TW201942374A - Nickel powder and production method therefor - Google Patents

Abstract

One of the problems addressed by the present invention is to provide: a nickel powder which has a high compacted density, and a small volume reduction under high temperature treatment; and a production method therefor. The nickel powder contains nickel particles, and among the Ni-Ni bonds, Ni-OH bonds, and Ni-O bonds derived from nickel oxide on the surface of the nickel particles, the proportion of Ni-Ni bonds is at least 50%, and the thermal shrinkage rate is at most 15% at 1200 DEG C. The proportion of Ni-Ni bonds and the thermal shrinkage rate are estimated by X-ray photoelectron spectroscopy and thermomechanical analysis, respectively.

Description

Nickel powder and manufacturing method thereof

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

Fine metal particles (metal powder) have been used in various fields. For example, nickel powder has been used as a raw material for internal electrodes of a multilayer ceramic capacitor (MLCC). The nickel powder can be produced by reducing a gas of nickel chloride with a reducing gas such as hydrogen. Alternatively, nickel powder can be produced by dispersing a nickel salt such as nickel oxide in a solvent and reducing it using a reducing agent such as hydrazine. The former is called the gas phase method, and the latter is called the liquid phase method. By appropriately treating the surface of the nickel powder obtained in this way, it is possible to control the characteristics or the behavior during sintering (see Patent Documents 1 and 2).

『Patent Literature』
Patent Document 1: Japanese Patent Publication No. 2014-29013 Patent Document 2: Japanese Patent Publication No. 2006-152439

One of the embodiments of the present invention is to provide a nickel powder that exhibits a high compression density and a small volume shrinkage during high-temperature processing, and a method for producing the same.

One of the related implementation forms of the present invention is a nickel powder. This nickel powder is located on the surface of Ni-Ni bond, Ni-OH bond and Ni-O bond derived from nickel oxide. The proportion of Ni-Ni bond is more than 50%, and the thermal shrinkage is 1200 ° C. 15% or less. The Ni-Ni bond ratio and thermal shrinkage were estimated by X-ray photoelectron spectroscopy and thermomechanical analysis, respectively.

One of the related implementation forms of the present invention is a method for manufacturing nickel powder. This method includes treating a raw nickel powder with a solution of a nitrogen-containing compound.

Hereinafter, each embodiment of the present invention will be described with reference to the drawings and the like. However, the present invention can be implemented in various aspects without departing from the gist of the present invention, and the interpreter is not limited to the description of the implementation modes of the following examples.

The nickel powder and its manufacturing method related to one embodiment of the present invention will be described below.

Nickel powder

Aggregate of nickel particles in the nickel powder system. The number average particle diameter of the nickel powder can be set to 50 nm or more and 500 nm or less, 50 nm or more and 300 nm or less, or 100 nm to 250 nm or less. Therefore, the nickel powder contains at least one kind of particles of nickel having a particle diameter in the above range. As the number average particle diameter, for example, the nickel powder can be observed by a scanning electron microscope, and the particle diameter of a plurality of particles (for example, 1,000 particles) can be measured, and the average value can be used. The particle size is the diameter of the smallest circle of the inscribed particles or the length of the long side of the quadrilateral of the smallest area of the inscribed particles. In addition, the nickel powder may contain particles of nickel together with an amine group-containing organic compound represented by a formula described below, for example.

The nickel atoms contained in the nickel particles exist in various bonded states. For example, the nickel atoms on the particle surface can not only adopt Ni-Ni bonding, but also Ni-OH bonding derived from surface hydroxyl groups, Ni-C bonding derived from carbonate (NiCO ₃ ), or The state of bonding such as Ni-O bonding of nickel oxide (NiO _X ). Ni-Ni bond, Ni-OH bond, and Ni-O bond on the surface of nickel particles of nickel powder, the proportion of Ni-Ni bond is more than 50%. The proportion of Ni-Ni bonding can be set to 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, on the surface of the nickel particles of the nickel powder, nickel exists as a zero-valent metal (metal nickel) at a ratio in the above range. In addition, the so-called nickel particle surface here refers to a region from the surface of the nickel particle to 5 nm or from the surface to 10 nm. Although the inventors have speculated, if the nitrogen-containing compound or the amine-containing organic compound is excluded, it is conceivable that the nickel particles constituting the nickel powder have Ni-OH bonds and Ni-O on the outermost surface. From the outermost surface of the bonded Ni, there are many Ni with Ni-Ni bonding.

