CN113735474B - Microwave absorption reinforced aggregate structure and preparation method and application thereof - Google Patents

Microwave absorption reinforced aggregate structure and preparation method and application thereof Download PDF

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CN113735474B
CN113735474B CN202110988439.XA CN202110988439A CN113735474B CN 113735474 B CN113735474 B CN 113735474B CN 202110988439 A CN202110988439 A CN 202110988439A CN 113735474 B CN113735474 B CN 113735474B
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aggregate
powder
microwave
absorbing
outer layer
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CN113735474A (en
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刘小明
韦德铭
赵昱
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Central South University
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Central South University
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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
    • C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
    • C04B18/02—Agglomerated materials, e.g. artificial aggregates
    • C04B18/023—Fired or melted materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y70/00—Materials specially adapted for additive manufacturing
    • B33Y70/10—Composites of different types of material, e.g. mixtures of ceramics and polymers or mixtures of metals and biomaterials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y80/00—Products made by additive manufacturing
    • 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
    • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
    • C04B20/10—Coating or impregnating
    • C04B20/1055—Coating or impregnating with inorganic materials
    • C04B20/1066—Oxides, Hydroxides
    • 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
    • C04B26/00—Compositions of mortars, concrete or artificial stone, containing only organic binders, e.g. polymer or resin concrete
    • C04B26/02—Macromolecular compounds
    • C04B26/26—Bituminous materials, e.g. tar, pitch
    • 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
    • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
    • C04B2111/0075—Uses not provided for elsewhere in C04B2111/00 for road construction

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  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Organic Chemistry (AREA)
  • Civil Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Composite Materials (AREA)
  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)

Abstract

The invention discloses a microwave absorption reinforced aggregate structure and a preparation method and application thereof, wherein the microwave absorption reinforced aggregate structure comprises a core structure and an outer layer structure which is wrapped outside the core structure in a shell shape; at least one hole is arranged in the core structure. The microwave absorption reinforced aggregate structure is printed and prepared by a 3D printing technology, can be used as an aggregate to be applied to asphalt concrete, has the characteristics of good microwave heating performance and strong heat conduction capability, is flexible in structural design, and has good adaptability to different use environments; the preparation method has the advantages of simple process, safety, reliability, convenient operation and low production cost, and can realize the precise regulation and control of the composition of the material on the micro scale.

Description

Microwave absorption reinforced aggregate structure and preparation method and application thereof
Technical Field
The invention relates to the field of road engineering materials, in particular to a microwave absorption reinforced aggregate structure and a preparation method and application thereof.
Background
By the end of 2019, the highway maintenance mileage in China reaches 495.31 kilometers, which accounts for 98.8% of the total highway mileage, wherein most of the roads are asphalt pavements, and the large-scale maintenance and modification of the existing asphalt roads become one of the centers of gravity of the roads in China. The traditional hot repair technology, the infrared heating technology and other technologies have the problems of low repair efficiency, large influence on environment and traffic and the like, and the microwave heating technology has the advantages of uniformity, rapidness, environmental protection, easiness in control and the like, so that the application prospect of the microwave heating technology in road maintenance and repair is very wide.
At present, microwave heating is widely applied to the food industry, and is gradually popularized in the industries of chemical engineering, ceramics and the like, but the effect of directly applying the microwave heating technology to the traditional asphalt concrete pavement is not good, because the microwave absorption and heating effects of common asphalt concrete are poor, the common method is to add a microwave absorption material to enhance the microwave absorption capacity of the asphalt concrete. When the wave absorbing material is added into the asphalt concrete in the form of a wave absorbing agent, the wave absorbing material mainly exists in the form of particles in asphalt slurry, asphalt accounts for less than 10% of the specific gravity of the asphalt concrete, most of the asphalt concrete still is aggregate with poor wave absorbing effect, the wave absorbing agent is limited in distribution in the asphalt concrete, and efficient microwave heating performance cannot be realized. Therefore, the magnetite is technically disclosed to be used as microwave absorption aggregate to replace the traditional aggregate, so that the microwave heating performance of the asphalt concrete is greatly enhanced, but the magnetite is more concentrated in production area distribution and high in transportation cost, and the popularization and the use of the magnetite are restricted. In addition, because the wave absorbing material with a single loss mechanism has a limited effect of improving the wave absorbing performance, in practical application, two or more than two microwave absorbing materials with different loss mechanisms are generally adopted, and the microwave absorbing capacity of the asphalt concrete is improved by simultaneously improving the complex dielectric constant and the complex permeability of the asphalt concrete, but the final microwave absorbing effect is optimal, and the wave absorbing material and the surrounding space need to have good impedance matching. When a plurality of wave-absorbing materials are added into asphalt concrete as aggregates, the larger particle size of the wave-absorbing materials causes that each material particle is only an isolated individual with a single loss mechanism, and each material particle cannot form a whole body which is well matched with the impedance of the surrounding space, so that the incident microwaves generate larger reflection on the surface of the aggregates.
