Calcium oxide-silica-boron oxide glass bonders, methods of making and using the same

Abstract

This invention provides a calcium oxide-silica-boron oxide glass binder, its preparation method, and its application, belonging to the technical field of binder materials. The preparation method of the CaO-SiO2-B2O3 glass binder provided by this invention adjusts the ratio of calcium oxide, silica, and boron oxide to adjust the transition temperature of the prepared glass binder, thereby improving its chemical stability. By adjusting the sintering temperature and time, the bonding strength, interfacial reliability, and reliability to sensitive materials of the glass binder are improved. Furthermore, by controlling the particle size of the glass binder, its surface energy is adjusted, enhancing its surface activity. This results in a CaO-SiO2-B2O3 glass binder with a temperature property temperature below 500℃. Sensors prepared with this CaO-SiO2-B2O3 glass binder exhibit good response repeatability and stable zero-point voltage.

Description

Technical Field

[0001] This invention relates to the field of adhesive materials technology, and in particular to a calcium oxide-silica-boron oxide glass adhesive, its preparation method, and its application. Background Technology

[0002] A sensor is considered to have long-term stability when its output signal (such as sensitivity or baseline reading) remains constant during continuous or repeated use. The working principle of a metal-oxide-semiconductor (MOS) gas sensor is that target gas molecules in the environment interact with adsorbed oxygen species on the surface, crystal planes, and grain boundaries of the MOS, leading to electron transfer at the interface and a corresponding change in resistance. From a functional perspective, the main role of the binder is to enhance the bonding strength between sensing materials, preventing material detachment or performance degradation caused by mechanical stress.

[0003] Currently used binders are mostly chitosan, styrene-butadiene rubber (SBR), alkali metal carbonates, tetraethyl orthosilicate (TEOS), and calcium sulfate. Since the operating temperature of metal oxide semiconductor gas sensors is typically between 200℃ and 400℃, at this temperature, most organic binders will decompose, carbonize, or oxidize, damaging the electrode structure and potentially releasing interfering gases. Inorganic salt binders may have insufficient adhesion for thick films or applications requiring high mechanical strength. Some inorganic binders (such as tetraethyl orthosilicate) may themselves have a weak response to gases, interfering with the signal of the main sensing material. Furthermore, most organic and inorganic binders also suffer from high manufacturing costs and demanding storage requirements. Improper storage can lead to binder deterioration, severely affecting the performance of gas sensor products. Summary of the Invention

[0004] The purpose of this invention is to provide a calcium oxide-silica-boron oxide glass binder, its preparation method, and its application. The calcium oxide-silica-boron oxide glass binder provided by this invention, also known as CaO-SiO2-B2O3 glass binder, has stable properties at temperatures below 500℃ and will not change, nor will it affect the structure of sensors and electrodes prepared from it. Moreover, the sensors prepared from it have good response repeatability and stable zero-point voltage.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a calcium oxide-silica-boron oxide glass binder, comprising the following steps: mixing CaO, SiO2 and B2O3, and then sequentially performing a first grinding, sintering, a second grinding, a first sieving, drying, a third grinding and a second sieving to obtain the calcium oxide-silica-boron oxide glass binder; The mass ratio of CaO, SiO2 and B2O3 is (5~10):(1~5):(6~11).

[0006] Preferably, the purity of CaO, SiO2, and B2O3 is analytical grade; the particle size of SiO2 is 3μm~8μm, and the particle size of CaO and B2O3 is independently 120~180μm.

[0007] Preferably, the mass ratio of CaO, SiO2 and B2O3 is 8:3:9.

[0008] Preferably, the sintering temperature is 1180~1380℃ and the sintering time is 1.5~3h.

[0009] Preferably, the second grinding is wet grinding; the liquid medium used in the second grinding is anhydrous ethanol; the equipment used in the second grinding is a ball mill; and the grinding time is 22-28 hours.

[0010] The present invention also provides a calcium oxide-silica-boron oxide glass adhesive, which is prepared by the preparation method described in the above technical solution.

