دانلود رایگان مقاله لاتین کامپوزیت اپوکسی از سایت الزویر
عنوان فارسی مقاله:
دکوراسیون گرافن بدون نقص nanoplatelets با آلومینا برای کامپوزیت های اپوکسی رسانای الکتریکی
عنوان انگلیسی مقاله:
Decoration of defect-free graphene nanoplatelets with alumina for thermally conductive and electrically insulating epoxy composites
سال انتشار : 2016
برای دانلود رایگان مقاله کامپوزیت اپوکسی اینجا کلیک نمایید.
مقدمه انگلیسی مقاله:
1. Introduction
With high integration and miniaturization of electronic devices, the rapid and efficient dissipation of accumulated heat has become more and more crucial for the normal function of various highperformance devices [1e7]. Thermally conductive polymer composites are one class of important thermal management materials for heat transport and dissipation, which are widely applied in applications including light-emitting diode (LED) and electronic packaging due to their lightweight and ease of processing [1e11]. Owing to the low thermal conductivity of most polymers (~0.2 W/ (mK)) [10,11], various thermally conductive fillers are used to enhance their thermal conductivities. Among these fillers, electrically insulating ceramic fillers, such as Al2O3 [12], BN [13] and AlN [14], can confer upon polymers high thermal conductivity while the filled composites maintain electrically insulating. Usually high loading (>50 wt%) is required to obtain polymer composites with satisfactory thermal conductivities, which seriously damages the mechanical properties of polymers and causes processing diffi- culties of the composites [5,7,11]. Compared to ceramic fillers, two-dimensional graphene has a higher thermal conductivity (~5300 W/(mK)) and is thus more efficient in improving the thermal conductivity of polymers [11,15]. However, its high electrical conductivity makes it impossible to prepare thermally conductive but electrically insulating polymer/ graphene composites because electrical conductivity is more sensitive to the content of graphene than thermal conductivity, and high electrical conductivity can be readily achieved at low loadingsof fillers [16,17] before obvious increases in thermal conductivity of polymer composites are found. If thermally and electrically conductive polymer composites are used for electronic devices, special structural design of electronic components has to be made to avoid electric short circuit occurring inside the devices [3]. To fully utilize the excellent thermal conductivity of graphene for electrically insulating polymer composites, various techniques have been developed to suppress its high electrical conductivity by constructing insulating nanoparticles or nanolayers on graphene surfaces [3,4,11]. Hsiao et al. [1] coated thermally reduced graphene oxide (TGO) with silica by a sol-gel method. With 1 wt% of the TGOsilica hybrid, its epoxy composite exhibited a thermal conductivity of 0.32 W/(mK) and an electrical insulating property (2.96 109 U m). However, the poor intrinsic thermal conductivity of silica coating and the low loading of the hybrid were responsible for the limited increase in thermal conductivity. Compared to TGO, which is usually thermally reduced at a moderate temperature of 1050 C and still bears oxygen-containing groups and defects and thus has a moderate thermal conductivity, high quality (defectfree) graphene nanoplatelets (GNPs), which are prepared by thermal annealing of TGO sheets at 2200 C, are more thermally conductive [18e20]. For instance, a high thermal conductivity of 1.35 W/(mK) was obtained for polyethylene glycol composite with only 5.3 wt% of defect-free GNPs [18]. Although defect-free GNPs are highly thermally conductive, their inert surface makes it difficult to be coated or decorated by electrically insulating nanomaterials. Fortunately, eco-friendly supercritical carbon dioxide (scCO2) fluid has been confirmed to be effective in wetting the inert surfaces owing to its zero surface tension and high diffusivity, precursors of inorganic nanoparticles can be adsorbed onto the surfaces of GNPs and are subsequently