Master of Science in Environmental Science, Youngstown State University, 2016, Department of Physics, Astronomy, Geology and Environmental Sciences

Lead shot is commonly used in shooting ranges throughout the world. When introduced into the environment, several factors such as wind and precipitation will aid in the breakdown of the lead (Pb) compound, as well as the transportation of the Pb throughout the soil in which it lands. Weathering and other environmental factors will cause the Pb to oxidize, potentially turning it into hydroxide, sulfate, carbonate, or a phosphate species. The amount of precipitation that falls annually in a Pb shot contaminated range contributes to lead distribution within the soil profile. Acid precipitation and acidic soils can solubilize the Pb making it more mobile. Conversely, organic matter, clays, and other mineral components can inhibit the mobility of soluble Pb because of sorption onto soil particles. Therefore, it is important to identify the type of soil, the permeability, porosity, pH, and organic matter content which will influence how much the Pb will migrate through the soil. It will also give insight to the future leaching potential. When Pb is subject to dissolution and erosion, it can leach into soil and groundwater, possibly causing health problems for humans and animals. Because of the potential impacts, this research examines the spatial distribution of Pb from munitions used at the Grand Valley Hunting Ranch in Orwell, Ohio, a property now owned and under ecological restoration plans by the Western Reserve Land Conservancy. A preliminary assessment of elevated Pb concentration in soils was determined using an X-ray Fluorescence Spectrometer (XRF). Four sample locations were established and were cored to further and more accurately analyze Pb concentrations in the soil. The four locations were located within the fall zone of the Pb shot. A fifth location outside of the fall zone was cored and designated as the reference. Each core was 60-90 cm in total length and divided into 2-5 cm segments and halved, resulting in 148 total samples. This depth provided a (open full item for complete abstract)

PHD, Kent State University, 2021, College of Public Health

Children from resettled refugee families (RRF) in the United States are a vulnerable group for childhood lead poisoning (CLP)-- an environmental hazard with multiple irreversible adverse health effects in children. My dissertation research aimed to assess CLP among children from RRF pre- and post-U.S. resettlement and understand CLP knowledge, attitudes, and practices, and prevention barriers (KAP-B) among Nepali-speaking Bhutanese (NSB) resettled refugee groups in northeast Ohio. Data from the post-resettlement refugee medical screening of 5,661 children resettled in Ohio from 2009 to 2016 were utilized to assess the prevalence of elevated blood lead level (EBLL)—defined as BLL ≥ 5 micrograms per deciliter (µg/Dl)— as a proxy for pre-resettlement exposure. Electronic medical records (EMR) data from an Akron Children's Hospital Outpatient Clinic were used in a retrospective cohort study to assess the incidence of EBLL in a sample of 6,283 children <6 years of age between 2009 to 2015. The primary language spoken at home was used as a proxy to classify children as either being from RRF or being from non-RRF (NRF) categories. A Nepali language questionnaire (KAP-B) was developed and used to assess current knowledge, attitudes, daily household practices, and barriers to prevention measures for CLP among 200 NSB RRF with at least one child ≤ 7 years in northeast Ohio. Overall, 27.1% of RR children <6 years in Ohio had an EBLL at the time of resettlement. Children from RRF from the South-Asian region (Afghanistan, Nepal, Bhutan, and Burma [56.2% - 31.8%]) had the highest EBLL prevalence. Of these, children from Nepali-speaking families had the highest EBLL incidence at 9.67 per 100 person-years. Children from RRF had 11 times the risk of EBLL than nonrefugee children. NSB parents surveyed demonstrated a low level of knowledge regarding CLP and prevention measures. While 80% of respondents lived in pre-1978 houses, only 27.5% perceived their house/neighborhood to (open full item for complete abstract)

