JP2022054639A - Top plate for cookers - Google Patents

Abstract

To provide a top plate for cookers that has high strength and is less prone to surface scratches.SOLUTION: A top plate for cookers has a glass plate having a cooking face to be in contact with a cooker and a back face opposite to the cooking face, and an inorganic layer provided in contact with the back face of the glass plate. The inorganic layer contains an alkali silicate represented by chemical formula R2O nSiO2 (R is an alkali metal element and n is a positive number).SELECTED DRAWING: Figure 1

Description

The present invention relates to a top plate for a cooker.

As the top plate for a cooker, a glass plate made of crystallized glass or the like having a low coefficient of thermal expansion is used. When a colorless glass plate is used as the glass plate, generally, in order to conceal the internal structure of the cooker, the back surface located on the opposite side to the cooking surface on which the cooking utensil is placed is used as a decorative layer in Patent Document 1. As described above, a porous inorganic layer made of an inorganic pigment and glass powder, and a protective layer made of a silicone-based resin or the like are provided.

The glass powder used for the inorganic layer has a high firing temperature, and a strong tensile stress is generated on the surface of the glass plate on which the inorganic layer is formed after cooling. Therefore, the strength of the top plate for the cooker is low.

Therefore, it is conceivable to provide only a protective layer without using an inorganic layer that lowers the strength of the glass plate. The top plate may be scratched.

In order to deal with these problems, in Patent Document 2, scratches are suppressed by providing a heat-resistant sliding layer made of graphite or the like.

JP-A-2010-9958

Although scratches are less likely to occur by providing the heat-resistant sliding layer, scratches due to strong scratching have not been suppressed.

In view of the above circumstances, an object of the present invention is to provide a top plate for a cooker, which has high strength and is not easily scratched on the back surface.

The cooking utensil top plate of the present invention is a cooking utensil top plate having a cooking surface in contact with a cooking utensil, a glass plate having a back surface facing the cooking surface, and an inorganic layer provided in contact with the back surface of the glass plate. The inorganic layer is characterized by containing an alkali silicate represented by the chemical formula R2O · _{nSiO 2 (} R is an alkali metal element and n is an arbitrary positive number).

Since alkaline silicate has a low melting point, tensile stress is less likely to occur on the glass plate after cooling, and it is possible to increase the strength of the top plate for cooking utensils.

In the top plate for a cooker of the present invention, it is preferable that R is at least one selected from Li, Na and K.

The top plate for a cooker of the present invention preferably contains 0.1% by mass or more of Li as an alkaline silicate.

The top plate for a cooker of the present invention preferably has an alkali silicate mass ratio of SiO ₂ / R ₂ O of 0.1 to 5.

In the top plate for a cooker of the present invention, the inorganic layer preferably contains 1 to 50% by mass of an inorganic filler.

The top plate for a cooker of the present invention preferably has an inorganic layer having a thickness of 1 to 50 μm.

In the top plate for a cooker of the present invention, the pencil hardness of the inorganic layer is preferably 3H or more.

The cooking top plate of the present invention has a cooking surface having a cooking surface in contact with a cooking utensil, a glass plate having a back surface facing the cooking surface, and an inorganic layer provided in contact with the cooking surface of the glass plate. The plate is characterized in that the inorganic layer contains an alkali silicate represented by the chemical formula R2O · _{nSiO 2 (} R is an alkali metal element, n is an arbitrary positive number).

According to the present invention, it is possible to provide a top plate for a cooker having high strength and scratches on the back surface.

It is a schematic cross-sectional view which shows the top plate for a cooker which concerns on 1st Embodiment of this invention. It is a schematic cross-sectional view which shows the top plate for a cooker which concerns on 2nd Embodiment of this invention.

Hereinafter, embodiments for carrying out the present invention will be described, but the present invention is not limited to the following embodiments and is based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that those of the following embodiments to which modifications, improvements, etc. have been made as appropriate fall within the scope of the present invention.

