DIELECTRIC PARTICLE SORTING APPARATUS

Abstract

The present invention provides a dielectric particle sorting apparatus. The dielectric particle sorting apparatus comprises: a chamber; a bottom electrode in the chamber; and a top electrode disposed at the top of the chamber so as to be spaced from the bottom electrode therein, wherein dielectric particles are positioned on the bottom electrode so that, when an alternating-current electric field is applied, the dielectric particles are electrified to be induced to flow upward, and thus the dielectric particles are sorted, and voltage and frequency are controlled so that the dielectric particles are controlled by particle size, weight, density, permittivity or surface area.

Claims

1. An apparatus for sorting dielectric powders, the apparatus comprising: a chamber; a lower electrode received in an inner space of the chamber; an upper electrode received in the inner space of the chamber and spaced apart from the lower electrode and disposed at an upper end of the inner space of the chamber; a first separation layer positioned between the upper electrode and the lower electrode received in the inner space of the chamber, wherein the first separation layer only partially overlaps each of the upper electrode and the lower electrode vertically; and a power applying means configured to generate an electric field of alternating current in an area between the lower electrode and the upper electrode, wherein the dielectric powders are positioned between the lower electrode and the first separation layer.

2. The apparatus for sorting the dielectric powders of claim 1, wherein the dielectric powder is a charged dielectric powder.

3. The apparatus for sorting the dielectric powders of claim 1, wherein the apparatus is configured to perform an electrically charging step of electrically charging the dielectric powders before the generation of the electric field of the alternating current.

4. The apparatus for sorting the dielectric powders of claim 3, wherein the electrically charging step includes application of an electric field, irradiation of UV, or generation of plasma for inducing dielectrophoresis of the dielectric powders.

5. The apparatus for sorting the dielectric powders of claim 3, wherein the electrically charging step includes filling the chamber with a first gas and then applying a voltage so that plasma is generated in a dielectric powder layer, and then filling the chamber with a second gas, wherein the first gas has a discharge starting voltage lower than a discharge starting voltage of the second gas.

6. The apparatus for sorting the dielectric powders of claim 1, wherein the dielectric powders are sorted based on a sorting criterion including a diameter, a weight, a density, a permittivity, or a surface area of the particle.

7. The apparatus for sorting the dielectric powders of claim 6, wherein the apparatus is configured to control each of a magnitude of the voltage and a frequency of the alternating current (AC), based on the sorting criterion.

8. The apparatus for sorting the dielectric powders of claim 1, wherein the apparatus further comprises a second separation layer received in the inner space of the chamber and positioned between the upper electrode and the lower electrode, wherein the second separation layer only partially overlaps each of the upper electrode and the lower electrode, wherein a vertical level of the second separation layer is different from a vertical level of the first separation layer.

9. The apparatus for sorting the dielectric powders of claim 9, wherein the apparatus further comprises a dielectric substrate stacked on an upper surface of the lower electrode.

10. An apparatus for sorting dielectric powders, the apparatus comprising: a chamber; a lower electrode received in an inner space of the chamber; an upper electrode received in the inner space of the chamber, wherein the upper electrode is positioned between an upper end of a main body of the chamber and the lower electrode so as to divide the inner space of the chamber into upper and lower portions, wherein the upper electrode only partially overlaps the lower electrode vertically; and a power applying means configured to applying alternating current power to the lower electrode and the upper electrode so that an electric field of the alternating current is generated between the lower electrode and the upper electrode, wherein the dielectric powders are positioned between the lower electrode and the upper electrode.

11. The apparatus for sorting the dielectric powders of claim 10, wherein the dielectric powder is a charged dielectric powder.

12. The apparatus for sorting the dielectric powders of claim 10, wherein the apparatus is configured to perform an electrically charging step of electrically charging the dielectric powders before the generation of the electric field of the alternating current.

13. The apparatus for sorting the dielectric powders of claim 12, wherein the electrically charging step includes application of an electric field, irradiation of UV, or generation of plasma for inducing dielectrophoresis of the dielectric powders.

14. The apparatus for sorting the dielectric powders of claim 12, wherein the electrically charging step includes filling the chamber with a first gas and then applying a voltage so that plasma is generated in a dielectric powder layer, and then filling the chamber with a second gas, wherein the first gas has a discharge starting voltage lower than a discharge starting voltage of the second gas.

15. The apparatus for sorting the dielectric powders of claim 10, wherein the dielectric powders are sorted based on a sorting criterion including a diameter, a weight, a density, a permittivity, or a surface area of the particle.

