Polymer composites formed from layered fillers with high surface volume ratio show enhanced reinforcement. Graphite oxide is a high modulus material that can be separated into thin layers with high surface area. The aim of this study is to prepare polymer layered graphite oxide composites using functionalised polyolefin to enhance compatibility with various forms of layered graphite oxide in varying concentration. Functionalised polyolefins reinforced with layered graphite oxides and expanded graphite oxides were prepared using solution blending and melt blending methods. Three different mixing methods with varying shear intensity were employed to prepare polymer layered graphite oxide composites. The crystalline structure, thermal and mechanical properties of the prepared polymer layered graphite oxide composites was studied. Oxidised graphite prepared from the Staudenmaier method and its exfoliated form were dispersed in poly(ethylene-co-methyl acrylate-co-acrylic acid) (EMAA) via solution blending to prepare EMAA layered composites. The thermal stability was determined using thermogravimetric analysis. The EMAA layered composites showed higher thermal stability in comparison with pure EMAA. The mechanical properties of these EMAA layered composites were determined through dynamic mechanical analysis. Shear modulus, yield stress and storage modulus of EMAA in the presence of graphite oxide fillers decreased. A solution blending method was used to prepare poly(propylene-grafted-maleic anhydride) layered expanded graphite oxide composites (PPMA-EGO). Two types of PPMA-EGO were prepared using different mixing methods - low and high shear were employed. The effects of preparative mixing methods on the PPMA-EGO properties were investigated. The mechanical properties of PPMA-EGO obtained from dynamic mechanical analysis indicated that EGO had a reinforcing effect on the elastic behaviour of PPMA-EGO. This is due to strong interfacial adhesion between PPMA and EGO as a result of hydrogen bonding. The elastic behaviour of PPMA-EGO was affected by the surface area of graphite flakes. Low sheared PPMA-EGO elastic behaviour was found to be higher compared with that of high sheared PPMA-EGO. A melt blending method was used to prepare PPMA-EGO with varying EGO concentration. The interconnected network structure of EGO in the PPMA-EGO was not observed as shown by its scanning electron microscopy images. Thermogravimetric analysis of PPMA-EGO indicates increased decomposition temperature of the PPMA matrix. Dynamic mechanical analysis showed enhanced storage modulus of PPMA-EGO. The maximum elastic modulus of PPMA-EGO was observed at 3 %wt of EGO. The electrical conductivity of PPMA-EGO was measured only for EGO concentrations above 2 %wt. The EGO concentration was found to be the most critical factor in the enhancement of the electrical conductivity of PPMA-EGO. Wide angle X-ray diffraction analysis of all polymer layered graphite oxide composites revealed no change in interlayer spacing of graphite layers, indicating the absence of EMAA intercalation in the graphite layers. The crystallisation temperature and crystallinity of all polymer layered graphite oxide composites were determined using differential scanning calorimetry. The results indicated that graphite oxide and expanded graphite oxides acted as nucleating agents in inducing the crystallisation of functionalised polyolefin in the layered composites. However, the degree of crystallinity of functionalised polyolefin decreased in the layered composites.

