JPH1161399A - Production of ceramic coated powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ceramic coated powder in which an uniform ceramic coated layer is formed on a particle surface. SOLUTION: When a powder particle is coated with a ceramic by a sputtering method while rotating a rotary barrel charged with the powder particles at a peripheral speed of >=0.1 m/min, a partial pressure ratio of a reaction gas in a sputtering gas is set to 10-70%, a crystal diameter calculated by a X ray diffraction peak half value width of a coated layer is <=100 nm, as taking a specific surface of a fine particle to be coated for Sm<2> /g and a density of a ceramic to coat for (m) g/m<3> , a ceramic coated layer is formed with a coated quantity X mass % so that a film thickness (t) μm assumed as uniformly coated one by one of powder particles as theoretically defined in a formula t= X/(100×m×S)}×10<6> is turned to a range 1×10<-3> -1×10<-1> . N2 , O2 , water vapor, hydrocarbon, etc., are used for a reaction gas source, a decomposed N, O, C, etc., are allowed to react with a target metal of Ti, Al, Cr, Zr, etc., flying from a sputtering source to be turned to a nitride, an oxide, a carbide, etc., further coating the powder particle surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an additive for a tool material,
The present invention relates to a method for producing a ceramic-coated powder suitable as a pigment or the like requiring decorativeness.

[0002]

2. Description of the Related Art Ceramic coatings such as TiN and TiC are applied to steel plates, glass substrates, metal members, ceramic members, and the like by various methods such as painting, thermal spraying, and vapor deposition. However, ceramic coating on powders of metals, glass, ceramics and the like is not common. In this regard, the powder sputtering method developed by the present applicant (see JP-A-2-153068 and JP-A-5-271920) is suitable for ceramic coating. In this method, a fluidized bed of powder is formed by rotation of a rotary barrel filled with powder, and the fluidized bed is subjected to sputtering to coat the surface of powder particles with a metal or the like. At this time, if a reactive atmosphere such as N ₂ , O ₂ , and hydrocarbon is used, the metal emitted from the sputtering source reacts with gas components in the atmosphere until reaching the target powder particles, and nitrides are formed. , Oxides, carbides, etc. are applied to the surface of the powder particles.

[0003]

In order to obtain a ceramic coating powder having a stable quality with a small amount of coating, it is required to uniformly coat the surface of the powder particles with the ceramic. However, it is difficult to uniformly form a coating layer of a ceramic, which is less ductile than a metal and is brittle, on the surface of the powder particles. For example, in the powder sputtering method described above, the powder being sputtered forms a fluidized bed in a rotating barrel, and the powder particles are sputtered while repeatedly colliding with each other. The collision between the powder particles causes a crack or peeling in the ceramic coating layer formed on the surface of the powder particles. As a result, the recovery rate of the powder having the required thickness and uniformly coated with the ceramics tends to decrease. The present invention has been devised to solve such a problem. By appropriately adjusting the partial pressure of the reactive gas, stirring conditions, and the amount of coating, the surface of the powder particles can be uniformly coated with ceramics. The purpose is to form a layer.

[0004]

In order to attain the object, the production method of the present invention comprises the steps of: rotating a rotary barrel loaded with powder particles at a peripheral speed of 0.1 m / min or more by a reactive sputtering method. When coating the particles with ceramics, the partial pressure ratio of the reactive gas in the sputtering gas is 10 to 70.
%, The crystallite diameter calculated from the X-ray diffraction half width at half maximum of the coating layer is 100 nm or less, the specific surface area of the fine particles to be coated is S (m ² / g), and the density of the ceramic to be coated is m ( g / m ³ ), the film thickness t (μm) assuming that the powder particles ideally defined by the formula (1) are uniformly and uniformly coated is 1 × 10 ⁻³ to 1 × 10 ^{−. The} ceramic coating layer is formed with a coating amount X (% by mass) so as to fall within the range of ¹ . t = {X / (100 × m × S)} × 10 ⁶ (1) As the reactive gas source, one or more of N ₂ , O ₂ , and hydrocarbons are used. N, O, C, etc. generated by the decomposition of N ₂ , O ₂ , hydrocarbons, etc. react with target metals, such as Ti, Al, Cr, Zr, flying from a sputtering source, and form nitrides, oxides, carbides, etc. To cover the surface of the powder particles.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS For powder sputtering, for example, FIG.
The following device is used. In this powder sputtering apparatus, a rotary barrel 1 is supported by two rolls 2, and one of the rolls 2 is rotated by a motor 3. Inside the rotary barrel 1, two sputtering sources 4 are arranged, and a metal from the sputtering source 4 flies toward the charged powder raw material 5. The inside of the rotary barrel 1 is maintained in an atmosphere containing a reactive gas. As the reactive gas, N ₂ is used for forming nitride.
, And oxides, O ₂ , and hydrocarbons, such as methane and acetylene, are used. The metal flying from the sputtering source reacts with the reactive gas and becomes a nitride, an oxide, a carbide, or the like, and adheres to the surface of the powder raw material 5.

