董立婷,胡丽娜,杜一枝.CaSO4液滴在超疏水表面上的蒸发结晶特性研究[J].表面技术,2024,53(8):202-209.
DONG Liting,HU Lina,DU Yizhi.Evaporative Crystallization Characteristics of CaSO4 Droplets on Superhydrophobic Surfaces[J].Surface Technology,2024,53(8):202-209 |
| CaSO4液滴在超疏水表面上的蒸发结晶特性研究 |
| Evaporative Crystallization Characteristics of CaSO4 Droplets on Superhydrophobic Surfaces |
| 投稿时间：2023-03-21 修订日期：2023-06-29 |
| DOI：10.16490/j.cnki.issn.1001-3660.2024.08.019 |
| 中文关键词: 超疏水表面 化学刻蚀法 盐液滴蒸发 固着液滴法 蒸发速率 接触角 方差分析 |
| 英文关键词:superhydrophobic surface chemical etching salt droplets evaporation sessile droplet method evaporation rate contact angle analysis of variance |
| 基金项目:自治区重点研发任务专项(2022B03028-4);省部级高层次人才引进计划(TCBR202106);省部级自然科学青年基金(2021D01C100) |
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| 中文摘要: |
| 目的 在铝基底上制备稳定的超疏水表面，研究其表面上硫酸钙液滴的蒸发结晶特性。方法 通过简单的化学刻蚀法制备了一种超疏水表面，基于温湿度可控的可视化平台开展固着硫酸钙液滴的蒸发过程实验研究。同时，基于温度和相对湿度，开发了多变量拟合二次回归模型来描述其对液滴蒸发速率的影响。结果 基底温度为40、50、60 ℃时，硫酸钙液滴和纯水液滴在亲水铝片表面上的蒸发模式均表现为CCR模式，在超疏水铝片表面上均表现为CCA模式。在超疏水铝片表面，纯水液滴与硫酸钙液滴的蒸发模式略有不同:在蒸发后期，硫酸钙液滴边缘盐分增加，在重力和Marangoni效应作用下，外部逐渐形成盐壳，接触半径呈上升趋势，说明超疏水表面不利于盐滴的钉扎。当蒸发速率较低时，在外部更容易形成盐壳，一旦外部形成盐壳，蒸发机制即发生了变化，液滴内部水分子需要克服盐壳内外的压差，并通过盐壳扩散进一步蒸发。结论 通过固着液滴实验验证了硫酸钙液滴的蒸发模式与基底温度无关，而与基底的润湿性有关，并且液滴的蒸发速率随着相对湿度的降低和温度的升高而增大。通过R2=0.993 7的多变量拟合二次回归模型，对影响液滴蒸发的因素进行了方差分析，结果表明:在超疏水表面上温度和相对湿度对硫酸钙液滴的蒸发速率均有显著影响。研究成果为矿井水的资源化利用提供了有效的理论支撑。 |
| 英文摘要: |
| In this paper, a superhydrophobic surface was prepared by chemical etching to study the evaporation crystallization characteristics of calcium sulfate droplets on the superhydrophobic surface and the influencing factors of calcium sulfate evaporation rate. In this study, calcium sulfate droplets were placed in a temperature- and humidity-controlled chamber for evaporation crystallization experiments according to the sessile droplet method, and the evaporation process of the droplets was visualized and recorded with a CCD camera until they were completely evaporated. Through image data processing, the contact angle, solid-liquid contact diameter and other parameters were determined, and the evaporation law of the droplet was further obtained. The evaporation experiment was performed using deionized water droplets and saturated calcium sulfate droplets with an initial volume of (3±0.1) μL at three different substrate temperatures (40±0.5), (50±0.5), (60±0.5) ℃ and three different humidity (30±5)%, (45±5)%, (60±5)%, respectively. At the same time, based on temperature and relative humidity, a multivariate fitting quadratic regression model was developed to describe its effect on the evaporation rate of droplets. The results showed that when the substrate temperature was 40, 50 and 60 ℃, the contact angle of calcium sulfate droplets and pure water droplets on the surface of hydrophilic aluminum sheet decreased linearly with the change of evaporation time. The first 90% of the evaporation of pure water droplets on the surface of the hydrophilic aluminum sheet maintained the CCR (constant contact radius) mode, and the last 10% showed the mixed mode; The entire evaporation process of calcium sulfate droplets on the surface of hydrophilic aluminum sheets showed the CCR mode. On the surface of the superhydrophobic aluminum sheet, pure water droplets and calcium sulfate droplets maintained the CCA (constant contact angle) mode in the first 60% of evaporation. In the late evaporation stage, evaporation modes of calcium sulfate droplets and pure water droplets were slightly different:pure water droplets in the evaporation processed sticky slip mode; while calcium sulfate droplets in the late evaporation stage edge salt increased. Under the action of gravity and Marangoni effect, the outside gradually formed a salt shell, the contact radius showed an upward trend, and the generated salt shell was likely to remove, indicating that the superhydrophobic surface was not conducive to the nailing of salt droplets. When the evaporation rate was low, it was more likely to form a salt shell on the outside. Once the salt shell was formed outside, the evaporation mechanism changed, and the water molecules inside the droplet needed to overcome the pressure difference between the inside and outside of the salt shell and further evaporate through the diffusion of the salt shell. In this paper, it is verified that the evaporation mode of calcium sulfate droplets is not related to the substrate temperature, but to the wettability of the substrate, and the evaporation rate of the droplets increases with the decrease of relative humidity and the increase of temperature. By fitting the quadratic regression model with R2=0.993 7 and analyzing the variance of the factors affecting droplet evaporation, the results show that temperature and relative humidity on the superhydrophobic surface have significant effects on the evaporation rate of calcium sulfate droplets. The research results of this paper provide effective theoretical support for the resource utilization of mine water. |
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