Silver-carbon adhesive for X-ray windows

Abstract

An X-ray window consists of a housing with a flange that encircles an opening. A thin film is located on the flange and spans the opening. An adhesive is sandwiched between an outer ring, the thin film, and the flange. The adhesive bonds the thin film to the housing. The adhesive consists of silver and carbon.

Description

Scope of the invention

[0001] The present application relates to X-ray windows. background

[0002] X-ray windows are designed to transmit a high percentage of X-rays, even low-energy X-rays. X-ray windows are used in expensive systems that require high reliability. High system requirements lead to demanding X-ray window properties. Brief description of the drawings (the drawings may not be to scale)

[0003] Fig. is a side cross-sectional view of an x-ray window 10 with an adhesive 13 sealing a thin film 12 to a housing 11. Fig. is a side cross-sectional view illustrating a first step in a method of manufacturing an X-ray window in which an adhesive 13 is applied to a flange 11f of a housing 11, to an outer ring 12o of a thin film 12, or to both. Reference numbers in the drawings 10 X-ray windows 11 housings 11a Opening 11f flange 12 Thin film 12o outer ring 13 Adhesive

[0004] Definitions. The following definitions, including their plural forms, apply to the entire patent application.

[0005] The terms “encircle” and “encircled by” here mean to surround or loop around, but these terms are not limited to a circular shape.

[0006] The term “MPa” used here means megapascals (10 6 Pascal).

[0007] As used here, the term "ring" refers to a shape that surrounds a circle or forms a loop, but this term is not limited to a circular shape.

[0008] As used herein, the terms "on," "disposed upon," "disposed at," and "disposed over" mean directly on or over another solid material in between. The terms "directly disposed upon," "adjacent," "contiguous," and "adjacent" imply direct and immediate contact.

[0009] Unless expressly stated otherwise, all temperature-dependent values ​​are those at 25° C. Detailed description

[0010] An X-ray window may consist of a thin film attached to a housing with an adhesive. Useful properties of X-ray windows include (1) low gas permeability, (2) low outgassing, (3) high strength, (4) low visible and infrared light transmission, (5) high X-ray flux, (6) low atomic number materials, (7) corrosion resistance, (8) high reliability, (9) low cost, (10) high temperature resistance, (11) thermal expansion coefficient compatibility, (12) a tight, reliable bond between the thin film, adhesive, and housing, and (13) high electrical conductivity. Each X-ray window design represents a balance between these properties.

[0011] A device that uses an X-ray window may have an internal vacuum. The internal vacuum can improve the device's performance. For example, an internal vacuum for an X-ray detector can minimize gas attenuation of the incoming X-rays and allow for easier cooling of the X-ray detector. Gas permeation through the X-ray window can degrade the internal vacuum. Therefore, low gas permeability is a desirable property of X-ray windows.

[0012] Outgassing from X-ray window materials can compromise the internal vacuum of the device. Therefore, selecting materials with low outgassing is prudent.

[0013] The X-ray window may be exposed to vacuum on one side and atmospheric pressure on the opposite side. Therefore, the thin film of the X-ray window must be strong enough to withstand this pressure difference.

[0014] Visible and infrared light can cause unwanted noise in the X-ray detector. The ability to block the transmission of visible and infrared light is another useful property of X-ray windows.

[0015] A high X-ray flux through a thin film of the X-ray window enables fast operation of the X-ray detector. Therefore, high X-ray transmittance through the thin film of the X-ray window is beneficial.

[0016] In some applications, the detection and analysis of low-energy X-rays is required. High transmittance for low-energy X-rays is therefore another useful property of thin film X-ray windows.

[0017] X-rays can be used to analyze a sample. X-ray noise from surrounding equipment, including the X-ray window, can interfere with a signal from the sample. X-ray noise from materials with high atomic numbers is more problematic. Therefore, it is helpful if the X-ray window is made of materials with low atomic numbers.

[0018] X-ray windows are used in corrosive environments and may be exposed to corrosive chemicals during manufacturing. Therefore, corrosion resistance is another useful property of an X-ray window.

[0019] The failure of X-ray windows is unacceptable in many applications. For example, X-ray windows are used in analytical instruments on Mars. High reliability is a useful property of X-ray windows.

[0020] X-ray window customers demand cost-effective X-ray windows with the above-mentioned features. Another aspect is reducing the cost of X-ray windows.

[0021] The ability to withstand high temperatures is a useful property of the X-ray window. The X-ray machine may need to withstand high temperatures during manufacturing, for example, during soldering.

[0022] Compatibility between the housing, the thin film, and the adhesive is beneficial. A small difference in the coefficient of thermal expansion between these materials can result in a more robust hermetic seal. This is especially important if the X-ray window is subject to large temperature fluctuations.

[0023] Another useful property of the adhesive is its strong bond to the housing and X-ray window. The housing and X-ray window are usually made of different materials, and the adhesive should bond well to both materials.

[0024] In a transmission target X-ray tube, electrons strike a target material at the X-ray window. These electrons can then flow to ground or a positive voltage. The resulting electric current can flow from the thin film to and through the adhesive, and then to and through the housing. Therefore, high electrical conductivity of the thin film, the adhesive, and the housing is advantageous.

[0025] The X-ray windows described herein and the X-ray windows manufactured by the methods described herein may exhibit these useful properties. Each example may exhibit one, some, or all of these useful properties.

