The invention relates to the reduction of the evaporation rate of platinum and Pt alloys upon their use at high temperatures (>1,200° C.) in an oxidizing atmosphere.
Platinum shall be understood to mean a platinum material that may contain fractions of further elements as common in the industry. This concerns, in particular, inevitable impurities.
A platinum alloy shall be understood to mean an alloy having platinum as the major fraction, in particular having in excess of 80% platinum. The remainder is preferably accounted for by rhodium and/or iridium.
The evaporation rate shall be understood to mean the rate at which the loss of material occurs. It can be expressed as mass loss per operation time.
Components made of platinum and PtRh10 are used for the melting and processing of glass in the glass industry. In the process, the temperatures of the components may be as high as 1,700° C. In this context, the service life of, e.g., feeder systems should be guaranteed to exceed 500 days. At high temperatures >1,200° C., platinum and rhodium are converted into volatile oxides which leads to a loss of material. Although the components are mechanically supported and surrounded in a thermally insulating manner by ceramic blocks, which concurrently affords a certain protection from oxidation, the evaporation rates are considerable. The loss of material increases markedly with temperature. This leads to a rapid decrease in the wall thickness which reduces the service life of the components drastically.
In laboratory experiments of the applicant using uncoated PtRh10 sheets of metal (thickness=0.8 mm) at 1,650° C. in air, approx. 4% loss of material over the period of 20 days has been observed to occur. Even a reduction of the temperature to 1,600° C. still leads to 2.4% loss of material over the period of 20 days. In use, evaporation rates of this magnitude lead to early failure of the component.
International patent application Publication No. WO 2002/044115 A2, U.S. Pat. No. 7,338,714 B2, and European patent application Publication EP 1 722 008 A2 are related to a coated metal part in glass manufacturing, wherein the metal part has, on its side facing the molten glass, a layer that is impermeable to H2 or H2 and O2.
In this context, preferably either the H2— or the H2— and O2— impermeable layer contains at least one glass or glass mixture, partly or fully crystallized or ceramic material.
In contrast, it is an object of the invention to provide a scavenging system for Pt, Rh or Ir in an oxidizing atmosphere at high temperatures. The surrounding ceramic layers should largely be kept free of noble metals.
It is another object of the invention to provide for prolongation of the service life and thus time of use of noble metal components made of platinum or alloys thereof during their use at high temperatures (>1,200° C.) in an oxidizing atmosphere—preferably by more than 80%.
For reduction of oxidation and ensuing losses of materials, an oxidation protection system has been developed that can surprisingly also be applied without any difficulty to very large components having a complex geometry. A flexible bandage made of a high-melting ceramic or metallic material has proven to be advantageous.
The objects are each met by components as well as by methods of the present invention described and claimed herein, including the preferred embodiments of the invention described below.
In this context, a bandage is characterized by its open porosity and preferably a large internal surface. An oxide ceramic material and/or a glass-forming material matched to the temperature of use can be introduced into the pores of the bandage. Note that network-forming materials, also called glass-forming materials, form the basic molecular structure of glass. No further substances are required for glass formation. Accordingly, quartz glass, for example, has SiO2 as its sole component. The following compounds are examples of network-forming materials: silicon dioxide (SiO2), boric trioxide (B2O3), phosphorous pentoxide (P2O5), diarsenic trioxide, also called arsenic trioxide (As2O3), germanium dioxide (GeO2), and diantimonypentoxide (Sb2O5).
This bandage involves a “soaked bandage” in the scope of the invention. The soaked bandage can be produced by soaking in or drop-wise application of or painting with a suspension. Components wrapped with the bandages afford the opportunity to completely wet the surface of the component at operating temperature and impede the access of oxygen. Complete wetting for long periods of time appears to be feasible only through the use of a bandage of this type. This is a particular advantage of the invention. The evaporation losses as compared to non-bandaged components are preferably reduced by more than 80%.
