Nanometer ruthenium dioxide and preparation method thereof

Abstract

The application discloses nano-ruthenium dioxide and a preparation method thereof, and belongs to the technical field of materials. The preparation method is a homogeneous hydrothermal method for preparing the product. By setting parameters of a reaction system, the nano-ruthenium dioxide product with high yield, high purity, high specific surface area and high crystallinity can be prepared in a short time.

Description

Technical Field

[0001] This invention relates to the field of materials technology, specifically to a nano-ruthenium dioxide and its preparation method. Background Technology

[0002] Due to its excellent chemical stability, high power load density, and low temperature coefficient of resistance, nano-ruthenium dioxide is widely used as the conductive phase component in resistive pastes.

[0003] However, existing nano-ruthenium dioxide production processes easily generate toxic RuO4 gas, requiring high standards for production processes and conditions. On the other hand, current nano-ruthenium dioxide powders are mainly prepared by chemical synthesis, but this method has certain uncontrollability and many factors affecting product quality, making it impossible to balance yield and quality. Especially in liquid-phase reaction systems, if the solution reaction is insufficient, it will not only affect the product yield but also lead to uneven particle dispersion and small specific surface area, which is not conducive to the preparation and performance assurance of subsequent resistance slurries. On the other hand, if a stable and mild reaction system is used to ensure sufficient product reaction, the production time will be too long, which is not conducive to industrial production. Summary of the Invention

[0004] Based on the deficiencies of existing technologies, the present invention aims to provide a method for preparing nano-ruthenium dioxide. This method prepares the product using a homogeneous hydrothermal process. By setting the parameters of the reaction system, nano-ruthenium dioxide products with high yield, high purity, high specific surface area, and high crystallinity can be prepared in a short time.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing nano-ruthenium dioxide includes the following steps:

[0007] A solution of water-soluble ruthenium source was prepared, and then a homogeneous hydrothermal reaction was carried out under closed conditions. The resulting reactants were then processed to obtain the nano-ruthenium dioxide.

[0008] The homogeneous hydrothermal reaction is carried out at a temperature ≥160℃ for a time ≥8h; the solute mass concentration of the solution is 8-21%.

[0009] In a second aspect, the present invention provides nano-ruthenium dioxide prepared by the aforementioned preparation method, wherein the nano-ruthenium dioxide has a purity ≥99.5% and a specific surface area of ​​170–195 m². 2 / g, with a crystallinity of 65-85%.

[0010] The beneficial effect of the present invention is that it provides a method for preparing nano-ruthenium dioxide. The method prepares the product in a homogeneous hydrothermal manner. By setting the parameters of the reaction system, nano-ruthenium dioxide products with high yield, high purity, high specific surface area and high crystallinity can be prepared in a short time. Attached Figure Description

[0011] Figure 1 This is a scanning electron microscope image of the nano-ruthenium dioxide obtained in Example 1 of the present invention.

[0012] Figure 2 This is a particle size distribution diagram of the nano-ruthenium dioxide obtained in Example 1 of the present invention.

[0013] Figure 3 The image shows the XRD pattern of the nano-ruthenium dioxide obtained in Example 1 of this invention.

[0014] Figure 4 This is a scanning electron microscope image of the nano-ruthenium dioxide obtained in Comparative Example 1 of the present invention. Detailed Implementation

[0015] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0016] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0017] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0018] The present invention is further illustrated below with specific embodiments:

[0019] A method for preparing nano-ruthenium dioxide includes the following steps:

[0020] A solution of water-soluble ruthenium source was prepared, and then a homogeneous hydrothermal reaction was carried out under closed conditions. The resulting reactants were then processed to obtain the nano-ruthenium dioxide.

[0021] The homogeneous hydrothermal reaction is carried out at a temperature ≥160℃ for a time ≥8h; the solute mass concentration of the solution is 8-21%.

