CN111018530A

CN111018530A - High-hardness ultra-light ceramic composite material and preparation method thereof

Info

Publication number: CN111018530A
Application number: CN201911306067.7A
Authority: CN
Inventors: 王金娥; 董明
Original assignee: Saifu Nano Technology Xuzhou Co ltd
Current assignee: Saifu Nano Technology Xuzhou Co ltd
Priority date: 2019-12-18
Filing date: 2019-12-18
Publication date: 2020-04-17

Abstract

A high-hardness ultra-light ceramic composite material and a preparation method thereof belong to the technical field of ceramic composite material preparation. The preparation method of the high-hardness and ultra-light ceramic composite material comprises the following steps: s1, weighing boron carbide powder, titanium-coated carbon nanotubes and silicon-coated carbon nanotubes; s2, mixing and sanding the boron carbide powder and the dispersion medium until the particle size D50 of the slurry is less than or equal to 1 mu m to obtain boron carbide slurry; s3, ball-milling the boron carbide slurry, the titanium-coated carbon nano tube and the silicon-coated carbon nano tube together to obtain uniform mixed slurry; s4, carrying out spray granulation on the mixed slurry, and then crushing and sieving to obtain mixed powder; and S5, transferring the mixed powder into a graphite mold, separating the mixed powder from the graphite mold and a pressure head by using graphite paper, and carrying out hot-pressing sintering to obtain the high-hardness ultra-light ceramic composite material. The invention takes boron carbide, titanium-coated carbon nano-tubes and silicon-coated carbon nano-tubes as raw materials, and generates titanium boride and silicon carbide through in-situ reaction, thereby not only improving the hardness of the matrix material, but also playing a role in reinforcing and toughening.

Description

High-hardness ultra-light ceramic composite material and preparation method thereof

Technical Field

The invention relates to a technology in the field of ceramic composite material preparation, in particular to a high-hardness ultra-light ceramic composite material and a preparation method thereof.

Background

Boron carbide has many excellent properties: next to the extraordinary hardness of diamond and cubic boron nitride (Mohs hardness of 9.3), is the most ideal high-temperature wear-resistant material; the density is very low, and the ceramic material is the lightest and can be used in the field of aerospace; the neutron absorption capacity is very strong, compared with pure elements B and Cd, the material has low cost, good corrosion resistance and good thermal stability, and can be widely used in nuclear industry; the chemical property is excellent, the compound does not react with acid, alkali and most inorganic compounds at normal temperature, and only slowly corrodes in a hydrofluoric acid-sulfuric acid and hydrofluoric acid-nitric acid mixture, so that the compound is one of the compounds with the most stable chemical property; also has the advantages of high melting point, high elastic modulus, low expansion coefficient, good oxygen absorption capacity and the like; and also a p-type semiconductor material, which can maintain semiconductor characteristics even at a very high temperature.

However, further development and application of boron carbide materials are severely affected by excessively high sintering temperatures and low fracture toughness. To solve these problems, a conventional method is to add a second phase material to a boron carbide matrix for the purpose of lowering the sintering temperature and improving toughness. At present, the method with more research and better effect is to introduce titanium boride into a boron carbide matrix through reaction sintering; in addition, silicon carbide is one of the most ideal additive phases of the high-hardness and light-weight boron carbide ceramic due to high hardness, low density and high elastic modulus.

Many researchers research that titanium boride is directly added into boron carbide for sintering, and find that the addition of titanium boride improves the toughness of the material to different degrees, but the method has the problems of uneven distribution of second-phase particles, incompatibility with a matrix, poor combination and the like; another study has shown that the addition of titanium carbide to boron carbide can be used to produce non-stoichiometric B by chemical reaction between the titanium carbide and boron carbide₄C_1-xThe change of the lattice constant of the boron carbide is caused, and the structural defect is generated, thereby accelerating the mass transfer process, promoting the sintering densification and achieving the purpose of reducing the sintering temperature; and the micro-crack deflection effect caused by residual stress can be generated by utilizing the mismatching of the thermal expansion coefficient of the reaction product titanium boride and the matrix boron carbide, so that the fracture toughness of the boron carbide is improved. However, the excess carbon produced by this method remains in the matrix because it is not properly treated, and significantly reduces the hardness of the matrix. Therefore, although the method reduces the sintering temperature and increases the toughness of the material to a certain extent, the hardness of the material is sacrificed, and the problem of toughening of high-hardness ceramic is not really solved.

