Modified calcium carbonate, modification method and use thereof

Abstract

The application discloses modified calcium carbonate, a modification method and application, wherein the modified calcium carbonate is calcium carbonate doped with magnesium ions; the modified calcium carbonate is obtained by doping magnesium ions in calcium carbonate, and is applied to insulating ceramics, so that the breakdown voltage and volume resistivity performance of the insulating ceramics are improved.

Description

Technical Field

[0001] This invention belongs to the field of calcium carbonate technology, and particularly relates to a modified calcium carbonate, a modification method, and its application. Background Technology

[0002] Calcium carbonate is a widely used auxiliary material with extensive applications in industries such as plastics, rubber, coatings, papermaking, and sealants. It is most commonly used as a filler to modify certain properties of related products.

[0003] Calcium carbonate is also used in industrial products such as ceramics, taking advantage of its chemical composition, thermal decomposition behavior, and positive impact on ceramic properties. Calcium carbonate begins to decompose at around 800℃, while ceramic firing temperatures exceed 1000℃. Therefore, when calcium carbonate is used as an auxiliary material in ceramics, it decomposes during firing, generating calcium oxide and carbon dioxide gas. The heat released in this process helps lower the sintering temperature, and the generated CaO acts as a flux, promoting the bonding between ceramic particles.

[0004] However, the use of calcium carbonate in ceramic products is currently relatively limited, and there is a lack of application development of calcium carbonate to help improve the performance of ceramic products. Summary of the Invention

[0005] This application addresses the problems of the prior art by proposing a modified calcium carbonate, a modification method, and its application.

[0006] The first aspect of this application provides a modified calcium carbonate, wherein the modified calcium carbonate is magnesium-doped calcium carbonate.

[0007] Preferably, the magnesium ion doping amount in the modified calcium carbonate is 30-60 mol%.

[0008] Preferably, the magnesium ion doping amount in the modified calcium carbonate is 45 mol%.

[0009] A second aspect of this application provides a modification method for obtaining the aforementioned modified calcium carbonate, the method comprising:

[0010] A solution is formed by mixing a soluble salt containing magnesium ions and a soluble salt containing calcium ions and then dissolving them in water.

[0011] The carbonates are mixed and then dissolved in water to form solution two;

[0012] Under stirring conditions, solution one is slowly added to solution two to form a precipitate. The resulting precipitate is then dried and ground into powder.

[0013] The resulting powder was heated to above 300°C and held at that temperature for at least 1 hour, then cooled.

[0014] Preferably, the carbonate is a sodium salt.

[0015] Preferably, the powder is heated at a temperature of 300–500°C.

[0016] A third aspect of this application provides an application of modified calcium carbonate, wherein the modified calcium carbonate is the modified calcium carbonate described above, and the application is to use the modified calcium carbonate as an auxiliary material in insulating ceramics.

[0017] Preferably, the amount of calcium carbonate powder added to the insulating ceramic does not exceed 1.5 wt%.

[0018] The beneficial effects of this invention are as follows: by doping magnesium ions into calcium carbonate to obtain modified calcium carbonate, its application in insulating ceramics helps to improve the breakdown voltage and volume resistivity performance of insulating ceramics. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments.

[0020] Example 1

[0021] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were prepared according to a Mg / (Mg+Ca) molar ratio of 1:10 and a (Mg+Ca) / CO3 molar ratio of 1:1.

[0022] Mg(NO3)2 and Ca(NO3)2 are mixed and dissolved in water to form solution one, and Na2CO3 is dissolved in water to form solution two. The sum of the concentrations of Ca and Mg in solution one is 0.4 mol / L.

[0023] Under stirring conditions, solution one is slowly added to solution two to form a precipitate. The resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve.

[0024] The resulting powder is heated to 300–500°C and kept at that temperature for 1–3 hours. After natural cooling, Mg-doped calcium carbonate powder is obtained.

[0025] Example 2

[0026] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were prepared according to a Mg / (Mg+Ca) molar ratio of 1.5:10 and a (Mg+Ca) / CO3 molar ratio of 1:1.

[0027] Mg(NO3)2 and Ca(NO3)2 are mixed and dissolved in water to form solution one, and Na2CO3 is dissolved in water to form solution two. The sum of the concentrations of Ca and Mg in solution one is 0.4 mol / L.

[0028] Under stirring conditions, solution one is slowly added to solution two to form a precipitate. The resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve.

