Nanoparticles reinforced polymer composite films have been widely studied for their enhanced mechanical, electrical and thermal properties compared with host polymer matrix. However, most research was conducted on incorporation of nanoparticles in polymer films to improve single property and there is a lack of research on the multifunctional polymer nanocomposite films. In this work, a scalable and continuous spray deposition process was developed for the production of nanoparticles reinforced multifunctional thermoplastic nanocomposite films. This process is capable of making a thin sheet of thermoplastic nanocomposites with high nanoparticle loadings. The smallest thickness can be 40um. The objective of this study is to design and optimize the thermoplastic nanocomposite films by utilizing nanoclay and helical carbon nanotube for multifunctional application: a) high electrical conductivity and thermal stability. Helical carbon nanotube paper based thermoplastic polyurethane nanocomposite films have been studied. The electrical conductivity and thermal stability of nanocomposite films increase a lot due to the incorporation of helical carbon nanotube paper with high electrical and thermal conductivity. The peculiar helical configuration of carbon nanotubes could greatly improve the interfacial bonding between carbon nanotubes and polymer matrix. b)High wear resistance and thermal stability. A nanoclay reinforced thermoplastic polyurethane nanocomposite coating was applied on the surface of leather. Due to the high hardness and thermal stability of nanoclay, the leather coated with nanocomposite film showed an improvement of wear resistance and thermal stability.

The properties of C/SiCN nanocomposites synthesized by thermal decomposition of polymer precursors were studied in this work. The novel polymer-to-ceramic process enables us to tailor the ceramic structure in atomic level by designing the starting chemicals and pyrolysis procedures. It is of both fundamental and practical significance to investigate the properties and structures relationship of the nanocomposites. In this work, we explored their application potential in using as anode of lithium-ion secondary batteries. The structure and structural evolution of C/SiCN nanocomposite were investigated by using XRD, FTIR, SEM, TEM, Solid state NMR and Raman spectroscopy. The results revealed the nanocomposites consisted of amorphous SiCxNx-4 matrix and carbon nanoclusters distributed within it. The size of the carbon was measured by Raman spectroscopy, varied with starting chemicals and pyrolysis temperature. The electronic properties of the C/SiCN nanocomposite were studied by measuring the IV curves and a.c. impedance. The d.c. conductivity increased with carbon content and pyrolysis temperatures. The impedance spectra and fitted equivalent circuit results confirmed the existence of two phases in the nanocomposite. The possibility of using C/SiCN as anode in lithium-ion secondary batteries was investigated by electrochemical measurements, namely cyclic voltammetry, galvanostatic cyclic test and electrochemical impedance spectroscopy. The galvanostatic measurements showed that the nanocomposite with 26% of carbon nanoclusters exhibited a specific capacity of 480 mAh/g, iv which is 30% higher than that of commercial graphite anode. The high capacity of the nanocomposites is attributed to the formation of a novel structure around C/SiCN interface. The excellent electrochemical properties, together with the simple, low-cost processing, make the nanocomposites very promising for Li-ion battery applications

Access to clean water is one of the world's foremost challenges that has been addressed on a large scale by membrane-based separation processes for the last six decades. Commercial membrane technology within one operation, reverse osmosis, has remained consistent since the late 1970s, however within the last two decades, access to nanotechnology has created a realm of study involving thin film nanocomposite (TFN) membranes, in which nanoparticles are incorporated into existing membrane designs. Desirable properties of the nanoparticles may positively impact qualities of the membrane like performance, anti-fouling behavior, and physical strength. In the present work, two types of nanoparticles have been evaluated for their potential as TFN additives: cellulose nanocrystals (CNCs) and metal-organic framework (MOF) nanorods. CNCs were chosen due to their high aspect ratios, mechanical strength, and potential for surface functionalization. MOF nanorods are also of interest given their aspect ratios and potential for functionalization, but they also possess defined pores, the sizes of which may be tuned with post-synthetic modification. Both CNCs and MOF nanorods were incorporated into TFN membranes via interfacial polymerization, and the resulting membranes were characterized using a variety of techniques to establish their performances, but also to gain insight into how the presence of each nanoparticle might be affecting the membrane active layer formation. A resulting CNC membrane (0.5 wt% loading) exhibited a 160% increase in water flux and an improvement in salt rejection to 98.98 ± 0.41 % compared to 97.53 ± 0.31 % for a plain polyamide control membrane. Likewise, a MOF nanorod membrane (0.01 wt% loading) with a high ratio of acid chain modification exhibited a 95% flux increase with maintained high salt rejection. For the CNCs, the flux increase is attributed to the formation of nanoscale voids along the length of each particle that form during the interfacial polymerization. These nanochannels introduce new rapid water transport pathways within the active layer of each membrane while maintaining ion rejection. The proposed mechanism for the MOF nanorods also introduces nanochannels into each membrane, but the presence of each nanorod's pore structure may offer another transport pathway for water molecules, one that varies with pore size. In combination, these results have allowed the study of molecular transport of water molecules and various ion species within the active layer of a thin film composite RO membrane. Understanding these phenomena will allow the development of smarter membrane materials to address present-day and future separations challenges. Carbon nanotubes are also demonstrated as surface modifiers for forward osmosis (FO) membranes to address issues unique to the FO process, namely reverse solute flux (RSF). This method shows promise, as a coating density of 0.97 g/m2 reduced RSF for many draw solution species, including a 55% reduction for sodium chloride. / Doctor of Philosophy / Access to clean water is one of the world's foremost challenges that has been addressed on a large scale by membrane-based separation processes for the last six decades. Commercial membrane technology within one operation, reverse osmosis, has remained consistent since the late 1970s, however within the last two decades, access to nanotechnology has created a recent realm of study in which nanoparticles are incorporated into existing membrane designs. It is desired to use nanotechnology, or nanoparticles to improve membrane performance, i.e. create a membrane with better rejection of unwanted ions or contaminants or improve the amount of water that passes through the membrane. In the present work, two types of nanoparticles have been evaluated for their potential as TFN additives: cellulose nanocrystals (CNCs) and metal-organic framework (MOF) nanorods. Both CNCs and MOF nanorods were incorporated into membranes and the resulting membranes were characterized using a variety of techniques to establish how the nanoparticles affected performance. A resulting CNC membrane (0.5 wt% loading) exhibited a 160% increase in water flux (the amount of water passing through an area in a given amount of time) and an improvement in salt rejection. Likewise, a MOF nanorod membrane with a high ratio of acid chain modification exhibited a 95% flux increase with maintained high salt rejection. For both the CNCs and the MOFs, these performance changes are attributed to new pathways within each membrane for water flow that exist due to the presence of the nanoparticles in each system. In combination, these results have allowed the study of transport of water molecules and various ion species in each membrane. Understanding these results will allow the development of smarter membrane materials to address present-day and future separations challenges.

