KR20190008128A - Material for radiating Heat and Method of forming the same - Google Patents

Abstract

A heat radiating material and a manufacturing method thereof are disclosed. The heat radiating material is formed by coating the surface of a carbon body with an amorphous carbon layer having amorphous properties. The heat radiating material exhibits high electrical resistance characteristics due to the amorphous carbon layer. However, the reduction of thermal conductivity by the amorphous carbon layer is negligible. Accordingly, the heat radiating material having high thermal conductivity and electrical insulation properties can be manufactured.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat dissipating material and a manufacturing method thereof, and more particularly, to a heat dissipating material having high electric insulation and thermal conductivity, and a manufacturing method thereof.

As the electronic devices are miniaturized and highly integrated, the characteristics and reliability of the device are deteriorated by heat generated during operation. This can be solved by designing the operating voltage and the consumed power such that the heat generated from the electronic elements is smoothly discharged to the outside, or the electronic element minimizes the generation of heat.

Particularly, efforts have been made to reduce power consumption by lowering the operating voltage of the electronic device and setting a rest period in which the operation is temporarily stopped. However, lowering the operating voltage of an electronic device has a certain limit in a CMOS-based semiconductor. In the case of a transistor-based electronic device, a low threshold voltage is realized through a reduction in the line width, a reduction in the thickness of the gate oxide film, and a scaling down of the active region. However, the side effect is a problem of malfunction such as short channel effect. Therefore, there are certain limitations in reducing the operating voltage or the consumed power in order to solve the heat problem generated in the electronic device.

In addition, a heat sink may be used to smoothly discharge the heat generated from the electronic device to the outside. Most of the materials used as heatsinks for heat dissipation are metal. Aluminum or copper is difficult to be molded, and there is a limit to widely applied as a heat-radiating material due to its high price. As an alternative, the use of carbon materials is discussed. Carbon materials are used as thermally conductive fillers due to their high thermal conductivity, low density, low cost and high processability. However, since carbon materials have electric conductivity other than high thermal conductivity, they may cause leakage current or short-circuit current when they are applied to an electronic device, thereby causing electrical damage or breakage of the electronic device.

To solve this problem, studies have been made on carbon materials having high thermal conductivity and low electric conductivity.

U.S. Patent No. 7886813 discloses a structure in which thermally conductive particles of metallic material and CNT are mixed in a polymer. The carbon material CNT is provided in the form attached to the metal particles, and the CNT-metal particle complex is dispersed in the polymer matrix. However, the above patent does not disclose a method for attaching CNTs to metal particles.

Korean Patent Registration No. 0841939 discloses a technique for producing a heat-radiating sheet by mixing / curing / pulverizing CNT and a curable resin to form a particulate phase, and mixing the powdery particulate phase with a polymer resin and a conductive powder. In the above patent, CNT or carbon fiber is coated with a polymer resin to form an outer coating. Therefore, there is a disadvantage in that it is advantageous in securing electrical insulation and forming a film phase, but has a low thermal conductivity.

Korean Patent No. 1692135 discloses a composite material using CNTs and fillers surface-treated with aluminum hydroxide. This is to ensure low electrical conductivity and high thermal conductivity. In this patent, surface treatment for CNT is preceded, and a polymer resin is used as a matrix for manufacturing a heat radiation sheet. The powder is a surface treated CNT and a ceramic particle which is a filler. However, the chemical stability and dispersibility of aluminum hydroxide may be a problem.

As described above, heat-radiating materials using carbon materials have various problems such as dispersibility, complicated manufacturing process, and low thermal conductivity. Therefore, despite the simple manufacturing process and the low process cost, the development of a high-quality heat-radiating material and a method of manufacturing the same is still required.

A first object of the present invention is to provide a heat dissipation material having a high thermal conductivity and a low electrical conductivity.

According to a second aspect of the present invention, there is provided a method of manufacturing a heat dissipation material to achieve the first technical object.

According to an aspect of the present invention, An amorphous carbon layer coating the surface of the carbon body; And a ceramic particle distributed on the surface or inside of the amorphous carbon layer.

According to another aspect of the present invention, there is provided a method of manufacturing a carbon nanotube composite material, comprising: mixing a carbon material, a functional polymer, and ceramic particles to form a mixture; And heat-treating the mixture to incompletely carbonize the functional polymer to form an amorphous carbon layer for coating the surface of the carbon body, and distributing the ceramic particles in the amorphous carbon layer and on the surface of the amorphous carbon layer The present invention also provides a method of manufacturing a heat dissipation material.

