Ultrahigh-temperature heat-proof/insulation integrated ZrC/Zr 2 C complex phase material and preparation method thereof
Technical Field
The invention relates to the technical field of ultra-high temperature ceramics, in particular to an ultra-high temperature heat-proof/insulation integrated ZrC/Zr 2 C complex phase material and a preparation method thereof.
Background
The zirconium carbide (ZrC) ceramic has excellent performances of high melting point, high hardness, corrosion resistance, irradiation resistance, ablation resistance and the like, and has wide application prospects in the fields of aerospace, aviation, metallurgy, chemical industry and the like. The existing preparation methods of zirconium carbide ceramics are mainly divided into preparation methods of zirconium carbide powder and zirconium carbide blocks. The preparation of the powder mainly comprises a high-temperature carbothermic reduction method, an active metal reduction method, a polymer ceramic precursor cracking method and the like; the preparation method of the block material mainly comprises pressureless sintering, hot-pressing sintering, spark plasma sintering and other methods.
Document 1 (Inter.J.Refrac.Met.hard mater.64 (2017) 98-105) reports ZrO 2 And carbon black C is used as a raw material to prepare ZrC nano powder at 1600 ℃, and the prepared powder is subjected to discharge plasma sintering at 2100 ℃ and 80MPa for 30 minutes to prepare a block material with the density of 97%.
ZrCl was reported in literature 2 (adv. Powder Tech.27 (2016) 1547-1551) 4 The initial temperature of the reaction temperature of the method for preparing ZrC powder by reacting with metallic sodium is 600 ℃, but the method has high raw material cost, complex reaction process and difficult control.
Document 3 (ceramic. Inter.41 (2015) 7359-7365) reports the use of ZrCl 4 Method for preparing ZrC powder from phenolic resin, zrCl in reaction process 4 First to form zirconium oxide ZrO by reaction with phenolic resin 2 Then ZrC powder can be prepared by carbothermic reduction reaction at the temperature of more than 1500 ℃.
Document 4 (j.adv.ceram.6 (2017) 165-167) reports a method for preparing ZrC powder by high-temperature carbothermal reduction reaction and then preparing a ZrC bulk material by pressureless sintering at 1850-2000 ℃.
Document 5 (mater. Design 104 (2016) 43-50) reports the preparation of carbon nanotubes and Nb-doped ZrC bulk materials by hot-press sintering.
Document 6 (J.Euro.Ceram.S.37 (2017) 3003-3007) reports preparation of doped ZrH by spark plasma sintering 2 A ZrC bulk material.
Document 7 (Key. Eng. Mater.37 (2013) 79-83) reports using NaCl-KCl-K 2 ZrF 6 The method for preparing the ZrC coating on the surface of the C/C composite material at 1200 ℃ by using the molten salt and the Zr powder.
However, the high thermal conductivity of zirconium carbide (ZrC) ceramic limits its use as an ultra-high temperature insulation material; and zirconium (Zr) carbide 2 C) Has low heat conductivity, and is a novel high-temperature resistant and ultra-high temperature resistant heat insulating material. Mixing zirconium carbide (ZrC) ceramic and zirconium carbide (Zr) 2 C) Preparation of novel ZrC/Zr by organic combination of ceramics 2 The C complex phase material has comprehensive performances of high temperature resistance, corrosion resistance, ablation resistance, heat insulation and the like, and can realize the integration of ultrahigh temperature prevention/heat insulation. However, the above documents are found by comparative analysis, and there is no existing method for preparing a novel ultrahigh-temperature integrated ZrC/Zr for preventing/insulating heat by using in-situ high-temperature carbothermic reduction reaction to prepare ZrC porous block material and then performing infiltration through high-temperature molten salt reaction 2 C, a method for preparing the composite material.
Disclosure of Invention
The invention aims to provide ultrahigh-temperature heat-insulation integrated ZrC/Zr 2 The C complex phase material has excellent performances of high temperature resistance, corrosion resistance, ablation resistance and the like, has low thermal conductivity, realizes the integration of ultrahigh temperature prevention/heat insulation and has wide application range; the invention also provides a preparation method of the compound, which has the advantages of low raw material cost, simple process and low equipment requirement and is suitable for large-scale production.
