Foam calcium phosphate-based coating for protection against extreme dynamic loads, method of preparation and use

Abstract

The application discloses a preparation method of a foam calcium phosphate-based energy-absorbing coating for extreme dynamic load protection, and belongs to the technical field of energy-absorbing coatings. The method comprises the following steps: S1, polyurethane sponge is respectively immersed in anhydrous ethanol, a NaOH solution and a dopamine solution for treatment, and then freeze-drying is performed; S2, the prepared polyurethane sponge is immersed in a sodium alginate gel solution to construct a dried gradient gel coating precursor; S3, the dried gradient gel coating precursor is immersed in a calcium phosphate deposition slurry to obtain a foam calcium phosphate coating precursor through an electric field orientation deposition method; and S4, a foam calcium phosphate-based energy-absorbing coating is prepared through a gradient sintering method. The application further provides the foam calcium phosphate-based coating prepared by using the above preparation method and application thereof. The preparation method of the foam calcium phosphate-based energy-absorbing coating for extreme dynamic load protection solves the problems of weak interfacial bonding strength, poor energy-absorbing and shock-absorbing effect and inability to resist explosion shock waves of existing explosion-proof coating materials and aerogel materials in an extreme dynamic load environment.

Description

Technical Field

[0001] This invention belongs to the technical field of building explosion-proof engineering materials, specifically relating to a method for preparing a foamed calcium phosphate-based coating for extreme dynamic load protection, and also relating to the foamed calcium phosphate-based coating for extreme dynamic load protection prepared by the above preparation method and its application. Background Technology

[0002] With the increasing demands for structural safety in industry and public facilities, the protective capability of building structures against explosive impacts, terrorist attacks, and industrial accidents has become a key technical indicator. Existing explosion-proof technologies mainly employ reinforced concrete structural reinforcement, fiber-reinforced composite material coating, and explosion-proof coating protection. Among these, explosion-proof coatings are widely used in the external wall protection of petrochemical facilities, military bunkers, and important public buildings due to their advantages such as convenient construction, lightweight efficiency, and strong repairability. Currently, commonly used explosion-proof coating materials are mainly polymer-based materials such as polyurea and polyurethane. Although they possess good toughness and ductility and can absorb explosive impact energy to a certain extent, they still suffer from insufficient interfacial bonding strength, poor high-temperature stability, and performance degradation after repeated impacts under extreme dynamic load environments. Furthermore, single polymer coatings cannot simultaneously meet the synergistic requirements of rigid impact resistance and flexible energy absorption, limiting their long-term application in building explosion-proof engineering.

[0003] Currently, researchers have obtained composite explosion-proof coating materials by optimizing the composition of polymer-based explosion-proof materials and adding inorganic reinforcing fillers. While these composite coating materials show improved compressive strength and energy absorption performance—for example, composite explosion-proof coatings prepared by adding carbon nanotubes, glass microspheres, or ceramic particles to a polyurea or epoxy resin matrix exhibit certain compressive strength (3-8 MPa) and impact energy absorption rate (40-55%)—practical applications still face challenges. The weak interfacial bonding between the inorganic filler and the organic matrix leads to low load transfer efficiency under explosive impact, making it prone to crack initiation and propagation at the interface, causing coating peeling and failure. Furthermore, the single pore size distribution results in a single stress wave dissipation path, hindering efficient absorption of broadband impact energy and thus limiting its application in building explosion-proof engineering. In addition, aerogel materials, due to their extremely high porosity, ultra-low density, and low thermal conductivity, are widely used for explosion-proof shock absorption and energy absorption. However, aerogel materials still have inherent high brittleness in use, which makes them prone to overall brittle fracture under explosive impact loads. Under continuous explosive shock wave loading, they are prone to interlayer slip and delamination, which prevents the formation of a continuous energy absorption interface and causes the overall structure to lose its integrity.

[0004] To address the aforementioned issues, researchers have modified aerogels by adjusting their composition, introducing reinforcing phases, or altering their pore structure. While composite aerogel materials have shown improved thermal insulation and lightweight properties—for example, composite aerogels prepared by adding carbon nanotubes, graphene, or polymer fibers to a silica aerogel matrix exhibit certain compressive strength (0.5–2.0 MPa) and compression resilience (30–50%)—practical applications still suffer from problems such as low load transfer efficiency due to weak interfacial bonding between the reinforcing phase and the matrix, leading to overall brittle fracture and interlaminar cracking under dynamic impact loads. Furthermore, the inherent high brittleness of single aerogel materials prevents them from effectively absorbing energy through plastic deformation or structural densification; the porous structure is prone to irreversible collapse during compression, resulting in low energy absorption efficiency (typically <40%). In addition, existing composite aerogels have uneven pore structure distribution and poor interlayer interface bonding strength. Under continuous loading of explosive shock waves, they are prone to interlayer slippage and delamination, and cannot form a continuous energy absorption interface, thus limiting their application in the field of building explosion protection engineering.

[0005] The Chinese invention patent "A Self-Dimming Transparent Composite Aerogel and Its Preparation Method", filed on June 15, 2017, with application number CN201710451818.9, provides a self-dimming transparent composite aerogel with excellent thermal insulation, transparency, lightweight, sound insulation, explosion-proof, shock absorption, and energy absorption properties. However, due to the inherent high brittleness of silica aerogel, the material is prone to overall fragmentation and interlayer cracking under explosive shock waves or dynamic impact loads, making it unable to effectively absorb energy through plastic deformation or structural densification. Furthermore, since the interlayer bonding is only physical, slippage, peeling, and delamination easily occur under the impact of explosive shock waves, leading to a loss of overall structural integrity and the inability to form a continuous energy absorption interface, thus limiting the material's application in building explosion-proof engineering.

[0006] The Chinese invention patent "A Silica Aerogel Composite Material and Molding Method," filed on July 3, 2013, with application number CN201310277646.X, adds expanded perlite to the existing silica aerogel composition and uses a pre-compression molding gel method to obtain an aerogel composite material, which is widely used in thermal insulation, shock absorption, and other fields. Although this aerogel has high compressive strength (3MPa), good flame retardancy (thermal conductivity at room temperature: 0.04w / mk), and excellent explosion-proof and shock absorption effects, it still suffers from the problem that shrinkage at high temperatures can cause the material's pore structure to collapse, thus failing to continuously block blast shock waves, limiting its application in the field of building explosion-proof engineering.

[0007] The Chinese invention patent "Integral Coordinated Concrete Explosion-Proof Wall," filed on September 23, 2020, with application number CN202011010948.7, introduces an explosion-proof polymer styrene-acrylic emulsion coating onto explosion-proof fiber concrete to construct a concrete explosion-proof wall. While this material possesses high strength and resistance to blast shock waves, it suffers from drawbacks. Because the energy-absorbing and damping layer is made of asphalt, rubber, and silicone resin-based materials and hardening additives through injection hardening, the hardened material exhibits high rigidity and poor elasticity. This results in extremely poor energy absorption and damping effects against low-frequency, small-amplitude vibrations and continuous micro-impacts (such as equipment operation vibrations, vehicle traffic impacts, and minor aftershocks of explosions), easily leading to structural resonance and exacerbating localized stress concentration within the wall.

[0008] To address the problems of weak interlayer bonding strength and uneven distribution of dense pore structure in the aforementioned invention patents, which prevent the formation of continuous energy absorption interfaces and result in poor shock absorption and energy dissipation performance, and the inability to continuously block explosive shock waves, a single aerogel material is needed. Furthermore, the high rigidity of the hardened energy-absorbing and shock-absorbing layer in a single explosion-proof coating also leads to poor energy absorption and shock absorption effects. Therefore, there is an urgent need for a foamed calcium phosphate-based energy-absorbing coating material for extreme dynamic load protection, applicable to explosion-proof, shock-absorbing, and energy-absorbing applications in building engineering. Summary of the Invention

[0009] The first objective of this invention is to provide a method for preparing a foamed calcium phosphate-based coating for protection against extreme dynamic loads, which solves the problems of weak interfacial bonding strength, poor energy absorption and shock absorption effect, and inability to resist explosive shock waves in existing explosion-proof coating materials and aerogel materials under extreme dynamic load environments.

[0010] A second objective of this invention is to provide a foamed calcium phosphate-based coating for extreme dynamic load protection prepared using the above-described preparation method.

[0011] A third objective of this invention is to provide the application of the aforementioned foamed calcium phosphate-based coating for protection against extreme dynamic loads.

[0012] The first technical solution adopted in this invention is: a method for preparing a foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection, the specific method of which is as follows:

[0013] S1. Preparation of polydopamine-modified polyurethane sponge: The polyurethane sponge was immersed in anhydrous ethanol, NaOH solution and dopamine solution respectively for treatment, rinsed and freeze-dried to obtain polydopamine-modified polyurethane sponge. S2. Constructing a gradient gel coating: Immerse polydopamine-modified polyurethane sponge in sodium alginate gel solution and construct a dried gradient gel coating precursor using the gradient template method. S3. Preparation of foamed calcium phosphate coating precursor: The dried gradient gel coating precursor is immersed in calcium phosphate deposition slurry, and the foamed calcium phosphate coating precursor is obtained by electric field directional deposition method. S4. A foamed calcium phosphate-based energy-absorbing coating was prepared by gradient sintering.

