Solid-waste-based alkali-activated composite material with thermoelectric effect and preparation method of solid-waste-based alkali-activated composite material

Abstract

The invention discloses a solid waste-based alkali-activated composite material with thermoelectric effect and a preparation method thereof, the composite material comprises the following components in parts by mass: 50-65 parts of low-calcium fly ash, 10-35 parts of blast furnace slag powder, 0-30 parts of solid waste residue, 52-68 parts of an alkali activator, 60-100 parts of river sand, 0.5-2 parts of a functional filler, 1.2-3.5 parts of recycled carbon fiber, 15-30 parts of mixing water, and 1-2 parts of a shrinkage reducing agent. The compressive strength of the obtained composite material is higher than 40 MPa, and the composite material has remarkable Seebeck and thermoelectric effects. According to the invention, crack control deformation, thermoelectric conversion and solid waste resource utilization of the composite material can be realized.

Description

Technical Field

[0001] This invention relates to a solid waste-based alkali-activated composite material with thermoelectric effect and its preparation method, belonging to the field of building materials technology. Background Technology

[0002] Thermoelectric materials enable the conversion of thermal energy into electrical energy, and have significant application value in fields such as distributed power generation, industrial waste heat recovery, and solid-state refrigeration. However, the large-scale application of traditional thermoelectric materials (such as bismuth telluride and lead telluride) is limited by the use of rare metals and the high cost of their preparation. Therefore, there is an urgent need to develop novel thermoelectric material systems that are low-cost, environmentally friendly, and possess excellent mechanical properties.

[0003] Against this backdrop, cement-based thermoelectric composite materials have been developed, offering advantages such as a wide availability of matrix materials, ease of integration with building structures, the ability to construct conductive networks by incorporating conductive phases, and simple molding processes. However, cement-based materials also suffer from inherent drawbacks, including high intrinsic thermal conductivity, strong electrical insulation, and high carbon emissions during production, which limit improvements in thermoelectric performance.

[0004] In contrast, alkali-activated materials, with their unique properties and advantages, have become an ideal alternative matrix to traditional silicate cement. Using industrial solid waste as the main raw material, alkali-activated materials are solidified and molded through a room-temperature alkali-activated reaction, significantly reducing carbon emissions. Their ion / electron synergistic conductivity mechanism and low matrix thermal conductivity make them more promising for thermoelectric performance regulation. Simultaneously, the strongly alkaline environment provides chemical compatibility for the stability of the functional phase.

[0005] However, regardless of whether it is cement-based or alkali-activated thermoelectric materials, current patented technologies are generally limited by the use of high-purity materials and energy-intensive processes (such as high-temperature annealing, plasma treatment, chemical vapor deposition, etc.), resulting in high production costs and complex preparation processes, and making it difficult to achieve large-scale solid waste disposal. For example, CN111302687A discloses a method for preparing cement-based thermoelectric materials using zinc oxide by combining ball milling and reducing atmosphere heat treatment, which is relatively complex and energy-intensive; CN110282927A discloses a bismuth telluride-carbon fiber composite cement-based thermoelectric material, which is relatively expensive and has a low Seebeck coefficient.

[0006] Therefore, a new solution is needed to address this problem. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a solid waste-based alkali-activated composite material with thermoelectric effect and its preparation method. It solves the problems of complex processes, difficulty in achieving large-scale solid waste disposal, high cost, and low Seebeck coefficient in the prior art.

[0008] The technical problem to be solved by this invention is achieved by the following technical solution: a solid waste-based alkali-activated composite material with thermoelectric effect, comprising the following raw materials by mass: 50-65 parts of low-calcium fly ash; 10-35 parts of blast furnace slag powder; Solid waste residue 0-30 parts; 52-68 parts of alkaline activator; 60-100 parts river sand; 0.5 to 2 parts of functional filler; Recycle 1.2 to 3.5 parts of carbon fiber; Mix in 15-30 parts water; Shrinkage reducer 1-2 parts.

