A multi-frequency data acquisition system is realized for subsurface conductivity imaging of biological tissues. The measurement procedures of the system at different frequencies are same. The only difference between the single frequency experiments and the multi-frequency experiments is the hardware, i.e. the sensor and the power amplifier used in the single frequency experiments was different than that were used in the multi-frequency experiments. To avoid confusion the measurement system with which the single frequency experiments were performed is named as prototype system and the measurement system with which the multi-frequency experiments were performed is named as multi-frequency system. This system uses magnetic excitation (primary field) to induce eddy currents inside the conductive object and measures the resulting magnetic field due to eddy currents (secondary field). For this purpose, two differential-coil sensors are constructed / one is for the single frequency measurements and the other is for the multi-frequency measurements. Geometrically the coils are same, the only difference between them is the radius of the wires wound on them. The sensor consists of two differentially connected identical receiver coils employed to measure secondary field and in between the receiver coils is placed a transmitter coil, which creates the primary field. The coils are coaxial. In the prototype system the transmitter coil is driven by a sinusoidal current of 300 mA (peak) at 50 kHz. In the multi-frequency system the transmitter coil is driven by a sinusoidal current of 217 mA (peak), 318 mA (peak), 219 mA (peak) and 211 mA (peak) at 30 kHz, 50 kHz, 60 kHz and 90 kHz, respectively. A data acquisition card (DAcC) is designed and constructed on a printed circuit board (PCB) for phase sensitive detection (PSD). The equivalent input noise voltage of the card was found as $146.80 hspace{0.1 cm}nV$. User interface programs (UIP) are prepared to control the scanning experiments via PC (HP VEE based UIP, LabVIEW based UIP) and to analyze the acquired data (MATLAB based UIP). A novel sensitivity test method employing resistive ring phantoms is developed. A relation between the classical saline solution filled vessel (45mm radius, 10 mm depth) phantoms and the resistive ring phantoms is established. The sensitivity of the prototype system to saline solutions filled vessels is 13.2 $mV/(S/m)$ and to resistive rings is 155.02 mV/Mho while the linearity is 3.96$%$ of the full scale for the saline solution filled vessels and 0.12$%$ of the full scale for the resistive rings. Also the sensitivity of the multi-frequency system is determined at each operation frequency by using resistive ring phantoms. The results are in consistence with the theory stating that the measured signals are linearly proportional with the square of the frequency. The signal to noise ration (SNR) of the prototype system is calculated as 35.44 dB. Also the SNR of the multi-frequency system is calculated at each operation frequency. As expected, the SNR of the system increases as the frequency increases. The system performance is also tested with agar phantoms. Spatial resolution of the prototype system is found 9.36 mm in the point spread function (PSF) sense and 14.4 mm in the line spread function (LSF) sense. Spatial resolution of the multi-frequency system is also found at each operation frequency. The results show that the resolving power of the system to distinguish image details increases as the frequency increases, as expected. Conductivity distributions of the objects are reconstructed using Steepest-Descent algorithm. The geometries and the locations of the reconstructed images match with those of the real images. The image of a living tissue, a leech, is acquired for the first time in the literature. Magnetic conductivity spectroscopy of a biological tissue is shown for the first time in electrical conductivity imaging via contactless measurements. The results show the potential of the methodology for clinical applications.

The thermal properties of hydrate bearing sediments remain poorly studied, in part due to measurement difficulties inside the hydrate stability envelope. In particular, there is a dearth of experimental data on hydrate-bearing sediments, and most available measurements and models correspond to bulk gas hydrates. However, hydrates in nature largely occur in porous media, e.g. sand, silt and clay. The purpose of this research is to determine the thermal properties of hydrate-bearing sediments under laboratory conditions, for a wide range of soils from coarse-grained sand to fine-grained silica flour and kaolinite. The thermal conductivity is measured before and after hydrate formation, at effective confining stress in the range from 0.03 MPa to 1 MPa. Results show the complex interplay between soil grain size, effective confinement and the amount of the pore space filled with hydrate on the thermal conductivity of hydrate-bearing sediments.

