CN108947578A - A kind of preparation method of high-temperature resistant silicon carbide-hafnium carbide foamed ceramics - Google Patents
A kind of preparation method of high-temperature resistant silicon carbide-hafnium carbide foamed ceramics Download PDFInfo
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Abstract
The invention discloses a kind of high-temperature resistant silicon carbide-hafnium carbide foamed ceramics preparation methods.This method is can be thermally cured characteristic Polycarbosilane and hafnium oxide powder and after three kinds of materials of polyurethane are fully ground mixing, it is added in mold, apply certain pressure, gas inside discharge powder obtains precast body, the foam preform is heat-treated again, the self-crosslinking solidification for realizing Polycarbosilane, finally carries out high temperature sintering in an inert atmosphere, obtains silicon carbide-carbon hafnium foamed ceramics.The preparation method is simple; process flow is few; it is at low cost; the use for avoiding solvent, is conducive to environmental protection, and the foamed ceramics linear shrinkage ratio prepared is less than 12%; the small 1.0g/cm3 of bulk density; between 60%~80%, flexural strength can use open porosity up to 2.0~2.3MPa in 1500 DEG C of long-times.
Description
Technical field
The invention belongs to ceramic foam technical fields, and in particular to one kind is can be thermally cured Polycarbosilane and hafnium oxide system
The preparation method of standby high-temperature resistant silicon carbide-hafnium carbide foamed ceramics.
Background technique
Traditional foam silicon carbide ceramics preparation process is complicated, mainly with silicon carbide powder and dispersing agent, sintering aid
Slurry is made in equal blendings, then impregnates to obtain precast body with organic foam template, and precast body is burnt through processes such as drying, exclusion organic matters
At obtaining foam silicon carbide ceramics.(Liang Hanqin, Yao Xiumin, Huang Zhengren, Liu Xue build liquid phase when silicon carbide ceramics liquid-phase sintering
Generating process [J] mechanical engineering material, 2015,39 (02): 34-37.；) beam Chinese qin has studied SiC foam ceramic post sintering mechanism:
SiC foam ceramics are mainly that glass phase generates the cladding of SiC particulate, connection function and cenotype mullite.And sintering aid
Introducing is also unfavorable for preparing SiC amount of substance than similar foam silicon carbide ceramics.Excessively high sintering temperature can generate big ashlar
Ying Xiang influences the intensity of material to micro-crack occur in later cooling procedure.
In recent decades, polymer precursor, such as Polycarbosilane, polysilazane, as the forerunner for preparing ceramic material
Body causes the great interest of people in recent years, and in 105272266 A of patent CN, Li Siwei only uses Polycarbosilane as foam
The precursor of ceramics prepares slurry with solvent xylene, using processed polyurethane foam as template, hanging product is made, first
By pre-oxidation treatment in convection oven, then through being sintered to obtain sic foam in high temperature furnace.Contain in its foamed ceramics prepared
The oxygen of 8wt% or more, oxygen exist with SiOxCy phase., at 1100 DEG C or more, violent decomposition reaction, such as following formula occur for SiOxCy for it
It is shown.
SiOxCy→SiC(s)+CO(g)+SiO(g)
The above decomposition reaction leads to the strength damage of foamed ceramics skeleton, and the use temperature for limiting foam silicon carbide ceramics exists
1100 DEG C or less.
Using the Polycarbosilane of polydimethylsiloxane cracking preparation as precursor, prepare in silicon carbide ceramics method, in inertia
In atmosphere, carbon of having more than needed in the silicon carbide ceramics that is pyrolyzed, carbon is unstable under high temperature aerobic conditions, is shown below.
C(s)+O2(g)→CO(g)
The above oxidation reaction leads to the damage of foamed ceramics, limits the use condition of foam silicon carbide ceramics.
The application environment of combined silicon carbide ceramic foam, it is possible in high temperature air atmosphere, reduce in silicon carbide ceramics
Carbon more than needed is the key point for improving its service performance.
The prior art is summarized: being made into slurry with silicon-carbide particle and binder and solvent, is with the organic matter of foaming structure
Template after dipping, is sintered, but disadvantage is obvious at 1300 DEG C or so: the uniformity of slurry it is difficult to ensure that, preparation process has
The use of solvent, is unfavorable for environmental protection；Using organic silane compound Polycarbosilane as precursor, polymer-derived method prepares foam pottery
Porcelain, this part research is rare, and technology waits to develop.
