CN106431491B - The blocky high preparation method than table mullite silicon carbide aerogel composite - Google Patents

The blocky high preparation method than table mullite silicon carbide aerogel composite Download PDF

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CN106431491B
CN106431491B CN201610885971.8A CN201610885971A CN106431491B CN 106431491 B CN106431491 B CN 106431491B CN 201610885971 A CN201610885971 A CN 201610885971A CN 106431491 B CN106431491 B CN 106431491B
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mullite
preparation
aerogel
composite
silicon source
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CN106431491A (en
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沈晓冬
吴晓栋
邵高峰
崔升
周洁
魏阳
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Nanjing Tech University
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Abstract

The present invention relates to a kind of blocky high preparation methods than table mullite silicon carbide aerogel composite.By the way that carbon source and silicon source are mixed; after hydrolysis; introducing can not only be used for coagulant but also as the silane coupling agent of silicon source; organic/silica/alumina composite aerogel is obtained through sol-gel, aging and supercritical drying; then carbonization treatment and high temperature carbon thermal reduction are carried out under inert atmosphere gas shield; it is burnt through reaction in-situ and subsequent air forged, finally prepares a kind of blocky high aerogel composite more anti-oxidant than table mullite/silicon carbide.The present invention has the advantages that materials are simple and technique is simple and direct, and technical process is easy to operate, large-scale production easy to accomplish.

Description

The blocky high preparation method than table mullite silicon carbide aerogel composite
Technical field
The invention belongs to the preparation process fields of aerogel material, are related to a kind of blocky high more multiple than table mullite silicon carbide Close the preparation method of aerogel material；It especially designs a kind of using a step sol-gel method combination supercritical drying process and heat The method of the blocky high composite aerogel more anti-oxidant than table mullite/SiC for the treatment of process condition preparation.
Background technique
Silicon carbide porous material is a kind of new function material, has that high temperature resistant, wear-resistant, thermal expansion coefficient is low, compares table The good characteristic that area is big and chemical stability is excellent, can be widely applied to catalyst carrier, high-temperature gas filter, film point From fields such as, sensors.But carbofrax material is in application process, is frequently encountered serious problem of oxidation, on 700 DEG C of left sides Right just to form silicon oxide layer on surface, this reduces its application to a certain extent.Mullite material is a series of by aluminium silicon The mineral of hydrochlorate composition are referred to as, and mullite is Al2O3-SiO2Binary compound uniquely stable in system has high temperature resistant, intensity Creep-resistant property and thermal stability high, thermal coefficient is small, high, while there is similar thermal expansion coefficient with carbofrax material. Therefore, the research of mullite complex silicon carbide porous material will be provided with wide prospect.Lot of domestic and foreign researcher is all right This porous material has carried out research, but current research mainly still utilizes mullite in-situ synthesized, by raw material Middle introducing carbofrax material occurs to aoxidize the silicon source in the silicon oxide layer and raw material to be formed using silicon carbide under high temperature Reaction is to form final silicon carbide/mullite composite porous material.
Aeroge equally has low-density, high ratio as a kind of light porous material for having three-D nano-porous structure The features such as surface area, high porosity, absorption, catalysis, it is heat-insulated and in terms of have wide application prospect.As can Carbofrax material and mullite material are prepared into porous aerogel structure, will be provided with more excellent service performance, current state The inside and outside relevant report about carbonization silica aerogel, (such as Chinese patent of patent No. CN102910926A), also about not Carry out the similar report of stone aerogel material, (Cluzel F, Larnac G, Phalippou J.Structure and thermal evolution of mullite aerogels[J].Journal of materials science,1991,26(22): 5979-5984), but there is no relevant document reports for silicon carbide/mullite aerogel composite.It will in this patent Mullite and carbonization silica aerogel progress are compound, pass through a step sol-gel method combination supercritical drying process and heat treatment work Skill condition prepares blocky high temperature resistant height composite aerogel more anti-oxidant than table mullite/SiC, and silicon carbide so can be improved The agglomeration property (carbonization silica aerogel agglomeration property very poor) of material, two can also preferably improve the antioxygen of carbofrax material Change performance.
