A method for precisely depositing an atomic-level barium titanate film on the surface of a nickel powder material

Abstract

The application discloses a method for precisely depositing an atomic BaTiO3 film on the surface of nickel powder. The method adopts a fluidized bed atomic layer deposition technology, and realizes self-limiting growth of the BaTiO3 film on the surface of the nickel powder by taking titanium-based and barium-based precursors and an oxidizing agent as reaction sources under the conditions of a deposition temperature of 200-400 DEG C and a reaction pressure in a range of 0.1 Torr to normal pressure, so as to form a nanoscale and thickness-controllable dense structure. The method can overcome defects such as poor film quality and fuzzy interface in traditional technologies, and the prepared core-shell structure Ni@BaTiO3 composite powder has the characteristics of uniform coating, strong bonding force, excellent oxidation resistance and the like, can significantly improve the sintering matching property and electrical property of a multilayer ceramic capacitor, and is suitable for the field of internal electrode materials of other electronic components.

Description

Technical Field

[0001] This invention belongs to the field of electronic ceramic materials and metal powder composite technology, specifically relating to a method for precisely depositing atomic-level barium titanate thin films on the surface of nickel powder materials. Background Technology

[0002] Multilayer ceramic capacitors (MLCCs), as core passive components of modern electronic systems, are hailed as the "rice of the electronics industry," their performance and reliability directly determining the overall level of consumer electronics, automotive electronics, and high-end military equipment. Traditional MLCCs primarily use the precious metal palladium (Pd) or its alloys for their internal electrodes, resulting in high material costs and becoming a key factor restricting further industrial development. In contrast, nickel (Ni), due to its excellent conductivity, good heat and corrosion resistance, and significant cost advantages, has become the preferred material for large-scale manufacturing of high-performance, high-reliability MLCC internal electrodes. Adopting nickel internal electrode technology is the mainstream technological path driving the evolution of MLCCs towards higher layer counts, smaller sizes, and lower costs. However, a series of severe technical challenges exist in the co-firing preparation process of nickel MLCC internal electrodes, seriously affecting the performance and yield of the final components.

[0003] First, nickel oxidation is a significant problem: to ensure that the barium titanate (BaTiO3)-based ceramic dielectric does not lose its insulating properties due to excessive reduction during sintering, it needs to be sintered in a reducing atmosphere with low oxygen partial pressure. However, this environment is still insufficient to completely suppress nickel surface oxidation, and the resulting nickel oxide (NiO) degrades the electrode conductivity. Second, there is a mismatch in sintering shrinkage rates: the sintering shrinkage behaviors of the nickel electrode and the ceramic dielectric differ, and during co-firing, uneven stress can easily lead to microscopic voids or cracks inside the electrode, weakening its current-carrying capacity. Finally, there is the problem of interfacial diffusion: at high temperatures, elemental interdiffusion and interfacial reactions occur between nickel and barium titanate, forming a defect layer. This not only increases the interfacial resistance but also affects the insulation resistance and long-term reliability of the capacitor.

[0004] To improve the compatibility of nickel electrodes with ceramic dielectrics, coating their surfaces with barium titanate to form core-shell composite powders is a key strategy. Currently, the main methods for preparing Ni / BaTiO3 composite powders include mechanical mixing and wet chemical synthesis (co-precipitation, sol-gel, hydrothermal methods, etc.). However, these methods all have significant limitations. Mechanical mixing results in poor uniformity of the composite powder, with uneven and weak coating layers; chemical co-precipitation methods are prone to particle agglomeration at high temperatures during calcination; sol-gel methods have high raw material costs, low reaction yields, and long gelation times; and solvothermal methods require sophisticated equipment, are technically challenging, and have relatively poor safety performance, making them unsuitable for industrial production.

