CN112458534A - Magnesium calcite mesoscopic crystal and preparation method of magnesium calcite crystal with adjustable morphology - Google Patents

Magnesium calcite mesoscopic crystal and preparation method of magnesium calcite crystal with adjustable morphology Download PDF

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CN112458534A
CN112458534A CN202011103265.6A CN202011103265A CN112458534A CN 112458534 A CN112458534 A CN 112458534A CN 202011103265 A CN202011103265 A CN 202011103265A CN 112458534 A CN112458534 A CN 112458534A
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magnesium
calcite
mesoscopic
crystal
calcium carbonate
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CN112458534B (en
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俞书宏
尚丽梅
蒋俊
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University of Science and Technology of China USTC
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C30B29/22—Complex oxides
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B28/00—Production of homogeneous polycrystalline material with defined structure
    • C30B28/04—Production of homogeneous polycrystalline material with defined structure from liquids
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/60—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape characterised by shape
    • C30B29/605—Products containing multiple oriented crystallites, e.g. columnar crystallites
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B7/00—Single-crystal growth from solutions using solvents which are liquid at normal temperature, e.g. aqueous solutions

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Abstract

The invention provides a magalcite mesoscopic crystal, and the magalcite mesoscopic crystal particles have a maize-like micro-morphology. According to the invention, pure amorphous calcium carbonate powder is used as a precursor, the protection effect of an organic additive on amorphous calcium carbonate is eliminated, the magnesium calcite mesoscopic crystal is prepared in a pure inorganic environment, the influence of an organic additive on a crystallization process is eliminated, the magnesium calcite mesoscopic crystal with a specific morphology can be obtained by controlling the crystallization condition of amorphous calcium carbonate in the pure inorganic environment, and favorable conditions are provided for the subsequent detailed research on the formation mechanism of the magnesium calcite mesoscopic crystal. In addition, different calcium-magnesium ratios play an important role in the invention, which can also bring possibility for revealing the formation mechanism of magnesium calcite mesoscopic crystals in marine organisms taking seawater as a living environment. The preparation method provided by the invention is simple, mild in condition, strong in controllability and suitable for subsequent research application and expansion.

Description

Magnesium calcite mesoscopic crystal and preparation method of magnesium calcite crystal with adjustable morphology
Technical Field
The invention belongs to the technical field of biomineralization, relates to a magnesium calcite mesoscopic crystal and a preparation method of the magnesium calcite, and particularly relates to a preparation method of the magnesium calcite mesoscopic crystal and a magnesium calcite crystal with adjustable morphology.
Background
Calcium carbonate is widely distributed in nature, and crystalline anhydrous crystal forms can be divided into three types: calcite, aragonite and vaterite. Aragonite: belonging to the orthorhombic system, Pnam space group, having a solubility constant logKsp in water at 25 ℃ of-8.33. It is commonly found in marine shells, such as mussels, oysters, scallops and nacres, which are made up of bricks-mud stacked structures with approximately 5% organic matter and 95% aragonite crystals. Researches show that the shell with the structure has good mechanical property so as to play a good protection role on organisms. Vaterite: belongs to a trigonal system, P63/mmc (194) space group, has a solubility constant logKsp of-7.91 in water at 25 ℃, is the most thermodynamically unstable phase with the highest solubility in water (the solubility constant logKsp of-8.48 in water at 25 ℃) in three anhydrous crystalline phases, and is very easily converted into a more stable calcite phase in the presence of water.
Among them, calcite is the most common one of natural minerals, and is also the most thermodynamically stable crystal phase of calcium carbonate, belonging to the hexagonal system, R-3c (167) space group. Ice winter stone is a colorless and transparent calcite mineral existing in nature, has good birefringence property, and is an important optical material. In daily life, calcite powder is often used as a filler in industrial production of paint, plastics, paper, rubber and the like. Calcite often contains Mn, Fe, Zn, Mg and other elements; when they reach a certain amount, crystalline phases such as manganese calcite, iron calcite, zinc calcite, magnesium calcite, etc. may be formed. For example, magnesium and calcium belong to the same main group, and calcium carbonate and magnesium carbonate belong to the same space group, so magnesium can be inserted into crystal lattices of calcite to obtain magnesium calcite, thereby inhibiting crack propagation and improving mechanical strength. The magnesium calcite is widely present in natural organisms such as sea urchin teeth, coral algae, calcium sponges and the like. In particular, magalcite in organisms such as sea urchin tips, eggshells, etc. is a mesostructure composed of many nanocrystals having a common crystal orientation, and has good single crystal characteristics as a whole.
However, most of the existing methods for synthesizing magnesium calcite mesoscopic crystals stay at the stage of needing organic additives, and detailed researches on the formation mechanism of the mesoscopic crystals are lacked. The mixed product of magalcite and aragonite phases was obtained in the presence of macromolecules extracted from the skeletons of corallium alga as reported in journal of advanced materials, 2000, page 38. The eleventh volume in journal of the "crystal growth design" 2011 at page 2866 reports that magnesium-containing amorphous calcium carbonate is crystallized under the condition that a polymer is used as an additive to obtain pure-phase magalcite polycrystal. The preparation of high-magnesium (53 mol%) calcite mesoscopic crystals by a coordination method is reported from the hundred thirty four volume at 1367 page of journal of american chemical society, 2012; the phase transition of amorphous calcium magnesium carbonate in lipid solutions to calcite mesoscopic crystals with a magnesium content of 20 mol% was reported from the journal of german applied chemistry, 2017, volume fifty-six, 16202. Although the two methods which use organic matters as additives and control crystallization conditions provide a new idea for preparing the magnesium calcite mesoscopic crystal, the formation mechanism needs to be further researched due to the influence of the organic additives, and the preparation process is relatively complicated.
Therefore, how to prepare the magnesium calcite mesoscopic crystal in a pure inorganic environment, simplify the preparation steps, and be free from the influence of organic materials so as to better explain the formation mechanism of the magnesium calcite in the following process remains a significant challenge in the field of biomineralization, has a very important meaning, and is one of the focuses of a plurality of prospective researchers in the field which pay attention to the magnesium calcite mesoscopic crystal.
