LU503143B1

LU503143B1 - Method for preparing single-crystal wollastonite under high-temperature and high-pressure condition

Info

Publication number: LU503143B1
Application number: LU503143A
Authority: LU
Inventors: Haiying Hu; Lidong Dai
Original assignee: Inst Geochemistry Cas
Priority date: 2021-12-09
Filing date: 2022-12-07
Publication date: 2023-06-07
Also published as: ZA202205905B; CN114318491A; CN114318491B

Abstract

Disclosed is a method for preparing single-crystal wollastonite under a high-temperature and high-pressure condition, including: preparing a single-crystal wollastonite cylinder sample in a glassy state using solid calcium nitrate tetrahydrate powder, solid iron(III) nitrate nonahydrate powder, solid manganese(II) nitrate tetrahydrate powder, liquid tetraethoxysilane and absolute ethyl alcohol äs starting materials; preparing water-sourced discs using solid natural talcum powder, solid a-phase goethite powder, solid flake manganite powder and solid slaked lime powder; and placing the water-sourced discs at two ends of the cylinder sample, and placing the cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube to prepare single-crystal wollastonite through a high-temperature and high-pressure reaction. The present invention fundamentally fills in the technical blank in preparing high-iron, high-manganese and high-water single-crystal wollastonite in the prior arl, so that large-grained high-iron, high-manganese and high-water single-crystai wollastonite experimental samples are obtained.

Description

METHOD FOR PREPARING SINGLE-CRYSTAL WOLLASTONITE UNDER

LU503143

HIGH-TEMPERATURE AND 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 single-crystal wollastonite under a high-temperature and high-pressure condition.

[0003] 2. Description of Related Art

[0004] Wollastonite (molecular formula: CasSisOy), as a silicate of a single-chain structure and an important end-member component of the wollastonite mineral series, is the most typical chain silicate mineral.

[0005] Pure single-crystal wollastonite 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 single-crystal wollastonite 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 single-crystal wollastonite under a high-temperature and high-pressure condition, comprising: preparing a single-crystal wollastonite cylinder sample in a glassy state using solid calcium nitrate tetrahydrate powder, solid iron(III) nitrate nonahydrate powder, solid manganese(II) nitrate tetrahydrate powder, liquid tetraethoxysilane and absolute ethyl alcohol as starting materials; preparing water-sourced discs using solid natural talcum powder, solid a-phase

LU503143 goethite powder, solid flake manganite powder and solid slaked lime powder; and placing the water-sourced discs at two ends of the cylinder sample, and placing the cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube to prepare single-crystal wollastonite through a high-temperature and high-pressure reaction.

[0009] Preferably, the purity of the solid calcium nitrate tetrahydrate powder is over 99.99%, the purity of the solid iron(II) nitrate nonahydrate powder is over 99.99%, the purity of the solid manganese(II) nitrate tetrahydrate 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 a-phase goethite powder is over 99%, the purity of the solid flake manganite powder is over 99%, the purity of the solid slaked lime powder is over 99%, and the concentration of the absolute ethyl alcohol is over 99.9%.

[0010] Preferably, the single-crystal wollastonite cylinder sample is prepared by:

[0011] Step 1, placing 42 ml of absolute ethyl alcohol into a 550 ml wide-mouth glass bottle;

[0012] Step 2, weighing, with an analytical balance, 10 g of the solid calcium nitrate tetrahydrate powder, 110 mg of the solid iron(IIl) nitrate nonahydrate powder and 60 mg of the solid manganese(IT) nitrate tetrahydrate powder according to wollastonite [(Ca, Fe, Mn)sSis09] chemometrics, and adding the weighed materials to the 42 ml of absolute ethyl alcohol;

[0013] Step 3, carefully adding, with a pipette, 9.9173 ml of the liquid tetracthoxysilane to the 42 ml of absolute ethyl alcohol according to the wollastonite chemometrics;

[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

LU503143 mixed solution for 24 hrs at room temperature and 900 rpm;

[0016] Step 6, opening the mouth, sealed with the plastic film, of the wide-mouth bottle to add 40 ml of a 69-70% nitric acid solution to the mixed solution, then sealing the mouth of the wide-mouth bottle again, and poking multiple 0.1 mm holes in a surface of the plastic film;

