Preparation method of Ca / SrxY1-xB6 metal hexaboride alloy

Abstract

The invention discloses a preparation method of a Ca / SrxY1-xB6 metal hexaboride alloy, a boron thermal reduction method is adopted, CaO or SrO, Y2O3 and B are used as precursors, CaB6 or SrB6 and YB6 are subjected to solid solution to synthesize the Ca / SrxY1-xB6 or SrxY1-xB6 metal hexaboride alloy, the method is simple and convenient, and by adjusting the proportion of B powder, other by-products (YB / YB12 / B6O) insoluble in acid are avoided, so that sample screening is more convenient. The Ca < x > Y < 1-x > B6 and the Sr < x > Y < 1-x > B6 synthesized by the method disclosed by the invention have relatively high hardness and superconductivity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal boride synthesis, and particularly relates to a hard Ca / Sr x Y 1-x B6 metal hexaboride alloy preparation method. BACKGROUND

[0002] As the "teeth" of modern industry, superhard materials (Vickers hardness > 40 GPa) are indispensable core materials in high-end manufacturing and precision machining fields, and their application ranges cover various fields. Traditional superhard materials, such as diamond (80-120 GPa) and cubic boron nitride (c-BN) (46-66 GPa), are mainly formed by light elements (B, C, N, O, etc.) through strong covalent bonds to form a three-dimensional network structure. This highly stable covalent bond network is the key factor for their excellent mechanical properties. However, despite their excellent hardness and wear resistance, their single function, intrinsic wide bandgap insulating properties (the bandgaps of diamond and c-BN are 5.47 eV and 6.36 eV, respectively) and easy oxidation at high temperatures seriously limit their application range in extreme conditions. In particular, in the fields of national strategic and technological frontiers such as quantum computing, controllable nuclear fusion, high-voltage devices, high-strength superconducting contacts, low-temperature electrical devices and high-frequency nanomechanical systems, traditional superhard materials are difficult to meet the dual demands of "mechanical support" and "superconducting transmission". This performance limitation directly promotes the development of superhard superconducting materials, a new research direction aimed at developing multifunctional material systems with ultra-high hardness and superconducting properties to meet the severe challenges of material application in extreme environments.

[0003] Boron (B) has electron-deficient characteristics and multiple bonding modes, making it an ideal element for preparing superhard superconducting materials. The small atomic radius (85 pm) and strong covalent bond formation ability of B atoms enable them to form various borides with heavy transition metals, rare earth metals and light alkali (earth) metals, and the boron content is significantly related to the material properties. Studies have shown that CaB6 and SrB6 are hard materials with high melting points. YB6 has the second highest superconducting transition temperature among metal borides. If CaB6 or SrB6 can form a solid solution with YB6, it is highly likely to obtain a hard superconducting material. Literature reports that different compositions of metal hexaborides have the same simple cubic structure and similar lattice parameters, making it easy to form solid solutions with other metal hexaborides, such as (La-Y)B6, (La-Ba)B6, (La-Ce)B6, (Ca-Sr)B6, (Sr-Ba)B6, (Eu-Y)B6. In addition, studies have shown that all ternary materials form solid solutions throughout the composition range, but the Y 3+ containing system is an exception because the Y 3 containing system is an exception because the Y+ The system produces a mixture of MB6 and YB4 crystals. Experimental studies show that pure-phase CaB6 and SrB6 can be easily prepared using metal oxides and boron powder via borate reduction, but YB4 and YB4 crystals tend to appear in the product during the preparation of YB6. 12 More stable impurity phases than YB6. However, we found that when preparing YB6 using the boronothermal reduction method, the type of impurity phase in the product can be controlled by adjusting the content of B. Therefore, by using the boronothermal reduction method to dissolve CaB6 and SrB6 with YB6 to form a metallic hexaboride alloy, and by adjusting the proportion of B in the reactants, it is highly promising to avoid YB2, YB4, and YB6 impurities. 12 The generation of impurity phases, resulting in a hard Ca / Sr material with superconductivity. x Y 1-x B6 solid solution. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a Ca / Sr that is simple to operate and has high hardness and superconductivity. x Y 1-x Preparation method of B6 metallic hexaboride alloy.

[0005] The technical problem of this invention is solved by the following technical solution: A metallic hexaboride alloy is Ca / Sr x Y 1-x B6, 0.2≤x≤0.7.

[0006] A Ca / Sr x Y 1-x The preparation method of B6 metallic hexaboride alloy includes the following steps: First, CaO (calcium oxide) or SrO (strontium oxide), Y2O3 (yttrium trioxide) and B (boron) powder are weighed in a certain proportion and placed in a ball mill jar for ball milling and mixing. The uniformly mixed precursor is placed in a mold and pressed into a block using a tablet press. The pressed block is then placed in an alumina ceramic boat and transferred to an argon-protected tube furnace. The furnace temperature is gradually increased to the synthesis temperature using a programmed temperature control method, and held at this temperature for 5 hours, and then slowly cooled to room temperature.

[0007] The reaction equation is CaO / SrO(s) + Y2O3(s) + B(s) → Ca / Sr x Y 1-x B6(s) + B2O3(s) + YBO3(s) + other byproducts (YB4 / YB 12 / B6O).

[0008] By adjusting the proportion of B powder, the generation of other by-products (YB4 / YB 12 / B6O) that are insoluble in acid is avoided, and the final product is immersed in a hydrochloric acid solution to remove YBO3 and B2O3 and other impurities, obtaining pure Ca / Sr x Y 1-x B6 powder sample; the amount of CaO or SrO and Y2O3 is adjustable from 1:3 to 2:1 in molar ratio, and the molar ratio of B powder needs to be determined according to the amount of CaO or SrO and Y2O3; too much B powder will produce B6O and YB 12 impurities that cannot be removed by acid treatment, and too little B powder will produce YB4 that cannot be removed by acid treatment; the synthesis temperature is 1550 ℃~1800 ℃, and the reaction time is 3~8 hours.

[0009] Preferably, the synthesis temperature is 1600 ℃.

[0010] Preferably, the reaction time is 5 hours.

[0011] According to the preferred scheme of the present application, Ca / Sr x Y 1-x B6 powder samples of different stoichiometric ratios can be prepared, and the powder samples are sintered under the conditions of 5 GPa and 1000 ℃ using a high-temperature high-pressure large-cavity press, obtaining bulk Ca / Sr x Y 1-x B6 materials that exhibit high hardness and superconductivity, such as Ca 0.35 Y 0.65 B6, Ca 0.42 Y 0.58 B6 and Ca 0.64 Y 0.36 B6 have Vickers hardness of 18.87±0.28 GPa, 20.22±2.39 GPa and 21.88±0.25 GPa, respectively; Sr 0.34 Y 0.66 B6, Sr 0.59 Y 0.41 B6 and Sr 0.65 Y 0.35 B6 have Vickers hardness of 9.19±0.98 GPa, 13.13±0.63 GPa and 22.35±0.21 GPa, respectively; Ca 0.35 Y 0.65 B6 and Ca 0.42 Y 0.58 B6 have superconducting transition temperatures of 2.5 K and 3.8 K, respectively; Sr 0.34 Y 0.66 B6, Sr 0.59 Y 0.41 B6 and Sr 0.65Y 0.35 The superconducting transition temperatures of B6 are 3.9 K, 5.8 K and 2.9 K respectively. The application has potential application in the field of hard superconducting.

[0012] In conclusion, the application has the following advantages: The application adopts boron thermal reduction method, and takes CaO or SrO, Y2O3 and B as precursors to synthesize Ca x Y 1-x B6 or Sr x Y 1-x B6 metal hexaboride alloy, which is simple and convenient. By adjusting the proportion of B powder, the generation of other by-products (YB / YB 12 / B6O) which is insoluble in acid is avoided, so that sample screening is more convenient. The Ca x Y 1-x B6 and Sr x Y 1-x B6 synthesized by the method of the application has high hardness and superconductivity. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 The X-ray diffraction pattern of the Ca 0.35 Y 0.65 B6 sample prepared in Example 1 is shown in Figure 1; Figure 2 The scanning electron microscope image of the Ca 0.35 Y 0.65 B6 sample prepared in Example 1 is shown in Figure 2; Figure 3 The transmission electron microscope image of the Ca 0.35 Y 0.65 B6 sample prepared in Example 1 is shown in Figure 3; Figure 4 The X-ray diffraction pattern of the Ca 0.42 Y 0.58 B6 sample prepared in Example 2 is shown in Figure 4; Figure 5 The scanning electron microscope image of the Ca 0.42 Y 0.58 B6 sample prepared in Example 2 is shown in Figure 5; Figure 6 The transmission electron microscope image of the Ca 0.42 Y 0.58 B6 sample prepared in Example 2 is shown in Figure 6; Figure 7 The X-ray diffraction pattern of the Ca 0.64 Y 0.36 B6 sample prepared in Example 2 is shown in Figure 7; Figure 8 The scanning electron microscope image of the Ca 0.64Y 0.36 Scanning electron microscope image of B6 sample; Figure 9 Ca 0.64 Y 0.36 Transmission electron microscope image of B6 sample; Figure 10 Sr 0.34 Y 0.66 X-ray diffraction pattern of B6 sample; Figure 11 Sr 0.34 Y 0.66 Scanning electron microscope image of B6 sample; Figure 12 Sr 0.34 Y 0.66 Transmission electron microscope image of B6 sample; Figure 13 Sr 0.59 Y 0.41 X-ray diffraction pattern of B6 sample; Figure 14 Sr 0.59 Y 0.41 Scanning electron microscope image of B6 sample; Figure 15 Sr 0.59 Y 0.41 Transmission electron microscope image of B6 sample; Figure 16 Sr 0.65 Y 0.35 X-ray diffraction pattern of B6 sample; Figure 17 Sr 0.65 Y 0.35 Scanning electron microscope image of B6 sample; Figure 18 Sr 0.65 Y 0.35 Transmission electron microscope image of B6 sample; Figure 19 Ca x Y 1-x Vickers hardness plot of B6 (x = 0.35, 0.42, 0.64); Figure 20 Sr x Y 1-x Vickers hardness plot of B6 (x = 0.34, 0.59, 0.65); Figure 21 Ca x Y 1-x The temperature dependence of the resistance of B6 (x = 0.35, 0.42, 0.64). Figure 22 Sr x Y 1-x The temperature dependence of the resistance of B6 (x = 0.34, 0.59, 0.65). DETAILED DESCRIPTION

[0014] The method of the present application is described in more detail in connection with the following examples. Unless otherwise specified, the reagents used are commercially available products which are used without further purification.

[0015] Example 1: Ca 0.35 Y 0.65 Preparation of B6 metal hexaboride alloy CaO (calcium oxide), Y2O3 (yttrium trioxide) and B (boron) powders were weighed in a molar ratio of 1:2:28 and placed in a ball mill jar for mixing; the mixed precursor was placed in a mold and pressed into a block using a tablet press; the pressed block was then placed in an alumina ceramic boat and transferred to a tube furnace under argon protection; the temperature of the furnace was raised from room temperature to 1200 °C at a rate of 10 °C / min, then raised from 1200 °C to 1600 °C at a rate of 5 °C / min, and held at this temperature for 5 hours, then lowered from 1600 °C to 1000 °C at a rate of 2 °C / min, and lowered from 1000 °C to 500 °C at a rate of 5 °C / min, and then naturally cooled to room temperature; the final product was immersed in a hydrochloric acid solution to remove YBO3 and B2O3 impurities, and a pure Ca / Sr x Y 1-x B6 powder sample. Figure 1 、 Figure 2 and Figure 3 are the X-ray diffraction patterns, scanning electron microscope images and high-resolution transmission electron microscope images of the Ca 0.35 Y 0.65 B6 samples prepared in this example. It can be seen that the obtained Ca 0.35 Y 0.65 B6 samples have good crystallinity and a size in the micron range.

[0016] Example 2: Ca 0.42 Y 0.58 B6 and Ca 0.64 Y 0.36 Preparation of B6 metal hexaboride alloy CaB6alloy can be realized by changing the molar ratio of CaO (calcium oxide), Y2O3 (yttrium trioxide) and B (boron) powder (1:1:18, or 2:1:26). 0.42 Y 0.58 B6and Ca 0.64 Y 0.36 Preparation of CaB6metallic hexaboride alloy. When the molar ratio of CaO (calcium oxide), Y2O3 (yttrium trioxide) and B (boron) powder is 1:1:18, Ca 0.42 Y 0.58 B6, Figure 4 、 Figure 5 and Figure 6 are its X-ray diffraction pattern, scanning electron microscope image and high-resolution transmission electron microscope image. It can be seen that Ca 0.42 Y 0.58 B6is micron-sized particles and has good crystallinity. When the molar ratio of CaO (calcium oxide), Y2O3 (yttrium trioxide) and B (boron) powder is 2:1:26, Ca 0.64 Y 0.36 B6, Figure 7 、 Figure 8 and Figure 9 are its X-ray diffraction pattern, scanning electron microscope image and high-resolution transmission electron microscope image. It can be seen that the sample is micron-sized particles and has good crystallinity.

[0017] Example 3: Sr x Y 1-x Preparation of SrB6(x=0.34, 0.59, 0.65) metallic hexaboride alloy SrB6alloy can be realized by changing the molar ratio of SrO (strontium oxide), Y2O3 (yttrium trioxide) and B (boron) powder (1:2:24, 1:1:16, 2:1:18). 0.34 Y 0.66 B6, Sr 0.59 Y 0.41 B6and Sr 0.65 Y 0.35 Preparation of SrB6metallic hexaboride alloy. When the molar ratio of SrO (strontium oxide), Y2O3 (yttrium trioxide) and B (boron) powder is 1:2:24, Sr 0.34 Y 0.66 B6, Figure 10 、 Figure 11 and Figure 12 are its X-ray diffraction pattern, scanning electron microscope image and high-resolution transmission electron microscope image. It can be seen that Sr 0.34 Y 0.66B6 is a micron-level particle and has good crystallinity. When the molar ratio of SrO (strontium oxide), Y2O3 (yttrium trioxide) and B (boron) powder is 1:1:16, Sr 0.59 Y 0.41 B6, Figure 13 、 Figure 14 and Figure 15 are the X-ray diffraction pattern, scanning electron microscope image and high-resolution transmission electron microscope image thereof. It can be seen that Sr 0.59 Y 0.41 B6 is a micron-level particle and has good crystallinity. When the molar ratio of SrO (strontium oxide), Y2O3 (yttrium trioxide) and B (boron) powder is 2:1:18, Sr 0.65 Y 0.35 B6, Figure 16 、 Figure 17 and Figure 18 are the X-ray diffraction pattern, scanning electron microscope image and high-resolution transmission electron microscope image thereof. It can be seen that Sr 0.65 Y 0.35 B6 is a micron-level particle and has good crystallinity.

[0018] Example 4: The Ca x Y 1-x B6 and Sr x Y 1-x B6 metal hexaboride alloy hardness and superconductivity test The samples obtained in Example 1, Example 2 and Example 3 were sintered under the conditions of 5 GPa and 1000 ℃ by using a high-temperature high-pressure large-cavity press to obtain Ca x Y 1-x B6 (x=0.35, 0.42, 0.64) and Sr x Y 1-x B6 (x=0.34, 0.59, 0.65) bulk samples. Hardness test found that Ca x Y 1-x B6 (x=0.35, 0.42, 0.64) and Sr x Y 1-x B6 (x=0.59, 0.65) have higher Vickers hardness. Figure 19 and Figure 20 are Ca x Y 1-x B6 (x=0.35, 0.42, 0.64) and Sr x Y 1-xThe hardness test results of B6(x = 0.34, 0.59, 0.65), in which the hardness values of CaB6, SrB6and YB6are from the literature. It can be seen that the hardness of Ca x Y 1-x B6and Sr x Y 1-x B6increases gradually, in which Ca x Y 1-x B6(x = 0.35, 0.42, 0.64) and Sr x Y 1-x B6(x = 0.59, 0.65) have higher Vickers hardness values, which are high-hardness materials. Figure 21 and Figure 22 are Ca x Y 1-x B6(x = 0.35, 0.42, 0.64) and Sr x Y 1-x The electrical transport test results of B6(x = 0.34, 0.59, 0.65). It can be seen that, except for Ca 0.64 Y 0.36 B6, all other samples show superconductivity, in which Ca 0.35 Y 0.65 B6and Ca 0.42 Y 0.58 The superconducting transition temperatures of B6, Ca 0.34 Y 0.66 B6, Sr 0.59 Y 0.41 B6and Sr 0.65 Y 0.35 B6are 2.5 K, 3.8 K, 5.8 K and 2.9 K, respectively. Therefore, Ca 0.35 Y 0.65 B6, Ca 0.42 Y 0.58 B6, Sr 0.59 Y 0.41 B6and Sr 0.65 Y 0.35 B6are hard superconducting materials, which have potential applications in the field of hard superconductors.

Claims

1. A metal hexaboride alloy, characterized by, The alloy is Ca / Sr x Y 1-x B6, 0.2≤x≤0.

7.

2. A method of producing the metal hexaboride alloy as claimed in claim 1, characterized by, The method comprises the following steps: CaO / SrO, Y2O3 and B powder are mixed uniformly in a specific molar ratio, pressed into a block, heated to a synthesis temperature, reacted, and a metal hexaboride alloy Ca / Sr is obtained x Y 1-x B6; CaO / SrO(s) + Y2O3(s) + B(s)→Ca / Sr x Y 1-x B6(s) + B2O3(s)+ YBO3(s).

3. The preparation method according to claim 2, characterized in that, The synthesis temperature is 1550-1800 DEG C, and the reaction time is 3-8 hours.

4. The production method according to claim 3, characterized by, The synthesis temperature is 1600 DEG C, and the reaction time is 5 hours.

5. The preparation method according to claim 2, characterized in that, YBO3 and B2O3 impurities are removed by immersing in a hydrochloric acid solution.

6. The preparation method according to claim 2, characterized in that, The pressed block is put into an alumina ceramic boat and transferred into a tube furnace for reaction under argon protection.

7. The preparation method according to claim 2, characterized in that, The molar ratio of CaO / SrO, Y2O3 is 1:3-2:1.

Images