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Sol-gel technique is one of the simplest techniques to prepare thin films and can provide almost single- or multi-component oxide coating on glass or metals surface. Coatings prepared by this technique have shown excellent chemical stability, oxidation control, and enhanced corrosion resistance for metal substrate. This book focuses on the advantages of nanostructured titanium dioxide coatings to many engineering applications and also explains the mechanisms of formation of the nanostructured titanium dioxide coatings including significant mechanical and physical properties. It also explains the structural properties of the nano-structured titania coatings. This book also illustrates the factors affecting particle size and morphology of titania coated samples.
Electroplating as a surface treatment technology can significantly improve the properties of working parts and components which has been widely applied in a variety of technical fields. Recently this surface treatment technology has been developed to synthesize nanocomposite coatings. The nanocomposite coatings show a significantly improved mechanical properties due to the second-phase dispersed nanoparticles in the coating matrix. However, it is hard to realize a good suspension of solid nano-sized particles in a plating solution and good dispersion of nano-sized particles in the composite coatings because of the large surface energy of nano-particles. The traditional methods such as magnetic agitation, air injection, and ultrasonic vibration are always difficult to fully prevent agglomeration of nano-sized particles as the surface effect. To achieve a good dispersion of the nanoparticles in composite coatings, sol-gel enhanced electroplating is developed at the University of Auckland and intensively investigated. The aim of this research is to study the electroplating of sol enhanced Ag/TiO2 composite coatings. In the present thesis, TiO2 solid particles and a transparent TiO2 sol was added into a traditional cyanide silver electroplating electrolyte in order to prepare two different types of composite coatings. The research was started with an electroplating of pure silver coatings from traditional cyanide bath. Then investigations were carried out on the solid powder enhanced composite coatings and sol-enhanced composite coatings focused on the effect of the powder and sol concentration. The microstructure, mechanical properties, electrical properties as well as colour difference of the composite coating were investigated in the research. Both of the sol and powder enhanced electroplating successfully added dispersed TiO2 nanoparticles into the Ag coating matrix and improved the mechanical properties compared to the pure silver coating. The sol enhanced nanocomposite coatings shows better dispersion and mechanical properties.
The sol-gel method is a powerful route of synthesis used worldwide. It produces bulk, nano- and mesostructured sol-gel materials, which can encapsulate metallic and magnetic nanoparticles, non-linear azochromophores, perovskites, organic dyes, biological molecules, etc.. This can have interesting applications for catalysis, photocatalysis; drug delivery for treatment of neurodegenerative diseases such as cancer, Parkinson's and Azheimer's. In this book, valuable contributions related to novel materials synthesized by the sol-gel route are provided. The effect of the sol-gel method to synthesize these materials with potential properties is described, and how the variation of the parameters during the synthesis influences their design and allows to adjust their properties according to the desired application is discussed.
Nano-composite coatings have wide applications for their superior mechanical and corrosion properties. Many efforts have been devoted to the development of different types of nano-composite coatings in the last decade. Various techniques are used to modify the coating microstructure at the nano scale in order to further improve the properties of coatings. We recently developed a novel method which combines sol-gel process and electrochemical deposition process to produce nano-composite coatings. This simple method can lead to a highly dispersed distribution of oxide nano-particles in the metal coating matrix, resulting in significantly improved mechanical properties. This Chapter introduces the principle of this innovative method, the basic theory behind the deposition process, and an overview of current results. It also describes the dopant technology that is derived from this novel technique. The future development potentials and industrial applications of these coatings are also discussed.
