WO2020202878A1 - Zirconium boride/boron carbide composite and method for manufacturing same - Google Patents

Abstract

To provide: a high-density zirconium boride/boron carbide composite having a Vickers hardness H_v of 23 GPa or more and a fracture toughness value K_IC of 9.0 MPa•m^1/2 or more, said zirconium boride/boron carbide being represented by ZrB₂/B₄C; and a method for manufacturing the same. The method according to the present invention comprises: a step for preparing a starting material by mixing an amorphous boron powder with an amorphous carbon powder to give a molar ratio B:C of (3.6-6.5):1; a step for weighing a ZrB₂ powder in such an amount as to give a theoretical ratio by volume to B₄C, which is synthesized from the starting material, ZrB₂/B₄C of 10/90-60/40 vol% and mixing with the starting material to give a mixed powder; and a step for molding the mixed powder using a die to give a molded article and then sintering the obtained molded article to thereby simultaneously synthesize and sinter the ZrB₂/B₄C composite.

Description

Zirconium boro / boron carbide composite and its manufacturing method

The present invention, zirconium boride / carbide boron _(ZrB 2 _{/ B} 4 C) composites, particularly Vickers hardness _{H v} is at least 23 GPa, fracture toughness value _{K IC} is 9.0 MPa ^{· m 1/2} or more dense ZrB ₂ / B 4 relates _C composite and a manufacturing method thereof.

Zirconium borohydride (ZrB ₂ ), which is an ultra-high temperature heat-resistant ceramic (UHTC) that has recently attracted attention in the field of engineering ceramics, is a covalent material having a high melting point of T _m = 3200 ° C., and is currently a UHTC for spacecraft. However, since it is a difficult-to-sinter material, it has been difficult to produce a dense and high-density sintered body.
For example, in Patent Document 1 below, a predetermined amount of Zr powder, a predetermined amount of tungsten (W) powder, and a predetermined amount of B powder are wet-mixed and then pressure-molded to obtain a molded product, and the molded product is discharged. A method for producing tungsten-added ZrB ₂ by plasma sintering [also known as pulse energization pressure sintering method] is disclosed. However, Vickers hardness (H _v) of the sintered body obtained using this manufacturing method is 20.7GPa at maximum, the mechanical properties further improve, to be particularly improve the strength properties at high temperatures It is desired.

Regarding UHTC that can be used in the atmosphere, the production of composites of ZrB ₂ / SiC, ZrB ₂ / B ₄ C, and ZrB ₂ / LaB ₆ mainly based on the metal borohydride ZrB ₂ has been studied. Since the high melting point compound is covalently bondable, it is difficult to sinter, and it is difficult to prepare a high-density sintered body. It is difficult to produce a high-density sintered body even by using a method (Pulsed Electric-current Pressure Sintering: PECPS).

Boron carbide (B ₄ C) is known as a material having a light weight (theoretical density D _x = 2.515 Mg · m ^-3 ) and a high melting point (T _m = 2450 ° C.), and is diamond or cubic nitride. Since it has a hardness (Vickers hardness H _v : 29 to 33 GPa) next to boron (c-BN), a composite composed of both ZrB ₂ and B ₄ C is also a material that has the potential to be used as UHTC. It is one.
However, _{B 4} to C is also difficult to sinter the material of covalent, the production of _ZrB 2 / _{B 4} C composite added to the ZrB ₂ requires high temperature and pressure that 2050 ~ 2150 ℃ / 30 ~ 50MPa , It is manufactured at high cost, and there are few reports of its production.

