KR20090124259A - Method for making nanostructured metal-ceramic composite - Google Patents

Abstract

PURPOSE: A method for manufacturing a nano-structured metal ceramic is provided to inhibit the growth of the crystal grain of metal ceramics and to improve the interface adhesion. CONSTITUTION: A method for manufacturing a nano-structured metal ceramic comprises the steps of ball milling a mixture of any one of a specific metal carbide or a specific metal nitride and a specific metal powder to obtain a nanoparticle; press molding and sintering the nano-structured mixture with applying the heat generated by the induction current or the impulse current; and blocking the induction current or the impulse current if there is no change of the shrinkage length of the nano-structured mixture, and cooling the press molded and sintered nano-structured mixture to a room temperature just before the induction current or the impulse current is blocked.

Description

METHOD FOR MAKING NANOSTRUCTURED METAL-CERAMIC COMPOSITE}

The present invention relates to a metal ceramic manufacturing method, and more particularly to a nanostructure metal ceramic manufacturing method.

Metal ceramic is a high strength / high toughness material that is press-formed and sintered by mixing metal oxide, metal carbide, metal nitride, etc. with specific metal powder. Also called metal ceramics, hot pressing machine, hot hydrostatic pressure (HIP; Hot) isostatic pressing).

For example, conventional metal ceramics are different depending on the particle size of a mixture of a metal oxide, a metal carbide, and a specific metal powder, but generally, the mixture is introduced into a hot compression molding machine or a hot hydrostatic pressure molding machine, and then is about 1000 ° C. or more. It is produced by pressing and sintering by heating at least 1 hour at high temperature.

In practice, tungsten carbide / cobalt (WC / Co) metal ceramics are press-molded and sintered by heating a mixture of tungsten carbide (WC) powder and cobalt (Co) powder, which is a metal carbide, at a temperature of approximately 1400 ° C. in a hot compression molding machine for 1 hour. Manufacture.

As described above, when a mixture of a metal oxide, a metal carbide, a metal nitride, and the like and a specific metal powder is heated at a high temperature for a long time and press-molded and sintered, crystal grains of the metal ceramic produced are grown, so that the particle size of the metal ceramic is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a mixture of a specific metal carbide or a specific metal nitride and a specific metal powder or a mixture of a specific metal oxide and a specific metal powder with a nanoparticle size. After nanopowdering by ball milling to have a structure, pressurizing the nanostructure mixture until there is no change in shrinkage length of the nanostructure mixture while applying heat generated by an induced current or a pulse current to the nanostructure mixture. It is to provide a nanostructure metal ceramic manufacturing method for forming a metal ceramic having a nanostructure of the particle size by molding and sintering.

In order to achieve the object of the present invention as described above, the nanostructured metal ceramic manufacturing method according to the present invention, a mixture of any one of a specific metal carbide or a specific metal nitride and a specific metal powder to see the particle size having a nanostructure. A first process of nanopowdering by milling; Pressurizing and sintering the nanostructure mixture while applying heat generated by an induced current or a pulse current to the nanostructure mixture; And a third step of blocking the induced current or the pulse current when the shrinkage length of the nanostructure mixture is not changed, and cooling the pressed and sintered nanostructure mixture to room temperature until just before the induction current or the pulse current is blocked. It is done.

In order to achieve the object of the present invention as described above, another nanostructured metal ceramic manufacturing method according to the present invention, the first step of nano-powdering a mixture of a specific metal oxide and a specific metal powder by a ball milling method; Pressurizing and sintering the nanostructure mixture while applying heat generated by an induced current or a pulse current to the nanostructure mixture; And a third step of blocking the induced current or the pulse current when the shrinkage length of the nanostructure mixture is not changed, and cooling the pressed and sintered nanostructure mixture to room temperature until just before the induction current or the pulse current is blocked. It is done.

According to the method for manufacturing a nanostructured metal ceramic according to the present invention as described above, since the heat generated by the induced current or the pulse current is applied to the mixture nano-powdered by the ball milling method so that the particle size has the nanostructure, the moisture ( For example, high temperature pressing and sintering operations can be performed within 2 to 5 minutes. As a result, it is possible to produce nanostructured metal ceramics at low cost while further limiting grain growth and improving interfacial bonding property as compared with the conventional art. Can be.

