Polycarbosilane non-melting pretreatment and cracking conversion method for three-dimensional ceramic
Technical Field
The invention relates to preparation of ceramic materials, in particular to a method for pretreating polycarbosilane without melting and converting polycarbosilane into three-dimensional ceramic through cracking.
Background
Silicon carbide (SiC), as an advanced ceramic material, has excellent properties such as good mechanical properties, wide band gap, high electron mobility, chemical stability, high temperature resistance, corrosion resistance, etc., and also exhibits excellent properties under severe environmental conditions such as high temperature, high frequency, high power, etc., is often used for manufacturing corrosion-resistant materials, wear-resistant materials, high-temperature structural components, diodes, etc., and has wide applications in the fields of microelectronic systems, machinery, petroleum, chemical industry, metallurgy, aerospace, national defense, etc.
At present, the silicon carbide ceramic can be obtained by preparation methods such as normal pressure sintering, hot pressing sintering, reaction sintering and the like. Chinese patent ZL 201110347554.5 discloses a preparation method of an impregnated reinforced silicon carbide machinable complex-phase ceramic, wherein graphite, yttrium oxide and alumina powder are used as sintering aids, the graphite, yttrium oxide and alumina powder are sintered at normal pressure to obtain a silicon carbide complex-phase ceramic matrix, and the silicon carbide complex-phase ceramic matrix is repeatedly impregnated with phenolic resin and silica sol and then is subjected to heat treatment for 1-4 hours at 1450-1550 ℃ under the protection of nitrogen at normal pressure to obtain the impregnated reinforced silicon carbide machinable complex-phase ceramic. Chinese patent ZL 201510515890.4 discloses a method for preparing SiC/TiC composite ceramic by a precursor method, which comprises the steps of dissolving polycarbosilane and titanium powder serving as raw materials, stirring, evaporating, drying and the like, cracking at 1050-1100 ℃ under the protection of inert atmosphere to obtain SiC/TiC composite powder, and performing hot-pressing sintering at 1500-1600 ℃ to obtain the SiC/TiC composite ceramic. Chinese patent ZL 201510580537.4 discloses a method for producing silicon carbide ceramics by reacting and sintering silicon carbide particles with a molding resin. Chinese patent ZL 201510369345.9 discloses a high-thermal-conductivity reaction-sintered silicon carbide ceramic material and a preparation method thereof, wherein graphene, carbon powder, a surfactant, a dispersant and a binder are used as sintering aids, and the silicon particles are paved under the vacuum condition of 1650-1800 ℃ for reaction sintering after ball milling, spray granulation and press forming to obtain the silicon carbide ceramic. However, the method has the problems of high sintering temperature, high production cost, difficulty in mass production and the like, or the addition of a sintering aid is often required, so that impurity phases are easily introduced to influence the product performance.
The precursor conversion method is a method and a process for preparing an inorganic ceramic material by carrying out thermal decomposition and conversion on an organic polymer, and has the unique advantages of designability of molecular structure, lower preparation temperature, no sintering additive, controllable ceramic components, high purity, good product performance and the like. The precursor conversion method is a breakthrough of the great research of the advanced ceramic preparation technology, and has wide application prospect in the aspect of preparing silicon carbide low-dimensional (such as fiber, film and coating) ceramic. Chinese patent CN 109456065A discloses a preparation method of silicon carbide ceramic fiber, a boron-containing silicon carbide precursor is synthesized by a one-pot method, and the high-temperature resistant silicon carbide ceramic fiber is prepared by melt spinning and ultraviolet crosslinking. Chinese patent CN 110105070A discloses a method for preparing continuous silicon carbide fiber with controllable electrical property and wide range by using a phenyl-containing polycarbosilane precursor. Chinese patent ZL 201410099387.0 discloses a method for preparing SiC/Al by taking polycarbosilane, SiC particles and aluminum powder as raw materials through precursor conversion method2O3A method for complex phase ceramic coating. At present, inorganic elements in the silicon carbide precursor ceramic material are expanded to partial metal elements, such as Al, Ti and the like. Chinese patent CN 109111574A discloses a preparation method of Si-Al-C-O fiber, which comprises the steps of preparing a polyaluminum carbosilane precursor from polycarbosilane and 8-hydroxyquinoline aluminum at high temperature and high pressure, and carrying out melt spinning and sintering to obtain the Si-Al-C-O fiber. Chinese patent ZL 201010617739.9 discloses a method for preparing compact silicon carbide/titanium carbide complex phase ceramic by using cyclopentadienyl titanium dichloride and hyperbranched polycarbosilane precursor. Although the advantages of the precursor conversion method are