Electron beam emitter electron emission window foil

Abstract

An electron exit window foil (106) for an electron beam emission device (100) having an electron beam generator (103) and operating in a corrosive environment (P1) is disclosed. The electron exit window foil (106) has a sandwich structure with an outer surface arranged to face the corrosive environment (P1) and an inner surface arranged to face the electron beam generator (103). The sandwich structure includes, from the outside to the inside, a protective layer for protecting the sandwich structure from the corrosive environment (P1), a Ti support layer for providing structural support to the sandwich structure, and an Al thermally conductive layer for conducting heat from the sandwich structure.

Description

Technical Field

[0001] The present invention relates to an electron emission window foil for an electron beam emitter operating in a corrosive environment. The present invention also relates to an electron beam emitter that emits electrons towards a packaging material to sterilize microorganisms, a food packaging machine having the electron beam emitter, and a method for packaging food in a package irradiated with electrons from the electron beam emitter.

Background Art

[0002] An electron beam emitter is used, for example, to irradiate an object with electrons for surface treatment. Such devices are commonly used in the food packaging industry where the electron beam provides efficient sterilization of packages such as plastic bottles or packaging materials that are later converted into packages.

[0003] The main advantage of electron beam sterilization is that it can avoid wet methods such as H2O2 (hydrogen peroxide), thus reducing the number of parts and devices required in a wet environment.

[0004] An electron beam emitter typically includes a filament connected to a power source, and the filament emits electrons. The filament, called an electron beam generator, is preferably disposed in a high vacuum to increase the mean free path of the emitted electrons, and an accelerator directs the emitted electrons towards the emission window. The electron emission window is provided to allow electrons to escape from the electron beam emitter, move outside the electron beam emitter, collide with the object to be sterilized, and release its energy on the surface of the object.

[0005] The electron emission window typically has a thin electron-permeable foil that is sealed to the electron beam emitter to maintain a vacuum inside the emitter. Furthermore, a grid-like cooling support plate (layer support structure) is provided to prevent the foil from collapsing due to the high vacuum. Titanium (Ti) is commonly used as the foil material because it has a good match between high melting point and electron permeability, and a thin foil can be obtained.

[0006] The problem with titanium foil is that it oxidizes, reducing its lifespan and operational stability. The atmosphere is rich in oxygen and a corrosive environment, and oxidation occurs because the foil is exposed to the atmosphere surrounding the electron beam emitter. In addition, oxidation or corrosion can also occur due to the plasma generated by electrons in the air emitted from the electron beam emitter.

[0007] To achieve a long lifespan for the emission window, it is desirable that the maximum temperature of the electron beam emitter does not exceed approximately 250°C during operation. Generally, high-performance electron beam emitters are designed to provide 22 kGy at 80 keV and a maximum of 100 m / min when used for sterilizing packaging materials in the form of a moving web. In such high-performance electron beam emitters, the amount of emitted electrons passing through the window may significantly exceed this limit, which may make it impossible to use plain Ti foil.

[0008] In filling machines, that is, machines designed to package, fill, and seal food products, sterilization is a crucial process not only for the packaging but also for the machine itself. Sterilization of such machines is preferably performed at startup, and the outside of the injection window is often exposed to chemicals used to sterilize the machine. Highly corrosive substances such as H2O2, commonly used in such applications, can damage the injection window by etching the Ti. Furthermore, over time, plasma generated by oxygen and electrons in the atmosphere can oxidize the Ti.

[0009] To overcome the aforementioned shortcomings, various solutions have been proposed to improve the characteristics of injection windows.

[0010] For example, Patent Document EP0480732B describes an injection window foil consisting of a Ti foil and a protective layer of Al that forms an intermetallic compound by thermal diffusion treatment of a Ti / Al structure. This solution is suitable for relatively thick injection windows, i.e., windows that allow for a protective layer thicker than 1 micron.

[0011] Patent document EP0622979A discloses an injection window foil comprising a Ti foil and a silicon oxide protective layer on the side of the injection foil facing the irradiated object. Although the Ti foil is protected by such a layer, silicon oxide is very brittle and can easily crack in areas where the foil flexes, i.e., in the areas between the grids of the support plate when a vacuum is provided. Due to this drawback, the foil of EP0622979A is unsuitable for applications where the injection foil exhibits local curvature, such as electron beam emitters that use a grid-shaped cooling plate positioned in contact with the injection foil.

