A method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing conditions

Abstract

This invention discloses a method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing, comprising: sealing serpentine sample powder under a vacuum of 10... –3 The steel cladding was placed inside the graphite furnace cylinder of the high-pressure vessel of a hot isostatic pressing (HIP) apparatus, and a graphite sealing cap was placed on top. Using argon as the pressure transmission medium, the temperature inside the sample chamber of the cylinder was raised to 800 °C and the pressure to 95.1 MPa using a multi-gradient cylinder heating and pressurization method, and the temperature and pressure were maintained for 8 hours. Then, the temperature inside the sample chamber of the cylinder was reduced to 167 °C and the pressure was reduced to 64.4 MPa. Finally, the pressure was released and the temperature was cooled to room temperature to obtain polycrystalline serpentine aggregate. This method fills the technical gap in the preparation of large-volume, water-rich magnesium silicate mineral experimental samples of high-density polycrystalline serpentine aggregate under high temperature and high pressure conditions.

Description

Technical Field

[0001] This invention belongs to the field of experimental sample synthesis technology of bulk layered oxygen-containing salt mineral aggregates – polycrystalline water-rich magnesium silicate minerals, and particularly relates to a method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing. Background Technology

[0002] In near-surface environments, serpentine, widely exposed at the surface, refers to a large class of super-magmatic minerals formed when olivine and pyroxene in the protolith readily serpentinate under low-temperature or medium-temperature hydrothermal alteration. Based on the geological temperature at which hydrothermal alteration occurs, it is further subdivided into low-temperature, medium-temperature, and high-temperature hydrothermal alteration. Generally, low-temperature hydrothermal alteration mainly includes: serpentinization, chalcedonyization, jasper-like alteration, opalization, alunitization, epidote alteration, and calcite alteration; medium-temperature hydrothermal alteration mainly includes: serpentinization, pyritization, silicification, chloritization, magnesite alteration, sericitization, clay alteration, talcification, galenamination, and sphalerite alteration; while high-temperature hydrothermal alteration mainly includes: skarnification, potassium feldspar alteration, tourmalinization, biotite alteration, topaz alteration, muscovite alteration, epidote alteration, and arsenopyrite alteration. Most ultramafic igneous rocks exposed at the surface have undergone hydrothermal alteration, primarily serpentinization, in which volatile water plays a crucial role. Taking the ultrabasic end-member component of forsterite as an example, serpentinization hydrothermal alteration occurs. The main alteration products observed in the field are serpentite, brucite, and magnesite, which in turn form a complex symbiotic / associated mineral assemblage. The specific alteration reaction process can be represented as follows:

[0003]

[0004]

[0005]

[0006] Taking ultrabasic enstatite as an example, after serpentinization and hydrothermal alteration, the main alteration products observed in the field are symbiotic / associated mineral assemblages of serpentine and talc. The specific alteration reaction process can be represented as follows:

[0007]

[0008] Serpentine, an alteration product exposed to air, can undergo further hydrothermal alteration under the influence of carbon dioxide. The main alteration products observed in the field are talc, magnesite, and quartz, which then form complex symbiotic / associated mineral assemblages. The specific alteration reaction process can be represented as follows:

[0009]

[0010]

[0011] Existing geological data indicate that the vast majority of serpentine collected in the field has undergone multiple phases of serpentinization and alteration, containing complex symbiotic / associated mineral assemblages such as brucite, talc, magnesite, and quartz, resulting in a relatively complex composition. In addition, various hydrothermal alteration processes of different geological origins, including serpentinization, talcification, tremolite alteration, chloritization, and sericitization, occur from different stratigraphic ages and tectonic periods. These hydrothermal alteration processes often intertwine, thus forming complexes with multiple associated mineral assemblages.

[0012] To investigate the formation mechanisms and occurrence principles of common geological disasters deep within the Earth, such as volcanoes, earthquakes, and debris flows, geologists typically employ multi-faceted, large-cavity high-pressure equipment, including hydrothermal autoclaves, piston cylinder presses, and rotary shear friction testing machines, to conduct simulation experiments on the solubility, friction coefficient, shear stress, and other physical parameters of large-volume polycrystalline serpentine aggregates under high temperature and pressure conditions. Obtaining a large-sized polycrystalline serpentine aggregate experimental sample (45.68 mm (diameter) × 70.23 mm (height)) is a crucial step in simulating these physical properties under high temperature and pressure conditions. Geologists typically use natural serpentine found in the field as a substitute for polycrystalline serpentine aggregates as experimental samples. However, natural serpentine has many drawbacks, including low sample density, a high content of impurity minerals (such as abundant brucite, talc, magnesite, quartz, and other silicate, oxide, and carbonate minerals), large and unevenly distributed single crystal grains of serpentine, the main constituent mineral, difficulty in eliminating optimal lattice orientation, and significant anisotropy of crystal axes. Consequently, many different high-temperature and high-pressure mineral and rock property simulation teams around the world use natural serpentine as the initial sample and employ multi-faceted large-cavity high-pressure equipment such as hydrothermal autoclaves, piston cylinder presses, and rotary shear friction testers. The experimental data on the physical properties of natural serpentine under high-temperature and high-pressure conditions obtained show significant differences, making it difficult to widely apply these experimental results to the interpretation of the formation mechanisms and occurrence mechanisms of geological disasters such as volcanoes, earthquakes, and debris flows.

[0013] In contrast, existing technologies, such as the YJ-3000t and Kawai-1000t quasi-hydrostatic presses, are used to prepare artificially synthesized island-shaped silicate mineral single crystal experimental samples under high temperature and high pressure conditions, as seen in patent {Dai Lidong and Hu Haiying. Chinese National Invention Patent: A method for preparing low-titanium dry forsterite single crystals under high temperature and high pressure conditions. Patent No.: ZL202111317925.5}. However, this method is limited to preparing island-shaped silicate mineral single crystal experimental samples rather than polycrystalline aggregate samples. The obtained island-shaped silicate mineral single crystals range in size from 100 micrometers to 425 micrometers, with uneven particle size distribution. The size of the obtained single crystal minerals is severely limited by the sample chamber volume. The cylindrical sample size of the high-temperature and high-pressure experimental product—single-crystal island-shaped silicate minerals—obtained by this method does not exceed 6 mm (bottom diameter) × 6 mm (height). Therefore, the size of the artificially synthesized island-shaped silicate mineral samples cannot meet the requirements for simulating the physical properties of minerals and rocks under high temperature and high pressure conditions in large-volume experiments. Although existing techniques, using quasi-hydrostatic presses such as the YJ-3000t and Kawai-1000t, can produce samples only a few millimeters in size, they are a relatively effective method for synthesizing single-crystal mineral samples under high temperature, high pressure, and quasi-hydrostatic conditions. However, when this method is applied to the synthesis of bulk polycrystalline serpentine aggregate samples (e.g., with a diameter greater than 40 mm), the top and bottom of the serpentine sample powder inevitably experience significant asymmetric shrinkage due to unidirectional compression during the high temperature, high pressure, and quasi-hydrostatic experiments. This results in numerous macroscopic voids and defects during the preparation of bulk polycrystalline mineral aggregate samples. These macroscopic voids and defects cause wrinkles or pores in the central part of the cross-section of the bulk polycrystalline serpentine aggregate, ultimately making it easy for the sample to undergo severe porosity or aggregation along the center of the wrinkles or pores. This is the unavoidable shrinkage and porosity effect during the synthesis of bulk polycrystalline mineral aggregate samples under high temperature, high pressure, and quasi-hydrostatic conditions. The shrinkage and porosity effects of these polycrystalline serpentine polymer samples lead to severe excessive deformation, resulting in numerous voids, folds, and cavities in the bulk polycrystalline serpentine polymer samples. This significantly affects the preparation results of the bulk polycrystalline serpentine polymer samples. Therefore, neither natural serpentine nor small-sized (no more than 6 mm) serpentine single crystal samples obtained in the laboratory can meet the minimum experimental sample size requirements for mineral and rock property simulation on multi-faceted, large-cavity high-pressure equipment such as hydrothermal autoclaves, piston cylinder presses, and rotary shear friction testing machines. To date, there is still no effective synthesis method.Therefore, it is particularly urgent to effectively synthesize a high-density, high-compactness, high-purity, and large-volume polycrystalline serpentine aggregate experimental sample that meets the needs of various high-temperature and high-pressure laboratory simulations in earth science research, especially for experimental simulation studies of the physical properties of large-volume layered oxygen-containing salt mineral aggregates—polycrystalline water-rich magnesium silicate minerals—under high-temperature and high-pressure conditions, such as solubility, friction coefficient, and shear stress. Summary of the Invention

