Method for preparing high-purity bulk polycrystalline orthorhombic augite rock under hot isostatic pressing conditions

Abstract

This invention discloses a method for preparing high-purity bulk polycrystalline orthorhombic pyroxene under hot isostatic pressing conditions. The method includes: sealing orthorhombic pyroxene sample powder under a vacuum of 10... –3 The sample chamber was placed in a steel bladder; the steel bladder 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; argon was used as the pressure transmission medium; a multi-gradient cylinder heating and pressurization method was used to raise the temperature inside the sample chamber to 1140 °C and the pressure to 93.8 MPa, and the temperature and pressure were maintained for 4.5 hours; a multi-gradient cylinder cooling and depressurization method was used to lower the temperature inside the sample chamber to 161 °C and the pressure to 48.5 MPa; finally, the pressure was released and the temperature was lowered to room temperature to obtain a polycrystalline orthorhombic pyroxene aggregate; this technique fills the technical gap in the preparation of large-volume experimental samples of high-density polycrystalline orthorhombic pyroxene aggregates under high temperature and high pressure conditions.

Description

Technical Field

[0001] This invention belongs to the field of experimental sample synthesis technology for bulk mafic magmatic intrusive rock aggregates – polycrystalline ultramafic pyroxene rocks, and particularly relates to a method for preparing high-purity bulk polycrystalline orthorhombic pyroxene rocks under hot isostatic pressing. Background Technology

[0002] Based on the structural relationship between the main mineral grains in the constituent igneous rocks, including the relationship between minerals and between minerals and volcanic glass / cryptocrystalline materials, the structural types of igneous rocks can be divided into: (1) Intergrowth structure: mineral grains interpenetrate with each other and grow together in a certain pattern. According to the morphology of the mineral intergrowth structure in igneous rocks, it can be further subdivided into: pictorial structure, striped structure and worm structure, among which (a) pictorial structure: typical igneous rocks with pictorial intergrowth structure, such as pegmatites, quartz with hexagonal bipyramidal crystal shape in this type of igneous rock is often regularly interpenetrated and embedded in potassium feldspar. Under the cross-polarized optical microscope, a large number of quartz crystals in the rock have the unique property of simultaneous extinction. During the magma cooling process, these binary system magmas composed of quartz and potassium feldspar crystallize simultaneously when the temperature drops to the co-junction point. Furthermore, for igneous rocks with intergrowth structures, those visible to the naked eye are called pictographic structures; those observable only under an optical microscope are called micropictographic structures; (b) Striped structures: typical igneous rocks with striped intergrowth structures, such as striped feldspar, in which potassium feldspar and sodium feldspar are regularly intergrowthed to form striped structures. Striped structures can be large or small, ranging from those clearly visible to the naked eye in igneous rock bodies to those only clearly visible through a high-powered optical microscope or X-ray diffraction. Based on the regular distribution and directional arrangement of striped structures, there are three different typical types of igneous rocks with striped structures: positive striped structures, anti-striped structures, and replacement striped structures; (c) Worm-like structures: typical igneous rocks with worm-like intergrowth structures, such as granite, in which fine and worm-like quartz are interspersed among feldspar minerals, and the extinction positions of quartz and feldspar are consistent, forming worm-like structures. According to the differences in the geological origin of worm structures, they are divided into co-attached worm structures and metasomatic worm structures. (2) Reaction edge structure: Minerals or captured crystals formed in the early geological process of magma crystallization inevitably react with magma. When this reaction is incomplete, a new mineral with a completely different composition is generated around the early-formed mineral. A reaction edge structure is formed between this new mineral and the mineral that completely or partially surrounds the early-crystallized mineral. According to the symmetry of the reaction edge structure, it is further divided into: reaction edge structure and secondary altered edge structure. (3) Zoning structure: Minerals or captured crystals formed in the early geological process of magma crystallization inevitably react with magma. When this reaction is incomplete, a new mineral of the same type is generated around the early-formed mineral. A zoning structure is formed between this new mineral and the mineral that completely or partially surrounds the early-crystallized mineral. For example, plagioclase often has obvious zoning structure characteristics. There are obvious differences in the end-member composition and optical orientation between the two minerals that form the zoning structure.When the core to the edge of the zoning structure exhibits a transition from basic to acidic, it is called a positive zoning structure; conversely, when the core to the edge of the zoning structure exhibits a transition from acidic to basic, it is called an anti-zoning structure. Generally speaking, in the products of geological processes under higher temperature and pressure—hypnotic rocks, subvolcanic rocks, and volcanic rocks—obvious zoning structures are exposed. (4) Inclusion structure: In igneous rocks, many smaller mineral grains are embedded within larger mineral grains, forming an inclusion structure, also known as a mosaic structure. Existing geological data shows that inclusion structures are relatively well-developed in ultrabasic and basic magmatic intrusive rocks such as peridotite, pyroxene, and gabbro. (5) Interstitial structure: Dark minerals, cryptocrystalline materials, glassy materials, etc., fill the gaps between transparent mineral microcrystals contained in igneous rocks, forming an interstitial structure. For example, non-granular minerals such as zeolite and chlorite fill the gaps between plagioclase mineral microcrystals, forming a plagioclase interstitial structure. In addition, igneous rocks also have a variety of different igneous rock structures, such as diabase, gabbro, granite, diorite, andesite, and trachyte.

