Rare earth composite zirconium carbide-silicon carbide ceramic and preparation method and application thereof

Abstract

The application provides a rare earth composite zirconium carbide-silicon carbide ceramic and a preparation method and application thereof. The composite zirconium carbide-silicon carbide ceramic comprises 5-15% of yttrium trioxide, 60-80% of zirconium carbide and 5-35% of silicon carbide, with the mass of the rare earth zirconium carbide-silicon carbide ceramic being 100%. The preparation method comprises the following steps: (1) mixing a zirconium carbide source solution and a silicon carbide source solution, and then sequentially performing desolventizing treatment and pyrolysis treatment to obtain a preliminary powder; (2) mixing a yttrium source with the preliminary powder in step (1), and then performing desolventizing treatment to obtain a ceramic powder, and sintering the ceramic powder to obtain the rare earth composite zirconium carbide-silicon carbide ceramic. The preparation method of the rare earth composite zirconium carbide-silicon carbide ceramic is efficient and controllable, the rare earth composite zirconium carbide-silicon carbide ceramic has excellent high-temperature ablation resistance, the density is about 99%, and the hardness can be higher than 1200HV0.1.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ultra-high temperature ceramics, and relates to a rare earth composite zirconium carbide-silicon carbide ceramic as well as a preparation method and application thereof. BACKGROUND

[0002] Refractory zirconium carbide (ZrC) has excellent high-temperature strength and high melting point (3540℃). Since the melting point of zirconium carbide is higher than that of zirconia, there is no solid phase transition in the heating process, and the high-temperature strength is high. Zirconium carbide has excellent ablation resistance at high temperatures, and its oxidation product ZrO2 has a melting point of 2677℃, and can withstand high-temperature environments above 2500℃.

[0003] CN116621577A discloses a kind of grain boundary and surface doped rare earth zirconium-based ceramic material and its preparation method and application. By the method of distribution doping, part of the doping elements are located at the grain boundary and surface of the rare earth zirconium-based ceramic material, and by adjusting the type and content of the doping elements at the grain boundary and surface, the sintering activity of the rare earth zirconium-based ceramic material is improved. The main doping elements include rare earth elements and cation doping elements. However, the ability of simple element doping to improve the performance of rare earth zirconium-based ceramics is limited. Therefore, it is necessary to further improve the performance of zirconium carbide by other methods.

[0004] SiC ceramic has the characteristics of high temperature resistance, thermal shock resistance, corrosion resistance, low expansion coefficient, good thermal conductivity and light weight, and is one of the important candidate materials for high-temperature structural ceramics. At the same time, silicon elements can be obtained in large quantities from the earth's crust, and the raw material source is stable and widely available. Adding SiC to carbide ceramics not only improves its sintering property, but also limits the abnormal growth of grains during sintering, greatly increasing the strength and toughness of the composite ceramic.

[0005] If a ZrC / SiC ceramic composite material is prepared, the combination of ZrC / SiC ceramic can not only play a synergistic role, but also the glassy SiO2 formed by high-temperature oxidation has fluidity, which can seal pores and fill cracks. At the same time, the fracture toughness of ZrC is very poor, which can be improved by the toughness of SiC. It is an excellent ablation-resistant material. However, the combination of ZrC / SiC ceramic also has the problems of high sintering temperature, low density and easy cracking of the ablation oxidation protective layer SiO2, and there is room for further improvement of the performance of the ceramic.

[0006] CN104478436A discloses a layered silicon carbide / zirconium carbide ultra-high temperature ceramic preparation method. The silicon carbide and zirconium carbide flow cast sheets are prepared by flow casting method, and then are alternately stacked. Vacuum sintering, by limiting the amount of polymethyl methacrylate, polyethylene glycol, ethanol and n-octanol, the smooth surface of the flow cast sheet is prepared without bubble generation, the glue removal, sintering temperature and heating rate, sintering pressure are controlled and limited, the layered ultra-high temperature ceramic interface is clear, the strength is moderate, the ceramic density is good, the crack propagation path can be changed to enhance the fracture toughness. However, the silicon carbide flow cast sheet and the zirconium carbide flow cast sheet of each layer are micron level, which is currently only suitable for example development and is not suitable for industrial large-scale production.

[0007] With the rapid development of the aerospace field, the speed of the aircraft is also developing towards high Mach, and the aerodynamic heating and airflow scour caused by high Mach puts high requirements on the ablation resistance of the material. Therefore, it is necessary to develop a new type of ultra-high temperature ablation-resistant ceramic material. SUMMARY

[0008] The purpose of the present application is to provide a rare earth composite zirconium carbide-silicon carbide ceramic and its preparation method and application. The density of the rare earth composite zirconium carbide-silicon carbide ceramic is about 99%, and the linear ablation rate is ≤9.60×10 -3 mm / s and the mass ablation rate is ≤6.50×10 -3 g / s when the plasma ablation is 300s at 2000℃.

