CN105174966A - Preparation method for in-situ synthesis of CNTs-toughened TiB2-based ultra-high-temperature ceramic material - Google Patents
Preparation method for in-situ synthesis of CNTs-toughened TiB2-based ultra-high-temperature ceramic material Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title claims abstract description 16
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- QFXZANXYUCUTQH-UHFFFAOYSA-N ethynol Chemical group OC#C QFXZANXYUCUTQH-UHFFFAOYSA-N 0.000 claims description 5
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- 238000005452 bending Methods 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 4
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- 229910052783 alkali metal Inorganic materials 0.000 claims description 2
- 150000001340 alkali metals Chemical class 0.000 claims description 2
- 229910052784 alkaline earth metal Inorganic materials 0.000 claims description 2
- 150000001342 alkaline earth metals Chemical class 0.000 claims description 2
- 125000004429 atom Chemical group 0.000 claims description 2
- QDMRQDKMCNPQQH-UHFFFAOYSA-N boranylidynetitanium Chemical compound [B].[Ti] QDMRQDKMCNPQQH-UHFFFAOYSA-N 0.000 claims description 2
- 125000004430 oxygen atom Chemical group O* 0.000 claims description 2
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- 229910016006 MoSi Inorganic materials 0.000 description 1
- 229910010037 TiAlN Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
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- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 description 1
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- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 description 1
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Abstract
The present invention discloses a preparation method for in-situ synthesis of a CNTs-toughened TiB2-based ultra-high-temperature ceramic material. The method comprises: restoring a MezOy / TiB2 catalyst precursor at the constant temperature to obtain a Me / TiB2 composite catalyst; introducing mixing gas of CH4 and N2 into the Me/TiB2 composite catalyst, so that CNTs is grown on the surface of TiB2 powder of the Me/TiB2 composite catalyst in an in-situ manner to obtain CNTs/TiB2 composite powder; and carrying out spark plasma sintering om the CNTs/TiB2 composite powder to obtain the CNTs-toughened TiB2-based ultra-high-temperature ceramic material. According to the method provided by the present invention, the fracture toughness, the thermal shock resistance and other mechanical properties of the TiB2-based ceramic material can be greatly improved.
Description
Technical Field
The invention relates to a preparation method of a composite material, in particular to a CNTs toughened TiB synthesized in situ2A method for preparing a superhigh temperature ceramic material.
Background
Overview TiB2The research history of ceramic materials, which was regarded as important in the last 50-60 years, was difficult to sinter and compact due to extremely strong covalent bonds, TiB2The research on ceramics falls into the valley, so the literature reports remaining at this stage mainly focus on the research on the basic physical properties; since the 80 s, based on TiB2The excellent properties and the advancement of sintering technology, which are considered by more and more researchers to be applied to aerospace materials, are slow to progress due to their extreme brittleness, poor thermal shock resistance and expensive manufacturing cost. It can be seen that the improvement of room temperature fracture toughness and thermal shock resistance to TiB2Ceramic materials are very important.
From the prior published literature reports, the TiB is improved2The fracture toughness of ceramic materials is to avoid large crack sources in the ceramic, which requires an improvement in TiB2The sintering technology of the ceramic is used for inhibiting the abnormal growth of crystal grains and the occurrence of stress concentration as much as possible, thereby obtaining the TiB with high density and low defect2A material. Currently, single phase TiB2The preparation of the ceramic mainly adopts the technologies of pressureless sintering, hot-pressing sintering, self-propagating high-temperature synthesis, Spark Plasma Sintering (SPS) and the like. However, it is difficult to completely eliminate TiB regardless of the sintering end2Microscopic defects in ceramics. Meanwhile, the brittle fracture of the ceramic material is mainly caused by crack propagation, and theoretically, the fracture toughness of the ceramic can be effectively improved by increasing the potential energy required to be overcome by crack propagation, consuming or converting the energy of crack propagation, dispersing the stress at the tip of the crack and the like. To this end, TiB2The toughening mode adopted by the ceramic mainly comprises layered toughening and composite tougheningToughness, etc. For single phase TiB2Ceramics, TiN/TiB2、TiAlN/TiB2、SiC/TiB2The layered ceramic exhibits high toughness, but the layered material is limited by high melting point and interface thermal matching, and a material with excellent comprehensive performance cannot be obtained. The composite toughening is to improve the toughness of the organism by adding a second term or multiple phases, and comprises the following steps: a) particle toughening (MoSi)2、CrSi2SiC, Fe, Ni), all of which are not more than 8.0 MPa. m, although the fracture toughness is improved1/2；b)ZrO2Phase change toughening, the room temperature toughening effect is good, but the effect at high temperature is not obvious, and the application in the aspect of high-temperature structural elements is greatly limited; c) the fiber/whisker is toughened, and the uniform dispersion of the fiber/whisker is difficult to realize; d) self-toughening, just starting, very limited in-situ formed toughening phase, and only native flaky or strip TiB is seen at present2The report of (1).
