Rozprawy doktorskie: „Sulfide (material)”

1

Owens, Gregg Russell. "An experimental investigation of the material response of graphite/polyphenylene sulfide". Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/101143.

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The material response of a graphite/polyphenylene sulfide (thermoplastic) composite system to a variety of loadings was experimentally investigated. Quasi-static tension tests were performed on specimens cut from unidirectional panels at angles of 0°, 90°, and 10° in order to the find material properties of the system. The moduli and strengths were compared to those of several other graphite/epoxy systems. The effect of molded-on end tabs on the strength and failure mode of 0° specimens was also assessed. Both quasi-static tension tests and cyclic tension-tension (R=0.1) fatigue tests were performed on (0/±45/90)_s and (0/90₃)_s specimens. A variety of NDT techniques were used to inspect the "as received" panels and to monitor the formation and growth of damage during quasi-static tension and cyclic fatigue testing. The "as received" panels were found to possess initial flaws that included warping of unidirectional panels, dense matrix cracking in all multi-directional laminates, and local matrix rich and matrix poor regions. The predominately observed damage mechanism occurring as a result of applied mechanical load was delamination. Comments on the ability of each NDT technique to locate and monitor damage occurring in each specimen type are also presented. A preliminary investigation of the creep response of ( ±45₂)_s specimens was performed. Seventy-two hour creep tests were performed at temperatures of 75°, 160°, 250°, and 350° Fahrenheit and at stress levels of 750 psi and 1000 psi. It was found that when testing specimens repeatedly, a strange stiffening phenomenon was observed to occur during the first creep test performed at 350°. After the initial creep test at 350° was performed, no further stiffening of the specimen occurred and all tests performed thereafter were found to be repeatable. The mechanism causing this stiffening phenomenon has not yet been determined, but such an effect is of obvious importance for design considerations and therefore warrants further study.
M.S.

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2

Simpson, Zachary Ian. "Advanced Materials for Energy Conversion and Storage: Low-Temperature, Solid-State Conversion Reactions of Cuprous Sulfide and the Stabilization and Application of Titanium Disilicide as a Lithium-Ion Battery Anode Material". Thesis, Boston College, 2013. http://hdl.handle.net/2345/3042.

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Thesis advisor: Dunwei Wang
In this work, we present our findings regarding the low-temperature, solid-state conversion of Cu₂S nanowires to Cu₂S/Cu₅FeS₄ rod-in-tube structures, Cu₂S/ZnS segmented nanowires, and a full conversion of Cu₂S nanowires to ZnS nanowires. These conversion reactions occur at temperatures as low as 105 degrees Celsius, a much lower temperature than those required for reported solid-state reactions. The key feature of the Cu₂S nanowires that enables such low conversion temperatures is the high ionic diffusivity of the Cu⁺ within a stable S sublattice. The second portion of this work will focus on the oxide-stabilization and utilization of TiSi₂ nanonets as a lithium-ion battery anode. This nanostructure, first synthesized in our lab, was previously demonstrated to possess a lithium storage capacity when cycled against a metallic Li electrode. However, with subsequent lithiation and delithiation cycles, the TiSi₂ nanonet structure was found to be unstable. By allowing a thin oxide layer to form on the surface of the nanonet, we were able to improve the capacity retention of the nanonets in a lithium-ion half-cell; 89.8% of the capacity of the oxide-coated TiSi₂ was retained after 300 cycles compared to 62.3% of the capacity of as-synthesized TiSi₂ nanonets after 300 cycles. The layered structure of C49 TiSi₂ exhibited in the nanonets allows for a specific capacity greater than 700 mAh g(-1), and the high electrical conductivity of the material in conjunction with the layered structure confer the ability to cycle the anode at rates of up to 6C, i.e., 10 minute charge and discharge cycles, while still maintaining more than 75% of the capacity at 1C, i.e., 1 hour charge and discharge cycles
Thesis (MS) — Boston College, 2013
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

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3

Russell, Blair Edward. "Material Characterization and Life Prediction of a Carbon Fiber/Thermoplastic Matrix Composite for Use in Non-Bonded Flexible Risers". Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/30797.

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In the effort to improve oil production riser performance, new materials are being studied. In the present case, a Polymer Matrix Composite (PMC) is being considered as a replacement for carbon steel in flexible risers manufactured by Wellstream Inc., Panama City, Florida. The Materials Response Group (MRG) at Virginia Tech had the primary responsibility to develop the models for long-term behavior, especially remaining strength and life. The MRG is also responsible for the characterization of the material system with a focus on the effects of time, temperature, and environmental exposure. The present work is part of this effort. The motivation to use a composite material in a non-bonded flexible riser for use in the offshore oil industry is put forth. The requirements for such a material are detailed. Strength analysis and modeling methods are presented with experimental data. The effect of matrix crystallinity on composite mechanical properties is shown. A new method for investigating matrix behavior at elevated temperatures developed. A remaining strength life prediction methodology is recalled and applied to the case of combined fatigue and rupture loading.
Master of Science

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4

Filho, Jorge Luis Rodrigues Pantoja. "Avaliação da utilização de diferentes materiais suporte na biofiltração de sulfeto de hidrogênio". Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-16062008-131937/.

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O sulfeto de hidrogênio é um gás que pode causar os mais diversos danos se lançado ao meio ambiente devido, principalmente, à sua elevada toxicidade, corrosividade, odores indesejáveis e alta demanda de oxigênio. Atualmente existem diferentes processos físico-químicos estabelecidos para o tratamento desse composto, entretanto são consideradas técnicas onerosas do ponto de vista econômico e ambiental. Os processos biológicos constituem-se como uma alternativa bastante interessante quando comparados aos processos físico-químicos, sendo que a biofiltração é o processo mais amplamente utilizado. Neste trabalho, foram avaliados três tipos diferentes de materiais suporte, sendo um sintético - espuma de poliuretano - e dois orgânicos - fibra de côco e bagaço de cana -, para a biofiltração de uma mistura gasosa contendo \'H IND.2\'S\'. Como inóculo, optou-se pela utilização de cultura mista originária de duas fontes: a) unidade de biofiltro aerado submerso pertencente ao Serviço Autônomo de Água e Esgoto da Cidade de São Carlos, b) unidade de lodos ativados pertencente a São Carlos S/A - Indústria de Papel e Celulose. A adaptação do inóculo foi realizada em meio nutriente específico. Foi observado um período de partida de somente 2 dias nos três sistemas. Com o intuito de avaliar o impacto do aumento progressivo das taxas de carregamento mássico no desempenho dos três biofiltros, os mesmos foram submetidos a taxas de 19, 32, 54 e 70 g/m³.h (concentrações afluentes médias de 184, 328, 526 e 644 ppm para tempo de retenção do gás de, aproximadamente, 50 segundos). As eficiências remoção média em todos os sistemas mantiveram-se sempre acima dos 99,3%. A capacidade eliminação máxima alcançada pelos biofiltros oscilou entre 74 e 80 g/m³.h. As perdas de carga verificadas no ensaio hidrodinâmico foram baixas, variando entre 0,59.\'10 POT.-2\' a 0,68 \'10 POT.-2\' mca, para a velocidade superficial utilizada durante o estudo. O modelo matemático empregado na previsão do desempenho dos sistemas ajustou-se bem aos dados experimentais. Portanto, pode-se concluir que os materiais suportes testados são adequados para a biofiltração de sulfeto de hidrogênio.
Hydrogen sulfide is a gas which has high restrictions regarding to its disposal in the environment, mainly, because of its high toxicity, malodors, high oxygen demand, etc. Currently, there are many different physical-chemical processes established in order to treat this compound, nevertheless they are considered expensive techniques by the point of economical and environmental views. Biological processes are very interesting alternatives when they are compared to the physical-chemical ones, and biofiltration is the most used process. In this work, three different materials as support media were evaluated, - a synthetic one - represented by the polyurethane foam, - two organic ones - represented by coconut fiber and sugar bagasse -, for a biofiltration of a gaseous mixture containing \'H IND.2\'S\'. Microorganisms were obtained from two sources: a) submerged aerated biofilter unit, b) activated sludge unit. Inoculum\'s adaptation was realized in specific nutrient media. It was observed a 2 days start-up period in the three systems. In order to evaluate some impact caused by the progressive increasing of mass loading rate on the biofilters performance, were applied rates of 19, 32, 54 e 70 g/m³.h (average influent concentrations of 184, 328, 526 e 644 ppm to the empty bed retention time of, approximately, 50 seconds). Average removal efficiencies in the systems were always above 99,3%. Maximum elimination capacities reached by the biofilters were in the range of 74 e 80 g/m³.h. Loss pressure verified by the hands of hydrodynamic essays varied between 0,59.\'10 POT.-2\' a 0,68.\'10 POT.-2\' mca, to a superficial velocity utilized during the work. Mathematical model used to predict the performance of the systems fitted reasonably the experimental data. Then, it can be concluded that the three packing materials are appropriated for the hydrogen sulfide biofiltration.

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5

Dilner, David. "Profitability = f(G) : Computational Thermodynamics, Materials Design and Process Optimization". Doctoral thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-191243.

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The thesis starts by giving a motivation to materials modeling as a way to increase profitability but also a possibility decrease the environmental impact. Fundamental concepts of relevance for this work are introduced, this include the materials genome, ICME and of course the CALPHAD method. As a demonstration promising results obtained by an ICME approach using genetic algorithms and CALPHAD on the vacuum degassing process are presented. In order to make good predictive calculations and process models it is important to have good thermodynamic descriptions. Thus most part of the work has concerned the thermodynamic assessments of systems of importance for steelmaking, corrosion and similar processes. The main focus has been the assessment of sulfur-containing systems and thermodynamic descriptions of the Fe-Mn-Ca-Mg-S, Fe-Ca-O-S, Fe-Mg-O and Mg-Mn-O systems are presented. In addition, heat capacity measurements of relevance for the Mg-Mn-O system have been performed. To summarize the efforts some application examples concerning thermodynamic calculations related to steelmaking and inclusion formation are shown.

QC 20160829

COMPASS

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6

Jiang, Tong. "Porous tin(IV) sulfide materials". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0007/NQ41557.pdf.

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7

Rijal, Upendra. "Suppressed Carrier Scattering in Cadmium Sulfide-Encapsulated Lead Sulfide Nanocrystal Films". Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1402409476.

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8

Marin, Riccardo <1987&gt. "Copper sulfide and copper indium sulfide nanoparticles: two optically active materials with a bright future". Doctoral thesis, Università Ca' Foscari Venezia, 2017. http://hdl.handle.net/10579/11971.

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In questa tesi presento i risultati dello studio di nanoparticelle (NPs) di rame indio solfuro e rame solfuro aventi differenti proprietà ottiche. Questi due materiali sono attualmente sotto meticolosa investigazione, poiché recenti studi li hanno confermati essere delle valide alternative rispetto ai materiali utilizzati al momento in molti campi applicativi. Ciò deriva dalla loro affidabilità, intrinseca non tossicità e dal loro essere relativamente economici. Queste NP possono essere utilizzate per la produzione, tra gli altri, di agenti teranostici, dispositivi fotovoltaici, sensori e LED. Lo scopo della mia ricerca è stato di sintetizzare tali NP con metodi semplici ed innovativi, al fine di impartire a tali NP specifiche caratteristiche, quali la possibilità di essere dispersi in solventi polari o proprietà ottiche migliori. In una seconda fase, ho studiato l’interazione di queste NP con NP a base di terre rare (RE) al fine di ottenere sistemi complessi con proprietà superiori.

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9

Beauvais, Jacques. "Gain optique dans le cadmium indium sulfide". Thesis, University of Ottawa (Canada), 1987. http://hdl.handle.net/10393/5316.

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10

Mbah, Jonathan Chinwendu. "Endurance materials for hydrogen sulfide splitting in electrolytic cell". [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002693.

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11

White, Richard James. "Synthesis and characterisation of complex sulfide materials with potential use as high temperature inorganic sulfide-ion conductors". Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/7824.

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12

Recatalá, Ferrandis David. "Photoactive Materials Based on Molybdenum Cluster Sulfides". Doctoral thesis, Universitat Jaume I, 2015. http://hdl.handle.net/10803/296561.

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Coordination Chemistry deals with the synthesis and study of the physicochemical properties of metal complexes. Cluster Chemistry is a subfield of Coordination Chemistry, which focuses on the functionalization of complexes in which two or more metal atoms are directly bonded. Over the past few years, Cluster Chemistry has attracted a growing interest among scientists from diverse areas, mainly due to the fascinating properties of these compounds. A historical evolution of the term cluster, as well as an outline of the role of coordinated ligands and structural types in the final properties of metal clusters are provided in Chapter 1.

This PhD Thesis is devoted to the synthesis, characterization and applications of two families of group VI metal clusters containing dithiolene or diimine ligands, as detailed in Chapter 2. The synthetic approaches employed for the preparation of a series of dinuclear M2Q2S2 cluster chalcogenides (M = Mo, W; Q = O, or S) bearing bifunctional dithiolene ligands are described in Chapter 3. These metal clusters present great potential for the design of heterometallic systems.

