Dissertations / Theses on the topic 'Nano-filled'

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.
Includes bibliographical references.
The incorporation of nanoparticles into engineering thermoplastic elastomers affords engineers an opportunity to formulate flexible, tough and multifunctional polymer nanocomposites that potentially rival the most advanced materials in nature. Development of these materials is difficult since thermodynamic and kinetic barriers inhibit the dispersal of inorganic, hydrophilic nanoparticles into inherently hydrophobic polymer matrices. Thermoplastic polyurethanes (TPUs) are particularly attractive nanocomposite matrix materials due to their vast range of potential applications (e.g. in artificial organs, coatings, foams, and active wear), their mechanical versatility, and tunable block-polymeric structure. In this thesis we explore methods for systematically nanoreinforcing such materials by exploiting the microphase structure, differential polarities and multiple thermomechanical phase transitions of the macromolecular blocks that constitute the elastomeric matrix. Using a solvent exchange technique we show that it is possible to preferentially nanoreinforce the hard micro-domains of thermoplastic elastomers with smectic clay nanofillers that have characteristic dimensions similar to the hard segment. The adhesion between the clay and the hard micro-domains coupled with the formation of a percolative network not only stiffens and toughens, but increases the heat distortion temperature (HDT) of the material. The discotic clay platelets induce morphological ordering over a range of length scales that results in significant thermomechanical enhancement and expands high temperature applications. This thesis seeks to further enhance the understanding and utility of thermoplastic polyurethane nanocomposites by answering two questions: (1) what thermo-physical interactions between nano-clay and elastomeric thermoplastic polyurethane are taking place? and (2) how can these thermo-physical interactions be exploited?
(cont.) To answer these questions the nano-reinforced-hard micro-domain morphology was monitored during deformation using in-situ wide angle x-ray scattering and combined with the results of extensive quasi-static mechanical testing which enabled the identification two characteristic relaxation times. A one-dimensional constitutive model to account for such morphological changes augmenting the previous model for unfilled polyurethanes developed by Qi and Boyce (2005) is discussed. Finally, the thermo-mechanical influence of nano-clay fillers on the shape memory effects exhibited by polyurethane nanocomposites is examined and multi-responsive shape memory polyurethane fibrous mats are developed via electrospinning. Quantifying and controlling the thermo-physical interactions between a block-copolymer with polar segments (e.g. thermoplastic polyurethane) and inorganic nanoparticles (e.g. nano-clay) is important for future nanocomposite processing strategies: the efficacy of nanoreinforcement hinges upon the close matching of characteristic length scale and the adhesion of the nanoparticles to the targeted polymer phase morphology. Exploiting the different polarity of the blocks in conjunction with solvent exchange approach developed in this thesis and solution processing techniques such as electro-spinning, offers an avenue toward the development of high performance, hierarchically-ordered materials that rival natural materials.
by Shawna M. Liff.
Ph.D.

No-flow underfill materials that cure during the solder reflow process is a relatively new technology. Although there are several advantages in terms of cost, time and processing ease, there are several reliability challenges associated with no-flow underfills. When micron-sized filler particles are introduced in no-flow underfills to enhance the solder bump reliability, such filler particles could prevent the solder bumps making reliable electrical contacts with the substrate pads during solder reflow, and therefore, the assembly yield would be adversely affected. The use of nano-sized filler particles can potentially improve assembly yield while offering the advantages associated with filled underfill materials. The objective of this thesis is to study the thermo-mechanical reliability of nano-filled epoxy underfills (NFU) through experiments and theoretical modeling. In this work, the thermo-mechanical properties of NFUs with 20-nm filler particles have been measured. An innovative residual stress test method has been developed to measure the interfacial fracture toughness. Using the developed residual stress method and the single-leg bending test, the mode-mixity-dependent fracture toughness for NFU-SiN interface has been determined. In addition to such monotonic interfacial fracture characterization, the interface crack propagation under thermo-mechanical fatigue loading has been experimentally characterized, and a model for fatigue interface crack propagation has been developed. A test vehicle comprising of several flip chips was assembled using the NFU material and the reliability of the flip-chip assemblies was assessed under thermal shock cycles between -40oC and 125oC. The NFU-SiN interfacial delamination propagation and the solder bump reliability were monitored. In parallel, numerical models were developed to study the interfacial delamination propagation in the flip chip assembly using conventional interfacial fracture mechanics as well as cohesive zone modeling. Predictions for interfacial delamination propagation using the two approaches have been compared. Based on the theoretical models and the experimental data, guidelines for design of NFUs against interfacial delamination have been developed.

