CA1285433C - Process and apparatus for coating particles with fine powder - Google Patents
Process and apparatus for coating particles with fine powderInfo
- Publication number
- CA1285433C CA1285433C CA000507757A CA507757A CA1285433C CA 1285433 C CA1285433 C CA 1285433C CA 000507757 A CA000507757 A CA 000507757A CA 507757 A CA507757 A CA 507757A CA 1285433 C CA1285433 C CA 1285433C
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- CA
- Canada
- Prior art keywords
- particles
- binder
- process according
- fine powder
- heating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
- C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
- C09C3/06—Treatment with inorganic compounds
- C09C3/063—Coating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
- B01J2/003—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic followed by coating of the granules
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
- B01J2/12—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic in rotating drums
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/17—Metallic particles coated with metal
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/18—Non-metallic particles coated with metal
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
- C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
- C04B41/4584—Coating or impregnating of particulate or fibrous ceramic material
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
- C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
- C09C1/62—Metallic pigments or fillers
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
- C09C3/00—Treatment in general of inorganic materials, other than fibrous fillers, to enhance their pigmenting or filling properties
- C09C3/006—Combinations of treatments provided for in groups C09C3/04 - C09C3/12
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/30—Particle morphology extending in three dimensions
- C01P2004/32—Spheres
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
Abstract
ABSTRACT OF THE DISCLOSURE
There is disclosed a process for coating particles, such as ceramic and metal cores, with fine powder, such as ceramic, metal or carbon powder. The process comprises providing a mixture comprising the particles and a binder which is capable of slowly melting to viscous state. Then the mixture is tumbled while slowly heating it to enable the binder to reach the viscous state while allowing the particles to be substantially covered with the binder. The next step includes cooling the mixture to about room temperature and thereafter breaking up the particles that may have agglomerated during the tumbling and heating to give individual particles covered with the binder. As a final step, the fine powder is added to the individual binder covered particles and the mixture is tumbled and heated again to the viscous state under conditions effective to provide a coating of the fine powder on the particles.
Additional heating may be carried out to remove the binder and leave particles exclusively coated with the fine powder.
Apparatus including a rotating cylinder, heating and cooling means. The resulting product has a more uniform micro-structure and higher bonding strength than a product resulting from a conventional mixing of ingredients.
There is disclosed a process for coating particles, such as ceramic and metal cores, with fine powder, such as ceramic, metal or carbon powder. The process comprises providing a mixture comprising the particles and a binder which is capable of slowly melting to viscous state. Then the mixture is tumbled while slowly heating it to enable the binder to reach the viscous state while allowing the particles to be substantially covered with the binder. The next step includes cooling the mixture to about room temperature and thereafter breaking up the particles that may have agglomerated during the tumbling and heating to give individual particles covered with the binder. As a final step, the fine powder is added to the individual binder covered particles and the mixture is tumbled and heated again to the viscous state under conditions effective to provide a coating of the fine powder on the particles.
Additional heating may be carried out to remove the binder and leave particles exclusively coated with the fine powder.
Apparatus including a rotating cylinder, heating and cooling means. The resulting product has a more uniform micro-structure and higher bonding strength than a product resulting from a conventional mixing of ingredients.
Description
This invention relates to a procèss and an apparatus for coating particles such as ceramic and metal cores, with fine powder, such as metal or ceramic powder.
More particularly, the present invention is concerned with a process of preparing cores coated with fine powder, the resulting product having a more uniform microstructure and higher bonding strength than a product resulting from a conventional mixing of the components.
In the production of composites containing a dispersion of particles, a uniform dispersion of particles and a strong adhesion of these particles to the matrix are required for the making of high performance composites.
Various techniques have been reported for the production of metal or ceramic coating on metal or ceramic cores:
1. Physical or chemical vapor deposition, 2. Electro- or electroless plating, 3. Precipitation of salts or hydroxides from solutions and their reduction or decomposition:
More particularly, the present invention is concerned with a process of preparing cores coated with fine powder, the resulting product having a more uniform microstructure and higher bonding strength than a product resulting from a conventional mixing of the components.
In the production of composites containing a dispersion of particles, a uniform dispersion of particles and a strong adhesion of these particles to the matrix are required for the making of high performance composites.
Various techniques have been reported for the production of metal or ceramic coating on metal or ceramic cores:
1. Physical or chemical vapor deposition, 2. Electro- or electroless plating, 3. Precipitation of salts or hydroxides from solutions and their reduction or decomposition:
4. Surface reaction of particles, and 5. Solid state sintering of particles.
Vapor deposition gives tight coatings of metals and ceramics (oxides, carbides, nitrides etc.), however, thick coatings are difficult to make or take a long time.
Furthermore, these kinds of coatings are limited to some materials having appropriate evaporation or reaction rate.
Plating is a popular method but the type of coating is limited to metals such as Ni, Co, Fe, Cr, Cu, etc., and the coating is usually thin. Precipitation based on decomposition techniques is applicable only to coatings of oxides which ~2~S433 can be reduced by hydrogen. Surface reaction leads to protective layers on the surface of particles by oxidation, carburization, nitridation and so on. However, these techniques are also limited by the kind of coating material and the thickness. Sintering is based on the adhesion of powders on the surface of the particles. In this case the uniformity of coatings seems to be a problem because it depends on the condition used for the mixing of the particles and on the diffusion of the constituents.
