Solidification/Stabilization (S/S) is a low cost remedial technology that is being used with success to remediate sites that contain higher molecular weight organic compounds, leading to a need to research the interaction of organic contaminants with cement-based S/S materials. The objective of this study was to examine the sorption levels of naphthalene to cement-based S/S materials. Batch testing was performed with S/S materials containing different amounts of organic carbon to investigate the sorption of naphthalene. It was found that sorption values varied, but appear to be dependent on the organic carbon present. Dynamic leach test (ANS16.1 methodology) and SPLP analysis results are presented for intact cement-based S/S materials. Contaminant migration modeling was performed to use the information obtained in the study to compare the sorption capacity of cement-based S/S systems. It was shown that cement-based S/S remediation systems can provide long-term protection against naphthalene contaminant migration.

Filter Cake, which contains leachable nickel and vanadium above the criteria in the Alberta Waste Control Regulation, is produced at an oil sands facility operated by Nexen Inc. and is currently being disposed in a landfill. Bench scale and field tests were performed with stabilization/solidification (S/S) treatment reagents such as Portland cement, fly ash, elemental sulphur, and CETCO Oilfield Service’s proprietary reagents to assess their efficacy at reducing leachable metals in Filter Cake. The CETCO reagents were the most effective treatment for reducing leachable nickel and vanadium in Filter Cake. Treatments with Portland cement were successful in bench scale tests, but inconsistent in field tests. The inconsistent results obtained for Portland cement may have been due to interferences of the cement reactions from factors such as fine particulates. S/S treatments of Filter Cake present a viable waste management option. However, the associated reduced cost and environmental impacts were not substantial.

No description available.

No description available.

This thesis reports theoretical and experimental investigations carried out to better understand the effect of process parameters on the microstructure of transient liquid phase (TLP) joint. The theoretical investigations were carried out using analytical and numerical models to simulate base metal dissolution and isothermal solidification stages of the TLP bonding process. The experimental investigation was carried out by using standard metallographic technique to study the microstructure of bonded materials using optical and Scanning Electron Microscopes. Deviation from parabolic relationship between solid/liquid interface migration and holding time during TLP bonding is suggested as a new alternate phenomenon responsible for the anomalous increase in processing time required to produce eutectic microconstituent free joint with increase in bonding temperature. The results of TLP joining of commercial pure nickel using a Ni-P filler alloy showed that an increase in bonding temperature would be beneficial provided that sufficient holding time is allowed for complete isothermal solidification of liquated insert. Otherwise, an increase in bonding temperature may result in formation of thicker deleterious eutectic along the TLP joint. Furthermore, it was observed that the joint centerline eutectic product and interface second phase particles that form during TLP bonding of Inconel 738 using Ni-P filler can be significantly reduced by post bond heat treatment. The effectiveness of this approach, however, requires proper selection of heat treatment temperature above Ni-P binary eutectic temperature.

The current UK strategy for radioactive waste management is to permanently store the waste in an underground repository. Final disposal of the radwaste may then be preceded by chemical conditioning and physical encapsulation. The objective of this work was to determine the extent of actinide immobilisation in cement. Since actinides are hazardous and costly to study directly, a chemical analogue approach to studying actinide immobilisation was adopted. Th(IV), Ce(III, IV) and Eu(III) were chosen as actinide simulants and their suitability assessed by a critical review of the literature. Ca(OH)₂ and C-S-H dominate the observed chemical properties of the aqueous phase in cement. As they are of such importance, it was these cement components which were used to investigate the reaction of the simulant elements with cement. The phases found to be predicted were ThO₂, ThSiO₄, Eu(OH)₃, Ca₂Eu₈(SiO₄)₆O₂, CeO₂, CeSiO₄ and Ca₂(SiO₄)₆O₂. CeSiO₄ and Ca₂Ce₈(SiO₄)O₂ are newly reported phases, produced by hydrothermal synthesis. Rietveld refinement confirmed CeSiO₄ to have the zircon structure, with space group 14₁/amd and cell parameters a = 6.9564(3) A, c = 6.1953 (4) A. Ca₂Ce₈(SiO₄)₆O₂ exhibits the apatite structure, with space group P6₃/m and cell parameters a = 9.4343(3) a, c = 6.8885(4) A. Preliminary solubility studies were carried out on all of the solubility-limiting phases. Phase impurity, poor crystallinity and incongruent solubility of phases hindered the generation of solubility product data. Nevertheless, these phases have naturally occurring analogues which are known to be environmentally stable and have low solubilities. On the basis of the experimental results obtained, it may be concluded that cement has the potential to be a very effective immobilisation matrix for actinide elements. Recommendations for future experiments using active elements are discussed.

This thesis reports theoretical and experimental investigations carried out to better understand the effect of process parameters on the microstructure of transient liquid phase (TLP) joint. The theoretical investigations were carried out using analytical and numerical models to simulate base metal dissolution and isothermal solidification stages of the TLP bonding process. The experimental investigation was carried out by using standard metallographic technique to study the microstructure of bonded materials using optical and Scanning Electron Microscopes. Deviation from parabolic relationship between solid/liquid interface migration and holding time during TLP bonding is suggested as a new alternate phenomenon responsible for the anomalous increase in processing time required to produce eutectic microconstituent free joint with increase in bonding temperature. The results of TLP joining of commercial pure nickel using a Ni-P filler alloy showed that an increase in bonding temperature would be beneficial provided that sufficient holding time is allowed for complete isothermal solidification of liquated insert. Otherwise, an increase in bonding temperature may result in formation of thicker deleterious eutectic along the TLP joint. Furthermore, it was observed that the joint centerline eutectic product and interface second phase particles that form during TLP bonding of Inconel 738 using Ni-P filler can be significantly reduced by post bond heat treatment. The effectiveness of this approach, however, requires proper selection of heat treatment temperature above Ni-P binary eutectic temperature.

A novel computer model of the evolution of columnar and equiaxed microstructure during alloy solidification has been developed. A control volume finite difference model of conduction heat transfer is applied to a two-dimensional domain bounded by a relatively cold mould. The initial condition is that of superheated liquid, and nucleation occurs either at the mould wall, leading to columnar dendritic growth, or within the bulk liquid, leading to the growth of equiaxed dendrites. The columnar front or the equiaxed grain boundaries are represented by computationally sharp interfaces, which separate liquid from partially solid alloy. Interpolation between discrete computational markers is employed to describe these interfaces, and a front-tracking technique is used to predict the evolution of the grain structure, via movement of the markers, across the fixed grid. The front velocity is determined via considerations of the kinetics of dendrite growth. The heat equation is fully coupled to the front-tracking algorithm by means of source terms which represent the evolution of latent heat due to the dendritic growth (advancing tips and thickening mushy zone). The model, applied to binary Al-Cu alloys, is computationally efficient. It predicts the variation of the extent of liquid undercooling ahead of the growing columnar front, and new metrics have been established to determine the likelihood of the formation of an equiaxed zone here. The employment of these metrics to establish the influence of heat extraction rate and alloy composition agrees with reports from the literature. The model does not distinguish between individual grains of the columnar zone, but it is shown that this is not an important limitation for most metal casting applications. Direct simulation of the nucleation and growth of multiple equiaxed crystals has been carried out, in which the nucleation and growth of individual grams can be observed via animation, and the influence of melt superheat and heat extraction rate on equiaxed solidification has been determined.

Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Description based on contents viewed July 8, 2009; title from PDF t.p. Includes bibliographical references (p. 47).

Thesis (Ph.D.). / Written for the Dept. of Physics. Title from title page of PDF (viewed 2009/06/11). Includes bibliographical references.