[0017] Step 7, placing the wide-mouth bottle on the high-temperature magnetic stirring heater coil, increasing a temperature of the heater coil to 110° C, and stirring the mixed solution for 24 hrs at 85°C and 1100 rpm;

[0018] Step 8, 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 120° C until the mixed solution in the whole wide-mouth bottle is completely desiccated;

[0019] Step 9, 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; placing the platinum crucible in a high-temperature muffle furnace, and increasing a temperature of the high-temperature muffle furnace to 1000° C at a rate of 650° C/h to calcine the mixed powder for 2.5 hrs; naturally cooling the high-temperature muffle furnace to room temperature, and then taking out the mixed sample powder;

[0020] Step 10, uniformly grinding and mixing the mixed sample powder in an agate mortar, and pressing the mixed sample powder into a ® 15.2 mm * 7.5 mm disc on a press, and stacking three discs up in the platinum crucible;

[0021] Step 11, 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 oxygen atmosphere furnace from a top of the oxygen atmosphere furnace; placing a cup, 700 ml, of secondary deionized cold water below a furnace body of the oxygen atmosphere furnace;

LU503143

[0022] Step 12, increasing a temperature of the platinum crucible to 1600° C at a rate of 650° C/h for constant-temperature calcining for 30 min; after the sample is calcined for 30 min, 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 wollastonite glass with uniform components; taking the quenched wollastonite sample in the glassy state out of the platinum crucible, and grinding the wollastonite sample into uniform sample powder in the agate mortar; and

[0023] Step 13, pressing the sample powder into a ® 3.8 mm * 3.4 mm cylinder on the press.

[0024] Preferably, the water-sourced discs are prepared by: pressing, on a press, natural talcum, a-phase goethite, flake manganite and slaked lime with a weight ratio of 2:1:1:1 into two ® 3.8 mm * 0.2 mm discs to obtain the water-sourced discs.

[0025] Preferably, placing the water-sourced discs at two ends of the cylinder sample, and placing the cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube to prepare single-crystal wollastonite through a high-temperature and high-pressure reaction are carried out by: placing the gold-palladium alloy tube 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 1200° C respectively for hot-pressing sintering, and performing a reaction for 22 hrs under a constant-lemperature and constant-pressure condition.

[0026] Preferably, during the high-temperature and high-pressure reaction, the temperature is calibrated with two sets of high-temperature nickel chromium-nickel silicon K-type metal thermocouples, each set of nickel chromium-nickel silicon K-type

LU503143 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 Nic, Sizy, a diameter of each said positive nickel-chromium metal alloy wire (KP) and each said negative nickel-silicon metal alloy wire (KN) is 0.3 mm correspondingly, and each set of high-temperature nickel chromium-nickel silicon K-type metal thermocouples is symmetrically placed on upper and lower sides of an outer wall of a sample cavity of the gold-palladium alloy tube, so that the temperature in the sample cavity is calibrated.

[0027] Preferably, after the reaction is performed for 22 hrs under the constant-temperature and constant-pressure condition, a temperature in a sample cavity is decreased to room temperature from 1200° C at a rate of 8° C/min; after the temperature in the sample cavity is decreased to the room temperature, a pressure in the sample cavity is decreased to normal pressure from 4.0 GPa at a rate of 0.4 GPa/h; 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 the single-crystal wollastonite is picked out under an Olympus microscope.

[0028] The present invention has the following beneficial effects:

[0029] According to the present invention, single-crystal wollastonite with a high iron content (6000-7000 ppm wt%), a high manganese content (5000-6000 ppm wt%), and a high water content (3000-4000 ppm wt%) is synthesized, and the synthesized single-crystal wollastonite is a pure substance and has good chemical stability.

[0030] 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 wollastonite has good properties such as high purity, large size and stable chemical properties, and more importantly, the iron content, manganese content and water content

LU503143 are high and controllable.

DETAILED DESCRIPTION OF THE INVENTION

[0031] The invention provides a method for preparing single-crystal wollastonite under a high-temperature and high-pressure condition, specifically comprising:

[0032] Step 1, solid calcium nitrate tetrahydrate powder (purity: >99.99%), solid iron(IIT) nitrate nonahydrate powder (purity: >99.99%), solid manganese(Il) nitrate tetrahydrate powder (purity: >99.99%), liquid tetraethoxysilane (purity: >99.99%), solid natural talcum powder (purity: >99%), solid a-phase goethite powder (purity: >99%), solid flake manganite powder (purity: >99%), solid slaked lime powder (purity: >99%), and absolute ethyl alcohol (concentration: >99.9%) are used as starting materials.