remarkable, certain difficulties exist in preparing silicon carbide three-dimensional ceramics. The low molecular weight polycarbosilane precursor is not easy to form at normal temperature and is difficult to convert into three-dimensional ceramics. The polycarbosilane can release a large amount of H in the pyrolysis process2、CH4And small molecular gases such as SiO and CO shrink the ceramic, so that the internal defects exist, the mechanical properties such as ceramic fracture toughness are poor, a large number of cracks are generated, and finally the ceramic is seriously damaged and cannot be molded. Chinese patent ZL 201711494377.7 discloses a method for preparing graphene/silicon carbide monolithic ceramic by high-temperature pyrolysis of graphene oxide-vinyltriethoxysilane-polycarbosilane precursorThe method makes a new breakthrough in the field of precursor ceramics, but the obtained monolithic ceramics have poor comprehensive performance. Chinese patent CN 110467467 a discloses a blending and re-cracking method, which enables graphene/silicon carbide monolithic ceramics to have higher ceramic yield and lower linear shrinkage, but the high-temperature cracking of the silicon carbide precursor still inevitably generates a large amount of small molecular gas, the ceramic surface still has many holes and defects on the microscopic scale, and the high temperature resistance and fracture toughness need to be improved, which limits the application of silicon carbide ceramics. Therefore, in order to further improve the structure/function integration level of the silicon carbide three-dimensional ceramic, reduce the holes and shrinkage of the ceramic and improve the fracture toughness of the ceramic, the key point is to carry out non-melting pretreatment modification on the silicon carbide precursor.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a simple and economic polycarbosilane non-melting pretreatment and cracking conversion method for three-dimensional ceramics, which is suitable for industrial production.
The invention also aims to provide a high-temperature-resistant 3D-SiC (Al, rGO) ceramic material which is prepared by adopting the polycarbosilane non-melting pretreatment and cracking conversion method thereof to obtain the three-dimensional ceramic and has high ceramic yield, high fracture toughness and low linear shrinkage.
The polycarbosilane non-melting pretreatment and cracking conversion method for three-dimensional ceramics comprises the following steps:
1) synthesis of three-dimensional silicon carbide polymer precursor
Polycarbosilane (PCS) and aluminum acetylacetonate (Al (acac)3) Dissolving the components in an organic solvent together, building a distillation device, quickly heating up under the protection of inert atmosphere to evaporate the organic solvent, then preserving heat, heating up and preserving heat for the second time to obtain a highly cross-linked hyperbranched aluminum-containing polycarbosilane solid, cooling, adding the organic solvent, dissolving and filtering to form a golden yellow transparent organic solution, pouring Graphene Oxide (GO) powder into deionized water to obtain a turbid aqueous solution, and performing ultrasonic dispersion on the organic solution and the aqueous solution respectively to obtain a hyperbranched aluminum-containing polycarbosilane solution and a graphene oxide dispersion solution; in the hyperbranched polymer containingAdding a Kansted platinum catalyst into an aluminum polycarbosilane solution, adding a Vinyl Triethoxysilane (VTES) crosslinking infusible pretreating agent and dilute hydrochloric acid into a graphene oxide dispersion liquid to adjust the solution to acidity, mixing the two solutions, placing the two solutions in a beaker for water bath heating reaction, simultaneously performing magnetic stirring, standing after the reaction is finished, taking out an upper layer product, performing reduced pressure distillation to obtain a precursor aluminum-containing polycarbosilane-vinyl triethoxysilane-graphene oxide (PACS-VTES-GO, PAVG for short) solid polymer, and grinding to obtain precursor PAVG powder;
in the step 1), the mass ratio of the polycarbosilane to the acetylacetone aluminum powder is preferably (40-60): 3; the organic reagent is preferably xylene; the inert atmosphere is preferably argon, and the flow rate is preferably 20-50 mL/min; the rapid heating is preferably carried out at a heating rate of 4-6 ℃/min to 145-155 ℃, and the heat preservation time is preferably 0.5-2 h; the second heating is preferably carried out at a heating rate of 2-4 ℃/min to 305-315 ℃, and the heat preservation time is preferably 4-6 h; the mass ratio of the hyperbranched aluminum-containing polycarbosilane to the graphene oxide powder is preferably (80-120): 1; the volume ratio of the organic solution, the aqueous solution, the vinyltriethoxysilane crosslinking non-melting pretreatment agent and the platinum catalyst is preferably (30-50): 2-5): 1; the concentration of the dilute hydrochloric acid is preferably 3-10 wt%, and the pH value is preferably adjusted to 1-3 when the dilute hydrochloric acid is adjusted to be acidic; the water bath heating temperature is preferably 50-70 ℃, the magnetic stirring speed is preferably 25-35 rpm, and the heat preservation time is preferably 0.4-0.6 h.
