KR100933547B1 - Milling method of homogeneous nano scale particle for amorphous materials with multi components system - Google Patents

Abstract

PURPOSE: A method for crushing nano-size particles of multi-component amorphous materials is provided to maximize the restriction of particles coagulation by removing moisture between particles and exposing the nano-size particles to an electromagnetic wave. CONSTITUTION: A method for crushing nano-size particles of multi-component amorphous materials includes a step for inputting mother materials to be crushed on a mill port having a space of 35% ~ 45%, and a step for rotating the mill port with the speed of 390rpm / min or more. The crushing method of the nano-size particles includes drying effects of the particles without particles coagulation.

Description

Milling Method of Homogeneous Nano Scale Particle for Amorphous Materials with Multi Components System

The present invention relates to a method of grinding an amorphous ceramic material into uniform nano-sized particles in a hybrid paste composition that simultaneously satisfies the functionality of conduction and insulation used in the electrical and electronics industry.

More specifically, the present invention is an initial synthetic phase and nano-crushing process of a multi-component amorphous ceramic material applicable to the production of a nano-hybrid paste for electrode formation in which a nano-sized amorphous ceramic material and a conductive metal material is mixed The invention relates to particle pulverization and drying treatment having the same phase as before pulverization. Therefore, through the present invention, the distribution of the multi-component amorphous particles will be presented a method having a homogeneous particle distribution of the spherical homogeneity of D ₅₀ = 250nm, D _max = 500nm, and the coarsening of the particles is suppressed. This will include methods for crushing nanoparticles and the removal of moisture that affects the coarsening of particles in the process of minimizing the surface energy proportional to the specific surface area of the material as well as the material's specific behavior.

A hybrid paste formed of conductive silver, an amorphous ceramic material, and a vehicle may be applied to various display electrodes and solar cell electrodes. In rheological properties such as printability required in hybrid pastes, coarse particles are the main target of management because they have a decisive effect on the passage of the paste through the capillary of the screen or ejector. That is, the control of uniform particles in the paste is closely related to the screen printer efficiency. In addition, the specific surface area that increases as the particles become finer has the advantage of increasing reaction rate, dissolution rate, and mixing degree.

In particular, the smartization of the electronic module is inevitably required to cope with the existing average particle size of> 3㎛ because it requires a hybrid paste that can be formed in a narrower and higher form than the conventional electrode dimensions. In this regard, it is expected to increase the demand for amorphous materials for nanohybrid pastes using new nanoparticles, which are required in the next-generation electrical and electronic industries and the renewable energy industry.

Chemical processes such as hydrothermal synthesis have been well known for the production of nanoparticles for single metal based silver materials, but research reports on nanoscale particle acquisition methods for multicomponent ceramic materials have not been investigated.

Typically, the grinding of the ceramic material uses a dry milling method. However, milled grains have a wide particle scattering range on a micrometer basis, and the grinding efficiency is not only dependent on the function of time, but there are no studies on grinding to induce uniform particle distribution. In addition, the ball mill pulverization using physical factors such as impact and abrasive friction has a deep correlation with the cause that the part of the pulverization energy applied to the particles is absorbed into the parent material and acts as a deformation energy to change the amorphous phase as the particles are pulverized.

In the wet grinding method, it is known that a part of the composition contained in the amorphous parent material is eluted in the solution in proportion to the grinding time, thereby accompanied by a change in pH. This means that the composition of the parent material changes due to the elution of certain components such as alkaline earth or alkali metal. Due to the impact energy absorption problem on the specific surface area of the particles during milling and the composition change due to elution, it was confirmed that there is a technical problem of crushing uniform nano-scale particles with the current grinding treatment technology.

From this point of view, this study will propose a uniform nano-sized particle grinding method, identification of the grinding mechanism and drying method to prevent intergranulation.

Accordingly, an object of the present invention is the shear energy that solves the technical problem of grinding the uniform nano-scale particles by the current grinding treatment technology due to the problem of absorption of impact energy on the specific surface area of the particles during the milling process and compositional changes due to elution. It is to provide a uniform nano-size particle grinding method of multi-component amorphous material of D ₅₀ = 250nm, D _max = 500nm particles using a grinding mechanism.

Another object of the present invention is to provide a drying method for preventing intergranulation.

In addition, the present invention has a problem of obtaining a uniform nano-sized particle distribution, drying method to suppress the aggregation of particles and a pulverization mechanism by synthesizing the ceramic amorphous material.

