JP2021096087A - Contrast agent for nondestructive inspection and nondestructive inspection method - Google Patents

Abstract

To provide a contrast agent for nondestructive inspection which is easy for a user to handle and is available for various materials, and a nondestructive inspection method.SOLUTION: The contrast agent for nondestructive inspection infiltrates into voids of an inspection object to be radiographed by an industrial X-ray apparatus and includes a dispersion where metallic particles are dispersed in a solvent.SELECTED DRAWING: Figure 3

Description

The present invention relates to a non-destructive inspection contrast agent and a non-destructive inspection method.

Non-destructive inspection is performed for the purpose of product evaluation and durability evaluation for industrial products and materials used for their production. In non-destructive inspection, an industrial X-ray device is used to visualize the internal structure of the inspected object. Since the X-ray transmittance differs depending on the composition of the object and the thickness of the object, the inside of the object to be inspected is detected by irradiating the object to be inspected with X-rays and detecting the X-rays that have passed through the inspected object with an X-ray detector. You can get an image. In an X-ray photograph developed from an X-ray film, the part strongly hit by the X-ray appears black, so even when the digital image obtained through the X-ray detector is displayed on the display device, it is presented to the user as a black-and-white gradation image. I often do it.

A contrast agent for X-ray photography is used to visualize cracks generated on the surface or inside of the object to be inspected by X-ray photography (see Patent Document 1 and Non-Patent Document 1). The contrast medium is introduced into the object to be inspected before the X-ray imaging in order to emphasize the black-and-white difference and photograph a specific portion in the X-ray image represented by shades of black and white, for example. Contrast media are generally used in the medical field and contain substances that cause a difference in X-ray transmittance between the organ to be examined and the surrounding tissue. The contrast medium is roughly divided into a positive contrast medium and a negative contrast medium depending on the difference in the appearance on the X-ray image, that is, whether the portion in which the contrast medium is injected appears whiter or blacker than the periphery. In Non-Patent Document 1, application of barium-based and iodine-based contrast media, which are positive contrast media, to crack detection of concrete is studied. The barium-based contrast agent is used as a suspension by mixing barium sulfate particles with a suspending agent and further adding water. Further, as the iodine-based contrast agent, a compound having a triiodobenzene ring is dissolved in water and used as an aqueous solution.

Further, Patent Document 1 proposes an X-ray contrast agent composed of an aqueous solution of cesium carbonate as a contrast agent used for detecting cracks in concrete. Since elements with higher atomic numbers tend to have higher X-ray absorption capacity, the use of compounds containing cesium (Cs), which has a higher atomic number than calcium (Ca), which is the main component of cement, as a contrast medium has been studied. ing. The X-ray absorption capacity can be expressed by the following equation (1).

I / I ₀ = exp (−μρχ) ・ ・ ・ (1)
In addition, I: transmitted X-ray intensity, I ₀ : incident X-ray intensity, μ: mass absorption coefficient, ρ: density, χ: thickness of substance.

Japanese Unexamined Patent Publication No. 7-134084

Koji Otsuka, "Study on Detection of Fine Cracks in Reinforced Concrete by X-ray Contrast Imaging", JSCE Proceedings, August 1992, No. 451 / V-17, pp. 169-178

According to Non-Patent Document 1, the barium-based contrast medium has a high viscosity, and it is difficult to inject it into a fine gap. Due to the nature of the solution called suspension, water and barium sulfate particles separate over time, resulting in poor use stability. Therefore, it is not suitable for industrial application. Since the iodine-based contrast medium is an aqueous solution, there is no separation problem unlike the barium-based contrast medium, and the kinematic viscosity is smaller than that of the barium-based contrast medium. According to Non-Patent Document 1, it occurs in reinforced concrete. It has been confirmed that injection is possible even in a gap of 0.65 mm. However, contrast media used in the medical field are pharmaceutical products and are expensive, so that they cannot be easily obtained and used by everyone.

The aqueous solution containing cesium carbonate proposed as an X-ray contrast agent in Patent Document 1 is an easily available but strongly alkaline solution. Therefore, depending on the material of the inspected object, the inspected object itself may be melted and deformed by a chemical reaction with a strong alkali, and its use as a polymer substance is particularly restricted. Users are also required to handle the solution carefully to avoid chemical burns due to contact.

