Дисертації: "Decomposition of metal trifluoroacetates"

1

Stillman, T. J. "A crystallographic investigation into the structure of the metal - trifluoroacetates." Thesis, Lancaster University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383545.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

2

Sykes, Martin Lewis. "Metal carbonyl decomposition and carbon decomposition in the A.G.R." Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315635.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

3

Coetzee, Anita. "Thermal decomposition of mixed metal oxalates." Thesis, Rhodes University, 1993. http://hdl.handle.net/10962/d1005053.

Повний текст джерела

Анотація:

The mixed metal oxalates, FeCu(ox)₂.3H₂0, CoCu(ox)₂.3H₂0, and NiCu(ox)₂.3.5H₂0, [ox = C₂0₄] have been prepared by coprecipitation from solution. The thermal behaviour of these compounds in nitrogen and in oxygen has been examined using thermogravimetry (TG), thermomagnetometry (TM), differential scanning calorimetry (DSC) and evolved gas analysis (EGA), and results are compared with results obtained for Cuox and Mox.yH₂0. The thermal behaviour of the mixed oxalates, MCU(OX)₂.xH₂0, differed from that of the individual metal oxalates, Cuox, Coox.2H₂0, Niox.2H₂0 and Feox.2H₂0. All three mixed oxalates on heating in N₂, first dehydrate and then decompose in at least two overlapping endothermic stages. Both CO and CO₂ were evolved in proportions which varied with the surrounding atmosphere, and from compound to compound, and with extent of reaction of a given compound. The mixed oxalates, MCU(OX)₂.xH₂0, do not show the exothermic behaviour characteristic of Cuox, and reasons for this are discussed. Thermochemical calculations were done and the enthalpies of formation of the hydrates and dehydrated oxalates were determined. It was found that the enthalpy of mixing was very small or within experimental error. X-ray powder diffraction patterns for the individual and mixed oxalates were compared. The pattern for Cuox differs from the patterns obtained for the other oxalates, confirming suggestions that Cuox has a structure different to most other transition metal oxalates. The kinetics of dehydration and decomposition of the mixed oxalates were investigated, using isothermal and programmed temperature TG and DSC experiments. The yield and composition of evolved gases during isothermal decomposition were measured and compared with the enthalpy changes. X-ray photoelectron spectroscopy studies provided some information on the electron environment of the metal atoms in the various oxalates.

Стилі APA, Harvard, Vancouver, ISO та ін.

4

Waechtler, Thomas, Yingzhong Shen, Alexander Jakob, Ramona Ecke, Stefan E. Schulz, Lars Wittenbecher, Hans-Josef Sterzel, et al. "Evaluation of Phosphite and Phosphane Stabilized Copper(I) Trifluoroacetates as Precursors for the Metal-Organic Chemical Vapor Deposition of Copper." Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200600315.

Повний текст джерела

Анотація:

Copper has become the material of choice for metallization of high-performance ultra-large scale integrated circuits. As the feature size is continuously decreasing, metal-organic chemical vapor deposition (MOCVD) appears promising for depositing the Cu seed layer required for electroplating, as well as for filling entire interconnect structures. In this work, four novel organophosphane and organophosphite Cu(I) trifluoroacetates were studied as precursors for Cu MOCVD. Details are reported on CVD results obtained with Tris(tri-n-butylphosphane)copper(I)trifluoroacetate, (ⁿBu₃P)₃CuO₂CCF₃. Solutions of this precursor with acetonitrile and isopropanol were used for deposition experiments on 100 mm Si wafers sputter-coated with Cu, Cu/TiN, and Al(2 % Si)/W. Experiments were carried out in a cold-wall reactor at a pressure of 0.7 mbar, using a liquid delivery approach for precursor dosage. On Cu seed layers, continuous films were obtained at low deposition rates (0.5 to 1 nm/min). At temperatures above 320°C, hole formation in the Cu films was observed. Deposition on TiN led to the formation of single copper particles and etching of the TiN, whereas isolating aluminum oxyfluoride was formed after deposition on Al(Si)/W. It is concluded that the formation of CF₃ radicals during decarboxylation has a negative effect on the deposition results. Furthermore, the precursor chemistry needs to be improved for a higher volatility of the complex.

Стилі APA, Harvard, Vancouver, ISO та ін.

5

Bocelli, Ludovica. "Catalytic decomposition of formic acid using supported metal nanoparticles." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11929/.

Повний текст джерела

Анотація:

Upgrade of hydrogen to valuable fuel is a central topic in modern research due to its high availability and low price. For the difficulties in hydrogen storage, different pathways are still under investigation. A promising way is in the liquid-phase chemical hydrogen storage materials, because they can lead to greener transformation processes with the on line development of hydrogen for fuel cells. The aim of my work was the optimization of catalysts for the decomposition of formic acid made by sol immobilisation method (a typical colloidal method). Formic acid was selected because of the following features: it is a versatile renewable reagent for green synthesis studies. The first aim of my research was the synthesis and optimisation of Pd nanoparticles by sol-immobilisation to achieve better catalytic performances and investigate the effect of particle size, oxidation state, role of stabiliser and nature of the support. Palladium was chosen because it is a well-known active metal for the catalytic decomposition of formic acid. Noble metal nanoparticles of palladium were immobilized on carbon charcoal and on titania. In the second part the catalytic performance of the “homemade” catalyst Pd/C to a commercial Pd/C and the effect of different monometallic and bimetallic systems (AuxPdy) in the catalytic formic acid decomposition was investigated. The training period for the production of this work was carried out at the University of Cardiff (Group of Dr. N. Dimitratos).

Стилі APA, Harvard, Vancouver, ISO та ін.

6

Makepeace, Joshua William. "Light metal amides for hydrogen storage and ammonia decomposition." Thesis, University of Oxford, 2014. https://ora.ox.ac.uk/objects/uuid:baf23b20-eab8-4baa-98a8-e0084bd85e39.

Повний текст джерела

Анотація:

Hydrogen has long been touted as an alternative fuel which could form the basis of a sustainable energy system: the hydrogen economy. This thesis advances the application of light metal amide materials in the realisation of this transformative potential. One of the most vexing technical challenges to the widespread adoption of hydrogen in transportation applications is its low volumetric energy density, which makes the storage of a sufficient amount of hydrogen in a vehicle very difficult. In their conventional application, light metal amides (M(NH₂)_x),where M is a Group I or II metal) have been promoted as a means of storing large quantities hydrogen in the solid state, significantly increasing this energy density. This thesis highlights the impressive characteristics of amide-based materials, primarily the facile nature of the reversibility of the hydrogen storage reaction, as a model for the development and optimisation of solid-state hydrogen stores. The study of the relationship between the crystal structures of the relevant materials and their hydrogen storage properties through in situ X-ray and neutron powder diffraction measurements is reported for the lithium amide - lithium hydride (Li-N-H) hydrogen store. These investigations provide strong evidence for ionic mobility as the basis of reversible hydrogen storage in the Li-N-H system. The hydrogen storage and release reactions are seen to progress through a continuum of non-stoichiometric states, a transformation which is facilitated by its topotactic nature. The structural and energetic properties of these non-stoichiometric phases are reported, showing that they are intrinsically disordered and thermodynamically unstable relative to their parent structures. The study of the behaviour of the Li-N-H system is extended to many tens of hydrogenation-dehydrogenation cycles to examine practical performance, confirming the mechanism of capacity loss through the formation of parasitic lithium hydride, and showing that the addition of nitrogen improves the cycling lifetime of the system. An unexplored aspect of light metal amide chemistry is also presented, where the hydrogen storage and release reactions of sodium amide are performed simultaneously. Together, these reactions effect the chemical decomposition of ammonia. Ammonia is a high energy density liquid hydrogen carrier which has been largely overlooked, partly due to the difficulty extracting its stored hydrogen. This work demonstrates a new method of ammonia decomposition which gives comparable performance to the expensive rare-metal catalysts which are currently used for the productions of high-purity hydrogen. A survey of the ammonia decomposition efficiency of a number of light metal amides and imides is presented, showing that it is not only amides which decompose into their constituent elements (such as sodium amide) which are active in ammonia decomposition, but also imide-forming amides. Indeed, imides and imide-forming amides are shown to be advantageous from the perspective of containing the catalyst material. Neutron diffraction and isotope exchange measurements provide some initial insights into the mechanism of reaction, identifying clear avenues for development of these systems, and inviting further discussion of the potential of ammonia as a sustainable energy vector.

Стилі APA, Harvard, Vancouver, ISO та ін.

7

Saunders, Andrew J. "Metal sulphur complexes and systematic investigation of their thermal decomposition." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432568.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

8

Tesfai, Teweldemedhim M. "Adsorption and decomposition of organophosphorus compounds on alumina supported metal oxides." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 1998. http://digitalcommons.auctr.edu/dissertations/1540.

Повний текст джерела

Анотація:

Diffuse reflectance infrared spectroscopy techniques have been employed to investigate the interaction and decomposition of DMMP alumina supported iron oxide catalysts differing in iron oxide loading. At room temperature, the low loading iron oxide catalysts have shown no significant activity toward the decomposition ofDMMP, and they behave similarly to alumina. For the low loading iron oxide catalysts, all the methyl stretching vibrations were observed and their relative intensities did not change as a function of exposure to DMMP. On the other hand, DMMP adsorbs dissociatively on the high loading iron oxides, 8.5 wt%10 iron and above. It appears that the P-CH3 bond dissociates upon adsorption of DMMP on the high loading supported iron oxide catalysts at room temperature. DMMP on alumina supported copper catalyst, 4.04 wt"10 Cu, has been observed to adsorb on the metal oxide through the P=O bond to a Lewis acid site. On the surface, adsorbed DMMP has been observed to decompose with loss of both the methoxy methyl groups and the phosphorus-bound methyl groups between 100 and 200'C. All the methyl groups are decomposed above 300 'c and only phosphate complexes are observed on the surface.

Стилі APA, Harvard, Vancouver, ISO та ін.