The bonding state of the nickel atom can be estimated as follows, for example, by using XPS (X-ray photoelectron spectroscopy) using a light source such as AlKα rays. The measurement energy range of Ni2p is set to 884 to 844 (eV), and the measurement energy range of C1s is set to 298 to 279 (eV). The area attributed to the spike of metallic nickel, that is, the peak derived from the Ni-Ni bond, was determined as the sum of the peak areas of 852.4 (eV) and 858.5 (eV). The peak area attributed to the Ni-O bond is determined as the peak area of 853.4 (eV), 854.2 (eV), 855.3 (eV), 858.2 (eV), 860.6 (eV), 863.2 (eV), and 865.4 (eV). sum. The area of the peak attributed to the Ni-OH bond was obtained in the following manner. First, find the sum of the peak areas of 854.5 (eV), 855.7 (eV), 857.4 (eV), 861.1 (eV), 862.4 (eV), and 865.4 (eV). The peak area of 288.5 (eV) attributed to the Ni-C bond is subtracted from this sum, and the peak area derived from the Ni-OH bond is determined. In addition, the peak position attributed to the peak of metallic nickel can be specified by using Ni as a standard. The position of the peak attributed to the peak of the Ni-O bond can be specified by using NiO as a standard. The peak position attributed to the peak of the Ni-OH bond can be specified by using Ni (OH) ₂ . The position of the spike due to the Ni-C bond can be specified by using NiCO ₃ . In this specification and the claims, the total area of the peak area attributed to the Ni-Ni bond, the area of the peak attributed to the Ni-O bond, and the area of the peak attributed to the Ni-OH bond accounted for The ratio is the ratio of metallic nickel obtained by XPS measurement.

Since nickel particles contain metallic nickel on the surface at a high ratio as described above, nickel powder exhibits excellent characteristics. For example, the thermal shrinkage estimated by thermomechanical analysis is as low as 15% or less at 1200 ° C. The heat shrinkage rate may be 5% or more and 14% or less, or 7% or more and 13% or less. In addition, the compressive density of the nickel powder also has a high value of 4.8 g / cm ³ or more and 6.0 g / cm ³ or less, or 5.0 g / cm ³ or more and 6.0 g / cm ³ or less.

The measurement value of the above thermomechanical analysis method can be obtained by the following measurement. First, nickel powder was formed into particles of 5 mm in height and 10 mm in height. The measurement conditions for the thermo-mechanical analysis method were determined as a temperature range: room temperature to 1200 ° C, a heating rate: 5 ° C / min, and a gaseous environment: a mixed gas of 2% H ₂ and 98% N ₂ at 300 mL / min. The shrinkage amount obtained from the height (length) of the particles at 1200 ° C. at the end of the shrinkage was made into a ratio to the original height, and the thermal shrinkage rate was determined. The above-mentioned compression density can be obtained by the following measurement. Add 3 wt% of camphor and acetone to 1 g of nickel powder and stir until the mixture is dry. The obtained nickel powder was shaped under a pressure of 0.5 t. The diameter, thickness, and weight of the formed body were measured, and the values obtained thereby were the compressed density.

Manufacturing method

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

The manufacturing conditions of the raw nickel powder can be appropriately selected. Nitrogen chloride is usually obtained by blowing chlorine gas on raw materials such as nickel particles, nickel powder, and nickel ingots. By gasifying the nickel chloride and bringing the chlorinated nickel gas into contact with a reducing gas such as hydrogen or hydrazine, a raw nickel powder can be obtained. This raw material nickel powder may be further treated with a sulfur-containing compound to form a film of nickel sulfide on the surface. The particle diameter of the raw nickel powder is not particularly limited, and raw nickel powder having a number average particle diameter of, for example, 50 nm or more and 500 nm or less, 50 nm or more and 300 nm or less, or 100 nm and 250 nm or less can be used.

The nickel powder can be produced by treating a raw material nickel powder and a mixed solution or solution containing a nitrogen-containing compound (hereinafter, this mixed solution or solution is also referred to as a dispersant). As a solvent. Lower alcohols of 1 to 4 carbons such as water, ethanol or propanol, glycol solvents such as ethylene glycol and propylene glycol, N, N-dimethylformamide, N, N-dimethyl Amidamine-based solvents such as acetamide, nitrile-based solvents such as acetonitrile, and cyclic carbonate-based solvents such as ethylene carbonate. Among them, water that is a nonflammable solvent and has low toxicity is suitable.

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

As the nitrogen-containing compound, a primary alkylamine or an aliphatic amidine can be selected. The carbon number of the primary alkylamine and the carbon number of the carbon or nitrogen alkyl group bonded to the aliphatic amido group are not limited, and may be selected from 1 or more and 18 or less. The alkyl group may be linear, cyclic, or branched. As the primary alkylamine, tetradecylamine (C ₁₄ H ₂₉ NH ₂ ) can be exemplified.

