LU503139B1

LU503139B1 - Method for preparing single-crystal spessartine under high-temperature and high-pressure condition

Info

Publication number: LU503139B1
Application number: LU503139A
Authority: LU
Inventors: Lidong Dai; Haiying Hu
Original assignee: Inst Geochemistry Cas
Priority date: 2021-12-08
Filing date: 2022-12-06
Publication date: 2023-06-06
Also published as: CN114369863B; ZA202205903B; CN114369863A

Abstract

Disclosed is a method for preparing single-crystal spessartine under a high-temperature and high-pressure condition, including: preparing a powdery spessartine sample in a glassy state using solid manganese(II) nitrate tetrahydrate powder, solid aluminum nitrate nonahydrate powder, solid zirconium(IV) nitrate pentahydrate powder, solid vanadium(III) 2,4-pentanedionate powder, liquid tetraethoxysilane and absolute ethyl alcohol as starting materials, and pressing the powdery sample into a Φ 3.8 mm (diameter) * 3.4 mm (height) cylinder; preparing water-sourced discs using natural serpentine, flake manganite and zirconium hydroxide as a water source; and placing the two water-sourced discs at two ends of the cylinder sample and then placing the cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube for a high-temperature and high-pressure reaction to obtain single-crystal spessartine. The present invention fundamentally fills in the technical blank in preparing high-vanadium, high-zirconium and high-water single-crystal spessartine in the prior art, so that large-grained high-vanadium, high-zirconium and high-water single-crystal spessartine experimental samples are obtained.

Description

METHOD FOR PREPARING SINGLE-CRYSTAL SPESSARTINE UNDER

LU503139

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 spessartine under a high-temperature and high-pressure condition.

[0003] 2. Description of Related Art

[0004] Spessartine (molecular formula: Mn3Al>[S104]3) is the most important gem mineral of the garnet group.

[0005] Pure single-crystal spessartine 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 spessartine under a high-temperature and high-pressure condition to fundamentally fill in the technical blank in preparing high-vanadium, high-zirconium and high-water single-crystal spessartine in the prior art so as to obtain large-grained high-vanadium, high-zirconium and high-water single-crystal spessartine experimental samples.

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

[0008] A method for preparing single-crystal spessartine under a high-temperature and high-pressure condition, comprising: preparing a powdery spessartine sample in a glassy state using solid manganese(IT) nitrate tetrahydrate powder, solid aluminum nitrate nonahydrate powder, solid zirconium(I'V) nitrate pentahydrate powder, solid vanadium(IIT) 1

2,4-pentanedionate powder, liquid tetraethoxysilane and absolute ethyl alcohol as starting

LU503139 materials, and pressing the powdery sample into a ® 3.8 mm * 3.4 mm cylinder; preparing water-sourced discs using natural serpentine, flake manganite and zirconium hydroxide as a water source; and placing two water-sourced discs at two ends of the cylinder sample and then placing the cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube for a high-temperature and high-pressure reaction to obtain single-crystal spessartine.

[0009] Preferably, the purity of the solid manganese(Il) nitrate tetrahydrate powder is over 99.99%, the purity of the solid aluminum nitrate nonahydrate powder is over 99.99%, the purity of the solid zirconium(IV) nitrate pentahydrate powder is over 99.99%, the purity of the solid vanadium(IIT) 2,4-pentanedionate powder is over 99.99%, the purity of the liquid tetraethoxysilane is over 99.99%, the purity of solid natural serpentine powder is over 99%, the purity of the solid flake manganite is over 99%, the purity of the solid zirconium hydroxide is over 99%, and the concentration of the absolute ethyl alcohol is over 99.9%.

