A spray drying technique assisted synthesis of barium titanate coated nickel particles material and method thereof

Abstract

The application relates to a spray drying technology assisted synthesis of barium titanate coated Ni particle material and a method thereof, and belongs to the technical field of metal powder material preparation. The method comprises the following steps: firstly, preparing a mixed solution by mixing metatitanic acid, barium hydroxide and nano and submicron Ni powder; secondly, synthesizing a Ni-based composite material intermediate by adopting a spray drying method; and finally, forming barium titanate coated Ni powder after sintering in a tube furnace. The barium titanate coated Ni inner electrode material is Ni@BaTiO3 spherical particles with a core-shell structure, the particles are core / shell microstructure, the shell layer is a barium titanate coating layer with a thickness of 10-15 nm, and the particle size is 100-150 nm. The required equipment can be scaled, the composition and microstructure are easy to control, the spherical degree and dispersity are high, the compactness is high, the repeatability is good, the particle size and distribution can be changed by adjusting process parameters, the oxidation resistance can be improved, good interface combination between the ceramic dielectric layer and the barium titanate coated Ni inner electrode material can be realized, and key problems such as mismatching of interfacial volume shrinkage and easy cracking in the sintering process can be solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal powder material preparation, and relates to a kind of spray drying technology assisted synthesis barium titanate coated Ni particle material and method thereof, and the metal powder prepared has excellent oxidation resistance and sintering performance. BACKGROUND

[0002] Multilayer ceramic capacitors (MLCC) play an important role in electronic components, and one of the key technologies is the selection and performance optimization of internal electrode materials. From the historical development, noble metals such as platinum and palladium were initially used as internal electrode materials, mainly due to their excellent oxidation resistance and stability at high temperatures. However, with the increasing demand for low-cost, high-performance MLCC devices and the increasing number of stack layers, expensive noble metal materials have gradually been replaced by nickel (Ni), a typical base metal electrode material. Nickel powder has the following advantages as an internal electrode material for MLCC: low cost (more economical than noble metals); high electrical conductivity (ensures excellent electrical conductivity of the electrode); low electrical migration rate (reduces performance degradation over time); good corrosion resistance and heat resistance (adapts to various working environments); and high sintering temperature (forms a stable structure when co-fired with ceramics). Therefore, nickel powder has become the most widely used internal electrode material in current MLCCs.

[0003] Nickel powder has obvious advantages in MLCCs, but its practical application still faces many technical challenges: for example, nickel is easily oxidized to form nickel oxide (NiO) during high-temperature sintering, and BaTiO3-based ceramic dielectric is easily reduced to a semiconductor when sintered in a low-oxygen partial pressure or reducing atmosphere; the sintering shrinkage rate of nickel internal electrodes does not match that of ceramic dielectric, and when ceramic films and Ni powder-containing internal electrodes are co-fired, the ceramic film cannot shrink together with the Ni film, the Ni film is stretched in the plane direction, and voids are easily generated inside the electrode, exacerbating the discontinuity of the electrode and possibly leading to interlayer peeling or structural defects. In addition, the mutual diffusion and chemical reaction between nickel and ceramic dielectric during sintering can also affect the stability of the interface, thereby weakening the long-term reliability of the capacitor. Currently, there are two main methods to improve the performance of nickel powder: one is to improve the microstructure of nickel powder, including crystallinity and particle size. Nickel powder with high crystallinity has good oxidation resistance, and small-particle-size nickel powder can form a dense and smooth nickel electrode at a lower sintering temperature, suitable for internal electrode paste for MLCCs. The second method is to modify the surface of nickel powder, and common methods include forming a coating layer on the surface, such as zirconium oxide (ZrO2), calcium carbonate (CaCO3), barium oxide (BaO), calcium zirconate (CaZrO3), strontium zirconate (SrZrO3), titanium dioxide (TiO2), and silicon dioxide (SiO2), to improve oxidation resistance and solve the problem of mismatched sintering shrinkage rate with ceramic.

[0004] Barium titanate (BaTiO3) is a lead-free piezoelectric ceramic material, which is widely used in MLCC and PTCR (Positive Temperature Coefficient of Resistance) fields due to its excellent high dielectric constant, low loss characteristics, and excellent piezoelectric and ferroelectric properties. It is known as the "pillar of the electronic ceramic industry". Patent CN103508736A proposes a two-step method for surface modification of nickel powder, combining normal pressure coating hydrothermal crystallization and normal pressure coating crystallization. The surface of the nickel powder particles is successfully coated with a barium titanate layer, effectively improving the oxidation resistance and sintering performance. However, the addition of excess chemicals increases production costs, limiting its large-scale application. In patent JP2004183027A, a chemical method is used to coat barium titanate ceramic dielectric material on the surface of nickel powder. Although it improves the oxidation resistance and sintering performance to some extent, the operation process is complex and the coating effect is not good. In patent CN118847991A, a physical vapor phase preparation method for in-situ coating of barium titanate on nickel powder is introduced. This method realizes the in-situ synthesis of barium titanate ceramic layer by co-evaporating multiple component targets in a hot plasma, significantly improving the shrinkage performance of the nickel electrode. However, this preparation process has some disadvantages such as difficulty in composition control and high energy consumption.