[0009] The present invention is further configured such that: the calcium oxide content of the low-calcium fly ash is in the range of 1%-10%; and the grade of the blast furnace slag powder is S95 or S105. The present invention is further configured such that: the solid waste residue is one or more of copper slag, steel slag, ferrosilicon manganese slag, and hot-dip galvanizing process zinc slag, and the specific surface area of ​​the powder after drying is 350~400 m². 2 / kg.

[0010] The present invention is further configured such that: the alkaline activator is a mixture of liquid water glass, sodium hydroxide and water, the silicate modulus ranges from 1.4 to 2.2, the solid content is 40%, and it is cooled for at least 5 hours after preparation.

[0011] The present invention is further configured such that the river sand is medium sand with a fineness modulus of 2.6 to 2.8.

[0012] The present invention is further configured such that the functional filler is one or more of nano copper oxide, nano iron oxide, nano manganese oxide and nano zinc oxide, with a particle size of less than 100 nm.

[0013] The present invention is further configured such that: the recycled carbon fiber is one or more of the following: decommissioned wind turbine blades, prepreg scraps, cured finished product waste, and resin processing losses, which are recycled after being processed by relevant processes; the recycled carbon fiber has a length of 6~12mm, an ultimate elongation of 1~2.5%, and a tensile strength of at least 1GPa.

[0014] The present invention is further configured such that the mixing water is tap water.

[0015] The present invention is further configured such that: the shrinkage reducing agent is a shrinkage reducing agent having a low molecular weight polyether or polyethylene glycol derivative, and the shrinkage reduction effect is not less than 15%.

[0016] A method for preparing a solid waste-based alkali-activated composite material with thermoelectric effect includes the following steps: (1) Weigh the dried raw materials; (2) Mix low-calcium fly ash, blast furnace slag powder, solid waste residue and functional filler in a mixer for 2 minutes until uniform, with a speed of 145±5 rpm; (3) Mix the powder from step (2) with dry river sand in a mixer for 1 minute at a speed of 145±5 rpm; (4) Prepare the aged alkaline activator and mix it with the mixture obtained in step (3), and add additional water and shrinkage reducer. First, stir at a speed of 145±5 rpm for 2 minutes, and then stir at a speed of 290±5 rpm for 1 minute until it is in a fluid state to obtain mortar slurry; (5) Add recycled carbon fiber to the mortar slurry obtained in step (4); stir for 1 min at a speed of 145±5 rpm; (6) The fresh mixture obtained in step (5) of high-speed mixing is at a speed of 290±5 rpm; (7) The mixture obtained in step (6) is placed into a test mold, vibrated to compact it, scraped flat, covered with plastic wrap, and after 24 hours, it is removed from the mold and sealed with a plastic bag. It is then cured at 20±2℃ for 28 days.

[0017] The beneficial effects of this invention are as follows: Semiconductor-characteristic solid waste residue is used as an alkali-excited precursor, rich in narrow-bandgap oxides such as Fe2O3 and CuO, which generates an intrinsic Seebeck effect under a temperature gradient. Micron-sized particles fill the pores of the matrix, increasing density. Recycled carbon fibers construct a long-range three-dimensional conductive network, improving conductivity. A 1.2–3.5% doping concentration increases fiber bridging and pull-out effects, enhancing the fracture toughness of the composite material. The introduction of nano-metal oxides improves the Seebeck coefficient through interfacial energy filtering, simultaneously strengthening phonon scattering to reduce thermal conductivity, and enhancing interfacial bonding through hydrogen bonding, synergistically suppressing crack propagation. This improves the mechanical and thermoelectric properties of the composite material and overcomes the brittleness bottleneck of thermoelectric materials. Simultaneously, the use of solid waste cementitious powder and solid waste reinforcing fiber reduces raw material costs and promotes the resource utilization of waste. The room-temperature preparation process reduces energy dependence and is simple and easy to produce. Detailed Implementation

[0018] To facilitate a clear understanding of the technical means, creative features, objectives, and effects of this invention, the invention will be further described below.