16. The apparatus for sorting the dielectric powders of claim 15, wherein the apparatus is configured to control each of a magnitude of the voltage and a frequency of the alternating current (AC), based on the sorting criterion.

17. The apparatus for sorting the dielectric powders of claim 10, wherein the apparatus further comprises a dielectric substrate spaced apart from the upper electrode and disposed on top of the upper electrode, wherein the dielectric substrate is disposed at an upper end of the inner space of the chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 is a view illustrating a structure of an apparatus for sorting dielectric powders according to the present disclosure.

[0027] FIG. 2 is a view illustrating a principle in which dielectric powders flow through an apparatus for sorting dielectric powders according to the present disclosure.

[0028] FIG. 3 is a diagram illustrating an AC electric field applied through the dielectric powders sorting apparatus of the present disclosure.

[0029] FIG. 4 is a view for illustrating behavior of dielectric powders starting to flow in the dielectric powders sorting apparatus of the present disclosure.

[0030] FIG. 5 is a view for illustrating behavior of dielectric powders under an AC electric field in the dielectric powders sorting apparatus of the present disclosure.

[0031] FIG. 6 is a diagram illustrating flow modes FF, TM, and LF of the dielectric powders in the apparatus for sorting the dielectric powders according to the present disclosure.

[0032] FIG. 7 is an image showing the flow modes FF, TM, and LF of the dielectric powders under application of AC high voltage through the dielectric powders sorting apparatus of the present disclosure.

[0033] FIG. 8 is a view illustrating the dielectric powders sorting apparatus used in each of Examples 1 to 3 of the present disclosure.

[0034] FIG. 9 shows images of the dielectric powders used in Example 1 of the present disclosure.

[0035] FIG. 10 shows images of the dielectric powders sorted through Example 1 of the present disclosure.

[0036] FIG. 11 shows images of the dielectric powders used in Example 2 of the present disclosure.

[0037] FIGS. 12 and 13 show images of the dielectric powders sorted through Example 2 of the present disclosure.

[0038] FIGS. 14 and 15 show images of the dielectric powders sorted through Example 3 of the present disclosure.

DETAILED DESCRIPTIONS

[0039] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The present disclosure may have various changes and may have various forms, and specific embodiments are illustrated in the drawings and will be described in detail herein. However, it should be understood that the present disclosure is not limited to the specific disclosed forms, but includes all modifications, equivalents, and substitutes included in the spirit and technical scope of the present disclosure. In describing the drawings, similar reference numerals are used for similar components.

[0040] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present disclosure. As used herein, the singular forms a and an are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms comprise, comprising, include, and including when used in this specification, specify the presence of the stated features, integers, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, operations, elements, components, and/or portions thereof.

[0041] Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0042] FIG. 2 is a view illustrating a principle in which dielectric powders flow through an apparatus for sorting dielectric powders according to the present disclosure.

[0043] Referring to FIG. 2, an attractive force Fa may act between the dielectric powders and the gravity F.sub.g may act on the dielectric powders before the electric field is generated in the inner space of the chamber. When the electric field is applied thereto, the electrostatic force F.sub.c in addition to the gravity F.sub.g and the attractive force Fa is applied to the dielectric powders. In this case, when the electrostatic force F.sub.c applied to the dielectric powders is greater than the sum of the gravity F.sub.g and the attractive force F.sub.d (F.sub.c>F.sub.g+Fa), the dielectric powders may move upwards under the electrostatic force F.sub.c.

[0044] The electrostatic force F.sub.c may be determined based on a charge amount q accumulated on the surface of the dielectric powders and the electric field E.sub.g in a gas space on top of the dielectric powders layer (F.sub.c=q.Math.E.sub.g). The attractive force Fa between the powder particles is proportional to the electric field Ep applied to the dielectric powders layer and the permittivity () of the dielectric powders (F.sub.aE.sub.p, ). In this case, since the electric field E.sub.g in the gas space on top of the dielectric powders layer and the electric field E.sub.p applied to the dielectric powders layer may be determined based on the magnitude of the voltage applied from the outside and a shape of the electrode. Thus, the apparatus for sorting the dielectric powder according to the present disclosure may easily sort the dielectric powders by adjusting the magnitude of the voltage to control the magnitude of the force applied to the dielectric powders. In the present disclosure, in addition to the voltage, factors for controlling the flow of the dielectric powders include a frequency, a charge amount q accumulated on the surface of the dielectric powder, and the like.

