A composite material containing rare earth elements and its preparation method

Abstract

This invention relates to a method for preparing a composite material, comprising: providing a preform composed of continuous carbon fibers, wherein the carbon fibers in the preform are arranged in a single layer and the fibers are aligned by a polyester mesh and an adhesive; mixing zirconium boride powder with silicon carbide and scandium oxide, mixing the mixed powder with a dispersion, and homogenizing by ball milling to prepare a slurry; laying the preform layer by layer in a mold, and impregnating each layer with the slurry to uniformly cover the fiber surface, the preforms being stacked at 0° configuration, and at least 30 layers are stacked to prepare a plate with a thickness of 3–3.5 mm; curing the plate at 80°C for 2 hours under vacuum to form a stable composite structure; and controlling the sintering time and temperature gradient to promote densification of the composite structure but prevent the formation of an interface layer.

Description

Technical Field

[0001] This invention belongs to the field of aerospace materials, and in particular relates to a composite material containing rare earth elements and its preparation method. Background Technology

[0002] Scandium (Sc) is an extremely rare, strategically important metal, widely used in aluminum-scandium alloys and solid oxide fuel cells. Currently, 24 scandium minerals have been discovered and officially approved by the International Mineralogical Association's Specialized Committee on Nomenclature and Classification of New Minerals (IMACNMNC). Scandium is primarily recovered as a byproduct from the smelting of aluminum, iron, nickel, titanium, tin, tungsten, and phosphate ores. Recently, scandium amphibole was discovered in the renowned Bayan Obo rare earth niobium-iron deposit in Baotou City, Inner Mongolia Autonomous Region, my country. The Bayan Obo deposit is the world's largest rare earth deposit, also containing abundant iron, scandium, thorium, and fluorite resources, possessing extremely important economic and social value. This deposit is characterized by its high grade and large tonnage, making it one of my country's most important rare earth industry bases. The Bayan Obo deposit is also a magical and rich mineral treasure trove; according to statistics, over 200 mineral species have been discovered there, including 18 new mineral species. Scandium amphibole is the 20th new mineral discovered in this deposit.

[0003] Scandium, a crucial associated metal in the Bayan Obo deposit, has remained largely untapped due to limited research. Since 2021, scientists have conducted systematic sampling at the Bayan Obo deposit, clarifying its occurrence, distribution patterns, and mineral assemblage based on detailed mineralogical studies. During the research, an anomalous mineral, scandium amphibole, was discovered. This discovery not only provides new theoretical support for the formation mechanism and enrichment patterns of scandium deposits but also offers new research directions for increasing the variety of usable scandium minerals in Bayan Obo and for the development and utilization of scandium and other strategically important metals.

[0004] Scandium, as one of the most expensive rare earth resources, is widely used in defense, metallurgy, aerospace, nuclear energy stations, electric light source materials, and new energy batteries, and has broad development prospects. The demand for more flexible and efficient payload drones is constantly expanding, and composite materials play a crucial role in the development of these high-performance drones, especially those with excellent lightweight and high-strength properties. Compared to metals and aluminum alloys, these composite materials have twice the Young's modulus while weighing half as much. Furthermore, high rigidity, corrosion resistance, thermal damping, and vibration damping characteristics are considered the most important properties for composite materials in drone applications.

[0005] Drones and aerospace technologies are primarily manufactured using aluminum, titanium, and steel, but the high weight of these materials limits the flight time of drones. In contrast, carbon fiber composites have a lower density. However, these composites are susceptible to mechanical damage when subjected to tensile, bending, and impact loads. Previous studies have investigated the effects of fiber orientation and fiber content on mechanical properties using different epoxy resins. However, the composites they prepared exhibited high brittleness, low elongation at break, and low impact strength.

[0006] How to fully utilize scandium resources to construct new composite materials is an urgent technical problem that needs to be solved in this field. Summary of the Invention

[0007] The present invention aims to solve at least one of the problems of the prior art by providing a composite material containing rare earth elements and a method for preparing the same.

[0008] According to one aspect of the present invention, a method for preparing a composite material is provided, comprising the following steps: providing a preform composed of continuous carbon fibers, wherein the carbon fibers in the preform are arranged in a single layer and the fibers are aligned by a polyester web and an adhesive; mixing zirconium boride powder with silicon carbide and scandium oxide, mixing the mixed powder with a dispersion, and homogenizing by ball milling to prepare a slurry; laying the preform layer by layer in a mold, and impregnating each layer with the slurry to uniformly cover the fiber surface, wherein the preform is stacked at 0°, and at least 30 layers are stacked to prepare a plate with a thickness of 3–3.5 mm; curing the plate at 80°C for 2 hours under vacuum to form a stable composite structure; controlling the sintering time and temperature gradient to promote densification of the composite structure but prevent the formation of an interface layer, wherein the interface layer is formed by the reaction of the Si-based phase in the sintering aid with the carbon in the carbon fibers, and determining whether an interface layer has formed by detecting the presence of submicron-sized silicon carbide particles between the fibers.

