CN102665969B

CN102665969B - Nickel powder and production method thereof

Info

Publication number: CN102665969B
Application number: CN201080052922.7A
Authority: CN
Inventors: 川上裕二; 石田荣治; 田中宏幸; 冈田美香; 金子勋
Original assignee: Sumitomo Metal Mining Co Ltd
Current assignee: Sumitomo Metal Mining Co Ltd
Priority date: 2009-09-24
Filing date: 2010-09-22
Publication date: 2015-03-04
Anticipated expiration: 2030-09-22
Also published as: JPWO2011037150A1; TW201129434A; TWI517914B; JP5626217B2; KR20120084730A; WO2011037150A1; KR101745030B1; CN102665969A

Abstract

Disclosed is a nickel powder having excellent crystallinity and a high shrink temperature, inhibiting sintering contraction even at high temperatures without affecting the decomposition temperature of the resin binder. Also provided is a production method for the nickel powder. The average particle diameter of the nickel powder is 0.05 - 0.3[Mu]m, crystalline diameter is 60% - 90% of specific surface area diameter, sulphur content is 0.1% - 0.5% by weight, and oxygen content is 0.4% - 1.5% by weight. The powder has a 2 - 15nm thick oxygen-containing surface coating layer with an outermost surface formed from a mixture of a nickel-sulphur compound and a nickel-oxygen compound. Furthermore, in x-ray photoelectron spectroscopy analysis, the outermost layer should preferably have an abundance ratio of 50% - 100% nickel sulphide in the sulphur compound and an abundance ratio of 0% - 50% of nickel hydroxide in the nickel-oxygen compound.

Description

Nickel micro mist and manufacture method thereof

Technical field

The present invention relates to a kind of nickel micro mist and manufacture method thereof.More specifically, the nickel micro mist that the electronic component-use electrode material relating to a kind of internal electrode as multilayer ceramic capacitor etc. uses and manufacture method thereof.

The application's application requirement priority that to be the Japanese Patent application number proposed based on Japan on September 24th, 2009 be " Patent 2009-219286 ", and carried out quoting for reference in this application to above-mentioned application.

Background technology

There is miniaturized requirement in electronic instrument in recent years, in order to tackle this requirement, also there is more micronized requirement to the nickel micro mist that the parts material as electronic instrument uses.Such as, in multilayer ceramic capacitor (MLCC:Multilayer Ceramic Capacitor), the small particle diameter of nickel micro mist is required, to tackle the filming of MLCC internal electrode material.Further, to MLCC nickel micro mist of future generation, not only require that its particle diameter reaches the small particle diameter of less than 0.2 μm, and also require that there is excellent high-quality in other characteristic.

For the manufacture of MLCC, such as, adopt and implement with the following method.

First, on ceramic dielectric raw cook, electrocondution slurry is carried out serigraphy, thus making internal electrode, wherein, described electrocondution slurry carries out mixing obtaining to using resins such as metal fine powder and ethyl celluloses (below sometimes referred to as " EC ") as organic solvents etc. such as the resin binder of main component and terpineols.Then, with the mode stacked dielectric raw cook making printed internal electrode alternately stacked, and pressing is carried out to form duplexer.Then, duplexer is cut into the size of regulation, after implementing the resin such as EC that the process of unsticking mixture to remove burn as resin binder use, burnt till to 1300 DEG C by high temperature and obtain ceramic body.Then, this ceramic body installs outer electrode, form multilayer ceramic capacitor.

At this, for the metal fine powder become in the electrocondution slurry of internal electrode, nickel micro mist becomes main flow, therefore, in the unsticking mixture process of duplexer, in order to prevent nickel micro mist to be oxidized, implements under the environment of the oxygen containing denier.

In the past, in this unsticking mixture operation, the thermal decomposition of adhesive obtained low temperature by the catalytic activity on nickel particles surface, such as, when adhesive is EC etc., had distinguished, near 260 DEG C, thermal decomposition had occurred.Now, the thermal decomposition of adhesive is only limited to the near surface of nickel particles, does not decompose other adhesive.Therefore, the gas produced by the exploded of adhesive can remain with the state being closed in its position, place, and this gas causes opening between nickel internal electrode layer and ceramic dielectric layer, there is the problem of internal electrode discontinuity or generation stripping thus.

On the other hand, in above-mentioned firing process, and through being usually used in compared with the ceramic dielectrics such as barium titanate in MLCC, the contraction initial temperature of the internal electrode material such as nickel powder is lower and percent thermal shrinkage is large.Thus, when burning till, the shrinkage degree caused by the sintering characteristic difference between ceramic dielectric with internal electrode material do not mate aggravation, exist be easy to the problem causing the fault of construction such as crackle or stripping.

In recent years, thin layer along with electrode, nickel powder is miniaturization more and more, and nickel powder is finer, and the catalytic activity on nickel powder surface is larger and to shrink initial temperature lower, and therefore, the problem of above-mentioned internal electrode discontinuity or crackle or stripping can become remarkable.When discontinuity or the crackle of a large amount of generation internal electrode or when peeling off, then cannot play the function of capacitor.

Therefore, someone proposes the method improving Problems existing in above-mentioned MLCC internal electrode formation nickel powder.

As above-mentioned proposal, such as, following patent document 1 ~ 4 can be enumerated.

< patent document 1>

In patent document 1, propose a kind of nickel Ultramicro-powder, its average grain diameter 0.1 ~ 1.0 μm, and sulfur content is 0.02 ~ 1.0%.In this proposal, as the manufacture method of nickel Ultramicro-powder, disclose a kind of gas phase reduction process of the nickel chloride steam undertaken by the one or both in sulphur and sulfide, and point out, by containing sulphur, excellent spherical nickel Ultramicro-powder can be obtained.Further, when as spherical particle, the high coating interior electrode of packed density can be formed in the manufacturing process of multilayer ceramic capacitor, and play the characteristic not cracking or peel off.

But, in patent document 1, although describe the effect suppressing crackle when making MLCC or delamination to occur, do not mention shrinkage character when burning till.Therefore, about obtaining at electrode thin layer and suppressing contraction when sintering to be unclear in the MLCC of miniaturization.Further, from the nickel Ultramicro-powder that nickel chloride steam obtains, contain chlorine at employing gas phase reduction process, thus be necessary to carry out washing to remove chlorine.Therefore, cause forming thick oxide layer on nickel Ultramicro-powder surface, and oxygen contained in final obtained nickel Ultramicro-powder increases considerably, and causes harmful effect thus to sintering behavior.Further, when carrying out drying after washing, likely can cause aggegation, even if add the subsequent handlings such as pulverizing, also cause aggegation serious owing to being Ultramicro-powder, shrinkage factor when burning till in actual use increases.Further, do not mention the decomposition behavior about adhesive during unsticking mixture at all.

< patent document 2>

In patent document 2, propose a kind of electrocondution slurry nickel by powder, its shape of particle is spherical, particle diameter is 0.1 ~ 1.0 μm, and containing 0.05 ~ 0.2% sulphur.Point out in this proposal: sulphur is mainly present in surface portion, and promote spheroidizing under the effect of this sulphur, can obtain shape of particle is spherical and that monodispersity is excellent nickel by powder.Further, as its manufacture method, in the steam of nickel chloride, vapour phase reduction reaction under disclosing the environment of sulfur-bearing, is implemented.

But, in the proposal described in this patent document 2, do not mention shrinkage character when burning till, unclear to the shrinkage character of obtained nickel by powder, owing to removing the cause of chlorine in gas phase reduction process, cause being formed with thick oxide layer on nickel Ultramicro-powder surface.Further, do not mention in this proposal about decomposition behavior during above-mentioned unsticking mixture.

< patent document 3>

In patent document 3, propose a kind of nickel by powder, it is that sulphur or sulfate clad surface by being scaled 0.02 ~ 0.20 quality % with sulphur forms.Point out in this proposal, by with sulphur or the coated nickel by powder of sulfate, form on nickel by powder surface the coating layer concentrated by nickel sulfide or nickelous sulfate, suppress the contraction under high temperature, obtain the nickel by powder that sintering characteristic is excellent.Further, as its manufacture method, the method for the gas of sulfur-bearing and nickel by powder being carried out to contact pairs is disclosed.

