DSpace Angular :: Browsing by Author "Rosenkranz, Andreas"

Browsing by Author "Rosenkranz, Andreas"

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A critical assessment of surface texturing for friction and wear improvement
(2017) Gachot, C.; Rosenkranz, Andreas; Hsu, S. M.; Costa, H. L.
Additive Manufacturing in the Maritime Industry: A Perspective on Current Trends and Future Needs
(2023) Garofalo, James; Shah, Raj; Thomas, Gavin; Shirvani, Khosro; Marian, Max; Rosenkranz, Andreas
Additive manufacturing (AM) has seen slow growth thus far in the maritime industry. Like other industries, maritime companies and institutions have started using AM for prototyping and product development needs but is now beginning to expand into production of end use parts and production tooling. The slow adoption can mainly be attributed to a previous lack of education in additive technology and strategies, current lack of reliability testing of additive machines in a marine environment, and the need for classification and certification of parts and machines before shipowners and crews will likely adopt for widespread use. This article provides a perspective of recent AM activities within the industry and discusses the need for research in key areas before widespread utilization can occur. Current use includes a recent push in maritime education, surveys of maritime workers and stakeholders, and fabrication of replacement parts, propellers, and boat hulls. Prospective key areas with the need for further research include 1) use-cases for replacement parts on ship, 2) economic feasibility of putting 3D printers on board, 3) standards, certification, and quality assurance, and 4) reliability and repeatability in a marine environment
Additively manufactured MAX- and MXene-composite scaffolds for bone regeneration- recent advances and future perspectives
(2023) Khabisi, Minufar Abdollahi; Shirini, Farhad; Shirini, Kasra; Khorsand, Hamid; Marian, Max; Rosenkranz, Andreas
Human bones can suffer from various injuries, such as fractures, bone cancer, among others, which has initiated research activities towards bone replacement using advanced bio-materials. However, it is still challenging to design bio-scaffolds with bone-inducing agents to regenerate bone defects. In this regard, MAX-phases and MXenes (early transition metal carbides and/or nitrides) have gained notable attention due to their unique hydrophilicity, bio-compatibility, chemical stability, and photothermal properties. They can be used in bone tissue engineering as a suitable replacement or reinforcement for common bio-materials (polymers, bio-glasses, metals, or hydroxyapatite). To fabricate bio-scaffolds, additive manufacturing is prospective due to the possibility of controlling porosity and creating complex shapes with high resolution. Until now, no comprehensive article summarizing the existing state-of-the-art related to bone scaffolds reinforced by MAX-phases and MXenes fabricated by additive manufacturing has been published. Therefore, our article addresses the reasons for using bone scaffolds and the importance of choosing the most suitable material. We critically discuss the recent developments in bone tissue engineering and regenerative medicine using MAX-phases and MXenes with a particular emphasis on manufacturing, mechanical properties, and bio-compatibility. Finally, we discuss the existing challenges and bottlenecks of bio-scaffolds reinforced by MAX-phases and MXenes before deriving their future potential.
Biomass-derived furfural conversion over Ni/CNT catalysts at the interface of water-oil emulsion droplets
(2020) Herrera, C.; Pinto-Neira, J.; Fuentealba Patiño, Denis Alberto; Sepulveda, C.; Rosenkranz, Andreas; Gonzalez, M.; Escalona, Néstor
Catalytic performance of 2D-Mxene nano-sheets for the hydrodeoxygenation (HDO) of lignin-derived model compounds
(2020) Blanco, E; Rosenkranz, Andreas; Espinoza-González, R; Fuenzalida, VM; Zhang, ZY; Suarez, S.; Escalona, N.
Combining multi-scale surface texturing and DLC coatings for improved tribological performance of 3D printed polymers
(2023) Marian, Max; Zambrano, Dario F.; Rothammer, Benedict; Waltenberger, Valentin; Boidi, Guido; Krapf, Anna; Merle, Benoit; Stampfl, Jürgen; Rosenkranz, Andreas; Gachot, Carsten; Grützmacher, Philipp G.