In this work, fracture, mechanical, and flammability tests, along with a modeling of the stability of nanocomposite columns under fire are presented for nano-filled Diglycidyl Ether of Bisphenol A epoxy. The nanofillers used are montmorillonite nanoclays and carbon nanofibers. Three types of nanocomposites are manufactured: epoxy-clay, epoxy-carbon nanofiber, and epoxy-clay-carbon nanofiber nanocomposites. Fracture tests performed include Izod impact and fracture toughness, for the determination of the net Izod impact strength, the stress intensity factor, and the critical energy release rate. With static mechanical tests the tensile and flexural properties of the nanocomposites are measured. Flammability tests made by cone calorimetry are used to determine the Heat Release Rate, Mass Loss Rate, time to ignition, to Peak of heat Release rate and to flameout, and total smoke and heat released. A mathematical modeling of the stability of columns, made of the same nanocomposites tested, burning continuously in one side is performed. Three configurations are considered: uniform burning along the span, and burning spot at the center and at the corner of the column. The testing and the mathematical modeling reveal the higher mechanical strength and superior flammability properties produced by addition of nanofiller

In last few decades much research work has been conducted on the development of most efficient crashworthy structures which can protect vehicle drivers, passengers or at least reduce the severity of the accident by absorbing kinetic impact energy in the event of an accident. Thin-walled tubes are most commonly used members as crashworthy structures. It has been shown that thin walled tubes, filled with foam materials, possess efficient energy-absorbing capability than the empty crashworthy structure. This characteristic of foam materials has led to the development of different new foam materials, which can absorb more impact energy. Nanotechnology is one of the emerging techniques used in development of advanced materials for engineering and other applications. One such application is in developing energy absorbing materials, which can be used in automotive and aerospace industry. The purpose of this thesis is to analyze properties of the thin walled tubes with respect to energy absorption capacity, when filled with carbon nano-foam. The application of such carbon nano foam in the bumper area of a particular vehicle model namely Dodge Caravan is analyzed at different speeds. To accomplish this study, the Ls-Dyna code, a non-linear dynamic finite element solver is utilized. First, experiment using compression tests are carried out to obtain the behavior of the foam material by adding different weight percentages of carbon nano fibers. Next, the axial crushing behavior of thin walled steel tube was observed. The energy absorption capabilities of this crashworthy tube are tabulated and results are compared with rigid polyurethane foam under similar conditions. Finally carbon nano foam is applied in the bumper area of a vehicle model to study its crashworthy behavior in frontal impact at different speeds of the vehicle.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.

Increasing loading level of precipitated calcium carbonate (PCC) in high value added communication-grade papers from bleached thermo-mechanical pulp (TMP) beyond the current level not only further reduces the production cost but also mitigates the shortage of good quality wood fibres. This thesis explores the possibility to retain increased amounts of PCC by taking advantage of the most recent developments in starch and nanoparticle technologies. Response surface methodology was used to optimize the addition strategy of chemicals and evaluate their effects in laboratory trials using mill samples. Empirical process models were also constructed to predict the retention and drainage results. It was found that linear high charge cationic starch S880 always resulted in highest retention for PCC preflocculation strategy and best drainage performance regardless of conventional chemical addition sequence or PCC preflocculation strategy. PCC preflocculation by starch resulted in higher breaking length and burst indices compared to the conventional chemical addition sequence. The relationship among starch properties, process conditions, and floc properties was established through the investigation of PCC aggregation kinetic and floc structure evolution to allow the judicious selection of starch for PCC preflocculation. The population balance modelling approach was adopted to describe PCC flocculation. It was found that the linear high charge cationic starch S880 is associated with lower collision efficiency; lower restructure rate and higher energy dissipation rate to break up the flocs compared to the low charge cationic starch S858. The presence of NaCl was found to affect the high charge cationic starch S880 but had no influence on the low charge cationic starch S858. The collision efficiency decreases with the increase of the shear rate for both starches. The knowledge of the floc aggregation, breakage and restructure under various process conditions is expected to enable the manipulation of the floc with specified size, strength, and structure for better retention and drainage.

