CN105217635A - A kind of preparation method of large size silicon-carbide nano wire - Google Patents
A kind of preparation method of large size silicon-carbide nano wire Download PDFInfo
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Abstract
The present invention relates to a kind of preparation method of silicon carbide nanometer line; In particular to a kind of batch preparation of overlength large size silicon-carbide nano wire.The present invention with molecular weight be 1000 ~ 1300, viscosity is that the metal-modified polymethyl silicane of 0.04 ~ 0.7PaS is for raw material; after metal-modified polymethyl silicane is immersed in substrate, take out, under protective atmosphere; carry out heat preservation sintering in 1200 DEG C ~ 1300 DEG C, obtain large size silicon-carbide nano wire.Preparation technology of the present invention is simple, efficient, can be applicable to large-scale industrialization application and produce.
Description
Technical field
The present invention relates to a kind of preparation method of silicon carbide nanometer line; In particular to a kind of batch preparation of overlength large size silicon-carbide nano wire.
Background technology
Nano wire refers to that a kind of radial upper size is lower than 100nm, far above the single crystal fibre of radial dimension on length direction, become current research emphasis with the physical and chemical performance of its little diameter, large length-to-diameter ratio, high anisotropic properties, unique geometry and excellence.In fields such as fundamental research and nano electron device, nanocomposite optical device, nano composite material, energy and material, biological medicines, there is important application prospect.
And as the silicon carbide nanometer line of semiconductor material, because it also has the extensive concern that the high temperature of bulk material excellence, chemical stability and mechanical property cause people.Lieber study group of Harvard University utilizes the SiC nanowire of atomic force microscope to preparation to carry out mechanics performance determining, find that the Young's modulus of single SiC nanowire is 610-660GPa, the maximum deflection intensity of SiC nanowire is 53.4GPa, is 10 times of carbon fiber.
Overlong nanowire refers to that length reaches grade or the even longer nano wire of centimetre-sized, when the length of nano wire reaches grand lighting level, greatly can simplify the preparation technology of SiC nanowire electron device, set up the bridge of Macrocosm and microcosm simultaneously, the application of nano wire is become a reality.
The method preparing now nano wire is numerous, but all there is following deficiency: 1) output of silicon carbide nanometer line growth is very low, the product below being substantially all gram; 2) purity of silicon carbide nanometer line is very low, except containing except silicon carbide, also has silicon-dioxide, carbon, various additives etc.; 3) length of silicon carbide nanometer line is short, is nearly all micron order, and only CAi study group obtains some millimetre-sized silicon carbide nanometer lines.This makes the application of silicon carbide nanometer line be limited by very large.
Summary of the invention
The deficiency that output is few, unstable, purity is low, length is short that the method that the present invention is directed to existing manufacture silicon carbide nanometer line exists, provides a kind of batch preparation of large size silicon-carbide nano wire.
The preparation method of a kind of large size silicon-carbide nano wire of the present invention; Comprise the steps:
With metal-modified polymethyl silicane for raw material, after metal-modified polymethyl silicane is immersed in substrate, take out, sinter under protective atmosphere, obtain large size silicon-carbide nano wire;
Described metal-modified polymethyl silicane molecular weight is 1000 ~ 1300, and viscosity is 0.04 ~ 0.07PaS, and the mol ratio of metallic element and Si is 0.5 ~ 1:100;
The carbonaceous substrate of described substrate to be porosity be 55-87%; Be preferably the carbonaceous substrate that porosity is 68-87%;
When sintering under protective atmosphere, the flow of Control protection gas is 8 ~ 10ml/min;
When sintering under protective atmosphere, carry out being warming up to 1200 DEG C ~ 1300 DEG C with the temperature rise rate of 5 ~ 10 DEG C/min and carry out heat preservation sintering at least 1h.
The preparation method of a kind of large size silicon-carbide nano wire of the present invention; In described metal-modified polymethyl silicane, involved metal is selected from least one in transition metal, at least one more preferably in iron, copper, zirconium, nickel, molybdenum.
The preparation method of a kind of large size silicon-carbide nano wire of the present invention; Described metal-modified polymethyl silicane is prepared by following method:
Step one
Aluminium powder is added in sodium sand, under protective atmosphere, stir, obtain sodium sand for subsequent use;
Step 2
By the mol ratio of Na and Si, Na:Si=2.5 ~ 1:2 ~ 1 is joined and is got sodium sand for subsequent use and monomer; Under protective atmosphere, first sodium sand is loaded in reactor, then add organic solvent; Stir, after being warming up to 70-85 DEG C, dividing and instill in reactor by joining the monomer got at least 2 times, stir, carry out back flow reaction; Obtain reacting rear liquid; Described monomer is dichloro methyl silane;
Step 3
Under protective atmosphere, carry out centrifugal treating to liquid after the reaction of step 2 gained, centrifugal gained liquid through distillation process, obtains polymethyl silicane under protective atmosphere;
Step 4
In mass ratio; Polymethyl silicane: linking agent=100:2 ~ 8, joins after getting polymethyl silicane, linking agent and is dissolved in organic solvent, under protective atmosphere, is warming up to 120 ~ 150 DEG C after 40 ~ 50 DEG C of stirring reactions, continues stirring reaction, obtains containing metal polymethyl silicane; Described linking agent is acetyl acetone salt; Described acetyl acetone salt is selected from least one in acetylacetone copper, methyl ethyl diketone zirconium, ferric acetyl acetonade, acetylacetonate nickel, two (methyl ethyl diketone) molybdenum oxide.