Master of Science (MS), Bowling Green State University, 2019, Geology

Blood lead levels (BLLs) in children of the Toledo, OH area have been elevated for decades, and numerous studies have linked the issue to soil contamination by lead (Pb) paint and leaded gasoline. Young children below the age of 4 years have proven the most susceptible to Pb poisoning due to their high Pb absorption rates and direct ingestion of Pb contaminated sources resulting from instinctive hand-to-mouth behaviors. This problem is significant because high BLLs can result in many pathological and developmental problems including irreversible fetal brain damage, brain damage to the developing prefrontal cortex, behavioral problems, violence, learning disabilities, and more. The objectives of this study were to determine the primary factors leading to Pb and other heavy metals contamination in community gardens located at or near contaminated soils in Toledo, OH. Given the rising popularity of urban community gardens, it is also important to understand the sustainability of current gardening practices for minimizing exposure to Pb. A total of 399 samples were collected across 27 community gardens, of which 218 including the soil profiles of 14 community gardens were analyzed for heavy metals using an ICP-OES. Soil profiles were collected down to 40 cm depth (or maximum achievable depth based on the presence of buried rubble from demolished structures, buried foundations, etc.), and subsampled at 5 cm intervals to observe its distribution with depth. Using historical maps such as the Sanborn Fire Insurance maps combined with measuring the distribution of lead within gardens across properties, it was found that drip zones, a 1-meter area of soil immediately surrounding structures containing lead paint, is the main predictor for high lead levels in community gardens. And given that many gardens are located at the sites of demolished structures, historical maps such as the Sanborn Fire Insurance maps proved critical for determining the locations of drip zones a (open full item for complete abstract)

PhD, University of Cincinnati, 2010, Engineering and Applied Science: Industrial Engineering

This research was initiated as a result of a project funded by the United States Environmental Protection Agency with the goals to: (a) examine the pollution prevention strategies to increase lead recycling and recovery and (b) identify the U.S. facilities receptive to implement such strategies. Since the majority of recycled lead is extracted from lead acid batteries (LAB), this work is centered on identifying the major sources of lead pollution in secondary lead smelters from battery recycling and identifying and evaluating readily deployable pollution prevention technologies for the secondary lead industry. Currently, there is limited information on recycling rates for LAB in the published literature. The Battery Council International determined that the recycling rates for recovering lead from spent LAB is approaching 99.2% for the 1999 to 2003 time period. Although very encouraging, such rates appear to be significantly higher than those reported for other countries. Therefore, its recycling efforts in the US has been unclear so as to determine the maximum opportunities for metal recovery and recycling in the face of significant demands for LAB particularly in the auto industry. In the first part of the research an evidence-based approach is utilized to: (1) determine recycling rates for lead recovery in the LAB product lifecycle for the U.S. market; and (2) quantify and identify opportunities where lead recovery and recycling can be improved. It was observed that 1) lead recovery and recycling has been stable between 1999-2006; (2) lead consumption has increased at an annual rate of 2.25%, thus, the values derived in this study for opportunities dealing with lead recovery and recycling underestimate the amount of lead in scrap and waste generated; and (3) the opportunities for maximizing lead recovery and recycling are centered on spent batteries left with consumers, mishandled LAB sent to auto wreckers, slag resulting from recycling technology process ineffic (open full item for complete abstract)

MS, University of Cincinnati, 2004, Medicine : Industrial Hygiene (Environmental Health)

Residential lead abatement work frequently involves multiple tasks occurring simultaneously, making it difficult to determine the concentrations of air lead associated with individual tasks. Previous reports on air lead concentration at lead abatement sites have revealed that although lead abatement tasks can generally be ranked according to air lead level, there is a wide range of lead levels associated with the tasks. The hypothesis involved in the first phase of this study was to determine whether the higher lead concentrations for tasks which generally have low geometric mean concentration are associated with nearby activities with higher geometric mean air lead concentration. In the second phase of the study, paint lead levels in Singapore were determined in housing of various ages and in paints currently available for purchase by the public.