Summary of the invention
It is provided a kind of blocky high than table mullite-carbon the purpose of the invention is to improve the shortcomings of the prior art The preparation method of SiClx aerogel composite, this method materials and simple process, microstructure controllability is good, the gas prepared Gel rubber material has the characteristics such as low-density, Gao Bibiao, anti-oxidant, high temperature resistant, while each with that can be prepared into after fiber composite The sample of kind shape, to realization aerogel material in fields such as catalyst carrier, high-temperature gas filter, UF membrane, sensors Application have positive production meaning.
The technical solution of the present invention is as follows: the blocky high preparation method than table mullite silicon carbide aerogel composite, Specific step is as follows:
(1) after evenly mixing by carbon source, formaldehyde, ethyl alcohol, water, silicon source, it in 20~50 DEG C of at a temperature of uniform stirring, obtains Organic/oxidation aluminum binary sol system of hydrolysis；
(2) silicon source is added in binary sol system obtained in step (1), continue 20~50 DEG C at a temperature of Even stirring, the ternary sol system being crosslinked；
(3) ternary sol system obtained in step (2) is poured into reaction in mold and places 10~30h to gel；
(4) Ageing solution will be added in step (3), is replaced in 25~75 DEG C of baking oven；
(5) wet gel obtained in step (4) is subjected to CO2Supercritical drying processing, obtain organic/formaldehyde/silica/ Alumina composite aeroge；
(6) composite aerogel obtained in step (5) is heat-treated under inert atmosphere gas shield, to obtain C/ mullite/SiC composite aerogel；
(7) C/ mullite/SiC composite aerogel obtained in step (6) is placed in air atmosphere and carries out Calcination for removing carbon, To obtain final blocky porous mullite/SiC aerogel composite；
Wherein: the carbon source, ethyl alcohol, water, silicon source in step (1) are according to 1:(1~4): (10~30): (1~5): (0.1~ 0.5) molar ratio uniformly mixes；Silicon source in step (2) is with carbon source according to molar ratio (0.5~5): 1 is mixed.
Carbon source described in preferred steps (1) is catechol-formaldehyde, resorcinol-formaldehyde, mixture cresol-formaldehyde, equal benzene Or mixtures thereof triphenol-one of formaldehyde or phenolic resin.Silicon source described in preferred steps (1) be Aluminium chloride hexahydrate, Or mixtures thereof one of ANN aluminium nitrate nonahydrate, aluminium secondary butylate or aluminium isopropoxide.
Silicon source described in preferred steps (2) is three aminopropyl triethoxysilanes, three tert-butyl peroxide silicon of vinyl Or mixtures thereof one of alkane, butadienyl triethoxysilane or γ-glycidyl ether oxygen propyl trimethoxy silicane.
Speed of agitator is 400~600rpm in preferred steps (1), and mixing time is 0.5~4h；Stirring turns in step (2) Speed is 400~600rpm, and mixing time is 0.1~2h.
Ageing solution described in preferred steps (4) is one of ethyl alcohol, methanol, acetone, ether, n-amyl alcohol or isopropanol Or mixtures thereof.
Drying means described in preferred steps (5) is that drying temperature is 50~70 DEG C, in autoclave pressure be 8~ 12MPa, outgassing rate are 5~20L/min, and drying time is 8~20h.
Displacement number is 3~6 times in preferred steps (5), each time swap is 12~for 24 hours.
Heat treatment temperature described in preferred steps (6) is between 1000~1500 DEG C；Heating rate be 2~10 DEG C/ Min, heat treatment time are 3~10h；Inert atmosphere protective gas is argon gas, nitrogen or helium.
The hot calcination temperature of air is between 400~800 DEG C described in preferred steps (7)；Heating rate be 3~5 DEG C/ Min, heat treatment time are 2~5h.
The utility model has the advantages that
(1) simple process.Using a step sol-gel method, while carbon source, silicon source and silicon source are introduced, and by subsequent Supercritical drying, carbonization and carbothermic reduction process, make silicon source and silicon source generate mullite phase at high temperature, and silicon source and carbon source generate Carborundum phase, finally again by carbon template at air forged burning-off, to finally be made blocky high more multiple than table mullite/silicon carbide Close aeroge.