In the present invention to achieve the above object in the ball mill grinding method of a multi-component amorphous material, the mill port so that the pulverized medium, IPA solution and the parent material to be pulverized in the mill port to ensure 35% to 45% of the empty space in the mill port Multi-component amorphous material of D50 = 250nm, Dmax = 500nm particles using a shear energy mechanism to grind the parent material between the rotating grinding medium and the grinding medium by rotating the mill pot at a high speed of 390 rpm / min or higher. A uniform nano size particle milling method of is provided.

In addition, in the present invention, 15 to 20%, 25 to 30% of the IPA solution and 15 to 20% of the parent material are added to the mill port so as to secure 35% to 45% of the empty space in the mill port at vol%. There is provided a uniform nano-sized particle grinding method of a multi-component amorphous material, characterized in that.

In addition, the present invention satisfies the following formula (1), the smaller the diameter of the mill pot, the shear energy is increased, so that the easy nano-sized particle distribution, characterized in that the uniform nano size of the multi-component amorphous material A particle grinding method is provided.

Where m is the mass of the ball, g is the acceleration of gravity, u is the circumferential velocity of the ball, R is the radius of the millport, r is the radius of the ball, and α is any angle to the vertical axis of the millport.

In the present invention, the nano-size particles pulverized by the pulverization method is exposed to a micro oven for 30 to 40 seconds to uniformly crush the nano-particles of the multi-component amorphous material, characterized in that the aggregation is suppressed through the drying between the particles. A method is provided.

In addition, in the present invention, by using the IPA solution in the grinding process, while grinding the Bi ₂ O ₃ -B ₂ O ₃ -ZnO-RO ₂ and P ₂ O ₅ -SnO-ZnO-based composite material while suppressing the elution of B and P It provides a uniform nano-size particle grinding method of a multi-component amorphous material, characterized in that.

The uniform nano-sized particle crushing method of the multi-component amorphous material using the shear energy pulverization mechanism according to the present invention obtains a uniform nano-sized particle distribution of D ₅₀ = 250 nm, D _max = 500 nm using shear stress. It can be effective.

In addition, the nano-size particle crushing method according to the present invention by exposing the nano-sized particles recovered by the condenser to the electromagnetic wave for several tens of seconds in the micro oven to easily remove the moisture adhered between the particles to maximize the particle aggregation There is an effect that can be easily dried without aggregation phenomenon between particles.

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

In the ball mill grinding method of the multi-component amorphous material of the present invention, a grinding medium, an IPA solution, and a parent material to be crushed are placed in the mill port so that 35% to 45% of the empty space in the mill port is secured, and the mill pot is 390 rpm. Uniform nano-sized particles of multi-component amorphous materials of D ₅₀ = 250 nm and D _max = 500 nm using a shear energy mechanism that pulverizes the parent material coming in between the rotating and rotating media by rotating at high speeds per minute / min or more Grinding method.

In the amount of the pulverized medium, IPA solution and the parent material to be crushed into the millport, the pulverized medium is 15 to 20%, so that 35% to 45% of the empty space in the millport is secured to the millport at vol%. Add 25-30% of IPA solution and 15-20% of parent material.

In the present invention, Bi ₂ O ₃ -B ₂ O ₃ -ZnO-RO ₂ (Korean Patent No. 10-0639689) and P ₂ O ₅ -SnO-ZnO-based amorphous composition synthesized at 780 ± 20 ℃ as a ground material Was used.

In order to grasp the characteristics of particle size and shape according to the grinding method from the synthesized bulk-form parent material, the particles by dry jet jet mill, wet bead mill, pulse laser and present inventors shear energy grinding method After comminution, comparative investigation was carried out.

First, the jet mill was pulverized under working conditions of 7.0 kgf / cm 2 of main air, 0.5 kgf / cm 2 of ejector, and 0.45 kgf / cm 2 of line.

Fig. 1 (a) shows the distribution of particle size distribution D ₅₀ = 2.5 μm and D _max = 25 μm by analyzing the distribution of particle sizes repeated three or more times using a jet mill.

As shown in FIG. 1 (b) showing the SEM micrograph of the microstructure of the particles, the coarse particles were observed to have an angular shape with a plate shape and corners. Although very limited, the particles of the inclined circular part of FIG. 1 (c) show that the spherical shape and the particles of about 250 nm are very limited. The characteristics of the particles pulverized by the jet mill generally showed that the small particles were mixed unevenly among the coarse particles, and FIG. 1 (a) analyzing the particle size distribution and FIGS. 1 (b) and (c) which observed the microstructure of the particles. Was found to match.