The present invention has been made to solve the above problems, and is a non-destructive inspection contrast agent that can be used for various materials because it has good penetration into fine voids of an object to be X-rayed. It is an object of the present invention to provide a non-destructive inspection method.

The first aspect of the present invention is a non-destructive inspection contrast agent that permeates the voids of an object to be X-rayed with an industrial X-ray apparatus, and is a dispersion liquid in which metal particles are dispersed in a solvent. Contrast medium for non-destructive inspection including.

A second aspect of the present invention is a non-destructive inspection method for an inspected object in which X-ray photography is performed with an industrial X-ray apparatus, in which a step of infiltrating a contrast agent into the voids of the inspected object and the inspected object are inspected. The step of installing an object between the X-ray irradiation unit and the X-ray detector in the industrial X-ray apparatus, and the X-ray detector that emits X-rays emitted from the X-ray irradiation unit and passes through the object to be inspected. The contrast agent comprises a step of detecting with the X-ray detector and a step of acquiring an X-ray image based on the X-ray detected by the X-ray detector, and the contrast agent is a non-destructive inspection contrast agent according to the first aspect of the present invention. It is a non-destructive inspection method.

According to the first aspect of the present invention, since it is a dispersion liquid in which metal particles are dispersed in a solvent, unlike a conventional barium-based contrast medium, it is separated over time due to the nature of the solution called the dispersion liquid. Problems can be reduced and usage stability can be improved. Since it has a lower viscosity than the conventional barium-based contrast medium, it can penetrate into fine gaps well. Fine structure by dispersing metal particles with high X-ray absorption ability in a solvent compared to plastics, polymer compounds, fibers, and composite materials, which are mainly composed of carbon (C), hydrogen (H), and oxygen (O). It is possible to provide a contrasting agent having improved visualization performance.

According to the second aspect of the present invention, a non-destructive inspection contrast medium containing a dispersion liquid in which metal particles are dispersed in a solvent is permeated into an object to be inspected, and X-ray photography is performed by an industrial X-ray apparatus. Therefore, in the X-ray image obtained by X-ray imaging, it becomes possible to visualize fine surface defects of the object to be inspected and fine internal piping that could not be detected by the conventional contrast medium.

It is a schematic diagram of the X-ray CT apparatus 1. It is explanatory drawing of the double pipe 30 which permeates a contrast medium. It is explanatory drawing of the double pipe 30 which permeates a contrast medium. It is an X-ray tomographic image of the XY plane at an arbitrary Z position of the double pipe 30 in which the contrast medium of the embodiment of the present invention is infiltrated and the double pipe 30 in which the contrast medium of the comparative example is infiltrated. It is a tomographic image which shows the penetration state into the through hole 33 of the contrast medium of the Example of this invention. It is a tomographic image showing the penetration state of the contrast medium of the comparative example into the through hole 33. It is a tomographic image of a glass plate that caused cracks. It is a tomographic image of a glass plate impregnated with the contrast medium of the embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Industrial X-ray equipment]
FIG. 1 is a schematic view of the X-ray CT apparatus 1.

The X-ray CT apparatus 1 includes an X-ray irradiation unit 11, an X-ray detector 12, and a rotation stage 13. In this X-ray CT apparatus 1, an object to be inspected is installed on a rotating stage 13 arranged between an X-ray irradiation unit 11 and an X-ray detector 12 arranged so as to face each other, and the inside is observed non-destructively. Is to do. The X-ray CT apparatus 1 whose inspection target is a machine part, a material used for an industrial product, or the like is also referred to as an industrial X-ray apparatus.

The X-ray irradiation unit 11 includes an X-ray tube as an X-ray source inside, and generates X-rays from the X-ray tube according to the tube voltage and tube current supplied from the high voltage generator 15. The high voltage generator 15 is controlled by the X-ray control unit 16, and the X-ray control unit 16 is connected to a personal computer PC in which control software for controlling the entire X-ray CT device is installed. The X-ray detector 12 is a combination of an image intensifier (I.I.) and a CCD camera, or an FPD (Flat Panel Detector), and is used as a personal computer PC via a CT image reconstruction calculation device 18. Be connected. The X-ray detector 12 is configured to be detachable from the rotating stage 13 in order to enlarge or reduce the fluoroscopic imaging region. Further, the rotary stage 13 can also be separated from the X-ray irradiation unit 11.