Alternatively, the nitrogen-containing compound may include a salt of a primary alkylamine and a carboxylic acid. As the carboxylic acid, for example, a carboxylic acid having a carbon number of 1 or more and 4 or less such as formic acid and acetic acid can be used. The salt of tetradecylamine and acetic acid can be mentioned as an example.

The aliphatic amidine 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 including a hydroxyl group. As the aliphatic amidine, for example, a compound represented by the following chemical formula can be used.

Here, R ¹ is selected from an alkyl group having 6 to 18 carbon atoms, R ² is selected from an alkyl group or alkenyl group having 1 to 4 carbon atoms, and X is selected from an alkylene group having 1 to 5 carbon atoms. base. As an example, undecyl (C ₁₁ H ₂₃ ), methyl, and ethylidene can be selected as R ¹ , R ² , and X, respectively. Examples of the tertiary amine having an alkyl group containing a hydroxyl group include triethanolamine.

The treatment of the nickel powder with a dispersant can be performed, for example, in the following manner. First, a slurry of raw nickel powder is prepared, that is, a mixture containing a solvent such as water and the raw nickel is prepared, and the slurry and a dispersant are mixed. In such a manner that the concentration of the raw material nickel powder in the mixed solution becomes 90% by weight or more and 99.5% by weight or less, and the concentration of the nitrogen-containing compound becomes 0.5% by weight or more and 10% by weight or less, the amount of the raw material nickel powder in the slurry is appropriately controlled. Amount or concentration and amount of dispersant. The obtained mixed liquid is stirred under an inert gas atmosphere such as nitrogen or argon. The stirring time can be set to 1 minute or more and 1 hour or less, 1 minute or more and 30 minutes or less, or 1 minute to 10 minutes, and typically 5 minutes. The stirring temperature is also not limited. For example, stirring can be performed at room temperature (15 ° C or more and 30 ° C or less or 15 ° C or more and 25 ° C or less), or heating can be performed while stirring. In the case of heating, the stirring temperature can be selected in a range of a temperature of 40 ° C or higher and a boiling point of the mixed solution or less. As shown in the examples, in particular, by processing at room temperature, the proportion of nickel atoms existing as metallic nickel on the surface can be effectively increased. Thereafter, the temperature was raised and dried under a stream of nitrogen. Drying can be set at 20 ° C or higher and 200 ° C or lower, or 110 ° C to 150 ° C, typically 120 ° C. After drying, the nickel powder can also be classified.

According to the above manufacturing method, since the proportion of nickel atoms existing as metallic nickel on the surface is high, nickel powders exhibiting high compression density and small thermal shrinkage can be manufactured.

It is known that when a nickel powder is fired and used for electronic parts such as electrodes, if the thermal contraction rate of the nickel powder is large, it will be accompanied by a large volume change due to heating, so it is easy to have damage or self-adjacent structures. Defects such as body peeling occur. On the other hand, compared with the case where the dispersant is not treated, in the nickel powder according to the embodiment, the proportion of nickel atoms existing on the surface as a zero-valent metal is higher. As a result, as shown in the examples, the inventors have found that the nickel powder exhibits a small shrinkage rate and has a large compression density. If the compression density is increased, the particle filling ratio per unit volume will be increased. Therefore, it is conceivable that the voids per unit volume will be sufficiently reduced when the member is formed before the high heat treatment, and the influence of the nickel particles will be mitigated even if the nickel particles shrink during firing. As a result, the occurrence of damage can be suppressed / reduced. In addition, as long as the thermal shrinkage ratio at a high temperature is small, the occurrence of breakage can be further suppressed. Therefore, it is possible to significantly suppress defects such as occurrence of damage during heating and firing or peeling from adjacent structures. Therefore, nickel powder can be used as a material for providing electronic components with high reliability with high yield.

『Examples』

Example 1

In this example, the results of evaluating the characteristics of the nickel powder manufactured according to the above manufacturing method will be described.

1-1. Manufacturing of nickel powder

15 g of raw nickel powder having a number average particle diameter of 170 nm manufactured by a gas phase method was dispersed in 100 mL of water to obtain a nickel slurry. Subsequently, the nitrogen-containing compound is dissolved in water to prepare an aqueous solution of the nitrogen-containing compound. As the nitrogen-containing compound, three kinds of CATION MA, SOFTILT AL-T, and ESLEAM 221P triethanolamine neutralized product manufactured by Nippon Oil Co., Ltd. were used. In addition, ESLEAM 221P triethanolamine neutralization line uses two kinds of active ingredients of nitrogen-containing compounds: 10% and 20%. The concentration of the nitrogen-containing compound in the total of the raw material nickel powder and the nitrogen-containing compound was set to 1.0% by weight and 2.0% by weight.