Due to the open porosity, non-soaked bandages are permeable to air and thus have little or no protective effect against an oxidizing atmosphere. Moreover, the adherence on components is rather insufficient due to thermal expansion. However, non-soaked bandages allow for scavenging noble metal oxides that escape despite evaporation protection. It is also feasible to first wrap with a soaked bandage and then with a non-soaked bandage over the first bandage.
The advantages of soaked bandages are:
The invention is illustrated in more detail by the following exemplary embodiments. As is the case in the remaining description, specification of parts and percentages refer to the weight unless specified otherwise.
Application of a protective bandage made of a ceramic material (Al2O3+28% SiO2) onto a PtRh10 sheet of metal having dimensions of: width 150 mm, length 200 mm, wall thickness 0.8 mm.
The bandage (thickness 5 mm) was soaked in a suspension consisting of Al2O3 powder (particle size: <2.5 μm) and water (30% by weight Al2O3 and 70% by weight water) and wrapped around the sheet of metal in 2 layers.
The sheet of metal was aged in a chamber furnace for 20 days at 1,650° C. on air.
The loss of material (PtRh10 sheet of metal) was 0.6%.
Application of a protective bandage made of a ceramic material (Al2O3+28% SiO2) onto a Pt Rh 10 sheet of metal having dimensions of: width 150 mm, wall thickness 0.8 mm, length 200 mm.
The bandage (thickness 5 mm) was wrapped around the sheet of metal in 2 layers. A suspension of Al2O3 powder (particle size: <2.5 μm) and water (30% by weight Al2O3 and 70% by weight water) was applied to the bandage.
The sheet of metal was aged in a chamber furnace for 20 days at 1,650° C. on air.
The loss of material (PtRh10 sheet of metal) was 0.9%.
Application of a protective bandage made of a ceramic material (Al2O3+28% SiO2) onto a Pt Rh 10 sheet of metal having dimensions of: width 150 mm, wall thickness 0.8 mm, length 200 mm.
The bandage (thickness 5 mm) was soaked in a suspension consisting of ZrO2 powder containing 5% Y2O3 (particle size: <5.5 μμm) and water (40% by weight ZrO2/Y2O3 and 60% by weight water) and wrapped around the sheet of metal in 2 layers.
The sheet of metal was aged in a chamber furnace for 20 days at 1,650° C. on air.
The loss of material (PtRh10 sheet of metal) was 1.1%.
Application of a protective bandage made of a ceramic material (Al2O3+28% SiO2) onto a Pt Rh 10 sheet of metal having dimensions of: width 150 mm, wall thickness 0.8 mm, length 200 mm.
The bandage (thickness 5 mm) was soaked in a suspension consisting of SiO2 powder (particle size: <2 μm) and water (30% by weight SiO2 and 70% by weight water) and wrapped around the sheet of metal in 2 layers.
The sheet of metal was aged in a chamber furnace for 20 days at 1,650° C. on air.
The loss of material (PtRh10 sheet of metal) was 0.5%.
Application of a protective bandage made of a Pt Rh 10 gauze and/or fleece onto a Pt Rh10 sheet of metal having dimensions of: width 150 mm, wall thickness 0.8 mm, length 200 mm.
The bandage (thickness approx. 0.5 mm) was wrapped around the sheet of metal. A suspension consisting of SiO2 powder (particle size: <2.5 μm) and water (30% by weight SiO2 and 70% by weight water) was applied to the bandage with a brush.
The sheet of metal was aged in a chamber furnace for 20 days at 1,650° C. on air.
The loss of material (PtRh10 sheet of metal) was 0.9%.
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.
Number | Date | Country | Kind |
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10 2010 047 896.2 | Oct 2010 | DE | national |
This application is a Section 371 of International Application No. PCT/EP2011/004959, filed Oct. 5, 2011, which was published in the German language on Apr. 19, 2012, under International Publication No. WO 2012/048811 A1 and the disclosure of which is incorporated herein by reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP11/04959 | 10/5/2011 | WO | 00 | 4/9/2013 |