Polymer components fabricated by additive manufacturing typically show only moderate strength and low temperature stability, possibly leading to severe wear and short lifetimes especially under dry tribological sliding. To tackle these shortcomings, we investigated the combination of single- and multi-scale textures directly fabricated by digital light processing with amorphous diamond-like carbon (DLC) coatings. The topography of the samples and conformity of the coatings on the textures are assessed and their tribological behaviour under dry conditions is studied. We demonstrate that the surface textures have a detrimental tribological effect on the uncoated samples. This changes with the application of DLC coatings since friction substantially reduces and wear of the textures is not observed anymore. These trends are attributed to the protection of the underlying polymer substrate by the coatings and a reduced contact area. The best tribological performance is found for a coating with highest hardness and hardness-to-elasticity ratios. Moreover, multi-scale textures perform slightly better than single-scale textures due to a smaller real contact area. Summarizing, we verified that the high flexibility and low production costs of 3D printing combined with the excellent mechanical and tribological properties of DLC results in synergistic effects with an excellent performance under dry sliding conditions
Effect of Ni Metal Content on Emulsifying Properties of Ni/CNTox Catalysts for Catalytic Conversion of Furfural in Pickering Emulsions
(2021) Herrera Hernández, Carla Pía; Pinto Neira, Josefa; Fuentealba Patiño, Denis Alberto; Sepúlveda, C.; Rosenkranz, Andreas; García-Fierro, J. L.; González, M.; Escalona, Néstor
Effects of Ti₃C₂T_x nano-sheets (MXenes) on the microstructural and electrochemical properties of SnO₂/Ti anodes
(2021) Gonzalez-Poggini, Sergio; Rosenkranz, Andreas; Wang, Bo; Hevia, Samuel; Yu, Jinhong; Colet-Lagrille, Melanie
The effects of the incorporation of Ti3C2Tx nano-sheets (MXenes) on the microstructure of SnO2/Ti electrodes and their electro-oxidation catalytic activity for the degradation of methyl red is studied in this work. MXenes-SnO2/Ti electrodes are fabricated by spin-coating followed by a thermal treatment under ambient atmospheric conditions using a solution containing MXene nano-sheets, SnCl2, citric acid and ethylene glycol as precursor. Energy-dispersive X-ray spectroscopy, Raman spectroscopy and Xray diffraction analyses of the MXenes-SnO2/Ti electrodes surface indicate the formation of SnO2-TiO2 films with Ti4+ ions incorporated into the lattice of SnO2 crystals. Cyclic voltammetry curves demonstrate that the oxygen evolution reaction is restrained by the MXenes-SnO2/Ti electrodes, while the methyl red electro-oxidation is enhanced - with kinetics following a pseudo-first-order model compared to the performance of (pure) SnO2/Ti electrodes. These results suggest that oxygen vacancies are formed in the crystal lattice of MXenes-SnO2/Ti electrodes, which act as charge carriers and increase the electrical conductivity of SnO2 as confirmed by the lower charge transfer resistance of MXenes-SnO2/Ti electrodes determined by electrochemical impedance spectroscopy analysis.
Evaluation of DLC, MoS2, and Ti3C2T thin films for triboelectric nanogenerators
(2022) Tremmel, Stephan; Luo, Xiongxin; Rothammer, Benedict; Seynstahl, Armin; Wang, Bo; Rosenkranz, Andreas; Marian, Max|Zhu, Laipan
Due to their cost-effective fabrication, easy integration, and low frequency working range, triboelectric nanogenerators (TENGs) demonstrate tremendous potential in green energy harvesting to power smart devices and the internet of things (IoT). However, there is an urgent need to synergistically maximize their output and improve their durability to ensure a long-lasting high performance. This study aims at elucidating the performance of protective thin films deposited on the wear-prone PTFE surface of TENGs including doped and undoped, single- and multi-layer hydrogenated DLC films, MoS2 coatings fabricated by physical vapor deposition and multi-layer Ti3C2Tx (MXene) films. The deposited coatings are characterized by electron microscopy, and Raman spectroscopy. Their triboelectric performance is analyzed for TENGs operating in contact separation and freestanding sliding modes. We verified that MXenes outperformed the other films in contact separation mode due to the good electron gain ability of functional oxygen and fluorine groups. In sliding mode, the undoped a-C:H coating performed on a comparable level to the uncoated reference and superior to the tungsten-doped DLC and MoS2 films. The film withstood long-term tests without notable signs of wear; merely the output slowly decreased with time due to graphitization and thus potential material transfer to the mating body.
