LU503141B1

LU503141B1 - Method for preparing high-nickel, high-zinc and high-water single-crystal diopside under high-temperature and high-pressure condition

Info

Publication number: LU503141B1
Application number: LU503141A
Authority: LU
Inventors: Haiying Hu; Lidong Dai
Original assignee: Inst Geochemistry Cas
Priority date: 2022-12-07
Filing date: 2022-12-07
Publication date: 2023-06-07

Abstract

Disclosed is a method for preparing high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition, including: preparing a diopside cylinder sample using solid calcium nitrate tetrahydrate powder, solid magnesium nitrate hexahydrate powder, solid nickel(II) nitrate hexahydrate powder, solid zinc nitrate hexahydrate powder, liquid tetraethoxysilane and absolute ethyl alcohol as starting materials; preparing water-sourced discs using solid natural talcum powder, solid nickel hydroxide powder and solid zinc hydroxide powder as starting materials; placing the water-sourced discs at two ends of the diopside cylinder sample and then placing the diopside cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube; and preparing high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition. The present invention fills in the technical blank in preparing high-nickel, high-zinc and high-water single-crystal diopside in the prior art, so that large-grained high-nickel, high-zinc and high-water single-crystal diopside experimental samples are obtained.

Description

METHOD FOR PREPARING HIGH-NICKEL, HIGH-ZINC AND HIGH-WATER

SINGLE-CRYSTAL DIOPSIDE UNDER HIGH-TEMPERATURE AND Hoos

HIGH-PRESSURE CONDITION

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The present invention belongs to the technical field of single-crystal mineral sample synthesis under a high-temperature and high-pressure condition, and particularly relates to a method for preparing high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition.

[0003] 2. Description of Related Art

[0004] Diopside (molecular formula: CaMg(SiOs):) contain a certain quantity of foreign ions such as sodium ions, zinc ions, manganese ions, nickel ions, aluminum ions, chromium ions and titanium ions.

[0005] Pure single-crystal diopside prepared in the prior art is non-hydrous and has a small particle size (nano-sized generally).

BRIEF SUMMARY OF THE INVENTION

[0006] The technical issue to be settled by the present invention is to provide a method for preparing high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition to solve the above-mentioned problems of the prior art.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition, comprising: preparing a diopside cylinder sample using solid calcium nitrate tetrahydrate powder, solid magnesium nitrate hexahydrate powder, solid nickel(IT) nitrate hexahydrate powder, solid

LU503141 zinc nitrate hexahydrate powder, liquid tetracthoxysilane and absolute ethyl alcohol as starting materials; preparing water-sourced discs using solid natural talcum powder, solid nickel hydroxide powder and solid zinc hydroxide powder as starting materials; placing the water-sourced discs at two ends of the diopside cylinder sample and then placing the diopside cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube; and preparing high-nickel, high-zinc and high-water single-crystal diopside high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition.

[0009] Preferably, the purity of the solid calcium nitrate tetrahydrate powder is over 99.99%, the purity of the solid magnesium nitrate hexahydrate powder is over 99.99%, the purity of the solid nickel(Il) nitrate hexahydrate powder is over 99.999%, the purity of the solid zinc nitrate hexahydrate powder is over 99.99%, the purity of the liquid tetraethoxysilane is over 99.99%, the purity of the solid natural talcum powder is over 99%, the purity of the solid nickel hydroxide powder is over 99.8%, the purity of the solid zinc hydroxide powder is over 99.4%, and the concentration of the absolute ethyl alcohol is over 99.9%.

[0010] Preferably, the diopside cylinder sample is prepared by:

[0011] Step 1, placing 62 ml of absolute ethyl alcohol into a 300 ml wide-mouth glass bottle;

[0012] Step 2, weighing, according to diopside chemometrics, 10 g of the solid magnesium nitrate hexahydrate powder, 9.2138 g of the solid calcium nitrate tetrahydrate powder, 100 mg of the solid nickel(IT) nitrate hexahydrate powder and 80 mg of the solid zinc nitrate hexahydrate powder, and adding the weighed materials into the 62 ml of absolute ethyl alcohol;

[0013] Step 3, adding, with a pipette, 18.2752 ml of the liquid tetraethoxysilane to the 62 ml of absolute ethyl alcohol according to the diopside chemometrics;

