Preparation method of cage-like lafeo3 nanomaterial and application thereof

Abstract

This invention provides a method for preparing cage-like LaFeO3 nanomaterials and their applications, relating to the field of gas-sensitive materials technology. The method for preparing cage-like LaFeO3 nanomaterials using ultrasound-assisted synthesis involves calcining LaFeO3 precursor powder at 780℃-830℃ for 2-6 hours to obtain cage-like LaFeO3 nanomaterials. These cage-like LaFeO3 nanomaterials have a cage-like porous structure with a diameter of 1μm-3μm and are composed of prismatic particles with a diameter of 20nm-70nm. The cage-like LaFeO3 nanomaterials prepared using this ultrasound-assisted synthesis method have a cage-like porous structure composed of prismatic particles, which increases the reaction area in contact with the tested ethanol gas or material.

Description

Technical Field

[0001] This invention relates to the field of gas-sensitive materials technology, and in particular to a method for preparing cage-like LaFeO3 nanomaterials and their applications. Background Technology

[0002] Ethanol is a colorless, volatile liquid, an important component in the manufacturing processes of many beverages and foods, and a common disinfectant and bactericide used for cleaning and disinfecting wounds. It is also used as a base ingredient in some medications, such as oral medications, topical ointments, and sprays. However, ethanol is also a flammable and explosive gas after evaporation, with an explosive range between 3.3-19% (3.3E4-1.9E5 ppm). Excessive ethanol can cause significant harm to the human body, easily damaging the nervous system and leading to safety accidents. Therefore, gas sensors are needed to monitor the gas produced after ethanol evaporation. Compared to spectrophotometry or mass spectrometry, which rely on complex, large-scale equipment and advanced technology, oxide semiconductor gas sensors have attracted much attention due to their advantages such as simplicity of use, high sensitivity, good stability, and fast response and recovery times.

[0003] In existing technologies, the perovskite ABO3 structure is a crystal structure where A represents a rare metal and B represents a transition metal ion. Lanthanum ferrite (LaFeO3) with the perovskite ABO3 structure is used in photocatalysis, electrochemistry, and magnetism. However, its near-sealed spherical shape results in a small reaction area in contact with the ethanol gas or material being tested.

[0004] Therefore, the aforementioned technical issues still need to be addressed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing cage-like LaFeO3 nanomaterials and their applications, thereby increasing the reaction area in contact with the tested ethanol gas or material.

[0006] To address the aforementioned technical problems, the embodiments of the present invention provide the following technical solutions:

[0007] The first aspect of this invention provides a method for preparing cage-like LaFeO3 nanomaterials using ultrasound-assisted synthesis, wherein LaFeO3 precursor powder is calcined at 780℃-830℃ for 2h-6h to obtain cage-like LaFeO3 nanomaterials.

[0008] The cage-like LaFeO3 nanomaterial has a cage-like porous structure with a diameter of 1μm-3μm and is composed of prismatic particles with a diameter of 20nm-70nm.

[0009] Furthermore, the preparation process of the LaFeO3 precursor powder is as follows:

[0010] The stirring step involves dissolving the mixture in deionized water and stirring at room temperature and pressure to obtain the first mixture.

[0011] The ultrasonic step involves subjecting the first mixture to ultrasonication at 300W-450W for 1-2 times, with each ultrasonication lasting 45 minutes and an interval of 10 minutes between adjacent ultrasonications, to obtain the second mixture.

[0012] The reaction step involves placing the second mixture in a reaction vessel and reacting it at 150℃-180℃ for 15-25 hours to obtain the third mixture.

[0013] The centrifugation and washing step involves cooling the third mixture to room temperature, followed by centrifugation and washing to obtain the fourth mixture.

[0014] In the grinding step, the fourth mixture is dried at 70℃-90℃ and then ground into powder to obtain LaFeO3 precursor powder.

[0015] Furthermore, the components of the mixture and their mass percentages include:

[0016] The content of lanthanum nitrate hexahydrate is 8.1%-8.6%, ferric nitrate hexahydrate is 7.4%-7.9%, anhydrous citric acid is 7.2%-7.7%, hexadecyltrimethylammonium bromide is 16%-18%, and deionized water is 58.5%-61%.

