Radiation degradation resistant inorganic oxide flake

Abstract

To provide an inorganic oxide flake excellent in radiation degradation resistance.SOLUTION: An inorganic oxide flake excellent in radiation degradation resistance includes SiO2, Al2O3, CaO, and Fe2O3 as principal constituents, where i) a total of SiO2 and Al2O3 is 40 mass% or more and 70 mass% or less, ii) Al2O3 / (SiO2+Al2O3) (a mass ratio) is in a range of 0.15 to 0.40, iii) Fe2O3 is 16 mass% or more and 25 mass% or less, and iv) CaO is 5 mass% or more and 30 mass% or less, in the inorganic oxide flake by oxide conversion.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to novel inorganic oxide flakes. More specifically, it relates to inorganic oxide flakes having excellent radiation degradation resistance.

Background Art

[0002] Glass flakes are widely used today as industrial materials. For example, when glass flakes are blended into a thermosetting resin constituting a lining material, the penetration of corrosive substances into the lining coating film layer is suppressed, so that the anticorrosion performance of the lining material is remarkably improved. Therefore, glass flakes are indispensable as a secondary raw material for heavy-duty anticorrosion lining materials. In addition, glass flakes are used as a reinforcing material or a filler for thermoplastic resins in the same manner as glass fibers. While glass fiber-reinforced resins are likely to have anisotropy in the mechanical strength and thermal shrinkage of molded products, molded products of glass flake-reinforced resins have less such anisotropy and are excellent in dimensional accuracy. Therefore, glass flakes are also indispensable as a secondary raw material for materials for precision equipment. In recent years, glass flakes with improved chemical durability (for example, International Patent Publication WO 2010 / 024283 A1 (Patent Document 1), corresponding US Patent Publication US 2011 / 0151261 A1 (Patent Document 2)), glass flakes with enhanced visible light absorption performance (for example, International Patent Publication WO 2004 / 076372 A1 (Patent Document 3), corresponding US Patent Publication US 2006 / 0048679 A1 (Patent Document 4)), etc., glass flakes with improved characteristics according to the intended use have been disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

[0004] However, since the base material of glass flakes is glass, they have the drawback of deteriorating when exposed to radiation. If the radiation degradation resistance of glass flakes can be improved, it would be possible to use them in equipment, devices, parts, and components that are exposed to radiation over a long period, such as nuclear power generation facilities and space equipment, and the applications would be expected to expand further. Therefore, the present inventor has worked on the development of a new inorganic oxide flake that replaces glass flakes and has excellent radiation degradation resistance. [Means for Solving the Problems]

[0005] As a result, the present inventor has found that in flakes made of inorganic oxides, when the total content of SiO 2 and Al 2 O 3 is within a specific range, the ratio of Al 2 to Al 2 O 3 in the total of SiO 2 O 3 is within a specific range, and further, when the contents of Fe 2 O 3 and CaO are each within a specific range, they become flakes with excellent radiation degradation resistance, and thus the present invention has been completed. That is, the present invention is an inorganic oxide flake containing SiO 2 , Al 2 O 3 , CaO, and Fe 2 O 3 as main components, in the above inorganic oxide flake in terms of oxide conversion, i) SiO 2 and Al 2 O 3The total is 40% by mass or more and 70% by mass or less, and ii) SiO 2 and Al 2 O 3 in the total of, the proportion (mass ratio) of Al 2 O 3 is in the range of 0.15 to 0.40, and iii) Fe 2 O 3 is 16% by mass or more and 25% by mass or less, and iv) CaO is 5% by mass or more and 30% by mass or less, which is characterized by the above. Since the inorganic oxide flakes of the present invention are excellent in radiation degradation resistance, they are suitable as a reinforcing material or a filler for a material constituting a radiation-irradiated part. As another aspect of the present invention, there is provided a method for producing inorganic oxide flakes excellent in radiation degradation resistance using industrial wastes such as fly ash, copper slag, and steel slag as raw materials. In the following description, i) to iv) above may be abbreviated as "the four requirements of the present invention related to the composition".

