A boron carbide composite material, a method for preparing the same, and an application thereof

Abstract

The application discloses a boron carbide composite material and a preparation method and application thereof. The boron carbide composite material comprises a fibrous boron carbide matrix, and an interface layer material is distributed between adjacent fibrous boron carbide matrices; the interface layer material comprises graphene oxide and / or boron nitride. The boron carbide composite material has a low thermal expansion coefficient and higher fracture work. The application further provides a preparation method and application of the boron carbide composite material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic materials, and particularly relates to a boron carbide composite material and a preparation method and application thereof. BACKGROUND

[0002] The service environment temperature of related components such as armor, thermoelectric field, engine high-temperature nozzle and the like is high, and the working environment needs frequent temperature rise and fall, and the phenomenon of object expansion and contraction with temperature is more serious. With the rapid development of the fields of aerospace, precision machining and the like, higher requirements are put forward for the thermal expansion coefficient regulation of materials. The material with low thermal expansion characteristics can greatly improve the thermal shock resistance and dimensional stability, and improve the measurement or machining precision. The matching thermal expansion coefficients between different components can also significantly reduce thermal stress, and further prolong the service life of the device. The boron carbide ceramic has excellent high-temperature thermal stability, thermoelectric performance and wear resistance, and at the same time has extremely high hardness only next to diamond and cubic boron nitride, and low density, so that it has certain application prospect in components such as armor, thermoelectric field, engine high-temperature nozzle and the like. However, due to the lack of independent slip system in the ceramic, the material is difficult to plastically deform to relax stress under stress, and from the microstructure, the root of brittleness lies in the existence of microcracks, which is easy to cause stress concentration, and the material breaks with the expansion of the cracks.

[0003] The boron carbide is difficult to sinter, and generally needs to add second-phase particles to improve the sintering activity and reduce the sintering temperature. The doped second-phase particles are called sintering aids. The commonly used sintering aids of boron carbide include metal titanium (8.6x10 -6 K -1 ), titanium carbide (7.74x10 -6 K -1 ), tungsten carbide (6.73x10 -6 K -1 ), titanium silicon carbide (9.1x10 -6 K -1 ) and the like. The addition of the sintering aid can significantly reduce the sintering difficulty of the boron carbide and reduce the cost, but the thermal expansion coefficients of these materials are higher than that of the boron carbide (5.73x10 -6 K -1 ), and with the change of the content of the added sintering aid, the thermal expansion coefficient of the boron carbide is increased, for example, the addition of 20wt% of titanium carbide in the boron carbide matrix can reduce the sintering temperature of the boron carbide from 2200 DEG C to 1900 DEG C, but the thermal expansion coefficient is increased from 5.73x10 -6 K -1 to 6.47x10 -6 K -1 .

[0004] In addition, the toughness of boron carbide ceramics is particularly low among ceramic materials. In the related art, the toughening of boron carbide is provided by adding a sintering aid to provide a second phase toughening effect, although the toughness is improved, the thermal expansion is increased. Therefore, it is necessary to develop a boron carbide ceramic composite material which has a low thermal expansion coefficient and at the same time has a higher fracture work. SUMMARY

[0005] The present application aims to at least solve one of the above technical problems existing in the prior art. To this end, the present application provides a boron carbide composite material having a low thermal expansion coefficient and at the same time having a higher fracture work.

[0006] The present application also provides a method for preparing a boron carbide composite material.

[0007] The present application also provides an application of a boron carbide composite material.

[0008] The first aspect of the present application provides a boron carbide composite material comprising a fibrous boron carbide matrix, and an interfacial layer material distributed between adjacent fibrous boron carbide matrices, the interfacial layer material comprising graphene oxide and / or boron nitride.

[0009] One of the technical solutions of the present application related to a boron carbide composite material has at least the following beneficial effects:

[0010] The boron carbide composite material of the present application comprises a fibrous boron carbide matrix, and an interfacial layer material distributed between adjacent fibrous boron carbide matrices. The purpose of selecting graphene oxide and / or hexagonal boron nitride as the interfacial layer material is that the thermal expansion coefficients of these two materials are relatively low (graphene oxide 2.8x10 -6 K -1 , boron nitride 4.5x10 -6 K -1 ), and at the same time have a layered structure, while boron carbide ceramics lack slip systems and are difficult to relax stress by slip, but the interlayer of these two materials can slip and thus relax stress, thereby improving toughness.

[0011] The boron carbide composite material of the present application has high damage resistance and adjustable low thermal expansion coefficient. Specifically, it has a lower thermal expansion coefficient, and the boron carbide composite material prepared by the method has a lower thermal expansion coefficient at 30-1000℃, the linear expansion coefficient is ≤5.5x10 -6 K -1 , which is lower than the 6.4677x10 -6 K -1 of the pure boron carbide matrix.

