Preparation method of brittle-fracture-resistant silicon carbide material
阅读说明：本技术 一种抗脆裂的碳化硅材料的制备方法 (Preparation method of brittle-fracture-resistant silicon carbide material ) 是由 赵烨坚 于 2021-07-06 设计创作，主要内容包括：本发明公开了一种抗脆裂的碳化硅材料的制备方法,通过将碳粉、多孔碳、氮化硼等材料混合、模压后烧结成型、后续加工制得成品,解决了现有技术中碳化硅韧性差、易脆断的缺陷。(The invention discloses a preparation method of a brittle fracture resistant silicon carbide material, which is characterized in that a finished product is prepared by mixing carbon powder, porous carbon, boron nitride and other materials, molding, sintering and forming and subsequent processing, and the defects of poor toughness and easy brittle fracture of silicon carbide in the prior art are overcome.)
1. A preparation method of a brittle fracture resistant silicon carbide material is characterized by comprising the following steps: the method comprises the following steps:
(1) preparing 100 parts of nano carbon powder, 15-30 parts of porous carbon material, 15-25 parts of boron nitride and 40-60 parts of adhesive according to the mass ratio; the materials are uniformly mixed for later use;
(2) in a mould, weighing silicon particles according to 1.8-2.3 times of the dosage of the nano carbon powder, paving a plurality of layers of silicon particles and a layer of mixed material, and pressing to obtain a blank; laying a layer of silicon particles on the top of the blank;
(3) heating the blank in a high-temperature vacuum furnace to 1400 ℃, heating to 1700 ℃ to 1800 ℃ at a heating rate of 15 ℃/min, and preserving heat for 3h to obtain a semi-finished product;
(4) and processing and polishing the semi-finished product to obtain a finished product.
2. The method of preparing a embrittlement-resistant silicon carbide material as claimed in claim 1, wherein: the preparation method of the porous carbon material comprises the following steps:
dispersing 30 parts of polyacrylonitrile in 100 parts of DMF solution according to the volume ratio, heating to 60 ℃, stirring for 3 hours, adding 20 parts of boric acid at 60 ℃, and continuing to stir for 1.5 hours; and then carrying out electrostatic spinning on the polyacrylonitrile fiber under the conditions that the spinning voltage is 18kV, the flow rate of the spinning solution is 1.0mL/h, the temperature is 40 ℃ and the receiving distance is 20cm to obtain the polyacrylonitrile fiber, drying the polyacrylonitrile fiber at the temperature of 100 ℃ for 1h, heating the polyacrylonitrile fiber to the temperature of 450 ℃ in the atmosphere of protective gas, keeping the temperature for 2h, continuing heating the polyacrylonitrile fiber to the temperature of 600 ℃ and keeping the temperature for 1h, and washing the polyacrylonitrile fiber with dilute hydrochloric acid to obtain the porous carbon material.
3. The method of preparing a embrittlement-resistant silicon carbide material as claimed in claim 1, wherein: the boron nitride is treated as follows:
mixing hexagonal boron nitride and concentrated sulfuric acid, heating to 170 ℃, stirring for 30-50 hours, and then drying at room temperature to prepare sulfuric acid intercalated boron nitride; adding a proper amount of saturated ammonia water into a crucible, placing the sulfuric acid intercalation boron nitride into the crucible, stirring the mixture for 3 hours at room temperature to prepare the single-layer boron nitride material with the ammonium sulfate crystals.
4. The method of preparing a embrittlement-resistant silicon carbide material as claimed in claim 1, wherein: the boron nitride is treated as follows:
mixing hexagonal boron nitride and concentrated sulfuric acid, heating to 170 ℃, stirring for 30-50 hours, and then drying at room temperature to prepare sulfuric acid intercalated boron nitride; adding a proper amount of absolute ethyl alcohol into the crucible, placing the sulfuric acid intercalated boron nitride into the crucible, heating the mixture to 100-120 ℃, and reacting for 3-4 hours to prepare the boron nitride material with the enlarged interlayer spacing.
5. The method of preparing a embrittlement-resistant silicon carbide material as claimed in claim 4, wherein: and after the boron nitride material for expanding the interlayer spacing is blended with the graphene, co-sintering at 800-1100 ℃ in a protective gas atmosphere to prepare the graphene intercalation boron nitride material.
