Self-insulation mortar and preparation method thereof

Abstract

The present application relates to the technical field of self-insulation mortar, and particularly relates to a self-insulation mortar and a preparation method thereof, which comprises the following components: Portland cement, gradient graphene aerogel skeleton, metal organic framework nanoparticles, photo-thermal phase change coupling microcapsules, magnetic field oriented Fe3O4 nanosheet, self-repairing microcapsules, silicon carbide nanowire aerogel, water reducing agent and fiber reinforced material. The present application introduces gradient graphene aerogel skeleton, photo-thermal phase change coupling microcapsules and other materials with excellent insulation performance to construct a multi-level insulation structure. The gradient graphene aerogel skeleton has extremely low thermal conductivity and high porosity, which can effectively prevent heat transfer; the photo-thermal phase change coupling microcapsules can absorb and release a large amount of heat during the phase change process, further improving the insulation effect of the mortar.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of self-insulation mortar, in particular to a self-insulation mortar and a preparation method thereof. BACKGROUND

[0002] With the continuous growth of global energy demand and the increasing awareness of environmental protection, building energy saving has become the focus of today's society. In the field of construction, wall insulation materials as the key link to reduce building energy consumption and improve energy utilization efficiency, their performance directly affects the overall energy-saving effect of buildings. Although traditional insulation mortar materials can meet the insulation needs to some extent, they often have limited insulation performance, insufficient durability, single function and other problems, which are difficult to meet the urgent demand of modern buildings for high-performance insulation materials.

[0003] Disadvantages in the prior art:

[0004] Limited insulation performance: The insulation performance of traditional insulation mortar mainly depends on its pore structure and the thermal conductivity of the material, but due to the limitations of the material itself, its insulation effect is often difficult to achieve the ideal state. In extreme weather conditions, traditional insulation mortar may not be able to effectively prevent heat transfer, resulting in increased building energy consumption.

[0005] Insufficient durability: Traditional insulation mortar is easily affected by environmental factors such as moisture erosion, temperature changes, ultraviolet radiation, etc. during long-term use, leading to gradual performance decline, even cracking, peeling and other problems, affecting the service life and safety of buildings.

[0006] Single function: Traditional insulation mortar mainly has insulation function, lacks other additional functions such as self-repair, light-heat conversion, phase change energy storage, etc. In modern buildings, the functional requirements for insulation materials are becoming higher and higher, and single-function insulation mortar has been difficult to meet market demand.

[0007] Poor structural stability: The internal structure of traditional insulation mortar is relatively loose, and the combination between components is not tight enough, resulting in poor mechanical properties, which is prone to deformation and damage under external force. At the same time, due to the lack of effective orientation control technology, the filler distribution in the mortar is uneven, further affecting the stability and reliability of its performance.

[0008] Poor construction performance: Traditional insulation mortar often has problems such as uneven mixing, easy delamination, poor flowability, etc. during construction, which makes it difficult to ensure the construction quality. In addition, the drying and curing time of some insulation mortar is relatively long, affecting the construction progress and efficiency.

[0009] Therefore, we propose a self-insulation mortar and a preparation method thereof to solve the above problems. SUMMARY

[0010] The present application aims at solving the problems existing in the prior art and provides a self-insulation mortar and a preparation method thereof.

[0011] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0012] The self-insulation mortar comprises the following components in parts by weight: 40-60 parts of Portland cement, 5-15 parts of density gradient graphene aerogel framework, 3-8 parts of metal organic framework nanoparticles, 8-15 parts of photo-thermal phase change coupling microcapsules, 2-5 parts of magnetic field oriented Fe3O4 nanosheets, 3-6 parts of self-repairing microcapsules, 4-10 parts of silicon carbide nanowire aerogel, 1-3 parts of water reducing agent and 1-3 parts of fiber reinforced material.

[0013] As a preferred technical scheme:

[0014] The self-insulation mortar as described above, wherein the metal organic framework nanoparticles are ZIF-8 or ZIF-67, the pore size is 1.1-1.5 nm, and the surface is modified by an amino silane coupling agent, and the thickness of the modified layer is 2-5 nm.

[0015] The self-insulation mortar as described above, wherein the shell layer of the photo-thermal phase change coupling microcapsules is rutile TiO2, and the thickness is 50-80 nm; and the core material is a eutectic salt of lauric acid and stearic acid mixed at a mass ratio of 6:4, the phase change temperature is 25-30℃, and the phase change latent heat is ≥270 J / g.

[0016] The self-insulation mortar as described above, wherein the horizontal arrangement of the magnetic field oriented Fe3O4 nanosheets is realized by applying an axial magnetic field of 0.3-0.8 T during construction, and the included angle between the in-plane direction of the nanosheets and the heat flow direction is ≤15°.

[0017] The self-insulation mortar as described above, wherein the fiber reinforced material is modified basalt fiber or silicon carbide whisker, the fiber length is 3-6 mm, the aspect ratio is ≥50:1, and the surface is treated by plasma grafting to form a nano-scale concave-convex structure.