Aiming at the current situation, the invention provides a CVD method for in-situ generation of CNTs and a preparation method of a discharge plasma sintering technology by combining the excellent toughening effect of Carbon Nanotubes (CNTs), so that the heat-proof material of the hypersonic aerocraft with high temperature resistance, ablation resistance and thermal shock resistance is obtained.
Disclosure of Invention
The invention provides a CNTs toughened TiB synthesized in situ2The preparation method of the ultrahigh-temperature ceramic material can obtain the TiB with high temperature resistance, good fracture toughness and thermal shock resistance2A base ceramic material. The invention also provides the CNTs toughened TiB obtained by the method2A base ceramic material and a method for testing the mechanical property of the ceramic material.
According to the invention, CNTs (carbon nanotubes) is synthesized in situ to toughen TiB2The preparation method of the ultrahigh-temperature ceramic material comprises the following steps:
s1 reduction of Me at constant temperaturezOy/TiB2Catalyst precursor to obtain Me/TiB2A composite catalyst; wherein Me isA metal catalyst, y represents MezOyThe number of oxygen atoms in the oxide molecule, z represents MezOyThe number of Me metal atoms in the oxide molecule;
s2, to Me/TiB2Introduction of the composite catalyst into CH4And N2Mixed gas of (2) to Me/TiB2TiB of composite catalyst2CNTs grow on the surface of the powder in situ to obtain CNTs/TiB2Compounding powder;
s3, CNTs/TiB2The composite powder is subjected to discharge plasma sintering to obtain CNTs toughened TiB2A basic ultra high temperature ceramic material.
Preferably, the method further comprises the following steps performed before step S1:
s01, mixing TiB2Powder addition containing Mex+Uniformly stirring the metal catalyst ions in the aqueous solution, and then dropwise adding a strong base solution Me while stirringx+The metal catalyst ion forms a hydroxide, thus obtaining Me (OH)x/TiB2A binary colloid mixed solution; wherein x represents Mex+The valence state of the metal catalyst ion;
s02, para Me (OH)x/TiB2Filtering the binary colloid mixed solution, and washing to be neutral to obtain Me (OH)x/TiB2A binary colloid;
s03, mixing Me (OH)x/TiB2Drying and grinding the binary colloid to obtain Me (OH)x/TiB2Powder;
s04, calcined Me (OH)x/TiB2Powder to obtain MezOy/TiB2A catalyst precursor.
Preferably, the strong base is a hydroxide of an alkali metal or an alkaline earth metal;
said Mex+The metal catalyst ion is Fe3+X is 3, y is 3, z is 2; or,
said Mex+The metal catalyst ion is Co2+X is 2, y and z are 1; or,
said Mex+The metal catalyst ion being Ni2+X is 2, y and z are 1.
Preferably, Me (OH) is added in step S02x/TiB2Standing the binary colloid mixed solution for 24 hours, filtering and cleaning to be neutral.
Preferably, in step S03, the temperature for drying is 80 ℃.
Preferably, in step S04, Me (OH)xThe powder is placed in an atmosphere protection furnace and calcined for 2 hours at the temperature of 400 ℃.
Preferably, step S1 is specifically: mixing Me with waterzOy/TiB2The catalyst precursor is placed in a constant temperature area of the tube furnace at N2Heating the constant temperature area to a reduction temperature under protection, and closing N2Then introducing H2To MezOy/TiB2Reducing the catalyst precursor to obtain Me/TiB2And (3) compounding a catalyst.
Preferably, the reduction temperature is 500-700 ℃, and the reduction time is 2 hours.
