Preparation method of precious metal modified WO3 gas sensor

Abstract

The invention belongs to the technical field of MEMS gas sensors, and particularly relates to a preparation method of a precious metal modified WO3 gas sensor. Comprising the following steps: step 1, weighing a proper amount of crystallized ammonium paratungstate (H42N10O42W12. XH2O), putting the weighed crystallized ammonium paratungstate in a sintering vessel, putting the sintering vessel in a high-temperature sintering furnace, and carrying out temperature programming; step 2, adding water into a product obtained in the step 1 to prepare a suspension, and loading the suspension onto an MEMS chip; 3, placing the chip in the step 2 in a high-temperature sintering furnace, and carrying out temperature programming; 4, placing the chip annealed in the step 3 in a magnetron sputtering instrument, and sputtering precious metal on the surface of the material; step 5, packaging the chip in the step 4 into an MEMS sensor through an MEMS packaging process; through cooperation of all the steps, the precious metal modified WO3 gas sensor prepared by the method has very high response to gas generated by heating a cable shell, the base line of the sensor in the air is stable, and the sensor can be used for detecting the early stage of a fire disaster to achieve the purpose of early warning of the cable fire disaster.

Description

Technical Field

[0001] The invention belongs to the technical field of MEMS gas sensors, and in particular relates to a method for preparing a noble metal modified WO3 gas sensor. Background Art

[0002] With the rapid development of the economy, the demand for power construction is also increasing, and the application of power cables is extremely extensive. As the application of power cables expands, the fires caused by them are also increasing. The occurrence of cable fire accidents has the hazards of burning cables and equipment, resulting in direct power outages, long repair time, delayed production, and serious impact on the production progress, efficiency and economic benefits of enterprises.

[0003] The main causes of power cable fire accidents are cable damage, poor contact, cable short circuit and line overload. These reasons will cause the cable to overheat, which will then cause a fire. Power cable fires are mainly divided into three stages: the first stage is the early stage of the fire, when the cable core conductor heats up, and the heat accumulates in abnormal parts, forming a local temperature rise and releasing organic gases; the second stage is the early stage of the fire, when the cable is in a smoldering state, accompanied by a large amount of smoke; the third stage is the late stage of the fire, when a large amount of open flames and thick smoke appear in the cable, and the fire spreads rapidly. Power cable materials are mainly polymer materials, such as polyvinyl chloride, cross-linked polyethylene, etc., which will release a large amount of gas when the temperature is too high or a fire occurs.

[0004] The existing MEMS gas sensors have low sensitivity to the gas released by the cable sheath when it is heated, and the sensor curve fluctuates greatly in the air, which is not conducive to the practical application of cable fire warning. A MEMS gas sensor with high sensitivity to the gas released when the cable is heated, fast response and good stability has been developed, which can be used to detect the early stage of fire and achieve the purpose of cable fire warning. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a method for preparing a noble metal modified WO3 gas sensor which has high sensitivity to the gas released by the cable sheath when heated and small baseline fluctuation in the air.

[0006] The object of the present invention is achieved by: a method for preparing a noble metal modified WO3 gas sensor, which comprises the following steps: Step 1: Weigh an appropriate amount of crystalline ammonium paratungstate (H 42 N 10 O 42 W 12 xH2O) in a sintering dish, placed in a high-temperature sintering furnace, and programmed to heat; Step 2, adding water to the product obtained in step 1 to prepare a suspension, and loading it onto the MEMS chip; Step 3, placing the chip in step 2 in a high-temperature sintering furnace and performing programmed temperature increase; Step 4, placing the chip annealed in step 3 in a magnetron sputtering device to sputter precious metals on the surface of the material; Step 5: Use the MEMS packaging process to package the chip in step 4 into a MEMS sensor.

[0007] For better effect, the material in step 1 is placed in a high-temperature sintering furnace and programmed to heat up at a rate of 3°C / min.

[0008] For better effect, the step 1 is placed in a high temperature sintering furnace and programmed to heat up to 600° C. at a heating rate of 3° C. / min, and then sintered at 600° C. for 2 h.

[0009] For better effect, the product obtained in step 1 is added with water to prepare a suspension, which is then loaded onto the MEMS chip, specifically, the prepared suspension is loaded onto the interdigital electrode region of the MEMS chip.

[0010] For better effect, in step 3, the chip in step 2 is placed in a high-temperature sintering furnace and programmed to heat up at a rate of 1°C / min.

[0011] For better effect, in step 3, the chip in step 2 is placed in a high-temperature sintering furnace and programmed to heat up to 500° C. at a heating rate of 1° C. / min, and then sintered at 500° C. for 2 hours.

