CN114839231B - Anti-interference gas-sensitive coating for semiconductor combustible gas sensor and preparation method and application thereof - Google Patents
Anti-interference gas-sensitive coating for semiconductor combustible gas sensor and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses an anti-interference gas-sensitive coating for a semiconductor combustible gas sensor, which is formed by coating and sintering mixed slurry, wherein the mixed slurry is prepared from the following raw materials: tin oxide, stannous sulfate, acid-washed asbestos, a catalytic carrier, a noble metal catalyst, tungsten trioxide, magnesium oxide, vanadium pentoxide, antimony pentoxide, tetraethyl silicate, formic acid, ethylene glycol, N-methylpyrrolidone, absolute ethyl alcohol and pure water; the invention also discloses a preparation method of the anti-interference gas-sensitive coating and application of the anti-interference gas-sensitive coating in a semiconductor combustible gas sensor. According to the invention, through the raw material collocation and coating process control of the anti-interference gas-sensitive coating, the sensitivity and stability of the gas-sensitive element are improved, the consistency of the gas-sensitive element is promoted, the anti-interference of the organic volatile gas containing hydroxyl of the semiconductor combustible gas sensor can be realized only by coating a single-layer gas-sensitive coating, the automatic production is convenient, the manufacturing cost is reduced, and the anti-interference gas-sensitive coating has good application effect and industrialization prospect.
Description
Technical Field
The invention belongs to the technical field of semiconductor gas sensors, and particularly relates to an anti-interference gas-sensitive coating for a semiconductor combustible gas sensor, and a preparation method and application thereof.
Background
The semiconductor gas sensor takes metal oxide as a gas-sensitive material, and the working principle of the semiconductor gas sensor is that the resistance value of the oxide is changed when the gas to be detected is subjected to oxidation/reduction reaction on the surface of the semiconductor metal oxide at a certain working temperature. The sensor has excellent gas-sensitive performance, wide measurement range, relatively simple manufacturing process and low price, is convenient for integrating and constructing a wireless sensor network, and is widely applied to monitoring of carbon oxides, nitrogen oxides, volatile organic compounds and other toxic, inflammable, explosive, polluted gases and the like. However, the operating temperature of the semiconductor sensor is generally above 200 ℃, which poses a threat to the life of the material while increasing energy consumption, and as the operating time of the semiconductor gas sensor is prolonged, zero drift and sensitivity decrease occur, and the response/recovery speed to the target gas is reduced. In contrast, the ability of the gas sensitive material to be interfered by external factors such as ambient temperature, humidity and air quality is to be improved, so as to enhance the repeatability and stability of the semiconductor gas sensor.
In order to solve the problem of cross interference of multi-component gas during detection, a patent with the application number of CN202010931457.X discloses an anti-gas interference MEMS gas sensor, wherein an oxide layer, a metal electrode layer, an insulating layer, a gas sensitive material layer and a separation membrane are sequentially formed on a silicon substrate; the aperture of the nano channel of the separation membrane is smaller than the movement diameter of the interference gas molecules, and the interference gas molecules are collided in the nano channel of the separation membrane in a large amount and cannot pass through the separation membrane by adding the separation membrane, so that the interference gas is blocked, the influence of the interference gas on the gas-sensitive material in the sensor is avoided, and the detection accuracy is improved.
In order to improve the sensitivity, selectivity and stability of the gas sensitive material, the base material is usually doped and modified, wherein the noble metal is doped with tin oxide (SnO) 2 ) Gas sensitive material applications are particularly commonHowever, when the noble metal catalyst (such as Pt, pb, au, ag, etc.) is used in some special gas atmospheres, the problems of catalyst poisoning, deactivation, etc. are easily caused, so that the gas-sensitive response characteristic of the sensor to the gas to be measured is deteriorated, and even the gas-sensitive activity is lost, which affects the use of the gas sensor to a certain extent. In order to avoid the deactivation of the gas sensitive material, patent application No. CN201810156850.9 discloses a double-coating methane gas sensor resisting organosilicon poisoning, and the adopted double coating is Pd (OAc) 2 Supported nano SnO 2 Microsphere sensitive material layer and Pt-doped Al 2 O 3 And SiO 2 The mixed antitoxic catalytic layer decomposes the easy-to-poison gas and the interference gas through the antitoxic catalytic layer on the surface of the sensitive material layer.
