阅读说明：本技术 干压永磁铁氧体及其制备方法和应用 (Dry-pressing permanent magnetic ferrite and preparation method and application thereof ) 是由 张海浪 刘国平 彭春兰 于 2021-08-25 设计创作，主要内容包括：本发明提供了一种干压永磁铁氧体及其制备方法和应用,本发明的方法包括称量、混料、预烧、破碎、细磨、分散、干压取向成型等步骤。本发明通过采用添加剂、分散剂和粘合剂,能够改善产品晶体的取向度,可以在不显著降低磁粉剩磁的情况下,明显提高材料的矫顽力,从而能够有效改善永磁铁氧体的磁性能,优化铁氧体磁性能的温度稳定性。本发明采用干压成型方式大大提高成型效率,又制备过程采用行星式球磨机高速研磨,不影响永磁铁氧体性能的同时可以大大缩短生产时间,提高整体生产效率,可快速生产；同等配方条件下,本发明的干压成型产品可以提高生产效率,节省生产成本,在各种原材料上不使用当前采取的镧钴联合取代获得高性能。(The invention provides a dry-pressing permanent magnetic ferrite, a preparation method and application thereof. By adopting the additive, the dispersing agent and the adhesive, the invention can improve the degree of orientation of product crystals, and can obviously improve the coercive force of the material under the condition of not obviously reducing the residual magnetism of the magnetic powder, thereby effectively improving the magnetic performance of the permanent magnetic ferrite and optimizing the temperature stability of the magnetic performance of the ferrite. According to the invention, the dry pressing forming mode is adopted to greatly improve the forming efficiency, and the planetary ball mill is adopted for high-speed grinding in the preparation process, so that the production time can be greatly shortened, the overall production efficiency can be improved and the rapid production can be realized while the performance of the permanent magnetic ferrite is not influenced; under the condition of the same formula, the dry-pressing formed product can improve the production efficiency, save the production cost and obtain high performance on various raw materials without jointly replacing the currently adopted lanthanum and cobalt.)

1. A preparation method of dry-pressing permanent magnetic ferrite is characterized by comprising the following steps: which comprises the following steps:

(1) mixing strontium carbonate and iron oxide red, and mixing materials by adopting a sand grinding mode;

(2) drying the mixed slurry, sieving and pre-sintering;

(3) after the pre-sintering is finished, obtaining a permanent magnet pre-sintering material, coarsely crushing the permanent magnet pre-sintering material, adding an additive, mixing to obtain a mixture, and then grinding;

(4) after fine grinding, drying and vibration grinding, adding camphor and calcium stearate;

(5) and (5) forming the magnetic powder dispersed in the step (4) into a blank in a magnetic field, and cooling to obtain the dry-pressed permanent magnetic ferrite.

2. The method of claim 1, wherein: in the step (1), the mol ratio of the strontium carbonate to the iron oxide red is 1: (5.7-6.2).

3. The method of claim 1, wherein: in the step (1), the grain diameter of the mixed slurry is 0.7-0.8 μm, and the sanding time is 1-3 h.

4. The method of claim 1, wherein: in the step (2), the temperature of the pre-sintering is 1320-1360 ℃, and the time of the pre-sintering is 1-3 h.

5. The method of claim 1, wherein: in the step (3), the particle size of the ground slurry is 0.7-0.8 μm.

6. The method of claim 1, wherein: in the step (3), the additive is selected from more than one of aluminum oxide, silicon dioxide, calcium carbonate, ammonium bicarbonate, kaolin and boric acid.

7. The method of claim 1, wherein: in the step (5), the strength of the magnetic field is 8000-.

8. The method of claim 1, wherein: in the step (5), the blank is subjected to heat preservation for 1-2h at the temperature of 1100-1300 ℃.

9. A dry-pressing permanent magnetic ferrite is characterized in that: which is obtained by the production method according to any one of claims 1 to 8.

10. Use of a dry-pressed permanent magnetic ferrite according to claim 9 in the field of semiconductors.

Technical Field

The invention belongs to the technical field of magnetic materials, and particularly relates to a dry-pressing permanent magnetic ferrite and a preparation method and application thereof.

