CN104692403B - Preparation method of single-phase mullite sol - Google Patents
Preparation method of single-phase mullite sol Download PDFInfo
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- CN104692403B CN104692403B CN201410696774.2A CN201410696774A CN104692403B CN 104692403 B CN104692403 B CN 104692403B CN 201410696774 A CN201410696774 A CN 201410696774A CN 104692403 B CN104692403 B CN 104692403B
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Abstract
The invention discloses a preparation method of single-phase mullite sol. The preparation method comprises the steps of preparing fresh aluminum hydroxide precipitate, preparing aluminum oxide suspension liquid, introducing a silicon source into the aluminum oxide suspension liquid, and carrying out decondensation on mixed suspension liquid, so as to prepare mullite sol. According to the preparation method, the requirement for inhibiting hydrolysis speed of aluminum alkoxide is avoided, process parameters such as pH value and environment humidity are not specially required, the process is simple, and the requirement on synthesis equipment is low; the preparation method is applicable to large-scale industrial production.
Description
Technical field
The present invention relates to a kind of preparation method of single-phase mullite sol, belongs to chemical technology field.
Background technology
Mullite (Mullite) is Al2O3-SiO2Unique stable compound in binary system, stoichiometric equation is
3Al2O3·2SiO2, natural mullite is very rare, and high performance mullite is by synthetic.Due to mullite have it is outstanding
Physical and chemical performance, such as excellent high-temperature oxidation resistant, creep resistant, corrosion-resistant, relatively low thermal coefficient of expansion and thermal conductivity are relatively low
Dielectric constant and dielectric loss, higher mechanical strength and toughness etc., the mullite ceramic with mullite as principal crystalline phase is recognized
To be a kind of ideal High-Temperature Engineering Ceramics.In recent decades, mullite is in high temperature heat structure, electromagnetism and optical field
Widely paid close attention to by increasingly, with wide future in engineering applications.
Due to being capable of low temperature preparation high-purity mullite powder, mullite fiber, mullite by " sol-gel " method
Material, mullite compact block, mullite coating etc., the research extremely research worker favor of mullite sol.According to mixing
Uniformity coefficient, mullite sol can be divided into single-phase glue and two-phase glue.The uniformity coefficient of single-phase glue mixing is high, belongs to molecule or atom
Mixing on level, preparation condition is more harsh.Arrangement of the Si-O-Al atomic groups in its amorphous state on atom level with not
Carry out stone structure similar, therefore mullite can be converted into by amorphous state in 1000 DEG C or so presomas.
Report the preparation method of several single-phase mullite sols in disclosed document patent both at home and abroad, most commonly seen one
The preparation method of the single-phase glue of kind of mullite be proposed by Hoffman et al (J.Am.Ceram.Soc.1984,67 (7)：
468-471).It is exactly in brief that first the aluminum nitrate with water of crystallization is dissolved in ethanol, then makes it with tetraethyl orthosilicate
Ethanol solution is mixed to get single-phase mullite sol.The core of the method is slow by limited crystallization water management hydrolytic process
Slowly and carry out step by step.Chinese patent CN1810722A discloses a kind of low temperature sintering technology of mullite ceramic, wherein using
The method is prepared for the single-phase colloidal sol of mullite.
There are document report (Joumal of sol-gel science and technology 1997,10：19-30；
Journal of sol-gel science and technology 1999,15：191-199), tert-butyl alcohol aluminum is adopted for aluminum
Source, tetraethyl orthosilicate is silicon source, and isopropanol or ethanol make solvent, by control ph, regulating environmental humidity, controls slow water
Solution, can also prepare single-phase mullite sol.Chinese patent CN 102602947A report one kind and do not adopt alcohol, water as solvent
Single-phase mullite sol preparation method, invention together does silicon source using solvable al inorganic salt, aluminium-alcohol salt, first by soluble aluminum
Salt is dissolved in organic solvent, with the pH value of acid-conditioning solution after, add alfol reactant salt 10-40 minutes, add silicon source water
After solution 12-36 hours, heating 10-60 hours form mullite sol.The core of such method is by control system environment
Realize slow hydrolysis.
