CN115490520A - Low-temperature preparation method of high-strength graphite or layered transition metal carbide densified macroscopic body - Google Patents
Low-temperature preparation method of high-strength graphite or layered transition metal carbide densified macroscopic body Download PDFInfo
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Abstract
The invention discloses a low-temperature preparation method of a high-strength graphite or layered transition metal carbide densified macroscopic body, which comprises the following steps: dissolving graphene powder or layered transition metal carbide powder in a solvent; uniformly dispersing graphene or layered transition metal carbide solution through ultrasonic treatment to obtain precursor slurry; drying the precursor slurry, and removing the solvent to obtain precursor powder; processing the precursor powder under the condition of specific humidity to obtain the precursor powder with the water content of 0-50 wt%; and carrying out hot-pressing densification treatment on the obtained precursor powder with different water contents to obtain the graphene or layered transition metal carbide densified macroscopic body. According to the invention, the densified macroscopic body is prepared by molding the graphene or the layered transition metal carbide under low-temperature hot pressing, the utilization rate of raw materials is high, the energy consumption can be effectively reduced, the pollution can be reduced, and the method has the advantages of simple process, simplicity and convenience in operation and safety, and has a prospect of large-scale application.
Description
Technical Field
The invention relates to the field of material preparation, in particular to a low-temperature preparation method of a high-strength graphite or layered transition metal carbide densified macroscopic body.
Background
Inorganic bulk materials, represented by bulk graphite, are important industrial materials. Bulk graphite is a material with a layered structure, the layers being joined by van der waals forces. The block graphite has good electrical conductivity, thermal stability and radiation resistance, has important application in the fields of machinery, metallurgy, semiconductors, energy, aerospace and the like, and is a material closely connected with the development of science and technology. In some special fields, high-strength graphite is required to be used, the high-strength graphite has better mechanical strength and thermal stability than common graphite, and has a large number of applications in the fields of atomic energy and aerospace, and the graphite with the compressive strength higher than 60MPa can be called as the high-strength graphite. The high-strength graphite is closely related to the development of high technology, and the preparation of the high-strength high-performance graphite is an important subject of material development.
The traditional preparation method of high-strength graphite is mainly prepared by sintering graphite particles and a binder. The process is complex, the sintering temperature is as high as 1800 ℃, the energy consumption is high and the pollution is serious. In order to solve the problems of high energy consumption and high cost of the traditional method, scientific research personnel invent a new processing technology, namely spark plasma sintering. Although spark plasma sintering can achieve rapid sintering to reduce energy consumption, it has the following difficult disadvantages: 1. sintering agents are required to be added, the density of the macroscopic body can be effectively improved in the liquefaction and re-solidification process of the sintering agents, but the residues of the sintering agents can also influence other properties of the graphite, such as thermal stability, thermal conductivity, electric conductivity and the like; 2. the rapid densification process cannot avoid the growth of a large amount of crystal grains, and the rapidly densified precursor powder easily generates micron-sized crystal grains and has adverse effects on the material performance.
Like graphite, MAX phase materials also have a layered structure. MAX phase (Ti) 3 AlC 2 Etc.) is a novel machinable ceramic material. Wherein M representsA transition metal element; a represents a main group element; x represents carbon and/or nitrogen. The MAX phase material can be widely used in the fields of high-temperature structural materials, electrode materials and the like. Similar to the problems encountered in synthesizing high strength graphite blocks, the method for synthesizing the MAX phase densified ceramic is complex and has high energy consumption.
At present, no perfect method is available for preparing a high-strength block material by compacting precursor powder.
Disclosure of Invention
The invention aims to solve the problem of how to prepare a high-strength graphite or layered transition metal carbide densified macroscopic body under the conditions of reducing energy consumption and pollution, and provides a low-temperature preparation method of the high-strength graphite or layered transition metal carbide densified macroscopic body.
The technical problem of the invention is solved by the following technical scheme:
the low temperature preparation process of densified macroscopic body of high strength graphite or laminated transition metal carbide includes the following steps:
s1, dissolving graphene powder or layered transition metal carbide powder in a solvent;
s2, uniformly dispersing graphene or layered transition metal carbide solution through ultrasonic treatment to obtain precursor slurry;
s3, drying the precursor slurry, and removing the solvent to obtain precursor powder;
s4, processing the precursor powder under a specific humidity condition to obtain precursor powder with specific water content;
s5, carrying out hot-pressing densification treatment on the obtained precursor powder with specific water content to obtain a graphene or layered transition metal carbide densified macroscopic body;
wherein the specific water content in step S4 is 0 to 50wt%.