[0019] A solid waste-based alkali-activated composite material with thermoelectric effect, comprising the following raw materials in parts by mass: 50-65 parts of low-calcium fly ash, wherein the calcium oxide content of the low-calcium fly ash is in the range of 1%-10%; 10-35 parts of blast furnace slag powder, with a grade of S95 or S105; Solid waste residue, 0-30 parts, is one or more of copper slag, steel slag, ferrosilicon manganese slag, and zinc slag from hot-dip galvanizing processes. The specific surface area of ​​the powder after drying is 350-400 m². 2 / kg; 52-68 parts of alkaline activator, which is a mixture of liquid water glass, sodium hydroxide and water, with a silicate modulus ranging from 1.4 to 2.2 and a solid content of 40%. After preparation, it should be cooled for at least 5 hours. River sand, 60-100 parts, specifically medium sand, with a fineness modulus of 2.6-2.8; 0.5 to 2 parts of functional filler, which is one or more of nano copper oxide, nano iron oxide, nano manganese oxide and nano zinc oxide, with a particle size of less than 100 nm; 1.2 to 3.5 parts of carbon fiber are recycled, which are one or more of the following: retired wind turbine blades, prepreg scraps, cured finished product waste, and resin processing loss, which are recycled after being processed by relevant processes. The recycled carbon fiber has a length of 6 to 12 mm, an ultimate elongation of 1 to 2.5%, and a tensile strength of at least 1 GPa. Mix in 15-30 parts water, specifically tap water; 1-2 parts of shrinkage reducer, which is a shrinkage reducer with low molecular weight polyether or polyethylene glycol derivative, with a shrinkage reduction effect of not less than 15%.

[0020] Example 1 (1) Weigh the raw materials: 55 parts of low calcium fly ash, 20 parts of blast furnace slag powder, 25 parts of copper slag, 60 parts of 1.5 modulus alkaline activator, 90 parts of river sand, 1 part of nano copper oxide, 1.5 parts of recycled carbon fiber for wind turbine blades, 22 parts of water, and 1.4 parts of shrinkage reducer. (2) Mix low-calcium fly ash, blast furnace slag powder, copper slag powder and nano copper oxide in a mixer for 2 minutes until uniform, with a speed of 145±5 rpm; (3) Mix the powder from step (2) with dry river sand in a mixer for 1 minute at a speed of 145±5 rpm; (4) Prepare the alkali activator after aging and mix it with the mixture obtained in step (3), and add additional water and shrinkage reducer. First, stir at a speed of 145±5 rpm for 2 minutes, and then stir at a speed of 290±5 rpm for 1 minute until it is in a fluid state to obtain mortar slurry; (5) Add recycled carbon fiber to the mortar obtained in step (4); stir for 1 min at a speed of 145±5 rpm; (6) The fresh mixture obtained in step (5) of high-speed mixing is at a speed of 290±5 rpm; (7) The mixture obtained in step (6) is placed into a test mold, vibrated to compact it, scraped flat, covered with plastic wrap, and after 24 hours, it is removed from the mold and sealed with a plastic bag. It is then cured at 20±2℃ for 28 days.

[0021] Example 2 (1) Weigh the raw materials: 55 parts of low calcium fly ash, 20 parts of blast furnace slag powder, 25 parts of ferrosilicon manganese slag, 60 parts of 1.5 modulus alkaline activator, 90 parts of river sand, 1 part of nano manganese oxide, 1.5 parts of recycled carbon fiber for wind turbine blades, 22 parts of water, and 1.4 parts of shrinkage reducer. (2) Mix low-calcium fly ash, blast furnace slag powder, ferrosilicon manganese slag powder and nano manganese oxide in a mixer for 2 minutes until uniform, with a speed of 145±5 rpm; (3) Mix the powder from step (2) with dry river sand in a mixer for 1 minute at a speed of 145±5 rpm; (4) Prepare the alkali activator after aging and mix it with the mixture obtained in step (3), and add additional water and shrinkage reducer. First, stir at a speed of 145±5 rpm for 2 minutes, and then stir at a speed of 290±5 rpm for 1 minute until it is in a fluid state to obtain mortar slurry; (5) Add recycled carbon fiber to the mortar obtained in step (4); stir for 1 min at a speed of 145±5 rpm; (6) The fresh mixture obtained in step (5) of high-speed mixing is at a speed of 290±5 rpm; (7) The mixture obtained in step (6) is placed into a test mold, vibrated to compact it, scraped flat, covered with plastic wrap, and after 24 hours, it is removed from the mold and sealed with a plastic bag. It is then cured at 20±2℃ for 28 days.