Disclosure of Invention
In view of the above, the technical problem to be solved by the present invention is to provide a magnesium calcite mesoscopic crystal and a method for preparing magnesium calcite, and particularly to a method for preparing a morphology-adjustable magnesium calcite crystal. The method can prepare the magnesium calcite mesoscopic crystal with a specific morphology in a pure inorganic environment, eliminates the protective effect of an organic additive on amorphous calcium carbonate and the influence on the crystallization process, and provides favorable conditions for the subsequent detailed research on the formation mechanism of the mesoscopic crystal.
The invention provides a magalcite mesoscopic crystal, and the magalcite mesoscopic crystal particles have a maize-like micro-morphology.
Preferably, the length of the magnesium calcite mesoscopic crystal particles is 1-2 μm;
the radial size of the magnesium calcite mesoscopic crystal particles is 0.5-1 mu m;
in the magnesium calcite mesoscopic crystal, the molar ratio of magnesium element to calcium element is (0.02-0.1): 1;
the magnesium calcite mesoscopic crystal particles have a microstructure formed by polygonal nano-blocks and/or nano-particle stacks.
Preferably, the particle size of the polygonal nano block is 30-50 nm;
the polygonal nano block has clear edge appearance;
the particle size of the nano particles is 10-50 nm;
the crystal plane indices of the magnesium calcite mesoscopic crystal particles include (-102), (202), (104) and (006).
The invention provides a preparation method of magnesium calcite, which comprises the following steps:
A) dispersing amorphous calcium carbonate powder into the calcium-magnesium mixed solution, standing and crystallizing to obtain magnesium calcite.
Preferably, the particle size of the amorphous calcium carbonate powder is 60-140 meshes;
the amorphous calcium carbonate includes amorphous calcium carbonate containing no additives;
the amorphous calcium carbonate includes amorphous calcium carbonate in which no additive is used in the preparation process of the amorphous calcium carbonate.
Preferably, the preparation process of the amorphous calcium carbonate specifically comprises the following steps:
will contain Ca2+And a solution containing CO3 2-The solution is mixed and reacted at low temperature to obtain amorphous calcium carbonate;
the low temperature is-4 to 0 ℃.
Preferably, the Ca is contained2+Ca in the solution of (1)2+The concentration is 0.01-0.2 mol/L;
said CO-containing3 2-Of the solution ofCO3 2-The concentration is 0.01-0.2 mol/L;
said Ca-containing2+The anion in the solution of (a) includes one or more of chloride ion, acetate ion and nitrate ion;
said CO-containing3 2-The cations in the solution of (a) include one or more of sodium ions, potassium ions, and ammonium ions;
the mixing reaction further comprises one or more steps of separating, washing and drying.
Preferably, the means of dispersion comprises ultrasonic dispersion;
the dispersing temperature is-4-60 ℃;
the molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution is (0.1-1): 1;
the concentration of magnesium ions in the calcium-magnesium mixed solution is 0.02-0.1 mol/L;
the mass-volume ratio of the amorphous calcium carbonate powder to the calcium-magnesium mixed solution is 1 mg: (0.02-8) mL.
Preferably, the molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution is (0.1-0.2): 1, magnesium calcite crystals are obtained;
the magnesium calcite crystal particles have a cylinder-like micro-morphology;
the length of the magnesium calcite crystal particles is 2-4 mu m;
the radial size of the magnesium calcite crystal particles is 1-2 mu m;
the magnesium calcite crystalline particles having a microstructure formed by stacking of primary nanoparticles;
the particle size of the primary nano-particles is 10-50 nm.
Preferably, the molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution is (0.25-0.7): 1, obtaining magnesium calcite mesoscopic crystals;
the molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution is (0.75-1): 1, obtaining another magnesium calcite crystal;
the other magnesium calcite crystal has a microstructure formed by a stack of nanoplates;
the radial size of the nano plate is 1-2 mu m;
the thickness of the nano plate is 50-100 nm;
the temperature of the standing crystallization is-4 to 60 ℃;
the standing crystallization time is 30 s-72 h;
the standing crystallization also comprises one or more steps of separation, washing and drying.
The invention provides a magalcite mesoscopic crystal, and the magalcite mesoscopic crystal particles have a maize-like micro-morphology. Compared with the prior art, the invention aims at the problems that the formation mechanism is difficult to carry out subsequent research and the preparation process is relatively complicated in the existing preparation method due to the use of the organic additive.
The magnesium calcite mesoscopic crystal with the specific morphology is obtained, and the method for preparing the magnesium calcite mesoscopic crystal in the pure inorganic environment is creatively designed. According to the invention, pure amorphous calcium carbonate powder is used as a precursor, the protection effect of an organic additive on amorphous calcium carbonate is eliminated, the magnesium calcite mesoscopic crystal is successfully prepared in a pure inorganic environment, the influence of an organic additive on a crystallization process is eliminated, the magnesium calcite mesoscopic crystal with a specific morphology can be obtained by controlling the crystallization condition of amorphous calcium carbonate in the pure inorganic environment, and a favorable condition is provided for the subsequent detailed research on the formation mechanism of the magnesium calcite mesoscopic crystal. In addition, different calcium-magnesium ratios play an important role in the invention, which can also bring possibility for revealing the formation mechanism of magnesium calcite mesoscopic crystals in marine organisms taking seawater as a living environment. The preparation method provided by the invention is simple, mild in condition, strong in controllability and suitable for subsequent research application and expansion.
Experimental results show that amorphous calcium carbonate powder is successfully obtained through low-temperature mixing, is dispersed in a calcium-magnesium mixed solution for crystallization, and is subjected to magnesium calcite under the condition of a proper calcium-magnesium ratio, the magnesium content can reach 8.67 mol%, and meanwhile, the selected electron diffraction result shows that the amorphous calcium carbonate powder has single crystal characteristics, so that the magnesium calcite can be determined to be mesoscopic crystals.