[0045] In the present disclosure, the charge amount q accumulated on the surface of the dielectric powders is the factor that affects the flow characteristics of the dielectric powders to the greatest extent. The charge amount q is most greatly influenced by the surface area (particle diameter and shape), density/permittivity (type of powder) of the dielectric powder, and may be affected by the kind of surrounding gas. When the dielectric powder is lightweight and the surface area thereof is large, the dielectric powders may flow very fast under the external electric field. When the dielectric powder is heavy and the surface area thereof is small, the dielectric powders may slowly flow under the external electric field. In addition, when the dielectric powders have the same weight, one having the spherical shape (the smaller surface area) may flow more slowly than another having the non-spherical shape may. That is, the particle having the non-spherical shape (the larger surface area), for example, the shape of plate-shaped, rod-shaped, cylindrical shape, etc. may flow faster. In the present disclosure, using the difference between the charge amounts of the dielectric powders, the powders may be sorted based on a diameter, shape, density, and permittivity of the particle.

[0046] FIG. 3 is a diagram illustrating a voltage applied through the dielectric powders sorting apparatus of the present disclosure.

[0047] Referring to FIG. 3, the voltage applied to the dielectric powders sorting apparatus of the present disclosure may be an AC high voltage of one selected from a sine wave, a square wave, a pulse wave, a triangle wave, a sawtooth wave, and the like. Preferably, the voltage may have a square wave. The square wave voltage has a rectangular waveform in which for one cycle, the waveform changes once and returns to an initial state. A time corresponding to one cycle may be defined as a period T, and the number of cycles included for one second may be defined as a frequency f.

[0048] In the dielectric powders sorting apparatus of the present disclosure, the applied voltage V.sub.m may be determined based on the sum of the voltage drop V.sub.g in the gas space, the voltage drop V.sub.p in the dielectric powders layer, and the voltage drop V.sub.d of the dielectric substrate (V.sub.m=V.sub.g+V.sub.p+2V.sub.d). In this regard, the voltage drop V.sub.g in the gas space and the voltage drop V.sub.p in the dielectric powders layer may affect the electric field E.sub.g in the gas space and the electric field E.sub.p applied to the dielectric powders layer, respectively. The electric field affects the upward flow of the dielectric powder. Thus, the upward flow distance of the dielectric powders may increase when a higher voltage is applied.

[0049] FIG. 4 is a view for illustrating behavior of dielectric powders that starts to flow in the dielectric powders sorting apparatus of the present disclosure.

[0050] Referring to FIG. 4, when the electric field of alternating current is generated in the chamber of the sorting apparatus of the present disclosure, a higher electric field may be applied to the inside of the dielectric powders layer than to an outside out of the dielectric powders layer (i.e. the gas space in which the dielectric powders may flow up). Accordingly, the dielectric powders particles may have the electric charges Q generated on the surface thereof, and thus, the electrostatic force F.sub.c enabling the upward flow thereof may be increased. The dielectric powders particles removed from the dielectric powders layer under the high electrostatic force F.sub.c are affected only by the electrostatic force F.sub.c and the gravity F.sub.g except for the attractive force F.sub.a between the dielectric powders. A force F.sub.net causing the dielectric powders removed from the dielectric powders layer to flow upwards may be expressed based on a following Equation 1.

[00001]$\begin{array}{cc}{F}_{\mathrm{net}}=F_c-F_g& \mathrm{Equation}1\end{array}$$F_{\mathrm{net}}=m.Math.a=q.Math.E_g-m.Math.g$$a=\frac{q.Math.E_g}{m}-g$

[0051] Referring to Equation 1, an acceleration a when the dielectric powders particles flow upwardly under the electric field may be derived based on the force F.sub.NET causing the dielectric powders removed from the dielectric powders layer to flow upwardly.

[0052] In this regard, when a distance between an upper end of the dielectric powders layer and a lower end of the dielectric substrate, that is, the maximum distance by which the dielectric powders can move in the inner space of the chamber may be defined as d.sub.g. A time T.sub.g taken for the dielectric powders to move by the space distance de may be derived using a following Equation 2 and based on the acceleration a and the spatial distance d.sub.g.

[00002]$\begin{array}{cc}{d}_g=\frac{1}{2}a.Math.t_g^2,& \mathrm{Equation}2\end{array}$

[0053] In the present disclosure, when the time T.sub.g taken for the dielectric powders to move by the space distance d.sub.g is smaller than a half period T/2 of the waveform of the voltage, the dielectric powders collide with the lower end of the dielectric substrate, and then drops toward the dielectric powders layer for the half period T/2. According to the present disclosure, using this technical principle, the first and second separation layers may be positioned at suitable positions in the area between the upper electrode and the lower electrode in the inner space of the chamber to sort the dielectric powders.