Evaluation of the surface fatigue behavior of amorphous carbon coatings through cyclic nanoindentation
(2021) Weikert, Tim; Wartzack, Sandro; Baloglu, Maximiliano V.; Willner, Kai; Gabel, Stefan; Merle, Benoit; Pineda, Fabiola; Walczak, Magdalena; Marian, Max; Rosenkranz, Andreas; Tremmel, Stephan
Diamond-like carbon (DLC) coatings, frequently used to reduce wear and friction in machine components as well as on forming tools, are often subjected to cyclic loading. Doping of DLC coatings with metals or metal carbides as well as the usage of multilayer architectures represent promising approaches to enhance toughness, which is beneficial for the coatings' behavior under cyclic loading. In this study, we utilized cyclic nanoindentation to characterize the tribologically induced surface fatigue behavior of single-layer tungsten-doped (a-C:H:W) and multilayer silicon oxide containing (a-C:H:Si:O/a-C:H)25 amorphous carbon coatings under cyclic loading. Columnar growth was observed for both coatings by focused ion beam microscopy and scanning electron microscopy, while the multilayer architecture of the (a-C:H:Si:O/a-C:H)25 coating was verified by the silicon content using glow-discharge optical emission spectroscopy. In cyclic nanoindentation of the (a-C:H:Si:O/a-C:H)25 multilayer coating, stepwise small changes in indentation depth were observed over several indentation cycles. The surface fatigue process of the single-layer a-C:H:W covered a smaller number of indentation cycles and was characterized by an early steep increase of the static displacement signal. Microscopical analyses hint at grain deformation, sliding at columnar boundaries, and grain detachment as underlying fatigue mechanisms of the a-C:H:W coating, while the (a-C:H:Si:O/a-C:H)25 multilayer coating showed transgranular crack propagation and gradual fracturing. In case of the (a-C:H:Si:O/a-C:H)25 multilayer coating, superior indentation hardness (HIT) and indentation modulus (EIT) as well as a higher HIT3/EIT2 ratio suggest a higher resistance to plastic deformation. A high HIT3/EIT2 ratio, being an indicator for hindered crack initiation, combined with the capability of stress relaxation in soft layers contributed to the favorable surface fatigue behavior of the (a-C:H:Si:O/a-C:H)25 multilayer coating observed in this cyclic nanoindentation studies
Failure Analysis of Slurry Pump Impeller Fractured at Collahuasi Mine
(2016) Ramos Moore, Esteban; Rosenkranz, Andreas
Influence of ex-situ annealing on the friction and wear performance of multi-layer Ti3C2Tx coatings
(2024) Boidi, Guido; Zambrano, Dario; Broens, Martin I.; Moncada, Daniel; Varga, Markus; Ripoll, Manel Rodriguez; Badisch, Ewald; Escalona, Nestor; Gruetzmacher, Philipp G.; Gachot, Carsten; Rosenkranz, Andreas
2D materials have gained momentum for lubrication purposes, which holds specifically true under more severe conditions such as elevated temperatures. Among them, MXenes are a new family of 2D materials, which offer an excellent electrical conductivity, tunable surface functionality, and outstanding mechanical properties. In the past five years, MXenes have been significantly studied for tribological applications due to their ability to form easy-to-shear tribofilms with excellent wear resistance. However, little is known regarding MXenes' tribological performance at elevated temperatures. Therefore, we systematically studied the tribological performance of spray-coated Ti3C2Tx coatings after thermal annealing at temperatures between 50 and 400 degrees C using linear-reciprocating ball-on-disc tribometry. Advanced materials characterization demonstrated that thermal annealing of MXenes results in the release of superficial and intercalated water, the removal of surface terminations, and the oxidation of Ti3C2Tx to TiO2. Consequently, the tribological performance of the annealed coatings deteriorated, which is particularly pronounced for thin coatings, high normal loads, and elevated annealing temperatures. Our results provide insight into the thermal stability of Ti3C2Tx coatings as well as the implications on their tribological performance.