The beads mill was pulverized under working conditions using a liquid transfer amount of 2 L / hr and a 0.3 mm ZrO ₂ ball. After milling with a bead mill, the microstructure of the particles was observed and shown in FIGS. 2 (a) and (b). The particles had a distribution of D ₅₀ = 1 μm and D _max = 2.5 μm, indicating that the D ₅₀ and D _max distribution changes significantly compared to jet mill crushed particles. However, it was judged that there is some distance from the result of obtaining the uniform nano-sized particles, and that the improvement of the treatment of the aqueous solution generated in the crushing and classification process is required.

Wet milling using bead mills rather than the dry method of jet mills was shown to be significantly improved to fine particles> 1 μm and maximum size particles (D _max = 2.5 μm). However, it was confirmed that the distribution of uniform nano-sized particles pursued by the present invention did not reach the target point only by the difference between the wet and dry grinding method and the selection of the grinding machine (see FIGS. 1 and 2).

The particle size, microstructure, and crystal structure of the sample produced by the Pulse LASER method that pulverizes the material by focusing the energy generated by the LASER oscillator with a magnifying glass and irradiating the energy to the object are shown in FIGS. 3 and 4, respectively. It was. As shown in FIG. 3, which is a microstructure analysis data using TEM, the particles are distributed with a very constant particle size as several nm. In addition, it shows a typical amorphous pattern as shown in Figure 4 showing the TEM diffraction pattern of the sample pulverized by the pulse laser method, which is well in accordance with the object of the present invention. However, it is possible to obtain several nano-sized particles by this method, but the yield is only 2mg / 4hr.

Figure 5 shows the observation of the fine structure pulverized in the present invention by Fe-SEM. As shown in FIGS. 5A and 5B, particles having a spherical shape of D ₅₀ = 250 nm and D _50max = 500 nm are uniformly distributed, and particles having a coarse size of several μm or more are not observed.

The present invention will be described in more detail based on the following examples. However, the present invention is not limited to the following examples.

EXAMPLE

Shear stress according to the present invention was performed in the following manner to obtain a uniform nano-sized particle distribution of D ₅₀ = 250nm, D _50max = 500nm. First, prepare the props for milling as shown in Table 1.

Item standard ZrO ₂ Ball 0.3 to 0.5 Mill pot P. E Bottle Isopropyl Alcohol (IPA) M. O. S Grade

20% ZrO ₂ balls, 30% IPA solution, and 20% parent material to be crushed are added to the mill pot at vol%, but the empty space must be at least ≥35%. Grind the particles by rotating the mill pot at high speed ≥390rpm / min. At this time, the centrifugal force field is generated so that the ball and the liquid do not rotate along the wall of the millport. Therefore, the initial state is gradually rotated to ≥390 rpm / min over time.

A general model of the grinding media moving in the mill pot when starting the rotary motion is shown in Figure 6 (a). When the rotational movement starts at point A, the grinding media starts to rotate to point B along the cylindrical wall and moves to point C as the speed increases. At point C, the force of the gravitational field is greater than the rotational force, so impact energy is generated when it falls to the point A of stationary state. However, the constant acceleration of the ball is governed by the rotational speed of the mill pot.

Inside the ball mill, the ball is subjected to centripetal force due to the centripetal force caused by gravity and the rotational speed of the ball mill. Therefore, the centrifugal force and centripetal force must be the same so that the ball existing at any angle α with respect to the vertical axis of the ball mill is attached to the wall of the mill pot. therefore,

Where m is the mass of the ball, g is the acceleration of gravity, u is the circumferential velocity of the ball, R is the radius of the millport, r is the radius of the ball, and α is any angle to the vertical axis of the ball mill.

At critical speed ( n _c ), α = 0 and cosα = 1

to be. R is smaller than R, so R-r ≒ R

to be. Grinding in the mill pot is usually performed at a rotational speed of about 65-80% of the critical rotational speed. To this end, in the millport process, in order to maximize the impact energy, the grinding media must be rotated according to Equation (1), which does not generate centrifugal force.

