Preparation Of Super-hydrophobic Porous Materials And Research Of Properties

Wetting as one of the properties of solid surface, usually expressed with static contact angle of a droplet in solid surface. Based on people's daily life and national defense needs, super-hydrophobic materials with special wettability (the static contact angle is greater than 150, the sliding angle is less than 10°) caused widespread concern in the scientific community. Inspired by the "lotus effect", it is conclusion that the wettability of solid surface is decided by the surface morphology and chemistry. Therefore, the idea of preparing a super-hydrophobic material is obtained. It is reported that water contact angle above 150° can be achieved either through using low surface energy materials to construct morphological structures directly or modifying the morphological structures with low surface energy materials. Many methods have been employed to obtain the super-hydrophobic surface, such as multiple grafting, plasma etching, electro-deposition, physical or chemical vapor deposition, chemical etching, spraying, sol-gel technique and electro-spinning. However, they are complicated and costly, which confines the practical application. Accordingly, the development of a simple and low-cost method is highly desired. In additions, the above-mentioned methods have main obstacle that they only are used to prepare surface hydrophobicity rather than pore hydrophobicity. For porous materials, it is a meaningful goal to improve pore hydrophobicity.In this work, the method of adding pore-forming agent was used to prepare porous ceramic carrier. In-situ hydrothermal and dipping methods were employed to prepare super-hydrophobic surface. To the best of our knowledge, this process to prepare hydrophobic porous material is not reported so far. Firstly, porosity as a macroscopic parameter is used to filter the preparation of porous ceramic materials and preparation methods. Secondly, surface area as microscopic parameter is used to obtain optimum conditions for preparing porous ceramics by orthogonal experiment. Afterwards, we investigated the factors impacting on the morphology of in-situ synthesis of cerium oxide. Meanwhile, the stability and hydrophobicity of internal pores of composite material also were studied. The main conclusions of this work are summarized as follows:(1) Preparation of porous ceramicThe porous ceramic supports were prepared by the method of adding pore-forming agent. The effect of porous ceramic performance was investigated by the type of aggregate, calcination temperature, the particle size and amount of pore-forming agent. Meanwhile, the calcination procedure was developed by TG curve. The optimum conditions of preparing porous ceramic carrier were determined by the orthogonal experiment. The results showed that the optimal conditions for the preparation of porous ceramic supports were that SiO2 and ZrO2 as matrix materials was 55%, MC with a dosage of 45% was used as a pore-forming agent, AIPO4 with a dosage of 5% was used as a binder, calcination temperature was 900? and calcination time was 2h, respectively. Under optimal conditions, the parameters of preparing porous ceramics support were showed below:porosity was 72.62%, specific surface area was 80.20m2/g, average pore diameter was 30.54nm and pore volume was 0.6122mL/g.(2) Constructing cerium oxide micro-/nanostructuresCerium oxide micro-/nanostructures were constructed on the ZrO2-SiO2 porous ceramic supports by in-situ hydrothermal method. The effects of synthesis temperature, time, template agents and precipitants on the cerium oxide morphology and uniformity were investigated. Nanocluster structure was obtained by using urea as a precipitant, and flowerlike structure was obtained by using ammonia as a precipitant. The parameters of composite material were showed below:porosity was 70.27%, specific surface area was 83.36m2/g, average pore diameter is 29.52nm, pore volume is 0.3199mL/g.(3) Hydrophobized and stability testThe super-hydrophobic composite materials with contact angle more than 150° and sliding angle approach to 0° were obtained after grafting with low concentration PFDTES. Pore hydrophobicity was investigated via homemade equipment and it was conclusion that the composite material was super-hydrophobic in pores. SEM results showed that the structure can be stable after treating CeO2 micro-/nanostructured composite materials at 800? for 2h. Therefore, it was indicated that the composite material had good thermal stability. To test the durability of the super-hydrophobic surfaces, the apparent contact angle was used to quantify the properties. Two kinds of solutions pH=1 and pH=13 were used to test chemical stability. At first, the water contact angle of the material is distributed between 150° and 160°. After 800h, water contact angle basically remains unchanged. This indicated that the super-hydrophobic materials resistance to acidity and alkalinity. Water contact angle remains unchanged after 48h in ultrasonic treating. This indicated that the composite materials had good mechanical stability. Meanwhile, thermal stability were also tested, the hydrophobicity has desirable stability below 400?.The super-hydrophobic material was placed into an autoclave under different temperature for a week, despite the degradation of the hydrophobicity with the temperature increasing, this material had desirable hydrothermal stability less than 80? for one week. These results also indicated that the material had good thermal and hydrothermal stability.