[0006] The inorganic oxide flakes of the present invention are obtained by melting a mixture of various inorganic oxides as raw materials and flaking the melt. Here, there is no substantial difference between the component ratio of the raw material mixture (hereinafter, may be simply abbreviated as the mixture) and the component ratio of the flakes obtained from the melt. Therefore, the component ratio of the raw material mixture can be used as the component ratio of the flakes. The inorganic oxide flakes of the present invention have SiO in the flakes 2 , Al 2 O 3 , Fe 2 O 3 , and CaO in the following ranges. After blending the raw materials, the mixture is melted to obtain the melt. Hereinafter, the melt of the raw material mixture may be simply referred to as the melt.

[0007] SiO in the inorganic oxide flakes of the present invention 2 and Al 2 O 3The total content of SiO is 40% by mass or more and 70% by mass or less. 2 is abbreviated as S component, and SiO 2 The content of Al may be expressed as [S]. 2 O 3 is abbreviated as A component, and Al 2 O 3 The content of [S] and [A] is sometimes expressed as [A]. If the total of [S] and [A] is outside the above range, i.e., if it is less than 40% by mass or more than 70% by mass, the melting temperature of the blend will be too high, or the viscosity of the melt will be too high or too low, making it difficult to form flakes.

[0008] In the inorganic oxide flakes of the present invention, SiO 2 and Al 2 O 3 Al in the total 2 O 3 The ratio ([A] / ([A]+[S])) (mass ratio) of SiO must be in the range of 0.15 to 0.40. 2 and Al 2 O 3 Al in the total 2 O 3 If the ratio is either less than 0.15 or more than 0.40, the blend is difficult to melt or the melt is difficult to flake.

[0009] In the inorganic oxide flakes of the present invention, Fe 2 O 3 The content of Fe must be 16 mass% or more. 2 O 3 If the Fe content of the inorganic oxide flakes is less than 16% by mass, the flakes have poor resistance to radiation deterioration. On the other hand, if the Fe content exceeds 25% by mass, the viscosity of the melt is too low, making it difficult to form the melt into flakes. 2 O 3 The content is preferably 25 mass % or less. From now on, Fe 2 O 3 is abbreviated as F component, and Fe 2 O 3The content of [F] may be indicated as [F].

[0010] In the inorganic oxide flakes of the present invention, the content of CaO is preferably 5% by mass or more and 30% by mass or less. When the content of CaO is less than 5% by mass, the melting start temperature of the blend increases, and the energy required for producing the inorganic oxide flakes increases, which is not preferable. The content of CaO is preferably 10% by mass or more. On the other hand, when the content of CaO exceeds 30% by mass, the viscosity of the melt is too low, making it difficult to form flakes. Hereinafter, CaO may be abbreviated as component C, and the content of CaO may be indicated as [C].

[0011] When obtaining the inorganic oxide flakes of the present invention, SiO 2 , Al 2 O 3 , Fe 2 O 3 , and as long as the ratio of CaO falls within the above range, there are no restrictions on the raw materials. Therefore, SiO 2 , Al 2 O 3 , Fe 2 O 3 , and each of CaO alone may be formulated as a starting material, but it is preferable in terms of cost to use a starting material prepared by blending a silica source rich in SiO 2 content, an alumina source rich in Al 2 O 3 content, an iron oxide source rich in Fe 2 O 3 content, and a calcium oxide source rich in CaO content. Examples of the silica source include, but are not limited to, amorphous silica, silica sand, fumed silica, and volcanic ash. Examples of the alumina source include, but are not limited to, alumina, mullite, and other ores. Examples of the silica-alumina source rich in both silica and alumina include, but are not limited to, kaolinite, montmorillonite, feldspar, and zeolite. Examples of the iron oxide source include, but are not limited to, iron oxide, iron hydroxide, and iron ore. Examples of the calcium oxide source include, but are not limited to, calcium carbonate, calcite, dolomite, and other ores.