9

Stell, Jonathan Kendrew. "An E.S.R. study of the decomposition of peroxides by metal ions." Thesis, University of York, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276493.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

10

Zhang, Yanping. "Nitric oxide decomposition over metal ion-modified Cu-ZSM-5 catalysts." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11260.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

11

Zhao, Qi. "Characterization and Thermal Decomposition Behavior of Carbon Nanotubes and Nanocomposites." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1378113311.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

12

Serra, Maia Rui Filipe. "Relation between surface structural and chemical properties of platinum nanoparticles and their catalytic activity in the decomposition of hydrogen peroxide." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/85149.

Повний текст джерела

Анотація:

The disproportionation of H₂O₂ to H₂O and molecular O₂ catalyzed by platinum nanocatalysts is technologically very important in several energy conversion technologies, such as steam propellant thrust applications and hydrogen fuel cells. However, the mechanism of H₂O₂ decomposition on platinum has been unresolved for more than 100 years and the kinetics of this reaction were poorly understood. Our goal was to quantify the effect of reaction conditions and catalyst properties on the decomposition of H₂O₂ by platinum nanocatalysts and determine the mechanism and rate-limiting step of the reaction. To this end, we have characterized two commercial platinum nanocatalysts, known as platinum black and platinum nanopowder, and studied the effect of different reaction conditions on their rates of H₂O₂ decomposition. These samples have different particle size and surface chemisorbed oxygen abundance, which were varied further by pretreating both samples at variable conditions. The rate of H₂O₂ decomposition was studied systematically as a function of H₂O₂ concentration, pH, temperature, particle size and surface chemisorbed oxygen abundance. The mechanism of H₂O₂ decomposition on platinum proceeds via two cyclic oxidation-reduction steps. Step 1 is the rate limiting step of the reaction. Step 1: Pt + H₂O₂ → H₂O + Pt(O). Step 2: Pt(O) + H₂O₂ → Pt + O₂ + H₂O. Overall: 2 H₂O₂ → O₂ + 2 H₂O. The decomposition of H₂O₂ on platinum follows 1st order kinetics in terms of H₂O₂ concentration. The effect of pH is small, yet statistically significant. The rate constant of step 2 is 13 times higher than that of step 1. Incorporation of chemisorbed oxygen at the nanocatalyst surface resulted in higher initial rate of H₂O₂ decomposition because more sites initiate their cyclic process in the faster step of the reaction. Particle size does not affect the kinetics of the reaction. This new molecular-scale understanding of the decomposition of H₂O₂ by platinum is expected to help advance many energy technologies that depend on the rate of H₂O₂ decomposition on nanocatalysts of platinum and other metals.
Ph. D.

Стилі APA, Harvard, Vancouver, ISO та ін.

13

Upton, J. R. "The application of quantitative time-of-flight mass spectrometry to study certain tungston (VI) oxidehalide decomposition reactions." Thesis, University of Salford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376883.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

14

Griffiths, David P. "Trying to decrease the decomposition rates of peracids (and Hâ‚‚Oâ‚‚) by solution-phase metal ions." Thesis, University of York, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423842.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

15

Al-Sousi, Ghareeb N. "Studies on the thermal decomposition behaviour, kinetics and electrical conductivity of the non-isothermal decomposition of pyridine mono carboxylic acids and some of their transition metal complexes." Thesis, Aston University, 2000. http://publications.aston.ac.uk/9623/.

Повний текст джерела

Анотація:

The thesis is divided into four chapters. They are: introduction, experimental, results and discussion about the free ligands and results and discussion about the complexes. The First Chapter, the introductory chapter, is a general introduction to the study of solid state reactions. The Second Chapter is devoted to the materials and experimental methods that have been used for carrying out the experiments. The Third Chapter is concerned with the characterisations of free ligands (Picolinic acid, nicotinic acid, and isonicotinic acid) by using elemental analysis, IR spectra, X-ray diffraction, and mass spectra. Additionally, the thermal behaviour of free ligands in air has been studied by means of thermogravimetry (TG), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC) measurements. The behaviour of thermal decomposition of the three free ligands was not identical Finally, a computer program has been used for kinetic evaluation of non-isothermal differential scanning calorimetry data according to a composite and single heating rate methods in comparison with the methods due to Ozawa and Kissinger methods. The most probable reaction mechanism for the free ligands was the Avrami-Erofeev equation (A) that described the solid-state nucleation-growth mechanism. The activation parameters of the decomposition reaction for free ligands were calculated and the results of different methods of data analysis were compared and discussed. The Fourth Chapter, the final chapter, deals with the preparation of cobalt, nickel, and copper with mono-pyridine carboxylic acids in aqueous solution. The prepared complexes have been characterised by analyses, IR spectra, X-ray diffraction, magnetic moments, and electronic spectra. The stoichiometry of these compounds was ML2x(H20), (where M = metal ion, L = organic ligand and x = water molecule). The environments of cobalt, nickel, and copper nicotinates and the environments of cobalt and nickel picolinates were octahedral, whereas the environment of copper picolinate [Cu(PA)2] was tetragonal. However, the environments of cobalt, nickel, and copper isonicotinates were polymeric octahedral structures. The morphological changes that occurred throughout the decomposition were followed by SEM observation. TG, DTG, and DSC measurements have studied the thermal behaviour of the prepared complexes in air. During the degradation processes of the hydrated complexes, the crystallisation water molecules were lost in one or two steps. This was also followed by loss of organic ligands and the metal oxides remained. Comparison between the DTG temperatures of the first and second steps of the dehydration suggested that the water of crystallisation was more strongly bonded with anion in Ni(II) complexes than in the complexes of Co(II) and Cu(II). The intermediate products of decomposition were not identified. The most probable reaction mechanism for the prepared complexes was also Avrami-Erofeev equation (A) characteristic of solid-state nucleation-growth mechanism. The tempemture dependence of conductivity using direct current was determined for cobalt, nickel, Cl.nd copper isonicotinates. An activation energy (ΔΕ), the activation energy (ΔΕ ) were calculated. The temperature and frequency dependence of conductivity, the frequency dependence of dielectric constant, and the dielectric loss for nickel isonicotinate were determined by using altemating current. The value of s parameter and the value of density of state [N(Ef)] were calculated.

Стилі APA, Harvard, Vancouver, ISO та ін.

16

Bruno, Deborah Suzanne. "Synthesis and thermal decomposition of [CM(CO)CH₂S(Ph)CH₂CH=CH₂] BF₄, M=Fe, Ru." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/27663.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

17

George, Lyci. "Structural Characterization of Metal Hydrides for Energy Applications." FIU Digital Commons, 2010. http://digitalcommons.fiu.edu/etd/233.

Повний текст джерела

Анотація:

Hydrogen can be an unlimited source of clean energy for future because of its very high energy density compared to the conventional fuels like gasoline. An efficient and safer way of storing hydrogen is in metals and alloys as hydrides. Light metal hydrides, alanates and borohydrides have very good hydrogen storage capacity, but high operation temperatures hinder their application. Improvement of thermodynamic properties of these hydrides is important for their commercial use as a source of energy. Application of pressure on materials can have influence on their properties favoring hydrogen storage. Hydrogen desorption in many complex hydrides occurs above the transition temperature. Therefore, it is important to study the physical properties of the hydride compounds at ambient and high pressure and/or high temperature conditions, which can assist in the design of suitable storage materials with desired thermodynamic properties. The high pressure-temperature phase diagram, thermal expansion and compressibility have only been evaluated for a limited number of hydrides so far. This situation serves as a main motivation for studying such properties of a number of technologically important hydrides. Focus of this dissertation was on X-ray diffraction and Raman spectroscopy studies of Mg2FeH6, Ca(BH4)2, Mg(BH4)2, NaBH4, NaAlH4, LiAlH4, LiNH2BH3 and mixture of MgH2 with AlH3 or Si, at different conditions of pressure and temperature, to obtain their bulk modulus and thermal expansion coefficient. These data are potential source of information regarding inter-atomic forces and also serve as a basis for developing theoretical models. Some high pressure phases were identified for the complex hydrides in this study which may have better hydrogen storage properties than the ambient phase. The results showed that the highly compressible B-H or Al-H bonds and the associated bond disordering under pressure is responsible for phase transitions observed in brorohydrides or alanates. Complex hydrides exhibited very high compressibility suggesting possibility to destabilize them with pressure. With high capacity and favorable thermodynamics, complex hydrides are suitable for reversible storage. Further studies are required to overcome the kinetic barriers in complex hydrides by catalytic addition. A comparative study of the hydride properties with that of the constituting metal, and their inter relationships were carried out with many interesting features.

Стилі APA, Harvard, Vancouver, ISO та ін.

18

Mitchell, Michael S. "Oxidation of biological molecules with bicarbonate-activated hydrogen peroxide and the decomposition of hydrogen peroxide catalyzed by manganese(II) and bicarbonate." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0004948.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

19

Agarwal, Kuldeep. "Physics Based Hierarchical Decomposition of Processes for Design of Complex Engineered Systems." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1322152146.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

20

Wasmund, Eric Bain Coley Ken. "A study of powder making by the decomposition of nickel carbonyl in an aerosol tube reactor." *McMaster only, 2005.

Знайти повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

21

RACIOPPI, STEFANO. "CHEMICAL BONDING IN METAL-ORGANIC SYSTEMS: NATURE, STRUCTURES AND PROPERTIES." Doctoral thesis, Università degli Studi di Milano, 2019. http://hdl.handle.net/2434/606271.

