Results have shown that flow batteries may be a solution in the future as an effective and environmental friendly method to an energy storage system (ESS). The technology is reliable and has a high efficiency that comes with low energy losses and a long lifetime. The range of possible fields is suitable for cutting energy peaks in the power grid, by always have a ready and available energy storage that balances the production. By comparing the advantages of flow batteries with conventional batteries it is mainly the fact that they can conserve energy for a long time without being self-discharged thanks to that the storage capacity is in principle endless and limited by the size of the electrolytes tanks that makes them a great energy storage system. The batteries won’t take any damage or decrease in performance when charging or discharging it or if you exhausts it to 100 % and leave it discharged for a long time. The only disadvantages with flow batteries are that they are built upon an advanced design and are built of components made of expensive materials. The main objective of this thesis is to develop an experimental basis for assessing a small pilot module of a flow battery with respect to how different concentrations of salts, flow rates and different currents/voltages affect the performance of the battery. We start by performing the experiment with a polymeric ion exchange membrane and see what values and the advantages and disadvantages it entails.

An active optical shutter for infrared light (3-5 μm) has been designed, exploiting the phase transition in thermochromic vanadium dioxide (VO2). A spin coating processing route for VO2 films has been adapted to manufacture reproducible depositions onto sapphire (Al2O3) substrates. The VO2 films have been characterized by X-ray powder diffraction (XRPD) and infrared spectroscopy (FTIR), showing 55 % transmittance in the open mode and 0.1 % in the closed mode. The VO2 film temperature determines the operating mode of the shutter, and a resistive circuit of gold was deposited on top of the film for heating purposes. Switching times from the open to the closed mode down to 15 ms have been measured. This work is a part of a comprehensive project at the Swedish Defence Research Agency (FOI), aiming to improve active components for protection against lasers. The shutter within this work is at this stage an early prototype, and needs further development and complementary systems such as a control unit to be implemented in an optical system.

Polyethylene (PE) is one of the most popular polymers used in daily life. However, saturated hydrocarbons cannot absorb the energy of light reaching to earth, so degradation process is rather slow which in return cause disposal problems. On the other hand, it was observed that in presence of oxygen and impurities in the polymer matrix, degradation can be rendered to shorter time intervals. This study covers investigation of effect of three different additives in UV induced oxidative degradation of polyethylene. In this work vanadium (III) acetylacetonate, serpentine and Cloisite 30B were used as additives both together and alone to follow photodegradation of polyethylene. Amount of vanadium (III) acetylacetonate was kept constant at 0.2 wt%, while serpentine and Cloisite 30B were used between 1 and 4 wt%. All compositions were prepared by using Brabender Torque Rheometer, and shaped as thin films by compression molding. Samples were irradiated by UV light up to 500 hours. Mechanical and spectroscopic measurements were carried out in certain time intervals to monitor the degradation. It can be concluded that all combinations of three additives showed the fastest degradation behavior compared to pure PE. In the absence of vanadium (III) acetylacetonate the degradation was slowed and fluctuations were observed in the residual percentage strain at break values. There was not a significant change in tensile strength of all samples. Carbonyl index values followed by FTIR were always in increasing manner. Thermal properties were also investigated by DSC Thermograms and they did not change significantly.

In this work, the steady-state performance of zeolite-based (Cu-ZSM-5) and vanadium-based honeycomb monolith catalysts was investigated in the selective catalytic reduction process (SCR) for NO removal using NH3. The aim was to delineate the effect of various parameters including pretreatment of the catalyst sample with H2, NH3-to-NO ratio, inlet oxygen concentration, and space velocity. The concentrations of the species (e.g. NO, NH3, and others) were determined using a Fourier Transform Infrared (FTIR) spectrometer. The temperature was varied from ambient (25 C) to 500 C. The investigation showed that all of the above parameters (except pre-treatment with H2) significantly affected the peak NO reduction, the temperature at which peak NO reduction occurred, and residual ammonia left at higher temperatures (also known as 'NH3 slip'). Depending upon the particular values of the parameters, a peak NO reduction of around 90% was obtained for both the catalysts. However, an accompanied generation of N2O and NO2 species was observed as well, being much higher for the vanadium-based catalyst than for the Cu-ZSM-5 catalyst. For both catalysts, the peak NO reduction decreased with an increase in space velocity, and did not change significantly with an increase in oxygen concentration. The temperatures at which peak NO reduction and complete NH3 removal occurred increased with an increase in space velocity but decreased with an increase in oxygen concentration. The presence of more ammonia at the inlet (i.e. higher NH3-to-NO ratio) improved the peak NO reduction but simultaneously resulted in an increase in residual ammonia. Pretreatment of the catalyst sample with H2 (performed only for the Cu-ZSM-5 catalyst) did not produce any perceivable difference in any of the results for the conditions of these experiments.

