To see the other types of publications on this topic, follow the link: Reactions in the solid state.
Dissertations / Theses on the topic 'Reactions in the solid state'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Reactions in the solid state.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Brown, Michael Ewart. "Reactions in the solid state." Link to this resource, 2005. http://eprints.ru.ac.za/252/.
Full textAbstract:
Thesis (D.Sc. (Chemistry)) - Rhodes University, 2006.[Appendix]. Dedication - Acknowledgements - Curriculum vitae - Biographical notes - Publication list - Introduction to my research - Commentary-books - Commentary-research papers - Conclusions.
2
Brown, Michael Ewart. "Reactions in the solid state." Thesis, Rhodes University, 2006. http://hdl.handle.net/10962/d1015762.
Full textAbstract:
I have chosen the title for this thesis, "Reactions in the Solid State", for two reasons: Firstly, it is broad enough to cover all of my areas of research, which have been: • Effects of irradiation on solids (PhD topic) • Silver refining (while at the Chamber of Mines) • Kinetics of decomposition of solids (with Dr A.K. Galwey and various others) • Techniques of thermal analysis • Pyrotechnic delay systems (with support from AECI Explosives) • Thermal and photostability of drugs (with Prof B.D. Glass) and, secondly, it was the title of the very successful book co-authored by Drs Andrew Galwey, David Dollimore and me. A large part of my research has been involved in the writing and editing of books, so these are covered in a separate commentary, while commentary on the more than 100 papers to which I have contributed forms the main part of this compilation. It is hoped that the electronic format will enable ready access of to all aspects of my research, including electronic versions of the original papers. The reader will need a copy of Adobe Acrobat Reader to access these.
3
Lusi, Matto. "Solid state reactions in crystal engineering." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508123.
Full text
4
Vitorica, Inigo. "Solid state supramolecular chemistry : gas-solid reactions and intermolecular interactions." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/3926/.
Full text
5
Heffelfinger, Jason Roy. "Ceramic surfaces, interfaces and solid-state reactions /." Diss., ON-CAMPUS Access For University of Minnesota, Twin Cities Click on "Connect to Digital Dissertations", 1997. http://www.lib.umn.edu/articles/proquest.phtml.
Full text
6
Laird, Rebecca Christine. "Functional diversity in templated solid state reactions." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/1347.
Full textAbstract:
Solid-state chemistry presents itself as a rapidly growing field of materials chemistry. When compared to solution phase chemistry, solid-state chemistry offers the potential for significant benefits to the researcher including better stereoselectivity and product selectivity as well as the ability to synthesize products that may be difficult to obtain in the solution phase. The solid-state [2+2] photocycloaddition reaction, as first demonstrated by Schmidt, exemplifies these benefits through the selective photoreaction of olefins. Within these benefits however, certain limitations such as unpredictable crystal packing and limited functional group diversity remain, limiting the applications and expansion of solid-state chemistry.
It has been our goal to overcome these limitations through the use of the template method, crystal engineering, and post-synthetic modification (PSM) techniques. As first developed by MacGillivray, the template method relies on supramolecular interactions within cocrystals to guide photostable olefins into photoacitve assemblies. While it does not provide overall control of crystal packing, it guides local packing within the crystal. Our work has focused on utilizing both the template method, as well as PSM techniques to develop a library of analogous, yet functionally diverse molecules to undergo the [2+2] photocycloaddition reaction in the solid state. To this end, we have performed the click reaction to generate a library of molecules and incorporate the 1,4 disubstituted 1,2,3 triazole ring within our olefinic systems. Our efforts to study the triazole ring as a functional group in the solid state and also to perform the [2+2] photocycloaddition on a click-derived molecule will be described within this thesis.
Additionally, we have sought to expand the template method through the development of the first non-covalently templated intramolecular [2+2] photocycloaddition reaction in the solid state. Our work towards understanding the effects on crystal packing due to functional group diversity on a template, as well as the design of a novel molecule able to undergo an intramolecular [2+2] photocycloaddition reaction will be presented in this thesis.
7
Clelland, Iain C. "Solid-state rearrangement reactions of acylated aminopyrazoles." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/14565.
Full textAbstract:
The thermally induced solid-state rearrangement reactions of acylated aminopyrazoles were investigated. The precursors were generally formed by mono-acylating 3-aminopyrazole with an acid chloride in solution, and obtaining an isolated individual isomer by dry fresh chromatography. The rearrangements proceed under remarkably mild conditions (at room temperature or below), at temperatures of up to 100°C below the melting point. The reaction can still occur in the melt but not to any extent in solution. The reaction proceeds in all cases from the 1 (r) 3-isomer and from the 2 (r) 3-isomer and for many acyl substituents the rearrangements occur in tandem with the 2-isomer rearranging to the 1- and 3-isomers concurrently. However the migration of the acyl group from the 1 (r) 2-isomer has not been seen as might have be expected. The solid-state rearrangements work for a wide range of acyl substituents, even occurring when the structure of the pyrazole ring is altered or when different ring systems are used (e.g. indazoles). The half-lives of reaction for individual acyl substituents and isomers vary from hours to years. The tendency is for the rearrangement of the 2 (r) 3-isomer to be faster than its counterpart 1 (r) 3, though there are exceptions to this. The overall conclusion is that, having investigated a wide range of migrating acyl substituents, neither steric, nor electronic, nor melting point factors, are responsible for controlling the rate of this solid-state rearrangement. A study of the crystal structures of a range of structurally diverse 1- and 2-acyl-3-aminoipyrazoles reveals that a non-Topochemical mechanism is operating and so the reactions are thought to take place at crystal defects. The reaction is observed not to occur throughout the bulk of the crystal when observed under a microscope and in addition the integrity of the crystal is not maintained throughout the reaction.
8
Khawam, Ammar. "Application of solid-state kinetics to desolvation reactions." Diss., University of Iowa, 2007. http://ir.uiowa.edu/etd/170.
Full text
9
Purser-Hallard, Beatrice. "Kinetics and mechanisms of solid-state phase transitions and reactions." Thesis, Open University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422026.
Full text
10
Sweeney, D. M. "Photoelectron spectroscopic studies of reactions at aluminium surfaces." Thesis, Bucks New University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371230.
Full text
11
Gray, Struan Marc. "Scanning tunnelling microscopy of metal reactions with silicon." Thesis, University of Cambridge, 1992. https://www.repository.cam.ac.uk/handle/1810/265404.
Full textAbstract:
I present the results of several investigations into the reactions that take place behveen transition metals and the silicon (111) surface. The ability of the STM to measure physical and electronic structure on an atomic-scale permitted the detailed study of several new phenomena. The reactions divide into hvo categories: a regime where less than a monolayer of metal was present; and a second one where enough metal was deposited on the surface to form a silicide. Silicides of cobalt and iron were grown from thin evaporated metal films, and the structures seen with the STM agreed \vith the results obtained previously by other groups using different techniques. In addition, two new effects were observed. Strongly localised noise, confined to the boundaries between iron silicide grains, indicated that the band structure was being distorted in these regions. Also, a new structure was discovered, involving the growth of a pure silicon overlayer on the surface of the silicide at high temperatures. The layer is thin enough for the interface between it and the buried silicide to perturb the surface, permitting details of the buried interface and its misfit dislocation netv.;ork to be inferred. Tungsten, tantalum and cobalt all adopted similar structures at submonolayer coverages. Domains of 7x7 reconstructed silicon were separated by surface dislocations, with metal islands at the nodes of the dislocation nehvork. The interiors of the islands were comprised of a 1ich variety of reconstructions, stabilised by the presence of the metal atoms. Areas of 5x5, 7x7, 9x9, 2x2, c(4x2). and ,/3xv3-R30 reconstructed surface could all be seen; and, for the first time, an l lxl 1 reconstruction was found. To set this ,vork in perspectiYe, a description of the clean silicon (111) surface and its 7x7 reconstruction is also given, and the theoretical and technological background to the microscope's operation discussed.
