Preparation method of low-temperature calcium titanate powder

Abstract

The invention discloses a preparation method of low-temperature calcium titanate powder, which sequentially comprises the following steps: mixing a calcium carbonate raw material and a titanium dioxide raw material according to a molar ratio of 0.95-1.05, adding boric acid accounting for 0.3-1.0 wt% of the raw materials, mixing the raw materials, grinding and crushing the mixed materials, and controlling 10-20% of the crushed mixed raw materials on a 150 mu m sieve, thereby obtaining the low-temperature calcium titanate powder. Putting the uniformly mixed raw materials into a high-temperature furnace to be calcined, setting the firing temperature to be 800-1000, the heating rate to be 5-10 DEG C / min and the firing time to be 2-4 hours, then cooling to room temperature according to the rate of 2-5 DEG C / min, crushing the fired product by a crusher, and grading to obtain the calcium titanate powder with compact particles. According to the invention, calcium carbonate and titanium dioxide are used as raw materials, an auxiliary agent is added at the same time, and a calcium titanate product can be obtained by mixing, crushing, high-temperature calcining, crushing and grading. According to the invention, a small amount of boric acid (0.3-1.0 wt%) is added as a sintering aid to promote sintering of the raw materials at a low temperature so as to form a calcium titanate product with compact particles.

Description

Technical Field

[0001] The invention relates to calcium titanate powder, in particular to a method for preparing low-temperature calcium titanate powder. Background Art

[0002] Calcium titanate is an inorganic substance with the chemical formula of CaTiO3. It belongs to the cubic crystal system and is a basic inorganic dielectric material with excellent dielectric, temperature, mechanical and optical properties. It is widely used in ceramic capacitors, PTC thermistors, microwave antennas, filters and stainless steel welding rods. At present, calcium titanate is generally prepared by solid phase sintering method, which includes the following processing steps:

[0003] 1) Weigh calcium carbonate and titanium dioxide in a molar ratio of 1:1 and add them into a ball mill;

[0004] 2) Add 3-5 parts of water to 1 part of the above raw materials by weight and add them into the ball mill;

[0005] 3) Ball milling for 18 to 24 hours;

[0006] 4) The flowing slurry obtained in step (3) is pressed into a filter press by a thick slurry pump to obtain a filter cake;

[0007] 5) The filter cake of step (4) is dried, broken, put into a bowl and calcined at 800-1000°C, cooled and crushed, inspected and packaged to obtain a high-purity calcium titanate powder.

[0008] The calcium titanate powder produced by the existing solid phase method at 800-1000℃ is fine in shape, poor in dispersion and compaction performance, and is easy to agglomerate, making it less suitable for specific scenarios such as composite plastics. The sintered dense powder particles need to be calcined at a high temperature of more than 1350℃, which requires a high kiln temperature and a difficult preparation process. The SEM photo of calcium titanate is shown in Figure 1 . Summary of the invention

[0009] The purpose of the present invention is to provide a preparation method of low-temperature calcium titanate powder. The melting temperature of B2O3 is about 450°C. It can be converted into a liquid phase in the mixed raw materials during the sintering and heating process. The raw material reaction sintering mode is changed from solid phase sintering to liquid phase sintering. The molten boron oxide can dissolve the alkaline oxide, and the liquid phase mass transfer promotes the particle arrangement and stacking to be more compact, accelerates the reaction process, and small particles are deposited on the surface of large particles, resulting in grain growth and grain shape changes, which are more compact. Boric acid can strongly absorb water in the air to generate boric acid; and the hydrogen bonds between boric acid molecules are very strong, it is not easy to absorb water and has stable physical and chemical properties. Therefore, boric acid is used as a raw material to introduce boron oxide raw materials. Calcium carbonate and titanium dioxide raw materials are added with auxiliary agents at the same time, and calcium titanate products can be obtained after mixed crushing, high-temperature calcination, crushing, and classification. The present invention promotes the sintering of raw materials at a relatively low temperature by adding a small amount of boric acid (0.3~1.0wt%) as a sintering aid to form a calcium titanate product with dense particles.

[0010] To achieve the above object, the present invention provides the following technical solutions.

[0011] The present application discloses a method for preparing low-temperature calcium titanate powder, which comprises the following steps in sequence: mixing a calcium carbonate raw material and a titanium dioxide raw material at a molar ratio of 0.95-1.05, adding 0.3-1.0wt% of boric acid to the raw materials for mixing, grinding and crushing the mixed materials, controlling the residue on a 150μm sieve of the crushed mixed raw materials to be 10%-20%, placing the uniformly mixed raw materials into a high-temperature furnace for calcination, setting the calcination temperature to 800-1000, the heating rate to 5-10°C / min, calcining for 2-4 hours, and then cooling to room temperature at a rate of 2-5°C / min, and crushing and classifying the calcined product by a pulverizer to obtain a calcium titanate powder with dense particles.

[0012] Preferably, in the above-mentioned method for preparing low-temperature calcium titanate powder, the titanium dioxide raw material is one or more of rutile titanium oxide and anatase titanium oxide.

[0013] The synthesis process of the present invention is simple, and the addition of boric acid as a sintering aid effectively improves the problem that the growth of powder particles is limited by the calcination temperature, reduces the calcination temperature, saves energy efficiency, and effectively improves the production and usability of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 Shown is a SEM photo of calcium titanate in the background technology;

[0016] Figure 2 Shown is a SEM photo of the product obtained in a specific embodiment of the present invention;

[0017] Figure 3 Shown is the XRD spectrum of the product obtained in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention are described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Specific embodiments

[0019] The titanium-containing raw material (99.5% purity rutile titanium dioxide) and calcium carbonate raw material (99.5% purity) are mixed at a molar ratio of 0.95~1.05, and the mass fraction of boric acid (98% purity) is 0.5%. Then the raw materials are mixed and crushed until 10~20% remain on the 150μm sieve. The crushed raw materials are placed in a high-temperature furnace for calcination, and the sintering temperature is set to 900℃, the heating rate is 5℃ / min, the sintering time is 4 hours, and then it is cooled to room temperature at 3℃ / min. The sintered product is crushed and graded using a pulverizer to obtain a calcium titanate powder product with an average particle size of 5~15μm.

[0020] Calcinated at 900℃, added with boric acid, bulk density: 0.92, SEM photos and XRD patterns of the product are shown in Figure 2 and Figure 3 .

[0021] This implementation mode is only an exemplary description of this patent and does not limit its protection scope. Personnel in this field may also make partial changes to it. As long as it does not exceed the spirit of this patent, it shall be regarded as an equivalent replacement of this patent and shall be within the protection scope of this patent.

Claims

1. A method for preparing low-temperature calcium titanate powder, characterized in that: The method comprises the following steps in sequence: mixing a calcium carbonate raw material and a titanium dioxide raw material at a molar ratio of 0.95-1.05, adding 0.3-1.0wt% of boric acid to mix the raw materials, grinding and crushing the mixed materials, controlling 10%-20% of the residue on a 150-μm sieve of the crushed mixed raw materials, putting the uniformly mixed raw materials into a high-temperature furnace for calcination, setting the calcination temperature to 800-1000, the heating rate to 5-10°C / min, calcining for 2-4 hours, then cooling to room temperature at a rate of 2-5°C / min, crushing and classifying the calcined product by a pulverizer to obtain calcium titanate powder with dense particles.

2. The method for preparing low-temperature calcium titanate powder according to claim 1, characterized in that: The titanium dioxide raw material is one or more of rutile titanium oxide and anatase titanium oxide.

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