Preparation method of high-density high-densification polycrystalline pyroxene diorite aggregate

Abstract

This invention discloses a method for preparing high-density, high-compactness polycrystalline pyroxene diorite aggregates, wherein the pyroxene diorite sample powder is completely sealed in a vacuum of 10... –3 The sample chamber was placed in a steel cladding; the cladding was then placed inside the graphite furnace cylinder of a hot isostatic pressing (HIP) apparatus, and a graphite sealing cap was placed on top. Using argon as the pressure transfer medium, a multi-gradient cylinder heating and pressurization method was employed to raise the temperature inside the cylinder sample chamber to 500 °C and the pressure to 86.4 MPa, and maintained at this temperature and pressure for 10 hours. A cooling rate of 11.41 °C / min and a depressurization rate of 0.62 MPa / min were then used to lower the temperature inside the cylinder sample chamber to 169 °C and the pressure to 68.5 MPa. Finally, the pressure was released and the sample was cooled to room temperature to obtain a polycrystalline pyroxene diorite aggregate sample. This method fills the technical gap in the preparation of large-volume experimental samples of highly dense polycrystalline pyroxene diorite 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 calc-alkaline series magmatic intrusive rocks aggregates – polycrystalline intermediate diorite-andesite, and particularly relates to a method for preparing high-density, high-compact polycrystalline pyroxene diorite aggregates. Background Technology

[0002] Diorite-andesite igneous rocks belong to the calc-alkaline series and have a Rittmann index of less than 3.3. They are typical saturated or weakly saturated silicate intermediate igneous rocks. The main mineral composition of diorite-andesite igneous rocks consists of 65%–80% transparent minerals—intermediate plagioclase—and 20%–35% dark minerals such as common amphibole, clinopyroxene, and biotite. They contain little or no quartz. In terms of regional geological characteristics, the rocks are divided into intrusive diorite-andesite type and extrusive diorite-andesite type intermediate igneous rocks. The intrusive intermediate diorite-andesite type igneous rocks can exhibit characteristics of basic igneous rocks transitioning from gabbro-basalt type represented by gabbro, or acidic igneous rocks transitioning from granite-rhyolite type represented by granite. The extrusive intermediate diorite-andesite type igneous rocks are often associated with or coexist with basic basalt and acidic rhyolite, and their geological genesis is very close, also showing obvious transitional characteristics. In terms of the spatial and temporal distribution of rocks in geological regions, extrusive intermediate diorite-andesite igneous rocks, represented by andesite, account for approximately 24% of the total igneous rock area and are widely distributed under various geological tectonic conditions. In contrast, intrusive intermediate diorite-andesite igneous rocks, represented by diorite, account for only about 2% of the total igneous rock area and are less abundant under different geological tectonic conditions. Subhedral granular textures are frequently exposed in diorite-andesite igneous rocks. Under predominantly basic conditions, plagioclase exhibits a high degree of euhedrality, similar to gabbroic and diabase textures. Under predominantly acidic conditions, plagioclase displays a subhedral shape, often accompanied by quartz or potassium feldspar infill, with a degree of euhedrality similar to monzogranite. Generally, shallow (or ultra-shallow) diorite widely exposed at the surface exhibits predominantly porphyritic textures, with less porphyritic-like textures. In terms of mineralogical composition, these diorites commonly feature a predominantly transparent mineral – intermediate plagioclase – and dark minerals – such as common amphibole, clinopyroxene, and biotite – occurring in phenocryst form, with a matrix exhibiting microgranular and fine-grained textures. Furthermore, in intermediate diorites – andesitic igneous rocks – banded and massive structures are the two most common structural types. In areas with strong assimilation and contamination, porphyritic structures are also observed, further subdividing them into: diorite, quartz diorite, pyroxene diorite, and microcrystalline diorite.

[0003] As an intermediate diorite-andesite igneous rock, diorite exhibits transitional characteristics with syenite and granite groups, primarily manifested in the following ways: When the alkali feldspar content increases, diorite can transition to monzonite to syenite; when the quartz content increases while the content of dark minerals decreases, diorite can transition to quartz diorite to plagioclase granite; when both alkali feldspar and quartz content increase, while the content of dark minerals decreases, diorite can transition to quartz monzonite, granodiorite, and granite. When the content of pyroxene and other dark minerals increases, diorite can transition to gabbro-diorite to gabbro. Natural diorite samples exposed in the field are generally aggregates composed of 67% banded plagioclase and 33% dark minerals. The transparent plagioclase is predominantly andesine, with well-developed plagioclase twinning and visible sodic zoisite and sericitization. The main dark minerals include amphibole, pyroxene, biotite, and quartz, as well as accessory and impurity minerals such as potassium feldspar, apatite, sphene, magnetite, ilmenite, and zircon. Based on the types and amounts of dark minerals contained in the diorite, it can be further subdivided into pyroxene diorite, biotite diorite, and amphibole diorite. Common pyroxene diorite samples have the following main mineralogical composition: andesine, common amphibole, and clinopyroxene.