[0005] Atomic layer deposition (ALD) technology offers an innovative solution to this problem due to its self-limiting and sequential reaction characteristics. This technology, through alternating pulsed precursors, can achieve atomically precise, uniform, dense, and compositionally controllable film deposition on powder surfaces with complex morphologies. For multi-component oxides such as BaTiO3, atomic-level precise modulation of composition can be achieved by separately controlling the cycling of barium and titanium precursors. Although existing work (such as Forge Nano's Atomic Armor technology) has demonstrated the potential of ALD powder coating, achieving high-quality BaTiO3 films on nickel powder surfaces remains challenging, especially matching the reaction temperature windows of the barium and titanium precursors.

[0006] To address the aforementioned issues, there is an urgent need to develop an ALD method specifically for nickel powder that enables atomically precise deposition, uniform and robust coating of BaTiO3 thin films, and is suitable for large-scale application. This method would have significant scientific and engineering value in overcoming the technological bottlenecks of high-end nickel electrode MLCCs and enhancing the competitiveness of core components. Summary of the Invention

[0007] This invention provides a method for precisely depositing atomic-level BaTiO3 thin films on the surface of nickel powder materials. The aim is to precisely control the reaction cycle and process parameters of barium and titanium precursors, and to design the film thickness, stoichiometry and crystallization state at the nanoscale to simultaneously solve the following problems: (1) suppressing high-temperature oxidation of nickel powder and avoiding conductivity degradation; (2) buffering thermal expansion mismatch stress and reducing electrode voids and cracks; (3) blocking nickel-dielectric interdiffusion and maintaining interface stability and insulation performance; (4) improving the dispersion of powder in slurry and improving the uniformity and density of the electrode layer.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for precisely depositing atomic-scale BaTiO3 thin films on the surface of nickel powder materials includes the following steps: (1) Pretreatment of nickel powder: The nickel powder is subjected to ultrasonic cleaning, vacuum dehydration and plasma activation; (2) The nickel powder obtained in step (1) is placed in an atomic layer deposition reactor. The airflow is adjusted to keep the nickel powder in a stable fluidized state. Under the conditions of deposition temperature of 150-400℃ and reaction pressure of 0.1 Torr to atmospheric pressure, titanium-based precursors and barium-based precursors and oxidants are used as reaction sources. Atomic layer deposition technology is used to perform high conformity and uniform deposition on the surface of nickel powder to prepare atomically dense BaTiO3 films. (3) After deposition, the nickel powder obtained in step (2) is heat-treated to obtain nickel powder coated with BaTiO3 film.

[0009] Furthermore, the particle size of the nickel powder mentioned in step (1) is 30-600 nm.

[0010] Furthermore, the pretreatment step in step (1) is as follows: the nickel powder is ultrasonically cleaned with 0.1 mol / L sodium carbonate solution for 20-60 min, then washed with deionized water until neutral, and placed in a vacuum drying oven at 60-90℃ for 1-4 h (to remove surface adsorbed water and some crystal water, and avoid water molecule interference in the subsequent atomic-level thin film coating process). Then, plasma activation treatment is performed (power 50-200W, treatment time 1-10 min) to enhance surface activity and improve precursor adsorption efficiency by etching and introducing oxygen-containing functional groups.

[0011] Furthermore, the titanium-based precursor in step (2) is tetra(dimethylamino)titanium or tetraisopropyl titanate; the barium-based precursor is β-diketone barium complex or barium metallocene; and the oxidant includes any one of water vapor or ozone.

[0012] Furthermore, the atomic layer deposition described in step (2) specifically includes: 1) Pulsed barium-based precursors, purged with nitrogen; 2) Subsequently, a BaO layer is formed by the pulsed oxidant reaction, followed by nitrogen purging again; 3) Next, pulse titanium-based precursors are purged with nitrogen; 4) Finally, the pulse oxidant reacts to form a TiO2 layer, and nitrogen is purged to complete one cycle.

[0013] Furthermore, the pulse time ratio of the titanium-based precursor to the oxidant is 2:1, the pulse time ratio of the titanium-based precursor to the oxidant is 1:1, the purging time for a single cycle is 10-90 seconds, and the total number of cycles is 100-300.

