CN112358286A

CN112358286A - Artificially synthesized tetragonal petalite and its preparing process

Info

Publication number: CN112358286A
Application number: CN202011388660.3A
Authority: CN
Inventors: 黄新开
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-12-02
Filing date: 2020-12-02
Publication date: 2021-02-12

Abstract

The invention relates to a manufacturing technology for artificially synthesizing tetragonal petalite, in particular to a technical scheme for synthesizing a specific silicate mineral crystal by taking abundant silicate minerals, chemical raw materials and the like as component raw materials and referring to the stoichiometric value range of natural petalite and the ceramic production process flow and technical means. The synthetic product tetragonal system petalite is an isomer of monoclinic system natural petalite, and the product is superior to natural petalite in lithium-containing grade, thermal negative expansion performance, material purity and other aspects. Meanwhile, the production and manufacturing cost of the product is inexpensive lower than the market price of imported petalite, and the product has positive and profound significance for breaking through the bottleneck constraint of natural petalite resources, widening the supply sources of heat-resistant ceramic raw materials and improving the quality of daily heat-resistant ceramic products.

Description

Artificially synthesized tetragonal petalite and its preparing process

Technical Field

The invention belongs to the field of artificial synthesis and manufacture of ceramic materials, and particularly relates to artificially synthesized tetragonal petalite and a manufacturing method thereof.

Background

The petalite has a special crystal structure, and is endowed with the material characteristics of negative expansion and near-zero expansion in a specific temperature range (room temperature-600 ℃) (the expansion coefficient is alpha = 0.26 multiplied by 10 at 600 ℃)^-6/° c); spodumene, which is also a lithium low expansion mineral, can only characterize the positive expansion material properties (the expansion coefficient is α =1.28 × 10 at 600 ℃) in the temperature range from room temperature to 600 ℃^-6/° c). Due to the material characteristics of negative expansion and near-zero expansion of the petalite, the petalite can generate enough binary or multi-element crystal phases in the complex phase ceramicThe thermal shock resistance of the petalite heat-resistant ceramic product can be greatly improved due to the micro-crack toughening effect caused by the stress of the ceramic product. In recent years, with deepening of the cognition of microstress and microcrack toughening mechanisms and continuous maturity of formulation technology in the field of heat-resistant ceramic materials, the rapid expansion of the application scale of petalite in the field of heat-resistant ceramic is promoted. Therefore, the hot tide for developing the petalite heat-resistant ceramic material is promoted while the petalite resource supply is short.

In the field of petalite low-expansion ceramic research and development, as early as 1988, a low-expansion ceramic and a preparation method thereof (with the publication number of CN 88100211A) were invented in Zhou Jian, and the patent discloses a technical scheme for manufacturing the low-expansion ceramic by introducing lithium carbonate into a common silicate ceramic material. The patent also states that the main crystal phase of the low expansion ceramic material is petalite solid solution. Perhaps limited by the research conditions at the time, the patent document does not provide qualitative detection, analysis reports on the relevant low expansion materials.

The patent also discloses a formula of a low-expansion ceramic material expressed by an illustrative mineral method, and the specific mass percentages are as follows: 37-39% of quartz, 49-52% of kaolin and 9-12% of lithium carbonate. The inventor calculates SiO in the patent formula according to the median formula of the parameters₂、Al ₂0₃、Li ₂0 mass percent (after removal of ignition reduction) is 70.11 percent, 22.02 percent and 4.80 percent respectively, and obviously, in the chemical composition, except for the content of lithium oxide which is fit for the stoichiometric range of the natural petalite, the stoichiometric values of the other two backbone elements of silicon and aluminum are far from the stoichiometric range of the natural petalite mineral. Furthermore, the inventor selects a combination formula (namely the highest silicon-aluminum ratio combination of the patent formula) of the exemplary minerals of the patent formula, wherein the quartz proportion is 39% at the upper limit, and the kaolin proportion is 49% at the lower limit, to calculate the silicon-aluminum molar ratio of the formula, and performs corresponding analysis and comparison on the silicon-aluminum molar ratio, so that the calculated highest silicon-aluminum molar ratio of the formula is 5.78, which is compared with the stoichiometric silicon-aluminum molar ratio of about 7.78 of the natural petalite, and is called cloud mud. General knowledge in materials science tells us that the materialsThe stoichiometry of a material is the basic basis for qualitative analysis of the material, and two silicate materials with a very different molar ratio of silicon to aluminum have the same properties as the material.

