CN111410241A - Preparation method of ruthenium dioxide for resistor slurry - Google Patents
Preparation method of ruthenium dioxide for resistor slurry Download PDFInfo
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Abstract
The invention relates to a preparation method of ruthenium dioxide for resistance paste, belonging to the technical field of inorganic materials and fine chemical engineering. According to the invention, parallel feeding is adopted, the feeding speeds of the ruthenium chloride solution and the aqueous alkali are controlled, the pH value of a reaction system can be stabilized to 7-8, the reaction system is far away from the isoelectric point of a precursor, the heat and mass transfer speeds are high, the ion movement and collision opportunities are accelerated, the particle growth speed is higher than the nucleation speed, the surface activity is correspondingly reduced after crystal nuclei grow, the intermolecular force is weakened, and the powder agglomeration tendency is reduced. Therefore, the prepared ruthenium dioxide powder has good uniformity, less agglomeration and greatly improved performance.
Description
Technical Field
The invention relates to a preparation method of ruthenium dioxide for resistance paste, belonging to the technical field of inorganic materials and fine chemical engineering.
Background
Ruthenium dioxide has high resistance stability and a wide resistance range, and is an important raw material of a conductive phase in the resistance paste. The resistance and other properties of the ruthenium dioxide glass glaze resistor depend on the preparation method and the treatment way of the ruthenium dioxide raw material to a great extent. The preparation methods of ruthenium dioxide are various, including a calcination method, a direct oxidation method, a sol-gel method, a chemical precipitation method and the like, and a hydrothermal method, a solid phase grinding method and the like are developed along with the improvement of the technology. The chemical precipitation method is the most extensive preparation method for synthesizing high-purity nano-particles, and has the advantages of simple process, convenient operation and better controllability compared with a calcination method and an oxidation method. The chemical precipitation method for preparing ruthenium oxide is divided into two methods, one is a hydrolysis method and the other is a reduction method. Wherein, Ni and Fe impurities are easily introduced when the reduction method is used for preparing ruthenium dioxide, the resistance film surface is poor when the reduction method is used, toxic and harmful substances (chlorine, ruthenium tetroxide and the like) are more in the preparation process, and the operation environment is severe; the method for synthesizing ruthenium dioxide by hydrolysis reaction has high production efficiency, does not introduce other impurity ions, and has safe and nontoxic preparation process and convenient operation.
At present, manufacturers at home and abroad mostly use hydrolytic chlororuthenic acid to prepare ruthenium dioxide, but toxic gases such as chlorine, ruthenium tetroxide and the like are discharged in the preparation process of the method, and the operation environment is severe. Meanwhile, in the process of preparing ruthenium dioxide by a hydrolysis method, the pH value at the hydrolysis end point has obvious influence on the final ruthenium dioxide powder, the hydrolysis is incomplete due to the excessively low pH value at the hydrolysis end point, peptization is easily formed in the washing process along with the increase of the pH value at the hydrolysis end point, the washing effect is not good due to the excessively low and high pH values of the hydrolysis, the workload is increased, the production period is prolonged, and the product yield is influenced; on the other hand, the pH at the end of the hydrolysis affects the dispersion effect of the ruthenium dioxide powder. Therefore, controlling the hydrolysis end point pH plays a critical role in the performance of the product.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide the preparation method of the ruthenium dioxide for the resistor slurry, the method can stably control the pH value of a reaction system to be in a required range, ions nucleate in the stable pH value system, and the obtained particles have good uniformity.
In order to achieve the purpose, the invention adopts the technical scheme that: a preparation method of ruthenium dioxide for resistor paste comprises the following steps:
(1) respectively preparing a ruthenium chloride solution and an alkali solution;
(2) determining the flow rate ratio of the ruthenium chloride solution to the alkali solution during the reaction, namely taking 100m L ruthenium chloride solution, adding the alkali solution while stirring, recording the dosage of the alkali solution as A m L when the reaction reaches the pH value of 7-8, and determining the flow rate ratio of the ruthenium chloride solution to the alkali solution as 100: A during the reaction;
(3) and (3) hydrolysis reaction: controlling the temperature of the ruthenium chloride solution and the aqueous alkali at 60-80 ℃, simultaneously adding the ruthenium chloride solution and the aqueous alkali according to the flow rate ratio determined in the step (2) under stirring, controlling the pH value of the solution at 7-8, and obtaining a solution containing ruthenium dioxide hydrate after complete hydrolysis;
(4) aging: aging the solution containing the ruthenium dioxide hydrate obtained in the step (3);
(5) washing with water: standing the aged solution containing the ruthenium dioxide hydrate, removing the supernatant, adding water, stirring, adjusting the pH value, standing, washing and filtering to obtain a filter cake;
(6) and (3) calcining: and heating and calcining the filter cake to obtain the ruthenium dioxide for the resistance slurry.
