Excellent Microwave Absorbing Property of Multiwalled Carbon Nanotubes with Skin–Core Heterostructure Formed by Outer Dominated Fluorination

Abstract

It is attractive that excellent microwave absorbing materials with novel structure are prepared. In this work, we present a novel skin–core strctured fluorinated multiwalled carbon nanotubes (MWCNTs) microwave absorbing material through selective fluorination of the outer shell of MWCNTs. Fluorine gas (F2) can attack defect sites to form CF2 at defect sites at low temperature. The preformed CF2 bond can prevent the permeation of F2 into inner tubes, bringing about the mere fluorination of the outer skin with inner tubes intact at high temperature (the sample is denoted as F-h-MWCNTs). As a result, composed of an outer insulating skin and inner conductive tubes, F-h-MWCNTs behave as a skin–core heterostructure and show excellent microwave absorbing property with minimal reflection loss up to −69 dB at a thickness of 1.5 mm when the filler loading is only 9.1 wt %. Based on the investigation of electromagnetic behavior of a fluorinated single-walled carbon nanotube (SWCNT), the strong microwave absorption capacity of F-h-MWCNTs was attributed to the skin–core heterostructure. The outer skin is a fluorinated layer behaving with good impedance matching, which is conducive to the transmission of electromagnetic waves. The inner tubes maintain intact after direct heating fluorination and show a strong ability of attenuating electromagnetic waves. Meanwhile, F-h-MWCNTs possess better dispersibility in epoxy, making F-h-MWCNTs a proper candidate to prepare advanced an composite with strong absorption and good mechanical property.

Improving Compressive Strength of Aramid Fiber by Introducing Carbon Nanotube Derivates Grafted with Oligomers of Different Conformations and Controlling Its Alignment

“…Based on previous research of our group, controlled fluorination of MWCNTs shell by two‐stage direct heating fluorination process can be realized, and FCNT with high fluorine content can be prepared . Element composition and structure of FCNT were characterized by XPS and TEM, as shown in Figure .…”

“…Then 80 kPa F 2 /N 2 mixture was injected into the chamber at 30 °C, followed by heating to 190 °C and keeping for 1 h. Afterward, it is was cooled to room temperature to get fluorinated FCNT. More details about the preparation process can be found in the author's previous paper …”

“…Fluorinated CNT (FCNT) is an emerging nanomaterial which owns excellent performance. The preparation condition is comparatively mild and CF bonds introduced after fluorination can serve as modification sites for other reactions . In this study, FCNT was prepared by direct fluorination to modify (Poly‐ p ‐phenylene‐benzimidazole‐terephthalamide) PBIA fibers.…”

A brief review for fluorinated carbon: synthesis, properties and applications

“…The demand for broadband microwave absorbing materials is increasing to prevent electromagnetic radiation from most modern electronic devices, such as computers and mobile phones. Due to their unique tubular nanostructure with extremely large aspect ratio, CNTs possess larger excluded volume, a smaller percolation threshold, and a lower additive amount, which endows CNTs with great potential as lightweight microwave absorbers [109].…”

Research on the Catalyst Used for Vertical Aligned Carbon Nanotube Arrays Prepared by Catalytic Chemical Vapor Deposition

“…碳纳米管中碳原子的σ-π再杂化使管外电子云密度 大大增加，从而赋予了碳纳米管优异的热、光、电和力学 等性质 [1]。垂直碳纳米管阵列(CNTAs)，是碳管垂直于基 底生长，形成平行紧密排列的宏观结构。阵列中的碳纳米 管具有较一致的长径比， 良好的取向、 较高的纯度等优点， 为碳纳米管以功能器件形式获得应用提供了可能,广泛地 应用于纳米电子器件 [2]， 超级电容器电极 [3]、 黑体材料 [4]、 吸波材料 [5]和热界面材料 [6]。另外，特殊的CNTAs可以 通过干法抽丝、抽膜直接形成连续的碳纳米管纤维或者薄 膜 [7,8]…”