RADIATION RESISTANT INORGANIC OXIDE FLAKES

Abstract

[Object] To provide inorganic oxide flakes having excellent resistance to radiation damage. [Solving Means] Inorganic oxide flakes mainly composed of SiO.sub.2, Al.sub.2O.sub.3, CaO, and Fe.sub.2O.sub.3 are presented. The mass percentages of the components in terms of oxide in the flakes are set as follows: i) the sum of SiO.sub.2 and Al.sub.2O.sub.3 is from 40% by mass to 70% by mass; ii) the ratio Al.sub.2O.sub.3/(SiO.sub.2+Al.sub.2O.sub.3) (mass ratio) is in the range of 0.15 to 0.40; iii) the content of Fe.sub.2O.sub.3 is from 16% by mass to 25% by mass; and iv) the content of CaO is from 5% by mass to 30% by mass. The inorganic oxide flakes have enhanced resistance to radiation damage.

Claims

1. Inorganic oxide flakes mainly composed of SiO.sub.2, Al.sub.2O.sub.3, CaO, and Fe.sub.2O.sub.3, wherein the mass percentages of the components in terms of oxide in said inorganic oxide flakes are as follows: i) the sum of SiO.sub.2 and Al.sub.2O.sub.3 is 40% by mass or more and 70% by mass or less, ii) Al.sub.2O.sub.3/(SiO.sub.2+Al.sub.2O.sub.3) (mass ratio) is in the range of 0.15˜0.40, iii) Fe.sub.2O.sub.3 is 16% by mass or more and 25% by mass or less, and iv) CaO is not less than 5% by mass but not more than 30% by mass.

2. A composition obtained by blending the inorganic oxide flakes of claim 1 to a thermoplastic resin or thermoplastic rubber.

3. The composition according to claim 2 for a part to be irradiated with radiation.

4. A composition obtained by blending the inorganic oxide flakes of claim 1 to a thermosetting resin or curable rubber.

5. A lining material composed of the composition according to claim 4.

6. The lining material according to claim 5 for a part to be irradiated with radiation.

7. A method for producing inorganic oxide flakes comprising a step of melting a mixture of silica source, alumina source, calcium oxide source, and iron oxide source, wherein the mass percentages of the components in terms of oxide in said mixture are as follows: i) the sum of SiO.sub.2 and Al.sub.2O.sub.3 is 40% by mass or more and 70% by mass or less, ii) Al.sub.2O.sub.3/(SiO.sub.2+Al.sub.2O.sub.3) (mass ratio) is in the range of 0.15˜0.40, iii) Fe.sub.2O.sub.3 is 16% by mass or more and not more than 25% by mass, iv) CaO is 5% by mass or more and 30% by mass.

8. The method for producing the inorganic oxide flakes according to claim 7, wherein the silica source or alumina source is fly ash.

9. The method for producing inorganic oxide flakes according to claim 7, wherein the iron oxide source is copper slag.

10. The method for producing inorganic oxide flakes according to claim 7, wherein the calcium oxide source is steel slag.

11. The method for producing the inorganic oxide flakes according to claim 7, wherein the silica source or the alumina source is basalt or andesite.

12. Use of inorganic oxide flakes containing SiO.sub.2, Al.sub.2O.sub.3, CaO, and Fe.sub.2O.sub.3 for apart to be irradiated by radiation, wherein in said inorganic oxide flakes in terms of oxides, i) the sum of SiO.sub.2 and Al.sub.2O.sub.3 is 40% by mass or more and 70% by mass or less, ii) Al.sub.2O.sub.3/(SiO.sub.2+Al.sub.2O.sub.3) (mass ratio) is in the range of 0.15˜0.40, iii) Fe.sub.2O.sub.3 is 16% by mass or more and 25% by mass or less, and iv) CaO is 5% by mass and not more than 30% by mass.