Drawings
FIG. 1 is a Scanning Electron Microscope (SEM) image of amorphous calcium carbonate powder prepared according to an example of the present invention;
FIG. 2 is a Transmission Electron Microscope (TEM) image and a selected electron diffraction (SAED) pattern of amorphous calcium carbonate powder prepared according to an example of the present invention;
FIG. 3 is an X-ray diffraction pattern of amorphous calcium carbonate powder prepared according to an example of the present invention;
FIG. 4 is a Scanning Electron Microscope (SEM) image of a crystalline product prepared in comparative example 1 of the present invention;
FIG. 5 is a Scanning Electron Microscope (SEM) image of a crystalline product prepared in example 1 of the present invention;
FIG. 6 is a Scanning Electron Microscope (SEM) image of a crystalline product prepared in example 2 of the present invention;
FIG. 7 is a Scanning Electron Microscope (SEM) image of a crystalline product prepared in example 3 of the present invention;
FIG. 8 is a Scanning Electron Microscope (SEM) image of a crystalline product prepared according to example 4 of the present invention;
FIG. 9 is a Scanning Electron Microscope (SEM) image of a crystalline product prepared according to example 5 of the present invention;
FIG. 10 is an X-ray diffraction pattern of crystalline products prepared in examples 1 to 5 of the present invention;
FIG. 11 is a Transmission Electron Microscope (TEM) image of a crystalline product obtained in example 3 of the present invention;
FIG. 12 is a thermogravimetric analysis (TGA) curve of the crystalline product obtained in example 3 of the present invention;
FIG. 13 is a selected electron diffraction (SAED) pattern of the crystalline product obtained in example 3 of the present invention;
fig. 14 is a Scanning Transmission Electron Microscope (STEM) image and a calcium-magnesium element distribution image of the crystalline product obtained in example 3 of the present invention.
Detailed Description
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
All of the starting materials of the present invention, without particular limitation as to their source, may be purchased commercially or prepared according to conventional methods well known to those skilled in the art.
All the raw materials of the invention are not particularly limited in purity, and the invention preferably adopts the purity of the conventional analytical purification or biomineralization technical field.
All the raw materials, the marks and the acronyms thereof belong to the conventional marks and acronyms in the field, each mark and acronym is clear and definite in the field of related application, and the raw materials can be purchased from the market or prepared by a conventional method by the technical staff in the field according to the marks, the acronyms and the corresponding application.
All the processes of the invention, the abbreviations thereof belong to the common abbreviations in the art, each abbreviation is clear and definite in the field of its associated use, and the ordinary process steps thereof can be understood by those skilled in the art from the abbreviations.
The invention provides a magalcite mesoscopic crystal, and the magalcite mesoscopic crystal particles have a maize-like micro-morphology.
The present invention is not particularly limited to the configuration of the micro-morphology having a corn-like shape (corncob shape), and the configuration structure may be a conventional corn-like configuration structure known to those skilled in the art, and those skilled in the art may select and adjust the configuration structure according to the actual application situation, the product requirement and the specific application, and the corn-like shape may also be regarded as an ellipse-like body, a spindle-like body, an airship-like shape or a silkworm pupa-like shape, as would be normally understood by those skilled in the art. In the present invention, the magnesium calcite mesoscopic crystal particles preferably have a multi-angular edge morphology, i.e. preferably have a multi-angular edge morphology like an ellipsoid, a spindle-like body, or an airship-like or silkworm pupa-like body.
The magnesium calcite mesoscopic crystal particles are not particularly limited in specific size in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific applications, the magnesium calcite mesoscopic crystal particles have the length of preferably 1-2 microns, more preferably 1.2-1.8 microns, and even more preferably 1.4-1.6 microns, in order to ensure the structural characteristics of the magnesium calcite mesoscopic crystals, improve the uniformity of the morphology and better facilitate the subsequent research on the formation mechanism of the mesoscopic crystals. The radial size of the magnesium calcite mesoscopic crystal particles is preferably 0.5-1 μm, more preferably 0.6-0.9 μm, and more preferably 0.7-0.8 μm.
In the magnesium calcite mesoscopic crystal, the molar ratio of the magnesium element to the calcium element is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the specific application, in order to ensure the structural characteristics of the magnesium calcite mesoscopic crystal, improve the uniformity of the morphology and better facilitate the subsequent research on the formation mechanism of the mesoscopic crystal, the molar ratio of the magnesium element to the calcium element in the magnesium calcite mesoscopic crystal is preferably (0.02-0.1): 1, more preferably (0.03 to 0.09): 1, more preferably (0.04 to 0.08): 1, more preferably (0.05 to 0.07): 1.
the magnesium calcite mesoscopic crystal particles preferably have the microscopic morphology formed by stacking polygonal nano-blocks and/or nano-particles, and more preferably the microscopic morphology formed by stacking polygonal nano-blocks or nano-particles. More specifically, the polygonal nano-blocks preferably have a sharp edge profile. Edge topography in the context of the present invention preferably means a polygonal nano-block with sharp corners. Likewise, the magnesium calcite mesoscopic crystal particles provided by the invention preferably have a sharp angular morphology as a whole.
The particle size of the polygonal nano block is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the specific application, in order to ensure the structural characteristics of the magnesium calcite mesoscopic crystal, improve the uniformity of the morphology and better facilitate the follow-up research on the formation mechanism of the mesoscopic crystal, the particle size of the polygonal nano block is preferably 30-50 nm, more preferably 34-46 nm, and more preferably 38-42 nm.
The particle size of the nanoparticles is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific applications, the particle size of the nanoparticles is preferably 10-50 nm, more preferably 15-45 nm, more preferably 20-40 nm, and more preferably 25-35 nm, in order to ensure the structural characteristics of magnesium calcite mesoscopic crystals, improve the uniformity of morphology and better facilitate the subsequent research on the formation mechanism of the mesoscopic crystals.
The crystal face index of the magalcite mesoscopic crystal particles is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirements and the specific application, and in order to ensure the structural characteristics of the magalcite mesoscopic crystals, improve the uniformity of the morphology and better facilitate the subsequent study on the formation mechanism of the mesoscopic crystals, the crystal face index of the magalcite mesoscopic crystal particles preferably comprises (-102), (202), (104) and (006).
The invention provides a preparation method of magnesium calcite, which comprises the following steps:
A) dispersing amorphous calcium carbonate powder into the calcium-magnesium mixed solution, standing and crystallizing to obtain magnesium calcite.
