CN113000845B - Bionic drag reduction surface and manufacturing method thereof - Google Patents
Bionic drag reduction surface and manufacturing method thereof Download PDFInfo
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- CN113000845B CN113000845B CN202110182804.8A CN202110182804A CN113000845B CN 113000845 B CN113000845 B CN 113000845B CN 202110182804 A CN202110182804 A CN 202110182804A CN 113000845 B CN113000845 B CN 113000845B
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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
- B22F7/004—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 comprising at least one non-porous part
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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
- 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
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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
- 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
- B22F3/24—After-treatment of workpieces or articles
- B22F3/26—Impregnating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
- B29C70/58—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising fillers only, e.g. particles, powder, beads, flakes, spheres
- B29C70/64—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts comprising fillers only, e.g. particles, powder, beads, flakes, spheres the filler influencing the surface characteristics of the material, e.g. by concentrating near the surface or by incorporating in the surface by force
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T70/00—Maritime or waterways transport
- Y02T70/10—Measures concerning design or construction of watercraft hulls
Abstract
The invention discloses a bionic drag reduction surface and a manufacturing method thereof. The surface with the drag reduction/antifouling function is realized by combining the sintering technology and the microstructure transfer printing. The method can accurately manufacture the double-layer drag reduction surface of the flexible package micro-bulge, and the sintered molding body and the filling modified PDMS enable the surface to have self-healing property and wear resistance, so that the method has wide application prospect. The invention has the unique advantages of simple process, low manufacturing cost, high production efficiency and repeatability, and provides a brand new solution for manufacturing the anti-fouling/drag-reducing surface.
Description
Technical Field
The present invention relates to a drag reduction structure, and more particularly, to a drag reduction structure and a method for manufacturing the same.
Background
In recent years, the shortage of energy is becoming severe, and research on drag reduction performance is becoming an important subject, while underwater drag reduction is a direction in which researchers are continuously pursuing optimization. The existing research shows that the drag reduction technology is mainly divided into an active drag reduction mode and a passive drag reduction mode according to whether energy is input or not, wherein the active drag reduction mode is not ideal in the active drag reduction mode in which the energy is required to be input and the drag reduction effect is not ideal, and the active drag reduction equipment is complex and the drag reduction effect is not good. While the rough surface has better drag reduction performance, and breaks through the traditional concept of smoother drag reduction effect, so the research on the passive drag reduction surface with regular bulges has been kept until now. For better drag reduction, many drag reducing structures and manufacturing methods are mentioned at the same time, such as precision machining techniques and roll manufacturing techniques to simulate shark grooves and 3D printing techniques and cast molding techniques to simulate dolphin surface structures. The regular raised surfaces produced by these methods have the advantage of high precision and good forming results, but under prolonged erosion of these surfaces by water currents, these produced drag reducing surfaces do not have wear, corrosion and dirt resistance, thus maintaining drag reducing function in the drag reducing surfaces of the present invention while improving the wear and corrosion resistance properties of these surfaces.
Disclosure of Invention
The invention aims to: the invention aims to provide a bionic drag reduction surface which adopts a convex hull structure, has drag reduction and antifouling functions and also has wear resistance, corrosion resistance and self-healing property; the second purpose of the invention is to provide a preparation method of the bionic drag reduction surface, which aims at the problem that the convex characteristics of the drag reduction surface with a convex hull structure are difficult to process and manufacture, a sintering mold is manufactured, sintering process is carried out by using sintering powder, and then modified PDMS is filled, so that the composite drag reduction surface with controllable surface shape and size and the characteristics of flexibility, hydrophobicity and wear resistance is prepared.
The technical scheme is as follows: the bionic drag reduction surface comprises a substrate, a sintering layer and a flexible layer which are sequentially arranged from bottom to top, wherein the sintering layer and the flexible layer form a convex hull structure; a nanoparticle filling transition layer is arranged between the sintering layer and the flexible layer.
The convex hull structure can be conical bulges, cylindrical bulges or spherical bulges, and can be designed according to actual needs.
