Der Einfluß von Merkaptan auf die Lebensdauer kolloider Lösungen von Schwefel

Ohne Zusammenfassung Uebersetzt von H. Erbring (Leipzig).     

Calorimetry to Evaluate Inclusion Mechanism in the Complexation Between 2-hydroxypropyl-β-cyclodextrin and Barbiturates in Aqueous Solution

Two different types (structures) of inclusion complexes with a 1:1 stoichiometry between barbiturates and 2-hydroxypropyl-β-cyclodextrin (HPCyD) were realized in aqueous solution using isothermal titration calorimetry and molecular dynamics simulation. The first type of complex with a higher association constant was entropy driven and the substituent R ₂ was inserted into the HPCyD cavity by hydrophobic interaction. The barbituric acid ring contributed to the second type of complex, which was characterized by large negative values of ΔH and small positive ΔS reflecting van der Waals interaction and/or hydrogen bonding formation between the hetero atoms in the barbituric acid ring and the secondary hydroxyl groups of HPCyD. This revised version was published online in July 2006 with corrections to the Cover Date.     

A water-soluble precursor of BaTiO3 and transparent BaTiO3 thin-films prepared from the solution by a water-based dip-coating technique

A new water-soluble precursor of BaTiO₃ was prepared from citratoperoxotitanate and barium citrate as the Ti and Ba sources, respectively. The water-soluble precursor was easily solved in water to form a stable solution, which produced BaTiO₃ by heat-treatment at 500 °C and above. A water-based dip-coating technique demonstrated a potential application as the coating solution of BaTiO₃. Transparent BaTiO₃ films were formed on the quartz-glass substrates with an increment of typically 9 nm per coating with 0.05 mol dm^?3 solution. The transmittance of the 180 nm-thick film attained almost 90 % at the maximum and the overall transmittance was above 60 % over the visible region. The polycrystalline film was composed of BaTiO₃ grains smaller than 200 nm. Although the film was an insulator, it was not suited for the dielectric application because of the structural problems due to the relatively low density and the thinness of the BaTiO₃ layer. The BaTiO₃ pellet obtained from the water soluble precursor by condensation, pyrolysis and sintering showed the good dielectric properties with ε_r = 3,500 and tan δ = 0.027 with a sintering temperature of 1,375 °C.     

Measurement of neutron elastic scattering cross sections for carbon at 134 MeV

Angular differential neutron elastic scattering cross sections have been measured by using a ⁷Li(p,n) quasi-monoenergetic neutron beam. The neutron beam whose peak energy is 134 MeV was incident upon a natural carbon sample, and the scattering neutrons were measured by liquid organic scintillators with the time-of-flight (TOF) technique. The results were compared with the existing experimental data measured by a recoil-proton telescope, and the evaluated nuclear data of JENDL/HE-2007 and ENDF/B-VII.0.     

Applicability of particle and heavy ion transport code PHITS to the shielding design of spacecrafts

Development of HZE particle transport codes is severely required for the shielding design of spacecrafts. One-dimensional deterministic codes are generally adopted in the shielding calculation because of their reasonable computational time, but three-dimensional Monte Carlo codes are also to be employed especially in the final step of the design with fully optimized geometries. We are therefore developing a general-purpose Monte Carlo code PHITS, which can deal with the transports of all kinds of hadrons and heavy ions with energies up to . For the purpose of examining the applicability of PHITS to the shielding design, neutron and charged particle spectra inside the Space Shuttle were calculated for an imaginary vessel whose shielding distribution is fitted to that of the real shuttle. Absorbed doses and dose equivalents were estimated from the spectra by applying fluence to dose conversion coefficients. The agreements between the calculated spectra or doses and the corresponding experimental data were generally satisfactory, especially for the neutron spectra, which have been barely reproduced by other studies. We therefore concluded that PHITS has a great possibility of playing an important role in the design study of spacecrafts.     

Copolymer Microstructure by High-Resolution NMR Studies

The monomer and configurational sequences of several radical copolymers between substituted styrenes and acrylates have been examined by analyzing the high-resolution NMR spectra with the previously reported treatment of the styrene-methyl methacrylate system. The analyses have led to the conclusion that the monomer sequence distribution is just as expected from the usual copolymerization theory with r ₁ and r ₂.     

