高压匀质处理对纳米纤维素自聚集特性及气凝胶结构的影响

 木材细胞壁的重要组成部分是许多直径在纳米尺度、具有高长径比、高比表面积和丰富表面基团的纤维素分子聚集体。基于“自下而上”的思想，利用层层分离法从木粉中分离出纳米尺度的基元纤丝。首先，通过化学和超声预处理并结合高压匀质处理的方法从木材中分离制备出纳米纤维素（CNF）；然后，通过冷冻干燥的方法将CNF 进一步组装加工成纳米纤维素气凝胶。研究发现，超声结合匀质的方法，可得到均匀纤丝化的CNF，具有低直径尺寸分布（纤丝直径为1～3 nm）和高长径比特征，但氢键作用的影响使得单根纤丝又易重构为簇、带状的聚集体形式。随着CNF 溶液浓度的增大，所形成的气凝胶密度增大，孔隙度降低，结构由以纤维为主，转变为纤丝交织的片层结构。本研究所得的气凝胶可广泛应用于包装、生物医药、吸附材料等领域。

Influence of High Pressure Homogenization on Self-aggregation and Formation of Aerogel Structure from Nanocellulose

Cellulose molecule aggregates are an important component of the cell wall of timber. They have diameters at the nanometer scale, high aspect ratio, high specific surface area and rich surface groups. This article is based on "bottom-up" academic thought, and layer-by-layer separation of the wood powder is used to prepare microfibril. By chemical pretreatment, high-intensity ultrasound treatment and high-pressure homogenization treatment, cellulose nanofiber (CNF) was isolated from the cell walls of wood cellulose, and CNF was further assembled into aerogels by freeze-drying method. The results show that by combining high-intensity ultrasonication and high-pressure homogenization, uniform CNF with diameters within 1 and 3 nm and their bundles and stripes can be obtained. The aerogels possess a network structure formed by nanofibers or their interwoven sheets.