Materials which can be changed in shape and size when exposed to a magnetic field are called magnetostrictive materials. The magnetostrictive material was developed for use in the many actuator industries. A single crystal of magnetostrictive material is used to maximize its magnetostrictive response. It can be produced by the crystal growth method. However, a single crystal from this method is limited in size and shape. The growth direction of a single crystal, sometimes, is different from its magnetostrictive axis. Capacitor discharge welding (CDW) is a high power density welding process at 10���-10��� Kelvin/second. The fusion zone of CDW is very small and the heat affected zone of CDW is rarely detectable. The amount of material affected by heat in the welding process is very small. The objective of this study is to use capacitor discharge welding (CDW) to join single crystal copper and determine the effect of CDW on the microstructure of the single crystal copper. To minimize the cost of using single crystal copper, low oxygen copper C101 (polycrystalline) is used as a replacement. By maximizing the weld strength, Response Surface Methodology (RSM) is used to find the optimum condition of single crystal copper. The single crystal copper was cut at different orientations and welded together with the one that had same orientation to compare the results. The metallography was used to study voids, fusion zone and dislocations of the single crystal copper after welding. After analyzing the effect of the CDW process on the single crystal, the effect of crystal orientation upon void formation was found statistically inconclusive. Small fusion zone as 0.09154 mm was found. No heat affected zone of single crystal was detected. Also, no microstructural damage was found along the fusion zone. Dislocation density before and after CDW were not different because there was no statistically significant difference between the etch pit density in the fusion zone and that outside the fusion zone. In summary, regardless of voids, CDW may be a useful method for welding single crystal metals. / Graduation date: 1999

A negatively biased substrate has several advantages over a grounded substrate in CMOS technology. The on-chip generation of this negative substrate bias has made chips easier to use when only a single supply is preferred. This project demonstrates two types of charge pump circuits used to generate negative voltages not only for biasing the substrate, but in a broader sense also for other purposes in CMOS technology. One other possible use is in conjunction with 'Guard Ring Diodes for Suppressing the Substrate Noise in Mixed-Mode CMOS Circuits'. This work proposes a reasonable approach to generate the forward biasing current for the guard ring diode whose depletion capacitance and the substrate lead inductance form a resonant circuit to provide very low substrate-to-ground impedance at specific frequencies. Given this emphasis on generating a reasonably predictable current source, the generated negative voltages are regulated using a feedback loop. The amplitude of this negative voltage can be determined exclusively by transistor sizes. Simulation results support the theoretical analysis in that accurate negative voltages and current sources can be generated on-chip, although there are some limitations. / Graduation date: 1996

Thesis (Ph. D.)--Ohio State University, 2006. / Full text release at OhioLINK's ETD Center delayed at author's request

Chapter 2 contains the continuum mechanical notions for the description of the plastic behavior of sheet metal under large deformations at room temperature. As such, it includes the kinematics of a continuum body, strain and stress definitions, and a general elasto-plastic constitutive model description. This last point is complemented by the definition of anisotropy, as well as the description of some yield criteria and hardening laws. Next, Chapter 3 defines the stress strain states required to be experimentally reproduced in order to describe the initial yield locus and its displacement in the stress axis representation during plastic deformation. A review of the available experimental equipment capable of reproducing the required stress strain states is presented in order to choose the best for further construction. After consideration, those deemed the highest performing are the Miyauchi device, able to perform simple shear tests and the bi-axial testing machine, able to perform plane strain and simple shear tests separately or simultaneously. This chapter presents the mechanical features of the Miyauchi device and the bi-axial test machine that were built at the M&S Laboratory, followed by a description of the optical strain gauge chosen that allows the computation of the strain field throughout the specimens deformation area. Chapter 4 focuses on the validation of the experimental equipment. First, the homogeneity of the stress and strain fields is verified. Then, the availability of performing the plane strain, simple shear, Bauschinger and orthogonal tests is checked. The repeatability (precision) of the tests is corroborated and the accuracy is validated by comparison with finite elements simulations. In Chapter 5, the identification methods are proposed and DC06 (0,8mm thick), DP1000 (1,6mm thick) and S320GD (0,69mm thick) steels are identified according to those methods. The initial yield surface for DC06 is identified by two methods (one using the strain measurements, the other using stress measurements) for two yield criteria, which are then compared with a texture-based yield criterion and the experimental points. The initial yield surface for the other two materials is described by the Hill 1948 yield criterion identified using strain measurements. The yield surface evolution (hardening) for DC06 and S320GD is described by the Teodosiu and Hu hardening law due to the observed mechanical behavior, i.e., the Bauschinger effect and strong influence of the pre-strain when strain-path changes take place. DP1000 exhibits a high Bauschinger effect and its flow stress is not influenced by the amount of pre-strain when reversing the load; hence, its behavior is described by a kinematic hardening law. Finally, in Chapter 6, conclusions about the present work are established and equipment improvement and further topics for research are proposed, namely, the study of texture evolution, the material axis rotation and the experimental validation of new yield criteria.

