JP3163074B2 - Surface coated nickel fine powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-coated nickel fine powder, and more particularly, to a high tap density, a high packing density of a nickel fine powder in a paste, and a high density electrode. particularly it relates to a surface-coated nickel fine powder having suitable properties for use as an internal electrode materials of the multilayer ceramic capacitor.

[0002]

2. Description of the Related Art A multilayer ceramic capacitor is obtained by alternately stacking ceramic dielectrics and internal electrodes in a layered form, pressing and firing, and integrating them by firing. The internal electrodes of such a multilayer ceramic capacitor are formed. In this case, a metal fine powder as an internal electrode material is made into a paste, printed on a ceramic base material using the paste, and a plurality of the printed base materials are laminated by heating and pressure bonding to be integrated. It is general to perform heating and firing in an atmosphere. Conventionally, platinum and palladium have been used as the internal electrode material. In recent years, a technique using a base metal such as nickel instead of a noble metal such as platinum or palladium has been developed and advanced.

In order to increase the capacitance per unit volume in a multilayer ceramic capacitor, it is necessary to make the thickness of each layer of an internal electrode smaller than that of a conventional electrode. It is necessary to use a metal fine powder which is small and has a large tap density.

For example, Japanese Unexamined Patent Publication No. Hei 8-246001 discloses a correlation between the average particle size of nickel fine powder and the tap density. For example, the particle size is 0.8 μm and the tap density is 4.6 g. / Cm ³ or more, or a particle size of 0.4
It is shown that cracks and delamination hardly occur when the tap density is 3.0 g / cm ³ or more at μm.

On the other hand, it is common practice to apply an organic rust preventive coating on the surface of a metal powder, such as copper powder, which is easily oxidized to prevent oxidation. However, surface treatment is not necessarily required for a metal powder that is not easily oxidized such as a nickel powder. Examples of using a fatty acid in the production of nickel powder are described in, for example, JP-B-61-39373 and JP-A-4-246102. Japanese Patent Publication No. 61-39373 discloses that a linear saturated fatty acid is added to nickel chloride powder and treated in a high-temperature atmosphere at 400 to 750 ° C. to decompose the linear saturated fatty acid. It is disclosed that a metal nickel powder that is less likely to be reoxidized can be obtained. Japanese Patent Application Laid-Open No. Hei 4-246102 discloses that when a metal fine powder such as a nickel fine powder is subjected to hydrogen reduction and surface cleaning, a linear fatty acid or a metal salt thereof is contained in a dispersed state in the metal fine powder. By performing the reduction treatment at 150 to 500 ° C., the heat generated when the oxide on the metal surface is reduced is absorbed as heat of vaporization when the fatty acid evaporates, and the aggregation of the metal fine powder due to local heat generation can be suppressed. It has been disclosed.

However, in the methods described in these publications, fatty acids are not present on the surface of the final nickel metal powder due to decomposition or evaporation. To increase the tap density of the nickel fine powder to increase the packing density of the nickel fine powder in the paste, or to increase the packing density of the nickel fine powder in the paste, thereby forming an electrode having a predetermined thickness. There is no description or suggestion that the thickness of the paste to be obtained can be reduced.

[0007]

SUMMARY OF THE INVENTION The present invention has a high tap density, a high filling density of nickel fine powder in a paste, and can form a high-density electrode. it has an object to provide a surface-coated nickel fine powder having suitable properties for use as a fee.

[0008]

The present inventors have SUMMARY OF THE INVENTION As a result of extensive studies in order to attain the aforementioned object, the surface having the above characteristics by carrying unsaturated fatty acids in the metallic nickel fine particle surface The present inventors have found that a coated nickel fine powder can be obtained and completed the present invention.

That is, the multilayer ceramic capacitor of the present invention
Surface coating nickel fine powder for the internal electrode, the surface coating two on the surface of the metal nickel fine particles unsaturated fatty acid is carried
It is characterized by being made of a finely-divided powder .

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The surface-coated nickel fine powder of the present invention has a saturated or unsaturated fatty acid supported on the surface of metal nickel fine particles. The metal nickel fine particles used are those produced by a dry method such as a gas-phase hydrogen reduction method of nickel salt vapor, and under specific conditions, an aqueous solution containing nickel salt is reduced and precipitated with a reducing agent. It may be manufactured by a wet method. When the surface-coated nickel fine powder of the present invention is used as a paste for forming an internal electrode of a multilayer ceramic capacitor, the particle size of the nickel fine particles used for the production is preferably 5 μm or less, more preferably 1 μm or less. preferable.