The ultrahigh-temperature heat-proof/insulation integrated ZrC/Zr 2 The preparation method of the C complex phase material comprises the steps of firstly taking zirconium dioxide and carbon black as raw materials, and synthesizing the porous material through high-temperature carbothermic reduction reactionPreparing the ultrahigh-temperature heat-proof/insulation integrated ZrC/Zr by taking NaCl-Zr or NaCl-KCl-Zr as a raw material and carrying out molten salt reaction infiltration on the raw material and the porous ZrC ceramic blank 2 C, a complex phase material.
Specifically, the ultrahigh-temperature heat-proof/insulation integrated ZrC/Zr 2 The preparation method of the C complex phase material comprises the following steps:
(1) Synthesizing a porous ZrC ceramic blank: mixing zirconium dioxide and carbon black by a wet method, then carrying out vacuum drying, then preparing a blank by a dry pressing forming process, and finally synthesizing a porous ZrC ceramic blank by a high-temperature carbothermic reduction reaction;
(2) Synthesis of ZrC/Zr 2 C, complex phase material: mixing NaCl-Zr or NaCl-KCl-Zr by a dry method to obtain mixed powder, embedding the porous ZrC ceramic blank in the mixed powder, and preparing the ultrahigh temperature integrated ZrC/Zr for heat prevention and insulation by molten salt reaction infiltration 2 C, complex phase material.
In the step (1), the molar ratio of zirconium dioxide to carbon black is ZrO 2 C =1, 3.0-3.5. Wherein the purity of the zirconium dioxide is more than or equal to 99.9wt%, and the granularity is 2-5 mu m; the purity of the carbon black is more than or equal to 99wt%.
In the step (1), the wet mixing conditions are as follows: zirconia balls and absolute ethyl alcohol are used as mixed media, the rotating speed is 80-150r/min, and the mixing time is 8-24h.
In the step (1), the vacuum drying temperature is 25-50 ℃, and the drying time is 8-48h; the pressure of dry pressing is 30-100MPa.
In the step (1), the atmosphere of the high-temperature carbothermic reduction reaction is vacuum or flowing argon, the reaction temperature is 1300-1600 ℃, the heating rate before 1250 ℃ is 10-20 ℃/min, the heating rate after 1250 ℃ is 2-5 ℃/min, and the reaction time is 1-4h.
In the step (2), the component composition of NaCl-Zr is NaCl: zr =1-3, the component composition of NaCl-KCl-Zr is (NaCl-KCl) Zr = 1-3.
In the step (2), the molten salt reaction infiltration conditions are as follows: firstly, heating to 850-1100 ℃ in argon, preserving heat for 1-4h, then heating to 1290-1350 ℃ and preserving heat for 1-4h.
The ultra-high temperature heat-proof/insulation deviceFormed ZrC/Zr 2 The C complex phase material is prepared by the preparation method. The material has excellent performances of high temperature resistance, corrosion resistance, ablation resistance and the like, has low thermal conductivity, realizes the integration of ultrahigh temperature prevention/heat insulation, has wide application range, and can be used as an integrated material for preventing and insulating heat to be applied in the fields of aerospace, aviation, metallurgy, nuclear industry and the like.
The invention adopts in-situ high-temperature carbothermic reduction reaction to prepare the porous ZrC ceramic block material, when ZrO is ZrO 2 And carbon black according to ZrO 2 C =1 (3 + x), when mixed (x = 0-0.5), the carbothermic reduction reaction during heating is shown in equation (1):
ZrO 2 +3C→ZrC+2CO (1)
the weight change, weight change rate, linear shrinkage and linear shrinkage rate of the sample during the reaction are shown in fig. 1, and it can be seen from fig. 1 that the carbothermic reduction reaction starts at 1260 ℃ and simultaneously shrinks with the sample, the weight loss and shrinkage reach the maximum when the temperature reaches 1490-1510 ℃, the maximum weight loss is about 30%, and the maximum volume shrinkage is about 66%. Because the weight loss and shrinkage are very large, the sample can be cracked seriously to cause pulverization, so that the high-temperature carbothermic reduction reaction can only be used for preparing ZrC powder and cannot be used for preparing a block material.