[0029] The resulting powder is heated to 300–500°C and kept at that temperature for 1–3 hours. After natural cooling, Mg-doped calcium carbonate powder is obtained.

[0030] Example 3

[0031] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were prepared according to a Mg / (Mg+Ca) molar ratio of 2:10 and a (Mg+Ca) / CO3 molar ratio of 1:1.

[0032] Mg(NO3)2 and Ca(NO3)2 are mixed and dissolved in water to form solution one, and Na2CO3 is dissolved in water to form solution two. The sum of the concentrations of Ca and Mg in solution one is 0.4 mol / L.

[0033] Under stirring conditions, solution one is slowly added to solution two to form a precipitate. The resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve.

[0034] The resulting powder is heated to 300–500°C and kept at that temperature for 1–3 hours. After natural cooling, Mg-doped calcium carbonate powder is obtained.

[0035] Example 4

[0036] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were prepared according to a Mg / (Mg+Ca) molar ratio of 2.5:10 and a (Mg+Ca) / CO3 molar ratio of 1:1.

[0037] Mg(NO3)2 and Ca(NO3)2 are mixed and dissolved in water to form solution one, and Na2CO3 is dissolved in water to form solution two. The sum of the concentrations of Ca and Mg in solution one is 0.4 mol / L.

[0038] Under stirring conditions, solution one is slowly added to solution two to form a precipitate. The resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve.

[0039] The resulting powder is heated to 300–500°C and kept at that temperature for 1–3 hours. After natural cooling, Mg-doped calcium carbonate powder is obtained.

[0040] Example 5

[0041] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were prepared according to a Mg / (Mg+Ca) molar ratio of 3:10 and a (Mg+Ca) / CO3 molar ratio of 1:1.

[0042] Mg(NO3)2 and Ca(NO3)2 are mixed and dissolved in water to form solution one, and Na2CO3 is dissolved in water to form solution two. The sum of the concentrations of Ca and Mg in solution one is 0.4 mol / L.

[0043] Under stirring conditions, solution one is slowly added to solution two to form a precipitate. The resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve.

[0044] The resulting powder is heated to 300–500°C and kept at that temperature for 1–3 hours. After natural cooling, Mg-doped calcium carbonate powder is obtained.

[0045] Example 6

[0046] The ingredients Mg(NO3)2, Ca(NO3)2·4H2O and Na2CO3 were prepared according to a Mg / (Mg+Ca) molar ratio of 3.5:10 and a (Mg+Ca) / CO3 molar ratio of 1:1.

[0047] Mg(NO3)2 and Ca(NO3)2 are mixed and dissolved in water to form solution one, and Na2CO3 is dissolved in water to form solution two. The sum of the concentrations of Ca and Mg in solution one is 0.4 mol / L.

[0048] Under stirring conditions, solution one is slowly added to solution two to form a precipitate. The resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve.

[0049] The resulting powder is heated to 300–500°C and kept at that temperature for 1–3 hours. After natural cooling, Mg-doped calcium carbonate powder is obtained.

[0050] Example 7

[0051] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were prepared according to a Mg / (Mg+Ca) molar ratio of 4:10 and a (Mg+Ca) / CO3 molar ratio of 1:1.

[0052] Mg(NO3)2 and Ca(NO3)2 are mixed and dissolved in water to form solution one, and Na2CO3 is dissolved in water to form solution two. The sum of the concentrations of Ca and Mg in solution one is 0.4 mol / L.

[0053] Under stirring conditions, solution one is slowly added to solution two to form a precipitate. The resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve.

[0054] The resulting powder is heated to 300–500°C and kept at that temperature for 1–3 hours. After natural cooling, Mg-doped calcium carbonate powder is obtained.

[0055] Example 8

[0056] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were prepared according to a Mg / (Mg+Ca) molar ratio of 4.5:10 and a (Mg+Ca) / CO3 molar ratio of 1:1.

[0057] Mg(NO3)2 and Ca(NO3)2 are mixed and dissolved in water to form solution one, and Na2CO3 is dissolved in water to form solution two. The sum of the concentrations of Ca and Mg in solution one is 0.4 mol / L.

[0058] Under stirring conditions, solution one is slowly added to solution two to form a precipitate. The resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve.

[0059] The resulting powder is heated to 300–500°C and kept at that temperature for 1–3 hours. After natural cooling, Mg-doped calcium carbonate powder is obtained.