(First Embodiment)
FIG. 1 is a schematic front sectional view showing a top plate for a cooker according to the first embodiment of the present invention. As shown in FIG. 1, the cooker top plate 1 (hereinafter, “cooker top plate 1” is simply referred to as “top plate 1”) includes a glass plate 2. The glass plate 2 has a cooking surface 2a which is a main surface on one side and a back surface 2b which is a main surface on the other side. The cooking surface 2a is a surface on which cooking utensils such as a pot and a frying pan are placed. The back surface 2b is a surface facing the heating device on the inner side of the cooker. Therefore, the cooking surface 2a and the back surface 2b are in a front-to-back relationship.

The glass plate 2 transmits at least a part of light at a wavelength of 380 to 780 nm. The glass plate 2 may be colored and transparent, but is preferably colorless and transparent from the viewpoint of further enhancing the aesthetic appearance of the top plate 1. In the present specification, colorless and transparent means that the average transmittance in the visible wavelength range at a wavelength of 380 to 780 nm is 70% or more.

In the top plate 1, heating and cooling are repeated. Therefore, it is preferable that the glass plate 2 has high heat resistance and a low coefficient of thermal expansion. Specifically, the softening temperature of the glass plate 2 is preferably 700 ° C. or higher, more preferably 750 ° C. or higher. The average coefficient of linear thermal expansion of the glass plate 2 at 30 ° C. to 750 ° C. is preferably in the range of −10 × ^10-7 / ° C. to +60 × ^10-7 / ° C., preferably −10 × ^10-7 . It is more preferably in the range of / ° C to +50 × ^10-7 / ° C, and even more preferably in the range of −10 × ^10-7 / ° C to +40 × ^10-7 / ° C. Therefore, it is preferable that the glass plate 2 is made of glass having a high glass transition temperature and low expansion, or crystallized glass having low expansion. Specific examples of the low-expansion crystallized glass include "N-0" manufactured by Nippon Electric Glass Co., Ltd. As the glass plate 2, for example, borosilicate glass or the like may be used in addition to the crystallized glass.

An inorganic layer 3 is provided on the back surface 2b of the glass plate 2. The inorganic layer 3 is provided in direct contact with the back surface 2b of the glass plate 2. Further, in the present embodiment, the surface of the inorganic layer 3 is exposed to the outside air. Therefore, only the inorganic layer 3 is laminated on the back surface 2b of the glass plate 2, and the other layers are not laminated. Of course, another layer may be laminated on the inorganic layer 3 or between the glass plate 2 and the inorganic layer 3, but this implementation is carried out from the viewpoint of further improving productivity and reducing stress. It is preferable that only the inorganic layer 3 is laminated as in the form.

The inorganic layer 3 may be provided on the cooking surface 2a of the glass plate 2. By doing so, the strength becomes higher and the cooking surface 2a is less likely to be scratched.

The inorganic layer 3 contains an alkali silicate represented by the chemical formula R ₂ O · nSiO ₂ (R is an alkali metal element, n is an arbitrary positive number). Since the alkali silicate has a low curing temperature, tensile stress is less likely to occur on the glass plate after cooling, and the strength of the top plate 1 can be increased.

The alkaline silicate is preferably at least one in which R is selected from Li, Na and K.

Examples of the alkaline silicate include lithium silicate, sodium silicate, potassium silicate and the like. These alkaline silicates may be used alone or in combination of two or more.

The alkaline silicate preferably contains 0.1% by mass or more of Li, more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more. If the amount of Li is too small, the water resistance becomes low and it tends to be deteriorated by the moisture in the air. If the alkali silicate layer is not exposed on the surface, it may not contain Li.

The mass ratio of the alkali silicate SiO ₂ / R _2O is preferably 0.1 to 5, more preferably 0.2 to 4.9, and particularly preferably 0.3 to 4.8. Is even more preferable. If the mass ratio SiO ₂ / R ₂ O is too small, the hardness of the inorganic layer 3 becomes low, and scratches are likely to occur. On the other hand, if the mass ratio SiO ₂ / R ₂ O is too large, the melting point becomes high, tensile stress is likely to occur in the glass plate 2 after cooling, and the strength of the top plate 1 tends to decrease.

The refractive index nd of the alkaline silicate is preferably 1.46 or more, 1.47 or more, 1.48 or more, and particularly preferably 1.49 or more. If the refractive index nd is too small, light is scattered due to the refractive index with the glass plate 2, and the design is liable to deteriorate.

The inorganic layer 3 preferably further contains an inorganic filler and an extender pigment.