[0012] In addition to the above, thermal power generation waste and metal refining waste can also be effectively used as one of the silica source, alumina source, iron oxide source, or calcium oxide source. As the above thermal power generation waste, fly ash and clinker ash can be used. Fly ash and clinker ash are rich in SiO 2 , Al 2 O 3 and are thus suitable as a silica-alumina source. However, since fly ash and clinker ash have a low Fe 2 O 3 content, it is difficult to obtain the inorganic oxide flakes of the present invention only with them. However, by adding an appropriate amount of an iron oxide source, the inorganic oxide flakes of the present invention can be obtained at low cost. Note that coal gasification slag (CGS: Coal Gasification Slag) produced as waste from integrated coal gasification combined cycle (IGCC) also has a chemical composition almost equivalent to that of fly ash and can thus be a silica-alumina source. Since coal gasification slag is granular, it has the advantage of excellent handleability. Examples of the metal refining waste mentioned above include steel slag and copper slag. Since steel slag has a high CaO content, it can be used as a calcium oxide source. Steel slag includes blast furnace slag, converter slag, and reducing slag. Since copper slag has a high Fe 2 O 3 content, it can be used as an iron oxide source. Therefore, appropriately, fly ash, clinker ash, or coal gasification slag can be used as the silica-alumina source, copper slag can be used as the iron oxide source, and steel slag can be used as the calcium oxide source. In a preferred embodiment, most of the silica-alumina source, iron oxide source, and calcium oxide source can be covered by industrial wastes such as such thermal power generation waste and metal refining waste. In addition, volcanic rocks typified by basalt and andesite can also be used as a silica-alumina source.

[0013] The inorganic oxide flakes of the present invention do not exclude the incorporation of inevitable impurities contained in the raw materials. Such impurities include MgO, Na 2 O, K 2 O, TiO 2 , CrO 2 etc. can be exemplified.

[0014] Since the inorganic oxide flakes of the present invention are rich in amorphousness, there is almost no strength reduction due to the peeling at the crystal phase / amorphous phase interface, and high-strength inorganic oxide flakes can be obtained. Here, the degree of amorphization as a measure of amorphousness is calculated by the following mathematical formula (1) from an X-ray diffraction (XRD) spectrum. Degree of amorphization (%) = [Ia / (Ic + Ia)] × 100 (1) (In the mathematical formula (1), Ic is the sum of the integrated values of the scattering intensities of the crystalline peaks when X-ray diffraction analysis is performed on the inorganic material, and Ia is the sum of the integrated values of the scattering intensities of the amorphous halo.) The degree of amorphization of the inorganic oxide flakes of the present invention usually shows a value of 90% or more, although it depends on the composition. When the degree of amorphization is high, it reaches 95% or more, and in the highest case, the flakes consist substantially of only the amorphous phase. Here, consisting substantially of only the amorphous phase means that only an amorphous halo is recognized in the X-ray diffraction spectrum and no peak of the crystalline phase is recognized.

[0015] The radiation degradation resistance of the inorganic oxide flakes of the present invention can be known by comparing the Vickers hardness of the inorganic oxide flakes before and after radiation irradiation.

Advantages of the Invention

[0016] According to the present invention, inorganic oxide flakes excellent in radiation resistance deterioration are created.

Brief Description of Drawings

[0017]

Figure 1

Embodiments for Carrying Out the Invention

[0018] Hereinafter, the content of the present invention will be specifically described with test examples. In the following test examples (Examples and Comparative Examples), the following are used as a silica source, an alumina source, a silica alumina source, an iron oxide source, and a calcium oxide source. <Silica source> · Silicon dioxide: reagent (hereinafter, SiO 2 (reagent) may be used for notation) <Alumina source> · Aluminum oxide: reagent (hereinafter, Al 2 O 3 (reagent) may be used for notation) <Silica alumina source> · Fly ash RM1: fly ash containing Fe 2 O 3 : 9%, SiO 2 : 62%, Al 2 O 3 : 18%, CaO: 3% by mass fraction <Iron oxide source> · Iron(III) oxide: reagent (hereinafter, Fe 2 O 3 (reagent) may be used for notation) · Copper slag RM2: copper slag containing Fe 2 O 3 : 9%, SiO 2 : 62%, Al 2 O 3 : 18%, CaO: 3% by mass fraction <Calcium oxide source> · Calcium oxide: reagent (hereinafter, CaO (reagent) may be used for notation) · Steel slag RM3: Fe by mass fraction of 100 2 O 3 : 1%, SiO 2 : 19%, Al 2 O 3 : 17%, CaO: 55% steel slag containing In addition, the component analysis of the above copper slag, steel slag, and fly ash is based on the fluorescence X-ray analysis method.