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

Nanostructured metal ceramic manufacturing method according to the present invention is carried out as follows.

First, a mixture of one of a specific metal carbide or a specific metal nitride and a specific metal powder is nanopowdered by a ball milling method so that the particle size has a nanostructure, or a ball mill of a mixture of a specific metal oxide and a specific metal powder. Nanopowdered by the method.

The metal carbide may be titanium carbide (TiC), iron carbide (Fe ₃ C), aluminum carbide (Al ₄ C ₃ ), and the like, and the metal nitride may be titanium nitride (TiN), iron nitride (Fe ₄ N), or nitride. Aluminum (AlN) etc. can be used. In addition, the metal powder mixed with the metal carbide or metal nitride may be silicon (Si) powder, preferably the metal powder mixed with 1 to 99% by weight of the metal carbide or 1 to 99% by weight of the metal nitride is silicon 1 to 99% by weight of (Si) powder can be used.

The metal oxide may be titanium monoxide (TiO), titanium dioxide (TiO ₂ ), titanium trioxide (Ti ₂ O ₃ ), iron monoxide (FeO), iron dioxide (Fe ₂ O ₃ ), nickel oxide (NiO) and the like. have. As the metal powder mixed with the metal oxide, aluminum (Al) powder may be used. Preferably, the metal powder mixed with 1 to 99% by weight of the metal oxide may use 1 to 99% by weight of aluminum (Al) powder. .

Such a mixture of metal carbide and silicon powder, or a mixture of metal nitride and silicon powder, or a mixture of metal oxide and aluminum powder has a particle size of 100 nm or less in order to speed up nanostructure metal ceramic production and solid phase substitution reaction rate. Preferably, nanopowdered. In the present invention, any method may be applied as long as it is a method capable of nanopowdering these mixtures. Particularly, it is most preferable to nanopowderize these mixtures by a ball milling method. Unlike other milling methods, the ball milling method is suitable for nano- ning powders because the energy applied during powder production is sufficiently large.

The nanopowder mixture as described above is then subjected to heat and pressure generated by an induced current or a pulse current, whereby the nanostructure mixture is press-molded and sintered during a solid phase substitution reaction to prepare a nanostructure metal ceramic. In this case, the nano-structured metal ceramic is preferably made in an atmospheric state or a vacuum state, the vacuum state may be set differently depending on the material, but preferably maintained at 0.01 to 1 torr, most preferably in order to suppress oxidation of metals. Maintain 0.04torr.

The pressure is preferably added at 10 to 1000 MPa, but can be at normal pressure. If the pressure range is less than 10MPa, there is a problem that the specimen can not be sufficiently densified, and if it exceeds 1000MPa there is a problem that the cost of manufacturing a device for manufacturing a nanostructured metal ceramic.

In addition, in the state in which the pressure is added, the nanostructure mixture is subjected to press molding and sintering by applying heat generated by an induction current or a pulse current, and specifically, without being in contact with the outside of the nanostructure mixture. Applying a high frequency induction current to an outer coil (e.g., a conductive metal coil such as a copper coil) that surrounds and press forming and sintering by indirectly heating the nanostructure mixture by Joule heat generated by the induced current, or The nanostructure mixture is heated, press-formed and sintered by Joule heat generated by the pulse current applied to the die member in which the structure mixture is received.

Here, the frequency of the high frequency induction current applied to the external coil is preferably 1 KHz to 100 KHz, and the period of the pulse current is preferably 1 Hz to 1 Hz. At this time, the frequency range of the induced current should be properly adjusted according to the size of the specimen because the penetration depth of the high frequency current depends on the frequency. In addition, the heating rate by heat generated indirectly by the high frequency induction current or heat generated by the pulse current is preferably set to 100 to 5000 ° C / min. If the heating rate is less than 100 ℃ / min takes a long time to sinter the crystal grains, there is a problem that the heating rate is faster than 5000 ℃ / min there is a problem that the thermal stress occurs in the specimen.

When pressure forming and sintering the nanostructure mixture while heating the induction current heating / pressurizing sintering method or the pulse current heating / pressurizing sintering method as described above, the shrinkage length decreases while the nanostructure mixture is densified by the continuously applied pressure. When the densification is completed and there is no longer a change in contraction length, at this point, the induced current or pulse current is blocked and the pressure is removed.

