KR20030079333A - A process for producing colored cubic zirconia by a skull melting method of high frequency induction heating - Google Patents

Abstract

PURPOSE: Provided is a process for producing a colored cubic zirconia of high value, which has beautiful color and gloss like natural jewelry and excellent durability, in large quantities with a low cost. CONSTITUTION: The process for producing a colored cubic zirconia by high frequency induction heating method comprises the steps of: mixing 75 to 85 wt% of ZrO2 with 15 to 20 wt% of Y2O3 based on the total weight of the mixture and a small amount of rare earth metal elements, and filling the mixture into a scull equipped with an inside heater; positioning the scull charged with the raw materials in a high frequency induction heating device, heating the heater by the high frequency of 25 to 150 kHz to melt the raw materials; maintaining the melted product at the temperature of about 3,000 deg.C to form initial crystal seeds; moving an induction coil gradually at the outside of the high frequency induction heating device with the speed of 3.0-6.0 mm/hr from bottom to top of the scull to grow the cubic zirconia single crystals; cooling the crystals for 24 hours or more after the completion of the crystal growth; separating the product from the scull, cooling the product for 24 hours or more under the ambient atmosphere, and isolating the single crystals from the product.

Description

A method for producing colored cubic zirconia by high frequency induction heating method {A PROCESS FOR PRODUCING COLORED CUBIC ZIRCONIA BY A SKULL MELTING METHOD OF HIGH FREQUENCY INDUCTION HEATING}

The present invention relates to a method for producing colored cubic zirconia by high frequency induction heating, and more particularly, to a colored high frequency induction cubic zirconia, which can replace natural gemstones, at a low cost. It relates to a method for producing cubic zirconia.

Cubic zirconia (Cubic Zirconia) is a high-purity ZrO ₂ with a high melting point as a main raw material and uniformly melted at a high temperature of 3,000 ℃, and then formed an initial crystal seed by precise temperature control and then grown in the same crystal orientation It is a single crystal made.

Since cubic zirconia is very stable and good optically and physically, when it is precisely processed, it looks very beautiful due to the refraction or dispersion characteristics of light.

In fact, the characteristics of diamonds, cubic zirconia, and sapphire are compared and listed in Table 1 below.

division Diamond Cubic zirconia Sapphire Spawn rate 0.044 0.060 0.018 Refractive index 2.42 2.16 1.76 density 3.5 5.91 4.00 Hardness 10 8.6 9.0

As described above, cubic zirconia has similar characteristics in general compared to diamond, and in particular, in terms of scattering degree, it is much superior to diamond or sapphire, and thus has a beautiful radiance than diamond.

In addition, by adding a rare earth-based element to the main component ZrO ₂ to produce a variety of colors cubic zirconia, the colored cubic zirconia thus prepared is used as a jewelry substitute to replace the existing natural jewelry.

Therefore, as the market of cubic zirconia expands rapidly, there is a demand for a method of mass-producing colored cubic zirconia that can reproduce the color of natural gemstones that meet the consumer's taste at a low production cost.

The present inventors have made intensive studies to find a method for increasing the added value and mass production of cubic zirconia used as a substitute for natural gemstones.

It is an object of the present invention to provide colored cubic zirconia of various colors, such as natural gemstones, giving a beautiful color and luster and excellent durability.

It is also an object of the present invention to provide a method for mass production of cubic zirconia, which can replace natural gemstones, at a low production cost.

1 is a manufacturing process diagram schematically showing a method of manufacturing colored cubic zirconia by the high frequency induction heating method of the present invention.

Hereinafter, the present invention will be described in detail.

In the present invention, in the production of colored cubic zirconia, 75 to 85% by weight of ZrO ₂ , 15 to 20% by weight of Y ₂ O ₃ and a small amount of rare earth-based elements mixed with the total weight of the total mixture is provided with a heating element therein After filling the skull with the raw material, and installing the skull filled with the raw material in the high frequency induction heating apparatus, the heating element is heated at a high frequency of 25 to 150 kHz to melt the raw material, and the initial melt is maintained while maintaining the obtained melt at a temperature of about 3,000 ° C. The seed of the high frequency induction heater, and slowly move the induction coil from the lower part of the skull to the upper part of the skull at a speed of 3.0 to 6.0 mm / hour to grow a single crystal of cubic zirconia, and when the growth is complete, After cooling for at least 24 hours, the packing material is separated from the scull and cooled in the air for at least 24 hours. High frequency induction to the production process of colored cubic zirconia by heating method as that made to the features.

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

1 schematically shows a manufacturing process of colored cubic zirconia by the high frequency induction heating method according to the present invention.