6. The method of preparing a embrittlement-resistant silicon carbide material as claimed in any one of claims 3, 4 and 5, wherein: the single-layer boron nitride material with the ammonium sulfate crystals and the boron nitride material for enlarging the interlayer spacing are prepared by mixing DMF (dimethyl formamide) as a solvent with isophorone diisocyanate (IPDI) to prepare IPDI grafted boron nitride; ferroferric oxide (Fe)3O4) After being coated by a silane coupling agent, the mixture is blended with IPDI grafted boron nitride to prepare BN @ Fe3O4。
7. The method of preparing a embrittlement-resistant silicon carbide material of claim 6, wherein: the ferroferric oxide is hollow ferroferric oxide microspheres.
8. The method of preparing a embrittlement-resistant silicon carbide material as claimed in claim 7, wherein: and after the hollow ferroferric oxide microspheres are blended with boric acid, heating to 450 ℃ to prepare porous ferroferric oxide with etched surfaces, and then washing and drying by using dilute hydrochloric acid to prepare the porous hollow ferroferric oxide material.
Technical Field
The invention relates to the technical field of mechanical sealing elements, in particular to the field of friction-resistant materials in mechanical sealing elements.
Background
The mechanical sealing part belongs to one of mechanical basic elements with precision and complex structure, and is a key part of equipment such as various pumps, reaction synthesis kettles, turbine compressors, submersible motors and the like. Whether the mechanical seal design is reasonable or not depends on the selection of friction pair materials to a great extent, the accidents of seal failure caused by improper selection of the friction pair materials are frequent, and the wear resistance and the service life of the friction pair materials depend on the characteristics of a sealing medium, the temperature and the pressure during use, the linear velocity of a sealing end face and other factors. The overall requirements for friction pair materials are wear resistance, heat resistance, corrosion resistance, impact resistance, thermal cracking resistance, and the like.
Silicon carbide is a typical covalent bond compound as a novel hard friction pair material. However, strong covalent bonds also cause silicon carbide ceramics to exhibit significant brittleness, have very low fracture toughness, are very sensitive to defects and cracks, and, although silicon carbide ceramics can withstand a single large impact force, are crushed upon impact, and have poor secondary impact resistance.
Disclosure of Invention
The invention aims to provide a preparation method of a friction pair material of a mechanical sealing element, which solves the problems in the background art.
In order to achieve the purpose, the invention provides the following technical scheme: the preparation method of the brittle fracture resistant silicon carbide material comprises the following steps
(1) Preparing 100 parts of nano carbon powder, 15-30 parts of porous carbon material, 15-25 parts of boron nitride and 40-60 parts of adhesive according to the mass ratio; the materials are uniformly mixed for later use.
(2) In a mould, weighing silicon particles according to 1.8-2.3 times of the dosage of the nano carbon powder, paving a plurality of layers of silicon particles and a layer of mixed material, and pressing to obtain a blank; and laying a layer of silicon particles on the top of the blank.
(3) And (3) heating the blank in a high-temperature vacuum furnace to 1400 ℃, heating to 1700 ℃ to 1800 ℃ at a heating rate of 15 ℃/min, and preserving heat for 3h to obtain a semi-finished product.
(4) And processing and polishing the semi-finished product to obtain a finished product.
Further, the preparation method of the porous carbon material is as follows:
dispersing 30 parts of polyacrylonitrile in 100 parts of DMF solution according to the volume ratio, heating to 60 ℃, stirring for 3 hours, adding 20 parts of boric acid at 60 ℃, and continuing to stir for 1.5 hours; and then carrying out electrostatic spinning on the polyacrylonitrile fiber under the conditions that the spinning voltage is 18kV, the flow rate of the spinning solution is 1.0mL/h, the temperature is 40 ℃ and the receiving distance is 20cm to obtain the polyacrylonitrile fiber, drying the polyacrylonitrile fiber at the temperature of 100 ℃ for 1h, heating the polyacrylonitrile fiber to the temperature of 450 ℃ in the atmosphere of protective gas, keeping the temperature for 2h, continuing heating the polyacrylonitrile fiber to the temperature of 600 ℃ and keeping the temperature for 1h, and washing the polyacrylonitrile fiber with dilute hydrochloric acid to obtain the porous carbon material.
