948 resultados para extraction and separation techniques


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Studies of authigenic phosphorus (P) minerals in marine sediments typically focus on authigenic carbonate fluorapatite, which is considered to be the major sink for P in marine sediments and can easily be semi-quantitatively extracted with the SEDEX sequential extraction method. The role of other potentially important authigenic P phases, such as the reduced iron (Fe) phosphate mineral vivianite (Fe(II)3(PO4)*8H2O) has so far largely been ignored in marine systems. This is, in part, likely due to the fact that the SEDEX method does not distinguish between vivianite and P associated with Fe-oxides. Here, we show that vivianite can be quantified in marine sediments by combining the SEDEX method with microscopic and spectroscopic techniques such as micro X-ray fluorescence (µXRF) elemental mapping of resin-embedded sediments, as well as scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) and powder X-ray diffraction (XRD). We further demonstrate that resin embedding of vertically intact sediment sub-cores enables the use of synchrotron-based microanalysis (X-ray absorption near-edge structure (XANES) spectroscopy) to differentiate between different P burial phases in aquatic sediments. Our results reveal that vivianite represents a major burial sink for P below a shallow sulfate/methane transition zone in Bothnian Sea sediments, accounting for 40-50% of total P burial. We further show that anaerobic oxidation of methane (AOM) drives a sink-switching from Fe-oxide bound P to vivianite by driving the release of both phosphate (AOM with sulfate and Fe-oxides) and ferrous Fe (AOM with Fe-oxides) to the pore water allowing supersaturation with respect to vivianite to be reached. The vivianite in the sediment contains significant amounts of manganese (~4-8 wt.%), similar to vivianite obtained from freshwater sediments. Our results indicate that methane dynamics play a key role in providing conditions that allow for vivianite authigenesis in coastal surface sediments. We suggest that vivianite may act as an important burial sink for P in brackish coastal environments worldwide.

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

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Thesis (Ph.D.)--University of Washington, 2016-08

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The aim of this study was to optimize the aqueous extraction conditions for the recovery of phenolic compounds and antioxidant capacity of lemon pomace using response surface methodology. An experiment based on Box–Behnken design was conducted to analyse the effects of temperature, time and sample-to-water ratio on the extraction of total phenolic compounds, total flavonoids, proanthocyanidins and antioxidant capacity. Sample-to-solvent ratio had a negative effect on all the dependent variables, while extraction temperature and time had a positive effect only on TPC yields and ABTS antioxidant capacity. The optimal extraction conditions were 95 oC, 15 min, and a sample-to-solvent ratio of 1:100 g/ml. Under these conditions, the aqueous extracts had the same content of TPC and TF as well as antioxidant capacity in comparison with those of methanol extracts obtained by sonication. Therefore these conditions could be applied for further extraction and isolation of phenolic compounds from lemon pomace.

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Experimental and analytical studies were conducted to explore thermo-acoustic coupling during the onset of combustion instability in various air-breathing combustor configurations. These include a laboratory-scale 200-kW dump combustor and a 100-kW augmentor featuring a v-gutter flame holder. They were used to simulate main combustion chambers and afterburners in aero engines, respectively. The three primary themes of this work includes: 1) modeling heat release fluctuations for stability analysis, 2) conducting active combustion control with alternative fuels, and 3) demonstrating practical active control for augmentor instability suppression. The phenomenon of combustion instabilities remains an unsolved problem in propulsion engines, mainly because of the difficulty in predicting the fluctuating component of heat release without extensive testing. A hybrid model was developed to describe both the temporal and spatial variations in dynamic heat release, using a separation of variables approach that requires only a limited amount of experimental data. The use of sinusoidal basis functions further reduced the amount of data required. When the mean heat release behavior is known, the only experimental data needed for detailed stability analysis is one instantaneous picture of heat release at the peak pressure phase. This model was successfully tested in the dump combustor experiments, reproducing the correct sign of the overall Rayleigh index as well as the remarkably accurate spatial distribution pattern of fluctuating heat release. Active combustion control was explored for fuel-flexible combustor operation using twelve different jet fuels including bio-synthetic and Fischer-Tropsch types. Analysis done using an actuated spray combustion model revealed that the combustion response times of these fuels were similar. Combined with experimental spray characterizations, this suggested that controller performance should remain effective with various alternative fuels. Active control experiments validated this analysis while demonstrating 50-70\% reduction in the peak spectral amplitude. A new model augmentor was built and tested for combustion dynamics using schlieren and chemiluminescence techniques. Novel active control techniques including pulsed air injection were implemented and the results were compared with the pulsed fuel injection approach. The pulsed injection of secondary air worked just as effectively for suppressing the augmentor instability, setting up the possibility of more efficient actuation strategy.