This work describes a model of the piezoresistive behavior in nanocomposite sensors. These sensors are also called flexible sensors because the polymer matrix allows for large deformations without failure. The sensors have conductive nanoparticles dispersed through an insulative polymer matrix. The insulative polymer gaps between nanoparticles are assumed to be possible locations for electron tunneling. When the distance between two nanoparticles is small enough, electrons can tunnel from one nanoparticle to the next and ultimately through the entire sensor. The evolution of this gap distance with strain is important to understand the overall conductivity of the strain sensor. The gap evolution was modeled in two ways: (1) applying Poisson's contraction to the sensor as a homogenous material, referred to as Simple Poisson's Contraction (SPC) and (2) modeling the nanoparticle-polymer system with Finite Element Analysis (FEA). These two gap evolution models were tested in a random resistor network model where each polymer gap was treated as a single resistor in the network. The overall resistance was calculated by solving the resistor network system. The SPC approach, although much simpler, was sufficient for cases where various orientations of nanoparticles were used in the same sensor. The SPC model differed significantly from the FEA, however, in cases where nanoparticles had specific alignment, e.g. all nanoparticles parallel to the tensile axis. It was also found that the distribution used to determine initial gap sizes for the polymer gaps as well as the mean of that distribution significantly impacted the overall resistivity of the sensor.Another key part of this work was to determine if the piezoresistivity in the sensors follows a percolation type behavior under strain. The conductance versus strain curve showed the characteristic s-curve behavior of a percolative system. The conductance-strain curve was also compared to the effective medium and generalized effective medium equations and the latter (which includes percolation theory) fit the random resistor network much more closely. Percolation theory is, therefore, an accurate way to describe this polymer-nanoparticle piezoresistive system.Finally, the FEA and SPC models were compared against experimental data to verify their accuracy. There are also two design problems addressed: one to find the sensor with the largest gauge factor and another to determine how to remove the characteristic initial spike in resistivity seen in nanocomposite sensors.

Carbon nanotubes are known as ideal fillers for polymer systems; the main advantage of carbon nanotubes over other nano-reinforcing particles is the combination of superior strength and stiffness with large aspect ratio. Carbon nanotubes may improve the mechanical, electrical and thermal properties of polymers, but to realise their potential in polymer systems uniform dispersion, strong interfacial adhesion and alignment of nanotubes within the polymer matrix are necessary. These properties are not easy to achieve and they are key challenges in producing CNT/Polymer system. This research was carried out in an attempt to understand how the properties of CNT/Polymer composite can be optimised by manipulation of additives, compounding and postcompounding conditions. Polypropylene/Multi-Walled Carbon Nanotube (PP/MCNT) composites were prepared by conventional twin screw extrusion. Dispersants and compatibilisers were used to establish good interaction between filler and polymer. Several different extruder screw configurations were designed and the properties of PP/MCNT composite prepared by each configuration investigated. The results indicated that the addition of carbon nanotubes without additives enhanced mechanical, electrical and thermal properties of polypropylene polymer. Incorporation of compatibilisers into PP/MCNT improved the stiffness but decreased the strength of the nanocomposite, whilst addition of dispersants decreased the mechanical properties of the nanocomposite. Addition of both additives at high concentration improved electrical conductivity and induced electrical percolation in the nanocomposite. Extruder screw configuration was found to have significant effect on the electrical conductivity whilst only slightly affecting mechanical properties of the nanocomposite, possibly due to the competition between dispersion and degradation of polymer chains and possible reduction of carbon nanotube length by intensive shear during compounding. The use of screw configuration with high mixing intensity promoted the dispersion of nanotubes and favoured the conduction process in the nanocomposite. Finally in an attempt to improve dispersion and alignment of carbon nanotubes, compounded PP/MCNT composite was subjected to micromoulding, fibre spinning and biaxial stretching processes and the resultant properties investigated. Application of post-compounding process was found to have significant effect on mechanical and rheological properties of the nanocomposite. Stiffness and strength of the nanocomposites treated by post-compounding processes were found to increase by up to 160% and 300%, respectively. The reinforcement effect of carbon nanotubes in the stretched nanocomposites was found to be the greatest. Rheological analysis suggested that the application of post-compounding processes enhanced dispersion of carbon nanotubes within the nanocomposite. Overall, this finding of this research has shown that carbon nanotubes can be incorporated into polypropylene using conventional equipment to provide significant improvement in properties. By careful choices of additives, compounding and postcompounding conditions, specific properties can be further enhanced. / Ministry of higher education in Kurdistan region in Iraq.