The preparation method of a kind of large size silicon-carbide nano wire of the present invention; In step one, in described sodium sand for subsequent use, the mass ratio of Al and Na is 1:12 ~ 1:15.
The preparation method of a kind of large size silicon-carbide nano wire of the present invention; In step one, the granularity of described aluminium powder is 30-50um, and the granularity of sodium sand is 0.5-10um;
The preparation method of a kind of large size silicon-carbide nano wire of the present invention; In step one, aluminium powder is added in sodium sand, under protective atmosphere, stir under normal temperature, obtain sodium sand for subsequent use; The speed stirred is 100-130 rev/min.
The preparation method of a kind of large size silicon-carbide nano wire of the present invention; In step one, described sodium sand is prepared by following proposal:
Being immersed in by sodium block is equipped with in the reactor of toluene, in protective atmosphere, sodium block is heated to 97-98 DEG C, stirs, until be cooled to room temperature after the complete fragmentation of sodium block; Obtain the sodium sand that granularity is 0.5 ~ 10um.
The preparation method of a kind of large size silicon-carbide nano wire of the present invention; In step one, organic solvent described in step 2 is selected from the one in toluene, dimethylbenzene, benzene, tetrahydrofuran (THF), methyl-sulphoxide.Described organic solvent is preferably toluene.
The preparation method of a kind of large size silicon-carbide nano wire of the present invention; In step 2, organic solvent with join the volume getting monomer ratio be 6:1 ~ 8:1.
The preparation method of a kind of large size silicon-carbide nano wire of the present invention; In step 2, join the monomer got and divide and add for 3-6 time in reactor, add at every turn and adopt the mode dripped to add, the speed of dropping is 20-30mL/min; After being added dropwise to complete, after stirring 120 ~ 180min, carry out dropping next time more at every turn;
The preparation method of a kind of large size silicon-carbide nano wire of the present invention; In step 2, when carrying out back flow reaction, condensing agent used is silicone oil with low viscosity; Described silicon oil viscosity is 10cps-15cps; The speed of described stirring is 100-130 rev/min.
The molecular weight of step 3 gained polymethyl silicane of the present invention is 800 ~ 900, and viscosity is 0.02 ~ 0.03PaS.Described polymethyl silicane has active si-h bond.
In order to the quality of further improving product, promote that reaction can thoroughly be carried out, in reaction process, continue to pass into shielding gas, by the flowing of shielding gas, both protected product, impel again reaction to carry out, until react completely toward the direction generating product.In step 4 of the present invention, in mass ratio; Polymethyl silicane: linking agent=100:2 ~ 8; joining after getting polymethyl silicane, linking agent is dissolved in organic solvent; continue to pass into shielding gas; 120 ~ 150 DEG C are warming up to behind 40 ~ 50 DEG C of stirring reaction 3-6 hours, preferably 4-5 hour; continue stirring reaction, the reactant gases that shielding gas is taken out of leads in aqueous sodium hydroxide solution, when aqueous sodium hydroxide solution pH value used does not change; stopped reaction, gained liquid is product.
In step 4 of the present invention, the volume ratio of organic solvent and polymethyl silicane is 5:1-1:1.Be preferably 2.5:1 ~ 0.8:1, more preferably 1.25:1 ~ 0.6:1.It is too many that organic solvent uses, then unfavorablely reduce costs, and uses and reaction will be caused very little thoroughly to complete.
In step 4 of the present invention, described organic solvent is selected from least one in toluene, dimethylbenzene, benzene, tetrahydrofuran (THF), methyl-sulphoxide.Be preferably toluene.
In step 4 of the present invention, described protective atmosphere is preferably nitrogen atmosphere.
In step 4 of the present invention, during stirring, controlling rotating speed is that 400-600 turns/min, and rotating speed is too low, then can not get the product of suitable molecular weight.Rotating speed is too high, then crosslinked, branched degree is excessive, and product is very glutinous, is unfavorable for the dipping in later stage.
The present invention plants the preparation method of large size silicon-carbide nano wire; Described substrate is carbon fiber felt or 2.5D carbon fabric perform.