[0017] Furthermore, the components of the mixture and their mass percentages include:

[0018] The composition of lanthanum nitrate hexahydrate is 8.4%, ferric nitrate hexahydrate is 7.6%, anhydrous citric acid is 7.5%, hexadecyltrimethylammonium bromide is 17%, and deionized water is 59.5%.

[0019] A method for preparing cage-like LaFeO3 nanomaterials using ultrasound-assisted synthesis, as provided in the first aspect of the present invention.

[0020] The second aspect of this invention provides an application of cage-like LaFeO3 nanomaterials. The cage-like LaFeO3 nanomaterials prepared by the method for preparing cage-like LaFeO3 nanomaterials with ultrasonic assistance provided in the first aspect of this invention are used as semiconductor gas-sensitive materials.

[0021] The third aspect of this invention provides an application of cage-like LaFeO3 nanomaterials. The cage-like LaFeO3 nanomaterials prepared by the method for preparing cage-like LaFeO3 nanomaterials using ultrasound-assisted synthesis provided in the first aspect of this invention are used in the preparation of ethanol gas sensors.

[0022] Furthermore, the preparation method of the ethanol gas sensor includes the following steps:

[0023] In the mixing step, the cage-like LaFeO3 nanomaterials are ground and then mixed with deionized water and anhydrous ethanol to form a paste, thus obtaining the first slurry.

[0024] In the first coating step, the first paste is evenly applied to the metal electrode of the alumina ceramic tube using screen printing, and the coating is applied 6 times.

[0025] The second coating step involves using a brush to apply the first slurry to the surface of the metal electrode other than the metal electrode end, with two coating layers.

[0026] In the welding step, the alumina ceramic tube treated in the second coating step is welded onto the six-pin base of the sensor, and a heating resistance wire is added to form a gas-sensitive element, wherein the two ends of the heating resistance wire are respectively welded to two heating ends located in the middle of the hexagonal base;

[0027] The aging step involves placing the gas-sensitive element on an aging table and aging it at 200-300°C for 48 hours to obtain an ethanol gas-sensitive sensor.

[0028] Furthermore, in the mixing step:

[0029] The cage-like LaFeO3 nanomaterials comprise 33%-35% by mass, the deionized water comprises 55%-58% by mass, and the anhydrous ethanol comprises 9%-12% by mass.

[0030] Furthermore, in the mixing step:

[0031] The cage-like LaFeO3 nanomaterial has a mass percentage of 34%, the deionized water has a mass percentage of 57%, and the anhydrous ethanol has a mass percentage of 10%.

[0032] Furthermore, the sensitivity model of the ethanol gas sensor is as follows:

[0033] S = Rg / Ra,

[0034] Where Rg is the stable resistance value of the ethanol gas sensor in ethanol gas, Ra is the stable resistance value of the ethanol gas sensor in air, and S is the sensitivity of the ethanol gas sensor.

[0035] Compared with the prior art, the method for preparing cage-like LaFeO3 nanomaterials using ultrasound-assisted synthesis provided by the first aspect of the present invention produces cage-like LaFeO3 nanomaterials with a porous structure composed of prismatic particles, which increases the reaction area in contact with the tested ethanol gas or material.

[0036] A second aspect of this invention provides a method for preparing cage-like LaFeO3 nanomaterials using ultrasound-assisted synthesis, based on the first aspect of this invention. The prepared cage-like LaFeO3 nanomaterials are used as semiconductor gas-sensitive materials. Because of the use of cage-like LaFeO3 nanomaterials, these nanomaterials can increase the reaction area in contact with the gas or material being measured.

[0037] A third aspect of this invention provides a method for preparing cage-like LaFeO3 nanomaterials using ultrasound-assisted synthesis, based on the first aspect of this invention. The prepared cage-like LaFeO3 nanomaterials are used in the fabrication of ethanol gas sensors. Because of the use of cage-like LaFeO3 nanomaterials, these nanomaterials can increase the reaction area in contact with the measured gas or material. Therefore, when used in the fabrication of ethanol gas sensors, the cage-like LaFeO3 nanomaterials exhibit very short response and recovery times, thus improving the sensitivity to ethanol gas. Attached Figure Description

[0038] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent upon reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of the invention are illustrated by way of example and not limitation, with the same or corresponding reference numerals denoteing the same or corresponding parts, wherein:

[0039] Figure 1 A flowchart illustrating the preparation process of LaFeO3 precursor powder is shown schematically.