Preferably, step S2 is specifically:
s21 at N2Heating the constant temperature area to 600-1100 ℃ under protection;
s22, introducing CH into the constant temperature area4And N2Keeping the mixed gas for 1 to 3 hours to ensure that the Me/TiB2TiB of composite catalyst2CNTs grow on the surface of the powder in situ to obtain CNTs/TiB2And (3) compounding the powder.
Preferably, CH4And N2The flow rate ratio of (A) is: 50 ml/min-300 ml/min.
Preferably, Me/TiB2CompoundingThe mass fraction of Me in the catalyst is as follows: 5 to 30 percent.
Preferably, when spark plasma sintering is performed, the temperature rise rate is: 100-200 ℃/min, the sintering temperature of the discharge plasma is 1200-1800 ℃, and the sintering pressure of the discharge plasma is as follows: 30 MPa-50 MPa, and the time of spark plasma sintering is 5 minutes-15 minutes.
According to another aspect of the invention, the CNTs toughened TiB obtained according to any one of the technical schemes is provided2A basic ultra high temperature ceramic.
The invention also provides a CNTs toughening TiB obtained according to any one of the technical schemes2The mechanical property test method of the ultrahigh-temperature-based ceramic comprises the following steps:
s41, determining CNTs toughening TiB to be tested2The mass fraction of CNTs in the ultrahigh-temperature ceramic material is as follows: the mass fraction is determined according to equation 1,
In the formula, M1Is CNTs/TiB2Mass of composite powder, M2Is Me/TiB2The mass of the composite catalyst;
s42 CNTs toughening TiB to be tested2Pretreatment of the base ceramic material: cutting the ceramic material to be tested by adopting a linear cutting technology, performing rough grinding and polishing, and then, chamfering four sides of the cut ceramic material to be testedAn angle;
s43, testing mechanical properties: the hardness of the ceramic material to be tested is measured on a Vickers hardness tester, the fracture toughness of the ceramic material to be tested is measured by a unilateral beam method, the bending strength of the ceramic material to be tested is measured by an electronic universal material testing machine, and the mass ablation rate of the ceramic material to be tested is measured by oxyacetylene.
In-situ generation of CNTs toughened TiB in embodiments of the invention2A method of making a base ceramic material comprising: reduction of Me at constant temperaturezOy/TiB2Catalyst precursor to obtain Me/TiB2A composite catalyst; to Me/TiB2Introduction of the composite catalyst into CH4And N2Mixed gas of (2) to Me/TiB2TiB of composite catalyst2CNTs grow on the surface of the powder in situ to obtain CNTs/TiB2Compounding powder; for CNTs/TiB2The composite powder is subjected to discharge plasma sintering to obtain CNTs toughened TiB2A base super ceramic. The method of the invention utilizes the CNTs generated in situ, so that the cracks in the ceramic can deflect and branch, the CNTs can be pulled out and the like when expanding, a large amount of energy is consumed, and the TiB is greatly improved2The fracture toughness and the thermal shock resistance of the base ceramic material; by adopting SPS sintering, the sintering time and sintering temperature can be effectively reduced, and the growth and carbonization of CNTs are inhibited, so that TiB (titanium boride) is obtained2The base ceramic material has better mechanical property.
The invention also provides a CNTs toughened TiB prepared by the preparation method2Ultra high temperature ceramics and with in situ synthesized CNTs toughened TiB according to the invention2All the beneficial effects of the preparation method of the ultrahigh-temperature ceramic material.
The invention also provides a CNTs toughening TiB prepared by the preparation method2A method for testing mechanical properties of ultrahigh-temperature-based ceramics.
Drawings
FIG. 1 shows the in situ synthesis of CNTs toughened TiB2A flow chart of a preparation method of the ultrahigh-temperature ceramic material;
FIG. 2 shows CNTs toughened TiB obtained according to example 2 of the present invention2The micro-morphology of the ultrahigh-temperature ceramic;
FIG. 3 shows CNTs toughened TiB obtained according to example 2 of the present invention2A base ultra high temperature ceramic material;
FIG. 4 shows CNTs toughened TiB obtained according to example 2 of the present invention2Fracture morphology of the ultrahigh temperature ceramic.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings by way of examples of preferred embodiments. It should be noted, however, that the numerous details set forth in the description are merely for the purpose of providing the reader with a thorough understanding of one or more aspects of the present invention, which may be practiced without these specific details.
