MB22–MB25)] and Lim/BMI [molar ratio = 1:1 (LB11)] resins. The ¹H‐NMR analysis of the model reaction products of Lim and Myr with N‐phenyl maleimide (PMI) in DMI at 150°C revealed that a Diels–Alder reaction for Myr/PMI and a vinyl copolymerization for Lim/PMI preferentially proceeded in addition to the occurrence of the ene reaction to some extent. The Fourier transform infrared data of the cured resins were consistent with the results of the model reactions. All of the cured resins, except for MB22, showed tan δ peak values and 10% weight loss temperatures that were higher than 330 and 440°C, respectively. The flexural strength and modulus values of the MBs were higher than those of LB11. Field emission scanning electron microscopy analysis revealed that MB22–MB24 were homogeneous, whereas some combined particles appeared in LB11. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Extended X-ray Absorption Fine Structure (EXAFS) Study on the local Environment around Copper in Low Thermal Expansion Copper Aluminosilicate Glasses

The local environment around copper in the Cu₂O·Al₂O₃·4SiO₃ and CuO·Al₂O₃·4SiO₂ glasses was investigated using the extended X-ray absorption fine structure (EXAFS) technique. It has been found that each Cu(I) in the former glass is coordinated to two oxygens through covalent Cu(I)-O bonds. This is the primary reason for its low thermal expansion coefficient (∼10 × 10⁻⁷ K⁻¹). In the latter glass, which was made by heating the former glass at 600°C in air, each Cu(II) is coordinated to four oxygens and the bonds are ionic in character, contributing to the increase in the thermal expansion coefficient to ∼30 × 10⁻⁷ K⁻¹.     

LIQUID FLOW IN IMPELLER REGION OF AN UNBAFFLED AGITATED VESSEL WITH UNSTEADILY FORWARD-REVERSE ROTATING IMPELLER

For an unbaffled agitated vessel with an unsteadily forward-reverse rotating impeller whose rotation proceeds with repeated acceleration, deceleration, and stop-reverse processes, the liquid flow in the impeller region was studied based on photographs showing path lines of tracer particles. An image series taken during one cycle of the forward-reverse rotation was analyzed to characterize the internal stream inside the impeller rotational region and the discharge stream outside its region when a disk turbine impeller with six flat blades was rotated unsteadily. Because of the unsteady flow generated inside the impeller rotational region, the velocity vector of outflow from its region fluctuated periodically with the change of the impeller rotation rate. The circumferential velocity was almost in phase with the impeller rotation rate, oscillating periodically. The radial velocity exhibited larger values in the process for the impeller from decelerating to stopping and reversal. The radial flow, whose velocity decreased downstream outside the impeller rotational region, was clarified to be transformed into upward and downward axial flows that are almost uniform in the circumferential direction throughout the region near the vessel wall.     

Measurement of infinite-dilution activity coefficients of alcohols in water using relative gas-liquid chromatographic method

Infinite-dilution activity coefficients of n-alcohols (C₁-C₈) in water were measured by using the relative gas-liquid chromatographic method proposed by Orbey and Sandler [1991]. The temperature range of measurement was 298 to 343 K. The g γ^⋚ values at 298.15 K varied from 1.72 (methanol) to 1970 (n-heptanol). ASOG, UNIFAC, modified UNIFAC (Dortmund), modified UNIFAC (Lyngby) group contribution methods could predict γ^⋚ to within 16.9, 28.8, 23.9 and 31.8 average percent error, respectively, for all systems and temperatures. This paper was presented at The 8th APCChE (Asia Pacific Confederation of Chemical Engineering) Congress held at Seoul between August 16 and 19, 1999.     

Continuous Processing of Monodispersed Titania Powders

A new continuous precipitation process for monodispersed ceramic powders using a static mixer was developed. Monodispersed TiO₂ powders were prepared continuously with high reproducibility and reliability by controlled hydrolysis of titanium ethoxide. Important steps were uniform and rapid mixing and aging using hydroxypropylcellulose as a dispersant. The concentrations of titanium ethoxide and water suitable to production of monodispersed TiO₂ powders lay within a limited range. A minimum aging period of 10 min was required to obtain monodispersed powders.