An aqueous solution of a nitrogen-containing compound is added to the nickel slurry at room temperature and in a nitrogen environment, and a mixed solution of two different kinds is prepared so that the concentration of the nitrogen-containing compound becomes the above-mentioned concentration, respectively. After stirring the mixed solution for 5 minutes, the supernatant was removed, washed with water three times, and further dried by heating to 120 ° C. under a nitrogen atmosphere to obtain a nickel powder. Samples that do not use nitrogen-containing compounds were also prepared as comparative examples to discuss the effects of nitrogen-containing compounds.

1-2. XPS measurement

According to the measurement method described in the above embodiment, the ratio of metallic nickel in each nickel powder is obtained. For the XPS measurement, k-alpha ⁺ manufactured by Thermo Fisher Scientific, Inc. was used. The peak area is obtained by the following method.

For the spectrum obtained by XPS measurement, the background is removed by the Shirley method, and then the waveform is separated by a function that combines the Lorentz function and the Gaussian function. The peaks separated by the waveform are attributed to each bond as shown in Table 1. The peak area of Ni-Ni bond is determined as the total area of Ni2p3 metal1 and metal2, the peak area of Ni-O bond is determined as the total area of Ni2p3, NiO1 to NiO7, and the peak area of Ni-C bond is determined It is the peak area of C1s scan A, and the peak area of Ni-OH bond is determined as the sum of the peak area of Ni2p3 scan I to scan N minus the peak area of Ni-C bond. The peak area ratio thus obtained was determined as the ratio of each bond.

The results are disclosed in FIGS. 1 to 4. Figures 1 to 4 are CATION MA (Figure 1), SOFTILT AL-T (Figure 2), ESLEAM 221P triethanolamine neutralized product (10% active ingredient) (Figure 3), ESLEAM 221P triethanolamine neutralized product ( 20% of active ingredient) (Figure 4) Measurement results of nickel powder produced as a nitrogen-containing compound. In these figures, the ratios of Ni-Ni bonding, Ni-OH bonding, and Ni-O bonding are expressed as percentages. As shown in these figures, it can be seen that the ratio of Ni-Ni bonding is increased regardless of the nitrogen-containing compound used compared to the case where no nitrogen-containing compound is used. In addition, it was confirmed that it is a general tendency that the ratio of Ni—Ni bonds increases as the concentration of the nitrogen-containing compound increases.

Here, after comparing the spectrum of nickel powder produced from ESLEAM 221P triethanolamine neutralized product (20% active ingredient) as a nitrogen-containing compound in the range of 390 eV to 410 eV with raw nickel powder, it can be seen that the relative A peak was generated at 398 eV in the raw nickel powder, and a peak was observed at 400 eV in the nickel powder (Figure 7). The peak of 398 eV is attributed to the spike of metal nitride, which can be considered to be derived from the Ni-N bond. On the other hand, the peak of 400 eV can be considered to originate from the amidine bond contained in the nitrogen-containing compound, which is also implied by the fact that the intensity of the peak will increase as the concentration of the nitrogen-containing compound increases. This fact implied that the nickel particles on the surface of the nickel powder according to the implementation form of the present invention adsorbed an organic compound having an amidino group. In other words, it can be said that the nickel powder contains an organic compound having an amido group.

1-3. Measurement of heat shrinkage

The thermal contraction rate was determined by the method described above using a nickel powder produced using ESLEAM 221P triethanolamine neutralized product (20% active ingredient) as a nitrogen-containing compound. The machine used was TMA8310 manufactured by Rigaku Co., Ltd.

The results are shown in FIG. 5. As shown in FIG. 5, when the nitrogen-containing compound is not used, it can be seen that the shrinkage rate is 18%, and the volume is greatly reduced by heating. In contrast, the shrinkage of nickel powders produced using nitrogen-containing compounds will decrease as the concentration of nitrogen-containing compounds increases, and the thermal shrinkage of 10% when the concentration of nitrogen-containing compounds is 2.0%. From this result, it was confirmed that the higher the proportion of nickel atoms existing as metallic nickel on the surface, the lower the thermal shrinkage of the nickel powder.

1-4. Compression density measurement

The nickel powder produced by using ESLEAM 221P triethanolamine neutralized product (20% active ingredient) as a nitrogen-containing compound was used to measure the compression density by the above method. The machine was measured using ENERPAC S.E manufactured by Toyo Oil Hydraulic Machinery Co., Ltd. The load was changed to 0.5 t, 1.0 t, and 3 t.

