Method for producing manganese-doped and high-hydrated nickel-magnetite single crystals at high temperature and high pressure

Abstract

The application discloses a preparation method of a manganese-doped and high-water-content nickel-magnetite monocrystal under high temperature and high pressure, which comprises the following steps: taking solid light green basic carbonate nickel inorganic compound powder, solid transparent red-brown flaky iron (III) citrate crystals, solid oxalic acid powder, solid pink manganese stearate powder, solid nickel hydroxide powder, solid natural water manganite powder and liquid dilute nitric acid as starting raw materials to prepare a nickel-magnetite powder sample mixture disc; after the nickel-magnetite powder sample mixture disc is calcined and quenched through a high-temperature oxygen atmosphere furnace, a cylindrical nickel-magnetite sample is prepared; after a water source disc is placed at two ends of the cylindrical nickel-magnetite sample and then sealed together, high-temperature and high-pressure reaction is carried out to obtain a nickel-magnetite monocrystal; and a large-granularity manganese-doped and high-water-content nickel-magnetite monocrystal is effectively synthesized and meets the needs of various high-temperature and high-pressure laboratory simulation earth science researches.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of synthesis of mineral single crystal samples, and particularly relates to a preparation method of manganese-doped and high-hydrated nickel magnetite single crystals under high temperature and high pressure. BACKGROUND

[0002] As an important end-member component of the magnetite subfamily of the spinel group of minerals, nickel magnetite, with a chemical composition formula of NiFe2O4, is an important oxide mineral rich in nickel and iron. The percentage of the chemical composition of the nickel magnetite mineralogy oxide can be expressed as: NiO / (NiO+Fe2O3) = 31.9% and Fe2O3 / (NiO+Fe2O3) = 68.1%. Generally, nickel magnetite is the most typical oxide mineral of the inverse spinel structure in nature, and in the corresponding unit cell, the nickel magnetite with the inverse spinel structure has a cubic closest packing ratio of 1, which exhibits very obvious physical and chemical characteristics of the inverse spinel structure. Existing geological data research shows that a large number of nickel-rich spinel minerals (NiFe2O4) are found in the Bon Accord nickel deposit of the basic-ultrabasic lava of the Barberton ophiolite belt in the Republic of South Africa. The ophiolite belt is mainly composed of outcropped serpentinite and schist, and the uranium-lead isotope dating result of zircon is 3250-3347 million years. The results of the chronology experiment of the Bon Accord nickel deposit confirm that the typical nickel magnetite is derived from the Archean stratum 3.4-3.6 billion years ago; the results of the field experiment petrology, crystal chemistry and Mossbauer spectroscopy confirm that the nickel magnetite in the ophiolite belt is associated with cobalt-iron spinel (NiFe2O4), iron spinel (FeAl2O4) and magnetite (Fe3O4) and other spinel group minerals. In addition, based on the radioactive rhenium-osmium isotope results of the platinum group elements of chondrite, geologists reveal that the nickel magnetite may also be part of the molten meteorite fragments generated by the large collision during the early formation of the earth, and these molten meteorite fragments form the granoblastic crystal structure exposed on the surface during the rapid quenching process when they pass through the atmosphere.

[0003] In the structure of the nickel magnetite, the transition metal element manganese is easy to occupy the tetrahedral position, thereby forming the isomorphism replacement of the A-site divalent cations. Since the nickel element and the doped manganese element in the lattice position have the same positive divalent valence in the nickel magnetite, the isomorphism replacement belongs to the equivalent isomorphism replacement. The manganese element (Mn) is located in the 4th period and the ⅦB group of the periodic table, has an atomic number of 25 and an atomic weight of 54.94, and has an outermost electron arrangement of 3d 5 4s 2Manganese is a silvery white metal, and its common valence states include +2, +4, +6 and +7. In the earth's crust, the abundance of manganese is 0.1%, and there are a large number of manganese nodule mines exposed in the ocean floor. On earth, the main manganese-containing minerals are pyrolusite (MnO2·xH2O), black manganese (Mn3O4) and manganese nodule. Existing geological studies have shown that manganese nodule, also known as polymetallic nodule, manganese ore ball, manganese ore group, manganese tumor, etc., as an important form of manganese element in the ocean floor, its main components are high manganese acid sub-titanium, high manganese acid iron, high manganese acid aluminum and other high manganese acid salts. The sources of manganese nodule include: (1) the manganese element released by the weathering of rocks on land, continent or island, which is brought to the ocean floor by seawater flow and then precipitates; (2) the manganese element transported from lava by the interaction between the gas produced by volcanic eruption and seawater and then deposited in seawater; (3) the manganese element from plankton, such as diatom and bacteria, which is released into seawater and then precipitates after the death of the plankton; (4) the manganese element from meteorite dust, which is released into seawater and then precipitates after the decomposition of meteorite dust.

[0004] The molecular structure of nickel magnetite with spinel structure does not contain water molecules or hydroxyl groups, and shows obvious nominal anhydrous mineral properties. However, previous experimental results on the water solubility of spinel under high temperature and high pressure conditions show that the amount of water dissolved by spinel can be as high as hundreds of ppm. Water is one of the most important volatile components in the main layers of the earth's interior, especially in the mantle transition zone from 410 km to 660 km (corresponding to pressure and temperature: 16.0-23.0 GPa and 1450-1800℃). The existing experimental research results of physical properties and spectroscopy of minerals and rocks under high temperature and high pressure conditions, such as conductivity, Brillouin scattering elastic wave velocity, thermal diffusivity, thermoelectric conductivity, and vacuum Fourier transform infrared spectroscopy, show that the trace amount of water in nominal anhydrous minerals can improve the physical and spectroscopic properties of minerals and rocks by several orders of magnitude, and has a very important influence on the mineral physics properties. Looking at the artificial synthesis of nickel magnetite in the field of materials science in domestic and foreign laboratories, the main methods include: ammonia or carbonate coprecipitation method, microemulsion method, high-temperature solid sintering method, high-pressure hydrothermal synthesis method, metal alkoxide sol-gel method, freeze-drying method, etc. Due to the existing synthesis technology, most of which adopts simple solution chemical reaction or direct physical grinding of sample powder, it is more suitable for preparing nanoscale nickel magnetite crystals. Since the field of high temperature and high pressure experimental geoscience usually requires micron-sized or larger particle mineral single crystal experimental samples, it is obvious that the nanoscale nickel magnetite samples obtained by previous material synthesis cannot meet the minimum particle size requirement. So far, there is no effective synthesis method. More geoscience researchers usually use natural nickel magnetite samples to replace artificial samples to meet the needs of high temperature and high pressure experimental geoscience research, but these natural samples have the disadvantage of uneven distribution of trace elements manganese. Therefore, it is particularly urgent to effectively synthesize a large particle manganese-doped and high water content nickel magnetite single crystal to meet the needs of various high temperature and high pressure laboratory simulation of geoscience research, especially the study of nickel magnetite single crystal lattice preferred orientation and crystal axis anisotropy under high pressure. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a preparation method of manganese-doped and high water content nickel magnetite single crystal under high temperature and high pressure, to completely solve the current technical blank of preparation of manganese-doped and high water content nickel magnetite large particle single crystal under high temperature and high pressure, and to obtain experimental samples of large particle manganese-doped and high water content nickel magnetite single crystal.

[0006] The technical scheme of the present application is:

[0007] A method for preparing a manganese-doped and high-hydrated nickel magnetite single crystal under high temperature and high pressure, the method comprising: preparing a nickel magnetite powder sample mixture wafer with solid light green basic nickel carbonate inorganic compound powder, solid transparent reddish-brown flaky iron(III) citrate crystals, solid oxalic acid powder, solid pink manganese stearate powder, solid nickel hydroxide powder, solid natural manganese ore powder, and liquid dilute nitric acid as starting materials; calcining and quenching the nickel magnetite powder sample mixture wafer in a high-temperature oxygen atmosphere furnace to prepare a cylindrical nickel magnetite sample; placing a water source sheet at both ends of the cylindrical nickel magnetite sample and sealing them together for high-temperature and high-pressure reaction to obtain a nickel magnetite single crystal.