The Chinese scholars Liezetimibe and the like take boron carbide, silicon nitride, a small amount of silicon carbide and titanium carbide as raw materials, alumina and yttrium oxide as sintering aids, prepare the ceramic composite material taking boron carbide-titanium boride-silicon carbide as a main phase under the hot pressing condition that the sintering temperature is 1800-1880 ℃ and the pressure is 30MPa, and the fracture toughness of the ceramic composite material can reach 5.6 MPa.m^1/2. However, the method has the disadvantages of more raw materials, complex reaction process among the raw materials, and various intermediate phases, and is difficult to obtain the high-purity ternary composite ceramic. In addition, the addition of the low-temperature liquid-phase sintering aid reduces the hardness and high-temperature mechanical properties of the material, thereby reducing the application range of the material and reducing the reliability of the material.

The present invention has been made to solve the above-mentioned problems occurring in the prior art.

Disclosure of Invention

The invention provides a high-hardness ultra-light ceramic composite material and a preparation method thereof aiming at the defects in the prior art, wherein boron carbide, titanium-coated carbon nanotubes and silicon-coated carbon nanotubes are used as raw materials, and high-hardness titanium boride and light, high-hardness and high-toughness silicon carbide are generated through in-situ reaction, so that the hardness of a base material is improved, and the function of reinforcing and toughening is also achieved.

The invention relates to a preparation method of a high-hardness and ultra-light ceramic composite material, which comprises the following steps:

s1, weighing the raw materials for later use according to the following weight percentage, wherein, the boron carbide powder accounts for 75-95%, the titanium-coated carbon nano tube accounts for 3-15%, the silicon-coated carbon nano tube accounts for 2-10%, and the total weight of the three raw materials is 100%;

s2, adding the boron carbide powder and the dispersion medium into a sand mill, and sanding for 0.5-1 h at the rotating speed of 1000-1500 r/min until the particle size D50 of the slurry is less than or equal to 1 mu m to obtain boron carbide slurry;

s3, transferring the boron carbide slurry prepared in the step S2 into a ball mill, adding weighed titanium-coated carbon nanotubes and silicon-coated carbon nanotubes, and performing ball milling for 1-2 hours at a rotating speed of 50-150 r/min to obtain uniform mixed slurry;

s4, performing spray granulation on the mixed slurry prepared in the step S3, and then crushing and sieving to obtain mixed powder;

s5, transferring the mixed powder prepared in the step S4 into a graphite mold, separating the mixed powder from the graphite mold and a pressure head by using graphite paper, applying pressure of 20-60 MPa through the pressure head, and carrying out hot pressing sintering in two stages under vacuum or argon atmosphere; and (3) heating to 1350-1500 ℃ in the first stage, preserving heat for 30-60 min, then entering the second stage, heating to 1900-2000 ℃, preserving heat for 1-2 h, and naturally cooling to obtain the high-hardness ultra-light ceramic composite material.

The invention relates to a high-hardness ultra-light ceramic composite material which is prepared by the method and comprises a boron carbide matrix, and titanium boride, silicon carbide and carbon nanotubes which are sintered in the boron carbide matrix through in-situ reaction of titanium-coated carbon nanotubes, silicon-coated carbon nanotubes and boron carbide.

Technical effects

Compared with the prior art, the invention has the following technical effects:

1) the method comprises the following steps of reacting boron carbide, titanium-coated carbon nanotubes and silicon-coated carbon nanotubes in situ to generate high-hardness titanium boride and light, high-hardness and high-toughness silicon carbide, wherein the reaction comprises two stages, namely a first stage B₄C+2Ti＝2TiB₂+ C, second stage Si + C ═ SiC; the free carbon generated in the first stage is consumed in the second stage, the influence on the performance of the ceramic composite material due to free carbon residue is avoided, and the titanium boride and the silicon carbide generated through the in-situ reaction have high purity, small crystal grains and uniform distribution, can effectively inhibit the growth of the crystal grains of the boron carbide matrix, not only improves the hardness of the matrix material, but also plays a role in reinforcing and toughening, and effectively improves the use reliability of the ceramic composite material;

2) titanium boride and silicon carbide with high hardness and carbon nanotubes with excellent performance in all aspects are simultaneously introduced into a boron carbide ceramic material system, so that the fracture toughness of the ceramic composite material is improved under the condition of not sacrificing the hardness of the ceramic composite material, and the application range of the ceramic composite material is effectively expanded;

3) the firing is carried out in two stages, the heating temperature of the first stage is obviously lower than that of the prior art, no waste water and waste gas is discharged in the whole firing process, the energy is saved, the environment is protected, the process is simple and easy to operate, and the product performance is stable.

