Growth of carbon nanotubes on clay: Unique nanostructured filler for high-performance polymer nanocomposites
Growth of carbon nanotubes on clay: Unique nanostructured filler for high-performance polymer nanocomposites
复制标题
DOI：
10.1002/adma.200501217
复制
发表时间：
2006-01-05
影响因子：
29.4
通讯作者：
Liu, TX
中科院分区：
文献类型：
--
作者：
Zhang, WD;Phang, IY;Liu, TX
粘土矿物具有层状结构，单位层厚约1纳米，尺寸从几纳米到几微米不等。每一层都是由四面体配位的硅原子熔合成氧化铝或氧化镁的八面体共边平面形成的。作为一种天然产物，粘土可以低成本获得大量的粘土，并已被广泛应用。粘土由于比表面积大、酸性强、吸附和离子交换能力强，多年来一直被广泛用作催化剂和催化载体。[1-3]例如，粘土负载的氧化钴是脱NOx反应的催化剂，[4]而粘土负载的氧化铁被用作费托催化剂。[5]已经证明，负载在氧化物上的铁、镍或钴纳米粒子是化学气相沉积(CVD)合成碳纳米管(CNTs)的有效催化剂。[6]自然，粘土也被用作催化CVD生长碳纳米管的载体。[7，8]此外，粘土小片是典型的二维(2D)纳米填料，用于结合到聚合物基质中，这在过去几十年中得到了深入的研究。[9-11]碳纳米管作为一维(1D)纳米材料，也被认为是制备聚合物纳米复合材料的理想增强填料，因为它们具有极高的机械强度和高的电导和热导率。[12-16]对于一维和二维纳米颗粒，最重要的问题是在聚合物基质中的均匀分散和与基质的强相互作用，从而使所获得的纳米复合材料具有纳米填料的固有性质。人们对粘土在聚合物基质中的插层和剥离进行了大量的研究[9-11]，同时也对碳纳米管在聚合物基质中的改性和分散进行了大量的研究。[17-19]在这里，我们展示了利用粘土负载的铁纳米颗粒作为碳纳米管生长的催化剂，然后将所制备的碳纳米管-粘土杂化纳米膜掺入尼龙-6(PA6)中以制备尼龙-6(PA6)/CNT-粘土复合材料。结果表明，在化学气相沉积过程中，由于铁离子插层到粘土层间以及碳纳米管在粘土片上的生长，粘土发生了膨胀剥离。所制备的碳纳米管-粘土杂化材料由一维纳米粘土片和多个一维纳米管组成，通过简单的熔融共混，有效地促进了粘土片和纳米管在聚合物中的均匀分散。这种方法大大简化了制备具有更好力学性能的聚合物纳米复合材料的整个过程。图1描述了制造纳米填料和聚合物纳米复合材料的过程。首先，用Fe(NO3)3溶液对钠基蒙脱土(Na+MMT)进行浸渍改性。Fe3+离子插层到蒙脱石的层间，经焙烧后转变为Fe2O3颗粒。在CVD生长碳纳米管的过程中，Fe_2O_3颗粒被原位还原为Fe颗粒，为碳纳米管的生长提供了种子。随着碳纳米管的生长，黏土的小片进一步分层，形成了由2D纳米黏土小片和几个附着的纳米管组成的3D纳米结构。将得到的碳纳米管-粘土杂化材料直接作为填料加入尼龙6中，采用熔融共混法制备了尼龙6/碳纳米管-粘土纳米复合材料。Na+蒙脱土及其衍生样品的X射线衍射图如图2所示：…
Clay minerals have a layered structure with unit layers about 1 nm thick and sizes ranging from several nanometers to several micrometers. Each layer is formed of tetrahedrally coordinated Si atoms fused into an edge-sharing octahedral plane of either alumina or magnesia.[1] As a natural product, clay can be obtained in large amounts at low cost and has been used for a wide range of applications. Because of its large surface area, strong acidity, and strong adsorption and ion-exchange ability, clay has been widely used as a catalyst and catalytic support for years.[1–3] For example, clay-supported cobalt oxide is the catalyst for the de-NOx reaction,[4] while clay-supported iron oxide has been used as a Fischer–Tropsch catalyst.[5] As has been demonstrated, iron, nickel, or cobalt nanoparticles supported on oxides are efficient catalysts for the synthesis of carbon nanotubes (CNTs) by chemical vapor deposition (CVD), which has proven to be a cost-efficient way of mass producing CNTs.[6] Naturally, clay has also been used as the support for catalytic CVD growth of CNTs.[7, 8] In addition, clay platelets are typical two-dimensional (2D) nanofillers for incorporation into polymeric matrices, which have been intensively studied in the past few decades.[9–11] Carbon nanotubes, as one-dimensional (1D) nanomaterials, have also been considered as ideal enhancement fillers for making polymer nanocomposites because of their extremely high mechanical strength and high electrical and thermal conductivity.[12–16] For both 1D and 2D nanofillers, homogeneous dispersion in polymeric matrices and strong interactions with the matrices—so as to enhance the as-obtained nanocomposites with the intrinsic properties of the nanofillers—are the most important issues. Much effort has been made in study of intercalation and exfoliation of clay in polymeric matrices,[9–11] while many studies have also been conducted on modification and dispersion of CNTs for incorporation in polymeric matrices.[17–19] Here we demonstrate the use of clay-supported iron nanoparticles as a catalyst for the growth of CNTs followed by incorporation of the as-prepared CNT–clay hybrid nanofillers into a nylon-6 (PA6) matrix to make PA6/CNT–clay composites. The results indicate that the clay has been swollen and exfoliated by the intercalation of iron ions into the clay interlayers and the growth of CNTs on the clay platelets by CVD. The as-prepared CNT–clay hybrid, which is the combination of a 2D nanoclay platelet and several 1D nanotubes, effectively promotes the homogeneous dispersion of both clay platelets and nanotubes in the polymeric matrix by simple melt blending. This method greatly simplifies the overall procedure for preparation of polymer nanocomposites with improved mechanical properties. Figure 1 depicts the procedure for making the nanofiller and the polymer nanocomposites. Firstly, the sodium montmorillonite (Na+MMT) was modified by impregnation with a Fe (NO3) 3 solution. Fe3+ ions were intercalated into the layers of montmorillonite and changed to Fe2O3 particles by calcination. During CVD growth of CNTs, the Fe2O3 particles were reduced to Fe particles in situ, which served as seeds for the growth of CNTs. The platelets of the clay were further delaminated as the CNTs grew on them, forming a 3D nanostructure consisting of a 2D nanoclay platelet and several attached nanotubes. The obtained CNT–clay hybrid was directly used as a filler by being incorporated into PA6 for preparation of PA6/CNT–clay nanocomposites by melt-blending. The X-ray diffraction (XRD) patterns of the Na+MMT and the samples derived from Na+MMT are shown in Figure 2 …