[0012] Therefore, there is a need for improvement in electron emission window foil used in electron beam emitters, particularly in emitters used for sterilizing packaging materials and packages in the food industry. [Overview of the project] [Problems that the invention aims to solve]

[0013] The object of the present invention is to overcome at least partially one or more of the limitations specified above in the prior art. In particular, the object is to provide an electron emission window foil that is more durable than foils of the prior art, especially foils used in electron beam emitters employed for sterilizing packaging materials and packages in the food industry. [Means for solving the problem]

[0014] According to a first aspect of the present invention, an electron emission window foil is provided for an electron beam emitter that operates in a corrosive environment and is equipped with an electron beam generator. The electron emission window foil has a sandwich structure having an outer surface arranged to face the corrosive environment and an inner surface arranged to face the electron beam generator. The sandwich structure comprises, from the outside inward, a protective layer of metal, for example, a precious metal, to protect the sandwich structure from the corrosive environment; a support layer of Ti (titanium) to structurally support the sandwich structure; and a thermal conductive layer of Al (aluminum) to transfer heat from the sandwich structure.

[0015] Electron injection window foil is advantageous in that the protective layer provides corrosion protection, the Ti layer provides the main structural support and necessary rigidity for the sandwich structure, and the Al layer plays a role in conducting and removing heat from the sandwich structure.

[0016] According to a second embodiment, the electron beam emitter is configured to operate in a corrosive environment. The electron beam emitter comprises a housing, an electron beam generator located inside the housing, and a layer support structure that forms part of the housing and has openings for emitting electrons generated by the electron beam generator. The electron emission window foil according to the first embodiment is placed on the layer support structure to seal the housing.

[0017] According to a third embodiment, a food packaging machine is provided which is configured to fold packaging material into a package, fill the package with food, and seal the package to contain the food. The food packaging machine is equipped with an electron beam emitter according to a second embodiment, which is configured to emit electrons toward the packaging material to kill microorganisms present on the packaging material.

[0018] According to a fourth aspect, a method for packaging food in a package is provided. This method includes providing a packaging material, irradiating the packaging material with an electron beam to kill microorganisms present on the packaging material, folding the packaging material into a package, filling the package with food, and sealing the package to contain the food therein. The irradiating includes irradiating the packaging material with an electron beam emitter as described in the third aspect.

[0019] The electron beam emitter, food packaging machine, and method for packaging food in a package of the present invention include the electron emission window foil according to the first aspect, have the same advantages as the electron emission window foil, and can include all embodiments and modifications of the electron emission window foil.

[0020] Other objects, features, aspects, and advantages of the present invention will be apparent from the following detailed description and the drawings.

[0021] Hereinafter, embodiments of the present invention will be illustratively described with reference to the accompanying schematic drawings.

Brief Description of the Drawings

[0022] [Figure 1] It is a perspective cross-sectional view of an electron beam emitter. [Figure 2] It is a cross-sectional view showing an electron emission window foil and a layer support structure of the electron emission window foil. [Figure 3a] It is a schematic cross-sectional view of an electron emission window foil according to different embodiments. [Figure 3b] It is a schematic cross-sectional view of an electron emission window foil according to different embodiments. [Figure 3c] It is a schematic cross-sectional view of an electron emission window foil according to different embodiments. [Figure 4] It is a schematic view showing an example of a food packaging machine. [Figure 5] It is a flowchart showing a method for packaging food.

Modes for Carrying Out the Invention

[0023] Referring to FIG. 1, an electron beam emitter 100 is shown. The electron beam emitter 100 includes a tubular housing 102 that holds an electron beam generator 103 arranged to generate and shape an electron beam, components related to the output of the electron beam, such as an electron emission window foil 106, and a support flange 104 that carries a foil support plate 108 for establishing a vacuum inside the emitter 100 to prevent the collapse of the window foil 106. Further, during the operation of the electron beam emitter 100, the foil 106 is exposed to excessive heat. The foil support plate 108 also serves the purpose of allowing the heat generated in the foil 106 when electrons pass through the foil 106 to escape. By keeping the temperature of the foil appropriate, a relatively long lifespan of the foil 106 can be obtained. The electron beam generating device 103 may be any suitable commercially available electron beam generating device.