It is unclear whether all intercalation techniques truly lead to the insertion of atoms between the graphite layers, or also lead to other effects which contribute to expansion. The objective of this project is to better understand the effects caused by different intercalation methods. Three intercalation methods were explored to determine the method which incurs the least damage to the surface and microstructure of the graphite intercalated compounds, yet achieves the best intercalation and therefore expansion. All the main findings are summarised below:  The gas phase sample had virtually no mass loss at the point where expansion took place. Therefore the intercalation was very efficient, producing large expansion without significant mass loss.  The mass loss that only occurs at the sublimation of iron chloride (320 ºC) indicates the excessive "un-intercalated" or residual iron chloride.  After oxidation, before purification, the gas phase sample has 25 % residual mass; this also proves the presence of impurities and residual iron chloride in the exfoliated sample. For the Hummers and electrochemical samples, expansion and mass loss occur over a wide temperature range, this indicates that graphite oxide was formed rather than the theoretically expected "insertion of atoms between the sheets".  The mass losses before 200 ˚C of the samples of the Hummers and electrochemical methods are more evidence that graphite oxide and graphite surface complexes with oxygen were produced.  The Hummers and electrochemical intercalation methods show similar expansion and mass loss curves, therefore it can be concluded that the reaction mechanism for both these methods is alike.  The gas phase method yields the best expansion of 250 % using the TMA, whereas both the other methods deliver approximately 220 %.  Using microwave expansion the electrochemical intercalation method yields the best bulk volume expansion of 1500 %, with the gas phase sample delivering a volume expansion of 1450 %. The Hummers samples are extremely damaged. This is clear from the several and deep oxidation pits visible throughout the basal plane of these samples. The basal plane and the edges are even eroded before purification and oxidation. This intercalation technique employs oxidisers in the preparation method which additionally oxidises the samples. This explains why the Hummers method renders the most damage. The residual material on the gas phase sample acts as catalysts making the sample very reactive and consequently damaging the surface during oxidation. The partially oxidised purified gas phase sample visibly shows the pits and roughened edges. There are two “types” of intercalation. The first intercalation “type” is the actual insertion of atoms or molecules between the graphite layers, whereas the other “type” of intercalation is the production of graphite oxide. The compound comprises carbon, oxygen and hydrogen, obtained by treating graphite with strong oxidisers. The functional groups usually found in graphite oxide are carbonyl (C=O), hydroxyl (-OH), phenol amongst others and also some impurities of sulphur when sulphuric acid is used. Both these intercalation types lead to expansion. It is recommended that a more efficient method for removal of residual material in the gas phase samples be explored. It is also recommended that more research be done to determine the reaction mechanisms during the three different intercalation methods. The graphite surface complexes of the intercalated compounds and the evolved gases during expansion should be analysed. / Dissertation (MEng)--University of Pretoria, 2015. / tm2015 / Chemical Engineering / MEng / Unrestricted

Made available in DSpace on 2014-12-17T14:07:16Z (GMT). No. of bitstreams: 1 AntonioCAM_DISSERT.pdf: 2526278 bytes, checksum: 858d8dc4858eb48a9d6ce6faab8763d4 (MD5) Previous issue date: 2014-02-26 / Universidade Federal do Rio Grande do Norte / Epoxy based nanocomposites with 1 wt % and 3 wt % of nanographite were processed by high shear mixing. The nanographite was obtained by chemical (acid intercalation), thermal (microwave expansion) and mechanical (ultrasonic exfoliation) treatments. The mechanical, electrical and thermal behavior of the nanocomposites was determined and evaluated as a function of the percentage of reinforcement. According to the experimental results, the electrical conductivity of epoxy was not altered by the addition of nanographite in the contents evaluated. However, based on the mechanical tests, nanocomposites with addition of 1 wt.% and 3 wt.% of nanographite showed increase in tensile strength of 16,62 % and 3,20 %, respectively, compared to the neat polymer. The smaller increase in mechanical strength of the nanocomposite with 3 wt.% of nanographite was related to the formation of agglomerates. The addition of 1 wt.% and 3 wt.% of nanographite also resulted in a decrease of 6,25 % and 17,60 %, respectively, in the relative density of the material. Thus, the specific strength of the nanocomposites was approximately 33,33 % greater when compared to the neat polymer. The addition of 1 wt.% and 3 wt.% of nanographite in the material increased the mean values of thermal conductivity in 28,33 % and 132,62 %, respectively, combined with a reduction of 26,11 % and 49,80 % in volumetric thermal capacity, respectively. In summary, it has been determined that an addition of nanographite of the order of 1 wt.% and 3 wt.% produced notable elevations in specific strength and thermal conductivity of epoxy / Nanocomp?sitos a base de resina ep?xi e nanografite foram processados por mistura de alto cisalhamento, com concentra??es de 1 % e 3 % p/p de refor?o. O nanografite foi obtido atrav?s de tratamentos: qu?mico (intercala??o ?cida), t?rmico (expans?o por microondas) e mec?nico (esfolia??o por ultrassom). Os comportamentos mec?nico, el?trico e t?rmico dos materiais obtidos foram analisados em fun??o da porcentagem de refor?o. De acordo com os resultados obtidos, n?o foram verificadas altera??es na condutividade el?trica do ep?xi com a adi??o de nanografite, nos percentuais estudados. Entretanto, com base nos ensaios mec?nicos observou-se que os nanocomp?sitos com adi??o de 1 % p/p e 3 % p/p de grafite expandido apresentaram aumento na resist?ncia ? tra??o de 16,62 % e 3,20 % respectivamente, em rela??o ao pol?mero puro. O menor aumento de resist?ncia mec?nica para os nanocomp?sitos com 3 % p/p de nanografite foi relacionado com a forma??o de aglomerados. A adi??o de 1 % p/p e 3% p/p de nanografite tamb?m resultou em uma diminui??o de 6,25 % e 17,60 %, respectivamente, na densidade relativa do pol?mero. Portanto, a eleva??o da resist?ncia espec?fica dos nanocomp?sitos foi de aproximadamente 33,33% para os dois nanocomp?sitos, em rela??o ao pol?mero puro. A adi??o de 1 % p/p e 3 % p/p de nanografite no material aumentou os valores m?dios de condutividade t?rmica em 28,33 % e 132,62 %, respectivamente, combinado com uma redu??o de 26,11 % e 49,80 %, respectivamente, na capacidade t?rmica volum?trica. Em resumo, verificou-se que uma adi??o de nanografite da ordem de 1 % e 3 % p/p produziram eleva??es not?veis na resist?ncia mec?nica espec?fica e condutividade t?rmica do ep?xi