Additionally, the hydrolysis rate of aluminium salt can also be controlled by adding various chelating agen in system, do not come so as to prepare
The single-phase colloidal sol of stone.Such as, Xiamen University Chen Li richnesses seminar with tert-butyl alcohol aluminum as silicon source, the tetraethyl orthosilicate of partial hydrolysiss is silicon
Source, addition ethyl acetoacetate is prepared for single-phase mullite as chelating agen, addition polyvinylpyrrolidone as into fine auxiliary agent
Colloidal sol, and be prepared for gelatinous fibre (Xiamen University's journal (natural science edition), 2009,48 (4)：610-612).
To sum up, prior art is in the preparation process of single-phase mullite sol, or high energy consumption, long preparation period, or
Technological parameter (such as pH value, temperature, ambient humidity) is required strict, need to add extra chelating agen, it is complex process, repeatable
Property difference and raw material is expensive alkoxide, it is unsatisfactory.
The content of the invention
It is an object of the invention to overcome prior art not enough, there is provided a kind of process is simple, energy consumption are low, manufacturing cycle
The preparation method of single-phase mullite sol that is short, inexpensive, being easy to high-volume synthesis.
The technical solution of the present invention：A kind of preparation method of single-phase mullite sol, is realized by following steps：
The first step, prepares fresh aluminum hydroxide precipitation,
The present invention at ambient temperature, with inorganic aluminate as raw material, obtains fresh by adding the method for excessive alkali
Aluminum hydroxide precipitation, does not use the aluminium-alcohol salt of costliness as raw material, reduces cost.This step can be prepared using following techniques
The method that general inorganic aluminate can be adopted to prepare the precipitation of aluminium hydroxide.
Inorganic aluminate is configured to into the aqueous solution that molar concentration is 0.2~2M, under the conditions of being kept stirring for, thereto progressively
Deca molar concentration is the inorganic alkali solution of 0.2~1.5M, until have precipitation generate after, then be stirred at room temperature 30min~
60min, subsequent filtration washing obtains solid matter.
The present invention is not particularly limited to inorganic aluminate species, can be using in common aluminum sulfate, aluminum chloride, aluminum nitrate
It is a kind of.The present invention is not particularly limited to inorganic base species, can adopt common ammonia, sodium hydroxide, potassium hydroxide, Ammonium bicarbonate food grade
In one kind, be optimal with ammonia.Inorganic aluminate, inorganic alkali concn are unsuitable excessive in the present invention, if concentration is too big, stir in room temperature
Mix, it is scattered inefficient, it may be desirable to a certain degree of heating, it is impossible to operated at room temperature, increased cost；And concentration
Precipitation is generated when too low very little.The present invention gives preferred concentration range, has taken into account ambient operation and precipitation yields.
The method for extracting solid matter is filter paper vacuum filtration or centrifugation.
Aluminum hydroxide precipitation prepared by this step is needed in subsequent step using preparing in 3 front hours, existing
Existing the using of system is optimal.
Second step, prepares aluminum oxide suspension,
The fresh aluminum hydroxide precipitation obtained in the first step is scattered in dehydrated alcohol, is stirred at room temperature, obtained
Aluminum oxide suspension；
Dehydrated alcohol is dispersant in this step, as long as aluminum hydroxide precipitation can be made uniformly to disperse, referring generally to
Consumption is aluminum hydroxide precipitation and dehydrated alcohol quality in the range of 1: 10~20, is selected also dependent on concrete condition.
Certain hour is stirred under room temperature, the aluminum oxide suspension of white is obtained.
3rd step, introduces silicon source in aluminum oxide suspension,
Holding is stirred at room temperature that condition is constant, according to the ratio of Al/Si mol ratios 3/1 to Deca silicic acid in aluminum oxide suspension
Ester, after esters of silicon acis is all dripped, continues to stir certain hour, and mixing time is typically not less than 2 hours.
This step esters of silicon acis species does not have particular/special requirement, can be methyl silicate, tetraethyl orthosilicate, positive silicic acid propyl ester, just
One kind in butyl silicate, it is the most frequently used for tetraethyl orthosilicate.