Chapter 4 is concerned with the preparation of an extensive family of mixed-ligand diimine-halide (or diimine-dithiolene) trinuclear molybdenum sulfides based on the Mo3S7 core. A great number of bipyridine and phenanthroline derivatives have been coordinated to these Mo3S7 units. The most important feature of the resulting cluster complexes of formula Mo3S7X4(diimine), where X = Cl, or Br, is their crystallization as [Mo3S7X4(diimine)·X]- aggregates, in which the sulfur axial atoms participate in non-bonding interactions with halide anions.

The physicochemical properties of both series of metal clusters mentioned above are explored in Chapters 5 and 6. The luminescence properties of bis(dithiolene) M2Q2S2 clusters (M = Mo, W; Q = O, or S), together with those of Mo3S7 clusters functionalized with imidazophenanthroline ligands are detailed in Chapter 5. These diimine Mo3S7 complexes exhibit luminescent anion sensing behavior. The optical limiting capabilities of both series of compounds, namely M2Q2S2- and Mo3S7-based clusters, are also described in Chapter 5 with the aim of finding correlations between molecular structures and third-order nonlinear optical functions.

Chapter 6 examines the electro- and photocatalytic activity of diimine Mo3S7 clusters immobilized on TiO2 nanoparticles toward the hydrogen evolution reaction. This study has been stimulated by the analogy between the structure of Mo3S7 and the catalytic active sites of MoS2 nanoparticles. The electrochemical properties of these TiO2 electrodes are assessed in two different media, that is, aqueous perchloric acid and sulfide-sulfite mixtures. The role of the diimine ligands in the adsorption process is also described in this Chapter.

All experimental procedures employed in this work, together with the characterization of all compounds are presented in Chapter 7. Finally, the general conclusions of this PhD Thesis are provided in Chapter 8.

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13

Powers, Max L. (Max Lyle). "Modeling tin sulfide grain growth during post-processing". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/89978.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014.
Cataloged from PDF version of thesis. "June 2014."
Includes bibliographical references (pages 32-33).
Tin sulfide (SnS) is a semiconductor material with both an indirect and direct bandgap at 1.1 eV and 1.3 eV respectively. Due to the availability of tin and sulfur, SnS is seen as a feasible alternative to the thin film CIGS and CdTe solar cells. With a direct bandgap of 1.1 eV and the ability to be produced as a thin film, the SnS solar cell should achieve high levels of efficiency of approximately 32% according to the Shockley-Queisser limit (Shockley, Queisser, 1961). However, the efficiency of most SnS systems is around 4% in low sun conditions (Hartman, 2011). To understand how to improve this efficiency, further research is being done on the grain structure and how grain growth occurs under different annealing conditions. After thermal evaporation deposition, three different conditions were varied during annealing to affect grain growth: time, temperature, and annealing atmosphere. The samples were also deposited on two different substrates, glass and molybdenum. The samples were coated with Pt/Pd and characterized using SEM imaging. The SEM images were segmented to collect grain area information from each sample. The characterization revealed that longer annealing times and higher annealing temperatures lead to faster and greater grain growth. The annealing atmosphere of the samples affected surface diffusion in that the greater the partial pressure of S2 gas present in the environment the greater the facilitation of grain growth. The key conclusion based on the experimental data was that the annealing grain growth mechanism for SnS films is secondary or abnormal grain growth. This was evidenced by the initial columnar structure, the bimodal grain area distribution, and the non-uniform grains present in the SEM images. Further research on grain boundary diffusion with respect to time and texture of the thin films is needed although they suggest secondary grain growth as well.
by Max L. Powers.
S.B.

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14

Kaur, Kuljeet. "Synthesis, evaluation, and applications of hydrogen sulfide-releasing supramolecular materials". Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/104204.

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H2S is a biologically relevant signaling gas that is endogenously produced throughout the body. The (patho)physiological roles of H2S have led researchers to develop various compounds that decompose to release H2S (H2S donors) for exogenous H2S administration. However, many small molecule H2S donors suffer from poor solubility, low stability, and lack of control over H2S release rates. As a result, there has been an increasing interest in utilizing supramolecular materials for exogenous H2S delivery. With growing potential applications of supramolecular H2S-releasing materials, it is important to explore their properties, e.g., solubility and stability under physiological conditions. We investigated the hydrolytic stability over a range of pH conditions of a series of peptides containing H2S-releasing S-aroylthiooximes (SATOs). The SATO-peptides showed structure–reactivity relationships with SATO ring substituents playing a crucial role in hydrolysis rates. Electron-donating substituents accelerate the rate of hydrolysis while electron-withdrawing substituents slows it down. We also explored their hydrolysis mechanisms at different pH values. SATO-peptides were then used to form hydrogels at 1 wt.% triggered by Ca2+. Hydrogels can be applied directly at a site of interest, potentially improving the efficacy of H2S compared with small molecule donors that diffuse away. We developed a H2S-releasing hydrogel capable of slowly releasing H2S locally to test its efficacy on intimal hyperplasia. The hydrogel delivered H2S over the period of several hours and inhibited the proliferation of human vascular smooth muscle cells (VSMCs) significantly better than fast-releasing NaSH salts. This study shows a promising application of supramolecular H2S-releasing materials over widely used sulfide salts. The macroscopic properties of peptide hydrogels could be further modulated to achieve additional control over the H2S release properties. We synthesized a series of peptide hydrogels incorporating different linker segments to study their effects on hydrogelation properties. Most peptides formed hydrogels but with significantly different rheological behavior. We found that peptides with flexible linkers such as ethyl, substituted O-methylene, and others, formed stronger hydrogels compared to those with more rigid linkers. Interestingly, we found that stiffer hydrogels released H2S over longer periods than softer ones by retarding the diffusion of a thiol trigger, likely due to bulk degradation of the soft gels but surface erosion of the stiff gels as they release H2S.
Doctor of Philosophy
H2S has long been known as a foul smelling gas until it was discovered that it is endogenously produced throughout the body and plays many (patho)physiological roles. Therapeutic benefits of H2S have led researchers to develop various compounds that release H2S (H2S donors) for exogenous H2S administration. However, many small molecule H2S donors suffer from poor solubility, low stability, and unregulated H2S release. As a result, there has been an increasing interest in utilizing materials for exogenous H2S delivery. With growing potential applications of H2S-releasing materials, it is important to explore their properties, e.g., solubility and stability under physiological conditions. We investigated the stability of a series of peptides containing H2S-releasing S-aroylthiooximes (SATOs) over a range of pH conditions. The stability of SATO-peptides was dependent on chemical makeup of the SATO part of the peptides. We also explored their hydrolysis mechanisms at different pH values. SATO-peptides were then used to form hydrogels triggered by Ca2+. Hydrogels can be applied directly at a site of interest, potentially improving the efficacy of H2S compared with small molecule donors that diffuse away. We developed a H2S-releasing hydrogel capable of slowly releasing H2S locally to test its efficacy on intimal hyperplasia. The hydrogel delivered H2S over the period of several hours and inhibited the proliferation of human vascular smooth muscle cells (VSMCs) significantly better than fast-releasing NaSH salts. This study shows a promising application of supramolecular H2S-releasing materials over widely used sulfide salts. The macroscopic properties of peptide hydrogels could be further modulated to achieve additional control over the H2S release properties. We synthesized a series of peptide hydrogels incorporating different linker segments to study their effects on hydrogelation properties. Most peptides formed weak to strong hydrogels with calcium chloride.We found that peptides with flexible linkers formed stronger hydrogels compared to those with more rigid linkers. Interestingly, we found that stiffer hydrogels released H2S over longer periods than softer ones.

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15

Cann, Jaclyn L. "Methodology for determining electronic transference numbers in molten sulfide melts". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111225.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 91-93).
Electrolysis of molten copper (I) sulfide (Cu2S) in a sulfide-based electrolyte is being investigated for use as a direct path for copper extraction to replace the conventional process of smelting and electrorefining [1]. The allure of an electrolysis process for metals extraction can be enhanced by increasing its faradaic efficiency, through, for example, decreasing the electronic transference number of the electrolyte. This thesis compares two methods of determining the electronic transference number in Cu2S - barium sulfide (BaS) electrolytes to determine whether one or both methods are wellsuited for use with these high-temperature electrolytes. The first method is a stepped potential chronoamperometry method, in which the electronic transference number is determined from the decay of the current after a voltage step. The second method is a faradaic efficiency method, where the ionic transference number is determined from the efficiency with which ions can be transported from one electrode to the other. The stepped potential chronoamperometry method estimates electronic transference numbers between 0.73 and 0.85, while the faradaic efficiency method estimates values between 0.12 and 0.34 for the same electrolyte. Three differences between the experiments are investigated: (1) the work functions of the electrodes used, (2) the additional alloying driving force in faradaic efficiency experiments, and (3) the tin impurities in the electrolyte. This analysis suggests that the difference between the work function of the electrode and the electron affinity of the electrolyte may be the dominant cause of the experimental discrepancy. Therefore, it is suggested that electrodes and electrolytes be chosen to maximize this difference to enhance the faradaic efficiency of copper extraction from Cu2S. The underlying physics of semiconductiviy in molten sulfides, however, remains unclear. Future study of the electronic structure and short range ordering of molten metal sulfides to better understand and predict electronic properties is needed.
by Jaclyn L. Cann.
S.M.

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Chmielowiec, Brian John. "Electrochemical engineering considerations for gas evolution in molten sulfide electrolytes". Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122158.

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Thesis: Sc. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references.
The current interrupt and galvanostatic electrochemical impedance spectroscopy techniques were utilized to characterize the ohmic, charge transfer, and mass transfer over-potential behavior of gas evolving electrodes in aqueous, molten chloride, and molten sulfide electrolyte solutions under steady-state natural convective flow conditions as a means to gain access to thermodynamic, physicochemical, and hydrodynamic properties of these systems. Previous efforts purposely chose operating conditions under which one or more sources of overpotential were negligible to facilitate analysis of the total overpotential observed at the expense of maintaining operating conditions of industrial relevance. This work represents a preliminary effort to understand the fundamental material properties of a molten sulfide electrolyte, by application of materials-blind electrochemical techniques that were validated on previously well characterized systems-oxygen evolution in aqueous KOH and chlorine evolution in eutectic LiCl-KCl-CsCl. For the first time, values are reported for the saturation concentration of dissolved sulfur gas, an approximate range of Schmidt number for dissolved sulfur, and natural convection limiting current densities in a molten sulfide electrolyte consisting of Cu₂S-BaS-La₂S₃ at 1300°C.
by Brian John Chmielowiec.
Sc. D.
Sc.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering

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17

Shi, Zhengqi. "Development of Metal Sulfide Semiconductor Light Absorbers for Solar Cell Application". University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1525474936984221.

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Santos, Figueroa Luis Enrique. "New approaches for the development of chromo-fluorogenic sensors for chemical species of biological, industrial and environmental interest". Doctoral thesis, Universitat Politècnica de València, 2015. http://hdl.handle.net/10251/43216.

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El presente proyecto de investigación está enfocado al desarrollo de sensores químicos fluoro-cromogénicos, para la detección y determinación de especies químicas de interés biológico, industrial y medioambiental de forma selectiva y con alta sensibilidad. En forma general, se busca el diseñar nuevos sistemas sensores basados en compuestos (receptores) formados por dos unidades: una unidad coordinante que interacciona con el anión a determinar y una unidad generadora de señal que alerta del reconocimiento molecular efectuado. Durante este estudio se están preparando diversas moléculas receptoras funcionalizandas con grupos modificadores de estructura para evaluar su influencia sobre las capacidades de detección y selectividad como receptores de especies específicas en diferentes condiciones y medios. Las diferentes aproximaciones en prueba implican a su vez el diseño y síntesis molecular, así como el análisis de las diferentes señales ópticas producidas en el reconocimiento, con el fin de diseñar sistemas de alta eficacia y eficiencia, y con posibilidades reales de aplicación.
Santos Figueroa, LE. (2014). New approaches for the development of chromo-fluorogenic sensors for chemical species of biological, industrial and environmental interest [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/43216
TESIS
Premiado

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19

Jyah, Strachan. "On Molybdenum Sulfides and Other Active Materials for Sustainable Energy Systems". Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/25375.