[0040] Figure 2 The XRD patterns of LaFeO3 precursor powder at calcination temperatures of 700℃, 800℃, and 900℃ are schematically shown.

[0041] Figure 3 The SEM image of LaFeO3 precursor powder at a calcination temperature of 700 °C is shown schematically.

[0042] Figure 4 The SEM image of LaFeO3 precursor powder at a calcination temperature of 800 °C is shown schematically.

[0043] Figure 5The SEM image of LaFeO3 precursor powder at a calcination temperature of 900 °C is shown schematically.

[0044] Figure 6 The response curves of LaFeO3 precursor powder to 100ppm ethanol at different working temperatures when calcined at 700℃, 800℃, and 900℃ are schematically shown.

[0045] Figure 7 The dynamic response recovery curve of LaFeO3 precursor powder to 100ppm ethanol at 300℃ is schematically shown.

[0046] Figure 8 A flowchart illustrating the fabrication method of an ethanol gas sensor is shown. Detailed Implementation

[0047] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Unless otherwise specified, the techniques used in the embodiments are conventional means well known to those skilled in the art.

[0048] It should be noted that, unless otherwise stated, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. In this document, relational terms such as “first” and “second” are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms “connected,” “linked,” etc., should be interpreted broadly, for example, referring to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection via an intermediate medium. The terms “comprising,” “including,” or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase “comprising…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0049] In a first aspect, embodiments of the present invention provide a method for preparing cage-like LaFeO3 nanomaterials using ultrasound-assisted synthesis. The method involves calcining LaFeO3 precursor powder at 780℃-830℃ for 2-6 hours to obtain cage-like LaFeO3 nanomaterials. The cage-like LaFeO3 nanomaterials have a cage-like porous structure with a diameter of 1μm-3μm and are composed of prismatic particles with a diameter of 20nm-70nm.

[0050] In this embodiment, the cage-like LaFeO3 nanomaterials prepared by the ultrasonic-assisted synthesis method are cage-like porous structures composed of prismatic particles, which increases the reaction area in contact with the tested ethanol gas or material.

[0051] As one possible embodiment, LaFeO3 precursor powder was calcined at 780°C for 6 hours to obtain cage-like LaFeO3 nanomaterials. The cage-like LaFeO3 nanomaterials are cage-like porous structures with a diameter of 1 μm, and are composed of prismatic particles with a diameter of 70 nm.

[0052] As one possible embodiment, LaFeO3 precursor powder was calcined at 830℃ for 2 hours to obtain cage-like LaFeO3 nanomaterials. The cage-like LaFeO3 nanomaterials are cage-like porous structures with a diameter of 3 μm, and are composed of prismatic particles with a diameter of 20 nm.

[0053] As one possible embodiment, LaFeO3 precursor powder was calcined at 800℃ for 4 hours to obtain cage-like LaFeO3 nanomaterials. The cage-like LaFeO3 nanomaterials are cage-like porous structures with a diameter of 1.5 μm, and are composed of prismatic particles with a diameter of 45 nm.

[0054] Example 1

[0055] like Figure 1As shown, the preparation process of LaFeO3 precursor powder includes stirring, ultrasonication, reaction, centrifugation and washing, and grinding. In the stirring step, a mixture of 8.1% lanthanum nitrate hexahydrate, 7.9% ferric nitrate hexahydrate, 7.2% anhydrous citric acid, and 18% hexadecyltrimethylammonium bromide (by mass percentage) is dissolved in 58.8% deionized water and stirred at room temperature and pressure to obtain a first mixture. In the ultrasonication step, the first mixture is ultrasonicated once at 450W for 45 minutes to obtain a second mixture. In the reaction step, the second mixture is reacted in a reactor at 180℃ for 15 hours to obtain a third mixture. In the centrifugation and washing step, the third mixture is cooled, centrifuged, and washed after cooling to room temperature to obtain a fourth mixture. In the grinding step, the fourth mixture is dried at 90℃ and then ground into powder to obtain LaFeO3 precursor powder.