At present, no matter a separation film or an antitoxic catalytic layer is added in the prior art, a gas sensitive element of a semiconductor gas sensor adopts a double-layer coating to realize anti-interference, the first layer is a thick-film type gas sensitive material coating and is made of SnO 2 The detection device is formed by mixing and coating semiconductor elements, realizes catalytic decomposition of reducing gas through charge transfer in the working process, and further completes detection of combustible gas; the second layer is made of SiO-containing 2 The solution of the components is coated, the rare earth element and/or the noble metal catalyst in the first layer of coating is coated, partial material gaps are filled, the surface binding force is increased, and the blocking or decomposition of interference gas is realized. However, in the processing process of the gas sensitive element, each parameter is not easy to regulate and control through multiple coating processes, the consistency of the gas sensitive element under multiple processes is difficult to guarantee, and the related equipment and energy consumption cost are high. Under the restriction of double-layer coating, because first coating thickness difference, there is the difference in height when leading to the printing coating of second time, can not reach lithography apparatus's level counterpoint, and then can only artifical manual coating, can't realize automatic coating, production efficiency is low. Moreover, after the gas sensitive element is used for a long time, the anti-interference coating is lost, or the anti-interference effect is invalid due to cracking of the secondary coating, so that the device gives a false alarm to a user in the using process.
Disclosure of Invention
Based on the defects of the prior art, the invention aims to provide the anti-interference gas-sensitive coating for the semiconductor combustible gas sensor, which can realize the anti-interference of the organic volatile gas containing hydroxyl groups by coating only a single layer; the invention also discloses a preparation method of the anti-interference gas-sensitive coating and application of the anti-interference gas-sensitive coating in a semiconductor combustible gas sensor, so that the sensitivity and stability of the gas-sensitive element are improved, and the consistency of the gas-sensitive element is improved.
In order to achieve the purpose, the invention adopts the technical scheme that:
an anti-interference gas-sensitive coating for a semiconductor combustible gas sensor is formed by coating and sintering mixed slurry, wherein the mixed slurry is prepared from the following raw materials in parts by weight: tin oxide (SnO) 2 ) 180 to 220 portions of stannous sulfate (SnSO) 4 ) 72 to 88 portions of acid-washed asbestos (CaMg) 3 (SiO 4 ) 2 ) 3.6 to 4.4 portions of catalyst carrier, 45 to 55 portions of catalyst carrier, 6.7 to 8.3 portions of noble metal catalyst and tungsten trioxide (WO) 3 ) 6.3 to 7.7 portions of magnesium oxide (MgO) 3.0 to 3.8 portions of vanadium pentoxide (V) 2 O 5 ) 2.7 to 3.3 portions of antimony pentoxide (Sb) 2 O 5 ) 1.4-1.8 parts of tetraethyl silicate (TEOS, siC) 8 H 20 O 4 ) 250 to 310 portions of formic acid (HCOOH) 330 to 400 portions of glycol (EG, (CH) 2 OH) 2 ) 100 to 125 portions of N-methyl pyrrolidone (NMP, C) 5 H 9 NO) 135-170 parts, absolute ethyl alcohol (EtOH, C) 2 H 5 OH) 140-175 parts, pure water (H) 2 O) 180 to 220 portions.
Preferably, the noble metal catalyst is prepared from platinum black (Pt) and palladium chloride (PdCl) 2 ) The mixture is prepared by mixing the following components according to the mass ratio of 4.
Preferably, the catalytic carrier adopts alumina (Al) 2 O 3 )。
The preparation method of the anti-interference gas-sensitive coating for the semiconductor combustible gas sensor comprises the following steps:
(1) Preparing raw materials of the mixed slurry according to parts by weight;
(2) Under the condition of grinding and mixing, mixing a catalytic carrier, a noble metal catalyst and pure water for 30-50 minutes, adding stannous sulfate, mixing for 20-40 minutes, heating to 120-180 ℃, keeping the temperature, mixing for 40-60 minutes, and cooling to room temperature; then adding tin oxide, absolute ethyl alcohol, N-methyl pyrrolidone, magnesium oxide, tungsten trioxide, vanadium pentoxide, antimony pentoxide, acid-washed asbestos, ethylene glycol, tetraethyl silicate and formic acid in sequence, and continuously mixing for 20-40 minutes to obtain mixed slurry;
(3) And (3) uniformly coating the mixed slurry obtained in the step (2), and sintering at 700-750 ℃ for 3-4 hours to obtain the anti-interference gas-sensitive coating.
Preferably, the mixed slurry in the step (3) is coated by a screen printing technology, and the coating thickness is 0.15-0.25 mm.
The anti-interference gas-sensitive coating is applied to a semiconductor combustible gas sensor, the semiconductor combustible gas sensor comprises a metal base and a gas-sensitive element packaged on the metal base, and the gas-sensitive element comprises a heating resistor layer, a heating electrode layer, a substrate, a test electrode layer and the anti-interference gas-sensitive coating which are sequentially arranged from bottom to top; the metal base is inserted with the heating pins and the signal measuring pins, the heating pins and the signal measuring pins are uniformly arranged in an array mode, the heating pins are electrically connected with the heating electrode layer, and the signal measuring pins are electrically connected with the testing electrode layer.