Background

The forming method of the anisotropic permanent magnetic ferrite usually adopts the traditional wet pressing forming process, and has the advantages of multiple aspects, such as good product performance and higher orientation degree of a green body. However, the disadvantages are very obvious, for example, because a large amount of moisture in the slurry needs to be removed in the forming process, the forming equipment is complex in design and manufacture, the forming speed is low due to complex procedures, the production efficiency is low, and the subsequent cleaning and grinding are also needed, so that the production efficiency is very inconvenient to improve. The dry pressing process is simple, the elimination of water is not required, the production efficiency is high, and the method is particularly suitable for certain products which have small volume and low product performance and need to be produced quickly.

Both wet-pressing and dry-pressing have their advantages and disadvantages, and the present efforts are directed to integrate their advantages, i.e., the performance of products can be infinitely close to that of wet-pressing products on the basis of dry-pressing. For dry pressing powder with the same formula, the better the orientation is, the higher the remanence is, but because the larger friction force exists among particles of the dry pressing powder, the orientation of a green body formed by dry pressing is worse than that of a green body formed by wet pressing, and the performance is lower.

Therefore, it is desirable to provide a permanent magnetic ferrite and a method for preparing the same, which allows the permanent magnetic ferrite to have excellent overall magnetic properties and can improve production efficiency. In addition, the factors such as cost and the like are comprehensively considered, the permanent magnetic ferrite material with higher cost performance is obtained, the permanent magnetic ferrite material with higher performance obtained by jointly replacing expensive rare metals such as lanthanum, cobalt and the like at present is improved, and the performance of the whole industrial chain is improved without bearing higher cost pressure.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a dry-pressing permanent magnetic ferrite and a preparation method and application thereof.

In order to achieve the above purpose, the solution of the invention is as follows:

in a first aspect, the invention provides a preparation method of a dry-pressed permanent magnetic ferrite, which comprises the following steps:

(1) mixing strontium carbonate and iron oxide red, and mixing materials by adopting a sand grinding mode;

(2) drying the mixed slurry, sieving and pre-sintering;

(3) after the pre-sintering is finished, obtaining a permanent magnet pre-sintering material, coarsely crushing the permanent magnet pre-sintering material, adding an additive, mixing to obtain a mixture, and then grinding;

(4) finely grinding, drying, grinding for 30min with a vibration mill, and adding Camphora and calcium stearate;

(5) and (5) forming the magnetic powder dispersed in the step (4) into a blank in a magnetic field, and cooling to obtain the dry-pressed permanent magnetic ferrite.

Preferably, in the step (1), the molar ratio of strontium carbonate to iron oxide red is 1: (5.7-6.2).

Preferably, in the step (1), the particle size of the mixed slurry is 0.7-0.8 μm, and the sanding time is 1-3 h.

Preferably, in the step (2), the temperature of the pre-sintering is 1320-1360 ℃, and the time of the pre-sintering is 1-3 h.

In the present invention, it is preferable that the particle size of the slurry after grinding in step (3) is 0.7 to 0.8. mu.m.

Preferably, in the present invention, in the step (3), the additive is one or more selected from the group consisting of alumina, silica, calcium carbonate, ammonium bicarbonate, kaolin, and boric acid.

Preferably, in step (5), the strength of the magnetic field is 8000-15000 Oe.

Preferably, in the step (5), the blank is subjected to heat preservation at the temperature of 1100-1300 ℃ for 1-2 h.

In a second aspect, the invention provides a dry-pressed permanent magnetic ferrite obtained by the preparation method.

In a third aspect, the invention provides an application of the dry-pressed permanent magnetic ferrite in the field of semiconductors.

Due to the adoption of the scheme, the invention has the beneficial effects that:

firstly, the invention can improve the degree of orientation of product crystals by adopting the additive, the camphor and the calcium stearate, and can obviously improve the coercive force of the material under the condition of not obviously reducing the residual magnetism of the magnetic powder, thereby effectively improving the magnetic performance of the permanent magnetic ferrite and optimizing the temperature stability of the magnetic performance of the ferrite. The permanent magnetic ferrite of the invention has excellent magnetic performance, simultaneously adopts a dry pressing forming mode to greatly improve the forming efficiency, adopts a planetary ball mill to grind at high speed in the preparation process, does not influence the performance of the permanent magnetic ferrite, can greatly shorten the production time, improves the overall production efficiency, and can be produced quickly.

