CN109721366A - A kind of preparation method of porous silicon carbide ceramic - Google Patents
A kind of preparation method of porous silicon carbide ceramic Download PDFInfo
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- CN109721366A CN109721366A CN201910090356.1A CN201910090356A CN109721366A CN 109721366 A CN109721366 A CN 109721366A CN 201910090356 A CN201910090356 A CN 201910090356A CN 109721366 A CN109721366 A CN 109721366A
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Abstract
The invention discloses a kind of methods for preparing porous silicon carbide ceramic, the following steps are included: (1), by the mixture heating reaction of liquid Polycarbosilane, radical initiator and thermal expansivity pore creating material containing unsaturated group, obtained product is the Polycarbosilane with porous structure crosslinking curing；(2) in an inert atmosphere, step (1) products therefrom is gradually heated up sintering, generates porous silicon carbide ceramic.10~360min reaction is kept the temperature in the step (1) at 60~200 DEG C, the temperature being sintered in the step (2) is 800~1800 DEG C.Preparation method provided by the invention have the advantages that it is easy to operate, easily molded, environmental-friendly, can based on different application require performance of control；The porous silicon carbide ceramic of acquisition has the advantages that internal component is uniform, porosity is high, cell size distribution is uniform, ceramic product is close to silicon carbide stoichiometric ratio.
Description
Technical field
The present invention relates to silicon carbide ceramics fields, and in particular to a kind of preparation method of porous silicon carbide ceramic.
Background technique
Since there are a large amount of stomatas, porous silicon carbide ceramic not only has the high temperature resistant of carbofrax material, wear-resistant, low-heat
The coefficient of expansion and excellent chemical stability also have low-density, high-specific surface area and good shock resistance.Therefore, more
Hole silicon carbide ceramics are that one kind has both structural and functional ceramic material, in catalysis, purification filtering, heat-insulation and heat-preservation, aviation
The numerous areas such as space flight and derived energy chemical have important application value.
There are many method for preparing porous silicon carbide ceramic, according to different pore structure and formation mechenism, have granulation mass area method,
Add pore creating material method, template duplicating method and direct foaming etc..
Addition pore creating material method is that pore creating material is added in ceramic batch or precursor, is sintered and is removed pore creating material, original is made
Space occupied by the agent of hole has reformed into stomata.This method has the characteristics that simple process, morphology controllable, porosity are high.Pore-creating
Agent mainly has various ammonium salts, carbon particle, inorganic salts, high molecular polymer, natural fiber etc..Such as Wang is to make with spherical starch
Starch, carborundum powder and sintering aid and gelling agent are uniformly mixed and obtain slurry, after starch removes at 600 DEG C by hole agent
Original position leaves spherical pore structures, subsequent that porous silicon carbide ceramic, hole is made using solid-phase sintering (2050~2150 DEG C of temperature)
Gap rate is close to 50% [Wang F, Yin J, Yao D, et al.Fabrication of porous SiC ceramics
through a modified gelcasting and solid state sintering.Materials Science&
Engineering A,2015,654:292-297.].Bai etc. is with Fe2O3For pore creating material, burn with silicon carbide powder to 2250 DEG C,
Fe2O3Gas is generated with silicon carbide reactor and leaves pore structure, to obtain porous silicon carbide ceramic, works as Fe2O3Additive amount is
When 30wt%, porosity is reachable~80% [Bai J, Yang X, Shi Y, et al.Fabrication of directional
SiC porous ceramics using Fe2O3as pore-forming agent.Materials Letters,2012,
78:192-194.].Wang Shaofeng etc. is with silicon-carbide particle and c-ZrO2Powder is raw material, and polyvinyl butyral is pore creating material, is passed through
It is dry-pressing formed, then [Wang Shaofeng, Wang Changan, Sun Jialin are anti-in situ through the obtained porous silicon carbide ceramic of pressureless sintering in air atmosphere
The preparation silicate journal for the porous SiC ceramics for answering zircon to combine, 2011,39:502-506.].Wherein, polyvinyl alcohol contracts
Accumulation gap between the decomposition and silicon-carbide particle of butyraldehyde generates stomata.The SiO that silicon-carbide particle surface oxidation generates2With ZrO2
Reaction in-situ generates zircon, and silicon-carbide particle is bonding by zircon and glass.When sintering temperature is 1500 DEG C, porous carbon
The apparent porosity of SiClx ceramics is 50.3%, and compressive strength reaches 38.7MPa.