The invention relates to a drag-reducing/antifouling surface with a double-layer structure, which consists of a metal plate substrate, a sintering layer/PDMS mixed with nano particles and a flexible PDMS colloid layer mixed with nano particles from bottom to top. The smooth metal substrate can be matched with other surfaces easily, and the actual application is carried out; the PDMS mixed with nano particles is filled in the porous sintered layer, so that metal corrosion caused by pores can be reduced, the wear resistance and the hydrophobicity of the drag reduction/antifouling surface are enhanced, and the antifouling property of the surface is further improved; the surface layer of the drag reduction/antifouling surface is also a PDMS colloid layer mixed with nano particles, and the PDMS colloid layer is used for ensuring the size requirement of the convex hull structure and protecting the wear resistance, the pollution resistance and the oxidation resistance of the convex hull structure under the impact of water flow, thereby prolonging the service life of the surface. The finally formed drag reduction/antifouling surface is convenient to manufacture, simple in process, strong in adaptability and good in application prospect, and breaks through the manufacturing mode of a conventional convex hull structure.
The invention also provides a manufacturing method of the bionic drag reduction surface, which is a manufacturing method of the sintered metal filling improved PDMS drag reduction/antifouling surface with raised features, and aims at the problem that the raised features of the drag reduction surface with a convex hull structure are difficult to process and manufacture, a sintering mold is manufactured, sintering process is carried out by using sintering powder, and then the improved PDMS is filled, so that the composite drag reduction surface with controllable surface shape and size and the characteristics of flexibility, hydrophobicity and wear resistance is prepared.
According to the invention, a metal plate is used as a substrate, sintered powder and the substrate are integrally sintered and molded by adopting a metal powder sintering technology, a porous sintered plate with a convex structure is formed by demolding, modified PDMS is filled by a vacuum filling method, and finally the filled modified PDMS anti-fouling/anti-drag surface with convex characteristics is prepared by high-temperature shaping.
The manufacturing method comprises the following steps:
(1) Placing the sintered powder in a mold with a pit structure, and vibrating and compacting; wherein, the pit structure is matched with the designed drag reduction surface convex hull structure;
(2) Cleaning the surface of a metal substrate by using an ultrasonic cleaning tool, placing the substrate on sintering powder, sintering and molding, and demolding to obtain a sintered plate;
(3) Immersing the cleaned sintered plate into PDMS solution, and vacuum extracting at room temperature to obtain a filling plate; wherein, the PDMS solution is mixed with nano particles. And (3) carrying out vacuum extraction treatment to enable the nano particles in the PDMS solution to be filled into the porous structure of the sintered plate, so as to obtain the sintered plate filled with the nano particles, and marking the sintered plate as a filling plate.
(4) Injecting PDMS solution into a mold with a pit structure, reversely buckling the filling plate into the mold, heating, solidifying and forming in a vacuum environment, cooling, and demolding to remove redundant colloid to obtain the final product.
In the step (1), the mold with the pit structure may be formed by pressing powder (graphite powder, silicon powder), milling in a machining center, and electroforming. The sintered powder is a mixture of metal powder and non-metal powder, wherein the metal powder is copper, iron, aluminum or silver, and the non-metal powder is ceramic or calcium carbonate. Preferably, the sintering powder is a mixed powder of copper powder and calcium carbonate in a mass ratio of 7-9:1. Copper powder and calcium carbonate are unreactive in sintering, but the mixed powder sintering can keep the pores in the middle composite layer to become larger and more, and is more beneficial to the infiltration of PDMS solution so as to improve the comprehensive drag reduction effect.
In the step (2), the sintering heat preservation temperature is 800-950 ℃, the heat preservation time is 2-3 h, and the heating rate of the sintering furnace cannot exceed 10 ℃/min. Preferably, the temperature is kept at 800-850 ℃ for 1-1.5 h, and then the temperature is kept at 900-950 ℃ for 1-1.5 h.