Japanese Unexamined Patent Publication No. 2008-297188

The present invention, Vickers hardness _{H v} is at least 23 GPa, fracture toughness value _{K IC} is an object of the present invention to provide a 9.0 MPa ^{· m 1/2} or more dense _ZrB 2 / _{B 4} C composite. Further, an object of the present invention is also to provide a manufacturing method of ZrB 2 / _B 4 _C composite having excellent physical properties mentioned above.
The present inventors have, as a result of various investigations, the carbon C of amorphous particles, boron B amorphous powder were homogeneously mixed in a predetermined molar ratio, and this mixture and ZrB ₂ powder When a green compact is prepared by mixing at a predetermined volume ratio and molding, and the green compact is pulsed and pressure-sintered (PECPS), a self-propagating high-temperature synthesis is performed during the PECPS heat treatment. : SHS) is induced, the temperature inside the sample rises above the external heating temperature, thereby, it has found that a composite of dense sintered is sintered ZrB 2 / _B 4 _C can be produced, and completed the present invention ..
Further, the present inventors have obtained a ZrB ₂ / B ₄ C composite having a volume ratio of 10/90 to 60/40 of ZrB ₂ / B ₄ C obtained by using the above production method, and the ZrB ₂ / B ₄ C composite has a Vickers hardness. It was also found that it is a high-density ceramic having excellent mechanical properties of H _v 23 GPa or more and a fracture toughness value of 9.0 MPa · m ^1/2 or more.

_ZrB 2 / _{B 4} C composite resolvable present invention the above problems, the Vickers hardness _{H v} is at least 23 GPa, fracture toughness value _{K IC} is at 9.0 MPa ^{· m 1/2} or more, zirconium boride / The theoretical volume ratio of boron carbide is 10/90 to 60/40 vol%.

Further, the present invention provides a _ZrB 2 / _{B 4} C composite having the above physical properties, the volume ratio of the theoretical zirconium boride / boron carbide is 40/60 ~ 60 / 40vol% , bending at 1000 ~ 1600 ° C. It is characterized in that the intensity σ _b is 500 MPa or more.

Further, _ZrB 2 / _{B 4} C composite of the present invention, the Vickers hardness _{H v} is at least 29 GPa, fracture toughness value _{K IC} is at 9.3 MPa ^{· m 1/2} or more, theoretical zirconium boride / boron carbide The volume ratio of the above is 20/80 to 50/50 vol%.

Further, the production method of the present invention for producing a ZrB 2 / _B 4 _C composite having the above physical properties,
Amorphous boron powder and amorphous carbon powder are mixed so as to have a molar ratio of B: C = (3.6 to 6.5): 1 (13.4 to 21.6 atomic% C). The process of preparing a starting material consisting of amorphous boron and amorphous carbon,
The zirconium boborate powder was weighed so that the theoretical volume ratio with the boron carbide synthesized from the starting material was ZrB ₂ / B ₄ C = 10/90 to 60/40 vol%, and the starting material was used. The process of mixing to obtain a mixed powder,
A step of performing mold molding using the mixed powder to obtain a molded product having a desired shape, sintering the obtained molded product, and synthesizing and simultaneously sintering a zirconium boride / boron carbide composite is included. It is characterized by.

Further, the present invention provides a _ZrB 2 / _{B 4} production method of C composite having the above characteristics, the sintering, in a vacuum of 10 Pa, a sintering temperature of 1800 ~ 2000 ° C., pressure of 10 ~ 100 MPa It is characterized by pulse energization pressure sintering under the condition of holding time of 5 to 30 minutes.

Further, the present invention provides a _ZrB 2 / _{B 4} production method of C composite having the above characteristics, the volume ratio of the theoretical of the ZrB ₂ and _{B 4} C is in the range of 20/80 ~ 50 / 50vol% It is also characterized by that.

By using the production method of the present invention, a high hardness and high fracture toughness composite having a composition of ZrB ₂ / B ₄ C = 10/90 to 60/40 vol%, which has not been reported in the past, can be produced in a short time with energy saving. Moreover, its mechanical properties (Vickers hardness _{H v)} also show a high degree of hardness 23.5 ~ 32.7GPa according to _{ZrB 2 / B 4 C = 10} /90 ~ 60 / 40vol% of the composition. Further, according to the present invention, it is possible to supply a composite having a high temperature bending strength of about 650 MPa or more from room temperature to 1600 ° C.

