JP3843318B2 - High density lithium aluminum oxide and synthesis method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lithium aluminum oxide having a high pressure phase, a high density of 3.50 g / cm ³ , and a method for producing the same, which has never been known so far. Specifically, a so-called shock wave compression method, which is known to generate and apply pressure by an instantaneous shock wave, is applied to a low-pressure phase lithium aluminum oxide crystal, and the crystal is converted to high-density lithium aluminum oxide. In addition, the present invention relates to a high-pressure phase, a high-density lithium aluminum oxide crystal, and a method for producing the same.
[0002]
[Prior art]
Conventionally, α-phase, β-phase and γ-phase are known as lithium aluminum oxides represented by the chemical formula LiAlO ₂ . Among them, the α phase has a density of 3.41 g / cm ³ , and the synthesis method is (1) reacting Al ₂ O ₃ and Li ₂ CO ₃ at 600 ° C., (2) AlO (OH) and Li ₂ Reaction with CO ₃ at 600 ° C. (3) Hydrothermal treatment of a mixture of Al ₂ O ₃ and Li ₂ CO ₃ at 140 ° C. and thermal decomposition of the resulting LiAl (OH) ₄ .H ₂ O at 400 ° C. (4) The above four methods are known in which a mixture of Al ₂ O ₃ and Li ₂ CO _3, a β phase or a γ phase is treated at 3.5 GPa and 850 ° C. for 30 minutes.
The β phase has a density of 2.69 g / cm ³ , and the synthesis method is a method of treating a mixture of Al ₂ O ₃ and Li ₂ CO ₃ at 1.8 GPa and 370 ° C., or Al ₂ O ₃ and Li ₂ CO _{3. A} method is known in which the mixture of No. 3 is hydrothermally treated at 240 ° C. and 0.04 GPa, and the resulting LiAl (OH) ₄ .H ₂ O is thermally decomposed at 400 to 800 ° C.
The γ phase has a density of 2.61 g / cm ³ , and the synthesis method is a method of reacting Al ₂ O ₃ and Li ₂ CO ₃ at 1100 ° C., or a method of heating the α phase or β phase at 800 to 1000 ° C. Etc. are known.
These synthesis conditions are all generated in a relatively low pressure region, and the synthesis conditions under a pressure exceeding 5 GPa of the present invention have never been found.
[0003]
[Problems to be solved by the invention]
The present invention provides a lithium aluminum oxide crystal having a high density which has not been known so far by applying a pressure in a high pressure region, that is, a novel high density lithium aluminum oxide crystal (chemical formula LiAlO ₂ ) and its It is intended to provide a manufacturing method. As means for applying the pressure in the high pressure region, a high-density lithium aluminum oxide is provided by applying a shock wave processing technique using a shock wave which is a conventional technique.
As a result, there has never been a field where this type of lithium compound has been used, for example, the field of various batteries and battery materials using the solid electrolyte itself or the solid electrolyte, and other technical fields. The aim is to provide high-density lithium-aluminum oxide with new properties and to provide a little freedom in material selection, thereby contributing to industrial development.
[0004]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have mixed an appropriate amount of copper powder with lithium aluminum oxide powder, press-molded to an appropriate density, an appropriate pressure on the molded body, It was discovered that if high pressure compression is applied for a short period of time under temperature, it can be converted into a new high pressure phase lithium aluminum oxide powder without changing the composition of the starting lithium aluminum oxide. is there.
The present invention has been made on the basis of this finding, and its configuration is based on the requirements described in (1) to (4).
That is, the first configuration is a high-pressure phase high-density lithium aluminum oxide, which is as follows.
(1) A high-pressure high-density lithium aluminum oxide represented by the chemical formula LiAlO ₂ and having a density of 3.50 g / cm ³ and a tetragonal crystal structure.
Moreover, the 2nd structure presents the synthesis | combining method of the compound of the said (1) description, and is as follows.
(2) A low-pressure phase lithium aluminum oxide powder represented by the chemical formula LiAlO ₂ is mixed with copper powder and pressure-molded, and the resulting compact is momentarily applied by a shock wave of 5 GPa or more and a pressurization time of 5 microseconds or less. Pressure is applied to convert the low-pressure phase crystalline lithium aluminum oxide into a high-pressure phase high-density lithium aluminum oxide having a tetragonal crystal structure with a density of 3.50 g / cm ³ represented by the chemical formula LiAlO _2. A method for synthesizing high-density lithium aluminum oxide by shock waves.
Furthermore, the third and fourth configurations are further limited to the synthesis method described in (2) above based on the starting materials, and are as follows.
(3) The low-pressure crystalline lithium aluminum oxide represented by the chemical formula LiAlO _{2 as the} starting material is selected from the group consisting of α-phase, β-phase, and γ-phase. The method for synthesizing high-density lithium aluminum oxide by shock waves according to item (2), characterized in that
(4) The high density lithium aluminum by shock wave as described in the above item (3), wherein the starting material is selected from γ-phase lithium aluminum oxide crystal powder having a density of 2.61 g / cm ^{3 in} particular. Synthesis method of oxide.
