# US 5,707,148 A · Catalytic calorimetric gas sensor

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- Number: US 5,707,148 A
- Document ID: US5707148A
- Status: Granted
- Kind: A
- Application number: 08/311,299
- Filed: 1994-09-23
- Granted: 1998-01-13
- Earliest claimed: 1994-09-23
- Assignees: Ford Global Technologies, LLC
- Inventors: Jacobus Hendrik Visser; Chaitanya Kumar Narula; Margherita Zanini-Fisher
- Web page: https://patentgrep.com/patent/US5707148A

## CPC

- G01N 27/16: caused by burning or catalytic oxidation of surrounding material to be tested, e.g. of gas
- C04B 41/009: {characterised by the material treated}
- C04B 41/52: Multiple coating or impregnating {multiple coating or impregnating with the same composition or with compositions only differing in the concentration of the constituents, is classified as single coating or impregnation}
- C04B 41/89: for obtaining at least two superposed coatings having different compositions
- G01N 25/30: using electric temperature-responsive elements
- C04B 2111/0081: {as catalysts or catalyst carriers}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- C04B: LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE {(roofing granules E04D7/005)}; CERAMICS (devitrified glass-ceramics C03C10/00); REFRACTORIES; TREATMENT OF NATURAL STONE

## Abstract

Disclosed is a method to make and an apparatus for monitoring the exhaust gas conversion efficiency of a catalytic converter. The catalytic calorimetric sensor disclosed includes a sol-gel processed washcoat and sol-processed catalytically active metal particles. Sol-gel processing creates a washcoat with high surface area and controlled porosity which increases the sensitivity, durability, and reproducibility of the resultant sensor.

## Claims

### Claim 1

A catalytic calorimetric sensor, comprising:
a substrate;
a temperature measuring layer disposed on said substrate; and
a sol-gel processed catalytic layer disposed on said temperature measuring layer to provide a thin catalytic layer having increased sensitivity.

### Claim 2 (depends on 1)

The sensor of claim 1, wherein said substrate comprises a low thermal conductivity material selected from the group consisting of aluminum oxide, silicon oxide, silicon nitride, polysilicon and combinations thereof.

### Claim 3 (depends on 1)

The sensor of claim 1, wherein said substrate is silicon micromachined.

### Claim 4 (depends on 1)

The sensor of claim 1, wherein said substrate has a thickness in the range of 500 to 1000 nm.

### Claim 5 (depends on 1)

The sensor of claim 1, wherein said temperature measuring layer comprises a temperature measuring device selected from the group consisting of a thermocouple, a temperature dependent metal resistor, a temperature dependent semiconductor resistor, a p-n junction semiconductor and a thermopile.

### Claim 6 (depends on 1)

The sensor of claim 1, wherein said sol-gel processed catalytic layer comprises:
a sol-gel processed washcoat, wherein said washcoat is selected from the group consisting of alumina, silica and mixtures thereof; and
a plurality of sol-gel processed catalytically active metal particles deposited on said sol-gel processed washcoat.

### Claim 7 (depends on 6)

The sensor of claim 6, wherein said catalytically active metal particles are noble metals selected from the group consisting of platinum, palladium, silver, gold, ruthenium, rhodium, osmium, iridium, and mixtures thereof.

### Claim 8 (depends on 1)

The sensor of claim 1, wherein said sol-gel processed catalytic layer comprises:
a sol-gel processed washcoat, wherein said washcoat is selected from the group consisting of alumina, silica and mixtures thereof; and
a plurality of catalytically active metal particles deposited on said sol-gel processed washcoat.

### Claim 9 (depends on 8)

The sensor of claim 8, wherein said catalytically active metal particles are noble metals selected from the group consisting of platinum, palladium, silver, gold, ruthenium, rhodium, osmium, iridium, and mixtures thereof.

### Claim 10 (depends on 1)

The sensor of claim 1, wherein said sol-gel processed catalytic layer comprises:
a sol-gel processed washcoat; and
a plurality of catalytically active metal particles deposited on said sol-gel processed washcoat such that the catalytic calorimetric gas sensor has an increased number of active sites and an enhanced sensitivity.

### Claim 11 (depends on 10)

The sensor of claim 10 wherein said catalytically active metal particles are sol-gel processed.