In the sputtering method for coating powder particles, since the coating area is large and the number of nucleation and growth sites of the sputtered particles is large, the partial pressure ratio of the reactive gas is 10 to 10 in comparison with coating on a plate material or the like. It is necessary to set a high value of 70%. Reactive gas partial pressure ratio of 10
%, The unreacted metal adheres to the surface of the powder raw material 5, and a required ceramic coating layer is not formed.
Conversely, if the partial pressure ratio exceeds 70%, the coating structure becomes irregular, the internal stress increases, and unreacted gas is mixed in, and the coating state deteriorates and the coating speed decreases.

Above the rotary barrel 1, a decompression processing chamber 7 having a heating coil 6 on its outer periphery is arranged. The bottom of the decompression processing chamber 7 is connected to the rotary barrel 1 via a supply pipe 9 provided with a valve 8. At a position below the valve 8, a gas introduction pipe 10 having a double pipe structure is inserted inside the supply pipe 9. The gas introduction pipe 10 is inserted into the inside of the rotary barrel 1 from the side, and the tip extends to the bottom of the rotary barrel 1. A branch pipe 11 is provided in the supply pipe 9 at a position below the valve 8, and a tip of the branch pipe 11 is connected to the fluid jet mill 12. The outlet side of the fluid jet mill 12 is connected to the upper part of the decompression processing chamber 7 via the circulation pipe 13. A valve 14 and a valve 15 are incorporated in the branch pipe 11 and the circulation pipe 13, and a solid-gas separation device 16 is connected to the circulation pipe 13.

The powder raw material 5 charged in the rotary barrel 1 is
Although there is no particular restriction on the type and material, glass, diamond, alumina, boron nitride, silicon carbide, silicon nitride, tungsten carbide, titanium and the like are used. After a predetermined amount of the powder raw material 5 is charged into the rotary barrel 1 and the pressure in the decompression processing chamber 7 is reduced, an Ar gas containing a reactive gas is introduced into the rotary barrel from the gas introduction pipe 10. The powder raw material 5 includes a branch pipe 11, a fluid jet mill 12, and a circulation pipe 1.
Heated by the heating coil 6 in the decompression processing chamber 7 via 3
After drying and degassing, it is dropped on the rotary barrel 1. The powder material 5 is sputtered by the sputtering source 4 under a reduced pressure atmosphere while rotating the rotary barrel 1 at a peripheral speed of 0.1 m / min or more under these conditions. The peripheral speed of the rotary barrel 1 greatly affects the stirring state of the powder raw material 5. In order to form a flow state suitable for sputtering, 0.1 m /
A peripheral speed of at least a minute is required. If the peripheral speed does not reach 0.1 m / min, the powder raw material 5 does not sufficiently fluidize, and the ratio of uncoated powder particles remaining increases.

After a predetermined time has elapsed, the sputtering is stopped, the pressure in the decompression processing chamber 7 is reduced, and
, A mixed gas of Ar and N ₂ is introduced, and the powder raw material 5 is sucked and returned to the decompression processing chamber 7 via the fluid jet mill 12 to loosen the powder raw material 5 which has been agglomerated during sputtering as much as possible into individual particles. By repeating this sputtering operation several times, a ceramic coating layer having a predetermined thickness is formed on the surface of the powder raw material 5. The powder having the ceramic coating layer formed to a predetermined thickness is recovered from the solid-gas separation device 16.

