Micromanufacturing consists of processes for producing structures, devices or systems with feature sizes measured in micrometers. Micromanufacturing began in the mid-1960's with microelectronics fabrication technology. In the 1980's, Micro-Electro-Mechanical Systems (MEMS) began to be developed, in which electrical and mechanical subsystems were integrated at small scales. More recently, Microtechnology-based Energy and Chemical Systems (MECS) have been developed that have led to improved heat and mass transfer in energy and chemical systems. At Oregon State University, new methods to fabricate MECS have been developed. One of the new methods involves microlamination--bonding thin strips of different materials together. This method has generated a high volume and low-cost approach to the production of high-aspect-ratio (height-to-width) structures. Past efforts to make microfloat valves using microlamination methods resulted in an 11:1 diodicity ratio. It was hypothesized that the valve had a ridge of redeposited material around the valve seat caused by the condensation and deposition of ablation ejecta during laser machining. The contribution of this thesis is the creation of a microfloat valve using an Electrochemical Micromachining (EMM) method. EMM methods are known to produce smooth surfaces, free of burrs or any other types of aspirates. Therefore, it was hypothesized that float valves made with EMM methods would improve valve performance. Four steps were involved in the creation of the microfloat valve: lamina formation, laminae registration, laminae bonding and component dissociation. A total of 9 laminae-some of which were made with 304 stainless steel 76.2 ��m thick, others of which were made with 50.8 ��m thick polyimide-made up the microfloat valve. Photolithography and EMM were used to form the lamina. Even though the laminae created by EMM were smaller in size than desired, the machined areas did not have redeposited material, and some areas had straight walls. In laminae registration, a two edge registration method was used. In the laminae bonding step, laminae were bonded by the adhesive method at 248��C under 135 kPa pressure for 13.5 minutes. In the component dissociation step, a capacitor dissociation method that was designed at OSU was used. Upon performance testing, the average diodicity ratio for the EMM valve was 12.45 over the range 0 kPa-450 kPa, indicating improved performance when compared to the Laser Ablation valve-which had an average 11.17 over the range 0 kPa-100 kPa. Microscope examination of valves revealed that statistically significant improvement in valve performance would require refinement of component dissociation methods. / Graduation date: 2000

Thesis (M.Sc.)(Microbiology)--University of Pretoria, 2006. / Includes summary. Includes bibliography. Available on the Internet via the World Wide Web.

Perchloroethylene (PCE) is a toxic contaminant that has been introduced into the environment over many years through industrial and agricultural wastes. Research has been done in the past to investigate PCE degradation by zero-valent iron (ZVI), green rust (GR) and a mixture of both. The combination of ZVI and green rust has been reported to be more effective for degrading PCE than either of them alone. Forming green rust electrochemically has the potential for depositing GR more effectively on the surface of ZVI where it will be able to more easily transfer electrons from ZVI to contaminants such as PCE. Therefore, the goal of this research was to determine the feasibility of electrochemically depositing green rust on zero-valent iron and to characterize it in terms of its composition, crystal properties and amount produced. XRD analysis was conducted to determine composition and crystal properties and a procedure was developed to measure the amount produced. Equipment was constructed to deposit green rust electrochemically onto ZVI. A chain of experiments with varying voltage, pH, time and amounts of ZVI were conducted to determine feasible experimental conditions for GR formation. Then, a method was developed to accurately measure the amount of surface oxides of iron deposited on the zero-valent iron substrate. This method was tested and found useful for measuring iron in: i) standard solutions of soluble iron with different concentrations of reagents; ii) suspensions with solid iron hydroxides by themselves; and iii) suspensions with solid iron hydroxides and ZVI. Electrochemical experiments were conducted and the amounts of iron hydroxides deposited on the ZVI surface were measured. XRD analysis of the deposits on the surface was conducted and the patterns of XRD-peaks were compared to that of type 2 – sulfate green rust.

