CN117023588A - Preparation system for controlling boron carbide crystal growth environment - Google Patents
Preparation system for controlling boron carbide crystal growth environment Download PDFInfo
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- CN117023588A CN117023588A CN202311013274.XA CN202311013274A CN117023588A CN 117023588 A CN117023588 A CN 117023588A CN 202311013274 A CN202311013274 A CN 202311013274A CN 117023588 A CN117023588 A CN 117023588A
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- 229910052580 B4C Inorganic materials 0.000 title claims abstract description 83
- INAHAJYZKVIDIZ-UHFFFAOYSA-N boron carbide Chemical compound B12B3B4C32B41 INAHAJYZKVIDIZ-UHFFFAOYSA-N 0.000 title claims abstract description 83
- 239000013078 crystal Substances 0.000 title claims abstract description 75
- 238000002360 preparation method Methods 0.000 title claims abstract description 45
- 239000002243 precursor Substances 0.000 claims abstract description 160
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 115
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 98
- 239000000843 powder Substances 0.000 claims abstract description 75
- 238000006243 chemical reaction Methods 0.000 claims abstract description 49
- 238000010438 heat treatment Methods 0.000 claims abstract description 42
- 238000000034 method Methods 0.000 claims abstract description 38
- 238000010891 electric arc Methods 0.000 claims abstract description 30
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical compound O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910052810 boron oxide Inorganic materials 0.000 claims abstract description 11
- 238000012546 transfer Methods 0.000 claims abstract description 11
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 5
- 229910002091 carbon monoxide Inorganic materials 0.000 claims abstract description 5
- 238000001354 calcination Methods 0.000 claims description 61
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 56
- 238000003756 stirring Methods 0.000 claims description 56
- 229910052796 boron Inorganic materials 0.000 claims description 55
- 239000011261 inert gas Substances 0.000 claims description 54
- 239000002002 slurry Substances 0.000 claims description 54
- 239000002994 raw material Substances 0.000 claims description 32
- 230000009471 action Effects 0.000 claims description 29
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 29
- 239000004094 surface-active agent Substances 0.000 claims description 27
- 239000008367 deionised water Substances 0.000 claims description 23
- 229910021641 deionized water Inorganic materials 0.000 claims description 23
- 238000001035 drying Methods 0.000 claims description 23
- 238000002955 isolation Methods 0.000 claims description 21
- PPWPWBNSKBDSPK-UHFFFAOYSA-N [B].[C] Chemical compound [B].[C] PPWPWBNSKBDSPK-UHFFFAOYSA-N 0.000 claims description 20
- 238000002156 mixing Methods 0.000 claims description 20
- 238000007789 sealing Methods 0.000 claims description 19
- 239000000463 material Substances 0.000 claims description 17
- 239000000203 mixture Substances 0.000 claims description 17
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 16
- 229910002804 graphite Inorganic materials 0.000 claims description 16
- 239000010439 graphite Substances 0.000 claims description 16
- 238000000227 grinding Methods 0.000 claims description 16
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 15
- 239000002826 coolant Substances 0.000 claims description 15
- 239000007789 gas Substances 0.000 claims description 15
- 229910052760 oxygen Inorganic materials 0.000 claims description 15
- 239000001301 oxygen Substances 0.000 claims description 15
- 239000012298 atmosphere Substances 0.000 claims description 13
- 230000008569 process Effects 0.000 claims description 13
- 239000000047 product Substances 0.000 claims description 12
- 239000002245 particle Substances 0.000 claims description 9
- 229910052786 argon Inorganic materials 0.000 claims description 8
- 230000000694 effects Effects 0.000 claims description 7
- 239000002202 Polyethylene glycol Substances 0.000 claims description 6
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims description 6
- 239000004327 boric acid Substances 0.000 claims description 6
- 239000006227 byproduct Substances 0.000 claims description 6
- 239000006229 carbon black Substances 0.000 claims description 6
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 6
- 239000002563 ionic surfactant Substances 0.000 claims description 6
- 239000004570 mortar (masonry) Substances 0.000 claims description 6
- 230000003647 oxidation Effects 0.000 claims description 6
- 238000007254 oxidation reaction Methods 0.000 claims description 6
- 229920001223 polyethylene glycol Polymers 0.000 claims description 6
- 238000010298 pulverizing process Methods 0.000 claims description 6
- 239000000126 substance Substances 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 5
- 238000005303 weighing Methods 0.000 claims description 5
- 229910011255 B2O3 Inorganic materials 0.000 claims description 4
- 239000000919 ceramic Substances 0.000 claims description 4
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims description 3
- 238000009825 accumulation Methods 0.000 claims description 3
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- RLGQACBPNDBWTB-UHFFFAOYSA-N cetyltrimethylammonium ion Chemical class CCCCCCCCCCCCCCCC[N+](C)(C)C RLGQACBPNDBWTB-UHFFFAOYSA-N 0.000 claims description 3
- 238000004891 communication Methods 0.000 claims description 3
- 150000002191 fatty alcohols Chemical class 0.000 claims description 3
- 230000005484 gravity Effects 0.000 claims description 3
- 239000002736 nonionic surfactant Substances 0.000 claims description 3
- 229940051841 polyoxyethylene ether Drugs 0.000 claims description 3
- 229920000056 polyoxyethylene ether Polymers 0.000 claims description 3
- 239000010453 quartz Substances 0.000 claims description 3
- 239000012495 reaction gas Substances 0.000 claims description 3
- 239000011819 refractory material Substances 0.000 claims description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 3
- 238000009423 ventilation Methods 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims description 2
- 238000001914 filtration Methods 0.000 claims description 2
- 238000010899 nucleation Methods 0.000 claims description 2
- 238000000926 separation method Methods 0.000 claims description 2
- 230000009467 reduction Effects 0.000 abstract description 11
- 238000004519 manufacturing process Methods 0.000 abstract description 6
- 239000007787 solid Substances 0.000 abstract description 2
- 239000002585 base Substances 0.000 description 13
- 238000006722 reduction reaction Methods 0.000 description 10
- 238000005245 sintering Methods 0.000 description 4
- 150000001875 compounds Chemical class 0.000 description 3
- 238000002109 crystal growth method Methods 0.000 description 3
- 238000007731 hot pressing Methods 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- 230000007547 defect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000003801 milling Methods 0.000 description 2
- 238000004729 solvothermal method Methods 0.000 description 2
- 229910052582 BN Inorganic materials 0.000 description 1
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000005273 aeration Methods 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 150000001721 carbon Chemical group 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 229910003460 diamond Inorganic materials 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000002920 hazardous waste Substances 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000010587 phase diagram Methods 0.000 description 1
- 238000011112 process operation Methods 0.000 description 1
- 239000012429 reaction media Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/90—Carbides
- C01B32/914—Carbides of single elements
- C01B32/991—Boron carbide
Abstract
The invention provides a preparation system for controlling a boron carbide crystal growth environment, which transfers a precursor into a reaction furnace with a reaction temperature through rapid carbothermic reduction, and transfers the precursor into a high-temperature electric arc furnace of a crystal growth reaction unit at the reaction temperature, wherein gas-phase boron oxide and solid carbon react at a temperature of above 1600 ℃. After entering the hot zone, the precursor is controlled to have an extremely high heating rate (10 3 ‑l0 5 K/s) reaches the reaction temperature, and the boron oxide sublimates rapidly and reacts with the closely mixed carbon source to generate boron carbide crystals. Carbon monoxide and excess boron oxide gas leave the high temperature electric arc furnace from the exhaust pipe. The invention can realize the preparation of the boron carbide powder with high purity, small granularity and high-density twin crystal at lower temperature and time, and has obvious advantages compared with the traditional carbothermic reduction method. In addition, the boron carbide crystal prepared by the method can realize near-theoretical density at lower temperature and in shorter residence time, so that the production process is more efficient.