[0008] The solid light green basic nickel carbonate inorganic compound powder has a purity of >99.99%, the solid transparent reddish-brown flaky iron(III) citrate crystals have a purity of >99.9%, the solid oxalic acid powder has a purity of >99.99%, the solid pink manganese stearate powder has a purity of >99.99%, the solid nickel hydroxide powder has a purity of >99%, and the solid natural manganese ore powder has a purity of >99%, and the liquid dilute nitric acid has a concentration of 10%.

[0009] The method for preparing the nickel magnetite powder sample mixture wafer comprises:

[0010] Step 1, weigh 60 milliliters of dilute nitric acid with a concentration of 10% into a notch beaker;

[0011] Step 2, weigh 5.0 grams of light green basic nickel carbonate inorganic compound powder into the notch beaker, and place a magnetic stirring rotor into the notch beaker;

[0012] Step 3, cover the notch beaker with a glass surface dish, and place the notch beaker on a high-temperature magnetic stirring hot plate in a fume hood, and stir at a speed of 700 revolutions per minute for 72 hours at room temperature;

[0013] Step 4, according to the stoichiometric ratio of nickel magnetite (Ni, Mn) Fe2O4, weigh 19.5343 grams of solid iron(III) citrate crystals and 60 milligrams of solid manganese stearate powder into the dilute nitric acid solution containing the basic nickel carbonate;

[0014] Step 5, cover the notch beaker with a glass surface dish;

[0015] Step 6, place the notch beaker on a high-temperature magnetic stirring hot plate in a fume hood, and stir at a speed of 800 revolutions per minute for 48 hours at room temperature;

[0016] Step 7, weigh 2 grams of solid oxalic acid powder into the notch beaker;

[0017] Step 8, place the beaker on the high temperature magnetic stirring hot plate in the fume hood, cover with a glass watch glass, stir at 1000 rpm for 36 hours at 80°C;

[0018] Step 9, remove the glass watch glass from the beaker, increase the temperature of the high temperature magnetic stirring hot plate to 110°C until the entire mixed solution in the beaker is evaporated;

[0019] Step 10, take out the mixed powder in the beaker and place it in a graphite crucible;

[0020] Step 11, place the graphite crucible containing the mixed powder into a muffle furnace, increase the temperature to 1100°C at a rate of 300°C / hour, and keep the temperature constant for 5 hours;

[0021] Step 12, reduce the temperature of the mixed powder to room temperature at a rate of 200°C / hour, and take out the mixed powder;

[0022] Step 13, place the mixed powder in a thick corundum mortar and grind for 1 hour to obtain a nickel magnetite powder sample mixture;

[0023] Step 14, cold-press the nickel magnetite powder sample mixture into 3 sample discs of Φ10.0mm x 3.0mm using a tungsten carbide die of a stainless steel tablet press.

[0024] The method for preparing a cylindrical nickel magnetite sample after calcination and quenching of the nickel magnetite powder sample mixture disc in a high-temperature oxygen atmosphere furnace comprises:

[0025] Step 15, place the 3 sample discs on top of each other at the bottom of a graphite crucible, drill symmetrical circular holes on the wall of the graphite crucible, hang a platinum-rhodium alloy wire through the symmetrical circular holes on the wall of the graphite crucible in the center of a high-temperature oxygen atmosphere furnace, and fix the two ends of the platinum-rhodium wire connected to the graphite crucible on a vertical four-hole alumina tube, with the upper end of the four-hole alumina tube fixed in the center of the dome of the furnace body;

[0026] Step 16, place a stainless steel container containing secondary deionized pure cold water on the side of the high-temperature oxygen atmosphere furnace;

[0027] Step 17, connect the top of the furnace body of the high-temperature oxygen atmosphere furnace to an argon inert gas cylinder, a proportionally adjustable carbon monoxide and carbon dioxide cylinder;

[0028] Step 18, open the valve of the argon inert gas cylinder for 30 minutes of continuous gas charging; under the protection of argon inert gas, heat the sample to 800°C at a rate of 400°C / hour;

[0029] Step 19, after the temperature in the furnace body reaches 800℃, switch the carbon monoxide gas cylinder and the carbon dioxide gas control valve, so that the volume ratio of carbon monoxide and carbon dioxide in the sample oxygen atmosphere furnace reaches 4:1;

[0030] Step 20, after the mixed gas flow with a volume ratio of 4:1 of carbon monoxide and carbon dioxide controls the oxygen fugacity in the sample chamber, increase the temperature of the sample chamber in the furnace body to 1450℃ at a rate of 200℃ / hour, and keep the temperature constant for 15 minutes;

[0031] Step 21, after the sample is kept at a temperature of 1450℃ for 15 minutes, pull out the graphite crucible containing the sample, the four-hole alumina tube, and the upper round cover of the furnace body together from the furnace body, and directly immerse them in a stainless steel container filled with secondary deionized pure cold water to quench the glassy nickel magnetite sample;

[0032] Step 22, take out the quenched glassy nickel magnetite sample from the graphite crucible and place it in a corundum mortar for grinding. The fine and homogeneous glassy nickel magnetite powder is placed in a vacuum drying box at 200℃ for 12 hours.

[0033] Step 23, on a cold isostatic pressing machine, cold-press the nickel magnetite glass powder using a tungsten carbide die to form a cylindrical nickel magnetite sample with a diameter of 4.0mm and a height of 4.0mm.

[0034] The method for obtaining a nickel magnetite single crystal by placing a water source sheet at both ends of the cylindrical nickel magnetite sample and then sealing them for high-temperature and high-pressure reaction includes:

[0035] Step 24, on a cold isostatic pressing machine, cold-press the nickel hydroxide powder and the natural hydrogrossular powder using a tungsten carbide die to form two pieces of water source sheets with a diameter of 4.0mm and a height of 0.1mm in a weight ratio of 4:1.

[0036] Step 25, seal the cylindrical nickel magnetite sample and the two pieces of water source sheets in a double-capsule structure experimental sample chamber composed of an inner graphite sleeve; place the cylindrical nickel magnetite sample in the center of the graphite inner sleeve; place the two pieces of water source sheets symmetrically at both ends of the graphite inner sleeve close to the sample; use gold-palladium alloy as the sealing material for the outer sleeve of the double-capsule structure sample chamber.

[0037] Step 26, place the double-capsule structure sample chamber composed of a graphite tube and a gold-palladium alloy tube in a typical 6-8 type multi-faceted top large cavity high-temperature and high-pressure equipment in the laboratory Kawai-1000t, set the pressure and temperature increasing rates to 0.5GPa / hour and 10℃ / minute respectively, and heat-press sinter under conditions of a pressure of 3.0GPa and a temperature of 1100℃, with a reaction time of 72 hours under constant temperature and pressure.

[0038] Step 27, under the condition of 3.0 GPa and 1100 DEG C, after constant temperature and constant pressure for 72 hours, the temperature in the sample cavity is reduced from 1100 DEG C to 800 DEG C at a cooling rate of 3 DEG C / min, and constant temperature is kept for 1 hour; then the temperature in the sample cavity is reduced from 800 DEG C to room temperature at a cooling rate of 5 DEG C / min;

[0039] Step 28, after the temperature in the sample cavity is reduced to room temperature, the pressure in the sample cavity is reduced from 3.0 GPa to normal pressure at a pressure reduction rate of 0.5 GPa / hour;

[0040] Step 29, after the high-temperature and high-pressure preparation reaction is completed, the sample is taken out from the Kawai-1000t typical 6-8 type multi-face top large cavity high-temperature and high-pressure equipment; the graphite tube and gold-palladium alloy tube wrapped around the sample are removed, and the cylindrical sample is cut in half from the center; under a 20-fold high-precision Olympus microscope, a nickel magnetite single crystal is selected.

