WO2009101607A1

WO2009101607A1 - A method for production of carbon composite material with modified microstructure and a carbon composite material produced thereof

Info

Publication number: WO2009101607A1
Application number: PCT/IB2009/051201
Authority: WO
Inventors: Jaan Leis; Maike KÄÄRIK; Mati Arulepp; Helle Kuura; Marko LÄTT; Andres Kuura
Original assignee: Carbon. Ee Oü
Priority date: 2008-02-14
Filing date: 2009-02-12
Publication date: 2009-08-20
Also published as: EE200800008A

Abstract

Method for production of microporous carbons with modified microstructure. Carbon is made from metal or metalloid carbides. The method applies the chlorination method for the catalytic transformation of carbide into carbon. The method gives possibility to make partially graphitic carbons with precisely predetermined porosity and graphitisation for the adsorption and electronic applications, which are based on processes in the surface of carbon.

Description

A method for making carbon composite material with modified microstructure and the carbon composite material produced by the method

FIELD OF THE INVENTION

The present invention relates to the synthesis of nanostructural, partly graphitized porous or non-porous carbon materials. The invention also relates to the improvement of the path of carbon synthesis, which includes halogenation of metal or metalloid carbides.

BACKGROUND OF INVENTION

Microporous carbon of carbide origin has a characterised narrow pore size distribution, as a result of which the given materials are very attractive in several important application fields, e.g. gas and liquid purification from contaminating impurities, especially those made up of small-sized molecules, desalination of drinking water, storage of low-molecular gases, electric energy storing devices, e.g. batteries and capacitors, etc. According to the international standards (IUPAC), pores with a size (diameter) less than 20 Λ (1 A = 0.1 nm) are considered micropores. The average pore size in carbidic carbon materials can reach up to 6-7 A. The porosity of carbidic carbon materials and the size of pores depend significantly on the temperature of the synthesis. The dependence of the pore size peak values on the chlorination temperature has been discussed in the article [Gogotsi et al. Nature Mat., Vol. 2, p. 591 (2003)].

Materials with even pore size distribution and extremely small-sized pores are, in real life, difficult to dry and poorly accessible by the adsorbed molecules. Post-treatment is applied to the microporous carbon in order to decrease the diffusional resistance. Prior art provides the oxidative methods for increasing the carbidic carbon pores, described for example by US6,602,742; 1186,697,249 and WO2004094307. Alternative methods describe the refraction of the surface layers of carbon particles, which improves the adsorptional qualities of the carbon material. Corresponding methods are described in the Estonian Patent Application No. P2Q040Q091 , 15.02.2006, which relates to the implementation of solid oxidant in the environment of the reaction between carbide and chlorine, and in the Estonian Patent Application No. P200500009, 15.12.2006, which relates to the gradual chlorination of carbide particles in the changeable temperature range. The latter method prescribes that the surface layer of carbide particles shall be chlorinated at higher temperature than the inside of the particles, based on the fact that the higher the chlorination temperature is the bigger is the average size of pores and the smaller is the diffusional resistance.

On the other hand, the synthesising temperature determines not only the size of the pores of the carbidic carbon material (CDC) but also the structural regularity of the carbon material at nano- and micro-level. Thus, the method for producing CDC enables to control through chlorination temperature the graphitisation of the carbon material. The higher the temperature the more structured is the carbon that evolves during the synthesis. The following chemical reaction describes the transformation of the mineral carbide into carbon:

