Flame-retardant composite thermoelectric material and fire warning system

Abstract

The application discloses a kind of flame-retardant composite thermoelectric materials, it includes: p-type composite film material and n-type composite film material, the p-type composite film material and the n-type composite film material are connected in series, wherein, the p-type composite film material is prepared using the following steps: a, drop into carbon nanotube ethanol dispersion liquid MXene, remove solvent after ultrasonic dispersion, obtain composite film material;B, the composite film material is dried, obtains p-type composite film material;The n-type composite film material is prepared using the following steps: c, p-type composite film material is soaked in PEI aqueous solution;D, the composite film material after soaking is taken out from PEI aqueous solution, then placed in vacuum drying oven and dried, obtains n-type composite film material.Simultaneously still discloses a kind of fire early warning system.

Description

Technical Field

[0001] This invention relates to the field of thermoelectric materials technology, and more specifically to a flame-retardant composite thermoelectric material and a fire early warning system. Background Technology

[0002] Fire has become one of the most destructive disasters globally, and its incidence has been steadily increasing in recent years. Furthermore, the widespread use of lightweight combustibles due to advancements in materials science has exacerbated the already challenging fire safety situation. Therefore, early fire warning is crucial. Currently, common fire alarms include ionization smoke detectors, semiconductor gas sensors, photoelectric smoke detectors, and electrochemical gas sensors. These alarms mostly detect the large amounts of smoke, gas, and flames produced after a fire occurs, providing long warning times. There are also temperature sensor-based alarms, but these often require batteries or external power sources, making them prone to false alarms in the event of a power outage. Moreover, batteries or external power sources are easily combustible during a fire, rendering the alarm unusable.

[0003] Thermoelectric materials have enormous application prospects in the energy field due to their heat-to-electric conversion properties. Self-powered thermoelectric materials have been successfully applied in deep space exploration (Voyager 1), and their applications are gradually expanding to low-quality heat harvesting, flexible wearable devices, and other areas to explore new applications in sensing, the Internet of Things, and other fields. Fire scenarios can provide an ideal high-temperature environment for thermoelectric materials. Therefore, exploring the application of thermoelectric materials in fire detection and monitoring through self-powered means under fire conditions is of paramount importance. However, current technologies lack composite thermoelectric materials with high flame retardancy that can be integrated with fire alarms for rapid early warning. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a flame-retardant composite thermoelectric material with good flame-retardant properties, which can provide rapid early warning when used in conjunction with a fire alarm in a fire scene through a self-powered method, and a fire early warning system having the flame-retardant composite thermoelectric material.

[0005] To solve the above-mentioned technical problems, according to one aspect of the present invention, a flame-retardant composite thermoelectric material is provided, comprising: a p-type composite film material and an n-type composite film material, wherein the p-type composite film material and the n-type composite film material are connected in series, wherein...

[0006] The p-type composite membrane material is prepared using the following steps:

[0007] a. Add MXene dropwise to the carbon nanotube ethanol dispersion, disperse by ultrasonication, remove the solvent, and obtain the composite membrane material;

[0008] b. Dry the composite membrane material to obtain the p-type composite membrane material;

[0009] The n-type composite membrane material is prepared using the following steps:

[0010] c. Immerse the p-type composite membrane material in a PEI aqueous solution;

[0011] d. Remove the soaked composite membrane material from the PEI aqueous solution and then dry it in a vacuum drying oven to obtain the n-type composite membrane material.

[0012] The further technical solution is as follows: before a, it also includes: a1, adding single-walled carbon nanotubes to ethanol and dispersing them by ultrasonication to obtain a carbon nanotube ethanol dispersion.

[0013] The further technical solution is as follows: In the case of a, the mass of MXene is 1-100% of the mass of single-walled carbon nanotubes.

[0014] The further technical solution is that the mass of the single-walled carbon nanotube is 10-18 mg.

[0015] The further technical solution is as follows: the mass of the single-walled carbon nanotube is 13.85 mg, and the mass of the MXene is 4.15 mg.