[0009] To achieve this purpose, the present application adopts the following technical solutions:

[0010] One of the purposes of the present application is to provide a rare earth composite zirconium carbide-silicon carbide ceramic, wherein the mass of the rare earth zirconium carbide-silicon carbide ceramic is 100%, the composite zirconium carbide-silicon carbide ceramic includes 5-15% yttrium trioxide, 60-80% zirconium carbide and 5-35% silicon carbide. The composite zirconium carbide-silicon carbide ceramic of the present application preferably includes 8-12% yttrium trioxide, 60-80% zirconium carbide and 5-35% silicon carbide.

[0011] The mass fraction of yttrium trioxide can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%, the mass fraction of zirconium carbide can be 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78% or 80%, and the mass fraction of silicon carbide can be 5%, 10%, 15%, 20%, 25%, 30% or 35%, but is not limited to the listed values, other values not listed in the range are also applicable.

[0012] The melting point of zirconium carbide in the rare earth composite zirconium carbide-silicon carbide ceramic in the application can be as high as 3540 DEG C, and after high-temperature ablation, the corresponding oxide ZrO2 is generated, and the melting point of the oxide is also as high as 2700 DEG C, so that the material has good ablation resistance; the added silicon carbide can play a synergistic role, and the glassy silicon oxide formed during high-temperature oxidation has fluidity, can seal pores, fill cracks, and prevent further oxidation of oxygen inward; by adding rare earth yttrium trioxide, not only the sintering aid effect can be achieved, but also the phase of the main material zirconia in the ablation oxide layer can be stabilized, and the volume change caused by the phase transition of zirconia from high temperature to low temperature can be prevented, so that the integrity of the oxide layer is maintained.

[0013] The second object of the application is to provide a preparation method of the rare earth composite zirconium carbide-silicon carbide ceramic according to the first object, and the preparation method comprises the following steps:

[0014] (1) mixing a zirconium carbide source solution and a silicon carbide source solution, and then sequentially performing desolventizing treatment and pyrolysis treatment to obtain a preliminary powder;

[0015] (2) mixing a yttrium source with the preliminary powder in step (1), and then performing desolventizing treatment to obtain a ceramic powder, and sintering the ceramic powder to obtain the rare earth composite zirconium carbide-silicon carbide ceramic.

[0016] In step (1) of the application, the zirconium carbide source solution and the silicon carbide source solution are mixed, and then the solvent is removed by rotary evaporation, so as to achieve molecular-level mixing of the zirconium carbide source and the silicon carbide source, finally improve the element uniformity of the ceramic, and through pyrolysis treatment, the organic small molecular compounds can be removed, so that the preliminary powder has higher sintering activity, and the subsequent ceramic sintering forming can be promoted.

[0017] In step (2) of the application, the yttrium source and the preliminary powder are mixed, and then desolventizing treatment is performed, so that the preliminary powder and the yttrium source are mixed at the molecular level, and the element consistency of the ceramic is improved.

[0018] As a preferred technical scheme of the application, the zirconium carbide source in the zirconium carbide source solution in step (1) comprises polycarbazirconium oxide and / or polyzirconium ethoxide.

[0019] The purity of the zirconium carbide source in the application is ≥99.9%.

[0020] Preferably, the solvent of the zirconium carbide source solution comprises dimethylbenzene.

[0021] The zirconium carbide source solution in the application directly purchases raw materials with a mass fraction of 66.7%.

[0022] The ceramic mass yield of the zirconium carbide source in step (1) of the application is 30-35%.

[0023] Preferably, the silicon carbide source in the silicon carbide source solution of step (1) comprises polycarbosilane.

[0024] The purity of the silicon carbide source of the present application is ≥ 99.9%.

[0025] Preferably, the solvent of the silicon carbide source solution comprises xylene.

[0026] The silicon carbide source solution of the present application is directly purchased from a raw material with a mass fraction of 50%

[0027] Preferably, the ceramic yield of the silicon carbide source in step (1) is 50-60%.

[0028] Preferably, the mass ratio of the zirconium carbide source solution and the silicon carbide source solution in step (1) is (0.75-3):1, wherein the mass ratio can be 0.75:1, 1:1, 1.25:1, 1.5:1, 1.75:1, 2:1, 2.25:1, 2.5:1, 2.75:1 or 3:1, etc., but not limited to the listed values, and other values not listed within the range of values are also applicable.

[0029] As a preferred technical solution of the present application, the desolventization treatment in step (1) comprises rotary evaporation.

[0030] Preferably, the temperature of the rotary evaporation is 75-85℃, wherein the temperature can be 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃ or 85℃, etc., but not limited to the listed values, and other values not listed within the range of values are also applicable.

[0031] Preferably, the temperature of the pyrolysis treatment in step (1) is 800-1000℃, wherein the temperature can be 800℃, 820℃, 840℃, 860℃, 880℃, 900℃, 920℃, 940℃, 960℃, 980℃ or 1000℃, etc., but not limited to the listed values, and other values not listed within the range of values are also applicable.

