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Ion irradiation combined with nanoindentation is a promising tool to study irradiation-induced hardening of nuclear materials including reactor pressure vessel (RPV) steels. For RPV steels, the major sources of hardening are nm-sized irradiation-induced dislocation loops and solute atom clusters, both representing barriers for dislocation glide. The dispersed barrier hardening (DBH) model provides a link between the irradiation-induced nanofeatures and hardening. However, a number of details of the DBH model still require consideration. These include the role of the unirradiated microstructure, the proper treatment of the indentation size effect (ISE), and the appropriate superposition rule of individual hardening contributions. In the present study, two well characterized RPV steels, each ion-irradiated up to two different levels of displacement damage, were investigated. Dislocation loops and solute atom clusters were characterized by transmission electron microscopy and atom probe tomography, respectively. Nanoindentation with a Berkovich indenter was used to measure indentation hardness as a function of the contact depth. In the present paper, the measured hardening profiles are compared with predictions based on different DBH models. Conclusions about the appropriate superposition rule and the consideration of the ISE (in terms of geometrically necessary dislocations) are drawn.

Mainly the original data for model establishment.

Surface-directed and preferentially oriented assemblies of nanomaterials can enable enhanced applications in e.g. catalysis or sensing. Coordination polymers, which can be even conducting, could be suitable materials for this purpose because of their facile surface anchoring. Hence, we coassembled rhodium paddle-wheel building blocks with bi- or trifunctional linkers in dip coatings that were produced by layer-by-layer approach on silicon wafers functionalized by thin nanocrystalline gold surfaces. These gold surfaces were decorated with a self-assembled monolayer (SAM) for coordination and binding to the Rh-units. As linkers, pyrazine, triazine and melamine were used, leading to rectangularly-shaped, hexagonally-shaped or needle-like crystals, respectively. The coordination polymers were produced by repeated dipping into the linker and paddle-wheel solution, each followed by a cleaning step. The crystals growth was followed by atomic force microscopy (AFM) grazing incidence small-angle X-ray scattering (GISAXS) and grazing incidence wide-angle X-ray scattering (GIWAXS). AFM and GISAXS revealed the shape and size of the crystals. GIWAXS disclosed their preferred orientation. It turned out that the automated dipping procedure does not lead to a strong alignment of crystallites along the dipping direction for the pyrazine-based deposits. However, these crystals are preferentially oriented with respect to the substrate normal direction. The crystallographic direction and the degree of the alignment depend on the number of deposition cycles. In the early phases of the deposition process, predominantly “lying” crystals were detected. With increasing number of the deposition cycles, the fraction of “standing” crystals became dominant. These crystals are oriented with their {010} directions perpendicular to the surface of the substrate. Still, “lying” and some tilted crystals were detected additionally. The study gives a deeper structural understanding of crystallite assem

The compositional, optical and structural stability of transparent conductive oxide SnO2:Ta (1.25 at.% Ta) thin films at 650 °C and 800 °C in air was studied under isothermal conditions. After the high-temperature treatment, the element composition and the optical spectra of the material were unchanged. The X-ray diffraction confirmed the conservation of a single rutile-type phase. Two strong Raman lines located out of the SnO2 phonon range indicated point defects in the material, which were identified as Sn vacancies and O interstitials by theoretical calculations. These point defects were partially healed out during the high-temperature treatment, without affecting the transmittance and reflectance of the material. Our study demonstrates an exceptional high in-air stability of Ta-doped SnO2 and encourages it for applications in fields, where transparent conductive oxides with high-temperature and oxidation stability are required. These are, e.g., selective transmitters for concentrated solar power or electrodes for dye-sensitized solar cells and dynamic random-access memories.

Germanium nanocrystals embedded in high-k dielectric matrices are of main interest for infrared sensing application, as a role model for Ge-based nano-electronics passivation or for nonvolatile memory devices. The capability of the size control of those nanocrystals via rapid thermal processing of superlattice structures is shown for the [Ge–TaZrOx/TaZrOx]n, [Ge–TaZrOx/SiO2/TaZrOx]6, and [TaZrOx/Ge–SiO2]n superlattice systems. All superlattices were deposited by radiofrequency magnetron sputtering. Transmission electron microscopy (TEM) imaging confirms the formation of spherically shaped nanocrystals. Raman scattering proved the crystallization of Ge above 700°C. The TaZrOx crystallizes above 770°C, associated with a phase separation of Ta2O5 and ZrO2 as confirmed by x-ray diffraction. For the composite layers having 3 nm and 6 nm thickness, the size of the Ge nanocrystals correlates with the deposited layer thickness. Thicker composite layers (above 9 nm) form two fractions of nanocrystals with different sizes. An additional SiO2 layer in the [Ge–TaZrOx/SiO2/TaZrOx]6 superlattice stacks facilitates the formation of larger and better separated Ge nanocrystals. The deposition of Ge-SiO2 composite layers separated by pure TaZrOx illustrates the barrier effect of TaZrOx against Ge diffusion. All three material systems allow the controlled formation of Ge nanocrystals in amorphous matrices at temperatures above 700 and below 770°C.

The transparent conductive tantalum doped tin oxide is a potential candidate for applications in concentrated solar power technology, dye-sensitized solar cells and dynamic random access memories [1], [2], [3]. In all these fields, high-temperature stability in air is mandatory to preserve its functionality. In this work we demonstrate the compositional and structural in-air-stability of SnO2:Ta thin films at 650 °C and 800 °C for 12 hours. While the element composition and optical spectra were unchanged and the X-ray diffractograms revealed the conservation of a single-phase rutile-type crystal structure, some strong Raman lines of SnO2:Ta underwent substantial changes upon tempering. Quantum ab initio calculations of pristine and Ta-doped SnO2 with systematically varied point defects indicated that preferentially Sn vacancies and excess O atoms are responsible for these strong and unexpected Raman signatures. These defects are partially healed during high-temperature exposure, but that does not affect the functionality of SnO2:Ta as transparent conductor under these harsh conditions. This study provides a comprehensive understanding of crystal and defect structure of Ta-doped SnO2 prior to and after high temperature treatment in air for the first time and encourages its application in different fields where high-T stability, transparency and conductivity are required. [1] F. Lungwitz et al., Transparent conductive tantalum doped tin oxide as selectively solar-transmitting coating for high temperature solar thermal applications, Solar Energy Mater. Solar Cells 199, 84 (2019), doi: 10.1016/j.solmat.2019.03.012 [2] R. Ramarajan, et al. Large-area spray deposited Ta-doped SnO2 thin film electrode for DSSC application, Solar Energy 211, 547-559 (2020), doi:10.1016/j.solener.2020.09.042. [3] C. J. Cho, et al. Ta-Doped SnO2 as a reduction-resistant oxide electrode for DRAM capacitors, Journal of