Further, the boron nitride is treated as follows:
mixing hexagonal boron nitride and concentrated sulfuric acid, heating to 170 ℃, stirring for 30-50 hours, and then drying at room temperature to prepare sulfuric acid intercalated boron nitride; adding a proper amount of saturated ammonia water into a crucible, placing the sulfuric acid intercalation boron nitride into the crucible, stirring the mixture at room temperature for 3 hours to prepare the single-layer boron nitride material with ammonium sulfate crystals.
Further, the boron nitride is treated as follows:
mixing hexagonal boron nitride and concentrated sulfuric acid, heating to 170 ℃, stirring for 30-50 hours, and then drying at room temperature to prepare sulfuric acid intercalated boron nitride; adding a proper amount of absolute ethyl alcohol into a crucible, placing the sulfuric acid intercalated boron nitride in the crucible, heating to 100-120 ℃, and reacting for 3-4 hours to prepare the boron nitride material with enlarged interlayer spacing.
Further, the boron nitride material with the enlarged interlayer spacing and the graphene are blended and then sintered together at 800-1100 ℃ in a protective gas atmosphere to prepare the graphene intercalation boron nitride material.
Further, the single-layer boron nitride material with ammonium sulfate crystals and the boron nitride material for expanding the interlayer spacing are blended with isophorone diisocyanate (IPDI) by taking DMF as a solvent to prepare IPDI grafted boron nitride; ferroferric oxide (Fe)3O4) After being coated by a silane coupling agent, the mixture is blended with IPDI grafted boron nitride to prepare BN @ Fe3O4。
Further, the ferroferric oxide is hollow ferroferric oxide microspheres.
Further, the hollow ferroferric oxide microspheres are mixed with boric acid, heated to 450 ℃ to prepare porous ferroferric oxide with etched surfaces, and then washed by dilute hydrochloric acid and dried to prepare the porous hollow ferroferric oxide material.
Compared with the prior art, the invention has the following beneficial effects:
1. the boron-containing coupling agent is adopted, so that the dispersion of silicon particles or silicon carbide particles is promoted, and meanwhile, the toughness of the product is improved by introducing boron atoms;
2. the porous carbon material is prepared, so that silicon atoms or boron atoms can enter pores of the porous carbon material, and on one hand, the dispersion of the boron atoms in a product is promoted, so that the mechanical property of the product is improved. On the other hand, the method overcomes the defect that when the traditional silicon carbide ceramic is sintered, a very thin SiO layer is formed2The oxide layer covers the surface of the silicon carbide crystal grains/whiskers to prevent the sintering defect, thereby obtaining high qualityA quantity of dense silicon carbide material;
3. the single-layer boron nitride is prepared, the mechanical property improvement effect of boron nitride doping on the silicon carbide material is improved, and the defect that the traditional hexagonal boron nitride improvement effect is limited is overcome; in addition, Fe is increased3O4The load rate on boron nitride improves the magnetism of the friction pair;
4. the graphene intercalation boron nitride is prepared, a shell layered material is formed, and the impact resistance/crack resistance of the silicon carbide is improved;
5. preparing porous hollow Fe3O4Material of increased Fe3O4Load rate on BN.
Detailed Description
In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easily understood, the invention is further explained by combining the specific embodiments.
The preparation method of the brittle fracture resistant silicon carbide material comprises the following steps
(1) Preparing 100 parts of nano carbon powder, 15-30 parts of porous carbon material, 15-25 parts of boron nitride and 40-60 parts of adhesive according to the mass ratio; the materials are uniformly mixed for later use.
The adhesive of the invention is mainly thermosetting phenolic resin, in particular thermosetting phenolic resin with a carbon residue rate of 54-56%.
(2) In a mould, weighing silicon particles according to 1.8-2.3 times of the dosage of the nano carbon powder, paving a plurality of layers of silicon particles and a layer of mixed material, and pressing to obtain a blank; and laying a layer of silicon particles on the top of the blank.
The silicon particles refer to granular silicon simple substance.
The pressing comprises two steps of cold pressing and hot pressing, and the specific description is as follows:
cold pressing: and uniformly filling the solid mixture into a mold with the diameter of 150mm multiplied by 200mm, and performing cold press molding on a hydraulic press, wherein the pressing pressure is 5 MPa.
