O-ethyl S-2-diisopropylaminoethyl methylphosphonothiolate (VX) and O-isobutyl-S-2-diethylaminoethyl methylphosphonothioate (R-VX), are considered chemical warfare agents due to their strong acetylcholinesterase-inhibiting properties. Subsequent to terrorist use of these V-type nerve agents in both Japan and the United States of America (the September 11, 2001 attacks) and the limited capability of anti-terrorist groups to detect such weapons, there has been an increased obligation by the Chemical Weapons Convection for specific detection and identification methods for VX and R-VX. Chemical and/or enzymatic hydrolysis yields sulfhydryl mimic products, diethylaminoethanethiol (DEAET) and dimethylaminoethanethiol (DMAET). This thesis investigates the electrocatalytic parameters of DEAET and DMAET using basal plane pyrolytic graphite electrodes (BPPGEs) modified with: (a) single-wall carbon nanotube (BPPGE-SWCNT); (b) SWCNT functionalised with cobalt (II) tetra-aminophthalocyanine by (i) physical (BPPGE-SWCNT-CoTAPc(mix)), (ii) chemical (BPPGE-SWCNT-CoTAPc(cov)) and (iii) electrochemical adsorption (BPPGE-SWCNT-CoTAPc(ads)) processes; (c) nickel powder (BPPGE-Ni); (d) BPPGE-Ni decorated with SWCNT (BPPGE-Ni-SWCNT), and (e) SWCNT functionalised with nickel (II) tetra-aminophthalocyanine (BPPGE-SWCNT-poly-NiTAPc). Electrochemical studies (performed by voltammetric and electrochemical impedance spectroscopic techniques) revealed that the SWCNT and SWCNT-CoTAPc(mix) films showed comparable electrocatalytic responses towards the detection of DEAET and DMAET whereas competitive electrochemical behaviour was seen between SWCNT and SWCNT-NiTAPc modified BPPGEs. Using the BPPGE-SWCNT-CoTAPc(mix), the estimated catalytic rate constants (k) and diffusion coefficients (D) were higher for DEAET than for the DMAET. Also, the detection limits of approximately 8.0 and 3.0µM for DMAET and DEAET were obtained with sensitivities of 5.0×10−2 and 6.0×10−2 AM−1 for DMAET and DEAET, respectively. Unlike BPPGE-SWCNT-CoTAPc(mix) that detected the two sulfhydryls at slightly different potentials, BPPGE-SWCNT did not. The BPPGE-Ni gave enhanced Faradaic response for the redox probe ([Fe(CN)6]3−/4−) and also displayed enhanced electrocatalytic behaviour towards the detection of DMAET and DEAET with high sensitivity (~23x10−3 AM−1) and low detection limits (4.0 – 9.0 µM range). In comparison to other electrodes reported in the literature, BPPGE-Ni exhibits more promising features required for a simple, highly sensitive, fast and less expensive electrode for the detection of the hydrolysis products of V-type nerve agents in aqueous solution. The efficient response of the BPPGE-Ni is attributed to the high microscopic surface area of the nickel powder. The poor response of the BPPGE-Ni-SWCNT suggests that the nickel impurity in SWCNT did not show any detectable impact on the heterogeneous electron transfer kinetics of SWCNT. Unlike the nickel powder, SWCNT and CoTAPc-SWCNT, the NiTAPc-SWCNT hybrid did not show significant electrocatalysis towards the detection of the sulfhydryls. It is interesting, however, to observe for the first time that SWCNT induced crystallinity on the electropolymer of NiTAPc, and that such electropolymer exhibit charge-storage /-transfer properties that greatly enhance the electrochemical response of nitric oxide. / Dissertation (MSc (Chemistry))--University of Pretoria, 2008. / Chemistry / unrestricted

This thesis discusses methods for the comparatively mild covalent functionalization of graphene. Several graphene models were investigated: polycyclic aromatic hydrocarbons (PAHs), chemical vapor deposition (CVD)-graphene on SiO2/Si substrate, graphite foil, graphite flakes, kish graphite and highly oriented pyrolytic graphite. The PAHs were viewed as graphene edge analogs with the following molecules representing different edge motifs: pyrene, perylene, benzo[a]pyrene, benzo[e]pyrene, triphenylene, acenapthylene, and anthracene. Ozone was used in combination with different solvents to functionalize PAHs, graphite, and CVD-graphene on SiO2/Si. Ozonation in water or methanol resulted in trapping of the carbonyl oxide intermediate that was formed in the reaction, producing a variety of functional groups. Ozonation in hydrogen peroxide solution with sonication promoted radical formation, possibly resulting in edge-oxidation of graphite. The regioselectivity for addition reactions (ozonolysis) and electrophilic aromatic substitution reactions with graphene edges is discussed. To achieve functionalization of the basal plane of graphite or graphene, white light irradiation was used in combination with several transfer hydrogenation reagents. Formic acid treatment under irradiation resulted in the expected hydrogenation, whereas iso-propanol treatment resulted in iso-propanol attachment to the graphene. The developed methods provide opportunities for graphene functionalization without the need for metal based reagents or harsh conditions.

