Method for preparing single-phase beta-CaSiO3 powder based on chlorine-based molten salt

Abstract

The invention discloses a method for preparing single-phase beta-CaSiO3 powder based on chlorine-based molten salt, and belongs to the technical field of ceramic powder materials. The method comprises the following steps: 1, mixing a salt material: weighing raw materials CaCO3 and SiO2 required by CaSiO3 and chlorine-based molten salt according to a ratio, pouring the raw materials into a ball milling tank containing zirconium oxide beads, carrying out ball milling and uniform mixing by taking absolute ethyl alcohol as a solvent, and then discharging, drying and sieving to obtain the mixed salt material; step 2, high-temperature calcination: putting the mixed salt material obtained in the step 1 into a crucible, and putting the crucible into a muffle furnace for high-temperature calcination to form a beta-CaSiO3 crystal phase; step 3, washing and desalting: adding deionized water into the mixture of beta-CaSiO3 and molten salt calcined in the step 2, stirring, then carrying out suction filtration, and washing for multiple times to remove the molten salt; and then drying to obtain the single-phase beta-CaSiO3 powder. The method disclosed by the invention has the characteristics of low synthesis temperature, simple process, short synthesis period, low cost, no pollution and industrial production, and the prepared beta-CaSiO3 powder based on the chlorine-based molten salt is high in purity and does not contain other impure phases.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic powder materials, and mainly to a method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt. Background Art

[0002] With the rapid development of mobile communications, a large amount of information needs to be transmitted at extremely high speeds. Therefore, dielectric materials used in microwave communications need to have a low dielectric constant (ε r <10) to achieve low signal delay. Common low-k materials include ceramic material systems such as alumina, silicates, vanadates, phosphates, and molybdates.

[0003] Among many low dielectric materials, CaSiO3 has excellent dielectric properties (ε r ~5-6, tanδ~3×10 -4 ), a sintering temperature (~1350°C) lower than Al2O3 (≥1600°C), and low cost, offering promising application prospects. CaSiO3 is the primary crystalline phase of calcium borosilicate glass-ceramics, consisting of α-CaSiO3 (high-temperature phase) and β-CaSiO3 (low-temperature phase). β-CaSiO3 is the primary component of the commercial material FerroA6.

[0004] Regarding the synthesis of CaSiO3 powder, many studies have attempted to obtain single α-CaSiO3 or β-CaSiO3 phases by adjusting the CaO-B2O3-SiO2 glass composition. However, these experiments require large amounts of work and the glass sintering temperature range is relatively narrow. Furthermore, the synthesis of single-phase β-CaSiO3 using traditional solid-phase methods is difficult due to the presence of SiO2 and Ca2SiO4. Other studies have used sol-gel and chemical precipitation methods to synthesize CaSiO3, but these methods are complex, energy-intensive, and have low yields.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The present invention aims to provide a method for preparing single-phase β-CaSiO3 powder using a chloride-based molten salt, addressing the technical issues of the existing solid-phase method, which is difficult to synthesize single-phase β-CaSiO3, and the complex and costly operation of other synthesis methods. The β-CaSiO3 powder prepared by the present method is high in purity, free of other impurities, and simple and low in cost.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] A method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt, the specific steps are as follows:

[0009] Step 1, mixed salt material: the raw materials CaCO3 and SiO2 required for CaSiO3 and chlorine-based molten salt are weighed in proportion and poured into a ball mill containing zirconium oxide beads, and anhydrous ethanol is used as a solvent to perform ball milling and mixing, and then the mixed salt material is obtained after discharging, drying and sieving;

[0010] Step 2, high-temperature calcination: the mixed salt material obtained in step 1 is placed in a crucible, and placed in a muffle furnace for high-temperature calcination at a sintering temperature of 1050-1150° C. to form a β-CaSiO3 crystal phase;

[0011] Step 3: Washing and removing salts: Add deionized water to the mixture of β-CaSiO3 and molten salt after calcination in step 2, stir, then filter, and wash with water several times to remove the molten salt; then dry to obtain single-phase β-CaSiO3 powder.

[0012] Optionally, in step 1, the mass ratio of the zirconia beads to the mixed salt is 5:1, the mass ratio of anhydrous ethanol to the mixed salt is 1:1, the ball milling speed is 250-300 r / min, and the ball milling time is 6-8 h.

[0013] Optionally, in step 1, the chlorine-based molten salt is sodium chloride or a mixed molten salt of sodium chloride and potassium chloride, and the ratio of the chlorine-based molten salt to the raw materials CaCO3 and SiO2 required for CaSiO3 is a mass ratio of (0.5-7):1.

[0014] Optionally, in step 1, the drying temperature and drying time are 60-100° C. and 8-12 hours respectively, and the sieve mesh is 60-120 mesh.

