The demand for mixed alcohols has grown since ether compounds were banned as gasoline octane improvers in North America. Molybdenum-based catalysts in sulfide form are an attractive catalyst system for the conversion of synthesis gas to alcohols, due to their excellent resistance to sulfur poisoning and high activity for the water-gas shift reaction. The higher alcohols activity over these catalysts is low, due to the formation of hydrocarbons and CO2. Although a number of catalysts have been developed for this purpose, not any are used commercially at this time. The main objective of this Ph.D. research is to develop a catalyst system that is capable of selectively producing higher alcohols, particularly ethyl alcohols from synthesis gas. In the present series of studies, the investigation of an alkali-promoted trimetallic Co-Rh-Mo catalyst system has led to improvements in product stream composition. The effect of different loadings of active metal (Mo), alkali (K) promoter, and metal promoters (Co and Rh) on higher alcohol synthesis from synthesis gas were investigated using commercially available multi-walled carbon nanotubes (MWCNTs) as the catalyst support. The role of support on higher alcohols synthesis was also studied using different supports, such as ã-Al2O3, activated carbons with different textural characteristics, and MWCNTs. The catalysts were prepared using the incipient wetness impregnation method and extensively characterized in both oxide and sulfide phases using different techniques. Transmission electron microscopy (TEM) results revealed that the metal particles were uniformly distributed inside and outside of the carbon nanotubes, and that metal dispersions were higher on the alkali-promoted trimetallic catalyst supported on MWCNTs. The existence of promoted and un-promoted MoS2 sites was confirmed by diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) studies of adsorbed CO over sulfided catalysts. Temperature programmed reduction (TPR) tests showed that the addition of metal promoters improved the reduction behaviour of the catalysts. XRD patterns showed that alkali-promoted catalysts were less crystalline compared to that of the catalyst not promoted with K. The formation of Co (Rh)-Mo-S species was evident in the XANES spectra of bimetallic and trimetallic alkali-promoted MoS2 catalysts. The activity and selectivity of the catalysts were assessed in a fixed-bed micro-reactor using temperature, pressure, and gas hourly space velocity in the ranges of 275 to 350°C, 800 to 1400 psig (5.529.65 Mpa), and 2.4 to 4.2 m3 (STP)/(kg of cat.)/h, respectively. The Ni-promoted catalyst showed higher activity towards the formation of hydrocarbons over that of alcohols. The total alcohols space time yield (STY) and higher alcohols selectivities are significantly higher over the activated carbon-supported catalysts compared to those supported on alumina. With increased content of K, the formation of alcohols increased and hydrocarbons formation rate was suppressed. The total alcohols STY increased with increased Co content over the Co-promoted MoS2-K/MWCNTs catalysts, whereas, the maximum ethyl alcohol and higher alcohols selectivities were observed on the catalyst promoted with 4.5 wt % Co. Over the Rh-promoted MoS2-K/MWCNTs catalysts, the maximum total alcohol yield, ethanol selectivity, and higher alcohols selectivity were observed on the catalyst with 1.5 wt % Rh. The MWCNT-supported alkali-promoted trimetallic catalyst with 9 wt % K, 4.5 wt % Co, 1.5 wt % Rh, and 15 wt % Mo showed the maximum higher alcohols STY and selectivity compared to other catalysts investigated. The textural properties of the support, such as average pore diameter, pore volume and surface area, could significantly influence the extent of reduction, morphology, adsorption and has direct influence on the synthesis of mixed alcohols from synthesis gas. The optimum higher alcohols STY and selectivity were obtained over the Co-Rh-Mo-K/MWCNT catalyst at 330°C, 1320 psi (9.1 Mpa), 3.8 m3 (STP)/(kg of cat./h) using a H2 to CO molar ratio value of 1.25. To predict the reaction rate for higher alcohols synthesis, the power law model was used for the reaction between CO and H2 on the catalyst surface and the data of this study are well fitted by the model. The activation energies of ethanol and higher alcohols obtained over Co-Rh-Mo-K/MWCNTs were low compared to those values reported in the literature. The sulfided alkali-promoted trimetallic Co-Rh-Mo catalyst supported on MWCNTs was stable over a period of 720 h of continuous reaction.

