Nickel alloy powder and method for producing nickel alloy powder

Abstract

To provide a nickel alloy powder having a relatively low content of chlorine and oxygen and a method for producing a nickel alloy powder.SOLUTION: There is provided a nickel alloy powder which contains 65 mass% to 80 mass% of nickel and 20 mass% to 35 mass% of molybdenum, respectively, and has a chlorine content of 0.05 mass% or less and the ratio of the oxygen content (mass%) to the BET specific surface area (m2 / g) is 0.25 (mass%-g / m2) or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to nickel alloy powder and a method for producing nickel alloy powder. [Background technology]

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

[0003] Among these, multilayer ceramic chip capacitors have a structure in which dielectric layers and internal electrode layers are alternately stacked, with external electrodes provided at both ends. The dielectric layers are made of materials mainly composed of ceramics with a high dielectric constant, such as barium titanate, and nickel-containing powder is used for the internal electrode layers.

[0004] To use nickel-containing powder in the manufacture of multilayer ceramic chip capacitors, the nickel-containing powder is mixed with an organic binder or the like to form a paste. Then, the paste containing nickel-containing powder and a green sheet made of ceramic powder are laminated together, and these are heated simultaneously to sinter the ceramic powder and nickel-containing powder, respectively, thereby forming the internal electrode layer and the dielectric layer.

[0005] Here, if the nickel-containing powder is a nickel powder that is substantially made of nickel, when the paste and green sheet, which are stacked together as described above, are heated simultaneously, the nickel powder may sinter at a different temperature than the ceramic powder, resulting in differences in their shrinkage behavior during sintering. As a result, defects such as delamination and cracks may occur in the multilayer ceramic chip capacitor.

[0006] To address this, one could consider using nickel alloy powder, such as those described in Patent Documents 1-3, instead of nickel powder, as the nickel-containing powder.

[0007] Patent Document 1 discloses "an electrode composition characterized by comprising an alloy powder mainly composed of nickel, to which a pentavalent or hexavalent transition metal element is added." More specifically, it states that "the transition metal element consists of at least one of Nb, Ta, V, Mo, and W," and that "the nickel content is 95 to 99.5 wt%, and the transition metal element content is 0.5 to 5 wt%."

[0008] Patent Document 2 describes "Ni alloy powder for conductive paste, characterized by comprising 70-99.9% by mass of Ni and 0.1-30% by mass of one or more elements selected from the group consisting of V, Cr, Zr, Nb, Mo, Ta, and W, and having an average particle size of 0.1-1 μm."

[0009] Patent Document 3 describes "a method for producing nickel alloy powder, characterized by obtaining nickel alloy powder with an average particle size of 10 nm or more and less than 100 nm by gas-phase hydrogen reduction of a mixed gas of nickel chloride gas and at least one metal chloride gas selected from tungsten, molybdenum, niobium, and tantalum at a temperature of 980°C or more and 1150°C or less." [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2000-49031 [Patent Document 2] Japanese Patent Publication No. 2002-60877 [Patent Document 3] Japanese Patent Publication No. 2009-13456 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] Incidentally, nickel alloy powder can be produced by a gas-phase reduction method, which involves contacting nickel chloride and alloying elemental metal chlorides in a gaseous state and reducing them.

[0012] However, nickel alloy powder produced by the gas-phase reduction method contains chlorine due to the use of chlorine in the production process. Nickel alloy powder containing chlorine may cause cracking and delamination when used, for example, in the manufacture of multilayer ceramic chip capacitors. Furthermore, nickel alloy powder may contain oxygen. If the oxygen content is sufficiently high, the shrinkage rate during firing increases, which may also lead to cracking and delamination.

[0013] This invention aims to solve these problems, and its objective is to provide nickel alloy powder with relatively low chlorine and oxygen content, and a method for producing nickel alloy powder. [Means for solving the problem]

[0014] After diligent research, the inventor discovered that by increasing the amount of reducing gas in a gas-phase reduction method, and then washing the resulting reaction product powder with water under an inert atmosphere, the chlorine content can be reduced while suppressing the increase in oxygen content.

