高反射近红外隔热薄膜的制备与研究

通过溶剂热法制备氯氧化铋(BiOCl)粒子，研究BiOCl粒子对近红外光的反射作用，将其应用于薄膜中制备成阻隔太阳光光热的复合薄膜。通过X射线衍射(XRD)和电子能谱(EDS)表征BiOCl的晶相结构和化学组成，采用扫描电子显微镜(SEM)观察其微观形貌。用紫外-可见光-近红外分光光度计分析BiOCl粒子在波长范围220~2 500 nm内的吸收和漫反射光谱。最后将BiOCl分散在聚乙烯醇(PVA)溶液中，采用涂覆工艺制备成BiOCl/PVA复合薄膜，研究BiOCl含量对薄膜隔热性能的影响。结果表明，在本实验中制备的BiOCl为尺寸均一的微球结构，外径为3~5 μm；由大量纳米片交织构成，形成开放的通道。禁带宽为3.69 eV，大于计算值2.62 eV，表明BiOCl粒子表面的光生载流子浓度发生了变化，使吸收边发生蓝移。BiOCl在可见光区(300~750 nm)平均反射率为67.3%，在近红外区(750~2 500 nm)平均反射率达到了99.8%以上。随着添加BiOCl含量的增加，PVA薄膜的隔热性能持续提高，当BiOCl添加量为1.5%时，使隔热箱内部的温度下降了4.5 ℃。由于近红外光的入射频率高于复合膜中BiOCl粒子本身的振动频率，引起了其振动粒子的高反射，对分布于近红外区的能量起到了很好的阻隔反射作用，降低了隔热箱内部的温度。

Preparation and Study of High Reflective Near Infrared Heat-Insulation Film

BiOCl was prepared by solvothermal method, and the reflection of BiOCl to near-infrared light was studied. The crystal structure and chemical composition of BiOCl were characterized by X-ray diffraction (XRD) and electron spectroscopy (EDS). Under the observation of scanning electron microscopy (SEM), BiOCl exhibited homogeneous flower-like microspheres with outer diameter of 3~5 μm, composing by intertwined nano-sheets with open channels. The absorption and reflection spectra of BiOCl were analyzed by UV-Vis-NIR spectrometer in the wavelength range of 220~2 500 nm. Its forbidden band width is 3.69 eV, which is greater than the calculated value of 2.62 eV. The results indicated that the photocatalytic concentration of BiOCl has changed, and the absorption edge was blue shifted. The reflectivity in the visible region (300~750 nm) is 67.3%, and it is over 99.8% in the near infrared region of 750~2 500 nm. Finally, BiOCl particles were dispersed in polyvinyl alcohol (PVA) solution to prepare film by coating process. With the increase of BiOCl content, the heat-insulation properties of BiOCl/PVA was improved accordingly. When the amount of BiOCl was 1.5%, the temperature inside of the insulation box decreased 4.5 ℃, the reason is the incident frequency of near-infrared light is higher than that of BiOCl particles, resulting in a high reflection. For the energy distribution in the near infrared region has been impeded and reflected, the temperature inside the insulation box was then reduced.