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To respond to the approaching climate crisis, the current energy landscape must shift towards sustainable, decarbonised systems. This shift will require the development of inexpensive and active energy conversion materials. The work within this thesis reports the investigation of several candidate materials, i.e. molybdenum sulfides and carbides, for use as catalysts and electrodes in energy conversion processes. These materials were chosen for their natural abundance, controllable morphologies, and varied chemistries. Chapter 1 focuses on the scope and potential of Chevrel phases (MxMo6S8) as catalytic materials. It includes both a critical literature review and original research on nanoparticulate catalysts that exhibited excellent performance for the hydrogen evolution reaction. Chapter 2 focuses on the various morphologies of MoS2 and incorporates two reviews: the first review summarises all known reports of 3R-MoS2 and clarifies inconsistencies with the literature. The second review rectifies the errors in the literature on hydrothermally produced 1T-MoS2 and provides best practice analysis instructions. The final section of Chapter 2 is an investigation into the effect of crystal disorder on the electrochemical performance of MoS2 in hybrid batteries in order to aid the optimisation of MoS2 electrodes. Chapter 3 is comprised of a study that elucidates the structure of a highly active lignin valorisation catalyst, Mo2CxNx-1/TiN. The analyses show that the titanium nitride and molybdenum carbide phases are intimately mixed and that the catalyst incorporates terminal Mo≡N motifs. Chapter 4 includes studies on the silver catalysed reduction of 4-nitrophenol; a ubiquitous model reaction. A detailed kinetic analysis of the reaction mechanism elucidates the role of oxygen during the induction period of the reaction. The research-level chemistry and protocols were then adapted to be used as a pedagogical tool.

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Krishnamoorthy, Aravind Ph D. Massachusetts Institute of Technology. "Modeling of mechanisms affecting the growth and breakdown of iron sulfide films". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104109.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 153-169).
Modeling the behavior of ionic materials in electrochemical environments is a topic of great scientific interest for important systems like like fuel cells, batteries, and catalysts and corrosion passive films. However, existing analytical and numerical models of such electrochemical systems like passive films are derived from mathematical expressions for the growth and degradation of the ionic material that are not derived from the rates of underlying physical processes and are instead merely benchmarked to experimental data. These models are intrinsically empirical and fall short of providing mechanistic insights into the physical processes occurring in the passive film that are required to design better-performing electrochemical materials. In this thesis, based on our understanding that overall film behavior is a collective outcome of several atomic-scale phenomena like defect formation and ionic diffusion that contribute to the growth and/or breakdown of the passive film, we construct a construct a novel multiscale modeling framework that explicitly models atomic scale phenomena and couples it to higher-length- scale description of the microstructure to estimate passive film behavior in a mechanistic way and we further demonstrate this capability on an ionic system of FeSx phases on a steel substrate. The primary contributions of the thesis are two-fold: We identified the atomistic mechanisms responsible for the growth and breakdown of iron sulfide phases, and also quantified non-empirically the kinetic parameters that govern the rate of these unit processes. We constructed a novel multiscale modeling framework that couples accurate modeling of atomic-scale unit processes to efficient modeling of the micron-scale behavior of the passive film that captures phenomena at multiple length scales ranging from point defect dynamics to microstructure formation and evolution. The thesis is divided into three sections, the first of which is devoted to investigating two unit processes (surface sulfidation and ionic diffusion) that contribute to the growth of iron sulfide phases and is primarily focused on quantifying the kinetic parameters involved in the sulfidation (adsorption energies and dissociation barriers) and ionic diffusion (diffusivities and migration barriers) processes. In this section, we use a combination of ab initio density functional theory and kinetic Monte Carlo to quantify the surface-defect-induced changes in the electronic structure (0.4 eV reduction in the band gap and the introduction of mid-gap states) that increase the reactivity of and the rate of sulfidation on FeS₂ (100) surfaces. We also use the d-band theory to explain the effect of surface coverage and surface charge (or electric potential) on the reactivity of the reactivity of the surface, and provide guidelines for more accurate calculation of reactivity metrics in realistic electrochemical conditions. Finally, through the use of high-accuracy hybrid DFT and NEB methods, coupled with kinetic Monte Carlo calculations, we resolve the influence of magnetic and vacancy ordering transitions on ionic migration barriers and diffusivity of pyrrhotite, Fe₁-xS. Specifically, we identify that the ionic migration barrier is unaffected by the local vacancy configuration in different pyrrhotite polytypes, but is strongly influenced by the local magnetic order imposed by strong antiferromagnetic superexchange interactions that exist in pyrrhotite, which is a finding that is also important for other scientifically important material systems like NiO. The next section of the thesis discusses the mechanistic pathways and kinetic parameters of two processes involved in the local degradation of iron sulfide passive films (vacancy agglomeration-induced pit initiation and hydrogen-evolution-assisted debonding). For the first process, we use first-principles modeling to explain experimental observations of non-Arrhenius vacancy concentrations and nanoscale pitting on the FeS₂ surface. We identify a mechanistic pathway comprising of concerted vacancy formation and diffusion unit processes that leads to the formation of vacancy agglomerates that serve as sites for nanopit initiation. We then use the same set of computational tools to identify another mode of failure in the layered iron sulfide phase, mackinawite. We identify through computational stress-strain curves that cathodically generated H2 molecules are detrimental to the mechanical stability of the mackinawite phase and cause localized degradation of the passive film and act as a precursor to pitting corrosion. The final section of the thesis describes the formulation of the multiscale modeling framework that incorporates the kinetics of film growth and breakdown mechanisms identified in previous sections. This novel coupled kMC and phase-field model is capable of describing the macroscale morphology, passivity and protectiveness of the passive film while also possessing sufficient resolution to simulate atomic scale dynamics occurring at the film interfaces, and represents a significant improvement in terms of mechanistic detail over existing analytical corrosion models especially for sour systems. We demonstrate the capability of the model in constructing kinetic stability diagrams, which extend the information contained in phase and Pourbaix diagrams by accounting for the relative rates for formation and dissolution of different iron sulfide phases. We also demonstrate the calculation of degradation maps, that help identify the dominant mechanisms behind the localized failure of the passive film at different environmental conditions (temperature, partial pressure of H₂S, electrode potential, pH etc) and thus identify environmental conditions where the passive film is stable against localized degradation. Finally, the direct coupling between atomic scale processes and overall film passivity allows us to identify the impact of different material properties (like vacancy formation energy and diffusivity) on the resistance of the passive film to pitting and localized corrosion.
by Aravind Krishnamoorthy.
Ph. D.

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Nguyen, Thao Ahn 1958. "Defect structures, phase relations and phase transformations of low temperature iron sulfide compounds". Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/92621.

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Aguilar, Luis Felipe. "Development of Sulfur Tolerant Materials for the Hydrogen Sulfide Solid Oxide Fuel Cell". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6979.

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One of the major technical challenges towards a viable H2S//Air SOFC is to identify and develop anode materials that are electronically conductive, chemically and electrochemically stable, and catalytically active when exposed to H2S-rich environments. The corrosive nature of H2S renders most traditional state-of-the-art SOFC anode materials (Ni, Pt, Ag) useless for long-term cell performance even at very low sulfur concentrations. In my doctoral thesis work, a new class of perovskite-based anodes was developed for potential use in SOFCs operating with H2S and sulfur-containing fuels. Cermets from this family of materials have shown excellent chemical stability and electrochemical performance at typical SOFC operating conditions. As an added benefit, they appear to preferentially oxidize H2S over hydrogen, as suggested by open circuit voltage, impedance spectra, and cell performance measurements obtained using various H2S-H2-N2 fuel mixtures. Cell power output values were among the highest reported in the literature and showed no significant deterioration during 48-hour testing periods. Impedance measurements indicated overall cell resistances decreased with increasing temperature and H2S content of the fuel. This behavior is starkly different from that of contemporary SOFC anodes, where the presence of H2S usually increases overall polarization resistance and ultimately destroys the cell. Results are promising due to the drastic improvement in sulfur tolerance compared to the current generation of SOFC power systems.

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Huggins, Gonzalez Angeire Sugey. "Galvanic Interactions in Sweet and Sour Environments". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1557002644383622.

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Weeraddana, Tharaka Missaka De Silva. "Synthesis, Characterization, and Exciton Physics of Colloidal Lead Sulfide Nanosheets". Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1591381301083136.

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MENDONÇA, Suzana Kelly Gomes de. "Caracterização de Solos Tiomórficos da várzea do Rio Camocim, Caaporã, PB". Universidade Federal Rural de Pernambuco, 2011. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/5353.

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Made available in DSpace on 2016-08-16T14:23:13Z (GMT). No. of bitstreams: 1 Suzana Kelley Gomes de Mendonca.pdf: 1457356 bytes, checksum: 55d06ce86944cd3f69644577e424587d (MD5) Previous issue date: 2011-02-25
Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq
Low lands in Brazil have a great potential for agriculture, however, they have some limitations due to the presence of high water table and severe risk of flooding. When located near by the sea cost, these floodplains can have influence of the sea water, resulting in the presence of sulfide soils, which, if drained, can develop sulfuric horizons. The sulfuric horizons are mainly characterized by high levels of acidity and exchangeable aluminum, which can result in serious environmental impact to the ecosystem. The agriculture use of these soils requires a deep knowledge of soil physical, chemical and mineralogical properties, in order to support the development of sustainable management practices. The objective of this work was to study chemical and mineralogical properties of acid sulfate soils formed in the floodplain of Camocim river, Caaporã municipality, state of Paraíba. The main aim was to support decisions on the viability of sugarcane cropping in these areas. Soils were characterized morphologically and samples were collected along a transect from the high land towards the river channel. Besides the routine physical, chemical and mineralogical analysis, other determinations were carried out involving total sulfur, incubation pH, soluble anions, electrical conductivity of the saturation extract and sequential iron extraction. The soils were classified as: Argisolic,Dystric Tb Haplic Gleysol (P1) Typic Sapric Sulfide Organosol (P2), Organosolic Orthic Sulfide Gleysol (P3 and P4). Soil distribution in the landscape of the Camocim river floodplain is mainly related to the relief, which determines drainage, water table and, consequently, the soil forming processes related to water excess. The presence of sulfuric horizons occur at the surface, in the very poorly drained soil profiles, and at 43 cm depth in the poorly drained soils close to the river channel. The studied acid sulfate soils do not have salinity at present time, and the high electrical conductivity is determined by the formation sulfuric acid (H+ + SO4 2-) from pyrite oxidation. Sugarcane crop decay in the floodplain of Camocim River, after one year of cultivation was a consequente of the sulfuric horizon formation after the implementation of the drainage system in soils with sulfide materials. The main soil minerals, indentified by X-ray diffraction, in the clay fraction were jarosite quartz, feldspars, kaolinite, smectite (essentially montmorillonite), illite and gibbsite. Quartz and feldspars were the minerals identified in sand and silt fractions. The results of the iron sequential extraction showed predominance of non crystalline iron oxides and very low amounts or absence of iron associated with pyrite, reflecting the advanced oxidation stage determined by the drainage system.
As áreas de várzeas no Brasil apresentam um grande potencial para a agricultura, no entanto, estas áreas apresentam algumas limitações ao uso agrícola devido à presença de lençol freático elevado e risco freqüente de inundação. Quando localizadas em áreas litorâneas, estas áreas podem sofrer influência marinha podendo apresentar solos tiomórficos que, quando drenados, formam horizonte sulfúrico, caracterizados principalmente pela elevada acidez, elevados teores de alumínio trocável, podendo causar sérios impactos ambientais no ecossistema onde ocorrem. A incorporação destas áreas no processo produtivo depende de um profundo conhecimento das propriedades físicas, mineralógicas e principalmente químicas, de forma a subsidiar o desenvolvimento de técnicas sustentáveis de manejo. Neste contexto, foi realizada a caracterização física, química, mineralógica, além da extração sequencial de ferro de solos tiomórficos desenvolvidos na várzea do rio Camocim, no município de Caaporã, PB. O objetivo do estudo foi identificar a ocorrência de solos tiomórficos e caracterizá-los, com o fim de obter subsídios para a tomada de decisão de incorporar estas áreas ao cultivo de cana-de-açúcar ou mantê-las nas condições naturais. Para tanto foi feito um transecto perpendicular ao canal principal do rio, a partir das terras altas, onde foram descritos e coletados quatro perfis de solo. Em campo foi realizada a caracterização morfológica dos perfis e coletadas amostras para as análises físicas, químicas e mineralógicas de rotina, além de análises específicas para determinação do enxofre total, pH de incubação, ânions solúveis, CE do extrato da pasta saturada e extração sequencial de ferro. Os solos foram classificados como Gleissolo Háplico Tb Distrófico argissólico (P1), Organossolo Tiomórfico Sáprico típico (P2) e Gleissolo Tiomórfico Órtico organossólico (P3 e P4). A distribuição dos solos na várzea do rio Camocim guarda estreita relação com o relevo, que condiciona a drenagem e, consequentemente, os processos de formação relacionados com o excesso de água. A presença de horizonte sulfúrico foi constatada a partir do horizonte superficial nos perfis muito mal drenados da planície de inundação, e a partir de 43 cm, nos solos mal drenados da ombreira. Os solos tiomórficos estudados não apresentam salinidade, sendo a alta condutividade elétrica resultante da formação de ácido sulfúrico proveniente da oxidação da pirita (H+ e SO4 2-). A degradação do canavial em grandes áreas da várzea do rio Camocim, após um ano de cultivo, foi consequência da formação do horizonte sulfúrico com a drenagem da área, tendo em vista que os materiais sulfídricos ocorrem desde a superfície. Os minerais identificados por DRX foram: jarosita, quartzo, feldspatos, caulinita, esmectita (essencialmente montmorilonita), ilita e gibbsita, na fração argila. Quartzo e feldspatos foram os minerais identificados nas frações areia e silte. Os valores da extração sequencial de ferro mostraram predomínio de formas não cristalinas de óxidos de ferro e baixíssimos teores ou ausência de ferro associado à pirita, indicando que os solos tiomórficos estudados apresentam avançado estágio de oxidação, promovido pela drenagem realizada na área de estudo na tentativa de viabilizar o cultivo da cana-de-açúcar.