[0015] The nickel alloy powder of this invention , Mo Ribdenum 20% to 35% by mass Includes Yes, The remainder consists of nickel and impurities. Chlorine content is 0.05% by mass or less, BET specific surface area (m²) 2 The ratio of oxygen content (mass%) to g is 0.25 (mass%·g / m³). 2 ) Below Furthermore, the average diameter based on the number of particles is 0.1 μm to 0.4 μm. It is.

[0016] The nickel alloy powder described above preferably has a chlorine content of 0.0001% to 0.03% by mass.

[0017] Further, the above-mentioned nickel alloy powder has a BET specific surface area (m 2 / g) where the ratio of oxygen content (mass%) is 0.10 (mass%·g / m 2 ) to 0.23 (mass%·g / m 2 ), which is preferable.

[0018] The method for producing the nickel alloy powder of the present invention is , Mo contains 20 mass% to 35 mass% of molybdenum Includes having The remainder consists of nickel and impurities. A method for producing a nickel alloy powder, comprising: bringing nickel chloride gas, molybdenum chloride gas and hydrogen a reducing gas into contact, alloying nickel and molybdenum while reducing nickel chloride gas and molybdenum chloride gas to obtain a reaction product powder; and a washing step of washing the reaction product powder with water under an inert atmosphere Furthermore, in the reduction step, the supply ratio of the hydrogen gas is set to 100 mol% to 200 mol%, which is the theoretical value required for the gas-phase reduction reaction. .

[0019] In the washing step of the above production method, it is preferable to use, as the water, water whose dissolved oxygen content has been reduced by supplying an inert gas into the water.

[0020] Further, in the washing step of the above production method, it is preferable to use, as the water, water having a dissolved oxygen content of less than 3 mg / L.

Effects of the Invention

[0021] The nickel alloy powder of the present invention has relatively low contents of chlorine and oxygen. According to the method for producing a nickel alloy powder of the present invention, an increase in oxygen content can be suppressed while effectively removing chlorine, and the method is suitable for producing the above-described nickel alloy powder.

Brief Description of Drawings

[0022] [Figure 1] It is a graph showing the relationship between temperature and shrinkage ratio in TMA analysis results of each of the nickel alloy powders of Examples 1 and 2 and nickel powder.

Mode for Carrying Out the Invention

[0023] Embodiments of this invention will be described in detail below. One embodiment of this invention provides a nickel alloy powder containing 65% to 80% by mass of nickel and 20% to 35% by mass of molybdenum. Its chlorine content is 0.05% by mass or less, and its BET specific surface area (m²) is 2 The ratio of oxygen content (mass%) to g is 0.25 (mass%·g / m³). 2 ) are as follows:

[0024] The reaction product powder produced by the gas-phase reduction method contains a relatively large amount of chlorine. It has been found that if this reaction product powder is simply washed with water in an atmospheric environment, even if the chlorine is removed, oxygen is incorporated due to the atmosphere during washing, causing oxidation and resulting in a nickel alloy powder with a high oxygen content. In contrast, in the manufacturing method of the embodiment of this invention, the atmosphere during the washing process when washing the reaction product powder with water is made an inert atmosphere. By performing the washing with water in an inert atmosphere, it is possible to produce nickel alloy powder with sufficiently low chlorine and oxygen content.

[0025] (Nickel alloy powder) Nickel alloy powder contains 65% to 80% by mass of nickel (Ni) and 20% to 35% by mass of molybdenum (Mo). Typically, nickel alloy powder contains 20% to 35% by mass of molybdenum, with the remainder being nickel and impurities.

[0026] Preferably, the nickel content is 70% to 80% by mass, and the molybdenum content is 20% to 30% by mass.

[0027] The nickel alloy powder of this embodiment has a chlorine (Cl) content of 0.05% by mass or less, and may be, for example, 0.0001% by mass to 0.03% by mass. Such a low chlorine content suppresses the occurrence of cracks and delamination during sintering. When the chlorine content is 0.01% by mass or less, it is measured by combustion-coulometric titration. More specifically, TOX-2100H manufactured by Mitsubishi Chemical Corporation is used as a chlorine content measuring apparatus. When the chlorine content exceeds 0.01% by mass, it is measured by silver nitrate titration. More specifically, GT-200 manufactured by Mitsubishi Chemical Corporation is used as the measuring apparatus.