The structure, proportion and process parameters of the product in the step of the magnesium calcite of the invention, and the corresponding optimization principle, and the selection, proportion and parameters of the structure in the magnesium calcite mesoscopic crystal, and the corresponding optimization principle, can preferably correspond to each other, and are not described in detail herein.
Firstly, amorphous calcium carbonate powder is dispersed in a calcium-magnesium mixed solution, and is subjected to standing crystallization to obtain magnesium calcite.
The specific selection of the amorphous calcium carbonate is not particularly limited in principle, and a person skilled in the art can select and adjust the amorphous calcium carbonate according to the actual application condition, the product requirements and the specific application. More specifically, the amorphous calcium carbonate preferably further includes amorphous calcium carbonate without using an additive in the process of preparing amorphous calcium carbonate, i.e., pure amorphous calcium carbonate powder.
The invention relates to a complete and refined integral preparation process, and the preparation process of the amorphous calcium carbonate is preferably as follows:
will contain Ca2+And a solution containing CO3 2-The solution is mixed and reacted at low temperature to obtain amorphous calcium carbonate.
The low-temperature is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific applications, the temperature of the low temperature is preferably-4-0 ℃, more preferably-3.5-0.5 ℃, more preferably-3-1 ℃, and more preferably-2.5-1.5 ℃ in order to ensure the structural characteristics of the magnesium-calcite mesoscopic crystal, improve the uniformity of the morphology, improve the controllability and the adjustability of the morphology in the preparation process and better facilitate the subsequent research on the formation mechanism of the mesoscopic crystal.
The invention is in principle directed to said Ca-containing2+Ca in the solution of (1)2+The concentration is not particularly limited, and the skilled in the art can select and adjust the concentration according to the actual application condition, the product requirement and the specific application, in order to ensure the structural characteristics of the magnesium calcite mesoscopic crystal, improve the uniformity of the morphology, improve the controllability and the adjustability of the morphology in the preparation process and better facilitate the subsequent research on the formation mechanism of the mesoscopic crystal, the calcium-containing mesoscopic crystal2+Ca in the solution of (1)2+The concentration is preferably 0.01 to 0.2mol/L, more preferably 0.04 to 0.16mol/L, more preferably 0.08 to 0.12 mol/L.
The invention is in principle directed to said CO-containing3 2-CO of the solution of3 2-The concentration is not particularly limited, and the skilled in the art can select and adjust the concentration according to the actual application condition, the product requirement and the specific application, in order to ensure the structural characteristics of the magnesium calcite mesoscopic crystal, improve the uniformity of the morphology, improve the controllability and the adjustability of the morphology in the preparation process and better facilitate the subsequent research on the formation mechanism of the mesoscopic crystal, the CO-containing mesoscopic crystal3 2-CO of the solution of3 2-The concentration is preferably 0.01 to 0.2mol/L, more preferably 0.04 to 0.16mol/L, and still more preferably 0.08 to 0.12 mol/L.
The invention is in principle directed to said Ca-containing2+The specific selection of the anion in the solution is not particularly limited, and a person skilled in the art can select and adjust the anion according to the actual application condition, the product requirement and the specific application2+The anion in the solution of (a) preferably comprises one or more of chloride, acetate and nitrate, more preferably chloride, acetate or nitrate.
The invention is in principle directed to said CO-containing3 2-The specific selection of the cation in the solution is not particularly limited, and a person skilled in the art can select and adjust the cation according to the actual application condition, the product requirement and the specific application3 2-The cation in the solution of (a) preferably includes one or more of sodium ion, potassium ion and ammonium ion, more preferably sodium ion, potassium ion or ammonium ion.
The invention integrates and refines the whole preparation process, ensures the structural characteristics of the magnesium calcite mesoscopic crystal, improves the uniformity of the appearance, improves the controllability and the adjustability of the appearance of the preparation process, and is better convenient for the subsequent research of the formation mechanism of the mesoscopic crystal, and preferably comprises one or more steps of separation, washing and drying after the mixing reaction, and more preferably comprises the steps of separation, washing and drying.
The specific conditions and modes of the separation, washing or drying are not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirements and the specific application. Specifically, the temperature may be 5 ℃ or lower. The washing is preferably low-temperature washing, and specifically can be below 5 ℃; the washing preferably comprises an alcohol wash. The drying preferably comprises vacuum drying.
The dispersion mode is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific applications.
The temperature of the dispersion is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific applications, the temperature of the dispersion is preferably-4-60 ℃, more preferably 5-50 ℃, more preferably 15-40 ℃, and more preferably 25-30 ℃ in order to ensure the structural characteristics of the magnesium calcite mesoscopic crystal, improve the uniformity of the morphology, improve the controllability and the adjustability of the morphology in the preparation process, and better facilitate the subsequent research on the formation mechanism of the mesoscopic crystal.
In the invention, the molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution is not particularly limited in principle, and a person skilled in the art can select and adjust the molar ratio according to actual application conditions, product requirements and specific applications, in order to ensure the structural characteristics of magnesium calcite mesoscopic crystals, improve the uniformity of morphology, improve the controllability and the adjustability of morphology of a preparation process and better facilitate the subsequent research on the formation mechanism of the mesoscopic crystals, the molar ratio of the calcium ions to the magnesium ions in the calcium-magnesium mixed solution is preferably (0.1-1): 1, more preferably (0.3 to 0.8): 1, more preferably (0.5 to 0.6): 1.
the concentration of magnesium ions in the calcium-magnesium mixed solution is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific applications, the magnesium-calcite mesoscopic crystal structure characteristics are guaranteed, the uniformity of morphology is improved, the controllability and the adjustability of morphology in the preparation process are improved, and the formation mechanism of the mesoscopic crystal is conveniently researched in the follow-up mode, wherein the concentration of the magnesium ions in the calcium-magnesium mixed solution is preferably 0.02-0.1 mol/L, more preferably 0.03-0.09 mol/L, more preferably 0.04-0.08 mol/L, and more preferably 0.05-0.07 mol/L.