[0019] <Adjustment of powder raw materials> In the following test examples, each of the silica source, alumina source, iron oxide source, and calcium oxide source is finely pulverized, and SiO 2 , Al 2 O 3 , Fe 2 O 3 , and CaO are blended so as to have a predetermined ratio and subjected to the test.

[0020] <Flaking test> The blend is subjected to a flaking test (evaluation of flaking processability) according to the following procedure. The outline of the test is shown in Figure 1. According to the following steps 1 to 4, the blend is melted and an attempt is made to flake the melt. Step 1: Charge approximately 60 grams of the inorganic oxide blend (fp) that is the raw material for the flakes into a crucible (1) with a diameter (D1) of 20 mm. Separately, prepare a Therman tube (2) with a diameter (D2) of 10 mm. The Therman tube (2) has an opening (21) with a diameter (Φ) of 2 mm at the bottom (upper part of Figure 1). Step 2: Heat the crucible (1) charged with the blend (fp) in an electric furnace (3) (left in the middle part of Figure 1). The electric furnace is heated according to a predetermined temperature rising program. The maximum temperature reached in the furnace is set at 1350 °C. It has been confirmed in advance that the temperature inside the crucible (1) and the melt (fm) follows a temperature approximately 50 °C lower than the furnace temperature. Step 3: Immediately remove the heated crucible (1) from the electric furnace (3), and push the Therman tube (2) downward from the upper part of the crucible (1). The inorganic oxide melt (fm) in the crucible (1) enters the inside of the Therman tube (2) through the opening (21) (right in the middle part of Figure 1). Step 4: Then, air is blown into the mouth (22) of the thimble tube (2) storing the melt (fm) at a pressure of about 10 MPa (lower left in Figure 1). When the melt (fm) has an appropriate viscosity, the melt swells to form a balloon (fb) of a hollow thin film (lower right in Figure 1). The balloon is crushed to obtain flakes. Based on the results of the flaking test by the above procedure, the flake processability is ranked as A, B, and C below. <Evaluation of flake processability> A: Through steps 1 to 4, a balloon is formed. B: Although reaching step 3 from step 1, since the viscosity of the melt is low, a balloon is not formed in step 4. C: Either the melting of the formulation (fp) does not start up to step 2, or since the viscosity of the melt is high, the melt does not enter the inside of the thimble tube (2) from the opening (21) in step 3.

[0021] [Preliminary test] Prior to a series of tests, the following preliminary tests were conducted. After appropriately blending a silica source, an alumina source, an iron oxide source, and a calcium oxide source, four samples with different SiO 2 , Al 2 O 3 , Fe 2 O 3 , CaO contents were formulated to obtain their melt-solidified products. Samples 3 and 4 satisfy all of the requirements of the present invention described above, but samples 1 and 2 lack requirement iii) regarding the Fe 2 O 3 content (Table 1). Regarding the samples of the obtained melt-solidified products, a radiation irradiation test was conducted under the condition of a gamma-ray irradiation dose of 50 kGy using cobalt 60 as a radiation source, the micro-Vickers hardness before and after irradiation was measured, and the strength retention rate of the samples after radiation irradiation was determined. The results are shown in Table 1. This result strongly indicates that when the iron oxide (Fe 2 O 3 ) content in the sample is 15% or more, the strength retention rate after radiation irradiation becomes significantly high.

[0022]

Table 1

[0023] [Example 1] To fly ash RM1, an appropriate amount of SiO 2 (reagent), Al 2 O 3 (reagent), Fe 2 O 3 (reagent), and CaO (reagent) were blended. In the blend, the contents of SiO 2 , Al 2 O 3 , Fe 2 O 3 , and CaO were, in terms of oxide conversion, [S]+[A]: 42% by mass, [A] / ([S]+[A]): 0.20, [F]: 19% by mass, and [C]: 17% by mass. As a result of the flaking test, a balloon with a film thickness of about 800 nm was obtained. The balloon was pulverized to obtain flakes. Analysis of the X-ray diffraction (XRD) spectrum revealed that the flakes were substantially amorphous. Next, a sample of the flakes was irradiated with radiation having a dose of 100 GGy using an electron beam as the radiation source. For the flake samples before and after radiation irradiation, the Vickers hardness was measured in accordance with JIS Z 2244, and the strength retention rate after radiation irradiation was calculated. As a result, the strength retention rate of the flakes after radiation irradiation was 90%, indicating excellent radiation resistance degradation properties (Table 2).

