Method of modifying surface of inorganic fibre, modified fibre and composite material
SUBSTANCE: invention relates to modification of the surface of inorganic fibre by forming a highly developed surface of inorganic fibre used as filler by forming carbon nanostructures on the surface of the fibres and can be used in producing high-strength and wear-resistant fibre composite materials. The method of modifying the surface of inorganic fibre involves the following steps: (a) soaking inorganic fibre with a solution of an α2 sinter fraction in organic solvents; (b) drying the soaked fibre; (c) heat treatment of the soaked inorganic fibre at 300-600°C; (d) depositing a transition metal salt onto the surface of the fibre heat treated according to step (c); (e) reducing the transition metal salt to obtain transition metal nanoparticles; (f) depositing carbon onto the transition metal nanoparticles to obtain carbon nanostructures on the surface of the fibre. The composite material contains modified fibre made using the method given above and a matrix of polymer or carbon.
EFFECT: high strength of the composite material in the cross direction relative the reinforcement plane by preventing surface deterioration when modifying with carbon nanostructures.
9 cl, 3 ex, 1 tbl, 5 dwg
The technical field.
The invention relates to the surface modification of inorganic fibers to create strong links between the components of composite material by forming a highly developed surface of the inorganic fiber used as filler, by forming the fibers of carbon nanostructures (ONS). This invention can find application in the production of high-strength and wear-resistant fibrous composite materials, in particular fiber polymer composites (ITCM), and carbon composite friction materials (FCOM).
The prior art.
Due to the unique mechanical and conductive properties, in addition to highly developed surface ONS are widely used as reinforcing filler in the composite materials of new generation.
Under the ONS refers to carbon nanotubes (CNTS) and carbon nanofibers (UNV).
CNTS are characterized by a hollow cylindrical structure formed by the carbon atoms constituting rolled into a cylinder graphene plane.
The difference UNV from CNTS is the stacking of graphene layers, which are located at an angle α relative to the axis of the filamentary particles. Depending on the angle α UNV can take different with Nocturne types. In the literature there are types of "Lenta", "stack", "stack of cones", "fish bone" and "spiral".
The analysis of patent information showed that there are two possible approaches to making the ONS in the composite material. The first path may include a method of dispersing ONS in the matrix material, and a second path - growing ONS directly on the surface of the fibers.
A method of directly dispersing ONS in the matrix material in the manufacturing process of a composite material has a number of disadvantages, chief among which is the difficulty of obtaining uniform distribution ONS in a matrix material.
This drawback is resolved when growing ONS directly on the surface of the fibrous filler, thereby providing a more uniform distribution of ONS in a matrix material: fixing ONS on the surface of the fibrous filler prevents agglomeration ONS in a matrix material, is particularly characteristic of CNTS. The technology of manufacturing of composite materials reinforced modified fibers can be carried out in the framework of the traditional methods of molding. In addition, raising ONS directly on the surface of the fiber may be allowed to reach large concentrations of ONS in the material, oriented mainly perpendicular to the arm is the dominant fibers, what is considered optimal for reinforcement in the z-direction. Additive ONS to the epoxy resin, in particular functionalized CNTS can change the speed of curing, the degree of conversion of resin and glass transition temperature [Prolongo S.G., Gude M.R., A. Urena The curing process of epoxy/amino-functionalized MWCNTs: Calorimetry, molecular modelling and electron microscopy. // J. Nanosci. Nanotechnol. 2009. V.9. P.6181-6187]. While the viscosity of the polymeric binder, modified CNTS increases significantly with increasing content of carbon nanotubes, which can lead to insufficient impregnation of the fibrous skeleton in the production ITCM [F.H. Gojny, M.H.G. Wichmann, Fiedler Century, W. Bauhofer, K. Schulte Influence of nano-modification on the mechanical and electrical properties of conventional fibre-reinforced composites. // Composites. 2005. V.36. P.1525-1535].
An additional advantage of the modification of the surface of the fibrous filler are also increasing thermal conductivity in the direction perpendicular to the plane of the reinforcement of a composite material, through the creation of conjugate nets from the ONS, which is extremely important to protect aircraft from lightning strikes, a problem which is growing along with the number of ITCM used in the construction of civil aviation. High conductivity in FCOM necessary for heat dissipation from the body of friction material and avoid local overheating, ultimately, to increase its wear during operation.
At the same time is formed more in aradhana the structure of the matrix material, adjacent to the fibrous filler, and also ensures that the increase in carbon in the interfacial layer in the manufacture FKOM liquid-phase method.
In the patent US 5149584 disclosed is a method of obtaining a composite material, comprising: (a) uglevodorodno structure consisting of carbon fibers grown on them carbon fibers having a branched, spiral, helical shape and crystallinity of more than 75%, and (b) a carbon matrix or a polymer matrix based on a thermoplastic or thermosetting resins.
Uglerazvedochnyh structure is obtained by growing ONS on the surface of the continuous carbon fibers by chemical vapor deposition from the gas phase (CVD, chemical vapor deposition) in a mixture of ethylene with hydrogen in the temperature range 500-700°C. using as a catalyst of growth ONS nanoparticles of transition metals or their alloys with metals copper subgroup generated by the recovery of salts and/or salts of the respective metals.
This known technical solution allows to improve the interlaminar shear strength ITCM with polyvinyl acetate matrix in 4.75 times.
