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• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/05—Mixtures of metal powder with non-metallic powder
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0408—Light metal alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0408—Light metal alloys
  • C22C1/0416—Aluminium-based alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0425—Copper-based alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/10—Alloys containing non-metals
  • C22C1/1036—Alloys containing non-metals starting from a melt
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/10—Alloys containing non-metals
  • C22C1/1078—Alloys containing non-metals by internal oxidation of material in solid state
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/10—Alloys containing non-metals
  • C22C1/1089—Alloys containing non-metals by partial reduction or decomposition of a solid metal compound
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C26/00—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes
  • C22C2026/005—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes with additional metal compounds being borides
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C26/00—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes
  • C22C2026/006—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes with additional metal compounds being carbides
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C26/00—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes

Definitions

• the present disclosure relates to a composite material and a method for producing the same, more particularly to a composite material containing inorganic particles and a matrix metal which binds the inorganic particles and a method for producing the same.
• Patent Literature 1 discloses a "diamond composite material comprising: a coated diamond particle including a diamond particle and a carbide layer coating a surface of the diamond particle and including an element of group 4 of the periodic table; and silver or a silver alloy binding such coated diamond particles together, with an oxygen content of 0.1 mass% or less" (see claim 1 in Patent Literature 1).
• Patent Literature 1 JP6292688B
• Patent Literature 1 a diamond composite material that is exceptionally thermally conductive and dense can be obtained by having as small oxygen content as possible in the diamond composite material.
• the paragraph [0118] of Patent Literature 1 presumes reasons for being able to obtain such a diamond composite material since "using a raw material of a powder of a group 4 compound including an element of group 4 of the periodic table can suppress oxidation of the element of group 4 of the periodic table in the production process and oxygen which may be present around a raw material can be reduced/removed by an effect of a particular element generated in a chemolysis of the above group 4 compound, and furthermore, the element of group 4 of the periodic table generated through the chemolysis can react with the diamond and thus efficiently form a carbide and thus enhance wettability with molten metal.”
• a thermal conductivity of a matrix metal of a composite material is likely to decrease if the addition amount of compounds including elements of group 4 of the periodic table (for example, titanium hydride) is increased in a production process of the composite material. Therefore, there is an upper limit to the amount of these elements to be added.
• titanium hydride (TiH 2 ) powders for example, are used to reduce oxygen by hydrogen generated by decomposition of titanium hydride, H 2 O formed by the hydrogen and the oxygen or the hydrogen is incorporated into a molten metal, and due to this, blowholes may be formed in the matrix metal. The blowholes deteriorate performance of the composite material.
• the present disclosure was developed in light of the above problems and provides a composite material having an excellent thermal conductivity and a method for producing the same without using, or only using a sufficiently reduced amount of, hydrides that may cause blowholes.
• a method for producing a composite material according to the present disclosure comprises the steps of:
• a method for producing a composite material according to the present disclosure may comprise the steps of:
• the metal oxide particles can function as an oxygen absorbent.
• the metal oxide particles can exhibit a gettering effect of trapping oxygen.
• the oxygen is trapped by the metal oxide particles, it is possible to prevent a decrease in thermal conductivity of the matrix metal caused by oxygen.
• the hydrogen generated by decomposition of titanium hydride is used to reduce oxygen, H 2 O or hydrogen is not generated and so the formation of blowholes can be prevented.
• the metal oxide particles are thermally stable, it is possible to prevent deterioration in physical properties of the matrix metal caused by the metal oxide particles.
• the composite material according to the present disclosure includes at least one type of inorganic particles selected from the group consisting of diamond particles and boron nitride particles (for example, h-BN particles or c-BN particles); a matrix metal which binds the inorganic particles; and metal oxide particles, and an oxygen content is higher than 0.1 mass% and a thermal conductivity is 300 W/m ⁇ K or more at room temperature.
• inorganic particles selected from the group consisting of diamond particles and boron nitride particles (for example, h-BN particles or c-BN particles); a matrix metal which binds the inorganic particles; and metal oxide particles, and an oxygen content is higher than 0.1 mass% and a thermal conductivity is 300 W/m ⁇ K or more at room temperature.
• the oxygen in the composite material is mainly derived from the metal oxide particles and so the decrease in the thermal conductivity of the matrix metal caused by oxygen is prevented thereby achieving a thermal conductivity of 300 W/m ⁇ K or more at room temperature.
• the metal oxide particles are thermally stable, deterioration in physical properties of the matrix metal caused by the metal oxide particles is also prevented.
