Increase in carbon dioxide emissions due to economic activity induce global warming. The strong increase in energy demand, mainly based on oil and coal, induces a rapid increase in CO2 in the atmosphere. Within Canada, the amount of human-produced carbon dioxide is considerable because a large portion of energy is supplied by burning of fossil fuels. The Reverse Water Gas Shift (RWGS) reaction is a promising catalytic process for the utilization and subsequent activation of carbon dioxide to carbon monoxide, which can be further converted into fuels such as gasoline. The current thesis studies the development of nano-catalytic systems for the RWGS reaction. Mono- and bi-metallic nanoparticles based on Cu, Fe, Ru and Pt were prepared using a polyol synthesis method. The catalytic performance of three different types of metal oxides (ionically conductive, mixed ionic-electronic conductive and non-conductive) was investigated for the RWGS reaction. Conductive metal oxides including samarium-doped ceria (SDC), ceria (CeO2), yttria-stabilized zirconia (YSZ) and iron III oxide (Fe2O3) were further used as the catalyst supports and the nanoparticles of Cu, Fe, CuxFe1-x (x = 50 and 95 at.%), Ru, Pt, Ru50Pt50 and RuxFe1-x (x = 80 and 90 at.%) were subsequently deposited on them. A stoichiometric mixture of H2 and CO2, i.e. H2/CO2 = 1, was used under atmospheric pressure in the temperature range of 300 - 600°C in order to evaluate the catalyst performance in terms of activity, stability and selectivity. Nanoparticles deposited on ceria-based supports (CeO2 and SDC) showed superior catalytic performance compared to other metal oxides. Among all the catalyst tested, 5 wt.% Ru50Pt50/CeO2 showed the highest CO yield and satisfactory stability for RWGS reaction. The second best catalytic systems were based on Ru90Fe10/CeO2 and Ru80Fe20/CeO2, which are more attractive from the practical point of view.

Thesis advisor: Michael J. Naughton / In this dissertation, I first discuss many different kinds of transparent conductors in Chapter one. In Chapter two, I focus on transparent conductors based on crackle temples. I and my colleagues developed three (one sputter-free and two fully all-solution) methods to fabricate metallic networks as transparent conductors. The first kind of all-solution process is based on crackle photolithography and the resulting silver networks outperform all reported experimental values, including having sheet resistance more than an order of magnitude lower than ITO, yet with comparable transmittance. The second kind of all-solution proceed transparent conductor is obtained by integrating crackle photolithography-based microwires with nanowires and electroplate welding. This combination results in scalable film structures that are flexible, indium-free, vacuum-free, lithographic-facility-free, metallic-mask-free, with small domain size, high optical transmittance, and low sheet resistance (one order of magnitude smaller than conventional nanowire-based transparent conductors). / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

No description available.

This is Part B of the Thesis. Here is the Link to Part A: http://hdl.handle.net/11375/17844 / <p> This report deals with the effects of various parameters on the resistance and the temperature coefficient of resistance (or the T.C.) of tin dioxide films doped with antimony and boron. The films were produced on cylindrical ceramic substrates by the hydrolysis of SnCl4 and SbCls in the presence of HCl and H3BO3. The T.C. was measured over the range of 25 to 150°C and averaged.</p> <p> Under normal conditions, the films were produced at 950°C with an antimony concentration of 0.457 molar % and a boron concentration of 2.73 molar %. Varying this firing temperature (from 800-1100°C) was found to have no effect on the resistance but increased the T.C. by 2 to 3 ppm/°C per degree change. Varying the antimony content from 0 to about 1 molar % was found to have little effect on resistance. The effect on T.C. was to increase it at lower Sb levels and then to decrease the T.C. as the level increased.</p> <p> Varying the boron content (0 to 4.46 molar %) was also found to have little effect on resistance. A decrease in T.C. with boron content was noted when only the boron was varied, but an increase in T.C. was found when HCl and H2O volumes were varied with the boron. The introduction of additional air into the system was found to have no effect.</p> <p> Film thicknesses were varied by controlling the chemical flowrates. Thinner films were found to have dramatically higher resistances and reduced T.C. values. It was observed that below a certain flowrate resistive failure occurred in the films. It was found in this study that within the statistical distribution of film values, those samples with above average resistance had below average T.C. values and vice-versa. Annealing in vacuum at 500°C was found to produce samples of reduced resistance and increased T.C. while the opposite was found with air annealed samples. Quickly cooled samples were found to be more stable.</p> / Thesis / Master of Engineering (MEngr)

No description available.