Synthesis of new compound Gd5Ni19 with a superlattice structure and hydrogen absorption properties

We successfully synthesized the new intermetallic compound Gd(5)Ni(19) and determined its crystal structure by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). The structure is a Sm(5)Co(19)-type superlattice structure (2H, space group P6(3)/mmc), and the lattice parameters were determined as a = 0.4950(1) nm and c = 3.2161(5) nm by X-ray Rietveld refinement. The XRD results agreed with the STEM analysis results. The P-C isotherm of Gd(5)Ni(19) was measured at 233 K. In the first absorption cycle, the maximum hydrogen capacity reached 1.07 H/M at 2.0 MPa. The sloping plateau was observed in the first absorption-desorption cycle. The maximum hydrogen capacity decreased by 0.87 H/M in the second absorption cycle, implying that hydrogen in the amount of H/M = 0.20 remained in the alloy before the second absorption-desorption cycle.     

The corrosion behavior of intermetallic compounds Ni3(Si,Ti) and Ni3(Si,Ti) + 2Mo in acidic solutions

The corrosion behavior of the intermetallic compounds homogenized, Ni₃(Si,Ti) (L1₂: single phase) and Ni₃(Si,Ti) + 2Mo (L1₂ and (L1₂ + Ni_ss) mixture region), has been investigated using an immersion test, electrochemical method and surface analytical method (SEM; scanning electron microscope and EPMA: electron probe microanalysis) in 0.5 kmol/m³ H₂SO₄ and 0.5 kmol/m³ HCl solutions at 303 K. In addition, the corrosion behavior of a solution annealed austenitic stainless steel type 304 was studied under the same experimental conditions as a reference. It was found that the intergranular attack was observed for Ni₃(Si,Ti) at an initial stage of the immersion test, but not Ni₃(Si,Ti) + 2Mo, while Ni₃(Si,Ti) + 2Mo had the preferential dissolution of L1₂ with a lower Mo concentration compared to (L1₂ + Ni_ss) mixture region. From the immersion test and polarization curves, Ni₃(Si,Ti) + 2Mo showed the lowest corrosion resistance in both solutions and Ni₃(Si,Ti) had the highest corrosion resistance in the HCl solution, but not in the H₂SO₄ solution. For instance, it was found that unlike type 304 stainless steel, these intermetallic compounds were difficult to form a stable passive film in the H₂SO₄ solution. The results obtained were explained in terms of boron segregation at grain boundaries, Mo enrichment and film stability (or strength).     

Hydration properties and compressive strength development of Low Heat Cement

For Low Heat Cement (LHC), its hydration reaction properties and compressive strength development were studied by quasi-elastic neutron scattering (QENS) and compressive strength test. In the QENS experiments, the amount of hydration products was estimated and the hydration behavior of LHC was revealed in the early hydration times of 7 days. Simultaneously, we compared the compressive strength of a mortar specimen made from LHC with the amount of hydration products. It was found that the compressive strength is strictly proportional to the amount of hydration products in the range from 15 h to 7 days of hydration.     

Activation of Water-Splitting Photocatalysts by Loading with Ultrafine Rh–Cr Mixed-Oxide Cocatalyst Nanoparticles

The activity of many water-splitting photocatalysts could be improved by the use of Rh^III–Cr^III mixed oxide (Rh_2−xCr_xO₃) particles as cocatalysts. Although further improvement of water-splitting activity could be achieved if the size of the Rh_2−xCr_xO₃ particles was decreased further, it is difficult to load ultrafine (<2 nm) Rh_2−xCr_xO₃ particles onto a photocatalyst by using conventional loading methods. In this study, a new loading method was successfully established and was used to load Rh_2−xCr_xO₃ particles with a size of approximately 1.3 nm and a narrow size distribution onto a BaLa₄Ti₄O₁₅ photocatalyst. The obtained photocatalyst exhibited an apparent quantum yield of 16 %, which is the highest achieved for BaLa₄Ti₄O₁₅ to date. Thus, the developed loading technique of Rh_2−xCr_xO₃ particles is extremely effective at improving the activity of the water-splitting photocatalyst BaLa₄Ti₄O₁₅. This method is expected to be extended to other advanced water-splitting photocatalysts to achieve higher quantum yields.