In order to ensure the structural characteristics of magnesium calcite mesoscopic crystals, improve the uniformity of the morphology, improve the controllability and the adjustability of the morphology of the preparation process and better facilitate the subsequent research on the formation mechanism of the mesoscopic crystals, the mass-to-volume ratio of the amorphous calcium carbonate powder to the calcium-magnesium mixed solution is preferably 1 mg: (0.02-8) mL, more preferably 1 mg: (0.05-6) mL, more preferably 1 mg: (0.1-4) mL, more preferably 1 mg: (0.4-2) mL.
In the invention, the morphology and the crystal structure of the finally prepared magnesium calcite crystal can be regulated and controlled by adjusting the molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution, and technicians in the field can select and adjust the magnesium calcite crystal according to actual application conditions, product requirements and specific application, in order to ensure the structural characteristics of the magnesium calcite mesoscopic crystal, improve the uniformity of the morphology, improve the controllability and the adjustability of the morphology in the preparation process and better facilitate the subsequent research on the formation mechanism of the mesoscopic crystal, the molar ratio of the calcium ions to the magnesium ions in the calcium-magnesium mixed solution is preferably (0.1-0.2): 1, more preferably (0.12 to 0.18): 1, more preferably (0.14 to 0.16): 1, obtaining magnesium calcite crystals. The molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution is preferably (0.25-0.7): 1, more preferably (0.3 to 0.65): 1, more preferably (0.35 to 0.6): 1, more preferably (0.4 to 0.55): 1, more preferably (0.45 to 0.5): and 1, obtaining magnesium calcite mesoscopic crystals. The molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution is (0.75-1): 1, more preferably (0.8 to 0.95): 1, more preferably (0.85 to 0.9): 1, obtaining another magnesium calcite crystal.
The invention has no particular limitation on the microcosmic appearance of the magalcite crystal particles in principle, and a person skilled in the art can select and adjust the microcosmic appearance according to the actual application condition, the product requirements and the specific application.
The magnesium calcite crystal particles are preferably 2-4 μm in length, more preferably 2.4-3.6 μm in length, and even more preferably 2.8-3.2 μm in length, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific applications. The radial size of the magalcite crystal particles is preferably 1-2 μm, more preferably 1.2-1.8 μm, and more preferably 1.4-1.6 μm.
The invention has no particular limitation on the microcosmic appearance of the magalcite crystal particles in principle, and a person skilled in the art can select and adjust the microcosmic appearance according to the actual application condition, the product requirements and the specific application.
The particle size of the primary nanoparticles is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific applications, the structural characteristics of magnesium calcite mesoscopic crystals are guaranteed, the uniformity of morphology is improved, the controllability and the adjustability of the morphology in the preparation process are improved, the formation mechanism of the mesoscopic crystals is conveniently researched in the follow-up mode, and the particle size of the primary nanoparticles is preferably 10-50 nm, more preferably 15-45 nm, more preferably 20-40 nm, and more preferably 25-35 nm.
The molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution is (0.75-1): 1, another magnesium calcite crystal is obtained. The specific morphology of the other magnesium calcite crystal is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirements and the specific application.
The specific morphology of the other magalcite crystal is not particularly limited in the present invention, and may be a conventional corn-like configuration structure well known to those skilled in the art, and those skilled in the art can select and adjust the crystal according to the actual application, product requirements and specific application, and preferably has an ellipse-like body, a spindle-like body, an airship-like body or a silkworm pupae-like body, as can be normally understood by those skilled in the art. In the present invention, the other magalcite crystal particles preferably have a rounded edge morphology, i.e. have an ellipsoid-like body, a spindle-like body, or an airship-like or silkworm pupa-like shape.
The radial size of the nano plate is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to the actual application condition, the product requirement and the specific application, in order to ensure the structural characteristics of the magnesium calcite mesoscopic crystal, improve the uniformity of the morphology, improve the controllability and the adjustability of the morphology in the preparation process and better facilitate the subsequent research on the formation mechanism of the mesoscopic crystal, the radial size of the nano plate is preferably 1-2 μm, more preferably 1.2-1.8 μm, and more preferably 1.4-1.6 μm.
The thickness of the nano-plate is not particularly limited in principle, and can be selected and adjusted by technicians in the field according to actual application conditions, product requirements and specific applications, the thickness of the nano-plate is preferably 50-100 nm, more preferably 60-90 nm, and more preferably 70-80 nm, in order to ensure the structural characteristics of magnesium calcite mesoscopic crystals, improve the uniformity of morphology, improve the controllability and the adjustability of morphology in the preparation process and better facilitate the subsequent research on the formation mechanism of the mesoscopic crystals.
In the invention, when the molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution is preferably (0-0.1): when the molar ratio of calcium ion is 0.1:1 or less, the aragonite phase crystal and the magalcite phase crystal can be obtained at the same time. The aragonite phase crystals have a straw-like or specifically straw bundle-like shape. Among them, the length is preferably 10 to 12 μm, more preferably 10.2 to 11.8 μm, still more preferably 10.5 to 11.5 μm, still more preferably 10.8 to 11.2 μm. The diameter is preferably 4 to 6 μm, more preferably 4.3 to 5.8 μm, more preferably 4.5 to 5.5 μm, and more preferably 4.8 to 5.2 μm.
The temperature of the standing crystallization is not particularly limited in principle, and can be selected and adjusted by a person skilled in the art according to actual application conditions, product requirements and specific applications, the structural characteristics of the magnesium calcite mesoscopic crystal are guaranteed, the uniformity of the morphology is improved, the controllability and the adjustability of the morphology in the preparation process are improved, the formation mechanism of the mesoscopic crystal is conveniently researched in the follow-up mode, and the temperature of the standing crystallization is preferably-4-60 ℃, more preferably 5-50 ℃, more preferably 15-40 ℃, and more preferably 25-30 ℃.
The standing crystallization time is preferably 30 s-72 h, more preferably 1-60 h, more preferably 10-50 h, more preferably 20-48 h, and particularly 48h, in order to ensure the structural characteristics of the magnesium calcite mesoscopic crystal, improve the uniformity of the morphology, improve the controllability and the adjustability of the morphology in the preparation process, and better facilitate the subsequent research on the formation mechanism of the mesoscopic crystal, the standing crystallization time is not particularly limited in principle, and a person skilled in the art can select and adjust the standing crystallization time according to the actual application condition, the product requirements and the specific application.
