Understanding of Dynamic Contacting Behaviors of Underwater Gas Bubbles on Solid Surfaces.
Understanding of Dynamic Contacting Behaviors of Underwater Gas Bubbles on Solid Surfaces.
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DOI：
10.1021/acs.langmuir.0c01551
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发表时间：
2020-08
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通讯作者：
Jingshan Qin;Daojin Zhou;Bairu Shi;Fanhong Chen;Liang Luo;Anuj Kumar;Cheng Wang;Xiao Lin;Siyu Sheng;Wenwen Xu;Zhicheng Shang;Congtian Cheng;Y. Kuang;Wen-Feng Lin;Haijun Xu;Xiaoming Sun
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作者：
Jingshan Qin;Daojin Zhou;Bairu Shi;Fanhong Chen;Liang Luo;Anuj Kumar;Cheng Wang;Xiao Lin;Siyu Sheng;Wenwen Xu;Zhicheng Shang;Congtian Cheng;Y. Kuang;Wen-Feng Lin;Haijun Xu;Xiaoming Sun
了解气泡在固体表面的动力学行为对工业上的含气电化学反应、矿物浮选等具有重要意义。接触角（θ）被广泛用于表征气泡在固体表面的润湿行为，但它通常在气泡前进（θa）和后退（θr）的范围内波动。虽然最稳定接触角（θms）被定义为液滴在固体表面上的最接近的有价值的近似接触角，但它并没有得到广泛的重视;精确的θms测量方法不足以描述气泡在固体表面上的润湿行为。在此，我们提出将θms取为θa和θr的平均值，作为非理想固体表面上气泡动力学行为的更精确描述，类似于固体表面上液滴的θms定义。通过记录不同润湿性固体表面上气泡的接触行为，验证了所提出的θms方法的可行性和准确性。此外，研究发现，当接触角θms接近90°时，接触角滞后（θa与θr之差）达到最大值，与基底的粗糙度（r）无关。最后，在此基础上，结合液-气界面张力（γlg）和气泡横向粘附力（θa，θr），定量描述了气泡在固体表面上的横向粘附力，即气泡在前进或后退过程中，作用于单个气泡在固体表面上的三相接触线（TPCL）上的横向粘附力。实验和理论数据共同证实，在θms~90°处，气泡运动速度达到最大值，即“超粘”状态，这是气泡沿固体表面沿着运动最缓慢的状态。
Understanding of dynamic behaviors of gas bubbles on solid surfaces has significant impacts on gas-involving electrochemical reactions, mineral flotation and so on in industry. Contact angle (θ) is widely employed to characterize the wetting behaviors of bubbles on solid surfaces; however, it usually fluctuates within the bubble's advancing (θa) and receding (θr) range. Although the term of most-stable contact angle (θms) was defined previously as the closest valuable approximation for thermodynamically meaningful contact angle for a droplet on solid surface, it has not been widely appreciated; and the precise θms measurement methods are inadequate to describe bubbles' wetting behaviors on solid surfaces. Herein, we proposed to take θms as the mean value of θa and θr, as a more accurate descriptor of gas bubbles' dynamic behaviors on non-ideal solid surface, as similar to the definition of droplets' θms on solid surfaces. The feasibility and accuracy of the proposed θms have been evidenced by recording the bubbles' contacting behaviors on solid surfaces with varied wettabilities. In addition, it was found that the contact angle hysteresis (δ), as the difference between θa and θr, reached its maximum value when θms approached to 90°, regardless of the roughness (r) of substrates. Finally, built on the above concept, lateral adhesion force (ƒ) of gas bubble on solid interface, which worked on the three-phase contact line (TPCL) of individual bubble on a solid surface against its lateral motion during the bubble advancing or receding process, was described quantitatively by combining θa, θr and liquid-gas interfacial tension (γlg). Experimental and theoretical data jointly confirmed that ƒ reached its maximum value at θms~90°, namely the "super-sticky" state, which described the dynamically most sluggish movement of bubble along the solid surface.