[0011] The present invention also provides an application of a calcium oxide-silica-boron oxide glass adhesive in a sensor, wherein the calcium oxide-silica-boron oxide glass adhesive is prepared by the preparation method described in the above technical solution, or the calcium oxide-silica-boron oxide glass adhesive.

[0012] Preferably, when the sensor is a hydrogen sensor, the method for preparing the hydrogen sensor using the calcium oxide-silica-borosilicate glass binder includes the following steps: After mixing calcium oxide-silica-boron oxide glass binder and tin dioxide, dry grinding and second wet grinding are performed in sequence. Then, PtCl4 solution is added and a third wet grinding is performed to obtain a sensitive material slurry. The sensitive material slurry was coated onto an alumina substrate with interdigitated electrodes and heating electrodes, and then subjected to room temperature air drying, heat treatment and natural cooling in sequence to obtain a pretreated substrate. The pre-processed substrate and the gas sensor base are encapsulated, and an aging process is performed using heated electrodes to obtain a hydrogen sensor.

[0013] Preferably, the mass of the calcium oxide-silica-boron oxide glass binder accounts for 1.5% to 6% of the mass of tin dioxide.

[0014] Preferably, the heating rate of the heat treatment is 1.5~3℃ / min, the temperature of the heat treatment is 650~720℃, and the time of the heat treatment is 0.5~2h.

[0015] This invention provides a method for preparing a calcium oxide-silica-boron oxide glass binder. By adjusting the ratio of calcium oxide, silica, and boron oxide, the transition temperature of the prepared glass binder is adjusted, thereby improving its chemical stability. By adjusting the sintering temperature and time, the bonding strength, interfacial reliability, and reliability to sensitive materials (i.e., it will not chemically react with sensitive materials or cause material poisoning) of the glass binder are improved. By controlling the particle size of the glass binder, its surface energy is adjusted, thereby enhancing its surface activity. Thus, a CaO-SiO2-B2O3 glass binder with a temperature property temperature below 500℃ is obtained. Furthermore, the sensor prepared with the CaO-SiO2-B2O3 glass binder exhibits good response repeatability and stable zero-point voltage. Attached Figure Description

[0016] Figure 1 This is a particle size distribution diagram of the sensitive material in the sensitive material slurry prepared in Application Example 1 of the present invention; Figure 2 (Figure showing the hydrogen sensor prepared according to Example 1 of this invention under test in an atmosphere of 2100ppm C3H8 and 5000ppm CH4). Figure 3 The hydrogen sensor prepared according to Example 1 of this invention is tested in an atmosphere of 100ppmCO and 5000ppmNH3. Figure 4 The hydrogen sensor prepared with the binder in Comparative Example 1 of this invention is tested in an atmosphere of 2100 ppm propane and 5000 ppm methane. Figure 5 The hydrogen sensor prepared for use case 1 of the present invention, and the hydrogen sensor prepared by the binder in Comparative Example 1 and Comparative Example 2, are tested in atmospheres of 1000ppmH2, 2100ppmC3H8, 5000ppmCH4 and 100ppmCO. Figure 6 The hydrogen sensor prepared for use in Example 1 of this invention, and the hydrogen sensor prepared by the binder in Comparative Example 1 and Comparative Example 2, are tested in an atmosphere of 50 ppm NH3 and 50 ppm C2H5OH. Figure 7 The hydrogen sensor prepared for application example 1 of this invention is shown in the response diagram of a 1000ppm H2 atmosphere test after intermittent aging at high and low temperatures. Detailed Implementation

[0017] This invention provides a method for preparing a calcium oxide-silica-boron oxide glass binder, comprising the following steps: mixing CaO, SiO2 and B2O3, and then sequentially performing a first grinding, sintering, a second grinding, a first sieving, drying, a third grinding and a second sieving to obtain a CaO-SiO2-B2O3 glass binder; The mass ratio of CaO, SiO2 and B2O3 is (5~10):(1~5):(6~11).

[0018] Unless otherwise specified, all raw materials used in this invention are commercially available products in the art.

