气泡在粗糙表面的润湿行为研究

Investigation of Wetting Behaviors for Air Bubble on Rough Surfaces

目前,润湿状态及粗糙度对气泡润湿行为的影响尚不清晰。为了系统研究气泡润湿行为,在强亲水至疏水范围内的液体中,对三种不同粗糙度(r)固体表面(S1 r=1.15、 S2 r=1.64、 S3 r=2.29)上气泡的表观接触角及润湿滞后效应进行实验,得出杨氏接触角、粗糙度与气泡润湿行为之间的定性关系。结果表明:气泡润湿行为符合摩擦力理论;表观接触角与润湿滞后效应随着粗糙度的增加而减小;在亲水状态中,气泡受浮力与静水压力挤压,出现失真的表观接触角;随着杨氏接触角的增加,亲水体系中表观接触角与润湿阻力系数均无明显变化,当接近中性润湿状态时,表观接触角服从气泡Cassie-Baxter方程,S1与S2的润湿滞后效应明显增强,且S2的增加幅度小于S1,而S3的润湿滞后效应无明显变化;当接近中性润湿状态时,S1上气泡的表观接触角与液滴后退角相等、液滴表观接触角与气泡前进角相等,而更为粗糙的固体表面(S2、S3)未出现此现象。

At present,the effects of wettability and roughness on bubble wetting behaviors are not clear.To systematically study the bubble wetting behaviors,bubble apparent contact angle and contact angle hysteresis experiments were conducted.And qualitative relationships between Young s contact angle,surface roughness and bubble wetting behaviors from strongly hydrophilicity to hydrophobicity on three solid surfaces with different surface roughness(S1 r=1.15,S2 r=1.64,S3 r=1.64).Results show that wetting behaviors of bubble follow the friction force theory.With the increase of roughness,the apparent contact angle and contact angle hysteresis decrease.Distorted apparent contact angles occur in hydrophilic states resulted from buoyancy and hydrostatic pressure.With increasing of Young s contact angle,the apparent contact angle and contact angle hysteresis keep unchanged under hydrophilic states.However,in neutrally-wet states,apparent contact angle starts following the Cassie-Baxter equation,contact angle hysteresis also significantly increases on the S1 and S2,and increasing rate of S2 is less than that of S1.Contact angle hysteresis of S3 keeps unchanged with different wetting states.When wettability reaches neutrally-wet state,bubble apparent contact angles are equal to drop receding angles,drop apparent contact angles are equal to bubble advancing angles for S1,while these phenomena do not present on more rough surfaces(S2,S3).