G. Wiegand

Hazardous Waste Disposal by Supercritical Fluids

In the presence of water or carbon dioxide in the supercritical state, organic materials can be oxidized by oxygen practically completely within seconds. The report contains descriptions of test rigs and experimental findings. Additional R&D work is necessary for technical-scale application in cleaning organically polluted liquid effluents.

Bio-inspired, large scale, highly-scattering films for nanoparticle-alternative white surfaces

Inspired by the white beetle of the genus Cyphochilus, we fabricate ultra-thin, porous PMMA films by foaming with CO2 saturation. Optimising pore diameter and fraction in terms of broad-band reflectance results in very thin films with exceptional whiteness. Already films with 60 µm-thick scattering layer feature a whiteness with a reflectance of 90%. Even 9 µm thin scattering layers appear white with a reflectance above 57%. The transport mean free path in the artificial films is between 3.5 µm and 4 µm being close to the evolutionary optimised natural prototype. The bio-inspired white films do not lose their whiteness during further shaping, allowing for various applications.

The viscosity of n-decane to high temperatures of 573 K and high pressures of 300 MPa

The dynamic viscosity of liquid n-decane has been measured with the “Oscillating Disk Method” from 293 K to 573 K and from 0.1 MPa to 300 MPa. A high pressure autoclave of 50 mm internal diameter contained between two rigid disks an oscillating stainless steel disk of 44 mm diameter suspended on a platinum-tungsten wire. Pressure was generated with a spindle press filled with a suitable hydraulic fluid separated from the n-decane. Thus heating and pressure variation could be performed at selected constant volumes. The density dependence of the viscosity could be determined. The viscosity increases at 373 K from 375 to 1602 μPa s in the pressure range from 0.1 to 200 MPa, at 473 K from 200 to 1114 μPa s in the pressure range from 10 to 300 MPa, and at 573 K from 223 to 675 μPa s in the pressure range from 60 to 300 MPa. The mean accuracy of the viscosity measurements is about 1.3 %. A polynomial function describing the viscosity variation with pressure and temperature is given. The maximum average deviation is 0.46 %, the mean average deviation between measured and calculated data is 0.11 %. The viscosity as a function of density is also shown. With Arrhenius plots, the energies of activation are obtained.

Oxidation of organic material in supercritical water and carbon dioxide

Publisher Summary This chapter discusses the oxidation of organic material in supercritical water and carbon dioxide. The industrial application of the supercritical water oxidation (SCWO) process strongly depends on the solution of two major technical problems: the corrosion of the reactor material when halogenated compounds are processed and the precipitation of inorganic product salts plugging the reactor. The methods of supercritical extraction and of supercritical oxidation in carbon dioxide can favorably be integrated in one process if the extracted solute has to be disposed. Salt precipitation and corrosion are the technical key problems of the economical solution that make the SCWO process an important tool for the treatment of hazardous organic wastes. The development of a corrosion resistant material may take a time too long for industrial implementation in a competitive market situation.

Bio-inspired micro-to-nanoporous polymers with tunable stiffness

Background: Inspired by structural hierarchies and the related excellent mechanical properties of biological materials, we created a smoothly graded micro- to nanoporous structure from a thermoplastic polymer. Results: The viscoelastic properties for the different pore sizes were investigated in the glassy regime by dynamic flat-punch indentation. Interestingly, the storage modulus was observed to increase with increasing pore-area fraction. Conclusion: This outcome appears counterintuitive at first sight, but can be rationalized by an increase of the pore wall thickness as determined by our quantitative analysis of the pore structure. Therefore, our approach represents a non-chemical way to tune the elastic properties and their local variation for a broad range of polymers by adjusting the pore size gradient.