Vol. 02, Issue 09,September 2017 Available Online: www.ajeee.co.in/index.php/AJEEE A NANO TECHNOLOGY PRODUCED SOL-GEL METHODS THROUGH AEROGEL
STRUCTURE Mrs. Swastika,
Research Scholar, Department of Faculty of Science (Electronics), Magadh University, Bodh Gaya, Bihar
Abstract:- Sol-gel processing facilitates effortless control of the composition, properties, and architecture of nano systems. For this reason, the technology has been adapted as a popular route for the preparation of nanostructures. The process supports the preparation of intricate three-dimensional networks extended throughout a liquid phase (a gel) through the agglomeration of nano particles dispersed within a colloidal suspension (sol). In order to gain a greater understanding of the process before exploring the possible applications of the technology, this chapter outlines the activities involved in sol-gel processing. The formation of sol-gel materials is explained by briefly focusing on the mechanisms of hydrolysis and condensation, in addition to ageing and drying of wet gels. Sol-gel processing can be used to form a range of architectures from fibres and films to fine powders and monoliths, however this chapter will focus on sol-gel processing for aerogels specifically.
Keywords:- Sol-gel, Nano-System, Nano-Structure, Liquid Phase, Aerogel Structures.
1. INTRODUCTION
Sol-Gel processing is due to the ease of control of the nano architecture throughout synthesis. The ability to tailor the structure of nano systems from primitive processing phases advocates the preparation of pure materials with improved properties. The advanced properties of such compounds afford their use, in the form of fibres, films, fine
powders and monoliths within a diverse range of applications. This chapter will introduce sol-gel processing with a particular focus on aerogels. Sol-gel processing generally includes four key stages, additional procedures are often incorporated in an attempt to enhance mechanical properties and characteristics of the gel.
Fig.1 Aerogel Structure
Vol. 02, Issue 09,September 2017 Available Online: www.ajeee.co.in/index.php/AJEEE 2. NANO TECHNOLOGY SYSTEMS
Nanotechnology is helping to considerably improve, even revolutionize, many technology and industry sectors:
information technology, homeland security, medicine, transportation, energy, food safety, and environmental science, among many others. Described below is a sampling of the rapidly growing list of benefits and applications of nanotechnology.
Many benefits of nanotechnology depend on the fact that it is possible to tailor the structures of materials at extremely small scales to achieve specific properties, thus greatly extending the materials science toolkit. Using nanotechnology, materials can effectively be made stronger, lighter, more durable, more reactive, more sieve-like, or better electrical conductors, among many other traits.
3. NANO MATERIALS AND PROCESSES
Nanoscale additives to or surface treatments of fabrics can provide lightweight ballistic energy deflection in personal body armor, or can help them resist wrinkling, staining, and bacterial growth.
Clear nanoscale films on eyeglasses, computer and camera displays, windows, and other surfaces can make them water- and residue-repellent, antireflective, self-cleaning, resistant to ultraviolet or infrared light, antifog, antimicrobial, scratch-resistant, or electrically conductive.
Nanoscale materials are beginning to enable washable, durable
―smart fabrics‖ equipped with flexible nanoscale sensors and electronics with capabilities for health monitoring, solar energy capture, and energy harvesting through movement.
Nano-engineered materials in automotive products include high- power rechargeable battery systems; thermoelectric materials for temperature control; tires with
cleaner exhaust and extended range.
Nanostructured ceramic coatings exhibit much greater toughness than conventional wear-resistant coatings for machine parts.
Nanotechnology-enabled
lubricants and engine oils also significantly reduce wear and tear, which can significantly extend the lifetimes of moving parts in everything from power tools to industrial machinery.
Nanoparticles are used increasingly in catalysis to boost chemical reactions. This reduces the quantity of catalytic materials necessary to produce desired results, saving money and reducing pollutants. Two big applications are in petroleum refining and in automotive catalytic converters.
Nano-engineered materials make superior household products such as degreasers and stain removers;
environmental sensors, air purifiers, and filters; antibacterial cleansers; and specialized paints and sealing products, such a self- cleaning house paints that resist dirt and marks.
Nanoscale materials are also being incorporated into a variety of personal care products to improve performance. Nanoscale titanium dioxide and zinc oxide have been used for years in sunscreen to provide protection from the sun while appearing invisible on the skin.