According to the present invention described above, a functional polymer containing a nitrogen atom is incompletely carbonized to form an amorphous carbon layer. The amorphous carbon layer covers the outer surface of the carbon body. This can lower the thermal conductivity and electrical conductivity of the carbon body. In addition, ceramic particles are distributed in the layered structure of the carbon body or on the surface of the carbon body, and on the inside and the surface of the amorphous carbon layer. Thermal conductivity can be ensured through the ceramic particles. The heat dissipation material produced through this shows high thermal conductivity and electrical insulation. In addition, when the heat-radiating composite material is manufactured, it has high workability and excellent heat radiation performance.

In addition, the carbonization process in the mixing and nitrogen atmosphere is very simple in the manufacturing process, and the manufacturing cost of the heat dissipation material can be reduced.

In addition, ceramic particles are provided on the bulk or surface of the amorphous carbon layer coated on the carbon body. The ceramic particles have a composition of oxide or nitride. Ceramic particles have a relatively high degree of dispersion compared to a conductive carbon body. Therefore, when a heat-radiating film, a heat-radiating sheet, or the like is manufactured using a heat-radiating material as a filler, high workability can be secured. In the manufacturing process of the heat-radiating sheet, the heat-radiating material needs to be dispersed evenly in the solvent, and the cohesion phenomenon with the heat-radiating materials should be avoided. In the present invention, since the ceramic particles are introduced onto the amorphous carbon layer, the aggregation phenomenon between the heat dissipation materials is minimized.

1 is a schematic view of a heat dissipation material according to a preferred embodiment of the present invention.
2 is a flowchart illustrating a method of manufacturing a heat dissipation material according to a preferred embodiment of the present invention.
Fig. 3 is an image showing crushed expanded graphite used in Production Example 1. Fig.
4 to 6 are images showing Raman spectrum according to a preferred embodiment of the present invention.
7 is a graph showing the thermal conductivity and the volume resistivity of the heat-radiating composite material according to the change of the content of silica particles according to Production Example 5. FIG.
8 is a graph showing the thermal conductivity of the heat-radiating composite according to Production Example 6. Fig.
9 is a graph showing the volume resistivity of the heat-radiating composite according to Production Example 6. Fig.
10 is a graph showing thermal conductivity and volume resistivity of a heat-radiating composite material when various ceramic particles are introduced according to Production Example 7. FIG.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example

1 is a schematic view of a heat dissipation material according to a preferred embodiment of the present invention.

Referring to FIG. 1, the heat dissipation material of this embodiment has a carbon body 100, an amorphous carbon layer 120, and ceramic particles 140.

The carbon body 100 may be formed of any one of graphite, expandable graphite, expanded graphite, graphene, carbon fiber, carbon nanofiber, and carbon nanotube (carbon nanotubes), and have a size of several hundred micrometers in the nanometer range. In particular, the carbon body may be a mixture of one or more of graphite, expandable graphite and expanded graphite. In addition, it is preferable that the carbon bodies 100 are provided in respective separated forms by pulverization.

The amorphous carbon layer 120 is provided in a coated form on the surface of the carbon body 100. The amorphous carbon layer 120 has a disordered chemical structure and is formed by incomplete combustion of the functional polymer. That is, complete carbonization is not generated, and the carbon layer is provided in a disordered state by incomplete carbonization. The amorphous carbon layer 120 includes carbon atoms and nitrogen atoms.

The functional polymer is a functional polymer containing nitrogen (N) in the polymer chain, such as poly (melamine-co-formaldehyde) methylated (PMF), polyoxazoline, polypyrrolidione, polyethyleneimine, polyvinylpyridine, chitin, polyamide, polyurethane, polyacrylonitrile, polyaniline and polycarbazole And at least one functional polymer selected from the group consisting of In particular, the functional polymer may be poly (melamine-co-formaldehyde) methylated (PMF), but is not limited thereto.

The ceramic particles 140 may be formed of a material selected from the group consisting of Al ₂ O ₃ , ZnO, TiO ₂ , FeO, MgO, SiO ₂ , ZrO _2), beryllium oxide (BeO), mullite _{(3Al 2 O 3 · 2SiO 2} ), steatite (MgO · SiO _2), boehmite _{(Al 2 O 3 · H 2} O), calcium carbonate (CaCO ₃₎ , magnesium carbonate (MgCO _3), boron nitride (BN), aluminum nitride (AlN), nitride titanium (TiN), silicon nitride (Si ₃ N _4), silicon carbide (SiC), carbide titanium (TiC), tungsten carbide (WC ), At least one of ceramics selected from the group consisting of molybdenum sulfide (MoS ₂ ), tungsten sulfide (WS ₂ ) and zinc sulfide (ZnS) having a size of several nanometers to nanometers. The ceramic particles 140 may be at least one kind of silicon oxide, but the present invention is not limited thereto.