Germanium nanocrystals embedded in high-k dielectric matrices are of main interest for infrared sensing application, as a role model for Ge-based nanoelectronics passivation or for nonvolatile memory devices. The capability of the size control of those nanocrystals via rapid thermal processing of superlattice structures is shown for the [Ge–TaZrOx/TaZrOx]n, [Ge–TaZrOx/SiO2/TaZrOx]6, and [ TaZrOx/Ge–SiO2]n superlattice systems. All superlattices were deposited by radiofrequency magnetron sputtering. Transmission electron microscopy (TEM) imaging confirms the formation of spherically shaped nanocrystals. Raman scattering proved the crystallization of Ge above 700°C. The TaZrOx crystallizes above 770°C, associated with a phase separation of Ta2O5 and ZrO2 as confirmed by x-ray diffraction. For the composite layers having 3 nm and 6 nm thickness, the size of the Ge nanocrystals correlates with the deposited layer thickness. Thicker composite layers (above 9 nm) form two fractions of nanocrystals with different sizes. An additional SiO2 layer in the [Ge– TaZrOx/SiO2/TaZrOx]6 superlattice stacks facilitates the formation of larger and better separated Ge nanocrystals. The deposition of Ge-SiO2 composite layers separated by pure TaZrOx illustrates the barrier effect of TaZrOx against Ge diffusion. All three material systems allow the controlled formation of Ge nanocrystals in amorphous matrices at temperatures above 700 and below 770°C.

Germanium nanocrystals embedded in high-k dielectric matrices are of main interest for infrared sensing application, as a role model for Ge-based nanoelectronics passivation or for nonvolatile memory devices. The capability of the size control of those nanocrystals via rapid thermal processing of superlattice structures is shown for the [Ge–TaZrOx/TaZrOx]n, [Ge–TaZrOx/SiO2/TaZrOx]6, and [ TaZrOx/Ge–SiO2]n superlattice systems. All superlattices were deposited by radiofrequency magnetron sputtering. Transmission electron microscopy (TEM) imaging confirms the formation of spherically shaped nanocrystals. Raman scattering proved the crystallization of Ge above 700°C. The TaZrOx crystallizes above 770°C, associated with a phase separation of Ta2O5 and ZrO2 as confirmed by x-ray diffraction. For the composite layers having 3 nm and 6 nm thickness, the size of the Ge nanocrystals correlates with the deposited layer thickness. Thicker composite layers (above 9 nm) form two fractions of nanocrystals with different sizes. An additional SiO2 layer in the [Ge– TaZrOx/SiO2/TaZrOx]6 superlattice stacks facilitates the formation of larger and better separated Ge nanocrystals. The deposition of Ge-SiO2 composite layers separated by pure TaZrOx illustrates the barrier effect of TaZrOx against Ge diffusion. All three material systems allow the controlled formation of Ge nanocrystals in amorphous matrices at temperatures above 700 and below 770°C.

Yb3Co4Ge13 is the first example of a Remeika phase with a 3D + 3 [space group P43n(a,0,0)000(0,a,0)000(0,0,a)000; a = 8:72328(1) Å, Q1 = Q2 = Q3 = 0:4974(2)] modulated crystal structure. A slight shift of the composition towards higher Ybcontent (i:e: Yb3:2Co4Ge12:8) leads to the disappearance of the satellite reflections and stabilization of the disordered primitive cubic [space group Pm3n, a = 8:74072(2) Å] Remeika prototype structure. The stoichiometric structurally modulated germanide is a metal with hole-like charge carriers, where Yb-ions are in a temperature dependent intermediate valence state of +2:60+2:66 for the temperature range 85-293 K. The valence fluctuations have been investigated by means of temperature dependent X-ray absorption spectroscopy, magnetic susceptibility and thermopower measurements

Yb3Co4Ge13 is the first example of a Remeika phase with a 3D + 3 [space group P43n(a,0,0)000(0,a,0)000(0,0,a)000; a = 8:72328(1) Å, Q1 = Q2 = Q3 = 0:4974(2)] modulated crystal structure. A slight shift of the composition towards higher Ybcontent (i:e: Yb3:2Co4Ge12:8) leads to the disappearance of the satellite reflections and stabilization of the disordered primitive cubic [space group Pm3n, a = 8:74072(2) Å] Remeika prototype structure. The stoichiometric structurally modulated germanide is a metal with hole-like charge carriers, where Yb-ions are in a temperature dependent intermediate valence state of +2:60+2:66 for the temperature range 85-293 K. The valence fluctuations have been investigated by means of temperature dependent X-ray absorption spectroscopy, magnetic susceptibility and thermopower measurements

Structure-based tissue engineering requires large-scale 3D cell/tissue manufacture technologies, to produce biologically active scaffolds. Special attention is currently paid to naturally pre-designed scaffolds found in skeletons of marine sponges, which represent a renewable resource of biomaterials. Here, an innovative approach to the production of mineralized scaffolds of natural origin is proposed. For the first time, a method to obtain calcium carbonate deposition ex vivo, using living mollusks hemolymph and a marine-sponge-derived template, is specifically described. For this purpose, the marine sponge Aplysin aarcheri and the terrestrial snail Cornu aspersum were selected as appropriate 3D chitinous scaffold and as hemolymph donor, respectively. The formation of calcium-based phase on the surface of chitinous matrix after its immersion into hemolymph was confirmed by Alizarin Red staining. A direct role of mollusks hemocytes is proposed in the creation of fine-tuned microenvironment necessary for calcification ex vivo. The X-ray diffraction pattern of the sample showed a high CaCO3 amorphous content. Raman spectroscopy evidenced also a crystalline component, with spectra corresponding to biogenic calcite. This study resulted in the development of a new biomimetic product based on ex vivo synthetized ACC and calcite tightly bound to the surface of 3D sponge chitin structure. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

Three-dimensional (3D) biopolymer-based scaffolds including chitinous matrices have been widely used for tissue engineering, regenerative medicine and other modern interdisciplinary fields including extreme biomimetics. In this study, we introduce a novel, electrochemically assisted method for 3D chitin scaffolds isolation from the cultivated marine demosponge Aplysina aerophoba which consists of three main steps: (1) decellularization, (2) decalcification and (3) main deproteinization along with desilicification and depigmentation. For the first time, the obtained electrochemically isolated 3D chitinous scaffolds have been further biomineralized ex vivo using hemolymph of Cornu aspersum edible snail aimed to generate calcium carbonates-based layered biomimetic scaffolds. The analysis of prior to, during and post-electrochemical isolation samples as well as samples treated with molluscan hemolymph was conducted employing analytical techniques such as SEM, XRD, ATR–FTIR and Raman spectroscopy. Finally, the use of described method for chitin isolation combined with biomineralization ex vivo resulted in the formation of crystalline (calcite) calcium carbonate-based deposits on the surface of chitinous scaffolds, which could serve as promising biomaterials for the wide range of biomedical, environmental and biomimetic applications. © 2020, The Author(s).