12
Lotnyk, Andriy, Stephan Senz, and Dietrich Hesse. "BaTiO 3 formation by solid state reactions on rutile single crystals." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196044.
Full text
13
Eckold, Götz. "Time resolved phonons as a microscopic probe for solid state reactions." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186610.
Full text
14
Eckold, Götz. "Time resolved phonons as a microscopic probe for solid state reactions." Diffusion fundamentals 12 (2010) 19, 2010. https://ul.qucosa.de/id/qucosa%3A13871.
Full text
15
Lotnyk, Andriy, Stephan Senz, and Dietrich Hesse. "BaTiO 3 formation by solid state reactions on rutile single crystals." Diffusion fundamentals 2 (2005) 51, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14384.
Full text
16
Monsegue, Niven. "Solid State Synthesis of Bulk Amorphous Ni – 50AT% Ti Alloy." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/31129.
Full textAbstract:
The mechanical alloying (MA) process and hot isostatic pressing (HIP) were used to synthesize bulk amorphous Ni-Ti alloy as an alternative to the traditional methods of casting multi-component metallic alloys. Samples milled cryogenically for 10 hours provided a homogeneous lamella structure with spacing of 30-110 nm. X-ray diffraction and transmission electron microscopy studies indicated that there were alloying and amorphous phase within the layers of the MA powder prior to annealing or HIPing. The amount of amorphous phase increased with time when the milled powder was annealed at a constant temperature and with temperature when annealing time was held constant. The microhardness of the powder correspondingly increased with the amount of amorphous formed in the powders. The HIPing of the MA powder produced a close to 100% amorphous compact with some dispersion of nanocrystals in the amorphous matrix. However, densification was not achieved.Master of Science
17
Oburn, Shalisa M. "Applications in supramolecular chemistry and solid-state reactivity: template-mediated solid-state reactions, dynamic covalent chemistry, mechanochemistry, and pharmaceutical co-crystals." Diss., University of Iowa, 2019. https://ir.uiowa.edu/etd/7004.
Full textAbstract:
Supramolecular chemistry and crystal engineering seek to control molecular packing in the solid state to influence the physical and chemical properties of crystalline solid materials. A goal of supramolecular chemistry that seeks to control molecular packing in the solid state focuses on exploiting non-covalent interactions to assemble molecules into desirable arrangements. Strategies implemented to control molecular packing rely on strong, directional interactions such as hydrogen bonding, halogen bonding, and metal coordination to direct localized arrangement of molecules in solids. In this context, small molecules can be used as linear templates in co-crystals to assemble reactive alkenes into specific geometries allowing reactivity in the solid state. A linear template method has been used to achieve [2+2] photocycloadditions of discrete assemblies containing alkenes to afford cyclobutanes in high stereospecificity and in quantitative yield.
Herein, we describe the use of a nonlinear template, in the form of 1,4-butynediol (1,4-bd), to pre-organize alkenes in the solid state. The nonlinear template of 1,4-bd hydrogen-bonds to the alkene 1,2-bis(N-pyridyl)ethene (where N = 3 or 4) to form 1D hydrogen-bonded polymers. The hydrogen-bonded polymer chains form infinite stacks which are sustained by C-H···O interactions occurring between polymer chains. The stacked alkenes undergo a UV-induced [2+2] photocycloaddition to produce rctt-tetrakis(N-pyridyl)cyclobutane photoproducts (where N = 3 and 4) in non-quantitative yields. The yield of the photoreaction is increased to nearly quantitative by applying a supramolecular catalysis approach with the 1,4-bd template.
Functional groups on reactant molecules can compete via non-covalent interactions with templates employed for the self-assembly process. One method to inhibit competition between functional groups involves chemically modifying a functional group employing a supramolecular protecting group. Here, we describe an acetyl supramolecular protecting group approach employed to mask alkenes containing phenolic and pyridyl functional groups. The acetyl protecting group prevents the phenolic substituents of the targeted alkene from participating in non-covalent interactions employed for the template-mediated self-assembly process. Thus, a cyclobutane molecule was obtained using the novel acetyl supramolecular protecting group strategy applied to a solid-state [2+2] photodimerization that affords a head-to-head cyclobutane. After deprotection, the resulting cyclobutane possessed tetrahedrally-disposed cis-hydrogen-bond-donor and cis-hydrogen-bond-acceptor groups. Thus, a purely organic three-dimensional hydrogen-bonded network based on a rare Michael O'Keeffe (mok) topology was constructed using an organic molecule synthesized in the organic solid state. The phenolic substituents of the cyclobutane adopt different orientations (syn-, anti-, and gauche-) to conform to the structural requirements of the mok net.
A challenge surrounding template-directed solid-state reactivity requires alkenes to be lined with functional groups that coordinate (or bind through other non-covalent interactions) to the template. Herein, we describe a dual approach of supramolecular assistance to covalent bond formation that utilizes a combination of imine and metal-organic chemistry to generate cyclobutanes lined with aldehyde groups. Specifically, dynamic imine chemistry was implemented to install a temporary recognition site on an aldehyde-containing alkene of cinnamaldehyde for a template-directed [2+2] photocycloaddition in the solid state. The resulting modified alkene aligns using Ag(I) ions into desirable arrangements for the covalent-bond-forming [2+2] photocycloaddition. The result is a 1D coordination polymer undergoes a UV-induced, regio-controlled [2+2] photocycloaddition in the solid state. The photoreaction proceeds stereospecifically with quantitative yield of the corresponding aldehyde-functionalized photodimer, α-truxilaldehyde. Additionally, we investigate the influence of the Ag(I) counterions on the assembly of imine containing alkenes to generate reactive assemblies for the purpose of producing aldehyde-containing cyclobutanes.
This dissertation also encompasses research pertaining to pharmaceutical solids and mechanical properties of organic molecular crystals. Specifically, we describe the discovery of two polymorphic co-crystals containing acetylsalicylic acid (aspirin) combined with 4,4’-bipyridine. The initial discovery of the form I polymorph was aided by mechanical dry-grinding, while an additional form II polymorph was revealed by rapid cooling in ethanol. The polymorphs differ by relative twists of carboxylic acid groups of the aspirin molecules and of the pyridyl rings of 4,4’-bipyridine. Additionally, the form I polymorph contains aspirin molecules that are linked via discrete catemeric methyl C-H···O interactions, while the form II polymorph is linked via both infinite methyl C-H···O catemers and centrosymmetric dimers. These results demonstrate the importance of dry mechanical grinding for the discovery of pharmaceutical co-crystals and polymorphs.
18
Alexander, S. J. "Discovery of heterometallic layered oxides using solid-state reactions of nano-precursors." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1348275/.
