Nickel-containing particle, method for producing nickel-containing particle, and slurry

Abstract

To provide: a nickel-containing particle in which thermal shrinkage at a predetermined temperature during heating is effectively suppressed; a method for producing a nickel-containing particle; and a slurry used for producing a nickel-containing particle.SOLUTION: A nickel-containing particle of the present invention has a nickel particle containing nickel, and a coating layer containing silicon which covers at least a part of a surface of the nickel particle. The nickel particle contains sulfur; and in an Si-Kα spectrum obtained by analysis with soft X-ray emission spectroscopy, a peak top position of a peak is 1735 eV or more, and a full width at half maximum of the peak is 10.5 eV or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to nickel-containing particles, a method for producing nickel-containing particles, and a slurry used for producing nickel-containing particles. [Background technology]

[0002] Nickel powder, which primarily contains nickel, is sometimes used as an electrode material for multilayer ceramic chip capacitors (MLCCs) used in electronic computers, including multi-function mobile phones, and as a material for nickel-metal hydride batteries and lithium-ion batteries, due to its excellent heat dissipation and electrical properties.

[0003] Among these, multilayer ceramic chip capacitors have a structure in which dielectric layers and internal electrode layers are alternately laminated, with external electrodes provided on both ends. The dielectric layers are made of ceramic powder primarily composed of a ceramic with a high dielectric constant, such as barium titanate. Meanwhile, the internal electrode layers can be made of powders of various metals or alloys. Recently, development of multilayer ceramic chip capacitors using fine nickel powder for the internal electrode layers has been progressing.

[0004] Techniques relating to nickel powder include those described in Patent Documents 1 to 5.

[0005] Patent Document 1 proposes, as "nickel-containing particles that are less likely to shrink during sintering," "nickel-containing particles that have a core particle containing Ni and a coating layer located on the surface of the particle and containing at least one element selected from Si, Al, Zr, and Sn, and that, when heated from 25°C to 800°C at a heating rate of 10°C / min in a thermomechanical analysis in a mixed atmosphere of 99% by volume of nitrogen and 1% by volume of hydrogen, have a shrinkage rate of 3.0% or less at 400°C and a shrinkage rate of 15.0% or less at 800°C, and that, when thermogravimetric analysis is performed in an air atmosphere, have a temperature of 250°C or higher and 350°C or lower when the mass increases by 0.5% relative to the mass at 25°C."

[0006] Patent Document 2 aims to "provide composite Ni microparticles that can prevent delamination during the firing process even for ultrafine particles with an average particle size of 0.2 μm or less, particularly 0.1 μm or less, and that can be used to thin the layers of ultrafine particle application products such as multilayer ceramic capacitors, as well as a manufacturing method and manufacturing apparatus for the same." Patent Document 2 also discloses "composite Ni microparticles characterized in that the surfaces of Ni or Ni alloy microparticles are coated with a material selected from the group consisting of Si, Si3N4, and SiO2 to a thickness of 1 to 5 nm, and the composite Ni microparticles have an average particle size of 0.07 to 0.50 μm."

[0007] Patent Document 3 describes a nickel fine powder having an average particle size of 0.05 to 0.3 μm, a crystallite size relative to the specific surface area of ​​60 to 90%, a sulfur content of 0.1 to 0.5% by mass, and an oxygen content of 0.4 to 1.5% by mass, and having a 2 to 15 nm thick coating layer containing oxygen on the surface, at least the outermost surface of the coating layer being composed of a mixture containing a nickel sulfur compound and a nickel oxygen compound. The nickel fine powder is highly pure and has excellent crystallinity, making it suitable for use in electronic devices and components. In particular, when used as nickel fine powder for forming internal electrodes of MLCCs, it can increase the shrinkage onset temperature and suppress shrinkage associated with sintering, thereby preventing structural defects such as cracking and peeling. Furthermore, by controlling the surface compound layer, the decomposition temperature of the resin binder can be made equal to that of the original resin binder, further preventing discontinuity or peeling of the internal electrodes. Furthermore, the method for producing the nickel fine powder is easy and feasible on an industrial scale, making it of great industrial value.

