RU2526453C2 - Ceramic composite material based on aluminium-oxygenic ceramics structured by nanostructures tin - Google Patents

Abstract

FIELD: nanotechnology.

SUBSTANCE: invention relates to the field of nanotechnology, in particular to production of high-strength and high-temperature resistant ceramic composite material based on aluminium-oxygenic ceramic structured in the amount of nanostructures (nanowires) TiN, and can be used in engineering, in articles of aerospace engineering, engine-building, metal-processing industry, in the units and details most important and subjected to extreme thermal cycling loads.

EFFECT: new ceramic composite material comprises aluminium-oxygenic matrix and the dispersed phase TiN at a ratio of wt %: Al₂O₃ - 84,1% and TiN - 15,9% with the diameter of TiN nanowires of 5 nm and has high strength properties: tensile strength at 3-point bending is 1262±20 MPa and fracture toughness is 9 MPa/m^1/2, whereby it can be successfully used in the extreme conditions of high temperature cycling loads at temperatures up to 1500°C in air.

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Description

The invention relates to the field of nanotechnology, in particular the production of high-strength and high-temperature resistant ceramic composite material based on alumina ceramics, structured in volume by TiN nanowires, and it can be used in mechanical engineering, including in the most important nodes and parts subject to extreme loads, in particular in aerospace engineering, engine materials, cutting materials for the metal industry, dentistry materials.

At present, composite materials based on a ceramic matrix structured by the dispersed phase of various chemical compositions are known [1-6].

A known method of coating various dispersed materials (filaments, particles with carbides or metal nitrides in the gas phase) [1]. However, the known method does not allow to obtain nanostructures (threads, particles), but offers a method for producing dispersed materials of micron sizes.

A known ceramic composite and the process for its production [2], which consists of particles of inorganic compounds (carbide, nitride, oxide, chromium boride, silicides and oxygen nitride) and particles and threads of Si ₃ N ₄ , Si ₂ N ₂ O or SiO ₂ . However, the known ceramic composite does not describe its mechanical characteristics, and the disadvantage of this method is the inability to obtain nanostructures (filaments, particles), but it offers a method for producing dispersed micron-sized materials.

Known ceramic cutting tool reinforced with filaments [3], which is made on the basis of a composite and relates to materials based on steel with deposited layers including an oxide matrix of 5-50% by volume and a dispersed phase of 10-40% by volume, in the form of uniformly dispersed filaments of carbides, nitrides and / or borides of titanium and / or zirconium. However, the known material has low enough mechanical properties to use it as a structural material. The disadvantage of the proposed ceramic composite is that the material has mechanical properties sufficient for a cutting tool and poor for a structural material.

Known ceramic composite material [4], which can be used in the manufacture of heat-loaded units and parts of promising gas turbine units and engines. Known material includes carbon fibers and a matrix obtained from a composition of the following chemical composition, wt.%: Si 20-35, C 25-40, SiO ₂ 5.5-6.0, HfO ₂ 5-8, SiC - the rest. However, the known material does not possess the necessary mechanical properties (in particular, fracture toughness, tensile strength at 3-point bending, etc.) for using products and parts made on its basis in extreme working conditions and aggressive environments. The disadvantage of the material is the use of the dispersed phase of micron sizes. The material is not structured at the nano level and does not possess the necessary mechanical properties (including fracture toughness, tensile strength at 3-point bending).

A known composite material based on an alumina matrix with a dispersed phase — SiC particles [5], which has a mixture of nano- and micronized particles. This material contains an alumina matrix with nano- and micro-sized particles of SiC. The material is obtained by mixing two powders, one of which is aluminum oxide with a particle size of about 1 μm, and the second is SiC with particles of about 1 μm with a particle size dispersion in the range from 100 nm to 1.9 μm, (The disadvantages of the known composite material are insufficiently high mechanical characteristics, including fracture toughness - K _C, and the tensile strength in three-point bending (σ _mfd) - This is due to the fact that the particles are evenly distributed over the volume of the matrix, in a composite material by mechanical mixing is not in . Possible Not uniform distribution of the disperse phase volume of matrix leads to a decrease of functional material properties, including fracture toughness - K _C, the tensile strength in three-point bending (σ _mfd).

Known composite material based on an alumina matrix with a dispersed phase based on TiN [6]. This patent is the closest achieved technical result to the claimed invention and is selected as a prototype. Moreover, in this patent (CN 102219483) the size of the dispersed phase nanoparticles is not indicated, but it is also indicated that microparticles of the dispersed phase are also present. The authors of the patent CN 102219483 note that the composite material is intended for use as a cutting tool. Consider the closest analogue (patent CN 102219483) can work as a cutting tool, and the maximum temperature of the cutting tool is 1000 ° C. The material we offer can be used in mechanical engineering, including the manufacture of elements and components of gas turbine engines, aerospace equipment, heat-loaded units and parts of promising gas turbine units and engines of gas, oil pumping, transport and energy systems operating in extreme conditions of high thermal cyclic loads at temperatures up to 1500 ° C in air.