[0010] Preferably, the powdery spessartine sample in the glassy state is prepared by:

[0011] Step 1, placing 50 ml of absolute ethyl alcohol into a 400 ml wide-mouth glass bottle;

[0012] Step 2, weighing, with an analytical balance, 10 g of the solid manganese(IT) nitrate tetrahydrate powder, 9.9633 g of the solid aluminum nitrate nonahydrate powder, 100 mg of the solid zirconium(IV) nitrate pentahydrate powder and 70 mg of the solid vanadium(lIT) 2,4-pentanedionate powder according to spessartine [Mns(AI, Zr,

V)2(S104)3] chemometrics, and adding the weighted materials to the 50 ml of absolute ethyl alcohol;

[0013] Step 3, adding, with a pipette, 9.3302 ml of the liquid tetraethoxysilane to 2 the 50 ml of absolute ethyl alcohol according to the spessartine chemometrics;

LU503139

[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 20 hrs at room temperature and 1000 rpm;

[0016] Step 6, opening the mouth, sealed with the plastic film, of the wide-mouth bottle to add 48 ml of a 69-70% nitric acid solution to the mixed solution; 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 90° C, and stirring the mixed solution for 24 hrs at 90°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 110° 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;

[0020] Step 10, placing the platinum crucible containing the mixed powder in a high-temperature muffle furnace, and increasing a temperature of the high-temperature muffle furnace to 1100° C at a rate of 650° C/h to calcine the mixed powder for 1 h;

[0021] Step 11, 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 ® 15.0 mm * 7.5 mm disc on a press, and stacking three discs up in the platinum crucible; 3

[0023] Step 13, hanging the platinum crucible containing the disc-shaped mixture

LU503139 sample in a middle of a high-temperature oxygen atmosphere fumace 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; placing a cup, 500 ml, of secondary deionized cold water below a fumace body of the oxygen atmosphere fumace:

[0024] Step 14, increasing a temperature of the platinum crucible containing the disc-shaped mixture sample to 1300° C at a rate of 600° C/h for constant-temperature calcining for 18 min; then, 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 spessartine glass with uniform components; and

[0025] Step 15, taking the spessartine glass, quenched with the secondary deionized cold water, out of the platinum crucible, and grinding the spessartine glass into uniform sample powder in the agate mortar; pressing the sample powder into a ® 3.8 mm * 3.4 mm cylinder.

[0026] Preferably, the water-sourced discs are prepared by: pressing, on a press, serpentine, flake manganite and zirconium hydroxide with a weight ratio of 2:2:1 into two

D 3.8 mm * 0.2 mm discs to obtain the water-sourced discs.

[0027] Preferably, placing two water-sourced discs at two ends of the cylinder sample and then placing the cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube for a high-temperature and high-pressure reaction to obtain single-crystal spessartine are carried out by: placing the gold-palladium alloy tube containing the 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 2.0 GPa/h and 50° C/min 4 respectively, increasing the pressure and the temperature to 7.0 GPa and 1100° C

LU503139 respectively for hot-pressing sintering, and performing a reaction for 18 hrs under a constant-temperature and constant-pressure condition.

[0028] Preferably, during the high-temperature and high-pressure reaction, the temperature 1s calibrated with two sets of high-temperature platinum-rhodium noble metal thermocouples, each set of high-temperature platinum-rhodium noble metal thermocouples is composed of two platinum-rhodium alloy wires that are made of different materials, the chemical composition of each said thermocouple is Ptzo%Rhzo% and

Pto4%4Rhe6%, a diameter of each said platinum-rhodium alloy wire is 0.25 mm correspondingly, and each set of high-temperature platinum-rhodium noble 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.

[0029] Preferably, after the reaction is performed for 20 hrs under the constant-temperature and constant-pressure condition, decreasing a temperature in a sample cavity to room temperature from 1100° C at a rate of 5° C/min; after the temperature in the sample cavity is decreased to the room temperature, decreasing a pressure in the sample cavity to normal pressure from 7.0 GPa at a rate of 0.7 GPa/h; 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 spessartine under a high-power Olympus microscope.

[0030] The present invention has the following beneficial effects:

[0031] According to the present invention, single-crystal spessartine with a high zirconium content (8000-9000 ppm wt%), a high vanadium content (7000-8000 ppm wt%) and a high water content (4000-5000 ppm wt%) is synthesized, and the single-crystal spessartine is a pure substance and has good chemical stability.

LU503139

[0032] 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 spessartine has good properties such as high purity, large size and stable chemical properties, and more importantly, the vanadium content, zirconium content and water content are high and controllable.