[0022] Currently, the most common process for preparing nano-ruthenium dioxide powder is hydrothermal synthesis. This method primarily involves pre-synthesizing intermediate products (ruthenium hydroxide, chlororuthenic acid, etc.) from a ruthenium source, then further converting them into hydrates, followed by calcination to obtain the final product. However, if preparation is carried out solely according to the theoretical process without human intervention, the resulting product will not only have low yield and purity but also exhibit significant agglomeration and a small specific surface area. Without subsequent multiple purification processes or ball milling, it cannot be used in the preparation of resistive slurries. Human intervention involves strictly controlling reaction conditions during intermediate product processing and introducing various additives to assist the reaction, such as introducing precipitants and controlling the introduction rate, and introducing pH adjusters to regulate pH in real time. However, this approach not only increases production difficulty and time but also introduces additional impurities, reducing product quality. Therefore, in the technical solution of this invention, an aqueous solution containing ruthenium is used as a raw material. Under closed conditions, a homogeneous hydrothermal reaction is carried out directly without introducing other materials. Under specific reaction system and reaction conditions, the water-soluble ruthenium source reacts directly and continuously with water to generate hydrated nano-ruthenium dioxide powder. There is no need to control the intermediate products, and there is no impurity contamination caused by the introduction of additional additives. After conventional impurity removal, calcination, and sieving, the resulting product is a powder product with high crystallinity, high purity, and high specific surface area, which is very suitable for the preparation of resistance slurry. Due to this special homogeneous reaction process, no free residual ruthenium ions will appear in the product system, the yield reaches 100%, and the production efficiency is significantly improved.

[0023] In some embodiments, the water-soluble ruthenium source includes ruthenium trichloride and its hydrate.

[0024] In some embodiments, the water-soluble ruthenium source is ruthenium trichloride and its hydrate.

[0025] In some embodiments, the solution is an aqueous solution of ruthenium trichloride.

[0026] In some embodiments, the solute mass content of the solution is a range of one or both of 8%, 10%, 13%, 14%, 15%, 16%, 18%, 20%, and 21%.

[0027] In the scheme described in this invention, unlike conventional hydrothermal reaction systems, under specific temperature and closed-environment homogeneous reaction conditions, ruthenium source and water directly react chemically to form hydrates without the need for additional additives (if additional substances such as pH adjusters and dispersants are introduced, it may introduce impurity ions and even affect the precipitation of hydrates). In this process, the initial solution concentration is crucial. If the concentration is too high, it may cause uneven particle size and poor dispersibility (forming secondary particles), resulting in a smaller specific surface area, lower crystallinity, and some raw materials failing to react, leading to a yield of less than 100%. Conversely, if the concentration is too low, although a 100% yield can be guaranteed, the specific surface area will be even smaller, failing to meet the requirements for subsequent applications.

[0028] In some embodiments, the sealing condition is in a closed hydrothermal reactor.

[0029] For example, in some embodiments, the solution is placed in a hydrothermal reactor for a homogeneous hydrothermal reaction.

[0030] In some embodiments, the ambient pressure inside the hydrothermal reactor is 0.3 to 4 MPa when the solution undergoes a homogeneous hydrothermal reaction.

[0031] When a homogeneous hydrothermal reaction is carried out in a hydrothermal reactor, the pressure reached by the formation of water vapor at a specific temperature can promote the formation and precipitation of hydrates. This process does not require concern about the impact of the introduction of external substances on product quality and yield. Under these reaction conditions, the temperature range setting is crucial. If the setting is improper, it will inevitably lead to insufficient pressure in the closed space, resulting in low product precipitation and poor quality.

[0032] For example, in some embodiments, the temperature during the homogeneous hydrothermal reaction is ≤220°C.

[0033] Specifically, the temperature during the homogeneous hydrothermal reaction is 180–220°C.

[0034] In some embodiments, the temperature during the homogeneous hydrothermal reaction is a range of one or both of 180°C, 190°C, 200°C, 210°C, and 220°C.

[0035] At higher temperatures, excessively rapid precipitation rates can lead to a certain reduction in the specific surface area of ​​the product. Considering energy consumption and quality, those skilled in the art can choose reaction conditions of 190–210°C.

[0036] In some embodiments, the homogeneous hydrothermal reaction takes 8 to 24 hours.

[0037] For example, in some embodiments, the time of the homogeneous hydrothermal reaction is a range of one or both of 8h, 10h, 12h, 15h, 18h, 20h, 22h, and 24h.

[0038] In some embodiments, the homogeneous hydrothermal reaction is carried out in a homogeneous reactor, the homogeneous reactor rotating at a speed of 2 to 8 rpm.

