A high-temperature and high-pressure hydrothermal kettle containing foamed metal crystal parts

Abstract

The invention discloses a high-temperature and high-pressure hydrothermal kettle containing foamed metal crystallization parts, which includes a hydrothermal reaction vessel placed in the autoclave body. There is a dissolution zone and a crystallization zone in the hydrothermal reaction vessel, and the setting in the crystallization zone is beneficial to A crystalline part for crystal growth, the crystalline part being made of metal foam. By setting crystallization parts made of metal foam in the crystallization area, using the structural characteristics of metal foam such as high specific surface area, a large number of nucleation sites suitable for crystal attachment are generated, and the fine mesh inside the metal foam can play a role Grasp the role of the crystal grains to prevent them from slipping into the dissolution zone. While absorbing the advantages of using metal wires and metal sheets as the crystallization carrier in the traditional temperature difference hydrothermal kettle, it solves the problem that the effective nucleation area is small and the grains that have grown into Defects such as falling, strong convection, and hindered transport greatly increase the crystallization efficiency, promote the further growth of crystal grains, and further increase the crystal yield.

Description

technical field [0001] The invention relates to a device for artificially growing crystals, in particular to a high-temperature and high-pressure hydrothermal kettle containing foamed metal crystal parts. Background technique [0002] The research on the method of artificially growing crystals began as early as the end of the nineteenth century, and has a history of more than one hundred years. The methods for growing single crystals mainly include flux method, hydrothermal method, gas phase method, zone melting method, etc. Among them, water The crystals grown by the thermal method have the characteristics of small thermal stress, small macroscopic defects, good crystal uniformity, and high transmittance. The hydrothermal crystal growth method specifically dissolves the raw material (solute) in the solvent, and takes appropriate measures to cause the supersaturated state of the solution (the saturated vapor pressure of the dilute phase increases), so that the solid phase pa...

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Problems solved by technology

[0005] 2. In hydrothermal crystallization, there is a violent transport process of nutrient salts inside the autoclave. The transport is from the hot end to the cold end of the autoclave, and the nutrient salts are cooled at the cold end and flow back to the hot end. It happens in the condensation process of nutrient salts (some crystals have a reverse temperature coefficient and may crystallize during the heating process). Although today's high-performance autoclaves can accurately control the temperature and widen the temperature difference, it is difficult to achieve amplified condensation (heating ) in the crystallization process section to slow down the convection of the solution in the kettle

[0006] 3. In order to solve the problem of severe convection in the hydrothermal crystallization process, internal baffle equipment has been installed between the dissolution zone and the crystallization zone at home and abroad. The internal baffle slows down the transportation of nutrient salts in a certain sense and enlarges the condensation The crystallization process increases the crystallization amount and the crystal nucleus. However, after the formation of the crystal nucleus, it will migrate to the dissolution zone or the position of the baffle with the force of gravity and transportation, and the utilization rate of the crystal nucleus is not high.

In the actual growth process, it often occurs that the crystal nuclei are difficult to grow (repeatedly dissolving crystals in the kettle), and the crystal grains block the baffle holes and cause growth stagnation.

[0007] 4. It has been reported in the literature to use wound or folded metal sheets, wires, etc. to produce crystallization regions and increase the area of ​​bonding sites. Although it plays the role of accepting crystal grains and slowing down the convection of the solution, the metal sheets and wires are not stable. The density is high, but the unit specific surface area is small, and the utilization rate of the index surface matching the crystal unit cell is still not high; on the other hand, if a large-area metal sheet or wire is used, it will hinder the transportation of nutrients

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