CN116023168B - Method for carrying out carbon reduction treatment on porous silicon-boron-nitrogen ceramic material and material prepared by method - Google Patents
Method for carrying out carbon reduction treatment on porous silicon-boron-nitrogen ceramic material and material prepared by method Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 170
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 157
- 229910010293 ceramic material Inorganic materials 0.000 title claims abstract description 110
- 239000000463 material Substances 0.000 title claims abstract description 85
- VGRSPALDTNRXMC-UHFFFAOYSA-N [B].[N].[Si] Chemical compound [B].[N].[Si] VGRSPALDTNRXMC-UHFFFAOYSA-N 0.000 title claims abstract description 83
- 238000000034 method Methods 0.000 title claims abstract description 81
- 230000009467 reduction Effects 0.000 title claims description 48
- 238000010438 heat treatment Methods 0.000 claims abstract description 138
- 230000008569 process Effects 0.000 claims abstract description 36
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 26
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000001301 oxygen Substances 0.000 claims abstract description 5
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 5
- 230000002829 reductive effect Effects 0.000 claims description 33
- 229910021426 porous silicon Inorganic materials 0.000 claims description 28
- 230000003068 static effect Effects 0.000 claims description 18
- 238000005336 cracking Methods 0.000 claims description 14
- 229910052582 BN Inorganic materials 0.000 claims description 10
- CFOAUMXQOCBWNJ-UHFFFAOYSA-N [B].[Si] Chemical compound [B].[Si] CFOAUMXQOCBWNJ-UHFFFAOYSA-N 0.000 claims description 10
- 230000000630 rising effect Effects 0.000 claims 2
- 229910021529 ammonia Inorganic materials 0.000 abstract description 9
- 239000003795 chemical substances by application Substances 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 25
- 238000001816 cooling Methods 0.000 description 15
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 8
- 239000011159 matrix material Substances 0.000 description 7
- 239000002243 precursor Substances 0.000 description 7
- 230000035484 reaction time Effects 0.000 description 6
- 239000000919 ceramic Substances 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000011153 ceramic matrix composite Substances 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 229910052581 Si3N4 Inorganic materials 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 238000005891 transamination reaction Methods 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 230000000670 limiting effect Effects 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000000197 pyrolysis Methods 0.000 description 2
- 238000004904 shortening Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000010301 surface-oxidation reaction Methods 0.000 description 2
- 238000007669 thermal treatment Methods 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000012700 ceramic precursor Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000005262 decarbonization Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 239000008204 material by function Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229920001709 polysilazane Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention relates to a method for removing carbon residues in a porous silicon-boron-nitrogen ceramic material and the material prepared by the method. The method takes the atmosphere containing oxygen and ammonia as a carbon removing agent, takes high-temperature treatment equipment as hardware support, and removes carbon residues in the porous silicon-boron-nitrogen ceramic material through the technological processes of microwave heating treatment, aerobic heating treatment and optionally only anaerobic heating treatment. The invention also relates to a material with low carbon residue and high dielectric property. The method can prepare the porous silicon-boron-nitrogen ceramic material with the residual carbon content less than 1 percent, has the advantages of simple operation, stable process and high removal efficiency, and can be widely applied to wave-transparent members of high-speed aircrafts.
Description
Technical Field
The invention relates to the technical field of functional materials, in particular to a method for carrying out carbon reduction treatment on a porous silicon-boron-nitrogen ceramic material and a material prepared by the method.
Background
The porous silicon boron nitride ceramic material is a porous silicon boron nitride ceramic-based material, often in the form of a fiber-reinforced porous silicon boron nitride ceramic-based composite material, such as a silicon nitride fiber-reinforced porous silicon boron nitride ceramic-based composite material. The material integrates the functions of high temperature resistance, wave transmission, bearing and the like, and is an ideal material for the radome of the aircraft, especially the high-speed aircraft.
The fiber reinforced porous silicon boron nitrogen ceramic matrix composite is mainly prepared by a Precursor Impregnation Pyrolysis (PIP) method, the forming process is simpler, the efficiency is higher, the prepared silicon boron nitrogen ceramic matrix composite has better mechanical property, and common ceramic precursors include polysilazane, polysilabozane and the like. The boron has the effect of inhibiting amorphous crystallization, so that the high-temperature stability of the composite material is better, and the polysilabozane has application advantages as a precursor.