However, it is preferable that the ceramic particles 140 are selected as a material having a high thermal conductivity.

In the heat dissipation material, the carbon body 100 has high thermal conductivity and electrical conductivity. In addition, the amorphous carbon layer 120 coated on the surface of the carbon body 100 blocks the phenomenon of electrically shorting neighboring carbon bodies 100. Accordingly, the amorphous carbon layer 120 reduces the electrical conductivity between the adjacent carbon bodies 100 and reduces the thermal conductivity.

The ceramic particles 140 may be dispersed in the amorphous carbon layer 120 or may be distributed on the surface of the amorphous carbon layer 120. If the carbon body 100 is formed with a certain gap between the layers in a multilayer structure such as expanded graphite or expandable graphite, the ceramic particles 140 may be charged into the gap between the layers. The ceramic particles 140 have a relatively low thermal conductivity as compared to a conductor and have a nonconductive property with low electrical conductivity. Therefore, the heat dissipation material can have a very low electrical conductivity by the ceramic particles 140 forming the outer edges of the carbon bodies having mostly plate-shaped shapes.

In addition, the amorphous carbon layer 120 occupies a majority of sigma bonds rather than pi bonds. In the process of carbonizing a functional polymer originally having a sigma bond, when complete carbonization proceeds, the polymer structure is decomposed and rearranged. During the carbonization process, the polymer structure is decomposed to remove CO, CO _2, or N ₂ gases, and carbon atoms are bonded and rearranged to form pie bonds extensively. Compared to the sigma bond, the pyrolytic structure has a high conductivity when pi bonds occupy a large number. However, when the incomplete carbonization process proceeds, the polymer structure is not completely decomposed, the polymer structure is incomplete, and the pie bond can not be formed, so that the polymer has a low electric conductivity.

Accordingly, the carbon body 100 has high thermal conductivity and electrical conductivity, and the amorphous carbon layer 120 coating the outer surface of the carbon body 100 has low thermal conductivity and electrical conductivity. The amorphous carbon layer 120 separates the heat dissipation materials individually, and the electrical short circuit between the heat dissipation materials is cut off. The ceramic particles 140 having a high thermal conductivity may be used for the amorphous carbon layer 120 and the amorphous carbon layer 120. The amorphous carbon layer 120 may be used as a heat dissipation material even if it is introduced into the outer portion of the carbon body 100. In order to further increase thermal conductivity and further lower electrical conductivity, Or is distributed on the surface of the amorphous carbon layer 120. [ Since the ceramic particles 140 have relatively high thermal conductivity and electrical insulating properties, the heat-radiating material coated with the amorphous carbon layer and the ceramic particles can have high thermal conductivity and low electric conductivity.

Further, the functional polymer needs to have a nitrogen atom in the chain. The nitrogen atoms are composed of the amorphous carbon layer 120 through the carbonization process and improve the dispersibility of the formed heat-radiating material. That is, the amorphous carbon layer 120 appears on the surface of the heat dissipation material, and the nitrogen atoms of the amorphous carbon layer 120 prevent aggregation of the heat dissipation materials in powder form. In addition, when the amorphous carbon layer that is incompletely carbonized includes nitrogen atoms, the amorphous carbon layer 120 may be firmly coated on the surface of the carbon body 100.

2 is a flowchart illustrating a method of manufacturing a heat dissipation material according to a preferred embodiment of the present invention.

Referring to FIG. 2, carbon bodies, functional polymers, and ceramic particles are mixed (S100).

If the size of the carbon body is larger than several tens of mu, a crushing process may be added for efficiency of mixing. In addition, a carbon material, a functional polymer, and ceramic particles may be distributed in a form such that a solvent or the like is selected and dispersed in a solution at the time of mixing.

The carbon body may be selected from the group consisting of graphite, expandable graphite, expanded graphite, graphene, carbon fiber, carbon nanofiber and carbon nanotube. nanotubes). < / RTI >

The functional polymer may include at least one selected from the group consisting of poly (melamine-co-formaldehyde) methylated (PMF), polyoxazoline, polypyrrolidione, polyethyleneimine, polyvinylpyridine, chitin, polyamide, polyurethane, polyacrylonitrile, polyaniline and polycarbazole And contains nitrogen (N) atoms in the polymer chain.

