CN100402419C - Method of preparing nano-carbon fiber using coal tar asphalt as raw material - Google Patents
Method of preparing nano-carbon fiber using coal tar asphalt as raw material Download PDFInfo
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- CN100402419C CN100402419C CNB2006100481134A CN200610048113A CN100402419C CN 100402419 C CN100402419 C CN 100402419C CN B2006100481134 A CNB2006100481134 A CN B2006100481134A CN 200610048113 A CN200610048113 A CN 200610048113A CN 100402419 C CN100402419 C CN 100402419C
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Abstract
The present invention relates to a method for preparing nano carbon fibre by using coal-tar pitch as raw material. It is characterized by that said method includes the following steps: using coal-tar pitch as raw material, using organic metal compound ferrocene as catalyst, using hydrochloric acid and deionized water as cleaning agent and using inert gas-argon gas as protective gas, in the tubular high-temperature furnal pyrolyzing chemical substance raw materials to make conversion from solid state to liquid state to gaseous state to liquid state to solid state form, make gaseous state molecular adsorption, decomposition, dissolution, diffusion and precipitation so as to obtain the nano carbon fibre product formed on the inner wall of quartz tube of tubular high-temperature furnace.
Description
Technical Field
The invention relates to a method for preparing carbon nanofibers by using coal tar pitch as a raw material, belonging to the technical field of preparation methods of organic compound carbon materials.
Background
Coal tar refined by taking coal as a raw material is an important industrial raw material, a large amount of residues, namely coal tar pitch, are generated after distillation and fraction extraction are carried out on the coal tar in the refining process, the yield of the residues is 50-60% of that of the coal tar, the residues are large by-products in the coal tar processing process, and reprocessing, re-refining and recycling of the coal tar pitch are important scientific research subjects in the coal tar processing industry.
The coal tar pitch is black solid at normal temperature of 20 + -3 deg.C, has no fixed melting point, is in glass phase, is softened after heating, is then melted, is brittle in winter and softened in summer, and has a density of 1.25-1.35g/cm3。
The coal tar pitch mainly comprises a mixture of aromatic hydrocarbon and derivatives of oxygen, sulfur and carbon, the element composition mainly comprises carbon, hydrogen, oxygen, sulfur and nitrogen, the content of carbon is up to 92-93%, and the coal tar pitch provides a rich carbon source for preparing a carbon material with high added value.
The coal tar pitch has high content of high molecular aromatic hydrocarbon, low sulfur content and ash content, good binding property and high coking value after carbonization, and is suitable for being used as a binder of a carbon material and for preparing pitch-based carbon fiber.
The preparation of carbon fibers by using coal tar pitch as a raw material is high added value utilization, and the preparation methods of the carbon fibers also have various forms, such as a melt spinning method, an explosion method, a co-carbonization method and the like, but have the defects and the defects of different degrees, some preparation methods are complex and have high cost, some preparation processes have serious pollution, some energy consumption is large, and some prepared products have low precision, low yield and low purity and are not ideal enough.
Disclosure of Invention
Object of the Invention
The invention aims to solve the defects of the background technology, coal tar pitch with the carbon content of 91.63% is used as a raw material, ferrocene is used as a catalytic additive, a tubular high-temperature furnace is used, carbon fiber materials are directly grown on the inner wall of a quartz tube in the tubular high-temperature furnace under the high-temperature state and under the protection of inert gas by adopting a catalytic gas phase growth method, carbon resources of the coal tar pitch are fully utilized to prepare nano-scale carbon fiber materials, and the purposes of simplifying the process flow, reducing the environmental pollution, reducing the energy consumption and improving the precision and the purity of the carbon fibers are achieved.