[0056] Example 2

[0057] like Figure 1 As shown, the preparation process of LaFeO3 precursor powder includes stirring, ultrasonication, reaction, centrifugation and washing, and grinding. In the stirring step, a mixture of 8.6% lanthanum nitrate hexahydrate, 7.4% ferric nitrate hexahydrate, 7.7% anhydrous citric acid, and 16% hexadecyltrimethylammonium bromide (by mass percentage) is dissolved in 60.3% deionized water and stirred at room temperature and pressure to obtain a first mixture. In the ultrasonication step, the first mixture is ultrasonicated twice at 300W for 45 minutes each time, with a 10-minute interval between adjacent ultrasonications, to obtain a second mixture. In the reaction step, the second mixture is reacted in a reactor at 150℃ for 25 hours to obtain a third mixture. In the centrifugation and washing step, the third mixture is cooled and then centrifuged and washed after cooling to room temperature to obtain a fourth mixture. In the grinding step, the fourth mixture is dried at 70℃ and then ground into powder to obtain LaFeO3 precursor powder.

[0058] Example 3

[0059] like Figure 1As shown, the preparation process of LaFeO3 precursor powder includes stirring, ultrasonication, reaction, centrifugation and washing, and grinding. In the stirring step, a mixture of 8.4% lanthanum nitrate hexahydrate, 7.6% ferric nitrate hexahydrate, 7.5% anhydrous citric acid, and 17% hexadecyltrimethylammonium bromide (by mass percentage) is dissolved in 59.5% deionized water and stirred at room temperature and pressure to obtain a first mixture. In the ultrasonication step, the first mixture is ultrasonicated twice at 380W for 45 minutes each time, with a 10-minute interval between adjacent ultrasonications, to obtain a second mixture. In the reaction step, the second mixture is reacted in a reactor at 165℃ for 20 hours to obtain a third mixture. In the centrifugation and washing step, the third mixture is cooled and then centrifuged and washed after cooling to room temperature to obtain a fourth mixture. In the grinding step, the fourth mixture is dried at 80℃ and then ground into powder to obtain LaFeO3 precursor powder.

[0060] In Examples 1, 2, and 3, the preparation process of the LaFeO3 precursor powder combined surfactant and ultrasound. The resulting LaFeO3 precursor powder was then used in a method for preparing cage-like LaFeO3 nanomaterials using ultrasound-assisted synthesis. All these methods successfully produced cage-like LaFeO3 nanomaterials with a porous, cage-like structure composed of prismatic particles. This increased the reaction area with the target gas or material, thus enabling gas sensing.

[0061] It should be noted that the surfactant is hexadecyltrimethylammonium bromide.

[0062] Comparative Example 1

[0063] The preparation process of LaFeO3 precursor powder is as follows: 8.5% lanthanum nitrate hexahydrate, 7.5% ferric nitrate hexahydrate, and 7.4% anhydrous citric acid by mass percentage are mixed and dissolved in 76.6% deionized water. After stirring at room temperature and pressure, the mixture is placed in a reaction vessel and reacted at 165℃ for 20h. After cooling to room temperature, it is centrifuged and washed, dried at 80℃, and then ground into powder to obtain LaFeO3 precursor powder.

[0064] Comparative Example 2

[0065] The preparation process of LaFeO3 precursor powder is as follows: 8.3% lanthanum nitrate hexahydrate, 7.7% ferric nitrate hexahydrate, 7.5% anhydrous citric acid, and 17% hexadecyltrimethylammonium bromide are mixed and dissolved in 59.5% deionized water. After stirring at room temperature and pressure, the mixture is placed in a reaction vessel and reacted at 165℃ for 20 hours. After cooling to room temperature, it is centrifuged and washed, dried at 80℃, and then ground into powder to obtain LaFeO3 precursor powder.