[0003] Orthopyroxene is a typical dark green, granular magmatic intrusive rock, belonging to the mafic ultramafic pyroxene group. Its silica content is less than 45%, and it is prone to fibrous serpentinization. Its variety is sericite. The main constituent minerals of orthopyroxene are orthopyroxene and clinopyroxene, with orthopyroxene content reaching 90%–100%. It contains small amounts of silicate minerals such as mica, amphibole, and olivine, as well as small amounts of spinel group minerals such as ilmenite, chromite, and magnetite. Based on the relative content of orthopyroxene and clinopyroxene in pyroxene rocks, they are classified into orthopyroxene rocks, two-pyroxene rocks, clinopyroxene rocks, and olivine-diopside rocks. Based on the different secondary minerals contained in the pyroxene rocks, they are classified into mica pyroxene rocks, amphibole pyroxene rocks, and serpentinized phlogopite pyroxene rocks, etc. Existing field petrological, regional geological, and geochemical research data indicate that the outcrops of metallic minerals such as cobalt, platinum, nickel, and chromium are closely related to orthopyroxene. Furthermore, the International Space Agency's research on the Martian meteorite collected from Alan Mountain in Antarctica revealed a unique Martian-accretionary orthopyroxene rock with a crystallization age of 450 million years. This rock is believed to possess characteristics of ancient Martian crustal material and is thus identified as an ancient rock from Mars. Nanoscale bacterial fossils, biological fossils, and organic molecules were also found within this orthopyroxene meteorite, leading to its classification as a meteorite biological specimen from another planet. The discovery of this orthopyroxene specimen is of paramount scientific significance and research value for unraveling the mystery of extraterrestrial life.

[0004] To investigate the formation mechanisms and occurrence principles of common geological hazards deep within the Earth, such as volcanoes, earthquakes, and debris flows, geologists typically employ high-pressure equipment with multiple large cavities, 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 orthorhombic pyroxene aggregates under high temperature and pressure conditions. Obtaining a large-sized polycrystalline orthorhombic pyroxene aggregate experimental sample (47.17 mm (diameter) × 68.19 mm (height)) is a crucial step in simulating these physical properties under high temperature and pressure conditions. Geologists typically use naturally occurring orthopyroxene rocks from the field as experimental samples instead of polycrystalline orthopyroxene rocks. However, natural orthopyroxene rocks suffer from numerous drawbacks, including low sample density, a high concentration of impurities (such as mica, amphibole, olivine, ilmenite, chromite, magnetite, and other layered, chain-like, island-like, and spinel-group silicate minerals), large and unevenly distributed orthopyroxene and clinopyroxene crystals (the main constituent minerals), difficulty in eliminating preferred lattice orientations, and significant anisotropy of crystal axes. Consequently, many different high-temperature and high-pressure mineral and rock property simulation teams worldwide use natural orthopyroxene rocks as initial samples and employ multi-faceted, large-cavity high-pressure equipment such as hydrothermal autoclaves, piston cylinder presses, and rotary shear friction testers. The experimental data obtained under high-temperature and high-pressure conditions for natural orthopyroxene rocks show significant differences, making it difficult to widely apply these experimental results to the interpretation of the formation mechanisms and occurrence principles of geological disasters such as volcanoes, earthquakes, and debris flows.

[0005] Compared with existing technologies, artificially synthesized island-shaped silicate mineral single crystal experimental samples can be prepared under high temperature and high pressure conditions using quasi-hydrostatic presses such as YJ-3000t and Kawai-1000t, as shown 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 rock aggregate samples. The obtained island-shaped silicate mineral single crystals have a particle size ranging from 100 micrometers to 425 micrometers, and the particle size distribution is uneven. 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 blocks. 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 large-volume polycrystalline orthorhombic pyroxene aggregate samples (e.g., with a diameter greater than 40 mm), the top and bottom of the orthorhombic pyroxene sample powder inevitably undergo significant asymmetric shrinkage due to unidirectional compression during high temperature, high pressure, and quasi-hydrostatic experiments. This results in numerous macroscopic voids and defects during the preparation of large-volume polycrystalline rock aggregate samples. These macroscopic voids and defects cause wrinkles or pores in the central part of the cross-section of the large-volume polycrystalline orthorhombic pyroxene aggregate, ultimately making the sample prone to severe porosity or aggregation along the center of the wrinkles or pores. This is the unavoidable shrinkage and porosity effect during the synthesis of large-volume polycrystalline rock aggregate samples under high temperature, high pressure, and quasi-hydrostatic conditions. The shrinkage and porosity effects of these polycrystalline orthopyroxene aggregate samples lead to severe excessive deformation, resulting in numerous voids, fracture wrinkles, and cavities in the prepared bulk polycrystalline orthopyroxene aggregate samples. This significantly affects the preparation results of bulk polycrystalline orthopyroxene aggregate samples. Therefore, neither natural orthopyroxene nor small-sized (no more than 6 mm) orthopyroxene samples obtained in the laboratory 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 testers. 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 orthorhombic pyroxene 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 solubility, friction coefficient, shear stress, and other properties of large-volume mafic magmatic intrusive rock aggregates—polycrystalline ultramafic pyroxene minerals and rocks under high-temperature and high-pressure conditions. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a method for preparing high-purity bulk polycrystalline orthorhombic pyroxene under hot isostatic pressing, thereby filling the technical gap in the preparation of bulk experimental samples of high-density polycrystalline orthorhombic pyroxene 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, and shear stress of bulk mafic magmatic intrusive rock aggregates—polycrystalline ultramafic pyroxene-like minerals and rocks—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.

[0007] The technical solution of this invention is:

[0008] A method for preparing high-purity bulk polycrystalline orthorhombic pyroxene under hot isostatic pressing, the method comprising: sealing orthorhombic pyroxene sample powder under a vacuum of 10... –3 The sample chamber was placed in a steel cladding; 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 it; argon was used as the pressure transmission medium; the temperature inside the sample chamber was raised to 1140 °C and the pressure was raised to 93.8 MPa using a multi-gradient cylinder heating and pressurization method, and the temperature and pressure were maintained for 4.5 hours; the temperature inside the sample chamber was lowered to 161 °C and the pressure was lowered to 48.5 MPa using a multi-gradient cylinder cooling and depressurization method; finally, the pressure was released and the temperature was lowered to room temperature to obtain polycrystalline orthorhombic pyroxene aggregate.