The wet chemical synthesis is a process of continuously conducting heat and mass transfer, the nucleation and growth of particles are influenced by the temperature, pH value and concentration of a system, the fluctuation range of the three is large, the particle size fluctuation is large, the obtained powder is seriously agglomerated, the performance of the powder is poor, and the electrical performance of the thin film resistor is directly influenced by the conductive phase.
The pH value of a system is a process which is constantly changed from low to high or from high to low, when the reaction passes through an isoelectric point, the particle agglomeration is very serious, although the reaction end point is far away from the isoelectric point, partial particles are dispersed, but a large number of particles can not be depolymerized due to the previous agglomeration. In the prior art, alkali is usually added into ruthenium chloride solution during hydrolysis, and due to the strong acidity of the ruthenium chloride solution, the pH value of the system is slowly increased from a negative value to an end-point pH value, and needs to pass through the isoelectric point of a precursor, so that agglomeration is aggravated, and the performance of the prepared powder is poor.
Compared with the prior art, the method has the greatest advantages that the pH value of the system can be stabilized, the pH value is far away from the isoelectric point of a precursor, the heat and mass transfer speed is high, the ion movement and collision opportunities are accelerated, the particle growth speed is higher than the nucleation speed, the surface activity is correspondingly reduced after crystal nuclei grow up, the intermolecular force is weakened, and the powder agglomeration tendency is reduced. Therefore, the prepared powder has good uniformity, less agglomeration and greatly improved performance.
The dosage of the alkali liquor is influenced by the following factors: the type of the alkali liquor, the concentration of the alkali liquor and the pH value adjusted to the alkali liquor; because the acidity of ruthenium chloride is different from manufacturer to manufacturer, although the concentration of ruthenium chloride can be determined, the amount of alkali added is different, so the amount of alkali A is not a fixed value. Therefore, a flow rate ratio test with a base was required before each batch of ruthenium chloride was reacted.
As a preferred embodiment of the preparation method, in the step (1), the concentration of ruthenium ions in the ruthenium chloride solution is 3-8 g/L, and the concentration of the alkali solution is 1-6 mol/L. the concentration of ruthenium ions has an influence on the preparation method, the lower the concentration is, the higher the specific surface area of the prepared ruthenium dioxide is, but the production efficiency is too low, and the concentration range meets the condition of higher specific surface area, the production efficiency is improved as much as possible, and the obtained proper reaction concentration.
In a preferred embodiment of the preparation method of the present invention, in the step (1), the base is at least one of potassium hydroxide, sodium hydroxide, potassium carbonate and sodium carbonate.
As a preferred embodiment of the production method of the present invention, in the step (2), the reaction is carried out to a pH of 7.5. The pH is used to determine the rate of addition and too large or too small a pH will result in an increased flow rate control fineness requirement.
As a preferable embodiment of the preparation method of the present invention, in the step (3), an acid solution or an alkali solution is used to control the pH value of the solution to 7-8.
As a preferable embodiment of the preparation method of the present invention, the acid solution is a hydrochloric acid solution, and the alkali solution is at least one of a potassium carbonate solution, a sodium carbonate solution, a potassium hydroxide solution, and a sodium hydroxide solution.
As a preferred embodiment of the preparation method, in the step (4), the aging temperature is 80-90 ℃ and the aging time is 1-2 h.
In a preferred embodiment of the preparation method of the present invention, in the step (5), the pH is adjusted to 5 to 7.
In the preferable embodiment of the preparation method of the present invention, in the step (6), the calcination temperature is 400 to 500 ℃, and the calcination time is 1 to 2 hours.
In a second aspect, the invention provides ruthenium dioxide for resistor paste prepared by the above preparation method.