[0014] The invention is further characterized by: The specific method for S1 is as follows: S1.1 Soak the block polyurethane sponge in anhydrous ethanol and sonicate for 30-60 min until it is evenly dispersed. Wash with deionized water and dry at room temperature for 12-24 h. Subsequently, the polyurethane sponge was immersed in a NaOH solution with a concentration of 1~2 mol / L and treated in a water bath at 50~70℃ for 2~5 h. After washing with deionized water, it was dried at room temperature for 12~24 h to obtain the pretreated polyurethane sponge. S1.2 Prepare a Tris-HCl buffer solution with a concentration of 30~60 mM and adjust the pH of the Tris-HCl buffer solution to 7.4~8.5. Then add dopamine hydrochloride to adjust the concentration of the above buffer solution to 1.5~2.5 mg / mL and store it in the dark to obtain the dopamine buffer solution. S1.3. Immerse the pretreated polyurethane sponge in dopamine buffer solution, place it on a shaker and shake it in the dark for 8-12 hours, then remove the polyurethane sponge and rinse it with deionized water. After completion, place the polyurethane sponge in an environment with a temperature of -20 to -40°C and a vacuum degree of 5 to 10 Pa, and freeze-dry it for 24 to 36 hours to obtain polydopamine-modified polyurethane sponge.

[0015] The specific method for S2 is as follows: S2.1 Slowly add sodium alginate powder to deionized water, stir in a water bath at 50~80℃ for 2~4 h until completely dissolved, and let stand to degas for 4~6 h to obtain sodium alginate gel solution. S2.2 Immerse the polydopamine-modified polyurethane sponge in sodium alginate gel solution and place it in a vacuum drying oven. Evacuate at a vacuum degree of -0.1~-0.5MPa for 20~30min. After completion, slowly release the gas at a release rate of 0.01~0.03 MPa / min to allow the sodium alginate gel solution to fully penetrate into the interior of the polyurethane sponge. Use filter paper to remove excess solution from the surface to obtain the modified polydopamine-modified polyurethane sponge. S2.3. Using a spray method, a gradient coating was constructed using CaCl2 solutions of different concentrations as crosslinking agents. After spraying, the modified polydopamine-modified polyurethane sponge was placed in a constant temperature and humidity chamber for 30-60 min and then removed. It was then placed in a refrigerator at 2-8℃ for 1-3 h and excess moisture was removed to obtain the gradient gel coating precursor. S2.4 The obtained gradient gel coating precursor is dried in an environment with a temperature of -20~-40℃ and a vacuum degree of 3~10 Pa for 36~48 h to obtain a dried gradient gel coating precursor.

[0016] In S2.1, the mass ratio of sodium alginate to deionized water is 10~30g:900~1200mL.

[0017] The specific method for constructing the gradient coating in S2.3 is as follows: A dense cross-linked layer was obtained by spraying a 0.8-1.2 wt.% CaCl2 solution onto the upper surface of the sponge at a depth of 0-2 mm for 10-20 s. A 0.3-0.5 wt.% CaCl2 solution was sprayed onto the middle layer of the sponge for 5-7 seconds to obtain an over-crosslinked layer. A buffer cross-linked layer is obtained by spraying a 0.05-0.2 wt.% CaCl2 solution at a depth of 5-10 mm in the inner layer of the sponge for 2-4 seconds.

[0018] The specific method for S3 is as follows: S3.1. Disperse the calcium phosphate source powder evenly in deionized water and stir for 5-10 min to obtain the initial calcium phosphate slurry; then, add the dispersant and adjust the pH to 9.5-10.5 with a 0.5-1 mol / L NaOH solution to obtain the calcium phosphate slurry. S3.2 Place the calcium phosphate slurry in a vacuum drying oven and degas it at a vacuum of -0.08 to -0.10 MPa for 20 to 40 minutes to obtain a stable and dispersed calcium phosphate deposition slurry. S3.3 Using a coaxial electric field deposition apparatus, calcium phosphate deposition slurry is circulated into the deposition apparatus at a flow rate of 15~25 mL / min, and the dried gradient gel coating precursor obtained in S2 is completely immersed in the calcium phosphate deposition slurry. Then, the pulse power supply is turned on, and the electric field strength is set to 60~100 V / cm, the pulse frequency is 100~150 Hz, and deposition is carried out for 30~60 min. After deposition, it is washed 2~4 times with deionized water and dried for 20~30 h at a temperature of -45~-55℃ and a vacuum degree of 5~15 Pa to obtain the electric field-assisted directional deposition modified foamed calcium phosphate coating precursor.

[0019] The calcium phosphate source powder in S3.1 is hydroxyapatite or tricalcium phosphate powder; The mass ratio of hydroxyapatite or tricalcium phosphate powder to deionized water is 20-40 g: 60-80 mL. The dispersant is ammonium polyacrylate or sodium polymethacrylate; The amount of dispersant added is 0.5~1.5% of the mass of the calcium phosphate source powder.

[0020] The specific method for S4 is as follows: First, the foamed calcium phosphate coating precursor obtained from S3 was placed in a tube furnace, and nitrogen was introduced to replace the air in the furnace. The temperature was increased from room temperature to 200-250℃ at a rate of 2-5℃ / min, and held at this temperature for 60-120 min under nitrogen atmosphere protection. Then, the temperature was increased to 300-350℃ at a rate of 1.0-3.0℃ / min, and held for 90-150 min. After this, the nitrogen supply was stopped, and the temperature was increased to 400-500℃ at a rate of 1.0-3.0℃ / min, held for 120-180 min, then increased to 550-650℃ and held for 60-120 min. Finally, the temperature was increased to 1050-1150℃ at a rate of 3.0-5.0℃ / min, held for 120-240 min, and then allowed to cool naturally to room temperature with the furnace to obtain the foamed calcium phosphate-based coating.

[0021] The second technical solution adopted in this invention is: a foam calcium phosphate-based energy-absorbing coating for extreme dynamic load protection prepared according to the above preparation method.

[0022] The third technical solution adopted in this invention is: the application of the foamed calcium phosphate-based energy-absorbing coating prepared by this invention in the field of structural protection materials technology.

[0023] The beneficial effects of this invention are: (1) The present invention provides a method for preparing a foam calcium phosphate-based coating for extreme dynamic load protection. In view of the problems of weak interfacial bonding and poor stress transmission in existing explosion-proof coatings, the method enhances the organic-inorganic interfacial bonding strength through a polydopamine active interfacial layer to suppress interfacial debonding under explosive impact. At the same time, a calcium alginate gradient cross-linking structure is constructed to achieve stress transmission step by step. The ionic cross-linking network improves the impact toughness and energy absorption efficiency through reversible fracture and recombination. (2) The method for preparing foam calcium phosphate-based coating for extreme dynamic load protection of the present invention addresses the problem that existing explosion-proof coatings cannot simultaneously achieve rigid impact resistance and energy dissipation. It adopts electric field-assisted directional deposition technology to make negatively charged calcium phosphate particles migrate directionally along electric field lines to the surface of the sponge skeleton, forming a highly ordered and dense ceramic precursor layer. The continuous grain boundary skeleton obtained after gradient sintering can resist the initial impact through the rigid skeleton, and can also induce microcracks to extend the energy dissipation path along the grain boundary. At the same time, the microporous structure absorbs energy through plastic collapse, realizing the integrated enhancement of "rigid impact resistance" and "microporous energy dissipation". (3) The method for preparing foam calcium phosphate-based coating for extreme dynamic load protection of the present invention addresses the problem of the single energy dissipation mechanism of existing explosion-proof coatings by using a gradient sintering process to construct a porous structure with Ca-OP covalent bonds as the core. This structure achieves the synergistic effect of bond angle bending elastic energy storage, interface friction energy dissipation and stress wave multiple reflections, and absorbs energy through "pseudo-plastic" progressive fracture under overload, so as to achieve the rigid-flexible synergistic enhancement of wall protection and explosion-proof structure after being combined with concrete matrix. (4) The foamed calcium phosphate-based coating prepared by the present invention, according to GB / T 29908-2013, is evaluated for its explosion-proof performance by shock wave strength. The shock wave overpressure attenuation rate under explosive impact load reaches more than 60%. According to GB / T20247-2006, the sound absorption performance of the material is tested in the range of 500~6000 Hz, and the average coefficient α is 0.90~0.99. In addition, according to GB / T 5210-2006, the adhesion of the material is evaluated by tensile strength. The results show that the tensile strength of the material is ≥5MPa. Detailed Implementation

[0024] The present invention will now be described in detail with reference to specific embodiments.

[0025] The present invention relates to a method for preparing a foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection, the specific method of which is as follows: S1. Preparation of polydopamine-modified polyurethane sponge: The polyurethane sponge was immersed in anhydrous ethanol, NaOH solution and dopamine solution respectively for treatment, rinsed and then freeze-dried to obtain polydopamine-modified polyurethane sponge. The specific method is as follows: S1.1 Soak the block polyurethane sponge in anhydrous ethanol and sonicate for 30-60 min until it is evenly dispersed. Wash with deionized water and dry at room temperature for 12-24 h. Subsequently, the polyurethane sponge was immersed in a NaOH solution with a concentration of 1~2 mol / L and treated in a water bath at 50~70℃ for 2~5 h. After washing with deionized water, it was dried at room temperature for 12~24 h to obtain the pretreated polyurethane sponge. S1.2 Prepare a Tris-HCl buffer solution with a concentration of 30~60 mM and adjust the pH of the Tris-HCl buffer solution to 7.4~8.5. Then add dopamine hydrochloride to adjust the concentration of the above buffer solution to 1.5~2.5 mg / mL and store it in the dark to obtain the dopamine buffer solution. S1.3. Immerse the pretreated polyurethane sponge in dopamine buffer solution, place it on a shaker and shake it in the dark for 8-12 hours, then remove the polyurethane sponge and rinse it with deionized water. After completion, place the polyurethane sponge in an environment with a temperature of -20 to -40°C and a vacuum degree of 5 to 10 Pa, and freeze-dry it for 24 to 36 hours to obtain polydopamine-modified polyurethane sponge.