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Simultaneous Localization and Mapping (SLAM) is a procedure used to determine the location of a mobile vehicle in an unknown environment, while constructing a map of the unknown environment at the same time. Mobile platforms, which make use of SLAM algorithms, have industrial applications in autonomous maintenance, such as the inspection of flaws and defects in oil pipelines and storage tanks. A typical SLAM consists of four main components, namely, experimental setup (data gathering), vehicle pose estimation, feature extraction, and filtering. Feature extraction is the process of realizing significant features from the unknown environment such as corners, edges, walls, and interior features. In this work, an original feature extraction algorithm specific to distance measurements obtained through SONAR sensor data is presented. This algorithm has been constructed by combining the SONAR Salient Feature Extraction Algorithm and the Triangulation Hough Based Fusion with point-in-polygon detection. The reconstructed maps obtained through simulations and experimental data with the fusion algorithm are compared to the maps obtained with existing feature extraction algorithms. Based on the results obtained, it is suggested that the proposed algorithm can be employed as an option for data obtained from SONAR sensors in environment, where other forms of sensing are not viable. The algorithm fusion for feature extraction requires the vehicle pose estimation as an input, which is obtained from a vehicle pose estimation model. For the vehicle pose estimation, the author uses sensor integration to estimate the pose of the mobile vehicle. Different combinations of these sensors are studied (e.g., encoder, gyroscope, or encoder and gyroscope). The different sensor fusion techniques for the pose estimation are experimentally studied and compared. The vehicle pose estimation model, which produces the least amount of error, is used to generate inputs for the feature extraction algorithm fusion. In the experimental studies, two different environmental configurations are used, one without interior features and another one with two interior features. Numerical and experimental findings are discussed. Finally, the SLAM algorithm is implemented along with the algorithms for feature extraction and vehicle pose estimation. Three different cases are experimentally studied, with the floor of the environment intentionally altered to induce slipping. Results obtained for implementations with and without SLAM are compared and discussed. The present work represents a step towards the realization of autonomous inspection platforms for performing concurrent localization and mapping in harsh environments.