LU503141

[0014] Step 4, putting a magnetic stirring rotor in the wide-mouth bottle, and sealing a mouth of the wide-mouth bottle with a plastic film with a thickness of 0.5 mm;

[0015] Step 5, placing the wide-mouth bottle on a high-temperature magnetic stirring heater coil, and enabling the high-temperature magnetic stirring heater coil to stir a mixed solution for 21 hrs at room temperature and 880 rpm;

[0016] Step 6, opening the mouth, sealed with the plastic film, of the wide-mouth bottle to add 44 ml of a 69-70% concentrated nitric acid solution to the mixed solution, and then sealing the mouth of the wide-mouth bottle again with the plastic film;

[0017] Step 7, poking multiple 0.1 mm holes in a surface of the plastic film;

[0018] Step 8, placing the wide-mouth bottle on the high-temperature magnetic stirring heater coil, increasing a temperature of the heater coil to 87° C, and stirring the mixed solution for 24 hrs at 87°C and 1071 rpm;

[0019] Step 9, removing the plastic film from the mouth of the wide-mouth bottle, and increasing the temperature of the high-temperature magnetic stirring heater coil to 111° C until the mixed solution in the whole wide-mouth bottle is completely desiccated;

[0020] Step 10, taking out the magnetic stirring rotor, taking, with a spoon, all mixed powder out of the wide-mouth bottle, and placing the mixed powder in a platinum crucible;

[0021] Step 11, placing the platinum crucible in a high-temperature muffle furnace, and increasing a temperature of the high-temperature muffle furnace to 1018° C at a rate of 760° C/h to calcine the mixed powder for 1.8 hrs; naturally cooling the mixed powder to room temperature, and taking out the mixed sample powder;

[0022] Step 12, uniformly grinding and mixing the mixed sample powder in an agate mortar, and pressing the mixed sample powder into a ® 15.1 mm * 7.2 mm disc on a press, and stacking three discs up in the platinum crucible;

[0023] Step 13, hanging the platinum crucible in a middle of a high-temperature

LU503141 oxygen atmosphere furnace having an open bottom, with a platinum wire connected to a wall of the platinum crucible, and injecting a gas mixture of hydrogen, argon and carbon dioxide into the platinum crucible from a top of the platinum crucible; and placing a cup, 690 ml, of secondary deionized cold water below a furnace body of the oxygen atmosphere furnace;

[0024] Step 14, increasing a temperature of the platinum crucible to 1450° C at a rate of 620° C/h for constant-temperature calcining for 29 min to melt the mixed powder into glassy-state diopside; applying a 10 A current to the platinum wire connected to the wall of the platinum crucible to fuse the platinum wire, so that the platinum crucible containing the sample falls into the secondary deionized cold water from a hearth of the oxygen atmosphere furnace to realize direct quenching of the sample at a high temperature, thus obtaining diopside glass with uniform components; taking the quenched diopside glass out of the platinum crucible, and grinding the diopside glass into uniform sample powder in the agate mortar; and

[0025] Step 15, pressing the sample powder into a ® 3.8 mm * 3.5 mm cylinder to obtain the diopside cylinder sample.

[0026] Preferably, preparing water-sourced discs using solid natural talcum powder, solid nickel hydroxide powder and solid zinc hydroxide powder as starting materials is carried out by: using natural talcum, nickel hydroxide and zinc hydroxide with a weight ratio of 4:1:1 as raw materials, and pressing the natural talcum, the nickel hydroxide and the zinc hydroxide into two ® 3.8 mm * 0.15 mm discs on a press to obtain the water-sourced discs.

[0027] Preferably, placing the water-sourced discs at two ends of the diopside cylinder sample and then placing the diopside cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube; and preparing high-nickel,

high-zinc and high-water single-crystal diopside high-nickel, high-zinc and high-water

LU503141 single-crystal diopside under a high-temperature and high-pressure condition. are carried out by: placing the gold-palladium alloy tube containing the diopside cylinder sample and the two water-sourced discs on a Kawai-1000t multi-anvil press, setting a pressure rise rate and a temperature rise rate to 1.5 GPa/h and 50° C/min respectively, increasing the pressure and the temperature to 4.0 GPa and 1000° C respectively for hot-pressing sintering, and performing a reaction for 14 hrs under a constant-temperature and constant-pressure condition; after the reaction is performed for 14 hrs under the constant-temperature and constant-pressure condition, decreasing a temperature in a sample cavity to room temperature from 1000° C at a rate of 10° C/min; after the temperature is decreased to the room temperature, decreasing a pressure in the sample cavity to normal pressure from 4.0 GPa at a rate of 0.4 GPa/h; and at the end of the high-temperature and high-pressure preparation reaction, taking an experimental sample out of the sample cavity, opening the gold-palladium alloy sample tube with a diamond slicer, and picking out the single-crystal diopside under an Olympus microscope.

