PROCESS FOR THE PRODUCTION OF SUBMICRONIC CARBON STRUCTURES WITH TUBULAR MORPHOLOGY, USING CERAMIC OR METALLIC SUBSTRATES THAT HAVE BEEN SUBJECTED TO THERMAL AND / OR THERMOQUIMIC TREATMENTS.
FIELD OF THE INVENTION The present invention aims to provide a process for the production of submicron carbon structures with tubular morphologies, whose diameters range from about 0.002 to about 0.300 micrometers and whose lengths are less than about 2000 micrometers. In this process, metallic or ceramic substrates are used that have been subjected to thermal or thermochemical previous treatments, which allows obtaining much higher amounts of submicron particles, in comparison to those obtained when using the traditional method that contemplates the use of a quartz substrate This production, in gram quantities per hour of submicron particles of carbon, is achieved by a thermal decomposition of liquid hydrocarbons, such as Toluene (C H3), Benzene (C6H6), Pyridine (C5NH5), Benzylamine (C7H9N), which are dissolved in organometallic compounds vgr., Ferrocene (FeCp2), Cobaltocene (CoCp2), Niclocene (NiCp2), under temperature conditions ranging from approximately 650 ° C to around 1 100 ° C, under inert atmospheres, such as atmospheres of Argon, Helium, Nitrogen, etc. The proposal to use metallic substrates made of steel, copper, aluminum or tungsten, instead of traditional quartz substrates or their variants, for the production of submicron carbon structures, is supported by an improvement in the amount of
Resulting product production. In addition, these substrates have the advantages of having a high coefficient of heat transfer, a longer useful life, as well as great ease of machining. Also, a greater security in the work is achieved, since said substrates now proposed are not as fragile and brittle as quartz. Submicron carbon particles with tubular morphologies can have various applications in the manufacture of reinforced composite materials involving plastics, coatings and metals.
BACKGROUND OF THE INVENTION Various methods of producing submicron carbon particles are known. Among these methods described in the prior art are: • Procedures of laser vaporization of graphite / metal targets, and the method of electric arc discharge with graphite and metal electrodes. Both processes involve energy sources of high intensity or power, as well as the use of organometallic catalysts, vgr. ferrocene, cobaltocene, niquelocene and a carbon source, for example graphite rods. With the aforementioned procedures, reported in the state of the art, submicron particles of monolayer are obtained, that is to say of a single layer, in low quantities, at a very high price and with a great presence of amorphous material, which may limit some applications where transparency is an important requirement (Fig. 1 and 2)
• Chemical Vapor Deposition CVD procedure. This process is based on the decomposition of hydrocarbons and / or organometals at elevated temperatures of about 650 ° C to about 1 100 ° C, on a quartz substrate, in a controlled atmosphere. Submicron carbon particles with tubular morphology can be single layer or
unilapa or multilayer or multilayer (Fig. 3), and are usually deposited in bundles aligned in a perpendicular orientation to the substrate. The most efficient methods for the manufacture of submicron particles have as a main element a substrate of silicon oxide (SiO) on which said particles are deposited. This element constitutes a high cost in the manufacture of submicron particles, besides being a fragile and difficult to obtain material. For all the inconveniences mentioned above, several alternatives have been studied to replace the conventional silicon oxide substrate, until now used.
DESCRIPTION OF THE INVENTION The present invention provides a new form of growth of submicron particles of carbon with tubular morphology, in massive quantities, on metallic materials of steel, copper, aluminum or tungsten, which have received a previous thermal or thermochemical treatment, which they are detailed later. Metallic substrates, previously treated, offer a change in their crystalline structure, which favors the growth of submicron particles. In this way, submicron carbon structures can be produced in greater quantity and at a lower cost. These substrates are used for chemical vapor deposition (Chemical Vapor Deposition: CVD), hydrocarbons, such as: Toluene (C7H3), Benzene (C6H6), Pyridine (C5NH5), Benzylamine (C7H9N), with organometallic components, ggr. Ferrocene (FeCp2), Cobaltocene (CoCp2), Niclocene (NiCp2) at temperatures in the range of about 650 ° C to about 1 100 ° C, under an atmosphere of inert gases, for example, under atmospheres of Argon, Helium, Nitrogen , etc. The substrates now proposed are considerably less expensive and easier to obtain than the conventional substrates hitherto employed, e.g. quartz.