[0016] The further technical solution is as follows: in step a, the ultrasonic dispersion time is 3-10 min, and the solvent is removed by vacuum filtration after ultrasonic dispersion.

[0017] The further technical solution is as follows: In step b, the drying temperature is 40-90℃ and the drying time is 3-12h.

[0018] The further technical solution is as follows: Specifically, c includes immersing the p-type composite membrane material in a PEI aqueous solution and vacuum immersing it at room temperature for 3-36 hours; wherein the concentration of the PEI aqueous solution is 0.5%-5%.

[0019] To solve the above-mentioned technical problems, according to another aspect of the present invention, a fire early warning system is provided, which includes a fire alarm and the above-mentioned flame-retardant composite thermoelectric material, wherein the flame-retardant composite thermoelectric material is connected to the fire alarm to provide power to the fire alarm.

[0020] The further technical solution is as follows: the fire early warning system also includes a wireless transmission module, which is connected to the flame-retardant composite thermoelectric material and the fire alarm.

[0021] Compared with existing technologies, the flame-retardant composite thermoelectric material of the present invention comprises a p-type composite film material and an n-type composite film material connected in series. In this invention, a p-type composite film material with high Seebeck coefficient and high conductivity is obtained by compositing single-walled carbon nanotubes with high Seebeck coefficient and transition metal carbide (MXene) with high conductivity. The p-type composite film material also possesses the high flame retardancy of MXene. Furthermore, an n-type composite film material is obtained by immersing the p-type composite film material in a polyethyleneimine (PEI) solution. It can be seen that the flame-retardant composite thermoelectric material of the present invention has high Seebeck coefficient, high conductivity, and high flame retardancy. When used in conjunction with a fire alarm, it can quickly provide power to the fire alarm in a fire scene through self-powered means, achieving rapid early warning and thus realizing intelligent response and identification of fire scenes. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of the preparation method of the flame-retardant composite thermoelectric material of the present invention.

[0023] Figure 2 This is a cross-sectional scanning electron microscope image of the flame-retardant composite thermoelectric material in Example 2. Detailed Implementation

[0024] To enable those skilled in the art to more clearly understand the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0025] The flame-retardant composite thermoelectric material of the present invention comprises a p-type composite film material and an n-type composite film material, wherein the p-type composite film material and the n-type composite film material are connected in series. Specifically, the preparation method of the flame-retardant composite thermoelectric material is as follows: Figure 1 As shown, it includes the following steps:

[0026] S101. Add single-walled carbon nanotubes to ethanol and disperse them by ultrasonication to obtain a carbon nanotube ethanol dispersion.

[0027] In this step, the ultrasonic dispersion time can be 30-60 min, and the mass of the single-walled carbon nanotubes (SWCNTs) can be 10-18 mg.

[0028] S102. Add MXene dropwise to the carbon nanotube ethanol dispersion, disperse by ultrasonication, and remove the solvent to obtain the composite membrane material.

[0029] In this step, the ultrasonic dispersion time can be 3-10 min, preferably 5 min, and the solvent is removed by vacuum filtration after ultrasonic dispersion, and the mass of MXene can be 1-100% of the mass of single-walled carbon nanotubes.

[0030] To control the thickness of the composite film to be consistent, the total mass of SWCNT / MXene in different proportions is controlled to be around 18 mg. Preferably, in some embodiments, the mass of the single-walled carbon nanotubes can be 13.85 mg and the mass of the MXene can be 4.15 mg.

[0031] S103. Dry the composite membrane material to obtain the p-type composite membrane material.

[0032] In this step, the drying temperature can be 40-90℃, preferably 60℃; the drying time can be 3-12h, preferably 6h, that is, the composite film material is dried at 60℃ for 6h.

[0033] As can be seen, the present invention combines single-walled carbon nanotubes with high Seebeck coefficients with high electrical conductivity transition metal carbides (MXene) to obtain p-type composite film materials with high Seebeck coefficients and high electrical conductivity, which greatly improves the thermoelectric performance of the material. In addition, MXene has high flame retardancy, which can also make the p-type composite film material have high flame retardancy, making it suitable for fire scenarios.