Hot pressing: the pressure is increased to 25MPa, the temperature is increased to 150 ℃ under the pressure of 25MPa, so that the B-stage phenolic resin is fully softened under certain pressure without obvious crosslinking and solidification, the temperature is kept for a period of time, then hot pressing is carried out again, the resin is enabled to flow viscously, fibers are infiltrated, the pores are reduced, the temperature is increased to 180 ℃ under the pressure-keeping state, the resin is heated to be partially crosslinked and solidified, the temperature is kept for 30min, then the secondary hot pressing is carried out to the preset thickness, so that bubbles generated in the solidification process are discharged, the pores are healed, and full densification is realized.
And covering a layer of silicon particles on the top of the green body after pressing.
(3) And (3) placing the blank body in a high-temperature vacuum furnace, heating to 1400 ℃, heating to 1700 ℃ to 1800 ℃ at a heating rate of 15 ℃/min, preserving heat for 3h, then closing a vacuum pump, filling argon to normal pressure, and cooling the sample along with the furnace. The reaction infiltration process is completed in the temperature range of 1680 ℃ to 1800 ℃, because of the non-wetting transition (theta 90 ℃) of BN and silicon liquid around 1650 ℃. The contact angle is 90 +/-5 degrees, and the wettability of the blank body to silicon liquid can be improved by siliconizing at the temperature of more than 1650 ℃, so that the siliconizing effect is improved. The content of SiC needed to be generated in the melting siliconizing process can be calculated according to the difference between the expected density and the density of the porous body before siliconizing, and further the theoretical silicon consumption in the reaction of Si and C can be calculated. And preparing a semi-finished product.
(4) And processing and polishing the semi-finished product to obtain a finished product.
Further, the preparation method of the porous carbon material is as follows:
dispersing 30 parts of polyacrylonitrile in 100 parts of DMF solution according to the volume ratio, heating to 60 ℃, stirring for 3 hours, adding 20 parts of boric acid at 60 ℃, and continuing to stir for 1.5 hours; and then carrying out electrostatic spinning on the polyacrylonitrile fiber under the conditions that the spinning voltage is 18kV, the flow rate of the spinning solution is 1.0mL/h, the temperature is 40 ℃ and the receiving distance is 20cm to obtain the polyacrylonitrile fiber, drying the polyacrylonitrile fiber at the temperature of 100 ℃ for 1h, heating the polyacrylonitrile fiber to the temperature of 450 ℃ in the atmosphere of protective gas, keeping the temperature for 2h, continuing heating the polyacrylonitrile fiber to the temperature of 600 ℃ and keeping the temperature for 1h, and washing the polyacrylonitrile fiber with dilute hydrochloric acid to obtain the porous carbon material. The formation of porous carbon fiber material was confirmed by SEM and TEM techniques.
The porous carbon material is mainly carbon fiber, and after treatment, a plurality of holes are formed on the wall and two ends of the carbon fiber.
The following tests were carried out according to different material ratios, the test methods being referred to the above description:
it can be seen from the above table that the porous carbon fiber has better positive effects on various parameters of the product than the commercially available common carbon fiber, and the performance of various parameters is improved by adding boron nitride. I guess that this is because silicon particles can enter the surface of carbon fiber or the recesses at both ends when melting, and then a silicon oxide layer will not be formed on the surface of carbon fiber or other carbon powder, preventing further sintering.
Further, the boron nitride is treated as follows:
mixing hexagonal boron nitride and concentrated sulfuric acid, heating to 170 ℃, stirring for 30-50 hours, and then drying at room temperature to prepare sulfuric acid intercalated boron nitride; adding a proper amount of saturated ammonia water into a crucible, placing the sulfuric acid intercalated boron nitride into the crucible, stirring the mixture for 3 hours at room temperature, and obtaining a single-layer boron nitride material (hereinafter referred to as single-layer boron nitride) with ammonium sulfate crystals.
Further, the boron nitride is treated as follows:
mixing hexagonal boron nitride and concentrated sulfuric acid, heating to 170 ℃, stirring for 30-50 hours, and then drying at room temperature to prepare sulfuric acid intercalated boron nitride; adding a proper amount of absolute ethyl alcohol into a crucible, placing the sulfuric acid intercalated boron nitride in the crucible, heating to 100-120 ℃, and reacting for 3-4 hours to obtain the boron nitride material with enlarged interlayer spacing (hereinafter referred to as large interlayer spacing boron nitride).
Further, the boron nitride material with the enlarged interlayer spacing and the graphene are blended and then sintered together at 800-1100 ℃ in a protective gas atmosphere to prepare the graphene intercalation boron nitride material. The blending herein is mainly mechanical.