(2) in-situ preparation carborundum phase.Currently when preparing silicon carbide/mullite composite material, be with silicon carbide micro-powder, Alumina powder is reaction raw materials, and the silicon oxide layer and oxidation reactive aluminum formed at high temperature by carborundum phase forms mullite Phase.And in the present solution, silicon carbide be also with it is generated in-situ, be to be obtained by the carbothermic reduction process of silicon source and carbon source at high temperature It arrives, therefore structure is finer, simultaneously because the presence of carbon template, the material porosity of preparation is higher, and specific surface area is bigger.
(3) silicon carbide prepared in this method/mullite aerogel material is complete bulk, simultaneously because mullite phase Introducing further improves the antioxygenic property of carbofrax material, this is for realizing aerogel material in catalyst carrier, high temperature The application in the fields such as pneumatic filter, UF membrane, sensor has positive meaning.
Detailed description of the invention
Fig. 1 is the height of bulk made from example 1 than table mullite/silicon carbide compound aerogel material photo in kind；
Fig. 2 is to adjust the differential responses object concentration (silicon source, silicon source and carbon source summation) obtained after ethanol content in example 2 The XRD diffraction pattern of the lower ternary aeroge system after 1400 DEG C of carbon thermal reductions.
Specific embodiment
Example 1
By catechol, formaldehyde, ethyl alcohol, water, Aluminium chloride hexahydrate, 1:2:17.4:2:0.18 is uniformly mixed in molar ratio Afterwards, the temperature at 20 DEG C, uniform stirring 0.5h under revolving speed 600rpm obtain organic/oxidation aluminum binary sol body of partial hydrolysis System.Then by three aminopropyl triethoxysilanes to be that 0.77:1 is added to above-mentioned binary sol system with catechol molar ratio In, continue the temperature at 20 DEG C, uniform stirring 0.1h under revolving speed 600rpm, is subsequently poured into reaction in mold and places 10h to gel Ethyl alcohol Ageing solution is added afterwards, displacement 3 times, each 12h are carried out in 25 DEG C of baking oven.Then CO is carried out to the wet gel2It is super to face Boundary is dried, and supercritical reaction temperature is 50 DEG C.Reaction kettle pressure is 10MPa, outgassing rate 5L/min, and drying time is Catechol/formaldehyde/silica/alumina composite aerogel is obtained after 20h.The composite aerogel is protected in argon atmosphere gas Shield is lower to carry out 1000 DEG C of heat treatments, and heating rate is 3 DEG C/min, soaking time 3h, so that it is compound to obtain C/mullite/SiC Aeroge.Finally obtained C/mullite/SiC composite aerogel is placed in air atmosphere and carries out Calcination for removing carbon at 500 DEG C, Heating rate 3 DEG C/min, soaking time 3h, to obtain the final porous mullite/SiC aerogel composite of bulk.Through Characterization discovery is crossed, bulk height is 0.25g/cm than table mullite/silicon carbide compound aerogel material density3, specific surface area For 134m2/ g, the oxidation resistance temperature than pure carbofrax material improve 98 DEG C.Obtained bulk height is than table mullite/silicon carbide The photo in kind of aerogel composite is as shown in Figure 1, it will be seen from figure 1 that mullite obtained/silicon carbide compound aeroge Material is bulk material, and the light green color of carbofrax material is presented in surface, although intensity is poor, porosity is high, specific surface area Greatly.
