CN111936254A

CN111936254A - Nickel powder and method for producing same

Info

Publication number: CN111936254A
Application number: CN201980023766.2A
Authority: CN
Inventors: 西岛一元; 大栗雅人; 浅井刚; 吉田贡
Original assignee: Toho Titanium Co Ltd
Current assignee: Toho Titanium Co Ltd
Priority date: 2018-03-29
Filing date: 2019-02-07
Publication date: 2020-11-13
Anticipated expiration: 2039-02-07
Also published as: JPWO2019187688A1; TWI735846B; KR102352835B1; TW201942374A; CN111936254B; JP6647458B1; KR20200111791A; WO2019187688A1

Abstract

One of the problems to be solved by the present invention is to provide a nickel powder exhibiting a high compression density and a small volume shrinkage under high-temperature treatment, and a method for producing the same. The nickel powder of the present invention comprises nickel particles, wherein the ratio of Ni-Ni bonds among Ni-Ni bonds, Ni-OH bonds on the surface of the nickel particles, and Ni-O bonds derived from nickel oxide is 50% or more, and the thermal shrinkage rate is 15% or less at 1200 ℃. The ratio of Ni-Ni bonds and the thermal shrinkage were estimated by X-ray photoelectron spectroscopy and thermomechanical analysis, respectively.

Description

Nickel powder and method for producing same

Technical Field

One embodiment of the present invention relates to a nickel powder and a method for producing the same.

Background

Fine metal particles (metal powder) are used in various fields, and for example, nickel powder is used as a material for internal electrodes of multilayer ceramic capacitors (MLCCs). The nickel powder can be produced by reducing a gas of nickel chloride with a reducing gas such as hydrogen gas. Alternatively, a nickel powder can be produced by dispersing a nickel salt such as nickel oxide in a solvent and reducing the nickel salt with a reducing agent such as hydrazine. The former is called a gas phase process and the latter is called a liquid phase process. By appropriately treating the surface of the nickel powder obtained by such a method, the characteristics and the behavior during sintering can be controlled (see patent documents 1 and 2).

Documents of the prior art

Patent document

Patent document 1: JP 2014-29013 publication;

patent document 2: JP 2006-152439 (Japanese unexamined patent publication No. 2006).

Disclosure of Invention

(problems to be solved by the invention)

An object of an embodiment of the present invention is to provide a nickel powder exhibiting a high compression density and a small volume shrinkage under high-temperature treatment, and a method for producing the same.

(means for solving the problems)

One embodiment of the present invention is a nickel powder. The nickel powder has a Ni-Ni bond ratio of 50% or more, a Ni-OH bond ratio, and a Ni-O bond ratio derived from nickel oxide on the surface thereof, and a heat shrinkage ratio of 15% or less at 1200 ℃. The ratio of Ni-Ni bonds and the thermal shrinkage were estimated by X-ray photoelectron spectroscopy and thermomechanical analysis, respectively.

One embodiment of the present invention is a method for producing a nickel powder. The method includes treating a raw nickel powder with a solution containing a nitrogen compound.

Drawings

Fig. 1 shows XPS measurement results of a nickel powder according to one embodiment of the present invention.

Fig. 2 shows XPS measurement results of the nickel powder according to one embodiment of the present invention.

Fig. 3 shows XPS measurement results of the nickel powder according to one embodiment of the present invention.

Fig. 4 shows XPS measurement results of the nickel powder according to one embodiment of the present invention.

Fig. 5 shows the results of thermomechanical analysis (TMA) of the nickel powder according to one embodiment of the present invention.

FIG. 6 shows the result of measuring the compressed density of the nickel powder according to one embodiment of the present invention.

Fig. 7 shows XPS measurement results of the nickel powder and the raw material nickel powder according to one embodiment of the present invention.

FIG. 8 shows a flow of production of a nickel powder according to one embodiment of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like. However, the present invention can be carried out in various forms without departing from the scope of the present invention, and the present invention should not be construed as being limited to the description of the embodiments illustrated below.

The nickel powder 100 according to one embodiment of the present invention and a method for producing the same will be described below.