The preparation process of the PDMS solution comprises the following steps: mixing PDMS, a PDMS curing agent and nano particles to obtain a mixed solution, wherein the mixing mass ratio of the PDMS to the PDMS curing agent to the nano particles is 10-15:1:2-3; stirring the mixed solution for 20-30 min at 400-450 rpm, and then performing ultrasonic treatment for 20-60min to obtain the PDMS mixed solution mixed with the nano particles. The nano particles can be metal powder or nonmetal powder, such as copper, iron, aluminum, ceramic, silicon dioxide, graphite powder, silicon powder or FeSiAl magnetic powder.
In the step (3), the vacuum degree of the vacuum extraction treatment is 10-0.01 Pa, and the vacuum treatment time is 20-60min.
Preferably, the PDMS solution in the step (3) is marked as a first solution, the PDMS solution in the step (4) is marked as a second solution, and the addition amount of the nano particles in the second solution is larger than that in the first solution; the plasticity of the PDMS silicone rubber on the surface is increased, the binding force of the flexible layer and the composite layer is enhanced, and the concentration of nano particles is higher, so that the surface hydrophobicity is further increased.
In the step (4), the heating temperature is 60-130 ℃, and the curing and molding time is 60-120min. After cooling, the composite board is completely separated from the graphite mold by adopting an uncovering type demolding method, and redundant materials are cut and removed to ensure the flatness of the board.
Optionally, the specific manufacturing process is as follows:
step 1), preparing a template with a pit structure by using a graphite material, and filling the graphite mould with sintered powder by adopting a vibration and compaction method as a negative mould. Cleaning the surface of the metal plate by using an ultrasonic cleaning tool, and placing the thin sheet on the sintered powder;
step 2), bonding the metal plate with the upper surface of the graphite die in a pressing mode, and finally putting the metal plate and the upper surface of the graphite die into a sintering furnace together for sintering and forming, solidifying and cooling, and then performing demoulding treatment to obtain a sintered plate;
step 3), cleaning the sintered plate, immersing the cleaned sintered plate into a PDMS organic solvent mixed with nano particles, filling the sintered plate in a vacuum extraction mode at room temperature, and taking out the filled plate;
and 4) injecting PDMS organic solvent mixed with nano particles into the graphite mould, reversely buckling the mixed solution filling board, putting the mixed solution filling board into the graphite mould, heating, solidifying and forming in a vacuum environment, cooling, demoulding and removing redundant colloid to obtain the composite anti-fouling/anti-drag board.
In the prior art, the convex hull surface is manufactured by mostly adopting a stamping forming technology, a metal flat plate is put into a pressing die, and the metal flat plate is integrally pressed and rapidly formed, but the defects of complex die manufacture and difficult processing of high-precision products exist; the surface of the convex hull structure is manufactured by adopting a compression casting molding technology, and the defects of difficult processing of a die and low casting yield are also present; the convex hull surface manufactured by the numerical control processing manufacturing method has obvious short plates in large-area molding and high manufacturing cost, the surface with the convex hull manufactured by the 3D printing technology in additive manufacturing has good yield by adopting nonmetal materials, but in the metal printing manufacturing process, the small-scale and high-precision convex structure is difficult to meet the manufacturing requirement.
The invention adopts the surface design of the raised characteristics, the preparation process of the metal powder sintering porous structure and the preparation process of the porous structure filling improved silicone rubber PDMS (polydimethylsiloxane), thereby realizing the preparation and the application of the flexible antifouling/drag reduction material with the patterned surface.
Sintering technology is widely used in the fields of filter elements and heat dissipation due to its good permeability and heat transfer under capillary forces for porous materials made of metal parts. Because the mechanical property of the material manufactured by the technology is poor, the surface is rough, and the secondary processing is difficult, the metal sintered manufactured part is rarely applied to the surface of equipment compared with the traditional casting. Polydimethylsiloxane (PDMS) is used as a chemically stable, nontoxic and abrasion-resistant silicone rubber, and is made into the most widely used organic polymer silicone material by virtue of transparency and unique hydrophobicity.