Automotive crash has garnered significant attention in the recent years with increasing fatality and safety concerns. Substantial effort and great amount of time and expertise has been directed towards the issues related to crashworthiness such as impact, rollover scenarios and restraint performance. Automotive rollover is one of those important concerns for the auto industry as the fatality rates and death causing conditions are vital compared to other crashes. In the past few decades, research has been focused towards developing efficient roof structure by implementing crashworthy structures, to protect or at least reduce the severity of the accident to the occupants of the vehicle during an event of a rollover. Studies have been carried in this area in developing efficient crashworthy structures. As the technology is evolving, researchers have found that thin walled tubes filled with foam materials possess high energy absorption properties compared to empty crashworthy structures. Further research in this has area led to the interference of nanotechnology, which implements emerging techniques in developing advanced materials for engineering applications. Scientists were able to develop low density, lightweight foams with high energy-absorption characteristics with these techniques. The purpose of this thesis is to analyze and evaluate the performance of low density carbon nanofoam (CNF) as an energy absorbing material in improving the roof strength of the vehicle. The LS- DYNA code, a non-linear dynamic finite element solver is utilized to accomplish this study. First, a three- point bending test simulation is carried as component level testing to analyze the behavior of foam materials. Then, the energy absorbing characteristics of a hollow tube is studied and the results are compared with regular polyurethane (PU) foam and carbon nanofoam inserts into the hollow tube, under similar conditions. Finally, PU foam and CNF is applied into the critical areas of roof supporting structures as two different conditions and static roof crush and dynamic inverted drop test simulations are conducted depicting an actual rollover scenario to study the crashworthy behavior of the vehicle roof with and without the foam. This study highlights that carbon nanofoam is found to be more effective compared to the regular polyurethane foam exhibiting better energy absorption characteristics.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering

L'usure des élastomères chargés réticulés génère souvent des faciès à rides, que l'on peut voir notamment sur les pneumatiques dans certaines conditions d’utilisation. Le but de cette étude est d’étudier ces rides, reproduites en laboratoire au moyen d'un tribomètre spécifique, afin d'en expliquer le mécanisme de formation. Des grandeurs telles que la perte de masse, le coefficient de frottement, la rugosité et les propriétés mécaniques de surface sont analysées. L'apparition d'un tel faciès est reliée à des aspects de vibrations dans le contact et de champ de contraintes de traction à l'arrière du contact. Les rides obtenues présentent parfois des languettes plus ou moins enroulées et évoluent vers des débris d'usure en forme de rouleaux. Ce faciès à rides s'estompe ensuite au cours de l'essai tribologique pour disparaître lorsque la distance glissée devient grande. Une approche énergétique permet de souligner les couplages existant entre les différentes propriétés du matériau, le frottement, le faciès et l'usure
The wear of filled rubber compounds often produces a ridge pattern which can be seen on tyres in certain driving conditions. The goal of this work is to study the ridges obtained in laboratory experiments on a specific tribometer and explain the mechanism of their formation. Parameters such as friction coefficient, loss of weight, rugosity and surface mechanical properties have been studied. The origin of this pattern is linked to contact vibrations and tensile stress field at the rear of the contact. The upper part of the ridges sometimes presents tongs which can be rolled and the ridges lead to roll shaped wear debris. The pattern then fades during the next part of the tribological test and disappears when the sliding distance becomes high. An energetical approach leads to emphasize the links between material properties, friction, pattern and wear

碩士
國防大學理工學院
化學工程碩士班
103
The study is divided into three parts, the first part of expanded graphite flake powder filled in the epoxy resin to the kneading manner by changing the mixing time, degassing time, adding a solvent to enhance the heat transfer coefficient. The second part of the epoxy resin as the base material, with different types of graphene different process parameters and flaking of expanded graphite flake as the filler material, through the traditional way of mixing to 15 wt.% of 1100xGnP. It`s k value can be increased to 1.68 W / m • K. Graphene has a high specific surface area, and graphene at 1 wt.% Loading level has improved significantly the effect of thermal conductivity, but with time increase the amount of filler, graphene contact resistance also increases, therefore, enhance the effect of reducing the graphene heat transfer coefficient. In addition, we found 300oC thermal reduction of 300xGnP, TIM development of all its good thermal conductivity and electrical insulation innate its low production cost and conducive to mass production. The third part, due to the thermal interface material in use often promised to insulation, and the resistivity of the carbon material itself is very low, so the simple use of a carbon material as filler material is unlikely, therefore its use boron nitride filler material high thermal conductivity characteristics and a high resistivity characteristic of this nano-carbon material composite of two materials, the thermal conductivity has to maintain and improve the resistivity characteristics. It was found in the use of low thermal expansion of the filling amount of flake graphite and boron nitride composite material, with the best thermal conductivity and high electrical resistivity, B50x11001 its k value of 1.81 W / m • K to resistance value ρ=1014 ohm-cm . In addition, we found that adding 5 wt.% of expanded graphite foil peeling while maintaining a high thermal conductivity and high resistivity condition, has reduced the maximum amount of boron nitride effective to reduce the cost of the thermally conductive composite material. Keyword: Graphene, Exfoliated expandable graphite, Thermal interface materials