[0008] Patent Document 4 describes "nickel powder characterized by containing 1.0 to 5.0 mass % of sulfur and having a 50% particle size of 0.09 μm or less."

[0009] Patent Document 5 describes a metal powder that includes metal particles containing a metal and sulfur at a bulk concentration of 0.01% by weight or more and 1.0% by weight or less, wherein the local sulfur concentration at a position 4 nm from the surface of the metal particles is 2 atomic % or more, and the bulk concentration and the local concentration are estimated by an inductively coupled plasma optical emission spectrometer and an energy dispersive X-ray spectrometer attached to a scanning transmission electron microscope, respectively, and states that the metal is nickel, copper, or silver. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] International Publication No. 2021 / 199694 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-232036 [Patent Document 3] International Publication No. 2011 / 037150 [Patent Document 4] International Publication No. 2015 / 156080 [Patent Document 5] International Publication No. 2020 / 004105 Summary of the Invention [Problem to be solved by the invention]

[0011] When nickel powder is used to manufacture products such as the multilayer ceramic chip capacitors described above, it may be made into a paste by incorporating it into an organic binder, etc. Then, a green sheet made of ceramic powder for the dielectric layers and a nickel powder paste for the internal electrode layers may be laminated, and they may be heated simultaneously to sinter the ceramic powder and nickel powder, respectively.

[0012] In this case, if the nickel powder shrinks significantly at a relatively low temperature during sintering, product defects such as separation of the internal electrode layers may occur due to differences in shrinkage behavior between the nickel powder and the ceramic powder. To prevent this, the nickel powder may be required to have heat resistance to a degree that prevents significant shrinkage at a predetermined temperature when heated. The nickel powders described in Patent Documents 1 to 5 have room for further improvement in terms of heat resistance.

[0013] The present invention aims to solve the above-mentioned problems, and its object is to provide nickel-containing particles in which thermal shrinkage at a predetermined temperature during heating is effectively suppressed, a method for producing nickel-containing particles, and a slurry used for producing nickel-containing particles. [Means for solving the problem]

[0014] As a result of intensive research, the inventors have found that nickel-containing particles whose surfaces are coated with a coating layer containing silicon and further contain sulfur may have improved heat resistance. Further research has revealed that such nickel-containing particles exhibit high heat resistance if the peak of the Si-Kα spectrum obtained by soft X-ray emission spectroscopy has a predetermined shape.

[0015] The nickel-containing particles of the present invention are nickel-containing particles having nickel particles containing nickel and a coating layer containing silicon that coats at least a portion of the surface of the nickel particles, wherein the nickel particles contain sulfur, and in the Si-Kα spectrum obtained by analysis by soft X-ray emission spectroscopy, the peak top position is 1735 eV or more and the full width at half maximum of the peak is 10.5 eV or less.

[0016] The silicon content of the nickel-containing particles is preferably 0.05% to 1.5% by mass.

[0017] The sulfur content of the nickel-containing particles is preferably 0.01% by mass to 1.0% by mass.

[0018] The nickel-containing particles may have a particle size of 50 nm to 300 nm.

[0019] The method for producing nickel-containing particles of the present invention is a method for producing nickel-containing particles having nickel particles containing nickel and a coating layer containing silicon that coats at least a portion of the surface of the nickel particles, and includes a coating step of applying a silicon coating to the nickel particles, and uses nickel particles in which the concentration ratio of the local sulfur concentration (atm%) at a position 2 nm deep from the surface to the local sulfur concentration (atm%) at a position 5 nm deep from the surface is 5 times or more.

[0020] The slurry of the present invention is used for producing nickel-containing particles having nickel particles containing nickel and a coating layer containing silicon that coats at least a portion of the surface of the nickel particles, as described above, and contains sulfur-containing nickel particles and a silicon additive.