converted to nanoparticles and nanosheets by calcination. With the help of scCO2, AlOOH [21] and MnO2 [22] were well decorated onto the inert surfaces of graphene [21e24]. However, the separated nanoparticles generally lead to loose and porous structures which will decrease the thermal conductivity of the hybrids. Recently, Zhang et al. [25] encapsulated carbon nanotubes (CNTs) with integrated Al2O3 layers by using a buffer solution. The same surface feature of graphene as CNTs should make it possible to construct compact and solid Al2O3 layers on GNPs. Nevertheless, to our best knowledge, few literature reported on the synthesis of thermally conductive but electrically insulating hybrids by coating electrically insulating layers onto the defect-free GNPs in the presence of scCO2 fluid or buffer solutions. Herein, by controlling the nucleation and hydrolysis process, Al2O3 nanoparticles and nanolayers are grown on GNPs with the assistance of scCO2 fluid and in a buffer solution, respectively. The synthesized Al2O3@GNP hybrids are efficient in enhancing the thermal conductivity of epoxy resin and retaining the electrical insulation of epoxy. 1 wt% of GNPs are already sufficient to make epoxy electrically conductive. The maximum loadings for keeping an electrical insulation of the epoxy composites are increased to 10 wt% for the hybrid prepared with the assistance of scCO2 (Al2O3@GNP-SC) with a thermal conductivity of 0.96 W/ (mK) and 12 wt% for the hybrid prepared in a buffer solution (Al2O3@GNP-BS) with a thermal conductivity of 1.49 W/(mK). These thermal conductivities are much higher than those publicly reported for thermally conductive and electrically insulating composites with much higher filler loadings [26,27], indicating the promising potential as efficient thermally conductive fillers for polymer composites. In addition, the influence of microstructures of the anchored Al2O3 on the composite properties is also investigated.
برای دانلود رایگان مقاله کامپوزیت اپوکسی اینجا کلیک نمایید.
کلمات کلیدی:
Decoration of defect-free graphene nanoplatelets with ... - INFONA https://www.infona.pl/.../bwmeta1.element.elsevier-06779c84-5485-31e4-aca5-f8639ee... by R Sun - 2016 - Cited by 3 - Related articles To solve this problem, electrically insulating Al2O3 is used to decorate high quality (defect-free) graphene nanoplatelets (GNPs). Aided by supercritical carbon ... Liquid Exfoliation of Defect-Free Graphene - Accounts of Chemical ... pubs.acs.org/doi/abs/10.1021/ar300009f by JN Coleman - 2012 - Cited by 405 - Related articles Mar 20, 2012 - The exfoliated nanosheets are free of defects and oxides and can be ... Liquid exfoliated graphene can be used for a range of applications: ... Physics, Chemistry and Applications of Nanostructures: Proceedings ... https://books.google.com/books?isbn=9814696536 V E Borisenko, S V Gaponenko, V S Gurin - 2015 - Science THIN FILMS BASED ON GRAPHENE NANOPLATELETS DECORATED BY ... grade of graphene depend on the quality of the material, type of defects, substrate, ... graphene is often used as a substrate for the synthesis of free-standing metal ... Enhancing the Heat Transfer Efficiency in Graphene–Epoxy ... pubs.acs.org/doi/abs/10.1021/acsami.5b03196 by F Du - 2015 - Cited by 19 - Related articles Jun 15, 2015 - Decoration of defect-free graphene nanoplatelets with alumina for thermally conductive and electrically insulating epoxy composites. Biocompatible Graphene for Bioanalytical Applications https://books.google.com/books?isbn=3662456958 Yuwei Hu, Fenghua Li, Dongxue Han - 2014 - Science ACS Nano 5, 1253–1258 (2011) Zhang, Y., Jiang, W.: Decorating graphene sheets ... decorated graphene core first generation PAMAM dendrimer for label free ... Functionalization of Graphene: Covalent and Non-Covalent ... pubs.acs.org/doi/pdfplus/10.1021/cr3000412 by V Georgakilas - 2012 - Cited by 1616 - Related articles Sep 25, 2012 - TEM images of the Au decorated graphene nanoplatelets after organic modification with ... thereby leaving it aromatic and defect free. However.