Description
Technical Field
The invention belongs to the technical field of synthesis and preparation of boron carbide, and relates to a preparation system for controlling the crystal growth environment of boron carbide, wherein the prepared synthesized boron carbide crystal particles have smaller particle size, lower free carbon and higher Luan Jing density.
Background
Boron carbide (B) 4 C) Is a gray black micropowder ceramic material, and has high melting point (2350 ℃), high hardness (9.3), high modulus, and low density (2.52 g/cm) 3 ) The composite material has the characteristics of good wear resistance, strong acid and alkali resistance, good neutron absorption capacity, low expansion coefficient and thermoelectric performance. Boron carbide is one of the three materials known to be the most rigid, next to diamond and cubic boron nitride. The crystal structure of boron carbide is rhombohedral, and a regular icosahedron element is composed of 12 boron atoms and one carbon atom. Boron carbide can be produced by carbon reduction of diboron trioxide in an electric furnace and is widely used in the fields of refractory materials, engineering ceramics, nuclear industry, aerospace, etc., such as manufacturing armor for tanks, bullet-proof garments, control rods, nozzles, etc.
Although boron carbide has many advantages, it has disadvantages such as high brittleness and low toughness. In order to improve the mechanical properties of boron carbide and improve the engineering application value of boron carbide, a plurality of methods are adopted in the prior art to prepare boron carbide long crystals. The boron carbide crystal growth refers to that under certain conditions, the growth direction and the growth rate of the boron carbide are controlled to form single crystals or polycrystal with larger size and higher integrity. At present, common boron carbide crystal growth methods include a compound crystal growth method, a solvothermal method, a hot pressing method and the like. The principle of the methods is that the non-equilibrium phase diagram or the phase change characteristic of the boron carbide is utilized, and the growth of the boron carbide from a solid phase or a liquid phase to a single direction is promoted under the conditions of proper temperature, pressure, time and the like. In the method, the compound crystal growth method adopts the compound of the boron source and the carbon source as the raw material, and the crystal is decomposed and grown at high temperature, so that the method has the advantages of easily available raw material and simple control, but the growth temperature is higher, and the yield is lower. The solvothermal method uses an organic solvent as a reaction medium, can grow at a lower temperature, is simple to operate, is easy to control a temperature field, is easy to introduce impurities, and has great difficulty in cleaning products. The hot pressing method adopts high temperature and high pressure, can inhibit the influence of impurities on the growth, and obtains longer single crystals, but has complex equipment, difficult operation and high production cost.
In the existing preparation method of boron carbide crystals, a carbothermic reduction method is also a relatively common method. The carbothermic reduction method is a method for preparing boron carbide crystals by mixing boric acid or boron oxide with carbon powder using carbon black as a reducing agent and then performing carbothermic reduction reaction at a high temperature. Its working principle is B 2 O 3 And C reacts at high temperature to form B 4 C crystal and CO gas, namely: 2B 2 O 3 +7C→B 4 C+6co. The main steps of preparing boron carbide crystal by carbothermic reduction method include: will B 2 O 3 Mixing with carbon powder according to a certain stoichiometric ratio; filling the mixture into a graphite crucible, and putting the graphite crucible into a high-temperature furnace; heating the furnace to 2000-2500 ℃ in an inert atmosphere; maintaining the temperature for a plurality of hours to finish the reaction; cooling and taking out the product. In the preparation process, high-quality B can be obtained by controlling atmosphere, temperature and raw material proportion 4 And C crystal.
Compared with other existing preparation methods of boron carbide crystals, the carbothermic reduction method has the advantages of simple and feasible reaction, simple equipment structure, small occupied area, high building speed and simple process operation, and the purity, granularity and phase composition of the boron carbide powder can be controlled by adjusting parameters such as reaction temperature, time, atmosphere and the like. However, when boron carbide crystals are produced by carbothermal reduction, problems and difficulties are faced, such as the production of boron carbide powder having a large size, a wide particle size distribution, a high metal impurity content, and the presence of unreacted free carbon. In addition, boron carbide is difficult to sinter, and other substances need to be added as sintering aids to reduce the sintering temperature, wherein carbon is one of the most commonly used sintering aids but can lead to the reduction of the mechanical properties of boron carbide. Hot pressing can produce high density boron carbide but requires very high temperatures. Spark sintering is an alternative densification method that can achieve high densities at lower temperatures and has limitations on grain growth, but requires special equipment and techniques.
Disclosure of Invention
Object of the invention
Aiming at the defects and the shortcomings of the prior art, the method aims at solving the prior utilizationThe invention provides a preparation system for controlling the boron carbide crystal growth environment, which is used for transferring a precursor into a reaction furnace with a reaction temperature by rapid carbothermic reduction, transferring the precursor powder into a high-temperature arc furnace of a crystal growth reaction unit at the reaction temperature, and reacting gas-phase boron oxide with solid carbon at 1600 ℃ or higher. After entering the hot zone, the precursor is controlled to have an extremely high heating rate (10 3 -l0 5 K/s) reaches the reaction temperature, and the boron oxide sublimates rapidly and reacts with the closely mixed carbon source to generate the boron carbon compound. Carbon monoxide and excess boron oxide gas leave the high temperature electric arc furnace from the exhaust pipe. The invention can realize the preparation of the boron carbide powder with high purity, small granularity and high-density twin crystal at lower temperature and time, and has obvious advantages compared with the traditional carbothermic reduction method. In addition, the boron carbide crystal prepared by the method can realize near-theoretical density at lower temperature and in shorter residence time, so that the production process is more efficient.
