Modified calcium carbonate, modification method and application

Abstract

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

Description

Technical Field

[0001] The invention belongs to the technical field of calcium carbonate, and in particular relates to modified calcium carbonate, a modification method and application. Background Art

[0002] Calcium carbonate is a widely used auxiliary material in the plastics, rubber, coatings, papermaking, sealants and other industries. It is commonly used as a filler to change certain properties of related products.

[0003] In addition, calcium carbonate is also used in industrial products such as ceramics because of its chemical composition, thermal decomposition behavior, and positive impact on ceramic properties. The initial decomposition temperature of calcium carbonate is around 800°C, and the firing temperature of ceramics will exceed 1000°C. Therefore, when calcium carbonate is used as an auxiliary material for ceramics, it will decompose during the firing process to generate calcium oxide and carbon dioxide gas. The heat released by the process itself helps to reduce the sintering temperature. At the same time, the generated CaO can be used as a flux to promote the bonding between ceramic particles.

[0004] However, the usage of calcium carbonate in ceramic products is relatively simple at present, and there is a lack of applied development of calcium carbonate to help improve the performance of ceramic products. Summary of the invention

[0005] In view of the problems of the prior art, the present application proposes a modified calcium carbonate, a modification method and an application.

[0006] In a first aspect, the present application provides a modified calcium carbonate, wherein the modified calcium carbonate is calcium carbonate doped with magnesium ions.

[0007] Preferably, the doping amount of magnesium ions in the modified calcium carbonate is 30 to 60 mol%.

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

[0009] The second aspect of the present application provides a modification method, which is used to obtain the modified calcium carbonate, and the method is:

[0010] A soluble salt containing magnesium ions and a soluble salt containing calcium ions are mixed and dissolved in water to form a solution 1;

[0011] The carbonates are mixed and dissolved in water to form solution 2;

[0012] Under stirring conditions, solution one is slowly added to solution two to generate a precipitate, and the resulting precipitate is dried and ground into powder;

[0013] The obtained powder is heated to above 300°C, kept at this temperature for more than 1 hour, and then cooled.

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

[0015] Preferably, the powder heating temperature is 300-500°C.

[0016] The third aspect of the present application provides an application of modified calcium carbonate, wherein the modified calcium carbonate is the modified calcium carbonate mentioned above, and the application is to use the modified calcium carbonate as an auxiliary material for 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 the present invention are as follows: modified calcium carbonate is obtained by doping magnesium ions in calcium carbonate, and the modified calcium carbonate is applied to insulating ceramics, thereby helping to improve the breakdown voltage and volume resistivity performance of the insulating ceramics. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution 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 dosed in 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 1, and Na2CO3 is dissolved in water to form solution 2. The sum of the concentrations of Ca and Mg in solution 1 is 0.4 mol / L.

[0023] Under stirring conditions, solution 1 is slowly added to solution 2 to generate a precipitate, the resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve;

[0024] The obtained powder is heated to 300-500° C., kept at this temperature for 1-3 hours, and then naturally cooled to obtain Mg-doped calcium carbonate powder.

[0025] Example 2

[0026] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were dosed in 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 1, and Na2CO3 is dissolved in water to form solution 2. The sum of the concentrations of Ca and Mg in solution 1 is 0.4 mol / L.

[0028] Under stirring conditions, solution 1 is slowly added to solution 2 to generate a precipitate, the resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve;

[0029] The obtained powder is heated to 300-500° C., kept at this temperature for 1-3 hours, and then naturally cooled to obtain Mg-doped calcium carbonate powder.

[0030] Example 3

[0031] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were dosed in 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 1, and Na2CO3 is dissolved in water to form solution 2. The sum of the concentrations of Ca and Mg in solution 1 is 0.4 mol / L.

[0033] Under stirring conditions, solution 1 is slowly added to solution 2 to generate a precipitate, the resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve;

[0034] The obtained powder is heated to 300-500° C., kept at this temperature for 1-3 hours, and then naturally cooled to obtain Mg-doped calcium carbonate powder.

[0035] Example 4

[0036] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were dosed at 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 1, and Na2CO3 is dissolved in water to form solution 2. The sum of the concentrations of Ca and Mg in solution 1 is 0.4 mol / L.

[0038] Under stirring conditions, solution 1 is slowly added to solution 2 to generate a precipitate, the resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve;

[0039] The obtained powder is heated to 300-500° C., kept at this temperature for 1-3 hours, and then naturally cooled to obtain Mg-doped calcium carbonate powder.