[0066] Comparative Example 3

[0067] The preparation process of LaFeO3 precursor powder is as follows: 8.5% lanthanum nitrate hexahydrate, 7.5% ferric nitrate hexahydrate, and 7.5% anhydrous citric acid by mass ratio are mixed and dissolved in 76.5% deionized water and stirred at room temperature and pressure. After stirring, the mixture is ultrasonicated twice at 370W for 45 min each time, with an interval of 10 min between adjacent ultrasonications. The mixture is placed in a reaction vessel and reacted at 165℃ for 20 h. After cooling to room temperature, the mixture is centrifuged and washed, dried at 80℃, and then ground into powder to obtain LaFeO3 precursor powder.

[0068]

[0069]

[0070] It should be noted that the surfactant refers to hexadecyltrimethylammonium bromide.

[0071] In this invention, the cage-like LaFeO3 nanomaterials possess a large porosity and specific surface area, thereby increasing the reaction area between the test gas and the cage-like LaFeO3 nanomaterials. The numerous pores allow for the passage of more test gas. Furthermore, the addition of ultrasound causes the prismatic particles to aggregate uniformly, thus maintaining the morphological composition.

[0072] Secondly, embodiments of the present invention provide an application of cage-like LaFeO3 nanomaterials. The cage-like LaFeO3 nanomaterials prepared by the ultrasonic-assisted synthesis method provided in the first aspect of the present invention are used as semiconductor gas-sensitive materials.

[0073] Thirdly, embodiments of the present invention provide an application of cage-like LaFeO3 nanomaterials. The cage-like LaFeO3 nanomaterials prepared by the ultrasonic-assisted synthesis method provided in the first aspect of the present invention are used in the preparation of ethanol gas sensors.

[0074] Example 4

[0075] like Figure 8As shown, the preparation method of the ethanol gas sensor includes a mixing step, a first coating step, a second coating step, a welding step, and an aging step. In the mixing step, cage-like LaFeO3 nanomaterials are ground and then mixed with deionized water and anhydrous ethanol to form a paste, obtaining a first slurry. The cage-like LaFeO3 nanomaterials account for 33% of the mass, deionized water for 58%, and anhydrous ethanol for 9%. In the first coating step, the first slurry is uniformly coated onto the metal electrodes of the alumina ceramic tube using screen printing, with six coating passes. In the second coating step, the first slurry is coated onto the surface of the metal electrodes, excluding the metal electrodes, using a brush, with two coating layers. In the welding step, the alumina ceramic tube treated in the second coating step is welded to a six-pin base of the sensor, and a heating resistance wire is added to form a gas-sensitive element. The two ends of the heating resistance wire are welded to two heating ends located in the middle of the hexagonal base. The aging process involves placing the gas-sensitive element on an aging table and aging it at 300°C for 48 hours to obtain an ethanol gas sensor.

[0076] Example 5

[0077] like Figure 8 As shown, the preparation method of the ethanol gas sensor includes a mixing step, a first coating step, a second coating step, a welding step, and an aging step. In the mixing step, cage-like LaFeO3 nanomaterials are ground and then mixed with deionized water and anhydrous ethanol to form a paste, obtaining a first slurry. The cage-like LaFeO3 nanomaterials comprise 35% by mass, deionized water comprises 55% by mass, and anhydrous ethanol comprises 10% by mass. In the first coating step, the first slurry is uniformly coated onto the metal electrodes of the alumina ceramic tube using screen printing, with six coating passes. In the second coating step, the first slurry is coated onto the surface of the metal electrodes, excluding the metal electrodes, using a brush, with two coating layers. In the welding step, the alumina ceramic tube treated in the second coating step is welded to a six-pin base of the sensor, and a heating resistance wire is added to form a gas-sensitive element. The two ends of the heating resistance wire are welded to two heating ends located in the middle of the hexagonal base. The aging process involves placing the gas-sensitive element on an aging table and aging it at 200°C for 48 hours to obtain an ethanol gas sensor.

[0078] Example 6

[0079] like Figure 8As shown, the preparation method of the ethanol gas sensor includes a mixing step, a first coating step, a second coating step, a welding step, and an aging step. In the mixing step, cage-like LaFeO3 nanomaterials are ground and then mixed with deionized water and anhydrous ethanol to form a paste, obtaining a first slurry. The cage-like LaFeO3 nanomaterials comprise 34% by mass, deionized water comprises 57% by mass, and anhydrous ethanol comprises 9% by mass. In the first coating step, the first slurry is uniformly coated onto the metal electrodes of the alumina ceramic tube using screen printing, with six coating passes. In the second coating step, the first slurry is coated onto the surface of the metal electrodes, excluding the metal electrodes, using a brush, with two coating layers. In the welding step, the alumina ceramic tube treated in the second coating step is welded to a six-pin base of the sensor, and a heating resistance wire is added to form a gas-sensitive element. The two ends of the heating resistance wire are welded to two heating ends located in the middle of the hexagonal base. The aging process involves placing the gas-sensitive element on an aging table and aging it at 250°C for 48 hours to obtain an ethanol gas sensor.