Preferably, the heating electrode layer and the testing electrode layer both adopt gear shaping electrodes, the end parts of the gear shaping electrodes are connected with conductive belts, the conductive belts are connected with leads, and the other ends of the leads are connected with the heating pins or the signal measuring pins. The metal base is provided with a required power supply for the heating resistor layer through the heating pins, so that the heating resistor layer can emit temperature under fixed conditions to the anti-interference gas-sensitive coating, the detected gas reaches the surface of the anti-interference gas-sensitive coating with fixed temperature and is subjected to oxidation-reduction reaction with free charges in the anti-interference gas-sensitive coating, the change of the resistance of the anti-interference gas-sensitive coating is caused along with charge transfer in the reaction process, the voltage change caused by the change of the resistance of the material measuring end is read through the gear shaping electrode of the testing electrode layer, and the detection of the gas concentration can be realized through the change of the voltage difference.
Preferably, the substrate is a 96% alumina substrate.
Preferably, the anti-interference gas-sensitive coating is applied to a semiconductor combustible gas sensor and is used for detecting methane, propane and isobutane gases, and resisting volatilization of alcohol and silane poisoning interference.
The raw materials of the mixed slurry and the equipment used in the preparation process are all common commercial products, and the SnO is 2 、WO 3 、MgO、V 2 O 5 、Sb 2 O 5 、Al 2 O 3 And the particle size of Pt is 50-150 nm.
The mixed slurry is SnO 2 (the energy band gap Eg is 3.5 eV) is used as a base material, and in a weakly acidic environment, bonds and reactions are carried out through unsaturated bonds of all nano materials, so that the stability of the gas sensitive element in a high-temperature working environment is improved; among them, WO 3 、MgO、V 2 O 5 The main function is to maintain the acid-base environment in the slurry preparation process, and W, mg and V and other transition elements in the formula jointly keep the balance in the sintered gas-sensitive material according to the activity of the elements; sb 2 O 5 The semiconductor characteristics of the semiconductor slurry are maintained in the mixed slurry, and the resistance value of the semiconductor slurry is adjusted; in addition, in the working process of the gas sensor, the reaction sensitivity depends on the activity and the content of the noble metal catalyst, the potential energy of the point positions of the W, V and Sb elements and the noble metal catalyst are complementary, the activity of the noble metal elements in a high-temperature environment is maintained, and the stability of the gas sensor in the working process is improved.
After high temperature sintering, snO 2 With WO 3 (Eg 2.7eV)、V 2 O 5 (Eg 2.8eV)、Sb 2 O 5 (Eg 3.0 eV) forms a semiconductor composite oxide, substitutional impurity defects and oxygen vacancy defects are generated in crystal lattices, the processes of releasing, transmitting, injecting and transporting of current carriers are facilitated, and the absorption and desorption processes and the response speed of test gas are promoted. Meanwhile, pt and PdCl are selected 2 As a noble metal catalyst, sufficiently adheres to Al by bonding 2 O 3 On a carrier, mixed with a metal oxide, may be addedThe active sites on the surface of the material are added, so that the material can adsorb more gas, electrons on the surface of the metal oxide material can be deprived, a depletion layer is formed, and when the material is exposed to reducing gas, the noble metal oxide can be rapidly reduced, so that the resistance value is obviously reduced, and the gas-sensitive property is improved. SnSO 4 Simultaneous participation in Al 2 O 3 By displacement reaction with a noble metal catalyst, SO 4 2- The stability of the noble metal element in the working process under the high-temperature condition is improved, the service life of the gas sensitive element in the whole combustible gas sensor is prolonged, and the product stability is improved.
The TEOS and pure water are hydrolyzed to generate SiO 2 By SiO 2 The surface unsaturated bond and organic volatile gas with hydroxyl (-OH) such as methanol, ethanol, etc. have bonding reaction, and the-OH group is prevented from directly contacting with noble metal catalyst in the working process, thereby reducing the interference of the gas. And, siO 2 The coupling is generated with Sb element in the formula, so that the stability of the coating of the whole device is improved, the detection of combustible gas is realized in the slurry preparation process, and the anti-interference effect can be met.
HCOOH and solvents such as EtOH, EG and the like participate in the intermediate reaction grinding agent in the reaction process to play a cross-linking effect, and the bonding force of the slurry and the substrate is increased due to the fact that the cross-linking form is matched with the acid-washing asbestos fiber in the high-temperature sintering process, and the coating is prevented from cracking in the sintering process.