Polymers are widely used as insulating materials in high voltage power apparatus because of their excellent electrical insulating properties and good thermomechanical behavior. However, under high electrical stress, polymeric materials can get deteriorated which can eventually lead to the failure of the insulation and thereby the power apparatus. Electrical treeing is one such phenomena whereby dendritic paths progressively grow from a region of high electrical stress and branch into conducting channels in a solid dielectric. The propagation of electrical trees is of particular interest for the power industry as it is one of the major causes of failure of high voltage insulation especially in high voltage cables, cast resin transformers as well as rotating machines. To improve the life time of the electrical insulation systems there is a need to improve the electrical treeing resistance of the insulating material for high voltage application. With the development of nanotechnology, polymer nanocomposites containing nano sized particles have drawn much attention as these materials are found to exhibit unique combinations of physical, mechanical and thermal properties that are advantageous as compared to the traditional polymers or their composites. Literature reveals that significant progress has been made with respect to the mechanical, optical, electronic and photonic properties of these functional materials. Some efforts have also been directed towards the study of dielectric/electrical insulation properties of these new types of materials. Considering the above facts, the present research work focuses on utilizing these new opportunities which have been opened up by the advent of nanocomposites to develop tree resistant insulating materials for high voltage power applications. Electrical treeing is a common failure mechanism in most of the polymeric insulation systems and hence electrical treeing studies have been carried out on two types of polymers (viz. polyethylene used in high voltage cable and epoxy used in rotating machines and resin cast transformers) along with three different types of nano-fillers, viz. Al2O3, SiO2 and MgO and with different filler loadings (0.1, 1, 3, 5 wt%). Furthermore, considering the fact that electrical treeing is a discharge phenomenon, the partial discharge characteristics during electrical tree growth in polymer nanocomposites was studied. As morphological changes in the polymer influence the electrical tree growth, the influence of nano-particle induced morphological changes on the electrical treeing has also been studied. Above all, an attempt has also been made to characterize and analyze the interaction dynamics at the interface regions in the polymer nanocomposite and the influence of these interface regions on the tree growth phenomena in polymer nanocomposites. A laboratory based nanocomposite processing method has been successfully designed and adopted to prepare the samples for treeing studies. Treeing experimental results show that there is a significant improvement in tree initiation time as well as tree inception voltage with nano-filler loading in polymer nanocomposites. It is observed that even with the addition of a small amount (0.1 and 1 % by weight) of nano-particles to epoxy results in the improvement of electrical treeing resistance as compared to the unfilled epoxy. In fact, different tree growth patterns were observed for the unfilled epoxy and epoxy nanocomposites. Surprisingly, even though there is not much improvement in tree inception time, a saturation tendency in tree growth with time was observed at higher filler loadings. To understand the influence of nano-particles on electrical treeing, the interaction dynamics in the epoxy nanocomposites were studied and it was shown that the nature of the bonding at the interface play an important role on the electrical tree growth in epoxy nanocomposites. The results of electrical treeing experiments in polyethylene nanocomposites obtained in this study also reveal some interesting findings. An improved performance of polyethylene against electrical treeing with the inclusion of nano-fillers is observed. It is observed that there is a significant improvement in the tree inception voltage even with low nano-filler loadings in polyethylene. Other interesting results such as change in tree growth pattern from branch to bush as well as slower tree growth with increase in filler loading were also observed. Another peculiar observation is that tree inception voltage increased with increase in filler loading upto a certain filler loadings (3 % by weight) and then decreased in its value at high filler loading. The morphology of polyethylene nanocomposites was studied and a good correlation between morphological changes and treeing results was observed. Effect of cross-linking on electrical treeing has also been studied and a better performance of cross-linking of nano-filled polyethylene samples as compared to the polyethylene samples without cross-linking was observed. The partial discharge (PD) activity during electrical tree growth was monitored and different PD characteristics for unfilled and nano-filled polyethylene samples were observed. Interestingly, a decrease in PD magnitude as well as the number of PD pulses with electrical tree growth in polyethylene nanocomposites was observed. It is known that PD activity depends on the tree channel conductivity, charge trapping and gas pressure inside the tree channel. The ingress of nano-particles into the tree channel influences the above known phenomena and affects the PD activity during electrical tree growth. The observed decrease in PD magnitude with increase in filler loading leads to the slow propagation of electrical trees in polyethylene nanocomposites. In summary, it can be concluded that polymer nanocomposites performed better against electrical treeing as compared to the unfilled and the conventional micron sized filled polymer composites. Even with low filler loading an improved electrical treeing resistance was observed in polymer nanocomposites. An optimum filler loading and a suitable filler to inhibit electrical treeing in the polymers studied are proposed. This work also establishes the fact that the characteristics of the interface region and the induced morphological changes have a strong influence on the electrical treeing behaviors of nanocomposites. These encouraging results showed that epoxy and polyethylene nanocomposites can be used as tree resistant insulating materials for high voltage applications. These results also contribute to widen the scope of applications of polymer nanocomposites in electrical power sector as well as development of multifunctional insulation systems.

