Graphites from the Zavalie deposit as active materials for lithium-ion batteries

We study the utility of standard graphites (GAK-2, GL-1, EUZ-M, and others) produced by the Zavalie Integrated Graphite Plant (ZGP) as active materials in lithium-ion batteries (LIBs). The structure and main electrochemical characteristics of these graphites are studied for choosing the best type of graphite and evaluating its utility for LIB production. The electrochemical characteristics of the best ZGP graphites and graphite for batteries produced by Superior Graphite Co. (USA), a worldwide leader of the graphite industry, are compared. Some tendencies in the effect of the structure and particle-size distribution on the electrochemical characteristics of graphite electrodes are determined. EUZ-M graphite modified by tin with amorphous carbon is prepared. The reversible capacity of this graphite in the cell against LiCoO₂ exceeds 400 mA h/g. The increased reversible capacity is due to the contribution of components having higher specific parameters; the cycling stability is due to the core-shell structure.     

超级微波消解-石墨炉原子吸收光谱法测定虾蛄中镉含量

目的 比较超级微波和普通微波消解方法,建立超级微波-石墨炉原子吸收法测定虾蛄中镉的方法。方法 分别采用超级微波和普通微波消化大虾标准物质,对比消解效果,优选消解方法,采用石墨炉原子吸收法测定,优化基改改进剂、灰化温度等工作参数,确定最佳的分析方法,同时加标回收验证方法的准确性与可靠性。结果 两种消解方法下测得结果均在参考值范围内,在选定方法条件下,镉在质量浓度0.0～2.0 μg/L范围内线性关系良好,相关系数γ=0.999,检出限为0.04 μg/L,定量限为0.12 μg/L,加标回收的准确度为88.5%～105.2%,精密度为2.93%～4.92%。结论 超级微波消解法优于普通微波消解,其耗酸量低、高效便捷、测得数据准确稳定,便于在基层推广,适用于批量虾蛄样品的镉污染监测工作。     

超级微波消解-石墨炉原子吸收光谱法测定不同类型土壤中的镉

目的 探讨并建立超级微波消解-石墨炉原子吸收法测定不同类型土壤镉含量的方法。方法 采用超级微波消解仪对样品进行前处理,对比不同消解体系的消解效果,选择合适的的消解体系,采用石墨炉原子吸收法测定镉浓度,同时优化基体改进剂、灰化温度等工作参数,确定最佳的分析条件。结果 在最优方法条件下,标准曲线在0.0～1.0 μg/L浓度范围内线性关系良好,相关系数γ=0.999,检出限浓度为0.04 μg/L,定量限浓度为0.12 μg/L,方法准确度为94.5%～109.8%,精密度为0.6%～5.4%,方法应用于不同类型土壤标准物质镉的测定,测得结果均在标准值范围内。结论 本方法方便快捷、准确高效、用酸量低、节约环保,便于在基层推广,适用于批量不同类型土壤样品镉的污染监测工作。     

浊点萃取-高分辨连续光源石墨炉原子吸收光谱法测定环境水样中的痕量铅

比较了三种不同的分离富集方法——共沉淀法、离子交换法和浊点萃取法对水样中痕量铅的富集效果,其中,浊点萃取法水样用量少、富集因子大、操作简便,故选取浊点萃取法对环境水样中的铅进行富集。采用浊点萃取-高分辨连续光源石墨炉原子吸收光谱法测定了采自北京市通惠河水样中的痕量铅。结果表明,该测定方法的检出限为0.08 μg·L-1,相对标准偏差为1.3%~4.5%(n=6),加标回收率为93%~108%,样品溶液的富集因子为29。通惠河13个采样点水样中铅含量均符合国家规定的地表水水质Ⅰ类水标准,且从通州区至朝阳区呈现铅含量逐渐减少的趋势。     

非等温差示扫描量热法(DSC)研究石墨对乙烯基酯树脂固化行为的影响

采用红外(IR)及非等温差示扫描量热法(DSC)研究了乙烯基酯树脂(VER)及石墨/VER复合体系的固化行为.结果表明:计算所得VER及石墨/VER复合体系的表观活化能Ea分别为46.15和79.82kJ.mol-1;反应级数n分别为0.950和0.951.复合体系中树脂的固化放热量的平均值ΔH比纯VER体系的约降低17%,一定程度上降低了树脂的固化反应程度;复合体系中树脂几乎不存在后固化现象.     

石墨改性碳布复合材料湿式摩擦磨损性能研究

采用树脂浸渍工艺制备了石墨质量分数0%～20%的5种碳布复合材料.借助扫描电镜和湿式摩擦试验机,研究了石墨含量对其表面形貌和摩擦磨损性能的影响.实验结果表明:石墨的固体润滑作用,主要造成了制动过程中动摩擦力矩的下降,而对锁止静摩擦力矩的影响却很小;石墨可以明显降低复合材料的动摩擦系数,并有助于提高动摩擦系数的稳定性;石墨的加入有效降低了碳布复合材料和对偶的磨损率,当石墨含量为15%时复合材料的磨损率最低.引入稳定系数对动摩擦系数的稳定性进行了定量分析,当石墨含量为10%时复合材料的动摩擦系数稳定性最好.     

