Papers by Dagmar Dietrich
Materialwissenschaft und Werkstofftechnik, 2017
Material Science and Engineering Technology 3 technologischen Transfers und des gemeinsamen kultu... more Material Science and Engineering Technology 3 technologischen Transfers und des gemeinsamen kulturellen Erbes der vorkolumbischen Kulturen geeignet.
Analytical and Bioanalytical Chemistry, Nov 1, 2002
The composition and structure of boron carbonitride (BCN) films were studied. The films were cont... more The composition and structure of boron carbonitride (BCN) films were studied. The films were continuously deposited on fibres by atmospheric pressure CVD. The precursors were ammonia, trimethyl borate and toluene. The composition was determined by photoelectron spectra of boron 1s, nitrogen 1s, carbon 1s and oxygen 1s. By fixing the C 1s peak at 285 eV, the position of the B 1s peak and the N 1s peak in the BCN films was equal to BN films. The C content of the films increases from about 6 at% to 60 at%, leaving the stoichiometric boron/nitrogen ratio as well as the oxygen content below 10 at% unchanged. Generally, the carbon content in the films is lower than predicted by the precursor ratios. Obviously, the insertion of carbon into the film is decreased in the presence of ammonia, which is known to etch carbon. With a decreasing ammonia/toluene ratio, the undesired effect in the reaction is suppressed and the carbon deposition becomes considerable. Transmission electron microscopic studies were performed on cross-sections of the coated fibres. High-resolution images generally show a hexagonal turbostratic structure with different orientation preferences of the atomic lamellae similar to hexagonal turbostratic boron nitride and pyrolytic carbon. When a noticeable carbon concentration (20 at%) is reached, the atomic sheets become uniformly distributed in all directions in space.
J Solid State Electrochem, 2011
NiCo–Al2O3 composite coatings were prepared by electrodeposition in a sulfamate plating bath cont... more NiCo–Al2O3 composite coatings were prepared by electrodeposition in a sulfamate plating bath containing Al2O3 particles to be co-deposited under sonication. For reliable determination of the microstructure, detailed studies on composite cross-sections were carried out by energy-dispersive spectrometer (matrix composition, particle content) and FE-SEM/electron backscattered diffraction data (particle distribution, grain size), accompanied by XRD analyses concerning texture, lattice parameter, grain size,
Journal of Thermal Spray Technology, 2015
The present paper is focused on the characterization of the differences between two microstructur... more The present paper is focused on the characterization of the differences between two microstructures that can be obtained using SPS technology, namely (i) columnar and (ii) two-zone microstructure including lamellas and fine unmelted particulates. The optimization of spray parameters was made, and the advanced microstructural studies of obtained coatings were performed. The work was focused on zirconia stabilized by yttria (YSZ, ZrO 2 + 14 wt.% Y 2 O 3 ) and both by yttria and ceria (YCSZ, ZrO 2 + 24 wt.% CeO 2 + 2.5 wt.% Y 2 O 3 ) which are frequently used as thermal barrier coatings. Two types of microstructure were achieved using two different plasma torches, namely SG-100 of Praxair and Triplex of Oerlikon Metco. The microstructure of prepared coatings was analyzed using scanning electron microscopy with secondary electrons detector and backscattered electrons. Energy dispersive spectroscopy was performed to analyze the chemical composition of sprayed coatings. By electron backscatter diffraction grain shape, size, and crystal orientation were determined. The analysis enabled the discussion of the coatings growth mechanism. Finally, the Shape From Shading technique was applied to recreate and to analyze 3D views of coatingsÕ topographies, and using laser confocal microscopy, the surface roughness was examined.
Microstructure studies on petrified wood samples from the Permian of Chemnitz applying backscatte... more Microstructure studies on petrified wood samples from the Permian of Chemnitz applying backscatter electron diffraction show the spatial distribution of silica polymorphs formed during the petrifaction process with a close correlation to the extant plant tissue. Detailed investigations were done on axial and cross sections of the vascular segments of the seed fern Medullosa stellata. It became apparent that the cell walls of the tracheids were preserved by microcrystalline quartz (chalcedony) and the cell lumina were preserved by extremely fine crystallised silica of low crystalline order with relationship to opal or moganite. A comparative analysis on mineral samples of moganite and chalcedony from the type locality Mogán, Gran Canaria, was added for verification.
The pathways to form fossilised wood are diverse. Especially volcanic-affected ecosystems and the... more The pathways to form fossilised wood are diverse. Especially volcanic-affected ecosystems and their deposits provide not only excellently preserved petrified wood, but also some of the most detailed insights into ancient biotas in general. Related fossil forests offer a broad range of preservational forms, such as permineralisations, petrifactions or charcoal remains. However, even examples that show preservation of plant tissues and reveal their internal anatomy in great detail often hide information about the fossilisation process. Therefore, in many cases taphonomic modes involved in fossilization remain largely unresolved or not completely understood. In this contribution we report on petrified wood from the lower Permian Donnersberg Formation of Kahlheckerhof, Rhineland/Palatinate. Specimens encompass a wide range from small fragments to nearly complete logs. The homogenous secondary xylem consists only of thick walled tracheids and parenchymatous rays. Growth rings were freque...