[0032] If the temperature of the pyrolysis treatment is too high, the degree of ceramicization of the precursor is too high, which is not conducive to the sintering of the ceramic; if the temperature of the pyrolysis treatment is too low, the precursor still contains organic matter, which causes pollution during the molding of the material.

[0033] Preferably, the heating rate of the pyrolysis treatment in step (1) is 1-5℃ / min, wherein the heating rate can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min, etc., but not limited to the listed values, and other values not listed within the range of values are also applicable.

[0034] Preferably, the yttrium source has a particle size of 50-75 µm, wherein the particle size can be 50 µm, 52 µm, 54 µm, 56 µm, 58 µm, 60 µm, 62 µm, 64 µm, 66 µm, 68 µm, 70 µm, 72 µm, 74 µm, or 75 µm, etc., but not only limited to the listed values, and other values not listed in the range are also applicable.

[0035] Preferably, the yttrium source has a particle size of 50-75 µm, wherein the particle size can be 50 µm, 52 µm, 54 µm, 56 µm, 58 µm, 60 µm, 62 µm, 64 µm, 66 µm, 68 µm, 70 µm, 72 µm, 74 µm, or 75 µm, etc., but not only limited to the listed values, and other values not listed in the range are also applicable.

[0036] Preferably, the yttrium source has a purity of ≥ 99.9%.

[0037] Preferably, the mass ratio of the yttrium source to the preliminary powder in step (2) is (0.053-0.18):1, wherein the mass ratio can be 0.053:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.11:1, 0.12:1, 0.13:1, 0.14:1, 0.15:1, 0.16:1, 0.17:1, or 0.18:1, etc., but not only limited to the listed values, and other values not listed in the range are also applicable.

[0038] Preferably, the mixing in step (2) is wet ball milling.

[0039] Preferably, the mixing in step (2) is wet ball milling.

[0040] Preferably, the medium for wet ball milling includes anhydrous ethanol.

[0041] Preferably, the ball-to-material ratio for wet ball milling is (8-10):1, wherein the ball-to-material ratio can be 8:1, 9:1, or 10:1, etc., but not only limited to the listed values, and other values not listed in the range are also applicable.

[0042] Preferably, the rotation speed for wet ball milling is 280-350 rad / min, wherein the rotation speed can be 280 rad / min, 290 rad / min, 300 rad / min, 310 rad / min, 320 rad / min, 330 rad / min, 340 rad / min, or 350 rad / min, etc., but not only limited to the listed values, and other values not listed in the range are also applicable.

[0043] Preferably, the time of the wet ball milling is 8-12h, wherein the time can be 8h, 9h, 10h, 11h or 12h, etc., but is not limited to the listed values, and other values not listed in the range are also applicable.

[0044] Preferably, after the wet ball milling, separation, drying and screening are sequentially performed, and then the desolventizing treatment of step (2) is performed.

[0045] Preferably, the desolventizing treatment of step (2) comprises rotary evaporation.

[0046] Preferably, the temperature of the rotary evaporation is 75-85℃, wherein the temperature can be 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃ or 85℃, etc., but is not limited to the listed values, and other values not listed in the range are also applicable.

[0047] Preferably, the ceramic powder is obtained by drying after the desolventizing treatment of step (2).

[0048] As a preferred technical solution of the present application, the sintering of step (2) comprises spark plasma sintering.

[0049] In the present application, the sintering adopts spark plasma sintering, which is a material sintering or synthesis technology that utilizes direct current pulse current to heat the sample and combines axial load to assist the densification of ceramics. Compared with traditional hot-press sintering, it can realize the densification of materials and the synthesis of new compounds in a short time. Spark plasma sintering significantly reduces the formation temperature and molding time, and produces plasma activation, discharge impact pressure and electric field assisted diffusion effects in the gap between powder particles.

[0050] Preferably, the atmosphere of the spark plasma sintering is inert atmosphere.

[0051] In the present application, the spark plasma sintering in inert atmosphere can avoid material oxidation.

[0052] As a preferred technical solution of the present application, the spark plasma sintering comprises one-stage sintering and two-stage sintering which are sequentially performed.

[0053] Preferably, the heating rate of the one-stage sintering is 100-120℃ / min, wherein the heating rate can be 100℃ / min, 102℃ / min, 104℃ / min, 106℃ / min, 108℃ / min, 110℃ / min, 112℃ / min, 114℃ / min, 116℃ / min, 118℃ / min or 120℃ / min, etc., but is not limited to the listed values, and other values not listed in the range are also applicable.