Повний текст джерела

Анотація:

The main purpose of my thesis is the application of theoretical and experimental methods for the study of the nature of the chemical bond and its effect on structures and properties in organome-tallic systems, like Metal Carbonyl Clusters and Coordination Polymers (CPs) featuring, in some of the cases under study, intrinsic porosity (in the following, PCP for Porous Coordination Polymers or MOFs for Metal-Organic Frameworks). Concerning metal clusters, we worked on high nuclearity metal carbonyl clusters, and, particularly, on those featuring semi-interstitial atoms. The chemical bonding and the related properties in these peculiar class of molecules are still a matter of discussion in the scientific community. Concerning the class of Metal-organic Frameworks, we focused our attention on azolate-based ligands as building blocks for the synthesis of MOFs, looking at their possible future application as ultra-low dielectric constant materials in electronic devices. Finally, we investigated the structural behavior of Coordination Polymers at non-ambient condition (high pressure, in the order of 0-8 GPa), to induce new interactions and attitudes like electric conductivity. This research required the application of a bunch of theoretical tools, assisted by accurate single crystal X-ray diffraction experiments in standard and not-standard conditions (low temperature and high pressure). Moreover, a protocol for comparing different energy decomposition methods was developed and successfully applied to investigate the bonding nature in simple and complex systems.

Стилі APA, Harvard, Vancouver, ISO та ін.

22

Nagy, Péter. "Formation and Decomposition of Platinum–Thallium Bond, Kinetics and Mechanism. Structural Characterization of Some Metal Cyanides in the Solid State." Doctoral thesis, KTH, Chemistry, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3803.

Повний текст джерела

Анотація:

The kinetic and mechanistic features of a new series ofplatinum-thallium cyano compounds containing a direct andunsupported by ligands metal-metal bond have been studied insolution, using standard mixandmeasurespectrophotometric technique and stoppedflow method.These reactions are interpreted as oxidative addition of the cspecies to the square planar Pt(CN)₄^2-complex. Each of these processes was found to befirst-order in Pt(CN)₄^2-, the corresponding TI^IIIcomplex and a cyanide ion donating species whichacts as a catalyst. Both di- and trinuclear complexes werestudied, and the kinetically significant thallium complexes intheir formation and the catalytically active cyanide sourcesare as follows: [(CN)₅PtTl(CN)₃]^3-: Tl(CN)₄(alkaline region), Tl(CN)₃(slightly acidic region) and CN; [(CN)₅PtTl(CN)]: Tl(CN)₂⁺and Tl(CN)₂⁺; [(CN)₅PtTlPt(CN)₅]^3-: [(CN)₅PtTl(CN)]and HCN. Appropriatemechanisms were postulated for the overall reactions in allcases, which include i) metalmetal bond formation stepand ii) coordination of an axial cyanide ion to the platinumcenter. Two experimentally indistinguishable kinetic modelswere proposed for the formation of the dinuclear complexeswhich are different in the sequence of the two steps. In thecase of the trinuclear complex, experimental evidence isavailable to exclude one of the alternative reaction paths, andit was proven that the metalmetal bond formation precedesthe axial cyanide coordination.

The cyanide ligands coordinated to TI^IIIin the PtTl complexes could be replacedsuccessfully with aminopolycarboxylates e.g.: mimda^2-, nta^3-, edta^4-. The [(CN)₅PtTl(edta)]^4-complex, with a direct metalmetal bond hasbeen prepared in solution by two different reactions: a)dissolution of [(CN)₅PtTl](s) in an aqueous solution of edta, b)directly from Pt(CN)₄^2-and Tl(edta)(CN)^2-. The decomposition reaction is greatlyaccelerated by cyanide and significantly inhibited by edta. Itproceeds through the [(CN)₅PtTl(CN)₃]^3-intermediate. The formation of [(CN)₅PtTl(edta)]^4-can proceed via two different pathways dependingon the ratio of the cyanide to the edta ligand concentrations.Thedirect pathat excess of edta means theformation of intermediate[(CN)4Pt···Tl(CN)(edta)]^4-, followed by a release of the cyanide from theTlcentre followed by coordination of a cyanide from thebulk to the Ptcentre of the intermediate. Theindirect pathdominates in the absence of extraedta and the formation of the PtTl bond occours betweenPt(CN)₄^2-and Tl(CN)4.

Homoligand MTl(CN)₄(M = Tl^I, K, Na) and, for the first time, Tl(CN)₃species have been synthesized in the solid stateand their structures solved by single crystal Xraydiffraction method. Interesting redox processes have been foundbetween TI^IIIand CNin nonaqueous solution and in Tl₂O₃-CNaqueous suspension. In the crystal structureof Tl(CN)₃·H₂O, the thallium(III) ion has a trigonal bypiramidalcoordination geometry with three cyanides in the trigonalplane, while an oxygen atom of the water molecule and anitrogen atom from a cyanide ligand attached to a neighboringthallium complex, form a linear OTlN fragment.Cyanide ligand bridges thallium units forming an infinitezigzag chain structure. Among the thallium(III) tetracyanocompounds, the isostructural M[Tl(CN)₄](M = Tl and K) and Na[Tl(CN)₄]·3H₂O crystallize in different crystal systems, but thethallium(III) ion has in all cases the same tetrahedralgeometry in the [Tl(CN)₄]unit.

Three adducts of mercury(II) (isoelectronic with TI^III) (K₂PtHg(CN)₆·2H₂O, Na₂PdHg(CN)₆·2H₂O and K₂NiHg(CN)₆·2H₂O) have been prepared from Hg(CN)₂and square planar transition metal cyanides M^II(CN)₄^2-and their structure have been studied by singlecrystal Xray diffraction, XPS and Raman spectroscopy inthe solid state. The structure of (K₂PtHg(CN)₆·2H₂O consists of strictly linear one dimensional wireswith Pt^IIand Hg^IIcenters located alternately, d_HgPt= 3.460 Å. The structure of Na₂PdHg(CN)₆·2H₂O and K₂NiHg(CN)₆·2H₂O can be considered as double salts, the lack ofheterometallophilic interaction between both the Hg^IIand Pd^IIatoms, d_HgPd= 4.92 Å, and Hg^IIand Ni^IIatoms, d_NiPd= 4.60 Å, seems obvious. Electronbinding energy values of the metallic centers measured by XPSshow that there is no electron transfer between the metal ionsin all three adducts. In solution, experimental findingsclearly indicate the lack of metalmetal bond formation inall studied Hg^IICN^-M^II(CN)4^2-systems (M = Pt, Pd and Ni). It is in contrary tothe platinumthallium bonded cyanides.

KEYWORDS:metalmetal bond, platinum, thallium,kinetics, mechanism, stopped flow, oxidative addition, cyanocomplexes, edta, redox reaction, metal cyanides, Xraydiffraction, Raman, NMR, mercury, palladium, nickel, onedimensional wire

Стилі APA, Harvard, Vancouver, ISO та ін.

23

Buselli, Lorenzo. "Study of Co-based hydrotalcite-derived mixed metal oxides partially modified with silver as potential catalysts for N2O decomposition." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11930/.

Повний текст джерела

Анотація:

Co-Al-Ox mixed metal oxides partially modified with Cu or Mg, as well as Ag were successfully prepared, characterized and evaluated as potential catalysts for the N2O decomposition. The materials were characterized by the following techniques: X-Ray Diffraction, Thermogravimetric Analysis (TGA), N2 Physisorption, Hydrogen Temperature-Programmed Reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). Ag-modified HT-derived mixed oxides showed enhanced activity compared to the undoped materials, the optimum composition was found for (1 wt.% Ag)CHT-Co3Al. The catalyst characterization studies suggested that the improved catalytic activity of Ag-promoted catalysts were mainly because of the altered redox properties of the materials.

Стилі APA, Harvard, Vancouver, ISO та ін.

24

Truong, Khai-Nghi Verfasser], Ullrich [Akademischer Betreuer] [Englert, and Wolfgang [Akademischer Betreuer] Stahl. "Design of mixed-metal coordination networks : synthesis, structural characterization, and thermal decomposition / Khai-Nghi Truong ; Ullrich Englert, Wolfgang Stahl." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1187346594/34.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

25

Truong, Khai-Nghi [Verfasser], Ullrich [Akademischer Betreuer] Englert, and Wolfgang [Akademischer Betreuer] Stahl. "Design of mixed-metal coordination networks : synthesis, structural characterization, and thermal decomposition / Khai-Nghi Truong ; Ullrich Englert, Wolfgang Stahl." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1187346594/34.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

26

Obi-Johnson, Bettie Jeanne. "Mechanistic analysis of the thermally induced decomposition of certain metal beta-diketonate precursors for chemical vapor deposition of electronic materials." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/30743.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

27

Driscoll, Darren Matthew. "Spectroscopic Studies of Small Molecule Adsorption and Oxidation on TiO2-Supported Coinage Metals and Zr6-based Metal-Organic Frameworks." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/100685.

Повний текст джерела

Анотація:

Developing a fundamental understanding of the interactions between catalytic surfaces and adsorbed molecules is imperative to the rational design of new materials for catalytic, sorption and gas separation applications. Experiments that probed the chemistry at the gas-surface interface were employed through the utilization of in situ infrared spectroscopic measurements in high vacuum conditions to allow for detailed and systematic investigations into adsorption and reactive processes. Specifically, the mechanistic details of propene epoxidation on the surface of nanoparticulate Au supported on TiO2 and dimethyl chlorophosphate (DMCP) decomposition on the surface of TiO2 aerogel-supported Cu nanoparticles were investigated. In situ infrared spectroscopy illustrates that TiO2-supported Au nanoparticles exhibit the unprecedented ability to produce the industrially relevant commodity chemical, propene oxide, through the unique adsorption configuration of propene on the surface of Au and a hydroperoxide intermediate (-OOH) in the presence of gaseous hydrogen and oxygen. Whereas, TiO2-supported Cu aerogels oxidize the organophosphate-based simulant, DMCP, into adsorbed CO at ambient environments. Through a variety of spectroscopic methods, each step in these oxidative pathways was investigated, including: adsorption, oxidation and reactivation of the supported-nanoparticle systems to develop full mechanistic pictures. Additionally, the perturbation of vibrational character of the probe molecule, CO, was employed to characterize the intrinsic µ3-hydroxyls and molecular-level defects associated with the metal-organic framework (MOF), UiO-66. The adsorption of CO onto heterogeneous surfaces effectively characterizes surfaces because the C-O bond vibrates differently depending on the nature of the surface site. Therefore, CO adsorption was used within the high vacuum environment to identify atomic-level characteristics that traditional methods of analysis cannot distinguish.
Doctor of Philosophy

Стилі APA, Harvard, Vancouver, ISO та ін.