The rotary stage 13 rotates with the Z axis orthogonal to the X axis along the X-ray optical axis L connecting the X-ray irradiation unit 11 to the X-ray detector 12 as the rotation axis R, and is driven in the XY direction by the stage drive mechanism 14. Can be moved in the horizontal direction and the vertical direction in the Z direction. The stage drive mechanism 14 is connected to the personal computer PC via the stage control unit 17. The stage moving mechanism for positioning the object to be inspected in the apparatus is limited to the one arranged below the rotating stage 13 like the stage driving mechanism 14 described with reference to FIG. It may be provided on the rotating stage 13 instead of the one.

The object to be inspected installed on the rotating stage 13 rotates when the rotating stage 13 is given a rotation about the rotation axis R. At this time, the X-rays emitted from the X-ray irradiation unit 11 are transmitted from a predetermined angle around the object to be inspected, that is, from each direction corresponding to the set rotation angle of the rotation stage 13, and the X-ray detector. Detected by 12. The X-ray transmission data detected by the X-ray detector 12 is taken into the CT image reconstruction calculation device 18.

The CT image reconstruction arithmetic unit 18 is composed of a computer including a ROM, RAM, a hard disk, etc. as a storage device for storing programs, detection data of the X-ray detector 12, and the like, and a CPU as an arithmetic unit. .. In the CT image reconstruction calculation device 18, a tomographic image (CT image) of the object to be inspected sliced along the plane along the XY plane is constructed by using the captured X-ray transmission data for an arbitrary rotation angle. .. The CT image is transmitted from the CT image reconstruction calculation device 18 to the personal computer PC, and is used for three-dimensional image formation by the three-dimensional image construction program installed in the personal computer PC.

A display device 23 such as a liquid crystal display and an input device 22 including a keyboard 22a and a mouse 22b are connected to the personal computer PC. The keyboard 22a and the mouse 22b are used by the operator for input in various operations. The display device 23 displays the CT image transmitted from the CT image reconstruction calculation device 18 to the personal computer PC, and also displays the three-dimensional image constructed by using the CT image. The function of the CT image reconstruction arithmetic unit 18 may be integrated with the personal computer PC and realized by one computer as a peripheral device or software of the computer.

The configuration of the X-ray CT device 1 has been described as an industrial X-ray device, but as another industrial X-ray device, a subject is placed between an X-ray tube and an X-ray detector. There is an X-ray fluoroscope in which a non-rotating stage is arranged. Further, the X-ray detector 12 may be a combination of an image intensifier (I.I.) and a CCD camera, or an IP (imaging plate) or a film may be used in addition to the FPD. ..

[Contrast agent for non-destructive inspection]
The non-destructive inspection contrast agent (hereinafter referred to as a contrast agent) according to the present invention has X-rays of fine voids such as microstructures in the object to be inspected and minute defects such as cracks and cracks in the object to be inspected. In order to visualize it by radiography, it penetrates into the fine voids of the object to be inspected.

Examples of the object to be inspected to be impregnated with the contrast agent include polymer materials such as metal, ceramic and resin, and composite materials such as CFRP (Carbon Fiber Reinforced Plastics). The object to be inspected may be a test piece after a material test that gives a test force by a material tester, a test piece after an environmental test that artificially creates a meteorological environment condition or a specific usage environment, etc. It may be a part or the like that requires defect detection at the time of molding and confirmation of fine piping.

The contrast agent is a dispersion liquid in which metal particles are dispersed in a solvent. As the metal, a metal having a high X-ray absorption ability is preferable. The contrast of X-ray images arises from the different X-ray absorption rates of substances. Taking an X-ray film as an example, in an X-ray photograph in which the film is developed, a portion exposed to strong light appears blacker. The element having a higher atomic number has a higher ability to shield X-rays, and in an X-ray photograph, a portion where X-rays are less likely to pass through appears white. Examples of such a metal include those having an atomic number equal to or higher than that of aluminum (Al) in the third period of the periodic table of elements. Preferably, the atomic number of titanium (Ti) or higher in the 4th period of the periodic table of elements can be mentioned. More specifically, for example, titanium (Ti), nickel (Ni), copper (Cu), palladium (Pd), silver (Ag), tin (Sn), gold (Au), lead (Pb), cobalt ( Co), chromium (Cr), indium (In) can be mentioned.