But it is above-mentioned based on powder sintering prepare porous silicon carbide exist be difficult to obtain uniform chemical component and part side
The problems such as method is low there are porosity.Precursor pyrolysis and hot pressing is that have to be pyrolyzed the polymer that can be converted into ceramics as raw material
Dissolvable and fusible property, and the ceramic temperature of conversion is low, ingredient is uniform.Wang etc. is fine with carbon fiber, carbon nanotube, nylon
Mixture of dimension, glass fibre, silica dioxide granule and glass fibre and silica dioxide granule etc. is template, and dipping solid-state is poly-
Carbon silane contents are the tetrahydrofuran solution of 25wt%, realize poly- carbon then in turn through evaporation of solvent, 160 DEG C of heat preservation 3h
Silane-cure, 1250 DEG C of sintering 0.5h and remove template obtain porous silicon carbide [Hao Wang, Inkyung Sung,
Xiaodong Li,DongPyo Kim.Fabrication of porous SiC ceramics with special
morphologies by sacrificing template method.Journal of Porous Materials 2004,
11:265–271.].Wherein, glass fibre with silica dioxide granule template is removed by HF solution etches；Carbon fiber, carbon are received
Mitron and nylon fiber template are removed by the lower 650 DEG C of calcinings of air atmosphere.It is with carbon fiber, carbon nanotube and nylon fiber
The pore volume for the porous silicon carbide ceramic that template obtains is only 0.001~0.006cm3/g.With glass fibre, silica dioxide granule
And the mixture of glass fibre and silica dioxide granule is the pore volume for the porous silicon carbide ceramic that template obtains between 0.26
~0.98cm3/ g, but remove removing template by HF solution etches, there are the time it is long, using dangerous chemical reagent, to environment not
The problems such as benefit.Diameter is added between 1.5~180 μm of volume fractions in Kotani etc. in the liquid Polycarbosilane containing allyl
Between 25~75% poly (methyl methacrylate) micro-sphere, after 200 DEG C of crosslinking curings, gradually heating sintering obtains porous silicon carbide
Silicon ceramics, porosity are up to 85% [Kotani M, Nishiyabu K, Matsuzaki S, Tanaka S.Processing of
polymer-derived porous SiC body using allylhydridopolycarbosilane(AHPCS)and
PMMA microbeads.Journal of the Ceramic Society of Japan 2011,119:563-569].But
Be 200 DEG C of crosslinking curings of liquid Polycarbosilane be by Si-H dehydrogenative condensation, resulting hydrogen easily lead to be formed it is irregular
Pore structure.And the organic pore-forming agents of high-content, in degradation, evolution ingredient is more, causes brokenly to porous silicon carbide ceramic structure
It is bad.
Summary of the invention
The purpose of the present invention is to provide a kind of preparation methods of porous silicon carbide ceramic, have easy, easily molded, environment
Close friend can be based on the advantages of different application requires performance of control, the porous silicon carbide ceramic of acquisition uniform, hole with internal component
Gap rate is high, cell size distribution uniformly, ceramic product close to silicon carbide stoichiometric ratio the advantages of.
Technical solution provided by the invention is a kind of preparation method of porous silicon carbide ceramic, comprising the following steps:
(1) by the mixture of liquid Polycarbosilane, radical initiator and thermal expansivity pore creating material containing unsaturated group
Heating is reacted, and obtained product is the Polycarbosilane with porous structure crosslinking curing；
(2) in an inert atmosphere, step (1) products therefrom is gradually heated up sintering, generates porous silicon carbide ceramic.
Reaction in the step (1) keeps the temperature 10~360min, the temperature being sintered in the step (2) at 60~200 DEG C
Degree is 800~1800 DEG C.
The present invention is based on addition pore creating material methods to prepare porous silicon carbide ceramic, and the pore creating material of selection is thermal expansivity pore-creating
Agent；The silicon carbide ceramics precursor of selection is the liquid Polycarbosilane containing unsaturated group, under radical initiator initiation,
Unsaturated group in structure crosslinks reaction.It may be implemented in thermal expansion by regulating and controlling temperature, initiator type and content etc.
