Patent Application
20250019803
The present invention relates to an Al-ND-based composite material.
Aluminum or aluminum alloys are widely used as structural materials for vehicles, buildings, and the like, mainly because aluminum or aluminum alloys have high strength per unit weight (specific strength). However, aluminum or aluminum alloys have lower strength per unit volume than steel, and thus research and development of aluminum alloys having higher strength are still in progress.
For example, Patent Document 1 discloses a composite material in which silicon carbide is dispersed in a metal matrix containing aluminum as the main component. However, because the composite material contains a large amount of silicon carbide, performance of the composite material is poor. Non-Patent Document 1 discloses a composite material in which nanodiamond obtained by a detonation method is dispersed in nickel.
The present invention aims to provide an aluminum-based composite material having high strength.
The present invention provides the following aluminum-nanodiamond-based composite material (Al-ND-based composite material).
According to the present invention, the strength of Al-based metals such as pure aluminum (pure Al) or aluminum-based alloys (Al-based alloys) can be increased.
A composite material according to an embodiment of the present invention contains an Al-based metal and nanodiamond (ND) particles, and the ND particles are dispersed in an Al-based metal matrix. The Vickers hardness of the composite material according to an embodiment of the present invention is preferably higher than that of an ND particles-free Al-based metal material by 10% or greater, more preferably 20% or greater, and even more preferably 30% or greater. Examples of Al-based metals include pure Al and Al-based alloys.
Al-based metals can be divided into wrought materials and cast materials, and wrought materials and cast materials can each be further divided into non-heat-treatable alloys and heat-treatable alloys. A preferred Al-based alloy contains, in addition to Al, at least one element selected from the group consisting of Cu, Mg, Mn, Si, Zn, Fe, Cr, Ga, V, Ni, B, Zr, and Ti. Examples of a more preferred Al-based metal include pure aluminum (1050, 1060, 1070, 1080, 1085, 1100, 1100A, 1200, 1230A), Al—Cu-based metals (2011, 2014, 2017, 2024, 2117, 2018, 2218, 2618, 2219, 2025, 2032), Al—Mn-based metals (3003, 3203, 3004, 3104, 3005, 3105), Al—Si-based metals (4032, 4043), Al—Mg-based metals (5005, 5050, 5052, 5154, 5254, 5454, 5060, 5082, 5182, 5083, 5086, 5110A, 5041), Al—Mg—Si-based metals (6061, 6005C, 6063, 6101, 6151, 6262), Al—Zn—Mg-based metals (7072, 7075, 7475, 7050, 7204, 7003), and Al—Fe-based metals (8021, 8079), all of which are presented in Table 1.
In the present specification, nanodiamond particles produced by a detonation method may be referred to as “detonation nanodiamond particles” or “DND particles”.
In addition to the DND particles, ND particles synthesized by a high-temperature high-pressure method, a chemical vapor deposition method, an impact compression method, an implosion method, or a cavitation method, or ND particles obtained by pulverizing bulk-size diamond synthesized by the above-described methods can be used as the ND particles used in the present invention. The ND particles are preferably DND particles.
The proportion of the ND particles in the Al-ND-based composite material is preferably from 0.1 to 30 mass %.
The average size of primary particles of the ND is preferably from 2 to 70 nm, more preferably from 2.5 to 60 nm, even more preferably from 3 to 55 nm, and particularly preferably from 3.5 to 50 nm. The average size of the primary particles can be determined by Scherrer equation based on the analysis result of the powder X-ray diffractometry (XRD). Examples of a measurement instrument of XRD include the Multipurpose X-ray Diffraction System with Built-in Intelligent Guidance (available from Rigaku Corporation).
The peak area ratio of sp2-carbon to sp3-carbon (sp2-carbon/sp3-carbon) of the DND particles is preferably from 0.01 to 7 or from 0.05 to 3, preferably from 0.1 to 1.2, from 0.1 to 0.5 is more preferable than from 0.1 to 1, and even more preferably from 0.1 to 0.3. The peak area ratio can be determined by microscopic Raman spectroscopy using, for example, a 325-nm laser and a microscopic Raman spectrometer. The peak area of sp2-carbon refers to the total area of two peaks that appear near 1250 cm−1 and 1328 cm−1, and the peak area of sp3-carbon refers to the total area of two peaks that appear near 1500 cm−1 and 1590 cm−1. Examples of the microscopic Raman spectrometer that can be used include LabRAM HR Evolution (available from Horiba, Ltd.), a microscopic laser Raman spectrometer.
The explosive for producing the DND particles is not limited, and known explosives of wide varieties can be used. Specific examples thereof include trinitrotoluene (TNT), cyclotrimethylene trinitramine (hexogen, RDX), cyclotetramethylene tetranitramine (octogen), trinitrophenyl methylnitramine (tetryl), pentaerythritol tetranitrate (PETN), tetranitromethane (TNM), triamino-trinitrobenzene, hexanitrostilbene, and diaminodinitrobenzofuroxan. One type of these can be used alone, or a combination of two or more types of these can be used.