tert-butyl 1-methoxycarbonyl-1-ferrocenecarbamate, Boc-NH-Fc-COOMe, (1) was synthesized according to the literature procedure and modified to 1-amino-n′-ferrocenemethylcarboxylate, 1,n′-H2N-Fc-COOCH3 (2) by removing the Boc-group with TFA/Et3N mixture in dichloromethane. Compound 2 reacted with alkylating agents like MeI, EtI, EtSCH2CH2Cl (MA) and (CN)(EtO)2P(O) (NA) to form MeNH-Fc-COOMe (3), EtNH-Fc-COOMe (4), EtSCH2CH2NH-Fc-COOMe (5), (EtO)2P(O)NH-Fc-COOMe (6), respectively. Cyclic voltammetry (CV) of these compounds showed different half-wave potential characteristics compared to aminoferrocene and was dependent on the nature of the substituents, which was rationalized by molecular orbital calculations. Electron donating groups (Me, Et and 2-chloroethyl ethylsulfide, MA) shifted the half-wave potential towards the cathodic direction while electron withdrawing group like diethyl cyanophosphonate, NA, shifted it toward anodic direction. Anodic to cathodic peak separation were found to be within 62-88 mV indicating a quasi-reversible system. <p>Hydrolysis of compound 1 resulted in the formation of tert-butyl 1-methoxycarbonyl-1-ferrocenecarboxylic acid, Boc-NH-Fc-COOH, (11) which was coupled with cystamine using the EDC/HOBt protocol to synthesize the cystamine conjugate [BocHN-Fc-CO-CSA]2 (12). This molecule is equipped with an amino group that directly linked to the redox receptor. Compound 12 was fully characterized by spectroscopic methods and by single crystal x-ray diffraction. The cystamine conjugate 12 formed films on gold substrates, which upon deprotection of the amino group, reacted with chemical warfare agents (CWAs) mimics, such as EtSCH2CH2Cl (MA), a simulant for the sulfur mustard HD, and (CN)(EtO)2P(O) (NA), a simulant for the nerve agent Tabun. Their reaction with the surface-bound ferrocene derivative results in the formation of N-substituted products. <p>CV measurements showed anodic shifts of the Fc redox potentials by 50 (±5) mV after exposure to MA, and NA. Measurements by quartz crystal microbalance (QCM) showed an increase in mass upon exposure to MA and NA. Ellipsometry measured a film thickness increase from 6 (±1) Å for the deprotected film to 10 (±4) Å for the film modified with MA and to 7 (±2) Å for the film modified with NA. The surfaces were analyzed by x-ray photoelectron spectroscopy (XPS) and clearly showed the attachment of the cystamine conjugate on the surface and its reaction with CWAs mimics.

Carbon materials are commonly studied as the electrode material for electrochemical double layer capacitance (EDLC) due to their high surface area. The present work aimed to leverage both EDLC and pseudocapacitance through chemical modification of multi-wall carbon nanotubes (MWCNTs) and onion-like carbon (OLC) with polyoxometalates (POMs) to further enhance the performance of these electrodes. Layer-by-layer (LbL) deposition of two commercially available POMs (PMo12O403- and SiMo12O404-) and three synthesized POMs (PMo11VO404-, PMo10V2O405- and PMo9V3O406-) has been investigated. A single-layer of POMs increased the area specific capacitance by approximately three-times, while superimposing of these POMs into two-layer coatings increased the capacitance by approximately five-times. The morphology and composition of these composite materials were investigated using Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS).

Carbon materials are commonly studied as the electrode material for electrochemical double layer capacitance (EDLC) due to their high surface area. The present work aimed to leverage both EDLC and pseudocapacitance through chemical modification of multi-wall carbon nanotubes (MWCNTs) and onion-like carbon (OLC) with polyoxometalates (POMs) to further enhance the performance of these electrodes. Layer-by-layer (LbL) deposition of two commercially available POMs (PMo12O403- and SiMo12O404-) and three synthesized POMs (PMo11VO404-, PMo10V2O405- and PMo9V3O406-) has been investigated. A single-layer of POMs increased the area specific capacitance by approximately three-times, while superimposing of these POMs into two-layer coatings increased the capacitance by approximately five-times. The morphology and composition of these composite materials were investigated using Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS).