[0041] During the high-temperature and high-pressure reaction, two groups of high-temperature resistant tungsten-rhenium thermocouples are used to calibrate the temperature; each group of tungsten-rhenium thermocouples is composed of two tungsten-rhenium alloys with different materials, and the chemical composition is W 95％ Re 5％ and W 74％ Re 26％ ; the tungsten-rhenium thermocouples are respectively installed at the upper and lower ends of the sample cavity.

[0042] The beneficial effects of the present application are:

[0043] The present application combines the related disciplines of geosciences such as mineral deposit science, mineralogy, marine geology, chronostratigraphy, isotopic geochronology, rare earth element geochemistry, field experimental petrology, mineral crystal chemistry, mineral Mossbauer spectroscopy, crystallography, mineralogy, magmatic petrology, sedimentary petrology, metamorphic petrology, deep earth material science, mineral material science, and nanogeochemistry, etc. The formation process of manganese-doped and high-water-containing nickel magnetite single crystals is simulated under high temperature and high pressure conditions by using a laboratory Kawai-1000t typical 6-8 type multi-face top large cavity high-temperature and high-pressure equipment. The present application relates to the main chemical reaction equation:

[0044] [NiCO3·2Ni(OH)2·4H2O]+6HNO3→3Ni(NO3)2+CO2+9H2O

[0045] Ni(NO3)2+2C6H5FeO7→NiFe2O4+2(NH3·H2O)+10CO+2CO2

[0046] NiFe2O4+C 36 H70 O4Mn→(Ni,Mn)Fe2O4+10CH4+12C2H2+2CO2+3H2

[0047] Ni(OH)2→NiO+H2O

[0048] Mn(OH)2→MnO+H2O

[0049] 2Mn(OH)2→Mn2O3+H2O+H2

[0050] The present application, the selected initial raw material basic nickel carbonate [chemical formula: NiCO3.2Ni(OH)2.4H2O] is a light green solid inorganic compound powder, which has stable chemical properties, slightly soluble in water, soluble in dilute acid and ammonia water, and is mainly used in the preparation and production of special cathode nickel plating film, nickel salt, etc. The selection of basic nickel carbonate solid powder is an excellent raw material for providing nickel element in artificial synthesized nickel magnetite due to its stable performance and the superior characteristics of easy solubility in dilute acid. The initial raw material iron (III) citrate [also known as: citric acid tri-iron, chemical formula: C6H5FeO7] is a transparent reddish-brown flaky crystal solid inorganic compound, which is insoluble in ethanol and soluble in water and dilute acid. Iron (III) citrate, as a typical edible citrate, can be used as an iron fortifier, an acidifier, a nutritional supplement, etc. in the field of food science research; and can be used as a radio pharmaceutical for monitoring iron metabolism abnormalities, hematopoietic function, etc. in the field of medical research. The selection of iron (III) citrate crystals is an excellent raw material for providing iron element in artificial synthesized nickel magnetite due to its superior characteristics of easy decomposition and strong chemical reaction activity in dilute acid solution. The initial raw material manganese stearate [chemical formula: C 36 H 70O4Mn] is a pink powder solid substance, insoluble in water, soluble in ether, chloroform, petroleum and other substances, and forms a gel with aromatic or aliphatic hydrocarbons, and is easily decomposed with strong acid. The present application selects a pink solid stearic acid manganese powder, which is an excellent raw material for providing trace elements manganese in artificial nickel magnetite because it is soluble in dilute nitric acid solution. The selected initial raw material nickel hydroxide [molecular formula: Ni(OH)2] is a typical nickel-rich aqueous powder solid substance. Nickel hydroxide dehydrates at a temperature of 230 DEG C to generate nickel oxide (NiO), while releasing a large amount of water. When the temperature reaches 450 DEG C, the dehydrated nickel hydroxide mineral occurs completely. The selected initial raw material water manganese [molecular formula: Mn(OH)2] is a typical manganese-rich aqueous mineral. Water manganese dehydrates at a temperature of 300 DEG C to generate pyrolusite (MnO). When the temperature rises to 560 DEG C, a second dehydration reaction occurs to generate manganese dioxide, while releasing a large amount of water. In the high-pressure sample chamber, the nickel hydroxide and water manganese containing water in a certain ratio are placed in the high-pressure sample chamber, and the dehydration reaction occurs under high temperature and high pressure conditions to generate a large amount of water, which provides a good water source for synthesizing manganese-doped and high-water-content nickel magnetite single crystals. In the chemical reaction product involved in the present application, NH3·H2O, CH4, C2H2, CO2, CO and H2 are obtained, which are high-temperature volatile substances.

[0051] The present application needs to synthesize manganese-doped nickel magnetite single crystals with high water content. The synthesized sample contains manganese-doped nickel magnetite single crystals which are matched with nickel mineral resources development and comprehensive utilization, and is widely used in the experimental simulation of mineral and rock physical and chemical properties under high temperature and high pressure conditions. Compared with the natural nickel magnetite samples exposed in nature, the present application may contain impurity ions such as magnesium ions, manganese ions and zinc ions. In the preparation process of manganese-doped and high-water-content nickel magnetite single crystals, the laboratory environment is pure, and the sample is in a sealed environment and does not contact impurities. The obtained manganese-doped and high-water-content nickel magnetite single crystals are pure substances with good chemical stability, which provides important experimental sample guarantee for the measurement of physical property parameters of manganese-doped and high-water-content nickel magnetite single crystals, especially the research of crystal axis anisotropy and lattice optimization orientation of nickel magnetite single crystal mineral physical and chemical properties under high pressure.

[0052] Compared with the synthetic nickel magnetite single crystals available in the prior art, the synthetic methods such as ammonia or carbonate coprecipitation method, microemulsion method, high-temperature solid sintering method, high-pressure hydrothermal synthesis method, metal alkoxide sol-gel method and freeze-drying method, the preparation method has obvious advantages such as simple operation process and short reaction time, and the obtained nickel magnetite single crystal has high purity, large size and stable chemical properties. Especially important is that the manganese content (2000-3000 ppm wt%) and water content (300-600 ppm) of the synthetic product of nickel magnetite are high, and the manganese content and water content can be completely controlled. The nickel magnetite single crystal particle size is large, and can completely meet the sample demand of conductivity, synchrotron X-ray diffraction, confocal Raman spectroscopy, vacuum Fourier transform infrared spectroscopy and other high-temperature and high-pressure single crystal mineral physical and spectral experimental simulation under high-temperature and high-pressure conditions on the diamond pressure chamber high-pressure equipment. The method provides important experimental sample guarantee for the measurement of physical property parameters of manganese-doped and high-water-content nickel magnetite single crystals, especially the research on the crystal lattice preferred orientation and crystal axis anisotropy of single crystal minerals under high pressure, and breaks through the technical bottleneck of the existing synthesis of nickel magnetite single crystals. DETAILED DESCRIPTION

[0053] A preparation method of manganese-doped and high-water-content nickel magnetite single crystals under high temperature and high pressure, comprising:

[0054] The solid light green basic nickel carbonate inorganic compound powder (purity: >99.99%), solid transparent reddish-brown flaky iron (III) citrate crystals (purity: >99.9%), solid oxalic acid powder (purity: >99.99%), solid pink manganese stearate powder (purity: >99.99%), solid nickel hydroxide powder (purity: >99%), solid natural manganese ore powder (purity: >99%) and liquid dilute nitric acid (concentration: 10%) are used as starting materials.