[0005]
The high-density lithium aluminum oxide of the high-pressure phase of the present invention starts from a low-pressure-phase lithium aluminum oxide powder represented by the chemical formula LiAlO ₂ , and is mixed with copper powder and pressure-molded at a pressure of 5 GPa or more. , Obtained by phase-transforming low-pressure phase lithium aluminum oxide into high-pressure phase spinel-type silicon oxynitride by instantaneous pressurization with a shock wave with a pressurization time of 5 microseconds or less. The high-pressure phase lithium aluminum oxide thus obtained has the same chemical composition as the low-pressure phase lithium aluminum oxide that is the starting powder compound.
The novel high-pressure phase compound obtained by the present invention is characterized in that the density is as high as 3.50 g / cm ³ , that is, it has been known so far for compounds of the same composition. An extremely high density material that was not present was obtained. Of course, a new compound is provided. Therefore, the present invention itself is an industrially useful invention. Although its physical properties have not yet been fully elucidated just because the density and crystal structure have been elucidated at this stage, the properties are not yet understood in an oxidizing atmosphere. We are confident that the remaining physical properties will be further elucidated and the development of applications will be dramatically advanced. In particular, it is expected to be used for electronic materials.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the method for synthesizing lithium aluminum oxide of the high pressure phase of the present invention, instantaneous impact compression is imparted to the object to be processed, and the material synthesis is performed using the high temperature and high pressure state generated there. The pressure method can be used. In this impact pressurization method, an apparatus is used in which a flying object is made to collide with a starting material container at high speed using explosives, and pressure is applied to the starting material by propagation of a shock wave generated at that time. Alternatively, an impact pressure method using explosives can be used.
FIG. 1 exemplifies a shock wave generation and shock treatment sample for carrying out the method of the present invention. Specifically, the starting material 2 is placed in a copper recovery container 3 for protecting against the destruction of shock waves, pressed from behind the starting material with a copper screw lid 4, and then embedded in a large iron circular container 1, And On the other hand, gunpowder guns are used to generate shock waves due to high-speed collisions. In order to increase the impact pressure, the flying object 5 is configured with a copper flying plate 7 attached to the front surface of a servo 6 made of high-density polyethylene.
[0007]
In this impact pressurization method, the conditions for forming the press-molded product and the impact pressurization conditions are important. The conditions for forming the pressure-molded body include the selection of the starting low-pressure phase lithium aluminum oxide powder and copper powder, the mixing conditions with the copper powder, the apparent density of the pressure-molded body, For example, distribution of voids.
The starting lithium aluminum oxide is preferably a γ phase, and the particle size is preferably 10 microns or less. This is because the volume change accompanying the phase transition is the largest from the γ phase and the smallest from the α phase. This is because when the particle size is increased, thermal equilibrium does not occur within the time of impact compression, resulting in a non-uniform reaction.
[0008]
Mixing the starting material lithium aluminum oxide with copper powder to form a pressure-molded body is necessary to make the impact conditions uniform and to increase the impact pressure and temperature. Copper powder mixes about 99-80 weight% with respect to lithium aluminum oxide powder. As the copper powder, a commercially available product having a particle size of 100 μm or less is used.
The pressure molding is performed by using a pressure rod as a piston in a starting material container with a hydraulic pump. The recovery container 3 is optimally a metal that does not react with lithium aluminum oxide, but it must be able to sufficiently protect the sample from destruction from shock waves, and a copper container is usually used.
[0009]
The apparent density of the green compact is important for controlling the impact temperature, and since the reaction speed must be sufficiently high and the temperature should not be such that lithium aluminum oxide decomposes and melts, the green compact has a theoretical density. 60% to 95% (as a porosity of 5 to 40%) is appropriate.
Moreover, it is desirable that the distribution of voids in the green compact is as uniform as possible. For this purpose, the particle size of the metal powder is desirably 50 microns or less. More preferably, it is about 10 μm.
[0010]
The condition of the impact environment requires a pressure of 5 GPa or more. If the pressure is increased to 80 GPa or more, the deformation of the container becomes large and the sample is decomposed or partially melted, making it difficult to collect the sample when the pressure is released. The temperature is preferably 500 ° C. or higher and 1500 ° C. or lower.
[0011]
Example 1:
12 mm diameter with an apparent density of 6.10 g / cm ³ (porosity 10%) by a mixture of 10% by weight of γ-type lithium aluminum oxide (chemical formula LiAlO ₂ ) powder of 0.5 to 10 μm and 90% by weight of copper powder. X A pressure molded body having a thickness of 2 mm was prepared. The apparent density of the mixture of lithium aluminum oxide and copper powder was adjusted by increasing or decreasing the molding pressure by pressing. The pressurizing feature was housed in a cylindrical copper recovery container having a thickness of 6 mm, and the pressurizing feature was pressed from behind with a copper screw lid without any gap, and then embedded in the center of a large iron circular container to obtain a target.