[0054] Preferably, the temperature of the first sintering is 1100-1300℃, wherein the temperature can be 1100℃, 1120℃, 1140℃, 1160℃, 1180℃, 1200℃, 1220℃, 1240℃, 1260℃, 1280℃ or 1300℃, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0055] Preferably, the holding time of the first sintering is 10-15min, wherein the holding time can be 10min, 11min, 12min, 13min, 14min or 15min, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0056] Preferably, the pressure of the first sintering is 40-60 Mpa, wherein the pressure can be 40 Mpa, 42 Mpa, 44 Mpa, 46 Mpa, 48 Mpa, 50 Mpa, 52 Mpa, 54 Mpa, 56 Mpa, 58 Mpa or 60 Mpa, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0057] Preferably, the temperature of the second sintering is 1600-2000℃, wherein the temperature can be 1600℃, 1650℃, 1700℃, 1750℃, 1800℃, 1850℃, 1900℃, 1950℃ or 2000℃, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0058] Preferably, the holding time of the second sintering is 10-15min, wherein the holding time can be 10min, 11min, 12min, 13min, 14min or 15min, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0059] Preferably, the holding time of the second sintering is 10-15min, wherein the holding time can be 10min, 11min, 12min, 13min, 14min or 15min, etc., but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0060] Preferably, the pressure of the two-stage sintering is 40-60 Mpa, wherein the pressure can be 42 Mpa, 44 Mpa, 46 Mpa, 48 Mpa, 50 Mpa, 52 Mpa, 54 Mpa, 56 Mpa, 58 Mpa or 60 Mpa, etc., but not limited to the listed values, and other values not listed in the range are also applicable.

[0061] As a preferred technical solution of the present application, the preparation method comprises the following steps:

[0062] (1) After mixing the zirconium carbide source solution and the silicon carbide source solution, sequentially performing desolventizing treatment and pyrolysis treatment to obtain a preliminary powder, the temperature of the pyrolysis treatment is 800-1000℃, and the heating rate is 1-5℃ / min;

[0063] (2) After mixing the yttrium source and the preliminary powder of step (1), performing desolventizing treatment to obtain a ceramic powder, and sintering the ceramic powder to obtain the rare earth composite zirconium carbide-silicon carbide ceramic, the sintering comprises discharge plasma sintering, and the discharge plasma sintering comprises sequentially performing one-stage sintering and two-stage sintering.

[0064] Among them, the one-stage sintering has a heating rate of 100-120℃ / min, a temperature of 1100-1300℃, a holding time of 10-15 min and a pressure of 40-60 Mpa, and the two-stage sintering has a heating rate of 25-50℃ / min, a temperature of 1600-2000℃, a holding time of 10-15 min and a pressure of 40-60 Mpa.

[0065] The third object of the present application is to provide the application of the rare earth composite zirconium carbide-silicon carbide ceramic as described in one of the objects, which is applied to the field of ultra-high temperature ceramics.

[0066] Compared with the prior art, the present application has the following beneficial effects:

[0067] (1) The rare earth composite zirconium carbide-silicon carbide ceramic prepared by the present application has a density of about 99%, and when ablated for 300s at 2000℃, the linear ablation rate is ≤9.60×10 -3 mm / s, and the mass ablation rate is ≤6.50×10 -3 g / s.

[0068] (2) The preparation method of the rare earth composite zirconium carbide-silicon carbide ceramic is efficient and controllable, the sintering process is faster and more stable than the traditional one, the ceramic elements are mixed uniformly and have good uniformity, and the ceramic has excellent high-temperature ablation resistance. BRIEF DESCRIPTION OF DRAWINGS

[0069] Figure 1 is a SEM image of the ceramic sample prepared in Example 1 of the present application.

[0070] Figure 2 is a surface morphology image of the ceramic sample prepared in Example 2 of the present application.

[0071] Figure 3 is a surface morphology image of the ceramic sample prepared in Comparative Example 1 of the present application.

[0072] Figure 4 is an XRD comparison chart of the ceramic samples prepared in Example 2 and Comparative Examples 1-2 of the present application.

[0073] Figure 5 is an EDS chart of the ablation region of the ceramic sample prepared in Example 2 of the present application after ablation.

[0074] Figure 6 is a high-magnification SEM image of the ceramic sample prepared in Example 3 of the present application after ablation.

[0075] Figure 7 is a SEM image of the ceramic sample prepared in Example 2 of the present application after ablation.

[0076] Figure 8 is a SEM image of the ceramic sample prepared in Comparative Example 1 of the present application after ablation. DETAILED DESCRIPTION

[0077] The technical solutions of the present application are further illustrated by specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations on the present application.

[0078] Example 1

[0079] This embodiment provides a rare earth composite zirconium carbide-silicon carbide ceramic. The composite zirconium carbide-silicon carbide ceramic comprises 5% yttrium trioxide, 71.25% zirconium carbide and 23.75% silicon carbide, based on the mass of the rare earth zirconium carbide-silicon carbide ceramic.