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Carrera, Lucie. "Caractérisation du transfert liquide/gaz du sulfure d’hydrogène dans les réseaux d’assainissement". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI137/document.

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Le sulfure d’hydrogène (H2S) est un gaz malodorant, dangereux, et responsable de la corrosion du béton dans les canalisations d’eaux usées. Ce dernier phénomène est très coûteux pour les collectivités. Le composé H2S est généré sous forme soluble dans les zones anaérobies des réseaux d’assainissement (biofilms, sédiments, zones stagnantes ou conduites forcées) et est ensuite émis dans l’atmosphère des canalisations sous forme gazeuse dans les conduites gravitaires. Des modèles sont nécessaires pour améliorer la conception et la gestion des systèmes de collecte des eaux usées. L’objectif de cette thèse est de mieux comprendre les mécanismes de transfert d’H2S lors de l’écoulement gravitaire d’un liquide saturé en gaz dissous. Nous avons développé des techniques de mesure du coefficient de transfert à l’interface liquide-gaz pour le sulfure d’hydrogène et pour l’oxygène. L’influence des conditions hydrodynamiques (vitesse d’eau), aérauliques (vitesse d’air) et de la surface d’échange a été étudiée dans différentes géométries : une cuve agitée de 5 L et une canalisation de 10 mètres de longueur. Nous avons ainsi pu établir la forte influence de la vitesse d’eau sur le coefficient de transfert global. Cette approche expérimentale a été complétée par une approche de modélisation. En utilisant la mécanique des fluides numérique, nous avons essayé de comprendre l’évolution du coefficient de transfert à partir des fluctuations hydrodynamiques locales observées à proximité de l’interface liquide gaz. Les paramètres les plus pertinents pour expliquer les observations effectuées semblent être les grandeurs liées à la turbulence. L’application future de ce type de corrélation serait l’estimation et la prévision des zones d’émissions d’H2S. Ainsi serait-il possible d’identifier les points nécessitant une surveillance et une maintenance particulière
Hydrogen sulfide (H2S) is a harmful and odorous compound which is also responsible for concrete corrosion in sewers. This phenomenon is costly for the communities. H2S is generated in anaerobic zones in sewer networks (biofilms, sediments, forced mains or stagnant zones), and released into the atmosphere under the form of H2S(g) in gravity pipes. Knowledge-based models are needed to improve the design and the management of wastewater collection systems. The objective of this PhD work is to better understand the mass transfer mechanisms of a water flow saturated in H2S when the flow becomes free. We plan to develop a technique to access the global mass transfer coefficient at the liquid- gas interface for H2S and O2. The effect of hydrodynamic, aeraulic conditions and the liquid-gas surface area on the transfer coefficient were studied in different geometries: small batch reactor of 5L and 10 meter sewer pipe device. A strong influence of the flow velocity on the global transfer coefficient was observed. This experimental approach was completed with a numerical approach. The use of computational fluid dynamics permitted to understand the behavior of transfer coefficient from local hydrodynamics fluctuations observed near the liquid/gas interface. The direct application of this kind of correlation would be the estimation of the transfer fluxes and the localization of hazardous areas for H2S concentration. Consequently it could be possible to identify the sensitive zones requiring a follow-up of the system or a strengthening of the structures

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DEL, GOBBO SILVANO. "Cadmium sulfide quantum dots: growth and optical properties". Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2009. http://hdl.handle.net/2108/873.

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Negli ultimi anni, c’è stato un rapido sviluppo delle tecniche di crescita dei materiali nanostrutturati, e un forte impulso è stato dato dall’introduzione delle tecniche di crescita colloidale. Tali tecniche consentono di crescere un ampia gamma di materiali nanostrutturati, metalli e semiconduttori, con elevata cristallinità, dimensioni ridotte (< 5 nm) e con una distribuzione delle dimensioni molto stretta. Il solfuro di cadmio (CdS) nanostrutturato ha promettenti future applicazioni tecnologiche, come ad esempio nei dispositivi optoelettronici, celle solari ad alta efficienza e come tracciante fluorescente in biologia. Tuttavia, per poter sfruttare al meglio le proprietà fisiche a favore delle citate applicazioni è di fondamentale importanza una conoscenza approfondita delle proprietà fisiche. In questa tesi, sono state studiate le proprietà optovibrazionali e optoelettroniche dei quantum dots (QDs) di solfuro di cadmio cresciuti tramite un metodo di crescita colloidale. Tramite i metodi di crescita colloidale è possibile produrre QDs con dimensione ridotta e una distribuzione della dimensione molto stretta. La sintesi dei CdS-QDs consiste nella termolisi a circa 260 °C dello stearato di cadmio in presenza di solfuro di idrogeno in un solvente organico altobollente (1-ottadecene). La velocità della crescita e la dimensione finale dei QDs sono regolate dalla presenza di una molecola surfattante, l’ossido di triottilfosfina (TOPO). In particolare, QDs con una determinata dimensione e con una sua distribuzione molto stretta possono essere ottenuti regolando opportunamente la temperatura di crescita, la concentrazione dei precursori e principalmente la concentrazione del surfattante e del tempo di reazione (crescita arrestata). La morfologia, la dimensione (diametro) e la distribuzione dei diametri sono state determinate tramite TEM. Tramite spettroscopia di assorbimento, si ottengono informazioni sugli stati elettronici, inoltre, sfruttando la relazione esistente tra la band gap e il diametro, si può determinare il diametro medio di un campione di QDs. Le proprietà emissive dei QDs sono state studiate tramite spettroscopia di fotoluminescenza (PL) e dall’energia della banda di PL si può ottenere una stima del diametro medio dei QDs. Dalla larghezza di banda degli spettri di assorbimento e di PL si può ottenere anche una stima sulla distribuzione del diametro dei QDs. Un estesa parte del lavoro riguarda lo studio delle proprietà vibrazionali dei CdS-QDs, tramite spettroscopia Raman. Queste indagini sono state effettuate su campioni di CdS-QDs cresciuti appositamente con diversi diametri. Per eseguire misure micro-Raman, i campioni di CdS-QDs coordinati da molecole di TOPO che hanno una consistenza gelatinosa, sono stati trattati con acido tioglicolico (TGA). Questo trattamento è necessario per avere CdS-QDs in forma di polvere, la quale è più adatta per essere studiata tramite spettroscopia Raman. Per evitare effetti termici negli spettri o il danneggiamento del campione, le misure micro-Raman devono essere effettuate con potenze del laser molto basse. Negli spettri Raman di CdS-QDs si osserva uno spostamento del picco del fonone LO verso frequenze più basse , in particolare, tale spostamento è più marcato per i QDs più piccoli, mentre, al crescere del diametro, la frequenza si avvicina progressivamente a quella del bulk. Questa diminuzione di frequenza è causata dall’espansione del cristallo che avviene nei QDs, con il conseguente indebolimento dei legami per i quali diminuisce la frequenza di risonanza. Oltre a questo, il confinamento quantistico dei fononi è visibile come un allargamento asimmetrico della linea dei fononi, e come l’apparizione di un nuovo picco a circa 270 cm-1. Alcune pubblicazioni assegnano questo picco ai modi di superficie, mentre altri lo descivono come la conseguenza delle nuove regole di selezione dovute dalla bassa dimensionalità. Lo studio ha anche lo scopo di comparare le previsioni teoriche basate sia sul modello “dielectric continuum” che sui fononi di superficie con i risultati sperimentali. È stata trovata una relazione tra i valori di frequenza dei fononi predetti teoricamente e i risultati sperimentali, in particolare, le frequenze dei fononi di superficie sono in accordo con i risultati sperimentali. In conclusione, lo scopo di questo studio consiste nello sviluppo di un metodo per crescere CdS-QDs con le caratteristiche fisiche desiderate (diamtero voluto e distribuzione di diametro stretta) per poterne poi effettuare uno studio sistematico delle proprietà vibrazionali ed elettroniche.
In recent years, there has been a rapid development of the growth techniques of nanostructured materials, and a particular breakthrough was given by the introduction of colloidal growth techniques. These techniques allow to grow by affordable facilities, a wide range of nanostructured materials, metals and semiconductors, with high crystallinity, reduced size, narrow size distribution. Nanostructured cadmium sulfide (CdS) has promising future applications as in the realization of optoelectronic devices, high efficiency solar cells as well as fluorescent biological probe. However, in order to fully exploit the potential technological applications, the study of the physical properties of such materials is of crucial importance. In this thesis, the optoelectronic and optovibrational properties of cadmium sulfide quantum dots (QDs) grown by colloidal chemical method are studied. By the means of colloidal growth, it is possible to grow QDs with reduced size and narrow size distribution. The synthesis of CdS-QDs consists in the thermolysis (T=260 °C) of cadmium stearate in presence of hydrogen sulfide in a high temperature boiling point solvent (1-octadecene). The growth rate and final QDs size are regulated by the presence of the surfactating molecule trioctylphosphine oxide (TOPO). QDs with a determined size and a narrow size distribution can be obtained properly adjusting the growth parameters such as temperature, precursors concentrations, and principally the surfactant concentration and reaction time (arrested growth). The QDs morphology, their size and their size distribution is determined by TEM imaging. By absorption spectroscopy, information regarding the electronic states in QDs are obtained, and exploiting the relation existing between band gap and QD diameter, the mean diameter of the QDS is determined. The emissive properties of the QDs are probed by photoluminescence spectroscopy (PL). From the energy of PL band, an estimation of the QDs diameter can be obtained. Based on the width of absorbance and PL bands, the width of QDs size distributions can be estimated. A large part of the work is concerned with the study of vibrational properties of CdS-QDs by Raman spectroscopy. These investigations are carried out on the CdS-QDs samples purposely grown with different average sizes. In order to perform micro-Raman measurements, the gel-like TOPO-coated CdS-QDs are treated to replace the TOPO layer by thioglycolic acid (TGA). This treatment is necessary in order to have powder-like CdS-QDs being more suitable to a Raman scattering study. To avoid thermal effects or damage to the sample, the micro-Raman measurements must to be performed using very low laser powers (on the sample). In the Raman spectra of CdS-QDs, a decrease of the phonon frequency (red-shift) with respect to the bulk CdS frequency is observed. In particular, the red-shift is expected to be more pronounced for the smallest QDs, while at the increasing of QDs size, the phonon frequency will approach progressively to the bulk value. This red-shift is caused by the lattice expansion and by a subsequent weakening of the bonds which causes a reduction of the resonance frequency. Beyond the red-shift, the quantum confinement is visible also as an asymmetric broadening of the phonon line and by the apparition of a new peak a circa 270 cm-1. Some reports assign this peak to surface modes, while other reports describe this mode as a consequence of new selection rules arising from the reduced dimensionality. The study has also the aim to cross check the theoretical prediction based on the dielectric continuum model and on the surface modes with the experimental results. A relation between the theory and the experiment has been found, in particular, the predicted surface frequencies are in good agreement with the experiments. In conclusion, the goal of this thesis work is to develop a method to grow CdS-QDs with the desired physical characteristics (narrow size distribution) suitable for a systematic study of optical properties (vibrational and electronic).

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Lenahan, Frances Daggett. "Photoconductivity and minority carrier lifetime in tin sulfide and gallium arsenide semiconductors for photovoltaics". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104147.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 54-55).
The growth and maintenance of the modern technological world requires immediate solutions in the field of clean, renewable energy. One prominent solution is the rapid advancement of solar cell technologies due to the wide availability of solar energy and the growing versatility of harnessing it. As efficiencies for these devices creep upwards, it becomes increasingly more important to find the greatest inhibiting factor. Through a solar cell simulator program (SCAPS), improvements in the minority-carrier lifetime of cell materials show not only significant improvements in cell efficiencies, but also an un-masking of improvements by other properties, which are inhibited when the lifetime is too short. This work aims to calculate the mobilitylifetime products ([mu][tau]) of gallium arsenide (GaAs) and annealed and un-annealed tin sulfide (SnS) with respective p-doping carrier concentrations of 1018 cm-3, 1016 cm-3, and 1015 cm-3 through photoconductivity measurements. Films are 1 [mu]m thick and have a four-bar and two-bar contact configuration to model carrier conductivity as a sheet. For calculations, two methods of modeling charge carrier generation are considered; a uniform generation throughout the film and a depth and wavelength-dependent generation. This work found values on the order of 10-1 cm2 V-1, 10-4 cm2 V-1, and 10-5 cm2 V-1, for GaAs, annealed SnS, and un-annealed SnS, respectively, for both methods of calculation. The simplified approach considering a uniform generation yielded lower results than the depth and wavelength dependent calculations by about a factor of two. All values were three to four orders of magnitude higher than those found in the literature. For this reason, it is believed that the majority-carrier is dominating measurements due to an inhibited minority-carrier lifetime.
by Frances Daggett Lenahan.
S.B.