The preparation method of a kind of large size silicon-carbide nano wire of the present invention; Using carbon fiber felt or 2.5D carbon fabric perform after growth substrate, be positioned in vacuum impregnation tank, vacuumize, sucked by metal-modified polymethyl silicane in impregnating autoclave, the temperature controlling metal modified polymethyl silicane is 60-120 DEG C, after vacuum impregnation 1-3 hour, to be layered in graphite frock and to move in pit furnace, after being first evacuated to below 2000Pa, passing into rare gas element, and the flow controlling rare gas element is 8-10ml/min; Then be warming up to 1200 DEG C-1300 DEG C with the temperature rise rate of 5-10 DEG C/min, and cool to room temperature with the furnace after being incubated 1-6h, obtain silicon carbide nanometer line; Described growth substrate is of a size of long 550mm × wide 550mm × high 15mm, the diameter of described pit furnace is 1.2m, is highly 1.6m; Under these conditions, the output of a stove can reach 100g level.
The preparation method of a kind of large size silicon-carbide nano wire of the present invention; The length of described large size silicon-carbide nano wire is 0.1-2 centimetre, preferably 0.5-2.5 centimetre, more preferably 1-3 centimetre, and diameter is 500-100nm, is preferably 150-100nm, more preferably 100-65nm.
Principle and advantage
1) nano wire that mode described in this patent grows belongs to the mode of large-scale production nano wire, and output is each, and every stove reaches 100g level.
2) mode that this patent adopts is presoma cracking process growing silicon carbide nano wire,, there is other impurity hardly in the very high purity of gained silicon carbide nanometer line.
3) in the presoma polymethyl silicane that this patent adopts, owing to have employed special sodium sand, while realization prepares polymethyl silicane on a large scale, also improve the activity of polymethyl silicane, as contained a large amount of active very high Si-H, Si-H, this is conducive to the activity keeping SiC crystal aufwuchsplate, make the growth that SiC nanowire can continue on the direction of one dimension, thus reach longer length.
3) this patent presoma used is metal-modified poly-silicomethane, and wherein the content of metal catalyst is 0.5% ~ 1%, and metal is scattered in presoma in an atomic fashion uniformly, the self-catalysis that metal produces.Catalytic effect is obviously better than additionally adding catalyzer.
4) this patent adopts porous insert to adsorb presoma as substrate, and slow releasing in process of growth, also contributes to the accumulation of nano wire at length direction, and final formed nano wire all reaches several centimetres, is the nano wire of macro-level.
5) nano wire that grows of mode described in this patent, has stabilizability, repeatable high.
Accompanying drawing illustrates:
Accompanying drawing 1 is that embodiment 1 has been prepared rear gained and is covered with the furnace wall of silicon carbide nanometer line and the photo of substrate;
Accompanying drawing 2 is the Local map that embodiment 1 has prepared rear growing silicon carbide nano wire furnace wall;
Accompanying drawing 3 is the macro morphology of embodiment 1 gained one section of silicon carbide nanometer line;
Accompanying drawing 4 is the scanning electron microscope (SEM) photograph (× 1000) of embodiment 1 silicon carbide nanometer line;
Accompanying drawing 5 is the scanning electron microscope (SEM) photograph (× 10000) of embodiment 1 silicon carbide nanometer line.
Can find out that the technique designed by the present invention can realize industrial applications completely from Fig. 1,2,3, the output of its single stove, single can be 100g level even more than.
The length of silicon carbide nanometer line all reaches about 3cm as can be seen from Figure 4, and does not substantially have small-sized silicon carbide nano wire.
Nanometer silicon carbide linear diameter is below 100nm as can be seen from Figure 5, and silicon carbide nanometer line is comparatively even, does not substantially have other impurity nodes.
Embodiment:
In the embodiment of the present invention, aluminium powder is added in sodium sand, under protective atmosphere, stir under normal temperature, obtain sodium sand for subsequent use; The speed stirred is 100 ~ 130 revs/min.
Described in the embodiment of the present invention, sodium sand is prepared by following proposal:
Being immersed in by sodium block is equipped with in the reactor of toluene, in nitrogen atmosphere, sodium block is heated to 97-98 DEG C, stirs, until be cooled to room temperature after the complete fragmentation of sodium block; Obtain the sodium sand that granularity is 0.5 ~ 10um.
In embodiment, substrate used is the matrix of carbon fiber felt, and it is of a size of long 550mm × wide 550mm × high 15mm.Porosity is 68-87%.