[0055] The high-purity solid basic nickel carbonate selected as the initial material in the application is a light green inorganic compound powder, which has stable chemical properties, is slightly soluble in water and soluble in dilute acid and ammonia water, and is mainly applied to the preparation and production of special cathode nickel-plated films, nickel salts and the like. In addition, it also has wide application in industrial pharmaceuticals, food additives and the like. The solid basic nickel carbonate powder is selected because of its stable performance and the superior characteristics of being easily soluble in dilute acid, and thus is an excellent raw material for providing nickel elements in the synthetic nickel magnetite.

[0056] The selected initial substance of high-purity solid-state iron (III) citrate is a transparent reddish-brown flaky crystal inorganic compound, insoluble in ethanol, soluble in water and dilute acid. As a typical edible citrate, iron (III) citrate can be used as iron fortifier, acidifier, nutritional supplement, etc. in the field of food science research, and can be used as radio pharmaceuticals for monitoring iron metabolism abnormalities and hematopoietic function in the field of medical research. The selection of iron (III) citrate crystal is because it can be easily decomposed and chemically reacted with dilute acid solution, and has the superior characteristics of strong chemical reactivity, so it is an excellent raw material for providing iron elements in artificial synthetic nickel magnetite.

[0057] The selected initial substance of high-purity solid-state oxalic acid is a metal chelating agent, and the purpose of the oxalic acid powder is to have a great influence on the bioavailability of minerals, and has a strong coordination function. When oxalic acid is combined with divalent nickel ions, the solubility can be greatly reduced, and then the complex sol of divalent nickel ions is formed in dilute nitric acid solution. At the same time, when oxalic acid is combined with transition metal cation manganese, due to its coordination function, a soluble transition metal cation complex is formed, and the solubility of divalent manganese metal cation in acid solution will be significantly enhanced, so that it is fully dissolved in dilute nitric acid solution.

[0058] The selected initial substance of high-purity solid-state nickel hydroxide belongs to a typical nickel-rich aqueous powder. When the temperature of nickel hydroxide is 230℃, a dehydration reaction occurs to generate nickel oxide, and a large amount of water is released. The selected initial substance of high-purity solid-state bixbyite belongs to a typical manganese-rich aqueous mineral. When the temperature of bixbyite is 300℃, a first dehydration reaction occurs to generate pyrolusite; when the temperature rises to 560℃, a second dehydration reaction occurs to generate manganese sesquioxide, and a large amount of water is released.

[0059] The selected initial substance of dilute nitric acid (concentration: 10%) is 60ml of 10% dilute nitric acid. If the concentration of nitric acid is too low, the solubility is limited, which may cause residual of basic nickel carbonate, iron (III) citrate, manganese stearate and oxalic acid powder. If the concentration of nitric acid is too high, the oxidation will be enhanced, which may cause rapid oxidation reaction or direct decomposition of basic nickel carbonate in the sample, and produce thick smoke, which may bring certain danger to the preparation.

[0060] Step 1, open the chemical fume hood, select a standard volume of 100ml volumetric flask, accurately weigh 60ml of 10% dilute nitric acid, put the glass transfer pipette in a 500ml notch beaker, move the liquid dilute nitric acid along the transfer pipette, and carefully move it all to the beaker. The notch beaker is selected as the reaction container mainly considering that after the beaker is covered on the glass surface, it is not completely sealed, and the generated gas can be easily volatilized in the fume hood.

[0061] Step 2, accurately weigh 5.0 grams of high purity light green basic nickel carbonate inorganic compound powder on a 10-microgram high-precision analytical balance, carefully add it to a 10% concentration of dilute nitric acid solution in a notch beaker, and place a magnetic stirring rotor.

[0062] Step 3, cover the notch beaker containing the dilute nitric acid solution with solid basic nickel carbonate powder with a glass surface dish, and place it on a high-temperature magnetic stirring hot plate in the fume hood. In order to fully dissolve the initial solid basic nickel carbonate powder in the dilute nitric acid solution and simultaneously cause hydrolysis and acidification reactions, the reaction conditions are room temperature, 700 rpm stirring speed, and reaction time of 72 hours.

[0063] Step 4, according to the stoichiometric ratio of nickel magnetite (Ni, Mn) Fe2O4, accurately weigh 19.5343 grams of high-purity solid iron (III) citrate crystals and 60 milligrams of high-purity solid manganese stearate powder on a high-precision analytical balance, and carefully add them to the dilute nitric acid solution containing basic nickel carbonate, respectively.

[0064] Step 5, cover the dilute nitric acid solution beaker containing solid basic nickel carbonate powder, solid iron (III) citrate crystals, and solid manganese stearate powder with a glass surface dish to ensure that the gases generated during the reaction are volatilized from the beaker notch, while avoiding the dilute nitric acid solution of the initial materials in the beaker from being splashed out during high-speed stirring, thereby causing danger and affecting the precision of nickel magnetite single crystal synthesis.

[0065] Step 6, place the beaker containing the sealed initial dilute nitric acid mixture and the magnetic stirring rotor in the fume hood on a high-temperature magnetic stirring hot plate at room temperature, 800 rpm stirring speed, and stirring time of 48 hours. Under these conditions, the initial solid basic nickel carbonate powder, solid iron (III) citrate crystals, and solid manganese stearate powder are completely dissolved in the dilute nitric acid solution mixture without any residue. At the same time, NH3·H2O, CH4, C2H2, CO2, CO, and H2 volatile substances are more easily volatilized in the fume hood.

[0066] Step 7, accurately weigh 2 grams of high purity solid oxalic acid powder on a high precision analytical balance, add high purity oxalic acid powder as an important metal chelating agent in the dilute nitric acid solution containing solid basic nickel carbonate powder, solid iron (III) citrate crystals and solid manganese stearate powder, the purpose of which is that the oxalic acid powder has a great influence on the bioavailability of minerals, has a strong coordination effect, when oxalic acid combines with divalent nickel ions, it can greatly reduce its solubility, and then form a complex sol of divalent nickel ions in dilute nitric acid solution; at the same time, when oxalic acid combines with divalent transition metal cation manganese, due to its coordination effect, it forms a soluble complex of divalent transition metal cation manganese, and the solubility of divalent manganese metal cation in acid solution will be significantly enhanced, so that it is fully dissolved in dilute nitric acid solution.

[0067] Step 8, place the gap beaker of the mixed solution on the high temperature magnetic stirring hot plate in the fume hood again, cover it with a glass surface dish, and set the condition parameters of the high temperature magnetic stirring hot plate at 80℃, 1000 rpm and stirring time of 36 hours, so that all the initial reagents form a uniform sol under the combined action of dilute nitric acid and oxalic acid mixed solution.

[0068] Step 9, remove the glass surface dish of the beaker, and adjust the temperature of the high temperature magnetic stirring hot plate to 110℃ until the mixed solution in the entire gap beaker is completely evaporated.

[0069] Step 10, take out the magnetic stirring rotor in the gap beaker on the high temperature magnetic stirring hot plate, and clean all the powder samples adhered to its surface into the beaker. Carefully take out all the mixed powder in the gap beaker with a medicine spoon and place it in a graphite crucible. The purpose of using a graphite crucible is that the carbon that constitutes the graphite crucible inevitably produces a certain concentration of carbon monoxide and carbon dioxide during high temperature calcination, thereby controlling the oxygen fugacity of the nickel magnetite sample in the graphite crucible, and finally realizing the valence of the valence metal cations nickel, iron and manganese of the nickel magnetite sample.

[0070] Step 11, place the graphite crucible containing the mixed powder into the muffle furnace under normal pressure and high temperature conditions, and raise the temperature to 1100℃ at a relatively low rate of 300℃ / hour, and keep the temperature constant for 5 hours. The purpose of the relatively slow high temperature calcination rate and the longer constant temperature time is to more favorably control the oxygen atmosphere in the graphite sample bin and more favorably remove the residual nitric acid, oxalic acid and other organic matter in the mixed powder.

