CN102665969A - Nickel powder and production method thereof - Google Patents

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 manufacturing approach thereof

Technical field

The present invention relates to a kind of nickel micro mist and manufacturing approach thereof.More detailed, relate to the employed nickel micro mist of electronic component-use electrode material and the manufacturing approach thereof of a kind of internal electrode as multilayer ceramic capacitor etc.

The japanese application number that the application is based on Japan's proposition on September 24th, 2009 is that the application of " the special 2009-219286 of hope " requires priority, and in this application above-mentioned application has been carried out quoting for your guidance.

Background technology

There is the requirement of miniaturization in electronic instrument in recent years, in order to tackle this requirement, also there is more micronized requirement in the parts as electronic instrument with the employed nickel micro mist of material.For example, in multilayer ceramic capacitor (MLCC:Multilayer Ceramic Capacitor), require the small particle diameterization of nickel micro mist, with the filmization of reply MLCC with the internal electrode material.And, MLCC of future generation is used the nickel micro mist, not only require its particle diameter to reach the small particle diameterization below the 0.2 μ m, and on other characteristic, also require to have good high-quality.

For the manufacturing of MLCC, for example, adopt following method to implement.

At first; On the ceramic dielectric raw cook; Electrocondution slurry is carried out serigraphy; Thereby the making internal electrode, wherein, said electrocondution slurry is to carrying out mixing resultant with metal fine powder and ethyl cellulose resins such as (following abbreviate as sometimes " EC ") as organic solvents such as the resin binder of main component and terpineol etc.Then, so that printed internal electrode replaces overlapping mode stacked dielectric raw cook, and carry out pressing and form duplexer.Then, duplexer is cut into the size of regulation, implement the unsticking mixture handle remove the resins such as EC that use as resin binder with burning after, burn till to 1300 ℃ through high temperature and to obtain ceramic body.Then, on this ceramic body, outer electrode is installed, is formed multilayer ceramic capacitor.

At this, as far as the metal fine powder in the electrocondution slurry that becomes internal electrode, the nickel micro mist becomes main flow, therefore, in the unsticking mixture of duplexer is handled, in order to prevent the oxidation of nickel micro mist, under the environment of the oxygen that contains denier, implements.

In the past, in this unsticking mixture operation, the thermal decomposition of adhesive obtained low temperatureization through the catalytic activity on nickel particles surface, for example, when adhesive is EC etc., has distinguished near 260 ℃ thermal decomposition takes place.At this moment, the thermal decomposition of adhesive is only limited to the near surface of nickel particles, does not decompose other adhesive.Therefore; The gas that exploded produced by adhesive can carry out residual with the state that is closed in its position, place; And this gas causes opening between nickel internal electrode layer and the ceramic dielectric layer, the problem that has the internal electrode discontinuity thus or peel off.

On the other hand, in above-mentioned firing process, compare with the ceramic dielectrics such as barium titanate in being usually used in MLCC, the contraction initial temperature of internal electrode materials such as nickel powder is lower and percent thermal shrinkage is big.Thereby, when burning till,, there is the problem that is easy to faults of construction such as causing crackle or peel off by the aggravation that do not match of the caused shrinkage degree of sintering characteristic difference between ceramic dielectric and the internal electrode material.

In recent years, along with the thin layerization of electrode, nickel powder is miniaturization more and more, and nickel powder is fine more, and the catalytic activity on nickel powder surface is just bigger and the contraction initial temperature is just low more, and therefore, above-mentioned internal electrode discontinuity or crackle or the problem of peeling off can become remarkable.When the discontinuity or the crackle of a large amount of generation internal electrodes or when peeling off, then can't play the function of capacitor.

Therefore, the someone has proposed to improve above-mentioned MLCC internal electrode and has formed the method with the problem that exists in the nickel powder.

As above-mentioned proposal, for example, can enumerate following patent documentation 1～4.

< patent documentation 1 >

In patent documentation 1, a kind of nickel ultra micro powder has been proposed, its average grain diameter 0.1～1.0 μ m, and sulfur content is 0.02～1.0%.In this is proposed, as the manufacturing approach of nickel ultra micro powder, disclose a kind of gas phase reduction process, and pointed out through containing sulphur through one in sulphur and sulfide or the nickel chloride steam that both carry out, can obtain good spherical nickel ultra micro powder.And, under situation, can in the manufacturing process of multilayer ceramic capacitor, form the high coating interior electrode of packed density, and bring into play the characteristic that does not crack or peel off as spherical particle.

But, in patent documentation 1,, do not mention the shrinkage character when burning till though put down in writing the effect that crackle or delamination when suppressing to make MLCC take place.Therefore, the contraction when suppressing sintering among the MLCC that obtains thin layerization and miniaturization at electrode is unclear.And, adopting gas phase reduction process from the nickel ultra micro powder that the nickel chloride steam is obtained, to contain chlorine, thereby be necessary to wash to remove chlorine.Therefore, cause forming thick oxide layer, and contained oxygen increases considerably in final resulting nickel ultra micro powder, thus sintering behavior is caused harmful effect on nickel ultra micro powder surface.And, when after washing, carrying out drying, might cause aggegation, even append subsequent handling such as pulverizing, also owing to being that the ultra micro powder causes aggegation serious, the shrinkage factor when burning till in actual use increases.And, the decomposition behavior of adhesive when at all not mentioning about the unsticking mixture.

< patent documentation 2 >

In patent documentation 2, propose a kind of electrocondution slurry and used nickel by powder, its shape of particle is that spherical, particle diameter is 0.1～1.0 μ m, and contains 0.05～0.2% sulphur.In this proposal, point out: sulphur mainly is present in surface portion, and under the effect of this sulphur, promotes spheroidizing, and can obtain shape of particle is nickel by powder spherical and that monodispersity is good.And,, disclose and in the steam of nickel chloride, implemented the vapour phase reduction reaction under the environment of sulfur-bearing as its manufacturing approach.

But, in the proposal that this patent documentation 2 is put down in writing, do not mention the shrinkage character when burning till, to the shrinkage character of the nickel by powder that obtained and unclear,, cause being formed with thick oxide layer on nickel ultra micro powder surface owing in gas phase reduction process, remove the cause of chlorine.And, the decomposition behavior when not mentioning in this proposal about above-mentioned unsticking mixture.

< patent documentation 3 >

In patent documentation 3, a kind of nickel by powder has been proposed, it is to form through sulphur that is scaled 0.02～0.20 quality % with sulphur or sulfate clad surface.In this proposal, point out,, form the overlay film layer that concentrates and form through nickel sulfide or nickelous sulfate, suppress the contraction under the high temperature, obtain the good nickel by powder of sintering characteristic on the nickel by powder surface through coating nickel by powder with sulphur or sulfate.And, as its manufacturing approach, the method that the gas of sulfur-bearing is contacted processing with nickel by powder is disclosed.

But, about the nickel by powder that is obtained, only put down in writing the high temperature effect of shrinking initial temperature, do not mention the decomposition behavior of above-mentioned unsticking mixture.And the shrinkage character when burning till is not paid attention to, owing to be not formed with the oxide-film of suitable thickness, infers that the shrinkage character when burning till is poor.

