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Item type:Publication, Access status: with files , Nanoindentation of supercrystalline nanocomposites: linear relationship between elastic modulus and hardness(Springer, 2022-04-15); ; ; ; Supercrystalline nanocomposites (SCNCs) are a new category of nanostructured materials, with organically functionalized nanoparticles assembled into periodic structures, reminiscent of atomic crystals. Thanks to this nanoarchitecture, SCNCs show great promise for functional applications, and understanding and controlling their mechanical properties becomes key. Nanoindentation is a powerful tool to assess the mechanical behavior of virtually any material, and it is particularly suitable for studies on nanostructured materials. While investigating SCNCs in nanoindentation, a linear proportionality has emerged between elastic modulus and hardness. This is not uncommon in nanoindentation studies, and here we compare and contrast the behavior of SCNCs with that of other material categories that share some of the key features of SCNCs: mineral-rich biocomposites (where mineral building blocks are packed into a protein-interfaced network), ultrafine grained materials (where the characteristic nano-grain sizes are analogous to those of the SCNC building blocks), and face-centered cubic atomic crystals (which share the typical SCNC periodic structure). A strong analogy emerges with biomaterials, both in terms of the hardness/elastic modulus relationship, and of the correlation between this ratio and the dissipative mechanisms occurring upon material deformation. Insights into the suitability of SCNCs as building blocks of the next-generation hierarchical materials are drawn.Publicationtype: Journal ArticleScopus© Citations 10 63 101 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Enabling cost-based support structure optimization in laser powder bed fusion of metalsSupport structures are essential to laser powder bed fusion (PBF-LB/M). They sustain overhangs, prevent distortion, and dissipate process-induced heat. Their removal after manufacturing is required, though, increasing the overall costs. Therefore, optimization is important to increase the economic efficiency of PBF-LB/M. To enable optimization focused on the support structures’ costs, a cost model is developed. The whole production process, including the design, manufacturing, and post-processing of a part, is considered by deriving formulas for the individual costs. The cost model is applied to a previously developed benchmark procedure. Additionally, a case study investigating different support layout strategies is conducted.Publicationtype: Journal ArticleScopus© Citations 2 95 253 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , On the Estimation of Thermal Activation Parameters for Portevin–Le Chatelier Effect from Nanoindentation Data(2019-10-01); The development of methods to ascertain the activation enthalpy, Δ Ea, for Portevin–Le Chatelier (PLC) effect is of interest as it facilitates understanding of the underlying mechanisms and the identification of solute species that age dislocations during deformation. Currently, most models for estimating Δ Ea are based on the critical strain, εc, for the onset of PLC during macroscopic uniaxial tests. However, an εc is not always observed, and some of the models incorporate unverified dependences. In this work, we present a nanoindentation-based approach for estimating Δ Ea and the activation volume for the phenomenon. The approach is based on a more theoretically sound foundation and obviates the need for εc. The derived parameters are in good agreement with reported values for the Al-Mg alloy studied herein. The results are discussed in terms of strain rate, indentation depth, and indenter geometry, and reveal the utility of the technique for investigations of PLC more generally.Publicationtype: Journal Article203 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Three-dimensional quantification of calcium salt-composite resorption (CSC) in vitro by micro-computed tomography (Micro-CT)The commonly applied cell-based, two-dimensional (2D) in vitro resorption assays for biomaterials are limited in a variety of cases, including high initial roughness of material surface, uncontrollable solubilization (or resorption) of the entire material surface, or complex three-dimensional (3D) structure of the bioactive material itself. All these make the accurate assessment and successful selection of the optimal bone substitute material difficult. In vivo, micro-computed tomography (micro-CT) has been widely applied for the analysis of bone physiology and pathology, as well as for the 3D analysis of scaffolds for bone tissue engineering. In this study, we show that micro-CT can also be applied for the in vitro analysis of osteoclast-mediated resorption of biomaterials. For our experiments, we chose a calcium salt-composite (composite of calcium sulphate (CSC), calcium carbonate, glycerin-1,2,3-tripalmiate), which evades common 2D in vitro resorption analysis as a result of its high surface roughness and material composition. Human osteoclasts were differentiated from precursor cells on the surface of the material for 28 days. Cells were analyzed for expression of tartrate-resistant acid phosphatase 5b (TRAP5b), multinuclearity, and size. Volumetric analysis of resorption was performed by micro-CT. Multinucleated osteoclasts developed on the surface of the material. TRAP5b expression of the cells on CSC was comparable with TRAP5b expression of cells cultivated on dentin for the first 3 weeks of culture. At day 28, TRAP5b expression, cell number, and size of the TRAP+ cells were reduced on the CSC when compared with cells on dentin. Volumetric anaylsis by micro-CT showed a strong cellular effect on resorption of CSC. We consider micro-CT to be a promising technique for 3D quantification of cell-based resorption that will allow the study of cellular resorption of materials in vitro, which were up to now confined to animal experimental analysis. © 2014 The Minerals, Metals & Materials Society.Publicationtype: Journal Article3