氧化石墨烯对水泥基复合材料自收缩的影响

氧化石墨烯(GO)表面富有大量的含氧基团,具有良好的亲水性,是新型纳米碳材料,会对水泥水化产物的形状及聚集态造成影响。本文将多层GO和水超声分散后形成GO分散液,对不同GO掺量的新拌水泥浆体的自收缩进行测试,并采用氮吸附法对其孔隙结构进行表征。结果表明,掺入GO会增加凝胶孔中的自由水,加快水泥水化速率,增大自收缩,且随着掺量的增加,自收缩会更加明显。由迟滞效应的特征推论出GO使得水泥浆体内部的孔隙呈现狭缝形。根据Kelvin方程的BJH法进行孔分布分析,探索GO对自收缩的调控机理。发现GO有助于细化内部孔径,使水泥浆体内部的大毛细孔向着小毛细孔转变,导致毛细孔压力增加,进而增加了水泥基复合材料的自收缩。     

Facile fabrication of integrated three-dimensional C-MoSe<Subscript>2</Subscript>/reduced graphene oxide composite with enhanced performance for sodium storage

Scrupulous design and fabrication of advanced electrode materials are vital for developing high-performance sodium ion batteries. Herein, we report a facile one-step hydrothermal strategy for construction of a C-MoSe₂/rGO composite with both high porosity and large surface area. Double modification of MoSe₂ nanosheets is realized in this composite by introducing a reduced graphene oxide (rGO) skeleton and outer carbon protective layer. The MoSe₂ nanosheets are well wrapped by a carbon layer and also strongly anchored on the interconnected rGO network. As an anode in sodium ion batteries, the designed C-MoSe₂/rGO composite delivers noticeably enhanced sodium ion storage, with a high specific capacity of 445 mAh·g^-1 at 200 mA·g^-1 after 350 cycles, and 228 mAh·g^-1 even at 4 A·g^-1; these values are much better than those of C-MoSe₂ nanosheets (258 mAh·g^-1 at 200 mA·g^-1 and 75 mAh·g^-1 at 4 A·g^-1). Additionally, the sodium ion storage mechanism is investigated well using ex situ X-ray diffraction and transmission electron microscopy methods. Our proposed electrode design protocol and sodium storage mechanism may pave the way for the fabrication of other high-performance metal diselenide anodes for electrochemical energy storage.

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“Quasi‐freestanding” Graphene‐on‐Single Walled Carbon Nanotube Electrode for Applications in Organic Light‐emitting Diode

An air‐stable transparent conductive film with “quasi‐freestanding” graphene supported on horizontal single walled carbon nanotubes (SWCNTs) arrays is fabricated. The sheet resistance of graphene films stacked via layer‐by‐layer transfer (LBL) on quartz, and modified by 1‐Pyrenebutyric acid N‐hydroxysuccinimide ester (PBASE), is reduced from 273 Ω/sq to about 76 Ω/sq. The electrical properties are stable to heat treatment (up to 200 ºC) and ambient exposure. Organic light‐emitting diodes (OLEDs) constructed of this carbon anode (T ≈ 89.13% at 550 nm) exhibit ≈88% power efficiency of OLEDs fabricated on an ITO anode (low turn on voltage ≈3.1 eV, high luminance up to ≈29 490 cd/m², current efficiency ≈14.7 cd/A). Most importantly, the entire graphene‐on‐SWCNT hybrid electrodes can be transferred onto plastic (PET) forming a highly‐flexible OLED device, which continues to function without degradation in performance at bending angles >60°.     

石墨烯及碳化硅增强铝基复合材料的冲击力学行为

采用微机控制电子万能实验机和分离式霍普金森压杆(SHPB)对石墨烯增强的铝基复合材料和碳化硅增强的铝基复合材料进行准静态压缩实验和动态冲击实验,研究石墨烯增强铝基复合材料在不同应变率下的冲击力学性能,采用SEM扫描电镜研究石墨烯增强的铝基复合材料和碳化硅增强的铝基复合材料的形貌特征。结果表明:在各个应变率载荷下,添加石墨烯和添加碳化硅都增强了铝合金的屈服强度,其中,添加石墨烯对铝合金的屈服强度提升更加明显,但不影响材料的应变硬化率;相较于在材料中添加碳化硅,添加石墨烯弱化了材料的应变率效应,在高应变率条件下,添加石墨烯降低了材料的强度极限;选取部分实验数据,拟合确定了添加石墨烯和添加碳化硅两种复合材料的J-C和Z-A本构方程的参数,并比较了两种本构模型的预测能力,对于本工作所研究的复合材料,J-C模型的预测能力更好。     