Laser Interference Patterning of Steel Surfaces - Influence on the Frictional Performance under Dry and Lubricated Sliding Conditions
(2016) Rosenkranz, Andreas; Gachot, Carsten; Ramos Moore, Esteban; Mucklich, Frank
Layered 2D Nanomaterials to Tailor Friction and Wear in Machine Elements—A Review
(2022) Marian, Max; Berman, Diana; Rota, Alberto; Jackson, Robert L.; Rosenkranz, Andreas
Recent advances in 2D nanomaterials, such as graphene, transition metal dichalcogenides, boron nitride, MXenes, allow not only to discover several new nanoscale phenomena but also to address the scientific and industrial challenges associated with the design of systems with desired physical properties. One of the great challenges for mechanical systems is associated with addressing friction and wear problems in machine elements. In this review, the beneficial properties of layered 2D materials that enable the control of their tribological behavior and make them excellent candidates for efficient friction and wear reduction in dry-running and boundary lubricated machine components are summarized. The recent studies highlighting the successful implementation of 2D structures when used as solid lubricant coatings or reinforcement phases in composites for various machine components including sliding and rolling bearings, gears, and seals are overviewed. The examples presented in the studies demonstrate the great potential for 2D materials to address the energy-saving needs by friction and wear reduction.
Microstructural and chemical characterization of the tribolayer formation in highly loaded cylindrical roller thrust bearings
(2016) Gachot, Carsten; Hsu, ChiaJui; Suárez, Sebastián; Grützmacher, Philipp; Rosenkranz, Andreas; Stratmann, Andreas; Jacobs, Georg
Nanometric thin films of non-doped diamond-like carbon grown on n-type (P-doped) silicon substrates as electrochemical electrodes
(2018) Hevia, Samuel; Bejide, M.; Durán Lagos, Boris Guido; Rosenkranz, Andreas; Ruiz, H.M.; Favre Domínguez, Mario; Río Quero, Rodrigo del
Nickel Nanopillar Arrays Electrodeposited on Silicon Substrates Using Porous Alumina Templates
(2020) Bejide, Matias; Contreras, Patricio; Homm, Pia; Duran, Boris; Garcia-Merino, Jose Antonio; Rosenkranz, Andreas; Denardin, Juliano C.; del Rio, Rodrigo; Hevia, Samuel A.
Nickel nanopillar arrays were electrodeposited onto silicon substrates using porous alumina membranes as a template. The characterization of the samples was done by scanning electron microscopy, X-ray diffraction, and alternating force gradient magnetometry. Ni nanostructures were directly grown on Si by galvanostatic and potentiostatic electrodeposition techniques in three remarkable charge transfer configurations. Differences in the growth mechanisms of the nanopillars were observed, depending on the deposition method. A high correlation between the height of the nanopillars and the charge synthesis was observed irrespective of the electrochemical technique. The magnetization measurements demonstrated a main dependence with the height of the nanopillars. The synthesis of Ni nanosystems with a controllable aspect ratio provides an effective way to produce well-ordered networks for wide scientific applications.