In an embodiment, the detonation nanodiamond particles of the present invention have a positive or negative zeta potential. The zeta potential of the detonation nanodiamond particles is preferably −70 mV or greater or 70 mV or less, and more preferably −60 mV or greater or 30 mV or less. In a preferred embodiment of the present invention, the detonation nanodiamond has a zeta potential of preferably from −70 to 70 mV, and more preferably from −60 to 30 mV.
When the ND particles according to an embodiment of the present invention are dispersed in water at a concentration of 3 mass %, the pH is preferably from 1 to 12. The shape of the ND particles according to an embodiment of the present invention is not limited, but is preferably, for example, spherical, ellipsoidal, or polyhedral.
The BET specific surface area of the ND particles according to an embodiment of the present invention is preferably from 20 to 900 m2/g, from 25 to 800 m2/g, from 30 to 700 m2/g, from 35 to 600 m2/g, from 50 to 500 m2/g, or from 100 to 400 m2/g, and more preferably from 200 to 300 m2/g. The BET specific surface area can be measured by nitrogen adsorption. Examples of a measurement instrument for the BET specific surface area include BELSORP-mini II (available from Microtrac BEL). The BET specific surface area can be measured under the following conditions, for example.
The DND particles, which are the preferred ND particles, can be a detonation crude product containing soot, but are preferably DND obtained by subjecting the detonation crude product to an acid treatment to remove sp2-carbon and metal impurities. The acid-treated DND may be further subjected to an alkali treatment, an annealing treatment, a gas-phase oxidation treatment, or the like. The acid treatment of the detonation crude product is preferably a mixed acid treatment using concentrated sulfuric acid and concentrated nitric acid. The amount of the acid used in the acid treatment is approximately from 5 to 48 parts by mass per 1 part by mass of the detonation crude product. The acid used in the acid treatment is preferably a strong acid and/or an acid having oxidizing properties, and examples thereof include hydrochloric acid, sulfuric acid, nitric acid, fuming sulfuric acid, fuming nitric acid, chromic acid, chromic anhydride, dichromic acid, permanganic acid, and perchloric acid. One or more of these acids may be used. An example of a more preferred acid is a mixed acid of concentrated sulfuric acid and concentrated nitric acid mixed in the ratio (volume ratio) of approximately 1 to 1. The temperature for the acid treatment is from 50 to 200° C., and the duration of the acid treatment is from 0.5 to 24 hours.
Alkali metal hydroxides such as sodium hydroxide and potassium hydroxide can be used in the alkali treatment. The temperature of the alkali treatment is from 30 to 150° C., and the duration of the alkali treatment is from 0.5 to 24 hours. The gas-phase oxidation treatment can be carried out at from 250 to 650° C. for from 0.5 to 20 hours. The annealing temperature is preferably 800° C. or higher, and the annealing time is 30 minutes or longer.
In the Al-ND-based composite material according to an embodiment of the present invention, the ND particles are preferably uniformly dispersed in the Al-based metal matrix. Such a composite material can be produced by mixing an Al-based metal powder and the ND particles, molding the mixture, and sintering the molded product. The Al-ND-based composite material may be a sintered compact, or may be a solution-treated product obtained by heat-treating the sintered compact in an atmosphere furnace and further cooling the sintered compact. The Al-based metal powder and the ND particles can be mixed using, for example, a ball mill, an attritor, a vibration mill, or the like. The molding can be performed by die molding, pressure molding such as rubber press molding, injection molding, or the like. The sintering can be performed by an air firing method, a hot press method, a spark plasma sintering (SPS) method, or the like. The sintering temperature is, for example, from 400 to 600° C., and the sintering duration is, for example, from 5 to 60 minutes. A milling aid may be used when mixing the Al-based metal powder and the ND particles. Examples of the milling aid include higher fatty acids such as stearic acid, palmitic acid, oleic acid, and linoleic acid; alcohols such as methanol, ethanol, propanol, butanol, and ethylene glycol; and inorganic fine particles such as those of glass and quartz. When the milling aid is used, it can be used in an amount of preferably from 0.1 to 3 mass %, more preferably from 0.5 to 2.5 mass %, and even more preferably from 1 to 2 mass % of the Al-based metal powder.
The average particle size of the Al-based metal powder to be mixed with the ND particles is preferably from 0.1 to 1000 μm, and more preferably from 1 to 100 μm. The average particle size of the Al-based metal powder can be determined by a light scattering method.
Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited by these examples.