Embodiment 1
In the present embodiment, metal-modified polymethyl silicane is prepared by following method:
Step one
Aluminium powder is added in sodium sand, under nitrogen atmosphere, stir, obtain sodium sand for subsequent use; , in described sodium sand for subsequent use, the mass ratio of Al and Na is 1:12; The granularity of described aluminium powder is 50um, and the granularity of sodium sand is 10um;
Step 2
By the mol ratio of Na and Si, Na:Si=2.5:1 joins and gets sodium sand for subsequent use and monomer (30kg); In a nitrogen atmosphere, first sodium sand is loaded in reactor, then add organic solvent toluene (organic solvent with join the volume getting monomer ratio be 6:1); Stir, after being warming up to 80 DEG C, divide and instill joining the monomer got in reactor for 3 times, add at every turn and adopt the mode dripped to add, the speed of dropping is 20mL/min; After being added dropwise to complete at every turn, carrying out dropping next time after stirring 120min again, carry out back flow reaction; Obtain reacting rear liquid; Described monomer is dichloro methyl silane; When carrying out back flow reaction, condensing agent used is silicone oil with low viscosity; Described silicon oil viscosity is 10cps-15cps; The speed of described stirring is 100-130 rev/min
Step 3
In a nitrogen atmosphere, carry out centrifugal treating to liquid after the reaction of step 2 gained, centrifugal gained liquid through distillation process, obtains polymethyl silicane under protective atmosphere; The molecular-weight average of gained polymethyl silicane is 800, and viscosity is 0.02PaS.
Step 4
In mass ratio; Polymethyl silicane: linking agent=100:2, join after getting polymethyl silicane, linking agent and be dissolved in (volume ratio of toluene and polymethyl silicane is 5:1) in organic solvent toluene, in a nitrogen atmosphere, 150 DEG C are warming up to after 40 DEG C of stirring reactions, continue stirring reaction, obtain containing metal polymethyl silicane; Described linking agent is two (methyl ethyl diketone) molybdenum oxide.Controlling stirring velocity during stirring is 400 turns/min.The molecular-weight average of the metal-modified poly-methylhydrosiloxane of gained is 1200, and viscosity is 0.06PaS;
After obtaining metal-modified polymethyl silicane, by substrate, be positioned in vacuum impregnation tank, vacuumize, sucked in impregnating autoclave by metal-modified polymethyl silicane, vacuum impregnation is after 3 hours, to be layered in graphite frock and to move in pit furnace, after being first evacuated to below 2000Pa, passing into rare gas element, and the flow controlling rare gas element is 10ml/min; Then be warming up to 1300 DEG C with the temperature rise rate of 10 DEG C/min, and cool to room temperature with the furnace after being incubated 6h, obtain silicon carbide nanometer line; The diameter of described pit furnace is 1.2m, is highly 1.6m; Under these conditions, the output of a stove is 127.8g.As can be seen from embodiment 1, the technology designed by the present invention can produce silicon carbide nanometer line by low cost rapid scale.Effectively solve prior art and cannot produce the difficult problem of silicon carbide nanometer line by low cost rapid scale.
Embodiment 2
In the present embodiment, metal-modified polymethyl silicane is prepared by following method:
Step one
Aluminium powder is added in sodium sand, under nitrogen atmosphere, stir, obtain sodium sand for subsequent use; , in described sodium sand for subsequent use, the mass ratio of Al and Na is 1:15; The granularity of described aluminium powder is 40um, and the granularity of sodium sand is 3um;
Step 2
By the mol ratio of Na and Si, Na:Si=2:1 joins and gets sodium sand for subsequent use and monomer (32kg); In a nitrogen atmosphere, first sodium sand is loaded in reactor, then add organic solvent toluene (organic solvent with join the volume getting monomer ratio be 8:1; Stir, after being warming up to 80 DEG C, divide and instill joining the monomer got in reactor for 4 times, add at every turn and adopt the mode dripped to add, the speed of dropping is 25mL/min; After being added dropwise to complete at every turn, carrying out dropping next time after stirring 150min again, carry out back flow reaction; Obtain reacting rear liquid; Described monomer is dichloro methyl silane; When carrying out back flow reaction, condensing agent used is silicone oil with low viscosity; Described silicon oil viscosity is 10cps-15cps; The speed of described stirring is 100-130 rev/min;
Step 3
In a nitrogen atmosphere, carry out centrifugal treating to liquid after the reaction of step 2 gained, centrifugal gained liquid through distillation process, obtains polymethyl silicane under protective atmosphere; The molecular-weight average of gained polymethyl silicane is 830, and viscosity is 0.022PaS.
Step 4
In mass ratio; Polymethyl silicane: linking agent=100:4, join after getting polymethyl silicane, linking agent and be dissolved in (volume ratio of toluene and polymethyl silicane is 5:1) in organic solvent toluene, in a nitrogen atmosphere, 120 DEG C are warming up to after 45 DEG C of stirring reactions, continue stirring reaction, obtain containing metal polymethyl silicane; Described linking agent is methyl ethyl diketone zirconium.Controlling stirring velocity during stirring is 500 turns/min.The molecular-weight average of the metal-modified polymethyl silicane of gained is 1000, and viscosity is 0.04PaS;
After obtaining metal-modified polymethyl silicane, by substrate, be positioned in vacuum impregnation tank, vacuumize, sucked in impregnating autoclave by metal-modified polymethyl silicane, vacuum impregnation is after 2.5 hours, to be layered in graphite frock and to move in pit furnace, after being first evacuated to below 2000Pa, passing into rare gas element, and the flow controlling rare gas element is 8ml/min; Then be warming up to 1300 DEG C with the temperature rise rate of 5 DEG C/min, and cool to room temperature with the furnace after being incubated 1h, obtain silicon carbide nanometer line; The diameter of described pit furnace is 1.2m, is highly 1.6m; Under these conditions, the output of a stove is 115g.