The invention provides a surface manufacturing method with a drag reduction/antifouling function based on a puffer surface structure, which combines a sintering technology and microstructure transfer printing to realize the surface with the drag reduction/antifouling function. The method can accurately manufacture the double-layer drag reduction surface of the flexible package micro-bulge, and the sintered molding body and the filling modified PDMS enable the surface to have self-healing property and wear resistance, so that the method has wide application prospect. The method has the unique advantages of simple process, low manufacturing cost, high production efficiency and repeatability, and provides a brand new solution for manufacturing the antifouling/drag reduction surface. The sintered layer is of a porous structure, a solvent is filled in the sintered porous layer by adopting a vacuum filling method so as to ensure that no pores exist on the surface, and a flexible layer is required to be filled again to ensure the designed bulge size because the size of the sintered layer is integrally reduced after cooling after sintering, and nano particles are added to improve the binding force and the antibacterial and antifouling capacity.
The beneficial effects are that:
(1) According to the invention, a porous metal sintering surface with regular raised patterns on the surface is manufactured by utilizing a metal powder sintering technology, and the filling of the plastic PDMS is combined to improve the sintering surface so as to improve the surface wear resistance, so that the antibacterial antifouling/drag reduction material applicable to the surface of equipment is prepared, and the antibacterial antifouling/drag reduction material is more suitable for actual demands.
(2) The invention combines the characteristics of the wear-resistant material manufactured by the sintering molding technology and the characteristics of flexibility and hydrophobicity of modified PDMS, and realizes low-cost batch manufacturing of the underwater antifouling, anti-drag and wear-resistant surfaces.
(3) The invention can realize the manufacture of double-layer drag reduction surfaces with internal metal support and external flexible coverage, and has wide application prospect.
(4) The sintered body filling modified rubber has a surface repairing function and can adapt to complex and severe marine environments; the surface wear resistance of the sintered body filled modified rubber is further, the raised structure is more resistant to water flow impact, and the reliability is high.
(5) The manufacturing method has the advantages of simple process, easy manufacture, no need of special equipment, low manufacturing cost and strong process adaptability.
(6) The antifouling/drag reduction plate is widely applicable to underwater equipment such as ships, submarines, underwater gliders and the like, and is applied to Jing Jiang; provides a brand new solution for the manufacture of antifouling and drag-reducing surfaces, and has the unique advantages of high precision, high efficiency, low cost and repeatability.
Drawings
FIG. 1 is a schematic representation of the structure of the drag reducing surface of the present invention.
FIG. 2 is a schematic of a manufacturing flow for a drag reducing surface.
Fig. 3 is a plot of PDMS planar contact angle test without added particles.
FIG. 4 is a photograph of a contact angle test of a drag reducing surface of the present invention.
FIG. 5 is a plot of drag reduction rate test results for drag reducing surfaces of the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples.
The schematic structural diagram of the drag reduction surface of the present invention is shown in fig. 1, which comprises a substrate 1, a sintering layer 2 and a flexible layer 3 sequentially arranged from bottom to top, wherein the sintering layer and the flexible layer together form a convex hull structure 4, and a nanoparticle filling transition layer is arranged between the sintering layer and the flexible layer.
FIG. 2 is a schematic illustration of a manufacturing process for a drag reducing surface, the manufacturing process comprising: and (3) manufacturing a die, filling sintered powder, sintering, solidifying and demolding, filling nano particles, heating and demolding, and finally obtaining the composite drag reduction plate.
Example 1:
in the embodiment, a graphite mold with a pit structure is manufactured by adopting a machining center for machining, and is used as a negative template of a drag-reducing/anti-fouling plate, nano copper powder is sintered and molded by adopting a sintering process, and then PDMS/SiO is configured 2 As a filler, a composite antifouling/drag reduction surface with controllable surface shape and size and flexible, hydrophobic and wear-resistant characteristics is prepared, as shown in figure 1, and the surface hydrophobicity test is shown in figure 4.
