Thèses : « Metal crystals »

1

Abser, Mohammed Nurul. « Synthesis of metal containing liquid crystals ». Thesis, University of Central Lancashire, 1991. http://clok.uclan.ac.uk/20372/.

Texte intégral

Résumé :

The primary objective of the present study was to develop mesogenic metal complexes. Part of this work was concerned with the synthesis of structural analogues of existing mesogenic bis-1,2-dithiolatonickel(II) complexes to explore the impact of structural variations on the mesophase behaviour of these complexes and to develop complexes with novel mesophase behaviour. The study was successfully continued to develop new mesogenic systems. The work has shown that replacement of the hydrogen atom at the 2-position of the metallodithiolato ring by a phenyl or alkyl group diminishes the tendency of mesophase formation of the system, although the melting temperatures of the 2-alkyl substituted derivatives are greatly reduced relative to the non-substituted analogues. A more general and shorter synthetic route - over literature methods - for tetra-substituted dithiolatonickel(II) complexes has been developed although the synthesised complexes were proved to be nonmesogenic. A novel synthetic route to bis[1-(2'-fluoro-4'-((S)-(+)-7-methylnonyl) phenyl)ethene-1,2-dithiolato]nickel(II) (4.42) has been developed and the compound was shown to posses ferroelectric behaviour, which unfortunately persist only over a very short temperature range (ca. 0.5°C). Attempts to restore this interesting phase by variation of the alkyl side chain length proved to be unsuccessful; extension of the chain length stabilises the mesophase, but with exclusion of the ferroelectric behaviour, while the reduction of the alkyl side chain length destabilises the mesogenic behaviour of the complexes. However, mixed ligand complexes were found to posses relatively wider mesophase range with a low crystal to liquid crystal transition temperatures (at or near room temperature). Insufficient amounts of these materials have been obtained to date for the ferroelectric properties to be examined. Attempts to synthesise complexes with 3'-fluoro substitutents were unsuccessful due to the exclusive formation of the "incorrect" isomer in the preceding synthetic step. A number of bis[methylidenearoylhydrazinato]nickel(H) complexes have been shown to posses mesogenic properties. The short chain homologue of these complexes showed a nematic phase while the higher homologues gives smectic mesophases. The corresponding Cu(II) complexes were found to be prone to decomposition just above their transition temperatures. Alkyl or aryl substituents at the azomethine carbon of the nickel derivatives results in non-mesogenic systems.

Styles APA, Harvard, Vancouver, ISO, etc.

2

Steele, J. M. « Metal oxide single crystals as gas sensors ». Thesis, University of Kent, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233273.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

3

Styring, Peter. « Neutral and ionic metal-containing liquid crystals ». Thesis, University of Sheffield, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285012.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

4

Brown, Stephen James. « The Czochrlaski growth and characterisation of single crystals of lead molybdate ». Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364392.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

5

Sparkes, Robert P. « Carbocations in palladium crystals ». Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249213.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

6

Cobb, Stephen Hal. « Gas-phase characterization of the molecular electronic structure of metal clusters and metal cluster oxidation ». Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/30417.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

7

Krishnamurthy, Vivek. « Theoretical investigation of photonic crystal and metal cladding for waveguides and ». Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28214.

Texte intégral

Résumé :

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Klein, Benjamin; Committee Member: Alavi, Kambiz; Committee Member: Allen, Janet K.; Committee Member: Buck, John; Committee Member: Gaylord, Tom; Committee Member: Yoder, Douglas.

Styles APA, Harvard, Vancouver, ISO, etc.

8

Nunes, Silvia Irene. « Grain growth in sintered Zn0 ceramics / ». Thesis, Connect to this title online ; UW restricted, 1990. http://hdl.handle.net/1773/10594.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

9

Tal, Amir. « THREE-DIMENSIONAL MICRON-SCALE METAL PHOTONIC CRYSTALS VIA MULTI-PHOTON DIRECT LASER WRITING AND ELECTROLESS METAL DEPOSITION ». Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3889.

Texte intégral

Résumé :

Three-dimensional (3D) metal photonic crystals (MPCs) can exhibit interesting electromagnetic properties such as ultra-wide photonic or "plasmonic" band gaps, selectively tailored thermal emission, extrinsically modified absorption, and negative refractive index. Yet, optical-wavelength 3D MPCs remain relatively unexplored due to the challenges posed by their fabrication. This work explores the use of multi-photon direct laser writing (DLW) coupled with electroless metallization as a means for preparing MPCs. Multi-photon DLW was used to prepare polymeric photonic crystal (PC) templates having a targeted micron-scale structure and form. MPCs were then created by metallizing the polymeric PCs via wet-chemical electroless deposition. The electromagnetic properties of the polymeric PCs and the metallized structures were characterized using Fourier transform infrared spectroscopy. It is shown that metallization transforms the optical properties of the structures from those of conventional 3D dielectric PCs to those consistent with 3D MPCs that exhibit ultra-wide photonic band gaps. These data demonstrate that multi-photon DLW followed by electroless deposition provides a viable and highly flexible route to MPCs, opening a new path to metal photonic materials and devices.
M.S.
Optics and Photonics
Optics and Photonics
Optics MS

Styles APA, Harvard, Vancouver, ISO, etc.