But, about obtained nickel by powder, only describe the high temperature effect of shrinking initial temperature, do not mention the decomposition behavior of above-mentioned unsticking mixture.Further, shrinkage character when burning till is not paid attention to, owing to not being formed with the oxide-film of suitable thickness, so infer that shrinkage character when burning till is poor.

< patent document 4>

In patent document 4, disclose a kind of nickel by powder, its average grain diameter is 0.05 ~ 1.0 μm and sulphur is 100 ~ 2000ppm relative to the content of gross weight.And, disclose: adopting ESCA(ElectronSpectroscopy for Chemical Analysis) in surface analysis that this nickel by powder is carried out, result from the peak intensity of the sulphur atom be combined with nickle atom, change from particle surface to center position, its intensity becomes maximum on the distance particle surface position dark more than 3nm, and the degree of depth of the sulfur-bearing of this nickel by powder is thick reaches 30nm.As its manufacture method, disclose: the nickel by powder of sulfur-bearing is scattered in non-oxidizing gas environment, make it contact with oxidizing gas in 300 ~ 800 DEG C of temperature ranges and carry out the surface oxidation treatment of short time.In this proposal, be not also oxidized when carrying out unsticking mixture in oxidizing gas environment, the Volume Changes caused by the redox in burning till is few and do not have the fault of construction such as crackle or delamination, can manufacture excellent laminated electronic component.

But, in this proposal, although evaluate the oxidative resistance of obtained nickel by powder, any not open to shrinkage character when burning till.In addition, the decomposition behavior about above-mentioned unsticking mixture is not mentioned.Further, owing to making fine nickel by powder contact with oxidizing gas at high operating temperatures, the phenomenon of the likely nickel by powder generation spontaneous combustion because of abrupt oxidization.Therefore, the thickness of oxide-film is thickening, infers and is difficult to form suitable thickness.

Prior art document

Patent document

Patent document 1: Japanese Unexamined Patent Publication 11-80817 publication

Patent document 2: Japanese Unexamined Patent Publication 11-80816 publication

Patent document 3: Japanese Unexamined Patent Publication 2004-244654 publication

Patent document 4: Japanese Unexamined Patent Publication 2008-223068 publication

Summary of the invention

The problem that invention will solve

The present invention proposes in view of the above problems, its object is to, a kind of excellent in crystallinity is provided, shrink initial temperature high, reach a high temperature before the nickel micro mist that suppressed of contraction that occurs with sintering, also provide a kind of decomposition temperature improving resin binder with the nickel micro mist making it reach the decomposition temperature equal extent original with resin binder.

Solve the method for problem

The present inventor studies intensively the nickel micro mist by the excellent in crystallinity manufactured by hot plasma, found that: be special value by setting the oxygen containing coating thickness on nickel micro mist surface, contraction initial temperature when burning till and shrinkage character can be improved, and, by controlling the form of nickel sulfide contained in this clad, the decomposition temperature can improving resin binder reaches the decomposition temperature equal extent original with resin binder to make it.And then, undertaken gasifying by hot plasma and condense and obtain sulfur-bearing nickel micro mist, this sulfur-bearing nickel micro mist is held in weak oxide gaseous environment and makes surface be oxidized lentamente, the form obtaining clad but also the aforementioned nickel sulfide not only with specific thickness thus obtains the nickel micro mist controlled, and completes the present invention based on above-mentioned discovery.

Namely, nickel micro mist of the present invention, it is characterized in that, average grain diameter is 0.05 ~ 0.3 μm, size of microcrystal relative to specific area particle diameter be 60 ~ 90%, sulfur content be 0.1 ~ 0.5 quality % and oxygen content is 0.4 ~ 1.5 quality %, have on surface thickness be 2 ~ 15nm containing oxygen clad, and at least the outermost of this clad is made up of the mixture containing nickel sulfide and nickel oxide.

At this, preferred aforementioned clad contains nickel oxygen compound and is made up of following two layers, namely by being present in the layer containing nickel sulfide of most surface side and being present in not forming containing the layer of nickel sulfide of inner face side.

And, preferably in x-ray photoelectron spectroscopy (XPS) is analyzed, the content of the nickel sulfide in the sulfide contained by outermost than be 50% ~ 100%, the content ratio of nickel hydroxide in nickel oxide is 0 ~ 50%, the content of the nickelous sulfate in preferred aforementioned outmost nickel sulfide is than below 40%.

And then the layer containing nickel sulfide in preferred aforementioned clad, is made up of following two layers further, namely by being present in the layer containing nickelous sulfate of most surface side and being present in forming as the layer of nickel sulfide mainly containing nickel sulfide of inner face side.Further, preferred clad has the inclined concentration gradient of sulphur in the scope of distance below most surface 10nm, and the CONCENTRATION DISTRIBUTION of the nickel sulfide in preferred aforementioned clad becomes maximum at aforementioned outermost.

Nickel micro mist of the present invention, is characterized in that, when adopting thermo-mechanical analysis device to measure, shrinkage factor when being heated to 1300 DEG C in reproducibility environment is less than 15%.

And, preferred above-mentioned nickel micro mist obtains by the following method: in reducibility gas environment, carry out gasifying based on hot plasma and make the devaporation of generation obtain the nickel micro mist of sulfur-bearing, the nickel micro mist of this sulfur-bearing being held in weak oxide gaseous environment and obtaining.

The manufacture method of nickel micro mist of the present invention, comprising: raw material preparation process, and preparation sulfur content is the nickel raw material of 0.1 ~ 0.5 quality %; Micronizing operation, in the reducing gas environment containing non-active gas and hydrogen, makes prepared nickel material gasification by hot plasma, and makes the produced nickel devaporation containing sulphur and oxygen and carry out micronizing; Recovery process, is cooled the micronizing nickel after micronizing and is reclaimed; And eremacausis operation, is held in reclaimed micronizing nickel and makes the eremacausis of micronizing nickel surface in oxygen containing weak oxide non-reactive gas ambient and obtain nickel micro mist.

At this, the maintenance temperature preferably in eremacausis operation is less than 100 DEG C, and the oxygen content preferably in eremacausis operation in non-reactive gas ambient is 1 ~ 5 capacity %.

Further, in raw material preparation process, preferably prepare the nickel of sulfur content 0.1 ~ 0.5 quality % in advance as nickel raw material, or the nickel oxide containing sulphur is coordinated with nickel and prepares the nickel raw material that sulfur content is 0.1 ~ 0.5 quality %.

In addition, as hot plasma, preferably use catalytic behavior of materials.

The effect of invention

High and the excellent in crystallinity of the purity of nickel micro mist of the present invention, is suitable for as electronic instrument/parts material.During the nickel micro mist formed in particular as the internal electrode of MLCC, can improve and shrink initial temperature and the contraction that produces with sintering can be suppressed, therefore, it is possible to prevent the generation of the fault of construction such as crackle or stripping.In addition, by control surface compound layer, the decomposition temperature equal extent that the decomposition temperature of resin binder reaches original with resin binder can be made, therefore can prevent the discontinuity of internal electrode or the generation of stripping further.Further, the manufacture method of above-mentioned nickel micro mist is simple and easy and can be applicable in the production of industrially scalable, and its industrial value is very large.

Accompanying drawing explanation

Fig. 1 represents to adopt FE-AES(Flied emission Auger electron spectroscopy) analyze the result of the depth direction of the nickel micro mist of embodiment 1.

Fig. 2 represents the result adopting FE-AES to analyze the depth direction of the nickel micro mist of embodiment 3.

Fig. 3 is the result of the depth direction representing the nickel micro mist adopting FE-AES com-parison and analysis example 2.

Fig. 4 is the curve map representing each layer thickness in embodiment 1 ~ 4 and comparative example 2.

Fig. 5 is the result of the EC thermal decomposition characteristic of the nickel micro mist representing embodiment and comparative example.

