CN109574014B - B4C fiber felt and preparation method thereof - Google Patents

B4C fiber felt and preparation method thereof Download PDF

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CN109574014B
CN109574014B CN201811229766.1A CN201811229766A CN109574014B CN 109574014 B CN109574014 B CN 109574014B CN 201811229766 A CN201811229766 A CN 201811229766A CN 109574014 B CN109574014 B CN 109574014B
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fiber felt
activated carbon
carbon fiber
molten salt
magnesium powder
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CN109574014A (en
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丁冬海
种小川
肖国庆
任耘
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Xian University of Architecture and Technology
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Xian University of Architecture and Technology
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    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM

Abstract

The invention discloses a4The C fiber felt is characterized by comprising raw materials and a molten salt auxiliary agent, wherein the raw materials comprise activated carbon fiber felt, boron trioxide and magnesium powder, and the molten salt auxiliary agent comprises MgCl2、NaCl、Na2B4O7Or K2CO3Said B is4The C fiber felt is prepared by taking an activated carbon fiber felt as a template and adopting a molten salt auxiliary sintering method. B prepared by the invention4The C fiber felt has good oxidation resistance and high mechanical strength while keeping the activated carbon fiber felt porous, large length-diameter ratio and rich three-dimensional appearance, the preparation method is simple in preparation process, controllable in reaction process and high in yield, and can be used for preparing ceramic materials, antioxidant materials or adsorption/wave-absorbing materials in high-temperature environments.

