JP2004149360A - High density lithium aluminum oxide and method for synthesizing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide lithium aluminum oxide having a high density of 3.50g/cm<SP>3</SP>unknown so far, though α phase having a density of 3.41g/cm<SP>3</SP>, β phase having a density of 2.69g/cm<SP>3</SP>and γ phase having a density of 2.61g/cm<SP>3</SP>are known so far in the order of decreasing density as lithium aluminum oxide comprising light elements represented by the formula LiAlO<SB>2</SB>. <P>SOLUTION: The high density lithium aluminum oxide is obtained by compacting low pressure phase lithium aluminum oxide powder represented by the formula LiAlO<SB>2</SB>, charging the resulting compact into a device shown by figure 1, applying an instantaneous pressurizing force of ≥5 GPa by shock waves to the compact for a pressurization time of ≤5 microseconds to bring the compact into a reaction, and then separating and recovering the compact. This compact is identified as a new compound having a tetragonal system crystal structure different from the structure of the starting material by an X-ray diffraction method. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a lithium aluminum oxide having a high-pressure phase and a high density of 3.50 g / cm ³ , which has never been known before, and a method for producing the same. Specifically, a so-called shock-wave compression method, which is known to generate and apply a pressing force by an instantaneous shock wave, is applied to a low-pressure phase lithium aluminum oxide crystal, and the crystal is converted to a high-density lithium aluminum oxide. And 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 its synthesis method is (1) reacting Al ₂ O ₃ and Li ₂ CO ₃ at 600 ° C., (2) AlO (OH) and Li ₂ CO ₃ is reacted at 600 ° C. (3) A mixture of Al ₂ O ₃ and Li ₂ CO ₃ is hydrothermally treated at 140 ° C., and the obtained LiAl (OH) ₄ .H ₂ O is thermally decomposed at 400 ° C. And (4) treating a mixture of Al ₂ O ₃ and Li ₂ CO _3, a β phase and a γ phase at 3.5 GPa and 850 ° C. for 30 minutes are known.
The β phase has a density of 2.69 g / cm ³ , and is synthesized by treating a mixture of Al ₂ O ₃ and Li ₂ CO ₃ at 1.8 GPa and 370 ° C. or by mixing 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 obtained 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 is synthesized by a method of reacting Al ₂ O ₃ with Li ₂ CO ₃ at 1100 ° C. or a method of heating an α phase or a β phase at 800 to 1000 ° C. Etc. are known.
These synthesis conditions are all generated in a relatively low pressure region, and there is no example of synthesis conditions under a pressure exceeding 5 GPa according to the present invention.
[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, that is, a novel high-density lithium aluminum oxide crystal (chemical formula: LiAlO ₂ ) by applying a pressure in a high pressure region, It is intended to provide a manufacturing method. As means for applying 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, the field of using lithium compounds of this kind, such as the field of various batteries and battery materials using the solid electrolyte itself or the solid electrolyte itself, and other technical fields, has never been seen before. The purpose is to provide lithium aluminum oxide, a high-density material with new properties, to provide a degree of freedom in selecting the material, thereby contributing to the development of industry.
[0004]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, mixed an appropriate amount of copper powder with lithium aluminum oxide powder, pressed and molded to an appropriate density, and applied an appropriate pressure to the molded product. It has been found that if shock compression is applied for a short period of time at a certain temperature at a certain temperature, it can be converted to a new high-pressure phase lithium aluminum oxide powder without changing the composition of the starting material lithium aluminum oxide. is there.
The present invention has been made on the basis of this finding, and the configuration thereof 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, and is as follows.
(1) A high-pressure phase 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.
The second configuration provides a method for synthesizing the compound according to the above (1), 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 pressed, and the resulting compact is instantaneously applied with a shock wave of 5 GPa or more and a pressing 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 density of 3.50 g / cm ³ represented by the chemical formula LiAlO ₂ and a tetragonal crystal structure. A method for synthesizing a high-density lithium aluminum oxide using a shock wave.
Further, the third and fourth configurations further limit the synthesis method described in (2) based on the starting materials, and are as follows.
