A semiconductor co exhaust gas sensor for a ship and use thereof

Abstract

The application belongs to the technical field of gas sensors, and relates to a semiconductor CO tail gas sensor for a ship and application thereof. The semiconductor CO tail gas sensor has a MEMS micro-heating plate as a main body structure, and through the synergistic design of a SnO2 / ZnO / CuO ternary heterojunction and a porous nanostructure formed by a metal oxide, a dynamic temperature control algorithm and a differential signal processing are combined, so that the sensitivity, selectivity and environmental adaptability of the sensor are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor technology, and relates to a semiconductor CO exhaust gas sensor for ships and its application. Background Technology

[0002] During ship operation, the complex environment of the ship's cabin, including high humidity (70%~95%), salt spray corrosion, and temperature fluctuations (-20℃~60℃), makes traditional electrochemical or catalytic combustion CO exhaust gas sensors susceptible to environmental influences, resulting in short lifespans and high power consumption (typically >100mW). Furthermore, traditional marine CO exhaust gas sensors often use SnO2-based sensors, which require high-temperature operation (200~400℃), high power consumption (>50mW), and low sensitivity (detection limit >10ppm), failing to meet the stringent IMO (International Maritime Organization) standards for monitoring ship CO exhaust gas concentrations (alarm threshold 50ppm, detection limit ≤5ppm). Existing sensors are also prone to cross-interference from gases such as H2 and CH4 in low-concentration CO exhaust gas detection, lack self-calibration capabilities, and exhibit poor long-term stability. Therefore, the development of more sensitive and lower-power CO exhaust gas sensors is urgently needed, which would be crucial for the safe operation of ships. Summary of the Invention

[0003] The first objective of this invention is to provide a semiconductor CO exhaust gas sensor for ships. The sensor is a high-performance semiconductor CO exhaust gas sensor based on ternary heterojunction materials and MEMS integration technology. Through the collaborative innovation of material modification, device optimization and intelligent algorithms, the detection accuracy and reliability are significantly improved, and the problems of low sensitivity, high power consumption, poor anti-interference and insufficient environmental adaptability of traditional CO sensors are effectively solved.

[0004] The second objective of this invention is to provide the application of the aforementioned CO exhaust gas sensor in ship environmental monitoring, especially in the field of CO exhaust gas monitoring.

[0005] To address the aforementioned technical problems, the present invention provides a semiconductor CO exhaust gas sensor for ships, comprising a MEMS micro-heating plate;

[0006] The MEMS micro-heating plate includes a silicon substrate, and sequentially deposited insulating layer, heat insulation layer, heating element, and sensitive material layer; wherein,

[0007] The sensitive material forming the sensitive material layer includes SnO2 / ZnO / CuO ternary porous nanomaterials.

[0008] Specifically, in the aforementioned marine semiconductor CO exhaust gas sensor, the MEMS micro-heating plate includes:

[0009] The insulating layer includes a SiO2 material layer; and / or,

[0010] The thermal insulation layer includes an Al2O3 material layer; and / or,

[0011] The heating element includes a Pt heating resistor.

[0012] Specifically, in the aforementioned marine semiconductor CO exhaust gas sensor, the MEMS micro-heating plate includes:

[0013] The thickness of the insulating layer is 0.8-1.2 μm; and / or,

[0014] The thickness of the insulation layer is 0.8-1.2 μm; and / or,

[0015] The heating elements are arranged in a serpentine pattern.

[0016] Specifically, the shipboard semiconductor CO exhaust gas sensor further includes an encapsulation layer and an electrode layer; wherein,

[0017] The encapsulation layer includes a PTFE film and an encapsulation framework; and / or,

[0018] The electrode layer includes Au interdigitated electrodes.

[0019] This invention also discloses a method for fabricating a semiconductor CO exhaust gas sensor for ships as described above, including the step of fabricating the MEMS micro heating plate, specifically including the following steps:

[0020] S1. The desired SnO2 / ZnO / CuO ternary porous nanomaterials were synthesized by the sol-gel method, and the sensitive material slurry was prepared.

[0021] S2. The insulating layer and the heat insulation layer are sequentially deposited on the surface of the silicon substrate, and the heating element is integrated to obtain the MEMS micro heating plate substrate;

[0022] S3. The sensitive material slurry is coated onto the surface of the MEMS micro heating plate substrate, and the sensitive material layer is formed by annealing to obtain the desired MEMS micro heating plate.

[0023] Specifically, in the method for fabricating the semiconductor CO exhaust gas sensor for ships, step S1 specifically includes:

[0024] S11. Dissolve SnCl4·5H2O:Zn(NO3)2·6H2O:Cu(NO3)2·3H2O in an ethanol-water mixed solvent according to the molar ratio of SnCl4·5H2O:Zn(NO3)2·6H2O:Cu(NO3)2·3H2O = (4-6):(2-4):(1-3), add 8-12wt% template agent and mix to obtain a sol; preferably, the volume ratio of ethanol to water is 4:1.

[0025] S12. The sol is subjected to a hydrothermal reaction at 60-100℃, and after centrifugation and drying, it is calcined at 400-600℃ under a protective atmosphere to obtain ternary porous nanospheres.

[0026] S13. Mix the ternary porous nanospheres with terpineol at a mass ratio of 1:(4-6) to obtain the desired sensitive material slurry.

[0027] Specifically, in the method for fabricating the semiconductor CO exhaust gas sensor for ships, step S2 specifically includes:

[0028] S21. A SiO2 insulating layer is deposited on the surface of the silicon substrate, and the Pt heating resistor is integrated to form a serpentine arrangement; S22. 15-25wt% Al2O3 sol is spin-coated and annealed at 250-350℃ to form an Al2O3 heat insulation layer.

