On the manufacture of silver-BaCe0.5Zr0.3Y0.16Zn0.04O3−δ composites for hydrogen separation membranes

Abstract

Mixed protonic electronic conduction a b s t r a c t Silver-BaCe 0.5 Zr 0.3 Y 0.16 Zn 0.04 O 3Àd (Ag/BCZYZ) composites were investigated due to their potential application as hydrogen separation membranes, with emphasis on their fabrication and characterization. A precursor powder of BCZYZ was prepared via a wet chemical route and characterized by XRD, SEM and dilatometry. The precursor powder was coated with silver using Tollens reaction and then sintered under a variety of conditions. It was possible to obtain dense samples with a low level of non-percolating silver (2 vol%).Silver was present even if sintered at 1300 C as it remained trapped in the ceramic matrix.The overall conductivity of a dense sample with 2 vol% of silver increased when compared to pure BCZYZ, and in particular the grain boundary resistance decreased considerably. A measurement of the open circuit voltage in fuel cell mode indicates the presence of mixed electronic-protonic conductivity in the composite.

Influence of manganite powder grain size and Ag-particle coating on the magnetocaloric effect and the active magnetic regenerator performance

“…5a shows the thermal conductivity of the sintered pellets made up of small grain, large grain and silver coated large grain particle of LCSMO. The trends are similar to our previous reports showing that in pellet form, large grain samples have higher j [9] because of fewer grain boundaries, and grain boundary resistance (electrical and thermal) is greatly diminished by the introduction of silver [9,15,29].…”

“…A portion of large particle LCSMO sample and the LCMO were coated with Ag. The technique used here is based on the Tollens' reaction which was recently used to manufacture metal ceramic composites [15,29]. The manganite particles were suspended in a solution of AgNO 3 and concentrated KOH that was subsequently cleared with a few drops of NH 4 OH.…”

Oxygen Reduction, Transport and Separation in Low Silver Content Scandia-Stabilized Zirconia Composites

“…There were three initial nominal compositions: a nominally pure ScSZ, a composite with 10 wt% Ag, and one with 20 wt% Ag. The ScSZ particles were suspended in water and coated with silver using Tollens' reagent 16,20 as follows. A few drops of concentrated NH 4 OH (27-30%) were added to 30 ml of AgNO 3 (0.1 M) resulting in a precipitate which was then cleared by adding more drops of ammonia (approximately 40 drops in total).…”

“…Although currently scandia is a relatively expensive material, ScSZ's growing use as electrolyte in solid oxide fuel cells may lower its price. 14 The use of Tollens' reagent to fabricate metal ceramic composites for a variety of purposes has been reported recently in applications such as oxygen separation, 5 methane reforming, 15 hydrogen separation, 16 magnetic refrigeration 17 and anode fabrication. 18,19 In this work, the composite membrane fabrication is presented in detail that allows reproducibility and it is followed by characterization by SEM, XRD and conductivity tests.…”

Mass Transport in (La0.8Sr0.2)0.95CrxFe1–xO3−δ–Scandia-Stabilized Zirconia Dual-Phase Composite as a Dense Layer in Oxygen Transport Membranes

“…Ceramic membranes are currently used in a range of diverse applications, allowing significant improvement in industrial processes: producing high-purity oxygen, hydrogen production by a hydrocarbon conversion process, partial oxidation of methane to syngas, oxidative coupling of methane to C 2 products, etc. − Among the types of membrane reactors proposed, oxygen transport membranes (OTMs) for the generation of syngas and heat by directly supplying oxygen and fuel gas are of increasing interest, with significantly lower operational expenditure and dramatic improvements in energy efficiency. − For an OTM, the mixed ionic–electronic conducting (MIEC) dense ceramic separation layer is one of the fundamental components of the device . In a typical membrane reactor, one side of the dense layer is under high oxygen partial pressure whereas the other side is exposed to low oxygen partial pressure.…”