[0026] As in Fig. As shown, the X-ray window 10 may include a housing 11 with a flange 11f encircling an opening 11a. The housing 11 may comprise metal. Examples of materials for the housing 11 include iron, nickel, or both.

[0027] A thin film 12 can be disposed on the flange 11f and span the opening 11a. Examples of materials for the thin film 12 include beryllium, amorphous carbon, boron, silicon nitride, aluminum, or combinations thereof. The thin film 12 can consist of multiple layers, with each layer made of one or more of the aforementioned materials.

[0028] An adhesive 13 can be applied between an outer ring 12o of the thin film 12 and the flange 11f. The adhesive 13 can be an epoxy. The adhesive 13 can secure the thin film 12 to the housing 11. The adhesive 13 can be adjacent to the flange 11f. The adhesive 13 can be adjacent to the thin film 12. The adhesive 13 can form a hermetic seal between the flange 11f and the thin film 12.

[0029] The adhesive 13 can be made of materials that meet the above-mentioned properties of the X-ray window 10. The adhesive 13 can contain, for example, silver and carbon. The adhesive 13 can contain ≥ 30 wt% or ≥ 50 wt% silver. The adhesive 13 can contain ≤ 60 wt% silver or ≤ 70 wt% silver. The adhesive 13 can contain ≥ 0.01 wt% and ≤ 1 wt% graphene. An example of an adhesive 13 is G6E-HTNS, sold by Graphene Laboratories, Inc.

[0030] The adhesive 13 may contain ≥ 10 wt% and ≤ 30 wt% epoxy resin. The adhesive 13 may contain ≥ 10 wt% and ≤ 30 wt% methyl-5-norbornene-2,3-dicarboxylic anhydride (CAS 25134-21-8). The adhesive 13 may contain ≥ 1 wt% and ≤ 5 wt% glycerin (CAS 56-81-5). The adhesive 13 may contain ≥ 1 wt% and ≤ 5 wt% trimellitic anhydride (CAS 552-30-7). The adhesive 13 may contain ≤ 0.1 wt% imidazole (CAS 228-32-4).

[0031] The adhesive 13 may have a hardness that ensures a permanent hermetic seal between the flange 11f and the thin film 12. For example, the adhesive 13 may have a Shore hardness of at least 50 D, at least 60 D, at least 70 D, or at least 80 D.

[0032] The adhesive 13 may have a flexural modulus that helps reduce the elongation of the thin film during temperature fluctuations. For example, the adhesive 13 may have a flexural modulus of ≥ 50 MPa, ≥ 100 MPa, or ≥ 130 MPa. The adhesive 13 may have a flexural modulus of ≤ 200 MPa, ≤ 350 MPa, or ≤ 600 MPa.

[0033] The adhesive 13 may have a volume resistivity that allows electrical current to flow from the thin film 12 to the flange 11f. For example, the adhesive 13 may have a volume resistivity of ≤ 0.005 Ω-cm, ≤ 0.01 Ω-cm, or ≤ 0.1 Ω-cm.

[0034] The X-ray window made of the materials described here can withstand high temperatures. For example, the X-ray window can withstand temperatures of ≥ 250° C or ≥ 300° C without deterioration. Proceedings

[0035] A method for manufacturing an X-ray window may comprise some or all of the following steps: In a first step ( Fig. ) an adhesive 13 may be applied to a flange 11f of a housing 11, to an outer ring 12o of a thin film 12, or to both.

[0036] In a second step ( Fig. ), the thin film 12 can be placed on the flange 11f, wherein the thin film 12 spans an opening 11a enclosed by the flange 11f and the adhesive 13 is located between the thin film 12 and the flange 11f.

[0037] A third step ( Fig.) may include curing the adhesive 13 to create a hermetic seal between the thin film 12 and the flange 11f. Example minimum curing temperatures are ≥ 30° C, ≥ 45° C, or ≥ 55° C. Example maximum curing temperatures are ≤ 70° C, ≤ 90° C, ≤ 150° C, or ≤ 350° C. Example curing times are ≥ 30 minutes and ≤ five hours.

Claims

[1] An X-ray window comprising: a housing with a flange encircling an opening; a thin film disposed on the flange and spanning the opening; an adhesive between an outer ring of the thin film and the flange, the adhesive securing the thin film to the housing; and the adhesive contains silver and carbon. [2] The X-ray window of claim 1, wherein the adhesive is adjacent to the flange and the thin film and forms a hermetic seal between the flange and the thin film. [3] X-ray window according to claim 1, wherein the adhesive contains ≥ 10% by weight and ≤ 30% by weight of epoxy resin. [4] X-ray window according to claim 1, wherein the adhesive contains ≥ 30 weight percent and ≤ 60 weight percent silver. [5] X-ray window according to claim 1, wherein the adhesive contains ≥ 50 weight percent and ≤ 70 weight percent silver. [6] X-ray window according to claim 1, wherein the adhesive contains ≥ 0.01 weight percent and ≤ 1 weight percent graphene. [7] X-ray window according to claim 1, wherein the adhesive contains ≥ 10 wt% and ≤ 30 wt% methyl-5-norbornene-2,3-dicarboxylic anhydride. [8] X-ray window according to claim 1, wherein the adhesive contains ≥ 1% by weight and ≤ 5% by weight of glycerin. [9] X-ray window according to claim 1, wherein the adhesive contains ≥ 1% by weight and ≤ 5% by weight trimellitic anhydride. [10] X-ray window according to claim 1, wherein the adhesive contains ≤ 0.1% by weight of imidazole.

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