< patent documentation 4 >

In patent documentation 4, a kind of nickel by powder is disclosed, its average grain diameter is 0.05～1.0 μ m and sulphur with respect to the content of gross weight is 100～2000ppm.And; Disclose: in the surface analysis of adopting ESCA (Electron Spectroscopy for Chemical Analysis) that this nickel by powder is carried out; Result from the peak intensity of the sulphur atom that combines with nickle atom; Be to change to center position from particle surface, its intensity becomes maximum on the position dark above 3nm apart from particle surface, and the thick 30nm that reaches of the degree of depth of the sulfur-bearing of this nickel by powder.As its manufacturing approach, disclose: the nickel by powder of sulfur-bearing is scattered in the non-oxidizing gas environment, makes it in 300～800 ℃ of temperature ranges, contact and carry out the surface oxidation treatment of short time with oxidizing gas.In this is proposed, in the oxidizing gas environment, to carry out under the situation of unsticking mixture oxidation not taking place yet, the Volume Changes that is caused by the redox in burning till is few and do not have faults of construction such as crackle or delamination, can make good laminated electronic component.

But in this was proposed, although the oxidative resistance of the nickel by powder that obtained is estimated, the shrinkage character when burning till did not have any open.In addition, do not mention decomposition behavior about above-mentioned unsticking mixture.And, because fine nickel by powder is contacted with oxidizing gas, might be because of the phenomenon of abrupt oxidization nickel by powder generation spontaneous combustion.Therefore, the thickness thickening of oxide-film is inferred to be difficult to form suitable thickness.

The prior art document

Patent documentation

Patent documentation 1: japanese kokai publication hei 11-80817 communique

Patent documentation 2: japanese kokai publication hei 11-80816 communique

Patent documentation 3: TOHKEMY 2004-244654 communique

Patent documentation 4: TOHKEMY 2008-223068 communique

Summary of the invention

The problem that invention will solve

The present invention proposes in view of the above problems; Its purpose is; A kind of excellent in crystallinity is provided, shrinks the nickel micro mist that initial temperature is high, follow before reaching a high temperature contraction that sintering takes place to be able to suppress, a kind of decomposition temperature of improving resin binder also is provided so that it reaches the nickel micro mist with the original decomposition temperature equal extent of resin binder.

Solve the method for problem

The inventor studies intensively the nickel micro mist of the excellent in crystallinity through the hot plasma manufacturing; The result finds: the oxygen containing coating thickness through setting nickel micro mist surface is a special value; Can improve contraction initial temperature and shrinkage character when burning till; And,, can improve the decomposition temperature of resin binder so that it reaches the decomposition temperature equal extent original with resin binder through controlling the form of nickel sulfide contained in this clad.And then; Gasify and condense through hot plasma and obtain sulfur-bearing nickel micro mist; This sulfur-bearing nickel micro mist remained in make the surface that oxidation takes place in the weak oxide property gaseous environment lentamente; Obtain not only have the clad of specific thickness but also the controlled nickel micro mist of form of aforementioned nickel sulfide thus, and accomplished the present invention based on above-mentioned discovery.

Promptly; Nickel micro mist of the present invention; It is characterized in that; Average grain diameter be 0.05～0.3 μ m, size of microcrystal with respect to the specific area particle diameter be 60～90%, sulfur content is that 0.1～0.5 quality % and oxygen content are 0.4～1.5 quality %, what have thickness on the surface and be 2～15nm contains the oxygen clad, and the outermost of this clad is made up of the mixture that contains nickel sulfide and nickel oxide at least.

At this, preferred aforementioned clad contains the nickel oxygen compound and is made up of following two layers, promptly is made up of layer that contains nickel sulfide that is present in face side and the layer that does not contain nickel sulfide that is present in inner face side.

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

And then, contain the layer of nickel sulfide in the preferred aforementioned clad, further constitute by following two layers, promptly constitute by layer that contains nickelous sulfate that is present in face side and the layer that mainly contains nickel sulfide as nickel sulfide that is present in inner face side.And, having the inclination concentration gradient of sulphur in the scope of preferred clad below the most surperficial 10nm of distance, the CONCENTRATION DISTRIBUTION of the nickel sulfide in the preferred aforementioned clad becomes maximum at aforementioned outermost.

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

And; Preferred above-mentioned nickel micro mist obtains through following method: in the reducibility gas environment; Gasify and make the devaporation of generation obtain the nickel micro mist of sulfur-bearing based on hot plasma, the nickel micro mist of this sulfur-bearing is remained in the weak oxide property gaseous environment obtain.

The manufacturing approach of nickel micro mist of the present invention comprises: the preparation of raw material operation, and the preparation sulfur content is the nickel raw material of 0.1～0.5 quality %; The micronizing operation in containing the reducing gas environment of non-active gas and hydrogen, makes the nickel material gasification of being prepared through hot plasma, and makes the nickel devaporation that contains sulphur and oxygen that is produced and carry out micronizing; Recovery process cools off and reclaims the micronizing nickel after the micronizing; And the eremacausis operation remains in the micronizing nickel that is reclaimed and makes the eremacausis of micronizing nickel surface in the oxygen containing weak oxide property non-active gas environment and obtain the nickel micro mist.

At this, preferably the maintenance temperature in the eremacausis operation is below 100 ℃, and preferably the oxygen content in the non-active gas environment is 1～5 capacity % in the eremacausis operation.

And in the preparation of raw material operation, the nickel of preferably preparing sulfur content 0.1～0.5 quality % in advance is as the nickel raw material, and the nickel oxide that perhaps will contain sulphur cooperates with nickel and prepares the nickel raw material that sulfur content is 0.1～0.5 quality %.

In addition, as hot plasma, preferably use the high-frequency induction plasma.

The effect of invention

The purity height and the excellent in crystallinity of nickel micro mist of the present invention are suitable for using material as electronic instrument/parts.When the internal electrode of MLCC forms the nickel micro mist of usefulness, can improve and shrink initial temperature and can suppress the contraction of following sintering to produce, the generation of fault of construction such as therefore can prevent crackle or peel off.In addition,, can make the decomposition temperature of resin binder reach the decomposition temperature equal extent original, therefore can further prevent the discontinuity of internal electrode or the generation of peeling off with resin binder through the control surface compound layer.And the manufacturing approach of above-mentioned nickel micro mist is simple and easy and can be applicable in the production of industrially scalable, and the value in its industry is very big.

Description of drawings

Fig. 1 is that expression adopts FE-AES (an emission Auger electron spectroscopy) to analyze the result of depth direction of the nickel micro mist of embodiment 1.

Fig. 2 is that expression adopts FE-AES to analyze the result of depth direction of the nickel micro mist of embodiment 3.

Fig. 3 is that expression adopts FE-AES to analyze the result of depth direction of the nickel micro mist of comparative example 2.

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

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

The specific embodiment

Below, with reference to accompanying drawing, specify the suitable specific embodiment of the present invention by following order.