In thin amorphous carbon (a-C) films being in contact with a thin nickel layer, metal-induced crystallization and layer exchange (LE) occur at temperatures lower than 700 °C. Analysis of thin film stacks with different architectures (a-C/Ni, Ni/a-C and Ni/a-C/Ni) by means of ion beam analysis, Raman spectroscopy, X-ray diffraction and transmission electron microscopy revealed that the degree of LE and the structural quality of the crystallized carbon layers depend on the initial layer sequence. A LE degree of approx. 93 % was found for Ni/a-C bilayers, where graphenic layers formed on the Ni surface, whereas in a-C/Ni bilayers only 83 % of carbon was transferred from the surface towards the fused silica substrate. The diffusion of carbon in the outward direction produces turbostratic carbon with basal planes oriented parallel to the Ni surface, while for the inward direction planar and curved turbostratic structures coexist. The crystallization and the LE are driven by the crystallization energy of a-C. The LE is mediated by the wetting of the Ni grain boundaries by carbon. The directionality of the LE was explained primarily by the difference in the surface and interface energies in the a-C/Ni and Ni/a-C stacks that were obtained from thermodynamic considerations.

In thin amorphous carbon (a-C) films being in contact with a thin nickel layer, metal-induced crystallization and layer exchange (LE) occur at temperatures lower than 700 °C. Analysis of thin film stacks with different architectures (a-C/Ni, Ni/a-C and Ni/a-C/Ni) by means of ion beam analysis, Raman spectroscopy, X-ray diffraction and transmission electron microscopy revealed that the degree of LE and the structural quality of the crystallized carbon layers depend on the initial layer sequence. A LE degree of approx. 93 % was found for Ni/a-C bilayers, where graphenic layers formed on the Ni surface, whereas in a-C/Ni bilayers only 83 % of carbon was transferred from the surface towards the fused silica substrate. The diffusion of carbon in the outward direction produces turbostratic carbon with basal planes oriented parallel to the Ni surface, while for the inward direction planar and curved turbostratic structures coexist. The crystallization and the LE are driven by the crystallization energy of a-C. The LE is mediated by the wetting of the Ni grain boundaries by carbon. The directionality of the LE was explained primarily by the difference in the surface and interface energies in the a-C/Ni and Ni/a-C stacks that were obtained from thermodynamic considerations.

The catalytic graphitization with layer exchange (LE) of amorphous carbon in thin film stacks with Ni was investigated as a function of the initial stacking order. Bilayer and triple layer stacks were exposed to heating ramps up to 700 °C. Raman spectroscopy showed the formation of a layered graphitic structure after the annealing. During outwards LE, as C is transported towards the sample surface, a smooth layer with graphitic planes parallel to the interface with the substrate has formed through a 2D growth. A significant restructuring of the Ni layer appeared during inwards LE, as C is transported towards the substrate. Here, the fragmentation of the Ni layer, as well as the regions with turbulence-like and folding defects indicated a 3D growth. The degree of LE, quantified by ion beam analysis, is 95 % and 80 % for the outand inwards direction, respectively. Based on the calculation of surface and interface energies of the initial and final states, thermodynamic estimations pointed to the wetting of Ni grain boundaries by C atoms as the initial driving force for the LE and allowed a consistent understanding of the LE directionality and of the final thin film microstructure.

The graphitization of amorphous carbon in thin film stacks with Ni was investigated in situ as a function of the initial stacking order, temperature and time by Rutherford backscattering spectrometry and Raman spectroscopy. Four different bilayer and triple layer stacks were exposed to heating ramps up to 700 °C. The graphitization occurred simultaneously with a layer exchange (LE) and was completed during the applied heating ramp. The temperature-resolved measurements allowed the determination of the onset temperatures and transition rates for the respective stacking order. Finally, the activation energies for the graphitization of the amorphous carbon were estimated for both LE directions. In combination with thermodynamic calculations, this in situ study allowed to identify metal-induced crystallization with LE via wetting and diffusion along grain boundaries as mechanism responsible for the graphitization of amorphous carbon thin films in contact with Ni, instead of bulk dissolution/precipitation. The proposed model can potentially be used to estimate the catalytic transformation of group 14 elements in contact with transition metals.

The catalytic graphitization with layer exchange (LE) of amorphous carbon in thin film stacks with Ni was investigated as a function of the initial stacking order. Bilayer and triple layer stacks were exposed to heating ramps up to 700 °C. Raman spectroscopy showed the formation of a layered graphitic structure after the annealing. During outwards LE, as C is transported towards the sample surface, a smooth layer with graphitic planes parallel to the interface with the substrate has formed through a 2D growth. A significant restructuring of the Ni layer appeared during inwards LE, as C is transported towards the substrate. Here, the fragmentation of the Ni layer, as well as the regions with turbulence-like and folding defects indicated a 3D growth. The degree of LE, quantified by ion beam analysis, is 95 % and 80 % for the outand inwards direction, respectively. Based on the calculation of surface and interface energies of the initial and final states, thermodynamic estimations pointed to the wetting of Ni grain boundaries by C atoms as the initial driving force for the LE and allowed a consistent understanding of the LE directionality and of the final thin film microstructure.

The catalytic graphitization with layer exchange (LE) of amorphous carbon in thin film stacks with Ni was investigated as a function of the initial stacking order. Bilayer and triple layer stacks were exposed to heating ramps up to 700 °C. Raman spectroscopy showed the formation of a layered graphitic structure after the annealing. During outwards LE, as C is transported towards the sample surface, a smooth layer with graphitic planes parallel to the interface with the substrate has formed through a 2D growth. A significant restructuring of the Ni layer appeared during inwards LE, as C is transported towards the substrate. Here, the fragmentation of the Ni layer, as well as the regions with turbulence-like and folding defects indicated a 3D growth. The degree of LE, quantified by ion beam analysis, is 95 % and 80 % for the outand inwards direction, respectively. Based on the calculation of surface and interface energies of the initial and final states, thermodynamic estimations pointed to the wetting of Ni grain boundaries by C atoms as the initial driving force for the LE and allowed a consistent understanding of the LE directionality and of the final thin film microstructure.

The catalytic graphitization with layer exchange (LE) of amorphous carbon in thin film stacks with Ni was investigated as a function of the initial stacking order. Bilayer and triple layer stacks were exposed to heating ramps up to 700 °C. Raman spectroscopy showed the formation of a layered graphitic structure after the annealing. During outwards LE, as C is transported towards the sample surface, a smooth layer with graphitic planes parallel to the interface with the substrate has formed through a 2D growth. A significant restructuring of the Ni layer appeared during inwards LE, as C is transported towards the substrate. Here, the fragmentation of the Ni layer, as well as the regions with turbulence-like and folding defects indicated a 3D growth. The degree of LE, quantified by ion beam analysis, is 95 % and 80 % for the outand inwards direction, respectively. Based on the calculation of surface and interface energies of the initial and final states, thermodynamic estimations pointed to the wetting of Ni grain boundaries by C atoms as the initial driving force for the LE and allowed a consistent understanding of the LE directionality and of the final thin film microstructure.

