A method for preparing a nickel-doped and high-hydrated monoclinic cobalt-chromite ore under high temperature and high pressure

Abstract

The application discloses a preparation method of a nickel-doped and high-hydrated cobalt-chromium-iron ore monocrystal under high temperature and high pressure, and the method comprises the following steps: preparing a cylindrical cobalt-chromium-iron ore sample by taking solid basic cobalt carbonate powder, solid chromium (III) acetate hydroxide crystal powder, solid nickel stearate, solid oxalic acid powder, solid chromium hydroxide powder, solid nickel hydroxide powder and liquid dilute nitric acid as starting raw materials; preparing water source sheets by taking chromium hydroxide powder and nickel hydroxide powder in a weight ratio of 4:1; placing two water source sheets at two ends of the cylindrical cobalt-chromium-iron ore sample respectively and then putting them into a double-capsule structure sample bin; and obtaining a cobalt-chromium-iron ore monocrystal after high-temperature and high-pressure reaction, so that the blank of the preparation technology of the nickel-doped and high-hydrated cobalt-chromium-iron ore large-grain monocrystal under the current high-temperature and high-pressure condition is solved, and the experimental sample of the nickel-doped and high-hydrated cobalt-chromium-iron ore large-grain monocrystal is obtained.

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 nickel-doped and high-hydrated cobalt-chromic iron ore single crystals under high temperature and high pressure. BACKGROUND

[0002] Generally, geologists divide spinel group minerals according to the difference of the B-site cations occupying the octahedral sites in the general formula (AB2O4) of spinel group minerals: (1) when the lattice B is occupied by trivalent aluminum ions, it is called spinel sub-group minerals, and the typical end-member components of spinel minerals mainly include: spinel (crystal chemical formula: MgAl2O4), hercynite (crystal chemical formula: FeAl2O4), manganosite (crystal chemical formula: MnAl2O4), gahnite (crystal chemical formula: ZnAl2O4) and the like; (2) when the lattice B is occupied by trivalent iron ions, it is called magnetite sub-group minerals, and the typical end-member components of spinel minerals mainly include: magnetite (crystal chemical formula: Fe3O4), magnesioferrite (crystal chemical formula: MgFe2O4), manganosite (crystal chemical formula: MnFe2O4), germanate magnetite (crystal chemical formula: GeFe2O4), nickel magnetite (crystal chemical formula: NiFe2O4), zinc ferrite (crystal chemical formula: ZnFe2O4), copper ferrite (crystal chemical formula: CuFe2O4) and the like; (3) when the lattice B is occupied by trivalent chromium ions, it is called chromite sub-group minerals, and the typical end-member components of spinel minerals mainly include: chromite (crystal chemical formula: FeCr2O4), magnesiochromite (crystal chemical formula: MgCr2O4), nickel chromite (crystal chemical formula: NiCr2O4), manganochromite (crystal chemical formula: MnCr2O4), cobalt chromite (crystal chemical formula: CoCr2O4) and the like; (4) when the lattice B is occupied by trivalent vanadium ions or divalent iron ions, it is called titanomagnetite sub-group minerals, and the typical end-member components of spinel minerals mainly include: vanadium magnetite (crystal chemical formula: FeV2O4), titanomagnetite (crystal chemical formula: TiFe2O4), linwoodite (crystal chemical formula: SiFe2O4) and the like, which are four main types of spinel. The classification and naming method of this spinel group mineral not only covers 2-3 type structure spinel such as magnesiochromite, manganosite, zinc chromite and the like, but also covers 4-2 type structure spinel such as linwoodite, titanomagnetite and the like, which is the most scientific among the numerous classifications and names of spinel group minerals so far. As an important end-member component of the chromite sub-group of spinel group minerals, cobalt chromite has a crystal chemical formula of CoCr2O4, and is a 2-3 type structure spinel group oxide mineral rich in cobalt and chromium. The percentage of cobalt chromite mineralogical oxide chemical composition can be expressed as: CoO / (CoO+Cr2O3) = 33% and Cr2O3 / (CoO+Cr2O3) = 67%. Due to the relatively high content of chromium in cobalt chromite, cobalt chromite is an important raw material for industrial preparation of chromium.Generally, the cobalt-chromite is a typical oxide mineral with a spinel structure in nature. In the corresponding unit cell, the cobalt-chromite with an inverse spinel structure has a cubic closest packing ratio of 0, which shows obvious physical and chemical characteristics of the spinel structure.

[0003] Generally, the natural cobalt-chromite exposed in nature shows physical and optical characteristics of complete extinction in the laboratory orthogonal polarized light microscopic observation, that is, homogeneous minerals, and the cobalt-chromite crystal is an opaque, black, metallic luster, shell-shaped fracture, greenish gray streak and equiaxed mineral homogeneous body. The natural cobalt-chromite is often associated with nickel-containing oxide minerals and silicate minerals such as awaruite, nickel-chromite, nickeliferous olivine, etc., and is mainly produced in the contact zone of quartzite and serpentinized ultramafic rock, and is formed by replacing chromite in platy niobite. The Barberton-Makhonjwa Mountains in the northeastern region of the Republic of South Africa expose the oldest geological tectonic unit in the world so far, the Capwal Craton geological body. The main stratigraphic era of the surface exposed rock in this area is the Paleoarchean, covering the mixed gneiss complex of 3.8 billion years ago and the volcanic sedimentary green schist layer of 3.4-3.1 billion years ago. Through mineral crystal composition chemical analysis, geoscientists found cobalt-chromite single crystal minerals in the Barberton greenstone belt rock body of the Capwal Craton geological body in South Africa. In addition, cobalt-rich cobalt-chromite single crystal mineral inclusions were also found in sapphire single crystals from the Bopha Rai County in the central region of Thailand. Geologists carefully selected 20 sapphire single crystal particles from the Bopha Rai County, and used micro-area electron probe and proton accelerator mass spectrometry analysis to find that the cobalt-chromite single crystal existed in the center of the gem-grade sapphire mineral inclusion. The crystal shows a good euhedral shape and is associated with cobalt spinel, while the cobalt-chromite single crystal is wrapped by glass phase dark minerals, and the whole inclusion is about 200 microns in size. Further research has confirmed that in addition to the discovery of cobalt-rich cobalt-chromite single crystal mineral inclusions in sapphire single crystals from the Bopha Rai County in the central region of Thailand, potassium feldspar inclusions, Na-Mg-Al-rich hornblende inclusions and pyrrhotite inclusions were also found. The paragenetic mineral assemblage of cobalt-chromite, cobalt spinel and glass phase dark minerals in the inclusions indicates that the region has experienced a series of complex geological processes such as lower crust basalt magma dominated thermal alteration and magma mixing.

