Nano-composite reinforced graphite tailing-based geopolymer material and preparation method thereof

Abstract

The invention discloses a nano-composite reinforced graphite tailing-based geopolymer material and a preparation method thereof. The nano-composite reinforced graphite tailing-based geopolymer material is prepared from the following components in parts by weight: 50 to 70 parts of slag, 20 to 40 parts of graphite tailings, 10 to 15 parts of alkaline excitant, 0.05 to 0.2 part of nano-diamond and 0.03 to 0.1 part of graphene oxide. Wherein the graphene oxide is reduced graphene oxide subjected to low-temperature thermal reduction treatment. By implementing the invention, the mechanical property and durability of the geopolymer material can be remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, and particularly relates to a nano-composite reinforced graphite tailing-based geopolymer material and a preparation method thereof. BACKGROUND

[0002] As a new type of green cementitious material, the geopolymer material is gradually replacing the traditional cement due to its low carbon emission and high durability. In the prior art, industrial solid wastes are often used for geopolymer preparation. Although the slag-fly ash system geopolymer has high strength, it has insufficient acid corrosion resistance and is dependent on high-grade raw materials, which limits the cost. The microcrystalline quartz and aluminosilicate minerals contained in the graphite tailing can act as nucleation sites in the geopolymerization process to promote the precipitation and growth of geopolymer gel. However, the slag-graphite tailing system geopolymer has the following disadvantages: first, the coarse graphite tailing particles lead to internal pore connectivity in the geopolymer, and the chloride ion permeability coefficient is greater than 1x10 -12 m 2 / s, the impermeability of the geopolymer material is insufficient; second, the corrosion resistance is limited, and the 30d strength loss in a 5% sulfuric acid solution is greater than 25%; third, the 28d compressive strength of the geopolymer material is usually less than 80MPa, and the mechanical properties are difficult to meet the requirements of special engineering. Adding nano materials to the slag-graphite tailing system geopolymer can improve the mechanical properties to some extent, but the nano materials are prone to uneven dispersion in the system, and the nano materials are prone to agglomeration, which increases defects. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a nano-composite reinforced graphite tailing-based geopolymer material and a preparation method thereof, which can significantly improve the mechanical properties and durability of the geopolymer material.

[0004] To solve the above problems, the present application discloses a nano-composite reinforced graphite tailing-based geopolymer material, characterized in that it comprises the following components by weight: 50-70 parts of slag, 20-40 parts of graphite tailing, 10-15 parts of alkaline activator, 0.05-0.2 parts of nano diamond, and 0.03-0.1 parts of graphene oxide; wherein the graphene oxide is reduced graphene oxide treated by low-temperature thermal reduction.

[0005] As an improvement of the above technical solution, the particle size of the nano diamond is 10-50nm; and the sheet thickness of the graphene oxide is 1-3nm.

[0006] As an improvement of the above technical solution, the low-temperature thermal reduction treatment comprises the following steps:

[0007] heat at a rate of 2-4℃ / min to 200-300℃ and keep the temperature for 60-120min.

[0008] Ramp up at a rate of 3℃ / min to 5℃ / min to 300℃ to 400℃, and keep for 30min to 60min;

[0009] Cool down to room temperature naturally under vacuum environment.

[0010] As an improvement of the above technical solution, the nanodiamond is a nanodiamond pretreated by a silane coupling agent, and the silane coupling agent is one or more of KH-550, KH-560, KH-792, and A-151.

[0011] As an improvement of the above technical solution, the weight ratio of the nanodiamond to the graphene oxide is 1:(0.3-0.5).

[0012] As an improvement of the above technical solution, the alkaline activator includes sodium hydroxide and water glass, the weight ratio of the sodium hydroxide to the water glass is 1:(2-5), and the modulus of the water glass is 1.2-1.5.

[0013] Correspondingly, the application also discloses a preparation method of the nanocomposite reinforced graphite tailings-based polymer material.

[0014] The graphene oxide and the alkaline activator are mixed and stirred uniformly to obtain a first component;

[0015] The nanodiamond is treated by a silane coupling agent and dried to obtain a second component;

[0016] The slag and the graphite tailings are dried and stirred uniformly, and then the first component and the second component are sequentially added and stirred uniformly, so that the nanocomposite reinforced graphite tailings-based polymer material is obtained.

