RU2484060C2 - Boron suboxide-based composite materials - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: boron suboxide-based composite material contains boron suboxide and a second phase in bound form, the second phase containing a boride and uniformly distributed in the boron suboxide. The composite material has crack resistance of more than 3.5 MPa·m^0.5, and hardness of more than 25 GPa. The borides are selected from a group comprising borides of group IV-VIII transition metals and borides of platinum group metals. In particular, the boride can be selected from a group comprising borides of iron, cobalt, nickel, titanium, tungsten, hafnium, tantalum, zirconium, rhenium, molybdenum, chromium, manganese and niobium. The boride can also be a boride of a platinum group metal, preferably palladium boride. Furthermore, the second phase can contain one or more oxides. According to the disclosed method of producing the composite material, a boron suboxide source is brought into contact with a boride or source thereof and the obtained mass is sintered at temperature of 1750-1900°C.

EFFECT: obtaining boron suboxide-based materials with high strength and crack resistance.

22 cl, 22 ex, 1 tbl, 4 dwg

Description

Technical field

The present invention relates to a composite material based on boron suboxide (lower oxide).

State of the art

The creation of synthetic superhard materials with hardness values approaching or even exceeding the hardness of diamond is of great interest to material scientists. Diamond with a Vickers hardness of 70 to 100 GPa is the hardest known material, followed by cubic boron nitride (H _V / Vickers hardness / - about 60 GPa) and boron suboxide, referred to herein as B ₆ O. In order monocrystals ₆ About under a load of 0.49 N and 0.98 N, hardness values of 53 GPa and 45 GPa, respectively, are determined, similar to hardness values of cubic boron nitride [9].

It is known that B ₆ O can also be non-stoichiometric, i.e. can exist in the form of B ₆ O _1-x (where x is in the range 0-0.3). Such non-stoichiometric forms are included in the definition of B ₆ O. The strong covalent bonds and the short interatomic bond length of these materials contribute to their exceptional physical and chemical characteristics, such as high hardness, low (mass) density, high thermal conductivity, high chemical inertness and excellent wear resistance [12]. US Pat. No. 5,330,937 (Ellison-Hayashi et al.) Reported the formation of boron suboxide powders with a nominal composition of B ₃ O, B ₄ O, B ₆ O, B ₇ O, B ₈ O, B ₁₂ O, B ₁₅ O and B ₁₈ O. Potential industrial applications are discussed in Japanese Patent No. 7034063 (Kurisuchiyan et al.) And US Pat. No. 5,456,735 (Ellison-Hayashi et al.) And include use in grinding (grinding) wheels, abrasives and cutting tools.

Several technologies are used to obtain boron suboxide, and they include methods such as the interaction of elemental boron (B) with boron oxide (B ₂ O ₃ ) under conditions of sufficiently high pressure and high temperature [1]. US 3660031 (Holcombe Jr. et al.) Mentions other methods for producing boron suboxides, for example, by reducing boron oxide (B ₂ O ₃ ) with magnesium or by reducing zinc oxide with elemental boron. However, each of these known methods has disadvantages that inhibit the possibility of using this material in industry. For example, in the reduction of B ₂ O ₃ with magnesium, a solid solution of magnesium and contaminants of magnesium boride in the suboxide are obtained, while the reduction of magnesium oxide with boron gives only a relatively small yield of boron suboxide and is very ineffective. US Pat. No. 3,660,031 (Holcombe Jr. et al.) Discloses the preparation of B ₇ O by reduction of zinc oxide by elemental boron at temperatures of 1200 ° C.-1500 ° C. It is reported that the hardness value of this material under a load of 100 g is 38.2 GPa, and the density is 2.6 g · cm ^-3 . Crack resistance (fracture toughness) of this material is not considered.

Petrak et al. [3] investigated the mechanical and chemical characteristics of hot pressed B ₆ O and presented microhardness values of 34–38 GPa. US Pat. No. 5,330,937 (Ellison-Hayashi et al.) Discloses the preparation of B ₆ O with the addition of magnesium (approximately 6%), which yields average Knoop hardnesses of KHN _{100 of} 34-36 GPa.