[0019] In this invention, the CaO, SiO2, and B2O3 are all of analytical grade. The particle size of the SiO2 is preferably 3 μm to 8 μm, more preferably 5 μm; the particle sizes of the CaO and B2O3 are independently preferably 120 to 180 μm, more preferably 140 to 160 μm. The mass ratio of CaO, SiO2, and B2O3 is preferably 8:3:9. This invention improves the chemical stability of the prepared glass binder by adjusting the ratio of calcium oxide, silicon dioxide, and boron oxide, thereby improving the performance stability and response repeatability of the sensor subsequently prepared from the binder.

[0020] In this invention, the sintering temperature is preferably 1180~1380℃, more preferably 1250℃. In this invention, the sintering time is preferably 1.5~3h, more preferably 2h.

[0021] In this invention, the first grinding is preferably performed by grinding thoroughly in a mortar for 5 minutes. This invention ensures thorough mixing of different raw materials through the first grinding. In this invention, the second grinding is preferably wet grinding; the liquid medium used for the second grinding is preferably anhydrous ethanol; the equipment used for the second grinding is preferably a ball mill; and the grinding time is preferably 22-28 hours. This invention reduces the particle size of the binder through the second grinding, as excessively large particle sizes may reduce the uniformity of the sensitive layer and affect the response speed. In this invention, the first sieving is preferably performed through a 500-mesh sieve. This invention removes glass binder particles with a particle size greater than 25 μm through the first sieving. This invention does not have special limitations on the drying method; any well-known technical solution can be used to remove residual liquid. In this invention, the third grinding is preferably performed by grinding thoroughly in a mortar for 10 minutes. This invention grinds the dried and agglomerated binder into granular powder through the third grinding. In this invention, the second sieving is preferably performed through a 500-mesh sieve. This invention removes glass binder particles with a particle size greater than 25 μm through the second sieving.

[0022] The present invention also provides a calcium oxide-silica-boron oxide glass adhesive, which is prepared by the preparation method described in the above technical solution.

[0023] The present invention also provides an application of a calcium oxide-silica-boron oxide glass adhesive in a sensor, wherein the calcium oxide-silica-boron oxide glass adhesive is prepared by the preparation method described in the above technical solution, or the calcium oxide-silica-boron oxide glass adhesive.

[0024] In this invention, when the sensor is a hydrogen sensor, the method for preparing the hydrogen sensor using the calcium oxide-silicon dioxide-borosilicate glass binder preferably includes the following steps: After mixing calcium oxide-silica-boron oxide glass binder and tin dioxide, dry grinding and second wet grinding are performed in sequence. Then, PtCl4 solution is added and a third wet grinding is performed to obtain a sensitive material slurry. The sensitive material slurry was coated onto an alumina substrate with interdigitated electrodes and heating electrodes, and then subjected to room temperature air drying, heat treatment and natural cooling in sequence to obtain a pretreated substrate. The pre-processed substrate and the gas sensor base are encapsulated, and an aging process is performed using heated electrodes to obtain a hydrogen sensor.

[0025] In this invention, the tin dioxide is preferably centrifuged until the resistivity of the supernatant is less than 50 Ω·cm before use. In this invention, the mass of the CaO-SiO2-B2O3 glass binder preferably accounts for 1.5% to 6% of the mass of the tin dioxide, more preferably 2% to 5%, and even more preferably 3%. This invention controls the mass ratio of calcium oxide-silica-boron oxide glass binder to tin dioxide within the above range to avoid excessive binder causing a surge in the sensor's sensitive resistance, while also avoiding insufficient binder leading to poor mechanical strength adhesion to the ceramic substrate. In this invention, the dry grinding time is preferably 4 to 8 minutes. In this invention, the second wet grinding time is preferably 50 to 70 minutes; the liquid medium used is preferably deionized water; during the second wet grinding process, a portion of deionized water is first added for grinding, and then a portion of deionized water is added every 15 minutes until grinding reaches 50 to 70 minutes. In this invention, the concentration of the PtCl4 solution is preferably 0.015 g / mL. In this invention, the amount of PtCl4 solution used is 104 μL, which is converted to the percentage of Pt atoms to tin dioxide by weight. In this invention, the preferred time for the third wet grinding process is 40-55 min.