In the production of base metals by smelting of sulphide ore concentrates, large amounts of iron are rejected with iron silicate slags. These slags contain Ni, Cu and Co in concentrations up to several percent units. Extraction of the entrapped base metals using high pressure oxidative acid leaching (HPOXAL) was investigated in this work. Crystalline slags containing fayalite (Fe2SiO4), magnetite (Fe3O4), silica (SiO2) and matte (MeSn<1) were found to be highly amenable to leaching at 250°C, 90 psi (6.2 bar) O2 partial pressure and 70 g/L initial H2SO4. Extractions of Ni, Co and Cu exceeded 90% within 15-20 min and arrived at 95-97% after 45 min. The residues of leaching were identified as aggregates of crystalline hematite (Fe2O3) and amorphous silica. Dissolution of fayalite and magnetite was shown to be acid driven. Since HPOXAL operates with substoichiometric additions of sulphuric acid (10-20% of the stoichiometric requirement), acid regeneration facilitated by iron oxidation and hydrolysis is crucial to high rates of leaching. Low acidities (<10 g/L) were shown to cause precipitation of ferrous sulphate, slowing acid regeneration and slag dissolution. Elevated acidities (>70 g/L) result in excessive concentrations of Fe(III) in the leach solution, complicating downstream processing. The use of pyrrhotite tailings, an environmentally hazardous waste, as a substitute of sulphuric acid in slag leaching was investigated. Oxidative co-leaching of pyrrhotite tailings with naturally cooled converter slag at 250°C, 90 psi (6.2 bar) O2, 68 g/L equivalent H2SO4 was shown to have kinetics comparable to adding sulphuric acid with final extractions reaching 95-97% in 45 min. Granulation of slag melt can produce an amorphous solid solution of SiO2 and metal oxides. Amorphous slag is not amenable to HPOXAL due to the formation of a passive layer of silica. Leaching of amorphous slag at low temperatures was shown to proceed nearly to completion. The difference in the leachability of amorphous slag at high and low temperatures is explained in terms of the rate of silicic acid re-polymerization leading to closure of pores in the leached layer.

In the production of base metals by smelting of sulphide ore concentrates, large amounts of iron are rejected with iron silicate slags. These slags contain Ni, Cu and Co in concentrations up to several percent units. Extraction of the entrapped base metals using high pressure oxidative acid leaching (HPOXAL) was investigated in this work. Crystalline slags containing fayalite (Fe2SiO4), magnetite (Fe3O4), silica (SiO2) and matte (MeSn<1) were found to be highly amenable to leaching at 250°C, 90 psi (6.2 bar) O2 partial pressure and 70 g/L initial H2SO4. Extractions of Ni, Co and Cu exceeded 90% within 15-20 min and arrived at 95-97% after 45 min. The residues of leaching were identified as aggregates of crystalline hematite (Fe2O3) and amorphous silica. Dissolution of fayalite and magnetite was shown to be acid driven. Since HPOXAL operates with substoichiometric additions of sulphuric acid (10-20% of the stoichiometric requirement), acid regeneration facilitated by iron oxidation and hydrolysis is crucial to high rates of leaching. Low acidities (<10 g/L) were shown to cause precipitation of ferrous sulphate, slowing acid regeneration and slag dissolution. Elevated acidities (>70 g/L) result in excessive concentrations of Fe(III) in the leach solution, complicating downstream processing. The use of pyrrhotite tailings, an environmentally hazardous waste, as a substitute of sulphuric acid in slag leaching was investigated. Oxidative co-leaching of pyrrhotite tailings with naturally cooled converter slag at 250°C, 90 psi (6.2 bar) O2, 68 g/L equivalent H2SO4 was shown to have kinetics comparable to adding sulphuric acid with final extractions reaching 95-97% in 45 min. Granulation of slag melt can produce an amorphous solid solution of SiO2 and metal oxides. Amorphous slag is not amenable to HPOXAL due to the formation of a passive layer of silica. Leaching of amorphous slag at low temperatures was shown to proceed nearly to completion. The difference in the leachability of amorphous slag at high and low temperatures is explained in terms of the rate of silicic acid re-polymerization leading to closure of pores in the leached layer.

