Heating apparatus and method for making the same
View Patent ↗A heating apparatus includes a heating element adapted to be disposed on a substrate. The heating element includes electrodes and a multi-layer conductive coating of nano-thickness disposed between the substrate and electrodes. The multi-layer conductive coating has a structure and composition which stabilize performance of the heating element at high temperatures. The multi-layer conductive coating may be produced by spray pyrolysis.
1. A heating apparatus including a heating element adapted to be disposed on a substrate, the heating element comprising:
electrodes;
a multi-layer conductive coating of about 50 nm to about 70 nm each layer in thickness disposed between the substrate and electrodes; and
a multi-layer insulating coating disposed between the multi-layer conductive coating and the substrate.
2. The heating apparatus as claimed in claim 1 , wherein the multi-layer conductive coating comprises an oxide coating including a source metal selected from the group consisting of tin, indium, cadmium, tungsten, titanium and vanadium.
3. The heating apparatus as claimed in claim 1 , wherein the electrodes comprises glass ceramic frit based ink including a source metal selected from the group consisting of platinum, gold, silver, palladium and copper.
4. The heating apparatus as claimed in claim 1 , wherein each layer of the multi layer insulating coating is about 30 nm to about 50 nm in thickness.
5. The heating apparatus as claimed in claim 1 , wherein the multi-layer insulating coating comprises sol-gel derived silicon dioxide.
6. The heating apparatus as claimed in claim 1 , further comprising a surfactant on the substrate, the surfactant comprising perfluoralkyl surfactant of a concentration between about 0.01 and about 0.001% w/w with sodium dioctyl sulphosuccinate of a concentration between 0.1 and about 0.01% w/w.
7. The heating apparatus as claimed in claim 1 , further comprising a temperature monitor and control system integrated with the heating element of the heating apparatus, the temperature monitor and control system comprising an analog-to-digital converter for measuring temperature and a pulse-width modulation drive for regulating power supply.
8. A heating apparatus including a heating element adapted to be disposed on a substrate, the heating element comprising:
electrodes;
a multi-layer conductive coating of about 50 nm to about 70 nm each layer in thickness disposed between the substrate and electrodes, the multi-layer conductive coating produced by spray pyrolysis; and
a multi-layer insulating coating disposed between the multi-layer conductive coating and the substrate.
9. The heating apparatus as claimed in claim 8 , wherein the spray pyrolysis is carried out at a temperature of about 650° C. to about 750° C.
10. The heating apparatus as claimed in claim 8 , wherein the spray pyrolysis is carried out at a spray pressure of about 0.4 MPa to about 0.7 MPa.
11. The heating apparatus as claimed in claim 8 , wherein the spray pyrolysis is carried out at a spray head speed of less than 1000 mm per second.
12. The heating apparatus as claimed in claim 8 , wherein the spray pyrolysis is carried out by alternating spray passes in a direction of about 90 degrees to each other.
13. The heating apparatus as claimed in claim 8 , wherein the electrodes are disposed on the conductive coating by screen printing.
14. The heating apparatus as claimed in claim 8 , wherein each layer of the multi layer insulating coating is about 30 nm to about 50 nm in thickness.
15. The heating apparatus as claimed in claim 8 , wherein the multi-layer insulating coating is disposed on the substrate by dip coating, using tetra ethoxy ortho silicate as a base precursor, and each layer of the multi-layer insulating coating is hydrolysed, dried and fired at about 500° C.
16. The heating apparatus as claimed in claim 8 , further comprising a temperature monitor and control system integrated with the heating element of the heating apparatus, the temperature monitor and control system comprising an analog-to-digital converter for measuring temperature and a pulse-width modulation drive for regulating power supply.
17. A method of making a heating element of a heating apparatus, the method comprising the steps of:
providing a substrate;
disposing a multi-layer insulating coating on the substrate;
producing a multi-layer conductive coating of about 50 nm to about 70 nm each layer in thickness by spray pyrolysis on the multi-layer insulating coating; and
disposing electrodes on the conductive coating.
18. The method of making a heating element of a heating apparatus as claimed in claim 17 , wherein each layer of the multi-layer insulating coating is about 30 nm to about 50 nm in thickness.