[0034] S104. Immerse the p-type composite membrane material in PEI aqueous solution.

[0035] In this invention, the concentration of the PEI aqueous solution is 0.5%-5%, preferably 1%.

[0036] Specifically, the step includes: immersing the p-type composite membrane material in a PEI aqueous solution and vacuum immersing it at room temperature for 3-36 hours, preferably 12 hours.

[0037] S105. Remove the soaked composite membrane material from the PEI aqueous solution and then dry it in a vacuum drying oven to obtain the n-type composite membrane material.

[0038] In this step, the composite membrane material soaked in step S104 is taken out of the PEI aqueous solution and dried. The drying temperature can be 40-90℃, preferably 60℃; the drying time can be 3-12h, preferably 6h, that is, the composite membrane material is placed at 60℃ for 6h to dry.

[0039] S106. Connect the p-type composite membrane material and the n-type composite membrane material in series to obtain a flame-retardant composite thermoelectric material.

[0040] In this step, each p-type composite film material and an n-type composite film material can be connected in series to obtain a pair of pn thermoelectric materials. The flame-retardant composite thermoelectric material can be composed of at least one pair of pn thermoelectric materials.

[0041] The preparation methods of the p-type composite film material and the n-type composite film material in the flame-retardant composite thermoelectric material of the present invention are described below with reference to specific embodiments:

[0042] Example 1

[0043] (1) At room temperature, 15 mg of single-walled carbon nanotubes were added to ethanol and ultrasonically dispersed for 30 min;

[0044] (2) Add 3 mg of MXene to the carbon nanotube ethanol dispersion obtained in step (1) above, continue ultrasonic dispersion for 5 min, remove the solvent by vacuum filtration, and obtain composite membrane material (SWCNT:MXene 10 / 2wt%).

[0045] (3) The composite membrane material obtained in step (2) is dried at 60°C for 6 hours to obtain the p-type composite membrane material;

[0046] (4) Immerse the p-type composite membrane material obtained in step (3) in a 1% PEI aqueous solution and vacuum immerse it at room temperature for 12 hours.

[0047] (5) Take the composite membrane obtained in step (4) out of PEI and dry it in a vacuum drying oven at 60°C for 6 hours to obtain n-type composite membrane material.

[0048] The thermoelectric properties of the p-type and n-type composite film materials obtained according to the formulation in this embodiment are as follows: The conductivity of the prepared p-type composite film material is 879.61 S / cm. -1 The Seebeck coefficient is 45.92 μVK. -1 The power factor is 185.48 μWm. -1 K -2 The conductivity of the obtained n-type composite membrane material is 1773.52 S / cm. -1 The Seebeck coefficient is -33.75 μVK. -1 The power factor is 203.75 μWm. -1 K -2 .

[0049] Example 2

[0050] The method is similar to that in Example 1, and the specific steps are as follows:

[0051] (1) At room temperature, 13.8 mg of single-walled carbon nanotubes were added to ethanol and ultrasonically dispersed for 30 min;

[0052] (2) Add 4.2 mg of MXene to the carbon nanotube ethanol dispersion obtained in step (1) above, continue ultrasonic dispersion for 5 min, remove the solvent by vacuum filtration, and obtain composite membrane material (SWCNT:MXene 10 / 3wt%).

[0053] (3) The composite membrane material obtained in step (2) is dried at 60°C for 6 hours to obtain the p-type composite membrane material; the cross-sectional scanning electron microscope image of the p-type composite membrane material obtained in this embodiment is shown below. Figure 2 As shown, it can be seen that the p-type composite membrane material is a layered composite material.

[0054] (4) Immerse the p-type composite membrane material obtained in step (3) in a 1% PEI aqueous solution and vacuum immerse it at room temperature for 12 hours.