In combination with the above reasons, the microwave heating process for asphalt concrete in the prior art still has the problems of poor heating effect and low efficiency.
Disclosure of Invention
The invention provides a microwave absorption reinforced aggregate structure and a preparation method and application thereof, which are used for solving the technical problems of weak wave absorption capability of the aggregate of the existing asphalt concrete pavement, poor repairing effect by adopting a microwave heating technology and low efficiency.
In order to solve the technical problems, the invention adopts the following technical scheme:
a microwave absorption reinforced aggregate structure comprises a core structure and an outer layer structure; the outer layer structure is wrapped outside the core structure in a shell shape; at least one hole is arranged in the core structure.
The technical scheme is characterized in that material boundaries are formed inside the aggregate structure due to the existence of the holes in the core structure, and the propagation path of the microwave in the aggregate is lengthened due to the fact that the microwave is scattered and reflected at different medium interfaces, so that the loss proportion of the microwave in the core structure is increased, more microwave energy is converted into heat energy, and the microwave absorption efficiency and the energy conversion efficiency of the microwave absorption reinforced aggregate structure can be improved.
As a further preferable mode of the above technical solution, the holes are through-type or closed-type, and the shape of the holes is one or a combination of several of regular hexagon, circle, rectangle and triangle. The holes can be open structures penetrating through the core structure and the outer layer structure of the whole aggregate structure, or can be closed structures only existing in the core structure or the core structure and the outer layer structure; the inventor finds that the shape and the size of the holes can influence the equivalent dielectric constant of the structure, so that the wave absorbing effect of the structure is influenced, and in addition, the material stress on the edges of the holes is different when the aggregates are stressed. Therefore, the shape of the hole is defined as one or a combination of several of regular hexagon, circle, rectangle and triangle by comprehensively considering the mechanical property and the wave absorbing effect.
As a further preferable mode of the above-described aspect, the outer layer structure has a lower magnetic permeability and a lower dielectric constant than the core structure. According to the impedance matching principle, the dielectric constant and the magnetic conductivity of the outer layer structure material are adjusted, so that the outer layer structure and the surrounding space have better impedance matching; meanwhile, the holes in the core structure and the outer layer structure can jointly adjust equivalent electromagnetic parameters of the aggregate structure to meet impedance matching requirements, and the proportion of incident microwaves at the interface of the wave-absorbing aggregate structure is increased, so that the overall wave-absorbing capacity and the energy conversion efficiency of the aggregate structure are obviously improved.
As a further preferable mode of the above technical solution, the thermal conductivity of the outer layer structure is higher than the thermal conductivity of the core structure. Compared with the material of the core structure, the material of the outer layer structure in the technical scheme has higher heat conductivity coefficient, the design can enable the aggregate structure to have gradient heat conductivity coefficient from inside to outside, and heat generated by the core structure can be rapidly transferred to the surrounding space, so that the heating efficiency of the aggregate structure to the asphalt concrete is improved.
As a further preferred option of the above technical solution, the core structure and the outer layer structure are respectively composed of wave-absorbing materials of different kinds and proportions. The selection principle of the types and the proportions of the wave-absorbing materials of the core structure is that the sum of the conductance loss, the dielectric loss and the magnetic loss of the core structure obtained by compounding is maximum on the basis of larger dielectric constant and magnetic conductivity; the selection principle of the types and the proportions of the wave-absorbing materials of the outer layer structure is that the relative dielectric constant and the relative magnetic conductivity of the outer layer structure obtained by compounding are as close as possible to the theoretical values meeting the impedance matching condition on the basis of having a higher heat conductivity coefficient than that of the core structure.