[0018] The second aspect of the present application provides a preparation method of the self-insulation mortar, comprising the following steps: S1 density gradient graphene aerogel framework pre-preparation: preparing a graphene oxide dispersion liquid (injecting a mold, forming an ice crystal template by gradient freezing at a rate of-5℃ / min, vacuum freeze-drying at-50℃ and hydrogen reduction at 500-800℃, and obtaining a density gradient of 0.1-0.8 g / cm 3S1: density gradient graphene aerogel skeleton preparation: graphene oxide was dispersed in deionized water to form a homogeneous suspension, and the suspension was transferred into a Teflon-lined stainless steel autoclave, and the autoclave was placed in a 25℃ water bath for 12-16h to obtain a graphene oxide hydrogel; the graphene oxide hydrogel was placed in a freeze-drying device, and the temperature was controlled at -80℃, and the vacuum degree was controlled at 0.01-0.05MPa, and the graphene oxide hydrogel was freeze-dried for 12-16h to obtain a graphene oxide aerogel; the graphene oxide aerogel was placed in a tube furnace, and the temperature was raised to 650℃ at a rate of 5℃ / min, and the graphene oxide aerogel was reduced by hydrogen for 2h to obtain a density gradient graphene aerogel skeleton; S2: functional component premixing: the portland cement, the density gradient graphene aerogel skeleton, the metal organic framework nanoparticles, and the silicon carbide nanowire aerogel were put into a planetary mixer, and dry mixing was performed at a speed of 200-400rpm for 10-15min to form a base mixture; S3: response component loading: the photo-thermal phase change coupled microcapsules, the Fe3O4 nanosheets, the fiber reinforced material, and the self-repairing microcapsules were sequentially added to the base mixture of S2, and a water solution of water reducing agent was sprayed, and wet mixing was performed at a speed of 600-800rpm for 5-8min under nitrogen protection to form a mortar slurry; S4: magnetic field orientation forming: the mortar slurry obtained in S3 was injected into a mold, and a 0.3-0.8T axial magnetic field was immediately applied and maintained for 10-15min to make the Fe3O4 nanosheets directionally arranged along the horizontal direction, and then the magnetic field was removed and cured for 24h; S5: surface activation treatment: the cured mortar was treated by low-temperature plasma to generate a nano-SiO2 active layer on the surface, and finally a self-insulation mortar product was obtained.

[0019] As a preferred technical scheme:

[0020] The preparation method of the self-insulation mortar as described above, in step S3, the nitrogen flow of the nitrogen protection is 10-15L / min, and the wet mixing temperature is controlled at 20-25℃.

[0021] The preparation method of the self-insulation mortar as described above, in step S1, the gradient freezing process is divided into three-stage temperature interval control: first stage: from 25℃ to 0℃ at a rate of -3℃ / min, and ice crystals grow along the vertical direction; second stage: 0℃ for 10min to form a continuous ice crystal template; third stage: from 0℃ to -50℃ at a rate of -8℃ / min to induce the directional stacking of graphene oxide sheets; and the hydrogen reduction process is performed at 650℃ for 2h with a heating rate of 5℃ / min.

[0022] The preparation method of the self-insulation mortar as described above, in step S4, the curing by standing adopts segmented humidity control: first stage: relative humidity ≥95%, temperature 20±2℃, to make the cement hydration product wrap the functional filler; second stage: relative humidity is reduced to 60-70%, and the temperature is increased to 35±2℃ to accelerate the stabilization of the oriented structure of the Fe3O4 nanosheets; after the curing is completed, microwave-assisted drying treatment is performed for 30-60min to make the water content ≤1.5%.

[0023] The preparation method of the self-insulation mortar as described above, further comprising step S6: composite radiation cooling coating spraying: the cured mortar is sprayed with BaSO4@PDMS suspension, and a coating with a thickness of 50-80μm is formed by spraying at a pressure of 0.2-0.5MPa, and then solidified at 80℃ for 1h to obtain a composite insulation mortar.

[0024] Compared with the prior art, the application has the beneficial effects of:

[0025] The gradient graphene aerogel framework, the photo-thermal-phase change coupled microcapsule and the silicon carbide nanowire aerogel jointly form a multi-level heat preservation structure, thereby improving the heat preservation performance of the mortar from the aspects of reducing heat conduction, heat storage and heat regulation.

[0026] The fiber reinforced material and the magnetic field oriented Fe3O4 nanosheet are cooperated with each other, thereby enhancing the toughness and crack resistance of the mortar, optimizing the internal structure of the mortar and improving the mechanical stability of the mortar.

[0027] The metal organic framework nanoparticles and the self-repairing microcapsule expand the functions of the mortar and enhance the self-repairing ability of the mortar, and the metal organic framework nanoparticles and the self-repairing microcapsule jointly constitute a composite system with multiple functions.

[0028] The surface activation treatment and the composite radiation cooling coating spraying improve the surface performance and protection ability of the mortar, and the surface activation treatment and the composite radiation cooling coating spraying are cooperated with other internal functional components, thereby improving the overall performance and service life of the self-insulation mortar. BRIEF DESCRIPTION OF DRAWINGS

[0029] Fig. 1 Figure 4 is an appearance diagram of the embodiment four of the application after 50 freeze-thaw cycles.

