With the progress of microfabrication and nanofabrication technologies, there has been a reawakened interest in the possibility of controlling the propagation of light in various materials periodically structured at a scale comparable to, or slightly smaller than the wavelength. We can now engineer materials with periodic structures to implement a great variety of optical phenomena. These include well known effects, such as dispersing a variety of wavelength to form a spectrum and diffracting light and controlling its propagation directions, to new ones such as prohibiting the propagation of light in certain directions at certain wavelengths and localizing light with defects in some artificially synthesized dielectric materials. Advances in this field have had tremendous impact on modern optical and photonic technologies. This doctoral research was aimed at investigating some of the physics and applications of periodic structures for building blocks of the optical communication and interconnection system. Particular research emphasis was placed on the exploitation of innovative periodic structure-based optical and photonic devices featuring better functionality, higher performance, more compact size, and easier fabrication. Research topics extended from one-dimensional periodic-structure-based wavelength-division-multiplexing (WDM) optical interconnects (beam wavelength selection devices), and liquid crystal beam steerers (beam steering devices), to two-dimensional periodic-structure-based silicon photonic-crystal thermo-optic and electro-optic modulators (beam switching devices). This research was specifically targeted to seek novel and effective solutions to some long-standing technical problems, such as the limited wavelength coverage of coarse WDM devices, small bandwidth of highly dispersed dense WDM devices, low deflection efficiency of high-resolution liquid crystal beam steerers, slow switching speed, large device size, and high power consumption of silicon optical modulators, among others. For each subtopic, research challenges were presented and followed by the proposed solutions with extensive theoretical analysis. The proposals were then verified by experimental implementations. Experimental results were carefully interpreted and the future improvements were also discussed.

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In recent years, nanostructured and amorphous metals have become more prominent in scientific research. Their unique characteristics and their vastly superior mechanical properties have lead to emerging technical applications however the use of these materials is only in its infancy. To further growth the industrial applications for these advanced materials, joining processes capable of maintaining the unique aspects of the microstructure are required. / Joining of two beveled plates has been accomplished by use of the Cold Spray process. This process uses a converging diverging nozzle to accelerate micron sized powder towards a substrate. The strength of the resulting joint has been compared to freeforms made of powder of the same composition. No significant difference was observed in the mechanical properties between the freeforms and the weldments and examination of the fracture surface showed that the strength of the interface is higher than the strength of the freeform itself. / A weld repair experiment has also been performed where the ElectroSpark Deposition process (ESD) has successfully been used to transfer amorphous material from an electrode to an amorphous substrate without crystallizing either material. This result is of crucial importance as it signifies that these extremely expensive and heat sensitive materials can be repaired when in-service wear causes damage. This process, due to its inherently fast cooling rate, has also successfully been used to transform a crystalline AlCoCe alloy into an amorphous deposit atop both amorphous and crystalline substrates.

Bulk nanostructured silver components were fabricated from nano-sized powder using a shockwave consolidation technique. The grain size evolution during compaction, the mechanical properties of the bulk components, and the effect of surface finish on the mechanical behavior were studied. X-Ray diffraction, transmission electron microscopy (TEM), atomic force microscopy (AFM), microhardness, compression testing and shear punch testing at room temperature were used to characterize the materials. Upon consolidation, the average grain size calculated from image analysis of the TEM micrographs was 49+/-22 nm, showing the feasibility of maintaining a nanostructure upon dynamic consolidation. The hardness of the bulk nanostructured components was constant across the diameter with an average of 83+/-1 HV. Compression results showed strength about 390+/-10 MPa and ductility of 23+/-2%, which is well above strength level obtainable from strain hardened Ag components. The AFM results show that samples possessing a surface roughness of 267 nm exhibited a brittle behavior and a reduction in strength of 35% when compared to the smoother surfaces. Dimples were observed for the samples exhibiting plasticity, while an intergranular pattern was identified for the brittle materials. Fracture toughness of 0.2 MPa m was calculated, which confirms the strong relationship between fracture toughness and defects observed in nanomaterials.

In this thesis, high temperature vapor deposition method has been extensively used to synthesize nanomaterials. One of the as-synthesized nanostructures is superlattice-structured nanohelix, which is made of two types of alternating and periodically distributed long crystal strips. The manipulation of the nanohelix showed super-elasticity and special fracture mechanism. The other widely studied nanomaterial is vertically aligned ZnO nanowire array, which is epitaxially grown on GaN and SiC substrates. Several manipulation methods such as e-beam lithography (EBL), dielectrophoresis, and in situ direct manipulation, have been developed, so that the mechanical and electrical properties of a single nanowire can be characterized, which provide essential references for fabricating bridged nanowire based devices. Specifically, an improved atomic force microscope (AFM) based method has been developed to accurately measure the elastic modulus of bridged ZnO nanowires. Bridged nanostructure is an extremely important configuration in planar MEMS/NEMS devices and this new approach provides insights to the importance of boundary conditions. Novel physical and statistical models have been firstly developed to obtain better estimate of elastic modulus. For electrical properties of bridged nanowires, it is found that the direct contact of ZnO nanowire and Au electrodes displays a back-to-back Schottky behavior. Self-assembled monolayer (SAM) can improve the mechanical contact and increase the conductance. These devices with Schottky contacts show much better UV sensing performance than the ones with Ohmic contacts. Barrier height change is believed to play an important role in a lot of sensors. A thermionic emission-diffusion model is deduced to successfully explain the current change in a strain sensor. This thesis clearly exhibits the unique properties of ZnO nanomaterials and provides deeper understanding to methodologies as well as the phenomena. With further exploration, ZnO nanomaterials should be able to better understood and utilized, and come close to the next step of commercialization.

Polyvinyl alcohol (PVA) has been widely used in fibre and paper industries. Due to its excellent biocompatibility, biodegradability, water solubility and gas permeability, PVA has recently attracted enormous interest in special applications such as biochemical, biomedical and environmental-friendly packaging materials. However, its poor thermal aging resistance, miserable solvent resistance and insufficient mechanical property have greatly restricted PVA’s further applications. / To overcome these drawbacks of PVA, in the present study, silica nanoparticles are introduced into PVA matrix to prepare a polyvinyl alcohol/silica (PVA/SiO²) nanocomposite by incorporating self-assembly and solution compounding techniques. Different from other conventional processes for preparing nanocomposites such as sol-gel process, intercalation and physical blending, the process developed in this study is simple, universal, low cost, yet effective, and easy to be scaled up for industrial exploitation. / Thesis (PhD)--University of South Australia, 2006.

Thesis (M.S.)--State University of New York at Binghamton, Department of Chemistry and Materials Science & Engineering, 2006. / Includes bibliographical references (leaves 49-53).