[0026] The preparation method of this invention first modifies polyurethane foam with polydopamine, then immerses it in a Tris-HCl buffer solution containing dopamine and shakes it in the dark to generate a polydopamine biomimetic coating on its surface in situ. By utilizing the π-π stacking effect between the catechol groups and the urethane groups on the surface of the polyurethane foam, a high-density active interface layer is constructed on the surface of the organic template. This effectively inhibits the interface debonding and crack propagation between the coating and the foam calcium phosphate matrix under explosive impact load, thereby improving the energy absorption efficiency of the overall structure under dynamic loading.

[0027] S2. Constructing a gradient gel coating: Immerse polydopamine-modified polyurethane sponge in sodium alginate gel solution and construct a dried gradient gel coating precursor using the gradient template method. The specific method is as follows: S2.1 Slowly add sodium alginate powder to deionized water, stir in a water bath at 50~80℃ for 2~4 hours until completely dissolved, and let stand to degas for 4~6 hours to obtain sodium alginate gel solution; wherein, the mass ratio of sodium alginate to deionized water is 10~30g:900~1200mL.

[0028] S2.2 Immerse the polydopamine-modified polyurethane sponge in sodium alginate gel solution and place it in a vacuum drying oven. Evacuate at a vacuum degree of -0.1~-0.5MPa for 20~30min. After completion, slowly release the gas at a release rate of 0.01~0.03 MPa / min to allow the sodium alginate gel solution to fully penetrate into the interior of the polyurethane sponge. Use filter paper to remove excess solution from the surface to obtain the modified polydopamine-modified polyurethane sponge. S2.3. Using a spray method, a gradient coating was constructed using CaCl2 solutions of different concentrations as crosslinking agents. After spraying, the modified polydopamine-modified polyurethane sponge was placed in a constant temperature and humidity chamber for 30-60 min and then removed. It was then placed in a refrigerator at 2-8℃ for 1-3 h and excess moisture was removed to obtain the gradient gel coating precursor. The specific method for constructing gradient coatings is as follows: A dense cross-linked layer was obtained by spraying a 0.8-1.2 wt.% CaCl2 solution onto the upper surface of the sponge at a depth of 0-2 mm for 10-20 s. A 0.3-0.5 wt.% CaCl2 solution was sprayed onto the middle layer of the sponge for 5-7 seconds to obtain an over-crosslinked layer. A buffer cross-linked layer is obtained by spraying a 0.05-0.2 wt.% CaCl2 solution at a depth of 5-10 mm in the inner layer of the sponge for 2-4 seconds.

[0029] S2.4 The obtained gradient gel coating precursor is dried in an environment with a temperature of -20~-40℃ and a vacuum degree of 3~10 Pa for 36~48 h to obtain a dried gradient gel coating precursor.

[0030] The gradient template method was used to construct a calcium alginate gradient gel coating, enabling the sponge to form a gradient cross-linked structure from the surface to the inner layer. This facilitates the gradual transfer and dissipation of stress from the surface to the inner layer under impact loads, effectively inhibiting the instantaneous propagation of cracks. Simultaneously, the Ca in the calcium alginate gel... 2+ The ionic crosslinking network formed with -COOH can undergo reversible fracture and recombination under dynamic loading, thereby further improving the overall impact toughness and energy absorption efficiency of the coating.

[0031] S3. Preparation of foamed calcium phosphate coating precursor: The dried gradient gel coating precursor is immersed in calcium phosphate deposition slurry, and the foamed calcium phosphate coating precursor is obtained by electric field directional deposition; the specific method is as follows: S3.1. Disperse the calcium phosphate source powder evenly in deionized water and stir for 5-10 min to obtain the initial calcium phosphate slurry; then, add the dispersant and adjust the pH to 9.5-10.5 with a 0.5-1 mol / L NaOH solution to obtain the calcium phosphate slurry. Among them, the calcium phosphate source powder is hydroxyapatite or tricalcium phosphate powder; The mass ratio of hydroxyapatite or tricalcium phosphate powder to deionized water is 20-40 g: 60-80 mL. The dispersant is ammonium polyacrylate or sodium polymethacrylate; The amount of dispersant added is 0.5~1.5% of the mass of the calcium phosphate source powder.

[0032] S3.2 Place the calcium phosphate slurry in a vacuum drying oven and degas it at a vacuum of -0.08 to -0.10 MPa for 20 to 40 minutes to obtain a stable and dispersed calcium phosphate deposition slurry. S3.3 Using a coaxial electric field deposition apparatus, calcium phosphate deposition slurry is circulated into the deposition apparatus at a flow rate of 15~25 mL / min, and the dried gradient gel coating precursor obtained in S2 is completely immersed in the calcium phosphate deposition slurry. Then, the pulse power supply is turned on, and the electric field strength is set to 60~100 V / cm, the pulse frequency is 100~150 Hz, and deposition is carried out for 30~60 min. After deposition, it is washed 2~4 times with deionized water and dried for 20~30 h at a temperature of -45~-55℃ and a vacuum degree of 5~15 Pa to obtain the electric field-assisted directional deposition modified foamed calcium phosphate coating precursor.

[0033] A foamed calcium phosphate coating precursor was prepared using an electric field-assisted directional deposition method. Driven by an electric field, the precursor migrated directionally along the electric field lines and densely packed together, forming a highly ordered and dense ceramic precursor layer. Under explosive impact loads, the highly ordered grains, through their alignment, induced microcracks to propagate along grain boundaries, extending the crack propagation path and dissipating energy. Simultaneously, the dense ceramic layer resisted the initial impact through its rigid framework, while the remaining microporous structure further absorbed energy through plastic collapse. This achieved a synergistic enhancement mechanism of "rigid impact resistance" and "microporous energy dissipation," improving the overall explosion-proof, shock-absorbing, and energy-absorbing performance of the coating.

[0034] S4. A foamed calcium phosphate-based energy-absorbing coating was prepared by a gradient sintering method. The specific method is as follows: First, the foamed calcium phosphate coating precursor obtained from S3 was placed in a tube furnace, and nitrogen was introduced to replace the air in the furnace. The temperature was increased from room temperature to 200-250℃ at a rate of 2-5℃ / min, and held at this temperature for 60-120 min under nitrogen atmosphere protection. Then, the temperature was increased to 300-350℃ at a rate of 1.0-3.0℃ / min, and held for 90-150 min. After this, the nitrogen supply was stopped, and the temperature was increased to 400-500℃ at a rate of 1.0-3.0℃ / min, held for 120-180 min, then increased to 550-650℃ and held for 60-120 min. Finally, the temperature was increased to 1050-1150℃ at a rate of 3.0-5.0℃ / min, held for 120-240 min, and then allowed to cool naturally to room temperature with the furnace to obtain the foamed calcium phosphate-based coating.

[0035] This invention utilizes a gradient sintering process to calcine the precursor, resulting in a multi-level porous structure with neck connections throughout the coating. This structure, through the grain boundary strengthening effect of the neck connection region formed by Ca-OP covalent bonds, combined with the "pinning effect" and stress dispersion mechanism in the multi-level porous structure, achieves a synergistic enhancement of rigid support and ductile energy absorption. Simultaneously, the neck connection region undergoes elastic deformation under impact loads through bond angle bending and bond length expansion, reversibly storing some energy. Furthermore, the multi-level porous structure extends the stress wave propagation path through multiple reflections and scattering. These combined factors ensure the structural integrity of the material, achieving efficient dissipation of impact energy. In summary, the coating material prepared by this invention possesses high interfacial bonding strength and excellent explosion-proof, shock-absorbing, and energy-absorbing properties, making it suitable for engineering applications in building explosion protection, structural protection, and extreme dynamic load environments.

[0036] A foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection was prepared according to the preparation method.

[0037] Application of foamed calcium phosphate-based energy-absorbing coatings in the field of structural protection materials technology.

[0038] This invention relates to a coating prepared from polydopamine-modified polyurethane sponge via gradient template construction, electric field-assisted directional deposition, and gradient sintering. First, an active interface layer is introduced onto the surface of the polyurethane sponge through biomimetic modification with polydopamine. The catechol groups interact with the amino ester functional groups on the sponge surface via π-π stacking, thereby enhancing the coating's compressive strength. Second, a calcium alginate gradient gel coating is constructed using a gradient template method. By spraying different concentrations of CaCl2 crosslinking agent onto the surface, middle, and inner layers of the sponge, a gradient crosslinking structure from dense to porous is formed, achieving the gradual transfer and dissipation of stress under impact loads. Subsequently, electric field-assisted directional deposition technology is used to directionally migrate negatively charged calcium phosphate particles along the electric field lines to the surface of the sponge skeleton, forming a highly ordered and dense ceramic precursor layer. The coating thickness and uniformity are precisely controlled by adjusting the electric field strength, pulse frequency, and deposition time. Finally, the precursor is calcined using a gradient sintering process, causing neck connections with Ca-OP covalent bonds as the core between the calcium phosphate particles, constructing a hierarchical porous structure. The multi-level porous structure dissipates energy under impact loads through interfacial friction, stress wave scattering, and progressive fracture of neck bonding, giving the coating both rigid impact resistance and tough energy absorption properties, making it suitable for the field of building explosion protection engineering.