Step 1): the method comprises the steps of machining a template of a conical pit with the height of 0.3mm and the bottom diameter of 1mm by adopting a machining center, milling, drilling and fine grinding, filling nano copper powder (50-200 nm) into a graphite die by adopting a vibration and compaction method, removing redundant powder by adopting a scraper, and ensuring the edge of the die to be clean. Taking metal copper flakes with the same length and width as the die sizes, cleaning the surface of a metal plate by using an ultrasonic cleaning tool, placing the flakes on sintering powder and trimming;
step 2): the metal copper plate, the copper filling powder and the upper surface of the graphite die are tightly attached by an indirect pressure applying mode, and finally the metal copper plate, the copper filling powder and the upper surface of the graphite die are put in a sintering furnace in a proportion of 5:1, are kept at 850 ℃ for 1h and at 950 ℃ for 1h, wherein the heating rate of the sintering furnace cannot exceed 10 ℃ per minute, and are subjected to demoulding treatment after solidification and cooling, so that a sintered copper plate (the volume is reduced by about 5-20 percent);
step 3): PDMS, PDMS curing agent and hydrophobic SiO 2 (5-100 nm) blending PDMS organic solvent mixed with nano particles according to the weight of 10:1:2, stirring the mixed solution for 20min at the rotating speed of 450rpm, and then carrying out ultrasonic treatment for 20-60min to obtain PDMS solution mixed with nano particles with the concentration of 0.5-2 mg/ml. Immersing the sintered plate in alcohol, washing for 30-60min with ultrasonic washing instrument, vacuum degree of 10-0.01 Pa, and calciningImmersed in hydrophobic SiO of the junction plate 2 Mixing PDMS organic solvent of nano particles, vacuum extracting at room temperature for 20-50min for filling, taking out the filling plate, suspending and standing for 20min to remove residual organic solvent;
step 4): PDMS, PDMS curing agent and hydrophobic SiO 2 (5-100 nm) preparing PDMS organic solvent mixed with nano particles according to the weight of 10:1:3, slowly injecting into a graphite mould, wherein the injection volume is about 5-15% of that of a copper plate, reversely buckling the plate, putting the plate into the graphite mould, tightly attaching the plate, heating the plate to 100 ℃ in a vacuum environment, curing and forming for 100min, cooling, and demoulding to remove excessive colloid to obtain the composite anti-fouling/anti-drag plate.
Example 2:
the graphite mold with the pit structure is manufactured by adopting a machining center, is used as a negative template of a drag-reducing/anti-fouling plate, adopts a sintering process to sinter and mold nano copper powder/calcium carbonate, and then is provided with PDMS/graphite powder as a filler to prepare the composite anti-fouling/drag-reducing surface with the characteristics of black surface paint, controllable size, flexibility, hydrophobicity and wear resistance.
Step 1): manufacturing templates of conical pits with the height of 0.3mm and the bottom diameter of 1mm by adopting a machining center to process, milling, drilling and fine grinding, preparing nano copper powder (100-200 nm)/calcium carbonate mixed powder according to the ratio of 8:1, filling the mixed powder into a graphite mold by adopting a vibration and compaction method, removing redundant powder by adopting a scraping plate, and ensuring the edge of the mold to be clean. Taking metal copper flakes with the same length and width as the die sizes, cleaning the surface of a metal plate by using an ultrasonic cleaning tool, placing the flakes on sintering powder and trimming;
step 2): the metal copper plate, the copper filling powder and the upper surface of the graphite mold are tightly attached by an indirect pressure applying mode, and finally are put into a sintering furnace in a flat way, nitrogen and hydrogen with the proportion of 5:1 are filled, the temperature is kept for 1h at 850 ℃ and 1h at 900 ℃, wherein the temperature rising rate of the sintering furnace cannot exceed 10 ℃ per minute, and demoulding treatment is carried out after solidification and cooling, so that a sintered copper plate (the volume is reduced by about 5-20 percent);
step 3): PDMS, PDMS curing agent and graphite powder (5-50 nm) according to the weight of 10:1:2, mixing the mixed solution with PDMS organic solvent of mixed nano particles, stirring at 450rpm for 20min, then performing ultrasonic treatment for 20-60min, and obtaining PDMS solution of mixed nano particles with the concentration of 0.5-2 mg/ml. Immersing the sintered plate in PDMS organic solvent mixed with nano particles, vacuum extracting at room temperature for 20-50min for filling, taking out the filled plate, suspending and standing for 20min to remove residual organic solvent;
step 4): PDMS, PDMS curing agent and graphite powder (100-300 nm) are mixed according to the weight of 10:1:3, PDMS organic solvent mixed with nano particles is slowly injected into a graphite mould, the injection volume is about 5-15% of that of a copper plate, a standing plate is reversely buckled and placed into the graphite mould and tightly attached, the graphite mould is heated to 120 ℃ in a vacuum environment for curing and molding for 120min, and after cooling, the composite anti-fouling/anti-drag plate is obtained after demoulding and removing excessive colloid.