The shape of the inorganic filler is not particularly limited, but from the viewpoint of handling, it is preferably granular, plate-shaped, or scaly.

The average particle size of the inorganic filler is preferably 1 to 40 μm from the viewpoint of dispersibility in the inorganic layer 3. Here, the average particle diameter is a median diameter derived from the volume distribution measured by the laser diffraction / scattering method. The average particle size of the inorganic filler is more preferably 10 μm or more, further preferably 20 μm or more. Further, the average particle size of the inorganic filler is more preferably 35 μm or less, and further preferably 30 μm or less.

The Mohs hardness of the inorganic filler is preferably 5 or more, more preferably 8 or more. If the Mohs hardness is too high, the scratch suppressing effect does not increase and the cost increases. Therefore, the Mohs hardness is preferably 9 or less. Examples of the flake-shaped inorganic filler having a Mohs hardness of 5 or more include alumina, magnesia, glass, orthoclase, quartz, and diamond. Here, the "Mohs hardness" is the Mohs hardness divided into 10 stages from 1 to 10.

The extender pigment contained in the inorganic layer 3 is an inorganic pigment powder different from the above-mentioned inorganic filler having a Mohs hardness of 5 or more. The extender pigment is not particularly limited, but for example, talc, mica, or the like can be used. These extender pigments may be used alone or in combination of two or more. Although the extender pigment has a lower effect of suppressing scratches than the inorganic filler, it can further enhance the heat resistance and impact resistance of the top plate 1.

The average particle size of the extender pigment is preferably 1 to 50 μm from the viewpoint of dispersibility in the inorganic layer 3. Here, the average particle diameter is a median diameter derived from the volume distribution measured by the laser diffraction / scattering method. The average particle size of the extender pigment is more preferably 10 μm or more, further preferably 15 μm or more. Further, the average particle size of the extender pigment is more preferably 45 μm or less, and further preferably 40 μm or less.

Chain-shaped nanoparticles can be added to adjust the viscosity at the time of coating. Specifically, 20% or less of silica, alumina and the like can be added. These can suppress shrinkage during drying, but if the amount added is large, the adhesiveness is lowered and it is easy to cause peeling or the like.

The inorganic layer 3 preferably contains an inorganic coloring pigment for coloring the top plate 1. The inorganic coloring pigment contained in the inorganic layer 3 is not particularly limited as long as it is a colored inorganic substance. Examples of the inorganic coloring pigment include a white pigment powder such as TiO ₂ powder, ZrO ₂ powder or ZrSiO ₄ powder, a blue inorganic pigment powder containing Co, a green inorganic pigment powder containing Co, and a yellow inorganic pigment containing Ti. Examples thereof include pigment powder, Co—Si-based red inorganic pigment powder, brown inorganic pigment powder containing Fe, and black inorganic pigment powder containing Cu.

Specific examples of the blue inorganic pigment powder containing Co include Co-Al-based or Co-Al-Ti-based inorganic pigment powder. Specific examples of the Co-Al-based inorganic pigment powder include CoAl ₂ O ₄ powder. Specific examples of the Co-Al-Ti-based inorganic pigment powder include CoAl ₂ O ₄ -TiO ₂ -Li ₂ O powder.

Specific examples of the green inorganic pigment powder containing Co include Co—Al—Cr-based or Co—Ni—Ti—Zn-based inorganic pigment powder. Specific examples of the Co—Al—Cr-based inorganic pigment powder include Co ₍ Al, Cr) _2O4 powder. Specific examples of the Co—Ni—Ti—Zn-based inorganic pigment powder include (Co, Ni, Zn) ₂ TiO ₄ powder and the like.

Specific examples of the yellow inorganic pigment powder containing Ti include Ti—Sb—Cr-based or Ti—Ni-based inorganic pigment powder. Specific examples of the Ti—Sb—Cr-based inorganic pigment powder include Ti (Sb, Cr) O ₂ . Specific examples of the Ti—Ni-based inorganic pigment powder include Ti (Sb, Ni) O ₂ .

Specific examples of the brown inorganic pigment powder containing Fe include Fe—Zn-based inorganic pigment powder. Specific examples of the Fe—Zn-based inorganic pigment powder include (Zn, Fe) Fe ₂ O ₄ powder.