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For this project I prepared a series of recitals featuring music for horn and percussion, in which the horn part featured extended horn techniques. For this project, I considered anything beyond the open or muted horn an extended technique. These techniques range from the common hand-stopped note passages to complex new techniques involving half-valves, multi-phonics, and more, for new sounds desired by the composer. There are several pieces written for solo horn and percussion, with ensembles ranging from simple duets to solo horn with a full percussion ensemble. However, few include extended techniques for the horn. All of these select pieces are lesser known because of their difficulty, primarily because of the challenge of the extended techniques requested by the composer. In the introduction to this paper I give a brief background to the project, where the current repertoire stands, and my experiences with commissioning works for this genre. I then give a brief history and how-to on the more common extended techniques, which were found in almost every piece. I separated these techniques so that they could be referenced in the performance notes without being extremely repetitive in their description. Then follows the main performance notes of the repertoire chosen, which includes a brief description of the piece itself and a longer discussion for performers and composers who wish to learn more about these techniques. In this section my primary focus is the extended techniques used and I provide score samples with permission to further the education of the next musicians to tackle this genre. All works performed for this project were recorded and accompany this paper in the Digital Repository at the University of Maryland (DRUM). The following works were included in this project: o Howard J. Buss, Dreams from the Shadows (2015) o Howard J. Buss, Night Tide (1995) o George Crumb, An Idyll for the Misbegotten, trans. Robert Patterson (1986/1997) o Charles Fernandez, Metamorphosis: A Horn’s Life, “Prenatal and Toddler” (2016, unfinished) o Helen Gifford, Of Old Angkor (1995) o Douglas Hill, Thoughtful Wanderings… (1990) o Pierre-Yves Level, Duetto pour Cor en Fa et Percussion (1999) o David Macbride, Elegy for Horn and Timpani (2009) o Brian Prechtl, A Song of David (1995) o Verne Reynolds, HornVibes (1986) o Pablo Salazar, Cincontar (2016) o Mark Schultz, Dragons in the Sky (1989) o Faye-Ellen Silverman, Protected Sleep (2007) o Charles Taylor, Sonata for Horn and Marimba (1991) o Robert Wolk, Tessellations (2016) With this project, I intend to promote these pieces and the techniques used to encourage more works written in this style, and reveal to fellow horn players that the techniques should not prevent these great works from being performed. Due to the lack of repertoire, I successfully commissioned new pieces featuring extended techniques, which were featured in the final recital.

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The aim of this study was to compare two processes for the extraction of R-phycoerythrin (R-PE) from the red seaweed Grateloupia turuturu: ultrasound-assisted extraction (UAE) and ultrasound-assisted enzymatic hydrolysis (UAEH). Process efficiencies were both evaluated by the yield of R-PE extraction and by the level of liquefaction. Experiments were conducted at 40 and 22 °C, for 6 h, using an enzymatic cocktail and an original ultrasonic flow-through reactor. R-PE appeared very sensitive to temperature, thus 22 °C is strongly recommended for its extraction by UAEH or UAE. However, the higher processing temperature (40 °C) clearly increased the extraction of water-soluble compounds (up to 91% of liquefaction). These two new processes are thus promising alternatives for the extraction of water-soluble components including R-PE, from wet seaweeds, with extraction yields at least similar to conventional solid–liquid extraction.

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Humans have a high ability to extract visual data information acquired by sight. Trought a learning process, which starts at birth and continues throughout life, image interpretation becomes almost instinctively. At a glance, one can easily describe a scene with reasonable precision, naming its main components. Usually, this is done by extracting low-level features such as edges, shapes and textures, and associanting them to high level meanings. In this way, a semantic description of the scene is done. An example of this, is the human capacity to recognize and describe other people physical and behavioral characteristics, or biometrics. Soft-biometrics also represents inherent characteristics of human body and behaviour, but do not allow unique person identification. Computer vision area aims to develop methods capable of performing visual interpretation with performance similar to humans. This thesis aims to propose computer vison methods which allows high level information extraction from images in the form of soft biometrics. This problem is approached in two ways, unsupervised and supervised learning methods. The first seeks to group images via an automatic feature extraction learning , using both convolution techniques, evolutionary computing and clustering. In this approach employed images contains faces and people. Second approach employs convolutional neural networks, which have the ability to operate on raw images, learning both feature extraction and classification processes. Here, images are classified according to gender and clothes, divided into upper and lower parts of human body. First approach, when tested with different image datasets obtained an accuracy of approximately 80% for faces and non-faces and 70% for people and non-person. The second tested using images and videos, obtained an accuracy of about 70% for gender, 80% to the upper clothes and 90% to lower clothes. The results of these case studies, show that proposed methods are promising, allowing the realization of automatic high level information image annotation. This opens possibilities for development of applications in diverse areas such as content-based image and video search and automatica video survaillance, reducing human effort in the task of manual annotation and monitoring.

