Disperse Amphiphilic Submicron Particles as Non‐Covalent Supports for Cationic Homogeneous Catalysts

A simple method for the effective immobilization of homogeneous catalysts on polystyrene colloids via non‐covalent binding is demonstrated. Stable latices with sufficiently high loading of accessible borate anions are prepared via emulsion polymerization. Incorporation of cationic rhodium complexes, supported via their borate counter‐anion is efficient, and these supported homogeneous catalysts maintain constant catalytic activity for CC hydrogenation during several recycles, with very low metal leaching.     

An evaluative approach to correlate machinability,microstructures, and material properties of gamma titanium aluminides

Several generations of gamma titanium aluminides have been developed over time, and they are nowadays commercially available. The differences in chemical composition, as well as the thermal treatments, greatly influence the properties of the alloys. This implies considerable effects on the production process performances. Benchmark trials were performed on three γ-TiAl alloys: Ti–48Al–2Cr–2Nb, Ti–43.5Al–4Nb–1Mo–0.1B, and Ti–45Al–2Nb–2Mn + 0.8 vol.% TiB₂ XD, focusing on machinability and material characterization. The extremely dissimilar results obtained when turning and milling can be traced back to the different microstructures, as well as to the alloying elements, factors both affecting the mechanical and thermal material properties.     

Dephosphorization equilibria between pure molten iron and CaO-saturated FeOn–CaO–CaF2 slags

Metal-slag refining reactions have been investigated to determine dephosphorization equilibria in steelmaking using CaO-saturated FeO_n–CaO–CaF₂ slags low in P₂O₅ content. Slag compositions have been optimized to achieve maximum partition ratios wt.%(P₂O₅)/wt.%[P] and minimum phosphorus contents in pure molten iron at 1 550 and 1 600°C. FeO_n–CaO–CaF₂ slags prove to be most effective dephosphorizers. Optimal slag compositions are between 10 and 20 wt.% FeO_n. Attempts were also made to present phosphate capacities fractions of free oxygen ions and theoretical optical basicities Λ as a function of the FeO_n content of slags. Dephosphorization capacity of FeO_n–CaO–CaF₂ slags is compared with that of FeO_n–CaO–SiO₂ and FeO_n–CaO–Al₂O₃ slags.     

Desoxidationsgleichgewichte von Titan,Aluminium und Zirconium in Eisenschmelzen bei 1600 °C

Verwendung einer Doppelelektrolytzelle aus ZrO₂(CaO) mit ThO₂(Y₂O₃)-Beschichtung zur Untersuchung der Desoxidationsgleichgewichte Fe–O–Ti, Fe–O–Al und Fe–O–Zr bei 1600 °C über EMK-Messung sowie Probenahme und chemische Analyse. Ermittlung der Sauerstoffaktivitäten in Abhängigkeit vom Gehalt an Titan, Aluminium oder Zirconium in der Eisenschmelze sowie der Gleichgewichtskonstanten und Wirkungsparameter e^x_x. Vergleich der analytisch bestimmten und thermodynamisch berechneten Sauerstoffgehalte.     

A combinatorial method for the generation of normally distributed random numbers

The proposed method generates standard normal variablesx. In 84.27% of all cases sampling from the centre \((|x| \leqslant \sqrt 2 )\) of the normal distribution is carried out using a variant ofJ. v. Neumann's algorithm for the generation of exponentially distributed random numbers. For sampling from the tails \((|x| > \sqrt 2 )\) the same method byJ. v. Neumann is combined with an acceptance-rejection approach ofG. Marsaglia.     

A general material law of plasticity and its numerical application

FE-codes for numerical simulations of metal forming processes need very general material laws. In this paper constitutive equations are proposed which include real-time and endochronic effects as well as kinematical hardening and a variable Hill-anisotropy. The law presented here is denoted in terms of strain spaces. The objective rates occurring in the evolutional rules of internal parameters include the concept of plastic spin to avoid physically meaningless oscillations of stresses in case of shear processes. Additionally an integrational scheme is presented which works very robustly and highly precisely even if very large strain differences occur within one time-step of the integration.