Method and system for controlled synthesis of nanodiamonds

Abstract

Method and system for controlled nanodiamond synthesis based on treating of a specially prepared solid carbon source target including carbon containing material in liquid media by irradiation energy beam focused at a predetermined distance from the target surface and having parameters to produce a light-hydraulic effect impacting the target surface and leading to the forming of diamond nanocrystals.

Claims

1. A method of controlled synthesis of nanodiamonds comprising steps of; providing a carbon source target including a binder mixed with non-diamond carbon particles containing material; providing a layer of liquid on the surface of said carbon source target; generating an irradiation energy beam; and focusing said irradiation energy beam above said carbon source target on a selected area located within the layer of the liquid at a predetermined distance from the surface of said carbon source target.

2. The method of claim 1 wherein said binder includes low melting solid hydrocarbons.

3. The method of claim 2 wherein said low melting solid hydrocarbons includes an organic wax.

4. The method of claim 1 wherein said liquid includes water.

5. The method of claim 4 wherein said water is deionized water.

6. The method of claim 1 wherein said layer of liquid on the surface of the carbon source target is provided by immersing the carbon source target into the liquid.

7. The method of claim 1 wherein said carbon particles containing material includes at least one of fullerene, amorphous carbon, graphite and solid hydrocarbons.

8. The method of claim 1 wherein said carbon particles containing material is in a form of soot.

9. The method of claim 1 wherein said irradiation energy beam is produced by at least one laser.

10. The method of claim 9 wherein said at least one laser being operated at least one wavelength within the range of about 532 to 1320 nm.

11. The method of claim 10 wherein said irradiation energy beam is produced by at least one laser pulse.

12. The method of claim 11 wherein said at least one laser pulse has a width in the range of about 0.001 to about 5 microseconds.

13. The method of claim 12 wherein said irradiation energy beam has intensity in the range of about 10 to about 10 W/cm.

14. The method of claim 1 wherein said predetermined distance from the surface of the carbon source target is in the range of about 0.1 to about 20 mm.

15. The method of claim 14 wherein said predetermined distance from the surface of the carbon source target is about 2-3 mm.

16. The method of claim 1 and further comprising steps of purification of the synthesized nanodiamonds by applying a flotation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a simplified schematic view of an exemplary system 10 of the invention for nanodiamond synthesis, according to one embodiment of the invention;

(3) FIGS. 2A and 2B illustrate results of Thermo Gravimetric Analysis for nanodaimonds obtained by detonation or explosive based technique and present invention synthesis accordingly; and

(4) FIGS. 3A and 3B illustrate Raman spectra obtained for nanodiamonds produced by detonation and present invention synthesis accordingly;

DETAILED DESCRIPTION OF EMBODIMENTS

(5) Reference is made to FIG. 1, illustrating a simplified schematic view of an exemplary system 10 of the invention for nanodiamond synthesis, according to one embodiment of the invention. The system 10 includes a holding assembly, e.g. including a vessel 11 for accommodating a carbon containing carbon source target 12 immersed in liquid. The system also includes an irradiation energy assembly 13 configured for producing an irradiation energy beam 14, directed towards the carbon source target 12 and focusing the irradiation energy beam 14 onto a selected area 15. The selected area 15 is located within the liquid above a surface 16 of the carbon source target 12 on a predetermined distance d from the surface 16. As illustrated in FIG. 1, the vessel 11 could include a window 17 transparent to the irradiation energy beam 14 passing therethrough. The irradiation energy source 13 includes a beam forming optics, e.g. focusing unit 18 arranged for focusing the irradiation energy beam 14 onto the selected area 15. It should be noted that focusing unit could be designed for providing irradiating spot of desired shape, e.g. line-shaped, etc. When required, the system 10 may include at least one stage/conveyer 19 configured for providing a relative displacement of the selected area 15 along a plane 20 that can be visualized at the distance d above the surface 16. It should be understood that the providing of the relative displacement can be implemented by moving either the carbon source target 12 or the irradiation energy beam 14. Alternatively, the providing of the relative displacement can be implemented by moving both carbon source target 12 and the irradiation energy beam 14 in respect of each other.

