Method for preparing high-density and high-toughness (HfTiZrNbTa) N / AlN composite ceramic through rapid sintering

Abstract

The invention provides a method for preparing high-density and high-toughness (HfTiZrNbTa) N / AlN composite ceramic through rapid sintering, which comprises the following steps: weighing raw materials HfO2, ZrO2, TiO2, Nb2O5, Ta2O5 and Si3N4 according to a molar ratio, adding ethanol and grinding balls, carrying out ball milling and mixing, drying, grinding and sieving; then pressing the mixed powder into blocks, putting the blocks into a graphite crucible, putting the graphite crucible into a non-pressure furnace, heating to 1800 DEG C, preserving heat and presintering for 60 minutes in an Ar atmosphere, removing SiO generated by reaction on the surface of the graphite crucible, and grinding and sieving; the obtained (HfTiZrNbTa) N and AlN are weighed, ethyl alcohol and grinding balls are added, and mixed powder is obtained through ball milling, mixing, drying, grinding and sieving; and filling the mixed powder into a graphite mold, putting the graphite mold into a plasma sintering furnace, heating to 2100 DEG C, preserving heat for 10 minutes under the condition of 40MPa, and cooling along with the furnace after sintering is completed. The density of the ceramic is improved through rapid sintering of a spark plasma sintering method, meanwhile, the toughness of the ceramic is modified and improved by adding aluminum nitride, and the defects that high-entropy nitride ceramic is difficult to densify and large in brittleness are overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of high-entropy ceramic materials, and in particular to a method for preparing high-density and high-toughness (HfTiZrNbTa) N / AlN composite ceramics by rapid sintering. Background Art

[0002] High-entropy ceramics (HECs) generally refer to multicomponent solid solutions composed of five or more metal cations in equal or nearly equal amounts. In recent years, high-entropy ceramics have become a research hotspot in the ceramics field due to their single crystal structure and excellent physical and chemical properties. High-entropy nitride ceramics, in particular, possess high melting points, high hardness, good oxidation resistance, and excellent mechanical properties. These properties make them promising for broad application in extreme environments such as high temperature, high pressure, and severe corrosion.

[0003] However, existing high-entropy nitride ceramics are produced through pressureless / hot-pressing sintering, which fails to achieve the ideal density. Furthermore, high-entropy nitride ceramics suffer from poor toughness. Consequently, the difficulties of densification and brittleness hinder their widespread industrial application.

[0004] Therefore, it is necessary to improve the sintering method and take modification measures in order to prepare high-entropy nitride ceramics with excellent strength and toughness. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing high-density and high-toughness (HfTiZrNbTa)N / AlN composite ceramics by rapid sintering, which improves the density of the ceramics by rapid sintering through the spark plasma sintering method, and at the same time improves the toughness of the ceramics by adding aluminum nitride, thereby improving the shortcomings of high-entropy nitride ceramics such as difficulty in densification and high brittleness.

[0006] The present invention provides a method for preparing a high-density and high-toughness (HfTiZrNbTa) N / AlN composite ceramic by rapid sintering, comprising the following steps: (1) Weigh the raw materials in a molar ratio of HfO2:ZrO2:TiO2:Nb2O5:Ta2O5:Si3N4=2:2:2:1:1:10, put them into a mixing tank, add appropriate amount of ethanol and grinding balls, place them on a mixer to mix, then separate the grinding balls, dry, grind and sieve the materials to obtain a mixed powder; (2) Put the mixed powder obtained in step (1) into a mold, and press into a block on a vertical hydraulic machine. Cut the carbon paper and graphite felt according to the inner diameter of the graphite crucible, put the carbon paper and graphite felt into the graphite crucible, and then put the block into the graphite crucible, and put the graphite felt and carbon paper on the block; (3) Put the graphite crucible into a pressureless furnace, heat to a pre-sintering temperature of 1800℃, and keep the temperature for pre-sintering for 60min under Ar atmosphere. After pre-sintering, take out the block in the crucible, remove the SiO generated on the surface by reaction, and grind and sieve the material to obtain (HfTiZrNbTa)N powder; (4) Take (HfTiZrNbTa)N and AlN obtained in step (3), wherein the addition amount of AlN is 2-6wt% of the total weight of the mixed material, put the mixed material into a mixing tank, add an appropriate amount of ethanol and grinding balls, mix on a mixer, then separate the grinding balls, and dry, grind and sieve the material to obtain (HfTiZrNbTa)N mixed powder; (5) Put the mixed powder obtained in step (4) into a graphite mold, put it into a plasma sintering furnace, heat to a sintering temperature of 2100℃, and keep the temperature for 10min under a pressure of 40MPa for sintering reaction. After sintering, the high-density high-toughness (HfTiZrNbTa)N / AlN composite ceramic material is obtained by furnace cooling.