[0071] Step 12, reduce the mixed sample powder in the graphite crucible in the muffle furnace to room temperature at a rate of 200℃ / hour, which is a relatively slow cooling rate compared to the heating rate, which is more likely to form a honeycomb-like loose sample powder, and carefully take out the mixed sample powder.

[0072] Step 13, the honeycomb loose nickel magnetite sample powder is placed in a superhard thick corundum mortar, and is fully ground for 1 hour to obtain a fine-grained and homogenized powder experimental sample.

[0073] Step 14, the homogenized and fine-grained nickel magnetite powder sample mixture is cold-pressed into 3 sample discs with a diameter of Φ10.0mm x 10.0mm by means of a high-precision tungsten carbide die of a stainless steel tablet press. The 3 cold-pressed sample mixtures are vertically stacked together and carefully placed at the bottom of a graphite crucible.

[0074] Step 15, two symmetrical circular holes with a diameter of 1.0mm are drilled on the wall of the graphite crucible containing the 3 stacked samples using a high-speed electric drill. A 0.5mm platinum-rhodium alloy wire is carefully threaded through the two 1.0mm symmetrical circular holes in the wall of the graphite crucible, and is suspended in the center of the high-temperature oxygen atmosphere furnace. The platinum-rhodium wire connected to the two ends of the graphite crucible is fixed to a vertical four-hole alumina tube with a hole diameter of 0.6mm and an outer diameter of 5.0mm and a length of 40cm. The upper end of the four-hole alumina tube is fixed in the center of the round cover that can be put into and pulled out of the furnace body at any time.

[0075] Step 16, a 3-liter stainless steel container containing secondary deionized pure cold water is placed on the side of the high-temperature oxygen atmosphere furnace in advance, which is used to quickly cool the sample by directly pulling it out of the high-temperature oxygen atmosphere furnace and immersing it in the 3-liter secondary deionized water in the cold water stainless steel container at a very high temperature, which is mainly to avoid the re-oxidation / reduction of the variable elements nickel, iron and manganese during the slow cooling process of the furnace body, to achieve rapid quenching of the sample and to completely retain the glassy nickel magnetite sample.

[0076] Step 17, at the top of the furnace body of the high-temperature oxygen atmosphere furnace, the argon inert gas cylinder, the proportionally adjustable carbon monoxide and carbon dioxide cylinders are connected to each other, the amount of gas introduced into the sample chamber is controlled by a manometer, and each gas can be switched and adjusted at any time by a valve during the high-temperature calcination process of the sample. In this invention, argon inert gas is used to provide an absolutely reducing oxygen atmosphere environment when the temperature of the furnace body is below 800℃.

[0077] The present application adopts the proportionally adjustable carbon monoxide and carbon dioxide, and aims to well control the oxygen fugacity in the high-temperature calcination process of the sample when the furnace temperature is higher than 800℃. When the furnace temperature is higher than 800℃, the continued introduction of argon inert gas will cause the over-reduction in the sample chamber, and will make the variable valence elements nickel, iron and manganese be reduced into metal nickel, iron and manganese in turn. Therefore, when the temperature is higher than 800℃, the proportionally adjustable carbon monoxide and carbon dioxide mixed gas is adopted to control the oxygen fugacity of the sample in the high-temperature oxygen atmosphere furnace chamber, and the reaction principle is that The arbitrary oxygen partial pressure in the sample chamber can be well adjusted, and the valence of the variable valence metal elements nickel, iron and manganese in the manganese-doped and high-water nickel magnetite single crystal can be controlled.

[0078] The highest rated temperature of the high-temperature oxygen atmosphere furnace is 1800℃. The circulating cooling water of the high-temperature oxygen atmosphere furnace is opened to reduce the temperature of the upper and lower furnace, and to avoid the high temperature of the whole furnace, which may cause the leakage of carbon monoxide and carbon dioxide, and thus causes danger.

[0079] The high-sensitivity argon, carbon monoxide and carbon dioxide concentration monitoring alarm is opened to avoid the gas leakage in the high-temperature calcination process of the oxygen atmosphere furnace, and to ensure the safety of the operator.

[0080] Step 18, the argon inert gas valve is opened, the pointer button controlled by the gas pressure gauge is rotated, and the gassing is continued for 30 minutes, and the purpose is to appropriately expel the excess air in the sample chamber. Under the protection of the argon inert gas, the sample is high-temperature calcined to 800℃ at a temperature rising rate of 400℃ / hour.

[0081] Step 19, after the temperature in the furnace is 800℃, the carbon monoxide gas cylinder and the carbon dioxide gas control valve are quickly switched, the pointer button controlled by the gas pressure gauge is rotated, and the volume ratio of the carbon monoxide and carbon dioxide passing through the sample oxygen atmosphere furnace reaches 4:1, and the purpose is that the carbon monoxide and carbon dioxide mixed gas with the volume ratio can well adjust the oxygen fugacity in the sample chamber in the high-temperature calcination process.

[0082] Step 20, after the mixed gas flow of carbon monoxide and carbon dioxide with a volume ratio of 4:1 to control the oxygen fugacity in the sample chamber reaches stability, which takes about 3-5 minutes, the temperature of the sample chamber in the furnace is increased to 1450℃ at a heating rate of 200℃ / hour, and the sample is calcined at constant temperature for 15 minutes to melt into glassy nickel-magnetite. During the heating process of the high-temperature oxygen atmosphere furnace, the sample chamber is subjected to two different heating rates of 400℃ / hour and 200℃ / hour in different temperature ranges of room temperature-800℃ and 800℃-1450℃, respectively. The present application applies a slower heating rate as the temperature of the sample chamber in the high-temperature oxygen atmosphere furnace increases, which is more conducive to the formation of strong ionic bonds such as Ni-O, Fe-O, and Mn-O in manganese-doped nickel-magnetite single crystals; it can more accurately control the temperature of the sample chamber in the high-temperature oxygen atmosphere furnace; and it can completely avoid the overheating of local areas in the furnace due to the imbalance of heat transfer in the sample chamber, thereby easily damaging the heating body of the oxygen atmosphere furnace.

[0083] The purpose of this high-temperature calcination process of carbon monoxide and carbon dioxide mixed gas controlled oxygen atmosphere is to provide purer nickel-magnetite glassy material for the synthesis of large-particle manganese-doped and high-hydrated nickel-magnetite single crystals; the high-temperature calcination under oxygen atmosphere can better control the valence of the variable valence metal elements nickel, iron, and manganese in the product; and the high calcination temperature of 1450℃ can ensure that the substances that may affect sample preparation, such as volatile substances, nitric acid, oxalic acid, and organic matter, are completely volatilized after high-temperature calcination in the muffle furnace.

[0084] The constant temperature calcination lasts for 15 minutes, and a relatively short calcination time is adopted because the nickel-magnetite powder will melt rapidly at a temperature higher than 1400℃. If the calcination time is too short, some residual initial powder may exist in the melted nickel-magnetite product, which seriously affects the chemical composition of the prepared nickel-magnetite sample; if the calcination time is too short, it is not conducive to the full chemical diffusion of metal cations such as nickel ions, iron ions, and manganese ions, nor is it conducive to the formation of stable chemical bonds of strong ionic bonds such as Ni-O, Fe-O, and Mn-O in nickel-magnetite; if the calcination time is too short, the doped manganese element will be distributed unevenly in the nickel-magnetite, thereby seriously affecting the preparation effect; and if the calcination time is too short, the density of the product will be reduced, making it difficult to form high-density nickel-magnetite glass. However, a calcination time higher than 15 minutes may lead to excessive melting, causing the nickel-magnetite sample to adhere firmly to the graphite crucible wall, which is difficult to clean and increases the cost of sample preparation.