[0009] Preferably, the dispersion is ethanol.

[0010] Preferably, the ratio of zirconium diboride powder to silicon carbide and scandium oxide is: 90% zirconium diboride, 5% silicon carbide, and 5% scandium oxide.

[0011] Preferably, a vacuum state is achieved through the following steps: covering the surface of the plate with a breathable cloth or a porous isolation membrane; covering the mold and the plate with a vacuum bag and sealing all edges; installing a sealing strip at the opening of the vacuum bag and connecting a vacuum pump pipeline; using a vacuum pump to extract air from the bag to create a negative pressure environment, so that the ceramic slurry is uniformly adsorbed into the preform; adjusting the vacuum pressure to apply pressure evenly to the plate, avoiding local defects or uneven impregnation.

[0012] Preferably, the specific parameters for controlling the sintering time and temperature gradient are as follows: the cured composite structure is placed in a hot press and sintered at a temperature range of 1900°C, with a pressure of 20 to 40 MPa applied during the sintering process.

[0013] According to another aspect of the present invention, a method for preparing a composite material is provided, comprising the following steps: providing a preform composed of continuous carbon fibers, wherein the carbon fibers in the preform are arranged in a single layer and the fibers are aligned by a polyester web and an adhesive; mixing zirconium boride powder with silicon carbide and lanthanum oxide, mixing the mixed powder with a dispersion, and homogenizing by ball milling to prepare a slurry; laying the preform layer by layer in a mold, and impregnating each layer with the slurry to uniformly cover the fiber surface, wherein the preform is stacked at 0°, and at least 30 layers are stacked to prepare a plate with a thickness of 3–3.5 mm; curing the plate at 80°C for 2 hours under vacuum to form a stable composite structure; controlling the sintering time and temperature gradient to promote densification of the composite structure but prevent the formation of an interface layer, wherein the interface layer is formed by the reaction of the Si-based phase in the sintering aid with the carbon in the carbon fibers, and determining whether an interface layer has formed by detecting the presence of submicron-sized silicon carbide particles between the fibers.

[0014] Preferably, the dispersion is ethanol.

[0015] Preferably, the ratio of zirconium diboride powder to silicon carbide and scandium oxide is: 90% zirconium diboride, 5% silicon carbide, and 5% scandium oxide.

[0016] Preferably, a vacuum state is achieved through the following steps: covering the surface of the plate with a breathable cloth or a porous isolation membrane; covering the mold and the plate with a vacuum bag and sealing all edges; installing a sealing strip at the opening of the vacuum bag and connecting a vacuum pump pipeline; using a vacuum pump to extract air from the bag to create a negative pressure environment, so that the ceramic slurry is uniformly adsorbed into the preform; adjusting the vacuum pressure to apply pressure evenly to the plate, avoiding local defects or uneven impregnation.

[0017] Preferably, the specific parameters for controlling the sintering time and temperature gradient are as follows: the cured composite structure is placed in a hot press and sintered at a temperature range of 1900°C, with a pressure of 20 to 40 MPa applied during the sintering process.

[0018] The technical solution provided by this invention effectively removes oxides covering the surface of boride grains and promotes the formation of layered ternary compounds containing rare earth metals, boron, and carbon. These phases may play a role in the load transfer mechanism and promote a toughening mechanism similar to bridging fracture zones. A reusable composite material suitable for harsh environments has been developed. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0020] Figure 1 An X-ray diffraction pattern of a sintered sample provided according to an embodiment of the present invention is shown.

[0021] Figure 2 A microstructure diagram of a comparative example sample provided according to an embodiment of the present invention is shown.

[0022] Figure 3 A microstructure diagram of the sample of Example 1 provided according to an embodiment of the present invention is shown. Detailed Implementation

[0023] The following examples are provided to help those skilled in the art better understand the present invention. It should be noted that the following examples are not intended to limit the scope of protection claimed by the present invention, but are merely illustrative. Unless otherwise specified, the raw materials, reagents, or devices mentioned in the following examples are commercially available or obtained through known existing methods.

[0024] The urgent need for materials capable of operating at high temperatures for extended periods has driven scientific research to explore materials with increasingly challenging performance combinations. For example, most engine components and assemblies for propulsion or hypersonic aircraft are exposed to significant heat fluxes and subjected to thermomechanical stresses. Therefore, materials used in such applications must combine chemical stability in oxidizing environments above 1800°C with sufficient mechanical strength.

[0025] Ultra-high temperature ceramics (UHTCs) compounds have been identified as potential candidate materials for operation under harsh conditions due to their melting points exceeding 3000 °C and their resistance to ablation. Although studies on UHTCs have successfully fabricated high-density and high-strength composites (strengths exceeding 1000 MPa), their low fracture toughness (3–4 MPa·m1 / 2) remains a concern. 2 The low thermal shock resistance (several hundred degrees) and low thermal shock resistance remain the main problems for these materials in harsh environments.

[0026] Example 1

[0027] The following raw materials were used: Zirconium boride (purchased from Suzhou Napo Materials Technology Co., Ltd., D50 (μm) 0.3-1; purity (wt.%) > 99.0; main impurity content (%) C, O < 1.0). Silicon carbide (99.9%, size 0.45μm). Scandium oxide (Tianjin Seventeen Elements Technology Co., Ltd., 99.9%, particle size 1-2μm). Lanthanum oxide (MDL No.: MFCD00011071, NACRES: NA.23). Carbon fiber XN80 (GRANOC YARN, diameter 7μm, fibers arranged in a single layer, fiber alignment achieved through polyester web and adhesive).

[0028] The comparative example consisted of 95 vol% zirconium boride and 5 vol% silicon carbide. Example 1 consisted of 90 vol% zirconium boride, 5 vol% silicon carbide, and 5 vol% scandium oxide. Example 2 also consisted of 90 vol% zirconium boride, 5 vol% silicon carbide, and 5 vol% lanthanum oxide. The powders were uniformly mixed in ethanol by ball milling for 24 hours, then ground using silicon nitride balls, followed by drying the ethanol in a rotary evaporator and sieving. These powder mixtures were then added to deionized water containing a dispersant to prepare an aqueous slurry. The solids content was 38 vol%, and the Duramax D3005 content ranged from 2.3 to 4 wt%, relative to the mass of the dry powder.

[0029] The composite material is impregnated with three types of slurry using a manual lay-up method, with the fiber layers arranged in a 0 / 0° configuration. At least 30 layers are stacked to prepare a sheet with a thickness of 3-3.5 mm. A vacuum bag technique, similar to that used in organic polymer impregnation, is employed, and the material is cured at 80°C for 2 hours in a conventional air furnace under normal pressure. The vacuum state is achieved through the following steps: covering the sheet surface with a breathable cloth or porous isolation membrane; covering the mold and sheet with a vacuum bag and sealing all edges; installing a sealing strip at the opening of the vacuum bag and connecting the vacuum pump pipeline; using the vacuum pump to remove air from the bag, creating a negative pressure environment so that the ceramic slurry is uniformly adsorbed into the preform; adjusting the vacuum pressure and applying it evenly to the sheet to avoid localized defects or uneven impregnation. Subsequently, hot pressing sintering is performed at 1900°C using a pressure of 20-40 MPa, depending on the sintering aid. The aim is to control the sintering time and temperature gradient to promote the densification of the composite structure while preventing the formation of an interface layer. The interface layer is formed by the reaction between the Si-based phase in the sintering aid and the carbon in the carbon fiber. The presence of submicron-sized silicon carbide particles between the fibers is used to determine whether an interface layer has formed.

[0030] Microstructure analysis

[0031] The microstructure and phase composition of polished and fractured surfaces were analyzed using field emission scanning electron microscopy (FE-SEM, Carl Zeiss Sigma NTS GmbH) and an energy-dispersive X-ray spectroscopy probe (EDS, INCA Energy 300, Oxford Instruments). Samples were cut from sintered billets using diamond blades and polished to a surface finish of 0.25 μm using a semi-automatic polishing machine (Tegramin-25, Struers). Polished samples were cleaned with ethanol, dried under infrared light, and finally cleaned for 3 minutes at 50 W using a plasma cleaner (ColibrìPlasma RF 50 kHz, Gambetti). Sample fragments from the sintered billets were manually ground and passed through a 325 μm sieve for X-ray diffraction analysis (using a Bruker D8 Advance instrument, Bruker).

[0032] Transmission electron microscopy (TEM) samples of selected sintered ceramics were prepared by cutting a 3 mm diameter disk from the bulk material and mechanically grinding it to a thickness of approximately 80 μm. A 60 μm deep groove was created in the center of the disk using a diamond-coated concave tool, bringing the central sample thickness to 20 μm. Further thinning was then performed using an argon ion beam until pores appeared. Additionally, a portion of the sintered material was ground into a fine powder using an agate mortar, suspended in isopropanol, and ultrasonically dispersed until homogeneous. The suspension was then dropped onto a copper grid covered with an ultrafine carbon film to prepare TEM samples. Electron diffraction peaks were resolved using the commercial software JEMS. The volume fractions of the fiber and ceramic phases were measured using Image-Pro Analyser 7.0 software, following the guidelines of ISO 13383-1 Method A2.

[0033] Mechanical property testing

[0034] Samples measuring 2.0 mm × 2.5 mm × 25 mm (thickness × width × length) were cut from the sintered billet along the fiber direction. A 0 / 0° configuration was used to minimize data dispersion caused by the 0 / 90° layer sequence after sample processing.

[0035] The room temperature bending strength was measured using a universal testing machine (Zwick Roell Z050 GmbH&Co, KF, Ulm-Einsingen, Germany), with a fully articulated 4-point steel clamp, a lower span of 20 mm, an upper span of 10 mm, and a loading rate of 1 mm / min, in accordance with ISO / DIS14704 standard.

[0036] High-temperature flexural strength testing at 1500°C was conducted according to EN 843-1:2006, the standard for advanced technical ceramics, using a screw-driven testing machine (1195, INSTRON) equipped with a semi-hinged alumina 4-point clamp with a lower span of 20 mm and an upper span of 10 mm. Samples were heated to 1500°C at a rate of 10°C / min under an inert atmosphere, held at that temperature for 15 minutes, and then tested with a loading rate of 1 mm / min. Fracture toughness (KIc) was measured using a notched beam (CNB) according to EN 14425-3 (2010). The test bar dimensions were 2.5 mm × 2.0 mm × 25 mm (thickness × width × length), with the notch cut using a 0.1 mm thick diamond saw. The notch tip depth and average side length were approximately 0.12 and 0.80 times the beam thickness, respectively. The same instrument as for room-temperature flexural strength testing was used, and at least three samples were used for each property test.

[0037] Results and Discussion

[0038] X-ray diffraction analysis

[0039] like Figure 1 As shown, XRD analysis of the cross-section of the sintered sample revealed that the main peak was zirconium boride, with small amounts of zirconium carbide and silicon carbide. For the example sample, the zirconium boride peak was observed to shift to the right and broaden at a high 2θ angle. This may be attributed to the formation of a (zirconium, scandium)boron solid solution with a shorter lattice, as scandium and zirconium have very similar atomic radii, and the boron scandium signal also appears in the same region. Additionally, some new peaks were detected at a higher 2θ angle, possibly belonging to a rare-earth-based second phase, such as layered diborides and dicarbides, but their intensities were too low to definitively determine their properties.

[0040] Microstructure of sintered composite materials

[0041] After sintering, the ratio of zirconium boride to silicon carbide remained constant in all samples, indicating that no significant reaction occurred in silicon carbide. However, a significant reduction in silicon carbide content was observed in the sample of Example 1, approximately 1% by volume, suggesting that a reaction involving silicon carbide occurred in this sample. Conversely, no pure rare earth oxides were found in any composition; instead, a novel scandium / lanthanum-boron-carbon phase was discovered. The volume fraction of the scandium / lanthanum-boron-carbon phase was comparable to the nominal values ​​of the corresponding oxides. In all cases, the addition of rare earth oxides led to a reduction in porosity, with lanthanum oxide being the most effective sintering aid.

[0042] like Figure 2As shown, the microstructure of the comparative sample is characterized by the uniform distribution of fibers and silicon carbide particles within the zirconium boride matrix. The figures show the microstructure of the comparative sample: a) the microstructure reveals porosity and fiber cross-section insertion; b) details of the fiber / matrix interface and the corresponding EDS spectra. The figures indicate that porosity is primarily present at the zirconium boride grain boundaries, and no grain growth was observed after sintering. In all cases, the fibers were firmly attached to the matrix, and some zirconium carbide was found at the fiber / matrix interface, which is a product of the reduction reaction between zirconium oxide and carbon in the fibers. No other phases were detected by EDS analysis.

[0043] like Figure 3 As shown, for the Example 1 sample, most of the scandium was found to exist in the form of a (zirconium, scandium)boron solid solution surrounding pure zirconium boride grains, while a higher zirconium carbide content was detected compared to the comparative sample. The figures show the microstructure of the Example samples: a) an overall view showing porosity and fiber cross-section insertion, b) details of the fiber / matrix interface, and c) the formation of (Zr,Sc)B2 solid solution grains in the ceramic matrix. According to thermodynamic simulations at 1900°C and below 1 mbar pressure, scandium oxide is unstable under these conditions and decomposes in the presence of carbon, generating CO and elemental scandium.

[0044] TEM observations confirmed the formation of a phase containing lanthanum, boron, and carbon around the carbon fibers. To identify this phase, although the crystal was located on the fiber and the fiber's diffraction pattern showed concentric rings, the superimposed dot pattern identified it as lanthanum diboride dicarbide. It is reasonable to infer that the lanthanum diboride dicarbide formed around the fiber.

[0045] Mechanical properties

[0046] The performance of Examples 1 and 2 is generally improved compared to that of the comparative examples.

[0047] The room temperature flexural strength of all samples was in the range of 300–400 MPa, increasing with decreasing porosity. Compared to the comparative examples, the room temperature flexural strength of the composites in Examples 1 and 2 increased by approximately 100 MPa, and by approximately 200 MPa when tested at 1500°C under an argon atmosphere. At 1500°C, the strength of all materials increased by approximately 60% compared to room temperature values, while the fracture behavior changed from flexible to brittle. This phenomenon is attributed to stress relaxation. At high temperatures, all samples exhibited linear behavior until fracture. Small bends of 50–100 N were observed in the curves for the comparative and Example 1 samples at room temperature. This bend can be attributed to premature fracture of the matrix, followed by load transfer to the fibers. For the comparative and Example 2 samples, the curve behavior was primarily dominated by the fiber reinforcement, with the fibers and matrix sharing the load until fracture. For the Example 2 sample, a slope change was observed at low loads, possibly related to microcracks present after sintering.

[0048] In the notched cut test, the fracture toughness of the sample from Example 1 was 10–11 MPa·m. 0.5 It was significantly higher than that of the comparative sample (approximately 8 MPa·m). 0.5 The toughness of the sample in Example 2 reached 17 MPa·m. 0.5 The differences can be attributed to the presence of layered phases, which may act as additional compliant phases, namely layered ternary carbides and nitrides, where the formation of bending bands and bridging between interfaces are the cause of failure-resistant behavior.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a composite material, characterized in that, Includes the following steps: A preform composed of continuous carbon fibers is provided, wherein the carbon fibers are arranged in a single layer and fiber alignment is achieved by a polyester mesh and an adhesive. Zirconium boride powder was mixed with silicon carbide and scandium oxide. The mixed powder was then mixed with a dispersion and homogenized by ball milling to prepare a slurry. The ratio of zirconium boride powder to silicon carbide and scandium oxide was 90% zirconium boride, 5% silicon carbide, and 5% scandium oxide. The preforms are laid layer by layer in the mold, and the slurry is impregnated between each layer to uniformly cover the fiber surface. The preforms are stacked in a 0° configuration, and at least 30 layers are stacked to prepare a board with a thickness of 3–3.5 mm. Under vacuum, the board is cured at 80°C for 2 hours to form a stable composite structure. Controlling the sintering time and temperature gradient promotes the densification of the composite structure but prevents the formation of an interface layer. The interface layer is formed by the reaction of the Si-based phase in the sintering aid with the carbon in the carbon fiber. The presence of submicron-sized silicon carbide particles between the fibers is used to determine whether an interface layer has formed. The specific parameters for controlling the sintering time and temperature gradient are as follows: the cured composite structure is placed in a hot press and sintered at a temperature range of 1900°C, with a pressure of 20 to 40 MPa applied during the sintering process.

2. The method according to claim 1, characterized in that, The dispersion is ethanol.

3. The method according to claim 1, characterized in that, A vacuum state is achieved through the following steps: The surface of the plate is covered with a breathable cloth or a porous isolation membrane; Cover the mold and the sheet material with a vacuum bag and seal all edges; Install a sealing strip at the opening of the vacuum bag and connect the vacuum pump pipeline; A vacuum pump is used to remove air from the bag, creating a negative pressure environment, so that the slurry is uniformly adsorbed into the preform. Adjust the vacuum pressure to apply pressure evenly to the plate, avoiding local defects or uneven impregnation.

Images