From the above analysis, it can be determined that the stoichiometric values of the above patented formulations are closer to the stoichiometric range of β -spodumene. The stoichiometric parameters of the method do not have the material elements for generating the petalite as the main crystal phase. Therefore, the main crystal phase of the product of the above patent formula has a higher possibility that: a solid solution of beta-spodumene.

It should be noted that the product of the above patent formula is a solid-liquid two-phase sintered body, and as a barren material, its single-component forming property obviously cannot meet the requirement of scale production of daily heat-resistant ceramics. In addition, the above patent formula is to synthesize the low expansion material by introducing lithium salt in the whole chemical industry. In recent years, the situation that the price of chemical lithium salt is high and low brings difficult-to-overcome economic and technical obstacles for implementing the technical scheme.

Disclosure of Invention

The invention provides artificially synthesized tetragonal petalite and a manufacturing method thereof, which are used for getting rid of the dilemma that the existing low-expansion ceramic material production technology is difficult to produce a full-crystalline petalite material. The product of the invention, artificially synthesized tetragonal petalite, belongs to a full-crystalline petalite artificial mineral, the product performance meets the large-scale production requirement of daily heat-resistant ceramics, and the product can completely replace natural petalite which is a high heat-resistant formula raw material.

In order to solve the technical problems, the invention adopts the following technical scheme:

the artificially synthesized tetragonal petalite comprises the following chemical components: 74.0-80.0 Wt% SiO₂13.0 to 17.0Wt% of Al ₂0₃3.7-4.8 Wt% of Li ₂0, 0.0-2 Wt% of RO fluoride, and the balance of trace impurities carried in natural minerals and ignition reduction, and the tetragonal petalite also comprises 1-3 Wt% of natural petalite powder introduced in addition to the chemical components, wherein the SiO is₂ 、Al ₂0₃ 、Li ₂0 as a ternary skeleton materialThe RO fluoride is used as a mineralizer material, and the natural petalite is used as a seed crystal material.

The natural petalite can be used as an initial material of a seed crystal agent material, and is subsequently replaced by artificially synthesized tetragonal petalite powder.

Further, the SiO₂Introduced from silicate minerals, said Al ₂0₃Introduced from aluminosilicate minerals or aluminium-containing compounds, said Li₂0 is introduced by lithium-containing mineral spodumene or chemical lithium salt, and the RO fluoride is introduced by natural fluorine mineral or chemical raw material fluoride.

Preferably, the SiO₂Introduced from quartz or other aluminosilicate minerals, the Al ₂0₃Introduced from kaolin, pyrophyllite, alumina or aluminium hydroxide, the Li ₂0 is introduced by spodumene, lithium carbonate, lithium fluoride, lithium chloride or lithium hydroxide, and the RO fluoride is introduced by fluorite, fluorapatite, calcium fluoride, magnesium fluoride or barium fluoride.

Furthermore, the component grinding process adopts wet ball milling or dry grinding, and the average particle size of the other components is required to be less than or equal to 4 microns except that the natural petalite powder is kept with the fineness of 100-150 meshes.

The invention relates to a manufacturing method of artificially synthesized tetragonal petalite, which adopts a wet processing process, and comprises the following specific process flows: formula metering → batch charging and grinding → slurry discharging, screening, homogenizing → filter pressing and mud pressing → drying and powder making → blank mixing → press forming → green body drying → kiln charging and roasting.

The manufacturing method of artificially synthesized tetragonal petalite can also adopt a dry processing technology, and the specific technological process is as follows: formulation metering → blank mixing → press forming → blank drying → kiln loading and roasting.

When dry processing is adopted, raw materials can be ground into powder by a jaw crusher and a superfine grinding machine, or superfine powder of a composition material can be directly introduced to be blended into wetting powder suitable for compression molding for entering a subsequent molding process.

