CN109396446B - Hierarchical porous composite material filter body and preparation method thereof - Google Patents

Hierarchical porous composite material filter body and preparation method thereof Download PDF

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CN109396446B
CN109396446B CN201811385921.9A CN201811385921A CN109396446B CN 109396446 B CN109396446 B CN 109396446B CN 201811385921 A CN201811385921 A CN 201811385921A CN 109396446 B CN109396446 B CN 109396446B
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powder
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diameter
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particles
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CN109396446A (en
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崔洪芝
魏娜
李振奎
王欢欢
徐瑞琪
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Shandong University of Science and Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F7/00—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression
    • B22F7/002—Manufacture of composite layers, workpieces, or articles, comprising metallic powder, by sintering the powder, with or without compacting wherein at least one part is obtained by sintering or compression of porous nature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/05—Metallic powder characterised by the size or surface area of the particles
    • B22F1/052—Metallic powder characterised by the size or surface area of the particles characterised by a mixture of particles of different sizes or by the particle size distribution
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/02—Compacting only
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/11—Making porous workpieces or articles
    • B22F3/1103—Making porous workpieces or articles with particular physical characteristics
    • B22F3/1109—Inhomogenous pore distribution
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C47/00—Making alloys containing metallic or non-metallic fibres or filaments
    • C22C47/14—Making alloys containing metallic or non-metallic fibres or filaments by powder metallurgy, i.e. by processing mixtures of metal powder and fibres or filaments
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C49/00—Alloys containing metallic or non-metallic fibres or filaments
    • C22C49/02—Alloys containing metallic or non-metallic fibres or filaments characterised by the matrix material
    • C22C49/12—Intermetallic matrix material
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C49/00—Alloys containing metallic or non-metallic fibres or filaments
    • C22C49/14—Alloys containing metallic or non-metallic fibres or filaments characterised by the fibres or filaments
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/12—Special parameters characterising the filtering material
    • B01D2239/1208—Porosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/12—Special parameters characterising the filtering material
    • B01D2239/1216—Pore size
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps

Abstract

The invention discloses a multi-level hole composite material filter and a preparation method thereof, which is prepared from Fe powder, Si powder, Al powder, Ti powder and SiC powder with different grain diameterswPowder, B4The powder C is used as raw material, the raw material is pressed into round green bodies by a layered compression molding method from bottom to top, the grain sizes of the mixed raw material are sequentially increased, the thickness of each layer of round green body is gradually increased from bottom to top, and then the pressed round green bodies are subjected to segmented pressureless sintering, so that filter bodies with different multistage apertures from bottom to top and with gradually larger apertures are formed. The porous material of the invention is made of Fe3(Si1‑x,Alx) Surrounding SiC as a matrixw、B4C particles forming a dense skeleton, and Al is formed on the surface of the skeleton2O3The protective film is corrosion-resistant, oxidation-resistant and friction-resistant; at the same time because of the presence of SiC in the skeletonw、B4The ceramic phase such as C, etc. also improves the strength and reduces the coefficient of linear expansion, thereby reducing the regenerative heating stress.

Description

Hierarchical porous composite material filter body and preparation method thereof
Technical Field
The invention relates to a filter body with controllable pore diameter and distribution and a preparation process thereof, in particular to an intermetallic compound/ceramic composite material filter body with a hierarchical pore structure and a preparation method thereof. The filter body has simple preparation process, wide raw material source and low cost, and is suitable for tail gas and waste liquid purifying and filtering components in the automobile, chemical industry and metallurgical industry, supporting bodies for photo-thermal seawater desalination and the like. Belonging to the field of material synthesis and processing.
Background
The filter body is an important part for separating, grading, purifying and enriching mixed gas or liquid, is also a key part for purifying tail gas and waste liquid in the industries of automobiles, chemical engineering and metallurgy and reducing pollution, and requires that the filter body material has high corrosion resistance, wear resistance and heat resistance, and also has high permeability and sufficient strength. Common inorganic material filters can be classified into ceramic and metal. Such as:
US patent 2011097259a1 discloses a ceramic foam having a porosity gradient, with axial and radial porosity gradients.