The saturated or unsaturated fatty acid used for producing the surface-coated nickel fine powder of the present invention has a general formula of C _n H
A saturated fatty acid represented by _{2n + 1} COOH, or a general formula C _n H
_{2n-1 COOH, C n H} 2n-3 COOH, C n H 2n-5 COO
It is an unsaturated fatty acid represented by H or the like. Although the difference between the case where these saturated fatty acids are used and the case where unsaturated fatty acids are used is not clear, experimental results suggest that the use of unsaturated fatty acids tends to give better results.

[0012] Such saturated fatty acids include enanthates
Acid (C₆H₁₃COOH), caprylic acid (C₇H_FifteenCOO
H), pelargonic acid (C₈H₁₇COOH), capric acid
(Decanoic acid) (C₉H₁₉COOH), undecylic acid (C
_TenH_{twenty one}COOH), lauric acid (C₁₁H_{twenty three}COOH),
Tridecylic acid (C₁₂H_{twenty five}COOH), myristic acid (C
₁₃H₂₇COOH), pentadecylic acid (C₁₄H₂₉COO
H), palmitic acid (C _FifteenH₃₁COOH), heptadeci
Luic acid (C₁₆H₃₃COOH), stearic acid (C₁₇H₃₅C
OOH), nonadecanoic acid (C₁₈H₃₇COOH), Araki
Acid (C₁₉H₃₉COOH), behenic acid (C_{twenty one}H₄₃COO
H) and the like.

The unsaturated fatty acids include acrylic acid.
(CH_Two= CHCOOH), crotonic acid or isocrot
Acid (CH_ThreeCH = CHCOOH), undecylic acid (C
H_Two= CH (CH_Two)₈COOH), oleic acid or
Lidic acid (C₁₇H₃₃COOH), Cetreic acid_,bra
Sidic acid or erucic acid (C_{twenty one}H₄₁COOH), sorbin
Acid (C_FiveH₇COOH), linoleic acid (C₁₇H₃₁COO
H), linolenic acid (C ₁₇H₂₉COOH), arachidonic acid
(C₁₉H₃₁COOH) and the like.

In the surface-coated nickel fine powder of the present invention, as the amount of the fatty acid carried increases, the tap density of the surface-coated nickel fine powder increases, and the packing density of the nickel fine powder in the paste increases. An electrode having a high density can be formed. Such an effect clearly appears when the amount of the fatty acid carried is 0.01% by weight or more based on the weight of nickel, and becomes remarkable when it becomes 0.05% by weight or more. However, when the amount of the fatty acid carried is increased and a paste is prepared using such a surface-coated nickel fine powder, part of the fatty acid carried on the surface of the nickel fine particles separates from the surface of the nickel fine particles and is contained in the paste. Will elute. Therefore, the amount of the fatty acid carried is preferably 0.01 to 1% by weight, more preferably 0.05 to 0.5% by weight, based on the weight of nickel.

When the surface-coated nickel fine powder of the present invention is produced, that is, when a fatty acid is supported on the surface of the metal nickel fine particles, a solution in which the fatty acid is dissolved in a diluting solvent is mixed with the nickel fine powder. Preferably, the solution is adapted to the surface of the nickel fine powder, and then the excess solution is separated, for example, by suction filtration, and then dried. As such a diluting solvent, any solvent can be used as long as it can dissolve the fatty acid, and for example, acetone, ethanol, methanol, propanol and the like can be used.

In the surface-coated nickel fine powder of the present invention, by supporting a fatty acid on the surface of the metal nickel fine particles, the tap density of the surface-coated nickel fine powder is increased, and the packing density of the nickel fine powder in the paste is increased. Thus, a high-density electrode can be formed. The reason for this is not clear, but it is thought to be due to a reduction in the frictional resistance of the powder.

When the surface-coated nickel fine powder of the present invention is settled in an organic solvent (eg, terpineol) used for preparing a conductive paste, the settling density of the untreated nickel fine powder is determined. An unexpected result was obtained, which was higher than that of.

