CN107916452B - Preparation method of calcium carbonate whiskers with continuously controllable morphology - Google Patents

Abstract

The invention discloses a preparation method of calcium carbonate whiskers with continuously controllable morphology, which comprises the following steps: adding calcium oxide into deionized water, digesting at a certain temperature, adding a crystal form control agent, uniformly stirring, introducing carbon dioxide gas at a certain flow rate by using a double-tube ventilation device to perform carbonation reaction, and finally performing suction filtration, washing and drying on the obtained suspension to obtain a sample. The invention is characterized in that the prepared multi-arm whisker is a calcium carbonate whisker with a new appearance, and the number of the whisker branches can be controlled by reaction conditions. The crystal whisker is used as a filling material of a composite material, and has great advantages in the aspects of improving the chemical property, the mechanical property and the like of the composite material.

Description

A kind of preparation method of continuous and controllable morphology of calcium carbonate whiskers

technical field

The invention relates to the technical field of inorganic material preparation, in particular to a preparation method of calcium carbonate whiskers with continuous and controllable morphology.

Background technique

Inorganic whiskers have a relatively complete structure and few defects, their strength and modulus are close to the theoretical values of complete crystals, and their flame retardant properties are better than organic whiskers, making them ideal reinforcement and toughening materials for composite materials, such as ZnO, SiC , potassium titanate, mullite, aluminum borate, etc. have been industrialized, but large-scale application is hindered due to high cost, while calcium carbonate whiskers have a wide range of raw materials and low production costs, and can even be prepared using industrial waste residues. The most important inorganic whisker material.

At present, domestic and foreign scholars have done a lot of research on the preparation of aragonite calcium carbonate whiskers, and there are mainly five types of preparation methods: (1) metathesis method; (2) Ca(HCO ₃ ) ₂ thermal decomposition method; (3) urea water solution method; (4) sol-gel method; (5) carbonation method. Among them, the carbonation method is the most researched and mature method at home and abroad. Due to the simple preparation process and low cost, it is expected to realize the industrialization of calcium carbonate at the earliest.

The research on the shape control technology of calcium carbonate products at home and abroad has progressed rapidly. Researchers have synthesized calcium carbonate in various crystal forms, such as spindle, cubic, chain, flake, spherical, needle, etc., but the multi-arm whisker rarely seen. Through the analysis of the structure, we found that the multi-armed whiskers have greater advantages in improving chemical properties and mechanical properties, because the multi-armed whiskers have more functional groups than single whiskers, and when used as fillers, their "pinning" "The effect is stronger, so the chemical properties and mechanical properties are better than rod whiskers. Therefore, our research goal is to find a preparation method for multi-armed calcium carbonate whiskers. Considering that increasing the position of the whiskers to continue crystallization can make the whiskers grow into a multi-arm structure, we try to use a double-tube ventilation device to conduct Experiments, based on the carbonation method, prepared multi-armed calcium carbonate whiskers. It has been confirmed that the whiskers prepared by this method are multi-armed structures, and the number of branch arms of the whiskers can be controlled according to the reaction conditions.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for preparing calcium carbonate whiskers with continuous and controllable morphology, which is characterized in that a carbonation method is used to synthesize multi-arm calcium carbonate whiskers by means of a double-pipe ventilation device to obtain the branches of the whiskers. The number of arms is 2 to 16. The specific implementation is as follows:

Step 1, weigh a certain amount of calcium oxide, add it into deionized water to obtain a _Ca (OH) suspension with a concentration of 0.1-0.3mol/L, and heat it to digest it;

Step 2, taking magnesium chloride as crystal form control agent, adding water to dissolve, and adding magnesium chloride solution to the digested Ca(OH) ₂ suspension, stirring to make it uniform;

Step 3, using a double-pipe ventilation device to introduce carbon dioxide gas to the bottom of the reaction device to carry out carbonation reaction, after the reaction is completed, the obtained precipitate is subjected to suction filtration, washing, and drying to obtain a sample.

In the above technical solution, the temperature for heating and digestion in the step 1 is 70-100°C.

The amount of magnesium chloride added in the step 2 is to make the magnesium-calcium molar ratio 1:1～2.5:1.

In the step 3, the carbon dioxide gas flux is usually 60-150 ml/min.

The double-pipe ventilation device described in the step 3 can be a three-necked round-bottomed flask, and carbon dioxide enters the round-bottomed flask simultaneously from the openings on both sides thereof.

Preferably, in the step 3, the carbonation reaction time is 2 to 3 hours, the number of arms of the obtained sample calcium carbonate whiskers is 2 to 16, and the number of arms of the whiskers varies with the reaction time, such as when the carbonation reaction The time is 2h, the obtained product is mainly whiskers containing 4 branches, when the carbonation reaction time is 2.5h, the obtained products are mainly whiskers containing 5-7 branches, when the carbonation reaction time is 3h , the obtained products are mainly whiskers with more than 10 branches, and the number of calcium carbonate whiskers can be adjusted by adjusting the carbonation reaction time.