As a flying object, a copper desk as a collision plate was attached to the main body made of high-density polyethylene and used to generate the necessary impact pressure. An impact treatment of 33 GPa was performed by accelerating the flying object speed to 1.5 Km / second with a gunpowder gun and causing it to collide. The impact temperature was calculated through thermodynamic analysis and was about 900 ° C. The impact pressure was calculated from the velocity of the flying object and from the one-dimensional analysis using the impedance matching method.
After the impact treatment, the pressurizable form was taken out from the collection container, and the pressure-formed form was removed by treatment for 5 hours or more in a nitric acid solution, and the precipitate was washed with water and dried to obtain a powder.
The resulting powder was identified by X-ray powder diffraction. The obtained diffraction pattern was found to be a novel high-pressure phase lithium aluminum oxide as shown in (1) of FIG. On the other hand, (2) in FIG. 2 shows an X-ray diffraction diagram of the starting material, γ-phase lithium aluminum oxide, for comparison. From the detailed analysis of the obtained diffraction pattern, the impact-recovered sample contains a small amount of impurities, but the new high-density phase has a tetragonal crystal structure, and its lattice constant is a = 0.3879 nm, b = It was determined to be 0.8303 nm. As a result, the density was calculated to be 3.50 g / cm ³ . The particle diameter of the new high-pressure phase lithium aluminum oxide synthesized from the observation result of the sample obtained by the impact treatment with an electron microscope was composed of nanoparticles of 100 nm or less. Electron energy loss spectroscopy confirmed that lithium and aluminum are 6-coordinated in a new high-pressure phase lithium aluminum oxide. Therefore, it was clarified that the obtained new LiAlO ₂ was an unprecedented compound.
[0012]
The present invention investigates how a substance is affected by high-pressure treatment with a shock wave, in particular, investigates the state of the substance in the high-pressure phase, and conducts basic exploration of the substance, including conversion to a new substance. As part of my research, I was researching what happens when lithium aluminum compounds composed of light elements are subjected to high-pressure treatment using shock waves. It has been found that high-density lithium-aluminum oxide crystals exist and can be synthesized. Therefore, this corresponds to an industrially useful invention. In addition, it is expected that research and development will proceed greatly in various fields in the future. At this stage, the physical properties and the like are not repeatedly described, that is, a high-density crystal can be produced. As a result, for example, solid electrolytes and battery materials that are one of the application fields of lithium compounds, for example, improved durability compared to conventional materials, and other properties have been achieved more than ever. Is expected, and in this application, it is expected to have a special effect. Of course, as shown above, the physical properties and characteristics of the lithium aluminum oxide of the present invention are in a very high density state. Is expected to open the way for new application development.
[0013]
【The invention's effect】
As described above in detail, according to the present invention, a lithium aluminum oxide crystal having an extremely high density is provided, and a high pressure phase lithium aluminum oxide is converted from a low pressure phase lithium aluminum oxide with a high conversion rate by a single impact treatment. It has become possible to manufacture in large quantities, and as such provides a very industrially useful invention.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an embodiment of an apparatus for the present invention.
FIG. 2 is a graph showing an X-ray powder diffraction diagram.
[Explanation of symbols]
1: Iron circular container 2: Starting material 3: Copper recovery container 4: Copper screw lid 5: Flying object 6: High density polyethylene servo 7: Copper flying plate

Claims (4)

A high-density lithium aluminum oxide having a density of 3.50 g / cm ³ represented by the chemical formula LiAlO ₂ and having a tetragonal crystal structure. The low-pressure phase lithium aluminum oxide powder represented by the chemical formula LiAlO ₂ is mixed with copper powder and pressure-molded, and the resulting molded body is given an instantaneous pressure by a shock wave of 5 GPa or more and a pressurization time of 5 microseconds or less. And converting the low-pressure phase crystalline lithium aluminum oxide into a high-pressure phase high-density lithium aluminum oxide having a tetragonal crystal structure with a density of 3.50 g / cm ³ represented by the chemical formula LiAlO _2. A method for synthesizing high-density lithium aluminum oxide by shock waves. The crystalline lithium aluminum oxide of the low pressure phase represented by the chemical formula LiAlO _{2 as} a starting material is characterized by using any one crystalline lithium aluminum oxide of the group consisting of an α phase, a β phase, and a γ phase. A method for synthesizing high-density lithium aluminum oxide by shock waves according to claim 2. 4. The shock wave according to claim ^{3, wherein} a γ-phase lithium aluminum oxide crystal powder having a density of 2.61 g / cm ³ is selected as the low-pressure phase crystalline lithium aluminum oxide represented by the chemical formula LiAlO _2. Synthesis method of high-density lithium aluminum oxide.

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