Transition metal borides, methods of making and use thereof
The preparation of transition metal borides by reducing metal-assisted low-temperature liquid-phase reaction overcomes the limitations of high-temperature and high-pressure preparation, and achieves efficient and low-cost preparation of pure-phase transition metal borides with excellent chemical and mechanical stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN UNIV OF SCI & TECH
- Filing Date
- 2024-02-05
- Publication Date
- 2026-05-19
AI Technical Summary
The preparation of transition metal borides in existing technologies requires stringent conditions such as high temperature and high pressure or laser fusion, which limits their design and research. Furthermore, the non-uniformity of the reaction leads to the generation of impurities and impure materials.
Transition metal borides were prepared using reducing metal-assisted reactions. The reaction was carried out at low temperature in liquid phase by mixing reducing metals such as tin powder or magnesium powder with boron powder, controlling the reaction temperature at 850–950 °C, and obtaining pure phase transition metal borides by acid washing and centrifugation.
A uniform reaction was achieved at a lower temperature, reducing preparation costs and yielding transition metal borides with high chemical, thermal, and mechanical stability. Impurity formation was avoided, and the reaction was more complete, resulting in materials with uniform size and morphology.
Smart Images
Figure CN117985729B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of ceramic material preparation technology, specifically relating to a transition metal boride, its preparation method, and its application. Background Technology
[0002] Boron's unusual intrinsic chemical properties give transition metal borides an extremely diverse range of structures. Boron is a metalloid with an intermediate electronegativity value (2.04) between metals and nonmetals. In transition metal borides, the constituent elements can form a rich variety of bonding modes, including metallic (MM / MB), ionic (MB), and covalent (BB) bonds. Another inherent characteristic of boron is that it has fewer valence electrons than valence orbitals. This electron-deficient characteristic allows boron atoms to exhibit a rich variety of covalent bond modes in different boride lattices. The abundant chemical bonding modes in borides are not found in other transition metal compounds, such as transition metal sulfides, oxides, and nitrides. This unique structure leads to distinctive properties in transition metal borides, such as high melting points, high hardness, good electrical conductivity, and strong oxidation resistance, making them widely used in high-temperature and highly corrosive environments, such as cutting tools, wear parts, and thermal protective coatings in the aerospace industry. In addition, their surface catalytic properties have also attracted widespread attention, with the metal and boron ends containing a large number of highly efficient sites, and the borene layer in the borides also exhibiting high activity.
[0003] Currently, the common preparation method involves mixing transition metal compounds with boron powder and calcining them. This method often requires stringent experimental conditions such as high temperature and high pressure or laser fusion, which greatly limits the design and research of transition metal borides. Therefore, further exploration of efficient, low-cost, and easy-to-operate preparation processes for transition metal borides is of significant research and application importance. Summary of the Invention
[0004] This invention provides a method for preparing transition metal borides with the assistance of reducing metals. By using the lower melting temperature of the reducing metal, the reactants are transformed from a solid-phase reaction to a liquid-phase reaction. This reduces the reaction temperature and increases the contact range of the reactants, resulting in a more uniform reaction.
[0005] The objective of this invention is achieved through the following technical solution:
[0006] A method for preparing transition metal borides using reducing metals, characterized by comprising the following steps:
[0007] Step 1: Mix the transition metal compound with the reducing metal and boron powder evenly, place it in an alumina crucible, and heat it to 850-950℃ at a heating rate of 5-10℃ / min under an Ar and N2 atmosphere, and hold it at that temperature for 3-6 hours.
[0008] Step 2: Under a protective atmosphere, the mixture is annealed and then cooled to room temperature before the reactants are removed.
[0009] Step 3: After acid washing of the reactants, filter or centrifuge them, and dry them to obtain transition metal borides.
[0010] Preferably, the transition metal compound, reducing metal, and boron powder are prepared according to a stoichiometric ratio, with a molar ratio of boron powder to transition metal compound ≥2, to ensure sufficient reaction and minimize boron powder loss during grinding. After the three powders are thoroughly mixed, they are placed in an alumina crucible, which is then transferred to a tube furnace. An inert gas is introduced, and the temperature is raised to 850–950°C and held for 3–6 hours to obtain transition metal borides. These are then acid-washed, filtered or centrifuged, and dried to obtain the final transition metal borides.
[0011] Preferably, the protective atmosphere is an inert atmosphere, such as argon or nitrogen.
[0012] Preferably, the reducing metal is, but is not limited to, tin powder, magnesium powder, aluminum powder, etc.
[0013] Preferably, the drying step can be performed using oven drying or freeze drying.
[0014] Preferably, the transition metal compound is, but is not limited to, molybdenum sulfide, molybdenum oxide, molybdenum chloride, tantalum sulfide, niobium oxide, tungsten sulfide, and tungsten oxide.
[0015] Preferably, the molar ratio of the transition metal compound, reducing metal, and boron powder is 1:2 to 10:3 to 8.
