Nanomechanical and dynamic mechanical properties of rubber–wood–plastic composites

This article presents the assessment of bulk and in situ mechanical properties of rubber–wood–plastic composites (RubWPC) and their correlations, aiming to obtain a thorough understanding of mechanical behaviour of RubWPC, which is an essential prerequisite in realising their optimal design and applications. Dynamic mechanical analysis results showed that the composites treated with multiple coupling agents (combination of maleic anhydride polyethylene [MAPE] and bis(triethoxysilylpropyl)tetrasulfide and combination of MAPE and vinyltrimethoxysilane) exhibited greater storage modulus than both the untreated and single coupling agent treated composites owing to their superior interfacial bonding quality. The shift of relaxation peak and T g towards higher temperatures observed in the treated composites confirmed the enhancement of interfacial interaction and adhesion. Nanoindentation analysis suggested that the composite with optimised interface (MAPE and Si69 treated) possessed better nanomechanical property (elastic modulus) due to the resin penetration into cell lumens and vessels and the reaction between cell walls and coupling agents.

Microstructure and Nanomechanical Property of Plasma-Sprayed Nanostructured Yb2SiO5 Environmental Barrier Coatings

In this study, nanostructured Yb2SiO5 coatings were prepared by atmospheric plasma spraying (APS) using nanostructured Yb2SiO5 feedstocks. Conventional Yb2SiO5 coatings were selected for comparison. The microstructure and nanomechanical property of the nanostructured and conventional Yb2SiO5 coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and nano-indentation. Results indicate that the surface of the nanostructured Yb2SiO5 coatings is uniform and denser than the conventional Yb2SiO5 coatings. In addition, Weibull distribution analysis shows that the molten state of the nanostructured Yb2SiO5 coatings present a mono-modal distribution, whereas the conventional Yb2SiO5 coatings show a bi-modal distribution, i.e. molten and unmelted zones. The nanostructured Yb2SiO5 coatings have a higher elastic modulus than the conventional Yb2SiO5 coatings (167.37077 ± 16.88070 GPa versus 153.72856 ± 19.69907 GPa), reflecting their high density.

Quasi-static and dynamic nanomechanical characterization of PMMA/ZnO nanocomposite thick films synthesized by ultrasonication and spin-coating

Polymer nanocomposite films, comprising of polymethylmethacrylate (PMMA) as the matrix and zinc oxide (ZnO) nanoparticles as reinforcement, have been prepared using ultrasonication and spin-coating techniques, with ZnO content up to 20 wt.%. The effect of the processing on the microstructure and nanomechanical properties have been investigated. The nanocomposite film thickness is found to vary from 2.4 ± 0.2 µm for pristine PMMA to 33.1 ± 0.5 µm for PMMA/20 wt.% ZnO nanocomposite. Quasi-static nanoindentation showed that the indentation modulus varied from 4.68 ± 0.07 GPa for pristine PMMA to 5.04 ± 0.14 GPa for PMMA/20 wt.% ZnO nanocomposite, while the indentation hardness varied from 275.94 ± 5.67 MPa to 292.39 ± 10.88 MPa in the same range. However, the highest indentation modulus and the highest hardness are exhibited by PMMA/10 wt.% ZnO nanocomposite. Scanning electron microscopy of the synthesized films provided the evidence behind such variation in material properties. In addition, the experimentally obtained elastic moduli were compared with values predicted by using Eshelby-Mori-Tanaka micromechanics. Nanoindenter-based dynamic mechanical analysis of the PMMA nanocomposite thin films revealed the variation of storage modulus, loss modulus and loss factor of the films in the frequency range of 10 Hz to 201.5 Hz. For all PMMA/ZnO nanocomposites, the storage modulus is found to increase monotonically from 10 Hz to ∼100 Hz, beyond which the values reached a plateau. The loss modulus and loss factor for all PMMA/ZnO nanocomposites are found to decrease with increasing frequency. These results form an essential step toward establishing process-structure-nanomechanical property relationships for PMMA/ZnO nanocomposite films.

The viscoelasticity of adherent cells follows a single power-law with distinct local variations within a single cell and across cell lines

Nanomechanical property map of a live cell generated by AFM-based force-distance curves.

An atomic force microscope integrated with a helium ion microscope for correlative nanoscale characterization

In this work, we report on the integration of an atomic force microscope (AFM) into a helium ion microscope (HIM). The HIM is a powerful instrument, capable of imaging and machining of nanoscale structures with sub-nanometer resolution, while the AFM is a well-established versatile tool for multiparametric nanoscale characterization. Combining the two techniques opens the way for unprecedented in situ correlative analysis at the nanoscale. Nanomachining and analysis can be performed without contamination of the sample and environmental changes between processing steps. The practicality of the resulting tool lies in the complementarity of the two techniques. The AFM offers not only true 3D topography maps, something the HIM can only provide in an indirect way, but also allows for nanomechanical property mapping, as well as for electrical and magnetic characterization of the sample after focused ion beam materials modification with the HIM. The experimental setup is described and evaluated through a series of correlative experiments, demonstrating the feasibility of the integration.

Biomimetic Design for a Dual Concentric Porous Titanium Scaffold with Appropriate Compressive Strength and Cells Affinity

In repairing or replacing damaged bones, a dual concentric porous titanium scaffold (P-Tix-y) has emerged as a promising bio-mimic design. Herein, various P-Tix-y were made and sintered with relatively dense (x = 10, 20, or 30% porosity) and loose (y = 45, 55, or 65 porosity) structures. Firstly, NaCl was used as the pore-forming additive and followed by a hydrothermal removal method. The compressive strength of the as-formed P-Tix_y and surface morphology, nanomechanical property, and cells’ affinity on the cross-sectioned surface of P-Tix_y (CP-Tix_y) were then characterized. The results demonstrate that the compressive strength of P-Ti10_45, P-Ti20_45, or P-Ti20_55 exhibits a relatively mild decline (e.g., in the range of 181 and 97 MPa, higher than the required value of 70 MPa) and suitable porosities for the intended structure. Nano-hardness on the solid surface of CP-Tix_y shows roughly consistent with that of CP-Ti (i.e., ~8.78 GPa), thus, the porous structure of CP-Tix_y remains mostly unaffected by the addition of NaCl and subsequent sintering process. Most of the surfaces of CP-Tix_y exhibit high fibroblast (L929) cell affinity with low cell mortality. Notably, in the hFOB 1.19 cell adhesion and proliferation test, CP-Ti20_55 and CP-Ti20_65 reveal high cell viability, most probably relating with the assembly of dual porosities with interconnected pores. Overall, the sample P-Ti20_55 provides a relatively load-bearable design with high cell affinity and is thus promising as a three-dimensional bio-scaffold.