[0029] S23. Simulate the heater temperature distribution using COMSOL to ensure that the temperature uniformity error in the central area is ≤ ±2℃.

[0030] Specifically, in the method for fabricating the semiconductor CO exhaust gas sensor for ships, step S3 specifically includes:

[0031] S31. The sensitive material paste is coated onto the surface of the MEMS micro heating plate substrate by screen printing, and the coating thickness is controlled to be 5-15μm.

[0032] S32. The MEMS micro heating plate substrate is annealed in air at 300-400℃ to obtain the final product.

[0033] Specifically, the method for preparing the shipboard semiconductor CO exhaust gas sensor further includes:

[0034] S4. Install electrodes and design a differential Wheatstone bridge and a lock-in amplifier circuit, and integrate the signal processing circuit with a dynamic temperature control algorithm; S5. Encapsulate the MEMS micro heating plate with a PTFE breathable membrane and a stainless steel skeleton to obtain the required semiconductor CO exhaust gas sensor.

[0035] The present invention also discloses the application of the aforementioned semiconductor CO exhaust gas sensor for ships in the field of ship environmental monitoring, especially CO exhaust gas monitoring.

[0036] The marine semiconductor CO exhaust gas sensor of this invention uses a MEMS micro-heating plate as the main structure and employs a synergistic design of a SnO2 / ZnO / CuO ternary heterojunction and porous nanostructure formed by metal oxides. Combined with a dynamic temperature control algorithm and differential signal processing, this significantly improves the sensor's sensitivity, selectivity, and environmental adaptability. The SnO2 / ZnO / CuO porous nanospheres (specific surface area ≥150 m² / g, pore size 2~5 nm) synthesized via a sol-gel method utilize the p-type doping of CuO and the n-type characteristics of SnO2 / ZnO to form a pn heterojunction interface. The interface barrier of 0.8 eV significantly reduces the activation energy of the CO oxidation reaction (1.2 eV for traditional materials), lowering the operating temperature from 200~400℃ for traditional sensors to 80~150℃, and increasing sensitivity by more than 3 times (5 ppm CO response value ≥15, traditional sensors ≤5). The high specific surface area and short diffusion path of the porous nanostructure shorten the response time by 50% (T0). 90 <10 seconds). Combined with a dynamic temperature control algorithm (temperature rises by 10~15℃ for every 10% increase in RH), it effectively suppresses competitive adsorption of water molecules, with sensitivity fluctuation of <5% at 95% RH (compared to >30% for traditional sensors). Differential Wheatstone bridge and lock-in amplifier technology (signal-to-noise ratio ≥60 dB) further offsets baseline drift, making the detection limit as low as 0.1 ppm (compared to ≥10 ppm for traditional sensors), meeting the monitoring requirements for ultra-low concentration CO exhaust gas in marine environments.

[0037] The marine semiconductor CO exhaust gas sensor described in this invention further achieves high energy efficiency and long lifespan through innovation in MEMS micro-hotplate and corrosion-resistant packaging technology. It integrates a Pt serpentine heater (200 nm thick, heating efficiency ≥85%) and an Al2O3 insulation layer (thermal conductivity <2 W / m·K) using silicon-based MEMS technology, enabling the micro-hotplate to heat up to 120°C within 10 seconds, reducing power consumption to 18mW (compared to >50mW for traditional ceramic substrates). Combined with intermittent operation (annual average power consumption <3mW), battery life is extended to over 10 years (compared to 1-2 years for traditional sensors). The packaging uses a 316L stainless steel frame (salt spray corrosion rate <0.001 mm / year) and a PTFE breathable membrane (0.5 μm pore size, breathability remains >95% after 500 hours of salt spray testing), solving the problems of easy corrosion and membrane clogging associated with traditional ABS shells. Experiments show that the sensor can operate continuously for 6 months at 85% humidity and 40℃ with a response decay rate of <5% (traditional sensors >30%) and a lifespan of >3 years, far exceeding the requirements of IMO ship monitoring standards.

[0038] The marine semiconductor CO exhaust gas sensor described in this invention achieves high-precision self-calibration and anti-interference capabilities through intelligent algorithms and system integration. An adaptive calibration algorithm based on an STM32L4 microcontroller (performing zero-point calibration every 24 hours with N2 and machine learning to compensate for aging) ensures a detection error of <5% over 3 years, extending the calibration cycle from one month in traditional methods to one year. A lock-in amplifier modulates the signal with a 1 kHz square wave, combined with a digital low-pass filter (cutoff frequency 10 Hz), effectively suppressing 1 / f noise and improving the signal-to-noise ratio from 40 dB in traditional DC measurements to 60 dB. The sensor exhibits a cross-sensitivity of <5% for 100 ppm H2 / CH4 (compared to >20% for traditional sensors) and <3% for NO2 / C2H5OH, solving the problem of interference from complex gases in marine environments. Experimental data shows that the sensor's linearity R0 in the CO range of 0.1–100 ppm is [insert value here]. 2 With a signal repeatability error of <2% at a concentration of >0.99 and 5 ppm, it meets the requirements for high-precision and high-reliability monitoring, and features high sensitivity, low power consumption, strong anti-interference and strong environmental adaptability. Attached Figure Description

[0039] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the CO exhaust gas sensor structure described in this invention;

[0041] Figure 2 The images show the microstructure (TEM images) of the sensitive material prepared in Example 1; where (a) is a high-resolution transmission electron microscope (HRTEM) image; (b) is a standard electron diffraction (SAED) image; and (c) is an elemental mapping image.

[0042] Figure 3 This is a simulation diagram of the temperature field distribution of the MEMS micro-hot plate in Example 1;

[0043] Figure 4 The image shows a comparison of the salt spray test results of the sensor in Example 1; where the corrosion status of the conventional sensor (a) and the housing of the present invention (b) is compared after 500 hours of salt spray testing.