Colour changes in composite resins after immersion in beverages such as coffee, tea, alcohol beverage and carbonated drinks have been reported. Although much work has been done to determine the staining susceptibility of composite resins to various liquid beverages, effects of spices on colour stability of composite resins have not been fully researched. Objectives: The aim of this study is to evaluate the colour stability of nano-filled (Filtek Supreme™) and micro-hybrid (Gradia Direct™) composite resins finished with either Sof-Lex™ discs or mylar strips upon exposure to turmeric, paprika and tamarind. Materials and methods: Twenty cylindrical specimens were fabricated from two commercially available composite resins; Filtek Supreme XT™ (3M ESPE, St Paul, MN) and Gradia Direct X™(GC AMERICA). The top surfaces of the specimen were polished with Sof–Lex™ aluminium oxide discs (3M/ESPE, St Paul, MN USA) while the bottom surfaces were mylar strips finished. All samples were subjected to 500 thermocycling rounds between 5 and 55 ºC with 20 seconds dwell time prior to immersion in staining solution. Twenty specimens from each type of composite were then randomly divided into 4 groups (n=5) and immersed in each staining solutions (0.1% turmeric, paprika and tamarind) and distilled water (control) at 37 ºC. Colour measurement at baseline, after thermocycling, 24 hours (1 day), 72 hours (3 days) and 168 hours (7 days) of immersion in staining solutions were recorded with a reflection spectrophotometer under the D65 (daylight) illuminant using CIE L* a* b* parameters. Repeated measures analysis of variance (ANOVA) and Bonferroni post hoc tests were used to determine the significance and possible interactions of each factor. Results: Among all the staining solutions tested, the highest colour deviation was obtained in the turmeric group, with mean colour change (ΔE) ranging between 17.92 and 55.25. Paprika recorded mean colour change (ΔE) ranging between 1.28 and 3.72, while tamarind produced mean colour change (ΔE) ranging between 1.12 and 5.42. The effect of finishing method on colour stability of composite resins appeared to be dependent on the type of composite resin. Filtek Supreme™ with mylar strips finished generally resulted in significantly more colour changes compared with specimens polished Sof-Lex™ discs, while Gradia Direct™ finished with mylar strips were found to be more resistant to colour changes. Colour change (ΔE) values were significantly influenced by the staining solutions, types of materials and finishing methods. Conclusion: Within the limitations of this study, all spices used (turmeric, paprika and tamarind) have a potential to stain composite resins; with turmeric causing the most severe discolouration regardless of the type of composite resin or finishing technique employed. The result of this study also suggests that different materials respond differently to staining by spices when either finished with mylar strips or polished with Sof-Lex™ discs. Also, contemporary composite resins available in the market e.g. nano-composite and micro-filled hybrid composite are still susceptible to discolouration by exogenous factors despite advancement in the development of resin based restorative material.
Thesis (D.Clin.Dent.) -- University of Adelaide, School of Dentistry, 2012