(II) technical scheme
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
the preparation system for controlling the boron carbide crystal growth environment at least comprises a raw material preparation unit, a raw material mixing unit, a precursor drying unit, a precursor calcining unit, a precursor crushing unit, a precursor conveying unit and a crystal growth reaction unit, and is characterized in that,
-the raw material preparation unit comprises at least a boron source and a carbon source, wherein the boron source is high-purity boric acid or boric oxide, and the carbon source is high-activity carbon black or graphite;
the raw material mixing unit at least comprises a first container and a second container which are arranged adjacently, wherein the boron source is dispersed in deionized water in an inner cavity of the first container in a stirring manner and forms boron slurry; dispersing the carbon source in deionized water in an inner cavity of a second container in a stirring manner, and adding a surfactant to form carbon slurry; pouring the carbon slurry into the first container, fully stirring and mixing the carbon slurry and the boron slurry, and heating the carbon slurry in the stirring process to fully evaporate water in the mixture to form a carbon-boron paste;
the precursor drying unit at least comprises a low-temperature oven, wherein the low-temperature oven is connected with a first container through a material conveying pipeline I, and the carbon-boron paste formed in the first container is conveyed into the low-temperature oven through the material conveying pipeline I and is sufficiently dried and heated in the temperature environment to form a dried precursor;
The precursor calcining unit at least comprises a medium-temperature calcining box, wherein the inner cavity of the medium-temperature calcining box is in an inert gas atmosphere, and after the dried precursor formed in the low-temperature oven is conveyed to the medium-temperature calcining box, the dried precursor is fully calcined under the action of medium-temperature environment and constant inert gas flow to remove various organic matters and redundant carbon and oxygen remained in the dried precursor, and finally the dried precursor is formed into a calcining block;
the precursor crushing unit at least comprises a grinding and crushing device, wherein the calcined block in the medium-temperature calcining box is conveyed to the grinding and crushing device through a conveying device after being cooled to room temperature, and is crushed into precursor powder with the granularity of hundred micrometers;
the precursor delivery unit comprising at least a screw feeder, a sealing hopper and a cold pipe feeder, wherein,
the screw feeder is arranged in a horizontal state as a whole and comprises a feeding end and a discharging end,
the sealing hopper is used for storing precursor powder meeting the granularity requirement, the whole body of the sealing hopper is of a sealed structure, the bottom of the sealing hopper is communicated with the feeding end of the screw feeder through a gate valve,
the cold pipe feeder is integrally arranged in a vertical state and is a hollow tubular part, the top of the cold pipe feeder is communicated with an inert gas source through a pipeline, a side wall of the cold pipe feeder, which is close to the top, is provided with a feed inlet communicated with the discharge end of the screw feeder, the side wall of the cold pipe feeder is sleeved with a cooling medium sleeve, the cooling medium sleeve is communicated with a low-temperature cooling medium source through a communication pipeline to form a cooling medium circulation loop, and the bottom opening end of the cold pipe feeder is formed into a discharge port of the cold pipe feeder;
The long crystal reaction unit comprises a vertical high-temperature electric arc furnace which is in a closed state as a whole, wherein,
two arc-shaped plate-shaped graphite electrodes which are oppositely arranged are arranged in the side wall of the inner cavity of the high-temperature electric arc furnace,
the bottom of the inner cavity center of the high-temperature electric arc furnace is provided with a disk-shaped supporting base, the top surface of the supporting base is at least fixedly provided with a cylindrical high-temperature isolation container which is concentrically arranged with the supporting base and is provided with an opening at the top, the high-temperature isolation container is internally and at least fixedly provided with a heat-resistant crucible which is concentrically arranged with the high-temperature isolation container and is provided with an opening at the top, a radial gap is arranged between the heat-resistant crucible and the high-temperature isolation container, the bottom of the high-temperature isolation container is provided with a vent hole which is communicated with the inner cavity of the disk-shaped supporting base, the bottom of the disk-shaped supporting base is provided with an exhaust port which is communicated with the inner cavity of the disk-shaped supporting base, and the exhaust port is communicated with the outside through an exhaust pipeline,
the cold pipe feeder penetrates through the top of the high-temperature electric arc furnace and stretches into the top opening of the heat-resistant crucible, precursor powder in the cold pipe feeder falls into the heat-resistant crucible under the action of gravity and reacts in a high-temperature environment to generate boron carbide crystals, the boron carbide crystals generated by the reaction accumulate in the heat-resistant crucible, and gas byproducts including carbon monoxide and excessive boron oxide gas generated by the reaction and inert gas leave the system through a gap between the heat-resistant crucible and the high-temperature isolation container, a vent hole at the bottom of the high-temperature isolation container, an exhaust port at the bottom of the disc-shaped support base and an exhaust pipeline in sequence.
Preferably, in the raw material preparation unit, the mass ratio of raw material components between the boron source and the carbon source after metering and weighing is kept in the range of 10:7-10:8.5 so as to ensure the completeness of the subsequent reaction between the two components and the purity of the product.
Preferably, in the raw material mixing unit, the first container and the second container are open containers with open tops and closed bottoms, wherein,
at least one heating device is arranged on the outer wall of the first container, at least one stirring device is arranged in the inner cavity of the first container, and the boron source is dispersed in deionized water in a stirring mode by the aid of the first stirring device under the temperature environment of about 80 ℃ in the inner cavity of the first container to form boron slurry;
the bottom of the second container is provided with at least one jacking and tilting device, and at least one second stirring device is arranged in the inner cavity of the second container, and the carbon source is dispersed in deionized water in a stirring manner by the second stirring device in the inner cavity of the second container, and is added with a surfactant to form carbon slurry;
after the carbon source is formed into carbon slurry, the carbon slurry in the second container is slowly poured into the first container at a small inclination angle under the action of the jacking tilting device and is fully stirred and mixed with the boron slurry under the action of the first stirring device, and the heating device is in a starting state in the stirring process, and the heating time is at least enough to ensure that the moisture in the mixture is fully evaporated to form a carbon-boron paste.
Further, in the raw material mixing unit, the surfactant added in the process of forming the carbon slurry is a polyethylene glycol ether nonionic surfactant, a polyoxyethylene ether surfactant, a fatty alcohol polyethylene glycol ether surfactant, a sodium dodecyl sulfate salt type ionic surfactant or a cetyl trimethyl ammonium salt type ionic surfactant.
Preferably, in the raw material mixing unit, the stirring time of the boron source and the carbon source in the inner cavities of the first container and the second container is about 30min, so that the boron source and the carbon source are fully dispersed in deionized water; the heating degree of the heating device is not more than 100 ℃.
Preferably, in the precursor drying unit, the drying heating temperature of the oven is between 120 ℃ and 140 ℃ and the drying time is not less than 12 hours.
Preferably, in the precursor calcining unit, the intermediate temperature calcining box is a closed box body and forms an air circulation loop with an inert gas source through a gas pipeline, so that the inner cavity of the intermediate temperature calcining box is in inert gas atmosphere, the intermediate temperature calcining box is connected with a low temperature oven through a material conveying pipeline II, and after the dried precursor formed in the low temperature oven is conveyed to the intermediate temperature calcining box through the material conveying pipeline II, the dried precursor is fully calcined under the action of the intermediate temperature environment and constant inert gas flow to remove various organic matters including surfactants and redundant carbon and oxygen remained in the dried precursor, and finally the dried precursor is formed into a calcined block.
Further, in the precursor calcining unit, the medium-temperature calcining box is a tubular electric furnace, the inert gas is argon, the dried precursor is calcined under the constant argon flow in the tubular electric furnace, the calcining temperature is not more than 600 ℃, and the calcining time is not more than 10min, so that various organic matters including surfactants and redundant carbon and oxygen remained in the dried precursor are removed, and meanwhile, the crystal structure and chemical composition of the follow-up boron carbide product are not obviously influenced.
Preferably, in the precursor crushing unit, the grinding and crushing device is a quartz mortar or a ceramic mortar, and the grinding process needs to be slowly applied to prevent the generation of large heat, and the granularity of the precursor powder after grinding is kept between 125 and 425 μm.
