Niedrigemittierende (Low‐E) Schichten auf KFZ‐Verglasungen

The influence of low‐emissivity coatings on the outside surface of car glazing Low‐e‐coatings on the outer surface of architectural glazing are used for several years to prevent fog and frost for a clear view in the winter. Also for outdoor parked cars at night they were successfully tested. In the article, the occurrence of condensation on automotive glazing is simulated depending on the weather conditions, the emissivity of the outer surface, day or night, parking or moving vehicle. It is shown that the risk of outside condensation arises from the cooling down of the car cabin below the outside air temperature. The highest risk occurs for inclined windshields at night with clear sky and no wind. With decreasing emissivity, however, it decreases sharply. Further calculations show that due to low‐e‐coatings on the outer surface the solar energy balance Q_bal.i of the vehicle cabin increases during daytime. At low solar irradiance this has a positive effect on the cabin climatisation during the heating season, especially in the morning time after outdoor parking. At high irradiation in midsummer, the air conditioner is however only slightly loaded more both when parking as well as driving. With increasing vehicle speed, the heat transfer by the wind compensates more and more the heat radiation to the sky, i. e. the influence of the emissivity on Q_bal.i decreases.     

PVD‐Schutzschichten für Werkzeuge des Präzisionsblankpressens

PVD protective coatings for precision molding tools Precision glass molding (PGM) is a replicative hot forming process for the production of complex optical components, such as aspherical lenses for digital and mobile phone cameras or optical elements for laser systems. The efficiency and thus also the profitability of the PGM depend on the unit price per pressed component, which correlates primarily with the service lifetime of the pressing tools. To increase tool lifetime, the tool surfaces are coated with protective coatings based on precious metals or carbon using physical vapour deposition (PVD). The PVD coating technology enables the deposition of thin coatings, which also follow more complex surface geometries and achieve a high surface quality. PVD coatings are also commonly used to protect tools from wear and corrosion. This paper presents two chromium‐based nitride hard coatings produced by an industrial PVD unit and investigated for their applicability for PGM. Two different coating architectures were implemented, on the one hand a single coating chromium aluminium nitride (Cr,Al)N coating and on the other hand a nanolaminar CrN/AlN coating with alternating layers of chromium nitride and aluminium nitride. The latter is a coating consisting of hundreds of nano‐layers, only a few nanometers thick. Both coatings, (Cr,Al)N and CrN/AlN, each have a thickness of s ～ 300 nm in order to follow the tool contour as closely as possible. The properties of the coating systems, which are of particular relevance for PGM, are considered. These include on the one hand the adhesion of glass, the roughness and topography of the surface and the adhesion between the coating and the tool material. In addition, the barrier effect of the coatings against diffusion of oxygen was investigated. In order to reproduce the thermal boundary conditions of the PGM, thermocyclic aging tests are performed and their influence on the different properties is described.     

UV‐verstärkte Silberschichten

UV‐enhanced Ag‐coatings with optimized environmental stability For the construction of optical instruments, mirrors with silver (Ag) coatings are of great importance, because Ag has the highest reflectivity of all metals from the visible (VIS) throughout the infrared (IR) spectral range. Investigations performed at IOF show, that the deposition of a closed and dense protective layer is a necessary but not a sufficient condition for the effective protection of silver: hygroscopic particles can harm even silver coatings protected by a previously defect‐free protective layer. In order to improve the protection, a nanolaminate approach for Ag‐protection has been developed. By this approach, both the environmental stability and the optical performance can be optimized.     

Plasmagestützte Beschichtung von Bauteilen bei niedrigen Temperaturen

The deposition of wear resistant coatings is possible nowadays at low temperature by the Plasma Assisted CVD process using metall organic precursors. Thus a coating of temperature sensitive materials like aluminium, magnesium and polymer at low temperature is realised. The wear resistant coatings TiCN and ZrCN were deposited on light metals at a temperature below 160°C. The mechanical properties of the layers show the potential of the coatings for parts with wear and friction. The surface hardness, the abrasive wear and the friction value are improved compared to the properties of substrate material and steel. Transparent BCN‐coatings can be used as scratch resistant coatings on polymers like polycarbonate. The layers offers good transmission by high hardness.     