In some embodiments, the hot press densification process in step S5 includes the steps of:
s5-1, putting the precursor powder into a mould;
s5-2, carrying out hot pressing on the precursor powder by using a die;
wherein the hot pressing conditions include: hot pressing in certain atmosphere at 100-1000 MPa and 5-300 deg.c for 1 min-72 hr.
In some embodiments, the conditions of the hot pressing further comprise: the heating rate is 1-10 ℃/min; the atmosphere may be air, nitrogen or vacuum.
In some embodiments, the optimal conditions for hot pressing include: the temperature is 25-200 ℃, the pressure is 200-500 MPa, and the heat preservation and pressure maintaining time is 1-24 hours.
In some embodiments, the preferred range of the specified water content is from 2 to 10 wt.%.
In some embodiments, the hot-pressing densification process in step S5 employs a two-plate hot press, a constant-temperature hot press, a table hot press, a vacuum hot press, or an isostatic hot press.
In some embodiments, further comprising the steps of:
and S6, performing high-temperature sintering treatment on the densified macroscopic body obtained in the step S5, so that the strength of the block material is higher.
In some embodiments, the high temperature sintering process comprises: pressureless high-temperature sintering, hot-pressing sintering or plasma sintering; the sintering temperature of the high-temperature sintering treatment is between 800 and 3000 ℃.
In some embodiments, the solvent in step S1 may be water, ethanol, isopropanol, or N-methylpyrrolidone.
In some embodiments, the preparation method of the graphene powder in step S1 includes a mechanical exfoliation method, a chemical exfoliation method, an electrochemical exfoliation method, or a chemical vapor deposition method; wherein the reduction method of the graphene oxide prepared by the chemical stripping method comprises a thermal reduction method and a chemical reduction method; wherein the thermal reduction temperature is 100-600 ℃, and the reagents used in the chemical reduction method are hydrazine hydrate, hydroiodic acid, vitamin C and NaBH 4 Zinc powder; the oxygen content of the obtained graphene is 1-30 wt%.
In some embodiments, the layered transition metal carbide powder in step S1 is prepared by an electrochemical exfoliation method or a fluorine-containing reagent exfoliation method; exfoliated layered transitionsThe chemical composition of the metal carbide is Ti 2 CT x 、V 2 CT x 、Nb 2 CT x 、Mo 2 CT x 、(Ti 2-y Nb y )CT x 、(V 2-y Nb y )CT x 、 (Ti 2-y V y )CT x 、W 1.33 CT x 、Nb 1.33 CT x 、Mo 1.33 CT x 、Nb 2 CT x 、V 2 CT x 、Ti 3 C 2 T x 、Ta 4 C 3 T x 、 Zr 3 C 2 T x 、Nb 4 C 3 T x And Mo 2 TiC 2 T x Wherein T represents a functional group; the oxygen content of the obtained layered transition metal carbide is 1 to 30wt%.
In some embodiments, the graphene powder or layered transition metal carbide powder has an average grain size of 0.3 to 50um and a thickness of 0.3 to 100nm.
Compared with the prior art, the invention has the advantages that:
the invention provides a low-temperature preparation method of a high-strength graphite or layered transition metal carbide densified macroscopic body, which utilizes nano-sized layered material graphene or layered transition metal carbide (MXene) to prepare a macroscopic bulk material, uses graphene or layered transition metal carbide powder as a raw material, uses the raw materials which are common materials in commercial production, reduces the cost of the raw materials, and avoids the problems of high energy consumption and high pollution caused by the traditional sintering method. According to the invention, through a low-temperature hot pressing method, the gaps of the layered material powder are reduced, and the interaction area between layers is increased, so that the strength of the macroscopic body is enhanced, the prepared densified macroscopic body has the characteristics of high density, high strength, high thermal stability and high chemical stability, the mechanical property is excellent, the formability and the processability are good, and the strength of the graphite densified macroscopic body prepared by low-temperature hot pressing is higher than that of a graphite block sintered at high temperature.