[EN] The development of new and more complex polymeric materials involves challenging problems to basic sciences. The relationship between structure and molecular dynamics assumes great importance for the future development of novel technologies based on such polymers. Thus, the understanding of how small changes in the chemical structure affect the properties of the material is essential to progress in the technological and scientific area. An in-depth analysis of the molecular mobility leads to establish the structure-properties relationships. On this basis, the main aim of the present work is to study the molecular mobility of two different families of polymeric materials. For this purpose, the experimental techniques mainly used were Differential Scanning Calorimetry (DSC) and Dielectric Relaxation Spectroscopy (DRS). The first family of polymers characterized was a series of chemically cross-linked copolymers composed by Vinylpyrrolidone (VP) and Butyl Acrylate (BA) monomers. In the first place, the influence of the monomer molar ratio (XVP/YBA) on the copolymer properties was studied. Thus, a Fourier Transform Infrared Spectroscopy (FTIR) analysis verified dipole-dipole interactions between amide groups. The influence of these interactions on several parameters related to the molecular mobility was evidenced by the DSC, DRS and Dynamic Mechanical Analysis (DMA) techniques. Secondly, the effect of the cross-link density on the molecular dynamics of 60VP/40BA copolymers was analyzed using DSC and DRS. One single glass transition was detected by DSC measurements. The DRS analysis showed that an increase of the cross-linking produced a typical effect on the alpha process dynamics. However, the beta process, which possessed typical features of pure JG relaxation, unexpectedly lost the intermolecular character for the highest cross-linker content. The fastest gamma process was relatively unaffected. The second family of polymeric materials studied was a series of segmented polycarbonatediol polyurethane (PUPH) modified with different amounts of expanded graphite (EG) conductive filler. Scanning Electron Microscopy (SEM), X-ray diffraction measurements and FTIR analysis demonstrated a homogeneous dispersion of the EG filler in the matrix. DRS was used to study the dielectric properties of the PUPH/EG composites. The dielectric permittivity of the composites showed an insulator to conductor percolation transition with the increase of the EG content (2030 wt%). The addition of expanded graphite to the matrix caused a dramatic increase in the electrical conductivity of ten orders of magnitude, which is an indication of percolative behavior. / [ES] El desarrollo de nuevos materiales poliméricos de mayor complejidad produce un desafío cada vez mayor en el área de las ciencias básicas. La relación entre la estructura y la dinámica molecular resulta de gran importancia para el desarrollo de nuevas tecnologías basadas en estos materiales poliméricos. Así, una mayor comprensión de cómo pequeños cambios en la estructura química afectan a las propiedades de los materiales resulta esencial para el progreso científico y tecnológico. Un análisis en profundidad de la movilidad molecular permite establecer las relaciones estructura-propiedades. Partiendo de esta base, el principal objetivo del presente trabajo es el estudio de la movilidad molecular de dos familias diferentes de materiales poliméricos. Para ello, las técnicas experimentales utilizadas fueron principalmente la Calorimetría Diferencial de Barrido (DSC) y la Espectroscopia de Relajación Dieléctrica (DRS). La primera familia de polímeros caracterizada fue una serie de copolímeros entrecruzados químicamente compuestos por los monómeros Vinilpirrolidona (VP) y Acrilato de Butilo (BA). En primer lugar, se estudió la influencia de la proporción molar de monómero (XVP/YBA) en las propiedades del copolímero. A través de un análisis por Espectroscopia de Infrarrojo por Transformada de Fourier (FTIR), se verificó la existencia de interacciones dipolo-dipolo entre los grupos amida. Mediante el análisis por DSC, DRS y Análisis Dinamomecánico (DMA), se evidenció la influencia de estas interacciones en diferentes parámetros relacionados con la movilidad molecular. En segundo lugar, se analizó el efecto de la densidad de entrecruzamiento en la dinámica molecular de los copolímeros 60VP/40BA usando DSC y DRS. A través de las medidas de DSC se observó una única transición vítrea