CN111268716A

CN111268716A - Carbon material-coated tetrapod-like zinc oxide, carbon material with hollow tetrapod-like structure, filling mold and preparation method thereof

Info

Publication number: CN111268716A
Application number: CN202010206640.3A
Authority: CN
Inventors: 杨杰; 陈武峰; ***
Original assignee: Ashine New Carbon Material Changzhou Co ltd
Current assignee: Ashine New Carbon Material Changzhou Co ltd
Priority date: 2020-04-01
Filing date: 2020-04-01
Publication date: 2020-06-12
Anticipated expiration: 2040-04-01
Also published as: CN111268716B

Abstract

The invention discloses tetrapod-like zinc oxide coated with a carbon material, the carbon material with a hollow tetrapod-like structure, a filling model and a preparation method thereof. Which comprises the following steps: taking the tetrapod-like zinc oxide as a template, carrying out solid-liquid separation on a mixed suspension of the tetrapod-like zinc oxide and a carbon source, drying, and carbonizing and sintering the dried material to obtain the tetrapod-like zinc oxide coated with a carbon material; the mixed suspension may also contain a foaming agent or surfactant. The carbon material with a hollow four-needle-shaped structure can be used as a space filler to enhance the electrical effect of materials such as plastics, rubber and even metals due to the extremely strong field electron emission effect.

Description

Carbon material-coated tetrapod-like zinc oxide, carbon material with hollow tetrapod-like structure, filling mold and preparation method thereof

Technical Field

The invention relates to the technical field of three-dimensional carbon materials, in particular to tetrapod-like zinc oxide coated with a carbon material, the carbon material with a hollow tetrapod-like structure, a filling model and a preparation method of the filling model.

Background

Carbon materials have many allotropes, such as graphite, diamond, fullerene, carbon nanotubes, graphene, and the like. The carbon material has various micro textures according to the graphitization degree. Meanwhile, the carbon material is a material with abundant dimensionality (from zero dimension to three dimensions); the morphology can be powder, fiber, foam and film. Carbon electrodes made from carbon materials are generally fully polarized, and their electrical conductivity is still strongly dependent on heat treatment processes, micro-morphology, hybridization, heteroatom content, and other factors. Furthermore, the amphoteric character of the carbon material makes it possible to obtain electrons as well as to lose electrons.

The existing multiple mature chemical or physical activation methods enable the preparation of materials with large specific surface area and controllable microstructure, and the two properties are considered as electrode materials.

At present, no carbon material with a tetrapod-like structure is used for preparing an electrode.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The present invention is directed to provide a tetrapod-like zinc oxide coated with a carbon material, a carbon material having a hollow tetrapod-like structure, a filling mold, and a method for preparing the same to solve the above-mentioned problems.

The invention is realized by the following steps:

a preparation method of tetrapod-like zinc oxide coated with a carbon material comprises the following steps: taking the tetrapod-like zinc oxide as a template, carrying out solid-liquid separation on a mixed suspension of the tetrapod-like zinc oxide and a carbon source, drying, and carbonizing and sintering the dried material to obtain the tetrapod-like zinc oxide coated with a carbon material; the mixed suspension may also contain a foaming agent or surfactant.

After the tetrapod-like zinc oxide is mixed with the carbon source, the carbon source is physically adsorbed on the surface of the tetrapod-like zinc oxide, and the carbon source is coated on the surface of the template. A foaming agent or a surfactant is added to the suspension containing the carbon source coated tetrapod-like zinc oxide to prevent the agglomeration phenomenon during the subsequent re-drying process. The foaming agent or the surfactant can reduce the surface tension of the suspension, prevent the direct solid-liquid separation and the serious agglomeration of the sample, and influence the integrity of the four-needle structure.

The foaming agent is a chemical agent that generates a large amount of bubbles in a short time, and the surfactant may be an anionic surfactant, a cationic surfactant, or a nonionic surfactant. The anionic surfactant may be a detergent.

Drying to obtain loose sample, and final carbonizing and sintering to obtain carbon material coated tetrapod-like zinc oxide.

In a preferred embodiment of the present invention, the carbon source is tannic acid, chlorogenic acid, gallic acid, ellagic acid or (-) -epigallocatechin gallate.