[0021] The silicon additive preferably comprises particulate silicon dioxide and / or an organosilicon compound. [Effects of the Invention]

[0022] The nickel-containing particles of the present invention are effectively prevented from thermally shrinking at a predetermined temperature when heated. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a graph showing an example of a Si-Kα spectrum obtained by analyzing nickel-containing particles by soft X-ray emission spectroscopy. [Figure 2] 1 is a graph showing the results of an analysis of sulfur concentration in the depth direction of nickel particles (core particles) of Example 1 and Comparative Example 1 by STEM-EDS. DETAILED DESCRIPTION OF THE INVENTION

[0024] An embodiment of the present invention will be described below. The nickel-containing particles according to one embodiment of the present invention comprise a nickel particle (core particle) and a coating layer that covers at least a portion of the surface of the nickel particle. The coating layer contains silicon. The nickel particles primarily contain nickel, and it is essential that they further contain sulfur.

[0025] Furthermore, in the Si-Kα spectrum obtained when the nickel-containing particles are analyzed by soft X-ray emission spectroscopy (SXES), the peak top position is 1735 eV or more and the full width at half maximum of the peak is 10.5 eV or less.

[0026] If nickel particles containing not only nickel but also sulfur have a silicon-containing coating layer on their surface and the Si-Kα spectrum peak has the above-mentioned shape, the nickel-containing particles will have excellent heat resistance, although the reason is not entirely clear. When heated, these nickel-containing particles do not undergo significant thermal shrinkage within a specified temperature range. As a result, when the nickel-containing particles are used to manufacture multilayer ceramic chip capacitors, the shrinkage behavior can be matched to that of the ceramic powder during sintering, which may reduce the occurrence of product defects.

[0027] In particular, when nickel particles containing a relatively large amount of sulfur near the surface of the nickel particles are coated to produce nickel-containing particles, the silicon in the coating layer inhibits the liquefaction of the sulfur component in the surface layer during sintering of the nickel-containing particles, which is thought to further suppress the diffusion of nickel present in the depths of the nickel-containing particles between adjacent nickel-containing particles, resulting in a delay in sintering and more effective suppression of thermal shrinkage.

[0028] (composition) The nickel particles constituting a part of the nickel-containing particles contain mainly nickel (Ni) but also sulfur (S). Therefore, the nickel-containing particles containing nickel particles contain sulfur.

[0029] The sulfur content of the nickel-containing particles is preferably 0.01% by mass to 1.0% by mass. If the sulfur content is too low, sintering may proceed at a low temperature. On the other hand, if the sulfur content is too high, oxidation may occur during firing, generating gas, which may cause delamination. The sulfur content is measured by ICP emission spectroscopy in accordance with JIS K0116. The sulfur content of nickel particles, which will be described later, can also be measured in the same manner.

[0030] The coating layer present on at least a portion of the surface of the nickel particles contains silicon (Si). The silicon content of the nickel-containing particles is preferably 0.05% by mass to 1.5% by mass, more preferably 0.08% by mass to 1.2% by mass. The heat resistance of the nickel-containing particles is improved by containing a certain amount of silicon. On the other hand, if the silicon content of the nickel-containing particles is too high, the effect of improving heat resistance may be reduced. The silicon content is measured by X-ray diffraction (XRD). The silicon content is calculated as a value converted into a SiO2 weight ratio.

[0031] (particle size) The particle size of the nickel-containing particles is, but is not limited to, for example, 50 nm to 300 nm, typically 80 nm to 300 nm. Nickel powder composed of such fine nickel-containing particles is particularly suitable for applications such as the aforementioned multilayer ceramic chip capacitor.

[0032] The particle size here means the number-average diameter. To measure the particle size of the nickel-containing particles, the major axes of 500 to 1000 particles in an SEM image taken at a predetermined magnification for each particle size are measured, and the number-average value is taken as the particle size.

[0033] (SXES Si-Kα spectrum) When nickel-containing particles are analyzed for silicon content using soft X-ray emission spectroscopy, a Si-Kα spectrum, as shown in Figure 1, is obtained as the energy distribution of characteristic X-rays (Kα rays) emitted from the Si element in the nickel-containing particles when irradiated with X-rays.

[0034] In the nickel-containing particles of this embodiment, the peak top position Pt of the peak in the Si-Kα spectrum is 1735 eV or higher. The full width at half maximum Wh of the peak, i.e., the full width Wh of the peak at an intensity (Sp / 2) that is half the peak top intensity Sp of the peak, is 10.5 eV or lower. Here, the peak top position Pt refers to the value of x at which the function f(x), fitted as a linear combination of multiple Gaussian functions in the Si-Kα spectrum, takes the maximum value Sp. The full width W of the peak refers to the range of x within which the value of the function f(x) is equal to or greater than Sp / 2.