Efficient and economic treatment of low concentration organic pollutants in water, wastewater or industrial process streams is normally very difficult to achieve. Activated carbon has been widely used for contaminant adsorption, but there are problems associated with its regeneration. In this work, a novel, non-porous, highly-conducting graphite intercalation compounds material (GIC) is used. The use of such an adsorbent can significantly reduce the time required to achieve both equilibrium and electrochemical regeneration. This character allows the design of an innovative treatment process that can adsorb contaminants and electrochemically regenerate itself simultaneously within a single unit. A novel liquid-lift reactor for water treatment by an adsorption and electrochemical regeneration process is developed in this work. Batch experiments are carried out to determine the adsorption kinetics and equilibrium isotherm of adsorption Acid Violet 17 onto the GIC adsorbent. The experimental kinetic data are analyzed using the pseudo-first order, pseudo-second order, intra-particle diffusion and three-stage kinetic models. The linear pseudo-second order model offers the highest r2 correlation coefficient. The experimental isotherm data are analyzed using Langmuir, Freundlich and Tempkin isotherm models. The non-linear Langmuir model gives the highest r2 correlation coefficient. High regeneration efficiency (more than 90%) over a number of cycles is obtained by passing a charge of 6.4 C g-1 of the GIC adsorbent, at a current density of 5 mA cm-2 using a batch, sequential adsorption (60 min) and electrochemical regeneration (30 min) process. The simultaneous adsorption and regeneration process indicates that 100 % AV 17 can be removed in 60 min (4L of 100 mg L-1 AV 17 solution, 140g of the GIC adsorbent, current density of 5mA cm-2). The flow behaviour in the electrochemical reactor has been studied using a pulse tracer technique. The residence time distribution shows that the flow behaviour in the liquid-spouted reactor can be regarded as a plug flow in series with a continuous stirred tank reactor. For the batch adsorption system, a “parallel adsorption barren well hypothesis” is proposed in this thesis. For the batch simultaneous adsorption and electrochemical regeneration system, a multi-parameter model is proposed in this thesis.

The University of Manchester Greg BlackThesis submitted for the degree of Doctor of EngineeringIrradiated Graphite Waste: Analysis and Modelling of Radionuclide Production with a View to Long Term Disposal23rd June 2014The UK has predominantly used graphite moderator reactor designs in both its research and civil nuclear programmes. This material will become activated during operation and, once all reactors are shutdown, will represent a waste legacy of 96,000 tonnes [1]. The safe and effective management of this material will require a full understanding of the final radiological inventory. The activity is known to arise from impurities present in the graphite at start of life as well as from contamination products transported from other components in the reactor circuit. The process is further complicated by radiolytic oxidation which leads to considerable weightloss of the graphite components. A comprehensive modelling methodology has been developed and validated to estimate the activity of the principle radionuclides of concern, 3H, 14C, 36Cl and 60Co. This methodology involves the simulation of neutron flux using the reactor physics code WIMS, and radiation transport code MCBEND. Activation calculations have been performed using the neutron activation software FISPACT. The final methodology developed allows full consideration of all processes which may contribute to the final radiological inventory of the material. The final activity and production pathway of each radionuclide has been researched in depth, as well as operational parameters such as the effect of changes in flux, fuel burnup, graphite weightloss and irradiation time. Methods to experimentally determine the activity, and distribution of key radionuclides within irradiated graphite samples have been developed in this research using a combination of both gamma spectroscopy and autoradiography. This work has been externally validated and provides confidence in the accuracy of the final modelling predictions. This work has been undertaken as part of the EU FP7 EURATOM Project: CARBOWASTE, and was funded by the Office for Nuclear Regulation.