The graphitization of amorphous carbon in thin film stacks with Ni was investigated in situ as a function of the initial stacking order, temperature and time by Rutherford backscattering spectrometry and Raman spectroscopy. Four different bilayer and triple layer stacks were exposed to heating ramps up to 700 °C. The graphitization occurred simultaneously with a layer exchange (LE) and was completed during the applied heating ramp. The temperature-resolved measurements allowed the determination of the onset temperatures and transition rates for the respective stacking order. Finally, the activation energies for the graphitization of the amorphous carbon were estimated for both LE directions. In combination with thermodynamic calculations, this in situ study allowed to identify metal-induced crystallization with LE via wetting and diffusion along grain boundaries as mechanism responsible for the graphitization of amorphous carbon thin films in contact with Ni, instead of bulk dissolution/precipitation. The proposed model can potentially be used to estimate the catalytic transformation of group 14 elements in contact with transition metals.

Metal-induced crystallization with and without layer exchange (MIC w/o LE) is a method to decrease the crystallization temperature of amorphous group 14 elements (G14E) by up to several hundred degrees. In situ experiments are expected to provide new insights into thin film evolution and elementary process steps of MIC w/o LE and to improve existing models of this type of phase transformation. While MIC w/o LE has been widely studied for Si and Ge in contact with catalytic metals, there exist only a few studies for the crystallization of amorphous carbon. Therefore, in this contribution in situ Rutherford backscattering spectrometry (RBS), Raman spectroscopy and spectroscopic ellipsometry studies were performed during annealing of amorphous carbon/nickel (a-C/Ni) layer stacks at temperatures up to 750°C. Due to its small lattice mismatch with the basal plane of graphite and high diffusivity of C atoms, Ni is a suitable catalyst for the growth of graphene and crystalline graphitic nanostructures. During the annealing of an a-C/Ni layer stack covalent bonds between the carbon atoms at the catalyst interface are weakened. Liberated carbon atoms can move along the interface and diffuse along the grain boundaries into the Ni layer towards the catalyst surface, where nucleation and grain growth of graphitic crystallites occur. Our in situ studies showed a change in the stacking sequence between C and Ni layers under defined experimental conditions. According to in situ Raman measurements, this mechanism occurs independent of the stacking sequence, while the velocity of the LE differs significantly. As observed in time and temperature resolved Raman spectra, the position of the G peak and the I(D)/I(G) ratio changed according to the Three-Stage-Model by Ferrari and Robertson, confirming the transformation of amorphous carbon to nc-graphite. With the in situ RBS measurements more insight into LE was given. Here peak positions of C and Ni were shifted, indicating a change of

Metal-induced crystallization (MIC) with and without layer exchange (LE) is a method to decrease the crystallization temperature of amorphous group 14 elements by up to several hundred degrees. In situ experiments are expected to provide new insights into thin film evolution and elementary process steps of MIC and to improve existing models of this type of phase transformation. In this contribution in situ Rutherford backscattering spectrometry (RBS), Raman spectroscopy and spectroscopic ellipsometry studies were performed during annealing of amorphous carbon/nickel (a-C/Ni) layer stacks at temperatures up to 750°C. LE was observed independently of the initial stacking sequence, while transformation rate and temperature differ significantly. The positions of the G, D and 2D Raman lines as well as the I(D)/I(G) ratio changed during the LE process. These were assigned in agreement with the Three-Stage-Model [1], confirming the transformation of a-C to nc-graphite. In situ RBS measurements demonstrated an opposite shift of the C- and Ni- related backscattering energies, proving that LE and graphitization occur simultaneously. [1] Ferrari et al., Phys. Rev. B 61 (2000) 14095

Metal-induced crystallization with and without layer exchange (MIC w/o LE) is a method to decrease the crystallization temperature of amorphous group 14 elements (G14E) by up to several hundred degrees. In situ experiments are expected to provide new insights into thin film evolution and elementary process steps of MIC w/o LE and to improve existing models of this type of phase transformation. While MIC w/o LE has been widely studied for Si and Ge in contact with catalytic metals, there exist only a few studies for the crystallization of amorphous carbon. Therefore, in this contribution in situ Rutherford backscattering spectrometry (RBS), Raman spectroscopy and spectroscopic ellipsometry studies were performed during annealing of amorphous carbon/nickel (a-C/Ni) layer stacks at temperatures up to 750°C. Due to its small lattice mismatch with the basal plane of graphite and high diffusivity of C atoms, Ni is a suitable catalyst for the growth of graphene and crystalline graphitic nanostructures. During the annealing of an a-C/Ni layer stack covalent bonds between the carbon atoms at the catalyst interface are weakened. Liberated carbon atoms can move along the interface and diffuse along the grain boundaries into the Ni layer towards the catalyst surface, where nucleation and grain growth of graphitic crystallites occur. Our in situ studies showed a change in the stacking sequence between C and Ni layers under defined experimental conditions. According to in situ Raman measurements, this mechanism occurs independent of the stacking sequence, while the velocity of the LE differs significantly. As observed in time and temperature resolved Raman spectra, the position of the G peak and the I(D)/I(G) ratio changed according to the Three-Stage-Model by Ferrari and Robertson, confirming the transformation of amorphous carbon to nc-graphite. With the in situ RBS measurements more insight into LE was given. Here peak positions of C and Ni were shifted, indicating a change of

Session: Thin films type of contribution: Poster Metal-induced crystallization with and without layer exchange (MIC w/o LE) is a method to decrease the crystallization temperature of amorphous group 14 elements (G14E) by up to several hundred degrees. In situ experiments are expected to provide new insights into thin film evolution and elementary process steps of MIC w/o LE and to improve existing models of this type of phase transformation. While MIC w/o LE has been widely studied for Si and Ge in contact with catalytic metals, there exist only a few studies for the crystallization of amorphous carbon. Therefore, in this contribution in situ Rutherford backscattering spectrometry (RBS), Raman spectroscopy and spectroscopic ellipsometry studies were performed during annealing of amorphous carbon/nickel (a-C/Ni) layer stacks at temperatures up to 750°C. Due to its small lattice mismatch with the basal plane of graphite and high diffusivity of C atoms, Ni is a suitable catalyst for the growth of graphene and crystalline graphitic nanostructures. During the annealing of an a-C/Ni layer stack covalent bonds between the carbon atoms at the catalyst interface are weakened. Liberated carbon atoms can move along the interface and diffuse along the grain boundaries into the Ni layer towards the catalyst surface, where nucleation and grain growth of graphitic crystallites occur. Our in situ studies showed a change in the stacking sequence between C and Ni layers under defined experimental conditions. According to in situ Raman measurements, this mechanism occurs independent of the stacking sequence, while the velocity of the LE differs significantly. As observed in time and temperature resolved Raman spectra, the position of the G peak and the I(D)/I(G) ratio changed according to the Three-Stage-Model by Ferrari and Robertson, confirming the transformation of amorphous carbon to nc-graphite. With the in situ RBS measurements more insight into LE was given. Here peak positions