The invention grinds and mixes all raw materials to prepare mixed slurry, and then coats the mixed slurry on the ceramic signal electrode surface with heating function through the screen printing technology, and forms the anti-interference gas-sensitive coating after high-temperature sintering.
Drawings
FIG. 1 is a Raman spectrum (Raman) of the tamper resistant gas sensitive coating described in example 1;
FIG. 2 is a Scanning Electron Microscope (SEM) representation of the antijamming gas-sensitive coating described in example 1;
FIG. 3 is an X-ray energy spectrum analysis (EDS) of the tamper resistant gas sensitive coating described in example 1;
FIG. 4 is a schematic structural diagram of the semiconductor combustible gas sensor;
FIG. 5 is a schematic cross-sectional view of the gas sensor of FIG. 4;
FIG. 6 is a top view of FIG. 5;
FIG. 7 is a dynamic response curve of the semiconductor combustible gas sensor to different concentrations of methane gas;
fig. 8 is a graph of the response value of the semiconductor combustible gas sensor to methane concentration when detecting methane.
Detailed Description
In order to make the technical purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention are further described below with reference to specific examples, but the examples are intended to illustrate the present invention and should not be construed as limiting the present invention, and those who do not specify any particular technique or condition in the examples are performed according to techniques or conditions described in documents in the art or according to product specifications.
The tin oxide in the following examples is purchased from Meclin, has the model number of T817641, and has the particle size of 50-70 nm; platinum black was purchased from alatin, model P113302, particle size 10nm; palladium chloride is purchased from Aladdin, model P282904, and particle size is 70nm; alumina was purchased from Michelin, model A800207, with a particle size of 150nm; stannous sulfate was purchased from alatin, model number S112918, particle size 0.1mm; magnesium oxide is available from Mecanol, model number M813080, and particle size is 100nm; tungsten trioxide is purchased from Michelin, model T818835, and has a particle size of 150nm; vanadium pentoxide is purchased from alatin, with a model of V112535, and a particle size of 80nm; antimony pentoxide was purchased from alatin, type a100109, with a particle size of 20nm; acid-washed asbestos from alatin, type a104830; tetraethyl silicate was purchased from Michael and was model T819505. The semiconductor combustible gas sensor is different from a GK4 plane semiconductor methane sensor of Henan Sensco sensing technology, inc. in coating.
Example 1
A preparation method of an anti-interference gas-sensitive coating for a semiconductor combustible gas sensor comprises the following steps:
(1) Preparing raw materials of mixed slurry:
2.0g of tin oxide, 0.8g of stannous sulfate, 0.04g of acid-washed asbestos, 0.5g of alumina, 0.06g of platinum black, 0.015g of palladium chloride, 0.07g of tungsten trioxide, 0.034g of magnesium oxide, 0.03g of vanadium pentoxide, 0.016g of antimony pentoxide, 3.0mL of tetraethyl silicate, 3.0mL of formic acid, 1.0mL of ethylene glycol, 1.5mL of N-methylpyrrolidone, 2.0mL of absolute ethyl alcohol and 2.0mL of pure water;
(2) Preparing mixed slurry:
mixing platinum black, palladium chloride, aluminum oxide and pure water for 40min by adopting planetary ball milling equipment (the volume of a tank body is 20 mL) in a closed wet milling mixing mode, adding stannous sulfate, mixing for 30min, heating to 180 ℃ at the speed of 30 ℃/min, keeping the temperature, mixing for 50min, and cooling to room temperature; then sequentially adding tin oxide, absolute ethyl alcohol, N-methyl pyrrolidone, magnesium oxide, tungsten trioxide, vanadium pentoxide, antimony pentoxide, acid-washed asbestos, ethylene glycol, tetraethyl silicate and formic acid, and continuously mixing for 30min to obtain mixed slurry;
(3) And (3) coating the mixed slurry obtained in the step (2) on a gas sensor by adopting a screen printing technology, wherein the coating thickness is 0.2mm, then placing the gas sensor in a muffle furnace, heating to 730 ℃ at a heating rate of 50 ℃/min, and sintering at a constant temperature for 3.5 hours.