According to the present invention, rare earth elements for color development are first mixed with ZrO ₂ and Y ₂ O ₃ as main components by adding 0.01 to 2% by weight based on the total weight of the mixture. The main components ZrO ₂ and Y ₂ O ₃ may be used in the range of 75 to 85 wt% and 15 to 20 wt%, respectively, based on the total weight of the mixture.

Rare earth elements are used in trace amounts to small amounts as raw materials used for color development. Examples of the rare earth-based elements usable in the present invention include cubic zirconia in the group consisting of Er ₂ O ₃ , Co ₃ O ₄ , Nd ₂ O ₃ , V ₂ O ₅ , CeO ₂ , Pr ₆ O ₁₁ , NiO, and the like. According to the desired color development can be used arbitrarily selected.

The mixed raw materials as described above are filled in a skull to which a high frequency induction heating apparatus is attached. In order to efficiently melt the raw material, a high-frequency heating element is installed in the center of the skull, and a graphite ring is preferably used as the heating element.

When all the raw materials are melted by high frequency, the temperature of the melt is maintained at a high temperature of about 3000 ° C. in order to obtain seeds of initial crystals. When a crystal seed is formed in this way, the induction coil outside the skull is then moved from the bottom of the skull to the top at a speed of 3 to 6 mm per hour to induce the melt to grow in the same crystal orientation. The single crystal produced at this time is grown to a size of 4.0 to 4.8 mm per hour.

The cubic zirconia crystals obtained as described above can effectively express color variations and desired colors.

When the single crystal growth is completed, the skull is removed from the high frequency induction heating apparatus, cooled within the skull for at least 24 hours, the packing material is separated from the inside of the skull, cooled at least for 24 hours in an atmospheric atmosphere, and the single crystal site is isolated.

According to the CIE color coordinates that display the color quantitatively as a symbol or a numerical value, it can be seen that the isolated cubic zirconia has excellent color development and gloss in each desired color. The CIE color coordinates for colored cubic zirconia prepared by the method of the present invention described above are described in the Examples below.

Colored cubic zirconia containing rare earth-based elements prepared according to the method of the present invention may exhibit various colors such as white, yellow, pink, and so on, and may substitute natural gemstones such as diamond, amethyst, peridot and the like.

Hereinafter, the present invention will be described in more detail with reference to the following Examples.

Example 1 Preparation of Pink Cubic Zirconia

450 kg of ZrO ₂ , 90 kg of Y ₂ O ₃ , 35 kg of Er ₂ O _3, and traces of Co ₃ O ₄ were mixed using a drum mixer. The mixed raw materials were filled in a skull in which the graphite heating element of the high frequency induction heating apparatus was embedded, and the raw materials were melted at a high frequency of 25 kHz. The temperature of the melt was maintained at 3,000 ° C. to produce an initial crystal seed and the induction coil was moved to the top of the skull at a speed of 3-6 mm per hour to grow single crystals at a speed of 4.0-4.8 mm per hour. The scull containing the growth-filled material was removed from the induction heating apparatus, cooled by the skull itself for at least 24 hours, and the filler was separated from the skull again, and then cooled in the air for at least 24 hours, and then the resulting cubic zirconia was separated.

The resulting cubic zirconia was pink, and the CIE color coordinates thereof are shown in Table 2 below.

sample x y Y One 0.3371 0.2931 50.43 2 0.3386 0.2917 55.32 3 0.3380 0.2924 55.32 4 0.3383 0.2908 52.84

As shown in Table 2, the pink cubic zirconia prepared according to the present invention was not only excellent in color but also excellent in productivity.

Example 2 Preparation of Amethyst Cubic Zirconia

Colored cubic zirconia was prepared in the same manner as in Example 1, except that 480 kg of ZrO ₂ , 100 kg of Y ₂ O ₃ , and 1.5 kg of Co ₃ O ₄ were used as raw materials.

The resulting cubic zirconia had the same color as amethyst, and the CIE color coordinates thereof are shown in Table 3 below.

sample x y Y One 0.1910 0.0589 2.83 2 0.2154 0.0894 2.53 3 0.2223 0.0834 2.33 4 0.2471 0.0964 2.52

As shown in Table 3, the amethyst cubic zirconia prepared according to the present invention was not only excellent in color but also excellent in productivity.

Example 3 Preparation of Lavender Cubic Zirconia

Colored cubic zirconia was prepared in the same manner as in Example 1, except that 240 kg of ZrO ₂ , 50 kg of Y ₂ O _3, and 6 kg of Nd ₂ O ₃ were used as raw materials.

