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US 2003/0201172 A1Published application
NOx-decomposing electrode and NOx concentration-measuring apparatus
AssigneeNGK Insulators, Ltd.
InventorsKunihiko Nakagaki, Hideyuki Suzuki, Sang Jae Lee, Osamu Nakasone
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Abstract
A detecting electrode comprises a first cermet electrode layer formed directly on a solid electrolyte layer and a second cermet electrode layer formed on the first cermet electrode layer. The ratio between Pt and Rh in the first cermet electrode layer ranges from 100:0 to 25:75 by weight. The ratio between Pt and Rh in the second cermet electrode layer ranges from 25:75 to 0:100 by weight.
Claims10
A NOx-decomposing electrode for decomposing or reducing NOx, in which oxygen is produced by decomposing NOx by said electrode,
- said NOx-decomposing electrode having a multilayered structure comprising a plurality of cermet electrode layers each of which includes an alloy of Pt—Rh and a ceramic component, and
- said respective cermet electrode layers having different ratios between Pt and Rh in said alloys of Pt—Rh.
A NOx concentration-measuring apparatus comprising:
- a first oxygen pump means for introducing a measurement gas from outside into a first hollow space so that a partial pressure of oxygen in said measurement gas is controlled to be a predetermined value;
- and
- a second oxygen pump means for pumping out oxygen from said measurement gas having said partial pressure of oxygen controlled by said first oxygen pump means and controlling said partial pressure of oxygen to be a predetermined value at which a NOx component is reduced or decomposed to pump out oxygen produced when said NOx component existing in an atmosphere in a second hollow space is reduced or decomposed,
- wherein a concentration of NOx in said measurement gas is determined by detecting a pumping current flowing in accordance with a pumping action of said second oxygen pump means of said NOx concentration-measuring apparatus,
- a NOx-decomposing electrode of said second oxygen pump means for reducing or decomposing said NOx component has a multilayered structure comprising a plurality of cermet electrode layers each of which includes an alloy of Pt—Rh and a ceramic component,
- said NOx-decomposing electrode is formed on a ceramic substrate, and
- said respective cermet electrode layers have different ratios between Pt and Rh.
4 more elements
A NOx concentration-measuring apparatus comprising:
- a first oxygen pump means for introducing a measurement gas from outside into a first hollow space so that a partial pressure of oxygen in said measurement gas is controlled to be a predetermined value;
- and
- a second oxygen pump means for pumping out oxygen from said measurement gas having said partial pressure of oxygen controlled by said first oxygen pump means and controlling said partial pressure of oxygen to be a predetermined value at which a NOx component is reduced or decomposed to pump out oxygen produced when said NOx component in an atmosphere in a second hollow space is reduced or decomposed,
- wherein a concentration of NOx existing in said measurement gas is determined by detecting a pumping current flowing in accordance with a pumping action of said second oxygen pump means of said NOx concentration-measuring apparatus,
- a NOx-decomposing electrode of said second oxygen pump means for reducing or decomposing said NOx component has a multilayered structure comprising a plurality of cermet electrode layers each of which includes an alloy of Pt—Rh and a ceramic component,
- said NOx-decomposing electrode is formed on a ceramic substrate,
- said respective cermet electrode layers have different ratios between Pt and Rh in said alloy of Pt—Rh, and
- among proportions of Pt in said respective cermet electrode layers, a proportion of Pt in said cermet electrode layer as a lowermost layer formed directly on said ceramic substrate is maximum and a proportion of Pt in said cermet electrode layer as an uppermost layer is minimum.
5 more elements
A NOx concentration-measuring apparatus comprising:
- a first oxygen pump means for introducing a measurement gas from outside into a first hollow space so that a partial pressure of oxygen in said measurement gas is controlled to be a predetermined value;
- and
- a second oxygen pump means for pumping out oxygen from said measurement gas having said partial pressure of oxygen controlled by said first oxygen pump means and controlling said partial pressure of oxygen to be a predetermined value at which a NOx component is reduced or decomposed to pump out oxygen produced when said NOx component existing in an atmosphere in a second hollow space is reduced or decomposed,
- wherein a concentration of NOx existing in said measurement gas is determined by detecting a pumping current flowing in accordance with a pumping action of said second oxygen pump means of said NOx concentration-measuring apparatus,
- a NOx-decomposing electrode of said second oxygen pump means for reducing or decomposing said NOx component has a multilayered structure comprising a plurality of cermet electrode layers each of which includes an alloy of Pt—Rh and a ceramic component formed directly on a ceramic substrate,
- said respective cermet electrode layers are formed along said ceramic substrate,
- said respective cermet electrode layers have different ratios between Pt and Rh in said alloy of Pt—Rh, and
- among proportions of Pt in said respective cermet electrode layers, a proportion of Pt is minimum in said cermet electrode layer formed at a central portion of said NOx-decomposing electrode and a proportion of Pt is maximum in said cermet electrode layer formed at a circumferential edge of said NOx-decomposing electrode.
5 more elements
Dependencies are inferred from the claim text.