[0012] The boron carbide composite material has more excellent damage resistance and greater fracture work. The crack around the indentation of the traditional bulk boron carbide ceramic is long, and the indentation after being preserved for 10 s under the force of 5 kg can cause a fine crack of about 50 microns long on the surface of the material. After the indentation is prepared by the same method, the boron carbide composite material of the present application is absorbed after encountering the second phase material and does not expand to the nearby boron carbide surface, proving that it has higher damage resistance. Through the fracture curve calculation, the fracture work of the boron carbide composite material of the present application is as high as 879.93 J / m 2 .

[0013] The boron carbide composite material of the present application has extremely high fracture work, the composite components have a hindering effect on the crack propagation, and when the low-resistance material is compounded, the processability of the boron carbide can be improved.

[0014] According to some embodiments of the present application, the linear expansion coefficient of the boron carbide composite material is ≤5.5*10 -6 K -1 .

[0015] According to some embodiments of the present application, the fracture work of the boron carbide composite material is ≥800 J / m 2 .

[0016] The second aspect of the present application provides a method for preparing a boron carbide composite material, comprising the following steps:

[0017] Mixing the boron carbide ceramic powder with the polymer solution and ball milling to obtain a ceramic slurry;

[0018] Mixing the interface layer material with the polymer solution and ball milling to obtain an interface layer slurry;

[0019] Extruding the ceramic slurry and the interface layer slurry from the inner needle and the outer needle of the coaxial nozzle, respectively, to obtain an interface layer material coated boron carbide fibrous body;

[0020] After the interface layer material coated boron carbide fibrous body is pressed into a shape, it is subjected to isostatic pressing and hot-pressing sintering to obtain the boron carbide composite material.

[0021] The technical scheme of the method for preparing a boron carbide composite material of the present application has at least the following beneficial effects:

[0022] The preparation method of the present application does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are easy to obtain, the production cost is low, and the industrial production is easy.

[0023] In the preparation method, the boron carbide ceramic powder is mixed with a polymer solution by ball milling to obtain a ceramic slurry, and the interfacial layer material is mixed with a polymer solution by ball milling to obtain an interfacial layer slurry. The polymer solution can be prepared in two parts, one part of the polymer solution is used to coat the boron carbide forming, and the other part of the polymer solution is used to coat the graphene oxide or boron nitride forming.

[0024] According to some embodiments of the present application, the preparation method of the ceramic powder comprises: mixing the boron carbide ceramic powder with a sintering aid by ball milling to obtain the ceramic powder.

[0025] According to some embodiments of the present application, the sintering aid comprises titanium carbide and Ti3AlC2.

[0026] According to some embodiments of the present application, the content of the sintering aid in the boron carbide matrix is 5wt%-20wt%.

[0027] The primary factor for selecting the sintering aid is to sinter the boron carbide to be dense. By hot pressing method, it can be fully dense. When Ti3AlC2 is used as a sintering aid, it can be sintered and densified at 1700℃ by plasma discharge. Without hot pressing, the metal carbide needs to be sintered and densified at 2100℃, and the content is larger. Therefore, different sintering aids and contents can be selected according to the existing experimental conditions.

[0028] According to some embodiments of the present application, the polymer solution comprises a polymer and a solvent, and the polymer in the solvent is 0.1g-0.15g per milliliter.

[0029] According to some embodiments of the present application, the polymer solution comprises a polymer and a thermoplastic polyurethane, and the mass ratio of the polymer and the thermoplastic polyurethane is 1-10:1.

[0030] According to some embodiments of the present application, the polymer solution comprises a polymer and a thermoplastic polyurethane, and the mass ratio of the polymer and the thermoplastic polyurethane is 5-10:1.

[0031] According to some embodiments of the present application, the polymer solution comprises a polymer and a thermoplastic polyurethane, and the mass ratio of the polymer and the thermoplastic polyurethane is 5:1.

[0032] Because the thermoplastic polyurethane has a certain elasticity, replacing the polymer component can obtain a more elastic fiber.

[0033] According to some embodiments of the present application, the polymer comprises at least one of polyether sulfone and polyacrylonitrile.

[0034] According to some embodiments of the present application, the solvent comprises at least one of N-methyl pyrrolidone and N,N-dimethylformamide.

[0035] In the preparation method of the present application, the principle of wet spinning is used. The function of the polymer solution is to make phase inversion forming by the different solubility of the polymer in two different solvents. First, the polymer (polyether sulfone or polyacrylonitrile) is dispersed in its respective good solvent (N-methyl pyrrolidone or N,N-dimethylformamide). At this time, the long molecular chain of the polymer is opened, and the macroscopic manifestation is that the particles of polyether sulfone or polyacrylonitrile are dissolved. The suspension of the ceramic powder mixed with the polymer solution is immersed in deionized water, and water is a poor solvent for polyether sulfone or polyacrylonitrile. The solvent of polyether sulfone or polyacrylonitrile is more likely to diffuse in water, at which time the polyether sulfone or polyacrylonitrile loses the solvent, the long molecules re-agglomerate, and the macroscopic manifestation is precipitation. Since there is ceramic powder in the solution, the ceramic powder is wrapped and formed during the precipitation process.