The invention integrates and refines the whole preparation process, ensures the structural characteristics of the magnesium calcite mesoscopic crystal, improves the uniformity of the appearance, improves the controllability and the adjustability of the appearance in the preparation process, and is better convenient for the subsequent research on the formation mechanism of the mesoscopic crystal, and after standing and crystallizing, the preparation method preferably comprises one or more steps of separation, washing and drying, and more preferably comprises the steps of separation, washing and drying.
The specific conditions and modes of the separation, washing or drying are not particularly limited in principle, and a person skilled in the art can select and adjust the separation, washing or drying according to the actual application condition, the product requirements and the specific application. The washing preferably comprises a water wash and/or an alcohol wash. The drying preferably comprises vacuum drying.
The invention integrates and refines the whole preparation process, ensures the structural characteristics of magnesium calcite mesoscopic crystals, improves the uniformity of the appearance, improves the controllability and the adjustability of the appearance in the preparation process, and is more convenient for the subsequent research on the formation mechanism of the mesoscopic crystals, and the preparation method can specifically comprise the following steps:
(S1) with CaCl2Solution and Na2CO3Directly mixing the solution at a certain low temperature, centrifuging and washing at low temperature, and drying to obtain pure amorphous calcium carbonate powder; specifically, the water-free calcium chloride solution and the water-free sodium carbonate solution can be used; the ethanol used for washing needs to be placed in a refrigerator in advance for cooling; controlling the temperature to be 4 ℃ during centrifugal separation; amorphous calcium carbonate powder is obtained by means of vacuum drying.
(S2) ultrasonically dispersing the powder in a calcium-magnesium mixed solution, and standing for crystallization to obtain magnesium calcite mesoscopic crystals. Wherein, when standing for crystallization after ultrasonic dispersion is uniform, stirring and vibration are avoided.
The invention provides a magnesium calcite mesoscopic crystal and a preparation method of a magnesium calcite crystal with adjustable morphology. The preparation method can control the slow nucleation growth process of the amorphous precursor in the mineralized solution. The invention obtains a magnesium calcite mesoscopic crystal with a specific morphology, and designs a method for preparing the magnesium calcite mesoscopic crystal in a pure inorganic environment. According to the invention, pure amorphous calcium carbonate powder is used as a precursor, the protection effect of an organic additive on amorphous calcium carbonate is eliminated, the magnesium calcite mesoscopic crystal is successfully prepared in a pure inorganic environment, the influence of an organic additive on a crystallization process is eliminated, the magnesium calcite mesoscopic crystal with a specific morphology can be obtained by controlling the crystallization condition of amorphous calcium carbonate in the pure inorganic environment, and a favorable condition is provided for the subsequent detailed research on the formation mechanism of the magnesium calcite mesoscopic crystal. In addition, different calcium-magnesium ratios play an important role in the invention, which can also bring possibility for revealing the formation mechanism of magnesium calcite mesoscopic crystals in marine organisms taking seawater as a living environment. The preparation method provided by the invention is simple, mild in condition, strong in controllability and suitable for subsequent research application and expansion.
Experimental results show that amorphous calcium carbonate powder is successfully obtained through low-temperature mixing, is dispersed in a calcium-magnesium mixed solution for crystallization, and is subjected to magnesium calcite under the condition of a proper calcium-magnesium ratio, the magnesium content can reach 8.67 mol%, and meanwhile, the selected electron diffraction result shows that the amorphous calcium carbonate powder has single crystal characteristics, so that the magnesium calcite can be determined to be mesoscopic crystals.
In order to further illustrate the present invention, the following examples are provided to describe a mesoscopic crystal of magnesium calcite and a method for preparing magnesium calcite, but it should be understood that these examples are implemented on the premise of the technical scheme of the present invention, and the detailed embodiments and specific procedures are given, only for further illustrating the features and advantages of the present invention, not for limiting the claims of the present invention, and the scope of the present invention is not limited to the following examples.
Examples 2 to 6 and comparative example 1
Preparation of amorphous calcium carbonate powder:
(1) configuring 25mL of 0.1M CaCl2Solution and 25mL of 0.1M Na2CO3A solution;
(2) rapidly mixing the two solutions in an ice-water bath, and stirring for about 30 s;
(3) centrifuging the gelatinous solution obtained in the step (2) at 5000 revolutions for 1min, rapidly dispersing the precipitated product in the glacial ethanol, and repeating the separation process;
(4) after the product in the step (3) is repeatedly washed with ethanol for three times, the product is placed in a vacuum oven at 40 ℃ for drying, and finally the powder product is stored in a dryer for standby.
The amorphous calcium carbonate powder prepared according to the invention was characterized.
Referring to fig. 1, fig. 1 is a Scanning Electron Microscope (SEM) image of amorphous calcium carbonate powder prepared according to an example of the present invention.
As can be seen from FIG. 1, the microscopic particle size of the amorphous calcium carbonate prepared by the invention is 40-50 nm.
Referring to fig. 2, fig. 2 is a Transmission Electron Microscope (TEM) image and a selected electron diffraction (SAED) pattern of amorphous calcium carbonate powder prepared according to an example of the present invention.
As can be seen from fig. 2, the electron diffraction of the amorphous calcium carbonate prepared according to the present invention in the red mark region is halo rather than bright ring, which proves that amorphous calcium carbonate is obtained rather than crystalline.
Referring to fig. 3, fig. 3 is an X-ray diffraction pattern of amorphous calcium carbonate powder prepared according to an example of the present invention.
As can be seen in fig. 3, the XRD pattern had only two bulges and no distinct peaks were present, further demonstrating that the resulting product was amorphous.
(a) Weighing 50mg of the amorphous calcium carbonate powder, and ultrasonically dispersing the amorphous calcium carbonate powder in 20ml of mixed solution with different calcium-magnesium ratios;
referring to table 1, table 1 shows specific calcium-magnesium ratios and contents in comparative examples and examples of the present invention.