[0028] Preferably, during the high-temperature and high-pressure reaction, the temperature in the high-pressure sample cavity is calibrated with two sets of high-temperature nickel chromium-nickel silicon K-type metal thermocouples, and each set of nickel chromium-nickel silicon K-type metal thermocouples is composed of a nickel-chromium metal alloy wire and a nickel-silicon metal alloy wire that are made of different materials; the chemical composition of a positive pole KP of each said thermocouple is NisoxCT10%; the chemical composition of a negative pole KN of each said thermocouple is Nin7%Siz%; correspondingly, a diameter of each said positive nickel-chromium metal alloy wire KP and each negative nickel-silicon metal alloy wire

KN is 0.3 mm; and each set of nickel chromium-nickel silicon K-type metal thermocouples is symmetrically placed on upper and lower sides of an outer wall of the sample cavity of the gold-palladium alloy tube, so that the temperature in the sample

LU503141 cavity is calibrated.

[0029] The present invention has the following beneficial effects:

[0030] According to the present invention, single-crystal diopside with a high nickel content (8000-9000 ppm wt%), a high zinc content (6000-7000 ppm wt%), and a high water content (2000-3000 ppm wt%) is synthesized, and the obtained high-nickel, high-zinc and high-water single-crystal diopside is a pure substance and has good chemical stability.

[0031] The method provided by the present invention has the obvious advantages of simple operation process, short reaction time and the like, the obtained single-crystal diopside has good properties such as high purity, large size and stable chemical properties, and more importantly, the nickel content, zinc content and water content are high and controllable.

DETAILED DESCRIPTION OF THE INVENTION

[0032] A method for preparing high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition uses solid calcium nitrate tetrahydrate powder (purity: >99.99%), solid magnesium nitrate hexahydrate powder (purity: >99.99%), solid nickel(II) nitrate hexahydrate powder (purity: >99.999%), solid zinc nitrate hexahydrate powder (purity: >99.99%), liquid tetraethoxysilane (purity: >99.99%), solid natural talcum powder (purity: >99%), solid nickel hydroxide powder (purity: >99.8%), solid zinc hydroxide powder (purity: >99.4%) and absolute ethyl alcohol (concentration: >99.9%) as starting materials, and comprises:

[0033] Step 1, 62 ml of absolute ethyl alcohol is placed into a 300 ml wide-mouth glass bottle.

[0034] Step 2, 10 g of the high-purity solid magnesium nitrate hexahydrate powder,

9.2138 g of the high-purity solid calcium nitrate tetrahydrate powder, 100 mg of the

LU503141 high-purity solid nickel(IT) nitrate hexahydrate powder and 80 mg of the high-purity solid zinc nitrate hexahydrate powder are weighed with a high-precision analytical balance according to diopside (CaMg(Ni, Zn)SizOs) chemometrics, and are carefully added to the 62 ml of absolute ethyl alcohol.

[0035] Step 3, 18.2752 ml of the high-purity liquid tetraethoxysilane is carefully added to the 62 ml of absolute ethyl alcohol with a pipette according to the diopside chemometrics.

[0036] Step 4, a magnetic stirring rotor is put in the wide-mouth bottle containing a mixed solution of solid magnesium nitrate hexahydrate, solid calcium nitrate tetrahydrate, solid nickel(IT) nitrate hexahydrate, solid zinc nitrate hexahydrate, the liquid tetracthoxysilane and the absolute ethyl alcohol, and a mouth of the wide-mouth bottle is sealed with a plastic film with a thickness of 0.5 mm to prevent the initial solution in the wide-mouth bottle from splashing during the high-speed stirring process, which may otherwise compromise the synthesis accuracy of a sample.