Property pore creating material volume expansion while carry out liquid Polycarbosilane crosslinking curing molding, thus obtain have porous structure crosslinking
Cured Polycarbosilane, then porous silicon carbide ceramic is obtained through sintering process.The use of thermal expansivity pore creating material can substantially reduce
Pore creating material dosage avoids pore creating material from largely degrading to porous silicon carbide ceramic structural damage；Radical initiator is catalyzed liquid
Polycarbosilane crosslinking curing is not related to the reaction of Si-H dehydrogenative condensation, is avoided that simple heat cross-linking solidifies a large amount of hydrogen generated to knot
The destruction of structure, finally available porosity is greater than 80%, internal component is uniform, cell size distribution is uniform and gained ceramic product
Porous silicon carbide ceramic of the middle C/Si between 1.04~1.20.
At least while comprising two kinds of structural units shown in formula (I) and formula (II) in the liquid Polycarbosilane structure:
Wherein, R1Selected from H or methyl；
R2Selected from one of following group:
-CH2- CH=CH2,-C ≡ CH ,-CH=CH2,
-O-CH2- CH=CH2,
To obtain suitable crosslinking degree, the molar content of formula (II) structural unit, which accounts in the liquid Polycarbosilane, to be owned
The 1/30~1/5 of the molar content of structural unit；
To obtain C/Si than the porous silicon carbide ceramic closer to 1, preferably, R1Selected from H.
The thermal expansivity pore creating material is selected from the decomposable solid chemical compound for generating gas or includes low-boiling compound
Microcapsules.The decomposable solid chemical compound for generating gas is selected from ammonium hydrogen carbonate, sodium bicarbonate, calcium bicarbonate, 4,4 '-oxos
One of double benzene sulfonyl hydrazides, unifor or azodicarbonamide or at least two combination；It is described to include low boiling point
Acrylate polymer microcapsules or polyacrylonitrile and acrylic amide of the microcapsules of compound selected from interior hydrocarbon-containiproducts
Copolymer microcapsules, they are to include the microballoon of liquid low boiling point hydrocarbon using thermal plastic high polymer as shell, heating
Afterwards, high polymer shell softens, and liquid hydrocarbon vaporization therein, capsule body is expanded because of the pressure of generation.Gained is porous
The abscess-size and density of silicon carbide ceramics mainly by the decomposable solid chemical compound for generating gas or include low-boiling compound
Microcapsules size, dosage and ingredient influence.
From post-processing angle consider, preferably, the thermal expansivity pore creating material be selected from 4,4 '-oxobenzenesulfonyl hydrazide,
Gas is generated when unifor, azodicarbonamide etc. decompose and residue is degradable through high-temperature process；Also selected from interior
Microcapsules containing low-boiling compound, and microcapsule shell is to remain few polymer, such as polymethyl methacrylate after degrading.
Preferably, the radical initiator is selected from oil-soluble azo or organic peroxy class initiator, thus easily
Disperse in liquid Polycarbosilane.
Preferably, also adding other auxiliary agents in the liquid Polycarbosilane, the auxiliary agent includes activated monomer, the work
Property monomer be selected from contain two or more acrylate-based, methacrylates, vinyl, allyl, ethylene oxy
The compound of base or allyl oxygroup, such as tripropylene glycol diacrylate, diethylene glycol diacrylate, diethoxy bis-phenol
A diacrylate, triethylene glycol divinyl ether, trimethylolpropane trimethacrylate, pentaerythritol triacrylate.It is active single
Physical efficiency participates in the crosslinking curing process of liquid Polycarbosilane and the crosslinking curing rate of regulation liquid Polycarbosilane, makes thermal expansivity
The expansion rate of pore creating material and the crosslinking curing rate of liquid Polycarbosilane match.