Detailed description of the invention

Below, with reference to accompanying drawing, describe in detail by following order and be suitable for the specific embodiment of the present invention.

1. nickel micro mist

1-1. average grain diameter

1-2. size of microcrystal

1-3. sulfur content

1-4. oxygen content

2. the manufacture method of nickel micro mist

2-1. raw material preparation process

2-2. micronizing operation

2-3. recovery process

2-4. eremacausis operation

3. embodiment

<1. nickel micro mist >

Nickel micro mist in an embodiment of the present invention, it is characterized in that, average grain diameter is 0.05 ~ 0.3 μm, size of microcrystal is specific area particle diameter 60 ~ 90%, sulfur content is 0.1 ~ 0.5 quality % and oxygen content is 0.4 ~ 1.5 quality %, there is on surface the oxygen containing clad of thickness 2 ~ 15nm, and at least the outermost of this clad is made up of the mixture containing nickel sulfide and nickel oxide.

Nickel micro mist has the oxygen containing clad of thickness 2 ~ 15nm on its surface, and at least the outermost of this clad is made up of the mixture containing nickel sulfide and nickel oxide.At this, so-called outermost, refer to and adopt AES(AugerElectron Spectroscopy under not by the states that etch obtained nickel micro mist such as sputterings) scope involved by analysis of carrying out, typically refer to the scope of distance most surface about 2 ~ 3nm.

The thickness of the clad containing oxygen (atom) that nickel micro mist has is 2 ~ 15nm, is more preferably 5 ~ 15nm.If the thickness of clad is lower than 2nm, then can not get improving the effect of contraction initial temperature when burning till and shrinkage factor.Further, even if the thickness of clad is more than 15nm, also can not get improving the effect of contraction initial temperature when burning till and shrinkage factor.Its reason is, when burning till, this clad has the generation such as crackle, stripping, and the nickel being present in inner face is showed out, thus the effect of clad reduces.

In addition, the outermost of nickel micro mist is made up of the mixture containing nickel sulfide and nickel oxide.Thus, while the reaching a high temperature of contraction initial temperature when burning till can be made, suppress the contraction produced with sintering.Think that its reason is, nickel sulfide hinders the solid-state diffusion of nickel between nickel particles.When paying close attention to nickel sulfide and nickel oxide, if the outermost of clad is the state that substantially only there is nickel oxide, then at MLCC(Monolithic Ceramic Chip Capacitors) burn till time week reduction gaseous environment used under, surface cannot be obtained and reduced and the effect making contraction initial temperature high temperature.On the other hand, because outermost exists nickel sulfide and nickel oxide, the carrying out of sintering can being postponed and make the reaching a high temperature of contraction initial temperature when burning till, suppressing with sintering the contraction caused simultaneously.

Aforementioned nickel sulfide (nickel sulphur compound), can take nickel sulfide (NiS), oxidized nickelous sulfate (NiSO ₄) form.Namely the nickel sulfide, in clad is the compound containing nickel sulfide, nickelous sulfate etc.

On the other hand, aforementioned nickel oxide (nickel oxygen compound), the nickel hydroxide (Ni (OH) nickel oxide (NiO) can be taked, being generated by adsorbed water ₂) form.Namely the nickel oxide in clad is the compound containing nickel oxide, nickel hydroxide etc.

Further, preferred clad contains nickel oxide and to be two-layerly made up of following, is namely made up of the layer containing nickel sulfide being present in most surface side and the layer not containing nickel sulfide that is present in inner face side.Because clad to be two-layerly made up of above-mentioned, the sulfur content in clad can be reduced thus and the contraction initial temperature that can improve when burning till and shrinkage factor.That is, the layer containing nickel oxide by being present in inner face side supplements the raising of contraction initial temperature and the shrinkage factor caused based on nickel sulfide, can improve the improvement effect of shrinking initial temperature and shrinkage factor further.Further, the effect of the heat decomposition temperature low temperature of suppression resin binder described later can be improved.

On the other hand, if only form with desired thickness the layer that one deck contains nickel sulfide and nickel oxide, although then can reach the improvement of above-mentioned effect, sulfur content contained in the clad on surface increases, and likely produces corrosive gas when burning till.Therefore, when as electronic component-use materials'use, the likely circuit of etching electronic parts or electronic equipment.

In addition, nickel micro mist in an embodiment of the present invention, preferably in x-ray photoelectron spectroscopy (XPS) is analyzed, the content of the nickel sulfide in nickel sulfide contained near most surface than be 50% ~ 100%, the content ratio of nickel hydroxide in nickel oxide is 0 ~ 50%.

As the nickelous sulfate of chemical state near most surface and the content ratio of nickel sulfide, obtain by analyzing the peak obtained based on XPS analysis.The content compared lower than 50%, i.e. nickelous sulfate at the content of above-mentioned nickel sulfide compares more than under the state of 50%, and the degree of oxidation on nickel micro mist surface is high, and nickel oxide or the nickel hydroxide on surface increase.In this state, contraction initial temperature when burning till and shrinkage factor is likely caused to increase, agglutinating property is reduced.In order to keep agglutinating property good, the content of nickelous sulfate ratio is preferably made to be adjusted to less than 40%.In addition, based on XPS analysis involved by scope, normally distance about most surface 5nm scope, refer to this scope near most surface.

On the other hand, if the content ratio of the nickel hydroxide in the nickel oxide near most surface is more than 50%, then nickel micro mist hydrophily increase, thus slurry make after from resinous principle deprives moisture, slurry viscosity is increased, therefore cannot to use as slurry instability.

As the nickelous sulfate of the chemical state near most surface and the content ratio of nickel sulfide, the heat decomposition temperature using resins such as ethyl celluloses (EC) as the resin binder of main component for making slurry is also had an impact, but the content only by nickel sulfide is inadequate than height, by being set as the nickel sulfide that crystallinity is high and nickelous sulfate, the catalytic activity of nickel can be suppressed, thus the low temperature of the heat decomposition temperature of resin binder can be suppressed.

The crystallinity of nickel sulfide and nickelous sulfate, such as, confirms by the analysis adopting the electron ray diffraction (TEM-EDX) of transmission electron microscope to carry out.If the diffraction spot in TEM-EDX (inflection ス Port Star ト) belongs to the degree that can be identified, can say that crystallinity is good, the effect of the heat decomposition temperature low temperature suppressing resin binder can be obtained.Nickel micro mist of the present invention has confirmed the diffraction spot of nickel sulfide and nickelous sulfate in aforementioned TEM-EDX.

In the nickel micro mist of an embodiment of the present invention, the layer containing nickel sulfide in preferred above-mentioned clad also has two-layer formation, namely by being present in the layer containing nickelous sulfate of most surface side and being present in forming as the layer of nickel sulfide mainly containing nickel sulfide of inner face side.Because the nickel sulfide on micro mist surface is easily oxidized, therefore by containing the nickelous sulfate of already oxidised state in most surface side, the oxidation of nickel micro mist can be prevented.If the aforementioned layer containing nickelous sulfate is thickening, then the content of above-mentioned nickel sulfide is than reducing, and therefore below preferred distance most surface 5nm, is more preferably 2 ~ 3nm.On the other hand, owing to there is the above-mentioned main layer containing nickel sulfide, the content ratio of the nickel sulfide near most surface can be made to reach enough degree.At this, the so-called main layer containing nickel sulfide, refers to the diffraction spot that can confirm nickel sulfide in aforementioned TEM-EDX and the state that can not confirm the diffraction spot of nickelous sulfate.