1. Nickel powder

The nickel powder 100 is an aggregate of nickel particles, and the number average particle diameter of the nickel powder 100 may be 50nm or more and 500nm or less, 50nm or more and 300nm or less, or 100nm or more and 250nm or less. Therefore, nickel powder 100 contains particles of at least one kind of nickel having a particle diameter in the above range. As the number average particle diameter, for example, the particle diameters of a plurality of particles (for example, 1000 particles) are measured by observing the nickel powder 100 with a scanning electron microscope, and the average value is used. The particle size is the diameter of the smallest circle of inscribed particles or the length of the long side of the quadrangle of the smallest area of inscribed particles. The nickel powder 100 may include nickel particles and an amide group-containing organic compound represented by the following formula, for example.

The nickel atoms contained in the nickel particles exist in various bonding states. For example, the nickel atoms on the particle surface may be not only Ni-Ni bonds but also Ni-OH bonds derived from surface hydroxyl groups or from carbonate (NiCO)₃) And a Ni-C bond derived from nickel oxide (NiOx). The nickel powder 100 has a Ni-Ni bond ratio of 50% or more among Ni-Ni bonds, Ni-OH bonds, and Ni-O bonds on the surface of nickel particles. The ratio of Ni — Ni bonds may be 50% or more and 95% or less, 65% or more and 93% or less, 76% or more and 93% or less, or 85% or more and 93% or less. That is, nickel exists as the 0-valent metal (metallic nickel) in the above-described range on the surface of the nickel particles of the nickel powder 100. Here, the surface of the nickel particle means a region of 5nm or 10nm from the surface of the nickel particle. According to the presumption of the inventors, when considered in addition to the nitrogen-containing compound and the amide group-containing organic compound, it is considered that Ni having Ni — OH bonds and Ni — O bonds is present in a small amount on the outermost surface side of the nickel particles constituting the nickel powder 100, and Ni having Ni — Ni bonds is present in a large amount from the outermost surface to the inner side.

The bonding state of the nickel atom can be estimated, for example, by XPS (X-ray photoelectron spectroscopy) using a light source such as an AlK α ray in the following manner. The measured energy range of Ni2p is 884 to 844(eV), and the measured energy range of C1s is 298 to 279 (eV). The area of the peak attributed to metallic nickel, that is, the peak derived from the Ni-Ni bond was set to the sum of the peak areas of 852.4(eV) and 858.5 (eV). The peak areas ascribed to Ni-O bonds were set to the sum of the peak areas of 853.4(eV), 854.2(eV), 855.3(eV), 858.2(eV), 860.6(eV), 863.2(eV), and 865.4 (eV). The peak area attributed to the Ni-OH bond was determined in the following manner.First, the sum of peak areas of 854.5(eV), 855.7(eV), 857.4(eV), 861.1(eV), 862.4(eV), and 865.4(eV) was determined. The peak area attributed to 288.5(eV) bonded to Ni-C was subtracted from the sum to set the peak area attributed to Ni-OH bond. Further, if Ni is used as a standard, the peak position of the peak attributed to metallic nickel can be specified. If NiO is used as a standard, the peak position of the peak attributed to the Ni-O bond can be specified. If Ni (OH) is used₂Then, the peak position of the peak attributed to the Ni-OH bond can be specified. If NiCO is used₃Then the peak position attributed to the Ni-C bond can be specified. In the present specification and claims, the ratio of the peak area attributed to the Ni — Ni bond to the sum of the peak area attributed to the Ni — Ni bond, the peak area attributed to the Ni — O bond, and the peak area attributed to the Ni — OH bond is the ratio of metallic nickel determined by XPS measurement.

As described above, since the nickel particles contain metallic nickel at a high ratio on the surface, the nickel powder 100 exhibits excellent characteristics. For example, the thermal shrinkage rate as estimated by thermomechanical analysis is as low as 15% or less at 1200 ℃. The heat shrinkage rate may be 5% or more and 14% or less, or 7% or more and 13% or less. Further, the compressed density of the nickel powder 100 was 4.8g/cm³Above and 6.0g/cm³Below, or 5.0g/cm³Above and below 6.0g/cm³High value of (c).