In this research, X-ray Diffraction is used to detect the existence of the In metal signal of the Indium Nitride (InN) through the analysis of two samples grown from the plasma-assisted molecular beam epitaxy (PAMBE). Sample A was grown on the Al2O3(0001) substrate with Gallium Nitride as a buffer layer, while Sample B was grown directly on the Si(111) substrate. Through X-ray Diffraction, we discovered the In(101) signal on Sample A and the InN(10-11) signal on Sample B. However, the two peaks of both signals were so close that it was difficult to differentiate them. Besides, the scanning electron microscope failed to show the existence of the In metal on the surface of both InN samples. Therefore, the high temperature XRD was employed to identify the true signal based on the different melting points between InN and In. Further, an acid etching method was also applied to recognize the existence of the In metal on the surface of the sample.

Investment casting has been an important form of metal casting for many years, but little is understood about the fluid flows that occur during mold filling. A key to quality castings is the understanding and control of the fluid flows that are present when the mold is filled with molten metal. It is thought that with a greater understanding of these flows, better control can be maintained and the end result will be a more efficient process that produces better parts. The subject of this thesis is the experimental study of the fluid mechanics of filling a small part mold. The experiments included tests on different downsprues, wells, runners, and chokes. The collected data were analyzed and the following recommendations were made: The shape of the downsprue, whether tapered or straight, does not seem to be important as long as the minimum area is small enough to provide the required choking. The use of a well has contributed to the smoothness of a flow, but its effect can be provided instead by chokes. Overflow chokes in the horizontal portions of the mold seem to be more effective than choking in the downsprue, but the use of both improves the flow. While runner extensions and underflow chokes might help to reduce impurities, they do little to help the smoothness of the flow. / Graduation date: 1991