Comparative example:
the graphite mold with the pit structure is manufactured by adopting a machining center to be used as a negative template of the drag-reducing/anti-fouling plate, the nano copper powder is sintered and molded by adopting a sintering process, and then PDMS is arranged as a filler to prepare the composite anti-fouling/drag-reducing surface with controllable surface shape and size and the characteristics of flexibility, hydrophobicity and wear resistance, and the surface hydrophobicity is tested as shown in figure 3.
Step 1): manufacturing templates of conical pits with the height of 0.3mm and the bottom diameter of 1mm by adopting a machining center to process, milling, drilling and fine grinding, preparing nano copper powder (100-200 nm)/calcium carbonate mixed powder according to the ratio of 8:1, filling the mixed powder into a graphite mold by adopting a vibration and compaction method, removing redundant powder by adopting a scraping plate, and ensuring the edge of the mold to be clean. Taking metal copper flakes with the same length and width as the die sizes, cleaning the surface of a metal plate by using an ultrasonic cleaning tool, placing the flakes on sintering powder and trimming;
step 2): the metal copper plate, the copper filling powder and the upper surface of the graphite mold are tightly attached by an indirect pressure applying mode, and finally are put into a sintering furnace in a flat way, nitrogen and hydrogen with the proportion of 5:1 are filled, the temperature is kept for 1h at 850 ℃ and 1h at 900 ℃, wherein the temperature rising rate of the sintering furnace cannot exceed 10 ℃ per minute, and demoulding treatment is carried out after solidification and cooling, so that a sintered copper plate (the volume is reduced by about 5-20 percent);
step 3): and (3) preparing PDMS organic solvent mixed with nano particles by using PDMS and PDMS curing agent according to the weight of 10:1, stirring the mixed solution at the rotating speed of 450rpm for 20min, and then carrying out ultrasonic treatment for 20-60min to obtain the PDMS organic solvent. Immersing the sintered plate into PDMS organic solvent, vacuum extracting at room temperature for 20-50min for filling, taking out the filled plate, suspending and standing for 20min to remove residual organic solvent;
step 4): and 3, slowly injecting PDMS organic solvent according to the blending proportion in the step 3 into a graphite mold, wherein the injection volume is about 5-15% of that of the copper plate, reversely buckling the static plate, putting the static plate into the graphite mold, tightly attaching the static plate, heating, solidifying and forming the static plate in a vacuum environment, cooling, and demolding to remove excessive colloid to obtain the composite anti-fouling/anti-drag plate.
When the drag reduction plates obtained in the examples and the comparative examples are tested, the binding force between the flexible surface layer and the sintered layer can be increased in both examples 1 and 2, and compared with the comparative examples, the binding effect is increased by 20-50% and the wear resistance is improved by 30-50%. As shown in FIGS. 3 and 4, siO is mixed 2 The combination of the PDMS organic solvent and the sintered layer of the particles can effectively increase the hydrophobicity of the composite drag reduction plate, the contact angle can be increased by 30-50 degrees, and the antibacterial and antifouling properties of the surface can be further increased by 20-45%. As shown in FIG. 5, the double-layer structure of the flexible surface layer and the sintered layer has resistance reduction performance in a water tunnel test, and the resistance reduction rate is 10-15%, so that the resistance reduction performance is greatly improved.