[0037] Step 5, the wide-mouth bottle containing the sealed initial mixed solution and magnetic stirring rotor is placed on a high-temperature magnetic stirring heater coil, and in order to dissolve the starting materials, namely the solid magnesium nitrate hexahydrate, the solid calcium nitrate tetrahydrate, the solid nickel(II) nitrate hexahydrate, the solid zinc nitrate hexahydratea and the liquid tetracthoxysilane, in the absolute ethyl alcohol, the high-temperature magnetic stirring heater coil is made to stir the materials at room temperature and 880 rpm for 21 hrs, so that the materials are sufficiently dissolved without residues.

[0038] Step 6, the mouth, sealed with the plastic film, of the wide-mouth bottle is opened, 44 ml of a 69-70% concentrated nitric acid solution is added to the mixed solution to accelerate the preparation reaction of diopside, and then the mouth of the wide-mouth bottle is sealed again with the plastic film to prevent the initial solution in the wide-mouth

LU503141 bottle from splashing during the high-temperature stirring process, which may otherwise compromise the synthesis accuracy of the sample.

[0039] Step 7, multiple 0.1 mm small holes are poked in the surface of the plastic film with sharp tweezers to allow volatile substances such as NHz*H»>O, CO and Oz produced during the reaction to be volatilized more easily and to prevent concentrated nitric acid in the wide-mouth bottle from splashing during the high-temperature stirring process, which may otherwise compromise the synthesis accuracy of the sample.

[0040] Step 8, the wide-mouth bottle is placed on the high-temperature magnetic stirring heater coil, and the temperature of the heater coil is increased to 87° C, and the mixed solution is stirred at a high temperature of 87° C and a high speed of 1071 rpm for 24 hrs, so that all initial reagents are thoroughly dissolved in a mixed solution of the absolute ethanol and the concentrated nitric acid.

[0041] Step 9, the plastic film sealing the mouth of the wide-mouth bottle is removed, and the temperature of the high-temperature magnetic stirring heater coil is increased to 111° C until the mixed solution in the whole wide-mouth bottle is completely desiccated.

[0042] Step 10, the magnetic stirring rotor is taken out, and all mixed powder in the wide-mouth bottle is taken out carefully with a spoon and is placed in a platinum crucible.

[0043] Step 11, the platinum crucible containing the mixed powder is placed in a high-temperature muffle furnace, and the temperature of the high-temperature muffle furnace is increased to 1018° C at a rate of 760° C/h to calcine the mixed powder for 1.8 hrs at a high temperature to remove residual nitric acid and organic matter in the mixed powder; and the mixed powder is slowly and naturally cooled to room temperature, and then the mixed sample powder is taken out.

[0044] Step 12, a calcined powdery mixture sample is uniformly ground and

LU503141 mixed in an agate mortar, and is then pressed into a ® 15.1 mm (diameter) * 7.2 mm (height) disc on a press, and three discs are stacked up in the platinum crucible.

[0045] Step 13, the platinum crucible containing the disc-shaped mixture sample is hung in the middle of a high-temperature oxygen atmosphere furnace having an open bottom, with a platinum wire connected to a wall of the platinum crucible, and a gas mixture of hydrogen, argon and carbon dioxide is injected into the platinum crucible from a top of the platinum crucible to control the oxygen atmosphere in a furnace body during the high-temperature calcining process.

[0046] Step 14, a cup, 690 ml, of secondary deionized cold water is placed below the furnace body of the oxygen atmosphere furnace, so that the sample can be directly quenched at a high temperature.

[0047] Step 15, the temperature of the platinum crucible containing the disc-shaped mixture sample is increased to 1450° C at a rate of 620° C/h for constant-temperature calcining for 29 min to melt the disc-shaped mixture sample into glassy-state diopside. Generally, the melting point of diopside is 1391° C, so when the temperature is over 1391° C, the diopside will be in a glassy state. The high-temperature calcining process under the controlled oxygen atmosphere is carried out to provide a purer mixture initial material, namely the diopside glass, to realize the synthesis of large-sized high-nickel, high-zinc and high-water single-crystal diopside; the high-temperature calcination under the oxygen atmosphere can better control the valence state of the variable-valence element, namely metallic manganese, in the product; and the relatively short calcination time ensures that the diopside can be quickly melted into a glass phase when the temperature is over 1391° C and possible residual substances that may affect the sample preparation, such as water, organic matter and nitric acid can be volatilized completely. After the sample is calcined at 1450° C for 29 min, a 10 A high-power current is applied to the platinum wire connected to the wall of the platinum crucible to fuse the