<p>Metal hydrides hydrogen storage materials have the ability to reversibly absorb and release large amounts of hydrogen at low temperature and pressure. In this study, metal hydride materialsemployed as negative electrodes in Ni-MH batteries are investigated. Attention is on AB5 alloys due to their intermediate thermodynamic properties. However, AB5 alloys a have&nbsp / tendency of forming oxide film on their surface which inhibits hydrogen dissociation and penetration into interstitial sites leading to reduced capacity. To redeem this, the materials were micro-encapsulated by electroless deposition with immersion in Pd and Pt baths. PGMs were found to increase activation, electrochemical activity and H2 sorption kinetics of the MH alloys. Between the two catalysts the one which displayed better performance was chosen. The materials were characterized by X-ray difractommetry, and the alloys presented hexagonal CaCu5 &ndash / type&nbsp / structure of symmetry P6/mmm. No extra phases were found, all the modified electrodes displayed the same behavior as the parent material. No shift or change in peaks which corresponded to Pd or Pt were observed. Scanning Electron Microscopy showed surface morphology of the materials modified with Pd and Pt particles, the effect of using different reducing agents (i.e., N2H4 and NaH2PO2), and alloys functionalized with &gamma / -aminosopropyltrietheosilane solution prior to Pd deposition. From all the surface modified alloys, Pt and Pd particles were observed on the&nbsp / surface of the AB5 alloys. Surface modification without pre-functionalization had non-uniform coatings, but the prefunctionalized exhibited more uniform coatings. Energy dispersive X-ray Spectroscopy and Atomic Absorption Spectroscopy determined loading of the Pt and Pd on the surface of all the alloys, and the results were as follows: EDS ( Pt 13.41 and Pd 31.08wt%), AAS (Pt 0.11 and Pd 0.78wt%). Checking effect of using different reducing agents N2H4 and NaH2PO2 for electroless Pd plating the results were as follows: EDS (AB5_N2H4_Pd- 7.57 and AB5_NaH2PO2_Pd- 31.08wt%), AAS (AB5_N2H4_Pd- 11.27 and AB5_NaH2PO2_Pd- 0.78wt%). For the AB5 alloys pre-functionalized with &gamma / -APTES, the results were: EDS (10.24wt%) and AAS (0.34wt%). Electrochemical characterization was carried out by charge/discharge cycling controlled via potential to test the AB5 alloy. Overpotential for unmodified, Pt and Pd modified&nbsp / electrodes were -1.1V, -1.24V, and -1.60V, respectively. Both modified electrodes showed discharge overpotentials at lower values implying higher specific power for the battery in comparison with the unmodified electrodes. However, Pd electrode exhibited higher specific power than Pt. To check the effect of the reducing agent the results were as follows: AB5_ N2H4_Pd (0.4V) and AB5_NaH2PO2_Pd (-0.2V), sodium hypophosphite based alloy showing lower overpotential values, implying it had higher specific power than hydrazine based bath. Alloy prefunctionalized with &gamma / -APTES, the overpotential was (0.28V), which was higher than -0.2V of the alloy without pre-functionalization, which means pre-functionalization with &gamma / -APTES did not improve the performance of the alloy electrode. Polarization resistance of the electrodes was investigated with Electrochemical Impedance Spectroscopy. The unmodified alloy showed high resistance of&nbsp / 21.6884 while, both Pt and Pd modified electrodes exhibited decrease 14.7397 and 12.1061 respectively, showing increase in charge transfer for the modified electrodes. Investigating the effect of the reducing agent, the alloys exhibited the following results: (N2H4 97.8619 and NaH2PO2 12.1061) based bath. Alloy pre-functionalized with &gamma / -APTES displayed the&nbsp / resistance of 9.3128. Cyclic Voltammetry was also used to study the electrochemical activity of the alloy electrodes. The voltammograms obtained displayed the anodic current peak at -0.64V&nbsp / o -0.65V for the Pt and Pd modified electrodes, respectively. Furthermore, the electrode which was not coated with Pt or Pd the current peak occurred at -0.59V. The Pd and Pt coated&nbsp / alloy electrodes represented lower discharge overpotentials, which are important to improve the battery performance. Similar results were also observed with alloy electrodes Pd modified&nbsp / using N2H4 (-0.64V) and NaH2PO2 (-0.65V). For the electrode modified with and without &gamma / -APTES the over potentials were the same (-0.65V). PGM deposition has shown to significantly&nbsp / improve activation and hydrogen sorption performance and increased the electro-catalytic activity of these alloy electrodes. Modified electrodes gave better performance than the unmodified&nbsp / electrodes. As a result, Pd was chosen as the better catalyst for the modification of AB5 alloy. Based on the results, it was concluded that Pd electroless plated using NaH2PO2 reducing agent&nbsp / had better performance than electroless plating using N2H4 as the reducing agent. Alloy electrode pre-functionalized with &gamma / -APTES gave inconsistent results, and this phenomenon needs to&nbsp / be further investigated. In conclusion, the alloy modified with Pd employing NaH2PO2 based electroless plating bath exhibited consistent results, and was found to be suitable candidate for&nbsp / use in Ni-MH batteries.</p>

This research collected surface (<15 cm) sediments from estuarine and coastal zones off southwestern Taiwan. Basic sediment parameters, including grain size, and total organic carbon (TOC) and total inorganic carbon (TIC) concentrations were analyzed. For heavy metals (Fe, Mn, Cd, Cu, Ni, Pb, and Zn), total metal concentrations and metal fractions separated by sequential extraction techniques were determined. This study also obtained several previously collected sediment cores in the Gaoping Canyon area that had been dated by other researchers. Results obtained in this study are used in order to understand the distribution patterns of heavy metals in coastal sediments off southwestern Taiwan, and related to regional environmental changes regarding heavy metals. The distribution of heavy metal fractions and their geochemical significances were studied. Results obtained in this study indicate that physicochemical characteristics of sediments largely affected heavy metal distribution in coastal sediments off southwestern Taiwan. Regional flow patterns contributed to the observed distribution patterns. Higher heavy metal concentrations were found in sediments collected near the Gaoping river mouth, the Gaoping Canyon and its nearby continental slope, and a narrow banded offshore region off the Anping-Tainan urban areas. These results reflect the distribution of fine-grained sediments in the studied area. Vertical profiles of heavy metals in four dated cores showed drastic increases of heavy metal concentrations since 1995-2000, and some extent of decreases during 2003-2006 in two of the cores. Although actions of environmental protection regarding heavy metal pollution had taken place in this region, decreases in sediment heavy metals were mostly attributed to episodic typhoon and possibly sediment slumping events. With the recently intensified landslides and mud flows in the upper reaches of the river that would bring upstream soils and particles to the estuarine region, leading to the decrease of metal concentrations in the Gaoping estuarine sediments, a more significant decreasing trend in sediment metal concentrations can be speculated for the future.