[0012] For better effect, in step 3, the chip in step 2 is placed in a high-temperature sintering furnace, programmed to heat up, sintered at 500° C. for 2 hours, and then cooled naturally.

[0013] For better effect, in step 4, the chip annealed in step 3 is placed in a magnetron sputtering device to sputter precious metals on the surface of the material, and the power is set to 60W during sputtering.

[0014] For better effect, in step 4, the chip annealed in step 3 is placed in a magnetron sputtering device to sputter precious metal on the surface of the material, and the sputtering time is set to 10-40s.

[0015] For better effect, in step 4, the chip annealed in step 3 is placed in a magnetron sputtering device to sputter precious metal on the surface of the material, and the sputtered precious metal is Pt or Au.

[0016] Beneficial effects of the present invention: A method for preparing a noble metal modified WO3 gas sensor of the present invention comprises the steps of: 1. weighing an appropriate amount of crystalline ammonium paratungstate (H 42 N 10 O42 W 12 ·xH2O) in a sintering dish, placing it in a high-temperature sintering furnace, and performing a programmed temperature increase; step 2, adding water to the product obtained in step 1 to prepare a suspension, and loading it onto a MEMS chip; step 3, placing the chip in step 2 in a high-temperature sintering furnace, and performing a programmed temperature increase; step 4, placing the chip annealed in step 3 in a magnetron sputtering instrument, and sputtering precious metals on the surface of the material; step 5, packaging the chip in step 4 into a MEMS sensor through a MEMS packaging process; through the coordination of the steps, the precious metal-modified WO3 gas sensor prepared by the present invention has a high response to the gas generated by the heating of the cable casing, and the baseline of the sensor in the air is stable, which can be used to detect the early stage of fire and achieve the purpose of cable fire early warning. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a schematic flow chart of a method for preparing a noble metal modified WO3 gas sensor.

[0018] Figure 2 It is a schematic diagram of the response curves of different sensors to the gas released by the YJV22 cable at different heating temperatures in the preparation method of the precious metal modified WO3 gas sensor of the present invention.

[0019] Figure 3 It is a schematic diagram of the response curves of different sensors to the gas released by the YJY23 cable at different heating temperatures in the preparation method of the precious metal modified WO3 gas sensor of the present invention.

[0020] Figure 4 It is a schematic diagram of the resistance fluctuation curves of different sensors in the air in a method for preparing a noble metal-modified WO3 gas sensor of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings.

[0022] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0023] The following will be combined with the drawings in the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Noble metal modification can significantly improve the sensing performance of semiconductor metal oxide (SMOs) gas sensors. Its internal mechanism can be summarized into two main aspects, namely, the electronic sensitization effect introduced by metal-semiconductor contact and the chemical sensitization effect introduced by the spillover effect. First, during the electronic sensitization process, due to the work function difference between the noble metal and the semiconductor, the electrons in the n-type SMO or the holes in the p-type SMO will be transferred between the noble metal and the SMOs until the Fermi level is balanced. The resulting gold-semiconductor contact will affect the carrier transport and the change of gas sensing performance. Secondly, during the chemical sensitization process, the noble metal has excellent catalytic properties, which can promote the dissociation of oxygen molecules on the surface of the material and produce more reactive chemically adsorbed oxygen. These chemically adsorbed oxygen will be distributed on the surface of the SMOs material in large quantities due to the spillover effect and will react with more target gas molecules. Therefore, the chemical sensitization effect is also called the spillover effect.

[0025] At the same time, noble metal modification can also effectively improve the selectivity of SMOs gas sensors, and its related mechanisms can be discussed from three aspects. First, the specific reaction between specific noble metals and specific gases. Second, the intensity of the coupling effect between specific noble metals and gas molecules will affect the improvement of selectivity. Third, since the adsorption of gas molecules on the surface of noble metals is a prerequisite for any possible catalytic reaction, the selective adsorption of gas molecules on the surface of specific noble metals at different temperatures will also affect the selectivity of the noble metal-modified SMOs sensor.

[0026] The present invention is based on a WO3 gas sensor and provides a method for preparing a noble metal modified WO3 gas sensor, comprising the following steps: Step 1: Weigh an appropriate amount of crystalline ammonium paratungstate (H 42 N 10 O 42 W 12 xH2O) in a sintering dish, placed in a high-temperature sintering furnace, and programmed to heat; Step 2, adding water to the product obtained in step 1 to prepare a suspension, and loading it onto the MEMS chip; Step 3, placing the chip in step 2 in a high-temperature sintering furnace and performing programmed temperature increase; Step 4, placing the chip annealed in step 3 in a magnetron sputtering device to sputter precious metals on the surface of the material; Step 5: Use the MEMS packaging process to package the chip in step 4 into a MEMS sensor.