The dispersion liquid can be produced as a colloidal solution, for example, by dropping an aqueous metal salt solution into a solution containing a dispersant and a reducing agent. As a method for producing a dispersion liquid of a colloidal solution, the method for producing a dispersion liquid described in JP-A-2015-3970 can be adopted. Examples of the metal salt when the metal is silver include silver acetate, silver carbonate, silver oxide, silver sulfate, silver nitrite, silver chlorate, silver sulfide, silver chromate, silver nitrate, silver dichromate and the like. Can be done. When the metal is a metal other than silver among the metals exemplified above, the corresponding compound can be mentioned as the metal salt. The metal salt added dropwise to the solution containing the dispersant and the reducing agent is reduced by the reducing agent to form metal particles. The dispersant is adsorbed on the surface of the metal particles to form colloidal particles, and the colloidal particles are uniformly dispersed in the solution to stabilize the colloidal solution. The average particle size of the metal particles is, for example, preferably about 0.5 to 300 nm (nanometers), more preferably 1 to 100 nm. Such metal particles having an average particle size of nanometer size are also referred to as metal nanoparticles.

Since the reducing agent residue and the dispersant are present in the colloidal solution in addition to the metal particles, cleaning is performed after the colloidal particles are formed. After that, a pH adjuster is added to prepare a dispersion having a final pH of 6-11. By adjusting the pH, the dispersion of metal particles can be stabilized. Further, by adjusting the pH to a neutral range (for example, pH 6 to 8), it becomes easy for the user to handle it, and it can be used as a contrast medium of various materials.

Examples of the solvent for dispersing the metal particles include water; an alcohol solvent such as ethanol, methanol, butanol, propanol and isopropanol; an ether solvent such as 1,4-dioxane and tetrahydrofuran (THF); and aroma such as pyridine and pyrrole. Group heterocyclic compound solvent; amide solvent such as N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMA); nitrile solvent such as acetonitrile; aldehyde solvent such as acetaldehyde. .. The type and amount of the solvent, the mixing ratio when two or more kinds of solvents are mixed, and the like are adjusted according to the metal concentration, the viscosity of the solution, the surface tension, and the like.

The dispersion liquid can be prepared by dispersing metal nanoparticles produced by a so-called thermal decomposition method in a suitable organic solvent (dispersion medium) in a suspended state. The thermal decomposition method is a method for producing metal nanoparticles by thermal decomposition of a metal-amine complex compound. The nanoparticles here mean that the size of the primary particles (average primary particle diameter) determined from the particle size distribution by the dynamic light scattering method is less than 1000 nm. Further, the size of the particles is intended to be the size excluding the protective agent (stabilizer) present (coating) on the surface. As a method for producing silver nanoparticles by a thermal decomposition method, the production method described in JP-A-2015-131991 can be adopted.

The metal-amine complex compound is produced by mixing an aliphatic hydrocarbon amine (protective agent) and a metal compound at room temperature. When the metal is silver, the metal compound is a carboxylic acid such as silver formate, silver acetate, silver oxalate, silver malonate, silver benzoate, and silver phthalate, which are easily decomposed by heating to produce metallic silver. Silver; silver halide such as silver fluoride, silver chloride, silver bromide, silver iodide; silver sulfate, silver nitrate, silver carbonate and the like can be used. Silver oxalate is preferable from the viewpoint that metallic silver is easily generated by decomposition and impurities other than silver are less likely to be generated. Silver oxalate is advantageous in that it has a high silver content, metallic silver can be obtained as it is by thermal decomposition without the need for a reducing agent, and impurities derived from the reducing agent are unlikely to remain. When the metal is a metal other than silver among the above-exemplified metals, the metal compound is easily decomposed by heating to produce the desired metal, for example, a metal carboxylate; a metal halide; Metal salt compounds such as metal sulfate, metal nitrate, and metal carbonate can be used. Of these, metal oxalates are preferably used from the viewpoint that metals are easily generated by decomposition and impurities other than metals are unlikely to be generated.