石墨烯表面改性及其在聚合物导电复合材料中的应用研究

石墨烯作为一种新型的二维碳纳米材料,引起了科学家们极大的兴趣。其中石墨烯/聚合物复合材料具有优异的导电性能,广泛应用于电子、电气等领域。石墨烯片层易于团聚,在聚合物基体中分散不均匀,严重影响了石墨烯/聚合物复合材料的导电性能,需要对石墨烯及其衍生物进行表面改性。表面改性能有效地提高石墨烯在聚合物基体中的分散性,改善石墨烯与聚合物基体的相容性。文中介绍了石墨烯的共价改性(亲核取代反应、亲电取代反应、缩聚反应)和非共价改性(表面活性剂吸附、杂化修饰)的方法,以及对石墨烯/聚合物复合材料导电性的影响,总结了2种改性法的优缺点,最后展望了石墨烯改性及其在聚合物导电复合材料应用方面的研究方向。     

Graphene‐Bonded and ‐Encapsulated Si Nanoparticles for Lithium Ion Battery Anodes

Silicon (Si) has been considered a very promising anode material for lithium ion batteries due to its high theoretical capacity. However, high‐capacity Si nanoparticles usually suffer from low electronic conductivity, large volume change, and severe aggregation problems during lithiation and delithiation. In this paper, a unique nanostructured anode with Si nanoparticles bonded and wrapped by graphene is synthesized by a one‐step aerosol spraying of surface‐modified Si nanoparticles and graphene oxide suspension. The functional groups on the surface of Si nanoparticles (50–100 nm) not only react with graphene oxide and bind Si nanoparticles to the graphene oxide shell, but also prevent Si nanoparticles from aggregation, thus contributing to a uniform Si suspension. A homogeneous graphene‐encapsulated Si nanoparticle morphology forms during the aerosol spraying process. The open‐ended graphene shell with defects allows fast electrochemical lithiation/delithiation, and the void space inside the graphene shell accompanied by its strong mechanical strength can effectively accommodate the volume expansion of Si upon lithiation. The graphene shell provides good electronic conductivity for Si nanoparticles and prevents them from aggregating during charge/discharge cycles. The functionalized Si encapsulated by graphene sample exhibits a capacity of 2250 mAh g^?1 (based on the total mass of graphene and Si) at 0.1C and 1000 mAh g^?1 at 10C, and retains 85% of its initial capacity even after 120 charge/discharge cycles. The exceptional performance of graphene‐encapsulated Si anodes combined with the scalable and one‐step aerosol synthesis technique makes this material very promising for lithium ion batteries.     

<Emphasis Type="Italic">In situ</Emphasis> synthesis of graphene oxide/gold nanorods theranostic hybrids for efficient tumor computed tomography imaging and photothermal therapy

Graphene oxide/gold nanorod (GO/GNR) nanohybrids were synthesized with a GO- and gold-seed-mediated in situ growth method at room temperature by mixing polystyrene sulfonate (PSS) functionalized GO, secondary growth solution, and gold seeds. Compared with ex situ preparation methods of GO/GNRs or graphene (G)/GNRs, the in situ synthesis of GO/GNRs addressed the issue of the aggregation of the GNRs before their attachment onto the GO. The method is straightforward and environment-friendly. The GO/GNRs showed a remarkable photothermal effect in vitro. The temperature of the GO/GNR nanohybrids increased from 25 to 49.9 °C at a concentration of 50 μg/mL after irradiation with an 808-nm laser (0.4 W/cm²) for 6 min. Additionally, the GO/GNRs exhibited good optical and morphological stability and photothermal properties after six cycles of laser irradiation. Upon injection of the GO/GNRs into xenograft tumors, excellent computed tomography (CT) imaging properties and photothermal effect were obtained. The preclinical CT agent iohexol was combined with the GO/GNRs and further enhanced CT imaging. Therefore, the GO/GNR nanohybrids have great potential for precise CT-image-guided tumor photothermal treatment.

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Monolithic and Flexible ZnS/SnO2 Ultraviolet Photodetectors with Lateral Graphene Electrodes

A continuing trend of miniaturized and flexible electronics/optoelectronic calls for novel device architectures made by compatible fabrication techniques. However, traditional layer‐to‐layer structures cannot satisfy such a need. Herein, a novel monolithic optoelectronic device fabricated by a mask‐free laser direct writing method is demonstrated in which in situ laser induced graphene‐like materials are employed as lateral electrodes for flexible ZnS/SnO₂ ultraviolet photodetectors. Specifically, a ZnS/SnO₂ thin film comprised of heterogeneous ZnS/SnO₂ nanoparticles is first coated on polyimide (PI) sheets by a solution process. Then, CO₂ laser irradiation ablates designed areas of the ZnS/SnO₂ thin film and converts the underneath PI into highly conductive graphene as the lateral electrodes for the monolithic photodetectors. This in situ growth method provides good interfaces between the graphene electrodes and the semiconducting ZnS/SnO₂ resulting in high optoelectronic performance. The lateral electrode structure reduces total thickness of the devices, thus minimizing the strain and improving flexibility of the photodetectors. The demonstrated lithography‐free monolithic fabrication is a simple and cost‐effective method, showing a great potential for developement into roll‐to‐roll manufacturing of flexible electronics.