Preparation method of temperature interference resistant composite conductive ink

Abstract

The application discloses a preparation method of a temperature interference resistant composite conductive ink and belongs to the field of functional composite materials and printed electronics technology. The method comprises acidizing pretreatment of carbon nanotubes, mixing Ti3C2, CNT and CMC according to a specific ratio and ultrasonic dispersion. By regulating the content of Ti3C2 and CNT, the opposite temperature response characteristics of the two are utilized to realize resistance change offset, so that the conductivity change rate of the solidified film is not more than 7.5% within 20 DEG C to 100 DEG C. The application is suitable for flexible sensors and electronic devices with high temperature stability requirements.

Description

Technical Field

[0001] This invention belongs to the field of functional composite materials and printed electronics technology, specifically relating to a method for preparing a temperature-resistant composite conductive ink. After curing, the conductive ink forms a composite conductive film; the conductivity change rate of this film within a temperature range of 20℃ to 100℃ does not exceed 7.5%. The product of this invention is suitable for flexible electronic devices with stringent temperature stability requirements. Background Technology

[0002] With the rapid development of flexible electronics technology, wearable devices, electronic skin, and health monitoring systems built using printed electronics processes are gradually being applied on a large scale. The sensing layer of these devices is typically formed by curing conductive ink, utilizing the structural changes of a percolation network constructed from conductive fillers under external forces to achieve signal response. However, flexible electronic devices often face thermo-mechanical multi-field coupling environments in practical applications. Conventional carbon-based / metal-polymer conductive inks are limited by the strong temperature dependence of the intrinsic resistance of the conductive fillers and the mismatch in thermal expansion coefficients between the matrix and the fillers, leading to significant nonlinear drift in the resistance signal and severely affecting measurement accuracy. Existing external circuit compensation or algorithm calibration schemes not only increase system power consumption but also struggle to cope with complex nonlinear drift. Therefore, developing composite conductive inks that can spontaneously suppress temperature interference is a key technical challenge that urgently needs to be overcome in this field, and it has profound significance for promoting technological innovation and industrialization of next-generation high-performance flexible sensors. Summary of the Invention

[0003] This invention aims to provide a method for preparing a temperature-resistant composite conductive ink. The conductive ink, when cured to form a composite conductive film, exhibits a conductivity change rate of no more than 7.5% within a temperature range of 20℃ to 100℃, making it suitable for applications requiring high temperature stability, such as flexible electronic devices.

[0004] The technical solution of this invention is: A method for preparing a temperature-resistant CMC-Ti3C2 / CNT composite conductive ink, the specific process of which is as follows: (1) Add single-walled carbon nanotubes (CNTs) to a nitric acid solution and heat under reflux at 60℃~90℃ (preferably 60℃~80℃, more preferably 60℃~65℃) for 4 h~5 h, preferably 4 h~4.5 h, more preferably 4 h~4.2 h; wherein, the mass ratio of HNO3 to CNTs is 33∶1~37∶1, preferably 35~36∶1, and the molar concentration of the nitric acid solution is 15mol / L~16mol / L, preferably 15.2~15.5mol / L; after the reaction is completed, collect the solid product by centrifugation and dry it in an environment of 60℃~80℃ (preferably 60℃~70℃, more preferably 60℃~65℃) to obtain acidified CNTs.

[0005] (2) Add titanium carbide (Ti3C2), CNTs obtained after step (1) and CMC to deionized water, stir and mix to obtain a mixed suspension; wherein, the mass ratio of Ti3C2 to acidified CNT is 1:99 to 1:199 (preferably 1:99 to 1:150, more preferably 1:99 to 1:120), 85 to 95 wt% (preferably 88 to 92 wt%, more preferably 89 to 90 wt%), and the total mass of the solid phase is the sum of the mass of Ti3C2, acidified single-walled carbon nanotubes and carboxymethyl cellulose; (3) The obtained mixed suspension is subjected to ultrasonic-assisted dispersion treatment with an ultrasonic power of 300 W to 500 W and a time of 1 h to 3 h to form a uniform composite dispersion, which is the CMC-Ti3C2 / CNT composite conductive ink.

[0006] In step (2), the mass solid content of the mixed suspension is 1 wt% to 5 wt%, preferably 2 wt% to 4 wt%, and more preferably 3 wt% to 3.5 wt%.

[0007] The CMC-Ti3C2 / CNT composite conductive ink was prepared by the method described above.

[0008] The CMC-Ti3C2 / CNT composite conductive ink prepared by the above method has a conductivity change rate of no more than 7.5% in the temperature range of 20℃ to 100℃ after curing.