Drawings
Figure 1 is a flow diagram of a low temperature method for making high strength graphite or layered transition metal carbide densified macroscopic bodies in an embodiment of the present invention;
fig. 2a is an SEM image of graphene used in experimental example 1 of the present invention;
figure 2b is an SEM image of the graphite densified macroscopic body prepared in experimental example 1 of the present invention.
Fig. 3a is a schematic diagram of water absorption capacity of graphene powder in experimental example 2 of the present invention at different relative humidities;
FIG. 3b is a schematic view showing the compressive strength of a graphite densified macroscopic body obtained at a temperature of 45 ℃, a pressure of 300MPa and a hot-pressing time of 1 minute to 24 hours in Experimental example 2 of the present invention;
FIG. 3c is a schematic diagram showing the compressive strength of a graphite densified macroscopic body obtained by hot-pressing graphene stored under different humidities for two hours at 45 ℃ and 300MPa in Experimental example 2 of the present invention;
fig. 3d is a schematic view of the vickers hardness test of the graphite densified macroscopic body obtained by storing the graphene powder for two days in the environment with the humidity of 33% and hot-pressing the graphene powder at the temperature of 45 ℃ and the pressure of 300MPa for two hours in the experimental example 2 of the present invention;
FIG. 4a is a schematic diagram of a graphite densified macroscopic body obtained by in-situ surface processing and molding in Experimental example 4 of the present invention;
FIG. 4b is a schematic representation of a 0.156mm thick graphite densified macroscopic body obtained by thermoforming in Experimental example 4 of the present invention;
FIG. 4c is a schematic representation of a 1.455mm thick graphite densified macroscopic body obtained by hot press molding in Experimental example 4 of the present invention;
FIG. 5 shows Ti obtained by hot pressing at 45 ℃ and 300MPa for two hours in Experimental example 5 of the present invention 3 AlC 2 Compressive strength profiles of blocks and MXene densified macros.
Detailed Description
The invention will be further described with reference to the drawings and preferred embodiments. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
It should be noted that the terms of orientation such as left, right, up, down, top and bottom in the present embodiment are only relative concepts to each other or are referred to the normal use state of the product, and should not be considered as limiting.
The preparation of densified macroscopic bodies by a bottom-up process offers the possibility of solving the problem. The graphene, which is a single-layer atomic crystal having a honeycomb structure in which carbon atoms are connected by covalent bonds, can be obtained by exfoliating graphite. Graphene is the strongest and hardest material known at present, and has ultrahigh electrical and thermal conductivity, huge specific surface area and special optical properties. The layered transition metal carbide (MXene) can be obtained by etching and stripping MAX phase materials, and the special layered structure and the abundant surface functional groups of the MXene enable the MXene to be widely applied to different fields such as energy storage, supercapacitors, pressure sensors, electromagnetic shielding and the like. By processing graphene/MXene, a high-strength densified macroscopic body can be prepared, and the strength is improved while the material performance is ensured.
In conclusion, the graphene/MXene processing can be used for preparing the high-strength graphite or layered transition metal carbide densified macroscopic body, can solve the problems of energy consumption and pollution of sintering and forming of the traditional material, and has important theoretical research value and practical application significance.
The technical problem to be solved by the embodiment of the invention is to overcome the problem of overhigh molding temperature of materials such as high-strength graphite and the like, and provide a low-temperature molding method for preparing a densified macroscopic body by using graphene or layered transition metal carbide (MXene) powder. The macroscopic body has the characteristics of high density, high strength, high thermal stability and high chemical stability. The preparation method has the advantages of simple process, simple and convenient operation, no need of complex equipment and low preparation energy consumption.
As shown in fig. 1, the low temperature preparation method of the high strength graphite or layered transition metal carbide densified macroscopic body of the embodiment of the present invention:
graphene/MXene powder is used as a raw material, and a high-strength and densified macroscopic body is formed by layered accumulation of precursor powder under the driving of hot pressing of a die method. Wherein the compression strength of the graphite densified macroscopic body reaches 80-200 MPa, and the compression strength of the layered transition metal carbide densified macroscopic body reaches 500-800 MPa.
The low-temperature preparation method of the high-strength graphite or layered transition metal carbide densified macroscopic body takes graphene or MXene powder as a raw material, and the graphene or MXene powder is formed by a die hot-pressing method, and the preparation process comprises the following specific steps of:
(1) Dissolving graphene or MXene powder in a solvent, wherein the solvent can be water, ethanol, isopropanol or N-methylpyrrolidone.