[0009] The method of raising the temperature to 1140 °C and the pressure to 93.8 MPa within the cylinder sample chamber using a multi-gradient cylinder heating and pressurization approach includes: raising the temperature to 600 °C and the pressure to 68.1 MPa within the temperature range of room temperature–600 °C using a heating rate of 18.30 °C / min and a pressurization rate of 0.71 MPa / min; raising the temperature to 1040 °C and the pressure to 87.2 MPa within the medium temperature range of 600 °C–1040 °C using a heating rate of 12.57 °C / min and a pressurization rate of 0.55 MPa / min, and maintaining this temperature and pressure for 1.0 hour; and raising the temperature to 1140 °C within the high temperature range of 1040 °C–1140 °C using a heating rate of 5 °C / min and a pressurization rate of 0.33 MPa / min. The temperature and pressure were increased to 93.8 MPa, and the temperature and pressure were maintained for 4.5 hours.

[0010] The method of reducing the temperature inside the cylinder sample chamber to 161 °C and the pressure to 48.5 MPa using a multi-gradient cylinder cooling and depressurization method includes: after maintaining a constant temperature and pressure of 93.8 MPa and 1140 °C for 4.5 hours, the temperature inside the cylinder sample chamber is reduced to 1040 °C and the pressure to 89.7 MPa at a cooling rate of 5 °C / min and a depressurization rate of 0.21 MPa / min, and then maintained at the same temperature and pressure for 1.0 hour; after maintaining the same temperature and pressure for 1.0 hour, the temperature inside the cylinder sample chamber is reduced to 161 °C and the pressure to 48.5 MPa at a cooling rate of 16.28 °C / min and a depressurization rate of 0.76 MPa / min.

[0011] Beneficial effects of this invention:

[0012] 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 advanced geochemistry, ore genesis, rock rheology, geodynamics, hot isostatic pressing materials science, hot isostatic powder metallurgy, seismology, igneous magmatism, high-pressure rheology, mineral physics, deep Earth materials science, high-pressure materials science, materials science, and high-pressure experimental mineralogy, large-volume, highly dense polycrystalline orthorhombic pyroxene 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.

[0013] The initial raw material selected for this invention is orthorhombic pyroxene collected in the field, without any alteration, with a fresh surface, and free of impurities. This orthorhombic pyroxene sample powder is crushed into uniformly sized polycrystalline rock 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 the orthorhombic pyroxene sample powder is in a completely sealed environment protected by argon inert gas. The steel sheath containing the orthorhombic pyroxene sample powder is 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 pressure to form a large, highly dense polycrystalline orthorhombic pyroxene aggregate. The prepared polycrystalline orthorhombic pyroxene aggregate sample can be widely used in diagenetic and mineralization experimental simulation studies of the physicochemical properties of minerals and rocks under high temperature and high pressure conditions.

[0014] The steel cladding dimensions used in the hot isostatic pressing test of this invention are: 57.14 mm (outer diameter) × 85.62 mm (height) × 3 mm. The obtained large-size polycrystalline orthorhombic pyroxene aggregate samples can reach a diameter of 47.17 mm and a height of 68.19 mm. During the hot isostatic pressing (HIP) experiment of the polycrystalline orthorhombic pyroxene aggregate samples under high temperature and high pressure, inert argon gas is used as the pressure transmission medium. By increasing the temperature and compressing the inert argon gas, the orthorhombic pyroxene sample powder is subjected to uniform pressure and temperature in all directions, effectively avoiding the adverse effects of shrinkage porosity and porosity during the HIP experiment. The inert argon gas ensures that the orthorhombic pyroxene sample powder in the sample chamber is completely isolated from the air, effectively preventing redox reactions between the orthorhombic pyroxene sample powder and air during the HIP experiment. Furthermore, this invention avoids the traditional high-pressure chemical reaction method, which may introduce impurity ions during the preparation of polycrystalline orthorhombic pyroxene aggregate samples due to the potential addition of excessive chemical reagents.

[0015] This invention employs a multi-gradient hot isostatic pressing (HIP) process, first increasing pressure and then increasing temperature, to prepare polycrystalline orthorhombic pyroxene 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 orthorhombic pyroxene 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 rock 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 orthorhombic pyroxene aggregate experimental samples with near-theoretical density and extremely high sample strength.

[0016] 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 orthorhombic pyroxene aggregate experimental samples under 93.8 MPa and 1140 °C conditions. 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 mafic magmatic intrusive rock aggregates—polycrystalline ultramafic pyroxene-like 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

[0017] 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 orthorhombic pyroxene aggregate change curves over time are shown.

[0018] Figure 2 To obtain fine-grained orthorhombic pyroxene 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 orthorhombic pyroxene sample before the hot isostatic pressing experiment were obtained using a high-magnification, high-precision Olympus SZX16 research-grade stereomicroscopic imaging platform.