[0085] Step 21, after the sample is kept at the temperature of 1450℃ for 15 minutes, the graphite crucible containing the sample, the four-hole alumina tube and the upper round cover of the furnace body are taken out of the furnace body and directly immersed in a 3-liter stainless steel container containing cold deionized water for rapid quenching of the nickel magnetite glass. The purpose of rapid quenching is to well preserve the glassy nickel magnetite sample with uniform composition at high temperature.

[0086] Step 22, the quenched glassy nickel magnetite sample is carefully taken out of the graphite crucible and ground in a corundum mortar to obtain fine and compositionally uniform sample powder. The glassy nickel magnetite powder is placed in a vacuum drying box at 200℃ for 12 hours.

[0087] Step 23, the nickel magnetite glass powder is cold-pressed into a cylindrical sample with a diameter of 4.0mm and a height of 10.0mm using a high-precision tungsten carbide die on a cold isostatic press. The cold-pressed nickel magnetite sample has a diameter of 4.0mm and a height of 4.0mm.

[0088] To obtain high-water-content nickel magnetite, we use a weight ratio of 4:1 of nickel hydroxide powder (molecular formula: Ni(OH)2) and natural hydroxymanganite powder (molecular formula: Mn(OH)2) as the water source. The mixture of nickel hydroxide and hydroxymanganite is chosen as the water source based on the following considerations: First, both nickel hydroxide and hydroxymanganite are typical water-containing substances with low dehydration temperatures. The dehydration temperature of nickel hydroxide is 230℃, while the two-step dehydration temperatures of manganese hydroxide are 300℃ and 560℃, respectively. Therefore, this dehydration temperature condition is within the lower temperature range of the process of preparing manganese-doped nickel magnetite single crystals under high temperature and high pressure, which ensures that the manganese-doped nickel magnetite single crystals are in a water environment for a long enough time to ensure the diffusion of lattice water and the formation of lattice occupation. Second, both nickel hydroxide and hydroxymanganite are rich in nickel and manganese, which can well control the nickel activity and manganese activity during the preparation of manganese-doped and high-water-content nickel magnetite single crystals under high temperature and high pressure. Finally, the dehydration products of the weight ratio of 4:1 of nickel hydroxide and natural hydroxymanganite placed at both ends of the sample are nickel oxide, manganite and manganese sesquioxide, which do not react with the sample, ensuring the purity of the manganese-doped and high-water-content nickel magnetite single crystal sample. In addition, by adjusting the weight ratio of nickel hydroxide and natural hydroxymanganite providing the water-containing substance and the corresponding height of the water source sheet, the water content in the manganese-doped nickel magnetite single crystal sample can be adjusted.

[0089] Step 24, in a cold isostatic press, the nickel hydroxide powder and the natural hydrohausmannite powder are cold-pressed into two pieces of water source sheet with a weight ratio of 4:1 by using a high-precision Φ4.0mm(diameter)×10.0mm tungsten carbide grinding tool.

[0090] Step 25, the cylindrical nickel magnetite sample (size: Φ4.0mm(diameter)×4.0mm(height)) and the two pieces of water source sheet (size: Φ4.0mm(diameter)×0.1mm(height)) are sequentially sealed in the experimental sample bin of the double-capsule structure of the inner sleeve-graphite tube (size: Φ4.4mm(outer diameter)×4.4mm(height), wall thickness of 0.2mm) and the outer sleeve-gold-palladium alloy tube (size: Φ4.6mm(outer diameter)×4.6mm(height), wall thickness of 0.1mm). In the present application, the manganese-doped nickel magnetite sample is placed in the middle of the graphite inner sleeve; and the two pieces of water source sheet of nickel hydroxide and natural hydrohausmannite with a weight ratio of 4:1 are placed symmetrically close to the sample at the two ends of the graphite inner sleeve.

[0091] In the present application, the inner sleeve of the double-capsule structure sample bin uses graphite as the sealing material, the main purpose of which is to control the oxygen fugacity value of the sample cavity within the controlled range of carbon monoxide and carbon dioxide, and ultimately to realize the valence state of the variable valence metal elements nickel, iron and manganese of the nickel magnetite sample.

[0092] The outer sleeve of the double-capsule structure sample bin in the present application uses gold-palladium alloy as the sealing material, the main purpose of which is: first, using gold-palladium alloy sealing to isolate the material or element exchange between the sample and other surrounding pressure transmission materials, effectively avoiding the pollution of the sample during the preparation of the nickel magnetite sample under high temperature and high pressure; second, using gold-palladium alloy sealing can effectively prevent water from escaping from the sample tube during the preparation of the nickel magnetite sample under high temperature and high pressure; finally, in the present application, the double-capsule structure sample bin composed of graphite tube and gold-palladium alloy tube forms a more airtight oxygen atmosphere environment, better controls the oxygen fugacity in the sample bin, and thus more effectively restricts the valence state of the variable valence metal elements nickel, iron and manganese of the nickel magnetite sample.

[0093] Step 26, nickel-magnetite is one of the important nickel-rich and iron-rich oxide minerals in the lower crust and upper mantle region of the Earth and other terrestrial planets. In order to truly simulate the growth environment of nickel-magnetite in the lower crust of the Earth and other terrestrial planets, and to reverse the temperature and pressure conditions for the stable existence of the nickel-magnetite mineral phase, a double capsule structure sample container composed of a graphite tube and a gold-palladium alloy tube was placed on a Kawai-1000t typical 6-8 type multi-faceted top large cavity high temperature and high pressure equipment in the laboratory. The pressure and temperature were set to 3.0 GPa and 1100°C, respectively, and the pressure and temperature were increased at a rate of 0.5 GPa / hour and 10°C / minute, respectively. The reaction time was 72 hours at constant temperature and pressure.

[0094] The preparation process of the high pressure of 3.0 GPa and the sintering temperature of 1100 DEG C selected by the application is completely designed based on the physical and chemical properties of the nickel magnetite itself. The specific purposes are as follows: first, the preparation process of the high temperature and high pressure conditions, the relatively slow pressure and temperature rising rate and the long constant temperature and constant pressure reaction time can completely ensure the complete mineral phase transformation from the initial nickel magnetite glass phase powder to the nickel magnetite crystal phase, and the final product of the nickel magnetite mineral phase can stably exist under the temperature and pressure conditions; second, the preparation process of the high temperature and high pressure conditions, the relatively slow pressure and temperature rising rate and the long constant temperature and constant pressure reaction time can significantly increase the self-diffusion and chemical diffusion coefficient of metal cations such as nickel ions, iron ions and manganese ions, so as to realize the isovalent substitution of manganese ions for metal nickel ions in the nickel magnetite crystal, and the reaction is complete and there is no free manganese element residue, and then a perfect transition metal element manganese doped nickel magnetite single crystal sample is formed; third, the preparation process of the high temperature and high pressure conditions, the relatively slow pressure and temperature rising rate and the long constant temperature and constant pressure reaction time can completely ensure the formation of stable chemical bonds such as Ni-O, Fe-O and Mn-O, so as to avoid the uneven distribution of the doped manganese element in the nickel magnetite, and then a uniform manganese doped nickel magnetite single crystal sample of isometric system is realized; fourth, the preparation process of the high temperature and high pressure conditions, the relatively slow pressure and temperature rising rate and the long constant temperature and constant pressure reaction time can make the combination of the nickel hydroxide and the water-containing substance of the natural hydroxylapatite of the weight ratio of 4:1 to have a dehydration reaction, and a large amount of water is generated, and the final dehydration product is a mixed oxide of nickel oxide and manganese sesquioxide, and at the same time, the water is fully diffused in the manganese doped nickel magnetite single crystal in the sample bin, and then the nickel magnetite sample has a high enough water content; finally, the preparation process of the high temperature and high pressure conditions, the relatively slow pressure and temperature rising rate and the long constant temperature and constant pressure reaction time can make the manganese element in the final preparation product of the nickel magnetite more uniformly distributed, and at the same time, the density, strength and particle size of the product are increased, so that a manganese doped nickel magnetite single crystal sample with uniform element distribution, high mechanical strength, large density and other superior physical and chemical properties is prepared.