Clad in the nickel micro mist of an embodiment of the present invention, can be the layer that the layer containing nickel sulfide and nickel oxide is clearly distinguished with inner nickel portion, but clad also can have the concentration gradient of the inclination of sulphur (atom) in the scope of distance below most surface 10nm.That is, the concentration that also can be formed as sulphur (atom) is the enriched layer that slowly reduces of direction internally.At this, the enriched layer of so-called sulphur, refers to the layer that sulphur (atom) exists, and can easily adopt AES(auger electrons analysis of spectrum) confirm.In addition, the CONCENTRATION DISTRIBUTION of sulphur can have peak in clad, but preferred concentration peak is positioned at outermost (distance most surface about 2 ~ 3nm).Wherein, be sometimes attached with carbon (C) on the surface at nickel micro mist, based in the analysis of AES, there is the problem that correctly cannot identify the position of nickel micro mist most surface.In this case, such as, when the C concentration of most surface (sputter depth is the position of 0nm) in AES analyzes is more than 10 atom %, as long as using the most surface of the interior location of the most surface 1 ~ 2nm on distance analysis as the nickel micro mist of reality.By making outmost sulphur concentration become maximum, agglutinating property and resin binder can be improved to the effect of heat decomposition temperature.

Preferably in clad, the enriched layer thickness of sulphur is 2 ~ 10nm.If the enriched layer thickness of sulphur is more than 10nm, then likely cause the generation of corrosive gas when burning till, corrosion occurs the circuit of electronic unit or electronic equipment problem.

In addition, preferred above-mentioned nickel micro mist obtains by the following method: in reducibility gas environment, carry out gasifying based on hot plasma and make the devaporation of generation and obtain the nickel micro mist of sulfur-bearing, the nickel micro mist of this sulfur-bearing being held in weak oxide gaseous environment and obtaining.By using hot plasma, the nickel steam gasified out just is cooled condensation fast once from heating region, and solidifies from the state of complete droplet treatment, and the nickel therefore after micronizing not only substantially reaches spheroidizing but also crystallinity is high.

For the nickel micro mist with this formation, when being heated to 1300 DEG C in reducibility gas environment, its shrinkage factor is less than 15% in the mensuration adopting thermo-mechanical analysis device to carry out.Be less than 15% based on the shrinkage factor in the mensuration adopting thermo-mechanical analysis device to carry out, time in for the thin layer electrode of MLCC, the electrode crackle that the contraction that agglutinating property when can prevent because of burning till causes is poor to bring or the generation of stripping.In addition, the low temperature of the heat decomposition temperature of the resin binder when unsticking mixture is also suppressed.

Below, the main composition key element of nickel micro mist is described in detail.

<1-1. average grain diameter >

The average grain diameter of nickel micro mist is 0.05 ~ 0.3 μm.If the average grain diameter of nickel micro mist is lower than 0.05 μm, then aggegation becomes violent, can not be scattered in slurry equably, is difficult to form electrode by coating.In addition, owing to there is aggegation powder, therefore, apparent particle diameter increases, and not only cannot correspond to the electrode of filming, and the contraction that sintering during because burning till causes increases.On the other hand, if average grain diameter is more than 0.3 μm, then can not correspond to the electrode of filming.By average grain diameter is adjusted to 0.05 ~ 0.3 μm, it can be made to be scattered in equably in slurry and the electrode that may correspond in filming.

<1-2. size of microcrystal >

The size of microcrystal of nickel micro mist is 60 ~ 90% of specific area particle diameter.The progress impact of size of microcrystal on sintering is large.The nickel micro mist that crystallinity is well, namely size of microcrystal is large relative to specific area particle diameter, with have same degree particle diameter nickel micro mist compared with, it is high to shrink initial temperature, and by sintering, the shrinkage factor that causes is little.By setting size of microcrystal be 60 ~ 90% of specific area particle diameter, the effect that is multiplied of the effect that the effect that crystallinity can be utilized to bring is brought with clad, obtains good contraction initial temperature and shrinkage factor.If size of microcrystal is less than 60% of specific area particle diameter, then the crystallinity of nickel micro mist is poor, therefore can not get good contraction initial temperature and shrinkage factor.The upper limit of size of microcrystal contrast table area particle diameter can more than 90%, but to obtain relative to specific area particle diameter be 100%, the nickel micro mist that is namely made up of monocrystalline is difficulty and unrealistic.

<1-3. sulfur content >

The sulfur content of preferred nickel micro mist is 0.1 ~ 0.5 quality %, more preferably more than 0.2 quality % and lower than 0.5 quality %.If sulfur content is lower than 0.1 quality %, then the formation of surface coating layer is insufficient, and fully cannot obtain the contraction high temperature effect of initial temperature and the minimizing effect of shrinkage factor when burning till.Further, if sulfur content is at below 0.2 quality %, improves even if then shrink initial temperature, sometimes also fully cannot obtain the minimizing effect of shrinkage factor.On the other hand, if sulfur content is more than 0.5 quality %, be then difficult to the clad obtaining oxygen containing suitable thickness, the generation of corrosive gas when burning till can be caused, corrosion occurs the circuit of electronic unit or electronic instrument problem.Further, near 800 DEG C, produce a large amount of SOx gas, produce the crackle, stripping etc. of electrode.

<1-4. oxygen content >

The oxygen content of preferred nickel micro mist is 0.4 ~ 1.5 quality %.If oxygen content is lower than 0.4 quality %, then the formation of surface coating layer is insufficient, can not get good contraction initial temperature and shrinkage factor.In addition, the surface-active of nickel micro mist is high, therefore, also likely can cause violent oxidation reaction even if heat a little in an atmosphere.If oxygen content is more than 1.5 quality %, then when burning till in the week reduction gaseous environment of hydrogen etc., the generation of gas becomes violent and causes the crackle of electrode, stripping etc.

As mentioned above, at the nickel micro mist of present embodiment, have the clad of the average grain diameter of regulation, the sulfur content of regulation, the oxygen content of regulation and specific thickness, the outermost of clad is made up of the mixture that the crystallinity containing nickel sulfide and nickel oxide is high.Thus, contraction initial temperature can not only be improved, and the contraction with sintering can be suppressed.Further, the catalytic activity of nickel can be suppressed, can make near the heat decomposition temperature high temperature of resin binder to the original decomposition temperature of resin binder.

The manufacture method > of < 2. nickel micro mist

The manufacture method (hereinafter referred to as " this method for making ") of the nickel micro mist of an embodiment of the present invention, comprising: raw material preparation process, and preparation sulfur content becomes the nickel raw material of 0.1 ~ 0.5 quality %; Micronizing operation, in the reducing gas environment containing non-active gas and hydrogen, makes prepared nickel raw material generating gasification by hot plasma, and makes the produced nickel devaporation containing sulphur and oxygen, thus makes its micronizing; Recovery process, is cooled the micronizing nickel after micronizing and is reclaimed; And eremacausis operation, is held in reclaimed micronizing nickel in oxygen containing weak oxide non-reactive gas ambient, thus makes the eremacausis of micronizing nickel surface, obtain nickel micro mist.Below, each operation is described in detail.

< 2-1. raw material preparation process >

Raw material preparation process is the operation regulating sulfur content contained in nickel raw material.In raw material preparation process, from nickel, nickel oxide, sulfide, at least select nickel to coordinate, to make the sulfur content in nickel raw material become 0.1 ~ 0.5 quality %, and obtain nickel raw material.In this raw material preparation process, the mode being 0.1 ~ 0.5 quality % with the sulfur content in the sulfur content of obtained nickel micro mist and nickel raw material carries out coordinating.For sulphur, can be included in any one in the nickel or nickel oxide used as raw material, also can coordinate as sulfide.

Further, in raw material preparation process, preferably prepare in advance sulfur content be the nickel of 0.1 ~ 0.5 quality % as nickel raw material, or the nickel oxide of sulfur-bearing is coordinated with nickel and is prepared the nickel raw material that sulfur content is 0.1 ~ 0.5 quality %.If selective oxidation nickel is as nickel source, then likely in subsequent processing, i.e. micronizing operation, be mixed into nickel oxide, therefore, select nickel as nickel source.In addition, if coordinate sulfide, then likely sulphur skewness in obtained nickel micro mist.

Sulfur content is the nickel of 0.1 ~ 0.5 quality %, being by impregnated in the aqueous solution of sulfide by nickel, making sulphur be adsorbed in nickel surface to obtain.Based on the sulfide amount in the aqueous solution, the content of sulphur easily can be regulated.After in aqueous sulphur being adsorbed in nickel surface, usual method can be adopted to carry out drying.