[0040] Example 5

[0041] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were dosed in 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 1, and Na2CO3 is dissolved in water to form solution 2. The sum of the concentrations of Ca and Mg in solution 1 is 0.4 mol / L.

[0043] Under stirring conditions, solution 1 is slowly added to solution 2 to generate a precipitate, the resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve;

[0044] The obtained powder is heated to 300-500° C., kept at this temperature for 1-3 hours, and then naturally cooled to obtain Mg-doped calcium carbonate powder.

[0045] Example 6

[0046] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were dosed in 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 1, and Na2CO3 is dissolved in water to form solution 2. The sum of the concentrations of Ca and Mg in solution 1 is 0.4 mol / L.

[0048] Under stirring conditions, solution 1 is slowly added to solution 2 to generate a precipitate, the resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve;

[0049] The obtained powder is heated to 300-500° C., kept at this temperature for 1-3 hours, and then naturally cooled to obtain Mg-doped calcium carbonate powder.

[0050] Example 7

[0051] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were dosed in 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 1, and Na2CO3 is dissolved in water to form solution 2. The sum of the concentrations of Ca and Mg in solution 1 is 0.4 mol / L.

[0053] Under stirring conditions, solution 1 is slowly added to solution 2 to generate a precipitate, the resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve;

[0054] The obtained powder is heated to 300-500° C., kept at this temperature for 1-3 hours, and then naturally cooled to obtain Mg-doped calcium carbonate powder.

[0055] Example 8

[0056] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were dosed at 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 1, and Na2CO3 is dissolved in water to form solution 2. The sum of the concentrations of Ca and Mg in solution 1 is 0.4 mol / L.

[0058] Under stirring conditions, solution 1 is slowly added to solution 2 to generate a precipitate, the resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve;

[0059] The obtained powder is heated to 300-500° C., kept at this temperature for 1-3 hours, and then naturally cooled to obtain Mg-doped calcium carbonate powder.

[0060] Example 9

[0061] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were dosed in 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 1, and Na2CO3 is dissolved in water to form solution 2. The sum of the concentrations of Ca and Mg in solution 1 is 0.4 mol / L.

[0063] Under stirring conditions, solution 1 is slowly added to solution 2 to generate a precipitate, the resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve;

[0064] The obtained powder is heated to 300-500° C., kept at this temperature for 1-3 hours, and then naturally cooled to obtain Mg-doped calcium carbonate powder.

[0065] Example 10

[0066] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were dosed in 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 1, and Na2CO3 is dissolved in water to form solution 2. The sum of the concentrations of Ca and Mg in solution 1 is 0.4 mol / L.

[0068] Under stirring conditions, solution 1 is slowly added to solution 2 to generate a precipitate, the resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve;

[0069] The obtained powder is heated to 300-500° C., kept at this temperature for 1-3 hours, and then naturally cooled to obtain Mg-doped calcium carbonate powder.

[0070] Embodiment 11

[0071] Mg(NO3)2, Ca(NO3)2·4H2O, and Na2CO3 were dosed in 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 1, and Na2CO3 is dissolved in water to form solution 2. The sum of the concentrations of Ca and Mg in solution 1 is 0.4 mol / L.

[0073] Under stirring conditions, solution 1 is slowly added to solution 2 to generate a precipitate, the resulting precipitate is dried at 100°C, ground into powder, and passed through a 1000-mesh sieve;

[0074] The obtained powder is heated to 300-500° C., kept at this temperature for 1-3 hours, and then naturally cooled to obtain Mg-doped calcium carbonate powder.

[0075] Preparation Example 1

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

[0077] Weigh 50 kg of high-alumina bauxite, 50 kg of aluminum oxide and 0.5 kg of calcium carbonate powder and add them into a ball mill for ball milling at 500 r / min for 8 h to obtain a mixture;

[0078] The mixture, ball stone and water are placed in a ball mill with a mass ratio of 1:2:1.5, and the working conditions are 500r / min, 15h, sieved with 400 mesh, iron removed, and then mud pressed, aged for 72h, vacuum mud kneading, forming, blanking and drying are carried out in sequence to obtain blanks;

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

[0080] Comparative Example 1

[0081] The difference from Preparation Example 1 is that 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 methods for insulating materials - Part 1: Tests at power frequency”.

[0083] The volume resistivity of the insulating ceramics prepared in Preparation Example 1 and Comparative Example 1 was tested in accordance with GB / T 31838.2-2019 “Test method for volume resistivity and surface resistivity of solid insulating materials”.