1. nickel micro mist

1-1. average grain diameter

1-2. size of microcrystal

1-3. sulfur content

1-4. oxygen content

2. the manufacturing approach of nickel micro mist

2-1. preparation of raw material operation

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 be 0.05～0.3 μ m, size of microcrystal be the specific area particle diameter 60～90%, sulfur content is that 0.1～0.5 quality % and oxygen content are 0.4～1.5 quality %; The oxygen containing clad that has thickness 2～15nm on the surface, and the outermost of this clad is made up of the mixture that contains nickel sulfide and nickel oxide at least.

The nickel micro mist has the oxygen containing clad of thickness 2～15nm on its surface, and the outermost of this clad is made up of the mixture that contains nickel sulfide and nickel oxide at least.At this; So-called outermost; Be meant and the nickel micro mist that is obtained do not carried out the related scope of analysis that adopts AES (Auger Electron Spectroscopy) to carry out under the etched state, typically refer to the scope about the 2～3nm of surface of distance through sputter etc.

The thickness of the clad that contains oxygen (atom) that the nickel micro mist is had is 2～15nm, more preferably 5～15nm.If the thickness of clad is lower than 2nm, then can not get improving contraction initial temperature and the effect of shrinkage factor when burning till.And,, also can not get improving contraction initial temperature and the effect of shrinkage factor when burning till even the thickness of clad surpasses 15nm.Its reason is, generation such as crackle is arranged, peel off on this clad when burning till the nickel that is present in inner face is showed out, thereby the effect of clad reduces.

In addition, the outermost of nickel micro mist is to be made up of the mixture that contains nickel sulfide and nickel oxide.Thus, when can make the reaching a high temperature of contraction initial temperature when burning till, suppress the contraction of following sintering to produce.Think that its reason is, nickel sulfide has hindered 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 for only exist the state of nickel oxide basically; Then when the burning till of MLCC (Monolithic Ceramic Chip Capacitors) under the used week reduction gaseous environment, can't obtain the surface and reduced and make the effect of shrinking initial temperature high temperatureization.On the other hand, because outermost exists nickel sulfide and nickel oxide, can postpone the carrying out of sintering and make the reaching a high temperature of contraction initial temperature when burning till, the contraction that inhibition simultaneously follows sintering to cause.

Aforementioned nickel sulfide (nickel sulphur compound) can be taked nickel sulfide (NiS), oxidized nickelous sulfate (NiSO ₄) form.Promptly, the nickel sulfide in the clad, be the compound that contains nickel sulfide, nickelous sulfate etc.

On the other hand, aforementioned nickel oxide (nickel oxygen compound), the nickel hydroxide (Ni (OH) that can take nickel oxide (NiO), generate through adsorbed water ₂) form.Being the nickel oxide in the clad, is the compound that contains nickel oxide, nickel hydroxide etc.

And preferred clad contains nickel oxide and two-layerly is made up of following, promptly is made up of layer that contains nickel sulfide that is present in face side and the layer that does not contain nickel sulfide that is present in inner face side.Because clad two-layerly is made up of above-mentioned, can reduce the sulfur content in the clad thus and can improve contraction initial temperature and the shrinkage factor when burning till.That is, come to replenish the contraction initial temperature and the raising of shrinkage factor that causes based on nickel sulfide, can further improve the effect of improving of contraction initial temperature and shrinkage factor through the layer that contains nickel oxide that is present in inner face side.And, the effect of the heat decomposition temperature low temperatureization of the inhibition resin binder of stating after can improving.

On the other hand, if only form the layer that one deck contains nickel sulfide and nickel oxide with desired thickness, though then can reach the improvement of above-mentioned effect, sulfur content contained in the clad on surface increases, and might when burning till, produce corrosive gas.Therefore, when using, might corrode the circuit of electronic unit or electronic equipment as the electronic component-use material.

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 the contained nickel sulfide of near surface than be 50%～100%, the content ratio of nickel hydroxide in the nickel oxide is 0～50%.

As the nickelous sulfate of near surface chemical state and the content ratio of nickel sulfide, can obtain based on the peak that XPS analysis obtained through analyzing.The content of above-mentioned nickel sulfide than be lower than 50%, be the content of nickelous sulfate than surpassing under 50% the state, the degree of oxidation on nickel micro mist surface is high, the nickel oxide or the nickel hydroxide on surface increase.In this state, might cause that contraction initial temperature and shrinkage factor when burning till increase, make agglutinating property to reduce.In order to keep agglutinating property good, the content ratio of nickelous sulfate is adjusted into below 40%.In addition, based on the related scope of the analysis of XPS, the scope of distance about the most surperficial 5nm normally, near surface is meant this scope.

On the other hand; If the content of the nickel hydroxide in the nickel oxide of near surface is than surpassing 50%, then the hydrophily of nickel micro mist increases, and from resinous principle, captures moisture thereby make the back at slurry; Slurry viscosity is increased, therefore as the slurry instability and can't use.

As the nickelous sulfate of the chemical state of near surface and the content ratio of nickel sulfide; To being used to make also exerting an influence of slurry with the heat decomposition temperature of ethyl cellulose resins such as (EC) as the resin binder of main component; But only depending on the content of nickel sulfide is not enough than height; Through being set at high nickel sulfide of crystallinity and nickelous sulfate, can suppressing the catalytic activity of nickel, thereby can suppress the low temperatureization of the heat decomposition temperature of resin binder.

The crystallinity of nickel sulfide and nickelous sulfate, for example, the analysis that can carry out through the electron ray diffraction (TEM-EDX) that adopts transmission electron microscope is confirmed.If the diffraction spot (inflection ス Port Star ト) among the TEM-EDX belongs to the degree that can be identified, we can say that crystallinity is good, can obtain to suppress the effect of the heat decomposition temperature low temperatureization of resin binder.Nickel micro mist of the present invention has been 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 that contains nickel sulfide in the preferred above-mentioned clad also has a two-layer formation, promptly is made up of layer that contains nickelous sulfate that is present in face side and the layer that mainly contains nickel sulfide as nickel sulfide that is present in inner face side.Because the nickel sulfide on micro mist surface is oxidized easily, therefore, can prevent the oxidation of nickel micro mist through contain the nickelous sulfate of already oxidised state in face side.If the aforementioned layer thickening that contains nickelous sulfate, then the content of above-mentioned nickel sulfide is than reducing, so below the most surperficial 5nm of preferred distance, more preferably 2～3nm.On the other hand, owing to there is the above-mentioned layer that mainly contains nickel sulfide, can make the content ratio of the nickel sulfide in the near surface reach enough degree.At this, the so-called layer that mainly contains nickel sulfide is meant the state that in aforementioned TEM-EDX, can confirm the diffraction spot of nickel sulfide and 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 that contains nickel sulfide and nickel oxide and inner nickel portion are clearly distinguished, but clad also can have the concentration gradient of the inclination of sulphur (atom) in apart from the scope below the most surperficial 10nm.That is the concentration that, also can form sulphur (atom) is to the slow enriched layer that reduces of internal direction.At this, the enriched layer of so-called sulphur is meant the layer that sulphur (atom) exists, and can easily adopt AES (auger electrons analysis of spectrum) to confirm.In addition, the CONCENTRATION DISTRIBUTION of sulphur can have the peak in clad, but the preferred concentration peak position is in outermost (about the most surperficial 2～3nm of distance).Wherein, on nickel micro mist surface, be attached with carbon (C) sometimes, in the analysis based on AES, the problem of the most surperficial position of nickel micro mist can't be correctly discerned in existence.In this case, for example in AES analyzes the C concentration on surface (sputter depth is the position of 0nm) surpass under the situation of 10 atom %, as long as with the interior location of the surface 1～2nm on the distance analysis surface as the nickel micro mist of reality.Through making outmost sulphur concentration become maximum, can improve agglutinating property and resin binder effect to heat decomposition temperature.