[0009] The advantages of this invention are: (1) A conductive paste based on CMC-Ti3C2 / CNT was developed. After curing on the surface of a flexible polymer, the system forms a conductive network: Ti3C2 provides a continuous conductive path, CNT reduces the interfacial contact resistance, and CMC acts as a binder to anchor the conductive filler. Under the above synergistic effect, the conductivity of the obtained cured film at 20°C reaches 800 S / m (four-probe method).

[0010] (2) Due to the opposite trend of the conductivity of Ti3C2 and CNT with temperature, the resistance change is offset by matching their ratio. The conductivity change rate of this conductive film layer does not exceed 7.5% in the range of 20℃ to 100℃, and it has excellent resistance to temperature interference. Attached Figure Description

[0011] Figure 1 This is a process flow diagram of the preparation process of the CMC-Ti3C2 / CNT composite conductive ink in Example 1 of the present invention.

[0012] Figure 2 An optical photograph of the CMC-Ti3C2 / CNT composite conductive ink in Example 1 of this invention.

[0013] Figure 3 The graph shows the conductivity variation curves of the CMC-Ti3C2 / CNT composite conductive ink cured film prepared in Example 1 of this invention at different temperatures.

[0014] Figure 4 The graph shows the conductivity variation curves of the CMC-Ti3C2 / CNT composite conductive ink cured film prepared in Example 2 of this invention at different temperatures.

[0015] Figure 5 This is a viscosity comparison chart of the CMC-Ti3C2 / CNT composite conductive ink prepared in Example 2 of the present invention.

[0016] Figure 6 The graph shows the conductivity variation of the CMC-Ti3C2 / CNT composite conductive ink cured film prepared in Comparative Example 1 of this invention at different temperatures.

[0017] Figure 7 The viscosity variation curves of composite conductive inks with different CMC mass fractions in Comparative Example 2 of this invention are shown. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] Example 1 like Figure 1 As shown, the preparation method of temperature-resistant CMC-Ti3C2 / CNT composite conductive ink is as follows: (1) Single-walled carbon nanotubes (CNTs) were added to a nitric acid solution and heated under reflux at 60°C for 4 hours. The mass ratio of HNO3 to CNTs was 35:1, and the concentration of the nitric acid solution was 15 mol / L. After the reaction was completed, the solid product was collected by centrifugation and dried in a vacuum drying oven at 80°C for 12 hours to obtain acidified CNTs.

[0020] (2) Add titanium carbide (Ti3C2), CNTs obtained after step (1) and CMC to deionized water and stir to mix to obtain a mixed suspension; wherein, the mass ratio of Ti3C2 to CNT is 1:99, and carboxymethyl cellulose accounts for 90 wt% of the total mass of the solid phase, and the total mass of the solid phase is the sum of the masses of Ti3C2, acidified single-walled carbon nanotubes and carboxymethyl cellulose; the mass solid content of the mixed suspension is 3 wt%.

[0021] (3) The obtained mixed suspension was subjected to ultrasonic-assisted dispersion treatment with an ultrasonic power of 300 W and a time of 3 h to form a uniform composite dispersion, which is the CMC-Ti3C2 / CNT composite conductive ink.

[0022] Figure 2 Optical images of the temperature-resistant CMC-Ti3C2 / CNT composite conductive ink prepared in Example 1 of this invention. As shown in the figure, the conductive ink is black, and its viscosity at 25°C is 1.2 × 10⁻⁶. 4 mPa·s.

[0023] Figure 3 To investigate the conductivity variation curves of a 20 μm thick cured film formed on the glass surface by applying CMC-Ti3C2 / CNT composite conductive ink to the surface of insulating glass and curing it at 25°C for 10 minutes, the following tests were conducted. The results showed that the conductivity of the cured film at 20°C was 800 S / m (four-probe method), and the conductivity variation rate of the film layer within the range of 20°C to 100°C did not exceed 7.27%.

[0024] Example 2 The preparation process and conditions are the same as in Example 1, except that the CMC content is kept constant. In step (2), the mass ratio of Ti3C2 to CNT is 1:149 and 1:199, respectively. The total mass of the solid phase is the sum of the masses of Ti3C2, acidified single-walled carbon nanotubes and carboxymethyl cellulose.

[0025] Figure 4The temperature-resistant CMC-Ti3C2 / CNT composite conductive ink prepared in Example 2 of this invention was coated onto the surface of insulating glass and cured and dried at 20°C for 10 minutes to form a 20 μm thick cured film on the glass surface. The conductivity change curves at different temperatures were obtained. The films prepared with Ti3C2 to CNT mass ratios of 1:149 and 1:199, respectively, showed conductivity change rates of no more than 6.1% and 3.2% within the range of 20°C to 100°C.