Preferably, the liquid Polycarbosilane, the microcapsules for including low-boiling compound, activated monomer and free radical draw
The weight ratio for sending out agent is 100:60~120:0~5:1, wherein contains R2The molar content of structural unit account for liquid Polycarbosilane
In all structural units molar content 1/25~1/6, the R in liquid Polycarbosilane1For H, R2One in following group
Kind:
The microcapsules for including low-boiling compound are selected from polyacrylonitrile-acrylamide foam microspheres or polymethyl
Acid esters foam microspheres, the activated monomer are selected from diethylene glycol diacrylate, triethylene glycol divinyl ether, diethoxy bis-phenol
A diacrylate or trimethylolpropane trimethacrylate, the radical initiator be selected from peroxidized t-butyl perbenzoate or
Dilauroyl peroxide；The density of the porous silicon carbide ceramic of preparation is 0.171~0.470g/cm3, porosity be 80.2~
93.5%, C/Si ratio is 1.04~1.20.
Preferably, the liquid Polycarbosilane, decomposable solid chemical compound, activated monomer and the free radical for generating gas
The weight ratio of initiator is 100:20~30:0~1:1~3, wherein contains R2The molar content of structural unit account for the poly- carbon of liquid
The 1/10 of the molar content of all structural units in silane, the R in liquid Polycarbosilane1For H, R2One in following group
Kind:
-CH2- CH=CH2,-C ≡ CH；
The decomposable solid chemical compound for generating gas is selected from 4,4 '-oxobenzenesulfonyl hydrazide or sodium bicarbonate, described
Activated monomer is selected from diethylene glycol diacrylate, and the radical initiator is selected from isopropyl benzene hydroperoxide or benzoyl peroxide first
Tert-butyl acrylate；The density of the porous silicon carbide ceramic of preparation is 0.231~0.369g/cm3, porosity be 85.5~89.2%,
C/Si ratio is 1.06~1.11.
Preferably, the sintering is carried out under condition of negative pressure in step (2), the negative pressure is lower than 1 atmosphere
Pressure carries out, to be conducive to the evolution of catabolite, avoids in sintering process, destruction of the pressure increase to porous structure, and
It can speed up degradation, to obtain the higher porous silicon carbide of porosity.
Preferably, in an inert atmosphere, step (1) products therefrom is gradually warming up to 800 in the step (2)
~1400 DEG C, the porous silicon carbide of generation is in amorphous state.
Preferably, in an inert atmosphere, step (1) products therefrom is gradually warming up to 1450 in the step (2)
~1800 DEG C, the porous silicon carbide of generation is in crystalline state.The crystal phase of the crystalline state porous silicon carbide includes α-SiC and β-SiC.
It is needed based on different application, in step (2), sintering temperature is adjustable, such as works as the application of gained porous silicon carbide ceramic
In heat-insulated field, sintering temperature suggestion is between 800~1400 DEG C, and amorphous state, thermal conductivity is mainly presented in silicon carbide at this time
Rate is low；When gained porous silicon carbide ceramic is applied to electromagnetic shielding and catalytic field, sintering temperature suggestion is between 1400~1800
Between DEG C, silicon carbide Step crystallization and crystallinity increases, thermal conductivity and electromagnetic wave shielding with the raising of sintering temperature at this time
It can also improve.
After step (2), formed after targeted post processing mode removal thermal expansivity pore creating material pore-creating can be taken
New compound or residue.Such as generated when the thermal expansivity pore creating material is selected from sodium bicarbonate, calcium bicarbonate decomposes
Gas but there is new solid-oxide to be formed simultaneously, after step (2), dilute hydrochloric acid can be used and impregnate removal；When the heat is swollen
Swollen property pore creating material is selected from the microcapsules for including low-boiling compound, if causing carbon to remain after sintering, after step (2), in
500~800 DEG C of 30~120min of heat preservation under air atmosphere, to remove wherein remaining carbon；Furthermore it also can choose nothing after being pyrolyzed
Remaining microcapsules such as include the polymethyl methacrylate microcapsules of low-boiling compound as thermal expansivity pore creating material, gather
Methyl methacrylate just thermally decomposes completely before 400 DEG C, is sintered in conjunction with negative pressure, no longer needs to carry out after step (2)
Calcination for removing carbon under air atmosphere.