[0054] FIG. 5 is a view for illustrating behavior of dielectric powders particles under the AC electric field in the dielectric powders sorting apparatus of the present disclosure. (T/2<t.sub.g)

[0055] Referring to FIG. 5, when the time T.sub.g taken for the dielectric powders to move by the space distance d.sub.g is greater than the half period T/2 of the waveform of the voltage, that is, when the space distance d.sub.g by which the dielectric powders may flow is sufficiently large, and the frequency of the waveform of the voltage is high, the dielectric powders starting to flow may flow upwardly in an accelerated manner by a distance d for one half period (0 to T2) of the waveform of the voltage. Then, when the polarity thereof is reversed, the dielectric powders may flow upwardly in a decelerated manner by a distance d for the other half period (T2 to T) of the waveform of the voltage. In this regard, when the frequency condition of the voltage is d.sub.g<d+d, the dielectric powders may behave in a fully fluidized flow (FF) mode in which all of the dielectric powders flow to reach the upper dielectric substrate. When the frequency condition of the voltage is d.sub.g=d+d, the dielectric powders may behave in a trap mode (TM) in which the dielectric powders substantially touch the upper dielectric substrate. When the frequency condition of the voltage is d.sub.g>d+d, the dielectric powders may behave in a low fluidized flow (LF) mode. The flow modes will be described with reference to FIG. 6.

[0056] FIG. 6 is a diagram illustrating the flow modes FF, TM, and LF of the dielectric powders in the apparatus for sorting the dielectric powders according to the present disclosure.

[0057] Referring to FIG. 6, according to the present disclosure, the dielectric powders may behave in the three flow modes of FF, TM, and LF using the dielectric powders sorting apparatus. d+d may be increased according to the increase in the external applied voltage and the increase in the surface area of the dielectric powders particles. d+d may be decreased according to the increase in each of the frequency of the externally applied voltage, the density of the powder particles, and the permittivity thereof. Therefore, in the dielectric powders sorting apparatus of the present disclosure, the separating means such as the first and second separation layers may be positioned at the position corresponding to d.sub.g, and the size of d+d may be adjusted by controlling the magnitude and frequency of the externally applied voltage, thereby easily sorting the dielectric powders.

[0058] FIG. 7 is an image showing the flow modes FF, TM, and LF of the dielectric powders in the AC high voltage through the dielectric powders sorting apparatus of the present disclosure.

[0059] Referring to FIG. 7, images of the FF, TM, and LF modes as performed using the dielectric powders sorting apparatus of the present disclosure are shown. In the FF mode, a signification portion of the dielectric powders flow upwardly from the lower electrode to the upper electrode. In the TM mode, the dielectric powders flow upwardly from the lower electrode but do not reach the upper electrode and moves to a position closer thereto. However, in the LF mode, the upward flow distance of the dielectric powders is very small.

[0060] Hereinafter, the apparatus for sorting the dielectric powders according to the present disclosure will be described in more detail with reference to specific Examples and Comparative Examples. However, Examples of the present disclosure are merely embodiments of the present disclosure, and the scope of the present disclosure is not limited to the following Examples.

EXAMPLES

[Experimental Apparatus]

[0061] FIG. 8 is a view illustrating the dielectric powders sorting apparatus used in each of Examples 1 to 3 of the present disclosure.

[0062] Referring to FIG. 8, the dielectric powders sorting apparatus has a structure including a lower electrode, an alumina substrate having a thickness of about 1 mm and disposed on the lower electrode, and a top electrode GND disposed between an upper end of the main body of the chamber and the alumina substrate. The dielectric powders were placed on the alumina substrate and the upper electrode. An experiment was performed.

[Experimental Conditions]

[0063] Experimental conditions using the dielectric powders sorting apparatus are indicted in Table 1 as set forth below.

TABLE-US-00001 TABLE 1 Examples Voltage (kVpp) Frequency (Hz) Example 1 20 200, 300 (A100 + A10 mixed powders) Example 2 20 100 to 500 (A100 + AB100 mixed powders) Example 3 14 to 24 200 (A100 AB100 mixed powders) *Voltage Applying Means: High Voltage Amplifier and Function Voltage Generator *Voltage: square wave alternating current * Voltage Range: 14 to 24 kVpp (Peak th Peak Voltage) * Voltage frequency range: 100 to 500 Hz * Discharge gas: Air

Example 1

[0064] In Example 1 of the present disclosure, alumina ceramic powders for an abrasive agent having different particle diameters were used. Specifically, a mixture of alumina ceramic powers (A100) having a size of 100 m and alumina ceramic powers (A10) having a size of 10 m was used. The frequency was changed to 200 and 300 Hz at a voltage of 20 kVpp to sort the dielectric powders based on the particle size.