[0026] Figure 5 This is a viscosity comparison of the temperature-resistant CMC-Ti3C2 / CNT composite conductive ink prepared in Example 2 of the present invention. The composite conductive inks prepared with Ti3C2 to CNT mass ratios of 1:149 and 1:199 have viscosities of 1.2112 × 10⁻⁶. 4 mPa·s and 1.2103×10 4 The viscosity of the ink is approximately the same as that of the composite ink prepared in Example 1, which ensures that it has excellent rheological properties during the printing process.

[0027] Comparative Example 1 The preparation process and conditions are the same as in Example 1, except that the CMC content is kept constant, and the mass ratio of Ti3C2 to CNT in step (2) is adjusted to 1:0 (pure Ti3C2), 1:9, 1:19, 1:299, 1:399 and 0:1 (pure CNT), respectively, to keep the CMC content constant. The CMC accounts for 90 wt% of the total mass of the solid phase, and the total mass of the solid phase is the sum of the masses of Ti3C2, acidified single-walled carbon nanotubes and carboxymethyl cellulose.

[0028] Figure 6 The figures show the conductivity variation curves of the cured films obtained after curing the composite conductive ink prepared in Comparative Example 1 at different temperatures. The results indicate that Ti3C2 exhibits a positive temperature coefficient, while CNTs exhibit a negative temperature coefficient. The cured films of the two materials show opposite conductivity-temperature response characteristics. By adjusting the mass ratio of Ti3C2 to CNTs, self-compensation of conductivity can be achieved. When the mass ratio of Ti3C2 to CNTs is 1:0 (pure Ti3C2), 1:9, 1:19, 1:299, 1:399, and 0:1 (pure CNTs), the conductivity variation rate of the cured films all exceeds 7.5%.

[0029] Comparative Example 2 The preparation process and conditions are the same as in Example 1, except that the mass ratio of Ti3C2 to acidified CNTs is kept constant at 1:99, and the mass fraction of CMC in the total solid phase in step (2) is adjusted to 18 wt%, 38 wt%, 58 wt%, 78 wt%, and 98 wt%. The total solid phase mass is the sum of the masses of Ti3C2, acidified single-walled carbon nanotubes, and carboxymethyl cellulose. Figure 7 The viscosity variation curves of the composite conductive ink with different CMC mass fractions prepared in the control group of Comparative Example 2 are shown. The results indicate that the composite conductive inks with CMC mass fractions of 18 wt%, 38 wt%, 58 wt%, and 78 wt% in the total solid phase have low viscosity and high fluidity, which is unfavorable for stable coating processing on the substrate. When the CMC mass fraction in the total solid phase is 98 wt%, the viscosity of the composite conductive ink increases significantly (>2×10⁻⁶). 4 (mPa·s), rheological properties deteriorate, making it unsuitable for patterning processes such as printing.

Claims

1. A method for preparing a temperature-resistant composite conductive ink, characterized in that, Includes the following steps: (1) Single-walled carbon nanotubes (CNTs) were mixed with nitric acid solution (HNO3) and heated under reflux; wherein the mass ratio of HNO3 to CNTs was 30:1 to 40:1, and the concentration of nitric acid solution was 15 mol / L to 16 mol / L; after the reaction was completed, solid-liquid separation was performed, the solid product was collected and dried to obtain acidified CNTs; (2) Add titanium carbide (Ti3C2), CNTs obtained after treatment in step (1), and carboxymethyl cellulose (CMC) to water and stir to mix to obtain a mixed suspension; wherein, the mass ratio of Ti3C2 to acidified CNTs is 1:99 to 1:199, and carboxymethyl cellulose accounts for 85 to 95 wt% of the total mass of the solid phase, and the total mass of the solid phase is the sum of the masses of Ti3C2, acidified single-walled carbon nanotubes and carboxymethyl cellulose; (3) The mixed suspension is uniformly dispersed to form a uniform composite dispersion, and carboxymethyl cellulose-titanium carbide / carbon nanotube (CMC-Ti3C2 / CNT) composite conductive ink is obtained.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of nitric acid solution to single-walled carbon nanotubes is 33:1 to 37:1; the concentration of the nitric acid solution is 15 mol / L to 15.8 mol / L.

3. The preparation method according to claim 1, characterized in that: In step (1), the temperature of the heating reflux is 60 ℃~90 ℃; the heating reflux time is 4 h~5 h; and the drying temperature is 60 ℃~80 ℃.

4. The preparation method according to claim 1, characterized in that: In step (2), the mass solid content of the mixed suspension is 1 wt% to 5 wt%.

5. The preparation method according to claim 1, characterized in that: In step (3), the uniform dispersion treatment is an ultrasonic-assisted uniform dispersion treatment. The power of the ultrasonic-assisted treatment is 300 W to 500 W, and the time is 1 h to 3 h.

6. A CMC-Ti3C2 / CNT composite conductive ink prepared by the preparation method according to any one of claims 1 to 5.

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