Preferably the enriched layer thickness of sulphur is 2～10nm in clad.If the enriched layer thickness of sulphur surpasses 10nm, the problem of corrosion takes place in the circuit that then might cause generation, electronic unit or the electronic equipment of corrosive gas when burning till.

In addition; Preferred above-mentioned nickel micro mist obtains through following method: in the reducibility gas environment; Gasify and make the devaporation of generation and obtain the nickel micro mist of sulfur-bearing based on hot plasma, the nickel micro mist of this sulfur-bearing is remained in the weak oxide property gaseous environment obtain.Through using hot plasma, in a single day the nickel steam that has gasified comes out just to be cooled off fast to condense from the plasma zone, and solidify from the state of complete droplet treatment, so the nickel after the micronizing not only reaches spheroidizing basically but also crystallinity is high.

As far as having the nickel micro mist of this formation, when in the reducibility gas environment, being heated to 1300 ℃, its shrinkage factor is below 15% in the mensuration that adopts the thermo-mechanical analysis device to carry out.Shrinkage factor based in the mensuration that adopts the thermo-mechanical analysis device to carry out is below 15%, when being used for the thin layer polarizing electrode of MLCC, can prevent electrode crackle that contraction difference that the agglutinating property when burning till causes is brought or the generation of peeling off.The low temperatureization of the heat decomposition temperature of resin binder when in addition, also being suppressed at the unsticking mixture.

Below, the main composition key element of detailed description nickel micro mist.

< 1-1. average grain diameter >

The average grain diameter of nickel micro mist is 0.05～0.3 μ m.If the average grain diameter of nickel micro mist is lower than 0.05 μ m, then aggegation becomes acutely, can not be scattered in equably in the slurry, is difficult to form electrode through coating.In addition, owing to there is the aggegation powder, therefore, apparent particle diameter increases, not only can't be corresponding to the electrode of filmization, and the contraction increase that causes of the sintering when burning till.On the other hand, if average grain diameter surpasses 0.3 μ m, then can not be corresponding to the electrode of filmization.Through average grain diameter being adjusted into 0.05～0.3 μ m, it is scattered in equably also can be corresponding to the electrode of filmization in the slurry.

< 1-2. size of microcrystal >

The size of microcrystal of nickel micro mist is 60～90% of a specific area particle diameter.Size of microcrystal is big to the progress influence of sintering.Crystallinity is good, be the size of microcrystal nickel micro mist big with respect to the specific area particle diameter, compare with the nickel micro mist of particle diameter with same degree, it is high to shrink initial temperature, the shrinkage factor that is caused by sintering is little.Through setting size of microcrystal is 60～90% of specific area particle diameter, can utilize the effect that multiplies each other of the effect that effect that crystallinity brings and clad bring, and 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 surpass 90%, but to obtain with respect to the specific area particle diameter be 100%, the nickel micro mist that promptly is 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 surpasses 0.2 quality % and is lower than 0.5 quality %.If sulfur content is lower than 0.1 quality %, then the formation of surface coating layer is insufficient, and shrinks the high temperature effect of initial temperature and the minimizing effect of shrinkage factor can't fully obtain to burn till the time.And,, also can't fully obtain the minimizing effect of shrinkage factor sometimes if sulfur content below 0.2 quality %, improves even then shrink initial temperature.On the other hand,, then be difficult to obtain the clad of oxygen containing suitable thickness, can cause that the problem of corrosion takes place the circuit of generation, electronic unit or the electronic instrument of corrosive gas when burning till if sulfur content surpasses 0.5 quality %.And, near 800 ℃, produce a large amount of SOx gas, produce electrode crackle, peel off etc.

< 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 might cause violent oxidation reaction even in atmosphere, heat a little.If oxygen content surpasses 1.5 quality %, when then in the week reduction gaseous environment of hydrogen etc., burning till, the generation of gas becomes violent and causes the crackle of electrode, peels off etc.

As stated; Nickel micro mist at this embodiment; Have the average grain diameter of regulation, the sulfur content of regulation, the oxygen content of regulation and the clad of specific thickness, the outermost of clad is made up of the high mixture of the crystallinity that contains nickel sulfide and nickel oxide.Thus, the contraction initial temperature not only can be improved, and the contraction of sintering can be suppressed to follow.And, can suppress the catalytic activity of nickel, can make near the original decomposition temperature of heat decomposition temperature high temperatureization to the resin binder of resin binder.

＜2. the manufacturing approach of nickel micro mist＞

The manufacturing approach of the nickel micro mist of an embodiment of the present invention (below be called " this method for making ") comprising: the preparation of raw material operation, and the preparation sulfur content becomes the nickel raw material of 0.1～0.5 quality %; The micronizing operation in containing the reducing gas environment of non-active gas and hydrogen, makes the nickel raw material generating gasification of being prepared through hot plasma, and makes the nickel devaporation that contains sulphur and oxygen that is produced, thereby makes its micronizing; Recovery process cools off the micronizing nickel after the micronizing and reclaim; And the eremacausis operation remains in the micronizing nickel that is reclaimed in the oxygen containing weak oxide property non-active gas environment, thereby makes the eremacausis of micronizing nickel surface, obtains the nickel micro mist.Below, specify each operation.

＜2-1. preparation of raw material operation＞

The preparation of raw material operation is the operation of regulating sulfur content contained in the nickel raw material.In the preparation of raw material operation, from nickel, nickel oxide, sulfide, select nickel to cooperate at least, so that the sulfur content in the nickel raw material becomes 0.1～0.5 quality %, and obtain the nickel raw material.In this preparation of raw material operation, be that sulfur content in the nickel raw material is that the mode of 0.1～0.5 quality % cooperates and gets final product with the sulfur content of resulting nickel micro mist.As far as sulphur, can be included in the nickel that uses as raw material or in the nickel oxide any one and get final product, also can be used as sulfide and cooperate.

And in the preparation of raw material operation, the nickel of preferably preparing sulfur content in advance and be 0.1～0.5 quality % is as the nickel raw material, perhaps the nickel oxide of sulfur-bearing cooperated with nickel and prepares the nickel raw material that sulfur content is 0.1～0.5 quality %.If selective oxidation nickel is as the nickel source, then might be, be to sneak into nickel oxide in the micronizing operation at subsequent processing, therefore, select nickel as the nickel source.In addition, if cooperate sulfide, then might sulphur skewness in resulting nickel micro mist.

Sulfur content is the nickel of 0.1～0.5 quality %, is through nickel being impregnated in the aqueous solution of sulfide, making sulphur be adsorbed in nickel surface and obtain.Based on the sulfide amount in the aqueous solution, can easily regulate the content of sulphur.In the aqueous solution, sulphur is adsorbed in after the nickel surface, can adopts usual method to carry out drying.