Secondly, under the same formula condition, the dry-pressing formed product has slightly low performance but is close to the wet-pressing formed product, the production efficiency can be improved, the production cost is saved, and the high performance is obtained without jointly replacing the currently adopted lanthanum and cobalt on various raw materials, so that the production cost is reduced.

Thirdly, different from the current mainstream wet pressing forming which needs surface grinding and cleaning, the permanent magnetic ferrite prepared by the invention does not need the operation and directly finishes the preparation process and enters the detection stage.

Detailed Description

The invention provides a dry-pressing permanent magnetic ferrite and a preparation method and application thereof.

< method for producing dry-pressed permanent magnetic ferrite >

The preparation method of the dry-pressing permanent magnetic ferrite comprises the following steps:

(1) mixing materials: selecting iron oxide red and strontium carbonate (both are materials commonly used in the permanent magnet material industry) suitable for the permanent magnetic ferrite, wherein the mol ratio of the strontium carbonate to the iron oxide red is 1: (5.7-6.2) mixing in a sand grinding mode;

(2) and pre-burning: drying and sieving the mixed slurry, and placing the slurry in a muffle furnace for presintering;

(3) crushing and fine grinding: after the pre-sintering is finished, obtaining a permanent magnet pre-sintering material, coarsely crushing the permanent magnet pre-sintering material by using a vibration mill, adding an additive, mixing to obtain a mixture, and then placing the mixture in a planetary ball mill for high-speed grinding;

(4) and dispersing: finely grinding, drying, performing vibromilling for 30min by using a vibromill after drying, then adding 1 wt% of camphor and 0.5 wt% of calcium stearate, and dispersing after uniformly mixing;

(5) and dry pressing orientation molding: and (4) forming the magnetic powder dispersed in the step (4) into a blank in a magnetic field, and cooling to obtain the dry-pressed permanent magnetic ferrite.

In the step (1), the grain diameter of the mixed slurry is 0.7-0.8 μm, so that the magnetic powder grain orientation degree is improved to improve the performance of the magnetic material. The sanding time is 1-3 h.

In step (1), the molar ratio of strontium carbonate to iron red is preferably 1: 6.

In the step (2), the temperature of the pre-sintering is 1320-1360 ℃, and the time of the pre-sintering is 1-3 h.

Pre-burning: and drying and sieving the sanded slurry, and then placing the slurry in a muffle furnace for presintering. The presintering temperature is 1320 ℃, and the heat preservation time is 2 h. The determination of the pre-sintering temperature and the heat preservation time is the common influence of the previous experiment and the next experiment, the pre-sintering result is that the mixture is reacted as completely as possible to produce the permanent magnetic ferrite, so if the particle size is larger during the mixing, the temperature and the heat preservation time can be properly increased to ensure the completeness of the pre-sintering. However, this does not mean that the particle size can be infinitely large, and the present invention does not give further experiments and will not be further described.

In the step (3), the particle size of the ground slurry is 0.7 to 0.8. mu.m.

In step (3), the additive is selected from Al₂O₃、SiO₂、CaCO₃、NH₄HCO₃Kaolin and H₃BO₃More than one of them. The additives are added in this step, mixed and finely ground.

In fact, in step (4), camphor has the dual properties of a dispersant and a binder, and mainly has dispersion lubrication when not compressed and mainly has cohesiveness after compression, but easily sticks to walls when ball-milling and mixing, and is easily agglomerated, so that the particle size is too large and difficult to screen. Calcium stearate is inferior to camphor in cohesiveness, but has good lubricity but poor mechanical strength after molding. The two are used together, the effect is good, the bonding effect and the dispersing effect are good, the orientation degree and the mechanical strength are good after molding, and the particularly good matching is 1 wt% of camphor and 0.5 wt% of calcium stearate.

By adopting the preparation process, the compound of camphor and calcium stearate is used for the dispersion effect and the bonding effect, and Al is also used₂O₃、SiO₂、CaCO₃、NH₄HCO₃Kaolin and H₃BO₃The dry-pressing forming effect is better, the performance is closer to the wet-pressing forming effect, the coercive force of the material is obviously improved, and the magnetic performance of the permanent magnetic ferrite can be effectively improved.