Compared with the existing technology for preparing calcium carbonate whiskers, the present invention has outstanding features and remarkable progress:

1. The use of a double-pipe ventilation device to introduce CO ₂ gas is beneficial to increase the position of continued crystallization on the whisker, increase the growth point, and make the whisker grow into a multi-arm structure;

2. The morphology of the prepared whiskers is multi-armed, and the number of branch arms of the whiskers can be continuously controlled. The whisker functional groups of the multi-arm structure are more than that of a single whisker, and the "pinning" effect of the filler is better. Strong, with better chemical and mechanical properties.

Description of drawings

Fig. 1 is the scanning electron microscope photograph of embodiment 1 whisker;

Fig. 2 is embodiment 2 whisker scanning electron microscope photograph;

Fig. 3 is the scanning electron microscope photograph of embodiment 3 whiskers;

Figure 4 is a schematic diagram of the double-pipe ventilation device used in the present invention.

Detailed ways

Example 1

Step 1: Add calcium oxide into deionized water to obtain a Ca(OH) ₂ suspension with a concentration of 0.1 mol/L, and heat it to 70°C for 2 hours;

Step 2: Weigh magnesium chloride as the crystal form control agent, make the ratio of magnesium to calcium 1:1, add water to dissolve, and add the magnesium chloride solution to the digested Ca(OH) ₂ suspension, stir for 0.5h to make it uniform; Step 3: A three-necked round-bottomed flask was used, and _CO gas was introduced into the bottom of the reaction device at a flux of 150 ml/min from both sides to carry out carbonation reaction;

Step 4: The carbonization reaction is completed after 2 hours, and the obtained precipitate is subjected to suction filtration, washing, and drying to obtain a sample.

The number of arms of the prepared calcium carbonate whiskers is mainly 4, and its SEM image is shown in Figure 1.

Example 2

Step 1: Add calcium oxide into deionized water to obtain a Ca(OH) ₂ suspension with a concentration of 0.2 mol/L, and at the same time heat to 80 °C and digest for 2 h;

Step 2: Weigh magnesium chloride as the crystal form control agent, make the ratio of magnesium to calcium 2:1, add water to dissolve, add the magnesium chloride solution to the digested Ca(OH) ₂ suspension, stir for 0.5h to make it uniform; Step 3: A three-necked round-bottomed flask was used, and _CO gas was introduced into the bottom of the reaction device at a flux of 100 ml/min from both sides to carry out carbonation reaction;

Step 4: The carbonization reaction is completed after 2.5 hours, and the obtained precipitate is subjected to suction filtration, washing, and drying to obtain a sample.

The number of arms of the prepared calcium carbonate whiskers is mainly about 7, and its SEM image is shown in Figure 2.

Example 3

Step 1: Add calcium oxide into deionized water to obtain a Ca(OH) ₂ suspension with a concentration of 0.3 mol/L, heat it to 100° C., and digest for 2 hours;

Step 2: Weigh magnesium chloride as crystal form control agent, make the ratio of magnesium to calcium 2.5:1, add water to dissolve, add magnesium chloride solution to the digested Ca(OH) ₂ suspension, stir for 0.5h to make it uniform;

Step 3: adopting a three-necked round-bottomed flask, and feeding _CO gas into the bottom of the reaction device at a flux of 60 ml/min from both sides to carry out carbonation reaction;

Step 4: The carbonization reaction is completed after 3 hours, and the obtained precipitate is subjected to suction filtration, washing, and drying to obtain a sample.

The number of arms of the prepared calcium carbonate whiskers can be as high as 16, and the SEM image is shown in Figure 3.

Claims (3)

1. A preparation method of calcium carbonate whiskers with continuously controllable morphology comprises the following specific steps:

step 1, weighing a certain amount of calcium oxide, adding the calcium oxide into deionized water to obtain Ca (OH) with the concentration of 0.1-0.3mol/L₂Heating the suspension to digest it;

step 2, weighing magnesium chloride as a crystal form control agent, adding water for dissolving, and adding a magnesium chloride solution into digested Ca (OH)₂Stirring the suspension liquid to be uniform;

3, introducing carbon dioxide gas to the bottom of the reaction device by using a double-pipe ventilation device, carrying out carbonation reaction, and carrying out suction filtration, washing and drying on the obtained precipitate after the reaction is finished to obtain a sample; the double-tube ventilating device is a three-mouth round-bottom flask, carbon dioxide enters the round-bottom flask from openings on two sides of the round-bottom flask simultaneously, and carbonation reaction is carried out for 3 hours; wherein the flux of carbon dioxide gas is 60-150 ml/min;

the obtained sample mainly contains calcium carbonate whiskers containing more than 10 branch arms.

2. The method for preparing calcium carbonate whiskers with continuously controllable morphology according to claim 1, characterized in that: the temperature of heating digestion in the step 1 is 70-100 ℃.

3. The method for preparing calcium carbonate whiskers with continuously controllable morphology according to claim 1, characterized in that: the adding amount of the magnesium chloride in the step 2 is such that the molar ratio of magnesium to calcium is 1: 1-2.5: 1.

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