RU2484059C2 - Boron suboxide-based composite material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: composite material contains boron suboxide and a second phase which contains a mixture of at least two metal oxides, neither of which is a boron-containing oxide. At least one of the oxides can be selected from a group comprising oxides of group IIA, IIIA and IVA elements. Also, at least one of the oxides can be a rare-earth metal oxide selected from a group comprising oxides of scandium, yttrium and lanthanide elements. The second phase of the composite material can also contain a boride and particularly a boride selected from a group comprising borides of group IV-VIII transition metals. To produce the composite material, boron suboxide grains are mixed with metal oxides and the reaction mass is sintered at temperature of 1740-1900°C and pressure of 200 MPa.

EFFECT: improved crack resistance of the composite material.

22 cl, 13 ex, 1 tbl, 5 dwg

Description

Technical field

The 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 material known, followed by cubic boron nitride (H _V / Vickers hardness / approximately 60 GPa) and boron suboxide, referred to here as B ₆ O. For single crystals of B ₆ O 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 produce 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 Pat. No. 3,660,031 (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 production of B ₆ O with the addition of magnesium (approximately 6%), which yields average Knoop hardness (KHN ₁₀₀ ) of 34-36 GPa.

Attempts have been made to improve the mechanical properties of B ₆ O, primarily its crack resistance, by creating composites based on B ₆ O with other solid materials such as diamond [4], boron carbide [5] and CBN (cubic boron nitride, English 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 ( _Hv about 46 GPa) were recorded for composites, the crack resistance did not exceed 1 again. 8 MPa · m ^0.5 . In this case, the best value was obtained with composites B ₆ O-kNB.

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].

SUMMARY OF THE INVENTION

In accordance with the invention, a composite material based on boron suboxide comprising boron suboxide and a second phase, the second phase containing a mixture of at least two metal oxides, none of which is an oxide containing boron, is created.

In this description of the invention, 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 can include two or more thermodynamic phases.

At least one of the oxides may be selected from the group consisting of oxides of elements from groups IA, IIA, IIIA and IVA of the periodic table of the periodic elements, and in particular, it may be selected from the group consisting of Al ₂ O ₃ , SiO ₂ , MgO, CaO, BaO, and SrO.

In a first embodiment of the invention, at least one of the oxides may be a rare earth metal oxide. The rare earth metal oxide can be selected from the group consisting of scandium, yttrium, which is preferred, and elements from the range of lanthanides, and may also be a mixture of rare earth oxides.

In addition to metal oxides, the second phase may also include an oxide containing boron, for example B ₂ O ₃ or borate.

In a first preferred embodiment of the invention, one of the oxides is Al ₂ O ₃ and the other oxide is selected from the group consisting of SiO ₂ , MgO, CaO, BaO and SrO.

In another preferred embodiment of the invention, one of the oxides is a rare earth metal oxide and the other oxide is selected from the group consisting of Al ₂ O ₃ , SiO ₂ , MgO, CaO, BaO and SrO.

The amount of oxide present in the composite material of the invention varies depending on the desired properties of the composite, in particular hardness and crack resistance, as well as the type of oxide. Typically, a mixture of oxides is present in an amount up to 20% by volume of the composite material. As for many types of oxides, they are usually present in an amount of up to 10 vol.% Of the composite material, and as for other oxides, these oxides are usually present in an amount of up to 5 vol.% Of the composite material.

In addition, the second phase of the composite material may contain boride and, in particular, boride selected from the group comprising transition metal borides of the fourth to eighth groups of the periodic system of elements. Any reference to "boride" means monoboride, diboride and any other type of boride. In particular, the boride can be selected from the group consisting of borides of iron, cobalt, nickel, titanium, tungsten, tantalum, hafnium, zirconium, rhenium, molybdenum and chromium. It may also be a platinum group metal boride, preferably palladium boride. Solid borides, such as TiB ₂ , W ₂ B _5, and ReB ₂ , may be present in the composite material in greater amounts than relatively soft borides, for example borides formed from Fe, Ni, and Co.

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 proposed in the invention includes boron suboxide, usually in the form of particles or granules, and the 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 (uniformly) distributed in boron suboxide. The second phase may be amorphous or partially crystalline.