[0033] Step 2, 42 ml of absolute ethyl alcohol is placed into a 550 ml wide-mouth glass bottle.

[0034] Step 3, 10 g of the high-purity solid calcium nitrate tetrahydrate powder, 110 mg of the high-purity solid iron(IIT) nitrate nonahydrate powder and 60 mg of the high-purity solid manganese(Il) nitrate tetrahydrate powder are weighed with a high-precision analytical balance according to wollastonite [(Ca, Fe, Mn)sSisO9] chemometrics, and are carefully added to the 42 ml of absolute ethyl alcohol;

[0035] Step 4, 9.9173 ml of the liquid tetracthoxysilane is carefully added to the 42 ml of absolute ethyl alcohol with a pipette according to the wollastonite chemometrics;

[0036] Step 5, a magnetic stirring rotor is put in the wide-mouth bottle containing a mixed solution of the solid calcium nitrate tetrahydrate powder, the solid iron(IIT) nitrate nonahydrate powder, the solid manganese(Il) nitrate tetrahydrate powder, the liquid tetraethoxysilane 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

LU503143 otherwise compromise the synthesis accuracy of wollastonite.

[0037] Step 6, 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 solid calcium nitrate tetrahydrate powder, solid iron(II) nitrate nonahydrate powder, solid manganese(II) nitrate tetrahydrate powder and liquid tetraethoxysilane, in the absolute ethyl alcohol, the high-temperature magnetic stirring heater coil is made to stir the materials at room temperature and 900 rpm for 24 hrs, so that the materials are sufficiently dissolved without residue.

[0038] Step 7, the mouth, sealed with the plastic film, of the wide-mouth bottle is opened, 40 ml of a 69-70% concentrated nitric acid solution is added to the mixed solution to accelerate the preparation reaction of wollastonite, 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 bottle from splashing during the high-temperature stirring process, which may otherwise compromise the synthesis accuracy of a sample.

[0039] Step 8, multiple 0.1 mm small holes are poked in the surface of the film with sharp tweezers to allow volatile substances such as NHz-H;0, CO, Hz and O2 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-speed stirring process, which may otherwise compromise the synthesis accuracy of wollastonite.

[0040] Step 9, the wide-mouth bottle is placed on the high-temperature magnetic stirring heater coil, and the temperature of the heater coil is increased to 110° C, and the mixed solution is stirred at a high temperature of 85° C and a high speed of 1100 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 10, the film sealing the mouth of the wide-mouth bottle is removed,

LU503143 and the temperature of the high-temperature magnetic stirring heater coil is increased to 120° C until the mixed solution in the whole wide-mouth bottle is completely desiccated.

[0042] Step 11, 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; 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 1000° C at a rate of 650° C/h to calcine the mixed powder for 2.5 hrs at a high temperature to remove residual nitric acid and organic matter in the mixed powder; and the high-temperature muffle furnace is slowly and naturally cooled to room temperature, and then the mixed sample powder is taken out.

[0043] Step 12, the calcined mixed sample powder is uniformly ground and mixed in an agate mortar, and is then pressed into a ® 15.2 mm (diameter) * 7.5 mm (height) disc on a press, and three discs are stacked up in the platinum crucible.

[0044] 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 oxygen atmosphere furnace from a top of the oxygen atmosphere furnace to control the oxygen atmosphere in a fumace body during the high-temperature calcining process; and a cup, 700 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.

[0045] Step 14, the temperature of the platinum crucible containing the disc-shaped mixture sample is increased to 1600° C at a rate of 650° C/h for constant-temperature calcining for 30 min to melt the disc-shaped mixture sample into glassy-state wollastonite. Generally, the melting point of wollastonite is 1540° C, so when the temperature is over 1540° C, the wollastonite will be in a glassy state. The

LU503143 high-temperature calcining process under the controlled oxygen atmosphere is carried out to provide a purer mixture initial material, namely the wollastonite glass, to realize the synthesis of large-grained high-iron, high-manganese and high-water single-crystal wollastonite; the high-temperature calcination under the oxygen atmosphere can better control the valence state of variable-valence elements, namely metallic iron and metallic manganese, in the product; and the relatively short calcination time ensures that the wollastonite can be quickly melted into a glass phase when the temperature is over 1540°

C and possible residual substances that may affect the sample preparation, such as water, organic matter and nitric acid can be volatilized completely.