LU503141 platinum wire, so that the platinum crucible containing the sample instantly falls into the secondary deionized cold water from a hearth of the oxygen atmosphere furnace to realize direct quenching of the sample at a high temperature, thus obtaining diopside glass with uniform components, wherein fast quenching ensures that the diopside sample in the glassy state is preserved in good condition at a high temperature. The diopside glass, quenched with the secondary deionized cold water, is taken out of the platinum crucible and is sufficiently ground into uniform sample powder in the agate mortar.

[0048] Step 16, the sample powder is placed on the press and is pressed into a ® 3,8 mm (diameter) * 3.5 mm (height) cylinder, and in order to obtain high-water diopside, natural talcum [molecular formula: Mgz(Si4O10)(OH)a], nickel hydroxide [Ni(OH)2] and zinc hydroxide [Zn(OH)z] with a weight ratio of 4:1:1 are used as a water source. The natural talcum, nickel hydroxide and zinc hydroxide, as typical hydrous minerals, will undergo a dehydration reaction when the temperature is over 643.4° C, thus being widely applied to common mineral combinations for providing a water source during high-temperature and high-pressure experimental simulation. By using the talcum, nickel hydroxide and zinc hydroxide with the weight ratio of 4:1:1, sufficient water can be released by dehydrated products of the hydrous minerals, the talcum, nickel hydroxide and zinc hydroxide, under a high-temperature and high-pressure condition to provide a water source for synthesizing the high-water diopside, and a large quantity of enstatite, quartz, nickel oxide and zinc oxide can be generated to control the silicon activity during the preparation process of the high-nickel, high-zinc and high-water single-crystal diopside in the sample cavity under the high-temperature and high-pressure condition. In addition, by using the natural talcum, nickel hydroxide and zinc hydroxide as a water source, all products of the dehydration reaction are magnesium-containing silicate minerals (enstatite) and oxides (quartz, nickel oxide and zinc oxide) that will not react with the diopside sample, so that the sample is effectively prevented from being contaminated during the

LU503141 preparation process

[0049] Step 17, the natural talcum, nickel hydroxide and zinc hydroxide with the weight ratio of 4:1:1 for providing a water source are placed on the press and pressed into two © 3.8 mm (diameter) * 0.15 mm (thickness) discs, which are sequentially placed at two ends of the sample, and the sample and the two water-sourced discs (the natural talcum, nickel hydroxide and zinc hydroxide with the weight ratio of 4:1:1 for providing a water source) are sealed in a ® 3.8 mm (inner diameter) * 4.0 mm (height) gold-palladium alloy sample tube with a wall thickness of 0.1 mm, wherein the gold-palladium alloy tube is made of an optimal sealing material that can effectively prevent water from escaping from the sample tube during the sample preparation process under the high-temperature and high-pressure condition.

[0050] Step 18, diopside is one of the important magnesium-containing silicate minerals in the mantle region of the earth and other terrestrial planets; in order to truly simulate the growth environment of diopside deep in the mantle region of the earth and other terrestrial planets and invert the temperature and pressure condition for the stable existence of the diopside mineral phase, the gold-palladium alloy tube containing the sample and the two water-sourced discs (the natural talcum, nickel hydroxide and zinc hydroxide with the weight ratio of 4:1:1 for providing a water source) is placed on a

Kawai-1000t multi-anvil press, a pressure rise rate and a temperature rise rate are set to 1.5 GPa/h and 50° C/min respectively, the pressure and the temperature are increased to 4.0 GPa and 1000° C respectively for hot-pressing sintering, and a reaction is performed for 14 hrs under a constant-temperature and constant-pressure condition.

