Automotive and aerospace industries require new lightweight materials that enhance payload and improve efficiency via vehicle weight reduction. Employing composites, such as fiber-reinforced polymers, is a common approach to reducing vehicle component weight. In this work, we examine the use of atomic layer deposition (ALD) to alter the interfacial chemistry in cellulose-reinforced epoxy composites. As produced, most cellulosics are hydrophilic and immiscible in industrially relevant hydrophobic polymers. In this study, a variety of ALD-derived surface modification schemes are explored to improve resin permeation within a fibrous, cellulose-based paper preform and to increase interfacial adhesion between the epoxy and the cellulose preform. Specifically, we consider surface modification of the cellulose paper with the ALD precursors trimethylaluminum (TMA) and titanium tetrachloride (TiCl₄) with a water oxidant to form aluminum oxide and titanium oxide-based surface chemistries. Few cycle ALD treatments (2-cycles) combined with an additional post-deposition heating step are found to make the cellulose preforms more hydrophobic. X-ray photoelectron spectroscopy verifies the presence of the metal oxide surface treatments and points towards high concentration of adsorbed adventitious carbon as the source for surface hydrophobicity. Tensile testing of laminated epoxy composites made from these cellulosic preforms indicates two mechanical property regimes depending on surface treatment: (1) high toughness and high strain for preforms that underwent only an ALD coating and (2) high modulus and high strength for preforms ALD coated and then heated at 120 °C in air. ALD treatments resulted in an 80% increase in toughness and a 47% increase in strain at break. ALD treatments with post-deposition heating resulted in a 16% increase in the elastic modulus and a 27% increase in the ultimate tensile strength. Here we propose a combination of cellulose/epoxy mechanical interlocking and interfacial adhesion as mechanisms to explain the difference in mechanical properties of the explored composites.

汽车和航空航天业需要新型轻质材料，这些材料可减轻车辆重量，从而增加有效负载并提高效率。采用复合材料，例如纤维增强的聚合物，是减轻车辆部件重量的常用方法。在这项工作中，我们研究了使用原子层沉积（ALD）来改变纤维素增强环氧复合材料的界面化学。生产时，大多数纤维素是亲水性的，不能与工业上相关的疏水性聚合物混溶。在这项研究中，探索了多种ALD衍生的表面改性方案，以改善纤维基，纤维素基纸预成型件中的树脂渗透性，并提高环氧树脂和纤维素预成型件之间的界面粘合力。特别，₄）与水氧化剂形成氧化铝和氧化钛基表面化学物质。很少有ALD循环处理（2个循环）与附加的沉积后加热步骤相结合，可以使纤维素预成型件具有更大的疏水性。X射线光电子能谱验证了金属氧化物表面处理的存在，并指出高浓度的吸附不定碳作为表面疏水性的来源。由这些纤维素预成型件制成的层压环氧复合材料的拉伸测试表明，取决于表面处理的两种机械性能范围：（1）仅进行ALD涂层的预成型件的高韧性和高应变；（2）ALD涂层的预成型件的高模量和高强度然后在空气中于120°C加热。ALD处理使韧性提高了80％，断裂应变提高了47％。沉积后加热进行的ALD处理使弹性模量增加了16％，极限抗拉强度增加了27％。在这里，我们提出了纤维素/环氧树脂机械互锁和界面粘合的组合作为解释所研究复合材料机械性能差异的机理。