10

Donnio, B. « Mesomorphic metal complexes of polycatenar stilbazoles : a structure/property study ». Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242211.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

11

Abdelaziz, Nayera. « Metal-Free and Metal-Based Photochemical Sensitization of Organic Azides in Solution, Crystals, and Cryogenic Matrices ». University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1624917700560401.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

12

Kim, Won. « Theoretical and semiempirical study of the A0+ state of NaI ». Title page, table of contents and summary only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phk485.pdf.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

13

Lau, Ka-yin. « Transition metal complexes of functionalized isocyanides as building blocks for molecular solid state materials / ». Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18933841.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

14

Humphrey, Mark Graeme. « Aspects of organometallic chemistry, particularly metal alkynyl and cluster chemistry ». Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09SD/09sdh9267.pdf.

Texte intégral

Résumé :

Includes bibliographical references. Details research carried out into the nonlinear optical properties of metal alkynyls, chiefly organoruthenium complexes, showing that these complexes can be designed to have very large NLO coefficients. Also demonstrates the utility of spectroscopic, electrochemical and copmutational aids as predictive tools for NLO materials. Also examines cluster synthesis, reactivity and physical properties using ruthenium clusters and hard-donor ligands, affording a series of cluster complrxes that provide structural models for industrially-important hydrotreating intermediates.

Styles APA, Harvard, Vancouver, ISO, etc.

15

Dickinson, Calum. « Metal oxide porous single crystals and other nanomaterials : an HRTEM study ». Thesis, University of St Andrews, 2007. http://hdl.handle.net/10023/217.

Texte intégral

Résumé :

Three-dimensional porous single crystals (PSCs) are a recent development in the growing world of mesoporous material. The mesoporosity allows for the material to retain their nanoproperties whilst being bulk in size. The current work concentrates on chromium oxide and cobalt oxide PSCs formed in the templates SBA-15 and KIT-6. HRTEM is the main technique used in this investigation, looking at the morphology and single crystallinity of these materials. A growth mechanism for the PSC material is proposed based on HRTEM observations. XRD studies revealed that the confinement effect, caused by the mesopores, reduces the temperature for both cobalt and chromium oxide crystallisation, as well as a different intermediate route from the metal nitrates. The properties of chromium oxide PSC are also investigated magnetically and catalytically. Some metal oxides in different templates are also presented, despite no PSC forming. HRTEM work on other nanomaterials, based on collaboration, is also presented.

Styles APA, Harvard, Vancouver, ISO, etc.

16

Eve, Jemimah Kate. « Adsorption and co-adsorption on metal single crystals at cryogenic temperatures ». Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313949.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

17

Butterfield, Martin Thomas. « Surface structure of ultrathin metal films deposited on copper single crystals ». Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/33132.

Texte intégral

Résumé :

Ultrathin films of Cobalt, Iron and Manganese have been thennally evaporated onto an fcc Copper (111) single crystal substrate and investigated using a variety of surface structural teclmiques. The small lattice mismatch between these metals and the Cu (111) substrate make them an ideal candidate for the study of the phenomena of pseudomorphic film growth. This is important for the understanding of the close relationship between film structure and magnetic properties. Growing films with the structure of their substrate rather than their bulk phase may provide an opportunity to grow materials with novel physical and magnetic properties, and hence new technological applications. Both Cobalt and Iron have been found to initially maintain a registry with the fee Cu (111) surface in a manner consistent with pseudomorphic growth. This growth is complicated by island rather than layer-by-layer growth in the initials stages of the film. In both cases a change in the structure of the film seems to occur at a point where the coalescence of islands in the film may be expected to occur. When the film does change structure they do not form a perfect over-layer with the structure of their bulk counterpart. The films do contain a number of features representative of the bulk phase but also contain considerable disorder and possibly remnants of fcc (111) structure. The order present in these films can be greatly improved by annealing. Manganese appears to grow with an fee Mn (111) lattice spacing and there is no sign of a change in structure in films of up to 4.61 ML thick. The gradual deposition and annealing of a film to 300°C, with a total deposition time the same as that for a 1 ML thick film, causes a surface reconstruction to occur that is apparent in a R30° (√3×√3) LEED pattern. This is attributed to the formation of a surface alloy, which is also supported by the local expansion of the Cu lattice in the (111) direction.