When soluble lithium salt is introduced into the lithium-containing chemical raw material, the blank preparation steps are as follows: (1) putting other raw materials except the soluble lithium salt into a stirrer, and firstly, uniformly mixing and stirring; (2) weighing water accounting for 8-10% of the total mass of the added powder, adding the soluble lithium salt weighed according to the formula into the water, and fully stirring to prepare a solution; and thirdly, starting the stirrer, adding the lithium salt solution into the powder in an atomization spraying mode, and spraying while stirring until the solution is sprayed and fully moistened and homogenized.

Further, the method also comprises the plasticizing treatment steps of the high-barren and low-plasticity formula, namely: organic high molecular material CMC, polyethylene glycol and polyacrylamide are used as plasticizer to prepare viscose liquid, and the viscose liquid is used to spray and stir the powder.

Further, the blank pressing comprises static pressure, extrusion and stamping, and the small strip-shaped or lath-shaped blocks with the length of 3-5 cm are manufactured after press forming.

Further, the kiln loading and roasting steps are as follows: and (3) putting the dried green body into a kiln, roasting at a heating rate of 3 ℃/min until the temperature is within a range of 1300-1350 ℃, cooling to 50 ℃, and then preserving heat for 2-3 hours, thereby finishing the kiln burning process.

The baked clinker green body can also be crushed into a silt-shaped product, and then classified according to the particle size (mesh number) of the powder according to the requirements of cities and customers, and put into the market.

Through the above description of the present invention, compared with the prior art, the present invention has the following beneficial effects:

1. the present invention uses silicate mineral, chemical material and other material as matrix material and refers to the stoichiometric range of natural petalite to constitute specific silicate mineral crystal-tetragonal petalite. The synthetic material is an isomer of natural petalite, belongs to a full-crystal phase petalite artificially-synthesized mineral material, and is superior to the natural petalite in lithium-containing grade, thermal negative expansion performance, material purity and other aspects. Meanwhile, the production and manufacturing cost of the artificially synthesized petalite is lower than the market price of imported petalite inexpensive, which has positive and profound significance for breaking through the bottleneck constraint of natural petalite resources, widening the supply sources of heat-resistant ceramic raw materials and improving the quality of daily heat-resistant ceramic products.

2. According to the invention, the principle of dual use of the soluble lithium salt and the insoluble lithium salt is adopted, and lithium ions ionized after the soluble lithium salt is dissolved in water are nanoparticles with high chemical activity and penetrating power, so that a strong promoting effect is generated on the later sintering reaction of the material.

3. The invention adopts fluoride as a mineralizer and is a technical measure specially carried by the artisan, and because fluorine ions have strong bond breaking capacity to silicon oxygen and aluminum oxygen bonds, the introduction of the fluoride can effectively promote the formation of crystal nuclei and the reconstruction of crystals.

4. According to the invention, natural petalite powder is introduced into the formula as a seed crystal agent, so that a good induction effect is generated on the crystal nucleus development in the crystallization process.

Drawings

Fig. 1 is an XRD analytical pattern of example 1.

FIG. 2 is a graph showing the dynamic coefficient of thermal expansion in example 1.

Fig. 3 is an XRD analytical pattern of example 2.

FIG. 4 is a graph showing the dynamic coefficient of thermal expansion in example 2.

FIG. 5 is a graph showing the dynamic coefficient of thermal expansion of example 3.

Detailed Description

The following describes specific embodiments of the present invention. Numerous details are set forth below in order to provide a thorough understanding of the present invention, but it will be apparent to those skilled in the art that the present invention may be practiced without these details.

Example 1

According to the metering requirement of the chemical components of the artificially synthesized petalite, the material feeding amount of a base material formula is set to be 100%, and the dry processing flow is adopted to sequentially weigh and feed the following materials:

weighing 54.0% of 1200-mesh commercial silicon micropowder, 35% of superfine kaolin powder, 3% of industrial lithium carbonate fine powder, 4% of lithium fluoride, 1% of barium fluoride and 3% of petalite fine powder (as an additive), and putting the materials into a spiral stirrer to stir and mix.

3 percent of anhydrous lithium chloride is weighed and prepared into 50 percent solution, and the dry powder material in stirring is sprayed while stirring in an atomization spraying mode until the lithium chloride solution is completely added with powder and the powder is uniformly wetted.

The stirred wet material is aged for 24 hours and enters a compression molding process.

