Gas sensitive materials for gas detection and method of making
View Patent ↗A gas sensitive material comprising SnO2 nanocrystals doped with In2O3 and an oxide of a platinum group metal, and a method of making the same. The platinum group metal is preferably Pd, but also may include Pt, Ru, Ir, and combinations thereof. The SnO2 nanocrystals have a specific surface of 7 or greater, preferably about 20 m2/g, and a mean particle size of between about 10 nm and about 100 nm, preferably about 40 nm. A gas detection device made from the gas sensitive material deposited on a substrate, the gas sensitive material configured as a part of a current measuring circuit in communication with a heat source.
1. A method of forming a gas sensitive material comprising the steps of:
providing a mixture of SnO 2 , InO 3 , and an oxide of a platinum group metal;
heating said mixture to a temperature sufficient to form nanocrystals; and
forming a multicomponent paste from the mixture, and wherein the heating comprises annealing the mixture.
2. The method of claim 1 further comprising the step of providing said platinum group metal as Pd, Pt, Ru, Ir, and/or combinations thereof.
3. The method of claim 2 further comprising the step of providing said platinum group metal as Pd.
4. The method of claim 1 further comprising the step of providing an additive in said mixture of SnO 2 , InO 3 , and an oxide of a platinum group metal.
5. The method of claim 4 wherein said additive comprises a surfactant, a blowing agent, and/or combinations thereof.
6. The method of claim 5 wherein the surfactant comprises between about 8% to about 20% of said mixture by weight and said blowing agent comprises between about 3% and about 6% of said mixture by weight.
7. The method of claim 5 wherein the surfactant comprises about 15% of said mixture by weight and said blowing agent comprises about 5% of said mixture by weight.
8. The method of claim 4 wherein the surfactant is stearic acid and the blowing agent is ammonium carbonate.
9. The method of claim 1 wherein said oxide of a platinum group metal comprises between about 2% and about 5% of the weight of said mixture and said InO 3 comprises between about 3% and about 12% of the weight of said mixture.
10. The method of claim 1 wherein said oxide of a platinum group metal comprises about 3% of the weight of said mixture and said InO 3 comprises about 6% of the weight of said mixture.
11. The method of claim 1 wherein the providing mixture of SnO 2 , InO 3 , and an oxide of a platinum group metal, comprises:
blending a Pd salt solution with SnO 2 and/or In 2 O 3 particles to associate the Pd with the particles, and converting the Pd salt to a dispersed Pd oxide; and
adding a surfactant and processing to produce a gas sensitive material.
12. A method of forming a gas sensitive material comprising the steps of:
providing a mixture of SnO 2 , In 2 O 3 , and an oxide of a platinum group metal;
heating said mixture to a temperature sufficient to form nanocrystals;
adding at least one of a surfactant and a blowing agent to form a multi-component paste composition; and
annealing the paste composition to remove one or both of the surfactant and the blowing agent.
13. The method of claim 12 wherein the surfactant comprises between about 8% to about 20% of the mixture of SnO 2 , InO 3 , and an oxide of a platinum group metal by weight and the blowing agent comprises between about 3% and about 6% of the mixture by weight.
14. The method of claim 12 wherein the multi-component paste composition is formed as a film.