2) Preparation of SiC (Al, rGO) p ceramic particles
Putting a part of PAVG powder of a precursor obtained in the step 1) in a graphite paper boat under the protection of inert atmosphere to perform high-temperature cracking in a tubular furnace to obtain cracked SiC (Al, rGO) p ceramic particles;
in the step 2), the inert atmosphere is preferably argon, and the gas flow rate is preferably 60-150 mL/min; the high-temperature cracking temperature is preferably 1300 ℃, the heating rate is preferably 3-5 ℃/min, and the heat preservation time is preferably 1-30 min.
3) Preparation of 3D-SiC (Al, rGO) ceramic
Adding the rest PAVG powder of the precursor in the step 1) and alcohol into the SiC (Al, rGO) p ceramic particles obtained in the step 2), performing ball milling, uniformly mixing, drying, performing tabletting molding, putting into an inert atmosphere tube furnace, and performing high-temperature sintering again to obtain 3D-SiC (Al, rGO) ceramic;
in the step 3), the mass of the cracked SiC (Al, rGO) p ceramic particles and the precursor PAVG powder is preferably (5-50): 10; the ball milling time is preferably 8-10 h; the pressure of the tabletting molding is preferably 30-50 MPa, and the pressure maintaining time is preferably 15-25 s; the inert atmosphere is preferably argon, and the gas flow rate is preferably 60-150 mL/min; the temperature of the secondary high-temperature sintering is preferably 1200-1400 ℃, the heating rate is preferably 3-5 ℃/min, and the heat preservation time is preferably 5-35 min.
4) Surface morphology modification of 3D-SiC (Al, rGO) ceramic
And (3) dipping the 3D-SiC (Al, rGO) ceramic obtained in the step (3) into liquid polycarbosilane, and sintering in an inert atmosphere tubular furnace again to obtain the 3D-SiC (Al, rGO) ceramic material with a more compact surface appearance.
In the step 4), the soaking time is preferably 20-30 h; argon is preferably selected as the inert atmosphere, and the gas flow rate is preferably 60-150 mL/min; the sintering temperature is preferably equal to the sintering temperature in the step 3), the heating rate is preferably 3-5 ℃/min, and the heat preservation time is preferably 1-30 min.
The 3D-SiC (Al, rGO) ceramic material contains four elements of Si, C, O and Al, and the Al is uniformly distributed in SiO in an atomic statexCyIn the amorphous phase, beta-SiC nanocrystals are embedded in SiO of composite rGOxCy/CfreeIn the amorphous phase, SiO is present2And (4) microcrystals.
The polymer precursor is prepared by taking aluminum acetylacetonate and vinyl triethoxysilane as crosslinking non-melting pretreatment agents, and performing non-melting pretreatment on polycarbosilane with a silicon-hydrogen bond and graphene oxide containing hydroxyl in a system to form an aluminum-containing polycarbosilane-vinyl triethoxysilane-graphene oxide three-dimensional network structure polymer. In the invention, by utilizing the characteristics of adjustable molecular structure, easy molding and conversion into inorganic ceramic of polycarbosilane, a novel and economic crosslinking infusible pretreatment modification technology and a cracking conversion ceramic method are developed, the crosslinking degree and molecular weight of a precursor are expanded to form a three-dimensional network structure, the evaporation of small molecular gas during cracking is reduced, the fracture toughness and high temperature resistance stability of the ceramic are improved, and a light high-strength 3D-SiC (Al, rGO) ceramic material with high ceramic yield, high fracture toughness and low linear shrinkage is provided for the application fields of severe environments such as high temperature.