[0039] Example 1 The present invention relates to a method for preparing a foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection, the specific method of which is as follows: Step 1: Preparation of polydopamine-modified polyurethane sponge by freeze-drying: First, the block polyurethane sponge was immersed in anhydrous ethanol and sonicated for 30 min until uniformly dispersed. It was then washed with deionized water and dried at room temperature for 12 h. Next, the polyurethane sponge was immersed in a 1 mol / L NaOH solution and treated in a 50℃ water bath for 2 h. It was then washed with deionized water and dried at room temperature for 12 h to obtain the pretreated polyurethane sponge. Next, a 30 mM Tris-HCl buffer solution was prepared and the pH was adjusted to 7.4. Then, dopamine hydrochloride was added to adjust the buffer concentration to 1.5 mg / mL, and the solution was stored in the dark. The pretreated sponge was immersed in 100 mL of dopamine solution, placed on a shaker, and shaken in the dark for 12 h. The polyurethane sponge was then removed and rinsed with deionized water. Finally, the polyurethane sponge was freeze-dried at -20℃ and a vacuum of 10 Pa for 24 h to obtain the polydopamine-modified polyurethane sponge.

[0040] Step 2: Construction of a gradient gel coating using the gradient template method: First, weigh 10 g of sodium alginate powder and slowly add it to 900 mL of deionized water. Stir in a 50℃ water bath for 2 h until completely dissolved, and let stand for 4 h to remove bubbles, obtaining a sodium alginate gel solution. Next, immerse the polydopamine-modified sponge obtained in Step 1 into the sodium alginate solution and place it in a vacuum drying oven, where it is evacuated at a vacuum of -0.5 MPa for 20 min. After completion, slowly degas at a degassing rate of 0.03 MPa / min to allow the solution to fully penetrate the sponge interior. Remove excess solution from the surface with filter paper to obtain the modified polydopamine-modified polyurethane sponge. Finally, using a spray method with CaCl2 solution as a crosslinking agent, a gradient coating is constructed. At the middle layer of the sponge (2 mm), spray with 0.3 wt.% CaCl2 solution for 5 s to obtain an over-crosslinked layer. At the inner layer of the sponge (5 mm), spray with 0.05 wt.% CaCl2 solution for 2 s to obtain a buffered crosslinked layer. After spraying, the sponge was placed in a constant temperature and humidity chamber for 30 minutes, then removed and placed in a 2°C refrigerator for 3 hours to remove excess moisture, thus obtaining the gradient gel coating precursor. The obtained precursor was dried in an environment with a temperature of -20°C and a vacuum degree of 10 Pa for 36 hours to obtain the gradient gel coating.

[0041] Step 3: Preparation of foamed calcium phosphate coating precursor by electric field directional deposition: First, 20 g of hydroxyapatite powder was weighed and uniformly dispersed in 60 mL of deionized water and stirred for 5 min to obtain an initial calcium phosphate slurry. Then, 0.5% (by weight of the powder) of ammonium polyacrylate was added as a dispersant, and the pH was adjusted to 10.5 with a 1 mol / L NaOH solution. After completion, the slurry was placed in a vacuum drying oven and degassed at a vacuum of -0.08 MPa for 20 min to obtain a stable and dispersed calcium phosphate deposition slurry. Next, a coaxial electric field deposition device was used to circulate the calcium phosphate deposition slurry into the deposition device at a flow rate of 15 mL / min, ensuring that the gradient gel coating precursor obtained in step 2 was completely immersed in the slurry. Then, a pulsed power supply was turned on, setting the electric field strength to 60 V / cm and the pulse frequency to 150 Hz for deposition, with a deposition time of 60 min. After deposition, the material was washed twice with deionized water and dried for 30 h at a temperature of -55℃ and a vacuum of 15 Pa to obtain the electric field-assisted directional deposition modified foam calcium phosphate coating precursor.

[0042] Step 4: Preparation of foamed calcium phosphate-based coating by gradient sintering method: First, the temperature is increased from room temperature to 200℃ at a heating rate of 2℃ / min and held at this temperature for 60 min under nitrogen atmosphere protection. Then, the temperature is increased to 300℃ at a heating rate of 1.0℃ / min and held for 90 min. After this, the nitrogen supply is stopped, and the temperature is increased to 400℃ at a heating rate of 3.0℃ / min and held for 180 min, then increased to 550℃ and held for 60 min. Finally, the temperature is increased to 1050℃ at a heating rate of 3.0℃ / min and held for 240 min, and then allowed to cool naturally to room temperature in the furnace to obtain the foamed calcium phosphate-based coating.

[0043] Example 2 A method for preparing a foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection and its applications are disclosed. The specific preparation process is as follows: Step 1: Preparation of polydopamine-modified polyurethane sponge by freeze-drying: First, the block polyurethane sponge was immersed in anhydrous ethanol and sonicated for 30 min until uniformly dispersed. It was then washed with deionized water and dried at room temperature for 12 h. Next, the polyurethane sponge was immersed in a 1 mol / L NaOH solution and treated in a 50℃ water bath for 2 h. It was then washed with deionized water and dried at room temperature for 12 h to obtain the pretreated polyurethane sponge. Next, a 60 mM Tris-HCl buffer solution was prepared and the pH was adjusted to 8.5. Then, dopamine hydrochloride was added to adjust the buffer concentration to 1.5 mg / mL, and the solution was stored in the dark. The pretreated sponge was immersed in 100 mL of dopamine solution, placed on a shaker, and shaken in the dark for 12 h. The polyurethane sponge was then removed and rinsed with deionized water. Finally, the polyurethane sponge was freeze-dried at -20℃ and a vacuum of 10 Pa for 36 h to obtain the polydopamine-modified polyurethane sponge.

[0044] Step 2: Construction of a gradient gel coating using the gradient template method: First, weigh 10 g of sodium alginate powder and slowly add it to 900 mL of deionized water. Stir in a 50℃ water bath for 4 h until completely dissolved, and allow to stand for 6 h to degas, obtaining a sodium alginate gel solution. Next, immerse the polydopamine-modified sponge obtained in Step 1 into the sodium alginate solution and place it in a vacuum drying oven, where it is evacuated at a vacuum of -0.5 MPa for 20 min. After completion, slowly degas at a degassing rate of 0.03 MPa / min to allow the solution to fully penetrate the sponge interior. Remove excess solution from the surface using filter paper to obtain the modified polydopamine-modified polyurethane sponge. Finally, using a spray method with CaCl2 solutions of different concentrations as crosslinking agents, a gradient coating is constructed. A 0.8 wt.% CaCl2 solution is sprayed onto the upper surface of the sponge at a depth of 2 mm for 10 s to obtain a dense crosslinked layer. A 5 mm section of the middle layer of the sponge was sprayed with a 0.3 wt.% CaCl2 solution for 5 s to obtain an over-crosslinked layer. A 10 mm section of the inner layer of the sponge was sprayed with a 0.05 wt.% CaCl2 solution for 2 s to obtain a buffered crosslinked layer. After spraying, the sponge was placed in a constant temperature and humidity chamber for 30 min, then removed and placed in an 8℃ refrigerator for 1 h to remove excess moisture, thus obtaining the gradient gel coating precursor. The obtained precursor was dried in an environment of -20℃ and 10 Pa vacuum for 48 h to obtain the gradient gel coating.

[0045] Step 3: Preparation of foamed calcium phosphate coating precursor by electric field directional deposition: First, 20 g of tricalcium phosphate powder was weighed and uniformly dispersed in 60 mL of deionized water and stirred for 5 min to obtain an initial calcium phosphate slurry. Then, 0.5% (by weight of the powder) of ammonium polyacrylate was added as a dispersant, and the pH was adjusted to 10.5 with a 1 mol / L NaOH solution. After completion, the slurry was placed in a vacuum drying oven and degassed at a vacuum of -0.08 MPa for 20 min to obtain a stable dispersed calcium phosphate deposition slurry. Next, a coaxial electric field deposition device was used to circulate the calcium phosphate deposition slurry into the device at a flow rate of 15 mL / min, ensuring that the gradient gel coating precursor obtained in Step 2 was completely immersed in the slurry. Then, a pulsed power supply was turned on, setting the electric field strength to 60 V / cm and the pulse frequency to 150 Hz for deposition, with a deposition time of 60 min. After deposition, the material was washed twice with deionized water and dried for 30 h at a temperature of -55℃ and a vacuum of 15 Pa to obtain the electric field-assisted directional deposition modified foam calcium phosphate coating precursor.

