Untersuchungen zur synthese von poly(butadien-co-propylenoxid) mit einem ziegler-natta-titankatalysatorsystem

After comparison of three catalyst systems, i.e. [Nd(Oct)₃/Al₂Cl₃ET₃/Al(i-But)₃, Ni(Oct)₂/BF₃OEt₂/AlEt₃ and Al(i-But)₃/I₂/TiCl₄] the titanium catalyst system was used for the copolymerization of 1,3-butadiene with propylene oxide. The effects of monomer ratio on copolymer composition, conversion, microstructure, molar mass and molar mass distribution as well as of time of polymerization and of the aluminium/titanium ratio were evaluted. The copolymerization parameters were determined according to Kelen-Tüd?s as r_butadiene = 0,9 and r_{propylene oxide} = 3,9. Copolymerization was confirmed by ¹³C NMR spectroscopy and extract evaluation combined with ¹H NMR spectroscopy.     

Computer simulation on the hydrodynamics of gas injection process in liquid steel

It is shown that with the aid of digital simulation methods complex multiphase interrelated systems, such as gas-injection process can be analysed. Interdependencies can be revealed and quantitative evaluation of characteristic system quantities are provided. The method of digital system simulation is a very convenient tool for process analysis or system engineering. Results of the computer-aided process simulations (Caps) yield a better understanding of complex phenomena and better aimed engineering of gas dispersion techniques in metallurgical processes. A particular interest of this investigation is to reveal the effect of mass-transfer rate on the hydrodynamic behaviour of a gas-injection process. The combined effects of total flow rate of injected gas and mass-transfer rate on the system quantities such as mixing power, induced liquid flow rate, holdup, interfacial area and volumetric mass transfer coefficient are evaluated under steady state conditions of the investigated systems and illustrated in simulation plots. The liquid velocity has a minor effect on bubble size at some distance from the orifice but controls the location of bubble breakup. The frequency of bubble breakup and final bubble size depends on the intensity of mass transfer. Mixing power due to gas bubbles and circulation velocity of the steel bath increase appreaciably if there is a chance of bath reactions producing more gas. The integral mean values of mixing power, induced velocity of liquid and holdup in plume, specific interfacial area and volumetric mass-transfer coefficient increase with increasing total flow rate of injected gas and intensity of mass transfer.     

Influence of experimental setup on observed values of mixing time in gas-stirred liquids

Mixing time of metallurgical reactors is gaining increasing importance. At first sight one single mixing time should be expected, being characteristic with regard to a given reactor and to given stirring conditions. The aim of the present paper is to call attention to the influence of the location of tracer injection and of the experimental method on the observed value of the mixing time. Two mixing times have been defined, namely “local mixing time” and “global mixing time”. The results have been compared with those of the literature. Partly, there is good agreement with some published correlations.     

The properties of CuInSe2-MnSe crystals

The composition and the impurity back-ground levels of (CuInSe₂)_1-x (MnSe)_2x alloy crystals are characterized by ion microprobe analyses. Room temperature photoreflectance (PR) and photoconductivity (PC) measurements in the temperature range 10 K ⪯ T ⪯ 300 K reveal changes in the point defect chemistry and a shift of the band gap with increasingx towards higher energies. Also, a deep luminescence feature at 0.89 eV is observed in Mn doped crystals, in addition to the contributions at 0.90 and 0.94 eV that appear in both doped and nominally undoped CuInSe₂. X-ray diffraction studies show that the chalcopyrite structure is retained to at leastx = 0.25.