[0044] Figure 5 This is the sensitivity test curve of the sensor in Example 1;

[0045] Figure 6This is a schematic diagram of the power consumption of the sensor during operation in Example 1; where (a) is the power consumption result in continuous mode; (b) is the power consumption result in on-demand mode, the blue solid line represents the operating current, and the red arrow represents the measurement time. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are part of this invention.

[0047] The present invention provides a semiconductor CO exhaust gas sensor for ships in the following embodiments, which includes a MEMS micro heating plate;

[0048] The MEMS micro-heating plate includes a silicon substrate, and sequentially deposited insulating layer, heat insulation layer, heating element, and sensitive material layer; wherein,

[0049] The sensitive material forming the sensitive material layer includes SnO2 / ZnO / CuO ternary porous nanomaterials.

[0050] In some specific embodiments, the MEMS micro heating plate includes:

[0051] The insulating layer includes a SiO2 material layer; and / or,

[0052] The thermal insulation layer includes an Al2O3 material layer; and / or,

[0053] The heating element includes a Pt heating resistor.

[0054] In some specific embodiments, the MEMS micro heating plate includes:

[0055] The thickness of the insulating layer is 0.8-1.2 μm; and / or,

[0056] The thickness of the insulation layer is 0.8-1.2 μm; and / or,

[0057] The heating elements are arranged in a serpentine pattern.

[0058] In some specific embodiments, the semiconductor CO exhaust gas sensor further includes an encapsulation layer and an electrode layer; wherein,

[0059] The encapsulation layer includes a PTFE film and an encapsulation framework; and / or,

[0060] The electrode layer includes Au interdigitated electrodes.

[0061] This invention also discloses a method for fabricating a semiconductor CO exhaust gas sensor for ships as described above, including the step of fabricating the MEMS micro heating plate, specifically including the following steps:

[0062] S1. The desired SnO2 / ZnO / CuO ternary porous nanomaterials were synthesized by the sol-gel method, and the sensitive material slurry was prepared.

[0063] S2. The insulating layer and the heat insulation layer are sequentially deposited on the surface of the silicon substrate, and the heating element is integrated to obtain the MEMS micro heating plate substrate;

[0064] S3. The sensitive material slurry is coated onto the surface of the MEMS micro heating plate substrate, and the sensitive material layer is formed by annealing to obtain the desired MEMS micro heating plate.

[0065] S4. Install the electrodes and design a differential Wheatstone bridge and a lock-in amplifier circuit, and integrate the signal processing circuit with a dynamic temperature control algorithm; S5. Encapsulate the MEMS micro heating plate with a PTFE breathable membrane and a stainless steel frame to obtain the required semiconductor CO exhaust gas sensor.

[0066] As an exemplary embodiment, the preparation method of a high-sensitivity, low-power semiconductor CO exhaust gas sensor for ships according to the present invention includes the following steps: S1, Synthesis and modification of sensitive materials: SnO2 / ZnO / CuO ternary heterojunction porous nanospheres are synthesized by sol-gel method, and their specific surface area and pore size distribution are controlled.

[0067] S2. MEMS hot plate fabrication: Integrating a Pt serpentine heater and an Al2O3 insulation layer on a silicon substrate to optimize thermal field distribution and energy efficiency; S3. Sensitive layer coating and annealing: Coating the sensitive material slurry onto the surface of the MEMS hot plate and annealing to form a porous sensitive layer; S4. Signal processing circuit integration: Designing a differential Wheatstone bridge and a lock-in amplifier circuit, combined with a dynamic temperature control algorithm; S5. Corrosion-resistant packaging and testing: Encapsulating the sensor with a PTFE breathable membrane and a 316L stainless steel frame, and passing salt spray and long-term stability tests.

[0068] In some specific embodiments, step S1 specifically includes:

[0069] S11. Dissolve SnCl4·5H2O:Zn(NO3)2·6H2O:Cu(NO3)2·3H2O in an ethanol-water mixed solvent (volume ratio 4:1) according to the molar ratio of SnCl4·5H2O:Zn(NO3)2·6H2O:Cu(NO3)2·3H2O=(4-6):(2-4):(1-3), add 8-12wt% template agent and mix to obtain a sol;

[0070] S12. The sol is subjected to a hydrothermal reaction at 60-100℃, and after centrifugation and drying, it is calcined at 400-600℃ under a protective atmosphere to obtain ternary porous nanospheres.

[0071] S13. Mix the ternary porous nanospheres with terpineol at a mass ratio of 1:(4-6) to obtain the desired sensitive material slurry.

[0072] As an exemplary implementation, step S1 further includes:

[0073] S11. Preparation of precursor solution: Dissolve SnCl4·5H2O : Zn(NO3)2·6H2O : Cu(NO3)2·3H2O = 5:3:2 in an ethanol-water mixed solvent (volume ratio 4:1), add 10 wt% P123 template agent, and sonicate for 20 minutes to form a homogeneous sol;

[0074] S12. Hydrothermal Synthesis and Calcination: The sol was transferred to a high-pressure reactor and hydrothermally reacted at 80℃ for 12 hours. After centrifugation and drying, it was calcined at 500℃ under a nitrogen atmosphere for 2 hours to obtain a specific surface area ≥150 m². 2 / g, ternary porous nanospheres with pore sizes of 2~5 nm were obtained; and the materials were characterized: the morphology, crystal form and porosity of the materials were verified by SEM, XRD and BET tests.

[0075] S13. Mix and grind SnO2 / ZnO / CuO nanospheres with terpineol at a mass ratio of 1:5 to form a uniform slurry.

[0076] In some specific embodiments, step S2 specifically includes:

[0077] S21. A SiO2 insulating layer is deposited on the surface of the silicon substrate, and the Pt heating resistor is integrated to form a serpentine arrangement; S22. 15-25wt% Al2O3 sol is spin-coated and annealed at 250-350℃ to form an Al2O3 heat insulation layer.

