基于Pickering乳液技术制备高强度和高透明的纤维素纳米纤维/聚苯乙烯复合材料

利用纤维素纳米纤(CNFs)稳定的油相中含有聚苯乙烯(PS)的O/W型Pickering乳液凝胶,经进一步真空过滤、溶剂洗涤和热压过程制备了CNFs增强的PS(CNFs/PS)复合材料.所得的C-CNFs/PS复合薄膜材料具有独特的多尺度的三维交联网络结构.其中,大部分PS以鹅卵石状镶嵌在微米级的三维交联网络结构中,而...     

纤维素纳米纤丝-还原氧化石墨烯/聚苯胺气凝胶柔性电极复合材料的制备与性能

利用高长径比的纤维素纳米纤丝（CNF）与片层结构的氧化石墨烯（GO）形成的CNF-GO复合水凝胶经抗坏血酸还原制备出CNF-还原氧化石墨烯（rGO）复合水凝胶材料。通过冷冻干燥法得到CNF-rGO复合气凝胶,并进一步通过苯胺单体在CNF-rGO复合气凝胶的孔道内原位聚合制备出CNF-rGO/聚苯胺（PANI）气凝胶柔性电极复合材料。研究了不同苯胺、CNF和GO的质量比对CNF-rGO/PANI气凝胶柔性电极复合材料的结构形貌和电化学性能的影响。结果表明,苯胺原位聚合后所得CNF-rGO/PANI复合气凝胶仍具有紧密的三维多孔网络结构。与rGO/PANI气凝胶电极复合材料相比,CNF-rGO/PANI气凝胶电极复合材料具有更理想的电容行为。当CNF与GO质量比为60∶40,PANI添加量为0.1 mol时,CNF-rGO/PANI气凝胶电极复合材料比电容可达85.9 Fg-1,且其电化学性能几乎不受弯曲程度的影响,展现出了良好的柔韧性和电化学性能。      

GNS/PMMA泡沫复合材料的制备及其电磁屏蔽性能

本文采用电泳法在泡沫镍表面沉积一层石墨烯,接着浸渍一层聚甲基丙烯酸甲酯,最后去除泡沫镍模板获得石墨烯/聚甲基丙烯酸甲酯泡沫复合材料。采用扫描电镜、四探针电导率仪及矢量网络分析仪等对材料的形貌结构及性能进行表征。结果表明该泡沫复合材料完整地继承了泡沫镍的三维骨架结构,石墨烯在聚合物骨架中相互连接形成全连通的导电网络,使得该复合材料具有良好的电导率及电磁屏蔽性能。孔径0.25mm、厚度1.5mm的该复合材料的电导率最大可达1.5S·m-1,在8~12GHz范围内,其电磁屏蔽效能最高可达12.7dB,其中吸收损耗占总损耗的99%。因此以吸收损耗为主要屏蔽机制的石墨烯/聚甲基丙烯酸甲酯泡沫复合材料是一种有前途的轻质、透气型电磁屏蔽材料。     

氧化石墨烯稳定的Pickering乳液及其聚合反应

通过改进的Hummers法制备氧化石墨烯(GO),以GO做稳定剂,甲基丙烯酸甲酯(MMA)为油相,制备了Pickering乳液,并研究了GO浓度、水相pH值对其稳定性的影响;通过加入引发剂成功进行了Pickering乳液聚合制备PMMA/GO复合微球,利用透射电镜对该复合微球的微观结构进行了表征。研究表明,GO稳定的Pickering乳液相比于SDBS稳定的普通乳液,液滴粒径更小且分散性更好;GO浓度对Pickering乳液的稳定性影响不大,但随其浓度的增加,Pickering乳液液滴尺寸变小,液滴更为分散;酸性连续相更有利于GO在油水界面的吸附而形成稳定的Pickering乳液,随着pH值增大,液滴尺寸逐渐变大,但碱性条件下乳液无法稳定存在;乳液聚合产物形貌为PMMA颗粒由GO片均匀包覆形成的复合微球,尺寸分布约200 nm左右。     

氧化石墨烯的Pickering乳液稳定性的影响因素

氧化石墨烯(GO)的两亲性及在水油体系中的乳化作用,使基于GO稳定的Pickering乳液成为近期的一个研究热点。文中简单介绍了Pickering乳液和GO的结构特点,综述了GO的微观结构、pH、油相、GO/油/水比、离子强度、GO的功能化、辅助稳定剂和金属纳米粒子表面修饰等因素对GO Pickering乳液稳定性的影响。通过调控上述因素使GO在油水界面处形成牢固的界面膜是获得稳定的GO Pickering乳液的关键。     

高温热还原石墨烯气凝胶/环氧树脂电磁屏蔽复合材料

以氧化石墨烯(GO)水分散液为原料采用简单的一步水热还原法制备了石墨烯水凝胶,通过定向冷冻和常规冷冻两种冷冻方法,冷冻干燥后制得了两种不同结构的石墨烯气凝胶,在不同温度下进行热退火处理,采用真空辅助浸渍回填法制备了不同结构热退火石墨烯气凝胶/环氧树脂复合材料.研究结果表明,在石墨烯含量仅为0.16％(质量分数)下,16...     

