The oxidative decoloration of Rhodamine B (RhB) was performed in a photochemical reactor which enables microwave (MW) and UV radiation to be applied simultaneously. We used an immersed microwave source, with no need for an oven. Controlling the temperature, MW power, and UV emission of the reactor all led to a greater overall control of the process. Due to the action of highly reactive hydroxyl radicals, the decoloration of RhB was followed online using a spectrograph. Complete decoloration occurred in four minutes, and 92% of mineralisation was obtained in 70 minutes. The experiments were performed at various temperatures (21°C, 30°C, 37°C, and 46°C), with and without hydrogen peroxide. The apparent reaction rate was used to calculate the apparent activation energy of the decoloration process:Ea=38±2 kJ/mol and40±2 kJ/mol with (400 mg/L) or without hydrogen peroxide, respectively. The lack of deviation from the linear behavior of the Arrhenius plot confirms that the application of MW does not affect theEaof the process. The apparent activation energy value found was compared with the few data available in the literature, which were obtained in the absence of MW radiation and are inconsistent.
The authors present a theoretical investigation of the thermal conductivity of SiC p based metalmatrix composites at various temperatures from a viewpoint of heat conduction mechanism across the SiC p /matrix interface. The interfacial thermal conductance associated with the electron-phonon (e-ph) coupling and the phonon-phonon (ph-ph) coupling is characterised using a simple calculational procedure. The predictions for the composite thermal conductivity obtained by a Hasselman and Johnson model incorporated into a Majumdar's relation reveal good correspondence with the experimental results and explore that the temperature dependent thermal conductivity is essentially governed by the competitive interaction of e-ph coupling and ph-ph coupling. This work also accounts for the temperature dependent thermal conductivity of SiC p based composites, which is sensitive to the particle size and volume fraction when these two materials properties lie within certain range.
An analytical model for the thermal conductivity of Cu/diamond composites with connected particles is presented by replacement of a cluster of connected particles with an equivalent polycrystal subsequently using a multiple effective medium approach. By applying this model to the measured thermal conductivity of Cu/diamond composites prepared by high pressure high temperature sintering technique reported in the literature, we show that it quite well describes the observed thermal conductivity enhancement induced by the connected particles. We estimate the value of connected particle loading in real composites and show that large particles are easier to form the bonding contact than small particles. The present work also demonstrates that the sensitivity of thermal conductivity contribution from the connected particles strongly depends on the particle size, and their pronounced thermal conductivity enhancement should lie within the certain particle size range.
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