DETAILED DESCRIPTION OF THE INVENTION

[0033] A method for preparing single-crystal spessartine under a high-temperature and high-pressure condition comprises:

[0034] Solid manganese(IT) nitrate tetrahydrate powder (purity: >99.99%), solid aluminum nitrate nonahydrate powder (purity: >99.99%), solid zirconium(IV) nitrate pentahydrate powder (purity: >99.99%), solid vanadium(IIT) 2,4-pentanedionate powder (purity: >99.99%), liquid tetraethoxysilane (purity: 99.99%), solid natural serpentine powder (purity: >99%), solid flake manganite (purity: >99%), solid zirconium hydroxide (purity: >99%) and absolute ethyl alcohol (concentration: >99.9%) are used as starting materials.

[0035] Step 1, 50 ml of absolute ethyl alcohol is placed into a 400 ml wide-mouth glass bottle.

[0036] Step 2, 10 g of the high-purity solid manganese(Il) nitrate tetrahydrate powder, 9.9633 g of the high-purity solid aluminum nitrate nonahydrate powder, 100 mg of the high-purity solid zirconium(IV) nitrate pentahydrate powder and 70 mg of the high-purity vanadium(Ill) 2,4-pentanedionate powder are accurately weighed with a high-precision analytical balance according to spessartine [Mns(AI, Zr, V)»(SiO4)3] chemometrics, and are carefully added to the 50 ml of absolute ethyl alcohol.

[0037] Step 3, 9.3302 ml of the high-purity liquid tetraethoxysilane is carefully 6 added to the 50 ml of absolute ethyl alcohol with a pipette according to the spessartine

LU503139 chemometrics.

[0038] Step 4, a magnetic stirring rotor is put in the wide-mouth bottle containing a mixed solution of the solid manganese(Il) nitrate tetrahydrate powder, the solid aluminum nitrate nonahydrate powder, the solid zirconium(IV) nitrate pentahydrate powder, the solid vanadium(IIT) 2,4-pentanedionate 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 otherwise compromise the synthesis accuracy of spessartine.

[0039] 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 solid manganese(Il) nitrate tetrahydrate, aluminum nitrate nonahydrate, zirconium(IV) nitrate pentahydrate, vanadium(IIl) 2,4-pentanedionate 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 1000 rpm for 20 hrs, so that the materials are sufficiently dissolved without residues.

[0040] Step 6, the mouth, sealed with the plastic film, of the wide-mouth bottle is opened, 48 ml of a 69-70% concentrated nitric acid solution is added to the mixed solution to accelerate the preparation reaction of pyrope, 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; multiple 0.1 mm small holes are poked in the surface of the film with sharp tweezers to allow volatile substances such as NH=eH20,

CaH4, CO, CO», Hz and Oz produced during the reaction to be volatilized more easily and 7 to prevent concentrated nitric acid in the wide-mouth bottle from splashing during the

LU503139 high-speed stirring process, which may otherwise compromise the synthesis accuracy of spessartine.

[0041] Step 7, the wide-mouth bottle is placed on the high-temperature magnetic stirring heater coil, and the temperature of the heater coil is increased to 90° C, and the mixed solution is stirred at a high temperature of 90° 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.

[0042] Step 8, the 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 110°

C until the mixed solution in the whole wide-mouth bottle is completely desiccated. 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 9, 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 1100° C at a rate of 650° C/h to calcine the mixed powder for 1 h 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 11, a calcined powdery mixture sample is uniformly ground and mixed in an agate mortar, and is then pressed into a ® 15.0 mm (diameter) * 7.5 mm (height) disc on a press, and three discs are stacked up in the platinum crucible.

[0045] Step 12, 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 8 a top of the platinum crucible to control the oxygen atmosphere in a furnace body during

LU503139 the high-temperature calcining process.

[0046] Step 13, a cup, 500 ml, of secondary deionized cold water is placed below the fumace body of the oxygen atmosphere fumace, so that the sample can be directly quenched at a high temperature.

[0047] Step 14, the temperature of the platinum crucible containing the disc-shaped mixture sample is increased to 1300° C at a rate of 600° C/h for constant-temperature calcining for 18 mins to melt the disc-shaped mixture sample into glassy-state spessartine. Generally, the melting point of spessartine is 1200° C, so when the temperature is over 1200° C, the spessartine 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 spessartine glass, to realize the synthesis of large-grained high-vanadium, high-zirconium and high-water single-crystal spessartine; the high-temperature calcination under the oxygen atmosphere can better control the valence state of variable-valence elements, namely metallic vanadium and metallic zirconium, in the product; and the relatively short calcination time ensures that the spessartine can be quickly melted into a glass phase when the temperature is over 1200° C and possible residual substances that may affect the sample preparation, such as water, organic matter and nitric acid can be volatilized completely.