[0014] Furthermore, the heat treatment in step (3) is performed at a temperature of 500-700℃, a heating rate of 5℃ / min, an inert gas atmosphere, and is held for 1-3 hours. The furnace is then cooled to room temperature so that BaTiO3 crystallizes to form a complete perovskite structure.

[0015] A BaTiO3-coated nickel powder with antioxidant properties, good sintering compatibility, high dielectric constant, and low dielectric loss is prepared by the above method. The BaTiO3-coated nickel powder has a core-shell structure, with a nickel particle core and a BaTiO3 film shell. The thickness of the BaTiO3 film is 0.5-15 nm, preferably 5-10 nm.

[0016] BaTiO3 thin films have the following properties: 1) Thin film structure: By controlling the number of atomic-level thin film coating process cycles (100-200 times), a continuous defect-free TiO2 thin film with a thickness of 5-10 nm and a surface roughness of <1 nm can be obtained; 2) Antioxidant properties: The initial oxidation temperature of the coated nickel powder in air is increased to 420-430℃, which is 120-130℃ higher than that of the untreated sample, and the high temperature stability is significantly enhanced. 3) Sintering compatibility: After coating with BaTiO3 film, the difference in sintering shrinkage between nickel powder and ceramic medium decreased from 22.5% to less than 4.5%, and the compatibility was significantly improved; 4) Dielectric properties: After being coated with BaTiO3, the nickel powder composite exhibits a high dielectric constant (>1500), while pure nickel powder does not have this property. This characteristic directly helps to improve the overall capacitance of MLCC.

[0017] 5) Loss characteristics: After coating with BaTiO3, the nickel powder composite exhibits low dielectric loss (≤0.025), while pure nickel powder is not suitable for this evaluation as a conductor. The low loss characteristic helps to improve the energy efficiency and working stability of MLCC.

[0018] The above-mentioned application of BaTiO3-coated nickel powder in the preparation of internal electrode materials for multilayer ceramic capacitors.

[0019] The above-mentioned BaTiO3-coated nickel powder is used in the preparation of ferroelectric memory, thermistor or piezoelectric device.

[0020] This invention provides an efficient method for uniformly depositing thin films on the surface of large quantities of powders by combining atomic layer deposition (ALD) with a fluidized bed reactor. This technology integrates the advantages of both processes: the fluidized bed suspends and thoroughly mixes particles in the gas flow, ensuring uniform contact and mass transfer; ALD, through the alternating and cyclical introduction of precursors and reactants, relies on its self-limiting surface reaction mechanism to grow conformally excellent films with atomic layer precision on the particle surface. The core of this technology includes optimizing the fluidized bed gas distributor (such as a concave perforated sieve plate) and integrating an ALD process suitable for powders. This design overcomes the difficulties of traditional ALD equipment in handling powders with high specific surface area, enabling batch processing. Combined with online monitoring technology to control the reaction process in real time, process conditions can be further optimized, thereby ensuring coating uniformity and consistency.

[0021] The beneficial effects of this invention are as follows: (1) Atomic-level thickness controllable: By adjusting the number of atomic layer deposition cycles, the thickness of barium titanate films in the range of 0.5-15 nm can be precisely controlled with a uniformity deviation of less than 5%.

[0022] (2) Uniform and firm coating: The obtained Ni@BaTiO3 core-shell powder has a complete, dense coating and strong bonding force, which can effectively block oxygen and inhibit the oxidation of nickel powder.

[0023] (3) Significantly improved performance: The initial oxidation temperature of nickel powder is increased from 300℃ to over 400℃, enhancing its oxidation resistance; the difference in shrinkage between the nickel powder and the ceramic medium during co-firing is reduced to less than 5%, improving the compatibility.

[0024] (4) Wide range of applications: This coated nickel powder is suitable for the internal electrodes of multilayer ceramic capacitors and can be used in ferroelectric memory, thermistors and piezoelectric devices.