However, certain carbon may be present in the silicon boron nitride ceramic matrix composite formed from precursor conversion, which has a significant impact on its dielectric properties. The existence of the carbon residues is mainly caused by insufficient contact between the precursor and ammonia gas in the ceramic process and insufficient transamination reaction under the condition that the precursor emits less gas in the curing process and the cured product is compact. Therefore, in order to improve the dielectric properties of such materials, it is highly desirable to provide a carbon reduction treatment process that reduces the residual carbon content of such materials.
Disclosure of Invention
In order to improve the performance of the porous silicon-boron-nitrogen ceramic material, especially improve the dielectric performance of the material, the invention reduces the carbon residue content of the material and reduces the influence of carbon residue on the performance, especially the dielectric performance by carrying out carbon reduction treatment on the material.
The first aspect of the invention provides a method for reducing carbon of a porous silicon boron nitrogen ceramic material, comprising the steps of:
(1) Providing a porous silicon boron nitrogen ceramic material to be subjected to carbon reduction treatment;
(2) Carrying out microwave heating treatment on the porous silicon-boron-nitrogen ceramic material to obtain a microwave heating treatment material;
(3) And carrying out aerobic heat treatment on the microwave heat treatment material to obtain the aerobic heat treatment material.
In a second aspect, the invention provides a porous silicon boron nitrogen ceramic material made according to the method of the first aspect of the invention.
Preferably, the carbon content of the carbon-reduced porous silicon-boron-nitrogen ceramic material produced by the method is reduced by 80%, preferably by 85%, more preferably by 90% relative to the porous silicon-boron-nitrogen ceramic material to be carbon-reduced. It is also preferred or further preferred that the carbon content of the carbon-reduced porous silicon-boron-nitrogen ceramic material produced by the method is less than 1%, preferably less than 0.8%.
(1) The method adopts the combination of the aerobic atmosphere and the anaerobic atmosphere as atmosphere components, and respectively utilizes the oxidability of oxygen and the replacement of ammonia gas, thereby greatly improving the removal rate and the removal efficiency of carbon residues, shortening the carbon removal time, and having the advantages of simple operation, stable process, high removal efficiency and the like.
(2) According to the method, a microwave heating treatment mode is adopted, free carbon residues dispersed in the ceramic material are selectively heated, and then subsequent atmosphere treatment is carried out, so that a good carbon removal effect can be achieved at a lower treatment temperature, and the surface oxidation damage of high-temperature heat treatment to the ceramic material is inhibited.
(3) The porous silicon nitride ceramic material obtained by the method has very low carbon content and thus excellent dielectric properties.
Compared with the prior art, the invention has the following technical advantages:
(1) The operation is simple and convenient. The operation is carried out by using common equipment without special equipment.
(2) The process is stable. The process is adopted for treatment, and the carbon removal effect of various different embodiments is good.
(3) The carbon residue removal efficiency is high. The method can reduce the residual carbon to more than 80% of the original carbon, and even to more than 90% of the original carbon.
(4) The material performance is excellent. The porous silicon-boron-nitrogen ceramic material prepared by the method has excellent performance.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention adopts the combination of the aerobic atmosphere and the anaerobic atmosphere as atmosphere components, and respectively utilizes the oxidability of oxygen and the replacement of ammonia gas, thereby greatly improving the removal rate and the removal efficiency of carbon, shortening the carbon removal time and having the characteristics of simple operation, stable process and high removal efficiency.
(2) According to the invention, a microwave heating treatment mode is adopted, and the dispersed carbon in the ceramic material is selectively heated and then subjected to subsequent atmosphere treatment, so that a better carbon removal effect can be achieved at a lower treatment temperature, and the surface oxidation of the ceramic material is inhibited.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below in connection with the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As described above, the first aspect of the present invention provides a method for reducing carbon in a porous silicon-boron-nitrogen ceramic material, the method comprising the steps of:
(1) Providing a porous silicon boron nitrogen ceramic material to be subjected to carbon reduction treatment; (2) Carrying out microwave heating treatment on the porous silicon-boron-nitrogen ceramic material to obtain a microwave heating treatment material; (3) And carrying out aerobic heat treatment on the microwave heat treatment material to obtain the aerobic heat treatment material.
The porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment is usually a ceramic matrix composite material prepared based on a dipping-cracking process (PIP process), a matrix of the porous silicon-boron-nitrogen ceramic material is a low-loss ceramic material, and residual carbon is divided into free carbon and non-free carbon. The non-free carbon is mainly due to insufficient cracking temperature or time, so that the precursor solidified substance is not completely cracked. The free carbon is mainly formed by insufficient ammonia gas or small contact area, and the precursor solidified substance is subjected to insufficient transamination reaction and is directly carbonized.
The free carbon is mainly dispersed in the ceramic material matrix in the form of tiny particles, so that the free carbon has higher conductivity, higher loss and stronger wave absorbing capacity. In the method, in the step (2), the free carbon can absorb microwaves and rapidly raise temperature so as to enable oxidation reaction to occur more easily, and meanwhile, the low-loss ceramic material matrix keeps a lower temperature because the low-loss ceramic material matrix hardly absorbs microwaves, so that the surface of the ceramic material is restrained from being oxidized, and the ceramic material has a better carbon removal effect after the subsequent heat treatment at a lower temperature. Therefore, the method can selectively remove the free carbon by adopting microwave heating treatment, thereby realizing the primary carbon reduction treatment of the porous silicon boron nitrogen ceramic material to be subjected to the carbon reduction treatment, and also preventing the surface of the ceramic material from being oxidized.
In the method, in the step (3), the porous silicon-boron-nitrogen ceramic material is subjected to aerobic heating treatment in an aerobic environment (namely, the heating treatment is carried out in the aerobic atmosphere), so that free carbon generated in the cracking process is oxidized and escapes in a gas form, and further carbon reduction treatment of the porous silicon-boron-nitrogen ceramic material is realized, and the dielectric property is further improved.
In some preferred embodiments, the methods of the present invention further comprise step (4): and performing anaerobic heat treatment on the aerobic heat treatment material to obtain the low-carbon residue porous silicon-boron-nitrogen ceramic material with reduced carbon residue content relative to the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment.
In the invention, the step (4) is additionally added in some preferred technical modes, and the porous silicon-boron-nitrogen ceramic material is subjected to anaerobic heating treatment in an anaerobic environment in the step, so that the non-free carbon which is not completely cracked and gas are subjected to transamination reaction, the non-free carbon is directly removed, and the degradation of dielectric properties caused by the conversion of the non-free carbon into the free carbon when the ceramic material is subjected to high temperature is avoided. These preferred embodiments of the present invention place the anaerobic treatment after the aerobic treatment, and since the ceramic material after the aerobic heating treatment has been partially decarbonized, it has a higher porosity than the porous silicon boron nitride ceramic to be decarbonized provided in step (1), so that ammonia gas is more likely to enter the inside of the ceramic material, thereby having a larger contact area, whereby the removal of non-free carbon can be further performed more effectively.
In some preferred embodiments, the porosity of the porous silicon boron nitride ceramic material to be carbon reduced is 10% to 50%, such as 10%, 20%, 30%, 40% or 50%. If the porosity is too low, the gas is difficult to penetrate deeply due to the too high density, and the carbon removal effect is weakened; if the porosity is too high, it may have little effect on the decarbonization, but too low a matrix content may not provide sufficient support for the ceramic material, resulting in a lower material strength.
It is also preferred that the carbon content (i.e., residual carbon content) of the porous silicon boron nitrogen ceramic material to be subjected to the carbon reduction treatment is 1 to 15wt%, for example, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt%. If the carbon content is too low, the reduction ratio of the carbon content after the treatment is possibly small (less than 80 percent), so that the difference of different embodiments is not easy to see, and a proper treatment mode is difficult to be optimized; if the carbon content is too high, the carbon element may become a main constituent element in the material, and does not conform to the characteristic that tiny carbon particles are dispersed in a low-loss matrix, and if larger particles are formed, the method can have a main reflection effect rather than an absorption effect on microwaves, which may lead to poor applicability.