Full textAbstract:
The synthesis of new solid-state materials is often a laborious task due to the low speed of diffusion in bulk solids, meaning each reaction requires hightemperatures and multiple steps. Shortening diffusion distances has been shown to increase reaction rates and lower reaction temperatures. This thesis addresses the need to increase the rate of solid-state materials discovery, by heat-treatment of nanosized precursors. The nano-precursors were synthesised using continuous hydrothermal flow synthesis, CHFS. In CHFS a flow of metal nitrate salts are brought into contact with a flow of supercritical water to precipitate metal oxides and/or hydroxides. The reaction between La(OH)3 and Ni(OH)2 co-precipitated using CHFS was investigated using in-situ X-ray diffraction. This resulted in the formation of La2NiO4 in 78 minutes, an order of magnitude faster than when using more traditional routes, highlighting the effectiveness of this approach. A high-throughput CHFS reactor was then used to synthesise La4Ni2.7M0.3O10-δ (where M = V, Cr, Mn, Fe, Co, Cu and Al). By calcining the nanoprecursors for these compositions in parallel it was possible to reduce the synthesis time to make twenty-four solid-state compounds to 12 hours. Structure and properties were screened and, La4Ni2.7V0.3O10-δ, La4Ni2.7Cr0.3O10-δ, La4Ni2.7Mn0.3O10-δ and La4Ni2.7Al0.3O10-δ were characterised. Subsequently this process was carried out using automation to increase the number of compositions synthesised. Firstly, for the La4Ni3-xFexO10-δ system (x = 0.0 – 3.0 and Δx = 0.1), 62 samples were synthesised, resulting in identifying a greatly increased phase boundary, up to a maximum Fe content of La4Ni2.06Fe0.94O10. Secondly for the La4Ni3-xMxO10-δ and La3Ni2-xMxO7-δ systems (x = 0.0 – 2.0. Δx = 0.2 and M = Mn, Al, Pd, Ga) in which 240 samples were synthesised. La4Ni3-xGaxO10-δ was isolated up to a maximum Ga content of x = 0.6, and La2Ni1-xPdxO4 could be synthesised with a maximum Pd content of x = 0.4.
19
Yang, Yuan. "Graphene as a Solid-state Ligand for Palladium Catalyzed Cross-coupling Reactions." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5488.
Full textAbstract:
Palladium-catalyzed carbon-carbon cross-coupling reactions have emerged a broadly useful, selective and widely applicable method to synthesize pharmaceutical active ingredients. As currently practiced in the pharmaceutical industry, homogeneous Pd catalysts are typically used in cross-coupling reactions. The rational development of heterogeneous catalysts for cross-coupling reactions is critical for overcoming the major drawbacks of homogeneous catalysis including difficulties in the separation, purification, and quality control process in drug production. In order to apply heterogeneous catalysis to flow reactors that may overcome this limitation, the catalyst must be strongly bound to a support, highly stable with respect to leaching, and highly active. While the primary role of supports in catalysis has been to anchor metal particles to prevent sintering and leaching, supports can also activate catalytic processes. In this study, by using a xi combined theoretical and experimental method, we probed the effect of graphene as support in the complex reaction cycle of Suzuki reactions. The density functional theory study provides a fundamental understanding of how a graphene support strongly binds the Pd nanoparticles and act as both an efficient charge donor and acceptor in oxidation and reduction reaction steps. Theoretical investigations prove that the Pd-graphene interaction promotes electron flow between the metal cluster and the defected graphene to reduce reaction barrier. The ability for graphene to both accept and donate charge makes graphene an unusually suitable support for multi-step catalytic processes that involve both oxidation and reduction steps. The computer-aided catalyst design with the atomic precise accuracy demonstrates the Pd/graphene catalyst can be further optimized and the first-row transition metal nanoparticles have great potential to replace Pd to catalyze the Suzuki reaction. The corresponding experimental study shows that the method to immobilize the Pd nanoparticles on the graphene is crucial to increasing the reactivity and stability of the resulted catalyst. A comparison of the activation energy and turn over frequency for a series of supported and homogeneous catalysts indicates that exposing palladium-graphene to defect inducing microwave radiation results in dramatically lower activation energies and higher turnover frequencies. Furthermore, the heterogeneity tests demonstrate the Suzuki reactions are carried out on the surface of the immobilized Pd nanoparticle agreeing with the theoretical results. A method to engineer the 2-D graphene support to a 3-D structure to minimize the re-stacking and agglomeration of the graphene lattice will also be introduced in this study.
20
Kochman, Michal. "Ab initio simulations of reactions occurring in molecular crystals." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/8906.
Full textAbstract:
Although the solid state may not usually be thought of as an environment suitable for chemical reactions under mild conditions, a growing number of organic compounds are known to undergo interesting and, in many cases, practically useful chemistry in the molecular crystal phase. Of particular interest are photochemical reactions occurring in molecular crystals, which possess a number of characteristic features that make them attractive to study using the methods of theoretical chemistry. Firstly, molecular packing and steric effects strongly influence the mechanistic course of reactions in the crystal phase, which in some cases enables clean and controllable chemistry, including synthetic reactions as well as reversibly switchable isomerisations accompanied by a change of the macroscopic properties of the crystal, such as shape and colour. Secondly, in part due to their fast (subpicosecond) timescales and relatively low conversion rates (of the order of a few per cent), many of these reactions present challenges to experimental techniques, which computer simulation methods are uniquely positioned to overcome. Finally, these systems lend themselves well to simulation using a hybrid combination of two ab initio electronic structure methods, one of which is used to describe the electronic excitation of a reactive molecule while the other is applied to the surrounding bulk lattice. This thesis describes the computational modelling of two such reactions: the syn-anti photoisomerisation of 7-(2-pyridyl)indole and the reversible cis-enol⇄trans-keto photoisomerisation of N-salicylidene-2-chloroaniline. The solid-state mechanisms and rates of both reactions are computed using the TD-DFT/DFT hybrid method, in the latter case validating a previously postulated reaction mechanism. Furthermore, the thermal (ground-state) tautomerisation reaction in the photochromic and non-photochromic polymorphs of N-salicylidene-2-chloroaniline is investigated through calculations at the DFT level of theory. The results of these calculations indicate that both polymorphs are thermochromic, but tautomeric equilibrium in the non-photochromic polymorph is more sensitive to temperature than in the photochromic polymorph. Additionally, a critical assessment is presented of the accuracy of the various emphab initio methods employed throughout this work.
21
Cooper, Richard John. "An investigation into the structures of some metallic alloys by neutron and x-ray scattering methods." Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245589.
Full text
22
Dutta, Saikat. "Solid-state reactions in co-crystals: applications in synthetic chemistry and materials science." Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/491.
Full textAbstract:
Chemistry is on the verge of a new era where the attention of chemists has shifted from covalent bonds to noncovalent interactions and their use as a predictable way to guide reactions pathways and product formation. Nature synthesizes elegant molecules under mild conditions and the designed syntheses have been demonstrated to be largely dependent on recognition, self-assembly and templating effects between molecular building blocks. Although covalent synthesis in fluidic medium via supramolecular control has been achieved with limited success, organic solid state has been of particular interest since it avoids solvent effects, and is able to provide unique materials with remarkable stereoselectivity under environment-friendly conditions. Although reactions in solids have resulted in a number of remarkable discoveries in chemistry and materials science, solid-state synthesis is generally not considered as a mainstream synthetic medium and solid-state reactions are seldom appreciated as an efficient way to access molecular targets. Owing to the limited number of solid-state reactions and the uncontrollable nature of crystal packing, solid state has not been utilized readily as a primary synthetic medium. In this context, reactions conducted in multicomponent molecular assemblies or co-crystals have been attracting much attraction in recent years as a general way of controlling the reactivity of molecules in solid state. A molecular component in the multicomponent molecular solid, acting as a linear template, has been shown to preorganize molecules in a modular way via intermolecular interactions and engineer their physical and/or chemical properties. The [2+2]photodimerization of olefins is a successful demonstration how templated solid state synthesis can efficiently synthesize complex targets that are synthetically challenging via conventional routes. In this dissertation, the generality and synthetic applicability of the templated synthetic approach in solid state will be described. How supramolecular interactions in molecular co-crystals precisely guide covalent bond formation in order to construct complex molecular targets will be demonstrated. Finally, co-crystallization will be shown as a general way to control optical properties in crystals.
