Fabrication of a micro catalytic combustor and performance evaluation

Abstract

Nowadays, due to development of MEMS (Micro Electro Mechanical Systems), it is possible to realize micro system such as MAV, micro robot, etc. Even though these micro systems become smaller and smaller in the aspect of size, these systems have to accomplish their missions or works precisely and punctiliously rather than conventional mechanical systems. However, efficiency of these systems is limited by its power system. Using recently the most efficient batteries, it is difficult to supply sufficient energy to these micro systems. Thus, recently, the researches to use hydro-carbon fuel which has high power density are investigated as an alternative candidate of existing batteries. In this thesis, the micro catalytic combustor, which is made of silicon wafer and Pyrex glass using MEMS technology, is developed. This micro combustor uses a catalytic combustion rather than gas phase combustion because gas phase combustion has many defects to be employed in micro combustion such as high heat loss and quenching of flame. Thus, micro combustor using catalytic reaction is developed to make power sources or heat sources for micro reformer and micro reactor. First of all, porous silicon is fabricated using p-type (100) silicon wafer by electro-chemical etching for substrate of catalyst. Mixed solution of dimethylformamide (DMF), hydrofluoric acid (HF) and water is used for electro-chemical etching. Through the conditions of 6.2mA/㎠ of current density, 92% of DMF + 4% of HF + 4% of water in volume ratio and 3 hours etching, porous silicon which is 1~2㎛ of average diameter and 30㎛ of average depth is fabricated. Secondly, to apply this fabricated porous silicon to catalyst substrate, platinum is coated on the internal surface of porous silicon by employing modified incipient wetness method. By this method, 1.12mg/$cm^2$ of platinum is loaded on the porous silicon. To validate the attachment of platinum catalyst to substrate of porous silicon, SEM (Scanning Electron ...