From the moment of applying pressure, induction current or pulse current to the nanostructure mixture as described above, from the moment when the nanostructure mixture reacts to solid phase and is fully densified, the moment when the pressure, induction current or pulse current is removed is no longer changed. Since it takes about 2 to 5 minutes, the present invention can produce a dense nanostructured metal ceramic in a short time without pore formation in the mixture.

Thereafter, the nanostructure mixture is cooled to room temperature, and the cooling may be performed according to a conventional method.

In addition, the post-treatment process is not required after the nanostructure metal ceramic is manufactured through the above process, so that the nanostructure metal ceramic can be manufactured in a short time using only a single process.

Nanostructured metal ceramic of the present invention as described above can be produced using an induction current heating / pressure sintering machine, or a pulse current heating / pressure sintering machine.

1 is an induction current heating / pressure sintering machine used to implement the nanostructure metal ceramic manufacturing method according to the present invention.

Referring to FIG. 1, the induction current heating / pressurizing sinterer 100 includes a die member 110, a pressing member 120, and an induction current generating member 130.

The die member 110 accommodates nanostructure mixtures such as nanopowdered metal carbide and silicon powder mixtures, metal nitride and silicon powder mixtures, or metal oxides and aluminum powder mixtures. Preferably, a through hole is formed therein and the nanostructure mixture is accommodated in the through hole. In addition, it is preferable to maintain the vacuum degree inside the through hole filled with the nanostructure mixture in the die member 110 to be 0.01 to 1 torr.

The pressing member 120 is to apply the pressure transmitted from the external pressure generating device to the nanostructure mixture inside the through hole, and is inserted into the upper and lower portions of the through hole to apply uniaxial pressure to the nanostructure mixture. That is, the nanostructure mixture is densified due to the pressure exerted by the pressing member 120, and the through hole and the pressing member 120 are operated in order to measure the change in shrinkage length of the nanostructure mixture, which is the degree of completion of the densification. A linear variable differential transformer (LVDT) may be attached to the portion. The pressure through the pressing member 120 is preferably added to 10 ~ 1000MPa.

The induction current generating member 130 is formed to be spaced apart from the periphery of the die member 110, and serves to generate an induction current. The induction current generating member 130 is made of a high frequency current coil, indirect heat is applied to the die member 110 and the nanostructure mixture by the induction current generated by the current applied to them to form a heat-forming and Sintering takes place.

At this time, the induction current frequency is preferably 1KHz ~ 100KHz flowing to the induction coil, the heating rate by the induced current generated in this way is preferably 100 ~ 5000 ℃ / min.

2 is a die assembly of a pulsed current heating / pressurizing sintering machine used to implement the nanostructured metal ceramic manufacturing method according to the present invention.

Conventional pulse current heating / pressure sintering machine is composed of a water-cooled vacuum chamber, a die assembly, a pulse current supply device, a pressurization device, a vacuum device, a cooling device, and various control and measuring devices. The water-cooled vacuum chamber is a container for controlling the atmosphere during heating / pressing molding and sintering. The water-cooled vacuum chamber is made of stainless steel, and has a double container having a viewing window for internal monitoring and a door for mounting the die assembly. Flow.

Referring to FIG. 2, the die assembly 200 of the pulse current heating / pressurizing sintering machine includes a punch 210 made of high purity graphite, a cylindrical die 220, and a pressure block 230 made of an insulating material such as alumina. The powder is filled in the inner space formed by the upper and lower punches 210 and the cylindrical die 220, and the vacuum degree, which is a process factor, is preferably about 0.01 to 1 torr, and may be in the air depending on the material. The pulse current supply device 300 supplies a pulse current to the specimen by the operation of the control switch 310, the pressurization device applies a uniaxial pressure to the punch 210 of the die assembly 200 through the pressure block 230, On the moving part of the hydraulic cylinder is fitted a linear displacement differential transformer (LVDT) which measures the change in length of the specimen. The pressure through the punch 210 is determined experimentally enough to sufficiently densify the specimen, and is preferably added at 10 to 1000 MPa. The pulse current is applied until the densification of the powder occurs during sintering after heating / pressing molding, and the period is preferably 1 Pa to 1 Pa, and the heating rate by the pulse current is preferably 100 to 5000 ° C./min. . Conventional rotary pumps and cooling water pumps may be used as the vacuum device and the cooling device, respectively. The control and measurement device controls process factors such as pressure and current, and measures various data in process progress.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

Example 1

Titanium dioxide (TiO ₂ ) and aluminum (Al) raw powders each having a particle size of 43 μm were prepared into a nanopowder having a size of about 37 nm using ball milling. After filling the nano-powder in the graphite die of the die member 110 of FIG. 1, a mechanical pressure of 60 MPa was applied and a vacuum atmosphere of 0.04 torr was made.