In the invention, the porous silicon boron nitrogen ceramic material to be subjected to carbon reduction treatment is prepared by adopting a PIP process. In some preferred embodiments, the porous silicon boron nitride ceramic material to be carbon-reduced is prepared by 3-6 cycles of an impregnation-pyrolysis process, for example, 3, 4, 5 or 6 cycles.
In other preferred embodiments, the microwave power used for the microwave heating treatment is 400-1200W and the time of the microwave heating treatment is 0.5-5 h. If the microwave power is too high, the carbon removal effect is not obviously improved after the carbon absorption microwaves reach the limit; if the microwave power is too low, carbon may absorb less microwaves, and the desired carbon removal effect may not be achieved. In addition, if the microwave heating treatment time is too short, the carbon removal effect may be weak; if the microwave heating treatment time is too long, the carbon removal effect may not be significantly improved.
In other preferred embodiments, the aerobic thermal treatment uses an aerobic atmosphere of atmospheric static air, atmospheric flowing air, or flowing oxygen.
In other preferred embodiments, the aerobic thermal treatment is performed at a treatment temperature of 300-900 ℃ (e.g., 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, or 900 ℃) for a treatment time of 1-10 hours (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 hours). If the treatment temperature of the aerobic heat treatment is too high, larger oxidation effect can be generated on the matrix, which is not beneficial to the stability of the material composition; if the treatment temperature is too low, the reaction may be insufficient, resulting in failure to achieve the desired carbon removal effect. In addition, if the treatment time is too short, the carbon removal effect may be weak; if the treatment time is too long, the oxidation effect on the substrate may be increased.
In other preferred embodiments, the temperature ramp up to the treatment temperature of the aerobic heat treatment is at a ramp up rate of 1 to 10 ℃/min, for example 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 ℃/min. In the heating process, if the temperature is raised too fast, it is possible; if the temperature is raised too slowly, it may be.
In other preferred embodiments, the oxygen-free atmosphere used for the oxygen-free heat treatment is atmospheric static ammonia or atmospheric flowing ammonia.
In other preferred embodiments, the anaerobic heat treatment is performed at a treatment temperature of 400-1000 ℃ (e.g., 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃ or 1000 ℃) for a treatment time of 1-10 hours (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 hours). If the treatment temperature of the anaerobic heat treatment is too high, larger damage can be caused to the reinforced fiber, so that the mechanical property of the material is lower; if the treatment temperature is too low, the reaction may be insufficient to result in a weak carbon removal effect. In addition, if the treatment time is too short, the carbon removal effect may be weak; if the treatment time is too long, the mechanical properties of the material may be reduced to some extent.
In other preferred embodiments, the temperature ramp rate to the treatment temperature of the anaerobic heat treatment is 1 to 10 ℃/min, for example 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 ℃/min. In the heating process, if the temperature is raised too fast, the reaction is insufficient, so that the carbon removal effect is weak; if the temperature is raised too slowly, the carbon removal effect is not improved obviously, and the mechanical property of the material is reduced to a certain extent.
In the method, parameters such as treatment atmosphere, temperature, time and the like can be regulated and controlled as appropriate, and the porous silicon-boron-nitrogen ceramic material prepared by the dipping-cracking process can be treated to obtain the ceramic material with lower carbon content.
In a second aspect, the invention provides a porous silicon boron nitrogen ceramic material made according to the method of the first aspect of the invention.
Preferably, the carbon content of the porous silicon boron nitrogen ceramic material subjected to the carbon reduction treatment prepared by the method is reduced by 80 to 90 percent relative to the porous silicon boron nitrogen ceramic material subjected to the carbon reduction treatment. It is also preferred or further preferred that the carbon content of the carbon-reduced porous silicon-boron-nitrogen ceramic material produced by the method is less than 1%.
Examples
The invention will be further illustrated by way of examples, which are intended to be illustrative and not limiting.