Orientador: José Antônio Malmonge / Resumo: O uso de nanocargas de carbono tais como nanotubos de carbono e nanolâminas de grafite (NLG), e/ou polímeros condutores em uma matriz polimérica, tem atraído à atenção de inúmeros pesquisadores que buscam sintetizar elastômeros eletricamente condutivos com amplo potencial aplicacional como dissipadores eletrostáticos, blindagem eletromagnética, sensores piezorresistivos, etc. Nesse trabalho, foram obtidos: (1) nanocompósitos de polianilina (PAni)/NLG com razão mássica anilina (An)/NLG entre 0 e 250%, utilizando ácido clorídrico como dopante (nanocompósitos PHN), e com razão mássica anilina An/NLG entre 0 e 950%, utilizando ácido dodecilbenzeno sulfônico (DBSA) como dopante (nanocompósitos PDN); (2) Blendas de borracha natural (BN)/PAni com diferentes razões BN/An, utilizando BN in natura (blendas BNP) e borracha pré-vulcanizada (BV), blendas BVP; e (3) Nanocompósitos de BN/PAni-NLG (BNP/NLG) e BV/PAni-NLG (BVP/NLG) com diferentes razões BN/An e 15% de NLG em relação a An (relação m/m). Em todas as sínteses a polimerização da anilina foi realizada in situ. Nos nanocompósitos de PAni/NLG a polimerização da PAni ocorreu sobre a superfície lisa das NLG sendo sua morfologia e grau de intercalação nas NLG influenciados pelo tipo de dopante utilizado. A condutividade elétrica máxima obtida para os nanocompósitos foi de 627 S.cm-1 e 582 S.cm-1 para nanocompósitos PHN contendo 200% de NLG e para nanocompósitos PDN contendo 600% de NLG, respectivamente. O aumento na estabilidade térmic... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The use of carbon nanofiller such as carbon nanotube and graphite nanosheet (GNS), and/or conductive polymers as filler to a polymer matrix, has attracted the attention of numerous researchers who seek to synthesize electrically conductive elastomers with broad application potential such as electrostatic dissipator, piezoresistive sensor and electromagnetic interference shielding . In this work were synthesized: (1) nanocomposites of polyaniline (PAni)/NLG with aniline (An)/NLG mass ratio between 0 and 250%, using hydrochloric acid as a dopant (PHN nanocomposites) and aniline An/NLG between 0 and 950%, using dodecylbenzene sulfonic acid (DBSA) as a dopant (PDN nanocomposites); (2) Natural rubber blends (BN)/PAni with different BN/An mass ratio, using BN in nature (BNP blends) and pre-vulcanized rubber BV, BVP blends; and (3) BN/PAni-NLG (BNP/NLG) and BV/PAni-NLG (BVP/NLG) nanocomposites with different BN/An mass ratios and 15% NLG with respect to An (m/m ratio). In all syntheses the polymerization of aniline was performed in situ. In the nanocomposites PAni/GNS the polymerization of PAni occurred on the GNS surface and their morphology and degree of intercalation in NLGs were influenced by the type of dopant. The higher electrical conductivity obtained for PHN and PDN composites were 627 S.cm-1 and 582 S.cm-1, respectively. The increase in the thermal stability of PAni in PAni/NLG nanocomposites was attributed to the intercalation of PAni among GNS and barrier properties pres... (Complete abstract click electronic access below) / Doutor

Graphite is the strongest diamagnet of all known materials to date. Recent studies of the thickness dependence of the resistance of graphite have demonstrated the heterogeneity of the charge distribution in bulk graphite and prompted the study of its magnetic properties. The studies of the thickness dependence of the magnetic susceptibility of graphite, done in this work, showed that two-dimensional interfaces between the crystalline (Bernal or rhombohedral stacking order) blocks in graphite make a dominant contribution to its diamagnetic susceptibility. Previously proposed models of diamagnetism in graphite are not suitable for explaining its magnetic properties, and therefore new concepts should be considered. Additionally, the studies of the transport and magnetic properties of graphite and multilayer graphene indicated the existence of superconductivity at the interfaces in well-ordered graphite. The possibility of creating permanent circulating currents around artificial holes in highly oriented graphite was studied by highly sensitive magnetization measurements. The obtained results provide hints for the possible existence of superconducting regions inside the bulk highly ordered graphite. In the present thesis, a further thickness dependent phenomenon on the depinning line (DL) of the flux line lattice of the high-Tc superconductor Bi2Sr2CaCu2O8+δ was studied. This geometrical effect shifts to notably lower temperatures in micrometer ring, compared with bulk crystals and thin flakes. The shift is related to a decrease in the overall pinning potential as a result of size effects, caused by: a) the thickness of the sample being smaller than the pinning correlation length, and b) the increase in the effective London penetration depth of the vortices (Pearl vortices). The large shift of the DL to lower temperatures may significantly influence the suitability of such elements for device applications in microstrip antennas and THz emitters.