RESUMEN
Inorganic thermochromic materials exhibit a tunable color gamut and a wide chromatic temperature range, indicating their potential for intelligent adaptive applications in thermal warning, temperature indication, thermal regulation, and interactive light-to-thermal energy conversion. However, most metal-oxide-based thermochromic materials show weak chromaticity adaption with the change of temperature, which needs further understanding of the microscopic principle to clarify the potential route to improve the contrast and identifiability for fabricating better thermochromic materials. Using perovskite-structure (AMO3) alkaline earth metal stannate (Ba1-xSrxSnO3, 0.0 ≤ x ≤ 1.0) as a model system, this paper reports for the first time the mechanism of the properties of thermally induced defect-enhanced charge transfer-type (CTT) thermochromic materials and the strategy for regulating their thermochromic properties by A-site cations. BaSnO3 exhibits continuously reversible thermochromic properties with high contrast from weak light yellow (b* = 11) to strong bright yellow (b* = 58) between room temperature and 550 °C. In-situ high-temperature X-ray diffraction (in-situ XRD), in-situ UV-vis absorption spectroscopy (in-situ UV-vis), thermogravimetric (TG), and electron paramagnetic resonance (EPR) spectra indicate that this excellent thermochromic phenomenon is attributed to the weakening of Sn-O bond hybridization at high temperatures, as well as the formation of a large number of oxygen vacancies at the top of the valence band, and the enhanced charge transfer resulting from the generation of impurity levels in the Sn2+ 5s2 intermediate. Replacing Ba2+ by Sr2+ in Ba1-xSrxSnO3 successfully tuned the thermochromic properties, which is attributed to the Sr2+ doping level-directed oxygen defect concentration and deoxygenation rate. The demonstrated defect-enhanced charge transfer behavior promotes a feasible route for lattice oxygen-mediated thermochromic materials and provides a fundamental relationship between thermally induced defects and colorimetry.
RESUMEN
Soft actuators inspired by the movement of organisms have attracted extensive attention in the fields of soft robotics, electronic skin, artificial intelligence, and healthcare due to their excellent adaptability and operational safety. Liquid crystal elastomer fiber actuators (LCEFAs) are considered as one of the most promising soft actuators since they can provide reversible linear motion and are easily integrated or woven into complex structures to perform pre-programmed movements such as stretching, rotating, bending, and expanding. The research on LCEFAs mainly focuses on controllable preparation, structural design, and functional applications. This review, for the first time, provides a comprehensive and systematic review of recent advances in this important field by focusing on reversible thermal response LCEFAs. First, the thermal driving mechanism, and direct and indirect heating strategies of LCEFAs are systematically summarized and analyzed. Then, the fabrication methods and functional applications of LCEFAs are summarized and discussed. Finally, the challenges and technical difficulties that may hinder the performance improvement and large-scale production of LCEFAs are proposed, and the development opportunities of LCEFAs are prospected.
RESUMEN
Large scale bone defects after bone tumor resection are difficult to reconstruct and repair, and there is also the possibility of tumor recurrence. Photothermal therapy (PTT) has the function of inhibiting tumor cells, but the risk of damage to normal cells is the main factor limiting the clinical application of PTT drugs, and most of them have a weak effect on regeneration for bone defects. Therefore, specific biomaterials that simultaneously eliminate bone tumors, have low toxicity, and promote osteogenesis have attracted considerable attention. In this paper, we successfully fabricated bioactive bredigite scaffolds (MS-BRT) functionalized with MoSe2 nanocrystals using a combination of 3D printing and hydrothermal methods. MS-BRT scaffolds not only have low toxicity and good osteogenic ability, but also have the ability to kill bone tumors by photothermal therapy. Using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and an infrared thermal camera, MoSe2 nanocrystals were demonstrated to be successfully modified on the surface of BRT scaffolds. The MoSe2 nanocrystals endow the scaffolds with excellent photothermal properties, which can be well controlled by varying the hydrothermal reaction time and laser power density. Furthermore, the MS-BRT scaffolds can effectively kill MG-63 and HeLa cells and promote the adhesion and proliferation of osteoblasts. The performance of osteoblastic activity was assessed by alkaline phosphatase staining and alizarin red S staining, which results suggest that both MS-BRT and BRT have favorable osteogenic properties. This study combines the photothermal properties of semiconducting MoSe2 nanocrystals with the osteogenic activity of bioceramic scaffolds for the first time, providing a broader perspective for the development of novel biomaterials with dual functions of bone tumor treatment and bone regeneration.
RESUMEN
In the present study, 98.6-99.5% dense in situ reinforced Ti6Al4V/TiB composites were manufactured with a newly developed approach based on hydrogen-assisted blended elemental powder metallurgy (BEPM). The approach includes the activation milling of titanium powder produced with hydrogenation-dehydrogenation (HDH-Ti powder) with finer TiB2 additives, following blending with TiH2 and master alloy (MA) powders, and final press-and-sinter operations. Scanning electron microscope (SEM) observations prove the formation of microstructures with improved density and homogeneous distribution of TiB reinforcements in a sintered Ti6Al4V matrix. Hardness and compressive tests validated the high mechanical characteristics of produced composites. The effect of preliminary milling time over 2-6 h and the ratio of hydrogenated and non-hydrogenated titanium powders used (TiH2 vs. HDH Ti) on microstructure and mechanical properties were studied to further optimize the processing parameters. Test results indicate the above approach can be regarded as a promising route for the cost-effective manufacturing of Ti6Al4V/TiB composite with reduced porosity, tailored microstructure uniformity, acceptable impurity level and, hence, mechanical characteristics sufficient for practice applications.