In the patent US 5413866 disclosed is a method of obtaining carbon fibers grown on it carbon fibers with a length of from 1 to 100 μm in a spiral and a branched form, which includes: (a) Sardinia the composition of the alloy catalyst for these carbon fiber, moreover, the composition of the alloy catalyst comprises a first metal selected from the metals of groups IB, and one or more metals of the second group of metals selected from Fe, Ni, Co and Zn, and (b) the processing of carbon fibers deposited on the surface of the respective catalyst components in the atmosphere of carbon-containing gas, the exposure of the treated catalyst of the carbon fibers of the carbon-containing gas at a temperature of from the decomposition temperature of the carbon-containing gas to the decontamination temperature of the catalyst alloy.
This solution leads to an increase in surface area to values lying in the interval from 50 to 800 m2/g, while the surface area for non-modified fibers corresponds to 1 m2/year
In the application US 2009/0186214 A1 discloses the closest method of surface modification of carbon fibers to the proposed.
In this technical solution is controlled by the uniformity of the distribution ONS size, density fill the surface of the fibers, the orientation of the ONS, the conductivity of the obtained materials. Method of surface modification of carbon fiber provides treatment of the fiber surface oxidizing gas at between 100 and 900°C, the subsequent formation of the catalyst on the surface of the fibers by immersion solution of catalyst and chemical vapour deposition growth of carbon nanomaterials at 600-900°C.
However, none of the methods of surface modification of fibers ONS listed above and in the number of such technical solutions (US 2008/0182108 A1, US 7132161 B2), is not given adequate attention to the problem of defect formation during the catalytic growth ONS. The fact that in the process of CVD particle transition metal may react not only with the carbon from the gas phase, but also with the surface of the carbon fiber, which leads to the formation of a large number of surface defects of fibrous filler. Ultimately, surface modification ONS leads to lower cutoff characteristics of the fibers and, accordingly, composite materials based on them.
The objective of the invention is to increase the strength of the composite in the transverse direction relative to the plane of the reinforcement, (the direction perpendicular to the axis of the reinforcement), as well as the prevention of destruction of the surface of the fibers in the modification of carbon nanostructures, which, ultimately, lead to a decrease in the mechanical properties of composite materials based on them.
The problem is solved by the method of surface modification of inorganic fibers for the reinforcement of composite materials, comprising the following stages:
(a) impregnating an inorganic fiber with a solution of α2faction pitch the organic solvent;
(b) subsequent drying of the impregnated fibers;
(C) heat treatment of the impregnated inorganic fiber at 300-600°C;
(d) coating the surface of the heat-treated in accordance with stage (in) fiber transition metal salt;
(d) recovering the salt of the transition metal to obtain nanoparticles of the transition metal;
(e) deposition of carbon nanoparticles of the transition metal with the production of carbon nanostructures on the surface of the fiber.
In private embodiments of the invention the problem is solved in that, as the inorganic fiber carbon fiber.
As the organic solvent at the stage of (a) possible use of quinoline or 1-methyl-2-pyrrolidone, in this case, the impregnation is performed with a solution with a concentration not exceeding 40·10-3g/l
In some particular embodiments of the invention also preferably heated to temperatures of heat treatment on the stage (C) to exercise at a speed not exceeding 5°C/min
The recovery process of the salt of the transition metal in some cases are in stage 2: restoration of the salt to the metal oxide by heat treatment in an inert atmosphere in the first stage and the recovery of metal oxide in hydrogen at second.
It is desirable that at stage (e) was carried out chemical precipitation of carbon from pleva orodno mixture at 600-800°C.
The task can be solved with modified fibers for reinforcement of composite materials, which contains inorganic fiber, the surface of which are carbon nanostructures filamentary form, and which is obtained in accordance with the previously described method of the invention.
The task is also solved by the use of a composite material which contains the above-described modified fiber and a matrix made of a polymer or carbon.
The composite material may be a fibrous polymer composite material or carbon-carbon composite material.
The invention consists in the following.
It was found that for the decision of a task requires the use of a protective layer on the inorganic fibers, preventing the penetration of the metal catalyst inside of the inorganic fiber. As such a protective layer, we used a layer applied by impregnation of inorganic fibers with a solution of α2faction pitch in organic solvents, followed by drying and heat treatment at 300-600°C.
The use of impregnating solution α2faction pitch in organic solvents containing heteroatoms, on the one hand due to the highest content is in it polycyclic aromatic structures with a higher degree of condensation compared with the γ-fraction and a β-fraction of the pitch. That is, the process of pyrolysis α2fraction of the pitch will be less volatile compounds, and, accordingly, a high content of coke in the protective coating. On the other hand the use of soluble α2fraction of the pitch is determined by the formation of a uniform carbon coating on the surface of the inorganic fibers in contrast to the original pitch binder containing no soluble coke particles (carboids).
Subsequent heat treatment allows to prepare the impregnated fiber to the subsequent stages of its modification by removal of volatile compounds and to increase the amount of carbon. At temperatures less than 300°C results in the release of volatile compounds that subsequent growth of the ONS can lead to poisoning of the catalyst. At temperatures above 600°C will be intensive pyrolysis, accompanied by a large loss of mass pitch of the protective layer.
Certain factors affecting the number of formed coke from pitch binder and volatile substances, is the speed of heating up to the temperature of the beginning of heat treatment of fibers impregnated with soluble α2fractions of coal tar pitch in an organic solvent. It is important that this speed was low (in some cases, this speed should not accepts the address 5°C/min).