[0048] Step 15, after the sample is calcined at 1300° C for 18 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 spessartine glass with uniform components, wherein fast quenching ensures that the spessartine sample in the glassy state is preserved in good condition at a high 9 temperature. The spessartine glass, quenched with the secondary deionized cold water, is

LU503139 taken out of the platinum crucible and is sufficiently ground into uniform sample powder in the agate mortar.

[0049] Step 16, the sample powder is placed on the press and pressed into a D 3.8 mm (diameter) * 3.4 mm (height) cylinder, and in order to obtain high-water spessartine, natural serpentine (molecular formula: Mg6S14010(OH)s), flake manganite (molecular formula: Mn(OH)») and zirconium hydroxide (molecular formula: Zr(OH)») with a weight ratio of 2:2:1 are used as a water source. The serpentine, flake manganite and zirconium hydroxide, as typical hydrous minerals, will undergo a dehydration reaction at a pressure of 7.0 GPa and a temperature over 802.4° 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 serpentine, flake manganite and zirconium hydroxide with the weight ratio of 2:2:1, sufficient water can be released by dehydrated products of the hydrous mineral, serpentine, under a high-temperature and high-pressure condition to provide a water source for synthesizing the high-water spessartine, and a large quantity of forsterite, enstatite and quartz can be generated to control the silicon activity during the preparation process of the high-vanadium, high-zirconium and high-water single-crystal spessartine in a sample cavity under the high-temperature and high-pressure condition. In addition, by using the natural serpentine, flake manganite and zirconium hydroxide as a water source, all products of the dehydration reaction are magnesium-containing silicate minerals (forsterite and enstatite) and oxides (pyrolusite, manganic oxide and quartz) that will not react with the spessartine sample, so that the sample is effectively prevented from being contaminated during the preparation process.

[0050] Step 17, the natural serpentine, flake manganite and zirconium hydroxide with the weight ratio of 2:2:1 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

LU503139 placed at two ends of the sample, and the sample and the two water-sourced discs (the serpentine, flake manganite and zirconium hydroxide with the weight ratio of 2:2:1 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.

[0051] Step 18, spessartine is one of the important silicate minerals containing magnesium and aluminum in the mantle region of the earth and other terrestrial planets; in order to truly simulate the growth environment of spessartine 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 spessartine mineral phase, the gold-palladium alloy tube containing the sample and the two water-sourced discs (the serpentine, flake manganite and zirconium hydroxide with the weight ratio of 2:2:1 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 2.5 GPa/h and 50° C/min respectively, the pressure and the temperature are increased to 7.0 GPa and 1100° C respectively for hot-pressing sintering, and a reaction is performed for 20 hrs under a constant-temperature and constant-pressure condition.

[0052] According to the present invention, the temperature in the high-pressure sample cavity is accurately calibrated with two sets of high-temperature platinum-rhodium noble metal thermocouples, which are suitable for various high-temperature corrosive occasions during industrial production and have been widely used for temperature measurement of glass, ceramic and industrial salt-bath furnaces. The high-temperature platinum-rhodium noble metal thermocouples are common noble metal thermocouples in many high-temperature and high-pressure mineral physics research laboratories at home 11 and abroad and can measure a maximum temperatures of 2315° C. Each set of

LU503139 high-temperature platinum-rhodium noble metal thermocouples is composed of two platinum-rhodium alloy wires that are made of different materials (the chemical composition is Pt7o0%,Rh30% and Pto4<Rh6%, and correspondingly, the diameter of each platinum-rhodium alloy wire is 0.25 mm), and each set of high-temperature platinum-rhodium noble 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.

[0053] Under a pressure of 7.0 GPa, the serpentine, flake manganite and zirconium hydroxide with the weight ratio of 2:2:1 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 802.4° C, so that a good water source is provided. Moreover, when the natural serpentine, flake manganite and zirconium hydroxide undergo the dehydration reaction under the high-temperature and high-pressure condition, a large quantity of mineral combinations of forsterite, enstatite, pyrolusite, manganic oxide and quartz will be generated to control the silicon activity during the preparation process of the high-vanadium, high-zirconium and high-water single-crystal spessartine in the sample cavity under the high-temperature and high-pressure condition.

