No abstract

No abstract

With the development of microelectronic devices having miniaturized and integrated electronic components, an efficient thermal management system with lightweight materials, which have outstanding thermal conductivity and processability, is becoming increasingly important. Recently, the use of polymer-based thermal management systems has attracted much interest due to the intrinsic excellent properties of the polymer, such as the high flexibility, low cost, electrical insulation, and excellent processability. However, most polymers possess low thermal conductivity, which limits the thermal management applications of them. To address the low thermal conduction of the polymer materials, many kinds of thermally conductive fillers have been studied, and the carbon-based polymer composite is regarded as one of the most promising materials for the thermal management of the electric and electronic devices. In addition, the next generation electronic devices require composite materials with various additional functions such as flexibility, low density, electrical insulation, and oriented heat conduction, as well as ultrahigh thermal conductivity. In this review, we introduce the latest papers on thermally conductive polymer composites based on carbon fillers with sophisticated structures to meet the above requirements. The topic of this review paper consists of the following four contents. First, we introduce the design of a continuous three-dimensional network structure of carbon fillers to reduce the thermal resistance between the filler–matrix interface and individual filler particles. Second, we discuss various methods of suppressing the electrical conductivity of carbon fillers in order to manufacture the polymer composites that meet both the electrical insulation and thermal conductivity. Third, we describe a strategy for the vertical alignment of carbon fillers to improve the through-plane thermal conductivity of the polymer composite. Finally, we briefly mention the durability of the thermal conductivity performance of the carbon-based composites. This review presents key technologies for a thermal management system of next-generation electronic devices.

Highly flexible and electrically-conductive multifunctional textiles are desirable for use in wearable electronic applications. In this study, we fabricated multifunctional textile composites by vacuum filtration and wet-transfer of graphene oxide films on a flexible polyethylene terephthalate (PET) textile in association with embedding Ag nanoparticles (AgNPs) to improve the electrical conductivity. A flexible organic transistor can be developed by direct transfer of a dielectric/semiconducting double layer on the graphene/AgNP textile composite, where the textile composite was used as both flexible substrate and conductive gate electrode. The thermal treatment of a textile-based transistor enhanced the electrical performance (mobility = 7.2 cm2·V−1·s−1, on/off current ratio = 4 × 105, and threshold voltage = −1.1 V) due to the improvement of interfacial properties between the conductive textile electrode and the ion-gel dielectric layer. Furthermore, the textile transistors exhibited highly stable device performance under extended bending conditions (with a bending radius down to 3 mm and repeated tests over 1000 cycles). We believe that our simple methods for the fabrication of graphene/AgNP textile composite for use in textile-type transistors can potentially be applied to the development of flexible large-area electronic clothes.

adhesive tape, revealed that graphite can be split into single-layer graphene, several graphene-preparation methods have been developed for fundamental research or specific applications, including chemical vapor deposition using catalytic metal substrates, [10] chemical exfoliation of graphite based on Hummers' method, [11] liquidphase exfoliation using surfactants, [12] and microwave exfoliation using ionic liquids. [13] Although the outstanding properties or device performance of graphene have already been demonstrated at the laboratory level, [10][11][12][13] they are easily lost or deteriorated during transfer to large scale production. Hence, a simple and cost-effective method and system for the mass production of high-quality and solution-processable graphene sheets need to be developed in order to apply "precious" graphene to a wide range of industrial applications.Motivated by these requirements for simple, fast, and environment-friendly methods for the production of high-quality graphene, Müllen and co-workers reported pioneering work on the direct exfoliation of graphite by electrochemical methods using both acidic [14] and nonacidic electrolyte systems. [15] The electrochemically exfoliated graphene (EEG) satisfies the seemingly irreconcilable requirements of excellent conductivity and solution processability in organic solvents, due to its moderate degree of oxidation, which facilitates its use in a number of applications, such as transparent conductive films and flexible supercapacitors, [16] organic field-effect transistors, [17] sensors, [18] lithium-ion batteries, [19] and 3D composites. [20] However, a cost-effective mass-production system has yet to be explored and consequently, the rational design of electrochemical cells is expected to upgrade the production of EEG from the laboratory scale to an industrial product.Despite recent advances in electrode design and the equipment engineering of electrochemical-exfoliation approaches, as summarized in Table S1 in the Supporting Information, technical issues, such as lowering production costs, designing simple cells, and improving production yields, still remain critical bottlenecks for industrial applications. In this study, we developed a low-cost system for the mass production of EEG using multiple graphite-stainless-steel electrodes (multicells). First, the EEG production cost was reduced by replacing the Herein, the development of a cost-effective system is reported for the mass production of electrochemically exfoliated graphene (EEG) using multiple graphite-stainless-steel electrodes (multicells) in a series configuration and its application to heat transfer. Exfoliation using series-configured multicells leads to the production of high-quality graphene (a few layers of graphene sheets with a low oxygen content and a high C/O ratio of 16.2) at a rate of 30 g per half hour (one-batch). Furthermore, EEG paper is fabricated by the vacuum filtration of the EEG dispersion, and further thermal annealing and mechanical-compression processes are used...