Chinese patent publication No. CN1287048A discloses a gradient ceramic membrane tube and a preparation method thereof, wherein the pore diameter of the membrane pores of the ceramic membrane tube is in gradient distribution which is continuously increased from inside to outside.
Chinese patent publication No. CN1532170A discloses a method for preparing a gradient pore ceramic filter element, which comprises mixing ceramic powder with different particle sizes with a high-temperature binder solution, ball-milling, spray-granulating, coating a layer of high-temperature binder on the surface of the ceramic powder to form orthopedic particles with different particle sizes, mixing the orthopedic particles with a forming binder, a pore-increasing agent and water to form blanks, respectively distributing the blanks into different mold layers according to different particle sizes, removing the mold layers, isostatic pressing, drying, and finally sintering the blanks at high temperature.
Chinese patent publication No. CN1623627A discloses a filter material with gradient distribution and a preparation method thereof, the filter material is a filter body with gradient distribution, which is built by several fibers and has reduced pore diameter from top to bottom, the continuous change of the gradient from top to bottom can selectively collect particles in the filtered fluid, the dirt receiving space is improved, and the filter resistance is reduced.
Chinese patent publication No. CN101564621A discloses a gradient pore structure titanium filter core and a preparation method thereof, the method comprises the steps of mixing titanium powder, titanium hydride powder and sodium chloride powder uniformly, mixing with a binder for granulation, preparing a blank by adopting a powder co-injection molding technology, degreasing, desalting and sintering to obtain the product, the product realizes high interface bonding strength, achieves a controllable pore structure, and realizes near-net forming in the technical aspect.
However, for metal filters, the oxidation resistance and the acid and alkali corrosion resistance of the metal filters are often poor, so that the service environment of the metal filters is greatly limited, and the service life of the metal filters is short; the ceramic filter body has low obdurability and poor thermal conductivity, the strength and the service life of the ceramic filter body are limited, and the preparation technology of the filter body has the defects of complex preparation process, single pore structure, high cost and the like.
The intermetallic compound material has the performance between that of metal and ceramic, and has the toughness of metal and the high temperature resistance of ceramic. Chinese patent publication No. CN1640528A discloses a method for preparing a titanium-aluminum intermetallic compound filter membrane, and simultaneously, the holes of the filter membrane are controlled by utilizing the partial diffusion effect of Al element, and the membrane can be welded with metal, thereby enlarging the application range of inorganic membranes. Fe3The Si-based intermetallic compound is probably a potential structural material due to the advantages of excellent corrosion resistance, oxidation resistance and friction resistance, low price of preparation raw materials, simple and convenient preparation method and the like, but the structural function development related to the Si-based intermetallic compound does not draw enough attention.
Therefore, the invention provides a multilevel pore structure intermetallic compound/ceramic composite material filter body, which utilizes the in-situ self-generated reaction between materials to form the intermetallic compound and the ceramic composite material, and forms multilevel gradient pores from bottom to top in the pressureless reaction sintering process through the layering and gradient blank making of the reaction materials with different particle sizes, thereby not only ensuring the high strength, high thermal conductivity, erosion resistance and high temperature resistance of the materials, but also improving the porosity and the filtration efficiency through the multilevel gradient pore structure design and preparation.
Disclosure of Invention
In order to overcome the technical defects of poor oxidation resistance and acid-base corrosion resistance of a metal filter body, low toughness and poor heat conductivity of a ceramic filter body, the invention provides a hierarchical porous composite material filter body.
The invention also provides a preparation method of the filter body.
