CN104178801B - A kind of High Temperature High Pressure hydro-thermal still containing foam metal crystallization parts - Google Patents

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

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

technical field

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

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 particles nucleate and grow in it, and finally obtain method for intact crystals.

The hydrothermal method has many advantages, such as allowing the crystal to grow at a temperature far below its melting point, and solving the problem that some crystals decompose before the melting point or crystal transformation occurs far below the melting point; the crystal growth process of the hydrothermal method can be Reduce the viscosity of the solution and overcome the disadvantages of high cooling viscosity of some crystals during the molten salt growth process and easy formation of glass bodies; hydrothermal growth crystals are easy to grow to obtain large, uniform crystals, and usually have a relatively complete shape and Unit cell; crystal growth by hydrothermal method can directly observe the crystal growth process, which is conducive to the accurate study of growth kinetics and thermodynamics; however, there are still the following shortcomings:

1. In the actual hydrothermal growth process, it is necessary to have seed crystals to create nucleation sites to complete the further growth of crystal nuclei, and seed crystal cultivation requires a long period, and the expansion of particle size and volume is also time-consuming and labor-intensive. There are very few seed crystals that reach the scale used for hydrothermal growth. What's more, some new crystals have no seed crystals or are difficult to obtain seed crystals (no spontaneous nucleation phenomenon), and a crystallization device is required to complete the actual growth. Crystal nucleation step.

2. In hydrothermal crystallization, there is a violent nutrient transport process inside the autoclave. The transport is from the hot end to the cold end of the autoclave, and the nutrient salt is cooled at the cold end and flows back to the hot end. In this way, the crystallization process is normal. 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.

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 amount of crystallization 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.

4. It has been reported in the literature that wound or folded metal sheets and wires are used to generate crystallization regions and increase the area of the binding sites. 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 large-area metal sheets and wires are used, the transportation of nutrients will be hindered.

Contents of the invention

The technical problem to be solved by the present invention is to provide a high-temperature and high-pressure hydrothermal kettle containing foamed metal crystal parts. The use of the autoclave can make crystal nucleation easier for difficult-to-crystallization or non-crystallization materials, make crystal grains grow faster, and increase crystal output at the same time.

The high-temperature and high-pressure hydrothermal kettle containing foamed metal crystallization parts according to the present invention includes a hydrothermal reaction vessel placed in the autoclave body. There is a dissolution zone and a crystallization zone in the hydrothermal reaction vessel. A grown crystalline part made of metal foam.

The metal foam material involved in the technical solution of the present invention has the structural characteristics of small specific gravity, high porosity, large specific surface area and large pore diameter. In the present invention, crystallization parts made of metal foam are arranged in the crystallization area, and a large number of nucleation sites suitable for crystal attachment are generated by utilizing the structural characteristics such as high specific surface area of metal foam, and the fine mesh inside the metal foam can act The effect of grasping the crystal grains has greatly increased the crystallization efficiency, and promoted the further growth of the grains, and the crystal yield has also been further improved.

In the above technical solution, it is preferable to use metal foam with the following structural parameters to make the crystalline part: the pore diameter is 0.01-10mm, the porosity is 50%-98%, the through-porosity ≥ 90%, and the bulk density is 0.05-1g/cm ³ , to obtain higher crystallization efficiency and crystal yield, and at the same time, it is more conducive to the growth of crystals with larger sizes.

In the above technical scheme, the metal foam is usually aluminum foam, copper foam, nickel foam, iron foam, silver foam, gold foam, platinum foam or foam alloy, wherein the foam alloy can specifically be copper tin foam alloy, copper foam Zinc foam alloy, titanium-nickel foam alloy or aluminum-magnesium foam alloy, etc.

In the above technical solution, the crystallized part may be a hollow or solid part made of metal foam with various shapes or structures. Because metal foam has low bulk density, light weight, and is easy to fold and cut, it is easy to make it into crystalline parts of any shape. Specifically, the crystalline part can be made of metal foam and exhibit any shape of linear structure, sheet structure, disc structure, tooth structure, column structure, cone structure, helical structure or solid structure.

In the above technical solution, the crystallization part can be connected to the container cover of the hydrothermal reaction container through precious metal wires. The precious metal wires are usually gold wires, silver wires, titanium wires or platinum wires.