As the inorganic fiber may be used carbon fiber, however, the carbon fiber of the invention is not limited to any specialist, the expert, understands that for growing nanostructures on the substrate is suitable not only carbon fiber, but other inorganic fibers, for example, carbide fibers [Veedu VP, Cao, A.Y., Li X.S., Ma K.G., Soldano, S., Kar S.; Ajayan P.M., Ghasemi - Nejhad. Multifunctional composites using reinforced laminae with carbon-nanotube forests. //Nat. Mater. 2006. V.5. P.457-462], fiber-based alumina [E.J. Garcia, B.L. Wardle, Hart, A.J., Yamamoto N. Fabrication and multifunctional properties of a hybrid laminate with aligned carbon nanotubes grown in situ. // The compos of the. Sci. Technol. 2008. V.68. P.2034-2041], [Wicks S.S., de Villoria R.G., B.L. Wardle Interlaminar and intralaminar reinforcement of composite laminates with aligned carbon nanotubes. // The compos of the. Sci. Technol. 2010. V.70. P.20-28], fibers [Zhu J., Imam, A., R. Crane, K. Lozano, V.N. Khabashesku, E.V. Barrera Processing a glass fiber reinforced vinyl ester composite with nanotube enhancement of interlaminar shear strength. // The compos of the. Sci. Technol. 2007. V.67. P.1509-1517].
In the most desirable embodiments of the invention, the organic solvent at the stage (a) use the quinoline or 1-methyl-2-pyrrolidone. These solvents are the most affordable and relatively cheap to implement the invention. It is advisable that when using these solvents, the concentration of the impregnating solution did not exceed 40·10-3g/l
It should be noted that can be used and the other is the development of organic solvents, containing heteroatoms, and the concentration of these solvents may be selected calculation or by experiment.
Salt of the transition metal may be deposited on the fibers by impregnation with a solution of this salt, but not limited to impregnation.
The restoration of the salt of the transition metal to obtain nanoparticles of the transition metal on stage (d) it is advisable to conduct one phase at a temperature lower than the growth temperature ONS. This operation avoids agglomeration of the metal particles of the catalyst at high temperature.
However, recovery of salt to metal may be held in two stages, for example, first with the restoration of the salt to the metal oxide by heat treatment in an inert atmosphere and subsequent recovery of the metal oxide in hydrogen to metal. In addition, as a catalyst, you can use any transition metal or a mixture thereof, or a mixture with other metals formed from salts of the respective metals.
The process of chemical deposition occurs in the temperature interval, the upper bound which is due to the loss of properties of the fiber, and the lower the slowing and even stopping the process of chemical deposition.
The most desirable to conduct the process of chemical vapor deposition at 600 To 800°C, because the ONS received in the data range of temperature, have optimal structural characteristics. The upper temperature limit is determined by the ability of the carbon coating to prevent chemical interaction between the metal catalyst particles from the surface of the inorganic fiber. At temperatures below 600°C, the catalytic growth is strongly inhibited and the formation ONS with disordered structure.
Thus obtained modified fiber for reinforcement of composite materials is an inorganic fiber, the surface of which are located ONS filamentous forms, not intertwine.
Nanostructures filamentous forms are as nanotubes and nanofibres.
The invention can be illustrated by the data shown in figure 1-5.
Figure 1 shows the image of the microstructure of fibrous filler, not subjected to surface modification, obtained by scanning electron microscope.
Figure 2-4 shows images of the microstructure of fibrous filler, modified ONS, respectively, at 600, 700 and 800°C, obtained by scanning electron microscope.
Figure 5 shows optical microscope images with polarized light from a hundred-fold increase for different samples, showing the comparison of deformation is azione-stress state in the matrix, reinforced fibers, modified at different temperatures, and finished fiber.
The invention is carried out as follows.
Allocated the solution α2fractions of coal tar pitch in an organic solvent by fractional separation medium temperature pitch (GOST 10200-83). For that, he took a portion of the pitch mass 100 g is repeatedly processed in boiling toluene in the flask periodically filtering the contents of the flask using a glass funnel with two paper filters and washing the residue also boiling toluene to obtain a clear filtrate. Next, the resulting α-fraction of the pitch was treated with 300 ml of 1-methyl-2-pyrrolidone, was kept in a drying Cabinet at a temperature of 100°C during the day in a closed flask. The precipitate (α1fraction) decantation, and the solution α2fractions of coal tar pitch used for impregnation. The concentration of the solution α2fraction of the pitch when it was 23·10-3g/l
Carbon fiber brand Chis-M-6K on THE 1916-146-05783346-96 with a length of approximately 10 cm was impregnated with the obtained solution.
The impregnated fibers were dried over infrared heating lamp at 250°C for 20 minutes.
Then the dried fibers coated with α2fraction of the pitch was heated to 400°C with a heating rate 3°C/min and held at this temperature for 150 mine is.
After heat treatment on the surface of the heat-treated fibers was applied salt of Nickel nitrate by impregnation from a solution of salt Ni(NO3)2in acetone (0.05 M).
Then there was the restoration of the salt with obtaining a catalyst in the form of nanoparticles of Nickel in size from 10 to 80 nm in the flow of H2(0.2 l/min) at 400°C for 15 minutes.
