United States Patent [19]
`Bae et al.
`
`[54] METHOD FOR MANUFACTURING
`SENDUST CORE POWDER
`
`[75]
`
`Inventors: Kwang Wook Bae; Jun Byun. both of
`Seoul. Rep. of Korea
`
`[73] Assignee: Samsung Electro-Mechanics Co., Ltd ..
`Kyongk:i-do. Rep. of Korea
`
`[21] Appl. No.: 692,063
`
`[22] Filed:
`
`Aug. 7, 1996
`
`(30]
`
`Foreign Application Priority Data
`
`(KR] Rep. of Korea .................. 1995-28376
`
`Aug. 31, 1995
`Int. Cl.6
`
`[51]
`
`................................ BOSO 1/02; B22F 9/08;
`B22F 9/02; B22F 9/06
`(52] U.S. Cl . .......................... 427/421; 148/104; 148/105;
`75/332; 75/337; 75/342; 75/768
`(58] Field of Search ..................................... 1481104. 105;
`75/332, 337, 342. 768; 427/421
`
`(56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`3,498,918
`3,551,532
`3,777,295
`4,177,089
`4,272,463
`4,956,011
`5,470,399
`
`3/1970 Copp ....................................... 148/104
`12/1970 Laird ......................................... 75/337
`12/1973 Laing ...................................... 148/104
`12/1979 Bankson ............................... 148/31.55
`6/1981 Oark et al ................................ 264/12
`9/1990 Nishida et al ............................ 75/230
`11/1995 Bae ......................................... 148/104
`
`FOREIGN PATENT DOCUMENTS
`
`I IIIII IIIIIII Ill llll llll llll lllll lllll llll llll lllll 11111111111111111
`US005756162A
`5,756,162
`(11] Patent Number:
`(45] Date of Patent:
`May 26, 1998
`
`62-250607 10/1987
`63-283300
`8/1990
`3-48241
`7/1991
`
`Japan.
`Japan ............................... C09D 1/02
`Japan .
`
`Primary Examiner-Shrive Beck
`Assistant Examiner-Michael Barr
`Auome),; Agent, or Firm-Lowe Hauptman Gopstein &
`Berner
`
`(57]
`
`ABSTRACT
`
`A method for manufacturing a powder for sendust core is
`disclosed which is used in power supplies, converters and
`invertors. and in which the sendust powder is manufactured
`by applying the atomizing process. and the powder is coated
`with a special ceramic mixture insulator, so that the core loss
`would be small after forming a product. The method for
`manufacturing the powder for a sendust core includes the
`steps of: preparing a sendust alloy melt composed of (in wt
`%) 4-13% of Si. 4-7% of Al, and balance of Fe under an
`inert atmosphere; spouting water with a pressure of
`1500-3500 psi to a flow of said sendust alloy melt through
`four or more nozzles having a diameter of 10-20 m.m, so as
`to form a relatively regular polyhedral powder; adding
`0.1-1.0 wt % of kaoline to the powder, and heat-treating it
`at a temperature of 700°-4l50° C. for 30 minutes or more
`under a reducing atmosphere; and carrying out a wet coating
`on the heat-treated powder by using 0.5-5% (relative to the
`weight of the powder) of a composite ceramic composed of
`milk of magnesia. kaoline and sodium silicate.
`
`60-145949 A2.