The invention utilizes CNTs (carbon nanotubes) generated in situ to lead the cracks in the ceramic to deflect and branch when expanding, pull out the CNTs and the like, consume a large amount of energy and further greatly improve the TiB2The fracture toughness and the thermal shock resistance of the base ceramic material; by adopting SPS sintering (spark plasma sintering), the sintering time and sintering temperature can be effectively reduced, and the growth and carbonization of CNTs (carbon nanotubes) can be inhibited, so that TiB (titanium boride) can be obtained2The base ceramic material has better mechanical property.
TiB2Cracks and crack propagation may occur at any position of the base ceramic material in order to effectively avoid TiB2Cracks and crack propagation occur in the base ceramic material, and TiB must be ensured2CNTs are uniformly distributed at any position of the base ceramic material, byThe deflection, the bifurcation, the extraction and the like of the CNTs consume a large amount of energy, increase the potential energy which needs to be overcome by crack propagation, consume or convert the energy of crack propagation, and disperse the stress at the tip of the crack, thereby effectively improving the fracture toughness of the ceramic. Me/TiB2Me metal catalyst in composite catalyst for catalyzing CH4Cleavage to yield CNTs, preferably, Me/TiB2When the mass fraction of Me in the composite catalyst is 5-30%, TiB2The growth condition and the distribution condition of CNTs on the surface of the ceramic powder are better, when Me/TiB2When the mass fraction of Me in the composite catalyst is 15%, TiB2The growth and distribution of CNTs on the surface of the ceramic powder are the best. To make TiB2CNTs are uniformly distributed on the surface of the ceramic powder, and the Me catalyst must be uniformly distributed on the TiB2The surface of the ceramic powder. The invention adopts a chemical vapor deposition method (also called CVD method) to generate Me/TiB in situ2Composite catalyst capable of making Me/TiB2The Me metal catalyst in the composite catalyst is uniformly distributed in the TiB2The surface of the powder. In step S1, MezOy/TiB2The catalyst precursor is placed in a constant temperature area of a closed environment, and is reduced under the constant temperature condition. Oxidants and other ingredients in air or in a closed environment readily react with MezOy/TiB2The reduction process of the catalyst precursor has an influence on the type and content of the product of the reduction reaction. To eliminate these adverse effects, according to a preferred embodiment of the invention, the closed environment is charged with N2And discharging other gas components in the closed environment. For example, Me may bezOy/TiB2The catalyst precursor is placed in a constant temperature area of the tube furnace at N2And raising the temperature of the constant-temperature area to the reduction temperature under protection. Preferably, the reduction temperature is 500 ℃ to 700 ℃, and more preferably, the reduction temperature is 600 ℃. After the temperature of the closed environment is stable, N is closed2Introduction of H2To Me2Ox/TiB2The catalyst precursor is reduced, preferably for 2 hours, to MezOy/TiB2Obtaining Me after the reduction of the catalyst precursor/TiB2And (3) compounding a catalyst. Wherein Me represents a metal catalyst.
To make MezOy/TiB2Me in catalyst precursorzOyIs uniformly distributed in TiB2The surface of the powder, according to a preferred embodiment of the present invention, further comprises, before step S1: preparation of Me by precipitation2Ox/TiB2The catalyst precursor specifically comprises:
s01, mixing TiB2Powder addition containing Mex+An aqueous solution of metal catalyst ions, such as a deionized water solution (e.g., a nitrate salt of Me in deionized water), with continuous stirring, wherein x represents Mex+The valence state of the metal catalyst ion. Dropwise adding a strong base solution in the process of continuous stirring so as to enable the metal catalyst ion Mex+Formation of Me (OH) by chemical reactionx. Me (OH) formed by the reactionxWith TiB added to the solution2Powder interaction to form Me (OH)x/TiB2A binary colloid mixed solution. The chemical reaction principle of this step is shown in formula 2:
Mex++OH-→Me(OH)xequation 2.
According to a preferred embodiment of the invention, the strong alkaline solution is a NaOH solution or a KOH solution. The influence of the choice of the metal salt catalyst is in TiB2Morphology, organization and performance of surface-generated CNTs. Preferably, Mex+The metal catalyst ion is Fe3+X is 3, y is 3, z is 2; fe when dropping strong alkaline solution3+Continuously precipitate as Fe3+When the precipitation is completed, the dropwise addition of the strong alkali solution is stopped.