[0035] If the peak top position Pt and full width at half maximum Wh of the peak in the Si-Kα spectrum are within the above ranges, the nickel-containing particles will not undergo significant thermal shrinkage at a predetermined heating temperature and will have excellent heat resistance.

[0036] In the Si-Kα spectrum, the higher the energy value of the peak top position Pt within the above range and the smaller the full width at half maximum Wh of the peak within the above range, the more likely the heat resistance will be improved. Therefore, it is preferable that the peak top position Pt be in the range of 1736 eV to 1740 eV. Furthermore, it is preferable that the full width at half maximum Wh of the peak be in the range of 8.0 eV to 10.5 eV.

[0037] Specifically, analysis of nickel-containing particles by soft X-ray emission spectroscopy is performed as follows: A dried sample of nickel-containing particles is pressed onto an indium foil, which is then fixed to the test table of the soft X-ray emission spectroscopy instrument with carbon tape, and the analysis is performed. Here, the accelerating voltage is 3 kV, the current is 45 to 50 nA, the measurement magnification is 30,000 times, the measurement time is 15 minutes per field of view, and the number of accumulated fields of view is 50 to 100.

[0038] (Manufacturing method) To produce the nickel-containing particles as described above, first, sulfur-containing nickel particles are prepared.

[0039] The nickel particle powder can be commercially available, or can be prepared by a gas phase method, a liquid phase method, etc. In particular, the gas phase reduction method in which nickel chloride gas is brought into contact with a reducing gas, or the spray pyrolysis method in which a thermally decomposable nickel compound is sprayed and thermally decomposed, are preferred in that the particle size can be easily controlled and spherical nickel particles can be efficiently obtained.

[0040] In most cases, the gas-phase reduction method involves a chlorination step in which a solid raw material containing elemental metallic nickel is evaporated by heating and brought into contact with chlorine gas to generate nickel chloride gas, and a reduction step in which the nickel chloride gas is reacted with a reducing gas such as hydrogen. Specifically, for example, in the chlorination step, chlorine gas is brought into contact with metallic nickel to continuously generate nickel chloride gas, and this nickel chloride gas is then supplied to the reduction step where it is brought into contact with a reducing gas, thereby continuously reducing the nickel chloride gas. Note that if the nickel chloride gas used in the reduction step is separately available, the chlorination step can be omitted.

[0041] The solid raw material to be subjected to the chlorination step can be in the form of granules, lumps, plates, or the like with a particle size of approximately 5 mm to 20 mm, and the nickel purity is preferably 99.5 mass% or more. In the chlorination step, the solid raw material is contacted with chlorine gas while being heated. The temperature at this time can be set to 800°C or higher to sufficiently promote the reaction, and to 1453°C or lower, which is the melting point of nickel. In consideration of the reaction rate and the durability of the chlorination furnace, the temperature is preferably in the range of 900°C to 1100°C. Nickel chloride gas is thereby produced.

[0042] In the reduction step, the nickel chloride gas is brought into contact with a reducing gas such as hydrogen to cause a reaction. At this time, an inert gas such as nitrogen or argon may be mixed with the nickel chloride gas at 1 mol % to 30 mol %. In addition, chlorine gas may be supplied in addition to the nickel chloride gas in the reduction step. When an inert gas or chlorine gas is supplied in the reduction step, the partial pressure of the nickel chloride gas can be adjusted, making it possible to control the particle size of the nickel particles and suppress the particle size variation. In addition, the reduction step may also be carried out using hydrogen sulfide, sulfur dioxide, sulfur halide (S n A sulfur-containing gas such as Cl2 (n is an integer of 2 or more), SF6, SF5Cl, or SF5Br can be supplied. This allows sulfur-containing nickel particles to be obtained after the reduction step. The temperature of the reduction reaction may be any temperature required for the reduction reaction or higher, but in order to produce solid nickel particles that are easy to handle, the temperature can be set to the melting point of nickel or lower, preferably 900°C to 1100°C, for example.