[0004] Nickel element, located in the fourth period of the periodic table of elements, the transition group of ferromagnetic metal elements, the main valence is 0, +2, +3 and +4. In nature, usually nickel element with iron element, is a kind of typical iron element, mainly exists in basic rock, super basic rock and the core, the common iron element mainly includes: nickel, titanium, iron, vanadium, chromium, manganese, cobalt, platinum group elements, etc. In the crystal structure of cobalt-chromite, the transition group of ferromagnetic metal nickel, can easily occupy the tetrahedral position, and then form the isomorphism substitution of A site divalent cation. Because in the crystal structure of cobalt-chromite, the metal cobalt element and the doped transition group of ferromagnetic metal nickel in the lattice position have the same positive divalent, so the isomorphism substitution belongs to equivalent isomorphism substitution. The transition group of ferromagnetic metal nickel with high purity has good ductility, high temperature resistance, oxidation resistance, corrosion resistance, easy processing and other superior physical and chemical properties, so it is widely used in mechanical manufacturing, fine chemical industry, high resistance alloy, aerospace, weapon manufacturing, special steel, precision electronic devices and many other core fields of manufacturing and industrial production of important raw materials, so it has been listed as a key strategic resource by many countries such as China, the United States and the European Union. The existing key strategic resource mineral resources research shows that the top ten countries of nickel mineral resources reserves in the world include: Australia, Brazil, Russia, New Caledonia, Cuba, Philippines, Indonesia, South Africa, China and Canada, the amount of nickel resources accounts for 90% of the total reserves of nickel mineral resources in the world, and China ranks ninth, the reserves of nickel resources account for less than 3%, which belongs to "less nickel" mineral resources country. In China, the distribution of nickel mineral resources is relatively concentrated, and the reserves in Gansu Province rank first, accounting for more than 2 / 3 of the total nickel resources in China. The metal nickel sulfide ore in Jinchuan County, Gansu Province, produced from Caledonian to late Indosinian, is the most famous. As a mineral resource, the land-based nickel mineral resources available for mining mainly include: nickel sulfide ore and laterite nickel ore. The resources of laterite nickel ore account for about 60% of the total reserves of nickel resources in the world, and the resources of nickel sulfide ore account for about 40% of the total reserves of nickel resources in the world.

[0005] The molecular structure of cobalt-chromic spinel does not contain water molecules or hydroxyl groups, and shows obvious nominal anhydrous mineral properties. However, previous studies on the water solubility of spinel under high temperature and high pressure conditions show that the amount of water dissolved in 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℃). Existing experimental studies on the 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 trace amounts of water in nominally anhydrous minerals can increase the physical and spectroscopic properties of minerals and rocks by several orders of magnitude, and have a very important influence on their mineral physics properties. Looking at the artificial synthesis of cobalt-chromic spinel in the field of laboratory materials science, the main methods include: high-temperature solid-phase reaction method, polymer gel method, carbonate chemical co-precipitation method, metal alkoxide sol-gel method, freeze-drying method, ammonia chemical co-precipitation method, microemulsion method, high-energy ball milling method, inorganic salt sol-gel method, and high-pressure powder hydrothermal method. Due to these existing synthesis techniques, most of which use simple solution chemical reactions or direct physical grinding of sample powders, followed by high-temperature sintering, they are more suitable for preparing nanoscale cobalt-chromic spinel crystals. In the field of high temperature and high pressure experimental earth science research, micron-sized or larger particle mineral single crystal experimental samples are usually required. Obviously, the nanoscale cobalt-chromic spinel samples obtained by previous material synthesis methods do not meet the minimum particle size requirement. So far, there is no effective synthesis method. More earth science researchers usually use natural cobalt-chromic spinel samples to replace artificial samples to meet the needs of high temperature and high pressure experimental earth science research. However, these natural samples have the disadvantage of uneven distribution of transition group ferromagnetic metal element nickel. Therefore, it is particularly urgent to effectively synthesize a large particle nickel-doped and high-water cobalt-chromic spinel single crystal that meets the needs of various high temperature and high pressure laboratory simulation earth science research, especially the study of cobalt-chromic spinel single crystal lattice preferred orientation and crystal axis anisotropy under high pressure. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a method for preparing a nickel-doped and high-water cobalt-chromic spinel single crystal under high temperature and high pressure, to solve the current technical blank of preparing a large particle nickel-doped and high-water cobalt-chromic spinel single crystal under high temperature and high pressure, and to obtain a large particle nickel-doped and high-water cobalt-chromic spinel single crystal experimental sample.

[0007] The technical solution of the present application is:

[0008] A method for preparing a nickel-doped and high-hydrated cobalt-chromium spinel single crystal under high temperature and high pressure, the method comprising: preparing a cylindrical cobalt-chromium spinel sample with solid basic cobalt carbonate powder, solid chromium (III) acetate hydroxide crystalline powder, solid nickel stearate, solid oxalic acid powder, solid chromium hydroxide powder, solid nickel hydroxide powder and liquid dilute nitric acid as starting materials; preparing a water source sheet with chromium hydroxide powder and nickel hydroxide powder in a weight ratio of 4:1; placing two water source sheets at both ends of the cylindrical cobalt-chromium spinel sample and then putting them into a double capsule structure sample bin; and then performing a high temperature and high pressure reaction to obtain a cobalt-chromium spinel single crystal.

[0009] The purity of the solid basic cobalt carbonate powder is >99.99%, the purity of the solid chromium (III) acetate hydroxide crystalline powder is >99.99%, the purity of the solid nickel stearate is >99.99%, the purity of the solid oxalic acid powder is >99.99%, the purity of the solid chromium hydroxide powder is >99%, the purity of the solid nickel hydroxide powder is >99%, and the concentration of the liquid dilute nitric acid is 10%.

[0010] The method for preparing the cylindrical cobalt-chromium spinel sample comprises:

[0011] Step 1, weigh 60 milliliters of dilute nitric acid with a concentration of 10% into a notch beaker;

[0012] Step 2, weigh 5.0 grams of solid basic cobalt carbonate powder into the notch beaker and put a magnetic stirring rotor into the notch beaker;

[0013] Step 3, cover the notch beaker with a glass surface dish, and place it on a high-temperature magnetic stirring hot plate in a fume hood, and react at a speed of 700 revolutions per minute for 72 hours at room temperature;

[0014] Step 4, according to the stoichiometric ratio of cobalt-chromium spinel (Co, Ni) Cr2O4, weigh 18.8038 grams of solid chromium (III) acetate hydroxide crystalline powder and 250 milligrams of nickel stearate powder into the notch beaker, respectively;

[0015] Step 5, cover the notch beaker with a glass surface dish;

[0016] Step 6, place the notch beaker covered with a glass surface dish on a high-temperature magnetic stirring hot plate in a fume hood, and react at a speed of 800 revolutions per minute for 48 hours at room temperature;

[0017] Step 7, weigh 2 grams of solid oxalic acid powder into the notch beaker;

[0018] Step 8, place the notch beaker again on the high-temperature magnetic stirring hot plate in the fume hood, cover it with a glass surface dish, and set the condition parameters of the high-temperature magnetic stirring hot plate to 80°C, 1000 revolutions per minute for 36 hours;

[0019] Step 9, remove the glass surface dish of 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 completely evaporated;

[0020] Step 10, remove the magnetic stirring rotor, and clean all the surface-bonded powder samples into the beaker, and use a medicine spoon to take out all the mixed powder in the beaker and put it into a graphite crucible;

[0021] Step 11, place the graphite crucible containing the mixed powder into the muffle furnace under normal pressure conditions, and increase the temperature to 1100°C at a rate of 300°C / hour, and keep the temperature constant for 5 hours;

[0022] Step 12, reduce the temperature of the mixture powder in the muffle furnace to room temperature at a rate of 200°C / hour, and take out the mixture sample powder;

[0023] Step 13, place the mixture sample powder in a corundum mortar and grind for 1 hour to obtain a cobalt-chromium-iron ore powder sample mixture;

[0024] Step 14, cold-press the cobalt-chromium-iron ore powder sample mixture into 3 sample discs of Φ10.0mm×3.0mm, and vertically stack the 3 cold-pressed sample mixtures together and place them at the bottom of the graphite crucible;

[0025] Step 15, hang the graphite crucible on the central axis of the high-temperature oxygen atmosphere furnace, and connect the two ends of the platinum-rhodium wire of the graphite crucible to the vertical four-hole alumina tube, and fix the upper end of the four-hole alumina tube to the center of the round cover that can be put into and pulled out of the furnace body at any time;

[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 argon inert gas cylinder, the proportionally adjustable carbon monoxide and carbon dioxide cylinders to the top of the high-temperature oxygen atmosphere furnace;