[0046] Step 4, preparation of the foamed calcium phosphate-based coating by gradient sintering: First, the temperature was increased from room temperature to 250℃ at a rate of 2℃ / min and held for 120 min under nitrogen atmosphere. Then, the temperature was increased to 350℃ at a rate of 1.0℃ / min and held for 150 min. After this, the nitrogen supply was stopped, and the temperature was increased to 500℃ at a rate of 3.0℃ / min and held for 120 min, followed by increasing to 650℃ and holding for 60 min. Finally, the temperature was increased to 1100℃ at a rate of 5.0℃ / min and held for 200 min, then allowed to cool naturally to room temperature in the furnace to obtain the foamed calcium phosphate-based coating.

[0047] Example 3 A method for preparing a foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection and its applications are disclosed. The specific preparation process is as follows: Step 1: Preparation of polydopamine-modified polyurethane sponge by freeze-drying: First, the block polyurethane sponge was immersed in anhydrous ethanol and sonicated for 40 min until uniformly dispersed. It was then washed with deionized water and dried at room temperature for 16 h. Next, the polyurethane sponge was immersed in a 2 mol / L NaOH solution and treated in a 55℃ water bath for 3 h. After washing with deionized water, it was dried at room temperature for 16 h to obtain the pretreated polyurethane sponge. Next, a 30 mM Tris-HCl buffer solution was prepared and the pH was adjusted to 7.4. Then, dopamine hydrochloride was added to adjust the buffer concentration to 1.5 mg / mL, and the solution was stored in the dark. The pretreated sponge was immersed in 80 mL of dopamine solution, placed on a shaker, and shaken in the dark for 10 h. The polyurethane sponge was then removed and rinsed with deionized water. Finally, the polyurethane sponge was freeze-dried at -30℃ and a vacuum of 8 Pa for 24 h to obtain the polydopamine-modified polyurethane sponge.

[0048] Step 2, Gradient Template Method for Constructing Gradient Gel Coating: First, weigh 15 g of sodium alginate powder and slowly add it to 1000 mL of deionized water. Stir in a 60℃ water bath for 4 h until completely dissolved, and allow to stand for 4 h to degas, obtaining sodium alginate gel. Second, immerse the polydopamine-modified sponge obtained in Step 1 into the sodium alginate solution and place it in a vacuum drying oven, where it is evacuated at a vacuum degree of -0.4 MPa for 25 min. After completion, slowly degas at a degassing rate of 0.02 MPa / min to allow the solution to fully penetrate the interior of the sponge, and remove excess solution from the surface with filter paper to obtain the modified polydopamine-modified polyurethane sponge. Finally, using a spray method with CaCl2 solutions of different concentrations as crosslinking agents, a gradient coating is constructed. At the middle layer of the sponge, 0.4 wt.% CaCl2 solution is sprayed for 6 s at a depth of 2 mm to obtain an over-crosslinked layer. A buffer cross-linking layer was obtained by spraying a 0.1 wt.% CaCl2 solution onto the inner 5 mm layer of the sponge for 3 s. After spraying, the sponge was placed in a constant temperature and humidity chamber for 40 min, then removed and placed in a 2℃ refrigerator for 3 h to remove excess moisture, thus obtaining the gradient gel coating precursor. The obtained precursor was dried in an environment of -30℃ and 7 Pa vacuum for 36 h to obtain the gradient gel coating.

[0049] Step 3: Preparation of foamed calcium phosphate coating precursor by electric field directional deposition: First, 30 g of hydroxyapatite powder was weighed and uniformly dispersed in 70 mL of deionized water and stirred for 10 min to obtain an initial calcium phosphate slurry. Then, 1.0% (by weight of the powder) of sodium polymethacrylate was added as a dispersant, and the pH was adjusted to 10.0 with a 0.8 mol / L NaOH solution. After completion, the slurry was placed in a vacuum drying oven and degassed at a vacuum of -0.09 MPa for 30 min to obtain a stable and dispersed calcium phosphate deposition slurry. Next, a coaxial electric field deposition device was used to circulate the calcium phosphate deposition slurry into the deposition device at a flow rate of 20 mL / min, ensuring that the gradient gel coating precursor obtained in Step 2 was completely immersed in the slurry. Then, a pulsed power supply was turned on, setting the electric field strength to 70 V / cm and the pulse frequency to 130 Hz for deposition, with a deposition time of 50 min. After deposition, the material was washed three times with deionized water and dried for 20 h at a temperature of -50℃ and a vacuum of 5 Pa to obtain the electric field-assisted directional deposition modified foam calcium phosphate coating precursor.

[0050] Step 4, Preparation of foamed calcium phosphate-based coating by gradient sintering: First, the temperature is increased from room temperature to 200℃ at a rate of 3℃ / min and held at this temperature for 60 min under nitrogen atmosphere protection. Then, the temperature is increased to 300℃ at a rate of 2.0℃ / min and held for 90 min. After this, the nitrogen supply is stopped, and the temperature is increased to 400℃ at a rate of 2.0℃ / min and held for 180 min, then increased to 550℃ and held for 80 min. Finally, the temperature is increased to 1150℃ at a rate of 3.0℃ / min and held for 220 min, and then allowed to cool naturally to room temperature in the furnace to obtain the foamed calcium phosphate-based coating.

[0051] Example 4 A method for preparing a foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection and its applications are disclosed. The specific preparation process is as follows: Step 1: Preparation of polydopamine-modified polyurethane sponge by freeze-drying: First, the block polyurethane sponge was immersed in anhydrous ethanol and sonicated for 40 min until uniformly dispersed. It was then washed with deionized water and dried at room temperature for 16 h. Next, the polyurethane sponge was immersed in a 1 mol / L NaOH solution and treated in a 55℃ water bath for 3 h. After washing with deionized water, it was dried at room temperature for 16 h to obtain the pretreated polyurethane sponge. Next, a 60 mM Tris-HCl buffer solution was prepared and the pH was adjusted to 8.5. Then, dopamine hydrochloride was added to adjust the buffer concentration to 2.0 mg / mL, and the solution was stored in the dark. The pretreated sponge was immersed in 80 mL of dopamine solution, placed on a shaker, and shaken in the dark for 10 h. The polyurethane sponge was then removed and rinsed with deionized water. Finally, the polyurethane sponge was freeze-dried at -30℃ and a vacuum of 8 Pa for 36 h to obtain the polydopamine-modified polyurethane sponge.

[0052] Step 2: Constructing a gradient gel coating using the gradient template method: First, weigh 15 g of sodium alginate powder and slowly add it to 1000 mL of deionized water. Stir in a 60℃ water bath for 4 h until completely dissolved, and allow to stand for 6 h to remove bubbles, obtaining a sodium alginate gel solution. Next, immerse the polydopamine-modified sponge obtained in Step 1 into the sodium alginate solution and place it in a vacuum drying oven, where it is evacuated at a vacuum of -0.4 MPa for 25 min. After completion, slowly degas at a degassing rate of 0.02 MPa / min to allow the solution to fully penetrate the sponge interior. Remove excess solution from the surface using filter paper to obtain the modified polydopamine-modified polyurethane sponge. Finally, using a spray method with CaCl2 solutions of different concentrations as crosslinking agents, a gradient coating is constructed. A 1.0 wt.% CaCl2 solution is sprayed onto the upper surface of the sponge at a depth of 2 mm for 15 s to obtain a dense crosslinked layer. A 5 mm section of the middle layer of the sponge was sprayed with a 0.4 wt.% CaCl2 solution for 6 s to obtain an over-crosslinked layer. A 10 mm section of the inner layer of the sponge was sprayed with a 0.1 wt.% CaCl2 solution for 3 s to obtain a buffered crosslinked layer. After spraying, the sponge was placed in a constant temperature and humidity chamber for 40 min, then removed and placed in an 8℃ refrigerator for 1 h to remove excess moisture, thus obtaining the gradient gel coating precursor. The obtained precursor was dried in an environment of -30℃ and 7 Pa vacuum for 48 h to obtain the gradient gel coating.

[0053] Step 3: Preparation of foamed calcium phosphate coating precursor by electric field directional deposition: First, 30 g of tricalcium phosphate powder was weighed and uniformly dispersed in 70 mL of deionized water and stirred for 10 min to obtain an initial calcium phosphate slurry. Then, 1.0% (by weight of the powder) of sodium polymethacrylate was added as a dispersant, and the pH was adjusted to 10.0 with a 0.8 mol / L NaOH solution. After completion, the slurry was placed in a vacuum drying oven and degassed at a vacuum of -0.09 MPa for 30 min to obtain a stable dispersed calcium phosphate deposition slurry. Next, a coaxial electric field deposition device was used to circulate the calcium phosphate deposition slurry into the device at a flow rate of 20 mL / min, ensuring that the gradient gel coating precursor obtained in Step 2 was completely immersed in the slurry. Then, a pulsed power supply was turned on, setting the electric field strength to 70 V / cm and the pulse frequency to 130 Hz for deposition, with a deposition time of 50 min. After deposition, the material was washed three times with deionized water and dried for 20 h at a temperature of -50℃ and a vacuum of 5 Pa to obtain the electric field-assisted directional deposition modified foam calcium phosphate coating precursor.

[0054] Step 4, preparation of the foamed calcium phosphate-based coating by gradient sintering: First, the temperature was increased from room temperature to 250℃ at a rate of 3℃ / min and held for 120 min under nitrogen atmosphere. Then, the temperature was increased to 350℃ at a rate of 2.0℃ / min and held for 150 min. After this, the nitrogen supply was stopped, and the temperature was increased to 500℃ at a rate of 2.0℃ / min and held for 120 min, followed by increasing to 650℃ and holding for 80 min. Finally, the temperature was increased to 1150℃ at a rate of 5.0℃ / min and held for 220 min, then allowed to cool naturally to room temperature in the furnace to obtain the foamed calcium phosphate-based coating.