Compared with the prior art, the invention has the following outstanding beneficial effects:
(1) the high-temperature-resistant 3D-SiC (Al, rGO) ceramic prepared by the invention is compact and crack-free, has excellent performances such as high ceramic yield (> 90%), low linear shrinkage (< 5%), high hardness and high fracture toughness, comprehensively strengthens the performance of the traditional silicon carbide polymer precursor ceramic, and has important significance for expanding the application of the ceramic in complex severe environments.
(2) The invention adopts Al (acac)3And VTES as crosslinking non-melting pretreating agent, and treating PCS with non-melting pretreatment to consume part of Si-H bonds on PCS chain to generate stable Si-O-Al bonds and Si-C bonds6The PCS three-dimensional space network structure with the rGO/VTES as the pivot greatly improves the molecular weight of the precursor, and introduces aluminum atoms and a graphene lamellar structure, so that the ceramic yield, high-temperature stability, fracture toughness and hardness can be improved, the shrinkage rate can be reduced, cracks can be eliminated, and a new scheme is provided for solving the problems of the existing silicon carbide precursor ceramic.
(3) The polycarbosilane crosslinking infusible pretreatment and the cracking conversion of the polycarbosilane crosslinking infusible pretreatment into 3D-SiC (Al, rGO) ceramic provided by the invention have simple and economic two-step process, the ceramic property can be regulated and controlled by adjusting the technical parameters such as the proportion of cracking ceramic/precursor, sintering temperature and the like, and the invention is convenient for popularization to realize industrial production.
Drawings
FIG. 1 is a graph of 3D-SiC (Al, rGO) ceramic sample samples prepared at different sintering temperatures of 1200 deg.C, 1300 deg.C, and 1400 deg.C.
FIG. 2 is an infrared (FTIR) spectrum of PCS, PACS and PAVG as powder samples. In FIG. 2The abscissa is the wave number (cm)-1)。
FIG. 3 is a graph of the linear shrinkage of 3D-SiC (Al, rGO) ceramics and the yield of the ceramics as a function of different sintering temperatures (1200 deg.C, 1300 deg.C, 1400 deg.C). In FIG. 3, the ordinate represents the linear shrinkage (%) and the ceramic yield (%) and the abscissa represents the ceramic sintering temperature (. degree. C.).
FIG. 4 is an X-ray diffraction (XRD) pattern of 3D-SiC (Al, rGO) ceramic at different sintering temperatures (1200 deg.C, 1300 deg.C, 1400 deg.C) and SiC (Al, rGO) p ceramic particles with a cracking temperature of 1300 deg.C. In fig. 4, the abscissa is 2 θ (°).
FIG. 5 is a Raman (Raman) spectrum of 3D-SiC (Al, rGO) ceramics at different sintering temperatures (1200 deg.C, 1300 deg.C, 1400 deg.C). In FIG. 5, the abscissa is the Raman shift (cm)-1)。
FIG. 6 is a series of 3D-SiC (Al, rGO) ceramic surface Scanning Electron Microscope (SEM) images. In fig. 6, (a) corresponds to a sintering temperature of 1200 ℃; (b) the corresponding sintering temperature is 1300 ℃; (c) the corresponding sintering temperature is 1400 ℃; (d) the surface morphology of the ceramic material is modified to correspond to 3D-SiC (Al, rGO) ceramic with the sintering temperature of 1300 ℃.
Detailed Description
The above-described scheme will be further explained with reference to specific embodiments.