Compared with the existing technology, the beneficial effects of the present invention are embodied in:
Porous silicon carbide silicon technology is prepared using silicon carbide powder compared to more existing, the present invention uses liquid Polycarbosilane for original
Pore creating material, can directly be uniformly dispersed by material without solvent.Using free radical cause crosslinking liquid Polycarbosilane not only be crosslinked fastly and
And help to reduce the degree for destroying regularity in forming process；Thermal expansivity microcapsules are as pore creating material, it is possible to reduce make
The dosage of hole agent and avoid destruction of the pyrolysis product to porous silicon carbide escaped since excessive pore creating material is degraded.Moreover,
By regulating and controlling temperature, radical initiator type and dosage and the dosage of activated monomer etc., thermal expansivity microcapsules can be made
The crosslinking curing rate of expansion rate and liquid Polycarbosilane matches, to obtain the porous silicon carbide ceramic of high porosity.
Whole preparation process is easy, and introducing impurity is few, ceramic product purity is high.
Detailed description of the invention
Fig. 1 is that embodiment 1 prepares porous silicon carbide ceramic process, wherein 1 foams for liquid Polycarbosilane and thermal expansivity
Agent and activated monomer mixing；2 be pattern after foaming；3 be that the material obtained after foaming is cut into regular size；4 be at high temperature
Reason forms porous silicon carbide ceramic；
Fig. 2 is the infrared spectrum before and after 1 Polycarbosilane of liquid containing acetenyl of embodiment under experimental conditions crosslinking curing,
Before middle curve 5 represents crosslinking curing, after curve 6 represents crosslinking curing；
Fig. 3 is 1 gained porous silicon carbide ceramic electromicroscopic photograph of embodiment；
Fig. 4 is 5 gained porous silicon carbide ceramic electromicroscopic photograph of embodiment；
Fig. 5 is 9 gained porous silicon carbide ceramic electromicroscopic photograph of embodiment；
Fig. 6 is 4 gained porous silicon carbide ceramic thermal conductivity curve graph of embodiment；
Fig. 7 is the XRD diagram of embodiment 4 and 5 gained porous silicon carbide ceramic of embodiment.
Specific embodiment
Below in conjunction with specific embodiment, present invention is further described in detail, it is necessary to be pointed out that the present embodiment is only used
It is further detailed in the present invention, should not be understood as limiting the scope of the invention.
The test method of porous silicon carbide ceramic prepared by the present invention includes:
Infrared spectrum analysis: it is tested using 6700 Fourier turn infrared instrument of U.S. Thermo Nicolet；
Scanning electron microscope: Hitachi company, Japan S-4800 field emission scanning electron microscope is used；
Constituent content analysis: carbon is using the test of U.S. LECO company CS844 type infrared absorption carbon and sulfur analytical instrument, oxygen member
Element is tested using Japan's HORIBA company EMGA-620 type oxygen-nitrogen analyzer, then the content of elemental silicon is obtained by minusing；
X-ray diffraction (XRD): it is tested using Bruker company, Germany D8 Advance type X-ray diffractometer；
Thermal conductivity: using resistance to (NETZSCH) instrument model of speeding of Germany: 457 MicroFlash laser of NETZSCH LFA is led
Hot instrument.
Embodiment 1
To the Polycarbosilane of liquid containing acetenyl (by 90% structural unitWith 10% structural unitComposition, number-average molecular weight 832g/mol) add commercial polypropylene nitrile-acrylic acid that mass fraction is 60wt%
Ester foaming microballoon, 3wt% diethylene glycol diacrylate and 1wt% peroxidized t-butyl perbenzoate are put into after mixing
0.5h is kept the temperature in 100 DEG C of baking ovens.Later, 1200 DEG C are risen to 5 DEG C/min heating rate under nitrogen atmosphere and keeps the temperature 1h, it is natural
After being cooled to 600 DEG C, it is passed through air and keeps the temperature 1h.
The density of the porous silicon carbide ceramic of acquisition is 0.302g/cm3；Porosity is 87.4%；Ceramic product chemical formula
For SiC1.09O0.10。
Embodiment 2
It is commercially available poly- the third of 80wt% to the Polycarbosilane of liquid containing acetenyl of structure shown in embodiment 1 addition mass fraction
Alkene nitrile-acrylate foam microspheres, 3wt% diethylene glycol diacrylate and 1wt% peroxidized t-butyl perbenzoate, mixing are equal
After even, it is put into 100 DEG C of baking ovens and keeps the temperature 0.5h.Later, 1200 DEG C are risen to 5 DEG C/min heating rate under nitrogen atmosphere and protected
Warm 1h after being naturally cooling to 600 DEG C, is passed through air and keeps the temperature 1h.