[0005] In the preparation process of composite materials and core-shell particle materials, the synthesis method is crucial. Common synthesis methods such as chemical vapor deposition, sol-gel method and hydrothermal method have certain limitations, such as complex operation and involvement of multiple chemicals, environmental pollution, etc. Spray drying, as a high-efficiency and multi-functional technology, shows great potential for industrialized expansion of application. Initially, this technology was used in the pharmaceutical industry to produce pure drug substances. Due to its simple operation, easy scalability, high yield and low environmental impact, it has attracted much attention and its application has rapidly expanded to cosmetics, textiles, electronic materials, microcapsules, controlled-release particles, composite microparticles, nanoparticles and liposomes. Today, spray drying technology has developed into a high-efficiency, simplified process, compact structure and excellent product quality process. Patent CN116675248A uses wollastonite as a silicon source, controls the temperature and acidity to control the solid-liquid reaction speed, and makes the wollastonite slowly generate silicon dioxide, which promotes the heterogeneous nucleation on the surface of nano-titanium dioxide, forming a uniform and continuous silica coating layer, greatly improving the light stability and dispersibility of titanium dioxide. Patent CN109638273A discloses a coating method for preparing positive electrode materials for sodium-ion batteries using spray drying. By precisely controlling process parameters such as inlet air temperature, feed rate, air flow rate and gas medium, the microstructure, particle distribution and performance of the powder can be effectively controlled. Spray drying technology has high production efficiency, excellent particle dispersibility, and can ensure the uniformity of the coating thickness. SUMMARY

[0006] The application provides a preparation method and technology of BaTiO3-coated Ni powder with high sintering temperature, low shrinkage and strong oxidation resistance, to solve the key technical problems of mismatching of shrinkage of Ni powder and ceramic medium during sintering of MLCC metal inner electrode and ceramic medium layer, and poor oxidation resistance of Ni powder. The method mixes metatitanic acid and barium hydroxide as main raw materials with nano and submicron nickel powder to form a uniform solution, uses a spray drying technology to obtain coated modified nickel powder, and then performs heat reaction treatment on the nickel powder in a N2 atmosphere to obtain Ni@BaTiO3 spherical particles with a core-shell structure. The coated nickel particle material is used as an inner electrode layer of the MLCC to improve the sintering shrinkage matching degree between the inner electrode layer and the medium layer (BaTiO3), reduce internal stress to prevent the generation of defects such as cracks and delamination, and improve electrode continuity and product qualification rate.

[0007] To achieve the above object, the technical scheme adopted by the application is:

[0008] A spray drying technology assisted synthesis of barium titanate coated Ni particle material and a method thereof. The barium titanate coated Ni inner electrode material is Ni@BaTiO3 spherical particles with a core-shell structure, which is a barium titanate coated modified Ni powder material obtained by coating treatment on Ni powder. The particle has a core / shell microstructure, the shell layer is a barium titanate coating layer with a thickness of 10-15 nm, and the particle size is 100-150 nm. The finished powder has good sphericity, crystallinity and purity.

[0009] The existence of the barium titanate coating layer improves the oxidation resistance and sintering performance of the powder, improves the continuity of the electrode, and thus improves the qualification rate and service life of the product.

[0010] The core / shell microstructure of the particle, the particle size and its distribution are controlled by controlling the ratio of barium hydroxide and metatitanic acid, the type and addition amount of the dispersing agent, and the spray drying process related parameters.

[0011] A spray drying technology assisted synthesis of barium titanate coated Ni particle material and a method thereof. The method first mixes metatitanic acid and barium hydroxide as raw materials with nano and submicron Ni powder to prepare a mixed solution; secondly, based on the obtained mixed solution, a Ni-based composite material intermediate is synthesized by a spray drying method; and finally, after sintering in a tube furnace (N2 atmosphere), the barium titanate coated Ni powder is formed. The method comprises the following steps:

[0012] Firstly, the Ni powder raw material is pretreated;

[0013] The Ni powder is added into a dilute sodium carbonate solution, and the solution is ultrasonically cleaned to obtain a basic solution containing the Ni powder; the basic solution containing the Ni powder after ultrasonic cleaning is cleaned with deionized water at room temperature to obtain the Ni powder after deionized water cleaning; the Ni powder is a nano or sub-micron powder or a mixed nano and sub-micron powder.

[0014] The second step is to configure the liquid;

[0015] At room temperature, the Ni powder after pretreatment in the first step and a dispersant are added into a solvent, and are dispersed by a homogenizer for 5-10 minutes, and then are ultrasonically treated for 10-30 minutes to obtain a suspension A; at room temperature, barium hydroxide is dissolved in an aqueous solution, and is ultrasonically dispersed and vibrated for 10-30 minutes, and then metatitanic acid is added, and is dispersed by a homogenizer for 10-30 minutes, and then is ultrasonically dispersed and vibrated for 10-30 minutes to obtain a suspension B; at room temperature, the suspension B is added into the suspension A, and is mechanically stirred for 6-12 hours to be fully mixed to obtain a suspension C for spray drying.

