Determination of the activities of the components of a ternary metallic system from the knowledge of its gas solubility

Derivation of polynomial equations as a function of two concentration variables to determine the activities of the components of a multicomponent system from the knowledge of its gas solubility. Development of polynomial functions to describe the hydrogen solubility of the mixed phase. Application of the polynomial equations to calculate the activity coefficients of the components iron, cobalt and silicon of the liquid ternary system iron–cobalt–silicon. Representation and discussion of the activities as isothermal planes as a function of two concentration variables.     

Chemical equilibria between silicon and slag melts

The equilibria between silicon and slags of the systems CaO-SiO₂, Na₂O-SiO₂, and CaO-SiO₂-Y with Y being A1₂O₃, MgO, TiO_x, B₂O₃, and Na₂O have been investigated in silica crucibles. The calcium content under silica-saturated CaO-SiO₂ slag is 262 parts per million (ppm) at 1500 °C. The aluminum and magnesium contents increase with increasing alumina or magnesium oxide contents, respectively, reaching about 1800 ppm Al at silica/mullite or about 390 ppm Mg at silica/protoenstatite saturation. Boron has a distribution ratio [B]/(B₂O₃) of 0.18. The sodium content under silica-saturated Na₂O-SiO₂ slag is 25 ppm at 1500 °C. In contrast, the titanium content of the silicon, if Y is TiO_x, and (Ti) is in the percent range, is highand varies with the titanium content of the slag according to [wt Pct Ti] = 2.7 √(wt pctTi). In other experiments, it is shown that metallurgical grade (MG) silicon can be purified from aluminum, magnesium, and calcium by treatment with suitable silicate slags.     

Contribution of physico-chemical properties of interfaces on dispersibility, adhesion and flocculation of filler particles in rubber

Reinforcing fillers are added to elastomeric compounds to improve and adjust several mechanical, dynamical, tribological, etc. properties with respect to different applications, i.e. for automotive tires, or technical rubber goods. Carbon black and precipitated silica are widely used as rubber reinforcing fillers; however, some new classes of nanosized substances like organophilic modified clay or carbon nanotubes are presently intensive studied as possible future filler systems in combination with carbon black or silica.An important parameter for the dispersibility and compatibility of the filler in the polymer matrix of rubber compounds is the surface energy and surface polarity of the solid filler particles. Therefore, we systematically measured and compared the dynamic contact angles of a collection of different filler types (carbon blacks, silica, carbon nanotubes and organoclays) using the Wilhelmy method, whereby the particles were fixed as a thin layer at a double-sided adhesive tape. From the contact angle values the polar and disperse part of the surface energies of the filler particles were calculated by fitting Fowkes formula. For an estimation of the compatibility of the fillers with different types of rubber polymers we additionally analyzed the surface energy and polarity of the gum (unfilled) elastomers. From the evaluated surface energies and polarities, thermodynamic predictors for the dispersibility (enthalpy of immersion), the adhesion between filler particles and polymer matrix in the nanocomposite, and for the flocculation behaviour of the particles in a rubber matrix (difference in the works of adhesion) were derived. These thermodynamic predictors improve considerably the compounding process of novel rubber nanocomposites with respect to target-oriented adjustment of rubber properties.     

Germany’s journey toward 14 Tesla human magnetic resonance

Multiple sites within Germany operate human MRI systems with magnetic fields either at 7 Tesla or 9.4 Tesla. In 2013, these sites formed a network to facilitate and harmonize the research being conducted at the different sites and make this technology available to a larger community of researchers and clinicians not only within Germany, but also worldwide. The German Ultrahigh Field Imaging (GUFI) network has defined a strategic goal to establish a 14 Tesla whole-body human MRI system as a national research resource in Germany as the next progression in magnetic field strength. This paper summarizes the history of this initiative, the current status, the motivation for pursuing MR imaging and spectroscopy at such a high magnetic field strength, and the technical and funding challenges involved. It focuses on the scientific and science policy process from the perspective in Germany, and is not intended to be a comprehensive systematic review of the benefits and technical challenges of higher field strengths.