23
Stojakovic, Jelena. "Supramolecular catalysis, discrete aromatic stacks and sequential reactions in the organic solid state." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/4766.
Full textAbstract:
The organic solid state is becoming more widely utilized to synthesize molecules that are inaccessible or difficult to realize from the liquid phase. A solid-state synthesis provides strict control of both geometry and stereochemistry. While essential for efficient and sustainable organic syntheses, catalysis in the organic solid state is expected to be difficult to achieve due to low diffusion rates of molecules in the crystals. However, recently a ditopic receptor was used as a small-molecule supramolecular catalyst to direct a topochemical [2+2] photodimerization of an olefin. To achieve catalytic turnover, mechanochemistry, in the form of a manual mortar-and-pestle dry grinding, had to be employed. A main obstacle in the manual grinding method is the fact that the mechanochemistry and photoreaction are conducted separately. Thus, an automated method that enables simultaneous grinding and irradiation would be preferred. However, such technology is not commercially available. We have developed a simple, readily accessible, and automated method to achieve the mechanochemical preparation of supramolecular materials. Importantly, method enables simultaneous grinding and irradiation. In effect, the vortex grinding serves as a ball mill that is UV irradiation transparent. The vortex method has been applied to the preparation of cocrystal and metal organic frameworks, as well as supramolecular catalysis. When conducted using vortex method, supramolecular catalysis proceeds four time faster than when conducted using manual grinding. Accelerated rate of catalysis is attributed to combination of external stress exerted by grinding and internal stress arising from photoreaction.
The scope of supramolecular catalysis is expanded to reaction of 2,2'-bpe, catalyzed by a similar ditopic receptor res. Importantly, in this system catalytic turnover proceeds spontaneously. The mechanism of catalysis was investigated using X-ray diffraction studies and gas-phase DFT calculations. The studies uncovered that 2,2'-bpe and 2,2'-tpcb undergo rotational motion to release accumulated stress akin to action of a supramolecular torsional spring.
We report an integration of aromatic stacks into discrete assemblies based on hydrogen bonds in the solid state. We used indolo[2,3-a]carbazole to organize aromatics into double, triple, and quadruple stacks within cocrystals. We also showed that aromatics within quadruple stack undergo topochemical [2+2] photodimerization to give a single photoproduct stereoselectively in up to maximal yield.
We reveal the first example of a product of a templated solid-state that acts as a template in subsequent reaction. Both reactions proceed in 100% yield and stereoselectively. We also report the unique case of polymorphism where both polymorphs are photoreactive and within one polymorph photoreaction proceeds in SCSC manner.
Due to effects of crystal packing, homology in solid state is difficult to achieve. We present the application of the template screening approach to solid-state photoreactivity among all olefins of a homologous series. To assess electronic effects of substituents on stability and hydrogen bonds of assemblies, we preformed gas-phase DFT calculations on a series of substituted assemblies. We found, that the strength of hydrogen-bonding varies and correlates with electronic nature of the substituents.
Lastly, we incorporated principles of supramolecular chemistry, solid-state reactivity, green chemistry and sustainability in undergraduate curriculum. In particular, students employ supramolecular chemistry to control photoreactivity in the organic solid state using the template approach. To form supramolecular assemblies, mechanochemistry, in form of mortar-and-pestle grinding, is used. To study reactivity in crystals, X-ray diffraction is used. Students are involved in all steps necessary to obtain crystal structure: growing suitable crystals, selection of the best crystals, data collection, solution, refinement and analysis of the crystal structures. Overall, students have hands-down experience in all aspects of crystallography. Although essential in chemical, biochemical, pharmaceutical and materials science, crystallography is rarely taught in undergraduates laboratories.
24
Lee, Dongwoo. "Nanocalorimetry Experiments and First-Principles Theoretical Studies of Solid-State Reactions in Nanolaminates." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493483.
Full textAbstract:
The extraordinary sensitivity and extremely small thermal mass of chip-based nanocalorimetry sensors allow the study of reactions in thin films over a broad range of heating rates, from isothermal to 10^5 K/s. First-principles calculations provide insight in the phase transformation and diffusion behavior of a material at the atomistic scale. Combination of nanocalorimetry and first-principles, therefore, is highly efficient and reliable to determine the atomistic-to-macroscopic response of materials. This thesis explores, through use of this combined approach, reactions in reactive multilayers to synthesize ultra-high temperature ceramic coatings.
We employ scanning AC and DC calorimetry techniques to investigate the synthesis of ZrB2 and carbon-doped ZrB2 using Zr/B and Zr/B4C multilayered reactive nanolaminates (MRNL). The solid-state reactions in these multilayers are shown to proceed in two distinct steps: an interdiffusion/amorphization step followed by a crystallization step. Measurements performed at heating rates ranging from 1,000 to 55,000 K/s allows determination of the kinetic parameters of the multilayer reactions, such as the activation energies of interdiffusion and crystallization. Low activation energies in the interdiffusion processes in the Zr/B MRNLs are found and amorphization is shown to facilitate fast transport of B atoms into Zr lattice. It has also been shown that C impurity atoms in the Zr/B4C MRNLs further reduce activation energies of interdiffusion and crystallization.
First-principles theoretical modeling provides insight in the amorphization processes in the Zr/B MRNLs and confirms the relatively low activation energies associated with the processes. The simulations further elucidate the effects of concentration (ZrBx, 0
25
Wright, Timothy Grahame. "Studies of some gas-phase oxidation reactions using electron spectroscopy and the electronic structure of some small molecules." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358873.
Full text
26
Bourret, Gilles. "Templated synthesis of Ag(I) and Cu (II) nanostructures: Solid state reactions and applications." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97047.