`
`8/1985
`
`Japan ............................. 0)4B 35/00
`
`4 Claims, 2 Drawing Sheets
`
`Sendust alloy preparation
`
`Atomizing
`
`Sendust powder
`
`Heat treatment
`
`Coating of insulator
`(composite ceramic)
`
`Petitioner Samsung and Google
`Ex-1015, 0001
`
`

`

`U.S. Patent
`
`May 26, 1998
`
`Sheet 1 of 2
`
`5,756,162
`
`Sendust alloy preparation
`
`' j
`
`Ingot
`
`"
`
`Crushing
`
`\I
`
`Sendust powder
`
`I
`
`Heat treatment
`
`Coating of insulator
`(sodium silicate)
`
`Fig. 1
`
`Petitioner Samsung and Google
`Ex-1015, 0002
`
`

`

`U.S. Patent
`
`May 26, 1998
`
`Sheet 2 of 2
`
`5,756,162
`
`Sendust alloy preparation
`
`Atomizing
`
`Sendust powder
`
`Heat treatment
`
`Coating of insulator
`(composite ceramic)
`
`Fig. 2
`
`Petitioner Samsung and Google
`Ex-1015, 0003
`
`

`

`5,756,162
`
`1
`METHOD FOR MANUFACTURING
`SENDUST CORE POWDER
`
`2
`Japanese Patent Application Publication No. Hei-3-48241
`is another example of a method for manufacturing Fe-Si(cid:173)
`Al alloy powder. In this method, the alloy melt is freely
`BACKGROUND OF THE INVENfION
`dropped through a nozzle of 5 mm into water to form coarse
`5 flake particles. Crushing is then carried out through one or
`1. Field of the Invention
`two steps. thereby obtaining the desired particle size.
`The present invention generally relates to a method for
`However. in this method also, the coarse flake particles
`manufacturing a powder for sendust core which is used in
`are crushed to obtain the final powder. Therefore, the insu(cid:173)
`power supplies, converters and invertors, and more
`lating coated layers are destroyed during the compression
`particularly. to a method for manufacturing a sendust core
`10 forming. resulting in large losses.
`powder in which the loss generated is small.
`The present invention relates to the atomizing method
`2. Description of the Prior Art
`which will be described below.
`Generally. a sendust core is a toroidal core which is
`Generally, the atomizing method is carried out in the
`manufactured by using an alloy powder having a composi(cid:173)
`following manner. Gas or water is spouted to the flow of a
`tion of 85Fe-9Si-6Al. It is a kind of a compression-formed
`melt, thereby manufacturing a powder. This atomizing
`steel core such as an iron powder core, permalloy powder
`method is widely used in fabrication of materials. However,
`core (MPP) and ferrite core, which is used as inductors or
`in the functional material fields of MPP core or Sendust core
`transformers. That is, it is an electronic component which is
`manufacture, the technique that the final powder is manu-
`used in power supply unit and the like.
`20 factured by the atomizing method has not been proposed,
`Generally, the sendust alloy is composed of 4-13% of Si,
`and the reason is as follows.
`4-7% of Al. and balance of Fe.
`First, in the case of the sendust alloy, it is composed of
`Among the above mentioned cores, the sendust core has
`highly oxidable elements. Therefore, in the case where the
`the highest magnetic flux density, is suitable for high current,
`melt is maintained in the air, the adjustment of the ingredi-
`and is most widely used. The characteristics of the core are
`25 ents is not easy.
`influenced most greatly by the state of the powder.
`Second, as shown in Japanese Patent Application Laid(cid:173)
`The sendust core powder is manufactured in the following
`open No. Sho-62-250607, when atomizing is carried out, the
`manner. As shown in FIG. 1. a sendust alloy is formed into
`powder has an almost spherical shape, and the desired
`an ingot. The ingot is then crushed with a jaw crusher, a
`particle size is difficult to obtain. Further, even after fabri-
`hammer mill. or an attrition mill. A heat treatment is carried .
`30 cation (which is the post process), the strengths cannot be
`out. The powder is then coated with sodium silicate for
`maintained. Therefore, after atomizing. crushing has to be
`insulation.
`carried out into the desired particle size. Therefore, it is
`The sendust core powder thus manufactured is then
`unavoidable that sharp corners are produced.
`subjected to a lubricant addition, forming. baking, evalua(cid:173)
`Further, in the case where water is used in the atomizing.
`tion of characteristics. followed by application of an outer
`35 the powder is formed in the shape of flat particles or
`coating ( organic polymer coating). to complete the sendust
`irregular particles.