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Wang, Rui. "Three Dimentional Investigation of Different Sulfide Inclusions in Steels by Using the Electrolytic Extraction Method". Thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-199666.

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30

Orndorff, Zenah Wilson. "Evaluation of Sulfidic Materials in Virginia Highway Corridors". Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/29183.

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Road construction through sulfidic materials in Virginia has resulted in localized acid rock drainage (ARD) that threatens water quality, fill stability, integrity of building materials, and vegetation management. The objectives of this study were: i) to develop a state-wide sulfide hazard rating map based on characterization of the geologic formations associated with acid roadcuts, ii) to estimate depth to sulfidic sediments in the Coastal Plain based on landscape relationships, and iii) to evaluate potential acidity testing procedures on diverse materials. Geologic formations associated with acid roadcuts were characterized by potential peroxide acidity (PPA) and S content, and grouped into four categories. Listed in order of increasing severity, these formations included: the Tabb Formation (Coastal Plain), the Lynchburg Group of the Ashe Formation (Blue Ridge), the Chesapeake Group and Lower Tertiary deposits (Coastal Plain), the Millboro shale, Marcellus shale, Chatanooga shale and Needmore Formation (Valley and Ridge), and the Quantico Formation (Piedmont). Evaluation of landscape parameters near Richmond, Virginia, indicated that the likelihood of encountering sulfidic materials within a given depth at a specific location was related to elevation and mapped soil types. Elevation and soil map units were assigned to risk classes to indicate the likelihood of encountering sulfides within a depth of 9 m. Comparison of PPA and S content for 296 diverse samples indicated that S may serve as a screening tool to evaluate materials without carbonates. Comparison of PPA and conventional Acid-Base Accounting (ABA) for 14 diverse samples indicated that PPA and ABA were highly correlated, with PPA yielding 0.60 to 0.95X the amount of acidity as ABA. Potential acidity by Soxhlet extraction and PPA were equivalent for 3 of 4 diverse samples. Average acidity and metal contents of leachate from Soxhlet extractors were correlated with acidity and metals of road drainage. Sulfide hazard analysis should be an essential step in the pre-design phase of highway construction and other earth-disturbing activities.
Ph. D.

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31

Herbert, Francis William. "Mechanisms governing the growth, reactivity and stability of iron sulfides". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98126.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 135-140).
The kinetics of electrochemical processes in ionic materials are fundamentally governed by dynamic events at the atomic scale, including point defect formation and migration, and molecular interactions at the surface. A corrosion system comprising an iron sulfide film (passive layer) formed on iron or steel in contact with an hydrogen sulfide (H₂S)- rich fluid can thus, in principle, be modeled by a series of unit reaction steps that control the rate of degradation under given thermodynamic conditions. This overarching thesis goal necessitates a concerted experimental and computational approach to determine the relevant kinetic parameters such as activation barriers Ea and rate constants v₀ for the homogeneous and heterogeneous reactions of interest. These fundamental values can be obtained experimentally via temperature-dependent measurements on pure, model iron sulfide samples. This thesis therefore consists of three case studies on the stable Fe-S phases pyrrhotite (Fe₁-xS) and pyrite (FeS₂) to identify the elementary corrosion mechanisms and their kinetic parameters. Pyrrhotite is of interest because the off-stoichiometry of this phase leads to relatively rapid bulk processes such as diffusion; pyrite has a comparitively inert bulk but this work showed that it has a chemically labile surface. The first study focuses on two basic, rate-controlling steps in the growth of pyrrhotite: cation diffusion and sulfur exchange at the surface. First, iron self-diffusivity *DFe is determined across the temperature range 170-400 °C through magnetokinetic studies of the diffusion-driven "[lambda]" magnetic transformation, as well as direct tracer diffusion measurements in Fe₁-xS crystals using secondary ion mass spectrometry (SIMS). This range encompasses the sponteneous magnetic and structural order-disorder temperature TN = 315 °C in pyrrhotite. The effect of spontaneous magnetization below TN is to increase the Fe vacancy migration energy by a combined 40% increasing Ea for diffusion from 0.83 eV in paramagnetic Fe₁-xS to ~1.20 eV in the fully magnetized state. An extrapolation of the Arrhenius law from the paramagnetic regime would therefore overestimate actual diffusivities by up to 10² times at 150 °C. Second, the surface exchange of sulfur from H₂S into the solid state in Fe₁-xS is measured using electrical conductivity relaxation, yielding Ea = 1.1 eV for sulfur incorporation into pyrrhotite. With their similar thermal dependence, there is no clear temperature crossover from cation diffusion- to surface exchange-limiting regimes, or vice versa. Instead, surface exchange is expected to constrain pyrrhotite growth for films under ~100 [mu]m thickness, beyond which diffusion becomes the rate limiting mechanism, independent of external driving factors such as temperature. The second study explores the role of surface electronic states on the electrochemical reactivity of pyrite. Charge transfer between a solid surface and an adsorbate such as H₂S requires the mutual availability of filled/empty electronic states at the same energy level. The semiconducting FeS₂(100) surface is predicted to have intrinsic surface states (SS's) from Fe and S dangling bonds, as well as extrinsic SS's related to delocalized defects at the surface, both of which would affect charge transfer characteristics. A novel, broadly-applicable methodology is developed in this thesis to quantify the energy and density of these SS's, based on experimental scanning tunneling microscopy / spectroscopy (STM/STS) in conjunction with first principles tunneling current modeling. As a result, a decreased surface band gap Eg of 0.4 eV, compared to 0.95 eV in bulk pyrite, is measured. The findings highlight the need to differentiate between bulk and surface electronic structure when assessing heterogeneous reactivity, and have implications for the use of FeS₂ in potential technological applications, for example as a photovoltaic adsorber. Finally, the dynamics of point defect formation and clustering on FeS₂(100) under high-temperature, reducing conditions are investigated to understand the stability of the surface under extreme conditions. Synchrotron x-ray photoelectron spectroscopy (XPS) is used to measure a formation energy [delta]Hf for sulfur vacancies in the topmost atomic layer of 0.1 eV up to approximately 240 °C. Above this temperature, however, point defects are shown to condense into surface pits as measured by scnaning tunneling microscopy (STM). The combined, experimental XPS and STM results are replicated with high precision by a kinetic Monte Carlo (kMC) simulation, developed by Aravind Krishnamoorthy towards his doctoral thesis, of surface degradation on realistic length-and timescales of 10-¹⁰ - 10-⁷ m and up to several hours, respectively. The findings have implications for the initiation of surface breakdown via pitting in ionic passive films, as well as providing a broader understanding of the non-stoichiometry of the pyrite surface. The common thread is a focus on events at the atomic and electronic scale, with an emphasis on point defects. The results thereby facilitate a bottom-up approach to modeling electrochemical processes such as corrosion in Fe-S phases, in which the unit steps are cast into probabilistic simulation tools. While the three studies here comprise only a partial examination of the atomic-scale events regulating the behavior of Fe-S passive layers, this approach makes inroads towards more accurate component lifetime prediction and the design of robust materials for aggressive environments. Moreover, the fundamental surface and bulk physical chemistry of iron sulfides explored in this work has implications beyond corrosion to other uses of these materials, including potential magnetic devices (Fe₁-xS) and earth-abundant photovoltaic and photoelectrochemical adsorbers (FeS₂).
by Francis William Herbert.
Ph. D.

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32

Silva, Marcos Aurelio Bomfim da 1983. "Propriedades físicas de gessos odontológicos tipo IV desidratados em temperatura ambiente e em forno de microondas". [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/288550.

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Orientador: Rafael Leonardo Xediek Consani
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
Made available in DSpace on 2018-08-17T13:52:59Z (GMT). No. of bitstreams: 1 Silva_MarcosAurelioBomfimda_M.pdf: 1487583 bytes, checksum: 9cb32f8fb3e02fe5c0534b01b7a60277 (MD5) Previous issue date: 2011
Resumo: O objetivo deste estudo foi verificar a influência da secagem em temperatura de laboratório (25±4ºC) e em forno de microondas sobre propriedades físicas de gessos odontológicos tipo IV: Elite Rock, Shera Premium e Durone IV. Os gessos foram proporcionados e espatulados mecanicamente a vácuo seguindo as recomendações dos fabricantes e vazado no molde com auxílio de vibrador mecânico. No Capítulo 1 foi avaliada a alteração dimensional, resistência à compressão e reprodução de detalhes dos gessos desidratados em forno de microondas e em temperatura de laboratório. Dois protocolos de desidratação com diferentes períodos de avaliação foram utilizados para os ensaios de alteração dimensional, resistência à compressão e reprodução de detalhes dos gessos foram utilizados e divididos em 4 grupos com: G1- temperatura de laboratório (25 ± 4ºC) no período de 2 horas; G2- temperatura de laboratório após 24 horas; G3- temperatura de laboratório após 7 dias e G4- microondas com potência de 800 W por 5 minutos após 2 horas. No Capitulo 2 foi avaliada a influência de diferentes potências de radiação do forno de microondas durante a secagem dos gessos sobre a alteração dimensional e resistência à compressão. Foram utilizados seis diferentes métodos de secagem e divididos em seis grupos: G1-temperatura ambiente no período de 2 horas; G2- temperatura ambiente no período de 24 horas; G3- temperatura ambiente no período de 7 dias; G4- microondas com potência de 200 W por 5 minutos; G5- microondas com potência média 400 W por 5 minutos e G6- microondas com potência alta 800 W por 5 minutos. Nos capítulos 1 e 2 para o ensaio de alteração dimensional linear foram confeccionadas amostras utilizando matriz metálica com entalhes de diferentes profundidades e distância entre as linhas de 2,5 mm. Em seguida, a superfície foi escaneada com resolução de 1200 dpi e analisada com software ImageTool 3.0. Para o ensaio de resistência à compressão foram confeccionados moldes de silicone polimerizada por condensação, a partir de uma matriz metálica cilíndrica medindo 20 mm de comprimento por 10 mm de diâmetro. Para o ensaio de reprodução de detalhes executada somente no capítulo 1, a análise foi feita na linha central da matriz reproduzida na superfície da amostra de gesso. Os dados foram submetidos à análise de variância (ANOVA) com dois fatores e as médias ao teste de Tukey com nível de 5% de significância. Capitulo 1: No G1, as três marcas comerciais apresentaram maiores níveis de expansão dimensional sendo diferentes estatisticamente entre os grupos 2, 3 e 4. Para o ensaio de resistência à compressão os gessos Elite Rock e Durone IV não apresentaram diferença estatística significante entre G2 e G4, exceto para Shera Premium não apresentando diferença entre G3 e G4. Os melhores índices de reprodução ocorreram para G3. Capítulo 2: Os valores de alteração dimensional para o gesso Elite Rock foram estatisticamente semelhantes entre G3 e G6 e entre G4,G5 e G2. O gesso Shera Premium apresentou maiores níveis de expansão para G1 em relação a G2, G3, G4, G5, G6. Para o gesso Durone IV o G5 apresentou os menos valores de expansão dimensional. Para as três marcas comerciais utilizadas, a desidratação em forno de microondas com potência de 200 W e em temperatura de laboratório após 7 dias promoveu resistência à compressão sem diferença estatística e significativamente maiores,com exceção do Shera Premium e Durone IV que produziram valores semelhantes com potência de 800 W e 400W respectivamente. Os gessos odontológicos tipo IV apresentaram melhora em suas propriedades com secagem em forno de microondas. A potência de 200 W a 800 W proporcionaram níveis de alteração dimensional similares aos desidratados em temperatura de laboratório após 24 horas e 7 dias. A potência de 200 W produz maiores valores de resistência à compressão para Elite Rock.
Abstract: The objective of this study was to assess the effect of drying laboratory temperature (25 ± 4 ° C) and in microwave oven on the physical properties of dental stone type IV: Rock Elite, Premium and Shera Durone IV. Plasters were proportionate and spatulate mechanically vacuum following the manufacturers recommendations and poured into the mold with the aid of mechanical vibrator. In Chapter 1 we evaluated the dimensional change, compressive strength and detail reproduction of plaster dried in a microwave oven and a temperature of the laboratory. Two different protocols of dehydration for tests of dimensional change, compressive strength and detail reproduction of plaster casts were used and divided into four groups: G1-temperature laboratory (25 ± 4 ° C) in 2 hours, G2- temperature laboratory after 24 hours, G3-temperature laboratory after 7 days and G4-microwave power of 800 W for 5 minutes after 2 hours. In Chapter 2 we evaluated the effects of different energy radiation from the microwave oven during the drying of plaster on the dimensional changes and compressive strength. We used six different methods of drying and divided into six groups: G1-room temperature within 2 hours; G2-room temperature within 24 hours; G3-temperature environment within 7 days: G4-microwave power of 200 W for 5 minutes and G5- average microwave power 400 W for 5 minutes, G6-high microwave power 800 W for 5 minutes. In chapters 1 and 2 for testing dimensional linear samples were prepared using metal matrix with notches of different depths and distance between lines of 2.5 mm. Then the surface was scanned at 1200 dpi and analyzed with software ImageTool 3.0. For testing the compressive strength silicone molds were prepared by condensation polymerized in cylindrical stainless steel mold measuring 20 mm by 10 mm in diameter. To test the reproduction of details performed only in chapter 1, the analysis was performed on the center line of the matrix reproduced on the sample surface of plaster. Data were subjected to analysis of variance (ANOVA) with two factors and the means with Tukey test at 5% level of significance. Chapter 1: In G1 of three commercial brands showed higher levels of dimensional expansion was statistically significant between groups 2,3 and 4. For testing the compressive strength gypsum Durone Elite Rock and IV showed no statistically significant difference between G2 and G4, except for Premium Shera no difference between G3 and G4. The highest rates of reproduction were to G3. Chapter 2: The values of dimensional change to the cast Elite Rock showed statistically similar values among and between G3 and G6, G4, G5 and G2. Gypsum Premium Shera had higher levels of expansion in G1 compared to G2, G3, G4, G5, G6. For plaster Durone IV G5 showed the least values of dimensional expansion. For the three trademarks used, drying in a microwave oven with a power of 200 W and temperature in the laboratory after 7 days promoted the compressive strength and not statistically significantly higher, except for the Premium and Shera Durone IV that produced similar values with power of 800 W and 400W respectively. Dental stone type IV showed improvement in their properties with drying in a microwave oven. The power of 200 W to 800 W gave similar levels of dimensional change in the dehydration temperature of the laboratory after 24 hours and 7 days. The power of 200 W produces higher values of compressive strength for Elite Rock.
Mestrado
Materiais Dentarios
Mestre em Materiais Dentários