Drawings

FIG. 1 is an SEM photograph of the mixed powder of example 1;

FIG. 2 is an SEM photograph of a high-hardness ultra-light ceramic composite material in example 1;

FIG. 3 is a BSE plot of a polished surface of a high-hardness, ultra-light weight ceramic composite material with cracks in example 1;

FIG. 4 is an XRD pattern of the high-hardness ultra-light ceramic composite material in example 1;

fig. 5 is an XRD pattern of the high-hardness ultra-light ceramic composite material in example 3.

Detailed Description

The invention is described in detail below with reference to the drawings and the detailed description.

The embodiment of the invention relates to a preparation method of a high-hardness and ultra-light ceramic composite material, which comprises the following steps:

s1, weighing the following raw materials in percentage by weight for later use: 75-95% of boron carbide powder, 3-15% of titanium-coated carbon nano tube, 2-10% of silicon-coated carbon nano tube and 100% of the total weight of the three raw materials;

s5, transferring the mixed powder prepared in the step S4 into a graphite mold, separating the mixed powder from the graphite mold and a pressure head by using graphite paper, applying pressure of 20-60 MPa through the pressure head, and carrying out hot pressing sintering in two stages under vacuum or argon atmosphere; the first stage is heating to 1350-1500 ℃ at the speed of 10-20 ℃/min, preserving heat for 30-60 min, then entering the second stage, heating to 1900-2000 ℃ at the speed of 5-10 ℃/min, preserving heat for 1-2 h, naturally cooling, and sintering to obtain the high-hardness and ultra-light ceramic composite material.

The purity of the boron carbide powder is more than or equal to 95 percent, and the average grain diameter D50 is less than or equal to 5 mu m.

The titanium-coated carbon nanotube is a carbon nanotube with a nano titanium layer uniformly plated on the surface, the particle diameter of titanium in the nano titanium layer is 5-50 nm, and the weight ratio of the nano titanium layer to the carbon nanotube is more than or equal to 4: 1.

the silicon-coated carbon nanotube is a carbon nanotube with a nano silicon layer uniformly plated on the surface, the particle size of silicon in the nano silicon layer is 5-50 nm, and the weight ratio of the nano silicon layer to the carbon nanotube is more than or equal to 7: 3.

the weight ratio of the dispersion medium to the raw material is 1: 1-2: 1; further preferably, deionized water or alcohol is used as the dispersion medium.

The ball milling equipment adopts a vertical ball mill or a horizontal ball mill, and the ball-material ratio in the ball milling process is 1: 1-10: 1.

in the process of spray granulation, the air inlet temperature is 190 +/-10 ℃, and the air outlet temperature is 100 +/-10 ℃.

Example 1

The embodiment relates to a preparation method of a high-hardness and ultra-light ceramic composite material, which comprises the following steps:

s1, weighing the following raw materials in percentage by weight for later use: 95% of boron carbide powder, 3% of titanium-coated carbon nano tube and 2% of silicon-coated carbon nano tube;

s2, adding boron carbide powder and dispersion medium deionized water into a sand mill, sanding for 1h at a rotating speed of 1500r/min, and stopping sanding until the particle size D50 of the slurry is less than or equal to 1 mu m to obtain boron carbide slurry;

s3, transferring the boron carbide slurry into a ball mill, adding weighed titanium-coated carbon nanotubes and silicon-coated carbon nanotubes, and ball milling at a rotating speed of 150r/min for 1h to obtain uniform mixed slurry;

s4, spray granulation of the mixed slurry: the air inlet temperature is 195 ℃, the air outlet temperature is 100 ℃, and then the air flow is crushed and sieved by a 200-mesh sieve to obtain mixed powder;

s5, transferring the mixed powder into a graphite mold, separating the mixed powder from the graphite mold and a pressure head by graphite paper, and sintering in a hot-pressing sintering furnace in an argon atmosphere; introducing argon, applying pressure of 50MPa through a pressure head, heating to 1500 ℃ at the speed of 20 ℃/min under the pressure of 50MPa, and preserving heat for 45 min; and then raising the temperature to 2000 ℃ at the speed of 10 ℃/min, preserving the temperature for 1h, naturally cooling, and sintering to obtain the high-hardness ultra-light ceramic composite material.

The prepared high-hardness ultra-light ceramic composite material comprises 95.5 percent of boron carbide, 1.0 percent of titanium boride, 2.2 percent of silicon carbide and 1.3 percent of carbon nano tubes according to the weight proportion.