The following tests were carried out according to different material ratios, the test methods being referred to the above description:
from this table, it can be seen that both single-layer boron nitride and large-layer-spacing boron nitride provide better enhancement of the parameter index of the silicon carbide product, compared to the latter, single-layer boron nitride providing a greater enhancement. The performance of the graphene intercalated boron nitride is more excellent, and people guess that after the graphene intercalation, the boron and the carbon are combined more tightly, and the toughening effect is better.
Item
Example 7
Example 8
Comparative example 6
Comparative example 7
Nano carbon powder
100
100
100
100
Porous carbon material
30
30
0
0
Commercially available carbon fiber
0
0
30
30
Silicon particles
200
200
200
200
Boron nitride
0
0
0
0
Single layer boron nitride
0
0
0
0
Large interlayer spacing boron nitride
0
0
0
0
Graphene intercalated boron nitride
15
0
15
0
Graphene
0
15
0
15
Phenolic resin
60
60
60
60
Bulk Density (g/cm)3)
3.27
3.24
2.70
2.58
Porosity (%)
2.81
2.97
4.84
4.85
Hardness (HRA)
97
96
96
94
Bending strength (MPa)
533
495
314
297
Coefficient of thermal conductivity (W/m. K)
127
125
103
100
Fracture toughness (MPaM)1/2)
4.18
3.89
3.85
3.59
According to experimental data, the modification effect of the modified boron nitride is similar to that of single-layer boron nitride in terms of parameters such as volume density and the like, but the modified boron nitride has certain differences with the single-layer boron nitride in terms of bending strength, fracture toughness and the like, the overall performance is not as good as that of the graphene intercalated boron nitride, and the method guesses that the graphene intercalated boron nitride forms a shell-like layer-by-layer structure and has a good blocking effect on cracks of silicon carbide.
Graphene, while potentially structurally similar to a single layer of boron nitride, differs from the nitrogen atoms, so that an asymmetric arrangement exists intrinsically in the hexagonal lattice in a single layer of boron nitride, unlike the carbon hexagons in graphene. Briefly, in graphene, cracks tend to cross the symmetrical hexagonal structure straight from top to bottom, opening the bond like a zipper. Due to the stress contrast between boron and nitrogen, the hexagonal structure of a single layer of boron nitride is slightly asymmetric, and the inherent asymmetry of this lattice can lead to crack branching and branching. And if the crack is bifurcated, it means that it is rotating. The presence of such turning cracks requires the expenditure of additional energy to further promote crack propagation, thereby making it more difficult for the crack to propagate, effectively enhancing the toughness of the material. We hypothesize that this is why monolayer boron nitride exhibits elasticity that exceeds that of graphene.
Further, the single layer belt is sulfuric acidMixing an ammonium crystal boron nitride material and a boron nitride material for enlarging interlayer spacing with isophorone diisocyanate (IPDI) by taking DMF as a solvent to prepare IPDI grafted boron nitride; ferroferric oxide (Fe)3O4) After being coated by a silane coupling agent, the mixture is blended with IPDI grafted boron nitride to prepare BN @ Fe3O4. According to the element distribution diagram of the XPS selected region, B, N, Fe elements and O elements are uniformly distributed in BN @ Fe3O4The surface of the sheet layer.
Item
Example 5
Example 6
Example 7
Example 9
Example 10
Example 11
Nano carbon powder
100
100
100
100
100
100
Porous carbon material
30
30
30
30
30
30
Commercially available carbon fiber
0
0
0
0
0
0
Silicon particles
200
200
200
200
200
200
Boron nitride
0
0
0
0
0
0
Single layer boron nitride
15
0
0
0
0
0
Single layer boron nitride @ Fe3O4
0
0
0
15
0
0
Large interlayer spacing boron nitride
0
15
0
0
0
0
Large interlayer spacing boron nitride @ Fe3O4
0
0
0
0
15
0
Graphene intercalated boron nitride
0
0
15
0
0
0
Graphene intercalation boron nitride @ Fe3O4
0
0
0
0
0
15
Phenolic resin
60
60
60
60
60
60
Bulk Density (g/cm)3)
3.24
3.18
3.27
3.22
3.15
3.25
Porosity (%)
2.96
3.14
2.81
2.97
3.15
2.80
Hardness (HRA)
97
96
97
97
96
97
Bending strength (MPa)
512
509
533
518
510
532
Coefficient of thermal conductivity (W/m. K)
127
122
127
126
123
127
Fracture toughness (MPaM)1/2)
4.04
4.01
4.18
4.02
4.00
4.19
Saturation magnetization (emu/g)
0
0
0
60.2
56.0
68.4
From the above test data, Fe3O4Introduction of (2) to Performance shadow of the products of the inventionThe noise can be approximately ignored, and the magnetic performance of the product is also obtained. The magnetic property is introduced, on one hand, the mechanical sealing element can be more tightly attached to the driving shaft when the shaft is embraced to move, the seepage of oil liquid is reduced, and the sealing failure is prevented. On the other hand, because silicon carbide has great damage to metal parts when being coupled with metal materials, the engineering application of the SiC friction material in wider fields is limited. According to the invention, magnetic ferroferric oxide particles are introduced, and after SiC wears a metal part, abraded metal scraps can be adsorbed on the surface of a mechanical sealing element, so that workers can conveniently clean metal scraps in the pump during regular maintenance, and the damage of the metal scraps to equipment, particularly precision equipment, is reduced.
