Saturday, February 13, 2016

The TEMAZr - O2 ALD Process for high surface area ZrO2 applications in a von Ardenne ALD reactor

A brilliant publication from Forschungszentrum Jülich and RWTH Aachen. Since I happen to have a PhD in using molecular oxygen for ALD of metal oxides - one of the few - I must say that this is the best paper the last 10 years or so. Alright, I know, only in the combination with metal iodides (one day they will come and dominate ...)

Jokes aside, if you want to get in there in porous material with large surface area and not have endless purge times to get the water out of there O2 is a very good choice - why didn´t I write that in my thesis? This must be the way also for particle ALD coatings.

Sternwarte Manfred v. Ardenne in Loschwitz, Plattleite (This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication)

As a side information, they used a Von Ardenne LS400C ALD-MOCVD reactor and you can find more information here about that one. Since this post anyway got sort of personal I can admit that Von Ardenne is my next door neighbor and that they have one of the coolest locations (photo above) you can think of. If you come to Dresden let me know and I will show you.

Von Ardenne LS400C ALD-MOCVD reactor

Atomic-layer-controlled deposition of TEMAZ/O2–ZrO2 oxidation resistance inner surface coatings for solid oxide fuel cells

Thomas Keuter, Georg Mauer, Frank Vondahlen, Riza Iskandar, Norbert H. Menzler, Robert Vaßen

Surface and Coatings Technology, Volume 288, 25 February 2016, Pages 211–220

Solid oxide fuel cells (SOFCs) directly convert the chemical energy of fuels into electrical energy with high efficiency. Under certain conditions oxygen can diffuse to the Ni/8 mol% Y2O3-doped ZrO2 substrate of anode-supported SOFCs, then the nickel re-oxidizes, leading to cracks in the electrolyte and cell failure thus limiting the durability of SOFCs. In order to improve the stability of SOFCs with respect to oxidation, the inner surface of the porous substrate is coated with a ZrO2 oxidation resistance layer using atomic layer deposition (ALD) with the precursors tetrakis(ethylmethylamino)zirconium (TEMAZ) and molecular oxygen. This TEMAZ/O2–ZrO2 ALD process has not yet been reported in the literature and hence, the development of the process is described in this paper. The inner surface of the porous substrate is coated with ZrO2 and the film thickness is compared with theoretical predictions, verifying the ALD model. Furthermore, the coating depth can be estimated using a simple analytical equation. The ALD ZrO2 film protects the nickel in the substrate against oxidation for at least 17 re-oxidation/re-reduction cycles. The ZrO2 inner surface coating is a highly promising candidate for enhancing the resistance of SOFCs to re-oxidation because of the excellent oxidation resistance and good cycling stability of the film.