OBJECTIVES AND ADVANTAGES OF THE INVENTION
The invention claimed herein is novel and inventive in the field of manufacturing submicron carbon particles with tubular morphology and has objectives that produce the above advantages. One of the main objectives of the present invention is to achieve the manufacture of submicron carbon structures with tubular morphology using metal or ceramic substrates that have been previously subjected to certain treatments, which include both thermal and thermochemical treatments. The methods for obtaining tubular submicron particles of carbon, hitherto reported in the literature, always use quartz substrates. The Chemical Vapor Deposition (CVD) method is used for the manufacture of these particles, and equipment similar to that used for the manufacture of submicron carbon particles with conventional tubular morphology is used, but now with the difference that the substrates used have been previously treated, with the consequent advantages that this brings. One of the advantages of this method is that production can be carried out continuously, in addition to obtaining large quantities of the resulting product, under controlled conditions. Most of the submicron particles thus obtained is single layer or multilayer. A further objective of the present invention is to increase the production of submicron carbon particles with tubular morphology by more than ten times, when a stainless steel substrate is used that has previously been subjected to a heat shock treatment. the present invention is to achieve the production of structures
submicron carbon with very pure tubular morphology, when a steel tube with SiOx film and thermal treatment is used as substrate. Another objective of the present invention is that, for the first time. the production of submicron particles of carbon with tubular morphology is reported, using substrates of copper, aluminum and tungsten. Another objective of the present invention is that the production of submicron carbon structures with tubular morphology grown in bundle-spiral is also reported, using as a substrate a thermochemically treated AISI 1018 steel tube, and in which an oxide is deposited. aluminum (A203). Another objective of the present invention is to achieve the formation of submicron particles of carbon with tubular morphology grown in bundle or bundle-spiral when a copper substrate is used. Another objective of the present invention is the manufacture of submicron carbon particles with multilayer or multilayer tubular morphology when a tungsten substrate is used. Another objective of the present invention is the manufacture of submicron carbon particles with multilayer or multilayer tubular morphology when an aluminum substrate is used. Another objective of the present invention is the greater production that is obtained and, thanks to the use of cheaper substrates, it is possible to improve the costs of manufacturing submicron carbon particles with tubular morphology. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 represents an illustrative scheme of the laser vaporization device capable of producing submicron particles within a quartz tube. Figure 2 represents an electric arc generating device capable of producing
submicron particles. Figure 3 represents an illustrative scheme of the Chemical Vapor Deposition CVD method, by means of a steam generator with quartz substrate for the manufacture of submicron particles of carbon with tubular morphology. Figure 4 represents scanning microscopy images of submicron carbon particles with tubular morphology grown on steel substrates with thermal treatment (thermal shock): Figure 5 represents scanning microscopy images of submicron carbon particles with tubular morphology, grown on steel substrates with heat treatment and film SiOx: Figure 6 represents scanning microscopy images of submicron carbon particles with tubular morphology, grown on steel substrates with thermochemical treatment: Figure 7 represents scanning microscopy images of submicron carbon particles with tubular morphology, grown in their copper treatment with heat treatment: Figure 8 represents scanning microscopy images of submicron carbon particles with tubular morphology, grown on aluminum substrate with heat treatment: Figure 9 represents scanning microscopy images of submicron carbon particles with morphology tubular, grown on tungsten substrate; DETAILED DESCRIPTION OF THE DRAWINGS Figure 1 shows a diagram for the manufacture of single-layer submicron carbon particles that are produced by laser vaporization inside a furnace (1) with a quartz tube at 1200 ° C, in where: The furnace (1) comprises a copper collector (2) cooled with water, one step
