Transparente und leitfähige Veredelung von Kunststoffoberflächen

Deposition Techniques for Transparent Conducting Thin‐Films on Glass and Polymer Substrates We report on thin films deposited at atmospheric pressures on glass and polymer substrates with various techniques. The introduced thin‐film materials show intrinsic properties being suitable for different applications while maintaining the principle properties of the substrates themselves (e. g. shape. rigidity/flexibility, transparency). With the main focus on optical and electronic applications the properties of the deposited films can be adjusted by the choice of coating material (e. g. metal oxide, CNT), the film's shape (compact, particulate) and the deposition process itself. We compare deposition and properties of different TCO‐materials with CNT‐based thin film techniques and demonstrate approaches for the integration of these processes in production lines.     

Transparente Elektroden aus Silber

Transparent electrodes made of silver Thin coatings of silver are used in heat control windows. They have a high conductivity and a high transmittance, especially in the visible range of the spectrum. The transmittance decreases in the near infrared, which can be compensated by gains due to an efficient utilisation of interferences. Silver coatings can be produced at low cost. Especially, it is possible to deposit them also on flexible foils. By additional dielectric layers, further demands can be fulfilled, without an impairment of the conductivity. Examples are the prevention of barriers, the adjustment of the work function or the stabilisation against subsequent processes. By this, silver electrodes are of specific interest for organic light emitting diodes or solar cells.     

Transparente Elektroden auf Kunststofffolien

Transparent electrodes have gained a considerable importance in various fields, like e.g. touchscreen devices. Future applications will require higher performance with regard to both electrical and optical properties and they will require lower cost. Today most electrodes are made of transparent conducting oxides like indium tin oxide (ITO). These materials can be sputtered from ceramic targets by dc sputtering processes with simple process control setups. Polymer films can be coated with these materials in vacuum roll coaters. These systems allow the sputtering processes to be run during an unwind‐rewind‐cycle of the roll. Sheet resistance values as low as 20 Ω_squ can be achieved by this technology. Lower resistance values require different approaches. A new and very effective solution is the superposition of the transparent oxide with a metal network. However, also approaches which completely base on organic materials are under investigation. These solutions benefit from the progress in organic conductors. They can be made without any vacuum coating technology. Besides the low sheet resistance also the mechanical robustness against bending is an important advantage of full‐organic approaches.     

Dünne ITO‐Schichten als leitfähige,transparente Elektroden. Thin films of ITO as conductive,transparent electrodes

This article deals with materials science aspects of In₂O₃:Sn (“ITO”) coatings and with the process technology of variants of sputtering used to obtain thin films with properties desired for specific applications. As an example, antistatic and antireflective coatings of monitor tubes are presented. The influence of sputter parameters such as substrate temperature, plasma excitation mode, sputter pressure and oxygen partial pressure on the quality of the films is discussed. It is shown how application‐oriented basic research helps to obtain recipes for materials design. Two basic aspects are discussed in more detail: the influence of an oxygen surplus in the films on microstructure and electrical properties and the correlation of electrical and optical parameters of the films.     

Transparente leitfähige Nitride

Transparent conductive nitrides – New perspectives in device design More than 20 years after the pioneer of the GaN LED Nobel laureate Shuji Nakamura published that germanium is an inferior dopand for GaN when compared to silicon we showed that the opposite is true in regard of achievable n-type doping concentration. With Ge-doped GaN now device performance can be improved and new device structures realized. As transparent highly conductive nitride (TCN) new application fields emerge for GaN, in particular the replacement of ITO. Besides many potential applications Ge-doped GaN layers also show interesting physics as a new quasiparticle, the Collexon.     