When a ceramic coating layer is formed on the powdery raw material 5 by such sputtering, the X of the coating layer
The crystallite diameter calculated from the half width of the X-ray diffraction peak is 100 n
m or less is necessary to form a uniform coating layer. The crystallite diameter calculated from the X-ray diffraction peak half width of the coating layer corresponds to the crystal grain size of the coating layer. Precipitate in columnar or granular form. Therefore, the crystallite diameter means the size of such a columnar or granular crystal layer, and by setting the crystallite diameter to 100 nm or less, the occurrence of coarse columnar crystals or coarse granular crystals that hinder uniform coating on the substrate is prevented. It is suppressed and a good coating is applied. If the crystallite diameter exceeds 100 nm, the growth of the film is hindered, so that a uniform coating layer is not formed, and there is a possibility that ceramics may adhere in a granular manner. Usually, in the surface treatment by the sputtering method, the characteristics are often affected by the coating thickness (film thickness) of the substrate. However, in the case of ceramic coating, since the coating state differs between powder particles, and it is difficult to measure the coating thickness of one fine powder particle, measurement using a film thickness meter or the like cannot be performed during coating on flowing powder. .

[0011] In this regard, the present inventors assume that when the specific surface area of the fine particles to be coated and the density, type, and properties of the ceramic to be coated are determined, the ceramics are uniformly coated on each of the powder particles. It has been found that a good coating state can be obtained when the coating thickness (film thickness) calculated by the coating amount is within the range specified in the present invention. That is, assuming that the ceramic is uniformly coated on each of the powder particles by reactive sputtering, the specific surface area of the coated fine particles is S (m ² / g), and the density of the coated ceramic is m (g / g). m ³ ), and when the coating amount is X (% by mass), the film thickness can be calculated as follows.

The weight of the ceramics coated on the powder per 1 g of the unit weight is represented by the following formula:
X / 100 (g). Similarly, the volume of the ceramics coated on the powder per 1 g of unit weight is calculated as X / (100 × m) (m) by dividing the coating weight X / 100 (g) by the density m (g / m ³ ). expressed. Here, assuming that ceramics having a volume of X / (100 × m) uniformly coats the powder, the specific surface area of the powder per unit weight is S (m ² / g). By dividing the volume X / (100 × m) of the ceramic by the specific surface area S of the powder, X / (100 × m × S) (m)
Is required. When the unit of the film thickness represented by these equations is converted from m to μm, the film thickness t (μm) is obtained as the above equation t = {X / (100 × m × S)} × 10 ⁶ .

Here, the film thickness t is 0.001 to 0.1 μm
When set so that the presence of uncoated particles caused by the variation of the coating amount inevitably generated between the powder particles is substantially eliminated, and the internal stress of the ceramic coating layer caused by the excessive coating is increased. Film peeling can be suppressed. The coating amount X such as to achieve such a film thickness is t
= {X / (100 × mx × S)} × 10 ⁶ = 1 × 10 ^-3
Since it is 1 × 1 ⁻¹ , X = (1 × 10 ⁻⁷ × ^mxS )
(1 × 10 ⁻⁵ × m × S). When the thickness t is less than 0.001 μm, a large number of uncoated particles are present due to the difference in the coating state between the powder particles, and the effect of the ceramic coating cannot be substantially obtained. Conversely 0.1
When the film thickness t exceeds μm, the coating rate on the powder particles is improved, but not only the cost is increased due to excessive coating, but also film peeling is likely to occur due to an increase in internal stress due to thermal distortion of the ceramic film, On the contrary, the uncoated particles increase due to the deterioration of the coated state. As a result, the peeled ceramic film may be mixed as fine particle impurities.

[0014]

【Example】

Example 1: Insulating ceramic powders having various particle diameters were mixed with each other so as to have a film thickness determined by the above-mentioned equation (1).
Weakly conductive ceramics such as iN, AlN, TiC, ZrN, and CrN were coated by reactive sputtering. Inner diameter 1
0 mm insulating die is filled with the coating powder, and the pressure is 10M.
After pressurizing with Pa, the electric resistance between the upper and lower electrodes was measured. Further, for comparison, an insulating die was filled with the powder raw material and the coating raw material at the same weight ratio, and the electric resistance was measured by similarly applying pressure. Of these, when the cubic BN powder was coated with TiN, the surface state of the coated powder whose electrical resistance was improved by at least two orders of magnitude compared to the powder raw material was observed, and as shown in FIG. The surface was uniformly covered with the TiN layer. On the other hand, when the surface state of the coated powder whose electric resistance was improved by one digit or more than the powder raw material was observed, FIG.
As shown in the figure, the TiN layer is not a film but a granular cubic BN.
It adhered to the surface of the powder particles.

