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振动流化原子层沉积反应器微纳米颗粒的流化特性研究及包覆性能测试

Study on Fluidization Characteristics and Coating Performance of Micro-Nano Particles in a Vibration Fluidized Atomic Layer Deposition Reactor

  • 摘要: 原子层沉积可在亚纳米甚至更小尺度范围实现对微纳米颗粒表面的精准调控,但传统静态原子层沉积反应器很难实现大量微纳米颗粒的改性,针对该问题本文自主搭建了内径为26 mm、高为350 mm的振动流化原子层沉积反应器以实现微纳米颗粒的批量化精准改性。微纳米颗粒易团聚难流化,要实现均匀沉积首先需解决微纳米颗粒均匀流化的问题,本文选取粒径为20 nm的TiO2和SiO2颗粒以及粒径为600μm的树脂颗粒研究其在自制振动流化床反应器内的流态化行为。初始床层高度为15 mm时,由于聚团间黏性力的差异,稳定流化时TiO2床层压降较高、床层膨胀率低,为鼓泡流化,SiO2床层压降较低、床层膨胀率高,为散式流化。通过SiO2颗粒示踪流化实验推断纳米颗粒团聚体流化过程中处于不断破裂和聚并的动态变化中。振动能够改善纳米颗粒流化过程中的沟流、结块现象,促进聚团破碎,降低颗粒最小流化速度,有助于提升气固接触效率。为检验自制原子层沉积反应器对纳米颗粒的包覆性能,在最优流化条件下以TiCl4和H2O为前驱体,TiO2纳米颗粒为基底,80℃下原子层沉积得到致密、均匀的无定型TiO2薄膜屏蔽颜料TiO2的光催化活性,提升其耐候性。30次原子层沉积循环后,无定型TiO2薄膜厚度达3.11 nm,其光催化活性较锐钛型TiO2抑制了约90%,光催化活性屏蔽效果显著。实验结果说明自制振动流化原子层沉积反应器可实现微纳米颗粒的精准改性,具有良好的应用前景。

     

    Abstract: Atomic layer deposition can achieve precise control of the surface of micro-nano particles in the sub-nanometer or even smaller scale. However, it is difficult to achieve the modification of a large number of micro-nano particles in the traditional static atomic layer deposition reactor. In order to solve this problem, a vibration fluidized atomic layer deposition reactor with an inner diameter of 26 mm and a height of 350 mm was built in this paper to realize the batch and precise modification of micro-nano particles. Micro-nano particles are easy to agglomerate and difficult to fluidize. In order to achieve uniform deposition, it is necessary to realize the uniform fluidization of micro-nano particles first. In this paper, TiO2 and SiO2 particles with a particle size of 20 nm and resin particles with a particle size of 600 μm were selected to study their fluidization behavior in our home-made vibration fluidized bed reactor. When the initial bed height was 15 mm, due to the difference of viscous force between the agglomerates, TiO2 had higher bed pressure drop and lower bed expansion rate than SiO2 during the fluidization, which showed agglomerate bubbling fluidization, and SiO2 bed pressure drop was low, bed expansion rate was high, SiO2 showed agglomerate particulate fluidization. The SiO2 particle tracer fluidization experiments show that during fluidization nanoparticle agglomerates are in a dynamic change of rupture and aggregation. Vibration can reduce the channeling and agglomeration in the fluidization process of nanoparticles, promote the breakup of agglomerates, reduce the minimum fluidization velocity of particles, and help to improve the gas-solid contact efficiency. In order to test the coating performance of the home-made atomic layer deposition reactor on nanoparticles, under the optimal fluidization conditions, at 80 ℃ using TiCl4 and H2O as precursors, deposition dense and uniform amorphous TiO2 film on TiO2 nanoparticles.The amorphous TiO2 film can suppress the photocatalytic activity and improve the weatherability of TiO2 pigment. After 30 cycles, the thickness of amorphous TiO2 film is about 3. 11 nm, and its photocatalytic activity is about 90% lower than that of anatase TiO2, and the photocatalytic activity suppression is remarkable. It is shown that a home-made vibration fluidized atomic layer deposition reactor can achieve precise modification of micro-nano particles with good application prospects.

     

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