Technical scheme
The chemical substances used in the invention are coal tar pitch, ferrocene, argon, hydrochloric acid and deionized water, and the combination ratio is as follows: in grams, milliliters and centimeters3Minute is a unit of measurement
Coal tar pitch: c559H690SN7O51.8g±0.018g
Ferrocene: fe (C)5H5)20.2g±0.002g
Argon gas: ar 120000cm3±200cm3
Hydrochloric acid: HCl 400 ml. + -. 5ml
Deionized water: h2O 2000ml±10ml
The preparation method of the invention comprises the following steps:
(1) selecting chemical feedstock
The chemical raw materials used are selected and subjected to purity control:
coal tar pitch: 98 percent of
Ferrocene: 98 percent of
Argon gas: 97 percent
Hydrochloric acid: the concentration is 38%
Deionized water: 99.99 percent
(2) Grinding and sieving
Respectively grinding and sieving the prepared coal tar pitch and ferrocene, and controlling the fineness;
① putting 18.0g of coal tar pitch raw material into a mortar, grinding with a grinding rod, sieving with a 200-mesh sieve, repeatedly grinding and repeatedly sieving to obtain 1.8g +/-0.018 g of fine powder with the particle size less than or equal to 75 μm;
② placing 2.0g ferrocene in a mortar, grinding with a grinding rod, sieving with a 200 mesh sieve, repeatedly grinding and repeatedly sieving to obtain fine powder with particle size of less than or equal to 75 μm, wherein the fine powder has a size of 0.2g + -0.002 g;
(3) cleaning quartz tube
Taking out the quartz tube in the tube type high-temperature furnace for cleaning:
① scrubbing the inner wall of the quartz tube with 200ml + -5 ml of hydrochloric acid;
② injecting 2000ml + -20 ml deionized water into the inner wall of the quartz tube for lavage;
(4) quartz raw material boat for ultrasonic cleaning
① placing the quartz boat in an ultrasonic cleaner, injecting hydrochloric acid 300ml + -10 ml, starting the ultrasonic cleaner, and cleaning with ultrasonic oscillation for 20min + -1 min;
② placing the quartz raw material boat cleaned by hydrochloric acid in another ultrasonic cleaner, injecting 600ml + -20 ml deionized water, and performing ultrasonic vibration cleaning for 30min + -2 min;
(5) dry quartz tube
Placing the quartz tube which is scrubbed and lavaged by hydrochloric acid and deionized water in a vacuum drying oven for drying at the temperature of 150 +/-5 ℃ for 30 +/-2 min;
(6) dry quartz raw material boat
Placing the quartz raw material boat subjected to ultrasonic cleaning by hydrochloric acid and deionized water in a vacuum drying oven for drying treatment at the temperature of 150 +/-5 ℃ for 30 +/-2 min;
(7) mixing of raw materials
Putting 1.8g +/-0.018 g of ground and sieved coal tar pitch and 0.2g +/-0.002 g of ferrocene fine powder into a beaker, stirring and mixing the fine powder for 15min +/-1 min by using a stirrer, and then putting the mixture into a quartz raw material boat;
(8) inert gas cleaning quartz tube
Placing the cleaned and dried quartz tube in a tubular high-temperature furnace, starting inert gas-argon, and introducing argon into the quartz tube for 600cm3±20cm3Expelling other harmful gases to make the quartz tube in argon atmosphere;
(9) boat for placing quartz raw material
Placing the quartz raw material boat filled with the coal tar pitch and ferrocene mixed fine powder in an inlet area, namely a low-temperature area, in a quartz tube of a tubular high-temperature furnace;
(10) conveying protective gas-argon
Closing the quartz tube, opening the argon bottle and the gas flowmeter, and continuously inputting argon into the quartz tube at the input speed of 150cm3Opening an air outlet valve and an air outlet flow meter at the same time;
(11) opening tubular high-temperature furnace and preparing carbon fiber
Starting the tubular high-temperature furnace, and controlling the temperature of the high-temperature furnace by a temperature controller program;
the middle section of the tubular high-temperature furnace is a high-temperature section, the front section is a feeding low-temperature section, and the rear section is a cooling low-temperature section;
the temperature of the tubular high-temperature furnace starts to rise from the normal temperature of 20 +/-3 ℃, the rising speed is 10 ℃/min, the rising time is 98min +/-5 min, the temperature is kept constant and kept for 40min +/-1 min when the temperature is 1000 +/-5 ℃ in a high-temperature area, the two sides of the high-temperature area are low-temperature areas, and the temperature of the low-temperature area is 450 +/-5 ℃;
pushing the quartz raw material boat to enter a temperature area of 450 +/-5 ℃:
controlling the quartz tube to move by using a guide rail controller, and slowly advancing the quartz raw material boat at the advancing speed of 3 mm/min;
carrying out chemical and physical reactions at a high temperature, and growing the carbon fiber in a gas phase:
the mixed fine powder of coal tar pitch and ferrocene is subjected to chemical and physical pyrolysis reaction at the temperature of 1000 +/-5 ℃, and the main reaction formula is as follows:
low-temperature zone reaction:
high-temperature zone reaction:
in the formula:
c-carbon
CH4-methane
CO-CO 2
H2-Hydrogen gas
CO2-carbon dioxide
H2S-hydrogen sulfide
Cn′Hm′-low hydrocarbon compounds
H2O-water vapor
N2-Nitrogen gas
The carbon fiber growth process:
① solid-liquid state
Firstly, the coal tar pitch begins to liquefy into a liquid state at the temperature of 450 +/-5 ℃;
② liquid-gas state
Pyrolysis of liquid coal tar pitch at 450 ℃ + -5 ℃ (low temperature) to produce CH4、CO、H2、N2、CO2、H2S gas and low hydrocarbon compound, and ferrocene is sublimated into gas;
③ gas-liquid state
At the high temperature of 1000 +/-5 ℃, the iron particles decomposed by the gaseous ferrocene are in a liquid state and become circular liquid drops under the action of surface tension, and are in a thermodynamic stable state;
④ liquid-solid state
Pyrolysis of generated CH4CO and low hydrocarbon compounds are adsorbed on the surface of the ferrocene particle and pyrolyzed into carbon to formactivated carbon atoms, the pyrolytic carbon is dissolved in droplets of the ferrocene particle to form a solid solution, when the carbon is in a supersaturated state, a graphite structure carbon layer is separated out, and under the action of osmotic pressure, surface tension and diffusion force, the ferrocene particle is supported, so that the carbon layer grows along the length direction, and meanwhile, the pyrolytic carbon is deposited on the outer wall of the carbon layer, the diameter of the pyrolytic carbon is increased, and carbon fibers are generated.
