CN1186152C - Method for preparing carbon-coated metal nano crystal - Google Patents
Method for preparing carbon-coated metal nano crystal Download PDFInfo
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- CN1186152C CN1186152C CNB021567379A CN02156737A CN1186152C CN 1186152 C CN1186152 C CN 1186152C CN B021567379 A CNB021567379 A CN B021567379A CN 02156737 A CN02156737 A CN 02156737A CN 1186152 C CN1186152 C CN 1186152C
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Abstract
The present invention relates to a method for preparing carbon-encapsulated metal nanocrystals. The method comprises the following steps: mixing or dissolving an aromatic compound and a transition metal compound, carrying out thermal polycondensation in inert atmosphere at 420 to 540 DEG C under the condition of self-pressure lifting for 5 minutes to 4 hours, extracting obtained thermal decomposition products with solvent, obtaining undissolved substances, namely the carbon-encapsulated metal nanocrystals. The raw materials used in the method are as follows: (A) the aromatic compound is a model aromatic compound containing alkyl substituted side chains and composed of one to six aromatic rings, refined coal tar, refined coal tar pitch, refined petroleum heavy oil or refined petroleum heavy oil pitch; (B) the transition metal compound is a cyclopentadienyl organo-transition metal compound, a carbonyl organo-transition metal compound, organo-transition metal acetylacetonate, transition metal acetate or transition metal nitrate; (C) the weight ratio of the aromatic compound to the transition metal compound is from 1:2 to 1:0.01; (D) the solvent is acetone, benzene or pyridine.
Description
Technical field the present invention relates to a kind of preparation method of carbon-clad metal nanocrystal, be with aromatic compound and transistion metal compound through dissolving mixes, thermal polycondensation reacts, extraction process obtains carbon-coated nano metal crystalline substance.
Background technology has found that along with Iijima in 1991 but the nano particle that carbon shell or CNT coat the second phase material has caused researcher's very big interest since the CNT of filler.Because carbon shell or CNT can be confined metallics in very little space, can avoid the influence of environment to nano metal material, solve the problem that nano metal particles can not stable existence in air; Owing to the existence of carbon coating layer, be expected to improve the compatibility between metal and the organism, thereby have broad application prospects in addition at biomedical aspect.In addition, different according to metallic and carbon base body, this material is expected as ion secondary battery cathode material lithium, electric wave shielding material, oxidation reduction catalyst, nuclear waste disposal material, fine ceramics material, magnetic material (magnetic ink, high density magnetic recording material etc.) etc.At present, people successfully prepare little fullerene molecule [the Y.Chai et al of the one or more metallic atoms of parcel, Fullerenes with metals inside, J.Phys.Chem.1991:95 (20): 7564-7568] and carbon nano-particle [the P.J.F.Harris et al of clad metal or metal carbides nanocrystal, Encapsulating uranium in carbon nanoparticlesusing a new technique, Carbon 1998:36:1859-1861], and the material of finding the novel structure of this class has peculiar electricity, optics and magnetic property are a kind of novel functional composite materials.
At present, the carbon-clad metal preparation of nano crystal mainly contains arc discharge method, chemical vapour deposition technique (CVD) and impregnating metal charring etc.Arc discharge method is the common method of preparation fullerene and CNT, change preparation condition, being about to metal precursor is embedded in the graphite electrode in advance, just can prepare nano-sized carbon clad metal crystalline substance [V.P.Dravid et al by the direct-current arc discharge, Controlled-size nanocapsules, Nature 1995:374:602]; [S H tsai et al such as Tsai, A novel technique for the formation of carbon-encapsulated metalnanoparticles on silicon, Carbon 2000:38:781-785] on silicon chip, prepare the carbon-clad metal nano nickel particles with plasma CVD method; [P.J.F.Harris et al such as Harris, Encapsulating uranium in carbon nanoparticles using a new technique, Carbon 1998:36:1859-1861] metal precursor is immersed in the porous carbon materials, obtain the carbon-clad metal nano particle by 1800 ℃ high-temperature heat treatment.The employed temperature of above-mentioned preparation method all higher (more than 1000 ℃), the complexity of pyroreaction makes product purity lower, beyond the de-carbon coating, also often mixing has random carbon granule, CNT and fullerene etc., the yield of target product is not only lower, and being difficult to control the extent of reaction, the preparation cost of material is corresponding very high, is difficult to realize mass preparation.The preparation method of the carbon-coated nano metallic particles that for this reason, seek a kind of simple possible, is easy to control and to develop its application be one of emphasis of this direction research at present.