MC_x + y/2CI₂ > xC +MCI_y

It is known that in the presence of d-metals the chlorination of TiC gives a significantly more graphitised carbon than without the d-metals. When an extensive CDC graphitisation takes place at temperatures exceeding 1200-1300⁰G₁ then, by employing catalytic additives, it is possible to elicit graphitisation at significantly lower temperatures [Leis, J. et al. Carbon 2002, 40, 1559]. Prior art describes how, by employing the catalyst, the chlorination temperature affects the nanostructure and average graphitisation of the carbidic carbon, however, it does not provide a way how, with the help of catalytic additives, to produce carbidic carbon particles with a layered structure, possessing a surface layer with higher graphitisation than that of the carbon in the inside of the particles. Also, prior art does not provide a method for producing, by catalytic chlorination of carbide, the nanoporous carbon material, the particles of which would be surrounded by graphitic carbon. The carbon material of that type could possess great potential as an electrode material of energy storage units, providing better electric contact between the particles when compared to fully amorphous nanoporous carbon. For example, document US6,O22,518 suggests that the surface graphitisation of the pyrolytic carbon material produced from mesophasic tar improves significantly the charge-discharge characteristics of carbon electrodes in Li-ion batteries. On the other hand, it is known that nanostructural carbon materials, or, carbon nanotubes are prospective sources of electron emission, with potential application in ultra-thin luminescent screens [Bonard, J.-M. et ai Appl. Phys. 1999, A 69, 245]. Carbon nanotubes evolve preferably by the catalytic precipitation of carbon atoms from the gaseous phase, whereby nano particles of Ni or Co are usually the catalysts. The document 1137,239,073 describes carbon material, which has nanotube-like structures pyrolytically precipitated onto its surface in the atmosphere of acetylene for the purpose of improving thθ emission qualities.

Prior art provides CDC of multi-wall nanotubes with similar structure that has been prepared in the presence of Ni, Co and Fe chlorides from aluminium carbide. Nanotubes were very short in that instance and rather resembled multi-wall carbon flakes, so the authors called the carbon nano-particles nanobarrels [Leis, J. et al. Carbon 2001 , 39, 2043 and Perkson, A. et al. Carbon 2003, 41, 1729]. However, documents describing prior art do not provide any carbon materials that, as a result of the catalytic halogenation of carbides, would acquire layered structure in which the outer layer nanostructure of carbon particles differs from the nanostructure of the inside of the particles, whereby the outer layer is formed by the hollow graphitic nanostructures resembling the nanotubes.

SUMMARY OF THE INVENTION

Current invention provides method for the preparation of carbon that would,guarantee the production of carbon materials with the desired porosity and graph itisation ratio. Invention describes the modification of the carbide halogenation process to improve the porous and graphitic structure of carbon produced during the process. General mass balance of carbon formation from carbides is described by the following chemical equation:

M_xC + xy / 2X₂ → C + xMX_y

In most cases, carbon with microporous structure is produced from metal and metalloid carbides at temperatures under 1000 ⁰C. Temperatures exceeding the latter increase the tendency of producing multi-layered πaπographitic lamellae and sheets that also cause the formation of larger micro- and mesopores. Current invention describes the method that allows, during carbide chlorination without additional oxidants and variation of chlorination temperature, to create in the particles of microporous carbon the pore size distribution that would ensure better access to the micropores with the size of 7-8 A, inside the carbon particles. The purpose of the invention is to create during halogeπation a somewhat more graphitic carbon in the surface layers of carbon than in the inside of the particles. The method is based on the fact that the average size of carbon pores depends on the graphitisation level of the carbon material, whereby the graph itisation level is affected through the chemical reagents with catalytic effect, added to the reaction environment. Since the chlorination of carbides is a solid-phase chemical process, the catalytic effect of the catalysts is manifested mainly only in the surface layers of the particles transformed from carbide to carbon. Thus, it is evident that the larger the particles of the halogeπated carbide are, the more effective is the result. Current invention regards various 8th - 10th group metals of the periodic system as suitable catalysts, e.g. Fe, Co, Ni or combinations thereof, whereby, the chlorides of given metals are preferably used.

Aspects treated bv the invention include:

- optimum catalyst concentration for preparing surface-graphitised microporous carbidic carbon;

- optimum catalyst concentration for chlorinating chemically passive carbides (e.g. SiC, B₄C) and preparing corresponding graphitic carbidic carbon;

- affecting the porosity and graphitisation ratio of carbidic carbon, depending on the size of the substrate particles and concentration of catalytic reagents. Catalysts compensate for the absence of carbide chlorination temperature. It is of particular importance with chemically passive carbides, e.g. SiC, B₄C etc. High synthesis temperature, that of reaching 1000 °C, sets high demands for the reactor material. Extremely high temperatures are tolerated, for example, by graphite- or ceramic reactors, which are inert to chlorine and strong Lewis acids. Using catalysts allows greater flexibility in the selection of reactor material when performing so-called "high-temperature" syntheses - for example, when preparing carbidic carbon with high level of graphitisation, one can use quartz reactors, which have the highest permitted temperature of just 1000-1100 ⁰C.