ZrB 2 / _B 4 is a flowchart showing a procedure in an example of the manufacturing method of the present invention for the production of _C composite, manufacturing conditions used in Examples are also shown together. It is an SEM image of the ZrB ₂ powder used as a starting material, and is an image taken at a magnification of 1000 times in the upper photograph and 2000 times in the lower photograph. It is a graph which shows the relative density of the green compact after uniaxial pressing, cold isostatic pressing (CIP), and the sintered body after PECPS. It is an XRD pattern of a sample corresponding to ZrB ₂ / B ₄ C = 50/50 vol% composition sintered at various PECPS temperatures, and the sintering temperature is 1600 ° C., 1700 ° C., 1800 ° C., 1900 ° C. in order from the bottom. .. ₃ is an SEM image of the fractured surface of ZrB ₂ / B ₄ C = 50/50 vol% composite sintered at various temperatures (1600 ° C., 1700 ° C., 1800 ° C., 1900 ° C.). It is a graph which shows the bulk density and the relative density of a sintered sample. An XRD pattern of a sample sintered at 1900 ° C. with different ZrB ₂ compositions. 3 is an SEM image of a fractured surface of a sintered sample with different ZrB ₂ compositions. It is a graph which shows the relationship between the ZrB ₂ content, the relative density, and the ZrB ₂ crystal grain size of the sintered body sintered at 1900 ° C. Of the sintered body sintered at 1900 ° C., is a graph showing the ZrB ₂ content, the Vickers hardness _{H v,} the relationship between the fracture toughness value _{K IC.} It is a graph which shows the result of the high temperature bending strength measurement of the sintered body (ZrB ₂ / B ₄ C = 30/70, 40/60, 50/50, 60/40 vol% composition) sintered at 1900 ° C.

First, a description will be given of each step in the _ZrB 2 / _{B 4} production method of C composites of the present invention. FIG. 1 is a flowchart showing a procedure in an example of the manufacturing method of the present invention.
In the first step, the amorphous boron powder and the amorphous carbon powder have a molar ratio of (3.6 to 6.5): 1 (13.4 to 21.6 atomic% C), preferably (3). Weighed so that it was 9.9 to 5.2): 1 (16.4 to 20.4 atomic% C), more preferably 4.4: 1, and mixed (preferably wet mixing) to carry out amorphous. A starting material in which quality boron and amorphous carbon are uniformly mixed is prepared. At this time, commercially available products can be used as they are as amorphous boron and amorphous carbon, and as boron powder, It is preferable to use one having an average particle size of about 1.5 μm, and it is preferable to use a carbon powder having an average particle size of about 30 nm.
In the above-mentioned wet mixing of amorphous boron and amorphous carbon, it is preferable to mix in alcohol (for example, ethanol) for a certain period of time using an alumina mortar and pestle, but the solvent is limited to this. It's not something.

In the next step, ZrB ₂ is based on the theoretical volume of boron carbide (B ₄ C, theoretical density 2.515 Mg · m ^-3 ) synthesized from the above mixture of amorphous boron and amorphous carbon. / B ₄ C = 10/90 to 60/40 vol% of zirconium borohydride (ZrB ₂ ) powder (average particle size: about 3 μm) is prepared, and this ZrB ₂ is added to the starting material and mixed. And obtain a mixed powder. At this time, it is preferable to carry out dispersion treatment in a solvent such as water or alcohol using, for example, an ultrasonic homogenizer to uniformly disperse ZrB ₂ and then perform drying.

In the final step, molding is performed using the mixed powder obtained in the above step to obtain a molded product having a desired shape, and the obtained molded product is sintered to synthesize a ZrB ₂ / B ₄ C composite at the same time. Sinter.
Uniaxial mold molding (uniaxial press) is generally used as a means for forming the molded body in this step, but the present invention is not limited to this, and the molded body is subjected to cold hydrostatic press (CIP) treatment or the like. After increasing the density, it is preferable to perform pulse energization pressure sintering. Further, in the present invention, it is preferable to heat the molded product before pulse energization pressure sintering in a vacuum to remove water and adsorbed gas on the surface of the fine particles constituting the molded product.
In the present specification, "synthetic simultaneous sintering" refers to a dense sintered body (ZrB ₂ / B ₄ C composite) from a homogeneous mixture of starting materials (a mixture of B and C containing a specific amount of ZrB ₂ ). It shall indicate that it is produced.