Preferably, Mex+The metal catalyst ion is Co2+X is 2, y and z are 1; co when dropping strong alkali solution2+Continuously precipitate as Co2+When the precipitation is completed, the dropwise addition of the strong alkali solution is stopped.
Preferably, Mex+The metal catalyst ion being Ni2+X is 2, y, z are1; co when dropping strong alkali solution2+Continuously precipitate as Co2+When the precipitation is completed, the dropwise addition of the strong alkali solution is stopped.
S02, para Me (OH)x/TiB2Filtering and cleaning the binary colloid mixed solution to be neutral. Preferably, Me (OH)x/TiB2Standing the binary colloid mixed solution for 24 hours, filtering again to remove the liquid solution, and then filtering to obtain Me (OH)x/TiB2Cleaning the binary colloid to neutral or nearly neutral to obtain Me (OH)x/TiB2A binary colloid.
S03, Me (OH) obtained in step S02x/TiB2The binary colloid is ground into powder after being dried. In one embodiment of the invention, Me (OH)x/TiB2The binary colloid is placed in a drying box at 80 ℃ for drying treatment.
S04, calcined Me (OH)xPowder to obtain MezOy/TiB2A catalyst precursor. In order to avoid the influence of other gases or active substances in the calcination environment on the calcination process, according to a preferred embodiment of the invention, Me (OH)xThe powder is calcined in an atmosphere-protecting furnace, e.g. in N2Calcining under protection. Preferably, in N2Calcining at 400 ℃ for 2 hours under protection to obtain a catalyst precursor Me required by synthesizing CNTszOy/TiB2。
After the step S1 is finished, stopping introducing H into the closed space2. Step S2 is started. In order to prevent the propagation of cracks in the ceramic material, in step S2, the fracture toughness and thermal shock resistance of the ceramic material can be effectively improved by increasing the potential energy to be overcome for crack propagation, consuming or transforming the energy for crack propagation, dispersing the stress at the crack tip, and the like. It is based on this idea that step S2 of the present invention is developed. The reaction temperature in step S2 is higher than the reaction temperature in step S1, and therefore, in step S2, N needs to be introduced into the sealed space again2And raising the temperature in the closed space to the reaction temperature of the present step, preferably, the present stepThe reaction temperature of the step is 600-1100 ℃. After the temperature in the closed space is stable, CH is introduced into the constant temperature area4And N2The mixed gas of (1). According to a preferred embodiment of the invention, CH4And N2The flow rate ratio of (A) is: 50 ml/min-300 ml/min, when CH4And N2Flow rate ratio of 150 ml/min: 300 ml/min, TiB2The CNTs on the surface of the ceramic powder have the best thickness uniformity and length uniformity. High temperature environment in closed space and Me/TiB2Under the catalytic action of the composite catalyst, CH4The cleavage yields carbon nanotube CNTs. In the reaction process, the reaction time in this step is preferably 1 to 3 hours. CH was turned off after the end of the reaction time4In N at2The constant temperature zone was cooled to room temperature under protection. CNTs produced by cracking in TiB2The surface of the powder grows in situ to obtain CNTs/TiB2And (3) compounding the powder. The brittle fracture of the ceramic material is mainly caused by the expansion of cracks, and the fracture toughness of the ceramic can be effectively improved by the methods of increasing the potential energy required to be overcome by crack expansion, consuming or converting the energy of crack expansion, dispersing the stress at the tip of the crack and the like. In the present invention, CNTs is in TiB2The surface in-situ growth of the powder can lead the cracks in the ceramic to deflect and branch when expanding, the CNTs to be pulled out and the like, consume a large amount of energy and further greatly improve the TiB2The fracture toughness and the thermal shock resistance of the base ceramic material.
S3, CNTs/TiB2The composite powder is subjected to spark plasma sintering (also known as SPS sintering). Preferably, CNTs/TiB are treated under vacuum2And performing spark plasma sintering on the composite powder. Preferably, the temperature rise rate when performing spark plasma sintering is: 100-200 ℃/min, the temperature of spark plasma sintering is 1200-1800 ℃, and the pressure is as follows: 30 MPa-50 MPa, and the time is 5 minutes-15 minutes. For CNTs/TiB2After the composite powder is subjected to spark plasma sintering, the CNTs toughened TiB is obtained2A base ceramic material. By adopting SPS sintering, the sintering time and sintering temperature can be effectively reduced, and the growth and carbonization of CNTs are inhibited, so that the CNTs toughen the TiB2The ultrahigh temperature ceramic material has better mechanical property.