Styles APA, Harvard, Vancouver, ISO, etc.

18

劉嘉賢 et Ka-yin Lau. « Transition metal complexes of functionalized isocyanides as building blocks for molecular solid state materials ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31214289.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

19

Innes, R. A. « Surface plasmon-polaritons and thermally-induced optical nonlinearities in liquid crystals ». Thesis, University of Exeter, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380733.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

20

Kim, Changsu. « Optical, laser spectroscopic, and electrical characterization of transition metal doped ZnSe and ZnS nano- and microcrystals ». Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2009r/kim.pdf.

Texte intégral

Résumé :

Thesis (Ph. D.)--University of Alabama at Birmingham, 2009.
Title from PDF title page (viewed Feb. 3, 2010). Additional advisors: Renato Camata, Derrick Dean, Chris M. Lawson, Andrei Stanishevsky, Sergey Vyazovkin. Includes bibliographical references (p. 133-140).

Styles APA, Harvard, Vancouver, ISO, etc.

21

Carson, Fabian. « Development of Metal–Organic Frameworks for Catalysis : Designing Functional and Porous Crystals ». Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-115819.

Texte intégral

Résumé :

Metal–organic frameworks, or MOFs, have emerged as a new class of porous materials made by linking metal and organic units. The easy preparation, structural and functional tunability, ultrahigh porosity, and enormous surface areas of MOFs have led to them becoming one of the fastest growing fields in chemistry. MOFs have potential applications in numerous areas such as clean energy, adsorption and separation processes, biomedicine, and sensing. One of the most promising areas of research with MOFs is heterogeneous catalysis. This thesis describes the design and synthesis of new, carboxylate-based MOFs for use as catalysts. These materials have been characterized using diffraction, spectroscopy, adsorption, and imaging techniques. The thesis has focused on preparing highly-stable MOFs for catalysis, using post-synthetic methods to modify the properties of these crystals, and applying a combination of characterization techniques to probe these complex materials. In the first part of this thesis, several new vanadium MOFs have been presented. The synthesis of MIL-88B(V), MIL-101(V), and MIL-47 were studied using ex situ techniques to gain insight into the synthesis–structure relationships. The properties of these materials have also been studied. In the second part, the use of MOFs as supports for metallic nanoparticles has been investigated. These materials, Pd@MIL-101–NH2(Cr) and Pd@MIL-88B–NH2(Cr), were used as catalysts for Suzuki–Miyaura and oxidation reactions, respectively. The effect of the base on the catalytic activity, crystallinity, porosity, and palladium distribution of Pd@MIL-101–NH2(Cr) was studied. In the final part, the introduction of transition-metal complexes into MOFs through different synthesis routes has been described. A ruthenium complex was grafted onto an aluminium MOF, MOF-253, and an iridium metallolinker was introduced into a zirconium MOF, UiO-68–2CH3. These materials were used as catalysts for alcohol oxidation and allylic alcohol isomerization, respectively.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 5: Manuscript.

Styles APA, Harvard, Vancouver, ISO, etc.

22

許國文 et Kwok-man Hui. « The chemistry of triosmium nitrite clusters ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31237083.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

23

Ng, Kwok-sing. « Plastic deformation of aluminium micro-specimens ». Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B4175802X.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

24

Hui, Kwok-man. « The chemistry of triosmium nitrite clusters / ». Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20666706.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

25

Li, Shiwen. « Metal nanoparticles encapsulated in membrane-like zeolite single crystals : application to selective catalysis ». Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10057/document.

Texte intégral

Résumé :

