Abwärme als Energiequelle Bartholomé, Kilian; König, Jan D.; Pernau, Hans‐Fridtjof ...
Physik in unserer Zeit,
03/2017, Letnik:
48, Številka:
2
Journal Article
Zusammenfassung
Die Verstromung von Abwärme ist ein vielversprechender Ansatz zur Steigerung der Energieeffizienz vieler Prozesse. Hierfür bietet die Thermoelektrik große Vorteile in Bezug auf ...Systemkomplexität, Wartungsfreiheit und Langzeitstabilität. In den letzten Jahren wurden neue, effizientere thermoelektrische Materialien entwickelt. Auch die Aufbautechnik wurde verbessert. Auf dieser Basis werden nun thermoelektrische Module in Systemen verschiedener Anwendungen erprobt. Dazu zählen Fahrzeuge, Blockheizkraftwerke und die industrielle Abwärmenutzung zum Beispiel in Stahlwerken. Durch Produktion im industriellen Maßstab kann die Thermoelektrik zukünftig so wirtschaftlich werden, dass sie auf vielen Anwendungsgebieten einen spürbaren Beitrag zur Senkung der CO
2
‐Emissionen leistet.
Abstract
Roughly a decade ago an outstanding thermoelectric Figure of merit
ZT
of 2.4 was published for nanostructured Bi
2
Te
3
/Sb
2
Te
3
‐based thin film superlattice (SL) structures. The results ...strongly fueled and renewed the interest in the development of efficient novel nanostructured thermoelectric materials. Several attempts were made to reproduce and improve the properties by using different methods, for example by replacing the cost‐intensive metal organic chemical vapor deposition (MOCVD) used to deposit the superlattices. This method‐oriented article shall give a critical overview over the most recent advances concerning growth, structural and electrical characterization, and theoretical understanding of Bi
2
Te
3
/Sb
2
Te
3
SL systems. Previously reported data as well as new results from our groups are presented. Selected additional results from closely related Bi
2
Te
3
‐ and Sb
2
Te
3
‐based nanolayered systems are also presented to enhance the discussion.
Abstract
In this work, the impact of heat treatment on the real structure of Bi
2
Te
3
/Sb
2
Te
3
multilayers is investigated. The material was heated in situ in the transmission electron microscope ...(TEM) and ex situ inside a furnace after preparing these layers with the so‐called nanoalloying deposition technique via molecular beam epitaxy (MBE) equipment. The samples were prepared as a lamella for TEM studies using focused ion beam technique. EDX elemental mapping and high angle annular dark field mode‐STEM were performed to monitor changes of the morphology and interdiffusion phenomena after heating up to 250 °C. A grain growth started during heating and the chemical layer structure was smeared out partly but remained in several grains and was found to be adjusted parallel to a major lattice plane in a crystallite. High resolution TEM shows polysynthetic twinning in a number of crystals.