[0036] According to some embodiments of the present application, the extrusion speed is 10 mL / h to 20 mL / h.

[0037] The ceramic slurry and the interfacial layer slurry are extruded from the inner needle and the outer needle of the coaxial nozzle, respectively, which can be extruded by a 21G-17G type coaxial needle. The inner needle is the ceramic slurry, and the outer needle is the interfacial layer slurry.

[0038] According to some embodiments of the present application, the pressure of the isostatic pressing is 150 MPa to 250 MPa.

[0039] According to some embodiments of the present application, the pressure holding time of the isostatic pressing is 10 min to 20 min.

[0040] According to some embodiments of the present application, the isostatic pressing comprises primary isostatic pressing and secondary isostatic pressing.

[0041] The function of the primary isostatic pressing is to prevent the sample from cracking during unidirectional pressing. The function of the secondary isostatic pressing is to make the sample more dense due to the pores in the sample after debinding.

[0042] Before the primary isostatic pressing, the process of pressing the boron carbide blank coated with the interfacial layer material can be by arranging the dried fiber blank unidirectionally and uniaxially pressing the blank.

[0043] After the primary isostatic pressing and before the secondary isostatic pressing, debinding is performed first.

[0044] The debinding process can be performed at 500°C to 700°C for 2h to 6h in an argon atmosphere.

[0045] After debinding, hot pressing sintering is performed.

[0046] According to some embodiments of the present invention, the hot pressing sintering temperature is 1900℃~1950℃.

[0047] According to some embodiments of the present invention, the pressure of the hot pressing sintering is 30 MPa to 40 MPa.

[0048] According to some embodiments of the present invention, the holding time for hot pressing sintering is 1h to 2h.

[0049] A third aspect of the invention provides the application of boron carbide composite materials in the manufacture of cutting tools, ballistic protection equipment, and high-temperature ceramic parts.

[0050] The present invention relates to a technical solution for the application of boron carbide composite materials in the manufacture of cutting tools, ballistic protection equipment, and high-temperature ceramic parts, which has at least the following beneficial effects:

[0051] The boron carbide composite material of this invention possesses high damage resistance, a controllable low coefficient of thermal expansion, superior damage resistance and fracture energy, and better machinability. Its performance is further enhanced when used in the manufacture of cutting tools, ballistic protection equipment, and high-temperature ceramic parts. Specifically:

[0052] The boron carbide composite material of this invention, when used to manufacture cutting tools, can resist high temperatures and wear, maintaining the sharpness of the tool. When used in ballistic protection equipment, it can exhibit excellent hardness and ballistic resistance. When used in high-temperature ceramic parts, due to its excellent high-temperature resistance, it can maintain the structural stability and hardness of the ceramic parts under extreme temperatures. Therefore, in applications requiring resistance to high-temperature environments while demanding high wear resistance and corrosion resistance, the boron carbide composite material of this invention can be used to manufacture high-temperature components, such as turbine blades, high-temperature bearings, nozzles, and reactors. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the structure of the boron carbide composite material of the present invention.

[0054] Figure 2 These are the test results of the linear expansion rate of the ceramic sample.

[0055] Figure 3 This is a comparison diagram of the microstructure of pure boron carbide and the composite material of this invention.

[0056] Figure 4 The results are from the three-point bending test of the composite material in Example 5.

[0057] Figure 5 These are the flexural strength test results of the composite materials in Examples 1 and 3.

[0058] Figure 6are the fracture toughness test results of the composite materials of examples 1 and 3.

[0059] Figure 7 is a schematic diagram of a shaped part product. DETAILED DESCRIPTION

[0060] The following are specific embodiments of the present application, and the technical solutions of the present application are further described in combination with the embodiments, but the present application is not limited to these embodiments.

[0061] In some embodiments of the present application, the present application provides a boron carbide composite material, referring to Figure 1 As shown in the figure, the boron carbide composite material of the present application comprises a fibrous boron carbide matrix, and an interfacial layer material is distributed between adjacent fibrous boron carbide matrices, and the interfacial layer material comprises graphene oxide and / or boron nitride.

