A review on MCFC matrix: State-of-the-art, degradation mechanisms and technological improvements.

Molten Carbonate Fuel Cells (MCFCs) are a promising technology as sustainable power generators as well as CO2 selective concentrators for carbon capture applications. Looking at the current cell configuration, several issues, which hinders a stable long-term operation of the system, are still unsettled. According to reference studies, the ceramic matrix is one of the most critical components in view of its high impact on the cell performance since it can influence both the stability and the reaction path. Indeed, it provides the structural support and holds the molten carbonates used as electrolyte, requiring a good mechanical strength despite of a porous structure, a high specific surface area and a sufficient electrolyte wettability to avoid the electrode flooding. The matrix structure, its key-features and degradation issues are discussed starting from the state-of-the-art lithium aluminate LiAlO2 usually strengthened with Al based reinforcement agents. Since the achievable performance is strictly dependent on manufacturing, a devoted section focuses on available techniques with a view also of their environmental impacts. Considering a still insufficient performance due to the material structural and chemical instability favoured by stressful working conditions, the electric conductive ceramics are presented as alternative matrixes permitting to increase the cell performance combining oxygen and carbonate ion paths.

Numerical Simulation of the Heat Transfer in the Cryoprobe of an Innovative Apparatus for Cryosurgery.

Cryosurgery is a rapidly developing discipline, alternative to conventional surgical techniques, used to destroy cancer cells by the action of low temperatures. Currently, the refrigeration is obtained via the adiabatic expansion of gases in probes used for surgeries, with the need of inherently dangerous pressurized vessels. The proposed innovative prototypal apparatus aims to reach the cryosurgical temperatures exploiting a closed-loop refrigeration system, avoiding the hazardous presence of pressurized vessels in the operating room. This study preliminarily examines the technical feasibility of the cryoablation with this machine focusing the attention on the cryoprobe design. Cryoprobe geometry and materials are assessed and the related heat transfer taking place during the cryoablation process is simulated with the aid of the computational fluid dynamics software ANSYS®Fluent. Parametric analyses are carried out varying the length of the collecting tubes and the inlet velocity of the cold carrier fluid in the cryoprobe. The values obtained for physical quantities such as the temperature reached in the treated tissue, the width of the obtained cold front, and the maximum pressure required for the cold carrier fluid are calculated and discussed in order to prove the effectiveness of the experimental apparatus and develop the machine further.