ABSTRACT
High optical performance coatings prepared by a liquid deposition process have been studied with focus on the parameters playing a role on the layer stacking ability. During the development of multilayer optical coatings, defects such as cracks, scattering and a refractive index gradient could appear. In order to understand the origins of these limitations, the investigation was performed on colloidal stacks of single and multi-materials. This study has rendered it possible to define the main process parameters as well as the physical and chemical parameters of the suspensions influencing the stacking capacity. This work is a first step to obtaining evidence of a relationship between the thin film microstructure induced by deposition conditions and the ability to achieve sol-gel thick films with good optical (homogeneous) and mechanical (crack-free) properties.
ABSTRACT
We describe the operation of a microbial fuel cell (MFC) system operating on a synthetic wastewater (acetic acid), under conditions of increasing nitrogen limitation. Two MFCs were operated under feed conditions which spanned a range of TKN/COD values of 1.6-28 mg/g. Stable operation was observed in all cases, even when no ammoniacal nitrogen was added to the cell. Improved electrochemical performance (measured as power density, W/m2) was observed as nitrogen limitation was imposed on the cells. Even with no ammonium addition, continuous function of the cell was maintained, at levels consistent with operation at balanced nutrient supplementation. The work has implicated biological nitrogen fixation as a potential source of nitrogen within the MFC. Whilst this hypothesis has yet to be confirmed, the work highlights the opportunity for continuous operation of microbial fuel cells utilising wastewaters with extremely low nitrogen levels, present in pulp and paper, pharmaceutical and petrochemical industries. Further, the described increases in some of the electrochemical indices (e.g. power density) under application of nitrogen limitation may provide a new approach to increasing fuel cell performance. Finally, the lack of any need to add supplemental nitrogen to a MFC-based wastewater treatment technology holds potential for significant financial and environmental savings.
