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991.
Evan P. Gray Cynthia L. Browning Charles A. Vaslet Kyle D. Gion Allen Green Muchun Liu Agnes B. Kane Robert H. Hurt 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(21)
Many layered crystal phases can be exfoliated or assembled into ultrathin 2D nanosheets with novel properties not achievable by particulate or fibrous nanoforms. Among these 2D materials are manganese dioxide (MnO2) nanosheets, which have applications in batteries, catalysts, and biomedical probes. A novel feature of MnO2 is its sensitivity to chemical reduction leading to dissolution and Mn2+ release. Biodissolution is critical for nanosafety assessment of 2D materials, but the timing and location of MnO2 biodissolution in environmental or occupational exposure scenarios are poorly understood. This work investigates the chemical and colloidal dynamics of MnO2 nanosheets in biological media for environmental and human health risk assessment. MnO2 nanosheets are insoluble in most aqueous phases, but react with strong and weak reducing agents in biological fluid environments. In vitro, reductive dissolution can be slow enough in cell culture media for MnO2 internalization by cells in the form of intact nanosheets, which localize in vacuoles, react to deplete intracellular glutathione, and induce cytotoxicity that is likely mediated by intracellular Mn2+ release. The results are used to classify MnO2 nanosheets within a new hazard screening framework for 2D materials, and the implications of MnO2 transformations for nanotoxicity testing and nanosafety assessment are discussed. 相似文献
992.
Guodong?Du Aziz?Tekin Earl?G.?Hammond L.?Keith?WoodEmail author 《Journal of the American Oil Chemists' Society》2004,81(5):477-480
The epoxidation of methyl linoleate was examined using transition metal complexes as catalysts. With a catalytic amount of
methyltrioxorhenium (4 mol%) and pyridine, methyl linoleate was completely epoxidized by aqueous H2O2 within 4 h. Longer reaction times (6 h) were needed with 1 mol% catalyst loading. Manganese tetraphenylporphyrin chloride
was found to catalyze the partial epoxidation of methyl linoleate. A monoepoxidized species was obtained as the major product
(63%) after 20 h. 相似文献
993.
目的 研究微生物在锰砂滤层去除地下水中所含的铁、锰过程中所起的作用。为生物法用于地下水除铁除锰的初期启动和生产运行提供依据.方法 试验分为两个阶段,第一阶段。在相同外界条件下,对经过人工接种的滤柱与自然成熟的滤柱进行去除率对比;第二阶段,对成熟滤料进行高温高压灭菌,将灭菌后的滤柱与同期运行的未灭菌滤柱进行去除率试验对比.结果 在运行10dN,两个滤柱的除锰效果出现明显差异,25dN,两个滤柱的除锰效果基本相同.经过灭菌的滤柱重新投入运行,仍然保持原有的除锰能力.结论 滤料的成熟期是一个相对的概念,采用生物接种的手段可以有效地缩短锰砂滤料的成熟期.微生物在除锰过程中起到的是促进作用而非决定性作用,包括物理吸附、化学氧化和催化的非生物因素不容忽视. 相似文献
994.
采用光学和扫描电子显微镜及能谱仪等手段,对进口的铁素体不锈钢棒制造的空调四通换向阀中的封头失效进行了分析。认为棒材内部存在的大量沿轴向分布的硫化锰夹杂物导致封头开裂,从而使空调四通换向阀产生失效。 相似文献
995.
吴显明 《武汉理工大学学报(材料科学英文版)》2006,21(3):54-56
1 IntroductionThin-filmlithium-ion batteries have attracted greatattention of researchfor possible use inimplantable medi-cal devices , CMOS-based integrated circuits ,radio fre-quency (RF) identification tags for inventory control andanti-theft protection[1],etc. Li Mn2O4thin films , aspromising cathode materials for thin-filmlithium-ion bat-teries, have been prepared by a few methods such aspulsedlaser deposition[2 ,3],electrospraying[4-9],RF mag-netron sputtering[10], laser ablation[11]… 相似文献
996.
采用软化学合成法合成出基面间距为0.70nm的层状二氧化锰(bir-MnO2),并利用表面吸附技术制备了层状二氧化锰/苯胺-邻甲氧基苯胺共聚物复合材料(bir-MnO2/P(An-co-oAs)),借助FTIR、XRD、SEM、TGA、四探针和充放电循环实验等测试手段对样品的结构与性能进行表征.结果表明,P(An-co-oAs)的引入,对复合材料中bir-MnO2的层状结构破坏较小,P(An-co-oAs)通过氢键和静电作用吸附在bir-MnO2的表面.与bir-MnO2相比,复合材料的电导率提高2个数量级.首次放电比容量由bir-MnO2的188mAh/g提高到复合材料的202mAh/g. 相似文献
997.
998.
Cheng Yang Yu Yao Yuebin Lian Yujie Chen Rahim Shah Xiaohui Zhao Muzi Chen Yang Peng Zhao Deng 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(16)
Transition metal oxides (TMOs) are regarded as promising candidates for anodes of lithium ion batteries, but their applications have been severely hindered by poor material conductivity and lithiated volume expansion. As a potential solution, herein is presented a facile approach, by electrospinning a manganese‐based metal organic framework (Mn‐MOF), to fabricate yolk–shell MnOx nanostructures within carbon nanofibers in a botryoid morphology. While the yolk–shell structure accomodates the lithiated volume expansion of MnOx, the fiber confinement ensures the structural integrity during charge/discharge, achieving a so‐called double‐buffering for cyclic volume fluctuation. The formation mechanism of the yolk–shell structure is well elucidated through comprehensive instrumental characterizations and cogitative control experiments, following a combined Oswald ripening and Kirkendall process. Outstanding electrochemical performances are demonstrated with prolonged stability over 1000 cycles, boosted by the double‐buffering design, as well as the “breathing” effect of lithiation/delithiation witnessed by ex situ imaging. Both the fabrication methodology and electrochemical understandings gained here for nanostructured MnOx can also be extended to other TMOs toward their ultimate implementation in high‐performance lithium ion batteries (LIBs). 相似文献
999.
In Situ Engineering of the Electrode–Electrolyte Interface for Stabilized Overlithiated Cathodes
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1000.
The ingenious design of a freestanding flexible electrode brings the possibility for power sources in emerging wearable electronic devices. Here, reduced graphene oxide (rGO) wraps carbon nanotubes (CNTs) and rGO tightly surrounded by MnO2 nanosheets, forming a 3D multilevel porous conductive structure via vacuum freeze‐drying. The sandwich‐like architecture possesses multiple functions as a flexible anode for lithium‐ion batteries. Micrometer‐sized pores among the continuously waved rGO layers could extraordinarily improve ion diffusion. Nano‐sized pores among the MnO2 nanosheets and CNT/rGO@MnO2 particles could provide vast accessible active sites and alleviate volume change. The tight connection between MnO2 and carbon skeleton could facilitate electron transportation and enhance structural stability. Due to the special structure, the rGO‐wrapped CNT/rGO@MnO2 porous film as an anode shows a high capacity, excellent rate performance, and superior cycling stability (1344.2 mAh g−1 over 630 cycles at 2 A g−1, 608.5 mAh g−1 over 1000 cycles at 7.5 A g−1). Furthermore, the evolutions of microstructure and chemical valence occurring inside the electrode after cycling are investigated to illuminate the structural superiority for energy storage. The excellent electrochemical performance of this freestanding flexible electrode makes it an attractive candidate for practical application in flexible energy storage. 相似文献