Preferably, in the precursor conveying unit, the cold pipe feeder is cooled by a cooling medium sleeve, the temperature in a hollow pipe-shaped cavity is controlled to be 400-500 ℃, and after the temperature in the inner cavity of the high-temperature arc furnace reaches at least 1600 ℃, a gate valve at the bottom of the sealing hopper is opened, and the precursor powder is conveyed into the cold pipe feeder under the action of a screw feeder and is led into the inner cavity of the high-temperature arc furnace under the wrapping of inert gas.
Further, before the temperature in the inner cavity of the high-temperature arc furnace is stabilized above 1600 ℃, the precursor powder is kept in the sealing hopper, after the furnace temperature is stabilized above 1600 ℃, a gate valve at the bottom of the sealing hopper is opened, the precursor powder is conveyed into the cold pipe feeder under the action of a screw feeder to keep relatively low temperature, and the precursor powder is introduced into the high-temperature arc furnace under the wrapping of inert gas.
Further, after the furnace temperature of the high-temperature electric arc furnace is stabilized to be more than 1600 ℃, opening a gate valve at the bottom of the sealing hopper, conveying the precursor powder into the cold pipe feeder under the action of a screw feeder according to the feeding rate of 1.5-3 g/min, and introducing the precursor powder into the high-temperature electric arc furnace under the wrapping of inert gas.
Further, the two graphite electrodes in the high-temperature arc furnace are electrically connected with a high-power supply through wires, so that a high-power arc is generated between the two graphite electrodes, the cold tube feeder stretches into the high-temperature arc furnace at a position which ensures that the precursor powder discharged from a discharge hole of the cold tube feeder is in a hot zone acted by high-temperature plasma flow between the high-power arcs, inert gas wrapping the precursor powder is used for preventing oxidation of the precursor powder and facilitating heat transfer, and finally the precursor powder enters the hot zone and then is mixed with the precursor powder in an amount of 10 percent 3 -10 5 The heating rate of K/s reaches a reaction temperature above 1600 ℃.
Further, the ventilation rate of the inert gas in the cold pipe feeder is 400-600 ml/min, and the inert gas in the passage wraps the precursor powder into a hot zone in the high-temperature electric arc furnace and is matched with the heating rate of the hot zone so as to realize the full conversion of the precursor powder into boron carbide crystals, and prevents oxidation of the precursor powder and facilitates heat transfer and prevents the reaction from being carried out due to the accumulation of gas byproducts generated by the reaction in the hot zone.
Preferably, in the long-crystal reaction unit, the high-temperature isolation container is made of graphite-type, ceramic-type or silicon-carbon-type high-temperature refractory materials.
The 2 nd invention aims to provide a preparation method for controlling the boron carbide crystal growth environment, which is based on the preparation system for controlling the boron carbide crystal growth environment, and is characterized by at least comprising the following steps:
SS1 preparation of raw materials
Providing high-purity boric acid or boric oxide as a boron source, and providing high-activity carbon black or graphite as a carbon source, wherein the mass ratio of raw material components between the boron source and the carbon source after metering and weighing is kept within the range of 10:7-10:8.5 so as to ensure the completeness of the subsequent reaction between the boron source and the carbon source and the purity of a product;
SS2 mixing of raw materials
Firstly, dispersing the boron source in deionized water in an inner cavity of a first container in a stirring manner and forming boron slurry; dispersing the carbon source in deionized water in an inner cavity of a second container in a stirring manner, and adding a surfactant to form carbon slurry;
secondly, pouring the carbon slurry into the first container and fully stirring and mixing the carbon slurry and the boron slurry, and heating the carbon slurry in the stirring process to fully evaporate water in the mixture to form a carbon-boron paste;
SS3 drying of precursors
Conveying the carbon-boron paste formed in the first container to a low-temperature oven through a material conveying pipeline I, and fully drying and heating the carbon-boron paste in the temperature environment to form a dry precursor;
SS4 calcination of precursors
After conveying the dried precursor prepared in the step SS3 to a medium-temperature calcination box in an inert gas atmosphere, fully calcining under the actions of the medium-temperature environment and constant inert gas flow to remove various organic matters and redundant carbon and oxygen remained in the dried precursor, and finally forming calcined blocks;
SS5 comminuting of precursors
Cooling the calcining block in the middle-temperature calcining box in the step SS4 to room temperature, and then conveying the cooled calcining block to the grinding and crushing device through a transfer device to crush the calcined block into precursor powder with the granularity of hundred micrometers;
SS6 precursor delivery and high temperature seeding
Firstly, maintaining precursor powder in the sealed hopper, simultaneously starting the high-temperature electric arc furnace and preheating until the temperature in the inner cavity of the furnace is stabilized above 1600 ℃;
secondly, after the furnace temperature of the high-temperature electric arc furnace is stabilized above 1600 ℃, opening a gate valve at the bottom of the sealing hopper, conveying precursor powder into the cold pipe feeder at a feeding rate of 1.5-3 g/min under the action of a screw feeder under the precursor that the inner cavity temperature of the cold pipe feeder is controlled at 400-500 ℃, and introducing the precursor powder into the high-temperature electric arc furnace under the wrapping of inert gas with a ventilation rate of 400-600 ml/min;
then, continuously introducing inert gas into the furnace body after the precursor powder finishes the boron carbide reaction under the high-temperature condition, stopping conveying the precursor powder to the high-temperature electric arc furnace, and continuously cooling the high-temperature electric arc furnace under the inert gas atmosphere to reduce the furnace temperature;
finally, after the furnace temperature of the high-temperature electric arc furnace is reduced to room temperature, collecting boron carbide crystal powder in the heat-resistant crucible in a cyclone separation and filtration mode, and removing impurities and gases in the boron carbide crystal powder.
Preferably, in the step SS2, the boron source is dispersed in deionized water in a stirring manner by the first stirring device under a temperature environment of about 80 ℃ in the inner cavity of the first container and forms boron slurry; the stirring time of the boron source and the carbon source in the inner cavities of the first container and the second container is about 30min, so that the boron source and the carbon source are fully dispersed in deionized water; the heating degree of the heating device is not more than 100 ℃.
Preferably, in step SS2, after the carbon source is formed into carbon slurry, the carbon slurry in the second container is slowly poured into the first container at a small inclination angle under the action of the jacking tilting device and is fully stirred and mixed with the boron slurry under the action of the first stirring device, and the heating device is in a starting state during stirring, and the heating period is at least enough to ensure that the moisture in the mixture is fully evaporated to form a carbon-boron paste.
Preferably, in the step SS3, the drying and heating temperature of the carbon-boron paste in the low-temperature oven is 120-140 ℃ and the drying time is not less than 12 hours.
Preferably, in step SS4, after the dried precursor is conveyed to the medium temperature calcination tank through the material conveying pipeline ii, the dried precursor is fully calcined under the medium temperature environment and the action of constant inert gas flow to remove various organic matters including surfactants and redundant carbon and oxygen remained in the dried precursor, and finally the dried precursor is formed into a calcined block.
Preferably, in step SS4, the dried precursor is calcined under a constant argon flow in the medium-temperature calcining chamber at a temperature not exceeding 600 ℃ for a time not exceeding 10 minutes, so as to remove various organic matters including surfactants and excessive carbon and oxygen remaining in the dried precursor, without significantly affecting the crystal structure and chemical composition of the subsequent boron carbide product.