[0080] The rare earth composite zirconium carbide-silicon carbide ceramic is prepared by a preparation method comprising the following steps:

[0081] (1) 45 g of a xylene solution of polyzirconium ethoxide with a mass fraction of 66.7% is mixed with 20 g of a xylene solution of polycarbosilane with a mass fraction of 50%, and the solvent xylene is removed by rotary evaporation at 80°C, and the mixed precursor powder is placed in a tube furnace in an argon atmosphere, heated to 1000°C at a rate of 2°C / min to obtain a preliminary pyrolysis precursor powder;

[0082] (2) Take 20g of the preliminary pyrolysis precursor powder and mix it with 1.05g of Y2O3 powder with a purity of 99.9% and a particle size of 65μm. Mix the powder with wet ball milling at a ball-to-material ratio of 10:1, a rotation speed of 300rad / min, and a time of 10h. Then remove the anhydrous ethanol by rotary evaporation, dry the powder in a vacuum oven at 60℃ for 12h, and finally sieve it to obtain the preliminary powder.

[0083] The initial powder was placed in a high-strength graphite mold with a diameter of 30 mm and sintered in a spark plasma sintering furnace. The sintering conditions were argon atmosphere, pressure of 50 MPa, heating to 1200 °C at 100 °C / min, holding at 125 min, then heating to 1800 °C at 25 °C / min, and holding at the highest temperature for 15 min. Finally, rare earth composite zirconium carbide-silicon carbide ceramic was obtained.

[0084] The SEM image of the rare earth composite zirconium carbide-silicon carbide ceramic prepared in this embodiment is shown below. Figure 1 As shown, from Figure 1 A clear distribution of light and dark areas can be seen. Due to the different elemental properties of zirconium and silicon, zirconium appears as a darker part, while the lighter part is mostly silicon. Overall, the phase separation of zirconium and silicon is obvious, and the elemental distribution is very uniform.

[0085] Example 2

[0086] This embodiment provides a rare earth composite zirconium carbide-silicon carbide ceramic, wherein the rare earth zirconium carbide-silicon carbide ceramic comprises 10% yttrium trioxide, 67.5% zirconium carbide and 22.5% silicon carbide by mass.

[0087] The rare-earth composite zirconium carbide-silicon carbide ceramic is prepared by the following method, which includes the following steps:

[0088] (1) Mix 45g xylene solution of 66.7% zirconium ethylene glycol and 20g xylene solution of 50% polycarbosilane, remove xylene solvent by rotary evaporation at 80°C, and place the mixed precursor powder in an argon atmosphere tube furnace and heat to 1000°C at 2°C / min to obtain preliminary pyrolysis precursor powder.

[0089] (2) Take 20g of the preliminary pyrolysis precursor powder and mix it with 2.22g of Y2O3 powder with a purity of 99.9% and a particle size of 65μm. Mix them together and perform wet ball milling with a ball-to-material ratio of 10:1, a rotation speed of 300rad / min, and a time of 10h. Then, remove the anhydrous ethanol by rotary evaporation, dry in a vacuum oven at 60℃ for 12h, and finally sieve to obtain the preliminary powder.

[0090] The preliminary powder is placed in a high-strength graphite mold with a diameter of 30 mm, and sintering is performed in a spark plasma sintering furnace under the following conditions: argon atmosphere, pressure of 50 MPa, temperature rising at 100 ℃ / min to 1200 ℃, then temperature rising at 25 ℃ / min to 1800 ℃, and holding at the highest temperature for 15 min, to finally obtain the rare earth composite zirconium carbide-silicon carbide ceramic.

[0091] The surface morphology of the rare earth composite ceramic prepared in this example is shown in FIG. 1. Figure 2 Figure 2 It can be seen that after the addition of yttrium trioxide, the ceramic surface is smoother, and there are no obvious pores, the apparent porosity of the ceramic is obviously reduced, and the density is improved.

[0092] Example 3

[0093] The rare earth composite zirconium carbide-silicon carbide ceramic provided in this example contains 15% yttrium trioxide, 63.75% zirconium carbide, and 21.25% silicon carbide, based on the total mass of the rare earth zirconium carbide-silicon carbide ceramic.

[0094] The rare earth composite zirconium carbide-silicon carbide ceramic is prepared by the following preparation method, which comprises the following steps:

[0095] (1) 45 g of a xylene solution of polyethanol zirconium with a mass fraction of 66.7% is mixed with 20 g of a xylene solution of polycarbosilane with a mass fraction of 50%, and the solvent xylene is removed by rotary evaporation at 80 ℃, and the mixed precursor powder is placed in an argon atmosphere tube furnace and heated to 1000 ℃ at a rate of 2 ℃ / min to obtain a preliminary pyrolysis precursor powder;

[0096] (2) 20 g of the preliminary pyrolysis precursor powder is mixed with 3.53 g of Y2O3 powder with a purity of 99.9% and a particle size of 65 μm, and wet ball milling is performed at a ball-to-material ratio of 10:1 and a rotation speed of 300 rad / min for 10 h, and then anhydrous ethanol is removed by rotary evaporation, and the mixture is dried in a vacuum oven at 60 ℃ for 12 h, and finally sieved to obtain a preliminary powder;

[0097] The preliminary powder is placed in a high-strength graphite mold with a diameter of 30 mm, and sintering is performed in a spark plasma sintering furnace under the following conditions: argon atmosphere, pressure of 50 MPa, temperature rising at 100 ℃ / min to 1200 ℃, then temperature rising at 25 ℃ / min to 1800 ℃, and holding at the highest temperature for 15 min, to finally obtain the rare earth composite zirconium carbide-silicon carbide ceramic.