[0014] The technical problem to be solved by this invention is to provide a method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing, thereby filling the technical gap in the preparation of large, water-rich magnesium silicate mineral experimental samples of high-density polycrystalline serpentine aggregates under high temperature and high pressure conditions. This method provides important experimental sample support for the experimental simulation study of the solubility, friction coefficient, shear stress, and other properties of bulk layered oxygen-containing salt mineral aggregates—polycrystalline water-rich magnesium silicate minerals—under high temperature and high pressure conditions on multi-faceted large-cavity high-pressure equipment such as hydrothermal autoclaves, piston cylinder presses, and rotary shear friction testers.

[0015] Technical solution of the present invention:

[0016] A method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing, the method comprising: sealing serpentine sample powder under a vacuum of 10... –3 The steel cladding was placed inside the graphite furnace cylinder of the high-pressure vessel of the hot isostatic pressing equipment, and a graphite sealing cap was placed on top. Using argon as the pressure transmission medium, the temperature inside the sample chamber of the cylinder was raised to 800 °C and the pressure was raised to 95.1 MPa using a multi-gradient cylinder heating and pressurization method, and the temperature and pressure were maintained for 8 hours. Then the temperature inside the sample chamber of the cylinder was reduced to 167 °C and the pressure was reduced to 64.4 MPa. Finally, the pressure was released and the temperature was lowered to room temperature to obtain polycrystalline serpentine polymer.

[0017] The method for preparing the serpentine sample powder includes:

[0018] Step 1: Select serpentine single-crystal mineral particles with a minimum particle size of 5.3 mm and a maximum particle size of 15.2 mm as initial samples;

[0019] Step 2: Place the selected serpentine single crystal particles on an ultrasonic cleaner, and use acetone, alcohol and deionized water as cleaning solutions in sequence for ultrasonic cleaning for 26 minutes.

[0020] Step 3: Select 300 grams of serpentine single crystal particles with complete crystal form, uniform color (bright green), fresh surface, and no impurities.

[0021] Step 4: Place the selected serpentine single crystal particles in a vacuum drying oven at 200 degrees Celsius and dry for at least 21 hours;

[0022] Step 5: Crush the dried serpentine single crystal particles into mineral single crystal particles with a particle size of less than 2 mm.

[0023] Step 6: Grind the mineral single crystal particles into serpentine mineral powder with a particle size of 16.12 micrometers to 25.33 micrometers;

[0024] Step 7: Pack the serpentine mineral powder into a sealed paper bag and dry it in a vacuum drying oven at 88 degrees Celsius for 20 days; to obtain serpentine sample powder.

[0025] The methods for preparing steel sheaths include:

[0026] Step 8: Select a 3 mm thick No. 20 low-carbon steel continuous casting slab as the initial raw material for the steel cladding sleeve. After heating to 200 °C, use a roughing mill and a finishing mill to cool it to the set temperature through laminar flow. Then, use a coiler to roll it into a steel strip coil. After three rolling processes and multiple hot rolling processes including edge trimming, a steel cladding sleeve with dimensions of 57.31 mm (outer diameter) × 85.36 mm (height) × 3 mm (wall thickness) is finally obtained. Select a 3 mm thick No. 20 low-carbon steel continuous casting slab as the initial raw material for the steel cladding sleeve cap. Using the same multiple hot rolling process, prepare the upper and lower sealing caps of the steel cladding sleeve. Weld the sleeve, upper and lower sealing caps together by high-temperature vacuum welding to prepare a complete steel cladding sleeve.

[0027] Methods for raising the temperature to 800 °C and the pressure to 95.1 MPa within the cylinder sample chamber using a multi-gradient cylinder heating and pressurization approach include:

[0028] Step 15: Within the temperature range of room temperature to 300 °C, using a heating rate of 15.05 °C / min and a pressurization rate of 0.91 MPa / min, raise the temperature inside the sample chamber of the cylinder to 300 °C and the pressure to 74.2 MPa; within the medium temperature range of 300 °C to 600 °C, using a heating rate of 15 °C / min and a pressurization rate of 0.71 MPa / min, raise the temperature inside the sample chamber of the cylinder to 600 °C and the pressure to 88.3 MPa; within the high temperature range of 600 °C to 800 °C, using a heating rate of 10 °C / min and a pressurization rate of 0.34 MPa / min, raise the temperature inside the sample chamber of the cylinder to 800 °C and the pressure to 95.1 MPa, and maintain the temperature and pressure for 8 hours.

[0029] Methods to reduce the temperature inside the cylinder sample chamber to 167 °C and the pressure to 64.4 MPa include:

[0030] Step 16: The temperature inside the sample chamber of the cylinder was reduced to 167 °C and the pressure was reduced to 64.4 MPa at a uniform cooling rate of 14.07 °C / min and a uniform pressure reduction rate of 0.68 MPa / min.

[0031] The beneficial effects of this invention are:

[0032] This invention organically combines general geology, magmatic petrology, crystallography, dynamics of Earth's structural evolution, ore field tectonic geology, crystal defect chemistry, meteoritics and Earth's origin, engineering geology, optical mineralogy, isotope geochemistry, genetic mineralogy, mining geology, introduction to geophysics, rock mechanics, mineralogy, petrography, geochemistry, ore deposit geology, mineral resource geology, sedimentary petrology, metamorphic petrology, regional field geology, structural geology, stratigraphy, geochronology, and experimental petrology. With a background in Earth science disciplines such as geochemistry, mineral genesis, rock rheology, geodynamics, hot isostatic pressing, hot isostatic powder metallurgy, seismology, igneous magmatism, high-pressure rheology, mineral physics, deep Earth science, high-pressure materials science, materials science, and high-pressure experimental mineralogy, large-volume, highly dense polycrystalline serpentine aggregate experimental samples were prepared under high temperature and high pressure conditions using an RD80×100‒2000–200 double 2000 type hot isostatic pressing equipment.