[0030] Fig. 2 Figure 4 is an appearance diagram of the embodiment four of the application after 50 freeze-thaw cycles. DETAILED DESCRIPTION

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. If there is a conflict between the definitions found within this specification and those found in incorporated documents or references, the definitions within this specification control. Unless otherwise specified, "mass, concentration, temperature, time, or other values or parameters are expressed in ranges, preferred ranges, or a series of upper preferred values and lower preferred values, it is to be understood that all ranges, preferred ranges, and individual values therefrom formed by any pair of any upper preferred value or any lower preferred value, whether separately disclosed or not, are expressly disclosed. For example, a range of 1-50 should be understood as including any number, combination of numbers, or sub-range selected from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, as well as all decimal values between the integers, such as 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. With respect to sub-ranges, "nested sub-ranges" extending from either end of the range are specifically contemplated. For example, exemplary nested sub-ranges of the range 1-50 can include 1-10, 1-20, 1-30, and 1-40 in one direction, or 50-40, 50-30, 50-20, and 50-10 in the other direction.

[0032] The application is further illustrated below with reference to specific examples. The experimental methods described in the following examples are conventional methods unless otherwise specified. The reagents and materials described are commercially available unless otherwise specified.

[0033] A self-insulation mortar comprises the following components in parts by weight: Portland cement 40-60 parts, density gradient graphene aerogel skeleton 5-15 parts (density gradient 0.1-0.8 g / cm 3 , axial thermal conductivity difference ≥ 10 times), metal organic framework (MOFs) nanoparticles 3-8 parts, photo-thermal-phase change coupling microcapsules 8-15 parts (core-shell structure, TiO2 shell thickness 50-100 nm, core material lauric acid-stearic acid eutectic salt), magnetic field oriented Fe3O4 nanosheet 2-5 parts (thickness ≤ 20 nm, aspect ratio ≥ 30:1), self-repairing microcapsules 3-6 parts (containing dicyclopentadiene and Grubbs catalyst, average particle size 30-50 μm), silicon carbide nanowire aerogel 4-10 parts (porosity ≥ 95%, wire diameter 50-100 nm), water reducing agent 1-3 parts, fiber reinforced material 1-3 parts.

[0034] Specifically, the metal organic framework nanoparticles are ZIF-8 or ZIF-67, the pore size is 1.1-1.5 nm, and the surface is modified by an amino silane coupling agent, and the thickness of the modified layer is 2-5 nm.

[0035] The shell layer of the light-heat-phase change coupled microcapsule is rutile TiO2, and the thickness is 50-80 nm; the core material is a eutectic salt of lauric acid and stearic acid mixed in a mass ratio of 6:4, the phase change temperature is 25-30℃, and the phase change latent heat is ≥270 J / g.

[0036] It should be noted that the horizontal arrangement of the magnetic field oriented Fe3O4 nanoplate is realized by applying an axial magnetic field of 0.3-0.8 T during construction, and the included angle between the in-plane direction of the nanoplate and the heat flow direction is ≤15°; the fiber reinforced material is modified basalt fiber or silicon carbide whisker, the fiber length is 3-6 mm, the aspect ratio is ≥50:1, and the surface is treated by plasma grafting to form a nano-scale concave-convex structure.

[0037] In the following examples one to four, the self-insulation mortar comprises the following components in parts by weight: Portland cement 45 parts, density gradient graphene aerogel skeleton 8 parts, metal organic framework nanoparticles (ZIF-8) 4 parts, light-heat-phase change coupled microcapsule 11 parts (core-shell structure, core material is lauric acid-stearic acid eutectic salt), magnetic field oriented Fe3O4 nanoplate 3 parts, self-repairing microcapsule 5 parts (containing dicyclopentadiene and Grubbs catalyst), silicon carbide nanowire aerogel 7 parts, water reducing agent 2 parts, and fiber reinforced material 2 parts (silicon carbide whisker).

[0038] Example one

[0039] A preparation method of a self-insulation mortar, comprising the following steps:

[0040] S1 Density gradient graphene aerogel skeleton preparation: inject graphene oxide dispersion solution (concentration 5 mg / mL) into a mold, form an ice crystal template by gradient freezing at a rate of -5℃ / min, and prepare a density gradient graphene aerogel skeleton with a density gradient of 0.1 g / cm 3 after vacuum freeze-drying at -50℃ and hydrogen reduction at 500℃;

[0041] The gradient freezing process is divided into three temperature interval controls: the first stage: from 25℃ to 0℃ at a rate of -3℃ / min, and the ice crystals grow in the vertical direction; the second stage: keep at 0℃ for 10 min to form a continuous ice crystal template; the third stage: from 0℃ to -50℃ at a rate of -8℃ / min to induce the oriented stacking of graphene oxide layers;

[0042] The hydrogen reduction process is kept at 650℃ for 2h, and the heating rate is 5℃ / min;

[0043] S2 functional component premixing: put Portland cement, aerogel skeleton obtained in S1, metal organic framework nanoparticles, and silicon carbide nanowire aerogel into a planetary mixer, dry mix at 200 rpm for 10 min to form a matrix mixture;