[0055] (5) Take the composite membrane obtained in step (4) out of PEI and dry it in a vacuum drying oven at 60°C for 6 hours to obtain n-type composite membrane material.

[0056] The thermoelectric properties of the p-type and n-type composite film materials obtained according to the formulation of this embodiment are as follows: The conductivity of the prepared p-type composite film material is 1270.97 S cm⁻¹. -1 The Seebeck coefficient is 43.43 μVK. -1 The power factor is 239.72 μWm. -1 K -2 The conductivity of the obtained n-type composite membrane material is 1387.05 S / cm. -1 The Seebeck coefficient is -31.97 μVK. -1 The power factor is 142.50 μWm. -1 K -2 .

[0057] Example 3

[0058] The method is similar to that of Example 1, except that the mass of single-walled carbon nanotubes and MXene was changed. Specifically, the mass of single-walled carbon nanotubes in step (1) was changed to 12.8 mg, and the mass of MXene in step (2) was changed to 5.2 mg. The thermoelectric properties of the p-type and n-type composite film materials finally prepared in this example are shown below: The conductivity of the p-type composite film material is 2335.51 S cm⁻¹. -1 The Seebeck coefficient is 26.35 μVK. -1 The power factor is 162.16 μWm. -1 K -2 The conductivity of the obtained n-type composite film material is 1202.62 S cm⁻¹. -1 The Seebeck coefficient is -33.32 μVK. -1 The power factor is 133.52 μWm. - 1 K -2 .

[0059] Example 4

[0060] The method is similar to that of Example 2, except that the vacuum immersion time in step (4) is changed to 24 hours. Specifically, the p-type composite membrane material obtained in step (3) is immersed in a 1% PEI aqueous solution under vacuum for 24 hours at room temperature. The thermoelectric properties of the p-type and n-type composite membrane materials finally prepared in this example are shown below: The conductivity of the prepared p-type composite membrane material is 2335.51 S cm⁻¹. -1 The Seebeck coefficient is 26.35 μV K. -1 The power factor is 162.16 μWm. -1 K -2 The conductivity of the obtained n-type composite film material is 1202.62 S cm⁻¹. -1 The Seebeck coefficient is -33.32 μVK. -1 The power factor is 133.52 μWm. -1 K -2 .

[0061] Example 5

[0062] The method is similar to that of Example 2, except that the PEI aqueous solution in step (4) is changed to 2%, that is, the p-type composite membrane material obtained in step (3) is immersed in a 2% PEI aqueous solution and vacuum-immersed at room temperature for 12 hours. The thermoelectric properties of the p-type composite membrane material and n-type composite membrane material finally prepared in this example are as follows: The conductivity of the prepared p-type composite membrane material is 2335.51 S cm. -1 The Seebeck coefficient is 26.35 μVK. -1 The power factor is 162.16 μWm. -1 K -2 The conductivity of the obtained n-type composite film material is 1202.62 S cm⁻¹. -1 The Seebeck coefficient is -33.32 μVK. -1 The power factor is 133.52 μWm. -1 K -2 .

[0063] In summary, this invention obtains a p-type composite film material with high Seebeck coefficient and high electrical conductivity by combining single-walled carbon nanotubes with high Seebeck coefficient and transition metal carbides (MXene) with high electrical conductivity. The p-type composite film material also possesses the high flame retardancy of MXene. Furthermore, an n-type composite film material is obtained by immersing the p-type composite film material in a polyethyleneimine (PEI) solution. Therefore, this invention comprises a flame-retardant composite thermoelectric material with p-type and n-type composite film materials connected in series, possessing high Seebeck coefficient, high electrical conductivity, and high flame retardancy.

[0064] In this invention, when the flame-retardant composite thermoelectric material composed of the p-type composite film material and the n-type composite film material prepared according to Example 1 of this invention is placed under a flame for combustion, the flame-retardant composite thermoelectric material maintains structural stability under the flame. The macroscopic structure after 1 minute of combustion is no different from that before combustion, demonstrating excellent flame-retardant performance. It can be seen that when a sponge is placed under a flame, the sponge immediately burns. However, when the flame-retardant composite thermoelectric material of this invention is wrapped around the sponge and then placed under a flame for combustion, the overall volume shrinks only slightly, and after 40 seconds, the overall volume tends to a certain value and no longer changes, demonstrating a prominent flame-retardant effect.