[0033] The initial raw material selected for this invention is gem-quality single-crystal serpentine particles collected in the field, which are crushed into uniform mineral single-crystal powder. The powder is then placed in a steel sheath and subjected to a series of processes including compaction, vacuuming, high-temperature degassing, high-temperature vacuum welding, argon filling, and furnace washing to ensure that the serpentine sample powder is in a completely sealed environment protected by argon inert gas. The steel sheath containing the serpentine sample powder is then placed in the sample chamber of an RD80×100‒2000–200 double 2000 type hot isostatic pressing (HIP) device, where it is sintered under high temperature and high pressure to form a large, highly dense polycrystalline serpentine aggregate. The prepared polycrystalline serpentine aggregate sample can be widely used in the experimental simulation research of diagenesis and mineralization of mineral and rock physicochemical properties under high temperature and high pressure conditions.

[0034] The steel sheath used in the hot isostatic pressing (HIP) experiment of this invention has the following dimensions: 57.31 mm (outer diameter) × 85.36 mm (height) × 3 mm (wall thickness). This allows for the production of large-sized polycrystalline serpentine polymer samples with diameters reaching 45.68 mm and heights reaching 70.23 mm. During the HIP experiment on the polycrystalline serpentine polymer samples under high temperature and high pressure conditions, inert argon gas is used as the pressure transmission medium. By increasing the temperature and compressing the inert argon gas, uniform pressure and temperature are applied to the serpentine sample powder in all directions, effectively avoiding the adverse effects of shrinkage cavities and porosity during the HIP experiment. The inert argon gas ensures complete isolation between the serpentine sample powder and air within the sample chamber, effectively preventing redox reactions between the serpentine sample powder and air during the HIP experiment. Furthermore, this invention avoids the traditional high-pressure chemical reaction method, which may introduce excessive chemical reagents during the preparation of polycrystalline serpentine polymer samples, potentially leading to the introduction of impurity ions.

[0035] This invention employs a multi-gradient hot isostatic pressing (HIP) process, first increasing pressure and then increasing temperature, to prepare polycrystalline serpentine aggregate experimental samples with excellent physicochemical properties such as fine crystal size, high density, and high purity. This breakthrough overcomes the technical bottleneck of synthesizing large-volume experimental samples of high-density polycrystalline serpentine aggregates. Furthermore, this invention's multi-gradient HIP process is not limited by the shape and size of the sample, allowing for the preparation of complex polycrystalline mineral samples with irregular shapes. Compared to existing technologies that use quasi-hydrostatic presses such as the YJ-3000t and Kawai-1000t to prepare artificially synthesized island-shaped silicate mineral single crystals under high temperature and high pressure conditions, this invention's multi-gradient HIP process can obtain polycrystalline serpentine aggregate experimental samples with near-theoretical density and extremely high sample strength.

[0036] This invention, based on an RD80×100‒2000–200 dual 2000-type hot isostatic pressing (HIP) device, employs a multi-gradient HIP molding process involving first increasing pressure and then increasing temperature. For the first time, it yields large-volume, uniformly distributed, high-density, highly compact, and high-strength polycrystalline serpentine aggregate experimental samples under conditions of 95.1 MPa and 800 °C. These samples can be widely applied to high-pressure equipment with multiple large cavities, such as hydrothermal autoclaves, piston cylinder presses, and rotary shear friction testing machines, to simulate the solubility, friction coefficient, and shear stress of large-volume layered oxygen-containing salt mineral aggregates—polycrystalline water-rich magnesium silicate mineral rocks—under high temperature and high pressure conditions. This provides crucial experimental sample support for systematically exploring the formation mechanisms and occurrence principles of common geological disasters such as deep-earth volcanoes, earthquakes, and debris flows. Attached Figure Description

[0037] Figure 1 To utilize the RD80×100‒2000–200 double 2000 type hot isostatic pressing equipment, and adopt a multi-gradient hot isostatic pressing molding process of first increasing pressure and then increasing temperature, the temperature and pressure in the sample chamber during the preparation of polycrystalline serpentine polymer are shown in the curves of temperature and pressure changes over time in the sample chamber.

[0038] Figure 2 To obtain fine-grained serpentine sample powder by crushing and grinding with the aid of a jaw crusher (model: BB 200) and a high-efficiency Retsch disc vibratory mill (model: RS200), optical microscopic observation results of the serpentine sample before the hot isostatic pressing experiment were obtained using a high-magnification, high-precision Olympus SZX16 research-grade stereomicroscopic imaging platform.

[0039] Figure 3 This document presents the optical microscopic observation results of the surface morphology and particle size distribution of a polycrystalline serpentine polymer sample obtained from a hot isostatic pressing experiment at 95.1 MPa and 800 °C, using the high-precision Olympus SZX16 research-grade stereomicroscopic imaging platform. Detailed Implementation

[0040] A method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing, comprising:

[0041] Step 1: Use elongated elliptical serpentine single crystal mineral particles as the initial sample. Use a high-precision Olympus SZX16 research-grade stereomicroscope to accurately measure the particle size of the initial sample. The smallest particle size of the serpentine single crystal is 5.3 mm, and the largest is 15.2 mm. If the particle size of the serpentine single crystal is too large, only a low-magnification, high-precision Olympus SZX16 research-grade stereomicroscope can be used for sample selection, making it difficult to accurately identify high-purity serpentine single crystals free of other symbiotic / associated minerals and impurities. If the particle size of the serpentine single crystal is too small, it is difficult to effectively separate the serpentine single crystal from silicate minerals, oxide minerals, and carbonate minerals rich in different components such as brucite, talc, magnesite, and quartz. Furthermore, this invention requires selecting a relatively large number of mineral single crystals, which will consume a significant amount of time and manpower.

[0042] Step 2: Place the selected serpentine single crystal particles on an ultrasonic cleaner, and use acetone, alcohol and deionized water as cleaning solutions in sequence for ultrasonic cleaning for 26 minutes to remove impurities from the sample surface.

[0043] Step 3: Under the high-magnification, high-precision Olympus SZX16 research-grade stereomicroscopic imaging platform, carefully select 300 grams of serpentine single crystal particles with complete crystal form, uniform color and bright green color, fresh surface and no other impurity minerals, to fully ensure that the initial sample of serpentine single crystal particles has high purity before the hot isostatic pressing experiment under high temperature and high pressure conditions.

[0044] Step 4: Place the carefully selected serpentine single crystal particles in a vacuum drying oven at 200 degrees Celsius for at least 21 hours to completely remove adsorbed water from the sample surface. If the temperature is too low, a certain amount of adsorbed water may adhere to the surface of the serpentine crystals, making it difficult to accurately weigh the initial sample of serpentine single crystal particles during further grinding. If the temperature is too high, it may cause the serpentine single crystals to decompose, ultimately severely affecting the preparation effect of the hot isostatic pressing experimental sample under high temperature and high pressure conditions.

[0045] Step 5: Place the initial sample of serpentine single crystal particles on a jaw crusher (model: BB 200), set the instrument's drive power to 1.5 kW, and use a crushing time of 3 minutes to crush the serpentine single crystal particles into mineral single crystal particles with a particle size of less than 2 mm. The purpose is to fully crush the sample to obtain serpentine single crystal particles with a medium particle size (less than 2 mm).

