A high-temperature resistant modified graphene heating paste for microcrystalline panels

Abstract

This invention discloses a high-temperature resistant modified graphene heating paste for microcrystalline panels. Graphene powder is chemically bonded to aluminosilicates, resulting in ceramic-modified graphene powder with improved dispersion in the heating paste. Furthermore, when combined with inorganic ceramic resin, it significantly enhances the adhesion to the microcrystalline glass surface. Simultaneously, the ceramic-modified graphene retains the original toughness of graphene, and after curing with ceramic resin, it increases the toughness of the film layer, reduces thermal stress at high temperatures, and thus improves heating stability. The high-temperature resistant modified graphene heating paste prepared by this invention effectively solves the problems of poor adhesion between existing graphene pastes and microcrystalline panels, and rapid performance degradation of the heating layer after long-term use. Moreover, the heating layer made with this heating paste exhibits uniform heating, stable heating temperature, and a long service life when heated to 300-380℃.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature heating, specifically relating to a high-temperature resistant modified graphene heating paste for microcrystalline plates. Background Technology

[0002] Currently, enterprises and factories using heating and drying processes generally require heating equipment below 400℃, primarily tunnel ovens and hot drying ovens. These devices mostly use resistance wire as the heating element. The heat transfer methods of resistance wire heating are mainly direct contact heat conduction and forced-air convection, which requires high precision in heat source temperature and heating uniformity. Furthermore, the slow heating rate of resistance wire results in significant power waste and a surge in electricity consumption during drying processes. High-power heating equipment must be energy-efficient to reduce costs.

[0003] Microcrystalline heating plates are a new type of product that can replace traditional resistance wires. Because of their uniform heat distribution and the fact that the heat transferred by far-infrared radiation can significantly accelerate the drying process and thus improve the efficiency of the drying process, they have attracted widespread attention.

[0004] The heating paste used in microcrystalline glass plates capable of generating temperatures of 300℃-600℃ uses silver powder, nickel powder, graphene powder, and carbon nanotubes as conductive media. It requires an organic binder and is fixed to the microcrystalline glass plate through high-temperature sintering. Commonly used organic binders include silicone resin and glass powder. Silicone resin has good temperature resistance, but under prolonged exposure to temperatures above 350℃, it can lose up to 20% of its weight. Heating pastes using silicone resin as a binder will exhibit varying degrees of cracking in the heating layer after long-term use. Conductive pastes made from a mixture of glass powder, terpineol, ethyl cellulose, graphene powder, and a small amount of solvent have a different specific gravity. When the sintering temperature reaches the melting point of the glass powder, the glass powder melts and flows downwards, mostly spreading on the surface of the microcrystalline glass plate, while the graphene powder concentrates on the upper part of the heating film layer. This results in numerous pores, preventing the formation of a dense film layer, and leading to excessively high resistance and low heating efficiency in the resulting heating layer. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a high-temperature resistant modified graphene heating slurry for microcrystalline plates. Its main components are ceramic-modified graphene powder and water-based inorganic ceramic resin. Specifically, the ceramic-modified graphene powder exhibits better dispersion performance in the heating slurry, and when combined with the inorganic ceramic resin, it significantly enhances the bonding force with the microcrystalline glass surface. The ceramic-modified graphene retains the original toughness of graphene, and when used in combination with the ceramic resin and cured, it increases the toughness of the film layer, reduces the thermal stress of the film layer at high temperatures, thereby improving heating stability and extending service life.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention first discloses a method for preparing ceramic-modified graphene powder, comprising the following steps:

[0008] S1. Mix graphene powder, potassium permanganate and concentrated sulfuric acid and stir at room temperature for 2-3 hours. Then continue stirring at 35-45℃ for 0.5-2 hours to form oxide groups at the edges of graphene. Add sufficient deionized water to dilute, and then terminate the reaction with excess hydrogen peroxide. First, filter and wash with hydrochloric acid to remove metal ions, and then filter and wash with deionized water until neutral to obtain graphene oxide filter cake.

[0009] S2. The graphene oxide filter cake is ultrasonically dispersed in deionized water, sodium aluminosilicate is added, and then ammonia is added to adjust the pH of the solution to 9-10. Hydrazine hydrate is then added, and the mixture is heated and stirred at 70-83°C for 2-4 hours to reduce the oxide groups at the graphene edges and graft aluminosilicate groups. The high temperature of 70-83°C allows for complete reduction of the graphene oxide while also decomposing excess hydrazine hydrate into non-toxic and harmless substances.