Further, as described in, for example, JP-A-8-136980, nickel fine powder obtained by a wet method in which an aqueous solution containing a nickel salt is reduced and precipitated with a reducing agent under specific conditions is used. When a multilayer capacitor is manufactured by using it as an internal electrode material, the volume change of the nickel fine powder during firing is large, and the volume change of the paste containing such nickel fine powder is large, resulting in frequent occurrence of delamination and cracks. It is known to be easy to do.

However, the surface-coated nickel fine powder of the present invention in which a fatty acid is supported on the surface of such nickel fine particles has a high tap density, and the packing density of the nickel fine powder in an organic solvent or paste becomes high. By using such a paste containing nickel fine powder, the coating thickness required to obtain an electrode having a predetermined thickness is reduced, and as a result, the volume change during firing is reduced, and delamination and cracks are extremely unlikely to occur. Become.

Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to such cases. Comparative Example 1 A solid skein soda (N) specified in JIS K1202
(244 g of aOH grade) was dissolved in pure water to give a total amount of 4 g.
It was adjusted to 30 ml with pure water to obtain an aqueous sodium hydroxide solution. On the other hand, nickel sulfate (NiSO ₄ · 6H
The ₂ O grade 22.2 wt% product) 448 g was dissolved in pure water (with hot water so as to more quickly complete dissolution), to obtain a nickel sulfate aqueous solution was adjusted with pure water so as to obtain a total amount of 1000ml Was. The obtained aqueous nickel sulfate solution was continuously added to the aqueous sodium hydroxide solution at an addition rate of 20 ml / min for 50 minutes. After the temperature of the hydroxide-containing slurry thus obtained was raised to 60 ° C, hydrazine 1
The hydroxide was reduced by adding 420 g of hydrate over 20 minutes. The obtained nickel fine particles are washed with pure water, and the washing is continued until the pH of the washing solution becomes 10 or less.
Thereafter, filtration and drying were performed according to a conventional method to obtain a fine nickel powder. The average particle size (ferret diameter, average particle size of primary particles) of the obtained nickel fine particles by SEM observation is 0.5 μm.
m.

Comparative Example 2 In the preparation method of Comparative Example 1, hydrazine 1 was added to reduce the hydroxide-containing slurry heated to 60 ° C.
Nickel fine powder was obtained in exactly the same manner as in Comparative Example 1 except that 420 g of the hydrate was not added over 20 minutes, but was added all at once. S of the obtained nickel fine particles
The average particle diameter (Ferre diameter) by EM observation was 0.2 μm.

Examples 1 to 12 Oleic acid was dissolved in 100 ml of a solvent of the type shown in Table 1 in an amount to give the concentration (% by weight) shown in Table 1.
In each solution, the nickel fine powder 10 prepared in Comparative Example 1 was added.
0 g was added and stirred sufficiently. Thereafter, the excess solution was removed by suction filtration, and dried overnight at 70 ° C. to obtain a fine nickel-coated surface powder having oleic acid supported on the surface of each fine particle.

With respect to the surface-coated nickel fine powder obtained in Examples 1 to 12, the amount of oleic acid carried (% by weight) based on the weight of nickel was measured by a weight loss method by heating. Further, for the surface-coated nickel fine powder obtained in Examples 1 to 12 and the nickel fine powder obtained in Comparative Example 1, the tap density (g / cc) was measured with a tap denser, and the specific surface area (m ² / g) was measured to measure the particle size distribution D ₅₀ diameter ([mu] m) by Microtrac measurements.
Table 1 shows the measurement results.

[0024]

[Table 1]

As is evident from the data shown in Table 1, the tap density of the surface-coated nickel fine powder of the present invention increases as the amount of oleic acid supported (% by weight) based on the weight of nickel increases. ing.

Examples 13 to 16 Fatty acids of the type shown in Table 2 were dissolved in 100 ml of acetone in such amounts that the concentrations shown in Table 2 were obtained. In each solution, 100 g of the nickel fine powder produced in Comparative Example 1 was added and sufficiently stirred. Thereafter, the excess solution was removed by suction filtration and dried overnight at 70 ° C. to obtain a fine nickel-coated nickel powder having stearic acid or decanoic acid supported on the surface of each fine particle.

With respect to the surface-coated nickel fine powder obtained in Examples 13 to 16, the carrying amount of stearic acid or decanoic acid on the basis of the weight of nickel was measured by a weight loss method by heating.
The tap density was measured by Tap Denser, measurement of specific surface area by the BET method, a particle size distribution was measured D ₅₀ in Microtrac measurements. Table 2 shows the measurement results.