According to the present invention, the synthesis temperature and catalyst have different effect on the structure of carbon. Temperature affects the relocation and association of carbon atoms uniformly over the entire material, while the effect of the catalyst is local, i.e. catalytic effect is manifested only on the contact surface of reacting particles (see Fig 1).

Since conversion of carbide into carbon, using halogen, is a solid-phase chemical process, it is evident that, the smaller the dimensions of the substrate are, the closer is the structure of catalytically synthesised product (C) to the structure of carbon (B) that has been produced without a catalyst.

Since catalyst metal chlorides dissolve to some extent in the by-product emerging in the chlorination of carbide - chlorides known as strong Lewis acids, then, it is likely that the catalyst does not affect only the transformation into carbon of the surface layers of carbide particles, but catalyst particles diffuse also depthwise. Thus, it is evident that the catalyst concentration in the reaction mixture is of particular importance. The higher the catalyst concentration, the more extensive is the graphittsation.

The effect of the catalyst concentration on the CDC structure can be assessed also from the position of the electronic structure of carbon atoms. Fe, Co and Ni as known catalysts of the generation of fullerenes and carbon nanotubes, promote, due to the catalysis mechanism assuming complexes between the metal and carbon atoms, the production of non-planar carbon atom configurations. Thus, catalytically generated carbon atoms are prevalently in sp²-hybridized state, however, due to non-planar structures, carbon-carbon bonds are deformed and bond lengths and valency angles correspond rather to the intermediate states of sp² and sp³ hybridization levels. In other words, if carbon in the state of sp², which corresponds to the planar graphitic carbon, is also known as a good conductor, then, due to the electronic interference, a certain shift is evident towards the sp³-hybridized carbon, i.e. carbon characteristic to diamond, and the material possesses the qualities of a semiconductor rather than those of metallic conductor.

On the other hand, it would be reasonable to assume that with the high concentration of the catalyst the dense settlement of catalytic active centres the generation speed of carbon atoms and chemical bonds between them significantly higher than the speed of atoms' relocation in space. The result is the production of energetically favourable layered graphite domains and turbostratic carbon. In order to bring about the specific effect of the catalyst on the generation of the CDC nanostructure, but not the extensive graphitisation of the carbon material, one can optimise the amount of the catalyst. By doing so, CDC structural and electronic parameters can be fine-tuned and carbon materials of desired porosity and graphitisation ratio, having high chemical purity, can be produced. Figure 1 displays schematically the surface-structured/graphitised carbon (C) according to the invention. The carbon of this kind is essential first of all in fields of application that are based on the adsorption and electronic processes occurring on the surface of the material, e.g. electron emission. BRIEF DESCRIPTION OF THE DRAWINGS

The following describes the method according to the invention with references to the figures where

Rg 1 displays schematically the generation of microporous carbidic carbon (C) with limited graphitisation when compared to the microporous (A) and graphitic (B) carbidic carbon known from prior art.

Fig 2 displays the dependence from catalyst concentration of N₂ adsorption isotherms of carbidic carbon materials, prepared by SiC catalytic chlorination.

Fig 3 displays X-ray diffraction spectra, which show the carbon material, produced according to the invention by the catalytic chlorination of SiC at the temperature of 900 ⁰C, have its graphitisation increased with the increase in the amount of the catalyst,

Fig 4 displays the dependence from the amount of the catalyst of the porosity and graphitisation of the carbon material, produced by the catalytic chlorination of SiC at the temperature of 900 ⁰C, Fig 5 displays the dependence between the relative graphitisation and pore sizes in carbon materials produced by the catalytic chlorination of SiC at the temperature of 900 ⁰C₁ ig 6 displays the N₂ adsorption isotherms of carbidic. carbon materials, prepared by B₄C catalytic chlorination at 1000 ⁰C, ig 7 displays the X-ray diffraction spectra of carbon materials, prepared by B₄C catalytic chlorination at 1000 ⁰C. DETAILED DESCRIPTION OF INVENTION

The mass balance of the silicon carbide chlorination reaction is expressed with the following equation (equation 1):

SiC + 2Cl₂ -> C + SiCI₄ (1) The equation assumes that, theoretically, one mol of silicon carbide gives one mol of carbon. The actual carbon yield is usually lower, since, due to the excess chlorine in the reaction environment, part of the carbon is taken out of the reaction environment as carboπ-tetrachloride resulting from the secondary reaction. The yields in the examples of current invention vary in the range of 90-95%, depending from the conditions of the reaction.