Angioplasty over the years has proven to be an excellent substitute for open heart surgery where an artery/vien, blocked by atherosclerosis, is expanded using a stent. Metallic and coated metallic stents have been used for angioplasty. Metal stents might induce blood clotting, release cytotoxic heavy metal ions which are potential inducers of allergies, clotting, immune reactions and hyperproliferation of smooth muscle cells and also lead to protein absorption which activates clotting factors. Biodegradable polymers have also been tried as stent materials, but the loss of radial strength over time is a big problem associated with them. The use of a hybrid stent, consisting of biodegradable polymer and biocompatible stainless steel, is proposed. The use of such a system would require excellent adhesion between the stent metal and the biodegradable polymer. This study presents the electrochemically induced micromechanical interlocking to enhance adhesion between 304 stainless steel and high density polyethylene. High density polyethylene was used instead of biodegradable polymer for initial investigation. Electrochemical etching on the stainless steel wire was accomplished by immersing a stainless steel wire in a sodium carbonate electrolyte while applying a known voltage through the wire. The electrochemical etching of the stainless steel wire resulted in pitting under suitable conditions. The etching time, voltage and electrolyte concentration were varied to achieve different pit sizes and pit distributions on the stainless steel wire. An image analysis was conducted using an image analysis software to find the exact pit size and pit distribution on the stainless steel wire from electrochemical etching. A statistical model based on design of engineering experiments was derived. Etched and the unetched wires were molded with high density polyethylene and a mechanical test was conducted to measure the force required to pull the wire out of the polymer and verified using calculations based on the pit size and pit distribution of the pits on the surface of the wire. Electrochemical etching produced burr free surface features. It was observed that the pH level in the electrolyte contributes to the pit size and pit distribution. The results of the statistical model were consistent with the experimental values and it was possible to optimize the electrochemical etching parameters for maximum pit size and pit distribution. It was also observed that while voltage and etching time contribute to pit size and pit distribution, the electrolyte concentration does not have significant effect on the pit size and pit distribution. The calculated pull out force and measured values were off by 22.7%. The lower value of calculated force could result from neglecting some of the smaller pits while performing the image analysis. The average adhesive strength of the etched samples was 276% higher than that of the unetched samples.

Over the past decade the focus of our group has been production of polycarbonates through environmentally friendly routes. Continuing with this tradition, one such route is the ring opening polymerization of cyclic carbonates. The aliphatic polycarbonate derived from trimethylene carbonate, (TMC, 1, 3-dioxan-2-one), has been studied extensively for its potential use as a biodegradable polymer in biomedical and pharmaceutical systems. Its important applications include sutures, drug delivery systems and tissue engineering. To date, majority of the literature concerning catalysts for polymerization of TMC has been restricted to the use of simple Lewis acids with a marked absence of well defined and characterized catalysts. Metal salen complexes have been effective in the ring opening of cyclohexene oxide and the copolymerization of epoxide and carbon dioxide. The ability of this system as a catalyst for the polymerization of cyclic carbonates to polycarbonates is reported in this dissertation. The salen ligand is among the most versatile ligands in chemistry. Our attempts to optimize the catalytic activity by manipulating the salen structure and reaction conditions are also discussed. Our initial efforts were concentrated in understanding the efficacy of Lewis acidic metal salen complexes (Al & Sn), as catalysts for this process. This was followed by the utilization of metal salen complexes of biometals as catalysts for the synthesis of these biodegradable polymers, as well as for the copolymerization of cyclic carbonates with cyclic esters. These copolymers are presently in great demand for their applications as sutures in the medical industry. During the course of our investigations, a novel method of synthesizing polytrimethylene carbonate, by the copolymerization of CO2 and trimethylene oxide, has come to our attention. Surprisingly this reaction has received very little scientific exposure. We observed that metal salen derivatives, along with n-alkyl ammonium salts, were effective catalysts for the selective coupling of CO2 and oxetane (trimethylene oxide) to provide the corresponding polycarbonate with only trace quantities of ether linkages. A section is also dedicated to our investigations in this area of research.