[0039] Existing conventional hydrothermal reaction systems are generally carried out in a static environment. However, such processes are time-consuming, and after product formation and solid precipitation, the uniformity of pressure, composition, and temperature distribution of the overall system decreases and fluctuates significantly, resulting in a decline in product quality and a low yield. In the present invention, the hydrothermal system is transformed into a homogeneous reaction system by using a reaction device with a built-in rotation function, such as a homogeneous reactor. This can effectively solve the problems of composition fluctuation and uneven spatial pressure distribution caused by ruthenium during hydrate precipitation. (Those skilled in the art can also use other reaction settings with similar functions, and are not limited to homogeneous reactors. For example, a magnetically controlled device can be used to set up a magnetic rotation field to homogeneously disperse the liquid-phase reaction system in real time.)

[0040] In some embodiments, the reactants are removed from the furnace after impurity removal, and the impurity removal process includes the following steps:

[0041] The reactants were placed in water, and the resulting mixture was adjusted to pH > 10. The supernatant was then separated and removed.

[0042] For example, in some embodiments, the mass ratio of the reactant to water is 1:(48-52).

[0043] In some embodiments, ammonia is used to adjust the pH of the mixture.

[0044] Using ammonia as a flocculant, hydrated nano-ruthenium dioxide in the hydrate can be rapidly precipitated, while unprecipitated impurities such as chloride ions will concentrate in the supernatant, achieving rapid separation and impurity removal.

[0045] Those skilled in the art can also use other methods to remove impurities, such as rinsing with organic solvents or using adsorbents for physical adsorption, and are not limited to the methods described above.

[0046] In some embodiments, after the separation and removal of the supernatant, the reactants are further dried at a temperature ≥80°C.

[0047] In some embodiments, the obtained reactants are purified and then calcined at a temperature of 300–600°C for 30–120 min.

[0048] The calcination process enables the dehydration and crystallization of hydrated nano-ruthenium dioxide. At the same time, the specific surface area and particle size of the crystallized powder can be controlled. Those skilled in the art can adjust the temperature parameters and reaction time in this process according to actual needs, thereby achieving the required size and specification distribution.

[0049] In some embodiments, the atmosphere during calcination is air, and the heating rate during calcination is 8–15 °C / min.

[0050] In some embodiments, the sieve mesh size is 250 mesh.

[0051] In each embodiment, the ruthenium dioxide nanoparticles prepared by the method have a purity ≥99.5% and a specific surface area of ​​170–195 m². 2 / g, with a crystallinity of 65-85%.

[0052] The preparation method described in this invention is simple and rapid, requiring only water as the raw material for ruthenium. The prepared nano-ruthenium dioxide has a high specific surface area and high crystallinity, and also has high purity, making it very suitable for preparing resistive pastes.

[0053] For example, in some embodiments, the specific surface area of ​​the nano-ruthenium dioxide is 170 m². 2 / g、172m 2 / g、176m 2 / g、180m 2 / g、182m 2 / g、185m 2 / g、186m 2 / g、188m 2 / g、190m 2 / g、195m 2 A value within the range of one or both of / g. In some embodiments, the specific surface area is 176m². 2 / g≤ to ≤ 194m 2 / g. In some embodiments, the crystallinity of the nano-ruthenium dioxide is within the range of one or any two of 65%, 68%, 70%, 71%, 72%, 75%, 78%, 80%, 81%, and 85%. In some embodiments, the crystallinity is between 68% and 81%.

[0054] In some embodiments, the primary particle size of the nano-ruthenium dioxide is 5–24 nm. In some embodiments, the nano-ruthenium dioxide satisfies: (D v90 -D v10 ) / D v50 =1.3~1.4.

[0055] Among them, D v10D represents the particle size of nano-ruthenium dioxide when the cumulative particle size distribution number reaches 10% based on a volume criterion. v50 D represents the particle size of nano-ruthenium dioxide when the cumulative particle size distribution number reaches 50% based on a volume criterion. v90 This refers to the particle size of nano-ruthenium dioxide when the cumulative particle size distribution reaches 90% based on a volume criterion.

[0056] For example, in some embodiments, the nano-ruthenium dioxide satisfies: (D v90 -D v10 ) / D v50 =A range of values ​​for one or any two of the following: 1.3, 1.32, 1.34, 1.35, 1.37, 1.38, 1.39, and 1.4.

[0057] The present invention also provides a resistive paste comprising the nano-ruthenium dioxide described in the present invention.

[0058] The nano-ruthenium dioxide particles of this invention have good dispersibility, uniform morphology, large specific surface area, high crystallinity, and high purity. When used to prepare resistive pastes, they can achieve comprehensive performance requirements such as good rheological and printing properties, high sintering density, good resistive stability, and low TCR.