As a further preferred aspect of the above technical solution, the core structure and the outer layer structure are made of wave-absorbing materials, and the wave-absorbing materials include at least two of a conductive loss material, a dielectric loss material, and a magnetic loss material. The electromagnetic parameters of the wave-absorbing material can change along with the change of microwave frequency, and the microwave heating frequency of the current industrial application is 915MHz, 2.45GHz and 5.8GHz, so that the wave-absorbing aggregate can have a certain microwave heating effect under the microwaves of different frequencies by selecting the combination of two or more different wave-absorbing materials. Meanwhile, good impedance matching performance requires a certain quantitative relationship between the relative dielectric constant and the relative magnetic permeability of the material, and the wave-absorbing material with a single loss mechanism is difficult to meet the requirements, so that two or more wave-absorbing materials with different loss mechanisms are required to improve the impedance matching of the aggregate, thereby enhancing the wave-absorbing performance of the aggregate.
As a further preferred option of the above technical solution, the electrical conduction loss material is one or a combination of several of graphite, carbon black, carbon nanotubes, graphene and carbon fibers; the dielectric loss material is one or a combination of more of silicon carbide, silicon nitride, titanium dioxide, zirconium dioxide, zinc oxide, aluminum oxide, manganese oxide and magnesium oxide; the magnetic loss material is one or a combination of more of ferrite, metal powder, iron nitride, carbonyl iron powder and hydroxyl iron powder.
As a further preferable mode of the above technical solution, the aggregate structure is spherical or polyhedral, the particle size of the aggregate structure is 5 to 30mm, the particle size of the core structure is 4 to 25mm, and the thickness of the outer layer structure is 1 to 5mm. As the specification has requirements on the gradation of the asphalt concrete, in order to replace natural aggregate with wave-absorbing aggregate as much as possible, the structure size is determined according to the particle size of the common aggregate, and the total particle size of the wave-absorbing aggregate can be flexibly designed according to the gradation requirements of the asphalt concrete in actual use. In addition, the sizes of the core structure and the outer layer structure can influence the equivalent electromagnetic parameters of the structure so as to influence the wave-absorbing performance, so that the sizes of the outer layer structure and the core structure can also be optimized by using simulation software, and the microwave heating performance of the wave-absorbing aggregate is further improved.
As a further preferable mode of the above technical solution, the outer layer structure and the core structure are formed by printing through a 3D printing technology.
Based on the same technical concept, the invention also provides a preparation method of the microwave absorption reinforced aggregate structure in the technical scheme, which comprises the following steps:
(1) Designing the size of each structure and the material parameters of each structure in the microwave absorption reinforced aggregate structure to generate model data;
(2) Uniformly mixing wave-absorbing material powder and binder powder according to different compositions to respectively prepare powder A for printing the core structure and powder B for printing the outer layer structure;
(3) Inputting the model data obtained in the step (1) into a 3D printer, setting a printing program, respectively filling the powder A and the powder B into a material box, and sintering layer by layer in a protective atmosphere environment to obtain an aggregate blank;
(4) And carrying out post-treatment on the aggregate blank to obtain the microwave absorption reinforced aggregate structure.
The technical scheme is that the wave-absorbing structure taking functional requirements as design guidance is combined with the emerging 3D printing technology, designers can fully excavate the potential of the structure according to the functional requirements by virtue of the advantage of integrated rapid molding of a complex structure of the 3D printing technology without being limited by the design of the traditional manufacturing mode, after the structure of the aggregate is optimized and improved aiming at a specific use environment, the traditional manufacturing mode also has intermediate links such as numerical control machine programming, mold design and manufacturing and the like, the wave-absorbing aggregate can be directly produced on the basis of a designed structure model in a rapid batch mode by utilizing the 3D printing technology, the production efficiency is improved, and the cost is greatly reduced. Meanwhile, the composition of the materials can be accurately regulated and controlled on a microscale by applying a 3D printing technology, the uniformity of the materials of all parts of the wave-absorbing aggregate is ensured by a manufacturing mode of printing and superposing layer by layer, electromagnetic parameters of the wave-absorbing aggregate can be close to a design target value by a designer through regulating and controlling the composition of the printing materials, and finally the wave-absorbing aggregate which better meets the design scheme in structure and material is manufactured.
As a further optimization of the technical scheme, the weight ratio of the wave-absorbing material to the binder is (0.5-0.85): (0.15-0.5).