Elektrisch leitfähige kohlenstofffaserverstärkte Kunststoffe (CFK) mit freiliegender Funktionsschicht

Efficient lightweight requires intelligent materials that meet versatile functions. One approach is to extend the range of properties of carbon‐fiber‐reinforced plastics (CFRP) by plating the fiber component. Functions such as thermal and electrical conductivity, contactability, solderability, and adhesion promoting are integrated on this road. When processing the metallized carbon fibers to carbon‐fiber‐reinforced plastics the functional layer is covered by the matrix polymer. Thus, it is no longer accessible for further proceeding. In this work, different strategies for the production of carbon‐fiber‐reinforced plastics with accessible functional layers are analyzed. Thereby, selective uncovering of the functional layer as well as proceeding the carbon‐fiber‐reinforced plastics and metal‐layers without damages are important criteria. An evaluation of the processes was carried out using microstructural investigations and adhesive tensile testing. Correlations between electrical conductivity measurements, wetting and joining experiments, surface machining and solderability can be derived.     

Leistungsfähige Spiegel für solarthermische Kraftwerke

High efficient mirrors for Concentrating Solar Power plants Mirrors are an essential component of CSP plants. Wet chemically coated silver mirrors supplied by Flabeg GmbH achieve an average specular and solar weighted reflectivity of 94.4%. Almost 30 years of field experience prove the durability of the coating. First surface mirrors could provide higher reflectivity, but so far either the necessary durability is not met or the costs are not competitive. Another approach to increase reflectivity is to equip the mirror with an antisoiling coating. This type of mirror is currently under field testing, showing already promising results. New paint systems for silvered mirrors will expand the locations for power plants to the shore or into tropical regions.     

Verallgemeinerungsfähige Merkmale und Besonderheiten des Sprühkompaktierens

Characteristic Features and Specific Qualifications of the Sprayforming Process to be Generalized The solidification and cooling process of spray formed materials predominates the extent of any segregation and separation process, which is conducive to avoid macro‐segregation and to diminish concentration of alloying components at the grain boundaries. The risk of coarse porosity or of hot cracking is reduced significantly by the momentum of the mass flow during spray deposition. This means that those materials which e.g. during the casting process tend to establish strong segregation effects and cavities and/or hot cracks as well as those which tend to create filaments of carbides, nitrides or sulphides during rolling can be generated by the spray forming process in large dimensions with chemical homogeneity and without any of those defects. A characteristic feature of spray formed materials is the fine equiaxed grain structure and the high ductility. Specific features of this new free forming process will be discussed.     

Eigenschaften amorpher transparenter leitfähiger Oxide (a‐TCOs)

Properties of amorphous transparent conducting oxides (a‐TCOs) In this contribution the optical and electrical properties of amorphous transparent conductive oxides (a‐TCOs) are analysed by means of atomistic material modelling. The investigation of model structures by computer simulations allows a deeper understanding of the physical phenomena. In the case of the a‐TCOs deep energy levels in the electronic band structure, that reduce for example the optical transparency, can be linked to structural defects on the atomic scale. This allows a well‐directed search for strategies which anneal these defects.     

Transparente Kratzschutzbeschichtungen für Kunststoff

Transparent scratch resistant coatings on plastics Today automotive glazing must show more and more functional properties and fulfill demands like low weight, easy assembling and demounting, high design flexibility and recycling properties. The increase of the glazed area as well as the integration of additional function into the glazing causes an increase of the total car weight, resulting in higher fuel consumption and therefore disadvantages concerning environment and resources. The substitution of ceramic glass by more lightweight transparent polymer materials like polycarbonate is a way to reduce the total weight of the car. As the resistance of polycarbonate against mechanical and chemical attack is limited, the surface must be protected by a transparent coating, for example based on silicon dioxide. Plasmapolymerization is a process well suited for the deposition of such coatings. This paper shows the state of the art of automotive glazing, describes innovative means for improving the surface properties of polycarbonate and demonstrates the potential of the process for the protection of searchlight lenses.     