[0051] According to the present invention, the temperature in the high-pressure sample cavity is accurately calibrated with two sets of high-temperature nickel chromium-nickel silicon K-type metal thermocouples. Because of its obvious advantages of good linear relationship between temperature and thermoelectric EMF, large

LU503141 thermoelectric EMF, high sensitivity, good thermal stability, high oxidation resistance and low price, the nickel chromium-nickel silicon K-type metal thermocouples are the most common thermocouples in many high-temperature and high-pressure mineral physics research laboratories at home and abroad and can measure a maximum temperatures of 1300° C. Each set of nickel chromium-nickel silicon K-type metal thermocouples is composed of a nickel-chromium metal alloy wire and a nickel-silicon metal alloy wire that are made of different materials (the chemical composition of a positive pole (KP) of each thermocouple is NisoxCr10%; the chemical composition of a negative pole (KN) of each thermocouple is Nig¢7%Sis%; and correspondingly, a diameter of each positive nickel-chromium metal alloy wire KP and each negative nickel-silicon metal alloy wire

KN is 0.3 mm), and each set of nickel chromium-nickel silicon K-type metal thermocouples is symmetrically placed on upper and lower sides of an outer wall of the sample cavity of the gold-palladium alloy tube, so that the temperature in the sample cavity is calibrated.

[0052] Under a pressure of 4.0 GPa, the natural talcum, nickel hydroxide and zinc hydroxide with the weight ratio of 4:1:1 sealed at the two ends of the gold-palladium alloy sample tube and used for providing a water source will undergo a dehydration reaction to release sufficient water when the temperature is increased to 643.4° C, so that a good water source is provided. Moreover, when the natural talcum, nickel hydroxide and zinc hydroxide undergo the dehydration reaction under the high-temperature and high-pressure condition, a large quantity of mineral combinations of enstatite, quartz, nickel oxide and zinc oxide will be generated to control the silicon activity during the preparation process of the high-nickel, high-zinc and high-water single-crystal diopside in the sample cavity under the high-temperature and high-pressure condition.

[0053] After the reaction is performed for 14 hrs under the constant-temperature and constant-pressure condition, the temperature in the sample cavity is decreased to room

LU503141 temperature from 1000° C at a rate of 10° C/min, Compared with the temperature rise rate (50° C/min) for sample preparation, a low temperature fall rate under a constant pressure is more beneficial for crystal growth of large-sized single-crystal diopside. After the temperature in the sample cavity is decreased to the room temperature, the pressure in the sample cavity is decreased to normal pressure from 4.0 GPa at a rate of 0.4 GPa/h.

[0054] Step 19, at the end of the high-temperature and high-pressure preparation reaction, an experimental sample is taken out of the sample cavity, the gold-palladium alloy sample tube is opened with a diamond slicer, and single-crystal diopside is picked out under a high-power Olympus microscope.

[0055] The obtained single-crystal diopside is a single phase without any other impurity phases. A test result obtained with an electron-probe microanalyzer (EPMA) shows that the single-crystal diopside has a molecular formula of CaMg[Siz0s]. A test result obtained with multifunctional inductively coupled plasma-mass spectrometry (ICP-MS) shows that the nickel content and zinc content of the single-crystal diopside are 8814 ppm wt% and 6892 ppm wt% respectively. A test result obtained with vacuum

Fourier transform-infrared spectroscopy (FT-IR) shows that the diopside has a high water content of 2680 ppm wt%.

[0056] The obtained high-nickel, high-zinc and high-water single-crystal diopside is an orthorhombic system with a space group of C2/c (no.15), lattice parameters: a = 9.752 À, b = 8.927 A and c = 5.256 A, a unit cell volume of 439.82 A3, an average particle size of 169 pm, and a maximum particle size of 421 um.

[0057] The high-nickel, high-zinc and high-water single-crystal diopside obtained through the method provided by the present invention has superior properties such as high purity, large size, and stable chemical properties, and more importantly, the nickel content, the zinc content and the water content are high and controllable. By changing the chemical dosage of the initial material, solid nickel(IT) nitrate hexahydrate powder, from 90.7655 mg to 102.1112 mg, the nickel content of the finally obtained high-nickel, high-zinc and FSO high-water single-crystal diopside is increased from 8000 ppm wt% to 9000 ppm wt%. By changing the chemical dosage of the initial material, solid zinc nitrate hexahydrate powder, from 69.6426 mg to 81.2497 mg, the zinc content of the finally obtained high-nickel, high-zinc and high-water single-crystal diopside is increased from 6000 ppm wt% to 7000 ppm wt%. By changing the weight ratio of the hydrous minerals, natural talcum powder, nickel hydroxide powder and zinc hydroxide, for providing a water source and the different heights of the two corresponding water-sourced discs, the total amount of water generated by the dehydration reaction of the hydrous minerals sealed in the gold-palladium alloy sample tube can be controlled, and thus, the water content of the high-nickel, high-zinc and high-water single-crystal diopside can be adjusted.