[0055] Example 5 A method for preparing a foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection and its applications are disclosed. The specific preparation process is as follows: Step 1: Preparation of polydopamine-modified polyurethane sponge by freeze-drying: First, the block polyurethane sponge was immersed in anhydrous ethanol and sonicated for 50 min until uniformly dispersed. It was then washed with deionized water and dried at room temperature for 20 h. Next, the polyurethane sponge was immersed in a 2 mol / L NaOH solution and treated in a 60℃ water bath for 4 h. After washing with deionized water, it was dried at room temperature for 20 h to obtain the pretreated polyurethane sponge. Next, a 30 mM Tris-HCl buffer solution was prepared and the pH was adjusted to 7.4. Then, dopamine hydrochloride was added to adjust the buffer concentration to 2.0 mg / mL, and the solution was stored in the dark. The pretreated sponge was immersed in 60 mL of dopamine solution, placed on a shaker, and shaken in the dark for 6 h. The polyurethane sponge was then removed and rinsed with deionized water. Finally, the polyurethane sponge was freeze-dried at -40℃ and a vacuum of 6 Pa for 24 h to obtain the polydopamine-modified polyurethane sponge.

[0056] Step 2, Gradient Template Method for Constructing Gradient Gel Coating: First, weigh 20 g of sodium alginate powder and slowly add it to 1100 mL of deionized water. Stir in a 70℃ water bath for 2 h until completely dissolved, and allow to stand for 4 h to degas, obtaining sodium alginate gel. Second, immerse the polydopamine-modified sponge obtained in Step 1 into the sodium alginate solution and place it in a vacuum drying oven, where it is evacuated at a vacuum degree of -0.2 MPa for 20 min. After completion, slowly degas at a degassing rate of 0.01 MPa / min to allow the solution to fully penetrate the interior of the sponge, and remove excess solution from the surface with filter paper to obtain the modified polydopamine-modified polyurethane sponge. Finally, using a spray method with CaCl2 solutions of different concentrations as crosslinking agents, a gradient coating is constructed. At the middle layer of the sponge, 0.5 wt.% CaCl2 solution is sprayed for 7 s at a depth of 2 mm to obtain an over-crosslinked layer. A buffer cross-linking layer was obtained by spraying a 0.15 wt.% CaCl2 solution onto the inner 5 mm layer of the sponge for 4 s. After spraying, the sponge was placed in a constant temperature and humidity chamber for 50 min, then removed and placed in a 2℃ refrigerator for 3 h to remove excess moisture, thus obtaining the gradient gel coating precursor. The obtained precursor was dried in an environment of -40℃ and 5 Pa vacuum for 36 h to obtain the gradient gel coating.

[0057] Step 3: Preparation of foamed calcium phosphate coating precursor by electric field directional deposition: First, 40 g of hydroxyapatite powder was weighed and uniformly dispersed in 80 mL of deionized water and stirred for 5 min to obtain an initial calcium phosphate slurry. Then, 1.5% (by weight of the powder) of ammonium polyacrylate was added as a dispersant, and the pH was adjusted to 9.5 with a 0.6 mol / L NaOH solution. After completion, the slurry was placed in a vacuum drying oven and degassed at a vacuum of -0.10 MPa for 35 min to obtain a stable dispersed calcium phosphate deposition slurry. Next, a coaxial electric field deposition device was used to circulate the calcium phosphate deposition slurry into the device at a flow rate of 25 mL / min, ensuring that the gradient gel coating precursor obtained in Step 2 was completely immersed in the slurry. Then, a pulsed power supply was turned on, setting the electric field strength to 80 V / cm and the pulse frequency to 110 Hz for deposition, with a deposition time of 40 min. After deposition, the material was washed four times with deionized water and dried for 30 h at a temperature of -45℃ and a vacuum of 15 Pa to obtain the electric field-assisted directional deposition modified foam calcium phosphate coating precursor.

[0058] Step 4, preparation of the foamed calcium phosphate-based coating by gradient sintering: First, the temperature was increased from room temperature to 200℃ at a rate of 4℃ / min and held for 60 min under nitrogen atmosphere. Then, the temperature was increased to 300℃ at a rate of 3.0℃ / min and held for 90 min. After this, the nitrogen supply was stopped, and the temperature was increased to 400℃ at a rate of 1.0℃ / min and held for 160 min, followed by increasing to 550℃ and holding for 100 min. Finally, the temperature was increased to 1050℃ at a rate of 3.0℃ / min and held for 160 min, then allowed to cool naturally to room temperature in the furnace to obtain the foamed calcium phosphate-based coating.

[0059] Example 6 A method for preparing a foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection and its applications are disclosed. The specific preparation process is as follows: Step 1: Preparation of polydopamine-modified polyurethane sponge by freeze-drying: First, the block polyurethane sponge was immersed in anhydrous ethanol and sonicated for 50 min until uniformly dispersed. It was then washed with deionized water and dried at room temperature for 20 h. Next, the polyurethane sponge was immersed in a 2 mol / L NaOH solution and treated in a 60℃ water bath for 4 h. After washing with deionized water, it was dried at room temperature for 20 h to obtain the pretreated polyurethane sponge. Next, a 60 mM Tris-HCl buffer solution was prepared and the pH was adjusted to 8.5. Then, dopamine hydrochloride was added to adjust the buffer concentration to 2.0 mg / mL, and the solution was stored in the dark. The pretreated sponge was immersed in 60 mL of dopamine solution, placed on a shaker, and shaken in the dark for 6 h. The polyurethane sponge was then removed and rinsed with deionized water. Finally, the polyurethane sponge was freeze-dried at -40℃ and a vacuum of 6 Pa for 36 h to obtain the polydopamine-modified polyurethane sponge.

[0060] Step 2, Gradient Template Method for Constructing Gradient Gel Coating: First, weigh 20 g of sodium alginate powder and slowly add it to 1100 mL of deionized water. Stir in a 70℃ water bath for 4 h until completely dissolved, and allow to stand for 6 h to degas, obtaining sodium alginate gel. Second, immerse the polydopamine-modified sponge obtained in Step 1 into the sodium alginate solution and place it in a vacuum drying oven, where it is evacuated at a vacuum degree of -0.2 MPa for 20 min. After completion, slowly degas at a degassing rate of 0.01 MPa / min to allow the solution to fully penetrate into the sponge. Remove excess solution from the surface with filter paper to obtain the modified polydopamine-modified polyurethane sponge. Finally, using a spray method with CaCl2 solutions of different concentrations as crosslinking agents, a gradient coating is constructed. A 1.2 wt.% CaCl2 solution is sprayed onto the upper surface of the sponge at a depth of 2 mm for 20 s to obtain a dense crosslinked layer. A 5 mm section of the middle layer of the sponge was sprayed with a 0.5 wt.% CaCl2 solution for 7 s to obtain an over-crosslinked layer. A 10 mm section of the inner layer of the sponge was sprayed with a 0.05 wt.% CaCl2 solution for 4 s to obtain a buffered crosslinked layer. After spraying, the sponge was placed in a constant temperature and humidity chamber for 50 min, then removed and placed in an 8℃ refrigerator for 1 h to remove excess moisture, thus obtaining the gradient gel coating precursor. The obtained precursor was dried in an environment of -40℃ and 5 Pa vacuum for 48 h to obtain the gradient gel coating.

[0061] Step 3: Preparation of foamed calcium phosphate coating precursor by electric field directional deposition: First, 40 g of tricalcium phosphate powder was weighed and uniformly dispersed in 80 mL of deionized water and stirred for 5 min to obtain an initial calcium phosphate slurry. Then, 1.5% (by weight of the powder) of ammonium polyacrylate was added as a dispersant, and the pH was adjusted to 9.5 with a 0.6 mol / L NaOH solution. After completion, the slurry was placed in a vacuum drying oven and degassed at a vacuum of -0.10 MPa for 35 min to obtain a stable dispersed calcium phosphate deposition slurry. Next, a coaxial electric field deposition device was used to circulate the calcium phosphate deposition slurry into the device at a flow rate of 25 mL / min, ensuring that the gradient gel coating precursor obtained in Step 2 was completely immersed in the slurry. Then, a pulsed power supply was turned on, setting the electric field strength to 80 V / cm and the pulse frequency to 110 Hz for deposition, with a deposition time of 40 min. After deposition, the material was washed four times with deionized water and dried for 30 h at a temperature of -45℃ and a vacuum of 15 Pa to obtain the electric field-assisted directional deposition modified foam calcium phosphate coating precursor.

[0062] Step 4, preparation of the foamed calcium phosphate-based coating by gradient sintering: First, the temperature was increased from room temperature to 250℃ at a rate of 4℃ / min and held for 120 min under nitrogen atmosphere. Then, the temperature was increased to 350℃ at a rate of 3.0℃ / min and held for 150 min. After this, the nitrogen supply was stopped, and the temperature was increased to 500℃ at a rate of 1.0℃ / min and held for 140 min, followed by increasing to 650℃ and holding for 100 min. Finally, the temperature was increased to 1050℃ at a rate of 5.0℃ / min and held for 160 min, then allowed to cool naturally to room temperature in the furnace to obtain the foamed calcium phosphate-based coating.

