碳纳米管（CNTs）是一类重要的一维碳质材料，由sp2/sp3杂化的碳原子构成，具有优异的电、力、光及热学特性。三维CNTs杂化材料具有相互连接的多孔结构、高的孔隙率、大的比表面积及高效的电子/声子传输通道，广泛应用于微电子、储能器件、导热材料及传感器等领域。目前，三维CNTs杂化材料的制备及性能研究已取得一定进展，常用的制备方法包括磁控溅射法、化学气相沉积法和溶胶凝胶法，但这些制备方法存在工艺比较复杂、成本昂贵等缺点。因此，寻找简便有效的方法制备结构和形貌可控的三维CNTs杂化材料，研究其组装机理及性能，对扩展CNTs的应用领域具有重要意义。本文以碳纳米管为基本构筑单元，通过不同组装方法制备了结构可控的三维CNTs杂化材料，并研究其组装机理、性能和应用。主要研究工作如下：1. 三维氮掺杂碳纳米管（N-CNTs）海绵的制备及性能研究。本文通过混合酸氧化N-CNTs得到了水溶性的N-CNTs，然后采用冰模板法制备了三维N-CNTs海绵。该制备方法简单易行，并且可以通过控制冷冻温度实现海绵内部结构的调控。制备的N-CNTs海绵不仅具有低密度和高柔性，而且在不同形变下的I-V曲线呈非线性。通过控制N-CNTs海绵的机械形变实现了对其电阻的控制，可用于应变传感器。2. 共价键连接的三维N-CNTs/Ag杂化海绵的制备及性能研究。为提高N-CNTs海绵的机械稳定性和其电阻对形变的灵敏度，本文采用超支化聚缩水甘油醚（HPG）作为桥梁将酸化的N-CNTs进行连接，同时HPG作为模板吸附Ag+，经过原位还原得到共价键连接的N-CNTs/Ag杂化粒子。N-CNTs/Ag杂化粒子通过冰模板法制备了柔性三维共价键连接的N-CNTs/Ag海绵，同时海绵内部孔径尺寸可通过冷冻温度进行调控。共价键作用提高海绵在压缩、振荡及弯曲形变下的结构稳定性，银纳米颗粒犹如联锁的纳米凸点增加海绵在形变过程中的接触面积。共价键和银纳米颗粒的协同作用使海绵在多次循环形变下保持高的稳定性和灵敏度，可用于应变传感器。3. 金字塔形状N-CNTs/Ag杂化海绵的制备及性能研究。进一步提高N-CNTs/Ag海绵电阻对形变的灵敏度，本文通过冰模板法制备了金字塔形状的N-CNTs/Ag海绵。制备过程涉及等级结构设计，包括纳米尺度上杂化粒子的设计，微米尺度上多孔材料的设计，宏观尺度上金字塔形状的设计。根据逾渗理论调控海藻酸钠和N-CNTs/Ag两者的比例，实现了杂化海绵在应变作用下电阻的突变，3%应变下的灵敏度最高达15。通过上端电极结构设计和金字塔形状海绵/聚二甲基硅氧烷复合材料的结构设计，证实了铜箔电极和导电海绵界面间的接触电阻在金字塔形状海绵的高灵敏度方面发挥主导作用。对金字塔形状海绵进行封装不仅提高海绵的机械稳定性，而且降低其在压缩过程中的能量损耗和塑性形变。4. 多功能氮掺杂碳纳米管基三维多孔材料的制备及性能研究。为丰富N-CNTs基多孔材料的功能性，通过层层自组装技术制备了多功能的三维多孔N-CNTs杂化材料（CHAs）。其中超支化聚酰胺胺可分散、稳定不同结构的功能性纳米粒子，提供阳离子层；海藻酸钠作为粘结剂将酸化的N-CNTs粘结在聚氨酯表面，提供阴离子层；聚氨酯海绵作为基体可有效地将CHAs受到的力转移到海绵骨架中。通过控制层层自组装的层数，得到了性能可控的CHAs。制备的CHAs具有高柔性、对功能性纳米粒子高的粘结力及优异的电阻-形变稳定性，可用于柔性导体、应变传感器和催化领域。5. 多功能折叠结构单壁碳纳米管（SCNTs）复合纸的制备及性能研究。三维多孔材料受到足够大的载荷压缩，其内部骨架发生滑移且不能恢复，形成纸状结构。受此启发，本文通过高速剪切分散-冷冻干燥-压缩成型的技术制备了多功能折叠结构的单壁碳纳米管复合纸。内部的折叠多孔结构，使制备的复合纸在多次拉伸弯曲和压缩弯曲过程中展现出优异的电阻-形变稳定性；同时利用折叠纸的隔间结构吸收储存石蜡制备相变材料，实现水滴在其表面接触角的控制。

Carbon nanotubes (CNTs), as important one-dimensional carbon materials, are composed of sp2/sp3-hybridized carbon atoms and possess fascinating electronic, mechanical, optical and thermal properties. Three-dimensional (3D) CNTs hybrid structures possess interconnected pores, high porosity, large specific surface area and exceptional transport channel of phonon/charge carriers, and are widely applied in the fields of microelectronics, energy storage, heat transfer, and sensor. Despite numerous advances in preparation and properties of 3D CNTs hybrid structures, the preparation processes, such as magnetron sputter deposition, chemical vapor deposition, and sol-gel method, are pretty complexed and expensive. Herein, it is highly desirable to develop simple and effective methods to assemble CNTs to form 3D porous hybrid architectures with controlled structure and morphology, and to investigate their assembly mechanism and properties, which plays an important role in enriching the applications of CNTs. In the work, CNTs as basic building blocks, are assembled into 3D hybrid architectures with controlled structure via different assembling approaches, and their corresponding assembling mechanism, properties and applications are also investigated. The main work is summarized as follows:1. Preparation and properties investigation of 3D N-doped CNTs (N-CNTs) sponges. N-CNTs are oxided in the mixture of H2SO4/HNO3 to be water-soluble, then 3D N-CNTs sponges are fabricated via ice template. The route is simple and feasible to control the structure in sponges via tuning the freezing temperature. The as-prepared sponges possess low density and high flexibility, and also exhibit nonlinear current-voltage (I-V) characteristics. Moreover, the sponges possess various electric resistance under different strains, which could be employed as strain-gauge sensors. 