In the state of continuously applying a pressure of 60 MPa, a high frequency induction current heating / pressurization sintering was started by applying a current of 14.4 mA to the external coil, that is, the induction current generating member 130 of FIG. 1. At this time, the heating rate by Joule heat generated by the induction current heating was to be 800 ℃ / min.

After sintering is started after heating / pressing molding, the shrinkage length change of the specimen is observed with a linear displacement differential transformer (LVDT) to remove the induced current and pressure at the point of stabilization without changing the length, and to cool to room temperature (Ti) and aluminum (Al ₂ O ₃₎ crystal grain size of each 90㎚ and 30nm of titanium oxide-aluminum oxide (Ti-Al ₂ O ₃₎ to give the ceramic.

After ball milling the titanium dioxide (TiO ₂ ) and aluminum (Al) raw powder in Example 1, before the high frequency induction current heating / pressure sintering, and after the high frequency induction current heating / pressure sintering change of temperature and shrinkage length, SEM (Scanning Electron Microscope) photographs and XRD (X-ray diffraction) patterns are shown in FIGS. 3 to 5, respectively.

Figure 3 shows the temperature change (■) and shrinkage displacement (●) according to the heating time by high frequency induction current heating / pressure sintering, the shrinkage length before the shrinkage length in a straight line (before heating / pressure sintering) 4 and 5, the final product phase of titanium-aluminum oxide (Ti-Al ₂ O ₃ ) ceramic phase did not appear, but after the shrinkage length was changed linearly (after heating / pressurizing sintering), the titanium- It was found that an aluminum oxide (Ti-Al ₂ O ₃ ) ceramic phase was formed. As can be seen from FIG. 3, the present invention indicates that a metal nanoparticle having a dense nano structure having almost no pores was produced in a short time within 2 minutes by using a high frequency induction current heating / pressurizing sintering method according to the present invention.

FIG. 4A is an SEM photograph showing a raw material powder of about 37 nm after ball milling, and FIG. 4B is an SEM photograph after heating / pressurizing sintering. In (a) of FIG. 4, only titanium dioxide (TiO ₂ ) and aluminum (Al) were present without difference after ball milling, but after heating / pressurizing sintering, as shown in (b) of FIG. 4, the final product was titanium-oxidized. The desired phase was obtained with an aluminum (Ti-Al ₂ O ₃ ) ceramic, from which it can be seen that the heating / pressing sintering was completed after the shrinkage length was changed linearly.

FIG. 5 is a photograph showing an XRD pattern, and as shown in FIG. 5A, heating / pressurization sintering does not occur after ball milling, and thus other peaks other than the titanium dioxide (TiO ₂ ) and aluminum (Al) phases are shown. Although it could not be observed, the titanium-aluminum oxide (Ti-Al ₂ O ₃ ) ceramic phase of the present invention is formed after the change in shrinkage length in a straight line by heating / pressing sintering as shown in FIG. It was confirmed that the unreacted titanium dioxide (TiO ₂ ) and aluminum (Al) peaks were not observed, indicating that the solid phase replacement reaction was completed.

Example 2

Nanostructure metal ceramic manufacturing method using the pulse current heating / pressure sintering machine is made of five steps, each step is as follows.

Step 1: The powder is ball milled to a size of 100 nm or less.

Step 2: The ball milled nanopowder is filled and mounted in a graphite die, ie, the cylindrical die 220 of FIG. 2, and brought to a vacuum of about 0.4 torr.

Step 3: Applying a pressure of 60 MPa to the nano powder to form a molded body.

Step 4: Applying a constant pulse current to the graphite die and the specimen by continuously applying a pressure of 60 MPa to the molded body, heating the specimen at a heating rate of 2000 ° C./min by Joule heat, and after the start of heating / pressing molding During sintering, the change in shrinkage length of the specimen is observed with a linear displacement differential transformer (LVDT) to remove the pulse current and pressure at the point of stabilization without change in length.