Example 1
In the embodiment, the porous silicon-boron-nitrogen ceramic material prepared by 4 times of the impregnation-cracking process is used as the porous silicon-boron-nitrogen ceramic material to be subjected to the carbon reduction treatment, the porosity of the material is about 30%, the carbon content is 5% by weight, the dielectric constant at room temperature is 8.1, and the dielectric loss is 0.088; the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment cannot be subjected to high-temperature test because the loss is larger than the test range).
The microwave power of the microwave heating step adopted in the embodiment is 800W, the reaction time is 1h, and the microwave heating treatment material is obtained, and the carbon content of the microwave heating treatment material is primarily reduced.
And (3) placing the microwave heating treatment material in a high-temperature furnace, heating to 600 ℃ at a heating rate of 2 ℃/min under normal pressure static air atmosphere, preserving heat for 5 hours, and cooling to room temperature to obtain the aerobic heat treatment material, wherein the carbon content of the aerobic heat treatment material is further reduced.
And (3) placing the aerobic heat treatment material in a high-temperature atmosphere furnace, heating to 650 ℃ at a heating rate of 2 ℃/min under a normal-pressure static ammonia atmosphere, preserving heat for 5 hours, and cooling to room temperature to obtain the porous silicon-boron-nitrogen ceramic material with further reduced carbon content.
Example 2
Otherwise, the aerobic treatment time was changed to 10 hours only as in example 1.
Specifically, in the embodiment, the porous silicon-boron-nitrogen ceramic material prepared by 4 times of circulation of the dipping-cracking process is used as the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment, the porosity of the material is about 30%, the carbon content is 5% by weight, the dielectric constant at room temperature is 8.1, and the dielectric loss is 0.088; the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment cannot be subjected to high-temperature test because the loss is larger than the test range).
The microwave power of the microwave heating step adopted in the embodiment is 800W, the reaction time is 1h, and the microwave heating treatment material is obtained, and the carbon content of the microwave heating treatment material is primarily reduced.
And (3) placing the microwave heating treatment material in a high-temperature furnace, heating to 600 ℃ at a heating rate of 2 ℃/min under normal pressure static air atmosphere, preserving heat for 10 hours, and cooling to room temperature to obtain the aerobic heat treatment material, wherein the carbon content of the aerobic heat treatment material is further reduced.
And (3) placing the aerobic heat treatment material in a high-temperature atmosphere furnace, heating to 650 ℃ at a heating rate of 2 ℃/min under a normal-pressure static ammonia atmosphere, preserving heat for 5 hours, and cooling to room temperature to obtain the porous silicon-boron-nitrogen ceramic material with further reduced carbon content.
Example 3
Otherwise, as in example 1, the anaerobic treatment time was changed to 10 hours only.
Specifically, in the embodiment, the porous silicon-boron-nitrogen ceramic material prepared by 4 times of circulation of the dipping-cracking process is used as the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment, the porosity of the material is about 30%, the carbon content is 5% by weight, the dielectric constant at room temperature is 8.1, and the dielectric loss is 0.088; the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment cannot be subjected to high-temperature test because the loss is larger than the test range).
The microwave power of the microwave heating step adopted in the embodiment is 800W, the reaction time is 1h, and the microwave heating treatment material is obtained, and the carbon content of the microwave heating treatment material is primarily reduced.
And (3) placing the microwave heating treatment material in a high-temperature furnace, heating to 600 ℃ at a heating rate of 2 ℃/min under normal pressure static air atmosphere, preserving heat for 5 hours, and cooling to room temperature to obtain the aerobic heat treatment material, wherein the carbon content of the aerobic heat treatment material is further reduced.
And (3) placing the aerobic heat treatment material in a high-temperature atmosphere furnace, heating to 650 ℃ at a heating rate of 2 ℃/min under a normal-pressure static ammonia atmosphere, preserving heat for 10 hours, and cooling to room temperature to obtain the porous silicon-boron-nitrogen ceramic material with further reduced carbon content.
Example 4
Otherwise as in example 2, only the anaerobic heat treatment step was omitted.