Preferably, the particle size of the wave-absorbing material powder is 10-100 μm, and the particle size of the binder powder is 10-150 μm. The particle size directly influences the fluidity of the composite powder for 3D printing, and also influences the process parameters during 3D printing, for example, the thickness of a single layer is mainly determined by the particle size, and too thick a layer influences the adhesion between layers, and too small a layer causes the powder adhesion phenomenon. In order to achieve a good 3D printing effect, the particle size and process parameters must be considered comprehensively, and too large or too small can affect the 3D printing forming effect, so that the range of the particle size is limited. In addition, the smaller the particle size, the higher the bulk density, which is more beneficial to improving the relative density and strength of the final aggregate, but the smaller the particle size means the higher the cost, and the limitation of the preferred embodiment on the particle size can not only meet the requirement of the strength of the final aggregate, but also reduce the cost as much as possible, thereby ensuring the effect of 3D printing.
As a further preferred aspect of the above technical solution, the wave-absorbing material is a combination of two or more of a conductive loss material, a dielectric loss material and a magnetic loss material; the conductive loss material is one or a combination of more of graphite, carbon black, carbon nanotubes, graphene and carbon fibers; the dielectric loss material is one or a combination of more of silicon carbide, silicon nitride, titanium dioxide, zirconium dioxide, zinc oxide, aluminum oxide, manganese oxide and magnesium oxide; the magnetic loss material is one or a combination of more of ferrite, metal powder, iron nitride, carbonyl iron powder and hydroxyl iron powder; the binder is one of PLA, ABS, TPU, nylon, CPE, PC, PP, PPSF, PETG, PVA, resin and paraffin.
As a further preferable mode of the above technical means, in the step (3), the powder is sintered by Selective Laser Sintering (SLS). Compared with other 3D printing technology types, the selective laser sintering technology has higher precision, is more suitable for manufacturing the aggregate with smaller size in the invention, and the aggregate obtained by adopting the laser sintering mode has higher density and better strength, and is easier to meet the requirement of the aggregate on the aspect of mechanical property.
As a further preferable mode of the above technical solution, in the sintering process, the operating parameters of the laser are as follows: the laser power is 5-400W, the scanning speed is 300-4000 mm/s, the scanning interval is 0.05-0.5 mm, the single-layer thickness is 0.05-0.5 mm, and the laser energy density is 0.01-0.2J/mm 2 . As mentioned above, the quality of the formed green body is closely related to the process parameters and the particle size of the powder, and the performance of different 3D printing devices is different, so that suitable process parameters should be determined according to the specific used 3D printing device and the powder condition, and the process parameters disclosed by the preferred scheme can significantly improve the quality of the prepared aggregate green body.
As a further preferable mode of the above technical solution, the post-treatment operation in step (4) is one or a combination of several of pressureless sintering, hot-pressing sintering, hot isostatic pressing sintering, reaction sintering, and microwave irradiation.
Based on the same technical concept, the invention also provides an application of the microwave absorption reinforced aggregate structure in the technical scheme or the microwave absorption reinforced aggregate structure prepared by the preparation method in the technical scheme, and the microwave absorption reinforced aggregate structure is used as aggregate to be applied to asphalt concrete.
Compared with the prior art, the invention has the advantages that:
(1) The wave-absorbing aggregate structure can be designed according to functional requirements and conditions; the core structure is provided with one or more holes, so that incident microwaves generate multiple reflection and scattering in the core structure, the loss ratio of the microwaves in the core structure is increased, and more microwave energy is converted into heat energy; the holes mainly affect the microwaves which are incident into the aggregate, an outer layer structure is arranged for reducing the reflection of the microwaves on the surface of the aggregate, and the dielectric constant and the magnetic conductivity of the material of the outer layer structure are adjusted according to the impedance matching principle, so that the outer layer structure and the surrounding space have better impedance matching, and the proportion of the incident microwaves at the interface of the wave-absorbing aggregate is increased; in addition, the outer layer structure material has high heat conductivity coefficient and has the function of quickly transferring the heat generated by the core structure to the surrounding space; in addition, the total particle size of the wave-absorbing aggregate can be flexibly designed according to the grading requirement of asphalt concrete, and the sizes of the outer layer structure and the core structure can also be optimized by using simulation software, so that the microwave heating performance of the wave-absorbing aggregate is further improved; the design ensures that the finally obtained aggregate structure has the characteristics of good microwave heating performance and strong heat conduction capability, the structural design is flexible, the aggregate structure has better adaptability to different use environments, and the material is greatly saved according to the structure of the functional design.
