Graphitic nanomaterials in the form of carbon onions, production method thereof and use of same

Patent metadata

Field	Value
Publication number	US-2016137506-A1
Application number	US-201414897480-A
Country	US
Kind code	A1
Filing date	Jun 11, 2014
Priority date	Jun 12, 2013
Publication date	May 19, 2016
Grant date	—

Abstract

The present invention relates to graphite nanomaterials in the form of onion-like carbons, the method of preparation thereof and the use thereof.

First claim

1 . Method for preparing onion-like carbons, comprising a step of exposing spherical nanodiamonds having a size of the crystalline core comprised between approximately 2 nm and approximately 10 nm, as measured by X-ray diffraction, to microwaves for a sufficient time t to lead to an increase in heat at the surface of the nanodiamonds such as to induce complete graphitization of the crystalline core, under low vacuum at a pressure less than or equal to approximately 10 −3 mbar,
and in particular wherein said nanodiamonds have an overall size comprised between approximately 2 nm and approximately 15 nm, in particular from approximately 4 nm to approximately 10 nm.

2 . Method according to claim 1 , wherein:
prior to exposure to microwaves, said nanodiamonds have sp 2 -hybridized carbon atoms at their surface, or are substantially devoid of sp 2 -hybridized carbon atoms at their surface and are subjected to partial surface graphitization, in particular by annealing under high vacuum, prior to exposure to microwaves, in order to obtain nanodiamonds that are partially graphitized at the surface, or prior to exposure to microwaves, said nanodiamonds have carbon-hydrogen bonds at their surface, or are substantially devoid of carbon-hydrogen bonds at their surface and have heteroelements such as oxygen, nitrogen or fluorine, and in particular more than 2 at. % of oxygen at said surface, and are subjected to partial surface hydrogenation, in order to obtain nanodiamonds that are partially hydrogenated at the surface.

3 . Method according to claim 1 , wherein the low vacuum in the enclosure in which the nanodiamonds are exposed to the microwaves corresponds to a pressure comprised between approximately 10 −4 mbar to 10 −3 mbar, in particular equal to approximately 10 −3 mbar.

4 . Method according to claim 1 , wherein said nanodiamonds:
are partially graphitized at the surface, or are substantially devoid of sp 2 -hybridized carbon atoms at their surface and are subjected, prior to exposure to microwaves, to partial surface graphitization.

5 . Method according to claim 1 , comprising the following steps:
a. Under low vacuum, pumping an enclosure, in particular constituted by a quartz tube, into which nanodiamonds partially graphitized at the surface have been introduced, in order to obtain a pressure comprised between approximately 10 −4 mbar and 10 −3 mbar, in particular a pressure of approximately 10 −3 mbar; b. Exposing said enclosure containing the nanodiamonds, partially graphitized at the surface, under low vacuum obtained in the preceding step, to microwaves the power of which is comprised between approximately 50 watts and approximately 2000 watts, the power being in particular approximately 300 watts, for a time t comprised between approximately 1 second and approximately 1 hour, in particular approximately 30 minutes, in order to induce complete graphitization of the crystalline core of the nanodiamonds and obtain onion-like carbons.

6 . Method according to claim 5 , further comprising, before the step of pumping under low vacuum, a step of partial surface graphitization of nanodiamonds that are substantially devoid of sp 2 -hybridized carbon atoms at their surface,
said graphitization in particular being carried out by annealing under high vacuum, in order to produce nanodiamonds that are partially graphitized at the surface.

7 . Method according to claim 1 , wherein said nanodiamonds, prior to exposure to microwaves:
have carbon-hydrogen bonds at their surface, or are substantially devoid of carbon-hydrogen bonds at their surface and have heteroelements such as oxygen, nitrogen or fluorine, and in particular more than 2 at. % of oxygen at said surface, and are subjected to partial surface hydrogenation, in order to obtain nanodiamonds that are partially hydrogenated at the surface, or are insufficiently hydrogenated at their surface and have heteroelements such as oxygen, nitrogen or fluorine, and in particular more than 2 at. % of oxygen at said surface, and are subjected to partial surface hydrogenation in order to obtain nanodiamonds that are partially hydrogenated at the surface.

8 . Method according to claim 7 , comprising the following steps:
a. Under low vacuum, pumping an enclosure, into which nanodiamonds partially hydrogenated at the surface have been introduced, in order to obtain a pressure comprised between approximately 10 −4 mbar and 10 −3 mbar, in particular a pressure of approximately 10 −3 mbar; b. Exposing said enclosure, containing the nanodiamonds partially hydrogenated at the surface, under low vacuum obtained in the preceding step, to microwaves the power of which is comprised between approximately 50 watts and approximately 2000 watts, the power being in particular approximately 300 watts, for a time t comprised between approximately 1 second and approximately 1 minute, in particular 30 seconds, in order to induce complete graphitization of the crystalline core of the nanodiamonds and obtain onion-like carbons.

9 . Method according to claim 8 , further comprising, before the step of pumping under low vacuum, a step of hydrogenation of nanodiamonds that are substantially devoid of carbon-hydrogen bonds at their surface and have heteroelements such as oxygen, nitrogen or fluorine, and in particular more than 2 at. % of oxygen at said surface, said hydrogenation in particular being carried out by microwave plasma, under a pressure of 14-15 mbar at a power from 50 W to approximately 2000 W, in particular 300 W, for 5 minutes to approximately 30 minutes, in particular 15 minutes,
in order to produce nanodiamonds that are partially hydrogenated at the surface.

10 . Method according to claim 1 , wherein the power absorbed by said nanodiamonds is substantially equal to 100% and the power reflected is substantially equal to 0%,
and in particular in which increasing the temperature in said enclosure under low vacuum containing partially graphitized nanodiamonds, or partially hydrogenated nanodiamonds, during exposure to microwaves for said time t, causes scintillation or emission of white light from said partially graphitized nanodiamonds, or from said partially hydrogenated nanodiamonds.

11 . Method according to claim 1 , wherein said onion-like carbons, obtained after exposure to microwaves, are exposed to UV, in particular in air and to a UV wavelength of approximately 172 nm, under an oxygen atmosphere in order to make the aforesaid onion-like carbons hydrophilic,
in particular in which the air pressure before UV exposure is adjusted to approximately 200 mbar, and in particular in which the UV exposure time is comprised between 1 minute and 4 hours, in particular 2 hours.

12 . Method according to claim 11 , wherein exposure to microwaves and exposure to UV are carried out in the same enclosure, in particular constituted by a quartz tube,
and in particular in which hydrogenation, exposure to microwaves and exposure to UV are carried out in the same enclosure, in particular constituted by a quartz tube.

13 . Product as obtained by the method according to claim 11 .

14 . Method according to claim 2 , wherein said nanodiamonds:
are partially graphitized at the surface, or are substantially devoid of sp 2 -hybridized carbon atoms at their surface and are subjected, prior to exposure to microwaves, to partial surface graphitization.

Assignees

• Comimsssariat A L En Atomique Et Aux En Alternatives
• Commissariat Energie Atomique

Inventors

• Arnault Jean-Charles
• Girard Hugues
• Petit Tristan

Classifications

• C01B32/18 Primary

  Nanoonions; Nanoscrolls; Nanohorns; Nanocones; Nanowalls · CPC title

• C01B31/0293 Primary

  Chemistry & Metallurgy · mapped topic

• H01G11/36

  Nanostructures, e.g. nanofibres, nanotubes or fullerenes · CPC title