It is known from prior art that the carbon produced by chlorinating silicon carbide at the temperature of 800-1100 ⁰C is, according to X-ray diffraction and high-resolution transmission electron microscopy (HRTEM) surveys with predominantly amorphous, microscopic structure. The carbon of that kind wields high BET special surface, approximately 1100 πf per gram, and is almost totally microporous, with a dominating pore size of ~7 A.

By adding catalyst to the reaction environment the chlorinating of silicon carbide produces carbon material with lower special surface and higher graphitisation, as is shown by nitrogen adsorption isotherms on Fig 2 and X-ray diffraction spectra on Fig 3. Rapid reaching of the plateau at adsorption isotherms and the identical rise of isotherms proves that the catalyst does not influence structure of micropores on the occasion of moderate catalyst amount, however, the number of micropores is directly dependant on the amount of the catalyst. Local effect of the catalyst is proven also by the Fig 5, which reveals that the graphitisation generated by the catalyst does not affect the average micropore size. Since no significant production of mesopores is witnessed with the decrease of micropores (i.e. from the hysteresis nitrogen desorption derived from the capillary condensation), it can be concluded that the catalyst causes in silicone carbide chlorination the formation of predominantly non- porous graphitic carbon. Thus, by changing the catalyst amount, it would be possible to control the porosity and graphitisation ratio at similar synthesis conditions (same chlorination temperature) (see Fig 4), or, in other words, the thickness of graphitic shell in the particles of microporous carbon received from silicone carbide. Fig 2 displays the dependence from catalyst concentration of N₂ adsorption isotherms of carbidic carbon materials, prepared by SiC catalytic chlorination. Fig 3 displays X- ray diffraction spectra, which show the carbon material, produced according to the invention by the catalytic chlorination of SiC at the temperature of 900 ^DC, have its graphitisation increased with the increase in the amount of the catalyst. The SiC diffraction spectrum, displayed as a comparison, proves the total transformation of carbide into carbon by chlorination. Fig 4 displays the dependence from the amount of the catalyst of the porosity and graphitisation of the carbon material produced by the catalytic chlorination of SiC at the temperature of 900 ⁰C and Fig 5, displays the dependence between the relative graphitisation and pore sizes in carbon materials produced by the catalytic chlorination of SiC at the temperature of 900 ⁰C, which proves that the increase in the graphitisation, resulting from the increase of the catalyst amount, does not reflect the structural change of the entire carbon material, but is rather a local phenomenon. The mass balance of the boron carbide chlorination reaction is expressed with the following equation (equation 2):

B₄C + 6Cl₂ → C + 4BCI₃ (2)

According to the chemical equation, an approximately similar quantity in weight of carbon is produced from boron carbide than from silicone carbide. However, the nanostructure of both carbons differs significantly from each other, deriving from the differences in the stoichiometries of source carbides and the greater division of carbon atoms in B₄C crystal lattice. Thus, the porosity of the carbon, obtained by chlorination of boron carbide, is higher and the pore size corresponds to the micro/mesopore material. By adding catalyst and varying its amount in the boron carbide chlorination environment, it would be possible, similarly with SiC chlorination, to vary in a wide range the porosity and graphitisation characteristics of the carbon material (see Fig 6 and Fig 7). Partly graphitised micro/mesoporous materials of that kind offer a good alternative to the various catalyst carriers and electrode materials of energy storage units used today.

Fig 6 displays the N₂ adsorption isotherms of carbidic carbon materials, prepared by B₄C catalytic chlorination at 1000 ⁰C. Fig 7 displays the X-ray diffraction spectra of carbon materials, prepared by B₄C catalytic chlorinatioπ at 1000 "C. The catalyst amount with regard to the carbide is shown on the figure.