[0017] As an improvement of the above technical solution, the mixing and stirring of the graphene oxide and the alkaline activator uniformly includes:

[0018] The graphene oxide and the alkaline activator are mixed and subjected to ultrasonic treatment, and the ultrasonic treatment time is 30min-35min, so that a suspension is obtained.

[0019] The suspension is subjected to ball milling, so that the graphene oxide suspension with a particle size of 5nm-10nm is obtained, that is, the first component; the ball milling pressure is 1500bar-2000bar, and the cycle number is 3-5.

[0020] As an improvement of the above technical solution, the drying and uniform stirring of the slag and the graphite tailings, and the sequential addition and uniform stirring of the first component and the second component include: high-speed stirring is performed, the stirring speed is 1000rpm-1200rpm, and the stirring time is 5min-10min.

[0021] As an improvement of the above technical solution, the graphite tailings are pretreated before being mixed by stirring, and the pretreatment comprises:

[0022] The graphite tailings are screened, and the screening particle size is 0.6mm-0.65mm.

[0023] The screened graphite tailings are ball milled into a powder with a specific surface area of 450m 2 / kg; the ball milling speed is 200r / min-250r / min, and the ball milling time is 15min-20min.

[0024] The implementation of the present application has the following beneficial effects:

[0025] 1. The nanocomposite reinforced graphite tailings-based geopolymer material provided by the present application uses slag and graphite tailings as cementitious materials, and uses an alkaline activator to realize polymerization; nanodiamonds and graphene oxide are added to realize multiscale synergistic reinforcement; the nanodiamonds have extremely high hardness, modulus and strength, and can enhance and toughen the material; in addition, the nanodiamonds can be filled into the micropores of the cementitious material to improve the compactness and interfacial bonding performance of the geopolymer material; higher compactness means that it is more difficult for harmful ions and water to invade, thereby significantly improving the impermeability and freeze-thaw resistance of the material and improving the durability; the graphene oxide can form a three-dimensional barrier network with the cementitious material, promote the generation of C-(A)-S-H gel, and refine the pore structure, thereby improving the compactness, resistance to chloride ion erosion, and mechanical properties of the geopolymer material.

[0026] 2. The nanodiamonds are pretreated with a silane coupling agent, which can act as a molecular bridge between the nanodiamonds and the matrix; under the bridging action of the silane coupling agent, a structure of nanodiamond-organic connecting chain-Si-O-matrix is formed, which significantly improves the adhesion of the nanodiamonds and the erosion resistance of the geopolymer material. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below.

[0028] The present application provides a nanocomposite reinforced graphite tailings-based geopolymer material, which comprises the following components by weight: 50-70 parts of slag, 20-40 parts of graphite tailings, 10-15 parts of an alkaline activator, 0.05-0.2 parts of nanodiamonds, and 0.03-0.1 parts of graphene oxide; wherein the graphene oxide is reduced graphene oxide treated by low-temperature thermal reduction.

[0029] The nanocomposite reinforced graphite tailings based geopolymer material provided by the application realizes polymerization by using slag and graphite tailings as cementitious materials and cooperating with an alkaline activator; the nanodiamond and graphene oxide are added to realize multi-scale synergistic reinforcement, the nanodiamond has extremely high hardness, modulus and strength, and can play a reinforcing and toughening effect; in addition, the nanodiamond can also be filled into the micropores of the cementitious material, so as to improve the compactness and interface bonding performance of the geopolymer material, the higher compactness means that it is more difficult for external harmful ions and moisture to invade, so that the impermeability and freeze-thaw resistance of the material are significantly improved, and the durability is improved; the graphene oxide can form a three-dimensional barrier network with the cementitious material, promote the generation of C-(A)-S-H gel and refine the pore structure, and improve the compactness, resistance to chloride ion erosion and mechanical properties of the geopolymer material.

[0030] In a preferred embodiment, the graphene oxide is reduced graphene oxide subjected to a low-temperature thermal reduction treatment, after the low-temperature thermal reduction treatment, part of the oxygen-containing groups (hydroxyl and epoxy groups are removed, and a small amount of carboxyl groups are retained) in the graphene oxide are adsorbed to polar molecules (H2O) through dipole-dipole interaction, the mobility is reduced, and the generation of C-(A)-S-H gel and the refinement of the pore structure are further promoted.