After skeletal muscle damage, satellite cells move towards the injured area to assist in regeneration. However, these cells are rare as their numbers depend on the age and composition of the injured muscle. This regeneration method often results in scar tissue formation along with loss of function. Although several treatment methods have been investigated, no muscle replacement treatment currently exists. Tissue engineering attempts to create, repair, and/or replace damaged tissue by combining cells, biomaterials, and tissue-inducing substances such as growth factors. Electrospinning produces a non-woven scaffold out of biomaterials with fiber diameters ranging from nanometers to microns to create an extracellular-like matrix on which cells attach and proliferate. Our focus is on synthetic polymers, specifically poly(D,L-lactide) (PDLA), poly(L-lactide) (PLLA), and poly(ε-caprolactone) (PCL). Skeletal muscle cells grown on electrospun scaffolds tend to elongate and fuse together thus, mimicking natural tissue. Electrical stimulation has been shown to increase the number of cells fused in culture and decreased the time needed in culture for cells to contract. Therefore, a conductive element was added to each scaffold, specifically polyaniline (PANi), gold nanoparticles (Au Nps), and multi-walled carbon nanotubes (MWCNT). Our project goal is to create a polymeric, conductive, and biocompatible scaffold for skeletal muscle regeneration. PANi and PDLA were mixed to form the following solutions 24% (83% PDLA/17% PANi), 24% (80% PDLA/20% PANi), 22% (75%PDLA/25% PANi), 29% (83% PDLA/17% PANi), and 29% (80% PDLA/20% PANi). Only the 75/25 electrospun scaffold was conductive and had a calculated conductivity of 0.0437 S/cm. Scaffolds with larger amounts of PANi were unable to be electrospun. PDLA/PANi scaffolds were biocompatible as primary rat skeletal muscle cells cultured in vitro did attach. However, the scaffolds shrunk, degraded easily, and became brittle. Although PDLA/PANi scaffolds were easily manufactured, our results indicate that this polymer mixture is not appropriate for skeletal muscle scaffolds. PLLA and Au Nps were electrospun together to form three composite scaffolds: 7% Au-PLLA, 13% Au-PLLA, and 21% Au-PLLA. These were compared to PLLA electrospun scaffolds. Measured scaffold conductivities were 0.008 ± 0.015 S/cm for PLLA, 0.053 ± 0.015 S/cm for 7% Au-PLLA, 0.076 ± 0.004 S/cm for 13% Au-PLLA, and 0.094 ± 0.037 S/cm for 21% Au-PLLA. It was determined via SEM with a Bruker energy dispersive x-ray spectrometer (EDS) that the Au Nps were not evenly distributed within the scaffolds as they had agglomerated. Rat primary muscle cells cultured on the three Au-PLLA scaffolds displayed low cellular activity. A second cell study was conducted to determine Au NPs toxicity. The results show that the Au Nps were not toxic to the cells and the low cellular activity may be a marker for myotube fusion. Elastic modulus and yield stress values for the three Au-PLLA scaffolds measured on days 0, 7, 14, 21, and 28 were much larger than skeletal muscle tissue. Due to the larger mechanical properties and Au Nps agglomeration, a third polymer and conductive element scaffold was investigated. PCL was chosen as the new synthetic polymer as it had a lower elastic modulus and high elongation. MWCNT were chosen as the conductive element as they disperse well within PCL when acid functionalized. A third component was added to the scaffold to help it move similar to skeletal muscle. Ionic polymer gels (IPG) are hydrogels that respond to an external stimulus such as temperature, pH, light, and electric field. A poly(acrylic acid)/poly(vinyl alcohol) (PAA/PVA) mixture is one type of IGP that responds to an electric field. The scaffolds were coaxially electrospun so that each fiber had a PCL-MWCNT interior with a PAA/PVA sheath. These scaffolds were compared to electrospun PCL and PCL-MWCNT ones. The addition of MWCNT to the PCL did increase scaffold conductivity. Actuation of the PCL-MWCNT-PAA/PVA scaffold occurred when 15V and 20V were applied. All three scaffolds had rat primary skeletal muscle cells attached but, more multinucleated cells with actin interaction were seen on PCL-MWCNT-PAA/PVA scaffolds. Once again the mechanical properties were greater than muscle, but because of its ability to actuate we believe the PCL-MWCNT-PAA/PVA scaffold has potential as a bioartificial muscle. Further characterization of the PCL-MWCNT-PAA/PVA included varying the ratios of PAA/PVA, smaller crosslinking times, and lower amounts of MWCNT. Four ratios, 83/17, 60/40, 50/50, and 40/60, were successfully coaxially electrospun with PCL and MWCNT. Overall, very few differences were seen between the four ratios in conductivity, cellular biocompatibility, actuation angular speed, and mechanical properties. The 83/17 and 40/60 ratios were chosen for additional investigation into mechanical properties and actuation. As the mechanical properties of the two types of scaffolds did not change significantly through degradation, lower PVA crosslinking times were tested. No significant effects were found and it was hypothesized that the evaporation of the solution played a role in the crosslinking process. The smaller MWCNT amount scaffolds also did not significantly affect the mechanical properties or the actuation angular speeds. More work into lowering the scaffold mechanical properties while increasing the actuation angular speed is necessary. Though the mechanical properties for the 83/17 and 40/60 scaffolds remained high compared to skeletal muscle, we also looked for differences in in vivo biocompatibility. Both scaffolds were implanted into the right vastus lateralis muscle of Sprague-Dawley rats. The left vastus lateralis muscle served as either the PBS injected sham surgery or an unoperated control. Biocompatibility was evaluated using enzymes, creatine kinase (CK) and lactate dehydrogenase (LDH), levels, fibrosis formation, inflammation, scaffold cellular infiltration, and neovascularization on days 7, 14, 21, and 28 post-implantation. Fibrotic tissue formation, inflammation, and elevated CK and LDH levels were observed initially but responses decreased during the four week study. Cells infiltrated the scaffolds and histological staining showed more fibroblasts than myogenic cells initially but over time, the fibroblasts decreased and myogenic cells increased. Neovascularization of both scaffolds was also recorded. PCL-MWCNT-PAA/PVA scaffolds were determined to be biocompatible, but some differences between the two types were noted. The 83/17 scaffolds caused less of a response from the body compared to the 40/60 scaffolds and had more myogenic cells attached. However, the 40/60 scaffolds had a larger number of blood vessels running through the scaffold. In conclusion, we have successfully fabricated a polymeric, conductive, and biocompatible scaffold that can actuate for skeletal muscle tissue engineering. Although our results are promising, more work is necessary to continue developing and refining the scaffold. / Ph. D.

