Synergistic Effect of Aligned Graphene Nanosheets in Graphene Foam for High‐Performance Thermally Conductive Composites

Graphene shows a great potential for high‐performance thermally conductive composite applications because of its extremely high thermal conductivity. However, the graphene‐based polymer composites reported so far only have a limited thermal conductivity, with the highest thermal conductivity enhancement (TCE) per 1 vol% graphene less than 900%. Here, a continuous network of graphene foam (GF), filled with aligned graphene nanosheets (GNs), is shown to be an ideal filler structure for thermally conductive composite materials. Compared to previous reports, a clear thermal percolation is observed at a low graphene loading fraction. The GNs/GF/natural rubber composite shows the highest TCE of 8100% (6.2 vol% graphene loading) ever reported at room temperature, which gives a record‐high TCE per 1 vol% graphene of 1300%. Further analyses reveal a significant synergistic effect between the aligned GNs and 3D interconnected GF, which plays a key role in the formation of a thermal percolation network to remarkably improve the thermal conductivity of the composites. Additionally, the use of this composite for efficient heat dissipation of light‐emitting diode (LED) lamps is demonstrated. These findings provide valuable guidance to design high‐performance graphene‐based thermally conductive materials, and open up the possibility for the use of graphene in high‐power electronic devices.     

石墨烯/金属复合材料力学性能的研究进展

综述了石墨烯/金属复合材料在力学性能研究方面的现状、进展及发展趋势,讨论了线弹性非均质材料的微观力学模型在阐明石墨烯强化机制中的作用,着重阐述了石墨烯的结构完整性以及分散方法的选择等对于提高石墨烯/金属复合材料力学性能的重要性,归纳了当前石墨烯强化金属基复合材料研究存在的问题,并从原料研制、理论探索、工艺开发和协同增强等方面指出了石墨烯/金属复合材料力学性能的研究趋势。     

石墨烯/环氧树脂复合材料的制备与力学性能

通过对氧化石墨热膨胀还原并用超声分散制备了石墨烯,并对所得产物进行分析表征。用超声分散和模具浇注成型法制备了石墨烯/环氧树脂纳米复合材料。研究了石墨烯含量对石墨烯/环氧树脂复合材料力学性能和断面形貌的影响,分析了石墨烯对环氧树脂的增强机理。结果表明,随着石墨烯含量的增加,石墨烯/环氧树脂复合材料的拉伸强度及模量先增加后减小;当石墨烯的质量分数为0.1%时,复合材料的拉伸强度达到最大值60.9MPa,比纯环氧树脂提高了16.88%;当石墨烯的质量分数为0.5%时,复合材料的拉伸模量达到最大值2833.3MPa,比纯环氧树脂提高了48.29%。     

氧化石墨烯/铜基复合材料的微观结构及力学性能

采用球磨和真空热压烧结方法成功制备氧化石墨烯/铜复合材料。利用OM,SEM,XRD,显微硬度计和电子万能试验机等分析球磨后的复合粉形貌,研究氧化石墨烯添加量对复合微观结构及力学性能的影响。结果表明:制备的氧化石墨烯/铜基复合材料组织致密,氧化石墨烯以片状形态较均匀地分布在铜基体中,并与铜基体形成良好的结合界面。氧化石墨烯质量分数为0.5%时,复合材料的综合力学性能较好,显微硬度和室温压缩强度分别为63HV和276MPa,相对于纯铜基体分别提高了8.6%和28%。其强化机理为剪切应力转移强化、位错强化和细晶强化。     

石墨烯改性聚氨酯超疏水泡沫的制备与表征

报道了一种将石墨烯共价接枝到聚氨酯泡沫表面制备超疏水泡沫的方法。制备过程包括4个主要环节:(1)利用优化的Hummers法制备氧化石墨烯;(2)通过十二烷二胺对氧化石墨烯进行改性在石墨烯表面引入伯胺基团;(3)制备含有腈基的聚氨酯泡沫;(4)通过伯胺与腈基反应将石墨烯化学接枝到聚氨酯泡沫表面制备超疏水泡沫。采用傅里叶变换红外光谱、原子力显微镜、热重分析对接枝产物进行表征,证明了带有伯胺的石墨烯已成功接枝到聚氨酯泡沫上。利用接触角、油水混合物对制备的超疏水泡沫进行测试。结果表明,此方法制备的超疏水聚氨酯泡沫具有优良的疏水性,聚氨酯泡沫与水的接触角由未改性的121.4°增大到166.2°,同时发现此方法制备的聚氨酯泡沫的超疏水性具有很好的稳定性。     

Cl‐Doped ZnO Nanowire Arrays on 3D Graphene Foam with Highly Efficient Field Emission and Photocatalytic Properties