[0025] (5) High adaptability: The method of the present invention is not only applicable to nickel powder, but also to the surface deposition of other metal materials, ceramic powders and other substrate materials, and has a wide range of application prospects. Attached Figure Description

[0026] Figure 1 : A schematic diagram of the atomic layer deposition system of the present invention; Figure 2 Schematic diagram of the barium titanate film deposition process on nickel powder surface; Figure 3 TEM image of Ni@BaTiO3 composite powder prepared in Example 1; Figure 4 Comparison of thermogravimetric analysis curves of Ni@BaTiO3 composite powder prepared in Example 1 and uncoated nickel powder in Comparative Example 1; Figure 5 : A schematic diagram of the structure of the Ni@BaTiO3 composite powder prepared in this invention applied to the internal electrode of an MLCC. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0028] Example 1: Deposition of a 5nm barium titanate thin film on the surface of nanoscale nickel powder Figure 1 This is a schematic diagram of the atomic layer deposition system of the present invention; Figure 2 This is a schematic diagram of the barium titanate film deposition process on the surface of nickel powder. The specific experimental steps are as follows: (1) Pretreatment: Nickel powder with an average particle size of 100 nm was added to a 0.1 mol / L sodium carbonate solution, ultrasonically cleaned for 30 min, centrifuged, repeatedly washed with deionized water until neutral, and dried in an 80℃ vacuum drying oven for 2 h to obtain clean nickel powder. Then, oxygen plasma was used for plasma activation treatment (power 150 W, treatment time 5 min) to enhance surface activity.

[0029] (2) Reactor loading and fluidization commissioning: Take 5g of the pretreated nickel powder obtained in step (1) and load it into a fluidized bed atomic layer deposition reactor. Record the initial bed height and powder mass. Use a differential pressure gauge to measure the bed pressure drop versus operating gas velocity curve. Visually observe and compare the effects of two different gas distributors, traditional flat sieve plates and concave perforated sieve plates, on particle fluidization. Using concave perforated sieve plates allows for more uniform gas distribution, resulting in a more stable fluidization state throughout the bed and avoiding abnormal phenomena such as channeling and throttling. Determine the critical fluidization velocity. U mf =7.64 cm / s. Based on the fixed fluidization number N = operating gas velocity... U Critical fluidization rate U mf We set N=1.2 to keep the nickel powder in a fluidized state to ensure that the precursor can uniformly contact each nickel powder particle before proceeding with the subsequent reaction.

[0030] (3) Atomic-level coating of BaTiO3 thin film: Reactor: Atmospheric pressure fluidized bed atomic-level thin-film coated reactor, with nitrogen as the fluidizing gas; The specific deposition process is as follows: 1) Barium source pulse: β-diketone barium complex was used as the barium source, and the pulse duration was 0.2s; 2) Purging: Purging with high-purity nitrogen for 30 seconds to thoroughly remove excess barium sources; 3) Reactant pulse: Water vapor pulses for 0.1s, reacting with the adsorbed barium source to form a BaO monolayer; 4) Purging: Purging with high-purity nitrogen for 30 seconds to remove byproducts; 5) Titanium source pulse: Tetra(dimethylamino)titanium is used as the titanium source, and the pulse duration is 0.1s; 6) Purging: Purging with high-purity nitrogen for 30 seconds to thoroughly remove excess titanium source; 7) Reactant pulse: Water vapor pulse for 0.1s reacts with the adsorbed titanium source to form a TiO2 monolayer; 8) Purging: Purging with high-purity nitrogen for 30 seconds to remove byproducts.

[0031] The above steps constitute a complete barium titanate deposition cycle, with a theoretical deposition thickness of approximately 0.05 nm per cycle. Repeating this cycle 100 times achieves a target deposition thickness of 5 nm.

[0032] The deposition temperature was set at 280℃ and the reaction pressure at 3 Torr.

[0033] (4) Post-processing: The nickel powder after the above deposition treatment was heated to 600°C in a nitrogen atmosphere at a heating rate of 5°C / min, held at that temperature for 2 hours, and then cooled to room temperature in the furnace to obtain BaTiO3 coated nickel powder (Ni@BaTiO3).