When performing pulse energization pressure sintering by the production method of the present invention, it can be carried out using a commercially available pulse energization pressure sintering apparatus.
In the case of pulsed energization pressurization sintering, under uniaxial pressurization (10 to 100 MPa), a large pulsed DC current (several tens to several hundreds of 100A to 1500A: this current value changes depending on the size of the sample) at a low voltage (several V). ) Is poured into a carbon plunger mold to induce a spark discharge phenomenon in the molded body, and high energy can be instantly generated between the particles to sinter the sample. Diffusion and self-burning synthesis (SHS) occur. Then, a dense sintered body (high density, fine crystal grain size) with suppressed grain growth is obtained by high-speed temperature rise (50 to 100 ° C./min) and short-time sintering (5 to 30 minutes) under high pressure. be able to.

In the present invention, boron B and microparticle powders of carbon C of amorphous, by pulse current pressure sintering a mixed powder obtained by mixing with zirconium boride ZrB ₂ powder, when Atsushi Nobori utilizing energy produced at the time of generating is _{B 4} C from B and C, and a relatively mild heat treatment conditions of 1900 ℃ / 50MPa / 10 min, it is possible to generate a _{B 4} C by the self-combustion synthesis. In the present invention, (4 · B + C) fine particles are arranged in the gap between the ZrB ₂ particles during molding, and at the time of PECPS, they also play a role as a binder that holds the ZrB ₂ particles together with the synthetic simultaneous sintering of B ₄ C. As a result, a dense sintered body can be obtained.

The pulse energization pressure sintering in the production method of the present invention is performed in a vacuum of 10 Pa or less under the conditions of a sintering temperature of 1800 to 2000 ° C., a pressing force of 10 to 100 MPa, and a holding time of 5 to 30 minutes. It is preferable, and more preferable conditions for pulse energization pressure sintering are a sintering temperature of 1850 to 1950 ° C., a holding time of 7 to 15 minutes, a pressing force of 30 to 70 MPa under a vacuum of 10 Pa or less, and 1900 ° C./50 MPa / The condition of 10 minutes is particularly preferable. At this time, if the pressing force is less than 10 MPa, the sintering density becomes low, and conversely, if it exceeds 100 MPa, the strength of the mold used for pulse energization pressure sintering has an upper limit and cannot be used. Further, when the sintering temperature is less than 1800 ° C., the density becomes low, and conversely, when the sintering temperature exceeds 2000 ° C., grain growth tends to occur, which is not preferable. The holding time is 5 to 30 minutes for sufficient compaction.

In the present invention, the ZrB _2, volume ratio _{B 4} C, which is synthesized from a mixture of amorphous B and amorphous C is in the range of _{ZrB 2 / B 4 C = 10} /90 ~ 60 / 40vol%, particularly in the case of the range of 20/80 ~ 50 / 50vol%, the Vickers hardness 29GPa or more, fracture toughness 9.3 MPa ^{· m 1/2} or more _ZrB 2 / _{B 4} C composite is obtained.
In contrast, even if the same low-temperature short-time sintering as described above using a mixture of commercial sintering-resistant of B _{4 C} powder and ZrB ₂ powder, Vickers hardness to produce a more ceramic 20GPa It is not possible.
Further, the ZrB ₂ / B ₄ C composite of the present invention obtained by using the above manufacturing method has excellent high temperature bending strength, and in particular, ZrB ₂ / B ₄ C = 40/60 to 60/40 vol%. In the case of composite, it exhibits high-temperature bending strength of 500 MPa or more in the temperature range of 1000 to 1600 ° C.
Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to Examples.

[Preparation example of high-density _ZrB 2 / _{B 4} C Composite
Commercially available amorphous boron (average particle size P _s : 1.5 μm) and amorphous carbon (average particle size P _s : 30 nm) are weighed so that the molar ratio is B: C = 4: 1. A starting material was prepared by wet mixing in ethanol for 30 minutes using an alumina milk pot and a milk stick.
On the other hand, the theoretical volume ratio (ZrB) of commercially available ZrB ₂ powder (average particle size P _s : 3 μm) to boron carbide B ₄ C synthesized from the above-mentioned mixture of amorphous boron and amorphous carbon. ₂ / _B 4 C) 0 / 100,10 / 90, 20/80, 30 / 70,40 / 60, 50 / 50,60 / 40,70 / 30 and were weighed so as the starting material which The mixture was added to and dispersed in ethanol using an ultrasonic homogenizer (frequency 20 kHz, output 300 W) for 30 minutes, and dried to obtain a mixed powder.