[0028] In addition, even when the ratio of the oxygen content to the BET specific surface area described below of the nickel alloy powder is high, cracks and delamination after sintering tend to easily occur. In contrast, in the nickel alloy powder of this embodiment, the BET specific surface area (m 2 / g) the ratio of oxygen content (% by mass) is 0.25 (% by mass·g / m 2 ) or less, and may be, for example, 0.10 (% by mass·g / m 2 ) to 0.23 (% by mass·g / m 2 ) in some cases. The oxygen content is measured by an inert gas fusion-infrared absorption method. For the measurement of oxygen content, EMGA-920 manufactured by Horiba, Ltd. is used.

[0029] The nickel alloy powder has a BET specific surface area of 1.5 m 2 / g to 6.0 m 2 / g in some cases. The BET specific surface area is measured by the BET method (gas adsorption method), and a fully automatic specific surface area measuring apparatus (Macsorb (registered trademark)) manufactured by Mountech Co., Ltd. can be used.

[0030] The nickel alloy powder may have an average circularity of 0.85 to 0.95. The average circularity is obtained as an average value of circularity C calculated as a ratio (B / A) of the perimeter A of the projected surface of the particle to the perimeter B of a circle having the same area as the projected surface, for 500 or more individual particles in an image obtained by observing the nickel alloy powder with a microscope.

[0031] The 10% particle size D10 of nickel alloy powder may range from 0.075 μm to 0.3 μm, the 50% particle size D50 from 0.1 μm to 0.4 μm, and the 90% particle size D90 from 0.15 μm to 0.6 μm. The 10% particle size D10, 50% particle size D50, and 90% particle size D90 are measured using a laser diffraction / scattering particle size distribution analyzer, and the particle size at which the cumulative frequency based on volume reaches 50%, 10%, and 90% is determined from the resulting particle size distribution graph. The SPAN value of nickel alloy powder is calculated using the formula: SPAN value = (D90 - D10) / D50, and may range from 0.5 to 0.8.

[0032] Nickel alloy powder may have an average particle diameter of 0.1 μm to 0.4 μm. This average diameter is determined by analyzing 500 copper particles present in a single field of view of a scanning electron microscope (SEM: Hitachi High-Technologies Corporation, product name SU5000) at a magnification of 30,000x using image analysis software (Mountec Co., Ltd., product name Macview4.0). The standard deviation of the average diameter of nickel alloy powder can range from 0.02 to 0.12. The standard deviation is determined by analyzing 500 copper particles present in one field of view of an SEM image at a magnification of 30,000x using a scanning electron microscope (SEM: Hitachi High-Technologies Corporation, product name SU5000), with image analysis software (Mountec Co., Ltd., product name Macview4.0). The CV value of nickel alloy powder can be between 0.2 and 0.3. The CV value is calculated by dividing the above standard deviation by the average diameter based on the above number of particles.

[0033] (Manufacturing method) The nickel alloy powder described above can be manufactured, for example, as follows.

[0034] Here, we prepare a reaction product powder generated by a gas-phase reduction method. This reaction product powder can be a commercially available product, but it can also be obtained by performing the gas-phase reduction method described below.

[0035] In the gas-phase reduction method, nickel chloride gas and molybdenum chloride gas are reduced in a mixed state, while the nickel and molybdenum contained therein are alloyed. Typically, this involves a chlorination step in which solid metallic nickel is reacted with chlorine to produce nickel chloride gas, and solid metallic molybdenum is reacted with chlorine to produce molybdenum chloride gas, and a reduction step in which nickel chloride gas, molybdenum chloride gas, and a reducing gas are reacted. Note that if nickel chloride gas and molybdenum chloride gas used in the reduction step are available separately, the chlorination step may be omitted.

[0036] In the chlorination process, for example, a nickel chloride furnace and a molybdenum chloride furnace separate from it may be used. In the nickel chloride furnace, a solid raw material containing metallic nickel is heated to, for example, 900°C to 1100°C to evaporate it, and this is brought into contact with chlorine gas to produce nickel chloride gas. In the molybdenum chloride furnace, a solid raw material containing metallic molybdenum is heated to, for example, 900°C to 1100°C to evaporate it, and this is brought into contact with chlorine gas to produce molybdenum chloride gas.