TABLE 1
Comparative example 1 Example 1 Example 2 Example 3 Example 4 Example 5
[Ca2+]/[Mg2+] 0:5 0.5:5 1:5 2:5 3.5:5 5:5
[Ca2+](mM) 0 5 10 20 35 50
[Mg2+](mM) 50 50 50 50 50 50
(b) Standing the dispersion liquid obtained in the step (a) and crystallizing the dispersion liquid at the temperature of 20 ℃ for 48 hours;
(c) centrifuging the crystallized product of step (b) at 6000 revolutions for 3min, washing with deionized water and ethanol respectively three times, and then placing the product dried in a vacuum oven at 40 ℃.
The crystalline products prepared in the examples of the invention and in the comparative examples were characterized.
Referring to fig. 4, fig. 4 is a Scanning Electron Microscope (SEM) image of the crystalline product prepared in comparative example 1 of the present invention.
As can be seen from FIG. 4, when the amount of calcium ion in the calcium-magnesium mixed solution is 0, the crystalline product is a straw or straw bundle-like aragonite phase crystal having a length of about 10 to 12 μm and a diameter (radial dimension) of about 4 to 6 μm.
Referring to fig. 5, fig. 5 is a Scanning Electron Microscope (SEM) image of a crystalline product prepared in example 1 of the present invention.
As can be seen from fig. 5, in the calcium-magnesium mixed solution, the molar ratio of calcium ions to magnesium ions was 0.1:1, the crystalline product includes aragonite phase crystals in the form of straw or straw bundles, and also includes magalcite crystals having a structure formed by stacking primary nanoparticles. Wherein the magalcite crystal particles have a cylindrical-like micro-morphology, the length of the magalcite crystal particles is about 2-4 μm, and the radial dimension is about 1-2 μm; the primary nanoparticles have a particle size of about 10 to 50 nm.
Referring to fig. 6, fig. 6 is a Scanning Electron Microscope (SEM) image of a crystalline product prepared in example 2 of the present invention.
As can be seen from fig. 6, in the calcium-magnesium mixed solution, the molar ratio of calcium ions to magnesium ions was 0.2: 1, the crystalline product is a magalcite crystal having magnesium formed from the primary nanoparticle stack. Wherein the magalcite crystal particles have a cylindrical-like micro-morphology, the length of the magalcite crystal particles is about 1-2 μm, and the radial dimension is about 1-2 μm; the primary nanoparticles have a particle size of about 10 to 50 nm.
Referring to fig. 7, fig. 7 is a Scanning Electron Microscope (SEM) image of a crystalline product prepared in example 3 of the present invention.
As can be seen from fig. 7, in the calcium-magnesium mixed solution, the molar ratio of calcium ions to magnesium ions was 0.4: 1, the crystalline product is a magalcite mesoscopic crystal with a maize-like microstructure. Wherein the magnesium calcite mesoscopic crystal has a microstructure formed by stacking polygonal nano-blocks, the length of magnesium calcite mesoscopic crystal particles is about 1-2 mu m, and the radial dimension is about 0.5-1 mu m; the particle size of the polygonal nano-block is about 30-50 nm. And magnesium calcite mesoscopic crystal particles and nano blocks formed by the magnesium calcite mesoscopic crystal particles have clear edge appearances to form typical edge angle appearances.
Referring to fig. 8, fig. 8 is a Scanning Electron Microscope (SEM) image of a crystalline product prepared in example 4 of the present invention.
As can be seen from fig. 8, in the calcium-magnesium mixed solution, the molar ratio of calcium ions to magnesium ions was 0.7: 1, the crystalline product is a magalcite mesoscopic crystal with a maize-like microstructure. Wherein the magnesium calcite mesoscopic crystal has a microscopic morphology formed by stacking polygonal nanoparticles, the length of the magnesium calcite mesoscopic crystal particles is about 1-2 mu m, and the radial size is about 0.5-1 mu m; the particle size of the nanoparticles is about 10-50 nm. And magnesium calcite mesoscopic crystal particles and nanoparticles formed by the magnesium calcite mesoscopic crystal particles have clear edge appearances to form typical edge angle appearances.
Referring to fig. 9, fig. 9 is a Scanning Electron Microscope (SEM) image of a crystalline product prepared in example 5 of the present invention.
As can be seen from fig. 9, in the calcium-magnesium mixed solution, the molar ratio of calcium ions to magnesium ions was 1:1, the crystallized product is magnesium calcite crystals with a silkworm pupa-like micro-morphology. Wherein the magalcite crystals have a microstructure formed by stacking of nano-plates, the length of magalcite crystal particles is about 1-2 μm, and the radial dimension is about 1-2 μm; the radial dimension of the nano plate is about 1-2 μm; the thickness is about 50 to 100 nm. The magnesium calcite crystal particles and the nano-plates formed by the same have clear edge and corner appearances, but begin to have smooth-edge appearances.
Referring to FIG. 10, FIG. 10 is an X-ray diffraction pattern of the crystalline product prepared in examples 1 to 5 of the present invention.
As can be seen from fig. 10, when the calcium ion is 0, the diffraction peaks of the crystalline product correspond one-to-one to the standard peaks of the aragonite phase; when the molar ratio of calcium ions to magnesium ions is 0.1: at 1, the crystalline product is a mixed phase of aragonite phase and magalcite; when the molar ratio of calcium ions to magnesium ions is 0.2: at 1, the crystalline product is a magalcite phase; the molar ratio of calcium ions to magnesium ions is 0.4: at 1, the crystalline product is a magnesium calcite phase with a magnesium content of 8.67 mol% (calculated on the basis of the shift in the (104) plane peak position); when the molar ratio of calcium ions to magnesium ions is 0.7: 1 and 1: at 1, the crystalline product is a magalcite phase.
The crystalline product prepared in example 3 of the present invention was further characterized.
Referring to fig. 11, fig. 11 is a Transmission Electron Microscope (TEM) image of the crystalline product obtained in example 3 of the present invention.