Numerical micro-texture optimization for lubricated contacts : a critical discussion
(2022) Marian, Max; Almqvist, Andreas; Rosenkranz, Andreas; Fillon, Michel
Despite numerous experimental and theoretical studies reported in the literature, surface micro-texturing to control friction and wear in lubricated tribo-contacts is still in the trial-and-error phase. The tribological behaviour and advantageous micro-texture geometries and arrangements largely depend on the contact type and the operating conditions. Industrial scale implementation is hampered by the complexity of numerical approaches. This substantiates the urgent need to numerically design and optimize micro-textures for specific conditions. Since these aspects have not been covered by other review articles yet, we aim at summarizing the existing state-of-the art regarding optimization strategies for micro-textures applied in hydrodynamically and elastohydrodynamically lubricated contacts. Our analysis demonstrates the great potential of optimization strategies to further tailor micro-textures with the overall aim to reduce friction and wear, thus contributing toward an improved energy efficiency and sustainability.
Optical and mechanical properties of Zr-oxide doped TiO₂/SiO₂anti-reflective coatings for PV glass covers
(2022) Zambrano-Mera, Dario F.; Espinoza-Gonzalez, Rodrigo; Villarroel, Roberto; Rosenkranz, Andreas; Carvajal, Nicolas; Pintor-Monroy, Maria I.; Montano-Figueroa, A. Gabriela; Arellano-Jimenez, Maria J.; Quevedo-Lopez, Manuel; Valenzuela, Paulina; Gacitua, William
Multi-layer systems are frequently used as anti-reflective coatings (ARCs) due to their excellent optical properties. However, these systems suffer from erosive degradation (wear), thus urgently seeking alternative ways to improve their mechanical properties while maintaining their optical response. To tackle this problem, we propose to dope multi-layer TiO2/SiO2 coatings with Zr-oxides to enhance their crystalline structure and density/ compactness, as well as to form Si-Zr-O bonds. We explore the effect of Zr-oxide doping on the microstructure as well as the optical and mechanical properties of multi-layer TiO2/SiO2 coatings with the overall aim to synergistically induce enhanced optical and mechanical properties. Therefore, homogeneous 250 nm thick multi-layer TiO2/SiO2 coatings doped with Zr-oxides (different atomic concentrations) were deposited on glass substrates by magnetron sputtering. Based on our analysis, Zr-doping improves the optical and mechanical properties simultaneously. Among all ARCs, the sample annealed at 400 C and doped with 1 at.-% Zr presented an excellent anti reflective behavior and the best mechanical performance. These characteristics point towards an improved mechanical resistance (outstanding durability) and optical efficiency thus rendering them excellent candidates for the protection of glass covers on solar panels.
Predicting EHL film thickness parameters by machine learning approaches
(2022) Marian, Max; Mursak, Jonas; Bartz, Marcel; Profito, Francisco J.; Rosenkranz, Andreas; Wartzack, Sandro
Non-dimensional similarity groups and analytically solvable proximity equations can be used to estimate integral fluid film parameters of elastohydrodynamically lubricated (EHL) contacts. In this contribution, we demonstrate that machine learning (ML) and artificial intelligence (AI) approaches (support vector machines, Gaussian process regressions, and artificial neural networks) can predict relevant film parameters more efficiently and with higher accuracy and flexibility compared to sophisticated EHL simulations and analytically solvable proximity equations, respectively. For this purpose, we use data from EHL simulations based upon the full-system finite element (FE) solution and a Latin hypercube sampling. We verify that the original input data are required to train ML approaches to achieve coefficients of determination above 0.99. It is revealed that the architecture of artificial neural networks (neurons per layer and number of hidden layers) and activation functions influence the prediction accuracy. The impact of the number of training data is exemplified, and recommendations for a minimum database size are given. We ultimately demonstrate that artificial neural networks can predict the locally-resolved film thickness values over the contact domain 25-times faster than FE-based EHL simulations (R² values above 0.999). We assume that this will boost the use of ML approaches to predict EHL parameters and traction losses in multibody system dynamics simulations.

Browsing by Author "Rosenkranz, Andreas"

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