Pyrolyzing the mixed fine powder of coal tar pitch and ferrocene at high temperature, forming solid-liquid-gas-liquid-solid state form conversion under the protection of inert gas, and growing a carbon fiber product on the inner wall of a quartz tube in a gaseous molecular adsorption-decomposition-dissolution-diffusion-precipitation-growth form;
(12) product furnace cooling
① closing the tube furnace;
② was cooled under argon at an argon feed rate of 150cm3Min to 20 +/-3 ℃;
③ cooling at 2 deg.C/min for 500 min;
(13) collecting the product
Closing the argon gas valve, opening the tubular high-temperature furnace, taking out the quartz tube, collecting the interlaced cluster-shaped carbon fibers, namely black, hollow and tubular carbon fiber products, on the inner wall of the quartz tube, and hermetically storing the carbon fibers in a clean, colorless and transparent glass container;
(14) detection, analysis, characterization
Analyzing, detecting and representing the color, appearance, components, carbon purity, carbon fiber diameter and length of the prepared interwoven cluster-shaped, black, hollow and tubularcarbon fiber product;
detecting and analyzing the crystal structure characteristics of the product by using an X-ray powder diffractometer;
analyzing the molecular structure and the vibration mode of the product by using a Raman spectrometer;
amplifying by 1000, 5000 and 10000 times by using a field emission scanning electron microscope, and carrying out appearance analysis on the product;
amplifying by 6 ten thousand times by using a high-resolution electron microscope, and analyzing the microstructure of the product;
(15) storage of
The prepared interwoven cluster-shaped, black, hollow and tubular carbon fibers are placed in a colorless and transparent glass container for closed storage, the storage temperature is 20 +/-3 ℃, the relative humidity is less than or equal to 40 percent, and the carbon fibers are placed in a dry, cool and clean environment to be fireproof, sun-proof, waterproof, dampproof and acid-base corrosion resistant.
The chemical substances required by the preparation are coal tar pitch, ferrocene, argon, hydrochloric acid and deionized water, and the optimal combination ratio is as follows: in grams, milliliters and centimeters3Minute is a unit of measurement
Coal tar pitch: c559H690SN7O51.8g
Ferrocene: fe (C)5H5)20.2g
Argon gas: ar 120000cm3
Hydrochloric acid: HCl 400ml
Deionized water: h2O 2000ml
The temperature of a high-temperature area for preparing the carbon fiber by the tubular high-temperature furnace is 1000 +/-5 ℃, the temperature rising speed is 10 ℃/min, the constant temperature, the heat preservation and the product growth time are 40 +/-1 min, the two sides of the high-temperature area are low-temperature areas, and the temperature of the low-temperature area is 450 +/-5 ℃.
The vapor grown carbon fiber is carried out at a high temperature, the mixed powder of coal tar pitch and ferrocene is subjected to a pyrolysis reaction at a temperature of 1000 +/-5 ℃, and the main reaction formula is as follows:
low-temperature zone reaction:
high-temperature zone reaction:
in the formula:
c-carbon
CH4-methane
H2-Hydrogen gas
CO2-carbon dioxide
H2S-hydrogen sulfide
Cn′Hm′-low hydrocarbon compounds
H2O-water vapor
N2-Nitrogen gas
And carrying out chemical and physical form conversion in the pyrolysis process, wherein the form conversion is as follows: the coal tar pitch carbon fiber is generated in a form of gas molecular adsorption, decomposition, dissolution, diffusion, precipitation and growth by solid-liquid-gas-liquid-solid.