[0059] The present invention is further illustrated below with specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention:

[0060] The ruthenium trichloride used in each embodiment and comparative example was a commercially available product, and the homogeneous reactor was a model HT-JX-8*250 manufactured by Shanghai Huotong Experimental Instrument Co., Ltd.

[0061] Example 1

[0062] The present invention discloses a nano-ruthenium dioxide and its preparation method, comprising the following preparation steps:

[0063] (1) Prepare a solution with a solute mass concentration of 18% by adding water with ruthenium trichloride as solute at room temperature, and stir thoroughly with magnetic stirring.

[0064] (2) Pour the solution into a 100 mL hydrothermal reactor, then place it in a homogeneous reactor, set the reaction temperature to 180 °C and the rotation speed to 4 rpm, and perform a homogeneous hydrothermal reaction for 12 h to obtain the reactants.

[0065] (3) First, mix the reactants with water at a mass ratio of 1:50 and stir for 30 minutes. Then, add ammonia water to adjust the pH of the mixture to above 10. Let it stand, remove the supernatant, and repeat this operation multiple times until chloride ions cannot be detected in the supernatant by the nitrate detection method.

[0066] (4) The reactants after impurity removal in step (3) are dried in an oven at 80°C, and then heated to 300°C at a rate of 10°C / min and calcined for 1 hour in an air atmosphere. After cooling, they are passed through a 250-mesh sieve to obtain the nano-ruthenium dioxide.

[0067] Example 2

[0068] The present invention describes a nano-ruthenium dioxide and its preparation method, which differs from Example 1 only in that the mass concentration of the solute in the solution in step (1) is 15%.

[0069] Example 3

[0070] The present invention describes a nano-ruthenium dioxide and its preparation method, which differs from Example 1 only in that the mass concentration of the solute in the solution in step (1) is 13%.

[0071] Example 4

[0072] The present invention describes a nano-ruthenium dioxide and its preparation method, which differs from Example 1 only in that the mass concentration of the solute in the solution in step (1) is 10%.

[0073] Example 5

[0074] The present invention describes a nano-ruthenium dioxide and its preparation method, which differs from Example 1 only in that the reaction temperature in step (2) is set to 220°C.

[0075] Example 6

[0076] The present invention provides a nano-ruthenium dioxide and its preparation method, which differs from Example 1 only in that the reaction temperature in step (2) is set to 200°C.

[0077] Comparative Example 1

[0078] A nano-ruthenium dioxide and its preparation method, comprising the following preparation steps:

[0079] (1) Prepare a solution with a solute mass concentration of 18% by adding water with ruthenium trichloride as solute at room temperature, and stir thoroughly with magnetic stirring.

[0080] (2) Pour the solution into a 100mL hydrothermal reactor, then place it in an oven and set the reaction temperature to 180℃ for 12h to obtain the reactants;

[0081] (3) First, mix the reactants with water at a mass ratio of 1:50 and stir for 30 minutes. Then, add ammonia water to adjust the pH of the mixture to above 10, let it stand, remove the supernatant, and repeat the operation several times until the removed supernatant does not contain chloride ions.

[0082] (4) The reactants after impurity removal in step (3) are dried in an oven at 80°C, and then heated to 300°C at a rate of 10°C / min and calcined for 1 hour in an air atmosphere. After cooling, they are passed through a 250-mesh sieve to obtain the nano-ruthenium dioxide.

[0083] Comparative Example 2

[0084] A method for preparing nano-ruthenium dioxide includes the following preparation steps:

[0085] (1) A solution with a mass concentration of 18% was prepared by adding water with ruthenium trichloride as solute at room temperature. The pH of the solution was then adjusted to 8 by ammonia titration and thoroughly stirred with magnetic stirring.

[0086] (2) Pour the solution into a 100mL hydrothermal reactor and then place it in a homogeneous reactor. Set the reaction temperature to 180℃ and the rotation speed to 4rpm for 12h of homogeneous hydrothermal reaction. After the reaction, no precipitate was found, so no further operation was performed.

[0087] Comparative Example 3

[0088] A nano-ruthenium dioxide and its preparation method, differing from Example 1 only in that the homogeneous hydrothermal reaction time in step (2) is 5 hours.

[0089] Comparative Example 4

[0090] A nano-ruthenium dioxide and its preparation method are disclosed, which differ from Example 1 only in that the mass concentration of the solute in the solution in step (1) is 27%.

