Thesis (Ph. D.)--University of Wisconsin, 1966. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2009. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 9, 2009) Includes bibliographical references.

<p>The purpose of this paper is to identify the current status of fuel cell technology and to establish whether said technology is mature enough to be implemented into the Swedish Armed Forces. The question to be answered in this paper is as follows: Can hydrogen gas and fuel cells be used as an alternative source of energy within the Swedish Armed Forces?</p><p>This paper is based on theoretical studies and reports from prior research done on fuel cells. By studying these facts a predictive answer has been obtained. The answer I have come to, is that the maturity of fuel cell technology is currently inadequate for the Swedish Armed Forces to implement, especially considering its harsh working conditions.</p>

The purpose of this paper is to identify the current status of fuel cell technology and to establish whether said technology is mature enough to be implemented into the Swedish Armed Forces. The question to be answered in this paper is as follows: Can hydrogen gas and fuel cells be used as an alternative source of energy within the Swedish Armed Forces? This paper is based on theoretical studies and reports from prior research done on fuel cells. By studying these facts a predictive answer has been obtained. The answer I have come to, is that the maturity of fuel cell technology is currently inadequate for the Swedish Armed Forces to implement, especially considering its harsh working conditions.

Hydrogen gas production occurs in permeable reactive iron barriers (PRBs) due to the anaerobic corrosion of granular iron. Once produced, this hydrogen gas can have detrimental physical effects on PRB performance. Corrosion-produced hydrogen may accumulate in pore spaces within the PRB, thereby reducing the porosity and permeability. It may also escape the PRB system, representing a lost electron resource that may otherwise be used in reductive remediation reactions. In addition to these physical effects of hydrogen on PRB performance, chemical interactions between hydrogen and iron also occur. Hydrogen may become absorbed by the iron and stored as an electron resource within lattice imperfections. It may also interact with iron surfaces to influence the corrosion rate of the iron. These chemical interactions between hydrogen and iron may impact the reactivity of the iron granules and therefore affect PRB performance. Currently, the chemical effects of hydrogen on PRB performance remain largely unexplored. In this study, the effect of hydrogen on iron reactivity was investigated by considering hydrogen absorption into iron and hydrogen induced changes to iron corrosion rates. Hydrogen absorption by iron creates a stored electron resource within the iron granules. Release of this stored hydrogen from trapping sites represents an additional electron resource that may be used in contaminant degradation reactions. Therefore, improved hydrogen absorption may contribute to increased iron reactivity. Hydrogen absorption by granular irons has been largely unexplored in PRB performance investigations and the effect of hydrogen absorption on contaminant remediation remains unknown. In this study, an investigation of the factors governing hydrogen absorption by three granular irons, H2Omet56, H2Omet58 and H2Omet86 was conducted. The results demonstrated that rapidly corroding H2Omet86 absorbed hydrogen at a higher rate than the other more slowly corroding irons. The presence of an oxide film on H2Omet56 appeared to improve the proportion of hydrogen absorption compared to the bare irons. Ultrasonic treatment was explored as potential method of release of trapped hydrogen for improved iron reactivity. Ultrasonic treatment appeared to be unsuccessful at releasing stored hydrogen from trapping sites, but further investigations into different ultrasound conditions as well as other methods of hydrogen release could prove useful. Hydrogen gas may also influence iron reactivity by interacting with iron surfaces to alter the corrosion rate of the iron. This may occur by processes such as hydrogen enhanced anodic dissolution, hydrogen induced cracking, enhanced pitting susceptibility and reduction of iron oxides by hydrogen gas. In this study, the effect of hydrogen on iron corrosion rates was assessed by treating two iron materials (H2Omet56 and Connelly) under high pressures of hydrogen for 14 d, then comparing the post-treatment corrosion rates of hydrogen treated irons to the post-treatment corrosion rates of corresponding irons treated under low hydrogen pressures for the same period. The results demonstrated that the post-treatment corrosion rate of high hydrogen treated H2Omet56 iron was lower than the post-treatment corrosion rate of low hydrogen treated H2Omet56 iron. Hydrogen treatment did not appear to affect the post-treatment corrosion rates of Connelly iron. The effect of hydrogen on the corrosion rate of H2Omet56 iron may be a result of hydrogen enhanced anodic dissolution. The presence of a continuous oxide film on Connelly iron appeared to inhibit the effect of hydrogen enhanced anodic dissolution on Connelly iron corrosion rates. The effects of iron oxide reduction by hydrogen and hydrogen induced pitting corrosion were also considered.