[0019] Figure 3 This document presents the optical microscopic observation results of the surface morphology and grain size distribution of a polycrystalline orthorhombic pyroxene aggregate sample, a product of hot isostatic pressing experiments conducted at 93.8 MPa and 1140 °C, using the high-precision Olympus SZX16 research-grade stereomicroscopic imaging platform. Detailed Implementation

[0020] A method for preparing high-purity bulk polycrystalline orthorhombic pyroxene rock under hot isostatic pressing conditions, comprising:

[0021] Step 1: A dense, massive orthopyroxene rock was used as the initial sample. A high-precision Olympus SZX16 research-grade stereomicroscope was used to accurately measure the grain size of the initial sample. The smallest orthopyroxene rock sample size was 5.8 mm, and the largest was 13.9 mm. If the orthopyroxene rock sample size 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 orthopyroxene rock samples free of other associated / symbiotic minerals and impurities. If the orthopyroxene rock sample size is too small, it is difficult to effectively separate the orthopyroxene rock from layered silicate minerals, chain silicate minerals, island silicate minerals, and spinel group minerals of different compositions, such as mica, amphibole, olivine, ilmenite, chromite, and magnetite. Furthermore, this invention requires selecting orthopyroxene rock samples with a relatively large weight, which will consume significant time and manpower.

[0022] Step 2: Place the selected orthopyroxene block sample on an ultrasonic cleaner and use acetone, alcohol and deionized water as cleaning solutions in sequence for ultrasonic cleaning for 21 minutes to remove impurities from the sample surface.

[0023] Step 3: Using a high-magnification, high-precision Olympus SZX16 research-grade stereomicroscopic imaging platform, carefully select 270 grams of orthorhombic pyroxene blocky sample with uniform dark green color, fresh surface, and no other impurity minerals to ensure that the initial orthorhombic pyroxene sample has high purity before the hot isostatic pressing experiment under high temperature and high pressure conditions.

[0024] Step 4: Place the carefully selected orthopyroxene block samples 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 orthopyroxene sample, making it difficult to accurately weigh the initial orthopyroxene sample during further grinding. If the temperature is too high, it may cause a decomposition reaction in the orthopyroxene, ultimately severely affecting the preparation effect of the hot isostatic pressing (HIP) experiment sample under high temperature and high pressure conditions.

[0025] Step 5: Place the initial sample of orthopyroxene on a jaw crusher (model: BB 200), set the instrument's drive power to 1.5 kW, and use an 8-minute crushing time to crush the orthopyroxene into rock particles with a diameter of less than 2 mm. The purpose is to fully crush the sample to obtain orthopyroxene samples with a medium particle size (less than 2 mm).

[0026] Step 6: Place the sample on a high-efficiency Retsch disc vibratory grinder (model: RS200), using a high-speed mode of 1320 rpm and setting the instrument's drive power to 1.5 kW. Grind the rock particles into fine-grained orthopyroxene sample powder with a particle size of 11.32 μm to 24.27 μm (see...). Figure 2 The amount of orthopyroxene sample ground in a single cycle was 100 grams, and the grinding time was 7 minutes. Orthopyroxene powder within this particle size range has a large specific surface area (surface area per unit weight of rock powder), which significantly increases the contact area between particles due to pressure and temperature. This is more conducive to forming strong cementing forces between the particles of the orthopyroxene powder during the hot isostatic pressing experiment of this invention, thereby greatly improving the compactness and density of the prepared fine-grained polycrystalline orthopyroxene aggregate sample.

[0027] Step 7: Considering that the orthopyroxene 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 85 degrees Celsius for 13 days to completely remove the adsorbed water on the surface of the sample powder.

[0028] Step 8: In the process of preparing polycrystalline orthorhombic pyroxene aggregate samples using an RD80×100‒2000–200 double 2000 type hot isostatic pressing (HIP) equipment, a sample steel cladding 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) cladding selected in this case has the following main superior properties: (1) The low-carbon steel (No. 20 steel) cladding does not react with the orthorhombic pyroxene 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) cladding can withstand the temperature of 1140 °C and the pressure of 93.8 °C required for the preparation of polycrystalline orthorhombic pyroxene aggregate samples under the HIP conditions of this invention. MPa; (3) The steel sheath material of low carbon steel (No. 20 steel) has good air tightness, which ensures that the powder of the orthorhombic pyroxene sample 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 (No. 20 steel) also has excellent properties such as relatively easy edge rolling, cutting, processing, deformation and welding performance.

[0029] 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 the orthorhombic pyroxene sample powder with dimensions of 57.14 mm (outer diameter) × 85.62 mm (height) × 3 mm (wall thickness).

[0030] 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 orthorhombic pyroxene sample powder.

[0031] Step 9: First, vacuum weld the sleeve and lower sealing cap of the steel cladding. Then, place the dried orthopyroxene sample powder inside the steel cladding. After a series of processes including compaction, vacuuming, high-temperature degassing, and high-temperature vacuum welding, the orthopyroxene sample powder is completely sealed in a vacuum of 10... –3 Pa is in the steel ladle sleeve.

[0032] Achieving such a low vacuum level within the steel-clad cavity requires at least 62 hours of evacuation, while simultaneously degassing the sample at 400 °C to ensure the orthopyroxene sample powder is completely in a sealed vacuum environment and that all moisture is removed. The orthopyroxene sample 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 orthopyroxene sample powder is fully compacted, which can ensure that a sufficient amount of orthopyroxene sample powder is sealed in the steel sleeve, which will help increase the density of the polycrystalline orthopyroxene aggregate of the hot isostatic pressing test product, thereby greatly improving the preparation effect of the final product bulk polycrystalline orthopyroxene aggregate sample; (2) ensuring that the orthopyroxene sample powder is fully compacted, which can ensure the filling amount of orthopyroxene sample powder sealed in the steel sleeve, which will help enhance the compactness between the orthopyroxene sample powder particles, effectively avoiding excessive deformation of the sample during the hot isostatic pressing test, thereby greatly improving the compactness of the final product bulk polycrystalline orthopyroxene aggregate 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 orthopyroxene sample powder inside it; (4) Under the condition of 400 °C, the orthopyroxene sample powder is degassed at high temperature, completely removing any water vapor that may be present in the sample powder; (5) The steel sheath is welded by high temperature vacuum, which effectively isolates the weld head from direct contact with air, and the high temperature oxidation of the metal weld point can be completely avoided, which will greatly enhance the sealing performance of the steel sheath.