The measured values of the thermomechanical analysis method were obtained by the following measurements. First, nickel powder 100 is molded into

A 10mm high mass. The measurement conditions for the thermomechanical analysis method were set to be in the temperature range: room temperature to 1200 ℃, temperature rising speed: 5 ℃/min, atmosphere: 2% H₂、98％N₂300 mL/min. The thermal shrinkage rate was determined as the ratio of the shrinkage amount determined from the height (length) of the briquette at 1200 ℃ at which shrinkage was completed to the original height. The compression density was determined by the following measurement. To 1g of nickel powder, 3 wt% of camphor and acetone were added, and the mixture was stirred until the mixture was dried. The obtained nickel powder was molded under a pressure of 0.5 t. The diameter, thickness, and weight of the formed body were measured, and the value thus obtained was the compressed density.

2. Manufacturing method

As shown in fig. 8, the nickel powder 100 according to the embodiment of the present invention can be produced by using a nickel powder as a raw material, treating the nickel powder with a nitrogen-containing compound, and drying the treated nickel powder. In this production method, a nickel powder produced by a gas phase method or a liquid phase method can be used as a raw material. Hereinafter, an example in which nickel powder produced by a vapor phase method (hereinafter, referred to as raw material nickel powder) is used as a raw material will be described.

The conditions for producing the raw material nickel powder can be appropriately selected. Generally, nickel chloride is obtained by blowing chlorine gas to a raw material such as a nickel briquette, nickel powder, or nickel ingot. The nickel chloride is gasified, and the nickel chloride gas is brought into contact with a reducing gas such as hydrogen or hydrazine, whereby a raw material nickel powder can be obtained. The raw material nickel powder may be further treated with a sulfur-containing compound to form a nickel sulfide coating on the surface. The particle size of the raw nickel powder is not particularly limited, and for example, a raw nickel powder having a number average particle size of 50nm or more and 500nm or less, 50nm or more and 300nm or less, or 100nm or more and 250nm or less may be used.

The nickel powder 100 can be produced by treating a raw material nickel powder with a mixed solution or solution containing a nitrogen-containing compound (hereinafter, the mixed solution or solution is also referred to as a dispersant). Examples of the solvent include water, a lower alcohol having 1 to 4 carbon atoms such as ethanol or propanol, a glycol solvent such as ethylene glycol or propylene glycol, an amide solvent such as N, N-dimethylformamide or N, N-dimethylacetamide, a nitrile solvent such as acetonitrile, and a cyclic carbonate solvent such as ethylene carbonate. Among them, water which is a non-flammable solvent and has low toxicity is preferable.

The nitrogen-containing compound is preferably a water-soluble nitrogen-containing compound. When water is used as the solvent, a nitrogen-containing compound having high solubility in water is used. The nitrogen-containing compound may be composed of a single component, or a mixture containing a plurality of components may be used as the nitrogen-containing compound.

As the nitrogen-containing compound, one selected from primary alkylamines or aliphatic amides is possible. The number of carbons of the primary alkylamine and the number of carbons of the alkyl group bonded to carbon or nitrogen of the aliphatic amide group are not limited and may be selected from 1 to 18. The alkyl group may be linear, cyclic or branched. As the primary alkylamine, there can be exemplified tetradecylamine (C)₁₄H₂₉NH₂)。

Alternatively, the nitrogen-containing compound may comprise a salt of a primary alkylamine with a carboxylic acid. As the carboxylic acid, for example, carboxylic acids having 1 to 4 carbon atoms such as formic acid and acetic acid can be used. As an example, a salt of tetradecylamine and acetic acid is mentioned.

The aliphatic amide may have a carboxyl group in the molecule. In this case, the nitrogen-containing compound may further include a tertiary amine having an alkyl group containing a hydroxyl group. As the aliphatic amide, for example, a compound represented by the following chemical formula can be used.