Doctor of Nursing Practice, Mount St. Joseph University , 2024, Department of Nursing

Heart failure is the leading cause of readmissions among chronic illnesses in the United States (Oh et al., 2021). Patients with chronic disease need correct knowledge and understanding about maintaining, monitoring, and managing their illness in their daily lives. However, patients with low health reading ability have a more challenging time with comprehension (Oh et al., 2021). It is imperative for acute care nursing staff to gain the ability to properly educate heart failure patients on the disease process to increase the patient's quality of life while decreasing their chance of hospital readmission. This project aimed to increase nursing knowledge related to heart failure and disease-specific education using smart-phrase technology to reduce heart failure 30-day readmission rates. After initial stakeholder meetings, staff education and training, and project implementation, the project did show a decrease in hospital admissions within the 12-week utilization period. The readmission data is under review to ensure the smart-phrase is still effective in current practice. The project achieved its goals, including improving nurse competency in heart failure and simplifying patient education.

Bachelor of Science (BS), Ohio University, 2024, Biological Sciences

Due to increasing industrialization and remaining lead paint and dust in older housing, there is evidence to suggest that human, bovine, and caprine milk could have elevated lead concentrations. Lead is neurotoxic and can cause damage to the developing brains of fetuses and breastfeeding infants, even at low concentrations. The study measured the lead content of breastmilk, cow's milk, and goat's milk samples in Ohio, and compared them to the safety limits set by the World Health Organization (WHO). Twenty lactating women provided samples of human milk and a sample of cow's and goat's milks from local dairies were collected. The milks were digested with nitric acid and hydrogen peroxide using a 1:5:2 ratio and analyzed for lead concentrations using an ICP-MS procedure following standard QA/QC guidelines. Overall, the milk samples' lead levels were within the safety limits set by the WHO and human milk lead levels were comparable to cow's and goat's milk lead levels. In a Pearson's Correlation test, two residence-related factors were found to be significantly correlated with higher lead levels in participants' milk samples, the year the house was built (p=0.001) and the number of years living in the house (p=0.013). The older the house, the more lead was found in milk samples. The longer a person had been living in the same house, the higher the lead concentrations were in milk. The other continuous variables were not significantly correlated with lead levels. In a Spearman's Rho test, a non-parametric test that measures dichotomous variables, there was a significant correlation between having grown up in a house where people smoked and having higher lead levels in milk (p = 0.01). When smoking in the childhood home was examined using a t-test, there was a difference in means although the association was not significant (non-smoking mean level 13.2 (n=17) vs smoking mean level 37.0 (n=3), p=0.26) as the sample was skewed. A non-parametric Mann-Whitney U test wa (open full item for complete abstract)

MCP, University of Cincinnati, 2024, Design, Architecture, Art and Planning: Community Planning

Proposed improvements to the US Environmental Protection Agency's Lead and Copper Rule would require all cities to remove their lead service lines (LSLs) in the next ten years. A persistent challenge that water system managers face is that homeowners refuse to have their LSL replaced despite the health consequences. Cincinnati, OH faces similar challenges, but Greater Cincinnati Water Works (GCWW) has removed over 5,000 LSLs since 2016 by offering various incentives to homeowners. This study focuses on a byproduct of GCWW's LSL replacement program: the positive effect of the LSL replacement on property values. Through a difference-in-differences approach, which compared the GCWW customers who replaced their LSL from 2016 to 2021 versus those customers without an LSL replacement, it was determined that the LSL replacement causes a 4.6 percent increase in home sale price in the three years after the replacement. This study is the first to look at how the Flint crisis affected the value of LSL replacement in another city and is an opportunity for water system managers to convey another “incentive” for LSL replacement.