[0024] Referring to FIG. 2, the electron emission window foil 106 is disposed on the foil support plate 108. The foil support plate 108 is arranged to face the inside of the electron beam emitter 100 so as to keep the inside of the emission window foil 106 under vacuum. The foil support plate 108 is provided with an opening 109 for allowing electrons to pass through. In FIG. 2, P1 represents the environment around the electron beam emitter 100 having atmospheric pressure, and P2 represents the vacuum inside the electron beam emitter 100. Since P1 contains air, that is, oxygen, it is a corrosive environment. Further, substances such as hydrogen peroxide may exist in the environment P1 and may come into contact with the emission window foil 106, and there is a possibility of generating a corrosive plasma by the electrons emitted from the electron beam emitter 100.

[0025] During manufacturing, for example, the foil support plate 108 made of Cu (copper) is preferably attached to the flange 104 that forms a part of the housing 102. The flange 104 and the housing 102 are generally made of stainless steel. The electron emission window foil 106 is adhered onto the foil support plate 108 to form a foil-frame subassembly. The foil-frame subassembly is then attached to the housing 102 to form a sealed housing.

[0026] Referring to Figures 3a to 3d, different embodiments of the electron emission window foil 106a to 106d are shown. In all embodiments, the electron emission window foil 106a to 106d has a sandwich structure 107 having an outer surface 2 positioned to face the corrosive environment P1 and an inner surface 16 positioned to face the electron beam generator 103.

[0027] In Figure 3a, the foil 106a has a sandwich structure 107 extending from the outer surface 2 to the inner surface 16, including a protective layer 4 containing a metal, such as a precious metal, a support layer 12 of Ti (titanium), and a heat conductive layer 12 of Al (aluminum). The main function of the protective layer 4 is to protect the sandwich structure 107 from a corrosive environment P1. The main function of the Ti layer 8 is to provide structural support and mechanical strength to the sandwich structure 107. The main function of the Al layer 12 is to transfer heat from the sandwich structure 107, particularly to the foil support plate 108. Each of layers 4, 8, and 12 may provide additional and complementary functions.

[0028] The precious metal may be Rh (rhodium). Alternatively, the precious metal may be Ru (ruthenium), Pd (palladium), Ag (silver), Os (osmium), Ir (iridium), Pt (platinum), or Au (gold).

[0029] The protective layer 4 may have a thickness of 50 nm to 200 nm, or a thickness of 70 nm to 150 nm.

[0030] The Ti layer may have a thickness of 5000nm to 8000nm, or 6500nm to 7200nm. The Al layer may have a thickness of 1000nm to 3000nm, or 2500nm to 3000nm.

[0031] Layers 4, 8, and 12 are attached to each other by appropriate conventional techniques. For example, Ti layer 8 may be a conventional foil made of Ti and may be manufactured by any appropriate process. Protective layer 4 may be provided by any appropriate process such as sputtering or thermal deposition, enabling the sandwich structure 107 to be provided with corrosive protection. Al layer 12 may be provided by any appropriate process such as sputtering or thermal deposition, and it is desirable that the foil bends into the opening of the foil support plate 108 while sufficiently improving the thermal conductivity to lower the temperature of the electron injection window foil 106a when a vacuum is applied. Instead of Al, other metals such as Cu (copper), Ag (gold), Au (silver), or Mo (molybdenum), or alloys thereof may be used for the thermal conductive layer.

[0032] By using the thicknesses described above for the layers and keeping the window foil 106 as thin as possible, the electron output is maximized. Therefore, the thickness of the protective layer 4 should be designed to protect the Ti layer from corrosion by hydrogen peroxide or other aggressive chemicals that may be present in specific applications, and from corrosion by plasma generated by electrons in the air. Furthermore, the thickness of the protective layer 4 needs to ensure airtightness and physical strength so that the Ti layer 8 is flexible enough to bend as a whole foil to fit the opening of the foil support plate 108 when a vacuum is applied. A further parameter may be the density required to allow electron transmission through the protective layer 206.

[0033] By placing the Al layer 12 and the protective layer 4 on opposite sides of the Ti foil, the stress on each layer can be reduced. For example, if Al is used as the thermal conductive layer and Rh as the protective layer, placing the Ti foil between these layers can reduce some of the stress generated during heating. This is due to the fact that the thermal expansion coefficient of Ti lies between that of Al and Rh.