[0031] Specifically, the low-temperature thermal reduction treatment comprises the following steps:

[0032] (1) The temperature is raised to 200-300 DEG C at a rate of 2-4 DEG C / min, and the temperature is kept for 60-120 min. The graphene oxide is initially reduced, and unstable oxygen-containing functional groups such as epoxy groups and hydroxyl groups are removed.

[0033] (2) The temperature is raised to 300-400 DEG C at a rate of 3-5 DEG C / min, and the temperature is kept for 30-60 min. The graphene oxide is more deeply reduced, and more stable groups such as carboxyl groups also begin to decompose.

[0034] (3) After the temperature keeping time ends, the graphene oxide sample is naturally cooled to room temperature in a vacuum environment.

[0035] In an embodiment, the particle size of the nanodiamonds is 10-50 nm, for example 20 nm, 25 nm, 30 nm, 35 nm or 40 nm, but is not limited thereto. The nanodiamonds have extremely high hardness, modulus and strength, and their ultra-small size and large specific surface area enable them to effectively combine with the cementitious material, significantly enhancing the mechanical properties. If the particle size of the nanodiamonds is too large, the larger particles are likely to become defects in the material. When subjected to external force, stress will be highly concentrated around the large particles, initiating micro-cracks first, resulting in a decrease in material strength and an increase in brittleness. If the particle size of the nanodiamonds is too small, hard agglomerates that are difficult to break will be produced, and the large specific surface area of the nanodiamonds will also cause the viscosity of the system to be too high, resulting in a serious decrease in processability. In addition, nanodiamonds with extremely small size and uniform particle size are difficult to process and have high costs.

[0036] In a preferred embodiment, the nanodiamonds are nanodiamonds pretreated with a silane coupling agent, and the silane coupling agent is one or more of KH-550, KH-560, KH-792 and A-151. The nanodiamonds are anchored to the matrix through C-O-Si bonds. The core is the use of a silane coupling agent, which acts as a molecular bridge between the nanodiamonds and the matrix. One end of the silane coupling agent is hydrolyzed to form Si-OH, which undergoes condensation reaction with the hydroxyl groups -OH on the surface of the matrix to form Si-O-matrix covalent bonds. The other end of the silane coupling agent has an organic functional group that is covalently connected to the functional groups on the surface of the nanodiamonds through chemical reaction. Finally, under the bridging action of the silane coupling agent, a structure of nanodiamond-organic connecting chain-Si-O-matrix is formed. This anchoring mode significantly improves the adhesion of the nanodiamonds and the ability of the geopolymer to resist erosion.

[0037] The thickness of the graphene oxide sheets is 1-3 nm, for example 1.25 nm, 1.5 nm, 2 nm, 2.5 nm or 2.75 nm, but is not limited thereto. The graphene oxide has a large number of functional groups such as hydroxyl groups and carboxyl groups that bond with the geopolymer Si-O-Si bonds. In addition, the graphene oxide surface contains a large number of hydroxyl groups, carboxyl groups and epoxy groups, which enable it to be highly dispersed in water to form a stable colloid. At the same time, the oxygen-containing functional groups form a hydrogen bond network (three-dimensional barrier network) with the geopolymer chains, improving the compactness, resistance to chloride ion erosion and mechanical properties of the geopolymer material.

[0038] In a preferred embodiment, the weight ratio of the nanodiamonds to the graphene oxide is 1:(0.3-0.5), for example 1:0.32, 1:0.35, 1:0.4, 1:0.42 or 1:0.46, but is not limited thereto. By limiting the weight ratio of the nanodiamonds to the graphene oxide, the nanodiamonds are used to improve the interface, and at the same time there is sufficient graphene oxide to form an effective crack barrier network.

[0039] The basic activator includes sodium hydroxide and water glass, the weight ratio of the sodium hydroxide and the water glass is 1:(2-5), and the modulus of the water glass is 1.2-1.5. The basic activator creates a strong alkali environment, OH-ions act as catalysts to accelerate the polycondensation reaction of the dissolved silicate and aluminate ions, and water molecules are removed to form Si-O-Al-O gel with a three-dimensional network structure. Among them, the modulus of the water glass directly affects the free OH - concentration and the content of soluble silicon species, and a lower modulus is selected to avoid alkali bleeding and shrinkage of the polymeric material.