[0060] Example 9

[0061] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were prepared according to a Mg / (Mg+Ca) molar ratio of 5:10 and a (Mg+Ca) / CO3 molar ratio of 1:1.

[0062] Mg(NO3)2 and Ca(NO3)2 are mixed and dissolved in water to form solution one, and Na2CO3 is dissolved in water to form solution two. The sum of the concentrations of Ca and Mg in solution one is 0.4 mol / L.

[0063] Under stirring conditions, solution one is slowly added to solution two to form a precipitate. The resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve.

[0064] The resulting powder is heated to 300–500°C and kept at that temperature for 1–3 hours. After natural cooling, Mg-doped calcium carbonate powder is obtained.

[0065] Example 10

[0066] The ingredients Mg(NO3)2, Ca(NO3)2·4H2O and Na2CO3 were prepared according to a Mg / (Mg+Ca) molar ratio of 6:10 and a (Mg+Ca) / CO3 molar ratio of 1:1.

[0067] Mg(NO3)2 and Ca(NO3)2 are mixed and dissolved in water to form solution one, and Na2CO3 is dissolved in water to form solution two. The sum of the concentrations of Ca and Mg in solution one is 0.4 mol / L.

[0068] Under stirring conditions, solution one is slowly added to solution two to form a precipitate. The resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve.

[0069] The resulting powder is heated to 300–500°C and kept at that temperature for 1–3 hours. After natural cooling, Mg-doped calcium carbonate powder is obtained.

[0070] Example 11

[0071] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were prepared according to a Mg / (Mg+Ca) molar ratio of 7:10 and a (Mg+Ca) / CO3 molar ratio of 1:1.

[0072] Mg(NO3)2 and Ca(NO3)2 are mixed and dissolved in water to form solution one, and Na2CO3 is dissolved in water to form solution two. The sum of the concentrations of Ca and Mg in solution one is 0.4 mol / L.

[0073] Under stirring conditions, solution one is slowly added to solution two to form a precipitate. The resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve.

[0074] The resulting powder is heated to 300–500°C and kept at that temperature for 1–3 hours. After natural cooling, Mg-doped calcium carbonate powder is obtained.

[0075] Preparation Example 1

[0076] The calcium carbonate powders obtained in Examples 1-11 were used as auxiliary agents to prepare insulating ceramics, as follows:

[0077] Weigh 50 kg of high-alumina bauxite, 50 kg of alumina and 0.5 kg of calcium carbonate powder and add them to a ball mill for ball milling. The working conditions are 500 r / min and 8 h to obtain a mixture.

[0078] The mixture, pebbles, and water were placed in a ball mill at a mass ratio of 1:2:1.5 and ball milled at 500 r / min for 15 h. The mixture was then sieved through a 400-mesh screen to remove iron. After that, the mixture was successively pressed, aged for 72 h, vacuum-kneaded, shaped, trimmed, and dried to obtain the blanks.

[0079] The obtained blank is pre-fired at 600℃ for 60 minutes, then heated to 1000℃ at a rate of 5℃ / min and held for 5 hours; then heated to 1300℃ at a rate of 10℃ / min and held for 30 minutes, and then naturally cooled to room temperature.

[0080] Comparative Example 1

[0081] Unlike Preparation Example 1, the calcium carbonate powder used to make the insulating ceramic is calcium carbonate powder that has not been doped with ions.

[0082] The breakdown voltage of the insulating ceramics prepared in Preparation Example 1 and Comparative Example 1 was tested in accordance with GB / T 1408.1-2016 "Electrical strength test method for insulating materials - Part 1: Test at power frequency".

[0083] The volume resistivity of the insulating ceramics prepared in Preparation Example 1 and Comparative Example 1 was tested according to GB / T 31838.2-2019 "Test Methods for Volume Resistivity and Surface Resistivity of Solid Insulating Materials".