Summary of the invention
Status in view of the above technology, the present invention is intended to provide it is a kind of with can be thermally cured Polycarbosilane and hafnium oxide prepare it is resistance to
High-temperature carborundum-hafnium carbide foamed ceramics preparation method.
Can be thermally cured Polycarbosilane and hafnium oxide powder and three kinds of materials of polyurethane as raw material.It is mixed into being fully ground excessively
After even, powder is added in mold, applies certain pressure to mold, and the gas inside powder is discharged and obtains precast body, then is pre- to this
Body processed is heat-treated, and is realized the self-crosslinking solidification of Polycarbosilane, is finally carried out high temperature pyrolysis sintering in an inert atmosphere, obtain
To silicon carbide-carbon hafnium foamed ceramics.The preparation method is simple, and process flow is few, at low cost, avoids the use of solvent, protects
There is very big practical application value and environmental protection to be worth for retaining ring border, sufficient raw.
In order to achieve the above technical purposes, the present invention at a certain temperature, is fully ground and can be thermally cured Polycarbosilane and two
Three kinds of materials of hafnium oxide powder and polyurethane, obtain uniformly mixed powder.Powder is added in mold again, one is applied to mold
Constant-pressure is discharged the gas inside powder and obtains precast body, in an inert atmosphere, is heat-treated to the precast body, herein mistake
Any chemical reaction and thawing, gasification etc. do not occur for Cheng Zhong, hafnium oxide powder and polyurethane, and Polycarbosilane completes the friendship of itself
Connection solidification, obtains precast body.Finally high temperature sintering is carried out to precast body in an inert atmosphere not foam in the process
With serious volume contraction phenomenon, polyurethane decomposes completely, and quality noresidue leaves volume, causes hole, can be thermally cured
Polycarbosilane is changed into silicon carbide ceramics and carbon more than needed, this carbon and hafnium oxide occur carbothermic reduction reaction and obtain hafnium carbide pottery
Porcelain finally obtains high-temperature resistant silicon carbide-hafnium carbide foamed ceramics.This foamed ceramics compact structure, can be in 1500 DEG C of long-times
Using.
That is, the technical solution of the present invention is as follows: one kind can be thermally cured Polycarbosilane and hafnium oxide prepares high-temperature resistant silicon carbide-
The preparation method of hafnium carbide foamed ceramics, includes the following steps:
(1) it under certain temperature, is fully ground and can be thermally cured Polycarbosilane, hafnium oxide and polyurethane, obtain powder；
(2) mold is added in powder, applies pressure, and the gas inside powder is discharged, foam preform is obtained, in inert atmosphere
In foam preform is heat-treated, realize that the self-crosslinking of heat cure Polycarbosilane solidify and the removing of solvent；
(3) foam preform is heat-treated in an inert atmosphere, realizes that the self-crosslinking of heat cure Polycarbosilane is solid
Change；
(4) in an inert atmosphere, high temperature sintering is carried out to the foam preform of crosslinking curing, obtains silicon carbide-hafnium carbide
Foamed ceramics；
Further, the step (1) is used as a kind of implementation, and detailed process is as follows: in the step (1), specific mistake
Journey is as follows:
It being mixed, is obtained with can be thermally cured Polycarbosilane, hafnium oxide and polyurethane in ball grinder high speed cryogrinding
Even mixed powder.It can be thermally cured quality 1:0.6:0.3~0.6 of Polycarbosilane, hafnium oxide and polyurethane three.
Preferably, the grinding temperature is not higher than 60 DEG C；
Preferably, the heat cure Polycarbosilane only contains three kinds of silicon, carbon, hydrogen elements；
Preferably, can be thermally cured Polycarbosilane is: Polycarbosilane (it is synthesized by the rearrangement of polydimethylsiloxane Pintsch process,
220~230 DEG C of softening point) and alkenyl silanes obtained by hydrosilylation.The amount of heat cure Polycarbosilane medium vinyl accounts for
The 20~50% of the si-h bond content of Polycarbosilane.
Further, the step (2) is used as a kind of implementation, and detailed process is as follows: mould is added in the powder mixed
In tool, apply pressure, after the gas inside powder is discharged, obtains precast body；
Preferably, the mould inside shape is unlimited, tubulose can be, rodlike, sheet or other geometrical morphologies；
Preferably, the pressure is 0.1~10MPa；
Further, a kind of implementation is used as in the step (3), detailed process is as follows: by precast body in inert atmosphere
In, 200 DEG C~300 DEG C are warming up to 1 DEG C/min~5 DEG C/min heating rate, keeps the temperature 1.5h~15h.