In addition, as the nickel oxide of sulfur-bearing, for example, can use the nickel oxide of calcining nickelous sulfate manufacturing.This nickel oxide all has commercially available usually, can analyze in the nickel oxide to cooperate nickel oxide after institute's sulfur content, so that the sulfur content in the nickel raw material becomes aequum.

As the nickel of nickel raw material use or the shape of nickel oxide, not special the qualification, but the easness from supplying with is preferably powder, and preferably its average grain diameter is 0.5～10 μ m.

< 2-2. micronizing operation >

The micronizing operation is in containing the reducing gas environment of non-active gas and hydrogen, makes the nickel raw material generating gasification that obtains in the preparation of raw material operation through hot plasma, and the nickel steam of generation is condensed and reaches micronized operation.

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

The nickel steam that produces based on hot plasma, condensing through quick cooling reaches micronizing.Compare with external heat mode etc.; The high-temperature area of hot plasma is narrow and small, and therefore, the nickel steam of gasification is condensing in the moving of plasma tail flame portion; Promptly condensed by cooling fast in the back of coming out from the plasma zone, even do not force cooling also not reach micronizing.Solidify because nickel is the state from complete droplet treatment, therefore, can form and reach spheroidizing basically and size of microcrystal is a micro mist more than 60%, that crystallinity is very high with respect to the specific area particle diameter.

In addition, the oxygen that contains 0.1～2.0 quality % in the preferred nickel raw material.If oxygen content is lower than 0.1 quality %, then sometimes steam produce less and stabilisation insufficient.In addition, if oxygen content surpasses 2.0 quality %, it is insufficient with the effect that combines again of nickel then to suppress oxygen through the hydrogen in the plasma, the excess oxygen content of final sometimes resulting nickel micro mist.

Nickel powder contains the oxygen of trace usually, even also in the nickel raw material, contain aerobic without nickel oxide.Owing in this method for making, used non-active gas-hydrogen plasma, therefore, can suppress the combination again of oxygen and nickel contained in the raw material.In addition, oxygen combines with hydrogen in the plasma and produces steam, thereby the water adsorption that makes trace is 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 the micronizing operation, adopt the method for micronization that is undertaken by hot plasma.As hot plasma, can use in direct-current plasma, the high-frequency plasma any, but preferably use high-frequency plasma.For example, in arc plasma process, exist electrode material (using tungsten-thorium usually) to take place to consume and sneak into the problem in the nickel micro mist as impurity as direct-current plasma.Measure through protective gas such as the non-active gas that flows etc. also can prevent sneaking into of impurity, but be inappropriate for continuous batch production.On the other hand, because the high-frequency plasma method is electrodeless,, can produce highly purified nickel micro mist by continuous batch so there is not the problem of sneaking into from the impurity of electrode material.

Do not limit non-active gas is special, but the preferred argon that does not generate compound with nickel that uses.

As far as the supply method of nickel raw material, as long as can aequum be supplied in the plasma with fixing speed.For example, when adopting nickel powder, can nickel powder be supplied in the plasma through transporting gas as raw material.

＜2-3. recovery process＞

Recovery process is the operation that reclaims after the micronizing nickel that generates in the micronizing operation is cooled off.In a single day because the high-temperature area of the hot plasma that in this method for making, uses is narrow,, make nickel be able to micronizing so come out to be cooled off fast immediately to condense from the plasma zone.At this moment, because nickel is micro mist, even therefore under the temperature below the freezing point of nickel, in case sintering just takes place the contact of micronizing nickel easily.Thereby, in the recovery process after the micronizing operation, be necessary micronizing nickel be scattered in the gas during, promptly adopt retracting device to cool off fully before reclaiming.

Chilling temperature is preferably below 120 ℃, more preferably below 50 ℃.In addition, as far as cooling, preferably to the overseas process of plasma slab fast cooling condense and reach micronized nickel and give the reducing gas environment or spray non-active gas and carry out.Especially, when the cost angle was considered, the preferred use and the gas of the same race that is used for the gaseous environment of plasma was so that recyclablely utilize again.In addition, for the generation that prevents to invade the plasma zone again, prevent oversize grain, preferably make cooling with gas when the plasma zone on every side forms rotating flow and cools off, be transported to retracting device.

< 2-4. eremacausis operation >

The eremacausis operation is that the micronizing nickel that is reclaimed is remained in the oxygen containing weak oxide property non-active gas environment, makes the micronizing nickel surface oxidation slowly take place to obtain the nickel micro mist.

For nickel micro mist isoreactivity micro mist, might in atmosphere vigorous oxidation take place and cause abnormal heating.Therefore, be necessary to be implemented in the oxygen containing non-active gas environment and will keep the eremacausis of stipulated time oxidize micro-powder nickel surface to handle through the micronizing nickel that recovery process reclaims.Handle through eremacausis, form oxygen containing clad on the surface of nickel micro mist.In addition,, then might cause the abnormal heating of micronizing nickel, therefore, preferably under air-tight state, be transferred to the eremacausis operation by recovery process if contact with atmospheric environment.

Through the eremacausis operation, form the clad that contains nickel sulfide and nickel oxide on the surface.The reason that clad forms is inferred for as follows.At first, in 2-2. micronizing operation, on the micronizing nickel surface, form the clad that contains nickel sulfide.The formation of nickel sulfide and nickel receives the domination of the standard free energy in each self-forming.At first, the nickel raw material evaporates in plasma, at first is nickel generation droplet treatment in cooling procedure.Be in the sulphur warp cooling after this of vaporized state, according to the standard free energy of formation (Ni of sulfide ₃S ₂＜H ₂S＜S), form Ni on nickel drop surface ₃S ₂Ni＞Ni during then, owing to the comparison fusing point ₃S ₂, therefore, when the nickel drop solidifies, be in aqueous Ni ₃S ₂Directly concentrate and form uniform clad on the surface at the micronizing nickel surface.

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

And,, infer it is through eremacausis operation surface oxidation to take place to make its increase though do not know the detailed reason that nickel oxide increases.Because the eremacausis operation is under oxygen containing weak oxide property gaseous environment, to implement, therefore, oxygen slowly spreads the oxidation of carrying out nickel to inner face side.Thus, be positioned at the layer that contains nickel sulfide below the micronizing nickel surface on do not have sulphur, form the layer do not contain nickel sulfide.Perhaps, think that nickel combines to diffusion into the surface and with outmost oxygen internally and forms oxide.

As oxygen containing non-active gas environment, preferably contain the oxygen of 1～5 capacity % and the gas of argon, more preferably contain 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, resulting nickel micro mist might be in atmosphere abrupt oxidization and cause abnormal heating.In addition, if oxygen surpasses 5 capacity %, then heating or oxidation proceed to inside sometimes, cause the thickness of clad to surpass 15nm.