Example 3:
the graphite mold with the pit structure is manufactured by adopting a machining center, is used as a negative template of a drag-reducing/anti-fouling plate, adopts a sintering process to sinter and mold nano copper powder/calcium carbonate, and then is provided with PDMS/graphite powder as a filler to prepare the composite anti-fouling/drag-reducing surface with the characteristics of black surface paint, controllable size, flexibility, hydrophobicity and wear resistance.
Step 1): manufacturing templates of conical pits with the height of 0.3mm and the bottom diameter of 1mm by adopting a machining center to process, milling, drilling and fine grinding, preparing nano copper powder (100-200 nm)/calcium carbonate mixed powder according to the ratio of 7:1, filling the mixed powder into a graphite mold by adopting a vibration and compaction method, removing redundant powder by adopting a scraping plate, and ensuring the edge of the mold to be clean. Taking metal copper flakes with the same length and width as the die sizes, cleaning the surface of a metal plate by using an ultrasonic cleaning tool, placing the flakes on sintering powder and trimming;
step 2): the metal copper plate, the copper filling powder and the upper surface of the graphite mold are tightly attached by an indirect pressure applying mode, and finally are put into a sintering furnace horizontally, nitrogen and hydrogen with the proportion of 5:1 are filled, the temperature is kept at 810 ℃ for 1.5h and 920 ℃ for 1.5h, wherein the heating rate of the sintering furnace cannot exceed 10 ℃ per minute, and demoulding treatment is carried out after solidification and cooling, so that a sintered copper plate (the volume is reduced by about 5-20 percent);
step 3): PDMS, PDMS curing agent and graphite powder (5-50 nm) according to the weight of 12:1:2, mixing PDMS organic solvent mixed with nano particles, stirring the mixed solution for 20min at the rotating speed of 450rpm, and then carrying out ultrasonic treatment for 20-60min to obtain PDMS solution. Immersing the sintered plate in PDMS organic solvent mixed with nano particles, vacuum extracting at room temperature for 20-50min for filling, taking out the filled plate, suspending and standing for 20min to remove residual organic solvent;
step 4): PDMS, PDMS curing agent and graphite powder (100-300 nm) are mixed according to the weight of 12:1:3, PDMS organic solvent mixed with nano particles is slowly injected into a graphite mould, the injection volume is about 5-15% of that of a copper plate, a standing plate is reversely buckled and placed into the graphite mould and tightly attached, the graphite mould is heated to 60 ℃ in a vacuum environment for curing and molding for 60min, and after cooling, the composite anti-fouling/anti-drag plate is obtained after demoulding and removing excessive colloid.
Example 4:
the graphite mold with the pit structure is manufactured by adopting a machining center, is used as a negative template of a drag-reducing/anti-fouling plate, adopts a sintering process to sinter and mold nano copper powder/calcium carbonate, and then is provided with PDMS/graphite powder as a filler to prepare the composite anti-fouling/drag-reducing surface with the characteristics of black surface paint, controllable size, flexibility, hydrophobicity and wear resistance.