Doctor of Philosophy, The Ohio State University, 2020, Anthropology

How do the environments and social structures that we create and modify to suit our needs affect the individuals that live and work within those environments? Bioarchaeology and political ecology provide novel means by which to understand how the environments we create, both social environments and our modifications of the natural environment, can affect the body and individuals' health disproportionately. This dissertation uses osteological analyses, historic records, trace element analysis (arsenic, barium, and lead), and isotopic analyses (various lead isotopes as well as strontium 87/86) to evaluate how different types of anthropogenic environments can be retained within and have an effect upon the body. Key in this dissertation is how anthropogenic environments and industrial practices transformed environments during the Industrial Revolution in England, and how individuals' interaction with their environments depended upon elements of their biosocial identity and the inequality present within society, both of which ultimately dictate what environments individuals can access. Accordingly, the anthropogenic processes that transformed environments in England and which were prevalent during the industrial period were a systemic threat that had far reaching consequences throughout the country, and possibly the world. This dissertation studies two archaeological collections of individuals from England during the Industrial Revolution. Neither collection is extreme in being either completely industrial and urban, or completely rural and agrarian. Instead, these collections fall within the mid-range of industrialization, though one is larger and more industrialized than the other. The more industrial population was buried at St. Hilda's parish in South Shields, a large industrial town with a variety of industries that include nearby coal mines and the construction of ships and steam engines. The more agrarian population was buried at St. Peter's church in Barton-u (open full item for complete abstract)

Master of Science (MS), Wright State University, 2018, Earth and Environmental Sciences

Lead (Pb) in public tap water is a national health concern and is the main pathway of human exposure to Pb. The City of Dayton has verified Pb pipelines and homes with Pb plumbing; thus, residents are at risk to Pb leaching into their tap water. I sampled water from 130 residential and 24 public water taps and measured Pb and copper (Cu). Five percent of samples exceeded the action level for Pb (> 15 µg/L) and none exceeded the action level for Cu. The City of Dayton's lead pipeline map identifies potential Pb exposure from Pb distribution pipes. However, the samples that exceeded Pb action level were from the first draw, indicating Pb-bearing plumbing and fixtures within Dayton homes drives Pb concentrations in my dataset. Most of the samples that exceeded action level were from homes assessed below Dayton's median household value and built before 1986.

MS, University of Cincinnati, 2002, Medicine : Environmental Health Sciences

Purpose. The purpose of this research was to determine the practicality of using airborne lead measurements obtained with field portable x-ray fluorescence (XRF) technology to manage worker protection programs. The NITON® XL-700 Series XRF was used to measure airborne lead samples from the U.S. Coast Guard Barque EAGLE while undergoing repairs at the Coast Guard Shipyard. Lead-based paint was used extensively during construction of EAGLE, which was completed in 1936 in Hamburg, Germany. Methods: 47 airborne lead samples were collected in 37 mm cassettes on mixed cellulose ester filters over two weeks. Twenty (20) personal and twenty-seven (27) area samples were obtained. Samples collected during week one were analyzed by XRF the following Sunday, when no work was scheduled on EAGLE. Samples obtained during week two were analyzed daily with field portable XRF. The samples were analyzed using NIOSH Method 7702, Lead by Field Portable XRF to determine lead mass. Using known air volume and lead mass, airborne lead concentration was calculated. To verify instrument performance, the samples were later analyzed by NIOSH Method 7082, Lead by Flame AAS. Results: The range of airborne lead concentrations was 8 to 939 μg/m 3 . With daily monitoring by field portable XRF, airborne lead concentration was reduced 77 percent from week one to week two. The average concentration was 176.9 μg/m 3 during the first week, while the average was 41.3 μg/m 3 during the second. With the exposure data gathered in near real-time, workers reduced concentration by implementing controls including vacuum equipped tools and improved ventilation. On twelve (12) occasions during week one, workers engaged in jobs that produced airborne lead concentrations that exceeded the action level. During week two, when daily monitoring by field portable XRF was instituted, workers exceeded the action level six (6) times. Conclusions: Provided that a sheltered workspace with minimal distractions is available to (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2016, Environment and Natural Resources