[0028] Step 18, open the argon inert gas valve for 30 minutes, and 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°C, switch the control valves of the carbon monoxide and carbon dioxide cylinders to make the volume ratio of carbon monoxide and carbon dioxide in the sample oxygen atmosphere furnace reach 4:1;

[0030] Step 20, further increase the temperature of the sample chamber in the furnace body to 1550°C at a rate of 200°C / hour, and keep the temperature constant for 15 minutes to melt the cobalt-chromium-iron ore into a glassy state;

[0031] Step 21, after the sample is baked at a temperature of 1550℃ for 15 minutes, the graphite crucible containing the sample, the four-hole alumina tube and the upper round cover of the furnace body are pulled out of the furnace body and directly immersed in a stainless steel container for quenching into a cobalt-chromium-iron ore glass;

[0032] Step 22, the quenched cobalt-chromium-iron ore glass is taken out of the graphite crucible, ground into fine particles and a sample powder with uniform composition in a corundum mortar, and the sample powder is placed in a vacuum drying box at a temperature of 200℃ for drying for 12 hours;

[0033] Step 23, the cobalt-chromium-iron ore glass sample powder is cold-pressed into a cylindrical cobalt-chromium-iron ore sample with a diameter of 4.0mm and a height of 4.0mm on a cold isostatic pressing machine using a tungsten carbide die.

[0034] The preparation method of the water source sheet is as follows:

[0035] Step 24, the chromium hydroxide powder and the nickel hydroxide powder are cold-pressed into two water source sheets with a diameter of 4.0mm and a height of 0.1mm on a cold isostatic pressing machine using a tungsten carbide die with a diameter of 4.0mm and a height of 10.0mm at a weight ratio of 4:1.

[0036] The method for obtaining a cobalt-chromium-iron ore single crystal after placing the two water source sheets at the two ends of the cylindrical cobalt-chromium-iron ore sample and then performing a high-temperature and high-pressure reaction includes the following steps:

[0037] Step 25, the cylindrical cobalt-chromium-iron ore sample is placed in the middle of the graphite inner layer sleeve of the double-capsule structure, and the two water source sheets are placed at the symmetric ends of the sample close to the sample; the inner layer sleeve of the experimental sample chamber of the double-capsule structure is a graphite tube, and the outer layer sleeve is a gold-palladium alloy tube;

[0038] Step 26, the sample chamber of the double-capsule structure is placed on a typical 6-8 type multi-faceted top large-cavity high-temperature and high-pressure equipment in the laboratory Kawai-1000t, and the pressure and temperature increasing rates are set to 0.5GPa / hour and 10℃ / minute respectively, the pressure and temperature are increased to 3.0GPa and 1150℃ respectively for hot-pressing sintering, and the reaction time is 72 hours at constant temperature and pressure;

[0039] Step 27, the temperature in the sample cavity is reduced from 1150℃ to 800℃ at a cooling rate of 3℃ / minute, and kept constant for 1 hour; then the temperature in the sample cavity is reduced from 800℃ to room temperature at a cooling rate of 5℃ / minute;

[0040] Step 28, after the temperature in the sample cavity is reduced to room temperature, the pressure in the sample cavity is reduced from 3.0GPa to normal pressure at a depressurization rate of 0.5GPa / hour;

[0041] After the high temperature and high pressure preparation reaction is completed, the sample is taken out, the graphite tube and the gold-palladium alloy tube wrapping the sample are removed, the cylindrical sample is cut in the middle by using a diamond wire cutting instrument, and a single crystal of cobalt-chromium-iron ore is selected under an Olympus microscope with 20 times.

[0042] During the high temperature and high pressure reaction, two groups of 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％ ; each group of tungsten-rhenium thermocouples is symmetrically arranged at the upper and lower ends of the double capsule structure sample bin composed of the graphite tube and the gold-palladium alloy tube.

[0043] The present application has the beneficial effects that:

[0044] The present application has the beneficial effects that:

[0045] 2CoCO3·3Co(OH)2·H2O+10HNO3→5Co(NO3)2+2CO2+9H2O3Co(NO3)2+2[Cr3(OH)2(OOCCH3)7]→3CoCr2O4+6(NH3·H2O)+4CH4+

[0046] 8CO2+16CO

[0047] CoCr2O4+C 36 H 70 NiO4→(Co,Ni)Cr2O4+17C2H2+2CO2+18H2

[0048] 2Cr(OH)3→Cr2O3+3H2O

[0049] Ni(OH)2→NiO+H2O

[0050] The invention, the selected initial raw material solid state of the basic cobalt carbonate [chemical formula: 2CoCO3·3Co(OH)2·H2O] is a purple red prism-shaped powder material, which has stable chemical properties, is soluble in dilute acid, soluble in liquid ammonia and almost insoluble in cold water, and is easy to decompose in hot water, and the main product is cobalt trioxide. The basic cobalt carbonate is an important raw material for the preparation of industrial catalysts and cobalt salts, and as an industrial additive, it is mainly used in the fields of ceramic industry, colorant, electronic products, magnetic materials and the like. The purple red prism-shaped basic cobalt carbonate powder is an excellent raw material for providing cobalt elements in the artificial synthesis of cobalt-chromium-iron ore due to its stable performance and the superior characteristics of being easily soluble in dilute acid. The initial raw material solid state of chromium acetate (III) hydroxide [also known as: chromium acetate (III) hydroxide or basic chromium acetate, chemical formula: Cr3(OH)2(OOCCH3)7] is a light gray green to blue crystalline powder, which is stable in chemical properties at room temperature, does not decompose, is non-toxic and soluble in water. Chromium acetate (III) hydroxide can be used as an industrial production of high-purity metal chromium, certain glaze, colored glass and the like. The selected chromium acetate (III) hydroxide crystalline powder is an excellent raw material for providing chromium elements in the artificial synthesis of cobalt-chromium-iron ore due to its superior characteristics of being easily decomposed and chemically reactive in dilute acid solution. The initial raw material solid state of nickel stearate [also known as: nickel stearate, chemical formula: C 36 H 70NiO4] is a green wax-like organic compound, mainly used as a surfactant and a catalyst for the production of tertiary amines. Because the water chemical activity of nickel stearate is high and it is soluble in dilute nitric acid solution, nickel stearate is an excellent raw material for providing transition group ferromagnetic metal elements nickel in the artificial synthesis of cobalt-chromium-iron ore. The initial raw material solid-state chromium hydroxide [molecular formula: Cr(OH)3] belongs to a typical gray-green chromium-containing aqueous powder substance, which can react with acid and strong base to produce corresponding chromium salt and water, showing the physical and chemical properties of a clear amphoteric hydroxide, which can be used for industrial production and raw material processing of trivalent chromium salt, chromium sesquioxide, chromium pigment, etc. Generally, chromium hydroxide undergoes dehydration reaction at a temperature of 500 DEG C, and the product is green chromium oxide (chrome green), while a large amount of water is released. The selected initial raw material solid-state nickel hydroxide [molecular formula: Ni(OH)2] belongs to a typical nickel-rich powder-like aqueous substance, and nickel hydroxide undergoes dehydration reaction at a temperature of 230 DEG C to generate nickel oxide (NiO), while a large amount of water is released, and the aqueous mineral nickel hydroxide undergoes complete dehydration at a temperature of 450 DEG C. In the high-pressure sample chamber, the chromium hydroxide and nickel hydroxide containing aqueous substances in a certain ratio are placed, and dehydration reaction occurs under high temperature and high pressure conditions to produce a large amount of water, which provides a good water source for synthesizing nickel-doped and high-aqueous cobalt-chromium-iron ore single crystals. In the chemical reaction product involved in the present application, NH3·H2O, CH4, C2H2, CO2, CO and H2 are all high-temperature volatile substances.