In the technical solution of the present invention, the structure other than the crystallization part is the same as that of the conventional hydrothermal autoclave in the prior art, and will not be described in detail here. In the technical solution of the present invention, the hydrothermal reaction vessel is a noble metal bushing tube commonly used in the prior art, specifically a gold bushing tube, a silver bushing tube or a platinum bushing tube.

In the technical solution of the present invention, the crystalline parts made of metal foam need to be pretreated before being put into an autoclave for use. Clean with absolute ethanol, then use acid solution (usually 0.1-1mol/L hydrochloric acid solution or sulfuric acid solution) to clean and remove the oxide film, and then use lye (usually 0.5-4mol/L sodium hydroxide solution or Potassium solution) to clean and degrease, then vacuum dry. The dried crystalline parts are weighed, and the volume is converted according to the density of the metal foam. When filling the autoclave with the solution, the volume occupied by the crystalline parts needs to be deducted to avoid pressure imbalance.

When the autoclave of the present invention actually grows crystals, it is necessary to select the metal foam used to make the crystal part according to the selected mineralizer. The agent reacts chemically.

Compared with the prior art, the present invention is characterized in that crystallization parts made of metal foam are arranged in the crystallization area, which produces the following beneficial effects:

First of all, the crystalline parts made of metal foam have good thermal conductivity, will not cause uneven heat transfer, local overcooling and overheating, etc., and can withstand high temperature, high pressure, high PH supercritical hydrothermal and solvent thermal environments, and are extremely stable crystals Attachment material; In addition, because metal foam has low bulk density, light weight, and is easy to fold and cut, it is easy to make it into crystal parts of any shape;

Secondly, 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 hold 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 defects of small effective nucleation area, drop of grown grains, too strong convection, and hindered transportation. The crystallization efficiency is greatly increased, and the crystal grains are further grown, and the crystal yield is also further improved.

Description of drawings

Fig. 1 is a schematic structural view of an embodiment of a high-temperature and high-pressure hydrothermal kettle containing foamed metal crystalline parts according to the present invention;

Figure 2 is a schematic diagram of the structure of several metal foam crystal parts suspended in the bushing tube, in which (a) is a structural schematic diagram of a helical structure crystal part, and (b) is a structural schematic diagram of a planar sheet-like spaced stacked crystal part , (c) is a schematic diagram of the crystal structure of the disk-shaped structure; (d) is a schematic diagram of the crystal structure of the tooth-shaped structure; (e) is a schematic diagram of the crystal structure of the hollow columnar structure; (f) is a linear structure Schematic diagram of the structure of the crystallization part;

Fig. 3 adopts the high-temperature and high-pressure hydrothermal kettle containing foamed metal crystalline parts of the present invention, the picture of the crystal that grows according to the method described in Example 2;

Fig. 4 is the XRD spectrum of the crystal grown by the method described in Example 2 by adopting the high-temperature and high-pressure hydrothermal kettle containing foamed metal crystalline parts of the present invention;

Fig. 5 adopts the high-temperature and high-pressure hydrothermal kettle containing foamed metal crystalline parts of the present invention, the picture of the crystal that grows according to the method described in Example 3;

Fig. 6 is the transmittance spectrum of the crystal grown by the method described in Example 3 using the high-temperature and high-pressure hydrothermal kettle containing the metal foam crystal part of the present invention;

Fig. 7 is a picture of crystals grown according to the method described in Example 4 by using the high-temperature and high-pressure hydrothermal kettle containing foamed metal crystal parts according to the present invention.

The labels in the figure are:

1 Self-tightening sealing kettle plug; 2 Fastening bolts; 3 Kettle cover; 4 Kettle body; 5 Bushing pipe; 6 Baffle plate; 7 Crystallization area;

detailed description

The present invention will be further described below with specific examples, but the present invention is not limited to these examples.