Ultrasonic slurry sampling electrothermal vaporization dynamic reaction cellTM inductively coupled plasma mass spectrometry (USS-ETV-DRC-ICP-MS) has been applied to the determination of As and Se in soil and sediment samples. The influences of instrument operating conditions and slurry preparation on the ion signals were reported. Ascorbic acid and Pd were used as the modifiers to enhance the ion signals. The background ions at the selenium masses were reduced in intensity significantly by using 1.5 ml min-1 H2 as reaction cell gas in the DRC while a q value of 0.65 was used. Since the sensitivities of As and Se in slurry solution and aqueous solution were quite different, standard addition method was used for the determination of As and Se in these samples. This method has been applied to the determination of As and Se in NIST SRM 2711 Montana soil and SRM 2709 San Joaquin soil reference materials and NRCC BCSS-1 marine sediment reference sample. The analysis results of the reference materials were agreed with the certified values. The method detection limits estimated from standard addition curves were about 0.046-0.082 and 0.019-0.024 mg g-1 for As and Se, respectively, in original soil and sediment samples.

Environmental concerns and energy security are two major forces driving the fossil fuel based energy system towards renewable energy. In this context, hydrogen is gaining more and more attention in this 21st century. Presently, hydrogen is produced from reformation of fossil fuels, a process that could not address above two problems. For this it needs to be produced from a renewable carbon neutral energy source. Biomass has been identified as such a renewable energy source. Conversion of biomass through thermo-chemical gasification process in the presence of steam could provide a viable renewable source of hydrogen. This thesis presents an innovative system based on chemical looping gasification for producing hydrogen-enriched gas from biomass. The other merit of this system is that it produces a pure stream of carbon dioxide by conducting in-process capture and regeneration of sorbent. A laboratory scale chemical looping gasification (CLG) system based on a circulating fluidized bed (CFB) is developed and tested. Experiments conducted to gasify sawdust in CFB-CLG system shows that it could produce a gas with as much as 80% hydrogen and as little as 5% carbon dioxide. A kinetic model is developed to predict the performance of the gasifier of a CFB-CLG system, and is validated against experimental results. To understand the science of biomass gasification in the presence of steam and CaO, a number of additional studies are conducted. It show that for higher hydrogen and lower carbon dioxide concentration in the product gas, the optimum values of steam to biomass ratio, sorbent to biomass ratio, and operating temperature are 0.83, 2.0 and 670oC respectively. In CFB-CLG system the sorbent goes through a series of successive calcination-carbonation cycles. Calcination studies in presence of three alternate media, nitrogen, carbon dioxide and steam show, that steam calcination is best among them. An empirical relation for calcination in presence of three media is developed. Owing to the sintering, irrespective of medium used for calcination, the conversion of CaO reduces progressively as it goes through alternate calcination-carbonation cycles. An additional empirical equation is developed to predict the loss in sorbent’s ability during carbonation.