Pressing the blank powder into a round strip-shaped or square blank body with the length of 3-5 CM. And airing the formed blank until the moisture content is below 3%, and then roasting in a kiln. The baking standard is as follows: the heating rate is as follows: 3 ℃ per minute; firing temperature: 1350 ℃; firing curve: after the sintering temperature is in place, the temperature is reduced by 50 ℃, and then the temperature is kept at 1300 ℃ for 2 hours, and the sintering is terminated at the point. And (3) crushing the sintered cooked blank, and grading the particle size (mesh number) of the powder so as to meet the requirements of different customers.

In example 1, XRD analysis was performed on the molded blank after firing, and as shown in fig. 1, the results showed that: the sample of the embodiment is consistent with the characteristic diffraction peak position of natural petalite, and the sample is identified as tetragonal petalite. Meanwhile, the sample of example 1 was also tested for its coefficient of expansion, which was negative at 20-600 ℃, and the end point of the test temperature was 600 ℃, as shown in fig. 2, and was α = -0.65 × 10^-6/℃。

Example 2

According to the metering requirement of the chemical components of the artificially synthesized petalite, the material feeding amount of a base material formula is set to be 100%, and a wet processing technology is adopted, and the method is sequentially operated according to the following steps.

Feeding at a first stage: weighing 55.0% of quartz sand, according to the following materials: ball: water-1: 1.5: 0.5, adding the mixture into a ball mill, and carrying out ball milling for 48 hours.

Feeding in a second stage: weighing 37% of kaolin refined mud (measured by dry weight), 8% of lithium fluoride, 3% of petalite ore powder sand (added amount), 80% of the second-stage feeding amount of water, and continuing to grind for 12 hours. And discharging slurry after grinding in place.

Referring to example 1, the flow of the subsequent process is continued to be completed: squeezing, drying, crushing, preparing pressed blank powder, pressing and forming, roasting, and crushing clinker until finished products are put in storage.

Since the formulation of this example does not incorporate a soluble lithium salt, the spraying of the lithium salt solution is omitted.

In example 2, XRD analysis was performed on the molded blank after firing, and as shown in fig. 3, the results showed that: the sample of the embodiment is consistent with the characteristic diffraction peak position of natural petalite, and the sample is identified as the tetragonal petalite. Meanwhile, the sample of example 2 was also tested for its expansion coefficient, which is negative at 20-600 ℃, and the end point of the test temperature is 600 ℃, and the expansion coefficient is α = -0.05 × 10, as shown in fig. 4^-6/℃。

Example 3

weighing 34.0% of 1200-mesh commercial silicon micropowder, 61.0% of 6.0-grade spodumene ultrafine powder, 2% of magnesium fluoride and 2% of petalite fine powder (the additional amount) and putting the weighed materials into a spiral stirrer for mixing. Weighing 3% of lithium chloride, and preparing into a lithium salt solution with the concentration of 40% for later use. Referring to example 1, the whole process flows of spraying the subsequent solution, homogenizing the blank powder, press forming, kiln loading and roasting (the firing temperature is 1340 ℃, the temperature is 1290 ℃ and is kept for 2 hours), crushing the clinker, grading the finished product and the like are continuously completed.

The expansion coefficient of the sample of example 3 was measured, and the results are shown in FIG. 4.

Example 4

According to the metering requirements of the chemical components of the artificially synthesized petalite, the superfine grinding processing is planned to be implemented by a wet process, and a ball milling mode of sectional feeding is adopted according to the fineness and the grindability of the fed minerals, and the method comprises the following specific steps:

the first stage of feeding is as follows: taking the total amount of the basic formula as 100%, respectively weighing 60% of 6.5-grade spodumene powder sand and 37% of quartz sand according to the specified formula ratio, and mixing the following materials: ball: the water proportion is 1: 1.5: 0.65 is added into a ball mill and ball milled for 48 hours.

The second stage is as follows: and (3) weighing 1 percent of petalite fine powder in addition to the basic feeding percentage (namely the external addition amount), and continuously grinding for 5 hours. Discharging the slurry after the slurry is in place, and continuously and sequentially operating as follows: homogenizing, sieving, press filtering, drying mud cake, and making into powder.