Therefore, when the electric resistance is improved by two digits or more, the case where the powder particles are uniformly coated with the ceramic (○) and the case where the degree of improvement of the electric resistance is less than two orders are unevenly coated (×) ), And the adhesion state of the coating material to each powder material was investigated. However, if the powder material is conductive T
On the other hand, in the case where i powder is coated with insulating Al ₂ O ₃ , conversely, when the electric resistance is reduced by two digits or more, the coating is uniform (○), and when the degree of decrease in the electric resistance is less than two digits, the coating is uneven. (X) was determined. As can be seen from Tables 1 to 4 showing the results of the determination, it was confirmed that a uniform coating layer was obtained in each case coated by reactive sputtering under the conditions specified in the present invention. On the other hand, the coating layer formed by the reactive sputtering deviating from the conditions specified in the present invention was a granular or island-shaped discontinuous coating.

[0016]

[0017]

[0018]

[0019]

Example 2: Insulating ceramic powder Al ₂
In O ₃ , the film thickness obtained from the above equation (1) is 5 × 10 ⁻² μm.
m was coated by reactive sputtering with a weakly conductive ceramic TiN. At this time, the reactive gas partial pressure ratio was set to a fixed value of 50%, and the crystallite diameter of the coating layer was set to a fixed value of 100 n.
m or less, and the barrel peripheral speed was changed. The electrical resistance of the obtained coating powder was measured in the same manner as in Example 1, and the effect of the peripheral speed of the barrel on the uniformity of the coating was investigated. As can be seen from the investigation results in FIG. 4, when the barrel peripheral speed is set to 0.1 m / min or more, a good uniformly coated powder can be obtained.

Example 3 Insulating ceramic powder Al ₂
In O ₃ , the film thickness obtained from the above formula (1) is 2 × 10 ⁻² μm.
m, weakly conductive ceramics TiN and TiC were coated by reactive sputtering. In addition, conductive particles A
g was coated with Al ₂ O ₃ under the same film thickness conditions. At this time, the barrel peripheral speed was maintained at a constant value of 0.1 m / min, the crystallite diameter of the coating layer was maintained at 100 nm or less, and the reactive gas partial pressure ratio was changed. The electric resistance of the obtained coated powder was measured in Example 1.
The effect of the partial pressure ratio of the reactive gas on the uniformity of the coating was investigated. In this example, the case where the electrical resistance changed by three digits was determined to be particularly excellent in the coating state (◎). As can be seen from the investigation results in FIG. 5, when the partial pressure ratio of the reactive gas is maintained in the range of 10 to 70%, a good coating state is obtained, and in particular, an excellent coating state is obtained at a partial pressure ratio of 30 to 50%. It turns out that it becomes.

Example 4: Insulating ceramic powder Al ₂
In O ₃ , the film thickness obtained from the above equation (1) is 1 × 10 ⁻² μm.
m was coated by reactive sputtering with a weakly conductive ceramic TiN. At this time, the peripheral speed of the barrel was set to a constant value of 0.1 m / min, and the partial pressure ratio of the reactive gas was set to a constant value of 50%.
, And the sputtering output and the substrate temperature were changed so as to obtain various crystal particle diameters. The electrical resistance of the obtained coating powder was measured in the same manner as in Example 1, and the effect of the crystallite diameter on the coating uniformity was investigated. In this example, the case where the electrical resistance changed by three digits was determined to be particularly excellent in the coating state (◎). As can be seen from the survey results in FIG.
It can be seen that when the crystallite diameter is set to 100 nm or less, a good coating state is obtained, and in particular, an excellent coating state is obtained when the crystallite diameter is 30 nm or less.

Example 5: Insulating ceramic powder Al ₂
O ₃ was coated with weakly conductive ceramics TiN and TiC by reactive sputtering while changing the film thickness obtained from the above-mentioned formula (1). Similarly, conductive particles Ag were coated with insulating ceramics Al ₂ O ₃ . At this time, the barrel peripheral speed was kept at a constant value of 0.1 m / min, the reactive gas partial pressure ratio was kept at a constant value of 50%, and the crystallite diameter of the coating layer was kept at 100 nm or less. The electrical resistance of the obtained coating powder was measured in the same manner as in Example 1, and the effect of the film thickness on the uniformity of the coating was investigated. In this example, the case where the electrical resistance changed by three digits was determined to be particularly excellent in the coating state (◎). As can be seen from the investigation results in FIG. 7, the film thickness was 1 × 10 ⁻³ to 1 × 1.
It can be seen that when the thickness is 0 ^-1 μm, a good coating state is obtained, and in particular, an excellent coating state is obtained in the range of 5 × 10 ^{−3 to} 5 × 10 ⁻² μm.