[0010] S3. Adjust the pH of the dispersion obtained in step S2 to 1-2 with hydrochloric acid, and stir thoroughly for 0.5-1 hour. Filter and wash until neutral. The resulting product is dried and ground to form ceramic-modified graphene powder. Adjusting the pH with hydrochloric acid makes the system acidic, thereby effectively dissolving various impurities contained in the target powder. Filtering and washing aim to reduce impurities, improve the purity of the target powder, and make its antioxidant properties more stable.

[0011] Further, in step S1, the graphene sheet diameter distribution is 5–10 μm, and the number of layers is 6–10. Preferably, the graphene powder is model WJ-GP550, which is independently produced by Hefei Microcrystalline Materials Technology Co., Ltd.

[0012] Further, in step S1, the concentrated sulfuric acid has a mass fraction of 98%, and the ratio of graphene powder, potassium permanganate, concentrated sulfuric acid, and deionized water is 2g:2.3-3.2g:20-32mL:85-100mL. The stirring speed in step S1 is 400-700rpm.

[0013] Further, in step S2, the ratio of the graphene oxide filter cake, sodium aluminosilicate, hydrazine hydrate, and deionized water is 1g:1.3-3.2g:0.3-1.1g:80-100g. The sodium aluminosilicate used has a particle size of 6-7μm.

[0014] The present invention also discloses a modified graphene slurry comprising the above-mentioned ceramic-modified graphene powder, wherein the raw materials are composed of the following by mass percentage: 14-18% ceramic-modified graphene powder, 80-85% deionized water, and 0.5-6% first additive. The first additive is at least two of the following: dispersant, wetting agent, defoamer, pH adjuster, and rheology modifier.

[0015] The modified graphene slurry is prepared by mixing ceramic-modified graphene powder, a first additive, and deionized water until homogeneous, followed by mechanical grinding. The mixing speed is 600–1500 rpm, and the mixing time is 20 min. The mechanical grinding is performed using a horizontal sand mill at a grinding speed of 2500–3500 rpm for 4–6 h.

[0016] This invention further discloses a high-temperature resistant modified graphene heating paste for microcrystalline plates, comprising the aforementioned modified graphene paste. The heating paste comprises the following components by mass percentage: 35-60% modified graphene paste, 30-55% binder, 0.5-3% second auxiliary agent, and 3-8.5% solvent.

[0017] Further: the binder is an aqueous inorganic ceramic resin; the second additive is at least one of a wetting agent, a defoamer, and a thickener; the solvent is one of ethylene glycol butyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether, and ethylene glycol.

[0018] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0019] 1. In the high-temperature resistant modified graphene heating slurry prepared by the present invention: (1) By grafting sodium aluminosilicate with graphene powder, the bonding force between graphene powder, ceramic resin and microcrystalline glass surface is increased, so that during the heating curing and cooling process, the range of volume change of graphene due to thermal expansion and contraction can be effectively reduced, thereby reducing the probability of pores appearing when the slurry is cured into a film; (2) The water-based inorganic ceramic resin contains small particle sizes, which can partially fill the pores on the surface of microcrystalline glass, thereby enhancing the bonding effect between the two; (3) The inorganic components in the water-based inorganic ceramic resin can reduce the linear expansion coefficient and shrinkage rate of the cured material, thereby reducing the internal stress of the cured material.

[0020] 2. When water-based inorganic ceramic resin is vitrified at high temperatures, it can combine with sheet-like graphene to form a dense film. This combination reduces the exposure of graphene to air. The surface graphene, after oxidation at high temperatures, protects the internal graphene, thus reducing the oxidation area. Oxidation increases the resistance of the graphene, leading to a decrease in power and heating temperature under the same voltage. This improves the heating stability and oxidation resistance of the heating layer. The ceramic-modified graphene retains its original toughness. When used in combination with ceramic resin and cured, it increases the toughness of the film and reduces thermal stress at high temperatures. Furthermore, inorganic ceramic resin has excellent high-temperature resistance, maintaining certain strength and performance at temperatures of 600–800℃, thereby improving heating stability and extending service life. Attached Figure Description

[0021] Figure 1 The curves showing the relationship between the thermal resistance and time when the heating plates made from the heating pastes of Examples 1-4 and Comparative Examples 1-2 are heated to 380°C.

[0022] Figure 2 The curves showing the relationship between thermal resistance and time when heating plates made from the heating pastes of Examples 1-4 and Comparative Examples 1-2 are heated to 560°C.