[0040] In a preferred embodiment, the slag is S95 grade slag, and the slag includes the following components in percentage by weight: CaO 33.87%-38.67%, SiO2 31.38%-37.65%, Al2O3 15.67%-21.34%, MgO 10.32%-15.87%, loss on ignition 0.25%-0.5%, and the balance is inevitable impurities.

[0041] The graphite tailings include the following components in percentage by weight: SiO2 59.59%-67.66%, CaO 13.75%-19.72%, Al2O3 9.21%-15.36%, Fe2O3 3.77%-8.74%, loss on ignition 5%-7%, and the balance is inevitable impurities.

[0042] More preferably, the slag includes the following components in percentage by weight: CaO 35.78%, SiO2 33.18%, Al2O3 16.62%, MgO 11.32%, loss on ignition 0.45%, and the balance is inevitable impurities. The graphite tailings include the following components in percentage by weight: SiO2 62.5%, CaO 15.55%, Al2O3 10.21%, Fe2O3 5.07%, loss on ignition 6.58%, and the balance is inevitable impurities.

[0043] Correspondingly, the application provides a preparation method of the above-mentioned nanocomposite reinforced graphite tailings-based polymeric material, including the following steps:

[0044] S1, mixing and stirring the graphene oxide and the basic activator uniformly to obtain a first component.

[0045] In an embodiment, S1 specifically includes the following steps:

[0046] S21, mixing the graphene oxide and the basic activator and performing ultrasonic treatment, the ultrasonic treatment time is 30 min-35 min, to obtain a suspension.

[0047] In a preferred embodiment, the graphene oxide is reduced graphene oxide subjected to a low-temperature thermal reduction treatment, the low-temperature thermal reduction treatment comprising the following steps:

[0048] S211, heating at a rate of 2℃ / min to 4℃ / min to 200℃ to 300℃, and maintaining for 60min to 120min.

[0049] S212, heating at a rate of 3℃ / min to 5℃ / min to 300℃ to 400℃, and maintaining for 30min to 60min.

[0050] S213, naturally cooling to room temperature under vacuum environment.

[0051] S22, ball milling the suspension to obtain a graphene oxide suspension with a particle size of 5nm to 10nm, i.e. the first component. The ball milling pressure is 1500bar to 2000bar, and the cycle number is 3 to 5.

[0052] S2, treating the nanodiamonds with a silane coupling agent, and drying to obtain the second component.

[0053] In an embodiment, S2 specifically comprises the following steps:

[0054] S21, mixing the silane coupling agent with anhydrous ethanol, and adding glacial acetic acid to adjust the pH value to 3 to 3.5 to obtain a silane coupling agent hydrolysate. The mass fraction of the silane coupling agent hydrolysate is 2% to 5%.

[0055] S22, immersing the nanodiamonds in the silane coupling agent hydrolysate, and stirring uniformly at 65℃ to 75℃. The stirring speed is 300rpm to 400rpm, and the reaction time is 6h to 8h.

[0056] S23, centrifugal washing, and drying the washed product at 55℃ to 65℃ for 24h to 28h to obtain the second component.

[0057] S3, drying and stirring the slag and graphite tailings uniformly, sequentially adding the first component and the second component, and stirring uniformly to obtain the nanocomposite reinforced graphite tailings-based polymer material.

[0058] In an embodiment, before drying and stirring the slag and graphite tailings uniformly, the graphite tailings are pretreated, and the pretreatment comprises:

[0059] S31, sieving the graphite tailings, and the sieving particle size is 0.6mm to 0.65mm.

[0060] S32, ball milling the sieved graphite tailings to a specific surface area ≥450m2 / kg. The rotation speed of the ball mill is 200r / min-250r / min, and the ball milling time is 15min-20min. The graphite tailings are further activated by ball milling through the ball mill, so that the pozzolanic activity of the graphite tailings is further activated. In a preferred embodiment, the D 50 of 10um-15um, and a specific surface area of 485m 2 / kg-495m 2 / kg, so that the pozzolanic activity of the graphite tailings is effectively activated.