(2) The preparation method disclosed by the invention is simple in process, safe, reliable and convenient to operate, and the wave-absorbing aggregate can be directly produced on the basis of a designed structural model in a rapid batch manner by using a 3D printing technology, so that the production efficiency is improved and the cost is greatly reduced; meanwhile, the composition of the materials can be accurately regulated and controlled on a microscale by applying a 3D printing technology, the uniformity of the materials of all parts of the wave-absorbing aggregate is ensured by a manufacturing mode of printing and superposing layer by layer, electromagnetic parameters of the wave-absorbing aggregate can be close to a design target value by a designer through regulating and controlling the composition of the printing materials, and finally the wave-absorbing aggregate which better meets the design scheme in structure and material is manufactured.
Drawings
FIG. 1 is a schematic structural view of a microwave absorption-reinforced aggregate structure of example 1;
FIG. 2 is a schematic cross-sectional view of the microwave absorbing reinforcing aggregate structure of example 1;
FIG. 3 is a schematic longitudinal sectional view of the microwave absorption-reinforced aggregate structure of example 1;
FIG. 4 is a schematic structural view of the microwave absorption-enhancing aggregate structure of example 2;
FIG. 5 is a schematic cross-sectional view of the microwave absorbing reinforcing aggregate structure of example 2;
FIG. 6 is a schematic longitudinal sectional view of the microwave absorption-reinforced aggregate structure of example 2;
FIG. 7 is a graph showing the surface temperature changes under microwave heating of Marshall test pieces of each example and comparative example.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
Example 1:
as shown in fig. 1 to 3, the microwave absorption reinforced aggregate structure of the present embodiment has a polyhedral shape, and includes a core structure and an outer layer structure (reference numeral 1 represents the outer layer structure, and reference numeral 2 represents the core structure in fig. 2 and 3), and the core structure is provided with a through-type hexagonal hole. The microwave absorption reinforced aggregate structures of the present example had 3 kinds of particle sizes of 10mm, 15mm, and 20mm, wherein the particle sizes of the core structures were 8mm, 12mm, and 15mm, respectively, and the thicknesses of the outer layer structures were 1mm, 1.5mm, and 2.5mm, respectively.
In the embodiment, the magnetic permeability of the outer layer structure is 1.534-0.138j, the dielectric constant is 3.352-0.313j, and the thermal conductivity is 32.2W/m.k; the magnetic permeability of the core structure is 1.783-0.527j, the dielectric constant is 5.732-0.713j, and the thermal conductivity is 21.6W/m.k.
The microwave absorbing reinforcing aggregate structure of the present example was prepared by the following steps:
(1) 3D models shown in figures 1, 2 and 3 are established in a computer by Solidworks software, and then slicing and layering processing are carried out on the designed three-dimensional models by layering software, wherein the layer thickness is 0.15mm.
(2) Weighing silicon carbide powder (dielectric loss material), ferroferric oxide powder (magnetic loss material) and polypropylene powder (binder) according to the weight ratio of 6. Adding silicon carbide powder and ferroferric oxide powder into a paraxylene solution, stirring at room temperature for 2 hours, heating to 110 ℃, adding polypropylene powder, stirring at constant temperature for 1 hour, and naturally cooling, washing, filtering and drying to obtain powder A. Mixing alumina powder, nickel-zinc ferrite powder and polypropylene powder according to a weight ratio of 7.
(3) Inputting the model data designed in the step (1) into a 3D printer, then respectively loading the powder A and the powder B prepared in the step (2) into a feed box of the 3D printer, setting the laser power at 15W, the scanning speed at 3200mm/s, the scanning distance at 0.3mm, the layer thickness at 0.15mm and the preheating temperature of a powder bed at 115 ℃. And starting the 3D printer, sintering and molding the powder layer by layer in a protective atmosphere environment, and naturally cooling and removing redundant powder to obtain an aggregate blank.
(4) And degreasing and presintering the aggregate blank, and then sintering the degreased blank in a vacuum pressureless manner to prepare a densified microwave absorption enhanced aggregate structure.
The microwave absorption reinforced aggregate structure of the embodiment is applied to asphalt concrete as an aggregate, and the specific method is as follows: according to the proportion of asphalt: mineral powder: natural aggregate: the wave-absorbing aggregate weight ratio is 5. The prepared standard marshall test piece was placed in a microwave oven and heated, the temperature curve is shown in fig. 7, after heating for 180s, the surface temperature of the test piece can reach 92.1 ℃, which is 58.7% higher than that of the common asphalt concrete (comparative example 1). The thermal conductivity of the test piece measured by a thermal conductivity meter was 4.6W/m.k, which is 2.42 times that of ordinary concrete (comparative example 1).