Implement the eremacausis treatment temperature, be preferably below 120 ℃, more preferably below 50 ℃.In addition, eremacausis is handled and can in the gaseous environment of mandatory cooling, do not carried out, can be in common room temperature range, for example can fully implement at 0～40 ℃.Through carrying out the eremacausis processing below 100 ℃, can obtain to have the nickel micro mist of clad.On the other hand; Surpass in 100 ℃ the temperature and oxygen containing non-active gas environment if remain in; Not only can advance oxidation and oxidation to proceed to inside tempestuously and cause the thickness of clad to surpass 15nm; And, be present in outmost nickel oxide and increase considerably, can not get postponing the effect of sintering sometimes.

Time as far as eremacausis is handled, get final product so long as under gaseous environment and temperature, can fully form the time of clad, but preferably be made as 2～24 hours.If be lower than 2 hours, then can not fully form clad sometimes.In addition, even the processing time surpasses 24 hours, also only can increase cost and not have effect.

And, can carry out eremacausis through washing and drying and handle.In when washing, in order to prevent to sneak into impurity, adopt pure water etc. and wash with usual way, make its dry getting final product then, but, preferably carrying out drying below 120 ℃ in a vacuum in order to prevent over oxidation.

Handle through this eremacausis, can obtain to be formed with the nickel micro mist of the clad that contains oxygen and specific thickness on the surface.Because the surface of this nickel micro mist is in stable state,, on manipulating, be very easy to so do not worry problem on fire.

Based on above-mentioned method for making; Under the state that the sulphur that is in vaporized state exists; The nickel steam condenses, micronizing; Therefore, can obtain easily that purity height and crystallinity are high, the surface is formed with the nickel micro mist of clad, and can obtains as multilayer ceramic capacitor of future generation with the nickel micro mist below the 0.2 used μ m of electrode material.And the nickel micro mist that adopts this method for making to obtain owing to be formed with clad on the surface, therefore, can improve the heat shrinkability characteristic of sintered body.And the surface of this nickel micro mist is by coverings such as organic matter, dispersants, so the preparation of slurry etc. easily and when sintering, also can shrink equably, also can prevent the generation of crackle etc.

＜3. embodiment＞

Below, according to embodiment, nickel micro mist and manufacturing approach thereof in further explain an embodiment of the present invention.But the present invention is not limited to these embodiment.

Embodiment

In the present embodiment, having adopted maximal input is the high-frequency plasma micro mist manufacturing installation (high-frequency plasma vibrating machine: TP-12020, Jeol Ltd. makes) of 200kW.In addition, the various mensuration in present embodiment and the comparative example are to carry out according to following method.

(1) transmission electron microscope (being designated as " TEM " down) is observed: adopt TEM (HF-2200, Hitachi Ltd. (Hitachi High-Technologies Corporation) makes) to observe.And, also implemented electron ray diffraction analysis (being designated as " EDX " down) (VANTAGE, NORAN makes).

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

(3) crystal size: adopt X-ray diffraction device (being designated as " XRD " down) (X ' PertPRO, PANalytical makes) to measure.

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

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

(6) superficial layer analysis: adopt the argon ion etching method, carry out the analysis of case depth direction through FE-AES (Model 680, and ULVAC-PHI Co., Ltd. makes).To thinking that being present in surperficial nickel, sulphur, oxygen, carbon analyzes.And, adopt XPS (ESCALAB220i-XL, VG Scientific makes) to analyze the nickel, sulphur, the oxygen that are considered to be 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.) makes); In nitrogen; With 5 ℃/minute programming rate, be the nickel micro mist of ethyl cellulose (EC) and independent nickel micro mist to be mixed with 5 weight % resin binders with respect to nickel micro mist physics respectively, gravimetry changes.Then, from the weight change of the nickel micro mist that is mixed with EC, deduct the weight change of independent nickel micro mist, obtain the weight change of the EC in the nickel micro mist.And, as the evaluation of the catalytic activity of nickel micro mist, the weight change of EC is carried out the decomposition rate that a subdifferential is obtained EC, and with the peak of the decomposition rate decomposition temperature as EC.

(8) evaluation of heat shrinkability characteristic: use about 0.15g sample; It is shaped to particle (pellet) shape (the about 1.5mm of φ 5mm * t); When applying the 10g load; In the reducibility gas environment that the mist that hydrogen constituted (200mL/ minute) by the nitrogen of 98 capacity % and 2 capacity % forms, adopt thermo-mechanical analysis device (being designated as " TMA " down) (TMA4000SA, Brooker AXS Co., Ltd. makes) to measure heat shrinkability characteristic.Temperature range is a room temperature to 1300 ℃, and programming rate is made as 5 ℃/minute.The temperature of shrinking 0.5% o'clock is estimated as shrinking initial temperature.And, the maximum of shrinking is estimated as shrinkage factor.

[embodiment 1]

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

In addition; As the nickel raw material, nickel by powder (nickel, Type255 have been used at 90 quality %; Average grain diameter is 2.2～2.8 μ m, and Inco Special Products and Inco Limited makes) in mix the nickel raw material that the nickel oxide (interpolation have an appointment 2 quality % sulphur) of 10 quality % forms.Sulfur content in the nickel raw material is 0.2 quality %, and oxygen content is 2 quality %.

This plasma is more than 10000 ℃, and therefore, the nickel material powder took place to evaporate and gasify in moment, and condensed in the low plasma tail flame portion of temperature, was able to micronizing.With resulting micronizing nickel; Mode not to be exposed in the atmospheric environment is transported to retracting device, in retracting device, remains in the environmental gas of argon-10 capacity % air (oxygen is about 2 capacity %) about 10 hours; Handle to carry out eremacausis, reclaim from device then.

The BET of the nickel micro mist that is obtained directly is 159nm.Through this nickel micro mist of XRD analysis; The size of microcrystal that adopts the Scherrer method to be obtained is 63% of BET footpath for

crystallite dimension, can know to have formed the nickel micro mist of crystallinity near monocrystalline.Sulphur and oxygen content are respectively 0.17 quality %, 0.68 quality %.Based on the result that TMA measured, shrinking initial temperature and be about 320 ℃, shrinkage factor is 11.0%.In addition, according to the analysis result of EDS, having confirmed only has 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 of expression FE-AES.Sulphur and oxygen are considered to form respectively nickel sulfide and nickel oxide.The thin thickness of oxygen containing clad is to 10nm.In addition, the thin thickness of the layer of sulfur-bearing is to 6nm.In addition, as nickel sulfide, contain 100% nickel sulfide.And, in the CONCENTRATION DISTRIBUTION of nickel sulfide, in the scope of distance surface 2～3nm concentration peak has appearred.Thickness and other example of each layer are shown among Fig. 4 in the lump.

[embodiment 2]

Except the hydrogen that will supply with plasma was made as 9L/ minute, operate equally with embodiment 1, obtained the nickel micro mist, and estimated.The BET of nickel micro mist directly is 152nm.Through this nickel micro mist of XRD analysis; The size of microcrystal that adopts the Scherrer method to be obtained is 85% of BET footpath for

crystallite dimension, can know to have formed the nickel micro mist of crystallinity near monocrystalline.Sulphur and oxygen content are respectively 0.24 quality %, 1.0 quality %.Based on the mensuration result of TMA, shrinking initial temperature and be about 360 ℃, shrinkage factor is 7.9%.Each evaluation result and other example are shown in Table 1 in the lump.

