Sand grain with water storage structure as well as preparation method and application of sand grain

Abstract

The invention discloses sand grains with a water storage structure and a preparation method and application thereof. The method comprises the steps that S1, sand grains with the grain size ranging from 0.1 mm to 1 mm are selected, the grain size distribution meets the condition that D50 is equal to 0.3 mm, clay impurities are screened out, and the sand grains are placed on a sand grain base plate (1) after being cleaned and dried; s2, nano silicate powder is uniformly sprayed on the surfaces of the sand grains through an electrostatic spraying technology, so that a silicate glass layer (5) is formed on the surfaces of the sand grains; s3, a microarray lens (3) is used for dividing a laser source into multiple laser beams, each laser beam irradiates the silicate glass layer (5) on each sand grain in a one-to-one mode, silicate powder and the surface layers of the sand grains are co-melted, and then an amorphous net-shaped structure is formed; s4, argon is used for spraying the amorphous net-shaped structure so that the amorphous net-shaped structure can be rapidly cooled, and then a porous heterojunction structure is formed on the surface of the sand grains; and S5, scanning the silicate glass layer (5) by using the laser again, so that the part of the silicate glass layer (5) is molten again, silicate is decomposed to generate gas, and cooling and curing are performed after bubbles are formed in the molten glass. According to the invention, the sand grains have a certain water storage characteristic.

Description

Technical Field

[0001] The present invention relates to the technical field of soil improvement and remediation, and in particular, to a sand particle with a water storage structure, a preparation method thereof, and an application thereof. Background Art

[0002] Currently, the methods for treating desertified soil mainly include chemical water retention agents, physical covering methods, and bionic water collection devices. Among them, chemical water retention agents (such as superabsorbent polymers) are effective in the short term, but are easily degraded and cause secondary pollution; physical covering methods (such as straw covering or plastic film) need to be frequently replaced, with high costs and easy to damage the ecology; bionic water collection devices (such as the bionic structure of beetle elytra) require external equipment and are difficult to be applied on a large scale. Summary of the Invention

[0003] In view of this, a first object of the present invention is to provide a method for constructing a water storage structure on the surface of sand particles, enabling the sand particles to have certain water storage characteristics.

[0004] To achieve the above object, the technical solution of the present invention is as follows: A method for constructing a water storage structure on the surface of sand particles, characterized by comprising the following steps: S1. Select sand particles with a particle size of 0.1 - 1 mm, and the particle size distribution conforms to D50 = 0.3 mm. After screening out clay impurities, washing, and drying, place them on a sand particle substrate; S2. Through electrostatic spraying technology, uniformly spray nano-silicate powder on the surface of the sand particles to form a silicate glass layer on the surface of the sand particles; S3. Use a microarray lens to divide a laser source into multiple laser beams, and each laser beam irradiates the silicate glass layer on each sand particle one by one, so that the silicate powder and the surface layer of the sand particle are melted together to form an amorphous network structure; S4. Spray argon on the amorphous network structure to quickly cool it, thereby forming a porous heterojunction structure on the surface of the sand particles; S5. Use a laser to scan the silicate glass layer again to locally remelt the silicate glass layer, decompose the silicate to generate gas, form bubbles in the molten glass, and then cool and solidify.

[0005] Preferably, it further includes: S6. Use atomic layer deposition to generate a TiO2 layer on the surface of the silicate glass layer; S7. Spray a mixed solution of polydimethylsiloxane and nano-SiO2 on the TiO2 layer, and then locally carbonize it by laser to form a hydrophobic channel; S8. Selectively oxidize dimethylsiloxane by plasma treatment to form a hydrophilic channel.

[0006] Preferably, the ratio of dimethyl silicone to nano-SiO2 is 4:1.

[0007] Preferably, the nano-silicate powder is Na2SiO3 or K2SiO3, with a particle size of 50-200 nm.