In order to carry out the method according to the invention, the source carbides could be selected also from among Si, Ti, B₁ Al₁ V₁ Zr, Nb, Hf, Mo, Ta and W carbides, although silicone carbide is preferably used as the source carbide.

The first embodiment of the method according to the invention uses for the catalyst a unicomponent chemical compound, with which the production of graphitised nanostructures is catalysed during carbide halogenation at the temperature T₁, without causing chemical modification of the carbon material. For the chemical compound the compound containing the periodic system element of 8 - 10th group is used, preferably a Co, Ni or Fe compound is selected, whereby, chloride is the preferred compound, whereby the amount of the chemical additive, used as the catalyst brought into surface contact with the source carbide, is used to determine to thickness of the layer graphitised at the temperature Ti and the nanostructure in the carbon composite material with modified microstructure.

In the preferred embodiment of the invention the catalyst is formed of the mixture of multiple-component CoCI₂, NiCI₂ and FeCI₃ equal partial samples so that the concentration of every component remains within the range of 0.1 -5.0 weight percentage with regard to the source carbide, whereby the average size of carbide particles is less than 10 micrometers.

The catalyst exists in the fine-dispersed solid form and shall be brought to surface contact with the source carbide by mechanical mixing with the source carbide.

In an alternative embodiment of the invention the catalyst is previously dissolved in a solvent and is then brought to surface contact with the source carbide, by mixing it with the source carbide, so that a paste-like substance is obtained from the catalyst and source carbide. Water or a selection made from among alcohols is used as a solvent, whereby the kind of solvent is used as catalyst solvent, which could be removed from the synthesis environment prior to halogenation without imposing chemical effect on carbide. In producing the paste-like substance of the source carbide and the catalyst, solvent is vaporised from the catalyst and source carbide paste prior to halogenation. For preparing the carbon composite material with modified microstructure according to the invention, by catalytic halogenation of crystalline or polycrystalline metal or metalloid, firstly, to the crystalline or polycrystailine metal or metalloid carbide is added the graphitisation-faciiitating catalyst, being in surface contact with it, then, given carbide and catalyst are heated in a non-oxidative environment to a corresponding reaction temperature Ti within the range T₁=SOO-ISOO ⁰C and halogenated in the temperature range from Ti=800-1200 ⁰C to T≤=20Q-12Q0 ⁰C, as a result of which a carbon composite material of controlled graphitisation is obtained, the surface layer of which corresponds to the graphitic carbon. It is clear to those skilled in the art that graphitisation stands for three-dimensional sets of grapheme layers, which are characterised by Bragg's (002) X-ray diffraction signal, and the inside of the carbon composite material is of predominantly non-graphitic porous structure.

Example 1 The following example describes the catalytic chlorination of SiC according to the invention in a quartz stationary bed reactor.

Silicone carbide (Sika Tech, FCP13C, 10.0 g), with average particle size of 0.8 μm, and previously prepared ethanol solution of catalysts were mixed into a paste from which solvent was vaporised at 70-100 ⁰C. Then, carbide, enriched with desired amount of the catalyst (0.1 weight percentage with regard to carbide), was placed into quartz reactor and flowed with Argon (2 l/min) until the reaction temperature (900 °C) was achieved. Thereafter the carbide was let to react with a flow of chlorine gas (99,999% assay) for 60 minutes at 900 ⁰C. Flow rate of chlorine was 1.5 l/min.

The by-product, StCU, was led out by the stream of the excess chlorine and passed through a water-cooled condenser into a collector. After that the reactor was flushed with Argon (2 l/min) and the reactor was ventilated for 60 minutes at 1000 ⁰C. After cooling of the reactor the obtained carbon powder (~3 g) was placed into quartz stationary bed reactor and treated with hydrogen gas (1.5 l/min) at 800 ^DC for 3.5 hours to dechlorinate completely the carbon material. During heating and cooling, the reactor was flushed with a slow stream of Argon (0.3 l/min). Final yield of the carbon material was 2.8 g (-93 % of theoretical). Table 1 presents the qualities of carbon material according to the invention, obtained by SiC chlorination according to the invention, as described in example 1.