In addition, as the nickel oxide of sulfur-bearing, such as, the nickel oxide of calcining manufactured by nickelous sulfate can be used.This nickel oxide has commercially available usually, can analyze in nickel oxide and coordinate nickel oxide after institute's sulfur content, becomes aequum to make the sulfur content in nickel raw material.

The nickel used as nickel raw material or the shape of nickel oxide, be not particularly limited, but from the easness supplied, be preferably powder, preferably its average grain diameter is 0.5 ~ 10 μm.

<2-2. micronizing operation >

Micronizing operation is in the reducing gas environment containing non-active gas and hydrogen, is made the nickel raw material generating gasification obtained in raw material preparation process by hot plasma, and makes the nickel steam of generation condensation occur and reach micronized operation.

For the hot plasma of high-frequency plasma, arc-plasma and so on, because heating region has the temperature of more than 10000 DEG C, therefore, import nickel raw material moment generating gasification wherein and become nickel steam.Such as, when using nickel oxide as nickel raw material, nickel oxide is decomposed into nickel and oxygen in hot plasma, is formed as nickel steam.

Based on the nickel steam that hot plasma produces, reach micronizing by cooling condensation fast.Compared with external heat mode etc., the high-temperature area of hot plasma is narrow and small, and therefore, the nickel steam of gasification condenses in the movement to plasma tail flame portion, out namely condensation is cooled rapidly afterwards, even if do not carry out pressure cooling also reach micronizing from heating region.Because nickel solidifies from the state of complete droplet treatment, therefore, it is possible to formed substantially reach spheroidizing and size of microcrystal relative to specific area particle diameter be more than 60%, micro mist that crystallinity is very high.

In addition, the oxygen containing 0.1 ~ 2.0 quality % in preferred nickel raw material.If oxygen content is lower than 0.1 quality %, then steam produces less and stabilisation is insufficient sometimes.In addition, if oxygen content is more than 2.0 quality %, then suppress oxygen insufficient with the effect be combined again of nickel by the hydrogen in plasma, the excess oxygen content of final obtained nickel micro mist sometimes.

The oxygen of nickel powder usually containing trace, even if also contain aerobic without nickel oxide in nickel raw material.Owing to employing non-active gas-hydrogen plasma in this method for making, therefore, it is possible to suppress combining again of oxygen contained in raw material and nickel.In addition, the hydrogen of oxygen in plasma is combined and produces steam, thus makes the water adsorption of trace in the surface of formed clad.Thus, micronized nickel surface reaches stabilisation, can obtain the micro mist that aggegation is few, dispersiveness is improved.

In micronizing operation, adopt the method for micronization undertaken by hot plasma.As hot plasma, any one in direct-current plasma, high-frequency plasma can be used, but preferably use high-frequency plasma.Such as, as in the arc plasma process of direct-current plasma, there is electrode material (usually using tungsten-thorium) and occur consume and be mixed into the problem in nickel micro mist as impurity.By the measure of the protective gas such as flowing non-active gas etc., also can prevent being mixed into of impurity, but be unsuitable for continuous batch production.On the other hand, because high-frequency plasma method is electrodeless, so there is not the problem that the impurity from electrode material is mixed into, highly purified nickel micro mist can be produced by continuous batch.

Non-active gas is not particularly limited, but preferably use does not generate the argon of compound with nickel.

For the supply method of nickel raw material, as long as aequum can be supplied in plasma with fixing speed.Such as, when adopting nickel powder as raw material, by transporting gas, nickel powder is supplied in plasma.

< 2-3. recovery process >

Recovery process is the operation carrying out after being cooled by the micronizing nickel generated in micronizing operation reclaiming.Because the high-temperature area of the hot plasma used in this method for making is narrow, so once out be cooled condensation fast immediately from heating region, nickel is made to be able to micronizing.Now, because nickel is micro mist, even if at the temperature therefore below the freezing point of nickel, just easily sinter once the contact of micronizing nickel.Thus, in the recovery process after micronizing operation, to be necessary during micronizing nickel is scattered in gas, namely adopt retracting device reclaim before cool fully.

Chilling temperature is preferably less than 120 DEG C, is more preferably less than 50 DEG C.In addition, for cooling, preferably reach micronized nickel to cooling condensation fast in the overseas process of plasma slab and give reducing gas environment or spray non-active gas to carry out.Especially, when considering from cost angle, preferably use with for the gas of the same race in the gaseous environment of plasma so that recyclable recycling.In addition, in order to prevent the generation invading heating region again, prevent oversize grain, while preferably making cooling gas form rotating flow to carry out around heating region and cool, retracting device is transported to.

<2-4. eremacausis operation >

Eremacausis operation is held in oxygen containing weak oxide non-reactive gas ambient by reclaimed micronizing nickel, makes micronizing nickel surface oxidation slowly occur to obtain nickel micro mist.

For nickel micro mist isoreactivity micro mist, likely there is vigorous oxidation in an atmosphere and cause abnormal heating.Therefore, the eremacausis process of implementing the micronizing nickel reclaimed by recovery process to be kept stipulated time oxidize micro-powder nickel surface in oxygen containing non-reactive gas ambient is necessary.By eremacausis process, form oxygen containing clad on the surface of nickel micro mist.In addition, if contact with atmospheric environment, then likely cause the abnormal heating of micronizing nickel, therefore, preferably under air-tight state, be transferred to eremacausis operation by recovery process.

Through eremacausis operation, form the clad containing nickel sulfide and nickel oxide on surface.The reason that clad is formed, is speculated as follows.First, in 2-2. micronizing operation, micronizing nickel surface forms the clad containing nickel sulfide.The formation of nickel sulfide and nickel, by the domination of the standard free energy in each self-forming.First, nickel raw material evaporates in the plasma, is first nickel generation droplet treatment in cooling procedure.The sulphur being in vaporized state through cooling after this, according to the standard free energy of formation (Ni of sulfide ₃s ₂< H ₂s < S), form Ni on nickel drop surface ₃s ₂.Then, Ni > Ni time owing to comparing fusing point ₃s ₂, therefore, when nickel drop solidifies, be in aqueous Ni ₃s ₂directly carry out concentrated at micronizing nickel surface and form uniform clad on surface.

Then, the hydrogen in the plasma of micronizing operation is attached to superficial layer with the steam carrying out being combined into from the oxygen of feed material degradation, therefore, thinks the mixture that can form nickel sulfide, nickelous sulfate, nickel oxide, nickel hydroxide near most surface.

Further, although do not know the detailed reason that nickel oxide increases, infer it is by eremacausis operation surface, oxidation occur and make it increase.Because eremacausis operation implements under oxygen containing weak oxide gaseous environment, therefore, oxygen slowly carries out the oxidation of nickel to inner face side diffusion.Thus, there is not sulphur in the micronizing nickel surface of below being positioned at the layer containing nickel sulfide, formed not containing the layer of nickel sulfide.Or, think that nickel diffuses to the surface from inside and carries out combining with outmost oxygen and form oxide.

As oxygen containing non-reactive gas ambient, preferably containing the oxygen of 1 ~ 5 capacity % and the gas of argon, more preferably containing the oxygen of 1 ~ 3 capacity % and the gas of argon.If oxygen is lower than 1 capacity %, then the formation of surface coating layer is insufficient, the nickel micro mist obtained likely abrupt oxidization and cause abnormal heating in an atmosphere.In addition, if oxygen is more than 5 capacity %, then heating sometimes or oxidation proceed to inside, cause the thickness of clad more than 15nm.

Implement the temperature of eremacausis process, be preferably less than 120 DEG C, be more preferably less than 50 DEG C.In addition, eremacausis process can not be carried out in the gaseous environment of mandatory cooling, can in common room temperature range, such as can fully implement at 0 ~ 40 DEG C.By carrying out eremacausis process below 100 DEG C, the nickel micro mist with clad can be obtained.On the other hand, if the temperature be held in more than 100 DEG C and in oxygen containing non-reactive gas ambient, not only can advance oxidation tempestuously and be oxidized and proceed to inside and cause the thickness of clad more than 15nm, and, be present in outmost nickel oxide to increase considerably, sometimes can not get the effect postponing sintering.

