Superhydrophobic structures on 316L stainless steel surfaces machined by nanosecond pulsed laser
Superhydrophobic structures on 316L stainless steel surfaces machined by nanosecond pulsed laser
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DOI：
10.1016/j.precisioneng.2018.01.004
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发表时间：
2018-04-01
影响因子：
3.6
通讯作者：
Qin, Yi
中科院分区：
文献类型：
--
作者：
Cai, Yukui;Chang, Wenlong;Qin, Yi
采用纳秒激光加工技术对AISI 316L不锈钢表面进行改性处理。首次建立了激光加工高斯微孔的几何模型和约束条件，预测了表面接触角，优化了结构几何形状，使其疏水性最大化。通过激光加工实验，研究了加工激光功率和微结构间距对加工表面形貌的影响。随后，测量水滴接触角以评估不同试样的疏水性。结果表明，在10 W和14 W激光功率下，随着微结构间距的增大，接触角增大，达到峰值后逐渐减小。在微结构间距较大的情况下，接触角随加工激光功率的增大而增大。在微结构间距相同的情况下，接触角随表面形貌十点高度的增加而增大，Sz比Sa（算术平均高度）更能表征高斯孔洞表面的疏水性。该研究表明，大的Sz是形成稳定和稳健的Cassie巴克斯特态的必要条件，即实现超疏水性的条件。实验结果表明，该模型能够准确预测接触角，并优化微结构的几何形状，以达到最大疏水性。
In this paper nanosecond laser machining process was developed to improve the hydrophobicity of AISI 316L stainless steel surface. A geometrical model of laser machined Gaussian micro hole, together with constrain conditions, was established for the first time to predict surface contact angle and optimize structure geometries for maximizing its hydrophobicity. The effects of processing laser power and pitch of microstructures on the topography of the machined surface were investigated through laser machining experiment. Subsequently, the water droplet contact angle was measured to evaluate the hydrophobicity of different specimens. Results show that under the laser power of 10 W and 14 W, with the increase of the pitch of microstructures, the contact angle increases until it reaches its peak value then drops gradually. Under the large pitch of microstructure, the contact angle will increase with the increase of the processing laser power. Under the same pitch of microstructure, the contact angle will increase with the increase of ten-point height of surface topography, Sz which is a better parameter than Sa (arithmetical mean height) to characterise hydrophobicity of surface with Gaussian holes. This study shows that large Sz is an essential condition to form the stable and robust Cassie Baxter state, i.e. a condition to achieve superhydrophobicity. The comparison between the predicted and measured contact angles in experiments shows that the proposed model can accurately predict contact angle and optimize the geometries of the microstructure to achieve maximum hydrophobicity.