The invention utilizes in-situ high-temperature carbothermic reaction to prepare the porous ZrC ceramic block material, and the key point is to control the carbothermic reduction process to slowly carry out the carbothermic reduction process, so that gas generated by the carbothermic reduction reaction is slowly released, and the contraction of a sample is very slow. The specific method is that after the sample is heated to 1250 ℃, the heating rate is controlled, namely the heating rate is reduced to 2-5 ℃/min, so that the carbothermic reduction reaction is slowly carried out, and the weight loss and the shrinkage rate of the sample are controlled.
The invention adopts NaCl (or NaCl-KCl) and Zr powder high-temperature molten salt to react and infiltrate to prepare the ultrahigh-temperature heat-insulation integrated ZrC/Zr 2 The preparation process of the C complex phase material comprises zirconium chloride steam or chloride steam disproportionation decomposition under the protection of argon and ordered carbon vacancy compound Zr 2 The process of the synthesis of C is shown in the equations (2) to (8):
firstly, the formation process of zirconium chloride steam is as follows:
4NaCl(g)+Zr(s)=ZrCl 4 (g)+4Na(g) (2)
3ZrCl 4 (g)+Zr(s)=4ZrCl 3 (g) (3)
2ZrCl 3 (g)+Zr(s)=3ZrCl 2 (g) (4)
ZrCl 2 (g)+Zr(s)=2ZrCl(g) (5)
on the surface of the porous in-situ high-temperature carbon thermal reduction reaction ZrC, disproportionation, replacement and reduction reactions are carried out to resolve the reaction formula of the metal Zr as follows:
ZrCl(g)=Zr(s)+ZrCl 2 (g) (6)
ZrCl 2 (g)=Zr(s)+2ZrCl 3 (g) (7)
the driving force for resolving Zr is the difference in Zr deposition activity between the metallic Zr powder and the porous ZrC matrix.
Reaction of active metal Zr with porous ZrC to form ZrC/Zr 2 The reaction process of the C complex phase material is as follows:
Zr(s)+ZrC(s)=Zr 2 C(s) (9)
2Zr(s)+C(s)=Zr 2 C (10)
preparing ZrC porous block material by in-situ high-temperature carbothermic reaction, and preparing ultrahigh-temperature anti-heat/heat-insulation integrated ZrC/Zr by high-temperature molten salt reaction infiltration 2 The process of the method of C complex phase material is shown in figure 2.
Compared with the prior art, the invention has the following beneficial effects:
(1) The method starts from zirconia and carbon black raw materials, prepares porous ZrC through high-temperature carbothermic reduction reaction under vacuum or argon protection, and then prepares ultra-high temperature heat prevention/insulation integrated Z through high-temperature molten salt reaction infiltrationrC/Zr 2 The C complex phase material has low raw material cost, simple process and low equipment requirement, and is suitable for large-scale production;
(2) The method has the advantages of low equipment requirement, mild reaction condition, simple process, small grain size of the synthesized porous ZrC ceramic blank, high porosity and high strength, and the prepared ultrahigh temperature ZrC/Zr for preventing/insulating heat integrally 2 The C complex phase material has excellent performances of high temperature resistance, corrosion resistance, ablation resistance and the like, has low thermal conductivity, and can realize the integration of ultrahigh temperature heat prevention/insulation;
(3) The invention relates to ultrahigh-temperature heat-insulation integrated ZrC/Zr 2 The C complex phase material has wide application range and can be used as an integrated material for heat insulation and protection in the fields of aerospace, aviation, metallurgy, nuclear industry and the like.
