Ti/SiO2 composite fabricated by powder metallurgy for orthopedic implant

Titanium/silica (Ti/SiO2) composites are fabricated using powder metallurgy (P/M). Nanoscale biocompatible SiO2 particles are selected as reinforcement for the Ti/SiO2 composite to enhance its biocompatibility and strength, especially when with high porosity. Effects of the SiO2 particle addition and sintering temperature on mechanical properties of the Ti/SiO2 composites are investigated. The results indicate that the mechanical property of Ti/SiO2 composites sintered at 1100°C are better than those at 900 and 1000°C. The strength of the Ti/SiO2 composites is significantly higher than that of pure titanium. The composite with the SiO2 content of 2wt% sintered at 1100°C for 4h shows an appropriate mechanical property with a relative density of 96.5%, a compressive strength of 1566MPa and good plasticity (an ultimate strain of 15.96%). In vitro results reveal that the Ti/SiO2 composite possesses excellent biocompatibility and cell adhesion. Osteoblast-like cells grow and spread well on the surfaces of the Ti/SiO2 composites. The Ti/SiO2 composite is a promising material for great potential used as an orthopedic implant material

Cu-based high-entropy two-dimensional oxide as stable and active photothermal catalyst

Abstract Cu-based nanocatalysts are the cornerstone of various industrial catalytic processes. Synergistically strengthening the catalytic stability and activity of Cu-based nanocatalysts is an ongoing challenge. Herein, the high-entropy principle is applied to modify the structure of Cu-based nanocatalysts, and a PVP templated method is invented for generally synthesizing six-eleven dissimilar elements as high-entropy two-dimensional (2D) materials. Taking 2D Cu2Zn1Al0.5Ce5Zr0.5Ox as an example, the high-entropy structure not only enhances the sintering resistance from 400 °C to 800 °C but also improves its CO2 hydrogenation activity to a pure CO production rate of 417.2 mmol g−1 h−1 at 500 °C, 4 times higher than that of reported advanced catalysts. When 2D Cu2Zn1Al0.5Ce5Zr0.5Ox are applied to the photothermal CO2 hydrogenation, it exhibits a record photochemical energy conversion efficiency of 36.2%, with a CO generation rate of 248.5 mmol g−1 h−1 and 571 L of CO yield under ambient sunlight irradiation. The high-entropy 2D materials provide a new route to simultaneously achieve catalytic stability and activity, greatly expanding the application boundaries of photothermal catalysis

Unlocking the mysterious polytypic features within vaterite CaCO3

Abstract Calcium carbonate (CaCO3), the most abundant biogenic mineral on earth, plays a crucial role in various fields such as hydrosphere, biosphere, and climate regulation. Of the four polymorphs, calcite, aragonite, vaterite, and amorphous CaCO3, vaterite is the most enigmatic one due to an ongoing debate regarding its structure that has persisted for nearly a century. In this work, based on systematic transmission electron microscopy characterizations, crystallographic analysis and machine learning aided molecular dynamics simulations with ab initio accuracy, we reveal that vaterite can be regarded as a polytypic structure. The basic phase has a monoclinic lattice possessing pseudohexagonal symmetry. Direct imaging and atomic-scale simulations provide evidence that a single grain of vaterite can contain three orientation variants. Additionally, we find that vaterite undergoes a second-order phase transition with a critical point of ~190 K. These atomic scale insights provide a comprehensive understanding of the structure of vaterite and offer advanced perspectives on the biomineralization process of calcium carbonate