吸放氢循环法制备钯纳米线研究

Palladium nanowires are widely used in the fields of catalyst, sensor, nano device assembly and so on. At present, palladium nanowires are mainly synthesized by template method and solution-phase growth method. Although these methods mentioned above can be simple and straightforward, they are limited in producing large scale single-crystal nanowires, also the nanowires may be contaminated during the template removing operations. Single-crystal nanowires with a diameter of about 150 nm was prepared by thermal cycling absorption process (TCAP) of palladium particles, which was a new nanowire preparing methods that never reported else where. The nanowires produced by the method possess many advantages such as great length-diameter ratio and cleaness. Preliminary experiments revealed that the stress induced by hydrogen atoms dissolving into metal lattice could be a critical factor in nanowire growing, but the growth discipline and mechanism of the nanowire was unclear. In order to clarify the growth mechanism of palladium nanowires, hydrogen absorption/desorption cycles will be performed on micron scale palladium particles prepared by means of the dipping-reducing process using palladium salt solution and magnetron sputtering technique, respectively. Eventually, based on the characterization of palladium nanowires and the exploring of the growth conditions, the growth mechanism of palladium nanowires will be proposed. The results of this project will deepen the knowledge of hydrogen impacting on metal microstructures and properties, meanwhile provide a new route for preparing one-dimensional nanowires.

钯纳米线广泛应用于催化剂、传感器、纳米器件组装等领域。目前钯纳米线制备方法主要有模板法和液相生长法，以上方法具有简单直接的优点，但也存在无法制备大尺寸单晶纳米线、制备过程对材料存在污染等缺点。申请人以金属钯颗粒为原料采用热致吸放氢循环法制备了直径150μm的单晶钯纳米线，该方法是一种新型的钯纳米线制备方法，制备产物具有长径比大、清洁等优点。初步试验结果表明氢原子溶入导致的晶格应力是金属钯纳米线生长的关键因素，但纳米线生长规律和机理尚不明确。为了研究氢致纳米线生长机理，本项目拟采用钯盐浸渍还原法、磁控溅射法制备微尺度钯颗粒样品，并对其进行吸放氢实验。通过探索钯纳米线生长条件，表征纳米线微观组织结构，最终揭示钯纳米线生长机制。该项目研究结果可以深化氢对金属材料结构性能影响的认识，同时为金属一维纳米材料的制备提出新思路。

钯纳米线可以用于化工行业的催化过程、传感器、纳米电子器件等等。目前，钯纳米线主要采用模板法和液相生长方法。现有方法具有直接高效的特点，但是无法制备特定取向单晶纳米线，同时在模板去除等化学过程中，纳米产物会受到污染。本项目提出了一种新的钯纳米线制备方法，采用钯颗粒经历多次吸放氢循环后，制备出直径150纳米、长度数十微米的钯纳米线产物。该方法制备的纳米线具有长径比高、无污染等优点。为研究钯纳米线生成机制，项目开展了不同基体钯复合材料制备研究、钯颗粒形貌控制研究并对制备的纳米线进行了结构表征。研究结果表明，多孔材料分散可以减少钯纳米线在吸放氢过程中的烧结团聚，同时将钯制备成高度共格的再结晶结构可以促进纳米线的生长。对其他储氢合金的研究表明，纳米线生长现象并非储氢合金的共性特征。对纳米线生长机制的研究表明，金属钯吸放氢过程的可逆相变及伴随的相变内应力的循环出现是钯纳米线生长的内在驱动力，其生长模式应为底部萌生增长模式，最终生长的钯纳米线内存在大量位错缺陷。