The silver nanoparticles produced by thermally decomposing a silver-amine complex compound at 80 to 120 degrees Celsius are, for example, 0.5 nm to 100 nm, preferably 0.5 nm to 50 nm, more preferably 0.5 nm to 35 nm, and further. It preferably has an average primary particle size of 0.5 nm to 32 nm or 0.5 nm to 25 nm.

By dispersing the metal nanoparticles produced by the thermal decomposition method in a suitable organic solvent (dispersion medium) in a suspended state, a dispersion liquid as a contrast agent composition can be prepared. Examples of the organic solvent for preparing the dispersion include aliphatic hydrocarbon solvents such as pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane and tetradecane; aromatics such as toluene, xylene and mesitylen. Hydrocarbon solvents; alcohol solvents such as methanol, ethanol, propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol and the like can be mentioned. The type and amount of the organic solvent, the mixing ratio when two or more kinds of solvents are mixed, and the like are adjusted according to the metal concentration, the viscosity of the solution, the surface tension, and the like.

Since the metal nanoparticles produced by the thermal decomposition method are stable coated metal nanoparticles coated with a protective agent, a dispersion liquid having excellent stability can be obtained. For example, a dispersion liquid having a silver concentration of 50% by weight in which silver nanoparticles produced using an aliphatic hydrocarbon amine as a protective agent is dispersed in an organic solvent causes aggregation and fusion at room temperature for a period of about 2 weeks. Not stable.

The content of the metal particles in the dispersion liquid as a contrast medium is preferably about 20 to 80% by weight. If the content of the metal particles is less than the lower limit, the X-ray absorption capacity is lowered due to the lack of metal density (ρ) when the contrast medium is infiltrated into the object to be inspected, and the contrast performance as the contrast medium is lowered. To do. Further, when the content of the metal particles is not more than the upper limit value, the viscosity of the contrast medium becomes high, and the permeability of the object to be inspected into the voids decreases. The content of the metal particles may be smaller as the atomic number of the metal is larger. When the metal of the metal particles is silver, the silver content is more preferably about 35 to 55% by weight.

Further, since the non-ionized metal particles themselves do not affect the pH of the solution, it is possible to supply the solution at a pH in the neutral range, which is easy for the user to handle. Furthermore, since the pH can be supplied as a solution in the neutral range, it becomes possible to provide a contrast agent for non-destructive inspection that can be used for various materials. In particular, by dispersing metal particles with high X-ray absorption capacity in a solvent compared to plastics, polymer compounds, fibers, and composite materials that are mainly composed of carbon (C), hydrogen (H), and oxygen (O), they are finer. It is possible to provide a contrast agent with improved structural visualization performance.

[X-ray CT imaging and evaluation]
(Evaluation 1)
The cracks generated in concrete, the carbon fibers constituting the composite material such as CFRP, and the voids on the adhesive surface between the carbon fibers and the plastic can be considered as capillaries extending from end to end of the object to be inspected. The results of examining the penetration of the contrast medium based on the capillary action by performing X-ray CT imaging after immersing a part of the object to be inspected in the contrast medium will be described below.

2 and 3 are explanatory views of the double pipe 30 for permeating the contrast medium. FIG. 2 is a plan view of the double pipe 30, and FIG. 3 is a view for explaining a state in which one end of the double pipe 30 is immersed in a contrast medium. FIG. 4 shows an X-ray tomographic image of the XY plane at an arbitrary Z position of the double pipe 30 impregnated with the contrast medium of the embodiment of the present invention and the double pipe 30 impregnated with the contrast medium of the comparative example. Is. FIG. 5 is a tomographic image showing a state of penetration of the contrast medium of the embodiment of the present invention into the through hole 33. FIG. 6 is a tomographic image showing the penetration state of the contrast medium of the comparative example into the through hole 33. In the tomographic image display settings of FIGS. 4 to 6, the portion having a high X-ray absorption rate is displayed in white, and the portion having a low X-ray absorption rate is displayed in black.

As shown in FIGS. 2 and 3, the object to be inspected is PEEK (poly) in which a through hole 33 having an inner diameter of 50 μm (micrometer) is formed in a pipe 31 of alloy steel (SUS) containing chromium and nickel in iron. It is a double pipe 30 into which a pipe 32 made of (ether ether ketone) resin is inserted. One end of the double pipe 30 is immersed in a contrast medium. After that, the permeation state of the contrast medium into the through hole 33 is confirmed by the tomographic image acquired by the X-ray CT imaging by the X-ray CT apparatus 1.