Crevice corrosion generally occurs on the crevice surface while the exterior or bold surfaces are not damaged. However, for copper and its alloys, the opposite is true; the bold surface is corroded while the crevice remains relatively corrosion-free. This unique type of corrosion is referred to as reverse crevice corrosion (RCC). In this research, commercially pure copper was chosen as the target metal to investigate RCC. Based on electrochemical measurements and surface analysis, reverse crevice corrosion was found to occur at room temperature. At elevated temperature only uniform corrosion was observed while under a deoxygenated environment, as expected, no corrosion was observed.<p> A multiple crevice assembly and a working electrode were designed especially for this research. Exposure test experiments were first performed at room temperature and 50 ºC. Several types of electrochemical tests were conducted including open circuit potential measurement, potentiodynamic measurement and electrochemical impendence spectroscopy (EIS). Atomic Force Microscopy (AFM) and Raman Spectroscopy were used to analyze the surfaces of the copper coupon.<p>The results of the exposure tests showed that RCC occurred at room temperature, but not at elevated temperature. Only uniform corrosion was observed at elevated temperature and no corrosion was occurred under a deoxygenated environment. It was found, based on the open circuit potential measurement, that the RCC process can be divided into three steps, a uniform corrosion phase, a corrosion slow-down step and a reverse crevice corrosion step. The first two steps can be combined into one phase, incubation phase. This hypothesis is supported with the results from Raman spectra and AFM. The EIS measurements revealed that the diffusion process from bulk solution to copper coupon surface is the rate controlling step for incubation phase and this diffusion process combined with the reduction of Cu (I) oxide in the crevice are the rate-controlling step corresponding to the last step.

In this work, a new electrochemical detection method was developed with the ability to determine a wide range of inorganic and organic species at, trace levels. In brief, the detection method takes advantage of all possible electrochemical reactions that may occur during scanning of the electrode potential. Changes in the detector response are mainly the result of inhibition of oxygen adsorption and hydrogen adsorption, alteration of electrical properties of the double layer, or redox processes of the adsorbate. Various electrochemical techniques were examined in the measurements; i.e. cyclic voltammetry, pulse amperometric detection, and square wave voltammetry. In those electrochemical techniques, the detection was carried out in a stripping mode after accumulation of analytes on the electrode surface. The smallest discernable signal is associated with about 0.1% surface coverage, which corresponds to the adsorption of about 10-18 mol of analyte on a ultramicroelectrode 5-[mu]m in radius. The response time of the detector to the concentration change in most cases is less than 1s. Electrochemical conditioning of the working electrode is sufficient to ensure a stable response for a period of several hours. It appears that square wave and cyclic voltammetry techniques are more suitable for the detection method. The linear dynamic range of the calibration curve depends on the characteristic of the analyte-electrode bond and redox processes of the analyte, which may occur at the electrode surface. For instance, for strongly adsorbing molecules the linear dynamic range extends over two orders of magnitude from about 10 -7 M to 10-5 M and for electroactive compounds from about 10-8 M to 10-4 M. In general, the relative standard deviation for replicate determinations was lower than 5%. Moreover, in these analyses, removal of oxygen from the analyzed solutions is not required.