The demand for mixed alcohols has grown since ether compounds were banned as gasoline octane improvers in North America. Molybdenum-based catalysts in sulfide form are an attractive catalyst system for the conversion of synthesis gas to alcohols, due to their excellent resistance to sulfur poisoning and high activity for the water-gas shift reaction. The higher alcohols activity over these catalysts is low, due to the formation of hydrocarbons and CO2. Although a number of catalysts have been developed for this purpose, not any are used commercially at this time. The main objective of this Ph.D. research is to develop a catalyst system that is capable of selectively producing higher alcohols, particularly ethyl alcohols from synthesis gas. In the present series of studies, the investigation of an alkali-promoted trimetallic Co-Rh-Mo catalyst system has led to improvements in product stream composition. The effect of different loadings of active metal (Mo), alkali (K) promoter, and metal promoters (Co and Rh) on higher alcohol synthesis from synthesis gas were investigated using commercially available multi-walled carbon nanotubes (MWCNTs) as the catalyst support. The role of support on higher alcohols synthesis was also studied using different supports, such as ã-Al2O3, activated carbons with different textural characteristics, and MWCNTs. The catalysts were prepared using the incipient wetness impregnation method and extensively characterized in both oxide and sulfide phases using different techniques. Transmission electron microscopy (TEM) results revealed that the metal particles were uniformly distributed inside and outside of the carbon nanotubes, and that metal dispersions were higher on the alkali-promoted trimetallic catalyst supported on MWCNTs. The existence of promoted and un-promoted MoS2 sites was confirmed by diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) studies of adsorbed CO over sulfided catalysts. Temperature programmed reduction (TPR) tests showed that the addition of metal promoters improved the reduction behaviour of the catalysts. XRD patterns showed that alkali-promoted catalysts were less crystalline compared to that of the catalyst not promoted with K. The formation of Co (Rh)-Mo-S species was evident in the XANES spectra of bimetallic and trimetallic alkali-promoted MoS2 catalysts. The activity and selectivity of the catalysts were assessed in a fixed-bed micro-reactor using temperature, pressure, and gas hourly space velocity in the ranges of 275 to 350°C, 800 to 1400 psig (5.529.65 Mpa), and 2.4 to 4.2 m3 (STP)/(kg of cat.)/h, respectively. The Ni-promoted catalyst showed higher activity towards the formation of hydrocarbons over that of alcohols. The total alcohols space time yield (STY) and higher alcohols selectivities are significantly higher over the activated carbon-supported catalysts compared to those supported on alumina. With increased content of K, the formation of alcohols increased and hydrocarbons formation rate was suppressed. The total alcohols STY increased with increased Co content over the Co-promoted MoS2-K/MWCNTs catalysts, whereas, the maximum ethyl alcohol and higher alcohols selectivities were observed on the catalyst promoted with 4.5 wt % Co. Over the Rh-promoted MoS2-K/MWCNTs catalysts, the maximum total alcohol yield, ethanol selectivity, and higher alcohols selectivity were observed on the catalyst with 1.5 wt % Rh. The MWCNT-supported alkali-promoted trimetallic catalyst with 9 wt % K, 4.5 wt % Co, 1.5 wt % Rh, and 15 wt % Mo showed the maximum higher alcohols STY and selectivity compared to other catalysts investigated. The textural properties of the support, such as average pore diameter, pore volume and surface area, could significantly influence the extent of reduction, morphology, adsorption and has direct influence on the synthesis of mixed alcohols from synthesis gas. The optimum higher alcohols STY and selectivity were obtained over the Co-Rh-Mo-K/MWCNT catalyst at 330°C, 1320 psi (9.1 Mpa), 3.8 m3 (STP)/(kg of cat./h) using a H2 to CO molar ratio value of 1.25. To predict the reaction rate for higher alcohols synthesis, the power law model was used for the reaction between CO and H2 on the catalyst surface and the data of this study are well fitted by the model. The activation energies of ethanol and higher alcohols obtained over Co-Rh-Mo-K/MWCNTs were low compared to those values reported in the literature. The sulfided alkali-promoted trimetallic Co-Rh-Mo catalyst supported on MWCNTs was stable over a period of 720 h of continuous reaction.