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

[0052] Compared with the synthetic cobalt-chromite monocrystal that can be seen in the prior art, the synthetic method of the present application has obvious advantages such as simple operation process and short reaction time, and the obtained cobalt-chromite monocrystal has superior physical and chemical properties such as high purity, large size and stable chemical properties. More importantly, the synthetic product of cobalt-chromite has high nickel content (8000-9000 ppm wt%) and high water content (400-500 ppm), and the nickel content and water content can be completely controlled. The cobalt-chromite monocrystal has large particle size, and can completely meet the sample requirements 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 nickel-doped and high-water cobalt-chromite monocrystal, especially the research on the 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 cobalt-chromite monocrystal. DETAILED DESCRIPTION

[0053] The preparation method of the present application specifically comprises:

[0054] The present application uses solid purple prismatic basic cobalt carbonate powder (purity: >99.99%), solid acetic acid (III) hydroxide crystal powder (purity: >99.99%), solid nickel stearate (purity: >99.99%), solid oxalic acid powder (purity: >99.99%), solid chromium hydroxide powder (purity: >99%), solid nickel hydroxide powder (purity: >99%) and liquid dilute nitric acid (concentration: 10%) as starting materials.

[0055] The high-purity solid basic cobalt carbonate selected as the initial material in the present application is a purple prismatic powder material, which has stable chemical properties, is soluble in dilute acid, soluble in liquid ammonia and almost insoluble in cold water, and is prone to decomposition reaction in hot water, and the main product is cobalt trioxide. Basic cobalt carbonate is an important raw material for the preparation of industrial catalysts and cobalt salts, and as an industrial additive, it is mainly used in the fields of ceramic industry, colorants, electronic products, magnetic materials and the like. The purple prismatic basic cobalt 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 cobalt elements in the synthetic cobalt-chromite.

[0056] The high-purity chromium acetate hydroxide selected as the initial substance is a light greenish green to bluish solid crystalline powder, which is stable in chemical properties at room temperature, does not decompose, is non-toxic and soluble in water. The chromium acetate hydroxide can be used as a raw material for the industrial production of high-purity metallic chromium, certain glazes, colored glass and the like. The selection of the chromium acetate hydroxide crystalline powder is because it can easily decompose and chemically react with dilute acid solution and has high chemical reactivity, and thus is an excellent raw material for providing chromium elements in the artificially synthesized cobalt-chromium-iron ore.

[0057] The high-purity solid nickel stearate selected as the initial substance is a green waxy organic compound, which is mainly used as a surfactant and a catalyst for the production of tertiary amines. Since the nickel stearate has high water chemical activity and is soluble in dilute nitric acid solution, the nickel stearate is an excellent raw material for providing transition group ferromagnetic metal elements nickel in the artificially synthesized cobalt-chromium-iron ore.

[0058] The high-purity solid oxalic acid selected as the initial substance is a chelating agent for metal substances, which aims to have a great influence on the bioavailability of mineral substances and has a strong coordination function. When oxalic acid is combined with divalent cobalt ions, the solubility of the divalent cobalt ions can be greatly reduced, and a complex sol of the divalent cobalt ions is formed in a dilute nitric acid solution. At the same time, when oxalic acid is combined with transition group ferromagnetic metal cation nickel, a soluble transition group ferromagnetic metal cation nickel complex is formed due to the coordination function of the oxalic acid. The solubility of the divalent nickel metal cation in an acid solution is significantly enhanced, so that the divalent nickel metal cation is fully dissolved in a dilute nitric acid solution. The high-purity solid chromium hydroxide selected as the initial substance is a typical grayish green chromium-containing aqueous powder substance, which can chemically react with both acids and strong bases to produce corresponding chromium salts and water, and exhibits the physical and chemical properties of an obvious amphoteric hydroxide. The chromium hydroxide can be used for the industrial production and raw material processing of trivalent chromium salts, dichromium trioxide and chromium pigments. Generally, the chromium hydroxide undergoes a dehydration reaction at a temperature of 500°C to produce green chromium oxide (chromium green), while releasing a large amount of water. The high-purity solid nickel hydroxide selected as the initial substance is a typical nickel-rich powder-like aqueous substance. The nickel hydroxide undergoes a dehydration reaction at a temperature of 230°C to produce nickel oxide (NiO), while releasing a large amount of water. The aqueous mineral nickel hydroxide undergoes complete dehydration at a temperature of 450°C.

[0059] The initial substance selected in the present application is dilute nitric acid (concentration: 10%), if the concentration of nitric acid is too low, it has limited solubility, which may cause residues of solid basic cobalt carbonate powder, solid acetic acid chromium (III) hydroxide crystalline powder, solid nickel stearate powder and solid oxalic acid powder; if the concentration of nitric acid is too high, it has enhanced oxidizing property, which may cause rapid oxidation reaction or direct decomposition of basic cobalt carbonate in the sample, and produce dense smoke, which may bring certain danger to the preparation.

[0060] Step 1, open the chemical fume hood, select a standard volume of 100 ml volumetric flask, accurately weigh 60 ml of dilute nitric acid with a concentration of 10%, place the glass transfer pipette in a 500 ml notch beaker, and carefully transfer the liquid dilute nitric acid along the transfer pipette to the beaker, and select the notch beaker as the reaction container. The main consideration is that after the beaker is covered on the glass surface dish cover, 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 solid purple-red prismatic basic cobalt carbonate powder on a 10 microgram high-precision analytical balance, and carefully add it to the dilute nitric acid solution with a concentration of 10% in the notch beaker, and place it in the magnetic stirring rotor.

[0062] Step 3, cover the notch beaker containing the dilute nitric acid solution with solid basic cobalt 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 material of solid basic cobalt carbonate powder in the dilute nitric acid solution, and at the same time make it undergo hydrolysis reaction and acidification reaction, the reaction conditions are room temperature, 700 rpm rotation speed and reaction time of 72 hours.

[0063] Step 4, according to the stoichiometric ratio of cobalt-chromite (Co, Ni) Cr2O4, accurately weigh 18.8038 grams of high-purity solid acetic acid chromium (III) hydroxide crystalline powder and 250 milligrams of high-purity solid nickel stearate powder on a high-precision analytical balance, and carefully add them to the dilute nitric acid solution containing basic cobalt carbonate powder, respectively.

[0064] Step 5, cover the dilute nitric acid solution beaker containing solid basic cobalt carbonate powder, solid acetic acid chromium (III) hydroxide crystalline powder and solid nickel stearate powder with a glass surface dish to ensure that the gas generated in the reaction is volatilized from the notch of the beaker, and at the same time avoid the dilute nitric acid solution of the initial material in the beaker from being splashed out during high-speed stirring, thereby causing danger and affecting the precision of cobalt-chromite single crystal synthesis.

[0065] Step 6, the beaker containing the mixed solution of the initial materials and the magnetic stirring rotor is placed on the high-temperature magnetic stirring hot plate in the fume hood, and the initial materials, i.e., the solid basic cobalt carbonate powder, the solid crystalline powder of chromium (III) acetate hydroxide, and the solid nickel stearate powder, are all dissolved in the mixed solution of dilute nitric acid without any residue under the conditions of room temperature, 800 rpm, and 48 hours of stirring time. At the same time, volatile substances such as NH3·H2O, CH4, C2H2, CO2, CO, and H2 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, and add high-purity oxalic acid powder as an important metal chelating agent to the dilute nitric acid solution containing solid basic cobalt carbonate powder, solid crystalline powder of chromium (III) acetate hydroxide, and solid nickel stearate powder. The purpose is that oxalic acid powder has a great influence on the bioavailability of minerals and has a strong coordination effect. When oxalic acid combines with divalent cobalt ions, it can greatly reduce its solubility, and further form a complex sol of divalent cobalt ions in the dilute nitric acid solution. At the same time, when oxalic acid combines with the transition group ferromagnetic metal cation nickel, due to its coordination effect, it forms a complex of soluble transition group ferromagnetic metal cation nickel, and the solubility of divalent nickel metal cations in acid solution will be significantly enhanced, so that it is fully dissolved in the dilute nitric acid solution.

