Nanoscaled Structures of Chlorate Producing Electrodes

Sodium chlorate is mainly used for production of chlorine dioxide (a pulp bleaching agent). Sodium chlorate is produced by an electrochemical process where chloride ions (from sodium chloride dissolved in water) are oxidized to chlorine on the anodes and hydrogen is evolved on the cathodes. The anode of this process consists of a metal plate coated with a catalytically active metal oxide film. The electrocatalytic properties of the anode coating film have been widely investigated due to the great importance of these electrodes in the electrochemical industry. The material properties are, however, not as well investigated, and the studies described in this thesis are an attempt to remedy this. Several standard material characterization methods were used, such as SEM, TEM, AFM, EDX, XRD, porosimetry and DSC. Also, a novel model system based on spin coated electrode films on smooth substrates was developed. The model system provided a way to design samples suitable for e.g. TEM, where the sample thickness is limited to maximum of 100 nm. This is possible due to the ability to control the film thickness by the spinning velocity when using the spin coating technique. It was shown here that the anode coating has a nanostructure. It consists of grains, a few tens of nanometers across. The nanostructure leads to a large effective area and thus provides an explanation of the superior catalytic properties of these coatings. The grains were also shown to be monocrystalline. The size of these grains and its origin was investigated. The calcination temperature, the precursor salt and (if any) doping material all affected the grain size. A higher calcination temperature yielded larger grains and doping with cobalt resulted in smaller grains and therefore a larger real area of the coating. Some preparation conditions also affected the microstructure of the coating; such as substrate roughness. The microstructure is for example the cracked-mud structure. A smoother substrate gave a lower crack density. The cathode of chlorate production is usually an uncoated metal plate, therefore 'less catalytically active'. It is, however, possible to activate the cathode by for example in situ additions to the electrolyte. It was shown here that sufficient addition of molybdate to the electrolyte resulted in a molybdenum film deposited on the cathode and thereby an increase of its surface area and an activation the hydrogen evolution reaction

CO2 project – CO2 effects on drivers’ state and performance

Carbon dioxide (CO 2) is an odourless and colourless compound present in the atmosphere at a concentration of approximately 400 parts per million (or ppm). While CO 2 is not toxic per se, exposures to very high concentrations (> 10000 ppm) may have moderate to severe implications for human health, e.g., high blood pressure, dizziness, nausea or even life-threatening conditions such as hypercapnia or loss of consciousness. Short-term exposures to moderate-high levels (1000-5000 ppm) are also known to produce mild symptoms such as fatigue, discomfort or headache. Moderate-high CO 2 levels have been detected inside vehicles. Evidence suggests that a large number of drivers may frequently expose themselves to CO2 concentrations that could affect their state and, more importantly, their ability to drive safely. This potential effect, however, has received no attention in the literature. To address this knowledge gap, the present project aimed to elucidate the possible effects of moderate- high CO 2 levels on driver fitness and performance. In addition, this project analyzed the influence of other factors, such as driver mental workload and driving time, on the effects of CO 2. This second objective builds on the idea highlighted by two recent reviews that CO 2 effects may be more easily detectable when task demands are sufficiently high. Besides learning about the role of CO 2 on driving safety, this project also aimed to provide recommendations to Senseair (partner in the project) on the calibration of future in-vehicle CO 2 sensors.  To address these objectives, a study was designed to be conducted on the VTI simulator in Linköping (Sweden). The simulator was placed inside a 24m 3 tent specially built for this project in order to manipulate and regulate the indoor CO 2 levels. This was done by means of a system that allowed pure CO 2 mixed with fresh air to be injected into the appropriate concentrations. The indoor CO 2 level was automatically regulated through sensors and a closed-control system. Specifically, thirty-two healthy adult participants (41 years old on average) performed two computerized cognitive tasks and drove the simulator under levels of 700 (normal indoor), 1500 and 3000 ppm in counterbalanced order.

Compact Non-Dispersive Infrared Multi-Gas Sensing Platform for Large Scale Deployment with Sub-ppm Resolution

We report on a novel, cost-effective non-dispersive infrared (NDIR) multi-gas sensor aimed at environmental air pollution monitoring. The rugged design of the K96 sensor core combines highest compactness and low-power consumption with our unique multi-channel cell design, featuring the detection of up to three different gases simultaneously, including CO2, CH4, N2O, and H2O. Our sensing platform allows the selection of the target gases as well as the concentration ranges, thus providing highly customizable gas sensor systems targeting application-specific gas monitoring settings. The sensor core comes with an implemented calibration model, and can address in real time any cross-sensitivity between the NDIR gas-sensing channels. We provide an immensely versatile sensing system while ensuring high sensing stability combined with high precision (2 and N2O, 4). The K96 multi-gas sensor core offers a resilient sensor solution for the increasing demand of compact monitoring systems in the field of environmental monitoring at reasonable costs for medium-to-high volumes

Physical and electrochemical properties of cobalt doped (ti,ru)O2 electrode coatings

The physical and electrochemical properties of ternary oxides Ti 0.7Ru0.3-xCoxO2 (x = 0.093 and x = 0) have been investigated and compared. Samples of three different thicknesses were prepared by spin-coating onto polished titanium to achieve uniform and well-defined coatings. The resulting electrodes were characterized with a variety of methods, including both physical and electrochemical methods. Doping with cobalt led to a larger number of micrometer-sized cracks in the coating, and coating grains half the size compared to the undoped samples (10 instead of 20 nm across). This is in agreement with a voltammetric charge twice as high, as estimated from cyclic voltammetry. There is no evidence of a Co 3O4 spinel phase, suggesting that the cobalt is mainly incorporated in the overall rutile structure of the (Ti,Ru)O2. The doped electrodes exhibited a higher activity for cathodic hydrogen evolution compared to the undoped electrodes, despite the fact that one third of the active ruthenium was substituted with cobalt. For anodic chlorine evolution, the activity was similar for both electrode types

The exfoliation equipment.

<p>a) The hydrodynamic tube shearing device with dispersion barrel and stirrer, b) the dispersion barrel during stirring (to avoid graphite flotation) and, c) a TEM-image of the processed material.</p

Particle size distribution.

<p>Particle size distribution from SEM image analysis.</p

Initial material.

<p>SEM-image of the initial graphite, before exfoliation (0 passes).</p

TEM-imaging.

<p>TEM-images of particles from the process. a) after 5 passes, a typical particle found in the suspension that fits the frame size 20×20 μm. The scale is 5 μm. b) after 10 passes, a typical particle that fits the frame size 2.5×2.5 μm. The scale is 1000 nm.</p

Thickness measurement.

<p>AFM image of a partly folded flake found in the suspension after 10 passes with corresponding height profile along the indication bar. The measured flake thickness was 9.12 nm and the flake fits frame size 7.5×7.5 μm.</p

Comparison of electrical resistivity and BET surface area for alternative conducting carbons.

<p><i>ρ</i> is the electrical resistivity, SSA is the specific surface area of the material, CB is carbon black and BG is battery graphite.</p