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the invention, parallel feeding is adopted, the feeding speeds of the ruthenium chloride solution and the aqueous alkali are controlled, the pH value of a reaction system can be stabilized to 7-8, the reaction system is far away from the isoelectric point of a precursor, the heat and mass transfer speeds are high, the ion movement and collision opportunities are accelerated, the particle growth speed is higher than the nucleation speed, the surface activity is correspondingly reduced after crystal nuclei grow, the intermolecular force is weakened, and the powder agglomeration tendency is reduced. Therefore, the prepared ruthenium dioxide powder has good uniformity, less agglomeration and greatly improved performance.
(2) The method adopts the hydrolysis of the ruthenium trichloride to prepare the ruthenium dioxide, has simple operation and can not generate toxic gas.
Detailed Description
To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to specific examples.
Example 1
One embodiment of the preparation method of ruthenium dioxide for resistor paste comprises the following steps:
(1) respectively preparing a ruthenium chloride solution and an alkali solution, adding deionized water into ruthenium chloride hydrate for dissolving, filtering, adding deionized water for diluting until the concentration of ruthenium ions in ruthenium chloride is 5 g/L to obtain a ruthenium chloride solution, wherein the concentration of the alkali solution is 3 mol/L, and filtering, wherein the alkali is potassium hydroxide;
(2) determining the flow rate ratio of the ruthenium chloride solution to the alkali solution during the reaction, namely taking 100m L ruthenium chloride solution, adding the alkali solution while stirring, recording the dosage of the alkali solution as 105m L when the reaction reaches the pH value of 7.5, and determining the flow rate ratio of the ruthenium chloride solution to the alkali solution during the reaction as 1: 1.05;
(3) and (3) hydrolysis reaction: controlling the temperature of the ruthenium chloride solution and the aqueous alkali at 60-80 ℃, simultaneously adding the ruthenium chloride solution and the aqueous alkali according to the flow rate ratio determined in the step (2) under stirring, controlling the pH value of the solution to be 7-8 by using acid liquor or alkali liquor, and obtaining a solution containing ruthenium dioxide hydrate after complete hydrolysis;
(4) aging: aging the solution containing the ruthenium dioxide hydrate obtained in the step (3), wherein the aging temperature is 80-90 ℃, and the aging time is 1.5 h;
(5) Washing with water: standing the aged solution containing the ruthenium dioxide hydrate, removing supernatant, adding water, stirring, adjusting the pH value to 5.5-6.0, standing, and washing by adopting a pouring method until the supernatant is free of Cl-(checking with silver nitrate), and performing suction filtration on the precipitate by using a sand core funnel to obtain a filter cake;
(6) and (3) calcining: and (3) putting the filter cake into an alumina crucible, placing the alumina crucible into a box-type high-temperature furnace, heating at the rate of 10 ℃/min, and keeping the temperature at 450 ℃ for 1.5h to obtain the ruthenium dioxide for the resistance slurry.
Example 2
One embodiment of the preparation method of ruthenium dioxide for resistor paste comprises the following steps:
(1) respectively preparing a ruthenium chloride solution and an alkali solution, adding deionized water into ruthenium chloride hydrate for dissolving, filtering, adding deionized water for diluting until the concentration of ruthenium ions in ruthenium chloride is 5 g/L to obtain a ruthenium chloride solution, wherein the concentration of the alkali solution is 3 mol/L, and filtering, wherein the alkali is sodium hydroxide;
(2) determining the flow rate ratio of the ruthenium chloride solution to the alkali solution during the reaction, namely taking 100m L ruthenium chloride solution, adding the alkali solution while stirring, recording the dosage of the alkali solution as 105m L when the reaction reaches the pH value of 7.5, and determining the flow rate ratio of the ruthenium chloride solution to the alkali solution during the reaction as 1: 1.05;
(3) and (3) hydrolysis reaction: controlling the temperature of the ruthenium chloride solution and the aqueous alkali at 60-80 ℃, simultaneously adding the ruthenium chloride solution and the aqueous alkali according to the flow rate ratio determined in the step (2) under stirring, controlling the pH value of the solution to be 7-8 by using acid liquor or alkali liquor, and obtaining a solution containing ruthenium dioxide hydrate after complete hydrolysis;
(4) aging: aging the solution containing the ruthenium dioxide hydrate obtained in the step (3), wherein the aging temperature is 80-90 ℃, and the aging time is 1.5 h;
(5) washing with water: standing the aged solution containing the ruthenium dioxide hydrate, removing supernatant, adding water, stirring, adjusting the pH value to 5.5-6.0, standing, and washing by adopting a pouring method until the supernatant is free of Cl-(checking with silver nitrate), and performing suction filtration on the precipitate by using a sand core funnel to obtain a filter cake;
(6) and (3) calcining: and (3) putting the filter cake into an alumina crucible, placing the alumina crucible into a box-type high-temperature furnace, heating at the rate of 10 ℃/min, and keeping the temperature at 450 ℃ for 1.5h to obtain the ruthenium dioxide for the resistance slurry.