For the time of eremacausis process, as long as the time of clad fully can be formed under gaseous environment and temperature, but be preferably set to 2 ~ 24 hours.If lower than 2 hours, then sometimes fully can not form clad.In addition, even if the processing time was more than 24 hours, also only can increases cost and there is no effect.

And, eremacausis process can be carried out by washing also drying.When washing, in order to prevent being mixed into impurity, employing pure water etc. are also washed with usual way, then make it dry, but in order to prevent over oxidation, preferably below 120 DEG C, carry out drying in a vacuum.

By this eremacausis process, can obtain and be formed containing oxygen and the nickel micro mist of the clad of specific thickness on surface.Because the surface of this nickel micro mist is in stable state, so do not worry problem on fire, be very easy on operation uses.

Based on above-mentioned method for making, under the state that the sulphur being in vaporized state exists, nickel steam condenses, micronizing, therefore, easily can obtain that purity is high and the nickel micro mist that crystallinity is high, surface is formed with clad, and can obtain as the multilayer ceramic capacitor electrode material of future generation nickel micro mist of less than 0.2 μm used.And the nickel micro mist adopting this method for making to obtain, owing to being formed with clad on surface, therefore, can improve the heat shrinkability characteristic of sintered body.Further, the surface of this nickel micro mist is not by the covering such as organic matter, dispersant, so the preparation of slurry etc. easily and also can shrink equably when sintering, also can prevent the generation of crackle etc.

< 3. embodiment >

Below, according to embodiment, further describe the nickel micro mist in an embodiment of the present invention and manufacture method thereof.But the present invention is not limited to these embodiments.

Embodiment

In the present embodiment, have employed the high-frequency plasma micro mist manufacturing installation (high-frequency plasma vibrating machine: TP-12020, Jeol Ltd. manufactures) that maximal input is 200kW.In addition, the various mensuration in the present embodiment and comparative example are carried out by the following method.

(1) transmission electron microscope (under be designated as " TEM ") is observed: adopt TEM(HF-2200, and Hitachi Ltd. (Hitachi High-Technologies Corporation) manufactures) observe.Further, electron ray diffraction analysis (under be designated as " EDX ") (VANTAGE, NORAN manufacture) has also been implemented.

(2) specific area particle diameter (under be designated as in " BET footpath "): adopt many sample B ET specific area measuring device (manufacture of Multisorb-16, Yuasa Ionics Co., Ltd.) measurement the specific area, and be converted into BET footpath.

(3) crystal size: adopt X-ray diffraction device (under be designated as " XRD ") (X ' PertPRO, PANalytical manufacture) to measure.

(4) mensuration of sulphur: adopt ICP emission spectrographic analysis device (SPS3000, Seiko electronics nanosecond science and technology Co., Ltd. (SII NanoTechnology Inc.) manufactures) to measure.

(5) mensuration of oxygen: adopt oxygen nitrogen and argon analytical equipment (manufacture of TC-336, LECO society) to measure.

(6) Surface layer analysis: adopt argon ion etching method, is manufactured by FE-AES(Model 680, ULVAC-PHI Co., Ltd.) carry out the analysis in case depth direction.To thinking that nickel, sulphur, oxygen, the carbon being present in surface is analyzed.Further, XPS(ESCALAB220i-XL, VG Scientific is adopted to manufacture) analyze and be considered to the nickel, sulphur, the oxygen that are present near surface.

(7) evaluation of the catalytic activity of nickel micro mist: adopt TG determinator (TG-DTA2000SR, Brooker AXS Co., Ltd. (Bruker AXS K.K.) manufactures), in nitrogen, with the programming rate of 5 DEG C/min, be mixed with the nickel micro mist of 5 % by weight resin binders and ethyl cellulose (EC) and independent nickel micro mist to relative to nickel micro mist physics respectively, gravimetry changes.Then, from be mixed with EC nickel micro mist weight change deduct the weight change of independent nickel micro mist, obtain the weight change of the EC in nickel micro mist.Further, as the evaluation of the catalytic activity of nickel micro mist, once differentiation is carried out to obtain the decomposition rate of EC to the weight change of EC, and using the decomposition temperature of the peak of decomposition rate as EC.

(8) evaluation of heat shrinkability characteristic: use about 0.15g sample, be shaped to particle (pellet) shape (φ 5mm × t is about 1.5mm), while applying 10g load, in the reducibility gas environment that the mist (200mL/ minute) be made up of the nitrogen of 98 capacity % and the hydrogen of 2 capacity % is formed, thermo-mechanical analysis device (under be designated as " TMA ") (manufacture of TMA4000SA, Brooker AXS Co., Ltd.) is adopted to measure heat shrinkability characteristic.Temperature range is room temperature to 1300 DEG C, and programming rate is set to 5 DEG C/min.Temperature during contraction 0.5% is evaluated as contraction initial temperature.Further, the maximum of contraction is evaluated as shrinkage factor.

[embodiment 1]

With plasma input power for about 60kW igniting high-frequency plasma, the total amount of adjustment argon is 209L/ minute, hydrogen is 45L/ minute, pressure of ambient gas is 60kPa, obtains stable plasma flame.By transporting gas (argon 10 liters/min), nickel raw material is supplied to plasma flame with 1kg/hr inner to prepare micro mist.

In addition, as nickel raw material, employ nickel by powder (nickel, the Type255 at 90 quality %, average grain diameter is 2.2 ~ 2.8 μm, and Inco Special Products and Inco Limited manufactures) in the nickel raw material of the nickel oxide sulphur of 2 quality % (interpolation have an appointment) of mixing 10 quality %.Sulfur content in nickel raw material is 0.2 quality %, and oxygen content is 2 quality %.

This plasma is more than 10000 DEG C, and therefore, nickel material powder gasifies there is evaporation instantaneously, and condenses in the plasma tail flame portion that temperature is low, is able to micronizing.By obtained micronizing nickel, be transported to retracting device in the mode be not exposed in atmospheric environment, in retracting device, be held in the environmental gas of argon-10 capacity % air (oxygen is about 2 capacity %) about 10 hours, to carry out eremacausis process, then reclaim from device.

The BET footpath of the nickel micro mist obtained is 159nm.By this nickel micro mist of XRD analysis, the size of microcrystal calculated by employing Scherrer method is crystallite dimension is 63% of BET footpath, knownly defines the nickel micro mist of crystallinity close to monocrystalline.Sulphur and oxygen content, be respectively 0.17 quality %, 0.68 quality %.Based on the result that TMA measures, contraction initial temperature is about 320 DEG C, shrinkage factor is 11.0%.In addition, according to the analysis result of EDS, confirm only have sulphur and oxygen in surface distributed.Each evaluation result and other example are shown in Table 1 in the lump.

Fig. 1 is the curve map of the analysis result representing FE-AES.Sulphur and oxygen are considered to form respectively nickel sulfide and nickel oxide.The thickness of oxygen containing clad is as thin as 10nm.In addition, the thickness of the layer of sulfur-bearing is as thin as 6nm.In addition, as nickel sulfide, containing the nickel sulfide of 100%.Further, in the CONCENTRATION DISTRIBUTION of nickel sulfide, in the scope of distance surface 2 ~ 3nm, there is concentration peak.By the thickness of each layer and other example shown in Figure 4 in the lump.

[embodiment 2]

Except the hydrogen of supply plasma was set to except 9L/ minute, operates similarly to Example 1, obtain nickel micro mist, and evaluate.The BET footpath of nickel micro mist is 152nm.By this nickel micro mist of XRD analysis, the size of microcrystal calculated by employing Scherrer method is crystallite dimension is 85% of BET footpath, knownly defines the nickel micro mist of crystallinity close to monocrystalline.Sulphur and oxygen content, be respectively 0.24 quality %, 1.0 quality %.Based on the measurement result of TMA, contraction initial temperature is about 360 DEG C, shrinkage factor is 7.9%.Each evaluation result and other example are shown in Table 1 in the lump.