Metal-induced crystallisation with layer exchange is applied on Ni/C bilayer stacks deposited by three PVD techniques on SiO2. The layer stacks were deposited at room temperature by either ion beam sputtering, direct current magnetron sputtering or high-power impulse magnetron sputtering. The influence of the Ni morphology on the layer exchange degree aLE and the resulting graphitic ordering is studied by atomic force microscopy, Rutherford backscattering spectrometry and Raman spectroscopy. The initial RMS roughness of the Ni top layer varied with the deposition technique by a factor of 20, from 0.3 to 6.1 nm. After annealing in UHV at up to 700°C, layer exchange was observed for all samples. Still, the layer exchange degree was affected by the roughness of the initial bilayer stack. The highest value of 96% was achieved for magnetron-sputtered samples, what is by ~35% higher than for the initially roughest Ni surfaces. Raman spectroscopy showed the formation of graphitic carbon, characterised by a strong 2D line, for all three bilayer stacks. The degree of graphitic ordering increased with decreasing Ni surface roughness.

The formation of orthorhombic (Zr,Ta)O2 was found in annealed thin Zr-Ta-O films with various tantalum concentrations deposited by co-sputtering a ZrO2 target and a mixed ZrO2/Ta2O5 target. In the as-deposited state, all films were amorphous. After annealing, tetragonal (Zr,Ta)O2 for [Ta]/([Ta]+[Zr]) < 0.19 and orthorhombic (Zr,Ta)O2 for [Ta]/([Ta]+[Zr]) > 0.19 were formed. Thin films with excess of tantalum ([Ta]/([Ta]+[Zr])> 0.5) decomposed into two orthorhombic phases upon crystallization: (Zr,Ta)O2 and tantalum-rich (Ta,Zr)2O5. The Rietveld analysis of Xray diffraction patterns revealed that the crystal structure of (Zr,Ta)O2 can be described with the non-centrosymmetric space group Pbc21. The broad range of tantalum concentrations, in which orthorhombic (Zr,Ta)O2 is formed as a single crystalline phase, is promising for the use of this compound in ferroelectric field effect transistors.

Metal-induced crystallization (MIC) with and without layer exchange (LE) is a method to decrease the crystallization temperature of amorphous group 14 elements by up to several hundred degrees. In situ experiments are expected to provide new insights into thin film evolution and elementary process steps of MIC and to improve existing models of this type of phase transformation. In this contribution in situ Rutherford backscattering spectrometry (RBS), Raman spectroscopy and spectroscopic ellipsometry studies were performed during annealing of amorphous carbon/nickel (a-C/Ni) layer stacks at temperatures up to 750°C. LE was observed independently of the initial stacking sequence, while transformation rate and temperature differ significantly. The positions of the G, D and 2D Raman lines as well as the I(D)/I(G) ratio changed during the LE process. These were assigned in agreement with the Three-Stage-Model [1], confirming the transformation of a-C to nc-graphite. In situ RBS measurements demonstrated an opposite shift of the C- and Ni- related backscattering energies, proving that LE and graphitization occur simultaneously. [1] Ferrari et al., Phys. Rev. B 61 (2000) 14095

© The Royal Society of Chemistry. In this study, self-prepared nanostructured CuO electrodes show no capacity decay for 40 cycles at 0.1C in Li metal cells. The reaction mechanisms of the CuO electrodes are investigated. With the help of in situ EIS, in situ XRD, TEM, XAS, SQUID, IC and GC-MS, it is found that the as-prepared CuO electrode undergoes significant phase and composition changes during the initial lithiation, with the transformation of CuO to nano-crystalline Cu. During the 1st delithiation, Cu is inhomogeneously oxidized, which yields a mixture of Cu2O, Cu2−xO and Cu. The incomplete conversion reaction during the 1st cycle is accompanied by the formation and partial decomposition of the solid electrolyte interphase (SEI) as the side reactions. Nevertheless, from the 1st to the 5th delithiation, the oxidation state of Cu approaches +2. After an additional formation step, the transformation to Cu and back to Cu2−xO remains stable during the subsequent long-term cycling with no electrolyte decomposition products detected. The LiNi1/3Mn1/3Co1/3O2 (NMC-111)/CuO full cells show high capacities (655.8 ± 0.6, 618.6 ± 0.9 and 290 ± 2 mA h g−1 at 0.1, 1 and 10C, respectively), within the voltage range of 0.7-4.0 V at 20 °C and a high capacity retention (85% after 200 cycles at 1C).

© The Royal Society of Chemistry. In this study, self-prepared nanostructured CuO electrodes show no capacity decay for 40 cycles at 0.1C in Li metal cells. The reaction mechanisms of the CuO electrodes are investigated. With the help of in situ EIS, in situ XRD, TEM, XAS, SQUID, IC and GC-MS, it is found that the as-prepared CuO electrode undergoes significant phase and composition changes during the initial lithiation, with the transformation of CuO to nano-crystalline Cu. During the 1st delithiation, Cu is inhomogeneously oxidized, which yields a mixture of Cu2O, Cu2−xO and Cu. The incomplete conversion reaction during the 1st cycle is accompanied by the formation and partial decomposition of the solid electrolyte interphase (SEI) as the side reactions. Nevertheless, from the 1st to the 5th delithiation, the oxidation state of Cu approaches +2. After an additional formation step, the transformation to Cu and back to Cu2−xO remains stable during the subsequent long-term cycling with no electrolyte decomposition products detected. The LiNi1/3Mn1/3Co1/3O2 (NMC-111)/CuO full cells show high capacities (655.8 ± 0.6, 618.6 ± 0.9 and 290 ± 2 mA h g−1 at 0.1, 1 and 10C, respectively), within the voltage range of 0.7-4.0 V at 20 °C and a high capacity retention (85% after 200 cycles at 1C).

Successive crystallization ofamorphous Cr-Zr-O thin films, formation of the (Cr,Zr)2O3/(Zr,Cr)O2 nanocomposites and the thermally induced changes in the hexagonal crystal structure of metastable (Cr,Zr)2O3 were investigated by means of in situ high-temperature synchrotron diffraction experiments up to 1100 °C. The thin films were deposited at room temperature by using reactive ion beam sputtering, and contained 3–15 at.% Zr. At low Zr concentrations, chromium-rich (Cr,Zr)2O3 crystallized first, while the crystallization of zirconium-rich (Zr,Cr)O2 was retarded. Increasing amount of zirconium shifted the onset of crystallization in both phases to higher temperatures. For 3 at.% of zirconium in amorphous Cr-Zr-O, (Cr,Zr)2O3 crystallized at 600 °C. At 8 at.% Zr in the films, the crystallization of (Cr,Zr)2O3 started at 700 °C. At 15 at.% Zr, the Cr-Zr-O films remained amorphous up to the annealing temperature of 1000 °C.Metastable hexagonal (Cr,Zr)2O3 accommodated up to ~3 at.% Zr. Excess of zirconium formed tetragonal zirconia, which was stabilized by chromium.