Then, after sizing the mixed powder thus obtained, uniaxial mold molding (20 mmφ, 75 MPa, addition of 3% acrylic / PVA) was performed, and then cold hydrostatic pressure (245 MPa, 3 minutes) was pressed. .. Then, the obtained molded body is heat-treated (950 ° C./2 h / vacuum), and further, using a commercially available pulse energization pressure sintering apparatus (using SPS Syntex Co., Ltd./SPS-510A), 10 Pa or less. under vacuum, the sintering temperature 1900 ° C., holding time 10 min, subjected to pulse current pressure sintering under a pressure 50 MPa, the 100 ° C. / minute heating rate condition, the sintered body _(ZrB 2 / _{B 4} C composite) Got
Regarding the evaluation of the manufactured sintered body, the phase characteristics were evaluated by the XRD pattern, the morphology was observed by the SEM image, and the Vickers hardness (JIS R 1610: 2003 Fine Ceramics Hardness Test Method, Load: The mechanical properties were evaluated by the fracture toughness value (measured at 2 kgf) and the fracture toughness value (using the IF method of the room temperature fracture toughness (toughness) test method for fine ceramics). For the bending strength σ _b at high temperature, a bending tester (Autograph-AG-X Plus, manufactured by Shimadzu Corporation) was used, and the bending strength at three points in the temperature range from room temperature to 1800 ° C in argon gas. Evaluated by test.

FIG. 2 is a scanning electron microscope (SEM) image (measured by FE-SEM, JEOL Ltd., JSM 7000) of ZrB ₂ powder (manufactured by JEOL Ltd.) used as a starting material. Is an image taken at a magnification of 1000 times, and the lower photograph is an image taken at a magnification of 2000 times.
From the photograph of FIG. 2, the particle size of ZrB ₂ powder used in Example approximately 2 ~ 4 [mu] m: an (average of about 3 [mu] m), it small variation was confirmed.

Table 1 below, when changing the ZrB ₂ composition, uniaxial pressing samples, CIP treated samples for the sintered samples, bulk density _{(D obs),} relative density _(D r), Vickers hardness _{(H V} ), fracture toughness _{(K IC)} are summarized. The relative density ( _Dr ) is measured by the so-called Archimedes method, in which the theoretical density is 100% and the bulk density is determined from the weight of the test piece in the air and the weight in water, and this bulk density is measured. The value obtained by dividing by the theoretical density is expressed in%.

FIG. 3 is a graph showing the relative densities of the green compact after the uniaxial press, the cold hydrostatic press (CIP), and the sintered body after the PECPS, and the theoretical density of the green compact is D _x (ZrB _2). ) = 6.119 Mg · m ^-3 , D _x (B) = 2.37 Mg · m ^-3 , D _x (C) = 1.8 Mg · m ^-3 .
From the results of FIG. 3, the relative density of the green compact obtained by the uniaxial press was 48.8 to 58.9% in the range of the ZrB ₂ content of 10 to 100 vol%, but the CIP treatment was performed. In some cases, it was confirmed that the value increased from 52.9 to 64.7%.
The relative density is higher in the case of ZrB ₂ / (4B + C) composite than in the case of ZrB ₂ (100 vol%) because the B in the gap between the particles of ZrB ₂ having a large particle size has a small particle size. It is probable that C was added and the relative density increased.
The relative density of the sintered body after PECPS showed a high value of 96.7% or more in the range of 0 to 70 vol% of ZrB ₂ .