Weighing 3.0% of anhydrous industrial lithium chloride according to the formula, weighing water according to 7% of the mass of the fed powder, adding the lithium chloride into water, and preparing into a lithium salt solution for later use. Firstly, putting the weighed powder into a spiral stirrer; and then adding the lithium chloride solution into the powder in a mist spraying mode, and spraying while stirring until the powder is thoroughly wetted and fully homogenized to obtain finished product blank powder with the water content of 6-7% and suitable for compression molding.

After the blank powder is aged for 24 hours, the subsequent procedures of the example 1 are referred to, and the forming, the roasting (the sintering temperature is 1310 ℃, the temperature is 1260 ℃, and the temperature is kept for 3 hours), the crushing and the granularity grading of the clinker blank are completed until the whole flow of artificial synthesis and manufacturing is completed.

Example 5

weighing 73.0% of 1200-mesh commercial silicon micropowder, 15.0% of superfine aluminum hydroxide powder, 1% of calcium fluoride, 4% of lithium fluoride fine powder, 4% of industrial lithium carbonate and 3% (of external addition amount) of petalite fine powder, and putting the materials into a spiral stirrer to stir and mix. Weighing 3% of lithium chloride to prepare a 50% lithium chloride solution, then continuing to finish the series of procedures of solution spraying, homogenizing treatment, compression molding, kiln loading and roasting (the firing temperature is 1340 ℃, the heat preservation is carried out for 2.5 hours at 1290 ℃), clinker crushing, finished product grading and the like according to the example 1, and finishing the whole flow of artificial synthesis and manufacturing.

As the embodiment belongs to a high-barren material and low-plasticity formula, a three-in-one adhesive with the content of 12% prepared by plasticizers such as CMC, polyethylene glycol, polyacrylamide and the like is additionally sprayed at the final stage of blank powder preparation, the spraying amount is 3-5%, and homogenization treatment is carried out after spraying.

Example 6

weighing 87.0 percent of high-silicon pyrophyllite fine powder, 2 percent of calcium fluophosphate fine powder, 8 percent of industrial lithium carbonate fine powder and 2 percent of petalite fine powder (the added amount) with 1200 meshes, and putting the fine powder into a spiral stirrer for mixing. 3 percent of lithium chloride (the added amount) is weighed to prepare a lithium chloride solution with the concentration of 40 percent. Referring to example 1, all the processes of subsequent spraying, blank uniformity, press forming, kiln loading and roasting (baking temperature is 1330 ℃, 1280 ℃ and heat preservation is 2 hours), clinker crushing, finished product classification and the like are continuously completed.

Example 7

According to the metering requirement of the chemical components of the artificially synthesized petalite, the material feeding amount of a base material formula is set to be 100 percent, and the following materials are weighed and fed in sequence according to the wet processing flow:

feeding at a first stage: 74.0% of quartz sand, 14% of gamma alumina and 2% of fluorite powder are weighed. According to materials: ball: the water proportion is 1: 1.5: and adding the mixture into a ball mill for ball milling for 48 hours, wherein the ball mill is used for 0.7-0.8.

Feeding in a second stage: 6 percent of lithium fluoride, 3 percent of lithium carbonate and 3 percent of petalite fine powder (as the addition amount of the formula) are weighed, water is added according to 70 percent of the two-stage addition amount, and the grinding is continued for 8 hours. And (4) discharging slurry, press-filtering, drying and crushing to prepare powder after grinding in place. 1% of lithium hydroxide monohydrate is weighed and prepared into solution by 8 times of water. Referring to example 1, the subsequent processes of liquid spraying, homogenizing, press forming, roasting (sintering temperature of 1320 ℃, 1270 ℃ and heat preservation for 2.5 hours) and the like are completed until the finished product is put in storage.

Since this example is a high-barren, low-plasticity formulation, plasticizing measures should be additionally taken to the powder in the final stage of preparing the blank. Namely, a three-in-one adhesive which is prepared by plasticizer CMC, polyethylene glycol and polyacrylamide and has a solid content of 12 percent is sprayed in an amount of 3 to 5 percent and is homogenized.

XRD analysis and expansion coefficient measurements were not performed on all examples, due to capital cost constraints. However, as can be seen from the XRD analysis of the above examples 1 and 2, the petalite artificially synthesized according to the present invention is most likely to be tetragonal petalite. From the expansion coefficient detection of the example 1 and the example 3, the petalite artificially synthesized by the invention has excellent thermal expansion performance of negative expansion or nearly zero expansion.

