Microstructural analyses of artificial ageing in 5 commercially and non-commercially available Zirconia dental implants
Journal of the European Ceramic Society Volume 40, Issue 10, August 2020, Pages 3642-3655
Objectives The presentin vitro study evaluated the effect of LTD (Low Temperature Degradation) on microstructural properties, phase transformation and micro-crack formation of 5 commercially and non-commercially available Zirconia dental implant systems.Methods Accelerated ageing at 134 °C and 2 bar pressure for 30 h was completed. Focused Ion Beam-Scanning Electron Microscopy (FIB/SEM), X-ray diffraction (XRD) and cathodoluminescence quantified phase transformation and micro-crack formation.Results Transformation of the tetragonal grains towards the monoclinic symmetry was observed in all systems. The highest depth was measured in non-commercial TAV dental with the largest grain size (8.7 μm). A micro-cracked layer was associated with the transformation zone. The ageing-related micro-crack formation was parallel to the surface for all groups and was deepest for the non-commercial TAV dental with the largest grain size (7.4 μm).Conclusion LTD following in vitro ageing using an autoclave was minimal for all implant systems investigated.Conclusions. XW does not have any significant effect on enamel and dentine microhardness.
An optimized TEM specimen preparation method of quantum nanostructures
HongguangWang,VesnaSrotBernhardFenk,GennadiiLaskin,JochenMannhart,Peter A.van Aken
MicronVolume 140, January 2021, 102979
Electron transparent TEM lamella with unaltered microstructure and chemistry is the prerequisite for successful TEM explorations. Currently, TEM specimen preparation of quantum nanostructures, such as quantum dots (QDs), remains a challenge. In this work, we optimize the sample-preparation routine for achieving high-quality TEM specimens consisting of SrRuO3 (SRO) QDs grown on SrTiO3 (STO) substrates. We demonstrate that a combination of ion-beam-milling techniques can produce higher-quality specimens of quantum nanostructures compared to TEM specimens prepared by a combination of tripod polishing followed by Ar+ ion milling. In the proposed method, simultaneous imaging in a focused ion-beam device enables accurate positioning of the QD regions and assures the presence of dots in the thin lamella by cutting the sample inclined by 5° relative to the dots array. Furthermore, the preparation of TEM lamellae with several large electron-transparent regions that are separated by thicker walls effectively reduces the bending of the specimen and offers broad thin areas. The final use of a NanoMill efficiently removes the amorphous layer without introducing any additional damage.
Interfacial nanoconnections and enhanced mechanistic studies of metallic coatings for molecular gluing on polymer surfaces
Dexin Che,Zhixin Kang,Hidetoshi Hirahara and Wei Li
Nanoscale Adv., February 2020, 2106-2113
Interfacial adhesion has been identified as being key for realizing flexible devices. Here, strong interfacial nanoconnections involving metallic patterns on polymer surfaces were fabricated via a molecular bonding approach, which includes UV-assisted grafting and molecular self-assembly. The interfacial characteristics of conductive patterns on liquid crystal polymer substrates were observed via transmission electron microscopy and atomic force microscopy infrared spectroscopy. The interfacial molecular layers have a thickness of 10 nm. Due to the successful molecular bonding modifications, interfacial adhesion has been sufficiently improved; in particular, the peel-related breakage sites will be located in the modified layers on the plastic surface beneath the interface after the metallic coatings are peeled off. Integrating X-ray photoelectron spectroscopy, infrared spectroscopy, and scanning electron microscopy results, the molecular bonding mechanism has been revealed: UV-assisted grafting and self-assembly result in the construction of interfacial molecular architectures, which provide nanosized connecting bridges between the metallic patterns and polymer surfaces. Such in-depth interfacial studies can offer insight into interfacial adhesion, which will impact on the development of metal/polymer composite systems and continue to push the improvement of flexible devices.
Ceramic-based thermoelectric generator processed via spray-coating and laser structuring
Open Ceramics Volume 1, May 2020, 100002
Processing technology to improve the manufacturing of thermoelectric generators (TEGs) is a growing field of research. In this paper, an adaptable and scalable process comprising spray-coating and laser structuring for fast and easy TEG manufacturing is presented. The developed process combines additive and subtractive processing technology towards an adaptable ceramic-based TEG, which is applicable at high temperatures and shows a high optimization potential. As a prototype, a TEG based on Ca3Co4O9 (CCO) and Ag on a ceramic substrate was prepared. Microstructural and thermoelectric characterization is shown, reaching up to 1.65 μW cm−2 at 673 K and a ΔT of 100 K. The high controllability of the developed process also enables adaptation for different kinds of thermoelectric materials.
Low Thermal Conductivity in Thermoelectric Oxide-Based Multiphase Composites
Mario Wolf, Kaan Menekse, Alexander Mundstock, Richard Hinterding, Frederik Nietschke, Oliver Oeckler & Armin Feldhoff
Journal of Electronic Materials 48, pages7551–7561(2019)
Thermoelectric oxide-based multiphase systems gain synergistic properties from different materials. Therefore, multiphase systems based on a thermoelectric oxide, combined with both a polymeric phase (Matrimid) and a highly electrically conducting phase (Ag, carbon black) have been investigated. Compared to single-phase porous Ca3Co4O9, the resulting composite materials showed a decreased electrical conductivity while reaching a high Seebeck coefficient of up to 200 μV/K as well as a 4 times lower thermal conductivity. The strongly enhanced phonon scattering in the multiphase system resulting in low thermal conductivity is an especially interesting concept to design thermoelectric multiphase materials. Additionally, Ioffe plots are revitalized to compare the resulting power factor and thermal properties of the composite materials. The significantly low thermal conductivity due to the heteromaterial interfaces in the composite materials especially underlines the potential of multiphase systems as thermoelectric materials.