[0046] Step 6: Place the sample on a high-efficiency Retsch disc vibratory mill (model: RS200), using the high-speed mode of 1100 rpm and setting the instrument's drive power to 1.5 kW, to grind the mineral single crystal particles into fine-grained serpentine mineral powder with a particle size of 16.12 μm to 25.33 μm (see...). Figure 2 The amount of single-crystal serpentine sample ground in a single cycle was 100 grams, and the grinding time was 6 minutes. Serpentine powder within this particle size range has a large specific surface area (surface area per unit weight of mineral powder), which significantly increases the contact area between particles due to pressure and temperature. This is more conducive to forming a strong bonding force between serpentine powder particles during the hot isostatic pressing experiment of this invention, thereby greatly improving the compactness and density of the prepared fine-grained polycrystalline serpentine polymer sample.

[0047] Step 7: Considering that the serpentine sample powder with a relatively fine particle size is easy to absorb water in the air, it is placed in a paper sealed bag and dried in a vacuum drying oven at 88 degrees Celsius for 20 days to completely remove the adsorbed water on the surface of the sample powder.

[0048] Step 8: In the process of preparing polycrystalline serpentine polymer samples using an RD80×100‒2000–200 double 2000 type hot isostatic pressing (HIP) equipment, a sample steel sheath was prepared using low-carbon steel of No. 20 steel. No. 20 steel refers to steel with a carbon content between 0.17% and 0.23%. The low-carbon steel (No. 20 steel) sheath selected in this case has the following main superior properties: (1) The low-carbon steel (No. 20 steel) sheath does not react with the serpentine sample powder, avoiding contamination of the sample during the HIP experiment and directly affecting the preparation effect; (2) The low-carbon steel (No. 20 steel) sheath can withstand the temperature of 800 °C and the pressure of 95.1°C required for the preparation of polycrystalline serpentine polymer samples under the HIP conditions of this invention. MPa; (3) The steel sheath material of low carbon steel (20 steel) has good air tightness, which ensures that the serpentine sample powder will not leak under high temperature, high pressure and argon gas pressure transmission medium conditions, and can also ensure the sealing of the steel sheath and the sealing of the weld during the vacuum exhaust process. All these properties are very reliable; (4) The steel sheath of low carbon steel (20 steel) also has excellent properties such as relatively easy edge rolling, cutting, processing, deformation and welding performance.

[0049] This invention selects a continuously cast slab of No. 20 low-carbon steel with a wall thickness of 3 mm as the initial raw material for the steel cladding. After heating it to 200 °C, it is cooled to the set temperature by laminar flow using a roughing mill and a finishing mill. It is then rolled into a steel strip coil by a coiler, and then undergoes multiple hot rolling processes including three rolling and edge trimming to finally obtain the cladding for the hot isostatic pressing test of serpentine sample powder with dimensions of 57.31 mm (outer diameter) × 85.36 mm (height) × 3 mm (wall thickness).

[0050] Similarly, a continuously cast slab of No. 20 low-carbon steel with a wall thickness of 3 mm was selected as the initial raw material for the steel cladding cover. The same hot rolling process was used to prepare the upper and lower sealing covers of the steel cladding. The sleeve, upper and lower sealing covers were welded together by high-temperature vacuum welding to prepare a complete steel cladding for the hot isostatic pressing experiment of serpentine sample powder.

[0051] Step 9: First, vacuum weld the sleeve and lower sealing cap of the steel cladding. Then, place the dried serpentine sample powder inside the steel cladding. After a series of processes including compaction, vacuuming, high-temperature degassing, and high-temperature vacuum welding, the serpentine sample powder is completely sealed in a vacuum of 10... –3 Pa is in the steel ladle sleeve.

[0052] Achieving such a low vacuum level within the steel-clad cavity requires at least 53 hours of evacuation, while simultaneously degassing the sample at 400 °C to ensure the serpentine powder is completely in a sealed vacuum environment and that all moisture is removed. The serpentine powder sealed within the steel cladding must be thoroughly compacted. –3 The series of processes, including extremely low vacuum, 400 °C high-temperature degassing, and high-temperature vacuum welding, are mainly aimed at: (1) ensuring that the serpentine sample powder is fully compacted, which can ensure that a sufficient amount of serpentine sample powder is sealed in the steel sleeve, which will help increase the density of the polycrystalline serpentine polymer of the hot isostatic pressing test product, thereby greatly improving the preparation effect of the final product bulk polycrystalline serpentine polymer sample; (2) ensuring that the serpentine sample powder is fully compacted, which can ensure the filling amount of serpentine sample powder sealed in the steel sleeve, which will help enhance the compactness between serpentine sample powder particles, effectively avoid the sample from deforming too much during the hot isostatic pressing test, thereby greatly improving the compactness of the final product bulk polycrystalline serpentine polymer sample; (3) maintaining 10 –3 The extremely low vacuum of Pa ensures that the steel sheath is easily deformed under high temperature and high pressure, thereby uniformly transmitting the high pressure borne by the steel sheath to the serpentine sample powder inside it; (4) Under the condition of 400 °C, the serpentine sample powder is degassed at high temperature, completely removing the water vapor that may exist in the sample powder; (5) The steel sheath is welded by high temperature vacuum, which effectively isolates the welding head from direct contact with air, and the high temperature oxidation of the metal welding point can be completely avoided, which will greatly enhance the sealing performance of the steel sheath.

[0053] Step 10: Carefully place the steel sleeve containing the serpentine sample powder into the graphite furnace cylinder of the high-pressure vessel of the hot isostatic pressing (HIP) equipment, and cover it with the graphite sealing cap. This invention uses an RD80×100‒2000–200 double 2000-type HIP equipment to densify the serpentine sample powder under high temperature and high pressure conditions. The graphite furnace cylinder is the core component of this equipment and also the heating element that achieves the extremely high sample chamber temperature of 2000 degrees Celsius.

[0054] Step 11: Turn on the main power switch, dedicated computer automatic program, exhaust fan and argon concentration detection alarm of the RD80×100‒2000–200 dual 2000 type hot isostatic pressing equipment in sequence. Because the hot isostatic pressing (HIP) equipment operates at a power of 30 kW / hour, it is an ultra-high-power, high-temperature, and high-pressure instrument. Therefore, to ensure the safety of the experimental operators, the main power switch must be kept off when the equipment is not in operation. To ensure automatic control and arbitrary adjustment of temperature and pressure during HIP experiments, a dedicated computer-controlled software program has been developed for this instrument. A dual-pipeline high-power exhaust system is used to prevent leakage of the inert argon gas pressure transmission medium during the HIP experiment of polycrystalline serpentine polymer samples under high temperature and pressure. Excessive argon concentration in the operating space could lead to asphyxiation for the operators. A high-sensitivity laboratory-specific argon concentration monitoring alarm is used. Its main purpose is to monitor the argon concentration in the sealed laboratory space during the operation of the HIP equipment in real time. Abnormal changes in argon concentration in the sealed space can also determine the operating status of high-pressure argon in the pipes and lines of the high-pressure device, ensuring the absolute safety of the operators during HIP experiments.