Example 3
One embodiment of the preparation method of ruthenium dioxide for resistor paste comprises the following steps:
(1) respectively preparing a ruthenium chloride solution and an alkali solution, adding deionized water into ruthenium chloride hydrate for dissolving, filtering, adding deionized water for diluting until the concentration of ruthenium ions in ruthenium chloride is 5 g/L to obtain the ruthenium chloride solution, wherein the concentration of the alkali solution is 3 mol/L, and the alkali is potassium carbonate;
(2) determining the flow rate ratio of the ruthenium chloride solution to the alkali solution during the reaction, namely taking 100m L ruthenium chloride solution, adding the alkali solution while stirring, recording the dosage of the alkali solution as 75m L when the reaction reaches the pH value of 7.5, and determining the flow rate ratio of the ruthenium chloride solution to the alkali solution during the reaction as 1: 0.75;
(3) and (3) hydrolysis reaction: controlling the temperature of the ruthenium chloride solution and the aqueous alkali at 60-80 ℃, simultaneously adding the ruthenium chloride solution and the aqueous alkali according to the flow rate ratio determined in the step (2) under stirring, controlling the pH value of the solution to be 7-8 by using acid liquor or alkali liquor, and obtaining a solution containing ruthenium dioxide hydrate after complete hydrolysis;
(4) aging: aging the solution containing the ruthenium dioxide hydrate obtained in the step (3), wherein the aging temperature is 80-90 ℃, and the aging time is 1.5 h;
(5) washing with water: standing the aged solution containing the ruthenium dioxide hydrate, removing supernatant, adding water, stirring, adjusting the pH value to 5.5-6.0, standing, and washing by adopting a pouring method until the supernatant is free of Cl-(checking with silver nitrate), and performing suction filtration on the precipitate by using a sand core funnel to obtain a filter cake;
(6) and (3) calcining: and (3) putting the filter cake into an alumina crucible, placing the alumina crucible into a box-type high-temperature furnace, heating at the rate of 10 ℃/min, and keeping the temperature at 450 ℃ for 1.5h to obtain the ruthenium dioxide for the resistance slurry.
Example 4
One embodiment of the preparation method of ruthenium dioxide for resistor paste comprises the following steps:
(1) respectively preparing a ruthenium chloride solution and an alkali solution, adding deionized water into ruthenium chloride hydrate for dissolving, filtering, adding deionized water for diluting until the concentration of ruthenium ions in ruthenium chloride is 3 g/L to obtain a ruthenium chloride solution, wherein the concentration of the alkali solution is 1 mol/L, and filtering, wherein the alkali is potassium hydroxide;
(2) determining the flow rate ratio of the ruthenium chloride solution to the alkali solution during the reaction, namely taking 100m L ruthenium chloride solution, adding the alkali solution while stirring, recording the using amount of the alkali solution as 309m L when the reaction reaches the pH value of 7, and determining the flow rate ratio of the ruthenium chloride solution to the alkali solution during the reaction as 1: 3.09;
(3) and (3) hydrolysis reaction: controlling the temperature of the ruthenium chloride solution and the aqueous alkali at 60-80 ℃, simultaneously adding the ruthenium chloride solution and the aqueous alkali according to the flow rate ratio determined in the step (2) under stirring, controlling the pH value of the solution to be 7-8 by using acid liquor or alkali liquor, and obtaining a solution containing ruthenium dioxide hydrate after complete hydrolysis;
(4) aging: aging the solution containing the ruthenium dioxide hydrate obtained in the step (3), wherein the aging temperature is 80-90 ℃, and the aging time is 1 h;
(5) washing with water: standing the aged solution containing the ruthenium dioxide hydrate, removing supernatant, adding water, stirring, adjusting the pH value to 5.0-5.5, standing, and washing by adopting a pouring method until supernatant is free of Cl-(checking with silver nitrate), and performing suction filtration on the precipitate by using a sand core funnel to obtain a filter cake;
(6) and (3) calcining: and (3) putting the filter cake into an alumina crucible, placing the alumina crucible into a box-type high-temperature furnace, heating at the rate of 10 ℃/min, and keeping the temperature at 400 ℃ for 1h to obtain the ruthenium dioxide for the resistance slurry.