para todos los entrecruzamientos. El análisis por DRS mostró como el incremento en entrecruzante produjo el típico efecto en la dinámica del proceso alpha, pero sin embargo, el proceso beta, que tenía las características típicas de una relajación JG, perdió de forma inesperada su carácter intermolecular para el mayor contenido en entrecruzante. El proceso gamma no se vio afectado. La segunda familia de materiales poliméricos estudiada fue una serie de poliuretanos segmentados (PUPH) modificados con diferentes cantidades de grafito expandido (EG), utilizado como relleno conductivo (desde 0 a 50% en peso). El análisis de los resultados obtenidos mediante Microscopía Electrónica de Barrido (SEM), Difracción de Rayos X y FTIR demostró la homogénea dispersión del relleno de EG en la matriz de PUPH. La técnica DRS se usó para estudiar las propiedades dieléctricas de los materiales compuestos PUPH/EG. La permitividad dieléctrica de los materiales mostró una transición de percolación desde aislante a conductor al incrementarse el contenido en EG (rango de 20-30% en peso). La adición de grafito expandido a la matriz de PUPH causó un incremento significativo en la conductividad dieléctrica de diez órdenes de magnitud, lo que indica el comportamiento de percolación. / [CAT] El desenvolupament de nous materials polimèrics de major complexitat produeix un desafiament cada vegada major en l'àrea de les ciències bàsiques. La relació entre l'estructura i la dinàmica molecular resulta de gran importància per al desenrotllament de noves tecnologies basades en aquests materials polimèrics. Així, una major comprensió de com petits canvis en l'estructura química afecten a les propietats dels materials, resulta essencial per al progrés científic i tecnològic. Un anàlisis en profunditat de la mobilitat molecular permet establir les relacions estructura-propietats. Partint d'aquesta base, el principal objectiu del present treball és l'estudi de la mobilitat molecular de dues famílies diferents de materials polimèrics. Per a això, les tècniques experimentals utilitzades van ser principalment la Calorimetria Diferencial de Rastreig (DSC) i l'Espectroscòpia de Relaxació Dielèctrica (DRS). La primera família de polímers caracteritzada va ser una sèrie de copolímers entrecreuats químicament compostos pels monòmers Vinilpirrolidona (VP) i Acrilat de Butilo (BA) . En primer lloc, es va estudiar la influència de la proporció molar de monòmer (XVP/YBA) en les propietats del copolímer. A través d'una anàlisi per Espectroscòpia d'Infraroig per Transformada de Fourier (FTIR), es va verificar l'existència d'interaccions dipol-dipol entre els grups amida. Mitjançant l'anàlisi per DSC, DRS i Anàlisi Dinamomecánico (DMA), es va evidenciar la influència d'aquestes interaccions en diferents paràmetres relacionats amb la mobilitat molecular. En segon lloc, es va analitzar l'efecte de la densitat d'entrecreuament en la dinàmica molecular dels copolímers 60VP/40BA mitjançant DSC i DRS. A través de les mesures de DSC es va observar una única transició vítria per a tots els continguts d'agent entrecreuant . L'anàlisi per DRS va mostrar com l'increment en agent entrecreuant va produir l'efecte esperat en la dinàmica del procés alfa. En canvi, el procés beta, que tenia les característiques típiques d'una relaxació JG, va perdre de forma inesperada el seu caràcter intermolecular per al major contingut en agent entrecreuant. El procés més ràpid gamma no es va veure afectat. La segona família de materials polimèrics estudiada va ser una sèrie de poliuretans segmentats (PUPH) modificats amb diferents quantitats de grafit expandit (EG) , utilitzat com a farcit conductiu (des de 0 a 50% en pes). L'anàlisi dels resultats obtinguts per mitjà de Microscòpia Electrònica de Rastreig (SEM), Difracció de Rajos X i FTIR va mostrar la dispersió homogènia del EG en la matriu de PUPH. La tècnica DRS es va utilitzar per a estudiar les propietats dielèctriques dels materials compostos PUPH/EG. La permitivitat dielèctrica dels materials va mostrar una transició de percolació des d'aïllant a conductor amb l'increment de contingut en EG (20-30% en pes). L'addició d'EG a la matriu de PUPH va causar un increment significatiu en la conductivitat dielèctrica, de deu ordes de magnitud. / Redondo Foj, MB. (2015). A contribution to the study of the molecular mobility in polymeric materials by Thermal and Dielectric Analysis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59457 / TESIS