And uniformly dispersing the graphene or the layered transition metal carbide solution by ultrasonic treatment to obtain precursor slurry. Processing the precursor powder according to different humidity conditions to obtain precursor powder with specific water content, in this embodiment, the processing is to dry precursor slurry and remove solvent to obtain precursor powder; the specific water content of the precursor powder is 0-50 wt%.
The graphene or MXene precursor powder can be obtained in the step 1, wherein the water content is obtained by placing dry precursor powder in different humidity environments and allowing the powder to absorb water spontaneously, the precursor powder is treated under different humidity conditions, the obtained powder has different water contents, the different water contents have large influence on the strength of the material, and the optimal range of the water content is 2-10 wt%.
(2) Placing the obtained graphene or MXene precursor powder with specific water content in a certain atmosphere for hot-pressing densification treatment, wherein the atmosphere in the hot-pressing densification process can be air, nitrogen or vacuum; the conditions of the hot-pressing densification treatment in this example were: the pressure is 100-1000 MPa, the temperature is 5-300 ℃, the heating rate is 1-10 ℃/min, the heat preservation and pressure maintaining time is 1-72 hours, the densification treatment is to put the precursor powder into a mould for hot pressing, and the demoulding is to obtain a graphene or layered transition metal carbide densified macroscopic body, wherein the water content refers to the ratio of water of the precursor powder after water absorption to the mass of the powder; the temperature is 25-200 ℃, the pressure is 200-500 MPa, and the heat preservation and pressure maintaining time is 1-24 hours, which is the optimal condition range; among them, the temperature is preferably 90 ℃. The pressure is preferably 300MPa and the time is preferably 2 hours. The hot-pressing densification can adopt a two-plate hot press, a constant-temperature hot press, a table hot press, a vacuum hot press or an equal static hot press;
(3) The obtained macroscopic body material can be further sintered at high temperature to obtain a block material with higher strength. For example, pressureless high-temperature sintering, hot-press sintering, plasma sintering, or the like. The sintering temperature is between 800 and 3000 ℃. Wherein the average grain size of the graphene/MXene powder is 0.3-50 um, and the thickness is 0.3-100 nm.
The preparation method of the graphene can be a mechanical stripping method, a chemical stripping method, an electrochemical stripping method or a chemical vapor deposition method. The reduction method of the graphene oxide prepared by the chemical stripping method is a thermal reduction method or a chemical reduction method. The thermal reduction temperature is 100-600 ℃, and the reagents used by the chemical reduction method are hydrazine hydrate, hydroiodic acid, vitamin C and NaBH 4 Zinc powder, etc. The oxygen content of the graphene is 1-30 wt%, and the oxygen content of the graphene affects the strength of the prepared block. Firstly, in the process of water absorption, the graphene containing much oxygen absorbs more water through the action of hydrogen bonds, thereby affecting the strength. In addition, hydrogen bonding by oxygen atoms may enhance bulk material interbed forces.
The preparation method of MXene is an electrochemical stripping method or a fluorine-containing reagent stripping method. The chemical composition of the stripped MXene is Ti 2 CT x 、V 2 CT x 、Nb 2 CT x 、Mo 2 CT x 、(Ti 2-y Nb y )CT x 、(V 2-y Nb y )CT x 、(Ti 2-y V y )CT x 、W 1.33 CT x 、Nb 1.33 CT x 、Mo 1.33 CT x 、Nb 2 CT x 、V 2 CT x 、 Ti 3 C 2 T x 、Ta 4 C 3 T x 、Zr 3 C 2 T x 、Nb 4 C 3 T x Or Mo 2 TiC 2 T x Wherein T represents a functional group. The oxygen content of MXene is 1-30 wt%.
According to the embodiment of the invention, the graphene/MXene powder is used as a molding material, and the high-strength graphite or layered transition metal carbide densified macroscopic body is prepared through low-temperature hot pressing. Different from the traditional powder sintering method, the method starts from graphene/MXene powder and utilizes Van der Waals force between hot-pressing reinforcing materials to obtain the high-strength graphite or layered transition metal carbide densified macroscopic body. The strength of the obtained densified macroscopic body is obviously improved compared with the strength of a block material sintered by the traditional method, and the densified macroscopic body has better mechanical property. Wherein the low temperature of the low temperature hot pressing is compared with the high temperature of thousands of degrees in the traditional method.