U.S. Patent No. 3,492,379, issued January 27, 1970, inventor G.B. Redding discloses particles of nuclear fuel which have been coated with a thermosetting resin having powdered graphite incorporated therein. Before coating, powdered graphite is mixed with the resin powder to make the mixed powders flowable without difficulty. The coating is essentially based on the set resin having carbon particles dispersed therein and there is no possibility to remove the resin while retaining only the carbon particles on the particles of nuclear fuels.
It i8 an object of the present invention to provide a process in which there is no limitation in terms of cores and coating materials.
It is another object of the present invention to provide a process for coating particles which enables to achieve a very thick coating of fine powder.
It is another object of the present invention to provide a coating process which is simple and at the same time gives tough coatings, consolidated around cores.
It i8 another object of the present invention to provide coated cores which are not only useful for making ~285433 composites containing a dispersion of particles, but may alqo be used to make porous composites and plasma or flame spray composite powders.
In accordance with the present invention, there is provided a process for coating particles with fine powder which comprises providing a mixture comprising the particles and a binder which is capable of slowly melting to viscous state. Then, the mixture is tumbled while slowly heating same to enable the binder to reach the viscous state while allowing the particles to be substantially covered with the binder. The next step includes cooling the mixture substantially to room temperature and thereafter breaking up particles that may have agglomerated during the tumbling and heating, to give individual particles covered with the binder. As a final step, the fine powder is added to the individual particles covered with the binder and the mixture is tumbled and heated again to the viscous state under conditions effective to provide a coating of the fine powder on the particles.
In accordance with a preferred embodiment of the present invention, the coated particles could be heated further to remove the binder leaving the particles exclusively coated with the fine powder.
The particles preferably consist of plaqtic or ceramic cores, for example, they are particles of A1203 and SiC or any suitable pla~tic material, or consist of metallic cores, such as particles of Fe, Ni, Co, Cr, Cu, Al, and alloys thereof.
The particles have a preferred mean diameter of about 40-750 ~m.
In accordance with a preferred em~odiment of the ~28S433 invention, the fine powder includes fine metal powders, a ceram~c powder, carban powder, or plastic powder.
They are preferably selected from the group consisting of Al, Cr, Fe, Ni, Co, Mo, Ti, Si, Cu and W powders and the like and have a preferred diameter of 1-10 ~Im.
In accordance with a preferred embodiment of the invention, a surfactant is added to fine powder to inhibit its agglomeration when coating the particles with the fine powder. The preferred surfactant comprises aluminum stearate.
Although any suitable binder can be used the preferred binder is polyethylene glycol or paraffin, such as CARBOWAX (Fisher Scientific Polyethylene Glycol 3350 technical grade) and PARVANTM 52 and 67 (Esso Imperial oil paraffin).
In accordance with a preferred embodiment of the invent-ion tumbling--is preferably carried-out in a rotating cylindrical container which is tilted with respect to the horizontal axis.
The ranges of ingredients may vary to a large extent. However, it has been found suitable to add about 5 to about 30 volume percent of the fine powder with respect to the volume of particles, preferably about 10 to about 15 volume percent.
On the other hand, the mixture of particles and binder may comprise about 0.5 to about 5 weight percent binder, preferably about 1 to 2 weight percent binder.
Both heating steps are usually carried out up to a temperature of about 80C, preferably about 60C.
Although any cooling means may be used, it is preferred that cooling be carried out by air blowing while the cylinder is rotating.
~ 285433 Whenever a surfactant i9 used, it is preferably added in an amount less than about 0.5 weight percent, most preferably less than about 0.1 weight percent.
According to the inventi~n, an apparatus for coating particles with fine powder may comprise a frame, a rotating cylinder mounted on the frame tilted with respect to the horizontal axis, an inlet in the cylinder for introducing material therein, means to cause rotation of the rotating cylinder, means for slowly heating the rotating cylinder, and means for cooling the heated content of said rotating cylinder to room temperature.
The invention is illustrated by means of the following drawing, in which:
FIGURE 1 is a schematic illustration of an apparatus adapted to coat particles according to the invention:
~ ~ ~FIGURE 2 shows~eight A12O3 cares coated with different metal powders, FIGURE 3 shows two Ni-coated A12O3 cores and two Ni-coated SiC cores.
Various experiments were made using different materials, conditions and apparatus and these will f;rst be discus~ed. It is understood however, that this invention is not to be restricted by the examples and that it should only be limited by the appended claims.
MATERIALS
A12O3 (Matfer Inc.: CorundumTM ~D grit)~ and Sic (Norton: CarborundumTM 24 grit, Fisher Scientific:
CarborundumTM 150 and 320 grit) particle~ were used as cores.
These cèramic cores have an irregular shape.
Al, Cr, Co, Mo and W (Cerac Inc.), Al tAlcan Aluminum Corp., Grade 105~, Ni (Sherritt Gordon Mines Limited, Grade NF-lM) and Fe (Q~ebec Metàl Powd~rs, Atomet 95) powders _ 5 _ ~ 285a~33 were used as coating constituents. Al (Cerac) powder contains flake. Al (Alcan) and Fe powders are nodular.
Cr, Ni, Co, Mo and W powders are granular.
Carbowax (Fisher Scientific, Polyethylene glycol 3350 Technical grade) and paraffin (Esso Imperial Oil, Parvan 52 and 67) were used as binders. The melting point of CarbowaxT is 58C and its freezing point is 48C, according to the measurement made by the inventors. Paraffins (ESSO
Imperial Oil: ParvanT 52 and 67) have a melting point of 52C
and 67C, respectively. Al-stearate (Sargent-Welch Scientific, technical grade) may be added to fine metal powders in order to prevent their agglomeration.