Specific examples of the black inorganic pigment powder containing Cu include Cu—Cr-based inorganic pigment powder and Cu—Fe-based inorganic pigment powder. Specific examples of the Cu—Cr-based inorganic pigment powder include Cu (Cr, Mn) _{2 O4} powder and Cu—Cr—Mn powder. Specific examples of the Cu—Fe-based inorganic pigment powder include Cu—Fe—Mn powder.

These inorganic coloring pigments may be used alone or in combination of two or more.

The inorganic filler and the inorganic coloring pigment may be individually dispersed in the inorganic layer 3, but from the viewpoint of design, a part of the inorganic coloring pigment may be adhered to the surface of the inorganic filler. .. For example, the inorganic coloring pigment can be attached to the surface of the inorganic filler by the high-speed airflow impact method. By using such an inorganic filler, a top plate 1 having a jewel-like luster can be obtained.

The average particle size of the inorganic coloring pigment is preferably 0.1 to 20 μm from the viewpoint of dispersibility in the inorganic layer 3. Here, the average particle diameter is a median diameter derived from the volume distribution measured by the laser diffraction / scattering method. The average particle size of the inorganic coloring pigment is more preferably 0.5 μm or more, further preferably 1 μm or more. Further, the average particle size of the inorganic coloring pigment is more preferably 15 μm or less, and further preferably 10 μm or less. The shape of the inorganic coloring pigment is not particularly limited, but a spherical shape is preferable from the viewpoint of impact resistance and dispersibility.

The content of the inorganic filler in the inorganic layer 3 is preferably in the range of 1 to 50% by mass from the viewpoint of suppressing scratches and designability. The content of the inorganic filler is more preferably 10% by mass or more, further preferably 15% by mass or more. The content of the inorganic filler is more preferably 35% by mass or less, and further preferably 25% by mass or less.

The content of the extender pigment in the inorganic layer 3 is preferably in the range of 5 to 40% by mass from the viewpoint of dispersibility. The content of the extender pigment is more preferably 10% by mass or more, further preferably 15% by mass or more. Further, the content of the extender pigment is more preferably 35% by mass or less, and further preferably 30% by mass or less.

Further, the content of the inorganic coloring pigment in the inorganic layer 3 is preferably in the range of 10 to 55% by mass from the viewpoint of design. The content of the inorganic coloring pigment is more preferably 15% by mass or more, further preferably 20% by mass or more. Further, the content of the inorganic coloring pigment is more preferably 40% by mass or less, and further preferably 30% by mass or less.

The thickness of the inorganic layer 3 can be appropriately set according to the light transmittance of the inorganic layer 3 and the like. The thickness of the inorganic layer 3 can be, for example, in the range of 1 to 50 μm. The thickness of the inorganic layer 3 is more preferably in the range of 10 to 15 μm.

The inorganic layer 3 preferably has a pencil hardness of 3H or more. Here, the pencil hardness is the hardness measured according to the pencil hardness test of JIS K5600-5-4 (1999). When the pencil hardness is 3H or more, it is possible to obtain the top plate 1 whose back surface is not easily scratched.

(Manufacturing method of top plate 1)
The top plate 1 can be manufactured, for example, by the following method.

First, a paste containing an alkaline silicate aqueous solution, an inorganic filler powder, an inorganic coloring pigment powder, and an extender pigment powder is prepared. Next, the prepared paste is directly applied onto the back surface 2b of the glass plate 2 and dried. Thereby, the top plate 1 having the inorganic layer 3 can be manufactured.

The application speed and viscosity of the paste can be appropriately set according to the contents of the alkaline silicate powder, the inorganic filler powder, the inorganic coloring pigment powder and the extender pigment powder contained in the inorganic layer 3. For example, when the content of the inorganic filler powder, the inorganic coloring pigment powder, and the extender pigment powder in the inorganic layer 3 is high, it is preferable to lower the viscosity of the paste and slow down the coating speed of the silicone resin. Examples of the method of lowering the viscosity of the paste include changing the type of heat-resistant resin and adding a solvent to the paste.

The drying temperature of the applied paste can be, for example, about 50 to 200 ° C. The drying time can be, for example, about 5 minutes to 1 hour.