[0046] Step 15, after the sample is calcined at 1600° C for 30 mins, a 10 A high-power current is applied 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 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 wollastonite glass with uniform components, wherein fast quenching ensures that the wollastonite sample in the glassy state is preserved in good condition at a high temperature; and the wollastonite sample in the glassy state, 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.

[0047] Step 16, the sample powder is placed on the press and pressed into a ® 3.8 mm (diameter) * 3.4 mm (height) cylinder, and in order to obtain high-water wollastonite, natural talcum (molecular formula: Mgs(Si4010)(OH)2), a-phase goethite (molecular formula: FeOOH), flake manganite (molecular formula: Mn(OH)z) and slaked lime (molecular formula; Ca(OH)z) with a weight ratio of 2:1:1:1 are used as a water source.

The natural talcum, a-phase goethite, flake manganite and slaked lime, as typical hydrous minerals, will undergo a dehydration reaction at a pressure of 4.0 GPa and a temperature

LU503143 over 800° 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 natural talcum, o-phase goethite, flake manganite and slaked lime with the weight ratio of 2:1:1:1, sufficient water can be released by dehydrated products of the hydrous mineral, natural talcum, under a high-temperature and high-pressure condition to provide a water source for synthesizing the high-water wollastonite, and a large quantity of enstatite and quartz can be generated to control the silicon activity during the preparation process of the high-iron, high-manganese and high-water single-crystal wollastonite in a sample cavity under the high-temperature and high-pressure condition. In addition, by using the natural talcum, a-phase goethite, flake manganite and slaked lime as a water source, all products of the dehydration reaction are silicate minerals (enstatite) and oxides (quartz, hematite, pyrolusite, unslaked lime and MnQ) that will not react with the wollastonite sample, so that the sample is effectively prevented from being contaminated during the preparation process.

[0048] Step 17, the natural talcum, a-phase goethite, flake manganite and slaked lime with the weight ratio of 2:1:1:1 for providing a water source are placed on the press and pressed into two ® 3.8 mm (diameter) * 0.2 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, o-phase goethite, flake manganite and slaked lime with the weight ratio of 2:1:1:1 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.

[0049] Step 18, wollastonite is one of the important calcium-rich silicate minerals in the mantle region of the earth and other terrestrial planets; in order to truly simulate the

LU503143 growth environment of wollastonite deep in the mantle region of the carth and other terrestrial planets and invert the temperature and pressure condition for the stable existence of the wollastonite mineral phase, the gold-palladium alloy tube containing the sample and the two water-sourced discs (the natural talcum, a-phase goethite, flake manganite and slaked lime with the weight ratio of 2:1:1:1 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 1200° C respectively for hot-pressing sintering, and a reaction is performed for 22 hrs under a constant-temperature and constant-pressure condition.

[0050] 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, which 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 temperature of 1300° C because of their obvious advantages of good linear relationship between temperature and thermoelectric EMF, large thermoelectric EMF, high sensitivity, good thermal stability, high oxidization resistance, low price and the like. 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 Niso%Crio%, the chemical composition of a negative pole (KN) of each thermocouple is Nis7%Si3%, the diameter of each positive nickel-chromium metal alloy wire (KP) and each negative nickel-silicon metal alloy wire (KN) is 0.3 mm correspondingly), and each set of high-temperature 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 accurately calibrated.

LU503143

[0051] Step 19, under a pressure of 4.0 GPa, the natural talcum, a-phase goethite, flake manganite and slaked lime with the weight ratio of 2:1:1:1 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 800°

C, so that a good water source is provided. Moreover, when the natural talcum, a-phase gocthite, flake manganite and slaked lime with the weight ratio of 2:1:1:1 undergo the dehydration reaction under the high-temperature and high-pressure condition, a large quantity of mineral combinations of enstatite, quartz, hematite, pyrolusite, unslaked lime and MnO will be generated to control the silicon activity during the preparation process of the high-iron, high-manganese and high-water single-crystal wollastonite in the sample cavity under the high-temperature and high-pressure condition.

