实验发现石蜡断面具有良好的超疏水性能,石蜡断面的水滴接触角达到152.4±3°,石蜡外表面水滴接触角为108±3°.利用铜网在石蜡表面复制其断面形貌,可快速制备大面积超疏水石蜡表面,接触角高达162.4±3°,滚动角小于3°.利用此超疏水石蜡表面设计出一种自动油水分离装置,可实现油水连续分离,收集正己烷速率可达0.67mL/s.扫描电子显微镜(SEM)观察发现石蜡断面粗糙度很高且存在较多连续和非连续的晶区,而石蜡外表面较光滑.扫描差示量热仪(DSC)和X射线衍射(XRD)证明石蜡具有一定的熔限和较高的结晶度.偏光显微镜(POM)观察石蜡熔体的冷却过程,发现冷却过程中有大量不同尺寸的结晶产生.实验结果表明:石蜡断面和石蜡外表面的超疏水性差别较大的原因在于断面具有较高的粗糙度,而外表面粗糙度较低,断面的高粗糙度来自于石蜡内部存在大量的连续晶相和非晶相.当石蜡断裂时,晶相一方面充当了应力集中点,导致断面出现不规则的裂纹;另一方面,晶相充当了微纳尺度的“填料”;晶相和非晶相在断裂面的凸起也会导致断面粗糙度高.
Superhydrophobicity of the paraffin fracture surface was discovered,the water contact angle (WCA) reaches 152.4 ±± 3°,higher than the 108 ± 3° of the outer surface.Superhydrophobic paraffin surfaces with a WCA of 162.4±3° and a sliding angle (SA) lower than 3°were fabricated by replicating the morphology of the fracture surface with a sheet of copper mesh.A device with a separating speed of 0.67mL/s for continuous oil-water separation was designed.The morphology of the obtained surface was investigated by scanning electron microscope (SEM).Differential scanning calorimetry (DSC),X-ray diffraction (XRD) and polarizing microscopy (POM)tested the narrow melting temperature range and high crystallinity of paraffin.Results show that the main cause for the superhydrophobicity of the fracture surface is the surface roughness.High roughness of paraffin fracture surface is caused by the continuous crystalline region and the scattered crystalline regions.When being fractured,the crystalline regions function as the concentration points and micro-size "fillers",leading to a rough morphology.
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