Attempts have been made to improve the mechanical properties of В ₆ О, primarily its crack resistance, by creating composites based on В ₆ О with other solid materials, such as diamond [4], boron carbide [5], and CBN (cubic boron nitride, Eng. cBN) [6]. Composites containing diamond and CBN were created under conditions of very high temperature and pressure. The goal was to create pseudobinary systems of composites that are more durable at grain boundaries (at grain boundaries) than systems made of pure B ₆ O. Even if high hardness values were recorded for composites (H _V - about 46 GPa), the crack resistance did not exceed 1 again 8 MPa · m ^0.5 . In this case, the best value was obtained with composites В ₆ О-кНБ.

WO 2007/029102 and [7] (Shabalala et al.) Disclose the creation of composites based on B ₆ O with aluminum compounds, which led to the formation of an aluminum borate phase at the grain boundary. The crack resistance was approximately 3.5 MPa · m ^0.5 with a corresponding hardness of 29.3 GPa. The aluminum phases present in the composite are soft and, although they can increase the crack resistance of the resulting composite, they do not contribute to an increase in the hardness of the composite as a whole. In addition, in addition to crystalline aluminum borate, a chemically unstable amorphous phase rich in boron oxide and microporosity was formed, which subsequently leads to a decrease in hardness [10, 11]. A method for producing a composite includes coating boron suboxide particles with a metal and sintering these metallized particles. The only valid example in the description of the invention relates to a second phase or phase of aluminum borate as a binder.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a composite material based on boron suboxide, comprising boron suboxide and a second phase in which the second phase contains boride.

In this description, the term "second phase" means everything that includes a composite material, except boron suboxide, moreover, it can be fully or partially crystalline or amorphous and may include two or more thermodynamic phases.

In addition, any reference to "boride" means monoboride, diboride and any other type of boride.

Boride can be selected from the group comprising transition metal borides of the fourth to eighth groups of the periodic system of elements. In particular, the boride may be selected from the group consisting of borides of iron, cobalt, nickel, titanium, tungsten, hafnium, tantalum, zirconium, rhenium, molybdenum and chromium.

It may also be a platinum group metal boride, preferably palladium boride.

The amount of boride present in the composite material varies depending on the nature of the boride and the required characteristics of the composite. As for solid borides, such as ZrB ₂ , HfB ₂ , W ₂ B ₅ (this boride has a uniformity region that includes WB ₂ ), Mo ₂ B ₅ , CrB ₂ , TiB ₂ , ReB ₂ , TaB ₂ and NbB ₂ , then boride is usually present in an amount up to 50% by volume of the composite. As for softer borides, such as borides of nickel, cobalt, iron, manganese, palladium and platinum, the boride is preferably present in an amount up to 10 vol.% Of the composite.

The second phase may also contain one or more oxides. This may be a rare earth metal oxide and, preferably, a rare earth metal oxide selected from the group consisting of scandium, yttrium, which is preferred, and elements of a number of lanthanides, or it may be a mixture of rare earth oxides. In addition, it can be a metal oxide from groups IA, IIA, IIIA and IVA of the periodic system of Mendeleev's elements. Preferred oxides of this type are, for example, Al ₂ O ₃ , SiO ₂ , MgO, CaO, BaO or SrO. The second phase may contain a mixture of these oxides.

Boron suboxide may be in the form of (macro) particles or granules. The boron suboxide particles or granules themselves are on average preferably small and can have a size in the range of 100 nm to 100 μm, preferably 100 nm to 10 μm.

Fine-grained boron suboxide can be obtained, for example, by grinding the material that is the source of boron suboxide. If grinding is carried out in the presence of a grinding agent containing iron or cobalt, then a certain amount of iron and (or) cobalt is introduced into the sintered material. As for the iron-free material, the milled powder can be washed with hydrochloric acid or the milling can be carried out using aluminum oxide tanks and grinding balls. It was found that to remove some excess of B ₂ O ₃ or H ₃ BO _3, it is better to rinse the milled powder in warm water or alcohols.

The composite material of the invention includes boron suboxide, usually in the form of particles or granules, and a second phase in a bound, coherent form. The content of the second phase in volume percent is preferably less than the content of boron suboxide, and it is evenly distributed in boron suboxide. The second phase may be amorphous or partially crystalline.