[0078] S23. Simulate the heater temperature distribution using COMSOL to ensure that the temperature uniformity error in the central area is ≤ ±2℃.

[0079] As an exemplary implementation, step S2 further includes:

[0080] S21. Silicon-based MEMS fabrication: SiO2 insulating layer (1 μm) and Pt serpentine heater (thickness 200 nm, linewidth 10 μm, spacing 5 μm) are sequentially deposited on a 4-inch silicon wafer; S22. Al2O3 thermal insulation layer preparation: Al2O3 sol (20 wt%) is spin-coated and annealed at 300℃ to form a thermal insulation layer with a thickness of 1 μm and a thermal conductivity <2 W / m·K;

[0081] S23. Thermal field simulation optimization: Simulate the heater temperature distribution using COMSOL to ensure that the temperature uniformity error in the central area is ≤ ±2℃.

[0082] In some specific embodiments, step S3 specifically includes:

[0083] S31. The sensitive material paste is coated onto the surface of the MEMS micro heating plate substrate by screen printing, and the coating thickness is controlled to be 5-15μm.

[0084] S32. The MEMS micro heating plate substrate is annealed in air at 300-400℃ to obtain the final product.

[0085] As an exemplary implementation, step S3 further includes:

[0086] S31. The paste is coated onto the surface of the MEMS micro heating plate substrate (10 μm thick) by screen printing, and Au interdigitated electrodes (20 μm wide and 30 μm apart) are covered.

[0087] S32. Anneal the MEMS micro heating plate substrate in air at 350°C for 1 hour.

[0088] As an exemplary implementation, step S4 further includes: S41, differential bridge design: a dual-channel Wheatstone bridge is adopted, one channel is connected to the sensitive element, and the other channel is connected to the reference element coated with Al2O3;

[0089] S42, Lock-in amplifier circuit: modulates the heater power supply with a 1 kHz square wave, demodulates the signal with an AD630, and performs digital filtering (cutoff frequency 10 Hz) in conjunction with an STM32L4 microcontroller; S43, Dynamic temperature control algorithm: preset humidity-temperature mapping table (for every 10% increase in humidity RH, the temperature rises by 10~15℃), and the PID algorithm adjusts the heating voltage in real time.

[0090] As an exemplary implementation, step S5 further includes:

[0091] S51. PTFE membrane encapsulation: A PTFE membrane with a pore size of 0.5 μm is hot-pressed onto the air inlet of a 316L stainless steel skeleton and bonded with epoxy resin (EP42HT-2). Curing conditions: 120℃ / 2 hours. S52. Salt spray test: A 500-hour neutral salt spray test is conducted according to GB / T 10125-2012 standard to verify a corrosion rate <0.001 mm / year. S53. Performance calibration: Sensitivity, response time, and cross-interference are tested within the CO concentration range of 0.1~100 ppm to ensure a detection limit ≤0.1 ppm, a response value ≥15 at 5 ppm, and H2 / CH4 cross-sensitivity <5%.

[0092] In the following embodiments of the present invention, the appendix is ​​used. Figure 1 Taking the sensor structure shown as an example, we designed and fabricated the required semiconductor CO exhaust gas sensor for ships.

[0093] As attached Figure 1 The CO exhaust gas sensor structure shown comprises, from top to bottom, an encapsulation layer (including a PTFE breathable membrane 1), a sensitive layer 2 (containing SnO2 / ZnO / CuO nanospheres), a Pt microheater 3 (i.e., a Pt heating resistor), an Al2O3 heat insulation layer (silicon substrate, etc., not shown), and a signal electrode 5. In the following embodiments of the present invention, the CO exhaust gas sensor with the above structure is prepared according to specific methods and parameters.

[0094] Preparation Example 1

[0095] Precursor solution preparation: Weigh SnCl4·5H2O (final concentration 0.5 mol / L), Zn(NO3)2·6H2O (final concentration 0.3 mol / L), and Cu(NO3)2·3H2O (final concentration 0.2 mol / L), and dissolve them in a mixed solvent of ethanol and deionized water (volume ratio 4:1) at a molar ratio of 5:3:2. Stir for 30 minutes until completely dissolved. Add block copolymer P123 (final concentration 10wt%) as a template agent and continue ultrasonic treatment for 20 minutes to form a homogeneous sol.

[0096] Hydrothermal synthesis and calcination: The sol was transferred to a polytetrafluoroethylene high-pressure reactor and hydrothermally reacted at 80°C for 12 hours to generate a precursor gel. The precipitate was separated by centrifugation, washed three times alternately with deionized water and ethanol, and vacuum dried at 80°C for 6 hours. The dried powder was placed in a tube furnace and calcined at 500°C at a rate of 5°C / min under a nitrogen atmosphere for 2 hours to obtain SnO2 / ZnO / CuO ternary porous nanospheres. The TEM morphology is shown in the attached figure. Figure 2As shown in the figure, (a) is a high-resolution transmission electron microscope (HRTEM) image, showing the characteristic interplanar spacing of different components (ZnO, CuO, SnO2); (b) is a standard electron diffraction (SAED) image, showing the crystal structure and crystal plane information of the material; and (c) is an element mapping diagram, showing the spatial distribution of Sn, O, Zn, and Cu elements in the material.

[0097] Furthermore, BET testing confirmed that the specific surface area of ​​the SnO2 / ZnO / CuO ternary porous nanospheres prepared in this embodiment is ≥150 m². 2 / g, pore size distribution concentrated in 2~5 nm (mesoporous structure is conducive to CO diffusion and adsorption); XRD analysis shows that SnO2 (tetragonal phase), ZnO (hexagonal wurtzite) and CuO (monoclinic phase) are matched in crystal form and there are no impurity peaks.

