This master thesis includes a literature study and experimental work to understandthe conditions where a binder phase layer, Co-capping, could be produced orinhibited, for three different cermet grades in order to suggest changes in thesintering processes and two production units. The effect of C activity and sinteringatmosphere, e.g. flow rate, pressure were investigated. The results show that the Co-capping occurs on the cooling stage, when the binder phase, Co, solidifies. Co-capping could be inhibited by using a high C activity and high pressure (50 bar). Itwas further found that Co-capping could be evaporated using low pressure, i.e. vacuum, which has not been discussed in earlier studies on Co-capping. Evaporation was also found to have a relation with the solidification temperature of the grades,since grades with higher solidification temperature get Co-capping at a highertemperature, which consequently will be exposed to higher temperatures.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1960. / Typescript (photocopy). Includes bibliographical references (leaves 92-97). Also issued in print.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1962. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 74-77).

Thesis (M.S.)--University of Michigan, Ann Arbor, 1960. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 92-97).

Thesis (M.S.)--University of Michigan, Ann Arbor, 1962. / Typescript (photocopy). Includes bibliographical references (leaves 74-77).

Indiana University-Purdue University Indianapolis (IUPUI)

Sediments serve as the ultimate sink for many hydrophobic organic compounds and thus present a residual environmental risk many years after sources of contamination are eliminated. Monitored natural attenuation and ex situ treatment processes are often ineffective for treatment; as such in situ remediation technologies (i.e., capping) are under review. A conventional in situ remediation technology for refractory sediment contaminants is placement of a clean layer of material as a cap. A series of design models was developed to predict the performance of caps composed of the traditional material, sand. A passive sampling method using polydimethylsiloxane (PDMS) fibers for evaluating the performance of caps was developed and tested in the laboratory. The results of the laboratory analysis showed the ability to measure pore water concentration profiles in caps, the consistency of profiles with design model predictions, and correlation of PDMS-derived concentrations with contaminant uptake in test organisms. Potentially more effective caps composed of permeable adsorptive materials (to retard contaminant migration) and impermeable materials (to divert groundwater flow) were placed along with a conventional sand cap in the Anacostia River in Washington DC in 2004. Field tests of this site showed the ability to measure in situ pore water concentration profiles in caps using a field-deployable version of the PDMS passive sampling device and demonstrated the necessity of pore water-based approaches for analyzing caps. A model for assessing the uptake rates of HOCs within PDMS fibers was developed and shown to predict the kinetics of HOC sorption into fibers. The model is based on external-mass transport processes, which through a series of analyses were shown to be more significant than internal diffusion in PDMS fibers. Using the PDMS approach, field bioaccumulation tests at the Anacostia site as well as at San Diego Bay and Hunters Point Naval Shipyard showed stronger correlation of PDMS-based pore water concentrations than solid-phase concentrations with observations of bioaccumulation in the field. The overall conclusions suggest that pore water concentrations can often be a better indicator of risk than bulk solid concentrations. / text

Contaminated surficial sediments represent a potential point of entry into the food web for environmental pollutants that are toxic to fish, wildlife, and humans. One approach for managing polluted sediments is in situ capping, the placement of clean fill material, such as sand, atop the polluted sediments. A cap stabilizes the underlying sediment and physically separates pollutants from benthic organisms that inhabit the sediment/water interface. Additionally, a sediment cap can be amended with sorbents to sequester hydrophobic organic chemicals. While the physical processes affecting contaminant transport in sediment caps are readily modeled, fate and transport processes mediated by sediment bacteria are location-specific and thus highly uncertain. Laboratory bench-scale tests were employed to aid in the design of a sediment cap in Onondaga Lake. Recognizing the importance of bacterial activity beneath the benthic zone for affecting the risks of contaminant exposure, anaerobic processes were emphasized. A combination of batch and column tests were used to determine whether (1) bacteria in sediments were capable of biotransforming methylated and chlorinated benzenes, (2) the ability to biotransform the contaminants of interest would be translated from the sediments to a sand cap, (3) the rate of biogenic gas production in sediments would threaten the integrity of a sand cap, and (4) the contribution of gas-phase contaminant transport to the overall transport of contaminants from the sediments was significant. The apparent anaerobic biotransformation of toluene in a sand cap was supported by detection of a genetic biomarker for anaerobic toluene degradation, the development of substantial biomass in the sand column, apparent anaerobic biotransformation of toluene in sediment slurries, and the concomitant reduction of iron in the sand column. The dissimilarity in bacterial community composition between sediment and sand cap samples suggests that contaminant biotransformation capability cannot be predicted from community analysis. For sediments that failed to demonstrate biotransformation potential, amending a sand column with organophilic clay proved effective at retarding transport of the contaminants of interest. This work advances methods for characterizing bacterial processes in sediments and demonstrates the potential for anaerobic biotransformation of organic contaminants in sand caps. / text

Thesis (M.S.)--University of Michigan, Ann Arbor, 1962. / Typescript (photocopy). Includes bibliographical references (leaves 42-45). Also issued in print.

Thesis (M.S.)--University of Michigan, Ann Arbor, 1981. / Typescript (photocopy). Includes bibliographical references (leaves 59-62). Also issued in print.