[0023] Figure 3 The curves showing the relationship between the thermal resistance and time of the heating plates made from the heating pastes of Comparative Examples 4 to 6 when heated to 380°C.

[0024] Figure 4 The curves show the relationship between the thermal resistance and time when the heating plates made from the heating pastes of Comparative Examples 4 to 6 are heated to 560°C. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments.

[0026] Examples 1-4 and Comparative Examples 1-2

[0027] This embodiment prepares a high-temperature resistant modified graphene heating slurry according to the following steps:

[0028] Step 1: Preparation of ceramic-modified graphene powder

[0029] S1. In a 250mL beaker, add 24mL of 98% concentrated sulfuric acid, 2g of graphene powder GP550, and 2.5g of potassium permanganate in sequence. Stir at room temperature for 2 hours, then stir in a 42℃ water bath for 1 hour. Add 100mL of water, and then add excess hydrogen peroxide to terminate the reaction (add until no bubbles emerge from the mixed solution within 3 minutes). First, filter and wash with hydrochloric acid to remove metal ions, and then filter and wash with deionized water until neutral to obtain graphene oxide filter cake.

[0030] S2. Take 1g of graphite oxide filter cake and ultrasonically disperse it in 100g of water. Add 1.5g of sodium aluminosilicate and stir thoroughly until evenly dispersed. Then add ammonia water to adjust the pH to 8-9. Add 2.57g of hydrazine hydrate and stir in an 80℃ water bath for 4 hours.

[0031] S3. Adjust the pH of the dispersion obtained in step S2 to 1-2 with 1 mol / L hydrochloric acid, stir the mixture thoroughly for 0.5 hours, filter, wash until neutral, dry at 120℃, and grind to obtain ceramic-modified graphene powder.

[0032] Step 2: Preparation of modified graphene slurry

[0033] Take 16g of ceramic-modified graphene powder, 3.8g of aqueous dispersant (Shenzhu Chemical SN-1788), 0.2g of defoamer (AFCONA-2508) and 80g of deionized water and mix them. Stir mechanically at 1200rpm for 20min, and then grind them in a horizontal sand mill until the fineness is below 20μm to obtain modified graphene slurry M1.

[0034] Take 16g of graphene powder WJ-GP550, 3.8g of aqueous dispersant (Shenzhu Chemical SN-1788), 0.2g of defoamer (AFCONA-2508) and 80g of deionized water and mix them. Stir mechanically at 1200rpm for 20min, then add it to a horizontal sand mill and grind it until the fineness is below 20μm to obtain the control graphene slurry M2.

[0035] 16g of graphene powder TNERGO-3 (diameter distribution of 1-5μm, layer distribution of 1-3 layers) produced by Chengdu Organic Chemistry Co., Ltd. of Chinese Academy of Sciences, 3.8g of aqueous dispersant (Shenzhu Chemical SN-1788), 0.2g of defoamer (AFCONA-2508) and 80g of deionized water were mixed and mechanically stirred at 1200rpm for 20min. Then, the mixture was added to a horizontal sand mill and ground until the fineness was below 20μm to obtain the comparative graphene slurry M3.

[0036] Step 3: Preparation of high-temperature resistant modified graphene heating slurry

[0037] According to the formula in Table 1, the graphene slurry obtained in step 2, the water-based inorganic ceramic resin (Guangdong Shanjin New Materials SJ-103), and the solvent (ethylene glycol butyl ether) are thoroughly mixed, and thickened with a thickener (BYK Chemical). 420) The viscosity was adjusted to 6000-9000 mPa·S to finally obtain high-temperature resistant modified graphene heating slurry and a graphene heating slurry as a comparison.

[0038] Comparative Example 3

[0039] S1. Using a heat-collecting magnetic stirring water bath, set the temperature to 50℃. Place a magnetic stir bar into a 50mL beaker, turn on the magnetic stirring switch, and add 9g of terpineol (Aladdin reagent), 9g of DBA (Tianjin Zhonghe Shengtai Chemical), 9g of DPM (Tianjin Zhonghe Shengtai Chemical), and 1.35g of ethyl cellulose (Aladdin reagent) with a viscosity of 50cP. Stop heating and stirring when the mixture becomes transparent to obtain a mixed organic liquid.

[0040] S2. Add 30g of low melting point glass powder D250 and 10g of graphene powder WJ-GP550 to the organic liquid in S1, mix and stir evenly, and grind with a three-roll mill until the fineness is ≤20μm to obtain a graphene heating slurry for comparison.

[0041] Comparative Example 4

[0042] The specific implementation method is the same as that of Comparative Example 3, except that the graphene powder added is the ceramic-modified graphene powder prepared above.