[0043] In the reduction process, nickel atoms are generated the moment nickel chloride gas and reducing gas come into contact, and ultrafine particles are generated and grow as the nickel atoms collide with each other. Nickel particles of a predetermined particle size can be obtained depending on the partial pressure, temperature, and other conditions of the nickel chloride gas in the reduction process. Since the amount of nickel chloride gas generated in the chlorination process depends on the amount of chlorine gas supplied, the amount of nickel chloride gas supplied to the reduction process can be adjusted by controlling the amount of chlorine gas supplied. This allows the particle size of the nickel particles to be effectively controlled.

[0044] The nickel particles obtained in the reduction step can be cooled. It is desirable to rapidly cool the gas flow from around 1000°C after the reduction reaction to about 400-800°C by blowing in an inert gas such as nitrogen. This prevents the formation of secondary particles due to aggregation of primary particles in the powder produced in the reduction step, allowing nickel particles of the desired particle size to be obtained. The nickel particles are then separated and recovered using, for example, a bag filter.

[0045] In addition to or instead of supplying a sulfur-containing gas in the reduction step, the nickel after the reduction step may be contacted with a sulfur-containing compound such as thiourea by dry or wet methods. Contact with the sulfur-containing compound results in a coating of the sulfur-containing compound on the surface of the nickel particles, or a nickel-sulfur compound layer is formed, resulting in sulfur-containing nickel particles (core particles). In the wet method, specifically, the sulfur-containing compound can be added to nickel particles in a liquid, or an aqueous solution or an alcohol solution such as ethanol or isopropanol of the sulfur-containing compound can be mixed. In this case, ultrasonic stirring or the like may be used. The amount of the sulfur-containing compound used can be adjusted so that the sulfur content of the nickel particles after contact is, for example, 0.01 to 1.0 mass%, preferably 0.05 to 0.5 mass%. The contact time may be 10 to 60 minutes, or even 15 to 30 minutes.

[0046] When a sulfur-containing gas is supplied in the reduction step, the nickel-containing particles obtained as a result tend to contain sulfur from the surface to a relatively deep position. On the other hand, when the nickel particles are contacted with a sulfur-containing compound after the reduction step, the local concentration of sulfur tends to be high near the surface layer inside the nickel-containing particles.

[0047] In the spray pyrolysis method, a thermally decomposable nickel compound is used as a raw material, and a solution of the raw material is sprayed to form fine droplets and heated at a high temperature to thermally decompose the nickel compound to produce nickel particles. Specifically, the raw material may contain at least one selected from the group consisting of nitrates, sulfates, oxynitrates, oxysulfates, chlorides, ammonium complexes, phosphates, carboxylates, and alkoxy compounds. When spraying the raw material to form droplets, water, alcohol, acetone, ether, etc. may be used as a solvent. The spraying method may be performed using ultrasound or a double-jet nozzle. The temperature to which the droplets are heated is preferably above the thermal decomposition temperature of the specified nickel compound used as the raw material and near the melting point of the metal.

[0048] In the liquid phase method, an aqueous nickel solution containing nickel sulfate, nickel chloride, or a nickel complex is contacted with an alkali metal hydroxide such as sodium hydroxide by addition or the like to produce nickel hydroxide. The nickel hydroxide is then reduced with a reducing agent such as hydrazine to obtain nickel particles. The nickel particle powder thus produced may be subjected to a crushing treatment as needed to obtain a uniform particle size.

[0049] The nickel particles obtained by the various methods described above preferably contain sulfur. This allows the nickel particles of the nickel-containing particles produced through the coating process described below to contain sulfur. The sulfur content of the nickel particles is preferably 0.01% by mass to 1.0% by mass, more preferably 0.05% by mass to 0.2% by mass. The sulfur content of the nickel particles can be adjusted by, for example, changing the flow rate of the sulfur-containing gas that can be supplied to the reduction process.

[0050] Furthermore, when the sulfur concentration (atm%) of the nickel particles is measured from the surface toward the depth, it is preferable that the ratio of the local sulfur concentration (atm%) at a position 2 nm in the depth direction from the surface to the local sulfur concentration (atm%) at a position 5 nm in the depth direction from the surface is 5 times or more. In this way, the presence of a certain amount of sulfur near the surface of the nickel particles acts with silicon in the coating layer formed in the coating step described below, suppressing the diffusion of nickel between the nickel-containing particles, thereby further improving heat resistance.