The 3D-SiC (Al, rGO) ceramic prepared by the invention is black, has good integrity, compact and smooth surface and no visible cracks or holes. The structural general formula of the polymer precursor PAVG is as follows:
FIG. 1 shows the graph of 3D-SiC (Al, rGO) ceramic samples prepared by sintering at 1200 deg.C, 1300 deg.C, 1400 deg.C. An infrared (FTIR) spectrum (figure 2) of the precursor PAVG shows that Si-C (780 cm) exists in the system-1)、Si–CH2–Si(1020cm-1)、Si–O–Si(1080cm-1)、Si–O–C(1100cm-1)、Si–CH3(1250cm-1)、C=C(1600cm-1)、Si–H(2100cm-1) And the like. The 3D-SiC (Al, rGO) ceramic of the invention has the following characteristics in the linear shrinkage rate and the relation curve chart (figure 3) of the ceramic yield and different sintering temperatures (1200 ℃, 1300 ℃, 1400 ℃): with the increase of the sintering temperature, the ceramic yield is reduced, and the linear shrinkage rate is increased. The SiC (Al, rGO) p ceramic particles and 3D-SiC (Al, rGO) ceramics have the following characteristics in an X-ray diffraction (XRD) pattern (fig. 4): the (111)/(220)/(311) crystal plane diffraction peak belonging to beta-SiC exists at the 2 theta position of 35.6 degrees/60.1 degrees/71.7 degrees, the intensities of the three peaks are gradually increased along with the increase of the sintering temperature, and the beta-SiC crystal peak in the 3D-SiC (Al, rGO) ceramic is stronger than that in the SiC (Al, rGO) p ceramic; the 2 theta is attributed to SiO at 20.9 DEG/26.6 DEG2The (100)/(011) crystal plane diffraction peak of (A) only appears in 3D-SiC (Al, rGO) ceramics, and the intensity of the peak is weakened along with the increase of the sintering temperature. The 3D-SiC (Al, rGO) ceramic has the following characteristics in the Raman (Raman) spectrum (fig. 5): at 1350cm-1(peak D) and 1600cm-1(G peak) there is a characteristic peak, which is respectively assigned to amorphous carbon and graphitization degree, and the ratio of D peak to G peak increases with the increase of sintering temperature. The 3D-SiC (Al, rGO) ceramic has the following characteristics in a Scanning Electron Microscope (SEM) image (fig. 6): the surface of the 3D-SiC (Al, rGO) ceramic is compact, and particles on the surface of the ceramic gradually increase and enlarge along with the increase of the sintering temperature; the surface of the 3D-SiC (Al, rGO) ceramic subjected to precursor impregnation and cracking is more compact.
Table 1 shows the hardness and fracture toughness of 3D-SiC (Al, rGO) ceramics at different sintering temperatures (1200 ℃, 1300 ℃, 1400 ℃).
TABLE 1
Specific preparation method examples are given below.
Example 1
1. 2g of PCS powder and 0.12g of acetylacetone aluminum powder are dissolved in 40mL of dimethylbenzene and then poured into a 150mL three-necked bottle, a distillation device is built, argon is introduced for protection, the flow rate is 35mL/min, the temperature is rapidly increased to 150 ℃ at the speed of 5 ℃/min under the magnetic stirring of 200rpm, the dimethylbenzene is evaporated to dryness, and the temperature is kept for 1 h;
2. heating the electric jacket to 310 ℃ at the speed of 3 ℃/min and preserving heat for 5h to obtain the highly crosslinked hyperbranched aluminum-containing polycarbosilane solid. After cooling, pouring a proper amount of dimethylbenzene into the bottle for dissolving and filtering to obtain 40mL of golden yellow transparent solution;
3. dispersing 0.02g of graphene oxide powder in 40mL of deionized water, and respectively ultrasonically dispersing the aqueous solution and the xylene solution obtained in the step 2 for 30 min;
4. adding 1mL of Kanst platinum catalyst into a xylene solution, adding 2mL of vinyltriethoxysilane cross-linking infusible pretreating agent and a proper amount of dilute hydrochloric acid (5 wt%) into an aqueous solution, and adjusting the pH value of the solution to 1-3;
5. the two solutions of step 4 were mixed in a beaker and reacted for 30min at 60 ℃ water bath conditions with a magnetic stirring rate of 30 rpm. After rotary evaporation, obtaining black solid and grinding the black solid to obtain PAVG powder;
6. and (3) putting the PAVG powder obtained in the step (5) into a crucible to be cracked at 1300 ℃, wherein the heating rate is 4 ℃/min, the heat preservation time is 1min, and the argon flow rate is 100mL/min, so that the cracked SiC (Al, rGO) p ceramic particles are obtained. Taking 0.6g of SiC (Al, rGO) p ceramic particles, 0.4g of PAVG powder, 4g of agate grinding balls and a proper amount of alcohol, ball-milling for 9 hours, and drying to obtain SiC (Al, rGO) p/PAVG powder;
7. weighing 0.5g of SiC (Al, rGO) p/PAVG powder obtained in the step 6, keeping the pressure for 20s under the pressure of 40MPa, pressing the powder into a wafer shape by using a die, putting the wafer shape into a tubular furnace, heating the wafer shape to 1200 ℃ at the heating rate of 4 ℃/min, sintering the wafer shape, keeping the temperature for 5min, keeping the argon flow rate at 100mL/min, and cooling the wafer along with the furnace to obtain the 3D-SiC (Al, rGO) ceramic.