[0033] Step 10: Carefully place the steel sleeve containing the orthopyroxene 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 orthopyroxene 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.

[0034] 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 orthorhombic pyroxene aggregate 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 pipelines and circuits of the high-pressure device, ensuring the absolute safety of the operators during HIP experiments.

[0035] 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.

[0036] 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 orthorhombic pyroxene sample powder compaction to complete the hot isostatic pressing 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.

[0037] Step 12: In this invention, argon gas is used as the pressure transmission medium. During the preparation of polycrystalline orthorhombic pyroxene aggregates on an RD80×100‒2000–200 dual 2000-type hot isostatic pressing (HIP) equipment, 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 rock powder, which is difficult to mold, the use of argon gas as the inert gas pressure transmission medium and the selection of 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 orthorhombic pyroxene aggregate products.

[0038] This invention employs a multi-gradient hot isostatic pressing (HIP) process, involving prior pressurization followed by heating, to synthesize large-volume experimental samples of high-density, high-compactness, and high-purity polycrystalline orthopyroxene aggregates. The target pressure and temperature for the HIP experiment are 93.8 MPa and 1140 °C, respectively. If the selected target pressure and temperature are too low, the steel cladding used to seal the orthopyroxene sample powder during the HIP experiment will not be sufficiently compressed and effectively deformed. This makes it difficult to fully compact and sinter the sample, severely affecting the preparation of the experimental product—large-volume, high-density, and high-compact polycrystalline orthopyroxene aggregate samples. Conversely, if the selected target pressure and temperature are too high, the polycrystalline mafic ultramafic pyroxene sample—orthopyroxene—will undergo a decomposition reaction during the HIP experiment, severely impacting the prepared polycrystalline orthopyroxene aggregate product.

[0039] 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 orthorhombic pyroxene 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 orthorhombic pyroxene sample powder, precise temperature and pressure calibration of the orthorhombic pyroxene sample cavity is performed. Finally, based on the RD80×100‒2000–200 double 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 orthorhombic pyroxene aggregate HIP experiment. The formula for calculating the amount of argon gas consumed is as follows:

[0040] (1)

[0041] (2)

[0042] In the formula: parameter P target The target pressure for preparing polycrystalline orthorhombic pyroxene aggregate 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 bottle The 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 orthorhombic pyroxene aggregate sample under high temperature and high pressure conditions.

[0043] Step 13, vacuuming, filling with argon gas and cleaning the furnace, the purpose of which is to completely remove the air from the sample chamber. The specific operation steps are as follows: (1) Vacuuming: turn on the gas vacuum pump control switch to evacuate the air 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.

[0044] 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 93.8 MPa and the target temperature of 1140 °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 orthorhombic pyroxene sample chamber of the cylinder, so that the sample chamber in the cylinder is pre-filled and pressurized to 46.8 MPa.

[0045] Step 15: Multi-gradient cylinder block heating and pressurization (see...) Figure 1Taking into account the target pressure and temperature for preparing polycrystalline orthorhombic pyroxene aggregate samples in hot isostatic pressing (HIP), 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: Within the temperature range of room temperature to 600 °C, a heating rate of 18.30 °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 68.1 MPa; within the medium temperature range of 600 °C to 1040 °C, a heating rate of 12.57 °C / min and a pressurization rate of 0.55 MPa / min were used to raise the temperature in the cylinder sample chamber to 1040 °C and the pressure to 87.2 MPa. The orthopyroxene sample, a polycrystalline mafic ultramafic pyroxene-like rock, was subjected to constant temperature and pressure for 1.0 hour to ensure thorough compaction and cementation. After 1.0 hour of constant temperature and pressure, the temperature inside the sample chamber was increased to 1140 °C and the pressure to 93.8 MPa within a high-temperature range of 1040 °C–1140 °C, using a heating rate of 5 °C / min and a pressurization rate of 0.33 MPa / min. As the temperature increased, the argon gas inside the sealed cylinder expanded dramatically, while the cylinder volume remained constant, meaning the argon gas volume was uniformly compressed, resulting in uniform high pressure. Ultimately, the pressure inside the sample chamber was maintained at 93.8 MPa. The orthopyroxene sample powder was then held at this maximum pressure and maximum temperature of 93.8 MPa and 1140 °C for 4.5 hours. Orthopyroxene rocks are important silicate rocks widely exposed in the Earth's mantle and ancient Martian crust. Their main constituent minerals (orthopyroxene and clinopyroxene) have relatively complex crystal morphology, obvious preferred lattice orientation, and anisotropic physicochemical properties.

[0046] This invention employs a multi-gradient hot isostatic pressing (HIP) process, involving prior pressurization followed by heating, to prepare polycrystalline orthorhombic pyroxene aggregates. The process involves holding the aggregate at 1040 °C for 1 hour during the heating and pressurization phases to ensure a sufficiently long, stepped holding time. If the holding time is too short, it becomes difficult to establish strong bonding between the particles of the orthorhombic pyroxene powder with its diverse crystal morphologies. Furthermore, it is challenging to overcome the influence of factors such as the preferred orientation and anisotropy of the orthorhombic pyroxene crystal lattice, thus affecting the density and strength of the final bulk polycrystalline orthorhombic pyroxene aggregate sample. Conversely, while a high-density and high-strength polycrystalline orthorhombic pyroxene aggregate can be obtained, the resulting bulk sample, subjected to prolonged high temperature and pressure, will experience particle growth, uneven particle distribution, and recrystallization, severely impacting the preparation results and increasing experimental costs.