The invention provides a composite material containing boron suboxide and boride and having both high crack resistance and high hardness. In particular, this composite material typically has a crack resistance of more than 3.5 MPa · m ^0.5 in combination with a Vickers hardness (H _V ) of more than 25 GPa. The crack resistance of this composite is preferably more than 3.5 MPa · m ^0.5 , and more preferably at least 4.0 MPa · m ^0.5, and even more preferably at least 5.0 MPa · m ^0.5 . The crack resistance (K _IC ) referred to herein was measured with an indenter indented, typically with a load of 5 kg. To determine the characteristics of the samples B ₆ O, discussed below, used the average of five obtained from the measurements. K _{IC was} determined by DCM using the Anstis equation [8]:

$$K_C=\delta {\left(\frac{E}{H}\right)}^{\frac{\mathrm{one}}{2}}\frac{\mathrm{<figure-callout\; id="3"\; label="P\; c"\; filenames="00000005.png"\; state="\{\{state\}\}">P\; </figure-callout>}}{c^{}}\left(\mathrm{one}\right)$$

where E is Young's modulus (elastic modulus), H is hardness, and δ is a constant that depends only on the indenter geometry. For this Young's modulus, 470 GPa was used. For a standard diamond pyramidal indenter, Vickers Anstis et al. Set the value δ = 0.016 ± 0.004 as the calibration constant, which was also used for these measurements.

The hardness of the composite material is preferably more than 25 GPa and more preferably at least 30 GPa. Vickers hardness was measured by applying a 5 kg load when pressed. The average of the five measured hardness values was used to characterize the samples of the composite based on B ₆ O.

Figure 1 shows the preferred lower threshold values in the range of hardness and crack resistance of the composite materials proposed in the present invention, in comparison with the known materials based on boron suboxide. It is assumed that the increased crack resistance of these types of composites can be due to many different factors, such as a change in the direction of the crack due to internal stresses, a mechanism for stopping (blocking) the crack that occurs in the formed second phases, and changes in the nature of the composition and properties at the boundaries between particles ₆ A. In addition, it was found that the actual sealing of the composite material during manufacture is improved by using a second phase which comprises an oxide ed ozemelnogo metal, alone or in admixture with other oxide or boride. Compaction can be over 95% of theoretical density. In particular, compaction of 98% -99% has been achieved. If oxide is present in the second phase, compaction can be achieved under milder temperature and pressure conditions.

The addition of oxide chemically stabilizes the amorphous grain boundary and increases the wear resistance of the composite. Such an amorphous grain boundary is formed as a result of the reaction between the oxide and B ₂ O ₃ during the liquid compaction phase. Together, they form a liquid oxide phase, which during cooling turns into a glass phase (i.e., an amorphous oxide grain boundary). To increase the wear resistance of the material, its chemical resistance and resistance to high temperatures, a low content of B ₂ O ₃ at the grain boundary is preferable. The molar ratio of B ₂ O ₃ / (B ₂ O ₃ + other oxides) is preferably less than 60, more preferably less than 30, and even more preferably less than 20.

The composite material proposed in the invention can be created by the following steps: providing a source of particles or granules of boron suboxide; contacting the source of boron suboxide with boride or a compound capable of forming boride to create a reactive mass and sintering the reactive mass to obtain a composite material based on boron suboxide. This method is a second feature of the invention.

Sintering preferably takes place at a relatively low temperature and under low pressure, i.e. at a pressure of less than 200 MPa and at a temperature not exceeding 1950 ° C. Preferably, low pressure sintering methods are used, such as hot pressing (GP), gas sintering under pressure, isostatic hot pressing (IGP), or spark plasma sintering (IPS). The IPS method is characterized by very fast heating and short exposure periods in isothermal conditions, in particular, a heating rate of 50-400 degrees Kelvin / min and exposure time in isothermal conditions of not more than 5 minutes. The hot pressing method is characterized by a heating rate of 10-20 degrees Kelvin / min and a holding time in isothermal conditions of about 15-25 minutes, usually 20 minutes.

Before sintering, boron suboxide can be mixed with the components necessary to obtain a second phase. Or, before sintering, boron suboxide can be coated with components of the second phase.

Upon contact with boron suboxide and subsequent sintering, the component for the second phase may be in the form of boride. Or, this component may be in the form of oxide or in another suitable form, which during sintering is converted into boride.