The mixed powder and the prepared high-hardness and ultra-light ceramic composite material were analyzed by a scanning electron microscope to obtain SEM photographs, as shown in fig. 1 and 2.

As can be seen from FIG. 1, the average particle size of the boron carbide powder is less than 1 μm, and the titanium-coated carbon nanotubes and the silicon-coated carbon nanotubes are uniformly dispersed in the boron carbide powder.

As can be seen from FIG. 2, the prepared high-hardness ultra-light ceramic composite material sample almost achieves complete densification, and no air holes exist; the fine crystal grains of titanium boride and silicon carbide with the grain size of about 1-2 mu m are uniformly distributed in the boron carbide matrix, occasionally, carbon nano tubes uniformly wrapped between the ceramic crystal grains are visible, fine and uniform micron-sized titanium boride and silicon carbide are formed between the matrix crystal grains through in-situ reaction, and the fine and uniform micron-sized titanium boride and silicon carbide are combined with the carbon nano tubes to prevent the growth of the boron carbide matrix crystal grains, so that the compactness of the ceramic matrix is ensured, and the hardness, the toughness and the reliability of the ceramic product are effectively improved; from the SEM photograph, it can be seen that the port morphology was irregular and there was a particle pull-out phenomenon, which is indicative of along-the-grain fracture. This phenomenon occurs because the coefficient of thermal expansion of titanium boride does not match that of the boron carbide matrix, residual stress is generated at the phase interface during the cooling of the sample from the sintering temperature to room temperature, and when crack propagation and a residual stress field occur, the crack always propagates along the weak link of the stress field. When the crack meets titanium boride particles, deflection and detour occur, so that the crack propagation path is increased, more energy is consumed, and the fracture toughness of the ceramic composite material is improved. This is well documented in the BSE graph shown in fig. 3: in FIG. 3, the background color is matrix boron carbide, the bright off-white color is titanium boride and the dark off-white color is silicon carbide, from which it is apparent that when a crack encounters a silicon carbide grain, the crack continues to propagate directly through the silicon carbide grain (shown in region I); while the cracks propagate to the titanium boride grains, they continue to propagate around the titanium boride grains along the titanium boride-boron carbide grain boundaries (indicated in zone II).

Example 2

s1, weighing the following raw materials in percentage by weight for later use: 85% of boron carbide powder, 9% of titanium-coated carbon nano-tubes and 6% of silicon-coated carbon nano-tubes;

s2, adding boron carbide powder and dispersion medium deionized water into a sand mill, sanding for 1h at the rotating speed of 1200r/min, and stopping sanding until the particle size D50 of the slurry is less than or equal to 1 mu m to obtain boron carbide slurry;

s3, transferring the boron carbide slurry into a ball mill, adding weighed titanium-coated carbon nanotubes and silicon-coated carbon nanotubes, and ball milling at a rotating speed of 120r/min for 1h to obtain uniform mixed slurry;

s5, transferring the mixed powder into a graphite mold, separating the mixed powder from the graphite mold and a pressure head by graphite paper, and sintering in a hot-pressing sintering furnace in an argon atmosphere; introducing argon, applying pressure of 50MPa through a pressure head, heating to 1500 ℃ at the speed of 20 ℃/min under the pressure of 50MPa, and preserving heat for 45 min; then the temperature is raised to the sintering temperature of 1950 ℃ at the speed of 10 ℃/min, the temperature is kept for 1.5h, and then the ceramic composite material with high hardness and ultra light weight is obtained after natural cooling.

The prepared high-hardness ultra-light ceramic composite material comprises 85.5 percent of boron carbide, 3.5 percent of titanium boride, 7.0 percent of silicon carbide and 4.0 percent of carbon nano tubes according to weight proportion.

Example 3

s1, weighing the following raw materials in percentage by weight for later use: 80% of boron carbide powder, 12% of titanium-coated carbon nano-tubes and 8% of silicon-coated carbon nano-tubes.

S2, adding boron carbide powder and dispersion medium deionized water into a sand mill, sanding for 1h at the rotating speed of 1000r/min until the particle size D50 of the slurry is less than or equal to 1 mu m, and stopping sanding to obtain boron carbide slurry;

s3, transferring the boron carbide slurry into a ball mill, adding weighed titanium-coated carbon nanotubes and silicon-coated carbon nanotubes, and ball milling at a rotating speed of 100r/min for 1h to obtain uniform mixed slurry;

s4, spray granulation of the mixed slurry: the air inlet temperature is 200 ℃, the air outlet temperature is 100 ℃, and then the air flow is crushed and sieved by a 200-mesh sieve to obtain mixed powder;

The prepared high-hardness ultra-light ceramic composite material comprises 80.3 percent of boron carbide, 5.0 percent of titanium boride, 9.3 percent of silicon carbide and 5.4 percent of carbon nano tubes according to the weight proportion.