(3) The crystalline lithium aluminum oxide of low pressure phase 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 a high-density lithium aluminum oxide by a shock wave according to the above item (2), characterized in that:
(4) The high-density lithium aluminum by shock wave as described in (3) above, wherein the starting material is selected from a gamma-phase lithium aluminum oxide crystal powder having a density of 2.61 g / cm ^3. A method for synthesizing an oxide.
[0005]
The high-pressure phase high-density lithium aluminum oxide 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 compacted, and subjected to a pressure of 5 GPa or more. A phase transition of the low-pressure phase lithium aluminum oxide to the high-pressure phase spinel-type silicon oxynitride by instantaneous pressurization by a shock wave having a pressurization time of 5 microseconds or less. The high-pressure phase lithium aluminum oxide has the same chemical composition as the low-pressure phase lithium aluminum oxide as the starting powder compound.
The novel high-pressure phase compound obtained by the present invention is characterized in that it has a density as high as 3.50 g / cm ³ , that is, compounds having the same composition are known so far. An extremely high-density material was obtained. Of course, the present invention provides a novel compound. Therefore, the present invention itself is an industrially useful invention. At this stage, its physical properties have only been elucidated for its density and crystal structure, but other chemical, mechanical, or electrical properties have not been fully elucidated yet. It is excellent in stability, and we are convinced that further physical properties will be elucidated in the future, and that the development of its applications will also progress dramatically. In particular, applications for electronic materials and the like are greatly expected.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
In the method for synthesizing the lithium aluminum oxide of the high-pressure phase of the present invention, instantaneous shock compression is applied to the object to be processed, and the material is synthesized by utilizing the high-temperature and high-pressure state generated therein. A pressure method can be used. In this impact pressurization method, a device is used in which a projectile is made to collide with a starting material container at a 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 an explosive can be used.
FIG. 1 illustrates 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 the starting material from shock wave destruction, pressed with a copper screw lid 4 from behind the starting material, and then embedded in a large iron circular container 1, and And On the other hand, an explosive gun is used to generate a shock wave due to a high-speed collision. In order to increase the impact pressure, the flying object 5 is configured by attaching a copper flying plate 7 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-formed body and the impact pressurization conditions are important. The conditions for forming the pressed body include the selection of the low-pressure phase lithium aluminum oxide powder and the copper powder, which are the starting materials, the mixing conditions with the copper powder, the apparent density of the pressed body, Examples include the distribution of voids.
The lithium aluminum oxide as a starting material preferably has a γ phase and a particle size of 10 μm or less. This is because the change in volume due to the phase transition is largest from the γ phase and smallest from the α phase. This is because, when the grain size becomes large, thermal equilibrium does not occur within the time of impact compression, resulting in a non-uniform reaction.
[0008]
It is necessary to mix the lithium aluminum oxide as a starting material with the copper powder to form a pressed body in order to make the impact conditions uniform and to increase the impact pressure and the impact temperature. Copper powder is mixed with lithium aluminum oxide powder in an amount of about 99 to 80% by weight. As the copper powder, a commercially available product having a particle size of 100 μm or less is used.
The pressure molding is performed in the starting material container by using a pressure rod as a piston by a hydraulic pump. The recovery container 3 is preferably made of a metal that does not react with lithium aluminum oxide, but it must be able to sufficiently protect the sample from destruction from a shock wave, and a copper container is usually used.
[0009]
The apparent density of the green compact is important for controlling the impact temperature, and it must be sufficiently high to increase the reaction rate and below the temperature at which the lithium aluminum oxide does not decompose or melt. Of about 60% to 95% (the porosity is 5 to 40%).
Moreover, it is desirable that the distribution of voids in the 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 impact environment conditions require a pressure of 5 GPa or more. When the pressure is increased to 80 GPa or more, the sample is decomposed or partially melted at the same time as the deformation of the container becomes large, and it becomes difficult to collect the sample when the pressure is released. The temperature is desirably 500 ° C to 1500 ° C.