Embodiment 3
In the present embodiment, metal-modified polymethyl silicane is prepared by following method:
Step one
Aluminium powder is added in sodium sand, under nitrogen atmosphere, stir, obtain sodium sand for subsequent use; , in described sodium sand for subsequent use, the mass ratio of Al and Na is 1:13; The granularity of described aluminium powder is the granularity of 30um sodium sand is 0.5um;
Step 2
By the mol ratio of Na and Si, Na:Si=2:1 joins and gets sodium sand for subsequent use and monomer (32kg); In a nitrogen atmosphere, first sodium sand is loaded in reactor, then add organic solvent toluene (organic solvent with join the volume getting monomer ratio be 7:1); Stir, after being warming up to 78 DEG C, divide and instill joining the monomer got in reactor for 5 times, add at every turn and adopt the mode dripped to add, the speed of dropping is 30mL/min; After being added dropwise to complete at every turn, carrying out dropping next time after stirring 180min again, carry out back flow reaction; Obtain reacting rear liquid; Described monomer is dichloro methyl silane; When carrying out back flow reaction, condensing agent used is silicone oil with low viscosity; Described silicon oil viscosity is 10cps-15cps; The speed of described stirring is 100-130 rev/min;
Step 3
In a nitrogen atmosphere, carry out centrifugal treating to liquid after the reaction of step 2 gained, centrifugal gained liquid through distillation process, obtains polymethyl silicane under protective atmosphere; The molecular-weight average of gained polymethyl silicane is 900, and viscosity is 0.03PaS.
Step 4
In mass ratio; Polymethyl silicane: linking agent=100:3.3, join after getting polymethyl silicane, linking agent and be dissolved in (volume ratio of toluene and polymethyl silicane is 2.5:1) in organic solvent toluene, in a nitrogen atmosphere, 130 DEG C are warming up to after 50 DEG C of stirring reactions, continue stirring reaction, obtain containing metal polymethyl silicane; Described linking agent is ferric acetyl acetonade.Controlling stirring velocity during stirring is 600 turns/min.The molecular-weight average of the metal-modified polymethyl silicane of gained is 1250, and viscosity is 0.064PaS;
After obtaining metal-modified polymethyl silicane, by substrate, be positioned in vacuum impregnation tank, vacuumize, sucked in impregnating autoclave by metal-modified polymethyl silicane, vacuum impregnation is after 3 hours, to be layered in graphite frock and to move in pit furnace, after being first evacuated to below 2000Pa, passing into rare gas element, and the flow controlling rare gas element is 10ml/min; Then be warming up to 1200 DEG C with the temperature rise rate of 5 DEG C/min, and cool to room temperature with the furnace after being incubated 2h, obtain silicon carbide nanometer line; The diameter of described pit furnace is 1.2m, is highly 1.6m; Under these conditions, the output of a stove is 183g.
Embodiment 4
In the present embodiment, metal-modified polymethyl silicane is prepared by following method:
Step one
Aluminium powder is added in sodium sand, under nitrogen atmosphere, stir, obtain sodium sand for subsequent use; , in described sodium sand for subsequent use, the mass ratio of Al and Na is 1:13; The granularity of described aluminium powder is the granularity of 30um sodium sand is 0.5um;
Step 2
By the mol ratio of Na and Si, Na:Si=1.5:1 joins and gets sodium sand for subsequent use and monomer (36kg); In a nitrogen atmosphere, first sodium sand is loaded in reactor, then add organic solvent toluene (organic solvent with join the volume getting monomer ratio be 7:1); Stir, after being warming up to 78 DEG C, divide and instill joining the monomer got in reactor for 5 times, add at every turn and adopt the mode dripped to add, the speed of dropping is 30mL/min; After being added dropwise to complete at every turn, carrying out dropping next time after stirring 180min again, carry out back flow reaction; Obtain reacting rear liquid; Described monomer is dichloro methyl silane; When carrying out back flow reaction, condensing agent used is silicone oil with low viscosity; Described silicon oil viscosity is 10cps-15cps; The speed of described stirring is 100-130 rev/min;
Step 3
In a nitrogen atmosphere, carry out centrifugal treating to liquid after the reaction of step 2 gained, centrifugal gained liquid through distillation process, obtains polymethyl silicane under protective atmosphere; The molecular-weight average of gained polymethyl silicane is 880, and viscosity is 0.028PaS.