If the radius of the mill pot, R is large, the effect on the grinding of particles is as follows. If the radius of the millport of R, the ball rotates above the critical velocity, n _c , the ball and the liquid will only be subjected to the constant velocity movement by centrifugal force along the cylindrical wall surface. And there is a part of the ball having only potential energy in the direction perpendicular to the gravitational field. At this time, the liquid containing fine particles of the crushed material collides with the crushed medium under the gravity field with energy corresponding to the rotational motion. This collision is transmitted as elastic energy to neighboring grinding media. This chain reaction has a value that is directly proportional to the surface area, which promotes grinding. In this case, the smaller the diameter, the greater the specific surface area. Therefore, assuming that the net force, FN, which affects grinding, is given by Eq. (6).

Where p is the potential energy of the grinding media, s is the constant velocity kinetic energy of the particles contained in the liquid, e is the shear energy that the particles deliver to the grinding media, and ρ is the elastic energy delivered to the adjacent media by the shear energy. Represent each.

In equation (6), the force F on the potential energy p, the constant velocity motion s of the particles, the shear energy e of the pulverized medium, and the elastic energy ρ transmitted by the shear is shown.

Where R is the mill pot radius and ω is the angular velocity, respectively.

In Eq. (7), as the radius, R, increases, the angular velocity ω increases and ultimately F increases. This shows that F depends on the change in radius and size of R because the increase in the proportional energy of the specific surface area acts as the energy contributing to the crushing. Therefore, elastic energy can be considered as a new term that contributes to crushing in the concept of independent of the critical velocity, n _c , in the existing constant velocity motion. However, this assumption assumes that the milling energy is neglected if the diameter of the mill pot is reduced. In fact, as the diameter of the mill pot increases, the grinding efficiency increases, but as the diameter of the mill port increases, the grinding efficiency is in good agreement with the tendency to decrease rapidly.

The impact energy (point C in Fig. 6 (a)), which is the grinding energy generated under the control of the constant rotational speed of constant velocity motion, is constant, while the finer the particle is, the larger the grinding energy is required in proportion to the specific surface area of the particle. Because of this, the grinding of the particles has obvious limitations. That is, it means that pulverization can be continued only when a larger value of energy is supplied than the surface area of the pulverization is always increased. This means that milling of millport using impact energy, etc., is very limited in crushing nano-sized particles. This is analogous to the conclusion that conventional grinding concepts cannot grind uniform nano-sized particle sizes.

From this point of view, the elastic modulus of amorphous material, EY = 0.55 × 1011Pa, shear modulus, Es = 0.23 × 1011Pa, which is inherently smaller than metal (EY = 2.0 ~ 3.6 × 1011Pa, Es = 0.84 ~ 1.50 × 1011Pa). Noted the characteristics. This means that pulverization by shear energy is easier than conventional impact energy, and in the study of the present invention, the pulverization method by shear force was devised as a model as shown in FIG. The centripetal force acting on the ball in the millport is the gravity of the ball (mg) and the centrifugal force (mu ² / R) is inversely proportional to the diameter of the millport. Therefore, by reducing the centrifugal force, the ball is rotated in place without being pulled by the rotating force of the mill pot, generating shear force due to friction between the rotating ball and the ball, and the shear force causes the raw material that comes in between the ball and the ball to be crushed. do. This method uses a new shear force grinding method rather than a ball drop impact in a conventional mill pot to allow uniform nano-sized particle grinding. In order to use this grinding method, the diameter of the mill pot can be reduced to minimize the centrifugal force, and a high specific gravity ball can satisfy this condition. In addition, in order to have a good mixing condition of the ball and the raw material, the more the specific gravity of the ball and the raw material is in a similar state, this grinding method may have a better effect.

As the particle pulverization proceeds through this series of repetitions, the energy of the surface energy increase is continuously given as the shear energy, so that the grinding efficiency is increased in proportion to the time and the particle specific surface area.

Picture of observation of the microstructure of the particles obtained by the method proposed in the present invention by FE-SEM as shown in Fig. 5 (a) and (b) by agglomeration between the fine particles by the spherical shape and the surface area to reduce the surface area of the particles between the particles Due to the morphology present, very uniform particle distribution and size were obtained at 200 ~ 300nm.

7 (a) and 7 (b) show XRD patterns before and after grinding, respectively. XRD data before and after milling were identified in amorphous patterns similar to those of typical silica materials, as shown in Figures 7 (a) and (b). This is because the pulverization method used in the present invention not only contributes to the pulverization but also the IPA non-polar solvent inhibits the generation of charge during the pulverization process. It is thought to be attributable to the effect of suppressing the phase change of the substance. This suggests that the nonpolar solution is closely related to the property of not generating charges.