A 99.9% aluminum powder (Al powder) having an average particle size of 30 μm and a detonation nanodiamond (DND) powder were used as starting materials. 10 g of pure aluminum powder, 0.1 g (I mass %) of the DND powder, and also 0.2 g (2 mass %) of stearic acid serving as a milling aid were weighed using an electronic balance. Tungsten carbide balls (20 balls having a diameter of 10 mm and 50 balls having a diameter of 5 mm) were placed into a tungsten carbide container, and the above-described powders were placed from above the balls. The container was sealed, and the inside of the container was evacuated by a vacuum pump. Then, the atmosphere inside the container was replaced with an argon atmosphere. The container was placed in a planetary ball mill “P-6 classic line”, available from FRITSCH, and a mechanical milling (MM) treatment was performed at a rotation speed of 300 rpm for 3 hours. For comparison, a powder with no DND added was subjected to the treatment in the same manner. Hereinafter, the DND-free Al powder is referred to as the pure Al sample, and the DND-containing powder is referred to as the pure Al+DND sample.
The pure Al powder and pure Al+DND powder after 3 hours of the MM treatment were sintered using a spark plasma sintering (SPS) method. The sintering conditions were as follows. The die (having an outer diameter of 30 mm and an inner diameter of 10 mm) and the punch (having a diameter of 10 mm) used were made of graphite. 2.0 g of each of the powders which had been subjected to the MM treatment was weighed using an electronic balance, placed in a die and sealed therein, and sintered. The sintering atmosphere was set to vacuum. The maximum load pressure was set to 50 MPa. Heating by pulse electric-current was performed for 8 min from room temperature to 400° C. (50° C./min), for 4 min to 500° C. (25° C./min), and for 5 min to 550° C. (10° C./min). The maximum temperature reached was 550° C., and the pressurization holding time was 15 min. The relative densities of the samples after sintering ranged from 99.0 to 101.0%. However, the ideal densities were 2.70 g/cm for pure Al and 2.71 g/cm3 for pure Al+DND.
The surfaces of the sintered compacts yielded by the SPS method were mirror-finished by emery polishing (#2000) and buffing (with a diamond abrasive of 3 μm and an alumina abrasive of 0.3 μm). A surface observation using an optical microscope revealed a dense microstructure with an average grain size of approximately 15 μm in the pure Al sintered compact and a lamellar microstructure in the pure Al+DND sintered compact. After the observation, a Vickers hardness test was performed using a hardness tester (HMV-G31FA-S—HC. Shimadzu Corporation) (
As shown in
An A7075 alloy powder having an average particle size of 30 μm and the DND powder were used as starting materials. 10 g of the A7075 alloy powder, 0.1 g (1 mass %) of the DND powder, and also 0.2 g (2 mass %) of stearic acid serving as a milling aid were weighed using an electronic balance. Tungsten carbide balls (20 balls having a diameter of 10 mm and 50 balls having a diameter of 5 mm) were placed into a tungsten carbide container, and the above-described powders were placed from above the balls. The container was sealed, and the inside of the container was evacuated by a vacuum pump. Then, the atmosphere inside the container was replaced with an argon atmosphere. The container was placed in a planetary ball mill “P-6 classic line”, available from FRITSCH, and a mechanical milling (MM) treatment was performed at a rotation speed of 300 rpm for 3 hours. For comparison, a powder with no DND added was subjected to the treatment in the same manner. Hereinafter, the DND-free powder is referred to as the A7075 sample, and the DND-containing powder is referred to as the A7075+DND sample.
The A7075 powder and the A7075+DND powder after 3 hours of the MM treatment were sintered using an SPS method. The sintering conditions were as follows. The die (having an outer diameter of 30 mm and an inner diameter of 10 mm) and the punch (having a diameter of 10 mm) used were made of graphite. 2.0 g of each of the powders which had been subjected to the MM treatment was weighed using an electronic balance, placed in a die and sealed therein, and sintered. The sintering atmosphere was set to vacuum. The maximum load pressure was set to 50 MPa. Heating by pulse electric-current was performed for 8 min from room temperature to 400° C. (50° C./min), for 4 min to 500° C. (25° C./min), and for 5 min to 550° C. (10° C./min). The maximum temperature reached was 550° C. and the pressurization holding time was 15 min. The relative densities of the samples after sintering ranged from 100.0 to 101.0%. However, the ideal densities were 2.80 g/cm3 for A7075 and 2.81 g/cm3 for A7075+DND.
The surfaces of the sintered compacts yielded by the SPS method were mirror-finished by emery polishing (#2000) and buffing (with a diamond abrasive of 3 μm and an alumina abrasive of 0.3 μm). A surface observation using an optical microscope revealed a dense microstructure with an average grain size of approximately 10 μm in the A7075 sintered compact and a lamellar microstructure in the A7075+DND sample. After the observation, a Vickers hardness test was performed using a hardness tester (HMV-G31FA-S—HC, Shimadzu Corporation) (
As shown in
Next, the sintered compacts were held at 500° C. for 1 hour in an atmosphere oven (Fulltech Inc., FT 101), taken out, and immediately water-cooled to perform a solution treatment (
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-041248 | Mar 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2023/007768 | 3/2/2023 | WO |