Abscheidung,Charakterisierung und Anwendung von Plasma‐Polymerschichten auf HMDSO‐Basis

Deposition, Characterisation and Application of HMDSO‐based Plasma Polymer Films High quality organosilicone coatings can be produced via plasma enhanced chemical vapor deposition of hexamethyldisiloxane (HMDSO). In this article aspects of deposition, analysis and application of HMDSO/O₂ processes are presented. The coatings’ organic/inorganic character can be adjusted by an appropriate combination of plasma power and gas mixture which is shown by XPS. Particularly multi layer and gradient layer systems can be deposited within the same process. Quantitative chemical depth profiling of such layer systems can be performed by secondary neutral mass spectrometry (SNMS). AFM investigations exhibit that the surface roughness of the coatings is determined by the appearance of hemispherical agglomerates, which is more pronounced, the more glass‐like the coatings are. As an example of use it is shown, that an appropriate HMDSO plasma treatment can distinctly improve the tribological behavior of elastomer devices. The presented work is done within a project of the German Federal Ministry of Education and Research (BMBF) entitled: “nano functionalization of interfaces for data‐, textile‐, building‐, medicine‐, bio‐, and aerospace‐ technology”.     

Deposition of superconducting Nb<Subscript>3</Subscript>Sn and high-purity Nb coatings on the rotor of a cryogenic gyroscope

Superconducting Nb₃Sn and high-purity niobium layers have been deposited onto a protective copper layer grown on a spherical beryllium substrate from molten salts, and their structure and superconducting properties have been studied. The results demonstrate that such coatings are suitable for use as working layers of the rotor of a cryogenic gyroscope.     

Mikrowellen‐PECVD für kontinuierliche Großflächenbeschichtung bei Atmosphärendruck

Microwave PECVD for continuous wide area coating at atmospheric pressure Plasma processes are applied for a variety of surface modifications. Examples are coatings to achieve an improved corrosion and scratch protection, or surface cleaning. Normally, these processes are vacuum based and therefore suitable to only a limited extend for large area industrial applications. By use of atmospheric pressure plasma technology integration in continuously working manufacturing lines is advantageously combined with lower costs and higher throughput. Microwave plasma sources present powerful modules for plasma enhanced chemical vapour deposition at atmospheric pressure. At Fraunhofer IWS processes and equipment as well as application specific materials are developed. The coatings are suitable for scratch resistant surfaces, barrier and corrosion protective layers or anti‐reflex layers on solar cells. The film properties achieved are comparable with those produced by low pressure processes.     

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.     

Funktionelle Schichten auf Metallen: Maßgeschneiderte Eigenschaften durch Sol‐Gel‐Technologie

Functional Layers on Metals: Tailored Properties by Sol‐Gel Technology The value of metal articles can be substantially enhanced by convenient surface coatings. Beside organic layers (e. g. paints) and inorganic layers (e. g. enamel) wellknown as coating materials, so‐called inorganic‐organic hybrid polymers set out to combine the advantages of both coating groups. For the manufacture of such hybrid materials functional particles with sizes of a few nanometers – so‐called nanoparticles – are synthesized in the sol‐gel process. The versatility of this procedure allows to cover an extreme variety of properties of the resulting layers. Thus, depending on their composition, sol gel coatings are suited as corrosion protection, as primer, as abrasion‐reducing coating or as easy‐to‐clean layer. A sufficient wetting and adhesion on vitually any substrate can be achieved by proper choice of functional groups and pretreatment steps.     

Herstellung und komplexe Charakterisierung von Metall‐Keramik‐Verbundschichten

Formation and characterization of metal‐ceramic coatings The influence of the formation process and used materials of metal‐ceramic coatings on the structural properties of the deposited layers were investigated and optimized to increase the mechanical properties. There the deposition of the metal‐ceramic‐layers occurred by a combination of electrophoretic and galvanic deposition with siloxane as bonding compound. Layers with a high ceramic content were successfully created. As ceramic components commercial silicon carbide and silicon nitride were used. Nickel and Copper respectively were applied as metal component to fill the porous ceramic structure with the aim to increase the strength of the layers, where nevertheless a pre nickel‐plating or pre cupper plating of the steel substrate X6Cr17 before ceramic component deposition had to be done to increase the adhesion of the layers. The layer characterization was made by optical microscopy and scanning and transmission electron microscopy, where especially the bonding of the single particles by the siloxane was in evidence.     

Self‐Assembly of Ferromagnetic Organic–Inorganic Perovskite‐Like Films

Perovskite‐based organic–inorganic hybrids hold great potential as active layers in electronics or optoelectronics or as components of biosensors. However, many of these applications require thin films grown with good control over structure and thickness—a major challenge that needs to be addressed. The work presented here is an effort towards this goal and concerns the layer‐by‐layer deposition at ambient conditions of ferromagnetic organic–inorganic hybrids consisting of alternating CuCl₄‐octahedra and organic layers. The Langmuir‐Blodgett technique used to assemble these structures provides intrinsic control over the molecular organization and film thickness down to the molecular level. Magnetic characterization reveals that the coercive field for these thin films is larger than that for solution‐grown layered bulk crystals. The strategy presented here suggests a promising cost effective route to facilitate the excellently controlled growth of sophisticated materials on a wide variety of substrates that have properties relevant for the high density storage media and spintronic devices.     