[0022] Example 3 (1) Weigh the raw materials: 55 parts of low calcium fly ash, 20 parts of blast furnace slag powder, 25 parts of steel slag, 65 parts of 1.6 modulus alkaline activator, 90 parts of river sand, 1 part of nano iron oxide, 1.5 parts of recycled carbon fiber from prepreg scraps, 20 parts of water, and 1.4 parts of shrinkage reducer. (2) Mix low-calcium fly ash, blast furnace slag powder, steel slag powder and nano iron oxide in a mixer for 2 minutes until uniform, with a speed of 145±5 rpm; (3) Mix the powder from step (2) with dry river sand in a mixer for 1 minute at a speed of 145±5 rpm; (4) Prepare the alkali activator after aging and mix it with the mixture obtained in step (3), and add additional water and shrinkage reducer. First, stir at a speed of 145±5 rpm for 2 minutes, and then stir at a speed of 290±5 rpm for 1 minute until it is in a fluid state to obtain mortar slurry; (5) Add recycled carbon fiber to the mortar obtained in step (4); stir for 1 min at a speed of 145±5 rpm; (6) The fresh mixture obtained in step (5) of high-speed mixing is at a speed of 290±5 rpm; (7) The mixture obtained in step (6) is placed into a test mold, vibrated to compact it, scraped flat, covered with plastic wrap, and after 24 hours, it is removed from the mold and sealed with a plastic bag. It is then cured at 20±2℃ for 28 days.

[0023] Example 4: (1) Weigh the raw materials: 55 parts of low calcium fly ash, 20 parts of blast furnace slag powder, 25 parts of hot-dip galvanizing process zinc slag, 65 parts of 1.6 modulus alkaline activator, 90 parts of river sand, 1 part of nano zinc oxide, 1.5 parts of recycled carbon fiber from prepreg scraps, 20 parts of water, and 1.4 parts of shrinkage reducer. (2) Mix low-calcium fly ash, blast furnace slag powder, zinc slag powder and nano zinc oxide in a mixer for 2 minutes until uniform, with a speed of 145±5 rpm; (3) Mix the powder from step (2) with dry river sand in a mixer for 1 minute at a speed of 145±5 rpm; (4) Prepare the alkali activator after aging and mix it with the mixture obtained in step (3), and add additional water and shrinkage reducer. First, stir at a speed of 145±5 rpm for 2 minutes, and then stir at a speed of 290±5 rpm for 1 minute until it is in a fluid state to obtain mortar slurry; (5) Add recycled carbon fiber to the mortar obtained in step (4); stir for 1 min at a speed of 145±5 rpm; (6) The fresh mixture obtained in step (5) of high-speed mixing is at a speed of 290±5 rpm; (7) The mixture obtained in step (6) is placed into a test mold, vibrated to compact it, scraped flat, covered with plastic wrap, and after 24 hours, it is removed from the mold and sealed with a plastic bag. It is then cured at 20±2℃ for 28 days.