Specifically, the same procedure as in example 1 was followed except that the aerobic treatment time was changed to 10 hours.
Specifically, in the embodiment, the porous silicon-boron-nitrogen ceramic material prepared by 4 times of circulation of the dipping-cracking process is used as the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment, the porosity of the material is about 30%, the carbon content is 5% by weight, the dielectric constant at room temperature is 8.1, and the dielectric loss is 0.088; the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment cannot be subjected to high-temperature test because the loss is larger than the test range). The microwave power of the microwave heating step adopted in the embodiment is 800W, the reaction time is 1h, and the microwave heating treatment material is obtained, and the carbon content of the microwave heating treatment material is primarily reduced.
And (3) placing the microwave heating treatment material in a high-temperature furnace, heating to 600 ℃ at a heating rate of 2 ℃/min under normal pressure static air atmosphere, preserving heat for 10 hours, and cooling to room temperature to obtain an aerobic heating treatment material serving as a final material product obtained through carbon reduction treatment, wherein the carbon content of the aerobic heating treatment material is further reduced relative to that of the microwave heating treatment material.
Example 5
Otherwise, as in example 2, only the microwave heating treatment step was omitted.
Specifically, in the embodiment, the porous silicon-boron-nitrogen ceramic material prepared by 4 times of circulation of the dipping-cracking process is used as the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment, the porosity of the material is about 30%, the carbon content is 5% by weight, the dielectric constant at room temperature is 8.1, and the dielectric loss is 0.088; the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment cannot be subjected to high-temperature test because the loss is larger than the test range).
And directly placing the porous silicon-boron-nitrogen ceramic material (without microwave heating treatment) to be subjected to carbon reduction treatment in a high-temperature furnace, heating to 600 ℃ at a heating rate of 2 ℃/min under a normal-pressure static air atmosphere, preserving heat for 10 hours, and cooling to room temperature to obtain the aerobic heat treatment material, wherein the carbon content of the aerobic heat treatment material is further reduced.
And (3) placing the aerobic heat treatment material in a high-temperature atmosphere furnace, heating to 650 ℃ at a heating rate of 2 ℃/min under a normal-pressure static ammonia atmosphere, preserving heat for 5 hours, and cooling to room temperature to obtain the porous silicon-boron-nitrogen ceramic material with further reduced carbon content.
Example 6
Otherwise, the microwave heating treatment step and the anaerobic treatment step are omitted in example 2.
Specifically, in the embodiment, the porous silicon-boron-nitrogen ceramic material prepared by 4 times of circulation of the dipping-cracking process is used as the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment, the porosity of the material is about 30%, the carbon content is 5% by weight, the dielectric constant at room temperature is 8.1, and the dielectric loss is 0.088; the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment cannot be subjected to high-temperature test because the loss is larger than the test range).
And (3) placing the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment in a high-temperature furnace, heating to 600 ℃ at a heating rate of 2 ℃/min under a normal-pressure static air atmosphere, preserving heat for 10 hours, and cooling to room temperature to obtain the aerobic heat treatment material serving as a final product.
Example 7
The process was carried out in essentially the same manner as in example 1, except that the materials shown in Table 1 and the process parameters shown in Table 2 were used.
Specifically, in the embodiment, the porous silicon-boron-nitrogen ceramic material prepared by 4 times of the impregnation-cracking process is used as the porous silicon-boron-nitrogen ceramic material to be subjected to the carbon reduction treatment, the porosity of the material is about 44%, the carbon content is 14% by weight, the dielectric constant at room temperature is 15, and the dielectric loss is 0.65; the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment cannot be subjected to high-temperature test because the loss is larger than the test range).
The microwave power of the microwave heating step adopted in the embodiment is 1000W, the reaction time is 0.5h, and the obtained microwave heating treatment material has primarily reduced carbon content.
And (3) placing the microwave heating treatment material in a high-temperature furnace, heating to 600 ℃ at a heating rate of 2 ℃/min under normal pressure static air atmosphere, preserving heat for 5 hours, and cooling to room temperature to obtain the aerobic heat treatment material, wherein the carbon content of the aerobic heat treatment material is further reduced.