Well dispersed aqueous suspensions containing single-walled carbon nanotubes (SWCNTs) from bulk powders were prepared with surfactant and without surfactant by acid functionalization. SWCNT coated electrodes were then prepared from the SWCNT aqueous suspensions using various methods to create uniform nanoporous networks of SWCNTs on various substrates and stainless steel (SST) current collectors for use as ultracapacitor electrodes. Drop coating, high voltage electro-spraying (HVES), inkjet printing, and electrophoretic deposition (EPD) methods were evaluated. Optical and scanning electron microscope images were used to evaluate the SWCNT dispersion quality of the various electrodes. Ultimately an EPD process was established which reliably produced uniform SWCNT nanoporous networks on SST substrates. The prepared SWCNT coated electrodes were characterized using cyclic voltammetry and their capacitance was determined. A correlation between extended EPD processing times, EPD processing temperatures, and electrode capacitance was quantified. Optimum EPD processing occurs where linear capacitance gains were observed for processing times less than 10 minutes. At processing times between 10 – 60 minutes a non-linear relationship demonstrated diminishing capacitance gains with extended EPD processing times. Likewise, optimum EPD processing occurs when the processing temperature of the SWCNT suspension is raised above room temperature. At processing temperatures from 45°C to 60°C an increase in capacitance was observed over the room temperature (22°C) electrodes processed for the same durations. Conversely, for processing temperatures less than room temperature, at 5°C, a decrease in capacitance was observed. It was also observed that SWCNT electrodes processed at 60°C processing temperatures resulted in 4 times the capacitance of 5°C electrodes for the same processing times, when the durations were 8 minutes or less. For samples with raised processing temperatures the time dependent capacitance gains were observed to be significantly diminished beyond 10 minute processing times. The SWCNT network thickness was also correlated to EPD processing temperature and capacitance. A linear relationship was identified between the SWCNT network thickness and the capacitance of the electrode. It was also observed that elevated processing temperatures increase the EPD deposition rate of SWCNTs, produce thicker SWCNT networks, and thus create electrodes with higher capacitance than electrodes processed at lower EPD processing temperatures. EPD of SWCNTs was demonstrated in this work to be an effective method for the fabrication of SWCNT ultracapacitor electrodes. Characterization of the process determined that optimal EPD processing occurs within the first 10 minutes of processing time and that elevated processing temperatures yield higher SWCNT deposition rates and higher capacitance values. In this work the addition of SWCNT nanoporous networks to SST electrodes resulted in increases in capacitance of up to 398 times the capacitance of the uncoated SST electrodes yielding a single 1cm2 electrode with a capacitance of 91mF and representing an estimated specific capacitance for the processed SWCNT material of 45.78F/g.

No description available.

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This study used electrospinning to fabricate a polyvinylidene fluoride (PVDF) piezoelectric nanofiber harvesting device with interdigitated electrode to capture ambient energy. According to d33 mechanical-electric energy conversion mode, the energy harvesting device can be applied on the low frequency ambient vibration and impact abilities for the transformation mechanical energy into electrical energy effectively. First, the PVDF powder was mixed in acetone solution uniformly and the dimethyl sulfoxide (DMSO) was mixed with multi-walled carbon nanotube (MWCNT) to prepare PVDF macromolecular solution. The mixed solution was filled in a metals needle injector and contacted hundreds of voltage. After the PVDF drop in the needle was subjected to high electric field, the drop overcame surface tension of the solution itself, then extremely fine PVDF fiber was formed and spun out. The electrospun was collected orderly using X-Y digital control stage and the linear diameter of electrospun can be controlled easily by adjusting the travelling speed of the stage. In the spinning process, as affected by stretching strain and electric field at the same time, the PVDF piezoelectric fiber resulted in electric polarization and transformed £] piezoelectric crystal phase, in which the dipoles are oriented in the same direction. Furthermore, MWCNT was added to improve the mechanical properties of fiber and increase £] phase, to enhance the tensile strength and piezoelectric property of PVDF fiber effectively. Finally, the photolithography was used to fabricate interdigitated electrodes with 100£gm gap on the flexible PI substrate. The PVDF fibers, with a length and diameter of approximately 1cm and 700-1000nm, were aligned on interdigitated electrodes and packaged with the PI film. In order to increase the conversion efficiency of piezoelectric fiber in d33 mode, the PVDF fibers were repolarized in a high electric field. The results showed that the PVDF fiber energy harvesting device can generate 15mV open-circuit voltage under low frequency vibration of 4Hz and generate above 30mV open-circuit voltage under 6Hz vibrations. As compared with the piezoelectric fiber not repolarized by interdigitated electrode, its output voltage was increased by1- 2 times.