Synthesis ONS were carried out in a flow type reactor by CVD method. Fiber samples with a length of 10 cm, mounted on a holder that was placed in the furnace in a zone of maximum temperature. Before synthesis were evacuating the system by the vacuum pump, missed argon during the whole time of heating to the required temperature (setpoint 0.25 l/min) and during the entire time of synthesis (setpoint 0,04 l/min), hydrogen was passed at a temperature of 400°C for 15 minutes at a setpoint of 0.2 l/min. as a carbon source in the experiment used the azeotropic mixture of benzene to cyclohexane. Feed azeotropic mixture began when reaching 700°C at a fixed flow rate (4 ml / hour). The feed mixtures were within 5-30 minutes. After cessation azeotropic mixture, the furnace was cooled to room temperature, after which the samples were removed from the oven.
Morphological features of the surface of the samples modified fibers was studied on the scan is the face of the microscope (see figure 2-4). For comparison, also shows the surface morphology of unmodified fibers (figure 1). As follows from the data presented in figure 2-4 carbon fiber, with the surface covered with a uniform layer of ONS filamentous forms, have more surface area than the original HC (figure 1).
Obtained in accordance with this example, fibers with a modified surface were tested on a universal tensile testing machine Tinius Olsen H5KS according to (ISO 11566:1996 Carbon fibre - Determination of tensile properties of single-filament specimens).
We have investigated that the surface modification of fibrous filler without the use of protective coatings in the temperature range CVD process 600-800°C leads to a loss of tensile strength carbon monofilaments up to 40%.
The strength of interfacial shear was determined on model polymer composite material include epoxy matrix carbon monofilament using polarization-optical method (or fragmentation).
To assess the strength of adhesion of the binder to the fibrous filler (strength at the interfacial shear) used polarization-optical (or fragmentation) method, which is performed on samples representing individual carbon fiber in an epoxy matrix. According to this method, we used EPoX is DNA the Epikote resin grade LR 285, and hardener brand Epikure LH 287. The components were mixed in a mass ratio of 100:40 (resin - hardener). Fragmentation method is the elongation of the sample in the form of dumbbells, containing a single fiber. Under load, the fiber is broken, and after repeated crushing the length of the resulting fragment is equal to the so-called critical fiber length, which is calculated shear strength of the interface - τ:
Where- tensile strength fibers; d is the diameter of the fiber and lwith- critical fiber length.
Observations of deformation and intense paintings was carried out on an optical microscope in polarized light. The analysis allows to judge about the nature of load transfer by shear deformation in the polymer matrix around the gap fiber. If the value of the critical length of the fiber (unresolved plot fragmented fibers) and area stratification in the sample is small, this indicates good contact between fiber and matrix (figure 5).
Production of carbon-carbon composite material.
To obtain the carbon-carbon composite material forming the workpiece from a mixture of discrete hydrocarbon with the surface-modified ONS in accordance with example 1, and pitch binder in powder form (environments is temperatury peck marks grade a, GOST 10200-83). The discrete length fibers is 50 mm, the Mass fraction of fibers with a pitch binder is 60 to 40%, respectively. The resulting billet is subjected to pressing under a pressure of 100 ATM, firing at a temperature of 1100°C, the high temperature impregnation pitch binder (GOST 1038-75) and carbonization at 700°C under a pressure of 200 atmospheres with subsequent high-temperature treatment at 2000°C in vacuum.
Tribological tests showed that surface modification of fibers ONS at a temperature CVD process 700°C leads to an increase of wear resistance of carbon-carbon composite material by 30% compared to the composite on the basis of the unmodified hydrocarbon.
Bending strength is increased by 25% compared with the composite on the basis of the unmodified hydrocarbon.
Obtaining a unidirectional composite material.
In the first step of forming a unidirectional composite material was obtained by winding prepreg modified continuous hydrocarbon impregnated in a polymeric binder, on a drum (drum winder method). The methodology used epoxy resin grade Epikote 827, and the hardener brand Aradur 976. The components were mixed in the ratio 1:1 (resin - hardener) equivalents. On the drum with a diameter of 30 cm was tied siliconized paper. This is verhnostny density layer of filaments is 180 g/m 2and the thickness of the monolayer composite - 0,15 mm On the drum is wound a single layer of the prepreg, and then cut. In the end lead up to 40 layers of prepreg, and then create a unidirectional plastic with a thickness of 6 mm under a pressure of 8 ATM at a temperature of 180°C for 4 hours
Strength in the interlayer shift was determined by short-beam method in accordance with the standard (ASTM D2344). The tests were carried out on samples with dimensions of 6 mm (thickness), 12 mm (width)40mm (length), using universal bursting machine H100KS ("Hounsfield"). Strength in the interlayer shift unidirectional polymer composite material reinforced hydrocarbon modified ONS at a temperature CVD process 700°C, an increase of 45%, than in the case of similar composite based on nemodifitsirovannykh HC.
1. Method of surface modification of inorganic fibers for the reinforcement of composite materials, characterized in that it comprises the following stages:
(a) impregnating an inorganic fiber with a solution of α2faction pitch in organic solvents;
(b) subsequent drying of the impregnated fibers;
(C) heat treatment of the impregnated inorganic fiber at 300-600°C,
(d) coating the surface of the heat-treated in accordance with stage (in) fiber transition metal salt;
(d) restoring the of transition metal salt to obtain nanoparticles of the transition metal;
(e) deposition of carbon nanoparticles of the transition metal with the production of carbon nanostructures on the surface of the fiber.