Example 5
One embodiment of the preparation method of ruthenium dioxide for resistor paste comprises the following steps:
(1) respectively preparing a ruthenium chloride solution and an alkali solution, adding deionized water into ruthenium chloride hydrate for dissolving, filtering, adding deionized water for diluting until the concentration of ruthenium ions in ruthenium chloride is 8 g/L to obtain a ruthenium chloride solution, wherein the concentration of the alkali solution is 6 mol/L, and filtering, wherein the alkali is potassium hydroxide;
(2) determining the flow rate ratio of the ruthenium chloride solution to the alkali solution during the reaction, namely taking 100m L ruthenium chloride solution, adding the alkali solution while stirring, recording the dosage of the alkali solution as 54m L when the reaction reaches the pH value of 8, and determining the flow rate ratio of the ruthenium chloride solution to the alkali solution during the reaction as 1: 0.54;
(3) and (3) hydrolysis reaction: controlling the temperature of the ruthenium chloride solution and the aqueous alkali at 60-80 ℃, simultaneously adding the ruthenium chloride solution and the aqueous alkali according to the flow rate ratio determined in the step (2) under stirring, controlling the pH value of the solution to be 7-8 by using acid liquor or alkali liquor, and obtaining a solution containing ruthenium dioxide hydrate after complete hydrolysis;
(4) aging: aging the solution containing the ruthenium dioxide hydrate obtained in the step (3), wherein the aging temperature is 80-90 ℃, and the aging time is 2 h;
(5) washing with water: standing the aged solution containing the ruthenium dioxide hydrate, removing supernatant, adding water, stirring, adjusting the pH value to 6.5-7.0, standing, and washing by adopting a pouring method until the supernatant is free of Cl-(checking with silver nitrate), and performing suction filtration on the precipitate by using a sand core funnel to obtain a filter cake;
(6) and (3) calcining: and (3) putting the filter cake into an alumina crucible, placing the alumina crucible into a box-type high-temperature furnace, heating at the rate of 10 ℃/min, and keeping the temperature at 500 ℃ for 2h to obtain the ruthenium dioxide for the resistance slurry.
Comparative example 1
The traditional wet chemical method for synthesizing powder comprises the following steps:
(1) preparing a ruthenium chloride solution, namely adding deionized water into ruthenium chloride hydrate for dissolving, filtering, and adding deionized water for diluting until the concentration of ruthenium ions in the ruthenium chloride is 5 g/L to obtain the ruthenium chloride solution;
(2) carrying out hydrolysis, namely heating the ruthenium chloride solution in a water bath at the temperature of 60-80 ℃, dropwise adding a KOH solution with the concentration of 3 mol/L while stirring, controlling the pH value of the end point to be 6.0 and the change range of the pH value to be 1.0-6.0, and generating ruthenium dioxide hydrate precipitate;
(3) aging: heating a solution containing ruthenium dioxide hydrate precipitate in a water bath, controlling the temperature to be 80-90 ℃, and stirring and aging for 2 hours;
(4) washing with water: standing the aged solution containing the ruthenium dioxide hydrate, removing supernatant, adding water, stirring, adjusting the pH value to 5-7, standing, and washing the supernatant to obtain the solutionLiquid without Cl-(checking with silver nitrate), and performing suction filtration on the precipitate by using a sand core funnel to obtain a filter cake;
(5) and (3) calcining: and (3) putting the filter cake into an alumina crucible, placing the alumina crucible into a box-type high-temperature furnace, heating at the rate of 10 ℃/min, and keeping the temperature at 400 ℃ for 2h to obtain the ruthenium dioxide for the resistance slurry.
In the comparative example, the change range of the pH value is 1.0-6.0.