[0063] Example 7 A method for preparing a foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection and its applications are disclosed. The specific preparation process is as follows: Step 1: Preparation of polydopamine-modified polyurethane sponge by freeze-drying: First, the block polyurethane sponge was immersed in anhydrous ethanol and sonicated for 60 min until uniformly dispersed. It was then washed with deionized water and dried at room temperature for 24 h. Next, the polyurethane sponge was immersed in a 2 mol / L NaOH solution and treated in a 70℃ water bath for 5 h. After washing with deionized water, it was dried at room temperature for 24 h to obtain the pretreated polyurethane sponge. Next, a 30 mM Tris-HCl buffer solution was prepared and the pH was adjusted to 7.4. Then, dopamine hydrochloride was added to adjust the buffer concentration to 2.5 mg / mL, and the solution was stored in the dark. The pretreated sponge was immersed in 50 mL of dopamine solution, placed on a shaker, and shaken in the dark for 8 h. The polyurethane sponge was then removed and rinsed with deionized water. Finally, the polyurethane sponge was freeze-dried at -20℃ and a vacuum of 5 Pa for 24 h to obtain the polydopamine-modified polyurethane sponge.

[0064] Step 2, Gradient Template Method for Constructing Gradient Gel Coating: First, weigh 30 g of sodium alginate powder and slowly add it to 1200 mL of deionized water. Stir in an 80℃ water bath for 2 h until completely dissolved, and allow to stand for 4 h to degas, obtaining sodium alginate gel. Second, immerse the polydopamine-modified sponge obtained in Step 1 into the sodium alginate solution and place it in a vacuum drying oven, where it is evacuated at a vacuum degree of -0.1 MPa for 30 min. After completion, slowly degas at a degassing rate of 0.03 MPa / min to allow the solution to fully penetrate the interior of the sponge, and remove excess solution from the surface with filter paper to obtain the modified polydopamine-modified polyurethane sponge. Finally, using a spray method with CaCl2 solutions of different concentrations as crosslinking agents, a gradient coating is constructed. At the middle layer of the sponge, 0.3 wt.% CaCl2 solution is sprayed for 5 s at a depth of 2 mm to obtain an over-crosslinked layer. A 0.2 wt.% CaCl2 solution was sprayed onto the inner 5 mm layer of the sponge for 2 s to obtain a buffer crosslinking layer. After spraying, the sponge was placed in a constant temperature and humidity chamber for 60 min, then removed and placed in a 2℃ refrigerator for 3 h to remove excess moisture, thus obtaining the gradient gel coating precursor. The obtained precursor was dried in an environment of -20℃ and 3 Pa vacuum for 36 h to obtain the gradient gel coating.

[0065] Step 3: Preparation of foamed calcium phosphate coating precursor by electric field directional deposition: First, 20 g of hydroxyapatite powder was weighed and uniformly dispersed in 60 mL of deionized water and stirred for 5 min to obtain an initial calcium phosphate slurry. Then, 1.0% (by weight of the powder) of sodium polymethacrylate was added as a dispersant, and the pH was adjusted to 10.0 with a 0.5 mol / L NaOH solution. After completion, the slurry was placed in a vacuum drying oven and degassed at a vacuum of -0.09 MPa for 40 min to obtain a stable and dispersed calcium phosphate deposition slurry. Next, a coaxial electric field deposition device was used to circulate the calcium phosphate deposition slurry into the device at a flow rate of 20 mL / min, ensuring that the gradient gel coating precursor obtained in Step 2 was completely immersed in the slurry. Then, a pulsed power supply was turned on, setting the electric field strength to 100 V / cm and the pulse frequency to 100 Hz for deposition, with a deposition time of 30 min. After deposition, the material was washed twice with deionized water and dried for 30 h at a temperature of -55℃ and a vacuum of 15 Pa to obtain the electric field-assisted directional deposition modified foam calcium phosphate coating precursor.

[0066] Step 4, preparation of the foamed calcium phosphate-based coating by gradient sintering: First, the temperature was increased from room temperature to 200℃ at a rate of 5℃ / min and held for 60 min under nitrogen atmosphere. Then, the temperature was increased to 300℃ at a rate of 2.0℃ / min and held for 90 min. After this, the nitrogen supply was stopped, and the temperature was increased to 400℃ at a rate of 2.0℃ / min and held for 140 min, followed by increasing to 550℃ and holding for 120 min. Finally, the temperature was increased to 1150℃ at a rate of 3.0℃ / min and held for 120 min, then allowed to cool naturally to room temperature in the furnace to obtain the foamed calcium phosphate-based coating.

[0067] Example 8 A method for preparing a foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection and its applications are disclosed. The specific preparation process is as follows: Step 1: Preparation of polydopamine-modified polyurethane sponge by freeze-drying: First, the block polyurethane sponge was immersed in anhydrous ethanol and sonicated for 60 min until uniformly dispersed. It was then washed with deionized water and dried at room temperature for 24 h. Next, the polyurethane sponge was immersed in a 2 mol / L NaOH solution and treated in a 70℃ water bath for 5 h. After washing with deionized water, it was dried at room temperature for 24 h to obtain the pretreated polyurethane sponge. Next, a 60 mM Tris-HCl buffer solution was prepared and the pH was adjusted to 8.5. Then, dopamine hydrochloride was added to adjust the buffer concentration to 2.5 mg / mL, and the solution was stored in the dark. The pretreated sponge was immersed in 50 mL of dopamine solution, placed on a shaker, and shaken in the dark for 8 h. The polyurethane sponge was then removed and rinsed with deionized water. Finally, the polyurethane sponge was freeze-dried at -20℃ and a vacuum of 5 Pa for 36 h to obtain the polydopamine-modified polyurethane sponge.

[0068] Step 2, Gradient Template Method for Constructing Gradient Gel Coating: First, weigh 30 g of sodium alginate powder and slowly add it to 1200 mL of deionized water. Stir in an 80℃ water bath for 4 h until completely dissolved, and allow to stand for 6 h to degas, obtaining sodium alginate gel. Second, immerse the polydopamine-modified sponge obtained in Step 1 into the sodium alginate solution and place it in a vacuum drying oven, where it is evacuated at a vacuum degree of -0.1 MPa for 30 min. After completion, slowly degas at a degassing rate of 0.01 MPa / min to allow the solution to fully penetrate into the sponge. Remove excess solution from the surface with filter paper to obtain the modified polydopamine-modified polyurethane sponge. Finally, using a spray method with CaCl2 solutions of different concentrations as crosslinking agents, a gradient coating is constructed. A 1.2 wt.% CaCl2 solution is sprayed onto the upper surface of the sponge at a depth of 2 mm for 20 s to obtain a dense crosslinked layer. A 5 mm section of the middle layer of the sponge was sprayed with a 0.5 wt.% CaCl2 solution for 7 s to obtain an over-crosslinked layer. A 10 mm section of the inner layer of the sponge was sprayed with a 0.2 wt.% CaCl2 solution for 4 s to obtain a buffered crosslinked layer. After spraying, the sponge was placed in a constant temperature and humidity chamber for 60 min, then removed and placed in an 8℃ refrigerator for 1 h to remove excess moisture, thus obtaining the gradient gel coating precursor. The obtained precursor was dried in an environment of -40℃ and 3 Pa for 48 h to obtain the gradient gel coating.

[0069] Step 3: Preparation of foamed calcium phosphate coating precursor by electric field directional deposition: First, 40 g of tricalcium phosphate powder was weighed and uniformly dispersed in 80 mL of deionized water and stirred for 10 min to obtain an initial calcium phosphate slurry. Then, 1.5% (by weight of the powder) of sodium polymethacrylate was added as a dispersant, and the pH was adjusted to 9.5 with a 0.5 mol / L NaOH solution. After completion, the slurry was placed in a vacuum drying oven and degassed at a vacuum of -0.10 MPa for 40 min to obtain a stable dispersed calcium phosphate deposition slurry. Next, a coaxial electric field deposition device was used to circulate the calcium phosphate deposition slurry into the deposition device at a flow rate of 20 mL / min, ensuring that the gradient gel coating precursor obtained in Step 2 was completely immersed in the slurry. Then, a pulsed power supply was turned on, setting the electric field strength to 100 V / cm and the pulse frequency to 100 Hz for deposition, with a deposition time of 30 min. After deposition, the material was washed twice with deionized water and dried for 20 h at a temperature of -45℃ and a vacuum of 5 Pa to obtain the electric field-assisted directional deposition modified foam calcium phosphate coating precursor.

[0070] Step 4, preparation of the foamed calcium phosphate-based coating by gradient sintering: First, the temperature is increased from room temperature to 250℃ at a rate of 5℃ / min and held for 120 min under nitrogen atmosphere. Then, the temperature is increased to 350℃ at a rate of 2.0℃ / min and held for 150 min. After this, the nitrogen supply is stopped, and the temperature is increased to 500℃ at a rate of 2.0℃ / min and held for 160 min, then increased to 650℃ and held for 120 min. Finally, the temperature is increased to 1150℃ at a rate of 5.0℃ / min and held for 120 min, and then allowed to cool naturally to room temperature in the furnace to obtain the foamed calcium phosphate-based coating.