2. The method according to claim 1, characterized in that the inorganic fiber carbon fiber.
3. The method according to claim 1, characterized by the fact that as an organic solvent in stage (a) use the quinoline or 1-methyl-2-pyrrolidone, and the impregnation is conducted by solution with a concentration not exceeding 40·10-3g/l
4. The method according to claim 1, characterized in that heating to temperatures of heat treatment in stage (b) carried out with a speed not exceeding 5°C/min
5. The method according to claim 1, characterized in that in stage (e) carry out chemical precipitation of carbon from the hydrocarbon mixture at 600-800°C.
6. The modified fiber for reinforcement of composite materials, characterized in that it comprises inorganic fiber, the surface of which are carbon nanostructures filamentous form and received in accordance with any of the preceding claims.
7. Composite material, characterized in that it contains a modified fiber according to claim 6 of the formula and a matrix made of a polymer or carbon.
8. Composite material according to claim 7, characterized in that represents hair is NISTO polymer composite material.
9. Composite material according to claim 7, characterized in that a represents a carbon-carbon composite material.
SUBSTANCE: invention relates to heterogeneous catalysis and can be used to recycle hydrocarbons and halogen-substituted hydrocarbons when producing composite materials, catalysts, sorbents and filters. Catalytic pyrolysis of hydrocarbons is carried out at 500-700°C on a catalyst obtained by dispersing articles of solid nickel and alloys thereof with other metals, e.g., iron, chromium, as a result of reaction with 1,2-dichloroethane vapour. The catalyst contains dispersed active nickel particles attached to carbon nanofibres with diameter 0.1-0.4 mcm. The starting material used is bromine- or chlorine-containing hydrocarbons, alkanes, olefins, alkynes or aromatic hydrocarbons, e.g., ethane, propane, acetylene, benzene. Output of carbon nanofibres is equal to or more than 600 g per 1 g metal.
EFFECT: high efficiency of the method.
5 cl, 2 dwg, 9 ex
SUBSTANCE: dust-like or granular solid substance is continuously sprayed onto the outer surface of a hollow drum substrate 2. After deposition, the catalyst on the revolving substrate enters reaction zone 3, into which carbon-containing gas is continuously fed through a gas-distributing collector 17, and gaseous pyrolysis products are continuously output through a nozzle 18. The reaction zone is heated with infrared heaters 7. The end product is removed from the substrate using a blade 9 and a cylinder brush 10, and then unloaded from the apparatus by an auger 14.
EFFECT: invention enables continuous synthesis of carbon fibre materials.
5 cl, 2 dwg, 2 ex
SUBSTANCE: invention can be used for creation of fillers of composite materials, gas-distributing layers in fuel elements, components of lubricants, hydrogen storage batteries, filter materials, carbon electrodes of lithium batteries, glue composites, carriers of catalysts, adsorbents, anti-oxidants during production of cosmetics, cold emission sources of electrons, modifying agents to special-purpose concrete, as well as for coatings screening microwave and RF radiation. Method involves pyrolysis of gaseous carbon-containing compounds on surface of metallised dust catalyst in flow reactor having the possibility of gas medium mixing. Aerosil particles containing clusters of the following metals on the surface as catalyst: nickel, cobalt or iron. Catalysts are obtained prior to the beginning of pyrolysis by reactivation of catalyst sprayed in reactor in current of hydrogen-containing gas at simultaneous mixing of gaseous medium. It is expedient to mix gaseous medium in reactor in fluidised bed mode with ultrasonic material dispersion. Outer diameter of obtained nanotubes is 5 to 35 nm; inner diameter is 4 to 12 nm; packed density is 0.3-0.4 g/cm3; total content of impurities is less than 1.2-1.5%; length is 0.5 to 3 mcm.
EFFECT: invention allows synthesising thinner nanotubes with high cleanliness, which have smaller spread in values as to diameters.
2 cl, 3 ex
SUBSTANCE: sprayed catalyst is deposited on the top surface of a rotating disc through the settling chamber of a reactor, heated to pyrolysis temperature, after which hydrocarbon gas is continuously supplied and gaseous pyrolysis products are removed, and at the end of the pyrolysis process, the end product is cooled together with the catalyst. When feeding into the settling chamber, the catalyst is stirred and aerated with an inert gas. The hydrocarbon gas is fed through a gas-distributing apparatus. Gas is released through an annular slit between the disc and the cowling of the gas-distributing apparatus. Gaseous pyrolysis products are removed through socket pieces in the top part of the housing. At the end of the pyrolysis process, heaters are switched off and the housing is cooled to a safe temperature, after which the disc rotary drive is switched on and the material treated with an agitator is moved by a scraper through a window in the bottom part of the housing and removed from the reactor through an auger-type storage bin, whose drive is simultaneously switched on with that of the disc. The apparatus for producing nano-structured carbon fibres has a housing fitted with heaters, in the top part of which there is a pipe for feeding hydrocarbon gas and a unit for feeding the catalyst, connected to the gas-distributing apparatus in form of an inverted funnel with a built-in settling chamber and a socket piece for outlet of pyrolysis products, and in the bottom part there is a window for unloading the ready product, above which there is a disc which is connected to a rotary drive and interacts with a fixed scraper. The gas-distributing apparatus is fitted with a cowling over the disc, on which an agitator which is kinematically linked to the disc is mounted, where agitator is mounted on the path of the disc in front of the scraper for unloading the end product through the window, which joins the auger-type storage bin fitted with an agitator. The batching unit is in form of a screw doser having a mixing device and an aerator-bridge breaking cone.