[0008] The second object of the present invention is to provide a sand particle with a water storage structure, which has certain water storage characteristics.

[0009] In order to achieve the above object, the technical solution of the present invention is: A sand particle with a water storage structure, comprising: A sand particle matrix; A silicate glass layer, which is fixed to the surface of the sand particle matrix by melting; A water storage layer, which is formed on the upper surface of the silicate glass layer and has a porous structure; Preferably, a protective coating is further provided on the water storage layer, and the protective coating has hydrophobic channels and hydrophilic channels.

[0010] The third object of the present invention is to provide a method for improving the water retention of sandy soil.

[0011] In order to achieve the above object, the technical solution of the present invention is: A method for improving the water retention of sandy soil, wherein the sand prepared by the above method is incorporated into the surface soil of the desert at a mass ratio of 15%-25%.

[0012] The technical effects of the present invention are mainly reflected in the following aspects: 1. Environmentally friendly and long-lasting: Without chemical additives, the lifespan of the glassy structure > 10 years; 2. Bionic and efficient: The water collection efficiency of the porous heterojunction structure reaches 0.5-1.2 L / m² every night; 3. Structure controllable: The porosity and hydrophilicity / hydrophobicity are precisely regulated by laser parameters; 5. Cost advantage: The single treatment cost is low, suitable for large-scale desert treatment. Description of the Drawings

[0013] Figure 1 Schematic diagram of the sand particle substrate in the embodiment; Figure 2 Schematic diagram of the principle of laser irradiation in the embodiment; Figure 3 Schematic diagram of the sand particle in the embodiment.

[0014] Reference numerals; 1. Sand particle substrate; 11. Accommodating groove; 2. Lithographic objective lens; 3. Microarray lens; 4. Sand particle matrix; 5. Silicate glass layer; 6. Water storage layer; 7. Protective coating. Detailed Description of the Invention

[0015] The following further details the specific embodiments of the present invention in conjunction with the accompanying drawings, so that the technical solutions of the present invention are easier to understand and master. Embodiment 1

[0016] This embodiment provides a method for constructing a water storage structure on the surface of sand grains, including the following steps: S1. Select sand grains with a particle size of 0.1 - 1 mm, and the particle size distribution conforms to D50 = 0.3 mm. After screening out clay impurities, washing, and drying, place them on the sand grain substrate 1.

[0017] In this step, clay impurities can be directly screened out by the particle size.

[0018] As Figure 1 shown, the sand grain substrate includes a plate body made of a black aluminum plate; a number of receiving grooves 11 for accommodating sand grains are distributed in a matrix on the plate body, and the processed sand grains can be placed one by one in the receiving grooves 11.

[0019] S2. Through electrostatic spraying technology, uniformly spray nano - silicate powder on the surface of the sand grains to form a silicate glass layer 5 on the surface of the sand grains.

[0020] The above - mentioned nano - silicate powder is Na2SiO3 or K2SiO3, with a particle size of 50 - 200 nm. The silicate glass layer 5 serves as a "molten medium", reducing the melting temperature of the sand grain surface (from 1700 °C of pure SiO2 to below 1200 °C), and reducing the laser energy consumption.

[0021] S3. Use a micro - array lens 3 to divide the laser source into multiple beams of laser (as Figure 2 shown), and each beam of laser irradiates the silicate glass layer 5 on each sand grain one by one, so that the silicate powder and the surface layer of the sand grain are melted together to form an amorphous network structure.

[0022] In this step, the laser parameters involved are: ultraviolet laser with a wavelength of 355 nm or 266 nm (shallow penetration depth, and the energy is concentrated on the surface); power density of 100 - 400 W / cm² (higher than the melting threshold of the sand grain surface but lower than the overall vaporization threshold); the scanning path is a spiral linear scan (coverage rate ≥ 90%), and the spot overlap rate is 30% - 50%; the pulse frequency is 5 kHz (pulse width 20 ns). This step realizes a continuous molten pool through the "thermal accumulation effect".