[0004] To investigate the formation mechanisms and occurrence paths 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 pyroxene diorite aggregates under high temperature and pressure conditions. Obtaining a large-sized experimental sample of polycrystalline pyroxene diorite aggregate, measuring 45.88 mm (diameter) × 72.41 mm (height), is a crucial step in simulating these physical properties under high temperature and pressure conditions. Geologists typically use naturally occurring pyroxene diorite found in the field as a substitute for polycrystalline pyroxene diorite as experimental samples. However, naturally occurring pyroxene diorite has several drawbacks: low sample density, numerous impurity minerals (such as biotite, quartz, potassium feldspar, apatite, sphene, magnetite, ilmenite, zircon, and various hydrous layered silicate, oxide, aluminosilicate, phosphate, island silicate, and spinel group minerals), and large and unevenly distributed and poorly lattice-rich crystals of the main constituent minerals, including andesite, common amphibole, and clinopyroxene. Due to numerous insurmountable drawbacks, such as the difficulty in eliminating optimal orientation and significant anisotropy of crystal axes, many different high-temperature and high-pressure mineral and rock property simulation teams around the world use natural pyroxene diorite as the initial sample and employ multi-faceted large-cavity high-pressure equipment such as hydrothermal autoclaves, piston cylinder presses, and rotary shear friction test machines. However, the experimental data on the physical properties of natural pyroxene diorite 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.

[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, 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 pyroxene diorite aggregates (e.g., with a diameter greater than 40 mm), the top and bottom of the pyroxene diorite sample powder inevitably experience 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 aggregates. These macroscopic voids and defects cause wrinkles or pores in the central part of the cross-section of the large-volume polycrystalline pyroxene diorite 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 aggregates under high temperature, high pressure, and quasi-hydrostatic conditions. The shrinkage and porosity effects of these polycrystalline pyroxene diorite aggregate samples lead to severe excessive deformation, resulting in numerous voids, fracture wrinkles, and cavities in the prepared bulk polycrystalline pyroxene diorite aggregate samples. This significantly affects the preparation results of bulk polycrystalline pyroxene diorite aggregate samples. Therefore, neither natural pyroxene diorite nor small-sized (no more than 6 mm) pyroxene diorite 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 pyroxene diorite 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 mineral and rock properties of large-volume calc-alkaline series magmatic intrusive rock aggregates—polycrystalline intermediate diorite-andesite 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-density, high-compact polycrystalline pyroxene diorite aggregates, thereby filling the technical gap in the preparation of large-volume experimental samples of high-compact polycrystalline pyroxene diorite 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 large-volume calc-alkaline series magmatic intrusive rock aggregates—polycrystalline intermediate diorite-andesite minerals and rock properties—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-density, high-compactness polycrystalline pyroxene diorite aggregates, the method comprising: completely sealing pyroxene diorite 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 a 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 500 °C and the pressure was raised to 86.4 MPa using a multi-gradient cylinder heating and pressurization method, and kept at the same temperature and pressure for 10 hours; the temperature inside the sample chamber was lowered to 169 °C and the pressure was lowered to 68.5 MPa using a cooling rate of 11.41 °C / min and a depressurization rate of 0.62 MPa / min; finally, the pressure was released and the temperature was lowered to room temperature to obtain a polycrystalline pyroxene diorite aggregate sample.

[0009] The methods for purging argon gas, the pressure-transmitting medium, include:

[0010] 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;

[0011] Step 14, Pre-pressurization of the sample chamber: Calculate the amount of inert argon gas required, at least 4 argon cylinders with an internal pressure of 15 MPa are needed; 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 pyroxene diorite sample chamber in the cylinder, so that the sample chamber in the cylinder is pre-pressurized to 57.9 MPa.

[0012] The method of raising the temperature to 500 °C and the pressure to 86.4 MPa within the cylinder sample chamber using a multi-gradient cylinder heating and pressurization approach includes: raising the temperature to 200 °C and the pressure to 69.1 MPa within the temperature range of room temperature to 200 °C using a heating rate of 10 °C / min and a pressurization rate of 0.56 MPa / min; raising the temperature to 400 °C and the pressure to 79.2 MPa within the temperature range of 200 °C–400 °C using a heating rate of 10 °C / min and a pressurization rate of 0.51 MPa / min within the temperature range of 400 °C–500 °C using a heating rate of 6.67 °C / min and a pressurization rate of 0.48 MPa / min within the temperature range of 400 °C–500 °C using a heating rate of 6.67 °C / min and a pressurization rate of 0.48 MPa / min within the temperature range of 500 °C and 86.4 MPa within the temperature chamber.