Example 6: The cubic BN powder was mixed with T so that the film thickness obtained from the above equation (1) was 1 × 10 ^-2 μm.
iN, TiC, TiCN were coated by reactive sputtering. At this time, the barrel peripheral speed was set to a constant value of 0.1 m / min,
The sputtering output and the substrate temperature were adjusted so that the partial pressure ratio of the reactive gas was maintained at a constant value of 50% and the crystal particle diameter was 10 to 30 nm. The BN powder coated by reactive sputtering was hot isostatically sintered at 2000 ° C., 10,000 atmospheres and 1 hour. The obtained sintered body is subjected to a strength test,
The transverse rupture force was measured. FIG. 8 shows the measurement results. In this example, the uncoated cubic B
A comparative example was prepared by mixing TiN, TiC, and TiCN with N powder and sintering them under the same conditions. As can be seen from the investigation results in FIG. 8, when the coated powder obtained according to the present invention was used as a sintering material, TiN, TiC, TiCN were simply used.
Compared to the sintered cubic BN powder mixed with
It can be seen that the transverse rupture strength has been significantly improved. This is because TiN, TiC, Ti uniformly coated on cubic BN powder
This is considered to be the result of CN sufficiently exerting the action as a binder for connecting the powder particles.

[0025]

As described above, in the present invention, sputtering is performed under the conditions where the crystallite diameter and the coverage are specified in an atmosphere in which the partial pressure ratio of the reaction gas is adjusted to 10 to 70%. In addition, a uniform ceramic coating layer can be formed on the surfaces of various powder particles. The ceramic coating powder obtained in this way completely coats the surface of the ceramic, utilizes the properties such as excellent adhesion between the ceramic layer and the substrate, and has a wide range of coating types and compositions. Since they are selected, they are used in a wide range of fields as additives for sintering, pretreatment agents for sintering materials, pigments for paints and resin moldings, dispersants having excellent catalytic activity, and the like.

[Brief description of the drawings]

FIG. 1 shows an example of an apparatus used for powder sputtering.

FIG. 2 is a photograph showing the structure of cubic BN powder particles uniformly coated with TiN.

FIG. 3 is a photograph showing the structure of cubic BN powder particles coated with TiN unevenly.

FIG. 4 is a graph showing the effect of barrel peripheral speed on film uniformity.

FIG. 5 is a graph showing the effect of a reactive gas partial pressure ratio on film uniformity.

FIG. 6 is a graph showing the effect of crystallite diameter on film uniformity.

FIG. 7 is a graph showing the effect of film thickness on film uniformity.

FIG. 8 is a graph showing that a sintered body obtained by sintering a powder uniformly coated according to the present invention has excellent transverse rupture strength.

[Explanation of symbols]

1: rotating barrel 2: roll 3: motor
4: sputtering source 5: powder raw material 6: heating coil 7: decompression processing chamber
8: Valve 9: Supply pipe 10: Gas introduction pipe 11: Branch pipe
12: Fluid jet mill 13: Circulation pipe 14: Valve 15: Valve 1
6: Solid-gas separation device

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[Procedure amendment]

[Submission date] August 11, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Aki Takeshima 7-1 Takaya Shinmachi, Ichikawa-shi, Chiba Inside Nisshin Steel R & D Co., Ltd. (72) Inventor Yasushi Shirai 7-1 Takaya Shinmachi, Ichikawa-shi, Chiba Nisshin Steel Co., Ltd.

Claims (3)

[Claims] 1. A rotating barrel loaded with powder particles is rotated at a peripheral speed.
Reactive sputtering while rotating at 0.1m / min or more
When coating powder particles with ceramics by the
The partial pressure ratio of the reactive gas in the ring gas is set to 10 to 70%.
And a crystal calculated from the X-ray diffraction peak half width of the coating layer.
Ratio table of fine particles having a diameter of 100 nm or less and being coated
The area is S (m^Two / G), the density of the ceramic to be coated
m (g / m ^Three ), The ideal defined by equation (1)
Assuming that the powder particles are uniformly coated uniformly
The thickness t (μm) is 1 × 10^-3~ 1 × 10^-1It will be in the range of
To form a ceramic coating layer with the coating amount X (mass%)
A method for producing a ceramic coated powder. t = {X / (100 × mx × S)} × 10⁶ ... (1) 2. The method according to claim 1, wherein one or more of N ₂ , O ₂ , and hydrocarbons are used as a reactive gas source. 3. The method for producing a ceramic-coated powder according to claim 1, wherein Ti, Al, Cr, Zr or an alloy or mixture containing these as a main component is used as a target metal.