[0037] In the reduction process, the nickel chloride gas and molybdenum chloride gas are respectively fed into a reduction furnace, for example, where they are further mixed with a reducing gas to cause a reduction reaction and alloy the nickel and molybdenum.

[0038] Alternatively, by connecting the nickel chloride furnace and the molybdenum chloride furnace to the reduction furnace, nickel chloride gas and molybdenum chloride gas can be generated in the chlorination process, respectively, and then supplied to the reduction process to allow reduction and alloying to occur, thereby enabling the chlorination and reduction processes to be carried out continuously.

[0039] In the reduction process, an inert gas such as nitrogen or argon can be supplied to the reduction furnace. By supplying an inert gas, the partial pressure of nickel chloride gas and molybdenum chloride gas can be adjusted, and the particle size and alloy composition of the reaction product powder and nickel alloy powder obtained thereafter can be controlled.

[0040] The supply ratio of hydrogen gas as a reducing gas supplied to the reduction furnace should preferably be 100 mol% or more, more preferably 110 mol% to 200 mol%, which is the theoretical value required for the gas-phase reduction reaction. Furthermore, it is desirable to appropriately adjust the partial pressure of molybdenum chloride gas supplied to the reduction furnace, the discharge rate, the ratio of hydrogen gas to molybdenum chloride gas, and the shape and structure of the nozzles that inject each gas into the reduction furnace.

[0041] The temperature inside the reduction furnace can be set to, for example, 980°C to 1150°C. From the viewpoint of obtaining nickel alloy powder with small particle size, it is better not to set the temperature too high, but if the temperature is too low, there is a risk of chloride precipitation.

[0042] After the reaction product powder is obtained in the reduction step, it is preferable to rapidly cool the reaction product powder to about 400°C to 800°C by supplying an inert gas such as low-temperature nitrogen, for example, in order to suppress the generation of secondary particles due to aggregation. After that, the reaction product powder is recovered using a bag filter or the like.

[0043] The reaction product powder generated as described above is then subjected to a washing process. In the washing process, the reaction product powder is washed with water, for example, by immersing it in pure water or other water. Through the washing process, the chlorine contained in the reaction product powder is effectively removed, and nickel alloy powder with a low chlorine content is obtained.

[0044] The washing process is carried out under an inert atmosphere such as nitrogen or argon. This suppresses oxidation of the reaction product powder during washing and prevents an increase in oxygen content.

[0045] For washing, for example, the reaction product powder can be added to water, stirred, allowed to stand to settle, and then the supernatant can be removed. This operation can be performed once or multiple times as needed.

[0046] Furthermore, it is preferable that the water used for washing has a dissolved oxygen content reduced to less than 3 mg / L. This is because if the dissolved oxygen content of the washing water is sufficiently high, the oxidation of the reaction-generated powder will proceed due to the dissolved oxygen, which may increase the oxygen content of the nickel alloy powder. From this perspective, it is desirable to reduce the dissolved oxygen content of the washing water by supplying an inert gas such as argon to the water and bubbling it before washing.

[0047] After the washing process, nickel alloy powder can be produced by drying and other treatments. This nickel alloy powder contains 65% to 80% by mass of nickel and 20% to 35% by mass of molybdenum, with relatively low levels of chlorine and oxygen. [Examples]

[0048] Next, we conducted tests to produce the nickel alloy powder of this invention, and the details of these tests are described below. However, this description is for illustrative purposes only and is not intended to be limiting.

[0049] In Examples 1 and 2, a reaction was carried out by mixing nickel chloride gas, molybdenum chloride gas, and a gas containing hydrogen gas as a reducing gas using a gas-phase reduction method to obtain a reaction product powder. In Example 2, the supply ratio of hydrogen gas was lower than in Example 1.

[0050] Subsequently, the reaction product powder was washed with water under an argon atmosphere. The water used for washing was pre-treated to reduce the dissolved oxygen content to less than 3 mg / L by bubbling with argon gas. The washing process consisted of adding water, stirring for 5 minutes, letting it stand for 10-15 minutes, sedimentation, and removal of the supernatant, repeated five times. After washing, the mixture was dried under an argon atmosphere to obtain nickel alloy powder.