EFFECT: obtaining nano-structured carbon fibres with high output of the product and high quality.
10 cl, 2 ex, 11 dwg
SUBSTANCE: invention relates to technology of producing fibrous carbon materials through pyrolysis of aromatic and non-aromatic hydrocarbons. A catalyst 9 is deposited on the top surface of a container 8. After sealing the reactor, inert gas is blown inside and heating elements 5 and the disc 6 rotary actuator 7 are switched on. Carbon-bearing gas is fed into the cavity between the cap 10 and the container 8 and the catalyst 9 is heated. Heating is then stopped and a forced cooling system is switched on. After lowering temperature in the reactor, the disc 6 rotary actuator 7 is switched off, the reactor is opened and the container 8 with nanotubes is removed.
EFFECT: invention enables to obtain multilayer carbon nanotubes with diametre of 15-50 nm.
3 cl, 8 dwg, 2 ex
FIELD: machine building.
SUBSTANCE: upon preliminary high temperature treatment catalyst of carbon nano-fibres growth is placed into reactor; reaction zone is heated to temperature of pyrolysis of carbon containing steam-gas mixture supplied into reactor. The mixture includes activators on base of sulphur containing or oxygen containing compounds. Further the mixture is conditioned at temperature of pyrolysis of the above said braids and the reactor is cooled. Linear rate of carbon containing steam-gas mixture supply is within interval from 20 to 300 mm/s.
EFFECT: production of long oriented braids of carbon nano-fibres with multi-layer structure.
9 cl, 5 dwg, 2 tbl, 22 ex
FIELD: production processes.
SUBSTANCE: method involves drawing of carbon fibre through solution with further heat treatment in flow-through gas medium. As solution there used is either solution containing pre-synthesised thin multi-layered carbon nanotubes functionalised with hydroxylic and carboxylic groups in dimethyl formamide or in dimethyl acetamide or in dimethyl sulfoxide with concentration of 0.1-10 g/l, or catalytic solution containing medium for forming embryos for growing nanotubes at heat treatment, and as catalytic solution there used is water solution Co(NO3)2 with concentration of 0.25 mol/l. As gas medium there used is medium containing gaseous hydrocarbon - methane, and heat treatment is performed by keeping it in reactor at temperature of 800-1000°C during 10-30 minutes.
EFFECT: increasing resistance to fibres being drawn from binding material.
4 cl, 5 ex, 6 dwg
SUBSTANCE: external diametre of carbon fibres is 15-100 nm. The fibrous structure includes a knot whereto said carbon fibres are connected so that the specified carbon fibres come out from the knot made from growing carbon fibres with size 1.3 times exceeding external diametre of carbon fibres. Once added to hard materials, such as resin, ceramics, metal, carbon fibrous structures taken even in small amount improve physical properties of materials, including electric, mechanical, or thermal properties, not mentioning other material properties.
EFFECT: improved thermal properties.
3 cl, 10 dwg, 4 tbl, 2 ex
SUBSTANCE: invention relates to technology of carbonic fibrous materials by catalystic pyrolysis. Receiving method is in reactor location into catalyst in the form of powdered alloy on the basis of aluminium and it is fed carbureted hydrogen gas. Gas feeding and withdrawal of pyrolysis light-end product is going on continuously. Carbureted hydrogen gas is preliminary heated in reactor till the temperature which is lower the pyrolysis beginning. Catalyst on nonmetallic bottom layer is heated higher the temperature of pyrolysis beginning by inductive method with alternating voltage with frequency 20 kHz. Finished product with catalyst is cooled.
EFFECT: receiving of nanoproduct without formation of freak carbon-base material on heated non-catalytic surfaces.
4 cl, 2 dwg, 2 ex
FIELD: technological processes.
SUBSTANCE: in lower part of reactor disk connected to rotation drive is installed, above which settling chamber open at the bottom is located, in which catalyst is sprayed in the form of powdered nickel-based alloy. Initial product - carbureted hydrogen gas - is continuously supplied to reactor and heated up to 600-1,150°C, and gaseous products of pyrolysis are also continuously discharged. Finished product and catalyst are cooled down. Prior reactor putting into operation, sticky film is installed under settling chamber on disk, and spraying device is switched on. After catalyst supply has been stopped, film is cut in pieces, and amount of catalyst settled on unit of film area is determined, by results of which uniformity of powdered catalyst supply is controlled. Settling of powdered catalyst is realised when disk and rotation drive are switched off and pressure is reduced.
EFFECT: obtainment of maximum efficiency and quality of fibrous carbonic structures at different sizes of powdered catalyst particles.
4 cl, 5 dwg, 2 ex
FIELD: process engineering.
SUBSTANCE: set of invention relates to method of producing composite element, to composite element and system for its production. Proposed method consists in loading billet into element forming medium to be filled with solvent containing catalytic material in solution or suspension. Fluid is drained from mould to form catalytic material sediment on billet and/or inner surface of forming medium. Forming medium is heated to feed carbon gas therein at conditions allowing the growing of carbon nanotubes on billet and/or forming medium surface. Then carbon gas is removed to feed liquid polymer material into forming medium to distribute polymer in billet and carbon nanotube structure, thus, forming finished composite material after curing of polymer.