The above description is only an embodiment of the present invention, but the design concept of the present invention is not limited thereto, and any insubstantial modifications made by using the design concept should fall within the scope of infringing the present invention.

Claims

1. The artificially synthesized tetragonal petalite is characterized by comprising the following chemical components: 74.0-80.0 Wt% SiO₂13.0 to 17.0Wt% of Al₂0₃3.7-4.8 Wt% of Li₂0, 0.0-2 Wt% of RO fluoride, and the balance of trace impurities carried in natural minerals and ignition reduction, and the tetragonal petalite also comprises 1-3 Wt% of natural petalite powder introduced in addition to the chemical components, wherein the SiO is₂ 、Al₂0₃ 、Li₂0 as a ternary framework material, the RO fluoride as a mineralizer material and the natural petalite as a seed crystal material.

2. The artificially synthesized tetragonal petalite as claimed in claim 1, wherein: the SiO₂Introduced from silicate minerals, said Al₂0₃Introduced from aluminosilicate minerals or aluminium-containing compounds, said Li₂0 is introduced by lithium-containing mineral spodumene or chemical lithium salt, and the RO fluoride is introduced by natural fluorine mineral or chemical raw material fluoride.

3. The artificially synthesized tetragonal petalite as claimed in claim 2, wherein: the SiO₂Introduced from quartz or other aluminosilicate minerals, the Al₂0₃Introduced from kaolin, pyrophyllite, alumina or aluminium hydroxide, the Li₂0 is introduced by spodumene, lithium carbonate, lithium fluoride, lithium chloride or lithium hydroxide, and the RO fluoride is made of fluorite, fluorapatite, calcium fluoride, magnesium fluorideOr barium fluoride.

4. The artificially synthesized tetragonal petalite as claimed in claim 1, wherein: the grinding process of the components adopts wet ball milling or dry grinding, and the average particle size of the other components is required to be less than or equal to 4 mu m except that the natural petalite powder is kept at the fineness of 100-150 meshes.

5. The method for producing artificially synthesized tetragonal petalite according to claim 1, wherein: the wet processing technology is adopted, and the specific technological process is as follows: formula metering → batch charging and grinding → slurry discharging, screening, homogenizing → filter pressing and mud pressing → drying and powder making → blank mixing → press forming → green body drying → kiln charging and roasting.

6. The method for producing artificially synthesized tetragonal petalite according to claim 1, wherein: the dry processing technology is adopted, and the specific technological process is as follows: formulation metering → blank mixing → press forming → blank drying → kiln loading and roasting.

7. The method for producing artificially synthesized tetragonal petalite according to claim 5 or 6, wherein: the lithium-containing chemical raw material introduces soluble lithium salt, and the blank preparation steps are as follows: (1) putting other raw materials except the soluble lithium salt into a stirrer, and firstly, uniformly mixing and stirring; (2) weighing water accounting for 8-10% of the total mass of the added powder, adding the soluble lithium salt weighed according to the formula into the water, and fully stirring to prepare a solution; and thirdly, starting the stirrer, adding the lithium salt solution into the powder in an atomization spraying mode, and spraying while stirring until the solution is sprayed and fully moistened and homogenized.

8. The method for producing artificially synthesized tetragonal petalite according to claim 7, wherein: also comprises a plasticizing treatment step for the high-barren and low-plasticity formula, namely: organic high molecular material CMC, polyethylene glycol and polyacrylamide are used as plasticizer to prepare viscose liquid, and the viscose liquid is used to spray and stir the powder.

9. The method for producing artificially synthesized tetragonal petalite according to claim 5 or 6, wherein: and pressing the blank into a strip-shaped or lath-shaped small block body with the length of 3-5 cm.

10. The method for producing artificially synthesized tetragonal petalite according to claim 5 or 6, wherein: the kiln loading and roasting steps are as follows: and (3) putting the dried green body into a kiln, roasting at a heating rate of 3 ℃/min until the temperature is within a range of 1300-1350 ℃, cooling to 50 ℃, and then preserving heat for 2-3 hours, thereby finishing the kiln burning process.