[0054] Step 19, after the reaction is performed for 20 hrs under the constant-temperature and constant-pressure condition, the temperature in the sample cavity is decreased to room temperature from 1100° C at a rate of 5° 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 spessartine. 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 12

7.0 GPa at a rate of 0.7 GPa/h. At the end of the high-temperature and high-pressure

LU503139 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 spessartine 1s picked out under a high-power Olympus microscope.

[0055] The obtained single-crystal spessartine is a single phase without any other impurity phases. A test result obtained with an electron-probe microanalyzer (EPMA) shows that the single-crystal spessartine has a molecular formula of Mn3Al>[S104]3. A test result obtained with multifunctional inductively coupled plasma-mass spectrometry (ICP-MS) shows that the vanadium content and zirconium content of the single-crystal spessartine are 7568 ppm wt% and 8770 ppm wt% respectively. À test result obtained with vacuum Fourier transform-infrared spectroscopy (FT-IR) shows that the spessartine has a high water content of 4559 ppm wt%.

[0056] The obtained high-vanadium, high-zirconium and high-water single-crystal spessartine is an isometric system with a space group of la3d (no.230), lattice parameters: a = 10.172 À, b = 10.172 À and c = 10.172 À, a unit cell volume of 809.685 A’, an average particle size of 198 um, and a maximum particle size of 571 um.

[0057] The high-vanadium, high-zirconium and high-water single-crystal spessartine 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 vanadium content, the zirconium content and the water content are high and controllable. By changing the chemical dosage of the initial material, solid vanadium(III) 2,4-pentanedionate powder, from 64.7491 mg to 73.9989 mg, the vanadium content of the finally obtained high-vanadium, high-zirconium and high-water single-crystal spessartine is increased from 7000 ppm wt% to 8000 ppm wt%. By changing the chemical dosage of the initial material, solid zirconium(IV) nitrate pentahydrate powder, from 91.2201 mg to 102.6226 mg, the zirconium content of the 13 finally obtained high-vanadium, high-zirconium and high-water single-crystal spessartine

LU503139 is increased from 8000 ppm wt% to 9000 ppm wt%. By changing the weight ratio of the hydrous minerals, natural serpentine powder, flake manganite and zirconium 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-vanadium, high-zirconium and high-water single-crystal spessartine can be adjusted. The obtained high-vanadium, high-zirconium and high-water single-crystal spessartine 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 spessartine, 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. 14

Claims

What is claimed is: LU503139

1. A method for preparing single-crystal spessartine under a high-temperature and high-pressure condition, comprising: preparing a powdery spessartine sample in a glassy state using solid manganese(Il) nitrate tetrahydrate powder, solid aluminum nitrate nonahydrate powder, solid zirconium(I'V) nitrate pentahydrate powder, solid vanadium(IIT) 2,4-pentanedionate powder, liquid tetraethoxysilane and absolute ethyl alcohol as starting materials, and pressing the powdery sample into a ® 3.8 mm * 3.4 mm cylinder; preparing water-sourced discs using natural serpentine, flake manganite and zirconium hydroxide as a water source; and placing two water-sourced discs at two ends of the cylinder sample and then placing the cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube for a high-temperature and high-pressure reaction to obtain single-crystal spessartine.

2. The method for preparing single-crystal spessartine under a high-temperature and high-pressure condition according to Claim 1, wherein the purity of the solid manganese(Il) nitrate tetrahydrate powder is over 99.99%, the purity of the solid aluminum nitrate nonahydrate powder is over 99.99%, the purity of the solid zirconium(IV) nitrate pentahydrate powder is over 99.99%, the purity of the solid vanadium(IIl) 2,4-pentanedionate powder is over 99.99%, the purity of the liquid tetraethoxysilane is over 99.99%, the purity of solid natural serpentine powder is over 99%, the purity of the solid flake manganite is over 99%, the purity of the solid zirconium hydroxide is over 99%, and the concentration of the absolute ethyl alcohol is over 99.9%.