Comparative example 2
The traditional wet chemical method for synthesizing powder comprises the following steps:
(1) preparing a ruthenium chloride solution, namely adding deionized water into ruthenium chloride hydrate for dissolving, filtering, and adding deionized water for diluting until the concentration of ruthenium ions in the ruthenium chloride is 5 g/L to obtain the ruthenium chloride solution;
(2) carrying out hydrolysis, namely heating the ruthenium chloride solution in a water bath at the temperature of 60-80 ℃, dropwise adding a KOH solution with the concentration of 3 mol/L while stirring, controlling the pH value of the end point to be 6.5 and the change range of the pH value to be 1.0-6.5, and generating ruthenium dioxide hydrate precipitate;
(3) aging: heating a solution containing ruthenium dioxide hydrate precipitate in a water bath, controlling the temperature to be 80-90 ℃, and stirring and aging for 2 hours;
(4) washing with water: standing the aged solution containing the ruthenium dioxide hydrate, removing supernatant, adding water, stirring, adjusting the pH value to 5-7, standing, and washing by adopting a pouring method until the supernatant is free of Cl-(checking with silver nitrate), and performing suction filtration on the precipitate by using a sand core funnel to obtain a filter cake;
(5) and (3) calcining: and (3) putting the filter cake into an alumina crucible, placing the alumina crucible into a box-type high-temperature furnace, heating at the rate of 10 ℃/min, and keeping the temperature at 400 ℃ for 2h to obtain the ruthenium dioxide for the resistance slurry.
In the comparative example, the change range of the pH value is 1.0-6.5.
Comparative example 3
The traditional wet chemical method for synthesizing powder comprises the following steps:
(1) preparing a ruthenium chloride solution, namely adding deionized water into ruthenium chloride hydrate for dissolving, filtering, and adding deionized water for diluting until the concentration of ruthenium ions in the ruthenium chloride is 5 g/L to obtain the ruthenium chloride solution;
(2) carrying out hydrolysis, namely heating the ruthenium chloride solution in a water bath at the temperature of 60-80 ℃, dropwise adding a KOH solution with the concentration of 3 mol/L while stirring, controlling the pH value of the end point to be 7.5 and the change range of the pH value to be 1.0-7.5, and generating ruthenium dioxide hydrate precipitate;
(3) aging: heating a solution containing ruthenium dioxide hydrate precipitate in a water bath, controlling the temperature to be 80-90 ℃, and stirring and aging for 2 hours;
(4) washing with water: standing the aged solution containing the ruthenium dioxide hydrate, removing supernatant, adding water, stirring, adjusting the pH value to 5-7, standing, and washing by adopting a pouring method until the supernatant is free of Cl-(checking with silver nitrate), and performing suction filtration on the precipitate by using a sand core funnel to obtain a filter cake;
(5) and (3) calcining: and (3) putting the filter cake into an alumina crucible, placing the alumina crucible into a box-type high-temperature furnace, heating at the rate of 10 ℃/min, and keeping the temperature at 400 ℃ for 2h to obtain the ruthenium dioxide for the resistance slurry.
In the comparative example, the change range of the pH value is 1.0-7.0.
Examples of effects
The resistance pastes prepared in examples 1 to 5 and comparative examples 1 to 3 were subjected to a performance test using ruthenium dioxide, and the test results are shown in table 1.
The product performance reaches the standard:
(1) comparison table: not less than 40m2/g。
(2) FE-SEM: the powder is spherical or quasi-spherical in shape and has no obvious agglomeration.
(3) Particle size distribution: d50 is less than 0.5 μm.
The test method comprises the following steps:
(1) particle size distribution: testing by adopting a laser particle size analyzer;
(2) comparison table: testing by using a specific surface area tester;
(3) when the conductive phase of the resistance paste is used as a conductive phase, the electrical property of the resistance paste is tested as follows:
a. firstly, preparing resistance paste, wherein the resistance paste comprises a conductive phase, a glass phase and an organic phase, ruthenium oxide prepared in different embodiments and comparative examples is used as the conductive phase, and the formula proportion of each component of the resistance paste is kept unchanged;
b. the resistance paste was prepared into resistors, and the average resistance values of thirty resistors in each example and comparative example were respectively tested; an average cold resistance temperature coefficient value (CTCR) at-55 ℃; an average thermal resistance temperature coefficient value (HTCR) at 155 ℃; average electrostatic discharge performance (ESD), ESD test conditions were: discharging the resistor under the condition of +/-5 kV for 3 times at 5kV and then discharging the resistor for 3 times at-5 kV, wherein the interval time of each time is 1s, and recording the resistance values before and after the test.