[0051] In Comparative Example 1, nickel alloy powder was produced in the same manner as in Example 1, except that the hydrogen gas supply ratio was slightly lower, the washing was performed in an atmospheric environment, and the dissolved oxygen content of the water used for washing was 7 mg / L. In Comparative Example 2, nickel alloy powder was produced in the same manner as in Example 2, except that the reaction product powder was not washed.

[0052] For each nickel alloy powder in Examples 1 and 2 and Comparative Examples 1 and 2, the chlorine content, oxygen content, BET specific surface area, average circularity, 10% particle size D10, 50% particle size D50, 90% particle size D90, SPAN value, average diameter, standard deviation, and CV value were determined using the method described above. The results are shown in Tables 1 and 2. In Table 1, the "increment" in oxygen (O) content refers to the oxygen content of the nickel alloy powder minus the oxygen content of the reaction product powder, and represents the increase in oxygen content due to washing.

[0053] [Table 1]

[0054] [Table 2]

[0055] As shown in Table 1, in Examples 1 and 2, washing the reaction product powder with water significantly reduced the chlorine content of the nickel alloy powder. Furthermore, although the nickel alloy powder in Examples 1 and 2 showed an increased oxygen content compared to the reaction product powder after washing, this increase was kept to a minimum.

[0056] Furthermore, the nickel alloy powders (Ni-Mo) from Examples 1 and 2, and the nickel powder (Ni) consisting substantially of only nickel, were analyzed using a thermomechanical analyzer (TMA, TMA8311 manufactured by Rigaku Corporation) to measure the shrinkage rate during heating. The measurement conditions involved creating a press-molded body of φ5 × 10 mmh and measuring it under a 2% H2-N2 atmosphere with continuous heating at 5°C / min. The results are shown in Figure 2. From the TMA analysis results in Figure 2, it was confirmed that Example 1 showed an 800°C improvement in the sintering start temperature (the temperature at which a shrinkage rate of 2%) compared to nickel powder (Ni alone), and Example 2 showed an improvement of 480°C.

[0057] In Comparative Example 1, washing the reaction product powder under an atmospheric environment significantly increased the oxygen content, resulting in a nickel alloy powder with a high oxygen content. In Comparative Example 2, no washing was performed, resulting in a nickel alloy powder containing a large amount of chlorine.

[0058] From the above, it has been found that this invention provides nickel alloy powder with relatively low chlorine and oxygen content.

Claims

1. Nickel alloy powder, It contains 20% to 35% by mass of molybdenum, with the remainder being nickel and impurities. Chlorine content is 0.05% by mass or less, BET specific surface area (m²) 2 The ratio of oxygen content (mass%) to ( / g) is 0.25 (mass%・g / m³). 2 ) and below, Nickel alloy powder with an average particle size of 0.1 μm to 0.4 μm.

2. The nickel alloy powder according to claim 1, wherein the chlorine content is 0.0001% by mass to 0.03% by mass.

3. BET specific surface area (m 2 The ratio of oxygen content (mass %) to (g) is 0.10 (mass %・g / m2) to 0.23 (mass %・g / m2). 2 The nickel alloy powder according to claim 1 or 2.

4. A method for producing a nickel alloy powder containing 20% ​​to 35% by mass of molybdenum, with the remainder being nickel and impurities, A reduction step involves contacting nickel chloride gas, molybdenum chloride gas, and hydrogen gas to reduce the nickel chloride gas and molybdenum chloride gas while alloying nickel and molybdenum to obtain a reaction product powder. The reaction product powder is washed with water in an inert atmosphere in a washing step. Includes, A method for producing nickel alloy powder, wherein in the reduction step, the supply ratio of hydrogen gas is set to 100 mol% to 200 mol%, which is the theoretical value required for the gas-phase reduction reaction.

5. The method for producing nickel alloy powder according to claim 4, wherein in the washing step, water is used in which the amount of dissolved oxygen has been reduced by supplying an inert gas to the water.

6. The method for producing nickel alloy powder according to claim 4 or 5, wherein in the washing step, water having a dissolved oxygen content of less than 3 mg / L is used as the water.

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