No abstract

No abstract

Micro-tubular solid oxide fuel cells (SOFCs) have been developed in recent years mainly due to their high specific surface area and fast thermal cycling. Previously, the fabrication of micro-tubular SOFC was achieved through multiple-step processes. [1][2][3] A support layer, for example anode-support, is first prepared and pre-sintered to provide mechanical strength to the fuel cell. The electrolyte layer is then deposited and sintered prior to the final coating of cathode layer. Each step involves at least one high temperature heat treatment, making the cell fabrication time-consuming and costly, with unstable control over cell quality. For a more economical fabrication of micro-tubular SOFC with reliability and flexibility in quality control, an advanced dry-jet wet extrusion technique, i.e. a phase-inversion-based coextrusion process, is developed. Using this technique, a dual-layer electrolyte/electrode (either anode or cathode) hollow fibre (HF) can be formed in a single step. Generally, the electrolyte and electrode materials are separately mixed with solvent and polymer binder to form the outer and inner layer spinning suspensions, respectively, before simultaneously co-extruded through a triple-orifice spinneret, passing through an air gap and finally into a non-solvent external coagulation bath. In the mean time, a stream of non-solvent internal coagulant is supplied through the central bore of the spinneret. Thickness of the two layers are largely determined by the design of the spinneret and can be adjusted by the corresponding extrusion rate, while the macrostructure or morphology of the prepared HF precursor can be controlled 1 Submitted to by adjusting co-extrusion parameters such as suspension viscosity, air gap, flow rate of internal coagulant, etc. The obtained dual-layer HF precursor is finally co-sintered once at high temperature as a procedure to remove polymer binder and form bounding between the ceramic materials. In our previous work, [4][5][6] a dual-layer HF support for micro-tubular SOFC, which consists of an electrolyte outer layer of approximately 80 µm supported by an asymmetric anode inner layer with 35 % finger-like voids length, was successfully fabricated using the co-extrusion/co-sintering process. A single cell that obtained after deposition of a multi-layer cathode onto the dual-layer HF produced the maximum power density of 0.59 W cm -2 at 570 o C.[6] Improvement on the structure of the dual-layer HFs was further performed by reducing the electrolyte layer thickness to as thin as 10 µm and the maximum power density of the corresponding cell markedly increased to about 1.11 W cm -2 at 600 o C. [7] Although this result has proved the potential of the dual-layer HF as a promising support for micro-tubular SOFC, the value of powder density was still slightly lower than the ramextruded anode-supported cell with similar electrolyte thickness and highly porous anode (about 1.29 W cm -2 at 600 o C).[8] One of the possible major reasons for the lower power output is the less effectiv...

No abstract

No abstract

No abstract

This article reviews the various techniques of immobilizing a photocatalyst into and onto the polymer membrane for pollutant removal and as a problem solver in handling suspended photocatalyst issues from the previous literature.

No abstract