Preferably, in step SS5, a slow force is required to prevent the generation of large heat during the milling process, and the particle size of the precursor powder after milling should be maintained at 125 to 425 μm.
(III) technical effects
Compared with the prior art, the preparation system for controlling the boron carbide crystal growth environment has the following beneficial and remarkable technical effects:
(1) Compared with the preparation system for controlling the boron carbide crystal growth environment, the preparation system has the advantages that the boron carbide prepared by the prior art is higher in purity, smaller in granularity, contains high-density twin crystals, and has lower free carbon content.
(2) Compared with the prior art, the preparation system for controlling the boron carbide crystal growth environment has lower reaction temperature and shorter preparation time, the reaction temperature is 200-300 ℃ lower than that of the prior art, the equipment time can be shortened by about 10%, and the preparation efficiency is greatly improved.
(3) Compared with the prior art, the preparation system for controlling the boron carbide crystal growth environment has lower energy consumption, greatly reduces the energy consumption in the preparation process due to the shortened reaction preparation time, does not generate hazardous waste in the preparation process, and greatly improves the environmental protection performance.
Drawings
FIG. 1 is a schematic diagram of a preparation system for controlling the environment of boron carbide growth in accordance with the present invention;
FIG. 2 is a schematic diagram of a partial structure of a preparation system for controlling a boron carbide crystal growth environment according to the present invention;
FIG. 3 is a schematic flow chart of a preparation method for controlling the boron carbide crystal growth environment.
Detailed Description
For a better understanding of the present invention, the following examples are set forth to illustrate the present invention. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of the invention. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting 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. The following describes the structure and technical scheme of the present invention in detail with reference to the accompanying drawings, and an embodiment of the present invention is given.
As shown in fig. 1, the preparation system for controlling the boron carbide crystal growth environment of the present invention comprises a raw material preparation unit 10, a raw material mixing unit 20, a precursor drying unit 30, a precursor calcining unit 40, a precursor pulverizing unit 50, a precursor conveying unit 60, a crystal growth reaction unit 70, and a separating device 80.
The raw material preparation unit 10 of the present invention includes at least a boron source, which is high-purity boric acid or boron oxide, and a carbon source, which is high-activity carbon black or graphite. The mass ratio of raw material components between the boron source and the carbon source after metering and weighing is kept in the range of 10:7-10:8.5 so as to ensure the completeness of the subsequent reaction between the two and the purity of the product.
The raw material mixing unit 20 at least comprises a first container and a second container which are adjacently arranged, wherein the boron source is dispersed in deionized water in an inner cavity of the first container in a stirring manner and forms boron slurry; dispersing a carbon source in deionized water in an inner cavity of a second container in a stirring manner, and adding a surfactant to form carbon slurry; the carbon slurry is poured into a first container and thoroughly mixed with the boron slurry, and heating is performed during the stirring process to enable moisture in the mixture to be thoroughly evaporated to form a carbon-boron paste. Preferably, the first container and the second container are open containers with open top and closed bottom, wherein the outer wall of the first container is at least provided with a heating device and the inner cavity of the first container is at least provided with a stirring device, and the boron source is dispersed in deionized water in a stirring manner by the first stirring device under the temperature environment of about 80 ℃ in the inner cavity of the first container to form boron slurry; at least one jacking and tilting device is arranged at the bottom of the second container, at least one second stirring device is arranged in the inner cavity of the second container, and the carbon source is dispersed in deionized water in a stirring manner by the second stirring device in the inner cavity of the second container, and is added with a surfactant to form carbon slurry; after the carbon source is formed into carbon slurry, the carbon slurry in the second container is slowly poured into the first container at a small inclination angle under the action of the jacking tilting device and is fully stirred and mixed with boron slurry under the action of the first stirring device, and the heating device is in a starting state in the stirring process, and the heating time is at least enough to ensure that the water in the mixture is evaporated to form a carbon-boron paste. In addition, the surfactant added in the formation of the carbon slurry is a polyethylene glycol ether nonionic surfactant, a polyoxyethylene ether surfactant, a fatty alcohol polyethylene glycol ether surfactant, a sodium dodecyl sulfate salt type ionic surfactant or a cetyl trimethylammonium salt type ionic surfactant. The stirring time of the boron source and the carbon source in the inner cavities of the first container and the second container is about 30min, so that the boron source and the carbon source are fully dispersed in deionized water; the heating degree of the heating device is not more than 100 ℃.
The precursor drying unit 30 comprises at least one low temperature oven connected with the first container through a material conveying pipeline I, and the carbon-boron paste formed in the first container is conveyed into the low temperature oven through the material conveying pipeline I and is fully dried and heated in the temperature environment to form a dried precursor. Preferably, the drying heating temperature of the oven is between 120 ℃ and 140 ℃ and the drying time is not less than 12 hours.
The precursor calcining unit 40 at least comprises a medium temperature calcining box, wherein the inner cavity of the medium temperature calcining box is in an inert gas atmosphere, and after the dried precursor formed in the low temperature oven is conveyed to the medium temperature calcining box, the dried precursor is fully calcined under the medium temperature environment and the action of constant inert gas flow to remove various organic matters and redundant carbon and oxygen remained in the dried precursor, and finally the dried precursor is formed into a calcining block. Preferably, the medium temperature calcination box is a closed box body and forms an air flow circulation loop with an inert gas source through a gas pipeline, so that the inner cavity of the medium temperature calcination box is in inert gas atmosphere, the medium temperature calcination box is connected with the low temperature oven through a material conveying pipeline II, and after the dried precursor formed in the low temperature oven is conveyed to the medium temperature calcination box through the material conveying pipeline II, the dried precursor is fully calcined under the action of medium temperature environment and constant inert gas flow to remove various organic matters including surfactants and redundant carbon and oxygen remained in the dried precursor, and finally the dried precursor is formed into a calcination block. In addition, the medium-temperature calcining box is a tubular electric furnace, inert gas is argon, the drying precursor is calcined in the tubular electric furnace under constant argon flow, the calcining temperature is not more than 600 ℃, and the calcining time is not more than 10 minutes, so that various organic matters including surfactants and redundant carbon and oxygen remained in the drying precursor are removed, and meanwhile, the crystal structure and chemical components of the follow-up boron carbide product are not obviously influenced.
The precursor pulverizing unit 50 comprises at least one grinding and pulverizing device, and the calcined block in the medium-temperature calcining box is cooled to room temperature and then conveyed to the grinding and pulverizing device through a transfer device to pulverize the precursor powder with the granularity of hundred micrometers. Preferably, the grinding and pulverizing device is a quartz mortar or a ceramic mortar, and the grinding process needs to be performed with a slow force to prevent the generation of large heat, and the particle size after grinding is kept between 125 and 425 μm.