The mixed slurry described in example 1 was directly coated on a ceramic substrate (coating thickness of 0.2 mm), and then sintered (heating to 730 ℃ at a heating rate of 50 ℃/min, and sintering at a constant temperature for 3.5 hours) to form a coating sample, and the coating sample was subjected to raman spectroscopy, scanning electron microscopy characterization, and X-ray energy spectroscopy, and the results are shown in fig. 1 to 3. From fig. 1, it can be observed that, compared with the raman spectrum of the standard rutile type tin oxide in the prior art, the raman spectrum of the antijam gas sensitive coating described in example 1 has no obvious difference in the overall shape, but has obvious relative right shift, which is probably caused by the defect of tin oxide crystal lattice caused by doping and recombination; in the low frequency region (less than400cm -1 ) Raman peaks also appear, possibly due to stacking disorder of various particles or defects in the crystal; 1000-1500 cm -1 And a plurality of small vibration peaks appear, wherein a corresponding silicon dioxide Raman peak indicates that the tetraethyl silicate in the mixed slurry forms crystalline silicon dioxide after hydrolysis and sintering. As can be seen from fig. 2, the micro-morphology of the anti-interference gas-sensitive coating is in a honeycomb discrete distribution, a large number of mesopores exist at the same time, the small molecule airflow of the combustible gas is captured by the noble metal catalyst through the mesopores, further, an oxidation-reduction reaction occurs, the potential change is caused to realize the detection of the combustible gas, the surface nano-silica is coated, the hydroxyl in alcohols is isolated, and the anti-alcohol interference is realized. As shown in fig. 3, the anti-interference gas-sensitive coating surface elements are obtained by qualitative and semi-quantitative analysis through an X-ray energy spectrum, and the weight percentages of the elements are as follows: sn79.46%, pd 2.48%, cl 1.99%, si 9.20%, O6.77%, the atomic percentage of each element is as follows: 44.67% of Sn, 1.55% of Pd, 3.74% of Cl, 21.84% of Si and 28.20% of O, wherein part of elements are sublimated after sintering, or oxidation-reduction reaction is carried out to volatilize in a gas manner, so that the content is low, and data is not shown under the analysis of an electronic probe.
As shown in fig. 4 to 6, the anti-interference gas-sensitive coating is applied to a semiconductor combustible gas sensor, where the semiconductor combustible gas sensor includes a protective cap 2, a metal base 1, and a gas-sensitive element 3 encapsulated on the metal base 1, and the gas-sensitive element 3 includes a heating resistor layer 305, a heating electrode layer 304, a substrate 303, a test electrode layer 302, and the anti-interference gas-sensitive coating 301, which are sequentially disposed from bottom to top; the metal base 1 is inserted with the heating pins 4 and the signal measuring pins 5, the heating pins 4 and the signal measuring pins 5 are uniformly arranged in an array, the heating pins 4 are electrically connected with the heating electrode layer 304, and the signal measuring pins 5 are electrically connected with the testing electrode layer 302. The heating electrode layer 304 and the testing electrode layer 302 both adopt a gear shaping electrode 306, the end of the gear shaping electrode 306 is connected with a conductive belt 307, the conductive belt 307 is connected with a lead 6, and the other end of the lead 6 is connected with a heating pin 4 or a signal measuring pin 5.
The metal base 1 provides a required power supply for the heating resistor layer 305 through the heating pins 4, so that the metal base sends out a temperature of a fixed condition to the anti-interference gas-sensitive coating 301, the detected gas reaches the surface of the anti-interference gas-sensitive coating 301 with the fixed temperature and carries out a chemical reaction with free charges inside the anti-interference gas-sensitive coating 301, the change of the material resistance of the anti-interference gas-sensitive coating 301 is caused along with charge transfer in the reaction process, the voltage change caused by the change of the material measuring end resistance is read through the slotting electrode 306 of the testing electrode layer 302, and the detection of the gas concentration can be realized through the change of the voltage difference.
Since the gas-sensitive characteristic of the semiconductor combustible gas sensor is affected by the operating temperature, the response of the semiconductor combustible gas sensor prepared in example 1 to methane (5000 ppm) at different operating temperatures (250 to 600 ℃) was examined. The method comprises the steps of carrying out repeated tests according to GB 15322.2-2003 standard conditions, using the existing data acquisition system to acquire the voltage of a partial pressure measuring resistor with a fixed resistance value matched with a sensor under the normal working condition of the sensor, and acquiring the response variation of a semiconductor gas-sensitive material of the sensor by acquiring the voltage variation of the partial pressure measuring resistor before and after gas injection so as to judge the gas-sensitive performance of the sensor.
The detection shows that the response value of the semiconductor combustible gas sensor to methane gradually increases along with the increase of the working temperature, the response value reaches the maximum when the working temperature is increased to 450 ℃, and the response value of the semiconductor combustible gas sensor to methane is reduced along with the further increase of the temperature. This is because, at lower temperatures, there is insufficient energy to support the gas sensitive reaction, and therefore as the temperature increases, the sensitivity increases; when the temperature is too high, the adsorption of the gas on the surface of the material becomes more difficult, i.e., the gas adsorbed on the surface of the material is desorbed without being reacted, resulting in a decrease in the number of molecules participating in the gas-sensitive process, thereby decreasing the sensitivity. The semiconductor combustible gas sensor of example 1 exhibited a maximum response (reading of 5000ppm methane minus zero) at 450 c of about 2.96V for 5000ppm methane.