The ceramic particles may be formed of any one selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), zinc oxide (ZnO), titanium oxide (TiO ₂ ), iron oxide (FeO), magnesium oxide (MgO), silicon oxide (SiO ₂ ), zirconium oxide _2), beryllium oxide (BeO), mullite _{(3Al 2 O 3 · 2SiO 2} ), steatite (MgO · SiO _2), boehmite _{(Al 2 O 3 · H 2} O), calcium carbonate (CaCO _3), magnesium carbonate (MgCO _3), boron nitride (BN), aluminum nitride (AlN), nitride titanium (TiN), silicon nitride (Si ₃ N _4), silicon carbide (SiC), carbide titanium (TiC), tungsten carbide (WC) , Molybdenum sulfide (MoS ₂ ), tungsten sulfide (WS ₂ ) and zinc sulfide (ZnS).

Subsequently, a carbonization process is performed on the mixture (S200).

It is preferable that the carbonization process proceeds from the first temperature to the second temperature. The first temperature and the second temperature may be set differently depending on the kind of the functional polymer used.

The first temperature refers to the temperature at which the functional polymer initiates rearrangement of the molecular structure by thermal energy. It is collectively referred to as carbonization point. Above the carbonization point, the functional polymer is rearranged and carbonization proceeds.

The second temperature has a value higher than the first temperature and is a temperature at which the fully carbonized state starts to progress. Full carbonization refers to the formation of burnt carbides into crystalline particles. In addition, the crystalline particles are formed by carbonization at the second temperature or higher, and the formed carbides have high electric conductivity because they have pi bonding.

Therefore, when the carbonization process is carried out at a temperature higher than the first temperature and lower than the second temperature, the functional polymer is not completely carbonized but incompletely carbonized, and is formed of an amorphous carbon layer. The amorphous carbon layer is predominantly sigma-bonded rather than pi-bonded and has low electrical conductivity.

In addition, it is preferable that the carbonization process proceeds in a nitrogen atmosphere in which oxygen is excluded. Through the application of heat energy in a nitrogen atmosphere, an amorphous carbon layer containing nitrogen and carbon atoms is formed on the surface of the carbon body.

A heat-radiating material is manufactured through the above-described process

PREPARATION EXAMPLE 1: Coating of amorphous carbon layer on graphite nanoplate 1

Ball milling for expanded graphite having an average major axis diameter of 300 mu m is performed. Zirconia balls with a diameter of 1 mm are used for ball milling, and isopropyl alcohol is used as a solvent. Whereby wet grinding is carried out. Wet milling is carried out at 2500 rpm for 90 minutes, and crushed expanded graphite is obtained.

Fig. 3 is an image showing crushed expanded graphite used in Production Example 1. Fig.

Referring to Fig. 3, the crushed pycrystalline graphite has an average diameter of the long axis of about 30 mu m. In particular, the diameter of the long axis of the crushed expanded graphite is preferably from 10 to 50 mu m. If the diameter of the crushed expanded graphite is less than 10 탆, the aggregation of the crushed and expanded graphite tends to be intensified. If the diameter of the crushed expanded graphite exceeds 50 탆, the amorphous carbon layer is not sufficiently coated at the end of the crushed expanded graphite or the like A problem arises. Although the diameters of the long axes of crushed expanded graphite are industrially preferable, mutually the diameters of the long axes of the crushed expanded graphite are preferably uniform, but the object of the present invention can be achieved if the diameter of the major axis of the crushed expanded graphite is limited to 10um to 50um in the production process.

Subsequently, 2.4 g of the functional polymer PMF was added to 80 mL of acetone, and the mixture was stirred and dissolved for 10 minutes to form a PMF solution. Powder expanded graphite (0.5 g), which is a carbon chain, was added to the prepared PMF solution, and the particles were dispersed by irradiating with ultrasonic wave for 1 hour at 500 W power to separate crushed expanded graphite into graphite nanoplate.

Then, the acetone was vacuum evaporated at 60 DEG C while stirring the suspension at 300 rpm to remove acetone as a solvent. Also, to remove residual acetone, the temperature was increased to 120 < 0 > C and removed under vacuum for 1 hour.

Finally, a sample mixed with PMF and graphite nanoplate was put into a furnace and subjected to heat treatment (HT) in a nitrogen atmosphere at a temperature of 400 ° C for 2 hours to form amorphous carbon nanotubes A structure coated with a carbon layer was synthesized.