Management of soil hazards in urban areas requires strategies that are scientifically effective and accepted by both the general public and public health regulators. Soil management options must consider all three of these components during evaluation. The concept of managing soil hazards to reduce contaminant exposure must be expanded to include considerations of soil function and soil health following remediation. Bioavailability assessments must be included with soil hazard assessments to improve hazard characterization. Soil hazard and soil health indicators can be combined in a comprehensive index, though the relative importance of each factor within the index will be site specific. Several recent studies have quantified contaminants in soil, such as lead (Pb), arsenic (As), and polycyclic aromatic hydrocarbons (PAHs), in many urban areas. When these findings are coupled with slow regulatory movement on potential management strategies, the public's perceived risk for potential exposure may increase. Such scenarios across the United States may reduce public support for widespread contaminant cleanup. Innovative interdisciplinary research initiatives are needed to: (1) evaluate potential contaminants and factors that contribute to healthy, functioning soil, (2) facilitate public and regulatory acceptance of potential soil hazards and treatments, and (3) communicate the public health implications of viable cleanup activities. These studies are particularly needed in vulnerable urban areas that demonstrate variable soil contaminant concentrations over small geographic spaces. Characterizing and addressing these soil contaminants will contribute to and benefit our society from public health, social, environmental, and economic perspectives. Soil contaminants and their impacts can be evaluated within the context of other exposures and individual characteristics, such as proposed in the developing field of exposome public health research. The results from this diss (open full item for complete abstract)

PhD, University of Cincinnati, 2014, Medicine: Epidemiology (Environmental Health)

Importance: Tooth decay is a significant public health problem in the United States. Greater rates of dental caries are observed in lead-exposed individuals, however the impact of prenatal and postnatal lead exposure on tooth decay in a longitudinal prospective study design has not been evaluated. Objective: To examine the relationship between prenatal, postnatal childhood lead exposure, risk of dental caries and salivary flow rate in late adolescence. Design: A longitudinal prospective cohort study measuring prenatal and postnatal blood lead levels from maternal, neonatal, early childhood, average childhood (quarterly and biannual from 3 to 78 months), late adolescence and measures of dental caries, gingival inflammation, bleeding, plaque, salivary flow, dietary intake and oral hygiene in late adolescence. Setting: Participants were given dental caries examinations and various questionnaires such as demographic, nutritional and oral hygiene questionnaires administered at a Cincinnati urban community pediatric clinic during late adolescence. Participants: Two hundred and six predominately African-American male and female adolescents (16 to 22 years of age) from the longitudinal Cincinnati Lead Study cohort were recruited. Main outcomes and Measures: Tooth decay quantified as the number of decayed, missing and filled surfaces (DMFS) in permanent teeth and the number of decayed, missing and filled permanent teeth (DMFT) and stimulated salivary flow rate. Results: A significant positive association between average childhood (3 to 78 months) blood lead levels and DMFS and DMFT during late adolescence between (16 to 22 years of age) was observed. A significant quadratic relationship was also observed at the highest average childhood blood lead levels, a downward trend was observed in DMFS and DMFT measured during late adolescence. Statistically significant covariates were the number of sealants present, lactobacilli count in saliva and maternal high sch (open full item for complete abstract)