`core product.
`Therefore, in the manufacture of structural materials, the
`In the above described sendust core powder manufactur(cid:173)
`irregular particles have large surface areas, and therefore, a
`ing method. the ingot is crushed into particles of a proper
`large driving force of sintering power is obtained, with the
`size, and therefore. it is uneconomical in view of the cost and
`40 result that the final density is increased.
`the number of process steps. Particularly, the powder has
`However. the powder has be coated with an insulating
`irregular sharp comers, and therefore, the coating efficiency
`material in the sendust core manufacture, and therefore, the
`is low. Further, during a high pressure forming. the coating
`destruction of the insulating layer during the fabrication has
`layers are damaged. with the result that the core loss is
`to be considered. Therefore. a powder of regular size is
`increased.
`45 required, while irregular particle sizes presents difficulties.
`To simplify the manufacturing process and to improve the
`Therefore, the atomizing technique using water has not
`ingot crushing method. a gas atomizing method is disclosed
`been applied to the manufacture of functional materials.
`in Japanese Patent Application Laid-open No. Sho-62-
`Third, in the case of the gas atomizing method, if the
`250607. In this method, a melted alloy is subjected to a gas
`desired particle size is to be obtained, the pressure of the
`atomizing process to prepare a crude spherical powder.
`spouting gas has to be high. Therefore, entrapped pores are
`Crushing is then carried out through one or two steps into
`formed within the particles owing to the high pressure
`particle sizes of 40-110 µm. Subsequently. the surface of the
`spouting gas. As a result. the characteristics of the powder
`powder is coated with an inorganic insulating material
`are degraded.
`(sodium silicate) to complete the core manufacture.
`That is, in the functional material of the present invention,
`Compared with the ingot crushing method, this method
`the step of coating an insulating material has to be neces(cid:173)
`has the advantages that the process is shortened, and seg(cid:173)
`sarily carried out, and the insulation coated powder has to be
`regation of the ingredients can be prevented.
`formed with a certain compression pressure. Even after the
`However. in this method, the spherical form is highly
`forming. the insulating layers should not be damaged.
`perfect, and therefore, the compression forming becomes
`Particularly, in the sendust core or MPP core, the forming
`difficult Even if the forming is realized, the strength of the
`pressure is about 18-24 ton/cm2
`• Therefore, if the particle
`formed body is very low, with the result that the product
`shape is irregular or if entrapped pores exist within the
`manufacturing is very difficult. Therefore, a crushing step is
`particles, a fatal result is invited.
`necessarily required.
`Therefore, the atomizing technique has not been applied
`Thus, in this method also, the crushing is carried out. and
`65 to the manufacture of the functional materials.
`therefore, sharp comers are produced. The insulating coating
`layers are destroyed during the compression forming. and
`Meanwhile, in the case where a press formed iron core is
`therefore, a large loss is resulted.
`manufactured by using a metal powder, the metal particles
`
`55
`
`60
`
`15
`
`50
`
`Petitioner Samsung and Google
`Ex-1015, 0004
`
`

`

`5,756,162
`
`3
`are insulated from one another for reducing the eddy current
`loss. Conventionally. sodium silicate or a polymer is used
`for insulating the particles, or the metal particles are slightly
`oxidized so as to insulate them.
`However. in the case where the metal particles are
`insulated. the insulation resistance is low. Therefore. at 100
`gausses, the core loss reaches 25-30 mW/cm2
`•
`
`SUMMARY OF THE INVENITON
`
`In order to overcome the above described disadvantages
`of the conventional techniques. the present inventors carried
`out study and experiments. and has come to propose the
`present invention based on the study and experiments.
`Therefore. it is the object of the present invention to
`provide a method for manufacturing a powder for a sendust
`core. in which the sendust powder is manufactured by
`applying the atomizing process, and the powder is coated
`with a special ceramic mixture insulator. so that the core loss
`is small after forming product.