From the above data it follows that with the same chemical composition of the composite material (the matrix is Al ₂ O ₃ and the dispersed phase based on TiN) for the closest analogue (patent CN 102219483) and the claimed object, their functional properties differ sharply. In our opinion, the main reason for the decrease in the functional properties of ceramic composite nanomaterials is the presence in the obtained materials of a dispersed phase (particles, for example, TiN) of micron and nanoscale sizes. Indeed, in the closest analogue (patent CN 102219483), the authors write about TiN nanoparticles, but do not prove the percentage of nanoparticles, for example, by dynamic light scattering or electron microscopy. Thus, in the considered patent CN 102219483 contains a mixture of micron particles and nanoscale, as in other, and other patent and literature sources, which do not indicate special conditions for obtaining and evidence of ~ 100% content of particles with sizes from 1 to 100 nm.

On the other hand, it should be noted that in our application the dispersed phase (TiN) is used in the form of nanowires. It is known [8] that scientific and technical data exist that the introduction of nanowires into a ceramic composite material increases the strength of the material.

It should be noted that for ceramics filled with threads (fibers), i.e. reinforced ceramics, it is typical to use fibers close in size to about 0.1 mm in diameter and higher, which leads to the emergence of numerous internal phase boundaries, and prevents a fundamental improvement in the functional properties of the composite.

Reinforcing ceramics with nanowires (provided in our project from 1 nm to 10 nm) TiN can dramatically increase the strength and fracture toughness of ceramics and thereby dramatically improve the mechanical properties of a composite material based on a ceramic matrix at elevated temperatures.

Thus, the application proposed a fundamentally new nanostructured material, in which, due to the production conditions, TiN nanowires (from 1 nm to 10 nm) are obtained, which allows improving the mechanical properties of samples at elevated temperatures (1500 ° C).

Returning to the general characteristics of the application, it should be noted that the technical task is to obtain a composite material based on a ceramic matrix, nanostructured by nanowires of 1-10 nm in size, having high mechanical characteristics and operating under extreme conditions of high thermal cyclic loads at temperatures up to 1500 ° C in air. The claimed invention is free from the shortcomings of the prior art, it is the technical result of improving the mechanical characteristics of the composite material at elevated temperatures (1500 ° C): tensile strength in three-point bending (σ _mfd).

The technical result is achieved by the fact that the proposed composite material consisting of an alumina matrix containing titanium nitride (TiN) in the form of nanowires, while the ratio of the components is as follows, wt.%:

aluminum oxide Al ₂ O ₃ - 84.1%

titanium nitride (TiN) - 15.9%,

with a diameter of TiN nanowires, 5 nm.

In the claimed invention, for the first time, based on an analysis of the array of patent and scientific information on the filing date of the application, it is proposed to use a material containing a dispersed phase in the form of TiN nanowires with a diameter of 5 nm to increase the mechanical properties of a composite material based on an alumina matrix and a dispersed phase.

A feature of the proposed material is the use of the method of surface structuring proposed by one of the authors [7]. Application of this method allows one to obtain material with TiN nanowires. As raw materials used dispersed particles of aluminum oxide (Al ₂ O ₃ ), low molecular weight substances - titanium tetrachloride (TiCl ₄ ) and ammonia (NH ₃ ).

The claimed invention was tested in laboratory conditions of St. Petersburg State University. The results of real-time studies confirming the achievement of a technical result are given in specific examples of the implementation of the claimed invention.

The essence of the claimed invention is illustrated by a specific example of the implementation of the method with tables.

Example 1

Samples of a composite material based on an alumina matrix and a dispersed phase with different TiN contents (wt.%) And different diameters of TiN nanowires (nm) were taken. To compare the mechanical characteristics of the composite materials of the claimed invention and the prototype, table 1 presents the mechanical properties of the composite material based on α Al ₂ O ₃ and the dispersed phase (titanium nitride nanowires) and the prototype material sample.

To investigate the mechanical strength of the compared sample of the ceramic composite material based on α Al ₂ O _3, and the dispersed phase (nanowires titanium nitride), and a sample of material of the prototype was measured tensile strength in three-point bending (σ _mfd) on the tensile testing machine AG - 50KNXD (Japan) in the resource Center for Innovative Composite Materials Technology, St. Petersburg State University. The distance between the supports in the cell of the tensile testing machine was 25 mm (for a sample of length L ~ 40 mm).

Calculating the ultimate strength in three-point bending (aizg) was performed according to the formula: σ = _mfd 3Rl / 2bh ^2, where P - breaking force; b and h are the width and height of the sample, respectively. The fracture toughness (K _C ) was also determined

The strength of chemical interatomic bonds, due to which ceramic materials have high hardness, chemical and thermal resistance, simultaneously determines their low ability to plastic deformation and tendency to brittle fracture (i.e. low crack resistance).