(6) It should be understood that the invention is not limited to the example of the system illustrated in FIG. 1. Hence, according to another example, the irradiation energy beam 14 can be arranged within the vessel 11 (not shown).

(7) Examples of carbon containing materials of carbon source target 12 may include, at least one of: fullerenes C.sub.60-C.sub.100, amorphous carbon, graphite, solid hydrocarbons, e.g., styrene, naphthalene, etc. The liquid into which the carbon source target 12 is immersed can, for example, be either water or water with a carbon containing substance, e.g., glycerin, ethanol, acetone, fatty acids, etc, that are transparent to irradiation energy beam 14. Likewise, the water may contain dissolved gases, such as noble gasses, CO.sub.2, etc. One of the purposes of the adding of gases in the liquid is to enhance the generated compression shock waves.

(8) Preferably, carbon containing materials of carbon source target 12 could be in the form of soot.

(9) In that case carbon source target 12 could further include hydrocarbon and liquid. According to this example, the focusing unit 18 can include an arrangement of optical lens or lenses (only one such a lens is shown in FIG. 1) for providing radiation spot of desired shape and dimension.

(10) An example of the irradiation energy source 13 includes, but is not limited to, a laser source 21 having such properties of the focused irradiation energy beam 14 so as to produce certain hydrodynamic effect impacting surface of carbon source target 12 and more specifically to provide conditions (e.g. temperature, pressure, etc.) sufficient for forming diamond cubic crystal structure. Such so called light-hydraulic effect was discovered and disclosed in 1963 year as Science Discovery registered in the USSR under number No. 65 in the name of A. Prokhorov et al.

(11) The essence of the present invention can be better understood from the following non-limiting examples which are intended to illustrate the present invention and to teach a person of the art how to make and use the invention. This example is not intended to limit the scope of the invention or its protection in any way.

(12) A layer of a mix of a commercially available fullerene C.sub.60-C.sub.100 with a binder having the thickness (width) in the range of 1-3 mm can be used as the carbon source target. Binder could include, low melting solid hydrocarbons, e.g. such as an organic wax. The layer can be placed on some substrate and immersed in deionized water.

(13) The thickness of the deionized water layer above the surface of the carbon source target can, for example, be in the range of 0.5 to 10 mm.

(14) In some embodiments carbon soot as carbon containing material for carbon source target could be used.

(15) Commercially available laser source operating at the wavelength in the range of 532 to 1064 nm can be used for producing the nanodiamonds, according to the present invention. At least one single rectangular pulse of the electromagnetic energy having the pulse width in the range of about 0.01 to about 5 microseconds can be applied to the selected area located within the liquid phase above the surface of the carbon source target. Laser pulse intensity may be in the range of about 10.sup.6 to about 10.sup.13 W/cm.sup.2 and preferably of about 10.sup.10 to about 10.sup.11 W/cm.sup.2. The predetermined distance between the selected area and the surface of the carbon source target can be in the range of 0.5 to 10 mm, preferably in the range of 2-5 mm.

(16) In one specific example, nanodiamonds with average size of nanodiamond particles between about 4 to about 5 nm have been obtained using laser pulses of 12 nanoseconds width with intensity of about 710.sup.10 and focused onto a selected area located within the liquid at a distance of about 3 mm above the surface of the carbon source target immersed into deionized water. After the irradiation the produced material is subjected to a cleaning step of separation of the synthesized nanodiamond material from the non-converted material and the binder.

(17) The present invention, in yet further aspect, may provide further cleaning or purification of the synthesized nanodiamond material. Nanodiamonds could be isolation and cleaned by flotation method in deionized water with further optional washing and drying.

(18) The following properties of the nanodiamond can be obtained by the process and system of the present invention:

(19) The purity of the nanodiamond powder is up to 99.99% by weight of nanodiamond particles as determined by conventional X-ray fluorescence (XRF) technique.