28

Allesson, Sara. "Sheet Metal Forming Simulations with Elastic Dies: Emphasis on Computational Cost." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-18236.

Повний текст джерела

Анотація:

The car industry produces many of their car parts by using sheet metal forming, where one of the most time-consuming phases is the development and manufacturing of new forming tools. As of today, when a new tool is to be evaluated in terms of usability, a forming simulation is conducted to predict possible failures before manufacturing. The assumption is then that the tools are rigid, and the only deformable part is the sheet metal itself. This is however not the case, since the tools also deform during the forming process. A previous research, which is the basis of this thesis, included a model with only elastic tools and showed results of high accuracy in comparison to using a rigid setup. However, this simulation is not optimal to implement for a daily based usage, since it requires high computational power and has a long simulation time. The aim and scope for this thesis is to evaluate how a sheet metal forming simulation with elastic tool consideration can be reduced in terms of computational cost, by using the software LS-DYNA. A small deviation of the forming result is acceptable and the aim is to run the simulation with a 50-75 % reduction of time on fewer cores than the approximate 14 hours and 800 CPUs that the simulation requires today. The first step was to alter the geometry of the tools and evaluate the impact on the deformations of the blank. The elastic solid parts that only has small deformations are deleted and replaced by rigid surfaces, making the model partly elastic. Later, different decomposition methods are studied to determine what kind that makes the simulation run faster. At last, a scaling analysis is conducted to determine the range of computational power that is to be used to run the simulations as efficient as possible, and what part of the simulation that is affecting the simulation time the most. The correlation of major strain deviation between a fully elastic model and a partly elastic model showed results of high accuracy, as well as comparison with production measurements of a formed blank. The computational time is reduced by over 90 % when using approximately 65 % of the initial computational power. If the simulations are run with even less number of cores, 10 % of the initial number of CPUs, the simulation time is reduced by over 70 %. The conclusion of this work is that it is possible to run a partly elastic sheet metal forming simulation much more efficient than using a fully elastic model, without reliability problems of the forming results. This by reducing the number of elements, evaluate the decomposition method and by conducting a scaling analysis to evaluate the efficiency of computational power.
Bilindustrin producerar många av sina bildelar genom att tillämpa plåtformning, där en av de mest tidskrävande faserna är utveckling och tillverkning av nya formningsverktyg. Idag, när ett nytt verktyg ska utvärderas med avseende på användbarhet, genomförs en formningssimulering för att förutsäga eventuella fel innan tillverkning. Antagandet är då att verktygen är stela och den enda deformerbara delen är själva plåten. Det är dock inte så, eftersom verktygen också deformeras under formningsprocessen. Tidigare forskning, som ligger till grund för detta examensarbete, inkluderade en modell med endast elastiska verktyg och visade resultat med hög noggrannhet i jämförelse med att använda stela verktyg. Simuleringen med elastiska verktyg är emellertid inte optimal att implementera för daglig användning, eftersom den kräver hög beräkningskraft och har en lång simuleringstid. Syftet och omfattningen av detta examensarbete är att utvärdera hur en plåtformningssimulering med elastiska verktyg kan minskas med avseende på beräkningskostnaden, genom att använda programvaran LS-DYNA. En liten avvikelse från formningsresultatet är acceptabelt, och målet är att köra simuleringen med en 50-75 % minskning av tiden på färre kärnor än ungefär 14 timmar och 800 processorer som simuleringen kräver idag. Det första steget är att ändra verktygets geometri och utvärdera inverkan på deformationerna av plåten. De elastiska solida verktygsdelarna som endast har små deformationer raderas och ersätts av stela ytor, vilket gör modellen delvis elastisk. Senare studeras olika dekompositionsmetoder för att avgöra vilka som gör simuleringen snabbare. Till sist utförs en skalningsanalys för att bestämma antalet processorer som ska användas för att köra simuleringen så effektivt som möjligt. Korrelationen av huvudtöjningarna mellan en helt elastisk modell och en delvis elastisk modell visade resultat av hög noggrannhet, såväl som jämförelse med produktionsmätningar av en format plåt. Beräkningstiden minskar med över 90 % när man använder ungefär 65 % av den ursprungliga beräkningskraften. Om simuleringarna körs med färre antal kärnor, cirka 10 % av ursprungligt antal CPUer, minskar simuleringstiden med 70 %. Slutsatsen av detta arbete är att det är möjligt att köra en delvis elastisk plåtformningssimulering mycket effektivare än att använda en helt elastisk modell, utan att de resulterar i pålitlighetsproblem. Detta genom att minska antalet element, utvärdera dekompositionsmetoden och genom att genomföra en skalningsanalys för att utvärdera effektiviteten av beräkningskraften.
Reduced Lead Time through Advanced Die Structure Analysis - Swedish innovation agency Vinnova

Стилі APA, Harvard, Vancouver, ISO та ін.

29

Bisaro, René. "Etude des proprietes et structure des couches minces de silicium deposees par decomposition thermique de silane." Paris 6, 1987. http://www.theses.fr/1987PA066267.

Повний текст джерела

Анотація:

La taille des grains, la texture, la morphologie de surface, la conductivite electrique et l'absorption optique sont etudies en fonction des parametres de depot. L'optimum des proprietes de transport des couches polycristallines est lie a un regime de cristallisation en phase solide. Etude du processus de cristallisation, effet d'impuretes dopantes. On met en evidence l'effet des liaisons disponibles et de leur etat de charge sur le mecanisme des cristallisation

Стилі APA, Harvard, Vancouver, ISO та ін.

30

Allehyani, Esam. "Synthesis and Characterization of PEO-PS-PEO Triblock Copolymer Conjugated with Ni-NTA for Biosensors." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2018. http://digitalcommons.auctr.edu/cauetds/157.

Повний текст джерела

Анотація:

Poly(ethylene oxide)-poly(styrene)-poly(ethylene oxide) triblock copolymer with di-hydroxyl terminated groups (HO-PEO-PS-PEO-OH) was conjugated with nitrilotriacetic acid (NTA) via esterification reaction using N,N'-Dicyclohexylcarbodiimide (DCC), 4-Dimethylaminopyridine (DMAP) and Dimethylformamide (DMF) as a solvent at 80 ○C. The poly(ethylene oxide)-poly(styrene)-poly(ethylene oxide) with NTA end groups (NTA-PEO-PS-PEO-NTA) was characterized and structure confirmed by 1H NMR, 13C NMR, and FT-IR spectroscopies. Thermogravimetric analysis (TGA) was carried out to investigate the thermal stability of the starting triblock copolymer poly(ethylene oxide)-poly(styrene)-poly(ethylene oxide) with di-hydroxyl terminated groups (HO-PEO-PS-PEO-OH) and the conjugated poly(ethylene oxide)-poly(styrene)-poly(ethylene oxide) functional polymer (NTA-PEO-PS-PEO-NTA). Surface morphologies of the (HO-PEO-PS-PEO-OH) and (NTA-PEO-PS-PEO-NTA) were studied by atomic force microscopy. In addition, the size distributions were determined using dynamic light scattering. The thermal behavior of the (HO-PEO-PS-PEO-OH) and (NTA-PEO-PS-PEO-NTA) were examined by differential scanning calorimetry (DSC). DSC thermograms indicate the formation of a two phase polymer matrix. The poly(ethylene oxide)-poly(styrene)-poly(ethylene oxide) with NTA functionalized end groups (NTA-PEO-PS-PEO-NTA) was bound or chelated with Ni(II) metal ion. The binding studies were carried out by ultraviolet-visible (UV-Vis) spectroscopy. The electronic behaviors of PEO-b-PS-b-PEO/ PS/ NTA-PEO-b-PS-b-PEO-NTA with ratio (1/5/1) and PEO-b-PS-b-PEO/ PS/ NTA-PEO-b-PS-b-PEO-NTA-Ni containing 1% of oxidized single-walled carbon nanotubes (SWCNTs) were investigated by I–V plots from Kelvin sensing. The I–V plots before sensitizing with protein varied from the I–V plots after binding with protein indicating that the composites may be used as active components in biosensors.

Стилі APA, Harvard, Vancouver, ISO та ін.

31

Pope, Matthew. "The titanium(IV) oxide photocatalysed decomposition of some common pollutants in water and the influence of metal ions on the photocatalytic process." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387774.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

32

Wang, Guanyu. "Interfacial Energy Transfer in Small Hydrocarbon Collisions with Organic Surfaces and the Decomposition of Chemical Warfare Agent Simulants within Metal-Organic Frameworks." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/100746.