And, the analysis result of FE-AES, the thin thickness of oxygen containing clad is to 14nm.And the thickness of the layer of sulfur-bearing is 8nm.Each layer thickness and other example are shown among Fig. 4 in the lump.

[embodiment 3]

Except having used as nickel powder the following nickel by powder, likewise operate with embodiment 1, obtained the nickel micro mist, and estimated.With 4kg nickel by powder (nickel; Type255; Average grain diameter is 2.2～2.8 μ m; Inco Special Products and Inco Limited makes) join in the 16L pure water that is adjusted to 50 ℃, add 18g NaHS hydrate (Sodium hydrosulfide n-hydrate), stirred 30 minutes.Carry out 1 pulp again (Re Pulp) then, filter, after the vacuum drying (36 hours), carry out fragmentation and as the nickel raw material.Sulfur content in the nickel raw material is 0.2 quality %, and oxygen content is 0.4 quality %.

The BET of nickel micro mist directly is 125nm.Through this nickel micro mist of XRD analysis; The size of microcrystal that adopts the Scherrer method to be obtained is 75% of BET footpath for

crystallite dimension, can know to have formed the nickel micro mist of crystallinity near monocrystalline.Sulphur and oxygen content are respectively 0.26 quality %, 0.99 quality %.Based on the result that TMA measured, shrinking initial temperature and be 330 ℃, 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 of expression FE-AES.The thin thickness of oxygen containing clad is to 10nm.In addition, the thickness of the layer of sulfur-bearing is 6nm.In addition, as nickel sulfide, contain 73% nickel sulfide, 27% nickelous sulfate.And, in the CONCENTRATION DISTRIBUTION of nickel sulfide, in the scope of distance surface 2～3nm concentration peak has appearred.Thickness and other example of each layer are shown among Fig. 4 in the lump.

[embodiment 4]

Except the addition with the NaHS hydrate is adjusted into the 36g, likewise operate with embodiment 3, obtained nickel by powder.The sulfur content of the nickel by powder that is obtained is that 0.37 quality %, oxygen content are 0.4 quality %.Except this nickel by powder is used as the nickel raw material, likewise operate with embodiment 1, obtained the nickel micro mist, and estimated.

The BET of nickel micro mist directly is 117nm.Crystallite dimension is 70% of BET footpath for size of microcrystal, can know to have formed the nickel micro mist of crystallinity near monocrystalline.Sulphur and oxygen content are respectively 0.39 quality %, 0.82 quality %.Based on the result that TMA measured, shrinking initial temperature and be 310 ℃, shrinkage factor is 12.8%.Each evaluation result is shown in Table 1 in the lump.

In addition, can know that through the analysis of FE-AES the thin thickness of oxygen containing clad is to 12nm.In addition, the thickness of the layer of sulfur-bearing is 10nm.Thickness and other example of each layer are shown among Fig. 4 in the lump.

[comparative example 1]

Except the gas that will be supplied to plasma be adjusted into argon total amount 180L/ minute, hydrogen 6L/ branch; And (average grain diameter is 2.2～2.8 μ m for nickel, Type255 only to use nickel by powder as the nickel raw material; Inco Special Products and Inco Limited makes) in addition; Likewise operate with embodiment 1, obtained the nickel micro mist, and estimated.In addition, the sulfur content in the nickel raw material is 0 quality %, and oxygen content is 0.05 quality %.

The BET of nickel micro mist directly is 169nm; Crystallite dimension is 49% of BET footpath for

size of microcrystal, can know it is the nickel micro mist of crystallinity difference.Do not contain sulphur, oxygen content is 0.63 quality %.Based on the result that TMA measured, shrinkage factor is 14.0%, and shrinking initial temperature is about 190 ℃.Each evaluation result is shown in Table 1 in the lump.

[comparative example 2]

The hydrogen that passes through that adopts one of prior art is reduced the nickel micro mist of chemical gas-phase reaction method manufacturing of nickel chloride steam, use as comparative example.The BET of this micro mist directly is 130nm, and crystallite dimension is 69% of BET footpath for

crystallite dimension.The content of sulphur and oxygen is respectively 0.18 quality %, 1.6 quality %.Based on the result that TMA measured, shrinking initial temperature and be 320 ℃, shrinkage factor is 15.5%.

Fig. 3 is the curve map of the analysis result of expression FE-AES.The thicker of oxygen containing clad reaches 16nm.In addition, the thickness of the layer of sulfur-bearing is 8nm.In addition, as nickel sulfide, contain 100% nickel sulfide.And, in the CONCENTRATION DISTRIBUTION of nickel sulfide, in the scope of distance surface 2～3nm concentration peak has appearred.The thickness of each layer is shown among Fig. 4 with other example.

Table 1

The embodiment 1～4 that adopts this method for making to obtain is that size of microcrystal/specific area particle diameter is the extraordinary nickel micro mist of crystallinity more than 60%.And, having formed the mixture that contains nickel sulfide and nickel oxide on the surface, oxygen containing coating thickness is below the 15nm, therefore, shrinks the initial temperature height, shrinkage factor is also little, has good heat shrinkability characteristic.

On the other hand, as far as the comparative example 1 of sulfur-bearing not, shrink that initial temperature is low, shrinkage factor big, heat shrinkability characteristic is poor.In addition, adopt through hydrogen and reduce the comparative example 2 of chemical gas phase reaction method manufacturing of nickel chloride steam, it becomes, and crystallinity is good, to shrink initial temperature high, but shrinkage factor is big.Think that its reason is,, need clean, and excessive cleaning can cause the oxidation on surface, thereby make oxygen containing clad thickening in order to remove chlorine owing to adopted the chemical gas phase reaction method.

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

[embodiment 5]

With the plasma input power is about 60kW igniting high-frequency plasma, and adjustment argon total amount is that 209L/ minute, hydrogen are that 45L/ minute, pressure of ambient gas are 60kPa, has obtained stable plasma flame.Through transporting gas (24 liters/minute of argons), will be supplied to plasma flame inside with 1kg/hr with embodiment 3 identical nickel raw materials, with the preparation micro mist.

With resulting micronizing nickel; Mode not to be exposed in the atmospheric environment is transported to retracting device, in retracting device, remains in the environmental gas of argon-10 capacity % air (oxygen is about 2 capacity %) about 10 hours; Handle to carry out eremacausis, reclaim from device then.

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

And,, use ethyl cellulose (EC) to make electrocondution slurry according to " evaluation of the catalytic activity of nickel micro mist " shown in above-mentioned (7).Adopt the TG determinator to measure the result of this electrocondution slurry, the heat decomposition temperature of EC is 339 ℃, 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, the curve map with the EC thermal decomposition characteristic result who representes the nickel micro mist is shown among Fig. 5.

[embodiment 6]

Except the hydrogen that will supply with plasma was adjusted into 9L/ minute, likewise operate with embodiment 5, obtained the nickel micro mist, and estimated.The BET of nickel micro mist directly is 123nm.The content of sulphur and oxygen is respectively 0.16 quality %, 1.0 quality %.