• the present disclosure provides a composite material having an excellent thermal conductivity and a method for producing the same without using, or only using a sufficiently reduced amount of, hydrides, such as titanium hydride, that may cause blowholes.
• Figure 1 is a sectional view schematically illustrating an embodiment of a composite material according to the present disclosure.
• a composite material 10 illustrated in the figure has a plurality of inorganic particles 1, a plurality of metal oxide particles 3, and a matrix metal 5.
• the metal oxide particles 3 are dispersed, and the oxygen content of the composite material 10 is higher than 0.1 mass%, or it may be 0.2 mass% or more or 0.3 mass% or more.
• the upper limit for the oxygen content of the composite material 10 is, for example, 1.0 mass%, or it may be 0.8 mass% or 0.6 mass%.
• the thermal conductivity is 300 W/m ⁇ K or more.
• the composite material 10 may have a thermal conductivity of 500 W/m ⁇ K or more or 600 W/m ⁇ K or more.
• the upper limit for the thermal conductivity of the composite material 10 is, for example, 700 W/m ⁇ K, or it may be 800 W/m ⁇ K or 1,000 W/m ⁇ K.
• As the composite material 10 has an excellent thermal conductivity, it can be used for a heat dissipation member.
• the composite material 10 may be in a form of a plate, or it may be molded into a desirable shape depending on the intended use.
• a material composing the inorganic particles 1 is a material selected from the group consisting of diamond, boron nitride (h-BN or c-BN), graphite, SiC, AIN, Si 3 N 4 , B 4 C, MgB 2 , Mg 3 N 2 , MgCl 2 , CaCl 2 , Mg 2 Si, carbon fibers, carbon nanotubes, TiC, WC, and TaC.
• the thermal conductivity of diamond is about 1,000 to 2,000 W/m ⁇ K.
• the thermal conductivity of c-BN is about 1,300 W/m ⁇ K.
• the thermal conductivity of SiC is about 150 to 500 W/m ⁇ K.
• the average particle diameter (median diameter D50) of the inorganic particles 1 is preferably 10 ⁇ m or more, more preferably 20 ⁇ m or more, and even more preferably 50 ⁇ m or more.
• the average particle diameter (median diameter D50) of the inorganic particles 1 is preferably 500 ⁇ m or less, more preferably 300 ⁇ m or less, and even more preferably 200 ⁇ m or less.
• the content rate of the inorganic particles 1 in the composite material 10 is preferably 35 volume% or more, more preferably 40 volume% or more, and even more preferably 45 volume% or more based on the volume of the composite material 10. In view of formability, this content rate is preferably 90 volume% or less, more preferably 85 volume% or less, and even more preferably 80 volume% or less.
• the metal oxide particles 3 include titanium oxide particles, cerium oxide particles, calcium titanate particles, and niobium oxide particles.
• the metal oxide particles 3 may be perovskite-type oxide particles.
• the thermal conductivity of titanium oxide is about 7 W/m ⁇ K.
• the thermal conductivity of cerium oxide is about 14 W/m ⁇ K.
• the thermal conductivity of calcium titanate is about 2 W/m ⁇ K.
• the thermal conductivity of niobium oxide is about 2 W/m ⁇ K.
• the average particle diameter (median diameter D50) of the metal oxide particles 3 is preferably 0.1 ⁇ m or more, more preferably 0.5 ⁇ m or more, and even more preferably 1 ⁇ m or more.
• the average particle diameter (median diameter D50) of the metal oxide particles 3 is preferably 200 ⁇ m or less, more preferably 100 ⁇ m or less, and even more preferably 50 ⁇ m or less.
• the content rate of the metal oxide particles 3 in the composite material 10 is, for example, 0.01 volume% or more, or it may be 0.05 volume% or more or 0.1 volume% or more based on the volume of the composite material 10. In view of formability, this content rate is preferably 5 volume% or less, more preferably 2 volume% or less, and even more preferably 1 volume% or less.
• the matrix metal 5 is present in between a plurality of the inorganic particles 1 and a plurality of the metal oxide particles 3 and binds these particles.
• a metal composing the matrix metal include copper, silver, aluminum, magnesium or an alloy of two or more metals selected from these.
• the content rate of the matrix metal 5 in the composite material 10 is preferably 10 volume% or more, more preferably 15 volume% or more, and even more preferably 20 volume% or more based on the volume of the composite material 10. In view of thermal conductivity, this content rate is preferably 65 volume% or less, more preferably 60 volume% or less, and even more preferably 55 volume% or less.
• Figure 2 is a sectional view schematically illustrating other embodiment of a composite material according to the present disclosure.