Further, in the step (4), as a kind of implementation, detailed process is as follows: detailed process is as follows: will walk
Suddenly (3) treated precast body under an inert atmosphere, with 1 DEG C/min~30 DEG C/min heating rate, be heated to 1400 DEG C~
1800 DEG C, 0.5h~5h hours are kept the temperature, then cools to room temperature, obtains foamed ceramics.The carbon of hafnium oxide and carbon at high temperature
Thermal reduction forms hafnium carbide:
C(s)+HfO2(s)→CO(g)+fC(s)。
Preferably, the foamed ceramics linear shrinkage ratio prepared is less than 12%, the small 1.0g/cm of bulk density3, open porosity
Between 60%~80%, flexural strength is up to 2.0~2.3Mpa.
Preferably, the SiC foam ceramics prepared can be used in 1500 DEG C of long-times.
The present invention is using heat cure Polycarbosilane (PVCS), hafnium oxide and polyurethane as raw material, in order to realize above-mentioned technology
Purpose, the present invention at a certain temperature, are fully ground and can be thermally cured three kinds of Polycarbosilane, hafnium oxide powder and polyurethane objects
Material, obtains uniformly mixed powder.Powder is added in mold again, applies certain pressure to mold, the gas inside powder is discharged
Precast body is obtained, in an inert atmosphere, is heat-treated, in the process, hafnium oxide powder and polyurethane to the precast body
Any chemical reaction and thawing, gasification etc. do not occur, completes the self-crosslinking solidification of Polycarbosilane, obtains foam preform.Most
High temperature sintering is carried out to foam preform in an inert atmosphere afterwards, in the process, foaming and serious volume contraction does not occur
Phenomenon polyurethane decomposes completely, and quality noresidue leaves volume, causes hole, can be thermally cured Polycarbosilane and is changed into carbon
SiClx ceramics and carbon more than needed, this carbon and hafnium oxide occur carbothermic reduction reaction and obtain carbonization hafnium ceramic, finally obtain resistance to height
Warm silicon carbide-carbon hafnium foamed ceramics.This foamed ceramics compact structure.1500 DEG C, after handling 1h in air atmosphere, intensity is protected
Stay rate 90% or more.
1, the present invention compared with prior art the advantages of:
2, raw material preparation of the invention is simple and is easy to get: prepared by Polycarbosilane commercial product, heat cure Polycarbosilane
Journey is simple, is easy to get, hafnium oxide, and commercial product is easy to get, polyurethane, and commercial product is easy to get.
3, in preparation process of the present invention, solvent is not used, environmental protection is conducive to；
4, preparation process of the present invention is simple, can prepare the foamed ceramics structural member of different morphologies；
5, foamed ceramics porosity of the present invention is controllable；
6, the present invention prepares silicon carbide ceramics with heat cure Polycarbosilane, contains silicon carbide and carbon in ceramic product, carbon is not
Conducive to the inoxidizability of ceramics, hafnium carbide is formed with the carbon thermal reduction of hafnium oxide and carbon at high temperature, carbon is changed into resistance to super
The hafnium carbide of high temperature becomes " useless " as " treasured ", finally obtains the complex phase ceramic of silicon carbide and hafnium carbide, improve the resistance to of ceramic foam
Warm nature energy；
7, the foamed ceramics intensity that the present invention is prepared is high, and heat resistance is excellent.
Detailed description of the invention
Fig. 1 is that the present invention can be thermally cured Polycarbosilane and hafnium oxide prepares high-temperature resistant silicon carbide-hafnium carbide foamed ceramics
Preparation flow schematic diagram；
Fig. 2 is polyurethane and foamed ceramics porosity.
Specific embodiment
Below with reference to embodiment, present invention is further described in detail, it should be pointed out that embodiment described below purport
It is being convenient for the understanding of the present invention, and is not playing any restriction effect to it.
Embodiment 1:
High-temperature resistant silicon carbide-hafnium carbide foamed ceramics preparation process is prepared can be thermally cured Polycarbosilane and hafnium oxide
It is as follows:
(1) raw material is ground
Mass ratio, PVCS:HfO2: polyurethane 1:0.6:0.3 at 30 DEG C, in inert atmosphere, is sufficiently mixed and grinds above three
Kind material, obtains uniformly mixed powder.