纤维素纳米纤丝增强聚合物纳米复合材料的研究进展

纤维素纳米纤丝具有优异的力学性能和天然的纳米网状结构,在其增强的聚合物复合材料中发挥了重要作用。本文综述了纤维素纳米纤丝增强亲水性聚合物(酚醛树脂、聚乙烯醇、淀粉等)及非亲水性聚合物(环氧树脂、聚乙烯、聚乳酸等)复合材料的加工制备与主要性能。针对纤维素纳米纤丝制备成本高、与非亲水性聚合物结合强度低等关键问题,提出了开展进一步研究的建议。     

高性能石墨烯电磁屏蔽材料的研究进展

近年来,电磁干扰及电磁兼容问题日益加剧,严重危害军民领域仪器、仪表等电子设备的安全运行,亟待开发出新型高性能电磁屏蔽材料。石墨烯是一种新型的二维碳纳米结构材料,具有优异的物理与化学性能,为柔性、轻薄、服役性能好的电磁屏蔽材料设计提供了新的解决方案。从电磁屏蔽的基本原理出发,介绍了电磁波屏蔽和损耗的机理及能量转化方式。进一步对石墨烯电磁屏蔽材料进行了系统地分类与归纳,综述了近年来石墨烯电磁屏蔽材料的屏蔽效能和研究进展,对石墨烯电磁屏蔽材料面临的挑战和发展前景进行了展望。     

Preparation of hydroxyapatite/poly(methyl methacrylate) and calcium silicate/poly(methyl methacrylate) interpenetrating hybrid composites

Hydroxyapatite/poly(methyl methacrylate) (HAp/PMMA) and calcium silicate/poly(methyl methacrylate) (CS/PMMA) composites were prepared by interpenetrating bulk polymerization of methyl methacrylate (MMA) monomer in porous structures of HAp and CS. The porous HAp and CS templates were prepared by mixing their calcined powders with poly(vinyl alcohol) (PVA) solution, shaping by uniaxial pressing and then firing at 1,100 °C for HAp and 900 °C for CS. The templates were soaked in the solution mixture of MMA monomer and 0.1 mol% of benzoyl peroxide (BPO) for 24 h. The pre-composites were then bulk polymerized at 85 °C for 24 h under nitrogen atmosphere. The microstructures of the composites showed the interpenetrating of PMMA into the porous HAp and CS structures. Thermogravimetric analysis indicated that the PMMA content in the HAp/PMMA and CS/PMMA composites were 13 and 26 wt%, respectively. Weight average molecular weights ( ) of PMMA were about 491,000 for HAp/PMMA composites and about 348,000 for CS/PMMA composites. Compressive strengths of these composites were about 90–131 MPa in which they were significantly higher than their starting porous templates.     

Morphological,electrical, electromagnetic interference (EMI) shielding,and tribological properties of functionalized multi-walled carbon nanotube/poly methyl methacrylate (PMMA) composites

The functionalized multi-walled carbon nanotubes (MWCNTs) had been prepared via Friedel–Crafts acylation with maleic anhydride. X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) confirmed the functionalization of MWCNTs. The composites with maleic anhydride modified MWCNTs (Mah-g-MWCNTs) and poly (methyl methacrylate) were then prepared by the in situ and ex situ solution polymerization system. The Electromagnetic Interference (EMI) shielding effectiveness (SE) of Mah-g-MWCNTs/PMMA composites increased with the increasing of the Mah-g-MWCNTs content, and the in situ system shows higher EMI SE value. The wear resistance was enhanced while the loading of the Mah-g-MWCNTs was above the percolation threshold, and the in situ system provides higher efficiency than that of ex situ system.     

Reduced graphene oxide deposited carbon fiber reinforced polymer composites for electromagnetic interference shielding

Reduced graphene oxide deposited carbon fiber (rGO-CF) was prepared by introducing GO onto CF surface through electrophoretic deposition method, following by reducing the GO sheets on CF with NaBH₄ solution. The rGO-CF was found to be more effective than CF to improve the electromagnetic interference (EMI) shielding property of unsaturated polyester (UP) based composites. With 0.75% mass fraction of rGO-CF, the shielding effectiveness of the composite reached 37.8 dB at the frequency range of 8.2–12.4 GHz (x-band), which had 16.3% increase than that of CF/UP composite (32.5 dB) in the same fiber mass fraction. The results suggest that rGO-CF is a good candidate for the use as a light-weight EMI shielding material.     