[0044] S3 response component loading: add photo-thermal-phase change coupling microcapsules, Fe3O4 nanosheets, fiber reinforcement, and self-repairing microcapsules into the matrix mixture of S2 in sequence, spray water reducing agent solution (water-cement ratio 0.25) at the same time, wet mix at 600 rpm for 5 min under nitrogen protection to form a mortar slurry;

[0045] The nitrogen flow under nitrogen protection is 10 L / min, the wet mixing temperature is controlled at 20°C, and the speed is adjusted in three stages during the wet mixing process: the first stage (1 min) is 600 rpm uniform stirring; the second stage (2 min) is 800 rpm pulse stirring (pulse frequency 2 Hz, duty cycle 50%); the third stage (5 min) is 400 rpm slow uniformity;

[0046] S4 magnetic field orientation forming: inject the mortar slurry obtained in S3 into a mold, immediately apply an axial magnetic field of 0.3 T and maintain for 10 min, so that the Fe3O4 nanosheets are oriented and arranged in the horizontal direction, then remove the magnetic field and cure for 24 h;

[0047] The curing adopts segmented humidity control: the first stage (1 h) is relative humidity ≥ 95%, temperature 20°C, so that the cement hydration product wraps the functional filler; the second stage (6 h) is relative humidity reduced to 60%, temperature increased to 33°C, to accelerate the stabilization of the oriented structure of Fe3O4 nanosheets;

[0048] After curing, microwave-assisted drying (frequency 2.45 GHz, power density 0.5 W / g) is performed for 30 min to make the water content ≤ 1.5%;

[0049] S5 surface activation treatment: the cured mortar is treated by low temperature plasma (Ar / O2 mixed gas, power 80 W, treatment time 3 min) to generate a nano-SiO2 active layer on the surface;

[0050] S6 composite radiation cooling coating spraying: the cured mortar is sprayed with BaSO4@PDMS suspension (solid content 25%), sprayed at a pressure of 0.2 MPa to form a coating with a thickness of 50 μm, then cured at 80°C for 1 h to obtain a composite thermal insulation mortar with a surface emissivity ≥ 0.93 (8 μm waveband).

[0051] Example Two

[0052] A preparation method of a self-insulating mortar, comprising the following steps:

[0053] S1 Density gradient graphene aerogel skeleton preparation: graphene oxide dispersion (concentration 6 mg / mL) was injected into a mold, and ice crystal templates were formed by gradient freezing at a rate of -5 °C / min, vacuum freeze-drying at -50 °C, and hydrogen reduction at 600 °C to obtain a density gradient graphene aerogel skeleton with a density of 0.2 g / cm 3 ;

[0054] The gradient freezing process was divided into three temperature interval controls: the first stage: from 25 °C to 0 °C at a rate of -3 °C / min, and ice crystals grew in the vertical direction; the second stage: 10 min at 0 °C to form a continuous ice crystal template; the third stage: from 0 °C to -50 °C at a rate of -8 °C / min to induce the oriented stacking of graphene oxide layers;

[0055] The hydrogen reduction process was carried out at 650 °C for 2 h, with a heating rate of 5 °C / min;

[0056] S2 Functional component premixing: silicate cement, the aerogel skeleton obtained in S1, metal organic framework nanoparticles, and silicon carbide nanowire aerogel were put into a planetary mixer and dry-mixed at a speed of 250 rpm for 12 min to form a matrix mixture;

[0057] S3 Response component loading: photo-thermal-phase change coupling microcapsules, magnetic field oriented Fe3O4 nanosheets, fiber reinforced materials, and self-repairing microcapsules were sequentially added to the matrix mixture of S2, and a water reducing agent aqueous solution (water-cement ratio 0.28) was sprayed, and the slurry body was wet-mixed at a speed of 650 rpm for 6 min under nitrogen protection;

[0058] The nitrogen flow rate of nitrogen protection was 11 L / min, the wet-mixing temperature was controlled at 22 °C, and the speed was adjusted in three stages during the wet-mixing process: the first stage (1 min): 600 rpm uniform stirring; the second stage (3 min): 800 rpm pulse stirring (pulse frequency 2 Hz, duty cycle 50%); the third stage (6 min): 400 rpm slow uniformity;

[0059] S4 Magnetic field orientation molding: the slurry body obtained in S3 was injected into a mold, and a 0.4 T axial magnetic field was immediately applied and maintained for 12 min to make the Fe3O4 nanosheets oriented in the horizontal direction, and then the magnetic field was removed and cured for 24 h;

[0060] The curing process adopted segmented humidity control: the first stage (2 h): relative humidity ≥ 95%, temperature 20 °C, to make the cement hydration product wrap the functional filler; the second stage (8 h): the relative humidity was reduced to 65%, and the temperature was increased to 35 °C to accelerate the stabilization of the oriented structure of Fe3O4 nanosheets;

[0061] After curing, the sand mortar is treated by microwave-assisted drying (frequency 2.45 GHz, power density 0.5 W / g) for 35 min to make the water content ≤1.5%;

[0062] S5 surface activation treatment: the cured sand mortar is treated by low-temperature plasma (Ar / O2 mixed gas, power 90 W, treatment time 4 min) to generate a nano-SiO2 active layer on the surface, and finally a self-insulation sand mortar product is obtained;

[0063] S6 composite radiation cooling coating spraying: the cured sand mortar is sprayed with a BaSO4@PDMS suspension (solid content 28%) at a pressure of 0.3 MPa to form a coating with a thickness of 60 μm, and then cured at 80℃ for 1 h to obtain a composite insulation sand mortar with a surface emissivity ≥0.93 (9 μm wave band).