APPARATUS
A cylindrical container, made from acrylic glass, was used for coating. The apparatus is schematically illustrated in Fig. 1. It consists of a cylinder which is tilted with respect to the horizontal axis 3. Heating means 5 are provided to heat the content of the cylinder to a suitable temperature and air cooling means 7 enable to cool the heated content to room temperature. During the rotation, the powder mass 9 move~ in both circular and axial directions along the length of the cylinder which reduces the tendency of powder accumulation at the ends of the cylinder, often causing the formation of large agglomerates.
Two cylinders with different sizes were used:
cy~inder I (45 mm I.D. x 95 mm) and cylinder II (50 mm I.D. x 125 mm). The cylinder I was heated by means of an air blower and cylinder II by means of an electric heating band. The temperature inside the cylinder was measured with a Cu/Fe-Ni thermocouple.
Vapor deposition gives tight coatings of metals and ceramics (oxides, carbides, nitrides etc.), however, thick coatings are difficult to make or take a long time.
Furthermore, these kinds of coatings are limited to some materials having appropriate evaporation or reaction rate.
Plating is a popular method but the type of coating is limited to metals such as Ni, Co, Fe, Cr, Cu, etc., and the coating is usually thin. Precipitation based on decomposition techniques is applicable only to coatings of oxides which ~2~S433 can be reduced by hydrogen. Surface reaction leads to protective layers on the surface of particles by oxidation, carburization, nitridation and so on. However, these techniques are also limited by the kind of coating material and the thickness. Sintering is based on the adhesion of powders on the surface of the particles. In this case the uniformity of coatings seems to be a problem because it depends on the condition used for the mixing of the particles and on the diffusion of the constituents.
U.S. Patent No. 3,492,379, issued January 27, 1970, inventor G.B. Redding discloses particles of nuclear fuel which have been coated with a thermosetting resin having powdered graphite incorporated therein. Before coating, powdered graphite is mixed with the resin powder to make the mixed powders flowable without difficulty. The coating is essentially based on the set resin having carbon particles dispersed therein and there is no possibility to remove the resin while retaining only the carbon particles on the particles of nuclear fuels.
It i8 an object of the present invention to provide a process in which there is no limitation in terms of cores and coating materials.
It is another object of the present invention to provide a process for coating particles which enables to achieve a very thick coating of fine powder.
It is another object of the present invention to provide a coating process which is simple and at the same time gives tough coatings, consolidated around cores.
It i8 another object of the present invention to provide coated cores which are not only useful for making ~285433 composites containing a dispersion of particles, but may alqo be used to make porous composites and plasma or flame spray composite powders.
In accordance with the present invention, there is provided a process for coating particles with fine powder which comprises providing a mixture comprising the particles and a binder which is capable of slowly melting to viscous state. Then, the mixture is tumbled while slowly heating same to enable the binder to reach the viscous state while allowing the particles to be substantially covered with the binder. The next step includes cooling the mixture substantially to room temperature and thereafter breaking up particles that may have agglomerated during the tumbling and heating, to give individual particles covered with the binder. As a final step, the fine powder is added to the individual particles covered with the binder and the mixture is tumbled and heated again to the viscous state under conditions effective to provide a coating of the fine powder on the particles.
In accordance with a preferred embodiment of the present invention, the coated particles could be heated further to remove the binder leaving the particles exclusively coated with the fine powder.
The particles preferably consist of plaqtic or ceramic cores, for example, they are particles of A1203 and SiC or any suitable pla~tic material, or consist of metallic cores, such as particles of Fe, Ni, Co, Cr, Cu, Al, and alloys thereof.
The particles have a preferred mean diameter of about 40-750 ~m.
In accordance with a preferred em~odiment of the ~28S433 invention, the fine powder includes fine metal powders, a ceram~c powder, carban powder, or plastic powder.
They are preferably selected from the group consisting of Al, Cr, Fe, Ni, Co, Mo, Ti, Si, Cu and W powders and the like and have a preferred diameter of 1-10 ~Im.
In accordance with a preferred embodiment of the invention, a surfactant is added to fine powder to inhibit its agglomeration when coating the particles with the fine powder. The preferred surfactant comprises aluminum stearate.
Although any suitable binder can be used the preferred binder is polyethylene glycol or paraffin, such as CARBOWAX (Fisher Scientific Polyethylene Glycol 3350 technical grade) and PARVANTM 52 and 67 (Esso Imperial oil paraffin).
In accordance with a preferred embodiment of the invent-ion tumbling--is preferably carried-out in a rotating cylindrical container which is tilted with respect to the horizontal axis.
The ranges of ingredients may vary to a large extent. However, it has been found suitable to add about 5 to about 30 volume percent of the fine powder with respect to the volume of particles, preferably about 10 to about 15 volume percent.
On the other hand, the mixture of particles and binder may comprise about 0.5 to about 5 weight percent binder, preferably about 1 to 2 weight percent binder.
Both heating steps are usually carried out up to a temperature of about 80C, preferably about 60C.
Although any cooling means may be used, it is preferred that cooling be carried out by air blowing while the cylinder is rotating.
~ 285433 Whenever a surfactant i9 used, it is preferably added in an amount less than about 0.5 weight percent, most preferably less than about 0.1 weight percent.
According to the inventi~n, an apparatus for coating particles with fine powder may comprise a frame, a rotating cylinder mounted on the frame tilted with respect to the horizontal axis, an inlet in the cylinder for introducing material therein, means to cause rotation of the rotating cylinder, means for slowly heating the rotating cylinder, and means for cooling the heated content of said rotating cylinder to room temperature.