[0011]
Example 1
A mixture of 10% by weight of γ-type lithium aluminum oxide (chemical formula LiAlO ₂ ) powder having a particle size of 0.5 to 10 μm and 90% by weight of copper powder has a diameter of 12 mm having an apparent density of 6.10 g / cm ³ (porosity of 10%). X A 2 mm-thick press-formed body was prepared. The apparent density of the pressed body of the mixture of lithium aluminum oxide and copper powder was adjusted by increasing or decreasing the forming pressure by pressing. The pressurized form was accommodated in a cylindrical copper recovery container having a thickness of 6 mm, and the pressurized form was pressed from behind with no gap with a copper screw cap, and then embedded in the center of a large iron circular container to serve as a target.
A copper desk of a collision plate was attached to a body made of high-density polyethylene as a flying object, and used to generate necessary impact pressure. An impact treatment of 33 GPa was performed by accelerating the projectile speed to 1.5 Km / sec with a gunpowder and causing a collision. Impact temperature was calculated through thermodynamic analysis and was approximately 900 ° C. The impact pressure was calculated from the measurement of the flying object velocity and one-dimensional analysis by the impedance match method.
After the impact treatment, the pressurized form was taken out of the recovery container, and the pressurized molded body was removed in a nitric acid solution for 5 hours or more, 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 revealed that it was a novel high-pressure phase lithium aluminum oxide as shown in FIG. On the other hand, FIG. 2 (2) shows an X-ray diffraction diagram of a γ-phase lithium aluminum oxide as a starting material, and compares it. From the detailed analysis of the diffractogram obtained, a small amount of impurities are contained in the shock recovery sample, but the new high-density phase has a tetragonal crystal structure, and its lattice constant is a = 0.3879 nm and 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 size of the lithium aluminum oxide of the novel high-pressure phase synthesized from the results of observation of the sample obtained by the impact treatment with an electron microscope was composed of nanoparticles having a size of 100 nm or less. Electron energy loss spectroscopy confirmed that both lithium and aluminum were hexacoordinate in the new high pressure phase lithium aluminum oxide. Therefore, it was clarified that the obtained new LiAlO ₂ was a compound that had never existed before.
[0012]
The present invention investigates how a substance is affected by applying a high-pressure treatment to a substance by a shock wave, in particular, investigates the state of the substance in a high-pressure phase, and conducts basic research on the substance, including conversion to a new substance. As part of our research, we were studying what happens when a high-pressure treatment with a shock wave is applied to a lithium aluminum compound composed of light elements. High-density lithium aluminum oxide crystals existed and could be synthesized, and this result was recognized to be of great significance academically, and was also identified as a novel compound per se. Therefore, this is an industrially useful invention. And it is expected that research and development will be greatly advanced in various fields in the future. At this stage, the physical properties and the like are not as described above, that is, a crystal having a high density can be produced. As a result, for example, solid electrolytes and battery materials, which are one of the fields of application of lithium compounds, are more effective than conventional materials in terms of durability and other properties. Is expected, and in this application, it is expected that a special action and effect can be exhibited. Of course, as shown above, the physical properties and properties of the lithium aluminum oxide of the present invention are extremely high-density, although the elucidation of the properties and properties is awaiting future research. Is expected to open the way for new application development.
[0013]
【The invention's effect】
As described in detail above, 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 can be converted at a high conversion rate from a low pressure phase lithium aluminum oxide in a single impact treatment. It has become possible to produce it in large quantities, and has itself provided an extremely 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 pattern.
[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 of a high-pressure phase having a density of 3.50 g / cm ³ represented by the chemical formula LiAlO ₂ and 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 pressed, and the resulting compact is given an instantaneous pressing force of 5 GPa or more and a pressing time of 5 μs or less by a shock wave. And converting the low-pressure crystalline lithium aluminum oxide to a high-pressure 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 a high-density lithium aluminum oxide by a shock wave. As a low-pressure crystalline lithium aluminum oxide represented by the chemical formula LiAlO _{2 as} a starting material, any one of a group consisting of α phase, β phase and γ phase crystalline lithium aluminum oxide is used. A method for synthesizing a high density lithium aluminum oxide by a shock wave according to claim 2. As crystals of lithium aluminum oxide of the low-pressure phase represented by the chemical formula LiAlO _2, in particular, characterized in that selects the γ phase lithium aluminum oxide crystal powder of density 2.61 g / cm ^3, due to shock waves according to claim 3, wherein A method for synthesizing high density lithium aluminum oxide.

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