JPH05103996A - Formation of carrier layer on metal substrate for catalyst - Google Patents

Abstract

PURPOSE:To form a ceramic carrier layer on a metal substrate for a catalyst so that the layer can tightly be fixed on the substrate with high adhesive strength. CONSTITUTION:A layer of a mixture of Pt, Au or a Pt-Au alloy as a noble metal component with Al2O3, ZrO2, NiO, Cr2O3, SiO3, MgO or a multiple oxide of them as a ceramic component is formed on the surface of a metal substrate for a catalyst by plasma spraying and then a ceramic carrier layer is formed on the mixture layer by plasma spraying, dipping, coating, spraying or other method. When the mixture layer is formed, the compsn. ratio is preferably varied in the cross-sectional direction so that the amt. of the noble metal component is made larger at the metal substrate side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a carrier layer for supporting a catalyst on a metal substrate of a combustion catalyst, an exhaust gas catalyst or the like.

[0002]

2. Description of the Related Art Conventionally, in order to form a catalyst-supporting carrier layer on a catalyst metal substrate, as described in JP-A-56-96726, an Al-containing stainless steel catalyst metal substrate is used. the the Al ₂ O ₃ layer is formed on the surface was heat-treated, the the Al ₂ O ₃ layer a ceramic carrier layer of high surface area is formed on the, was fixed and a catalyst for the metal substrate and the ceramic carrier layer. However, there is a clear interface between the catalytic metal substrate and the Al ₂ O ₃ layer, and stress due to the difference in the coefficient of thermal expansion between the metal and the ceramics concentrates on the interface, and peeling may occur. Therefore,
The combustion catalyst and the exhaust gas catalyst obtained by supporting the catalyst on the ceramics carrier layer have a problem in high temperature durability and have a short life.

[0003]

Therefore, the present invention is to provide a carrier layer forming method capable of firmly fixing a ceramics carrier layer to a metal substrate for catalyst with a strong adhesive force.

[0004]

One of the methods for forming a carrier layer on a metal substrate for a catalyst according to the present invention for solving the above-mentioned problems is to apply P on the surface of the metal substrate for a catalyst by plasma spraying.
Noble metal component of t, Au, or Pt-Au alloy and A
_{l 2 O 3, ZrO 2,} NiO, Cr 2 O 3, SiO 2, MgO to form a mixed layer of any of the ceramic components of these composite oxides, plasma spraying onto thereafter the mixed layer, dipping The method is characterized in that the ceramic carrier layer is formed by a method such as coating, spraying or the like.

Another method of forming a carrier layer on a metal substrate for a catalyst according to the present invention is such that, when forming the above mixed layer, the composition ratio of the noble metal component and the ceramic component is set on the metal substrate for a catalyst side. It is characterized in that it is changed in the cross-sectional direction so that

[0006]

As described above, according to the method for forming a carrier layer on a metal substrate for a catalyst of the present invention, a mixed layer of a noble metal component and a ceramic component that does not form a solid solution with each other and forms respective networks is formed on the metal substrate. Therefore, the metal base and the ceramics carrier layer are firmly adhered to each other, and the stress due to the difference in thermal expansion between the two is gentle in the mixed layer, the stress is moderated, and the ceramics carrier layer is kept from the metal substrate even at high temperature. Does not peel off. In particular, when the composition ratio of the noble metal component and the ceramics component in the mixed layer is changed in the cross-sectional direction, that is, the layer thickness direction so that the noble metal component is increased on the metal substrate side, the stress is further balanced and at the same time the metal substrate is , The mixed layer and the carrier layer have a stronger adhesion force and are not peeled off.

[0007]

EXAMPLE An example of a method for forming a carrier layer on a metal substrate for a catalyst of the present invention will be described. Pt is formed by plasma spraying on the surface of a metal substrate for a catalyst made of SUS (stainless steel).
And a mixed layer of Al ₂ O ₃ was formed. This mixed layer is the initial Pt9
Starting with the ratio of 9% and Al1%, the ratio is continuously changed to reduce Pt, and the final ratio is Pt5%, A
It is 95%. After that, an Al ₂ O ₃ carrier layer was formed on the mixed layer by plasma spraying.

On the other hand, to explain the conventional example, a stainless steel catalytic metal substrate containing Al is heat-treated to form an Al ₂ O ₃ layer on the surface, and then plasma spraying is performed on this Al ₂ O ₃ layer. To form an Al ₂ O ₃ carrier layer.

Thus, in this way, Al _{2 is} deposited on the metal substrate for catalyst.
O ₃ in the catalyst support of Examples and Conventional Example was formed a support layer over the thermal cycle of room temperature ← → 1000 ° C., subjected sander 500rpm the cross section with a load of 100 g, when the heat cycle is many cycles Al ₂ SEM observation of whether the O ₃ carrier layer was peeled off from the catalyst metal substrate by polishing revealed that the catalyst support of the conventional example was
The Al ₂ O ₃ carrier layer was peeled off in 7 cycles, but the Al ₂ O ₃ carrier layer of the catalyst support of the example was not peeled off until 20 cycles.

[0010]

As described above, according to the method for forming a carrier layer on a metal substrate for a catalyst of the present invention, the metal substrate does not form a solid solution with each other,
Since the mixed layer of the noble metal component and the ceramic component that forms each network is formed, the ceramic carrier layer formed on this mixed layer firmly adheres to the metal substrate through the mixed layer, and the difference in thermal expansion between the two The stress applied by the method becomes gentle in the mixed layer, and the ceramic carrier layer does not peel off from the metal substrate even at high temperature due to stress relaxation. In particular, if the composition ratio of the noble metal component and the ceramics component in the mixed layer is changed in the layer thickness direction so that the precious metal component is increased on the metal substrate side, the stress is further balanced and at the same time the metal substrate and the mixed layer are mixed. However, the adhesion force of the three members of the carrier layer becomes even stronger and does not separate. Therefore, the combustion catalyst and the exhaust gas catalyst obtained by supporting the catalyst on the carrier layer have excellent high-temperature durability and long life.

Claims (2)

[Claims] 1. A noble metal component of Pt, Au, or a Pt-Au alloy and Al ₂ O ₃ , ZrO ₂ , NiO, Cr ₂ O ₃ , SiO ₂ , MgO formed on the surface of a metal base for a catalyst by plasma spraying. The invention is characterized in that a mixed layer of any of these composite oxides with a ceramic component is formed, and then a ceramic carrier layer is formed on the mixed layer by a method such as plasma spraying, dipping, coating or spraying. A method for forming a carrier layer on a metal substrate for a catalyst. 2. The method for forming a carrier layer on a metal substrate for a catalyst according to claim 1, wherein the composition ratio of the noble metal component and the ceramics component of the mixed layer is such that the noble metal component is increased on the side of the metal substrate for a catalyst. A method for forming a carrier layer on a metal base for a catalyst, which comprises forming a mixed layer by changing the cross-sectional direction.