Sintering at a higher temperature of 1230 ℃ and the remanence follows CaCO₃The content is increased and the coercive force is increased along with CaCO₃The content increases and decreases. CaCO₃The amount of (B) is usually in the range of 0.2 to 1.4% by weight. H₃BO₃The magnetic powder is a good dispersing agent, is beneficial to the dispersion of magnetic powder in water, can effectively reduce the agglomeration of wet grinding slurry and improve the orientation degree; in the course of sintering, H₃BO₃And the magnetic material also plays a role of a cosolvent, is beneficial to controlling crystal grains and improving remanence. H₃BO₃The amount of (B) is usually in the range of 0.1 to 0.4% by weight. In SrFe₁₂O₁₉In (C) due to Al³⁺Radius of ion and Fe³⁺The ionic radii are similar and all are trivalent cations, therefore, Al³⁺Partially substituted (substituted) Fe³⁺Ions, increasing H_cbAnd H_cj. But at the same time the remanence is reduced. Adding a small amount of Al₂O₃After that, the magnet can be sintered at a wide temperature, H_cjGreatly improved magnetic performance consistency. Therefore, the addition amount is usually less than or equal to 3 percent.

Al₂O₃The content of SiO is more than 0 percent and less than or equal to 0.4 percent₂The content is more than 0 percent and less than or equal to 0.4 percent, and the content of other additives is not more than 3 percent. The method has the beneficial effects of improving the intrinsic coercivity of the product and improving the magnetic property of the product.

Based on the weight of the permanent magnetic ferrite pre-sintering material, the content of camphor is more than 0% and less than or equal to 1.4%, and the content of calcium stearate is more than 0% and less than or equal to 1.0%. The method has the beneficial effect that the adhesive force of the permanent magnetic ferrite can be improved.

In step (5), the strength of the magnetic field is 8000-. The purpose of the applied magnetic field strength is orientation, which can be accomplished with a suitable magnetic field strength without the need for an excessive applied magnetic field.

In the step (5), the blank is subjected to heat preservation for 1-2h at the temperature of 1100-1300 ℃.

In addition, the theory between wet and dry pressure was analyzed:

the wet compression molding is to disperse the magnetic powder in water or other organic liquid as solvent, the magnetic powder particles do not adhere, when the directional magnetic field is applied, the magnetic powder particles are easy to rotate, and the easy magnetization axis is consistent with the direction of the magnetic field, so the performance is high; however, the forming equipment is complex, a water pumping system is needed, and the forming equipment cannot be processed into small-size products, needs grinding and has high processing cost. Dry pressing is to fill the dried and scattered fine powder into a forming die cavity and add an oriented magnetic field for forming; because dehydration is not needed during pressing, the production efficiency is high, the equipment cost is low, and the method is particularly suitable for different devices and small devices which are difficult to produce by a wet method.

From the above orientation mechanism, dry press formability is slightly lower than wet press formability in that the degree of orientation is lower. The reason is two: on one hand, because no dispersion medium exists, the friction force among powder particles is increased, and the orientation degree of a formed body is low; on the other hand, in the process of preparing the fine powder, adhesion among powder particles cannot be avoided during high-temperature drying, the powder has poor dispersibility, and the orientation degree of a formed body is low.

< dry pressing permanent magnetic ferrite >

The dry-pressed permanent magnetic ferrite of the present invention is obtained by the above-mentioned preparation method.

< application of dry pressing permanent magnetic ferrite >

The dry-pressed permanent magnetic ferrite can be applied to the field of semiconductors.

The present invention will be further described with reference to the following examples.

Example 1:

the preparation method of the dry-pressed permanent magnetic ferrite of the embodiment comprises the following steps:

(1) mixing materials: selecting strontium carbonate and iron oxide red suitable for the permanent magnetic ferrite, mixing according to a molar ratio of 1:6, adopting a sanding mode for mixing, wherein the grain diameter of slurry after mixing is 0.7 mu m, and the sanding time is 1 h.

(2) And pre-burning: and drying and sieving the mixed slurry, and presintering in a muffle furnace at the presintering temperature of 1320 ℃ for 2 h.

(3) Crushing and fine grinding: after the presintering is finished, obtaining a permanent magnet presintering material, coarsely crushing the permanent magnet presintering material by using a vibration mill, and adding Al₂O₃、SiO₂、CaCO₃、NH₄HCO₃Kaolin and H₃BO₃Mixing to obtain a mixture, and then placing the mixture into a planetary ball mill for high-speed grinding, wherein the grain diameter of ground slurry is 0.7 mu m.