3. The method for preparing single-crystal spessartine under a high-temperature and high-pressure condition according to Claim 1, wherein the powdery spessartine sample in the glassy state is prepared by: Step 1, placing 50 ml of absolute ethyl alcohol into a 400 ml wide-mouth glass bottle; Step 2, weighing, with an analytical balance, 10 g of the solid manganese(II) nitrate tetrahydrate powder, 9.9633 g of the solid aluminum nitrate nonahydrate powder, 100 mg LU503139 of the solid zirconium(IV) nitrate pentahydrate powder and 70 mg of the solid vanadium(lIT) 2,4-pentanedionate powder according to spessartine [Mns(AI, Zr, V)2(S104)3] chemometrics, and adding the weighted materials to the 50 ml of absolute ethyl alcohol;

Step 3, adding, with a pipette, 9.3302 ml of the liquid tetraethoxysilane to the 50 ml of absolute ethyl alcohol according to the spessartine 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 20 hrs at room temperature and 1000 rpm;

Step 6, opening the mouth, sealed with the plastic film, of the wide-mouth bottle to add 48 ml of a 69-70% nitric acid solution to the mixed solution; 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 90° C, and stirring the mixed solution for 24 hrs at 90°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 110° 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;

Step 10, placing the platinum crucible containing the mixed powder in a high-temperature muffle furnace, and increasing a temperature of the high-temperature muffle furnace to 1100° C at a rate of 650° C/h to calcine the mixed powder for 1 h;

16

Step 11, naturally cooling the mixed powder to room temperature, and taking out the LU503139 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 ® 15.0 mm * 7.5 mm disc on a press, and stacking three discs up in the platinum crucible; Step 13, hanging the platinum crucible containing the disc-shaped mixture sample 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; placing a cup, 500 ml, of secondary deionized cold water below a furnace body of the oxygen atmosphere furnace; Step 14, increasing a temperature of the platinum crucible containing the disc-shaped mixture sample to 1300° C at a rate of 600° C/h for constant-temperature calcining for 18 min; then, 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 spessartine glass with uniform components; and Step 15, taking the spessartine glass, quenched with the secondary deionized cold water, out of the platinum crucible, and grinding the spessartine glass into uniform sample powder in the agate mortar; pressing the sample powder into a ® 3.8 mm * 3.4 mm cylinder.

4. The method for preparing single-crystal spessartine under a high-temperature and high-pressure condition according to Claim 1, wherein the water-sourced discs are prepared by: pressing, on a press, serpentine, flake manganite and zirconium hydroxide with a weight ratio of 2:2:1 into two ® 3.8 mm * 0.2 mm discs to obtain the water-sourced 17 discs. LU503139

5. The method for preparing single-crystal spessartine under a high-temperature and high-pressure condition according to Claim 1, wherein placing two water-sourced discs at two ends of the cylinder sample and then placing the cylinder sample together with the water-sourced discs in a gold-palladium alloy sample tube for a high-temperature and high-pressure reaction to obtain single-crystal spessartine are carried out by: placing the gold-palladium alloy tube containing the 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

2.0 GPa/h and 50° C/min respectively, increasing the pressure and the temperature to 7.0 GPa and 1100° C respectively for hot-pressing sintering, and performing a reaction for 18 hrs under a constant-temperature and constant-pressure condition.

6. The method for preparing single-crystal spessartine 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 platinum-rhodium noble metal thermocouples, each set of high-temperature platinum-rhodium noble metal thermocouples is composed of two platinum-rhodium alloy wires that are made of different materials, the chemical composition of each said thermocouple is Pt70Rh30% and Pto4%Rhe%, a diameter of each said platinum-rhodium alloy wire is 0.25 mm correspondingly, and each set of high-temperature platinum-rhodium noble 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 spessartine under a high-temperature and high-pressure condition according to Claim 5, wherein after the reaction is performed for hrs under the constant-temperature and constant-pressure condition, decreasing a temperature in a sample cavity to room temperature from 1100° C at a rate of 5° C/min; 18 after the temperature in the sample cavity is decreased to the room temperature, decreasing LU503139 a pressure in the sample cavity to normal pressure from 7.0 GPa at a rate of 0.7 GPa/h; 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 spessartine under a high-power Olympus microscope. 19