[0091] Comparative Example 5

[0092] A nano-ruthenium dioxide and its preparation method are disclosed, which differ from Example 1 only in that the mass concentration of the solute in the solution in step (1) is 4%.

[0093] Comparative Example 6

[0094] A nano-ruthenium dioxide and its preparation method are different from those in Example 1, except that the reaction temperature in step (2) is set to 160°C.

[0095] Example 1

[0096] To verify the properties and quality of the products prepared by the method described in this invention, the specific surface area and crystallinity of the products in the examples and comparative examples were measured; at the same time, the yield of the products in each method was statistically analyzed.

[0097] The specific surface area test was conducted using a McMurray Tik 3020 specific surface area analyzer. Before the test, the surface area was thoroughly dried. The test temperature was 180℃ and the degassing time was 1 hour. The data results were statistically analyzed using the adsorption branch.

[0098] Crystallinity was determined by XRD. Experimental conditions: Cu, Kα, Ni filter; tube voltage 40 kV, tube current 40 mA; scan speed 8° / min, scan angle 20-80°. Product yield was calculated based on the amount of ruthenium ions in the residual liquid phase after reactant formation. If no ruthenium ions were detected, the product yield was considered to be 100%. Otherwise, the actual yield was calculated as 100% × (amount of ruthenium ions in the raw material - amount of ruthenium ions in the residual liquid phase) / amount of ruthenium ions in the raw material.

[0099] The test results are shown in Table 1.

[0100] Table 1

[0101] product <![CDATA[Specific surface area (m 2 / g)]]> Crystallinity (%) Yield (%) Example 1 182 68 100 Example 2 185 71 100 Example 3 185 72 100 Example 4 194 75 100 Example 5 176 78 100 Example 6 186 81 100 Comparative Example 1 165 69 82 Comparative Example 2 / / / Comparative Example 3 180 23 76 Comparative Example 4 173 63 92 Comparative Example 5 156 68 100 Comparative Example 6 132 59 90

[0102] The test results show that the yield of the products in each embodiment was 100% during the preparation process, with no material waste. At the same time, the prepared products had a large specific surface area, high crystallinity, and excellent overall performance.

[0103] Electron microscopy was performed on the product of Example 1 (observed using a Zeiss Sigma 300 field emission scanning electron microscope with an accelerating voltage of 5 kV), and the results are as follows. Figure 1 As shown, the product has a small particle size, and the particle morphology is basically round or elliptical. The particle size of the product is in the range of 8-18 nm (analysis of 200 primary particles using nanomeasure software showed an average particle size of 18.68 nm), and no abnormal morphology was observed. The primary particles in the aggregate also showed a uniform distribution. The product was analyzed using a Malvern laser particle size analyzer-3000 (particle refractive index 4.800, particle absorptivity 0.100), and the results are as follows. Figure 2 As shown, (D) v90 -D v10 ) / D v50 =1.37, and the XRD pattern of the product is as follows: Figure 3 As shown, after comparison, it exhibits an ideal rutile phase; the product was treated with XRF melting method, and the product composition was determined using semi-quantitative full-spectrum analysis, as shown in Table 2.

[0104] Table 2

[0105]

[0106] It can be seen that the purity of the product can reach 99.65%, which fully meets the material purity requirements for resistance paste grade.

[0107] In contrast, the product in Comparative Example 1 was prepared using a conventional hydrothermal method. The same method was used to observe it, and the results were as follows: Figure 4As shown, the particle size of the product is not uniform and there is an obvious abnormal morphology of the crystals. Due to the formation of this abnormal morphology, the specific surface area of ​​the product is small and the crystallinity is less than 70%. In this process, since no additional additives are introduced, the hydrothermal reaction is incomplete, so the yield of the product is only 82%.

[0108] In contrast to the product of Comparative Example 1, the product preparation process of Comparative Example 2 is carried out using a homogeneous hydrothermal reaction. However, before implementation, an additional pH adjuster was introduced to adjust the alkalinity according to the existing hydrothermal method teaching, thereby promoting the formation of the intermediate product ruthenium hydroxide in the product. However, this approach actually caused the homogeneous hydrothermal reaction to fail, and no reaction products appeared after implementation. This fully demonstrates that the existing conventional hydrothermal process operation teaching is completely unsuitable for the homogeneous hydrothermal reaction system described in this invention.