[0064] Example Three

[0065] A preparation method of a self-insulation sand mortar, comprising the following steps:

[0066] S1 density gradient graphene aerogel skeleton pre-preparation: the graphene oxide dispersion solution (concentration 7 mg / mL) is injected into a mold, and the ice crystal template is formed by gradient freezing at a rate of -5℃ / min, and the density gradient graphene aerogel skeleton with a density gradient of 0.5 g / cm 3 is prepared by vacuum freeze-drying at -50℃ and hydrogen reduction at 700℃;

[0067] The gradient freezing process is divided into three temperature interval controls: the first stage: from 25℃ to 0℃ at a rate of -3℃ / min, and the ice crystals grow in the vertical direction; the second stage: 0℃ for 10 min to form a continuous ice crystal template; the third stage: from 0℃ to -50℃ at a rate of -8℃ / min to induce the oriented stacking of graphene oxide layers;

[0068] The hydrogen reduction process is carried out at 650℃ for 2 h with a heating rate of 5℃ / min;

[0069] S2 functional component premixing: the portland cement, the aerogel skeleton obtained in S1, the metal organic framework nanoparticles, and the silicon carbide nanowire aerogel are put into a planetary mixer, and dry mixed at a speed of 300 rpm for 14 min to form a base mixture;

[0070] S3 response component loading: the photo-thermal-phase change coupling microcapsules, Fe3O4 nanosheets, fiber reinforced materials, and self-repairing microcapsules are sequentially added to the base mixture of S2, and at the same time, the water reducing agent aqueous solution (water-cement ratio 0.31) is sprayed, and wet mixed at a speed of 700 rpm for 6 min under nitrogen protection to form a sand mortar slurry;

[0071] The nitrogen flow under nitrogen protection was 13 L / min, the temperature of wet mixing was controlled at 24°C, and the rotating speed was adjusted in three stages during the wet mixing process: the first stage (1 min): 600 rpm uniform stirring; the second stage (4 min): 800 rpm pulse stirring (pulse frequency 2 Hz, duty cycle 50%); and the third stage (7 min): 400 rpm slow uniformity;

[0072] S4 magnetic field orientation forming: the mortar slurry obtained in S3 was injected into a mold, and a 0.6 T axial magnetic field was immediately applied and maintained for 13 min, so that the Fe3O4 nanosheets were oriented and arranged in the horizontal direction, and then the magnetic field was removed and cured for 24 h;

[0073] The curing was performed by segmented humidity control: the first stage (4 h): relative humidity ≥ 95%, temperature 21°C, so that the cement hydration product wrapped the functional filler; the second stage (17 h): the relative humidity was reduced to 65%, and the temperature was increased to 36°C, to accelerate the stabilization of the oriented structure of the Fe3O4 nanosheets;

[0074] After the curing was completed, the mortar was treated by microwave-assisted drying (frequency 2.45 GHz, power density 0.5 W / g) for 40 min, so that the water content was ≤1.5%;

[0075] S5 surface activation treatment: the cured mortar was treated by low-temperature plasma (Ar / O2 mixed gas, power 110 W, treatment time 4 min), to generate a nano-SiO2 active layer on the surface;

[0076] S6 composite radiation cooling coating spraying: the cured mortar was sprayed with a BaSO4@PDMS suspension (solid content 32%), to form a coating with a thickness of 70 μm at a pressure of 0.4 MPa, and then cured at 80°C for 1 h, to obtain a composite thermal insulation mortar with a surface emissivity ≥ 0.93 (11 μm waveband).

[0077] Example Four

[0078] A preparation method of a self-insulation mortar, comprising the following steps:

[0079] S1 density gradient graphene aerogel skeleton pre-preparation: a graphene oxide dispersion solution (concentration 8 mg / mL) was injected into a mold, an ice crystal template was formed by gradient freezing at a rate of -5°C / min, and a density gradient graphene aerogel skeleton with a density gradient of 0.8 g / cm 3 was prepared by vacuum freeze-drying at -50°C and hydrogen reduction at 800°C;

[0080] The gradient freezing process is divided into three temperature interval controls: the first stage: from 25℃ to 0℃ at a rate of-3℃ / min, ice crystals grow along the vertical direction; the second stage: keep at 0℃ for 10min, form continuous ice crystal template; the third stage: from 0℃ to-50℃ at a rate of-8℃ / min, induce the oriented stacking of graphene oxide layers;

[0081] The hydrogen reduction process is kept at 650℃ for 2h, and the heating rate is 5℃ / min;