Made available in DSpace on 2014-07-29T15:12:42Z (GMT). No. of bitstreams: 1 Dissertacao Karina Vitti Klein.pdf: 68159 bytes, checksum: 393c40f7ec373b1126ad7cc6bebd1e9e (MD5) Previous issue date: 2008-05-14 / The new family mesoporosas molecular sieves, known as M41S, have been very studied since its discovery in 1992, with bigger prominence for MCM-41, that had its mesoporosa structure that allows ample applications in catalytic processes. In this work were studied two reactions conditions of preparation of the MCM-41 and three forms of nickel incorporation. In the synthesis of the MCM-41 the hidrotérmico treatment and in conditions was used surrounding, while in the incorporation, was used to impregnation of ions nickel and nanopartículas of nickel oxide, as well as the direct synthesis where the nickel was introduced in the structure of the MCM-41, during the synthesis. The gotten materials had been characterized by elementary nickel analysis, X-ray diffraction, nitrogen adsorption/desorption, FT-IR spectra, thermogravimetric analysis, thermoprogrammed reduction. The characterizations had indicated that it had the formation of the mesoporosa structure with periodic pore system, typical of the MCM-41, in both methods of synthesis, being able to be evidenced the biggest viability of the synthesis of the MCM-41 in the surrounding conditions. It can also be verified that it had nickel incorporation in all samples, independent of as this element was inserted. The introduced samples that had had nickel during the synthesis had presented greater excessively average diameter of pores in relation. After the characterization, the samples with nickel had been tested as in the reaction of conversion of carbon monoxide the high temperatures catalytic, known as HTS reaction, presenting activity. / As peneiras moleculares mesoporosas da família M41S têm sido muito estudadas desde sua descoberta em 1992, com maior destaque para MCM-41, devido sua estrutura mesoporosa que permite amplas aplicações em processos catalíticos. Neste trabalho estudou-se duas condições reacionais de preparação da MCM-41 e três formas de incorporação de níquel. Na síntese da MCM-41 utilizou-se o tratamento hidrotérmico e em condições ambiente, enquanto na incorporação, utilizou-se a impregnação de íons níquel e nanopartículas de óxido de níquel, assim como a síntese direta onde o níquel foi introduzido na estrutura da MCM-41, durante a síntese. Os materiais obtidos foram caracterizados por análise elementar de níquel, difração de raios X, análise de área superficial específica e porosidade, espectroscopia na região do infravermelho, análise termogravimétrica, redução termoprogramada. As caracterizações indicaram que houve a formação da estrutura mesoporosa com canais hexagonais unidirecionais, típica da MCM-41, em ambos os métodos de síntese, podendo ser constatado a maior viabilidade da síntese da MCM-41 nas condições ambientes. Pode-se verificar também que houve incorporação de níquel em todas as amostras, independente de como foi inserido. As amostras que tiveram níquel introduzido durante a síntese apresentaram maior diâmetro médio de poros em relação às demais. Posteriormente à caracterização, as amostras com níquel foram testadas como catalisadores na reação de conversão de monóxido de carbono com vapor d água para obtenção de gás hidrogênio a altas temperaturas, conhecida como a reação de HTS, apresentando atividade.

Tritium is a radioisotope of hydrogen and a component of emissions from the nuclear industry. It is also a radioisotope of concern for human and environmental health. The near future could see an increase in tritium production as experimental fusion reactors initiate first plasma. The greatest risk pathway is human ingestion of edible plants grown near sites of tritium emissions as they can acquire high levels of organically bound tritium (OBT). Recent studies at a tritium Beta-light facility in Pembroke, Ontario, Canada characterized by tritiated hydrogen gas (HT) emissions have identified high OBT:HTO ratios that are not consistent with current tritium transfer models. This suggests that there is an unidentified physical, chemical, or biological mechanism generating OBT in plant tissue. Laboratory experiments have been undertaken using deuterium gas (D2) as an analogue for atmospheric HT in controlled plant exposure experiments, and compared the observations with short-term exposures at the SRBT facility. While the deuterium results did not uncover a hidden pathway or enrichment mechanism, the SRBT exposures showed elevated tissue free water tritium (TFWT) in stems and leaves in the presence of atmospheric HT, and lacking HTO in both soils and surrounding air. This study proposes that hydrogenase activity in microbial communities hosted within the laminar boundary layer on the leaf surface, are responsible for HT oxidation to HTO that contributes directly to leaf waters used in photosynthesis.