The invention provides a composite material containing boron suboxide and a mixture of metal oxides, of which at least two oxides do not contain boron, 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 (Hv) 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 the DCM method using the Anstis equation [8]:

$$K_C=\delta {\left(\frac{E}{H}\right)}^{\frac{\mathrm{one}}{2}}\frac{\mathrm{<figure-callout\; id="3"\; label="P\; c"\; filenames="00000003.png"\; state="\{\{state\}\}">P\; </figure-callout>}}{c^{}}\left(\mathrm{one}\right)$$

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 B ₆ O. In addition, it was found that the actual compaction of the composite material during manufacture is improved by using a second phase, which contains a mixture of at least two oxides, none of which is an oxide containing boron. During compaction in the liquid phase, compaction can be in excess of 95% of the theoretical density, and when oxide is added, it can be achieved under milder conditions of temperature and pressure than compaction, which can be achieved in the absence of oxide in the second phase. In particular, a seal of 98-99% has been achieved.

The composite material proposed in the invention can be created by the following steps: providing a source of boron suboxide, preferably in the form of particles or granules; contacting the source of boron suboxide with a mixture of oxides in which at least two oxides do not contain boron 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 50-400K / 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 ° K / min and a holding time in isothermal conditions of about 15-25 minutes, usually 20 minutes.

In accordance with this method, based on the use of oxide, a stable liquid oxide phase is formed during sintering, which is then cooled to form second crystalline and (or) amorphous oxide phases in the final product. Oxides, especially if they are a mixture of Al ₂ O ₃ and SiO ₂ , react with the remaining B ₂ O ₃ and form amorphous phases between particles or granules of boron suboxide.

The addition of mixed oxides 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 oxides and B ₂ O ₃ during the liquid compaction phase. 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.

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.

Although the introduction of these components of the second phase in the form of their oxides before sintering may be preferable, the components of the second phase may also be present in the reaction mass in a different form allowing the formation of oxide (for example, nitrates, carbonates or oxalates forming oxides during decomposition or in the metallic state ), and can be oxidized in the reacting mass during sintering.

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 O with the addition of 2.62 wt.% Al ₂ O ₃ and 2.65 wt.% Y ₂ O ₃ obtained using a scanning electron microscope (SEM);

figure 3 - image of the sintered composite, created on the basis of B ₆ O with additives of 10 wt.% TiB ₂ , 2.0 wt.% Al ₂ O ₃ and 2.0 wt.% Y ₂ O ₃ obtained using SEM;

figure 4 - image of the sintered composite, created on the basis of B ₆ O with additives of 4 wt.% WO ₃ , 2.0 wt.% Al ₂ O ₃ and 0.53% MgO (from powder) obtained by SEM and showing the precipitated W ₂ B ₅ phase (white phase) with a particle size in the submicron range and a partially polished oxide intergranular boundary;

figure 5 - image of the composites of hot pressing, created on the basis of B ₆ O with additives Al-Y-Si, obtained using SEM and showing grain growth at a higher content of SiO ₂ .

Description of Embodiments

The invention is further illustrated by the following examples. The table gives a general idea of these materials and for comparison includes their measured characteristics of hardness and crack resistance. 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 B ₂ O powder was milled using an attritor (friction) mill with steel balls for 50 hours. Iron contaminants were removed by washing in HCl. Then the powder was washed in methanol to remove B ₂ O ₃ present in it. After grinding, the average particle size was 500 nm.

2 wt.% Al ₂ O ₃ and 2.65 wt.% Y ₂ O ₃ in methanol were added to the milled powder and milled for two hours using a planetary mill. The milled mixture was dried using a rotary evaporator, and then placed in a cell made of boron nitride (inside a graphite mold) and sintered using a hot press at a temperature of 1800 ° C and under a pressure of 50 MPa in argon for about 20 minutes . Received a fully compacted composite, including particles of boron suboxide, in which the second phase is evenly distributed. Radiography revealed the absence of a crystalline phase in the second phase. The grain boundary was an amorphous phase of the grain boundary containing Y ₂ O ₃ , Al ₂ O ₃ and residual B ₂ O ₃ .

The cross-sectional surface of the specimen was ground, and then, using a Vickers indenter, they were tested for hardness and crack resistance. Hardness was approximately 33.2 GPa under a load of 5 kg, and crack resistance was approximately 6.3 MPa · m ^0.5 .

The table summarizes the measured characteristics of this composite based on boron suboxide. The hot-pressed B ₆ O-based composite of the invention had higher hardness and crack resistance compared to pure B ₆ O and the composite obtained by Shabalala et al. (WO 2007/029102).