Les matériaux « coeur-coquille » composés d’une nanoparticule métallique encapsulée à l'intérieur de coquilles inorganiques (oxydes, carbone …) attirent de plus en plus l'attention par leurs propriétés particulières, en particulier dans le domaine de la catalyse. Les particules métalliques sont protégées par la coquille, qui empêche entre autres le frittage et la croissance des particules à haute température. Cependant, les coquilles sont généralement méso à macroporeuses et elles ne peuvent pas jouer le rôle de tamis moléculaire pour les molécules de taille nanométrique. En revanche, les zéolithes sont des solides cristallins microporeux dont les pores bien définis permettent une forte discrimination des réactifs basée sur la taille, la forme ou leur coefficient de diffusion. L’objectif de cette thèse visait à la synthèse de catalyseurs de type coeur-coquille dans lesquels la coquille est une zéolite microporeuse de structure MFI (silicalite-1 et ZSM-5), le coeur étant soit une particule de métal noble (Au, Ag, Pt, Pd), soit des alliages de ces différents métaux, soit enfin un métal de transition (Co, Ni, Cu). Ces catalyseurs ont été appliqués dans des réactions d'hydrogénation sélective (aromatiques substitués) et l'oxydation sélective de CO en présence d'hydrocarbures. Nous avons ainsi montré que la coquille zéolithique, tout en protégeant les particules du frittage, modifie la sélectivité des réactions en interdisant aux réactifs volumineux d’atteindre les sites catalytiques
Nanostructured yolk-shell materials, which consist of metal nanoparticle cores encapsulated inside hollow shells, attract more and more attention in material science and catalyst applications during the last two decades. Metal particles are usually highly mono-dispersed in size and isolated from each other by the shell, which prevents growth by sintering at high temperature. Because they are generally made of meso/macroporous oxides or amorphous carbon, shells cannot carry out molecular sieve-type separation of molecules at the nanometric scale. The aim of the present thesis was to synthesize yolk-shell catalyst with microporous zeolite shells (silicalite-1 and ZSM-5), containing noble (Au, Pt, Pd) transition (Co, Ni, Cu) and alloy metal nanoparticles. Zeolites are crystalline microporous solids with well-defined pores capable of discriminating nanometric reactants on the basis of size, shape and diffusion rate. Zeolite-based yolk-shell catalysts have been applied in selective hydrogenation (toluene and mesitylene) and oxidation (CO) reactions in the presence of hydrocarbons. Zeolite shells not only plaid a key role as membranes, thus changing selectivities as compared to conventional supported catalysts, but they also protected metal nanoparticles from sintering under reaction conditions

Styles APA, Harvard, Vancouver, ISO, etc.

26

Kamath, Amarjit. « Hydrothermal Synthesis and Structural Characterization of Single Crystals of Metal-Organic Hybrid Complexes ». Thesis, University of North Bengal, 2018. http://ir.nbu.ac.in/handle/123456789/2791.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

27

Boreland, Matt. « Laser crystallisation of silicon for photovoltaic applications using copper vapour lasers ». [Sydney : University of New South Wales], 1999. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN1999.0055/index.html.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

28

Antonelli, Sarah Bowen. « Studies of the thermal stability and crystallization behavior of electroless and evaporated nickel and cobalt alloy films / ». view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?did=1251855711&sid=1&Fmt=2&clientId=11238&RQT=309&VName=PQD.

Texte intégral

Résumé :

Thesis (Ph. D.)--University of Oregon, 2006.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 105-120). Also available for download via the World Wide Web; free to University of Oregon users.

Styles APA, Harvard, Vancouver, ISO, etc.

29

Ng, Kwok-sing, et 吳國勝. « Plastic deformation of aluminium micro-specimens ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B4175802X.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

30

Jan, Deng-Yang. « Syntheses and reactivity of cluster systems derived from unsaturated cluster ([mu]-H)̳2Os̳3(CO)̳1̳0 / ». The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487263399024287.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

31

Xie, Shunping. « Growth of silver dendrite crystals and liquid chromatographic analysis of water-soluble gold nanoclusters ». HKBU Institutional Repository, 2012. https://repository.hkbu.edu.hk/etd_ra/1436.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

32

Ahonen, P. P. « Aerosol production and crystallization of titanium dioxide from metal alkoxide droplets / ». Espoo [Finland] : Technical Research Centre of Finland, 2001. http://www.vtt.fi/inf/pdf/publications/2001/P439.pdf.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

33

Rohwer, Andrea Berenike. « Introducing organic molecular crystals into ultrafast electron diffraction ». Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95819.

Texte intégral

Résumé :