[0062] It can be understood that the boron carbide composite material of the present application comprises a fibrous boron carbide matrix, and an interfacial layer material is distributed between adjacent fibrous boron carbide matrices, and the purpose of selecting graphene oxide and / or hexagonal boron nitride for the interfacial layer is that the thermal expansion coefficients of these two materials are relatively low (graphene oxide 2.8x10 -6 K -1 , boron nitride 4.5x10 -6 K -1 ), and at the same time have a layered structure, while boron carbide ceramics lack slip systems and are difficult to relax stress by slipping, but slipping can occur between the layers of these two materials, thereby relaxing stress and improving toughness.

[0063] It can also be understood that the boron carbide composite material of the present application has high damage resistance and a controllable low thermal expansion coefficient. Specifically, it has a lower thermal expansion coefficient, and the boron carbide composite material prepared by the method has a lower thermal expansion coefficient at 30-1000℃, and the linear expansion coefficient is ≤5.5x10 -6 K -1 , which is lower than the 6.4677x10 -6 K -1 of the pure boron carbide matrix.

[0064] Further, the boron carbide composite material of the present application has more excellent damage resistance and greater fracture work. The crack propagation around the indentation of traditional bulk boron carbide ceramics is relatively long, and the indentation after pressure retention for 10s under a force of 5kg can cause a fine crack of about 50μm long on the surface of the material. After the indentation is prepared by the same method, the boron carbide composite material of the present application is absorbed after encountering the second phase material and does not propagate to the nearby boron carbide surface, proving that it has higher damage resistance. Through fracture curve calculation, the fracture work of the boron carbide composite material of the present application is as high as 879.93J / m 2 .

[0065] In addition, the boron carbide composite material of the present application has extremely high fracture work, the composite composition hinders the expansion of cracks, and when a low-resistance material is compounded, the processability of the boron carbide can be improved.

[0066] Regarding the brittleness of ceramics, it should be noted that due to the lack of independent slip system in ceramics, the material is difficult to plastically deform to relax stress under stress, and from the microstructure, the root cause of brittleness is the existence of microcracks, which can easily cause stress concentration, and the material will be broken as the cracks expand.

[0067] Regarding the thermal expansion coefficient, it should be noted that due to the phenomenon of expansion and contraction of objects with temperature, the thermal expansion coefficient represents the length change caused by unit temperature change. With the rapid development of aerospace, precision machining, integrated circuits, optical instruments and other fields, higher requirements are put forward for the control of the thermal expansion coefficient of materials. Materials with low expansion characteristics can greatly improve the thermal shock resistance and dimensional stability, and improve the measurement or machining precision; the matching of the thermal expansion coefficients between different components can significantly reduce the thermal stress, thereby prolonging the service life of the device.

[0068] Regarding the fracture work, it should be noted that it can be used as an indicator of material toughness, and the essence is the energy absorbed by material failure, which can more accurately reflect the whole process of material failure.

[0069] In some embodiments of the present application, the linear expansion coefficient of the boron carbide composite material is ≤5.5*10 -6 K -1 .

[0070] In some embodiments of the present application, the fracture work of the boron carbide composite material is ≥800J / m 2 .

[0071] In some other embodiments of the present application, a method for preparing a boron carbide composite material is provided, comprising the following steps:

[0072] Mixing and ball-milling the boron carbide ceramic powder and the polymer solution to obtain a ceramic slurry;

[0073] Mixing and ball-milling the interface layer material and the polymer solution to obtain an interface layer slurry;

[0074] Extruding the ceramic slurry and the interface layer slurry from the inner needle and the outer needle of the same coaxial nozzle, respectively, to obtain a boron carbide blank coated with an interface layer material;

[0075] After the boron carbide blank coated with the interface layer material is pressed into a shape, it is subjected to isostatic pressing and hot-pressing sintering to obtain the boron carbide composite material of the present application.

[0076] It can be understood that the preparation method of the present application does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are easy to obtain, the production cost is low, and the industrial production is easy.

[0077] In the preparation method, the boron carbide ceramic powder is mixed with the polymer solution for ball milling to obtain a ceramic slurry, and the interface layer material is mixed with the polymer solution for ball milling to obtain an interface layer slurry. One portion of the polymer solution can be used to wrap the boron carbide forming, and the other portion of the polymer solution can be used to wrap the graphene oxide or boron nitride forming.

[0078] In some embodiments of the present application, the preparation method of the ceramic powder comprises: mixing the boron carbide ceramic powder with a sintering aid for ball milling to obtain the ceramic powder.

[0079] In some embodiments of the present application, the sintering aid comprises titanium carbide and Ti3AlC2.

[0080] The primary factor for selecting the sintering aid is to sinter the boron carbide to be dense. The sintering aid can be fully densified by hot pressing. When Ti3AlC2 is used as the sintering aid, the boron carbide can be sintered and densified at 1700°C by plasma discharge. Without hot pressing, the metal carbide needs to be sintered and densified at 2100°C, and the content is larger. Therefore, different sintering aids and contents can be selected according to the existing experimental conditions.