Step 4
In mass ratio; Polymethyl silicane: linking agent=100:4, join after getting polymethyl silicane, linking agent and be dissolved in (volume ratio of toluene and polymethyl silicane is 2.5:1) in organic solvent toluene, in a nitrogen atmosphere, 130 DEG C are warming up to after 50 DEG C of stirring reactions, continue stirring reaction, obtain containing metal polymethyl silicane; Described linking agent is acetylacetone copper.Controlling stirring velocity during stirring is 600 turns/min.The molecular-weight average of the metal-modified polymethyl silicane of gained is 1050, and viscosity is 0.043PaS;
After obtaining metal-modified polymethyl silicane, by substrate, be positioned in vacuum impregnation tank, vacuumize, sucked in impregnating autoclave by metal-modified polymethyl silicane, vacuum impregnation is after 3 hours, to be layered in graphite frock and to move in pit furnace, after being first evacuated to below 2000Pa, passing into rare gas element, and the flow controlling rare gas element is 10ml/min; Then be warming up to 1250 DEG C with the temperature rise rate of 5 DEG C/min, and cool to room temperature with the furnace after being incubated 2h, obtain silicon carbide nanometer line; The diameter of described pit furnace is 1.2m, is highly 1.6m; Under these conditions, the output of a stove is 187g.
Embodiment 5
In the present embodiment, metal-modified polymethyl silicane is prepared by following method:
Step one
Aluminium powder is added in sodium sand, under nitrogen atmosphere, stir, obtain sodium sand for subsequent use; , in described sodium sand for subsequent use, the mass ratio of Al and Na is 1:13; The granularity of described aluminium powder is the granularity of 30um sodium sand is 1um;
Step 2
By the mol ratio of Na and Si, Na:Si=1:1 joins and gets sodium sand for subsequent use and monomer (34kg); In a nitrogen atmosphere, first sodium sand is loaded in reactor, then add organic solvent toluene (organic solvent with join the volume getting monomer ratio be 7:1); Stir, after being warming up to 78 DEG C, divide and instill joining the monomer got in reactor for 5 times, add at every turn and adopt the mode dripped to add, the speed of dropping is 30mL/min; After being added dropwise to complete at every turn, carrying out dropping next time after stirring 180min again, carry out back flow reaction; Obtain reacting rear liquid; Described monomer is dichloro methyl silane; When carrying out back flow reaction, condensing agent used is silicone oil with low viscosity; Described silicon oil viscosity is 10cps-15cps; The speed of described stirring is 100-130 rev/min;
Step 3
In a nitrogen atmosphere, carry out centrifugal treating to liquid after the reaction of step 2 gained, centrifugal gained liquid through distillation process, obtains polymethyl silicane under protective atmosphere; The molecular-weight average of gained polymethyl silicane is 850, and viscosity is 0.024PaS.
Step 4
In mass ratio; Polymethyl silicane: linking agent=100:4.4, join after getting polymethyl silicane, linking agent and be dissolved in (volume ratio of toluene and polymethyl silicane is 2.5:1) in organic solvent toluene, in a nitrogen atmosphere, 130 DEG C are warming up to after 50 DEG C of stirring reactions, continue stirring reaction, obtain containing metal polymethyl silicane; Described linking agent is acetylacetonate nickel.Controlling stirring velocity during stirring is 600 turns/min.The molecular-weight average of the metal-modified polymethyl silicane of gained is 1300, and viscosity is 0.07PaS;
After obtaining metal-modified polymethyl silicane, by substrate, be positioned in vacuum impregnation tank, vacuumize, sucked in impregnating autoclave by metal-modified polymethyl silicane, vacuum impregnation is after 3 hours, to be layered in graphite frock and to move in pit furnace, after being first evacuated to below 2000Pa, passing into rare gas element, and the flow controlling rare gas element is 10ml/min; Then be warming up to 1280 DEG C with the temperature rise rate of 5 DEG C/min, and cool to room temperature with the furnace after being incubated 2h, obtain silicon carbide nanometer line; The diameter of described pit furnace is 1.2m, is highly 1.6m; Under these conditions, the output of a stove is 131g.
Comparative example 1
In the present embodiment, metal-modified polymethyl silicane is prepared by following method:
Step one
Aluminium powder is added in sodium sand, under nitrogen atmosphere, stir, obtain sodium sand for subsequent use; , in described sodium sand for subsequent use, the mass ratio of Al and Na is 1:13; The granularity of described aluminium powder is the granularity of 30um sodium sand is 1.5um;
Step 2
By the mol ratio of Na and Si, Na:Si=1:1 joins and gets sodium sand for subsequent use and monomer (34kg); In a nitrogen atmosphere, first sodium sand is loaded in reactor, then add organic solvent toluene (organic solvent with join the volume getting monomer ratio be 7:1); Stir, after being warming up to 78 DEG C, divide and instill joining the monomer got in reactor for 5 times, add at every turn and adopt the mode dripped to add, the speed of dropping is 25mL/min; After being added dropwise to complete at every turn, carrying out dropping next time after stirring 180min again, carry out back flow reaction; Obtain reacting rear liquid; Described monomer is dichloro methyl silane; When carrying out back flow reaction, condensing agent used is silicone oil with low viscosity; Described silicon oil viscosity is 10cps-15cps; The speed of described stirring is 100-130 rev/min;
Step 3
In a nitrogen atmosphere, carry out centrifugal treating to liquid after the reaction of step 2 gained, centrifugal gained liquid through distillation process, obtains polymethyl silicane under protective atmosphere; The molecular-weight average of gained polymethyl silicane is 800, and viscosity is 0.02PaS.