Summary of the invention the purpose of this invention is to provide a kind of novel synthesis of carbon-coated nano metallic crystal, and its preparation technology only need mix through dissolving, thermal polycondensation reacts, extraction process just can obtain carbon-coated nano metal crystalline substance.If need further to improve the orderly degree of alignment that coats carbon-coating, can to the extraction sample carry out in the air atmosphere do not melt with inert atmosphere in charing handle.The method that the present invention proposes has characteristics such as raw material sources are abundant, technology is simple, the material preparation cost is low, purity is high, the metal types selectable range is wide, easily realizes large-scale production.
The method that the present invention proposes is evenly to mix with transistion metal compound or dissolve with aromatic compound, in inert atmosphere, in 420-540 ℃ of temperature range, carry out the thermal polycondensation reaction from boosting down, 5 minutes to 4 hours reaction time, the thermal decomposition product that obtains is handled through solvent extraction, and the solvent insoluble matter is carbon-coated nano metal crystalline substance; Raw materials used as follows:
(A) aromatic compound is to contain alkyl to replace the model aromatic compound that is made of 1-6 aromatic ring of side chain, refining coal tar, coal tar asphalt, black petroleum products or asphalt;
(B) transistion metal compound is cyclopentadienyl transition organo-metallic compound, carbonyl transition organo-metallic compound, acetylacetone based transition organo-metallic compound, transition metal acetate or transition metal nitrate;
(C) weight ratio of aromatic compound and transistion metal compound is 1: 2-1: 0.01.
(D) solvent is acetone, benzene or pyridine.
The above-mentioned model aromatic compound that is made of 1-6 aromatic ring that contains alkyl replacement side chain is: the condensed-nuclei aromatics that alkylbenzene, naphthalene, anthracene, phenanthrene or other fragrant number of rings are 2-6.The cyclopentadienyl transistion metal compound is: ferrocene, cobaltocene or dicyclopentadienyl nickel.The carbonyl transistion metal compound is: carbonyl iron, carbonyl cobalt or carbonyl nickel.Acetylacetone based transistion metal compound is: chromium acetylacetonate, acetylacetone,2,4-pentanedione platinum or palladium acetylacetonate.The transition metal acetate is: copper acetate, cobalt acetate, nickel acetate or ferric acetate.Transition metal nitrate is: ferric nitrate, cobalt nitrate or nickel nitrate.The charing that the solvent insoluble matter-carbon-coated nano metal crystalline substance obtain carries out in the not melt processed and inert atmosphere is handled in extraction handle in air atmosphere, obtain coating the carbon-coated nano metal crystalline substance that the orderly degree of alignment of carbon-coating improves.
The carbon shell is closely arranged around the nano metal nucleus in the material that the method that the present invention proposes prepares in the ordinary course of things, if need further to improve the orderly degree of alignment that coats carbon-coating, can in air atmosphere, carry out not melt processed between 250-350 ℃ and in inert atmosphere, carry out charing and handle (700-3000 ℃) the extraction sample.Do not melt and handle with charing that to be preparation carbon fiber and other material with carbon element be the known method commonly used of the crystallization degree that improves carbon, its can keep the fibre morphology of material on the one hand, can improve the crystallization degree of material on the other hand again.
The present invention is used contains model aromatic compound that aromatic compound that alkyl replaces side chain is hyperergic monocycle, dicyclo and the above number of rings of dicyclo thereof, refining coal tar or pitch, refining black petroleum products or asphalt; The condensed-nuclei aromatics that alkylbenzene, naphthalene, anthracene, phenanthrene or other fragrant number of rings are 2-6 in the model aromatic compound, the alkyl that these model aromatic compounds contain more amount replaces side chain (as methyl, ethyl etc.), to give condensed-nuclei aromatics, be beneficial to the reaction of metallizing thing and form nanometer clad metal crystalline substance with high chemical reactivity.The raw material that the present invention uses is the reactive stronger and cheap aromatic hydrocarbons organic compound that obtains easily under middle temperature (420-540 ℃) condition, and raw material sources are abundant.The model aromatic compound is pure with analyzing, and coal tar, petroleum residual oil, pitch are with refining, and their purity should be tried one's best height, especially constituent content such as N, S should be low as far as possible, otherwise N, S etc. will react with metallic, poisons the catalytic action of metal pair aromatic hydrocarbons.The alkyl that should contain more amount in this aromatic compound replaces side chain, to give its high thermal response activity.Otherwise be difficult to generate the carbon coated particle, obtain only for exposed metallic is dispersed in composite in the carbon base body, the selection principle of transition metal series compound is a little less than the effect between metal and ligand, and synthetic easily obtaining.