4th step, mix suspending lyolysis is coagulated,
Holding is stirred at room temperature that condition is constant, rubs to Deca in mixing suspension according to the ratio of Al/H+ mol ratios 1~10: 1
Your concentration is the diluted acid of 1~2M, it can be found that the white of suspension is taken off quickly during Deca, nattier blue breast occurs in system
Light, continues to stir the mullite sol that certain hour obtains pale yellow transparent.
The diluted acid of approximate quantity, solidifying using the big acidolysis of molar concentration, the micelle granule obtained in follow-up colloidal sol is less.This step
Rapid desired molar concentration scope is in 10-200nm interval optimum range value, beyond this scope by size controlling, it is possible to
Obtain the mullite sol of the big particle diameter of low concentration or cannot get stable sol.
Under equal conditions, the total addition level of diluted acid is bigger, and micelle granule is less in follow-up colloidal sol.This step requires that diluted acid adds
Dosage scope is in 10-200nm interval optimum, beyond this scope, it is possible to obtain the big grain of low concentration by size controlling
The mullite sol in footpath cannot get stable sol.
The present invention is not particularly limited to the species of diluted acid, can adopt conventional hydrochloric acid, nitric acid, sulphuric acid, formic acid, ice vinegar
One kind in acid, is optimal with nitric acid.Can be corresponding with inorganic aluminate when mineral acid is selected, so draw less in system
Enter several ions, it is convenient when the later stage uses, it is possible to use not homologous species.
The present invention is not to suppress the hydrolysis rate of aluminium-alcohol salt to make itself and estersil cohydrolysis by various control devices, but logical
Crossing the mode for adding acidolysis solidifying makes aluminum oxide suspension while solution is solidifying and esters of silicon acis cohydrolysis, so as to realize Al3+And Si4+
High evenness mixing on molecule or atom level.In the solution solidifying stage, can the concentration of diluted acid homogeneous for be formed with addition
Stable mullite sol is most important.On the one hand diluted acid is the solidifying inducement of solution, and silicic acid ester hydrolysis are on the one hand promoted again, is formed
Stable sol.
Present invention beneficial effect compared with prior art：
(1) present invention avoids the demand to suppressing aluminium-alcohol salt hydrolysis rate, does not have to technological parameters such as pH value, ambient humidities
There is special requirement, process is simple is low to synthesis device requirement, is suitable to large-scale industrial production；
(2) raw material types according to the present invention are few, it is only necessary to which tetraethyl orthosilicate, ethanol and a kind of inorganic aluminate, one kind are dilute
Acid, it is not necessary to adjust the proportioning between various silicon sources, and because technological process avoids the need to controlling aluminium-alcohol salt hydrolysis rate
Ask, it is not necessary to the pH value of additional acid-alkali accommodation reaction system, it is not necessary to additional chelating agen, effectively reduce raw material factor pair
The impact of single-phase mullite sol forming process, favorable repeatability.Main aluminium source raw material according to the present invention be al inorganic salt, valency
Lattice are cheap, are suitable to commercial Application；
(3) present invention whole process is carried out in room temperature, it is not necessary to heated, energy consumption is low, saves production cost, energy-conserving and environment-protective；
(4) manufacturing cycle of single-phase mullite sol that the present invention is greatly shortened, the whole production cycle is less than 3 days, far
Less than being hydrolyzed to the existing technology of preparing of core slowly；
(5) the single-phase mullite sol particle diameter of present invention preparation is little and distribution is homogeneous, and solid content is in 10% or so, Jing Guoxuan
Turn evaporation or stand after solvent flashing concentration, solid content can reach 30%, be suitable to (1000 DEG C or so) preparation fiber reinforcements of low temperature
Mullite composite, reduces damage of the high-temperature process (1200-1300 DEG C) needed for two-phase glue mullitization to reinforcing fiber
Wound, improves material property.
Description of the drawings
Fig. 1 is moulding process flow process figure of the present invention；
Fig. 2 is the powder obtained after 1050 DEG C of heat treatments after mullite sol of the present invention is xerogel in 80 DEG C of drying
The XRD figure of body, wherein " * " represents the characteristic peak of mullite.
Specific embodiment
Below in conjunction with accompanying drawing and instantiation, the present invention is described in detail.
Embodiment 1
Aluminum nitrate and tetraethyl orthosilicate are adopted for silicon source and silicon source, dust technology is liquefacient, prepares single-phase mullite molten
Glue.
Prepare as shown in figure 1, being realized by following steps：
The 1st, aluminum nitrate is configured to the aqueous solution of 1M, thereto the progressively ammonia of Deca 0.5M, until after having precipitation to generate,
30min is stirred at room temperature again, and subsequent filtering and washing obtains solid matter.
2nd, the solid matter for obtaining sucking filtration is scattered in dehydrated alcohol according to the ratio of mass ratio 1: 10, is stirred at room temperature
Mix the aluminum oxide suspension for obtaining white for 6 hours.
3rd, keep be stirred at room temperature it is constant, according to the ratio of Al/Si mol ratios 3/1 to the positive silicic acid of Deca in aluminum oxide suspension
Ethyl ester, after esters of silicon acis is all dripped, continues to stir 2 hours.
4th, keep be stirred at room temperature it is constant, according to Al/H+ mol ratios 4/1 dust technology from ratio to Deca 2M in suspension,
It can be found that the white of suspension is taken off quickly during Deca, there is nattier blue opalescence in system, treats dust technology whole Deca
After complete, continue stirring and obtain transparent mullite sol in 12 hours.
Laser particle analyzer is adopted to measure the mean diameter of the sol particle for 36nm.Obtained sample as seen from Figure 2
Product do not have dephasign, are pure mullite powders, and peak type is sharp, it was demonstrated that crystal property is relatively good.Meanwhile, at 1050 DEG C of heat
Reason temperature proves that mullite sol prepared by the present invention is single-phase glue.
Embodiment 2
Aluminum chloride and tetraethyl orthosilicate are adopted for silicon source and silicon source, dilute hydrochloric acid is liquefacient, prepares single-phase mullite sol.
Aluminum chloride is configured to into the aqueous solution of 0.5M, thereto the progressively potassium hydroxide aqueous solution of Deca 0.2M, until having
After precipitation is generated, then 60min is stirred at room temperature, subsequent filtering and washing obtains solid matter.The solid matter that sucking filtration is obtained
Ratio according to mass ratio 1: 20 is scattered in dehydrated alcohol, and the aluminium oxide suspension for obtaining white for 18 hours is stirred at room temperature
Liquid.
Holding be stirred at room temperature it is constant, according to the ratio of Al/Si mol ratios 3/1 to the positive silicic acid second of Deca in aluminum oxide suspension
Ester, after esters of silicon acis is all dripped, continues to stir 2 hours.
Holding be stirred at room temperature it is constant, according to Al/H+ mol ratios 10/1 dilute hydrochloric acid from ratio to Deca 1M in suspension, drop
Plus during it can be found that the white of suspension is taken off quickly, there is nattier blue opalescence in system, treats that dust technology is all dripped
Afterwards, continue to stir to obtain transparent mullite sol in 12 hours.The mean diameter of the sol particle is measured using laser particle analyzer
For 74nm.
Embodiment 3
Aluminum sulfate and tetraethyl orthosilicate are adopted for silicon source and silicon source, dilute sulfuric acid is liquefacient, prepares single-phase mullite sol.
Aluminum sulfate is configured to into the aqueous solution of 2M, thereto the progressively ammonia of Deca 1M, until after having precipitation to generate, then
Stir 60min under room temperature, subsequent centrifugation and washing obtains solid matter.The solid matter that sucking filtration is obtained is according to mass ratio
1: 10 ratio is scattered in dehydrated alcohol, and the aluminum oxide suspension for obtaining white for 6 hours is stirred at room temperature.
Holding be stirred at room temperature it is constant, according to the ratio of Al/Si mol ratios 3/1 to the positive silicic acid second of Deca in aluminum oxide suspension
Ester, after esters of silicon acis is all dripped, continues to stir 2 hours.
Holding be stirred at room temperature it is constant, according to Al/H+ mol ratios 1/1 dilute sulfuric acid from ratio to Deca 1M in suspension, drop
Plus during it can be found that the white of suspension is taken off quickly, there is nattier blue opalescence in system, treats that dust technology is all dripped
Afterwards, continue to stir to obtain transparent mullite sol in 12 hours.The mean diameter of the sol particle is measured using laser particle analyzer
For 17nm.
Embodiment 4
Aluminum nitrate and tetraethyl orthosilicate are adopted for silicon source and silicon source, dust technology is liquefacient, prepares single-phase mullite sol.
Aluminum nitrate is configured to into the aqueous solution of 1M, thereto the progressively ammonium bicarbonate soln of Deca 1.5M, until there is precipitation
After generation, then 60min is stirred at room temperature, subsequent filtering and washing obtains solid matter.The solid matter that sucking filtration is obtained according to
The ratio of mass ratio 1: 10 is scattered in dehydrated alcohol, and the aluminum oxide suspension for obtaining white for 18 hours is stirred at room temperature.
Holding be stirred at room temperature it is constant, according to the ratio of Al/Si mol ratios 3/1 to the positive silicic acid second of Deca in aluminum oxide suspension
Ester, after esters of silicon acis is all dripped, continues to stir 2 hours.
Holding be stirred at room temperature it is constant, according to Al/H+ mol ratios 3/1 dust technology from ratio to Deca 1M in suspension, drop
Plus during it can be found that the white of suspension is taken off quickly, there is nattier blue opalescence in system, treats that dust technology is all dripped
Afterwards, continue to stir to obtain transparent mullite sol in 24 hours.The mean diameter of the sol particle is measured using laser particle analyzer
For 45nm.
The molar concentration and addition of mean diameter and diluted acid has direct relation, knowable to embodiment 1,4, approximate quantity it is dilute
Acid, solidifying using the big acidolysis of molar concentration, the micelle granule obtained in follow-up colloidal sol is less；Knowable to embodiment 2,3,4, diluted acid
Total addition level it is bigger, micelle granule is less in follow-up colloidal sol.
Unspecified part of the present invention is known to the skilled person technology.
Claims (2)
1. a kind of preparation method of single-phase mullite sol, it is characterised in that comprise the following steps：
The first step, prepares fresh aluminum hydroxide precipitation；
Second step, prepares aluminum oxide suspension,
The fresh aluminum hydroxide precipitation obtained in the first step is scattered in dehydrated alcohol, is stirred at room temperature, aoxidized
Aluminum suspension；
3rd step, in aluminum oxide suspension silicon source is introduced,
Holding is stirred at room temperature constant, according to the ratio of Al/Si mol ratios 3/1 to Deca esters of silicon acis in aluminum oxide suspension, treats silicon
After acid esters is all dripped, continue stirring and obtain mixing suspension；
4th step, mix suspending lyolysis is coagulated,
Holding be stirred at room temperature it is constant, according to Al/H+The ratio of mol ratio 1~10: 1 continues to stir to Deca diluted acid in mixing suspension
Mix and obtain single-phase mullite sol；The molar concentration of the diluted acid is 1~2M.
2. the preparation method of a kind of single-phase mullite sol according to claim 1, it is characterised in that：The first step system
Standby fresh aluminum hydroxide precipitation, is realized by following steps,
A1.1, the inorganic aluminate aqueous solution that preparation molar concentration is 0.2~2M；
A1.2, step A1.1 prepare inorganic aluminate aqueous solution in Deca molar concentration be 0.2~1.5M inorganic alkali solution,
Until there is precipitation to generate, then 30min~60min is stirred at room temperature；
A1.3, fresh aluminum hydroxide precipitation will be obtained after precipitate filtration washing.
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| CN110004521B (en) * | 2019-02-28 | 2020-04-21 | 山东大学 | Preparation method of spinnable silicon-aluminum sol |
| CN111715202A (en) * | 2020-06-29 | 2020-09-29 | 沈阳三聚凯特催化剂有限公司 | Porous material and preparation method and application thereof |
| CN114538455B (en) * | 2022-04-09 | 2023-06-27 | 山东大学 | Low crystal transition temperature, small particle size and NO 3 Method for producing mullite sol with adjustable content |
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Non-Patent Citations (1)
| Title |
|---|
| "Mullite Formation from Mixtures of Alumina and Silica Sols: Mechanism and pH Effect";Carla C. Osawa et al，;《J. Braz. Chem. Soc.》;20051231;第16卷(第2期);实验部分，第252页左栏第3段和最后一段 * |
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