[0013] Beneficial effects of this invention:

[0014] 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 pyroxene diorite 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.

[0015] The initial raw material selected for this invention is pyroxene diorite collected in the field, without any alteration, with a fresh surface, and free of impurities. This pyroxene diorite sample powder is crushed into uniformly sized polycrystalline rock powder. It 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 pyroxene diorite sample powder is in a completely sealed environment protected by argon inert gas. The steel sheath containing the pyroxene diorite 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 into a large, highly dense polycrystalline pyroxene diorite aggregate. The prepared polycrystalline pyroxene diorite 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.

[0016] The steel cladding dimensions used in the hot isostatic pressing test of this invention are: 57.35 mm (outer diameter) × 84.64 mm (height) × 3 mm. The obtained large-size polycrystalline pyroxene diorite aggregate samples can reach a diameter of 45.88 mm and a height of 72.41 mm. During the hot isostatic pressing (HIP) experiment of the polycrystalline pyroxene diorite aggregate 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 pyroxene diorite sample powder in all directions, effectively avoiding the adverse effects of shrinkage porosity and porosity during the HIP experiment. The inert argon gas ensures complete isolation between the pyroxene diorite sample powder and air within the sample chamber, effectively preventing redox reactions between the pyroxene diorite 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 pyroxene diorite aggregate samples due to the potential addition of excessive chemical reagents.

[0017] This invention employs a multi-gradient hot isostatic pressing (HIP) process, first increasing pressure and then temperature, to prepare polycrystalline pyroxene diorite 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 pyroxene diorite 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, this invention's multi-gradient HIP process can obtain polycrystalline pyroxene diorite aggregate experimental samples with near-theoretical density and extremely high sample strength.

[0018] This invention, based on an RD80×100‒2000–200 double 2000-type hot isostatic pressing (HIP) device, employs a multi-gradient HIP molding process of first increasing pressure and then increasing temperature. For the first time, it obtains large-volume, uniformly distributed, high-density, high-compactness, and high-strength polycrystalline pyroxene diorite aggregate experimental samples under conditions of 86.4 MPa and 500 °C. These samples can be widely applied to experimental simulations of the solubility, friction coefficient, and shear stress properties of large-volume calc-alkaline series magmatic intrusive rock aggregates—polycrystalline intermediate diorite-andesite minerals—on multi-faceted, large-cavity high-pressure equipment such as hydrothermal autoclaves, piston cylinder presses, and rotary shear friction testing machines. This provides crucial experimental sample support for systematically exploring the formation mechanisms and occurrence mechanisms of common geological disasters such as deep-earth volcanoes, earthquakes, and debris flows. Attached Figure Description

[0019] 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 pyroxene diorite aggregate are shown in the curves of temperature and pressure changes over time in the sample chamber.

[0020] Figure 2 To obtain fine-grained pyroxene diorite 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 pyroxene diorite sample before the hot isostatic pressing experiment were obtained using a high-magnification, high-precision Olympus SZX16 research-grade stereomicroscopic imaging platform.

[0021] Figure 3 This document presents the optical microscopic observation results of the surface morphology and grain size distribution of a polycrystalline pyroxene diorite aggregate sample, a product of hot isostatic pressing experiments conducted at 86.4 MPa and 500 °C, using the high-precision Olympus SZX16 research-grade stereomicroscopic imaging platform. Detailed Implementation

[0022] A method for preparing high-density, highly compact polycrystalline pyroxene diorite aggregates includes:

[0023] Step 1: Square, dense, massive pyroxene diorite was used as the initial sample. A high-precision Olympus SZX16 research-grade stereomicroscopy platform was used to accurately measure the grain size of the initial sample. The smallest sample size of the pyroxene diorite was 4.9 mm and the largest sample size was 12.4 mm. If the sample size of pyroxene diorite is too large, only a low-magnification, high-precision Olympus SZX16 research-grade stereomicroscopy platform can be used for sample selection, making it difficult to accurately identify high-purity pyroxene diorite samples free of other associated / symbiotic minerals and impurities. If the sample size of pyroxene diorite is too small, it is difficult to effectively separate pyroxene diorite from hydrous layered silicate minerals, oxide minerals, aluminosilicate minerals, phosphate minerals, island silicate minerals, and spinel group minerals of different compositions, such as biotite, quartz, potassium feldspar, apatite, sphene, magnetite, ilmenite, and zircon. Furthermore, this invention requires the selection of pyroxene diorite samples with relatively large weights, which will consume a significant amount of time and manpower.