[0080] In Examples 4, 5, and 6, cage-like LaFeO3 nanomaterials were used. These cage-like LaFeO3 nanomaterials can increase the reaction area in contact with the gas or material being measured. Therefore, the ethanol gas sensor obtained by the preparation method of the ethanol gas sensor can be used for gas sensing.

[0081] LaFeO3 nanomaterials lose some of their La content during high-temperature calcination. 3+ and Fe 3+ This process creates oxygen vacancies. When LaFeO3 nanomaterials are exposed to air, oxygen in the air adsorbs onto the surface of the LaFeO3 nanomaterials and occupies the created vacancies, forming surface-adsorbed oxygen (O2-, O-, and O2-). During this process, a vacancy accumulation layer gradually forms on the surface of the LaFeO3 nanomaterials, resulting in a decrease in the resistance and an increase in the conductivity of the ethanol gas sensor.

[0082] LaFeO3 nanomaterials are typical P-type semiconductors. When LaFeO3 is placed in anhydrous ethanol, the oxygen previously absorbed by the LaFeO3 nanomaterials reacts with the reducing gas to generate CO2 gas and a large number of electrons. As a result, the electrons are released back into the conduction band of the LaFeO3 nanomaterials. At this time, the hole accumulation layer on the surface of the LaFeO3 nanomaterials becomes thinner, the resistance of the ethanol gas sensor increases, and the conductivity decreases.

[0083] In the first coating step of this invention, screen printing is used to uniformly coat the first slurry onto the metal electrode of the alumina ceramic tube, further enhancing the uniformity of the coating of the first slurry on the metal electrode. This increases the reaction area of ​​the cage-like LaFeO3 nanomaterials in the ethanol gas sensor in contact with the gas or material being measured.

[0084] In a specific embodiment, the sensitivity model of the ethanol gas sensor is: S = Rg / Ra, where Rg is the stable resistance value of the ethanol gas sensor in ethanol gas, Ra is the stable resistance value of the ethanol gas sensor in air, and S is the sensitivity of the ethanol gas sensor.

[0085] In this embodiment, cage-like LaFeO3 nanomaterials are used as the material for an ethanol gas sensor. The ethanol gas sensor prepared has a fast reaction time and recovery time. The synthesis process is simple, environmentally friendly and low-cost, and can be mass-produced.

[0086] For example, when the ultrasonic frequency is 400W and the gas-sensitive element is placed on an aging table for 48 hours, the cage-like LaFeO3 nanomaterials exhibit the best response to ethanol at an operating temperature of 300℃.

[0087] exist Figure 2 The absence of other diffraction peaks indicates that a pure phase has been obtained. The calcination temperature affects the crystallinity of the material; as the temperature increases, the crystallinity becomes stronger, and the diffraction peaks become sharper.

[0088] See Figure 3 When the calcination temperature is 700℃, a large number of broken particles appear.

[0089] See Figure 4 When the calcination temperature is 800℃, the number and diameter of the pores increase, forming a porous cage-like structure.

[0090] See Figure 5 When the calcination temperature is 900℃, the pores disappear, forming a closed spherical body.

[0091] The response value is obtained by measuring the change in resistance before and after the introduction of ethanol gas. Performance test graph is shown below. Figure 6 and Figure 7 .

[0092] See Figure 6 It can be seen that the sample calcined at 800℃ has the highest response value at the working temperature of 300℃, with a response value of 10.9.

[0093] See Figure 7As can be seen, the ethanol gas sensor has a very short response time and recovery time, which are 11.7 s and 4.5 s, respectively. This is mainly due to the porous cage-like structure, which provides a large surface area, giving LaFeO3 excellent ethanol gas sensing performance and thus enhancing its sensitivity to ethanol gas.