Polyelectrolytes are conductive polymers because of their ionic side group and PEDOT-S is one of those conductive polyelectrolytes. Previously, recombinant silk fibre has been dyed with PEDOT-S. PEDOT-S showed that it can be dyed with recombinant silk fibre over a very wide range of pH from 11 to 1.7. Previous experiments of dyeing recombinant silk fibre with PEDOT-S has shown that it is a very versatile process and can also be applied on other types of protein-based fibres, and that prompted me to dye wool and silk fibre from Bombyx Mori and make these fibres functionalized. So in this thesis dyeing of wool and silk fibres with PEDOT-S has been carried out. By this bottom-up approach of making an organic polymer electrically conductive and utilising the flexibility of organic polymer, one can integrate it in OLEDs and in smart textiles. In this thesis dyeing of silk and wool fibres with different dyeing pH has been carried out to maximise the exhaustion of dyes on to the fibres to acquire maximum conductance. Then the wool and silk fibres’ conductance and mechanical properties after dyeing were compared. Wool showed better conductance and mechanical properties as compare to silk after being dyed with PEDOT-S. These results helped to propose a model that tells about the interaction between protein-based fibres and polyelectrolytes and gives us better understanding of how these protein-based fibres show certain conductivity at different pH. Results also showed that these conductive fibres can be used further in special purposes and applications. / Program: Magisterutbildning i textilteknologi