Examples 2-4 describe SiC catalytic chlorination according to the invention in a quartz stationary bed reactor, which has been performed similarly with the example 1, differing only in the catalyst concentration, which was 0.5%, 1.0% and 5.0% with regard to carbide, respectively. Table 1 displays the qualities of the carbon material prepared according to respective examples.

Examples 5-7 describe B₄C catalytic chlorination according to the invention in a quartz rotary bed reactor, which has been performed similarly with the example 1 , differing only in the amount of source carbide, which was 15Og and the catalyst concentration which was 0.1%, 0.5% and 1.0% with regard to carbide, respectively. Chlorination temperature was 1OOO°C and the duration of chlorination was 6 to 7 hours. Table 2 displays the qualities of the carbon material prepared according to examples 5 to 7. The porous structure of synthesised carbon materials was characterised by using the nitrogen adsorption / desorption analysis methods. Low temperature nitrogen sorption experiments were performed using Gemini Sorptometer 2375 (Micromeritics). The specific surface area of carbon materials was calculated according to Brunauer- Emmet-Teller (BET) theory up to the nitrogen relative pressure (P/P_o) of 0.2. The total volume of pores was calculated from nitrogen adsorption at relative pressure (P/P_o) of 0.95. Micropore parameters were obtained by t-plot method.

Average pore size (APS) was calculated from the volume of the slit-shaped geometric shape according to the equation (equation 3):

in which V_p is the total volume of pores and S_BET is the carbon specific surface area according to BET theory.

X-ray diffraction measurements were performed by using CuKa radiation (λ = 1.54 A). Relative graphitisation was calculated according to the equation (equation 4):

X = ^{/o02 / /jo} 100% ₍4) in which /₀₀₂ and /10 are the intensities of corresponding Bragg diffraction signals and 14.3 is an empirical parameter.

Table 1

# Catalyst Specific Micropores Total volume Volume Relative surface pores micropores cone, area graphtt. area [weight %] Vp [cnf/gl V_micro [cm³/g] Vmicro [cm³/g] X [%]

SBET

[m^ε/αl

1 0.1 1092 1016 0.55 0.45 2

2 0.5 903 811 0.54 0.36 14

3 1.0 765 674 0.46 0.23 20

4 5.0 485 368 0.37 0.16 36

Table 2

# Catalyst Specific Volume Total volume Average pore size Relative surface micropores pores cone, [nm] graph it. area [weight %] Vm₁-_Cr₀ [cm³/g] Vp [cm7g] X [%]

SBET

5 0.1 1332 0.33 0.92 1.4 10

6 0.5 1163 0.29 0.84 1.5 28

7 1.0 871 0.23 0.72 1.6 41 Carbon specific surface area (SBET. S_mi_Cro) according to the invention according to BET theory, volume of pores according to nitrogen (Vt_ot, V_mj_Cro) sorption and relative graphitisations are presented in tables 1-2. Table 1 displays results which are based on the examples 1 to 4 of carbon synthesised from silicone carbide (Sika-Tech) at the temperature 900 ⁰C and Table 2 based on the examples 5 to 7 of carbon synthesised from boron carbide (H. C. Starck) at the temperature of 1000 ⁰C.

Comparison examples

The following comparison example 1 A describes the treatment of microporous carbon material prepared by SiC chlorination with the catalyst described in examples 1 -7.

Microporous carbon powder (0~1μm, 2g), with characteristics displayed in Table 3, was dispersed in the catalyst solution. Solvent was vaporised from the prepared paste at 70-100 ⁰C. Then, carbon, enriched with desired amount of the catalyst (1.0 weight percentage), was placed into quartz reactor and flowed with Argon (2 l/min) until the temperature of 600 ^DC was achieved. The duration of heating at the temperature of 600 ⁰C was 60 minutes, after which the reactor was let to cool to room temperature. The characteristics of carbon evaluated after the treatment are displayed in Table 3.

Comparison example 2A has been performed similarly with the comparison example 1A, differing in the treatment temperature, which was 1000 ⁰C. The characteristics of carbon evaluated after the treatment are displayed in Table 3.