[0034] Figure 3b shows another embodiment of the injection window foil 106b. The sandwich structure 107 of the injection window foil 106b includes a layer 10 of ZrO2 (zirconium dioxide) placed between the Ti layer 8 and the Al layer 12.

[0035] This ZrO2 layer 10 is advantageous in that it reduces or prevents diffusion between the Ti layer 8 and the Al layer 12. It also achieves good adhesion between the Ti layer and the Al layer. Alternatively, layer 10 could be Al2O3 instead of ZrO2. By preventing diffusion and reaction at the interface between the Ti and Al layers, the formation of intermetallic compounds, which could negatively alter the material properties, is prevented. In the case of a thin Ti layer, the physical strength may decrease. Furthermore, the presence of intermetallic compounds can reduce the thermal conductivity and corrosion resistance of the layer.

[0036] The ZrO2 layer 10 between the Ti layer 8 and the Al layer 12 may have a thickness of 10 nm to 30 nm, or it may have a thickness of 15 nm to 20 nm. The ZrO2 layer 10 may be provided by any suitable process such as sputtering or thermal deposition.

[0037] Figure 3c shows another embodiment of the injection window foil 106c. Here, the sandwich structure 107 of the injection window foil 106c includes a Zr (zirconium) layer 6 placed between the protective layer 4 and the Ti layer 8. The Zr layer 6 mainly functions as a bonding layer between the protective layer 4 and the Ti layer 8. The Zr layer 6 may have a thickness of 5 nm to 15 nm, or a thickness of 8 nm to 12 nm.

[0038] Figure 3d shows another embodiment of the injection window foil 106d. Here, the sandwich structure 107 of the injection window foil 106b includes a ZrO2 layer 14 on the Al layer 12, positioned facing the electron beam generator 103. This layer 14 is advantageous in that it protects the Al layer 12 from wear because it is the layer closest to, i.e., in contact with, the foil support plate 108. The ZrO2 layer 14 positioned on the Al layer 12 may have a thickness of 100 nm to 200 nm, or a thickness of 130 nm to 170 nm.

[0039] Further embodiments of the injection window foil are possible, for example, a foil in which the sandwich structure 107 corresponds to Figure 3a and has a Zr layer 6 between the protective layer 4 and the Ti layer 8. Another embodiment corresponds to the embodiment in Figure 3a and has a ZrO2 layer 14 on the side of the Al layer facing the electron beam generator 103. Another embodiment corresponds to Figure 3b and has a ZrO2 layer 14 on the side of the Al layer facing the electron beam generator 103.

[0040] In all embodiments of the window foil 106 described herein, different layers are joined to each other to form a sandwich structure 107, i.e., there are no gaps between the layers. Additional layers may be present in each embodiment of the window foil 106. Alternatively, in all embodiments of the window foil 106, the window foil 106 may not include any further layers other than those explicitly mentioned herein.

[0041] As described above, the electron beam emitter 100 is typically configured to operate in a corrosive environment P1. The electron beam emitter 100 includes a housing 102, an electron beam generator 103, and a layer support structure 108 that forms part of the housing 102 and has an opening 109 for emitting electrons 103 generated by the electron beam generator 100. An electron emission window foil according to one of the embodiments described above is placed on the layer support structure 108 for sealing the housing 102.

[0042] Referring to Figure 4, a food packaging machine 50 is illustrated. The packaging machine 50 is a conventional food packaging machine configured to fold packaging material 53 into a package 54, fill the package 54 with food 55, and seal the package 54 to contain the food 55 inside the package 54. The food may be a liquid dairy-based food, juice, or other liquid or semi-liquid food. The packaging material 53 may be a web formed by a central cellulose-based core layer covered with a barrier layer such as a plastic layer.

[0043] The packaging material 53 may be in the form of a roll 52 that is unwound when supplied to the machine 50. Electron beam emitters 100 and 102 are positioned on both sides of the packaging material to emit electrons 103 toward the surface of the packaging material 53. The emitted electrons kill any microorganisms that may be present on the packaging material 53, and the packaging material can be sterilized before it is folded into a package and filled with food.