And " evaluation of the catalytic activity of nickel micro mist " shown in above-mentioned (7) uses ethyl cellulose (EC) to make electrocondution slurry.Adopt the TG determinator to measure the result of this electrocondution slurry, the heat decomposition temperature of EC is 336 ℃, 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, the curve map with the EC thermal decomposition characteristic result who representes the nickel micro mist is shown among Fig. 5.

[embodiment 7]

As the sulfur content of nickel powder in the nickel raw material is 0.15 quality %; And serve as about 105kW igniting high-frequency plasma with the plasma input power; Adjustment argon total amount is that 209L/ minute, hydrogen are that 18L/ minute, pressure of ambient gas are 50kPa, has obtained stable plasma flame.Through transporting gas (24 liters/minute of argons), the nickel raw material is supplied to plasma flame inside with 2.2kg/hr, with the preparation micro mist.The BET of nickel micro mist directly 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 " shown in above-mentioned (7) uses ethyl cellulose (EC) to make electrocondution slurry.Adopt the TG determinator to measure the result of this electrocondution slurry, the heat decomposition temperature of EC is 336 ℃, and is equal with the heat decomposition temperature that EC is original.Each evaluation result and other example are shown in Table 2 in the lump.And, the EC thermal decomposition characteristic result's who representes the nickel micro mist curve map is shown among Fig. 5.

[embodiment 8]

As the sulfur content of nickel powder in the nickel raw material is 0.18 quality %; With the plasma input power is about 60kW igniting high-frequency plasma; Adjustment argon total amount is that 175L/ minute, hydrogen are that 6.4L/ minute, pressure of ambient gas are 60kPa, has obtained stable plasma flame.Through transporting gas (15 liters/minute of argons), the nickel raw material is supplied to plasma flame inside with 1.6kg/hr, with the preparation micro mist.The BET of nickel micro mist directly 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 " shown in above-mentioned (7) uses ethyl cellulose (EC) to make electrocondution slurry.Adopt the TG determinator to measure the result of this electrocondution slurry, the heat decomposition temperature of EC is 337 ℃, the heat decomposition temperature equal extent original with EC.Each evaluation result and other example are shown in Table 2 in the lump.The thin thickness of oxygen containing clad is to 10nm.And, as nickel sulfide, under the electron ray diffraction, be mottled, therefore, its crystallinity is very good.Can know according to XPS, calculate, contain 65% nickel sulfide, 35% nickelous sulfate at superficial layer with content ratio.

[comparative example 3]

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

In addition, " evaluation of the catalytic activity of nickel micro mist " shown in above-mentioned (7) uses ethyl cellulose (EC) to make electrocondution slurry.Adopt the TG determinator to measure the result of this electrocondution slurry, the heat decomposition temperature of EC is 280 ℃ and 339 ℃.Because the catalytic action of nickel, given birth to decomposition being lower than the occurs at low temperatures of the original heat decomposition temperature of EC more than 60 ℃.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 thin thickness is to 10nm.In addition, as nickel oxide, under the electron ray diffraction, be mottled, therefore, its crystallinity is very good.But, exist nickel sulfide to suppress the effect of catalytic activity because the decomposition temperature of EC by low temperatureization, is therefore thought.

Table 2

The embodiment 5～8 that adopts this method for making to obtain; Be formed with the mixture that contains nickel sulfide and nickel oxide on its surface; Particularly nickelous sulfate is high with the content ratio of nickel sulfide, has formed high nickel sulfide and the nickelous sulfate of crystallinity, therefore; The heat decomposition temperature of EC is 337 ℃, the heat decomposition temperature equal extent original with EC.

On the other hand, as far as the comparative example 3 of sulfur-bearing not, the decomposition temperature of EC is by low temperatureization, and is undesirable.

Industrial applicibility

Nickel micro mist in the embodiment of the present invention, the heat decomposition temperature equal extent that its heat decomposition temperature and EC are original is suitable for the nickel micro mist as the internal electrode formation usefulness of MLCC.And,, also be suitable for using with material as the wiring formation of electronic instrument, electronic unit because purity is high.

Claims (15)

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

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

2. nickel micro mist as claimed in claim 1 is characterized in that said clad contains nickel oxide, and two-layerly is made up of following, promptly is made up of with the layer that does not contain nickel sulfide that is present in inner face side the layer that contains nickel sulfide that is present in face side.

3. according to claim 1 or claim 2 nickel micro mist is characterized in that, is in the XPS analysis at x-ray photoelectron spectroscopy, the content of the nickel sulfide in the contained sulfide of outermost than be 50%～100%, the content ratio of nickel hydroxide in the nickel oxide is 0～50%.

4. nickel micro mist as claimed in claim 3 is characterized in that, the content ratio of the nickelous sulfate in the said outmost nickel sulfide is below 40%.

5. like each described nickel micro mist in the claim 1～4; It is characterized in that; The layer that contains nickel sulfide in the said clad also two-layerly is made up of following, promptly by the layer that contains nickelous sulfate that is present in face side be present in inner face side mainly contain the layer of nickel sulfide as nickel sulfide.

6. like each described nickel micro mist in the claim 1～5, it is characterized in that having the concentration gradient of the inclination of sulphur in the scope of said clad below the surperficial 10nm of distance.

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

8. like each described nickel micro mist in the claim 1～7, it is characterized in that when adopting the thermo-mechanical analysis device to measure, the shrinkage factor when in the reducibility gas environment, being heated to 1300 ℃ is below 15%.

9. like each described nickel micro mist in the claim 1～8; It is characterized in that; In the reducibility gas environment; Gasify and make the devaporation of generation and obtain the nickel micro mist of sulfur-bearing based on hot plasma, the nickel micro mist of this sulfur-bearing is remained in obtain said nickel micro mist in the weak oxide property gaseous environment.

10. the manufacturing approach of a nickel micro mist comprises:

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

The micronizing operation in containing the reducing gas environment of non-active gas and hydrogen, through the nickel material gasification of hot plasma with said preparation, makes the nickel devaporation that contains sulphur and oxygen that is produced and carries out micronizing;

Recovery process cools off and reclaims the micronizing nickel after the said micronizing; And

The eremacausis operation remains in the micronizing nickel of said recovery in the oxygen containing weak oxide property non-active gas environment, makes the micronizing nickel surface slowly carry out oxidation and obtains the nickel micro mist.

11. the manufacturing approach of nickel micro mist as claimed in claim 10 is characterized in that, the maintenance temperature in said eremacausis operation is below 100 ℃.

12. the manufacturing approach like claim 10 or 11 described nickel micro mists is characterized in that, the oxygen content in said eremacausis operation in the non-active gas environment is 1～5 capacity %.

13. manufacturing approach like each described nickel micro mist in the claim 10～12; It is characterized in that; In said preparation of raw material operation; Prepare the nickel that sulfur content is 0.1～0.5 quality % in advance as said nickel raw material, perhaps, the nickel oxide of sulfur-bearing is cooperated with nickel and prepare the nickel raw material that sulfur content is 0.1～0.5 quality %.

14. the manufacturing approach like each described nickel micro mist in the claim 10～13 is characterized in that, uses the high-frequency induction plasma as said hot plasma.

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

Have the oxygen containing clad of thickness 2～15nm on the surface, the outermost of this clad is made up of the mixture that contains nickel sulfide and nickel oxide.

Images