Anwendungsmöglichkeiten des Anionenaustausches mit Salpetersäure-Methanol-Gemischen für die Trennung der Seltenen Erden

Der Anionenaustausch mit Salpetersäure-Methanol-Gemischen kann erfolgreich zur Reindarstellung vieler Elemente genutzt werden. Es werden Möglichkeiten der praktischen Anwendung solcher Glemische für die Trennung der leichten Lanthaniden, für die Reinigung der Lanthaniden von Zr und Hf und die Ausnutzung fūr die Produktion von radioaktiven Isotopen genannt.     

Verteilungskoeffizienten von Ag,In, Re,Au, Hg,Tl, Pb und Bi in Salpetersäure-Methanol-Gemischen

Der Anionenaustausch unter Verwendung von Salpetersäure-Methanol-Gemischen ist in den letzten Jahren von einer Anzahl von Autoren untersucht worden [1, 2, 3, 4]. In einer früheren Arbeit hatten wir bereits auf seine praktisehc Anwendbarkeit für die Trennung der SK hingewiescn [5]. In der vorliegenden Arbeit werden von uns die Verteilungs-koeffizienten von Ag, In, Re, Au, Hg, Tl, Pb und Bi angegeben und Beispiele für mögliche Trennungen angeführt.     

4 × 4 Plastic Optical Fiber Star Coupler Incorporated with a Common Polymer Waveguide Optical Power Distribution Region

Abstract

Two types of 4 × 4 plastic optical fiber star couplers incorporated with a polymer waveguide as the optical power distributor are proposed, and their high performances are demonstrated. The characteristics of the proposed star coupler are investigated based on ray optics, and its power distribution performance is evaluated in terms of the flatness of the coupling ratio and the amount of the excess loss. Under the best conditions, the flatness of the coupling ratio and the excess loss of the fabricated device have been obtained as 2.0 dB and 2.5 dB, respectively.     

Layered TiO2 :PVK nano-composite thin films for photovoltaic applications

The influence of the solvent used for spin-coating on the homogeneity of poly(N-vinylcarbazole) (PVK) films is investigated. Homogenous films are obtained only by the use of toluene, solution in tetrahydrofuran (THF) and chloroform results in radially oriented inhomogeneities and films prepared by use of N-methylpyrrolidone and dimethylacetamide show particle formation during spin-coating. Layered nano-composite thin films are prepared by spin-coating a PVK film on top of a nano-structured titanium dioxide ( TiO2) layer. The TiO2 thin films are prepared by a sol-gel process using an amphiphilic copolymer as structure-directing agent. Structural characterisation of the TiO2 :PVK nano-composite films is done by field emission scanning electron microscopy (FESEM) and grazing-incidence small-angle scattering (GISAXS). Bare TiO2 films are probed for comparison. Light is basically only absorbed in the ultraviolet regime and absorption slightly increases upon addition of PVK, which makes the layered TiO2 :PVK nano-composite thin films good candidates for UV photovoltaic devices. Furthermore, absorption remains stable over a period of several days.     

Probe of I(Pj) atoms using two-photon resonant four-wave mixing spectroscopy following the 266-nm photodissociations of various alkyl and perfluoroalkyl iodides

Two-photon resonant four-wave mixing spectroscopy has been utilized successfully for probing I and I^∗ nascent from the 266 nm photodissociations of various alkyl and perfluoroalkyl iodides. The relative quantum yields for I^∗, as well as the recoil anisotropy parameters, were extracted. Recoil anisotropy parameters close to the limit value for parallel transition indicates that the ground-state I(²P_3/2) originates from the curve crossing from the initially prepared ³Q₀ to ¹Q₁ state. The curve-crossing probabilities for alkyl and perfluoroalkyl iodides were obtained and tried to explain using the well-known Landau-Zener model. In the cases of perfluoroalkyl iodides, it is necessary to consider the fluorination effect to describe the detailed dynamics observed in this study and has been revealed that the electronic effect due to fluorine atom substitution is dominant, leading to decrease in the curve-crossing probability.     

A Kinetic Study for the Noncatalytic Esterification of Palm Fatty Acid Distillate

In this work, the reaction scheme for the esterification of palm fatty acid distillate performed under the noncatalytic and high‐temperature condition (230–290°C) was investigated with a rigorous mathematical modeling. The esterification reaction was assumed to be the pseudo–homogeneous second‐order reversible reaction, and the mass transfer effectiveness factor (η) was introduced in the modeling framework to systematically and collectively consider both evaporation and reaction, which are simultaneously and competitively occurred in the liquid phase. The nonlinear programming problem was constructed with the objective function consisting of the errors between experimental data and the estimated values from the reaction model. The problem was solved by using the Nelder–Mead simplex algorithm to identify kinetic parameters, reaction rate constants, and mass transfer coefficients. The values of mass transfer coefficients were found to follow the Hertz–Knudsen relation and expressed as a function of reaction temperature. From the reaction rate constants obtained from the proposed kinetic models, the apparent activation energy was estimated to be 43.98 kJ/mol, which is lower than the value obtained from the reaction using heterogeneous catalysts. This low value indicates that reactants and products behave as an acid catalyst at relatively high operating temperature and constant pressure.     

Catalytic and Atom‐Economic C −C Bond Formation: Alkyl Tantalum Ureates for Hydroaminoalkylation

Atom‐economic and regioselective C ?C bond formation has been achieved by rapid C?H alkylation of unprotected secondary arylamines with unactivated alkenes. The combination of Ta(CH₂SiMe₃)₃Cl₂, and a ureate N,O‐chelating‐ligand salt gives catalytic systems prepared in situ that can realize high yields of β‐alkylated aniline derivatives from either terminal or internal alkene substrates. These new catalyst systems realize C?H alkylation in as little as one hour and for the first time a 1:1 stoichiometry of alkene and amine substrates results in high yielding syntheses of isolated amine products by simple filtration and concentration.