[0016] Further, the solvent in the suspension A includes a deionized water solvent, an ethanol, an ethylene glycol or the like organic solvent or a mixed solvent thereof, and the deionized water is preferred; the dispersant includes polyvinylpyrrolidone (PVP), polyethylene glycol, citric acid, sodium citrate or the like or one or more mixtures thereof;

[0017] Further, in the suspension A, the mass ratio of the Ni powder to the dispersant is 5:(1-3), and the concentration of the Ni powder is 4 g / 1 L.

[0018] Further, in the suspension B, the molar ratio of the metatitanic acid to the barium hydroxide is 1:1-1:4.

[0019] Further, the volume ratio of the suspension A to the suspension B is 10:1.

[0020] The third step is to prepare a Ni-based composite material intermediate by a spray drying method.

[0021] The spray drying equipment is adopted, and the suspension C prepared in the second step is used as a formal liquid material to prepare the Ni-based composite material intermediate. The specific process steps are as follows: the circulating air volume of the circulating fan in the spray drying equipment, the inlet air temperature, the outlet air pressure of the air compressor, the high-pressure gas flow, and the peristaltic pump speed are set; when the inlet air temperature display is the same as the set temperature display or the outlet temperature display has exceeded 90°C, and it is determined that the spray drying machine equipment has reached the preset various indexes and is normally and stably running, the formal liquid material (the suspension prepared in the first step) can be sprayed and dried, and the Ni-based composite material intermediate can be obtained after the spray drying.

[0022] The fourth step is to prepare a barium titanate coated Ni powder under N2 atmosphere.

[0023] The powder collected after spray drying is put into a tube furnace, the tube furnace is vacuumized, heated and decomposed at 500-700 DEG C, the duration is 4-6h, after the tube furnace is cooled to room temperature, the final powder product is collected.

[0024] The specific working principle and innovation points of the application are as follows:

[0025] The pre-processed nickel powder is mixed with barium hydroxide Ba(OH)2 and metatitanic acid TiO(OH)2 to prepare a composite material by a spray drying technique. Subsequently, a calcination heating is performed in a nitrogen atmosphere to obtain a BaTiO3-coated nickel powder capsule material. The basic principle is as follows: the feed solution or suspension is pumped into the drying chamber through the nozzle. Compressed air is sprayed from the air inlet pipe at a high speed, while the liquid material is sprayed from the feed pipe at a lower flow rate, and there is a significant relative velocity between the two. This relative movement generates friction and shear force between the gas and the liquid, which makes the liquid be pulled into a thin line and broken at the thin part of the line to form tiny droplets. Each droplet contains barium hydroxide and one or more metatitanic acid and nickel powder particles. The atomized droplets are in contact with the hot gas (usually air) in the drying chamber. During the process of passing through the drying chamber, energy and mass transfer occur on the surface of the droplets, and the solvent is rapidly evaporated. Finally, the dried material is separated from the drying medium by a cyclone separator and collected in a collection device. The collected powder product is a barium hydroxide-coated Ni and metatitanic acid composite material. Subsequently, a heating decomposition is performed in a tube furnace (N2 atmosphere), and the reaction TiO(OH)2+ Ba(OH)2= BaTiO3+ 2H2O occurs. In this process, the barium hydroxide and metatitanic acid coated on the surface of the nickel powder react to form barium titanate and water. After the water vapor evaporates, a barium titanate-coated nickel powder with a core-shell structure is formed. The parameters of spray drying have a great influence on the coating effect of the powder. The injection speed of the feed directly affects the size, trajectory and movement speed of the droplets. At the same time, the increase of the liquid amount per unit time means that more solvent needs to be evaporated in the same time. Generally, a lower solution feed rate can obtain better atomization effect and smaller droplet size. The drying process is a key stage for converting droplets into dry particles. In this stage, a higher drying temperature will accelerate the loss of solvent on the surface of the droplets, thereby reducing the number of undried particles adhering to the wall of the drying chamber, and thus increasing the yield. In addition, the drying temperature will also affect the speed of solute shrinkage, thereby changing the morphology of the particles. Therefore, theoretically, the inlet temperature should be as high as possible.However, in practical applications, the drying temperature still needs to be controlled within a reasonable range due to factors such as thermal stability of materials, energy consumption of equipment, and possible blockage of channels.

[0026] The innovation of the present application is to combine spray drying with chemical precipitation method, and propose a novel low-cost and green nano and sub-micron Ni@BaTiO3 core-shell structure metal powder preparation method. By adjusting the process parameters of spray drying, the types of dispersants, etc., the shortcomings of single chemical precipitation method are solved, such as difficulty in controlling the coating thickness, not suitable for large-scale production, and poor powder dispersibility.