An environmentally friendly, low‐cost, and large‐scale method is developed for fabrication of Cl‐doped ZnO nanowire arrays (NWAs) on 3D graphene foam (Cl‐ZnO NWAs/GF), and investigates its applications as a highly efficient field emitter and photocatalyst. The introduction of Cl‐dopant in ZnO increases free electrons in the conduction band of ZnO and also leads to the rough surface of ZnO NWAs, which greatly improves the field emission properties of the Cl‐ZnO NWAs/GF. The Cl‐ZnO NWAs/GF demonstrates a low turn‐on field (≈1.6 V μm⁻¹), a high field enhancement factor (≈12844), and excellent field emission stability. Also, the Cl‐ZnO NWAs/GF shows high photocatalytic efficiency under UV irradiation, enabling photodegradation of organic dyes such as RhB within ≈75 min, with excellent recyclability. The excellent photocatalytic performance of the Cl‐ZnO NWAs/GF originates from the highly efficient charge separation efficiency at the heterointerface of Cl‐ZnO and GF, as well as improved electron transport efficiency due to the doping of Cl. These results open up new possibilities of using Cl‐ZnO and graphene‐based hybrid nanostructures for various functional devices.     

Reduced Graphene Oxide‐GelMA Hybrid Hydrogels as Scaffolds for Cardiac Tissue Engineering

Biomaterials currently used in cardiac tissue engineering have certain limitations, such as lack of electrical conductivity and appropriate mechanical properties, which are two parameters playing a key role in regulating cardiac cell behavior. Here, the myocardial tissue constructs are engineered based on reduced graphene oxide (rGO)‐incorporated gelatin methacryloyl (GelMA) hybrid hydrogels. The incorporation of rGO into the GelMA matrix significantly enhances the electrical conductivity and mechanical properties of the material. Moreover, cells cultured on composite rGO‐GelMA scaffolds exhibit better biological activities such as cell viability, proliferation, and maturation compared to ones cultured on GelMA hydrogels. Cardiomyocytes show stronger contractility and faster spontaneous beating rate on rGO‐GelMA hydrogel sheets compared to those on pristine GelMA hydrogels, as well as GO‐GelMA hydrogel sheets with similar mechanical property and particle concentration. Our strategy of integrating rGO within a biocompatible hydrogel is expected to be broadly applicable for future biomaterial designs to improve tissue engineering outcomes. The engineered cardiac tissue constructs using rGO incorporated hybrid hydrogels can potentially provide high‐fidelity tissue models for drug studies and the investigations of cardiac tissue development and/or disease processes in vitro.     

A Cut‐Resistant and Highly Restorable Graphene Foam

High‐pressure resistant and multidirectional compressible materials enable various applications but are often hindered by structure‐derived collapse and weak elasticity. Here, a super‐robust graphene foam with ladder shape microstructure capable of withstanding high pressure is presented. The multioriented ladder arrays architecture of the foam, consisting of thousands of identically sized square spaces, endow it with a great deal of elastic units. It can easily bear an iterative and multidirectional pressure of 44.5 MPa produced by a sharp blade, and may completely recover to its initial state by a load of 180 000 times their own weight even under 95% strain. More importantly, the foam can also maintain structural integrity after experiencing a pressure of 2.8 GPa through siphoning. Computational modeling of the “buckling of shells” mechanism reveals the unique ladder‐shaped graphene foam contributes to the superior cut resistance and good resilience. Based on this finding, it can be widely used in cutting resistance sensors, monitoring of sea level, and the detection of oily contaminants in water delivery pipelines.     

骨组织工程支架材料及其力学性能

骨组织工程的研究是组织工程最为活跃的领域之一,如何制备理想的骨支架材料是当前的一个研究热点.通过人们的努力,目前已有多种骨组织工程支架材料问世.综述了各类骨组织工程支架材料的优缺点,对比了它们的力学性能,并对骨组织工程的前景进行了展望.     

Cell‐Assembled Graphene Biocomposite for Enhanced Chondrogenic Differentiation

Graphene‐based nanomaterials are increasingly being explored for use as biomaterials for drug delivery and tissue engineering applications due to their exceptional physicochemical and mechanical properties. However, the two‐dimensional nature of graphene makes it difficult to extend its applications beyond planar tissue culture. Here, graphene–cell biocomposites are used to pre‐concentrate growth factors for chondrogenic differentiation. Bone marrow‐derived mesenchymal stem cells (MSCs) are assembled with graphene flakes in the solution to form graphene‐cell biocomposites. Increasing concentrations of graphene (G) and porous graphene oxide (pGO) are found to correlate positively with the extent of differentiation. However, beyond a certain concentration, especially in the case of graphene oxide, it will lead to decreased chondrogenesis due to increased diffusional barrier and cytotoxic effects. Nevertheless, these findings indicate that both G and pGO could serve as effective pre‐concentration platforms for the construction of tissue‐engineered cartilage and suspension‐based cultures in vitro.     