[0026] In this invention, the preferred heating rate of the heat treatment is 1.5~3℃ / min, the preferred heat treatment temperature is 650~720℃, and the preferred heat treatment time is 0.5~2h. Through heat treatment, PtCl4 decomposes into Pt nanoparticles at the specified temperature, and these Pt nanoparticles uniformly adhere to the surface of the sensitive material. In this invention, the preferred voltage for the aging treatment is 5V; the preferred aging treatment time is 1.5~3 days. Through aging treatment, this invention brings the hydrogen sensor to a relatively stable state.

[0027] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] Unless otherwise specified, all experiments were repeated three times, and the results are expressed as averages.

[0029] The CaO, B2O3, and SiO2 powders used in this invention are all from Maclean's Reagent Company and are of analytical grade with a purity of 100%.

[0030] Example 1 A method for preparing a calcium oxide-silica-boron oxide glass binder includes the following steps: 30g of CaO, SiO2, and B2O3 are weighed in a mass ratio of 8:3:9 and thoroughly ground in an agate mortar for 5 minutes. The powder obtained from the first grinding is poured into an alumina crucible and sintered at a constant temperature of 1250℃ for 2 hours using a muffle furnace. The powder is then removed and quenched with deionized water to obtain granular glass. The granular glass is then ground a second time with anhydrous ethanol using a ball mill for 24 hours, passed through a 500-mesh sieve, dried, and then ground a third time in a mortar for 10 minutes. The resulting calcium oxide-silica-boron oxide glass binder, i.e., CaO-SiO2-B2O3 glass binder, is obtained. The average particle sizes of the CaO, SiO2, and B2O3 are 150 μm, 5 μm, and 150 μm, respectively.

[0031] Application Example 1 The method for preparing a hydrogen sensor using the CaO-SiO2-B2O3 glass binder described in Example 1 includes the following steps: 0.03 g of CaO-SiO2-B2O3 glass binder and 1 g of tin dioxide (centrifuged 7 times until the resistivity of the supernatant was less than 50 Ω·cm) were mixed and then dry-milled for 5 min. Then 1000 μL of deionized water was added and milled for 15 min. 500 μL of deionized water was added every 15 minutes until 60 min. Then 104 μL of PtCl4 solution (0.015 g / mL) was added and milled for another 45 min to obtain a sensitive material slurry. The average particle size of the sensitive material in the slurry was 0.85 μm. The CaO-SiO2-B2O3 glass binder accounts for 3% of the mass of tin dioxide; The sensitive material slurry was coated onto an alumina substrate with interdigitated electrodes and heating electrodes, and allowed to air dry at room temperature for 5 minutes. Then it was transferred to a muffle furnace and heated to 680°C at 2°C / min for 1 hour. After natural cooling, a pretreated substrate was obtained. The pre-treated substrate and the gas sensor base are encapsulated, and aged for 2 days using a heating electrode with a voltage of 5V to obtain a hydrogen sensor.

[0032] Figure 1 This is a particle size distribution diagram of the sensitive material in the sensitive material slurry prepared in Application Example 1 of this invention. Figure 1 It can be seen that the average particle size of the sensitive material in the sensitive material slurry prepared in Example 1 is 0.85 μm.

[0033] Comparative Example 1 The preparation method of MgO-B2O3-SiO2 binder (MBS) includes the following steps: MgO, SiO2, and B2O3 were weighed in a mass ratio of 6:3:1, and 30g were ground thoroughly in an agate mortar for 5 minutes. The powder obtained from the first grinding was poured into a graphite crucible and sintered at a constant temperature of 1100℃ in a muffle furnace for 2 hours. The powder was then removed and quenched with deionized water to obtain granular glass. The granular glass was then ground a second time with anhydrous ethanol in a ball mill for 24 hours. After passing through a 500-mesh sieve and drying, it was ground a third time in a mortar for 10 minutes and passed through a 500-mesh sieve to obtain a magnesium oxide-silicon dioxide-boron oxide glass binder, namely MgO-SiO2-B2O3 glass binder. The average particle sizes of the MgO, SiO2, and B2O3 are 50 μm, 5 μm, and 150 μm, respectively.