[0055] This invention uses argon as an inert gas as the pressure transfer medium. Argon is chosen because it is a colorless, tasteless, odorless, non-toxic, chemically stable, and thermally conductive inert gas. Compared with nitrogen, argon has more stable chemical properties and can completely maintain the chemical composition and process performance of the prepared material, thereby greatly improving the repeatability of the preparation molding process and the reliability of the product performance. However, in the hot isostatic pressing experiment, the main drawbacks of choosing nitrogen as the pressure transfer medium are as follows: (1) Under high temperature and high pressure conditions, nitrogen inevitably reacts with various metals or alloys, especially for samples containing multiple active metals such as titanium, aluminum, and zirconium. The samples will be nitrided, and a nitride layer will be formed on the surface of the sample, which will seriously change the mechanical properties and chemical composition of the prepared product; (2) When preparing oxide ceramics (such as alumina, zirconium oxide, etc.) or many other functional ceramics through hot isostatic pressing, if nitrogen is chosen as the pressure transfer medium, nitrogen can easily enter the crystal in the form of defects or vacancies during the high temperature and high pressure experiment. (3) Nitrogen used in industrial applications often contains trace amounts of water, carbon dioxide and oxygen. If the purification is incomplete or incomplete, the oxidation, denitrification and decarbonization reactions of the sample will be accelerated during the high temperature and high pressure experiment, which will seriously affect the physicochemical properties of the sample product. (4) Although nitrogen has a lower cost advantage compared to argon, for high-value-added hot isostatic pressing workpieces such as aerospace parts and medical implants, the aviation safety cost, health cost and scrap loss cost caused by the nitriding reaction are far greater than the gas pressure transmission medium cost of the hot isostatic pressing experiment itself. Compared with hydrogen, argon can be mixed with oxygen in the air in any proportion, and hydrogen may also cause an explosion hazard under high temperature and high pressure. Compared with other common inert gases such as helium and neon, argon has unique advantages such as good thermal conductivity and lower price.

[0056] This invention uses high-purity argon gas with a purity of 99.999% as the pressure transmission medium. Its main purpose is to: (1) inject argon gas into the cylinder through a high-pressure pipeline and with the help of a booster pump, and then heat it in the cylinder by a high-temperature resistant graphite furnace. The isotropic temperature and pressure will be uniformly transmitted to the serpentine sample powder pressing parts to complete the hot isostatic pressing molding experiment; (2) Argon gas has excellent thermal conductivity, so the temperature distribution in the furnace is relatively uniform; (3) Selecting high-purity inert gas argon gas isolates other gases in the environment and can completely avoid the steel cladding from being oxidized during the hot isostatic pressing experiment; (4) Selecting high-purity inert gas argon gas plays an important protective role for the core component of the RD80×100‒2000–200 double two thousand type hot isostatic pressing equipment - the graphite heating element, and extends its service life.

[0057] Step 12: In this invention, argon is used as the pressure transmission medium. During the preparation of polycrystalline serpentine polymers on an RD80×100‒2000–200 dual 2000-type hot isostatic pressing (HIP) device, a multi-gradient HIP molding process of first increasing pressure and then increasing temperature is employed. Given that the initial material of this invention is a mineral powder that is difficult to mold, using argon as the inert gas pressure transmission medium and selecting a multi-gradient HIP molding process of first increasing pressure and then increasing temperature can greatly improve the density and compactness of large-volume polycrystalline serpentine polymer products.

[0058] This invention employs a multi-gradient hot isostatic pressing (HIP) process, involving prior pressurization followed by heating, to synthesize bulk experimental samples of high-density, high-compactness, and high-purity polycrystalline serpentine polymers. The target pressure and temperature for the HIP experiment are 95.1 MPa and 800 °C, respectively. If the selected target pressure and temperature are too low, the steel sleeve used to seal the serpentine sample powder during the HIP experiment will not be sufficiently compressed and effectively deformed, making it difficult to fully compact and sinter the sample. This severely affects the preparation of the experimental product—a bulk, high-density, and high-compact polycrystalline serpentine polymer sample. Conversely, if the selected target pressure and temperature are too high, the polycrystalline, water-rich magnesium silicate mineral—serpentine—will decompose during the HIP experiment, significantly impacting the prepared polycrystalline serpentine polymer.

[0059] This invention uses argon gas as the pressure transmission medium. The target pressure and temperature values ​​are obtained by inputting argon gas into a gas cylinder. Therefore, before the hot isostatic pressing (HIP) experiment of serpentine sample powder, it is necessary to accurately calculate the amount of argon gas required for the target pressure and temperature values. Through multiple repeatable low-temperature high-pressure empty furnace HIP experiments, high-temperature low-pressure empty furnace HIP experiments, and high-temperature high-pressure empty furnace HIP experiments of serpentine sample powder, precise temperature and pressure calibration of the serpentine sample cavity is performed. Finally, based on the RD80×100‒2000–200 dual 2000-type HIP equipment, high-purity inert argon gas is selected as the pressure transmission medium to complete the sample preparation for a single large-volume polycrystalline serpentine polymer HIP experiment. The formula for calculating the amount of argon gas consumed is as follows:

[0060] (1);

[0061] (2);

[0062] In the formula: parameter P target The target pressure for preparing polycrystalline serpentine polymer samples under hot isostatic pressing (T) is based on the target temperature of the hot isostatic pressing experiment (T). target ) Perform the calculation; parameter P bottleThe pressure inside the cylinder represents the inert gas argon; parameter t represents the number of 40-liter large-volume and high-purity inert gas argon (purity: 99.999%) cylinders required to complete a single hot isostatic pressing experiment on a polycrystalline serpentine polymer sample under high temperature and high pressure conditions.

[0063] Step 13, vacuuming, filling with argon gas and washing the furnace, the purpose of which is to completely remove the air from the serpentine sample chamber. The specific operation steps are as follows: (1) Vacuuming: turn on the gas vacuum pump control switch to evacuate the air sealed in the high-pressure sample chamber that is directly connected to the gas vacuum pump. When the detection value of the vacuum degree instrument digital display reaches 10 –4 (1) When the pressure reaches 15 MPa, turn off the gas vacuum pump; (2) Fill the cylinder directly connected to the high-purity inert gas argon with argon gas, and stop filling the pressure medium when the pressure in the sample chamber reaches 15 MPa; (3) Clean the furnace: turn on the gas vacuum pump and pump the vacuum in the sample chamber to 10 MPa. –4 MPa, repeated evacuation and filling three times, thus completely removing all the air from the sample chamber.

[0064] Step 14: Pre-filling and pressurizing the sample chamber. Specific operation steps: (1) Calculate the amount of inert argon gas according to Formula 1 and Formula 2. In order to achieve the target pressure of 95.1 MPa and the target temperature of 800 °C, at least 4 argon cylinders with an internal pressure of 15 MPa are required; (2) Fill the argon cylinders with an internal pressure of 15 MPa evenly into the high-pressure pressurization tank of the hot isostatic pressing equipment. Then, through the high-pressure delivery pipeline, fill the cylinder with argon gas from the high-pressure pressurization tank, so that the pressure of the high-pressure pressurization tank and the pressure in the cylinder are balanced; (3) Turn on the diaphragm compressor and pump all the remaining argon gas in the high-pressure tank into the serpentine sample chamber of the cylinder, so that the sample chamber of the cylinder is pre-filled and pressurized to 56.1 MPa.