[0081] In some embodiments of the present application, the polymer solution comprises a polymer and a solvent, and the polymer in the solvent is 0.1g-0.15g per milliliter.

[0082] In some embodiments of the present application, the polymer solution comprises a polymer and a thermoplastic polyurethane, and the mass ratio of the polymer to the thermoplastic polyurethane is 1-10:1.

[0083] In some embodiments of the present application, the polymer solution comprises a polymer and a thermoplastic polyurethane, and the mass ratio of the polymer to the thermoplastic polyurethane is 5-10:1.

[0084] In some embodiments of the present application, the polymer solution comprises a polymer and a thermoplastic polyurethane, and the mass ratio of the polymer to the thermoplastic polyurethane is 5:1.

[0085] Since the thermoplastic polyurethane has a certain elasticity, the polymer composition can be replaced to obtain a more elastic fiber.

[0086] In some embodiments of the present application, the polymer comprises at least one of polyether sulfone and polyacrylonitrile.

[0087] In some embodiments of the present application, the solvent comprises at least one of N-methyl pyrrolidone and N,N-dimethylformamide.

[0088] In the preparation method of the present application, the principle of wet spinning is used. The role of the polymer solution is to cause phase inversion forming by the different solubility of the polymer in two different solvents. First, the polymer (polyether sulfone or polyacrylonitrile) is dispersed in its respective good solvent (N-methyl pyrrolidone or N,N-dimethylformamide). At this time, the long molecular chains of the polymer are opened, and the macroscopic manifestation is that the particles of polyether sulfone or polyacrylonitrile are dissolved. The suspension of the ceramic powder mixed with the polymer solution is immersed in deionized water, and water is a poor solvent for polyether sulfone or polyacrylonitrile. The solvent of polyether sulfone or polyacrylonitrile is more likely to diffuse in water. At this time, polyether sulfone or polyacrylonitrile loses the solvent, and the long molecules re-agglomerate. The macroscopic manifestation is that polyether sulfone or polyacrylonitrile is precipitated. During the precipitation process, the ceramic powder is wrapped and formed.

[0089] In some embodiments of the present application, the extrusion speed is 10 mL / h-20 mL / h.

[0090] The ceramic slurry and the interfacial layer slurry are extruded from the inner needle and the outer needle of the coaxial nozzle, respectively, which can be extruded through a 21G-17G type coaxial needle. The inner needle is the ceramic slurry, and the outer needle is the interfacial layer slurry.

[0091] In some embodiments of the present application, the pressure of the isostatic pressing is 150 MPa-250 MPa.

[0092] In some embodiments of the present application, the pressure holding time of the isostatic pressing is 10 min-20 min.

[0093] In some embodiments of the present application, the isostatic pressing includes primary isostatic pressing and secondary isostatic pressing.

[0094] The role of the primary isostatic pressing is to prevent the sample from cracking during unidirectional pressing. The role of the secondary isostatic pressing is to make the sample more dense due to the pores in the sample after debinding.

[0095] Before the primary isostatic pressing, the process of pressing the boron carbide blank coated with the interfacial layer material into a block can be by arranging the dried fiber blank unidirectionally and uniaxially pressing the blank into a block.

[0096] After the primary isostatic pressing and before the secondary isostatic pressing, debinding is performed first.

[0097] The debinding process can be performed at 500°C-700°C for 2h-6h in an argon atmosphere.

[0098] After debinding, hot pressing sintering is performed.

[0099] In some embodiments of the present application, the temperature of the hot pressing sintering is 1900°C-1950°C.

[0100] In some embodiments of the present application, the pressure for hot-press sintering is 30-40 MPa.

[0101] In some embodiments of the present application, the holding time for hot-press sintering is 1-2 h.

[0102] In some other embodiments of the present application, the present application provides the use of the boron carbide composite material in the preparation of cutting tools, ballistic protection equipment and high-temperature ceramic parts.

[0103] It can be understood that the boron carbide composite material of the present application has high damage resistance, controllable low thermal expansion coefficient, more excellent damage resistance, greater fracture work, and better machinability. When used in the preparation of cutting tools, ballistic protection equipment and high-temperature ceramic parts, the performance is better. Specifically:

[0104] It can also be understood that the boron carbide composite material of the present application used in the preparation of cutting tools can resist high temperature and wear, and maintain the sharpness of the tool. When used in ballistic protection equipment, it can have excellent hardness and ballistic performance. When used in high-temperature ceramic parts, it has excellent high-temperature resistance and can maintain the structural stability and hardness of the ceramic parts at extreme temperatures. Therefore, in application occasions that require resistance to high-temperature environment and high wear and corrosion resistance, the boron carbide composite material of the present application can be used to manufacture high-temperature parts, such as turbine blades, high-temperature bearings, nozzles, reactors, etc.