MS, University of Cincinnati, 2014, Arts and Sciences: Geology

Owing to its toxic nature, lead (Pb) in tap water (released from pipes, solder, and brass fittings) poses an important risk to human health. High concentrations of lead have recently been found to accumulate in iron corrosion scales formed in galvanized iron pipes in household plumbing, but the interaction between iron and lead in this situation is not well understood. Therefore, a model system of simulated iron-bearing corrosion scales in household plumbing was devised to isolate the variables that influence lead uptake. Continuous flow experiments were performed to test the interaction of lead with the iron minerals in corrosion scales in household plumbing, and to assess the influence of changing orthophosphate concentration on lead previously accumulated in the analog iron corrosion scales. Serving as laboratory analogs for the capture of lead by iron corrosion products, sediment filters impregnated with various iron oxy-hydroxides that represent actual iron corrosion scale solids were synthesized and tested in a laboratory apparatus. Water quality was monitored and the analog iron corrosion scales were analyzed. A mass balance was performed on lead to evaluate the effectiveness of the iron filter. Results showed that the presence of iron greatly enhances lead uptake by the sediment filter compared to the control containing no iron. Filter efficiency was evaluated using normalized ratios of lead, phosphorous, and copper uptake to the mass of iron (Fe) in the sediment filter. This revealed very different behaviors for the iron minerals. Lead uptake by the filter was highest with feroxyhyte (0.02 mg of Pb per mg of Fe), followed closely by lepidocrocite (0.01), and then by goethite (0.003), magnetite (0.002), and ferrihydrite (0.002). Variable uptake of phosphorous and copper was also observed. Phosphorous was most strongly associated with lepidocrocite, followed by ferrihydrite, feroxyhyte, and magnetite, but did not bind to goethite. Copper was taken up more (open full item for complete abstract)

Master of Science, The Ohio State University, 2013, Public Health

Objective: This study assessed the relationship between environmental lead exposure and blood lead levels of children living in treated homes in the city of Milwaukee. Methods: The U.S. Department of Housing and Urban Development (HUD) funded a prospective longitudinal study to assess the effectiveness of a Lead Hazard Control (LHC) program in the City of Milwaukee from 2000 - 2004. This analysis focuses on a subset of the study population of already treated homes that contained porch and soil environmental as sampling data as well as biological monitoring blood-lead data on 71 children 6 months to 24 months old who resided in these treated homes since birth. Multivariable regression and linear structural equation modeling procedures were used to explore the mechanisms and pathways for lead intake among these urban children and the relative contribution of various lead sources to lead contamination of house dust in homes that received lead hazard control treatments approximately 3-5 years prior to the date of sampling. Results: The prevalence estimates of blood lead concentrations in children above 5 and 10µg/dL were 68% and 25%, respectively. There were disparities in the prevalence of the measured blood lead levels among certain demographic groups. In this study, the prevalence of elevated blood-lead levels (BLL =5µg/dL) was higher in boys (75.7%) than girls (58.8%) and 86.8% of the African-American children have blood lead levels above 10µg/dL. Levels of lead in floor dust were directly and indirectly associated with blood lead via other environmental exposures. Race/ethnicity and the presence of interior lead-based painted components were the strongest predictors of elevated blood-lead levels. Conclusion: This study demonstrated that lead contaminated house dust is a significant source of and contributor to lead exposure for children. Interior floor dust levels and lead levels on window sills and troughs were found to be elevated (open full item for complete abstract)

PhD, University of Cincinnati, 2009, Medicine : Neuroscience/Medical Science Scholars Interdisiplinary

INTRODUCTION: Lead is a potent environmental toxicant. Childhood lead exposure is associated with persistent cognitive and behavioral deficiencies, suggesting underlying neuroanatomic changes. This dissertation is an investigation of the effects of childhood lead exposure on young adult gray matter volume and white matter structure. METHODS: We investigated a subset of the long-running Cincinnati Lead Study, a prospective birth cohort study investigating the effects of environmental lead exposure on a primarily black, urban inner-city cohort. Participants received 23 serial assessments of blood lead concentration during childhood, high-resolution volumetric magnetic resonance imaging at approximately 21 years of age, and diffusion tensor imaging at approximately 24 years of age. Associations between gray matter volume and mean childhood blood lead, and yearly mean blood lead levels from years 1 to 6, were investigated by adjusted voxel-wise multiple regression analysis using voxel-based morphometry (VBM) techniques. Associations between mean childhood lead levels and white matter diffusivity changes were investigated using adjusted multiple regression analyses. RESULTS: Mean childhood lead levels were associated with significant adult gray matter volume loss, particularly in the frontal lobes, and particularly in men. Analysis of yearly mean blood lead levels revealed that blood levels later in childhood were more strongly associated with adult gray matter volume loss than earlier blood lead levels. The most extensive and significant regions of lead-associated gray matter volume loss were found in the frontal lobes of men associated with lead levels measured later at 5 and 6 years of age. Investigation of white matter diffusivity changes by diffusion tensor imaging analysis revealed widespread changes in fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity. The observed patterns of diffusivity changes was consistent with signific (open full item for complete abstract)