Leistungsfähige Dünnschicht‐Beschichtung für die Photovoltaik

High‐performance thin‐film coating for photovoltaic applications The thin‐film photovoltaics market is large and is expected to grow continuously. Due to its huge potential regarding cost reduction and cell efficiency improvement, sputter‐etched ZnO:Al‐based TCO can make a sustainable contribution to achieve grid parity. One of the most promising approaches here is the large scale volume manufacturing of sputter‐etched TCO glass for thin film silicon solar cells. VON ARDENNE's leading process knowhow, applied to the highly productive and reliable PIA|nova coating system, allows for cost effective production and flexible adaptation of customer specific TCO requirements.     

p‐TCOs für Transparente Elektronik

p‐type TCOs for use in transparent electronics In this article, a new type of semiconducting material is introduced. Transparent conducting thin films are already established in our everydaylife. But the type of these so‐called ?TCOs”? is dominated by electron transport, that means they are n‐type. To get transparent p‐n‐junctions and therefore transparent electronics, the missing part is a transparent p‐type material. Researchers all over the world have found different approach to produce this new generation of materials. At the Fraunhofer Institute for Surface Engineering and Thin Films (IST) in Braunschweig it is now possible to produce these kind of thin films as well.     

Transparente Barriereschichten auf flexiblen Polymersubstraten

Transparent permeation barrier layers on flexible polymer substrates This paper reviews different vacuum based technologies for manufacturing transparent permeation barrier layers and layer stacks on flexible polymer substrates. With plasma assisted reactive evaporation, a cost‐efficient, highly productive process for food packaging applications is presented. Reactive dual magnetron sputtering is a technology for the deposition of oxide layers with a very low water vapor and oxygen transmission rate at a reasonable deposition rate. Many groups suggest multilayer stacks for the encapsulation of flexible electronic devices. In this paper, an all‐in‐vacuum inline concept for manufacturing such multilayers is presented. It is based on the combination of reactively sputtered barrier layers with interlayers grown by using a magnetron based PECVD process (Magnetron‐PECVD). Both, process parameters, such as deposition rate and process pressure, and important layer properties, such as morphology and the water vapor and oxygen transmission rate are compared for the different single and multi layer technologies.     

Schubtragfähigkeit von Mauerwerk aus Wärmedämmziegeln

Der Beitrag berichtet über zentrische und exzentrische Schubversuche an Mauerwerk aus Wärmedämmziegeln. Die Ergebnisse werden mit den aktuell gültigen Bemessungsansätzen in DIN 1053‐1 verglichen. Es wird gezeigt, dass die Versuchsergebnisse immer eine ausreichende Sicherheit gegenüber den Bemessungswerten nach DIN 1053‐1 aufweisen. Auch für Mauerwerk aus Wärmedämmziegeln mit allgemeiner bauaufsichtlicher Zulassung können somit die vereinfachten Bemessungsregeln der DIN 4149 ohne Abminderungen angewendet werden. In plane shear resistance of thermal insulating vertically perforated clay brick masonry. In plane shear tests on thermal insulating vertically perforated clay brick masonry are presented. The results are compared with the design rules from DIN 1053‐1. The test results exceeded the design predictions of DIN 1053‐1 by a significant safety margin. The simplified design rules from the German earthquake standard DIN 4149 can be applied to thermal insulating clay unit masonry with technical approvals without any reduction.     

Rost‐ und säurebeständige Stähle unter Komplexbeanspruchung

Rust and acid resistant steels under complex loading With corrosion fatigue investigations under different loadings (R = 0,27, ‐1 and 10) and with inner pressure tests a duplex steel (1.4462) and a super austenitic steel (1.3974) are compared. The investigations were carried out in 10 % HNO₃, artificial seawater according to DIN 50905 and in two very important liquids for application (artificial seawater according to DIN 50905 with H₂S aerated and water with chloride, fluoride, bromide, iodide). For comparison the same tests under only mechanical loads were done in acid free oil. The results show that the super austenitic steel has an significantly higher resistance against corrosion fatigue as the duplex steel under one‐ and three dimensional loads up to 10⁷ cycles. The proportion between the results in the corrosive liquids and the oil can be described by a factor. In artificial seawater factors between 0,67 and 0,92 and in 10 % HNO₃ between 0,67 and 0,83 were determined depending from the loading for the duplex steel. With the super austenitic steel factors between 0,86 and 1 in artificial seawater and between 0,7 and 1,0 in 10 % HNO₃ were received.