[0034] The structure and morphology of the BaTiO3-coated nickel powder coating layer are as follows: Figure 3 As shown, Figure 3 This is a bright-field HRTEM image of nickel powder coated with a BaTiO3 film. The image reveals that a continuous and uniform BaTiO3 film with an average thickness of approximately 5.2 nm was successfully coated on the nickel powder surface. The interface between the film and the nickel substrate is clear, with no obvious defects or peeling observed.

[0035] Thermal stability: Figure 4 The TGA test curves compared the oxidation behavior of nickel powder in air before and after coating. The initial oxidation temperature of the uncoated raw nickel powder was approximately 300℃. After coating with BaTiO3, the initial oxidation temperature of the composite powder significantly increased to 420℃, an increase of 120℃. This data indicates that a dense 5.2nm thick barium titanate layer can effectively form a physical and chemical barrier for the internal nickel core, greatly delaying oxygen diffusion and the reaction process.

[0036] Sintering compatibility: Thermomechanical analysis shows that the sintering shrinkage difference with the ceramic medium is only 4.5%, demonstrating good compatibility (test method reference: Evaluation of dilatometric techniques for studies of sintering kinetics). Dielectric properties: After being coated with a 5nm barium titanate film, the composite powder has a dielectric constant of 1580 and a loss of 0.025, exhibiting excellent energy storage characteristics and low energy loss.

[0037] Example 2: Deposition of a 10nm BaTiO3 thin film on the surface of submicron nickel powder (1) Pretreatment: Nickel powder with an average particle size of 10 nm was added to a 0.1 mol / L Na2CO3 solution, ultrasonically cleaned for 30 min, centrifuged, washed with deionized water until neutral, and placed in a vacuum dryer at 80 °C for 2 h. Then, it was activated by oxygen plasma (150 W, 5 min) to enhance surface activity.

[0038] (2) Reactor loading and fluidization commissioning: Take 5g of the pretreated nickel powder obtained in step (1) and load it into a fluidized bed atomic layer deposition reactor. Measure the change in bed pressure drop with gas velocity to determine its critical fluidization rate. U mf =4.97cm / s; then fix the fluidization number N=1.2, adjust the airflow to keep the nickel powder in a stable fluidized state, and then carry out the subsequent reaction.

[0039] (3) Atomic-level coating of BaTiO3 thin film: 1) Barium source pulse: β-diketone barium complex was used as the barium source, and the pulse duration was 0.2s; 2) Purging: Purging with high-purity nitrogen for 30 seconds to thoroughly remove excess barium sources; 3) Reactant pulse: Water vapor pulses for 0.1s, reacting with the adsorbed barium source to form a BaO monolayer; 4) Purging: Purging with high-purity nitrogen for 30 seconds to remove byproducts; 5) Titanium source pulse: Tetra(dimethylamino)titanium is used as the titanium source, and the pulse duration is 0.1s; 6) Purging: Purging with high-purity nitrogen for 30 seconds to thoroughly remove excess titanium source; 7) Reactant pulse: Water vapor pulse for 0.1s reacts with the adsorbed titanium source to form a TiO2 monolayer; 8) Purging: Purging with high-purity nitrogen for 30 seconds to remove byproducts.

[0040] The above steps constitute a complete barium titanate deposition cycle, with a theoretical deposition thickness of approximately 0.05 nm per cycle. This cycle is repeated 200 times, with a target deposition thickness of 10 nm. The deposition temperature is adjusted to 280 °C, and the reaction pressure is adjusted to 3 Torr.

[0041] (4) Post-processing: The nickel powder subjected to the above deposition treatment was heated to 600℃ at a rate of 5℃ / min and held for 2 hours under nitrogen protection, followed by furnace cooling to obtain BaTiO3-coated nickel powder. The average thickness of the BaTiO3-coated nickel powder coating layer was 9.8 nm. Thermal stability: The initial oxidation temperature of the composite powder is 430℃, which is 130℃ higher than that of the original sample, and the antioxidant performance is further improved; Electrical properties: Increased film thickness further improves dielectric properties, with a dielectric constant of 1620 and losses reduced to 0.023.