[0024] Example 5: (1) Weighing raw materials: 55 parts of low-calcium fly ash, 20 parts of blast furnace slag powder, 15 parts of copper slag, 10 parts of ferrosilicon manganese slag, 65 parts of 1.6 modulus alkaline activator, 90 parts of river sand, 0.5 parts of nano copper oxide, 0.5 parts of nano manganese oxide, 1.5 parts of recycled carbon fiber for wind turbine blades, 20 parts of water, and 1.4 parts of shrinkage reducer; (2) Mix low-calcium fly ash, blast furnace slag powder, copper slag powder, ferrosilicon manganese slag powder, nano copper oxide and nano manganese oxide in a mixer for 2 minutes until uniform, with a speed of 145±5 rpm. (3) Mix the powder from step (2) with dry river sand in a mixer for 1 minute at a speed of 145±5 rpm; (4) Prepare the alkali activator after aging and mix it with the mixture obtained in step (3), and add additional water and shrinkage reducer. First, stir at a speed of 145±5 rpm for 2 minutes, and then stir at a speed of 290±5 rpm for 1 minute until it is in a fluid state to obtain mortar slurry; (5) Add recycled carbon fiber to the mortar obtained in step (4); stir for 1 min at a speed of 145±5 rpm; (6) The fresh mixture obtained in step (5) of high-speed mixing is at a speed of 290±5 rpm; (7) The mixture obtained in step (6) is placed into a test mold, vibrated to compact it, scraped flat, covered with plastic wrap, and after 24 hours, it is removed from the mold and sealed with a plastic bag. It is then cured at 20±2℃ for 28 days.

[0025] Comparative Example 1 (1) Weigh the raw materials: 65 parts of low-calcium fly ash, 35 parts of blast furnace slag powder, 60 parts of 1.5 modulus alkaline activator, 90 parts of river sand, 22 parts of water, and 1.4 parts of shrinkage reducer; (2) Mix low-calcium fly ash and blast furnace slag powder in a mixer for 2 minutes until uniform, with a speed of 145±5 rpm; (3) Mix the powder from step (2) with dry river sand in a mixer for 1 minute at a speed of 145±5 rpm; (4) Prepare the alkali activator after aging and mix it with the mixture obtained in step (3), and add additional water and shrinkage reducer. First, stir at a speed of 145±5 rpm for 2 minutes, and then stir at a speed of 290±5 rpm for 1 minute until it is in a fluid state to obtain mortar slurry; (5) Add recycled carbon fiber to the mortar obtained in step (4); stir for 1 min at a speed of 145±5 rpm; (6) The fresh mixture obtained in step (5) of high-speed mixing is at a speed of 290±5 rpm; (7) The mixture obtained in step (6) is placed into a test mold, vibrated to compact it, scraped flat, covered with plastic wrap, and after 24 hours, it is removed from the mold and sealed with a plastic bag. It is then cured at 20±2℃ for 28 days.

[0026] The Seebeck coefficient, electrical conductivity, compressive strength, and flexural strength of the above embodiments were tested, and the test results are shown in Table 1.

[0027] Table 1 The difference between Example 2 and Example 1 is that 25 parts of ferrosilicon manganese slag and 1 part of nano-manganese oxide are used.

[0028] The difference between Example 3 and Example 1 is that the ingredients are: 25 parts steel slag, 65 parts 1.6 modulus alkaline activator, 1 part nano iron oxide, 1.5 parts recycled carbon fiber from prepreg scraps, and 20 parts water.

[0029] The difference between Example 4 and Example 1 is that the hot-dip galvanizing process zinc slag contains 25 parts, 1.6 modulus alkaline activator contains 65 parts, river sand contains 90 parts, nano zinc oxide contains 1 part, prepreg scrap recycled carbon fiber contains 1.5 parts, and water contains 20 parts.

[0030] The difference between Example 5 and Example 1 is that the ingredients are: 15 parts copper slag, 10 parts silicon manganese slag, 65 parts alkaline activator with a modulus of 1.6, 0.5 parts nano copper oxide, 0.5 parts nano manganese oxide, and 20 parts water.

[0031] The difference between Comparative Example 1 and Example 1 is that 65 parts of low-calcium fly ash, 35 parts of blast furnace slag powder, no solid waste residue, nanomaterials and recycled carbon fiber were used.

[0032] According to Table 1, the thermoelectric material prepared by the method for preparing solid waste-based alkali-activated composite materials with thermoelectric effect provided in this embodiment of the invention has a considerable thermoelectric effect, which can significantly improve the Seebeck coefficient and electrical conductivity of the concrete composite matrix; the thermoelectric characteristics change the functional properties of the material, which will be beneficial to the concrete composite material's ability to sense heat energy and convert it into electrical energy.