Drawings
FIG. 1 is a ZrO-system 2 And a graph of weight change, weight change rate, linear shrinkage and linear shrinkage rate of the sample in the high-temperature carbothermic reduction process with carbon black as a raw material;
FIG. 2 shows that ZrC porous ceramic body is prepared by in-situ high-temperature carbothermic reaction and then is infiltrated by high-temperature molten salt reaction to prepare novel ultra-high-temperature anti-heat-insulation integrated ZrC/Zr 2 C, a process flow diagram of the complex phase material;
FIG. 3 is a scanning electron micrograph of a ZrC porous ceramic green body prepared in example 1;
FIG. 4 shows integrated ZrC/Zr of ultra-high temperature anti/thermal insulation prepared in example 1 2 C, scanning electron microscope image of the complex phase material;
FIG. 5 is porous ZrC (a) and ZrC/Zr prepared in example 2 2 C, X-ray diffraction spectrum of the complex phase material (b);
FIG. 6 is a microscopic structure of porous ZrC embedded in uniformly mixed NaCl, KCl powder and Zr powder after infiltration treatment at 1100 ℃ for 2h in argon.
Detailed Description
The invention is described in detail below with reference to the figures and examples.
Example 1
(1) Synthesizing a porous ZrC ceramic blank: zrO of zirconium dioxide and carbon black which are used as raw materials according to a molar ratio 2 C =1, 3.1 weight,placing the mixture in a zirconia mixing tank, and mixing the zirconia balls and absolute ethyl alcohol on a mixer by taking zirconia balls and absolute ethyl alcohol as media, wherein the rotating speed of the mixer is 80r/min, and the mixing time is 24 hours; then, putting the uniformly mixed raw materials into a vacuum oven for drying treatment, wherein the drying temperature is 30 ℃, and the drying time is 48 hours; drying the ZrO 2 And placing the powder C in a high-strength steel mold, and performing dry pressing molding on a pressure molding machine, wherein the molding pressure is 45MPa; and (3) placing the demoulded blank in a high-temperature vacuum furnace, heating to 1250 ℃ at the speed of 15 ℃/min, then reducing the temperature rise speed to 2 ℃/min until 1450 ℃, preserving the temperature for 4h, and carrying out carbothermic reduction reaction to synthesize the porous ZrC ceramic blank, wherein the microstructure of the porous ZrC ceramic blank is shown in figure 3.
(2) Synthesis of ZrC/Zr 2 C complex phase material: weighing NaCl powder and Zr powder according to a molar ratio of NaCl to Zr =3, uniformly mixing by a dry method, embedding a porous ZrC ceramic blank in the uniformly mixed NaCl and Zr powder, heating to 940 ℃ in argon, preserving heat for 2h, performing disproportionation on zirconium chloride steam and chloride steam, heating to 1350 ℃, preserving heat for 4h, and preparing to obtain the ultrahigh-temperature integrated ZrC/Zr heat-insulation material 2 The microstructure of the C complex phase material is shown in figure 4.
Example 2
(1) Synthesizing a porous ZrC ceramic blank: zrO is prepared from zirconium dioxide and carbon black according to a molar ratio 2 Weighing 3.2 parts by weight of C =1, placing the weighed materials in a zirconia mixing tank, and mixing the materials on a mixer by taking zirconia balls and absolute ethyl alcohol as media, wherein the rotating speed of the mixer is 100 r/min, and the mixing time is 18h; then, putting the uniformly mixed raw materials into a vacuum oven for drying treatment, wherein the drying temperature is 50 ℃, and the drying time is 12 hours; drying the ZrO 2 And placing the powder C in a high-strength steel die, and performing dry pressing forming on a pressure forming machine, wherein the forming pressure is 100MPa; and (3) placing the demoulded blank in a high-temperature vacuum furnace, heating to 1250 ℃ at the speed of 15 ℃/min, then reducing the temperature rise speed to 5 ℃/min until 1500 ℃, preserving the temperature for 1h, and carrying out carbothermic reduction reaction to synthesize the porous ZrC ceramic blank, wherein the X-ray diffraction spectrum of the porous ZrC ceramic blank is shown in figure 5 (a).