FIG. 4 is an XRD pattern of a sample corresponding to a ZrB ₂ / B ₄ C = 50/50 vol% composition sintered at various PECPS temperatures (1600 ° C to 1900 ° C), and any of these XRD patterns , _{B 4} C observed peak indicating the production of (▲) found from this that, in the case of PECPS temperature above 1600 ° _C., it _ZrB 2 / _{B 4} C composite from ZrB 2 + (4B + C) mixture powder product It was confirmed that

FIG. 5 is an SEM image of the fractured surface of ZrB ₂ / B ₄ C = 50/50 vol% composites sintered at various temperatures (1600 ° C to 1900 ° C), and the relative densities of each composite are also shown. ing.
In this SEM photograph, the bright part is ZrB ₂ from the analysis (EDS analysis) result using the energy dispersive X-ray Spectrometer for the bright part and the dark part. It was confirmed that the dark part was B ₄ C, and it was confirmed that a very dense composite was obtained when the PECPS temperature was 1900 ° C.

Figure 6 is a graph showing the sintered sample _{(50vol% ZrB 2 / 50vol%} B 4 C), and sintering temperature, bulk density, a relationship between the relative density of the ZrB _2, bulk density and relative density Is also shown.
From the experimental results of FIG. 6, when performing PECPS at a temperature of 1900 ° C., the _ZrB 2 / _{B 4} C composite, the relative density of 99.8% or more dense ceramic is prepared, with a composition consisting of ZrB ₂ is It was confirmed that the density was only 70.3%.

FIG. 7 shows the XRD patterns of sintered samples (PECPS temperature: 1900 ° C.) with different ZrB ₂ compositions, and all of these XRD patterns show peaks (at the positions of the black diamonds) indicating the formation of B ₄ C. Peak) was observed, and from this, when PECPS was performed at a temperature of 1900 ° C., from the ZrB ₂ + (4B + C) mixed powder in the composition of ZrB ₂ / B ₄ C = 40/60 to 70/30 vol%. it was confirmed that ZrB ₂ / _{B 4} C composite is produced.

8 is different from ZrB ₂ composition had a sintered sample (PECPS Temperature: 1900 ° C.) is a SEM image of fracture surface, the relative density of each sintered body are also shown alongside.
From these SEM images, when PECPS was performed at a temperature of 1900 ° C., when the ZrB ₂ content increased (40 → 70 vol%), the relative density decreased slightly (100% → 99.35%), and ZrB ₂ It was confirmed that the crystal particle size (light-colored part) of was increased.

FIG. 9 is a graph showing the relationship between the ZrB ₂ content, the relative density, and the ZrB ₂ crystal grain size of the sintered body sintered at 1900 ° C.
Graph of Figure 9, if PECPS temperature is 1900 ° C., in _ZrB 2 / _{B 4} C composite content ZrB ₂ is 40 ~ 70 vol% composition, relative density of 99% or more of the dense sintered body is obtained, It is shown that as the content of ZrB ₂ increases (40 → 70 vol%), the crystal grain size of ZrB ₂ increases.

Figure 10 is a graph showing the mechanical properties of the sintered body sintered at 1900 ° C. (Vickers hardness H _v and fracture toughness value K _IC).
From the graph of FIG. 10, _ZrB 2 / _{B 4} C composite content ZrB ₂ is 10/90 ~ 60 / 40vol% composition, Vickers hardness _{H v} is at least 23 GPa, the fracture toughness value _{K IC} 9.0 MPa -It can be seen that it is a dense sintered body of m ^1/2 or more.
Further, in the graph of FIG. 10, the composite having a ZrB ₂ / B ₄ C = 20/80 to 50/50 vol% composition has a Vickers hardness H _v 29 GPa or more and a fracture toughness value K _IC 9.3 MPa · m ^1/2 or more. It is a dense sintered body, and the composite with ZrB ₂ / B ₄ C = 30/70 to 40/60 vol% composition has a Vickers hardness of H _v 31 GPa or more and a fracture toughness value of K _IC 9.8 MPa · m ^1/2. It shows that it is the above-mentioned dense sintered body.
On the other hand, the fracture toughness value of ZrB ₂ is 3.5 to 4.2 MPa · m ^1/2 , and the fracture toughness value of B ₄ C is 5.0 MPa · m ^1/2 or less. It was confirmed that the ZrB ₂ / B ₄ C composite obtained by using the above manufacturing method has a larger fracture toughness value than the ZrB ₂ and B ₄ C single-phase ceramics, and has excellent mechanical properties. It was.

