Synthesis and Characterization of Cellulose Fiber, Silica Nano Particle Xerogel, and Hybrids of Cellulose Nano Crystal/Silica Nano-Particle Xerogel for Thermal Insulation Application

Abstract

Wastes arising from industrial and economic activities include agricultural and forestry residues have been given new life by recent research and development because various industrial biotechnologies are using them and realizing their economic potential. Sugarcane bagasse (Saccharum officinarum), a fibrous residue left over after sugarcane juice is extracted, is one well-known example. The most common organic polymer found in natural materials like wood, cotton, and plant fibers that are sustainable and environmentally friendly is cellulose. In this dissertation work, the extraction of cellulose nano-crystal or cellulose micro-fibrils from sugarcane bagasse has been studied. It has been proposed in recent years that cellulose, as a smart material, can be used for high performance electronics applications like actuators, transistors, and energy storage devices. Light weight, dryness, affordability, significant deformation, low actuation voltage, and low power consumption are just a few of the many benefits of electro-active paper. The remarkable optical, mechanical, and electrical properties of cellulose and one dimensional nano-materials composites have prompted research into a range of industrial applications. The hybrid nano-structured materials that combine organic and inorganic components demonstrate the benefits of both types of materials. The synthesis of SiO2 nano-particle xerogel and the hybridization of cellulose-nano crystal with SiO2 nano particle xerogel materials serve as additional driving forces for this dissertation. The focus of our work is primarily to understand the mechanism contributing to the thermal stability of the system. We carried out detailed experimental investigation, like XRD, FTIR, combined Thermo gravimetric /differential thermal analyses, inductively coupled plasma optical emission spectroscopy, Thermal Conductivity Analyzer and Scanning electron microscopy. The Fourier transform infrared spectra show that cellulose nanocrystal features prevail even at 50 wt% silica nanoparticles in the hybrid materials. Such a high content of silica nano-particle originated from sugarcane bagasse ash contributes to the high thermal stability and insulation of the final hybrids, as seen by the thermogravimetric and thermal conductivity analyzer, respectively. During our investigation, we came across interesting results which allow using these materials for different technological applications including optical, electronics, biomedical, adsorption, and thermal insulation applications, etc. The dissertation comprises of seven chapters. The first chapter of the dissertation provides a brief introduction about the effects of agro-processing industrial waste on the economic growth and environmental pollution. A brief explanation on the useful mineral contents of the sugarcane bagasse and bagasse ashes. In Chapter-2, a brief exposure to the concept of cellulose, silica, sol-gel process, hydrolysis of sodium silicate and alkoxysilane, nano-structured materials, synthesis of nano-structured materials, synthesis of hybrids of CNC-SiO2 nano-particle xero-gel materials has been provided. The detail of the materials, methods, the experimental procedures characterization techniques used and some theory behind these techniques have been provided in chapter 3. Chapter 4 deals with the extraction, optimization and characterization of cellulose. We have found that the purity levels of cellulose, hemicelluloses and lignin to be 89.86 ± 0.17 wt%, 6.098 ± 0.017 wt% and 2.61 ± 0.019 wt%, respectively. Chapter 5 discusses about the synthesis of silica nano-particle xerogel. We have successfully extracted sodium silicate from the purified sugarcane bagasse ash sample mixed with 2.5 M NaOH solution by thermo chemical method, and finally silica nano-particle xerogel material was synthesized form the HCl hydrolysis of sodium silicate solution using the sol-gel technique combined with freeze drying. We found that the synthesized SiO2 nanoparticle xerogel material has an average crystallite size of 5.67 ±0.3nm in diameter. In chapter 6 we report the synthesis techniques for the hybrids of cellulose nano-crystal/ SiO2 nano-particles xerogel and the detailed investigation of the properties of hybrid xerogel using different experimental techniques. A one-pot HCl hydrolysis of the two precursor materials: purified cellulose fiber and sodium silicate solution, and condensation processes utilizing a sol-gel technique and the two step protocols combined with freeze-drying were employed to synthesize hybrids of cellulose nano-crystals and silica nano-particles xerogel material. The synthesized hybrid xerogel material exhibited a distinctive hybrid structure, with an average diameter of ~15±0.025 nm. The thermal stability and conductivity properties of the hybrids were also investigated by combined thermo-gravimetric/differential thermal analyses and Thermal conductivity analyzer. We found that the hybrids of CNC-SiO2nano-particle xerogels have high thermal stability and insulation performance which is suitable for building thermal insulation. Chapter 7 summarizes the results of the dissertation and suggests scope for future research. Generally, this research works enabled to demonstrate the potential for converting the aforementioned by-products into products like cellulose fiber, sodium silicate solution, cellulose nano crystal xerogel, silica nano particle xerogel, and hybrids of CNC/SiO2 nanoparticle xerogel materials with added values would allow factories to get benefits and also to reduce the amount of hazardous materials they discharge into nearby water-ways and other areas.to promote greater environmental responsibility