`In achieving the above object. the method for manufac(cid:173)
`turing a powder for a sendust core according to the present
`invention includes the steps of:
`preparing a sendust alloy melt composed of (in wt % )
`4-13% of Si, 4-7% of Al, and balance of Fe under an inert 25
`atmosphere;
`spouting water with a pressure of 1500-3500 psi to a flow
`of said sendust alloy melt through four or more nozzles
`having a diameter of 10-20 mm. so as to form a relatively
`regular polyhedral powder;
`adding 0.1-1.0 wt % of kaoline to said powder. and
`heat-treating it at a temperature of 700°-850° C. for 30
`minutes or more under a reducing atmosphere; and
`carrying out a wet coating on the heat-treated powder by 35
`using 0.5-5% (relative to the weight of the powder) of a
`composite ceramic composed of milk of magnesia. kaoline
`and sodium silicate.
`
`4
`During the preparation of the melt, the Al and Si which are
`highly oxidable are oxidized and consumed into slag.
`Therefore. the ingredient adjustment for the alloy is not easy.
`and therefore. this has to be prevented. Further. another
`5 reason is for minimizing the lowering of the fluidity of the
`melt. which is caused by the melt oxidation.
`Water supplied at a pressure of 1500-3500 psi is then
`spouted to a flow of said sendust alloy melt through four or
`more nozzles having a diameter of 10-20 mm. so as to form
`10 relatively regular polyhedral powder.
`H the diameter of the nozzle is less than 10 mm. the
`atomizing time is extended. Consequently. clogging of the
`nozzles may occur. or excessively fine particles are formed.
`with the result that the formed powder has too low a
`15 permeability. On the other hand. if the diameter of the
`nozzles is more than 20 mm. coarse and almost spherical
`powder is obtained. with the result that the product forming
`becomes difficult, and that the loss becomes large.
`Therefore. the diameter of the nozzle should be preferably
`20 10-20 mm.
`The number of the nozzles is four or more. and the reason
`for it is as follows. H the number of the nozzles is less than
`four, the shape of the powder may become flake. and
`therefore. products having a large core loss are apt to be
`formed.
`The nozzles should be preferably disposed equidistantly
`in the horizontal view. The reason is that if not equidistantly
`disposed. the powder may have an irregular elliptical shape.
`30 Meanwhile, in a vertical view. the height difference
`between the highest nozzle and the lowest nozzle should be
`preferably 5-20 mm.
`H the height difference is less than 5 mm. ordinary flake
`powder may be produced. On the other hand, if the height
`difference is more than 20 mm. lumps may adhere on the
`particles, thereby making the powder irregular.
`In the case where the number of the nozzles is even. two
`nozzles having the largest mutually facing distance should
`have preferably the same height.
`H the number of the nozzles is odd, the nozzles having the
`longest mutually facing distance form pairs. in such a
`manner that one nozzle forms only one pair. The nozzles
`forming this pair should have vertically same height.
`One nozzle which does not form a pair should be pref-
`45 erably disposed between the nozzles of the pair in a vertical
`view. The reason is as follows. That is. if a nozzle which
`does not form a pair is disposed at the highest position or at
`the lowest position, the shape of the particles will become
`irregular.
`Meanwhile, if the spouting pressure is less than 1500 psi,
`coarse and spherical powder is obtained. resulting in a great
`loss, as well as being weak in the formed strength. On the
`other hand. if the spouting pressure is more than 3500 psi.
`then the oxidation of the powder becomes severe. Further,
`the shape of the powder becomes irregular, and excessive
`fine particles are formed, so that forming into a core would
`be difficult. Further, the permeability is low, and therefore,
`optimum properties cannot be obtained.
`Then, 0.1-1 % of kaoline is put into the powder in weight
`% relative to the powder. Then it is heat-treated at a
`temperature of 700°-850° C. for 30 minutes or more under
`a hydrogen containing reducing atmosphere.
`The hydrogen containing atmosphere is composed of
`65 hydrogen and nitrogen.