[0098] Example 4

[0099] ​The embodiment provides a rare earth composite zirconium carbide-silicon carbide ceramic, the composite zirconium carbide-silicon carbide ceramic comprises 10% yttrium trioxide, 72% zirconium carbide and 18% silicon carbide, and the mass of the rare earth composite zirconium carbide-silicon carbide ceramic is 100%.

[0100] The rare earth composite zirconium carbide-silicon carbide ceramic is prepared by a preparation method comprising the following steps:

[0101] (1) 48g of a xylene solution of polyzirconium alcohol with a mass fraction of 66.7% is mixed with 16g of a xylene solution of polycarbosilane with a mass fraction of 50%, and xylene is removed by rotary evaporation at 80°C; the mixed precursor powder is placed in a tube furnace in an argon atmosphere, and is heated to 1000°C at a rate of 2°C / min to obtain a preliminary pyrolysis precursor powder;

[0102] (2) 20g of the preliminary pyrolysis precursor powder is mixed with 2.22g of Y2O3 powder with a purity of 99.9% and a particle size of 65μm, wet ball milling is performed at a ball-to-material ratio of 10:1 and a rotation speed of 300rad / min for 10h, then anhydrous ethanol is removed by rotary evaporation, and the mixture is dried in a vacuum oven at 60°C for 12h, and finally, screening is performed to obtain a preliminary powder;

[0103] The preliminary powder is placed in a high-strength graphite mold with a diameter of 30mm, and sintering is performed in a spark plasma sintering furnace under the following conditions: argon atmosphere, pressure of 50MPa, heating to 1200°C at a rate of 100°C / min, then heating to 1800°C at a rate of 25°C / min, and maintaining the highest temperature for 15min, to finally obtain the rare earth composite zirconium carbide-silicon carbide ceramic.

[0104] Embodiment 5

[0105] In the embodiment, step (1) is changed to heating to 700°C instead of heating to 1000°C, and other conditions are the same as those in embodiment 1.

[0106] Embodiment 6

[0107] In the embodiment, step (1) is changed to heating to 1200°C instead of heating to 1000°C, and other conditions are the same as those in embodiment 1.

[0108] Embodiment 7

[0109] In the embodiment, spark plasma sintering is replaced by conventional tube furnace sintering, and other conditions are the same as those in embodiment 1.

[0110] Embodiment 8

[0111] In this embodiment, except that the sintering conditions in step (2) are replaced with sintering in an argon atmosphere at a pressure of 50 MPa, heating to 1800°C at a rate of 100°C / min, and holding at the highest temperature for 15 min, all other conditions are the same as in Example 1.

[0112] Example 9

[0113] In this embodiment, except that the sintering conditions in step (2) are replaced with argon atmosphere, pressure 50 MPa, temperature rise to 1200℃ at 100℃ / min, and holding at the highest temperature for 15 min, all other conditions are the same as in Example 1.

[0114] Comparative Example 1

[0115] The difference between this comparative example and Example 1 is that Y2O3 was not mixed in step (2), while the other conditions are the same as in Example 1.

[0116] The surface morphology images of the ceramic sample prepared in this comparative example and the ceramic sample in Example 2 at the same magnification are shown below. Figure 3 As shown, Figure 3 and Figure 2 The comparison shows that, at the same magnification, the ceramic surface without yttrium trioxide has obvious pores, high apparent porosity, low density, and its ceramic performance is not as good as that of ceramics with yttrium trioxide.

[0117] Comparative Example 2

[0118] The difference between this comparative example and Example 1 is that the pyrolysis temperature of the mixed ceramic precursor in step (1) is increased to 1500℃ and Y2O3 is not mixed in step (2). All other conditions are the same as in Example 1.

[0119] The XRD patterns of the ceramic samples prepared in Example 2 and Comparative Examples 1-2 of this invention are as follows: Figure 4 As shown, through Figure 4 It can be seen that before the addition of yttrium trioxide, zirconium carbide was well formed after sintering of the powder and all of them had high crystallinity. After the addition of yttrium trioxide, the diffraction peaks of zirconium carbide disappeared, and a new yttrium-zirconium-oxygen phase appeared instead, which is related to the improvement of the ceramic's ablation resistance.

[0120] The ceramic samples prepared in Examples 1-9 and Comparative Examples 1-2 were subjected to performance tests. The test results are shown in Table 1. The test methods are as follows:

[0121] (1) The density and hardness properties of the ceramic samples prepared in Examples 1-9 and Comparative Examples 1-2 were tested;

[0122] (2) The ceramic samples prepared in Examples 1-9 and Comparative Examples 1-2 were subjected to high-temperature ablation resistance test under plasma ablation conditions of 2000℃ for 300s. The linear ablation rate and mass ablation rate after ablation were tested.