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22067号 / 工博第4648号 / 新制||工||1725(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 安田 秀幸, 教授 辻 伸泰, 教授 宇田 哲也 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22456号 / 工博第4717号 / 新制||工||1737(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 作花 哲夫, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 新制・論文博士 / 博士(工学) / 乙第13407号 / 論工博第4193号 / 新制||工||1762(附属図書館) / (主査)教授 安部 武志, 教授 作花 哲夫, 教授 阿部 竜 / 学位規則第4条第2項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Supraleitung in Graphit ist kein neues Thema. Dieser Effekt wurde bereits in den 1960er Jahren in Interkalationsverbindungen von Graphit gefunden. Die Supraleitung in reinem Graphit wurde bereits vor etwa 50 Jahren beschrieben. Kürzlich wurden in zweischichtigem Graphen, in dem die Graphenschichten um einen 'magischen' Winkeln um die c Achse verdreht wurden, flache Bänder in der elektronischen Bandstruktur nachgewiesen, welche mit der Entstehung von Supraleitung zusammenhängen. Wir haben die elektrischen Transporteigenschaften in Graphitproben mit unterschiedlichen Elektrodenkonfigurationen untersucht. Wir haben den elektrischen Widerstand von hochgeordnetem natürlichem und synthetischem Graphit mit Elektroden auf der Oberseite der ab Basalebene und auch parallel zur c Achse mit hoher Präzision gemessen und den Einfluss der hochleitenden Stapelfehler untersucht, an denen, eingebettet zwischen den kristallinen Graphitschichten, 2D-Grenzflächen entstehen, die ebenfalls flache Bänder aufweisen. Die Existenz einer gut geordneten rhomboedrischen Graphitphase in allen gemessenen Proben wurde durch Röntgenbeugungsmessungen nachgewiesen. Die Grenzflächen mit der hexagonalen Phase stellen laut theoretischer Vorhersagen einen möglichen Ursprung für die Hochtemperatursupraleitung dar. Die experimentellen Ergebnisse liefern eindeutige Beweise für körnige Supraleitung in diesen Materialien, z. B. einen schrittweisen Temperaturübergang bei ~ 350 K, magnetische Irreversibilität, Zeitabhängigkeit nach einer Feldänderung, die mit dem eingeschlossenen Fluss und Flusskriechen übereinstimmt, und den teilweise abgestoßenen magnetischen Fluss, welcher in Magnetisierungsmessungen beobchtet werden kann. Die Lokalisierung der körnigen Supraleitung an diesen 2D-Grenzflächen verhindert die Beobachtung widerstandsfreier elektrischer Ströme oder eines vollständigen Meißner-Zustands. Der Grund ist, dass die körnige Supraleitung in abgegrenzten Regionen an den Grenzflächen entsteht, welche in eine Multigraphen-Halbleitermatrix eingebettet sind. In dieser Arbeit wird eine detaillierte Untersuchung des Magnetowiderstands in verschiedenen Arten von Graphitproben bei niedrigen und hoch gepulsten Magnetfeldern vorgestellt. / Superconductivity in graphite is not a new topic. Its existence goes back to the 1960s when this effect was found in intercalation compounds of graphite. Superconductivity in pure graphite was reported already around 50 years ago and recently proved in bi-layer graphene, related to 'magic' angles between the graphene layers, twisted around the c axis, with the electronic band structure exhibiting flat bands. We have studied electrical transport properties in graphite samples with different electrode configurations. Measuring with high precision, the electrical resistance of highly ordered natural and synthetic graphite, with electrodes placed on the top of the ab basal plane, and also parallel to the c axis, we investigated the influence of the highly conducting stacking faults, referred as 2D interfaces, embedded between the crystalline regions of graphite, which also exhibit flat bands. The existence of well ordered rhombohedral graphite phase in all measured samples has been proved by x-ray diffraction measurements, suggesting its interfaces with the hexagonal phase as a possible origin of high-temperature superconductivity, predicted by theoretical studies. The results provide clear evidence of granular superconductivity, e.g., a step-like transition in temperature at ~ 350 K, magnetic irreversibility, time dependence after a field change, consistent with trapped flux and flux creep, and the partial magnetic flux expulsion from magnetization measurements. The localization of the granular superconductivity at these 2D interfaces prevents the observation of a zero resistance state or a full Meissner state. The reason is that the superconducting distribution is a mixture of superconducting patches at the interfaces, and they are embedded in a multigraphene semiconducting matrix. A detailed study of the magnetoresistance in different kinds of graphite samples at low and high-pulsed magnetic fields is presented in this work.