[0027] The beneficial effects of the present application are:

[0028] (1) The present application provides a process method combining traditional chemical method and spray drying method for preparing nano / sub-micron metal powder coating material. Compared with the traditional chemical method, the powder prepared by the method of the present application has the following advantages: the required equipment can be scaled up, the raw materials are economical and environmentally friendly, the production cost is low, the composition and microstructure are easy to control, it has high sphericity and dispersibility, high density, and good repeatability. By adjusting the process parameters, the particle size and its distribution can be changed.

[0029] (2) The dispersibility of Ni powder is effectively improved, and the agglomeration is reduced; it plays a protective role for the metal Ni core, making it not easy to oxidize and improving its oxidation resistance; at the same time, good interface bonding between the ceramic dielectric layer is realized, thereby relieving the key problems of mismatching of interfacial volume shrinkage and easy cracking during sintering. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 X-ray diffraction spectra of pure Ni powder prepared in Comparative Example 1 and barium titanate coated Ni powder prepared in Examples 1-3.

[0031] Figure 2 SEM image (a) and EDS element distribution of Ni (b), Ti (c), Ba (d), and O (e) of barium titanate coated Ni powder prepared in Example 2.

[0032] Figure 3 Line scanning element corresponding curve of barium titanate coated Ni powder prepared in Example 2; Figure 3 (a) in is a line scanning graph of Example 1; Figure 3 (b) in is a line scanning element distribution graph of Example 1.

[0033] Figure 4 SEM morphology of barium titanate coated Ni powder prepared in Examples 1-4; Figure 4(a) in FIG. 1 is an SEM morphology diagram of the barium titanate coated Ni powder prepared in Example 1; Figure 4 (b) in FIG. 1 is an SEM morphology diagram of the barium titanate coated Ni powder prepared in Example 2; Figure 4 (c) in FIG. 1 is an SEM morphology diagram of the barium titanate coated Ni powder prepared in Example 3; Figure 4 (d) in FIG. 1 is an SEM morphology diagram of the barium titanate coated Ni powder prepared in Example 4.

[0034] Figure 5 is the volume shrinkage rate of the pure Ni powder prepared in Comparative Example 1 and the barium titanate coated Ni powder prepared in Example 1.

[0035] Figure 6 is the volume shrinkage rate of the pure Ni powder prepared in Comparative Example 1 and the barium titanate coated Ni powder prepared in Example 2.

[0036] Figure 7 is the volume shrinkage rate of the pure Ni powder prepared in Comparative Example 1 and the barium titanate coated Ni powder prepared in Example 3.

[0037] Figure 8 is the volume shrinkage rate of the pure Ni powder prepared in Comparative Example 1 and the barium titanate coated Ni powder prepared in Example 4.

[0038] The above content of the present application will be further described in detail in combination with the specific embodiments, but the scope of the present application is not limited to the following examples:

[0039] Comparative Example 1:

[0040] I. Preparation process

[0041] The pure Ni powder without barium titanate coating is prepared as a comparative example, which is compared with the barium titanate coated Ni powder (Example 1).

[0042] First step, pretreatment of Ni powder raw material

[0043] 2g of Ni powder is added into a dilute sodium carbonate solution, and ultrasonic cleaning is performed to obtain an alkaline solution containing Ni powder; deionized water is used to clean the alkaline solution containing Ni powder after ultrasonic cleaning at room temperature of 25℃ to obtain Ni powder after deionized water cleaning;

[0044] Second step, preparation of the solution

[0045] At room temperature of 25℃, 2g of pretreated Ni powder and 0.4g of PVP dispersant are added into the aqueous solvent, and a homogenizer is used for dispersion for 5min, followed by ultrasonic treatment for 10min, and mechanical stirring for 6h to obtain a suspension A;

[0046] Third step, spray drying to prepare pure Ni powder

[0047] The pure Ni powder is prepared by using a spray drying device. The specific process steps are as follows: setting the circulating air volume of the ring fan (95%), the inlet air temperature (110°C), the outlet air pressure of the air compressor (5 kg), the high-pressure gas flow (6 L / min), the peristaltic pump speed (30), the inlet air temperature display and the setting temperature display, and the outlet temperature display being the same or the outlet temperature display being more than 90°C, and determining that the spray drying machine system has reached the preset various indexes and is running normally and stably, and then the formal liquid (the suspension prepared in the first step) spray drying process can be entered. Since the spray drying process is carried out in a hot air field, the dried powder can be adsorbed on the wall of the glass instrument due to electrostatic action, which is normal. The Ni metal powder can be obtained after spray drying.

[0048] II. Result analysis and characterization

[0049] As shown in the attached Figure 1 , it is the XRD diffraction pattern of the pure Ni powder, and the pure Ni powder has high crystallinity. As shown in the attached Figure 6 , it is the volume shrinkage rate curve of the pure Ni powder, and the final volume shrinkage rate is 24.76% in the sintering process in the range of 50-1200°C, and the volume shrinkage change is obviously greater than that of BaTiO3 powder.