As can be seen from fig. 11, in the calcium-magnesium mixed solution, the molar ratio of calcium ions to magnesium ions was 0.4: 1, the magnesium calcite mesoscopic crystal has clear edge appearance and clear edge angle. The topography was determined in conjunction with fig. 8.
Referring to FIG. 12, FIG. 12 is a thermogravimetric analysis (TGA) profile of the crystalline product obtained in example 3 of the present invention.
As can be seen from fig. 12, in the calcium-magnesium mixed solution, the molar ratio of calcium ions to magnesium ions was 0.4: when the crystal product is 1, the mass reduction of the crystal product at 430.17-593.43 ℃ corresponds to the decomposition of magnesium carbonate in the crystal product, and the mass reduction of the crystal product at 593.0-694.73 ℃ corresponds to the decomposition of calcium carbonate in the crystal product, and the magnesium content in the obtained magnesium calcite is calculated to be 7.90 mol% (similar to the calculation result of the magnesium content in XRD).
Referring to fig. 13, fig. 13 is a selected electron diffraction (SAED) pattern of the crystalline product obtained in example 3 of the present invention.
As can be seen from fig. 13, in the calcium-magnesium mixed solution, the molar ratio of calcium ions to magnesium ions was 0.4: 1, the electron diffraction pattern of the crystalline product shows single-crystal diffraction points arranged in order, which correspond to the four diffraction crystal faces of (-102), (202), (104) and (006), and the crystalline product is proved to have good single-crystal characteristics.
Referring to fig. 14, fig. 14 is a Scanning Transmission Electron Microscope (STEM) image and a calcium magnesium element distribution image of the crystalline product obtained in example 3 of the present invention.
As can be seen from fig. 14, in the calcium-magnesium mixed solution, the molar ratio of calcium ions to magnesium ions was 0.4: 1, the calcium and magnesium elements are uniformly distributed in the whole crystalline product, namely the magnesium calcite mesoscopic crystal with the maize-like micro-morphology, which shows that the magnesium elements are successfully embedded into the crystal lattice of the calcite and exist in the crystal form of the magnesium calcite.
The foregoing detailed description of the present invention provides a method for preparing magcalcite mesoscopic crystals and morphologically adjustable magcalcite crystals, which is described herein by way of specific examples that are intended to facilitate an understanding of the methods of the present invention and their core concepts, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any combination thereof. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. The scope of the invention is defined by the claims and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims (10)

1. Magalcite mesoscopic crystals, wherein the magalcite mesoscopic crystal particles have a maize-like microstructure.
2. The magalcite mesoscopic crystals of claim 1, wherein the magalcite mesoscopic crystal particles are 1-2 μ ι η in length;
the radial size of the magnesium calcite mesoscopic crystal particles is 0.5-1 mu m;
in the magnesium calcite mesoscopic crystal, the molar ratio of magnesium element to calcium element is (0.02-0.1): 1;
the magnesium calcite mesoscopic crystal particles have a microstructure formed by polygonal nano-blocks and/or nano-particle stacks.
3. The magalcite mesoscopic crystal according to claim 2, wherein the polygonal nano-pieces have a particle size of 30 to 50 nm;
the polygonal nano block has clear edge appearance;
the particle size of the nano particles is 10-50 nm;
the crystal plane indices of the magnesium calcite mesoscopic crystal particles include (-102), (202), (104) and (006).
4. The preparation method of magnesium calcite is characterized by comprising the following steps:
A) dispersing amorphous calcium carbonate powder into the calcium-magnesium mixed solution, standing and crystallizing to obtain magnesium calcite.
5. The method according to claim 4, wherein the amorphous calcium carbonate powder has a particle size of 60 to 140 mesh;
the amorphous calcium carbonate includes amorphous calcium carbonate containing no additives;
the amorphous calcium carbonate includes amorphous calcium carbonate in which no additive is used in the preparation process of the amorphous calcium carbonate.
6. The method according to claim 4, wherein the process for preparing amorphous calcium carbonate comprises the following steps:
will contain Ca2+And a solution containing CO3 2-The solution is mixed and reacted at low temperature to obtain amorphous calcium carbonate;
the low temperature is-4 to 0 ℃.
7. The method according to claim 6, wherein the Ca is contained2+Ca in the solution of (1)2+The concentration is 0.01-0.2 mol/L;
said CO-containing3 2-CO of the solution of3 2-The concentration is 0.01-0.2 mol/L;
said Ca-containing2+The anion in the solution of (a) includes one or more of chloride ion, acetate ion and nitrate ion;
said CO-containing3 2-The cations in the solution of (a) include one or more of sodium ions, potassium ions, and ammonium ions;
the mixing reaction further comprises one or more steps of separating, washing and drying.
8. The method of claim 4, wherein the means of dispersing comprises ultrasonic dispersion;
the dispersing temperature is-4-60 ℃;
the molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution is (0.1-1): 1;
the concentration of magnesium ions in the calcium-magnesium mixed solution is 0.02-0.1 mol/L;
the mass-volume ratio of the amorphous calcium carbonate powder to the calcium-magnesium mixed solution is 1 mg: (0.02-8) mL.
9. The preparation method according to claim 4, wherein the molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution is (0.1-0.2): 1, magnesium calcite crystals are obtained;
the magnesium calcite crystal particles have a cylinder-like micro-morphology;
the length of the magnesium calcite crystal particles is 2-4 mu m;
the radial size of the magnesium calcite crystal particles is 1-2 mu m;
the magnesium calcite crystalline particles having a microstructure formed by stacking of primary nanoparticles;
the particle size of the primary nano-particles is 10-50 nm.
10. The preparation method according to claim 4, wherein the molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution is (0.25-0.7): 1, obtaining magnesium calcite mesoscopic crystals;
the molar ratio of calcium ions to magnesium ions in the calcium-magnesium mixed solution is (0.75-1): 1, obtaining another magnesium calcite crystal;
the other magnesium calcite crystal has a microstructure formed by a stack of nanoplates;
the radial size of the nano plate is 1-2 mu m;
the thickness of the nano plate is 50-100 nm;
the temperature of the standing crystallization is-4 to 60 ℃;
the standing crystallization time is 30 s-72 h;
the standing crystallization also comprises one or more steps of separation, washing and drying.
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