Повний текст джерела

Анотація:

A molecular-level understanding of gas-surface energy exchange and reaction mechanisms will aid in the prediction of the environmental fate of pollutants and enable advances toward catalysts for the decomposition of toxic compounds. To this end, molecular beam scattering experiments performed in an ultra-high vacuum environment have provided key insights into the initial collision and outcome of critical interfacial processes on model systems. Results from these surface science experiments show that, upon gas-surface collisions, energy transfer depends, in subtle ways, on both the properties of the gas molecules and surfaces. Specifically, model organic surfaces, comprised of long-chain methyl- and hydroxyl-terminated self-assembled monolayers (SAMs) have been employed to test how an interfacial hydrogen bonding network may affect the ability of a gas-phase compound to thermally accommodate (typically, the first step in a reaction) with the surfaces. Results indeed show that small organic compounds transfer less energy to the interconnected hydroxyl-terminated SAM (OH-SAM) than to the organic surface with methyl groups at the interface. However, the dynamics also appear to depend on the polarizability of the impinging gas-phase molecule. The π electrons in the double bond of ethene (C2H4) and the triple bond in ethyne (C2H2) appear to act as hydrogen bond acceptors when the molecules collide with the OH-SAM. The molecular beam scattering studies have demonstrated that these weak attractive forces facilitate energy transfer. A positive correlation between energy transfer and solubilities for analogous solute-solvent combinations was observed for the CH3-SAM (TD fractions: C2H6 > C2H4 > C2H2), but not for the OH-SAM (TD fractions: C2H6 > C2H2 > C2H4). The extent of energy transfer between ethane, ethene, and ethyne and the CH3-SAM appears to be determined by the degrees of freedom or rigidity of the impinging compound, while gas-surface attractive forces play a more decisive role in controlling the scattering dynamics at the OH-SAM. Beyond fundamental studies of energy transfer, this thesis provides detailed surface-science-based studies of the mechanisms involved in the uptake and decomposition of chemical warfare agent (CWA) simulants on or within metal-organic frameworks (MOFs). The work presented here represents the first such study reported in with traditional surface-science based methods have been applied to the study of MOF chemistry. The mechanism and kinetics of interactions between dimethyl methylphosphonate (DMMP) or dimethyl chlorophosphate (DMCP), key CWA simulants, and Zr6-based metal-organic frameworks (MOFs) have been investigated with in situ infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD), and DFT calculations. DMMP and DMCP were found to adsorb molecularly (physisorption) to the MOFs through the formation of hydrogen bonds between the phosphoryl oxygen and the free hydroxyl groups associated with Zr6 nodes or dangling -COH groups on the surface of crystallites. Unlike UiO-66, the infrared spectra for UiO-67 and MOF-808, recorded during DMMP exposure, suggest that uptake occurs through both physisorption and chemisorption. The XPS spectra of MOF-808 zirconium 3d electrons reveal a charge redistribution following exposure to DMMP. Besides, the analysis of the phosphorus 2p electrons following exposure and thermal annealing to 600 K indicates that two types of stable phosphorus-containing species exist within the MOF. DFT calculations (performed by Professor Troya at Virginia Tech), were used to guide the IR band assignments and to help interpret the XPS features, suggest that uptake is driven by nucleophilic addition of a surface OH group to DMMP with subsequent elimination of a methoxy substituent to form strongly bound methyl methylphosphonic acid (MMPA). With similar IR features of MOF-808 upon DMCP exposure, the reaction pathway of DMCP in Zr6-MOFs may be similar to that for DMMP, but with the final product being methyl chlorophosphonic acid (elimination of the chlorine) or MMPA (elimination of a methoxy group). The rates of product formation upon DMMP exposure of the MOFs suggest that there are two distinct uptake processes. The rate constants for these processes were found to differ by approximately an order of magnitude. However, the rates of molecular uptake were found to be nearly identical to the rates of reaction, which strongly suggests that the reaction rates are diffusion limited. Overall, and perhaps most importantly, this research has demonstrated that the final products inhibit further reactions within the MOFs. The strongly bound products could not be thermally driven from the MOFs prior to the decomposition of the MOFs themselves. Therefore, new materials are needed before the ultimate goal of creating a catalyst for the air-based destruction of traditional chemical nerve agents is realized.
Doctor of Philosophy

Стилі APA, Harvard, Vancouver, ISO та ін.

33

Zhang, Xiaoqiao [Verfasser], Klaus [Akademischer Betreuer] Köhler, Klaus [Gutachter] Köhler, and Richard W. [Gutachter] Fischer. "Decomposition of Nitrous Oxide by Supported Transition Metal Catalysts: Structure-Activity Relationships / Xiaoqiao Zhang ; Gutachter: Klaus Köhler, Richard W. Fischer ; Betreuer: Klaus Köhler." München : Universitätsbibliothek der TU München, 2019. http://d-nb.info/1192911652/34.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

34

Zhang, Yirui S. M. Massachusetts Institute of Technology. "Understanding the pathway and mechanism of electrolyte decomposition on metal oxide surfaces in Li-ion batteries by in situ Fourier Transform Infrared Spectroscopy." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122227.

Повний текст джерела

Анотація:

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 69-75).
Understanding (electro)chemical reactions at the electrode-electrolyte interface (EEI) is crucial to promote the cycle life of lithium-ion batteries. In situ studies of EEI can provide new insights into reaction intermediates and soluble species not accessible by ex situ characterization of electrode surfaces. In this study, we developed an in situ Fourier Transform infrared spectroscopy (FTIR) method to investigate the (electro)chemical reactions at the interface between the electrolyte and composite positive electrode surface during charging. While ethyl methyl carbonate (EMC) and ethylene carbonate (EC) were stable against (electro)chemical oxidation on Pt up to 4.8 VL, dehydrogenation of both carbonates on the surface of LiNio.8Cooa.Mno.l02 (NMC81 1) electrodes was revealed by in situ FTIR spectra and density functional theory (DFT). Both solvents can dehydrogenate and form de-H EC and de-H EMC, respectively, with carbon atom binding to lattice oxygen and sticking on surface. De-H EC can further remove another hydrogen atom to form vinylene carbonate (VC) or bind together to form oligomers, both of which are soluble and hard to be accessed through ex-situ methods. In situ FTIR method successfully tracked detailed pathways of solvent decomposition on oxide surface, and electrochemical impedance spectroscopy (EIS) further confirmed the formation of a passivating layer from solvent decomposition on the surface. The impedance growth is oxide and solvation structure-dependent and it accounts for battery degrading. We finally proposed and verified multiple strategies to further improve the cycling stability of high-energy density positive electrode in Li-ion batteries.
by Yirui Zhang.
S.M.
S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering

Стилі APA, Harvard, Vancouver, ISO та ін.

35

Gross, Timothy M. "[Beta]-barium borate thin film formation on silicon through metal organic decomposition of two novel precursors, barium dimesitylborinate and barium (18-crown-6) cyclotriboroxane /." Online version of thesis, 2004. http://hdl.handle.net/1850/11802.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

36

El, Hamdi Lahfid Majid. "On the use of energy decomposition analyses to unravel the origin of the relative stabilities of isomers." Doctoral thesis, Universitat de Girona, 2013. http://hdl.handle.net/10803/124220.

Повний текст джерела

Анотація:

Structural isomers are molecules that have the same number and type of atoms but arranged in different manner. The isomerization energy is the energy difference between two isomers, i.e. the energy cost corresponding to the transformation of one isomer into another. In this thesis, the PhD student has focused on isomers that can be built from the same fragments, but simply connecting them differently, with a new methodology called "turn-upside-down." Basically one starts with the same two fragments and they are connected in different way to build the two isomers. Later, the energies involved in the bonding between the fragments are studied by an energy decomposition analysis in order to find the reason for the difference in stability between the two isomers. The computational results obtained have allowed us to justify the energy of isomerization of organic or inorganic or organometallic compounds
Isòmers estructurals són molècules que presenten el mateix nombre i tipus d’àtoms, però ordenats de diferent manera. L’energia d’isomerització és la diferència d’energia entre dos isòmers, o sigui, el cost energètic corresponent a la transformació d’un isòmer a l’altre. En aquesta tesi, el doctorand s’ha centrat en isòmers que es poden construir a partir dels mateixos fragments, però simplement unint-los de diferent manera, amb una nova metodologia anomenada “turn-upside-down”. Bàsicament es parteix dels mateixos dos fragments que unim de diferent manera per construir els dos isòmers. Posteriorment, les energies involucrades en la unió entre els fragments s’estudien amb una anàlisi de descomposició de l’energia per tal de saber la raó de la diferència d’estabilitat entre els dos isòmers. Els resultats computacionals obtinguts han permès justificar l’energia d’isomerització de compostos tant orgànics com inorgànics o organometàl·lics

Стилі APA, Harvard, Vancouver, ISO та ін.

37

Rico, Pérez Verónica. "Optimization of N2O decomposition RhOx/ceria catalysts and design of a high N2-selective deNOx system for diesel vehicles." Doctoral thesis, Universidad de Alicante, 2013. http://hdl.handle.net/10045/35739.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

38

Palan, Rohit Chandulal. "Pyroelectric Properties of Ferroelectric Lanthanum Bismuth Titanate Thin Films." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1000746504.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

39

Takriti, Salaheddin. "Echange isotopique dans les solides : iodate marque dans des periodates alcalins." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13085.

Повний текст джерела

Анотація:

Etude de l'echange isotopique initial et thermiquement active dans des periodates alcalins dopes par les iodates par precipitation et la decomposition des matrices. Presence d'un adjuvant lacunaire asssocie aux dopants

Стилі APA, Harvard, Vancouver, ISO та ін.

40

Frenzel, Peter, Andrea Preuß, Jörn Bankwitz, Colin Georgi, Fabian Ganss, Lutz Mertens, Stefan E. Schulz, Olav Hellwig, Michael Mehring, and Heinrich Lang. "Synthesis of Mg and Zn diolates and their use in metal oxide deposition." Royal Society of Chemistry, 2019. https://monarch.qucosa.de/id/qucosa%3A33722.

Повний текст джерела

Анотація:

The synthesis of complexes [M(OCHMeCH2NMeCH2)2] (5, M = Mg; 7, M = Zn) is described. Treatment of MeHNCH2CH2NMeH (1) with 2-methyloxirane (2) gave diol (HOCHMeCH2NMeCH2)2 (3), which upon reaction with equimolar amounts of MR2 (4, M = Mg, R = Bu; 6, M = Zn, R = Et) gave 5 and 7. The thermal behavior and vapor pressure of 5 and 7 were investigated to show whether they are suited as CVD (= chemical vapor deposition) and/or spin-coating precursors for MgO or ZnO layer formation. Thermogravimetric (TG) studies revealed that 5 and 7 decompose between 80–530 °C forming MgO and ZnO as evidenced by PXRD studies. In addition, TG-MS-coupled experiments were carried out with 7 proving that decomposition occurs by M–O, C–O, C–N and C–C bond cleavages, as evidenced from the detection of fragments such as CH4N+, C2H4N+, C2H5N+, CH2O+, C2H2O+ and C2H3O+. The vapor pressure of 7 was measured at 10.4 mbar at 160 °C, while 5 is non-volatile. The layers obtained by CVD are dense and conformal with a somewhat granulated surface morphology as evidenced by SEM studies. In addition, spin–coating experiments using 5 and 7 as precursors were applied. The corresponding MO layer thicknesses are between 7–140 nm (CVD) or 80 nm and 65 nm (5, 7; spin-coating). EDX and XPS measurements confirm the formation of MgO and ZnO films, however, containing 12–24 mol% (CVD) or 5–9 mol% (spin-coating) carbon. GIXRD studies verify the crystalline character of the deposited layers obtained by CVD and the spin-coating processes.