[0050] Example 1

[0051] First step, pretreatment of Ni powder raw material

[0052] 2g of Ni powder is added to a dilute sodium carbonate solution, and ultrasonic cleaning is performed to obtain an alkaline solution containing Ni powder; deionized water is used to clean the alkaline solution containing Ni powder after ultrasonic cleaning at room temperature of 25°C to obtain Ni powder after deionized water cleaning;

[0053] Second step, preparation of liquid

[0054] At room temperature, 2g of pretreated Ni powder and 0.4g of PVP dispersant are added to the aqueous solvent, dispersed for 5min by using a homogenizer, and then ultrasonic treatment is performed for 10min to obtain a suspension A; at room temperature, 0.855g of barium hydroxide is dissolved in an aqueous solution, ultrasonic dispersion vibration is performed for 10min, and then 0.49g of metatitanic acid is added, a homogenizer is used for dispersion for 5min, and then ultrasonic dispersion vibration is performed for 10min to obtain a mixed liquid B; at room temperature, the colloidal B is added to the suspension A, mechanical stirring is performed for 6h, and full mixing is performed to obtain a suspension C for spray drying.

[0055] Further, in the suspension A, the mass ratio of Ni powder to dispersant is 5:1, and the concentration of Ni powder is 4g / 1L.

[0056] Further, the molar ratio of metatitanic acid and barium hydroxide in the suspension B is 1:1.

[0057] Further, the suspension A is 500 ml and the suspension B is 50 ml.

[0058] Third step, preparation of Ni-based composite material intermediate by spray drying method;

[0059] The spray drying equipment is used to prepare the Ni-based composite material intermediate with the suspension prepared in the first step as the formal liquid. The specific process steps are as follows: the circulating air volume of the ring fan is set to 95%, the inlet air temperature is set to 110°C, the outlet air pressure of the air compressor is set to 5 kg, the high-pressure gas flow is set to 6 L / min, the peristaltic pump speed is set to 30, the inlet air temperature display is the same as the set temperature display or the outlet temperature display has exceeded 90°C, and it is determined that the spray drying machine equipment has reached the preset various indicators and is running normally and stably, then the spray drying process of the formal liquid (the suspension prepared in the first step) can be started.

[0060] Fourth step, preparation of barium titanate coated Ni powder under N2 atmosphere

[0061] The filtered powder is placed into a tube furnace, the equipment is vacuumized, heated and decomposed at 500°C for 4h, and after the tube furnace is cooled to room temperature, the final powder product is collected.

[0062] II. Result analysis and characterization

[0063] As shown in the accompanying Figure 1 , it is the XRD diffraction pattern of Ni@BaTiO3 powder. According to the standard PDF #79-2263 card, obvious Ni phase and cubic BaTiO3 diffraction peaks appear.

[0064] As shown in the accompanying Figure 2 , it is the EDS element distribution of Ni@BaTiO3 powder particles. The Ni element is concentrated in the spherical region, i.e. the Ni particle is the core, and the elements of Ba, Ti and O are uniformly distributed on the surface. Such core / shell structure particles have good sphericity. Combined with the XRD analysis result, it can be concluded that the shell layer is BaTiO3.

[0065] As shown in the accompanying Figure 3 , it is the EDS line scanning element distribution of Ni@BaTiO3 powder particles. As can be seen from the figure, the Ni element is concentrated in the middle part of the particle, and the elements of Ba, Ti and O are distributed in the edge region of the particle, which is consistent with the structure of Ni core and BaTiO3 shell.

[0066] As shown in the accompanying Figure 4(a) as shown, the morphology size distribution of Ni@BaTiO3 powder particles, from the figure it can be seen that the obtained powder particles present spherical morphology, with certain particle agglomeration.

[0067] As shown in the accompanying Figure 5 volume shrinkage curve of pure Ni powder, the final volume shrinkage rate in the sintering process in the range of 50-1200℃ is 24.76%, the volume shrinkage change is obviously greater than the shrinkage rate of BaTiO3 powder 4.2%, and the sintering shrinkage rate of the Ni@BaTiO3 powder of Example 1 is greatly reduced compared with Comparative Example 1, which is 10.36%, and the sintering resistance is significantly improved. This shows that the performance of the metal powder is significantly improved to some extent.

[0068] Example 2

[0069] Preparation process

[0070] Firstly, pretreatment of Ni powder raw material

[0071] 2g of Ni powder was added to a dilute sodium carbonate solution and ultrasonic cleaning was performed to obtain an alkaline solution containing Ni powder; deionized water was used to clean the alkaline solution containing Ni powder after ultrasonic cleaning at room temperature of 25℃ to obtain Ni powder after deionized water cleaning;

[0072] Secondly, preparation of the liquid

[0073] At room temperature, 2g of pretreated Ni powder and 1g of citric acid dispersant were added to an ethanol solvent, dispersed for 7min using a homogenizer, and then ultrasonic treatment was performed for 20min to obtain suspension A; at room temperature, 3.42g of barium hydroxide was dissolved in an aqueous solution, ultrasonic dispersion vibration was performed for 20min, and then 0.98g of metatitanic acid was added, a homogenizer was used for dispersion for 7min, and then ultrasonic dispersion vibration was performed for 20min to obtain suspension B; at room temperature, suspension B was added to suspension A, mechanical stirring was performed for 9h, and full mixing was performed to obtain suspension C for spray drying.