[0094] In this invention, the cage-like LaFeO3 nanomaterials possess a large porosity and specific surface area, thereby increasing the reaction area between the analyte gas and the cage-like LaFeO3 nanomaterials. Furthermore, the numerous porous structures allow for the passage of more analyte gas. Therefore, more active sites are provided, promoting additional chemical oxygen adsorption on the material surface, effectively facilitating charge transfer, and enhancing the gas-sensing performance of the material.

[0095] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a cage-like LaFeO3 nanomaterial by ultrasonic-assisted synthesis, characterized in that, LaFeO3 precursor powder was calcined at 780℃-830℃ for 2 h-6 h to obtain cage-like LaFeO3 nanomaterials. The cage-like LaFeO3 nanomaterial has a cage-like porous structure with a diameter of 1μm-3μm and is composed of prismatic particles with a diameter of 20nm-70nm. The preparation process of the LaFeO3 precursor powder is as follows: The stirring step involves dissolving the mixture in deionized water and stirring at room temperature and pressure to obtain the first mixture. The ultrasonic step involves subjecting the first mixture to ultrasonication twice at 300W-450W, with each ultrasonication lasting 45 minutes and an interval of 10 minutes between adjacent ultrasonications, to obtain the second mixture. The reaction step involves placing the second mixture in a reaction vessel and reacting it at 150℃-180℃ for 15-25 hours to obtain the third mixture. The centrifugation and washing step involves cooling the third mixture to room temperature, followed by centrifugation and washing to obtain the fourth mixture. The grinding step involves drying the fourth mixture at 70℃-90℃ and then grinding it into powder to obtain LaFeO3 precursor powder. The components and their mass percentages of the mixture include: The content of lanthanum nitrate hexahydrate is 8.1%-8.6%, ferric nitrate hexahydrate is 7.4%-7.9%, anhydrous citric acid is 7.2%-7.7%, hexadecyltrimethylammonium bromide is 16%-18%, and deionized water is 58.5%-61%.

2. The method according to claim 1, wherein the method is characterized by, The components and their mass percentages of the mixture include: The composition of lanthanum nitrate hexahydrate is 8.4%, ferric nitrate hexahydrate is 7.6%, anhydrous citric acid is 7.5%, hexadecyltrimethylammonium bromide is 17%, and deionized water is 59.5%.

3. The application of a cage-like LaFeO3 nanomaterial prepared by the method described in claim 1 or 2 as a semiconductor gas-sensitive material.

4. The application of a cage-like LaFeO3 nanomaterial prepared by the method described in claim 1 or 2 in the preparation of an ethanol gas sensor.

5. Use according to claim 4, characterized in that, The preparation method of the ethanol gas sensor includes the following steps: In the mixing step, the cage-like LaFeO3 nanomaterials are ground and then mixed with deionized water and anhydrous ethanol to form a paste, thus obtaining the first slurry. In the first coating step, the first paste is evenly coated onto the metal electrode of the alumina ceramic tube using screen printing, and the coating is applied 6 times. The second coating step involves using a brush to apply the first slurry to the surface of the metal electrode other than the metal electrode tip, with two coating layers. In the welding step, the alumina ceramic tube treated in the second coating step is welded onto the six-pin base of the sensor, and a heating resistance wire is added to form a gas-sensitive element, wherein the two ends of the heating resistance wire are respectively welded to two heating ends located in the middle of the six-pin base; The aging step involves placing the gas-sensitive element on an aging table and aging it at 200-300 °C for 48 hours to obtain an ethanol gas-sensitive sensor.

6. Use according to claim 5, characterized in that, In the mixing step: The cage-like LaFeO3 nanomaterials comprise 33%-35% by mass, the deionized water comprises 55%-58% by mass, and the anhydrous ethanol comprises 9%-12% by mass.

7. Use according to claim 5, characterized in that, The sensitivity model of the ethanol gas sensor is as follows: S=Rg / Ra, Where Rg is the stable resistance value of the ethanol gas sensor in ethanol gas, Ra is the stable resistance value of the ethanol gas sensor in air, and S is the sensitivity of the ethanol gas sensor.

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