[0052] Step 20, after the reaction is performed for 22 hrs at 4.0 GPa and 1200° C, the temperature in the sample cavity is decreased to room temperature from 1200° C at a rate of 8° 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 wollastonite.

[0053] Step 21, 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. 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 wollastonite is picked out under a high-power Olympus microscope.

[0054] The obtained single-crystal wollastonite is a single phase without any other impurity phases. A test result obtained with an electron-probe microanalyzer (EPMA) shows that the single-crystal wollastonite has a molecular formula of CazSisO9. A test result obtained with multifunctional inductively coupled plasma-mass spectrometry

LU503143 (ICP-MS) shows that the iron content and manganese content of the single-crystal wollastonite are 6430 ppm wt% and 5645 ppm wt% respectively. A test result obtained with vacuum Fourier transform-infrared spectroscopy (FT-IR) shows that the single-crystal wollastonite has a high water content of 3840 ppm wt%.

[0055] The obtained high-iron, high-manganese and high-water single-crystal wollastonite is a triclinic system with a space group of P1 (no.2), lattice parameters: a = 7.935 A, b = 7.324 A and c = 7.071 A, a unit cell volume of 397.956 A3, an average particle size of 202 um, and a maximum particle size of 579 pm.

[0056] The high-iron, high-manganese and high-water single-crystal wollastonite 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 iron content, the manganese content and the water content are high and controllable. By changing the chemical dosage of the initial material, solid iron(III) nitrate nonahydrate powder, from 102.6459 mg to 119.7536 mg, the iron content of the finally obtained high-iron, high-manganese and high-water single-crystal wollastonite is increased from 6000 ppm wt% to 7000 ppm wt%. By changing the chemical dosage of the initial material, solid manganese(IT) nitrate tetrahydrate powder, from 53.1461 mg to 63.7753 mg, the manganese content of the finally obtained high-iron, high-manganese and high-water single-crystal wollastonite is increased from 5000 ppm wt% to 6000 ppm wt%. By changing the weight ratio of the hydrous minerals, natural talcum powder, a-phase goethite powder, flake manganite power and slaked lime powder, 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 finally obtained high-iron, high-manganese and high-water single-crystal wollastonite is increased from 3000 ppm wt% to 4000 ppm wt%. The obtained high-iron,

LU503143 high-manganese and high-water single-crystal wollastonite can fully meet the requirements for physics experimental 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 wollastonite, and provides an important experimental sample support for exploring the lattice-preferred 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: LU503143

1. A method for preparing single-crystal wollastonite under a high-temperature and high-pressure condition, comprising: preparing a single-crystal wollastonite cylinder sample in a glassy state using solid calcium nitrate tetrahydrate powder, solid iron(II) nitrate nonahydrate powder, solid manganese(ll) nitrate tetrahydrate powder, liquid tetracthoxysilane and absolute ethyl alcohol as starting materials; preparing water-sourced discs using solid natural talcum powder, solid o-phase goethite powder, solid flake manganite powder and solid slaked lime powder; and placing the water-sourced discs at two ends of the cylinder sample, and placing the cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube to prepare single-crystal wollastonite through a high-temperature and high-pressure reaction.

2. The method for preparing single-crystal wollastonite 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 iron(III) nitrate nonahydrate powder is over 99.99%, the purity of the solid manganese(II) nitrate tetrahydrate 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 a-phase goethite powder is over 99%, the purity of the solid flake manganite powder is over 99%, the purity of the solid slaked lime powder is over 99%, and the concentration of the absolute ethyl alcohol is over 99.9%.

3. The method for preparing single-crystal wollastonite under a high-temperature and high-pressure condition according to Claim 1, wherein the single-crystal wollastonite cylinder sample is prepared by: Step 1, placing 42 ml of absolute ethyl alcohol into a 550 ml wide-mouth glass bottle; Step 2, weighing, with an analytical balance, 10 g of the solid calcium nitrate tetrahydrate powder, 110 mg of the solid iron(II) nitrate nonahydrate powder and 60 mg of the solid manganese(II) nitrate tetrahydrate powder according to wollastonite [(Ca, Fe, LU503143 Mn):Si309] chemometrics, and adding the weighed materials to the 42 ml of absolute ethyl alcohol;