[0105] The technical solutions of the present application will be better understood in combination with the specific embodiments below.

[0106] In the embodiments, the raw materials used are obtained from the market. The coaxial needle used for extrusion is a 21G-17G type needle from Huizhi electric spinning.

[0107] Example 1

[0108] In this embodiment, a boron carbide composite material is prepared, which has a fibrous boron carbide matrix, and an interfacial layer material is distributed between adjacent fibrous boron carbide matrices, and the interfacial layer material is graphene oxide.

[0109] The specific preparation method is as follows:

[0110] (1) Mix boron carbide ceramic powder and titanium carbide at a mass ratio of 4:1, and add alcohol with a content of 65% of the total powder for ball milling. After ball milling at a speed of 300 rpm for 12 h on the ball mill, take out, dry in an oven at 80°C, and then sieve through a 60-mesh sieve to obtain boron carbide ceramic mixed powder.

[0111] (2) Polyether sulfone was added to N-methyl pyrrolidone at a ratio of 1.25 g per 1 mL, and the polyether sulfone was completely dissolved by magnetic stirring at room temperature to obtain a polymer solution. The polymer solution prepared at this ratio had a proportion of 0.125 g / mL.

[0112] (3) The powder of (1) was mixed with the polymer solution in (2), and then was taken out after being ball-milled on a planetary ball mill at a speed of 300 rpm for 24 h, and was vacuumed in a vacuum pump for 10 min to remove air bubbles in the ceramic slurry.

[0113] (4) Graphene oxide was ball-mixed with the polymer solution in (2) as an interfacial layer material, and then was ball-milled at 300 rpm for 24 h to prepare a slurry containing 2 vol% of graphene oxide.

[0114] (5) The slurry in (3) was extruded from the inside of a coaxial needle, and the slurry in (4) was extruded from the outside of the coaxial needle, to prepare a fiber blank with a boron carbide matrix and an interfacial layer containing 2 vol% of graphene oxide. After phase inversion for 24 h, the fiber blank was dried in an oven at 60°C.

[0115] (6) The fiber blank with the interfacial layer material obtained in (5) was arranged in a unidirectional manner in a mold with a diameter of 50 mm, and four blocks with a diameter of 50 mm were pressed. The pressing was repeated four times, and the mold was rotated by 90° after each pressing. The preformed ceramic blocks were isostatically pressed in a cold isostatic pressing machine at a pressure of 200 MPa for 15 min. The blocks were heated in an argon atmosphere from room temperature to 500°C at a rate of 2°C / min, and then to 650°C at a rate of 1°C / min and kept for 4 h. The blocks were isostatically pressed again at a pressure of 200 MPa for 15 min. The blocks were heated to 1900°C at a pressure of 30 MPa and kept for 1 h to prepare boron carbide composite ceramics containing 2 vol% of graphene oxide.

[0116] Example 2

[0117] In this example, a boron carbide composite material was prepared, and the difference from Example 1 was that the content of graphene oxide in the slurry in step (4) was 4 vol%.

[0118] Example 3

[0119] A boron carbide composite material was prepared in this example, and the difference from Example 1 is that in step (4), the content of graphene oxide in the slurry is 6 vol%.

[0120] Example 4

[0121] A boron carbide composite material was prepared in this example, and the difference from Example 1 is that the interface layer material is hexagonal boron nitride. In step (4), the content of hexagonal boron nitride in the slurry is 4 vol%.

[0122] Example 5

[0123] A boron carbide composite material was prepared in this example, and the difference from Example 1 is that the interface layer material is graphene oxide.

[0124] The specific preparation method is as follows:

[0125] (1) Mix boron carbide ceramic powder and Ti3AlC2 in a mass ratio of 17:3, and add alcohol with a content of 50% of the total powder for ball milling. After ball milling on the ball mill at a speed of 260 rpm for 24 h, take out and dry.

[0126] (2) Dissolve polyether sulfone in N-methyl pyrrolidone at a ratio of 1 g per 1 mL, and completely dissolve the polyether sulfone in N-methyl pyrrolidone at room temperature by magnetic stirring to obtain a polymer solution. The polymer solution prepared at this ratio has a proportion of 0.1 g / mL.

[0127] (3) Mix the powder of (1) and the polymer solution in (2), and at the same time, ball mill on the planetary ball mill at a speed of 300 rpm for 24 h, and then take out and vacuumize in the vacuum pump for 10 min to remove air bubbles in the ceramic slurry.

[0128] (4) Ball mill graphene oxide as an interface layer material with the polymer solution in (2) to obtain a graphene oxide mixed slurry, and the content of graphene oxide is 6 vol% of the solution volume.