In the embodiment, the high-strength densified macroscopic body is obtained by hot-pressing graphene/MXene powder with the average grain size of 0.3-50 um and the thickness of 0.3-100 nm as a forming material under different conditions (temperature, humidity, pressure and atmosphere). Compared with other block material forming processes, the forming temperature of the embodiment of the invention is low, the process is simple, and the method is safe and efficient. The strength of the obtained high-strength graphite or layered transition metal carbide densified macroscopic body is higher than that of a block material sintered at high temperature (> 1800 ℃). The embodiment of the invention provides a new method for molding the high-strength graphite or layered transition metal carbide densified macroscopic body, the preparation process is simple, the energy consumption is low, and the prepared densified macroscopic body has excellent mechanical properties and wide application prospect.
Experimental example 1:
(1) 10mg of graphene oxide was weighed out. Dispersed in water, diluted to 0.3mg/mL, and observed the morphology under a scanning electron microscope, the result is shown in FIG. 2 a. Then weighing 1g of graphene oxide, freeze-drying in vacuum, and carrying out thermal reduction in a tube furnace in an argon atmosphere at the reduction temperature of 100-600 ℃.
(2) And (2) taking 150mg of the prepared graphene precursor powder and putting the graphene precursor powder into a cylindrical steel mold with the diameter of 6mm, or taking 200mg of the graphene precursor powder and putting the graphene precursor powder into a square steel mold with the diameter of 10mm multiplied by 10mm, and carrying out hot pressing treatment under the conditions that the pressure is 100-1000 MPa, the temperature is 5-300 ℃, and the heat preservation and pressure maintaining time is 1 minute-24 hours to obtain graphite densified macroscopic bodies with different shapes, wherein the compression strength is 80-200 MPa. The scanning electron micrograph of the graphite macroscopic body is shown in FIG. 2 b.
Experimental example 2:
(1) Weighing 1g of graphene oxide, freeze-drying in vacuum, and carrying out thermal reduction in a tube furnace at 300 ℃ under an argon atmosphere. The graphene powder is stored in different humidity environments for two days, and the water absorption capacity of the graphene powder at different relative humidity is shown in fig. 3 a.
(2) Putting the prepared graphene precursor powder with different water contents into a cylindrical steel mold with the diameter of 6mm, and referring to fig. 3b, wherein the compression strength of the graphite densified macroscopic body obtained by the method is 93-108 MPa, wherein the relative humidity is 0%, the temperature is 45 ℃, the pressure is 300MPa, and the hot pressing time is 1 min-24 h; the graphite densified macrostructures obtained by hot-pressing the graphene precursor powder with different water contents under the conditions of the pressure of 300MPa, the temperature of 45 ℃ and the heat preservation and pressure maintenance for 2 hours are shown in figures 3c and 3d, the compression strength is 95-143 MPa, and when the relative humidity is 33%, the Vickers hardness of the graphite densified macrostructure is 75HV 300 . The embodiment of the invention has simple operation method and simple flow, and the prepared graphite densified macroscopic body has high strength and the compression strength is higher than that of a graphite block sintered by a traditional method. Can obviously reduce the production cost of the high-strength graphite.
Experimental example 3:
weighing 150mg of commercial electrochemically stripped graphene precursor powder, putting the graphene precursor powder into a cylindrical steel mold with the diameter of 6mm, or putting 200mg of the graphene precursor powder into a square steel mold with the diameter of 10mm multiplied by 10mm, and carrying out hot pressing treatment under the conditions that the pressure is 100-1000 MPa, the temperature is 5-300 ℃, and the heat preservation and pressure maintaining time is 1 minute-24 hours to obtain graphite densified macroscopic bodies with different shapes, wherein the compressive strength is 100-200 MPa. At present, graphite blocks obtained by a sintering method have great difference in compressive strength due to process difference, and graphite with a compressive strength of 60MPa or more is generally called high-strength graphite, and the compressive strength of graphite blocks at a sintering temperature of 1800 ℃ is generally about 100 MPa. Therefore, the preparation method of the graphite densified macroscopic body of the embodiment of the invention not only reduces energy consumption and pollution, but also ensures the strength of the prepared graphite densified macroscopic body.