To combine the low density of magnesium with the corrosion resistance of aluminum in one componen... more To combine the low density of magnesium with the corrosion resistance of aluminum in one component, a joint processing has gained scientific interest. It has been shown, that Al-Mg compounds and components with the material combination AlMgSi1/MgAl3Zn can be produced successfully by hydrostatic co-extrusion and forging. The interface region consists of the two phases β (Al3Mg2) and γ (Al12Mg17) with a significant lower ductility than the basic materials. Because of this brittle property the interface is fragmented due to stress condition during further forming. Thus, the durability of the components is limited. To address this problem the influence of an additional heat treatment on the interface was investigated by applying Differential Scanning Calorimetry (DSC). The aim of this study was to investigate if a phase transformation occurs in the temperature range up to 400 °C and whether it can be measured. Due to the small interface volume of the extruded strands, it is difficult to...
Chemisch abgeschiedene Nickel-Phosphor-Schichten bieten gegenüber elektrolytisch hergestellten ve... more Chemisch abgeschiedene Nickel-Phosphor-Schichten bieten gegenüber elektrolytisch hergestellten verschiedene Vorteile und werden überwiegend in Automobil-, Elektro- und Telekommunikationsindustrie eingesetzt. Eine der Abscheidung folgende Wärmebehandlung ermöglicht die Steigerung von Härte und Verschleißfestigkeit der Schichten. Unter atmosphärischen Bedingungen geht das Tempern mit thermischer Oxidation der Nickeloberfläche einher. Durch gezielte Modifikation der Wärmebehandlungsatmosphäre kann die Oxidationsrate gezielt beeinflusst werden, um so ggf. eine Funktionalisierung der Nickeloxidschicht zu erreichen. Verschiedene Ansätze zur Modifikation der Wärmebehandlungsatmosphäre werden erprobt und mit Ergebnissen mikrostruktureller Untersuchungen diskutiert.
Materials Science Forum, 2015
Fresenius' Journal of Analytical Chemistry, 1998
The microstructure and the composition of CVD silicon carbide films used as fiber coatings in com... more The microstructure and the composition of CVD silicon carbide films used as fiber coatings in composite materials were investigated by photoelectron spectroscopy and transmission electron microscopy. The films with a uniform thickness of 50 nm consisted of small SiC grains with a mean diameter of 15 nm and showed a stripe contrast in bright field images. Large grains with diameters in the dimension of the film thickness were used for imaging the lattice structure by high-resolution electron microscopy. The results are discussed as a polytype of cubic lamellae of a few nanometers and intermediate random stacking sequences of hexagonal structure.
EMC 2008 14th European Microscopy Congress 1–5 September 2008, Aachen, Germany, 2008
ABSTRACT
EMC 2008 14th European Microscopy Congress 1–5 September 2008, Aachen, Germany, 2008
ABSTRACT Electroplated composites with incorporated nanoparticles become a key material in the fa... more ABSTRACT Electroplated composites with incorporated nanoparticles become a key material in the fabrication of microsystem devices. A good survey of composites with nickel matrix is given in [1]. Electrodeposition of alumina particles (13 nm diameter, content around 1 Wt %) in nickel from an acidic electrolyte has been investigated using a nickel sulfamate bath with a particle loading of 10 g/l. Direct current (DC) deposition was compared to pulse-reverse plating (PRP) which can facilitate higher amounts. Details are given in [2]. Materials properties depend on the particle distribution, their bonding to the matrix and their influence on the microstructure of the matrix which has been characterized by TEM, STEM, SEM and EBSD.
Surface and Coatings Technology, 2013
and sharing with colleagues.
Fresenius' Journal of Analytical Chemistry, 1998
SEM, EDS and GDOES investigations on ferrous ore and slag samples contribute to the local history... more SEM, EDS and GDOES investigations on ferrous ore and slag samples contribute to the local history of mining and metallurgy. Quantitative X-ray analysis confirms the ore to be limonite. The slag consists of fayalithe and incompletely reduced ore parts (iron scale). Additional calcium and charcoal inclusions were reactants of the bloomery process. The charcoal shows anatomical details of spruce (Picea abies (L.) Karst.). A multitude of typical trace elements was detected by GDOES both in ore and slag samples. The comparison of normalised GDOES signals for a series of constituents showed that the ore from the assumed deposit (Euba) was processed in the location (Sternmühlenthal), where the slag was discarded. The process was probably performed in the 17th century.
Fresenius' Journal of Analytical Chemistry, 1997
Crystalline strontium titanate layers were deposited on titanium anodes from Sr(OH) 2 aqueous ele... more Crystalline strontium titanate layers were deposited on titanium anodes from Sr(OH) 2 aqueous electrolyte solutions by a plasmachemical-electrochemical process of anodic spark deposition. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to study the properties of the polycrystalline material. Strontium titanate was deposited on the titanium anode surface as a ceramic layer from an aqueous electrolyte. The typical pore structure morphology of the anodic spark deposit (ASD) was characterized by SEM as well as fractures which provide an intimate contact between layer and substrate. XRD-study showed that the layers are composed of a mixture of SrTiO
Uploads
Papers by Dagmar Dietrich