Further, the analysis result of FE-AES, the thickness of oxygen containing clad is as thin as 14nm.Further, the thickness of the layer of sulfur-bearing is 8nm.By each layer thickness and other example shown in Figure 4 in the lump.

[embodiment 3]

Except employing except following nickel by powder as nickel powder, operating similarly to Example 1, obtaining nickel micro mist, and evaluating.By 4kg nickel by powder (nickel, Type255, average grain diameter is 2.2 ~ 2.8 μm, Inco Special Products and Inco Limited manufactures) join and be adjusted in the 16L pure water of 50 DEG C, add 18g NaHS hydrate (Sodium hydrosulfide n-hydrate), stir 30 minutes.Then carry out 1 time repulped (Re Pulp), carry out filtering, after vacuum drying (36 hours), carry out fragmentation and as nickel raw material.Sulfur content in nickel raw material is 0.2 quality %, and oxygen content is 0.4 quality %.

The BET footpath of nickel micro mist is 125nm.By this nickel micro mist of XRD analysis, the size of microcrystal calculated by employing Scherrer method is crystallite dimension is 75% of BET footpath, knownly defines the nickel micro mist of crystallinity close to monocrystalline.Sulphur and oxygen content, be respectively 0.26 quality %, 0.99 quality %.Based on the result that TMA measures, contraction initial temperature is 330 DEG C, shrinkage factor is 12.6%.Each evaluation result is shown in Table 1 in the lump.

Fig. 2 is the curve map of the analysis result representing FE-AES.The thickness of oxygen containing clad is as thin as 10nm.In addition, the thickness of the layer of sulfur-bearing is 6nm.In addition, as nickel sulfide, containing the nickel sulfide of 73%, the nickelous sulfate of 27%.Further, in the CONCENTRATION DISTRIBUTION of nickel sulfide, in the scope of distance surface 2 ~ 3nm, there is concentration peak.By the thickness of each layer and other example shown in Figure 4 in the lump.

[embodiment 4]

Except the addition of NaHS hydrate is adjusted to except 36g, operate similarly to Example 3, obtain nickel by powder.The sulfur content of the nickel by powder obtained is 0.37 quality %, oxygen content is 0.4 quality %.Except using this nickel by powder except nickel raw material uses, operate similarly to Example 1, obtain nickel micro mist, and evaluate.

The BET footpath of nickel micro mist is 117nm.Crystallite dimension is size of microcrystal is 70% of BET footpath, knownly defines the nickel micro mist of crystallinity close to monocrystalline.Sulphur and oxygen content, be respectively 0.39 quality %, 0.82 quality %.Based on the result that TMA measures, contraction initial temperature is 310 DEG C, shrinkage factor is 12.8%.Each evaluation result is shown in Table 1 in the lump.

In addition, known by the analysis of FE-AES, the thickness of oxygen containing clad is as thin as 12nm.In addition, the thickness of the layer of sulfur-bearing is 10nm.By the thickness of each layer and other example shown in Figure 4 in the lump.

[comparative example 1]

Except the gas being supplied to plasma being adjusted to argon total amount 180L/ minute, hydrogen 6L/ divides, and only use nickel by powder (nickel as nickel raw material, Type255, average grain diameter is 2.2 ~ 2.8 μm, Inco SpecialProducts and Inco Limited manufactures) beyond, operate similarly to Example 1, obtain nickel micro mist, and evaluate.In addition, the sulfur content in nickel raw material is 0 quality %, and oxygen content is 0.05 quality %.

The BET footpath of nickel micro mist is 169nm, and crystallite dimension is size of microcrystal is 49% of BET footpath, and known is the nickel micro mist of crystallinity difference.Not containing sulphur, oxygen content is 0.63 quality %.Based on the result that TMA measures, shrinkage factor is 14.0%, and shrinking initial temperature is about 190 DEG C.Each evaluation result is shown in Table 1 in the lump.

[comparative example 2]

By adopt one of prior art by hydrogen reduce nickel chloride steam chemical gas-phase reaction method manufactured by nickel micro mist, use as comparative example.The BET footpath of this micro mist is 130nm, and crystallite dimension is crystallite dimension is 69% of BET footpath.The content of sulphur and oxygen, is respectively 0.18 quality %, 1.6 quality %.Based on the result that TMA measures, contraction initial temperature is 320 DEG C, shrinkage factor is 15.5%.

Fig. 3 is the curve map of the analysis result representing FE-AES.The thickness of oxygen containing clad is thick reaches 16nm.In addition, the thickness of the layer of sulfur-bearing is 8nm.In addition, as nickel sulfide, containing the nickel sulfide of 100%.Further, in the CONCENTRATION DISTRIBUTION of nickel sulfide, in the scope of distance surface 2 ~ 3nm, there is concentration peak.The thickness of each layer is shown in Figure 4 together with other example.

Table 1

The embodiment 1 ~ 4 adopting this method for making to obtain is size of microcrystal/specific area particle diameters be more than 60% the extraordinary nickel micro mist of crystallinity.Further, define the mixture containing nickel sulfide and nickel oxide on surface, oxygen containing coating thickness is below 15nm, and therefore, contraction initial temperature is high, and shrinkage factor is also little, has good heat shrinkability characteristic.

On the other hand, for the comparative example 1 of not sulfur-bearing, shrink that initial temperature is low, shrinkage factor is large, heat shrinkability characteristic is poor.In addition, adopt by hydrogen reduce nickel chloride steam chemical gas phase reaction method manufactured by comparative example 2, it becomes, and crystallinity is good, to shrink initial temperature high, but shrinkage factor is large.Thinking that its reason is, owing to have employed chemical gas phase reaction method, needing to clean to remove chlorine, and excessive cleaning can cause the oxidation on surface, thus make oxygen containing clad thickening.

Then, have rated the catalytic activity of nickel micro mist.Evaluation method " evaluation of the catalytic activity of nickel micro mist " according to above-mentioned (7) is implemented.

[embodiment 5]

With plasma input power for about 60kW igniting high-frequency plasma, adjustment argon total amount is 209L/ minute, hydrogen is 45L/ minute, pressure of ambient gas is 60kPa, obtains stable plasma flame.By transporting gas (argon 24 liters/min), the nickel raw material identical with embodiment 3 is supplied to plasma flame inside with 1kg/hr, to prepare micro mist.

By obtained micronizing nickel, be transported to retracting device in the mode be not exposed in atmospheric environment, in retracting device, be held in the environmental gas of argon-10 capacity % air (oxygen is about 2 capacity %) about 10 hours, to carry out eremacausis process, then reclaim from device.

The BET footpath of the nickel micro mist obtained is 130nm.The content of sulphur and oxygen, is respectively 0.12 quality %, 0.90 quality %.

Further, " evaluation of the catalytic activity of nickel micro mist " according to above-mentioned (7), uses ethyl cellulose (EC) to make electrocondution slurry.Adopt TG determinator to measure the result of this electrocondution slurry, the heat decomposition temperature of EC is 339 DEG C, the heat decomposition temperature equal extent original with EC.Each evaluation result and other example are shown in Table 2 in the lump.In addition, by shown in Figure 5 for the curve map of the EC thermal decomposition characteristic result representing nickel micro mist.

[embodiment 6]

Except the hydrogen of supply plasma was adjusted to except 9L/ minute, operates similarly to Example 5, obtain nickel micro mist, and evaluate.The BET footpath of nickel micro mist is 123nm.The content of sulphur and oxygen, is respectively 0.16 quality %, 1.0 quality %.

Further, " evaluation of the catalytic activity of nickel micro mist " as shown in above-mentioned (7), uses ethyl cellulose (EC) to make electrocondution slurry.Adopt TG determinator to measure the result of this electrocondution slurry, the heat decomposition temperature of EC is 336 DEG C, the heat decomposition temperature equal extent original with EC.Each evaluation result and other example are shown in Table 2 in the lump.In addition, by shown in Figure 5 for the curve map of the EC thermal decomposition characteristic result representing nickel micro mist.