[0074] Further, in the suspension A, the mass ratio of Ni powder and dispersant is 2:1, and the concentration of Ni powder is 4g / 1L.

[0075] Further, in the suspension B, the molar ratio of metatitanic acid and barium hydroxide is 1:2.

[0076] Further, the suspension A is 500ml, and the suspension B is 50ml.

[0077] Thirdly, preparation of Ni-based composite material intermediate by spray drying method

[0078] The spray drying equipment is used to prepare the Ni-based composite material intermediate by using the suspension prepared in the first step as the formal liquid material. The specific process steps are as follows: the circulating air volume of the circulating fan in the spray drying equipment, the inlet air temperature, the outlet air pressure of the air compressor, the high-pressure gas flow, and the peristaltic pump speed are set; when the inlet air temperature display is the same as the set temperature display or the outlet temperature display has exceeded 90℃, and it is determined that the spray drying machine equipment has reached the preset various indexes and is running normally and stably, the spray drying process of the formal liquid material (the suspension prepared in the first step) can be started. The Ni-based composite material intermediate can be obtained after the spray drying.

[0079] Fourth step, heating under N2 atmosphere to prepare barium titanate coated Ni powder

[0080] The filtered powder is put into a tube furnace, the tube furnace is vacuumized, heated and decomposed at 600℃ for 5h, and the final powder product is collected after the tube furnace is cooled to room temperature.

[0081] II. Result analysis and characterization

[0082] As shown in the accompanying Figure 1 Fig. 1, it is the XRD diffraction pattern of the Ni@BaTiO3 powder, and according to the standard PDF#79-2263 card, the diffraction peaks of the Ni phase and the cubic phase BaTiO3 are obvious. It can be seen from the figure that the metal powder obtained by the method has good crystallinity.

[0083] As shown in the accompanying Figure 4 (b), it is the size distribution of the morphology of the Ni@BaTiO3 powder particles. It can be seen from the figure that the particles obtained by the method have good sphericity and dispersity.

[0084] As shown in the accompanying Figure 6 Fig. 3, it is the volume shrinkage rate curve of the pure Ni powder. During the sintering process in the range of 50-1200℃, the final volume shrinkage rate is 24.76%, which is obviously larger than the shrinkage rate of the BaTiO3 powder 4.2%. The sintering shrinkage rate of the Ni@BaTiO3 powder of Example 2 is similar to that of the BaTiO3 powder, which is only 5.96%. Compared with Comparative Example 1, it is shown that the performance of the metal powder is obviously improved to a certain extent.

[0085] Example 3

[0086] I. Preparation process

[0087] First step, pretreatment of Ni powder raw material

[0088] 2 g of Ni powder was added to a dilute sodium carbonate solution, and the solution was ultrasonically cleaned to obtain an alkaline solution containing Ni powder; the alkaline solution containing Ni powder after ultrasonication was washed with deionized water at room temperature of 25° C. to obtain Ni powder washed with deionized water;

[0089] 2. The second step is to prepare the liquid

[0090] At room temperature, 2 g of pretreated Ni powder and 2 g of polyethylene glycol dispersant were added to an aqueous solvent, dispersed with a homogenizer for 10 minutes, and then ultrasonically treated for 30 minutes to obtain a suspension A; at room temperature, 6.84 g of barium hydroxide was dissolved in an aqueous solution, ultrasonically dispersed and vibrated for 30 minutes, and then 0.98 g of titanic acid was added, dispersed with a homogenizer for 7 minutes, and then ultrasonically dispersed and vibrated for 20 minutes to obtain a mixed solution B; at room temperature, colloid B was added to suspension A, mechanically stirred for 9 hours, and fully mixed to obtain a suspension C for spray drying.

[0091] Furthermore, in the suspension A, the mass ratio of Ni powder to dispersant is 1:1, and the concentration of Ni powder is 4 g / 1L.

[0092] Furthermore, in the suspension B, the molar ratio of metatitanic acid to barium hydroxide is 1:4.

[0093] Furthermore, the suspension A is 500 ml and the suspension B is 50 ml.

[0094] The third step is to prepare the Ni-based composite intermediate by spray drying;

[0095] A spray drying device is used to prepare a Ni-based composite intermediate using the suspension prepared in the first step as the main liquid material. The specific process steps are: setting the circulating air volume and air inlet temperature of the spray drying device's central fan, the air compressor's outlet pressure, the high-pressure gas flow rate, and the peristaltic pump speed. When the air inlet temperature display is the same as the set temperature display or the outlet temperature display exceeds 90°C, and after confirming that the spray drying device has met various preset indicators and is operating normally and stably, the spray drying process of the main liquid material (the suspension prepared in the first step) can be started. After spray drying, the Ni-based composite intermediate can be obtained.