[0024] Step 2: Place the selected pyroxene diorite block sample on an ultrasonic cleaner and use acetone, alcohol and deionized water as cleaning solutions in sequence for ultrasonic cleaning for 18 minutes to remove impurities from the sample surface.

[0025] Step 3: Using a high-magnification, high-precision Olympus SZX16 research-grade stereomicroscopic imaging platform, carefully select 250 grams of pyroxene diorite blocky samples with uniform gray-black color, fresh surface, and no other impurity minerals to ensure that the initial pyroxene diorite sample has high purity before the hot isostatic pressing experiment under high temperature and high pressure conditions.

[0026] Step 4: Place the carefully selected pyroxene diorite block samples in a vacuum drying oven at 200 degrees Celsius for at least 18 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 pyroxene diorite sample, making it difficult to accurately weigh the initial sample during further grinding. If the temperature is too high, it may cause a decomposition reaction in the pyroxene diorite, ultimately severely affecting the preparation effect of the hot isostatic pressing (HIP) experiment sample under high temperature and high pressure conditions.

[0027] Step 5: Place the initial pyroxene diorite sample 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 pyroxene diorite into rock particles with a diameter of less than 2 mm. The purpose is to fully crush the sample to obtain medium-sized (less than 2 mm) pyroxene diorite samples.

[0028] Step 6: Place the sample on a high-efficiency Retsch disc vibratory grinder (model: RS200), using a high-speed mode of 1260 rpm and setting the instrument's drive power to 1.5 kW. Grind the rock particles into fine-grained pyroxene diorite sample powder with a particle size of 9.95 μm to 19.41 μm (see...). Figure 2 The amount of pyroxene diorite sample ground in a single cycle was 100 grams, and the grinding time was 7 minutes. Pyroxene diorite 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 effects. This is more conducive to forming strong cementing forces between the particles of the pyroxene diorite powder during the hot isostatic pressing experiment of this invention, thereby greatly improving the compactness and density of the prepared fine-grained polycrystalline pyroxene diorite aggregate sample.

[0029] Step 7: Considering that the fine-grained pyroxene diorite sample powder is very 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 14 days to completely remove the adsorbed water on the surface of the sample powder.

[0030] Step 8: In the process of preparing polycrystalline pyroxene diorite 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 pyroxene diorite sample powder, avoiding sample contamination during the HIP experiment and directly affecting the preparation effect; (2) The low-carbon steel (No. 20 steel) cladding can withstand the temperature of 500 °C and pressure of 86.4 required for the preparation of polycrystalline pyroxene diorite 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 pyroxene diorite 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.

[0031] 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 a steel cladding sleeve for hot isostatic pressing of pyroxene diorite sample powder with dimensions of 57.35 mm (outer diameter) × 84.64 mm (height) × 3 mm (wall thickness).

[0032] 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 pyroxene diorite sample powder.

[0033] Step 9: First, vacuum weld the sleeve and lower sealing cap of the steel cladding. Then, place the dried pyroxene diorite sample powder inside the steel cladding. After a series of processes including compaction, vacuuming, high-temperature degassing, and high-temperature vacuum welding, the pyroxene diorite sample powder is completely sealed in a vacuum of 10... –3 Pa is in the steel ladle sleeve.

[0034] Achieving such a low vacuum level within the steel-clad cavity requires at least 57 hours of evacuation, while simultaneously degassing the sample at 400 °C to ensure the pyroxene diorite sample powder is completely in a sealed vacuum environment and that all moisture is removed from the sample. The pyroxene diorite 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 pyroxene diorite sample powder is fully compacted, which can ensure that a sufficient amount of pyroxene diorite sample powder is sealed in the steel sleeve, which will help increase the density of the polycrystalline pyroxene diorite aggregate of the hot isostatic pressing test product, thereby greatly improving the preparation effect of the final product bulk polycrystalline pyroxene diorite aggregate sample; (2) ensuring that the pyroxene diorite sample powder is fully compacted, which can ensure the filling amount of pyroxene diorite sample powder sealed in the steel sleeve, which will help enhance the compactness between the pyroxene diorite 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 pyroxene diorite aggregate sample; (3) maintaining 10 –3The 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 pyroxene diorite sample powder sealed inside; (4) Under the condition of 400 °C, the pyroxene diorite 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 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.