The invention also provides a CNTs toughening TiB obtained by the method2CNTs toughened TiB based ultra high temperature ceramic materials2The components and the preparation method of the raw materials of the ultrahigh-temperature ceramic material refer to the CNTs toughened TiB generated in situ2The method of base ceramic materials will not be described in detail herein.
In order to test the CNTs toughened TiB obtained by the preparation method of the invention2The invention provides a mechanical property testing method of a superhigh temperature ceramic material, which comprises the following steps:
s41, determining CNTs toughening TiB to be tested2Mass fraction of CNTs in the basic ultra high temperature ceramic material. The deflection, bifurcation, and extraction of CNTs can consume a large amount of energy, increase the potential energy to be overcome for crack propagation, consume or convert the energy of crack propagation, and disperse crack tip stress, thus having an important effect on the mechanical properties of ceramics. The mass fraction of CNTs in the CNTs toughened TiB 2-based ultrahigh-temperature ceramic material to be tested is determined firstly before mechanical property test is carried out, so that the mechanical properties of the ceramic materials with different compositions can be compared more accurately. The mass fraction of CNTs can be determined according to equation 1,
In the formula, M1Is CNTs/TiB2Mass of composite powder, M2Is Me/TiB2Quality of the composite catalyst.
The shape and the surface smoothness of the ceramic sample to be tested also have obvious influence on the test result of the mechanical property test. In determining the CNTs toughening TiB to be tested2After the mass fraction of CNTs in the basic ultra-high temperature ceramic material, it is necessary to toughen the CNTs to be tested into TiB2And (4) pretreating the ultrahigh-temperature ceramic material. In step S42, the ceramic material to be tested is cut by using a wire cutting technique, and after rough grinding and polishing, four sides of the cut ceramic material to be tested are chamfered.
The items of the mechanical property test can be determined according to the actual use environment of the ceramic material to be tested. According to a preferred embodiment of the invention, the mechanical properties comprise: hardness, fracture toughness, flexural strength, and ablation rate. In step S43, the hardness of the ceramic material to be tested is measured on a vickers hardness tester, the fracture toughness of the ceramic material to be tested is measured by a single-sided beam method, the bending strength of the ceramic material to be tested is measured by an electronic universal material testing machine, and the mass ablation rate of the ceramic material to be tested is measured by oxyacetylene.
FIG. 2 shows CNTs toughened TiB obtained according to example 2 of the present invention2A micro-topography of the superhigh temperature ceramic.
FIG. 3 shows CNTs toughened TiB obtained according to example 2 of the present invention2Composition diagram of superhigh temperature ceramic, wherein ■ represents TiB2And ● represents CNTs.
FIG. 4 shows CNTs toughened TiB obtained according to example 2 of the present invention2Fracture morphology diagram of the superhigh temperature ceramic.
Compared with the prior art, the method utilizes the CNTs generated in situ, so that the deflection, the bifurcation, the extraction of the CNTs and the like can occur when cracks in the ceramic are expanded, a large amount of energy is consumed, and the TiB is greatly improved2The fracture toughness and the thermal shock resistance of the base ceramic material; by adopting SPS sintering, the sintering time and sintering temperature can be effectively reduced, and the growth and carbonization of CNTs are inhibited, so thatTiB2The base ceramic material has better mechanical property.
The following examples are given for the toughening of the in situ formed CNTs according to the present invention with TiB2The method of the base ceramic material is described in detail.