[0067] Step 8, the notch beaker of the mixed solution is placed again on the high-temperature magnetic stirring hot plate in the fume hood, covered with a glass surface dish, and the condition parameters of the high-temperature magnetic stirring hot plate are set to 80°C, 1000 rpm, and 36 hours of stirring time. All the initial reagents are subjected to the combined action of the mixed solution of dilute nitric acid and oxalic acid to form a uniform sol.

[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°C until the mixed solution in the entire notch beaker is completely evaporated.

[0069] Step 10, remove the magnetic stirring rotor in the notch 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 powders in the notch beaker with a medicine spoon and place them 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 cobalt-chromium-iron ore sample in the graphite crucible, and finally realizing the valence of the valence metal cations cobalt, chromium, and nickel of the cobalt-chromium-iron ore sample.

[0070] Step 11, the graphite crucible containing the mixture powder is raised to a temperature of 1100°C at a lower rate of 300°C / hour in a muffle furnace under normal pressure and high temperature conditions. The slower high temperature calcination rate and longer constant temperature time are intended to more favorably control the oxygen atmosphere in the graphite sample chamber and more favorably remove residual nitric acid, oxalic acid and other organic substances in the mixture powder.

[0071] Step 12, the mixture sample powder in the graphite crucible in the muffle furnace is lowered to room temperature at a rate of 200°C / hour. A slower cooling rate is selected compared to the heating rate to more easily form a honeycomb loose sample powder. The mixture sample powder is carefully removed.

[0072] Step 13, the honeycomb loose sample powder of cobalt-chrome-iron ore is placed in an ultra-hard thick corundum mortar and ground for 1 hour to obtain a fine-grained and homogenized powder experimental sample.

[0073] Step 14, the homogenized and fine-grained cobalt-chrome-iron ore powder sample mixture is cold-pressed into 3 sample discs of Φ10.0mm x 3.0mm using a high-precision tungsten carbide die of the stainless steel tablet press with a size of Φ10.0mm x 10.0mm. The 3 cold-pressed sample mixtures are stacked vertically and carefully placed at the bottom of the graphite crucible.

[0074] Step 15, two symmetrical circular holes with a diameter of 1.0mm are drilled symmetrically 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, suspended in the center of the high-temperature oxygen atmosphere furnace. The two ends of the platinum-rhodium wire connecting the graphite crucible are fixed to the vertical four-hole alumina tube with a hole diameter of 0.6mm. The outer diameter of the four-hole alumina tube is 5.0mm and the length is 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 stainless steel container containing 3 liters of secondary deionized pure cold water is placed on the side of the high-temperature oxygen atmosphere furnace in advance. The purpose is to quickly cool the graphite crucible containing the sample at very high temperature by directly pulling the sample out of the high-temperature oxygen atmosphere furnace and quickly immersing it in the 3-liter secondary deionized water in the cold stainless steel container, which is mainly to avoid the oxidation / reduction of the variable valence elements cobalt, chromium and nickel contained in the cobalt-chrome-iron ore sample during the slow cooling process of the furnace body, and to achieve rapid quenching of the sample and complete retention of the glassy cobalt-chrome-iron ore sample.

[0076] Step 17, the top of the furnace body of the high-temperature oxygen atmosphere furnace is connected with an argon inert gas cylinder, a proportionally adjustable carbon monoxide cylinder and a carbon dioxide cylinder, the amount of gas entering the sample chamber is controlled by a gas pressure gauge, and each gas can be switched and adjusted at any time during the high-temperature calcination of the sample. The argon inert gas is used in the present application, which provides an absolutely reduced oxygen atmosphere environment when the temperature of the furnace body is lower than 800 DEG C.

[0077] The present application uses proportionally adjustable carbon monoxide and carbon dioxide, which can well control the oxygen fugacity of the sample during high-temperature calcination when the temperature of the furnace body is higher than 800 DEG C. When the temperature of the furnace body is higher than 800 DEG C, continuing to introduce argon inert gas will cause over-reduction in the sample chamber, which may cause the variable valence elements cobalt, chromium and nickel to be reduced into metal cobalt, metal chromium and metal nickel in turn. Therefore, when the temperature is higher than 800 DEG C, the present application uses proportionally adjustable carbon monoxide and carbon dioxide mixed gas to control the oxygen fugacity of the sample in the high-temperature oxygen atmosphere furnace cavity, and the reaction principle is The oxygen partial pressure in the sample cavity can be well adjusted, and the valence of the variable valence metal elements cobalt, chromium and nickel in the nickel-doped and high-water-content cobalt-chromium-iron ore single crystal can be well controlled.

[0078] The highest rated temperature of the high-temperature oxygen atmosphere furnace is 1800 DEG C. The circulating cooling water of the high-temperature oxygen atmosphere furnace is opened to reduce the temperature of the furnace body, so as to avoid the temperature of the whole furnace body being too high, which may cause carbon monoxide and carbon dioxide to leak, thereby causing danger.

[0079] A high-sensitivity argon, carbon monoxide and carbon dioxide concentration monitoring alarm is opened to avoid gas leakage during the high-temperature calcination 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 gas is continuously filled for 30 minutes, which is used to properly expel the excess air in the sample chamber. The sample is subjected to high-temperature calcination at a temperature increasing rate of 400 DEG C / hour under the protection of argon inert gas to 800 DEG C.

[0081] Step 19, after the temperature in the furnace body is 800 DEG C, 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 carbon monoxide and carbon dioxide in the sample oxygen atmosphere furnace is 4:1, which is used to well adjust the oxygen fugacity in the sample chamber during the high-temperature calcination.

[0082] Step 20, after the volume ratio of 4:1 carbon monoxide and carbon dioxide control sample bin oxygen fugacity mixed gas flow to reach stable, the time required for this step is about 3-5 minutes, then the temperature of the sample bin in the furnace is increased to 1550℃ at a heating rate of 200℃ / h, and the temperature is kept constant for 15 minutes to melt into a glassy cobalt-chromium-iron ore. During the heating process of the high-temperature oxygen atmosphere furnace, the sample bin is heated at two different rates of 400℃ / h and 200℃ / h in different temperature ranges of room temperature-800℃ and 800℃-1550℃, respectively. The present application, with the temperature of the sample bin in the high-temperature oxygen atmosphere furnace, is more beneficial to the formation of strong ionic bonds such as Co-O, Cr-O and Ni-O in nickel-doped cobalt-chromium-iron ore; it can more accurately control the temperature of the sample bin in the high-temperature oxygen atmosphere furnace; it can completely avoid the imbalance of heat transfer of the sample bin, which leads to the overheating of the local area of the furnace body, and thus easily damages the heating body of the oxygen atmosphere furnace.

[0083] The present application uses carbon monoxide and carbon dioxide mixed gas to control the high-temperature roasting process in oxygen atmosphere, which aims to provide a more pure cobalt-chromium-iron ore glassy material for the synthesis of large particle nickel-doped and high water cobalt-chromium-iron ore single crystal; the high-temperature calcination under oxygen atmosphere can better control the valence of the variable valence metal elements cobalt, chromium and nickel in the product; the high calcination temperature of 1550℃ can ensure that the substances that may affect the sample preparation, such as volatile matter, nitric acid, oxalic acid and organic matter, are all completely volatilized after the muffle furnace high-temperature calcination.