And (3) placing the aerobic heat treatment material in a high-temperature atmosphere furnace, heating to 650 ℃ at a heating rate of 2 ℃/min under a normal-pressure static ammonia atmosphere, preserving heat for 5 hours, and cooling to room temperature to obtain the porous silicon-boron-nitrogen ceramic material with further reduced carbon content.
Example 8
The process was carried out in essentially the same manner as in example 1, except that the materials shown in Table 1 and the process parameters shown in Table 2 were used.
Specifically, in the embodiment, the porous silicon-boron-nitrogen ceramic material prepared by 4 times of the impregnation-cracking process is used as the porous silicon-boron-nitrogen ceramic material to be subjected to the carbon reduction treatment, the porosity of the material is about 20%, the carbon content is 10% by weight, the dielectric constant at room temperature is 11, and the dielectric loss is 0.23; the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment cannot be subjected to high-temperature test because the loss is larger than the test range).
The microwave power of the microwave heating step adopted in the embodiment is 500W, the reaction time is 1h, and the microwave heating treatment material is obtained, and the carbon content of the microwave heating treatment material is primarily reduced.
And (3) placing the microwave heating treatment material in a high-temperature furnace, heating to 600 ℃ at a heating rate of 2 ℃/min under normal pressure static air atmosphere, preserving heat for 5 hours, and cooling to room temperature to obtain the aerobic heat treatment material, wherein the carbon content of the aerobic heat treatment material is further reduced.
And (3) placing the aerobic heat treatment material in a high-temperature atmosphere furnace, heating to 650 ℃ at a heating rate of 2 ℃/min under a normal-pressure static ammonia atmosphere, preserving heat for 5 hours, and cooling to room temperature to obtain the porous silicon-boron-nitrogen ceramic material with further reduced carbon content.
Example 9
The process was carried out in substantially the same manner as in example 1, except that after the microwave treatment, the porous silicon nitride ceramic material was placed in a high temperature furnace, and the temperature was raised to 600 c at a temperature raising rate of 2 c/min under an atmospheric pressure flowing air atmosphere, and after 2 hours of heat preservation, it was cooled to room temperature, to obtain an initial heat-treated ceramic material.
And then placing the initial heat-treated ceramic material in a high-temperature atmosphere furnace, heating to 650 ℃ at a heating rate of 2 ℃/min under the atmosphere of flowing ammonia gas at normal pressure, preserving heat for 2 hours, and cooling to room temperature to obtain the silicon nitride ceramic material subjected to carbon removal treatment.
Example 10
The procedure was carried out in substantially the same manner as in example 1, except that the porous silicon nitride ceramic material was prepared by a gel casting process (porosity: about 30%, carbon content: 5% by weight, dielectric constant at room temperature: 8.0, dielectric loss: 0.083, and high-temperature test was impossible due to the loss being too large to exceed the test range).
Table 1. Various examples use porous silicon nitride ceramic material properties to be carbon reduction treated.
| Porosity of the porous material | Carbon content | Dielectric constant at room temperature | Dielectric loss | |
| Example 1 | 30％ | 5wt％ | 8.1 | 0.088 |
| Example 2 | 30％ | 5wt％ | 8.1 | 0.088 |
| Example 3 | 30％ | 5wt％ | 8.1 | 0.088 |
| Example 4 | 30％ | 5wt％ | 8.1 | 0.088 |
| Example 5 | 30％ | 5wt％ | 8.1 | 0.088 |
| Example 6 | 30％ | 5wt％ | 8.1 | 0.088 |
| Example 7 | 44％ | 14wt％ | 15 | 0.65 |
| Example 8 | 20％ | 10wt％ | 11 | 0.23 |
| Example 9 | 30％ | 5wt％ | 8.1 | 0.088 |
| Example 10 | 30％ | 5wt％ | 8.0 | 0.083 |
Table 2. The carbon reduction treatment process parameters used in each example.
Note that: "- -" means not proceeding.
Table 3. Carbon residue content and dielectric properties of the materials prepared in the examples.
Note that: "/" indicates undetected or undetectable.
