氧化程度对微细鳞片可膨胀石墨结构及膨胀性的影响

以平均粒径为19.71μm的天然微细鳞片石墨为原料,通过化学氧化法制备了具有不同氧化程度的可膨胀石墨,采用XRD、FTIR、Raman、SEM等对可膨胀石墨的结构与膨胀性进行了表征。结果表明:当氧化程度较低时制得的微细鳞片可膨胀石墨由石墨、石墨层间化合物和氧化石墨三相组成;随着氧化程度的增加,氧化石墨相含量与可膨胀石墨结构无序程度逐渐增高,石墨层间化合物相含量先增加后减少,石墨相含量则逐渐降低;氧化促使HSO4-或SO42-插入石墨层间,插入层间的HSO4-或SO42-量是决定可膨胀石墨膨胀容积的关键因素,制备的微细鳞片膨胀石墨的膨胀容积可达65.9mL·g-1。     

石墨消解–原子荧光法测定土壤中的汞和砷

采用石墨消解法对土壤样品进行预处理,用原子荧光光度法测定样品中汞和砷的含量。汞的质量浓度c在0.00~1.00μg/L范围内与荧光强度I线性相关,回归方程为I=849.47c–22.356,相关系数r2=0.999 9,检出限为0.001 8μg/g。砷的质量浓度在0.00~10.00μg/L范围内与荧光强度线性相关,回归方程为I=107.22c–28.994,相关系数r2=0.999 9,检出限为0.009 9μg/g。实际土壤样品5次平行测定汞和砷的相对标准偏差分别为6.2%~15.2%,0.8%~9.9%,用本法对黄土标准样品进行测定,测定结果在标准值允许范围内。     

质量控制图用于石墨炉原子吸收光谱法检测海水中铅元素

为保证海水中重金属检测结果的准确可靠,以铅元素为例,每个工作日使用石墨炉原子吸收光谱仪平行测定铅质控样2次,收集20组有效数据后,通过计算均值、标准差得出上下控制限、警告线及辅助限,绘制出在当前实验室环境条件、仪器设备、试剂药品和人员水平等因素条件下的质量控制图。该质量控制图不仅用于实际检测过程中对检测结果进行监控,还可为该实验室的人员考核、留样复测等实验室质量控制行为提供结果判定依据。     

Fabrication of exfoliated graphite reinforced silicone rubber composites - Mechanical,tribological and dielectric properties

The effect of exfoliated graphite (EG) on the mechanical, tribological and dielectric properties of the silicone rubber (QM) composites has been systematically investigated and analysed. Morphological analysis of the composites helps to understand the interfacial interaction between the filler and the rubber matrix as well as wear mechanism respectively. An enhancement in the mechanical, tribological and dielectric properties was observed with an increase in filler loading and better performance was observed at 7 phr of filler loading. The improvement in performance is attributed to the better interaction between the QM chains and the EG layers as evident from the AFM and TEM analysis. It is also evident from the Kraus plot which supports the reinforcing effect of EG in QM matrix.     

石墨相氮化碳/蒙脱石复合材料的制备及其可见光催化性能

为提高石墨相氮化碳(g-C₃N₄)对可见光的利用率及光催化效率,采用热聚合与直接负载等方法,将g-C₃N₄负载于蒙脱石表面,制备了g-C₃N₄/蒙脱石复合光催化材料,其结构经SEM, FT-IR及XRD表征。以罗丹明B(RhB)为目标污染物,研究了不同负载量g-C₃N₄/蒙脱石复合光催化剂的可见光催化性能。并分别以对苯醌、碘化钾和异丙醇为自由基捕获剂,研究了复合材料的光催化机理。结果表明：当g-C₃N₄的质量分数为83%(CN/M-83%)时,RhB经可见光照射1 h后,降解率达到99.2%。光催化速率常数为纯g-C₃N₄光催化速率常数的3.2倍。     

Direct diazotization of graphite nanoplatelets with melamine and their favorable application in epoxy resins

The ease of undesirable agglomeration and a low efficiency are two problems that restrict the application of graphite nanoplatelets (GNPs) in epoxy resins (EP). Herein, a new strategy with melamine (MEL) as the precursor to functionalize GNPs chemically, which form a bonding layer that is compatible with epoxy matrix, is reported. The MEL fragments with secondary amine groups were grafted uniformly on the GNPs surface by covalent junctions to exploit the diazonium chemistry. This behavior led to a better dispersion and a stronger interaction with the epoxy matrix and resulted in an enhanced glass transition temperature and bending strength, compared with the pure EP. When only 1 wt% functionalized GNPs (f‐GNPs) was used, the Tg of the modified EP raised of about 15°C compared with pure EP, and the bending strength increased by approximately 39%. The dielectric constant of the EP with f‐GNPs was impacted slightly, and the dielectric loss decreased. At 10⁵ Hz, the dielectric loss of the EP with 1 wt% f‐GNPs decreased by approximately 11% compared with pure EP. Therefore, diazotization modification of the GNPs is a useful approach to improve the compatibility in nanoparticle networks.     

Chemical‐Reductant‐Free Electrochemical Deuteration Reaction using Deuterium Oxide

We report a method for the electrochemical deuteration of α,β‐unsaturated carbonyl compounds under catalyst‐ and external‐reductant‐free conditions, with deuteration rates as high as 99 % and yields up to 91 % in 2 h. The use of graphite felt for both the cathode and the anode was key to ensuring chemoselectivity and high deuterium incorporation under neutral conditions without the need for an external reductant. This method has a number of advantages over previously reported deuteration reactions that use stoichiometric metallic reductants. Mechanistic experiments showed that O₂ evolution at the anode not only eliminates the need for an external reductant but also regulates the pH of the reaction mixture, keeping it approximately neutral.     

Graphite–boron composite heater in a Kawai-type apparatus: the inhibitory effect of boron oxide and countermeasures

We have investigated the performance of a graphite–boron composite (GBC) with 3?wt % boron as a precursor for a boron-doped diamond heater in a Kawai-type apparatus at 15?GPa. We first tested a machinable cylinder of GBC sintered at 1000°C in Ar/H₂ gas (99:1 molar ratio). Boron oxide (B₂O₃) formed during sintering frequently hindered the GBC heater from stable operation at temperatures higher than 1400°C by producing melt throughout the heater together with oxide and/or silicates. We then rinsed the GBC heater in hydrochloric acid to remove B₂O₃. After rinsing, we succeeded in stably generating temperatures higher than 2000°C. We also improved a molding process of different-sized GBC tubes for convenient use and tested the molded GBC heater. It was free from the B₂O₃ problem. The electromotive force of the W/Re thermocouple was successfully monitored up to 2400°C.     

A comparison of the magnetic properties of proton- and iron-implanted graphite

In this work we have investigated the changes of the magnetic properties of highly oriented pyrolytic graphite samples after irradiation either with ~3×10¹⁴ protons or 3.5×10¹³ ... 3.5×10¹⁴ iron ions with energies in the MeV range. Our results show that iron and proton irradiations can produce similar paramagnetic contributions depending on the implantation temperature. However, only protons induce a ferromagnetic effect.