Experimental example 4:
taking 1g of graphene precursor powder prepared in example 1, replacing the upper and lower top blocks of a forming die with copper products with rough surfaces, carrying out hot pressing at 45 ℃ and 300MPa for 30 minutes, and demoulding, as shown in fig. 4a, so as to prepare a graphite densified macroscopic body with a specific surface topography. 70mg and 1.2g of the graphene powder prepared in the embodiment 1 are respectively taken and hot-pressed for 2 hours at 45 ℃ and 300MPa, as shown in fig. 4b and 4c, graphite densified macroscopic bodies with different thicknesses can be obtained, the thicknesses are respectively 0.156mm and 1.455mm, the material prepared by the embodiment of the method has good processing performance, and block materials with different thicknesses can be prepared.
Experimental example 5:
(1) With Ti 3 AlC 2 And stripping with hydrofluoric acid or electrochemically to obtain MXene powder. Dissolving in water, heating and drying. Taking 150mg of stripped MXene precursor powder and 150mg of non-stripped Ti 3 AlC 2 And (3) powder.
(2) Mixing the MXene powder and unstripped Ti 3 AlC 2 The powder is respectively put into a cylindrical steel die with the diameter of 6mm and is subjected to hot pressing treatment under the conditions that the pressure is 100-1000 MPa, the temperature is 5-300 ℃, and the temperature and pressure are kept for 2 hours. As shown in FIG. 5, the compression strength of MXene densified macroscopic body was 500 to 800MPa. With unstripped Ti 3 AlC 2 The compression strength of the block formed by powder hot pressing is only 200-300 MPa. Therefore, the preparation method of the layered transition metal carbide densified macroscopic body provided by the embodiment of the invention greatly improves the strength of the layered transition metal carbide densified macroscopic body, and has low energy consumption in the preparation process, thereby having important practical significance.
Compared with the prior art, the embodiment of the invention solves the following pain point problems:
1. the traditional method has high energy consumption and high pollution;
2. the traditional sintering method has sintering additives, which affect the performance of the material at high temperature;
3. the traditional method has complex flow and high cost.
The currently predominant method for preparing graphite or MAX phase blocks is sintering with binders at high temperatures. Taking the preparation of graphite blocks as an example, the traditional method has a very complicated process, needs to graphitize the adhesive besides high-temperature sintering, and has high energy consumption, serious pollution and insurable cost. The high strength graphite blocks are typically up to 50 ten thousand per ton. The method adopts low-temperature hot pressing, the temperature is low, the flow is simple, and the cost of the adopted raw materials is as low as ten thousand yuan per ton. The production process has low cost and low energy consumption.
The embodiment of the invention has the following advantages:
(1) The method for preparing the high-strength densified bulk material by utilizing the graphene/MXene powder through low-temperature hot pressing from bottom to top is provided, wherein the bottom to top method is to prepare the bulk material with the macroscopic size by utilizing the nano-sized layered material graphene or MXene. The raw materials used are common materials produced in a commercial mode, the cost is low, the method is simple to operate, safe, efficient, low in energy consumption and low in pollution, the problems of high energy consumption and high pollution caused by the traditional sintering method are solved, and the method has a large-scale application prospect, wherein the high-strength graphite densified macroscopic body can be provided for nuclear power and aerospace related enterprises, and the high-strength layered transition metal carbide densified macroscopic body can be provided for battery industry related enterprises and applied to the field of energy storage.
(2) Through a low-temperature hot pressing method, gaps of the layered material powder are reduced, and the interaction area between layers is increased, so that the strength of the macroscopic body is enhanced, and the prepared densified macroscopic body is high in strength and excellent in mechanical property.
(3) According to the method for preparing the graphite or layered transition metal carbide dense macroscopic body, the graphene/MXene powder is molded under mild conditions, the utilization rate of raw materials is high, and the prepared material has excellent mechanical properties, good moldability and processability, and has the characteristics of high density, high strength, high thermal stability and high chemical stability.