Description

B4C fiber felt and preparation method thereof
Technical Field
The invention belongs to the technical field of inorganic non-metallic materials, and particularly relates to a B4C fiber felt and a preparation method thereof.
Background
Boron carbide (B)4C) The material not only has second-order hardness to diamond and cubic boron nitride, but also has other excellent physical and chemical properties, including low density, high melting point, high Young modulus, good hot spot property, high neutron absorption cross section, high thermal conductivity, low thermal expansion coefficient, high seebeck coefficient, chemical stability, acid and alkali resistance, oxygen absorption capacity and the like. Boron carbide is applied to tank armor, helicopters and other protection devices in the national defense industry, control rods and shielding systems in the nuclear power industry, nozzles and hard material cutters in the wear-resistant field, catalytic carriers and differential thermocouples of thermoelectric systems, and Boron Neutron Capture (BNCT) for treating cancers in the medical field. At present, the methods for preparing boron carbide mainly comprise a carbothermic method and a self-propagating high-temperature synthesis method. With the development of national defense industry and the continuous expansion of application fields, the application environment of boron carbide is more and more harsh, the toughness of a ceramic material can be enhanced by fibrous materials no matter the boron carbide material is used as a bulletproof back plate of an armor material or as an antioxidant used for a material in a high-temperature and ultrahigh-temperature environment, the toughness of the material is required to be improved while the excellent performance of the boron carbide material is maintained, and therefore the fibrous boron carbide needs to be researched urgently. To transmitThe traditional method for producing the boron carbide fiber is a Chemical Vapor Deposition (CVD) method, and not only has a complex production process and a long period, but also has overhigh cost of reaction equipment.
Disclosure of Invention
Aiming at the defects and shortcomings in the prior art, the invention aims to provide a B4C fiber felt and a preparation method thereof. Synthesizing B by using activated carbon fiber felt as carbon source and template4The preparation method of the C fiber felt is simple in preparation process, controllable in reaction process and high in yield.
In order to realize the task, the invention adopts the following technical scheme:
b4The C fiber felt is prepared by taking activated carbon fiber felt, diboron trioxide and magnesium powder as raw materials and adopting a molten salt auxiliary sintering method, wherein a molten salt auxiliary agent used in the molten salt auxiliary sintering method comprises MgCl2、NaCl、Na2B4O7Or K2CO3。
Further, the mass ratio of the raw materials to the molten salt auxiliary agent is 1: 1-1: 4.
Furthermore, the raw materials comprise, by mass, 3-11% of the activated carbon fiber felt, 42-50% of the diboron trioxide, 47-55% of the magnesium powder, and 100% of the sum of the activated carbon fiber felt, the diboron trioxide and the magnesium powder.
Further, the mass fraction of the activated carbon fiber felt in the raw material is 4.1%, the mass fraction of the boron trioxide in the raw material is 47.3%, and the mass fraction of the magnesium powder in the raw material is 48.6% in percentage by mass.
B4The preparation method of the C fiber felt takes the activated carbon fiber felt as a template and adopts a molten salt auxiliary sintering method to prepare the C fiber felt, and the molten salt auxiliary agent comprises MgCl2、NaCl、Na2B4O7Or K2CO3。
And further, taking the activated carbon fiber felt as a template, adding uniformly mixed boron trioxide and magnesium powder at two sides of the template, and adding the molten salt auxiliary agent for sintering.
Specifically, the activated carbon fiber felt comprises, by mass, 3% -11% of activated carbon fiber felt, 42% -50% of boron trioxide, 47% -55% of magnesium powder, and 100% of the sum of the activated carbon fiber felt, the boron trioxide and the magnesium powder, wherein the mass ratio of the sum of the activated carbon fiber felt, the boron trioxide and the magnesium powder to the molten salt auxiliary agent is 1: 1-1: 4.
Further, the activated carbon fiber felt is 4.1% by mass, the boron trioxide is 47.3% by mass, and the magnesium powder is 48.6% by mass.
Optionally, specifically:
(1) mixing boron trioxide with magnesium powder; then adding the molten salt auxiliary agent into the mixture of the diboron trioxide and the magnesium powder for mixing;
(2) adding the mixture obtained in the step (1) into a crucible, then paving an activated carbon fiber felt on the mixture, and finally paving the rest mixture on the uppermost layer;
(3) putting the crucible filled with the mixture in the step 2 into a tube furnace for sintering to obtain B4And C, fiber felt.
Compared with the prior art, the invention has the following advantages:
(1) the invention provides a4C fiber felt and a preparation method thereof. Specifically, an activated carbon fiber felt, boron trioxide and magnesium powder are used as raw materials, molten salt is used as an auxiliary agent, the activated carbon fiber felt is used as a fiber felt template, and a molten salt auxiliary sintering method is adopted for carrying out B4C, preparing the fiber felt, wherein the preparation process is simple, and the reaction process is easy to control; and the obtained product has high purity.
(2) The invention is prepared by a molten salt auxiliary sintering method4The C fiber felt takes the activated carbon fiber felt as a carbon source, so that the product has high purity, the reaction process is complete, and the raw materials are low in price and easy to obtain.
(3) B prepared by the invention4The C fiber felt keeps the shape of the activated carbon fiber felt template, and can obtain B with different reaction degrees and purities by controlling process parameters4And C, fiber felt.
(4) B prepared by the invention4The C fiber felt is not only used for ceramic materials or antioxidant materials, but also can be used for adsorbing materials and high-temperature wave-absorbing materials in a high-temperature environment by utilizing the shape of an activated carbon fiber template.
Drawings
FIG. 1 is a flow diagram of a manufacturing process of the present invention;
FIG. 2 is a sequence chart of the present invention for charging;
FIG. 3 shows B prepared in example 1 of the present invention4XRD pattern of fiber mat C;
FIG. 4 shows B prepared in example 1 of the present invention4SEM image of fiber felt, wherein (a), (b), (C) and (d) are photographs under different magnifications in sequence;
