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Thin Films for Coating Nanomaterials

机译:涂料纳米材料薄膜

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For nano-structured solids (those with one or more dimensions in the 1-100 nm range), attempts of surface modification can pose significant and new challenges. In traditional materials, the surface coating could be several hundreds nanometers in thickness, or even microns and millimeters. In a nano-structured material, such as particle or nanofibers, the coating thickness has to be substantially smaller than the bulk dimensions (100 nm or less), yet be durable and effective. In this paper, some aspects of effective nanometer scale coatings have been discussed. These films have been deposited by a non-line of sight (plasma)techniques; and therefore, they are capable of modifying nanofibers, near net shape cellular foams, and other high porosity materials. Two types of coatings will be focused upon: (a) those that make the surface inert and (b) those designed to enhance surface reactivity and bonding. The former has been achieved by forming 1-2 nm layer of -CF2- (and/or CF3) groups on the surface, and the latter by creating a nanolayer of SiO2-type compound. Nucleation and growth studies of the plasma-generated film indicate that they start forming as 2-3 nm high islands that grow laterally, and eventually completely cover the surface with 2-3nm film. Contact angle measurements indicate that these nano-coatings are fully functional even before they have achieved complete coverage of 2-3 nm. They should therefore be applicable to nano-structural solids.This is corroborated by application of these films on vapor grown nanofibers of carbon, and on graphitic foams. Coated and uncoated materials are infiltrated with epoxy matrix to form composites and their microstructure, as well as mechanical behaviors are compared. The results show that the nano-oxide coating can significantly enhance bond formation between carbon and organic phases, thereby enhancing wettability,dispersion, and composite behavior. The fluorocarbon coating, as expected, reduces bond formation, and therefore, effective as an inert layer to passivate nanomaterials.
机译:对于纳米结构固体(一种或多种尺寸在1-100 nm范围内的固体),尝试进行表面改性可能会带来重大而又新的挑战。在传统材料中,表面涂层的厚度可能为数百纳米,甚至是微米和毫米。在诸如颗粒或纳米纤维的纳米结构材料中,涂层厚度必须基本上小于整体尺寸(100nm或更小),但要持久且有效。在本文中,已经讨论了有效的纳米级涂料的一些方面。这些薄膜是通过非视线(等离子)技术沉积的。因此,它们能够改性纳米纤维,近净形多孔泡沫和其他高孔隙率材料。两种类型的涂料将集中在:(a)使表面呈惰性的涂料和(b)为增强表面反应性和粘结性而设计的涂料。前者是通过在表面上形成1-2 nm的-CF2-(和/或CF3)基团来实现的,后者是通过形成SiO2型化合物的纳米层来实现的。对等离子体产生的薄膜的成核和生长研究表明,它们开始形成为2-3 nm高的岛,该岛横向生长,并最终完全被2-3 nm的薄膜覆盖。接触角测量表明,这些纳米涂层甚至在达到2-3 nm的完全覆盖率之前就具有完整的功能。因此,它们应适用于纳米结构固体。通过在气相生长的碳纳米纤维和石墨泡沫上使用这些薄膜可以证实这一点。涂覆的和未涂覆的材料都渗透有环氧树脂基体,形成复合材料,并比较了它们的微观结构和机械性能。结果表明,纳米氧化物涂层可以显着增强碳相与有机相之间的键形成,从而增强润湿性,分散性和复合性能。如所期望的,碳氟化合物涂层减少了键的形成,因此有效地用作钝化纳米材料的惰性层。

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