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O desenvolvimento de métodos adequados que permitam o monitoramento de resíduos e contaminantes em alimentos é de suma importância pois é a única forma de garantir a segurança dos alimentos evitando danos à saúde do consumidor. Para isso, fazse necessário que estes métodos sejam rápidos, fáceis e de baixo custo, capazes de detectar a presença de resíduos em concentrações baixas e em diferentes matrizes. Este trabalho consistiu no desenvolvimento de método para determinação de 5 sedativos e 14 β-bloqueadores em amostras de rim suíno e posterior análise por Cromatografia Líquida Acoplada à Espectrometria de Massas em Série (LC-MS/MS). O procedimento de extração que melhor se adequou para análise destes compostos consistiu na pesagem de 2 g de amostra e adição de 10 mL de acetonitrila seguida de homogeneização com auxílio de Ultra-Turrax e mesa agitadora. Após extração, as amostras foram submetidas a duas técnicas de clean-up, sendo elas, congelamento do extrato à baixa temperatura e extração em fase sólida dispersiva (d-SPE) utilizando como sorvente Celite® 545. Uma etapa de concentração foi realizada com auxílio de concentrador de amostras sob fluxo de N2 e temperatura controlada. As amostras secas foram retomadas com metanol e analisadas utilizando sistema LC-MS/MS com Ionização por Eletrospray (ESI), operando no modo MRM positivo, coluna Poroshell 120 EC-C18 (3,0 x 50 mm, 2,7 μm) para separação dos analitos, e gradiente de fase móvel composta por (A) solução aquosa acidificada com 0,1% de ácido fórmico (v/v) e (B) metanol 0,1% ácido fórmico (v/v). Os parâmetros de validação avaliados foram linearidade, seletividade, efeito matriz, precisão, veracidade, recuperação, limite de decisão, capacidade de detecção, incerteza da medição, robustez, limite de detecção e de quantificação. Além disso foram observados os critérios de desempenho aplicáveis à detecção por espectrometria de massas e estabilidade dos compostos. A recuperação foi avaliada em 10 μg kg-1 e a veracidade em 5, 10 e 15 μg kg-1 apresentando resultados satisfatórios entre 70 - 85% e 90 - 101%, respectivamente. O limite de quantificação determinado foi de 2,5 μg kg-1 , exceto para carazolol que foi de 1,25 μg kg- 1 . O estudo de linearidade foi realizado entre 0 e 20 μg kg-1 apresentando coeficientes de determinação superiores a 0,98. Estes procedimentos foram realizados através de análise de matriz branca fortificada. Além disso, o presente método foi utilizado para analisar carazolol, azaperone e azaperol em amostras de ensaio colaborativo de rim suíno, apresentando resultados muito próximos aos reais. Portanto, é possível concluir que o método desenvolvido é adequado para análise de sedativos e β-bloqueadores através de extração dos compostos e limpeza do extrato eficientes utilizando procedimentos rápidos, fáceis e de baixo custo, garantindo resultados seguros e confiáveis.

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The purpose of the present PhD thesis is to investigate the properties of innovative nano- materials with respect to the conversion of renewable energies to electrical and chemical energy. The materials have been synthesized and characterized by means of a wide spectrum of morphological, compositional and photophysical techniques, in order to get an insight into the correlation between the properties of each material and the activity towards different energy conversion applications. Two main topics are addressed: in the first part of the thesis the light harvesting in pyrene functionalized silicon nanocrystals has been discussed, suggesting an original approach to suc- cessfully increase the absorption properties of these nanocrystals. The interaction of these nanocrystals was then studied, in order to give a deeper insight on the charge and energy extraction, preparing the way to implement SiNCs as active material in optoelectronic devices and photovoltaic cells. In addition to this, the luminescence of SiNCs has been exploited to increase the efficiency of conventional photovoltaic cells by means of two innovative architectures. Specifically, SiNCs has been used as luminescent downshifting layer in dye sensitized solar cells, and they were shown to be very promising light emitters in luminescent solar concentrators. The second part of the thesis was concerned on the production of hydrogen by platinum nanoparticles coupled to either electro-active or photo-active materials. Within this context, the electrocatalytic activity of platinum nanoparticles supported on exfoliated graphene has been studied, preparing an high-efficiency catalyst and disclosing the role of the exfoliation technique towards the catalytic activity. Furthermore, platinum nanoparticles have been synthesized within photoactive dendrimers, providing the first proof of concept of a dendrimer-based photocatalytic system for the hydrogen production where both sensitizer and catalyst are anchored to a single scaffold.