The whole process of preparing the coal tar pitch carbon fiber in the quartz tube of the tubular high-temperature furnace is carried out under the protection of inert gas-argon, and the input speed of the argon is 150cm3Min, total input amount is 120000cm3±200cm3。
The coal tar pitch carbon fiber grown in a gas phase at a high temperature has the product appearance of interweaving, clustering, black, hollow and tubular, the diameter of the product is 80-100nm, the fiber length is more than or equal to 100 mu m, and the inner diameter of the hollow tube is 40-50 nm.
Advantageous effects
The invention has obvious advancement compared with the background technology, it takes coal tar pitch as raw materials, takes organic metal compound ferrocene as catalyst, takes inert gas-argon as protective gas, under the state of high temperature 1000 ℃ +/-5 ℃, coal tar pitch + ferrocene mixed powder carries on pyrolysis reaction, carries on solid-liquid state-gas state-liquid state-solid state form conversion in the pyrolysis process, the gaseous molecule generates coal tar pitch carbon fiber by absorbing-decomposing-dissolving-diffusing-separating-growing form, the product carbon fiber is interlacing cluster shape, black, hollow, tubular, the fiber diameter is 80-100nm, the length is more than or equal to 100 μm, the hollow tube inner diameter is 40-50nm, the invention has short preparation process flow, the raw materials are abundant, the preparation cost is low, the product carbon fiber purity is high, the carbon content can reach 92.6 percent, the product yield is high and can reach 63 percent, the product carbon fiber has stable physical and chemical properties, high strength and high temperature resistance, and can be used in various industrial fields and carbon material fields.
Drawings
FIG. 1 is a flow chart of a carbon fiber preparation process
FIG. 2 is a graph showing the relationship between the temperature rise, temperature preservation and cooling temperature of the tubular high-temperature furnace and the time coordinate
FIG. 3 is a diagram showing the operation of the tube-type high-temperature furnace and the quartz tube
FIG. 4 is a state diagram of carbon fiber product field emission scanning electron microscope with 1000 times of cluster magnification
FIG. 5 is a 5000 times magnification interlacing state diagram of a carbon fiber product field emission scanning electron microscope
FIG. 6 is a drawing of a carbon fiber product field emission scanning electron microscope at 1 ten thousand times magnification in an interlaced state
FIG. 7 is a 6 ten thousand times magnified topography of a high-resolution electron microscope for carbon fiber products
FIG. 8 is an X-ray diffraction pattern of a carbon fiber product
FIG. 9 is a Raman scattering spectrum of a carbon fiber product
The part numbers shown in the figures are listed below:
1. the device comprises a tubular high-temperature furnace, 2 quartz tubes, 3 high-temperature regions, 4 low-temperature regions, 5 low-temperature regions, 6 raw material boats, 7 quartz tube cavities, 8guide rails, 9 guide rail controllers, 10 temperature controllers, 11 argon gas cylinders, 12 argon gas valves, 13 argon gas flowmeters, 14 air inlet tubes, 15 air outlet tubes, 16 air outlet valves, 17 air outlet flowmeters, 18 air outlet ports and 19 product regions.
Detailed Description
The invention is further described below with reference to the accompanying drawings:
FIG. 1 is a flow chart of the preparation process, and the preparation parameters are strictly controlled and operated sequentially.
The chemical substances of coal tar pitch, ferrocene, argon, hydrochloric acid and deionized water which are needed for preparation are strictly selected, and the purity and fineness are controlled, so that impurities are not involved, and a byproduct is prevented from being generated.
The required chemical substances are weighed strictly according to the proportion and cannot exceed the maximum and minimum range so as to avoid influencing the yield.
The inert protective gas-argon gas has both protective atmosphere and the function of removing other harmful gases, so that it must be completely conveyed, and must not be intermittent, and its conveying quantity must be sufficient so as to raise the purity of product.
The catalyst ferrocene is the most key chemical substance for preparing the carbon fiber, the preparation of the carbon fiber is directly influenced, when the ferrocene is not added, the product is carbon microspheres, the fiber cannot be formed, when the ferrocene is added according to the proportion, the product is the carbon fiber with vapor growth, in a word, the amount of the catalyst ferrocene influences the appearance, thediameter, the fiber length and the yield of the product, so the use amount of the ferrocene is strictly controlled, and the amount ratio of the coal tar pitch to the ferrocene is 1.8: 0.2, namely 9: 1.