4. SOL–GEL PROCESSING
Sol–gel processing is a typical wet- chemical technique for the fabrication of UC nanophosphors for applications as thin film coatings and glass materials. In the sol–gel process, colloidal dispersions of inorganic nanophosphors are prepared in alcohol water solutions by the hydrolysis and poly-condensation of metal alkoxide (or halide)-based precursors.
Calcination of the as-synthesized
Vol. 02, Issue 09,September 2017 Available Online: www.ajeee.co.in/index.php/AJEEE 5. SOL-GEL APPROACH
The motivation for the sol-gel processing compared to traditional glass melting or ceramic powder methods is first and foremost the potentially higher homogeneity and purity in addition to the lower processing temperatures associated with the approach. Using the sol-gel process, the production of bioglass and other ceramics has become an interesting research field for the past four decades.
Sol-gel process involves the synthesis of an inorganic network by mixing the metal alkoxides in solution.
This is then followed by hydrolysis, gelation, and low-temperature firing to produce a dense and stable glass or ceramic powder. The network structure of the gel can be modified by controlling hydrolysis and poly-condensation reactions during productions. Hence, structural variation can be produced without compositional changes.
6. SOL-GEL METHODS OF ANALYSIS The sol–gel processing technique to develop host materials for various biosensor devices has been explored continuously. The sol–gel process involves the transition of a system from a mostly liquid colloidal ―sol‖ into a solid ―gel‖
phase.
The sol–gel materials offer a number of advantages over conventional organic polymers as immobilization platforms for biosensors owing to their superior mechanical strength, porosity and high surface area, chemical inertness, hydrophilic nature, and above all, optical transparency (Bhatia et al., 2000). the applications of sol–gel process for the development of various biosensors for a wide range of applications have been published.
7. AEROGELS AS PROMISING MATERIALS FOR ENVIRONMENTAL REMEDIATION
Aerogel is a general term referring to any material derived from organic, inorganic, or hybrid molecular precursors that are usually prepared by sol-gel processing and an appropriate drying technology
with which the three-dimensional and highly porous network is conserved.
Aerogels were first introduced by S.
Kistler.
When he extracted the pore-filing liquid of wet gels using a supercritical drying (SCD) approach to obtain an air filled solid material with nearly the same dimensions as the original wet gel.
Although Kistler worked with a variety of different aerogels from various starting molecules, the subsequent studies mainly focused on silica (SiO2) type of aerogels.
The intricate multistage processing steps developed by Kistler resulted in aerogels becoming a forgotten material for about 30 years. However, during the past decades, by advances in aerogel synthesis and their drying technologies, different types of aerogels have emerged, including inorganic (such as SiO2, TiO2, Al2O3, ZrO2), organic (i.e., resorcinol- formaldehyde (RF), polyurethane, polyimide, polystyrene, etc.) and carbon (i.e., carbon, carbon nano-tubes (CNTs), graphene), semiconductor chalcogenide (i.e., CdS, CdSe, PbTe), natural-based aerogels (i.e., cellulose and other polysaccharides and various proteins) and, more recently, SiC-based aerogels.
Additionally, other than the single- component aerogels mentioned herein, the compositing of one of those aerogels with a specific component has often conferred an additional functionality such as mechanical strength, hydrophobicity, and catalytic features to the pristine materials and has improved the usefulness in for some high-performance applications.
Fig. 2 shows the evolution of aerogels after Kistler's invention as well as the growing number of publications containing the term ―aerogel‖ during the past 10 years. In fact, after the 2000s and following the significant advances in the synthesis process, aerogels have drawn significant attention by the scientific community. These advances even became more prominent by the introduction of new types of aerogels during the past few years.
Vol. 02, Issue 09,September 2017 Available Online: www.ajeee.co.in/index.php/AJEEE
Fig. 2 Evolution of aerogels 8. CONCLUSION
Sol-Gel processing is due to the ease of control of the nano architecture throughout synthesis. The ability to tailor the structure of nanosystems from primitive processing phases advocates the preparation of pure materials with improved properties. The advanced properties of such compounds afford their use, in the form of fibres, films, fine powders and monoliths within a diverse range of applications. The following problems should be addressed by the future research and development of aerogels. Efficient, inexpensive, environmentally-friendly and non-toxic solvent systems are necessary to improve the dissolution efficiency.
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