In order to achieve the purpose, the invention adopts the technical scheme that:
the multi-level hole composite material filter is characterized in that the filter is made of Fe powder, Si powder, Al powder, Ti powder and SiC powder with different grain diameterswPowder, B4C powder is used as a raw material, the raw material is pressed into round green bodies by a layered compression molding method from bottom to top, the grain sizes of the mixed raw materials are sequentially increased, the thickness of each layer of round green body is gradually increased from bottom to top, and then the pressed round green bodies are subjected to segmented pressureless sintering, so that filter bodies with different multistage apertures are formed, wherein the apertures of the filter bodies are gradually larger from bottom to top; the skeleton of the filter body is made of Fe3(Si1-x,Alx) The intermetallic matrix surrounding the SiCw、B4C particles, small amount of TiC + Fe3(C, B) particles distributed in Fe3(Si1-x,Alx) Of medium, and SiCwWhiskers (coarse) and TiB whiskers (formed by reaction, fine) are distributed in the pores, Ti2SiC is attached to SiCwGrown to be included in SiCwOn the whisker.
The raw material mol ratio of each layer of round blank is Fe: si: al: ti: SiCw：B4C is 3: 1: 1: 0.3: 1: 1; the in-situ authigenic reaction formula is: 3Fe + Si + Al +0.3Ti + SiCw+B4C→Fe3(Si1-x，Alx)+SiCw+B4C + a small amount of Ti2SiC+TiB+TiC+Fe3(C,B)。
The preparation method of the multistage pore composite material filter body comprises the following steps:
the first step is as follows: preparation of porous composite raw material
Firstly preparing Fe powder, Si powder, Al powder, Ti powder and SiC powder with different particle size rangeswPowder and B4Powder C, that is, the six original powders each comprised different particle size segments;
the second step is that: porous composite powder mixing preparation
The original powder prepared in the first step is mixed into a plurality of groups of mixed original powder according to the gradient change of the particle size, and the mixture ratio of the six kinds of original powder in each group of mixed original powder is required to be: fe: si: al: ti: SiCw： B4C＝3：1：1：0.3：1：1；
The third step: compression molding of porous composite materials
The mixed original powder with the grain diameter changing in a gradient way is loaded into a mould layer by layer in a mode that the grain diameter is gradually increased from bottom to top, and the mixed original powder is pressed once for each layer and finally pressed into a round blank; the thickness of a green body pressed by each layer of mixed powder is required to be increased from bottom to top in sequence:
the fourth step: reactive sintering of porous composites
Drying the pressed round blank, gradually increasing the calcining temperature to perform segmented pressureless sintering, and forming the compact porous composite material with the pore diameter in gradient distribution through diffusion migration in the reaction sintering process.
Further: in the second step, the particle size ranges of the six raw materials after grinding are respectively as follows: 5-50 μm of Si powder and Ti powder, 10-50 of Al powder, B4C is 1-10 μm, the diameter of the SiC whisker is 1-5 μm, and the length-diameter ratio is 5-15.
Further: in the third step, the round billet finally pressed is divided into three layers, wherein:
(1) the finest layer of particles is the finest: 5-10 μm of Fe powder, Si powder and Ti powder, 10-20 μm of Al powder, B4C is 1-3 μm, the diameter of the SiC whisker is 1-5 μm, the length-diameter ratio is less than 5, and the thickness of the blank is 2-3 mm;
(2) the particle size of the middle layer is increased: fe powder, Si powder, Ti powder 10-30 μm, Al powder 20-30 μm, B4C is 3-6 microns, the diameter of the SiC whisker is 1-5 microns, the length-diameter ratio is less than 10, and the thickness of the blank is 5-7 mm;
(3) the particles on the uppermost layer are the largest: fe powder, Si powder, Ti powder 30-50 μm, Al powder 30-50 μm, B4C is 6-10 mu m, the diameter of the SiC whisker is 1-5 mu m, the length-diameter ratio is less than 15, and the thickness of the blank is 10 mm.