[0043] Comparative Example 5

[0044] Weigh 17.5g of silicone resin (MK manufactured by Wacker Chemie), dissolve it in 15g of isophorone (Taiwan Taihe Technology Co., Ltd.) under stirring, add 25g of silicone intermediate (IC-368 manufactured by Shanghai Bohuai Chemical Co., Ltd.), then add 20g of PMA (Dow Chemical), 16g of graphene powder WJ-GP550, and 0.1g of aluminum catalyst PN-900 (Nanjing Pinning Coupling Agent Co., Ltd.), mix and stir evenly, and grind with a three-roll mill to a fineness of ≤20μm to obtain a graphene heating slurry for comparison.

[0045] Comparative Example 6

[0046] The specific implementation method is the same as that of Comparative Example 5, except that the graphene powder added is ceramic-modified graphene powder.

[0047] The heating pastes prepared in the various embodiments and comparative examples were printed onto a 15cm*15cm microcrystalline glass plate using a 120-mesh screen. Two parallel conductive silver lines, each 13cm*1cm in size and spaced 9cm apart, were printed on the microcrystalline glass plate. The heating paste was printed in 13cm*12cm lengths. During printing, 1.5cm of each conductive silver line was left uncovered, with the remaining portion completely covered by the heating paste. After printing, the plates were baked at 150℃ for 10 minutes, then sintered at 600℃ for 30 minutes. Performance was tested after cooling.

[0048] Table 1. Formulations of high-temperature resistant graphene heating slurry for each embodiment and Comparative Examples 1 and 2.

[0049] Modified graphene paste M1 60g 53g 46g 39g 0g 0g Graphene paste M2 0g 0g 0g 0g 60g 0g Graphene paste M3 0g 0g 0g 0g 0g 60g Water-based inorganic ceramic resin 50g 50g 50g 50g 50g 50g Solvent 8g 8g 8g 8g 8g 8g Thickening agent 2.5g 2.5g 2.5g 2.5g 2.5g 2.5g

[0050] Table 2. Test methods for the physicochemical properties of graphene heating slurry in each embodiment and comparative example.

[0051] Appearance Visual inspection — Fineness (μm) GB / T1724-79 Scratch plate fineness meter (QXD-100 type) Solid content (%) GB / T1732-93-2007 Constant temperature drying oven Dry film thickness GB / T13452.2-2008 Coating thickness tester Hardness (H) GB / T6739-2006 Pencil hardness tester Adhesion GB / T9286-1998 Cross-cut knife Time taken to heat to 342°C (min) GB / T7287-2008 Stopwatch, radiation thermometry instrument

[0052] Table 3 Comparison of the physicochemical properties of the high-temperature resistant modified graphene heating slurry in each embodiment and Comparative Examples 1 and 2

[0053]

[0054] Table 4 Comparison of physicochemical properties of exothermic slurries in Comparative Examples 3-6

[0055]

[0056] In Comparative Example 3, when the temperature reached the melting point of the glass powder, due to its high specific gravity, the glass powder melted and spread evenly on the substrate in liquid form, failing to connect well with the graphene. The graphene powder floated on the upper layer, resulting in poor adhesion and numerous pores after solidification. The resistance of the produced heating layer exceeded 3kΩ, the test voltage required to heat to 380℃ was too high, and there was a risk of burnout during the power-on process, thus failing to meet the test conditions.

[0057] Samples prepared according to Examples 1-4, Comparative Examples 1, 2, 4, 5, and 6 are designated A1, B1, C1, D1, E1, F1, G1, H1, and K1, respectively. The circuits are connected, and the test voltage is adjusted using an AC voltage regulator to ensure stable heating to 380°C within 0.5 hours. The power of the heating plate is recorded using a miniature power monitoring instrument, and the temperature is recorded using a radiation thermometer. Another sample is taken and designated A2, B2, C2, D2, E2, F2, G2, H2, and K2. According to GB / T7287-2008, the test voltage is adjusted to 1.35 times the original voltage. If the temperature is around 560°C, the voltage is fine-tuned to ensure stable heating to 560°C within 0.5 hours. The power of the heating plate is recorded using a miniature power monitoring instrument, and the temperature is recorded using a radiation thermometer. The heating process continues with the heating plate powered on. As shown in Tables 5 and 6, the power is calculated using the electric power formula. (U is the test voltage; P is the power of the heating plate) The thermal resistance R1 of the heating plate at different times and the thermal resistance R0 after 0.5 hours of heating can be calculated. Plot the relationship curve between the energizing time and the thermal resistance. If the ratio of thermal resistance R1 to R0 is not within the range of 85% to 115%, the heating test of the heating plate is terminated.