The resulting cubic zirconia had the same color as lavender, and the CIE color coordinates thereof are shown in Table 4 below.

sample x y Y One 0.2880 0.2668 42.88 2 0.2873 0.2650 44.51 3 0.2869 0.2636 42.82 4 0.2883 0.2699 46.14

As shown in Table 4, the lavender cubic zirconia prepared according to the present invention was not only excellent in color but also excellent in productivity.

Example 4 Preparation of Peridot Cubic Zirconia

Colored cubic zirconia was prepared in the same manner as in Example 1, except that 470 kg of ZrO ₂ , 100 kg of Y ₂ O ₃ , ₅ kg of Nd ₂ O _3, and 0.5 kg of V ₂ O ₅ were used as raw materials.

The resulting cubic zirconia had the same color as the peridot, and the CIE color coordinates thereof are shown in Table 5 below.

sample x y Y One 0.4531 0.4799 57.93 2 0.4438 0.4716 55.90 3 0.4440 0.4756 58.40 4 0.4384 0.4717 58.58

As shown in Table 5, the peridot cubic zirconia produced according to the present invention was not only excellent in color but also excellent in productivity.

Example 5 Preparation of Orange Cubic Zirconia

Colored cubic zirconia was prepared in the same manner as in Example 1, except that 245 kg of ZrO ₂ , 50 kg of Y ₂ O _3, and ₃ kg of CeO ₂ were used as raw materials.

The cubic zirconia obtained had an orange color, and the CIE color coordinates thereof are shown in Table 6 below.

sample x y Y One 0.3917 0.3166 15.78 2 0.3458 0.3157 13.43 3 0.3485 0.3195 18.42 4 0.4389 0.3214 19.63

As shown in Table 6, the orange cubic zirconia prepared according to the present invention was not only excellent in color but also excellent in productivity.

Example 6 Preparation of Yellow Cubic Zirconia

Colored cubic zirconia was prepared in the same manner as in Example 1, except that 245 kg of ZrO ₂ , 50 kg of Y ₂ O _3, and ₅ kg of Pr ₆ O ₁₁ were used as raw materials.

The obtained cubic zirconia was yellow, and the CIE color coordinates thereof are shown in Table 7 below.

sample x y Y One 0.4531 0.4799 57.93 2 0.4438 0.4716 55.90 3 0.4440 0.4756 58.40 4 0.4384 0.4717 58.58

As shown in Table 7, the yellow cubic zirconia prepared according to the present invention was not only excellent in color but also excellent in productivity.

Example 7 Preparation of Champaign Cubic Zirconia

Colored cubic zirconia was prepared in the same manner as in Example 1, except that 250 kg of ZrO ₂ , 50 kg of Y ₂ O ₃ , 1.0 kg of NiO, and a small amount of Co ₃ O ₄ were used as raw materials.

The resulting cubic zirconia had the same color as champagne, and the CIE color coordinates thereof are shown in Table 8 below.

sample x y Y One 0.3238 0.3230 65.87 2 0.3321 0.3198 66.72 3 0.3342 0.3178 64.28 4 0.3278 0.3205 64.98

As shown in Table 8, the champagne-colored cubic zirconia prepared according to the present invention was not only excellent in color but also excellent in productivity.

According to the method of the present invention, cubic zirconia can be mass-produced at a low production cost.

In addition, according to the method of the present invention, it is possible to mass-produce colored cubic zirconia of various colors having a beautiful color and luster like natural gemstone and excellent durability at low cost.

Claims (3)

In the preparation of colored cubic zirconia, 75 to 85% by weight of ZrO ₂ , 15 to 20% by weight of Y ₂ O ₃ and a small amount of rare earth elements are mixed in the skull with a heating element installed therein. After charging the skull filled with the raw material in a high frequency induction heating apparatus, the heating element was heated at a high frequency of 25 to 150 kHz to melt the raw material, and the seed of the initial crystal was kept while maintaining the obtained melt at a temperature of about 3,000 ° C. And induction coil outside the high frequency induction heating device to slowly move from the bottom of the skull to the top at a speed of 3.0 to 6.0 mm / hour to grow a single crystal of cubic zirconia, and when the growth is complete, cooling inside the skull for more than 24 hours Separating charges from the skull and then cooling them in the air for at least 24 hours and isolating single crystal sites from the separated charges Process for producing a colored cubic zirconia by high frequency induction heating method, as characterized in that comprising a. The method for producing colored cubic zirconia according to claim 1, wherein the rare earth element is added in an amount of 0.01 to 2% by weight based on the total weight of the mixture. According to claim 1 or 2, wherein the rare earth-based element is selected from the group consisting of Er ₂ O ₃ , Co ₃ O ₄ , Nd ₂ O ₃ , V ₂ O ₅ , CeO ₂ , Pr ₆ O ₁₁ NiO A method for producing colored cubic zirconia by high frequency induction heating method.