[0027] For better effect, in one embodiment, the step 1 is placed in a high temperature sintering furnace and programmed to heat up at a rate of 3° C. / min.

[0028] For better effect, in one embodiment, the step 1 is placed in a high temperature sintering furnace and programmed to heat up to 600° C. at a heating rate of 3° C. / min, and then sintered at 600° C. for 2 h.

[0029] For better effect, in one embodiment, the product obtained in step 1 is added with water to prepare a suspension, which is then loaded onto the MEMS chip, specifically, the prepared suspension is loaded onto the interdigital electrode region of the MEMS chip.

[0030] For better effect, in one embodiment, in step 3, the chip in step 2 is placed in a high-temperature sintering furnace and programmed to heat up at a rate of 1° C. / min.

[0031] For better effect, in one embodiment, in step 3, the chip in step 2 is placed in a high-temperature sintering furnace, programmed to heat up to 500°C at a heating rate of 1°C / min, and then sintered at 500°C for 2h.

[0032] For better effect, in one embodiment, in step 3, the chip in step 2 is placed in a high-temperature sintering furnace, programmed to increase the temperature, sintered at 500° C. for 2 hours, and then cooled naturally.

[0033] For better effect, in one embodiment, in step 4, the chip annealed in step 3 is placed in a magnetron sputtering device to sputter precious metals on the surface of the material, and the power is set to 60W during sputtering.

[0034] For better effect, in one embodiment, in step 4, the chip annealed in step 3 is placed in a magnetron sputtering device to sputter precious metal on the surface of the material, and the sputtering time is set to 10 to 40 seconds.

[0035] For better effect, in one embodiment, in step 4, the chip annealed in step 3 is placed in a magnetron sputtering device to sputter precious metal on the surface of the material, and the sputtered precious metal is Pt or Au.

[0036] In combination with the above, a specific embodiment of a method for preparing a noble metal modified WO3 gas sensor of the present invention comprises the following steps: Step 1: Weigh an appropriate amount of crystalline ammonium paratungstate (H 42 N 10 O 42 W 12 xH2O) in a sintering dish, placed in a high-temperature sintering furnace, programmed temperature rise, heating rate 3℃ / min, sintered at 600℃ for 2h; Step 2, adding water to the product obtained in step 1 to prepare a suspension, and loading the suspension into the interdigital electrode region of the MEMS chip; Step 3: Place the chip in step 2 in a high-temperature sintering furnace, use programmed heating, heating rate 1°C / min, sinter at 500°C for 2h, and cool naturally; Step 4, placing the chip annealed in step 3 in a magnetron sputtering instrument, setting the power to 60 W, sputtering the precious metal Pt on the surface of the material, and setting the sputtering time to 10-40 s; Step 5: Use the MEMS packaging process to package the chip in step 4 into a MEMS sensor.

[0037] In combination with the above, another specific embodiment of a method for preparing a noble metal modified WO3 gas sensor of the present invention comprises the following steps: Step 1: Weigh an appropriate amount of crystalline ammonium paratungstate (H 42 N 10 O 42 W 12 xH2O) in a sintering dish, placed in a high-temperature sintering furnace, programmed temperature rise, heating rate 3℃ / min, sintered at 600℃ for 2h; Step 2, adding water to the product obtained in step 1 to prepare a suspension, and loading the suspension into the interdigital electrode region of the MEMS chip; Step 3: Place the chip in step 2 in a high-temperature sintering furnace, use programmed heating, heating rate 1°C / min, sinter at 500°C for 2h, and cool naturally; Step 4: Place the chip annealed in step 3 in a magnetron sputtering instrument, set the power to 60 W, sputter the precious metal Au on the surface of the material, and set the sputtering time to 10-40 s; Step 5: Use the MEMS packaging process to package the chip in step 4 into a MEMS sensor.

[0038] For the WO3 gas sensor prepared by the present invention, Figure 2 (Response curves of different sensors to the gas released by YJV22 cable at different heating temperatures) are shown in the figure, where R0 is the resistance of the sensor in the air; Rs is the resistance of the sensor under the target gas; the sensitivity of the sensor to the gas S=Rs / R0. The smaller the value, the higher the sensitivity of the sensor to the gas; 20Au / WO3 means magnetron sputtering of Au target material for 20s at a power of 60W, and the rest are similar; from Figure 2 It can be seen that the sensitivity of pure WO3 sensor to the gas released by YJV22 cable at different heating temperatures is low, while the sensitivity of the sensor with surface sputtered precious metal Au or Pt is significantly improved.