Further: the fourth step of calcining is divided into two sections, in the first stage, the mixture is heated to 650 ℃ at the heating rate of 4 ℃/mi4, the temperature is kept for 2-3 h, and Al diffusion is mainly promoted, so that Al particles are rapidly diffused and reacted in a state close to a melting point, the Al particles are combined with Fe and Si particles, and three-dimensional communicated holes formed by reaction are reserved at each original Al particle position; in the second stage, the temperature is raised to 1200-1300 ℃ at the temperature raising rate of 8 ℃/mi4, the heat preservation time is 3h, and Fe is mainly promoted3(Si1-x,Alx) Is formed and mixed with SiCwWhisker and B4Combining the particles to obtain a composite material; by diffusion migration during reactive sintering, Fe3(Si1-x,Alx) As a matrix surrounding SiCwWhisker and B4C, forming compact porous composite.
Further: the drying in the fourth step means drying in a drying oven at 50 ℃ for 2 hours.
The positive effects of the present invention are explained below based on the reaction and action mechanism of the present invention.
1. The invention utilizes the in-situ self-generated reaction of materials in the pressureless reaction sintering process: 3Fe + Si + Al +0.3Ti + SiCw+B4C→Fe3(Si1-x，Alx)+SiCw+B4C + a small amount of Ti2SiC+TiB+TiC+Fe3(C, B) formation of Fe3(Si1-x,Alx) Intermetallic compound and SiCw、B4C, ceramic composite materials; secondly, reacting materials with different sizes are layered to form a gradient blank, and gradient holes with multi-level sizes are formed in the composite material by means of particle stacking physical pore forming and reaction pore forming in the non-pressure reaction process; the porous material has the advantages that: (ii) since the intermetallic compound is a matrix, the thermal conductivity is high, and Fe is a component3(Si1-x,Alx) In which Al is formed on the surface of the skeleton due to solid solution of Al2O3The protective film is corrosion-resistant, oxidation-resistant and friction-resistant; at the same time because of the presence of SiC in the skeletonw、B4The ceramic phase such as C, etc. also improves the strength and reduces the coefficient of linear expansion, thereby reducing the regenerative heating stress. Thus, from the material propertiesThe porous material has good erosion and wear resistance and good regeneration performance, and the service life is prolonged; the holes are three-dimensionally communicated, the pore diameter is in gradient and multistage, and the holes are fully distributed with thick and thin whiskers which are distributed in a staggered manner.
2. The porous composite material of the invention is prepared from Fe powder, Si powder, Al powder, Ti powder and SiCwPowder, B4The C powder is used as a raw material and is prepared by reaction sintering synthesis, and the preparation method is simple in process and low in cost. The porosity is regulated and controlled by changing the blank making pressure, the grain diameter of the raw material and the aperture size of the filter body. Therefore, the porosity is improved, the filtering resistance is reduced, the filtering efficiency and the filtering precision can be improved, the particles are not easy to block, and the backwashing regeneration is easy to realize. The filter body has simple preparation process, wide raw material source and low cost, and is suitable for tail gas and waste liquid purifying and filtering components in the automobile, chemical industry and metallurgical industry, supporting bodies for photo-thermal seawater desalination and the like. 3. The porous material of the invention is made of Fe3(Si1-x,Alx) Surrounding SiC as a matrixw、B4C particles forming a dense skeleton, and Al is formed on the surface of the skeleton2O3The protective film is corrosion-resistant, oxidation-resistant and friction-resistant; at the same time because of the presence of SiC in the skeletonw、 B4The ceramic phase such as C, etc. also improves the strength and reduces the coefficient of linear expansion, thereby reducing the regenerative heating stress.
4. The porous composite material has the characteristics of reduced pore diameter and pore diameter gradient from top to bottom; SiC is fully distributed in the holeswAnd TiB whiskers, wherein the porosity is 45.7-66.2%, and the compressive strength is 45.3-73.5 MPa. The pore diameter, the porosity, the maximum and minimum pore diameters and the gradient of the porous material can be adjusted by adjusting the particle size. The structure is beneficial to improving the porosity of the porous material, reducing the pressure drop, improving the filtering precision and efficiency and being beneficial to backwashing regeneration.