The invention is illustrated by means of the following drawing, in which:
FIGURE 1 is a schematic illustration of an apparatus adapted to coat particles according to the invention:
~ ~ ~FIGURE 2 shows~eight A12O3 cares coated with different metal powders, FIGURE 3 shows two Ni-coated A12O3 cores and two Ni-coated SiC cores.
Various experiments were made using different materials, conditions and apparatus and these will f;rst be discus~ed. It is understood however, that this invention is not to be restricted by the examples and that it should only be limited by the appended claims.
MATERIALS
A12O3 (Matfer Inc.: CorundumTM ~D grit)~ and Sic (Norton: CarborundumTM 24 grit, Fisher Scientific:
CarborundumTM 150 and 320 grit) particle~ were used as cores.
These cèramic cores have an irregular shape.
Al, Cr, Co, Mo and W (Cerac Inc.), Al tAlcan Aluminum Corp., Grade 105~, Ni (Sherritt Gordon Mines Limited, Grade NF-lM) and Fe (Q~ebec Metàl Powd~rs, Atomet 95) powders _ 5 _ ~ 285a~33 were used as coating constituents. Al (Cerac) powder contains flake. Al (Alcan) and Fe powders are nodular.
Cr, Ni, Co, Mo and W powders are granular.
Carbowax (Fisher Scientific, Polyethylene glycol 3350 Technical grade) and paraffin (Esso Imperial Oil, Parvan 52 and 67) were used as binders. The melting point of CarbowaxT is 58C and its freezing point is 48C, according to the measurement made by the inventors. Paraffins (ESSO
Imperial Oil: ParvanT 52 and 67) have a melting point of 52C
and 67C, respectively. Al-stearate (Sargent-Welch Scientific, technical grade) may be added to fine metal powders in order to prevent their agglomeration.
APPARATUS
A cylindrical container, made from acrylic glass, was used for coating. The apparatus is schematically illustrated in Fig. 1. It consists of a cylinder which is tilted with respect to the horizontal axis 3. Heating means 5 are provided to heat the content of the cylinder to a suitable temperature and air cooling means 7 enable to cool the heated content to room temperature. During the rotation, the powder mass 9 move~ in both circular and axial directions along the length of the cylinder which reduces the tendency of powder accumulation at the ends of the cylinder, often causing the formation of large agglomerates.
Two cylinders with different sizes were used:
cy~inder I (45 mm I.D. x 95 mm) and cylinder II (50 mm I.D. x 125 mm). The cylinder I was heated by means of an air blower and cylinder II by means of an electric heating band. The temperature inside the cylinder was measured with a Cu/Fe-Ni thermocouple.
- 6 _ ~85433 COATING PROCESS
The general procedure consists of adding particle~ -to be coated and the binder to container 1. The container is first rotated followed by heating until the binder becomes viscous. Then the mixture is cooled and the agglomerated particles are broken up by adding balls to the container.
The fine powder is then added to the particles in the container and the mixture is heated to provide a coating of the fine powder on the particles. If particles coated with fine powder, without binder is required, binder could be removed by heating. In some cases, Al-stearate i~ added to prevent the agglomeration of the fine powder.
Binder-coated ceramic cores and metal powders were charged into the cylinder. The cylinder was then heated and rotated simultaneously. The following process parameters were used:
Content of binder : 5 wt% (based on caramic cores).
Charge of metal ~ icleos 20 to 60 vol.% (Me/Me ~ ceramics).
Filling of cylinder : 5 to 10 vol.%.
Tilt angle : 30 or 45.
Rotation speed : 40 rpm.
Temperature : 60 to 85C.
Heating time: : 300 s for cylinder I: 600 s for cylinder II.
Agglutination time : 300 s for cylinder I, 600 s for cylinder II.
Cooling : Air blowing while cylinder rotating.
Metal-coated ceramic cores were separated from free metal powders by sieving. The proportion of the coating was determined by weight measurements.
~.285433 The size distribution of ceramic cores wa~ measured by sieving. The ~ize of metal powders was determined with the HIAC particle size analyser PA-720 (Pacific Scientific).
Particle shape and microstructure of coatings were observed by SEM.
A1203 (60 grit) cores were coated with different metal powders. The particle size of metal powders and the proportion of the coating are shown in Table 1. The volume mean diameter of metal particles was between 5 and 10 ~m.
The quantity of the metal powder charge was kept constant on a volume basis in order to make comparisons on the efficiency of the coating process. The typical appearance of the resulting coated cores is shown in Fig. 2.
Al (Cerac) powder gave perfect coating on A1203 ;; cores. An increase of the Al powder charge slightly increased the amount of the coating at the expense of its quality since it became fluffy owing to the poor adhesion of Al powders. The eoating with Al (Alcan) particles was also perfect and all ~ ~ of th~e AI charged was conQumed to form the coating. Cr ; 20 powder gave a fairly large amount of coating but some A12O3 ~cor s had defects. Ni powders yielded a very small amount of coating with many defects. Co and Mo powders showed non ~uniform coating growth: some A1203 cores had defects whereas ;the others became spherical with a thick coating, growing up to about 2 mm in diameter. W particles gave a thick coating which was nearly perfect.
~: :
:
, : ~ .
~ - - 8 -, TABLE I RESULTS OF AGGLUTINATION COATING ** ON A1203 CORES WITH VARIOUS METAL POWDERS.