[ solution 1]

Here, R1 is selected from an alkyl group having 6 or more and 18 or less carbon atoms, R2 is selected from an alkyl group or alkenyl group having 1 or more and 4 or less carbon atoms, and X is selected from an alkylene group having 1 to 5 carbon atoms. For example, an undecyl group (C11H23), a methyl group, and an ethylene group can be selected as R1, R2, and X, respectively. As the tertiary amine having an alkyl group containing a hydroxyl group, triethanolamine may be mentioned, for example.

The treatment of the nickel powder 100 with the dispersant can be performed, for example, as follows. First, a slurry of a raw material nickel powder, that is, a mixture containing a solvent such as water and a raw material nickel is prepared, and the slurry is mixed with a dispersant. The amount of the raw material nickel powder and the concentration and amount of the dispersant in the slurry are appropriately controlled so that the concentration of the raw material nickel powder in the mixed solution is 90 to 99.5 wt% and less and the concentration of the nitrogen-containing compound is 0.5 to 10 wt%. The obtained mixed solution is stirred in an inert gas atmosphere such as nitrogen or argon. The stirring time may be 1 minute or more and 1 hour or less, 1 minute or more and 30 minutes or less, or 1 minute or more and 10 minutes or less, and typically 5 minutes. The stirring temperature is not limited either, and for example, stirring may be performed at room temperature (15 ℃ to 30 ℃ or 15 ℃ to 25 ℃) while heating. In the case of heating, the stirring temperature may be selected within a range of 40 ℃ or higher and the boiling point of the liquid mixture or lower. As shown in the examples, the ratio of nickel atoms present as metallic nickel on the surface can be effectively increased, particularly by performing the treatment at room temperature. Thereafter, the temperature was raised, and drying was performed under a nitrogen gas flow. The drying may be carried out at 20 ℃ to 200 ℃ inclusive, or at 110 ℃ to 150 ℃ inclusive, typically at 120 ℃. After drying, the nickel powder 100 may be classified.

By the above production method, it is possible to produce the nickel powder 100 having a high ratio of nickel atoms present as metallic nickel on the surface and thus exhibiting a high compression density and a small heat shrinkage rate.

It is known that when a nickel powder is fired and used for electronic components such as electrodes, if the thermal shrinkage of the nickel powder is large, the nickel powder is heated to cause a large volume change, and thus defects such as cracks and separation from adjacent structures are likely to occur. In contrast, the nickel powder 100 according to the present embodiment has a higher ratio of nickel atoms present as 0-valent metal on the surface than the nickel powder 100 not treated with a dispersant. The inventor and the like found that: as a result, the nickel powder 100 showed a small shrinkage rate and had a large compression density as shown in examples. When the compression density is increased, the particle packing ratio per unit volume becomes high. Therefore, when a member is formed before high heat treatment, voids per unit volume are sufficiently reduced, and even when nickel particles shrink during firing, the effect thereof is alleviated, and as a result, it is considered that the occurrence of cracks can be suppressed/reduced. Further, if the thermal shrinkage rate at high temperature is reduced, the occurrence of cracks can be further suppressed. Therefore, it is possible to greatly suppress the occurrence of defects such as cracks and separation from the adjacent structure during the heat baking. Therefore, the nickel powder 100 can be used as a material for providing highly reliable electronic parts with a good yield.

(examples)

1. Example 1

In this example, the results obtained by evaluating the characteristics of the nickel powder 100 produced according to the above-described production method will be described.

1-1. production of Nickel powder

15g of a raw material nickel powder having a number average particle diameter of 170nm produced by a vapor phase method was dispersed in 100mL of water to obtain a nickel slurry. Next, the nitrogen-containing compound is dissolved in water to prepare an aqueous solution of the nitrogen-containing compound. As the nitrogen-containing compounds, three kinds of neutralization products of CATION MA and SOFTILT AL-T, ESLEAM221P triethanolamine manufactured by Nichigan oil Co., Ltd were used. In addition, ESLEAM221P triethanolamine-neutralized product contains 10% and 20% of nitrogen-containing compounds as effective components. The concentrations of the nitrogen-containing compounds in the total of the raw material nickel powder and the nitrogen-containing compound were 1.0 wt% and 2.0 wt%.