In this dissertation, I developed a Pd seeding method in association with electroless plating, to successfully metallize both lambda DNA and DNA origami templates on different surfaces. On mica surfaces, this method offered a fast, simple process, and the ability to obtain a relatively high yield of metallized DNA nanostructures. When using lambda DNA as the templates, I studied the effect of Pd(II) activation time on the seed height and density, and an optimal activation time between 10 and 30 min was obtained. Based on the Pd seeds formed on DNA, as well as a Pd electroless plating solution, continuous Pd nanowires that had an average diameter of ~28 nm were formed with good selectivity on lambda DNA. The selected Pd activation time was also applied to metallize "T"-shape DNA origami, and Au coated branched nanostructures with a length between 200-250 nm, and wire diameters of ~40 nm were also fabricated. In addition, I found that the addition of Mg2+ ion into the reducing agent and electroless plating solution could benefit the surface retention of Pd seeded DNA and Au plated DNA structures. This work indicated that DNA molecules were promising templates to fabricate metal nanostructures; moreover, the formation of Au metallized branched nanostructures showed progress towards nanodevice fabrication using DNA origami. Silicon surfaces were also used as the substrates for DNA metallization. More complex circular circuit DNA origami templates were used. To obtain high enough seed density, multiple Pd seeding steps were applied which showed good selectivity and the seeded DNA origami remained on the surface after seeding steps. I used distribution analysis of seed height to study the effect of seeding steps on both average height and the uniformity of the Pd seeds. Four-repeated palladium seedings were confirmed to be optimal by the AFM images, seed height distribution analysis, and Au electroless plating results. Both Au and Cu metallized circular circuit design DNA origami were successfully obtained with high yield and good selectivity. The structures were maintained well after metallization, and the average diameters of Au and Cu samples were ~32 nm and 40 nm, respectively. Electrical conductivity measurements were done on these Au and Cu samples, both of which showed ohmic behavior. This is the first work to demonstrate the conductivity of Cu metallized DNA templates. In addition, the resistivities were calculated based on the measured resistance and the size of the metallized structures. My work shows promising progress with metallized DNA and DNA origami templates. The resulting metal nanostructures may find use as conducting interconnects for nanoscale objects as well as in surface enhanced Raman scattering analysis.

Recently, conductive polymer/carbon nanomaterials have drawn attention for use in corrosion inhibition, sensors, energy storage devices, and coatings for electromagnetic shielding applications due to their good mechanical properties and electronic conductivity. Therefore, efforts have been made to find fast and facile methods for the synthesis and development of these hybrids that allow control over key parameters, such as the thickness of the conductive polymer coating. In this study, such hybrids were prepared using polyaniline (PANI) as the conductive polymer and vapor-grown carbon nanofibers (VGCNFs) as the carbon nanomaterial or filler by a semi-dilute in situ polymerization method to be evaluated for their effectiveness as corrosion inhibitory additives to alkyd paints. Spectroscopic, colorimetric, and electric properties of PANI-coated VGCNFs were investigated. The thickness of the PANI coating, along with other parameters, impacts the behavior and mechanisms by which the nanomaterial performs its role in a given application, particularly in the corrosion inhibition processes. Thus, different synthesis conditions, including pretreatment of the nanofibers, the presence of sodium dodecyl sulfate (SDS) surfactant, PreT-VGCNF/ANI ratios (w/w), and polymerization times were tested and their effects on the PANI thickness were microscopically and statistically evaluated. It was found that only different PreT-VGCNF/ANI ratios allowed definite control of the PANI thickness. No clear effect on the thickness was observed after three hours of polymerization. The presence of SDS and pretreatment of VGCNFs displayed a synergistic effect on the appearance and thickness of the PANI film. PANI-coated VGCNF additives, with PANI in the leucoemeraldine base (LEB) and emeraldine base (EB) forms, were synthesized using a PreT-VGCNF/ANI ratio of 0.4 in the presence of SDS. Cold-rolled steel coupons were coated with 20-30 ìm thick alkyd paint coatings, and their electrochemical behavior was investigated by open circuit potential (OCP) and electrochemical impedance (EIS) measurements. The results indicate that, overall, EB/VGCNF additive performed better as a corrosion inhibitor, followed by PreT-VGCNF and LEB/VGCNF additives.