[0082] S2 functional component premixing: put Portland cement, aerogel skeleton obtained in S1, metal organic framework nanoparticles, and silicon carbide nanowire aerogel into a planetary mixer, dry mix at a speed of 400rpm for 15min to form a matrix mixture;

[0083] S3 response component loading: add photo-thermal-phase change coupling microcapsules, Fe3O4 nanosheets, fiber reinforced materials, and self-repairing microcapsules into the matrix mixture of S2 in sequence, and spray water reducing agent solution (water-cement ratio 0.35) at the same time, wet mix at a speed of 800rpm for 8min under nitrogen protection to form a mortar slurry;

[0084] The nitrogen flow of nitrogen protection is 15L / min, and the wet mixing temperature is controlled at 25℃. The speed is adjusted in three stages during the wet mixing process: the first stage (2min): 600rpm uniform stirring; the second stage (5min): 800rpm pulse stirring (pulse frequency 2Hz, duty cycle 50%); the third stage (8min): 400rpm slow uniformity;

[0085] S4 magnetic field orientation forming: inject the mortar slurry obtained in S3 into a mold, immediately apply an axial magnetic field of 0.8T and maintain for 15min, so that the Fe3O4 nanosheets are arranged in the horizontal direction, and then remove the magnetic field and stand for 24h curing;

[0086] The standing curing adopts segmented humidity control: the first stage (6h): relative humidity ≥95%, temperature 22℃, so that the cement hydration product wraps the functional filler; the second stage (24h): the relative humidity is reduced to 70%, and the temperature is increased to 37℃, to accelerate the stabilization of the oriented structure of Fe3O4 nanosheets;

[0087] After the curing is completed, microwave assisted drying (frequency 2.45GHz, power density 0.5W / g) is used for 60min to make the water content ≤1.5%;

[0088] S5 surface activation treatment: the cured mortar is treated by low temperature plasma (Ar / O2 mixed gas, power 120W, treatment time 5min) to generate a nano-SiO2 active layer on the surface;

[0089] S6 composite radiant cooling coating spraying: the cured mortar is sprayed with BaSO4@PDMS suspension (solid content 35%), a coating with a thickness of 80 μm is formed by spraying at a pressure of 0.5 MPa, and then cured at 80°C for 1 h, to obtain a composite insulation mortar with a surface emissivity ≥ 0.93 (13 μm waveband).

[0090] Comparative Example One

[0091] A self-insulation mortar and a preparation method thereof, which are basically the same as those of Example Four, except that the density gradient graphene aerogel skeleton is not used (ordinary vitrified microbeads are used instead).

[0092] Comparative Example Two

[0093] A self-insulation mortar and a preparation method thereof, which are basically the same as those of Example Four, except that the 0.8T magnetic field in S4 is not applied, and the Fe3O4 nanosheets are randomly dispersed.

[0094] Comparative Example Three

[0095] A self-insulation mortar and a preparation method thereof, which are basically the same as those of Example Four, except that the self-repairing microcapsules are not added in S3.

[0096] Comparative Example Four

[0097] A self-insulation mortar and a preparation method thereof, which are basically the same as those of Example Four, except that the composite radiant cooling coating (S6 is not used).

[0098] The mortars prepared in the above Examples One to Four and Comparative Examples One to Four are detected:

[0099]

[0100] The results are as follows:

[0101] Table 1

[0102]

[0103] Table 2

[0104]

[0105] Table 3

[0106]

[0107] Table 4

[0108]

[0109] Table 5

[0110]

[0111] From the above Table 1, combined with Figs. 1-2 , the mortar preparation processes of Examples One to Four are stable, and the synergistic effect of the core components (gradient aerogel skeleton, magnetic field oriented Fe3O4 nanosheets, self-repairing microcapsules, and radiative cooling coating) is highly repeatable. The key performance indicators are as follows:

[0112] Dry density (about 380 kg / m3): significantly lower than traditional thermal insulation mortar (usually > 450 kg / m3), thanks to the lightweight and porous structure of the gradient aerogel skeleton.

[0113] Compressive strength (12.4-12.5 MPa): meets the requirements of GB / T 20473-2021 Type I thermal insulation mortar (≥ 10 MPa), resulting from the three-dimensional reinforcing network of gradient aerogel and carbonized silicon nanowires.

[0114] Thermal conductivity (0.027-0.029 W / m·K): close to the level of vacuum insulation panels (0.005-0.02 W / m·K), verifying the synergistic inhibition of multi-scale pores (MOFs nanoholes + aerogel mesopores) on heat conduction.

[0115] Durability (frost resistance 0.5%, water absorption 4.0%): self-repairing microcapsules effectively seal microcracks, combined with plasma hydrophobic treatment, significantly improving frost resistance and moisture resistance.

[0116] In other conditions, the same as Example Four and the comparative example:

[0117] 1. Comparative Example 1: without gradient aerogel skeleton (Table 2)

[0118] Performance degradation: thermal conductivity ↑ 60.7% (0.045 vs 0.028), compressive strength ↓ 34.4% (8.2 vs 12.5), frost resistance ↓ 540% (3.2% vs 0.5%).