[0015] Optionally, in the step 2, the heating rate during the high-temperature calcination process is 3 to 10° C. / min, and the holding time is 2 to 6 hours.

[0016] Optionally, in step three, the drying temperature and time are 80-120° C. and 6-12 hours, respectively.

[0017] Optionally, in step three, the filtrate is titrated with AgNO3 to check whether the chlorine-based molten salt is completely washed away; the phenomenon of complete removal of the chlorine-based molten salt by the AgNO3 titration test is that no white precipitate is generated in the filtrate.

[0018] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0019] The present invention has the characteristics of low synthesis temperature, simple process, short synthesis cycle, low cost, no pollution, and industrial production. The prepared chlorine-based molten salt-based β-CaSiO3 powder has high purity and does not contain other impurities. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 The XRD pattern of the β-CaSiO3 powder prepared in Examples 1 and 2 of the present invention;

[0022] Figure 2 This is the SEM image of the β-CaSiO3 powder prepared in Examples 1 and 2 of the present invention.

[0023] Figure 3 This is the XRD pattern of the β-CaSiO3 powder prepared in Comparative Examples 1, 2, and 3 of the present invention. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0025] The purpose of the present invention is to provide a method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt, thereby simplifying the production process and reducing production costs.

[0026] Furthermore, the method comprises the following steps:

[0027] Step 1, mixed salt material: the raw materials CaCO3 and SiO2 required for CaSiO3 and chlorine-based molten salt are weighed in proportion and poured into a ball mill containing zirconium oxide beads, and anhydrous ethanol is used as a solvent to perform ball milling and mixing, and then the mixed salt material is obtained after discharging, drying and sieving;

[0028] Step 2, high-temperature calcination: the mixed salt material obtained in step 1 is placed in a crucible, and placed in a muffle furnace for high-temperature calcination at a sintering temperature of 1050-1150° C. to form a β-CaSiO3 crystal phase;

[0029] Step 3: Washing and removing salts: Add deionized water to the mixture of β-CaSiO3 and molten salt after calcination in step 2, stir, then filter, and wash with water several times to remove the molten salt; then dry to obtain single-phase β-CaSiO3 powder.

[0030] Furthermore, in step 1, the molar ratio of the raw materials CaCO3 and SiO2 required for CaSiO3 is 1:1.

[0031] Furthermore, the chlorine-based molten salt in step 1 is sodium chloride or a mixed molten salt of sodium chloride and potassium chloride, and the mass ratio of the chlorine-based molten salt to the raw materials CaCO3 and SiO2 required for CaSiO3 is (0.5-7):1. More preferably, it is (2-5):1 or (2.5-4.5):1. The mixed molten salt can be a single species or a mixture of two or three species.

[0032] Furthermore, in step 1, the mass ratio of zirconia beads to mixed salt is 5:1, the mass ratio of anhydrous ethanol to mixed salt is 1:1, the ball milling speed is 250-300 r / min, and the ball milling time is 6-8 h.

[0033] Furthermore, in step 1, the drying temperature and the drying time are 60-100° C. and 8-12 hours respectively, and the sieving screen is 60-120 mesh.

[0034] Furthermore, in step 2, the heating rate during the high-temperature calcination process is 3 to 10° C. / min, and the holding time is 2 to 6 hours.

[0035] Furthermore, in step three, the drying temperature and time are 80-120° C. and 6-12 h, respectively.

[0036] Furthermore, in step three, the filtrate is titrated with AgNO3 to check whether the chlorine-based molten salt is completely washed away. The phenomenon of complete removal of the chlorine-based molten salt by AgNO3 titration is that no white precipitate is generated in the filtrate.

[0037] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Example 1

[0039] A method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt. The specific steps of the preparation method described in this embodiment are as follows:

[0040] Step 1. Mixing salt: weigh the raw materials CaCO3 and SiO2 according to the molar ratio of 1:1 required for CaSiO3, and sodium chloride as the molten salt, whose mass is 3 times the mass of CaCO3 and SiO2. After weighing, pour it into a ball mill containing zirconia beads, add about the same mass of anhydrous ethanol as solvent, and ball mill at a speed of 250-300r / min to mix. Ball mill for 6-8h, then discharge the material, dry it at 60-100℃ for 8-12h, and pass it through a 60-mesh sieve to obtain a mixed salt.

[0041] Step 2: High-temperature calcination: The mixed salt obtained in step 1 is placed in an alumina crucible, and placed in a muffle furnace for high-temperature calcination, with the temperature rising to 1100°C at a heating rate of 5°C / min, and kept at this temperature for 4 hours to form a β-CaSiO3 crystal phase.