Successive crystallization ofamorphous Cr-Zr-O thin films, formation of the (Cr,Zr)2O3/(Zr,Cr)O2 nanocomposites and the thermally induced changes in the hexagonal crystal structure of metastable (Cr,Zr)2O3 were investigated by means of in situ high-temperature synchrotron diffraction experiments up to 1100 °C. The thin films were deposited at room temperature by using reactive ion beam sputtering, and contained 3–15 at.% Zr. At low Zr concentrations, chromium-rich (Cr,Zr)2O3 crystallized first, while the crystallization of zirconium-rich (Zr,Cr)O2 was retarded. Increasing amount of zirconium shifted the onset of crystallization in both phases to higher temperatures. For 3 at.% of zirconium in amorphous Cr-Zr-O, (Cr,Zr)2O3 crystallized at 600 °C. At 8 at.% Zr in the films, the crystallization of (Cr,Zr)2O3 started at 700 °C. At 15 at.% Zr, the Cr-Zr-O films remained amorphous up to the annealing temperature of 1000 °C.Metastable hexagonal (Cr,Zr)2O3 accommodated up to ~3 at.% Zr. Excess of zirconium formed tetragonal zirconia, which was stabilized by chromium.

Semiconductor nanocrystals in dielectric matrices are of great interest for a broad range of applications, especially in the field of photon management in solar cells and for non-volatile memories. In this work we investigate the formation of crystalline Ge nanoparticles in superlattice stacks by flash lamp annealing. In detail, amorphous ZrO2/Ge and SiN/Ge superlattices confined by two SiO2 layers on Si were produced by magnetron-sputtering and plasma-enhanced chemical vapor deposition, respectively. Raman and TEM investigations reveal that, depending on the original Ge layer thickness, crystalline Ge nanoparticles with different aspect ratios will be formed under annealing. As shown by electrical measurements, these layers feature large charge trapping capabilities. We compare these two types of layer systems with regard to the formation process of the Ge nanoparticles, the trapped charge density, the memory window and the retention. Finally, the perspectives for non-volatile memories are discussed, if these layer stacks are downscaled to current device dimensions.

Ge-nanocrystals (NCs) were synthesized in amorphous TaZrOx by thermal annealing of co-sputtered Ge-TaZrOx layers. Formation of spherical shaped Ge-NCs with small variation of size, areal density, and depth distribution was confirmed by high-resolution transmission electron microscopy. The charge storage characteristics of the Ge-NCs were investigated by capacitance-voltage and constant-capacity measurements using metal-insulator-semiconductor structures. Samples with Ge-NCs exhibit a maximum memory window of 5 V by sweeping the bias voltage from −7 V to 7 V and back. Below this maximum, the width of the memory window can be controlled by the bias voltage. The fitted slope of the memory window versus bias voltage characteristics is very close to 1 for samples with one layer Ge-NCs. A second layer Ge-NCs does not result in a second flat stair in the memory window characteristics. Constant-capacity measurements indicate charge storage in trapping centers at the interfaces between the Ge-NCs and the surrounding materials (amorphous matrix/tunneling oxide). Charge loss occurs by thermal detrapping and subsequent band-to-band tunneling. Reference samples without Ge-NCs do not show any memory window

Semiconductor nanocrystals in dielectric matrices are of great interest for a broad range of applications, especially in the field of photon management in solar cells and for non-volatile memories. In this work we investigate the formation of crystalline Ge nanoparticles in superlattice stacks by flash lamp annealing. In detail, amorphous ZrO2/Ge and SiN/Ge superlattices confined by two SiO2 layers on Si were produced by magnetron-sputtering and plasma-enhanced chemical vapor deposition, respectively. Raman and TEM investigations reveal that, depending on the original Ge layer thickness, crystalline Ge nanoparticles with different aspect ratios will be formed under annealing. As shown by electrical measurements, these layers feature large charge trapping capabilities. We compare these two types of layer systems with regard to the formation process of the Ge nanoparticles, the trapped charge density, the memory window and the retention. Finally, the perspectives for non-volatile memories are discussed, if these layer stacks are downscaled to current device dimensions.

For temperatures above 750°C, TiAl alloys still show insufficient oxidation resistance and suffer from environmental embrittlement. This work focuses on the surface modification of alloys and development of coatings against environmental embrittlement, as well as on testing of mechanical properties after high temperature oxidation. Aluminum enriched coatings (between 50 and 60 at.%) containing alloying elements, i.e. Cr, Nb, Si, Y, to improve the oxidation behavior and the corrosion resistance have been produced by MO-CVD, CVD, PVD and thermal spraying techniques (HVOF, APS), and have subsequently been chemically modified with halogen elements, notably fluorine. The mechanical properties have been studied by means of 4-point bending and tensile tests on coated samples after 100h oxidation at 900 °C in laboratory air. The CVD process combined with fluorine treatment using plasma immersion implantation (PI³) of F offers the best combination to remedy environmental embrittlement. It has been shown in particular that 90% of the initial fracture strain and fracture stress can be maintained.

The isostructural decomposition of the titanium aluminium nitride supersaturated solid solution crystallising in the face centred cubic (fcc) crystal structure into the titanium-rich fcc-(Ti,Al)N and almost titanium-free fcc-(Al, Ti)N and the transformation of metastable fcc-(Ti,Al)N into the wurtzitic aluminium nitride are discussed from the crystallographic point of view by taking the observed orientation relationships between the adjacent phases into account. It is shown that the isostructural decomposition of fcc-(Ti,Al)N into Ti-rich fcc-(Ti,Al)N and fcc-(Al, Ti)N and the transformation of themetastable fcc-(Ti,Al)N into the thermodynamically stablewurtzitic phase are concurrent processes, which are controlled not only by the thermodynamic stability of the respective compound and by the diffusivity of Al and Ti, but also by the local lattice strains. A part of the local lattice strains is regarded to result from the lattice misfit at the interfaces between the titanium aluminium nitrides having different [Al]/ [Ti] concentration ratios and, in the case of the fcc/wurtzite-type interface, also having different crystal structures. The phase transition of the fcc-(Ti,Al)N to thewurtzitic onewas predicted to be facilitated by stacking faults. The results of crystallographic considerations were verified experimentally by using in situ high-temperature synchrotron diffraction experiments that were performed on cathodic arc evaporated (Ti,Al)N thin films containing titanium and aluminium in different amounts.