The density of the porous silicon carbide ceramic of acquisition is 0.262g/cm3, porosity 89.1%；Ceramic product chemical formula
For SiC1.11O0.14。
Embodiment 3
It is the commercially available poly- of 100wt% to the Polycarbosilane of liquid containing acetenyl of structure shown in embodiment 1 addition mass fraction
Acrlylonitrile-acrylate foam microspheres, 3wt% diethylene glycol diacrylate and 1wt% peroxidized t-butyl perbenzoate, mixing
After uniformly, it is put into 100 DEG C of baking ovens and keeps the temperature 0.5h.Later, 1200 DEG C are risen to simultaneously with 5 DEG C/min heating rate under nitrogen atmosphere
1h is kept the temperature, after being naturally cooling to 600 DEG C, air is passed through and keeps the temperature 1h.
The density of the porous silicon carbide ceramic of acquisition is 0.256g/cm3, porosity 89.3%；Ceramic product chemical formula
For SiC1.10O0.11。
Embodiment 4
It is the commercially available poly- of 120wt% to the Polycarbosilane of liquid containing acetenyl of structure shown in embodiment 1 addition mass fraction
Acrlylonitrile-acrylate foam microspheres, 3wt% diethylene glycol diacrylate and 1wt% peroxidized t-butyl perbenzoate, mixing
After uniformly, it is put into 100 DEG C of baking ovens and keeps the temperature 0.5h.Later, 1200 DEG C are risen to simultaneously with 5 DEG C/min heating rate under nitrogen atmosphere
1h is kept the temperature, after being naturally cooling to 600 DEG C, air is passed through and keeps the temperature 1h.
The density of the porous silicon carbide ceramic of acquisition is 0.211g/cm3, porosity 91.2%；Ceramic product chemical formula
For SiC1.09O0.13。
Embodiment 5
It is the commercially available poly- of 120wt% to the Polycarbosilane of liquid containing acetenyl of structure shown in embodiment 1 addition mass fraction
Acrlylonitrile-acrylate foam microspheres, 3wt% diethylene glycol diacrylate and 1wt% peroxidized t-butyl perbenzoate, mixing
After uniformly, it is put into 100 DEG C of baking ovens and keeps the temperature 0.5h.Later, 1600 DEG C are risen to simultaneously with 5 DEG C/min heating rate under nitrogen atmosphere
1h is kept the temperature, after being naturally cooling to 600 DEG C, air is passed through and keeps the temperature 1h.
The density of the porous silicon carbide ceramic of acquisition is 0.342g/cm3, porosity 85.8%；Ceramic product chemical formula
For SiC1.04O0.01。
Embodiment 6
To containing acrylate-based liquid Polycarbosilane (by 93% structural unitWith 7% structural unitComposition, number-average molecular weight 953/mol) mass fraction is added as commercially available poly- the third of 120wt%
Alkene nitrile-acrylate foam microspheres and 1wt% peroxidized t-butyl perbenzoate are put into 80 DEG C of baking ovens and keep the temperature after mixing
3h.Later, 1200 DEG C are risen to 5 DEG C/min heating rate under nitrogen atmosphere and keeps the temperature 1h, after being naturally cooling to 600 DEG C, led to
Enter air and keeps the temperature 1h.
The density of the porous silicon carbide ceramic of acquisition is 0.403g/cm3, porosity 83.2%；Ceramic product chemical formula
For SiC1.10O0.15。
Embodiment 7
It is commercially available the 4 of 20wt% to the Polycarbosilane of liquid containing acetenyl of structure shown in embodiment 1 addition mass fraction,
4 '-oxobenzenesulfonyl hydrazide and 3wt% isopropyl benzene hydroperoxide are put into 160 DEG C of baking ovens after mixing and keep the temperature 1h.Later,
1200 DEG C are risen to 5 DEG C/min heating rate under nitrogen atmosphere and keeps the temperature 1h, after being naturally cooling to 600 DEG C, are passed through air simultaneously
Keep the temperature 1h.