• a composite material 20 illustrated in the figure does not have the metal oxide particles 3 dispersed in the composite material 20 and has a region R3 where the metal oxide particles 3 exist in high concentration.
• the region R3 is formed on one surface 20a of the composite material 20.
• Figure 3 is a sectional view schematically illustrating other embodiment of a composite material according to the present disclosure.
• a composite material 30 illustrated in the figure has the region R3 removed from the composite material 20 illustrated in Figure 2 .
• the region R3 can be removed by grinding the side of the surface 20a of the composite material 20.
• the oxygen content of the composite material 30 is, for example, 0.10 mass% or less, or it may be 0.07 mass% or less, or it may substantially be zero.
• the lower limit for the oxygen content of the composite material 30 is, for example, 0.01 mass%.
• the composite material 30 may have a thermal conductivity of 600 W/m ⁇ K or more or 700 W/m ⁇ K or more.
• the upper limit for the thermal conductivity of the composite material 30 is, for example, 800 W/m ⁇ K, or it may be 900 W/m ⁇ K or 1,000 W/m ⁇ K.
• the production method includes the steps of:
• the composite material 10 is obtained by the above steps.
• various additives may be added into the mold 50 in the above step (a).
• the additives include a compound, such as a metal compound, including (i) an element of Ti, Cr, V, Mn, Nb, W, Mo, Fe, Co, Ni, Pd, Pt, Rh, Ta, Re, Zr, U, Ce, Si, B, Y, Mg, Zn, and/or a rare earth element (for example, an element that is a metal among these) and (ii) a specific element (specifically, at least one element of sulfur, nitrogen, hydrogen, or boron).
• a metal compound including (i) an element of Ti, Cr, V, Mn, Nb, W, Mo, Fe, Co, Ni, Pd, Pt, Rh, Ta, Re, Zr, U, Ce, Si, B, Y, Mg, Zn, and/or a rare earth element (for example, an element that is a metal among these) and (ii)
• the heating temperature in the step (b) is a temperature that is lower than the melting point of the metal particles 5p by, for example, 50 to 200°C.
• the heating duration is, for example, 5 to 60 minutes.
• the heating temperature in the above step (d) is a temperature that is higher than the melting point of the metal particles 5p by, for example, 50 to 200°C.
• the heating duration is, for example, 5 to 60 minutes.
• a first layer L1 is formed in the mold 50, and then a second layer L2 is formed on the first layer L1.
• the first layer L1 is composed of the inorganic particles 1.
• the second layer L2 is composed of the metal particles 5p and the metal oxide particles 3.
• the above additive may be formulated into at least one of the first layer L1 and the second layer L2 as necessary.
• the metal oxide particles 3 included in the second layer L2 have a larger average particle diameter than that of the inorganic particles 1 included in the first layer L1.
• the composite material 20 having the region R3 is obtained.
• the average particle diameter of the metal oxide particles 3 may not necessarily be larger than the average particle diameter of the inorganic particles 1. In other words, as long as the particle diameter of the metal oxide particles 3 is larger than the space formed by a plurality of the adjacent inorganic particles 1, at least some of the metal oxide particles 3 remain on the first layer L1.
• the region R3 is removed from the composite material 20 to obtain the composite material 30.
• the first layer L1 was composed of the inorganic particles 1 and the second layer L2 was composed of the metal particles 5p and the metal oxide particles 3 was demonstrated, but the first layer L1 may be composed of the inorganic particles 1 and the metal oxide particles 3, and the second layer L2 may be composed of the metal particles 5p.
• the first layer L1 contains the metal oxide particles 3
• the region containing a large amount of the metal oxide particles 3 cannot be removed afterwards as above.
• the oxygen contained in the matrix metal can be removed by the gettering effect of the metal oxide particles 3 when the molten product of the metal particles 5p enters the first layer L1.
• the above additive may be formulated into at least one of the first layer L1 and the second layer L2 as necessary.
• the present invention is not limited to the above embodiments.
• the above embodiments illustrated the production method including the steps of heating the metal oxide particles 3 in the mold 50 in reducing atmosphere to release the oxygen from the metal oxide particles 3; however, metal oxide particles 3A having oxygen defects may be, for example, prepared beforehand to fill the mold 50 (see Figure 6 ).
• the composite material 10 may be produced by the steps of:
• the metal oxide particles 3A may be obtained by subjecting the metal oxide particles 3 to reduction treatment.
• the metal oxide particles 3A may be used to produce the composite materials 20, 30.