(4) And dispersing: finely grinding, drying, grinding for 30min by using a vibration mill after drying, then adding 1 wt% of camphor and 0.5 wt% of calcium stearate, and dispersing after uniformly mixing.

(5) And dry pressing orientation molding: and (3) forming the magnetic powder dispersed in the step (4) into a blank in a magnetic field (the strength of the magnetic field is 8000Oe), preserving the temperature of the blank for 1h at 1100 ℃, and cooling to obtain the dry-pressed permanent magnetic ferrite.

Comparative example 1:

and wet pressing to form slurry, which is ball milled and is formed while orientation in a wet pressing press with the slurry being pumped to filter water.

Specifically, the method for preparing the wet-pressed permanent magnetic ferrite of the present comparative example includes the steps of:

(1) mixing materials: selecting strontium carbonate and iron oxide red suitable for the permanent magnetic ferrite, mixing according to a molar ratio of 1:6, adopting a sanding mode for mixing, wherein the grain diameter of slurry after mixing is 0.7 mu m, and the sanding time is 1 h.

(2) And pre-burning: and drying and sieving the mixed slurry, and presintering in a muffle furnace at the presintering temperature of 1320 ℃ for 2 h.

(3) Crushing and fine grinding: after the presintering is finished, obtaining permanent magnet presintering material, and vibratingThe mill coarsely crushes the permanent magnet pre-sintering material, and Al is added₂O₃、SiO₂、CaCO₃、NH₄HCO₃Kaolin and H₃BO₃Mixing to obtain a mixture, and then placing the mixture into a planetary ball mill for high-speed grinding, wherein the grain diameter of ground slurry is 0.7 mu m.

(4) Wet-pressing orientation forming: and (4) adding the slurry obtained in the step (3) into a wet pressing forming press under a magnetic field (the strength of the magnetic field is 8000Oe), carrying out orientation and pressure filtration simultaneously to obtain a blank, keeping the temperature of the blank at 1100 ℃ for 1h, and cooling to obtain the wet pressing permanent magnetic ferrite.

In step (3), the additive is added in the step, and in order to ensure the uniformity of the additive and the additive, the camphor and the calcium stearate are added simultaneously to ensure a single variable.

Comparative example 2:

the preparation method of the permanent magnetic ferrite of the present comparative example includes the steps of:

(1) mixing materials: selecting strontium carbonate and iron oxide red suitable for the permanent magnetic ferrite, mixing according to a molar ratio of 1:6, adopting a sanding mode for mixing, wherein the grain diameter of slurry after mixing is 0.7 mu m, and the sanding time is 1 h.

(2) And pre-burning: and drying and sieving the mixed slurry, and presintering in a muffle furnace at the presintering temperature of 1320 ℃ for 2 h.

(3) Crushing and fine grinding: and after the pre-sintering is finished, obtaining a permanent magnet pre-sintering material, coarsely crushing the permanent magnet pre-sintering material by using a vibration mill, and then placing the coarse magnet pre-sintering material in a planetary ball mill for high-speed grinding, wherein the particle size of ground slurry is 0.7 mu m.

(4) Wet-pressing orientation forming: and pressing and molding the sanded slurry into a blank, keeping the temperature of the blank at 1100 ℃ for 1h, and cooling to obtain the permanent magnetic ferrite.

Comparative example 3:

the preparation method of the dry-pressing permanent magnetic ferrite of the comparative example comprises the following steps:

(1) mixing materials: selecting strontium carbonate and iron oxide red suitable for the permanent magnetic ferrite, mixing according to a molar ratio of 1:6, adopting a sanding mode for mixing, wherein the grain diameter of slurry after mixing is 0.7 mu m, and the sanding time is 1 h.

(2) And pre-burning: and drying and sieving the mixed slurry, and presintering in a muffle furnace at the presintering temperature of 1320 ℃ for 2 h.

(3) Crushing and fine grinding: and after the pre-sintering is finished, obtaining a permanent magnet pre-sintering material, coarsely crushing the permanent magnet pre-sintering material by using a vibration mill, and then placing the coarse magnet pre-sintering material in a planetary ball mill for high-speed grinding, wherein the particle size of ground slurry is 0.7 mu m.

(4) And dispersing: sanding, drying, performing vibration milling for 30min by using a vibration mill after drying, and adding 1 wt% of camphor and 0.5 wt% of calcium stearate for dispersion.