The density of the porous silicon carbide ceramic of acquisition is 0.369g/cm3, porosity 85.5%；Ceramic product chemical formula
For SiC1.11O0.07。
Embodiment 8
It is the commercially available poly- of 120wt% to the Polycarbosilane of liquid containing acetenyl of structure shown in embodiment 1 addition mass fraction
Methacrylate foam microspheres, 3wt% triethylene glycol divinyl ether and 1wt% dilauroyl peroxide are put into after mixing
0.3h is kept the temperature in 110 DEG C of baking ovens.Later, 1200 DEG C are risen to 5 DEG C/min heating rate under vacuum conditions and keeps the temperature 2h.
The density of the porous silicon carbide ceramic of acquisition is 0.171g/cm3, porosity 93.5%；Ceramic product chemical formula
For SiC1.08O0.06。
Embodiment 9
To the Polycarbosilane of liquid containing allyl (by 90% structural unitWith 10% structural unitComposition, number-average molecular weight 794/mol) add commercially available sodium bicarbonate, 1wt% that mass fraction is 30wt%
Diethylene glycol diacrylate and 1wt% peroxidized t-butyl perbenzoate are put into 110 DEG C of baking ovens after mixing and keep the temperature 2h.
Later, 1000 DEG C are risen to 5 DEG C/min heating rate under nitrogen atmosphere and keeps the temperature 1h.Naturally it is cooled to room temperature, taking-up is placed in
Temperature is that 50 DEG C of concentration are ultrasonic 30min in the HCL aqueous solution of 1mol/L, is taken out.
The density of the porous silicon carbide ceramic of acquisition is 0.231g/cm3, porosity 89.2%；Ceramic product chemical formula
For SiC1.06O0.15。
Embodiment 10
To the liquid Polycarbosilane containing allyl ether (by 90% structural unitWith 10% structural unitComposition, number-average molecular weight 1102/mol) add the commercial polypropylene nitrile-the third that mass fraction is 60wt%
Acrylamide foam microspheres, 5wt% diethylene glycol diacrylate and 1wt% peroxidized t-butyl perbenzoate are put after mixing
Enter in 100 DEG C of baking ovens and keeps the temperature 0.5h.Later, 1200 DEG C are risen to 5 DEG C/min heating rate under nitrogen atmosphere and keeps the temperature 1h, from
After being so cooled to 600 DEG C, it is passed through air and keeps the temperature 1h.
The density of the porous silicon carbide ceramic of acquisition is 0.348g/cm3；Porosity is 86.2%；Ceramic product chemical formula
For SiC1.20O0.10。
Embodiment 11
To the Polycarbosilane of liquid containing acetenyl (by 96% structural unitWith 4% structural unit
Composition, number-average molecular weight 1769/mol) addition mass fraction be 60wt% commercial polypropylene nitrile-acrylate foaming it is micro-
Ball, 4wt% diethoxy bisphenol a diacrylate and 1wt% peroxidized t-butyl perbenzoate are put into 100 DEG C after mixing
0.5h is kept the temperature in baking oven.Later, 1200 DEG C are risen to 5 DEG C/min heating rate under nitrogen atmosphere and keeps the temperature 1h, Temperature fall
To after 600 DEG C, it is passed through air and keeps the temperature 1h.
The density of the porous silicon carbide ceramic of acquisition is 0.375g/cm3；Porosity is 85.4%；Ceramic product chemical formula
For SiC1.05O0.11。
Embodiment 12
To the Polycarbosilane of liquid containing acetenyl (by 84% structural unitWith 16% structural unitComposition, number-average molecular weight 598/mol) add commercial polypropylene nitrile-acrylate that mass fraction is 60wt%
Foam microspheres, 2wt% trimethylolpropane trimethacrylate and 1wt% peroxidized t-butyl perbenzoate are put into after mixing
0.5h is kept the temperature in 100 DEG C of baking ovens.Later, 1200 DEG C are risen to 5 DEG C/min heating rate under nitrogen atmosphere and keeps the temperature 1h, it is natural
After being cooled to 600 DEG C, it is passed through air and keeps the temperature 1h.