[0096] Step 4: Prepare barium titanate coated Ni powder by heating under N2 atmosphere

[0097] The filtered powder was placed in a tube furnace, the equipment was vacuumed, and thermal decomposition was performed at 700°C for 6 hours. After the tube furnace was cooled to room temperature, the final powder product was collected.

[0098] 3. Result Analysis and Characterization

[0099] As attachedFigure 1 As shown in Fig. 2, it is the XRD diffraction pattern of Ni@BaTiO3 powder, according to the standard PDF # 79-2263 card, there are obvious Ni phase and cubic phase BaTiO3 diffraction peaks, from the figure it can be seen that the metal powder obtained by the present application has good crystallinity.

[0100] As shown in Fig. 3, it is the SEM image of the pure Ni powder, from the figure it can be seen that the particle size distribution is uniform. Figure 4 As shown in Fig. 4, it is the particle size distribution of the Ni@BaTiO3 powder, from the figure it can be seen that the particle size distribution is uniform.

[0101] As shown in Fig. 5, it is the volume shrinkage curve of the pure Ni powder, during the sintering process in the range of 50-1200℃, the final volume shrinkage rate is 24.76%, the shrinkage rate of BaTiO3 powder is 4.2%, while the sintering shrinkage rate of the Ni@BaTiO3 powder of Example 3 is reduced to a certain extent, which is 14.88%, compared with Comparative Example 1, this indicates that the performance of the metal powder is obviously improved to a certain extent. Figure 7 Example 4

[0102] I. Preparation process

[0103] First step, pretreatment of Ni powder raw material

[0104] 2g of Ni powder was added to a dilute sodium carbonate solution, and ultrasonic cleaning was performed to obtain an alkaline solution containing Ni powder; deionized water was used to clean the ultrasonic alkaline solution containing Ni powder at room temperature of 25℃, and Ni powder after deionized water cleaning was obtained;

[0105] Second step, preparation of the liquid

[0106] At room temperature, 2g of pretreated Ni powder and 1g of citric acid dispersant were added to water and ethanol (volume ratio 1:1) solvent, and dispersed for 7min using a homogenizer, followed by ultrasonic treatment for 20min to obtain suspension A; at room temperature, 1.71g of barium hydroxide was dissolved in aqueous solution, and after ultrasonic dispersion vibration for 20min, 0.98g of metatitanic acid was added, and the homogenizer was dispersed for 7min, followed by ultrasonic dispersion vibration for 20min to obtain mixed solution B; at room temperature, colloidal B was added to suspension A, and mechanical stirring was carried out for 9h to obtain suspension C for spray drying.

[0107] Further, in the suspension A, the mass ratio of Ni powder and dispersant is 2:1, and the concentration of Ni powder is 4g / 1L.

[0108] Further, in the suspension B, the molar ratio of metatitanic acid and barium hydroxide is 1:1.

[0109] Further, in the suspension B, the molar ratio of metatitanic acid and barium hydroxide is 1:1.

[0110] Further, the suspension A is 500 ml, and the suspension B is 50 ml.

[0111] In the third step, the Ni-based composite material intermediate is prepared by a spray drying method.

[0112] The spray drying equipment is used to prepare the Ni-based composite material intermediate by using the suspension prepared in the first step as the formal liquid material. The specific process steps are as follows: the circulating air volume of the circulating fan in the spray drying equipment, the inlet air temperature, the outlet air pressure of the air compressor, the high-pressure gas flow, and the peristaltic pump speed are set; when the inlet air temperature display is the same as the set temperature display or the outlet temperature display has exceeded 90 DEG C, and it is determined that the spray drying machine equipment has reached the preset various indexes and is running normally and stably, the formal liquid (the suspension prepared in the first step) can be sprayed and dried.

[0113] In the fourth step, the barium titanate coated Ni powder is prepared by heating under N2 atmosphere.

[0114] The filtered powder is put into a tube furnace, the equipment is vacuumized, and heating decomposition is carried out at 600 DEG C for 5 hours; after the tube furnace is cooled to room temperature, the final powder product is collected.

[0115] II. Result analysis and characterization

[0116] As shown in Fig. 1, the particle size distribution of the Ni@BaTiO3 powder is shown in Fig. 2, and the morphology of the Ni@BaTiO3 powder particles is shown in Fig. 3. Figure 4 (b) shows the particle size distribution of the Ni@BaTiO3 powder particles, and it can be seen from the figure that the particles have good sphericity, and some small particles are aggregated.