Step 4
In mass ratio; Polymethyl silicane: linking agent=100:8, join after getting polymethyl silicane, linking agent and be dissolved in (volume ratio of toluene and polymethyl silicane is 2.5:1) in organic solvent toluene, in a nitrogen atmosphere, 130 DEG C are warming up to after 50 DEG C of stirring reactions, continue stirring reaction, obtain containing metal polymethyl silicane; Described linking agent is aluminium acetylacetonate.Controlling stirring velocity during stirring is 600 turns/min.The molecular-weight average of the metal-modified polymethyl silicane of gained is 1300, and viscosity is 0.07PaS;
After obtaining metal-modified polymethyl silicane, by substrate, be positioned in vacuum impregnation tank, vacuumize, sucked in impregnating autoclave by metal-modified polymethyl silicane, vacuum impregnation is after 3 hours, to be layered in graphite frock and to move in pit furnace, after being first evacuated to below 2000Pa, passing into rare gas element, and the flow controlling rare gas element is 10ml/min; Then be warming up to 1250 DEG C with the temperature rise rate of 5 DEG C/min, and cool to room temperature with the furnace after being incubated 2h, obtain silicon carbide nanometer line; The diameter of described pit furnace is 1.2m, is highly 1.6m; Under these conditions, the output of a stove is 2.7g.
Comparative example 2
In this comparative example, metal-modified polymethyl silicane is prepared by following method:
The synthetic method of polymethyl silicane is the prepared by sodium condensation method in prior art;
The molecular-weight average of gained polymethyl silicane is 400, and viscosity is 0.01PaS.
This step is prepared according to embodiment in patent CN101186704 7 (6-7 page) described method;
Entering in the 10L there-necked flask of pipe with agitator, prolong, nitrogen, add polymethyl silicane 3000g, trifluoromethyl siloxanes 30g, stirs under nitrogen protection, then adds AlCl
3600g, control larger nitrogen flow 1000 ~ 5000ml/min, after rapid stirring 1-2 hour, speed is down to 300-400 and turns left the right side, controlling temperature of reaction is 30 ~ 120 DEG C, abundant reaction about 15-24 hour, the HCl that reaction produces is by airway, until the gas that airway produces no longer makes pH test paper redden, i.e. and stopped reaction, filter through decompression, obtain aluminium modified polymethyl silicane.The molecular-weight average of the polymethyl silicane of aluminium modification is 680, and viscosity is 0.2PaS.
After obtaining the polymethyl silicane of aluminium modification, by substrate, be positioned in vacuum impregnation tank, vacuumize, sucked in impregnating autoclave by metal-modified polymethyl silicane, vacuum impregnation is after 3 hours, to be layered in graphite frock and to move in pit furnace, after being first evacuated to below 2000Pa, passing into rare gas element, and the flow controlling rare gas element is 10ml/min; Then be warming up to 1250 DEG C with the temperature rise rate of 5 DEG C/min, and cool to room temperature with the furnace after being incubated 2h, obtain silicon carbide nanometer line; The diameter of described pit furnace is 1.2m, is highly 1.6m; Under these conditions, the output of a stove is 1.79g.
By embodiment 1-5, comparative example 1 can be found out, only has transition metal modified polymethyl silicane, just has self-catalysis, prepares large size silicon-carbide nano wire; The viscosity of the metal modified polymethyl silicane prepared by this patent is low, is conducive to the homogeneous impregnation of later stage substrate and the grown on larger scale of large size silicon-carbide nano wire.
Claims (10)
1. the preparation method of a large size silicon-carbide nano wire; It is characterized in that: with metal-modified polymethyl silicane for raw material, after metal-modified polymethyl silicane is immersed in substrate, take out, sinter under protective atmosphere, obtain large size silicon-carbide nano wire;
Described metal-modified polymethyl silicane molecular weight is 1000 ~ 1300, and viscosity is 0.04 ~ 0.07PaS, and the mol ratio of metallic element and Si is 0.5 ~ 1:100;
The carbonaceous substrate of described substrate to be porosity be 55-87%;
When sintering under protective atmosphere, the flow of Control protection gas is 8 ~ 10ml/min;
When sintering under protective atmosphere, carry out being warming up to 1200 DEG C ~ 1300 DEG C with the temperature rise rate of 5 ~ 10 DEG C/min and carry out heat preservation sintering at least 1h.