Indiana University-Purdue University Indianapolis (IUPUI)
Background: Since the introduction of glass ionomer cements (GICs) in the 1970s, many attempts have been made to improve them and expand their application in restorative dentistry. Recently, GC America introduced a new glass ionomer restorative system called EQUIA. The manufacturer claims that this material has improved wear resistance by coating the surface of high-strength GIC with a nano-filled resin coating. Objective: The objective of this study was to measure the wear resistance and hardness of EQUIA and to compare it to other current restorative materials. Materials and Methods: Four different materials were used in this study: EQUIA, Fuji IX GP Extra, Fuji II LC and Z-100. Six specimens of each material were made and then tested in a toothbrush abrasion machine for 20,400 cycles, after which the amount of volume loss was calculated. Eight specimens of each material were made and tested in a three-body Alabama wear testing machine under a load of 75 N for 400,000 cycles. Four surface profiles were obtained from each specimen and volume loss was calculated using computer software. Five specimens of each material were made and Knoop microhardness was determined by using the mean of the three values from the top surface of the specimen. Results of each test were collected and compared with the other materials using one-way analysis of variance (ANOVA) at a significance level of 0.05. Results: Wear-resistance results showed that EQUIA has wear-resistance values comparable to composite resin and higher values than those for the high-strength GIC. The results also showed that Fuji II LC had the highest wear among all tested materials. Microhardness results showed that EQUIA has significantly lower microhardness than Fuji IX GP Extra and Z-100. Conclusion: Based on the results of the present study, it can be concluded that coating the surface of glass ionomer restorations with a nano-filled resin coat results in increasing the wear resistance and decreasing the microhardness of the material. Within the limitations of this study, EQUIA has comparable wear resistance to composite resin.

碩士
國立清華大學
電機工程學系
100
Photoacoustic (PA) imaging requires contrast agents which can enhance the contrast and efficiency of tumor targeting, own high thermal stability and long circulation time, and are effective in low doses in vivo. In this study, we developed magnetic porous nano-silica beads with pore-filled gold nanorods (FeAuNSBs) as a multi-functional contrast agent of photoacoustic imaging. It owns the merits of gold nanorods with silica coating – high biocompatibility, PA signal amplification and optical tunability for PA signal generation. The magnetic property of its embedded iron oxide is used to improve tumor targeting, i.e., magnetic targeting. Phantom experiments were performed to confirm the tunability of FeAuNSB’s optical absorbance in near-infrared light, which ranges from 600-900nm, which allows us to avoid the interference of blood. Experiments with exposure of the phantom to laser pulses demonsrated the higher photothermal stability of FeAuNSBs. The wavelength of peak optical absorption was also sustained. The magnetic targeting property of FeAuNSBs enhanced the contrast in tumor regions by approximately 17 dB. It was also found that the FeAuNSB aggregation caused by magnetic targeting increased the contrast in ultrasound imaging. The in-vivo experimental results showed that with the magnet targeting to a tumor, we obtained a high contrast increase of about 10 dB over the targeted region in PA and US images, which is higher than 2 dB achieved using conventional AuNRs. Overall, we proved the feasibility of FeAuNSBs as a good tumor targeting contrast agent of PA imaging. Future work will focus on verification of FeAuNSB’s performance on photothermal therapy with PA image guidance.

abstract: Traditionally, for applications that require heat transfer (e.g. heat exchangers),metals have been the go-to material for manufacturers because of their high thermal as well as structural properties. However, metals have some notable drawbacks. They are not corrosion-resistant, offer no freedom of design, have a high cost of production, and sourcing the material itself. Even though polymers on their own don’t show great prospects in the field of thermal applications, their composites perform better than their counterparts. Nanofillers, when added to a polymer matrix not only increase their structural strength but also their thermal performance. This work aims to tackle two of those problems by using the additive manufacturing method, stereolithography to solve the problem of design freedom, and the use of polymer nanocomposite material for corrosion-resistance and increase their overall thermal performance. In this work, three different concentrations of polymer composite materials were studied: 0.25 wt%, 0.5 wt%, and 1wt% for their thermal conductivity. The samples were prepared by magnetically stirring them for a period of 10 to 24 hours depending on their concentrations and then sonicating in an ice bath further for a period of 2 to 3 hours. These samples were then tested for their thermal conductivities using a Hot Disk TPS 2500S. Scanning Electron Microscope (SEM) to study the dispersion of the nanoparticles in the matrix. Different theoretical models were studied and used to compare experimental data to the predicted values of effective thermal conductivity. An increase of 7.9 % in thermal conductivity of the composite material was recorded for just 1 wt% addition of multiwalled carbon nanotubes (MWCNTs).
Dissertation/Thesis
Masters Thesis Mechanical Engineering 2020