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33

Foster, Jeffrey. "Synthesis, Properties, and Biology of Advanced H2S-Releasing Materials". Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/85401.

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Hydrogen sulfide (H2S) is an endogenously produced signaling gas involved in numerous cellular functions. At the appropriate concentration, exogenous administration of this gasotransmitter regulates vasodilation, promotes angiogenesis of endothelial cells, and generally exhibits beneficial effects as an anti-inflammatory and antioperoxidative agent. H2S is also capable of acting as a gaseous chemotherapeutic agent. Therefore, the therapeutic potential of exogenous delivery of H2S is vast. The delivery of H2S is complicated by its gaseous nature. Under physiologically relevant conditions, H2S is rapidly depleted from solution by oxidation and/or degassing. Therefore, direct exogenous delivery is difficult. To date, most studies have employed Na2S as a convenient H2S source. However, the rapid surge in H2S concentration upon Na2S dissolution followed by its rapid decline poorly mimics the sustained production of low concentrations of H2S that occurs in biological systems. We synthesized a library of S-aroylthiooximes (SATOs)—H2S-releasing compounds that more aptly mimic in vivo H2S concentrations. SATOs are synthesized via reaction of a S-aroylthiohydroxylamine and an aldehyde or ketone. SATOs release H2S in response to a thiol functionality. H2S release from SATOs could be controlled, with H2S release half-lives on the order of minutes to hours. SATO chemistry was utilized to prepare H2S-releasing polymers. Copolymers prepared using RAFT polymerization could be functionalized with SATOs with conversions > 99%, and these polymers released H2S on a similar timescale to our small molecule donors, confirming the viability of SATO formation as a post-polymerization modification strategy. SATO-functionalized polymer amphiphiles were prepared that self-assembled into micelles or vesicles based on their composition. H2S was released from these polymer assemblies more slowly than from the small molecules and statistical polymers. These H2S-releasing micelles were employed in in vitro cytotoxicity studies. H2S released from the micelles was found to be selectively toxic to human colon cancer cells compared with healthy fibroblasts. These polymeric micelle donors outperformed existing H2S donors in terms of their toxicity towards cancer cells. The observed enhanced toxicity was suspected to arise from the slow and sustained release of H2S from the micelles.
Ph. D.

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34

Hwang, Gyuweon. "Surface trap passivation and characterization of lead sulfide quantum dots for optical and electrical applications". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98741.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 113-119).
Quantum dots (QDs) are semiconductor nanocrystals having a size comparable to or smaller than its exciton Bohr radius. The small size of QDs leads to the quantum confinement effects in their electronic structures. Their unique optical properties, including a tunable emission from UV to IR, make QDs attractive in optoelectronic applications. However, further improvements in device performance are required to make them competitive. One well-known factor that presently limits the performance of QD thin film devices is sub-band-gap states, also referred to as trap states. For instance, trap states impair optical properties and device performance by providing alternative pathways for exciton quenching and carrier recombination. Chemical modification of QDs has been commonly used for passivating trap states and thereby improving QD devices. However, the influence of chemical modifications of ligands, QD surfaces, or synthetic routes on electrical properties of QD thin films is not sufficiently characterized. Suppressing the trap states in QD thin films is a key to improve the performance of QDbased optoelectronics. This requires fundamental understanding of trap state source, which is lacking in these materials. In this thesis, I pursue to find a systematic method to control density of trap states by exploring different characterization techniques to investigate trap states in QD thin films. These attempts provide insight to develop a rationale for fabricating better performing QD devices. This thesis focuses on the trap states in IR emitting lead sulfide (PbS) QD thin films, which have great potential for application in photovoltaics, light emitting diodes (LEDs), photodetectors, and bio-imaging. Previously, QD thin films are treated with different ligands to passivate trap states and thereby improve the device performance. Through my work, I pursued to unveil the electrical characteristics and chemical origin of trap states, and develop a strategy to suppress the trap states. First, I hypothesize that surface dangling bonds are a major source of trap states. An inorganic shell layer comprised of cadmium sulfide (CdS) is introduced to PbS QDs to passivate the surface states. Addition of CdS shell layers on PbS QDs yields an enhanced stability and quantum yield (QY), which indicates decreased trap-assisted exciton quenching. These PbS/CdS core/shell QDs have a potential for deep-tissue bio-imaging in shortwavelength IR windows of 1550-1900 nm. However, the shell layer acts as a transport barrier for carriers and results in a significant decrease in conductivity. This hinders the incorporation of the core/shell QDs in electrical applications. An improved reaction condition enables the synthesis of PbS/CdS QDs having a monolayer-thick CdS shell layer. These QDs exhibit QY and stability comparable to thick-shell PbS/CdS QDs. Incorporation of these thin-shell QDs improves external quantum efficiency of IR QD-LEDs by 80 times compared to PbS core-only QDs. In the second phase of my work, I explore capacitance-based measurement techniques for better understanding of the electrical properties of PbS QD thin films. For in-depth analysis, capacitance-based techniques are introduced, which give complementary information to current-based measurements that are widely used for the characterization of QD devices. Nyquist plots are used to determine the dielectric constant of QD films and impedance analyzing models to be used for further analysis. Mott-Schottky measurements are implemented to measure carrier concentration and mobility to compare PbS core-only and PbS/CdS core/shell QD thin films. Drive-level capacitance profiling is employed to characterize the density and energy level of trap states when QD films are oxidized. Lastly, I investigate the chemical origin of trap states and use this knowledge to suppress the trap states of PbS QD thin films. Photoluminescence spectroscopy and X-ray photoelectron spectroscopy show that standard ligand exchange procedures for device fabrication lead to the formation of sub-bandgap emission features and under-charged Pb atoms. Our experimental results are corroborated by density functional theory simulation, which shows that the presence of Pb atoms with a lower charge in QDs contributes to sub-bandgap states. The trap states generated after ligand exchange were significantly reduced by oxidation of under-charged Pb atoms using 1,4-benzoquinone. The density of trap states measured electrically with drive-level capacitance profiling shows that this reduces the electrical trap density by a factor of 40. In this thesis, I characterized trap states and showed that by suppressing the trap states we can modify the electrical properties of QD thin films, which influence the performance of QD devices directly. This work is a starting point to fully analyze the trap states in QD thin devices and thereby provides insight to design a rationale for fabricating better performing QD devices.
by Gyuweon Hwang.
Ph. D.

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35

Azhar, Bilal. "Experimental validation of the predicted emergent magnetism in diamagnetic cadmium sulfide (Cds) doped with boron". Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/132613.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, May, 2020
Cataloged from the official PDF version of thesis.
Includes bibliographical references (pages 41-42).
The large and persistent photoconductivity displayed by some semiconductors provides a way to control magnetism with light, through illumination-control of free carrier concentration and thereby magnetic interaction in dilute magnetic semiconductors. CdS is a wide band-gap semiconductor that displays large and persistent photoconductivity and is predicted to become magnetic when doped with certain dopants such as Boron[1]. In this work, we experimentally test the prediction of magnetic CdS:B, and lay groundwork for testing the hypothesis that magnetism can be controlled by photoconductivity. We make CdS:B nanoparticles by co-precipitation[2]. We use X-ray diffraction and plasma optical emission spectroscopy to quantify boron doping. We use magnetometry to confirm the presence of magnetic B.
by Bilal Azhar.
S.B.
S.B. Massachusetts Institute of Technology, Department of Materials Science and Engineering

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Sedlacek, Louise Mae. "Niobium sulfide : a study of the effects of pressure and substrate orientation on kinetics and structure". Thesis, Massachusetts Institute of Technology, 1987. https://hdl.handle.net/1721.1/127933.

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Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987.
Bibliography: leaf 36.
by Louise Mae Sedlacek.
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987.

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37

VERDEAU, TRUFFIER CAROLINE. "Influence des conditions d'elaboration sur la zone interfaciale de materiaux composites hautes performances a matrice thermoplastique". Paris, ENMP, 1988. http://www.theses.fr/1988ENMP0117.

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Microstructure et proprietesmecaniques de composites unidirectionnelles polyetherethercetone/ fibres carbone, sulfure de polyphenylene/fibres de carbone et polyetherimide/fibre de carbone. Influence de temps rapide, refroidissement lent etc. Essais mecaniques. Cohesion interne. Mise en evidence d'une phase "transcristalline". Modelisation du comportement viscolastique

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38

Roland, Paul Joseph. "Charge Carrier Processes in Photovoltaic Materials and Devices: Lead Sulfide Quantum Dots and Cadmium Telluride". University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1449857685.

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Watanabe, Joy Kimi. "Silicon preparation techniques for nucleation and growth studies of zinc sulfide deposited by atomic layer epitaxy". Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185938.

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Zinc sulfide with a direct bandgap of 3.6 eV is a potential candidate as blue-light emitting diodes and lasers. Initial growth of ZnS on Si(100) substrates by atomic layer epitaxy (ALE), a deposition technique in which film growth ideally proceeds in a 2-dimensional, layer-by-layer manner, has been investigated. The interaction between the first layer of atoms of the film and the substrate surface initiates film growth and affects the resulting structure. Work has focused on the effects of surface composition, (particularly on the role of sulfur) on the initial growth of ZnS on Si(100), and thus the chemical composition must be well controlled and characterized. Three methods have been used to process Si(100) substrates. The first was a wet chemical clean with either HF or H₂O passivation followed by a low temperature (700-800°C) anneal in UHV. The second processing method was ion sputter cleaning with a post-sputter anneal at 800-900°C. The third technique irradiated substrates held in UHV with a beam from a KrF excimer laser. Initial layers of ZnS (from Zn and H₂S) were then deposited onto processed substrates. Samples were characterized by in-situ angle resolved x-ray photoelectron spectroscopy (ARXPS) to determine the chemical composition of the surface and also the coverage and thickness of contamination and film layers. The main impurities on the surface were oxygen and carbon. The first two processing techniques had difficulty in either eliminating those impurities or caused additional contamination. Elimination of the impurities was achieved using excimer laser irradiation with a pre-dose of reactive gas. The substrate surface could also be chemically modified in a controlled manner using excimer laser irradiation. Deposition studies of initial sulfur and zinc layers onto the processed substrates determined the temperature during ALE growth should be held at 250-310°C. Uniform coverage of both sulfur and zinc was difficult to obtain, but experiments indicated sulfur adhesion improved with the presence of oxygen, and zinc adhesion improved when oxide or sulfide layers were present on the surface.

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40

Kappes, Mariano Alberto. "Evaluation of thiosulfate as a substitute for hydrogen sulfide in sour corrosion fatigue studies". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1322090561.

