Search

Solution-processable high refractive index materials are of immense interest for the production of optoelectronic devices, offering the prospect of high throughput, low cost and large area fabrication. In this thesis the optical characterisation of a relatively new type of optical material: the organic/inorganic molecular hybrid is presented. This molecular hybrid uses amorphous titanium oxide hydrates to cross-link polyvinyl alcohol (PVA) and in doing so enables the production of highly transparent thin film coatings with inorganic loadings approaching 100\%. The refractive index of the hybrid material is determined by probing Fabry-Perot oscillations in the transmittance spectra of thin films. This simultaneously demonstrates the high indices, low optical loss and excellent film quality possible for the hybrid. The refractive index is found to be tunable between 1.5 and 1.8 by adjusting the relative content of titanium. However, a simple thermal annealing process is shown to allow indices above 2, without compromising the transparency of the material. The index increase on thermal annealing is explained as the result of the large contraction that also occurs. The hybrid material is then used to fabricate several planar photonic structures. The first is a distributed Bragg reflector, in which the hybrid is deposited sequentially with a commercially available low index fluorinated polymer. The resulting structures have a high reflectance band that is controlled simply by the thicknesses of the high and low index layers. The DBRs demonstrate not only the excellent control of refractive index for the hybrid but also the ability to control layer thickness on the nanometre scale using dip coating. Infrared DBRs that are highly transparent in the visible are also fabricated as a possible application of the hybrid material system for heat management of glass clad buildings. Anti-reflective coatings are also demonstrated that remove 87\% of the reflectance from glass. This is achieved using a symmetrical bi-layer design, again dip cast from solution. Finally, all solution-processed optical microcavities are produced using the hybrid material. First, a simple defect is inserted into a DBR stack to induce a peak in transmittance inside the stop-band. This is then extended to include an emissive material: a perylene derivative, that is coupled to the cavity mode in order to alter its emission characteristics. This, to the best knowledge of the author, is the first demonstration of coupling in a solution-processed optical microcavity. Open Access

This report describes the development of an endoscopic camera for the purpose of exploring small underwater caverns. The project sponsor, Dr. Jeff Marliave of the Vancouver Aquarium, has been pursuing research into the hibernal behavior of rockfish in the waters of Howe Sound, and he required a device capable of maneuvering into the hibernation caverns and rock piles for observation of the fish. After several initial solutions were analyzed and tested, it became apparent that the most feasible idea was to modify an existing endoscopic camera by attaching it to a flexible, controllable arm, which has been named the "mechanical spine". This device was developed as a purely mechanical solution which would be simple to control, simple to build, and robust. There were several challenges to overcome during development. The device's user interface was required to be simple, accurate and unobtrusive, and durability was a major concern considering the operating conditions. Maximizing the penetration distance of the camera into the caverns was also an important design consideration. After several iterations of the design and subsequent discussions with Dr. Marliave's team, it became apparent that the device could achieve the minimal requirements of the project, but would require further development to be proven reliable and effective for continued use.

Clouds and Light is an interactive concept intended as an installation for the new UBC Student Union Building atrium space. It is built around the idea of participatory action and is meant to demonstrate the potential of the human body to generate large-scale kinetic motion and energy. The installation consists of an array of fabric shapes, each approximately 4- 5 meters in diameter, suspended from the atrium ceiling, each connected to a series of pulleys and gears through fabric cables. The pulleys are connected to the floor of the space in such a way that a person may pull on the cables, activating the gear system and causing the shapes to move in a wave-like pattern. This motion causes two main effects: as the fabrics of the shapes shift in space, the natural light entering the atrium through the many windows is diffused and filtered in a subtle, changing pattern; and the motion of the pulleys turns a generator, sending electrical energy to a series of LED lights which help to illuminate the installation. This project has been developed as a roughly 1/10 scale prototype, which demonstrated the concepts of power generation and user-induced motion as well as the aesthetics of the piece. Scaling this project up for the purpose of installation in the new SUB atrium is feasible, but will require further information on the structural makeup of the building as the intent is to suspend the piece from the existing structure. The materials, construction and installation process can potentially be made cost-effective; the details of this are discussed in two possible scenarios. Disclaimer: “UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report.”

It is well reported that the grain size of polycrystalline materials is important in determining mechanical properties. Within this thesis investigations are reported from an inter-comparison of grain size methods, the impact of an incomplete network of grain boundaries after chemical etching (missing boundaries) on grain size measurements and finally the relationship between grain size and the misorientation of grains. The experimental techniques used are manual grain size measurement methods, automatic image analysis and Electron Backscatter Diffraction (EBSD). The materials used are a ferritic, single phased, equi-axed steel (mild steel) and a ferrite/pearlite steel. The relative simplicity of the mild steel microstructure effectively removes complicating factors such as multi-phases or grain elongation allowing a more focused investigation into grain size methods. The ferrite/pearlite steel can be found more readily in industrial applications where impact toughness is an important property. Manual measurement methods and automatic image analysis are used for the inter-comparison of grain size methods. The manual methods are described in the standard ASTM E112, and are the lineal, planimetric, single circle and three circle methods. It is shown that there is a difference across the methods in the number of measurements required to obtain a specified accuracy. Also that sampling is critical to ensure that the measurements made are representative of the microstructure in that it is more important to measure more specimens than more fields of view within one specimen or many grains within one field of view. Automatic image analysis can provide a substantial database and thus is a useful grain sizing method. It is demonstrated that the number of pixels in a digital image forming a grain boundary, determined by the pixel resolution, will influence the measurements. Also from using digital images a specific number of grain boundaries are removed thus artificially creating missing boundaries making their impact on grain size measurements quantifiable. Manual and automatic measurements are conducted and it is shown that the mean grain size is relatively less affected by missing boundaries than might be perceived from a visual inspection. An EBSD map provides a complete network of grain boundaries since a boundary is formed from the orientation of one grain to another (misorientation), compared to standard metallographic techniques, e.g. chemical etching. EBSD maps are compared with optical images of the same fields of view and missing boundaries are then located. From this it is shown that there is a significant difference between two operators in determining the location of boundaries. EBSD is also used to investigate the correlation between the location of missing boundaries and the misorientation of the grains at that boundary and shows a trend of higher misorientation for boundaries not chemically etched up. The final section of this thesis is concerned with the relationship between the misorientation of small/small, small/large and large/large grains and the size of grains of the ferrite phase from the ferrite/pearlite steel. EBSD maps provide the misorientation data and are also used for grain sizing conducted on the automatic image analysis system. From the misorientation data the boundaries can be categorised as low or high angle and it is found that there are more low angle boundaries between small/small grains and small/large grains than between large/large grains.