[0044] Referring to Figure 5, a method for packaging food 55 in a package 54 is shown. This method includes the steps of providing packaging material 52 (71), irradiating the packaging material 53 with electrons 103 (72) to kill microorganisms present on the packaging material 53, folding the packaging material 53 to form a package 54 (73), filling the package 54 with food 55 (74), sealing the package 54 (75), and placing the food 55 inside the package 54. This is typically done using conventional methods and techniques. However, the irradiating (72) includes irradiating the packaging material 53 using the electron emitter 100 described above, which constitutes an electron beam emission window according to any of the embodiments described above.

[0045] Although various embodiments of the present invention have been described and demonstrated above, the present invention is not limited thereto and can be embodied in other ways within the scope of the subject matter defined in the following claims.

[0046] In one or more embodiments, the protective layer 4 shown in any of the figures, for example, Figures 3a, 3b, 3c and / or 3d, may include one or more of the following: - Precious metals, precious metal nitrides, precious metal carbides and / or precious metal oxides, preferably the precious metal being rhodium (Rh), ruthenium (Ru), palladium (Pd), silver, osmium, iridium (Ir), platinum (Pt), or gold (Au), and / or - Zirconium (Zr), zirconium carbide, zirconium nitride and / or zirconium oxide (ZrO2), and / or -Titanium (Ti), titanium carbide, titanium nitride and / or titanium oxide, and / or - Tantalum (Ta), tantalum carbide, tantalum nitride, and / or tantalum oxide, and / or - Niobium (Nb), niobium carbide, niobium nitride, and / or niobium oxide, and / or - Hafnium (Hf), hafnium carbide, hafnium nitride and / or hafnium oxide, and / or - Chromium (Cr) chromium carbide, chromium nitride and / or chromium oxide, and / or - Nickel (Ni), nickel carbide, nickel nitride and / or nickel oxide, and / or - Molybdenum (Mo), molybdenum carbide, molybdenum nitride, molybdenum oxide

[0047] The protective layer 4 may, for example, contain two or more of the aforementioned elements, and the protective layer 4 may contain (or be made of) the following alloys or any other type of chemical and physical combination: -Titanium, tantalum, hafnium, and / or -Titanium, tantalum, hafnium, zirconium, and / or -Titanium, tantalum, niobium, and / or - Titanium, Zirconium, Hafnium, Niobium, Tantalum

[0048] The protective layer 4 may consist of a metal, a metal nitride, and / or a metal oxide. For example, as described above, the protective layer 4 may be made from one or more metals, metal nitrides, and / or metal oxides. Optionally, the protective layer 4 may be made of a noble metal, a noble metal nitride, and / or a noble metal oxide, where the noble metals are rhodium (Rh), ruthenium (Ru), palladium (Pd), silver, osmium, iridium (Ir), platinum (Pt), or gold (Au).

Claims

1. An electron emission window foil (106, 106a) for an electron beam emitter (100) having an electron beam generator (103) and operating in a corrosive environment (P1), wherein the electron emission window foil (106, 106a) includes a sandwich structure (107) having an outer surface (2) arranged to face the corrosive environment (P1) and an inner surface (16) arranged to face the electron beam generator (103), The sandwich structure (107) extends from the outer surface (2) to the inner surface (16), A metal protective layer (4) for protecting the sandwich structure (107) from the corrosive environment (P1), A Ti support layer (8) for providing structural support to the sandwich structure (107), A thermal conductive layer (12) of Al for transferring heat from the sandwich structure (107), On the Al thermal conductive layer (12), a ZrO2 layer (14) is arranged so as to face the electron beam generator (103), An electron injection window foil (106, 106a) is provided.

2. The sandwich structure (107) further A ZrO is placed between the Ti support layer (8) and the Al thermal conductive layer (12) to reduce diffusion between the Ti support layer (8) and the Al thermal conductive layer (12). ２ It has a layer (10), The electron injection window foil (106b) according to claim 1.

3. The sandwich structure (107) further A layer of Zr (6) is provided between the protective layer (4) and the Ti support layer (8) and functions as a bonding layer between the protective layer (4) and the Ti support layer (8). The electron injection window foil (106c) according to claim 1 or 2.

4. The protective layer (4) comprises a noble metal, a noble metal nitride, a noble metal carbide and / or a noble metal oxide. The electron injection window foil (106d) according to any one of claims 1 to 3.