The detection method of the porosity and the compressive strength of the porous material is respectively based on the national standard GB/T1966-1996.
Drawings
FIG. 1 is a schematic diagram of raw materials with different particle sizes being filled into a mold;
FIG. 2 is a schematic view of the pore structure of the filter body;
FIG. 3 is a structural morphology diagram of the lowest layer pore of the filter body.
In the figure: 1-upper, 2-middle, 3-lower layer
Detailed Description
The preparation process of the present invention is further illustrated below with reference to the accompanying drawings and examples.
The preparation method of the multistage pore composite material filter body comprises the following steps:
the first step is as follows: preparation of porous composite raw material
Preparing Fe powder, Si powder, Al powder, Ti powder and SiC powder with different particle size ranges in advancewPowder and B4C, powder is specifically as follows:
the grain sizes of the Fe powder, the Si powder and the Ti powder are in three ranges of 5-10 microns, 10-30 microns and 30-50 microns;
the Al powder has three particle size ranges of 10-20 microns, 20-30 microns and 30-50 microns;
B4c is three particle size ranges of 1-3 microns, 3-6 microns and 6-10 microns;
SiC is three dimensions of the whisker with the diameter of 1-5 μm, the length-diameter ratio of less than 5, the diameter of 1-5 μm, the length-diameter ratio of less than 10, the diameter of 1-5 μm and the length-diameter ratio of less than 15;
the second step is that: porous composite powder mixing preparation
Mixing the above Fe powder, Si powder, Al powder, Ti powder, and SiC powder with the above particle size rangewPowder, B4And C, ball-milling six kinds of powder into three groups of mixed original powder in a gradient change manner according to the particle size, wherein the mixture ratio of the six kinds of powder is as follows: fe: si: al: ti: SiCw：B4C＝3：1：1：0.3：1：1；
And (3) filling the three groups of mixed original powder into a die in three layers according to a mode that the particle size gradually increases from bottom to top, wherein:
the finest layer of particles is the finest: 5-10 μm of Fe powder, Si powder and Ti powder, 10-20 μm of Al powder, B4C is 1-3 μm, the diameter of the SiC whisker is 1-5 μm, the length-diameter ratio is less than 5, and the thickness of the blank is 2-3 mm;
the particle size of the middle layer is increased: fe powder, Si powder and Ti powder are 10 to 30 μm, 20 to 30 μm of Al powder, B4C is 3-6 microns, the diameter of the SiC whisker is 1-5 microns, the length-diameter ratio is less than 10, and the thickness of the blank is 5-7 mm;
the particles on the uppermost layer are the largest: fe powder, Si powder, Ti powder 30-50 μm, Al powder 30-50 μm, B4C is 6-10 mu m, the diameter of the SiC whisker is 1-5 mu m, the length-diameter ratio is less than 15, and the thickness of the blank is 10 mm.
Each layer is required to be pressed and formed once, and finally, the round billet is pressed into the round billet shown in figure 1; as can be seen from FIG. 1, the round billet is divided into an upper layer 1, a middle layer 2 and a lower layer 3, and the thickness and the particle size of the mixed powder of the upper layer 1, the middle layer 2 and the lower layer 3 are gradually reduced.
