Einsatz von Entspannungsturbinen in CO2-Laseranlagen

Zusammenfassung Im Resonator von Laseranlagen werden ca. 20% der zugeführten Energie für den Laserstrahl genutzt. 80% der zugeführten Gesamtenergie werden mit dem Lasergas ungenutzt aus dem Resonator in den nachfolgenden W?rmeübertrager abgeführt. Um den Anlagenwirkungsgrad von Laseranlagen zu erh?hen, soll die ungenutzte Austrittsenergie aus dem Resonator in einer nachgeschalteten Entspannungsturbine in mechanische Energie umgesetzt werden, die zum Antrieb des Lasergasverdichters genutzt wird. Dadurch kann der Verdichter mit der vorhandenen Proze?energie angetrieben werden und der Anlagenwirkungsgrad vonη _A bis 0,20 aufη _A bis 0,34 erh?ht werden. Durch thermodynamische Proze?untersuchungen werden die erreichbaren Wirkungsgradsteigerungen von Laseranlagen ausgewiesen und die optimalen Parameterbereiche für die Druck-und Temperaturverh?ltnisse ermittelt. Das Leistungsverh?ltnis der gewonnenen Turbinenleistung zur notwendigen Verdichterleistung wird angegeben.     

25th Anniversary Article: Organic Field‐Effect Transistors: The Path Beyond Amorphous Silicon

Over the past 25 years, organic field‐effect transistors (OFETs) have witnessed impressive improvements in materials performance by 3–4 orders of magnitude, and many of the key materials discoveries have been published in Advanced Materials. This includes some of the most recent demonstrations of organic field‐effect transistors with performance that clearly exceeds that of benchmark amorphous silicon‐based devices. In this article, state‐of‐the‐art in OFETs are reviewed in light of requirements for demanding future applications, in particular active‐matrix addressing for flexible organic light‐emitting diode (OLED) displays. An overview is provided over both small molecule and conjugated polymer materials for which field‐effect mobilities exceeding > 1 cm² V^–1 s^–1 have been reported. Current understanding is also reviewed of their charge transport physics that allows reaching such unexpectedly high mobilities in these weakly van der Waals bonded and structurally comparatively disordered materials with a view towards understanding the potential for further improvement in performance in the future.     

Technofunctional Properties of Films Made From Ethylene Vinyl Acetate/Whey Protein Isolate Compounds

One challenge faced by the plastics industry is that crude oil will become scarcer and more expensive in the future. Furthermore, an increase in plastic waste is leading to a strongly growing demand for sustainable alternatives to traditional, crude oil‐based polymers in the packaging sector. The aim of this study was to investigate the influence of the incorporation of whey protein isolates (WPIs) on the technofunctional properties of ethylene vinyl acetate (EVA) films. The compounding EVA with WPI was conducted in a co‐rotating twin‐screw extruder at varying processing temperatures. WPI and hydrolysed WPI with a degree of hydrolysis of 10% were used up to 35% (w/w) as filler. The tensile strength and elongation at break of the resulting EVA‐based films decreased significantly with increasing filler content. Because of the hydrophilicity of WPI, the water vapour permeability of the films increased. Advantageously, the oxygen barrier was enhanced by 50–80% compared with that of pure EVA films, which offered the potential of using whey proteins as a filler in compounds for packaging materials for their oxygen barrier properties. In addition, this study provides a promising perspective on the thermoplastic processing of whey protein formulations in the future. Copyright © 2013 John Wiley & Sons, Ltd.     

Carcass maturity and dicationic salts affect preblended, low-fat, low-sodium restructured beef

Preblending A- and C-maturity muscles with MgCl(2) and/or CaCl(2) was investigated in low-fat, low-sodium restructured beef. Products were formulated to contain: 1) 80% chunks, preblended 12h with 0.05% MgCl(2), 0.05% CaCl(2), or a combination of each (0.1%) and 0.4% sodium tripolyphosphate (STPP) and 2) 20% mince preblended 12h with 0.05% of each dicationic salt or the combination of dicationic salts (0.1%), 0.4% STPP, and 1.0% NaCl. This formulation achieved a raw product NaCl content of 0.2%. Additionally, a control was formulated with chunks and mince that contained no dicationic salt. CaCl(2) decreased raw and cooked pH and cook yield, and increased cohesiveness; whereas, MgCl(2) increased cook yield and myosin solubility. Total protein solubility was not affected by muscle maturity or dicationic treatment. Myosin solubility of the combination treatment was greater for C-maturity muscle (57 months) compared to A-maturity muscle (20 months) formulations. Control, C-maturity muscle treatments contained more insoluble and total collagen (p < 0.05), and these treatments were more cohesive (p < 0.05) than control, A-maturity treatments. The combination of CaCl(2) and MgCl(2) increased hardness of A-maturity products, but it decreased hardness of C-maturity products. In addition to increasing hardness of A-maturity products, the combination treatment lowered (p < 0.05) cook yield for these products.     