[0007] Preferably, in steps (1) and (4), the mixer is a two-dimensional mixer, the rotating speed of the mixer is 140rpm, the grinding balls are ZrO2 grinding balls, the ball diameter of the grinding balls is 1-2mm, the ball-to-material mass ratio is 3:1, the mixing time is 8-10h, the drying temperature is 80℃, and the drying time is 5-10h.

[0008] Preferably, in step (2), the inner diameter of the mold is 2cm, 3.5g of powder is taken each time, the pressure for pressing is 3t, and the holding time is 60s.

[0009] Preferably, in step (3), the heating step is: first, heat to 1000℃ at a heating rate of 10℃ / min, and then heat to 1800℃ at a heating rate of 8℃ / min.

[0010] Preferably, in step (5), the heating rate is 10-15℃ / min.

[0011] Preferably, in step (4), the addition amount of AlN is 2wt% of the total weight of the mixed material.

[0012] Preferably, in the step (1), grinding in a marble mortar and then passing through a 60-mesh screen; in the step (3), grinding in a marble mortar and then passing through a 60-mesh screen; in the step (4), grinding in a marble mortar and then passing through a 100-mesh screen.

[0013] The working principle of the present application: on the one hand, the present application utilizes SPS sintering to prepare ceramics with high density. Discharge plasma sintering (SPS) provides an extremely powerful and efficient means for ceramic materials to achieve ultra-high relative density (usually > 98%, even close to 100% theoretical density) through its unique high-efficiency internal heating, strong non-thermal activation effect, rapid low-temperature sintering and pressure-assisted synergy, especially for the preparation of high-performance fine / nano-crystalline ceramics and difficult-to-sinter ceramics. On the other hand, the present application uses aluminum nitride (AlN) to toughen the ceramic. Aluminum nitride is a kind of nitride with excellent performance, which can play a great role in optimizing the mechanical properties of materials such as hardness, strength and toughness, and improving the densification degree of materials. When the crack propagates in the matrix and encounters high-modulus and high-hardness aluminum nitride particles, the crack tends to bypass the particles or deflect at the particle / matrix interface. This forces the crack propagation path to change from a straight line to a zigzag path. These mechanisms can achieve the toughening effect of AlN ceramic particles on (HfTiZrNbTa)N high-entropy nitride ceramics.

[0014] The beneficial effects of the present application: the present application improves the densification of ceramics by rapid sintering through discharge plasma sintering method, and improves the toughness of ceramics by adding aluminum nitride, which improves the shortcomings of difficult densification and high brittleness of high-entropy nitride ceramics, and the prepared ceramic material has the characteristics of high strength, high density and high toughness. In addition, the present application uses discharge plasma rapid sintering (SPS) to prepare nanoscale AlN toughened (HfTiZrNbTa)N high-entropy nitride ceramic, which has the advantages of rapid sintering and simple process compared with other preparation methods of high-entropy ceramic materials. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 XRD images of high-entropy ceramics with different AlN addition amounts; Figure 2 SEM images of high-entropy ceramics with 2wt.% AlN addition amount; Figure 3 EDS element distribution map of high-entropy ceramics with 2wt.% AlN addition amount; Figure 4 Density change graph of high-entropy nitride ceramics with different AlN contents, (a) bulk density, (b) relative density, (c) porosity; Figure 5Fracture toughness variation chart of high-entropy ceramics with different AlN addition amounts. DETAILED DESCRIPTION

[0016] In order to make the technical scheme of the present application easier to understand, the technical scheme of the present application is described clearly and completely in the form of specific embodiments in combination with the drawings.