Full textAbstract:
This Thesis presents the synthesis of novel 1D, 2D, and 3D Ag(I) and Cu(II) nanostructures and their use as sacrificial templates to make functional nanomaterials. New soft template methods were developed for the synthesis of AgCN and Cu(OH)2 nanostructures. Polymeric organic nanotubes were successfully used to synthesize AgCN nanowires, while the precipitation of Cu(OH)2 nanofibers was templated in water microdroplets. Both methods benefit from the versatility of soft templates and allows for a control of both the size and the morphology of the nanostructures produced. The conversion of these precursors into metallic and semi-conductive nanomaterials was achieved via chemical and electrochemical reduction, and thermolysis. Chemical reduction of the AgCN nanowires leads to the fabrication of conductive arrays on nylon filter substrates, while the thermolysis of the Cu(OH)2 spherical assemblies yields photoresponsive semi-conductive porous CuO spheres. The electrochemical reduction of the native Ag(I) and Cu(II) one-dimensional nanostructures was investigated in aqueous solution at gold/glass/gold junctions. The solid-solid conversion involved in the electrochemical reduction process was studied via cyclic voltammetry, chronoamperometry, and electronic microscopy. The strong influence of the reduction potential on the nanomaterials produced allowed for the fabrication of a range of Ag(0) nanostructures, including nanoparticles, nanoprisms, nanofibers and porous networks. Electrochemical reduction of Au/Mz+/Au junctions leads to the formation of an excellent electrical contact between the two gold electrodes. This technique was expanded to include ionically-conductive Ag2S nanowires which form metallic/ionic-conductor heterojunctions.Keywords: nanostructure, nanowire, template, emulsion, electrochemistry, silver, cyanide, copper, oxide, heterojunction, sacrificial templateCette Thèse présente la synthèse de nouvelles nanostructures d'argent(I) et de cuivre(II) utilisées comme structures sacrificielles dans la fabrication de matériaux fonctionnels. De nouvelles méthodes basées sur des « template » souples ont été développées pour la synthèse de nanostructures de cyanure d'argent et d'hydroxyde de cuivre. Des nanotubes de polymères organiques ont été utilisés avec succès pour synthétiser des nanofils de AgCN, tandis que la précipitation de Cu(OH)2 a été confinée dans des microgouttes d'eau pour produire des aggrégats sphériques de nanofibres de Cu(OH)2. Ces deux méthodes bénéficient de la versatilité des « template » souples en permettant de contrôler la taille et la morphologie des nanostructures produites. La conversion de ces précurseurs en nanomatériaux métalliques ou semi-conducteurs a été réalisée par réduction chimique et électrochimique, ainsi que par thermolyse. La réduction chimique des nanofils de cyanure d'argent a permis la fabrication de nanostructures conductrices ordonnées à la surface de filtres de nylon. La thermolyse des sphères de Cu(OH)2 a produit des sphères poreuses et semi-conductrices composées de CuO, qui sont sensibles à la lumière. La réduction électrochimique des structures unidimensionnelles de Ag(I) et de Cu(II) a été réalisée en milieu aqueux sur des jonctions or/verre/or. La conversion solide-solide opérée durant la réduction électrochimique a été étudiée par voltammétrie cyclique, chronoamperométrie et microscopie électronique. La grande influence du potentiel de réduction sur les nanomatériaux ainsi produits a permis la fabrication d'un grand nombre de nanostructures d'argent(0), dont : des nanoparticules, des nanoprismes, des nanofibres et des réseaux poreux. La réduction électrochimique de jonctions Au/Mz+/Au conduit à la formation d'excellents contacts électriques entre les deux électrodes d'or. Cette technique a été appliquée à des nanofils conducteurs d'ions pour former des hétérojonctions.
27
Page, Samuel John. "The use of solid state NMR to monitor reactions and doping in inorganic materials." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/113823/.
Full textAbstract:
Solid state nuclear magnetic resonance (NMR) is a powerful probe of inorganic materials systems. Through carefully changing materials compositions and synthesis methods, the impact on the local structure can be investigated. These have been applied to three main materials sectors: Paramagnetic materials in NMR have traditionally suffered from poor resolution due to broadening experienced at the nuclei from localised unpaired electrons. In this work, a fast magic angle spinning (MAS) and low field approach has been applied to these paramagnetic cathode materials to improve this resolution, and elucidate structural information from the investigated materials. The resolution gained from these techniques has been used to highlight differences observed in the 7Li shifts of lithium iron phosphate (LFP) produced by different synthesis techniques. This was found to be related to the cell volume of the LiFePO4 phase. Furthermore, the investigation of V doped LFP by 7Li and 31P MAS NMR has resulted in the observation of many common impurities resulting from synthesis. Additionally, 31Presonances could be identified that were related to V near the phosphorus site, indicating successfully doping in some of the higher Li containing samples. Through 29Si and 17O MAS NMR, changes in the local structure between Ca and Zn doped Stöber nanoparticles are observed. Similarly to other Ca containing materials, incorporation of Ca into the Stöber network has been shown to disrupt Sibridging bonds promoting the formation of non-bridging bonds in the silica network. However, addition of Zn tells a different story. This is first observed in the static measurements, where incorporation of high amounts of Zn leads to no evidence of hydroxyls observed in the Stöber network. Whereas, high resolution transmission electron microscopy (HRTEM) and density functional theory (DFT) calculations confirm the presence of crystalline Zn2SiO4 -II in the nanoparticles. Finally, activation of two series of synthetic sodium- and aluminium substituted calcium silicate hydrate (C-(N)-(A)-S-H) geopolymers are investigated. Increasing the CaO has been shown to increase the disorder of the silica network, and also to promote the increase of crystallinity of the systems through observation of calcium aluminate phases. Additionally, increasing the amount of aluminium relative to the silicon in the system, promotes more of these crystalline phases to form.
28
Su, Tina Yu-Ting. "The dehydrogenation reactions between LiH and organic amines for solid state hydrogen storage systems." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7863/.
Full textAbstract:
Hydrogen is considered as an appealing alternative to fossil fuels in the pursuit of sustainable, secure and prosperous growth in the UK and abroad. However there exists a persisting bottleneck in the effective storage of hydrogen for mobile applications in order to facilitate a wide implementation of hydrogen fuel cells in the fossil fuel dependent transportation industry. To address this issue, new means of solid state chemical hydrogen storage are proposed in this thesis. This involves the coupling of LiH with three different organic amines: melamine, urea and dicyandiamide. In principle, thermodynamically favourable hydrogen release from these systems proceeds via the deprotonation of the protic N-H moieties by the hydridic metal hydride. Simultaneously hydrogen kinetics is expected to be enhanced over heavier hydrides by incorporating lithium ions in the proposed binary hydrogen storage systems. Whilst the concept has been successfully demonstrated by the results obtained in this work, it was observed that optimising the ball milling conditions is central in promoting hydrogen desorption in the proposed systems. The theoretical amount of 6.97 wt% by dry mass of hydrogen was released when heating a ball milled mixture of LiH and melamine (6:1 stoichiometry) to 320 °C. It was observed that ball milling introduces a disruption in the intermolecular hydrogen bonding network that exists in pristine melamine. This effect extends to a molecular level electron redistribution observed as a function of shifting IR bands. It was postulated that stable phases form during the first stages of dehydrogenation which contain the triazine skeleton. Dehydrogenation of this system yields a solid product Li2NCN, which has been rehydrogenated back to melamine via hydrolysis under weak acidic conditions. On the other hand, the LiH and urea system (4:1 stoichiometry) desorbed approximately 5.8 wt% of hydrogen, from the theoretical capacity of 8.78 wt% (dry mass), by 270 °C accompanied by undesirable ammonia and trace amount of water release. The thermal dehydrogenation proceeds via the formation of Li(HN(CO)NH2) at 104.5 °C; which then decomposes to LiOCN and unidentified phases containing C-N moieties by 230 °C. The final products are Li2NCN and Li2O (270 °C) with LiCN and Li2CO3 also detected under certain conditions. It was observed that ball milling can effectively supress ammonia formation. Furthermore results obtained from energetic ball milling experiments have indicated that the barrier to full dehydrogenation between LiH and urea is principally kinetic. Finally the dehydrogenation reaction between LiH and dicyandiamide system (4:1 stoichiometry) occurs through two distinct pathways dependent on the ball milling conditions. When ball milled at 450 RPM for 1 h, dehydrogenation proceeds alongside dicyandiamide condensation by 400 °C whilst at a slower milling speed of 400 RPM for 6h, decomposition occurs via a rapid gas desorption (H2 and NH3) at 85 °C accompanied by sample foaming. The reactant dicyandiamide can be generated by hydrolysis using the product Li2NCN.