Since Dr. Disiich of Germany prepared a glass lens by the sol-gel method around 1970, sol-gel science and technology has continued to develop. Since then this field has seen remarkable technical developments as well as a broadening of the applications of sol-gel science and technology. There is a growing need for a comprehensive reference that treats both the fundamentals and the applications, and this is the aim of "Handbook of Sol-Gel Science and Technology."The primary purpose of sol-gel science and technology is to produce materials, active and non-active including optical, electronic, chemical, sensor, bio- and structural materials. This means that sol-gel science and technology is related to all kinds of manufacturing industries. Thus Volume 1, "Sol-Gel Processing," is devoted to general aspects of processing. Newly developed materials such as organic-inorganic hybrids, photonic crystals, ferroelectric coatings, photocatalysts will be covered. Topics in this volume include: Volume 2, "Characterization of Sol-Gel Materials and Products, "highlights the important fact that useful materials are only produced when characterization is tied to processing. Furthermore, characterization is essential to the understanding of nanostructured materials, and sol-gel technology is a most important technology in this new field. Since nanomaterials display their functional property based on their nano- and micro-structure, "characterization" is very important. Topics found in Volume 2 include: Sol-gel technology is a versatile technology, making it possible to produce a wide variety of materials and to provide existing substances with novel properties. This technology was applied to producingnovel materials, for example organic-inorganic hybrids, which are quite difficult to make by other fabricating techniques, and it was also applied to producing materials based on high temperature superconducting oxides. "Applications of Sol-Gel Technology," (Volume 3), will cover applications such as:
This completely updated and expanded second edition stands as a comprehensive knowledgebase on both the fundamentals and applications of this important materials processing method. The diverse, international team of contributing authors of this reference clarify in extensive detail properties and applications of sol-gel science and technology as it pertains to the production of substances, active and non-active, including optical, electronic, chemical, sensor, bio- and structural materials. Essential to a wide range of manufacturing industries, the compilation divides into the three complementary sections: Sol-Gel Processing, devoted to general aspects of processing and recently developed materials such as organic-inorganic hybrids, photonic crystals, ferroelectric coatings, and photocatalysts; Characterization of Sol-Gel Materials and Products, presenting contributions that highlight the notion that useful materials are only produced when characterization is tied to processing, such as determination of structure by NMR, in-situ characterization of the sol-gel reaction process, determination of microstructure of oxide gels, characterization of porous structure of gels by the surface measurements, and characterization of organic-inorganic hybrid; and Applications of Sol-Gel Technology, covering applications such as the sol-gel method used in processing of bulk silica glasses, bulk porous gels prepared by sol-gel method, application of sol-gel method to fabrication of glass and ceramic fibers, reflective and antireflective coating films, application of sol-gel method to formation of photocatalytic coating films, and application of sol-gel method to bioactive coating films. The comprehensive scope and integrated treatment of topics make this reference volume ideal for R&D scientists and engineers across a wide range of disciplines and professional interests.
Pretreatments are thin, adherent, and protective layers deposited directly on cleaned metal surfaces to enhance the performance of the multi-coat finishing system on metal and alloy substrates. Regulatory and environmental considerations dictate that industries replace the extant toxic and hazardous chromate-based pretreatments used for aluminum alloys with more sustainable ones. Two new families of organic-inorganic hybrid (OIH) pretreatments for aluminum alloys have been developed using customized silane-type sol-gel precursors--Epoxy-silane and Bis-ureasil--as primary components. Two series of sol-gel compositions varying in concentrations of silane precursor, organic corrosion inhibitor, and nano-silica particles have been prepared and used to deposit OIH pretreatments on aluminum alloy substrates (AA-2024-T3). The corrosion resistance performance of these OIH pretreatments has been studied by electrochemical impedance spectroscopy (EIS), direct current (DC) polarization resistance, and neutral salt spray test and compared with the resistance performance conventional hexavalent chromium-based pretreatment, as a benchmark and industry standard for Al alloys. This research specifically investigates the effects of key components of sol-gel compositions on the corrosion performance of the OIH pretreatments on Al-2024-T3. Using the Box-Behnken Design of Experiment (DoE) methodology and Minitab software for analysis, the key factors affecting corrosion performance have been identified and sol-gel compositions optimized. This study revealed that for both families of OIH pretreatments, the film deposited in the sol-gel bath containing 25% by weight of precursor provided the best performance. Furthermore, incorporation of nano-silica particles to an optimum level of 5% by weight led to a remarkable improvement of the corrosion-resistance performance of the pretreatments for both families. This study has also very clearly shown that the use of the organic corrosion inhibitor mercaptobenzthiazole is effective in enhancing the corrosion-resistance performance of both families of pretreatments when used at the optimum level of 3% by weight. A comparison of the corrosion-resistance performance of the two families of OIH pretreatments with chromate conversion coating (control) showed that pretreatments based on epoxy-silane precursor when used at optimum compositions clearly outperform chromate conversion coatings used as a control in this study. Furthermore, OIH based on a bis-ureasil precursor, while showing a slightly lower performance than its epoxy-silane counterpart, is comparable or slightly superior to the commercial conversion coating when used at optimum compositions.