The chemical material proportion for preparing the coal tar pitch carbon fiber is determined in a preset numerical range and is measured in grams and centimeters3Milliliter and minute are measured units, and kilogram and meter are used for industrial preparation3Liter and minute are measured units, and the product is measured unit in nanometer.
The preparation of the nano-scale carbon fiber is a very strict technological process, the preparation steps are strictly controlled, particularly the vapor growth temperature and time are strictly limited, the high temperature of a tubular high-temperature furnace is 1000 +/-5 ℃, is the key of the vapor growth carbon fiber, is the main steps of pyrolysis and form conversion, and is strictly operated.
The coal tar pitch and ferrocene are carefully selected, ground, sieved and repeatedly sieved with a 200-mesh screen to ensure the fineness of the raw materials.
The quartz tube and the quartz raw material boat are main parts for preparing the growing carbon fiber, and need to be strictly cleaned, dried and kept clean.
FIG. 2 is a graph showing the relationship between the temperature rise, temperature maintenance, and cooling temperature of a tubular high-temperature furnace and time, wherein when the temperature of the furnace is raised from 20 ℃ + -3 ℃ to 1000 ℃ + -5 ℃, the temperature is intersected at the point A, and is a high-temperature zone, namely an A-B zone, and a product generation zone, the temperature is reduced and cooled from 1000 ℃ + -5 ℃, the temperature is reduced to 20 ℃ + -3 ℃ along with the furnace, the time is required to be 500min,and the whole temperature rise, temperature maintenance, and temperature reduction are performed under the protection of argon gas.
FIG. 3 is a diagram showing the operating state of a tubular high temperature furnace, wherein the tubular high temperature furnace 1 is horizontal, the temperature controller 10 is arranged at the right part, the quartz tube 2 is arranged in the middle, the middle section of the tubular high temperature furnace 1 is a high temperature region 3, the left side section is a low temperature region 4, the right side section is a low temperature region 5, a guide rail 8 is arranged in the tubular high temperature furnace 1, the left end of the guide rail 8 is provided with a guide rail controller 9, the quartz tube 2 is arranged on the guide rail 8 in the tubular high temperature furnace 1, the left end in the quartz tube 2 is provided with a raw material boat 6, the quartz tube 2 is internally provided with a quartz tube cavity 7, the middle part is a product region 19, the left end of the quartz tube 2 is connected with an air inlet tube 14, an argon gas flowmeter 13, an argon gas valve 12 and a gas cylinder 11, the right end of the quartz tube 2 is connected with an air outlet tube 15, an argon gas outlet valve 16, so as to keep the argon in the quartz tube balanced and safe.
The left part is the argon gas inlet direction, the right part is the gas outlet, the raw material boat 6 enters the low temperature section 4 of the tubular high temperature furnace from the left part on the track 8, then gradually enters the high temperature region 3 under the program control of the controller, the moving speed is 3mm/min, the temperature of the tubular high temperature furnace is controlled by the program of the temperature controller 10, and the position and the direction of each part are correct.
FIG. 4 is a diagram showing a state of clusters of a product magnified 1000 times by a field emission scanning electron microscope, showing uneven black, cluster interlacing, and a scale unit of 10 μm.
FIG. 5 is a view showing the interlaced state of the product at 5000 times magnification of a field emission scanning electron microscope, in which carbon fibers are irregularly arranged and the scale unit is 1 μm.
FIG. 6 is a view showing the interlaced state of the product obtained by magnifying the product by 1 ten thousand times with a field emission scanning electron microscope, wherein the carbon fibers are arranged in irregular stripes, and the scale unit is 1 μm.
FIG. 7 is a state diagram of high resolution electron microscope with 6 ten thousand times magnification, the product of carbon nanofiber is hollow and tubular, and the scale unit is 50 nm.
Fig. 8 shows a product X-ray diffraction pattern, in which the ordinate is a diffraction intensity index and the abscissa is a diffraction angle 2 θ, both peaks in the pattern are characteristic peaks of amorphous carbon, 2 θ is 26.1 ° corresponding to C (002), 2 θ is 44.3 ° corresponding to C (100).