Through past research, it is known that carbon nanotubes have the potential of enhancing the thermal performance of heat transfer fluids. The research is of importance in electronics cooling, defense, space, transportation applications and any other area where small and highly efficient heat transfer systems are needed. However, most of the past work discusses the experimental results by focusing on the effect of varying concentration of carbon nanotubes (CNTs) on the thermal performance of CNT nanofluids. Not much work has been done on studying the effect of processing variables. In the current experimental work, accurate measurements were carried out in an effort to understand the impact of several key variables on laminar flow convective heat transfer. The impact of ultrasonication energy on CNT nanofluids processing, and the corresponding effects on flow and thermal properties were studied in detail. The properties measured were viscosity, thermal conductivity and the convective heat transfer under laminar conditions. Four samples of 1 wt % multi walled carbon nanotubes (MWCNT) aqueous suspensions with different ultrasonication times were prepared for the study. Direct imaging was done using a newly developed wet-TEM technique to assess the dispersion characteristics of CNT nanofluid samples. The results obtained were discussed in the context of the CNT nanofluid preparation by ultrasonication and its indirect effect on each of the properties. It was found that the changes in viscosity and enhancements in thermal conductivity and convective heat transfer are affected by ultrasonication time. The maximum enhancements in thermal conductivity and convective heat transfer were found to be 20 % and 32 %, respectively, in the sample processed for 40 minutes. The thermal conductivity enhancement increased considerably at temperatures greater than 24 °C. The percentage enhancement in convective heat transfer was found to increase with the axial distance in the heat transfer section. Additionally, the suspensions were found to exhibit a shear thinning behavior, which followed the Power Law viscosity model.

The present research work aims to develop a new heat transfer fluid by combining multiwalled carbon nanotubes (MWCNT) and microencapsulated phase change materials (MPCMs). Stable nanofluids have been prepared using different sizes of multiwalled carbon nanotubes and their properties like thermal conductivity and viscosity have been measured. Microencapsulated phase change material slurries containing microcapsules of octadecane have been purchased from Thies Technology Inc. Tests have been conducted to determine the durability and viscosity of the MPCM slurries. Heat transfer experiments have been conducted to determine the heat transfer coefficients and pressure drop of the MWCNT nanofluids and MPCM slurries under turbulent flow and constant heat flux conditions. The MPCM slurry and the MWCNT nanofluid have been combined to form a new heat transfer fluid. Heat transfer tests have been conducted to determine the heat transfer coefficient and the pressure drop of the new fluid under turbulent flow and constant heat flux conditions. The potential use of this fluid in convective heat transfer applications has also been discussed. The heat transfer results of the MPCM slurry containing octadecane microcapsules was in good agreement with the published literature. The thermal conductivity enhancement obtained for MWCNTs with diameter (60-100 nm) and length (0.5-40?m) was 8.11%. The maximum percentage enhancement (compared to water) obtained in the heat transfer coefficient of the MWCNT nanofluid was in the range of 20-25%. The blend of MPCMs and MWCNTs was highly viscous and displayed a shear thinning behavior. Due to its high viscosity, the flow became laminar and the heat transfer performance was lowered. It was interesting to observe that the value of the maximum local heat transfer coefficient achieved in the case of the blend (laminar flow), was comparable to that obtained in the case of the MPCM slurry (turbulent flow). The pressure drop of the blend was lower than that of the MWCNT nanofluid.

This thesis research investigates the adhesion mechanisms of protein molecules to surfaces of biomaterials. New understanding in such adhesion mechanisms will lead to materials design and surface engineering in order to extend the lifespan of implants. The present research evaluates and analyzes the adhesive strength of proteins on pure High Density Polyethylene (HDPE), Single Wall Carbon Nanotube (SWCNT) enhanced HDPE composites, Ti-C:H coating and Ti6Al4V alloys (grade 2). The adhesive strength was studied through fluid shear stress and the interactions between the fluid and material surfaces. The adhesive strength of protein molecules was measured through the critical shear strength that resulted through the fluid shear stress. The effects of surface and material properties, such as roughness, topography, contact angle, surface conductivity, and concentration of carbon nanotubes on adhesion were analyzed. Research results showed that the surface roughness dominated the adhesion. Protein was sensitive to micro-scale surface roughness and especially favored the nano-porous surface feature. Results indicated that the unpurified SWCNTs influenced crystallization of HDPE and resulted in a nano-porous structure, which enhanced the adhesion of the protein onto a surface. Titanium hydrocarbon coating on silicon substrate also had a porous topography which enhanced its adhesion with protein, making it superior to Ti6Al4V.

No description available.