Table 1 list of the main instruments used in the examples
Table 2 list of main reagents or materials used in the examples
| Name (R) | Purity of | Origin of origin |
| TiB2Powder of | ＞99％ | Shanghai Seawa Material science and technology Co Ltd |
| Ferric nitrate | ＞99％ | Xiamen science development glass instrument limited |
| Cobalt nitrate | ＞99％ | Xiamen science development glass instrument limited |
| Nickel nitrate | ＞99％ | Xiamen science development glass instrument limited |
| Anhydrous ethanol | Xiamen science development glass instrument limited | |
| Sodium hydroxide | ＞99％ | Xiamen science development glass instrument limited |
Example 1
Preparation of Me by precipitationzOy/TiB2Catalyst precursor: mixing TiB2Adding proper amount of Fe (NO) into the powder3)3·9H2Continuously stirring in a magnetic stirrer in the deionized water solution of O, and simultaneously dropwise adding NaOH water solution with certain concentration to Fe3+Completely precipitating, standing the solution for 24 hr, filtering, washing to pH 7 to obtain Me (OH)x/TiB2A binary colloid. Drying the colloid in a drying oven at 80 deg.C, and grinding to obtain Me (OH)xPowder, Me (OH)xThe powder is placed in an atmosphere-protecting furnace at N2Calcining at 400 ℃ for 2 hours under protection to obtain Me (OH)xDecomposing to obtain Me required by synthesizing CNTszOy/TiB2A catalyst precursor.
Formation of CNTs/TiB2Composite powder: weighing a certain mass of MezOy/TiB2The catalyst precursor is put into a constant temperature area of the tube furnace and is positioned in N2Raising the temperature to the reduction temperature of 600 ℃ under protection, and then closing N2Introduction of H2Reduction for 2 hours to obtain Me/TiB2Composite catalyst, after the reaction is completed, H is reacted2Closing and re-introducing N2Raising the furnace temperature to 950 ℃, and introducing CH after the temperature is stable4And N2Mixed gas of (2), CH4And N2Flow rate ratio of 150 ml/min: 300 ml/min, and keeping the temperature for 2 hours to ensure that the CNTs are in TiB2Growing the powder surface in situ; after the reaction is completed, CH is turned off4In N at2Under protection, the sample is cooled to room temperature along with the furnace to obtain CNTs/TiB2And (3) compounding the powder.
And (3) calcining: for CNTs/TiB2The composite powder is subjected to discharge plasma sintering at a heating rate of 200 ℃/min-1Pressurizing to 30MPa, heating to a specified temperature, and then preserving heat at 1600 ℃ for 10 minutes to obtain the sintered CNTs toughened TiB2A base ceramic material.
And (3) testing mechanical properties: firstly, calculating the mass fraction of CNTs in a ceramic material to be tested, then cutting the ceramic material to be tested by adopting a linear cutting technology, and chamfering four edges of the cut ceramic material to be tested after coarse grinding and polishing. Measuring the hardness to be tested on a Vickers hardness tester; measuring the fracture toughness to be tested by adopting a single-edge beam method; measuring the bending strength to be tested by adopting an electronic universal material testing machine; the mass ablation rate to be tested was tested using oxyacetylene and recorded at 3.5MW/m2The highest surface temperature to be tested after 100 seconds of oxyacetylene ablation of heat flux density.
Mass fraction of CNTs to be tested, and CNTs toughened TiB2The mechanical properties of the base ceramic material are shown in table 4.
Examples 2 to 4
The procedure was carried out in the same manner as in example 1 except that the contents shown in Table 3 were used.
TABLE 3 Metal catalyst ions and other Process conditions used in the examples
TABLE 4 CNTs toughened TiB made in the examples2Mechanical property data of base ceramic material
The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention.
Claims (10)
1. CNTs (carbon nanotubes) toughened TiB (titanium-boron) synthesized in situ2The preparation method of the ultrahigh-temperature ceramic material comprises the following steps:
s1 reduction of Me at constant temperaturezOy/TiB2Catalyst precursor to obtain Me/TiB2A composite catalyst; wherein Me represents a metal catalyst, y represents MezOyThe number of oxygen atoms in the oxide molecule, z represents MezOyThe number of Me metal atoms in the oxide molecule;
s2, to Me/TiB2Introduction of the composite catalyst into CH4And N2Mixed gas of (2) to Me/TiB2TiB of composite catalyst2CNTs grow on the surface of the powder in situ to obtain CNTs/TiB2Compounding powder;
s3, CNTs/TiB2The composite powder is subjected to discharge plasma sintering to obtain CNTs toughened TiB2A basic ultra high temperature ceramic material.