[0065] This invention also provides a fire early warning system, comprising a fire alarm and the aforementioned flame-retardant composite thermoelectric material. The flame-retardant composite thermoelectric material is connected to the fire alarm to provide it with electrical power. Based on the above design, when the flame-retardant composite thermoelectric material is used in conjunction with the fire alarm, the fire scene can provide a high-temperature environment for the flame-retardant composite thermoelectric material. Through the thermo-electric conversion performance of the flame-retardant composite thermoelectric material itself, it can supply power to the fire alarm quickly through self-powered operation, achieving rapid early warning and enabling intelligent response and identification of fire scenes.

[0066] Furthermore, the fire early warning system may also include a wireless transmission module, which is connected to the flame-retardant composite thermoelectric material and the fire alarm. In the event of a fire, the flame-retardant composite thermoelectric material quickly supplies power to the wireless transmission module, enabling the wireless transmission module to send a signal to the fire alarm, thereby providing a fire early warning.

[0067] The operation of the fire early warning system of the present invention will be described below in conjunction with specific application scenarios:

[0068] Application Scenario 1

[0069] Using the p-type composite membrane material and n-type composite membrane material prepared in Example 2 above, a series-type device assembly strategy is adopted to assemble a pn thermoelectric material. Then, at least one pn thermoelectric material is assembled in series to obtain a flame-retardant composite thermoelectric material. The cold end of the flame-retardant composite thermoelectric material is wrapped with fire-resistant insulation cotton, and the hot end is exposed, forming an "L"-shaped structure.

[0070] Specifically, flame-retardant composite thermoelectric materials containing 1, 2, 5, and 10 pairs of PN thermoelectric materials were prepared using different amounts of PN thermoelectric materials. These different flame-retardant composite thermoelectric materials were then connected to fire alarms, with the alarm threshold set to 10mV. Under flame conditions, the flame-retardant composite thermoelectric materials containing 1, 2, 5, and 10 pairs of PN thermoelectric materials provided warning times of 8.0s, 3.4s, 2.3s, and 1.6s, respectively.

[0071] Furthermore, when the fire alarm repeatedly issues warnings, the warning time shows a stepwise increasing trend with the increase of the number of repetitions. When the flame-retardant composite thermoelectric material connected to the fire alarm in the fire warning system is a flame-retardant composite thermoelectric material containing 5 pairs of pn thermoelectric materials, the warning time of the fire alarm is still within 5 seconds after approximately 50 cycles of warning.

[0072] Application Scenario 2

[0073] Using the p-type composite membrane material and n-type composite membrane material prepared in Example 2 above, a series-type device assembly strategy is adopted to assemble a pn thermoelectric material. Then, at least one pn thermoelectric material is assembled in series to obtain a flame-retardant composite thermoelectric material. The cold end of the flame-retardant composite thermoelectric material is wrapped with fire-resistant insulation cotton, and the hot end is exposed, forming an "L"-shaped structure.

[0074] Flame-retardant composite thermoelectric materials containing 1, 5, and 10 pairs of pn thermoelectric materials were prepared using different numbers of pn thermoelectric materials. These different flame-retardant composite thermoelectric materials were then connected to fire alarms with an alarm threshold of 10 mV. The effects of different distances from heat waves and the number of pn thermoelectric material pairs on early warning performance were investigated.

[0075] Specifically, flame-retardant composite thermoelectric materials containing 1 pair, 5 pairs, and 10 pairs of PN thermoelectric materials were placed approximately 10 cm above the flame of an alcohol lamp. At this distance, the warning times of the fire alarm were 11.4 s, 5.7 s, and 3.2 s, respectively. Then, flame-retardant composite thermoelectric materials containing 1 pair, 5 pairs, and 10 pairs of PN thermoelectric materials were placed approximately 15 cm above the flame of an alcohol lamp. At this distance, the warning results of the fire alarm were no alarm triggered, alarm with a warning time of 10.4 s, and alarm with a warning time of 5.6 s, respectively.