EFFECT: increased impact strength.
9 cl, 11 dwg
SUBSTANCE: method to compact porous products includes loading products into a reaction chamber with induction coils, submersion of products and coils into a liquid precursor of compacting material, induction heating of products to temperature sufficient to generate steam, subsequent pyrolysis of steam and deposition of compacting matrix material in pores of products. Induction heating of porous products includes efficient control of power of AC current supplied to coils. Control of applied power is carried out in compliance with dynamic changes of electric characteristics of a porous product to be compacted, as it is compacted. Periodically frequency of alternating electric current supplied to induction coils is measured, difference of measured frequencies of supplied AC current is calculated, and the according calculated value is compared to frequency variation setpoint. Control of supplied level of current power is carried out in accordance with comparison of according calculated variation of frequency with frequency variation setpoint.
EFFECT: improved efficiency of the method.
10 cl, 27 dwg
SUBSTANCE: method to compact porous substrates, such as braking stocks made of carbon fibre, is carried out using liquid source substance, cyclohexane or toluene. Stocks of carbon fibre are submerged into liquid source substance, which fills pores of a stock, and induction heating of the stock is carried out to the temperature sufficient for pyrolysis of liquid source substance (1600-2400°C). At the same time extent of chemical purity of liquid source substance makes approximately from 80 to 99.6%.
EFFECT: reduced consumption of fresh or new liquid source substance by maintenance of purity of liquid source substance, used for compaction, below the level of chemical purity.
13 cl, 6 tbl, 8 dwg
SUBSTANCE: procedure for fabrication of reinforced stuffing box of thermo-expanded graphite consists of manufacture of first and second work pieces of thermo-expanded graphite, in arrangement of reinforcing filler with glue coating between them, in fabrication of package and in successive treatment of package under pressure. As a glue coating there is used a film glue on base of copolymer of ethylene and vinyl-acetate. First there is formed the first work piece of thermo-expanded graphite. Reinforcing filler impregnated with melted polymer glue is laid on the first work piece. The second work piece of thermo-expanded graphite is formed on surface of impregnated reinforcing filler by supplying powder of thermo-expanded graphite onto said surface and by successive preliminary rolling. Further, the package is processed under pressure by finish rolling. The disclosed here procedure is implemented for fabrication of reinforced graphite foil used for production of braided stuffing box.
EFFECT: upgraded mechanical properties in wide range of temperature.
11 cl, 1 ex, 1 tbl
SUBSTANCE: invention relates to carbon-carbon composite materials (CCCM). The method of producing carbon-carbon composite materials with density of 1.2-2.1 g/cm3 involves applying protective coatings on carbon filler and/or saturation with carbon-containing compositions, making modules from fibre carbon filler materials grouped in a given order, wherein the thickness of the wall of the module is equal to at least the thickness of the carbon filler. The frame is then assembled by merging modules into a single packet, followed by cold or hot pressing and/or sewing with a thread or rods on one of the coordinates of the workpiece coinciding or not coinciding with the alignment of the filler in the module until achieving density of 0.1-0.8 g/cm3. CCCM material is obtained by saturating the frame with pyrocarbon in the medium of gaseous or liquid hydrocarbons.
EFFECT: high strength and density of CCCM.
8 cl, 11 dwg, 2 tbl
SUBSTANCE: invention relates to the technology of producing composite materials and methods of making housing elements of aircraft and space-rocket articles. Disclosed is a multilayer composite material which contains carbon-carbon layers and/or carbon-metal layers, joined by intermediate porous layers of carbonised carbon and comprising mainly carbon-carbon and carbon-metal parts of the composite material. Each of the carbon-carbon layers (K) on both sides of are coated with layers of carbonitride compounds of titanium and silicon (T), and inner intermediate porous layers of the carbonised carbon (E) contain copper-titanium layers (M). The carbon-metal part of the composite material contains aluminium-lithium (A) and magnesium-lithium layers (B,C,F), reinforced with carbon fibre (D), inner porous layers of carbonised carbon with copper-titanium surface layers, heated or cooled with inert gas using plasma heating or a gas-liquid medium based on an inert gas. The invention also discloses methods and devices for making a cowling, a cut off half-sphere, a shell and a half-shell using the disclosed composite material.
EFFECT: achieving good specific strength characteristics, brittle fracture resistance, heat resistance, erosion resistance, high reflecting and absorption capacity of the composite material, which significantly lowers weight, increases resistance to heat and meterorite effects, increases reliability of aerospace articles.
21 cl, 2 tbl, 27 dwg
SUBSTANCE: invention relates to composite materials based on thermally expanded graphite, particularly reinforced sheet materials, and can be used in making lining and other articles, for example flexible heaters, pipes, lining for high-temperature furnaces etc. The reinforced graphite foil contains thermally expanded graphite and reinforcing elements in form of threads made from carbon fibre with linear density of 10-35 tex, uniformly distributed on the width of the foil and lying along the fabric of the foil. Thickness of the reinforcing elements is not more than 75% of the thickness of the reinforced foil. The method of making said foil involves making a workpiece, having two layers of thermally expanded graphite with density of 0.05-0.20 g/cm3 and carbon fibre threads uniformly distributed in between and lying along the fabric of the foil, the said threads having linear density of 10-35 tex, followed by moulding the foil from the said workpiece.