As is known, most ceramic materials have low viscosity and ductility and, accordingly, low crack resistance. The fracture toughness of crystalline ceramics is about 1-2 MPa / m ^1/2 , while for metals it is more than 40 MPa / m ^1/2 . Note that the fracture toughness (K _C ) is a characteristic of the ability of a material to resist the onset of motion and the development of cracks under mechanical and other influences. In the claimed invention, the achievement of a technical result, i.e. the increase in fracture toughness (K _C ) consisted in the use of a ceramic material containing TiN nanowires. A developing crack in ceramics meets nanowires on its way and does not spread further.

The fracture toughness was determined when testing for concentrated (3-point) bending of the specimen with a notch, the bending base was 14.5 mm. The distance between supports for samples with a length of l ~ 40 mm was 25 mm. The notch was made with a diamond circular saw with a cutting edge thickness of 0.4 mm. The error in determining the tensile strength is ± 8%.

As follows from table 1, a composite material based on an alumina matrix and a dispersed phase with different TiN content (wt.%) And different diameter of TiN nanowires (nm) at a certain content of dispersed TiN, can significantly increase the tensile strength in 3-point bending. Moreover, the optimum range of the content of TiN is dispersed in the range of 10 wt.% To 25.1 wt.%, Since it is this range characterized by high values of ultimate strength during 3-point flexural (σ _mfd).

Table 1 Sample nanowire thickness, nm Strength at 3-point bending, MPa The fracture toughness, MPa / m ^1/2 The initial sample of nano α Al ₂ O ₃ - 450 2 sample No. 1 TiN wt.% 3.8 one 1120 ± 20 7 sample No. 2 TiN wt.% 10,1 3 1178 ± 22 9 sample No. 3 TiN wt.% 15.9 5 1262 ± 20 9 sample No. 4 TiN wt.% 25.1 10 1244 ± 20 9 Samples of the prototype (see patent CN 102219483) Al ₂ O ₃ 62.16%; TiN 37, 0%; nano TN-6.38% -37.01%; microns TiN 0-19.13%; 897 9.6

Example 2

Studies have been conducted on the thermal stability of samples for use at 1500 ° C. Samples were calcined at a temperature of 1500 ° C for 10 hours at a load of 5 MPa. Then, studies were again conducted on the fracture toughness of the samples.

Samples of a composite material based on an alumina matrix and a dispersed phase with different TiN contents (wt.%) And different diameters of TiN nanowires (nm) were taken. Table 2, which compares the mechanical properties of samples under thermal loading, shows the fracture toughness during thermal loading of a composite material based on α Al ₂ O ₃ structured by titanium nitride nanowires and a prototype material sample.

The data in table 2 confirm that the obtained ceramic material in the temperature range of 1300-1500 ° C with a load of 5 MPa can ensure stable operation of the material, since the fracture toughness has maximum values and does not change.

table 2 Sample The fracture toughness, MPa / m ^1/2 1300 ° C 1500 ° C sample No. 1 TiN wt.% 3.8 7 7 sample No. 2 TiN wt.% 10,1 9 9 sample No. 3 TiN wt.% 15.9 9 9 sample No. 4 TiN wt.% 25.1 9 9 Samples of the prototype (see patent CN 102219483) there is no data there is no data

As can be seen from the above examples, the inventive ceramic composite material based on alumina ceramics, structured in bulk by TiN nanostructures (nanowires), has significant advantages over known analogues, which, as shown by testing, consist in increasing mechanical strength properties - increasing tensile strength at 3 point bending up to 1262 ± 20 MPa and high fracture toughness values (9 MPa / m ^1/2 ). Testing of the claimed ceramic composite material containing Al ₂ O ₃ and the dispersed phase (titanium nitride nanowires) shows that it can be used in mechanical engineering, including the manufacture of elements and components of gas turbine engines, aerospace equipment, heat-loaded nodes and parts of promising gas turbine installations and engines of gas, oil pumping, transport and energy systems operating under extreme conditions of high thermal cyclic loads at temperatures up to 1500 ° C spirit. The inventive material can be successfully used not only as a cutting tool, for example, in the metalworking industry, but also replace expensive imported materials in dentistry.

List of references

1. US patent 4,810,530 from March 7, 1989

2. Patent EP 0 286 127, 10/19/1994

3. Patent EP 0 283 454 of July 31, 1991

4. Patent RU 2447039 dated 05/10/2010

5. Dong, YL, Xu, FM, Shi, XL, Zhang, ZJ, Yang, JM, Tan, Y., Fabrication and mechanical properties of nano- / micro-sized Al ₂ O ₃ / SiC composites, Materials Science and Engineering A, 2009, v. 504, No. 1-2, p. 49-54

6. Patent CN 102219483 (China) dated May 4, 2011 (prototype)

7. V.M. Smirnov, J. General Chemistry, 2002, v. 72, No. 4, p. 590

8. F. Matthews, R. Rawlings, Composite materials. Mechanics and Technology, Moscow, Technosphere, 2004, 408 pp.

Claims (1)

Ceramic composite material based on an alumina matrix and a dispersed phase, characterized in that the material contains, wt.%: Al ₂ O ₃ - 84.1% and TiN - 15.9% with a diameter of TiN nanowires of 5 nm.