三维结构石墨烯气凝胶/环氧树脂复合材料的制备和电磁屏蔽性能

以三维结构的石墨烯气凝胶为填料,通过真空浸渍的方法,将环氧树脂浸入并固化,制备石墨烯气凝胶/环氧树脂复合材料.利用FT-IR,XPS和XRD等测试手段,研究制备过程和炭化处理中石墨烯气凝胶的化学结构变化.实验结果表明:氧化石墨烯和聚酰胺酸,通过物理吸附的方式,形成石墨烯气凝胶.300℃热处理使得聚酰胺酸亚胺化成聚酰亚胺,氧化石墨烯得到部分还原.随着炭化温度的提高,石墨烯气凝胶中的石墨烯片层还原程度越高,聚酰亚胺炭化程度越高.与此同时,扫描电镜和光学显微镜结果表明,炭化处理和真空浸渍后,石墨烯气凝胶仍然可以保持良好的三维网络结构.在此基础上,石墨烯气凝胶作为导电填料,利用其三维网络结构,使得对应的复合材料具有良好的导电性能和电磁屏蔽性能.在石墨烯气凝胶含量仅为6.23％(质量分数)时,复合材料的电导率就可以达到252 S·m-1,电磁屏蔽效能高达75 dB.     

Graphene oxide/ferrofluid/cement composites for electromagnetic interference shielding application

This paper deals with the preparation of graphene oxide-ferrofluid-cement nanocomposites to evaluate the electromagnetic interference (EMI) shielding effectiveness (SE) in the 8.2-12.4 GHz frequency range. It has been observed that incorporation of graphene oxide (30 wt%) along with an appropriate amount of ferrofluid in the cement matrix leads to a shielding effectiveness of 46 dB (>99% attenuation).The presence of graphene oxide and ferrofluid in the cement leads to strong polarizations and magnetic losses that consequently result in higher shielding effectiveness compared to pristine cement. The resulting nanocomposites have shown Shore hardness of 54 and dc conductivity of 10.40 S cm( - 1). SEM reveals the homogeneous dispersion of graphene oxide and ferrofluid in the cement matrix.     

纳米氧化石墨烯/聚丁二酸丁二醇酯复合材料的制备与性能

以天然石墨为原料,利用改进的HUMMERS'法制备了氧化石墨烯(GO);采用原位复合方式制备了纳米氧化石墨烯/聚丁二酸丁二醇酯(GO/PBS)复合材料,并对其性能进行了研究。结果表明:适量GO的加入能更有效地加快GO/PBS复合材料的结晶速度;GO的加入,提高了GO/PBS复合材料的力学性能和酶降解速率;随着GO添加量的增加,复合材料晶体尺寸减小,GO起到了成核剂的作用。     

Segregated poly(vinylidene fluoride)/MWCNTs composites for high-performance electromagnetic interference shielding

Conductive polymer composites (CPCs) that contain a segregated structure have attracted significant attentions because of their promising for fulfilling low filler contents with high electromagnetic interference (EMI) properties. In the present study, segregated poly(vinylidene fluoride) (PVDF)/multi-walled carbon nanotubes (MWCNTs) composites were successfully prepared by mechanical mixing and hot compaction. The PVDF/MWCNTs samples with 7 wt% filler content possess high electrical conductivities and high EMI shielding effectiveness (SE), reaching 0.06 S cm⁻¹ and 30.89 dB (in the X-band frequency region), much higher than lots of reported results for CNT-based composites. And the EMI SE greatly increased across the frequency range as the sample thickness was improved from 0.6 to 3.0 mm. The EMI shielding mechanisms were also investigated and the results demonstrated absorption dominating shielding mechanism in this segregated material. This effective preparation method is simple, low-cost, and environmentally-friendly and has potential industrial applications in the future.     

Polymer/carbon based composites as electromagnetic interference (EMI) shielding materials

The extensive development of electronic systems and telecommunications has lead to major concerns regarding electromagnetic pollution. Motivated by environmental questions and by a wide variety of applications, the quest for materials with high efficiency to mitigate electromagnetic interferences (EMI) pollution has become a mainstream field of research. This paper reviews the state-of-the-art research in the design and characterization of polymer/carbon based composites as EMI shielding materials. After a brief introduction, in Section 1, the electromagnetic theory will be briefly discussed in Section 2 setting the foundations of the strategies to be employed to design efficient EMI shielding materials. These materials will be classified in the next section by the type of carbon fillers, involving carbon black, carbon fiber, carbon nanotubes and graphene. The importance of the dispersion method into the polymer matrix (melt-blending, solution processing, etc.) on the final material properties will be discussed. The combination of carbon fillers with other constituents such as metallic nanoparticles or conductive polymers will be the topic of Section 4. The final section will address advanced complex architectures that are currently studied to improve the performances of EMI materials and, in some cases, to impart additional properties such as thermal management and mechanical resistance. In all these studies, we will discuss the efficiency of the composites/devices to absorb and/or reflect the EMI radiation.     

Characterization and properties of in situ emulsion polymerized poly(methyl methacrylate)/graphene nanocomposites

Poly(methyl methacrylate) (PMMA)/graphene nanocomposites were prepared by in situ emulsion polymerization. Raman and Fourier transform infrared spectra showed that PMMA polymer contained partially reduced graphite oxide. Dynamic mechanical analysis and differential scanning calorimetry analysis showed that graphene in the PMMA matrix acted as reinforcing filler; it enhanced the storage moduli and glass transition temperatures of the nanocomposites. Thermogravimetric analysis showed that the thermal stability of the nanocomposites increased by ca. 35 °C. The electrical conductivity of nanocomposite with 3 wt.% graphite oxide was 1.5 S m⁻¹ at room temperature.