Abstract Ammonia is one of valuable chemicals which are commonly used in various industrial factors. It is also a typical pollutant, and has a long-term impact on human health for toxicity characteristics. This study was to investigate the performance, product selectivity and kinetics in oxidation of ammonia solution in WAO process over Cu/ACF catalyst. The operation parameters in continuous WAO process were performed as follows: initial concentration of ammonia in ranging from 200 ppm to 1000 ppm, pH at 12, velocity of influent at below 3.0 ml/min, temperature ranging from 443K to 463K and pressure at 3.0 MPa. In the experiments of catalyst selection, we decided to use 5% Cu/ACF catalyst for its high conversion and selectivity in oxidation of ammonia. A conversion of 95.42% in oxidation of ammonia was achieved under 463K and the product selectivity of N2 was raised from 53% to 85%. We found that Cu/ACF and ACF catalysts both had the good conversion and selectivity in oxidation of ammonia in WAO process. In the long-term test of catalyst stability, Cu/ACF had a bad stability after 48 hours reaction in WAO process. The tests such as XRD, SEM and EA were also determined. The kinetics of WAO over Cu/ACF catalyst in oxidation of ammonia using Power-Rate Law was presented. The apparent reaction order and activated energy were obtained.

In this work the conditions for which a (0,90,90,0,0,90)s BMI-carbon fiber laminate will initiate transverse microcracking are determined for the fabrication of a cryogenic fuel tank for use in a Reusable Launch Vehicle (RLV). This is accomplished using a quadratic interaction criterion failure analysis on the total stress state at possible launch conditions. There are three major sources of stress, that is, thermal residual stress, internal pressure stress, and applied load stress, that are evaluated at the launch stage to determine the total stress state. To assess the accuracy of the analysis the well known X-33 cryogenic fuel tank failure was analyzed as an example. The results of the X-33 example show that the analysis accurately portrays the failure of the X-33 and provides evidence that the analysis can be used to provide reliable conditions for the initiation of microcracking. The final result of this study is a range of launch conditions that can be used without the initiation of microcracking and a limiting range of conditions that cause complete microcracking throughout the laminate.

The performance characteristics of pure hydrogen PEMFC (called HFC) stacks made with heterogeneous carbon fiber bipolar plates are studied in this thesis. In addition, the problem that the heterogeneous carbon fiber bipolar plate leaks in the high gas pressure is also solved in this studies so that the new plate can be used to the high current power sources. Because of the gas leakage of the first generation stack at high inlet gas pressure, the fuel supply is insufficient in the high current density. A 4-cell PEMFC stack made with this new bipolar plate is built with weight 370 g and volume 385 cm3 without a fan. The total power out of the 4-cell stack is about 30 W at room temperature. The specific power and volumetric power densities are 81 mW/g and 78 mW/cm3, respectively. The average power density is about 160 mW/cm2, but the power density of a single-cell can reach a value about 220 mW/cm2. The insufficient fuel supply cause that the power density of 4-cell PEMFC stack is lower than single cell, so it is necessary to solve the gas leakage at high pressure. Our experiment found that gas leakage occurs in heterogeneous bipolar plates can be relate to the insufficient or improper hot-pressing temperature, time and pressure while we are making the carbon fiber bunches. So the processes in making new carbon fiber bunches include water expansion, uniform glue adding, high hot-pressing pressure, and using proper temperature and enough solidification time. The airtight of the second generation of heterogeneous carbon fiber bipolar plates improves obviously with the new processes. No leakage occurs for gas pressure under 1atm. We expect that this design can be used to high inlet pressure. It is also quite suitable for various high-power electrical sources.