[0098] Preparation Example 2

[0099] Precursor solution preparation: Weigh SnCl4·5H2O (final concentration 0.4 mol / L), Zn(NO3)2·6H2O (final concentration 0.2 mol / L), and Cu(NO3)2·3H2O (final concentration 0.1 mol / L), and dissolve them in a mixed solvent of ethanol and deionized water (volume ratio 4:1) at a molar ratio of 4:2:1. Stir for 30 minutes until completely dissolved. Add block copolymer P123 (concentration 10 wt%) as a template agent and continue ultrasonic treatment for 20 minutes to form a homogeneous sol.

[0100] Hydrothermal synthesis and calcination: The sol was transferred to a polytetrafluoroethylene high-pressure reactor and hydrothermally reacted at 80°C for 12 hours to generate a precursor gel; the precipitate was separated by centrifugation, washed three times alternately with deionized water and ethanol, and vacuum dried at 80°C for 6 hours; the dried powder was placed in a tube furnace and calcined at 500°C at a rate of 5°C / min for 2 hours under a nitrogen atmosphere to obtain SnO2 / ZnO / CuO ternary porous nanospheres.

[0101] Preparation Example 3

[0102] Precursor solution preparation: Weigh SnCl4·5H2O (final concentration 0.6mol / L), Zn(NO3)2·6H2O (final concentration 0.4mol / L), and Cu(NO3)2·3H2O (final concentration 0.3mol / L), and dissolve them in a mixed solvent of ethanol and deionized water (volume ratio 4:1) at a molar ratio of 6:4:3. Stir for 30 minutes until completely dissolved. Add block copolymer P123 (concentration 10 wt%) as a template agent and continue ultrasonic treatment for 20 minutes to form a homogeneous sol.

[0103] Hydrothermal synthesis and calcination: The sol was transferred to a polytetrafluoroethylene high-pressure reactor and hydrothermally reacted at 80°C for 12 hours to generate a precursor gel; the precipitate was separated by centrifugation, washed three times alternately with deionized water and ethanol, and vacuum dried at 80°C for 6 hours; the dried powder was placed in a tube furnace and calcined at 500°C at a rate of 5°C / min for 2 hours under a nitrogen atmosphere to obtain SnO2 / ZnO / CuO ternary porous nanospheres.

[0104] Comparative Preparation Example 1

[0105] The preparation method of the porous nanospheres described in this comparative example is the same as that in Example 1, except that the raw materials include SnCl4·5H2O (0.5 mol / L) and Zn(NO3)2·6H2O (0.3 mol / L) in a molar ratio of 5:3.

[0106] Comparative Preparation Example 2

[0107] The preparation method of the porous nanospheres described in this comparative example is the same as that in Example 1, except that the raw materials include SnCl4·5H2O (0.5 mol / L) and Cu(NO3)2·3H2O (0.2 mol / L) in a molar ratio of 5:2.

[0108] Example 1

[0109] Silicon-based MEMS process: A SiO2 insulating layer (1 μm) is deposited on a 4-inch silicon wafer using conventional methods, and Pt micro-heaters (200 nm thick, 10 μm serpentine linewidth, 5 μm spacing) are arranged in a serpentine pattern. The patterned structure is formed by photolithography and ion beam etching. Al2O3 sol (20 wt%) is then spin-coated and annealed at 300℃ to form a thermal insulation layer (1 μm thick, thermal conductivity <2 W / m·K), which covers the surface of the heaters.

[0110] Sensitive layer coating and annealing: The SnO2 / ZnO / CuO nanospheres obtained in Preparation Example 1 were mixed with terpineol at a mass ratio of 1:5 and ground to form a uniform slurry; the slurry was coated onto the surface of the Al2O3 layer (10 μm thick) by screen printing, covering the Au interdigitated electrodes (20 μm wide and 30 μm spaced); annealing was carried out in air at 350°C for 1 hour to remove the organic binder and form a porous sensitive layer.

[0111] Thermal field simulation verification: COMSOL Multiphysics was used to simulate the temperature distribution of the heater under 3V voltage. The temperature uniformity error in the central region was ≤±2℃. The results are attached. Figure 3 As shown.

[0112] Differential Wheatstone Bridge: Design a dual-channel bridge circuit: one channel is connected to the sensitive element (exposed to CO exhaust gas), and the other channel is connected to the inert reference element (a blank sensor coated with Al2O3); the bridge output voltage is amplified 100 times by an instrumentation amplifier (AD623) to suppress common-mode noise.

[0113] Lock-in amplifier and digital filtering: The AD630 lock-in amplifier is used to drive the heater with a 1 kHz square wave, synchronously demodulate the resistance change signal of the sensitive layer, and extract the effective components of low frequency (0.1~10 Hz); the signal is acquired by the built-in ADC of STM32L4 and digital low-pass filtering is performed (cutoff frequency 10 Hz), and the signal-to-noise ratio is improved to >60 dB.

[0114] Dynamic temperature control algorithm: Preset temperature-humidity mapping table: When the ambient humidity rises from 70% to 95%, the heating temperature linearly increases from 80℃ to 150℃ (suppressing H2O molecule adsorption); the microcontroller adjusts the Pt heater voltage (0~5V) in real time through the PID algorithm, with a response time of <5 seconds.

[0115] Breathable membrane encapsulation: A PTFE membrane (0.5 μm pore size, 50 μm thickness) is hot-pressed onto the air inlet window of a 316L stainless steel frame (8 mm outer diameter), achieving an air permeability >500 mL / (min·cm). 2 • atm); High-temperature resistant epoxy resin (EP42HT-2) is used to bond the PTFE membrane to the skeleton, and the curing conditions are 120℃ / 2 hours.