[0129] (5) The size of the selected coaxial nozzle is as follows: the inner diameter of the inner needle is 0.3 mm, the outer diameter is 0.5 mm, the inner diameter of the outer needle is 0.7 mm, and the outer diameter is 1.0 mm. The slurry of (3) is extruded from the inside of the coaxial needle, and the slurry of (4) is extruded from the outside of the coaxial needle. After phase inversion for 24 h, the fiber blank is placed in an oven at 60°C for drying.

[0130] (6) The fiber green body with interface layer material obtained in (5) is placed in a mold with a diameter of 50 mm in a unidirectional arrangement, and is pressed in a uniaxial press at a pressure of 20 MPa for 2 min. The pre-formed ceramic block is isostatically pressed in a cold isostatic press at a pressure of 100 MPa for 15 min. The block after the first isostatic pressing is heated in an argon atmosphere from room temperature to 500°C at a rate of 2°C / min, then to 600°C at a rate of 1°C / min and kept for 4 h. The block is then prepared into boron carbide composite ceramic at 1900°C and a pressure of 30 MPa for 1 h.

[0131] Performance test

[0132] The relevant performance of the composite materials prepared in Examples 1 to 4 was tested with pure boron carbide without a composite interface layer material as a reference.

[0133] Table 1 is the linear thermal expansion test results of boron carbide composite ceramics under different compositions.

[0134] Linear thermal expansion test method: In the Netzsch DIL 402Expedis Classic thermal dilatometer, the sample is cut and polished into a cuboid about 10 mm long, 3 mm wide and 4 mm high. The sample is placed in the tester. First, the influence of the thermal expansion of the instrument during temperature rise is deducted by testing the standard sample. The push rod is pressed against the 10 mm long ends of the sample. At this time, the push rod will maintain a pressure of 0.5 N. When the temperature rises, the sample expands and shrinks. The internal sensor of the device will maintain a pressure of 0.5 N. Therefore, the displacement sensor will test the length change of the sample. In an argon atmosphere, the temperature is raised from 30°C to 1000°C at a rate of 5°C / min. Finally, the average linear thermal expansion coefficient of the sample in the temperature range can be calculated. The specific test standard can refer to GB / T 16535-2008 Fine Ceramic Linear Thermal Expansion Coefficient Test Method: Top Rod Method.

[0135] Table 1 Linear thermal expansion test results of boron carbide composite ceramics under different compositions

[0136]

[0137] Figure 2The linear expansion rates of samples without graphene oxide or boron nitride composites and those composited with graphene oxide and boron nitride were compared at temperatures ranging from 30°C to 1000°C, with the same TiC2 content as a sintering aid. It can be seen that the linear expansion rates of samples composited with boron nitride and graphene oxide were reduced, with the 0.5-6 GO samples showing a significant difference compared to pure boron carbide. Calculations showed that the average coefficient of thermal expansion decreased between 30-1000°C. When a composite material was prepared using 6 vol% graphene oxide with a boron carbide matrix, the coefficient of thermal expansion was 5.43256 × 10⁻⁶. -6 K -1 This is lower than the 6.4677×10 of the pure boron carbide matrix. -6 K -1 .

[0138] Figure 3 In the figures, (a) and (b) show the microstructure of pure B4C bulk material, and (c) and (d) show the microstructure of the composite material prepared in Example 5 of this invention. It can be observed that the crack propagation around the indentation in pure boron carbide ceramic is relatively long. After holding the indentation at 5 kg force for 10 s, a fine crack approximately 50 μm long can be created on the material surface. After preparing the indentation using the same method, from... Figure 3 As can be seen from (d) in the figure, the cracks in the boron carbide composite material prepared by the method of the present invention did not extend to the nearby boron carbide surface after encountering graphene oxide, which proves that its damage resistance is improved.

[0139] A three-point bending test was performed on a sample of pure boron carbide and composite 6 vol% graphene oxide (Example 5) using a mechanical testing machine. The results are as follows: Figure 4 As shown. Figure 4 The plotted image shows the force-displacement curve during the test. In the fracture curve of the pure boron carbide sample, it can be observed that after the load reaches its maximum point, it rapidly decreases. This is because the internal cracks in the material propagate rapidly at this point, leading to complete fracture. In contrast, the sample in Example 3 exhibits a stepped fracture pattern. After reaching the maximum bending force, only partial fracture occurs because some of the internal cracks are absorbed as they propagate into the graphene oxide. The area under the force-displacement curve reflects the fracture work of the entire fracture process. The calculated fracture work of pure boron carbide is 157.21 J / m. 2 The sample in Example 3 increased to 879.93 J / m³. 2 .

[0140] Figure 5 These are the results of the bending strength test. It can be seen that after hot pressing, the mechanical properties of the sample exhibit anisotropy when tested in different directions.

[0141] Figure 6The fracture toughness test result is shown. It can be seen that the conductivity of boron carbide is improved and the resistivity is reduced due to the addition of graphene oxide, so that the difficult-to-process boron carbide can be processed into different shapes.