(20) The size of the nanodiamond particles produced according to the present invention is of about 2-10 nm and is mainly distributed between 4 and 5 nm as determined by conventional tunneling electron microscopy (TEM), i.e. is very uniform.

(21) In specific examples nanodiamond powder of the present invention could be characterized by at least one of the following: incombustible residue of 0.004%, Dseta (Zeta) potential: +45 (pH=7) and aggregate size in water: 5-50 nm.

(22) FIGS. 2A and 2B illustrate results of Thermo Gravimetric Analysis (TGA) for samples produced by detonation or explosive based technique and present invention technique accordingly. TGA graph for nanodiamond sample prepared in accordance with present invention (FIG. 2B) exhibits relatively narrow temperature range of decomposition: 250 C. in comparison with 390 C. for sample produced by detonation or explosive based technique. Presence of fracture at T=590 C. in FIG. 2A graph indicates heterogeneity of the material. This fracture is not presented in FIG. 2B graph characterizing sample prepared according to the present invention.

(23) FIGS. 3A and 3B illustrates Raman spectra for nanodiamond samples produced by detonation or explosive based technique and present invention method accordingly. Intensive peak at 1323 cm.sup.1 of spectrum of FIG. 3B corresponds to higher diamond phase content in sample produced by present invention compared to detonation or explosive based technique (FIG. 2A). Shifts of peak corresponding to the diamond from 1332 cm.sup.1 to 1322 cm.sup.1 (FIG. 3A) and to 1323 cm.sup.1 (FIG. 3B), as well as the shifts of G-line from 1590 cm.sup.1 to 1620 cm.sup.1 and 1625 cm.sup.1 could confirm average nanodiamond size of about 2-6 nm. Additional peak at Raman spectra of FIG. 3A at 1350 cm.sup.1 indicates the presence of particles with sizes 30-50 nm and the peak at 1585 cm.sup.1 indicates the presence of graphite.

(24) Potential fields of application of the nanodiamond of the present invention include, but are not limited to, machine building, shipbuilding, space&aircrait industry, abrasive and medical tools, electronics, semiconductors manufacturing, electrical engineering, medicine, precise tooling, chemistry, biology, etc. For example, the nanodiamond produced by the method and system of the present invention could be used as additives to polishing pastes and suspensions for preparing highly precise materials for radio engineering, electronics, optics, medicine and machine building. In such applications, the nanodiamonds facilitate to reduce roughness of the treated surfaces to a few nanometers, or less. Moreover, the nanodiamonds obtained by the method and system of the present invention may be used in technologies of polymerization from solutions and melts, chemical curing, electron-beam, gas-flame and electrostatic spraying. Likewise, the nanodiamonds obtained by the method and system of the present invention can be used in preparing lubrication substances and lubricant-coolant liquids, for example, as additives to motor and transmission oils.

(25) Furthermore, the nanodiamond obtained by the method and system of the present invention can be used in the metal plating technologies, where the nanodiamonds can be used along with metals, such as Cr, Ni, Cu, Au, Ag, Zn, Sn, Al, NiB, etc, Although the example of utilization of the method and system of the present invention was shown for production of nanodiamond, the technique can also be used, mutatis mutandis, for producing cubic boron nitride (CBN). CBN is similar to diamond in its polycrystalline structure and is also bonded to a carbide base. CBN is of great interest for a multitude of applications. CBN could work effectively in cutting tools for most common work materials, with the exception of titanium, or titanium-alloyed materials, because of its extreme hardness and therefore brittleness. CBN combines a number of extreme properties, such as great hardness and rigidity, optical transparency over a large wavelength range, chemical resistance and high thermal conductivity.

(26) It is to be understood that the terminology employed herein are for the purpose of description and should not be regarded as limiting.

(27) Those skilled in the art will readily appreciate that various modifications and changes can be applied to the embodiments of the invention as hereinbefore described without departing from its scope defined in and by the appended claims.