[0084] The present application uses a relatively short roasting time of 15 minutes, because the cobalt-chromium-iron ore powder will melt rapidly at a temperature higher than 1500℃. If the roasting time is too short, there may be some residual initial powder in the cobalt-chromium-iron ore melted product, which seriously affects the chemical composition of the prepared cobalt-chromium-iron ore sample; if the roasting time is too short, it is not conducive to the chemical diffusion of cobalt ions, chromium ions and nickel ions; it is also not conducive to the formation of strong ionic bonds such as Co-O, Cr-O and Ni-O in cobalt-chromium-iron ore; if the roasting time is too short, the transition group ferromagnetic metal nickel element will be distributed unevenly in the cobalt-chromium-iron ore, which will seriously affect the preparation effect; if the roasting time is too short, the density of the product will be reduced, and it may be difficult to form high-density cobalt-chromium-iron ore glass. However, if the roasting time is higher than 15 minutes, it may lead to excessive melting, which will make the cobalt-chromium-iron ore sample firmly adhere to the graphite crucible wall, difficult to clean, and also increase the cost of sample preparation.

[0085] Step 21, after the sample is baked at a temperature of 1550°C for 15 minutes, the graphite crucible containing the sample, the four-hole alumina tube and the upper round cover of the furnace body are pulled out of the furnace body and directly immersed in a 3-liter stainless steel container containing secondary deionized pure cold water to rapidly quench the cobalt-chrome-iron ore glass. The purpose of rapid quenching is to well preserve the glassy cobalt-chrome-iron ore sample with uniform composition at high temperature.

[0086] Step 22, the quenched glassy cobalt-chrome-iron ore sample is carefully taken out of the graphite crucible and ground in a corundum mortar to obtain fine and uniform composition sample powder. The glassy cobalt-chrome-iron ore powder is placed in a vacuum drying box at 200°C and dried for 12 hours.

[0087] Step 23, the cobalt-chrome-iron ore glass powder is cold-pressed on a cold isostatic pressing machine using a high-precision Φ4.0mm (diameter) x 10.0mm tungsten carbide die to form a Φ4.0mm (diameter) x 4.0mm (height) cylindrical cobalt-chrome-iron ore sample.

[0088] In order to obtain high water content of cobalt-chromium-iron ore, the present application adopts chromium hydroxide powder (molecular formula: Cr(OH)3) and nickel hydroxide powder (molecular formula: Ni(OH)2) with a weight ratio of 4:1 as the water source. The mixture of chromium hydroxide and nickel hydroxide is selected as the water source, mainly based on the following considerations: first, chromium hydroxide and nickel hydroxide are both typical water-containing substances, and the dehydration temperature is relatively low. High-purity solid-state chromium hydroxide is a typical gray-green chromium-containing water-containing powder substance. Generally, chromium hydroxide will undergo a dehydration reaction at a temperature of 500 DEG C, and the product is green chromium green (Cr2O3), while a large amount of water is released. High-purity solid-state nickel hydroxide is a typical nickel-rich powder water-containing substance. Nickel hydroxide will undergo a dehydration reaction at a temperature of 230 DEG C, and the product is nickel oxide (NiO), while a large amount of water is released. When the temperature reaches 450 DEG C, the water-containing mineral nickel hydroxide will undergo complete dehydration. Therefore, this dehydration temperature condition is in the lower temperature range of the process of preparing nickel-doped cobalt-chromium-iron ore single crystals under high temperature and high pressure conditions, that is, it can be realized, which fully guarantees that the nickel-doped cobalt-chromium-iron ore single crystal is in a water environment for a long enough time to ensure the full diffusion of the sample lattice water and the formation of lattice occupation. Secondly, chromium hydroxide and nickel hydroxide are both chromium-rich and nickel-rich substances, which can well control the chromium activity and nickel activity of the main lattice occupation in the process of preparing nickel-doped and high-water cobalt-chromium-iron ore single crystals in the sample cavity under high temperature and high pressure conditions. Finally, the dehydration end products of the water source substance combination of chromium hydroxide and nickel hydroxide with a weight ratio of 4:1 placed at both ends of the sample are chromium green, nickel oxide and other oxides. All these products will not chemically react with the sample, ensuring the purity of the sample of nickel-doped and high-water cobalt-chromium-iron ore single crystals. In addition, by adjusting the weight ratio of chromium hydroxide and nickel hydroxide as the water source water-containing substance and the corresponding height of the water source sheet, the water content in the nickel-doped and high-water cobalt-chromium-iron ore single crystal sample can be adjusted.

[0089] Step 24, in the cold isostatic press, chromium hydroxide powder and nickel hydroxide powder are cold pressed into two pieces of water source sheet with a weight ratio of 4:1 and a high-precision Φ4.0mm(diameter)×10.0mm tungsten carbide grinding tool, which is cold pressed into Φ4.0mm(diameter)×0.1mm(height).

[0090] Step 25, cylindrical sample of cobalt-chromite (size: Φ4.0mm (diameter) x 4.0mm (height)) and two pieces of water source sheet (size: Φ4.0mm (diameter) x 0.1mm (height)) are sealed in the experimental sample chamber of the double capsule structure of the inner sleeve-graphite tube (size: Φ4.4mm (outer diameter) x 4.4mm (height), wall thickness of 0.2mm) and outer sleeve-gold-palladium alloy tube (size: Φ4.6mm (outer diameter) x 4.6mm (height), wall thickness of 0.1mm) in turn. The sample of nickel-doped cobalt-chromite is placed in the middle of the graphite inner sleeve, and the two pieces of water source sheet with a weight ratio of 4:1 of chromium hydroxide and nickel hydroxide are placed at the symmetrical ends of the graphite inner sleeve close to the sample.

[0091] The inner sleeve of the double capsule structure sample chamber of the present application uses graphite as the sealing material, the main purpose of which is to control the oxygen fugacity value of carbon monoxide and carbon dioxide in the sample chamber, and ultimately to constrain the valence of the variable valence metal elements cobalt, chromium and nickel in the cobalt-chromite sample.

[0092] The outer sleeve of the double capsule structure sample chamber of the present application uses gold-palladium alloy as the sealing material, the main purpose of which is: first, to use gold-palladium alloy sealing to isolate the exchange of substances or elements between the sample and other surrounding pressure transmission materials, effectively avoiding contamination of the cobalt-chromite sample during its preparation under high temperature and high pressure; second, to use gold-palladium alloy sealing to effectively prevent water from escaping from the sample tube during the preparation of the cobalt-chromite sample under high temperature and high pressure; finally, the present application uses a double capsule structure sample chamber composed of a graphite tube and a gold-palladium alloy tube to form a more airtight oxygen atmosphere environment, better control the oxygen fugacity in the sample chamber, and thus more effectively constrain the valence of the variable valence metal elements cobalt, chromium and nickel in the cobalt-chromite sample.

[0093] Step 26, cobalt-chromite is one of the important cobalt-rich and chromium-rich oxide minerals in the lower crust and upper mantle of the Earth and other terrestrial planets, in order to truly simulate the growth environment of cobalt-chromite 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 cobalt-chromite mineral phase, the double capsule structure sample chamber composed of a graphite tube and a gold-palladium alloy tube is placed on a typical 6-8 type multi-faceted top large cavity high temperature and high pressure equipment Kawai-1000t in the laboratory, the pressure and temperature are set to 3.0GPa and 1150℃ respectively, the heating and pressure rate is set to 0.5GPa / hour and 10℃ / minute respectively, and the reaction time is 72 hours under constant temperature and pressure.

