Inkjet Printed Thin Film Electrodes for Lithium-Ion Batteries

With the miniaturization of wireless electronics, the demand for ever-smaller energy storage devices has increased. Thin film batteries can meet this need by providing higher energy densities at smaller scales than conventional lithium-ion batteries. However, the fabrication of thin films batteries by vapor deposition methods typically involves expensive equipment and high temperatures, which limits their commercial application. This thesis reports the development of an inexpensive inkjet printing method of fabricating thin film electrodes for thin film lithium-ion batteries. Inks containing various electrode materials were first developed and optimized in terms of physical properties to ensure ideal jetting conditions. Then, thin film anodes comprised of silicon and titanium dioxide were fabricated with a household inkjet printer and their physical and electrochemical properties were characterized. Critical parameters involved in inkjet printing (e.g. the polymer binder used and the electrode thickness) were thoroughly studied, based on which high-capacity and stable anodes were finally achieved. Overall, this work demonstrates the efficacy and future potential of using inkjet printing for fabricating thin film battery electrodes

Cellular Flame Instabilities

The onset of Darrieus Landau and thermo-diffusive instabilities in an exploding spherical laminar flame is marked by the value of the Peclet number, Pecl, which is dependent upon the Markstein number. Values of Pecl for a number of different mixtures have been measured at 0.5 and 1.0 MPa in a spherical explosion bomb. These values are presented as a function of the flame speed Markstein number, Mab, and it is found that neither different pressures nor the different mixtures have a great effect on this correlation. Values derived from much larger scale atmospheric explosions of methane/air and propane/air also closely follow the same correlation. This suggests data from high pressure laboratory explosions might be used to predict the effects of large scale atmospheric explosions. Findings from other workers follow the same trend, although different detailed results can arise from both different definitions of Markstein number, and different measurement techniques. Because of the importance of a necessary minimal stretch rate to stabilise a flame, a more logical and fundamental criterion for the onset of this type of instability is one based on the flame stretch rate, such as a critical Karlovitz stretch factor, Kcl. As a result, the correlations are also expressed in terms of Kcl, instead of Pecl. As Masr becomes highly negative, the regime of stability is severely reduced

Burning Velocity and Markstein Length Blending Laws for Methane/Air and Hydrogen/Air Blends

Because of the contrasting chemical kinetics of methane and hydrogen combustion, the development of blending laws for laminar burning velocity, ul, and Markstein length for constituent mixtures of CH4/air and H2/air presents a formidable challenge. Guidance is sought through a study of analytical expressions for laminar burning velocity. For the prediction of burning velocities of blends, six blending laws were scrutinised. The predictions were compared with the measured burning velocities made by Hu et al. under atmospheric conditions [1]. These covered equivalence ratios ranging from 0.6 to 1.3, and the full fuel range for H2 addition to CH4. This enabled assessments to be made of the predictive accuracy of the six laws. The most successful law is one developed in the course of the present study, involving the mass fraction weighting of the product of ul, density, heat of reaction and specific heat, divided by the thermal conductivity of the mixture. There was less success from attempts to obtain a comparably successful blending law for the flame speed Markstein length, Lb, despite scrutiny of several possibilities. Details are given of two possible approaches, one based on the fractional mole concentration of the deficient reactant. A satisfactory empirical law employs mass fraction weighting of the product ulLb

A novel approach to non-segmented flow analysis. Part 2. A prototype high-performance analyser

A high-performance continuous flow analyser is described, based on gas pressure driven carrier and reagents controlled by computer switched solenoid valves. The principal characteristics of the analyser are discussed and examples of its performance are provided in the form of results obtained using a standard procedure for the determination of Cr(VI). The system was also tested in use with real samples using an ammonium ion analysis on potable and effluent water samples, and the results compared with those obtained using a segmented continuous flow method operated at the Laboratory of the Government Chemist

Measurement of turbulence characteristics in a large scale fan-stirred spherical vessel

Particle Image Velocimetry, PIV, is employed to characterise the near-homogeneous, isotropic, turbulence generated inside a large spherical vessel by four rotating fans. Spatial and temporal distributions of mean and root mean square, rms, velocity fluctuations are investigated, as well as integral length scales, L, Taylor microscales, λ, and Kolmogorov length scales, η, in the fan speed range, 1000–6000 rpm. Mean velocities are about 10% of the turbulence velocity, u' and turbulence is close to homogeneous and isotropic in the central volume. This volume decreases with increasing fan speed, and its radius and other characteristics are expressed in terms of the fan speed. At each speed, the mean gas velocity scarcely varies with time. Relationships are presented for the variations of u' and L with fan speed, temperature and pressure. A new relationship between the autocorrelation function and integral length scale is obtained, for when Taylor's hypothesis is invalid

Flame speed and particle image velocimetry measurements of laminar burning velocities and Markstein numbers of some hydrocarbons