From the data in the above table, it can be seen that increasing the aerobic heat treatment time can significantly improve the carbon removal effect, and increasing the anaerobic heat treatment time can also submit the carbon removal effect, but the improvement is smaller than the aerobic heat treatment. Without the anaerobic treatment, the carbon removal effect is slightly reduced. If the microwave heating treatment is not carried out, the carbon removal effect is obviously poor. In addition, the method is not only suitable for the porous silicon boron nitrogen ceramic material prepared by the PIP process, but also suitable for the porous silicon nitride ceramic material prepared by the non-PIP process. Also, while the effectiveness of the anaerobic heat treatment is less pronounced than that of the aerobic treatment, this may be due to the fact that carbon residues are present predominantly in the form of free carbon in the cracked silicon nitride material, and that non-free carbon which is not completely cracked is relatively less, whereas anaerobic heat treatment acts predominantly on this portion of carbon. However, although the content of non-free carbon is relatively small, the high-temperature dielectric properties of the material are still greatly affected, because the non-free carbon is converted into free carbon at high temperature, and the influence of carbon on the dielectric properties at high temperature is more remarkable.
In general, the method has the advantages of simple operation, stable process, high residual carbon removal efficiency and the like, does not basically change the basic properties of the porous silicon-boron-nitrogen ceramic material, and is particularly suitable for the carbon reduction treatment of the porous silicon-boron-nitrogen ceramic material.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A method for reducing carbon of a porous silicon boron nitride ceramic material, the method comprising the steps of:
(1) Providing a porous silicon boron nitrogen ceramic material to be subjected to carbon reduction treatment;
(2) Carrying out microwave heating treatment on the porous silicon-boron-nitrogen ceramic material to obtain a microwave heating treatment material;
(3) Carrying out aerobic heat treatment on the microwave heat treatment material to obtain an aerobic heat treatment material;
(4) Performing anaerobic heat treatment on the aerobic heat treatment material to obtain a low-carbon residue porous silicon-boron-nitrogen ceramic material with reduced carbon residue content relative to the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment, wherein:
the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment is prepared by an impregnation-cracking process;
the aerobic heat treatment is carried out in an atmosphere of normal pressure static air, normal pressure flowing air or flowing oxygen, wherein the treatment temperature of the aerobic heat treatment is 300-900 ℃ and the treatment time is 1-10 h;
the anaerobic atmosphere adopted by the anaerobic heat treatment is normal-pressure static ammonia gas or normal-pressure flowing ammonia gas, the treatment temperature of the anaerobic heat treatment is 400-1000 ℃, and the treatment time is 1-10 h.
2. The method according to claim 1, characterized in that:
the porosity of the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment is 10% -50%.
3. The method according to claim 2, characterized in that:
the carbon content of the porous silicon boron nitrogen ceramic material to be subjected to carbon reduction treatment is 1-15 wt%.
4. A method according to any one of claims 1 to 3, characterized in that: the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment is prepared by 3-6 times of dipping-cracking process circulation.
5. A method according to any one of claims 1 to 3, characterized in that:
the microwave power adopted by the microwave heating treatment is 400-1200W, and the time of the microwave heating treatment is 0.5-5 h.
6. The method according to claim 1, characterized in that:
and the temperature rising rate of the aerobic heat treatment during the process of rising the temperature to the treatment temperature is 1-10 ℃/min.
7. The method according to claim 1, wherein:
and heating to the treatment temperature of the anaerobic heat treatment at a heating rate of 1-10 ℃/min.
8. A porous silicon boron nitride ceramic material made according to the method of any one of claims 1 to 7.
9. The porous silicon-boron-nitrogen ceramic material of claim 8, wherein:
compared with the porous silicon-boron-nitrogen ceramic material to be subjected to carbon reduction treatment, the carbon content of the porous silicon-boron-nitrogen ceramic material subjected to carbon reduction treatment prepared by the method is reduced by more than 80%.
10. The porous silicon-boron-nitrogen ceramic material according to claim 8 or 9, wherein the carbon content of the porous silicon-boron-nitrogen ceramic material subjected to carbon reduction treatment is less than 1%.
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