磁性材料包覆碳纳米螺旋的原子层沉积方法及其吸波性能研究

Chiral material is a research focus of microwave absorbing materials. Carbon nanocoils are representative chiral materials with many advantages such as light weight, high electrical conductivity and good stability, thus much attention has been attached to them. However, carbon nanocoils show dominantly dielectric loss, and very low magnetic loss due to weak magnetic properties. Therefore, it is quite necessary to incorporate them with magnetic materials, to improve impedance matching, increase the magnetic loss, broaden the absorption bandwidth, and enhance absorption. Traditional coating methods have no good control over coating quality and thickness of produced films. Atomic layer deposition (ALD) has outstanding advantages in deposition process, conformal thickness, and precise thickness control. In this project ALD will be applied to coat carbon nanocoils with magnetic films. The effect of coating material type, thickness, and deposition conditions etc. on the magnetic properties, permittivity, permeability, and microwave absorbing performance of the coated samples will be investigated. The key factors affecting the microwave absorbing properties will also be studied. A protective layer will be deposited by ALD on the magnetic coatings to study its influence on the stability of magnetic coatings. Theoretical calculation of microwave absorbing properties of the coated samples will be conducted. Chiral parameter of the carbon nanocoils will be determined by fitting and comparing the measured values with the calculated ones. The absorbing mechanism of the carbon nanocoils will be discussed. These investigations will lead to reasonable understandings for the microwave microwave-absorbing performance of the coated nanocoils, provide important theoretical basis for the design of new chiral microwave-absorbing nanomaterials with light weight, high efficiency, broad bandwidth, and good stability, and promote this research to generate an important progress.

手征材料是吸波材料的研究热点。碳纳米螺旋具有手征性、质轻、导电和稳定性好等优点，因而受到高度重视。但由于其基本无磁性，主要体现介电损耗，磁损耗很小，因此很有必要与磁性材料复合，以改善阻抗匹配、增加磁损耗、拓宽频带及提高吸收。传统包覆方法对包覆质量和厚度很难进行有效控制。原子层沉积（ALD）在沉积工艺、均匀性、厚度控制等方面具有突出优势。本项目将利用ALD 包覆磁性材料于碳纳米螺旋表面。研究包覆材料种类、厚度、沉积条件等因素对复合物磁性、介电常数、磁导率以及吸波性能的影响，找出影响吸波性能的关键因素。利用ALD 对磁性包覆层添加保护层，研究其对磁性层稳定性的影响。对吸波性能进行理论计算并与实测值对比拟合，对包覆产物的手征参数进行标定，并探讨吸波机理。通过这些研究得到高效的手征纳米复合吸波材料，为设计轻质、高效、宽频、稳定性好的新型手征纳米吸波材料提供理论依据，促进此领域的研究取得突破性进展。

手征材料是吸波材料的研究热点。碳纳米螺旋具有手征性、质轻、导电和稳定性好等优点，因而受到高度重视。但由于其基本无磁性，主要体现介电损耗，磁损耗很小，因此很有必要与磁性材料复合，以改善阻抗匹配、增加磁损耗、拓宽频带及提高吸收。传统包覆方法对包覆质量和厚度很难进行有效控制。原子层沉积（ALD）在沉积工艺、均匀性、厚度控制等方面具有突出优势。本项目从微波吸收的原理入手，利用原子层沉积，将磁性材料与碳材料很好地复合在一起，开发出了一系列具有优异吸波性能的吸波材料，并得到规律性的认识。本项目利用ALD制备了窄尺寸分布的Cu纳米粒子，能够催化生长接近100%纯的碳纳米螺旋。基于实验和计算结果，详细探讨了不同碳纳米结构对催化剂尺寸依赖的生长机理。利用ALD，将Fe3O4、Ni等磁性材料与石墨烯、ZnO等材料复合在一起，可通过控制磁性纳米粒子尺寸及其分布，有效调控复合材料的电磁参数，获得高效的吸收性能。我们还制备了磁性纺锤体-导电聚合物的复合吸波材料，以及Ni-Al2O3-ZnO同轴多界面纳米线吸波材料，并深入研究了复合材料的电磁损耗机理，这些复合材料均表现出优异的吸波性能。此外，利用ALD，制备磁性和非磁性多层交替膜包覆的碳纳米螺旋复合材料，展现出优异的吸波性能，可归因于有效的阻抗匹配、交替多层纳米结构和复合材料的螺旋形貌以及磁性组分高效的磁损耗。同时，我们制备了导电性从外到内逐渐增加的五层梯度复合膜包覆碳纤维的核壳结构吸波材料，并可通过调控梯度膜的单层厚度对吸收性能进行精确调控。