In this work, Bi^sub 2^Te^sub 3^-Sb^sub 2^Te^sub 3^ superlattices were prepared by the nanoalloying approach. Very thin layers of Bi, Sb, and Te were deposited on cold substrates, rebuilding the ...crystal structure of V^sub 2^VI^sub 3^ compounds. Nanoalloyed superlattices consisting of alternating Bi^sub 2^Te^sub 3^ and Sb^sub 2^Te^sub 3^ layers were grown with a thickness of 9 nm for the individual layers. The as-grown layers were annealed under different conditions to optimize the thermoelectric parameters. The obtained layers were investigated in their as-grown and annealed states using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray (EDX) spectroscopy, transmission electron microscopy (TEM), and electrical measurements. A lower limit of the elemental layer thickness was found to have c-orientation. Pure nanoalloyed Sb^sub 2^Te^sub 3^ layers were p-type as expected; however, it was impossible to synthesize p-type Bi^sub 2^Te^sub 3^ layers. Hence the Bi^sub 2^Te^sub 3^-Sb^sub 2^Te^sub 3^ superlattices consisting of alternating n- and p-type layers showed poor thermoelectric properties. PUBLICATION ABSTRACT
These recommendations were systematically developed on behalf of the Network for Early Onset Cystic Kidney Disease (NEOCYST) by an international group of experts in autosomal dominant polycystic ...kidney disease (ADPKD) from paediatric and adult nephrology, human genetics, paediatric radiology and ethics specialties together with patient representatives. They have been endorsed by the International Pediatric Nephrology Association (IPNA) and the European Society of Paediatric Nephrology (ESPN). For asymptomatic minors at risk of ADPKD, ongoing surveillance (repeated screening for treatable disease manifestations without diagnostic testing) or immediate diagnostic screening are equally valid clinical approaches. Ultrasonography is the current radiological method of choice for screening. Sonographic detection of one or more cysts in an at-risk child is highly suggestive of ADPKD, but a negative scan cannot rule out ADPKD in childhood. Genetic testing is recommended for infants with very-early-onset symptomatic disease and for children with a negative family history and progressive disease. Children with a positive family history and either confirmed or unknown disease status should be monitored for hypertension (preferably by ambulatory blood pressure monitoring) and albuminuria. Currently, vasopressin antagonists should not be offered routinely but off-label use can be considered in selected children. No consensus was reached on the use of statins, but mTOR inhibitors and somatostatin analogues are not recommended. Children with ADPKD should be strongly encouraged to achieve the low dietary salt intake that is recommended for all children.
We develop a tractable dynamic model of productivity growth and technology spillovers that is consistent with the emergence of real world empirical productivity distributions. Firms can improve ...productivity by engaging in in-house R\&D, or alternatively, by trying to imitate other firms' technologies, subject to the limits of their absorptive capacities. The outcome of both strategies is stochastic. The choice between in-house R\&D and imitation is endogenous, and based on firms' profit maximization motive. Firms closer to the technological frontier face fewer imitation opportunities, and choose in-house R\&D, while firms farther from the frontier try to imitate more productive technologies. The equilibrium choice leads to a balanced-growth equilibrium featuring persistent productivity differences even when starting from ex-ante identical firms. The long-run productivity distribution can be described as a traveling wave with tails following a Pareto as can be observed in the empirical data.
The gastrointestinal tract consists of an enormous surface area that is optimized to efficiently absorb nutrients, water, and electrolytes from food. At the same time, it needs to provide a tight ...barrier against the ingress of harmful substances, and protect against a reaction to omnipresent harmless compounds. A dysfunctional intestinal barrier is associated with various diseases and disorders. In this review, the role of intestinal permeability in common disorders such as infections with intestinal pathogens, inflammatory bowel disease, irritable bowel syndrome, obesity, celiac disease, non-celiac gluten sensitivity, and food allergies will be discussed. In addition, the effect of the frequently prescribed drugs proton pump inhibitors and non-steroidal anti-inflammatory drugs on intestinal permeability, as well as commonly used methods to assess barrier function will be reviewed.
Abwärme als Energiequelle Bartholome, Kilian; Konig, Jan D; Pernau, Hans-Fridtjof ...
Physik in unserer Zeit,
03/2017, Letnik:
48, Številka:
2
Journal Article
Zusammenfassung Die Verstromung von Abwärme ist ein vielversprechender Ansatz zur Steigerung der Energieeffizienz vieler Prozesse. Hierfur bietet die Thermoelektrik große Vorteile in Bezug auf ...Systemkomplexität, Wartungsfreiheit und Langzeitstabilität. In den letzten Jahren wurden neue, effizientere thermoelektrische Materialien entwickelt. Auch die Aufbautechnik wurde verbessert. Auf dieser Basis werden nun thermoelektrische Module in Systemen verschiedener Anwendungen erprobt. Dazu zählen Fahrzeuge, Blockheizkraftwerke und die industrielle Abwärmenutzung zum Beispiel in Stahlwerken. Durch Produktion im industriellen Maßstab kann die Thermoelektrik zukunftig so wirtschaftlich werden, dass sie auf vielen Anwendungsgebieten einen spurbaren Beitrag zur Senkung der CO2-Emissionen leistet.
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