Metal Volume Charge Metal content Powder mean(g) Me/(Me + A1203) Diameter (Vol. %) (ym) A1203~ Metal* Charge Product .
Al 10.4 ZO 3 19 11 (Cerac) Al 10.4 20 6 31 14 (Cerac) Al 8.3 20 6 31 31 (Alcan) Cr 6.1 20 16 32 25 Cr* _ 20 16 32 24 Ni 8.7 20 20 32 5 Co 7.1 20 20 32 16 Mo 7.1 20 23 32 18 W 4.6 20 43 31 2S
* Cr particles above 38 ym were removed by sieving.
Sample : Al O (60 grit, Carbowax 5 Wt%) .
Me~a~ particle3 (no binder).
* Container : cylinder II, Tilt angle: 45.
Rotation speed : 40 rpm, Temp.: 70C, Time : 10 min.
~.285433 The coating efficiencies of metal powders are in the following sequence: Al (Alcan), Cr = W, Co = Mo, Al (Cerac), Ni. Al (Cerac) powders yielded perfect coating in spite of its low amount which probably resulted from their flaky particles. Al flakès were agglutinated in lamellae on A12O3 surface. Since Cr powder contained may large particles, the surface of the coating was rough. Even if large metal particles above 38 um were removed, the amount of Cr coating changed little (Table 1). It has been observed that ~r particle of about 50 ~m diameter can be agglutinated on 250 ~m A12O3 cores.
The effects of paraffin and Carbowax binders were studied with the A12O3-Al (Alcan) system. The results are shown in Table II. The proportion of coating produced during the agglutination i8 about the same for both binders. Most of Al powder was agglutinated onto A12O3 cores forming a perfect coating. A similar effect was also observed with Co and Mo.
A12O3 cores coated with paraffin have lower flowing charac-teristics.
TABLE II EFFECT OF PARAFFIN AND CARBoWAX IN
THE A12O3-AL SYSTEM.
BinderMeltingMetal content pointAl/(Al + A12O ) Ob~ervation (C) (vol. %) 3 Charge* Product Paraffin 52 48 47 Perfect coating (Cerac) including large Paraffin 67 48 47 (Cerac) 30Carbowax 58 48 47 Perfect coating * Sample: A12O3 (60 grit, binder 5 wt%) 20 g, Al (Alcan, no binder) 12 g.
The other conditions were the same as in Table 1.
~285433 TABLE III EFFECT OF THE SIZE OF CERAMIC CORES ON THE
AGGLUTINA~ION OF Al AND Ni.
Ceramic Core Temp. Charge * Metal content (g) Me/(Me+ Ceramic) Core size (Vol. %) (ym) (~C) A123 SiC Ni Al Charge Product (60 grLt1 180- 70 20 _20 _ 32 5 SiC 500_ 60 _ 10 12_ 31 .19 (24 grit) 1000 SiC 500- 65 _ 10 _ 5 38 38 (24 grit) 1000 SiC 500- 65 _ 10 10 55 55 (24 grit) 1000 SiC 75- 65 _ 10 _ 10 55 49 (150grit) 106*
SiC 75- 80 _ 10 _ 10 55 53 (lSOgrit) 106*
SiC 32- 65 _ 10 _ 10 55 39 (320grit) 45*
: SiC 32- 85 _ 10 _ 10 55 35 (320grit) 45 _ * Sample : A1203 (60 grit) and SiC (24, 150, 320 grit) (Carbowax 5 wt%). Ni and Al (Alcan) (no binder).
Container : cylinder I for SiC (24 grit) - Ni system, cylinder II for the others.
Tilt angle : 45, rotation ~peed: 40 rpm, Time: S-10 min.
~Z85433 The coating of nickel is one of the most difficult to perform. The effects of paraffin, Carbowax and Al-stearate added to the Ni powder were thus investigated with A1203 cores.
The results are shown in Table IV. For a 1 wt% addition of paraffin or Carbowax to Ni powder, the increase in the mass of the Ni coating was small for paraffin-doped A1203 cores. The contents of paraffin and Carbowax in the Ni powder were increased up to 5 wt% for Carbowax- doped A1203 cores. In this case, Ni coating apparently increased, but the Ni coa~ing contained defects and the product included agglomerates of Ni powder. The addition of Al-stearate to the Ni powder increased the thickness of the coating. However, the Ni coating on paraffin-doped A1203 cores was imperfect. On the other hand, Ni coating on Carbowax-doped A1203 cores became nearly perfect for Ni coating above 9 vol.%.
~85433 'c æ~ ~ ~ a O
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~ ~8S4~3 With no addition of Al-stearate many coating defects were observed on the edges of irregular shape cores, owing to the fact that edges are subjected to collisions and are left uncoated. On the other hand, Al-stearate-doped Ni powder perfectly covered irregular A12O3 cores, even their edges.
When undoped Fe particles were used, the resulting coating corresponded to 24 vol. % and defects were observed on the edges. On the other hand, the addition of Al-stearate to Fe powder reduced the Fe coating to 15 vol.%, but Al-stearate doped Fe powder perfectly covered SiC cores.
The addition of Al-stearate to Ni powder is effective only up to 0.2 wt% and no further increase of the ~i coating is observed above this value.
The effect of the addition of Al-stearate to metal powder is noteworthy. Al-stearate is a surfactant and, when the molecules are adsorbed on metal particles, the long carbon chains inhibit the agglomeration of the metal powder.