The effects of the structure of new carbon fiber bunch heterogeneous unipolar plates on the performance of PEMFC are studied in this thesis. Internal structure of carbon fiber bunches can be modified by embedding different thickness or number of copper plates in the glue bonding area to increase the air permeability of carbon fiber bunches in its soft end. We can add different thickness or amount of coppers at the middle of bonding area, making the carbon fiber bunches soft side to form parallel to the longitudinal fiber bunch with a small flow channel. We can also make a trench at the appropriate place of the soft side of the carbon fiber bunches to form an extra air passage. In order to make the above flow channel, a new process for making the carbon fiber bunches is developed also. This process will be easier to produce a variety of different structures of carbon fiber bunch. Finally, several different experiments are performed to help us to understand the effect of the carbon fiber bunch structure on the performance and find out the best structure of the carbon fiber bunches. The carbon fiber bunch structures of the test cells on the anode side are all the same, but the carbon fiber bunch structures of on cathode side are all different. Experiments show that there are two structures among all test structures displayed better gas permeability. The first one is two 0.2 mm copper plates embedded within both sides of the glue ends of a cathode carbon fiber bunch, so that a small longitudinal flow channel are formed in soft end of the cathode carbon fiber bunch. When the HFC operates at room temperature and by air-breathing, the highest performance of the HFC can reach a value of 185 mW/cm2. The second one is a 0.2 mm copper plate embedded in the center of the glue end of a carbon fiber bunch, and then three 2 mm wide serrated slots are cut on the soft end of the carbon fiber bunch. The highest performance of the HFC can reach a value of 190 mW/cm2. The highest performance of the HFC with no copper plate and no slot structure can only reach a value 160 mW/cm2. The second design can increase the no structure cell performance 18.8%. Therefore, the internal structures of carbon fiber bunches are significant to affect on the fuel cell performance, and its internal design must be considered.

In this paper a proton exchange membrane fuel cell (called PEMFC) stack was developed to power or charge 3C products without any voltage transformer. PEMFC stacks made with traditional bipolar plates to generate a high voltage are usually by accumulating multiple single fuel cells together. The design with traditional heavy and large bipolar plates is inconvenient for 3C products to generate a high voltage in a finite volume. To solve this problem, a heterogeneous carbon fiber bunch unipolar plate is adopted to replace traditional bipolar plates, and a special membrane electrode assembly (called MEA) with multiple sets of banded electrodes is used to replace a traditional MEA that is made with only a set electrodes. With this new design, the fuel cell voltage can easily increase in a layer. The designed stack can provide multiple voltages and currents by proper series and/or parallel connections. The variable voltage 16-cell fuel cell is composed of 4-layer 4-banded type MEAs and 5 heterogeneous carbon fiber bunch bipolar plates. The 16-cell stack is divided into 4 sets. Each set of 4 series connection cell is arranged in a line in 4 different layers. The 4-cell sets can connect by series/parallel on the two ends of the stack. The total volume of the 16-cell stack is 385cm3 and its weight is 365g. The new design can power or charge certain 3C products directly. If 2 sets of 4-cell fuel cells are connected in series, the stack can provide 2A at 3.6V. With the above 2 sets of 2*4-cell connected in parallel, the stack can provide 3.5A at 3.6V. If the 4 sets of 4-cell are all connected in series, the stack can provide 1.8 A at 7.2V. These voltages and currents derived from these stacks can power or charge a mobile phone, a photo camera and a video camera directly. If a higher voltage or current are needed, two or more 16-cell stacks can be connected in series XI or parallel. Then notebooks or any other 3C products in which higher power are needed can be driven.

<p>The exploitation of sandwich structures as a means toachieve high specific strength and stiffness is relatively new.Therefore, the knowledge of its damage tolerance is limitedcompared to other structural concepts such as truss bars andmonocoque plate solutions.</p><p>Several aspects of the damage tolerance of sandwichstructures are investigated. The influence of impact velocityonresidual strength is investigated. Sandwich panels withfaces of glass fiber reinforced vinylester are impacted bothwith very high velocity and quasi static. The residual strengthafter impact is found to be similar for both cases of impactvelocity.</p><p>Curved sandwich beams subjected to opening bending momentare studied. Faceñcore debonds of varying size areintroduced between the compressively loaded face sheet and thecore. Finite element analysis in combination with a pointstress criterion is utilized to predict the residual strengthof the beams. It is shown that it is possible to predict thefailure load of the beams with face-core debond.</p><p>Using fractography the governing mode of failure ofcompressively NCF-carbon is characterized. Sandwich panelssubjected to compression after impact are shown to fail byplastic micro buckling.</p><p>The residual compressive strength after impact of sandwichpanels is investigated. Sandwich panels with face sheets ofnon-crimp fabric (NCF) carbon are subjected to different typesof impact damages. Predictions of residual strength are madeusing the Budiansky, Soutis, Fleck (BSF) model. The residualstrength is tested, and the results are compared topredictions. Predictions and tests correlate well, and indicatethat the residual strength is dependent on damage size and notthe size of the damaged panel.</p><p>A study of the properties of a selection of fiberreinforcements commonly used in sandwich panels is conducted.The reinforcements are combined with two types of core materialand three types of matrix. Also the influence of laminatethickness is tested. Each combination materials is tested inuni-axial compression, compressive strength after impact andenergy absorption during quasi static indentation. Thespecimens which are tested for residual strength are eithersubjected to quasi-static or dynamic impact of comparableenergy level. Prediction of the residual strength is made andcorrelates reasonably whith the test results. The tests showthat if weight is taken into account the preferred choice offiber reinforcement is carbon.</p>