29
Wilson, A. "Fundamental studies of gas reactions with the surface of solid state semiconductor gas sensor." Thesis, Lancaster University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371067.
Full text
30
Spencer, Jonathan Edmund Downing. "A study of organotitanium coupling agents for adhesion promotion and of chemical reactions on alumina surfaces by inelastic electron tunnelling spectroscopy." Thesis, City University London, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254964.
Full text
31
Howell, Robert H. "Synthesis of fluorophlogopite using solid-state reaction techniques." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-03302010-020107/.
Full text
32
Frankovsky, Rainer. "Iron based superconductors and related compounds synthesized by solid state metathesis and high temperature reactions." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-157843.
Full text
33
Williams, Robert Earl Jr. "Simulation and Characterization of Cathode Reactions in Solid Oxide Fuel Cells." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16309.
Full textAbstract:
In this study, we have developed a dense La0.85Sr0.15MnO3-δ (LSM) Ce0.9Gd0.1O1.95 (GDC) composite electrode system for studying the surface modification of cathodes. The LSM and GDC grains in the composite were well defined and distinguished using energy dispersive x-ray (EDX) analysis. The specific three-phase boundary (TPB) length per unit electrode surface area was systematically controlled by adjusting the LSM to GDC volume ratio of the composite from 40% up to 70%. The TPB length for each tested sample was determined through stereological techniques and used to correlate the cell performance and degradation with the specific TPB length per unit surface area.
An overlapping spheres percolation model was developed to estimate the activity of the TPB lines on the surface of the dense composite electrodes developed. The model suggested that the majority of the TPB lines would be active and the length of those lines maximized if the volume percent of the electrolyte material was kept in the range of 47 57%. Additionally, other insights into the processing conditions to maximize the amount of active TPB length were garnered from both the stereology calculations and the percolation simulations.
Steady-state current voltage measurements as well as electrochemical impedance measurements on numerous samples under various environmental conditions were completed. The apparent activation energy for the reduction reaction was found to lie somewhere between 31 kJ/mol and 41 kJ/mol depending upon the experimental conditions. The exchange current density was found to vary with the partial pressure of oxygen differently over two separate regions. At relatively low partial pressures, i0 had an approximately dependence and at relatively high partial pressures, i0 had an approximately dependence. This led to the conclusion that a change in the rate limiting step occurs over this range.
A method for deriving the electrochemical properties from proposed reaction mechanisms was also presented. State-space modeling was used as it is a robust approach to addressing these particular types of problems due to its relative ease of implementation and ability to efficiently handle large systems of differential algebraic equations. This method combined theoretical development with experimental results obtained previously to predict the electrochemical performance data. The simulations agreed well the experimental data and allowed for testing of operating conditions not easily reproducible in the lab (e.g. precise control and differentiation of low oxygen partial pressures).
34
Smith, Shelley Hunnings. "Solid State Effects in the Reactions of the Meta and Pura Trifluorodiazomethane/Beta-Cyclodextrin Inclusion Complexes." W&M ScholarWorks, 1990. https://scholarworks.wm.edu/etd/1539625588.
Full text
35
Hwang, Christine. "Crystal structures and solid state reactions of maleic anhydride and of a cyclohexenone and its photoproduct." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/27966.
Full textAbstract:
Two sets of structures were determined by X-ray crystallographic techniques, one of maleic anhydride (2,5-furandione) and the other of 4-phenyl-4-p-bromophenylcyclohex-2-en-1-one and its photoproduct, trans-5-phenyl-6-p-bromophenylbicyclo[3.1.0]hexan-2-one.
Analysis of maleic anhydride included a room temperature redetermination of the crystal structure. This was done to improve parameters and simplify comparison of the room temperature and low temperature data. The structure determination at 104k resulted in the location of bonding electrons in the double bond. Thermal motions of both sets of data showed that translational motion was greatest along an axis parallel to the carbonyl bonds. Libration was found to be greatest about this axis also.
The second set of structures was done to examine the migration pattern of aryl groups upon irradiation of a diarylcyclohexenone. The major photoproduct was formed by migration of the p-bromophenyl group. The resulting bicyclohexanone had the aryl groups trans to each other.Science, Faculty of
Chemistry, Department of
Graduate
36
Monsegue, Niven. "Characterizing the Effects of Mechanical Alloying on Solid State Amorphization of Nanoscaled Multilayered Ni-Ti." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/28373.
Full textAbstract:
Equiatomic composition of Ni and Ti was cryomilled with varying milling times to create Ni-Ti lamella structures with average spacings of 50 nm, 470 nm, and 583 nm in powder particles to vary the interfacial surface area per volume. These surfaces form interfaces for diffusion that are essential for solid state amorphization during low temperature annealing. To compare solid state amorphization in a relatively defect free multilayer system, elemental Ni and Ti were deposited by electron beam physical vapor deposition on titanium plates with comparable spacing as above. Both milled and deposited multilayers were annealed between 225 and 350°C for up to 50 hours.
X-ray diffraction characterization and in situ annealing was conducted on cryomilled and deposited multilayers of Ni-Ti. Based on this characterization, an amorphization model based on the Johnson-Mehl-Avrami nucleation and growth equation has been established to predict the amorphization of both cryomilled and deposited multilayers. Cryomilled powders experienced much larger amorphization rates during annealing than that of deposited multilayer structures, for all layer spacings. This superior amorphization is seen despite the formation of amorphous phase during the milling process; the amount of which increases with increasing milling time. The difference in amorphization rates between cryomilled and deposited multilayers is attributed to excess driving force due to the extensive preexisting defects in the powders caused by cryomilling.
Serial 3D reconstruction of cryomilled Ni-Ti powders was done by scanning electron microscopy and focused ion beam. Through 3D reconstruction it was observed that a random and non-linear lamella structure has been formed in cryomilled powders. Furthermore, lamellar spacing was seen to become smaller with increased milling time while at the same time becoming more homogeneous through the material's volume. 3D reconstruction of cryomilled Ni-Ti offers a unique insight into the microstructures and surface areas of cryomilled powder particles that has never been accomplished.Ph. D.
37
Lee, Jong-Heon. "Synthesis of TiC by shock-assisted solid-state reaction sintering." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/32830.
Full text
38
Netherton, Matthew Russell. "Asymmetric induction and reaction selectivity in solid state organic photochemistry." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0012/NQ61151.pdf.
Full text
39
Leoni, Stefano. "Theoretical and Experimental Investigations on Solid State Reactions: Phase Transition Mechanisms, Ionic Conduction, Domain Formation and Interface Reactivity." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-79219.
Full textAbstract:
In the practice of solid state chemistry, structural phase transitions are fairly common events. Nonetheless, their understanding, in terms of both: A rationalization of the observed changes in symmetry pattern and; An understanding of the mechanisms allowing for a particular transformation, are outstanding problems. The thermodynamic classification of phase transitions distinguishes between first and second order transitions, on the basis of the discontinuous behavior of quantities related to first or second derivatives of the free energy, respectively. Small atomic displacements are typically associated with second order phase transitions, and latent heat changes amount to a few calories per gram only. Additionally, the symmetries of the phases surrounding the transition are typically in the relation of a group and a subgroup. Reconstructive phase transitions, on the contrary, involve breaking of (large) parts of the bond scaffolding of the initial structure, and exhibit drastic changes at the transition point, with large latent heat and hysteresis effects. The corresponding atomic displacements can be in the order of the lattice parameters, and no group-subgroup is found, between the symmetry of the phases. These type of transitions have generally a strong first-order character.