[0142] The resistivity of the composite materials prepared in Examples 1 to 3 was tested with pure boron carbide without a composite interface layer material as a reference, and the results are shown in Table 2.

[0143] Table 2 Resistivity test results

[0144] Sample No. pure B4C Example 1 Example 2 Example 3 Resistivity (Ω x m) 7.8 x 10 -2 ]] 3.8 x 10 -3 ]] 5.0 x 10 -2 ]]> 3.9 x 10 -3 ]]

[0145] As can be seen from Table 2, the addition of graphene oxide with lower resistivity can reduce the resistivity of the overall composite material, but due to the formation of a graphene oxide grid-like structure inside, the addition content does not present a simple linear change to the overall resistivity of the composite material.

[0146] Figure 7 The figure of various shape samples of the composite material prepared in Example 2 processed on an electric spark cutting machine is shown. Due to the addition of graphene oxide, the overall resistivity of boron carbide is reduced, and it is easier to process into heterogeneous complex shapes on an electric spark cutting machine.

[0147] Finally, it should be noted that in the preparation method of the composite material of the present application, the polyacrylonitrile can be dissolved in N-methyl pyrrolidone or N,N-dimethylformamide to prepare a polymer solution with a concentration of 0.1 g / mL to 0.15 g / mL. Meanwhile, the polymer component can be replaced with polyether sulfone: thermoplastic polyurethane = 5:1, dissolved in N-methyl pyrrolidone to prepare a polymer solution with a concentration of 0.1 g / mL to 0.15 g / mL.

[0148] The sintering aid material can be selected according to different sintering processes and conditions.

[0149] The final sintering process of the ceramic material can be changed according to the sintering requirements of different material systems.

[0150] The present application has been described in detail above in combination with the examples, but the present application is not limited to the above examples, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present application.

Claims

1. A boron carbide composite material, characterized by, The boron carbide composite material comprises fibrous boron carbide matrix, and interface layer material distributed between adjacent fibrous boron carbide matrix, the interface layer material is graphene oxide, the linear expansion coefficient of the boron carbide composite material is less than or equal to 5.5*10 -6 K -1 -1 2 , and the fracture work of the boron carbide composite material is greater than or equal to 800 J / m The boron carbide composite material is prepared by the following method: The boron carbide ceramic powder is mixed with a polymer solution and ball milled to obtain a ceramic slurry; The interface layer material is mixed with a polymer solution and ball milled to obtain an interface layer slurry, and the content of graphene oxide in the interface layer slurry is 6vol%; The ceramic slurry and the interface layer slurry are respectively extruded from the inner needle and the outer needle of a coaxial nozzle to obtain a boron carbide blank coated with the interface layer material; After the boron carbide blank coated with the interface layer material is press-formed, it is subjected to isostatic pressing and hot-pressing sintering to obtain the boron carbide composite material.

2. A method of making the boron carbide composite of claim 1, characterized in that, The method comprises the following steps: The boron carbide ceramic powder is mixed with a polymer solution and ball milled to obtain a ceramic slurry; The interface layer material is mixed with a polymer solution and ball milled to obtain an interface layer slurry; The ceramic slurry and the interface layer slurry are respectively extruded from the inner needle and the outer needle of a coaxial nozzle to obtain a boron carbide blank coated with the interface layer material; After the boron carbide blank coated with the interface layer material is press-formed, it is subjected to isostatic pressing and hot-pressing sintering to obtain the boron carbide composite material.

3. The method of claim 2, wherein, The polymer solution comprises a polymer and a solvent, and the content of the polymer in the solvent is 0.1 g-0.15 g per milliliter; or, the polymer solution comprises a polymer and a thermoplastic polyurethane, and the mass ratio of the polymer to the thermoplastic polyurethane is 1-10:

1.

4. The method of claim 3, wherein, The polymer comprises at least one of polyether sulfone and polyacrylonitrile.

5. The method of claim 3, wherein, The solvent comprises at least one of N-methyl pyrrolidone and N,N-dimethylformamide.

6. The method of claim 2, wherein, The extrusion speed is 10 mL / h-20 mL / h.

7. The method of claim 2, wherein, The pressure of the isostatic pressing is 150 MPa-250 MPa; and / or, the pressure holding time of the isostatic pressing is 10 min-20 min.

8. The method of claim 2, wherein, The temperature of the hot-pressing sintering is 1900 ℃-1950 ℃; and / or, the pressure of the hot-pressing sintering is 30 MPa-40 MPa; and / or, the holding time of the hot-pressing sintering is 1 h-2 h.

9. Use of the boron carbide composite material according to claim 1 in the preparation of cutting tools, ballistic protection equipment and high-temperature ceramic parts.

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