An experimental investigation on the furnace and CO₂ laser densification of sol-gel derived SiO₂-TiO₂-Al₂O₃ planar optical waveguides was performed. Solutions containing equal mole fractions of tetraethoxysiline [Si(C₂H₅O)₄], titanium ethoxide [Ti(C₂H₅O)₄], aluminum tri-sec-butoxide [Al(C₄H₉O)₃] were used to spin films with a nominal 2:2:1 molar SiO₂-TiO₂-Al₂O₃ composition. Emphasis was placed on determining what effects the densification techniques had on film shrinkage, index change, crystallization and composition. Film shrinkage and refractive index change were found to be similar for both densification techniques. Fully dense, amorphous film were obtained with both methods. After densification, further heating caused titania crystalline phases to form with both processing techniques. However, anatase formed in the furnace fired films while rutile formed in the laser irradiated films.

GASAR porous metals are produced by melting under a partial pressure of hydrogen and then casting into a mold that ensures directional solidification. Hydrogen is driven out of solution and grows as cylindrical pores normal to the solidification front. Experiments have been performed to produce GASARs from pure Ni and Inconel 718, a nickel-base superalloy. The processing variables studied in these experiments included the pressure of H₂(g), total pressure, superheat, and solidification rate. An analysis that considers heterogeneous bubble nucleation was developed that identifies processing conditions in which H₂(g) bubbles are stable in the liquid before solidification. It is hypothesized that these conditions lead to low porosity because the bubbles float out of the melt and are not incorporated into the final porosity. Experimental data are shown to support this hypothesis.

Prehistoric and traditional ceramics contain a wide range of tempers (non-plastic inclusions), including sand, sherd (grog), sponge spicules, phytoliths (siliceous bark ash), diatomite, organic fibers, shell, calcite, mica and asbestos. The use of these materials in traditional and archaeological ceramics and their association with cooking pottery and thermal shock resistance are examined. The thermal shock parameters that are relevant to low-fired ceramics are identified and tested. The primary factor in the thermal shock resistance is identified as fracture toughness. By increasing the amount and size range of temper additions, and by selecting tempers that are platy and fibrous, fracture toughness can be enhanced. Secondary factors include porosity, thermal expansion and relative strength. These parameters are tested employing fracture energy and thermal expansion measurements, and quench tests.

The interactions of CP-Ti and Ti-6Al-4V with investment molds with alumina/silica and yttria/silica face coat systems, and yttria crucibles were studied. It was found that the thickness of the reaction layer (alpha case) was the same, whether a yttria/silica or alumina/silica face coat was used, indicating that it is the silica binder truly which reacts with the titanium. Furthermore, it was found that only the yttria crucible was inert to reacting with titanium when it was used as a mold. When titanium was heated in yttria crucibles, however, and held just above the liquidus for 15 s and 30 s, oxygen and yttrium were found in the resulting samples. This indicates that commercial castings requiring longer solidification times might not be free of the alpha case even when produced in a 100% yttria mold system.

The Long Beach Water Department (LBWD) treatment plant presently employs conventional methods to treat groundwater sources which exhibit a characteristic color caused by naturally occurring organic matter. The incorporation of ozone into the treatment process train was investigated to enhance color removal. The effective dose and contact time required to meet the secondary color standard was found to be a function of initial color content of the water. UV absorbance was found to be a good surrogate parameter for color. Correlations using raw and ozonated water data exhibited a coefficient of determination (r²) of 0.81 and 0.70, respectively. The determination of a reaction kinetic model to describe color disappearance with ozone contact time was inconclusive. The ozone contact system was found to be mass transfer limited at ozone doses greater than 5.0 mg/l.

PS-based nonionic, but polar, diblock copolymers (polystyrene-b-polymethacrylates, polystyrene-b-polyacrylates, polystyrene-b-poly(dimethyl siloxane)) have been systematically studied using the Langmuir film balance (LFB) technique, transmission electron microscopy (TEM), and atomic force microscopy (AFM). It has been found that these nonionic copolymers can form 2D surface micelles as has been found for ionic diblocks such as polystyrene-b-poly(vinyl pyridinium iodide) diblocks. This suggests that formation of surface micelles is a general phenomenon among AB diblock copolymers. Both structural parameters (aggregation number, aggregate size distribution, corona length and thickness, morphologies, boundaries etc.) and the response to conditions (temperature of the subphase, surface tension of the subphase, hysteresis, compression rates, etc.) have been explored for the monolayers formed from these materials. Many of these diblocks exhibit plateaus or inflections in their isotherms. Experimental data allow for the calculation of the thermodynamic parameters $ rm ( Delta S sb{t}$ and $ rm Delta H sb{t})$ associated with the transitions. Differences between the $ rm Delta S sb{t}$ and $ rm Delta H sb{t}$ values observed with the nonionic diblocks in question and the ionic diblocks studied before suggests that the nonionic diblocks monolayers have unique properties. Different mechanisms of the transitions(s) are proposed for samples which have one transition plateau or inflection and samples which have multiple transitions or inflections. A scaling theory-based calculation of the corona length and $ pi$-A isotherm are reasonably consistent with experimental data and thus provides a useful tool in these studies. Selected properties (i.e. subphase surface tension, waiting time etc.) for several ionic diblocks were also studied. Finally, the minimum chain lengths for circular micelles were calculated using a scaling theory methodology.