Metastable phases are often used to design materials with outstanding properties, which cannot be achieved with thermodynamically stable compounds. In many cases, the metastable phases are employed as precursors for controlled formation of nanocomposites. This contribution shows how the microstructure of crystalline metastable phases and the formation of nanocomposites can be concluded from X-ray diffraction experiments by taking advantage of the high sensitivity of X-ray diffraction to macroscopic and microscopic lattice deformations and to the dependence of the lattice deformations on the crystallographic direction. The lattice deformations were determined from the positions and from the widths of the diffraction lines, the dependence of the lattice deformations on the crystallographic direction from the anisotropy of the line shift and the line broadening. As an example of the metastable system, the supersaturated solid solution of titanium nitride and aluminium nitride was investigated, which was prepared in the form of thin films by using cathodic arc evaporation of titanium and aluminium in a nitrogen atmosphere. The microstructure of the (Ti,Al)N samples under study was tailored by modifying the [Al]/[Ti] ratio in the thin films and the surface mobility of the deposited species.

For temperatures above 750°C, TiAl alloys still show insufficient oxidation resistance and suffer from environmental embrittlement. This work focuses on the surface modification of alloys and development of coatings against environmental embrittlement, as well as on testing of mechanical properties after high temperature oxidation. Aluminum enriched coatings (between 50 and 60 at.%) containing alloying elements, i.e. Cr, Nb, Si, Y, to improve the oxidation behavior and the corrosion resistance have been produced by MO-CVD, CVD, PVD and thermal spraying techniques (HVOF, APS), and have subsequently been chemically modified with halogen elements, notably fluorine. The mechanical properties have been studied by means of 4-point bending and tensile tests on coated samples after 100h oxidation at 900 °C in laboratory air. The CVD process combined with fluorine treatment using plasma immersion implantation (PI³) of F offers the best combination to remedy environmental embrittlement. It has been shown in particular that 90% of the initial fracture strain and fracture stress can be maintained.

Due to their excellent density-specific properties, titanium aluminide (TiAl) alloys have been identified as high-payoff materials for advanced aerospace and power generation applications in the medium-temperature (600°-750°C) range. They have recently been applied as structural materials for turbine blades in the low-pressure section of the GEnx jet engine. These alloys, however, are prone to both oxidation and embrittlement when exposed to oxidizing environments at temperatures above ~ 750°C. Under such conditions, TiAl alloys form a mixed (TiO2+Al2O3) non-protective oxide scale resulting from the difference in both the growth kinetics of the two oxides, and the chemical activity of the constituent elements, Ti and Al. Thus, for high-temperature (> 750°C) applications, an oxidation protection coating is needed to prevent environmental damage of the base alloy without degrading its initial mechanical properties. The present work has focused on the development of coatings for the efficient oxidation protection of TiAl alloys at high temperatures. Aluminum-rich TiAl coatings (50 to 60 at.%Al) have been produced by either chemical vapor deposition (MO-CVD), physical vapor deposition (PVD) or thermal spraying (HVOF, APS) techniques onto a GE alloy (Ti-48Al-2Cr-2Nb) qualified for aerospace applications. The coating surface has then been modified by plasma immersion ion implantation (PIII) of fluorine to promote the formation of a protective alumina-containing scale relying on the so-called halogen effect. For the PIII processing, either difluoromethane and argon (CH2F2/Ar) or silicon tetrafluoride and argon (SiF4/Ar) has been used as the F-containing precursor gas. The resulting F-implanted coatings have been exposed to oxidative/corrosive environments at 850°C for 350 h, and have shown a high degree of oxidation resistance. The mechanical properties of the coated samples have been examined by 4-point bend, tensile and fatigue testing after oxidation in laboratory air a

Local reversible structural changes in SrTiO3 single crystals in an external electric field are induced by oxygen redistribution. We present in-situ X-ray diffraction measurements during and immediately after electroformation. Several reflections are monitored and show an elongation of the cubic unit cell of strontium titanate. Raman investigations verify that the expansion of the unit cell involves a transition from the centro-symmetric to a lower symmetry phase. During a complete formation cycle, including the hold time of the electric field and relaxation time without field, two different dynamics are observed for the reversible transitions from cubic symmetry to tetragonal distortion: a slow one during the increase of the lattice constant in field direction and a fast one after switching off the electric field. Based on the experimental data we propose the formation of a polar strontium titanate unit cell at room temperature stabilized by the electric field, which is referred to as migration-induced field-stabilized polar (MFP) phase.

Aluminum enriched coatings have been developed for titanium aluminide alloys. It has been shown that Metal Organic Chemical Vapor Deposition (MO-CVD) and Physical Vapor Deposition (PVD) processes combined with fluorination of the coating enables to reduce significantly the embrittlement of TiAl alloys through oxidation. Even after oxidation at 900 °C for 100h, the coatings exhibit suitable adhesion and 90 % of the fracture toughness and ductility of the alloy are maintained.

It is well known that the room temperature ductility of gamma-based titanium aluminide alloys is significantly reduced after exposure to elevated temperatures. In some cases exposure can even lead to brittle fracture on reloading of an initially ductile alloy. However the original ductility can be restored if around 30 to 50 µm of the exposed surface is removed before testing. In an attempt to reduce this problem, the effect of coatings combined with halogen treatment on the tensile behaviour of cast + HIPed Ti-48Al-2Cr-2Nb has been investigated. This talk will give a general outline of the embrittlement problem and present current ideas that have been postulated to explain the embrittlement mechanism. Additionally the protective coating methods used in the study will be presented; mechanical test results of specimens that had undergone protective coating treatments are compared to those obtained for un-treated specimens after being oxidised at 900°C for 100 hours.

Due to their excellent density-specific properties, titanium aluminide (TiAl) alloys have been identified as high-payoff materials for advanced aerospace and power generation applications in the medium-temperature (600°-750°C) range. They have recently been applied as structural materials for turbine blades in the low-pressure section of the GEnx jet engine. These alloys, however, are prone to both oxidation and embrittlement when exposed to oxidizing environments at temperatures above ~ 750°C. Under such conditions, TiAl alloys form a mixed (TiO2+Al2O3) non-protective oxide scale resulting from the difference in both the growth kinetics of the two oxides, and the chemical activity of the constituent elements, Ti and Al. Thus, for high-temperature (> 750°C) applications, an oxidation protection coating is needed to prevent environmental damage of the base alloy without degrading its initial mechanical properties. The present work has focused on the development of coatings for the efficient oxidation protection of TiAl alloys at high temperatures. Aluminum-rich TiAl coatings (50 to 60 at.%Al) have been produced by either chemical vapor deposition (MO-CVD), physical vapor deposition (PVD) or thermal spraying (HVOF, APS) techniques onto a GE alloy (Ti-48Al-2Cr-2Nb) qualified for aerospace applications. The coating surface has then been modified by plasma immersion ion implantation (PIII) of fluorine to promote the formation of a protective alumina-containing scale relying on the so-called halogen effect. For the PIII processing, either difluoromethane and argon (CH2F2/Ar) or silicon tetrafluoride and argon (SiF4/Ar) has been used as the F-containing precursor gas. The resulting F-implanted coatings have been exposed to oxidative/corrosive environments at 850°C for 350 h, and have shown a high degree of oxidation resistance. The mechanical properties of the coated samples have been examined by 4-point bend, tensile and fatigue testing after oxidation in laboratory air a