[0058] Table 5: Test parameters of heating plates made from the heating pastes of Examples 1-4 and Comparative Examples 1-2 when they stably heat up to 380°C

[0059]

[0060] Table 6: Test parameters of heating plates made from the heating pastes of Examples 1-4 and Comparative Examples 1-2 when they stably heat up to 560°C

[0061]

[0062]

[0063] Table 7: Test parameters of heating plates made from the heating pastes of Comparative Examples 4-6 when they stably heat up to 380℃

[0064]

[0065] Table 8: Test parameters of heating plates made from the heating pastes of Comparative Examples 4-6 when they stably heat up to 560℃.

[0066]

[0067] Combined with Tables 1-8, Figures 1 to 4 Based on the data, it can be concluded that the modified graphene heating slurry prepared in Examples 1-4 of this invention has the following advantages compared with the comparative example:

[0068] 1. It can improve the heating uniformity of the heating layer;

[0069] 2. It has good thermal stability;

[0070] 3. It can significantly extend the service life under high temperature.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make corresponding adjustments and improvements without departing from the principle of the present invention, and these adjustments and improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing ceramic-modified graphene powder, characterized in that, Includes the following steps: S1. Mix graphene powder, potassium permanganate and concentrated sulfuric acid and stir at room temperature for 2-3 hours. Then stir at 35-45℃ for 0.5-2 hours to form oxide groups at the edges of graphene. Add sufficient deionized water to dilute and then terminate the reaction with excess hydrogen peroxide. First, filter and wash with hydrochloric acid to remove metal ions, then filter and wash with deionized water until neutral to obtain graphene oxide filter cake. S2. The graphene oxide filter cake is ultrasonically dispersed in deionized water, sodium aluminosilicate is added, and then ammonia is added to adjust the pH of the solution to 9-10. Then hydrazine hydrate is added, and the mixture is heated and stirred at 70-83°C for 2-4 hours to reduce the graphene edge oxide groups and graft aluminosilicate groups. The ratio of the amount of graphene oxide filter cake, sodium aluminosilicate, hydrazine hydrate and deionized water is 1g:1.3-3.2g:2.5-3.1g:80-100g. S3. Adjust the pH of the dispersion obtained in step S2 to 1-2 with hydrochloric acid, and stir the reaction thoroughly for 0.5-1 hour. Filter and wash until neutral. The resulting product is dried and ground to form ceramic-modified graphene powder.

2. The preparation method according to claim 1, characterized in that: In step S1, the graphene has a sheet diameter distribution of 5~10μm and a layer distribution of 6~10 layers.

3. The preparation method according to claim 1, characterized in that: In step S1, the mass fraction of concentrated sulfuric acid is 98%, and the ratio of graphene powder, potassium permanganate, concentrated sulfuric acid and deionized water is 2g: 2.3~3.2g: 20~32mL: 85~100mL.

4. The preparation method according to claim 1, characterized in that: In step S2, the sodium aluminosilicate has a particle size of 6~7 μm.

5. A ceramic-modified graphene powder prepared by the preparation method according to any one of claims 1 to 4.

6. A modified graphene slurry comprising the ceramic-modified graphene powder as described in claim 1.

7. The modified graphene slurry according to claim 6, characterized in that, The modified graphene slurry comprises the following components by mass percentage: 14-18% ceramic-modified graphene powder, 80-85% deionized water, and 0.5-6% first additive.

8. The modified graphene slurry according to claim 7, characterized in that: The first additive is at least two of the following: dispersant, wetting agent, defoamer, pH adjuster, and rheology modifier.

9. A high-temperature resistant modified graphene heating paste for microcrystalline panels, comprising the modified graphene paste according to claim 7 or 8; wherein the raw materials in the heating paste are composed of the following components by mass percentage: modified graphene paste 35-60%, binder 30-55%, second auxiliary agent 0.5-3%, and solvent 3-8.5%; wherein, The adhesive is an aqueous inorganic ceramic resin.

10. The high-temperature resistant modified graphene heating paste for microcrystalline plates according to claim 9, characterized in that: The second additive is at least one of a wetting agent, an antifoaming agent, and a thickener; the solvent is one of ethylene glycol butyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether, and ethylene glycol.

11. A microcrystalline plate using the high-temperature resistant modified graphene heating paste as described in claim 9 or 10.

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