This thesis has evaluated how electrical surface resistance can be measured on conductive coated textiles using two different probes. The electrical surface resistance is a measurement for how difficult it is for current to flow through a material. For textiles, the surface resistance can be measured using four metallic plates, that measure the difference between current supply and voltage drop, this method is called a linear four-point probe.   There is no standard method for measuring the electrical surface resistance on conductive textiles. Therefore, it is not possible to compare textiles made by different producers. It is also not possible to decide what the true resistance is and as conductive textiles are becoming more popular to use, this has started to become a problem in the industry.   Two probes with electrodes of different dimensions were used to evaluate how different electrodes would affect the measured resistance. Measurements were conducted on conductive coated textiles with varying parameters, like coating thickness, sample size and textile construction, to show how the electrical resistance properties differ depending on what probe was used.   It was found that in contrast to other research on conductive textiles and collinear four-point probes, the probes used in this study could detect electrical anisotropic properties. The resistance was different depending on what angle it was measured in. This was found for both a thicker coating and a thinner one. It was also found that the probes could detect a correlation between the angular resistance and the textile construction used.   By measuring the resistance on small samples with the same dimension as the probes electrodes, the resistance was increased compared to when measurements were conducted on samples with dimensions significantly larger than the probes.   Furthermore, the results showed that increasing the distance between the inner electrodes of the probe decreased the measured resistance for both large and small samples. Additionally, it was found that by increasing the width of the outer electrodes the resistance was decreased, an increase in outer electrode width also made it easier to detect electrical anisotropic properties.

George Kelly's Personal Construct Theory, especially as subsumed within the “conversational science" paradigm developed by Thomas and Harri-Augstein, is fundamentally a framework for a geometry of personal meaning in which all of the dimensions of distinction within a person’s experience are like the dimensions of geometric space. A person's system of constructs is not just a framework for predicting the attributes of future events; it is a coordinate system for navigating the dimensionality of experience. The work of F. M. Alexander is primarily concerned with the "psycho-physical unity of the individual," and thus with the continuity of experience. The present work has two aims. The first, drawing on the work of Merleau-Ponty and John Dewey, and culminating in the concept of "Conductive Reasoning", is to lay a theoretical foundation for a synthesis of the practical work of Kelly and Alexander. The primary premise is that the act of comprehending is an embodied act, and as such is as subject to the conditions of the coordination of the whole person as is any other act. The second, practical, aim has been to develop a conversational methodology for dealing with learning in a more fully embodied way. This method of "conductive conversation," formally derived from the "Learning Conversation," evolved from the author's teaching experience with the Alexander Technique. Appendix 1, "A Conversational Introduction to Conductive Reasoning," is an interactive conversational structure which incorporates a development of these concepts in the context of personal experiments for generating the kinds of experiences from which the reader may draw something of the intended meaning, and some skill in using the conductive conversational tools for exploring embodied dimensions in their own meaning. It is intended as a piece that will stand on its own as a conversational research instrument for personal scientists.

Lead-tin solder has been widely used as interconnection material in electronics packaging for a long time. In response to environmental legislation, the lead-tin alloys are being replaced with lead-free alloys and electrically conductive adhesives in consumer electronics. Lead-free solder usually require higher reflow temperatures than the traditional lead-tin alloys, which can cause die crack and board warpage in assembly process, thereby impacting the assembly yields. The high tin content in lead-free solder forms tin whiskers, which has the potential to cause short circuits failure. Conductive adhesives are an alternative to solder reflow processing, however, conductive adhesives require up to 80 wt% metal filler to ensure electrical and thermal conductivity. The high loading content degrades the mechanical properties of the polymer matrix and reduces the reliability and assembly yields when compared to soldered assemblies. Carbon nanotubes (CNTs) have ultra high aspect ratio as well as many novel properties. The high aspect ratio of CNTs makes them easy to form percolation at low loading and together with other novel properties make it possible to provide electrical and thermal conductivity for the polymer matrix while maintaining or even reinforcing the mechanical properties. Replacing the metal particles with CNTs in conductive adhesive compositions has the potential benefits of being lead free, low process temperature, corrosion resistant, electrically/thermally conductive, high mechanical strength and lightweight. In this paper, multiwall nanotubes (MWNTs) with different dimensions are mixed with epoxy. The relationships among MWNTs dimension, volume resistivity and thermal conductivity of the composite are characterized. Different loadings of CNTs, additives and mixing methods were used to achieve satisfying electrical and mechanical properties and pot life. Different assembly technologies such as pressure dispensing, screen and stencil printing are used to simplify the processing method and raise the assembly yields. Contact resistance, volume resistivity, high frequency performance, thermal conductivity and mechanical properties were measured and compared with metal filled conductive adhesive and traditional solder paste.