`The reason for carrying out the heat treatment is for
`removing the oxides and impurities formed during the
`
`BRIEF DESCRIPflON OF TIIE DRAWINGS
`
`The above · object and other advantages of the present
`invention will become more apparent by describing in detail
`the preferred embodiment of the present invention with
`reference to the attached drawings in which:
`FIG. 1 is a flow chart showing the conventional process
`for manufacturing the powder for sendust core; and
`FIG. 2 is a flow chart showing the process for manufac(cid:173)
`turing the powder for sendust core according to the present
`invention.
`
`40
`
`50
`
`55
`
`DEfAILED DESCRlPTION OF THE
`PREFERRED EMBODIMENT
`H the powder for sendust core according to the present
`invention is to be manufactured, as shown in FIG. 2, a
`sendust melt has to be prepared. The sendust melt is com(cid:173)
`posed of 4-13% of Si. 4-7% of Al, and balance of Fe. and
`is prepared under an inert gas atmosphere such as nitrogen
`(N2) or argon (Ar).
`When preparing the sendust alloy melt according to the 60
`present invention, ferro-silicon (Fe-Si). and ferro(cid:173)
`aluminum (Fe-Al). Si and Al are used to adjust the
`composition of the melt rather than only the metallic Al and
`Si. The reason is that the alloy ingredients can be adjusted
`in a short period of time.
`The reason why the melt is prepared under an inert
`atmosphere is as follows.
`
`Petitioner Samsung and Google
`Ex-1015, 0005
`
`

`

`5,756,162
`
`5
`atomizing process. The reason for adding kaoline during the
`heat treatment is for preventing the agglomeration of the
`powder.
`The temperature and time for the heat treatment are
`limited in view of the proper removal of the oxides and 5
`impurities which have been formed during the atomizing.
`The heat-treated powder is adjusted as to its particle size,
`so that the particle size would be suitable to its application.
`For example. when a product having a permeability of
`125µ is to be manufactured. the particle distribution of the
`powder should be preferably 25% of 120 meshes ( 125 µm)
`or less. 20% of 200 meshes (75 µm) or less. and 55% of 325
`meshes (45 µm). The tolerance for each mesh range is ±5%.
`If a product having a permeability of 60µ is to be 15
`manufactured, the powder should preferably have a particle
`size of 325 meshes (45 µm) or less.
`Then a composite ceramic is wet-coated on the above
`described heat-treated powder by using 0.5-5 wt % of
`composite ceramic relative to the total powder.
`The composite ceramic is composed of magnesia, kaoline.
`and sodium silicate. It is also preferable to additionally add
`talc and potassium hydroxide.
`
`6
`The height difference of the nozzles was 10 mm.
`Then kaoline powder in a amount of 0.5% was added to
`the above powder, and then. a reduction treatment was
`carried out at 700° C. for one hour under a hydrogen
`containing atmosphere (containing 25% of N 2 and 75% of
`H2),
`Then in order to manufacture a core having a permeability
`of 125µ. the particle size distribution was made to include:
`24% of 120 meshes or below. 21 % of 200 meshes or below.
`10 and 55% of 325 meshes or below.
`Then on the heat treated powder. the composite ceramic
`of the present invention and sodium silicate as an insulating
`material were coated by using 1.2% of them.
`The composite ceramic used here included talc. magnesia.
`kaoline. sodium silicate and potassium hydroxide. Further
`the composite ceramic had a resistivity of 300xl08MQ-cm
`and a density of 2.7 g/cm3
`•
`Then a core was manufactured by using the powder. and
`20 the core loss was checked, and the results are shown in Table
`1 below.
`The outside diameter of the core was 20 mm<j). and the
`core loss was measured at 100 KHz and 100 gausses.