Example 2:
as shown in fig. 4 to fig. 6, the microwave absorption reinforced aggregate structure of the present embodiment is spherical, and includes a core structure and an outer layer structure (reference numeral 1 represents the outer layer structure, and reference numeral 2 represents the core structure in fig. 5 and fig. 6), and the core structure is provided with a through-type hexagonal hole; the microwave absorption reinforced aggregate structures of the present example had 3 kinds of particle sizes of 10mm, 15mm, and 20mm, wherein the particle sizes of the core structures were 8mm, 12mm, and 15mm, respectively, and the thicknesses of the outer layer structures were 1mm, 1.5mm, and 2.5mm, respectively.
In the embodiment, the magnetic permeability of the outer layer structure is 1.517-0.127j, the dielectric constant is 3.341-0.287j, and the thermal conductivity is 31.3W/m.k; the magnetic permeability of the core structure is 1.617-0.496j, the dielectric constant is 5.523-0.674j, and the thermal conductivity is 19.7W/m.k.
The microwave absorbing reinforcing aggregate structure of the present example was prepared by the following steps:
(1) 3D models shown in figures 4, 5 and 6 are established in a computer by Solidworks software, and then slicing and layering processing are carried out on the designed three-dimensional models by layering software, wherein the thickness of the layers is 0.15mm.
(2) Weighing titanium dioxide powder (dielectric loss material), barium ferrite powder (magnetic loss material) and nylon 12 (binder) powder according to a weight ratio of 5. Adding titanium dioxide powder and barium ferrite powder into a paraxylene solution, stirring at room temperature for 2h, heating to 110 ℃, adding nylon 12 powder, stirring at constant temperature for 1h, naturally cooling, washing, filtering and drying to obtain powder A. Mixing alumina powder, nickel-zinc ferrite powder and nylon 12 powder according to a weight ratio of 6.
(3) Inputting the model data designed in the step (1) into a 3D printer, then respectively loading the powder A and the powder B prepared in the step (2) into a feed box of the 3D printer, setting the laser power at 10W, the scanning speed at 2000mm/s, the scanning interval at 0.3mm, the layer thickness at 0.15mm and the preheating temperature of a powder bed at 170 ℃. And starting the 3D printer, sintering and molding the powder layer by layer in a protective atmosphere environment, and naturally cooling and removing redundant powder to obtain an aggregate blank.
(4) And degreasing and presintering the aggregate blank, and then sintering the degreased blank under vacuum and no pressure to prepare the densified microwave absorption enhanced aggregate structure.
The microwave absorption reinforced aggregate structure of the embodiment is applied to asphalt concrete as an aggregate, and the specific method is as follows: according to the proportion of asphalt: mineral powder: natural aggregate: the wave-absorbing aggregate weight ratio is 5. The prepared standard marshall test piece was placed in a microwave oven and heated, the temperature curve of which is shown in fig. 7, and after heating for 180s, the surface temperature of which could reach 90.3 ℃, which is 55.4% higher than that of the ordinary asphalt concrete (comparative example 1). The thermal conductivity of the test piece measured by a thermal conductivity meter was 4.3W/m.k, which is 2.26 times that of ordinary concrete (comparative example 1).
Comparative example 1:
a standard Marshall specimen was prepared according to a bitumen to ore powder to natural aggregate weight ratio of 5.8, a grading type of AC-16, and placed in a microwave oven for heating, the temperature profile of which is shown in FIG. 7, and after heating for 180s, the surface temperature was 58.1 ℃. The thermal conductivity of the test piece was measured by a thermal conductivity meter and was 1.9W/m.k.
Comparative example 2:
a standard marshall test piece was prepared according to a bitumen to ore powder to natural aggregate to magnetite weight ratio of 5.8, a grading type of AC-16, and placed in a microwave oven for heating, the temperature profile of which is shown in fig. 7, and after heating for 180 seconds, the surface temperature was 86.2 ℃. The thermal conductivity of the test piece was measured by a thermal conductivity meter and was 3.1W/m.k.