The coupling agent may be a commonly used silane coupling agent, such as KH550, KH580, or (4- (triethoxysilyl) phenyl) boronic acid (hereinafter referred to as coupling agent # 1) or (4- (5, 5-dimethyl-1, 3, 2-dioxophthalic anhydride-2-yl) phenyl) triethoxysilane (hereinafter referred to as coupling agent # 2).
The preparation method of the coupling agent (4- (triethoxysilyl) phenyl) boric acid comprises the following steps:
boron oxide and isopropanol are used as raw materials, and the triisopropyl borate is prepared by heating for 4h at the temperature of 100-120 ℃. And then reacting with tetrachlorosilane and p-dibromobenzene in an inert gas atmosphere at the low temperature of-78 ℃ for 20min to obtain the (4- (trichloro silicon) phenyl) boric acid.
Adding 1mol of (4- (trichlorosilyl) phenyl) boric acid into a three-neck flask by taking petroleum ether as a solvent, stirring until the boric acid is dissolved, and introducing nitrogen as protective gas. And adding 2.1mol of ethanol and 0.6mol of sodium ethoxide into another beaker, heating to 40 ℃, then slowly adding the mixture into a three-neck flask, and collecting a reaction product to obtain the (4- (triethoxysilyl) phenyl) boric acid with the yield of about 96% and the purity of about 97%. The structure of the product can be determined by nuclear magnetism and infrared spectrum characterization.
The preparation method of (4- (5, 5-dimethyl-1, 3, 2-dioxophthalic anhydride-2-yl) phenyl) triethoxysilane is as follows: dissolving neopentyl glycol and the (4- (trichlorosilyl) phenyl) boric acid at normal temperature by using dichloromethane as a solvent, and stirring for 12 hours for reaction to obtain the neopentyl glycol. The yield was about 93% and the purity was about 96%. The structure of the product can be determined by nuclear magnetic and infrared spectrum characterization.
Item
Example 11
Example 12
Example 13
Example 14
Example 15
Example 16
Nano carbon powder
100
100
100
100
100
100
Porous carbon material
30
30
30
30
30
30
Commercially available carbon fiber
0
0
0
0
0
0
Silicon particles
200
200
200
200
200
200
Boron nitride
0
0
0
0
0
0
Single layer boron nitride @ Fe3O4
0
0
0
0
0
5
Large interlayer spacing boron nitride @ Fe3O4
0
0
0
0
0
5
Graphene intercalation boron nitride @ Fe3O4
15
15
15
15
15
5
Phenolic resin
60
60
60
60
60
60
KH550
0
15
0
0
5
5
Coupling agent 1#
0
0
15
0
5
5
Coupling agent 2#
0
0
0
15
5
5
Bulk Density (g/cm)3)
3.25
3.25
3.26
3.26
3.24
3.18
Porosity (%)
2.80
2.81
2.77
2.75
2.82
2.82
Hardness (HRA)
97
97
97
97
97
97
Bending strength (MPa)
532
534
552
548
530
530
Coefficient of thermal conductivity (W/m. K)
127
127
125
123
126
126
Fracture toughness (MPaM)1/2)
4.19
4.19
4.32
4.30
4.17
4.18
Saturation magnetization (emu/g)
68.4
70.4
72.3
72.2
67.9
68.0
As can be seen from the above table, the addition of the coupling agent slightly increases the saturation magnetization of the product of the present invention, and we guess that the addition of the coupling agent causes less agglomeration of ferroferric oxide, more uniform dispersion and more loading, and the porous carbon fiber also obtains better dispersion because agglomerated particles are difficult to load on the surface of BN due to the relationship between the size and the weight. In addition, the coupling agent 1# and the coupling agent 2# are added, and certain boron element is contained, so that the dispersibility of the ferroferric oxide is improved, and the mechanical property, particularly the bending resistance of the product is improved to a certain extent.