Particle image velocimetry, PIV, is described for measuring laminar burning velocities during flame propagation in spherical explosions, by the measurement of the flame speed and gas velocity just ahead of the flame. Measurements made in this way are compared with those obtained from the flame speed method, which is based on the flame front propagation speed and the ratio of unburned to burned gas densities. Different values arise between the two methods, and the principal reason is the common assumption in the flame speed method that the burned gas density is at the equilibrium, burned gas, adiabatic temperature. When allowance is made for the effects of flame stretch rate and Lewis number on this density, the differences in burning velocities are significantly decreased. The PIV methodology enables mass rate of burning velocities to be expressed in terms of the burning velocity at zero stretch rate and the Markstein numbers for strain rate and flame curvature. Burning velocities and Markstein numbers are presented for methane, i-octane, ethanol, and n-butanol over a range of equivalence ratios at atmospheric pressure and, in the case of n-butanol, also over a range of pressures. Account is taken of the low stretch rate at which a laminar flame becomes unstable, and, below which, the burn rate increases due to the enhanced flame surface area. The critical stretch rates for the transition are identified. In measuring Markstein numbers, there is a dependency upon the isotherm employed for the measurement of the stretch rate. This aspect is studied by comparing measurements with two different isotherms. It is concluded that the measured PIV flame measurements might under-estimate the Markstein numbers by about 12%

Results of an industrial survey on the use of surface texture parameters

In 1999, CIRP conducted an industrial survey of the use of surface texture parameters [1]. In the seventeen years since, much has changed, with the most important advancement being the introduction of areal surface texture parameters as described in ISO 25178-2 [2]. There has also been the release of commercial software packages for the calculation of surface texture parameters and, therefore, it is expected that industry is starting to embrace areal surface texture characterisation. Industry is also increasingly using more optical instruments, which are often inherently areal in nature. These factors bring to light the need for a new parameter survey, to investigate whether industry really has been adopting areal surface texture parameters. This study used an online survey to obtain information about the current use of surface texture parameters in industry. The survey features both profile and areal surface texture parameters defined in specification standards ISO 4287 [3], ISO 25178-2 [2], ISO 12085 [4] and ISO 13565-2/3 [5, 6]. The survey was open to responses for eight months and obtained a total of 179 responses from a variety of industrial users of surface texture parameters spread across thirty-two countries. Responses from the survey offer information about the usage of individual surface texture parameters, highlighting any parameters that are unpopular and may require attention. The survey also enables participants to share their opinion on the current range of parameters in use, giving an insight into the perception of surface texture parameters in industry. The results from the survey highlight a strong adoption by industry of the areal surface texture parameters defined in ISO 25178-2. In comparison to the 1999 survey, there has also been an overall increase in the use of profile surface texture parameters, and an increase in the variety of parameters used, particularly for the ISO 4287 roughness parameters, suggesting a better understanding of the range of parameters available and their uses. Conversely, this increase in parameter variety could be due to the greater computational power available to users of surface texture parameters, allowing them to use more parameters with little cost. The results of the surface texture parameter survey will serve as an indication of the current state of the industry to those interested in the widespread acceptance and evolution of surface texture parameters. The analysis of the survey will identify common potential improvement areas in surface texture parameter selection and provide a starting point from which to better promote the current selection and better educate the users

A novel approach to non-segmented flow analysis: Part 4. Aluminium in river waters

A rapid and precise method is developed for the determination of aluminium in water. The results demonstrate that the calibration range of the assay can be extended by a simple manipulation of the control program of the flow analyser. An RSD of 1.8% is achieved for injection of standards and the theoretical limit of detection is estimated at 0.33 ppm alum (equivalent to 18 ppb Al3+). The method is applied to monitoring of environmental samples

Bio-economic evaluation of pasture-cropping, a novel system of integrating perennial pastures and crops on crop-livestock farms

Pasture-cropping is a novel approach to increase the area of perennial crops in mixed sheep and cropping systems. It involves planting annual cereals directly into a living perennial pasture. There is interest in subtropical grasses as they are winter dormant and their growth profile is potentially well suited to pasture-cropping. However, a wide range of factors can affect the uptake of such systems. This paper assesses the relative importance of factors that can influence decisions to introduce pasture-cropping. In this paper the research question is: what factors predispose a farm to take up a new technology such as (1) subtropical grass and (2) subtropical grass that is pasture-cropped. The analysis uses the MIDAS model of a central wheatbelt farm in Western Australia. The results suggest the adoption of subtropical grasses is likely to be strongly influenced by soil mix; feed quality; and whether the farm is predominantly grazing or cropping and by the presence of meat versus wool producing animals. The same factors are relevant for subtropical grass that is pasture-cropped but in addition yield penalties due to competition between the host perennial and the companion cereal become important. The results suggest the level of forage production by subtropical grass is less important but this factor is likely to become more important if feed quality can be improved.Environmental Economics and Policy,