[0095] The temperature is accurately calibrated by two groups of high-temperature tungsten-rhenium thermocouples. The tungsten-rhenium thermocouple has the advantages of good temperature-potential linear relationship, reliable thermal stability and low price, can realize the temperature calibration range of 0-2300 DEG C, and is widely used in the fields of high-pressure mineral physics experiment, high-new metallurgical industry, high-temperature electronic thermoelectric system structure engineering, space carrier, nuclear reactor and other fields of ultra-high temperature temperature calibration. Each group of tungsten-rhenium thermocouples is composed of two kinds of tungsten-rhenium alloys with different materials, and the chemical composition is W 95％ Re 5％ and W 74％ Re 26％The tungsten-rhenium thermocouple metal wires with a diameter of 0.1 mm are connected at one end and suspended into a spiral shape by using a bench clamp; the other end of the tungsten-rhenium thermocouple metal wires with a diameter of 0.1 mm is connected to the positive and negative poles of a high-power welding stabilized direct-current power source respectively. The output current control knob of the high-power welding stabilized direct-current power source is adjusted so that a larger current is passed through the metal wires, the spiral tungsten-rhenium high-temperature thermocouple wire is completely immersed in the saturated sodium chloride solution, is melted, and is welded into a spherical shape, and the oxide layer on the surface of the spherical thermocouple wire is removed. Two groups of hot tungsten-rhenium thermocouples are prepared by using the same technical scheme, and each group of tungsten-rhenium thermocouples is symmetrically arranged at the upper and lower ends of a double-capsule structure sample chamber composed of a graphite tube and a gold-palladium alloy tube. In the application, the tungsten-rhenium double thermocouples are arranged at the upper and lower ends of the sample chamber, which can not only realize accurate temperature calibration in the sample cavity but also accurately indicate the temperature gradient at the upper and lower ends of the sample chamber, so that the nickel-magnetite sample is ensured to be in a stable constant-temperature zone during the synthesis process.

[0096] Step 27, after the temperature is kept constant and the pressure is kept constant for 72 hours under the condition of 3.0 GPa and 1100 DEG C, the temperature in the sample cavity is reduced from 1100 DEG C to 800 DEG C at a cooling rate of 3 DEG C / minute, and the temperature is kept constant for 1 hour; then the temperature in the sample cavity is reduced from 800 DEG C to room temperature at a cooling rate of 5 DEG C / minute. By using the stepwise cooling and the heating rate (10 DEG C / minute) relative to the sample preparation, the superior physical and chemical properties of the manganese-doped nickel-magnetite single crystal sample with uniform manganese element distribution, high mechanical strength and large density are further improved by using a relatively slow constant-pressure cooling rate, the stress unevenness of the sample caused by the too fast cooling rate is completely avoided, the nickel-magnetite crystal is not cracked and damaged, and the preparation process is more beneficial to the crystal growth of the large-grain nickel-magnetite single crystal, so that the preparation of the large-grain nickel-magnetite single crystal sample with a size of 100 microns is realized.

[0097] Step 28, after the temperature in the sample cavity is reduced to room temperature, the pressure in the sample cavity is reduced from 3.0 GPa to normal pressure at a depressurization rate of 0.5 GPa / hour. In addition, in the application, the preparation process of the manganese-doped and high-hydrated nickel-magnetite single crystal sample obtained by hot-pressing sintering is pure and free of any impurities introduced from the sample itself and high-pressure sample assembly.

[0098] Step 29, after the high-temperature and high-pressure preparation reaction is completed, the sample is taken out from the Kawai-1000t typical 6-8 type multi-surface top large-cavity high-temperature and high-pressure equipment. The graphite tube and the gold-palladium alloy tube of the double-capsule structure sample chamber wrapping the sample are carefully removed, and the cylindrical sample is cut in half from the middle by using a high-precision diamond wire cutting instrument. The nickel-magnetite single crystal is selected under a 20-fold high-precision Olympus microscope.

[0099] The obtained nickel magnetite single crystal is a single phase without any other impurity phase; the electron probe (EPMA) detection result shows that the molecular formula of the obtained nickel magnetite single crystal is NiFe2O4; the multi-functional ion mass spectrometer (ICP-MS) detection result shows that the manganese content in the obtained nickel magnetite single crystal is 2419 ppm wt%; the vacuum Fourier transform infrared spectroscopy (FT-IR) detection result shows that the water content of the obtained nickel magnetite single crystal sample is 472 ppm wt, and the nickel magnetite single crystal has a relatively high water content.

[0100] The obtained manganese-doped and high-water-content nickel magnetite single crystal is of a cubic crystal system, the space group is Fd3m (no. 227), the lattice parameter is α = β = γ = 90°, and the unit cell volume is The average particle size is 162 microns, and the maximum particle size is 520 microns.

[0101] The obtained manganese-doped and high-water-content nickel magnetite single crystal has high purity, large particle size, stable chemical properties, high mechanical strength and other superior properties, and more importantly, the manganese content is high (2419 ppm wt%), and the manganese content in the nickel magnetite single crystal can be completely controlled. By changing the chemical reagent amount of the added initial solid high-purity manganese stearate powder from 49.5959 mg to 74.3940 mg, the corresponding manganese content in the obtained manganese-doped and high-water-content nickel magnetite single crystal sample can be finally realized from 2000 ppm wt% to 3000 ppm wt%; by changing the weight ratio of the water-containing substances nickel hydroxide powder and natural water manganese ore powder and adjusting the different heights of the corresponding two water source pieces, the total water amount generated by the dehydration reaction of the water-containing substances in the sample bin of the double-capsule structure composed of the graphite tube and the gold-palladium alloy tube can be controlled, and finally the water content in the nickel magnetite sample can be adjusted. The obtained manganese-doped and high-water-content nickel magnetite single crystal can completely meet the needs of physical experiment simulation of minerals in the lower crust and upper mantle of the earth and other terrestrial planets under high temperature and high pressure conditions, and breaks through the technical bottleneck of the existing nickel magnetite single crystal synthesis, and provides important experimental sample support for the study of the lattice preferred orientation and the anisotropy of the crystal axis of the single crystal mineral in the lower crust and upper mantle of the earth and other terrestrial planets under high temperature and high pressure conditions.