2. the preparation method of a kind of large size silicon-carbide nano wire according to claim 1; It is characterized in that: at least one in metallic element chosen from Fe involved in described metal-modified polymethyl silicane, copper, zirconium, nickel, molybdenum.
3. the preparation method of a kind of large size silicon-carbide nano wire according to claim 1; It is characterized in that: described metal-modified polymethyl silicane is prepared by following method:
Step one
Aluminium powder is added in sodium sand, under protective atmosphere, stir, obtain sodium sand for subsequent use;
Step 2
By the mol ratio of Na and Si, Na:Si=2.5 ~ 1:2 ~ 1 is joined and is got sodium sand for subsequent use and monomer; Under protective atmosphere, first sodium sand is loaded in reactor, then add organic solvent; Stir, after being warming up to 70-85 DEG C, dividing and instill in reactor by joining the monomer got at least 2 times, stir, carry out back flow reaction; Obtain reacting rear liquid; Described monomer is dichloro methyl silane;
Step 3
Under protective atmosphere, carry out centrifugal treating to liquid after the reaction of step 2 gained, centrifugal gained liquid through distillation process, obtains polymethyl silicane under protective atmosphere;
Step 4
In mass ratio; Polymethyl silicane: linking agent=100:2 ~ 8, joins after getting polymethyl silicane, linking agent and is dissolved in organic solvent, under protective atmosphere, is warming up to 120 ~ 150 DEG C after 40 ~ 50 DEG C of stirring reactions, continues stirring reaction, obtains containing metal polymethyl silicane; Described linking agent is acetyl acetone salt; Described acetyl acetone salt is selected from least one in acetylacetone copper, methyl ethyl diketone zirconium, ferric acetyl acetonade, acetylacetonate nickel, two (methyl ethyl diketone) molybdenum oxide.
4. the preparation method of a kind of large size silicon-carbide nano wire according to claim 1; It is characterized in that: in step one,
The granularity of described aluminium powder is 30-50um, and the granularity of sodium sand is 0.5-10um;
In described sodium sand for subsequent use, the mass ratio of Al and Na is 1:12 ~ 1:15.
5. the preparation method of a kind of large size silicon-carbide nano wire according to claim 1; It is characterized in that:
In step one, organic solvent described in step 2 is selected from the one in toluene, dimethylbenzene, benzene, tetrahydrofuran (THF), methyl-sulphoxide;
In step 2, organic solvent with join the volume getting monomer ratio be 6:1 ~ 8:1;
In step 2, join the monomer got and divide and add for 3-6 time in reactor, add at every turn and adopt the mode dripped to add, the speed of dropping is 20-30mL/min; After being added dropwise to complete, after stirring 120 ~ 180min, carry out dropping next time more at every turn;
In step 2, when carrying out back flow reaction, condensing agent used is silicone oil with low viscosity; Described silicon oil viscosity is 10cps-15cps; The speed of described stirring is 100-130 rev/min.
6. the preparation method of a kind of large size silicon-carbide nano wire according to claim 1; It is characterized in that: the molecular weight of step 3 gained polymethyl silicane is 800 ~ 900, and viscosity is 0.02 ~ 0.03PaS.
7. the preparation method of a kind of large size silicon-carbide nano wire according to claim 1; It is characterized in that:
In step 4, the volume ratio of organic solvent and polymethyl silicane is 5:1-1:1;
In step 4, during stirring, controlling rotating speed is that 400-600 turns/min.
8. the preparation method of a kind of large size silicon-carbide nano wire according to claim 1; It is characterized in that: described substrate is carbon fiber felt or 2.5D carbon fabric perform.
9. the preparation method of a kind of large size silicon-carbide nano wire according to claim 8; It is characterized in that: using carbon fiber felt or 2.5D carbon fabric perform after growth substrate, be positioned in vacuum impregnation tank, vacuumize, sucked by metal-modified polymethyl silicane in impregnating autoclave, the temperature controlling metal modified polymethyl silicane is 60-120 DEG C, after vacuum impregnation 1-3 hour, to be layered in graphite frock and to move in pit furnace, after being first evacuated to below 2000Pa, passing into rare gas element, and the flow controlling rare gas element is 8-10ml/min; Then be warming up to 1200 DEG C-1300 DEG C with the temperature rise rate of 5-10 DEG C/min, and cool to room temperature with the furnace after being incubated 1-6h, obtain silicon carbide nanometer line; Described growth substrate is of a size of long 550mm × wide 550mm × high 15mm, the diameter of described pit furnace is 1.2m, is highly 1.6m; Under these conditions, the output of a stove can reach 100g level.
10. the preparation method of a kind of large size silicon-carbide nano wire according to claim 1-9 any one; It is characterized in that: the length of described large size silicon-carbide nano wire is 1-3 centimetre, and diameter is 100-65nm.
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