Crevice corrosion generally occurs on the crevice surface while the exterior or bold surfaces are not damaged. However, for copper and its alloys, the opposite is true; the bold surface is corroded while the crevice remains relatively corrosion-free. This unique type of corrosion is referred to as reverse crevice corrosion (RCC). In this research, commercially pure copper was chosen as the target metal to investigate RCC. Based on electrochemical measurements and surface analysis, reverse crevice corrosion was found to occur at room temperature. At elevated temperature only uniform corrosion was observed while under a deoxygenated environment, as expected, no corrosion was observed.<p> A multiple crevice assembly and a working electrode were designed especially for this research. Exposure test experiments were first performed at room temperature and 50 ºC. Several types of electrochemical tests were conducted including open circuit potential measurement, potentiodynamic measurement and electrochemical impendence spectroscopy (EIS). Atomic Force Microscopy (AFM) and Raman Spectroscopy were used to analyze the surfaces of the copper coupon.<p>The results of the exposure tests showed that RCC occurred at room temperature, but not at elevated temperature. Only uniform corrosion was observed at elevated temperature and no corrosion was occurred under a deoxygenated environment. It was found, based on the open circuit potential measurement, that the RCC process can be divided into three steps, a uniform corrosion phase, a corrosion slow-down step and a reverse crevice corrosion step. The first two steps can be combined into one phase, incubation phase. This hypothesis is supported with the results from Raman spectra and AFM. The EIS measurements revealed that the diffusion process from bulk solution to copper coupon surface is the rate controlling step for incubation phase and this diffusion process combined with the reduction of Cu (I) oxide in the crevice are the rate-controlling step corresponding to the last step.

tert-butyl 1-methoxycarbonyl-1-ferrocenecarbamate, Boc-NH-Fc-COOMe, (1) was synthesized according to the literature procedure and modified to 1-amino-n′-ferrocenemethylcarboxylate, 1,n′-H2N-Fc-COOCH3 (2) by removing the Boc-group with TFA/Et3N mixture in dichloromethane. Compound 2 reacted with alkylating agents like MeI, EtI, EtSCH2CH2Cl (MA) and (CN)(EtO)2P(O) (NA) to form MeNH-Fc-COOMe (3), EtNH-Fc-COOMe (4), EtSCH2CH2NH-Fc-COOMe (5), (EtO)2P(O)NH-Fc-COOMe (6), respectively. Cyclic voltammetry (CV) of these compounds showed different half-wave potential characteristics compared to aminoferrocene and was dependent on the nature of the substituents, which was rationalized by molecular orbital calculations. Electron donating groups (Me, Et and 2-chloroethyl ethylsulfide, MA) shifted the half-wave potential towards the cathodic direction while electron withdrawing group like diethyl cyanophosphonate, NA, shifted it toward anodic direction. Anodic to cathodic peak separation were found to be within 62-88 mV indicating a quasi-reversible system. <p>Hydrolysis of compound 1 resulted in the formation of tert-butyl 1-methoxycarbonyl-1-ferrocenecarboxylic acid, Boc-NH-Fc-COOH, (11) which was coupled with cystamine using the EDC/HOBt protocol to synthesize the cystamine conjugate [BocHN-Fc-CO-CSA]2 (12). This molecule is equipped with an amino group that directly linked to the redox receptor. Compound 12 was fully characterized by spectroscopic methods and by single crystal x-ray diffraction. The cystamine conjugate 12 formed films on gold substrates, which upon deprotection of the amino group, reacted with chemical warfare agents (CWAs) mimics, such as EtSCH2CH2Cl (MA), a simulant for the sulfur mustard HD, and (CN)(EtO)2P(O) (NA), a simulant for the nerve agent Tabun. Their reaction with the surface-bound ferrocene derivative results in the formation of N-substituted products. <p>CV measurements showed anodic shifts of the Fc redox potentials by 50 (±5) mV after exposure to MA, and NA. Measurements by quartz crystal microbalance (QCM) showed an increase in mass upon exposure to MA and NA. Ellipsometry measured a film thickness increase from 6 (±1) Å for the deprotected film to 10 (±4) Å for the film modified with MA and to 7 (±2) Å for the film modified with NA. The surfaces were analyzed by x-ray photoelectron spectroscopy (XPS) and clearly showed the attachment of the cystamine conjugate on the surface and its reaction with CWAs mimics.