[0051] The local sulfur concentration of nickel particles can be observed, for example, using a scanning transmission electron microscope (STEM-EDS) equipped with an energy dispersive X-ray spectrometer. Specifically, nickel particles are dispersed in a resin, and the resin is cured. A cross-section is then exposed using a cross-section polisher (CP), and a thin-film sample is prepared by planar sampling using a focused ion beam (FIB). The sample thickness is approximately 100 nm, and the nickel particles are formed into a thin film of this thickness. The resulting thin film is then subjected to EDS measurement along a line passing through the center of the nickel particles to obtain the local concentration. The EDS measurement conditions can be selected, for example, as follows: an acceleration voltage of 200 kV, a probe diameter of 1 nm, a pitch width of 3 nm, and a measurement time of 15 seconds per point.

[0052] Thereafter, a coating step is carried out to coat the powder of nickel particles with silicon. By the coating step, at least a portion of the surface of the nickel particles (core particles) is covered with a coating layer containing silicon, and a powder of nickel-containing particles can be obtained.

[0053] In the coating step, the specific method is not particularly limited as long as the nickel particles are brought into contact with silicon and a coating layer is formed on the surface thereof. For example, powder of nickel particles can be added to a slurry in which a silicon additive is suspended in a liquid such as water, and the mixture can be stirred to mix.

[0054] The silicon additive contained in the slurry is preferably a granular silicon dioxide (SiO2) and / or organosilicon compound having a carbon-silicon bond. Specific examples of organosilicon compounds include silicon resinate and silicone oil. The average particle size of the granular silicon additive is preferably 20 nm to 50 nm.

[0055] The mass ratio of the silicon additive contained in the slurry can be 1% to 75%. This makes it easier to adjust the silicon content of the nickel-containing particles to a predetermined range. In addition, the slurry may contain a dispersant or the like.

[0056] The stirring speed during mixing may be 3000 rpm to 5000 rpm, the stirring time may be 1 hour to 20 hours, and the liquid temperature may be 10°C to 60°C.

[0057] It is believed that when nickel particles are mixed into the slurry, the nickel particles come into contact with the silicon additive in the slurry and a coating reaction occurs, forming a silicon-containing coating layer on the surface of the nickel particles.

[0058] After mixing the nickel particles with the slurry, the slurry is dried. At this time, the slurry can be heated, for example, to a temperature of 60 to 80°C in an argon atmosphere. If the temperature is too low, drying will take a long time, and if the temperature is too high, there is a concern that unwanted hydroxides and the like will be produced.

[0059] After drying, a powder of nickel-containing particles is obtained in which at least a portion of the surface of the nickel particles (core particles) is covered with a coating layer containing silicon. These nickel-containing particles tend to have a peak top position and full width at half maximum in the Si-Kα spectrum of soft X-ray emission spectroscopy that are within a predetermined range. As a result, when the nickel-containing particles are heated, it is thought that the reaction product of the sulfide on the particle surface and the silicon component suppresses thermal shrinkage at relatively low temperatures. [Example]

[0060] Next, nickel-containing particles according to the present invention were produced as prototypes, and their effects were confirmed. The following description will be given, however, for illustrative purposes only and is not intended to be limiting.

[0061] Examples 1 and 2 Using the gas-phase reduction method, the aforementioned chlorination and reduction steps were carried out, followed by contact with a sulfur-containing compound, to produce a powder of nickel particles (core particles) with a particle size of 180 nm. Contact with the sulfur-containing compound was carried out by adding an ethanol solution of the sulfur-containing compound to a liquid containing the nickel particles and applying ultrasonic waves at room temperature (20°C) for 30 minutes. The particles were then dried in an air current dryer and heated in the air at 200°C for 30 minutes. By varying the amount of sulfur-containing compound added, several types of nickel particles with different sulfur contents were obtained, as shown in Table 1. In addition, the concentration ratio (C2 / C1) of the local sulfur concentration C2 (atm%) at a position 2 nm deep from the surface of the nickel particle to the local sulfur concentration C1 (atm%) at a position 5 nm deep from the surface of the nickel particle was 5.5 times in Example 1 and 7.8 times in Example 2.

