Surface-modified nanodiamond, liquid dispersion containing surface-modified nanodiamond, and composite material
Provided is a surface-modified nanodiamond that has high dispersibility in an organic solvent or in a resin and that can maintain the characteristics described above even in a high-temperature environment of 200° C. or higher. The surface-modified nanodiamond according to an embodiment of the present invention has a structure in which a surface of a nanodiamond particle is modified by a group represented by Formula (1) below. In the formula, R 1 to R 4 are the same or different and each represent an aliphatic hydrocarbon group having from 1 to 25 carbons. Note that at least one of R 1 to R 4 is an aliphatic hydrocarbon group having from 10 to 25 carbons. Furthermore, an atomic bond of the carbon atom in the formula bonds to the surface of the nanodiamond particle.
1. A surface-modified nanodiamond having a structure in which a surface of a nanodiamond particle is modified by a group represented by Formula (1) below:
where R 1 to R 4 are the same or different and each represent an aliphatic hydrocarbon group having from 1 to 25 carbons, at least one of R 1 to R 4 is an aliphatic hydrocarbon group having from 10 to 25 carbons, and an atomic bond of the carbon atom in the formula bonds to the surface of the nanodiamond particle,
wherein a particle size, D50, is from 20 to 200 nm.
2. The surface-modified nanodiamond according to claim 1 , wherein a thermal decomposition of the surface-modified nanodiamond is a temperature of 250° C. or higher.
3. A nanodiamond liquid dispersion comprising an organic solvent and a surface-modified nanodiamond described in claim 1 , wherein the nanodiamond liquid dispersion includes the surface-modified nanodiamond in a proportion from 0.0001 to 10 parts by mass per 100 parts by mass of the organic solvent.
4. A composite material comprising a resin and the surface-modified nanodiamond described in claim 1 .
5. The composite material according to claim 4 , wherein the composite material is a molten mixture of the resin and the surface-modified nanodiamond.
6. The composite material according to claim 4 , wherein the resin is a thermoplastic resin having a glass transition temperature or a melting point of 150° C. or higher.
7. The surface-modified nanodiamond according to claim 1 , wherein two or three groups selected from R 1 to R 4 are each an aliphatic hydrocarbon group having from 10 to 25 carbons, and the other group(s) are each an aliphatic hydrocarbon group having from 1 to 9 carbons.
8. The surface-modified nanodiamond according to claim 1 , wherein R 1 is an aliphatic hydrocarbon group having from 10 to 25 carbons, and R 2 , R 3 , and R 4 are each an aliphatic hydrocarbon group having from 1 to 9 carbons.
9. The surface-modified nanodiamond according to claim 1 , wherein a sum of number of carbons of R 1 and R 2 is from 20 to 50, and a sum of number of carbons of R 3 and R 4 is from 2 to 10.
10. The surface-modified nanodiamond according to claim 1 , wherein a sum of number of carbons in R 1 , R 2 , R 3 , and R 4 is from 22 to 60.
11. A method for giving a mechanical strength to a resin, the method comprising mixing the surface-modified nanodiamond according to claim 1 with the resin.
12. A method for giving a high refractive index to a resin, the method comprising mixing the surface-modified nanodiamond according to claim 1 with the resin.
13. A method for giving a thermal conductivity to a resin, the method comprising mixing the surface-modified nanodiamond according to claim 1 with the resin.
14. A method for producing an antifriction agent, the method comprising mixing the surface-modified nanodiamond according to claim 1 with the resin.
15. A method for producing a lubricant, the method comprising mixing the surface-modified nanodiamond according to claim 1 with the resin.
16. A method for producing a mechanical strength-imparting agent for a resin, the method comprising mixing the surface-modified nanodiamond according to claim 1 with the resin.
17. A method for producing a high refractive index-imparting agent for a resin, the method comprising mixing the surface-modified nanodiamond according to claim 1 with the resin.
18. A method for producing a thermal conductivity-imparting agent for a resin, the method comprising mixing the surface-modified nanodiamond according to claim 1 with the resin.
19. A method for producing a composite material, the method comprising kneading the surface-modified nanodiamond according to claim 1 and a resin at a temperature that is equal to or higher than a glass transition temperature or a melting point of the resin to produce a composite material of these.