The preparation of the brilliant material of carbon-coated nano metal provided by the invention is at high temperature to the catalytic action of organic aromatic hydrocarbon substance thermal polycondensation reaction and the carbon reduction principle to metal according to metal, metallic compound and carbon source are chosen and the principle of mating is that the two intersolubility is better, the reactivity height.At first the transistion metal compound with above-mentioned carbon raw material aromatic compound and source metal evenly mixes by a certain percentage, place autoclave then, air several rear enclosed kettle in the inert gas replacement still, be warming up to predetermined temperature from boosting, stop certain hour then, the cooling release, residue is through solvent extraction commonly used such as acetone, benzene or pyridine in the still, remove unreacted reactant and light component, dried solvent insoluble matter is target product---carbon-coated nano metal crystal composite material.This material core is the nano metal crystal, and shell is generally by closely constituting around the several layers of height-oriented graphite flake layer of examining interior metal.The ratio of carbon source and source metal is decided according to need, is generally 1: 2-1: 0.01, and ratio is too low, and the content of metal is low excessively in the composite of preparation, and nano-crystalline granule is little, and metal will not have the effect of functionalization; Ratio is too high, and carbon and metal can not be fine compound, and the brilliant particle of the metal of formation is bigger.Reaction temperature generally is controlled between 420-540 ℃, and temperature is low excessively, and the thermal decomposition of carbon raw material not exclusively or is not decomposed, and light component and yield that end-product will contain more amount are low; Temperature is too high, and reaction is violent, and the pressure height is difficult to control, also can be too high to the requirement of pressurized equipment, and cause manufacturing cost high.Reaction time generally is controlled at not to be waited by 4 hours in 5 minutes, mainly decided according to the reactivity of carbon source metallizing thing and reaction temperature.Generally speaking, the reaction time is too short, and the pyrolysis of carbon raw material is incomplete, and yield is on the low side; Overlong time, except that generating carbon-coated nano metal crystalline substance, the growing amount of on-catalytic agraphitic carbon is also corresponding to be increased, and the purpose product purity reduces, and time consumption and energy consumption, has improved preparation cost.It is nanocrystalline that method provided by the invention only need be passed through mixing (preferably dissolving), thermal polycondensation, extraction process just can obtain carbon-clad metal, system generally is lower than 10.0Mpa from rising final pressure under mesophilic condition, has that technology is simple, the metal types selectable range is wide, the yield advantages of higher.
The specific embodiment
Embodiment 1
Evenly mix by weight 1: 0.2 ratio with catalytic cracking turpentole slurry oil (constituent content is wt%:C 88.86, and H 9.42, C/H0.97, N≤0.3) and the pure ferrocene of analysis, place autoclave.Adding thermal response under mechanical agitation and the nitrogen protection continuously, heating rate is kept 3 ℃/min, stops 1 hour down at 420 ℃, obtains thermal decomposition product, and yield is 50wt%, and system reaches 5.0Mpa from the power of boosting.With the pyridine is that solvent carries out thermosol extracting repeatedly (80 ℃ of temperature) to product, fades to achromaticity and clarification until filtrate.Filter residue after the oven dry is carbon-coated nano metal crystalline substance, yield 60%.Results of elemental analyses shows that the weight percentage of metallic iron is about 9.0%, and the content of carbon is 90.0%.This product is carried out the analysis of X-ray diffraction (XRD) and transmission electron microscope (TEM), and the result shows and is mainly iron simple substance by the metallic that obtains (α-Fe), particle diameter is dispersed in the carbon base body between 30-80nm, and is closely coated by carbon-coating.The extracting yield is 60%.
Embodiment 2
Method of operating is with embodiment 1, and turpentole residual oil is 1: 0.01 with the weight ratio of analyzing pure ferrocene, and all the other conditions are constant, obtains mainly nano-iron particle/carbon composite by α-Fe constitutes, particle diameter is distributed in 10-50nm through charing and solvent extraction.Interlamellar spacing (d
002) be 0.346nm, for further improving the crystallization degree of carbon, nano-iron particle/carbon composite is handled again the d of carbon after 30 minutes 1700 ℃ of charings 300 ℃ of oxidation processes
002Value is decreased to 0.339nm, illustrates that the orderly degree of alignment of carbon is improved largely.
Embodiment 3
Method of operating is with embodiment 1, and turpentole residual oil is 1: 2 with the weight ratio of analyzing pure ferrocene, and all the other conditions are constant, obtains mainly nanometer iron/carbon composite by α-Fe constitutes, particle diameter is distributed in 60-300nm through charing and solvent extraction.
Embodiment 4
To analyze pure durol and evenly mix by weight 1: 0.30 ratio, put into the autoclave temperature reaction, obtain black powder after 4 hours in 540 ℃ of stops of whole temperature with the pure ferrocene of analysis, again after acetone normal temperature dissolves and washes away, obtain the purpose material, its yield is about 25%, the final pressure 7.0Mpa of system.XRD and tem analysis show that product is the Fe about particle diameter 10nm
3C crystal, surface are arranged several layers of regular continuous carbon-coating parcel, and the extracting yield is 25%.