Embodiment 1: High-temperature and high-pressure hydrothermal kettle containing foamed metal crystallization parts for hydrothermal growth of crystals

As shown in Figure 1, the high-temperature and high-pressure hydrothermal kettle containing foamed metal crystal parts according to the present invention includes a kettle body 4 and a kettle cover 3, and the kettle cover 3 is provided with a self-tightening mechanism that cooperates with the opening of the inner cavity of the kettle body 4. Sealed kettle plug 1, the kettle body 4 and kettle cover 3 are connected by fastening bolts 2; a bushing pipe 5 is placed in the inner cavity of the autoclave body 4, and a middle and lower part of the bushing pipe 5 is placed Baffles 6 with openings in the center and edges (the opening ratio is 7-10%). The baffles 6 divide the space inside the liner pipe 5 into a lower dissolution zone 9 and an upper crystallization zone 7 . In the crystallization zone 7, the crystallization part 8 made of foam metal is suspended on the top of the liner pipe 5 (such as on the pipe cover of the liner pipe 5) by precious metal wire; placed in the dissolution zone 9), and fill the liner tube 5 with a mineralizer. A certain amount of deionized water or distilled water is filled in the interlayer between the autoclave and the liner tube 5 to maintain the pressure balance inside and outside the liner tube 5 and prevent the liner tube 5 from breaking or being crushed. If the caliber of the liner pipe 5 adopted is relatively large, it is necessary to add a hanging basket 10 in the liner pipe 5 , and place the compost in the hanging basket 10 .

In the above embodiment, the culture material and the mineralizer are selected according to the existing conventional technology according to the crystal to be cultured. The bushing tube 5 may be a gold bushing tube 5 , a silver bushing tube 5 or a platinum bushing tube 5 , and the precious metal wire may be a gold wire, a silver wire or a platinum wire. Described crystalline part 8 can be made of foamed metal with various shapes or structures, hollow or solid parts, specifically, crystalline part 8 can be made of foamed metal and presents a linear structure (as shown in Fig. 2(f) ), planar sheet-like spaced stacking structure (as shown in Figure 2(b)), disk-shaped structure (as shown in Figure 2(c), tooth-shaped structure (as shown in Figure 2(d)), hollow columnar structure (as shown in Figure 2(d) 2 (e)), helical structure (as shown in Figure 2 (a)) or other arbitrary shapes such as cone structure. The metal foam preferably has the following structural parameters: the aperture is 0.01～10mm, and the porosity is 50%-98%, porosity ≥ 90%, bulk density 0.05-1g/cm ³ , specifically aluminum foam, copper foam, nickel foam, iron foam, silver foam, gold foam, Platinum foam or foam alloy, the foam alloy may specifically be copper-tin foam alloy, copper-zinc foam alloy, titanium-nickel foam alloy or aluminum-magnesium foam alloy.

Example 2: Using the device of the present invention to grow scandium-doped zinc oxide single crystal by hydrothermal method

The crystalline part is made of nickel foam with the following structural parameters: 0.1-0.5mm pore diameter, >90% porosity, 95% through-porosity, and 0.85g/cm ³ volume density.

In this embodiment, the crystalline part 8 made of nickel foam with the above structural parameters has a continuous tooth-like structure, and the crystalline part 8 is cleaned with absolute ethanol for 5 minutes under ultrasonic conditions, and then washed with 0.1 mol/L hydrochloric acid The solution was washed for 20s, and then washed in 4mol/L KOH solution for 20s, and then vacuum-dried. Build the used autoclave of present embodiment afterwards by the structure of device shown in Fig. 1, wherein liner pipe 5 adopts the gold liner pipe 5 of Φ 22 (liner pipe 5 internal diameters are 22mm), and precious metal wire adopts gold wire, will dry The crystal part 8 is suspended on the top of the gold bushing tube 5 (ie on the cap of the gold bushing tube 5 ) with a gold wire, as shown in FIG. It is measured that the unfilled volume of the liner tube 5 is 57ml, the filling raw material (ie compost) is 22.24g of high-purity zinc oxide particles, the doping amount of scandium is ≤0.003g, the mineralizer is KOH of 4mol/L, and the inner filling degree After filling, seal and weld the cover of the liner tube 5 and the liner tube 5; put the sealed liner tube 5 into the autoclave body 4, between the liner tube 5 and the interlayer of the autoclave Fill with 70% deionized water by volume. The sealed autoclave was placed in a two-stage heating resistance furnace. Set the average temperature of the dissolution zone 9 to 380°C, and the average temperature of the crystallization zone 7 to 360°C, keep it for 5 days and then cool to room temperature with the furnace. The autoclave and the liner tube 5 were turned on, and about 12 g of spontaneous nucleated crystals were obtained on the crystallization part 8 made of nickel foam, with a maximum crystal size of 8.57mm×3.73mm×3.86mm, as shown in Figure 3. Figure 4 is the XRD pattern of the obtained crystals. Experimental results show that the crystallization effect of the autoclave is good after the crystallization part 8 is added.