微弧氧化一步制备石墨-PTFE共添加的自润滑膜层

在Na2SiO3-KOH基础电解液中添加不同的固体润滑微粒,利用微弧氧化技术在LY12铝合金上制备了含有固体润滑剂的微弧氧化膜层.利用傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)和扫描电子显微镜(SEM)研究了未添加、添加聚四氟乙烯(PTFE)和石墨-PTFE共添加微弧氧化膜层的组成和微结构.采用往复球-盘试验机评价了膜层的摩擦学性能.结果表明:加入到电解液中的固体润滑剂在微弧氧化过程中成功进入到膜层中,从而得到含有固体润滑剂的复合膜层.添加PTFE的微弧氧化膜层相较于未添加的膜层具有更小的摩擦系数,而石墨-PTFE共添加能够进一步降低膜层的摩擦系数.     

基于氧化石墨烯信号放大的化学发光法联合检测甲胎蛋白和癌胚抗原

提出了一种基于信号放大技术的流动注射化学发光免疫传感器, 用于联合检测人血清中甲胎蛋白(AFP)和癌胚抗原(CEA)的含量. 该传感器首先用表面接枝羧基的氧化石墨烯来吸附固定辣根过氧化物酶(HRP)标记的二抗, 制得信号放大型免疫探针. 然后用合成的磁性介孔材料Fe₃O₄/SiO₂来吸附固定AFP和CEA的单克隆抗体, 用磁铁将其吸附在两个检测池内壁. 当待检样品和信号放大型免疫探针陆续注射进入相应检测池, 发生夹心式免疫反应, 形成的免疫复合物被磁条吸附在检测池内壁. 随后加入鲁米诺和H₂O₂发光底物, 与酶标记物发生酶促增强的化学发光反应, 并通过控制设在两个管路上的开关来控制鲁米诺和H₂O₂的流通, 相继检测两个检测池中的化学发光信号, 从而实现两种待测物的同时检测.     

Confined State and Electronic Transport in an Artificial Graphene-Based Tunnel Junction

Artificial graphene structures embedded in semiconductors could open novel routes for studies of electron interactions in low-dimensional systems. We propose a way to manipulate the transport properties of massless Dirac fermions in an artificial graphene-based tunnel junction. Velocity-modulation control of electron wave propagation in the different regions can be regarded as velocity barriers. Transmission probability of electron is
affected profoundly by this velocity barrier. We find that there is no confinement for Dirac electron as the velocity ratioξ is less than 1, but when the velocity ratio is larger than 1 the confined state appears in the continuum band. These localized Dirac electrons may lead to the decreasing of transmission probability.     

Enhanced Specificity and Sensitivity for the Determination of Nickel(II) by Square-wave Adsorptive Cathodic Stripping Voltammetry at Disposable Graphene-modified Pencil Graphite Electrodes

Chemical sensors relying on graphene-based materials have been widely used for electrochemical determination of metal ions and have demonstrated excellent signal amplification. This study reports an electrochemically reduced graphene oxide (ERGO)/mercury film (HgF) nanocomposite-modified pencil graphite electrode (PGE) prepared through successive electrochemical reduction of graphene oxide (GO) sheets and an in situ plated HgF. The ERGO-PG-HgFE, in combination with dimethylglyoxime (DMG) and square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV), was evaluated for the determination of Ni²⁺ in tap and natural river water samples. A single-step electrode pre-concentration approach was employed for the in situ Hg-film electroplating, metal-chelate complex formation, and non-electrolytic adsorption at –0.7 V. The current response due to nickel-dimethylglyoxime [Ni(II)-DMG₂] complex reduction was studied as a function of experimental paratmeters including the accumulation potential, accumulation time, rotation speed, frequency and amplitude, and carefully optimized for the determination of Ni²⁺ at low concentration levels (μg?L^?1) in pH 9.4 of 0.1 M NH₃–NH₄Cl buffer. The reduction peak currents were linear with the Ni²⁺ concentration between 2 and 16?μg?L^?1. The limits of detection and quantitation were 0.120?±?0.002?µg?L^?1 and 0.401?±?0.007?µg?L^?1 respectively, for the determination of Ni²⁺ at an accumulation time of 120?s. The ERGO-PG-HgFE further demonstrated a highly selective stripping response toward Ni²⁺ determination compared to Co²⁺. The electrode was found to be sufficiently sensitive to determine metal ions in water samples at 0.1?µg?L^?1, well below the World Health Organization standards.