[0016] Preferably, the boron powder has a particle size of 1–20 μm.
[0017] Preferably, the selected centrifugal speed is 500 to 2000 rpm.
[0018] Preferably, the transition metal borides are prepared by heating to 850–950°C at a heating rate of 5–10°C / min and holding at that temperature for 3–6 hours.
[0019] The present invention also discloses transition metal borides, which are obtained by the above-mentioned reducing metal-assisted preparation method for transition metal borides. These transition metal borides are a class of boron-containing alloy materials with ordered crystal structures and well-defined stoichiometry, and have high chemical, thermal and mechanical stability. The structural characteristics are manifested by the presence of boron atom layers in the crystal structure, which are divided into two types: graphene-like boron layers and wrinkled boron layers.
[0020] The present invention also discloses a ceramic material, characterized in that the material comprises the aforementioned transition metal borides.
[0021] Beneficial effects:
[0022] 1) Transition metal borides have attracted much attention as widely used ceramic materials, but their preparation often requires high-temperature and high-pressure reaction conditions. This invention proposes that by using reducing metals as an aid, the reaction temperature can be greatly reduced, allowing for the preparation of transition metal borides in a single step at a lower temperature.
[0023] 2) The reaction is more complete in a liquid environment, which promotes the formation of transition metal borides with good dispersion, relatively uniform size and morphology. At the same time, the uniform reaction environment can avoid the formation of more phases.
[0024] 3) In the preparation process of the transition metal borides described in this invention, the reaction temperature is in the range of 850–950°C. Therefore, the selection of the reducing metal needs to consider reducing the reaction temperature while avoiding the introduction of new impurities. Reducing the transition metal compound to elemental metal and reacting it with boron powder during the reaction process can simplify the preparation of transition metal borides.
[0025] 4) The preparation process of the transition metal borides described in this invention involves the addition of an excessive amount of boron powder, mainly because the lighter boron powder is easily lost during the mixing process. Furthermore, boron powder has an extremely high melting point (2177–2301°C) and often remains in a powder state during the reaction, making it difficult to fully contact the transition metal compounds; therefore, an excessive amount of boron powder is added.
[0026] 5) In this invention, the raw material ratio, boron powder particle size, and reaction temperature are the main factors in preparing pure-phase transition metal borides. Since the raw material mixing cannot be completely uniform, the reducing metal and boron powder should be in excess. Furthermore, the smaller the boron powder particle size, the easier it is to react uniformly with the metal. By uniformly increasing the temperature, the transition metal compound preferentially reacts with the reducing metal to obtain the transition metal element, which then reacts with the boron powder. This process requires temperatures above 850°C. After acid washing, transition metal boride particles of different sizes are obtained using different centrifugation rates. Attached Figure Description
[0027] Figure 1 The XRD pattern of MoB2 prepared in Example 1 of this invention;
[0028] Figure 2 SEM image of MoB2 prepared in Example 1 of this invention;
[0029] Figure 3 The XRD pattern of MoB2 prepared in Example 2 of this invention;
[0030] Figure 4 SEM image of MoB2 prepared in Example 2 of this invention;
[0031] Figure 5 The image shows the XRD pattern of MoB2 prepared in Example 3 of this invention.
[0032] Figure 6 This is a SEM image of MoB2 prepared in Example 3 of the present invention;
[0033] Figure 7 The image shows the XRD pattern of MoB2 prepared in Example 4 of this invention.
[0034] Figure 8 This is a SEM image of MoB2 prepared in Example 3 of the present invention;
[0035] Figure 9 This is a schematic diagram of the structure of the transition metal boride of the present invention. Detailed Implementation
[0036] The present invention will be further described in detail with reference to specific embodiments. Unless otherwise specified, the methods described herein are conventional methods. Unless otherwise specified, the raw materials are all available from publicly available commercial sources. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.
[0037] Example 1
[0038] 1) Add MoS2, Sn powder, and B powder to a mortar and grind them in a stoichiometric ratio of 1:2.5:3 to obtain a uniform mixed powder and put it into a crucible.
[0039] 2) Place the crucible in a tube furnace and heat it to 900℃ at a heating rate of 5℃ / min under an argon atmosphere. Hold the temperature for 5 hours. After the furnace cools to room temperature, remove the reaction product.
[0040] 3) Add the obtained reaction product to 2M HCl solution for washing and stirring for 3 hours. Then wash repeatedly with deionized water 3 to 5 times. After filtration, place the product in a freeze dryer overnight to obtain MoB2 particles with good morphology.
[0041] The obtained samples were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the results are shown in the figure. Figure 1 and Figure 2 XRD results showed that the diffraction peak positions of the obtained product were consistent with the standard card NO. 65-8684 of α-MoB2. SEM images showed that MoB2 consisted of particles ranging from 0.1 to 2 μm in size. This was significantly different from the sintering and agglomeration observed in transition metal borides prepared under typical high-temperature and high-pressure conditions. This MoB2 was composed of a large number of particles smaller than 1 μm, exhibiting an excellent porous structure with interconnected and undamaged channels.
[0042] Example 2
[0043] The difference between this embodiment and Embodiment 1 is that no reducing metal is added.
[0044] 1) Add MoS2 and B powder to a mortar and grind them in a stoichiometric ratio of 1:3 to obtain a uniform mixed powder and put it into a crucible.
[0045] 2) Place the crucible in a tube furnace and heat it to 900℃ at a heating rate of 5℃ / min under an argon atmosphere. Hold the temperature for 5 hours. After the furnace cools to room temperature, remove the reaction product.
[0046] 3) Add the obtained reaction product to 2M HCl solution and wash and stir for 3 hours. Then wash repeatedly with deionized water 3 to 5 times, filter, and place the product in a freeze dryer overnight.
[0047] The obtained samples were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the results are shown in the figure. Figure 3 and Figure 4 XRD results showed that the sample was still MoS2 powder, corresponding to standard card NO.77-1716. SEM images also confirmed that it remained bulk MoS2.
[0048] Example 3
[0049] 1) MoO3, Sn powder, and B powder are added to a mortar and ground in a stoichiometric ratio of 1:2.5:8 to obtain a uniform mixed powder, which is then placed into a crucible.
[0050] 2) Place the crucible in a tube furnace and heat it to 850°C at a heating rate of 5°C / min under an argon atmosphere. Hold the temperature for 3 hours. After the furnace cools to room temperature, remove the reaction product.
[0051] 3) The obtained reaction product was added to 2M HCl solution for washing and stirring for 3 hours. Then it was washed repeatedly with deionized water 3 to 5 times. After filtration, the product was placed in a freeze dryer overnight to obtain pure phase β-MoB2 with a morphology of 10-20 μm loose bulk structure. The corresponding XRD standard card is NO.73-0704.
[0052] Figure 5 and Figure 6 The images show the XRD and SEM images of MoB2 prepared in Example 3. As can be seen, transition metal borides can be obtained in one step with simple reducing metal assistance; MoB2 is composed of a large number of fine nanosheets.
[0053] Example 4
[0054] 1) Add MoS2, Mg powder, and B powder to a mortar and grind them in a stoichiometric ratio of 1:4:3 to obtain a uniform mixed powder and put it into a crucible.
[0055] 2) Place the crucible in a tube furnace and heat it to 900℃ at a heating rate of 5℃ / min under an argon atmosphere. Hold the temperature for 5 hours. After the furnace cools to room temperature, remove the reaction product.
[0056] 3) Add the obtained reaction product to 2M HCl solution and wash and stir for 3 hours. Then wash repeatedly with deionized water 3 to 5 times, filter, and dry the product in a 60-degree oven overnight.
[0057] The obtained samples were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the results are shown in the figure. Figure 7 and Figure 8 XRD results showed that the obtained product contained a mixed phase of two MoB2 phases. SEM images revealed that the MoB2 phases resembled an anthill, possessing numerous interconnected channels. Therefore, the method for preparing transition metal borides using reducing metal-assisted synthesis of this invention is simple, convenient, and suitable for industrial application.
[0058] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.
Claims
1. A method for preparing transition metal borides using reducing metals, characterized in that, Includes the following steps: Step 1: Mix the transition metal compound with the reducing metal and boron powder in a certain molar ratio, place the mixture in an alumina crucible, and heat it to 850-950℃ at a heating rate of 5-10℃ / min under an Ar and N2 atmosphere, and hold it at that temperature for 3-6 hours. Step 2: Under a protective atmosphere, the mixture is annealed and then cooled to room temperature before the reactants are removed. Step 3: After acid washing of the reactants, filter or centrifuge, and dry to obtain transition metal borides; the acid washing and drying process includes washing with dilute hydrochloric acid, then washing with deionized water two to three times, followed by filtration or centrifugation and drying; the acid washing method is as follows: transfer the reaction product to hydrochloric acid with a concentration of 1-3M and stir for 0.5-3 hours; the transition metal compounds include, but are not limited to, molybdenum sulfide, molybdenum oxide, molybdenum chloride, tantalum sulfide, niobium oxide, tungsten sulfide, and tungsten oxide; the particle size of the boron powder is 1-20 μm; the molar ratio of the transition metal compound: reducing metal: boron powder is 1:2-10:5-8; the selected centrifugation speed is 500-2000 rpm.
2. Transition metal borides, obtained by the reducing metal-assisted preparation method for transition metal borides as described in claim 1, wherein the transition metal borides are a class of boron-containing alloy materials with ordered crystal structures and well-defined stoichiometry, and have high chemical, thermal and mechanical stability; the structural feature is the presence of boron atom layers in the crystal structure, which are divided into two types: graphene-like boron layers and wrinkled boron layers.
3. A ceramic material, characterized by: The material includes the transition metal boride as described in claim 2.