The contrast agent of this example is a silver nanoparticle dispersion liquid having 50% by weight of silver particles in which silver nanoparticles having an average particle diameter of 20 to 60 nm are dispersed in a hydrocarbon / alcohol-based mixed solvent, and has a viscosity of 8.0. It is about 12.0 mPa · s (millipascal seconds). As such a contrast agent, for example, silver nanoparticle ink "Picosil" manufactured by Daicel Corporation (Picosil is a registered trademark of Daicel Corporation) can be adopted. As shown in FIG. 2, by immersing one end of the double pipe 30 in this contrast medium for 3 minutes, the contrast medium was infiltrated into the through hole 33 to obtain an object to be inspected for X-ray CT imaging. As the contrast medium of the comparative example, an aqueous solution of cesium carbonate having a concentration of 50%, which has been conventionally known as a contrast medium for detecting cracks in concrete, was used. One end of the double pipe 30 was immersed in the contrast medium of the comparative example for 15 minutes to prepare an object to be inspected for X-ray CT imaging.

The X-ray CT imaging was performed at the same time by arranging the double pipe 30 immersed in the contrast medium of this example and the double pipe 30 immersed in the contrast medium of the comparative example side by side on the rotating stage 13. .. In FIG. 4, the right side of the paper surface is the double pipe 30 immersed in the contrast medium of this example, and the left side of the paper surface is the double pipe 30 immersed in the contrast medium of the comparative example.

In an X-ray image, contrast is basically added by the difference in X-ray absorption of a substance. The mass absorption coefficient of a substance having a higher atomic number tends to be higher, and the X-ray absorption coefficient is higher as the mass absorption coefficient of the substance is higher. Since the pipe 31 is SUS containing iron, nickel, etc., the X-ray absorption rate is higher than that of other regions, and the tomographic image obtained by X-ray CT imaging shows white. Since the main constituent elements of plastics such as PEEK resin forming the pipe 32 are carbon (C), hydrogen (H), and oxygen (O), the X-ray absorption rate is lower than that of other regions, and X In the tomographic image obtained by line CT imaging, it appears black. The contrast medium of this example contains silver having an atomic number larger than that of the PEEK resin, and the cesium of the cesium carbonate solution of the comparative example also has an atomic number larger than that of the PEEK resin. If the contrast medium is sucked up into the through hole 33, the shape of the through hole 33 appears white in the tomographic image obtained by X-ray CT imaging.

In the tomographic image shown in FIG. 5, the shape of the through hole 33 appears white, and the through hole 33 reaches the end opposite to the side where the silver nanoparticle dispersion liquid is immersed in the contrast medium of the double pipe 30. It was confirmed that it had penetrated inside. That is, the contrast medium of this embodiment is not injected into the test object in a state where pressure is applied to the contrast medium using a syringe or the like, but the contrast medium is permeated into the voids of the test object by capillary action. It was confirmed that The solvent of the cesium carbonate solution as a comparative example is 100% water, whereas the solvent of the dispersion liquid of the present invention preferably has a surface tension smaller than that of water. Specifically, since the surface tension of water is 72 mN / m (millinewton per meter), the surface tension of the solvent of the dispersion is preferably 50 mN / m or less, and further 35 mN / m or less. Is more preferable. The mixing ratio of the hydrocarbon / alcohol-based mixed solvent as the solvent of the dispersion liquid of this example is adjusted so as to be within a preferable range of surface tension.

On the other hand, in the tomographic image shown in FIG. 6, the cesium carbonate solution is sucked up into the through hole 33 only about 0.1 mm on the side of the double pipe 30 immersed in the contrast medium. Further, when comparing FIGS. 5 and 6 in which CT images are taken at the same time, there is no difference in the contrast between the PEEK resin region of the pipe 32 and the region of the through hole 33 in which the contrast medium has penetrated between the examples and the comparative examples. .. That is, the dispersion liquid in which the metal particles are dispersed has higher permeability to fine voids than the cesium carbonate solution, and a tomographic image having the same contrast as the cesium carbonate solution can be obtained.

From the results of the above-mentioned X-ray CT imaging, it was confirmed that the dispersion liquid in which the metal particles were dispersed was effective as a contrast agent used for non-destructive inspection.