[0065] Step 15: Multi-gradient cylinder block heating and pressurization (see...) Figure 1Taking into account the target pressure and temperature for preparing polycrystalline serpentine polymer samples in the hot isostatic pressing (HIP) experiment, as well as the safety, reliability, and durability of the graphite heating element itself, a multi-gradient cylinder heating and pressurization HIP experimental procedure was precisely controlled and automatically adjusted. The specific steps are as follows: In the temperature range of room temperature–300 °C, a heating rate of 15.05 °C / min and a pressurization rate of 0.91 MPa / min were used to raise the temperature in the cylinder sample chamber to 300 °C and the pressure to 74.2 MPa; in the medium temperature range of 300 °C–600 °C, a heating rate of 15 °C / min and a pressurization rate of 0.71 MPa / min were used to raise the temperature in the cylinder sample chamber to 600 °C and the pressure to 88.3 MPa; in the high temperature range of 600 °C–800 °C, a heating rate of 10 °C / min and a pressurization rate of 0.34 MPa / min were used. A pressurization rate of MPa / min was used to raise the temperature inside the sample chamber to 800 °C and the pressure to 95.1 MPa. As the temperature increased, the argon gas inside the sealed cylinder expanded dramatically. Since the cylinder volume remained constant, the argon gas volume was uniformly compressed, resulting in uniform high pressure. Ultimately, the pressure inside the sample chamber was maintained at 95.1 MPa, ensuring that the layered, water-rich magnesium silicate mineral serpentine was fully compacted and cemented. The serpentine sample powder was held at 95.1 MPa and 800 °C for 8 hours. Serpentine is an important rock-forming mineral in the shallow regions of deep subduction zones. It is a triclinic mineral with a Cm space group and low symmetry, exhibiting relatively complex crystal morphology, distinct lattice orientation preferences, and anisotropic physicochemical properties.

[0066] This invention employs a multi-gradient hot isostatic pressing (HIP) process, first increasing pressure and then increasing temperature, to prepare polycrystalline serpentine polymer samples. Under a target pressure of 95.1 MPa and a target temperature of 800 °C, the samples are held at this temperature for 8 hours to ensure a sufficiently long holding time. If the holding time is too short, it is difficult to form strong bonding forces between the low-symmetry and diverse crystal morphologies of serpentine mineral particles, and it is also difficult to overcome the influence of many unfavorable factors such as the preferred lattice orientation and anisotropy of the serpentine mineral, thus affecting the density and strength of the final bulk polycrystalline serpentine polymer sample. Conversely, if the holding time is too long, although a highly dense and strong polycrystalline serpentine polymer can be obtained, the final bulk polycrystalline serpentine polymer sample will experience particle growth, uneven particle distribution, and recrystallization under prolonged high temperature and high pressure, severely affecting the preparation effect and resulting in higher experimental costs.

[0067] Step 16: Cooling and depressurizing the cylinder. After the serpentine sample powder has been kept at a constant temperature and pressure of 95.1 MPa and 800 °C for 8 hours, the temperature of the sample chamber in the cylinder is reduced to 167 °C and the pressure is reduced to 64.4 MPa at a relatively slow and uniform cooling rate of 14.07 °C / min and a uniform depressurization rate of 0.68 MPa / min. The relatively slow and uniform cooling and depressurization rates are adopted mainly because if the cooling and depressurization rates are too fast, the internal stress of the steel cladding will not be fully released, which will cause the large polycrystalline serpentine polymer sample product to directly break and fracture, thus seriously affecting the preparation effect.

[0068] This invention selects a sample chamber temperature of 167 °C because this temperature falls within the safe temperature range (160 °C–180 °C) that the RD80×100‒2000–200 dual 2000-type hot isostatic pressing (HIP) equipment can withstand direct pressure relief. If the sample chamber temperature exceeds 180 °C, the resulting internal pressure is too high, which could easily damage the graphite heating furnace and potentially cause a safety accident with the HIP equipment. Conversely, if the sample chamber temperature is below 160 °C, the resulting internal pressure is too low, making it difficult to ensure that the argon inert pressure-transmitting medium sealed within the sample chamber is completely expelled during the pressure relief process in the HIP experiment.

[0069] Step 17, Depressurization. First, allow the argon gas in the hot isostatic pressing (HIP) cylinder to flow freely back to the high-pressure pressurization tank through the pipeline. Then, when the cylinder pressure and the high-pressure pressurization tank pressure reach equilibrium, turn on the diaphragm compressor to vent the gas in the cylinder and discharge all residual gas through the pipeline.

[0070] Step 18, Cooling. After all the inert argon gas in the pipeline has been completely removed, the cooling system connected to the hot isostatic pressing furnace body continues to be turned on, and the natural cooling program is started to reduce the temperature inside the furnace from 167 °C to room temperature (~25 °C).

[0071] Step 19: Set the control program for the hot isostatic pressing (HIP) equipment, open the furnace chamber, carefully remove the polycrystalline serpentine polymer steel-clad workpiece sealed after the HIP experiment, and accurately measure the dimensions of the steel cladding after the HIP forming experiment: 51.31 mm (outer diameter) × 75.36 mm (height). Compare the volume of the steel cladding before the HIP experiment and calculate the volume shrinkage rate (η) of the steel cladding before and after the HIP experiment. 钢包套 Its calculation formula can be expressed as: η 钢包套 =(V 实验前钢包套 –V 实验后钢包套 ) / V 实验前钢包套 The shrinkage rate (η × 100%) is 23.57%. This invention exhibits such a large volumetric shrinkage rate (η) of the steel sheath. 钢包套=23.57%), confirming that the steel sleeve used to seal and encapsulate the serpentine sample powder underwent sufficient compression and effective deformation during the hot isostatic pressing experiment.

[0072] Step 20: Using a high-speed diamond saw blade cutter with a 1.0 mm thick diamond saw blade, the polycrystalline serpentine polymer sample was carefully peeled from the steel ladle. The weight of the sample after the experiment was accurately measured to be 299 grams, and the tare weight of the steel ladle was 500 grams. This indicates that the weight of the serpentine sample remained essentially unchanged before and after the multi-gradient hot isostatic pressing (HIP) experiment, which involved increasing pressure followed by increasing temperature. Further precise measurements were taken of the dimensions of the polycrystalline serpentine polymer sample obtained after the HIP experiment: 45.68 mm (diameter) × 70.23 mm (height). Comparing the initial volume of serpentine powder encapsulated in the steel ladle before the HIP experiment, the volume shrinkage rate (η) of the sample before and after the HIP experiment was calculated. 蛇纹石 Its calculation formula can be expressed as: η 蛇纹石 =(V 实验前蛇纹石 –V 实验后蛇纹石 ) / V 实验前蛇纹石 The volume shrinkage rate (η × 100%) is 26.14%. This invention achieves such a large volume shrinkage rate (η × 100%) for serpentine sample powder. 蛇纹石 =26.14%), confirming that during the hot isostatic pressing experiment, the serpentine sample powder placed in the steel cladding was fully compacted and sintered under high temperature and high pressure conditions.

[0073] This invention utilizes an RD80×100‒2000–200 dual 2000-type hot isostatic pressing (HIP) apparatus to synthesize a polycrystalline serpentine polymer from the initial material—a single-phase serpentine single crystal—which is then crushed into medium-sized serpentine single crystal particles, ground into fine serpentine powder, and finally synthesized into the final product. Employing a multi-gradient HIP process that first increases pressure and then increases temperature, high-density, high-compactness, high-purity, and bulk polycrystalline serpentine polymers are prepared. No other impurity phases are introduced during the entire preparation process, and the purity of the resulting polycrystalline serpentine polymer sample can reach 100%.