A new method of incipient melting temperature (IMT) detection, continuous heating and fracture (CHF) method, has been developed in which a constant strain rate tensile or torsion deformation is applied to a specimen whose temperature is simultaneously increased. The IMT is determined in a single test and any phase transformations before the IMT will also be detected by the effects on the stress vs. strain behavior in the same experiment. This method also provides information about the effect of phase transformation and temperature on the mechanical behaviour of steel near the incipient melting temperature. / By means of such tests, the incipient melting behaviour of a series of steels with carbon levels from 0.031 to 0.45 wt% was examined. For the steels containing 0.08-0.097%C and about 1.5%Mn, it was found that incipient melting occurs in the two phase ($ gamma$+$ delta$) region in the temperature range from 1470-1480$ sp circ$C, and is significantly influenced by microalloying elements. In the ultra-low carbon steel (0.031%C), the IMT is in the single phase $ delta$ region at 1495 $ sp circ$C, and for the medium carbon steels containing 0.3-0.42%C (hyper-peritectic) it is in the $ gamma$ single phase in the temperature range of 1401-1414$ sp circ$C. Comparison between the IMT obtained from CHF testing and the solidus temperature calculated from K-O model showed that these two values are extremely close. Since there is no nucleation barrier for melting, it seems that the CHF testing can delineate the solidus temperature in steel. (Abstract shortened by UMI.)

The effect of Si addition on the interaction between recrystallization and precipitation during multipass deformation has been investigated in terms of the no-recrystallization temperature (Tnr), the minimum temperature at which recrystallization can be completed. The Tnr was measured in three Nb microalloyed steels with Si concentrations ranging from 0.01 to 0.48wt.%. Continuous cooling conditions were employed, with interpass times of 20--200s and strains of 0.2 and 0.35 applied at a strain rate of 2s -1. / It was observed that for similar Nb contents, the Tnr increased with Si level, but appeared to saturate at long interpass times. In addition, high strains also reduced the influence of Si on the Tnr. This behaviour can be attributed to the acceleration of the Nb(C,N) precipitation kinetics by the addition of Si. With increasing interpass time or strain, the precipitates start to coarsen and, in consequence, the pinning effect due to precipitation is reduced. Therefore, under these conditions, the effectiveness of Si addition in raising the Tnr is diminished.

The superior mechanical properties of carbon nanotubes would make them excellent candidates for the next generation of composite materials. Researchers have tried to demonstrate the potential of that novel material with various degree of success. In order to complement the experimental efforts in this new field, the modeling of these new material systems is required. One challenge when modeling nanotube composites is the large scale span between the nanotube itself and the final component. The present study focuses on the creation of a framework and methodology to span three orders of magnitude in scale with interconnected models that relate performance of single-walled carbon nanotubes (SWNT) at the nanometer scale to a nano-array, nano-wire and micro-fiber with self-similar geometries. The geometry chosen is the helical array composed of discontinuous SWNT. The five elastic constants of the twisted SWNT fibers are then predicted using a finite element analysis combined with the strain energy method. It is shown that the Young's modulus of carbon nanotube fiber decreases dramatically even for small twist angles (less than 20°) without any contribution to the transverse properties. Moreover, it was shown that adding the polymer and its properties can have important effects on the elastic properties of the SWNT/polymer fiber. Finally, this model is compared to the experimental data and theoretical models found in the literature.

The issue of mold cooling is one, which presents a foundry with a dilemma. On the one hand; the use of air for cooling is safe and practical, however, it is not very effective and high cost. On the other hand, water-cooling can be very effective but it raises serious concerns about safety, especially with a metal such as magnesium. An alternative option that is being developed at McGill University uses heat pipe technology to carry out the cooling. / The experimental program consisted of designing a permanent mold to produce AZ91E magnesium alloy and A356 aluminum alloy castings with shrinkage defects. Heat pipes were then used to reduce these defects. The heat pipes used in this work are novel and are patent pending. They are referred to as McGill Heat Pipes. / Computer modeling was used extensively in designing the mold and the heat pipes. Final designs for the mold and the heat pipes were chosen based on the modeling results. / Laboratory tests of the heat pipe were performed before conducting the actual experimental plan. The laboratory testing results verified the excellent performance of the heat pipes as anticipated by the model. / An industrial mold made of H13 tool steel was constructed to cast nonferrous alloys. The heat pipes were installed and initial testing and actual industrial trials were conducted. This is the first time where a McGill heat pipe was used in an industrial permanent mold casting process for nonferrous alloys. / The effects of cooling using heat pipes on AZ91E and A356 were evaluated using computer modeling and experimental trials. Microstructural analyses were conducted to measure the secondary dendrite arm spacing, SDAS, and the grain size to evaluate the cooling effects on the castings. The modeling and the experimental results agreed quite well. The metallurgical differences between AZ91E and A356 were investigated using modeling and experimental results. Selected results from modeling, laboratory and industrial trials are presented. The results show a promising future for heat pipe technology in cooling permanent molds for the casting of nonferrous alloys.