(Evaluation 2)
Next, another evaluation of the effectiveness of crack detection by the contrast medium according to the present invention will be described. In this evaluation, a commercially available slide glass (glass plate) for microscopic observation with cracks was used as the object to be inspected. FIG. 7 is a tomographic image of a glass plate in which a crack is generated. FIG. 8 is a tomographic image of a glass plate impregnated with a contrast medium according to an embodiment of the present invention. In the tomographic image display settings of FIGS. 7 and 8, the portion having a high X-ray absorption rate is displayed in white, and the portion having a low X-ray absorption rate is displayed in black.

The glass plates of FIGS. 7 and 8 are the same glass plates. In the tomographic image of FIG. 8, after X-ray CT imaging of the glass plate not impregnated with the contrast medium of FIG. 7, the contrast medium is dropped on the starting point of the crack generated in the glass plate, and the surplus is removed. It was obtained by performing X-ray CT imaging under the same conditions as in the case of 7. By comparing FIGS. 7 and 8 in the same cross section, the effectiveness of crack detection by a contrast medium was examined.

In the tomographic image of the glass plate impregnated with the contrast medium in FIG. 7, the cracked portion is in a state of nothing, that is, it is a void without a substance that absorbs X-rays, so that it appears blacker than the glass region. On the other hand, in the tomographic image shown in FIG. 8, the crack portion appears brighter (whiter) than the surrounding glass region, and it can be confirmed that the silver nanoparticle dispersion liquid dropped on the crack starting point has permeated. In addition, the indistinct crack portion indicated by the arrow in FIG. 7 is clear in FIG. 8 in which the contrast medium is infiltrated, as compared with the tomographic image of FIG. 7 which is the result of CT imaging before the contrast medium is infiltrated. It became possible to observe. That is, it was confirmed that the dispersion liquid in which the metal fine particles were dispersed permeated into the fine voids, and a tomographic image having a large contrast was obtained as compared with the case where the contrast medium was not permeated.

From the results of the above-mentioned X-ray CT imaging, it was confirmed that the dispersion liquid in which the metal fine particles were dispersed was effective as a contrast agent used for detecting cracks in the object to be inspected.

[Aspect]
It will be understood by those skilled in the art that the above-described exemplary embodiments are specific examples of the following embodiments.

(Item 1) The contrast agent for non-destructive inspection according to one aspect is a contrast agent that penetrates into the voids of an object to be X-rayed by an industrial X-ray apparatus, and metal particles are dispersed in a solvent. Contains a dispersion of

According to the non-destructive inspection contrast medium described in item 1, since it is a dispersion liquid in which metal particles are dispersed in a solvent, unlike conventional barium-based contrast media, due to the nature of the solution, which is a dispersion liquid, The problem of separation over time can be reduced and use stability can be improved. Since it has a lower viscosity than conventional barium-based contrast media, it can be easily injected into minute gaps. Fine structure by dispersing metal particles with high X-ray absorption ability in a solvent compared to plastics, polymer compounds, fibers, and composite materials, which are mainly composed of carbon (C), hydrogen (H), and oxygen (O). It is possible to provide a contrasting agent having improved visualization performance. The voids of the test object include microspaces that are not filled with solids and liquids, such as cracks, defects, and microstructures on the surface and / or inside of the test object.

(Item 2) In the contrast medium for non-destructive inspection according to item 1, the metal particles have an average particle size of 0.5 nm or more and 300 nm or less.

According to the contrast medium for non-destructive inspection described in item 2, the metal particles are fine metal particles having an average particle size of 0.5 nm or more and 300 nm or less and having a particle shape within a predetermined range. Penetration of the object to be inspected into the fine voids becomes better.

(Item 3) In the non-destructive inspection contrast agent according to item 1, the metal particles are at least one kind of metal selected from the elements having atomic numbers equal to or higher than aluminum in the third period of the periodic table.

According to the non-destructive inspection contrast agent described in Section 3, the elements having atomic numbers higher than that of aluminum in the third period of the periodic table are mainly carbon (C), hydrogen (H), and oxygen (O). Since it is an element having an atomic number higher than that of plastic and carbon fiber, it is possible to provide an effective contrast agent for crack detection of a product composed of plastic and carbon fiber by selecting at least one kind of metal from these elements. it can.