Boron suboxide for pre-sintered reaction mass is usually used in the form of particles or granules and preferably has an average grain size in the range from 100 nm to 20 microns, and more preferably in the range from 100 nm to 10 microns.

The composite material proposed in the invention can be used in cutting work and in parts subject to wear. In addition, it can be crushed to the formation of small solid particles and used in abrasive work. Moreover, this composite can be used for coating armor / defenses, for example, protecting against damage by firearms and, in particular, for body armor.

Brief Description of the Drawings

Below the invention is described in more detail with reference to the accompanying drawings, which show:

figure 1 is a graph showing comparative values of hardness and crack resistance for composites based on B ₆ O proposed in this invention, and known materials of this type;

figure 2 - image of the sintered composite, created on the basis of B ₆ About with the addition of 10 wt.% TiB ₂ , 2.0 wt.% Al ₂ O ₃ and 2.0 wt.% Y ₂ O ₃ obtained using scanning electron a microscope (example 5);

figure 3 - image of a sintered composite based on B ₆ O with additives of 4 wt.% WO ₃ , 2.0 wt.% Al ₂ O ₃ obtained by SEM and showing the precipitated W ₂ B ₅ phase (white phase ) with a particle size in the submicron range and partially polished oxide grain boundary (example 4);

figure 4 - includes 5 images of samples based on pure B ₆ O and B ₆ O with additives, hot pressed, obtained using SEM (white phase - Pd ₂ B, and gray phase - B ₆ O; dark spots - residual pores).

Description of Embodiments

The invention is further illustrated by the following examples. Table 1 gives an overview of these materials and for comparison includes their measured hardness and fracture toughness characteristics. Both terms are used in these examples: "second phase" and "grain boundary phase". These terms are used interchangeably and refer to the same phase.

In this description of the invention, the term "second phase" means everything that includes a composite material, except boron suboxide, which may be fully or partially crystalline or amorphous and may include two or more thermodynamic phases.

Example 1

The starting powder B ₆ O was milled using a jet mill. The average particle size after grinding was 2.3 μm. The milled powder B ₆ O was added 2 wt.% Al ₂ O ₃ (including wear of alumina balls), 2 wt.% Y ₂ O _3, 2 wt.% ZrO ₂ (i.e. TZP, stabilized with 3 moles of yttrium oxide) and 0.53 wt.% MgO in isopropanol and grind for six hours using an attritor mill with balls of Al ₂ O ₃ . A second sample was prepared without the addition of Y ₂ O ₃ . The milled mixture was dried using a rotary evaporator, and then placed in a graphite mold (matrix) coated with hexagonal NB and sintered in argon using the IPA method at a heating rate of 50 ° K / min and a holding time of 5 minutes.

Received a fully compacted composite, including particles of boron suboxide, in which the second phase is evenly distributed. In the sample containing Y ₂ O ₃ , along with an amorphous grain boundary, borides ZrB ₂ and ZrB _{12 were formed} . In the sample without the addition of Y ₂ O ₃ , an additional crystalline phase containing Al ₁₈ B ₄ O _{33 was} detected by X-ray diffraction. MgO together with residual B ₂ O ₃ and a small amount of Al ₂ O ₃ formed an amorphous phase of the intergranular boundary. Such an amorphous phase of the intergrain boundary is more stable than that formed only with Al ₂ O ₃ (Shabalala). A typical feature consisting in the formation of micropores was not observed, as a result of which the hardness values were higher. ZrO _{2 is} converted to ZrB ₂ and partially ZrB ₁₂ . It should be mentioned that the maximum values for ZrB ₁₂ are slightly different compared to the standard values, this indicates that a part of yttrium or aluminum can be dissolved in the lattice.

The cross-sectional surface of the sample was ground, and then, using a Vickers indenter, they were tested for hardness and crack resistance. The hardness under a load of 0.4 kg was approximately 36.9 GPa, and the crack resistance was approximately 4 MPa · m ^0.5 .