The results are shown in Table 2 and FIG. 6. As can be understood from Table 2 and FIG. 6, it can be seen that the higher the concentration of the nitrogen-containing compound, that is, the higher the proportion of nickel atoms existing as metallic nickel on the surface, the more the compressed density of nickel powder tends to increase . For example, compared to the nickel powder of the comparative example, when the concentration of the nitrogen-containing compound in the total of the raw material nickel powder and the nitrogen-containing compound was 2.0% by weight, it was confirmed that the compression density increased by 15%.

As the implementation forms of the present invention, as long as the above-mentioned implementation forms do not contradict each other, they can be appropriately combined and implemented. In addition, according to the display device of each embodiment, a person with ordinary knowledge in the technical field who adds, deletes, or changes a design as appropriate, or adds, omits, or changes a condition of a process, need only have the gist of the present invention It is included in the scope of the present invention.

Even if it is another effect that is different from the effect caused by the aspects of the above-mentioned implementation modes, those who can be clearly known from the description of this specification or those with ordinary knowledge in the technical field can easily predict it. It can of course be understood as being facilitated by the present invention.

no.

[Figure 1] XPS measurement results of a nickel powder related to one of the implementation forms of the present invention.

[Fig. 2] XPS measurement results of nickel powder related to one of the implementation forms of the present invention.

[Figure 3] XPS measurement results of a nickel powder related to one of the implementation forms of the present invention.

[Fig. 4] XPS measurement results of nickel powder related to one of the implementation forms of the present invention.

[Figure 5] Thermomechanical analysis (TMA) results of nickel powders related to one of the implementation forms of the present invention.

[Figure 6] Measurement results of the compression density of the nickel powder related to one of the implementation forms of the present invention.

[Figure 7] XPS measurement results of nickel powder and raw material nickel powder related to one of the implementation forms of the present invention.

[Fig. 8] Manufacturing process of nickel powder, one of the implementation forms of the present invention.

Claims (13)

A nickel powder comprising nickel particles, wherein Ni-Ni bonds, Ni-OH bonds, and Ni-O bonds derived from nickel oxide are located on the surface of the aforementioned nickel particles, and are estimated by X-ray photoelectron spectroscopy. Among them, the ratio of Ni-Ni bonding is 50% or more, and the thermal shrinkage rate estimated by the thermomechanical analysis method is 15% or less at 1200 ° C. The nickel powder according to claim 1, wherein the number average particle diameter of the foregoing nickel powder is 50 nm or more and 500 nm or less. The nickel powder according to claim 1, further comprising a sulfonylamine-containing organic compound. A method for manufacturing nickel powder, comprising: treating raw material nickel powder with a mixed solution or solution containing a nitrogen-containing compound. The method according to claim 4, wherein the treatment is performed at a temperature selected from a range of 15 ° C to 30 ° C. The method according to claim 4, wherein the nitrogen-containing compound is selected from the group consisting of primary alkylamines and aliphatic amidines. The method according to claim 4, wherein the nitrogen-containing compound comprises a salt of a primary alkylamine and a carboxylic acid. The method according to claim 6, wherein the aliphatic amidine includes a carboxyl group in the molecule. The method according to claim 8, wherein the aforementioned aliphatic amidine is represented by the following chemical formula: R ¹ is an alkyl group having 6 to 18 carbon atoms, R ² is an alkyl or alkenyl group having 1 to 4 carbon atoms, and X is an alkylene group having 1 to 5 carbon atoms. The method according to claim 4, wherein the aforementioned treatment is such that the aforementioned raw material nickel powder and the aforementioned nitrogen-containing compound are 90% by weight or more and 99.5% by weight or less, and the aforementioned nitrogen-containing compound is 0.5 It is performed at a concentration of not less than 10% by weight and not more than 10% by weight. The method according to claim 4, wherein the aforementioned raw material nickel powder system is produced by a gas phase method. The method according to claim 4, wherein the solvent of the aforementioned solution is water. The method according to claim 4, wherein the aforementioned treatment is performed among Ni-Ni bonding, Ni-OH bonding and Ni-O bonding due to nickel oxide contained in the nickel particles contained in the nickel powder, The ratio of Ni-Ni bonding is 50% or more, and the thermal shrinkage of the nickel powder is 15% or less at 1200 ° C. The foregoing ratio of the Ni-Ni bonding and the thermal shrinkage ratio are respectively Estimated by X-ray photoelectron spectroscopy and thermomechanical analysis.