[0047] Step 16: Multi-gradient cylinder cooling and depressurization. After the orthopyroxene sample powder was kept at a constant temperature and pressure of 93.8 MPa and 1140 °C for 4.5 hours, the temperature inside the cylinder sample chamber was reduced to 1040 °C and the pressure to 89.7 MPa using a cooling rate of 5 °C / min and a depressurization rate of 0.21 MPa / min, and kept at the same temperature and pressure for 1.0 hour. After being kept at the same temperature and pressure for 1.0 hour, the temperature inside the cylinder sample chamber was reduced to 161 °C and the pressure was reduced to 48.5 MPa using a slower cooling rate of 16.28 °C / min and a slower depressurization rate of 0.76 MPa / min. Compared to the pressurization process, a slower cooling and depressurization rate is adopted. This is 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 lead to the fragmentation and damage of the large-volume polycrystalline orthorhombic pyroxene aggregate product, thus seriously affecting the preparation effect.

[0048] This invention selects a sample chamber temperature of 161 °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 excessive internal pressure can easily damage the graphite heating furnace and may also cause a safety accident with the HIP equipment. Conversely, if the sample chamber temperature is below 160 °C, the resulting low internal pressure makes it difficult to ensure that the argon inert pressure-transmitting medium sealed within the sample chamber is completely removed during the pressure relief process in the HIP experiment.

[0049] 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.

[0050] 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 161 °C to room temperature (~25 °C).

[0051] Step 19: Set the control program for the hot isostatic pressing (HIP) equipment, open the furnace chamber, carefully remove the polycrystalline orthorhombic pyroxene polymer steel-clad workpiece sealed after the HIP experiment, and accurately measure the dimensions of the steel cladding after the HIP forming experiment: 53.17 mm (outer diameter) × 78.19 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 20.93%. This invention exhibits such a large volumetric shrinkage rate (η) of the steel sheath. 钢包套 =20.93%), confirming that the steel cladding used to seal and enclose the orthopyroxene sample powder was fully compressed and effectively deformed during the hot isostatic pressing experiment.

[0052] Step 20: Using a high-speed diamond saw blade cutter with a 1.0 mm thick diamond saw blade, the polycrystalline orthorhombic pyroxene aggregate sample was carefully peeled from the steel ladle. The weight of the sample after the experiment was accurately measured to be 269 grams, and the tare weight of the steel ladle was 500 grams. This indicates that the weight of the orthorhombic pyroxene 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 orthorhombic pyroxene aggregate sample obtained after the HIP experiment: 47.17 mm (diameter) × 68.19 mm (height). Comparing the initial volume of the orthorhombic pyroxene 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. 斜方辉石岩 Its calculation formula can be expressed as: η 斜方辉石岩 =(V 实验前斜方辉石岩 –V 实验后斜方辉石岩 ) / V 实验前斜方辉石岩 The volume shrinkage rate (η × 100%) is 23.28%. This invention exhibits such a large volume shrinkage rate (η) in orthorhombic pyroxene sample powder. 斜方辉石岩 =23.28%), confirming that during the hot isostatic pressing experiment, the orthopyroxene sample powder placed in the steel cladding was fully compacted and sintered under high temperature and high pressure conditions.

[0053] This invention utilizes an RD80×100‒2000–200 dual 2000-type hot isostatic pressing (HIP) apparatus to synthesize a polycrystalline orthopyroxene aggregate from the initial material—a single-phase orthopyroxene—through crushing into medium-sized orthopyroxene particles, grinding into fine-grained orthopyroxene powder, and finally. Employing a multi-gradient HIP process of first increasing pressure and then increasing temperature, high-density, high-compactness, high-purity, and large-volume polycrystalline orthopyroxene aggregate is produced. No other impurity phases are introduced during the entire preparation process, and the purity of the resulting polycrystalline orthopyroxene aggregate sample can reach 100%.

[0054] Under epoxy resin inlay protection, a representative sample (21 mm × 21 mm cross-section) was cut from the polycrystalline orthorhombic pyroxene aggregate workpiece, a product of hot isostatic pressing experiments. 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 grain size distribution characteristics of the experimental product—the polycrystalline orthorhombic pyroxene aggregate—were tested. The test results (see...) Figure 3 The polycrystalline orthorhombic pyroxene aggregate 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 cladding, inert argon gas pressure transmission 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 uniform particle distribution, no particle growth, and no recrystallization in the polycrystalline orthorhombic pyroxene aggregate. 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 orthorhombic pyroxene aggregate products, including particle growth, uneven particle distribution, and recrystallization.