Example 2
1. 2g of PCS powder and 0.12g of acetylacetone aluminum powder are dissolved in 40mL of dimethylbenzene and then poured into a 150mL three-necked bottle, a distillation device is built, argon is introduced for protection, the flow rate is 35mL/min, the temperature is rapidly increased to 150 ℃ at the speed of 5 ℃/min under the magnetic stirring of 200rpm, the dimethylbenzene is evaporated to dryness, and the temperature is kept for 1 h;
2. heating the electric jacket to 310 ℃ at the speed of 3 ℃/min and preserving heat for 5h to obtain the highly crosslinked hyperbranched aluminum-containing polycarbosilane solid. After cooling, pouring a proper amount of dimethylbenzene into the bottle for dissolving and filtering to obtain 40mL of golden yellow transparent solution;
3. dispersing 0.02g of graphene oxide powder in 40mL of deionized water, and respectively ultrasonically dispersing the aqueous solution and the xylene solution obtained in the step 2 for 30 min;
4. adding 1mL of Kanst platinum catalyst into a xylene solution, adding 2mL of vinyltriethoxysilane cross-linking infusible pretreating agent and a proper amount of dilute hydrochloric acid (5 wt%) into an aqueous solution, and adjusting the pH value of the solution to 1-3;
5. the two solutions of step 4 were mixed in a beaker and reacted for 30min at 60 ℃ water bath conditions with a magnetic stirring rate of 30 rpm. After rotary evaporation, obtaining black solid and grinding the black solid to obtain PAVG powder;
6. and (3) putting the PAVG powder obtained in the step (5) into a crucible to be cracked at 1300 ℃, wherein the heating rate is 4 ℃/min, the heat preservation time is 1min, and the argon flow rate is 100mL/min, so that the cracked SiC (Al, rGO) p ceramic particles are obtained. Taking 0.6g of SiC (Al, rGO) p ceramic particles, 0.4g of PAVG powder, 4g of agate grinding balls and a proper amount of alcohol, ball-milling for 9 hours, and drying to obtain SiC (Al, rGO) p/PAVG powder;
7. weighing 0.5g of SiC (Al, rGO) p/PAVG powder obtained in the step 6, keeping the pressure for 20s under the pressure of 40MPa, pressing the powder into a wafer shape by using a die, putting the wafer shape into a tube furnace, heating the wafer shape to 1300 ℃ at the heating rate of 4 ℃/min, sintering the wafer shape, keeping the temperature for 5min, keeping the argon flow rate at 100mL/min, and cooling the wafer along with the furnace to obtain the 3D-SiC (Al, rGO) ceramic.
8. And (3) dipping the 3D-SiC (Al, rGO) ceramic obtained in the step (7) in liquid PCS for 24h, putting the liquid PCS in a tubular furnace, heating to 1300 ℃ at a heating rate of 4 ℃/min, sintering, keeping the temperature for 5min, and keeping the argon flow rate at 100mL/min to obtain the 3D-SiC (Al, rGO) ceramic with a more compact surface appearance.