Examples 2-4

Boron suboxide composites were prepared under the same conditions as described in Example 7, but replacing ZrO ₂ with HfO ₂ , WO _3, and TiB _2, respectively, in the ratios indicated in Table 1. Compaction was carried out at a temperature of 1850 ° C and 1900 ° C . At a temperature of 1850 ° C, a density of 96-98% was observed. At a temperature of 1900 ° C, a density of more than 98% was observed. In Example 8, the same density was observed both at the first and at the second temperature, this indicates that when ZrO ₂ is added, the compaction characteristic is slightly better than when HfO ₂ or WO _{3 is} added.

A certain amount of Al ₁₈ B ₄ O ₃₃ and boride were also formed in these samples. The formation of microporosity, as in WO 2007/029102 (Shabalala et al. And [9]), did not occur, which indicates an increase in the stability of the phase of the grain boundary. In addition to the oxide phase, borides were also formed in all examples (HfB ₂ , W ₂ B ₅ , which is a composition with a region of uniformity, and is also sometimes referred to as WB ₂ - both W ₂ B ₅ and WB _{2 are used} , since the detailed determination of lattice constants (parameters) was not performed).

Examples 5-7

Boron suboxide composites were prepared under the same conditions as those described in Example 1, but by mixing the milled powder with 10% TiB ₂ in Example 5 or 5% TiH ₂ and 2% Al ₂ O ₃ (including wear of aluminum oxide balls during grinding) in example 6. The composite in example 7 was obtained by direct reaction sintering, using B (boron) and TiO ₂ as starting materials.

The materials, density, phase compositions and characteristics are shown in Table 1. These data showed that the addition of Y ₂ O ₃ / Al ₂ O ₃ significantly enhances the compaction. Compaction of additive compositions can be completed at a temperature of 1850 ° C, while compaction of pure B ₆ O powders at this temperature is possible only up to 95% of the theoretical density. The same density as in the case of pure material can be achieved at temperatures 50-100 ° C lower. Rapid compaction of the material with additives Y ₂ O ₃ / Al ₂ O ₃ begins at a temperature of 1350-1370 ° C, while compaction of pure material begins only at 1450 ° C. The microstructures of materials with the addition of Y ₂ O ₃ / Al ₂ O ₃ show the presence of such a liquid, since crystalline phases of the grain boundary (second phase) were not detected. Images obtained with a scanning electron microscope show a uniform distribution of Y ₂ O ₃ / Al ₂ O ₃ additives in ternary (three-row) compounds. The grain size of the material cannot be determined, but from microphotographs obtained by SEM, we can conclude that the grain size does not exceed 1 μm, i.e. grain growth does not occur.

Adding 10 wt.% TiB ₂ in the composition In ₆ About + Y ₂ O ₃ / Al ₂ O ₃ does not change the characteristics of the seal.

Figure 3 shows the microstructure of the material of example 10, showing that the particle size of TiB ₂ is in the range of 1-2 μm and visible oxide grain boundary.

The microstructure of the material with additives WO ₃ (example 9) is shown in Fig.4. The material has an almost 100% density and the formation of borides is visible. The particle size of the released borides is less than 1 micron.

These data prove the possibility of creating dense superhard materials based on В ₆ О without high pressure. A stronger compaction of these materials compared to pure B ₆ O is associated with the formation of a liquid phase during compaction.

Examples 8-11

B ₆ O powder was obtained by synthesis from boric acid and an amorphous boron powder as described in the literature. The average particle size of the synthesized powder was 1-2 μm. PdCl _{2 was} used as a source for the deposition of Pd on B ₆ O powder. PdCl ₂ (in a mass corresponding to 2 or 5 vol.% Pd) was dissolved in 1 M HCl and B ₆ O powder was added. This mixture was stirred and dried using a rotary evaporator. Dried Pd / B ₆ O powders were loaded into an aluminum oxide bath and placed in a tube furnace. The furnace was heated to 400 ° C for 1 hour before the decomposition of PdCl ₂ with the formation of Pd. The furnace was cooled to room temperature.

For all hot pressing experiments, a single axis hot pressing press was used. Hot pressing was carried out in an argon medium. For hot pressing, a plunger made of HDD was used (hexagonal boron nitride, English - hBN) and a graphite mold with an insert from HDD. Samples were obtained with a diameter of 18 mm and a height of 3-4 mm. Pd / B ₆ O powders were hot pressed at temperatures up to 1900 ° C and under a pressure of 50 MPa. The composition and compaction parameters of the samples are shown in table 1. Figure 4 includes 5 images of samples obtained by hot pressing of pure B ₆ O and B ₆ O with additives obtained by SEM.