5. The noble metal is rhodium (Rh), ruthenium (Ru), palladium (Pd), silver, osmium (Os), iridium (Ir), platinum (Pt), or gold (Au), and / or - Zirconium (Zr), zirconium carbide, zirconium nitride and / or zirconium oxide (ZrO ２ ), and / or, -Titanium (Ti), titanium carbide, titanium nitride and / or titanium oxide, and / or - Tantalum (Ta), tantalum carbide, tantalum nitride, and / or tantalum oxide, and / or - Niobium (Nb), niobium carbide, niobium nitride, and / or niobium oxide, and / or - Hafnium (Hf), hafnium carbide, hafnium nitride and / or hafnium oxide, and / or - Chromium (Cr) chromium carbide, chromium nitride and / or chromium oxide and / or, - Nickel (Ni), nickel carbide, nickel nitride and / or nickel oxide, and / or - Molybdenum (Mo), molybdenum carbide, molybdenum nitride, molybdenum oxide, -Titanium, tantalum, hafnium, and / or combinations thereof, -Titanium, tantalum, hafnium, zirconium, and / or combinations thereof, -Titanium, tantalum, niobium, and / or combinations thereof, -Titanium, zirconium, hafnium, niobium, tantalum and / or combinations thereof, The electron injection window foil (106, 106a) according to claim 4, comprising one or more of the above.

6. The protective layer (4) has a thickness of 50 nm to 200 nm, or a thickness of 70 nm to 150 nm, as described in any one of claims 1 to 5, electron injection window foil (106, 106a).

7. The Ti support layer has a thickness of 5,000 nm to 8,000 nm, or a thickness of 6,500 nm to 7,200 nm, according to any one of claims 1 to 6, the electron injection window foil (106, 106a).

8. The Al thermal conductive layer has a thickness of 1,000 nm to 3,000 nm, or a thickness of 2,500 nm to 3,000 nm, as described in any one of claims 1 to 7, for the electron injection window foil (106, 106a).

9. ZrO between the Ti support layer (8) and the Al heat conduction layer (12) ２ The electron injection window foil (106b) according to claim 2, wherein the layer (10) has a thickness of 10 nm to 30 nm, or a thickness of 15 nm to 20 nm.

10. The electron injection window foil (106c) according to claim 3, wherein the Zr layer (6) has a thickness of 5 nm to 15 nm, or a thickness of 8 nm to 12 nm.

11. ZrO is placed on the Al thermal conductive layer (12) on the side facing the electron beam generator (103). ２ The layer (14) has a thickness of 100 nm to 200 nm, or a thickness of 130 nm to 170 nm. The electron injection window foil (106d) according to claim 4.

12. An electron beam emitter (100) arranged to operate in a corrosive environment (P1), Housing (102) and An electron beam generator (103) is located inside the housing (102), A layer support structure (108) forms a part of the housing (102) and has an opening (109) for releasing electrons (103) generated by the electron beam generator (100), An electron injection window foil (106) according to any one of claims 1 to 11, disposed on the layer support structure (108) for sealing the housing (102), An electron beam emitter equipped with [a specific feature].

13. A food packaging machine (50) is configured to fold packaging material (53) into a package (54), fill the package (54) with food (55), and seal the package (54) to contain the food (55) inside the package (54), The aforementioned food packaging machine (50) An electron beam emitter (100) is positioned to emit electrons (103) toward the packaging material (53) to kill microorganisms present on the packaging material (53), Equipped with, The electron beam emitter (100) is the electron beam emitter (100) described in claim 12. Food packaging machine (50).

14. A method of packaging food (55) in a package (54), The aforementioned method, The packaging material (52) is provided (71), The packaging material (53) is irradiated with an electron beam (103) (72) to kill any microorganisms present on the packaging material (53). The packaging material (53) is folded (73) to form a package (54), The package (54) is filled with food (55) (74), To contain the food (55) inside the package (54), the package (54) is sealed (75). This includes, The irradiation (72) is a method comprising irradiating the packaging material (53) using the electron beam emitter (100) described in claim 12.

15. The electron injection window foil (106, 106a) according to any one of claims 1 to 11, wherein the protective layer (4) is made of a metal, a metal nitride and / or a metal oxide, and the metal is a precious metal such as rhodium (Rh), ruthenium (Ru), palladium (Pd), silver, osmium (Os), iridium (Ir), platinum (Pt), or gold (Au).

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