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This paper reviews the use of domestic microwave ovens as plasma reactors for applications ranging from surface cleaning to pyrolysis and chemical synthesis. This review traces the developments from initial reports in the 1980s to today’s converted ovens that are used in proof-of-principle manufacture of carbon nanostructures and batch cleaning of ion implant ceramics. Information sources include the US and Korean patent office, peer-reviewed papers, and web references. It is shown that the microwave oven plasma can induce rapid heterogeneous reaction (solid to gas and liquid to gas/solid) plus the much slower plasma-induced solid state reaction (metal oxide to metal nitride). A particular focus of this review is the passive and active nature of wire aerial electrodes, igniters, and thermal/chemical plasma catalyst in the generation of atmospheric plasma. In addition to the development of the microwave oven plasma, a further aspect evaluated is the development of methodologies for calibrating the plasma reactors with respect to microwave leakage, calorimetry, surface temperature, DUV-UV content, and plasma ion densities. [ABSTRACT FROM AUTHOR]

This paper evaluates the use of an air based atmospheric pressure plasma jet for the activation of carbon fibre epoxy composites. In addition the performance of the jet in the removal of a 5-8 nm thick layer of FreKote 710-NC from the composite surface prior to heat-cured epoxy adhesive bonding was also investigated. The plasma treated composites were examined using thermal infra-red imaging, WCA, profilometry and SEM. A reflectance-IR technique was used to monitor the removal of FreKote as well as changes in the functional chemistry of the plasma treated composite surface. The optimised plasma pre-treatment conditions were identified which help to maximise composite-to-composite adhesive bond strength based on LST. This involved a treatment at a 14 mm nozzle to composite distance and scan rate of 30 mm/s. The air plasma process was bench marked against a manual methanol solvent wipe process, for the removal of FreKote. Both the plasma and the solvent wipe treatments yielded similar composite to composite bond strengths, demonstrating that both were successful in the removal of the FreKote. A comparison was also made between the plasma treated composite and a composite which had been grit blasted using 50 µm aluminium oxide grit. A 7% enhancement in lap-shear strength was achieved with the plasma treatment compared to grit blasting. [ABSTRACT FROM AUTHOR]

The implementation of statistical quality control methods for monitoring and control of powder abrasion/deposition is of increasing importance in a manufacturing environment. For the wider adoption of both current and new powder coating technologies, quality control systems need to be developed, which are easily installed, non-invasive and work in real time. This study evaluates the use of a dual electro-acoustic and electrostatic surface-charge measurement technique as means of realising real-time process control. Simultaneous changes in the signals were obtained under both powder flow-on and -off conditions and also for edge detection of the substrate. It was discovered that the most important variables which governed changes in the acoustic response signal were due to variations in the deposition pressure and stand-off distance, whilst those for the electrostatic response signal came from changes in particle size and deposition stand-off distance. A phenomenological predictive equation was developed based on a two-level full factorial design with five variables for both response factors. The coefficients of determination, r 2 , for the models were 93% and 98%, respectively, with respective χ 2 probability values of 99% and 99.5%. This enabled the use of specific limits for any variation of variables amongst those tested to be set up, resulting in the apparatus necessary for the development of a sensitive continuous control system. Examining variations in surface roughness with electrostatic signal was observed to show a linear relationship, decreasing at a rate of 0.19 μm per 0.01 eV, as the effective particle size of Al 2 O 3 was increased. [ABSTRACT FROM AUTHOR]

Abstract: The hybrid copper oxide–copper sulfate water-splitting thermochemical cycle involves two principal steps: (1) hydrogen production from the electrolysis of water, SO2(g) and CuO(s) at room temperature and (2) the thermal decomposition of the CuSO4 product to form oxygen and SO2, which is recycled to the first step. A four-reaction version of the cycle (known in the literature as Cycle H-5) was used as the basis of the present work. For several of the four reactions, a rotating batch reactor sequence is proposed in order to overcome equilibrium limitations. Pinch technology was used to optimize heat integration. Sensitivity analyses revealed it to be economically more attractive to use a 10°C approach to minimize heat loss (rather than 20°C). Using standard Aspen Plus features and the Peng–Robinson equation of state for separations involving oxygen and sulfur oxides, a proposed flowsheet for the cycle was generated to yield “Level 3” results. A cost analysis of the designed plant (producing 100 million kmol/yr hydrogen) indicates a total major equipment cost of approximately $45 million. This translates to a turnkey plant price (excluding the cost of the high-temperature heat source or electrolyzer internals) of approximately $360 million. Based on a $2.50/kg selling price for hydrogen, gross annual revenue could be on the order of $500 million, resulting in a reasonable payback period when all capital and operating costs are considered. Previous efficiency estimates using Level 1 and Level 2 methods gave the process efficiency in the neighborhood of 47–48%. The Level 3 efficiency computation was 24–25% depending on the approach temperature used for recuperation. If the low quality heat rejected by the process can be recovered and used elsewhere, the Level 3 analysis could be as high as 51–53%. [Copyright &y& Elsevier]

Abstract: A systematic procedure for identifying the number of parameters of a model that can be estimated uniquely by nonlinear regression is presented. The objective function to be minimized is in the form of weighted sum of squares of residuals. The assumptions inherent in the choice of weights and the validity of the parameters estimated are verified by statistical tests. The procedure is illustrated by considering the estimation of parameters for Monod kinetics. Simulated data containing known measurement noise are used initially to illustrate the procedure. Finally, parameters are estimated from different sets of experimental data, and the validity and the uniqueness of the parameters are presented. [Copyright &y& Elsevier]

Atmospheric pressure plasma systems are routinely used to treat the surfaces of thermally sensitive materials. There are wide ranges of commercial plasma jet systems available, and for the end user, it can be difficult to directly compare the power outputs of these sources. This paper evaluates the use of a thermal imaging technique in order to provide a semiquantitative evaluation of energy output from plasma jets. The evaluation involved a comparison of the thermal energy transfer obtained from three commercially available atmospheric pressure plasma jet systems: 1) PlasmaTreat’s Openair; 2) Dow Corning’s PlasmaStream; and 3) SurFx’s Atomflo. [ABSTRACT FROM PUBLISHER]