(2) plastotype
Powder is added in mold, and internal morphology is disc-shape, applies 0.3Mpa pressure, and the gas inside powder is discharged,
Obtain foam preform.
(3) it is heat-treated organic foam precast body
Organic foam precast body is put into furnace, after vacuumizing displacement high pure nitrogen three times, by organic foam in indifferent gas
In atmosphere, 220 DEG C are warming up to the heating rate of 3 DEG C/min, keeps the temperature 3h.
(4) sintering prepares silicon carbide-carbon hafnium foamed ceramics
In argon atmosphere, by step (3) treated precast body with the heating rate of 1 DEG C/min, it is heated to 1600
DEG C, 4h hours are kept the temperature, then cools to room temperature, obtains black bright foamed ceramics.Bulk density 0.7g/cm3, open porosity
60%, flexural strength reaches 2.3MPa.
By foam silicon carbide ceramics obtained above in air atmosphere after 1500 DEG C of processing 1h；Strength retention ratio is
96%.
Embodiment 2:
High-temperature resistant silicon carbide-hafnium carbide foamed ceramics preparation process is prepared can be thermally cured Polycarbosilane and hafnium oxide
It is as follows:
(1) raw material is ground
Mass ratio, PVCS:HfO2: polyurethane 1:0.6:0.4 at 30 DEG C, in inert atmosphere, is sufficiently mixed and grinds above three
Kind material, obtains uniformly mixed powder.
(2) plastotype
Powder is added in mold, and internal morphology is square shape, applies 0.5Mpa pressure, and the gas inside powder is discharged
Body obtains foam preform.
(3) it is heat-treated organic foam precast body
Organic foam precast body is put into furnace, after vacuumizing displacement high pure nitrogen three times, by organic foam in indifferent gas
In atmosphere, 220 DEG C are warming up to the heating rate of 2 DEG C/min, keeps the temperature 6h.
(4) sintering prepares silicon carbide-carbon hafnium foamed ceramics
In argon atmosphere, by step (3) treated precast body with the heating rate of 3 DEG C/min, it is heated to 1650
DEG C, 3h hours are kept the temperature, then cools to room temperature, obtains black bright foamed ceramics.Bulk density 0.6g/cm3, open porosity
70%, flexural strength reaches 2.1MPa.
By foam silicon carbide ceramics obtained above in air atmosphere after 1500 DEG C of processing 1h；Strength retention ratio is
95%.
Embodiment 3:
High-temperature resistant silicon carbide-hafnium carbide foamed ceramics preparation process is prepared can be thermally cured Polycarbosilane and hafnium oxide
It is as follows:
(1) raw material is ground
Mass ratio, PVCS:HfO2: polyurethane 1:0.6:0.6 at 30 DEG C, in inert atmosphere, is sufficiently mixed and grinds above three
Kind material, obtains uniformly mixed powder.
(2) plastotype
Powder is added in mold, and internal morphology is cylindrical shape, applies 0.3Mpa pressure, and the gas inside powder is discharged,
Obtain foam preform.
(3) it is heat-treated organic foam precast body
Organic foam precast body is put into furnace, after vacuumizing displacement high pure nitrogen three times, by organic foam in indifferent gas
In atmosphere, 220 DEG C are warming up to the heating rate of 2 DEG C/min, keeps the temperature 6h.
(5) sintering prepares silicon carbide-carbon hafnium foamed ceramics
In argon atmosphere, by step (3) treated precast body with the heating rate of 5 DEG C/min, it is heated to 1700
DEG C, 6h hours are kept the temperature, then cools to room temperature, obtains black bright foamed ceramics.Bulk density 0.5g/cm3, open porosity
81%, flexural strength reaches 2.0MPa.
By foam silicon carbide ceramics obtained above in air atmosphere after 1500 DEG C of processing 1h；Strength retention ratio is
95%.
Following table 1 is the intensity contrast of embodiment in air before and after the processing:
Table 1.