[0094] The preparation process of the high pressure of 3.0 GPa and the sintering temperature of 1150 DEG C selected by the application is completely designed based on the physical and chemical properties of cobalt-chromite itself. The specific purposes are as follows: firstly, the preparation process of high temperature and high pressure, relatively slow pressure and temperature rising rate and long constant temperature and constant pressure reaction time can completely ensure the complete mineral phase transformation from the initial cobalt-chromite glass phase powder to the cobalt-chromite crystal phase, and the final product cobalt-chromite mineral phase can exist stably under the temperature and pressure conditions; secondly, the preparation process of high temperature and high pressure, relatively slow pressure and temperature rising rate and long constant temperature and constant pressure reaction time can significantly increase the self-diffusion coefficient and chemical diffusion coefficient of metal cations such as cobalt ions, chromium ions and nickel ions, so that the equivalent isomorphism replacement of nickel ions on metal cobalt ions in cobalt-chromite crystal is realized, and the reaction is complete and there is no free nickel element residue, thereby forming a perfect transition group ferromagnetic metal element nickel-doped cobalt-chromite single crystal sample; thirdly, the preparation process of high temperature and high pressure, relatively slow pressure and temperature rising rate and long constant temperature and constant pressure reaction time can completely ensure the formation of stable chemical bonds such as Co-O, Cr-O and Ni-O, thereby avoiding the uneven distribution of the doped transition group ferromagnetic metal nickel element in cobalt-chromite, and realizing the uniform nickel-doped cobalt-chromite single crystal of isometric system; fourthly, the preparation process of high temperature and high pressure, relatively slow pressure and temperature rising rate and long constant temperature and constant pressure reaction time can make the dehydrated reaction of the water-containing substance combination of chromium hydroxide and nickel hydroxide with a weight ratio of 4:1, generate a large amount of water, and the final dehydrated product is mixed oxides such as chromium green and nickel oxide, and at the same time, the water diffuses in the nickel-doped cobalt-chromite single crystal in the sample bin, thereby ensuring that the cobalt-chromite sample has a high enough water content; finally, the preparation process of high temperature and high pressure, relatively slow pressure and temperature rising rate and long constant temperature and constant pressure reaction time can make the nickel element in the final preparation product cobalt-chromite more uniformly distributed, and at the same time, the density, strength and particle size of the product are increased, thereby preparing the nickel-doped and high-water-content large-grained isometric cobalt-chromite single crystal sample with uniform element distribution, high mechanical strength and large density and other superior physical and chemical properties.

[0095] The temperature is accurately calibrated by two groups of high-temperature-resistant tungsten-rhenium thermocouples during the high-temperature and high-pressure reaction. 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-tech metallurgical industry, high-temperature electronic thermoelectric system structure engineering, space carrier, nuclear reactor and other 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 different materials and with a diameter of 0.1 mm are connected at one end and suspended into a cluster shape by using a bench clamp; the other end of the tungsten-rhenium thermocouple metal wires with different materials and 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 cluster-shaped 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 the 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. According to the application, the tungsten-rhenium double thermocouples are arranged at the upper and lower ends of the sample chamber, so that the temperature in the sample cavity can be accurately calibrated, and the temperature gradient at the upper and lower ends of the sample chamber can be accurately indicated, thereby ensuring that the cobalt-chromium-iron ore sample is in a stable constant temperature zone during sample synthesis.

[0096] Step 27, after constant temperature and pressure for 72 hours under the conditions of 3.0 GPa and 1150℃, the temperature in the sample cavity is reduced from 1150℃ to 800℃ at a cooling rate of 3℃ / min, and is kept constant for 1 hour; then the temperature in the sample cavity is reduced from 800℃ to room temperature at a cooling rate of 5℃ / min. The stepwise cooling and the heating rate (10℃ / min) relative to the sample preparation, and the relatively slow constant pressure cooling rate can further improve the superior physical and chemical properties of the nickel-doped cobalt-chromium-iron ore single crystal sample, such as uniform distribution of nickel element, high mechanical strength and large density, and completely avoid the non-uniform stress of the sample caused by the too fast cooling rate, thereby causing cracks and damage of the cobalt-chromium-iron ore crystal, and the preparation process is more conducive to the crystal growth of the large-grained cobalt-chromium-iron ore single crystal, thereby realizing the preparation of the large-grained cobalt-chromium-iron ore single crystal sample with a size of hundreds of microns.

[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, the preparation process of the nickel-doped and high-hydrated cobalt-chromium-iron ore single crystal sample obtained by hot-pressing sintering is pure and free of any impurities introduced from the sample itself, high-pressure sample assembly and the like.

[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 wrapped around the sample are carefully removed, and the cylindrical sample is cut in half from the center by using a high-precision diamond wire cutting instrument. The cobalt-chromium-iron ore single crystal is selected under a 20-fold high-precision Olympus microscope.

[0099] The cobalt-chromite ore single crystal obtained by the application is a single phase without any other impurity phase; the electron probe (EPMA) detection result shows that the molecular formula of the obtained cobalt-chromite ore single crystal is CoCr2O4; the multi-functional ion mass spectrometer (ICP-MS) detection result shows that the nickel content in the obtained cobalt-chromite ore single crystal is 8547 ppm wt%; and the vacuum Fourier transform infrared spectroscopy (FT-IR) detection result shows that the water content of the obtained cobalt-chromite ore single crystal sample is 466 ppm wt, and the cobalt-chromite ore single crystal sample has a relatively high water content.

[0100] The nickel-doped and high-water-content cobalt-chromite ore single crystal obtained by the application is 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 182 microns, and the maximum particle size is 569 microns.

[0101] The nickel-doped and high-water-content cobalt-chromite ore single crystal sample obtained by the application has high purity, large particle size, stable chemical properties, high mechanical strength and other superior properties, and more importantly, the nickel content is high (8547 ppm wt%), and the nickel content in the cobalt-chromite ore single crystal can be completely controlled. By changing the amount of the added initial solid-state high-purity nickel stearate chemical reagent from 233.9948 mg to 263.2442 mg, the corresponding nickel content in the obtained nickel-doped and high-water-content cobalt-chromite ore single crystal sample is finally realized from 8000 ppm wt% to 9000 ppm wt%; by changing the weight ratio of the water-containing substances, chromium hydroxide powder and nickel hydroxide 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 double-capsule structure sample bin composed of the graphite tube and the gold-palladium alloy tube is controlled, and the water content in the cobalt-chromite ore single crystal is finally realized. The obtained nickel-doped and high-water-content cobalt-chromite ore single crystal sample can completely meet the needs of physical experiment simulation of minerals in the lower crust and upper mantle regions of the Earth and other terrestrial planets under high temperature and high pressure conditions, and breaks through the technical bottleneck of the existing cobalt-chromite ore single crystal synthesis, and provides important experimental sample support for the study of the lattice preferred orientation and the crystal axis anisotropy of single crystal minerals in the lower crust and upper mantle regions of the Earth and other terrestrial planets under high temperature and high pressure conditions.