Two different mixed solutions were prepared by adding an aqueous solution of a nitrogen-containing compound to a nickel slurry at room temperature under a nitrogen atmosphere so that the concentration of each nitrogen-containing compound became the above concentration. After the mixed solution was stirred for 5 minutes, the supernatant was removed, washed three times with water, and further heated to 120 ℃ under a nitrogen atmosphere to be dried, thereby obtaining nickel powder 100. A sample in which no nitrogen-containing compound was used was also prepared as a comparative example, and the influence of the nitrogen-containing compound was examined.

XPS assay

The ratio of metallic nickel in each nickel powder 100 was determined according to the measurement method described in the above embodiment. XPS measurement was performed using k-alpha + manufactured by Thermo Fisher Scientific Co. The peak area was determined by the following method.

The spectrum obtained by XPS measurement was subjected to waveform separation using a function in which a lorentz function and a gaussian function were combined after background subtraction using the Shirley method. The peaks after waveform separation were assigned to the keys as shown in table 1. The peak area of Ni-Ni bond is the sum of the peak areas of Ni2p3 metal1 and metal2, the peak area of Ni-O bond is the sum of the peak areas of Ni2p3, NiO1 to NiO7, the peak area of Ni-C bond is the peak area of C1s scan A, and the peak area of Ni-OH bond is the value obtained by subtracting the peak area of Ni-C bond from the sum of the peak areas of Ni2p3 scan I to scan N. The peak area ratio thus obtained was taken as the ratio of each bond.

[ Table 1]

TABLE 1 results of wave crest separation

The results are shown in fig. 1 to 4. Fig. 1 to 4 are measurement results of the nickel powder 100 produced using the nitrogen-containing compound, namely, the catalyst MA (fig. 1), the SOFTILT AL-T (fig. 2), the ESLEAM221P triethanolamine-neutralized product (active ingredient 10%) (fig. 3), and the ESLEAM221P triethanolamine-neutralized product (active ingredient 20%) (fig. 4), respectively. In these figures, the ratio of Ni-Ni bonds, Ni-OH bonds, and Ni-O bonds is expressed in percentage. As shown in these figures, it is found that the ratio of Ni — Ni bonds is increased when any nitrogen-containing compound is used as compared with when no nitrogen-containing compound is used. In addition, it was confirmed that: as a general tendency, the ratio of Ni — Ni bonds increases as the concentration of the nitrogen-containing compound increases.

Here, comparing the spectra of the raw material nickel powder and the nickel powder 100 produced using ESLEAM221P triethanolamine neutralized product (effective component 20%) as a nitrogen-containing compound in the range of 390eV to 410eV, it is known that: the raw material nickel powder showed a peak at 398eV, and the nickel powder 100 showed a peak at 400eV (FIG. 7). The peak at 398eV is a peak attributed to metal nitride, and is considered to be derived from Ni-N bond. On the other hand, it is considered that the peak of 400eV is derived from the amide bond contained in the nitrogen-containing compound, which also indicates that the peak intensity increases as the concentration of the nitrogen-containing compound increases. This suggests that: the nickel powder 100 according to the embodiment of the present invention has an amide group-containing organic compound adsorbed on the surface of the nickel particles. In other words, it can be said that the nickel powder 100 contains an organic compound having an amide group.

1-3 determination of thermal shrinkage

The heat shrinkage rate was determined by the above method using the nickel powder 100 produced using an ESLEAM221P triethanolamine-neutralized product (active ingredient 20%) as a nitrogen-containing compound. The apparatus used was TMA8310 manufactured by Rigaku corporation.

The results are shown in FIG. 5. As shown in fig. 5, when no nitrogen-containing compound was used, the shrinkage was 18%, and it was found that the volume was significantly reduced by heating. On the other hand, with respect to the nickel powder 100 produced using the nitrogen-containing compound, the shrinkage rate decreases as the concentration of the nitrogen-containing compound increases, and the thermal shrinkage rate is 10% at a concentration of 2.0% of the nitrogen-containing compound. From these results, it was confirmed that: the higher the ratio of nickel atoms present as metallic nickel on the surface, the lower the thermal shrinkage of the nickel powder 100 is exhibited.