[0123] The structure and morphology of the ceramic samples were tested, such as... Figures 5-8 As shown. The EDS image of the ablation zone of the rare earth composite zirconium carbide-silicon carbide ceramic prepared in Example 2 is shown below. Figure 5 As shown, through Figure 5 EDS analysis revealed that zirconium oxide was the main component in the oxide protective layer, with molten silica filling the gaps between the zirconium oxides, while yttrium was distributed evenly, with some areas of concentration.

[0124] The high-magnification SEM image of the rare earth composite zirconium carbide-silicon carbide ceramic prepared in Example 3 after ablation is shown below. Figure 6 As shown, through Figure 6 As can be seen, in the ablation center region, the oxide layer is uneven and consists of many white particles and molten material. The discontinuously distributed white particles are mainly ZrO2, and the gaps between the particles are filled with a glassy SiO2-ZrO2 binary mixture. Further increasing the magnification speed reveals many zirconia dendrites, which are crystallizations caused by the rapid cooling of ZrO2.

[0125] The SEM image of the ceramic sample after ablation in Example 2 is shown below. Figure 7 As shown, Figure 7 When the zirconium content is low, the ablation surface shows many grooves and is very uneven, indicating severe oxygen erosion into the ceramic. The SEM image of the ceramic sample in Comparative Example 1 after ablation is shown below. Figure 8 As shown, Figure 8 When the zirconium content increases, there is more molten oxide material in the ablation zone, which provides better protection. (SEM images of Comparative Example 1 and Example 2 are at the same magnification).

[0126] Table 1

[0127]

[0128] The table above shows that, based on the data from Examples 1, 2, and 3, as the amount of Y2O3 added increased from 5% to 10% and then to 15%, the ceramic density remained almost above 99%, the ceramic hardness increased, and the linear ablation rate first increased and then decreased. The ceramic with 10% Y2O3 content was relatively more resistant to ablation, while the ceramic with 15% Y2O3 content suffered more severe ablation, indicating that more Y2O3 is not necessarily better.

[0129] From the data comparison of Example 2 and Example 4, it can be found that when the proportion of ZrC in the ceramic increases, the hardness of the ceramic increases, the linear ablation rate decreases, and the ablation resistance improves. This is because the proportion of ZrC in the ceramic increases, and the properties of the ceramic are more biased towards ZrC. ZrC is harder and has a higher melting point than SiC. However, the increase in the proportion of ZrC also makes the ceramic more difficult to sinter and form.

[0130] From the data comparison of Example 5-6 and Example 1, it can be found that if the pyrolysis temperature of the mixed precursor is too high, the ceramicization degree of the powder is too high, and there are still many pores after the sintering process. These pores will become channels for oxygen to oxidize the ceramic intensively during the ablation process, thereby increasing the ablation degree of the material. If the pyrolysis temperature is too low, the powder will continue to release reaction gas during the sintering process, which will hinder the densification process of the ceramic, reduce the density of the ceramic, and reduce the performance of the ceramic.

[0131] From the data comparison of Example 7 and Example 1, it can be found that after replacing the spark plasma sintering with conventional tube furnace sintering, the sample is still powdery, showing very low sintering activity, and cannot be normally sintered into a ceramic block. This is mainly because the temperature and pressure of conventional tube furnace sintering are lower than those of spark plasma sintering, and there is no current activation sintering effect produced by spark plasma sintering.

[0132] From the data comparison of Example 8-9 and Example 1, it can be found that after replacing the two-stage sintering of spark plasma sintering with one-stage sintering, the density of the ceramic decreases and the ablation resistance decreases, indicating that two-stage heating is a more suitable gradient heating process and is more conducive to the densification of the ceramic. After reducing the highest sintering temperature of spark plasma sintering, the density of the ceramic decreases sharply. This is because the melting point of zirconium carbide is very high, so it must be sintered at a higher temperature. A lower temperature is not conducive to the sintering of the ceramic, thereby reducing the performance of the ceramic.

[0133] From the data comparison of Comparative Example 1 and Example 1, it can be found that after adding rare earth oxide Y2O3, the density of the ceramic is further improved to more than 99%, almost completely dense, and the hardness is also improved. More importantly, the linear ablation rate of the ceramic after ablation decreases, and Y2O3 improves the ablation resistance of the ceramic.

[0134] From the data comparison of Example 2 and Comparative Examples 1-2, it can be found that if the pyrolysis temperature of the mixed precursor is too high, the ceramicization degree is higher and the crystallinity is stronger, the density of the sintered ceramic decreases, and the ceramic has more voids. Oxygen is more easily oxidized through these voids during the ablation process, thereby reducing the ablation resistance.