PREPARATION EXAMPLE 2: Coating of amorphous carbon layer on graphite nanoplate 2

The procedure was carried out under the same conditions as in Production Example 1 except that the heat treatment temperature in the nitrogen atmosphere in the furnace was set to 600 캜.

PREPARATION EXAMPLE 3: Coating of amorphous carbon layer on graphite nanoplate 3

The process was carried out under the same conditions as in Production Example 1 except that the heat treatment temperature in a nitrogen atmosphere in the furnace was set at 800 占 폚.

4 to 6 are images showing Raman spectrum according to a preferred embodiment of the present invention.

Referring to FIG. 4, a Raman spectrum of the graphite nanoplate described in Production Example 1 is shown. That is, a graphite nanolate plate formed by adding 0.5 g of expanded graphite to 80 mL of acetone and irradiating ultrasonic waves at 500 W power for 1 hour without introducing PMF as a functional polymer in Production Example 1 is disclosed.

In the Raman spectrum peak denoted by G in the vicinity of 1580 cm ^-1 is the inherent peak appearing on the graphite-related substance, the peak marked with D in the vicinity of 1350 cm ^-1 is the inelastic scattering by phonons having a wavelength of 1350 cm ^-1 and energy And is a peak that appears due to the presence or absence of a defect. That is, as the vacancy, interstitial or substitutional defect increases in the graphite nanoplate, the intensity of the peak increases.

Therefore, the higher the value of G / D, the higher the crystallinity of the material, and the lower the value of G / D, the closer to the amorphous state due to the lower crystallinity.

In Fig. 4, G / D shows a high value of 8.2. This means that the carbon structure on the graphite surface exhibits a certain crystallinity.

Referring to FIG. 5, a Raman spectrum of the heat dissipation material manufactured in Production Example 1 is disclosed.

The value of G / D is 1.2, which is much lower than that of FIG. This is due to the amorphous carbon layer formed on the surface of the carbon body. That is, the low crystallinity due to the amorphous carbon layer generated in the carbonization process appears as a low G / D value. Through this process, formation of an amorphous carbon layer having high electrical insulation can be confirmed through incomplete carbonization process.

Referring to FIG. 6, a Raman spectrum of the heat dissipation material produced in Production Example 3 is disclosed.

The G / D value is 2.3. It can be interpreted that the amorphous carbon layer is not sufficiently formed on the surface of the carbon body, and a crystalline carbon layer is partially formed on the surface of the carbon body by complete carbonization. That is, it can be seen that the crystalline carbon layer is formed due to complete combustion at the surface of the carbon body at 800 ° C. at which complete combustion or carbon crystal is produced.

≪ Preparation Example 4 >: Preparation of heat-radiating composite material using graphite nanoplate coated with amorphous carbon layer

In this Production Example 4, the heat-radiating materials manufactured by Production Examples 1 to 3 are used to form heat-dissipating composite materials.

2.56 g of an epoxy resin (bisphenol F type, Momentive, Epon-862) was dissolved in 80 mL of acetone solvent, and 0.25 g of an amorphous carbon-coated carbon body formed in Production Examples 1 to 3 as a filler was dissolved Were mixed to form a mixed solution. That is, heat-radiating materials are used as fillers for manufacturing heat-radiating composite materials.

The resulting mixed solution was dispersed and mixed for 1 hour through ultrasound dispersion of 500 W power, and then 2.176 g of a hardener (acid anhydride series, Hitachi chemicals, HN-2200) and an accelerator (amine series, Sigma Aldrich, N, N -dimethylbenzylamine) was added, and the solvent acetone was removed through a vacuum pump.

The solvent was removed, and the remaining slurry was subjected to primary curing in a vacuum oven at 80 ° C for 1 hour while bubbles were removed. After the primary curing, the slurry was filled in a mold, and the mixture was heated and cured at 120 ° C for 2 hours Polymer complexes. Through this, a disc-shaped heat-radiating composite material having a thickness of 1 mm and a diameter of 12.7 mm is manufactured.

For comparison, a heat-dissipating composite material of the same size is formed using only crushed and expanded graphite as a filler material, which is not coated with an amorphous carbon material.

The filler of the graphite nanoplate coated with the amorphous carbon layer of Production Examples 1 to 3 in this Production Example is set to have a weight ratio of 5 wt% with respect to the manufactured heat-radiating composite. In addition, the filler made of crushed expanded graphite for comparison also had 5 wt% of the heat-dissipating composite material.