[0084] In the test results, the breakdown voltage and volume resistivity of comparative example 1 are the lowest, which are 12 kV / mm and 5.6×10 ^13 Ω·cm; In Preparation Example 1, after the calcium carbonate powder is doped with magnesium ions, the breakdown voltage and volume resistivity of Examples 1 to 11 are improved, and as the magnesium ion doping content increases, the breakdown voltage and volume resistivity first increase and then decrease. The breakdown voltage of Examples 5 to 10 exceeds 15 kV / mm, and the volume resistivity exceeds 1×10 ^14 Ω·cm, the optimal value is the insulating ceramic prepared in Example 8, whose breakdown voltage and volume resistivity are 16.4 kV / mm and 3.3×10 ^14 Ω·cm, correspondingly, the molar mass percentage of magnesium ions in the calcium carbonate powder of Example 8 is 45 mol%.

[0085] By doping magnesium ions into calcium carbonate to replace the original calcium ions, lattice defects are formed. The radius of the doped magnesium ions is smaller than that of the calcium ions, resulting in distortion of the original lattice. This distortion causes the distance between atoms in the lattice to change. At the same time, the presence of magnesium ions can promote the nucleation and growth of calcium carbonate, making the grains more uniform and dense, thereby increasing the stability of the lattice and requiring a higher temperature for decomposition. Therefore, when calcium carbonate is used as an auxiliary material for insulating ceramics, the decomposition temperature of calcium carbonate is increased during the firing process, and the time for calcium carbonate to decompose and release carbon dioxide gas and calcium oxide is delayed to a certain extent. The carbon dioxide gas escaping in the high-temperature stage helps to promote the densification of the material. The calcium oxide produced in the high-temperature stage can continue to play a fluxing role, promote the bonding between ceramic particles, reduce porosity, improve the microstructure, and promote sufficient sintering. The sintered insulating ceramics have a higher density, thereby increasing the volume resistivity and breakdown voltage.

[0086] Preparation Example 2

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

[0088] Preparation Example 3

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

[0090] Preparation Example 4

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

[0092] Preparation Example 5

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

[0094] The breakdown voltage of the insulating ceramics prepared in Preparation Examples 2 to 5 was tested according to GB / T 1408.1-2016 “Electrical strength test methods for insulating materials - Part 1: Tests at power frequency”.

[0095] The volume resistivity of the insulating ceramics prepared in Preparation Examples 2 to 5 was tested in accordance with GB / T 31838.2-2019 “Test method for volume resistivity and surface resistivity of solid insulating materials”.

[0096] In the test results, it was found that although the addition amount of calcium carbonate powder increased, it did not significantly improve the breakdown voltage and volume resistivity performance of the insulating ceramic products. On the contrary, when the addition amount of calcium carbonate powder exceeded 1.5wt%, the breakdown voltage and volume resistivity of the insulating ceramic products tended to decrease significantly.

[0097] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them.

Claims

1. A modified calcium carbonate, characterized in that, The modified calcium carbonate is calcium carbonate doped with magnesium ions.

2. A modified calcium carbonate according to claim 1, characterized in that, The doping amount of magnesium ions in the modified calcium carbonate is 30-60 mol%.

3. A modified calcium carbonate according to claim 2, characterized in that, The doping amount of magnesium ions in the modified calcium carbonate is 45 mol%.

4. A modification method, characterized in that: The modification method is used to obtain a modified calcium carbonate as described in any one of claims 1 to 3, and the method is: A soluble salt containing magnesium ions and a soluble salt containing calcium ions are mixed and dissolved in water to form a solution 1; The carbonates are mixed and dissolved in water to form solution 2; Under stirring conditions, solution one is slowly added to solution two to generate a precipitate, and the resulting precipitate is dried and ground into powder; The obtained powder is heated to above 300°C, kept at this temperature for more than 1 hour, and then cooled.

5. A modification method according to claim 4, characterized in that: The carbonate is a sodium salt.

6. A modification method according to claim 4, characterized in that: The powder heating temperature is 300-500°C.

7. An application of modified calcium carbonate, characterized in that: The modified calcium carbonate is a modified calcium carbonate as described in any one of claims 1 to 3, and the application is to use the modified calcium carbonate as an auxiliary material for insulating ceramics.

8. The use of a modified calcium carbonate according to claim 7, characterized in that: The added amount of calcium carbonate powder in the insulating ceramic is not more than 1.5 wt %.