[embodiment 7]

Be 0.15 quality % as the sulfur content of nickel powder in nickel raw material, and with plasma input power for about 105kW igniting high-frequency plasma, adjustment argon total amount is 209L/ minute, hydrogen is 18L/ minute, pressure of ambient gas is 50kPa, obtains stable plasma flame.By transporting gas (argon 24 liters/min), nickel raw material is supplied to plasma flame inside with 2.2kg/hr, to prepare micro mist.The BET footpath of nickel micro mist is 130nm.The content of sulphur and oxygen, is respectively 0.2 quality %, 0.85 quality %.

In addition, " evaluation of the catalytic activity of nickel micro mist " as shown in above-mentioned (7), uses ethyl cellulose (EC) to make electrocondution slurry.Adopt TG determinator to measure the result of this electrocondution slurry, the heat decomposition temperature of EC is 336 DEG C, and the heat decomposition temperature original with EC is equal.Each evaluation result and other example are shown in Table 2 in the lump.Further, by shown in Figure 5 for the curve map of the EC thermal decomposition characteristic result representing nickel micro mist.

[embodiment 8]

Be 0.18 quality % as the sulfur content of nickel powder in nickel raw material, with plasma input power for about 60kW igniting high-frequency plasma, adjustment argon total amount is 175L/ minute, hydrogen is 6.4L/ minute, pressure of ambient gas is 60kPa, obtains stable plasma flame.By transporting gas (argon 15 liters/min), nickel raw material is supplied to plasma flame inside with 1.6kg/hr, to prepare micro mist.The BET footpath of nickel micro mist is 86nm.The content of sulphur and oxygen, is respectively 0.27 quality %, 1.30 quality %.

In addition, " evaluation of the catalytic activity of nickel micro mist " as shown in above-mentioned (7), uses ethyl cellulose (EC) to make electrocondution slurry.Adopt TG determinator to measure the result of this electrocondution slurry, the heat decomposition temperature of EC is 337 DEG C, the heat decomposition temperature equal extent original with EC.Each evaluation result and other example are shown in Table 2 in the lump.The thickness of oxygen containing clad is as thin as below 10nm.Further, as nickel sulfide, in mottled under electron ray diffraction, therefore, its crystallinity is very good.According to XPS, calculate with content ratio, contain the nickel sulfide of 65%, the nickelous sulfate of 35% at superficial layer.

[comparative example 3]

Except being except 0 quality % as the sulfur content in nickel powder setting nickel raw material, other operates with the condition identical with embodiment 8.The BET footpath of nickel micro mist is 147nm.Oxygen content is 0.79 quality %.

In addition, " evaluation of the catalytic activity of nickel micro mist " as shown in above-mentioned (7), uses ethyl cellulose (EC) to make electrocondution slurry.Adopt TG determinator to measure the result of this electrocondution slurry, the heat decomposition temperature of EC is 280 DEG C and 339 DEG C.Due to the catalytic action of nickel, give birth to decomposition in the occurs at low temperatures of the heat decomposition temperature more than 60 DEG C original lower than EC.Each evaluation result and other example are shown in Table 2 in the lump.

The oxygen containing clad of the nickel powder of comparative example 3, its thickness is as thin as below 10nm.In addition, as nickel oxide, in mottled under electron ray diffraction, therefore, its crystallinity is very good.But, because the decomposition temperature of EC is by low temperature, therefore think that there is nickel sulfide suppresses the effect of catalytic activity.

Table 2

The embodiment 5 ~ 8 adopting this method for making to obtain, the mixture containing nickel sulfide and nickel oxide is formed on its surface, particularly nickelous sulfate and the content of nickel sulfide are than high, define the high nickel sulfide of crystallinity and nickelous sulfate, therefore, the heat decomposition temperature of EC is 337 DEG C, the heat decomposition temperature equal extent original with EC.

On the other hand, for the decomposition temperature of the not comparative example 3, EC of sulfur-bearing by low temperature, undesirable.

Industrial applicibility

Nickel micro mist in one embodiment of the present invention, its heat decomposition temperature and the original heat decomposition temperature equal extent of EC, be suitable for the nickel micro mist formed as the internal electrode of MLCC.Further, because purity is high, the wiring formation material be also suitable for as electronic instrument, electronic unit uses.

Claims

1. a nickel micro mist, is characterized in that, the average grain diameter of described nickel micro mist is 0.05 ~ 0.3 μm, size of microcrystal is specific area particle diameter 60 ~ 90%, sulfur content be 0.1 ~ 0.5 quality % and oxygen content is 0.4 ~ 1.5 quality %, and

There is on surface the oxygen containing clad of thickness 2 ~ 15nm, and at least the outermost of this clad is made up of the mixture containing nickel sulfide and nickel oxide,

In x-ray photoelectron spectroscopy and XPS analysis, the content of the nickel sulfide in the sulfide contained by outermost than be 50% ~ 100%, the content ratio of nickel hydroxide in nickel oxide is 0 ~ 50%.

2. nickel micro mist as claimed in claim 1, it is characterized in that, described clad contains nickel oxide, and is made up of two-layer as follows, namely by being present in the layer containing nickel sulfide of most surface side and being present in not forming containing the layer of nickel sulfide of inner face side.

3. nickel micro mist as claimed in claim 1, it is characterized in that, the content ratio of the nickelous sulfate in described outmost nickel sulfide is less than 40%.

4. the nickel micro mist according to any one of claims 1 to 3, it is characterized in that, the layer containing nickel sulfide in described clad, is also made up of two-layer as follows, namely by being present in the layer containing nickelous sulfate of most surface side and being present in the layer mainly containing nickel sulfide as nickel sulfide of inner face side.

5. nickel micro mist as claimed in claim 1, it is characterized in that, described clad has the concentration gradient of the inclination of sulphur in the scope apart from surperficial below 10nm.

6. nickel micro mist as claimed in claim 5, it is characterized in that, the CONCENTRATION DISTRIBUTION of the nickel sulfide in described clad reaches maximum at described outermost.

7. nickel micro mist as claimed in claim 1, is characterized in that, when adopting thermo-mechanical analysis device to measure, shrinkage factor when being heated to 1300 DEG C in reducibility gas environment is less than 15%.

8. nickel micro mist as claimed in claim 1, it is characterized in that, in reducibility gas environment, carry out gasifying based on hot plasma and make the devaporation of generation and obtain the nickel micro mist of sulfur-bearing, the nickel micro mist of this sulfur-bearing being held in weak oxide gaseous environment and obtaining described nickel micro mist.

9. a manufacture method for nickel micro mist, comprising:

Raw material preparation process, preparation sulfur content is the nickel raw material of 0.1 ~ 0.5 quality %;

Micronizing operation, in the reducing gas environment containing non-active gas and hydrogen, by the nickel material gasification of hot plasma by described preparation, makes the produced nickel devaporation containing sulphur and oxygen and carries out micronizing;

Recovery process, is cooled the micronizing nickel after described micronizing and is reclaimed; And

Eremacausis operation, is held in the micronizing nickel of described recovery in the weak oxide non-reactive gas ambient containing 1 ~ 5 capacity % oxygen, makes micronizing nickel surface slowly carry out being oxidized and obtaining nickel micro mist.

10. the manufacture method of nickel micro mist as claimed in claim 9, it is characterized in that, the maintenance temperature in described eremacausis operation is less than 100 DEG C.

The manufacture method of 11. nickel micro mists as described in claim 9 or 10, it is characterized in that, in described raw material preparation process, the nickel that sulfur content is 0.1 ~ 0.5 quality % is prepared in advance as described nickel raw material, or, the nickel oxide of sulfur-bearing is coordinated with nickel and is prepared the nickel raw material that sulfur content is 0.1 ~ 0.5 quality %.

The manufacture method of 12. nickel micro mists as claimed in claim 9, is characterized in that, uses catalytic behavior of materials as described hot plasma.