Thesis(M.Sc.(Chemistry)) -- University of Limpopo, 2019 / The quest for renewable, sustainable and environmentally compatible energy sources have been on-going for decades. Green technology such as hydrogen fuel cell has attained much attention as an alternative energy carrier to carbon-based fuels owing to its renewability and cleanliness. However, hydrogen gas feed to the fuel cell can easily be ignited if its concentration is above 4 wt.% at room temperature. Thus, hydrogen safety mechanisms such as hydrogen sensors are vital to guarantee people‘s safety in the hydrogen infrastructure. Sensors based on metals and metal oxides have been widely applied for hydrogen gas detection. Nonetheless, these materials are only sensitive to hydrogen gas at elevated temperatures (˃ 100 °C) and they also possess low surface area (< 20 m2/g). Hence in this work, we present polyaniline (PANI) doped with cobalt-based zeolitic benzimidazolate framework (CoZIF) and zinc-ZIF to fabricate (PANI-CoZIF and PANIZnZIF) composite nanofibers as effective electrocatalysts for hydrogen gas sensing application. The composites were synthesised through chemical oxidative polymerisation of aniline monomer in the presence of 3.6 wt.% CoZIF and ZnZIF, respectively. The structural properties of the synthesised materials were studied using Ultraviolet visible (UV-vis), X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman spectroscopy and simultaneous thermal analysis (STA). FTIR, Raman and XRD studies showed successful synthesis of CoZIF, ZnZIF and their composites. Furthermore, the studies indicated the co-existence of both CoZIF and ZnZIF in the PANI matrix upon composites formation, indicated by reduction in crystalline size, decrease in band gap and increase in thermal stability. as compared to the neat PANI. Morphological characteristics of the prepared samples were investigated usingscanning electron microscopy (SEM) and transmission electron microscopy (TEM) coupled with both energy dispersive spectroscopy and X-ray (EDS/EDX). PANICoZIF revealed the grafting of CoZIF on to the surface of PANI matrix while PANI-ZnZIF composite showed that PANI is wrapping the cube nanofiber-like structures of ZnZIF also supported by selected area electron diffraction (SAED). Cyclic voltammetry (CV), Tafel analysis and turn over frequencies (TOFs) were performed to study the electrochemical performance of the synthesised materials through hydrogen evolution reaction (HER) for gas sensing. Both composites presented drastic enhancement in the catalytic H2 evolution at 0.033 mol.L-1 H2SO4 with the Tafel slope of 160 mV/dec and exchange current density of 3.98 A.m-2 for PANI-CoZIF composite, while the Tafel slope and exchange current density for PANIZnZIF composite were 246 mV/dec and 5.01 A.m-2, respectively. Moreover, the TOFs of the PANI-CoZIF composite (0,117 mol H2.s-1) was higher as compared to neat PANI (0.040 mol H2.s-1). The TOF values for PANI and PANI-ZnZIF composite were 0.04 and 0.45 mol H2.s-1, respectively. In addition, the chronoamperometric (CA) results exhibited the significant improvement in the electrochemical hydrogen sensing ability of PANI-CoZIF and PANI-ZnZIF composites with higher current response and sensitivity values of 12 and 10.8 µA.mmol.L-1 H2, respectively. The composites exhibited faster steady state response time of 5 s for PANI-CoZIF composite and 4 s for PANI-ZnZIF composite accompanied by lower detection limit (5.27 µmol.L-1) as compared to the neat PANI matrix. The high electrochemical current response is due to extraordinary specific surface area, more accessible active sites available for the electrolyte provided by CoZIF and ZnZIF and high conductivity supplied by PANI. These results proved that the PANI-CoZIF and PANI- ZnZIF composites are suitable electrocatalytic materials for hydrogen gas sensing application through HER in acidic medium. These results further suggest that the safety of people in mining sectors and other industries can be addressed through simple electrocatalytic gas sensing systems.