[0117] As shown in Fig. 4, the volume shrinkage rate curve of the pure Ni powder is shown in Fig. 5, and the sintering process of the volume shrinkage rate curve of the pure Ni powder in the range of 50 DEG C to 1200 DEG C is shown in Fig. 6. Figure 8 The volume shrinkage rate of the pure Ni powder in the sintering process in the range of 50 DEG C to 1200 DEG C is 24.76%, and the volume shrinkage change is obviously greater than the shrinkage rate of the BaTiO3 powder 4.2%; compared with the comparative example 1, the shrinkage rate of the example 4 at about 1200 DEG C is 20.46%, which indicates that the performance of the metal powder is obviously improved to a certain extent.

[0118] The above only describes the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for synthesizing barium titanate-coated Ni inner electrode material assisted by spray drying technology, characterized in that: The method first uses metatitanic acid and barium hydroxide as raw materials, mixes them with nano- and submicron nickel powders to prepare a mixed solution; secondly, a Ni-based composite intermediate is synthesized based on the obtained mixed solution by a spray drying method; finally, the barium titanate-coated nickel powder is formed after sintering in a tube furnace, and the tube furnace sintering is carried out under an N2 atmosphere; The method specifically comprises the following steps: The first step is to pretreat the Ni powder raw material; Adding Ni powder to a dilute sodium carbonate solution and ultrasonically cleaning the solution to obtain an alkaline solution containing Ni powder; washing the alkaline solution containing Ni powder after ultrasonication to obtain Ni powder washed with deionized water; The second step is to prepare the feed liquid; The Ni powder and dispersant after the first step pretreatment are added to a solvent, dispersed, and ultrasonically treated to obtain a suspension A, wherein the mass ratio of Ni powder to dispersant in suspension A is 5:(1-3); barium hydroxide is dissolved in an aqueous solution at room temperature, ultrasonically dispersed and vibrated, and then metatitanic acid is added. After dispersion, ultrasonic dispersion and vibration are performed again to obtain a suspension B, wherein the molar ratio of metatitanic acid to barium hydroxide in suspension B is 1:1-1:4; suspension B is added to suspension A at room temperature, mechanically stirred for 6-12 hours, and thoroughly mixed to obtain a suspension C for spray drying; The third step is to prepare the Ni-based composite intermediate by spray drying; A spray drying device is used to prepare a Ni-based composite intermediate using the suspension C prepared in the second step as the main liquid material; Step 4: preparing barium titanate-coated Ni powder by heating under N2 atmosphere; The powder collected after spray drying is placed in a tube furnace, the tube furnace is vacuumed, and a heating decomposition treatment is performed at a certain temperature. After the tube furnace is cooled to room temperature, the final powder product is collected; The solvent in the suspension A includes one or more combinations of deionized water, ethanol, and ethylene glycol; the dispersant includes one or more mixtures of polyvinyl pyrrolidone (PVP), polyethylene glycol, citric acid, and sodium citrate; The concentration of Ni powder in the suspension A is 4 g / 1 L; The volume ratio of the suspension A to the suspension B is 10:1; The dispersion time in the suspension A is 5 to 10 minutes, and the ultrasonic treatment time is 10 to 30 minutes; The ultrasonic dispersion vibration time in the suspension B is 10 to 30 minutes, the dispersion time after adding titanic acid is 10 to 30 minutes, and the ultrasonic dispersion vibration time is again 10 to 30 minutes; In the fourth step, the temperature of the thermal decomposition treatment is 500-700° C. and the time is 4-6 hours.

2. The method for spray drying-assisted synthesis of barium titanate-coated Ni inner electrode material according to claim 1, characterized in that: In the first step, the Ni powder is nanometer or submicron level or a mixed powder of nanometer and submicron level.

3. The method for spray drying-assisted synthesis of barium titanate-coated Ni inner electrode material according to claim 1, characterized in that: The specific process of the third step is: setting the circulating air volume and air inlet temperature of the central fan of the spray drying equipment, the outlet pressure of the air compressor, the high-pressure gas flow rate, and the peristaltic pump speed; when the air inlet temperature display is the same as the set temperature display or the outlet temperature display has exceeded 90°C, and it is determined that the spray drying equipment has reached various preset indicators and is operating normally and stably, the formal liquid material spray drying process is entered, and a Ni-based composite material intermediate can be obtained after spray drying.

4. A spray drying technology-assisted synthesis of barium titanate-coated Ni particle material prepared by the method according to any one of claims 1 to 3, characterized in that: The barium titanate-coated Ni inner electrode material is a Ni@BaTiO3 spherical particle with a core-shell structure. It is a barium titanate-coated modified Ni powder material obtained by coating Ni powder. Its particles have a core / shell microstructure, the shell layer is a barium titanate coating layer, the thickness of which is in the range of 10~15nm, and the particle size is between 100~150nm.

5. The spray drying technology-assisted synthesis of barium titanate-coated Ni particle material according to claim 4, characterized in that: The core / shell microstructure, particle size and distribution of the particles are regulated by controlling the ratio of barium hydroxide and metatitanic acid, the type and addition amount of the dispersant and parameters related to the spray drying process.

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