[0033] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention, all of which fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A solid waste-based alkali-activated composite material with thermoelectric effect, characterized in that, By weight, it includes the following raw materials: 50-65 parts of low-calcium fly ash; 10-35 parts of blast furnace slag powder; Solid waste residue 0-30 parts; 52-68 parts of alkaline activator; 60-100 parts river sand; 0.5 to 2 parts of functional filler; Recycle 1.2 to 3.5 parts of carbon fiber; Mix in 15-30 parts water; Shrinkage reducer 1-2 parts.

2. The solid waste-based alkali-activated composite material with thermoelectric effect according to claim 1, characterized in that: The calcium oxide content of the low-calcium fly ash is in the range of 1%-10%; the grade of blast furnace slag powder is S95 or S105.

3. The solid waste-based alkali-activated composite material with thermoelectric effect according to claim 1, characterized in that: The solid waste residue is one or more of copper slag, steel slag, ferrosilicon manganese slag, and zinc slag from hot-dip galvanizing processes, and the specific surface area of ​​the powder after drying is 350~400 m². 2 / kg.

4. The solid waste-based alkali-activated composite material with thermoelectric effect according to claim 1, characterized in that: The alkaline activator is a mixture of liquid water glass, sodium hydroxide, and water, with a silicate modulus ranging from 1.4 to 2.2 and a solid content of 40%. After preparation, it should be cooled for at least 5 hours.

5. A solid waste-based alkali-activated composite material with thermoelectric effect according to claim 1, characterized in that: The river sand is medium sand with a fineness modulus of 2.6 to 2.

8.

6. The solid waste-based alkali-activated composite material with thermoelectric effect according to claim 1, characterized in that: The functional filler is one or more of nano copper oxide, nano iron oxide, nano manganese oxide and nano zinc oxide, with a particle size of less than 100 nm.

7. A solid waste-based alkali-activated composite material with thermoelectric effect according to claim 1, characterized in that: The recycled carbon fiber is one or more of the following: decommissioned wind turbine blades, prepreg scraps, cured finished product waste, and resin processing losses, which are recycled after being processed by relevant processes; the recycled carbon fiber has a length of 6~12mm, an ultimate elongation of 1~2.5%, and a tensile strength of at least 1GPa.

8. A solid waste-based alkali-activated composite material with thermoelectric effect according to claim 1, characterized in that: The mixing water is tap water.

9. A solid waste-based alkali-activated composite material with thermoelectric effect according to claim 1, characterized in that: The shrinkage reducing agent is a low molecular weight polyether or polyethylene glycol derivative, with a shrinkage reduction effect of not less than 15%.

10. A method for preparing a composite material according to any one of claims 1-9, characterized in that, Includes the following steps: (1) Weigh the dried raw materials; (2) Mix low-calcium fly ash, blast furnace slag powder, solid waste residue and functional filler in a mixer for 2 minutes until uniform, with a speed of 145±5 rpm; (3) Mix the powder from step (2) with dry river sand in a mixer for 1 minute at a speed of 145±5 rpm; (4) Prepare the aged alkaline activator and mix it with the mixture obtained in step (3), and add additional water and shrinkage reducer. First, stir at a speed of 145±5 rpm for 2 minutes, and then stir at a speed of 290±5 rpm for 1 minute until it is in a fluid state to obtain mortar slurry; (5) Add recycled carbon fiber to the mortar slurry obtained in step (4); stir for 1 min at a speed of 145±5 rpm; (6) The fresh mixture obtained in step (5) of high-speed mixing is at a speed of 290±5 rpm; (7) The mixture obtained in step (6) is placed into a test mold, vibrated to compact it, scraped flat, covered with plastic wrap, and after 24 hours, it is removed from the mold and sealed with a plastic bag. It is then cured at 20±2℃ for 28 days.

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