@article{RymarczykCzerwoszRichter2011, author = {Rymarczyk, Joanna and Czerwosz, Elzbieta and Richter, Asta}, title = {Topography and nanomechanical properties of Pd-C films}, series = {Central European Journal of Physics}, volume = {9}, journal = {Central European Journal of Physics}, number = {2}, issn = {2391-5471}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-9649}, pages = {300 -- 306}, year = {2011}, abstract = {Atomic force microscopy (AFM) topographical studies and results of nanoindentation experiment for several palladium-carbon films (Pd-C film) deposited on various substrates and with varying palladium content are presented. Pd-C films were prepared by a physical vapor decomposition (PVD) process and next were modified by a chemical vapor decomposition (CVD) method to obtain carbonaceous porous structure with dispersed palladium nanograins and a variation in roughness. The dependence of film topography on the kind of substrate such as Al2O3, Mo polycrystalline foil and fused silica was studied by AFM. Nanomechanical properties such as hardness and the reduced indentation modulus were determined by nanoindentation. A comparison of these values for films with different Pd content deposited on various substrates is presented.}, language = {en} } @article{MaierClausiusRichteretal.2021, author = {Maier, Petra and Clausius, Benjamin and Richter, Asta and Bittner, Benjamin and Hort, Norbert and Menze, Roman}, title = {Crack Propagation in As-Extruded and Heat-Treated Mg-Dy-Nd-Zn-Zr Alloy Explained by the Effect of LPSO Structures and Their Micro- and Nanohardness}, series = {Materials}, volume = {14}, journal = {Materials}, number = {13}, publisher = {MDPI}, issn = {1996-1944}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14194}, year = {2021}, abstract = {The investigation of the crack propagation in as-extruded and heat-treated Mg-Dy-Nd-Zn-Zr alloy with a focus on the interaction of long-period stacking-ordered (LPSO) structures is the aim of this study. Solution heat treatment on a hot extruded Mg-Dy-Nd-Zn-Zr (RESOLOY®) was done to change the initial fine-grained microstructure, consisting of grain boundary blocky LPSO and lamellar LPSO structures within the matrix, into coarser grains of less lamellar and blocky LPSO phases. C-ring compression tests in Ringer solution were used to cause a fracture. Crack initiation and propagation is influenced by twin boundaries and LPSO lamellae. The blocky LPSO phases also clearly hinder crack growth, by increasing the energy to pass either through the phase or along its interface. The microstructural features were characterized by micro- and nanohardness as well as the amount and location of LPSO phases in dependence on the heat treatment condition. By applying nanoindentation, blocky LPSO phases show a higher hardness than the grains with or without lamellar LPSO phases and their hardness decreases with heat treatment time. On the other hand, the matrix increases in hardness by solid solution strengthening. The microstructure consisting of a good balance of grain size, matrix and blocky LPSO phases and twins shows the highest fracture energy.}, language = {en} } @inproceedings{RymarczykCzerwoszRichter2009, author = {Rymarczyk, Joanna and Czerwosz, Elzbieta and Richter, Asta}, title = {FEM modelling of nanoindentation experiment for nanostructural Me-carbon film (Me = Pd, Ni)}, series = {Proc. SPIE 7502, Photonics Applications in Astronomy, Communications, Industry, and High-Energy Physics Experiments 2009}, booktitle = {Proc. SPIE 7502, Photonics Applications in Astronomy, Communications, Industry, and High-Energy Physics Experiments 2009}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14837}, year = {2009}, abstract = {This work presents a comparison of numerical simulation and experimental data for nanoindentation studies of nanostructural Me-carbonaceous films (where Me = Pd or Ni). Films containing palladium or nickel nanograins embedded in a carbonaceous matrix were synthesized by a PVD process. The topography of films was characterized by AFM and the mechanical properties were analyzed by nanoindentation. Nanoindentation experiments were performed with a tip made of diamond with a shape of a 90° cube corner three-sided pyramid in a Hysitron Triboscope. The finite element method (FEM) was used to simulate the indentation experiment in such heterogeneous material on nanoscale.}, language = {en} } @unpublished{RichterAnwandChenetal.2017, author = {Richter, Asta and Anwand, Wolfgang and Chen, Chun-Liang and B{\"o}ttger, Roman}, title = {Evaluation of defect formation in helium irradiated Y2O3 doped W-Ti alloys by positron annihilation and nanoindentation}, series = {Journal of Nuclear Materials}, journal = {Journal of Nuclear Materials}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-10048}, year = {2017}, abstract = {Helium implanted tungsten-titanium ODS alloys are investigated using positron annihilation spectroscopy and nanoindentation. Titanium reduces the brittleness of the tungsten alloy, which is manufactured by mechanical alloying. The addition of Y2O3 nanoparticles increases the mechanical properties at elevated temperature and enhances irradiation resistance. Helium ion implantation was applied to simulate irradiation effects on these materials. The irradiation was performed using a 500 kV He ion implanter at fluences around 5 × 1015 cm-2 for a series of samples both at room temperature and at 600 °C. The microstructure and mechanical properties of the pristine and irradiated W-Ti-ODS alloy are compared with respect to the titanium and Y2O3 content. Radiation damage is studied by positron annihilation spectroscopy analyzing the lifetime and the Doppler broadening. Three types of helium-vacancy defects were detected after helium irradiation in the W-Ti-ODS alloy: small defects with high helium-to-vacancy ratio (low S parameter) for room temperature irradiation, larger open volume defects with low helium-to-vacancy ratio (high S parameter) at the surface and He-vacancy complexes pinned at nanoparticles deeper in the material for implantation at 600 °C. Defect induced hardness was studied by nanoindentation. A drastic hardness increase is observed after He ion irradiation both for room temperature and elevated irradiation temperature of 600 °C. The Ti alloyed tungsten-ODS is more affected by the hardness increase after irradiation compared to the pure W-ODS alloy.}, language = {en} } @inproceedings{RichterRies1999, author = {Richter, Asta and Ries, Ronald}, title = {Mechanical properties of fullerite and diamondlike carbon films using surface acoustic waves and nanoindentation}, series = {Proc. SPIE 3725, International Conference on Solid State Crystals '98: Epilayers and Heterostructures in Optoelectronics and Semiconductor Technology, (8 April 1999)}, booktitle = {Proc. SPIE 3725, International Conference on Solid State Crystals '98: Epilayers and Heterostructures in Optoelectronics and Semiconductor Technology, (8 April 1999)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14840}, pages = {94 -- 101}, year = {1999}, abstract = {C60 and amorphous diamond-like carbon (DLC) films have been grown by thermal evaporation and laser ablation techniques at different substrate temperatures and on various substrates. The elastic modulus and the hardness of the films have been investigated by surface acoustic waves and nanoindentation. Both methods are completely new and designed for investigations of very thin films. For homogeneous C60 films the Young's modulus was found to be 14 GPa and the Poisson's ratio of 0.2. The measured nanohardness of 167 MPa corresponds with the microhardness value of 130 MPa. There is a correlation between deposition techniques and hardness as well as Young's modulus for DLC films.}, language = {en} }