The fourth step: reactive sintering of porous composites
And (3) drying the pressed and formed blank body in a drying oven at 50 ℃ for 2h, and then sintering the blank body in a segmented and pressureless manner. The first stage is mainly to promote Al diffusion. Heating to 650 ℃ at a heating rate of 4 ℃/min, and preserving heat for 2-3 h, so that the Al particles are rapidly diffused and reacted in a state close to a melting point, and are combined with Fe and Si particles, and three-dimensional communication holes formed by reaction are left at the positions of the original Al particles. The second stage is mainly promoting Fe3(Si1-x,Alx) Is formed and mixed with SiCwWhisker and B4And C, combining the particles to obtain the composite material. The temperature is raised to 1200-1300 ℃ at the temperature raising rate of 8 ℃/min, and the heat preservation time is 3 h. By diffusion migration during reactive sintering, Fe3(Si1-x,Alx) As a matrix surrounding SiCwWhisker and B4And C, forming a skeleton of the compact porous composite material. The specific reaction formula is as follows:
(1)3Fe+Si+Al→Fe3(Si1-x,Alx)
(2)5Ti+B4C→4TiB+TiC
(3)Fe+B4C→Fe3(C,B)+FeB+Fe2B
(4)2Ti+SiC→Ti2SiC
the above reactions are combined as follows:
(5)3Fe+Si+Al+0.3Ti+SiCw+B4C→Fe3(Si1-x,Alx)+SiCw+B4c + a small amount of Ti2SiC+ TiB+TiC+Fe3(C,B)
Wherein SiCw、B4C mainly plays a role of adding ceramic, and simultaneously provides Si, B and C sources due to a small amount of decomposition to respectively form a small amount of Ti with Ti and Fe2SiC、TiB、TiC、Fe3(C, B) for Fe3(Si1-x,Alx) The matrix plays a strengthening role.
In order to verify the positive effects of the invention, after sintering, the porous body of the invention is cooled to 450 ℃ along with a furnace, taken out and cooled in air, and then the performance of the material is detected according to the structural morphology, and the result shows that after reaction sintering, the physical stacking holes among reactant particles and three-dimensional communication holes formed by reaction form different multi-stage pore diameters, wherein the pore diameter ranges from 5 to 60 micrometers, the uppermost layer is 35 to 60 micrometers, the thickness is about 10 micrometers, the middle layer is 10 to 35 micrometers, the thickness is about 5 micrometers, and the pore diameter of the lowermost layer is 5 to 10 micrometers, and the thickness is about 2 micrometers. From top to bottom, the smaller the pore diameter, the thinner the thickness; SiC is fully distributed in the holeswAnd TiB whiskers, wherein the porosity is 45.7-66.2%, and the compressive strength is 45.3-73.5 MPa, the pore structure of the filter body is shown as the attached drawing 2, the pore structure of the lowermost layer of the filter body is shown as the attached drawing 3, and as can be seen from the attached drawing, the pores are three-dimensionally communicated, and coarse whiskers and fine whiskers which are distributed in a staggered manner are distributed in the pores. The pore diameter, the porosity, the maximum and minimum pore diameters and the gradient of the porous material can be adjusted by adjusting the particle size. The multi-stage pore structure is beneficial to improving the porosity of the porous material, reducing the pressure drop, improving the filtering precision and efficiency and being beneficial to backwashing regeneration.

Claims (7)

1. The multi-level hole composite material filter is characterized in that the filter is made of Fe powder, Si powder, Al powder, Ti powder and SiC powder with different grain diameterswPowder, B4C powder is used as raw material, the raw material is pressed into round blank bodies by adopting a layered compression molding method, the grain sizes of the mixed raw material are sequentially increased from bottom to top, the thickness of each layer of round blank body is gradually increased from bottom to top, and then the round blank bodies formed by compression are subjected to segmented pressureless burningForming a plurality of stages of filter bodies with different apertures from bottom to top and with gradually larger apertures; the skeleton of the filter body is made of Fe3(Si1-x,Alx) The intermetallic matrix surrounding the SiCw、B4C particles, small amount of TiC + Fe3(C, B) particles distributed in Fe3(Si1-x,Alx) Medium, coarse SiCwThe powder and the fine TiB whiskers formed by reaction are distributed in the holes, and Ti2SiC is attached to SiCwGrown to surround SiCwPowdering;