In the coating according to the invention, therefore, Al-stearate may improve the dispersion of metal powder giving a perfect coating on ceramic surface of cores including particle edges.
''il'
The general procedure consists of adding particle~ -to be coated and the binder to container 1. The container is first rotated followed by heating until the binder becomes viscous. Then the mixture is cooled and the agglomerated particles are broken up by adding balls to the container.
The fine powder is then added to the particles in the container and the mixture is heated to provide a coating of the fine powder on the particles. If particles coated with fine powder, without binder is required, binder could be removed by heating. In some cases, Al-stearate i~ added to prevent the agglomeration of the fine powder.
Binder-coated ceramic cores and metal powders were charged into the cylinder. The cylinder was then heated and rotated simultaneously. The following process parameters were used:
Content of binder : 5 wt% (based on caramic cores).
Charge of metal ~ icleos 20 to 60 vol.% (Me/Me ~ ceramics).
Filling of cylinder : 5 to 10 vol.%.
Tilt angle : 30 or 45.
Rotation speed : 40 rpm.
Temperature : 60 to 85C.
Heating time: : 300 s for cylinder I: 600 s for cylinder II.
Agglutination time : 300 s for cylinder I, 600 s for cylinder II.
Cooling : Air blowing while cylinder rotating.
Metal-coated ceramic cores were separated from free metal powders by sieving. The proportion of the coating was determined by weight measurements.
~.285433 The size distribution of ceramic cores wa~ measured by sieving. The ~ize of metal powders was determined with the HIAC particle size analyser PA-720 (Pacific Scientific).
Particle shape and microstructure of coatings were observed by SEM.
A1203 (60 grit) cores were coated with different metal powders. The particle size of metal powders and the proportion of the coating are shown in Table 1. The volume mean diameter of metal particles was between 5 and 10 ~m.
The quantity of the metal powder charge was kept constant on a volume basis in order to make comparisons on the efficiency of the coating process. The typical appearance of the resulting coated cores is shown in Fig. 2.
Al (Cerac) powder gave perfect coating on A1203 ;; cores. An increase of the Al powder charge slightly increased the amount of the coating at the expense of its quality since it became fluffy owing to the poor adhesion of Al powders. The eoating with Al (Alcan) particles was also perfect and all ~ ~ of th~e AI charged was conQumed to form the coating. Cr ; 20 powder gave a fairly large amount of coating but some A12O3 ~cor s had defects. Ni powders yielded a very small amount of coating with many defects. Co and Mo powders showed non ~uniform coating growth: some A1203 cores had defects whereas ;the others became spherical with a thick coating, growing up to about 2 mm in diameter. W particles gave a thick coating which was nearly perfect.
~: :
:
, : ~ .
~ - - 8 -, TABLE I RESULTS OF AGGLUTINATION COATING ** ON A1203 CORES WITH VARIOUS METAL POWDERS.
Metal Volume Charge Metal content Powder mean(g) Me/(Me + A1203) Diameter (Vol. %) (ym) A1203~ Metal* Charge Product .
Al 10.4 ZO 3 19 11 (Cerac) Al 10.4 20 6 31 14 (Cerac) Al 8.3 20 6 31 31 (Alcan) Cr 6.1 20 16 32 25 Cr* _ 20 16 32 24 Ni 8.7 20 20 32 5 Co 7.1 20 20 32 16 Mo 7.1 20 23 32 18 W 4.6 20 43 31 2S
* Cr particles above 38 ym were removed by sieving.
Sample : Al O (60 grit, Carbowax 5 Wt%) .
Me~a~ particle3 (no binder).
* Container : cylinder II, Tilt angle: 45.
Rotation speed : 40 rpm, Temp.: 70C, Time : 10 min.
~.285433 The coating efficiencies of metal powders are in the following sequence: Al (Alcan), Cr = W, Co = Mo, Al (Cerac), Ni. Al (Cerac) powders yielded perfect coating in spite of its low amount which probably resulted from their flaky particles. Al flakès were agglutinated in lamellae on A12O3 surface. Since Cr powder contained may large particles, the surface of the coating was rough. Even if large metal particles above 38 um were removed, the amount of Cr coating changed little (Table 1). It has been observed that ~r particle of about 50 ~m diameter can be agglutinated on 250 ~m A12O3 cores.
The effects of paraffin and Carbowax binders were studied with the A12O3-Al (Alcan) system. The results are shown in Table II. The proportion of coating produced during the agglutination i8 about the same for both binders. Most of Al powder was agglutinated onto A12O3 cores forming a perfect coating. A similar effect was also observed with Co and Mo.
A12O3 cores coated with paraffin have lower flowing charac-teristics.
TABLE II EFFECT OF PARAFFIN AND CARBoWAX IN
THE A12O3-AL SYSTEM.
BinderMeltingMetal content pointAl/(Al + A12O ) Ob~ervation (C) (vol. %) 3 Charge* Product Paraffin 52 48 47 Perfect coating (Cerac) including large Paraffin 67 48 47 (Cerac) 30Carbowax 58 48 47 Perfect coating * Sample: A12O3 (60 grit, binder 5 wt%) 20 g, Al (Alcan, no binder) 12 g.
The other conditions were the same as in Table 1.
~285433 TABLE III EFFECT OF THE SIZE OF CERAMIC CORES ON THE
AGGLUTINA~ION OF Al AND Ni.