Стилі APA, Harvard, Vancouver, ISO та ін.

41

Jost, Pierre. "Apport de technique informatiques a l'etude des complexes polynucleaires du nolybdene vi : equilibres de formation et cinetique de condensation en milieu nacl 0,1 m." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13112.

Повний текст джерела

Анотація:

La methode proposee consiste a combiner la methode de la surface potentiometrique de bye-lefebvre, une methode de regression non lineaire et une methode de simulation statistique. Etude des equilibres de formation des isopolyanions molybdiques. On propose un mecanisme de type sn2 pour les reactions de decondensation et d'hydrolyse des ions trimolybdiques et tetramolybdiques

Стилі APA, Harvard, Vancouver, ISO та ін.

42

Zhao, Yanyan. "Synthesis and characterisation of metal (Fe, Ga, Y) doped alumina and gallium oxide nanostructures." Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/20529/1/Yanyan_Zhao_Thesis.pdf.

Повний текст джерела

Анотація:

It is well known that nanostructures possess unique electronic, optical, magnetic, ferroelectric and piezoelectric properties that are often superior to traditional bulk materials. In particular, one dimensional (1D) nanostructured inorganic materials including nanofibres, nanotubes and nanobelts have attracted considerable attention due to their distinctive geometries, novel physical and chemical properties, combined effects and their applications to numerous areas. Metal ion doping is a promising technique which can be utilized to control the properties of materials by intentionally introducing impurities or defects into a material. γ-Alumina (Al2O3), is one of the most important oxides due to its high surface area, mesoporous properties, chemical and thermal properties and its broad applications in adsorbents, composite materials, ceramics, catalysts and catalyst supports. γ-Alumina has been studied intensively over a long period of time. Recently, considerable work has been carried out on the synthesis of 1D γ-alumina nanostructures under various hydrothermal conditions; however, research on the doping of alumina nanostructures has not been forthcoming. Boehmite (γ-AlOOH) is a crucial precursor for the preparation of γ-Alumina and the morphology and size of the resultant alumina can be manipulated by controlling the growth of AlOOH. Gallium (Ga) is in the same group in the periodic table as aluminum. β-Gallium (III) oxide (β-Ga2O3), a wide band gap semiconductor, has long been known to exhibit conduction, luminescence and catalytic properties. Numerous techniques have been employed on the synthesis of gallium oxide in the early research. However, these techniques are plagued by inevitable problems. It is of great interest to explore the synthesis of gallium oxide via a low temperature hydrothermal route, which is economically efficient and environmentally friendly. The overall objectives of this study were: 1) the investigation of the effect of dopants on the morphology, size and properties of metal ion doped 1D alumina nanostructures by introducing dopant to the AlOOH structure; 2) the investigation of impacts of hydrothermal conditions and surfactants on the crystal growth of gallium oxide nanostructures. To achieve the above objectives, trivalent metal elements such as iron, gallium and yttrium were employed as dopants in the study of doped alumina nanostructures. In addition, the effect of various parameters that may affect the growth of gallium oxide crystals including temperature, pH, and the experimental procedure as well as different types of surfactants were systematically investigated. The main contributions of this study are: 1) the systematic and in-depth investigation of the crystal growth and the morphology control of iron, gallium and yttrium doped boehmite (AlOOH) under varying hydrothermal conditions, as a result, a new soft-chemistry synthesis route for the preparation of one dimensional alumina/boehmite nanofibres and nanotubes was invented; 2) systematic investigation of the crystal growth and morphology and size changes of gallium oxide hydroxide (GaOOH) under varying hydrothermal conditions with and without surfactant at low temperature; We invented a green hydrothermal route for the preparation of α-GaOOH or β-GaOOH micro- to nano-scaled particles; invented a simple hydrothermal route for the direct preparation of γ-Ga2O3 from aqueous media at low temperature without any calcination. The study provided detailed synthesis routes as well as quantitative property data of final products which are necessary for their potential industrial applications in the future. The following are the main areas and findings presented in the study: • Fe doped boehmite nanostructures This work was undertaken at 120ºC using PEO surfactant through a hydrothermal synthesis route by adding fresh iron doped aluminium hydrate at regular intervals of 2 days. The effect of dopant iron, iron percentage and experimental procedure on the morphology and size of boehmite were systematically studied. Iron doped boehmite nanofibres were formed in all samples with iron contents no more than 10%. Nanosheets and nanotubes together with an iron rich phase were formed in 20% iron doped boehmite sample. A change in synthesis procedure resulted in the formation of hematite large crystals. The resultant nanomaterials were characterized by a combination of XRD, TEM, EDX, SAED and N2 adsorption analysis. • Growth of pure boehmite nanofibres/nanotubes The growth of pure boehmite nanofibres/nanotubes under different hydrothermal conditions at 100ºC with and without PEO surfactant was systematically studied to provide further information for the following studies of the growth of Ga and Y doped boehmite. Results showed that adding fresh aluminium hydrate precipitate in a regular interval resulted in the formation of a mixture of long and short 1D boehmite nanostructures rather than the formation of relatively longer nanofibres/nanotubes. The detailed discussion and mechanism on the growth of boehmite nanostructure were presented. The resultant boehmite samples were also characterized by N2 adsorption to provide further information on the surface properties to support the proposed mechanism. • Ga doped boehmite nanostructures Based on this study on the growth of pure boehmite nanofibre/nanotubes, gallium doped boehmite nanotubes were prepared via hydrothermal treatment at 100ºC in the presence of PEO surfactant without adding any fresh aluminium hydrate precipitate during the hydrothermal treatment. The effect of dopant gallium, gallium percentage, temperature and experimental procedure on the morphology and size of boehmite was systematically studied. Various morphologies of boehmite nanostructures were formed with the increase in the doping gallium content and the change in synthesis procedure. The resultant gallium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA. • Y doped boehmite nanostructures Following the same synthesis route as that for gallium doped boehmite, yttrium doped boehmite nanostructures were prepared at 100ºC in the presence of PEO surfactant. From the study on iron and gallium doped boehmite nanostructures, it was noted both iron and gallium cannot grow with boehmite nanostructure if iron nitrate and gallium nitrate were not mixed with aluminium nitrate before dissolving in water, in particular, gallium and aluminium are 100% miscible. Therefore, it’s not necessary to study the mixing procedure or synthesis route on the formation of yttrium doped boehmite nanostructures in this work. The effect of dopant yttrium, yttrium percentage, temperature and surfactant on the morphology and size of boehmite were systematically studied. Nanofibres were formed in all samples with varying doped Y% treated at 100ºC; large Y(OH)3 crystals were also formed at high doping Y percentage. Treatment at elevated temperatures resulted in remarkable changes in size and morphology for samples with the same doping Y content. The resultant yttrium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA. • The synthesis of Gallium oxide hydroxide and gallium oxide with surfactant In this study, the growth of gallium oxide hydroxide under various hydrothermal conditions in the presence of different types of surfactants was systematically studied. Nano- to micro-sized gallium oxide hydroxide was prepared. The effect of surfactant and synthesis procedure on the morphology of the resultant gallium oxide hydroxide was studied. β-gallium oxide nanorods were derived from gallium oxide hydroxide by calcination at 900ºC and the initial morphology was retained. γ-gallium oxide nanotubes up to 65 nm in length, with internal and external diameters of around 0.8 and 3.0 nm, were synthesized directly in solution with and without surfactant. The resultant nano- to micro-sized structures were characterized by XRD, TEM, SAED, EDX and N2 adsorption. • The synthesis of gallium oxide hydroxide without surfactant The aim of this study is to explore a green synthesis route for the preparation of gallium oxide hydroxide or gallium oxide via hydrothermal treatment at low temperature. Micro to nano sized GaOOH nanorods and particles were prepared under varying hydrothermal conditions without any surfactant. The resultant GaOOH nanomaterials were characterized by XRD, TEM, SAED, EDX, TG and FT-IR. The growth mechanism of GaOOH crystals was proposed.

Стилі APA, Harvard, Vancouver, ISO та ін.

43

Zhao, Yanyan. "Synthesis and characterisation of metal (Fe, Ga, Y) doped alumina and gallium oxide nanostructures." Queensland University of Technology, 2008. http://eprints.qut.edu.au/20529/.