(Item 4) In the non-destructive inspection contrast agent according to item 1, the metal particles are at least one kind of metal selected from elements having atomic numbers equal to or higher than titanium in the fourth period of the periodic table.

According to the non-destructive inspection contrast agent described in Section 4, the elements having atomic numbers higher than that of titanium in the 4th period of the periodic table are higher than calcium (Ca) and silicon (Si), which are the main constituents of cement. Since it is an element having a large atomic number, it is possible to provide a contrasting agent effective for detecting cracks and cracks in concrete by selecting at least one kind of metal from these elements.

(Item 5) In the contrast medium for non-destructive inspection according to any one of items 1 to 4, the solvent is water or an organic solvent.

According to the non-destructive inspection contrast medium described in item 5, the metal particles are dispersed in an appropriate solvent (dispersion medium) according to the material of the object to be inspected and the properties of the metal, thereby forming the inside of the object to be inspected. It is possible to penetrate more into the fine voids.

(Section 6) A non-destructive inspection method for an object to be inspected, in which an X-ray image is taken with an industrial X-ray apparatus, in which a step of infiltrating a contrast agent into the voids of the inspected object and the inspected object are subjected to the industry. A step of installing between the X-ray irradiation unit and the X-ray detector in the X-ray apparatus for use, and a step of detecting the X-rays irradiated from the X-ray irradiation unit and passing through the object to be inspected by the X-ray detector. The contrast agent comprises a step of acquiring an X-ray image based on the X-ray detected by the X-ray detector, and the contrast agent is a non-destructive inspection contrast according to any one of items 1 to 5. It is an agent.

According to the non-destructive inspection method according to the sixth item, a contrast medium for a non-destructive inspection containing a dispersion liquid in which metal particles are dispersed in the solvent according to any one of the first to fifth items is used as an object to be inspected. Because the image is taken with an industrial X-ray device, the X-ray image obtained by X-ray photography is covered by the difference in color due to the difference in X-ray absorption capacity, which could not be detected by conventional contrast media. It is possible to visualize minute surface defects of the inspection object and fine piping inside. The X-ray image includes a fluoroscopic image (still image) obtained by simple imaging, a three-dimensional image constructed from X-ray transmission data obtained by CT imaging, and a tomographic image thereof.

The above description is for the purpose of explaining the embodiment of the present invention, and does not limit the present invention.

1 X-ray CT device 11 X-ray irradiation unit 12 X-ray detector 13 Rotating stage 14 Stage drive mechanism 15 High voltage generator 16 X-ray control unit 17 Stage control unit 18 CT image reconstruction calculation device 22 Input device 23 Display device 30 Double piping 31 piping 32 piping 33 through hole PC personal computer

Claims (6)

A non-destructive inspection contrast agent that permeates the voids of an object to be X-rayed with an industrial X-ray apparatus and contains a dispersion liquid in which metal particles are dispersed in a solvent. In the non-destructive inspection contrast agent according to claim 1,
The metal particles are non-destructive inspection contrast agents having an average particle size of 0.5 nm or more and 300 nm or less. In the non-destructive inspection contrast agent according to claim 1,
A non-destructive inspection contrast agent, wherein the metal particles are at least one kind of metal selected from elements having an atomic number higher than that of aluminum in the third period of the periodic table. In the non-destructive inspection contrast agent according to claim 1,
The metal particle is a non-destructive inspection contrast agent, which is at least one kind of metal selected from elements having an atomic number of titanium or higher in the fourth period of the periodic table. In the non-destructive inspection contrast agent according to any one of claims 1 to 4.
A contrast agent for non-destructive inspection, wherein the solvent is water or an organic solvent. It is a non-destructive inspection method for objects to be inspected that performs X-ray photography with an industrial X-ray device.
The step of infiltrating the contrast medium into the voids of the object to be inspected,
The step of installing the object to be inspected between the X-ray irradiation unit and the X-ray detector in the industrial X-ray apparatus, and
A step of detecting X-rays irradiated from the X-ray irradiation unit and passing through the object to be inspected by the X-ray detector, and
The step of acquiring an X-ray image based on the X-ray detected by the X-ray detector, and
Including
The non-destructive inspection method, wherein the contrast medium is the non-destructive inspection contrast medium according to any one of claims 1 to 5.

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