[0119] Reason:

[0120] Ordinary vitrified microbeads (pore size 50-100 μm) cannot inhibit gas heat transfer through the Knudsen effect (heat conduction approaches vacuum when the average free path of gas molecules > pore size).

[0121] Lack of gradient aerogel's axial thermal conductivity difference (10-100 times), heat flow cannot be deflected along the low thermal conductivity path.

[0122] Large pores absorb water, leading to increased frost damage.

[0123] 2. Comparative Example 2: without magnetic field orientation (Table 3)

[0124] Performance degradation: thermal conductivity ↑ 25% (0.035 vs 0.028), compressive strength ↓ 19.2% (10.1 vs 12.5), thermal storage coefficient ↓ 18.8% (2.6 vs 3.2).

[0125] Reason:

[0126] Fe3O4 nanosheet disorderly distributed, thermal flow path tortuosity decreased (Maxwell-Eucken model predicts in-plane thermal conductivity increased).

[0127] Nanosheet partial agglomeration triggered microcracks, weakened mechanical properties and frost resistance.

[0128] 3. Comparative Example 3: No self-healing microcapsules (Table 4)

[0129] Performance degradation: frost resistance ↑ 460% (2.8% vs 0.5%), water absorption ↑ 100% (8.0% vs 4.0%), thermal conductivity ↑ 7.1% (0.030 vs 0.028).

[0130] Reason:

[0131] Microcracks did not repair to form thermal bridge effect (thermal conductivity slightly increased).

[0132] Water seeped through cracks during freeze-thaw cycles, causing frost heaving damage (frost resistance decreased significantly).

[0133] 4. Comparative Example 4: No radiative cooling coating (Table 5)

[0134] Performance degradation: thermal storage coefficient ↓ 12.5% (2.8 vs 3.2), daytime surface temperature rise ↑ 5°C, water absorption ↑ 62.5% (6.5% vs 4.0%).

[0135] Reason:

[0136] Lack of high infrared emissivity of BaSO4@PDMS coating (≥0.93 in 8-13 μm band), unable to reduce surface temperature by radiative cooling.

[0137] The hydrophobicity of the surface nanosilica layer (S5) is weaker than the coating, leading to an increase in water absorption.

[0138] In summary, the gradient aerogel skeleton is lightweight and high-strength, and its multi-level pore structure (1.2 nm MOFs hole + 50 nm aerogel hole) reduces the thermal conductivity through the Knudsen effect and phonon scattering. The magnetic field oriented Fe3O4 nanosheet optimizes the heat flow path through anisotropic thermal resistance, improving the thermal insulation efficiency (in-plane / out-of-plane thermal conductivity ratio 15:1). Self-repairing microcapsules are the key to durability, blocking moisture penetration and thermal bridge effects by dynamically repairing microcracks. The radiative cooling coating actively manages heat by reflecting sunlight and radiating infrared heat, reducing surface temperature by 5°C.

[0139] The density gradient graphene aerogel skeleton has extremely low thermal conductivity and a unique three-dimensional structure, effectively preventing heat transfer and forming a basic insulation layer. The photo-thermal phase change coupled microcapsules absorb and release a large amount of heat in the phase change temperature range, achieving heat storage and regulation. The two work together, the density gradient graphene aerogel skeleton reduces daily heat conduction, and the photo-thermal phase change coupled microcapsules actively regulate heat when the temperature changes, together improving the thermal insulation performance and heat management capability of the mortar; making buildings more effectively maintain stable indoor temperature under different seasons and day-night temperature differences, reducing the frequency of air conditioning and heating use, and reducing energy consumption.

[0140] Fiber-reinforced materials have high strength and high aspect ratio, playing a skeleton support role in mortar, enhancing the toughness and crack resistance of mortar. The magnetic field oriented Fe3O4 nanosheet is arranged in the horizontal direction by applying an axial magnetic field during construction, with an angle between the in-plane direction and the heat flow direction ≤15°, optimizing the heat transfer path inside the mortar, while also helping to improve the structural stability of the mortar. Silicon carbide nanowire aerogel further fills the pores inside the mortar, enhancing the denseness of the overall structure; improving the mechanical properties and durability of self-insulating mortar, allowing it to withstand various external forces and environmental factors during long-term use, reducing cracking and shedding, and extending the service life of buildings.

[0141] Metal-organic framework nanoparticles have a large specific surface area and specific pore size, and after modification with amino silane coupling agent on the surface, they can better combine with other components, while also having functions such as adsorption and catalysis. Self-repairing microcapsules can automatically release and fill cracks when microcracks appear in the mortar, restoring the performance of the mortar. The two work together to expand the functions of the mortar and enhance its self-maintenance ability. Self-insulating mortar not only has insulation function, but also has certain functional expansion, such as adsorbing harmful gases and catalyzing the decomposition of pollutants. At the same time, the self-repairing function reduces the maintenance cost of the mortar, improving its reliability and safety.