[0109] In this homogeneous hydrothermal reaction system, as can be clearly seen from Examples 1-4 and Comparative Examples 4 and 5, the reaction raw materials of the product of the present invention only require water and a ruthenium source, without any other additives. In this process, the concentration of the prepared solution will directly affect the product generation efficiency. If the concentration is too high, the reactants will not be generated sufficiently and uniformly, or even the reaction will be incomplete. If the concentration is too low, although the yield can be guaranteed to reach 100%, the specific surface area of ​​the product will be much lower than that of the product in the examples, and it will also fail to meet the usage requirements.

[0110] On the other hand, as can be seen from Examples 1, 5-6 and Comparative Example 6, the temperature of the homogeneous hydrothermal reaction also directly affects the reaction effect. If the reaction temperature is too low, the reaction process will not be complete, the product yield will be low, and the product quality will be poor. As the temperature increases, the reaction degree reaches completeness, and the quality of the reactants formed is also significantly improved. However, after reaching a certain level, the quality of the reactants will not continue to improve. Considering the quality and production consumption, a reaction temperature below 210°C is most suitable.

[0111] Finally, under the aforementioned reaction conditions, the reaction and formation efficiency of the hydrated reactants are directly proportional to the reaction time. If the reaction time is insufficient, as shown in Comparative Example 3, the water vapor in the closed system has not yet formed sufficient reaction pressure, and the internal system temperature has not reached a suitable level, resulting in a large amount of ruthenium source remaining in the reaction liquid, leading to poor product quality and low yield.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing nano-ruthenium dioxide, characterized in that, Includes the following steps: A solution of water-soluble ruthenium source was prepared, and then a homogeneous hydrothermal reaction was carried out under closed conditions. The resulting reactants were then processed to obtain the nano-ruthenium dioxide. The homogeneous hydrothermal reaction is carried out at a temperature ≥160℃ for a time ≥8h; the solute mass concentration of the solution is 8-21%.

2. The method for preparing nano-ruthenium dioxide as described in claim 1, characterized in that, The water-soluble ruthenium source includes ruthenium trichloride and its hydrate.

3. The method for preparing nano-ruthenium dioxide as described in claim 1, characterized in that, The water-soluble ruthenium source is ruthenium trichloride and its hydrate.

4. The method for preparing nano-ruthenium dioxide as described in claim 1, characterized in that, The temperature during the homogeneous hydrothermal reaction is ≤220℃.

5. The method for preparing nano-ruthenium dioxide as described in claim 1, characterized in that, The homogeneous hydrothermal reaction takes 8 to 24 hours.

6. The method for preparing nano-ruthenium dioxide as described in claim 1, characterized in that, The solution is placed in a hydrothermal reactor and then subjected to a homogeneous hydrothermal reaction in a homogeneous reactor at a rotation speed of 2 to 8 rpm, and / or the ambient pressure inside the hydrothermal reactor during the homogeneous hydrothermal reaction is 0.3 to 4 MPa.

7. The method for preparing nano-ruthenium dioxide as described in claim 1, characterized in that, The resulting reactants are subjected to a purification process, which includes the following steps: The reactants were placed in water, and the resulting mixture was adjusted to pH > 10. The supernatant was then separated and removed.

8. The method for preparing nano-ruthenium dioxide as described in claim 1, characterized in that, The resulting reactants are purified and then calcined at a temperature of 300–600°C for 30–120 min.

9. The nano-ruthenium dioxide prepared by the method for preparing nano-ruthenium dioxide according to any one of claims 1 to 8, characterized in that, The nano-ruthenium dioxide has a purity of ≥99.5% and a specific surface area of ​​170–195 m². 2 / g, with a crystallinity of 65-85%.

10. The nano-ruthenium dioxide as described in claim 9, characterized in that, The primary particle size of the nano-ruthenium dioxide is 5–24 nm.

11. The nano-ruthenium dioxide as described in claim 9, characterized in that, The nano-ruthenium dioxide satisfies: (D v90 -D v10 ) / D v50 =1.3~1.4; Among them, D v10 D represents the particle size of nano-ruthenium dioxide when the cumulative particle size distribution number reaches 10% based on a volume criterion. v50 D represents the particle size of nano-ruthenium dioxide when the cumulative particle size distribution number reaches 50% based on a volume criterion. v90 This refers to the particle size of nano-ruthenium dioxide when the cumulative particle size distribution reaches 90% based on a volume criterion.

12. A resistive paste, characterized in that, This includes nano-ruthenium dioxide prepared by the preparation method according to any one of claims 1 to 8, or nano-ruthenium dioxide according to any one of claims 9 to 11.

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