Further, the ferroferric oxide is hollow ferroferric oxide microspheres, and the preparation method comprises the following steps:
FeCl is added3·6H2Mixing O and organic alcohol, and then adding sodium acetate and ammonium acetate to obtain emulsion, wherein the FeCl is3·6H26.75g of O, 15.5g of ammonium acetate and 2.5g of sodium acetate, wherein the FeCl is3·6H2The mass-to-volume ratio of O to the organic alcohol is 6.75 g: 300 ml; the organic alcohol comprises diethylene glycol and ethylene glycol, and the volume ratio of the diethylene glycol to the ethylene glycol is 2: 1;
reacting the emulsion at 200 ℃ for 12 hours to obtain a reaction solution;
obtaining magnetic particles in the reaction liquid to obtain the ferroferric oxide hollow magnetic nanoparticles;
the specific steps for obtaining the magnetic particles in the reaction solution include: attracting the reaction liquid to the supernatant liquid by a magnet to be colorless, and removing the supernatant liquid to obtain the magnetic particles;
the method also comprises the following steps after the magnetic particles in the reaction liquid are obtained: washing the magnetic particles one or more times with a mixed solution of water and ethanol;
the cleaning step is followed by the steps of: and drying the magnetic particles at 65-75 ℃ for 18-28 hours.
Further, the hollow ferroferric oxide microspheres are mixed with boric acid, heated to 450 ℃ to prepare porous ferroferric oxide with etched surfaces, and then washed by dilute hydrochloric acid and dried to prepare the porous hollow ferroferric oxide material.
Item
Example 13
Example 14
Example 15
Nano carbon powder
100
100
100
Porous carbon material
30
30
30
Commercially available carbon fiber
0
0
0
Silicon particles
200
200
200
Boron nitride
0
0
0
Graphene intercalation boron nitride @ Fe3O4
15
0
0
Graphene intercalated boron nitride @ hollow Fe3O4
0
15
0
Graphene intercalation boron nitride @ porous hollow Fe3O4
0
0
15
Phenolic resin
60
60
60
Coupling agent 1#
15
15
15
Bulk Density (g/cm)3)
3.26
3.26
3.26
Porosity (%)
2.77
2.75
2.75
Hardness (HRA)
97
97
97
Bending strength (MPa)
552
553
555
Coefficient of thermal conductivity (W/m. K)
125
125
127
Fracture toughness (MPaM)1/2)
4.32
4.38
4.38
Saturation magnetization (emu/g)
72.3
74.5
77.1
Free silicon content
≤0.9
≤0.7
≤0.7
As can be seen from the above table, the graphene intercalated boron nitride @ porous hollow Fe in example 153O4The magnetic performance of the product is improved most obviously, the influence on the mechanical performance of the product is minimum, the formula is the most suitable material formula, and in the detailed elite production process, an applicant can independently allocate the product formula according to actual requirements, so that the comprehensive balance of cost, production period and product performance is achieved.
The average friction coefficient of the SiC material of the embodiment 15 is between 0.45 and 0.50, the friction curve is relatively stable, and the mass wear rate is 2.7 mg/time and is far lower than that of a common SiC material (13.33 mg/time) under the friction conditions of 0.6MPa of pressure and 6000r/min (20m/s) of rotating speed.
The data of the above examples show that the product prepared by the invention has the advantages of high bending strength, large fracture toughness, low porosity, excellent magnetism and the like, is a ceramic matrix composite material with very excellent mechanical properties, and can be used for producing various mechanical sealing elements.
While there have been shown and described what are at present considered the fundamental principles and essential features of the invention and its advantages, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description of the embodiments is for clarity only, and those skilled in the art should make the description as a whole, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
- 上一篇：一种医用注射器针头装配设备
- 下一篇：SiC-HfB-(2)双层复合材料的制备方法