[0024] [Examples 2 to 8] SiO 2 (reagent), Al 2 O 3 (reagent), Fe 2 O 3 (reagent), and CaO (reagent) were blended. By changing the blending amounts, in terms of oxide conversion, the total of SiO 2 and Al 2 O 3 , the total of SiO 2 and Al 2 O 3 , and the proportion of Al 2O 3 ratio (mass ratio), Fe 2 O 3 amount (mass %), CaO amount (mass %) were varied to prepare various raw material formulations, and the same flaking test as in Example 1 was conducted (Table 2). As a result, for all the formulations, the melt formed a hollow thin film balloon similar to that in Example 1 and showed good flaking processability. Also, as a result of analyzing the X-ray diffraction (XRD) spectrum, it was found that all the flake samples were substantially amorphous. Next, in the same manner as in Example 1, each flake sample was subjected to a radiation irradiation test, and the strength retention rate after radiation irradiation was determined. As a result, the strength retention rate was 90% or more in all cases, and the flakes were excellent in radiation resistance deterioration (Table 2).

[0025] [Table 2]

[0026] From Table 2, it is clear that flakes can be obtained from all the formulations that satisfy the "four requirements of the present invention related to the composition", and all the flakes are excellent in radiation resistance deterioration.

[0027] [Comparative Examples 1 to 8] SiO 2 (reagent), Al 2 O 3 (reagent), Fe 2 O 3 (reagent), CaO (reagent) were varied in the amounts of oxide conversion, SiO 2 and Al 2 O 3 total (mass %), SiO 2 and Al 2 O 3 ratio of Al 2 O 3 in the total of (mass ratio), Fe 2 O 3 amount (mass %), CaO amount (mass %) were varied to prepare raw material formulations, and attempts were made to conduct the same tests as in Example 1. The results are shown in Table 3.

[0028] [Table 3]

[0029] From Table 3, it can be seen that if any one of the "four requirements of the present invention related to the composition" is lacking, it is difficult to form flakes or the radiation resistance deterioration property of the obtained flakes is poor. That is, when the value of [S]+[A] is less than the lower limit of requirement i), the viscosity of the melt is too low, and as a result, flakes cannot be formed (Comparative Example 1). On the other hand, when the value of [S]+[A] exceeds the upper limit of requirement i), the viscosity of the melt is too high, so it is difficult to form flakes (Comparative Example 2). When the value of [A] / ([S]+[A]) is less than the lower limit of requirement ii), the viscosity of the melt is too low, and as a result, flakes cannot be formed (Comparative Example 3). When the value of [A] / ([S]+[A]) exceeds the upper limit of requirement ii), the viscosity of the melt is too high, so it becomes difficult to form flakes (Comparative Example 4). When the value of [F] is less than the lower limit of requirement iii), the radiation resistance deterioration property is poor (Comparative Example 5). The strength retention rate of the sample in Comparative Example 5 after radiation irradiation is 60%. When the value of [F] exceeds the upper limit of requirement iii), the viscosity of the melt is too low, and as a result, flakes cannot be formed (Comparative Example 6). When the value of [C] is less than the lower limit of requirement iv), the viscosity of the melt is too low, and as a result, flakes cannot be formed (Comparative Example 7). When the value of [C] exceeds the upper limit of requirement iv), the viscosity of the melt is too high, so flakes cannot be formed (Comparative Example 8).