(2) Synthesis of ZrC/Zr 2 C, complex phase material: and mixing NaCl powder, KCl powder and Zr powder according to a molar ratio of NaCl to KCl to Zr =1Weighing, uniformly mixing by a dry method, embedding the porous ZrC ceramic blank in uniformly mixed NaCl, KCl and Zr powder, heating to 850 ℃ in argon, preserving heat for 4 hours, performing disproportionation decomposition on zirconium chloride steam and chloride steam, heating to 1300 ℃, preserving heat for 2 hours, and preparing the ultrahigh-temperature heat-insulation-preventing integrated ZrC/Zr 2 The X-ray diffraction spectrum of the C complex phase material is shown in figure 5 (b).
Example 3
(1) Synthesizing a porous ZrC ceramic blank: zrO of zirconium dioxide and carbon black which are used as raw materials according to a molar ratio 2 Weighing 3.5 parts by weight of C =1, placing the weighed materials in a zirconia mixing tank, and mixing the materials on a mixer by taking zirconia balls and absolute ethyl alcohol as media, wherein the rotating speed of the mixer is 120 r/min, and the mixing time is 12h; then, putting the uniformly mixed raw materials into a vacuum oven for drying treatment, wherein the drying temperature is 45 ℃, and the drying time is 18h; drying the ZrO 2 And placing the powder C in a high-strength steel mold, and performing dry pressing molding on a pressure molding machine, wherein the molding pressure is 80MPa; and placing the demoulded blank in a high-temperature vacuum furnace, heating to 1200 ℃ at the speed of 20 ℃/min, then reducing the temperature rise speed to 3 ℃/min until 1600 ℃, preserving the temperature for 2h, and carrying out carbothermic reduction reaction to synthesize the porous ZrC ceramic blank.
(2) Synthesis of ZrC/Zr 2 C, complex phase material: weighing NaCl powder and Zr powder according to a molar ratio of NaCl to Zr =2 2 C, complex phase material.
Example 4
(1) Synthesizing a porous ZrC ceramic blank: zrO is prepared from zirconium dioxide and carbon black according to a molar ratio 2 Weighing 3.3 parts of C =1, placing the weighed materials in a zirconia mixing tank, and mixing the materials on a mixer by taking zirconia balls and absolute ethyl alcohol as media, wherein the rotating speed of the mixer is 150r/min, and the mixing time is 8 hours; then, putting the uniformly mixed raw materials into a vacuum oven for drying treatment, wherein the drying temperature is 40 ℃, and the drying time is 24 hours; drying the ZrO 2 And placing the powder C in a high-strength steel die, and performing dry pressing forming on a pressure forming machine, wherein the forming pressure is 50MPa; and placing the demoulded blank in a high-temperature vacuum furnace, heating to 1250 ℃ at the speed of 10 ℃/min, then reducing the temperature rise speed to 5 ℃/min until 1580 ℃, preserving the temperature for 3h, and carrying out carbothermic reduction reaction to synthesize the porous ZrC ceramic blank.
(2) Synthesis of ZrC/Zr 2 C complex phase material: weighing NaCl powder, KCl powder and Zr powder according to a molar ratio of NaCl to KCl to Zr =1.5 2 C, complex phase material.
Example 1-4 preparation of ultra-high temperature Integrated ZrC/Zr with prevention and insulation 2 The performance index of the C complex phase material is shown in Table 1.
TABLE 1 ultra-high temperature heat-proof integrated ZrC/Zr prepared in examples 1-4 2 Performance index of C complex phase material
Item
|
ZrC ceramic
|
Example 1
|
Example 2
|
Example 3
|
Example 4
|
Thermal conductivity at room temperature, W/m.K
|
32.5
|
5.3
|
5.2
|
4.9
|
4.5
|
1000K thermal conductivity, W/m.K
|
35.2
|
3.7
|
3.6
|
3.3
|
3.2
|
Vickers hardness, GPa
|
21.8
|
12.7
|
12.5
|
12.3
|
11.8
|
Flexural strength, MPa
|
435
|
296
|
273
|
230
|
190
|
Compressive strength, GPa
|
980
|
842
|
837
|
794
|
720
|
Fracture toughness, MPa.m 1/2 |
4.3
|
3.5
|
3.2
|
3.1
|
2.7 |