Fiber Reinforced Polymer (FRP) sheets can provide incredible structural strength while weighing only a fraction as much as steel. When applied to piles the FRP provides strengthening through both concrete confinement and tensile reinforcement. Mainly used in structural repair, its application is relatively simple in theory. However, many factors(some avoidable, some not) can interfere with the bond between FRP and concrete. When this bond is interrupted the strength of the repair becomes compromised.This thesis examines 2 new methods of improving FRP bond to concrete piles during the time the resin is curing. These methods are compared using 3 types of testing, both nondestructive and otherwise: acoustic analysis, infrared thermography, and pull-off testing. Therefore not only FRP bond improvement techniques are compared but also the techniques for bond evaluation. Findings have shown a definite correlation between non destructive testing and destructive pull-off testing, as well as bond improvement both above and below the waterline when a pressure bag system is used.

Due to its unique characteristics, carbon fiber is one of the leading materials for light weight, high strength and stiffness applications in composite materials. The development of carbon fibers approaching theoretical strengths and stiffness is a continuing process which has led to improved mechanical and physical properties over the recent years. Improvements in carbon fiber properties are directly dependent on the quality of the precursor fiber. Research and development of PAN precursor fiber requires extensive experimentation to determine how processing conditions affect the structure and properties of the precursor fibers. Therefore, it is the goal of this thesis to analyze the results of varying coagulation rates on fiber shape, density and porosity, to determine the effect of cross-sectional shape, density, and fiber diameter on the tensile strength of the fiber, and to investigate the most effective method for the reduction of fiber diameter. Results indicate a low temperature, high solvent concentration coagulating bath leads to a rounder cross section with lower void content. Reduction in fiber diameter was found to increase tensile strength while increased molecular orientation experienced during high draw down ratios led to an increase in fiber modulus.

The push towards larger diameter space telescope mirrors has caused the space industry to look at lightweight, deformable alternatives to the traditional monolithic mirror. One possible solution to the dilemma is to use the piezoelectric properties of certain materials to create a lightweight, deformable mirror. Current piezoelectric deformable mirror designs use individual actuators, creating an immensely complex system as the mirrors increase in size. The objective of this thesis is to aid in the design and development of lightweight, deformable mirrors for use in space based telescopes. Two topics are considered to aid this development. A doubly curved, lightweight, bimorph mirror is investigated. The fabrication method entails forming a thin film piezoelectric polymer into a doubly curved shape using a specially designed forming machine. The second topic entails the finite element modeling of a composite mirror substrate with a piezoceramic actuator backing. The model is generated using a meshing program designed to generate off-centered spot loads of electric potential. These spot loads simulate the actuation due to an electron gun. The effects of spot location and size on mirror deformation are examined.

Carbon fiber is one of the leading materials for high strength and modulus, and light weight applications. Improvements in carbon fiber properties are directly dependent on all aspects of manufacture, especially the process of stabilization. Therefore, it is the goal of this thesis to study the effects of the temperature and strain profile of the stabilization process, and the resulting carbon fiber tensile properties. In addition, the precursor fibers used were spun under two different draw ratios, to study the effects of the spinning parameters. Results indicated through DMA studies that completeness of stabilization reactions can be gauged by the peak and leveling of induced stress while fibers are stabilized in isostrain conditions. Through this method, carbon fiber tensile properties were maintained from the prior methods, but saved significant time for processing. Stress vs. strain tests throughout the stabilization process created a baseline for understanding the maximum capable strain on fibers throughout the stabilization process. Lastly, this information was summarized, combined, and basic mechanical engineering principles discussed for a continuous stabilization furnace with strain control, so that further research into the stabilization process can incorporate carbon fibers made with in situ stretch control.