Step 5: Cool the specimen to room temperature.

The method for producing a nanostructured metal ceramic according to the present invention described above is not limited to the above embodiments, and has a general knowledge in the field of the present invention without departing from the gist of the present invention as claimed in the following claims. Anyone who grows has the technical spirit to the extent that anyone can make various changes.

1 is an induction current heating / pressure sintering machine used to implement the nanostructure metal ceramic manufacturing method according to the present invention.

2 is a die assembly of a pulsed current heating / pressurizing sintering machine used to implement the nanostructured metal ceramic manufacturing method according to the present invention.

Figure 3 is a graph showing the temperature change (■) and shrinkage displacement (●) according to the heating time by the induced current.

4 is a SEM (Scanning Electron Microscope) photograph of the nanopowder powdered by a ball milling method and a SEM photograph of the nanostructured metal ceramic (b) prepared after heating / pressurizing sintering by an induction current.

5 is an XRD (X-ray diffraction) pattern of a nanostructured metal ceramic (b) prepared after heating / pressurizing sintered by a mixture (a) and an induction current nanopowdered by a ball milling method.

<Explanation of symbols for the main parts of the drawings>

100: induction current heating / pressure sintering machine 110: die member

120: pressing member 130: induction current generating member

200: die assembly 210: punch

220: cylindrical die 230: pressure block

300: pulse current supply device 310: control switch

Claims (6)

A first process of nanopowdering a mixture of any one of a specific metal carbide or a specific metal nitride and a specific metal powder by a ball milling method so that the particle size has a nanostructure; Pressurizing and sintering the nanostructure mixture while applying heat generated by an induced current or a pulse current to the nanostructure mixture; And A third step of blocking the induced current or the pulse current if there is no change in the shrinkage length of the nanostructure mixture, and cooling the pressed and sintered nanostructure mixture to room temperature until immediately before the induced current or the pulse current is blocked; Nanostructured metal ceramic manufacturing method, characterized in that consisting of. The method of claim 1, wherein A mixture of 1 to 99% by weight of any one of titanium carbide (TiC), iron carbide (Fe ₃ C) and aluminum carbide (Al ₄ C ₃ ) and 1 to 99% by weight of silicon (Si) powder, or titanium nitride (TiN), Nanopowdering a mixture of 1 to 99% by weight of any one of iron nitride (Fe ₄ N) and aluminum nitride (AlN) and 1 to 99% by weight of silicon (Si) powder so that the particle size is 100 nm or less. Nanostructured metal-ceramic manufacturing method characterized in that. The method of claim 1, wherein in the second process The nanostructure mixture was subjected to a pressure of 10 to 10 while applying heat generated by an induced current having a frequency of 1 KHz to 100 KHz or a pulse current having a period of 1 Hz to 1 Hz at a rate of 100 to 5000 ° C./min. Method for producing a nanostructured metal ceramic, characterized in that the pressing and sintering at 1000MPa. A first step of nanopowdering a mixture of a specific metal oxide and a specific metal powder by a ball milling method; Pressurizing and sintering the nanostructure mixture while applying heat generated by an induced current or a pulse current to the nanostructure mixture; And A third step of blocking the induced current or the pulse current if there is no change in the shrinkage length of the nanostructure mixture, and cooling the pressed and sintered nanostructure mixture to room temperature until immediately before the induced current or the pulse current is blocked; Nanostructured metal ceramic manufacturing method, characterized in that consisting of. The method of claim 4, wherein in the first step 1 to 99% by weight of any one of titanium monoxide (TiO), titanium dioxide (TiO ₂ ), titanium trioxide (Ti ₂ O ₃ ), iron monoxide (FeO), iron dioxide (Fe ₂ O ₃ ), and nickel oxide (NiO) And nano-powdering the mixture of 1 to 99% by weight of aluminum (Al) powder so as to have a particle size of 100 nm or less by a ball milling method. The method of claim 4, wherein in the second process The nanostructure mixture was subjected to a pressure of 10 to 10 while applying heat generated by an induced current having a frequency of 1 KHz to 100 KHz or a pulse current having a period of 1 Hz to 1 Hz at a rate of 100 to 5000 ° C./min. Method for producing a nanostructured metal ceramic, characterized in that the pressing and sintering at 1000MPa.

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