`
`Test
`pi«e
`
`Insulating
`Powder
`fonnation condition
`
`Conven-
`tional 1
`Conven-
`tional 2
`Comparative
`
`Inventive
`
`Crushing Oxidation
`method
`Crushing
`Sodium
`method
`silicate
`Inventive Sodium
`method
`silicate
`(1.2%)
`Inventive Composite
`ceramic
`method
`(1.2%)
`
`TABLE 1
`
`Nozzle
`dia
`(mm)
`
`Fluid
`pressure
`(psi)
`
`Core
`loss
`(mW/cm3
`
`Powder
`) shape
`
`30
`
`27
`
`20
`
`13
`
`1600
`
`13
`
`1600
`
`16
`
`**Irregular
`polyhedral
`Irregular
`polyhedral
`•Ahnost regular
`polyhedral
`
`Almost regular
`polyhedral
`
`*"Almost regular polyhedral" refers to powder particles having no sharp corners, and no
`second lumps (satellite).
`••"irregular polyhedraf" refers to powder particles having sharp corners.
`
`In the composite ceramic, magnesia ia added to improve
`insulation, kaoline is added to strengthen the insulating
`layer. and sodium silicate is added as a binder. Talc serves 45
`as a lubricant for the insulating layer, and potassium hydrox(cid:173)
`ide acts as an insulating agent.
`After a baking of one hour at 700° C., the composite
`ceramic has a resistivity of 200x106MQ-cm or more, and a
`• This resistivity value of the 50
`density of 2.3-3.0 g/cm3
`composite ceramic is higher than the case of the sodium
`silicate insulation or than the case of the oxidation insula(cid:173)
`tion.
`After manufacturing the powder for sendust core in the 55
`above described manner, a sendust core is manufactured. In
`this case, the sendust core shows superior characteristics
`with a small loss.
`Now the present invention will be described based on
`actual examples.
`
`<EXAMPLE 1>
`A melt which was composed of Fe-9.6% Si-5.5% Al was
`prepared under a nitrogen atmosphere by using ferro-Si.
`ferro-Al. Si and Al. To the flow of the melt. water was 65
`spouted through four nozzles having a diameter of 13 mm
`each. at a pressure of 1600 psi, thereby forming a powder.
`
`Based on the method of Example 1, an oxidation
`insulation. a sodium silicate insulation. and the composite
`ceramic insulation were carried out on the powder in manu(cid:173)
`facturing the final powder as shown in Table 2 below. The
`a core having an outside diameter of 20 mm<j)) was manu(cid:173)
`factured by using the above powder. Then the core loss was
`60 measured in the same manner as that of Example 1. and the
`measured results are shown in Table 2 below.
`
`As shown in Table 1 above, the inventive material which
`was coated with the composite ceramic of the present
`invention after being formed into the powder according to
`the present invention was low in the core loss compared with
`the conventional materials 1 and 2.
`
`<EXAMPLE2>
`
`The composite ceramic used here included talc. magnesia,
`kaoline, sodium silicate and potassium hydroxide. while its
`resistivity was 300x108Mil-cm. and its density was 2.7
`g/cm3.
`
`Petitioner Samsung and Google
`Ex-1015, 0006
`
`

`

`5,756.162
`
`8
`
`What is claimed is:
`1. A method for manufacturing a powder for a sendust
`core, comprising the steps of:
`
`7
`
`TABLE 2
`
`Insulation
`
`Oxidized insulation
`(1.2%)
`Sodium silicate
`insulation ( 1.2%)
`Composite ceramic
`insulation (1.2%)
`Composite ceramic
`insulation ( 1.4%)
`
`Core loss
`(mW/cm3
`)
`
`Powder shape
`
`27
`
`20
`
`16
`
`12
`
`Almost regular polyhedral
`
`Almost regular polyhedral
`
`Almost regular polyhedral
`
`Almost regular polyhedral
`
`5
`
`10
`
`15
`
`preparing in an inert atmosphere a sendust alloy melt
`composed of 4-13 wt% of Si, 4-7 wt % of Al. and
`balance of Fe;
`electing water with a pressure of 1500-3500 psi to a flow
`of said sendust alloy melt through at least four nozzles
`having a diameter of 10-20 mm, so as to form a
`substantially regular polyhedral powder;
`adding 0.1-1.0 wt % of kaolin to said powder. and
`heat-treating said powder and kaolin at a temperature of
`700°-850° C. for at least 30 minutes under a reducing
`atmosphere; and
`carrying out a wet coating on the heat-treated powder by
`using 0.5-5 wt %, relative to the weight of said powder.