As described above, in the production method of the present embodiment, since the melting point of the alkaline silicate is low, the paste containing the alkaline silicate powder, the inorganic filler powder, the coloring pigment powder, and the extender pigment powder is formed on the glass plate 2. Since the top plate 1 is manufactured by directly applying it on the back surface 2b of the glass plate 2 and drying it, there is no step of baking the glass frit on the back surface 2b of the glass plate 2. Therefore, tensile stress is unlikely to occur on the back side of the glass plate 2, and the top plate 1 is unlikely to be damaged when a load or impact is applied to the cooking surface 2a of the glass plate 2.

A low melting point glass powder such as B2O3 _- ZnO is baked on the back surface _2b of the glass plate 2 so as to be porous, and after baking, the pores are filled with a paste containing an alkaline silicate powder and dried. You may let me. By doing so, since the surface of the inorganic layer 3 exposed to the outside air becomes a layer containing an alkali silicate, it is possible to obtain a top plate 1 having high strength and scratches on the back surface.

The top plate 1 manufactured as described above tends to have a high breaking strength of 70 MPa or more. The breaking strength is more preferably 80 MPa or more, further preferably 90 MPa or more.

A temperature sensor or the like may be mounted on the inorganic layer 3 by using silicone grease or the like. However, when the top plate 1 is heated, if the inorganic layer is porous, the silicone grease may invade the inside of the inorganic layer 3, and the stain of the silicone grease may be visually recognized from the cooking surface 2a side. The layer 3 is preferably dense.

(Second embodiment)
FIG. 2 is a schematic cross-sectional view showing a top plate for a cooker according to a second embodiment of the present invention. As shown in FIG. 2, in the top plate 1, a protective layer 4 is further provided on the inorganic layer 3. The protective layer 4 preferably contains a heat-resistant resin, an inorganic filler, an extender pigment, and an inorganic coloring pigment. By providing the protective layer 4, the structure inside the cooker can be concealed more effectively.

Examples of the heat-resistant resin include silicone resins. The silicone resin is preferably, for example, a silicone resin in which the functional group directly bonded to the silicon atom is at least one of a methyl group and a phenyl group.

The content of the silicone resin in the protective layer 4 is preferably in the range of 20 to 50% by mass from the viewpoint of heat resistance and impact resistance. The content of the silicone resin is more preferably 25% by mass or more, further preferably 30% by mass or more. The content of the silicone resin is more preferably 45% by mass or less, further preferably 40% by mass or less.

The inorganic layer 3, the inorganic filler, the extender pigment, and the inorganic coloring pigment are as described in the first embodiment.

The method for forming the protective layer 4 is the same as the method for forming the inorganic layer 3.

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

(Example 1)
First, 65% by mass of alkaline silicate, which is a 1: 1 mixture of sodium silicate and lithium silicate, 15% by mass of Cu-Fe-Mn-based black pigment (average particle size: 1 μm), and talc extender pigment. (Average particle size: 20 μm) 10% by mass and alumina filler powder (Morse hardness: 9, average particle size: 25 μm) 10% by mass were mixed and then made into a paste. Next, this paste is applied to a transparent crystallized glass plate (manufactured by Nippon Electric Glass Co., Ltd., trade name "N-0", average linear thermal expansion coefficient at 30 to 750 ° C.: 0.5 × ^10-7 / ° C., thickness 4 mm). The entire back surface of the glass was screen-printed so that the thickness was 20 μm. Then, it was dried at 100 ° C. for 10 minutes and further dried at 200 ° C. for 15 minutes to form an inorganic layer, and a top plate (top plate) for a cooker was prepared. An aqueous solution of sodium silicate and lithium silicate mixed 1: 1 was applied to a plate glass and dried to obtain a film thickness of 100 μm, and then the refractive index nd (refractive index of the d-line) was measured by an Abbe refractive index meter (d-line refractive index). As a result of measurement by Atago), it was 1.495.