Claims

1. A method for producing a manganese-doped and high-hydrated nickel-magnetite single crystal under high temperature and high pressure, characterized by: The method comprises: using light green solid basic nickel carbonate inorganic compound powder, transparent red-brown solid flaky iron (III) citrate crystals, solid oxalic acid powder, solid pink manganese stearate powder, solid nickel hydroxide powder, solid natural manganese ore powder, and liquid dilute nitric acid as starting materials to prepare a nickel magnetite powder sample mixture disc; the nickel magnetite powder sample mixture disc is calcined and quenched in a high-temperature oxygen atmosphere furnace to prepare a cylindrical nickel magnetite sample; the water source sheet is placed at both ends of the cylindrical nickel magnetite sample, and then the two are sealed together for high-temperature and high-pressure reaction to obtain a nickel magnetite single crystal; the method for preparing the cylindrical nickel magnetite sample after the nickel magnetite powder sample mixture disc is calcined and quenched in a high-temperature oxygen atmosphere furnace comprises: Step 15, place three sample discs on the bottom of a graphite crucible, and open symmetrical circular holes on the wall of the graphite crucible; use platinum-rhodium alloy wire to hang in the middle of the high-temperature oxygen atmosphere furnace through the symmetrical circular holes on the wall of the graphite crucible; connect the platinum-rhodium wire at both ends of the graphite crucible to the vertical four-hole alumina tube, and fix the upper end of the four-hole alumina tube in the middle of the circular cover of the furnace body; Step 16, place a stainless steel container containing secondary deionized pure cold water on the side of the high-temperature oxygen atmosphere furnace; Step 17, connect the top of the furnace body of the high-temperature oxygen atmosphere furnace with the argon inert gas cylinder, the proportionally adjustable carbon monoxide and carbon dioxide cylinders; Step 18, open the valve of the argon inert gas cylinder for 30 minutes of continuous inflation; under the protection of argon inert gas, the sample is high-temperature calcined at a temperature increasing rate of 400 °C / hour to 800 °C; Step 19, after the temperature in the furnace body reaches 800 °C, switch the carbon monoxide and carbon dioxide gas control valves to make the volume ratio of carbon monoxide and carbon dioxide in the sample oxygen atmosphere furnace reach 4:1; Step 20, after the mixed gas flow with a volume ratio of 4:1 of carbon monoxide and carbon dioxide controls the oxygen fugacity in the sample bin, increase the temperature of the sample bin in the furnace body to 1450 °C at a temperature increasing rate of 200 °C / hour, and constant temperature roasting for 15 minutes; Step 21, after the sample is constant temperature roasted at 1450 °C for 15 minutes, pull out the graphite crucible containing the sample, the four-hole alumina tube, and the upper circular cover of the furnace body from the furnace body, and directly immerse them in the stainless steel container containing secondary deionized pure cold water to quench into a glassy nickel magnetite sample; Step 22, take out the quenched glassy nickel magnetite sample from the graphite crucible and place it in a corundum mortar for grinding to form fine and composition-uniform glassy nickel magnetite powder; the glassy nickel magnetite powder is placed in a vacuum drying box under the condition of 200 °C for drying for 12 hours; Step 23, use tungsten carbide molds to cold-press the nickel magnetite glass powder on a cold isostatic pressing machine to form a cylindrical nickel magnetite sample with a diameter of Φ 4.0 mm and a height of 4.0 mm.

2. The method of claim 1, wherein the method is characterized by: Solid light green basic nickel carbonate inorganic compound powder purity > 99.99%, solid transparent reddish-brown flaky iron (III) citrate crystals purity > 99.9%, solid oxalic acid powder purity > 99.99%, solid pink stearic acid manganese powder purity > 99.99%, solid nickel hydroxide powder purity > 99%, solid natural manganese ore powder purity > 99%, and liquid dilute nitric acid concentration 10%.

3. The method of claim 1, wherein the method is characterized by: The sample disc preparation method comprises: Step 1, weigh 60 milliliters of dilute nitric acid with a concentration of 10% into a notch beaker; Step 2, weigh 5.0 grams of light green basic nickel carbonate inorganic compound powder into the notch beaker, and put a magnetic stirring rotor into the notch beaker; Step 3, cover the notch beaker with a glass surface dish, and place the notch beaker on a high-temperature magnetic stirring hot plate in the fume hood, and react at a speed of 700 revolutions / minute at room temperature for 72 hours; Step 4, according to the stoichiometric ratio of nickel magnetite (Ni, Mn) Fe2O4, weigh 19.5343 grams of solid iron (III) citrate crystals and 60 milligrams of solid stearic acid manganese powder into the dilute nitric acid solution containing the basic nickel carbonate; Step 5, cover the notch beaker with a glass surface dish; Step 6, place the notch beaker on a high-temperature magnetic stirring hot plate in the fume hood, and stir at a speed of 800 revolutions / minute at room temperature for 48 hours; Step 7, weigh 2 grams of solid oxalic acid powder into the notch beaker; Step 8, place the notch beaker on the high-temperature magnetic stirring hot plate in the fume hood, cover it with a glass surface dish, and stir at a speed of 1000 revolutions / minute at 80 °C for 36 hours; Step 9, remove the glass surface dish of the beaker, and adjust the temperature of the high-temperature magnetic stirring hot plate to 110 °C until the mixed solution in the entire notch beaker is completely evaporated; Step 10, take out the mixed powder in the notch beaker and place it in a graphite crucible; Step 11, place the graphite crucible containing the mixed powder into a muffle furnace, increase the temperature to 1100 °C at a heating rate of 300 °C / hour, and keep the temperature constant for 5 hours; Step 12, reduce the temperature of the mixture powder to room temperature at a cooling rate of 200 °C / hour, and take out the mixture powder; Step 13, place the mixture powder in a thick corundum mortar and grind for 1 hour to obtain a nickel magnetite powder sample mixture; Step 14, cold-press the nickel magnetite powder sample mixture into a sample disc with a diameter of Φ 10.0 mm and a thickness of 3.0 mm by means of a tungsten carbide mold of a stainless steel tablet press, and obtain three sample discs.

4. The method of claim 1, wherein the method is characterized by: The method for placing the water source disc at both ends of the cylindrical nickel magnetite sample and then sealing them together for high-temperature and high-pressure reaction to obtain a nickel magnetite single crystal comprises: Step 24, on a cold isostatic pressing machine, cold-press nickel hydroxide powder and natural manganese ore powder into two water source discs with a diameter of Φ 4.0 mm and a height of 0.1 mm by means of a tungsten carbide mold according to a weight ratio of 4:

1. Step 25, seal the cylindrical nickel magnetite sample and two pieces of water source sheet in the experimental sample container of double capsule structure of inner layer sleeve-graphite tube; the cylindrical nickel magnetite sample is placed in the middle of the graphite inner layer sleeve; the two pieces of water source sheet are placed close to the symmetric two ends of the sample of the graphite inner layer sleeve; the outer layer sleeve of the double capsule structure sample container uses gold-palladium alloy as the sealing material; Step 26, place the double capsule structure sample container composed of graphite tube and gold-palladium alloy tube in the laboratory Kawai-1000t typical 6-8 type multi-faceted top large cavity high temperature and high pressure equipment, set the pressure increasing rate and temperature increasing rate to be 0.5 GPa / hour and 10 °C / minute respectively, heat and press sinter under the conditions of pressure and temperature of 3.0 GPa and 1100 °C respectively, and the reaction time is 72 hours of constant temperature and constant pressure; Step 27, after 72 hours of constant temperature and constant pressure under the conditions of 3.0 GPa and 1100 °C, reduce the temperature in the sample cavity from 1100 °C to 800 °C at a cooling rate of 3 °C / minute, and keep constant temperature for 1 hour; then reduce the temperature in the sample cavity from 800 °C to room temperature at a cooling rate of 5 °C / minute; Step 28, after the temperature in the sample cavity is reduced to room temperature, reduce the pressure in the sample cavity from 3.0 GPa to normal pressure at a depressurization rate of 0.5 GPa / hour; Step 29, after the high temperature and high pressure preparation reaction is completed, take out the sample from the Kawai-1000t typical 6-8 type multi-faceted top large cavity high temperature and high pressure equipment; remove the graphite tube and gold-palladium alloy tube of the double capsule structure sample container wrapping the sample, cut the cylindrical sample in the middle; under the 20 times high-precision Olympus microscope, select the nickel magnetite single crystal.

5. The method for preparing manganese-doped and high-water-content nickel magnetite single crystals under high temperature and high pressure according to claim 1, characterized in that: During the high temperature and high pressure reaction, the temperature was calibrated by two groups of high temperature resistant tungsten-rhenium thermocouples. Each group of tungsten-rhenium thermocouples is composed of two tungsten-rhenium alloys with different materials, and the chemical composition is W 95% Re 5% and W 74% Re 26% ; the tungsten-rhenium thermocouples are respectively installed at the upper and lower ends of the sample bin.