8 (a) and (b) show the entrained copper analysis with particle reduction. 8 (a) shows that the glass transition temperature (Tg) before grinding is 380 ° C and the glass softening temperature is around 420 ° C. In 8 (b), which observed the entrained copper of the nano-crushed particles, the glass transition temperature was lowered ≥100 ° C to 270 ° C Tg and glass softening temperature around 370 ° C. As the surface area of the particles decreased, the surface driving force, reactivity, and dissolution rate increased, which could be used as a clear evidence of typical ultra-fine particle behavior, which indicates the possibility of low temperature sintering.

The following is a description of the separation and drying method of aqueous solution. In the present invention, nano-sized particle separation and solution material recovery are as follows. The milled particles are separated from the milling medium and the particles by the apparatus shown in FIG. 9. In the method of recovering the solution, it is possible to recover the solution by sedimenting the separated liquid, or easily recovering the liquid using a condenser maintained at ≤80 ° C. However, setting higher than the IPA boiling point can reduce the condensation time, but be careful of dangers such as explosions. When the remaining powder is dried after the solution recovery, homogeneous nano-sized particles are obtained, but the pulverized product exhibits a very large flocculation phenomenon between particles in proportion to the drying temperature. In order to prevent this, natural drying is preferable, but when moisture is attached to the particles in proportion to the drying time, it is difficult to remove only moisture without agglomeration of the particles because the charge balances with the fine particles. Therefore, in order to solve this problem, attention has been paid to the idea that the electromagnetic field of the micro oven generates friction heat by molecular rotation of the material. When the nano-sized particles recovered by the condenser were exposed to electromagnetic waves for several tens of seconds in a micro oven, the moisture adhering between the particles was easily removed, and thus the drying was easily performed while maximizing particle aggregation.

1A, 1B and 1C show the distribution and SEM microstructure of the particles milled with a jet mill, respectively.

2a and 2b show the microstructure of the particles milled with a bead mill.

Figure 3 shows the microstructure of the particles obtained by the pulse laser method.

Figure 4 shows the TEM pattern of the sample prepared by the pulse laser.

Figure 5 shows the microstructure of the particles milled by the method of the present invention.

6a and 6b show the impact energy and shear energy model of the grinding media, respectively.

Figure 7 shows the XRD pattern before and after nano-size milling.

8a and 8b are shown by comparing the TG / DTA graph with the change in particle size, respectively.

9 is an example of the apparatus used to separate the solution and the classification of the ground particles.

Claims (5)

In the mill pot grinding method of a multi-component amorphous material, Grinding media, IPA solution and the parent material to be crushed in the mill pot are put into the millport to secure 35% to 45% of the empty space in the millport, and the milling port rotates by rotating at a high speed of 390 rpm / min or more. A method for crushing uniform nano-sized particles of multi-component amorphous materials of D ₅₀ = 250 nm and D _max = 500 nm using a shear energy mechanism for crushing the parent material between the grinding media. The method of claim 1, The milling medium is characterized in that 15 to 20%, 25 to 30% IPA solution and 15 to 20% of the parent material is added to the millport so that 35% to 45% of empty space in the millport is secured. Uniform nano-size particle milling of component amorphous materials. The method of claim 1, Satisfying the following formula (1), the smaller the diameter of the mill pot, the shear energy is increased, the nanoscale particle grinding method of multi-component amorphous material, characterized in that easy nano-sized particle distribution is induced.

Where m is the mass of the ball, g is the acceleration of gravity, u is the circumferential velocity of the ball, R is the radius of the millport, r is the radius of the ball, and α is any angle to the vertical axis of the millport. The method of claim 1, The nano-sized particles pulverized by the pulverization method are recovered through a condenser, and the collected particles are placed in a beaker and exposed to electromagnetic waves for 30 to 40 seconds in a micro oven, thereby suppressing aggregation by drying between the particles. Uniform nano-size particle milling of component amorphous materials. The method of claim 1, By using the IPA solution during the grinding process Bi ₂ O ₃ -B ₂ O ₃ -ZnO-RO ₂ and P ₂ O ₅ -SnO-ZnO-based composite material characterized in that the grinding while suppressing the elution of B and P Uniform nano-size particle grinding of multicomponent amorphous materials.

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