Example 2
By catechol, formaldehyde, ethyl alcohol, water, Aluminium chloride hexahydrate, 1:3:25.3:3:0.32 is uniformly mixed in molar ratio Afterwards, the temperature at 30 DEG C, uniform stirring 1h under revolving speed 500rpm obtain organic/oxidation aluminum binary sol system of partial hydrolysis. Then by butadienyl triethoxysilane to be that 2:1 is added in above-mentioned binary sol system with catechol molar ratio, after Continue the temperature at 30 DEG C, uniform stirring 0.5h under revolving speed 500rpm, be subsequently poured into mold reaction to gel, place after 20h plus Enter acetone Ageing solution, displacement 4 times, each 18h are carried out in 60 DEG C of baking oven.Then CO is carried out to the wet gel2Supercritical drying Dry processing, supercritical reaction temperature are 60 DEG C.Reaction kettle pressure is 12MPa, outgassing rate 10L/min, drying time 10h After obtain catechol/formaldehyde/silica/alumina composite aerogel.By the composite aerogel in argon atmosphere gas shield Lower to carry out 1400 DEG C of heat treatments, heating rate is 5 DEG C/min, soaking time 5h, to obtain the compound gas of C/mullite/SiC Gel.Finally obtained C/mullite/SiC composite aerogel is placed in air atmosphere and carries out Calcination for removing carbon at 700 DEG C, is risen Warm 5 DEG C/min of rate, soaking time 4h, to obtain the final porous mullite/SiC aerogel composite of bulk.By Characterization discovery, bulk height are 0.32g/cm than table mullite/silicon carbide compound aerogel material density3, specific surface area is 156m2/ g, the oxidation resistance temperature than pure carbofrax material improve 94 DEG C.Adjust the differential responses object concentration obtained after ethanol content Under (silicon source, silicon source and carbon source summation) after 1400 DEG C of carbon thermal reductions ternary aeroge system XRD diffraction pattern such as Fig. 2 institute Show, it can be seen from the figure that after 1400 DEG C of carbon thermal reductions, when reactant concentration is located at 20%~45%, in material There is more apparent silicon carbide and mullite phase, while also containing a large amount of carbon template in material, but passes through subsequent After air calcination heat treatment, structure is not collapsed, and material still shows the complete bulk of Fig. 1.
Example 3
By resorcinol, formaldehyde, ethyl alcohol, water, ANN aluminium nitrate nonahydrate in molar ratio 1:4:30:5:0.46 after evenly mixing, The uniform stirring 2h at 35 DEG C of temperature, revolving speed 500rpm obtains organic/oxidation aluminum binary sol system of partial hydrolysis.So Three aminopropyl triethoxysilanes are continued with being that 5:1 is added in above-mentioned binary sol system with resorcinol molar ratio afterwards The uniform stirring 1.5h at 35 DEG C of temperature, revolving speed 400rpm is subsequently poured into reaction in mold and is added after placing 25h to gel Ethyl alcohol Ageing solution carries out displacement 5 times, every time for 24 hours in 70 DEG C of baking oven.Then CO is carried out to the wet gel2Supercritical drying Processing, supercritical reaction temperature are 55 DEG C.Reaction kettle pressure is 9MPa, outgassing rate 20L/min, after drying time is 13h Obtain resorcin/formaldehyde/silica/alumina composite aerogel.By the composite aerogel under the protection of nitrogen atmosphere gas 1350 DEG C of heat treatments are carried out, heating rate is 8 DEG C/min, soaking time 6h, to obtain the compound airsetting of C/mullite/SiC Glue.Finally obtained C/mullite/SiC composite aerogel is placed in air atmosphere and carries out Calcination for removing carbon at 800 DEG C, is heated up Rate 5 DEG C/min, soaking time 2h, to obtain the final porous mullite/SiC aerogel composite of bulk.By table It levys existing, bulk height is 0.22g/cm than table mullite/silicon carbide compound aerogel material density3, specific surface area is 156m2/ g, the oxidation resistance temperature than pure carbofrax material improve 125 DEG C.
Example 4
By 1,3,5-trihydroxybenzene, formaldehyde, ethyl alcohol, water, aluminium secondary butylate in molar ratio 1:1.4:12:1.6:0.25 after evenly mixing, The uniform stirring 3h at 40 DEG C of temperature, revolving speed 400rpm obtains organic/oxidation aluminum binary sol system of partial hydrolysis.So Afterwards by three tert-butyl peroxide silane of vinyl to be that 3:1 is added in above-mentioned binary sol system with 1,3,5-trihydroxybenzene molar ratio, Continue the temperature at 40 DEG C, uniform stirring 1.3h under revolving speed 400rpm, is subsequently poured into mold reaction to gel, after placing 15h N-amyl alcohol Ageing solution is added, displacement 3 times, each 18h are carried out in 50 DEG C of baking oven.Then CO is carried out to the wet gel2It is super to face Boundary is dried, and supercritical reaction temperature is 70 DEG C.Reaction kettle pressure is 9.5MPa, outgassing rate 15L/min, drying time To obtain 1,3,5-trihydroxybenzene/formaldehyde/silica/alumina composite aerogel after 8h.By the composite aerogel in helium atmosphere gas Protection is lower to carry out 1500 DEG C of heat treatments, and heating rate is 5 DEG C/min, soaking time 10h, to obtain C/mullite/SiC Composite aerogel.Finally obtained C/mullite/SiC composite aerogel is placed in air atmosphere at 600 DEG C calcine and is removed Carbon, heating rate 3 DEG C/min, soaking time 5h, to obtain the final porous mullite/SiC composite aerogel material of bulk Material.It is found by characterization, bulk height is 0.26g/cm than table mullite/silicon carbide compound aerogel material density3, compare table Area is 186m2/ g, the oxidation resistance temperature than pure carbofrax material improve 156 DEG C.