Funktionelle Schichten durch UV‐ und Elektronenstrahlhärtung

UV (EB) Curable Functional Coatings Composition, curing kinetics and application potential of acrylate based UV(EB) curable coatings are described. To formulate these coatings a manifold of acrylate oligomers exhibiting either ether, ester, epoxy or urethane functionality can be used as binders whereas acrylate monomers are applied as reactive thinners. Coatings with special functional properties such as resistance against chemicals, scratch and abrasion resistance, UV‐protection and flexibility can be applied on substrates such as paper, plastic films, wood and engineered wood, aluminum etc. Additionally, liquid acrylates can be favourably applied to produce microstructured or super smooth surfaces: the acrylate is brought into contact with either a structurized or a polished drum and rapidly cured in contact with the cylinder surface. Scratch and abrasion resistant coatings are obtained from acrylate nanocomposites. These formulations contain up to 30 w% SiO₂ nanoparticles covered by a polysiloxane shell.     

Superharter Kohlenstoff abgeschieden mit gepulstem Hochstrombogen als Nanoschutzschicht f�r Magnetspeicherplatten

Superhard amorphous Carbon films (ta‐C) deposited by pulsed High‐Current Arc (HCA) possess a good perspective to be used as future ultrathin protective coatings for magnetic hard disks. The ta‐C coatings meet all demands concerning the mechanical, chemical and tribological properties required for corrosion and wear protective coatings with thicknesses of 2‐3nm. From the current point of view the deposition technique also qualifies for an industrial mass production. Consequently there is a very good prospect that in near future the High‐Current Arc technique will be the method of choice for Carbon deposition in industrial hard disk drive production.     

Thermal stability of CrN<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> nanometric coatings deposited on stainless steel

Thin CrN _x coatings are often used as protective coatings for steel. In these applications, coated parts might be subjected to high temperatures that can alter the coatings structural and mechanical properties. In this work, the properties of nanometric CrN _x coatings deposited by reactive magnetron sputtering on AISI 304L stainless steel were studied by transmission electron microscopy, glazing incident X-ray diffraction, Atomic Force Microscopy, and nanoindentation. The effect of annealing, both in air and vacuum, on the coating crystal structure, surface morphology and hardness were also investigated. It was found that annealing in vacuum-induced phase transformation from CrN to Cr₂N, while after annealing in air only Cr₂O₃ phase was present. Surface roughness did not increase for annealing in vacuum. CrN _x coatings with higher Cr₂N phase content showed lower roughness increase for annealing in air. Measured hardness was >10 GPa for as-deposited CrN _x samples. An increase in hardness up to >20 GPa was found for vacuum-annealed samples.     

Multifunctional FeCo/TiN Multilayer Thin Films with Combined Magnetic and Protective Properties

Coatings with thicknesses ranging from a few nanometer up to several micrometer produced by physical vapor deposition (PVD) processes have been established in engineering technologies since the early 1980s. In particular, magnetron sputtered wear resistance coatings are industrially established and capable to enhance tool lifetimes significantly. However, in cases where optical inspection of a coating in use is not possible, an intrinsic sensor function of the film would be beneficial. Therefore, the development of wear resistant coatings with an integrated sensor functionality based on the insertion of a magnetoelastic ferromagnetic phase is suggested. In combination with appropriate read‐out electronics such a film system would be ready for online monitoring of the coatings' actual state (e.g., strain, temperature, volume loss). This paper focuses on the development of wear resistance coatings which simultaneously supply beneficial mechanical properties as well as ferromagnetic properties optimized for online non‐contact read‐out applications. Multilayer coatings obtained through alternate stacking of magnetron sputtered TiN and FeCo layers with a nominal total thickness of 1000 nm were produced as a model system meeting the above conditions. The bilayer period was varied down to 2.6 nm while the individual layer thickness ratio t_TiN/t_FeCo was determined by the deposition rates and maintained constant at a value of about 3/1. The films were vacuum annealed ex situ in a static magnetic field subsequent to the deposition. The constitution of the as‐deposited and annealed coatings as well as their mechanical (nanohardness, Young's modulus) and magnetic properties (magnetization hysteresis, frequency‐dependent permeability) are described. Finally, the suitability of the coatings for the use in remote‐interrogable wear sensor applications is briefly discussed.     