the invention is described in further detail below with reference to the accompanying figures 1-4 and examples.
Detailed Description
The activated carbon fiber felt is a high-efficiency adsorption material which is prepared from natural or artificial fibers through special processes such as high temperature, catalysis and the like and surpasses granular activated carbon, contains a highly developed microporous structure, has small and uniform pore diameter and simple structure, and has high adsorption rate for adsorbing small molecular substances, high adsorption speed and easy desorption. The contact area with the adsorbate is large, and the adsorbate can be uniformly contacted and adsorbed, so that the adsorbing material can be fully utilized. The efficiency is high, various fine surface states such as fibers, felts, cloth and paper are provided, pores are directly opened on the surfaces of the fibers, the diffusion path of adsorbates to an adsorption position is short, and the external surface area of the adsorbates is two orders of magnitude higher than the internal surface area. Has the characteristics of large specific surface area, high adsorption and desorption capacity, high adsorption and desorption speed, good purification effect and the like.
The invention takes activated carbon fiber as a carbon source, boron oxide as a boron source and magnesium as a reducing metal, and the reaction is carried out according to the following chemical equation: 2B2O3+6Mg+C→B4And C +6 MgO. In the reaction process, firstly, magnesium reduces boron oxide to generate boron simple substance and magnesium oxide, then, the simple substance boron reacts with carbon to generate boron carbide, and finally, the magnesium oxide is removed by an acid washing method, wherein a specific preparation process flow chart is shown in figure 1. B prepared by the invention4C fiber felt retaining activated carbon fibersThe shape of the felt template, the preparation process is simple, and the reaction process is easy to control.
The present invention is described below by way of example, but the present invention is not limited to the following embodiments, and those skilled in the art to which the present invention pertains can make several simple deductions or substitutions without departing from the spirit of the present invention, and all of them should be considered as belonging to the protection scope of the present invention. Mg, activated carbon fiber felt and B provided by the invention2O3The raw materials are mixed according to the mass percentage, and the molten salt is taken as an auxiliary agent to prepare the B by a sintering method4C, fiber felt, as shown in figure 1. Phase analysis was performed using a Japanese D/Max 2400 type X-ray diffraction (XRD) analyzer (Cu target, Ni plate), and the microstructure of the product powder was observed with a Japanese SU 6600 type field emission Scanning Electron Microscope (SEM).
According to the mass percentage, the activated carbon fiber felt in the raw material is 3-11%, the diboron trioxide in the raw material is 42-50%, the magnesium powder in the raw material is 47-55%, and the sum of the mass percentages of the activated carbon fiber felt, the diboron trioxide and the magnesium powder is 100%.
Example 1:
in the present example, an activated carbon fiber felt (carbon content not less than 90.0%, Jiangsu Sutong carbon fiber Co., Ltd.), magnesium powder (purity not less than 99.9%, Changsha long-term metal material Co., Ltd.) and diboron trioxide (purity not less than 98.8%, Youli electronics and chemical industry Co., Ltd., Xian city) were used as raw materials, and anhydrous MgCl was used2(Fuchen chemical reagent plant of Tianjin City) is molten salt, and comprises, by mass, 4.1% of activated carbon fiber felt, 47.3% of boron trioxide, 48.6% of magnesium powder, and MgCl2The mass ratio of (A) to (B) is 1: 4.
(1) As shown in figure 2, according to the mass percentage, the weighed boron trioxide and magnesium powder are ground and mixed in a mortar; mixing MgCl2Adding the mixture of the diboron trioxide and the magnesium powder into the mixture for mixing; weighing half mass of uniformly mixed diboron trioxide, magnesium powder and MgCl2The mixture is placed in a crucible, then the activated carbon fiber felt is spread on the mixture, and thenThe other half of the boron trioxide, the magnesium powder and the MgCl are added2The mixture is spread on the uppermost layer.
(2) And putting the crucible filled with the materials into a tube furnace, vacuumizing, introducing argon, heating by program temperature control, keeping the temperature at 1000 ℃ for 2 hours, cooling, turning off a power supply after the temperature of the furnace is reduced to room temperature, opening a furnace cover, and taking out the materials.
(3) Putting the material obtained in the step (2) into excessive hydrochloric acid with the concentration of 10 wt% for acid washing to remove MgO and residual Mg in the product, finally performing ultrasonic oscillation water washing to remove impurities such as molten salt and the like, and drying at 90 ℃ for 24 hours to obtain B4And C, fiber felt. The chemical equation based on the acid washing reaction is MgO +2H+→Mg2++H2O。
The product was analyzed by XRD and SEM. In which the XRD pattern of fig. 3 shows that the product contains very much boron carbide and incompletely reacted carbon, indicating that boron carbide is obtained by the method and that the activated carbon fiber is not completely reacted. The SEM image in FIG. 4 is a microscopic morphology with multiple magnification in sequence, and it can be seen that the product after reaction is a layer of boron carbide formed on the surface of the activated carbon fiber, and the original fibrous morphology of the activated carbon fiber is maintained.
Example 2:
same as example 1, but different from example 1 in that Na is used2B4O7Is molten salt, and comprises, by mass, 3% of activated carbon fiber felt, 42% of boron trioxide, 55% of magnesium powder, and Na2B4O7The mass ratio of (A) to (B) is 1: 3.
Example 3:
the same as example 1, but different from example 1, NaCl is used as molten salt, and the mass percentage of the activated carbon fiber felt in the raw material is 3%, the mass percentage of the diboron trioxide in the raw material is 50%, the mass percentage of the magnesium powder in the raw material is 47%, and the mass ratio of the raw material to the NaCl is 1: 4.
Example 4:
same as example 1, but different from example 1 in that K2CO3Is molten salt, and comprises 11% of activated carbon fiber felt, 42% of boron trioxide and the like47% of medium magnesium powder, raw materials and K2CO3The mass ratio of (A) to (B) is 1: 1.