Ce travail est consacré a l'intercalation de deux typesC d'éspèces dans des structures lamellaires : d'une part de lithium dans FeWO4C1, d'autre part des ions complexes vanadate dans des hydroxydes doubles lamellaires. La réaction du lithium dans FeWO4C1 est réversible dans le domaine de composition FeWO4C1. L'analyse structurale sur monocrstal de FeWO4C1 et de l'affinement par la methoe de rietveld une foorte modification de l'environnement du fer lors de l'intercalation.<br />Des hydroxydes doubles lamellaires dérivés de Ni(OH)2 contenant des chaînes métavanadate intercalées ont été préparés par la chimie douce. Ces matériaux ont été caractérisés par diffraction des rayons X, spectroscopie infrarouge, analyser thermogravimétrique, analyse chimique et RMN du vanadium. L'étude du processus d'intercalation montre que des ions diperoxovanadate sont insérés de prime abord pouis polycondensent spontanément pour donner des chaînes métavanadate. La RMN du vanadium met en évidence le couplage de ce comportement à un phénomène de greffage, également spontané, des entités insérées aux feuillets.

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Justin Schwartz, Florida State University, College of Engineering, Dept. of Mechanical Engineering. Title and description from dissertation home page (viewed June 17, 2004). Includes bibliographical references.

A redox flow battery (RFB) is an electrochemical energy storage device in which the storage medium is in the form of liquid electrolyte, which is stored in external reservoirs separate from the cell stack. The storage capacity of such systems is limited by the size of the external tanks, making the RFB an ideal technology for grid level energy storage. The vanadium redox flow battery (VRB) is a particularly attractive variant of the RFB, due to its use of a single transition-metal element in both the positive and negative electrolytes. However, the performance of the VRB is affected by the cross-over of electrolytes through the ion-exchange membrane which separates the positive and negative electrolytes. Cross-over causes degradation of energy storage efficiency and long term capacity loss. Previous studies of ion cross-over have focused primarily on the measurement of ion diffusion across ion exchange membranes in the absence of electrical current. In this work a novel VRB cell is described in which ion cross-over can be measured directly in the presence and absence of electrical current. Measurements are made of cross-over using this cell with three different types of ion exchange membrane in both charge and discharge modes. The results reported in this work show that the rate of ion cross-over can be greatly enhanced or suppressed depending upon the magnitude of the current flow and its direction relative to the ion concentration gradient. / text

No description available.

Tribocorrosion is a term used to describe the material degradation due to the combination of electrochemical and tribological processes. Due to a synergetic effect, the material loss can be larger than the sum of the losses due to wear and corrosion acting separately. In this thesis, the synergy of wear and corrosion was investigated for different types of material, namely the Ti-6Al-4V alloy, the SS316L stainless steel coated with a thin film of Diamond Like Carbon (DLC), and the SS301 stainless steel coated with a thin film of chromium silicon nitride (CrSiN). / A tribocorrosion apparatus was designed and constructed to conduct wear experiments in corrosive media. Sliding ball-on-plate configuration was used in this design, where the contact between the ball and the specimen is totally immersed in the test electrolyte. The specimen was connected to a potentiostat to control its electrochemical parameters, namely the potential and the current. Electrochemical techniques were used to control the kinetics of corrosion reactions, and therefore it was possible to assess separately the role of corrosion and wear in the total degradation of material, and to evaluate the synergy between them. / For Ti-6Al-4V, it was found that the corrosion and tribocorrosion depend strongly on the structure of the material. The alpha-equiaxed microstructure with fine dispersed beta-phase exhibited the best corrosion resistance. The corrosion resistance was found to decrease when the basal plane was preferentially aligned parallel to the surface, which is attributed to a low resistance to charge transfer in the oxide films formed on this plane. On the other hand, when wear and corrosion were involved simultaneously, the oxide layer protecting the substrate against dissolution was mechanically destroyed leading to a high corrosion rate. It was found that the hardness was the most important factor determining the tribocorrosion behavior of the Ti-6Al-4V alloy; samples with high hardness exhibited less mechanical wear, less wear-enhanced corrosion, and less corrosion-enhanced wear. / For DLC coatings, it was found that interface engineering plays a crucial role in the tribocorrosion behavior of DLC films. DLC films with nitrided interface layer (SS\N3h\DLC) were shown to have very poor tribocorrosion resistance; the DLC film delaminated from the substrate after 50 cycles of sliding wear at 9 N load in Ringer's solution. It should be mentioned that a previous study performed at Ecole Polytechnique de Montreal [4] has shown that the same coating resisted 1800 cycles of dry wear at 22 N without delamination. This demonstrates clearly the effect of corrosion on the wear resistance of DLC films. The use of a-SiN:H bond layer between the SS316L substrate and the DLC film improved significantly the tribocorrosion behavior of the coating. This layer acts as a barrier against corrosion reaction; the polarization resistance was 5.76 GO.cm2 compared to 27.5 MO.cm2 and 1.81 MO.cm2 for the DLC-coated SS316L with nitrided interface layer and the bare substrate, respectively. / For CrSiN coatings, it was also shown that nitriding treatment of the substrate prior to deposition reduces significantly the tribocorosion resistance of the CrSiN-coated SS301 substrates. This is attributed to the peculiar morphology of the nitrided surface prior to deposition. The high relives at the grain boundaries of the substrate may be the reason for the generation, during sliding wear, of defects in the film, which makes the infiltration of the liquid easier, and consequently leads to the destruction of the CrSiN film.