[0116] Salt spray protection test: Neutral salt spray test was conducted according to GB / T 10125-2012 standard: 5% NaCl solution, continuous spraying at 35℃ for 500 hours. The results are attached. Figure 4 As shown in the figure. After the test, the PTFE membrane did not expand or peel off, and the corrosion area on the stainless steel skeleton surface was <0.1%.

[0117] The sensor prepared in this embodiment is labeled as SZC-ternary.

[0118] Example 2

[0119] Silicon-based MEMS process: A SiO2 insulating layer (1 μm) is deposited on a 4-inch silicon wafer using conventional methods, and Pt micro-heaters (200 nm thick, 10 μm serpentine linewidth, 5 μm spacing) are arranged in a serpentine pattern. The patterned structure is formed by photolithography and ion beam etching. Al2O3 sol (15 wt% concentration) is then spin-coated and annealed at 350℃ to form a thermal insulation layer (1 μm thick, thermal conductivity <2 W / m·K) covering the surface of the heaters.

[0120] Sensitive layer coating and annealing: The SnO2 / ZnO / CuO nanospheres obtained in Preparation Example 1 were mixed with terpineol at a mass ratio of 1:4 and ground to form a uniform slurry; the slurry was coated onto the surface of the Al2O3 layer (10 μm thick) by screen printing, covering the Au interdigitated electrodes (20 μm wide and 30 μm spaced); annealing was carried out in air at 350°C for 1 hour to remove the organic binder and form a porous sensitive layer.

[0121] Example 3

[0122] Silicon-based MEMS process: A SiO2 insulating layer (1 μm) is deposited on a 4-inch silicon wafer using conventional methods, and Pt micro-heaters (200 nm thick, 10 μm serpentine linewidth, 5 μm spacing) are arranged in a serpentine pattern. The patterned structure is formed by photolithography and ion beam etching. Al2O3 sol (25 wt% concentration) is then spin-coated and annealed at 250°C to form a thermal insulation layer (1 μm thick, thermal conductivity <2 W / m·K) covering the surface of the heaters.

[0123] Sensitive layer coating and annealing: The SnO2 / ZnO / CuO nanospheres obtained in Preparation Example 1 were mixed with terpineol at a mass ratio of 1:6 and ground to form a uniform slurry; the slurry was coated onto the surface of the Al2O3 layer (10 μm thick) by screen printing, covering the Au interdigitated electrodes (20 μm wide and 30 μm spaced); annealing was carried out in air at 350°C for 1 hour to remove the organic binder and form a porous sensitive layer.

[0124] Comparative Example 1

[0125] The sensor described in this comparative example (pure SnO2) uses pure SnO2 nanomaterials, and the remaining fabrication processes (MEMS micro-hot plate, electrodes, encapsulation) are exactly the same as in Example 1, labeled as S-pure. This control is used to verify the synergistic effect of ternary composite materials.

[0126] Comparative Example 2

[0127] The sensor described in this comparative example (SnO2 / ZnO binary): uses the SnO2 / ZnO binary nanomaterial prepared in Comparative Preparation Example 1, and the remaining processes are exactly the same as in Example 1, labeled as SZ-binary. This comparative example is used to verify the necessity of introducing CuO to form a pn heterojunction.

[0128] Comparative Example 3

[0129] The sensor described in this comparative example (SnO2 / CuO binary): used the same SnO2 / CuO binary nanomaterial as that prepared in Comparative Preparation Example 2, and the remaining processes were exactly the same as in Example 1, labeled as SC-binary. This control was used to verify the role of ZnO in modulating the band structure and gas-sensitive response.

[0130] Experimental Example

[0131] This embodiment further calibrates and tests the performance of the sensors prepared in Example 1 and Comparative Examples 1-3.

[0132] 1. Sensitivity Calibration

[0133] Introduce 0.1~100 ppm CO (with N2 as the balance gas) into a standard air chamber and record the rate of change of sensor resistance (R). a / R g ).

[0134] Install the sensor in the test chamber and introduce high-purity N2 as the baseline gas at a flow rate of 500 mL / min for 30 minutes until the sensor resistance value stabilizes (fluctuation <1%). Record the baseline resistance value R at this point. a (Resistance in air).

[0135] Different concentrations of CO exhaust gas (0.1, 0.5, 1, 5, 10, 50, 100 ppm) were sequentially introduced through a dynamic gas mixing system. Ventilation was maintained for 10 minutes at each concentration point, and the sensor resistance value R was recorded under steady-state conditions. g (Resistance in the gas). After testing at each concentration point, the test chamber was cleaned with high-purity N2 for 20 minutes to restore the baseline.

[0136] Calculate the sensor response value at each concentration point, defined as the rate of change of resistance: Response value = R a / R g .

[0137] Repeat the above steps 3 times and take the average value as the final response value.

[0138] The results are attached. Figure 5 The curve shown.

[0139] The results showed that when the exhaust gas reached 5 ppm CO, the response value was ≥15, the detection limit was 0.1 ppm (signal-to-noise ratio SNR=3), and the linearity R... 2 >0.99.

[0140] 2. Cross-interference test

[0141] 100 ppm of H2, CH4, NO2, and C2H5OH were introduced into the sensor respectively, and its response value was measured.

[0142] The sensor was installed in the test chamber, and high-purity N2 was introduced as the baseline gas at a flow rate of 500 mL / min for 30 minutes until the sensor resistance value stabilized. The baseline resistance value R at this point was recorded. a .

[0143] Turn off N2, introduce 100 ppm CO standard gas, maintain for 10 minutes, and record the resistance value R of the sensor after it stabilizes. g (CO). This response value S co =R a / R g (CO) will be used as the benchmark for calculating cross sensitivity.

[0144] The test chamber was cleaned with high-purity N2 for 20 minutes to restore the sensor resistance to the baseline.