2. The method of claim 1, wherein the method further comprises the following step performed before step S1:
s01, mixing TiB2Powder addition containing Mex+Uniformly stirring the metal catalyst ions in the aqueous solution, and then dropwise adding a strong base solution Me while stirringx+The metal catalyst ion forms a hydroxide, thus obtaining Me (OH)x/TiB2A binary colloid mixed solution; wherein x represents Mex+The valence state of the metal catalyst ion;
s02, para Me (OH)x/TiB2Filtering the binary colloid mixed solution, and washing to be neutral to obtain Me (OH)x/TiB2A binary colloid;
s03, mixing Me (OH)x/TiB2Drying and grinding the binary colloid to obtain Me (OH)x/TiB2Powder;
s04, calcined Me (OH)x/TiB2Powder to obtain MezOy/TiB2A catalyst precursor.
3. The method of claim 2, wherein the strong base is a hydroxide of an alkali metal or alkaline earth metal;
said Mex+The metal catalyst ion is Fe3+X is 3, y is 3, z is 2; or,
said Mex+The metal catalyst ion is Co2+X is 2, y and z are 1; or,
said Mex+The metal catalyst ion being Ni2+X is 2, y and z are 1.
4. The method of claim 1, wherein step S1 is performed by: mixing Me with waterzOy/TiB2The catalyst precursor is placed in a constant temperature area of the tube furnace at N2Heating the constant temperature area to a reduction temperature under protection, and closing N2Then introducing H2To MezOy/TiB2Reducing the catalyst precursor to obtain Me/TiB2And (3) compounding a catalyst.
5. The method of claim 4, wherein the reduction temperature is 500 ℃ to 700 ℃ and the reduction time is 2 hours.
6. The method of claim 4, wherein the step S2 is performed by:
s21 at N2Heating the constant temperature area to 600-1100 ℃ under protection;
s22, introducing CH into the constant temperature area4And N2Keeping the mixed gas for 1 to 3 hours to ensure that the Me/TiB2TiB of composite catalyst2CNTs grow on the surface of the powder in situ to obtain CNTs/TiB2And (3) compounding the powder.
7. The method of claim 6, wherein CH4And N2The flow rate ratio of (A) is: 50 ml/min-300 ml/min.
8. The method of claim 1, wherein the spark plasma sintering is performed at a ramp rate of: 100-200 ℃/min, the sintering temperature of the discharge plasma is 1200-1800 ℃, and the sintering pressure of the discharge plasma is as follows: 30 MPa-50 MPa, and the time of spark plasma sintering is 5 minutes-15 minutes.
9. The method according to any one of claims 1 to 8Toughening of the resulting CNTs to TiB2A basic ultra high temperature ceramic material.
10. CNTs toughened TiB obtained according to any one of claims 1 to 82The mechanical property test method of the ultrahigh-temperature ceramic material comprises the following steps:
s41, determining the mass fraction of CNTs in the ceramic material to be tested: the mass fraction is determined according to equation 1,
In the formula, M1Is CNTs/TiB2Mass of composite powder, M2Is Me/TiB2The mass of the composite catalyst;
s42, pretreatment of the ceramic material to be tested: cutting the ceramic material to be tested by adopting a linear cutting technology, and chamfering the four edges of the cut ceramic material to be tested after coarse grinding and polishing;
s43, testing mechanical properties: the hardness of the ceramic material to be tested is measured on a Vickers hardness tester, the fracture toughness of the ceramic material to be tested is measured by a unilateral beam method, the bending strength of the ceramic material to be tested is measured by an electronic universal material testing machine, and the mass ablation rate of the ceramic material to be tested is measured by oxyacetylene.
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| CN113151770A (en) * | 2021-02-08 | 2021-07-23 | 广东正德材料表面科技有限公司 | Composite coating and preparation method thereof |
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| CN102978434A (en) * | 2012-12-13 | 2013-03-20 | 北京科技大学 | Short fiber-particle synergetically-reinforced copper-based composite material and preparation method thereof |
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| CN101462882A (en) * | 2009-01-21 | 2009-06-24 | 武汉理工大学 | Ultrafast sintering method for preparing carbon nano-tube reinforced ceramic |
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| CN108383537B (en) * | 2018-03-13 | 2020-12-11 | 哈尔滨工业大学 | In-situ synthesized carbon nanotube/hafnium boride nanocomposite and preparation method thereof |
| CN113151770A (en) * | 2021-02-08 | 2021-07-23 | 广东正德材料表面科技有限公司 | Composite coating and preparation method thereof |
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