Example 2

A boron suboxide composite was prepared using the same components and conditions as described in Example 1, except that the amount of Y ₂ O ₃ and Al ₂ O ₃ components was halved, while maintaining the ratio between them. The resulting composite was completely densified and was also found to contain Y ₂ O ₃ , Al ₂ O ₃ and residual B ₂ O ₃ . Its hardness was 30.4 GPa, and crack resistance - 6.0 MPa · m ^0.5 .

Example 3

A boron suboxide composite was prepared using the same components and conditions as described in Example 1, except that the components for the second phase included an additional 1.0 wt.% SiO ₂ . The resulting composite was completely densified and included an amorphous phase of the grain boundary containing Y ₂ O ₃ , Al ₂ O ₃ and residual B ₂ O ₃ . Its hardness was 33.5 GPa, and crack resistance - 5.0 MPa · m ^0.5 .

Example 4

The original B ₆ O powder was ground in an ethanol solution using an attritor mill with alumina balls. After grinding, the suspension was dried using a rotary evaporator. In the table, wear of aluminum oxide balls was included in the overall composition of the materials.

2.62 wt.% Al ₂ O ₃ and 2.65 wt.% Y ₂ O ₃ in isopropanol were added to the milled powder and milled for two hours using a planetary mill. The milled mixture was dried using a rotary evaporator, and then a fast spark plasma sintering was carried out using graphite molds (matrices) with thin graphite films. To avoid interaction with graphite, thin graphite films were coated with a suspension of NB (boron nitride, Eng. BN). The milled mixture was sintered using the IPA method at a heating rate of 50K / min, a temperature of 1740 ° C and a pressure of 115 MPa in argon for about 5 minutes. The heating rate was 50K / min. Since they used a non-conductive lining or a coating of hexagonal NB (English hBN), the compaction process was rather a quick hot pressing than IPA, which is characterized by the passage of current through the powder.

Received a fully compacted composite, including particles of boron suboxide, in which the second phase is evenly distributed. 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 was approximately 33.4 ± 0.6 GPa under a load of 0.4 kg, and the crack resistance was approximately 4.3 MPa · m ^0.5 .

Example 5

A boron suboxide composite was prepared using the same components and conditions as described in Example 4, except that the milled mixture was sintered at a temperature of 1800 ° C and a pressure of 80 MPa using the same IPA method as in the example 4. The resulting composite was completely compacted. He had a hardness of 33 GPa under a load of 0.4 kg and a crack resistance of 4 MPa · m ^0.5 .

Example 6

A boron suboxide composite was prepared using the same components and conditions as described in Example 4, except that 2.0 wt.% Al ₂ O ₃ and 2.0 wt.% Y ₂ O were added to the milled powder ₃ and sintered at a temperature of 1850 ° C and under a pressure of 50 MPa. The resulting composite was completely densified and also included Y ₂ O ₃ , Al ₂ O ₃ and some residual B ₂ O ₃ . It had a hardness of 32.1 GPa and a crack resistance of 4 MPa · m ^0.5 .

Example 7

The original B ₆ O powder was milled using a jet mill. The average particle size after grinding was 2.3 μm. 2 wt.% Al ₂ O ₃ , 2 wt.% Y ₂ O ₃ and 2 wt.% ZrO ₂ (i.e., TZP stabilized with 3 mol.% Yttrium oxide) in isopropanol were added to the milled B ₆ O powder and milled for six hours using an attritor mill with balls of Al 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.

In addition to the sample containing Y ₂ O ₃ (example 7a), a sample was obtained that did not contain Y ₂ O ₃ (example 7b). Received a fully compacted composite, including particles of boron suboxide, in which the second phase is evenly distributed. In the sample with the addition of Y ₂ O _3, in addition to ZrB ₂ and, in part, ZrB ₁₂ , an amorphous oxide phase of the grain boundary was observed. In the material of Example 7b, without adding Y ₂ O ₃ , a crystalline oxide phase (Al ₁₈ B ₄ O ₃₃ ) was detected by X-ray diffraction in the second phase. 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, in part, 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 was approximately 36.9 GPa (sample 7b) and 34.2 GPa (sample 7a) under a load of 0.4 kg, and crack resistance was approximately 4 MPa · m ^0.5 .

Examples 8-10

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 the table. Sealing 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 7b, the same density was observed at both the first and second temperatures, indicating a slight improvement in compaction performance when ZrO _{2 was} added, compared to that obtained when HfO ₂ or WO _{3 was} added.