Thermal conductivity and volume resistivity are measured for the manufactured heat-radiating composites. For comparison, the thermal conductivity and the volume resistivity of a heat-radiating composite using only crushed expanded graphite as a filler are measured.

Sample Carbonized PMF (wt%) Crushed expanded graphite (wt%) Thermal conductivity
(W / mK) Volume resistivity
(Ω · cm) Production Example 1 63.4 36.6 0.32 10 ¹² Production Example 2 46.5 53.5 0.36 10 ⁸ Production Example 3 29.6 70.4 0.40 10 ⁶ Crushed expanded graphite 0 100 0.62 10 ²

In Table 1, the carbonized PMF and crushed expanded graphite constitute the filler of this embodiment, and the values converted in terms of wt% based on the filler are shown. In the filler provided in Production Example 1, the highest amount of carbonized PMF appears, and the volume resistivity shows the highest value. Since the volume resistivity and the thermal conductivity are in inverse proportion, the thermal conductivity of the heat-radiating composite using the heat-dissipating material of Production Example 1 is the lowest. On the other hand, when only crushed expanded graphite is used as filler, it shows the highest thermal conductivity but the lowest volume resistivity.

For use as a heat-radiating composite material, the volume resistivity should be 10 ⁹ Ω · cm or more. It can also be seen that the sample of Preparation Example 1 in which the heat treatment was performed at 400 ° C exhibited the highest volume resistivity. This indicates that the amorphous carbon layer is very well coated on the surface of the carbon body. In the case of PMF, it is known that carbonization starts at about 350 ° C. Therefore, it is found that it is necessary to set the carbonization temperature within the range from the carbonization initiation temperature to 150 캜 in order to form the amorphous carbon layer through the incomplete carbonization and ensure the volume resistivity of 10 ⁹ Ω · cm or more. That is, when PMF is used as a functional polymer, it is preferable to perform carbonization at a temperature of 350 ° C to 500 ° C to form an amorphous carbon layer. If the temperature exceeds the above temperature range, the amount of coating of the amorphous carbon layer is decreased, so that the necessary volume resistance can not be secured, and it becomes difficult to obtain the characteristics of the non-conductor.

PREPARATION EXAMPLE 5 Optimization of the content of ceramic particles

According to Production Example 1, silica is injected into ceramic particles in the process of manufacturing a heat dissipation material.

7 is a graph showing the thermal conductivity and the volume resistivity of the heat-radiating composite material according to the change of the content of silica particles according to Production Example 5. FIG.

Referring to FIG. 7, in Production Example 1, silica particles are charged as ceramic particles to produce a heat-radiating material. The manufactured heat-radiating material is made of a heat-dissipating composite material according to Production Example 4 described above. The heat-radiating material containing silica particles is used as a filler in Production Example 4. [ The filler is fixed to have a weight ratio of 5 wt% based on the heat-radiating composite.

The x-axis in Fig. 7 represents the weight ratio wt% of the silica particles to the filler. The y-axis also discloses thermal conductivity and volume resistivity, respectively. When the silica particles are employed as the ceramic particles, the change in thermal conductivity is not large. However, the volume resistivity shows a high variation. When the weight ratio of the silica particles based on the filler is 5 wt% to 15 wt%, the heat radiation composite material has a volume resistivity of 10 ¹³ Ω · cm or more. Therefore, it is preferable that the ceramic particles have a weight ratio of 5 wt% to 15 wt% based on the filler.

Even if the weight ratio of the ceramic particles in the filler material is changed, the change in the thermal conductivity is low because the filler material is fixed at 5 wt% in the heat dissipation composite material. That is, when the weight ratio of the filler to the heat-radiating composite is fixed, the thermal conductivity does not change significantly even if the weight ratio of the ceramic particles is changed in the filler. Therefore, it can be understood that the volume resistivity of the heat-radiating composite material greatly depends on the weight ratio of the ceramic particles of the heat-radiating material as the filler, and the thermal conductivity of the heat-radiating composite material does not depend on the weight ratio of the ceramic particles in the heat-

≪ Production Example 6 >: Production of a heat-radiating composite material in which the content of the heat-radiating material is changed

In Production Example 5, the weight ratio of the silica particles based on the heat dissipation material is fixed to 9 wt%, the content of the filler as the heat dissipation material is changed, and the heat dissipation composite material is manufactured. The heat-radiating composite material is produced according to Production Example 4, but changes only the content ratio of the filler.

8 is a graph showing the thermal conductivity of the heat-radiating composite according to Production Example 6. Fig.