[0071] Table 1 shows the comparative test results of the foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection in the embodiments with existing materials: Table 1. Comparison of shock wave overpressure attenuation rate and sound absorption coefficient between the present invention and different materials.

[0072] As shown in the table above, compared with YX-2ES two-component coatings, halloysite nanotube-modified polyurea, multifunctional ceramic foams, and ceramic nanofiber aerogels, the calcium phosphate-based foam coating prepared in this invention is made from polydopamine-modified polyurethane sponge through gradient template construction, electric field-assisted directional deposition, and gradient sintering processes. First, an active interface layer is introduced onto the surface of the polyurethane sponge through biomimetic modification with polydopamine. The catechol groups and the amino ester functional groups on the sponge surface generate π-π stacking interactions, thereby enhancing the compressive strength of the coating. Second, a calcium alginate gradient gel coating is constructed using a gradient template method. By spraying different concentrations of CaCl2 crosslinking agent onto the surface, middle, and inner layers of the sponge, a gradient crosslinking structure from dense to porous is formed, achieving the stepwise transfer and dissipation of stress under impact loads. Subsequently, electric field-assisted directional deposition technology is used to directionally migrate negatively charged calcium phosphate particles along the electric field lines to the surface of the sponge skeleton, forming a highly ordered and dense ceramic precursor layer. The coating thickness and uniformity are precisely controlled by adjusting the electric field strength, pulse frequency, and deposition time. Finally, the precursor is calcined using a gradient sintering process to form neck connections between calcium phosphate particles, with Ca-OP covalent bonds at their core, creating a hierarchical porous structure. Under impact loads, this hierarchical porous structure dissipates energy through a synergistic process of interfacial friction, stress wave scattering, and progressive fracture of the neck bonds, giving the coating both rigid impact resistance and tough energy absorption properties, making it suitable for use in building explosion-proof engineering. In summary, the foamed calcium phosphate-based energy-absorbing coating prepared in this invention for extreme dynamic load protection possesses high explosion-proof and shock-absorbing properties, and is expected to have broad application prospects in the field of building explosion-proof engineering materials technology.

Claims

1. A method for preparing a foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection, characterized in that, The specific method is as follows: S1. Preparation of polydopamine-modified polyurethane sponge: The polyurethane sponge was immersed in anhydrous ethanol, NaOH solution and dopamine solution respectively for treatment, rinsed and freeze-dried to obtain polydopamine-modified polyurethane sponge. S2. Constructing a gradient gel coating: Immerse polydopamine-modified polyurethane sponge in sodium alginate gel solution and construct a dried gradient gel coating precursor using the gradient template method. S3. Preparation of foamed calcium phosphate coating precursor: The dried gradient gel coating precursor is immersed in calcium phosphate deposition slurry, and the foamed calcium phosphate coating precursor is obtained by electric field directional deposition method. S4. A foamed calcium phosphate-based energy-absorbing coating was prepared by gradient sintering.

2. The method for preparing the foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection according to claim 1, characterized in that, The specific method of S1 is as follows: S1.1 Soak the block polyurethane sponge in anhydrous ethanol and sonicate for 30-60 min until it is evenly dispersed. Wash with deionized water and dry at room temperature for 12-24 h. Subsequently, the polyurethane sponge was immersed in a NaOH solution with a concentration of 1~2 mol / L and treated in a water bath at 50~70℃ for 2~5 hours. After washing with deionized water, it was dried at room temperature for 12~24 hours to obtain the pretreated polyurethane sponge. S1.2 Prepare a Tris-HCl buffer solution with a concentration of 30~60 mM and adjust the pH of the Tris-HCl buffer solution to 7.4~8.

5. Then add dopamine hydrochloride to adjust the concentration of the above buffer solution to 1.5~2.5 mg / mL and store it in the dark to obtain the dopamine buffer solution. S1.

3. Immerse the pretreated polyurethane sponge in dopamine buffer solution, place it on a shaker and shake it in the dark for 8-12 hours, then remove the polyurethane sponge and rinse it with deionized water. After completion, place the polyurethane sponge in an environment with a temperature of -20 to -40°C and a vacuum degree of 5 to 10 Pa, and freeze-dry it for 24 to 36 hours to obtain polydopamine-modified polyurethane sponge.

3. The method for preparing the foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection according to claim 1, characterized in that, The specific method of S2 is as follows: S2.1 Slowly add sodium alginate powder to deionized water, stir in a water bath at 50~80℃ for 2~4 h until completely dissolved, and let stand to degas for 4~6 h to obtain sodium alginate gel solution. S2.2 Immerse the polydopamine-modified polyurethane sponge in sodium alginate gel solution and place it in a vacuum drying oven. Evacuate at a vacuum degree of -0.1~-0.5MPa for 20~30min. After completion, slowly release the gas at a release rate of 0.01~0.03 MPa / min to allow the sodium alginate gel solution to fully penetrate into the interior of the polyurethane sponge. Use filter paper to remove excess solution from the surface to obtain the modified polydopamine-modified polyurethane sponge. S2.

3. Using a spray method, a gradient coating was constructed using CaCl2 solutions of different concentrations as crosslinking agents. After spraying, the modified polydopamine-modified polyurethane sponge was placed in a constant temperature and humidity chamber for 30-60 min and then removed. It was then placed in a refrigerator at 2-8℃ for 1-3 h and excess moisture was removed to obtain the gradient gel coating precursor. S2.4 The obtained gradient gel coating precursor is dried in an environment with a temperature of -20~-40℃ and a vacuum degree of 3~10 Pa for 36~48 h to obtain a dried gradient gel coating precursor.

4. The method for preparing the foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection according to claim 3, characterized in that, In S2.1, the mass ratio of sodium alginate to deionized water is 10~30g:900~1200mL.

5. The method for preparing the foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection according to claim 3, characterized in that, The specific method for constructing the gradient coating in S2.3 is as follows: A dense cross-linked layer was obtained by spraying a 0.8-1.2 wt.% CaCl2 solution onto the upper surface of the sponge at a depth of 0-2 mm for 10-20 s. A 0.3-0.5 wt.% CaCl2 solution was sprayed onto the middle layer of the sponge for 5-7 seconds to obtain an over-crosslinked layer. A buffer cross-linked layer is obtained by spraying a 0.05-0.2 wt.% CaCl2 solution at a depth of 5-10 mm in the inner layer of the sponge for 2-4 seconds.

6. The method for preparing the foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection according to claim 5, characterized in that, The specific method of S3 is as follows: S3.

1. Disperse the calcium phosphate source powder evenly in deionized water and stir for 5-10 min to obtain the initial calcium phosphate slurry; then, add the dispersant and adjust the pH to 9.5-10.5 with a 0.5-1 mol / L NaOH solution to obtain the calcium phosphate slurry. S3.2 Place the calcium phosphate slurry in a vacuum drying oven and degas it at a vacuum of -0.08 to -0.10 MPa for 20 to 40 minutes to obtain a stable and dispersed calcium phosphate deposition slurry. S3.

3. Using a coaxial electric field deposition device, the calcium phosphate deposition slurry is circulated into the deposition device at a flow rate of 15~25mL / min, and the dry gradient gel coating precursor obtained in S2 is completely immersed in the calcium phosphate deposition slurry. Subsequently, the pulse power supply was turned on, and the electric field strength was set to 60~100 V / cm, the pulse frequency to 100~150 Hz for deposition. The deposition time was 30~60 min. After deposition, the material was washed 2~4 times with deionized water and dried for 20~30 h at a temperature of -45~-55℃ and a vacuum degree of 5~15 Pa to obtain the electric field-assisted directional deposition modified foam calcium phosphate coating precursor.

7. The method for preparing the foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection according to claim 6, characterized in that, The calcium phosphate source powder in S3.1 is hydroxyapatite or tricalcium phosphate powder; The mass ratio of the hydroxyapatite or tricalcium phosphate powder to the volume ratio of deionized water is 20-40 g: 60-80 mL. The dispersant is ammonium polyacrylate or sodium polymethacrylate; The amount of dispersant added is 0.5 to 1.5% of the mass of the calcium phosphate source powder.

8. The method for preparing the foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection according to claim 7, characterized in that, The specific method of S4 is as follows: First, the foamed calcium phosphate coating precursor obtained from S3 was placed in a tube furnace, and nitrogen was introduced to replace the air in the furnace. The temperature was increased from room temperature to 200-250℃ at a rate of 2-5℃ / min, and held at this temperature for 60-120 min under nitrogen atmosphere protection. Then, the temperature was increased to 300-350℃ at a rate of 1.0-3.0℃ / min, and held for 90-150 min. After this, the nitrogen supply was stopped, and the temperature was increased to 400-500℃ at a rate of 1.0-3.0℃ / min, held for 120-180 min, then increased to 550-650℃ and held for 60-120 min. Finally, the temperature was increased to 1050-1150℃ at a rate of 3.0-5.0℃ / min, held for 120-240 min, and then allowed to cool naturally to room temperature with the furnace to obtain the foamed calcium phosphate-based coating.

9. A foamed calcium phosphate-based energy-absorbing coating for extreme dynamic load protection prepared by any of the preparation methods described in claims 1 to 8.

10. The application of the foamed calcium phosphate-based energy-absorbing coating as described in claim 9 in the field of structural protection materials technology.

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