As shown in fig. 1 and 2, the precursor delivery unit 60 of the present invention comprises at least a screw feeder 62, a sealing hopper 61 and a cold pipe feeder 63, wherein the screw feeder 62 is arranged in a horizontal state as a whole and comprises a feed end and a discharge end; the seal hopper 61 is used for storing precursor powder meeting the particle size requirement, the whole body of the seal hopper is in a sealed structure, and the bottom of the seal hopper is communicated with the feeding end of the screw feeder 62 through a gate valve; the cold pipe feeder 63 is integrally arranged in a vertical state and is integrally a hollow tubular member, the top of the cold pipe feeder 63 is communicated with an inert gas source through a pipeline, a feed port communicated with the discharge end of the screw feeder 62 is arranged on the side wall close to the top of the cold pipe feeder, a cooling medium sleeve is sleeved outside the side wall of the cold pipe feeder, the cooling medium sleeve is communicated with a low-temperature cooling medium source through a communication pipeline to form a cooling medium circulation loop, and the bottom opening end of the cold pipe feeder 63 is formed into the discharge port of the cold pipe feeder.
Preferably, the cold pipe feeder 63 is cooled by its cooling medium jacket, the temperature in the hollow tubular cavity is controlled at 400-500 ℃, and after the temperature in the inner cavity of the high temperature arc furnace reaches at least 1600 ℃, the gate valve at the bottom of the sealing hopper 61 is opened, and the precursor powder is conveyed into the cold pipe feeder under the action of the screw feeder 62 and is introduced into the inner cavity of the high temperature arc furnace under the entrainment of inert gas.
As shown in fig. 1 and 2, the long crystal reaction unit 70 of the present invention comprises a vertical high temperature electric arc furnace in a closed state, wherein two arc-shaped plate-shaped graphite electrodes 71 are arranged in the side wall of the inner cavity of the high temperature electric arc furnace in an opposite way, a disk-shaped supporting base is arranged at the bottom of the inner cavity center of the high temperature electric arc furnace, at least one cylindrical high temperature isolation container 72 which is arranged concentrically with the supporting base and has an open top is fixedly arranged on the top surface of the supporting base, at least one heat-resistant crucible 73 which is arranged concentrically with the supporting base and has an open top is fixedly arranged in the high temperature isolation container 72, a radial gap is arranged between the heat-resistant crucible 73 and the high temperature isolation container 72, a vent hole which is communicated with the inner cavity of the disk-shaped supporting base is arranged at the bottom of the high temperature isolation container 72, and the vent hole is communicated with the outside through a vent line. The cold pipe feeder 63 is inserted into the top opening of the refractory crucible 73 through the top of the high temperature arc furnace, the precursor powder in the cold pipe feeder 63 falls into the refractory crucible 73 under the action of gravity and reacts in the high temperature environment to produce boron carbide crystals, the boron carbide crystal powder produced by the reaction accumulates in the refractory crucible 73, and the gas by-products including carbon monoxide and excess boron oxide gas produced by the reaction and inert gas leave the system sequentially through the gap between the refractory crucible 73 and the high temperature isolation container 72, the vent hole at the bottom of the disk-shaped support base, and the exhaust line.
Preferably, the precursor powder is held in the sealed hopper 61 until the temperature in the inner chamber of the high temperature arc furnace stabilizes above 1600 ℃, the furnace temperature stabilizingAfter 1600 c or more, the gate valve sealing the bottom of the hopper 61 is opened, and the precursor powder is fed into the cold pipe feeder 63 under the action of the screw feeder 62 to be kept at a relatively low temperature, and is introduced into the high temperature arc furnace under the entrainment of the inert gas. After the furnace temperature of the high temperature arc furnace has stabilized to 1600 ℃ or higher, the precursor powder is fed into the cold pipe feeder 63 at a feed rate of 1.5 to 3g/min by the screw feeder 62 and introduced into the high temperature arc furnace under the entrainment of the inert gas. The two graphite electrodes in the high-temperature arc furnace are electrically connected with a high-power supply through wires, so that a high-power arc is generated between the two graphite electrodes 71, the cold pipe feeder 63 stretches into the high-temperature arc furnace at a position which ensures that precursor powder discharged from a discharge hole of the cold pipe feeder is in a hot zone acted by high-temperature plasma flow between the high-power arcs, inert gas wrapping the precursor powder is used for preventing oxidation of the precursor powder and facilitating heat transfer, and finally the precursor powder enters the hot zone and then is mixed with the precursor powder to form a mixture of the precursor powder and the high-temperature plasma 3 -10 5 The heating rate of K/s reaches a reaction temperature above 1600 ℃. In addition, the aeration rate of the inert gas in the cold pipe feeder 63 is 400-600 ml/min, and the inert gas in the passage is used for wrapping the received precursor powder into a hot zone in the high-temperature arc furnace and matching the heating rate of the hot zone so as to realize the full conversion of the precursor powder into boron carbide crystals, and preventing oxidation of the precursor powder and facilitating heat transfer and preventing the reaction from being carried out due to the accumulation of gas byproducts generated by the reaction in the hot zone.
As can be seen from table 1 below, the boron carbide powder prepared according to the present invention has smaller particle size, lower free carbon and impurity content, higher grain boundary bicrystal density, and higher relative density and microhardness than the existing commercial boron carbide powder. These performance advantages demonstrate that the boron carbide production methods and systems of the present invention can achieve higher purity, better stoichiometry control, finer grain size, and more defect incorporation.
TABLE 1 Properties of boron carbide powder prepared according to the invention
The object of the present invention is fully effectively achieved by the above-described embodiments. Those skilled in the art will appreciate that the present invention includes, but is not limited to, those illustrated in the drawings and described in the foregoing detailed description. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.
