硼酸锌晶须的晶面调控对改性效果的影响研究

Whiskers are one-dimension single crystal materials with specific length-diameter ratios, which have been widely used as strengthening and toughening materials in composites due to their perfect crystal structures and high length-diameter ratios. Surface modifications are required before whiskers are added into composites. Effective surface modifications can be achieved through studying the interactions between different exposed faces of whiskers and different functional groups of modifiers. This proposal is aimed to study Zinc borate whiskers with a formula of 4ZnO•B2O3•H2O. Firstly, theoretical simulation will be proposed to speculate the acting model and absorption ability of inorganic ions onto different exposed faces of whiskers, and the stabilities of different organic groups combining different crystal faces. Secondly, 4ZnO•B2O3•H2O whiskers with controlled morphology are scheduled to be hydrothermally synthesized with the 2ZnO•3B2O3•7H2O as starting material and inorganic ions as crystal face controller. And the crystal faces are chemically tailored through the study of the effect of inorganic ions on the growth of 4ZnO•B2O3•H2O whiskers with different exposed faces. Finally, modifiers with different functional groups will be chosen according to the properties of different exposed faces, and the modified whiskers are characterized before added into the polypropylene composites. Modification effect will be evaluated through testing the mechanical performance of composites.

晶须是具有一定长径比的单晶，因其近乎完整的晶体结构和长径比高的特点，是一种优秀的补强增韧材料。研究表明，对于实现复合材料的增强，晶须的表面改性是关键，针对不同暴露晶面的物化性质有针对性地选择改性官能团进行匹配性研究是解决问题的有效途径。本项目以4ZnO•B2O3•H2O晶须为研究对象，通过理论模拟计算，推测无机配体离子在不同暴露晶面的作用方式、吸附能力及不同有机官能团在晶面结合的稳定性；以2ZnO•3B2O3•7H2O为原料，无机配体离子为晶面调控剂，水热法制备出形貌可控的4ZnO•B2O3•H2O晶须；研究微量无机配体离子诱导作用下，4ZnO•B2O3•H2O晶须不同暴露面生长的规律性，实现特定生长晶面的化学裁剪；同时，根据晶须不同暴露面的物化性质，选择不同改性剂进行匹配性及改性研究，对改性后的晶须进行测试、表征，通过聚丙烯复合材料的制备及力学性能的测试对改性效果进行评价、反馈。

本项目以2ZnO•3B2O3•7H2O为原料通过一步水热法制备了形貌均一的4ZnO•B2O3•H2O晶须，研究了不同无机离子对4ZnO•B2O3•H2O晶须水热形貌及暴露晶面的影响。试验发现，SO42 –的加入能有效调控晶须的长径比和暴露晶面。当无SO42 –加入时，晶须长径比仅为20，晶面暴露面为(30-1)、(0-10)和(103)；当SO42加入量为0.012 mol∙L-1时，晶须长径比可达100以上，晶面暴露面为(-101)、(101)和(010)。同时，通过水热调控的方式，制备出了长径比大致相同，暴露晶面不同的4ZnO•B2O3•H2O晶须用以开展晶须--PP复合材料的制备及力学性能测试研究工作。试验发现，晶面暴露为(-101)、(101)、(010)的晶须复合材料力学性能优于暴露面为(30-1)、(0-10)、(103)的晶须复合材料。. 利用硼酸盐溶液在不同条件下可以缩聚、解聚的特点，设计了晶须母液循环利用方案，制备了形貌均匀的2ZnO•3B2O3•7H2O、3ZnO•5B2O3•14H2O和4ZnO•B2O3•H2O，并探讨了晶体生长机理，为晶须的规模生产奠定了基础。. 根据Zn2(BO3)(OH)0.75F0.25与4ZnO•B2O3•H2O晶体具有相同空间结构及相似晶胞参数的特点，用OH对F进行化学计量取代，构建了4ZnO•B2O3•H2O晶体的空间模型，并模拟计算了-OH，-COOH、-SH在(-101)晶面的吸附行为，研究了不同基团在(-101)晶面的优先吸附能力的大小。