[0084] Among the test results, Comparative Example 1 had the lowest breakdown voltage and volume resistivity, at 12 kV / mm and 5.6 × 10⁻⁶ kV / mm, respectively. ^13 Ω·cm; In Preparation Example 1, after doping calcium carbonate powder with magnesium ions, the breakdown voltage and volume resistivity of Examples 1-11 were improved. Furthermore, with increasing magnesium ion doping content, the breakdown voltage and volume resistivity showed a trend of first increasing and then decreasing. The breakdown voltage of Examples 5-10 all exceeded 15 kV / mm, and the volume resistivity all exceeded 1 × 10⁻⁶. ^14 The optimal value is Ω·cm for the insulating ceramic prepared in Example 8, with a breakdown voltage of 16.4 kV / mm and a volume resistivity of 3.3 × 10⁻⁶ kV / mm. ^14 Ω·cm, corresponding to a molar mass percentage of magnesium ions in the calcium carbonate powder of Example 8 of 45 mol%.

[0085] By doping calcium carbonate with magnesium ions, which replace the original calcium ions and create lattice defects, the smaller radius of the magnesium ions distorts the original lattice. This distortion alters the interatomic distances within the lattice. Simultaneously, the presence of magnesium ions promotes the nucleation and growth of calcium carbonate, resulting in more uniform and dense grains, thus increasing lattice stability and requiring higher decomposition temperatures. Therefore, when calcium carbonate is used as an auxiliary material in insulating ceramics, the decomposition temperature is increased during firing, delaying the release of carbon dioxide and calcium oxide. The carbon dioxide released at high temperatures helps promote material densification. The calcium oxide produced at high temperatures continues to act as a flux, promoting bonding between ceramic particles, reducing porosity, improving microstructure, and promoting thorough sintering. This results in sintered insulating ceramics with higher density, thereby increasing volume resistivity and breakdown voltage.

[0086] Preparation Example 2

[0087] The calcium carbonate powder obtained in Example 8 was used as an auxiliary agent to prepare insulating ceramics. The difference from the preparation example 1 is that the amount of calcium carbonate powder added was 1 kg.

[0088] Preparation Example 3

[0089] The calcium carbonate powder obtained in Example 8 was used as an auxiliary agent to prepare insulating ceramics. The difference from the preparation example 1 is that the amount of calcium carbonate powder added was 1.5 kg.

[0090] Preparation Example 4

[0091] The calcium carbonate powder obtained in Example 8 was used as an auxiliary agent to prepare insulating ceramics. The difference from the preparation example 1 is that the amount of calcium carbonate powder added was 2 kg.

[0092] Preparation Example 5

[0093] The calcium carbonate powder obtained in Example 8 was used as an auxiliary agent to prepare insulating ceramics. The difference from the preparation example 1 is that the amount of calcium carbonate powder added was 2.5 kg.

[0094] The breakdown voltage of the insulating ceramics prepared in Examples 2 to 5 was tested in accordance with GB / T 1408.1-2016 "Electrical strength test method for insulating materials - Part 1: Test at power frequency".

[0095] The volume resistivity of the insulating ceramics prepared in Examples 2 to 5 was tested according to GB / T 31838.2-2019 "Test Methods for Volume Resistivity and Surface Resistivity of Solid Insulating Materials".

[0096] The test results showed that although the amount of calcium carbonate powder added was increased, it did not significantly improve the breakdown voltage and volume resistivity of the insulating ceramic products. On the contrary, when the amount of calcium carbonate powder added exceeded 1.5 wt%, the breakdown voltage and volume resistivity of the insulating ceramic products showed a significant decreasing trend.

[0097] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.

Claims

1. An application of modified calcium carbonate, characterized in that, The modified calcium carbonate is magnesium-doped calcium carbonate; The magnesium ion doping amount in the modified calcium carbonate is 30-60 mol%. The modified calcium carbonate is used as an auxiliary material for insulating ceramics; The amount of calcium carbonate powder added to the insulating ceramic shall not exceed 1.5 wt%. The modified calcium carbonate is prepared as follows: a soluble salt containing magnesium ions and a soluble salt containing calcium ions are mixed and dissolved in water to form solution one; a carbonate is mixed and dissolved in water to form solution two; under stirring conditions, solution one is slowly added to solution two to generate a precipitate; the precipitate is dried and ground into powder; the powder is heated to above 300°C and kept at that temperature for more than 1 hour, and then cooled. The raw materials for the insulating ceramic include high-alumina bauxite and alumina.

2. The application of the modified calcium carbonate according to claim 1, characterized in that, The modified calcium carbonate contains 45 mol% magnesium ions.

3. The application of the modified calcium carbonate according to claim 1, characterized in that, The carbonate is a sodium salt.

4. The application of the modified calcium carbonate according to claim 1, characterized in that, The powder is heated at a temperature of 300–500 °C.