Claims (22)
1. The preparation system for controlling the boron carbide crystal growth environment at least comprises a raw material preparation unit, a raw material mixing unit, a precursor drying unit, a precursor calcining unit, a precursor crushing unit, a precursor conveying unit and a crystal growth reaction unit, and is characterized in that,
-the raw material preparation unit comprises at least a boron source and a carbon source, wherein the boron source is high-purity boric acid or boric oxide, and the carbon source is high-activity carbon black or graphite;
the raw material mixing unit at least comprises a first container and a second container which are arranged adjacently, wherein the boron source is dispersed in deionized water in an inner cavity of the first container in a stirring manner and forms boron slurry; dispersing the carbon source in deionized water in an inner cavity of a second container in a stirring manner, and adding a surfactant to form carbon slurry; pouring the carbon slurry into the first container, fully stirring and mixing the carbon slurry and the boron slurry, and heating the carbon slurry in the stirring process to fully evaporate water in the mixture to form a carbon-boron paste;
the precursor drying unit at least comprises a low-temperature oven, wherein the low-temperature oven is connected with a first container through a material conveying pipeline I, and the carbon-boron paste formed in the first container is conveyed into the low-temperature oven through the material conveying pipeline I and is sufficiently dried and heated in the temperature environment to form a dried precursor;
the precursor calcining unit at least comprises a medium-temperature calcining box, wherein the inner cavity of the medium-temperature calcining box is in an inert gas atmosphere, and after the dried precursor formed in the low-temperature oven is conveyed to the medium-temperature calcining box, the dried precursor is fully calcined under the action of medium-temperature environment and constant inert gas flow to remove various organic matters and redundant carbon and oxygen remained in the dried precursor, and finally the dried precursor is formed into a calcining block;
The precursor crushing unit at least comprises a grinding and crushing device, wherein the calcined block in the medium-temperature calcining box is conveyed to the grinding and crushing device through a conveying device after being cooled to room temperature, and is crushed into precursor powder with the granularity of hundred micrometers;
the precursor delivery unit comprising at least a screw feeder, a sealing hopper and a cold pipe feeder, wherein,
the screw feeder is arranged in a horizontal state as a whole and comprises a feeding end and a discharging end,
the sealing hopper is used for storing precursor powder meeting the granularity requirement, the whole body of the sealing hopper is of a sealed structure, the bottom of the sealing hopper is communicated with the feeding end of the screw feeder through a gate valve,
the cold pipe feeder is integrally arranged in a vertical state and is a hollow tubular part, the top of the cold pipe feeder is communicated with an inert gas source through a pipeline, a side wall of the cold pipe feeder, which is close to the top, is provided with a feed inlet communicated with the discharge end of the screw feeder, the side wall of the cold pipe feeder is sleeved with a cooling medium sleeve, the cooling medium sleeve is communicated with a low-temperature cooling medium source through a communication pipeline to form a cooling medium circulation loop, and the bottom opening end of the cold pipe feeder is formed into a discharge port of the cold pipe feeder;
The long crystal reaction unit comprises a vertical high-temperature electric arc furnace which is in a closed state as a whole, wherein,
two arc-shaped plate-shaped graphite electrodes which are oppositely arranged are arranged in the side wall of the inner cavity of the high-temperature electric arc furnace,
the bottom of the inner cavity center of the high-temperature electric arc furnace is provided with a disk-shaped supporting base, the top surface of the supporting base is at least fixedly provided with a cylindrical high-temperature isolation container which is concentrically arranged with the supporting base and is provided with an opening at the top, the high-temperature isolation container is internally and at least fixedly provided with a heat-resistant crucible which is concentrically arranged with the high-temperature isolation container and is provided with an opening at the top, a radial gap is arranged between the heat-resistant crucible and the high-temperature isolation container, the bottom of the high-temperature isolation container is provided with a vent hole which is communicated with the inner cavity of the disk-shaped supporting base, the bottom of the disk-shaped supporting base is provided with an exhaust port which is communicated with the inner cavity of the disk-shaped supporting base, and the exhaust port is communicated with the outside through an exhaust pipeline,
the cold pipe feeder penetrates through the top of the high-temperature electric arc furnace and stretches into the top opening of the heat-resistant crucible, precursor powder in the cold pipe feeder falls into the heat-resistant crucible under the action of gravity and reacts in a high-temperature environment to generate boron carbide crystals, the boron carbide crystals generated by the reaction accumulate in the heat-resistant crucible, and gas byproducts including carbon monoxide and excessive boron oxide gas generated by the reaction and inert gas leave the system through a gap between the heat-resistant crucible and the high-temperature isolation container, a vent hole at the bottom of the high-temperature isolation container, an exhaust port at the bottom of the disc-shaped support base and an exhaust pipeline in sequence.
2. The preparation system for controlling a boron carbide crystal growth environment according to claim 1, wherein the mass ratio of raw material components between the boron source and the carbon source after metering and weighing is kept in a range of 10:7-10:8.5 in the raw material preparation unit so as to ensure the completeness of the subsequent reaction between the two and the purity of the product.
3. The system for preparing a boron carbide crystal growth environment according to claim 1, wherein the first container and the second container are open-top and closed-bottom containers in the raw material mixing unit, wherein,
at least one heating device is arranged on the outer wall of the first container, at least one stirring device is arranged in the inner cavity of the first container, and the boron source is dispersed in deionized water in a stirring mode by the aid of the first stirring device under the temperature environment of about 80 ℃ in the inner cavity of the first container to form boron slurry;
the bottom of the second container is provided with at least one jacking and tilting device, and at least one second stirring device is arranged in the inner cavity of the second container, and the carbon source is dispersed in deionized water in a stirring manner by the second stirring device in the inner cavity of the second container, and is added with a surfactant to form carbon slurry;
After the carbon source is formed into carbon slurry, the carbon slurry in the second container is slowly poured into the first container at a small inclination angle under the action of the jacking tilting device and is fully stirred and mixed with the boron slurry under the action of the first stirring device, and the heating device is in a starting state in the stirring process, and the heating time is at least enough to ensure that the moisture in the mixture is fully evaporated to form a carbon-boron paste.
4. The system for preparing a boron carbide crystal growth environment according to claim 3, wherein the surfactant added in the formation of the carbon slurry in the raw material mixing unit is a polyethylene glycol ether nonionic surfactant, a polyoxyethylene ether surfactant, a fatty alcohol polyethylene glycol ether surfactant, a sodium dodecyl sulfate salt type ionic surfactant or a cetyltrimethylammonium salt type ionic surfactant.
5. The preparation system for controlling the boron carbide crystal growth environment according to claim 1, wherein in the raw material mixing unit, the stirring time of the boron source and the carbon source in the inner cavities of the first container and the second container is about 30min, so that the boron source and the carbon source are fully dispersed in deionized water; the heating degree of the heating device is not more than 100 ℃.
6. The system for preparing a boron carbide crystal growth environment according to claim 1, wherein in the precursor drying unit, the drying heating temperature of the oven is between 120 ℃ and 140 ℃ and the drying time is not less than 12 hours.
7. The preparation system for controlling boron carbide crystal growth environment according to claim 1, wherein in the precursor calcining unit, the intermediate temperature calcining box is a closed box body and forms an air flow circulation loop with an inert gas source through a gas pipeline, so that the inner cavity of the intermediate temperature calcining box is in inert gas atmosphere, the intermediate temperature calcining box is connected with a low temperature oven through a material conveying pipeline II, and after the dried precursor formed in the low temperature oven is conveyed to the intermediate temperature calcining box through the material conveying pipeline II, the dried precursor is fully calcined under the action of the intermediate temperature environment and constant inert gas flow to remove various organic matters including surfactants and redundant carbon and oxygen remained in the dried precursor, and finally the dried precursor is formed into a calcined block.
8. The system according to claim 7, wherein the intermediate temperature calcination tank is a tubular electric furnace, the inert gas is argon, and the dry precursor is calcined in a constant argon flow in the tubular electric furnace at a calcination temperature of not more than 600 ℃ for not more than 10 minutes, so as to remove various organic matters including surfactants and excessive carbon and oxygen remaining in the dry precursor without significantly affecting the crystal structure and chemical composition of the subsequent boron carbide product.
9. The system according to claim 1, wherein the precursor pulverizing unit is a quartz mortar or a ceramic mortar, the grinding process is performed by slowly applying a force to prevent generation of large heat, and the particle size of the precursor powder is maintained at 125-425 μm.
10. The system according to claim 1, wherein the precursor feeding unit is configured such that the cold pipe feeder is cooled by a cooling medium jacket, the temperature in the hollow pipe-shaped cavity is controlled to 400-500 ℃, and after the temperature in the high temperature arc furnace cavity reaches at least 1600 ℃, the gate valve at the bottom of the sealing hopper is opened, and the precursor powder is fed into the cold pipe feeder by the screw feeder and is introduced into the cavity of the high temperature arc furnace under the entrapment of inert gas.