[0042] The performance test results of Example 1, Example 2, and the same batch of nickel powder without coating treatment (Comparative Example 1) are shown in Table 1. Table 1 Performance Comparison of Examples and Comparative Examples

[0043] The above performance results show that the BaTiO3-coated nickel powder prepared in this invention has significantly improved antioxidant properties and sintering compatibility, fully meeting the application requirements of MLCC internal electrode materials.

[0044] Application Examples The BaTiO3-coated nickel powder prepared in the examples was applied to the following fields: (1) Inner electrode material of multilayer ceramic capacitor: As the main functional phase of MLCC inner electrode paste, the initial oxidation temperature is increased to 420-430℃, which is 120-130℃ higher than that of untreated material; the difference in sintering shrinkage rate between the composite powder and the ceramic dielectric is reduced from 22.5% to less than 4.5%; the dielectric constant of the composite powder is >1500 and the loss is ≤0.025, which significantly improves the reliability and life of the capacitor and reduces the manufacturing cost.

[0045] (2) Absorbing filler: The Ni core provides magnetic loss and conductive network, while the BaTiO3 shell provides dielectric loss and impedance matching, synergistically improving broadband absorption and shielding effectiveness, while solving the problems of easy oxidation and poor dispersibility of pure nickel powder. It can be used as an absorbing filler for 5G base station filters and added to the polymer matrix. The absorption performance is significantly improved compared with uncoated nickel powder. In the 2-18GHz frequency band, the reflection loss is increased from -28dB to below -42dB, and the absorption bandwidth (reflection loss ≤-10dB) is widened from 3.2GHz to 8.5GHz. The powder dispersibility is greatly improved, the sedimentation rate is reduced from 0.8mm / h to 0.12mm / h, and the material mechanical strength is increased from 18MPa to 35MPa, effectively suppressing signal crosstalk and improving the stability of the filter.

[0046] (3) Lithium-ion battery anode material: The Ni core provides high conductivity / lithium storage activity, while the BaTiO3 shell constructs a stable structure, provides ion transport channels, and suppresses side reactions, thereby improving the rate performance and cycle life of energy storage devices. As a composite anode material for lithium-ion batteries, it shows a significant improvement in performance compared to pure nickel powder anodes. The initial coulombic efficiency increases from 68% to over 88%, and the capacity retention rate after 1000 cycles increases from 52% to 83%. The electrode internal resistance decreases from 180mΩ to 55mΩ, and the rate performance is significantly optimized. The discharge capacity at 10C rate increases from 420mAh / g of pure nickel powder to 680mAh / g, effectively solving the problem of volume expansion of pure nickel powder (expansion rate decreases from 28% to 7.8%) and extending the battery cycle life.

[0047] (4) Electrocatalytic hydrogen evolution electrode material: The Ni core provides catalytic active sites and a conductive substrate, while the BaTiO3 shell provides high specific surface area, light response, and stability, synergistically improving catalytic efficiency and resistance to poisoning. As the core active material of the electrocatalytic hydrogen evolution electrode for water electrolysis, it exhibits significantly improved catalytic performance compared to pure nickel powder electrodes, reaching 10 mA·cm⁻¹. -2 At the current density, the hydrogen evolution overpotential decreased from 310 mV to 185 mV, and the Tafel slope decreased from 125 mV·dec -1 Reduced to 68mV·dec -1 The electrode conductivity was optimized, the contact resistance was reduced from 220mΩ to 48mΩ, the long-term catalytic stability was significantly improved, and the current density decay rate after 100h of continuous electrolysis was reduced from 23% to 4.5%, effectively reducing the energy consumption of water electrolysis for hydrogen production and extending the service life of the electrode.