1-4 measurement of compressed Density

The compressive density was measured by the above method using the nickel powder 100 produced using an ESLEAM221P triethanolamine-neutralized product (active ingredient 20%) as a nitrogen-containing compound. The apparatus was measured using ENERPAC S.E manufactured by Toyo Hydraulic pressure machinery, Inc. with loads of 0.5t, 1.0t, and 3 t.

The results are shown in table 2 and fig. 6. As can be understood from table 2 and fig. 6, it is found that the higher the concentration of the nitrogen-containing compound is, that is, the higher the ratio of nickel atoms present as metallic nickel on the surface is, the higher the compression density of the nickel powder 100 tends to be. For example, when the concentration of the nitrogen-containing compound in the total of the raw material nickel powder and the nitrogen-containing compound is 2.0 wt%, it is confirmed that the 15% compressive density is increased as compared with the nickel powder of the comparative example.

[ Table 2]

The embodiments described above as embodiments of the present invention can be combined and implemented as appropriate as long as they are not contradictory to each other. Further, those skilled in the art can add or delete components or change the design, or add or omit steps or change the conditions as appropriate based on the display device of each embodiment, and the scope of the present invention is included as long as the gist of the present invention is achieved.

Even if the operation and effect is different from the operation and effect produced by the aspects of the above embodiments, the operation and effect which is clear from the description of the present specification or can be easily predicted by a person skilled in the art is naturally understood to be produced by the present invention.

Description of the reference symbols

100: nickel powder

Claims

1. A nickel powder comprising nickel particles,

the ratio of Ni-Ni bonds among Ni-Ni bonds, Ni-OH bonds, and Ni-O bonds derived from nickel oxide on the surface of the nickel particles estimated by X-ray photoelectron spectroscopy is 50% or more,

the thermal shrinkage rate estimated by a thermomechanical analysis method is 15% or less at 1200 ℃.

2. The nickel powder according to claim 1,

the number average particle diameter of the nickel powder is 50nm to 500 nm.

3. The nickel powder according to claim 1, further comprising an amide group-containing organic compound.

4. A method for producing nickel powder, which comprises treating a raw material nickel powder with a mixed solution or a solution containing a nitrogen-containing compound.

5. The method of claim 4, wherein,

the treatment is carried out at a temperature selected from the range of 15 ℃ or higher and 30 ℃ or lower.

6. The method of claim 4, wherein,

the nitrogen-containing compound is selected from primary alkyl amine and aliphatic amide.

7. The method of claim 4, wherein,

the nitrogen-containing compound comprises a salt of a primary alkylamine with a carboxylic acid.

8. The method of claim 6, wherein,

the aliphatic amide contains a carboxyl group in the molecule.

9. The method of claim 8, wherein,

the aliphatic amide is represented by the following chemical formula,

[ solution 1]

R1 is an alkyl group having 6 to 18 carbon atoms, R2 is an alkyl or alkenyl group having 1 to 4 carbon atoms, and X is an alkylene group having 1 to 5 carbon atoms.

10. The method of claim 4, wherein,

the treatment is performed so that the concentration of the raw nickel powder in the total of the raw nickel powder and the nitrogen-containing compound is 90 wt% or more and 99.5 wt% or less, and the concentration of the nitrogen-containing compound is 0.5 wt% or more and 10 wt% or less.

11. The method of claim 4, wherein,

the raw material nickel powder is produced by a vapor phase method.

12. The method of claim 4, wherein,

the solvent of the solution is water.

13. The method of claim 4, wherein,

the treatment is performed so that the ratio of Ni-Ni bonds among Ni-Ni bonds, Ni-OH bonds, and Ni-O bonds derived from nickel oxide contained in the nickel powder is 50% or more, and the heat shrinkage of the nickel powder is 15% or less at 1200 ℃,

the ratio of the Ni — Ni bond and the thermal shrinkage ratio were estimated by X-ray photoelectron spectroscopy and thermomechanical analysis, respectively.