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Three-dimensional Direct Numerical Simulations combined with Particle Image Velocimetry experiments have been performed on a hemisphere-cylinder at Reynolds number 1000 and angle of attack 20◦. At these flow conditions, a pair of vortices, so-called “horn” vortices, are found to be associated with flow separation. In order to understand the highly complex phenomena associated with this fully threedimensional massively separated flow, different structural analysis techniques have been employed: Proper Orthogonal and Dynamic Mode Decompositions, POD and DMD, respectively, as well as criticalpoint theory. A single dominant frequency associated with the von Karman vortex shedding has been identified in both the experimental and the numerical results. POD and DMD modes associated with this frequency were recovered in the analysis. Flow separation was also found to be intrinsically linked to the observed modes. On the other hand, critical-point theory has been applied in order to highlight possible links of the topology patterns over the surface of the body with the computed modes. Critical points and separation lines on the body surface show in detail the presence of different flow patterns in the base flow: a three-dimensional separation bubble and two pairs of unsteady vortices systems, the horn vortices, mentioned before, and the so-called “leeward” vortices. The horn vortices emerge perpendicularly from the body surface at the separation region. On the other hand, the leeward vortices are originated downstream of the separation bubble, as a result of the boundary layer separation. The frequencies associated with these vortical structures have been quantified.

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Sampling and preconcentration techniques play a critical role in headspace analysis in analytical chemistry. My dissertation presents a novel sampling design, capillary microextraction of volatiles (CMV), that improves the preconcentration of volatiles and semivolatiles in a headspace with high throughput, near quantitative analysis, high recovery and unambiguous identification of compounds when coupled to mass spectrometry. The CMV devices use sol-gel polydimethylsiloxane (PDMS) coated microglass fibers as the sampling/preconcentration sorbent when these fibers are stacked into open-ended capillary tubes. The design allows for dynamic headspace sampling by connecting the device to a hand-held vacuum pump. The inexpensive device can be fitted into a thermal desorption probe for thermal desorption of the extracted volatile compounds into a gas chromatography-mass spectrometer (GC-MS). The performance of the CMV devices was compared with two other existing preconcentration techniques, solid phase microextraction (SPME) and planar solid phase microextraction (PSPME). Compared to SPME fibers, the CMV devices have an improved surface area and phase volume of 5000 times and 80 times, respectively. One (1) minute dynamic CMV air sampling resulted in similar performance as a 30 min static extraction using a SPME fiber. The PSPME devices have been fashioned to easily interface with ion mobility spectrometers (IMS) for explosives or drugs detection. The CMV devices are shown to offer dynamic sampling and can now be coupled to COTS GC-MS instruments. Several compound classes representing explosives have been analyzed with minimum breakthrough even after a 60 min. sampling time. The extracted volatile compounds were retained in the CMV devices when preserved in aluminum foils after sampling. Finally, the CMV sampling device were used for several different headspace profiling applications which involved sampling a shipping facility, six illicit drugs, seven military explosives and eighteen different bacteria strains. Successful detection of the target analytes at ng levels of the target signature volatile compounds in these applications suggests that the CMV devices can provide high throughput qualitative and quantitative analysis with high recovery and unambiguous identification of analytes.