Embodiment 5
Method of operating is with embodiment 4, and metallic compound is changed to iron tetracarbonyl, stops 5 minutes for 540 ℃ in whole temperature, and it is constant to keep other condition, obtains carbon-coated nano iron crystal.Because the iron tetracarbonyl reactivity is very strong, the required reaction time is shorter.
Embodiment 6
Method of operating is with embodiment 4, and metallic compound is changed to chromium acetylacetonate, and it is constant to keep other condition, obtains carbon-coated nano Cr metal crystalline substance.
Embodiment 7
Method of operating is with embodiment 4, and it is constant to keep other condition, and metallic compound uses ferric nitrate, and the result finally obtains the carbon-coated nano metal crystalline substance based on iron oxide.
Embodiment 8
To analyze pure naphthalene and cobalt acetate evenly mixed by weight 1: 0.30, put into the autoclave temperature reaction, after stopping 4 hours, 540 ℃ of whole temperature obtain black powder, again after acetone normal temperature dissolves and washes away, obtain the purpose material, its yield is about 25%, and XRD and tem analysis show that product is mainly Co and CoO, average grain diameter about 50nm, is dispersed in the carbon that is undefined structure.
Claims (8)
1, a kind of preparation method of carbon-coated nano metal crystalline substance, be evenly to mix with transistion metal compound or dissolve with aromatic compound, in inert atmosphere, in 420-540 ℃ of temperature range, carry out the thermal polycondensation reaction from boosting down, 5 minutes to 4 hours reaction time, the thermal decomposition product that obtains is handled through solvent extraction, and the solvent insoluble matter is carbon-coated nano metal crystalline substance; Raw materials used as follows:
(A) aromatic compound is to contain alkyl to replace the model aromatic compound that is made of 1-6 aromatic ring of side chain, refining coal tar, coal tar asphalt, black petroleum products or asphalt;
(B) transistion metal compound is cyclopentadienyl transition organo-metallic compound, carbonyl transition organo-metallic compound, acetylacetone based transition organo-metallic compound, transition metal acetate or transition metal nitrate;
(C) weight ratio of aromatic compound and transistion metal compound is 1: 2-1: 0.01;
(D) solvent is acetone, benzene or pyridine.
2, preparation method according to claim 1 is characterized in that: the model aromatic compound that is made of 1-6 aromatic ring that contains alkyl replacement side chain is the condensed-nuclei aromatics that methylbenzene, naphthalene, anthracene, phenanthrene or other fragrant number of rings are 2-6.
3, preparation method according to claim 1 is characterized in that: the cyclopentadienyl transistion metal compound is: ferrocene, cobaltocene or dicyclopentadienyl nickel.
4, preparation method according to claim 1 is characterized in that: the carbonyl transistion metal compound is: carbonyl iron, carbonyl cobalt or carbonyl nickel.
5, preparation method according to claim 1 is characterized in that: acetylacetone based transistion metal compound is: chromium acetylacetonate, acetylacetone,2,4-pentanedione platinum or palladium acetylacetonate.
6, preparation method according to claim 1 is characterized in that: the transition metal acetate is: copper acetate, cobalt acetate, nickel acetate or ferric acetate.
7, preparation method according to claim 1 is characterized in that: transition metal nitrate is: ferric nitrate, cobalt nitrate or nickel nitrate.
8, preparation method according to claim 1, it is characterized in that: the charing that the solvent insoluble matter carbon-coated nano metal crystalline substance obtain carries out in the not melt processed and inert atmosphere is handled in extraction handle in air atmosphere, obtain coating the carbon-coated nano metal crystalline substance that the orderly degree of alignment of carbon-coating improves.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN100434210C (en) * | 2005-01-17 | 2008-11-19 | 武汉科技大学 | Carbon-clad metal nano particle and its preparing method |
| CN100455383C (en) * | 2006-11-03 | 2009-01-28 | 大连理工大学 | Method for preparing carbon-coated metal nano material whose particle diameter is controllable |
| CN101176915B (en) * | 2006-11-09 | 2010-05-26 | 南京大学 | Method for preparing nano metallic nickel granular material coating with carbon |
| CN102208616A (en) * | 2011-05-09 | 2011-10-05 | 北京化工大学 | Preparation method of carbon-coated transition metal nano hollow particle |
| CN106001549B (en) * | 2016-05-11 | 2018-02-06 | 江油核宝纳米材料有限公司 | The preparation method of carbonyl process nickel bag graphite |
| CN107520464A (en) * | 2017-09-01 | 2017-12-29 | 江苏科技大学 | A kind of method for preparing iron nano-particle/major diameter carbon nano tube compound material |
| CN108480623B (en) * | 2018-04-25 | 2020-12-15 | 北京化工大学 | Macroscopic preparation method of carbon-coated metal nanoparticles |
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