[0145] The following interfering gases are introduced in sequence:

[0146] ① Introduce 100 ppm H2, maintain for 10 minutes, and record the resistance value R after stabilization. g (H2), calculate the response value ;

[0147] ② Clean the test chamber with N2 until it reaches the baseline;

[0148] ③ Repeat the above process to test 100 ppm CH4, 10 ppm NO2, and 50 ppm C2H5OH respectively, and calculate the respective response values. .

[0149] The test for each interfering gas was repeated 3 times, and the average value of the response was used for calculation.

[0150] The test results of this experiment show that the sensor prepared in this invention has a cross sensitivity of <5% for H2 / CH4 and <3% for NO2 / C2H5OH.

[0151] 3. Long-term stability verification

[0152] In this experimental example, it was continuously operated for 6 months in an environment of 85% humidity and 40℃ to test its long-term stability.

[0153] Before the test began, the initial response value S0 of all sensors to 5 ppm CO was measured under standard conditions (25°C, 50% RH).

[0154] The sensor was continuously powered on in the test environment and operated in an intermittent mode (1 hour of active measurement per day).

[0155] Subsequently, the sensor was removed monthly and its response value S to 5 ppm CO was measured again under the same standard conditions.

[0156] The test results for this experiment are attached. Figure 6 As shown, (a) represents the power consumption result in continuous mode; and (b) represents the power consumption result in on-demand mode.

[0157] As can be seen, the response value attenuation rate of the sensor prepared by this invention is <5% (compared to >30% for conventional sensors).

[0158] 4. Response / Recovery Time Test

[0159] In this experimental example, a response / recovery time test was conducted to evaluate the sensor's dynamic response speed to changes in CO concentration.

[0160] Under standard testing conditions (25℃, 50% RH), a dynamic gas mixing system was used to rapidly switch the gas in the test chamber from high-purity N2 to 5 ppm CO within 1 second, and then quickly switch back to high-purity N2. The gas flow rate was 500 mL / min.

[0161] The specific testing steps are as follows:

[0162] ① The sensor remains stable in an N2 environment, and the baseline resistance R0 is recorded;

[0163] ② Quickly introduce 5 ppm CO and continuously record the change in resistance over time until the resistance reaches 90% of the stable value R0. This period is defined as the response time T. 90 ;

[0164] ③ Quickly switch back to high-purity N2 and continuously record the resistance value until the resistance recovers from R0 to 90% of the initial baseline resistance R0. This period is defined as the recovery time T. 10 .

[0165] In this experimental example, the response time T of the sensor to 5 ppm CO was tested. 90 <10 seconds, recovery time T 10 <15 seconds.

[0166] The results show that the sensor can quickly capture sudden changes in CO concentration and reset in time, meeting the needs of ship environments for real-time monitoring and rapid alarm.

[0167] 5. Power Consumption Test

[0168] In this experimental example, in order to verify the low power consumption characteristics of the sensor, its power consumption in different operating modes was accurately measured.

[0169] Test equipment: A high-precision digital source meter was used to power the sensor and simultaneously measure its voltage and current during operation. A digital multimeter was used to monitor the real-time voltage across the Pt heating resistor.

[0170] The specific testing steps are as follows:

[0171] ① In CO-free air, adjust the heating voltage to stabilize the micro-heating plate at an operating temperature of 120℃. Record the operating voltage and current at this time, and calculate the steady-state power consumption. ;

[0172] ② Simulate intermittent operation mode in practical applications: Set the sensor to perform a measurement every 5 minutes. Each measurement cycle is as follows: heat the micro-hotplate from room temperature to 120°C within 1 second, maintain this temperature for 30 seconds to collect data, and then turn off the heater to enter sleep mode. Record the current-time curve for one complete cycle and calculate the average power consumption.

[0173] In this experimental example, the steady-state power consumption of the sensor at 120℃ was tested to be 18mW; in intermittent operation mode, its annual average power consumption was <3mW.

[0174] This result fully demonstrates that the present invention achieves extremely low energy consumption through MEMS micro-hot plate and intelligent circuit design, which can extend battery life to more than 10 years.

[0175] 6. Environmental adaptability test

[0176] To verify the reliability of the sensor in the complex environment of a ship's cabin, this experimental example tested its performance fluctuations under different temperature and humidity conditions.

[0177] The test was conducted in a climate chamber with controlled temperature and humidity. The CO concentration was fixed at 5 ppm, and the temperature and humidity of the test environment were varied.

[0178] The specific testing steps are as follows:

[0179] ① Set the ambient humidity to 50% RH, change the temperature (-20°C, 0°C, 25°C, 40°C, 60°C), and measure the sensor response value after the temperature stabilizes at each temperature point;

[0180] ② Set the ambient temperature to 25°C and vary the relative humidity (30% RH, 70% RH, 85% RH, 95% RH). After the humidity stabilizes at each point, measure the sensor's response value. This test simultaneously disables and enables the dynamic temperature control algorithm to verify its compensation effect.

[0181] The test results for this experimental example are as follows:

[0182] ① Within the temperature range of -20℃ to 60℃, the sensor response value fluctuates by less than ±8%, demonstrating good stability in a wide temperature range.

[0183] ② When the humidity increases from 30% RH to 95% RH, the uncompensated response value decreases by approximately 25%;

[0184] ③ After enabling the dynamic temperature control algorithm, the fluctuation of the sensor response value is suppressed to within ±5% within the same humidity change range.

[0185] This result demonstrates that the dynamic temperature control strategy employed in this invention can effectively counteract the interference of high humidity environments, greatly improving the sensor's environmental adaptability and data reliability in real-world applications.

[0186] 7. Comparison with other sensors

[0187] In this experimental example, the performance of traditional SnO2 sensors and electrochemical sensors in the existing technology was compared, and the results are summarized in Table 1 below.