13. The use of an inorganic oxide flakes for a part to be irradiated with radiation according to claim 12, wherein the part to be irradiated with radiation is any one of the following: a) a nuclear reactor building, a nuclear reactor containment vessel, piping inside a nuclear reactor facility, and a decommissioning robot; b) a space station building, a space station, an artificial satellite, a planetary exploration satellite, and a space suit; and c) medical devices utilizing particle beams.

Description

BRIEF DESCRIPTION OF DRAWING

[0049] FIG. 1 is a diagram showing an outline of the flake test.

MODE(S) FOR CARRYING OUT THE INVENTION

[0050] Hereinafter, the present invention will be specifically described with reference to Test Examples.

[0051] In the following Test Examples (Examples, Comparative Examples), the following materials are used as a silica source, an alumina source, a silica alumina source, an iron oxide source, and a calcium oxide source.

[0052] <Silica Source>

[0053] Silicon dioxide: Silicon dioxide reagent (hereinafter, may be referred to as SiO.sub.2 (reagent))

[0054] <Alumina Source>

[0055] Aluminum oxide: Aluminum oxide reagent (hereinafter, may be referred to as Al.sub.2O.sub.3 (reagent))

[0056] <Silica Alumina Source>

[0057] Fly ash RM1: Fly ash containing Fe.sub.2O.sub.3:9%, SiO.sub.2:62%, Al.sub.2O.sub.3:18%, CaO:3% by mass

[0058] <Iron Oxide Source>

[0059] Iron (III) oxide: Iron (III) oxide reagent (hereinafter, may be referred to as Fe.sub.2O.sub.3 (reagent))

[0060] Copper slag RM2: Copper slag containing Fe.sub.2O.sub.3:9%, SiO.sub.2:62%, Al.sub.2O.sub.3:18%, CaO:3% by mass

[0061] <Calcium Oxide Source>

[0062] Calcium oxide: Calcium oxide reagent (hereinafter, may be referred to as CaO (reagent))

[0063] Steel slag RM3: Steel slag containing Fe.sub.2O.sub.3:1%, SiO.sub.2:19%, Al.sub.2O.sub.3:17%, CaO:55% by mass

[0064] The component analysis of copper slag, steel slag, and fly ash is based on a fluorescent X-ray analysis method.

[0065] <Preparation of Powder Raw Materials>

[0066] In the following Test Example, each of the silica source, the alumina source, the iron oxide source, and the calcium oxide source is pulverized, and SiO.sub.2, Al.sub.2O.sub.3, Fe.sub.2O.sub.3, CaO are blended according to a predetermined ratio, and are subjected to the test.

[0067] <Flake Test>

[0068] The sample of the formulated raw materials is subjected to a flake test (evaluation of processability into flakes) according to the following steps 1 to 4 as stated below. An outline of the test is shown in FIG. 1.

[0069] Step 1: Approximately 60 grams of the formulated raw materials (fp), which is the raw material for flakes, is placed in a crucible (1) having a diameter (D1) of 20 mm. Separately, a Tammann tube (2) having a diameter (D2) of 10 mm is prepared. The Tammann tube (2) has an opening (21) having a diameter (D) of 2 mm at the bottom (upper part of FIG. 1).

[0070] Step 2: The crucible (1) in which the formulated raw materials (fp) is loaded is heated in the electric furnace (3) (middle left of FIG. 1). The electric furnace is heated by a predetermined temperature raising program. The maximum temperature inside the furnace is set to 1350° C. The temperature inside the crucible (1) and the melt (fin) is confirmed in advance at a temperature substantially 50° C. lower than the temperature inside the furnace.

[0071] Step 3: Immediately remove the crucible (1) after temperature rise from the electric furnace (3), and push the Tammann tube (2) downward from the upper part of the crucible (1). The melt (fin) in the crucible (1) enters the inside of the Tammann tube (2) through the opening (21) (middle right in FIG. 1).