[0074] Under epoxy resin inlay protection, a representative sample (19 mm × 19 mm cross-section) was cut from the polycrystalline serpentine polymer workpiece, a product of the hot isostatic pressing experiment. The sample underwent epoxy resin inlay protection, cutting, grinding, and surface polishing. Using a high-precision Olympus SZX16 research-grade stereomicroscopic imaging platform, the surface morphology and particle size distribution characteristics of the polycrystalline serpentine polymer sample were tested. The test results are shown in (see...). Figure 3The polycrystalline serpentine polymer exhibits clear grain boundary continuity, with minimal differences in the proportion of sample particles of different sizes, demonstrating a distinctly uniform particle size distribution. This invention utilizes a fully sealed steel sheath, inert argon gas as the pressure transfer medium, and a consistently closed vacuum environment for the sample powder during the hot isostatic pressing (HIP) experiment. This effectively isolates the sample from gases such as nitrogen, oxygen, and water vapor, thus achieving a uniform particle distribution, free from particle growth and recrystallization in the polycrystalline serpentine polymer. Compared to existing technologies that use quasi-hydrostatic presses such as the YJ-3000t and Kawai-1000t to synthesize island-shaped silicate mineral single crystals under high temperature and high pressure, this invention employs a multi-gradient HIP process that first increases pressure and then increases temperature, effectively overcoming numerous drawbacks of polycrystalline serpentine polymer products, including particle growth, uneven particle distribution, and recrystallization.

[0075] High-resolution scanning electron microscopy was used to observe the microstructure of the polycrystalline serpentine polymer sample obtained from the hot isostatic pressing experiment, and precise density tests were performed. The obtained polycrystalline serpentine polymer had a density as high as 99.8%, exhibiting extremely high compactness. In the hot isostatic pressing (HIP) experiment, this invention improves the following specific experimental scheme to ensure the acquisition of highly dense polycrystalline serpentine polymer samples: (1) a higher pre-pressurization pressure (56.1 MPa); (2) a multi-gradient gradually decreasing cylinder heating mode, i.e., in the low-temperature zone of the HIP experiment (room temperature–300 °C), the heating rate is 15.05 °C / min; in the medium-temperature zone (300 °C–600 °C), the heating rate is 15 °C / min; and in the high-temperature zone (600 °C–800 °C), the heating rate is 10 °C / min; (3) a multi-gradient gradually decreasing cylinder pressure mode, i.e., in the low-pressure zone of the HIP experiment (56.1 MPa–74.2 MPa), the pressure rate is 0.91 MPa / min; and in the medium-pressure zone (74.2 MPa–88.3 MPa), the pressure rate is 0.91 MPa / min. Under pressure conditions of MPa, the pressurization rate is 0.71 MPa / min and under pressure conditions of 88.3 MPa–95.1 MPa, the pressurization rate is 0.34 MPa / min; (4) The relatively slow cylinder uniform cooling and depressurization mode, under pressure conditions of 95.1 MPa–64.4 MPa, the uniform cooling rate and depressurization rate are 14.07 °C / min and 0.68 MPa / min, respectively; (5) The long-term constant temperature and constant pressure mode, at the highest temperature (800 °C) and the highest pressure (95.1 MPa), ensures a sufficiently long constant temperature and constant pressure of 8 hours. All these optimized and improved hot isostatic pressing (HIP) experimental schemes can promote sufficient diffusion and particle aggregation between serpentine sample powders during HIP, eliminate the adverse effects of dendritic formation between sample powders, and thus form a uniform equiaxed grain structure; they can also promote the uniform isotropic temperature and pressure transfer during HIP, prevent the occurrence of local weaknesses or cracks, and thus greatly improve the compactness of the polycrystalline serpentine polymer sample produced by HIP. In addition, this invention applies a higher temperature (800 °C), a higher pressure (95.1 MPa), and a sufficiently long heat and pressure holding time (8 hours) to promote the formation of good bonding force between the particles of serpentine sample powder, thereby greatly improving the density and strength of the polycrystalline serpentine polymer sample produced by hot isostatic pressing. It also effectively overcomes the unavoidable temperature gradient, pressure gradient, and many adverse factors such as pores, voids, cracks, and healing defects in the prepared product that exist in the existing technology for synthesizing island silicate mineral single crystals by means of quasi-hydrostatic presses such as YJ-3000t and Kawai-1000t.

[0076] The Archimedes method using organically combined deionized water and the water intrusion method for porous complex structures were employed to accurately measure the density of polycrystalline serpentine polymer samples obtained from hot isostatic pressing experiments. The measured density of the polycrystalline serpentine polymer was 2.78 g / cm³. 3 This density value falls exactly within the theoretical density of 2.44 g / cm³ for naturally collected serpentine, as measured by geologists. 3 –2.80 g / cm 3 Within the specified range, the obtained bulk polycrystalline serpentine polymer samples exhibited extremely high density. The achievement of such high-density polycrystalline serpentine polymer products is highly related to the optimized molding process employed during this hot isostatic pressing experiment, including pretreatment of the serpentine sample powder raw material, selection of a No. 20 steel sample cladding, a reasonable cooling and depressurization hot isostatic pressing molding process, and high-temperature degassing at 400 °C. The serpentine sample powder raw material pretreatment, namely fine-grained serpentine mineral powder with a particle size of 16.12 micrometers to 25.33 micrometers, is used. Serpentine in this particle size range has a large specific surface area, which significantly increases the contact area between sample particles, making it more conducive to the formation of strong and good bonding force, thereby greatly improving the density of the prepared polycrystalline serpentine polymer sample. A 3 mm thick 20# low-carbon steel continuous casting slab is used as the steel cladding, possessing excellent physical properties such as low strength, low hardness, high plasticity, and good toughness. This allows the high pressure borne by the steel cladding to be uniformly transferred to the serpentine sample powder enclosed within it, thus greatly improving the density of the prepared polycrystalline serpentine polymer sample. An optimized and improved cooling and depressurization hot isostatic pressing process is adopted, especially the use of a slow, uniform, and multi-gradient cylinder depressurization mode (pressurization rate: 0.34 MPa / min – 0.91 MPa / min; depressurization rate: 0.68). (MPa / min) ensures that the internal stress of large-volume polycrystalline serpentine polymer workpieces is fully released, effectively overcoming the adverse effects of delamination, cracks, and fissures in the sample product, and greatly improving the density of the polycrystalline serpentine polymer sample. A high-temperature degassing optimization molding process at 400 °C is employed, sealing the serpentine sample powder in a steel sleeve and subjecting it to high-temperature vacuum degassing at 400 °C to minimize residual gas, thereby obtaining a polycrystalline serpentine polymer experimental sample with a very uniform density distribution under hot isostatic pressing. In contrast, existing technologies, such as the synthesis of island silicate mineral single crystals using quasi-hydrostatic presses like the YJ-3000t and Kawai-1000t, inevitably generate internal friction due to the unidirectional pressing, leading to uneven density distribution and delamination problems in the experimental product.

Claims

1. A method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing, characterized in that: The method includes: sealing serpentine sample powder in a vacuum chamber with a vacuum degree of 10. –3 The steel cladding was placed inside the graphite furnace cylinder of the high-pressure vessel of the hot isostatic pressing equipment, and a graphite sealing cap was placed on top. Using argon as the pressure transmission medium, the temperature inside the sample chamber of the cylinder was raised to 800 °C and the pressure was raised to 95.1 MPa using a multi-gradient cylinder heating and pressurization method, and the temperature and pressure were maintained for 8 hours. Then the temperature inside the sample chamber of the cylinder was reduced to 167 °C and the pressure was reduced to 64.4 MPa. Finally, the pressure was released and the temperature was lowered to room temperature to obtain polycrystalline serpentine polymer.