2. Preparation and properties investigation of covalently bonded 3D N-CNTs/Ag hybrid sponges. To enhance the mechanical stability and strain-sensitivity of N-CNTs based sponges, we develop a versatile method of introducing covalent linkage between individual N-CNTs utilizing hyperbranched polyglycerol (HPG) as bridges and decorating the N-CNTs with Ag nanoparticles (NPs) using HPG as templates simultaneously, which gives rise to covalently bonded N-CNTs/Ag hybrids. The resultant hybrids are assembled into covalently bonded sponges by ice template, and the pore size of the sponges could be controlled via freezing temperature. The covalent bonding endows the sponges with structural stability under compression, oscillation, and bending modes; and the Ag NPs on the compartmental films can be considered as interlocked nanodomes to generate huge variation of contact area under mechanical deformation. These novel designs featuring interlocked geometry and covalent bonding allow the hybrid sponges to possess excellent stability and sensitivity as strain-gauge sensors. 3. Preparation and properties investigation of pyramidal N-CNTs/Ag sponges. To further enhance the strain-sensitivity of N-CNTs/Ag sponges, pyramidal N-CNTs/Ag hybrid sponges are fabricated via ice template. The key novelty is to tune hierarchical structure, which includes nanostructure (design of N-CNTs/Ag hybrids), microstructure (design of porous sponges) and macrostructure (design of pyramidal shape). According to percolation theory, the resistance mutation of sponges could be achieved via tuning the ratio between the conductive fillers and alginate, and the gauge factor (GF) is 15 under strain of 3%. The high sensitivity mainly originates from the contact resistance between the interfaces of conductive sponge and copper electrode, which is confirmed by top electrode design and structure design of sponges/polydimethylsiloxane (PDMS), respectively. Encapsulated sponges not only possess robust mechanical stability, but also have low energy dissipation and plastic deformation under compression.4. Preparation and properties investigation of multifunctional porous N-CNTs hybrid architectures (CHAs). To enrich the multifunctionality of CHAs, layer-by-layer (LbL) assembly is employed to incorporate various functional nanomaterials with N-CNTs into such 3D porous CHAs. The key novelty to assemble such binary CHAs lies in synthesis of hyperbranched polyamidoamine as surfactant and cationic layer for immobilizing various nanostructured materials, selection of alginate bonding oxided N-CNTs as anionic layer, and selection of polyurethane (PU) sponges as skeletons tranferring load from CHAs to PU skeletons under deformation. The properties of CHAs could be tuned via controlling the number of deposited layer. The as-prepared CHAs possess high flexibility, strong adhesion to functional nanoparticles, and excellent resistance-strain stability, so that they could be employed as flexible conductors, strain-gauge sensors and heterogeneous catalysts, respctively. 5. Preparation and properties investigation of multifunctional folded structured single-walled CNTs (SCNTs) hybrid paper. Sponges could be transformed into paper-like architectures when enough load is applied to prevent the recovery of skeletons in sponges. Inspired by the structure changes, multifunctional folded SCNTs-based papers are developed via a series of processes including homogenizing-freeze drying-compression technique. The folded porous structure enables the SCNTs hybrid papers to possess excellent electric resistance-strain stability during tension and compression bending process. Meanwhile, the compartmental structure absorbs paraffin to obtain phase-change composites, on which the contact angle of water could be controlled.