[0072] Step 4: Subsequently, air is blown from the entrance (22) of the Tammann tube (2) storing the melt (fin) at a pressure of about 10 MPa (lower left in FIG. 1). When the melt (fm) has a moderate viscosity, the melt swells to form a hollow thin film balloon (fb) (lower right in FIG. 1). Flakes are obtained by crushing the balloon.

[0073] Based on the results of the flake test according to the above procedure, the flake processability is evaluated and ranked as A, B, or C as follows.

[0074] <Evaluation of Flake Processability> [0075] A: After step 1 to step 4, a balloon is formed. [0076] B: Although step 3 is reached from step 1, a balloon is not formed in step 4 because the viscosity of the melt is too low. [0077] C: Since the melting of the formulated raw materials (fp) does not start even after step 2 or the viscosity of the melt is too high, the melt does not enter the inside of the Tammann tube (2) from the opening (21) during step 3.

[0078] [Preliminary Test]

[0079] Prior to the series of Test Examples, the following preliminary tests were conducted.

[0080] Four types of samples having different SiO.sub.2, Al.sub.2O.sub.3, Fe.sub.2O.sub.3, CaO contents were prepared by appropriately blending a silica source, an alumina source, an iron oxide source, and a calcium oxide source.

[0081] Each of the four samples thereof was melted and solidified. Samples 3 and 4 satisfy all of the requirements i) to vi) of the present invention as described above, but samples 1 and 2 lack requirement iii) for Fe.sub.2O.sub.3 content (Table 1).

[0082] The sample of the solidified melt thus obtained was irradiated under the condition of a gamma irradiation amount of 50 kGy using cobalt 60 as a source, and the micro-Vickers hardness before and after irradiation was measured, and the strength retention rate of the sample after irradiation was determined.

[0083] The results are shown in Table 1. The results strongly indicate that when the iron oxide (Fe.sub.2O.sub.3) content in the sample is 15% or more, the strength retention rate after irradiation becomes remarkably enhanced.

TABLE-US-00001 TABLE 1 Sample Sample Sample Sample Unit 1 2 3 4 Fe.sub.2O.sub.3[F] mass % 3 11 16 19 SiO.sub.2[S] 51 52 48 42 Al.sub.2O.sub.3[A] 12 18 12 14 CaO[C] 20 9 17 13 Others 14 10 7 12 [S + A] mass % 63 70 60 56 [A]/([S] + [A]) mass 0.19 0.26 0.20 0.25 ratio [F] mass % 3 11 16 19 [C] 20 9 17 13 Strength retention rate 30 58 99 99 after irradiation[%]

Example 1

[0084] Fly ash RM1 was blended with an appropriate amount of SiO.sub.2 (reagent), Al.sub.2O.sub.3 (reagent), Fe.sub.2O.sub.3 (reagent), and CaO (reagent). The content of SiO.sub.2, Al.sub.2O.sub.3, Fe.sub.2O.sub.3, and CaO in the formulation is [S]+[A]: 42% by mass, [A]/([S]+[A]): 0.20, [F]: 19% by mass, [C]: 17% by mass.

[0085] As a result of the flake test, a balloon having a film thickness of about 800 nm was obtained. The balloon was crushed to obtain flakes.

[0086] Analysis of the X-ray diffraction (XRD) spectrum revealed that the flakes were substantially amorphous.

[0087] Next, the flake sample was irradiated with radiation having a dose of 100 GGy using an electron beam as a source.

[0088] The Vickers hardness was measured in accordance with JIS Z 2244 for flake samples before and after irradiation, and the strength retention rate after irradiation was calculated. As a result, the strength retention rate of the flakes after irradiation was 90%, and the resistance to radiation damage was excellent (Table 2).