Claims (10)

1. the blocky high preparation method than table mullite silicon carbide aerogel composite, the specific steps of which are as follows:
(1) after evenly mixing by carbon source, formaldehyde, ethyl alcohol, water, silicon source, it in 20~50 DEG C of at a temperature of uniform stirring, is hydrolyzed It is organic/oxidation aluminum binary sol system；
(2) silicon source is added in binary sol system obtained in step (1), continue 20~50 DEG C at a temperature of uniformly stir It mixes, the ternary sol system being crosslinked；
(3) ternary sol system obtained in step (2) is poured into reaction in mold and places 10~30h to gel；
(4) Ageing solution will be added in the gel of step (3), is replaced in 25~75 DEG C of baking oven；
(5) wet gel obtained in step (4) is subjected to CO2Supercritical drying processing, obtains organic/formaldehyde/silica/oxidation Aluminium composite aerogel；
(6) composite aerogel obtained in step (5) is heat-treated under inert atmosphere gas shield, to obtain C/ not Carry out stone/SiC composite aerogel；
(7) C/ mullite/SiC composite aerogel obtained in step (6) is placed in air atmosphere and carries out Calcination for removing carbon, thus Obtain final blocky porous mullite/SiC aerogel composite；
Wherein: the carbon source, formaldehyde, ethyl alcohol, water, silicon source in step (1) are according to 1:(1~4): (10~30): (1~5): (0.1~ 0.5) molar ratio uniformly mixes；Silicon source in step (2) is with carbon source according to molar ratio (0.5~5): 1 is mixed.
2. preparation method according to claim 1, it is characterised in that carbon source described in step (1) be catechol, Or mixtures thereof one of benzenediol, mixture cresol or 1,3,5-trihydroxybenzene.
3. preparation method according to claim 1, it is characterised in that silicon source described in step (1) is six chloride hydrates Or mixtures thereof one of aluminium, ANN aluminium nitrate nonahydrate, aluminium secondary butylate or aluminium isopropoxide.
4. preparation method according to claim 1, it is characterised in that silicon source described in step (2) is three aminopropyls, three second Oxysilane, three tert-butyl peroxide silane of vinyl, butadienyl triethoxysilane or γ-glycidyl ether oxygen propyl three Or mixtures thereof one of methoxy silane.
5. preparation method according to claim 1, it is characterised in that speed of agitator is 400~600rpm in step (1), is stirred Mixing the time is 0.5~4h；Speed of agitator is 400~600rpm in step (2), and mixing time is 0.1~2h.
6. preparation method according to claim 1, it is characterised in that Ageing solution described in step (4) be ethyl alcohol, methanol, Or mixtures thereof one of acetone, ether, n-amyl alcohol or isopropanol.
7. preparation method according to claim 1, it is characterised in that drying process described in step (5) is drying temperature It is 50~70 DEG C, pressure is 8~12MPa in autoclave, and outgassing rate is 5~20L/min, and drying time is 8~20h.
8. preparation method according to claim 1, it is characterised in that the number replaced in step (4) is 3~6 times, every time Time swap be 12~for 24 hours.
9. preparation method according to claim 1, it is characterised in that heat treatment temperature described in step (6) 1000~ Between 1500 DEG C；Heating rate is 2~10 DEG C/min, and heat treatment time is 3~10h；Inert atmosphere protective gas is argon gas, nitrogen Gas or helium.
10. preparation method according to claim 1, it is characterised in that the hot calcination temperature of air described in step (7) exists Between 400~800 DEG C；Heating rate is 3~5 DEG C/min, and calcination time is 2~5h.
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CN110028048B (en) * 2019-04-04 2023-04-28 南京工业大学 Preparation method of high-temperature-resistant light silicon nitride aerogel material
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