[0042] Step 3: Washing and desalting: Add deionized water to the mixture of β-CaSiO3 and sodium chloride molten salt calcined in step 2 and stir, then filter and wash with water 3 to 4 times to remove the molten salt; titrate the filtrate with AgNO3, and when no white precipitate is generated in the filtrate, it indicates that the sodium chloride molten salt has been completely washed away; then dry at 80 to 120°C for 6 to 12 hours, and grind to obtain single-phase β-CaSiO3 powder.

[0043] The β-CaSiO3 powder prepared in this embodiment was subjected to XRD analysis. Figure 1 As shown in FIG, the diffraction peaks of β-CaSiO3 prepared in this embodiment are consistent with those of the standard card, and there are no obvious miscellaneous peaks, indicating that the phase composition is single-phase β-CaSiO3; the β-CaSiO3 powder prepared in this embodiment was subjected to scanning electron microscopy analysis, as shown in FIG. Figure 2 As shown in (a), the β-CaSiO3 prepared in this embodiment is nearly rod-shaped / columnar particles with good dispersibility.

[0044] Example 2

[0045] A method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt. The specific steps of the preparation method described in this embodiment are as follows:

[0046] Step 1. Mixed salt: According to the molar ratio of CaCO3 and SiO2 required for CaSiO3 of 1:1, sodium chloride and potassium chloride are used as mixed molten salt, the mass of which is 3 times the mass of CaCO3 and SiO2, and the molar ratio of sodium chloride to potassium chloride is 1:1. After weighing, pour the materials into a ball mill containing zirconia beads, add about the same mass of anhydrous ethanol as a solvent, and ball mill at a speed of 250-300r / min to mix. Ball mill for 6-8h, then discharge the materials, dry them at 60-100℃ for 8-12h, and pass them through a 60-mesh sieve to obtain a mixed salt.

[0047] Step 2: High-temperature calcination: The mixed salt obtained in step 1 is placed in an alumina crucible, and placed in a muffle furnace for high-temperature calcination, with the temperature rising to 1100°C at a heating rate of 5°C / min, and kept at this temperature for 4 hours to form a β-CaSiO3 crystal phase.

[0048] Step 3: Washing and desalting: Add deionized water to the mixture of β-CaSiO3 calcined in step 2 and the mixed molten salt of sodium chloride and potassium chloride, and stir, then filter and wash with water 3 to 4 times to remove the molten salt; titrate the filtrate with AgNO3, and when no white precipitate is generated in the filtrate, it indicates that the sodium chloride molten salt is completely washed away; then dry at 80 to 120°C for 6 to 12 hours, and grind to obtain a single-phase β-CaSiO3 powder.

[0049] The β-CaSiO3 powder prepared in this embodiment was subjected to XRD analysis. Figure 1 As shown in FIG, the diffraction peaks of β-CaSiO3 prepared in this embodiment are consistent with those of the standard card, and there are no obvious miscellaneous peaks, indicating that the phase composition is single-phase β-CaSiO3; the β-CaSiO3 powder prepared in this embodiment was subjected to scanning electron microscopy analysis, as shown in FIG. Figure 2 As shown in (b), the β-CaSiO3 prepared in this embodiment is in the form of block-shaped particles.

[0050] Example 3

[0051] A method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt. The specific steps of the preparation method described in this embodiment are as follows:

[0052] Step 1. Mixed salt: according to the molar ratio of CaCO3 and SiO2 required for CaSiO3 of 1:1, sodium chloride and potassium chloride are used as mixed molten salt, the mass of which is 1 times the mass of CaCO3 and SiO2, and the molar ratio of sodium chloride to potassium chloride is 1:1. After weighing, pour the materials into a ball mill containing zirconia beads, add about the same mass of anhydrous ethanol as a solvent, and ball mill at a speed of 250-300r / min to mix. Ball mill for 6-8h, then discharge the material, dry it at 60-100℃ for 8-12h, and pass it through a 60-mesh sieve to obtain a mixed salt.

[0053] Step 2: High-temperature calcination: The mixed salt obtained in step 1 is placed in an alumina crucible, and placed in a muffle furnace for high-temperature calcination, with the temperature rising to 1100°C at a heating rate of 5°C / min, and kept at this temperature for 4 hours to form a β-CaSiO3 crystal phase.

[0054] Step 3: Washing and desalting: Add deionized water to the mixture of β-CaSiO3 calcined in step 2 and the mixed molten salt of sodium chloride and potassium chloride, and stir, then filter and wash with water 3 to 4 times to remove the molten salt; titrate the filtrate with AgNO3, and when no white precipitate is generated in the filtrate, it indicates that the sodium chloride molten salt is completely washed away; then dry at 80 to 120°C for 6 to 12 hours, and grind to obtain a single-phase β-CaSiO3 powder.