The book provides a short introduction to the sol-gel process, principles in modification of the sols and technical details of the application on textiles, covering in particular the chemical content of the topic. New properties of textiles gained from nanosols are summarized and explained in a broad range, focusing on the mechanical and thermal stability, repellent properties, optical properties, antistatic coatings and bioactive coatings. An active discussion is held on the bioactive modifications, because this wide and interesting field offers a high potential for many new applications, e.g. in medicine. Besides basic research, this book will also provide examples on the transition of academic research to customer products.
Water-based inorganic-organic hybrid sol-gel coatings were developed on aluminium. The coatings were based upon epoxy-silane, glycidoxypropyltrimethoxysilane (GPTMS) and methyltrimethoxysilane (MTMS) as inorganic silane precursors crosslinked with the organic polymer, hexamethylmethoxymelamine (HMMM). The aim of the present work was to modify the hybrid sol-gel coating to obtain hydrophobic properties which could be achieved by either lowering the surface energy or increasing the surface roughness of the coatings. Lowering of surface energy was achieved by incorporating various fluoro-alkylsilanes (FASs) with two different chain lengths, of 3 and 17 fluorine atoms. The subsequent water contact angles achieved were 100° and 110° respectively for FAS modification. As a result, a commercial fluoro emulsion (FE) which was a water based six carbon atom perfluoro polymer, was employed as co-precursor. A substantial improvement in hydrophobicity was achieved with FE modification resulting in contact angle of 118°. Further, the surface roughness of the fluorinated sol-gel coating was enhanced by incorporating various nano-particles with different size, surface area and surface chemistry, namely nano-Zinc Oxide (ZnO), hexadecyltrimethoxysilane (HDTMS) modified nano-silica, dichlorodimethylsilane (DDS) modified nano-silica and hexamethyldisilazane (HMDZ) modified nano-silica. Out of these HMDZ nano-silica modification resulted in maximum hydrophobicity with contact angle of 125° and sliding angle of 25° on aluminium surface. Furthermore an independent study was carried out on application of as developed composite coatings on chemically and mechanically roughened aluminium surfaces. It was found that contact angle increases up to 130° using techniques like chemical etching, plasma etching, sand blasting and grinding etc. The as developed nano-composite coatings when applied on other non-metallic substrate such as glass, cotton, cardboard, paper, concrete and wood, it showed excellent hydrophobicity with a contact angle of > 135°. Furthermore, all the substrates showed a sliding angle of about 15°.The as developed coatings were characterised for their chemical and morphological structures, using techniques including FTIR, XPS, SEM and AFM. The wetting properties were analysed using contact angle goniometry. The performance of the as developed coatings was evaluated by determining corrosion resistance, hardness, adhesion and scratch resistance properties. Finally, the role of nano-particles distribution was studied in detail. It was found that maximum hydrophobic properties were achieved at optimum concentration of nano-particles.
Aluminum alloys used in aeronautical industry are susceptible to corrosion. The solution to this problem is base chromate materials, which have been heavily regulated and restricted. The development of alternatives begins in the 1970s and the 2000s, where some potential methodologies were established. The sol-gel process is one of these methods, in which thin oxide layers are deposited on the metal substrate. An important aspect is the fact of possible combinations among types of oxides and the incorporation of an organic compound to improve the performance of the films; moreover, this allows the addition of inhibitors and nanomaterials, making this method an interesting and versatile way to obtain a coating. In this chapter, we will describe the importance of the use of coating synthesized via sol-gel in the corrosion protection of metal surfaces. The advantages and disadvantages of using modified sol-gel polymer films and hybrid system coatings will also be discussed, as well as the methodologies for the chemical characterization and the feasibility of evaluating the mechanical properties of the coatings.