of argon gas (3), a high power laser (4), the deposit of nanotubes (5) and white graphite (6). In the first reports of the laser vaporization technique it is indicated that a conversion of graphite (6) to submicron particles of a layer of the order of 70 to 90% is obtained. These are found in the condensed vapor resulting from the material that the laser (4) evaporated. The material to be evaporated consists of a graphite compound with cobalt and nickel (6) which is located inside an oven (1) at 1200 ° C. Two consecutive pulses of high-power laser (4) are used to evaporate the target and a flow of argon gas transports the submicron particles produced to a copper collector (2) cooled with water. Figure 2 shows the electric arc generating device capable of producing submicron particles of carbon when a plasma is formed when current flows between two graphite rods, where the water inlets (7) are introduced to the device, as well as the conduits of helium flow (9) and Teflon (11), observing elements of water cooling (12), a manometer (13) and another conduit that goes to the vacuum pump (14). The graphite rods (10) are inside the device, while the vacuum seals (15) are outwards as well as the water outlets (8). The electric arc between graphite electrodes is a traditional tool for generating high temperatures required to vaporize carbon atoms until they are converted into plasma (> 3000 ° C). This technique has been used to produce single and multi-layer submicron particles, and bundles of multilayer submicron particles. The typical operating conditions of an arc to produce submicron particles involve the use of two graphite rods (10) of 5 to 20 mm in diameter separated by 1 mm. A voltage of 20-25 V is applied between the bars and a direct electric current of 50-120A flows between the bars (10). The arch is submerged in a helium atmosphere (9)
at 500 torr with a flow of 5-15 ml / s for reasons of cooling. While submicron particles are formed, the length of the positive electrode (anode) decreases. Figure 3 shows a diagram of the device to produce submicron particles of carbon using an ultrasonic steam generator (16) where a cylinder (18) of inert gas of 9.5 m3, which serves to drag the steam that is generated, feeds inert gas into the system. The ultrasonic generator (16) is a glass container with an inlet for the inert gas on one side and a wide-mouth outlet on the upper part through which the vapors formed by the oscillation of the electric piezo located at the bottom of the container. This glass container also has a glass coil inside that can serve to cool the solvents in case of rising temperature. The vapors are fed to a quartz tube (17) of approximately 2.54 cm to 5.08 cm (1 - 2 in). of diameter and of around 1 to 1.20 m in length that crosses two furnaces 19 and 19 'horizontal tubular electric mark Barnstead International model F 21 135 with temperature control where the heating is carried out at the desired temperature of between approximately 650 ° C and 1000 ° C. At the end an acetone trap (20) made of glass is connected, which is nothing more than a closed glass container in which the vapors coming out of the quartz tube on acetone are bubbled so that they do not leave the environment . Figure 4 shows scanning microscopy images (electronic scanning) of submicron carbon particles with tubular morphology grown on steel substrates with heat treatment (thermal shock) in a FEI microscope.; model XL30 FEG / SFEG Faithful Emission Gun of high resolution. a) Image of particles grown on treated steel substrate, increased 201 1 times
size. b) Image of particles grown on treated steel substrate, increased by 2514 times its size. Figure 5 shows images of scanning microscopy (electronic scanning) of submicron carbon particles with tubular morphology, grown on steel substrates with heat treatment and film with SiOx, in a FEI microscope, model XL30 FEG / SFEG True Emission High resolution gun, a) Image of submicron particles grown in heat treated steel and silicon film, increased 50 times its size. b) Image of submicron particles grown in heat treated steel and silicon film, increased 150 times its size. Figure 6 shows scanning microscopy images (electronic scanning) of submicron carbon particles with tubular morphology grown on steel substrates with thermochemical treatment obtained in a FEI electronic microscope, model XL30 FEG / SFEG Fiel Emission Gun high resolution . a) Image of particles grown in steel chemically treated with silicon increased 150 times its size. b) Image of particles grown in chemically treated steel with aluminum augmented 100 times its size. Figure 7 shows scanning microscopy images (electronic scanning) of submicron carbon particles with tubular morphology grown on copper substrate with heat treatment obtained in a FEI electronic microscope, model XL30 FEG / SFEG Fiel Emission Gun high resolution , a) Image of particles grown on copper substrate with heat treatment increased 101 times its size.