Examples 2-8

[0089] By changing the blending ratio of SiO.sub.2 (reagent), Al.sub.2O.sub.3 (reagent), Fe.sub.2O.sub.3 (reagent), CaO (reagent), samples having different formulation in the values of i) the sum of SiO.sub.2 and Al.sub.2O.sub.3, ii) the ratio (mass ratio) of Al.sub.2O.sub.3 to the sum of SiO.sub.2 and Al.sub.2O.sub.3, iii) Fe.sub.2O.sub.3, or iv) CaO were prepared. Subsequently the same flake test as in Example 1 was performed on each of samples (Table 2).

[0090] As a result, for each of the formulations, the melt formed a hollow thin film balloon similar to that of Example 1, and showed good flake processability.

[0091] Analysis of the X-ray diffraction (XRD) spectrum revealed that all of the flake samples were substantially amorphous.

[0092] Subsequently, as in Example 1, each flake sample was subjected to a radiation irradiation test to determine the strength retention rate after irradiation. As a result, the strength retention rate was 90% or more in all cases, and the flakes were excellent in resistance to radiation damage (Table 2).

TABLE-US-00002 TABLE 2 Unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Components [S] + [A] Mass % 42 68 58 58 59 54 68 50 in flake [A]/([S] + [A]) Mass ratio 0.20 0.20 0.17 0.30 0.20 0.20 0.20 0.20 [F] Mass % 19 18 1.9 19 18 23 19 16 [C] 17 7 17 17 17 17 7 28 Evaluation Radiation Excellent Excellent Excellent Excellent Excellent Excellent Excellent Excellent item resistance Flake test A A A A A A A A

[0093] From Table 2, it is clear that flakes can be obtained from all of the formulations satisfying the “the four compositional requirements of the invention”, and that all flakes are excellent in resistance to radiation damage.

Comparative Examples 1˜8

[0094] By changing the blending ratio of SiO.sub.2 (reagent), Al.sub.2O.sub.3 (reagent), Fe.sub.2O.sub.3 (reagent), CaO (reagent), samples having different formulation in the values of i) the sum of SiO.sub.2 and Al.sub.2O.sub.3, ii) the ratio (mass ratio) of Al.sub.2O.sub.3 to the sum of SiO.sub.2 and Al.sub.2O.sub.3, iii) Fe.sub.2O.sub.3, or iv) CaO were prepared. Subsequently each sample was subjected to the same test as in Example 1.

TABLE-US-00003 TABLE 3 Com. Com. Com. Com. Com. Com. Com. Com. Unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Components [S] + [A] Mass % 38 72 44 58 63 50 70 46 in flake [A]/([S] + [A]) Mass ratio 0.20 0.20 0.13 0.42 0.20 0.20 0.20 0.20 [F] Mass % 19 16 23 19 14 27 19 16 [C] 17 5 26 17 17 17 3 32 Evaluation Radiation poor item resistance Flake test C B C B A C B C

[0095] From Table 3, it can be seen that if the sample does not satisfy any one of the “the four compositional requirements of the invention”, the sample is difficult to be processed into flakes or the obtained flakes are poor in resistance to radiation damage.

[0096] That is, if the sum of [S]+[A] does not meet the lower limit of requirement i), the viscosity of the melt is too low, and flakes cannot be formed (Comparative Example 1). On the other hand, when the sum of [S]+[A] exceeds the upper limit of requirement i), the viscosity of the melt is too high, so it becomes to form flakes (Comparative Example 2).

[0097] If the value of [A]/([S]+[A]) does not meet the lower limit of requirement ii), flakes cannot be formed as a result of too low viscosity of the melt (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, making it difficult to form flakes (Comparative Example 4).

[0098] When the value of [F] does not meet the lower limit of requirement iii), resistance to radiation damage is inferior (Comparative Example 5). The intensity retention rate after irradiation of the sample of Comparative Example 5 is 60%. When the value of [F] exceeds the upper limit of requirement iii), flakes cannot be formed due to too low viscosity of the melt (Comparative Example 6).

[0099] If the value of [C] is less than the lower limit of requirement iv), flakes cannot be formed as a result of too low viscosity of the melt (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).