[0135] The applicant states that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by those skilled in the art, and all of them fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for producing a rare earth composite zirconium carbide-silicon carbide ceramic, characterized by, The rare earth composite zirconium carbide-silicon carbide ceramic comprises 5-15% yttrium trioxide, 60-80% zirconium carbide and 5-35% silicon carbide, based on 100% of the mass of the rare earth composite zirconium carbide-silicon carbide ceramic. The preparation method comprises the following steps: (1) mixing a zirconium carbide source solution and a silicon carbide source solution, and then sequentially performing desolventizing treatment and pyrolysis treatment to obtain a preliminary powder; (2) mixing a yttrium source with the preliminary powder obtained in step (1), and then performing desolventizing treatment to obtain a ceramic powder, and sintering the ceramic powder to obtain the rare earth composite zirconium carbide-silicon carbide ceramic; The mixing in step (2) is wet ball milling, and the medium of the wet ball milling comprises anhydrous ethanol; The sintering in step (2) comprises discharge plasma sintering, and the discharge plasma sintering comprises sequentially performing one-stage sintering and two-stage sintering; The one-stage sintering has a temperature of 1100-1300℃ and a heating rate of 100-120℃ / min; The two-stage sintering has a temperature of 1600-2000℃ and a heating rate of 25-50℃ / min.

2. The production method according to claim 1, characterized by, The zirconium carbide source in the zirconium carbide source solution in step (1) comprises polycarbomethoxypolyzirconium.

3. The production method according to claim 1, characterized by, The solvent of the zirconium carbide source solution comprises dimethylbenzene.

4. The method of claim 1, wherein, The silicon carbide source in the silicon carbide source solution in step (1) comprises polycarbosilane.

5. The preparation method according to claim 1, characterized in that, The solvent of the silicon carbide source solution comprises dimethylbenzene.

6. The method of claim 1, wherein, The mass ratio of the zirconium carbide source solution and the silicon carbide source solution in step (1) is (0.75-3):

1.

7. The preparation method according to claim 1, characterized in that, The desolventizing treatment in step (1) comprises rotary evaporation.

8. The preparation method according to claim 7, characterized in that, The rotary evaporation has a temperature of 75-85℃.

9. The method of claim 1, wherein, The pyrolysis treatment in step (1) has a temperature of 800-1000℃.

10. The method of claim 1, wherein, The pyrolysis treatment in step (1) has a heating rate of 1-5℃ / min.

11. The method of claim 1, wherein, The yttrium source in step (2) comprises yttrium oxide powder.

12. The method of claim 1, wherein, The particle size of the yttrium source is 50-75µm.

13. The method of claim 1, wherein, The mass ratio of the yttrium source to the preliminary powder in step (1) in step (2) is (0.053-0.18):

1.

14. The method of claim 1, wherein, The ball-to-material ratio of the wet ball milling is (8-10):

1.

15. The method of claim 1, wherein, The rotation speed of the wet ball milling is 280-350rad / min.

16. The method of claim 1, wherein, The wet ball milling is performed for 8-12h.

17. The method of claim 1, wherein, After the wet ball milling, separation, drying and sieving are sequentially performed, and then the desolventizing treatment in step (2) is performed.

18. The method of claim 1, wherein, The desolventizing treatment in step (2) comprises rotary evaporation.

19. The method of claim 18, wherein, The rotary evaporation has a temperature of 75-85℃.

20. The method of claim 1, wherein, The ceramic powder obtained after the desolventizing treatment in step (2) is dried.

21. The method of claim 1, wherein, The atmosphere of the discharge plasma sintering is inert atmosphere.

22. The method of claim 1, wherein, The one-stage sintering has a holding time of 10-15min.

23. The method of claim 1, wherein, The one-stage sintering has a pressure of 40-60 Mpa.

24. The method of claim 1, wherein, The two-stage sintering has a holding time of 10-15min.

25. The method of claim 1, wherein, The two-stage sintering has a pressure of 40-60 Mpa.

26. The method of claim 1, wherein, The preparation method comprises the following steps: (1) mixing a zirconium carbide source solution and a silicon carbide source solution, and then sequentially performing desolventizing treatment and pyrolysis treatment to obtain a preliminary powder, wherein the pyrolysis treatment has a temperature of 800-1000℃ and a heating rate of 1-5℃ / min; (2) mixing the yttrium source with the preliminary powder of step (1), and then performing desolventizing treatment to obtain a ceramic powder, and sintering the ceramic powder to obtain the rare earth composite zirconium carbide-silicon carbide ceramic, wherein the sintering comprises spark plasma sintering, and the spark plasma sintering comprises one-stage sintering and two-stage sintering performed in sequence; wherein the one-stage sintering has a temperature rising rate of 100-120 ℃ / min, a temperature of 1100-1300 ℃, a holding time of 10-15 min, and a pressure of 40-60 Mpa, and the two-stage sintering has a temperature rising rate of 25-50 ℃ / min, a temperature of 1600-2000 ℃, a holding time of 10-15 min, and a pressure of 40-60 Mpa.

27. Use of a rare earth composite zirconium carbide-silicon carbide ceramic produced by the production method according to any one of claims 1 to 26, characterized in that The rare earth composite zirconium carbide-silicon carbide ceramic is applied to the field of ultra-high temperature ceramics.

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