[0061] In an embodiment, before the slag and the graphite tailings are dried and uniformly stirred, the slag is dried to a water content of <1%.

[0062] In an embodiment, the slag, the graphite tailings, the first component and the second component are stirred at a high speed, the stirring speed is 1000rpm-1200rpm, and the stirring time is 5min-10min.

[0063] Through mechanical dispersion of graphene oxide, stable dispersion of nanodiamonds and stirring mixing, a nanocomposite reinforced graphite tailings-based polymer material with good performance and uniform dispersion is finally obtained.

[0064] The application is further described below with specific examples:

[0065] Example 1

[0066] The embodiment provides a nanocomposite reinforced graphite tailings-based polymer material, which comprises the following components in parts by weight: 50 parts of slag, 20 parts of graphite tailings, 10 parts of alkaline activator, 0.05 parts of nanodiamonds and 0.03 parts of graphene oxide.

[0067] The graphene oxide is reduced graphene oxide subjected to low-temperature thermal reduction treatment, and the low-temperature thermal reduction treatment comprises the following steps:

[0068] The temperature is raised to 250℃ at a rate of 3℃ / min, and the temperature is kept for 80min;

[0069] The temperature is raised to 350℃ at a rate of 4℃ / min, and the temperature is kept for 40min;

[0070] The temperature is naturally cooled to room temperature under vacuum.

[0071] A preparation method of a nanocomposite reinforced graphite tailings-based polymer material, comprising the following steps:

[0072] S1, mixing and uniformly stirring the graphene oxide and the alkaline activator to obtain a first component.

[0073] S2, the nanodiamonds are treated with a 2wt% solution of KH550 in ethanol, and dried at 60°C to obtain a second component.

[0074] S3, the slag and graphite tailings are dried and stirred uniformly, the first component and the second component are added in turn, and stirred at a speed of 1200 rpm for 5 min to obtain a nanocomposite reinforced graphite tailings based geopolymer material

[0075] Example 2

[0076] The example provides a nanocomposite reinforced graphite tailings based geopolymer material, which comprises the following components by weight: slag 70 parts, graphite tailings 40 parts, alkaline activator 15 parts, nanodiamonds 0.2 parts, and graphene oxide 0.1 parts.

[0077] The rest are the same as in example 1.

[0078] Example 3

[0079] The example provides a nanocomposite reinforced graphite tailings based geopolymer material, which comprises the following components by weight: graphite tailings 60 parts, slag 30 parts, alkaline activator 12 parts, nanodiamonds 0.1 parts, and graphene oxide 0.05 parts.

[0080] The rest are the same as in example 1.

[0081] Comparative Example 1

[0082] The comparative example provides a geopolymer material, which is different from example 1 in that the nanodiamonds are not included in the components.

[0083] The rest are the same as in example 1.

[0084] Comparative Example 2

[0085] The comparative example provides a geopolymer material, which is different from example 1 in that the nanodiamonds in the components are not pretreated with silane coupling agent.

[0086] The rest are the same as in example 1.

[0087] Comparative Example 3

[0088] The comparative example provides a geopolymer material, which is different from example 1 in that the graphene oxide and nanodiamonds are not included in the components.

[0089] The rest are the same as in example 1.

[0090] Comparative Example 4

[0091] The comparative example provides a geopolymer material, which is different from example 1 in that the graphene oxide is not included in the components.

[0092] The rest are the same as example 1.

[0093] Comparative example 5

[0094] This comparative example provides a geopolymer material, which is different from example 1 in that the alkaline activator is not included in the components.

[0095] The rest are the same as example 1.

[0096] Comparative example 6

[0097] This comparative example provides a geopolymer material, which is different from example 1 in that the alkaline activator and graphene oxide are not included in the components.

[0098] The rest are the same as example 1.

[0099] Comparative example 7

[0100] This comparative example provides a geopolymer material, which is different from example 1 in that the alkaline activator, nanodiamond and graphene oxide are not included in the components.

[0101] The rest are the same as example 1.