2. The method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing according to claim 1, characterized in that: The method for preparing the serpentine sample powder includes: Step 1: Select serpentine single-crystal mineral particles with a minimum particle size of 5.3 mm and a maximum particle size of 15.2 mm as initial samples; Step 2: Place the selected serpentine single crystal particles on an ultrasonic cleaner, and use acetone, alcohol and deionized water as cleaning solutions in sequence for ultrasonic cleaning for 26 minutes. Step 3: Select 300 grams of serpentine single crystal particles with complete crystal form, uniform color (bright green), fresh surface, and no impurities. Step 4: Place the selected serpentine single crystal particles in a vacuum drying oven at 200 degrees Celsius and dry for at least 21 hours; Step 5: Crush the dried serpentine single crystal particles into mineral single crystal particles with a particle size of less than 2 mm. Step 6: Grind the mineral single crystal particles into serpentine mineral powder with a particle size of 16.12 micrometers to 25.33 micrometers; Step 7: Pack the serpentine mineral powder into a sealed paper bag and dry it in a vacuum drying oven at 88 degrees Celsius for 20 days; to obtain serpentine sample powder.

3. The method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing according to claim 1, characterized in that: The methods for preparing steel sheaths include: Step 8: Select a 3 mm thick No. 20 low-carbon steel continuous casting slab as the initial raw material for the steel cladding sleeve. After heating to 200 °C, use a roughing mill and a finishing mill to cool it to the set temperature through laminar flow. The slab is then coiled into a steel strip coil by a coiler. After three rolling processes and multiple hot rolling processes including edge trimming, a steel cladding sleeve with dimensions of 57.31 mm (outer diameter) × 85.36 mm (height) × 3 mm (wall thickness) is finally obtained. Select a 3 mm thick No. 20 low-carbon steel continuous casting slab as the initial raw material for the steel cladding sleeve cap. Using the same multiple hot rolling process, prepare the upper and lower sealing caps of the steel cladding sleeve. Weld the sleeve, upper and lower sealing caps together by high-temperature vacuum welding to prepare a complete steel cladding sleeve.

4. The method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing according to claim 1, characterized in that: The serpentine sample powder was sealed in a vacuum of 10. –3 The method in the steel cladding of Pa includes: placing the dried serpentine sample powder inside the steel cladding, and then performing compaction, vacuuming, high-temperature degassing, and high-temperature vacuum welding to completely seal the serpentine sample powder under a vacuum of 10. –3 The serpentine sample powder was placed in a steel cladding at Pa; vacuum was applied for at least 53 hours, and the powder was degassed at 400 °C.

5. The method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing according to claim 1, characterized in that: The argon gas purity is 99.999%; the formula for calculating the amount of argon gas consumed is: (1)； (2)； In the formula: parameter P target The target pressure for preparing polycrystalline serpentine polymer samples under hot isostatic pressing is based on the target temperature T of the hot isostatic pressing experiment. target Perform calculations; parameter P bottle The pressure inside the cylinder represents the inert gas argon; parameter t represents the number of 40-liter cylinders with 99.999% argon purity required to complete a single hot isostatic pressing experiment on a polycrystalline serpentine polymer sample under high temperature and high pressure conditions.

6. The method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing according to claim 1, characterized in that: The methods for purging argon gas, the pressure-transmitting medium, include: Step 13, Vacuuming, Argon Filling, and Furnace Cleaning: Vacuuming: Turn on the gas vacuum pump control switch to evacuate the air from the high-pressure sample chamber directly connected to the gas vacuum pump. The vacuum level will rise when the digital display of the vacuum gauge reaches 10... –4 At MPa, turn off the gas vacuum pump; Fill the cylinder directly connected to argon gas with argon gas, and stop filling when the pressure in the sample chamber reaches 15 MPa; Clean the furnace: Turn on the gas vacuum pump and evacuate the vacuum in the sample chamber to 10 MPa. –4 MPa, repeat the evacuation and filling three times to completely remove all the air from the sample chamber; Step 14, Pre-pressurization of the sample chamber: Calculate the amount of argon gas and prepare at least 4 argon cylinders with an internal pressure of 15 MPa; uniformly fill the 15 MPa argon cylinders into the high-pressure pressurization tank of the hot isostatic pressing equipment, and then freely fill the cylinder with the argon gas from the high-pressure pressurization tank through the high-pressure delivery pipeline, so that the pressure in the high-pressure pressurization tank and the pressure in the cylinder reach equilibrium; turn on the diaphragm compressor to pump all the remaining argon gas in the high-pressure tank into the serpentine sample chamber of the cylinder, so that the sample chamber in the cylinder is pre-pressurized to 56.1 MPa.

7. The method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing according to claim 1, characterized in that: Methods for raising the temperature to 800 °C and the pressure to 95.1 MPa within the cylinder sample chamber using a multi-gradient cylinder heating and pressurization approach include: Step 15: Within the temperature range of room temperature to 300 °C, using a heating rate of 15.05 °C / min and a pressurization rate of 0.91 MPa / min, raise the temperature inside the sample chamber of the cylinder to 300 °C and the pressure to 74.2 MPa; within the medium temperature range of 300 °C to 600 °C, using a heating rate of 15 °C / min and a pressurization rate of 0.71 MPa / min, raise the temperature inside the sample chamber of the cylinder to 600 °C and the pressure to 88.3 MPa; within the high temperature range of 600 °C to 800 °C, using a heating rate of 10 °C / min and a pressurization rate of 0.34 MPa / min, raise the temperature inside the sample chamber of the cylinder to 800 °C and the pressure to 95.1 MPa, and maintain the temperature and pressure for 8 hours.

8. The method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing according to claim 1, characterized in that: Methods to reduce the temperature inside the cylinder sample chamber to 167 °C and the pressure to 64.4 MPa include: Step 16: The temperature inside the sample chamber of the cylinder was reduced to 167 °C and the pressure was reduced to 64.4 MPa at a uniform cooling rate of 14.07 °C / min and a uniform pressure reduction rate of 0.68 MPa / min.

9. The method for preparing high-density bulk polycrystalline serpentine under hot isostatic pressing according to claim 1, characterized in that: Methods for obtaining polycrystalline serpentine polymers by depressurization and cooling to room temperature include: Step 17, Depressurization: Allow the argon gas in the cylinder of the hot isostatic pressing equipment to flow freely back to the high-pressure pressurizing tank through the pipeline; when the cylinder pressure and the high-pressure pressurizing tank pressure reach equilibrium, turn on the diaphragm compressor to release the gas in the cylinder and discharge all the residual gas through the pipeline. Step 18, Cooling: After all the inert argon gas in the pipeline has been completely removed, the cooling system connected to the furnace body of the hot isostatic pressing equipment continues to be turned on, and the natural cooling program is started to reduce the temperature inside the furnace from 167 °C to room temperature. Step 19: Set the control program for the hot isostatic pressing equipment, open the furnace chamber, and remove the polycrystalline serpentine polymer steel cladding that was sealed after the hot isostatic pressing experiment. Step 20: Use a diamond saw blade cutter to peel the polycrystalline serpentine polymer sample from the steel ladle.

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