FIG. 9 shows the Raman scattering spectrum of the product, with intensity index on the ordinate and Raman shift value (cm) on the abscissa-1) Has two Raman peaks at 1362cm-1Is defect induced D mode at 1584cm-1The nearby raman peak is the G mode reflecting the degree of order and symmetry of the carbon material. I isG/ID1.07, the prepared VGCFs have higher graphitization degree and certain defects,
example 1:
each preparation device is in a quasi-working state;
selecting chemical raw materials and controlling the purity of the chemical raw materials;
grinding and sieving:
putting 18.0g of coal tar pitch raw material into a mortar, grinding by using a grinding rod, sieving by using a 200-mesh sieve, repeatedly grinding and repeatedly sieving to leave 1.8g +/-0.018 g of fine powder;
placing 2.0g of ferrocene into a mortar, grinding by using a grinding rod, sieving by using a 200-mesh sieve, repeatedly grinding and repeatedly sieving to leave 0.2g +/-0.002 g of fine powder;
cleaning a quartz tube:
scrubbing the inner wall of the quartz tube by using 200ml of hydrochloric acid;
irrigating the inner wall of the quartz tube with 2000ml of deionized water;
cleaning the quartz raw material boat:
cleaning with 300ml hydrochloric acid and ultrasonic cleaner for 20min + -1 min;
washing with deionized water 600ml for 30min + -2 min;
drying the quartz tube and the quartz raw material boat:
respectively drying in a vacuum drying oven at 150 + -5 deg.C for 30min + -2 min;
mixing raw materials:
1.8g plus or minus 0.018g of fine coal tar pitch powder and 0.2g plus or minus 0.002g of fine ferrocene powder are mixed and stirred uniformly;
cleaning a quartz tube with argon:
argon gas is introduced into the quartz tube for 600cm3±20cm3Expelling harmful gas and opening the gas outlet valve;
placing a quartz raw material boat:
placing the coal tar pitch and ferrocene mixed fine powder into a quartz raw material boat, and placing the quartz raw material boat into an inlet area, namely a low-temperature area, in a quartz tube of a tubular high-temperature furnace;
inputting argon:
argon gas is fed into the quartz tube at a speed of 150cm3Min, controlling the flow by a gas flowmeter, and controlling the gas output by a gas outlet flowmeter;
preparing coal tar pitch nano carbon fiber:
opening a tubular high-temperature furnace to heat up, wherein the temperature is increased from 20 ℃ to 1000 +/-5 ℃, the heating speed is 10 ℃/min, the heating time is 98min +/-5 min, the constant temperature is kept for 40min +/-1 min, the two sides of a high-temperature area are low-temperature areas, and the temperature of the low-temperature area is 450 +/-5 ℃;
the guide rail controller controls and pushes the quartz tube and the quartz raw material boat to enter a high-temperature area from an inlet low-temperature area, and the pushing speed is 3 mm/min;
carrying out chemical and physical pyrolysis reactions at high temperature, and carrying out form conversion on coal tar pitch under the catalysis of ferrocene
Solid-liquid-gas-liquid-solid;
gaseous molecular adsorption, decomposition, dissolution, diffusion, precipitation and growth;
generating nano carbon fibers on the inner wall of the quartz tube in a gas phase manner;
and (3) cooling:
closing the tubular high-temperature furnace, and cooling to 20 +/-3 ℃ along with the furnace under the protection of argon;
collecting a product:
closing the argon gas valve, opening the tubular high-temperature furnace, taking out the quartz tube, and collecting the interlaced cluster-shaped carbon fibers, namely black, hollow and tubular nano carbon fiber products, on the inner wall of the quartz tube;
the whole preparation process is completed through the technical procedures.
Claims (3)
1. A method for preparing carbon nanofibers by using coal tar pitch as a raw material is characterized by comprising the following steps: the used chemical substance raw materials are coal tar pitch, ferrocene, ammonia gas, hydrochloric acid and deionized water, and the weight of the coal tar pitch and the ferrocene is as follows:
coal tar pitch: 1.8 g. + -. 0.018g
Ferrocene: 0.2 g. + -. 0.002g
The preparation method comprises the following steps:
(1) selecting chemical feedstock
The chemical raw materials used are selected and subjected to purity control:
coal tar pitch: 98 percent of
Ferrocene: 98 percent of
Argon gas: 97 percent
Hydrochloric acid: the concentration is 38%
Deionized water: 99.99 percent
(2) Grinding and sieving
Respectively grinding and sieving the prepared coal tar pitch and ferrocene, and controlling the fineness;
① putting 18.0g of coal tar pitch raw material into a mortar, grinding with a grinding rod, sieving with a 200-mesh sieve, repeatedly grinding and repeatedly sieving to obtain 1.8g +/-0.018 g of fine powder with the particle size less than or equal to 75 μm;
② placing 2.0g ferrocene in a mortar, grinding with a grinding rod, sieving with a 200 mesh sieve, repeatedly grinding and repeatedly sieving to obtain fine powder with particle size of less than or equal to 75 μm, wherein the fine powder has a size of 0.2g + -0.002 g;
(3) cleaning quartz tube