This diploma thesis deals with an issue of lithium-ion batteries, primarily with negative (anode) electrode materials. Natural graphite in two forms, namely flake and expanded graphite, is used in the thesis as active electrode material. It is concerned with study of their capacity and output characteristics depending on the pressing pressure and discharging current. The first part of thesis consists of theory and describes basic principles and the composition of lithium-ion batteries. Materials, their characteristics used in production and theoretical description of measurement techniques are presented then. The second part of the thesis is focused on production, assembling and measurement of the characteristics of the produced electrodes. The aim of the thesis is finding the effects of changes of pressing pressure on the capacity, stability during cycling and stability at higher loads.

No description available.

This thesis deals with lithiation of negative electrode li-ion batteries. In this thesis is used several electrode materials: carbon, FeCl3, lithiated carbon electrodes and silicon carbide. Reduction of irreversible capacity lithium-ion batteries leads to increased capacity and also we can use new materials as a positive electrode. Thesis deals with the differences in the properties of materials using lithiation and their use in practice

This thesis deals with the replacement of the lid gasket of the primary collector of the steam generator VVER 1000. Original sealing by nickel rings is replaced by kammprofile gasket with expanded graphite layers. The thesis compare the properties of both types of gaskets and the new and the original configuration of flange joint which have been calculated according to EN 1591. The results are compared and conclusions arising therefrom are presented. The work includes results of FEM analysis of the new configuration of the flange joint. There is also a description of the main components of the nuclear power plants VVER 1000 primary circuit in the introductory part which focused on the construction and operation of the steam generator and its primary collector.

Presented work investigates the problem of secondary lithium-ion cells and the different available cathode materials. We have prepared samples of LiFePO4 with the addition of different kinds of carbon materials such as Super P, Vulcan and expanded graphite. We have always created the sample with and without surfactant. Developed samples were compared by measuring electrochemical methods (cyclic voltammetry, charge and discharge cycles and impedance spectroscopy). We also modeled the three-point cell for measuring electrochemical electrode materials.

This diploma work is engaged in replacement of gasket main dividing plane of reactor coolant pumps in nuclear power plant Paks. Of the newly suggested gasket is kammprofile gasket with expanded graphite layer. This work contain suggestion and calculation of new sealing a knot and calculation existing sealing the knot. Results are confrontacion and sequentially is discussed influence on main dividing plane HCČ 317 by use the new and the existing gasket. In this work is contained description brief of legislation. This legislation must keep by design components dedicated for nuclear equipment. Next this work contain view of the most important sealing knots used in primary system of Nuclear Power Plant type VVER 440.