[0017] Example 1 The method for rapidly sintering to prepare high-density high-toughness (HfTiZrNbTa)N / AlN composite ceramic of the present embodiment comprises the following steps: (1) Take hafnium dioxide (HfO2) 14.3305 g, zirconium dioxide (ZrO2) 8.3889 g, titanium dioxide (TiO2) 5.4371 g, niobium pentoxide (Nb2O5) 9.0484 g, tantalum pentoxide (Ta2O5) 9.5520 g, and silicon nitride (Si3N4) 47.7523 g, put the raw materials into a 500 ml polyethylene mixing tank, add 340 mL of ethanol, and then add ZrO2 grinding balls with a diameter of 1-2 mm according to a ball-to-material mass ratio of 3:1, place the mixing tank on a two-dimensional mixer, and mix at a speed of 140 rpm for 8-10 h, then separate the grinding balls, place the material in a drying oven, and dry at a temperature of 80℃ for 5-10 h, grind in a mortar, and then pass through a 60 mesh sieve to obtain a mixed powder; (2) Take 3.5 g of the mixed powder obtained in step (1) and place it in a mold with an inner diameter of 2 cm, press it into a block-shaped material on a vertical hydraulic press at a pressure of 3 t for 60 s, cut a circular carbon paper and graphite felt with a diameter of 2 cm, place them in a graphite crucible in the order of carbon paper, graphite felt, and carbon paper, and then place the block-shaped material in the graphite crucible, and sequentially place graphite felt and carbon paper on the block-shaped material; (3) Place the graphite crucible in a pressureless furnace, first heat it at a rate of 10℃ / min to 1000℃, then heat it at a rate of 8℃ / min to a pre-sintering temperature of 1800℃, and keep it at this temperature for 60 min under an Ar atmosphere, then take out the block-shaped material from the crucible, remove the SiO generated on the surface of the block-shaped material, grind and sieve the material to obtain (HfTiZrNbTa)N powder; (4) Take 17.64 g of (HfTiZrNbTa)N obtained in step (3) and 0.36 g of AlN (2 wt%), wherein the amount of AlN added is 2-6 wt% of the total weight of the mixture, and put the mixture into a mixing tank and add 70 mL of ethanol, then add ZrO2 grinding balls with a diameter of 1-2 mm according to a ball-to-material mass ratio of 3:1, and put the mixing tank on a two-dimensional mixer and mix at a speed of 140 rpm for 8-10 h, then separate the grinding balls, and put the material in a drying oven and dry at a temperature of 80°C for 5-10 h, grind in a mortar and sieve through a 60-mesh sieve to obtain (HfTiZrNbTa)N mixed powder; (5) Take 18 g of the mixed powder obtained in step (4) and put it into a graphite mold, and put it into a plasma sintering furnace, heat it to a sintering temperature of 2100°C at a heating rate of 10-15°C / min, and sinter it under a pressure of 40 MPa for 10 min, and then cool it in the furnace to obtain a high-density high-toughness (HfTiZrNbTa)N / AlN composite ceramic material.

[0018] Example 2: The method for rapidly sintering high-density high-toughness (HfTiZrNbTa)N / AlN composite ceramics of this example is different from that of Example 1 in that in step (4), 17.28 g of (HfTiZrNbTa)N and 0.72 g of AlN (4 wt%) are taken.

[0019] Example 3: The method for rapidly sintering high-density high-toughness (HfTiZrNbTa)N / AlN composite ceramics of this example is different from that of Example 1 in that in step (4), 16.92 g of (HfTiZrNbTa)N and 1.08 g of AlN (6 wt%) are taken.

[0020] Comparative Example: The comparative example is different from Example 1 in that in step (4), 18.00 g of (HfTiZrNbTa)N is taken without adding AlN (0 wt%).

[0021] High-density high-toughness (HfTiZrNbTa)N / AlN composite ceramic material samples were prepared by the preparation methods of Examples 1-3 and the comparative example. The phase composition of the ceramic was analyzed by X-ray diffraction (XRD, Shimadzu-6000, Japan). Scanning electron microscopy (FESEM, Sigma, Zeiss, Germany) was used. The bending resistance was measured using a universal testing machine (CMT5305 MASTECH SYSTEMS CO., LTD.). A Vickers hardness tester (HV-30BZ Changzhou Taylor Instrument Technology Co., Ltd.) was used.

[0022] By Figures 1 to 5 It can be seen that when the mass ratio of (HfTiZrNbTa)N to AlN in the composite ceramic material is 98:2, the toughness of the ceramic material is greatly enhanced. At the same time, the relative density of the material is also greatly improved.