comparative example

As a comparative experiment of Example 2, only a gold wire is suspended in the crystallization area 7 to replace the crystallization part 8 made of nickel foam in Example 2, and other processes and conditions are the same as in Example 2. The experimental results show that the crystal nuclei are not attached to the gold wire and the tube wall, and only crystal grains with a diameter of ≤2 mm are collected at the bottom of the gold bushing tube 5 and the welding seam of the nozzle of the gold bushing tube 5. The total weight of the crystal grains is about for 3g.

Embodiment 3: Adopt the device hydrothermal method of the present invention to grow KTP (potassium titanyl phosphate) single crystal

The crystalline parts are made of silver foam with the following structural parameters: porosity ≥ 85%, number of pores: 80-110PPI, thickness: (0.2-2.5) ± 0.05mm, specific surface area ≥ 10㎡/g.

In the present embodiment, the crystalline part 8 made of foamed silver with the above structural parameters is in a disc-shaped structure, specifically, it is arranged in a disc shape from the center of the circle to the outer spiral disk, and the crystalline part 8 made under ultrasonic conditions is used without Wash with water and ethanol for 5 minutes, then wash with 0.1mol/L hydrochloric acid solution for 20s, then wash with 4mol/L KOH solution for 20s, and then vacuum dry. Build the used autoclave of present embodiment afterwards by the structure of device shown in Fig. 1, wherein liner pipe 5 adopts the gold liner pipe 5 of Φ 22 (liner pipe 5 internal diameters are 22mm), and precious metal wire adopts gold wire, will dry The crystallization part 8 is suspended on the top of the gold bushing tube 5 (i.e. on the cap of the gold bushing tube 5) with a gold wire, as shown in Figure 2(c), and all the other structures are the same as in Embodiment 1. It is measured that the liner pipe 5 has a non-filling volume of 56.5ml, and the filling material is 22g of potassium titanyl phosphate raw material, and the mineralizer is a mixed solution of potassium dihydrogen phosphate of 0.25mol/L and dipotassium hydrogen phosphate of 2.5mol/L. The inner filling degree is 70%. After the filling is completed, seal and weld the cover of the liner tube 5 and the liner tube 5; put the sealed liner tube 5 into the autoclave body 4, 65% volume of deionized water is filled between the interlayers. The sealed autoclave was placed in a two-stage heating resistance furnace. Set the average temperature of the dissolution zone 9 to 510°C, and the average temperature of the crystallization zone 7 to 450°C, keep it for 10 days and then cool to room temperature with the furnace. The autoclave and the liner tube 5 were turned on, and about 15 g of spontaneous nucleated crystals were obtained on the foamed silver crystallization part 8, with a maximum crystal size of 10.06mm×8.27mm×3.71mm, as shown in FIG. 5 . The transmittance of the obtained crystal was tested, and its transmittance spectrum is shown in Figure 6, which is completely consistent with the KTP standard spectrum. It can be seen that the optical quality of the crystal obtained above is very excellent.

After applying for a lot of tests, it is known that adding crystallization parts 8 made of metal foam in the autoclave can create a large number of nucleation sites, and directly obtain large-sized crystals, which is different from the traditional use of gold wires, gold sheets and gold frames. Compared with the method of obtaining KTP crystals in the seed crystal state (the crystal quality obtained in a single growth is <10g, and the maximum crystal particle size is ≤5mm), the autoclave of the present invention can effectively increase the volume and quality of spontaneous nucleation.

Embodiment 4: Using the device of the present invention to grow lithium iron phosphate single crystal by hydrothermal method

The crystalline part is made of copper foam with the following structural parameters: 0.6mm pore diameter, >92% porosity, 98% through-porosity, and 0.6g/cm ³ bulk density.