石墨烯含量对铜基石墨烯复合材料力学和电学性能的影响

为改进铜基复合材料的力学和电学性能,向铜基体分别加入0.2%、0.3%、0.4%(质量分数)的石墨烯,充分混合后,采用放电等离子烧结技术(SPS)制备了石墨烯/铜(G/Cu)复合材料。通过扫描电镜(SEM)、拉曼(Raman)光谱和XRD等表征了复合材料微观结构,测试了其硬度、屈服强度、抗压强度和导电率等性能,以确定石墨烯在铜基体中的合适掺杂量。结果表明:随着石墨烯含量的降低,其力电性能显著提高。当石墨烯质量分数为0.2%时,G/Cu复合材料的综合性能(力学及电学性能)达到最好匹配,实现了铜基材料的高强度、高导电性:其抗压强度和屈服强度分别为557.23 MPa和256 MPa,相对于用SPS方法制备的纯铜分别提高了59.21%和70.7%;电导率为52.3 MS/m,其IACS高达91.8%。     

环氧树脂复合材料的制备及力学性能

通过配方设计,以硅烷偶联剂改性的空心玻璃微珠(HGB)为填料,端羧基液体丁腈橡胶(CTBN)为增稠剂和增韧剂,环氧树脂(EP)为基体,经变温分段固化技术制备环氧树脂/端羧基丁腈橡胶/空心玻璃微珠(EP/CTBN/HGB)三元泡沫复合材料并研究其力学和流变性能。结果表明,CTBN使得复合材料由脆性断裂变为韧性断裂;CTBN劣化了复合材料模量而HGB弥补了复合材料模量;当CTBN、HGB含量分别为12%(质量分数)和30%(体积分数)时,三元复合材料的冲击、弯曲、拉伸强度及弯曲模量均优于纯EP。另外,纯环氧树脂和EP/CTBN共混物的黏度呈现出牛顿流体的流变行为,而三元共混物的黏度表现出明显的剪切变稀现象。     

石墨烯包覆玻璃纤维复合材料的制备及其电学性能研究

以牛血清白蛋白(BSA)改性玻璃纤维表面, 利用静电吸附原理制备氧化石墨包覆的玻璃纤维复合材料, 采用氢碘酸还原氧化石墨得到石墨烯包覆玻璃纤维导电材料。利用X射线衍射(XRD)和傅立叶变换红外光谱仪(FT-IR)等表征样品的物相结构和基团类型, 扫描电镜(SEM)表征石墨烯包覆玻璃纤维的形貌特征。当氧化石墨分散液pH低于6时, 随着pH减小, 包覆效果变得更明显。通过粒径/Zeta电位仪表征氧化石墨和BSA在不同pH下的Zeta电位, 结果表明BSA等电点约为5.3, 氧化石墨的等电点小于3。得到的石墨烯包覆玻璃纤维导电材料的电导率达到4.5 S/m, 制备的导电玻璃纤维具有一定的柔性, 在弯曲后仍能保持原有的导电性能; 导电玻璃纤维在高于100℃热处理后, 由于石墨烯在高温下可以继续还原, 其电导率得到一定的提高, 表明制备的导电玻璃纤维可以在较高温度下使用。     

石墨烯纳米片/密胺复合泡沫性能增强机制研究

目的 探究三聚氰胺与甲醛原料比例、发泡剂正戊烷含量、乳化剂OP-10含量和固化剂甲酸含量对密胺泡沫发泡过程的影响及作用机理,并制备石墨烯纳米片/密胺复合泡沫材料,改善密胺泡沫力学性能,提高密胺泡沫材料热稳定性以及阻燃性。方法 通过调整原料比例、改变不同助剂的掺量探究发泡工艺对泡沫结构的影响,并研究石墨烯纳米片对复合泡沫性能的增强机制。对样品进行力学性能测试,并通过扫描电子显微镜和热重分析仪对泡沫微观结构和热力学性能进行分析。结果 当三聚氰胺与甲醛物质的量之比为1︰3~1︰4时,预聚体交联度高,结构完整;当正戊烷质量分数为33%时,能够为预聚体提供足够的成核点;当甲酸质量分数为8%时,固化速度适宜;当OP-10质量分数为4%~6%时,有效降低了界面张力。添加石墨烯纳米片使复合泡沫最高压缩强度达到23.86 kPa,最高残碳率上升为8.24%,热导率仅上升0.006 W/(m.K),保持了良好的保温隔热性能。结论 甲醛与三聚氰胺的物质的量之比会影响预聚体交联程度;正戊烷因其低沸点而促进了泡沫成核;甲酸通过为基体提供更多的交联点加速了固化速度;OP-10在发泡过程中通过调整与发泡剂的相容性以及作为表面活性剂发挥了作用。石墨烯纳米片的添加提高了复合泡沫的力学性能,在保持低密度和低热导率的同时进一步增强了其热稳定性及其阻燃能力。