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Les méthodes de design et de construction des routes développés dans le sud canadien ont maintenant besoin d’être adaptés aux environnements nordiques du pays afin de prévenir le dégel dramatique du pergélisol lors de la construction d’une nouvelle route. De plus, le réchauffement climatique occasionne présentement d’importants problèmes de stabilité des sols dans le nord canadien. Ces facteurs causent des pertes importantes au niveau des capacités fonctionnelles et structurales de l’Alaska Highway au Yukon sur un segment de plus de 200 km situé entre le village de Destruction Bay et la frontière de l’Alaska. Afin de trouver des solutions rentables à long terme, le ministère du transport du Yukon (en collaboration avec le Federal Highway Administration du gouvernement américain, Transports Canada, l’Université Laval, l’Université de Montréal et l’Alaska University transportation Center) a mis en place 12 sections d’essais de 50 mètres de longueur sur l’autoroute de l’Alaska près de Beaver Creek en 2008. Ces différentes sections d’essais ont été conçues pour évaluer une ou plusieurs méthodes combinées de stabilisation thermique telles que le drain thermique, le remblai à convection d’air, le pare-neige / pare-soleil, le remblai couvert de matières organiques, les drains longitudinaux, le déblaiement de la neige sur les pentes et la surface réfléchissante. Les objectifs spécifiques de la recherche sont 1) d’établir les régimes thermiques et les flux de chaleur dans chacune des sections pour les 3 premières années de fonctionnement ; 2) de documenter les facteurs pouvant favoriser ou nuire à l’efficacité des systèmes de protection et ; 3) de déterminer le rapport coûts/bénéfices à long terme pour chacune des techniques utilisées. Pour ce faire, une nouvelle méthode d’analyse, basée sur la mesure de flux d’extraction de chaleur Hx et d’induction Hi à l’interface entre le remblai et le sol naturel, a été utilisée dans cette étude. Certaines techniques de protection du pergélisol démontrent un bon potentiel durant leurs 3 premières années de fonctionnement. C’est le cas pour le remblai à convection d’air non-couvert, le remblai à convection d’air pleine largeur, les drains longitudinaux, le pare-soleil / pare-neige et la surface réfléchissante. Malheureusement, des problèmes dans l’installation des drains thermiques ont empêché une évaluation complète de leur efficacité.

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Efficient energy storage holds the key to reducing waste energy and enabling the use of advanced handheld electronic devices, hydrid electric vehicles and residential energy storage. Recently, Li-ion batteries have been identified and employed as energy storage devices due to their high gravimetric and volumetric energy densities, in comparison to previous technologies. However, more research is required to enhance the efficiency of Li-ion batteries by discovering electrodes with larger electrochemical discharge capacities, while maintaining electrochemical stability. The aims of this study are to develop new microwave-assisted synthesis routes to nanostructured insertion cathodes, which harbor a greater affinity for lithium extraction and insertion than bulk materials. Subsequent to this, state-of-the-art synchrotron based techniques have been employed to understand structural and dynamic behaviour of nanostructured cathode materials during battery cell operation. In this study, microwave-assisted routes to a-LiFePO4, VO2(B), V3O7, H2V3O8 and V4O6(OH)4 have all been developed. Muon spin relaxation has shown that the presence of b-LiFePO4 has a detrimental effect on the lithium diffusion properties of a-LiFePO4, in agreement with first principles calculations. For the first time, a-LiFePO4 nanostructures have been obtained by employing a deep eutectic solvent reaction media showing near theoretical capacity (162 mAh g–1). Studies on VO2(B) have shown that the discharge capacity obtained is linked to the synthesis method. Electrochemical studies of H2V3O8 nanowires have shown outstanding discharge capacities (323 mAh g–1 at 100 mA g–1) and rate capability (180 mAh g–1 at 1 A g–1). The electrochemcial properties of V4O6(OH)4 have been investigated for the first time and show a promising discharge capacity of (180 mAh g–1). Lastly, in situ X-ray absorption spectroscopy has been utilised to track the evolution of the oxidation states in a-LiFePO4, VO2(B) and H2V3O8, and has shown these can all be observed dynamically.