Landau theory accounts for continuous, second-order phase transitions. As a phenomenological theory, it does not establish the existence of a phase transition, which remains an experimental fact. It only bridges microscopic characteristics, like space-group symmetries and structural changes, or phonon softening effects, with measurable macroscopic quantities. Therein, distortions are carried by an order parameter, which fully specifies the form of the analytical variational free energy. The latter is continuous and derivable with respect to temperature, pressure and atomic displacement, at the transition point.
First order, non-continuous phase transitions are still within the scope of Landau theory in the mentioned special case of the existence of a group-to-(isotropic) subgroup relationship. In the majority of cases, however, and for the most interesting phase transitions (for basic and applied research), such a relationship is missing, making the choice of an order parameter less straightforward. Most of the allotropic transformations of the elements, many intermetallic systems, and numerous insulating systems belongs to this class. This class also includes most interesting and fundamental electronic effects, like metallization in perovskites or spinel oxides for example.
This very simple fact of a missing symmetry condition has helped reinforcing the opinion of first-order phase transitions being a world apart, and possibly contributed to discouraging a firm theory to develop, able to account for their transformation mechanisms and the change of physical properties across phase transition. The thermodynamic distinction between first and second order phase transitions is too narrow, as, in case of first order phase transitions, it embraces both weakly discontinuous transition and reconstructive ones, where bonds are being strongly modified. Especially, a mean to qualify the distance between two structures (geometric, with respect to symmetry, a.s.o.), is missing. Clearly, a group-subgroup relationship may, and typically does imply shortest shifting distances, as a tiny atomic displacement can already do for a symmetry lowering. Naively, missing such a relation means no constraints, and apparently no means to conclude at a connection of two structures in general, let alone a full mechanistic analysis.
First order phase transitions proceed by nucleation and subsequent growth of the new phase from the initial one. Different from (second-order) continuous phase transitions, they do imply coexistence of the transforming motifs. The discontinuity in some order parameter between the two phases is driven by lowering of the free energy as the new phase forms. However, close to the transition, the original phase remains metastable, and a fluctuation is needed to cause the formation of the new phase to set in. Such a process responds to thermal changes, and depending on the height of the nucleation barrier, its rate may be slower or faster. In the former case, large deviations from equilibrium may be required to achieve transformation to the stable phase, which means that large hysteresis effects will be observed in the course of transformation.
The intent of this work consists in giving a face to the intermediate configurations appearing in first order phase transitions, in solid-solid reconstructive processes. Apart of a mechanistic elucidation, consisting in answering the question “Which atomic displacements bring structural motif A into structural motif B ?”, another purpose of this work is a rather pedagogical one, that is, showing that first-order phase transitions can be understood in detail, not only in principle but in fact. The core of the examples illustrated in this work is concerned with phase transformations where pressure represents the thermodynamic controlling parameter. Pressure is extensively used in chemical synthesis, as a mean to achieve novel properties, optical or mechanical just to mention a few. Additionally, reports on novel high-pressure polymorphs are regularly appearing. In this sense, pressure is a relevant parameter for approaching fundamental questions in solid state chemistry.
40
Huang, Mantao. "Voltage control of electrical, optical and magnetic properties of materials by solid state ionic transport and electrochemical reactions." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127898.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 139-153).
Reversible post-fabrication control of material properties enables devices that can adapt to different needs or environmental conditions, and brings additional levels of functionality, paving the way towards applications such as reconfigurable electronics, reconfigurable antennas, active optical devices and energy efficient data storage. One promising way of achieving the controllability is through solid-state ionic transport and electrochemical reactions in thin film structures, where the properties of materials can be electrically controlled by a gate voltage in an addressable way. Here we explore using such ionic gating method to control the electrical, optical and magnetic properties of solid-state thin film layers, and show that large modification can be achieved for a wide range of properties. We demonstrate a new type of three terminal resistive switching device where the resistivity of a thin film conductive channel can be controlled by a gate voltage. We demonstrate solid-state ionic gating of the optical properties of metals and oxides and show the versatility of the approach by implementing voltage-controlled transmission, thin film interference, and switchable plasmonic colors. We also show that the approach allows for voltage control of ferrimagnetic order, demonstrating voltage induced 180-degree switching of the Néel vector, as a new way of magnetic bit writing. These findings extend the scope of voltage programmable materials and provide insights into the mechanisms of voltage controlled material properties by solid-state ionic transport and electrochemical reactions.
by Mantao Huang.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Materials Science and Engineering
41
Ness, J. N. "The microstructure of reaction-bonded silicon carbide." Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373687.
Full text
42
Yao, Bo. "N MULTILAYER THIN FILM REACTIONS TO FORM L10 FEPT AND EXCHANGE SPRING MAGNETS." Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4024.
Full textAbstract:
FePt films with the L10 phase have potential applications for magnetic recording and permanent magnets due to its high magnetocrystalline anisotropy energy density. Heat treatment of n multilayer films is one approach to form the L10 FePt phase through a solid state reaction. This thesis has studied the diffusion and reaction of n multilayer films to form the L10 FePt phase and has used this understanding to construct exchange spring magnets. The process-structure-property relations of n multilayer films were systematically examined. The transmission electron microscopy (TEM) study of the annealed multilayers indicates that the Pt layer grows at the expense of Fe during annealing, forming a disordered fcc FePt phase by the interdiffusion of Fe into Pt. This thickening of the fcc Pt layer can be attributed to the higher solubilities of Fe into fcc Pt, as compared to the converse. For the range of film thickness studied, a continuous L10 FePt product layer that then thickens with further annealing is not found. Instead, the initial L10 FePt grains are distributed mainly on the grain boundaries within the fcc FePt layer and at the Fe/Pt interfaces and further transformation of the sample to the ordered L10 FePt phase proceeds coupled with the growth of the initial L10 FePt grains. A comprehensive study of annealed n films is provided concerning the phase fraction, grain size, nucleation/grain density, interdiffusivity, long-range order parameter, and texture, as well as magnetic properties. A method based on hollow cone dark field TEM is introduced to measure the volume fraction, grain size, and density of ordered L10 FePt phase grains in the annealed films, and low-angle X-ray diffraction is used to measure the effective Fe-Pt interdiffusivity. The process-structure-properties relations of two groups of samples with varying substrate temperature and periodicity are reported. The results demonstrate that the processing parameters (substrate temperature, periodicity) have a strong influence on the structure (effective interdiffusivity, L10 phase volume fraction, grain size, and density) and magnetic properties. The correlation of these parameters suggests that the annealed n multilayer films have limited nuclei, and the subsequent growth of L10 phase is very important to the extent of ordered phase formed. A correlation between the grain size of fcc FePt phase, grain size of the L10 FePt phase, the L10 FePt phase fraction, and magnetic properties strongly suggests that the phase transformation of fccL10 is highly dependent on the grain size of the parent fcc FePt phase. A selective phase growth model is proposed to explain the phenomena observed. An investigation of the influence of total film thickness on the phase formation of the L10 FePt phase in n multilayer films and a comparison of this to that of FePt co-deposited alloy films is also conducted. A general trend of greater L10 phase formation in thicker films was observed in both types of films. It was further found that the thickness dependence of the structure and of the magnetic properties in n multilayer films is much stronger than that in FePt alloy films. This is related to the greater chemical energy contained in n films than FePt alloy films, which is helpful for the L10 FePt phase growth. However, the initial nucleation temperature of n multilayers and co-deposited alloy films was found to be similar. An investigation of L10 FePt-based exchange spring magnets is presented based on our understanding of the L10 formation in n multilayer films. It is known that exchange coupling is an interfacial magnetic interaction and it was experimentally shown that this interaction is limited to within several nanometers of the interface. A higher degree of order of the hard phase is shown to increase the length scale slightly. Two approaches can be used to construct the magnets. For samples with composition close to stoichiometric L10 FePt, the achievement of higher energy product is limited by the average saturation magnetization, and therefore, a lower annealing temperature is beneficial to increase the energy product, allowing a larger fraction of disordered phase. For samples with higher Fe concentration, the (BH)max is limited by the low coercivity of annealed sample, and a higher annealing temperature is beneficial to increase the energy product.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Materials Science & Engr PhD
43
Boldovjaková, Tatiana. "Post-polymerační modifikace polyolefinů pro přípravu hydroxylovaných makroiniciátorů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2020. http://www.nusl.cz/ntk/nusl-432943.
