Defect chemistry, transport properties and thermodynamic stability of acceptor doped and undeoped layered La 2 NiO 4
type: CreativeWork
description: The market for oxygen has grown significantly because many industrial processes require oxygen. At present oxygen is produced on industrial scale mainly by cryogenic distillation of air. This is a very energy intensive process and economic operation is possible only on a large scale. An alternative method, relatively new development is dense oxide ceramic membranes which can exclusively separate oxygen from air at high temperature that has the advantage of direct supply of oxygen in membrane reactors for the (partial) oxidation of hydrocarbons. Two types of dense membranes can be distinguished, the solid oxide electrolytes and the mixed ionic electronic conductors. The latter type of membrane is the subject of research of this thesis. During of oxygen transport two basic processes occur in a single-phase ceramic membrane at steady state are discussed. In the bulk, coupled diffusion of oxygen ions and electrons takes place, while exchange reactions of oxygen from the lattice with molecular oxygen in the gas phase occurs at both interfaces of the membrane.Ceramic oxides materials with perovskite related structures, e.g. the K2NiF4 structure have been reported to exhibit substantial oxygen permeation flux, which makes these attractive candidates for High-temperature oxygen separation. In contrast to perovskite-type membranes, the oxygen flux in these materials supported by oxygen interstitial ions. In this work La2NiO4 based membranes was evaluated with respect to their transport properties, stability in different atmospheres and their aging. The structure of La2NiO4 may be described as an intergrowth of rocksalt La2O3 layers and perovskite LaNiO3 layers. The rocksalt layers accommodate interstitial oxygen, whereas the perovskite layers host oxygen vacancies, according to theoretical calculations on point defect formation and migration. The phasal composition of the ceramic powder prepared by a modified Pechini process, was analysed by X-ray diffraction. The prepared d…
abstract: The market for oxygen has grown significantly because many industrial processes require oxygen. At present oxygen is produced on industrial scale mainly by cryogenic distillation of air. This is a very energy intensive process and economic operation is possible only on a large scale. An alternative method, relatively new development is dense oxide ceramic membranes which can exclusively separate oxygen from air at high temperature that has the advantage of direct supply of oxygen in membrane reactors for the (partial) oxidation of hydrocarbons. Two types of dense membranes can be distinguished, the solid oxide electrolytes and the mixed ionic electronic conductors. The latter type of membrane is the subject of research of this thesis. During of oxygen transport two basic processes occur in a single-phase ceramic membrane at steady state are discussed. In the bulk, coupled diffusion of oxygen ions and electrons takes place, while exchange reactions of oxygen from the lattice with molecular oxygen in the gas phase occurs at both interfaces of the membrane.Ceramic oxides materials with perovskite related structures, e.g. the K2NiF4 structure have been reported to exhibit substantial oxygen permeation flux, which makes these attractive candidates for High-temperature oxygen separation. In contrast to perovskite-type membranes, the oxygen flux in these materials supported by oxygen interstitial ions. In this work La2NiO4 based membranes was evaluated with respect to their transport properties, stability in different atmospheres and their aging. The structure of La2NiO4 may be described as an intergrowth of rocksalt La2O3 layers and perovskite LaNiO3 layers. The rocksalt layers accommodate interstitial oxygen, whereas the perovskite layers host oxygen vacancies, according to theoretical calculations on point defect formation and migration. The phasal composition of the ceramic powder prepared by a modified Pechini process, was analysed by X-ray diffraction. The prepared d…
author: Dragan, Mirela-Anca
language: eng
keywords: info:eu-repo/classification/ddc/660, Technische Chemie, Defect chemistry, La2NiO4, ceramic membranes, oxygen permeation, oxygen transport, thermodynamic stability
date published: 2006
date modified: 2026-07-30T19:43:02Z
provider: RWTH Aachen University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Publikationsserver der RWTH Aachen University