Повний текст джерела

Анотація:

It is well known that nanostructures possess unique electronic, optical, magnetic, ferroelectric and piezoelectric properties that are often superior to traditional bulk materials. In particular, one dimensional (1D) nanostructured inorganic materials including nanofibres, nanotubes and nanobelts have attracted considerable attention due to their distinctive geometries, novel physical and chemical properties, combined effects and their applications to numerous areas. Metal ion doping is a promising technique which can be utilized to control the properties of materials by intentionally introducing impurities or defects into a material. γ-Alumina (Al2O3), is one of the most important oxides due to its high surface area, mesoporous properties, chemical and thermal properties and its broad applications in adsorbents, composite materials, ceramics, catalysts and catalyst supports. γ-Alumina has been studied intensively over a long period of time. Recently, considerable work has been carried out on the synthesis of 1D γ-alumina nanostructures under various hydrothermal conditions; however, research on the doping of alumina nanostructures has not been forthcoming. Boehmite (γ-AlOOH) is a crucial precursor for the preparation of γ-Alumina and the morphology and size of the resultant alumina can be manipulated by controlling the growth of AlOOH. Gallium (Ga) is in the same group in the periodic table as aluminum. β-Gallium (III) oxide (β-Ga2O3), a wide band gap semiconductor, has long been known to exhibit conduction, luminescence and catalytic properties. Numerous techniques have been employed on the synthesis of gallium oxide in the early research. However, these techniques are plagued by inevitable problems. It is of great interest to explore the synthesis of gallium oxide via a low temperature hydrothermal route, which is economically efficient and environmentally friendly. The overall objectives of this study were: 1) the investigation of the effect of dopants on the morphology, size and properties of metal ion doped 1D alumina nanostructures by introducing dopant to the AlOOH structure; 2) the investigation of impacts of hydrothermal conditions and surfactants on the crystal growth of gallium oxide nanostructures. To achieve the above objectives, trivalent metal elements such as iron, gallium and yttrium were employed as dopants in the study of doped alumina nanostructures. In addition, the effect of various parameters that may affect the growth of gallium oxide crystals including temperature, pH, and the experimental procedure as well as different types of surfactants were systematically investigated. The main contributions of this study are: 1) the systematic and in-depth investigation of the crystal growth and the morphology control of iron, gallium and yttrium doped boehmite (AlOOH) under varying hydrothermal conditions, as a result, a new soft-chemistry synthesis route for the preparation of one dimensional alumina/boehmite nanofibres and nanotubes was invented; 2) systematic investigation of the crystal growth and morphology and size changes of gallium oxide hydroxide (GaOOH) under varying hydrothermal conditions with and without surfactant at low temperature; We invented a green hydrothermal route for the preparation of α-GaOOH or β-GaOOH micro- to nano-scaled particles; invented a simple hydrothermal route for the direct preparation of γ-Ga2O3 from aqueous media at low temperature without any calcination. The study provided detailed synthesis routes as well as quantitative property data of final products which are necessary for their potential industrial applications in the future. The following are the main areas and findings presented in the study: • Fe doped boehmite nanostructures This work was undertaken at 120ºC using PEO surfactant through a hydrothermal synthesis route by adding fresh iron doped aluminium hydrate at regular intervals of 2 days. The effect of dopant iron, iron percentage and experimental procedure on the morphology and size of boehmite were systematically studied. Iron doped boehmite nanofibres were formed in all samples with iron contents no more than 10%. Nanosheets and nanotubes together with an iron rich phase were formed in 20% iron doped boehmite sample. A change in synthesis procedure resulted in the formation of hematite large crystals. The resultant nanomaterials were characterized by a combination of XRD, TEM, EDX, SAED and N2 adsorption analysis. • Growth of pure boehmite nanofibres/nanotubes The growth of pure boehmite nanofibres/nanotubes under different hydrothermal conditions at 100ºC with and without PEO surfactant was systematically studied to provide further information for the following studies of the growth of Ga and Y doped boehmite. Results showed that adding fresh aluminium hydrate precipitate in a regular interval resulted in the formation of a mixture of long and short 1D boehmite nanostructures rather than the formation of relatively longer nanofibres/nanotubes. The detailed discussion and mechanism on the growth of boehmite nanostructure were presented. The resultant boehmite samples were also characterized by N2 adsorption to provide further information on the surface properties to support the proposed mechanism. • Ga doped boehmite nanostructures Based on this study on the growth of pure boehmite nanofibre/nanotubes, gallium doped boehmite nanotubes were prepared via hydrothermal treatment at 100ºC in the presence of PEO surfactant without adding any fresh aluminium hydrate precipitate during the hydrothermal treatment. The effect of dopant gallium, gallium percentage, temperature and experimental procedure on the morphology and size of boehmite was systematically studied. Various morphologies of boehmite nanostructures were formed with the increase in the doping gallium content and the change in synthesis procedure. The resultant gallium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA. • Y doped boehmite nanostructures Following the same synthesis route as that for gallium doped boehmite, yttrium doped boehmite nanostructures were prepared at 100ºC in the presence of PEO surfactant. From the study on iron and gallium doped boehmite nanostructures, it was noted both iron and gallium cannot grow with boehmite nanostructure if iron nitrate and gallium nitrate were not mixed with aluminium nitrate before dissolving in water, in particular, gallium and aluminium are 100% miscible. Therefore, it’s not necessary to study the mixing procedure or synthesis route on the formation of yttrium doped boehmite nanostructures in this work. The effect of dopant yttrium, yttrium percentage, temperature and surfactant on the morphology and size of boehmite were systematically studied. Nanofibres were formed in all samples with varying doped Y% treated at 100ºC; large Y(OH)3 crystals were also formed at high doping Y percentage. Treatment at elevated temperatures resulted in remarkable changes in size and morphology for samples with the same doping Y content. The resultant yttrium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA. • The synthesis of Gallium oxide hydroxide and gallium oxide with surfactant In this study, the growth of gallium oxide hydroxide under various hydrothermal conditions in the presence of different types of surfactants was systematically studied. Nano- to micro-sized gallium oxide hydroxide was prepared. The effect of surfactant and synthesis procedure on the morphology of the resultant gallium oxide hydroxide was studied. β-gallium oxide nanorods were derived from gallium oxide hydroxide by calcination at 900ºC and the initial morphology was retained. γ-gallium oxide nanotubes up to 65 nm in length, with internal and external diameters of around 0.8 and 3.0 nm, were synthesized directly in solution with and without surfactant. The resultant nano- to micro-sized structures were characterized by XRD, TEM, SAED, EDX and N2 adsorption. • The synthesis of gallium oxide hydroxide without surfactant The aim of this study is to explore a green synthesis route for the preparation of gallium oxide hydroxide or gallium oxide via hydrothermal treatment at low temperature. Micro to nano sized GaOOH nanorods and particles were prepared under varying hydrothermal conditions without any surfactant. The resultant GaOOH nanomaterials were characterized by XRD, TEM, SAED, EDX, TG and FT-IR. The growth mechanism of GaOOH crystals was proposed.

Стилі APA, Harvard, Vancouver, ISO та ін.

44

Yang, Jing. "Synthesis and characterisation of metal oxyhydroxide and oxide nanomaterials." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/45712/1/Jing_Yang_Thesis.pdf.

Повний текст джерела

Анотація:

In this work, a range of nanomaterials have been synthesised based on metal oxyhydroxides MO(OH), where M=Al, Co, Cr, etc. Through a self-assembly hydrothermal route, metal oxyhydroxide nanomaterials with various morphologies were successfully synthesised: one dimensional boehmite (AlO(OH)) nanofibres, zero dimensional indium hydroxide (In(OH)3) nanocubes and chromium oxyhydroxide (CrO(OH)) nanoparticles, as well as two dimensional cobalt hydroxide and oxyhydroxide (Co(OH)2 & CoO(OH)) nanodiscs. In order to control the synthetic nanomaterial morphology and growth, several factors were investigated including cation concentration, temperature, hydrothermal treatment time, and pH. Metal ion doping is a promising technique to modify and control the properties of materials by intentionally introducing impurities or defects into the material. Chromium was successfully applied as a dopant for fabricating doped boehmite nanofibres. The thermal stability of the boehmite nanofibres was enhanced by chromium doping, and the photoluminescence property was introduced to the chromium doped alumina nanofibres. Doping proved to be an efficient method to modify and functionalize nanomaterials. The synthesised nanomaterials were fully characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED), scanning electron microscopy (SEM), BET specific surface area analysis, X-ray photoelectron spectroscopy (XPS) and thermo gravimetric analysis (TGA). Hot-stage Raman and infrared emission spectroscopy were applied to study the chemical reactions during dehydration and dehydroxylation. The advantage of these techniques is that the changes in molecular structure can be followed in situ and at the elevated temperatures.

Стилі APA, Harvard, Vancouver, ISO та ін.

45

Thevenin, Philippe. "Catalytic combustion of methane." Doctoral thesis, KTH, Chemical Engineering and Technology, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3402.

Повний текст джерела

Анотація:

Catalytic combustion is an environmentally benign technologywhich has recently reached the stage of commercialization.Palladium is the catalyst of choice when considering gasturbines fuelled with natural gas because of its superioractivity for methane oxidation. Several fundamental issues arestill open and their understanding would result in animprovement of the technology. Hence, the work presented inthis thesis aims at the identification of some of theparameters which govern the combustion activity ofpalladium-based catalysts.

The first part of this work gives a background to catalyticcombustion and a brief comparison with other existingtechnologies. Paper I reviews some of the issues related tomaterial development and combustor design.

The second part of this thesis consists of an experimentalinvestigation on palladium-based catalysts. The influence ofthe preparation method onthe properties of these catalystmaterials is investigated in Paper II. Paper III examines theactivity of the following catalysts: Pd/Al2O3, Pd/Ba-Al2O3 andPd/La-Al2O3. Specific attention is given to the metal-supportinteraction which strongly affects the combustion activity ofpalladium. The effect of doping of the support by addition ofcerium is reported in Paper IV.

Finally, the deactivation of combustion catalysts isconsidered. The various deactivation processes which may affecthigh temperature combustion catalysts are reviewed in Paper V.Paper VI focuses on the poisoning of supported palladiumcatalysts by sulphur species. Palladium exhibits a higherresistance to sulphur poisoning than transition metals.Nevertheless, the nature of the support material plays animportant role and may entail a severe loss of activity whensulphur is present in the fuel-air mixture entering thecombustion chamber.

Keywords: catalytic combustion, gas turbine, methane,palladium, alumina, barium, lanthanum, oxidation, preparation,temperature-programmed oxidation (TPO), decomposition,reoxidation, X-ray photoelectron spectroscopy (XPS),metal-support interaction, deactivation, sulphur, poisoning.The cover illustration is a TEM picture of a 100 nm palladiumparticle supported on alumina

Стилі APA, Harvard, Vancouver, ISO та ін.

46

Souza, Felipe Thiago Caldeira de. "Catalisadores a base de Ni e Fe ancorados em alumina e CeCo2 para decomposição do metano: produção de hidrogênio e nanotubos de carbono." Universidade Federal de Alagoas, 2015. http://www.repositorio.ufal.br/handle/riufal/1897.