Claims (4)

1. B4The preparation method of the C fiber felt is characterized in that the C fiber felt is prepared by taking an activated carbon fiber felt as a template and adopting a molten salt auxiliary sintering method, wherein the molten salt auxiliary agent comprises MgCl2、NaCl、Na2B4O7Or K2CO3；
Adding uniformly mixed diboron trioxide and magnesium powder to two sides of a template which is an activated carbon fiber felt, and adding the molten salt auxiliary agent for sintering;
the activated carbon fiber felt is 3-11% in mass fraction, the diboron trioxide is 42-50% in mass fraction, the magnesium powder is 47-55% in mass fraction, the sum of the activated carbon fiber felt, the diboron trioxide and the magnesium powder is 100% in mass fraction, and the mass ratio of the sum of the activated carbon fiber felt, the diboron trioxide and the magnesium powder to the molten salt auxiliary agent is 1: 1-1: 4.
2. B as claimed in claim 14The preparation method of the C fiber felt is characterized in that the activated carbon fiber felt is 4.1 percent, the boron trioxide is 47.3 percent and the magnesium powder is 48.6 percent by mass percent.
3. B as claimed in claim 1 or 24The preparation method of the C fiber felt is characterized by comprising the following specific steps:
(1) mixing boron trioxide with magnesium powder; then adding the molten salt auxiliary agent into the mixture of the diboron trioxide and the magnesium powder for mixing;
(2) adding the mixture obtained in the step (1) into a crucible, then paving an activated carbon fiber felt on the mixture, and finally paving the rest mixture on the uppermost layer;
(3) putting the crucible filled with the mixture in the step 2 into a tube furnace for sintering to obtain B4And C, fiber felt.
4. B according to any one of claims 1 to 34Preparation of C fiber feltB prepared by the method4And C, fiber felt.
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CN109970066B (en) * 2019-04-23 2022-09-30 桂林理工大学 Method for rapidly preparing boron carbide dendritic nano-fibers
CN114920247B (en) * 2022-05-20 2023-05-26 哈尔滨工业大学 Preparation method of boron carbide nanowire based on NaCl shape regulator
CN114940498A (en) * 2022-05-20 2022-08-26 西安建筑科技大学 Superfine B 4 C powder, preparation method and application for preparing microwave absorbent

Citations (5)

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CN105502398A (en) * 2016-03-01 2016-04-20 郑州大学 Method for synthesizing tantalum carbide superfine powder through molten salt assisted magnesiothermic reduction
CN107129305A (en) * 2017-05-10 2017-09-05 东北大学 A kind of situ-combustion synthesis prepares B4The method of fiber C
CN107226472A (en) * 2017-05-10 2017-10-03 东北大学 A kind of situ-combustion synthesis prepares B4The method of C nano pipe

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NL253482A (en) * 1959-07-06 1964-03-25
CN101570438A (en) * 2009-04-17 2009-11-04 上海应用技术学院 Method for preparing superfine boron carbide powder
CN105502398A (en) * 2016-03-01 2016-04-20 郑州大学 Method for synthesizing tantalum carbide superfine powder through molten salt assisted magnesiothermic reduction
CN107129305A (en) * 2017-05-10 2017-09-05 东北大学 A kind of situ-combustion synthesis prepares B4The method of fiber C
CN107226472A (en) * 2017-05-10 2017-10-03 东北大学 A kind of situ-combustion synthesis prepares B4The method of C nano pipe

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