Full textAbstract:
The diploma thesis deals with post-polymerization hydroxylation of polypropylene in solid state. Regarding the literature review, polypropylene was hydroxylated by radical grafting in aqueous solution of potassium persulfate at 100 °C, under nitrogen atmosphere for 60 minutes. Hydroxylation of polypropylene was performed at different concentrations of potassium persulfate (1; 5; 10 mol. %) and two different water/potassium persulfate molar ratios. The effects of reaction system composition and reaction conditions on reaction efficiency, extent of side reactions, thermal and rheological properties of hydroxylated polypropylene were evaluated. The presence and concentration of hydroxyl groups on polypropylene surface was determined by structural analysis (FTIR, XPS), while the highest efficiency was achieved in the presence of nonionic wetting agents, using 10 mol. % potassium persulfate and at lower water/potassium persulfate molar ratio. Based on changes in polypropylene structure, the modification took place mainly in the amorphous phase of the polymer. In addition to hydroxylation, concurrent side reactions have been reported, in particular the oxidation of wetting agents and polypropylene, which has resulted in chain cleavage, reducing the average molecular weight of the polypropylene.
44
Chen, Kezheng. "Origin of Polarization Behavior in All-Solid-State Lithium-Ion Battery Using Sulfide Solid Electrolyte." Kyoto University, 2018. http://hdl.handle.net/2433/235998.
Full text
45
Ina, Toshiaki. "Study on Cathodic Reaction Mechanism of All Solid State Electrochemical Devices." Kyoto University, 2012. http://hdl.handle.net/2433/157658.
Full textAbstract:
Kyoto University (京都大学)0048
新制・課程博士
博士(人間・環境学)
甲第16947号
人博第590号
新制||人||141(附属図書館)
23||人博||590(吉田南総合図書館)
29622
京都大学大学院人間・環境学研究科相関環境学専攻
(主査)教授 内本 喜晴, 教授 杉山 雅人, 教授 田部 勢津久, 准教授 藤原 直樹, 准教授 雨澤 浩史
学位規則第4条第1項該当
46
Fitzgerald, Emma T. "Studies of surface reaction mechanisms for chemical beam epitaxial growth." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317723.
Full text
47
French, Catherine Louise. "Surface science investigations of reaction mechanisms in semiconductor growth and etching." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305988.
Full text
48
Murrell, M. P. "A study of the oxidation mechanisms of silicon, using nuclear reaction analysis." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293545.
Full text
49
Fujiwara, Koichi. "Synthesis of Fullerene Derivatives with Novel Structures by the Solid-State Reaction." 京都大学 (Kyoto University), 2002. http://hdl.handle.net/2433/149781.
Full text
50
Souza, Gledison Rogerio de. "Estudo das reações em estado sólido das ligas Pt-Rh-Tr 70:15:15% (m/m) e Pt-Ir 70:30% com Hg, empregando técnicas eletroquímicas e termoanalíticas /." Araraquara : [s.n.], 2008. http://hdl.handle.net/11449/105735.
Full textAbstract:
Resumo: A finalidade deste trabalho foi estudar as reações em estado sólido das ligas Pt-Rh-Ir 70:15:15% (m/m) e Pt-Ir 70:30% (m/m) com Hg, empregando técnicas eletroquímicas e termoanalíticas. O preparo dos sistemas para os estudos eletroquímicos (VC) e de análise térmica (TG/DTG) consistiu em fazer eletrodeposições de Hg no substrato metálico, com o auxílio das técnicas de voltametria cíclica (VC), gerando um filme de Hg e compostos intermetálicos. A partir desses estudos foi possível evidenciar o ataque efetivo do Hg sobre o substrato, e a formação de compostos intermetálicos de caráter covalente, do tipo: PtHg, PtHg2, RhHg2 e PtHg4, que foram caracterizados com o auxílio das seguintes técnicas de análise de superfície: Microanálise por EDX, mapeamento dos elementos, obtenção de micrografias eletrônica de varredura e difratometria de Raios X (XRD). Essas análises de superfície revelaram também, uma distribuição homogênea do Hg e a presença de um filme de intermetálicos sobre a superfície do substrato. Os resultados deste trabalho demonstraram que a liga de Pt-Rh-Ir 70:15:15% (m/m) apresenta uma reatividade intermediária, comparada às ligas de Pt-Ir 80:20% (m/m) e Pt-Ir 70:30% (m/m). Assim, a liga de Pt-Ir 70:30% (m/m) é a que apresentou menor reatividade.Abstract: The purpose of this work was to study the reactions in the solid state of alloys Pt-Rh-Ir 70:15:15% (m/m) and Pt-Ir 70:30% (m/m) with Hg, employing the electrochemical and thermoanalytical techniques. The preparation of the systems for electrochemical (VC) and thermoanalytical (TG/DTG) studies consisted to make electrodepositions of Hg in the metallic substrate, using cyclic voltammetry techniques (VC) to generate a film of Hg and intermetallic compounds. From these studies, it was possible to show the actual attack of Hg on the substrate, and the formation of intermetallic compounds of covalent character, such as: PtHg, PtHg2, RhHg2 and PtHg4, which were characterized using these analysis of surface techniques: EDX microanalysis, mapping of the elements, scanning electronic microscopy and and X-ray Diffraction (XRD). These analysis also revealed a homogenous distribution of the Hg and the presence of a film of intermetallic compounds on the surface of the substrate. The results of this study showed that the Pt-Rh-Ir 70:15:15% (m/m) alloy presents an intermediate reactivity, compared to Pt-Ir 80:20% (m/m) and Pt-Ir 70:30% (m/m) alloy. So, the Pt-Ir 70:30% (m/m) alloy that was presented the lower reactivity.
Orientador: Fernando Luis Fertonani
Coorientador: Ieda Aparecida Pastre Fertonani
Banca: Marisa Spirandeli Crespi
Banca: Luci Diva Brocardo Machado
Banca: Jivaldo do Rosário Matos
Banca: Assis Vicenti Benedetti
Doutor