[0102] The geopolymer materials prepared in example 1 to example 3 and comparative example 1 to comparative example 7 are cured, and the specific steps are as follows: the prepared geopolymer material is poured into a test mold to prepare a test sample, which is then cured in steam at 60℃ for 24h, and then cured in a standard curing room (RH≥95%, 25℃) for 28d to obtain a geopolymer finished product sample. The performance of the geopolymer finished product samples obtained in example 1 to example 3 and comparative example 1 to comparative example 7 is detected, and the specific results are as follows:

[0103]

[0104] The above is the preferred embodiment of the application. It should be noted that for those skilled in the art, without departing from the principles of the application, a number of improvements and refinements can be made, which are also considered within the scope of protection of the application.

Claims

1. A nanocomposite reinforced graphite tailings geopolymer material, characterized in that, The composition comprises the following components in parts by weight: 50-70 parts slag, 20-40 parts graphite tailings, 10-15 parts alkaline activator, 0.05-0.2 parts nanodiamond, and 0.03-0.1 parts graphene oxide; wherein the graphene oxide is reduced graphene oxide that has undergone low-temperature thermal reduction treatment.

2. The nanocomposite reinforced graphite tailings geopolymer material as described in claim 1, characterized in that, The nanodiamond has a particle size of 10 nm to 50 nm; The thickness of the graphene oxide sheets is 1 nm to 3 nm.

3. The nanocomposite reinforced graphite tailings geopolymer material as described in claim 1, characterized in that, The low-temperature thermal reduction treatment includes the following steps: Heat to 200℃~300℃ at a rate of 2℃ / min~4℃ / min, and hold for 60min~120min; Heat to 300℃~400℃ at a rate of 3℃ / min~5℃ / min, and hold for 30min~60min; It was allowed to cool naturally to room temperature in a vacuum environment.

4. The nanocomposite reinforced graphite tailings geopolymer material as described in claim 1, characterized in that, The nanodiamond is nanodiamond pretreated with a silane coupling agent, and the silane coupling agent is one or more of KH-550, KH-560, KH-792, and A-151.

5. The nanocomposite reinforced graphite tailings geopolymer material as described in claim 1, characterized in that, The weight ratio of the nanodiamond to graphene oxide is 1:(0.3-0.5).

6. The nanocomposite reinforced graphite tailings geopolymer material as described in claim 1, characterized in that, The alkaline activator comprises sodium hydroxide and water glass, wherein the weight ratio of sodium hydroxide to water glass is 1:(2-5), and the modulus of the water glass is 1.2-1.

5.

7. A method for preparing a nanocomposite reinforced graphite tailings geopolymer material as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Graphene oxide and an alkaline activator are mixed and stirred until homogeneous to obtain the first component; The nanodiamonds were treated with a silane coupling agent and dried to obtain the second component; The slag and graphite tailings are dried and stirred evenly. The first component and the second component are added in sequence and stirred evenly to obtain the nanocomposite reinforced graphite tailings macropolymer material.

8. The method for preparing the nanocomposite reinforced graphite tailings geopolymer material as described in claim 7, characterized in that, The process of mixing and stirring graphene oxide and alkaline activator to achieve uniformity includes: Graphene oxide and an alkaline activator were mixed and subjected to ultrasonic treatment for 30 to 35 minutes to obtain a suspension. The suspension was ball-milled to obtain a graphene oxide suspension with a particle size of 5 nm to 10 nm, which is the first component; the ball milling pressure was 1500 bar to 2000 bar, and the number of cycles was 3 to 5.

9. The method for preparing the nanocomposite reinforced graphite tailings geopolymer material as described in claim 7, characterized in that, The process of drying and mixing the slag and graphite tailings, and then adding the first and second components in sequence and mixing them evenly includes: high-speed mixing at a speed of 1000 rpm to 1200 rpm for 5 min to 10 min.

10. The method for preparing the nanocomposite reinforced graphite tailings geopolymer material as described in claim 7, characterized in that, Before mixing, the graphite tailings are pretreated, the pretreatment including: The graphite tailings were screened to a particle size of 0.6 mm to 0.65 mm. The sieved graphite tailings were ball-milled to a specific surface area ≥ 450 m². 2 / kg powder; the ball milling speed is 200r / min~250r / min, and the ball milling time is 15min~20min.

Images