In order to examine the sensing characteristics of the semiconductor combustible gas sensor in example 1 on methane gas, the response recovery of the semiconductor combustible gas sensor on methane gas with different concentrations (50-5000 ppm) is detected; meanwhile, in order to verify the repeatability of the detection of methane by the semiconductor combustible gas sensor described in example 1, the sensor was subjected to 15 consecutive detections at different times and at a working temperature of 450 ℃. The detected characteristic curve is shown in fig. 7, and the response data (sensor reading values) for different concentrations of methane gas are shown in table 1.
By detecting the response recovery condition of the semiconductor combustible gas sensor in the embodiment 1 to 5000ppm methane at 450 ℃, the response and recovery time of the semiconductor combustible gas sensor in the embodiment 1 to 5000ppm methane at 450 ℃ are calculated to be 3s and 20s respectively, and the semiconductor combustible gas sensor has higher response recovery speed.
As can be seen from table 1, the sensor showed good response recovery at different methane concentrations. In addition, as the concentration of the tested methane increases, the response value of the semiconductor combustible gas sensor shows obvious step-shaped distribution, the change of the response value and the concentration of the methane are approximately in a linear relation, and a fitting curve is shown in fig. 8. In addition, the sensor has a response value of about 0.28V to methane as low as 50ppm, and shows good low-concentration methane detection capability.
The semiconductor combustible gas sensor responds quickly after contacting methane gas and recovers quickly when contacting air, and the response and recovery characteristics are almost consistent during the whole test period. And the maximum response value of the sensor has only small amplitude change. This demonstrates that the semiconductor combustible gas sensor has good repeatability for methane gas at an operating temperature of 450 ℃.
Table 1 results (unit/V) of the measurement of methane concentration by the semiconductor combustible gas sensor described in example 1
Example 2
The preparation method of the anti-interference gas-sensitive coating for the semiconductor combustible gas sensor is characterized in that the mixed slurry is prepared from the following raw materials in parts by weight: 1.8g of tin oxide, 0.72g of stannous sulfate, 0.036g of acid-washed asbestos, 0.45g of alumina, 0.056g of platinum black, 0.014g of palladium chloride, 0.063g of tungsten trioxide, 0.03g of magnesium oxide, 0.027g of vanadium pentoxide, 0.014g of antimony pentoxide, 2.7mL of tetraethyl silicate, 3.0mL of formic acid, 1.0mL of ethylene glycol, 1.5mL of N-methylpyrrolidone, 2.0mL of anhydrous ethanol and 2.0mL of pure water.
Example 3
The preparation method of the anti-interference gas-sensitive coating for the semiconductor combustible gas sensor is characterized in that the mixed slurry is prepared from the following raw materials in parts by weight: 2.2g of tin oxide, 0.88g of stannous sulfate, 0.044g of acid-washed asbestos, 0.55g of aluminum oxide, 0.064g of platinum black, 0.016g of palladium chloride, 0.077g of tungsten trioxide, 0.038g of magnesium oxide, 0.033g of vanadium pentoxide, 0.018g of antimony pentoxide, 3.3mL of tetraethyl silicate, 3.0mL of formic acid, 1.0mL of ethylene glycol, 1.5mL of N-methylpyrrolidone, 2.0mL of anhydrous ethanol and 2.0mL of pure water.
Comparative example 1
A preparation method of an anti-interference gas-sensitive coating for a semiconductor combustible gas sensor comprises the following steps:
(1) Preparing raw materials of coating slurry:
first coating slurry: 2.0g of tin oxide, 1.4g of stannous sulfate, 0.08g of acid-washed asbestos, 0.2g of aluminum oxide, 0.08g of platinum black, 0.01g of palladium chloride, 0.08g of tungsten trioxide, 0.01g of antimony pentoxide, 0.06g of nickel oxide, 0.07g of ferric oxide, 0.04g of copper oxide, 2.0mL of pure water and 2.5mL of absolute ethyl alcohol;
second coating slurry: 2.0g of tetraethyl silicate, 1.5mL of absolute ethyl alcohol, 0.1mL of hydrochloric acid and 1.5mL of dibutyl ether;
(2) Preparing a first coating slurry:
mixing platinum black, palladium chloride, aluminum oxide, tin oxide, acid-washed asbestos, antimony trioxide, ferric oxide, tungsten trioxide, nickel oxide and copper oxide for 60min by adopting an agate grinding bowl in a mixing mode of manual grinding and dry grinding in a dust-free clean environment, then adding pure water and absolute ethyl alcohol to continue grinding for 60min, and obtaining first coating slurry when the materials show no obvious particles and agglomeration by hand feeling confirmation in the grinding process;
preparing a second coating slurry:
sequentially introducing tetraethyl silicate, absolute ethyl alcohol, hydrochloric acid and dibutyl ether into a brown reagent bottle, and mixing clockwise for 15min in a hand-shaking manner, and then mixing counterclockwise for 15min to obtain a second coating slurry;
(3) And (3) coating the first coating slurry obtained in the step (2) on a gas sensitive element, wherein the coating thickness is 0.2mm, then sintering for 3 hours at 630 ℃, coating a second coating, wherein the coating thickness is 0.05mm, and sintering for 1.5 hours at 450 ℃.