Thesis (MSc)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Organic molecular salts have a wide range of physical properties which can be chemically tailored by minor variations of their substituents. These characteristics include high degrees of anisotropy, electrical conductivity ranging from superconducting to insulating, and structural changes in the crystal lattice during first order phase transitions brought about by minimal changes in temperature, effective pressure, and in some cases even light. Hence, these materials are particularly interesting for the development of molecular electronics and also as study materials in solid state physics. The family of copper-dimethyl-dicyanoquinone-diimine (Cu(DMe-DCNQI)2) salts forms part of the radical anion salt subclass of organic molecular crystals and is of particular interest due to its extraordinarily high conductivity compared to other quasi one-dimensional organic conductors. Its metal-to-insulator phase transition is characterised by conductivity jumps across several orders of magnitude within a few kelvin. Over the past three decades the metallic and insulating phases, as well as the transition behaviour have been investigated extensively utilising a broad spectrum of methods amongst others electrical conductivity, electron spin resonance, and re ectivity measurements, x-ray photoelectron and infrared spectroscopy, x-ray diffraction, and dilatometry. Fast light-switching between phases has been observed in partially deuterated forms of Cu(DCNQI)2 on sub-100-ps time scales. Furthermore, the phase transition is believed to be induced by a deformation of the crystalline lattice and a charge density wave formation which are detectable in diffraction images. Therefore we want to investigate this metal-to-insulator phase transition structurally and temporally via ultrafast electron diffraction. The technique of ultrafast electron diffraction employs the fundamentals of pump-probe spectroscopy: One of the two femtosecond pulsed laser beams excites the thin, crystalline sample, while the other - after being converted into a pulsed electron beam via the photoelectric effect - forms a diffraction image of the sample's lattice structure. The arrival time of the two pulses at the sample can be varied by a few femtoseconds with respect to each other enabling the resolution of ultrafast structural dynamics of the crystal's atomic lattice via electron diffraction. During the work presented in this thesis the sample preparation and characterisation leading to a successful introduction of Cu(DCNQI)2 into our ultrafast electron diffraction setup is presented. A diffraction pattern of comparable quality to that of a commercially available transmission electron microscope was recorded of the metallic state of partially deuterated d6 Cu(DCNQI)2. Subsequent analysis of the obtained diffraction data and further studies of the low temperature state { including simulations as well as experiments { have narrowed down the factors still making the diffraction pattern evasive. Possible solutions to experimental challenges are proposed to make the documentation of structural ultrafast dynamics in these organic molecular salts an attainable goal in the future.
AFRIKAANSE OPSOMMING: Organiese molekulêre soute het `n wye verskeidenheid van fisiese eienskappe wat chemies verander kan word deur geringe variasie in die samestelling van die sout. Hierdie eienskappe sluit in `n hoë graad van anisotropie, elektriese geleidingsvermoë wat strek van supergeleiding tot elektriese isolasie, en strukturele veranderinge in die kristalstruktuur tydens eerste orde fase-oorgange wat veroorsaak word deur geringe veranderinge in temperature, effektiewe druk en in sommige gevalle selfs lig. Gevolglik is hierdie material besonder interessant vir die ontwikkeling van molekulêre elektronika en ook as studiemateriaal in vastetoestandfisika. Die familie van koperdimetieldisianokinoondiimien (Cu(DMe-DCNQI)2) soute vorm `n deel van die radikaal-anioon-sout subklas van organiese molekulêre kristalle en is van besondere belang as gevolg van hulle buitengewone hoë elektriese geleidingsvermoë in vergelyking met ander kwasi-eendimensionele organiese geleiers. Die metaal-na-isolator fase-oorgang van hierdie kristal word gekenmerk deur die verandering van die geleidingsvermoë met verskeie ordegroottes binne `n paar kelvin. Gedurende die laaste drie dekades is die metaal en isolator fases, asook die oorgangsgedrag deeglik ondersoek met behulp van `n wye verskeidenheid van metodes wat onder andere elektriese geleidingsvermoë, elektron-spin resonans en reeksiemetings, x-straal fotoelektron en infrarooi spektroskopie, x-straal diffraksie en dilatometrie insluit. Vinnige skakeling tussen fases is waargeneem in gedeeltelik gedeuteerde vorms van Cu(DCNQI)2 op `n sub-100-ps tydskaal. Daar word verder geglo dat die fase-oorgang geïnduseer word deur `n deformasie van die kristalstruktuur en die vorming van `n ladingsdigtheidgolf wat meetbaar is in elektrondiffraksiebeelde. Om hierdie rede wil ons die metaal-na-isolator fase-oorgang se struktuur- en tydafhanklikheid ondersoek deur gebruik te maak van ultra-vinnige elektron diffraksie. Die tegniek van ultra-vinnige elektron diffraksie maak gebruik van die beginsels van pomp-toets spektroskopie: Een van die twee femtosekonde laserpulse wek die dun kristallyne monster op, terwyl die ander na omskakeling in `n elektronpuls via die foto-elektriese effek `n diffraksiebeeld van die monster se kristalstruktuur vorm. Die aankomtyd van die twee pulse by die monster kan met `n paar femtosekondes ten opsigte van mekaar verander word om die tydresolusie van die ultra-vinnige strukturele dinamika van die kristal se atoomstruktuur deur elektrondiffraksie moontlik te maak. In hierdie tesis word die monstervoorbereiding en karakterisering wat gelei het tot suksesvolle eksperimente op Cu(DCNQI)2 in ons ultra-vinnige elektron diffraksie opstelling behandel. `n Diffraksie patroon waarvan die kwaliteit vergelykbaar is met die van `n kommersiëel beskikbare transmissie elektron mikroskoop is gemeet vir die metaalfase van gedeeltelik gedeuteerde d6 Cu(DCNQI)2. Daaropvolgende analiese van die gemete diffraksiedata en verdere studies van die lae temperatuur toestand wat simulasies sowel as eksperimente insluit het `n klein aantal faktore uitgewys wat steeds die deteksie van die isolatorfase se ladingsdigtheidgolf se kenmerkende diffraksiepatroon verhoed. Moontlike oplossings tot eksperimentele uitdagings word voorgestel om die dokumentering van strukturele ultra-vinnige dinamika in hierdie organiese molekulêre soute `n haalbare toekomstige doelwit te maak.