Co3O4 protective coatings prepared by Pulsed Injection Metal Organic Chemical Vapour Deposition

Cobalt oxide films were grown by Pulsed Injection Metal Organic Chemical Vapour Deposition (PI-MOCVD) using Co(acac)₃ (acac=acetylacetonate) precursor dissolved in toluene. The structure, morphology and growth rate of the layers deposited on silicon substrates were studied as a function of deposition temperature. Pure Co₃O₄ spinel structure was found for deposition temperatures ranging from 360 to 540 °C. The optimum experimental parameters to prepare dense layers with a high growth rate were determined and used to prepare corrosion protective coatings for Fe-22Cr metallic interconnects, to be used in Intermediate Temperature Solid Oxide Fuel Cells.     

Structure and properties of Nb<Subscript>3</Subscript>Sn coatings produced by unsteady-current electrocodeposition of Nb and Sn

We have studied the effect of electric-current mode on the structure and characteristics of niobium stannide coatings produced by electrochemical coreduction of niobium and tin ions at the cathode in molten salts. The results demonstrate that single-phase Nb₃Sn coatings with a superconducting transition temperature T _c = 17.3–17.9 K can be obtained using unsteady-current deposition. The coatings produced in galvanostatic mode and by ac deposition at a frequency of 50 Hz have a columnar grain structure. Current-reversal deposition with pulse ratios above 7–9 results in a layered microstructure with layers parallel to the substrate surface, instead of the columnar microstructure, and ensures a considerably higher critical current.     

Grundlageneigenschaften und Verschleißverhalten von HfB2- und Hf(B,N)-Schichtsystemen

Investigation of Fundamental Properties and Tribological Behaviour of HfB₂ and Hf(B,N) Coatings Thin films of HfB₂ and Hf(B,N), including intermediate layers of pure titanium, were sputtered in a rf sputtering unit on steel substrates. The deposition parameters bias-voltage and deposition pressure in the case of HfB₂ and the nitrogen flow concerning to Hf(B,N) were systematically varied. The characterization of the coatings includes fundamental properties such as thickness, hardness, adhesion and cohesion, structure, morphology, residual stresses and wear resistance of the coatings resulting from the plate on cylinder tribometer. The hardness values, analysed with the Vickers and the indentation depth method (Universal hardness), were extremely high for HfB₂ films, deposited with low deposition pressure or high bias voltage applied on the substrate. These results are probably caused by high residual stresses in the coating. The best wear properties could be obtained by testing the hardest coatings.     

Thermal cycling and isothermal oxidation behavior of quadruple EB‐PVD thermal barrier coatings

Increase of energy efficiency by increasing the turbine inlet temperature is the main driving force for further investigations regarding new thermal barrier coating materials. Today, thermal barrier coatings consisting of yttria stabilized zirconia are state of the art. In this study, thermal barrier coatings consisting of 7 weight percent yttria stabilized zirconia (7YSZ) and pyrochlore lanthanum zirconate (La₂Zr₂O₇) were deposited by electron beam physical vapor deposition. Regarding thermal cycling and isothermal oxidation behavior different layer architectures such as mono‐, double‐ and quadruple ceramic layers were investigated. The thermal shock behavior was examined by thermocycle tests at temperatures in the range between T = 50 °C ‐1,150 °C. Additionally, the isothermal oxidation behavior at a temperature of T = 1,150 °C with dwell times of t= 50 h and t = 100 h was studied in the present work. The conducted research concerning the behavior of various thermal barrier coating systems under thermal cycle and isothermal load highlights the potential of multilayer thermal barrier coatings for operating in high temperature areas.     

Substrate Selection for Full Exploitation of Organic Semiconductor Films: Epitaxial Rubrene on β‐Alanine Single Crystals

Rubrene (RUB) is one of the most studied organic semiconductors because, in the orthorhombic single‐crystal phase, it exhibits a record exciton diffusion length and one of the highest charge carrier mobilities ever reported. Here, thin films of oriented crystalline RUB are successfully grown in vacuum on millimeter‐sized (010)‐β‐alanine (β‐ala) single crystals with a step‐growth protocol, exploiting organic epitaxy. The experimental characterization demonstrates that these RUB films grow in the orthorhombic polymorph with the (100)_RUB plane in contact with the (010)_β‐ala surface and with precise azimuthal orientations. A complementary study of the RUB(100)/β‐ala(010) interface, performed by computational simulations, confirms the epitaxial relations expected by considering the molecular scale corrugations of the surfaces. Moreover, thanks to the wide transparency region of β‐ala, the RUB absorption bands in the UV range are directly detected for the first time. Finally, removal of the water‐soluble substrate enables the integration of the films in field effect transistors as high quality active organic layers. The characteristics of such RUB‐based devices confirm the quality and versatility of epitaxial thin films for use in organic electronics.