• diamond particles are illustrated as a preferred example for the inorganic particles 1, but the diamond particles may have a coated layer (not shown) composing the outermost layer of the diamond particles, or the diamond particles may be boron-doped.
• the coated layer include a titanium coated layer, a chromium coated layer, and a boron-doped layer (diamond particles with only the surface layer doped with boron).
• having the titanium coated layer on the diamond particles further improves the wettability of the diamond particles to the matrix metal due to the titanium carbide layer present at the interface between the surface of the diamond particle body and the matrix metal.
• the present disclosure relates to the following:
• average particle diameter used in the present disclosure indicates a median diameter D50 obtained from a particle diameter distribution of particles, and the median diameter D50 indicates a particle diameter with the cumulative volume reaching at 50% from the small particle diameter side in the particle diameter distribution obtained by laser diffraction method.
• the temperature inside the mold was increased to 600°C and was kept at 600°C for 10 minutes. By doing this, oxygen was released from the titanium oxide particles, and the oxygen released from the titanium oxide particles was discharged to the outside of the mold. Then, after increasing the temperature inside the mold from 600°C to 780°C, the mold was sealed, and the contents were heated at 950°C for 10 minutes. By doing this, the metal particles were melted, and the oxygen released from the molten product of the metal particles was absorbed by the titanium oxide particles. After decreasing the temperature inside the mold, a composite material for the example was collected from the mold. The resulting composite material had a diameter of 30 mm and a thickness of about 0.4 mm.
• a composite material for the example was produced similarly to the example 3. It should be noted that the titanium oxide particles A were heated at 1,000°C for 4 hours under vacuum atmosphere to subject the titanium oxide particles A to reduction treatment.
• cerium oxide particles instead of the titanium oxide particles A as the reduction treated metal oxide particles and mixing 44 parts by volume of the diamond particles with 0.6 parts by volume of the cerium oxide particles to obtain the first mixed powder
• a composite material for the example was produced similarly to the example 4. It should be noted that the cerium oxide particles were heated at 1,000°C for 8 hours under vacuum atmosphere to subject the cerium oxide particles to reduction treatment.
• a composite material for the example was produced similarly to the example 4. It should be noted that the calcium titanate particles were heated at 1,200°C for 8 hours under vacuum atmosphere to subject the calcium titanate particles to reduction treatment.
• niobium oxide particles instead of the titanium oxide particles A as the reduction treated metal oxide particles and mixing 44 parts by volume of the diamond particles with 0.2 parts by volume of the niobium oxide particles to obtain the first mixed powder
• a composite material for the example was produced similarly to the example 4. It should be noted that the niobium oxide particles were heated at 1,000°C for 8 hours under vacuum atmosphere to subject the niobium oxide particles to reduction treatment.
• a composite material for the comparative example was obtained similarly to the example 1.
• the temperature inside the mold was increased to 600°C and was kept at 600°C for 10 minutes.
• the mold was sealed, and the contents were heated at 950°C for 10 minutes.
• a composite material for the comparative example was collected from the mold.
• the composite materials for the examples and the comparative example were broken into small pieces, and a total weight of about 0.1 g was provided as a test piece for each measurement.
• the oxygen concentration of the test piece was measured using an oxygen/nitrogen analyzer (EMGA-930 manufactured by HORIBA, Ltd.) under the heating condition of a furnace temperature at 2,400°C for 110 seconds.
• Tables 1 and 2 indicate the average values of the three test pieces for each of the examples and the comparative example.
• test piece (size: 30 mm diameter and 0.3 mm thickness) was produced from each of the composite materials for the examples and the comparative example.
• a thermal diffusion coefficient of the test piece at room temperature was measured by temperature wave method using a thermal diffusion coefficient measuring device (TA35 manufactured by Bethel Co., Ltd.) to calculate thermal conductivity of the test piece.
• Tables 1 and 2 indicate the average values of the three test pieces for each of the examples and the comparative example.
• Example 1 Example 2
• Example 3 Example 4
• Example 4 Mixing ratio for raw material powders [parts by volume] Diamond particles 44 44 44 44 Titanium hydride particles 2 2 2 2
• Metal particles 54 54 54 Metal oxide particles Titanium oxide particles A 0.6 - 0.6 0.6 Titanium oxide particles B - 0.3 - - Oxygen content [mass%] 0.11 0.11 0.30 0.33 Thermal conductivity [W/m ⁇ K] 600 612 632 635 [Table 2]
• Example 5 Example 6
• Example 7 Comparative example 1 Mixing ratio for raw material powders [parts by volume] Diamond particles 44 44 44 Titanium hydride particles 2 2 2 2

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