In these samples, without the addition of Y ₂ O ₃ , a certain amount of Al ₁₈ B ₄ O ₃₃ and boride were also formed. 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 (Fig. 4). 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 detailed determination of the lattice constant parameters was not performed). The addition of Y ₂ O ₃ inhibits the crystallization of Al ₁₈ B ₄ O ₃₃ in the amorphous oxide phase of the grain boundary or in the second phase.

Examples 11-13

The boron suboxide composite in Example 11 was prepared under the same conditions as those described in Example 1, except that Y ₂ O ₃ in Example 1 was replaced with SiO ₂ . Examples 12-13 were obtained in the same manner as example 7. The resulting composite was completely densified.

Materials, density, phase compositions and characteristics of all the obtained composites are shown in the table. These data showed that the addition of Y ₂ O ₃ / Al ₂ O ₃ significantly enhances 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 (SEM) 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.

The addition of 10 wt.% TiB ₂ to the composition B ₆ O + Y ₂ O ₃ / Al ₂ O ₃ does not change the compaction characteristic.

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 9C) is depicted in figure 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 B ₆ O 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.

Information sources

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12. Rutz H.L., Day D.E. and Spencer C.F., J. Am. Ceram. Soc., 1990, T. 73, No. 6, p. 1788.

Claims (22)

1. A composite material based on boron suboxide, comprising boron suboxide and a second phase, the second phase containing a mixture of at least two metal oxides, none of which is an oxide containing boron, the second phase being uniformly distributed in boron suboxide and at least one metal oxide is selected from oxides of elements of groups IIA, IIIA and IVA of the Periodic system of elements or is a rare earth metal oxide. 2. The composite material according to claim 1, in which the rare earth metal oxide is selected from the group comprising yttrium oxide, scandium oxide and oxides of elements of a number of lanthanides. 3. The composite material according to claim 1, wherein at least one of the oxides is selected from the group consisting of Al ₂ O ₃ , SiO ₂ , MgO, CaO, BaO, and SrO. 4. The composite material according to claim 1, in which one of the oxides is Al ₂ O ₃ and the other oxide is selected from the group consisting of SiO ₂ , MgO, CaO, BaO and SrO. 5. The composite material according to claim 1, wherein one of the oxides is a rare earth metal oxide and the other oxide is selected from the group consisting of Al ₂ O ₃ , SiO ₂ , MgO, CaO, BaO and SrO. 6. The composite material according to claim 1, in which the second phase also includes boride. 7. The composite material according to claim 6, in which the boride is selected from the group comprising borides of transition metals of the fourth to eighth groups of the Periodic system of elements. 8. The composite material according to claim 7, in which the boride is selected from the group comprising borides of iron, cobalt, nickel, titanium, tungsten, tantalum, hafnium, zirconium, rhenium, molybdenum and chromium. 9. The composite material according to claim 1, in which the mixture of oxides is present in an amount up to 20 vol.% Of the composite material. 10. The composite material according to claim 1, in which the mixture of oxides is present in an amount up to 10 vol.% Of the composite material. 11. The composite material according to claim 1, in which the mixture of oxides is present in an amount up to 5 vol.% Of the composite material. 12. The composite material according to claim 1, in which the boron suboxide is in the form of particles or granules. 13. 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. 14. The composite material according to item 13, in which the average grain size of the particles or granules of boron suboxide is in the range from 100 nm to 10 μm. 15. The composite material according to claim 6, in which boron suboxide is present in an amount of at least 50 vol.% Of the composite material. 16. The composite material according to claim 1, the crack resistance of which is more than 3.5 MPa · m ^0.5 . 17. The composite material according to claim 1, the hardness of which is more than 25 GPa. 18. The method of obtaining a composite material based on boron suboxide according to claims 1-17, comprising the stages in which:
provide a source of boron suboxide;
introducing a source of boron suboxide into contact with a mixture of metal oxides in which at least two oxides do not contain boron, or with compounds or metals capable of forming such a mixture of oxides to create a reactive mass; and
sintering the reaction mass to obtain a composite material based on boron suboxide at a temperature of 1740-1900 ° 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. 18, in which the reacting mass is sintered at a heating rate of 10-20 K / min and exposure time in isothermal conditions of 15-60 minutes 22. The method according to p. 18, in which the said contacting of boron suboxide with a mixture of oxides, or compounds, or metals is carried out by mixing.

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