Claims

1. A method for preparing nickel-doped and high-hydration cobalt-chromite single crystals under high temperature and high pressure, characterized in that: The method includes: preparing a cylindrical cobalt-chromium iron ore sample using solid basic cobalt carbonate powder, solid chromium acetate (III) hydroxide crystalline powder, solid nickel stearate, solid oxalic acid powder, solid chromium hydroxide powder, solid nickel hydroxide powder, and liquid dilute nitric acid as starting materials; preparing water source plates using chromium hydroxide powder and nickel hydroxide powder in a weight ratio of 4:1; placing two water source plates at both ends of the cylindrical cobalt-chromium iron ore sample and then placing them together into a double-cell structure sample chamber; and then performing a high-temperature and high-pressure reaction to obtain cobalt-chromium iron ore single crystals; the preparation method of the cylindrical cobalt-chromium iron ore sample includes: Step 14: Cold press the cobalt chromite powder sample mixture into 3 sample discs with a diameter of Φ 10.0 mm × 3.0 mm. Place the 3 cold-pressed sample discs vertically together at the bottom of the graphite crucible. Step 15: The graphite crucible is suspended in the center of the high-temperature oxygen atmosphere furnace. The two ends of the platinum-rhodium metal wire connecting the graphite crucible are fixed to the vertical four-hole alumina tube. 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. Step 16: Place a stainless steel container filled with deionized pure cold water on the side of the high-temperature oxygen atmosphere furnace. Step 17: Connect the top of the high-temperature oxygen atmosphere furnace to an argon inert gas cylinder and a carbon monoxide and carbon dioxide cylinder with adjustable ratios. Step 18: Open the argon inert gas valve and continue to purge for 30 minutes. Under the protection of argon inert gas, calcine the sample to 800 °C at a heating rate of 400 °C / hour. Step 19: After the furnace body temperature reaches 800 °C, switch the control valves of the carbon monoxide cylinder and the carbon dioxide cylinder to make the volume ratio of carbon monoxide and carbon dioxide passing through the sample oxygen atmosphere furnace reach 4:

1. Step 20: Raise the temperature of the sample chamber inside the furnace to 1550 °C at a heating rate of 200 °C / hour, and calcine at a constant temperature for 15 minutes to melt it into a glassy state of cobalt chromite. Step 21: After the sample is calcined at a constant temperature of 1550 °C for 15 minutes, the graphite crucible containing the sample, the four-hole alumina tube, and the round cover on the furnace body are pulled out of the furnace body together and directly immersed in a stainless steel container to quench into cobalt chromite glass. Step 22: Take the quenched cobalt-chromium-iron ore glass out of the graphite crucible, grind it into fine and uniform sample powder in a corundum mortar, and place the sample powder in a vacuum drying oven at 200 °C for 12 hours. Step 23: The cobalt chromite glass sample powder is cold-pressed into a cylindrical cobalt chromite sample with a diameter of Φ 4.0 mm × height of 4.0 mm using a tungsten carbide mold on a cold isostatic press.

2. The method for preparing nickel-doped and high-hydration cobalt-chromite single crystals under high temperature and high pressure according to claim 1, characterized in that: Solid basic cobalt carbonate powder with a purity >99.99%, solid chromium acetate (III) hydroxide crystalline powder with a purity >99.99%, solid nickel stearate with a purity >99.99%, solid oxalic acid powder with a purity >99.99%, solid chromium hydroxide powder with a purity >99%, solid nickel hydroxide powder with a purity >99%, and liquid dilute nitric acid with a concentration of 10%.

3. The method for preparing nickel-doped and high-hydration cobalt-chromite single crystals under high temperature and high pressure according to claim 1, characterized in that: The preparation method of the cobalt-chromite powder sample mixture includes: Step 1: Weigh out 60 ml of 10% dilute nitric acid and add it to a notched beaker; Step 2: Weigh out 5.0 grams of solid basic cobalt carbonate powder and add it to a notched beaker, then place a magnetic stirring rotor inside. Step 3: Cover the notched beaker with a glass watch glass and place it on a high-temperature magnetic stirring plate in a fume hood. React at room temperature for 72 hours at a speed of 700 rpm. Step 4: According to the stoichiometric ratio of cobalt chromite (Co,Ni)Cr2O4, weigh out 18.8038 g of solid chromium acetate (III) hydroxide crystalline powder and 250 mg of nickel stearate powder, and add them to the notched beaker mouth respectively; Step 5: Cover the notched beaker with a glass watch glass. Step 6: Place the notched beaker covered with a glass watch glass on a high-temperature magnetic stirring plate in a fume hood and stir at room temperature, 800 rpm for 48 hours. Step 7: Weigh out 2 grams of solid oxalic acid powder and add it to the notched beaker; Step 8: Place the notched beaker back on the high-temperature magnetic stirring plate in the fume hood, cover it with a glass watch glass, and set the conditions of the high-temperature magnetic stirring plate to 80 °C and 1000 rpm for 36 hours. Step 9: Remove the glass watch glass from the beaker, and increase the temperature of the high-temperature magnetic stirring plate to 110°C until the mixed solution in the entire notched beaker is completely evaporated. Step 10: Remove the magnetic stirring rotor and clean all the powder sample adhering to the surface into the beaker. Use a spatula to remove all the mixed powder from the notched beaker and place it in the graphite crucible. Step 11: The graphite crucible containing the mixed powder is heated to 1100 °C at a heating rate of 300 °C / hour using a muffle furnace under normal pressure, and held at that temperature for 5 hours. Step 12: Cool the mixture powder in the muffle furnace to room temperature at a cooling rate of 200 °C / hour, and remove the mixture sample powder; Step 13: Place the mixed sample powder in a corundum mortar and grind for 1 hour to obtain a mixture of cobalt chromite powder sample.

4. The method for preparing nickel-doped and high-hydration cobalt-chromite single crystals under high temperature and high pressure according to claim 1, characterized in that: The preparation method of the water source tablet is as follows: Step 24: On a cold isostatic press, chromium hydroxide powder and nickel hydroxide powder are cold-pressed in a 4:1 weight ratio using a tungsten carbide mold with a diameter of 4.0 mm and a height of 10.0 mm to form two water source sheets with a diameter of 4.0 mm and a height of 0.1 mm.

5. The method for preparing nickel-doped and high-hydration cobalt-chromite single crystals under high temperature and high pressure according to claim 1, characterized in that: The method of obtaining cobalt-chromium-iron ore single crystals by placing two water source plates at opposite ends of a cylindrical cobalt-chromium-iron ore sample and then placing them together into a double-capsule structured sample chamber, followed by a high-temperature and high-pressure reaction, includes: Step 25: Place the cylindrical cobalt-chromium-iron ore sample in the center of the graphite inner sleeve of the double-capsule structure; place two water source plates at the symmetrical ends of the graphite inner sleeve close to the sample; the inner sleeve of the double-capsule experimental sample chamber is a graphite tube, and the outer sleeve is a gold-palladium alloy tube. Step 26: Place the sample chamber with the double-capsule structure on a typical 6-8 type multi-faceted top large cavity high temperature and high pressure equipment in the laboratory, set the pressure increase rate and the temperature increase rate to 0.5 GPa / hour and 10 °C / minute, respectively, and raise the pressure and temperature to 3.0 GPa and 1150 °C for hot pressing sintering. The reaction time is 72 hours at constant temperature and pressure. Step 27: Then, at a cooling rate of 3 °C / min, reduce the temperature inside the sample chamber from 1150 °C to 800 °C and hold the temperature for 1 hour; then, at a cooling rate of 5 °C / min, reduce the temperature inside the sample chamber from 800 °C to room temperature. Step 28: After the temperature inside the sample chamber drops to room temperature, reduce the pressure inside the sample chamber from 3.0 GPa to atmospheric pressure at a depressurization rate of 0.5 GPa / hour. Step 29: After the high temperature and high pressure preparation reaction is completed, the sample is taken out, and the graphite tube and gold-palladium alloy tube of the double-capsule sample chamber that encapsulates the sample are removed. The cylindrical sample is cut from the middle using a diamond wire cutter, and the cobalt-chromium-iron ore single crystal is selected under a 20x Olympus microscope.

6. The method for preparing nickel-doped and high-hydration cobalt-chromite 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 using two sets of tungsten-rhenium thermocouples; each set of tungsten-rhenium thermocouples was composed of two different tungsten-rhenium alloys with the chemical composition W. 95% Re 5% and W 74% Re 26% Each set of tungsten-rhenium thermocouples is symmetrically placed at the upper and lower ends of the double-capsule sample chamber composed of graphite tubes and gold-palladium alloy tubes.