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41

Jones, Sean Charles. "Effects of the Methyltrimethoxysilane Coupling Agent on Phenolic and Miscanthus Composites Containing Calcium Sulfite Scrubber Material". OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/836.

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The purpose of this research is to test the effects of methyltrimethoxysilane coupling agent on composite material containing calcium sulfite obtained from the Southern Illinois Power Co-operative. This scrubber material and the miscanthus plant are of interest due to their use in coal burning power plants to reduce toxic emission. When calcium sulfate is passed through coal fire gas emissions it absorbs mercury and sulfur. In these composites it is used as filler to reduce cost. Miscanthus is a source of both cellulose reinforcement and some natural resin. This plant has low care requirements, little mineral content, useful energy return, and positive environmental effects. Under investigation is whether a post-cure procedure or a silane coupling agent will positively impact the composite. Hot pressing alone may not be enough to fully cure the phenolic. It is hoped that the silane will increase the strength characteristics of the composite by enhancing adhesion between the calcium sulfite and phenolic resin. Possible effects on the miscanthus by the silane will also be tested. Phenolic is being utilized because of its recycling and biodegradable properties along with cost effectiveness in mass production. Composite mechanical performance was measured through 3-point bending to measure flexural strength and strain at breakage. A dynamic mechanical analyzer (DMA) was used to find thermomechanical properties. The post-cure was found to be effective, particularly on the final composite containing silane. When methyltrimethoxysilane was added to the miscanthus prior to fabrication, it was found to reduce flexural strength and density. However the addition of methyltrimethoxysilane to the calcium sulfite altered thermo-mechanical properties to a state more like pure phenolic, with added flexibility and thermal stability.

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42

Júnior, Antonio Carlos Roveda. "Reatividade química de um novo nitrosilsulfito complexo trans-[Ru(NH3)4(isn)(N(O)SO3)](PF6), e desenvolvimento de filmes de amido doadores de óxido nítrico". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/75/75135/tde-26072016-144608/.

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Na busca por novos materiais doadores de óxido nítrico (NO), o presente trabalho descreve o desenvolvimento de um filme à base de amido de mandioca, no qual foi incorporado um nitrosilo complexo de rutênio, e o estudo da liberação de NO nesse material. O nitrosilo complexo trans-[Ru(NH3)4(isn)NO](BF4)3 (RuNOisn; isn = isonicotinamida) apresenta a propriedade de liberar NO de forma controlada, por meio de fotólise (λirr = 310-370 nm) e de redução química. A incorporação desse complexo em filmes de amido foi realizada em condições brandas, resultando em um novo material para o armazenamento e liberação de NO, designado como CSx-RuNOisn. Os ensaios espectroscópicos indicaram que a esfera de coordenação do complexo RuNOisn permaneceu inalterada durante a produção dos filmes. A exposição de CSx-RuNOisn à luz (λirr = 355 nm) levou à liberação de NO e provavelmente à formação do fotoproduto trans [RuIII(NH3)4isn(H2O)]3+ no filme. A reação desse aquocomplexo de rutênio(III) com solução aquosa contendo nitrito de sódio regenerou o complexo de partida, RuNOisn. A identificação e quantificação do NO liberado durante a fotólise foi efetuada por meio da reação com oximioglobina. Durante o tempo de irradiação de 17 minutos, foram liberados 5,02 ± 0,12 μM de NO (10, 04 ± 0,24 nmol NO em 2 mL). Os ensaios de liberação de NO desencadeada por redução foram realizados utilizando-se L-cisteína como redutor. O fluxo de NO liberado a partir da reação com cisteína perdurou por mais de 7 horas, alcançando-se concentrações fisiologicamente relevantes, com fluxo médio de 1,9 pmol NO s-1 cm-2 de filme. Esse valor é comparável àquele produzido por células endoteliais, em que o fluxo de NO é de 1,67 pmol s-1 cm-2. Os resultados preliminares de degradação dos filmes in vivo sugerem que o material foi degradado pelo organismo em 30 dias. Todos os resultados alcançados sugerem que o filme CSx-RuNOisn é um candidato promissor para aplicações em meio biológico. Um novo complexo de rutênio contendo o ligante nitrosilsulfito (N(O)SO3 -) foi isolado, trans [Ru(NH3)4(isn)(N(O)SO3)](X) (isn = isonicotinamida, X = PF6- ou SiPF6 2-), e a sua estrutura cristalina determinada por difração de raio-X. A síntese desse complexo foi realizada por meio da reação entre trans-[Ru(NH3)4(isn)(NO)]3+ e íons sulfito (SO32-). O ataque nucleofílico do SO32- ocorreu no nitrogênio do ligante nitrosônio (NO) coordenado ao centro metálico de rutênio ([Ru-NO+]), originando o ligante O=N-SO3-: [RuNO+]3+ + SO32- →[Ru(N(O)SO3)]+. Observou-se que em meio aquoso, no intervalo de pH de 7,4 a 5,2 o complexo trans [Ru(NH3)4(isn)(N(O)SO3)]+ é estável, e a velocidade de decomposição (labilização do ligante isn) variou de k = 0,86 a 3,07 × 10-5 s-1. Em soluções mais ácidas (tampão ácido acético/acetato pH 4,2, 3,9, ou 1,0 M ácido trifluoroacético) o complexo trans-[Ru(NH3)4(isn)(N(O)SO3)]+ decompõe-se formando o respectivo nitrosilo complexo trans- [RuII(NH3)4(isn)NO+]3+. A reação do íon trans-[Ru(NH3)4(isn)(N(O)SO3)]+ com íons hidróxido (OH-) dá origem ao respectivo nitro complexo trans-[Ru(NH3)4(isn)(NO2)]+, que foi caracterizado por RMN de 15N e por espectroscopia eletrônica. As constantes de velocidade para essa reação são k = 6,16 ± 0,22 M-1 s-1 à T = 25oC, e k = 2,15 ± 0,07 M-1 s-1 à T = 15oC. A reação entre o nitrosilo complexo trans [RuII(NH3)4(isn)NO+]3+ e íons OH- também resulta na formação do nitro complexo trans-[Ru(NH3)4(isn)(NO2)]+. Neste caso, a constante de velocidade foi estimada entre k = 47-58 M-1 s-1 à T = 25oC, e o valor obtido experimentalmente à T = 15oC foi de k = 10,53 ± 0,29 M-1 s-1. O espectro eletrônico do íon complexo trans [Ru(NH3)4(isn)(N(O)SO3)]+ em meio aquoso apresentou uma banda larga com λ max = 362 nm (ε ∼6000 M-1 cm-1), atribuída por cálculos teóricos às seguintes transições: transferência de carga do metal para o ligante (TCML) Ru → N(O)SO3 e Ru → isn, e também d → d. Os ensaios preliminares de fotólise (λ irrad = 355 nm) do complexo trans[Ru(NH3)4(isn)(N(O)SO3)](PF6) em solução de tampão fosfato (pH 7,4) sugerem a formação das seguintes espécies nos intervalos iniciais de fotólise: i) NO, ii) SO3 •-, e iii) isn (labilizado do complexo). O mecanismo para a formação desses produtos ainda está sob investigação.
Aiming the production of new nitric oxide releasing materials (NORM), this work reports the development of a cassava starch based film, in which a ruthenium nitrosyl complex was impregnated, and evaluate the NO release from this film. Ruthenium nitrosyl complex trans-[Ru(NH3)4(isn)NO](BF4)3 (RuNOisn; isn = isonicotinamide) is able to release NO in a controlled manner through both photolysis (λirr = 310-370 nm) and chemical reduction. The incorporation of such complex into the starch-based films was performed under mild conditions, yielding a new material able to store and release NO, abbreviated as CSx-RuNOisn. Spectroscopic analysis of CSx-RuNOisn indicated that the coordination sphere of RuNOisn remained intact during film production. Exposure of CSx-RuNOisn to long wave UV-light (λirr = 355 nm) leads to NO release and likely to the formation of the paramagnetic photoproduct trans-[RuIII(NH3)4isn(H2O)]3+ in the film. Reaction of this aquoruthenium(III) complex with aqueous nitrite regenerates RuNOisn in the film. Delivery of NO upon photolysis of CSx-RuNO isn was verified and quantified by trapping with oxymyoglobin. The calculated concentration of NO released from the film was 5.02 ± 0.12 μM (10.04 ± 0.24 nmol NO in a 2 mL) after approximately 17 min of irradiation (500 laser pulses at 2 s intervals). Moreover, NO release upon chemical reduction was carried out using L-cysteine as a reductant. Cysteine-mediated NO delivery from CSx-RuNOisn persisted for more than 7 h, during which physiologically relevant NO concentrations were liberated (average flux of 1.9 pmol NO s-1 cm-2 of film). This value is comparable to that produced by endothelial cells (1.67 pmol s-1 cm-2). Preliminary results about the biodegradation of the films in vivo suggest that the films were completely absorbed by the organism in a period of 30 days. These results suggest that CSx-RuNOisn is a promising candidate for use in biological applications. A new nitrosylsulphito complex bearing the ligand (N(O)SO3-) was isolated, trans-[Ru(NH3)4(isn)(N(O)SO3)](X) (isn = isonicotinamide, X = PF6- or SiPF6-), and its structure was determined by X-Ray crystallography. This complex was obtained by the reaction between trans-[Ru(NH3)4(isn)(NO)]3+ and sulfite ions (SO32-). X-Ray results confirmed that the nucleophilic attack of the sulphite anion (SO32-) was on the nitrogen atom of the nitrosyl ligand (NO) coordinated to the ruthenium center ([Ru-NO+]), yielding the ligand O=N-SO3-: [RuNO+]3+ + SO32- → [Ru(N(O)SO3)]+. Complex trans- [Ru(NH3)4(isn)(N(O)SO3)]+ is stable in aqueous solution from pH 7.4 to 5.2, and the decomposition rates (k) (due to the isn labilization) are in the range of k = 0.86-3.07 × 10-5 s-1. In more acidic conditions, (acetate buffer pH 4.2, 3.9, and trifluoroacetic acid solution 1.0 M) complex trans-[Ru(NH3)4(isn)(N(O)SO3)]+ is converted into the respective nitrosyl trans-[RuII(NH3)4(isn)NO+]3+. Reaction of trans-[Ru(NH3)4(isn)(N(O)SO3)]+ and hydroxide ions (OH-) yielded the nitro complex trans-[Ru(NH3)4(isn)(NO2)]+, which was characterized by 15N NMR and electronic spectroscopy. Rate constants for such reaction are k = 6.16 ± 0.22 M-1 s-1 at 25oC, and k = 2.15 ± 0.07 M-1 s-1 at 15oC. In the case of complex trans-[RuII(NH3)4(isn)NO+]3+, its reaction with OH- also yield the nitro complex trans-[Ru(NH3)4(isn)(NO2)]+. The estimated rate constant for such reaction was k = 46.9-57.6 M-1 s-1 at 25oC, and the experimental value obtained at 15oC was k = 10.53 ± 0.29 M-1 s-1. The ion complex trans-[Ru(NH3)4(isn)(N(O)SO3)]+ showed an intense and broad band at 362 nm (ε∼6000 M-1 cm-1) in aqueous solutions, which was assigned by DFT calculations to the following transitions: metal to ligand charge transfer (MLCT) Ru→N(O)SO3 and Ru→isn, and d→d as well. Preliminary photolysis assays (λirrad = 355 nm) performed with complex trans-[Ru(NH3)4(isn)(N(O)SO3)](PF6) in phosphate buffer solution (pH 7,4) suggests that the following species have been formed (in the initial photolysis period): i) NO, ii) SO3•-, and iii) isn (labilized). The whole mechanism to yield such products is still under investigation.

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43

Oyetunde, Temidayo Timothy. "Novel precursors for chalcogenide materials". Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/novel-precursors-for-chalcogenide-materials(db26161b-217b-4ee1-9767-d8fb82dc608b).html.