[0023] Under laser irradiation, the silicate powder and the surface layer of the sand grain (SiO2) are melted together to form a flowing molten pool; in the molten pool, the SiO2 network and Na⁺ / K⁺ ions undergo bonding recombination to form a [SiO4]⁻⁺ amorphous network structure. Micro - convection is generated on the surface of the molten pool due to the Marangoni effect, promoting the spontaneous nucleation of pores.

[0024] S4. Spray argon gas onto the amorphous network structure to rapidly cool it, thereby forming a porous heterojunction structure on the surface of the sand grains.

[0025] In this step, the flow rate of argon gas is 10 - 20 L / min, and the cooling rate is ≥500 K / s. During the rapid cooling process, the amorphous network structure forms a "mechanical interlock + chemical bonding" heterojunction interface with the unmelted crystalline sand grain matrix 4, and the interfacial bonding strength is >50 MPa.

[0026] S5. Use a laser to scan the silicate glass layer 5 again to locally remelt the silicate glass layer 5. The silicate decomposes to produce gas, forming bubbles in the molten glass and then cooling and solidifying.

[0027] In this step, the silicate decomposes to produce gas, forming bubbles in the molten glass and then cooling and solidifying. Different pore sizes and densities of pores can be generated by controlling the scanning power and speed of the laser. The main function is to achieve water adsorption and storage, and the thickness is in the micron range.

[0028] The principle of bubble nucleation in the molten pool is as follows: Local high temperature during the melting process causes the decomposition of silicate (for example, 2Na2SiO3 → 2Na2O + 3SiO2 + O2↑), releasing gas to form bubbles; the bubbles are "frozen" by the rapidly cooled glass layer, forming a honeycomb-like porous structure.

[0029] In this step, the pore structure and surface chemical properties can also be dynamically regulated by laser parameters, as follows: Low power + high scanning speed (200 W / cm², 1 m / s): Generate small pore size (50 - 100 nm) and high density pores (porosity 70%), suitable for high humidity areas; High power + low scanning speed (400 W / cm², 0.1 m / s): Generate large pore size (300 - 500 nm) and low density pores (porosity 30%), suitable for arid areas.

[0030] S6. Use atomic layer deposition to generate a TiO2 layer on the surface of the silicate glass layer 5.

[0031] In this step, the thickness of the TiO2 layer can be 5 nm, which can enhance the ultraviolet stability to a certain extent. The precursor of the TiO2 layer is TiCl4 + H2O, and the temperature is 150 °C.

[0032] S7. Spray a mixed solution of polydimethylsiloxane and nano-SiO2 on the TiO2 layer, and then locally carbonize it by laser to form a hydrophobic channel.

[0033] In this step, the above hydrophobic channels are actually a lattice composed of large-aperture pores; the ratio of dimethylsiloxane to nano-SiO₂ used is 4:1; the laser power is 20 W / cm². The contact angle of the formed hydrophobic channels is 150°.

[0034] S8. Selectively oxidize dimethylsiloxane by plasma treatment to form hydrophilic channels.

[0035] In this step, O₂ plasma is used for plasma treatment with a power of 100 W for 5 min; the contact angle of the formed hydrophilic channels is 30°, thus simulating the "hydrophilic protrusions + hydrophobic grooves" structure of the beetle's back shell. The area carbonized by the laser forms a graphitized structure with antioxidant properties, and at this time, the plasma treatment cannot oxidize it, while the untreated area can be oxidized to form hydrophilic channels.

[0036] The sand grain structure prepared according to the above steps is as Figure 3 shown, including a sand grain matrix 4, a silicate glass layer 5, a water storage layer 6, and a protective coating 7; among them, the silicate glass layer 5 is completed by steps S2 - S4, and the water storage layer 6 is completed by step S5; the protective coating 7 is completed by steps S6 - S8.

