CaCO3 fouling on microscale–nanoscale hydrophobic titania–fluoroalkylsilane films in pool boiling

Micrometer–nanometer hydrophobic titania–fluoroalkylsilane composite coatings were prepared on substrates based on liquid‐phase deposition. Coatings and crystallization forms were characterized with instruments of surface analyses. Experimental facilities of pool boiling were established to evaluate heat and mass transfer on coated surfaces in deionized water and saturated calcium carbonate solution. Obvious pool boiling enhancement was observed on thinner microscale–nanoscale hydrophobic titania–fluoroalkylsilane composite films at higher heat fluxes compared to that on thicker titania–fluoroalkylsilane coatings or on titania coatings and stainless steel surfaces. Lower fouling resistance was obtained on titania–fluoroalkylsilane coatings in pool boiling of saturated calcium carbonate solution and crystal form was aragonite, which was different from calcite on titania coatings. Results of inhibition of fouling and enhancement of heat transfer on titania–fluoroalkylsilane coatings were contributed to special surface microscale–nanoscale structure and material wettability. Asymptotic model was used to fit experimental data of fouling resistance, and reasonable agreement was obtained. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2662–2678, 2013     

单分散氟烷基改性双疏SiO2球的制备

本文通过化学嫁接法引入氟烷基,对溶胶-凝胶法制得的单分散二氧化硅进行改性,得到了油水双疏的纳米二氧化硅小球,并考察了水和氟烷基硅烷对颗粒形貌及双疏性的影响。采用傅立叶红外光谱仪(FTIR)、扫描电子显微镜(SEM)、接触角测量仪(CA)及热重分析(TG)对产物进行了表征。结果表明,一定范围内延迟氟烷基硅烷的加入时间和增加水含量,可得到分散性、均匀性和双疏性都较好的表面改性SiO2球。增加氟烷基硅烷量,改性SiO2球的双疏性增强,但是分散性和均匀性变差,并出现了不规则形貌颗粒。     

氟硅烷改性水性丙烯酸二级分散体的制备与涂层性能

将1,1,3,3-四甲基-1,3-二乙烯硅氮烷(DVDZ)和甲基丙烯酸六氟丁酯(EINECS)进行Micheal加成反应,合成2,2,3,4,4,4-六氟丁基-3-(二(二甲基(乙烯基)硅基)氨基)-2-甲基丙酸酯(DVE)功能有机氟硅单体,与甲基丙烯酸甲酯(MMA)、甲基丙烯酸羟乙酯(HEMA)等单体混合,以偶氮二异丁腈(AIBN)为引发剂,异丙醇(IPA)为溶剂,合成氟硅烷改性水性丙烯酸二级分散体。然后,将其与异氰酸酯固化剂混合,制备了双组分水性聚氨酯(2K-WPU)涂膜。通过FTIR、1HNMR、TG、SEM、XPS对DVE和2K-WPU进行表征和检测,结果表明:随着DVE质量分数的增加,丙烯酸二级分散体的粒径增大,黏度降低,涂膜的耐水性增强,铅笔硬度和附着力减弱。当DVE质量分数为6%时,吸水率为8.2%,接触角为91.5?,热失重10%和50%时的温度分别为220.9和438.5℃,涂膜耐热、耐水和耐酸碱等性能均有提升。     

氟化SiO2纳米颗粒双疏涂层的制备及性能研究

采用氟化硅烷偶联剂对合成的单分散SiO2纳米颗粒进行表面接枝改性,并通过旋涂法将制备的氟化SiO2颗粒沉积在硅晶基板上.采用粒径分析仪、傅里叶变换红外光谱仪(FTIR)、热重分析仪(TG-DTA)、扫描电镜(SEM)和接触角测量仪对氟化SiO2纳米颗粒涂层的表面形貌、化学组成、接枝密度和润湿性能进行分析表征.结果表明:氟化硅烷偶联剂在SiO2纳米颗粒表面的接枝密度为5.94 nm-2;制备的氟化SiO2纳米颗粒薄膜具备微纳米双重复合网络结构,增加了涂层表面的粗糙程度;氟化SiO2纳米颗粒涂层展现出超疏水和强疏油性能,水和柴油在氟化SiO2纳米颗粒薄膜上的接触角分别为158.4°和125.7°.