リチウム酸素電池のためのナノポーラスグラフェンの電気化学

要約のみTohoku University陳明偉課

Extraordinary tensile strength and ductility of scalable nanoporous graphene

While the compressive strength-density scaling relationship of ultralight cellular graphene materials has been extensively investigated, high tensile strength and ductility have not been realized in the theoretically strongest carbon materials because of high flaw sensitivity under tension and weak van der Waals interplanar bonding between graphene sheets. In this study, we report that large-scale ultralight nanoporous graphene with three-dimensional bicontinuous nanoarchitecture shows orders of magnitude higher strength and elastic modulus than all reported ultralight carbon materials under both compression and tension. The high-strength nanoporous graphene also exhibits excellent tensile ductility and work hardening, which are comparable to well-designed metamaterials but until now had not been realized in ultralight cellular materials. The excellent mechanical properties of the nanoporous graphene benefit from seamless graphene sheets in the bicontinuous nanoporosity that effectively preserves the intrinsic strength of atomically thick graphene in the three-dimensional cellular nanoarchitecture

Efficacy and feasibility of proximal radioulnar derotational osteotomy and internal fixation for the treatment of congenital radioulnar synostosis

Abstract Background The aim of this study was to assess the feasibility and efficacy of proximal radioulnar derotational osteotomy followed by internal fixation for the treatment of congenital radioulnar synostosis (CRUS). Methods Between May 2008 and August 2016, 31 patients (36 forearms) with CRUS who underwent derotational osteotomy at the proximal radioulnar synostosis site were evaluated. There were 20 boys and 11 girls. The mean age at the time of surgery was 4.87 ± 3.06 (range, 2 to 13) years. The forearm was derotated to the goal position (20 degrees of supination to 10 degrees of pronation) using plates for internal fixation and plaster splints for external immobilization. Pre- and postoperative positions of the forearm were recorded; forearm function was evaluated based on the classification system proposed by Failla et al. Results The mean follow-up duration was 55.19 ± 27.10 (24 to 123) months. The mean initial pronation deformity was 62.92 ± 7.11 (55 to 80) degrees. The mean correction achieved was 70.86 ± 9.58 (50 to 90) degrees, resulting in a mean final position of 7.94 ± 7.25 degrees of supination (20 degrees of supination to 10 degrees of pronation). Based on the Failla classification system, 2 forearms were rated as good, 30 were rated as fair, and 4 were rated as poor preoperatively. At the final follow-up, 34 forearms were rated as excellent and 2 were rated as good. All patients achieved bone union after 2 months. Complications occurred in three patients (two transient nerve palsies and one compartment syndrome), and the overall complication rate was 9.7%. Conclusions Proximal radioulnar derotational osteotomy followed by plate fixation is a safe and feasible procedure with a low complication rate. The technique can effectively improve the function of the forearm. Level of evidence IV Retrospective case serie

Engineering the internal surfaces of three-dimensional nanoporous catalysts by surfactant-modified dealloying

Tuning the ratio of facets in materials can affect catalytic activity but methods to achieve this can be difficult to control. Here, using surfactants during dealloying, the authors prepare nanoporous gold with controlled facet ratios and show how it can significantly improve electrocatalytic activity

Operando characterization of cathodic reactions in a liquid-state lithium-oxygen micro-battery by scanning transmission electron microscopy

Abstract Rechargeable non-aqueous lithium-oxygen batteries with a large theoretical capacity are emerging as a high-energy electrochemical device for sustainable energy strategy. Despite many efforts made to understand the fundamental Li-O2 electrochemistry, the kinetic process of cathodic reactions, associated with the formation and decomposition of a solid Li2O2 phase during charging and discharging, remains debate. Here we report direct visualization of the charge/discharge reactions on a gold cathode in a non-aqueous lithium-oxygen micro-battery using liquid-cell aberration-corrected scanning transmission electron microscopy (STEM) combining with synchronized electrochemical measurements. The real-time and real-space characterization by time-resolved STEM reveals the electrochemical correspondence of discharge/charge overpotentials to the nucleation, growth and decomposition of Li2O2 at a constant current density. The nano-scale operando observations would enrich our knowledge on the underlying reaction mechanisms of lithium-oxygen batteries during round-trip discharging and charging and shed lights on the strategies in improving the performances of lithium-oxygen batteries by tailoring the cathodic reactions