In ₆ O with the addition of 5 vol.% Pd, they were first hot pressed at 1600 ° C under a pressure of 50 MPa for 30 minutes. This sample (16B ₆ O5Pd) had an open porosity of 26.7% and a density of 1.75 g / cm ³ . The SEM image clearly showed high porosity. Measurements to determine the mechanical properties were not performed due to the very low density. The density obtained for the hot-pressing sample at 1900 ° C (19B ₆ O5Pd) reached a theoretical density. In addition, grain growth was observed.

The phase analysis showed that the phase of the grain boundary (second phase) is mainly formed by Pd ₂ B. The same phase formed by boride was observed in all other samples obtained by hot pressing of Pd / B ₆ O. In the sample obtained by hot pressing of Pd / B ₆ O at a temperature of 1900 ° C, a hardness of 22.5 GPa was noted, which is much lower than the hardness of pure B ₆ O. However, a very high crack resistance (13.5 MPa · m ^0.5 ) was achieved.

Due to the enhanced grain growth with the addition of 2 vol.% Pd, the sintering temperature was reduced. When sintering for 20 minutes at a temperature of 1750 ° C, a completely dense sample was also not obtained, but this sample was better than the sample with the addition of 5 vol.% Pd sintered at 1600 ° C (see table 1). The SEM image clearly showed high porosity (7.3%). As a result of hot pressing at 1800 ° C, an almost completely compacted material was obtained. This specimen had a hardness of Hv _{5 of} 28 GPa and a crack resistance of 5.1 MPa · m ^0.5 . These values were higher than those obtained with sample 175B ₆ O2Pd sintered at a temperature of 1750 ° C.

The density values of these materials showed that compaction occurs in the temperature range 1750 ° C-1900 ° C. Both samples, densified at 1750 ° C and 1900 ° C, showed some residual porosity. During compaction, the formation of Pd ₂ B took place even at a sintering temperature as low as 1600 ° C. This proves that Pd reacts with B ₆ O to form a liquid phase containing boron (the softening temperature of Pd ₂ B is 994 ° C). However, compaction occurs only at temperatures above 1600-1700 ° C. SEM images of the samples showed that insufficient wetting may be the cause of this, at least at low temperatures. The strong grain growth at hot pressing temperatures (1800 ° C-1900 ° C) confirms that at least at high temperatures B ₆ O dissolves in the formed liquid, which contributes to sintering, since it reduces the temperature at about 100 ° C at which dense samples to be prepared. During cooling, the resulting liquid recrystallized, forming Pd ₂ B at the grain boundaries, as seen in the X-ray diffraction patterns.

The hardness recorded with sample 19B ₆ O5Pd was lower than with sample 18B ₆ O2Pd. A decrease in the amount of Pd ₂ B and a decrease in sintering temperature led to an increase in hardness (Table 1). In addition, it is important to note that hardness can be measured under a load of 5 kg. The values presented for B ₆ O-based composites in the literature were obtained under a maximum load of 200 g, with the exception of Shabalala, which presented hardness values under a load of 0.5 kg and 5 kg.

The crack resistance obtained for sample 19B ₆ O5Pd was very high (13.5 MPa · m ^0.5 ). However, the hardness decreased to 22 GPa. Reducing the content of Pd significantly increases hardness, but at the same time reduces crack resistance.

Examples 12-22

B ₆ O powder was obtained by synthesis from boric acid and amorphous boron powder by the method described in the literature [7]. The average particle size of the synthesized powder was 1-2 μm. B ₆ O powder was milled in an attritor (friction) mill using steel balls to obtain particles with an average size of 500 nm. Contaminants from steel balls were removed by washing with hydrochloric acid (HCl). Then additives Fe and Cr, Fe, FeO, FeB, Ni, NiO, NiB, Cr, CrO ₃ , CrB ₂ and Co were added to obtain the compositions indicated in Table 1. For all hot pressing experiments, a single-axis hot pressing was used. Hot pressing was carried out in an argon medium. Samples were obtained with a diameter of 18 mm and a height of 3-4 mm. The mixtures were sintered under the conditions indicated in Table 1. High densities could be obtained at 1850 ° C.