Styles APA, Harvard, Vancouver, ISO, etc.

34

Yu, Xin [Verfasser], et Hans-Joachim [Akademischer Betreuer] Freund. « Ultra-thin silicate films on metal single crystals / Xin Yu. Gutachter : Hans-Joachim Freund ». Berlin : Technische Universität Berlin, 2013. http://d-nb.info/1065664958/34.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

35

Klingstedt, Miia. « Characterizing cavity containing materials using electron microscopy : A study of metal oxides, mesoporous crystals and porous material containing nanosized metal-particles ». Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-64164.

Texte intégral

Résumé :

This thesis concerns the characterization of novel materials by utilizing electron microscopy techniques. The examined materials contain cavities with certain attributes that enables desired properties for applications such as gas separation, catalysis and fuel cells. The specimens concerned herein belong to the following groups of materials: Metal oxides in the Sb-W-Mo-O system; ordered mesoporous silicas and carbons; hollow spheres containing Au-nanoparticles; zeolite LTA incorporated with mesopores; metal organic frameworks doped with nickel. With scanning electron microscopy (SEM) and transmission electron microscopy (TEM) you get vast possibilities within the field of characterization. This thesis utilizes conventional electron microscopy techniques such as imaging, energy-dispersive spectroscopy and electron diffraction as well as reconstruction techniques, such as exit-wave reconstruction, electron tomography and electron crystallography. Furthermore, the sample preparation technique cross-section polishing has been used in conjunction with low voltage SEM studies. The scientific approach is to gain knowledge of nano-sized cavities in materials, in particular their shape, size and content. The cavities often have irregularities that originates from the synthesis procedure. In order to refine the synthesis and to understand the properties of the material it is required to carefully examine the local variations. Therefore average characterization techniques such as crystallography needs to be combined with local examination techniques such as tomography. However, some of the materials are troublesome to investigate since they to some extent bring limitations to or gets easily damaged by the applied characterization technique. For the development of novel materials it is essential to find means of overcoming also these obstacles.
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 6: Submitted.

Styles APA, Harvard, Vancouver, ISO, etc.

36

Bouzaid, Jocelyne M. « Supramolecular selection in molecular and framework co-crystals ». Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/70216/1/Jocelyne_Bouzaid_Thesis.pdf.

Texte intégral

Résumé :

An ongoing challenge in chemistry and crystal engineering is the synthesis of functional materials with predictable structures and customisable properties. This may be achieved by crystallising mixtures of different compounds. Co-crystals formed through this method have predictable structures and their properties may be tuned by varying the ratio of the compounds in the crystallising solution. This thesis examines single crystals formed by the co-crystallisation of metal complexes that have similar structures but different physical or chemical properties. A variety of new compounds with interesting properties were prepared, characterised and their significance in the context of crystal engineering was explored.

Styles APA, Harvard, Vancouver, ISO, etc.

37

Schaaff, T. Gregory. « Preparation and characterization of thioaurite cluster compounds ». Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/30858.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

38

Uddin, Salah. « Semi-analytical and numerical modeling of microsegregation for solidifying metallic alloys ». Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=112587.

Texte intégral

Résumé :