Step 1): manufacturing templates of conical pits with the height of 0.3mm and the bottom diameter of 1mm by adopting a machining center to process, milling, drilling and fine grinding, preparing nano copper powder (100-200 nm)/calcium carbonate mixed powder according to the ratio of 9:1, filling the mixed powder into a graphite mold by adopting a vibration and compaction method, removing redundant powder by adopting a scraping plate, and ensuring the edge of the mold to be clean. Taking metal copper flakes with the same length and width as the die sizes, cleaning the surface of a metal plate by using an ultrasonic cleaning tool, placing the flakes on sintering powder and trimming;
step 2): the metal copper plate, the copper filling powder and the upper surface of the graphite mold are tightly attached by an indirect pressure applying mode, and finally are put into a sintering furnace in a flat mode, nitrogen and hydrogen with the proportion of 5:1 are filled, the temperature is kept for 1.5h at 825 ℃ and 1h at 930 ℃, wherein the heating rate of the sintering furnace cannot exceed 10 ℃ per minute, and demoulding treatment is carried out after solidification and cooling, so that a sintered copper plate (the volume is reduced by about 5-20 percent);
step 3): PDMS, PDMS curing agent and graphite powder (5-50 nm) according to the weight of 14:1:2, mixing PDMS organic solvent mixed with nano particles, stirring the mixed solution for 20min at a rotating speed of 450rpm, and then carrying out ultrasonic treatment for 20-60min to obtain PDMS solution. Immersing the sintered plate in PDMS organic solvent mixed with nano particles, vacuum extracting at room temperature for 20-50min for filling, taking out the filled plate, suspending and standing for 20min to remove residual organic solvent;
step 4): PDMS, PDMS curing agent and graphite powder (100-300 nm) are mixed according to the weight of 14:1:3, PDMS organic solvent mixed with nano particles is slowly injected into a graphite mould, the injection volume is about 5-15% of that of a copper plate, a standing plate is reversely buckled and placed into the graphite mould and tightly attached, the standing plate is heated to 60 ℃ in a vacuum environment for curing and molding for 60min, and after cooling, the composite anti-fouling/anti-drag plate is obtained after demoulding and removing excessive colloid.
The drag reducing plates obtained in examples 3 and 4 were tested, and the test results were identical to those of example 2, and the drag reducing test results of examples 2 to 4 were superior to those of example 1.
Claims (5)
1. A biomimetic drag reducing surface, characterized by: the device comprises a substrate, a sintering layer and a flexible layer which are sequentially arranged from bottom to top, wherein the sintering layer and the flexible layer form a convex hull structure, and a nanoparticle filling transition layer is arranged between the sintering layer and the flexible layer; the substrate is a copper substrate, a stainless steel substrate or an aluminum substrate; the sintered layer is of a porous structure, and PDMS mixed with nano particles is filled in the sintered porous layer by adopting a vacuum filling method; the flexible layer consists of a PDMS colloid layer mixed with nano particles; the sintering layer is formed by mixing nano copper powder and calcium carbonate, and the mass ratio of the nano copper powder to the calcium carbonate is 7-9:1; the nano particles are copper, iron, aluminum, ceramic, silicon dioxide, graphite powder, silicon powder or FeSiAl magnetic powder.
2. A method of producing a biomimetic drag reducing surface as in claim 1, comprising the steps of:
(1) Placing the sintered powder in a mold with a pit structure, and compacting;
(2) Placing a substrate on the sintering powder, wherein the substrate is a copper substrate, a stainless steel substrate or an aluminum substrate, sintering and molding, and demolding to obtain a sintered plate; the sintering powder is formed by mixing nano copper powder and calcium carbonate, and the mass ratio of the nano copper powder to the calcium carbonate is 7-9:1;
(3) Immersing the cleaned sintered plate into PDMS solution, and vacuum extracting at room temperature to obtain a filling plate; wherein, nano particles are mixed in the PDMS solution, and the nano particles are copper, iron, aluminum, ceramics, silicon dioxide, graphite powder, silicon powder or FeSiAl magnetic powder; the PDMS solution is prepared by mixing PDMS, a PDMS curing agent and nano particles, wherein the mass ratio of the PDMS to the PDMS curing agent to the nano particles is 10-15:1:2-3;
(4) Injecting PDMS solution into a mold with a pit structure, reversely buckling the filling plate into the mold, heating, solidifying and forming in a vacuum environment, cooling, and demolding to remove redundant colloid to obtain the final product.
3. The method of producing a biomimetic drag reducing surface according to claim 2, wherein: in the step (2), the sintering heat preservation temperature is 800-950 ℃, the heat preservation time is 2-3 h, and the heating rate of a sintering furnace cannot exceed 10 ℃/min.
4. The method of producing a biomimetic drag reducing surface according to claim 2, wherein: in the step (3), the vacuum degree is 10-0.01 Pa, and the vacuum treatment time is 20-60min.
5. The method of producing a biomimetic drag reducing surface according to claim 2, wherein: in the step (4), the heating temperature is 60-130 ℃, and the curing and molding time is 60-120min.
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