[0188] Table 1 Comparison of Sensor Performance Indicators

[0189]

[0190] As can be seen, the CO exhaust gas sensor described in this invention has the characteristics of high sensitivity, low power consumption, strong anti-interference ability and strong environmental adaptability.

[0191] 8. Comparison with the comparative scheme sensor

[0192] The sensors described in Example 1 and Comparative Examples 1-3 were subjected to parallel experiments under the same test conditions (such as the sensitivity, cross-interference, and stability test methods described in the previous experimental examples). The comparison results of key performance indicators are summarized in Table 2 below.

[0193] Table 2 Sensor Performance Comparison Table

[0194]

[0195] Analysis of the experimental data above demonstrates that the ternary heterojunction sensor of this invention possesses synergistic advantages. The sensor of this invention significantly outperforms single-material and binary material sensors in all key performance indicators. This proves that the pn heterojunction formed by SnO2, ZnO, and CuO effectively reduces the reaction activation energy and improves the selectivity and sensitivity to CO exhaust gas.

[0196] The sensor of this invention also has excellent selectivity and stability: the sensor of this invention has extremely low cross sensitivity to interfering gases such as H2, and exhibits excellent long-term stability in high temperature and high humidity environments. This is due to the intrinsic properties of ternary materials and the compensation effect of dynamic temperature control algorithm, which effectively overcomes the inherent defects of traditional MOX sensors.

[0197] In summary, the CO exhaust gas sensor described in this invention features high sensitivity, low power consumption, strong anti-interference ability, and strong environmental adaptability.

[0198] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A semiconductor CO exhaust gas sensor for ships, characterized in that, Including MEMS micro heating plates; The MEMS micro-heating plate includes a silicon substrate, and sequentially deposited insulating layer, heat insulation layer, heating element, and sensitive material layer; wherein, The sensitive material forming the sensitive material layer includes SnO2 / ZnO / CuO ternary porous nanomaterials.

2. The marine semiconductor CO exhaust gas sensor according to claim 1, characterized in that, In the MEMS micro heating plate: The insulating layer includes a SiO2 material layer; and / or, The thermal insulation layer includes an Al2O3 material layer; and / or, The heating element includes a Pt heating resistor.

3. The semiconductor CO exhaust gas sensor for ships according to claim 2, characterized in that, In the MEMS micro heating plate: The thickness of the insulating layer is 0.8-1.2 μm; and / or, The thickness of the insulation layer is 0.8-1.2 μm; and / or, The heating elements are arranged in a serpentine pattern.

4. The marine semiconductor CO exhaust gas sensor according to any one of claims 1-3, characterized in that, The semiconductor CO exhaust gas sensor further includes an encapsulation layer and an electrode layer; wherein... The encapsulation layer includes a PTFE film and an encapsulation framework; and / or, The electrode layer includes Au interdigitated electrodes.

5. A method for preparing a semiconductor CO exhaust gas sensor for ships as described in any one of claims 1-4, characterized in that, The steps involved in fabricating the MEMS micro heating plate include the following steps: S1. The desired SnO2 / ZnO / CuO ternary porous nanomaterials were synthesized by the sol-gel method, and the sensitive material slurry was prepared. S2. The insulating layer and the heat insulation layer are sequentially deposited on the surface of the silicon substrate, and the heating element is integrated to obtain the MEMS micro heating plate substrate; S3. The sensitive material slurry is coated onto the surface of the MEMS micro heating plate substrate, and the sensitive material layer is formed by annealing to obtain the desired MEMS micro heating plate.

6. The method for preparing a semiconductor CO exhaust gas sensor for ships according to claim 5, characterized in that, Step S1 specifically includes: S11. Dissolve SnCl4·5H2O:Zn(NO3)2·6H2O:Cu(NO3)2·3H2O = (4-6):(2-4):(1-3) in an ethanol-water mixed solvent, add 8-12wt% template agent and mix to obtain a sol. S12. The sol is subjected to a hydrothermal reaction at 60-100℃, and after centrifugation and drying, it is calcined at 400-600℃ under a protective atmosphere to obtain ternary porous nanospheres. S13. Mix the ternary porous nanospheres with terpineol at a mass ratio of 1:(4-6) to obtain the desired sensitive material slurry.

7. The method for preparing a semiconductor CO exhaust gas sensor for ships according to claim 5, characterized in that, Step S2 specifically includes: S21. A SiO2 insulating layer is deposited on the surface of the silicon substrate, and Pt heating resistors are integrated to form a serpentine arrangement; S22. 15-25wt% Al2O3 sol is spin-coated and annealed at 250-350℃ to form an Al2O3 heat insulation layer. S23. Simulate the heater temperature distribution using COMSOL to ensure that the temperature uniformity error in the central area is ≤ ±2℃.

8. The method for preparing a semiconductor CO exhaust gas sensor for ships according to claim 5, characterized in that, Step S3 specifically includes: S31. The sensitive material paste is coated onto the surface of the MEMS micro heating plate substrate by screen printing, and the coating thickness is controlled to be 5-15μm. S32. The MEMS micro heating plate substrate is annealed in air at 300-400℃ to obtain the final product.

9. The method for preparing a marine semiconductor CO exhaust gas sensor according to any one of claims 5-8, characterized in that, The method further includes: S4. Install electrodes and design a differential Wheatstone bridge and a lock-in amplifier circuit, and integrate the signal processing circuit with a dynamic temperature control algorithm; S5. Encapsulate the MEMS micro heating plate with a PTFE breathable membrane and a stainless steel skeleton to obtain the required semiconductor CO exhaust gas sensor.

10. The application of the semiconductor CO exhaust gas sensor for ships according to any one of claims 1-4 in the field of ship environmental monitoring.

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