Comparative example 2
A preparation method of an anti-interference gas-sensitive coating for a semiconductor combustible gas sensor comprises the following steps:
(1) Preparing raw materials of coating slurry:
first coating slurry: 2.0g of tin oxide, 0.8g of stannous sulfate, 0.04g of acid-washed asbestos, 0.5g of alumina, 0.06g of platinum black, 0.015g of palladium chloride, 0.07g of tungsten trioxide, 0.016g of antimony pentoxide, 0.06g of nickel oxide, 0.07g of ferric oxide, 0.04g of copper oxide, 2.0mL of pure water and 2.5mL of absolute ethyl alcohol;
second coating slurry: 2.0g of tetraethyl silicate, 1.5mL of absolute ethyl alcohol, 0.1mL of hydrochloric acid and 1.5mL of dibutyl ether;
(2) Preparing a first coating slurry:
mixing platinum black, palladium chloride, aluminum oxide, tin oxide, acid-washed asbestos, antimony trioxide, ferric oxide, tungsten trioxide, nickel oxide and copper oxide for 60min by adopting an agate grinding bowl in a mixing mode of manual grinding and dry grinding in a dust-free clean environment, then adding pure water and absolute ethyl alcohol to continue grinding for 60min, and obtaining first coating slurry when the materials show no obvious particles and agglomeration by hand feeling confirmation in the grinding process;
preparing a second coating slurry:
sequentially introducing tetraethyl silicate, absolute ethyl alcohol, hydrochloric acid and dibutyl ether into a brown reagent bottle, and mixing clockwise for 15min in a hand-shaking manner, and then mixing counterclockwise for 15min to obtain a second coating slurry;
(3) And (3) coating the first coating slurry obtained in the step (2) on a gas sensitive element, wherein the coating thickness is 0.2mm, then sintering for 3 hours at 630 ℃, coating a second coating, wherein the coating thickness is 0.05mm, and sintering for 1.5 hours at 450 ℃.
Gas sensor samples were prepared according to the method of example 1 and comparative examples 1 and 2.
The gas sensors with the anti-interference gas-sensitive coatings prepared in example 1 and comparative examples 1 and 2 were subjected to performance tests. The results of the gas sensor of example 1 and comparative examples 1 and 2 applied to a semiconductor combustible gas sensor are shown in table 2, and the data shown in table 2 are the readings of the instrument. The reading in the 2000ppm alcohol vapor environment is reduced to zero, namely the response value of the sensor to 2000ppm alcohol, and the value in the 5000ppm methane gas concentration is reduced to zero, namely the response value of the sensor to 5000ppm methane. And subtracting 2000ppm of alcohol response value from 5000ppm of methane response value to obtain the alcohol interference resistance difference value.
TABLE 2 gas sensitive Performance test results (units/V) of example 1 and comparative examples 1 and 2
As can be seen from Table 2, according to example 1, compared with comparative examples 1 and 2, in both the 2000ppm alcohol interference environment and the 5000ppm methane environment, the difference between methane and the interference gas can reach a drop of over 700mV, and the response value and sensitivity of the gas sensor prepared in example 1 to 5000ppm methane are higher than those of comparative examples 1 and 2. In addition, the effective service life of the comparative examples 1 and 2 is 6 months, the second coating fails after being continuously electrified for 6 months, the anti-interference effect cannot be continuously realized, and the measurement result is influenced; and the anti-interference gas-sensitive coating in the embodiment 1 can be repeatedly used for more than 6 months, the measurement result is stable, and the anti-interference effect can be still effectively realized.