These data prove the possibility of creating dense superhard materials based on В ₆ О without high pressure. The phases present in the obtained ceramics, as well as the characteristics obtained by measurement, are shown in Table 1. The second phases were uniformly distributed in the B ₆ O matrix. The grain size ranged from 1 to 5 microns. In Example 12, except for B ₆ O, no crystalline phases were detected (the reason for this is probably the concentration below the detection limit). Regardless of the initial composition (i.e., oxide, metal, or boride), the addition of Fe, Co, Ni, and Pd in the second phase resulted in the formation of boride. Under sintering conditions, these borides are liquid, and such a liquid-metal medium accelerates compaction. During cooling, borides crystallize from the melt. These borides are not as solid as TiB ₂ , and therefore a minimum amount of these additives is recommended, preferably within 1-2% by volume. If, in addition, stable oxides are present in the composition, then such oxides lead to the formation of a separate oxide melt, which can increase the toughness and compaction.

Claims (22)

1. A composite material based on boron suboxide, comprising boron suboxide and a second phase in a bound form, the second phase containing boride and uniformly distributed in boron suboxide, with a fracture toughness of the composite material exceeding 3.5 MPa · m ^0.5 , the hardness of the composite material exceeds 25 GPa and borides are selected from the group including transition metal borides of the fourth to eighth groups of the Periodic system of elements and borides of metals of the platinum group. 2. The composite material according to claim 1, wherein the boride is selected from the group consisting of borides of iron, cobalt, nickel, titanium, tungsten, hafnium, tantalum, zirconium, rhenium, molybdenum, chromium, manganese and niobium. 3. The composite material according to claim 1, wherein the platinum group metal boride is palladium boride. 4. The composite material according to claim 1, in which the boride is a solid boride and is present in an amount up to 50 vol.% Of the composite material. 5. The composite material according to claim 4, in which the boride is selected from the group comprising ZrB ₂ , HfB ₂ , w ₂ s ₅ , Mo ₂ B ₅ , CrB ₂ , TiB ₂ , ReB ₂ , TaB ₂ and NbB ₂ . 6. The composite material according to claim 1, in which boride is present in an amount up to 10 vol.%. 7. The composite material according to claim 6, in which the boride is selected from the group comprising borides of nickel, cobalt, iron, manganese, palladium and platinum. 8. The composite material according to claim 1, in which the second phase also contains one or more oxides. 9. The composite material of claim 8, in which the oxide is a rare earth metal oxide. 10. The composite material according to claim 9, in which the rare earth metal oxide is selected from the group comprising oxides of scandium, yttrium and elements of a number of lanthanides. 11. The composite material of claim 10, wherein the rare earth metal oxide is yttrium oxide. 12. The composite material of claim 8, in which the oxide is an oxide of an element from groups IIA, IIIA and IVA of the Periodic system of elements. 13. The composite material according to item 12, in which the second oxide is selected from the group comprising Al ₂ O ₃ , SiO ₂ , MgO, CaO, BaO and SrO. 14. The composite material of claim 8, in which the second phase contains a mixture of oxides. 15. The composite material according to claim 1, in which boron suboxide is used in the form of particles or granules. 16. The composite material according to claim 1, in which the average grain size of the particles or granules of boron suboxide is in the range from 100 nm to 100 μm. 17. The composite material according to clause 16, in which the average grain size of the particles or granules of boron suboxide is in the range from 100 nm to 10 μm. 18. A method of producing a composite material based on boron suboxide according to claims 1-17, comprising the steps of:
provide a source of boron suboxide,
introducing a source of boron suboxide into contact with boride or a compound capable of forming such boride to create a reactive mass and
sintering the reaction mass to obtain a composite material based on boron suboxide at a temperature of 1750-1900 ° C. 19. The method according to p, in which the reaction mass is sintered under a pressure of less than 200 MPa. 20. The method according to p. 18, in which the reacting mass is sintered at a heating rate of 50-400 K / min and exposure time in isothermal conditions not more than 5 minutes 21. The method according to p, in which the reacting mass is sintered at a heating rate of 8-10 K / min and exposure time in isothermal conditions of 15-25 minutes 22. The method according to p, in which the contacting of boron suboxide with boride or compound is carried out by mixing.

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