[0065] FIG. 9 shows images of the dielectric powders used in Example 1 of the present disclosure.

[0066] Referring to FIG. 9, it may be identified that in the mixed powders used in Example 1 of the present disclosure, A100 and A10 are uniformly mixed with each other.

[0067] FIG. 10 shows images of the dielectric powders sorted through Example 1 of the present disclosure.

[0068] Referring to FIG. 10, it may be identified that when the powders are sorted under conditions of the voltage 20 kVpp and the frequency 200 Hz, the mixed powders having a higher content of A10 are accumulated on the upper electrode, whereas the mixed powders having a higher content of A100 are accumulated on the alumina substrate. It may be identified that the particles of A100 and A10 are not completely separated from each other under conditions of the voltage 20 kVpp and the frequency 200 Hz. It may be identified that when the dielectric powders are sorted while the magnitude of the voltage is fixed and the frequency is changed to 300 Hz, only the powders of A10 are accumulated on the upper electrode.

[0069] The time for which the powder particles rise or fall is shorter as the frequency increases. When a voltage of the same magnitude is applied, and when a lower frequency (200 Hz) is applied, the particle (A100 having the smaller surface area relative to a weight and being heavy,) can reach the separation layer. However, when a higher frequency (300 Hz) is applied, only particles that can relatively easily move (A10 having the larger surface area relative to the weight and being light) can reach the separation layer and be sorted. Accordingly, it may be identified that the homogeneous powders may be easily sorted using the dielectric powders sorting apparatus of the present disclosure.

Example 2: Separation of Dielectric Powders Based on Frequency

[0070] In Example 2 of the present disclosure, a mixture of alumina ceramic powers (A100) having a size of 100 m and alumina balls (AB100) having a size of 100 m was used. The frequency was changed to a value in range of 100 to 500 Hz at a voltage of 20 kVpp to sort the dielectric powders.

[0071] FIG. 11 shows images of the dielectric powders used in Example 2 of the present disclosure.

[0072] Referring to FIG. 11, it may be identified that in the mixed powders used in Example 2 of the present disclosure, A100 and AB100 are uniformly mixed with each other. It may be identified that AB100 is generally spherical and the deviation of the particle diameters thereof is large.

[0073] FIGS. 12 and 13 show images of the dielectric powders sorted through Example 2 of the present disclosure.

[0074] The powders are sorted under conditions of the voltage 20 kVpp and the frequency in a range of 100 Hz to 500 Hz. Referring to FIGS. 12 and 13, it may be identified that regarding the AB100, particles P1 having a large particle diameter are accumulated on the upper electrode as the frequency decreases from 500 Hz to 100 Hz, while regarding A100, particles P1 having greater sphericity are accumulated thereon as the frequency decreases from 500 Hz to 100 Hz. After terminating the sorting experiment based on the magnitude of the frequency, the powders P2 accumulated on the alumina substrate are checked. In this regard, it may be identified that AB100 particles having a large particle diameter are accumulated thereon.

[0075] Thus, it may be identified that the mixed powders having different surface areas may be easily sorted by controlling the frequency in the dielectric powders sorting apparatus of the present disclosure.

Example 3: Separation of Dielectric Powders Based on Magnitude of Voltage

[0076] In Example 3 of the present disclosure, the same mixed powder as the mixed powder used in Example 2 was used. The frequency is fixed to 200 Hz and the voltage is changed from 14 to 24 kVpp by 2 kVpp to sort the dielectric powders.

[0077] FIGS. 14 and 15 show images of the dielectric powders sorted through Example 3 of the present disclosure.

[0078] Referring to FIGS. 14 and 15, the dielectric powders P1 accumulated on the upper electrode are checked. It may be identified that as the magnitude of the applied voltage is increased, AB100 particles having a relatively uniform shape and AB100 particles having a large particle diameter are accumulated on the upper electrode. Further, after terminating the separation experiment based on the magnitude of the voltage, the dielectric powders P2 accumulated on the alumina substrate are checked. In this regard, it may be identified that AB100 particles having a large particle diameter are accumulated thereon.

[0079] It may be identified that using the dielectric powders sorting apparatus of the present disclosure, the mixed powders having different surface areas may be easily sorted by controlling the voltage.

[0080] Although the present disclosure has been described above with reference to preferred embodiments of the present disclosure, those skilled in the art will appreciate that various modifications and changes may be made to the present disclosure without departing from the spirit and scope of the present disclosure as set forth in the following Claims.