`of a composite ceramic composed of milk of magnesia.
`kaolin and sodium silicate, said composite ceramic
`having a resistivity greater than 200xl06Mil-cm and a
`density of 2.3-3.0 g/cm3 after baking for one hour,
`wherein said nozzles are disposed equidistantly from each
`other in a horizontal view. and a height difference
`between a highest nozzle and a lowest nozzle is about
`5-20 mm.
`2. The method as claimed in claim 1, wherein:
`talc and potassium hydroxide are added to said composite
`ceramic.
`3. The method as claimed in claim 1, wherein, when the
`number of said nozzles is even, two opposing nozzles are
`disposed at the same height, and when the number of said
`nozzles is odd, the nozzles are arranged to form mutually
`facing pairs in such a manner that one nozzle forms only one
`pair, the nozzle within the same pair having the same height,
`and the odd nozzle which does not form one of a pair being
`vertically disposed between nozzles forming one of a pair.
`4. The method as claimed in claim 2. wherein, when the
`number of said nozzles is even, two opposing nozzles are
`disposed at the same height. and when the number of said
`nozzles is odd. the nozzles are arranged to form mutually
`facing pairs in such a manner that one nozzle forms only one
`45 pair, the nozzle within the same pair having the same height,
`and the odd nozzle which does not form one of a pair being
`vertically disposed between nozzles forming one of a pair.
`
`<EXAMPLE3>
`By using ferro-Si. ferro-Al, Si and Al, there was prepared
`a melt of Fe-9.6% Si-5.5% Al under a nitrogen atmosphere.
`Then water was spouted to the flow of the melt at the
`conditions of Table 3 below, thereby forming a powder.
`Then like in Example 1. a reduction treatment and an
`adjustment of the particle size distribution were carried out. 20
`The composite ceramic of the present invention was coated
`on the powder. Then a core of 20 mmq> was formed by using
`the powder, and then, the core loss was measured in the same
`manner as that of Example 1. The measured results are
`shown in Table 3 below.
`The composite ceramic used here included talc. magnesia.
`kaoline, sodium silicate and potassium hydroxide, while its
`resistivity was 300x 108Mn-cm. and its density was 2.7
`g/cm3.
`
`25
`
`30
`
`35
`
`40
`
`TABLE3
`
`Amount of
`insulator
`
`Nozzle
`dia
`(mm)
`
`Fluid
`presswe
`(psi)
`
`Core
`loss
`(mW/cm3
`
`) Shape of powder
`
`1.2%
`1.2%
`1.2%
`1.2%
`1.2%
`1.2%
`1.4%
`1.4%
`
`9
`13
`22
`13
`13
`13
`13
`15
`
`1600
`1600
`1600
`1200
`3800
`2000
`2000
`2700
`
`27
`16
`20
`22
`23
`12
`10
`8
`
`Irregular polyhedral
`Almost regular polyhedral
`Almost coarse spherical
`Almost coarse spherical
`Tmy & iiregular
`A1most regular polyhedral
`A1most regular polyhedral
`A1most regular polyhedral
`
`According to the present invention as described above. a
`melt is subjected to an atomizing process, and a quick
`cooling is carried out so as to manufacture a powder. Further,
`a composite ceramic is used to insulate the powder particles,
`so that the resistivity would be raised. Therefore, when the
`powder is formed into a sendust core, the core loss is
`lowered.
`
`* * * * *
`
`Petitioner Samsung and Google
`Ex-1015, 0007
`
`