11. The system for producing boron carbide crystal growth environment control of claim 10, wherein the precursor powder is held in the sealed hopper until the temperature in the inner chamber of the high temperature arc furnace is stabilized above 1600 ℃, and after the furnace temperature is stabilized above 1600 ℃, a gate valve at the bottom of the sealed hopper is opened, the precursor powder is conveyed to the cold tube feeder under the action of a screw feeder to be kept at a relatively low temperature, and is introduced into the high temperature arc furnace under the wrapping of inert gas.
12. The system for preparing a boron carbide crystal growth environment according to claim 11, wherein after the furnace temperature of the high temperature arc furnace is stabilized to 1600 ℃ or higher, a gate valve at the bottom of the sealing hopper is opened, and the precursor powder is fed into the cold pipe feeder at a feed rate of 1.5-3 g/min by a screw feeder and is introduced into the high temperature arc furnace under the entrainment of inert gas.
13. The system of claim 12, wherein the two graphite electrodes in the high temperature arc furnace are electrically connected to a high power source through wires so that a high power arc is generated between the two graphite electrodes, and the cold pipe feeder is inserted into the high temperature arc furnace at a position to ensure that the precursor powder discharged from the discharge port is in a hot zone acted by a high temperature plasma flow between the high power arcs, and an inert gas is used to prevent oxidation of the precursor powder and facilitate heat transfer, and finally the precursor powder enters the hot zone and then is fed by 10 3 -10 5 The heating rate of K/s reaches a reaction temperature above 1600 ℃.
14. The system according to claim 13, wherein the inert gas in the cold pipe feeder is vented at a rate of 400-600 ml/min, and the inert gas in the passage is used to entrain the precursor powder into the hot zone of the high temperature electric arc furnace and to match the heating rate of the hot zone to achieve sufficient conversion of the precursor powder into boron carbide crystals, and to prevent oxidation of the precursor powder and to facilitate heat transfer and to prevent the reaction from occurring due to the accumulation of gaseous by-products generated by the reaction in the hot zone.
15. The system for preparing a boron carbide crystal growth environment according to claim 1, wherein the high-temperature isolation container is made of graphite-type, ceramic-type or silicon-carbon-type high-temperature refractory materials in the crystal growth reaction unit.
16. A preparation method for controlling the boron carbide crystal growth environment based on the preparation system for controlling the boron carbide crystal growth environment according to any one of the claims 1 to 15, characterized in that the preparation method at least comprises the following steps:
SS1 preparation of raw materials
Providing high-purity boric acid or boric oxide as a boron source, and providing high-activity carbon black or graphite as a carbon source, wherein the mass ratio of raw material components between the boron source and the carbon source after metering and weighing is kept within the range of 10:7-10:8.5 so as to ensure the completeness of the subsequent reaction between the boron source and the carbon source and the purity of a product;
SS2 mixing of raw materials
Firstly, dispersing the boron source in deionized water in an inner cavity of a first container in a stirring manner and forming boron slurry; dispersing the carbon source in deionized water in an inner cavity of a second container in a stirring manner, and adding a surfactant to form carbon slurry;
secondly, pouring the carbon slurry into the first container and fully stirring and mixing the carbon slurry and the boron slurry, and heating the carbon slurry in the stirring process to fully evaporate water in the mixture to form a carbon-boron paste;
SS3 drying of precursors
Conveying the carbon-boron paste formed in the first container to a low-temperature oven through a material conveying pipeline I, and fully drying and heating the carbon-boron paste in the temperature environment to form a dry precursor;
SS4 calcination of precursors
After conveying the dried precursor prepared in the step SS3 to a medium-temperature calcination box in an inert gas atmosphere, fully calcining under the actions of the medium-temperature environment and constant inert gas flow to remove various organic matters and redundant carbon and oxygen remained in the dried precursor, and finally forming calcined blocks;
SS5 comminuting of precursors
Cooling the calcining block in the middle-temperature calcining box in the step SS4 to room temperature, and then conveying the cooled calcining block to the grinding and crushing device through a transfer device to crush the calcined block into precursor powder with the granularity of hundred micrometers;
SS6 precursor delivery and high temperature seeding
Firstly, maintaining precursor powder in the sealed hopper, simultaneously starting the high-temperature electric arc furnace and preheating until the temperature in the inner cavity of the furnace is stabilized above 1600 ℃;
secondly, after the furnace temperature of the high-temperature electric arc furnace is stabilized above 1600 ℃, opening a gate valve at the bottom of the sealing hopper, conveying precursor powder into the cold pipe feeder at a feeding rate of 1.5-3 g/min under the action of a screw feeder under the precursor that the inner cavity temperature of the cold pipe feeder is controlled at 400-500 ℃, and introducing the precursor powder into the high-temperature electric arc furnace under the wrapping of inert gas with a ventilation rate of 400-600 ml/min;
Then, continuously introducing inert gas into the furnace body after the precursor powder finishes the boron carbide reaction under the high-temperature condition, stopping conveying the precursor powder to the high-temperature electric arc furnace, and continuously cooling the high-temperature electric arc furnace under the inert gas atmosphere to reduce the furnace temperature;
finally, after the furnace temperature of the high-temperature electric arc furnace is reduced to room temperature, collecting boron carbide crystal powder in the heat-resistant crucible in a cyclone separation and filtration mode, and removing impurities and gases in the boron carbide crystal powder.
17. The method according to claim 16, wherein in the step SS2, the boron source is dispersed in deionized water by the first stirring means in a stirring manner at a temperature of about 80 ℃ in the inner cavity of the first container to form boron slurry; the stirring time of the boron source and the carbon source in the inner cavities of the first container and the second container is about 30min, so that the boron source and the carbon source are fully dispersed in deionized water; the heating degree of the heating device is not more than 100 ℃.
18. The method according to claim 16, wherein in step SS2, after the carbon source is formed into a carbon slurry, the carbon slurry in the second container is slowly poured into the first container at a small inclination angle by the jacking and tilting device and is fully stirred and mixed with the boron slurry by the first stirring device, and the heating device is activated during stirring for a period of time at least sufficient to ensure that the water in the mixture is fully evaporated to form a carbon-boron paste.
19. The method according to claim 16, wherein in step SS3, the carbon-boron paste is dried at a low temperature oven at a temperature of 120 ℃ to 140 ℃ for a drying time of not less than 12 hours.
20. The method according to claim 16, wherein in step SS4, the dried precursor is fed to the intermediate temperature calcination tank through a material feed line ii, and is sufficiently calcined under the action of the intermediate temperature environment and a constant inert gas flow to remove various organic matters including surfactants and excessive carbon and oxygen remaining in the dried precursor, thereby forming a calcined block.
21. The method according to claim 16, wherein in step SS4, the dried precursor is calcined under a constant argon flow in the medium-temperature calcination tank at a temperature of not more than 600 ℃ for not more than 10 minutes to remove various organic matters including surfactants and excessive carbon and oxygen remaining in the dried precursor without significantly affecting the crystal structure and chemical composition of the subsequent boron carbide product.
22. The method according to claim 16, wherein in the step SS5, the grinding process is performed with a slow force to prevent generation of large heat, and the particle size of the ground precursor powder is maintained at 125 to 425 μm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311013274.XA CN117023588A (en) | 2023-08-10 | 2023-08-10 | Preparation system for controlling boron carbide crystal growth environment |
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