Nanostructured Thermoelectric Materials and High-Efficiency Power-Generation Modules

For thermoelectric applications, the best materials have high electrical conductivity and thermopower and, simultaneously, low thermal conductivity. Such a combination of properties is usually found in heavily doped semiconductors. Renewed interest in this topic has followed recent theoretical predictions that significant increases in performance are possible for nanostructured materials, and this has been experimentally verified. During exploratory synthetic studies of chalcogenide-based bulk thermoelectric materials it was discovered that several compounds spontaneously formed endotaxially embedded nanostructures. These compounds have some of the best known properties for bulk thermoelectric materials in the 500–800 K temperature range. Here we report our continued efforts to better understand the role of the nanostructures while concurrently furthering the development of these new materials (for example n-type lead–antimony–silver–tellurium, and p-type lead–antimony–silver–tin–tellurium) into thermoelectric power-generation devices.     

Advanced X-ray methods for chalcogenide thin film analysis

This contribution reports advances made by very useful X-ray methods for the analysis of chalcopyrite based thin films. First, a suitable grazing incidence X-ray diffraction (GIXRD) setup which effectively enables depth sensitive analysis of chalcogenide thin films is described. A novel peak profile analysis method facilitates compositional depth profiling of Cu(In,Ga)(S,Se)₂ thin films. In situ growth studies of chalcogenide thin films using energy dispersive X-ray diffraction (EDXRD) require collimated, high flux X-ray excitation available at synchrotron light sources. The benefits of time resolved EDXRD analysis for the understanding of growth mechanisms are demonstrated. Finally the progress in the quantification of thin bilayer systems by soft X-ray emission spectroscopy (S-XES) is reported. Using the information of the relative emission intensities of particular elements in chalcogenide materials it is possible to accurately determine cover layer thickness in the nanometer scale of thin and even rough layers.     

Fragen der Lärmminderung in der chemischen Industrie (Geräuschsituation innerhalb und außerhalb der Werke)

Questions of noise reduction in the chemical industry (noise levels inside and outside industrial sites) . In the chemical industry there are hardly any noise problems as far as working conditions are concerned. However, certain difficulties are to be expected in the neighbourhood of chemical plant. Open-air plants require special nosie reduction measures at many individual noise sources. Safety aspects must have priority. The increased demands necessitate inclusion of piping and equipment in acoustic planning. There should be adequate transition zones separating industrial and residential areas, but owing to lack of town planning desirable screening distances hardly exist. New plants can now be built with noise levels some 7 to 10 dB (A), in certain cases even more than 10 dB (A), lower than ten years ago.     

A Concept for an Integrated Process Scheme for By-Products from Rice and Sugarcane Processing

The material use of agricultural by-products helps to not only reduce severe environmental problems, but also permits the production of value-added products at the same time. Extensive experiments produced and tested different erosion control blankets, adsorbents, and soil improvers from rice straw, rice husks, and bagasse. This led to the creation of an integrated process scheme, which permits side streams from one branch to be reused in other process branches. This integrated process scheme is presented that is demonstrated and supported by the material balance numbers based on the test results.     

Raman scattering analysis of Cu-poor Cu(In,Ga)Se2 cells fabricated on polyimide substrates: Effect of Na content on microstructure and phase structure

This work reports the Raman scattering surface and in-depth resolved analysis of Cu-poor Cu(In,Ga)Se₂ (CIGS) grown on polyimide substrates. In order to study the effect of Na on the formation and microstructure of the CIGS and the corresponding Cu-poor ordered vacancy compound (OVC) phases, a NaF precursor layer with different thicknesses was deposited on the Mo-coated substrates before growing of the samples. The Raman spectroscopy data are correlated with the analysis of the samples by Auger electron spectroscopy and scanning electron microscopy. These data corroborate the significant role of Na on the inhibition of Ga-In interdiffusion and on the formation of the MoSe₂ interfacial phase at the back region of the layers. Presence of Na also leads to an enhancement in the formation of the chalcopyrite CIGS phase and a decrease in the occurrence of the dominant OVC phase at the surface region. This study confirms the strong dependence of the microstructure and phase distribution in CIGS absorber layers on the Na available during their growth.     

Phases in copper-gallium-metal-sulfide films (metal=titanium, iron, or tin)

The incorporation of metal impurities M (M = Ti, Fe, or Sn) into CuGaS₂ films is investigated experimentally as a function of impurity concentration. Films are synthesized by thermal co-evaporation of the elements onto glass/Mo substrates heated to 400 °C-570 °C. The compositions of the resulting films are measured by energy-dispersive X-ray spectroscopy and the structures of the present phases are studied by X-ray diffraction. The formation of Cu-M-S ternary phases is observed in a wide range of conditions. Films of Cu-Ga-Ti-S, synthesized at 500 °C, show the presence of a cubic modification of CuGaS₂ and Cu₄TiS₄. Alloying of CuGaS₂ and tetragonal Cu₂SnS₃ is observed for substrate temperatures of 450 °C. A miscibility gap opens at 500 °C and above with separate Sn-rich and Ga-rich phases. Similarly, alloys of CuFeS₂ and CuGaS₂ are only found in Cu-Ga-Fe-S films synthesized at lower substrate temperature (400 °C), whereas at 500 °C a miscibility gap opens leading to separate Fe-rich and Ga-rich phases.     

Efimov physics from a renormalization group perspective

We discuss the physics of the Efimov effect from a renormalization group viewpoint using the concept of limit cycles. Furthermore, we discuss recent experiments providing evidence for the Efimov effect in ultracold gases and its relevance for nuclear systems.