[0035] Step 10: Carefully place the steel sleeve containing the pyroxene diorite 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 pyroxene diorite sample powder under high temperature and high pressure conditions. The graphite furnace cylinder is the core component of this equipment and the heating element that achieves the extremely high sample chamber temperature of 2000 degrees Celsius.

[0036] 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 on polycrystalline pyroxene diorite 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.

[0037] 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.

[0038] 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 pyroxene diorite sample powder compaction piece 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.

[0039] Step 12: In this invention, argon gas is used as the pressure transmission medium. During the preparation of polycrystalline pyroxene diorite aggregates on an RD80×100‒2000–200 double 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 pyroxene diorite aggregate products.

[0040] 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 pyroxene diorite aggregates. The target pressure and temperature for the HIP experiment are 86.4 MPa and 500 °C, respectively. If the selected target pressure and temperature are too low, the steel cladding used to seal the pyroxene diorite 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 pyroxene diorite aggregate sample. Conversely, if the selected target pressure and temperature are too high, the polycrystalline calc-alkaline intermediate diorite-andesite intrusive rock-pyroxene diorite sample will undergo a decomposition reaction during the HIP experiment, thus having an extremely adverse effect on the prepared polycrystalline pyroxene diorite aggregate product.

[0041] 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 pyroxene diorite 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 molding experiments, high-temperature low-pressure empty furnace HIP molding experiments, and high-temperature high-pressure empty furnace HIP molding experiments of pyroxene diorite sample powder, precise temperature and pressure calibration of the pyroxene diorite 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 pyroxene diorite aggregate HIP experiment. The formula for calculating the amount of argon gas consumed is as follows:

[0042] (1)

[0043] (2)

[0044] In the formula: parameter P target The target pressure for preparing polycrystalline pyroxene diorite aggregate samples under hot isostatic pressing is based on the target temperature (T) of the hot isostatic pressing experiment.target ) Perform the calculation; parameter P bottle The parameter t represents the internal pressure of the inert gas argon in the cylinder; the 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 pyroxene diorite aggregate sample under high temperature and high pressure conditions.

[0045] 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.

[0046] 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 86.4 MPa and the target temperature of 500 °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 membrane compressor and pump all the remaining argon gas in the high-pressure tank into the pyroxene diorite sample chamber in the cylinder, so that the sample chamber in the cylinder is pre-filled and pressurized to 57.9 MPa.

[0047] Step 15: Multi-gradient cylinder block heating and pressurization (see...) Figure 1Taking into account the target pressure and temperature for preparing polycrystalline pyroxene diorite aggregate samples in the thermostatic 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–200 °C, a heating rate of 10 °C / min and a pressurization rate of 0.56 MPa / min were used to raise the temperature in the cylinder sample chamber to 200 °C and the pressure to 69.1 MPa; in the medium temperature range of 200 °C–400 °C, a heating rate of 10 °C / min and a pressurization rate of 0.51 MPa / min were used to raise the temperature in the cylinder sample chamber to 400 °C and the pressure to 79.2 MPa; in the high temperature range of 400 °C–500 °C, a heating rate of 6.67 °C / min and a pressurization rate of 0.48 MPa / min were used. A pressurization rate of MPa / min was used to raise the temperature inside the sample chamber to 500 °C and the pressure to 86.4 MPa, maintaining this temperature and pressure for 10 hours to ensure thorough compaction and cementation of the polycrystalline calc-alkaline intermediate diorite-andesite intrusive rock-pyroxene diorite sample. As the temperature increased, the argon gas inside the sealed chamber expanded dramatically, while the chamber volume remained constant, indicating that the argon gas volume was uniformly compressed, thus generating uniform high pressure. Ultimately, the pressure inside the sample chamber was maintained at 86.4 MPa. Pyroxene diorite is formed by the fractional crystallization of partially melted lithospheric mantle and is widely exposed in global or regional cratons. Its isotopic geochemical dating results can be used to identify magmatic hydrothermal activity at different tectonic stages, as well as the complex crystal morphology, distinct lattice preferred orientation, and anisotropic physicochemical properties of its main constituent minerals (andesite, amphibole, and clinopyroxene).

[0048] This invention employs a multi-gradient hot isostatic pressing (HIP) process, involving first increasing pressure and then increasing temperature, to prepare polycrystalline pyroxene diorite aggregates. The pyroxene diorite sample powder is held under pressure and temperature of 86.4 MPa and 500 °C for 10 hours to ensure a sufficiently long stepped holding time. If the holding time is too short, it is difficult to form strong cementation between the particles of the pyroxene diorite sample powder with its diverse crystal morphologies, and it is also difficult to overcome the influence of many unfavorable factors such as the preferred orientation and anisotropy of the pyroxene diorite crystal lattice, thus affecting the density and strength of the final bulk polycrystalline pyroxene diorite aggregate sample. Conversely, if the holding time is too long, although a highly dense and strong polycrystalline pyroxene diorite aggregate can be obtained, the final bulk polycrystalline pyroxene diorite aggregate sample will experience particle growth, uneven particle distribution, and recrystallization under prolonged high temperature and pressure, severely affecting the preparation effect and resulting in higher experimental costs.

[0049] Step 16: Multi-gradient cooling and depressurization of the cylinder. After the pyroxene diorite sample powder was kept at a constant temperature and pressure of 86.4 MPa and 500 °C for 10 hours, a relatively slow cooling rate of 11.41 °C / min and a relatively slow depressurization rate of 0.62 MPa / min were used to reduce the temperature in the cylinder sample chamber to 169 °C and the pressure to 68.5 MPa. Compared with the pressurization process, a slower cooling and depressurization rate was used mainly because if the cooling and depressurization rate was too fast, the internal stress of the steel cladding would not be fully released, which would lead to the fragmentation and damage of the large-volume polycrystalline pyroxene diorite aggregate product, thus seriously affecting the preparation effect.

[0050] This invention selects a sample chamber temperature of 169 °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.

[0051] 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.

[0052] 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 169 °C to room temperature (~25 °C).

[0053] Step 19: Set the control program for the hot isostatic pressing (HIP) equipment, open the furnace chamber, carefully remove the polycrystalline pyroxene diorite polymer steel-clad workpiece sealed after the HIP experiment, and accurately measure the dimensions of the steel clad after the HIP forming experiment: 51.88 mm (outer diameter) × 82.41 mm (height). Compare the volume of the steel clad before the HIP experiment and calculate the volume shrinkage rate (η) of the steel clad 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 20.32%. This invention exhibits such a large volumetric shrinkage rate (η) of the steel sheath.钢包套 =20.32%), confirming that the steel cladding used to seal and encapsulate the pyroxene diorite sample powder underwent sufficient compression and effective deformation during the hot isostatic pressing experiment.

[0054] Step 20: Using a high-speed diamond saw blade cutter with a 1.0 mm thick diamond saw blade, the polycrystalline pyroxene diorite aggregate sample was carefully peeled from the steel ladle. The weight of the sample after the experiment was accurately measured to be 249 grams, and the tare weight of the steel ladle was 500 grams. This indicates that the weight of the pyroxene diorite 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 pyroxene diorite aggregate sample obtained after the HIP experiment: 45.88 mm (diameter) × 72.41 mm (height). Comparing the initial volume of the pyroxene diorite 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. 辉石闪长岩 Its calculation formula can be expressed as: η 辉石闪长岩 =(V 实验前辉石闪长岩 –V 实验后辉石闪长岩 ) / V 实验前辉石闪长岩 The volume shrinkage rate (η × 100%) is 22.56%. This invention exhibits such a large volume shrinkage rate (η × 100%) in pyroxene diorite sample powder. 辉石闪长岩 =22.56%), confirming that during the hot isostatic pressing experiment, the pyroxene diorite sample powder placed in the steel cladding was fully compacted and sintered under high temperature and high pressure conditions.

[0055] This invention utilizes an RD80×100‒2000–200 double 2000-type hot isostatic pressing (HIP) apparatus to synthesize a polycrystalline pyroxene diorite aggregate from the initial material—a single-phase pyroxene diorite—through crushing into medium-sized pyroxene diorite particles, grinding into fine-grained pyroxene diorite powder, and finally synthesizing the final product. A multi-gradient HIP process, involving prior pressurization followed by heating, is employed to prepare high-density, highly compact, high-purity, and large-volume polycrystalline pyroxene diorite aggregate. No other impurity phases are introduced during the entire preparation process, resulting in a polycrystalline pyroxene diorite aggregate sample with 100% purity.

[0056] Under epoxy resin inlay protection, representative samples (20 mm × 20 mm cross-section) were cut from the polycrystalline pyroxene diorite aggregate workpiece, a product of hot isostatic pressing experiments. These samples underwent epoxy resin inlay protection, cutting, grinding, and surface polishing. The surface morphology and grain size distribution characteristics of the experimental product—the polycrystalline pyroxene diorite aggregate—were then tested using a high-precision Olympus SZX16 research-grade stereomicroscopic imaging platform. The test results (see...) Figure 3The polycrystalline pyroxene diorite 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 a uniform particle distribution, absence of particle growth, and no recrystallization in the polycrystalline pyroxene diorite 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 forming process that first increases pressure and then increases temperature, effectively overcoming numerous drawbacks of polycrystalline pyroxene diorite aggregate products, including particle growth, uneven particle distribution, and recrystallization.

[0057] High-resolution scanning electron microscopy was used to observe the microstructure of polycrystalline pyroxene diorite aggregate samples obtained from hot isostatic pressing experiments, and precise density tests were performed. The obtained polycrystalline pyroxene diorite aggregates 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 pyroxene diorite aggregate samples: (1) a higher pre-pressurization pressure (57.9 MPa); (2) a multi-gradient gradually decreasing cylinder heating mode, i.e., in the low-temperature zone (room temperature–200 °C), the heating rate is 10 °C / min; in the medium-temperature zone (200 °C–400 °C), the heating rate is 10 °C / min; in the high-temperature zone (400 °C–500 °C), the heating rate is 6.67 °C / min; (3) a multi-gradient gradually decreasing cylinder pressurization mode, i.e., in the low-pressure zone (57.9 MPa–69.1 MPa), the pressurization rate is 0.56 MPa / min; in the medium-pressure zone (69.1 MPa–79.2 MPa), the pressurization rate is 0.51 MPa / min. MPa / min; High pressure zone: 79.2 MPa–86.4 MPa pressure conditions, the pressurization rate is 0.48 MPa / min; (4) Sufficiently long cylinder constant temperature and pressure mode, that is, during the hot isostatic pressing experiment, at the highest temperature (500 °C) and the highest pressure (86.4 MPa), ensure a sufficiently long constant temperature and pressure of 10 hours. All these optimized and improved hot isostatic pressing experimental schemes can promote full diffusion and particle aggregation between pyroxene diorite sample powders during the hot isostatic pressing experiment, eliminate the adverse effects of dendritic structure formation between sample powders, and thus form a uniform equiaxed grain structure; can promote the uniform occurrence of isotropic temperature and pressure transmission during the hot isostatic pressing experiment, prevent the occurrence of local weak points or cracks, and thus greatly improve the compactness of the polycrystalline pyroxene diorite aggregate sample of the hot isostatic pressing experiment product. In addition, this invention applies a higher temperature (500 °C), a higher pressure (86.4 MPa), and a sufficiently long heat and pressure holding time (10 hours) to promote the formation of good cementation between the particles of pyroxene diorite sample powder, thereby greatly improving the density and strength of the polycrystalline pyroxene diorite aggregate sample produced by hot isostatic pressing. It also effectively overcomes the unavoidable temperature gradient, pressure gradient, and many adverse factors such as pores, fissures, 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.

[0058] 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 pyroxene diorite aggregate samples obtained from thermostatic pressing experiments. The measured density of the polycrystalline pyroxene diorite aggregate was 2.96 g / cm³. 3 This density value falls exactly within the theoretical density of 2.85 g / cm³ for naturally collected pyroxene diorite, as measured by geologists. 3 -3.01 g / cm 3 Within the specified range, the obtained large-volume polycrystalline pyroxene diorite aggregate samples exhibited extremely high density. The achievement of such high-density polycrystalline pyroxene diorite aggregate products is highly related to the optimized molding process employed during this hot isostatic pressing experiment, including pretreatment of the pyroxene diorite 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 pyroxene diorite sample powder raw materials, specifically fine-grained pyroxene diorite sample powder with a particle size of 9.95 μm to 19.41 μm, is crucial. Pyroxene diorite within this particle size range has a large specific surface area, significantly increasing the contact area between sample particles. This promotes stronger cementation and greatly enhances the density of the prepared polycrystalline pyroxene diorite aggregate sample. A 3 mm thick 20# low-carbon steel continuous casting slab serves 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 enclosed pyroxene diorite sample powder, further increasing the density of the prepared polycrystalline pyroxene diorite aggregate sample. An optimized and improved hot isostatic pressing process is employed, particularly using a relatively slow multi-gradient cylinder pressurization mode (pressurization rate: 0.48 MPa / min – 0.56 MPa / min; depressurization rate: 0.62). (MPa / min) ensures that the internal stress of large-volume polycrystalline pyroxene diorite 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 pyroxene diorite aggregate sample. A high-temperature degassing optimization molding process is implemented at 400 °C. The pyroxene diorite sample powder is sealed in a steel sleeve and subjected to high-temperature vacuum degassing at 400 °C to minimize gas residue, thereby obtaining polycrystalline pyroxene diorite 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-density, highly compact polycrystalline pyroxene diorite aggregate, characterized in that: The method includes: completely sealing the pyroxene diorite 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 a 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 500 °C and the pressure was raised to 86.4 MPa using a multi-gradient cylinder heating and pressurization method, and kept at the same temperature and pressure for 10 hours; the temperature inside the sample chamber was lowered to 169 °C and the pressure was lowered to 68.5 MPa using a cooling rate of 11.41 °C / min and a depressurization rate of 0.62 MPa / min; finally, the pressure was released and the temperature was lowered to room temperature to obtain a polycrystalline pyroxene diorite aggregate sample.

2. The method for preparing a high-density, high-compactness polycrystalline pyroxene diorite aggregate according to claim 1, characterized in that: The method for preparing the pyroxene diorite sample powder includes: Step 1: Select square, dense, massive pyroxene diorite samples with a minimum sample size of 4.9 mm and a maximum sample size of 12.4 mm as initial samples; Step 2: Place the selected pyroxene diorite on an ultrasonic cleaner and use acetone, alcohol and deionized water as cleaning solutions in sequence for ultrasonic cleaning for 18 minutes. Step 3: Select 250 grams of pyroxene diorite blocky samples that are uniformly grayish-black in color, have a fresh surface, and are free of impurities. Step 4: Place the selected pyroxene diorite block samples in a vacuum drying oven at 200 degrees Celsius and dry for at least 18 hours; Step 5: Crush the pyroxene diorite block sample into rock particles with a diameter of less than 2 mm; Step 6: Grind the rock particles into pyroxene diorite sample powder with a particle size of 9.95 micrometers to 19.41 micrometers; Step 7: Place the pyroxene diorite sample powder in a sealed paper bag and dry it in a vacuum drying oven at 85 degrees Celsius for 14 days.

3. The method for preparing a high-density, high-compactness polycrystalline pyroxene diorite aggregate according to claim 1, characterized in that: The methods for preparing steel sheaths include: 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 three rolling processes and multiple hot rolling processes including edge trimming to finally obtain a steel cladding sleeve with dimensions of 57.35 mm (outer diameter) × 84.64 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 a high-density, high-compactness polycrystalline pyroxene diorite aggregate according to claim 1, characterized in that: The pyroxene diorite sample powder was completely 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 pyroxene diorite sample powder inside the steel cladding; and finally, compacting, vacuuming, high-temperature degassing, and high-temperature vacuum welding to completely seal the pyroxene diorite sample powder under a vacuum of 10... –3 The sample was placed in a steel bladder containing Pa; vacuum was applied for at least 57 hours, while the sample was degassed at 400 °C.

5. The method for preparing a high-density, high-compactness polycrystalline pyroxene diorite aggregate 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 pyroxene diorite aggregate samples under hot isostatic pressing is based on the target temperature (T) of the hot isostatic pressing experiment. 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 pyroxene diorite aggregate sample under high temperature and high pressure conditions.

6. The method for preparing a high-density, high-compactness polycrystalline pyroxene diorite aggregate 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 inert argon gas required, which necessitates at least four argon cylinders with an internal pressure of 15 MPa. Evenly fill the 15 MPa argon cylinders into the high-pressure pressurization tank of the hot isostatic pressing equipment. Then, through a high-pressure delivery pipeline, freely fill the cylinder with the argon gas from the high-pressure pressurization tank, thus balancing the pressure in the high-pressure pressurization tank and the cylinder. Turn on the diaphragm compressor to pump all the remaining argon gas from the high-pressure tank into the pyroxene diorite sample chamber in the cylinder, pre-pressurizing the sample chamber to 57.9 MPa.

7. The method for preparing a high-density, high-compactness polycrystalline pyroxene diorite aggregate according to claim 1, characterized in that: The method of raising the temperature to 500 °C and the pressure to 86.4 MPa within the cylinder sample chamber using a multi-gradient cylinder heating and pressurization approach includes: raising the temperature to 200 °C and the pressure to 69.1 MPa within the temperature range of room temperature to 200 °C using a heating rate of 10 °C / min and a pressurization rate of 0.56 MPa / min; raising the temperature to 400 °C and the pressure to 79.2 MPa within the temperature range of 200 °C–400 °C using a heating rate of 10 °C / min and a pressurization rate of 0.51 MPa / min within the temperature range of 400 °C–500 °C using a heating rate of 6.67 °C / min and a pressurization rate of 0.48 MPa / min within the temperature range of 400 °C–500 °C using a heating rate of 6.67 °C / min and a pressurization rate of 0.48 MPa / min within the temperature range of 500 °C and 86.4 MPa within the temperature chamber.

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