Taking out the quartz tube in the tube type high-temperature furnace for cleaning:
① scrubbing the inner wall of the quartz tube with 200ml + -5 ml of hydrochloric acid;
② injecting 2000ml + -20 ml deionized water into the inner wall of the quartz tube for lavage;
(4) quartz raw material boat for ultrasonic cleaning
① placing the quartz boat in an ultrasonic cleaner, injecting hydrochloric acid 300ml + -10 ml, starting the ultrasonic cleaner, and cleaning with ultrasonic oscillation for 20min + -1 min;
② placing the quartz raw material boat cleaned by hydrochloric acid in another ultrasonic cleaner, injecting 600ml + -20 ml deionized water, and performing ultrasonic vibration cleaning for 30min + -2 min;
(5) dry quartz tube
Placing the quartz tube which is scrubbed and lavaged by hydrochloric acid and deionized water in a vacuum drying oven for drying at the temperature of 150 +/-5 ℃ for 30 +/-2 min;
(6) dry quartz raw material boat
Placing the quartz raw material boat subjected to ultrasonic cleaning by hydrochloric acid and deionized water in a vacuum drying oven for drying treatment at the temperature of 150 +/-5 ℃ for 30 +/-2 min;
(7) mixing of raw materials
Putting 1.8g +/-0.018 g of ground and sieved coal tar pitch and 0.2g +/-0.002 g of ferrocene fine powder into a beaker, stirring and mixing the fine powder for 15min +/-1 min by using a stirrer, and then putting the mixture into a quartz raw material boat;
(8) inert gas cleaning quartz tube
Placing the cleaned and dried quartz tube in a tubular high-temperature furnace, starting inert gas-argon, and introducing argon into the quartz tube for 600cm3±20cm3Expelling other harmful gases to make the quartz tube in argon atmosphere;
(9) boat for placing quartz raw material
Placing the quartz raw material boat filled with the coal tar pitch and ferrocene mixed fine powder in an inlet area, namely a low-temperature area, in a quartz tube of a tubular high-temperature furnace;
(10) conveying protective gas-argon
Closing the quartz tube, opening the argon bottle and the gas flowmeter, and continuously inputting argon into the quartz tube at the input speed of 150cm3Opening an air outlet valve and an air outlet flow meter at the same time;
(11) opening tubular high-temperature furnace and preparing carbon fiber
Starting the tubular high-temperature furnace, and controlling the temperature of the high-temperature furnace by a temperature controller program;
the middle section of the tubular high-temperature furnace is a high-temperature section, the front section is a feeding low-temperature section, and the rear section is a cooling low-temperature section;
the temperature of the tubular high-temperature furnace starts to rise from the normal temperature of 20 +/-3 ℃, the rising speed is 10 ℃/min, the rising time is 98min +/-5 min, the temperature is kept constant and kept for 40min +/-1 min when the temperature is 1000 +/-5 ℃ in a high-temperature area,the two sides of the high-temperature area are low-temperature areas, and the temperature of the low-temperature area is 450 +/-5 ℃;
pushing the quartz raw material boat to enter a temperature area of 450 +/-5 ℃:
controlling the quartz tube to move by using a guide rail controller, and slowly advancing the quartz raw material boat at the advancing speed of 3 mm/min;
carrying out chemical and physical reactions at a high temperature, and growing the carbon fiber in a gas phase:
the mixed fine powder of coal tar pitch and ferrocene is subjected to chemical and physical pyrolysis reaction at the temperature of 1000 +/-5 ℃, and the main reaction formula is as follows:
low-temperature zone reaction:
high-temperature zone reaction:
in the formula:
c-carbon
CH4-methane
CO-CO 2
H2-Hydrogen gas
CO2-carbon dioxide
H2S-hydrogen sulfide
Cn′Hm′-low hydrocarbon compounds
H2O-water vapor
N2-Nitrogen gas
The carbon fiber growth process:
① solid-liquid state
Firstly, the coal tar pitch begins to liquefy into a liquid state at the temperature of 450 +/-5 ℃;
② liquid-gas state
Pyrolysis of liquid coal tar pitch at 450 ℃ + -5 ℃ (low temperature) to produce CH4、CO、H2、N2、CO2、H2S gas and low hydrocarbon compound, and ferrocene is sublimated into gas;
③ gas-liquid state
At the high temperature of 1000 +/-5 ℃, the iron particles decomposed by the gaseous ferrocene are in a liquid state and become circular liquid drops under the action of surface tension, and are in a thermodynamic stable state;
④ liquid-solid state
Pyrolysis of generated CH4CO and low hydrocarbon compounds are adsorbed on the surface of the ferrocene particle and pyrolyzed into carbon to form activated carbon atoms, the pyrolytic carbon is dissolved in droplets of the ferrocene particle to form a solid solution, when the carbon is in a supersaturated state, a graphite structure carbon layer is separated out, and under the action of osmotic pressure, surface tension and diffusion force, the ferrocene particle is supported, so that the carbon layer grows along the length direction, and meanwhile, the pyrolytic carbon is deposited on the outer wall of the carbon layer, the diameter of the pyrolytic carbon is increased, and carbon fibers are generated.