[0030] [Example 9] In this example, a production example of inorganic oxide flakes excellent in radiation resistance deterioration property using fly ash, copper slag, and steel slag as industrial waste as raw materials is shown. 50 parts by mass of fly ash RM1 was blended as a silica-alumina source, 30 parts by mass of copper slag RM2 was blended as an iron oxide source, and 20 parts by mass of steel slag RM3 was blended as a calcium oxide source. In the blend, SiO 2 , Al 2 O 3 , Fe2 O 3 、and the contents of CaO, in terms of oxide conversion, are [S]+[A]: 59% by mass, [A] / ([S]+[A]): 0.23, [F]: 21% by mass, and [C]: 13% by mass. The said raw material formulation was subjected to the same test as in Example 1. As a result, the rank of flake processability was A, and the strength retention rate after radiation irradiation was 87%.

Industrial Applicability

[0031] The inorganic oxide flakes of the present invention are suitable as a reinforcing material or filler for resins and rubbers. Examples of the resin include thermoplastic resins and thermosetting resins. Examples of the thermoplastic resin include, but are not limited to, polypropylene, ABS resin, AS resin, polyphenylene ether, polyamide, polyamideimide, and polyketone. Examples of the rubber include thermoplastic rubbers. In addition, the inorganic oxide flakes of the present invention can be suitably used as a secondary raw material for improving the corrosion resistance of lining materials and paints. Examples of the base material for lining materials and paints include, but are not limited to, thermosetting resins such as vinyl ester resins and epoxy resins, and curable rubbers. The above-mentioned resins, rubbers, or coating materials blended with the inorganic oxide flakes of the present invention are excellent in radiation degradation resistance. Therefore, they are suitable as materials constituting a radiation-irradiated part. Representative examples of the radiation-irradiated part include equipment, devices, and members in the fields of nuclear power, aerospace, and medicine. As equipment, devices, and members in the nuclear power field, · Equipment, devices, and members for nuclear power generation, · Equipment, devices, and members for the mining and processing of uranium ore, · Equipment, devices, and members for the secondary processing of nuclear fuel (including the conversion, enrichment, re-conversion, shaping, and MOX production of the same fuel), · Equipment, devices, and members for the storage, processing, and reprocessing of spent nuclear fuel, · Equipment, devices, and members for the storage, processing, and disposal of radioactive waste, · Transport equipment and members for uranium ore, secondary processed nuclear fuel, spent nuclear fuel, or radioactive waste, ·Other nuclear-related facilities, equipment, and components may be mentioned. More specific examples of the above-mentioned facilities, equipment, and components for nuclear power generation include reactor buildings (including research reactors and test reactors), reactor containment vessels, in-pipe of reactor facilities, and decommissioning robots. As facilities, equipment, and components in the aerospace field, ·Space base buildings, space stations, artificial satellites, planetary exploration satellites, spacesuits, etc. may be mentioned. As facilities, equipment, and components in the medical field, ·Medical devices using particle beams can be mentioned. The above usage examples are illustrated for the purpose of showing the usefulness of the inorganic oxide flakes of the present invention and do not limit the scope of the present invention.

Explanation of symbols

[0032] 1 Crucible 2 Tharman tube 21 Opening 22 Mouth 3 Electric furnace D1 Diameter of the crucible H1 Height of the crucible D2 Diameter of the Tharman tube H2 Height of the Tharman tube Φ Diameter of the opening fp Raw material formulation, inorganic oxide formulation fm Melt, inorganic oxide melt fb Balloon P Load pressure

Claims

1. SiO 2 , Al 2 O 3 , CaO, and Fe 2 O 3 An inorganic oxide flake mainly composed of In the inorganic oxide flakes calculated as oxide, i) SiO 2 and Al 2 O 3 The total of is 40% by mass or more and 70% by mass or less, ii) Al 2 O 3 / (SiO 2 +Al 2 O 3 ) (mass ratio) is in the range of 0.15 to 0.40, iii) Fe 2 O 3 is 16% by mass or more and 25% by mass or less, iv) Radiation-deterioration-resistant inorganic oxide flakes, wherein CaO is 5% by mass or more and 30% by mass or less.

2. A composition comprising a thermoplastic resin or a thermoplastic rubber and the inorganic oxide flakes of claim 1 blended therein.

3. A composition comprising a thermosetting resin or a curable rubber and the inorganic oxide flakes of claim 1 blended therewith.

4. A lining material comprising the composition according to claim 3.

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