[0034] Comparative Example 2 The preparation method of ZnO-B2O3-SiO2 binder (referred to as ZBS) includes the following steps: ZnO, SiO2 and B2O3 were weighed in a mass ratio of 6:3:1, and 30g were ground thoroughly in an agate mortar for 5 minutes. The powder obtained from the first grinding was poured into an alumina crucible and sintered at 1100℃ in a muffle furnace for 2 hours. The powder was then removed and quenched with deionized water to obtain granular glass. The granular glass was then ground for 24 hours with anhydrous ethanol in a ball mill, and then passed through a 500-mesh sieve. After drying, it was ground for 10 minutes and passed through a 500-mesh sieve to obtain calcium oxide-silicon dioxide-boron oxide glass binder, namely ZnO-SiO2-B2O3 glass binder. The average particle size distributions of the ZnO, SiO2, and B2O3 are 300±50 nm, 5 μm, and 150 μm, respectively.

[0035] Using the three low-melting-point microcrystalline glass binder powders—CaO-B2O3-SiO2 (CBS), MgO-B2O3-SiO2 (MBS), and ZnO-B2O3-SiO2 (ZBS)—prepared by melt quenching and physical ball milling as described in the above examples and comparative examples, hydrogen sensors were fabricated according to the same method as in Application Example 1. The difference from Application Example 1 was that different binder doping ratios were set, with 1.5 wt%, 3.0 wt%, 4.5 wt%, and 6.0 wt% of tin dioxide by mass, respectively. PtCl4 solution was not added to avoid the influence of precious metals, in order to analyze the influence of the binder and to corroborate the bonding and promoting effect of the binder. For each of the three binders, four doping amounts were set, repeated three times, for a total of 36 sensors. After aging, the hydrogen sensors made with different glass binder materials and ratios were tested under different gas atmospheres. Simultaneously, their adhesion to the alumina ceramic substrate was tested.

[0036] The experimental results include: the above 36 sensors tested a total of six gases: propane, methane, carbon monoxide, ammonia, ethanol, and hydrogen. The test results were summarized and analyzed, the sensor response magnitudes were statistically analyzed, and R was defined. air / R res The higher the ratio of the response ratio, the better the sensor response. Where R... air R is the resistance of the sensor in air. air This represents the resistance of the sensor in the test gas atmosphere.

[0037] Figure 2 The figure shows the test results of the hydrogen sensor prepared for example 1 of the present invention under an atmosphere of 2100ppm C3H8 and 5000ppm CH4. Figure 3 The figure shows the test results of the hydrogen sensor prepared for example 1 of the present invention under an atmosphere of 100ppmCO and 5000ppmNH3. Figure 4This image shows the hydrogen sensor prepared with the binder in Comparative Example 1 of this invention under test in an atmosphere of 2100 ppm propane and 5000 ppm methane. Figures 2-4 It is known that sensors doped with different glass binder powders respond differently to various gases. In principle, the degree to which they affect the binding ability of the sensitive material with air varies greatly.

[0038] Figure 5 The hydrogen sensor prepared for Example 1 of this invention, and the hydrogen sensor prepared by the binder in Comparative Example 1 and Comparative Example 2, are tested in atmospheres of 1000ppmH2, 2100ppmC3H8, 5000ppmCH4 and 100ppmCO. Figure 6 The figures show the hydrogen sensor prepared in Real-Time Example 1, and the hydrogen sensors prepared in Comparative Examples 1 and 2, tested under atmospheres of 50 ppm NH3 and 50 ppm C2H5OH, respectively. Figure 5 , 6 It can be seen that the response voltage values ​​of sensors prepared by doping with glass binders of different mass percentages under different gases are relatively stable values ​​of voltage response under a certain gas atmosphere.

[0039] In summary, considering the good response ratio and sensor repeatability (i.e., the consistency of the ratios of the three sensors), the sensor prepared with 3.0 wt% CaO-B2O3-SiO2 (CBS) has the best repeatability. ZnO-B2O3-SiO2 (ZBS) can have a prominent response but poor consistency, making it suitable for schemes that do not prioritize sensor consistency and highlight performance. Furthermore, the binder strength test results show that CaO-B2O3-SiO2 (CBS) has the highest mechanical strength.