Titanium aluminides exhibit quite good mechanical properties even at elevated temperatures for aeronautic and automobile applications. Their low specific density (half of classical nickel based super alloys) makes them attractive for applications where the mass is a critical parameter, i.e. rotating pieces. At elevated temperatures they suffer of environmental embrittlement by hot gases, which deteriorates drastically their mechanical properties and still hampers their use to temperatures above 500°C in industrial applications. In this work, coatings involving reactive elements such Cr, Y combined with the halogen effect (fluorine surface treatment) have been developed using MO-CVD, CVD, PVD and HVOF techniques. The coatings were characterized as produced and after annealing by means of glancing XRD, GDEOS to analyze their structure, homogeneity and composition, respectively. The adhesion properties of the coatings were measured by using impact tests before and after oxidation. The oxidation behavior of the produced coatings was evaluated in the temperature range of the industrial use, e.g. 600-850°C whereas corrosion tests were conducted using Na2SO4-NaCl mixtures in dry and wet environments. After oxidation/corrosion test post-mortem analysis was carried out using SEM-EDX, EPMA analysis to investigate the oxide layer composition, structure and the corrosion products, respectively. Mechanical properties losses of coated specimens after oxidation/corrosion due to embrittlement were evaluated using 4 point bending test combined with acoustic emission. It was shown that some of the developed coatings reduce the embrittlement sensibility of these alloys.

The effect of microstructure on the thermal stability and hardness of the cathodic arc evaporated Ti0.5Al0.5N coatings was investigated with the aid of the in-situ high-temperature X-ray diffraction experiments, which were accompanied by high-resolution transmission electron microscopy (HRTEM) and nanoindentation measurements. The microstructure of the coatings was modified through the choice of the bias voltage in the deposition process. It was found that the bias voltage affects strongly the uniformity of the local distribution of titanium and aluminum in the coatings. The nonuniform distribution of the elements contributes to the formation of lattice strains at the crystallite and phase boundaries. The lattice strains at the crystallite boundaries increase the hardness of the coatings; the lattice strains at the phase boundaries improve their thermal stability. A certain nonuniformity of the distribution of the metallic species in the coatings is regarded as advantageous. However, a great nonuniformity in the distribution of the metallic species accelerates the degradation of the coatings at high temperatures. As a measure for the nonuniformity of the distribution of the atomic species in the as-deposited (Ti, Al) N samples, the stress-free lattice parameter of fcc-(Ti, Al) N is suggested.

Various nominally undoped, hydrothermally or melt grown (MG) ZnO single crystals have been investigated by standard positron lifetime measurements. Furthermore, optical transmission measurements and structural characterizations have been performed; the content of hydrogen in the bound state was determined by nuclear reaction analysis. A positron lifetime of 165-167 ps, measured for a brownish MG ZnO sample containing (0.30 +/- 0.03) at.-% of bound hydrogen, matches perfectly the value found for colorless MG ZnO crystals. The edge shift, observed in the "blue light domain" of the optical absorption for the former sample with respect to the latter samples, is estimated to be 0.70 eV, and found equal to a value reported previously. The possible role of zinc interstitials as well as nitrogen-related defects is considered and discussed. Microstructure analysis by X-ray diffraction and transmission electron microscopy revealed the presence of stacking faults in MG crystals in a high concentration, which suggests these defects to be responsible for the observed positron lifetime.

The influence of the microstructure of the as-deposited cathodic arc evaporated Ti1-xAlxN coatings and, in particular, the influence of the intrinsic lattice strains on their thermal stability were investigated by insitu synchrotron high temperature glancing angle X-ray diffraction (HT-GAXRD) experiments up to 850 °C. The microstructure of the as-deposited coatings was adjusted by the bias voltage (UB=−40 V, UB=−80 V and UB=−120 V) and by the [Al]/([Ti]+[Al]) ratio (0.4, 0.5 and 0.6) of the used Ti–Al targets. The microstructure evolution during annealing was described in terms of the phase composition of the coatings, the aluminium content, aluminium distribution and residual lattice strains in fcc-(Ti,Al)N. Independent of the deposition parameters ([Al]/([Ti]+[Al]) ratio and bias voltage), all coatings contained a mixture of fcc-(Ti, Al)N, fcc-AlN and w-AlN after annealing at 850 °C. The [Al]/([Ti]+[Al]) ratio was found to control the amount of fcc-(Ti,Al)N, whereas the bias voltage was mainly responsible for the relative amount of fcc-AlN and w- AlN. Finally, the interplay between lattice strains and the kinetics of the spinodal decomposition of fcc-(Ti, Al)N was illustrated.

Titanium aluminides exhibit quite good mechanical properties even at elevated temperatures for aeronautic and automobile applications. Their low specific density (half of classical nickel based super alloys) makes them attractive for applications where the mass is a critical parameter, i.e. rotating pieces. At elevated temperatures they suffer of environmental embrittlement by hot gases, which deteriorates drastically their mechanical properties and still hampers their use to temperatures above 500°C in industrial applications. In this work, coatings involving reactive elements such Cr, Y combined with the halogen effect (fluorine surface treatment) have been developed using MO-CVD, CVD, PVD and HVOF techniques. The coatings were characterized as produced and after annealing by means of glancing XRD, GDEOS to analyze their structure, homogeneity and composition, respectively. The adhesion properties of the coatings were measured by using impact tests before and after oxidation. The oxidation behavior of the produced coatings was evaluated in the temperature range of the industrial use, e.g. 600-850°C whereas corrosion tests were conducted using Na2SO4-NaCl mixtures in dry and wet environments. After oxidation/corrosion test post-mortem analysis was carried out using SEM-EDX, EPMA analysis to investigate the oxide layer composition, structure and the corrosion products, respectively. Mechanical properties losses of coated specimens after oxidation/corrosion due to embrittlement were evaluated using 4 point bending test combined with acoustic emission. It was shown that some of the developed coatings reduce the embrittlement sensibility of these alloys.

We will report on a new casting technique basing on old recipes from the 17. and 18. century to produce new pipes approaching the quality of the old ones. Materials studies of old and new metal probes were performed by metallography and other methods. Different casting variants as well as the influence of hammering the casted metal plates onto the microstructure were investigated. In the course of these studies special consideration was devoted to the restoration projects at Borgentreich/Westfalen (Eule) and Stralsund/Vorpommern (Wegscheider).

We have developed a new casting technique basing on old recipes from the 17. and 18. century to restaurate old lead pipes as well as to produce new pipes approaching the quality of the old ones. Materials studies of old and new metal probes were performed by metallography, scanning electron microscopy, and x-ray diffraction analysis. Different casting variants as well as the influence of hammering the casted metal plates onto the microstructure were investigated. Moreover we investigated by PIXE (Proton induced X-ray Emission) the residuals of old glue on the old pipes which remaining from tin foil adornment. In this manner we positioned the pipe directly in front of an external ion beam and analysed it without cutting pieces away from the metal pipe.