In this embodiment, the crystalline part 8 made of foamed copper having the above structural parameters has a hollow columnar structure, wherein the column height of the cylindrical structure is 150mm, the inner diameter is 30mm, and the thickness is 2.5mm. The prepared crystal part 8 was cleaned with absolute ethanol for 5 minutes under ultrasonic conditions, then washed with 0.1 mol/L hydrochloric acid solution for 20 seconds, and then washed with 4 mol/L KOH solution for 20 seconds, and then vacuum-dried. Build the used autoclave of the present embodiment by the structure of device shown in Figure 1 afterwards, wherein liner pipe 5 adopts the gold liner pipe 5 of Φ 42 (liner pipe 5 inner diameters are 38mm), and precious metal wire adopts gold wire, will dry The crystal part 8 is suspended on the top of the gold bushing tube 5 (ie on the cap of the gold bushing tube 5 ) with a gold wire, as shown in Figure 2(e), and all the other structures are the same as in Embodiment 1. The measured liner tube 5 has a non-filling volume of 710ml, and the filling material is 20g of carbon-coated lithium iron phosphate powder (Guilin Jiuyi New Energy Materials Co., Ltd.), the mineralizer is saturated lithium dihydrogen phosphate solution, and the inner filling degree is 75%, after filling, seal and weld the cover of the liner tube 5 and the liner tube 5; put the sealed liner tube 5 into the autoclave body 4, between the liner tube 5 and the interlayer of the autoclave Fill to 70% volume with deionized water. The sealed autoclave was placed in a two-stage heating resistance furnace. Set the average temperature in the dissolution zone 9 to 480°C, and set the average temperature in the crystallization zone 7 to 450°C, keep it for 5 days and then cool to room temperature with the furnace. The autoclave and the liner tube 5 were turned on, and about 5 g of spontaneously nucleated crystals were obtained on the crystallization part 8 made of foamed copper, with a maximum crystal size of 280*150*80 μm ³ , as shown in FIG. 7 . The crystallized product obtained in this example is a lithium iron phosphate single crystal in the form of a hexagonal prism, and the single crystal is analyzed by x-ray single crystal diffraction, and the unit cell structure is obtained as D162h, Pbnm space group, wherein α=β=γ=90°. The unit cell parameters measured by the X-ray single crystal diffraction data of the sample (the structure is analyzed, refined and data output in the SHELXL-97 (Sheldrick, 1997) software program. R1=0.0234, wR ₂ (I>2σ) = 0.0581; R1 = 0.0225, wR ₂ (all) = 0.0589). The crystal density calculated from the test data is 3.6061g/cm ³ , which is higher than that reported in the literature (Yuri Janssen, Dhamodaran Santhanagopalan, et al. ReciprocalSaltFluxGrowthofLiFePO4SingleCrystalswithControlledDefectConcentrations[J]. Chem. Mater. 2013, 25, 4574-4584) and ICSD database data.

The above test proves that the autoclave with crystal part 8 made of metal foam is especially suitable for the research and development of seedless and difficult-to-grow new crystals.

Claims (4)

1. A high-temperature and high-pressure hydrothermal kettle containing foamed metal crystallization parts, comprising a hydrothermal reaction vessel placed in the autoclave still body (4), there is a dissolution zone (9) and a crystallization zone (7) in the hydrothermal reaction vessel ), which is characterized in that: a crystallization part (8) conducive to crystal growth is arranged in the crystallization area (7), and the crystallization part (8) is made of foamed metal; the structural parameters of the foamed metal are: the aperture is 0.01-10mm , the porosity is 50%-98%, the through-porosity ≥ 90%, and the bulk density is 0.05-1g/cm ³ . 2. The high-temperature and high-pressure hydrothermal kettle containing metal foam crystal parts according to claim 1, characterized in that: said metal foam is aluminum foam, copper foam, nickel foam, iron foam, silver foam, gold foam, foam Platinum or foam alloy. 3. The high-temperature and high-pressure hydrothermal kettle containing foamed metal crystallization parts according to claim 1 or 2, characterized in that: said crystallization parts (8) are connected to the container cover of the hydrothermal reaction vessel through precious metal wires. 4. The high-temperature and high-pressure hydrothermal kettle containing foamed metal crystalline parts according to claim 1 or 2, characterized in that: the described crystalline parts (8) have a linear structure, a disk structure, a tooth structure, a columnar structure, Conical, helical or solid structures.