[0028]

[Table 2]

As is apparent from the data shown in Table 2, the tap density of the surface-coated nickel fine powder of the present invention is improved by supporting and coating stearic acid or decanoic acid on the surface of the nickel fine particles. ing.

Examples 17 to 40 Saturated fatty acids and unsaturated fatty acids of the type shown in Table 3 were dissolved in 100 ml of a solvent of the type shown in Table 3 in such amounts as to give the concentrations shown in Table 3. In each solution, 100 g of the nickel fine powder produced in Comparative Example 1 was added and sufficiently stirred. Thereafter, excess solution was removed by suction filtration, and 70
° C overnight, various saturated fatty acids on the surface of each fine particle,
A surface-coated nickel fine powder carrying unsaturated fatty acids was obtained.

[0031] The surface-coated nickel fine powder obtained in Example 17 to 40, the tap density was measured by Tap Denser, the specific surface area measured by a BET method, a particle size distribution was measured D ₅₀ in Microtrac measurements. The measurement results are as shown in Table 3.

[0032]

[Table 3]

As is clear from the data shown in Table 3, various saturated fatty acids and unsaturated fatty acids are supported and coated on the surface of the nickel fine particles, whereby the tap density of the surface-coated nickel fine powder of the present invention is obtained. Is improving.

Examples 41 to 47 and Comparative Example 3 The surface-coated nickel fine powder obtained in Examples 1 to 7 and the nickel fine powder obtained in Comparative Example 1 were used as samples.
5 g was weighed, and each fine powder was treated with α-terpineol 1.
The mixture was placed in a 2 cc container together with 5 cc, a small amount of beads was further added, and the mixture was shaken with a paint shaker for 2 hours. Thereafter, the container was allowed to stand still and spontaneously settled, and the height (thickness of the nickel fine powder layer) (mm) from the container bottom after 24 hours was measured.
From the height and the bottom area of the container (0.79 cm ² ), the sedimentation density (g / cm ³ ) in α-terpineol was calculated. The measured values and calculated values are as shown in Table 4.

[0035]

As is clear from the data shown in Table 4, the surface-coated nickel fine powder of the present invention having a fatty acid supported on its surface has a smaller sedimentation volume than the nickel fine powder having no fatty acid supported thereon. It was confirmed that the sedimentation density was high. That is, it was confirmed that the packing density of the nickel fine powder was increased even when the paste was formed.

Example 48 Comparative Example 1 used in Example 3 using acetone as a solvent
Example 3 was the same as Example 3 except that the nickel fine powder having an average particle size (feret diameter) of 0.2 μm produced in Comparative Example 2 was used instead of the nickel fine powder having an average particle size (feret diameter) of 0.5 μm produced in To obtain a surface-coated nickel fine powder carrying oleic acid on the surface of the fine particles. With respect to the surface-coated nickel fine powder, the tap density (g / cc) is measured by a tap denser, the specific surface area (m ² / g) is measured by a BET method, and the particle size distribution D ₅₀ diameter (μm) is measured by a microtrack measurement. It was measured. Table 5 shows the measurement results.

[0038]

[0039]

As described above, the surface-coated nickel fine powder according to the present invention has a high tap density, a high packing density of the nickel fine powder in the paste, and therefore a coating thickness of the paste for obtaining an electrode having a predetermined thickness. Can be made thinner,
In particular, as an internal electrode material for multilayer ceramic capacitors,
Alternatively, it has characteristics suitable for use as a material for a conductive paste.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-341501 (JP, A) JP-A-5-148505 (JP, A) JP-A-10-280005 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B22F 1/00 B22F 1/02

Claims (3)

(57) [Claims] Multilayer ceramic Con which to 1. A surface of the metal nickel fine particles unsaturated fatty acid, characterized in that it is carried
Nickel fine powder with surface coating for internal electrodes of densa . Wherein unsaturated fatty gully Nord acid, linolenic acid 及
The surface-coated nickel fine powder for an internal electrode of a multilayer ceramic capacitor according to claim 1, wherein the powder is at least one of oleic acid and oleic acid . 3. The surface for an internal electrode of a multilayer ceramic capacitor according to claim 1, wherein the amount of the unsaturated fatty acid carried is 0.01 to 1% by weight based on the weight of nickel. Coated nickel fine powder.