[0037] Among them, the silicate glass layer 5 is fixed to the surface of the sand grain matrix 4 by melting; the water storage layer 6 is formed on the upper surface of the silicate glass layer 5 and has a porous structure; the protective coating 7 has hydrophobic channels and hydrophilic channels. Example Two

[0038] Based on Example One, this example aims to provide a method for improving the water retention property of sandy soil, specifically: mixing the sand made in Example One into the desert surface soil at a mass ratio of 15% - 25%, and the depth is preferably 0 - 10 cm.

[0039] Adopting the above scheme, the desert surface soil has the following characteristics: Water adsorption: When the night temperature drops, the porous glass layer adsorbs moisture in the air through capillary action (the adsorption amount reaches 0.8 L / m²·night under the condition of humidity > 60%); Water release: When the day temperature rises, the hydrophobic-hydrophilic gradient structure controls the slow release of water through the pores (the release rate is 0.05 - 0.1 L / m²·h), maintaining the soil humidity > 15%; Long-term stability: After 100 wet-dry cycles, the water retention capacity decays by < 5% (the decay of traditional chemical water-retaining agents is > 50%).

[0040] Of course, the above are only typical examples of the present invention. In addition, the present invention can also have many other specific implementation manners. Any technical solution formed by equivalent substitution or equivalent transformation falls within the scope of protection required by the present invention.

Claims

1. A method for constructing a water storage structure on the surface of sand particles, characterized in that: The following steps are involved: S1, select sand with a particle size of 0.1-1 mm, and the particle size distribution meets the requirement of D50=0.3 mm, sieve out clay impurities, wash and dry the sand, and then place it on the sand substrate (1); S2, using electrostatic spraying technology, uniformly spraying nano-silicate powder on the surface of the sand to form a silicate glass layer (5) on the surface of the sand; S3, using a micro-array lens (3) to divide the laser source into multiple laser beams, each laser beam irradiates the silicate glass layer (5) on each sand grain one by one, so that the silicate powder and the surface layer of the sand grains are eutectic, thereby forming an amorphous network structure; S4, spraying the amorphous network structure with argon gas to rapidly cool it, thereby forming a porous heterojunction structure on the surface of the sand particles; S5. Use laser to scan the silicate glass layer (5) again to partially re-melt the silicate glass layer (5). The silicate decomposes to generate gas, which forms bubbles in the molten glass and then cools and solidifies.

2. A method for constructing a water storage structure on the surface of sand particles as claimed in claim 1, characterized in that: include: S6, forming a TiO2 layer on the surface of the silicate glass layer (5) by an atomic layer deposition method; S7, spraying a mixed solution of polydimethylsiloxane and nano-SiO2, and then locally carbonizing by laser to form a hydrophobic channel; S8. Selectively oxidize dimethylsiloxane by plasma treatment to form a hydrophilic channel.

3. A method for constructing a water storage structure on the surface of sand particles as claimed in claim 2, characterized in that: The ratio of dimethylsiloxane to nano-SiO2 is 4:

1.

4. A method for constructing a water storage structure on the surface of sand particles as claimed in claim 1, characterized in that: The nano silicate powder is Na2SiO3 or K2SiO3, with a particle size of 50-200nm.

5. A sand grain with a water storage structure, characterized in that: include: Sand matrix (4); a silicate glass layer (5) fixed to the surface of the sand matrix (4) by melting; The water storage layer (6) is formed on the upper surface of the silicate glass layer (5) and has a porous structure.

6. The sand with water storage structure as claimed in claim 5, characterized in that: A protective coating (7) is also provided on the water storage layer (6), and the protective coating (7) has a hydrophobic channel and a hydrophilic channel.

7. A method for improving the water-holding property of sandy soil, characterized in that: The sand prepared according to any one of the methods described in claims 1 to 4 is mixed into the desert surface soil at a mass ratio of 15% to 25%.

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