Pyrolyzing the mixed fine powder of coal tar pitch and ferrocene at high temperature, forming solid-liquid-gas-liquid-solid state form conversion under the protection of inert gas, and growing a carbon fiber product on the inner wall of aquartz tube in a gaseous molecular adsorption-decomposition-dissolution-diffusion-precipitation-growth form;
(12) product furnace cooling
① closing the tube furnace;
② under the protection of argonCooling down at an argon inlet rate of 150cm3Min to 20 +/-3 ℃;
③ cooling at 2 deg.C/min for 500 min;
(13) collecting the product
Closing the argon gas valve, opening the tubular high-temperature furnace, taking out the quartz tube, collecting the interlaced cluster-shaped carbon fibers, namely black, hollow and tubular carbon fiber products, on the inner wall of the quartz tube, and hermetically storing the carbon fibers in a clean, colorless and transparent glass container;
(14) detection, analysis, characterization
Analyzing, detecting and representing the color, appearance, components, carbon purity, carbon fiber diameter and length of the prepared interwoven cluster-shaped, black, hollow and tubular carbon fiber product;
detecting and analyzing the crystal structure characteristics of the product by using an X-ray powder diffractometer;
analyzing the molecular structure and the vibration mode of the product by using a Raman spectrometer;
amplifying by 1000, 5000 and 10000 times by using a field emission scanning electron microscope, and carrying out appearance analysis on the product;
amplifying by 6 ten thousand times by using a high-resolution electron microscope, and analyzing the microstructure of the product;
(15) storage of
The prepared interwoven cluster-shaped, black, hollow and tubular carbon fibers are placed ina colorless and transparent glass container for closed storage, the storage temperature is 20 +/-3 ℃, the relative humidity is less than or equal to 40 percent, and the carbon fibers are placed in a dry, cool and clean environment to be fireproof, sun-proof, waterproof, dampproof and acid-base corrosion resistant.
2. The method for preparing the carbon nanofibers by using the coal tar pitch as the raw material according to claim 1, is characterized in that: the required chemical raw materials are coal tar pitch and ferrocene, and the combined proportion is as follows: measured in grams
Coal tar pitch: 1.8g
Ferrocene: 0.2g
3. The method for preparing the carbon nanofibers by using the coal tar pitch as the raw material according to claim 1, wherein the method comprises the following steps: the coal tar pitch carbon fiber grown in a gas phase at a high temperature has the product appearance of interweaving, clustering, black, hollow and tubular, the diameter of the product is 80-100nm, the fiber length is more than or equal to 100 mu m, and the inner diameter of the hollow tube is 40-50 nm.
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| CN104477874B (en) * | 2014-11-19 | 2016-04-13 | 太原理工大学 | A kind of preparation method of nano thin-layer structure Carbon Materials |
| CN107994229A (en) * | 2017-10-31 | 2018-05-04 | 常州富思通管道有限公司 | A kind of preparation method of novel lithium iron phosphate anode |
| CN108940134B (en) * | 2018-06-20 | 2020-07-31 | 东南大学 | Continuous reaction device and method for coal tar pitch ball oxidation infusibility |
| CN110482909A (en) * | 2019-08-13 | 2019-11-22 | 南京林业大学 | High heat conducting nano carbon fiber modifying asphalt preparation method |
| CN111377432B (en) * | 2020-03-24 | 2021-07-20 | 中国科学院化学研究所 | Method for preparing layered nano carbon material by coal solvent heat treatment |
| CN114590800B (en) * | 2022-04-03 | 2024-05-10 | 昆明理工大学 | Method for continuously preparing graphene by magnetic drive sliding arc plasma high-voltage discharge |
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| CN1273216A (en) * | 1999-05-06 | 2000-11-15 | 中国科学院金属研究所 | Process for preparing large-quantity nm-class carbon fibres by using growth promoter of sulfur |
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| CN1273216A (en) * | 1999-05-06 | 2000-11-15 | 中国科学院金属研究所 | Process for preparing large-quantity nm-class carbon fibres by using growth promoter of sulfur |
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