In summary, the embodiments of the present invention provide a novel low-temperature preparation method for a high-strength graphite or layered transition metal carbide densified macroscopic body, which greatly reduces the temperature required by the conventional sintering technology, greatly alleviates the problems of energy consumption and pollution during the material preparation process, and the strength of the graphite densified macroscopic body prepared by low-temperature hot pressing is higher than that of the graphite bulk body sintered at high temperature. In the method, graphene/MXene powder is used as a molding material to prepare the high-strength densified graphite or layered transition metal carbide macroscopic body.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several equivalent substitutions or obvious modifications can be made without departing from the spirit of the invention, and all the properties or uses are considered to be within the scope of the invention.
Claims (12)
1. The low-temperature preparation method of the high-strength graphite or layered transition metal carbide densified macroscopic body is characterized by comprising the following steps of:
s1, dissolving graphene powder or layered transition metal carbide powder in a solvent;
s2, uniformly dispersing graphene or layered transition metal carbide solution through ultrasonic treatment to obtain precursor slurry;
s3, drying the precursor slurry, and removing the solvent to obtain precursor powder;
s4, processing the precursor powder under a specific humidity condition to obtain precursor powder with specific water content;
s5, carrying out hot-pressing densification treatment on the obtained precursor powder with specific water content to obtain a graphene or layered transition metal carbide densified macroscopic body;
wherein the specific water content in step S4 is 0 to 50wt%.
2. The method of claim 1, wherein said hot press densification treatment of step S5 comprises the steps of:
s5-1, putting the precursor powder into a die;
s5-2, carrying out hot pressing on the precursor powder by using a mould;
wherein the hot pressing conditions include: hot pressing in certain atmosphere at 100-1000 MPa and 5-300 deg.c for 1 min-72 hr.
3. The method of claim 2, wherein the hot pressing conditions further comprise: the heating rate is 1-10 ℃/min; the atmosphere may be air, nitrogen or vacuum.
4. The method of claim 2, wherein the optimal conditions for hot pressing comprise: the temperature is 25-200 ℃, the pressure is 200-500 MPa, and the heat preservation and pressure maintaining time is 1-24 hours.
5. The method of claim 1, wherein the specific water content is optimally in the range of 2 to 10wt%.
6. The method according to claim 1, wherein the hot-pressing densification treatment in step S5 employs a two-plate hot press, a constant-temperature hot press, a table hot press, a vacuum hot press, or an isostatic hot press.
7. The method of claim 1, further comprising the steps of:
and S6, performing high-temperature sintering treatment on the densified macroscopic body obtained in the step S5, so that the strength of the block material is higher.
8. The method of claim 7, wherein the high temperature sintering process comprises: pressureless high-temperature sintering, hot-pressing sintering or plasma sintering; the sintering temperature of the high-temperature sintering treatment is between 800 and 3000 ℃.
9. The method of claim 1, wherein the solvent in step S1 can be water, ethanol, isopropanol, or N-methylpyrrolidone.
10. The method according to claim 1, wherein the graphene powder is prepared in step S1 by a mechanical exfoliation method, a chemical exfoliation method, an electrochemical exfoliation method, or a chemical vapor deposition method; wherein the reduction method of the graphene oxide prepared by the chemical stripping method comprises a thermal reduction method and a chemical reduction method; wherein the thermal reduction temperature is 100-600 ℃, and the reagents used by the chemical reduction method are hydrazine hydrate, hydroiodic acid, vitamin C and NaBH 4 Zinc powder; the oxygen content of the obtained graphene is 1-30 wt%.
11. The method according to claim 1, wherein the layered transition metal carbide powder is prepared by an electrochemical exfoliation method or a fluorine-containing reagent exfoliation method in step S1; the chemical composition of the exfoliated layered transition metal carbide is Ti 2 CT x 、V 2 CT x 、Nb 2 CT x 、Mo 2 CT x 、(Ti 2-y Nb y )CT x 、(V 2-y Nb y )CT x 、(Ti 2-y V y )CT x 、W 1.33 CT x 、Nb 1.33 CT x 、Mo 1.33 CT x 、Nb 2 CT x 、V 2 CT x 、Ti 3 C 2 T x 、Ta 4 C 3 T x 、Zr 3 C 2 T x 、Nb 4 C 3 T x And Mo 2 TiC 2 T x Wherein T represents a functional group; the oxygen content of the obtained layered transition metal carbide is 1 to 30wt%.
12. The method of claim 1, wherein the graphene powder or layered transition metal carbide powder has an average grain size of 0.3 to 50um and a thickness of 0.3 to 100nm.
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