(Example 2)
First, the B ₂ O ₃ -ZnO-based glass powder was mixed with 65% by mass of the black pigment, 10% by mass of the talc extender pigment, and 10% by mass of the alumina filler powder, and then made into a paste. Next, this paste was screen-printed on the entire back surface of the glass plate so as to have a thickness of 20 μm, and then fired at 780 ° C. so as to be porous. After that, an aqueous solution prepared by mixing sodium silicate and water in a ratio of 1: 1 was applied by spraying so as to fill the pores. Then, it was dried at 100 ° C. for 10 minutes and further dried at 200 ° C. for 15 minutes to form an inorganic layer, and a top plate (top plate) for a cooker was prepared. An aqueous solution of sodium silicate was applied to a plate glass and dried to obtain a film thickness of 100 μm, and then the refractive index nd (refractive index of the d-line) was measured with an Abbe refractive index meter (manufactured by Atago). It was 49.

(Example 3)
The silicone resin 67% by mass (resin solid content), the black pigment 12% by mass, the talc extender pigment 12% by mass, and the alumina filler powder 9% by mass were mixed and then made into a paste. Next, this paste was screen-printed on an inorganic layer formed by the same method as in Example 1 so as to have a thickness of 20 μm. Then, it was dried at 100 ° C. for 10 minutes, and further dried at 200 ° C. for 15 minutes to form a protective layer, and a top plate (top plate) for a cooker was prepared.

(Comparative Example 1)
The B ₂ O ₃ -ZnO-based glass powder was mixed with 65% by mass of the black pigment, 10% by mass of the talc extender pigment, and 10% by mass of the alumina filler powder, and then made into a paste. Next, this paste was screen-printed on the entire back surface of the glass plate so as to have a thickness of 20 μm, and then fired at 900 ° C. to make it dense, and a top plate for a cooker (top plate) on which an inorganic layer was formed was formed. ) Was produced.

The fracture strength, stains, and pencil hardness of the prepared Examples 1 to 3 were evaluated. The results are shown in Table 1. As is clear from Table 1, in Examples 1 to 3, the breaking strength was as high as 120 MPa or more and the pencil hardness was as high as 4 H or more. On the other hand, Comparative Example 1 had a low fracture strength of 60 MPa.

The breaking strength was measured using a bending strength tester using jigs for the upper ring (diameter 12.5 mm) and the lower ring (diameter 30 mm).

For stains, black silicone was applied on the inorganic layer or protective layer of the top plate, and the stain was left at 250 ° C. for 1000 hours. The case where the organic matter, moisture, etc. contained in the silicone or the silicone resin did not soak into the inorganic layer was evaluated as "○", the case where it soaked into the protective layer was evaluated as "Δ", and the case where it soaked into the inorganic layer was evaluated as "x".

The pencil hardness was measured by a pencil hardness test (JIS K5600-5-4 (1999)) on the side of the top plate on which the above layer was formed.

1 Top plate for cooker 2 Glass plate 2a Cooking surface 2b Back surface 3 Inorganic layer 4 Protective layer

Claims (9)

The cooking surface that the cooking utensils come in contact with,
A glass plate having a back surface facing the cooking surface and
A top plate for a cooker having an inorganic layer provided in contact with the back surface of the glass plate.
The cooking top plate is characterized in that the inorganic layer contains an alkali silicate represented by the chemical formula R ₂ O · nSiO ₂ (R is an alkali metal element and n is an arbitrary positive number). The cooker top plate according to claim 1, wherein R is at least one selected from Li, Na and K. The cooking top plate according to claim 1 or 2, wherein the alkaline silicate contains 0.1% by mass or more of Li. The top plate for a cooker according to any one of claims 1 to 3, wherein the mass ratio of the alkali silicate SiO ₂ / R ₂ O is 0.1 to 5. The top plate for a cooker according to any one of claims 1 to 4, wherein the inorganic layer contains 1 to 50% by mass of an inorganic filler. The top plate for a cooker according to any one of claims 1 to 5, wherein the thickness of the inorganic layer is 1 to 50 μm. The top plate for a cooker according to any one of claims 1 to 6, wherein the pencil hardness of the inorganic layer is 3H or more. The top plate for a cooker according to any one of claims 1 to 7, wherein the refractive index nd of the alkaline silicate is 1.46 or more. The cooking surface that the cooking utensils come in contact with,
A glass plate having a back surface facing the cooking surface and
A top plate for a cooker having an inorganic layer provided in contact with the cooking surface of the glass plate.
The cooking top plate is characterized in that the inorganic layer contains an alkali silicate represented by the chemical formula R ₂ O · nSiO ₂ (R is an alkali metal element and n is an arbitrary positive number).

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