Claims (9)
1. a kind of prepare high-temperature resistant silicon carbide-hafnium carbide foamed ceramics preparation side can be thermally cured Polycarbosilane and hafnium oxide
Method, it is characterized in that: including the following steps:
(1) Polycarbosilane, hafnium oxide and polyurethane will be can be thermally cured to be ground, the powder being uniformly mixed；
(2) powder mixed is added in mold, applies pressure, the gas inside powder is discharged, obtains precast body；
(3) precast body is heat-treated in an inert atmosphere, realizes that the self-crosslinking of Polycarbosilane is solid；
(4) high temperature sintering is carried out to the precast body after crosslinking curing in an inert atmosphere, obtains silicon carbide-carbon hafnium foam pottery
Porcelain.
2. preparing high-temperature resistant silicon carbide-hafnium carbide bubble as described in claim 1 can be thermally cured Polycarbosilane and hafnium oxide
The preparation method of foam ceramics, it is characterized in that: the Polycarbosilane that can be thermally cured is: Polycarbosilane and vinyl silanes pass through silicon
Addition reaction of hydrogen obtains；The Polycarbosilane is synthesized by the rearrangement of polydimethylsiloxane Pintsch process；
Preferably, the heat cure Polycarbosilane only contains three kinds of silicon, carbon, hydrogen elements.Ethylene in heat cure Polycarbosilane
The amount of base accounts for the 20~50% of the si-h bond content of Polycarbosilane；
Preferably, Polycarbosilane molecular weight 1700~1900 or so, 220~240 DEG C of softening point, by polydimethylsiloxane height
Anneal crack solution resets synthesis.
3. preparing high-temperature resistant silicon carbide-hafnium carbide bubble as described in claim 1 can be thermally cured Polycarbosilane and hafnium oxide
The preparation method of foam ceramics, it is characterized in that: detailed process is as follows in the step (1):
It being mixed with can be thermally cured Polycarbosilane, hafnium oxide and polyurethane in ball grinder high speed cryogrinding, uniformly being mixed
The powder of conjunction；It can be thermally cured quality 1:0.6:0.3~0.6 of Polycarbosilane, hafnium oxide and polyurethane three；
Preferably, the grinding temperature is not higher than 60 DEG C.
4. preparing high-temperature resistant silicon carbide-hafnium carbide bubble as described in claim 1 can be thermally cured Polycarbosilane and hafnium oxide
The preparation method of foam ceramics, it is characterized in that: detailed process is as follows in the step (2): mold is added in the powder mixed
In, apply pressure, after the gas inside powder is discharged, obtains precast body；
Preferably, the mould inside shape is unlimited, tubulose can be, rodlike, sheet or other geometrical morphologies；As
It is preferred that the pressure is 0.1~10MPa.
5. preparing high-temperature resistant silicon carbide-hafnium carbide bubble as described in claim 1 can be thermally cured Polycarbosilane and hafnium oxide
The preparation method of foam ceramics, it is characterized in that: detailed process is as follows in the step (3):
In an inert atmosphere by precast body, 200 DEG C~300 DEG C are warming up to 1 DEG C/min~5 DEG C/min heating rate, heat preservation
1.5h~15h.
6. preparing high-temperature resistant silicon carbide-hafnium carbide bubble as described in claim 1 can be thermally cured Polycarbosilane and hafnium oxide
The preparation method of foam ceramics, it is characterized in that: detailed process is as follows in the step (4):
Under an inert atmosphere by step (3) treated precast body, it with 1 DEG C/min~30 DEG C/min heating rate, is heated to
1400 DEG C~1800 DEG C, 0.5h~5h hours are kept the temperature, then cools to room temperature, obtains foamed ceramics；Hafnium oxide and carbon are in height
Carbon thermal reduction under temperature forms hafnium carbide:
C(s)+HfO2(s)→CO(g)+HfC(s)。
7. preparing high-temperature resistant silicon carbide-hafnium carbide bubble as claimed in claim 6 can be thermally cured Polycarbosilane and hafnium oxide
The preparation method of foam ceramics, it is characterized in that: the foamed ceramics linear shrinkage ratio that the step (4) is prepared is less than 12%, volume is close
Spend small 1.0g/cm3, open porosity is between 60%~80%, and flexural strength is up to 2.0~2.3Mpa.
8. preparing high-temperature resistant silicon carbide-hafnium carbide bubble as claimed in claim 6 can be thermally cured Polycarbosilane and hafnium oxide
The preparation method of foam ceramics, it is characterized in that: the foamed ceramics prepared can be used in 1500 DEG C of long-times.
9. a kind of high-temperature resistant silicon carbide-hafnium carbide foamed ceramics is made using preparation method described in the claims 1-8.
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