[0023] It should be noted that the embodiments described herein are only part of the embodiments of the present application, not all the implementation manners of the present application, the embodiments are only exemplary, and the role is only to provide a more intuitive and clear way to understand the content of the present application, and is not a limitation on the technical solutions of the present application. Without departing from the concept of the present application, all other embodiments that can be thought of by those of ordinary skill in the art without creative labor, and other simple replacements and various changes of the technical solutions of the present application, all belong to the protection scope of the present application.

Claims

1. A method for preparing high-density and high-toughness (HfTiZrNbTa) N / AlN composite ceramics by rapid sintering, characterized in that: The following steps are involved: (1) Weigh the raw materials in a molar ratio of HfO2:ZrO2:TiO2:Nb2O5:Ta2O5:Si3N4=2:2:2:1:1:10, put them into a mixing tank, add appropriate amount of ethanol and grinding balls, place them on a mixer to mix, then separate the grinding balls, dry, grind and sieve the materials to obtain a mixed powder; (2) Weighing the mixed powder obtained in step (1) and placing it into a mold, pressing it into a block material on a vertical hydraulic press, cutting carbon paper and graphite felt according to the inner diameter of the graphite crucible, placing the carbon paper and graphite felt into the graphite crucible, then placing the block material therein, and placing the graphite felt and carbon paper on the block material; (3) Place the graphite crucible in a pressureless furnace, heat it to a pre-sintering temperature of 1800°C, and pre-sinter it for 60 minutes in an Ar atmosphere. After the pre-sintering is completed, take out the block material in the crucible, remove the SiO generated by the surface reaction, and grind and sieve the material to obtain (HfTiZrNbTa)N powder; (4) Weigh the (HfTiZrNbTa)N and AlN obtained in step (3), wherein the amount of AlN added is 2-6 wt% of the total weight of the mixture, put the mixture into a mixing tank, add an appropriate amount of ethanol and grinding balls, place the mixture on a mixer to mix, then separate the grinding balls, dry, grind and sieve the material to obtain a (HfTiZrNbTa)N mixed powder; (5) The mixed powder obtained in step (4) is weighed and loaded into a graphite mold, which is then placed in a plasma sintering furnace. The temperature is raised to a sintering temperature of 2100°C and kept at 40 MPa for 10 minutes for sintering reaction. After sintering, the temperature is lowered as the furnace is cooled to obtain a high-density and high-toughness (HfTiZrNbTa)N / AlN composite ceramic material.

2. The method for preparing high-density and high-toughness (HfTiZrNbTa)N / AlN composite ceramics by rapid sintering according to claim 1, characterized in that: In the steps (1) and (4), a two-dimensional mixer is used as the mixer, the rotation speed of the mixer is 140 rpm, the grinding balls are ZrO2 grinding balls, the ball diameter of the grinding balls is 1-2 mm, the ball-to-material mass ratio is 3:1, the mixing time is 8-10 h, the drying temperature is 80° C., and the drying time is 5-10 h.

3. The method for preparing high-density and high-toughness (HfTiZrNbTa)N / AlN composite ceramics by rapid sintering according to claim 1, characterized in that: In step (2), the inner diameter of the mold is 2 cm, 3.5 g of powder is weighed each time, the pressing pressure is 3 t, and it is maintained for 60 s.

4. The method for preparing high-density and high-toughness (HfTiZrNbTa)N / AlN composite ceramics by rapid sintering according to claim 1, characterized in that: In the step (3), the heating step is: first heating to 1000°C at a heating rate of 10°C / min, and then heating to 1800°C at a heating rate of 8°C / min.

5. The method for preparing high-density and high-toughness (HfTiZrNbTa)N / AlN composite ceramics by rapid sintering according to claim 1, characterized in that: In the step (5), the heating rate is 10-15°C / min.

6. The method for preparing high-density and high-toughness (HfTiZrNbTa)N / AlN composite ceramics by rapid sintering according to claim 1, characterized in that: In the step (4), the amount of AlN added is 2 wt% of the total weight of the mixture.

7. The method for preparing high-density and high-toughness (HfTiZrNbTa)N / AlN composite ceramics by rapid sintering according to claim 1, characterized in that: In the step (1), the mixture is ground in an agate mortar and then passed through a 60-mesh screen; in the step (3), the mixture is ground in an agate mortar and then passed through a 60-mesh screen; in the step (4), the mixture is ground in an agate mortar and then passed through a 100-mesh screen.

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