Ceramic Core Temp. Charge * Metal content (g) Me/(Me+ Ceramic) Core size (Vol. %) (ym) (~C) A123 SiC Ni Al Charge Product (60 grLt1 180- 70 20 _20 _ 32 5 SiC 500_ 60 _ 10 12_ 31 .19 (24 grit) 1000 SiC 500- 65 _ 10 _ 5 38 38 (24 grit) 1000 SiC 500- 65 _ 10 10 55 55 (24 grit) 1000 SiC 75- 65 _ 10 _ 10 55 49 (150grit) 106*
SiC 75- 80 _ 10 _ 10 55 53 (lSOgrit) 106*
SiC 32- 65 _ 10 _ 10 55 39 (320grit) 45*
: SiC 32- 85 _ 10 _ 10 55 35 (320grit) 45 _ * Sample : A1203 (60 grit) and SiC (24, 150, 320 grit) (Carbowax 5 wt%). Ni and Al (Alcan) (no binder).
Container : cylinder I for SiC (24 grit) - Ni system, cylinder II for the others.
Tilt angle : 45, rotation ~peed: 40 rpm, Time: S-10 min.
~Z85433 The coating of nickel is one of the most difficult to perform. The effects of paraffin, Carbowax and Al-stearate added to the Ni powder were thus investigated with A1203 cores.
The results are shown in Table IV. For a 1 wt% addition of paraffin or Carbowax to Ni powder, the increase in the mass of the Ni coating was small for paraffin-doped A1203 cores. The contents of paraffin and Carbowax in the Ni powder were increased up to 5 wt% for Carbowax- doped A1203 cores. In this case, Ni coating apparently increased, but the Ni coa~ing contained defects and the product included agglomerates of Ni powder. The addition of Al-stearate to the Ni powder increased the thickness of the coating. However, the Ni coating on paraffin-doped A1203 cores was imperfect. On the other hand, Ni coating on Carbowax-doped A1203 cores became nearly perfect for Ni coating above 9 vol.%.
~85433 'c æ~ ~ ~ a O
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*
~ ~8S4~3 With no addition of Al-stearate many coating defects were observed on the edges of irregular shape cores, owing to the fact that edges are subjected to collisions and are left uncoated. On the other hand, Al-stearate-doped Ni powder perfectly covered irregular A12O3 cores, even their edges.
When undoped Fe particles were used, the resulting coating corresponded to 24 vol. % and defects were observed on the edges. On the other hand, the addition of Al-stearate to Fe powder reduced the Fe coating to 15 vol.%, but Al-stearate doped Fe powder perfectly covered SiC cores.
The addition of Al-stearate to Ni powder is effective only up to 0.2 wt% and no further increase of the ~i coating is observed above this value.
The effect of the addition of Al-stearate to metal powder is noteworthy. Al-stearate is a surfactant and, when the molecules are adsorbed on metal particles, the long carbon chains inhibit the agglomeration of the metal powder.
In the coating according to the invention, therefore, Al-stearate may improve the dispersion of metal powder giving a perfect coating on ceramic surface of cores including particle edges.
''il'
Claims (28)
1. A process for coating ceramic or metallic particles with fine powder selected from metal powders, ceramic powders, and carbon or plastic powders which comprises:
a. providing a mixture comprising said particles and a binder which is capable of slowly melting to viscous state at temperatures up to about 85°C, b. tumbling said mixture while slowly heating same to enable said binder to reach said viscous state while allowing said particles to be substantially covered with said binder, c. cooling the mixture substantially to room temperature and thereafter breaking up agglomerates that have formed during said tumbling and heating, to give individual particles covered with said binder, d. adding said fine powder to said individual particles covered with said binder and tumbling and heating again to said viscous state under conditions effective to provide a coating of said fine powder on said particles.
a. providing a mixture comprising said particles and a binder which is capable of slowly melting to viscous state at temperatures up to about 85°C, b. tumbling said mixture while slowly heating same to enable said binder to reach said viscous state while allowing said particles to be substantially covered with said binder, c. cooling the mixture substantially to room temperature and thereafter breaking up agglomerates that have formed during said tumbling and heating, to give individual particles covered with said binder, d. adding said fine powder to said individual particles covered with said binder and tumbling and heating again to said viscous state under conditions effective to provide a coating of said fine powder on said particles.
2. Process according to claim 1, which further comprises:
e. heating said coated particles to remove said binder leaving said particles exclusively coated with said fine powder.
e. heating said coated particles to remove said binder leaving said particles exclusively coated with said fine powder.
3. Process according to claim 1, wherein said particles consist of ceramic cores selected from the group consisting of particles of oxides, borides, nitrides, silicides and carbides.
4. Process according to claim 1, wherein said particles consist of metallic cores selected from Fe, Ni, Co, Cr, Cu, Al and alloys thereof.
5. Process according to claim 1, wherein said particles have a mean diameter of about 40-750 µm.
6. Process according to claim 1, wherein said fine powder is selected from the group consisting of fine metal powders.
7. Process according to claim 1, wherein said fine powder is a ceramic powder.
8. Process according to claim 1, wherein said fine powder is carbon powder.
9. Process according to claim 1, wherein said fine powder is plastic powder.
10. Process according to claim 6, wherein said fine metal powders are selected from the group consisting of Al, Cr, Fe, Ni, Co, Mo, Ti, Si, Cu and W.
11. Process according to claim 6, wherein said fine metal powders have a mean diameter of 5-10 µm.
12. Process according to claim 1, which comprises adding a surfactant to said fine powder to inhibit agglomer-ation thereof when coating said particles with said fine powder.
13. Process according to claim 12, wherein said surfactant comprises aluminum stearate.
14. Process according to claim 1, wherein said binder is selected from the group consisting of polyethylene glycol and paraffin.