Example 9

[0100] In this example, an example to produce inorganic oxide flakes with excellent radiation resistance is presented using only fly ash, copper slag, and steel slag, which are all industrial waste.

[0101] A raw material formulation was prepared by blending 50 parts by mass of fly ash RM1 as a silica alumina source, 30 parts by mass of copper slag RM2 as an iron oxide source, and 20 parts by mass of steel slag RM3 as a calcium oxide source. Here, the content of SiO.sub.2, Al.sub.2O.sub.3, Fe.sub.2O.sub.3, and CaO in the formulation is [S]+[A]: 59% by mass, [A]/([S]+[A]): 0.23, [F]: 21% by mass, [C]: 13% by mass.

[0102] The 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 irradiation was 87%.

INDUSTRIAL APPLICABILITY

[0103] The inorganic oxide flakes of the present invention are suitable as reinforcing materials or fillers of resins and rubbers. Examples of the resin include a thermoplastic resin and a thermosetting resin. Examples of the thermoplastic resin include, but are not limited to, polypropylene, ABS resin, AS resin, polyphenylene ether, polyamide, polyamideimide, and polyketone. Examples of rubber include thermoplastic rubber.

[0104] The inorganic oxide flakes of the present invention can be suitably used as auxiliary raw materials for improving anti-corrosion properties of lining materials and paints. Examples of the base material of lining material and of the paint include, but are not limited to, thermosetting resins such as vinyl ester resins and epoxy resins and curable rubbers.

[0105] The resin, rubber, or coating material containing the inorganic oxide flakes of the present invention is excellent in resistance to radiation damage. Therefore, it is suitable as a material constituting the irradiated portion. Facilities, equipment, and materials in the fields of nuclear power, aerospace, and medical care can be mentioned as representative examples of irradiated portion.

[0106] Examples of the facilities, instruments, and members in the field of nuclear power include: [0107] facilities, instruments, and members for nuclear power generation; [0108] facilities, instruments, and members for mining and processing uranium ores; [0109] facilities, instruments, and members for secondary processing treatment of nuclear fuel (including conversion, concentration, reconversion, molding processing, and MOX manufacturing of the same fuel); [0110] facilities, instruments, and members for storage, treatment, and retreatment of used nuclear fuel; [0111] facilities, instruments, and members for storage, treatment, and disposal of radioactive waste; [0112] transport instruments and members for uranium ores, secondary processing products of nuclear fuel, used nuclear fuels, or radioactive waste; and [0113] other nuclear-related facilities, instruments, and members.

[0114] More specific examples of the facilities, instruments, and members for nuclear power generation include reactor buildings (including research reactors and test reactors), reactor containment vessels, piping in nuclear reactor facilities, and decommissioning robots.

[0115] Examples of the facilities, instruments, and members used in the field of aerospace include a space base building, a space station, an artificial satellite, a planetary exploration satellite, and a space suit.

[0116] Examples of the facilities, instruments, and members used in the field of medicine include medical devices that utilize particle beams.

[0117] The above examples of use are illustrating for the purpose of demonstrating the usefulness of the inorganic oxide flakes of the present invention, and do not limit the scope of the present invention.

EXPLANATIONS OF LETTERS OR NUMERALS

[0118] 1 CRUCIBLE [0119] 2 TAMMANN TUBE [0120] 21 OPENING [0121] 22 ENTRANCE [0122] 3 ELECTRIC FURNACE [0123] D1 DIAMETER OF CRUCIBLE [0124] H1 HEIGHT OF CRUCIBLE [0125] D2 DIAMETER OF TAMMANN TUBE [0126] H2 HEIGHT OF TAMMANN TUBE [0127] Φ OPENING DIAMETER [0128] fp FORMULATED RAW MATERIAL [0129] fm RAW MATERIAL MELT, MELT [0130] fb BALLOON [0131] P LOADED PRESSURE