Due to the introduction of Restriction of Hazardous Substances (RoHS) directive Pb containing solders have been banned from the electronics industry and a reliable replacement for the Sn-Pb solder is being sought for by industry around the globe. Medical and Defense industries are currently exempt from the directive and use Sn-Pb solder in their manufacturing process. The switch to lead-free has led component manufacturers to use different lead-free solders, thus causing mixed solder joints of lead-free components with Sn-Pb paste. In this study, mixed assembly microstructures and mechanical properties were examined. Furthermore, six novel lead-free solders were prepared using SAC105 solder doped with elements: Ti, Ni, Mn, La, Ce and Y. The solidification microstructures, fracture behavior and wetting properties of these solders were evaluated to find a suitable replacement for SAC105 solder.

Organic Light Emitting Diodes (OLEDs) are widely viewed as next generation platform for flat panel displays and solid state lighting. Currently, OLED efficiency is not high due to high driving voltage. Molybdenum trioxide (MoO3) is ideal for p-type doping of the wide bandgap organic semiconductor 4,4’-bis-9-carbozyl biphenyl (CBP). With p-type doped CBP layer as Hole Transport Layer (HTL), driving voltage can be significantly reduced. Effective design for doped OLED structure consists of a HTL with doped layer from 20nm to 40nm and MoO3 concentration above 5%, the optimized OLED with doped CBP HTL present an 18% improvement over a standard device with CBP HTL at 100mA/cm2. Injection is found to be the principle cause of the reduction of driving voltage and shows close relations to doped layer thickness. Also charge balance is an important factor for high current efficiency, doped layer can be used as tools to promote charge balance.

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).

Scanning electron microscope, X-ray diffraction and photoluminescence measurements were conducted on Be(x)Zn(1−x)O nanowires prepared by electrochemical and hydrothermal deposition to study their morphology, structure and optical properties. The bowing parameter for nanowires prepared by electrochemical and hydrothermal deposition was found to be 4.8 eV and 3.6 eV, respectively. It was observed that for electrochemical deposition, it is more difficult for Be(2+) to incorporate in the crystal lattice than Zn(2+). The electrochemical deposited samples exhibited stronger deep level emissions, indicating a higher density of deep level states. A home-made Optically Stimulated Luminescence (OSL) system was successfully constructed and calibrated with Al2O3:C and BeO. The OSL lifetime measurements on electrochemical deposited samples showed there were measurable OSL signals even on 500 nm long Be(x)Zn(1−x)O nanowires. The lifetimes of these OSL signals were found to decrease with increasing Be concentration. Be(x)Zn(1−x)O nanowires show considerable promise as new OSL materials.

Aluminum Doped Zinc Oxide (AZO) produced by radio frequency (RF) magnetron sputtering is thought to be the prospective replacement of the de facto standard indium tin oxide (ITO) anode in organic solar cells. In order to achieve a proper resistivity and transmittance of AZO thin film compared to ITO, a systematic study was done to optimize the sputtering conditions. In this work, two primary parameters: target-substrate distance and sputtering power, were optimized, and a optimized film thickness was determined. A poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) bulk-heterojunction organic solar cell was fabricated based on the optimized parameters and the power conversion efficiency reached 0.83%. A theoretical analysis is given to explain the optimization process. This work provides a clear pathway to substitute AZO for ITO in organic solar cells for future mass production.

Due to the introduction of Restriction of Hazardous Substances (RoHS) directive Pb containing solders have been banned from the electronics industry and a reliable replacement for the Sn-Pb solder is being sought for by industry around the globe. Medical and Defense industries are currently exempt from the directive and use Sn-Pb solder in their manufacturing process. The switch to lead-free has led component manufacturers to use different lead-free solders, thus causing mixed solder joints of lead-free components with Sn-Pb paste. In this study, mixed assembly microstructures and mechanical properties were examined. Furthermore, six novel lead-free solders were prepared using SAC105 solder doped with elements: Ti, Ni, Mn, La, Ce and Y. The solidification microstructures, fracture behavior and wetting properties of these solders were evaluated to find a suitable replacement for SAC105 solder.

Organic Light Emitting Diodes (OLEDs) are widely viewed as next generation platform for flat panel displays and solid state lighting. Currently, OLED efficiency is not high due to high driving voltage. Molybdenum trioxide (MoO3) is ideal for p-type doping of the wide bandgap organic semiconductor 4,4’-bis-9-carbozyl biphenyl (CBP). With p-type doped CBP layer as Hole Transport Layer (HTL), driving voltage can be significantly reduced. Effective design for doped OLED structure consists of a HTL with doped layer from 20nm to 40nm and MoO3 concentration above 5%, the optimized OLED with doped CBP HTL present an 18% improvement over a standard device with CBP HTL at 100mA/cm2. Injection is found to be the principle cause of the reduction of driving voltage and shows close relations to doped layer thickness. Also charge balance is an important factor for high current efficiency, doped layer can be used as tools to promote charge balance.

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).

Scanning electron microscope, X-ray diffraction and photoluminescence measurements were conducted on Be(x)Zn(1−x)O nanowires prepared by electrochemical and hydrothermal deposition to study their morphology, structure and optical properties. The bowing parameter for nanowires prepared by electrochemical and hydrothermal deposition was found to be 4.8 eV and 3.6 eV, respectively. It was observed that for electrochemical deposition, it is more difficult for Be(2+) to incorporate in the crystal lattice than Zn(2+). The electrochemical deposited samples exhibited stronger deep level emissions, indicating a higher density of deep level states. A home-made Optically Stimulated Luminescence (OSL) system was successfully constructed and calibrated with Al2O3:C and BeO. The OSL lifetime measurements on electrochemical deposited samples showed there were measurable OSL signals even on 500 nm long Be(x)Zn(1−x)O nanowires. The lifetimes of these OSL signals were found to decrease with increasing Be concentration. Be(x)Zn(1−x)O nanowires show considerable promise as new OSL materials.

The effects of crosslinking on EVA foaming are studied in this thesis. A fundamental approach was applied to describe the influences of crosslinking on EVA/gas viscosities, gas solubility and diffusivity in EVA, EVA foaming nucleation and early stage of bubble growth, which leads to a better understanding of the plastic foaming mechanism. Although crosslinked polyolefin foaming technology has been well applied in industry, more fundamental and thorough studies are demanded to understand the mechanism, which can serve to improve the present technology. The shear and extensional viscosities have been measured for the chemically crosslinked EVA with dissolved gas which could not be found from literature. Furthermore, by controlling the crosslinking agent amount, the polymer melt strength/viscosity can be controlled, so as to obtain optimum foam morphology. The crosslinking also has effects on the diffusivity and solubility of a blowing agent inside EVA. The solubility and the diffusivity of the blowing agent in the EVA decrease with the crosslinking degree increases. The diffusivity decrease makes more gas is utilized for the foaming rather than leak out of the polymer matrix quickly. This thesis also presents the fundamental studies on the effects of crosslinking on cell nucleation and early bubble growth. Theoretical work and in-situ visualization experimental results indicate that partial crosslinking leads to higher cell nucleation density and slower bubble growth, both of which benefit a fine-cell foam morphology generation. Last but not least, an optimized foaming process was conducted to produce chemically crosslinked EVA foams with large expansion ratios in a batch system, using a chemical blowing agent. The results determine that an optimal crosslinking degree is critical for the crosslinked EVA foaming with maximum expansion ratio. Furthermore, all research results not only benefit the foaming of crosslinked EVA, but also serve the better production of other crosslinked polyolefin foams.