[0040] Taking the hydrogen sensor prepared in Application Example 1 as an example, tests revealed that the hydrogen sensor doped with CaO-SiO2-B2O3 glass binder, after 200 cycles of intermittent 15-minute power-on aging at a temperature 80 degrees Celsius above ambient temperature (ambient temperature approximately 26°C), (power on for 15 minutes, then power off, sensor exposed to ambient temperature for 15 minutes, then power on again for 15 minutes, repeated 200 times), and then subjected to hydrogen gas priming tests under the same concentration atmosphere (e.g., sensor in a 200 ppm H2 atmosphere), underwent a 100-day intermittent test to verify the repeatability of the sensor's response voltage, yielding the following results: Figure 7 As shown. By Figure 7The analysis shows that the test response results fluctuated around the average value of 4.4351, with a standard deviation of approximately 0.146 and a relative deviation (RSD, coefficient of variation, representing the relative dispersion) of approximately 3.29%. The zero-point voltage data was affected by temperature, humidity, and recovery time, but the overall data remained relatively stable with little variation. The response repeatability was poor or highly volatile (RSD may be >15%) for binders doped with nanomaterials (graphene, carbon nanotubes, etc.) and organic binders.

[0041] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a calcium oxide-silica-borosilicate glass adhesive, characterized in that, Includes the following steps: After mixing CaO, SiO2 and B2O3, the mixture is subjected to the following processes in sequence: first grinding, sintering, second grinding, first sieving, drying, third grinding and second sieving, to obtain calcium oxide-silica-boron oxide glass binder. The mass ratio of CaO, SiO2 and B2O3 is (5~10):(1~5):(6~11).

2. The preparation method according to claim 1, characterized in that, The purity of CaO, SiO2, and B2O3 is all analytical grade; the particle size of SiO2 is 3μm~8μm, and the particle size of CaO and B2O3 is independently 120~180μm.

3. The preparation method according to claim 1, characterized in that, The mass ratio of CaO, SiO2, and B2O3 is 8:3:

9.

4. The preparation method according to claim 1, characterized in that, The sintering temperature is 1180~1380℃, and the sintering time is 1.5~3h.

5. The preparation method according to claim 1, characterized in that, The second grinding is wet grinding; the liquid medium used in the second grinding is anhydrous ethanol; the equipment used in the second grinding is a ball mill; and the grinding time is 22-28 hours.

6. A calcium oxide-silica-borosilicate glass adhesive, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 5.

7. The application of a calcium oxide-silica-borosilicate glass binder in a sensor, characterized in that, The calcium oxide-silica-boron oxide glass adhesive is prepared by the preparation method described in any one of claims 1 to 5, or the calcium oxide-silica-boron oxide glass adhesive described in claim 6.

8. The application according to claim 7, characterized in that, When the sensor is a hydrogen sensor, the method for preparing the hydrogen sensor using the calcium oxide-silicon dioxide-borosilicate glass binder includes the following steps: After mixing calcium oxide-silica-boron oxide glass binder and tin dioxide, dry grinding and second wet grinding are performed in sequence. Then, PtCl4 solution is added and a third wet grinding is performed to obtain a sensitive material slurry. The sensitive material slurry was coated onto an alumina substrate with interdigitated electrodes and heating electrodes, and then subjected to room temperature air drying, heat treatment and natural cooling in sequence to obtain a pretreated substrate. The pre-processed substrate and the gas sensor base are encapsulated, and an aging process is performed using heated electrodes to obtain a hydrogen sensor.

9. The application according to claim 8, characterized in that, The mass of the calcium oxide-silica-boron oxide glass binder is 1.5% to 6% of the mass of tin dioxide.

10. The application according to claim 8, characterized in that, The heating rate of the heat treatment is 1.5~3℃ / min, the temperature of the heat treatment is 650~720℃, and the time of the heat treatment is 0.5~2h.

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