15. Process according to claim 1, wherein said tumbling is carried out in a rotating cylindrical container which is tilted with respect to horizontal axis.
16. Process according to claim 1, which comprises adding about 5 to about 30 volume percent of said fine powder with respect to the volume of said particles.
17. Process according to claim 16, which comprises adding about 10 to about 15 volume percent of said fine powder with respect to the volume of said particles.
18. Process according to claim 1, wherein the mixture of particles and binder comprises about 0.5 to about 5 weight percent binder.
19. Process according to claim 18, wherein said mixture comprises about 1 to 2 weight percent binder.
20. Process according to claim 1, wherein heating in steps b. and c. is carried out up to a temperature of about 80°C.
21. Process according to claim 1, wherein heating is carried out with a heat-exchange jacket.
22. Process according to claim 20, wherein said heating is carried out up to a temperature of about 60°C.
23. Process according to claim 15, wherein said cooling is carried out by air blowing while said cylinder is rotating.
24. Process according to claim 12, which comprises adding less than about 0.5 weight percent surfactant.
25. Process according to claim 24, which comprises adding less than about 0.1 weight percent surfactant.
26. A process of coating ceramic particles with fine metallic powder which comprises:
a. providing a mixture comprising ceramic cores selected from the group consisting of Al2O3 and SiC particles, and a binder selected from the group consisting of poly-ethylene glycol and paraffin, said binder being present in an amount of about 0.5 to about 5 weight percent of said ceramic cores, said binder being capable of reaching viscous state, b. tumbling said mixture in a rotating cylindrical container which is tilted with respect to horizontal axis, while heating said mixture to a temperature up to about 80°C
to enable said binder to reach said viscous state, and allowing said particles to be substantially covered with said binder, c. cooling the mixture of binder covered particles substantially to room temperature and thereafter breaking up particles that may have agglomerated during said tumbling and heating by tumbling same with ball means, to give individual particles covered with said binder, d. adding a fine metal powder selected from the group consisting of Al, Cr, Fe, Ni, Co, Mo and W to said individual particles covered with binder and tumbling and heating again in said rotating cylindrical container at a temperature up to about 80°C to said viscous state under conditions effective to provide a coating of said fine metallic powder on said particles.
a. providing a mixture comprising ceramic cores selected from the group consisting of Al2O3 and SiC particles, and a binder selected from the group consisting of poly-ethylene glycol and paraffin, said binder being present in an amount of about 0.5 to about 5 weight percent of said ceramic cores, said binder being capable of reaching viscous state, b. tumbling said mixture in a rotating cylindrical container which is tilted with respect to horizontal axis, while heating said mixture to a temperature up to about 80°C
to enable said binder to reach said viscous state, and allowing said particles to be substantially covered with said binder, c. cooling the mixture of binder covered particles substantially to room temperature and thereafter breaking up particles that may have agglomerated during said tumbling and heating by tumbling same with ball means, to give individual particles covered with said binder, d. adding a fine metal powder selected from the group consisting of Al, Cr, Fe, Ni, Co, Mo and W to said individual particles covered with binder and tumbling and heating again in said rotating cylindrical container at a temperature up to about 80°C to said viscous state under conditions effective to provide a coating of said fine metallic powder on said particles.
27. Apparatus for coating particles with fine powder which comprises a frame, a rotating cylinder mounted on said frame tilted with respect to horizontal axis, an inlet in said cylinder for introducing material therein, means to cause rotation of said rotating cylinder, means for slowly heating said rotating cylinder, and means for cooling heated content of said rotating cylinder to room temperature.
28. A process for coating particles with fine powder which comprises:
a. providing a mixture comprising said particles and a binder which is capable of slowly melting to viscous state, b. tumbling said mixture while slowly heating same to enable said binder to reach said viscous state while allowing said particles to be substantially covered with said binder, c. cooling the mixture substantially to room temperature and thereafter breaking up particles that may have agglomerated during said tumbling and heating, to give individual particles covered with said binder, d. adding said fine powder to said individual particles covered with said binder and tumbling and heating again to said viscous state under conditions effective to provide a coating of said fine powder on said particles, and e. heating said coated particles to remove said binder leaving said particles exclusively coated with said fine powder.
a. providing a mixture comprising said particles and a binder which is capable of slowly melting to viscous state, b. tumbling said mixture while slowly heating same to enable said binder to reach said viscous state while allowing said particles to be substantially covered with said binder, c. cooling the mixture substantially to room temperature and thereafter breaking up particles that may have agglomerated during said tumbling and heating, to give individual particles covered with said binder, d. adding said fine powder to said individual particles covered with said binder and tumbling and heating again to said viscous state under conditions effective to provide a coating of said fine powder on said particles, and e. heating said coated particles to remove said binder leaving said particles exclusively coated with said fine powder.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000507757A CA1285433C (en) | 1986-04-28 | 1986-04-28 | Process and apparatus for coating particles with fine powder |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000507757A CA1285433C (en) | 1986-04-28 | 1986-04-28 | Process and apparatus for coating particles with fine powder |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1285433C true CA1285433C (en) | 1991-07-02 |
Family
ID=4132986
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000507757A Expired - Fee Related CA1285433C (en) | 1986-04-28 | 1986-04-28 | Process and apparatus for coating particles with fine powder |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1285433C (en) |
-
1986
- 1986-04-28 CA CA000507757A patent/CA1285433C/en not_active Expired - Fee Related
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