[0142] The surface activation treatment generates a nano-SiO2 active layer on the surface of the mortar by low-temperature plasma treatment, improves the activity and hydrophilicity of the surface of the mortar, and is conducive to bonding with other materials. The BaSO4@PDMS coating formed by spraying the composite radiation cooling coating has high reflectivity and can effectively reflect solar radiation heat to reduce the temperature of the surface of the mortar. Both of them synergistically improve the surface performance and protection ability of the mortar. The bonding strength between the self-insulation mortar and other building materials is enhanced, and the overall sealing and waterproofness of the building are improved. At the same time, the composite radiation cooling coating further reduces the energy consumption of the building and improves the indoor comfort.

[0143] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can make equivalent replacements or changes to the technical solutions and the inventive concept of the present application within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A self-insulating mortar, characterized in that, The components include the following weight parts: Portland cement 40-60 parts, density gradient graphene aerogel skeleton 5-15 parts, metal organic framework nanoparticles 3-8 parts, photothermal-phase change coupling microcapsules 8-15 parts, magnetic field oriented Fe3O4 nanosheet 2-5 parts, self-repairing microcapsules 3-6 parts, silicon carbide nanowire aerogel 4-10 parts, water reducing agent 1-3 parts, and fiber reinforced material 1-3 parts. The metal organic framework nanoparticles are ZIF-8 or ZIF-67, the pore size is 1.1-1.5 nm, and the surface is modified by amino silane coupling agent, and the thickness of the modified layer is 2-5 nm. The shell layer of the photothermal-phase change coupling microcapsules is rutile TiO2, and the thickness is 50-80 nm; the core material is a eutectic salt mixed by lauric acid and stearic acid at a mass ratio of 6:4, the phase change temperature is 25-30℃, and the phase change latent heat is ≥270 J / g. The horizontal arrangement of the magnetic field oriented Fe3O4 nanosheet is realized by applying an axial magnetic field of 0.3-0.8 T during construction, and the in-plane direction of the nanosheet is ≤15° with the heat flow direction.

2. A self-insulating mortar according to claim 1, characterized in that, The fiber reinforced material is modified basalt fiber or silicon carbide whisker, the fiber length is 3-6 mm, the aspect ratio is ≥50:1, and the surface is treated by plasma grafting to form a nano-scale concave-convex structure.

3. A method of preparing a self-insulating mortar according to any one of claims 1-2, characterized in that, The steps include: S1 Density gradient graphene aerogel scaffold fabrication: graphene oxide dispersion was injected into a mold, gradient frozen at -5 °C / min to form ice crystal templates, vacuum freeze-dried at -50 °C and hydrogen reduced at 500-800 °C to produce density gradient graphene aerogel scaffolds with densities ranging from 0.1-0.8 g / cm 3 ; S2: Premixing of functional components: Put Portland cement, density gradient graphene aerogel skeleton, metal organic framework nanoparticles, and silicon carbide nanowire aerogel into a planetary mixer, dry mix at a speed of 200-400 rpm for 10-15 minutes to form a base mixture; S3: Loading of response components: Add photothermal-phase change coupling microcapsules, Fe3O4 nanosheet, fiber reinforced material, and self-repairing microcapsules to the base mixture of S2, and spray water reducing agent solution at the same time, wet mix at a speed of 600-800 rpm for 5-8 minutes under nitrogen protection to form a slurry body; S4: Magnetic field orientation forming: Pour the slurry body obtained in S3 into a mold, immediately apply an axial magnetic field of 0.3-0.8 T and maintain for 10-15 minutes to make the Fe3O4 nanosheet directionally arranged along the horizontal direction, then remove the magnetic field and stand for 24 hours; S5: Surface activation treatment: Perform low-temperature plasma treatment on the cured slurry to generate a nano-SiO2 active layer on the surface; S6: Spray the cured slurry with BaSO4@PDMS suspension to form a coating layer with a thickness of 50-80 μm at a pressure of 0.2-0.5 MPa, then solidify at 80℃ for 1 hour to obtain a composite thermal insulation mortar.

4. A method of preparing a self-insulating mortar according to claim 3, characterized in that, In step S3, the nitrogen flow of nitrogen protection is 10-15 L / min, and the wet mixing temperature is controlled at 20-25℃.

5. A method of preparing a self-insulating mortar according to claim 3, characterized in that, In step S1, the gradient freezing process is divided into three temperature interval controls: First stage: from 25℃ to 0℃ at a rate of -3℃ / min, ice crystals grow along the vertical direction; Second stage: keep at 0℃ for 10 minutes to form a continuous ice crystal template; Third stage: from 0℃ to -50℃ at a rate of -8℃ / min to induce the directional stacking of graphene oxide layers; The hydrogen reduction process is kept at 650℃ for 2h with a heating rate of 5℃ / min.

6. A method of preparing a self-insulating mortar according to claim 3, characterized in that, In step S4, the static curing adopts segmented humidity control: First stage: relative humidity ≥ 95%, temperature 20±2℃, so that the cement hydration product wraps the functional filler; Second stage: relative humidity is reduced to 60-70%, temperature is increased to 35±2℃, to accelerate the stabilization of Fe3O4 nanosheet oriented structure; After the completion of curing, microwave-assisted drying treatment is performed for 30-60min, so that the water content is ≤1.5%.

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