Through detection, both the embodiment 2 and the embodiment 3 have the gas-sensitive performance equivalent to that of the embodiment 1, the product has good consistency, the detection data has good stability, and the detection interval for methane gas is 100-10000 ppm; under the conditions that the gas concentration is 5000ppm and the working temperature is 250-450 ℃, the reading value of the semiconductor combustible gas sensor is 3.8-4.0V (corresponding to the response value is 2.8-3.0V), and the response time is about 3s; under the general environment, the recovery time of the semiconductor combustible gas sensor is about 20s, the semiconductor combustible gas sensor is applied to the environment with good exhaust equipment, the recovery time of the semiconductor combustible gas sensor is less than 10s, and after the semiconductor combustible gas sensor is repeatedly used for 12 months, the response value is not obviously attenuated. The invention adopts a layer of coating to realize the anti-interference of organic volatile gas containing hydroxyl groups of the semiconductor combustible gas sensor, avoids material decomposition, phase change and oxidation caused by repeated high-temperature sintering, and simultaneously reduces the damage of a plurality of working procedures to the mechanical property of the substrate.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (7)
1. An anti-interference gas-sensitive coating for a semiconductor combustible gas sensor is characterized by being formed by coating and sintering mixed slurry, wherein the mixed slurry is prepared from the following raw materials in parts by weight: 180 to 220 parts of tin oxide, 72 to 88 parts of stannous sulfate, 3.6 to 4.4 parts of acid-washed asbestos, 45 to 55 parts of catalytic carrier, 6.7 to 8.3 parts of noble metal catalyst, 6.3 to 7.7 parts of tungsten trioxide, 3.0 to 3.8 parts of magnesium oxide, 2.7 to 3.3 parts of vanadium pentoxide, 1.4 to 1.8 parts of antimony pentoxide, 250 to 310 parts of tetraethyl silicate, 330 to 400 parts of formic acid, 100 to 125 parts of ethylene glycol, 135 to 170 parts of N-methylpyrrolidone, 140 to 175 parts of absolute ethyl alcohol and 180 to 220 parts of pure water;
the preparation method of the anti-interference gas-sensitive coating for the semiconductor combustible gas sensor comprises the following steps:
(1) Preparing raw materials of the mixed slurry according to parts by weight;
(2) Mixing a catalytic carrier, a noble metal catalyst and pure water for 30 to 50 minutes under the condition of grinding and mixing, then adding stannous sulfate, mixing for 20 to 40 minutes, heating to 120 to 180 ℃, keeping the temperature, mixing for 40 to 60 minutes, and cooling to room temperature; then sequentially adding tin oxide, absolute ethyl alcohol, N-methyl pyrrolidone, magnesium oxide, tungsten trioxide, vanadium pentoxide, antimony pentoxide, acid-washed asbestos, ethylene glycol, tetraethyl silicate and formic acid, and continuously mixing for 20 to 40 minutes to obtain mixed slurry;
(3) Uniformly coating the mixed slurry obtained in the step (2), and sintering at 700-750 ℃ for 3-4 hours to obtain an anti-interference gas-sensitive coating;
the anti-interference gas-sensitive coating is applied to a semiconductor combustible gas sensor: the device is used for detecting methane, propane and isobutane and resisting the interference of alcohol volatilization.
2. The tamper resistant gas sensitive coating for a semiconductor combustible gas sensor of claim 1, wherein: the noble metal catalyst is prepared by mixing platinum black and palladium chloride according to a mass ratio of 4.8-1.2.
3. The tamper resistant gas sensitive coating for a semiconductor combustible gas sensor of claim 1, wherein: the catalytic carrier is alumina.
4. The tamper resistant gas sensitive coating for a semiconductor combustible gas sensor of claim 1, wherein: and (3) coating the mixed slurry in the step (3) by adopting a screen printing technology, wherein the coating thickness is 0.15-0.25 mm.
5. The use of the tamper resistant gas sensitive coating of any of claims 1 to 3 in a semiconductor combustible gas sensor comprising a metal base and a gas sensitive element encapsulated on the metal base, wherein: the gas-sensitive element comprises a heating resistor layer, a heating electrode layer, a substrate, a test electrode layer and the anti-interference gas-sensitive coating which are sequentially arranged from bottom to top; the metal base is inserted with the heating pins and the signal measuring pins, the heating pins and the signal measuring pins are uniformly arranged in an array mode, the heating pins are electrically connected with the heating electrode layer, and the signal measuring pins are electrically connected with the testing electrode layer.
6. The use of the tamper resistant, gas sensitive coating of claim 5 in a semiconductor combustible gas sensor, wherein: the heating electrode layer and the testing electrode layer both adopt gear shaping electrodes, the end parts of the gear shaping electrodes are connected with conductive belts, lead wires are connected onto the conductive belts, and the other ends of the lead wires are connected with the heating pins or the signal measuring pins.
7. The use of the tamper resistant, gas sensitive coating of claim 5 in a semiconductor combustible gas sensor, wherein: the substrate is a 96% alumina substrate.
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