the raw material mol ratio of each layer of round blank is Fe: si: al: ti: SiCw：B4C is 3: 1: 1: 0.3: 1: 1; the in-situ authigenic reaction formula is: 3Fe + Si + Al +0.3Ti + SiCw+B4C→Fe3(Si1-x，Alx)+SiCw+B4C + a small amount of Ti2SiC+TiB+TiC+Fe3(C,B)。
2. A method for preparing a multi-level hole composite material filter body is characterized in that,
the first step is as follows: preparation of porous composite raw material
Firstly preparing Fe powder, Si powder, Al powder, Ti powder and SiC powder with different particle size rangeswPowder and B4Powder C, that is, the six original powders each comprised different particle size segments;
the second step is that: porous composite powder mixing preparation
The original powder prepared in the first step is mixed into a plurality of groups of mixed original powder according to the gradient change of the particle size, and the mixture ratio of the six kinds of original powder in each group of mixed original powder is required to be: fe: si: al: ti: SiCw：B4C＝3：1：1：0.3：1：1；
The third step: compression molding of porous composite materials
The mixed original powder with the grain diameter changing in a gradient way is loaded into a mould layer by layer in a mode that the grain diameter is gradually increased from bottom to top, and the mixed original powder is pressed once for each layer and finally pressed into a round blank; the thickness of a green body pressed by each layer of mixed powder is required to be increased from bottom to top in sequence:
the fourth step: reactive sintering of porous composites
Drying the pressed round blank, gradually increasing the calcining temperature to perform segmented pressureless sintering, and forming the compact porous composite material with the pore diameter in gradient distribution through diffusion migration in the reaction sintering process.
3. The method for preparing a multi-stage pore composite filter according to claim 2, wherein the particle sizes of the six raw materials after grinding in the second step are respectively in the following ranges: 5-50 μm of Fe powder, Si powder, Ti powder, 10-50 of Al powder, B4C is 1 to 10 μm, SiCwThe powder has a diameter of 1-5 μm and a length-diameter ratio of 5-15.
4. The method of making a multigraded pore composite filter body of claim 2, wherein in the third step the final pressed round billet is divided into three layers, wherein:
(1) the finest layer of particles is the finest: 5-10 μm of Fe powder, Si powder and Ti powder, 10-20 μm of Al powder, B4C is 1 to 3 μm, SiCwThe powder diameter is 1-5 μm, the length-diameter ratio is less than 5, and the thickness of the blank is 2-3 mm;
(2) the particle size of the middle layer is increased: fe powder, Si powder, Ti powder 10-30 μm, Al powder 20-30 μm, B4C is 3 to 6 mu m, SiCwThe powder diameter is 1-5 μm, the length-diameter ratio is less than 10, and the thickness of the blank is 5-7 mm;
(3) the particles on the uppermost layer are the largest: fe powder, Si powder, Ti powder 30-50 μm, Al powder 30-50 μm, B4C is 6 to 10 mu m, SiCwThe powder diameter is 1-5 μm, the length-diameter ratio is less than 15, and the thickness of the blank is 10 mm.
5. The method for preparing a multi-stage porous composite filter body according to claim 2, wherein the step four, the step of segmented pressureless sintering is divided into two stages, the first stage is heated to 650 ℃ at a heating rate of 4 ℃/min, and the temperature is kept for 2-3 h, mainly to promote Al diffusion, so that Al particles are rapidly diffused and reacted in a state close to a melting point, and combined with Fe and Si particles, and each original Al particle is bonded with each original Al particleLeaving three-dimensional communicating holes formed by reaction at the positions of the particles; in the second stage, the temperature is raised to 1200-1300 ℃ at the temperature rise rate of 8 ℃/min, and the heat preservation time is 3h, mainly promoting Fe3(Si1-x,Alx) Is formed and mixed with SiCwPowder, B4Combining the particles to obtain a composite material; by diffusion migration during reactive sintering, Fe3(Si1-x,Alx) As a matrix surrounding SiCwPowder, B4C, forming compact porous composite.
6. The method for preparing a multi-stage pore composite filter body according to claim 2, wherein the round billet drying in the fourth step is drying in a drying oven at 50 ℃ for 2 h.
7. The use of the multi-stage porous composite filter body of claim 1 in exhaust gas and waste liquid purification and filtration components in the automotive, chemical and metallurgical industries and in supports for photothermal seawater desalination.
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