Controllable Fabrication, Characterization And Performance Researches Of Metal Oxides And Metal Sulfides

Design and modification of the micro-and nanostructured units have become one of the most hot topics at the forefront in recent years. Due to the nanoscale effects, scientists have more creative freedom to the synthesis of new materials with specific properties according to their own wishes. Applications of new properties, new principles and new methods for constructing the reasonable nanodevices and surface modification of traditional materials are pregnant with new breakthroughs. This paper choose the typical metal oxide (Al2O3, ZnO) and metal sulfide (ZnS) as research objects, we discuss the selection of synthesis technique, experimental process regulation and control, together with the growth mechanism in order to achieve the controllable preparation of different structured morphologies. Based on intrinsic properties of materials and morphology characteristics, we systematically study their corresponding humidity sensing functions, field emission properties and wetting behavior, especially the bionic design of superhydrophobic surfaces and so on. The main researches and innovations could be divided into the following sections: (1) High-performance humidity sensors based on high-field porous anodized alumina films (PAA) that fabricated in H3PO4-H2O-C2H5OH electrolytes. We employ the electrochemical anodization style for the preparation of PAA films under high-field of195V. Subsequently, isotropic chemical etching is carried out in5wt%phosphoric acid at45℃for appropriate times of15min,30min and40min to get different pore structures and distribution of anion impurities in the surface of the pore sidewalls. It is the first time to realize the construction and property studies of humidity sensors based on high-field phosphoric-acid PAA films. The experimental result indicates that humidity-sensitive regions of operation and the sensitivity over a wide humidity range of humidity sensors on the basis of high-field PAA films can be adjusted by isotropic chemical etching for the appropriate time, moreover, they also show short response and recovery times due to their ordered large pore sizes. This work provides an effective and rapid way to construct a humidity sensor with high performance.(2) Controllable growth of diverse alumina architectures and their morphology-dependent wettability. This work reports the self-assembly of diverse nanostructured alumina films under high-field anodization in oxalic-acid electrolytes, and obtained different surface morphologies by adjusting reaction parameters. It confirms that heat-driven dissolution, inhomogeneous distribution of anion concentration in nanopore sidewalls and the concentration gradient of oxalic acid solution along nanopore channels are crucial to the formation of diverse alumina films. Surface wettability of these alumina films was evaluated by contact angle (CA) measurement, and the contact mode between the alumina surfaces and water droplets can be converted from wenzel model of porous structure to Cassie model of alumina nanowire pyramids. Specially, the lotus-like nanowire pyramids of alumina surfaces present self-cleaning superhydrophobic and superoleophilic properties. To our knowlegde, it’s the first time to prepare superhydrophobic surfaces of alumina films with no surface modification. It could be applicable in oil-water separation, antifouling, self-cleaning and other fields.(3) Morphology-dependent field emission properties and wetting behavior of ZnO nanowire arrays with different structural parameters. In this study, we realize a controllable growth of ZnO nanowire arrays with different structural parameters by facile thermal evaporation of ZnS precursors, and study their field emission properties and wetting behavior. Different structural parameters are controlled by changing the thickness of coated Au film layer together with substrate locations. The result indicates that field emission properties and wetting behavior are morphology-dependent on the structure of ZnO nanowire arrays. The nanowire arrays in small diameter and high aspect ratio exhibited the best FE performance showing a low turn-on field (4.1V μm-1) and a high field-enhancement factor (1745.8). Meanwhile, CA values on the surface of ZnO nanowire array films is proportional to their void ratios.(4) A facile synthesis of two-dimensional ZnO nanoflake arrays with superhydrophobic surface and resistant to acid and alkali solutions over a wide pH range, and ultraviolet-induced wettabilty conversion is studied. This work provides the synthesis of two-dimensional (2D) oriented ZnO nanoflakes on aluminum substrate through low-temperature hydrothermal technique, and presents the detailed growth process and its explanation of growth mechanism. By a surface treatment with a low surface energy material (stearic acid, C18H36O2), wettability was converted from superhydrophilicity to superhydrophobicity. The highly water-repellent ZnO surface demonstrated excellent chemical resistance in both acid and alkaline conditions over a wide pH range (2.3～12.1), ultraviolet irradiation was applied to induce wettability conversion and surface chemical composition is confirmed by X-ray photoelectron spectroscopy (XPS) to analyse the chemical or physical changes of the coated stearic acid.(5) Preparation and properties of ZnS superhydrophobic surface with hierarchical structure. Preparation and mechanism of superhydrophobic surface have been widely studied. However, most of the researches are concentrated on oxides and organic material system with low surface energy. How to enlarge the research system to high surface energy materials is a concern. As a typical Ⅱ-Ⅵ semiconductor with wide bandgap, ZnS has many advantages over photocatalysis, electrical properties, and luminescence, while little reports on its wetting behavior. In this work, we fabricate a novel ZnS hierarchical structure via chemical vapor deposition, explain the growth mechanism, and realize the self-cleaning superhydrophobic surface of ZnS which has intrinsic hydrophilic character. This study would be beneficial to give rise to the researches of other intrinsic hydrophilic materials and the construction of their superhydrophobic surface.