PhD, University of Cincinnati, 2001, Medicine : Environmental Health Sciences

Lead is a toxic substance and a ubiquitous environmental contaminant. Many studies have shown its negative health effects on psychological development, neuromotor system and many other body organs. Lead was added to paint in the form of white lead to reinforce the paint and produce a tough and flexible film. It is estimated that more than 3 million tons of lead have been used in the form of lead-based paint in the U.S. during the past 100 years. As a result, about 38 million homes still contain leaded paint. For this reason, hundreds of millions of dollars have been spent in the U.S. for lead hazard control. The leaded particles aerosolized during lead hazard reduction work are a health hazard for the workers. Significant levels of leaded particles representing health hazards are aerosolized during lead abatement. Few studies regarding these aerosols have been performed. The two main goals of the research described in this dissertation were 1) to characterize the airborne leaded particles and 2) to apply the acquired knowledge to the evaluation of various lead hazard control procedures. The first goal was to investigate the fundamental characteristics of the particles aerosolized during lead abatement. An Environmental Test Chamber was designed and constructed in the Kettering building at the University of Cincinnati. Wood doors coated with lead-based paint were abated in the chamber by dry scraping, wet scraping, or dry machine sanding. The airborne particle concentration was measured with the Grimm particle size spectrometer. The size distribution of the airborne particles changed substantially with time. The airborne particle concentration for each specific size was found to decay exponentially in calm air condition. Size selective air sampling on filters and subsequent laboratory lead analysis of them showed no significant effect of particle size on the percent lead. The second goal was achieved by the following three studies. The first study was to investigate (open full item for complete abstract)

Master of Science, The Ohio State University, 2007, Mechanical Engineering

The three transport properties that make up the thermoelectric figure of merit can be decoupled by the use of certain techniques. In this work, we investigate the effect of two such methods on the thermoelectric properties: (1) Use of rare earth dopants with f-orbitals situated close to the Fermi level, thus resulting in a high thermopower, and (2) use of nanostructured bulk materials with size quantization effects that would affect transport properties of the material. In the first part, we examine the effect of rare-earth dopant in PbSe by using a sequence of samples of pure PbSe (for reference), and PbSe doped with Ce, Pr, Nd, Eu, Gd and Yb. We report the magnetic susceptibility data, as well as a full set of galvanomagnetic and thermomagnetic measurements, from which we deduce the carrier's transport properties, specifically density, mobility, density-of-states effective mass and scattering exponent. In short, the trivalent rare earth atoms act as donors; the mobility of the rare-earth alloys is decreased by mechanisms that we will discuss, while the scattering exponent is not affected. The effective mass is increased, but not sufficiently to overcome the mobility decrease and increase the weighted mobility or improve the thermoelectric performance of the material, except potentially Pb 1-xNd xSe. In the second part, we developed a nanocomposite of PbTe and PbSe, made from core-shell structured nanoparticles sintered together. At a core size of ~20 nm, the core is expected to show size-quantization effects, and confine energy levels at discrete values. Such a confinement would lead to an enhancement in the Seebeck coefficient through the interaction of the discrete energy levels with the host density of states. Moreover, the nanostructures in the matrix should lead to a reduction in the lattice thermal conductivity. In the nanocomposite samples, we did not find the expected Seebeck enhancement, presumably due to the wide size distribution of the cores leading to (open full item for complete abstract)

Master of Science, The Ohio State University, 1950, Graduate School

Master of Science, The Ohio State University, 1961, Graduate School