In this study, two semi-analytical models of microsegregation were developed to predict the concentration fields of solute in the liquid and solid regions for dendritic solidification of binary metallic alloys. Both models assume that the growing dendrites are cylindrical in shape. This assumption is more realistic compared to the common assumptions of plate-like dendrites that most of the earlier researchers employed in their microsegregation modeling study. The solute redistribution profile, in the developing solid layer, necessary to determine the back diffusion parameter was derived from Fick's second law for the model without coarsening. The application of this parameter in a wide range of conditions and the use of its basic form in the model with coarsening was verified. The concept of coordinate transformation and enhancement of back-diffusion Fourier number were used in deriving the model which took into account the coarsening of dendrites. The models are then extended to deal with rapid solidification, peritectic transformations and multi-component systems and the results were compared with relevant experimental data. A good agreement between the model predictions and experimental results was found.
The second part of this study was focused on developing a fully numerical microsegregation model. The numerical model built upon a previously proposed phase change model which relied upon a coordinate transformation technique. The model was extended to deal with moving boundaries with solute diffusion. A suitable computational procedure was developed to solve the model equations which are strongly coupled to each other. To verify the accuracy of the present algorithm with regard to the capability of tracking the moving interfaces, analytical solution of the Stefan problem was used for verification purposes. A good agreement between the model predictions and the analytical solution was found. Evolution of concentration fields during solidification was calculated in the growing solid as well as in the shrinking liquid regions for rectangular, cylindrical and spherical dendrite geometries. The effects of various cooling conditions and relevant parametric values on microsegregation were analyzed and discussed.

Styles APA, Harvard, Vancouver, ISO, etc.

39

Winston, Erick B. « Dielectric spectroscopy and simulation of cryptophane and metal-organic framework crystals containing internal molecular rotors ». Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3303831.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

40

Gagné, Olivier C. « Bond lengths and bond valences of ions bonded to oxygen : their variability in inorganic crystals ». Acta Crystallographica B, 2015. http://hdl.handle.net/1993/31697.

Texte intégral

Résumé :

A large amount of information concerning interatomic distances in the solid state is available, but little has been done in recent times to comprehensively filter, summarize and analyze this information. Here, I examine the distribution of bond lengths for 135 ions bonded to oxygen, using 180,331 bond lengths extracted from 9367 refined crystal structures collected from the Inorganic Crystal Structure Database (ICSD). The data are used to evaluate the parameterization of the bond-length—bond-valence relation of the bond-valence model. Published bond-valence parameters for 135 cations bonded to oxygen, and the various methods used in their derivation, are evaluated. New equations to model the relation are tested and the common form of the equation is found to be satisfactory. A new method (the Generalized Reduced Gradient Method, GRG method) is used to derive new bond-valence parameters for 135 cations bonded to oxygen, leading to significant improvements in fit for many of the ions. The improved parameterization is used to gain crystal-chemical insight into the milarite structure. A literature review of 350+ published compositions is done to review the end-members of the milarite group and to identify compositions that should have been described as distinct minerals species. The a priori bond-valences are calculated for minerals of this structure, and are used to examine the controls of bond topology on site occupancy, notably by localizing the major source of strain of the structure (the B site). Examination of the compositions of all known milarite-group minerals shows that compositions with a fully occupied B site are less common than those with a vacant B site, in accord with the idea that the B site is a local region of high strain in the structure. The bond-length distributions for the ions of the alkali and alkaline-earth metal families are examined. Variations in mean bond-lengths are only partly explained by the distortion theorem of the bond-valence model. I have found that bond length also correlates with the amount of vibrational displacement of the constituent ions. The validity of some uncommon coordination numbers, e.g., [3]-coordinated Li+, [3]-coordinated Be2+, is confirmed.
October 2016

Styles APA, Harvard, Vancouver, ISO, etc.

41

Förster, Daniel F. [Verfasser]. « EuO and Eu on metal crystals and graphene : interface effects and epitaxial films / Daniel F. Förster ». München : Verlag Dr. Hut, 2012. http://d-nb.info/1020298677/34.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

42

張碧玉 et Pik-yuk Christine Cheung. « Crystal structure analysis of imido, nitrido and oxo complexes of rhenium (V), osmium (VI) and ruthenium (III) and some complexes oftrinuclear gold (I) ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1991. http://hub.hku.hk/bib/B31210211.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

43

Cheung, Pik-yuk Christine. « Crystal structure analysis of imido, nitrido and oxo complexes of rhenium (V), osmium (VI) and ruthenium (III) and some complexes of trinuclear gold (I) / ». [Hong Kong : University of Hong Kong], 1991. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13138327.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

44

Miller, Paul. « Zinc Oxide : A spectroscopic investigation of bulk crystals and thin films ». Thesis, University of Canterbury. Physics and Astronomy, 2008. http://hdl.handle.net/10092/3618.