[0062] Thereafter, the powder of each nickel particle was coated to cover at least a part of the surface of the nickel particle (core particle) with a coating layer containing silicon, thereby producing nickel-containing particles. Specifically, the powder of nickel particles was introduced into and mixed with a slurry containing the silicon additive shown in Table 1, and the slurry was stirred for 1 hour. This resulted in the production of nickel-containing particles.

[0063] (Comparative Example 1) Nickel particles manufactured by another company were obtained. The concentration ratio (C2 / C1) of the local sulfur concentration C2 (atm%) at a position 2 nm deep from the surface of the nickel particle to the local sulfur concentration C1 (atm%) at a position 5 nm deep from the surface of the nickel particle was 1.9 times. Coating was performed on these particles in the same manner as in Example 1 to obtain nickel-containing particles.

[0064] (Comparative Example 2) A powder of nickel particles was produced by the same method as in Examples 1 and 2, except that the powder of nickel particles was not coated. The concentration ratio (C2 / C1) of the local sulfur concentration C1 (atm%) at a position 5 nm deep from the surface of the nickel particle to the local sulfur concentration C2 (atm%) at a position 2 nm deep from the surface of the nickel particle was 9.9 times.

[0065] (evaluation) The sulfur content (S content) and silicon content (Si content) of each nickel-containing particle obtained as described above were measured by the methods described above, and the results are shown in Table 1. The results of the analysis of the sulfur concentration in the depth direction by STEM-EDS for the nickel particles of Example 1 and Comparative Example 1 are shown in Figure 2. The particle size of the nickel-containing particles was 180 nm.

[0066] In addition, each nickel-containing particle was analyzed by soft X-ray emission spectroscopy (SXES) according to the procedures and conditions described above to obtain an Si-Kα spectrum, and then the peak top position and full width at half maximum of the Si-Kα spectrum were confirmed. The results are shown in Table 1.

[0067] Furthermore, a test was conducted to confirm the heat resistance of each nickel-containing particle. In this test, the nickel-containing particle was heated at 800°C to form a fired film, and the fired film was photographed and visually inspected to evaluate the heat resistance according to the following criteria. Maintains particle shape △ Partially maintains particle shape × Particle shape is not maintained

[0068] [Table 1]

[0069] From the above, it is suggested that the nickel-containing particles of the present invention may be capable of effectively suppressing thermal shrinkage at a predetermined temperature when heated. [Explanation of symbols]

[0070] Sp Peak top intensity Pt peak top position Wh peak full width at half maximum

Claims

1. Nickel-containing particles comprising nickel particles containing nickel and a coating layer containing silicon that coats at least a portion of the surface of the nickel particles, the nickel particles contain sulfur; Nickel-containing particles having a peak top position of 1735 eV or more and a full width at half maximum of 10.5 eV or less in a Si-Kα spectrum obtained by soft X-ray emission spectroscopy.

2. The nickel-containing particles according to claim 1, wherein the silicon content is 0.05% by mass to 1.5% by mass.

3. The nickel-containing particles according to claim 1 or 2, wherein the sulfur content is 0.01% by mass to 1.0% by mass.

4. 3. The nickel-containing particles according to claim 1, wherein the particle size is 50 nm to 300 nm.

5. A method for producing nickel-containing particles having nickel particles containing nickel and a coating layer containing silicon that coats at least a portion of the surface of the nickel particles, comprising: The method includes a coating step of coating nickel particles with silicon, A method for producing nickel-containing particles, in which the nickel particles have a concentration ratio of the local sulfur concentration (atm %) at a position 2 nm deep from the surface to the local sulfur concentration (atm %) at a position 5 nm deep from the surface that is 5 times or more.

6. A slurry used for producing nickel-containing particles having nickel particles containing nickel and a coating layer containing silicon that coats at least a portion of the surface of the nickel particles, A slurry containing sulfur-containing nickel particles and a silicon additive.

7. 7. The slurry of claim 6, wherein the silicon additive comprises particulate silicon dioxide and / or an organosilicon compound.

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