Table 3

# Catalyst Specific Micropores Total volume Volume Relative cone, surface pores micropores area graphit. area [weight %] Vp [cm³/g]

V_m(cro [cm³/g] V_micro [cm³/g] X [%]

[m^a/c)l source 982 907 0.48 0.40 3% material

1A 1.0 1011 980 0.47 0.43 4%

2A 1.0 978 926 0.48 0.41 4%

The results of comparison example reveal that the qualities of carbon materials described in the embodiment examples of current invention cannot be achieved by the method known from prior art (US6,O22,518), which relates to preparing the surface-graphitised carbon material by heating in the inert atmosphere the carbon material of organic origin, being brought to contact with the catalyst.

It is evident to the one skilled in the art that the embodiment examples of current invention can be adapted to any mineral carbides or carbide combinations. The surface or pore size distribution of the carbon according to current invention can be modified further when needed, using for example the after-treatment with gaseous or liquid chemical reagents or oxidants active with regard to carbon.

Claims

1. Method for preparing the carbon composite rη^jerjai with modified microstructure by catalytic halogenation of crystalline or polyorystalline metal or metalloid, characterised in that to the crystalline or polycrystalline metal or metalloid carbide is added the graphitisation-facilitating catalyst, being in surface contact with it, then, given carbide and catalyst are heated in a non-oxidative environment to a corresponding reaction temperature Ti within the range Ti =800-1200 ^DC and halogenated in the temperature range from

⁰C to T₂=200-1200 ⁰C₁ as a result of which a carbon composite material of controlled graphitisation is obtained, the surface layer of which corresponds to the graphitic carbon, whereas graphitisation stands for three-dimensional sets of grapheme layers, which are characterised by Bragg's (002) X-ray diffraction signal, and the inside of the carbon composite material is of predominantly non-graphitic, porous structure.

2. The method according to claim 1 , characterised in that for the catalyst a unicomponent chemical compound is used, with which the production of graphitised nanostructures is catalysed during carbide halogenation at the temperature Ti, without causing chemical modification of the carbon material.

3. Method according to claim 2, which is characterised in that for the chemical compound the compound containing the periodic system element of 8 - 10th group is used, preferably a Co, Ni or Fe compound is selected, whereby, chloride is the preferred compound.

4. Method according to claim 1 , characterised in that for the catalyst a combination of several chemical compounds from among the periodic system elements of 8 - 10th group is used, with which the production of graphitised nanostructures is catalysed during carbide chlorination at the temperature T-i, without causing chemical modification of the carbon material.

5. Method according to claims 1 to 4, characterised in that the catalyst exists in the fine-dispersed solid form and shall be brought to surface contact with the source carbide by mechanical mixing with the source carbide.

6. Method according to claims 1 to 4, characterised in that the catalyst is previously dissolved and then brought to surface contact with the source carbide, mixing it with the source carbide, so that a paste-like substance is obtained from the catalyst and source carbide.

7. Method according to claim 6, characterised in that a solvent is used as a catalyst dilutant, which could be removed from the synthesis environment prior to halogenation without imposing chemical effect on carbide.

8, Method according to claim 7, characterised in that the solvent is vaporised from the catalyst and source carbide paste prior to halogenation.

9. Method according to claim 1 , characterised in that the amount of the chemical additive, used as the catalyst brought into surface contact with the source carbide, is used to determine to thickness of the layer graphitised at the temperature T₁ and the nanostructure in the carbon composite material with modified microstructure.

10. Method according to claim 1 , characterised in that the source carbide is selected from among Si, Ti, B, Al₁ V, Zr, Nb, Hf₁ Mo, Ta and W carbides, with silicone carbide being preferably used as the source carbide.

11. Method according to claim 1 , characterised in that the catalyst is preferably formed of the mixture of multiple component CoCI₂, NiCI₂ and FeCl₃ equal partial samples, so that the concentration of every component remains within the range of 0.1-5.0 weight percentage with regard to the source carbide, whereby the average size of carbide particles is less than 1 o micrometers.

12. Method according to claim 7, characterised in that the solvent is selected from water and alcohols.

13. Carbon material, which is manufactured by using any of the methods described in claims 1 to 12.