[0055] High-resolution scanning electron microscopy was used to observe the microstructure of the polycrystalline orthorhombic pyroxene aggregate sample obtained from the hot isostatic pressing experiment, and precise density tests were performed. The obtained polycrystalline orthorhombic pyroxene aggregate 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 orthorhombic pyroxene aggregate samples: (1) a higher pre-pressurization pressure (46.8 MPa); (2) a multi-gradient gradually decreasing cylinder heating mode, i.e., in the low-temperature zone (room temperature–600 °C), the heating rate is 18.30 °C / min; in the medium-temperature zone (600 °C–1040 °C), the heating rate is 12.57 °C / min; and in the high-temperature zone (1040 °C–1140 °C), the heating rate is 5 °C / min; (3) a multi-gradient gradually decreasing cylinder pressurization mode, i.e., in the low-pressure zone (46.8 MPa–68.1 MPa), the pressurization rate is 0.71 MPa / min; and in the medium-pressure zone (68.1 MPa–87.2 MPa), the pressurization rate is 0.71 MPa / min. Under pressure of MPa, the pressurization rate is 0.55 MPa / min and under pressure of 87.2 MPa–93.8 MPa, the pressurization rate is 0.33 MPa / min; (4) The cylinder cooling mode with gradually steepening gradients, that is, under temperature conditions of 1140 °C–1040 °C in the high temperature zone, the cooling rate is 5 °C / min and under temperature conditions of 1040 °C–161 °C in the medium and low temperature zone, the cooling rate is 16.28 °C / min; (5) The cylinder depressurization mode with gradually steepening gradients, that is, under pressure conditions of 93.8 MPa–89.7 MPa in the high pressure zone, the depressurization rate is 0.21 MPa / min and under pressure conditions of 89.7 MPa–48.5 MPa in the medium and low pressure zone, the depressurization rate is 0.76 MPa / min. MPa / min; (6) Multi-gradient cylinder constant temperature and pressure mode, that is, when the temperature and pressure of the heating and pressurization process in the hot isostatic pressing experiment are 1040 °C and 87.2 MPa, the constant temperature and pressure is maintained for 1.0 hours; at the highest temperature (1140 °C) and the highest pressure (93.8 MPa), the constant temperature and pressure is maintained for a sufficiently long time of 4.5 hours; when the temperature and pressure of the cooling and pressurization process in the hot isostatic pressing experiment are 1040 °C and 89.7 MPa, the constant temperature and pressure is maintained for 1.0 hours.All these optimized and improved hot isostatic pressing (HIP) experimental schemes can promote sufficient diffusion and particle aggregation between orthorhombic pyroxene 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 transmission during HIP, prevent the occurrence of local weaknesses or cracks, and thus greatly improve the compactness of the polycrystalline orthorhombic pyroxene aggregate sample produced by HIP. In addition, this invention applies a higher temperature (1140 °C), a higher pressure (93.8 MPa), and a sufficiently long heat and pressure holding time (4.5 hours) to promote the formation of good cementing force between the particles of the orthopyroxene sample powder, thereby greatly improving the density and strength of the polycrystalline orthopyroxene aggregate 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 using quasi-hydrostatic presses such as YJ-3000t and Kawai-1000t.

[0056] The Archimedes method using organically combined secondary deionized water and the water intrusion method for porous and complex structures were employed to accurately measure the density of polycrystalline orthorhombic pyroxene aggregate samples obtained from hot isostatic pressing experiments. The measured density of the polycrystalline orthorhombic pyroxene aggregate was 3.31 g / cm³. 3 This density value falls exactly within the theoretical density of 3.22 g / cm³ for naturally collected orthorhombic pyroxene rock, as measured by geologists. 3 -3.34 g / cm 3Within the specified range, the obtained bulk polycrystalline orthorhombic pyroxene aggregate samples exhibited extremely high density. The achievement of such high-density polycrystalline orthorhombic pyroxene aggregate products is highly related to the optimized molding process employed during this hot isostatic pressing experiment, including pretreatment of the orthorhombic pyroxene sample powder raw material, selection of No. 20 steel sample cladding, a reasonable cooling and depressurization hot isostatic pressing molding process, and high-temperature degassing at 400 °C. Pretreatment of orthopyroxene sample powder raw materials, specifically fine-grained orthopyroxene sample powder with a particle size ranging from 11.32 μm to 24.27 μm, is crucial. Orthopyroxene within this particle size range has a large specific surface area, significantly increasing the contact area between sample particles. This promotes stronger bonding and greatly enhances the density of the prepared polycrystalline orthopyroxene aggregate sample. A 3 mm thick, continuously cast slab of No. 20 low-carbon steel is used as the steel cladding. This cladding possesses excellent physical properties, including low strength, low hardness, high plasticity, and good toughness. It effectively transmits the high pressure borne by the cladding uniformly to the orthopyroxene sample powder enclosed within, further increasing the density of the prepared polycrystalline orthopyroxene aggregate sample. An optimized and improved cooling and depressurization hot isostatic pressing process is employed, particularly using a more symmetrical multi-gradient cylinder depressurization mode (pressurization rate: 0.33 MPa / min – 0.71 MPa / min; depressurization rate: 0.21 MPa / min). (MPa / min – 0.76 MPa / min) ensures that the internal stress of large-volume polycrystalline orthorhombic pyroxene aggregate 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 orthorhombic pyroxene aggregate sample. A high-temperature degassing optimization molding process at 400 °C is used, sealing the orthorhombic pyroxene sample powder in a steel sleeve and performing high-temperature vacuum degassing at 400 °C to minimize gas residue, thereby obtaining polycrystalline orthorhombic pyroxene aggregate experimental samples 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-purity bulk polycrystalline orthorhombic pyroxene rock under hot isostatic pressing, characterized in that: The method includes: sealing orthopyroxene sample powder in a vacuum of 10... –3 The sample chamber was placed in a steel cladding; 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 it; argon was used as the pressure transmission medium; the temperature inside the sample chamber was raised to 1140 °C and the pressure was raised to 93.8 MPa using a multi-gradient cylinder heating and pressurization method, and the temperature and pressure were maintained for 4.5 hours; the temperature inside the sample chamber was lowered to 161 °C and the pressure was lowered to 48.5 MPa using a multi-gradient cylinder cooling and depressurization method; finally, the pressure was released and the temperature was lowered to room temperature to obtain polycrystalline orthorhombic pyroxene aggregate.

2. The method for preparing high-purity bulk polycrystalline orthorhombic pyroxene rock under hot isostatic pressing according to claim 1, characterized in that: The orthopyroxene sample powder was sealed in a vacuum of 10. –3 The methods in the steel ladle sleeve of Pa include: Step 1: Select orthopyroxene rocks with a minimum sample size of 5.8 mm and a maximum sample size of 13.9 mm as initial samples; Step 2: Place the selected orthopyroxene rock on an ultrasonic cleaner and use acetone, alcohol and deionized water as cleaning solutions in sequence for ultrasonic cleaning for 21 minutes. Step 3: Select 270 grams of orthorhombic pyroxene block samples that are uniformly dark green in color, have a fresh surface, and are free of impurities. Step 4: Place the selected orthopyroxene block samples in a vacuum drying oven at 200 degrees Celsius and dry for at least 21 hours. Step 5: Crush the dried orthopyroxene block sample into rock particles with a diameter of less than 2 mm. Step 6: Grind the rock particles into orthopyroxene sample powder with a particle size of 11.32 micrometers to 24.27 micrometers; Step 7: Pack the orthopyroxene sample powder into a paper sealed bag and dry it in a vacuum drying oven at 85 degrees Celsius for 13 days.

3. The method for preparing high-purity bulk polycrystalline orthorhombic pyroxene rock under hot isostatic pressing according to claim 1, characterized in that: The method for preparing the steel cladding includes: Step 8: Select a continuous casting slab of No. 20 low carbon steel with a wall thickness of 3 mm, heat it to 200 °C, and then use the roughing mill and finishing mill to cool it to the set temperature through laminar flow. The slab 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 a steel cladding sleeve with dimensions of 57.14 mm (outer diameter) × 85.62 mm (height) × 3 mm (wall thickness). A continuous casting slab of No. 20 low-carbon steel with a wall thickness of 3 mm was selected. The same hot rolling process was used to prepare the upper and lower sealing caps of the steel cladding. The cladding, upper and lower sealing caps were welded together by high-temperature vacuum welding to prepare a complete steel cladding.

4. The method for preparing high-purity bulk polycrystalline orthorhombic pyroxene under hot isostatic pressing according to claim 1, characterized in that: The orthopyroxene sample powder was sealed in a vacuum of 10. –3 The method in the steel cladding of Pa includes: vacuum welding the sleeve and lower sealing cap of the steel cladding; then placing the dried orthopyroxene sample powder inside the steel cladding; and finally, compacting, vacuuming, high-temperature degassing, and high-temperature vacuum welding to completely seal the orthopyroxene sample powder under a vacuum of 10... –3 The sample is placed in a steel bladder containing Pa; vacuuming must be carried out for at least 62 hours, and the sample is simultaneously degassed at 400 °C.

5. The method for preparing high-purity bulk polycrystalline orthorhombic pyroxene rock 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: ； ； In the formula: parameter P target The target pressure for preparing polycrystalline orthorhombic pyroxene aggregate 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 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 orthorhombic pyroxene aggregate sample under high temperature and high pressure conditions.

6. The method for preparing high-purity bulk polycrystalline orthorhombic pyroxene rock 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: Turn on the gas vacuum pump control switch to evacuate the air sealed in the high-pressure sample chamber, which is directly connected to the gas vacuum pump. Evacuate until the vacuum level instrument's digital display 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 process three times; 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 orthorhombic pyroxene sample chamber of the cylinder, so that the sample chamber in the cylinder is pre-pressurized to 46.8 MPa.

7. The method for preparing high-purity bulk polycrystalline orthorhombic pyroxene rock under hot isostatic pressing according to claim 1, characterized in that: The method of raising the temperature to 1140 °C and the pressure to 93.8 MPa within the cylinder sample chamber using a multi-gradient cylinder heating and pressurization approach includes: raising the temperature to 600 °C and the pressure to 68.1 MPa within the temperature range of room temperature–600 °C using a heating rate of 18.30 °C / min and a pressurization rate of 0.71 MPa / min; raising the temperature to 1040 °C and the pressure to 87.2 MPa within the medium temperature range of 600 °C–1040 °C using a heating rate of 12.57 °C / min and a pressurization rate of 0.55 MPa / min, and maintaining this temperature and pressure for 1.0 hour; and raising the temperature to 1140 °C within the high temperature range of 1040 °C–1140 °C using a heating rate of 5 °C / min and a pressurization rate of 0.33 MPa / min. The temperature and pressure were increased to 93.8 MPa, and the temperature and pressure were maintained for 4.5 hours.

8. The method for preparing high-purity bulk polycrystalline orthorhombic pyroxene rock under hot isostatic pressing according to claim 1, characterized in that: The method of reducing the temperature inside the cylinder sample chamber to 161 °C and the pressure to 48.5 MPa using a multi-gradient cylinder cooling and depressurization method includes: after maintaining a constant temperature and pressure of 93.8 MPa and 1140 °C for 4.5 hours, the temperature inside the cylinder sample chamber is reduced to 1040 °C and the pressure to 89.7 MPa at a cooling rate of 5 °C / min and a depressurization rate of 0.21 MPa / min, and then maintained at the same temperature and pressure for 1.0 hour; after maintaining the same temperature and pressure for 1.0 hour, the temperature inside the cylinder sample chamber is reduced to 161 °C and the pressure to 48.5 MPa at a cooling rate of 16.28 °C / min and a depressurization rate of 0.76 MPa / min.

9. The method for preparing high-purity bulk polycrystalline orthorhombic pyroxene rock under hot isostatic pressing according to claim 1, characterized in that: Methods for obtaining polycrystalline orthorhombic pyroxene aggregates by depressurization and cooling to room temperature include: Step 17, Depressurization: First, 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; then, 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 161 °C to room temperature. Step 19: Open the furnace chamber and remove the steel ladle-clad workpiece; Step 20: Use a diamond saw blade cutter to peel the polycrystalline orthorhombic pyroxene aggregate sample from the steel sheath.

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