title: Fabrication and characterization of high-temperature microreactors with thin film heater and sensor patterns in silicon nitride tubes.
abstract: In this paper the fabrication and electrical characterization of a silicon microreactor for high-temperature catalytic gas phase reactions, like Rh-catalyzed catalytic partial oxidation of methane into synthesis gas, is presented. The microreactor, realized with micromachining technologies, contains silicon nitride tubes that are suspended in a flow channel. These tubes contain metal thin films that heat the gas mixture in the channel and sense its temperature. The metal patterns are defined by using the channel geometry as a shadow mask. Furthermore, a new method to obtain Pt thin films with good adhesive properties, also at elevated temperatures, without adhesion metal is implemented in the fabrication process. Based on different experiments, it is concluded that the electrical behaviour at high temperatures of Pt thin films without adhesion layer is better than that of Pt/Ta films. Furthermore, it is found that the temperature coefficient of resistance (TCR) and the resistivity of the thin films are stable for up to tens of hours when the temperature-range during operation of the microreactor is below the so-called "burn-in" temperature. Experiments showed that the presented suspended-tube microreactors with heaters and temperature sensors of Pt thin films can be operated safely and in a stable way at temperatures up to 700 degrees C for over 20 h. This type of microreactor solves the electrical breakdown problem that was previously reported by us in flat-membrane microreactors that were operated at temperatures above 600 degrees C.
authors.affiliation: Transducers, Science Technology Group, MESA+ Research Institute, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands. r.m.tiggelaar@utwente.nl
authors.forename: R M
authors.initials: RM
authors.lastname: Tiggelaar
authors.forename: J W
authors.initials: JW
authors.lastname: Berenschot
authors.forename: J H
authors.initials: JH
authors.lastname: de Boer
authors.forename: R G P
authors.initials: RG
authors.lastname: Sanders
authors.forename: J G E
authors.initials: JG
authors.lastname: Gardeniers
authors.forename: R E
authors.initials: RE
authors.lastname: Oosterbroek
authors.forename: A
authors.initials: A
authors.lastname: van den Berg
authors.forename: M C
authors.initials: MC
authors.lastname: Elwenspoek
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D002384:Catalysis; D004581:Electronics; D004867:Equipment Design; D005740:Gases / Q000737:chemistry; D006358:Hot Temperature; D008832:Microchemistry / Q000295:instrumentation* / Q000379:methods; D010984:Platinum / Q000737:chemistry; D012680:Sensitivity and Specificity; D017655:Silicon Compounds / Q000737:chemistry*; D013499:Surface Properties; D013635:Tantalum / Q000737:chemistry; D013696:Temperature
chemical_list: D005740:Gases; D017655:Silicon Compounds; D010984:Platinum; D013635:Tantalum; C032734:silicon nitride