Texte intégral

Résumé :

The optical properties of zinc oxide crystals and thin films prepared by different methods are investigated. Single crystal zinc oxide samples prepared by melt and hydrothermal growth techniques were obtained. The influence of polarity and growth method on the optical properties were studied and correlated with their electronic properties. Thin films prepared by molecular beam epitaxy (MBE) and sputtering were studied and the influence of growth conditions and post growth treatment on the optical properties of the films was investigated. The photo-luminescence (PL) of bulk zinc oxide was examined at high resolution. Line widths of less than 0.1 meV were observed. More than a dozen different transitions in the near band edge region (NBE 360-380 nm) were noted, several of which displayed a separation of <0.5 meV which goes some way to illustrating the complexity of the system. Attempts were made, with some success, to reconcile the two main competing identification systems of the NBE transitions and explanations for some of the discrepancies are provided. The controversial deep level transitions in the visible part of the spectrum are fit with 3 Gaussians and their identities discussed with relation to the available literature. The presence of copper impurities was detected in annealed films and a model to explain their behaviour under annealing conditions is hypothesised. Films grown by MBE here at the University of Canterbury are shown to have PL line widths of as little as 2.2 meV, the ratio of active oxygen species in the growth chamber during deposition is shown to effect the optical quality of the films. It is shown that annealing can improve the optical quality of the films and various other methods of influencing the films properties are discussed. Reactive, magnetron, direct current sputtering is shown to be the optimal method of growth for maximising both optical and piezo-electric properties. Optimum annealing temperatures were found at 900 and 1100 ℃ with a local minimum at 1000 ℃. X-ray diffraction, atomic force and scanning electron microscopy measurements in addition to optical PL measurements show the influence of annealing on the polycrystalline sputtered ZnO films. Films grown on glass, silicon, sapphire and quartz were shown to display similar behaviour under annealing conditions. It was found that zinc oxide based devices were liable to be chemically unstable at temperatures above 1100 ℃. The piezo electric properties of the films were examined and attempts were made to prepare a zinc oxide film optimised for both optical quality and piezoelectric properties for possible future applications of a hybrid opto-mechanical coupled devices.

Styles APA, Harvard, Vancouver, ISO, etc.

45

Gullapalli, Vikranth. « Study of Metal Whiskers Growth and Mitigation Technique Using Additive Manufacturing ». Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc804972/.

Texte intégral

Résumé :

For years, the alloy of choice for electroplating electronic components has been tin-lead (Sn-Pb) alloy. However, the legislation established in Europe on July 1, 2006, required significant lead (Pb) content reductions from electronic hardware due to its toxic nature. A popular alternative for coating electronic components is pure tin (Sn). However, pure tin has the tendency to spontaneously grow electrically conductive Sn whisker during storage. Sn whisker is usually a pure single crystal tin with filament or hair-like structures grown directly from the electroplated surfaces. Sn whisker is highly conductive, and can cause short circuits in electronic components, which is a very significant reliability problem. The damages caused by Sn whisker growth are reported in very critical applications such as aircraft, spacecraft, satellites, and military weapons systems. They are also naturally very strong and are believed to grow from compressive stresses developed in the Sn coating during deposition or over time. The new directive, even though environmentally friendly, has placed all lead-free electronic devices at risk because of whisker growth in pure tin. Additionally, interest has occurred about studying the nature of other metal whiskers such as zinc (Zn) whiskers and comparing their behavior to that of Sn whiskers. Zn whiskers can be found in flooring of data centers which can get inside electronic systems during equipment reorganization and movement and can also cause systems failure.Even though the topic of metal whiskers as reliability failure has been around for several decades to date, there is no successful method that can eliminate their growth. This thesis will give further insights towards the nature and behavior of Sn and Zn whiskers growth, and recommend a novel manufacturing technique that has potential to mitigate metal whiskers growth and extend life of many electronic devices.

Styles APA, Harvard, Vancouver, ISO, etc.

46

Karolak, Michael [Verfasser], et Alexander [Akademischer Betreuer] Lichtenstein. « Electronic Correlation Effects in Transition Metal Systems : From Bulk Crystals to Nanostructures / Michael Karolak. Betreuer : Alexander Lichtenstein ». Hamburg : Staats- und Universitätsbibliothek Hamburg, 2013. http://d-nb.info/1045730556/34.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

47

Zhao, Liang. « Optical properties of two-dimemsional Van der Waals crystals : from terahertz to visible ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1433378350.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

48

Parala, Harish. « Precursor routes to selected metal and semiconductor nanomaterials crystals, composites, colloids of Au, GaN, InN, CdSe and TiO₂ / ». [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=96870901X.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

49

Parala, Harish. « Precursor routes to selected metal and semiconductor nanomaterials crystals, composites, colloids of Au, GaN, InN, CdSe and TiO2 / ». [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=96870901X.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

50

Norfleet, David Matthew. « Sample size effects related to nickel, titanium and nickel-titanium at the micron size scale ». Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1187038020.

Texte intégral

Styles APA, Harvard, Vancouver, ISO, etc.

Thèses sur le sujet « Metal crystals »

Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres