CN100345800C - Injectiong coagulation shaping technology of high performance graphite product - Google Patents
Injectiong coagulation shaping technology of high performance graphite product Download PDFInfo
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- CN100345800C CN100345800C CNB2005100423596A CN200510042359A CN100345800C CN 100345800 C CN100345800 C CN 100345800C CN B2005100423596 A CNB2005100423596 A CN B2005100423596A CN 200510042359 A CN200510042359 A CN 200510042359A CN 100345800 C CN100345800 C CN 100345800C
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Abstract
The present invention relates to an injection moulding technique of graphite products, which belongs to the field of inorganic nonmetal materials. The present invention is characterized in that graphite used as the carbon source is mixed with an organic monomer, a crosslinking agent a dispersant and water so as to prepare carbon pulp, and the pH value of the carbon pulp is adjusted; an initiator is added to the carbon pulp, and the initiator and the carbon pulp are evenly stirred; the obtained mixture is injected in a mould in a certain shape, put still at the room temperature of-80DEG C for 10 minutes to 12 hours, and then demoulded so as to obtain the biscuit of the graphite product; the biscuit of the graphite product is sintered to obtain the graphite product. Owing to the injection moulding in-situ solidification, the graphite powder in the product eliminates the directional arrangement so as to realize the isotropy of the product; the microscopic structure of the product is very even so as to greatly enhances the reliability of the product; the biscuit of the product is high in intensity and be used for various kinds of mechanical processing so as to reduce the sintered processing allowance and reduce the production cost of the product; the shape of the product can be freely designed according to needs, and therefore, the present invention has the unique advantages in the preparation of products in complicated shape.
Description
Technical field
The present invention relates to a kind of injectiong coagulation shaping technology of graphite product, belong to field of inorganic nonmetallic material.Be mainly used in fields such as refractory materials, scratch-resistant material, lubricant, electrical carbon material, coating.
Background technology
The preparation of high-performance carbon element and graphite material is the very long process of a high energy consumption.Traditional method prepares carbon element or graphite composite material by organic precursor, need generally need 5 cycles, time consumption and energy consumption through several carbonization, greying, densification under condition of high voltage.Adopt hot-formingly can reduce cost by contrast, shorten preparation time, limit, can only be sheet or column, so goods still need further processing, thereby prolonged the finished product preparation cycle, increased the cost of product yet resulting product is shaped as hot pressing die.If can reduce the preparation energy consumption, shorten preparation cycle, realize the complicated shape once shaped, then high-performance carbon element and graphite material preparation cost will reduce significantly, make it be widely used in economy and national defense construction.Everything all suddenly waits to seek a kind of new forming method, to overcome the deficiency of traditional technology.
Injectiong coagulation shaping technology is that nineteen ninety U.S.'s Oak Ridge MAJanny of National Key Laboratory and professor OOOmatete study invention, its thinking is the concentrated suspension with the high solid volume fraction of low viscosity, under catalyzer and action of evocating, make the organic monomer crosslinking polymerization in the concentrated suspension become tridimensional network, thereby make the powder particle in-situ curing molding in the concentrated suspension.
Injectiong coagulation shaping technology has following several big advantage: the microstructure that (1) annotates the parison body that congeals into is very even, and the inhomogeneous contraction in the time of can avoiding burning till like this improves the reliability of ceramic component greatly.(2) annotate the green strength height of the parison body that congeals into, can be with mechanical workout.(3) near-net-shape, the high contraction of solid volume fraction of annotating the type concentrated suspension that congeals into is little, can realize near-net-shape.Greatly reduce the machining amount in precise ceramic component later stage.(4) sample shape depends primarily on and annotates the pattern tool that congeals into, and therefore can according to actual needs and freely design (5) does not have particular requirement to moulding stock.(6) need not mold pressing, etc. specific installations such as static pressure, reduce preparation cost greatly, help the large-scale production of product.
Because injectiong coagulation shaping technology is compared with other traditional ceramics moulding process and is had many superiorly, causes the common concern of expert in the ceramic boundary, makes this technology obtain very fast development, and has obtained in practice to apply.The investigator of Oak Ridge National Laboratory will apply the notes type that congeals in practice the end of the year in 1996, and obtained the annual achievements of U.S. 1996 and promoted prize, there are three companies (AlliedSignal Ceramic Components, LoTEC Inc.andCeramic Magnetics Inc.) to obtain the permission to use of this technology.
China had carried out systematic research work to gel-casting technology in recent years, mainly concentrate on the high performance structure ceramic field, carry out the research of gel-casting technologies such as aluminum oxide, silicon carbide, silicon-dioxide, zirconium white and matrix material thereof, obtained some breakthrough progress.At present, China's researcher successfully is applied to gel-casting technology in the production of alumina ceramic substrate and meticulous fused quartz ceramic goods.But with graphite is that carbon source prepares high volume solid load graphite carbon slurry, prepares high-performance carbon element and graphite material with injectiong coagulation shaping technology, does not appear in the newspapers as yet both at home and abroad.
Summary of the invention
The purpose of this invention is to provide a kind of Injectiong coagulation shaping technology of high performance graphite product, it can overcome long, the shortcoming that can not the once shaped complicated shape of existing graphite product moulding process high energy consumption, cycle.
A kind of Injectiong coagulation shaping technology of high performance graphite product is characterized in that: (1) is carbon source with the graphite powder, is mixed with the carbon slurry with organic monomer, linking agent, dispersion agent and water, and the pH value of regulating this carbon slurry is in 11.0～14.0 scopes; (2) then, add radical initiator and stir with the carbon slurry; (3) the gained mixture is injected mould, the mould that will fill this mixture subsequently leaves standstill insulation and/or heating, and temperature range is room temperature～80 ℃, required time: 10 minutes-12 hours, treat that the carbon slurry solidifies; (4) biscuit is deviate from from mould, promptly obtained the graphite product biscuit after the drying; (5) the above-mentioned biscuit of sintering obtains graphite product; Described dispersion agent is alkylphenol polyoxyethylene, tween or peregal.
Injectiong coagulation shaping technology of high performance graphite product provided by the invention possesses following advantage: the graphite powder has been eliminated and has been aligned because of the notes type in-situ solidifying that congeals in the goods, thereby can realize the isotropy of goods; Microstructure is very even, improves the reliability of goods greatly; Goods biscuit intensity height can carry out every mechanical workout, therefore can reduce and burn till the post-treatment surplus, reduces the production of articles cost; Article shape can freely design as required, thereby has its exclusive advantage in the preparation of complicated shape goods.
Description of drawings
Fig. 1 is a graph of a relation between graphite powder ξDian Wei and pH value and the tensio-active agent.Band △, ◆ the symbol line represent respectively without tensio-active agent handle and through the graphite powder ξDian Wei of tensio-active agent sodium laurylsulfonate processing with the pH changing conditions.PH value scope among the figure is 1.50-11.50.
Fig. 2 for graphite carbon slurry under fixedly dispersion agent sodium laurylsulfonate and solid load condition, viscosity and carbon are starched graph of a relation between the pH value.Dispersion agent sodium laurylsulfonate consumption is the 1.0wt% of carbon slurry total mass among the figure, and solid load is: 25vol%.
Fig. 3 is a graph of a relation between carbon slurry viscosity and the dispersion agent sodium laurylsulfonate consumption under fixed pH value and the solid load condition.The pH value of carbon slurry is 7.0 among the figure, and graphite powder solid load is: 25.0vol%.
Fig. 4 is under fixing dispersant dosage and the potential of hydrogen condition, graph of a relation between carbon slurry viscosity and the solid load.Two dispersion agent sodium laurylsulfonates (being designated as dispersant A), alkylphenol polyoxyethylene (being designated as dispersant B) consumption are 1.0wt% among the figure, and the pH value of carbon slurry is 11.20; SV25, SV28, SV37 represent respectively that solid volume content is in the carbon slurry: 25vol%, 28vol%, 37vol% among the figure.
Fig. 5 is the mechanical property comparison diagram of the graphite biscuit sample of employing conventional moulded moulding and this prepared.(a) is the bending strength of conventional moulded moulding graphite biscuit sample among the figure; (b) be the bending strength of the graphite biscuit sample of this prepared.
Embodiment
(1) preparation of graphite carbon slurry and relevant performance test.
Take by weighing organic monomer acrylamide 150 grams, linking agent N, N '-methylene-bisacrylamide 25 grams, dispersion agent sodium laurylsulfonate 20 grams add in the distilled water, at room temperature stir, above reagent is fully dissolved, be made into 1000 ml solns, regulate pH to 11.0 with strong aqua; Above solution is changed in the aluminum oxide ball milling jar, add the alumina lap ball, take by weighing 750 gram Graphite Powder 99s again and join in the ball grinder,, amount to 24 hours, promptly get the graphite carbon slurry with 800 rev/mins rotating speed ball milling.
Carbon source described in the present invention is natural graphite or synthetic graphite; The content of graphite in the carbon slurry is 20vol%-50vol%.Organic monomer is the organic compound that contains vinyl, allyl group, acrylate, acrylamide or acrylic-functional, and linking agent is N, N '-methylene-bisacrylamide; Organic monomer and content of crosslinking agent sum are the 5wt%-20wt% of content of graphite.Dispersion agent is sodium laurylsulfonate, alkylphenol polyoxyethylene, tween or peregal; The content of dispersion agent in the carbon slurry is: 0.1wt%-5wt%; The pH value of regulating the graphite carbon slurry is 11.0-14.0.
Measure Graphite Powder 99 surface ξDian Wei and can quantitatively understand electrostatic repulsion size between powder, the stability of prediction graphite carbon slurry.As shown in Figure 1, the iso-electric point of the graphite powder that is untreated is about pH=4.5, and the ξDian Wei maximum value is about pH=8.5; After the tensio-active agent sodium laurylsulfonate is handled, be negative value in the ξDian Wei pH scope shown in the figure, and absolute value raises with pH and increases, when pH=11, ξDian Wei reaches-50mV.As seen after handling through tensio-active agent, very big change has taken place in the surface potential of graphite powder in water, electrostatic repulsion increases between the graphite granule, thereby make powder be tending towards disperseing and the sinking of not reuniting, this helps the stable suspersion of graphite powder in carbon slurry, can be stablized, evenly, the graphite carbon slurry of low viscosity, high solid loading.
As shown in Figure 2, when the carbon slurry was adjusted to alkalescence (pH=11.20) by neutral (pH=7.6), the viscosity of carbon slurry reduced significantly, and its flowability is greatly improved, thereby more helps the injection molding of carbon slurry.This conforms to the result of study of Fig. 1, and Graphite Powder 99 surface ξDian Wei raises with pH in the carbon slurry increases, and promptly electrostatic repulsion increases between the graphite granule, and promptly showing as the carbon slurry viscosity on macroscopic view increases with the pH value and remarkable decline.
As shown in Figure 3, the carbon slurry viscosity is increased to 1.00wt% with dispersant by 0.50wt% earlier and reduces, and the carbon slurry viscosity reaches mnm. (0.54Pa.S) when content is 1.00wt%.Continue to increase dispersant dosage to 1.50wt% and 2.00wt%, the viscosity of carbon slurry increases on the contrary.This shows that the flowability of carbon slurry is responsive to the amount ratio of dispersion agent, departs from the remarkable increase that optimum amount will cause viscosity.
As seen from Figure 4, when using the dispersion agent sodium laurylsulfonate, along with solid load increases to 28vol% (SV28) by 25vol% (SV25), the carbon slurry viscosity significantly rises thereupon; The carbon slurry viscosity reduces significantly with the increase of rotating speed on the other hand, presents the shear shinning phenomenon, and this is the common a kind of rheological charactristics of high concentrated suspension.When rotating speed big (＞30 rev/mins), the viscosity number of carbon slurry tends towards stability.In addition, different dispersion agent kinds also differ widely to dispersion, the stabilization of graphite carbon slurry.When using the dispersion agent alkylphenol polyoxyethylene, the flowability of graphite carbon slurry significantly improves, solid load be the carbon slurry viscosity of 37vol% (SV37) still less than using dispersion agent sodium laurylsulfonate solid load to be the carbon of 28vol% (SV28) slurry, and with use dispersion agent sodium laurylsulfonate solid load approaching as the carbon slurry viscosity of 25vol% (SV25).As seen the selection of dispersion agent to obtain to stablize, evenly, high solid loading, low viscosity graphite carbon slurry be vital.
(2) add initiator
Add each 18 milliliters of the initiator 2wt% ammonium persulphate and the 2wt% Tetramethyl Ethylene Diamine aqueous solution in the above-mentioned graphite carbon slurry that makes, and make it to stir with the carbon slurry with ball milling or electronic stirring means, mixing time is 30 minutes.After mixing, in vacuum mixer, remove the bubble in the carbon elimination slurry.
Radical initiator described in the present invention is Sodium Persulfate, Potassium Persulphate, ammonium persulphate, Tetramethyl Ethylene Diamine or their all or part of mixtures; The content of initiator in the carbon slurry is 0.005wt%-0.5wt%.