Considerable efforts are being devoted to designing enhanced molecular magnetic materials, in particular single molecule magnets (SMMs) that can meet the requirements for future technologies such as quantum computing and spintronics. A current trend in the field is enhancing the global anisotropy in metal complexes using single-ion anisotropy. The work in this dissertation is devoted to the synthesis and characterization of new building blocks of the highly anisotropic early transition metal ion V(III) with the aim of incorporating them into heterometallic molecular materials. The results underscore the importance of tuning the local coordination environments of metal ions in order to ensure enhanced single ion anisotropy. A family of mononuclear axially distorted vanadium (III) compounds, A[L_(3)VX_(3)] (3-9) (X = F, Cl or Br, A^(+) = Et_(4)N^(+), nBu_(4)N^(+) or PPN^(+) , L_(3) = Tp or Tp* (Tp = tris(-1-pyrazolyl)borohydride), Tp* = tris(3,5-dimethyl-1-pyrazolyl)borohydride)), and [Tp*V(DMF)_(3)](PF_(6))_(2) were studied. Replacement of the Tp ligand in 3 with the stronger π-donor Tp* results in a near doubling of the magnitude of the axial zero-field splitting parameter D_(z) (D_(z) = -16.0 cm^(-1) in 3, and -30.0 cm^(-1) in 4) as determined by magnetic measurements. Such findings support the idea that controlling the axial crystal field distortion is an excellent way to enhance single-ion anisotropy. High Field-High Frequency EPR measurements on 4 revealed an even higher D value, -40.0 cm^(-1). Interestingly, compound 4 exhibits evidence for an out-of-phase ac signal under dc field. In another effort, a new series of vanadium cyanide building blocks, PPN[V(acac)_(2)(CN)_(2)]∙PPNCl (13) (acac = acetylacetonate), A[V(L)(CN)_(2)] (A^(+) = Et_(4)N^(+), L = N,N'-Ethylenebis(salicylimine) (14), A = PPN^(+), L = N,N'-Ethylenebis(salicylimine) (15), L = N,N'-Phenylenebis(salicylimine) (16), and L = N,N'-Ethylenebis(2-methoxysalicylimine) (17)) were synthesized. Magnetic studies revealed moderate Dz values (-10.0, 5.89, 3.7, 4.05 and 4.36 cm^(-1) for 13-17 respectively). The first family of cyanide-bridged lanthanide containing molecules with a trigonal bipyramidal (TBP) geometry, (Et_(4)N)_(2)[(Re(triphos)(CN)_(3))_(2)(Ln(NO_(3))_(3))_(3)]-∙4CH_(3)CN (19-27 with Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy and Ho) were prepared using the [(triphos)Re(CN)_(3)]^(-) building block, results that add valuable information to our database of compounds with a TBP geometry. Magnetic studies revealed diverse magnetic responses including slow relaxation of the magnetization at zero field for 25 and 26 , an indication of SMM behavior.