The above description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described examples. Modifications and variations that may occur to those skilled in the art without departing from the spirit and scope of the invention are to be considered as within the scope of the invention.

Claims (9)

1. A microwave absorption reinforced aggregate structure is characterized by comprising a core structure and an outer layer structure; the outer layer structure is wrapped outside the core structure in a shell shape; at least one hole is arranged in the core structure; the magnetic permeability and the dielectric constant of the outer layer structure are lower than those of the core structure, and the heat conductivity coefficient of the outer layer structure is higher than that of the core structure; the materials of the core structure and the outer layer structure comprise at least two of an electric conduction loss material, a dielectric loss material and a magnetic loss material; the outer layer structure and the core structure are printed and formed through a 3D printing technology.
2. The microwave absorption reinforced aggregate structure according to claim 1, wherein the holes are through-type or closed-type, and the shape of the holes is one or a combination of several of regular hexagon, circle, rectangle and triangle.
3. The microwave absorbing and reinforcing aggregate structure according to claim 1, wherein the electrically conductive lossy material is one or a combination of graphite, carbon black, carbon nanotubes, graphene and carbon fibers; the dielectric loss material is one or a combination of more of silicon carbide, silicon nitride, titanium dioxide, zirconium dioxide, zinc oxide, aluminum oxide, manganese oxide and magnesium oxide; the magnetic loss material is one or a combination of more of ferrite, metal powder, iron nitride, carbonyl iron powder and hydroxyl iron powder.
4. The microwave absorption reinforced aggregate structure according to any one of claims 1 to 3, wherein the aggregate structure is spherical or polyhedral, the particle size of the aggregate structure is 5 to 30mm, the particle size of the core structure is 4 to 25mm, and the thickness of the outer layer structure is 1 to 5mm.
5. A method of preparing a microwave absorbing reinforcing aggregate structure according to any one of claims 1 to 4, comprising the steps of:
(1) Designing the size of each structure and the material parameters of each structure in the microwave absorption reinforced aggregate structure to generate model data;
(2) Uniformly mixing wave-absorbing material powder and binder powder according to different compositions to respectively prepare powder A for printing the core structure and powder B for printing the outer layer structure; the wave-absorbing material comprises at least two of a conductive loss material, a dielectric loss material and a magnetic loss material;
(3) Inputting the model data obtained in the step (1) into a 3D printer, setting a printing program, respectively filling the powder A and the powder B into a material box, and sintering layer by layer in a protective atmosphere environment to obtain an aggregate blank;
(4) And carrying out post-treatment on the aggregate blank to obtain the microwave absorption reinforced aggregate structure.
6. The preparation method of the microwave absorption reinforced aggregate structure according to claim 5, wherein the weight ratio of the wave-absorbing material to the binder is (0.5-0.85): (0.15-0.5); the particle size of the wave-absorbing material powder is 10-100 mu m, and the particle size of the adhesive powder is 10-150 mu m; the conductive loss material is one or a combination of more of graphite, carbon black, carbon nanotubes, graphene and carbon fibers; the dielectric loss material is one or a combination of more of silicon carbide, silicon nitride, titanium dioxide, zirconium dioxide, zinc oxide, aluminum oxide, manganese oxide and magnesium oxide; the magnetic loss material is one or a combination of more of ferrite, metal powder, iron nitride, carbonyl iron powder and hydroxyl iron powder; the binder is one of PLA, ABS, TPU, nylon, CPE, PC, PP, PPSF, PETG, PVA and paraffin.
7. The method for preparing a microwave absorption enhanced aggregate structure according to claim 5, wherein in the step (3), the powder is sintered by adopting a Selective Laser Sintering (SLS) mode; in the sintering process, the working parameters of the laser are as follows: the laser power is 5-400W, the scanning speed is 300-4000 mm/s, and the scanning interval is 0.05-0.5mm, the thickness of the single-layer is 0.05 mm-0.5 mm, and the laser energy density is 0.01-0.2J/mm 2 。
8. The method for preparing a microwave absorbing and reinforcing aggregate structure according to claim 5, wherein the post-treatment operation in step (4) is one or a combination of pressureless sintering, hot-pressing sintering, hot isostatic pressing sintering, reaction sintering and microwave irradiation.
9. Use of a microwave absorbing reinforced aggregate structure according to any one of claims 1 to 4 or a microwave absorbing reinforced aggregate structure obtained by a method according to any one of claims 5 to 8 as an aggregate in asphalt concrete.
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