b) Image of submicron particles of carbon grown in copper increased 1257 times its size. Figure 8 shows images of scanning microscopy (electronic scanning) of submicron carbon particles with tubular morphology grown on aluminum substrate with heat treatment obtained in a FEI electronic microscope, model XL 30 FEG / SFEG Faithful Emission Gun high resolution. a) Image of submicron particles of carbon grown on aluminum substrate with thermal treatment increased 40 times. b) Image of submicron particles of carbon grown in aluminum increased 500 times. Figure 9 shows scanning microscopy images (electronic scanning) of submicron carbon particles with tubular morphology grown on tungsten substrates obtained in a FEI electronic microscope, model XL30 FEG / SFEG Faithful Emission Gun of high resolution a) Image of submicron carbon particles grown on tungsten substrate augmented 100 times its size. b) Image of submicron carbon particles grown on tungsten substrate augmented 1000 times its size. PREFERRED EMBODIMENT OF THE INVENTION The process of mass production of submicronic carbon particles comprises the following steps: 1. The dissolution, during a period of time of about 15 to about 20 minutes by means of an ultrasonic bath, of about 2 to about 5% of an organometallic compound selected from the group comprising Ferrocene (FeCp2), Cobaltocene (CoCp2), Niquelocene (NiCp2), in a hydrocarbon selected from
group comprising Toluene (C7H3), Benzene (C6H6), Pyridine (CsNHs), Benzylamine (C7H9N). After this period of mixing time, approximately 1 to about 3% of H20 is added to have a better purity of submicron particles or, what is the same, a lower presence of amorphous material 2. - The placement of the solution above in the steam generator, which may be of the atomizing nozzle type or of an ultrasonic generator. 3. - The connection of the steam generator with the steel tube that has been previously subjected to a thermal shock, or the connection to a quartz tube in which the ceramic or metal substrates have been introduced with thermochemical treatment, or aluminum , copper or tungsten with heat treatment. 4. - The stage of flowing an inert gas of high purity selected from the group comprising Argon, Helium, Nitrogen, etc.; once the system is sealed, at a rate of less than 0.5 1 / min. 5. - The heating of the tubular furnaces at a temperature within the range of about 650 ° C to about 1000 ° C. 6. - Increase in the flow of inert gases, once the desired temperature is reached at 2-3 1 / min. At the same time, the steam generator begins to operate, and so continues to do so for the next 15 to 60 minutes approximately. Said steam generator is of the atomizing nozzle type or of the ultrasonic generator type. 7.- The ovens are turned off and the system is allowed to cool down, after the steam generator's operating time has elapsed, until the ambient temperature is reached, keeping the inert gas supply in a ratio of 0.5 1 / min. 8.- Once the system reaches room temperature, the steel or quartz tube is removed with the ceramic or metal substrates with thermochemical treatment, or the substrates of copper, aluminum or tungsten and, with an elongated spatula, scrape the walls
of the tube in the area where the ovens favored the dissociation and deposition reactions. The material obtained is a black powder produced in a ratio of about 4 to about 35 grams per hour consisting of submicron cylindrical carbon particles of diameters from about 0.002 to about 0.300 micrometers and lengths less than about 2000 micrometers and with a presence reduced of amorphous material. Procedure for the preparation of the steel tube, which is to be used as a substrate by means of a heat treatment
1. The steel tube, i.e. the substrate, is introduced into a tubular furnace system of high temperature. 2. The system is heated to a temperature, within the range of about 850 ° C to about 1000 ° C, and is maintained for a period of time of about 25 to about 45 min. 3. Once this time has elapsed, the ovens are turned off and the steel tube is removed, which is subjected to a strong thermal shock with a flow of nitrogen (N2) liquid at high pressure, or is introduced in cold water to lower its temperature violently. 4. After subjecting the tube to thermal shock, the inner walls of said tube are ground with diamond stones at a speed of approximately 2500 revolutions per minute, by means of a device mounted in a conventional drill. 5. The inner walls of the tube are cleaned with a solvent selected from the group comprising acetone and / or alcohol. 6. The tube is ready to deposit the submicron cylindrical carbon and / or silicon particles. (Fig. 3)
Procedure to prepare the steel tube to be used as substrate with a SiOx film and a heat treatment.