Step 3, carefully adding, with a pipette, 9.9173 ml of the liquid tetracthoxysilane to the 42 ml of absolute ethyl alcohol according to the wollastonite 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 enabling the high-temperature magnetic stirring heater coil to stir a mixed solution for 24 hrs at room temperature and 900 rpm;

Step 6, opening the mouth, sealed with the plastic film, of the wide-mouth bottle to add 40 ml of a 69-70% nitric acid solution to the mixed solution, then sealing the mouth of the wide-mouth bottle again, and poking multiple 0.1 mm holes in a surface of the plastic film;

Step 7, placing the wide-mouth bottle on the high-temperature magnetic stirring heater coil, increasing a temperature of the heater coil to 110° C, and stirring the mixed solution for 24 hrs at 85°C and 1100 rpm;

Step 8, 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 120° C until the mixed solution in the whole wide-mouth bottle is completely desiccated;

Step 9, 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; placing the platinum crucible in a high-temperature muffle furnace, and increasing a temperature of the high-temperature muffle furnace to 1000° C at a rate of 650° C/h to calcine the mixed powder for 2.5 hrs; naturally cooling the high-temperature muffle furnace to room temperature, and then taking out the mixed sample powder;

Step 10, uniformly grinding and mixing the mixed sample powder in an agate mortar, LU503143 and pressing the mixed sample powder into a ® 15.2 mm * 7.5 mm disc on a press, and stacking three discs up in the platinum crucible; Step 11, 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 oxygen atmosphere furnace from a top of the oxygen atmosphere furnace; placing a cup, 700 ml, of secondary deionized cold water below a furnace body of the oxygen atmosphere furnace; Step 12, increasing a temperature of the platinum crucible to 1600° C at a rate of 650° C/h for constant-temperature calcining for 30 min; after the sample is calcined for 30 min, 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 wollastonite glass with uniform components; taking the quenched wollastonite sample in the glassy state out of the platinum crucible, and grinding the wollastonite sample into uniform sample powder in the agate mortar; and Step 13, pressing the sample powder into a ® 3.8 mm * 3.4 mm cylinder on the press.

4, The method for preparing single-crystal wollastonite under a high-temperature and high-pressure condition according to Claim 1, wherein the water-sourced discs are prepared by: pressing, on a press, natural talcum, o-phase goethite, flake manganite and slaked lime with a weight ratio of 2:1:1:1 into two ® 3.8 mm * 0.2 mm discs to obtain the water-sourced discs.

5. The method for preparing single-crystal wollastonite under a high-temperature and high-pressure condition according to Claim 1, wherein placing the water-sourced discs at two ends of the cylinder sample, and placing the cylinder sample together with the LU503143 water-sourced discs in a gold-palladium alloy sample tube to prepare single-crystal wollastonite through a high-temperature and high-pressure reaction are carried out by: placing the gold-palladium alloy tube 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 1200° C respectively for hot-pressing sintering, and performing a reaction for 22 hrs under a constant-temperature and constant-pressure condition.

6. The method for preparing single-crystal wollastonite under a high-temperature and high-pressure condition according to Claim 5, wherein during the high-temperature and high-pressure reaction, the temperature is calibrated with two sets of high-temperature nickel chromium-nickel silicon K-type metal thermocouples, 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 Nivxox%Cr1i0%, the chemical composition of a negative pole (KN) of each said thermocouple is Nig7 Siz, a diameter of each said positive nickel-chromium metal alloy wire (KP) and each said negative nickel-silicon metal alloy wire (KN) is 0.3 mm correspondingly, and each set of high-temperature nickel chromium-nickel silicon K-type metal thermocouples is symmetrically placed on upper and lower sides of an outer wall of a sample cavity of the gold-palladium alloy tube, so that the temperature in the sample cavity is calibrated.

7. The method for preparing single-crystal wollastonite under a high-temperature and high-pressure condition according to Claim 5, wherein after the reaction is performed for 22 hrs under the constant-temperature and constant-pressure condition, a temperature in a sample cavity is decreased to room temperature from 1200° C at a rate of 8° C/min; after the temperature in the sample cavity is decreased to the room temperature, a pressure in the sample cavity is decreased to normal pressure from 4.0 GPa at a rate of 0.4 GPa/h; at LU503143 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 the single-crystal wollastonite is picked out under an Olympus microscope.