Hybrid organic-inorganic nanocomposites have received considerable attention during the last five years due to their unexpected properties. This work incorporated nanodispersed organically modified montmorillonite clay into polydicyclopentadiene resin matrices. Montmorillonite consists of 1 nm platelet sheets with a 2:1 structure, consisting of an alumina octahedral layer sandwiched between two silica tetrahedral layers. The relative weak forces between platelets allow small molecules like water, solvents and monomers as well as polymers, to enter into the interlayer spacings between the platelet sheets. In-situ polymerization of highly delaminated clay/dicyclopentadiene(DCPD) dispersions was used to prepare clay/polydicyclopentadiene (polyDCPD) nanocomposites. Highly delaminated composites were characterized using X-ray diffraction, X-ray scattering and high resolution TEM. Composites with 0.5-1 weight percent of clay had higher Tg values and flexural moduli. The flow properties of the organically-modified montmorillonite/DCPD liquid dispersions were examined using a co-rotating viscometer. The dispersions with clay concentrations higher than 0.5wt% clay in DCPD showed thixotropic flow behavior. Small angle neutron scattering (SANS) experiments were performed to obtain anisotropic scattering of highly delaminated clay in DCPD due to the orientation of clay platelets and tactoids in the shear field. No anisotropic scattering was observed. The reason for this unexpected result is not yet understood. Highly delaminated organically-modified clay composites were examined using small angle neutron scattering (SANS) and ultra small angle neutron scattering (USANS). The SANS data from 0.5, 1 and 2wt% clay/polyDCPD composites with 2 different types of clay were fitted to the stacked disk model. The average number of clay layers per tactoid was predicted by fitting the experimental data to the stacked disk model. Extensive high-resolution TEM analyses were performed on the same samples to obtain the average numbers of clay layers per tactoid. Two finite element models, one for the intercalated clay/polyDCPD nanocomposite and one for the exfoliated clay/polyDCPD nanocomposite, were developed. The effects of these different dispersion geometries for seven platelets in the polyDCPD matrix on the stress distributions were examined. The exfoliated platelet model showed reduced deformations and uniform stress distributions. The highest stress concentrations were found on the platelets? surfaces and where platelets were in close proximity.

The work presented in this thesis can be divided into two research areas. First, two sets of organic-inorganic hybrid nanocomposites containing phenolic resin/trisilanolphenyl-POSS and phenolic resin/octa(aminophenyl)-T8-POSS nanocomposites were synthesized and the morphology and properties were investigated. Octa(aminophenyl)-T8-polyhedral silsesquioxane is an octafunctional-T8-POSS containing eight aniline-like amino groups, one on each corner silicon atom. It was synthesized in our laboratory by an improved two-step reaction sequence; nitration (HNO3) and reduction (HCOOH/Et3N). Varying amounts of POSS were codissolved with a resole phenolic resin in organic solvent. This was followed by solvent removal and thermal curing. Intermolecular interactions in these nanocomposites were probed by FT-IR. The micro-morphology and aggregation state of POSS were investigated using SEM, TEM, and WAXD studies. The thermal and mechanical properties and thermal stabilities of these composites were investigated by DMTA, DSC, and TGA. Second, two types of carbon-covered mono- and bimetallic (Sn, and Sn/Sb alloy) nanorods for use as anode materials in lithium ion batteries were synthesized by a thermal chemical vapor deposition method. Commercial antimony and tin oxide (Sb3O4/SnO2) nanopowders and added tin (IV) oxide (SnO2) nanoparticles (~19 nm) were used as the precursors for the growth of bimetallic Sn/Sb alloy and monometallic Sn nanorods, respectively. In addition, the shape of the products recovered were different when different hydrocarbon gas flow rates were used for growing intermetallic nanorods in carbon templates. Acetylene and methane were the gases tried. The morphologies and structures of the intermetallic nanorods in carbon templates were investigated using SEM and TEM and proved by X-EDS, XRD, and XPS studies.

No description available.

No description available.

No description available.