(5) And dry pressing orientation molding: and (3) forming the magnetic powder dispersed in the step (4) into a blank in a magnetic field (the strength of the magnetic field is 8000Oe), preserving the temperature of the blank for 1h at 1100 ℃, and cooling to obtain the dry-pressed permanent magnetic ferrite.

The prior art is as follows:

at present, the existing materials are molded by dry pressing, and related properties are directly put after experiments for comparison to illustrate the superiority of the invention.

The above example 1, comparative example 1 to comparative example 3 are prepared by the process of the present invention, and are directly used for comparison to show that the dry pressing molding under the same conditions can be close to the wet pressing molding, so that the advantages of both dry pressing and wet pressing are achieved. Compared with the prior art, the results of the invention are not directly prepared, and the performance is superior and inferior.

The performance of the prepared permanent magnetic ferrite is measured by adopting a joint permanent magnetic material measuring device, as shown in table 1.

Table 1 the results of the relevant tests are shown in the table below

Sequence of	Remanence (mT)	Coercive force (kA/m)	Intrinsic coercive force (kA/m)	Maximum magnetic energy product (KJ/m)3)
					Example 1	390	230	235	27.1
Comparative example 1	409	245	251	28.0
					Comparative example 2	311	201	224	14.2
Comparative example 3	302	175	211	12.3
					Prior Art	395	236	240	28.1

Examples1 compared with the comparative example 1, the difference of remanence is only 19mT, the difference of coercive force is only 15kA/m, the difference of intrinsic coercive force is only 16kA/m, and the difference of maximum energy product is less than 1KJ/m³. The difference between the dry-pressing forming and the wet-pressing forming is small, but the dry-pressing forming has the advantage obviously higher than the wet-pressing forming.

Compared with the comparative example 3, the comparative example 2 has the difference of 9mT in remanence, 26kA/m in coercive force, 13kA/m in intrinsic coercive force and 2KJ/m or less in maximum energy product³. The results also demonstrate that the difference between the wet-press forming and the dry-press forming of the present invention can be reduced.

Compared with the comparative example 2, the comparative example 1 has the advantages that the remanence is improved by 98mT, the coercive force is improved by 44kA/m, the intrinsic coercive force is improved by 27kA/m, and the maximum magnetic energy product is improved by nearly 14KJ/m³. The types of the additives and the amount of the additives added in the invention can obviously improve the performance of the permanent magnetic ferrite, and the magnetic performance is obviously improved under the same condition.

Compared with the comparative example 3, the remanence of the example 1 is improved by 88mT, the coercive force is improved by 55kA/m, the intrinsic coercive force is improved by 24kA/m, and the maximum energy product is improved by nearly 15KJ/m³. This shows that the additive added in the invention is effective, and can obviously improve the magnetic performance of the permanent magnetic ferrite.

Compared with the prior art, in example 1, the difference of remanence is 5mT, the difference of coercive force is 6kA/m, the difference of intrinsic coercive force is 5kA/m, and the difference of maximum energy product is 1KJ/m³. The prior art is the current Antt dry pressing material, the difference is not large, and almost no difference exists, but the Antt material is added with expensive rare earth metals such as lanthanum, cobalt and the like, so that the cost of the material is undoubtedly improved, and the product of the invention has incomparable advantages in cost performance.

From the comparison of the experimental results, it can be seen that when the raw materials are the same, the magnetic performance of the permanent magnetic ferrite obtained by the conventional wet pressing method is the best, and the performance of the permanent magnetic ferrite obtained by the dry pressing method is lower than that obtained by the wet pressing method, and as compared with example 1 and comparative example 1, and compared with comparative example 2 and comparative example 3, the dry pressing formability is lower than that obtained by the wet pressing. The experimental result of the embodiment 1 is obviously close to that of the dry-pressed permanent magnetic ferrite substituted by lanthanum and cobalt at present, which shows that the preparation method and the additive of the invention can obviously improve the magnetic property of the permanent magnetic material, reduce the cost, improve the product performance in the whole industry and simultaneously avoid higher production cost.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. It will be readily apparent to those skilled in the art that various modifications to these embodiments and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments. Those skilled in the art should appreciate that many modifications and variations are possible in light of the above teaching without departing from the scope of the invention.