FIG. 11 is a graph showing the results of high temperature bending strength measurement of a sintered body (ZrB ₂ / B ₄ C = 30/70, 40/60, 50/50, 60/40 vol% composition) sintered at 1900 ° C. Is.
From the results of FIG. 11, it was confirmed that in the case of a composite of ZrB ₂ / B ₄ C = 40/60 to 60/40 vol%, a high temperature bending strength of 500 MPa or more is exhibited in a temperature range of 1000 to 1600 ° C. .. In the case of a composite having a composition of 30/70 vol%, 40/60 vol%, and 50/50 vol%, the bending strength σ _b at room temperature is about 850 MPa, which is a value (450 MPa) reported so far for monolithic ZrB ₂ ceramics. ) Was found to be about twice as high.
From the above measurement results, the ZrB ₂ / B ₄ C composite of the present invention has a large bending strength at a high temperature of up to 1600 ° C., especially when ZrB ₂ / B ₄ C = 40/60 to 60/40 vol%. It was confirmed that.

In the production method of the present invention, a high melting point, the ZrB ₂ powder is a sintering-resistant material, (3.6 to 6.5): A mixture of amorphous B and C of 1 molar ratio When pulsed energization and pressure sintering is performed, a ZrB ₂ / B ₄ C composite can be produced by synthetic simultaneous sintering, and the composite obtained with a composition of ZrB ₂ / B ₄ C = 10/90 to 60/40 vol% is high. It has a relative density and has high hardness and high fracture toughness.
ZrB 2 / _B 4 _C composite of the present invention, since a material which is excellent in terms of heat resistance, various applications where high hardness and high fracture toughness, heat resistance is desired, for example, the inner wall material and the high-temperature turbine, Fusion It is useful as ultra-high temperature heat-resistant ceramics (UHTC) used for furnace materials of furnaces and outer wall materials of ultra-sonic aircraft outside the atmosphere.

Claims (6)

1. The Vickers hardness H _v is 23 GPa or more, the fracture toughness value K _IC is 9.0 MPa · m ^1/2 or more, and the theoretical volume ratio of zirconium borate / boron carbide is 10/90 to 60/40 vol%. A zirconium boride / boron carbide composite.
2. The first aspect of the present invention, wherein the theoretical volume ratio of zirconium borate / boron carbide is 40/60 to 60/40 vol%, and the bending strength σ _{b at} 1000 to 1600 ° C. is 500 MPa or more. Zirconium boro / boron carbide composite.
3. The Vickers hardness H _v is 29 GPa or more, the fracture toughness value K _IC is 9.3 MPa · m ^1/2 or more, and the theoretical volume ratio of zirconium borate / boron carbide is 20/80 to 50/50 vol%. A zirconium boride / boron carbide composite.
4. A method for producing zirconium boroboroides / boron carbide composites.
   Amorphous boron powder and amorphous carbon powder are mixed so as to have a molar ratio of B: C = (3.6 to 6.5): 1, and amorphous boron and amorphous carbon are mixed. The process of preparing a starting material consisting of
   The zirconium boborate powder was weighed so that the theoretical volume ratio with the boron carbide synthesized from the starting material was ZrB ₂ / B ₄ C = 10/90 to 60/40 vol%, and the starting material was used. The process of mixing to obtain a mixed powder,
   A step of performing mold molding using the mixed powder to obtain a molded product having a desired shape, sintering the obtained molded product, and synthesizing and simultaneously sintering a zirconium boride / boron carbide composite is included. A method for producing a zirconium boride / boron carbide composite.
5. The feature is that the sintering is pulse energization pressure sintering under the conditions of a sintering temperature of 1800 to 2000 ° C., a pressing force of 10 to 100 MPa, and a holding time of 5 to 30 minutes in a vacuum of 10 Pa or less. The method for producing a zirconium borohydride / boron carbide composite according to claim 4.
6. The method for producing a zirconium borohydride / boron carbide composite according to claim 4 or 5, wherein the theoretical volume ratio of ZrB ₂ and B ₄ C is in the range of 20/80 to 50/50 vol%.

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