[0048] (5) Functional material for multilayer PTCR thermistors: The PTC effect of BaTiO3 combined with the conductive pathway of the Ni core can be used to fabricate low-cost, high-reliability multilayer thermistors / varistors. As a functional layer and inner electrode composite material for multilayer PTCR thermistors, it shows significant performance improvement compared to the uncoated nickel powder and BaTiO3 mixture system, with the Curie temperature adjusted from 105℃ to 135℃ and the resistance change rate reduced from 10 3 Upgraded to 10 4 The above measures include: improved sintering density, reduced porosity from 18% to 5.2%, and reduced the difference in sintering shrinkage between the sintering density and the ceramic matrix from 11.8% to 3.8%; optimized long-term working stability, with a resistance drift rate reduced from 8.6% to 2.1% after 500 hours of continuous operation at a constant temperature of 150℃, making it suitable for scenarios such as motor starting and lithium battery overcurrent protection.

[0049] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for precisely depositing atomic-level BaTiO3 thin films on the surface of nickel powder materials, characterized in that: Includes the following steps: (1) Pretreatment of nickel powder: The nickel powder is subjected to ultrasonic cleaning, vacuum dehydration and plasma activation; (2) The nickel powder obtained in step (1) is placed in an atomic layer deposition reactor. The airflow is adjusted to keep the nickel powder in a stable fluidized state. Under the conditions of deposition temperature of 150-400℃ and reaction pressure of 0.1 Torr to atmospheric pressure, titanium-based precursors and barium-based precursors and oxidants are used as reaction sources. Atomic layer deposition technology is used to perform high conformity and uniform deposition on the surface of nickel powder to prepare atomically dense BaTiO3 films. (3) After deposition, the nickel powder obtained in step (2) is heat-treated to obtain nickel powder coated with BaTiO3 film.

2. The method according to claim 1, characterized in that: The particle size of the nickel powder mentioned in step (1) is 30-600 nm.

3. The method according to claim 1, characterized in that: The pretreatment steps in step (1) are as follows: the nickel powder is ultrasonically cleaned with 0.1 mol / L sodium carbonate solution for 20-60 min, then washed with deionized water until neutral, placed in a vacuum drying oven and dried at 60-90℃ for 1-4 h, and then subjected to plasma activation treatment to enhance surface adsorption activity.

4. The method according to claim 1, characterized in that: The titanium-based precursor in step (2) is tetra(dimethylamino)titanium or tetraisopropyl titanate; the barium-based precursor is β-diketone barium complex or barium metallocene; the oxidant includes any one of water vapor or ozone.

5. The method according to claim 1, characterized in that: The atomic layer deposition described in step (2) specifically includes: 1) Pulsed barium-based precursors, purged with nitrogen; 2) Subsequently, a BaO layer is formed by the pulsed oxidant reaction, followed by nitrogen purging again; 3) Next, pulse titanium-based precursors are purged with nitrogen; 4) Finally, the pulse oxidant reacts to form a TiO2 layer, and nitrogen is purged to complete one cycle.

6. The method according to claim 5, characterized in that... The pulse time ratio of the titanium-based precursor to the oxidant is 2:1, and the pulse time ratio of the titanium-based precursor to the oxidant is 1:

1. The purging time for a single cycle is 10-90 seconds, and the total number of cycles is 100-300.

7. The method according to claim 1, characterized in that: The heat treatment in step (3) is performed at a temperature of 500-700℃, with a heating rate of 5℃ / min, in an inert gas atmosphere, and is held for 1-3 hours before being cooled to room temperature in the furnace.

8. A BaTiO3-coated nickel powder with antioxidant properties, good sintering compatibility, high dielectric constant, and low dielectric loss, characterized in that: It is prepared by the method described in any one of claims 1 to 7. The BaTiO3-coated nickel powder has a core-shell structure, with the core being nickel particles and the outer shell being a BaTiO3 film with a thickness of 0.5-15 nm.

9. The application of BaTiO3-coated nickel powder as described in claim 8 in the preparation of internal electrode materials for multilayer ceramic capacitors.

10. The application of BaTiO3-coated nickel powder as described in claim 8 in the preparation of ferroelectric memory, thermistor or piezoelectric device.

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