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Metal chalcogenides (sulfides, selenides and tellurides) are materials of current interest due to their peculiar properties such as optoelectronic, magnetooptic, thermoelectric and piezoelectric displays. These semiconducting materials have potential applications in solar cell devices, infrared detectors and ambient thermoelectric generators. Previously, these materials have been deposited by multiple-source precursor route with several problems associated with this technique. This work describes the synthesis of metal complexes (Zn, Cd, Fe, Ni, Pd, Pt) using the imidodichalcogenodiphosphinate ligand (Woollins ligand). Their thermal decomposition together with structural and spectroscopy analysis was carried out. The complexes were used as single source precursors for the deposition of cadmium selenide, cadmium phosphide, cadmium sulfide, zinc selenide, iron selenide and the tellurides of nickel, palladium, platinum and iron as thin films and powders. These were deposited by AACVD and pyrolysis. The deposited thin films and powders were characterised by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), X-ray photoelectron spectroscopy (XPS) and superconducting quantum interference device (SQUID). The cadmium complexes [Cd{iPr2P(Se)NP(Se)iPr2}2] and [Cd{iPr2P(S)NP(Se)iPr2}2] deposited the mixture of hexagonal CdSe and monoclinic Cd2P3 films at the flow rate of 160 sccm at 475 and 500 °C. At the flow rate of 240 sccm, only hexagonal CdSe was deposited from [Cd{iPr2P(Se)NP(Se)iPr2}2] at all temperatures. Hexagonal CdS and the mixture of orthorhombic Cd6P7/cubic Cd7P10 were deposited from [Cd{iPr2P(S)NP(S)iPr2}2]. The zinc complexes [Zn{iPr2P(Se)NP(Se)iPr2}2] and [Zn{iPr2P(S)NP(Se)iPr2}2] both deposited cubic ZnSe at all temperatures with the flow rates of 160 and 240 sccm. The iron complexes [Fe{(SePPh2)2N}2] and [Fe{(SePPh2NPPh2S)2N}2] deposited orthorhombic FeSe2 mixed with monoclinic Fe3Se4 by pyrolysis at 500 and 550 °C. An unresolved pattern was observed from the complex [Fe{(SePPh2NPPh2S)2N}2] at 550 °C. XPS analysis of the deposited FeSe2 showed the surface oxidation of the material, while the magnetic measurements on the sample using SQUID confirmed its ferromagnetic properties. The telluride complexes of nickel, palladium, platinum and iron deposited the metal telluride respectively as: hexagonal NiTe, hexagonal PdTe, hexagonal PtTe2 (mixed with rhombohedral PtTe) and hexagonal FeTe2. Conductivity studies on NiTe and PdTe revealed them to be insulators, while the magnetic measurements on FeTe2 indicated its antiferromagnetic behaviour.

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Monahan, Bradley Michael. "Synthesis and Characterization of Phase-pure Copper Zinc Tin Sulfide (Cu2ZnSnS4) Nanoparticles". University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1404732007.

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45

Sinsermsuksakul, Prasert. "Development of Earth-Abundant Tin(II) Sulfide Thin-Film Solar Cells by Vapor Deposition". Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10987.

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To sustain future civilization, the development of alternative clean-energy technologies to replace fossil fuels has become one of the most crucial and challenging problems of the last few decades. The thin film solar cell is one of the major photovoltaic technologies that is promising for renewable energy. The current commercial thin film PV technologies are based on $Cu(In,Ga)Se_2$ and CdTe. Despite their success in reducing the module cost below $1/Wp, these absorber materials face limitations due to their use of scarce (In and Te) and toxic (Cd) elements. One promising candidate for an alternative absorber material is tin monosulfide (SnS). Composed of cheap, non-toxic and earth-abundant elemental constituents, SnS can potentially provide inexpensive PV modules to reach the global energy demand in TW levels. Because of the high volatility of sulfur and various oxidation states of tin, non- stoichiometric chemical composition, traces of other phases $(i.e. Sn, Sn_2S_3, and SnS_2)$, and elemental impurities (e.g. oxygen) are usually observed in SnS films obtained from various reported deposition techniques. First, we present a process to prepare pure, stoichiometric, single-phase SnS films from atomic layer deposition (ALD). The as-deposited SnS films exhibit several attractive properties, including suitable energy band gaps $(E_{g,}~ 1.1 – 1.3 eV)$, a large absorption coefficient $(\alpha > 10^4 cm^{˗1})$, and a proper carrier concentration $([p] ~ 10^{15} – 10^{16} cm^{˗3})$. Then, heterojunction solar cells were fabricated from p-type SnS and n-type zinc oxysulfide (Zn(O,S)). A record high active-area efficiency of 2.46 % was achieved via conduction band offset engineering by varying the oxygen-to-sulfur ratio in Zn(O,S). Finally, we address two approaches potentially used for improving a device efficiency of the SnS solar cell. First, via doping to create an n-type SnS, a p-n homojunction device could be made. We present the processes and the results of doping SnS films with antimony and chlorine, potential n-type dopants. Second, by post-deposition heat treatment, an improvement in the transport properties of SnS film can be achieved. We discuss the effect of temperature and an annealing ambient $(N_2, H_2S$, and sulfur) on grain growth and the electrical properties of annealed SnS films.
Chemistry and Chemical Biology

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46

Hartman, Katherine Ph D. Massachusetts Institute of Technology. "Annealing for intrinsic point-defect control and enhanced solar cell performance : the case of H₂S and tin sulfide (SnS)". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98163.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 163-171).
This thesis explores the possibility of tin monosulfide (SnS) as a new and promising solar cell absorber material. Out of many other Earth-abundant binary semiconductors, it was selected for study because it has a strong absorption coefficient, high majority carrier mobility, and a promising initial report of a 1.3 % solar cell. Tin sulfide does not have the toxicity or scarcity issues that will plague CdTe and CIGS thin film manufacturers as the PV industry grows toward the terawatt level. Growth of SnS is explored using RF sputtering and thermal evaporation. Thermal evaporation yielded phase pure films and a SnS solar cell device stack was developed using a ZnOxSy film as the n-type buffer layer. It is hypothesized that annealing in H₂S/H₂ gas mixtures will improve film morphology, control majority carrier concentration and reduce sulfur vacancy mid-gap states. Using the Kröger-Vink defect equilibria model of defect concentrations and DFT-calculated enthalpy of formations for intrinsic defects, predictions are made for how a particular anneal temperature and sulfur partial pressure will affect the carrier concentration in SnS. A custom H₂S/H₂ gas annealing furnace was built to explore the range of annealing parameters that are predicted to be promising for SnS photovoltaic development. Results have found that neither of these two models are adequate to explain the observed change in carrier concentration after annealing the thin films. However, results have shown the ability to manipulate majority carrier concentration in SnS thin films by up to 2 orders of magnitude with short (<1 hour) anneals. Certain annealing conditions are also found to greatly increase grain growth. The results of these improved annealing parameters and enlarged grains are seen in a 98.4 % relative efficiency improvement from as-deposited to annealed thermally evaporated SnS solar cells. A new and unique experimental tool has been created and a framework established for further research of intrinsic point defects in SnS material. Research using these new tools will yield even greater efficiency increases for the Earth-abundant PV material, tin sulfide.
by Katherine Hartman.
Ph. D.

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47

Ling, Yuanbing 1970. "Direct preparation of alpha-calcium sulfate hemihydrate from sulfuric acid". Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84283.

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In this work, the crystallization of alpha-calcium sulfate hemihydrate in sulfuric acid solution and the correlation between its properties and preparation conditions by reaction of sulfuric acid with lime (CaO) have been thoroughly investigated. The research involved the study of conversion-dissolution of calcium sulfate dihydrate in H2SO4 solution, the measurement of solubilities, thermo-dynamic calculations and the preparation of alpha-CaSO4 ·0.5 H2O via different methods of reactive mixing of H2SO4 and CaO. It was found that the calcium sulfate solids can saturate the sulfuric acid solutions in only 5 minutes. The solubility of calcium sulfate hemihydrate in 0--3.0M H 2SO4 solution at 100°C was experimentally determined and thermodynamic calculations with the aid of FactSage and OLI have led to establishment of the phase diagram for the CaSO4-H2SO 4-H2O system. An operating window has been determined in terms of H2SO4 concentration, temperature and time within which alpha-hemihydrate can be produced by reaction of lime with H 2SO4. This window is defined as 0.6--1.1M H2SO 4 (steady-state concentrations), 98--105°C and 1 hour retention time. Dihydrate was found to form as intermediate phase quickly converting to hemihydrate. The kinetics of conversion depends on the acidity level.
For the standard preparation procedure of adding lime into hot sulfuric acid, alpha-hemihydrate grows in the c-axis direction much more rapidly than in other directions ending in the form of fine needle crystals. Also, independent of the shape of the seed particles, the resultant crystals of hemihydrate are needle-shaped, which suggests a "dissolution-recrystallization" mechanism. Upon prolonged equilibration in their acid-preparation solution hemihydrate needle-shape crystals become fibrous and eventually convert to anhydrite. It is believed that uptake of SO42- instead of Ca2+ is the rate-determining step in the hemihydrate crystallization process. The hot SO42--rich environment rendered most of the additives (particularly organic) tried ineffective. Trivalent cations such as Fe3+ and Al3+, are the only ones found to modify the crystal morphology from needle-shape to small "grain" type morphology.
Slow addition of H2SO4 solution to slaked lime - reverse procedure was found to favor the production of alpha-hemihydrate with column-shaped as opposed to needle-shaped crystal morphology within otherwise the same operating window, 0.6--1.1M H2SO4. Preliminary assessment of the properties of the alpha-hemihydrate materials synthesized in this work showed them to compare satisfactorily with other materials produced by conversion of dihydrate to hemihydrate.

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48

Mayer, Matthew T. "Ionic and electronic behaviors of earth-abundant semiconductor materials and their applications toward solar energy harvesting". Thesis, Boston College, 2013. http://hdl.handle.net/2345/3034.

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Thesis advisor: Dunwei Wang
Semiconductor devices offer promise for efficient conversion of sunlight into other useful forms of energy, in either photovoltaic or photoelectrochemical cell configurations to produce electrical power or chemical energy, respectively. This dissertation examines ionic and electronic phenomena in some candidate semiconductors and seeks to understand their implications toward solar energy conversion applications. First, copper sulfide (Cu₂S) was examined as a candidate photovoltaic material. It was discovered that its unique property of cation diffusion allows the room-temperature synthesis of vertically-aligned nanowire arrays, a morphology which facilitates study of the diffusion processes. This diffusivity was found to induce hysteresis in the electronic behavior, leading to the phenomena of resistive switching and negative differential resistance. The Cu₂S were then demonstrated as morphological templates for solid-state conversion into different types of heterostructures, including segmented and rod-in-tube morphologies. Near-complete conversion to ZnS, enabled by the out-diffusion of Cu back into the substrate, was also achieved. While the ion diffusion property likely hinders the reliability of Cu₂S in photovoltaic applications, it was shown to enable useful electronic and ionic behaviors. Secondly, iron oxide (Fe₂O₃, hematite) was examined as a photoanode for photoelectrochemical water splitting. Its energetic limitations toward the water electrolysis reactions were addressed using two approaches aimed at achieving greater photovoltages and thereby improved water splitting efficiencies. In the first, a built-in n-p junction produced an internal field to drive charge separation and generate photovoltage. In the second, Fe₂O₃ was deposited onto a smaller band gap material, silicon, to form a device capable of producing enhanced total photovoltage by a dual-absorber Z-scheme mechanism. Both approaches resulted in a cathodic shift of the photocurrent onset potential, signifying enhanced power output and progress toward the unassisted photoelectrolysis of water
Thesis (PhD) — Boston College, 2013
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

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49

Lemoine, Pascale. "Combinaisons ternaires soufrées formées par l'europium et un second métal : exemples de dérivés de l'europium à valence mixte; synthèse, structures et propriétés physiques". Paris 6, 1986. http://www.theses.fr/1986PA066416.

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L'études des combinaisons ternaires soufrées formées par l'europium et un second métal conduit dans de nombreux cas a des composes qui ne contiennent que de l'europium divalent, tels que Eu3Sb4S9, EuLn2S4 (Ln: Dy—Lu, Y) et Eu1,1Bi2S4. . Dans ces trois composes Eu (ii) présente un environnement 8-prismatique et le second métal, un environnement octaédrique. Dans Eu3Sb4S9, le doublet 5s2 non-engagé de Sb (iii) crée de larges tunnels au sein de la structure. Les composés EuLn2S4 ont une structure de type CaFe2O4. Le réseau du composé Eu1, 1Bi2S4 contient de larges canaux partiellement occupés par des atomes d'europium divalent d'environnement 9-prismatique. Dans quelques cas, lorsque le second métal est susceptible de stabiliser partiellement la valence iii de l'europium, des composés à valence mixte sont obtenus, tels Eu2BiS4 et Eu2CuS3 qui contiennent les deux valences de l'europium, mais de façon différenciée par des sites cristallographiques distincts. Dans Eu2BiS4, Eu(ii) a un environnement 7-prismatique, Eu (iii), 7-octaedrique et Bi (iii), octaédrique. Dans Eu2CuS3, Eu (ii) a un environnement 8-prismatique, Eu(iii), octaédrique et Cu (i),tétraédrique. Dans ces deux composés, il existe des feuillets perpendiculaires à l'axe b, de formule Eurs(3) (r = Cu ou Bi). Tous ces composés sont paramagnétiques et semi-conducteurs. Cette étude met en évidence la stabilité de l'état divalent de l'europium dans les sulfures et la nécessité pour obtenir des composes à valeur mixte ou intermédiaire de l'europium, de modifier les conditions d'études, telles que la température et la pression.

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50

HARAKUNI, PRASAN B. "MECHANISTIC INVESTIGATION OF THE SULFIDE LAYER FORMED AT THE RUBBER-STEEL TIRE CORD INTERFACE". University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1172866725.

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