EFFECT: obtaining uniform and strong reinforced foil.
4 cl, 1 ex, 1 tbl
SUBSTANCE: reinforced graphite foil comprises at least one flattened cord of carbon fibres evenly spread along foil width as reinforcing element. Specific density of cord is from 10 to 70 g/m2. Fibres in cord are connected to each other without formation of woven cloth. Glue coating may be applied onto cord.
EFFECT: improved sealing properties of foil due to improved strength of foil with preservation of its resilience.
6 cl, 1 ex, 1 tbl
SUBSTANCE: one or more than one two-dimensional fibrous fabric from carbon fibres or precursors of carbon fibres is impregnated with sol-gel by solution or colloid suspension, providing for possibility of dispersion of discrete ceramic particles to remain on fibrous fabric. Sol-gel solution contains precursor of oxide, and colloid suspension - oxide, selected from the following group: TiO2, ZrO2, HfO2, SiO2. Fibrous stock is made by means of application of layers formed of two-dimensional fabric made of carbon fibres or precursors of carbon fibres, besides, at least some of layers are at least partially formed of previously impregnated two-dimensional fabric. Layers are connected to each other, and thermal treatment is carried out at the temperature of 1400-1750°C, afterwards fibrous stock is sealed with carbon matrix. In process of thermal treatment particles of oxide are transformed into particles of carbide.
EFFECT: possibility to controllably change concentration of ceramic particles in stock and achievement of required mechanical properties.
14 cl, 5 ex, 11 dwg
SUBSTANCE: method involves electric contact heating of porous elongated workpiece more than temperature of thermal dissociation of chemical reagent, movement of workpiece through reactor, supply of reaction mixture to reactor, removal of reaction products from reactor and cooling of workpiece; at that, heating of workpiece, its cooling, supply of reaction mixture and removal of reaction products are performed periodically; at that, reaction mixture is supplied to reactor at the stage of cooling the workpiece during 1-10 s. After this time is over, reaction products are removed from reactor till residual pressure of 10-2-10-3 atm is reached, and then the cycle is repeated till the required thickness of the deposited layer is reached. Reaction mixture is supplied to reactor at the cooling stage at least once. Band from compacted thermal expanded graphite, or nonwoven fibrous carbon or silicone-carbide materials, or bundles of carbon or silicone-carbide fibres are used as workpiece.
EFFECT: increase of homogeneous deposition of pyrolytic material as to thickness of elongated workpieces.
3 cl, 1 ex, 3 tbl
SUBSTANCE: invention relates to physics of low-temperature plasma and plasma chemistry, as well as electrical engineering and electrophysics, and specifically to acceleration techniques and can be used to generate high-enthalpy jets of carbon-bearing electrodischarge plasma and obtain ultrafine crystalline phases of hard and superhard materials. The method involves conducting a plasma chemical synthesis in the shock wave of an impact-wave structure of a hypervelocity pulsed jet of carbon-bearing electrodischarge plasma which flows into a closed sealed volume filled with nitrogen gas, wherein synthesis is carried out in a shock wave arising from the reaction of two synchronous equal-enthalpy hypervelocity jets of carbon-bearing electrodischarge plasma, flowing in opposite directions on the same axis from shafts of two identical accelerators, wherein the hypervelocity pulsed jets of the carbon-bearing electrodischarge plasma are generated at equal pulse current of the power supply of the accelerators with amplitude of 140 kA, discharge power of 145 MW and delivered energy of 30 kJ. The method is realised in apparatus which is in form of a cylindrical electroconductive shaft placed coaxially inside a solenoid 8 and made from graphite, inside which there is a fuse 5 made from ultrafine carbon material which electrically connects the beginning of the cylindrical electroconductive shaft and a centre electrode, which is connected to one terminal of the power supply circuit of the accelerator, the second terminal of which is connected to the end of the solenoid 8, further from the centre electrode; the second end of the solenoid 8 is electrically connected to the beginning of the shaft; the vertex of the centre electrode, the beginning of the shaft and the beginning of the solenoid lie in one plane which is perpendicular to the axis of the shaft, and the housing 7 of the centre electrode unit is made from magnetic material and overlaps the area where the fuse 5 is located, the length of the part which overlaps the area where the fuse is located being equal to 40-50 mm, and its outer surface is cone-shaped, wherein the shaft of the accelerator is in form of an inner 1 and an outer 2 current-conducting cylinder, coaxially placed one inside the other and electrically connected on the entire mating surface, and the centre electrode is composed of a tip 3 and a tail 4; the inner cylinder 1 and the tip 3 are made from graphite, the outer cylinder 2 is made from hard nonmagnetic metal and the tail 4 is made from structural metal with high electroconductivity; the free ends of the shafts of both accelerators are mounted by through insulator-sealers 20 in axial holes of disc-shaped metal covers 21, which are hermetically connected to opposite ends of the cylindrical metal housing 22 of the reactor chamber, while providing opposite, coaxial and symmetrical arrangement of shafts on the longitudinal axis of the reactor chamber which is filled with nitrogen gas.
EFFECT: invention increases output of the expected phase of carbon nitride and reduces content of impurities in the dynamic synthesis product.
2 cl, 1 dwg