TABLE 1
As can be seen from Table 1, the performance parameters of the ruthenium dioxide for the resistance paste prepared in the examples 1 to 5 meet the product performance standards, and the performances are superior to those of the comparative examples 1 to 3.
The synthesis of the nano powder by the wet chemical reaction has the biggest difficulty that the agglomeration of the powder is inevitable due to the high activity of the nano powder, the agglomeration is inevitable in a polar medium, the agglomeration can only be reduced by a method during the synthesis, and the influence of the agglomeration can be effectively reduced by controlling the reaction conditions. Comparative examples 1-3 adopt the traditional wet chemistry method to synthesize powder, add alkali into ruthenium chloride during hydrolysis, because of the strong acidity of ruthenium chloride aqueous solution, the pH value of the system slowly rises from a negative value to a terminal pH value, and needs to pass through the isoelectric point of the precursor, so that agglomeration is aggravated, and the prepared powder has poor performance.
In the embodiments 1 to 5 of the invention, the feeding speed of ruthenium chloride and alkali is controlled by parallel feeding, so that the pH of the reaction system can be stabilized within the range of 7 to 8, and the powder performance is greatly improved. The preparation process has the advantages that the pH value of the system can be stabilized, the isoelectric point of the precursor is far away, the heat and mass transfer speed is high, the ion movement and collision opportunities are accelerated, the particle growth speed is higher than the nucleation speed, the surface activity is correspondingly reduced after crystal nuclei grow up, the intermolecular force is weakened, and the powder agglomeration tendency is reduced. Therefore, the prepared ruthenium dioxide powder has small particle size, good uniformity, less agglomeration and greatly improved performance.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (10)
1. A preparation method of ruthenium dioxide for resistor paste is characterized by comprising the following steps:
(1) respectively preparing a ruthenium chloride solution and an alkali solution;
(2) determining the flow rate ratio of the ruthenium chloride solution to the alkali solution during the reaction, namely taking 100m L ruthenium chloride solution, adding the alkali solution while stirring, recording the using amount of the alkali solution as Am L when the reaction reaches a pH value of 7-8, and determining the flow rate ratio of the ruthenium chloride solution to the alkali solution during the reaction as 100: A;
(3) and (3) hydrolysis reaction: controlling the temperature of the ruthenium chloride solution and the aqueous alkali at 60-80 ℃, simultaneously adding the ruthenium chloride solution and the aqueous alkali according to the flow rate ratio determined in the step (2) under stirring, controlling the pH value of the solution at 7-8, and obtaining a solution containing ruthenium dioxide hydrate after complete hydrolysis;
(4) aging: aging the solution containing the ruthenium dioxide hydrate obtained in the step (3);
(5) washing with water: standing the aged solution containing the ruthenium dioxide hydrate, removing the supernatant, adding water, stirring, adjusting the pH value, standing, washing and filtering to obtain a filter cake;
(6) and (3) calcining: and heating and calcining the filter cake to obtain the ruthenium dioxide for the resistance slurry.
2. The method according to claim 1, wherein in the step (1), the concentration of ruthenium ions in the ruthenium chloride solution is 3 to 8 g/L, and the concentration of the alkali solution is 1 to 6 mol/L.
3. The method according to claim 1, wherein in the step (1), the base is at least one of potassium hydroxide, sodium hydroxide, potassium carbonate and sodium carbonate.
4. The method according to claim 1, wherein in the step (2), the reaction is carried out to a pH of 7.5.
5. The method according to claim 1, wherein in the step (3), the pH of the solution is controlled to 7 to 8 by using an acid solution or an alkali solution.
6. The method according to claim 5, wherein the acid solution is a hydrochloric acid solution, and the alkali solution is at least one of a potassium carbonate solution, a sodium carbonate solution, a potassium hydroxide solution, and a sodium hydroxide solution.
7. The method according to claim 1, wherein in the step (4), the aging temperature is 80 to 90 ℃ and the aging time is 1 to 2 hours.
8. The method according to claim 1, wherein in the step (5), the pH is adjusted to 5 to 7.
9. The method according to claim 1, wherein in the step (6), the calcination temperature is 400 to 500 ℃ and the calcination time is 1 to 2 hours.
10. Ruthenium dioxide for resistor paste prepared by the preparation method according to any one of claims 1 to 9.
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