The obtained high-nickel, high-zinc and high-water single-crystal diopside can fully meet the requirements for experimental physics simulation of minerals in the mantle region of the earth and other terrestrial planets under a high-temperature and high-pressure condition, breaks through the existing technical bottlenecks in the synthesis of single-crystal diopside, and provides an important experimental sample support for exploring the optimal orientation and crystal axis anisotropy of single-crystal minerals in the mantle region of the earth and other terrestrial planets under a high-temperature and high-pressure condition,

Claims

What is claimed is: LU503141

1. A method for preparing high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition, comprising: preparing a diopside cylinder sample using solid calcium nitrate tetrahydrate powder, solid magnesium nitrate hexahydrate powder, solid nickel(II) nitrate hexahydrate powder, solid zinc nitrate hexahydrate powder, liquid tetraethoxysilane and absolute ethyl alcohol as starting materials; preparing water-sourced discs using solid natural talcum powder, solid nickel hydroxide powder and solid zinc hydroxide powder as starting materials; placing the water-sourced discs at two ends of the diopside cylinder sample and then placing the diopside cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube; and preparing high-nickel, high-zinc and high-water single-crystal diopside high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition.

2. The method for preparing high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition according to Claim 1, wherein the purity of the solid calcium nitrate tetrahydrate powder is over 99.99%, the purity of the solid magnesium nitrate hexahydrate powder is over 99.99%, the purity of the solid nickel(II) nitrate hexahydrate powder is over 99.999%, the purity of the solid zinc nitrate hexahydrate powder is over 99.99%, the purity of the liquid tetraethoxysilane is over 99.99%, the purity of the solid natural talcum powder is over 99%, the purity of the solid nickel hydroxide powder is over 99.8%, the purity of the solid zinc hydroxide powder is over 99.4%, and the concentration of the absolute ethyl alcohol is over 99.9%.

3. The method for preparing high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition according to Claim 1, wherein the diopside cylinder sample is prepared by: Step 1, placing 62 ml of absolute ethyl alcohol into a 300 ml wide-mouth glass bottle;

Step 2, weighing, according to diopside chemometrics, 10 g of the solid magnesium LU503141 nitrate hexahydrate powder, 9.2138 g of the solid calcium nitrate tetrahydrate powder, 100 mg of the solid nickel(IT) nitrate hexahydrate powder and 80 mg of the solid zinc nitrate hexahydrate powder, and adding the weighed materials into the 62 ml of absolute ethyl alcohol;

Step 3, adding, with a pipette, 18.2752 ml of the liquid tetracthoxysilane to the 62 ml of absolute ethyl alcohol according to the diopside chemometrics;

Step 4, putting a magnetic stirring rotor in the wide-mouth bottle, and sealing a mouth of the wide-mouth bottle with a plastic film with a thickness of 0.5 mm;

Step 5, placing the wide-mouth bottle on a high-temperature magnetic stirring heater coil, and cnabling the high-temperature magnetic stirring heater coil to stir a mixed solution for 21 hrs at room temperature and 880 rpm;

Step 6, opening the mouth, sealed with the plastic film, of the wide-mouth bottle to add 44 ml of a 69-70% concentrated nitric acid solution to the mixed solution, and then sealing the mouth of the wide-mouth bottle again with the plastic film;

Step 7, poking multiple 0.1 mm holes in a surface of the plastic film;

Step 8, placing the wide-mouth bottle on the high-temperature magnetic stirring heater coil, increasing a temperature of the heater coil to 87° C, and stirring the mixed solution for 24 hrs at 87°C and 1071 rpm;

Step 9, removing the plastic film from the mouth of the wide-mouth bottle, and increasing the temperature of the high-temperature magnetic stirring heater coil to 111° C until the mixed solution in the whole wide-mouth bottle is completely desiccated;

Step 10, taking out the magnetic stitring rotor, taking, with a spoon, all mixed powder out of the wide-mouth bottle, and placing the mixed powder in a platinum crucible;

Step 11, placing the platinum crucible in a high-temperature muffle furnace, and increasing a temperature of the high-temperature muffle furnace to 1018° C at a rate of