Fig. 4 is an XRD pattern of the high-hardness ultra-light ceramic composite material prepared in example 1, and fig. 5 is an XRD pattern of the high-hardness ultra-light ceramic composite material prepared in example 3. Comparing the two figures can see that: the two ceramic composite materials mainly have diffraction peaks of boron carbide, titanium boride and silicon carbide, and peaks of simple substance titanium and simple substance silicon are not seen, which indicates that the raw materials react completely in the sintering process, and the added titanium and silicon both generate the titanium boride and the silicon carbide in situ; fig. 5 also shows the diffraction peak of the carbon nanotubes, while fig. 4 shows almost no peak of the carbon nanotubes, which is not detected because the amount of the carbon nanotubes added in example 1 is small and is substantially wrapped inside the ceramic material.

The high-hardness ultra-light ceramic composite materials prepared in example 1, example 2 and example 3 were subjected to performance tests at room temperature, and the results are shown in table 1.

Table 1 comparative table of performance test

Item	Example 1	Example 2	Example 3	Common boron carbide-based composite ceramics
					Theoretical density g/cm³	2.541	2.599	2.627	2.522
Actually measured density g/cm³	2.539	2.598	2.626	/
					Relative density	99.92	99.96	99.96	/
Hardness GPa	35.76	36.23	35.91	20～30
					Fracture toughness MPa m^1/2	6.12	6.35	6.57	2.9～3.7
Bending strength MPa	622.1	639.8	657.7	300～500

As can be seen from Table 1, the density of the high-hardness ultra-light ceramic composite material prepared by the embodiment of the invention is more than 99.9%, and the test performance at room temperature is remarkably improved compared with that of common boron carbide-based composite ceramic.

It is to be emphasized that: the above embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention in any way, and all simple modifications, equivalent changes and modifications made to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.

Claims

1. The preparation method of the high-hardness and ultra-light ceramic composite material is characterized by comprising the following steps of:

2. The preparation method of the high-hardness and ultra-light ceramic composite material as claimed in claim 1, wherein the purity of the boron carbide powder is not less than 95%, and the average particle size D50 is not more than 5 μm.

3. The method for preparing the high-hardness and ultra-light ceramic composite material according to claim 1, wherein the titanium-coated carbon nanotube is a carbon nanotube with a nano titanium layer uniformly plated on the surface, the titanium particle size in the nano titanium layer is 5-50 nm, and the weight ratio of the nano titanium layer to the carbon nanotube is more than or equal to 4: 1.

4. the preparation method of the high-hardness and ultra-light ceramic composite material according to claim 1, wherein the silicon-coated carbon nanotubes are carbon nanotubes with the surface uniformly coated with a nano silicon layer, the particle size of silicon in the nano silicon layer is 5-50 nm, and the weight ratio of the nano silicon layer to the carbon nanotubes is not less than 7: 3.

5. the method for preparing the high-hardness and ultra-light ceramic composite material according to claim 1, wherein the weight ratio of the dispersion medium to the raw materials is 1: 1-2: 1.

6. the method for preparing a high-hardness and ultra-light-weight ceramic composite material according to claim 5, wherein deionized water or alcohol is used as the dispersion medium.

7. The method for preparing the high-hardness and ultra-light ceramic composite material according to claim 1, wherein the ball-to-material ratio in the ball milling process is 1: 1-10: 1.

8. the method for preparing the high-hardness and ultra-light ceramic composite material according to claim 1, wherein the air inlet temperature is 190 +/-10 ℃ and the air outlet temperature is 100 +/-10 ℃ in the spray granulation process.

9. The method for preparing a high-hardness and ultra-light ceramic composite material according to claim 1, wherein the temperature is raised to 1350-1500 ℃ at a rate of 10-20 ℃/min in the first stage, and the temperature is raised to 1900-2000 ℃ at a rate of 5-10 ℃/min in the second stage.

10. The high-hardness ultra-light ceramic composite material is characterized by comprising a boron carbide matrix, and titanium boride, silicon carbide and carbon nanotubes which are sintered in the boron carbide matrix through in-situ reaction of titanium-coated carbon nanotubes, silicon-coated carbon nanotubes and boron carbide.