Referring to FIG. 8, thermal conductivity according to the weight ratio of the filler is disclosed. Also, the case of preparing the filler with expanded graphite before the crushing process by replacing the crushed expanded graphite in the filler is also compared at the same time.

The thermal conductivity increases as the weight ratio of filler increases in the heat-dissipating composite. That is, when the weight ratio of the heat-radiating material of the present invention increases in the heat-radiating composite material, the thermal conductivity is increased and can be used as a heat-dissipating electronic material.

In particular, when expanded graphite is used as a carbon sieve in a filler, the higher the filler content, the higher the thermal conductivity. This is because the amorphous carbon layer can not sufficiently coat the surface of expanded graphite having a relatively large major axis diameter. When the expanded graphite of the heat-radiating material is exposed, it is directly connected to the expanded graphite of the adjacent heat-radiating material, or the thermal conductivity is rapidly increased due to the reason that the amorphous carbon layer can not cover it.

9 is a graph showing the volume resistivity of the heat-radiating composite according to Production Example 6. Fig.

Each of the heat-dissipating composite materials is the same as that described in Fig. In FIG. 9, the x-axis represents the weight ratio of the filler based on the heat-dissipating composite material when graphite nanoplate using crushed expanded graphite as the carbon material is used. The y-axis represents the volume resistivity of the heat-radiating composite.

In Fig. 9, when expandable graphite is used as the carbon body, the volume resistivity decreases sharply as the weight ratio of the heat-radiating material as the filler increases. That is, it exhibits a volume resistance of not more than 10 ⁹ ? 占 에서 at not less than about 8 wt%. On the other hand, when the graphite nanoplate of crushed expanded graphite is used as the carbon material, the volume resistance is gradually reduced even if the weight ratio of the heat-radiating material as the filler is increased. Even at 18 wt% filler, the volume resistivity is maintained at 10 ⁹ Ω · ㎝ or more.

8 and 9, it is necessary that the heat-radiating composite material has a thermal conductivity of 0.4 W / m · K or more and a volume resistivity of 10 ⁹ Ω · cm or more. Therefore, the weight ratio of the heat-radiating material as the filler in the heat-dissipating composite material in which the graphite nanoplate is used as the carbon body is preferably 10 wt% to 18 wt%.

≪ Preparation Example 7 >: Preparation of heat-radiating composite material and evaluation of physical properties according to kinds of ceramic particles

In this production example, various ceramic particles are used for heat-dissipating materials. The production of the heat dissipation material is according to Production Example 1. Therefore, a graphite nanoplate using crushed expanded graphite is used as the carbon sieve. PMF is used as the functional polymer, and the carbonization temperature is 400 占 폚. In addition, the weight ratio of the ceramic particles based on the produced heat-radiating material is 9 wt%.

Various types of ceramic particle sizes have a distribution of 100 nm to 5 um. The ceramic particles are introduced is AlN, BN, SiO _2, SiC and Al ₂ O _3.

10 is a graph showing thermal conductivity and volume resistivity of a heat-radiating composite material when various ceramic particles are introduced according to Production Example 7. FIG.

Referring to FIG. 10, thermal conductivity and volume resistivity of a heat-dissipating composite fabricated using AlN, BN, SiO ₂ , SiC, and Al ₂ O ₃ ceramic particles, respectively, are disclosed. Particularly, as described above, the ceramic particles are produced according to Production Example 1, and each has a weight ratio of 9 wt% based on the heat dissipation material. In addition, the five types of heat-radiating materials manufactured are made of the heat-radiating composite according to Production Example 4, and are formed at a weight ratio of 15 wt% based on the heat-radiating composite.

In Fig. 10, the heat-radiating composite using SiC as ceramic particles exhibits a thermal conductivity of 0.7 W / m · K or more, but exhibits a low volume resistivity of less than 10 ⁹ Ω · cm. Indicating that it can not be used as a heat-dissipating electronic material due to its low volume resistivity. In addition, the heat-radiating composite using Al ₂ O ₃ as the ceramic particles exhibits a high thermal conductivity of 0.7 W / m · K or more, but exhibits a low volume resistivity of less than 10 ⁸ Ω · cm.

On the other hand, the heat-radiating composite material using AlN, BN or SiO ₂ as the ceramic particles exhibits a high thermal conductivity of 0.6 W / m · K or more and a high volume resistivity of 10 ⁹ Ω · cm or more. Therefore, it can be seen that AlN, BN or SiO ₂ is suitable for the ceramic particles for manufacturing the heat-radiating composite.