Повний текст джерела

Анотація:

The catalytic decomposition of the methane (DCM) can be recognized as a promising reaction for the production of COx-free hydrogen. At the same time the production of hydrogen formation occurs structured carbonaceous material, carbon nanotubes (NTC), which have intrinsic characteristics, such as flexibility, high thermal and electrical conductivity, high chemical and mechanical stability. This study aimed to the synthesis of catalytic materials for DCM reaction involving two distinct synthesis routes, metal-chitosan complexation preparation support (Al2O3) followed by anchoring (CeO2) and subsequently the active phase Ni or Fe, and replica method for the synthesis support (Al2O3) followed by the docking Ni or Fe. The catalytic activity of the catalysts synthesized were studied varying the temperature of reduction and reaction by checking the effect of conversion into nanostructured carbonaceous material as well as assessing the quality the NTC formed. The results showed that the nickel-containing species had higher methane conversions when compared with the iron catalysts. The variation of reaction conditions yielded different levels of carbon (1.83 to 13.71%), and more favorable at lower temperatures. The presence of nickel catalysts CeO2 inhibit carbon formation on the metal particle due to the redox properties of cerium become promising for hydrogen production. The catalytic activity of the catalysts synthesized by the replica method showed a similar tendency to catalysts synthesized by metal complexation - chitosan, wherein the nickel catalyst results presented satifastórios with carbon contents in the range from 0 to 31%.
Conselho Nacional de Desenvolvimento Científico e Tecnológico
A decomposição catalítica do metano (DCM) pode ser reconhecida com uma reação promissora para a produção de hidrogênio livre de COx. Paralelamente à produção de hidrogênio, ocorre a formação de materiais carbonáceos estruturados, os nanotubos de carbono (NTC), que possuem características intrínsecas, tais como, flexibilidade, elevada condutividade térmica e elétrica, alta estabilidade química e mecânica. Este trabalho teve como objetivo a síntese de materiais catalíticos para a reação de DCM envolvendo duas rotas de síntese distintas, complexação metal-quitosana para preparação do suporte (Al2O3) seguido da ancoragem (CeO2) e posteriormente as fases ativas Ni ou Fe, e o método da réplica para a síntese do suporte (Al2O3) seguido da ancoragem de Ni ou Fe. A atividade catalítica dos catalisadores sintetizados foi estudada variando a temperatura de redução e reacional, verificando o efeito da conversão em materiais carbonáceos nanoestruturados, bem como avaliando a qualidade dos NTC formados. Os resultados mostraram que as espécies contendo níquel obtiveram maiores conversões do metano quando comparados com os catalisadores de ferro. A variação das condições reacionais proporcionou diferentes teores em carbono (1,83 a 13,71%), sendo mais favorável em baixas temperaturas. A presença de CeO2 nos catalisadores de níquel inibiu a formação de carbono sobre a partícula metálica devido às propriedades redox do cério, tornando-se promissores para produção de hidrogênio. A atividade catalítica dos catalisadores sintetizados pelo método da réplica apresentou tendência similar aos catalisadores sintetizados via complexação metal – quitosana, no qual o catalisador de níquel apresentou resultados satifastórios com teores de carbono na faixa de 0 a 31%.

Стилі APA, Harvard, Vancouver, ISO та ін.

47

El, Bakouri El Farri Ouissam. "Electronic structure, chemical bonding, and electronic delocalization of organic and inorganic systems with three-dimensional or excited state aromaticity." Doctoral thesis, Universitat de Girona, 2017. http://hdl.handle.net/10803/565444.

Повний текст джерела

Анотація:

Aromaticity is a key concept in chemistry, used by chemists to explain the structure, stability, and reactivity of many compounds. Aromatic compounds are present in industrial processes as well as in living systems. Initially, the realm of aromatic molecules was limited to cyclic benzenoid systems. Over the years, this concept has been expanded to heterosystems, metal clusters, fullerenes, and more exotic molecules. In this thesis, the analysis of electronic structure, chemical bonding, and electronic delocalization of organic and inorganic systems that possess three-dimensional or excited state aromaticity is studied in detail using state-of-the-art computational tools. We mainly focus our attention on the study of the aromaticity of different polycyclic conjugated hydrocarbons, fullerenes and small inorganic clusters. Yet, we also analyze the chemical bonding of different inorganic clusters
L'aromaticitat és un concepte clau en química, utilitzat pels químics per explicar l'estructura, l'estabilitat i la reactivitat de molts compostos. Els compostos aromàtics estan presents tant en els processos industrials com en sistemes vius. Al principi, l’àmbit de les molècules aromàtiques estava limitat a sistemes benzenoids cíclics. Amb el pas del temps, aquest concepte s'ha ampliat a sistemes heterocíclics, clústers metàl·lics, ful·lerens i altres molècules més exòtiques. En aquesta tesi, l'anàlisi de l'estructura electrònica, l'enllaç químic i la deslocalització electrònica de sistemes orgànics i inorgànics que posseeixen aromaticitat tridimensional o en estat excitat són estudiats amb detall utilitzant eines computacionals d'última generació. Ens centrem principalment en l’estudi de l'aromaticitat de diferents hidrocarburs policíclics conjugats, ful·lerens i petits clústers inorgànics. Tanmateix, també analitzem l'enllaç químic dels diferents clústers inorgànics

Стилі APA, Harvard, Vancouver, ISO та ін.

48

Erbe, Manuela, Jens Hänisch, Thomas Freudenberg, Anke Kirchner, Stefan Kaskel, Ingolf Mönch, Ludwig Schultz та Bernhard Holzapfel. "Improved REBa₂Cu₃O₇₋ₓ (RE ═ Y, Gd) structure and superconducting properties by addition of acetylacetone in TFA-MOD precursor solutions". Royal Society of Chemistry, 2014. https://tud.qucosa.de/id/qucosa%3A36162.

Повний текст джерела

Анотація:

For developing commercially utilized high-performance high-temperature superconductors, the fabrication of biaxially textured (RE)Ba₂Cu₃O₇₋ₓ (REBCO, RE ═ Y, Gd) coated conductors via metal–organic decomposition of trifluoroacetate precursors (TFA-MOD) has become an interesting strategy for industrial scale-up due to low costs and simple operation. However, the hygroscopic nature of commonly used precursor solutions makes them very sensitive to water pollution through air humidity. This can lead to a degradation of the final microstructure, which in return deteriorates critical current densities. Here, we present a new method to overcome that problem by using a moderator of 2,4-pentanedione (acac) in a pre-existing REBCO precursor solution. Our results show that even initially low-performance solutions can be enhanced to such an extent that they finally outperform standard high-performance solutions and the temperature window for their optimal growth widens significantly. Scanning electron microscopy gives evidence of considerable microstructural improvements, e.g. avoidance of pore formation and grooves, reduction of buckling and surface granularity. X-ray investigations indicate texture improvements, and electrical measurements reveal that transport critical current densities (Jc) increase in self-field and applied magnetic fields. For YBCO, a molar ratio of acac/RE ═ 0.64 is most effective and leads to an increase of the maximum pinning force density Fmaxp from 1.0 to 2.4 GN mˉ³ at 77 K. For GdBCO, a broad window of annealing temperatures (790–840°C) is possible for films with Jc values above 2.9 MA cmˉ² and Fmaxp above 3 GN mˉ³ at 77 K.

Стилі APA, Harvard, Vancouver, ISO та ін.

49

Ahmad, Shah Masood. "Filling the Structure-Reactivity Gap: in silico approaches to rationalize the design of molecular catalysts." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3422346.

Повний текст джерела

Анотація:

The design of molecular catalysts is an ambitious task implying the fundamental issue of relating the molecular structure to the reactivity, i.e., to the catalytic activity. The rationalization of the experimental data is often not straightforward and mechanistic schemes are not transferrable when the conditions of the process are changed or the catalyst is modified even slightly. Computer-aided investigations proved to be a more and more valid support in the last decade, but in most of the cases the aim is limited to investigate in detail the catalytic mechanism of a specific reaction and no general conclusions are drawn that can be used as a guide for designing novel catalysts for the same or analogous processes. In this Project, a computational approach has been set up to investigate the family of organometallic complexes displaying catalytic activity toward [2+2+2] cycloadditions of unsaturated molecules. In a recent book (Transition-metal-mediated aromatic ring construction, John Wiley & Sons, 2013, Chapter 4), Ken Tanaka describes Rhodium mediated [2+2+2] cycloadditions and writes ‘…Although mechanistic aspects of these reactions attract interest, only a few studies have been reported in specific catalysts and substrates…’. Thus this project, abbreviated with the acronym of STREGA (Filling the Structure-Reactivity Gap: in silico approaches to rationalize the design of molecular catalysts), aims at filling the gap between the goldmine of experimental data on this class of very important reactions and their mechanistic rationalization with the purpose of outlining the essential electronic and structural features of the catalyst leading to optimal performance, selectivity, and product yield. In particular, the roles of different metal, different ancillary ligands, different aromatic ligands, and substrates have been accurately investigated; existing data from the literature were also employed for this analysis. Larger polycyclic ligands can in principle host more than a metal center; for example, Cr can be coordinated to the benzene moiety of a rhodium indenyl complex. This might lead to interesting inter metal cooperative effects which might enhance or inhibit the catalytic activity; thus bimetallic catalysts have been considered. The effect of different cooperative metal nuclei was explored changing from Cr to Mo and W, which all belong to Group 6. Finally, the role of the polycyclic aromatic ligand was investigated and found that indeed it is an important factor since it influences rhodium hapticity and consequently its reactivity. All these results allowed to establish a solid structure-activity relationship which is of general validity for rhodium half-sandwich catalysts towards alkyne [2+2+2] cycloadditions and likely is transferrable to analogous Co, Ru, and Ir based fragments.

Стилі APA, Harvard, Vancouver, ISO та ін.

50

F, Huang H., and 黃祥峰. "Sheet Metal Flattening by Decomposition of Features from Solid Models." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/08467382316827566622.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Дисертації з теми "Decomposition of metal trifluoroacetates"

Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями