CN112374892B

CN112374892B - Controllable niobium carbide-tantalum carbide solid solution micron cube and preparation method thereof

Info

Publication number: CN112374892B
Application number: CN202011318998.1A
Authority: CN
Inventors: 耿欣; 温广武; 徐文喆; 陈春强; 王鹏
Original assignee: Shandong University of Technology
Current assignee: Shandong University of Technology
Priority date: 2020-11-23
Filing date: 2020-11-23
Publication date: 2022-08-16
Anticipated expiration: 2040-11-23
Also published as: CN112374892A

Abstract

The invention relates to a novel process for preparing a high-purity (C)A niobium carbide-tantalum carbide solid solution controlled micron cube and a preparation method thereof, belonging to the technical field of ceramic powder preparation. The method is characterized in that: NbC, TaC and Co powder are used as raw materials, the raw materials are uniformly mixed according to the mass ratio of NbC to TaC to Co (0.01-3.99) to 1, and the mixed powder is preformed and subjected to heat treatment: heating to 1200-1700 ℃ at a heating rate of 2-100 ℃/min under an inert atmosphere, preserving heat for 0.5-120 h, and cooling to room temperature. Soaking the prepared block body by using 1-15.2 mol of nitric acid solution until the cobalt-containing metal matrix is completely corroded and dissolved; cleaning and drying the rest powder to obtain niobium carbide-tantalum carbide solid solution (Nb) _x Ta _1‑x C,0<x<1) A microcube. The invention has the advantages of low preparation temperature, simple process, short period, low requirement on equipment, energy conservation and no pollution. The prepared cube has the advantages of uniform particle size distribution, high purity, excellent mechanical property and good heat conductivity; is suitable for the fields of new energy, aerospace, hypersonic missiles and the like.

Description

Controllable niobium carbide-tantalum carbide solid solution micron cube and preparation method thereof

Technical Field

The invention relates to a controllable niobium carbide-tantalum carbide solid solution micro cube and a preparation method thereof, belonging to the technical field of ceramic powder preparation.

Background

Niobium carbide (NbC) and tantalum carbide (TaC) belong to the same group of ultra-high temperature ceramics, both of which exhibit a crystal structure of the cubic NaCl type, the space group being Fm3m, the lattice constants being 0.4469 nm and 0.4455 nm, respectively, α = β = γ =90 °, the metal Nb, Ta atoms being located at the six vertices and the face center of the NbC, TaC unit cells, respectively, the C atom occupying the center of each edge and the center of the unit cell.

NbC and TaC are used as one member of transition metal carbide, are super-hard multifunctional materials with high hardness (15-20 GPa), strong mechanical wear resistance and excellent chemical stability, do not react with most chemical substances, are insoluble in water, are insoluble in inorganic acid and are slightly soluble in sulfuric acid and hydrofluoric acid. The melting points of NbC and TaC are 3600 ℃ and 3983 ℃ respectively, and the thermal expansion coefficients are 6.6 multiplied by 10 respectively ⁻⁶ K ⁻¹ And 6.3X 10 ⁻⁶ K ⁻¹ . NbC has good conductivity and a resistivity of 35. mu. omega. cm. The TaC has excellent high-temperature oxidation resistance, ablation resistance, thermal shock resistance and thermal stability besides the advantage of retaining a part of metal Ta, and is a material which can only keep a certain mechanical property within the range of 2900-3200 ℃.

Because NbC and TaC have excellent characteristics of high hardness, high wear resistance, high melting point, good chemical stability and the like, the NbC and TaC are widely applied to the design and manufacture of various superhard materials: (1) complex phase ceramic: NbC and TaC are generally used as raw materials of ceramic materials, and the metal ceramics prepared from the NbC and TaC have high hardness, high melting point, excellent chemical stability and electrical conductivity, and are widely applied to the fields of wear-resistant parts, cutting tool materials, electrode materials and the like. (2) Aerospace components: many aerospace device components, such as turbine rotors, blades, engine nozzles, and nuclear reactor structural components, are typically operated at very high temperatures, and therefore have high material requirements. NbC and TaC have extremely high melting points and are often used in aerospace applications. And NbC as an aerospace material can be strengthened along with the rise of temperature, and the strength of the material reaches the peak value of the strength strengthening at about 800 ℃. The matrix of the aerospace component is changed from brittleness to plasticity along with the rise of temperature, under the condition, a certain amount of NbC particles are mixed into an aerospace material part, so that the strengthening effect of the plastic matrix is enhanced, and the high-temperature strengthening effect is obviously improved, so that the composite material added with NbC has very good heat-resistant strength. The TaC is mainly applied to thermal protection systems of aircrafts such as hypersonic missiles, space shuttle aircrafts, space shuttles and the like. For example, the material can be used as a throat liner material of a solid rocket engine and key parts of an ultra-high-speed aircraft, such as a wing leading edge, a tail leading edge, a nose cone and a hot end of the engine; TaC ceramics are considered to be the best alternative to refractory metals, C/C or C/SiC composites.

Liuyubao et al in the thesis "niobium carbide synthesis and application research progress" said that NbC can be fused with other superhigh temperature structural ceramics (such as TiC, TaC, ZrC, etc.) to form homogeneous isomorphous solid solution. The solid solution can keep the excellent properties of carbide components and improve the comprehensive performance; such as niobium carbide-tantalum carbide solid solution (Nb) _x Ta _1-x C) Besides the common characteristics of excellent mechanical property, good chemical stability, high temperature resistance and the like of NbC and TaC; and also has excellent heat conduction and electric conduction performance. But NbC and TaC are strong covalent bond compounds, so that NbC and TaC have lower self-diffusion coefficientForming a niobium carbide-tantalum carbide solid solution (Nb) _x Ta _1-x C) Higher temperatures are required, even with high pressures. Cherkhenko et al, in the paper "Features of the electronic structure of the isoelectronic solutions Nb _x Ta _1-x C' in the presence of Nb _x Ta _1-x The preparation temperature of C needs to exceed 2000 ℃ (2130-2530 ℃ is adopted in the research), the required energy consumption is high, and the preparation cost is high, so that the application of C is limited.

The invention is based on a liquid phase sintering process, namely a melting-precipitation mechanism; NbC powder, TaC powder and metal Co powder are used as raw materials, and the raw material powder is uniformly mixed and pre-pressed into a block; heat treatment is carried out at a lower temperature; subsequently, the cobalt-containing metal matrix is dissolved by corrosion by using an acid solution, thereby obtaining a niobium carbide-tantalum carbide solid solution (Nb) _x Ta _1-x C) The cube has the advantages of excellent mechanical property, good heat conduction and electric conduction performance, high temperature resistance, good chemical stability and the like. The preparation method can be realized under normal pressure and lower heat treatment temperature, and has the advantages of simple preparation process, low equipment requirement, short period, energy conservation, no pollution and the like. Prepared Nb _x Ta _1-x The C cubic ceramic powder has uniform size distribution, high purity, no other impurities, excellent mechanical, heat conduction and electrical conductivity, and is suitable for the fields of new energy, aerospace, hypersonic guided missiles and the like.

Disclosure of Invention

The purpose of the invention is to solve the original Nb _x Ta _1-x The problems that C ceramic powder is difficult to prepare (high preparation temperature and high pressure are needed), the energy consumption is high and the like are solved, and the lower-temperature liquid-phase sintered Nb is provided _x Ta _1-x The preparation process of the ceramic powder does not cause pollution and saves energy. The technical scheme is as follows: (1) NbC powder, TaC powder and Co powder are taken as main raw materials; weighing and uniformly mixing the powder according to the mass ratio of (0.01-3.99) to 1; and pre-pressing and molding the uniformly mixed powder (block). (2) The precast block is subjected to high-temperature heat treatment, and the process comprises the following steps: heating to 1200-17 deg.C at a heating rate of 2-100 deg.C/min under inert atmosphere (such as nitrogen)Preserving heat for 0.5-120 h at 00 ℃, and then cooling to room temperature along with the furnace. (3) Preparing 1-15.2 mol of nitric acid solution; soaking the prepared Nb _x Ta _1-x C-Co block until the cobalt-containing metal matrix is completely corroded and dissolved; cleaning and drying the residual powder to obtain the niobium carbide-tantalum carbide solid solution (Nb) _x Ta _1-x C) A microcube.

The working principle of the invention is as follows: (a) cobalt powder is taken as a metal phase matrix, NbC and TaC particles can be wetted at high temperature and react with the NbC and TaC particles, and the reaction equation is as follows:

x·NbC _(s) +(1-x)·Co _(s) ⇄Nb _x -Co _{(1-x) (s,l)} +x·C _(s) (1)

y·TaC _(s) + (1-y)·Co _(s) ⇄Ta _y -Co _{(1-y) (s,l)} +y·C _(s) (2)

in summary, the overall reaction equation is summarized as follows:

x·NbC _(s) + y·TaC _(s) +(1-x-y)·Co _{(s, l)} →Nb _x -Ta _y -Co _{(1-x-y) (s, l)} +(x+y)·C _(s) (3)

Nb _x -Ta _y -Co _{(1-x-y) (s, l)} + C _(s) →(Nb _x ,Ta _y )C _(s) +(1-x-y) ·Co _{(s, l)} (4)

co reacts with NbC and TaC powder in the high-temperature heating process to generate Co-Nb-Ta alloy and carbon (melting process); on the other hand, the resulting Co-Nb-Ta alloy reacts with carbon to produce Nb _x Ta _1-x C infinite solid solution (precipitation process). Wherein x is the mole percentage of Nb in the Co-Nb alloy generated by the reaction of NbC and Co; y is the mole percentage of Ta in the Co-Ta solid solution alloy formed by dissolving TaC into Co; further l and s represent liquid and solid respectively.

(b) The formed Co-Nb-Ta solid solution alloy can change the mass transport mechanism of NbC and TaC. Based on a dissolution-reprecipitation mechanism, edges and corners, micro-protrusions and fine particles of large particles are dissolved in Co to form a Co-Nb-Ta alloy, and when the content of Nb and Ta in the alloy reaches saturation, the alloy reacts with carbon to react on the surface of the particlesRe-precipitation of Nb on the surface _x Ta _1-x C infinite solid solution. When the process reaches thermodynamic equilibrium, the grains will exhibit a shape with minimal interfacial energy; according to the Wulff theorem, the equilibrium shape of crystals is related to the interfacial energies of the crystals and their crystallographic orientations. He believes that the crystal shape at equilibrium should satisfy the following relationship:

2γ ₁ /h ₁ =2γ ₂ /h ₂ =···=2γ _i /h _i = λ (constant) (5)

Where h is the vertical distance from the center of the crystal to each crystal plane and γ is the interfacial tension (i.e., surface energy per unit area) of that crystal plane. Nb produced by NbC and TaC both having cubic crystal structure _x Ta _1-x The C solid solution ceramic particles exhibit a prismatic, cubic shape.

The invention has the following advantages:

(1) ultra-high temperature Nb prepared by the invention _x Ta _1-x The C solid solution cube has the advantages of low preparation temperature, simple operation steps, safety, reliability, energy conservation, high purity, no impurities and the like;

(2) the solid solution powder prepared by the invention has excellent mechanical properties, high strength and hardness, better heat conduction and electric conduction performance, high temperature resistance and chemical corrosion resistance.

Drawings

FIG. 1 is a Nb prepared in example 1 _x Ta _1-x XRD spectrum of the C solid solution ceramic powder.

FIG. 2 is the Nb prepared in example 1 _x Ta _1-x SEM photograph of the C solid solution ceramic powder.

FIG. 3 is the Nb prepared in example 1 _x Ta _1-x EDS spectrogram of C solid solution ceramic powder.

FIG. 4 is the Nb prepared in example 2 _x Ta _1-x XRD spectrum of the C solid solution ceramic powder.

FIG. 5 is the Nb prepared in example 2 _x Ta _1-x SEM photograph of the C solid solution ceramic powder.

FIG. 6 is the Nb prepared in example 2 _x Ta _1-x EDS spectrogram of C solid solution ceramic powder.

FIG. 7 is the Nb prepared in example 3 _x Ta _1-x XRD spectrum of the C solid solution ceramic powder.

FIG. 8 is the Nb prepared in example 3 _x Ta _1-x SEM photograph of the C solid solution ceramic powder.

FIG. 9 is a Nb prepared in example 3 _x Ta _1-x EDS spectrogram of C solid solution ceramic powder.

Detailed Description

The technical solution of the present invention is not limited to the specific examples listed below, and includes any combination of the specific embodiments.

Example 1:

taking niobium carbide, tantalum carbide and cobalt powder as raw materials, uniformly mixing the niobium carbide, tantalum carbide and cobalt powder according to a mass ratio of 9:1:10 (the molar ratio is 0.5:0.03:1), then pre-pressing and molding the mixed powder, putting the pressed green body into a crucible, and putting the crucible into a furnace. Heating to 1500 ℃ at the heating rate of 5 ℃/min under the inert atmosphere (nitrogen and oxygen-free), preserving heat for 1.5h, and slowly cooling along with the furnace to obtain the metal ceramic block. Soaking the block in 8 mol/L nitric acid solution until the Co-Nb-Ta alloy matrix is completely corroded and dissolved; filtering the obtained powder, cleaning and drying to obtain Nb with cubic block morphology _x Ta _1-x C micron ceramic powder.

Prepared Nb _x Ta _1-x C, performing X-ray diffraction phase analysis (XRD), and testing to obtain an XRD spectrum as shown in figure 1. The five XRD peaks detected correspond to the (111), (200), (220), (311) and (222) crystal planes of the cubic NbC phase (PDF-01-089-3830); no other crystal impurities. In addition, the above XRD peaks are all shifted toward high angles compared to the diffraction peak of standard NbC, which indicates that Ta atoms replace Nb atoms in the NbC lattice to form Nb _x Ta _1-x C solid solution, causing lattice contraction.

Prepared Nb _x Ta _1-x The ceramic powder was subjected to Scanning Electron Microscope (SEM) testing, and its microstructure is shown in fig. 2. FIG. 2(a) shows Nb _x Ta _1-x C, the ceramic powder shows a cube shape with edges and corners; FIG. 2(b) illustrates the cube having a side length of 5-10 μm; compared with NbC and TaC original powder with irregular morphology, the particles are converted into cubic Nb with regular shape in a Co alloy matrix after high-temperature heat treatment at 1500 DEG C _x Ta _1-x C。

The chemical composition of the prepared powder was analyzed by an Energy Dispersive Spectrometer (EDS) equipped on a scanning electron microscope, and the spectrum thereof is shown in fig. 3. This shows that the grains contain three elements of Nb, Ta and C, the signal of Nb element is strong, and the signal of Ta element is relatively weak. The result shows that Ta is dissolved in NbC lattice to form Nb _x Ta _1-x C solid solution.

Example 2:

niobium carbide, tantalum carbide and cobalt powder are used as raw materials, the niobium carbide, tantalum carbide and cobalt powder are uniformly mixed according to the mass ratio of 1:1:2 (the molar ratio is 0.28:0.15:1), then the mixed powder is pre-pressed and formed, the pressed green body is placed into a crucible, and the crucible is placed into a furnace. Heating to 1500 ℃ at the heating rate of 5 ℃/min under the inert atmosphere (nitrogen and oxygen-free), preserving heat for 1.5h, and slowly cooling along with the furnace to obtain the metal ceramic block. Soaking the block in 8 mol/L nitric acid solution until the Co-Nb-Ta alloy matrix is completely corroded and dissolved; filtering the obtained powder, cleaning and drying to obtain Nb with cubic block morphology _x Ta _1-x C micron ceramic powder.

Prepared Nb _x Ta _1-x C, X-ray diffraction phase analysis (XRD) is carried out, and an XRD spectrum obtained by the test is shown in figure 4. The five XRD peaks detected correspond to the (111), (200), (220), (311) and (222) crystal planes of cubic NbC (PDF-01-089-3830); or (111), (200), (220), (311) and (222) crystal faces corresponding to cubic TaC (PDF-01-089-3830); no other crystal impurities. In addition, the above XRD peaks are all shifted toward high angles compared to the diffraction peak of standard NbC, and are all shifted toward low angles compared to the diffraction peak of standard TaC, indicating that substitution of Ta atoms for Nb atoms in the NbC lattice forms Nb atoms _x Ta _1-x C solid solution, causing lattice shrinkage; or Nb atoms replacing Ta atoms in TaC lattice to form Nb _x Ta _1- _x C solid solution, causing lattice expansion.

Prepared Nb _x Ta _1-x The ceramic powder C was subjected to Scanning Electron Microscope (SEM) testing and its microstructure is shown in fig. 5. FIG. 5(a) shows Nb _x Ta _1-x C, the ceramic powder shows a cube shape with edges and corners; FIG. 5(b) illustrates the cube having a side length of 3-7 μm; compared with NbC and TaC original powder with irregular morphology, the particles are converted into cubic Nb with regular shape in a Co alloy matrix after high-temperature heat treatment at 1500 DEG C _x Ta _1-x C。

The chemical composition of the prepared powder was analyzed by an Energy Dispersive Spectrometer (EDS) equipped on a scanning electron microscope, and the spectrum thereof is shown in fig. 6. This shows that the particles contain three elements of Nb, Ta and C, and the signals of Nb element and Ta element are both strong and have similar strength. The result shows that Ta is dissolved in NbC crystal lattice or Nb is dissolved in TaC crystal lattice to form Nb _x Ta _1-x C solid solution.

Example 3:

niobium carbide, tantalum carbide and cobalt powder are used as raw materials, the niobium carbide, tantalum carbide and cobalt powder are uniformly mixed according to the mass ratio of 1:9:1 (the molar ratio is 0.056:0.28:1), then the mixed powder is pre-pressed and formed, the pressed blank body is placed into a crucible, and the crucible is placed into a furnace. Heating to 1500 ℃ at the heating rate of 5 ℃/min under the inert atmosphere (nitrogen and oxygen-free), preserving heat for 1.5h, and slowly cooling along with the furnace to obtain the metal ceramic block. Soaking the block in 8 mol/L nitric acid solution until the Co-Nb-Ta alloy matrix is completely corroded and dissolved; filtering the obtained powder, cleaning and drying to obtain Nb with cubic block morphology _x Ta _1-x C micron ceramic powder.

Prepared Nb _x Ta _1-x C, X-ray diffraction phase analysis (XRD) is carried out, and an XRD spectrum obtained by the test is shown in figure 7. The five XRD peaks detected correspond to the (111), (200), (220), (311) and (222) crystal planes of the cubic TaC phase (PDF-01-089-3830); no other crystal impurities. In addition, the above XRD peaks are all shifted toward low angles compared to the diffraction peak of standard TaC, which indicates that Nb atoms substitute for TaC latticeIn which Ta atom forms Nb _x Ta _1-x C solid solution, causing lattice expansion.

Prepared Nb _x Ta _1-x The ceramic powder C was subjected to Scanning Electron Microscope (SEM) testing, and its microstructure is shown in fig. 8. FIG. 8(a) shows Nb _x Ta _1-x C, the ceramic powder shows a cube shape with edges and corners; FIG. 8(b) illustrates the cube having a side length of 2-5 μm; compared with NbC and TaC original powder with irregular morphology, the particles are converted into cubic Nb with regular shape in a Co alloy matrix after high-temperature heat treatment at 1500 DEG C _x Ta _1-x C。

The chemical composition of the prepared powder was analyzed by an Energy Dispersive Spectrometer (EDS) equipped on a scanning electron microscope, and the spectrum thereof is shown in fig. 9. This shows that the particles contain three elements of Nb, Ta and C, the Ta element signal is strong, and the Nb element signal is relatively weak. It is explained that Nb is dissolved in TaC lattice to form Nb _x Ta _1-x C solid solution.

Example 4:

niobium carbide, tantalum carbide and cobalt powder are used as raw materials, the niobium carbide, tantalum carbide and cobalt powder are uniformly mixed according to the mass ratio of 0.01:3.99:1 (the molar ratio is 0.0056:1.22:1), then the mixed powder is pre-pressed and formed, and the pressed green body is placed in a crucible and placed in a furnace. Raising the temperature to 1200 ℃ at a heating rate of 100 ℃/min in an inert atmosphere (nitrogen and oxygen-free), preserving the heat for 120h, and slowly cooling along with the furnace to obtain the Co-Nb-Ta-C system cermet block. Soaking the block in 1 mol/L nitric acid solution until the Co-Nb-Ta alloy matrix is completely corroded and dissolved; filtering the obtained powder, cleaning and drying to obtain Nb with cubic block morphology _x Ta _1-x C micron ceramic powder.

Example 5:

niobium carbide, tantalum carbide and cobalt powder are used as raw materials, the niobium carbide, tantalum carbide and cobalt powder are uniformly mixed according to the mass ratio of 3.99:0.01:1 (the molar ratio is 2.24:0.0031:1), then the mixed powder is pre-pressed and formed, and the pressed green body is placed in a crucible and placed in a furnace. Heating to 1700 deg.C at 2 deg.C/min under inert atmosphere (nitrogen, oxygen-free), and maintainingThe temperature is 0.5h, and the Co-Nb-Ta-C system metal ceramic block can be obtained after furnace slow cooling. Soaking the block in 15.2 mol/L nitric acid solution until the Co-Nb-Ta alloy matrix is completely corroded and dissolved; filtering the obtained powder, cleaning and drying to obtain Nb with cubic block morphology _x Ta _1-x C micron ceramic powder.

Claims

1. A preparation method of a controllable niobium carbide-tantalum carbide solid solution micron cube is characterized by comprising the following steps: (1) uniformly mixing NbC, TaC and Co powder serving as raw materials according to the mass ratio of NbC to TaC to Co (0.01-3.99) to 1, and then pre-pressing and molding the mixed powder; (2) transferring the blank into a furnace for heat treatment, heating to 1500 ℃ at the heating rate of 5 ℃/min in the nitrogen and oxygen-free atmosphere, preserving heat for 1.5h, and then cooling to room temperature to obtain a metal ceramic block; (3) soaking the prepared block body by using 8 mol/L nitric acid solution until the cobalt-containing metal matrix is completely corroded and dissolved; cleaning and drying the residual powder to obtain niobium carbide-tantalum carbide solid solution (Nb) _x Ta _1-x C, 0<x<1) A micron cube.