[0039] like Figure 3(The response curves of different sensors to the gas released by YJY23 cable at different heating temperatures) are shown in Figure 2. Figure 3 It can be seen that the sensitivity of pure WO3 sensor to the gas released by YJY23 cable at different heating temperatures is low, while the sensitivity of the sensor with surface sputtered precious metal Au or Pt is significantly improved.

[0040] like Figure 4 (Resistance fluctuation curve of different sensors in air) Figure 4 It can be seen that the resistance value of the pure WO3 sensor in the air fluctuates greatly, but after sputtering precious metal Au or Pt on the WO3 surface, the fluctuation of the sensor in the air is significantly reduced and the stability is improved.

[0041] In summary, a method for preparing a noble metal modified WO3 gas sensor of the present invention comprises the steps of: 1. weighing an appropriate amount of crystalline ammonium paratungstate (H 42 N 10 O 42 W 12 ·xH2O) in a sintering dish, placing it in a high-temperature sintering furnace, and performing a programmed temperature increase; step 2, adding water to the product obtained in step 1 to prepare a suspension, and loading it onto a MEMS chip; step 3, placing the chip in step 2 in a high-temperature sintering furnace, and performing a programmed temperature increase; step 4, placing the chip annealed in step 3 in a magnetron sputtering instrument, and sputtering precious metals on the surface of the material; step 5, packaging the chip in step 4 into a MEMS sensor through a MEMS packaging process; through the coordination of the steps, the precious metal-modified WO3 gas sensor prepared by the present invention has a high response to the gas generated by the heating of the cable casing, and the baseline of the sensor in the air is stable, which can be used to detect the early stage of fire and achieve the purpose of cable fire early warning.

[0042] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0043] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a noble metal modified WO3 gas sensor, characterized in that: It includes the following steps: Step 1: Weigh an appropriate amount of crystalline ammonium paratungstate (H 42 N 10 O 42 W 12 xH2O) in a sintering dish, placed in a high-temperature sintering furnace, and programmed to heat; Step 2: Add water to the product obtained in step 1 to prepare a suspension, and load it onto the MEMS chip; Step 3: Place the chip in step 2 in a high-temperature sintering furnace and perform programmed temperature increase; Step 4: Place the chip annealed in step 3 in a magnetron sputtering device to sputter precious metals on the surface of the material; Step 5: Use the MEMS packaging process to package the chip in step 4 into a MEMS sensor.

2. The method for preparing a noble metal-modified WO3 gas sensor according to claim 1, wherein: The sintering furnace in step 1 is placed in a high temperature sintering furnace and programmed to heat up at a heating rate of 3°C / min.

3. The method for preparing a noble metal-modified WO3 gas sensor according to claim 2, wherein: The material in step 1 is placed in a high-temperature sintering furnace and programmed to heat up to 600° C. at a heating rate of 3° C. / min, and then sintered at 600° C. for 2 h.

4. The method for preparing a noble metal-modified WO3 gas sensor according to claim 1, wherein: The product obtained in step 1 is added with water to prepare a suspension, which is then loaded onto the MEMS chip. Specifically, the suspension is loaded onto the interdigital electrode region of the MEMS chip.

5. The method for preparing a noble metal modified WO3 gas sensor according to claim 1, wherein: In step 3, the chip in step 2 is placed in a high-temperature sintering furnace and programmed to heat up at a heating rate of 1°C / min.

6. The method for preparing a noble metal-modified WO3 gas sensor according to claim 5, wherein: In the step 3, the chip in step 2 is placed in a high-temperature sintering furnace, programmed to heat up to 500° C. at a heating rate of 1° C. / min, and then sintered at 500° C. for 2 hours.

7. The method for preparing a noble metal modified WO3 gas sensor according to claim 6, wherein: In the step 3, the chip in step 2 is placed in a high-temperature sintering furnace, programmed to heat, sintered at 500° C. for 2 hours, and then cooled naturally.

8. The method for preparing a noble metal modified WO3 gas sensor according to claim 1, wherein: In the step 4, the chip annealed in the step 3 is placed in a magnetron sputtering device to sputter precious metal on the surface of the material, and the power during sputtering is set to 60W.

9. The method for preparing a noble metal modified WO3 gas sensor according to claim 8, wherein: In step 4, the chip annealed in step 3 is placed in a magnetron sputtering device to sputter precious metal on the surface of the material, and the sputtering time is set to 10 to 40 seconds.

10. The method for preparing a noble metal modified WO3 gas sensor according to claim 9, wherein: In step 4, the chip annealed in step 3 is placed in a magnetron sputtering device to sputter a precious metal on the surface of the material, wherein the sputtered precious metal is Pt or Au.

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