Electrically bioactive coating on Ti with bi-layered SnO2-TiO2 hetero-structure for improving osteointegration

SnO2–TiO2 surface with the bi-layered structure on Ti provides internal electric stimulation to promote osteointegration of implant.</p

Enhanced Osseointegration of Hierarchically Structured Ti Implant with Electrically Bioactive SnO₂-TiO₂ Bilayered Surface

The poor osseointegration of Ti implant significantly compromise its application in load-bearing bone repair and replacement. Electrically bioactive coating inspirited from heterojunction on Ti implant can benefit osseointegration but cannot avoid the stress shielding effect between bone and implant. To resolve this conflict, hierarchically structured Ti implant with electrically bioactive SnO2–TiO2 bilayered surface has been developed to enhance osseointegration. Benefiting from the electric cue offered by the built-in electrical field of SnO2–TiO2 heterojunction and the topographic cue provided by the hierarchical surface structure to bone regeneration, the osteoblastic function of basic multicellular units around the implant is significantly improved. Because the individual TiO2 or SnO2 coating with uniform surface exhibits no electrical bioactivity, the effects of electric and topographic cues to osseointegration have been decoupled via the analysis of in vivo performance for the placed Ti implant with different surfaces. The developed Ti implant shows significantly improved osseointegration with excellent bone–implant contact, improved mineralization of extracellular matrix, and increased push-out force. These results suggest that the synergistic strategy of combing electrical bioactivity with hierarchical surface structure provides a new platform for developing advanced endosseous implants

Improving strength-ductility synergy in a TRIP metastable β-Zr alloy containing heterogeneous α precipitates

In this study, a simple two-step heat treatment is proposed to design a TRIP metastable β-Zr alloy with good strength-ductility synergy by introducing heterogeneous α precipitates. The heterogeneous α precipitates mainly consist of necklace-like α at β grain boundaries and a small amount of randomly distributed intragranular α. Compared with the sample consisting of single β phase with yield strength of 683 MPa and ductility of 14.6%, yield strength of the designed two samples with heterogeneous α precipitates increases to 781 MPa and 842 MPa respectively, while the ductility increases to 15.3% and decreases to 13.6% respectively. The microstructure analysis shows that the dominant deformation mechanisms of the sample containing single β phase are β to α′ martensitic transformation and domaination of α′ martensite, accompanied by kinking band, and {101¯1}α′ twinning. For samples with heterogeneous α precipitates, the precipitation of α will increase the triggering stress of the kinking band, resulting in an increase in the yield strength at early stage of deformation. More importantly, the unique heterogeneous α structure brings a gently cutting effect of the necklace-like α on β grains and a traversability of the intragranular α to the growing α′ martensite, making the β to α′ martensitic transformation and domaination of α′ martensite slightly inhibited, together with the absorption and transfer of plastic deformation energy by α precipitates endow the alloy with high ductility. The present work can provide inspiration for improving the strength-ductility synergy of metastable β-Zr or β-Ti alloy through heterogeneous precipitate structure design

Graphite felt incorporated with MoS2/rGO for electrochemical detoxification of high-arsenic fly ash

Accumulation of high-arsenic fly ash (HAFA) poses a serious environmental threat due to the toxicity of As and release of other heavy metals especially Cr. In this work, a novel graphite felt (GF) cathode modified with the nanoscale MoS2/reduced graphene oxide (rGO) heterojunction is prepared by blending with PTFE emulsion for efficient synergistic oxidative dissolution of As(III) and Cr(III) in HAFA. By taking advantage of the p-n junction characteristics of the heterojunction and appropriate hydrophobicity of the PTFE coating, the modified GF efficiently utilizes both dissolved O-2 and gaseous O-2 in the 2e(-) oxygen reduction reaction (ORR). Our theoretical assessment indicates that gaseous O-2 adsorbs stably on sulfur vacancies and is reduced by electrons transmitted from rGO. Experimentally, the modified GF shows superior ORR catalytic activity as exemplified by a high peak current density of 8.41 mA cm(-2) and onset potential of 0.53 V vs. RHE. center dot OH generated by the Cr and Fe-triggered autocatalysis mechanism promotes oxidization of As(III) and Cr(III) in detoxification of HAFA resulting in 96.1% As removal as well as 70.74% Cr removal in 135 min. The modified GF with excellent stability and durability has immense industrial prospect in detoxification of HAFA and treatment of other types of As-containing hazardous wastes

Oxygen Vacancy Enhanced Gas-Sensing Performance of CeO₂/Graphene Heterostructure at Room Temperature

Oxygen vacancies (O_v) as the active sites have significant influences on the gas sensing performance of metal oxides, and self-doping of Ce³⁺ in CeO₂ might promote the formation of oxygen vacancies. In this work, hydrothermal process is adopted to fabricate the composites of graphene and CeO₂ nanoparticles, and the influences of oxygen vacancies as well as Ce³⁺ ions on the sensing response to NO₂ are studied. It is found that the sensitivity of the composites to NO₂ increases gradually, as the proportion of Ce³⁺ relative to all of the cerium ions is increased from 14.6% to 50.7% but decreases after that value. First-principles calculations illustrate that CeO₂ becomes metallic at the Ce³⁺ proportion of <50.7%, the chemical potential of electrons on surface decreases, and the Fermi level shifts upward due to the existence of low-electronegativity Ce³⁺ ions, resulting in reduced Schottky barrier height (SBH) at the CeO₂/graphene interface, enhanced interfacial charge transfer, and high gas sensing performance. However, deep energy level will be induced at the Ce³⁺ proportion of >50.7%, and the Fermi level is pinned at the interface. As a result, the density of free electrons is reduced, leading to increased SBH and poor gas sensing response. It demonstrates that an appropriate concentration of oxygen vacancies in CeO₂ is needed to enhance the gas sensing performance to NO₂