As described above, in the present invention, the functional polymer containing nitrogen atoms is incompletely carbonized to form an amorphous carbon layer. The amorphous carbon layer covers the outer surface of the carbon body. This can lower the high electrical conductivity of the carbon body. In addition, ceramic particles are distributed in the layered structure of the carbon body or on the surface of the carbon body, and on the inside and the surface of the amorphous carbon layer. The thermal conductivity can be further increased through the ceramic particles. The heat dissipation material produced through this shows high thermal conductivity and electrical insulation. In addition, when the heat-radiating composite material is manufactured, it has high processability due to an increase in dispersibility and shows excellent heat radiation performance.

In addition, the carbonization process in the mixing and nitrogen atmosphere is very simple in the manufacturing process, and the manufacturing cost of the heat dissipation material can be reduced.

In addition, ceramic particles are provided on the bulk or surface of the amorphous carbon layer coated on the carbon body. The ceramic particles have a composition of oxide or nitride. Ceramic particles have a relatively high degree of dispersion compared to a conductive carbon body. Therefore, when a heat-radiating film, a heat-radiating sheet, or the like is manufactured using a heat-radiating material as a filler, high workability can be secured. In the manufacturing process of the heat-radiating sheet, the heat-radiating material needs to be dispersed evenly in the solvent, and the cohesion phenomenon with the heat-radiating materials should be avoided. In the present invention, since the ceramic particles are introduced onto the amorphous carbon layer, the aggregation phenomenon between the heat dissipation materials is minimized.

100: Carbon body 120: Amorphous carbon layer
140: Ceramic particles

Claims (14)

Carbon bodies;
An amorphous carbon layer coating the surface of the carbon body; And
Wherein the amorphous carbon layer comprises ceramic particles distributed on or inside the amorphous carbon layer. The carbon material according to claim 1, wherein the carbon material is at least one selected from the group consisting of graphite, expandable graphite, expanded graphite, graphene, carbon fiber, carbon nanofiber, And carbon nanotubes. 2. The heat dissipation material according to claim 1, wherein the carbon nanotubes are carbon nanotubes. 3. The heat dissipation material according to claim 2, wherein the carbon body is a graphite nanoplate having expanded and graphitized expanded graphite having a major axis diameter of 10 to 50 [mu] m. The heat dissipation material according to claim 1, wherein the amorphous carbon layer is formed by incompletely carbonizing the functional polymer and contains nitrogen atoms and forms a sigma bond. 5. The method of claim 4, wherein the functional polymer is selected from the group consisting of poly (melamine-co-formaldehyde) methylated (PMF), polyoxazoline, polypyrrolidione, polyethyleneimine, polyvinylpyridine, chitin, polyamide, polyurethane, polyacrylonitrile, polyaniline or polycarbazole. A heat dissipation material characterized by comprising. The heat dissipation material according to claim 1, wherein the ceramic particles include AlN, BN or SiO ₂ . The heat dissipation material according to claim 6, wherein the ceramic particles have a weight ratio of 5 wt% to 15 wt% based on the heat dissipation material. Mixing a carbon body, a functional polymer, and ceramic particles to form a mixture; And
Heat-treating the mixture to incompletely carbonize the functional polymer to form an amorphous carbon layer for coating the surface of the carbon body, and distributing the ceramic particles in the amorphous carbon layer and on the surface of the amorphous carbon layer Method of manufacturing a heat dissipation material. 9. The method of claim 8, further comprising forming a graphite nanoplate having a major axis diameter of 10 [mu] m to 50 [mu] m through mechanical grinding of expanded graphite or expandable graphite to the carbon body prior to forming the mixture Wherein the heat-dissipating material is a thermosetting resin. The method of claim 8, wherein the functional polymer comprises a nitrogen atom and the amorphous carbon layer has a sigma bond. 11. The method of claim 10, wherein the functional polymer is selected from the group consisting of poly (melamine-co-formaldehyde) methylated (PMF), polyoxazoline, polypyrrolidione, polyethyleneimine, polyvinylpyridine, chitin, polyamide, polyurethane, polyacrylonitrile, polyaniline or polycarbazole. Wherein the heat dissipation material is a thermosetting resin. The method of claim 10, wherein the functional polymer is incompletely carbonized through heat treatment in a nitrogen atmosphere. [14] The method of claim 12, wherein the heat treatment of the functional polymer is performed at a temperature not lower than the carbonization start temperature and lower than the complete carbonization temperature. 14. The method of claim 13, wherein the functional polymer is PMF, and the heat treatment is performed at a temperature of 350 to 500 < 0 > C.

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