1. The tetraethyl orthosilicate, (TEOS), is placed in an ultrasonic generator.
2. The ultrasonic generator is connected to the treated, rectified and clean steel pipe, which is inside a cylindrical kiln system, with an outer steel jacket that allows the flow of air or other gas between the steel pipe and the jacket. 3. The steel tube is connected to a collection trap, for example water or acetone, to capture the waste gases. 4. The temperature of the ovens is raised to a temperature range of about 650 ° C to about 1000 ° C. 5. The ultrasonic generator containing the solution of tetraethyl orthosilicate (TEOS) is activated for an approximate period of 15 to 30 minutes, and an inert gas is flowed through the generator to take the microdroplets of solution inside the tube. Dissociation and deposition reactions occur inside the tube in the exposed area at elevated temperatures. 6. -After the previous stage, the ovens are turned off and liquid nitrogen is flowed in the space between the tube and the steel jacket, with the purpose of causing a thermal shock in the steel tube. 7. -The ultrasonic generator is removed with the solution of tetraethyl orthosilicate, (TEOS) and, the tube thus obtained, is ready to be used directly in the process for the production of submicron carbon structures. The steel tube to be used in obtaining submicron particles of carbon may be a tube that has only been subjected to a heat shock treatment, or
It may well be a tube that has been subjected to SiOx deposition prior to its thermal shock treatment. The selection of one or another tube changes the result in the production of submicron particles. When only a heat-treated tube is used, submicron particles and a lot of amorphous carbon are produced (Fig.4). When the heat treatment is done and SiOx is deposited, more submicron carbon particles are produced and almost submicron particles of silicon oxide are spherical. (Fig.5), without so much presence of amorphous material Procedure to prepare steel substrates with thermochemical treatment
1. A mixture of chemical compounds is prepared with approximately 2% of ammonium fluoride (NH4F), about 8% of aluminum chip or shot (Al) and about 90% of alumina (A1203) by weight. Also, an approximately 2% mixture of ammonium fluoride (NH4F), about 8% silicon dioxide (Si02) and about 90% alumina (Al203) can alternatively be used. 2. Place the mixture in AISI 1018 steel tubes about 2"in diameter with one of its ends closed and that is perfectly clean and free of grease or any other material 3. Seal the tube on top with a lid of the same steel, to generate an internal pressure derived from the dissociation of ammonium fluoride (NH4F), as well as from the reaction with the elements present in aluminum (Al) and ammonium fluoride (NHF). of aluminum (A1XF), ammonia (NH3) and hydrogen (H) and the latter generates a pressure of approximately 150 Psi 4. The tube described is placed in a vertical furnace at a temperature in the range of approximately 850 ° to around 1 100C °, during a period of time around
from 5 hours to approximately 8 hours With this temperature and time a layer of approximately 0.5 mm thickness of an aluminum oxide layer (A1203) is obtained. 5. During heating of the tube, an inert gas is introduced into the furnace to avoid the presence of oxygen. 6.- The oven is turned off and the tubes are allowed to cool to room temperature 7. - The inner walls of the tube are cleaned and trimmed to obtain a bit of substrate. The pieces should be of a size that allows their subsequent introduction into a quartz tube. 8. - The substrate is deposited inside a quartz tube to start the process of manufacturing submicron carbon particles with tubular morphology. Said particles will be deposited on the aluminum-silicon substrate and will have a spiral growth. (Fig. 6). Procedure to prepare metallic substrates of copper, aluminum or tungsten.
1. - The substrates are placed inside an oven. 2. The oven temperature is raised to a temperature in the range of about 850 ° C to about 1000 ° C, for a period of time of approximately 20 to 50 minutes. 3. - The oven is turned off and the substrates are allowed to cool to room temperature. 4. - Substrates, once cold, are surface cleaned with an abrasive material, such as pumice or sandpaper. 5. - The substrates are cleaned with a solvent, for example acetone or alcohol, to remove surface impurities 6. - The substrates are introduced inside a quartz tube and this is ready so that the production of submicron particles of carbon can be started that were deposited on the substrates (Fig. 7, 8 and 9).
Metallic substrates can be introduced into the quartz tube without the indicated treatment, but the production of submicron particles will be much lower than that achieved when using substrates with thermal treatment and subsequent cleaning. Various modifications of the invention, in addition to those described herein, will be apparent to those skilled in the art from the foregoing description. Such modifications are also contemplated within the scope of the following claims: