CN113173772B - Method for manufacturing polycrystalline alumina fiber gasket - Google Patents
Method for manufacturing polycrystalline alumina fiber gasket Download PDFInfo
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- CN113173772B CN113173772B CN202110506731.3A CN202110506731A CN113173772B CN 113173772 B CN113173772 B CN 113173772B CN 202110506731 A CN202110506731 A CN 202110506731A CN 113173772 B CN113173772 B CN 113173772B
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/24—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing alkyl, ammonium or metal silicates; containing silica sols
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B14/38—Fibrous materials; Whiskers
- C04B14/46—Rock wool ; Ceramic or silicate fibres
- C04B14/4618—Oxides
- C04B14/4625—Alumina
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/20—Mortars, concrete or artificial stone characterised by specific physical values for the density
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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Abstract
The invention discloses a method for manufacturing a polycrystalline alumina fiber liner, which comprises the steps of forming a precursor fiber aggregate after wet forming of precursor fibers, then carrying out heat treatment on the precursor fiber aggregate to convert the precursor fiber aggregate into the polycrystalline alumina fiber aggregate, and finally gluing and shaping the polycrystalline alumina fiber aggregate to prepare the polycrystalline alumina fiber liner.
Description
Technical Field
The invention relates to the technical field of fiber gaskets, in particular to a method for manufacturing a polycrystalline alumina fiber gasket.
Background
The air pollution prevention and control work in China faces unprecedented challenges, the control of tail gas pollution of mobile machinery and non-road mobile machinery has important significance for reducing pollutants such as NOx, PM2.5 and the like in air, and the current main technical route is to add a tail gas post-treatment system on the basis of reducing the original emission of an engine and treat the pollutants through gas-solid catalytic reaction.
The core of the tail gas after-treatment system is a catalytic unit which comprises a ceramic carrier, a liner and a metal shell. The gasket is usually arranged in the gap between the ceramic carrier and the metal shell and mainly plays a role of fixing, sealing and heat insulation. The gasket is typically an inorganic fiber based material and needs to be sufficiently secured by friction at ambient temperatures to engine exhaust temperatures.
The composition of the liner is primarily inorganic fibers and sometimes includes functional fillers and binders. The polycrystalline alumina fiber is one of common inorganic fibers of a gasket, the main components of the polycrystalline alumina fiber are alumina and silica, the content of the alumina is generally 65 to 98wt.%, the content of the silica is generally 2 to 35wt.%, and the polycrystalline alumina fiber with the content of the alumina being about 72% and the content of the silica being about 28% is generally called polycrystalline mullite fiber. The typical preparation method of the polycrystalline alumina fiber is a sol-gel method, namely, aluminum salt is condensed to prepare gel, then the gel is converted into precursor fiber by using a spinning method of spinning or spinning, and the precursor fiber is converted into a target product polycrystalline alumina fiber after heat treatment.
The current commercial polycrystalline alumina fiber liner comprises two types, namely a needle-punched polycrystalline alumina fiber liner and a papermaking polycrystalline alumina fiber liner. The difference in performance between the two is mainly reflected in the uniformity of the areal density distribution of the liner, the peel strength and the aged areal pressure. The distribution uniformity of the density of the gasket surface has a direct influence on the distribution uniformity of the pressure formed by the gasket on the ceramic carrier in the packaging unit, and influences the reliability and the service life of the packaging unit. The peel strength of the liner reflects the tightness of the bond between the liner layers, and too low a peel strength may result in the liner not being able to fit completely between the ceramic carrier and the metal shell. The aging surface pressure of the gasket reflects the residual capability of the gasket for providing fixing force for the ceramic carrier after long-term use, and the ceramic carrier is easy to loosen and fall off in the running process of a vehicle due to the excessively low aging surface pressure, so that the packaging unit is scrapped.
The needle punching method is to tile the polycrystalline alumina fiber with the fiber length of more than or equal to 30mm into a blanket, then to punch, and to form a fiber bundle by the movement of the barbed needle in the vertical direction of the fiber blanket to construct the connection between layers, so as to form the three-dimensional resilient structure of the pad. Because the long fiber is difficult to tile, the uniformity of the surface density of the gasket cannot be ensured. In addition, in producing a higher areal density liner, the needle travel is too great, the number of fibers at the end of the fiber bundle becomes less, and fiber breakage in the fiber bundle becomes more severe, resulting in a significant reduction in the peel strength of the liner. The polycrystalline alumina fiber liner is prepared by uniformly dispersing polycrystalline alumina short fibers in water, adding a binder to perform wet forming, or coating a glue after the wet forming, drying and shaping. Compared with a needle punching method, the papermaking method has the advantages that the weight distribution of fibers in unit area is more uniform, layers are connected through the organic adhesive, and the high peel strength can be still achieved under the condition of high areal density. However, the process of the papermaking process requires the use of staple fibers.
If the short fiber is directly prepared by adjusting the process parameters in the spinning stage, the diameter of the fiber is enlarged, the shot is increased, and the performance of the fiber is reduced. The common method is to carry out short cutting treatment on the polycrystalline alumina fiber, and the process inevitably causes damage to the structure of the fiber, so that the defects such as cracks exist on the fiber, and the aging surface pressure of the gasket is further influenced.
Therefore, it is a problem to be studied to provide a polycrystalline alumina fiber gasket and a method for manufacturing the same, which can ensure the uniformity of the areal density distribution of the gasket, while still having good peel strength at higher areal densities and improving the aged areal pressure of the gasket.
Disclosure of Invention
The invention aims to provide a polycrystalline alumina fiber liner which has good peeling strength at higher areal density and improves the aging surface pressure of the liner while ensuring the uniformity of the areal density distribution of the liner, and a manufacturing method thereof.
The purpose of the invention is realized as follows:
a method for manufacturing a polycrystalline alumina fiber gasket is characterized in that: a polycrystalline alumina fiber gasket is composed of polycrystalline alumina fibers, an organic binder and an inorganic binder, wherein the weight proportion of the polycrystalline alumina fibers is more than 80 percent, the weight proportion of the organic binder is 2 to 20 percent, and the weight proportion of the inorganic binder is 0~5 percent; the polycrystalline alumina fiber comprises alumina and silica, and the weight ratio of the alumina to the silica is (72-85): (15-28); the manufacturing method of the polycrystalline alumina fiber gasket comprises the following steps:
step 1: preparing sol-gel, mixing an aluminum source and a silicon source according to a set molar ratio, adding a spinning auxiliary agent and a colloid stabilizer, and concentrating to obtain the sol-gel, wherein the aluminum-silicon weight ratio is (65-98): (35-2) a colloid with the viscosity of 0.1 to 10 Pa · s;
step 2: spinning to prepare precursor fiber, and preparing the colloid in the step 1 into the precursor fiber by a spinning method or a blowing method;
and step 3: adjusting the length of the precursor fiber in the step 2 and preparing precursor fiber dispersion liquid;
drying the precursor fiber collected in the step 2 at 100-200 ℃ for 5-60min to fully dry the surface of the precursor fiber so as to prevent the precursor fiber from forming adhesion in the next step; then shortening the precursor fiber by using a method capable of forming concentrated stress to obtain uniform precursor fiber dispersion liquid; the average length of the precursor fiber is 1.5-20.0 mm, and the method capable of forming concentrated stress in the step 3 is to use a high-speed vibrating blade for cutting, then soak the precursor fiber in a hydrophobic liquid medium to enable the concentration of the precursor fiber in the hydrophobic liquid medium to be 0.1-5 wt.%, stir the precursor fiber with high shear force, and stir the precursor fiber for 20-1800 s
And 4, step 4: preparing a precursor fiber aggregate by wet forming, and conveying the precursor fiber dispersion liquid uniformly dispersed in the step (3) into a vacuum filtration device for wet forming to obtain a precursor fiber aggregate;
and 5: preparing a polycrystalline alumina fiber assembly by heat treatment, keeping the precursor fiber assembly in the step 4 at 200 ℃ for more than 2 hours, then heating to the heat treatment end point temperature at the heating rate of 0.5-10.0 ℃/min, keeping the heat at the heat treatment end point temperature for 5-60min, and finally cooling to room temperature to obtain the polycrystalline alumina fiber assembly;
step 6: gluing and hot-pressing to prepare a polycrystalline alumina fiber pad, combining a pre-prepared organic binder and an inorganic binder with the polycrystalline alumina fiber aggregate in the step 5 by using an atomization spraying or integral dipping method, transferring the glued polycrystalline alumina fiber aggregate between two hot plates with the constant temperature of 80-250 ℃, compressing to 150-500kg/m < 3 >, and preserving the heat for 1-30min, wherein the organic binder in the polycrystalline alumina fiber aggregate is fully formed into a film and fully restricts the fiber, and removing the organic binder from the hot plates and cooling to room temperature to obtain the polycrystalline alumina fiber pad.
An aluminum source in the sol in the step 1 is a reaction product of an acidic substance, aluminum powder and water under a heating reflux condition, or a commercially available aluminum salt is used, a silicon source in the sol is TEOS and silica sol, a spinning auxiliary agent is a water-soluble high polymer with fiber forming capability, and the concentration of the spinning auxiliary agent is 0.1-15wt.%; the colloid stabilizer is water-soluble organic acid, and the concentration is 0.1 to 15wt.%.
When preparing precursor fiber by using the spinning method in the step 2, the colloid enters a spinning disc rotating at a high speed through a charging pipe, is spun out through a small hole formed in the side of the spinning disc under the action of centrifugal force, is stretched by the centrifugal force to form continuous liquid drops, is further stretched, dried and shaped into precursor fiber under the action of hot air, and finally the precursor fiber is collected on a fiber collecting belt at the bottom of a fiber forming cover.
The average length of the precursor fiber in the step 3 is 2 to 10.0mm; the concentration of the precursor fiber in a hydrophobic liquid medium is 0.1 to 1wt.%.
The final temperature of the heat treatment in the step 5 is 1000 to 1350 ℃, and a commercial heating furnace is adopted as equipment for the heat treatment.
In the step 6, the weight ratio of the organic binder in the polycrystalline alumina fiber pad is 2-20%, the weight ratio of the inorganic binder in the polycrystalline alumina fiber pad is 0~5%, and the weight ratio of the polycrystalline alumina fiber in the polycrystalline alumina fiber pad is more than 80%.
The invention has the beneficial effects that: the precursor fiber can be regarded as a multilayer structure with dry and hard surface and gel inner core, and compared with the polycrystalline alumina fiber, the precursor fiber has certain self-repairing capability after generating defects under the action of stress, thereby overcoming the defects that the prior papermaking method uses high pressure and high shear to generate local stress when the fiber is pretreated and adjusted in length, inevitably damages the polycrystalline alumina fiber structure and generates defects, and the rebound capability and the aging durability are reduced, so that the aging surface pressure of the invention is obviously improved compared with the prior papermaking method, and the surface density distribution uniformity and the peeling strength of the invention are obviously improved compared with the needling method.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a process flow diagram of the present invention.
FIG. 2 is a graph comparing the coefficient of variation of areal density of the polycrystalline alumina fiber mat of the present invention.
FIG. 3 is a graph comparing the peel strength of polycrystalline alumina fiber liners of the present invention.
FIG. 4 is a graph comparing the aged face pressure of a polycrystalline alumina fiber mat of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.
A polycrystalline alumina fiber liner is composed of polycrystalline alumina fibers, an organic binder and an inorganic binder, wherein the weight proportion of the polycrystalline alumina fibers is more than 80 percent, the weight proportion of the organic binder is 2-20 percent, and the weight proportion of the inorganic binder is 0~5 percent; and the polycrystalline alumina fibers comprise alumina and silica in a weight ratio of (72-85): (15-28).
As shown in fig. 1, a method for manufacturing a polycrystalline alumina fiber mat includes the steps of: step 1: preparing sol-gel, mixing an aluminum source and a silicon source according to a set molar ratio, adding a spinning auxiliary agent and a colloid stabilizer, and concentrating to obtain the sol-gel, wherein the aluminum-silicon weight ratio is (65-98): (35-2) colloid with the viscosity of 0.1 to 10 Pa.s, or mixing an aluminum source and a silicon source according to a set molar ratio, and concentrating to obtain the aluminum-silicon mixture with the weight ratio of (65-98): (35-2), and then adding a spinning auxiliary agent and a colloid stabilizer.
The aluminum source in the sol in the step 1 is a reaction product of an acidic substance, aluminum powder and water under a heating reflux condition, or a commercially available aluminum salt is used, the acidic substance can be aluminum chloride, hydrochloric acid, aluminum sulfate, sulfuric acid, aluminum nitrate, nitric acid, formic acid, acetic acid, lactic acid and the like and a mixture thereof, and the aluminum salt is basic aluminum chloride, aluminum lactate and the like.
The silicon source in the sol is TEOS or silica sol, and SiO is preferably used 2 15 to 50 percent of silica sol. The spinning auxiliary agent is water-soluble high molecular polymer with fiber forming ability, such as polyvinyl alcohol, polyethylene oxide, polyethylene glycol, polyacrylamide, polyvinylpyrrolidone, sucrose, starch or soluble derivatives of cellulose, such as acetic acid modified starch, hydroxyethyl starch, methyl cellulose or ethyl cellulose, etc. The concentration of the spinning auxiliary agent is 0.1 to 15wt.%.
The colloid stabilizer is water-soluble organic acid, such as lactic acid, acetic acid, citric acid, etc., with a concentration of 0.1-15wt.%.
Step 2: spinning to prepare precursor fiber, and preparing the colloid in the step 1 into the precursor fiber by a spinning method or a blowing method.
When the spinning method is used for preparing precursor fibers, the colloid enters a spinning disc rotating at a high speed through a charging pipe, is spun out through small holes formed in the side of the spinning disc under the action of centrifugal force, is stretched by the centrifugal force to form continuous liquid drops, is further stretched, dried and shaped into precursor fibers under the action of hot air, and finally is collected on a fiber collecting belt at the bottom of a fiber forming cover.
When the blowing method is used for preparing the precursor fiber, the colloid is sprayed out from the small holes on the spinneret plate, is stretched and shaped into the precursor fiber in high-speed airflow, and finally the precursor fiber is collected on a fiber collecting belt at the bottom of the fiber forming cover.
And step 3: adjusting the length of the precursor fiber in the step 2 and preparing precursor fiber dispersion liquid, and drying the precursor fiber collected in the step 2 at the temperature of 100-200 ℃ for 5-60min to ensure that the surface of the precursor fiber is sufficiently dried so as not to form adhesion in the next step; then the precursor fiber is shortened by a method capable of forming concentrated stress, and uniform precursor fiber dispersion liquid is obtained.
The average length of the precursor fiber in the step 3 is 1.5-20.0 mm, preferably 2.0-10.0 mm, and the method capable of forming concentrated stress is to use a blade which vibrates at a high speed to cut, then soak the precursor fiber in a hydrophobic liquid medium to enable the concentration of the precursor fiber in the hydrophobic liquid medium to be 0.1-5 wt.%, preferably 0.1-1wt.%, stir with high shearing force, and stir for 20-1800 s. The high shear stirring is performed by a stirring paddle capable of generating high shear force on the liquid.
The method for measuring the average length of the precursor fiber comprises the steps of observing and measuring under a microscope with magnification of 400x to 1000x after sampling, sampling from different positions until the total measurement amount reaches 125 precursor fibers or more, taking 0.5mm as a statistical basic unit, and taking the average value of the fiber length in a statistical result.
Hydrophobic liquid medium refers to liquids having a contact angle with water of more than 90 deg., typically mineral oils or the like. The precursor fiber is dispersed by using the hydrophobic liquid medium, so that the fiber can be effectively prevented from being dissolved and eroded due to the interaction between the hydrophilic group on the surface of the precursor fiber and the hydrophilic liquid phase.
And 4, step 4: preparing a precursor fiber aggregate by wet forming, and conveying the precursor fiber slurry uniformly dispersed in the step (3) into a vacuum filtration device for wet forming to obtain a precursor fiber aggregate; the vacuum filtration device generally comprises a continuously moving or stationary forming net, a vacuum box with at least one side having a certain aperture ratio, and a vacuum forming device. Commercially available vacuum filtration devices such as batch fiber forming machines, flat-wire formers, cylinder formers, inclined-wire formers and the like, which are commonly used in the papermaking industry, can be used. For the hydrophobic liquid after suction filtration, it is preferable to collect and reuse it.
And 5: preparing a polycrystalline alumina fiber assembly by heat treatment, keeping the precursor fiber assembly in the step 4 at 200 ℃ for more than 2 hours, then heating to the heat treatment end point temperature at the heating rate of 0.5-10.0 ℃/min, keeping the heat at the heat treatment end point temperature for 5-60min, and finally cooling to room temperature to obtain the polycrystalline alumina fiber assembly; the temperature of the heat treatment end point is 1000-1350 ℃, and the heat treatment equipment adopts commercial heating furnaces including muffle furnaces, vacuum furnaces, bell-jar kilns, roller kilns, tunnel kilns and the like.
And 6: gluing and hot-pressing to prepare a polycrystalline alumina fiber gasket, combining a pre-prepared organic binder and an inorganic binder with the polycrystalline alumina fiber aggregate in the step 5 by using an atomization spraying or integral dipping method, wherein the use amounts of the organic binder and the inorganic binder are enough to completely cover the whole part of the polycrystalline alumina fiber aggregate, the weight ratio of the organic binder in a final product is 2-20% no matter in the length direction or the thickness direction, and by using proper equipment design and process parameters, the polycrystalline alumina fiber aggregate which is uniformly distributed and glued in the polycrystalline alumina fiber aggregate is transferred between two hot plates with the constant temperature of 80-250 ℃, compressed to 150-500kg/m < 3 > and kept warm for 1 30min, at the moment, the organic binder in the polycrystalline fiber aggregate is fully formed into a film and fully restricts the alumina fiber, and the polycrystalline alumina fiber gasket is obtained after cooling to room temperature from the space between the hot plates.
In the step 6, the weight ratio of the organic binder in the polycrystalline alumina fiber pad is 2-20%, the weight ratio of the inorganic binder in the polycrystalline alumina fiber pad is 0~5%, and the weight ratio of the polycrystalline alumina fiber in the polycrystalline alumina fiber pad is more than 80%.
The method for measuring the surface density distribution uniformity of the prepared polycrystalline alumina fiber pad comprises the following steps: the polycrystalline alumina fiber mat was cut without space into 100mm x 100mm square sample blocks.
When the wet forming is continuous production, the width direction of the forming net needs to be taken out completely during the wet forming, and the sampling quantity in the length direction is consistent with the width direction.
When the wet forming is intermittent production, the square sample block should be cut off from the whole lining pad.
And weighing the square sample blocks one by using an analytical balance with the precision of at least 0.001g, and dividing the weight of each sample block by the area of 0.01m2 to obtain the surface density of each sample block. And (4) calculating the ratio of the standard deviation and the average value of the surface density of all the sample blocks, namely the coefficient of variation of the surface density of the gasket. The smaller the coefficient of variation of the areal density of the liner, the more uniform the areal density distribution.
The method for measuring the peeling strength of the polycrystalline alumina fiber liner comprises the following steps: cutting the polycrystalline alumina fiber liner sheet into strips of 200mm by 50mm;
when the wet forming is continuous production, the dimension of 200mm should be taken from the width direction of the forming net in the wet forming, and when the wet forming is intermittent production, the orientation of the sample strip is not required.
Stripping the sample strip by 50mm from the half thickness of the sample strip along the direction vertical to the thickness, respectively clamping the stripped parts at two sides by using a clamp, carrying out relative separation movement on the clamp at the speed of 10mm/min, measuring the pulling force required by moving the clamp in the whole stripping process, and defining the ratio of the stable value of the pulling force to 50mm as the stripping strength of the liner.
The method for measuring the aging surface pressure of the polycrystalline alumina fiber gasket comprises the following steps: the method comprises the steps of clamping a polycrystalline alumina fiber gasket in two parallel flat plates which are provided with heating devices, heating to 900 ℃, then dynamically adjusting a gap between the two flat plates to enable the density of the gasket to be continuously and cyclically changed between 400kg/m < 3 > and 333kg/m < 3 >, recording the pressure when the density of the gasket is 333kg/m < 3 > in each cyclic process by using a high-precision pressure sensor, dividing the pressure by the area of the gasket, and converting to obtain the pressure provided by the gasket. The pressure provided by the gasket at the 2500 th cycle was taken as the aging surface pressure of the gasket.
The first embodiment is as follows:
940g of crystalline aluminum chloride (with the content of 97%) is dissolved in 3200g of water, 500.5g of metal aluminum powder (with the granularity of 70-100 meshes and the aluminum content of more than 99%) is added, the mixture is stirred and reacted at 80 ℃ until the solution is completely clear, a small amount of water volatilizes in the reaction process, and a very small amount of unreacted metal aluminum powder is filtered out, so that a colorless and transparent basic aluminum chloride aqueous solution with the aluminum oxide content of 27.8wt.% and the aluminum/chlorine molar ratio of 1.97 is obtained.
To this aqueous aluminum chlorohydrate solution were added in the order of 35g of citric acid (citric acid monohydrate content 99%), 2202g of alkaline silica sol (average particle diameter 7 nm, silica content 20%), 1285g of aqueous polyvinyl alcohol solution (type 2088, concentration 5 wt.%).
After mixing uniformly, the mixture was distilled under heating at atmospheric pressure to obtain a colloid having a viscosity of 1.6 pas (measured at 25 ℃ C.) and a good spinnability.
And spinning by using a spinning disc with the diameter of 120mm, the height of 30mm and the aperture of 0.3mm to form fibers, wherein the rotating speed of the spinning disc is 3500 rpm, the hot air temperature is 45 ℃, and the colloid feeding amount is 1.5L/hr, so that 3500g of precursor fibers with the weight ratio of aluminum to silicon (calculated according to metal oxides) of 72 and the average diameter of 6~8 mu m are obtained.
Drying the precursor fiber in a 120 ℃ forced air drying oven for 30min, then putting all the precursor fiber into 500kg paraffin oil, stirring in a four-inclined-blade turbine type stirrer for 600s, and sampling to observe that the average fiber length is 7.5mm.
Pumping the slurry into a gap type fiber forming machine, and performing suction filtration under the vacuum degree of-50 kPa to obtain precursor fiber assemblies with the size of 1725 × 865 × 37mm and the wet weight of 5591 g.
And (3) putting the precursor fiber aggregate in a blast drying oven, preserving the heat for 2.5 hours at the temperature of 200 ℃, transferring the precursor fiber aggregate into a muffle furnace, gradually heating to 1300 ℃ at the heating rate of 8 ℃/min, preserving the heat for 30min, and cooling to the room temperature. The resulting polycrystalline alumina fiber aggregates shrunk in size to 1200 x 600 x 26mm, reduced in weight to 1573g, and reduced in fiber average diameter to 4~6 μm.
Immersing the polycrystalline alumina fiber aggregate in a mixed solution containing 10wt.% of modified starch and 1% of acidic silica sol for 15s, taking out, extruding out excessive water, clamping between two parallel flat plates preheated to 160 ℃, compressing to 300kg/m < 3 >, preserving heat for 25min, and cooling to room temperature. A polycrystalline alumina fiber mat of size 1200 x 600 x 13mm, weight 1728g, with an areal density of 2400g/m2, a bulk density of 185kg/m3, a peel strength of 62N/m and an aged areal pressure of 56kPa was obtained.
Example two:
preparing glue by using methyl acetic acid, adding 600g of metal aluminum powder (the granularity is 70-100 meshes, the aluminum content is more than 99%) into a mixed acid of 3888g of formic acid and 791g of acetic acid, adding water to adjust the aluminum concentration (calculated by alumina) in the solution to about 15wt.%, heating and carrying out reflux reaction at the temperature of 90-100 ℃, filtering out a very small amount of unreacted metal aluminum powder, and obtaining a transparent aluminum methyl acetate polymerization solution. 2202g of acidic silica sol (average particle diameter 7 nm, silica content 20%), 1355 g of polyvinylpyrrolidone in aqueous solution (type K90, concentration 3%) and 45 g of lactic acid were added. The above liquids were mixed uniformly, and then heated under reduced pressure and distilled under a vacuum of-0.7 MPa to obtain a colloid having a viscosity of 2.1 pas (measured at 25 ℃ C.) and good spinnability. The fibers were spun using a spinneret having a hole diameter of 0.2mm, a hole pitch of 8.0mm and a number of 800 holes. The spinning conditions are that the hot air temperature is 85 ℃, the colloid feeding amount is 3.1L/hr, and 3478g of precursor fiber with the aluminum-silicon weight ratio (calculated according to metal oxide) of 72 and the average diameter of 7-10 μm is obtained.
Drying the precursor fiber in a forced air drying oven at 140 ℃ for 45min, putting all the precursor fiber into 500kg of paraffin oil, stirring the mixture in a four-inclined-blade turbine type stirrer for 1200s, and sampling to observe that the average fiber length is 5.5mm.
Pumping the slurry into a gap type fiber forming machine, and performing suction filtration under the vacuum degree of-50 kPa to obtain precursor fiber assemblies with the size of 1725 × 865 × 30mm and the wet weight of 8101 g.
And (3) keeping the temperature of the precursor fiber aggregate in a blast drying oven at 200 ℃ for 2.5 hours, transferring the precursor fiber aggregate into a muffle furnace, gradually heating to 1300 ℃ at the heating rate of 6 ℃/min, then keeping the temperature for 30min, and cooling to room temperature. The resulting polycrystalline alumina fiber aggregates shrunk in size to 1200 x 600 x 22mm, reduced in weight to 1573g, and reduced in fiber average diameter to 5~7 μm.
Immersing the polycrystalline alumina fiber aggregate in a mixed solution containing 10wt.% of modified starch and 1% of acidic silica sol for 15s, taking out, extruding out excessive water, clamping between two parallel flat plates preheated to 160 ℃, compressing to 300kg/m < 3 >, preserving heat for 25min, and cooling to room temperature. A polycrystalline alumina fiber mat of 1200 x 600 x 12mm size and 1728g weight was obtained with an areal density of 2400g/m2, a bulk density of 200kg/m3 and an aged areal pressure of 62kPa.
Example three:
the ratio of aluminum to silicon is 85: 1185g of crystalline aluminum chloride (97 percent in content) is dissolved in 4765g of water, 581g of metal aluminum powder (325-350 meshes in particle size and more than 99 percent in aluminum content) is added, the mixture is stirred and reacted at 50 ℃ until the solution is completely clear (a small amount of water volatilizes in the reaction process), and a very small amount of unreacted metal aluminum powder is filtered out, so that a colorless and transparent basic aluminum chloride aqueous solution with the aluminum/chlorine molar ratio of 1.83 and the aluminum oxide content of 22.8wt.% is obtained. 1179g of basic silica sol (average particle diameter 25 nm, silica content 20%), 1190g of aqueous polyvinyl alcohol solution (1799 type, concentration 8 wt.%) and 150g of acetic acid were added to the basic aluminum chloride aqueous solution. After mixing uniformly, the mixture was heated under reduced pressure at a vacuum of-0.6 MPa to distill under reduced pressure, and a colloid having a viscosity of 7.6 pas (measured at 25 ℃ C.) and good spinnability was obtained.
The fibers were spun using a spinneret having a hole diameter of 0.2mm, a hole pitch of 8.0mm and a number of 800 holes. Spinning conditions are that the hot air temperature is 45 ℃, the colloid feeding amount is 4L/hr, and precursor fiber with the weight ratio of 3761g of aluminum silicon (calculated according to metal oxide) of 85 and the average diameter of 8-12 mu m is obtained.
The precursor fiber was dried in a 120 ℃ forced air drying oven for 30min, then all the fibers were put into 500kg of paraffin oil, stirred in a four-pitched blade turbine type stirrer for 540s, and the average fiber length was observed to be 7.0mm by sampling.
Pumping the slurry into a gap type fiber forming machine, and performing suction filtration under the vacuum degree of-50 kPa to obtain precursor fiber assemblies with the size of 1725 × 865 × 17mm and the wet weight of 5376 g.
And (3) putting the precursor fiber aggregate in a blast drying oven, preserving the heat for 2.5 hours at the temperature of 200 ℃, transferring the precursor fiber aggregate into a muffle furnace, gradually heating to 1300 ℃ at the heating rate of 5 ℃/min, preserving the heat for 30min, and cooling to the room temperature. The resulting polycrystalline alumina fiber aggregates shrunk in size to 1200 x 600 x 26mm, reduced in weight to 1573g, and reduced in fiber average diameter to 6~8 μm.
Immersing the polycrystalline alumina fiber aggregate in a mixed solution containing 10wt.% of modified starch and 1% of acid silica sol for 15s, taking out, extruding out excessive water, clamping between two parallel flat plates preheated to 170 ℃, compressing to 300kg/m < 3 >, preserving heat for 25min, and cooling to room temperature. A polycrystalline alumina fiber mat of 1200 x 600 x 12mm size and 1728g weight was obtained with an areal density of 2400g/m2, a bulk density of 200kg/m3 and an aged areal pressure of 49kPa.
Example four:
on the basis of the first embodiment, 2330g of the precursor fiber is taken out, and drying, wet forming, heat treatment, gluing and hot pressing are carried out according to the method and parameters in the first embodiment. A polycrystalline alumina fiber mat of 1200 x 600 x 8.6mm size and weight 1152g was obtained with an areal density of 1600g/m2, a bulk density of 185kg/m3, a peel strength of 65N/m and an areal density coefficient of variation of 2.25.
Example five:
and repeating the processes of glue making and spinning on the basis of the first embodiment, taking 6989g of the prepared precursor fiber, and carrying out drying, wet forming, heat treatment, glue coating and hot pressing according to the method and parameters in the first embodiment. A polycrystalline alumina fiber mat of 1200 x 600 x 8.6mm in size and 2592g in weight was obtained with an areal density of 3600g/m2, a bulk density of 185kg/m3, a coefficient of variation of the areal density of 1.77 and a peel strength of 60N/m.
The following are comparative examples of the present invention:
comparative example one: the domestic commercial polycrystalline alumina fiber blanket. Alumina content 72wt.%, areal density 1400g/m 2 The bulk density of the alloy is 128kg/m 3 The areal density coefficient of variation of the comparative example one was 3.96, the peel strength was 29N/m, and the aged areal pressure was 39kPa, the areal density coefficient of variation of the polycrystalline alumina fiber mat of the comparative example one was large and the areal density uniformity was poor as compared with the examples one, four, and five, the peel strength of the polycrystalline alumina fiber mat of the comparative example one was poor as compared with the examples one, four, and five, and the aged areal pressure of the polycrystalline alumina fiber mat of the comparative example one was low as compared with the examples one, two, three, four, and five;
comparative example two: carrying out wet forming, gluing and hot pressing on domestic commercial polycrystalline alumina loose cotton (the content of alumina is 72 wt.%) according to the method and parameters in the first example to obtain the bulk density of 2400g/m 2 The bulk density of the alloy is 200kg/m 3 The polycrystalline alumina fiber mat aged 33kPa was compared to comparative example two, example one, example two, example three, example four, and example five, with comparative example twoSecondly, the aging surface pressure of the polycrystalline alumina fiber gasket is low;
comparative example three: crushing and breaking up the domestic commercial polycrystalline alumina fiber blanket in the comparative example I by using a high-speed vibrating blade, disassembling the polycrystalline alumina fiber blanket into loose cotton, and then carrying out wet forming, gluing and hot pressing according to the method and parameters in the example I to obtain the polycrystalline alumina fiber blanket with the areal density of 2400g/m 2 The bulk density of the alloy is 200kg/m 3 And a polycrystalline alumina fiber mat having an aged face pressure of 11kPa, the polycrystalline alumina fiber mat of comparative example three has a lower aged face pressure than the polycrystalline alumina fiber mats of examples one, two, three, four, and five;
comparative example four: on the basis of the first example, namely, other experimental conditions and technical characteristics are the same as those of the first example, the precursor fiber length of the fourth comparative example is too short, the fiber length mode is 1.0mm, and the polycrystalline alumina fiber gasket with the aging surface pressure of 14kPa is obtained, and the aging surface pressure of the polycrystalline alumina fiber gasket of the fourth comparative example is lower than that of the first example, the second example, the third example, the fourth example and the fifth example.
Comparative example five: on the basis of the first embodiment, namely other experimental conditions and technical characteristics are the same as those of the first embodiment, the different technical characteristics are that the length of the precursor fiber of the fifth embodiment is too long, the mode of the fiber length is 25.0mm, the polycrystalline alumina fiber gasket with the area density variation coefficient of 4.64 and the aging surface pressure of 29kPa is obtained, compared with the first embodiment, the fourth embodiment and the fifth embodiment, the polycrystalline alumina fiber gasket of the fifth embodiment has large area density variation coefficient and poor area density uniformity, compared with the first embodiment, the second embodiment, the third embodiment, the fourth embodiment and the fifth embodiment, the polycrystalline alumina fiber gasket of the fifth embodiment has low aging surface pressure.
Comparative example six: on the basis of example one, that is, other experimental conditions and technical features are the same as those of example one, except that comparative example six uses a water-dispersed precursor fiber in a wet forming step, the precursor fiber is dissolved and cannot be formed, and the aging surface pressure of the polycrystalline alumina fiber pad of comparative example six is lower than that of example one, example two, example three, example four and example five.
Comparative example seven: on the basis of example one, that is, other experimental conditions and technical features were the same as those of example one, except that the end point temperature of the heat treatment of the precursor fiber was set to 900 ℃ in comparative example seven, and the aging surface pressure of the polycrystalline alumina fiber mat of comparative example seven was low as compared with those of example one, example two, example three, example four and example five.
Comparative example eight: on the basis of the first example, namely other experimental conditions and technical characteristics are the same as those of the first example, except that the hot pressing step is omitted after the sizing is carried out on the eighth comparative example, and the polycrystalline alumina fiber liner of the eighth comparative example has small peel strength compared with the first example, the fourth example and the fifth example.
As shown in fig. 2, the polycrystalline alumina fiber backing has a uniform areal density: from the first, fourth and fifth examples and the first and fifth comparative examples, it can be seen that the larger the variation coefficient of the areal density, the more uneven the effect is, the worse the effect is.
As shown in fig. 3, the polycrystalline alumina fiber liner peel strength: from the first, fourth and fifth examples and the first and eighth comparative examples, the greater the peel strength, the better the effect.
As shown in fig. 4, the polycrystalline alumina fiber mat aged face pressure: from the first, second and third examples and the first, second, third, fourth and seventh comparative examples, it can be seen that the effect is better when the surface pressure is aged.
In conclusion, the alumina fiber mat produced is best in 3 aspects of areal density uniformity, peel strength, aged areal pressure, using only the solution described in the present protocol.
According to the invention, the precursor fiber aggregate is formed after wet forming is carried out on the precursor fiber, then the precursor fiber aggregate is subjected to heat treatment to be converted into the polycrystalline alumina fiber aggregate, and finally the polycrystalline alumina fiber aggregate is subjected to gluing and shaping to prepare the polycrystalline alumina fiber gasket, so that the aging surface pressure is obviously improved compared with the traditional papermaking method, and the surface density distribution uniformity and the peel strength are obviously improved compared with the needling method.
Reference throughout this specification to the description of "one embodiment," "an example," "a specific example," or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (5)
1. A method for manufacturing a polycrystalline alumina fiber gasket is characterized in that: the polycrystalline alumina fiber pad consists of polycrystalline alumina fibers, an organic binder and an inorganic binder, wherein the weight proportion of the polycrystalline alumina fibers is more than 80 percent, the weight proportion of the organic binder is 2 to 20 percent, and the weight proportion of the inorganic binder is 0~5 percent; the polycrystalline alumina fiber comprises alumina and silica, and the weight ratio of the alumina to the silica is (72-85): (15-28); the manufacturing method of the polycrystalline alumina fiber gasket comprises the following steps:
step 1: preparing sol-gel, mixing an aluminum source and a silicon source according to a set molar ratio, adding a spinning auxiliary agent and a colloid stabilizer, and concentrating to obtain the sol-gel, wherein the aluminum-silicon weight ratio is (65-98): (35-2) a colloid with the viscosity of 0.1 to 10 Pa · s;
step 2: spinning to prepare precursor fiber, and preparing the colloid in the step 1 into the precursor fiber by a spinning method or a blowing method;
and step 3: adjusting the length of the precursor fiber in the step 2 and preparing precursor fiber dispersion liquid;
drying the precursor fiber collected in the step 2 at 100-200 ℃ for 5-60min to fully dry the surface of the precursor fiber so as to prevent the precursor fiber from forming adhesion in the next step; then shortening the precursor fiber by using a method capable of forming concentrated stress to obtain uniform precursor fiber dispersion liquid; the average length of the precursor fiber is 1.5-20.0 mm, and the method capable of forming concentrated stress in the step 3 is to use a high-speed vibrating blade for cutting, then soak the precursor fiber in a hydrophobic liquid medium to enable the concentration of the precursor fiber in the hydrophobic liquid medium to be 0.1-5 wt.%, stir the precursor fiber with high shearing force, and stir the precursor fiber for 20-1800 s;
and 4, step 4: preparing a precursor fiber aggregate by wet forming, and conveying the precursor fiber dispersion liquid uniformly dispersed in the step (3) into a vacuum filtration device for wet forming to obtain a precursor fiber aggregate;
and 5: preparing a polycrystalline alumina fiber assembly by heat treatment, keeping the precursor fiber assembly in the step 4 at 200 ℃ for more than 2 hours, then heating to the heat treatment end point temperature at the heating rate of 0.5-10.0 ℃/min, keeping the heat at the heat treatment end point temperature for 5-60min, and finally cooling to room temperature to obtain the polycrystalline alumina fiber assembly;
step 6: gluing and hot-pressing to prepare a polycrystalline alumina fiber pad, combining a pre-prepared organic adhesive and an inorganic adhesive with the polycrystalline alumina fiber aggregate in the step 5 by using an atomization spraying or integral dipping method, transferring the glued polycrystalline alumina fiber aggregate between two hot plates with the constant temperature of 80-250 ℃, and compressing to 150-500kg/m 3 And keeping the temperature for 1 to 30min, wherein the organic binder in the polycrystalline alumina fiber aggregate is fully formed into a film, the fibers are fully restrained, and the polycrystalline alumina fiber liner is obtained after the polycrystalline alumina fiber aggregate is removed from a hot plate and cooled to room temperature.
2. The method of manufacturing a liner of crystalline alumina fibers according to claim 1, wherein: an aluminum source in the sol in the step 1 is a reaction product of an acidic substance, aluminum powder and water under a heating reflux condition, or a commercially available aluminum salt is used, a silicon source in the sol is TEOS or silica sol, a spinning auxiliary agent is a water-soluble high polymer with fiber forming capability, and the concentration of the spinning auxiliary agent is 0.1-15wt.%; the colloid stabilizer is water-soluble organic acid, and the concentration is 0.1 to 15wt.%.
3. The method of manufacturing a liner of crystalline alumina fibers according to claim 1, wherein: when the spinning method is used for preparing the precursor fiber in the step 2, the colloid enters the spinning disc rotating at a high speed through the feeding pipe, is spun out through small holes formed in the side of the spinning disc under the action of centrifugal force, is stretched by the centrifugal force to form continuous liquid drops, is further stretched and dried and shaped under the action of hot air to form the precursor fiber, and finally the precursor fiber is collected on a fiber collecting belt at the bottom of the fiber forming cover.
4. The method of manufacturing a liner of crystalline alumina fibers according to claim 1, wherein: the average length of the precursor fiber in the step 3 is 2 to 10.0mm; the concentration of the precursor fiber in a hydrophobic liquid medium is 0.1 to 1wt.%.
5. The method of manufacturing a liner of crystalline alumina fibers according to claim 1, wherein: the final temperature of the heat treatment in the step 5 is 1000 to 1350 ℃, and a commercial heating furnace is adopted as equipment for the heat treatment.
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