The density of the porous silicon carbide ceramic of acquisition is 0.470g/cm3；Porosity is 80.2%；Ceramic product chemical formula
For SiC1.14O0.09。
As can be seen that porous silicon carbide ceramic preparation method provided by the invention is easy to operate, it is swollen to introduce heat from attached drawing 1
Swollen property pore creating material, liquid Polycarbosilane expansion multiplying power are big；Figure it is seen that can under thermal expansivity pore creating material exaggerated conditions
Realize that the unsaturated group in liquid Polycarbosilane crosslinks reaction, mechanism of crosslinking is that free radical opens unsaturated group reunion
It closes；From attached drawing 3~5 as can be seen that using different thermal expansivity pore creating materials, being heat-treated to different temperature and using different
The liquid Polycarbosilane of structure all can get porous silicon carbide ceramic；It is from attached drawing 6 as can be seen that obtained by embodiment 4
Porous silicon carbide ceramic has low-down thermal conductivity；From attached drawing 7 as can be seen that making porous carbon by improving heat treatment temperature
SiClx ceramics are from amorphous to crystal phase transition.In addition, by elemental analysis, porous silicon carbide ceramic oxygen content obtained compared with
Low, C/Si has near stoichiometric proportion.
Claims (10)
1. a kind of preparation method of porous silicon carbide ceramic, which comprises the steps of:
(1) by the mixture heating of liquid Polycarbosilane, radical initiator and thermal expansivity pore creating material containing unsaturated group
It is reacted, obtained product is the Polycarbosilane with porous structure crosslinking curing；
(2) in an inert atmosphere, step (1) products therefrom is gradually heated up sintering, generates porous silicon carbide ceramic.
2. the preparation method of porous silicon carbide ceramic according to claim 1, which is characterized in that in the step (1)
Reaction keeps the temperature 10~360min at 60~200 DEG C, and the temperature being sintered in the step (2) is 800~1800 DEG C.
3. the preparation method of porous silicon carbide ceramic according to claim 1, which is characterized in that described to contain unsaturated group
Liquid Polycarbosilane structure at least while comprising two kinds of structural units shown in formula (I) and formula (II):
Wherein, R1Selected from H or methyl；
R2Selected from one of following group:
-CH2- CH=CH2,-C ≡ CH ,-CH=CH2,
-O-CH2- CH=CH2,
4. the preparation method of porous silicon carbide ceramic according to claim 3, which is characterized in that formula (II) structural unit
Molar content accounts for 1/30~1/5 of the molar content of all structural units in the liquid Polycarbosilane containing unsaturated group.
5. the preparation method of porous silicon carbide ceramic according to claim 1, which is characterized in that the thermal expansivity pore-creating
Agent is selected from the decomposable solid chemical compound for generating gas or the microcapsules for including low-boiling compound.
6. the preparation method of porous silicon carbide ceramic according to claim 5, which is characterized in that the heat-swellable property is made
Hole agent is selected from 4,4 '-oxobenzenesulfonyl hydrazide, unifor, azodicarbonamide；Or low-boiling compound is included, shell
For the microcapsules of polymethyl methacrylate.
7. the preparation method of porous silicon carbide ceramic according to claim 1, which is characterized in that in the step (1),
Activated monomer is added in mixture, the activated monomer, which is selected from, contains two or more acrylate-based, metering systems
One of perester radical, vinyl, allyl, ethyleneoxy or compound of allyl oxygroup.
8. the preparation method of porous silicon carbide ceramic according to claim 1, which is characterized in that in the step (2),
Gradually heating sintering under condition of negative pressure.
9. the preparation method of porous silicon carbide ceramic according to claim 8, which is characterized in that in the step (2),
In inert atmosphere, step (1) products therefrom is gradually warming up to 800~1400 DEG C, the porous silicon carbide of generation is in amorphous
State.
10. the preparation method of porous silicon carbide ceramic according to claim 8, which is characterized in that in the step (2),
In an inert atmosphere, step (1) products therefrom is gradually warming up to 1450~1800 DEG C, the porous silicon carbide of generation is in crystallization
State.
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| WO2023168490A1 (en) * | 2022-03-08 | 2023-09-14 | University Of Tasmania | Preceramic resins and porous polymer-derived ceramics |
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