[0055] Comparative Example 1

[0056] Unlike the above examples, this comparative example does not add chlorine-based molten salt. The β-CaSiO3 powder is synthesized by traditional solid phase reaction method. The calcination temperature is 1100°C. Other aspects are the same as those of the examples. XRD analysis of the β-CaSiO3 powder prepared in this comparative example shows that Figure 3 As shown, the powder phase composition obtained in this comparative example contains, in addition to β-CaSiO3, a large amount of SiO2 and Ca2SiO4 phases.

[0057] Comparative Example 2

[0058] Unlike the above examples, this comparative example does not add chlorine-based molten salt. The β-CaSiO3 powder is synthesized by traditional solid phase reaction method. The calcination temperature is 1150℃. Other aspects are the same as the examples. XRD analysis of the β-CaSiO3 powder prepared in this comparative example shows that Figure 3 As shown, the phase composition of the powder obtained in this comparative example is compared with that in comparative example 1, and the relative content of β-CaSiO3 is increased, but a certain amount of SiO2 and Ca2SiO4 phases are still present.

[0059] Comparative Example 3

[0060] Unlike the above examples, the present comparative example does not add chlorine-based molten salt, and the β-CaSiO3 powder is synthesized by the traditional solid phase reaction method. The calcination temperature is 1200°C, and the other aspects are the same as those of the examples. The CaSiO3 powder prepared in this comparative example is subjected to XRD analysis. Figure 3 As shown, the phase composition of the powder obtained in this comparative example is transformed into α-CaSiO3. In addition, there are small amounts of Ca3Si2O7 and β-CaSiO3.

[0061] In summary, the β-CaSiO3 powder prepared by the present invention based on chlorine-based molten salt has higher purity than that of solid-phase method, other liquid-phase methods, etc., does not contain other impurities, and this method has low synthesis temperature, simple process and low cost.

[0062] This specification describes various embodiments in a progressive manner, and emphasizes the differences between each embodiment and other embodiments. The same or similar parts in various embodiments are referenced to each other.

[0063] The specific examples of the present invention are used to illustrate its principles and implementation methods, and are intended to help understand the methods and core concepts of the present invention. For those skilled in the art, the specific implementation methods and application scope may be adjusted according to the concepts of the present invention. Therefore, the content of this specification should not be construed as limiting the present invention.

Claims

1. A method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt, characterized in that: The method comprises the following steps: Step 1, mixed salt: weigh the raw materials CaCO3 and SiO2 required for CaSiO3 and the chlorine-based molten salt in proportion and pour them into a ball mill containing zirconium oxide beads, use anhydrous ethanol as solvent, perform ball milling and mixing, and then obtain the mixed salt after discharging, drying and sieving; Step 2, high temperature calcination: the mixed salt material obtained in step 1 is placed in a crucible, and placed in a muffle furnace for high temperature calcination, the sintering temperature is 1050-1150° C., to form a β-CaSiO3 crystal phase; Step 3: Washing and removing salt: Add deionized water to the mixture of β-CaSiO3 and molten salt after calcination in step 2, stir, then filter, and wash with water for multiple times to remove the molten salt; then dry to obtain single-phase β-CaSiO3 powder.

2. A method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt according to claim 1, characterized in that: In the step 1, the molar ratio of the raw materials CaCO3 and SiO2 required for CaSiO3 is 1:

1.

3. A method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt according to claim 1 or 2, characterized in that: In the step 1, the chlorine-based molten salt is one or more of sodium chloride, sodium chloride and potassium chloride, and the ratio of the raw materials CaCO3 and SiO2 required for the chlorine-based molten salt and CaSiO3 is a mass ratio of (0.5-7):

1.

4. A method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt according to claim 1, characterized in that: In the step 1, the mass ratio of the zirconium oxide beads to the mixed salt is 5:1, the mass ratio of anhydrous ethanol to the mixed salt is 1:1, the ball milling speed is 250-300 r / min, and the ball milling time is 6-8 h.

5. A method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt according to claim 1, characterized in that: In the step 1, the drying temperature and drying time are 60-100° C. and 8-12 hours respectively, and the sieve mesh is 60-120 meshes.

6. A method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt according to claim 1, characterized in that: In the step 2, the heating rate during the high temperature calcination is 3 to 10° C. / min, and the holding time is 2 to 6 hours.

7. A method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt according to claim 1, characterized in that: In the step three, the drying temperature and time are 80-120° C. and 6-12 hours respectively.

8. A method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt according to claim 1, characterized in that: In the step 3, the filtrate is titrated with AgNO3 to check whether the chlorine-based molten salt is completely washed away.

9. A method for preparing single-phase β-CaSiO3 powder based on chlorine-based molten salt according to claim 8, characterized in that: In step 3, the AgNO3 titration test shows that the chlorine-based molten salt is completely removed, and no white precipitate is generated in the filtrate.

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