760° C/h to calcine the mixed powder for 1.8 hrs; naturally cooling the mixed powder to LU503141 room temperature, and taking out the mixed sample powder;

Step 12, uniformly grinding and mixing the mixed sample powder in an agate mortar, and pressing the mixed sample powder into a ® 15.1 mm * 7.2 mm disc on a press, and stacking three discs up in the platinum crucible;

Step 13, hanging the platinum crucible in a middle of a high-temperature oxygen atmosphere furnace having an open bottom, with a platinum wire connected to a wall of the platinum crucible, and injecting a gas mixture of hydrogen, argon and carbon dioxide into the platinum crucible from a top of the platinum crucible; and placing a cup, 690 ml, of secondary deionized cold water below a furnace body of the oxygen atmosphere furnace;

Step 14, increasing a temperature of the platinum crucible to 1450° C at a rate of 620° C/h for constant-temperature calcining for 29 min to melt the mixed powder into glassy-state diopside; applying a 10 A current to the platinum wire connected to the wall of the platinum crucible to fuse the platinum wire, so that the platinum crucible containing the sample falls into the secondary deionized cold water from a hearth of the oxygen atmosphere furnace to realize direct quenching of the sample at a high temperature, thus obtaining diopside glass with uniform components; taking the quenched diopside glass out of the platinum crucible, and grinding the diopside glass into uniform sample powder in the agate mortar; and

Step 15, pressing the sample powder into a @ 3.8 mm * 3.5 mm cylinder to obtain the diopside cylinder sample.

4, The method for preparing high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition according to Claim 1, wherein preparing water-sourced discs using solid natural talcum powder, solid nickel hydroxide powder and solid zinc hydroxide powder as starting materials is carried out by:

using natural talcum, nickel hydroxide and zinc hydroxide with a weight ratio of 4:1:1 as LU503141 raw materials, and pressing the natural talcum, the nickel hydroxide and the zinc hydroxide into two ® 3.8 mm * 0.15 mm discs on a press to obtain the water-sourced discs.

5. The method for preparing high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition according to Claim 1, wherein placing the water-sourced discs at two ends of the diopside cylinder sample and then placing the diopside cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube; and preparing high-nickel, high-zinc and high-water single-crystal diopside high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition. are carried out by: placing the gold-palladium alloy tube containing the diopside cylinder sample and the two water-sourced discs on a Kawai-1000t multi-anvil press, setting a pressure rise rate and a temperature rise rate to 1.5 GPa/h and 50° C/min respectively, increasing the pressure and the temperature to 4.0 GPa and 1000° C respectively for hot-pressing sintering, and performing a reaction for 14 hrs under a constant-temperature and constant-pressure condition; after the reaction is performed for 14 hrs under the constant-temperature and constant-pressure condition, decreasing a temperature in a sample cavity to room temperature from 1000° C at a rate of 10° C/min; after the temperature is decreased to the room temperature, decreasing a pressure in the sample cavity to normal pressure from 4.0 GPa at a rate of 0.4 GPa/h; and at the end of the high-temperature and high-pressure preparation reaction, taking an experimental sample out of the sample cavity, opening the gold-palladium alloy sample tube with a diamond slicer, and picking out the single-crystal diopside under an Olympus microscope.

6. The method for preparing high-nickel, high-zinc and high-water single-crystal diopside under a high-temperature and high-pressure condition according to Claim 1,

wherein during the high-temperature and high-pressure reaction, the temperature in the LU503141 high-pressure sample cavity is calibrated with two sets of high-temperature nickel chromium-nickel silicon K-type metal thermocouples, and each set of nickel chromium-nickel silicon K-type metal thermocouples is composed of a nickel-chromium metal alloy wire and a nickel-silicon metal alloy wire that are made of different materials; the chemical composition of a positive pole KP of each said thermocouple is NisoxCr10%; the chemical composition of a negative pole KN of each said thermocouple is Nis74Sis3%; correspondingly, a diameter of each said positive nickel-chromium metal alloy wire KP and each negative nickel-silicon metal alloy wire KN is 0.3 mm; and each set of nickel chromium-nickel silicon K-type metal thermocouples is symmetrically placed on upper and lower sides of an outer wall of the sample cavity of the gold-palladium alloy tube, so that the temperature in the sample cavity is calibrated.