Example 3
1. 2g of PCS powder and 0.12g of acetylacetone aluminum powder are dissolved in 40mL of dimethylbenzene and then poured into a 150mL three-necked bottle, a distillation device is built, argon is introduced for protection, the flow rate is 35mL/min, the temperature is rapidly increased to 150 ℃ at the speed of 5 ℃/min under the magnetic stirring of 200rpm, the dimethylbenzene is evaporated to dryness, and the temperature is kept for 1 h;
2. heating the electric jacket to 310 ℃ at the speed of 3 ℃/min and preserving heat for 5h to obtain the highly crosslinked hyperbranched aluminum-containing polycarbosilane solid. After cooling, pouring a proper amount of dimethylbenzene into the bottle for dissolving and filtering to obtain 40mL of golden yellow transparent solution;
3. dispersing 0.02g of graphene oxide powder in 40mL of deionized water, and respectively ultrasonically dispersing the aqueous solution and the xylene solution obtained in the step 2 for 30 min;
4. adding 1mL of Kanst platinum catalyst into a xylene solution, adding 2mL of vinyltriethoxysilane cross-linking infusible pretreating agent and a proper amount of dilute hydrochloric acid (5 wt%) into an aqueous solution, and adjusting the pH value of the solution to 1-3;
5. the two solutions of step 4 were mixed in a beaker and reacted for 30min at 60 ℃ water bath conditions with a magnetic stirring rate of 30 rpm. After rotary evaporation, obtaining black solid and grinding the black solid to obtain PAVG powder;
6. and (3) putting the PAVG powder obtained in the step (5) into a crucible to be cracked at 1300 ℃, wherein the heating rate is 4 ℃/min, the heat preservation time is 1min, and the argon flow rate is 100mL/min, so that the cracked SiC (Al, rGO) p ceramic particles are obtained. Taking 0.6g of SiC (Al, rGO) p ceramic particles, 0.4g of PAVG powder, 4g of agate grinding balls and a proper amount of alcohol, ball-milling for 9 hours, and drying to obtain SiC (Al, rGO) p/PAVG powder;
7. weighing 0.5g of SiC (Al, rGO) p/PAVG powder obtained in the step 6, keeping the pressure for 20s under the pressure of 40MPa, pressing the powder into a wafer shape by using a die, placing the wafer shape in a tubular furnace, raising the temperature to 1400 ℃ at the temperature rise speed of 4 ℃/min, sintering, keeping the temperature for 5min, keeping the argon flow speed at 100mL/min, and cooling along with the furnace to obtain the 3D-SiC (Al, rGO) ceramic.
The above-described embodiments are merely preferred embodiments of the present invention, and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention. The invention takes PCS as raw material and takes Al (acac)3And VTES is a crosslinking non-melting pretreating agent, GO is a crosslinking non-melting pretreating auxiliary agent, a silicon carbide ceramic precursor PAVG with a three-dimensional network structure is prepared by utilizing a crosslinking non-melting pretreating modification technology, and SiC (Al, rGO) p ceramic particles are obtained through high-temperature cracking, wherein the SiC (Al, rGO) p ceramic particles with the cracking temperature of 1300 ℃ have the best comprehensive performance, so that the SiC (Al, rGO) p ceramic particles and the SiC (Al, rGO) p ceramic particles are mixed to obtain the silicon carbide ceramic precursor PAVGPAVG precursor powder is subjected to ball milling and mixing, 3D-SiC (Al, rGO) ceramic is obtained through a further precursor conversion process, and finally the surface appearance of the ceramic is modified through a liquid PCS impregnation pyrolysis method, so that the ceramic is further densified, and the 3D-SiC (Al, rGO) ceramic material with excellent comprehensive performance can be obtained. The PAVG precursor obtained after the polycarbosilane is subjected to non-melting pretreatment has high molecular weight and high crosslinking degree, so that the escape of small molecular gas during cracking is greatly improved, the ceramic yield of the precursor is improved, and the shrinkage rate is reduced. The Al-O-Si network structure of the 3D-SiC (Al, rGO) ceramic at the grain boundary can block crack propagation, the sliding effect of graphene and particles and micropores generated by ball-milling and re-sintering can help to relax stress, and aluminum atoms can achieve the purpose of particle dispersion toughening, which are beneficial to improving the fracture toughness of the precursor ceramic. In addition, aluminum atoms can inhibit SiOxCyThe decomposition of the phase further hinders the growth of beta-SiC microcrystals, thereby improving the hardness and the high temperature resistance stability of the precursor ceramic.