(3) the carbon slurry solidifies
The mixture that (two) step was made injects mould.The mould that will fill this mixture is subsequently put into the fixed temperature and humidity baking oven, and in 60 ℃ of insulations 30 minutes, the carbon slurry solidified.
(4) demoulding, drying and product testing
Graphite biscuit after solidifying is deviate from from mould, placed slow drying of room temperature environment or heated constant temperature 40 ℃ and 80% time drying of relative humidity.Behind the described graphite forming of green body, process, modify processing, comprise mechanical workouts such as cutting, boring, polishing, polishing.After treating the goods complete drying, test its mechanical property and microtexture.Simultaneously the conventional dry platen press is prepared that sample is characterized and as a comparison.
Described heated constant temperature temperature is 35-40 ℃, and relative humidity is 75-85%.
As shown in Figure 5, the mechanical property of graphite biscuit sample that adopts conventional moulded moulding preparation is far below the graphite biscuit sample of this prepared: the former bending strength less than 5MPa (Fig. 5 a) and latter's bending strength 10-25MPa (Fig. 5 b).Because product of the present invention possesses better mechanical property,, reduce the process redundancy after product burns till, the preparation cost of reduction product so adopt the graphite biscuit sample of this prepared before sintering, can cut, hole, dig and every mechanical workout such as mill.
(5) sintering densification
Under the nitrogen atmosphere protection; divide three phases to finish: (1) is warming up to 600 ℃ with 1 ℃ of/minute clock rate; insulation is 1 hour under this temperature; (2) be warming up to 1200 ℃ with 1 ℃ of/minute clock rate then; insulation is 1 hour under this temperature; (3) be warming up to 2800 ℃ with 10 ℃ of/minute clock rate subsequently, insulation is 1 hour under this temperature.Wherein, the fs is non-carbon component (SO
2, HCN etc.) burning lose (burn-out), subordinate phase is organic carbonization (carbonization), the phase III is goods greying (graphitization) and densification (densification) process.
Claims (4)
1. Injectiong coagulation shaping technology of high performance graphite product, it is characterized in that: (1) is carbon source with the graphite powder, is mixed with the carbon slurry with organic monomer, linking agent, dispersion agent and water, the pH value of regulating this carbon slurry is in 11.0～14.0 scopes; (2) then, add radical initiator and stir with the carbon slurry; (3) the gained mixture is injected mould, the mould that will fill this mixture subsequently leaves standstill insulation and/or heating, and temperature range is room temperature～80 ℃, required time: 10 minutes-12 hours, treat that the carbon slurry solidifies; (4) biscuit is deviate from from mould, promptly obtained the graphite product biscuit after the drying; (5) the above-mentioned biscuit of sintering obtains graphite product; Described dispersion agent is alkylphenol polyoxyethylene, tween or peregal.
2. by the described technology of claim 1, it is characterized in that described carbon source is natural graphite or synthetic graphite; The content of graphite in the carbon slurry: 20vol%-50vol%, described organic monomer are the organic compound that contains vinyl, allyl group, acrylamide or acrylic-functional; Described linking agent is N, N '-methylene-bisacrylamide; Described monomer and content of crosslinking agent sum are the 5wt%-20wt% of content of graphite; The content of described dispersion agent in the carbon slurry is: 0.1wt%-5wt%.
3. by the described technology of claim 1, it is characterized in that described radical initiator is Sodium Persulfate, Potassium Persulphate, ammonium persulphate, Tetramethyl Ethylene Diamine or their all or part of mixtures; The content of initiator in the carbon slurry is: 0.005wt%-0.5wt%.
4. by the described technology of claim 1, it is characterized in that described graphite biscuit takes out after drying from mould and is treated to dry at ambient temperature and/or is to carry out under the condition of 75-85% in heating, constant temperature 35-40 ℃ and relative humidity.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101774210A (en) * | 2010-03-31 | 2010-07-14 | 黑龙江科技学院 | Self-consolidation forming method of natural graphite |
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| CN102485688B (en) * | 2009-09-29 | 2014-05-14 | 黄柱联 | Graphite material |
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| 胶凝注模成型工艺的研究进展 刘开琪等，耐火材料，第38卷第5期 2004 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101774210A (en) * | 2010-03-31 | 2010-07-14 | 黑龙江科技学院 | Self-consolidation forming method of natural graphite |
| CN101774210B (en) * | 2010-03-31 | 2011-10-19 | 黑龙江科技学院 | Self-consolidation forming method of natural graphite |
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