[0076] Application Scenario 3

[0077] Using the p-type composite membrane material and n-type composite membrane material prepared in Example 2 above, a series-type device assembly strategy is adopted to assemble a pn thermoelectric material. Then, at least one pn thermoelectric material is assembled in series to obtain a flame-retardant composite thermoelectric material. The cold end of the flame-retardant composite thermoelectric material is wrapped with fire-resistant insulation cotton, and the hot end is exposed, forming an "L"-shaped structure.

[0078] Specifically, a flame-retardant composite thermoelectric material containing 10 pairs of pn thermoelectric materials is connected to a wireless signal transmission module. After connection, the entire assembly is embedded in the building wall. The wireless signal transmission module connects to external electronic devices via Bluetooth. Under normal circumstances, when the wireless signal transmission module is inactive, the electronic device does not issue a warning signal. However, when a fire occurs, the flame-retardant composite thermoelectric material generates a thermoelectric voltage, driving the wireless signal transmission module to send a signal to the electronic device via Bluetooth. The electronic device then displays a fire hazard warning. Therefore, the flame-retardant composite thermoelectric material of this invention can be successfully applied in the field of fire early warning, and by transmitting fire signals to electronic devices via wireless signal transmission, it achieves intelligent response and identification of fire scenarios.

[0079] In summary, the flame-retardant composite thermoelectric material of this invention possesses a high Seebeck coefficient, high electrical conductivity, and high flame retardancy. When used in conjunction with a fire alarm, it can quickly provide power to the fire alarm in a fire scenario through self-powered operation, enabling rapid early warning and thus achieving intelligent response and identification of fire scenarios.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Those skilled in the art can make various equivalent changes and improvements based on the above embodiments, and all equivalent variations or modifications made within the scope of the claims should fall within the protection scope of the present invention.

Claims

1. A flame-retardant composite thermoelectric material, characterized in that, include: A p-type composite membrane material and an n-type composite membrane material are connected in series. The p-type composite membrane material is prepared using the following steps: a1. Add single-walled carbon nanotubes to ethanol and disperse them by ultrasonication to obtain a carbon nanotube ethanol dispersion. a. Add MXene dropwise to the carbon nanotube ethanol dispersion, disperse ultrasonically, and remove the solvent to obtain a composite membrane material; wherein the mass of the single-walled carbon nanotube is 10-18 mg, the mass of MXene is 1-100% of the mass of the single-walled carbon nanotube, the ultrasonic dispersion time is 3-10 min, and the solvent is removed by vacuum filtration after ultrasonic dispersion. b. Dry the composite membrane material to obtain the p-type composite membrane material; wherein the drying temperature is 40-90℃ and the drying time is 3-12h. The n-type composite membrane material is prepared using the following steps: c. Immerse the p-type composite membrane material in a PEI aqueous solution under vacuum at room temperature for 3-36 hours; wherein the concentration of the PEI aqueous solution is 0.5%-5%; d. Remove the soaked composite membrane material from the PEI aqueous solution and then dry it in a vacuum drying oven to obtain the n-type composite membrane material.

2. The flame-retardant composite thermoelectric material as described in claim 1, characterized in that, The mass of the single-walled carbon nanotube is 13.85 mg, and the mass of the MXene is 4.15 mg.

3. A fire early warning system, characterized in that, The invention includes a fire alarm and the flame-retardant composite thermoelectric material as described in any one of claims 1-2, wherein the flame-retardant composite thermoelectric material is connected to the fire alarm to provide power to the fire alarm.

4. The fire early warning system as described in claim 3, characterized in that, The fire early warning system also includes a wireless transmission module, which is connected to the flame-retardant composite thermoelectric material and the fire alarm.

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