Primary energy and economic analysis of combined heating, cooling and power systems

In this paper, the primary energy consumption and the economic viability of a combined heating, cooling and power (CHCP) system are derived. The focus is on small-scale applications in the range below 100 kW_H/70 kW_C/58 kW_el. CHCP is discussed between the boundaries of combined heating and power (CHP) and combined cooling and power (CCP) using a lumped parameter model. The method used is independent of a specific load profile for a building; only the full-load hours for heating and cooling are needed to predict the economic viability. German data is used for the example. A sensitivity analysis reveals the parameters with the highest impact on the primary energy consumption and the energy costs. The primary energy factors, the energy prices and the electric efficiency of the CHP are the dominating parameters. Increasing electricity prices favour the introduction of CHP and CHCP systems whereas increasing gas prices inhibit it. The energy cost analysis is extended to an economic analysis taking maintenance and investment costs into account. One result of this paper is a simple diagram which shows how many annual operation hours are needed for heating and cooling with CHCP to be more economical than a reference system.     

Anisotropy of Charge Transport in a Uniaxially Aligned and Chain‐Extended,High‐Mobility,Conjugated Polymer Semiconductor

Charge transport in the ribbon phase of poly(2,5‐bis(3‐alkylthiophen‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT)—one of the most highly ordered, chain‐extended crystalline microstructures available in a conjugated polymer semiconductor—is studied. Ribbon‐phase PBTTT has previously been found not to exhibit high carrier mobilities, but it is shown here that field‐effect mobilities depend strongly on the device architecture and active interface. When devices are constructed such that the ribbon‐phase films are in contact with either a polymer gate dielectric or an SiO₂ gate dielectric modified by a hydrophobic, self‐assembled monolayer, high mobilities of up to 0.4 cm² V^?1 s^?1 can be achieved, which is comparable to those observed previously in terrace‐phase PBTTT. In uniaxially aligned, zone‐cast films of ribbon‐phase PBTTT the mobility anisotropy is measured for transport both parallel and perpendicular to the polymer chain direction. The mobility anisotropy is relatively small, with the mobility along the polymer chain direction being higher by a factor of 3–5, consistent with the grain size encountered in the two transport directions.     

The Control of Shrinkage and Thermal Instability in SU‐8 Photoresists for Holographic Lithography

The negative‐tone epoxy photoresist, SU‐8, expands ≈1% by volume after postexposure baking. However, if the maximum optical fluence is comparable to that at the insolubility threshold, as in a holographic exposure, the developed resist shrinks (≈35% by volume) due to the removal of light oligomers not incorporated into the polymeric network. IR spectroscopy shows that, at this level of exposure, only 15% of the epoxy groups in the insoluble polymer have reacted; consequently microstructural elements soften and collapse at >100 °C. When the light oligomers are removed, the sensitivity of the resist is unchanged, provided that 5% (w/w) of a high‐molecular‐weight reactive plasticizer (glycidoxy‐terminated polyethylene glycol) is added, but it shrinks less on development and, when used as a photonic crystal template, shows improved uniformity with less cracking and buckling. Reinforcing the polymer network by reaction with the polyfunctional amine (bis‐N,N′‐(3‐aminopropyl)ethylenediamine) increases the extent of cross‐linking and the thermal stability, allowing inverse replicas of photonic crystal templates to be fabricated from both Al:ZnO and Zr₃N₄ using atomic layer deposition at temperatures up to 200 °C.     

Very Low Degree of Energetic Disorder as the Origin of High Mobility in an n‐channel Polymer Semiconductor

Charge transport is investigated in high‐mobility n‐channel organic field‐effect transistors (OFETs) based on poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2), Polyera ActivInk? N2200) with variable‐temperature electrical measurements and charge‐modulation spectroscopy. Results indicate an unusually uniform energetic landscape of sites for charge‐carrier transport along the channel of the transistor as the main reason for the observed high‐electron mobility. Consistent with a lateral field‐independent transport at temperatures down to 10 K, the reorganization energy is proposed to play an important role in determining the activation energy for the mobility. Quantum chemical calculations, which show an efficient electronic coupling between adjacent units and a reorganization energy of a few hundred meV, are consistent with these findings.