Tannic acid also known as tannic acid (C)₇₆H₅₂O₄₆) Alias: T-ZnO, tannic acid, gallotannic acid, tanning, larch baking glue, diprotic acid, carbonic acid, tannic acid and gentle acid.

Tannic acid (tannic acid) is selected as a carbon source, the tannic acid is weak acid, and a tannic acid solution prepared from the tannic acid is weak acid. The mixing time of the tannic acid solution and the tetrapod-like zinc oxide should be strictly controlled to prevent excessive chemical reaction between the two and destroy the physical structure of the tetrapod-like zinc oxide.

In other embodiments, chlorogenic acid, gallic acid, ellagic acid, and (-) -epigallocatechin gallate may also be used as one of the carbon sources.

In the preferred embodiment of the present invention, the concentration of tannic acid is 100-200 mg/ml.

In a preferred embodiment of the present invention, the solid-liquid separation is suction filtration or air drying, and the drying is vacuum drying, air drying or freeze drying.

When the solid-liquid separation mode is air drying, uninterrupted shaking is needed to enable the sample to form uniform particles.

In a preferred embodiment of the present invention, the vacuum drying is low-temperature vacuum drying, and the low-temperature vacuum drying is vacuum drying at 30-50 ℃, the vacuum degree is less than or equal to 100Pa, and the time of the low-temperature vacuum drying is preferably 2-3 h.

If the sample is treated by adopting a high-temperature drying technology, the sample can be more seriously caked, so that the sample needs to be dried in a milder mode. The carbon material is kept in a soft state before sintering, and a spatial tetrapod-like structure is maintained. The dried tannic acid coated tetrapod zinc oxide samples were in the form of loose small yellow particles.

In a preferred embodiment of the present invention, the ratio of the tetrapod-like zinc oxide to the carbon source is 1-4:1 by mass.

If the carbon source is too small, the template cannot be completely coated, and a complete four-needle carbon structure cannot be formed.

In a preferred embodiment of the present invention, the ratio of the tetrapod-like zinc oxide to the carbon source is 2:1 by mass. The content of the carbon source determines the thickness of the surface layer of the hollow tetrapod-like carbon material prepared in the later period.

In a preferred embodiment of the present invention, the above-mentioned tetrapod-like zinc oxide is prepared by a high-temperature gas phase oxidation method.

The tetrapod-like zinc oxide prepared by the high-temperature gas-phase oxidation method has a uniform and complete structure, and the tetrapod-like zinc oxide prepared by other methods has poor structure uniformity and unstable structure size.

In a preferred embodiment of the present invention, the length of the whisker of the tetrapod-like zinc oxide is 10 to 100 μm. Too small a whisker size is likely to crosslink with the template itself.

In a preferred embodiment of the present invention, the mixing time of the tetrapod-like zinc oxide and the carbon source is 1-15 min.

When the carbon source is tannic acid, acid-base adsorption can occur when the tannic acid is mixed with the tetrapod-like zinc oxide, and the mixing time of the tetrapod-like zinc oxide and the carbon source needs to be strictly controlled in order to avoid the long-time acid-base adsorption to destroy the physical structure of the template.

In a preferred embodiment of the present invention, the mixing time of the tetrapod-like zinc oxide and the carbon source is 2-3 min.

In a preferred embodiment of the present invention, the carbonization and sintering is performed by placing the dried material in a tube furnace and performing a heat treatment in an inert gas atmosphere.

In a preferred embodiment of the present invention, the temperature of the heat treatment is less than 900 ℃.

Treatment above 900 c may cause the tip ends of the four-pin structure to retract slightly, affecting the integrity of the four-pin structure. When the carbon source is tannic acid, the carbonization degree can be stably maintained at 700 ℃.

The temperature of the heat treatment is determined by the TGA curve of the carbon source, and the inventor experimentally determined that the tannic acid can stabilize a part of the residual carbon after the heat treatment at 700 ℃, and the physical structure of the template (the tetrapod-like zinc oxide) is not affected at the temperature.

TGA test conditions: argon, 10 ℃/min; test range: 30 to 1000 ℃. The residual carbon content of tannic acid at 700 ℃ is about 5%.

In a preferred embodiment of the present invention, the temperature of the heat treatment is 700-. The heat treatment time is 2.5-3 h.

In the preferred embodiment of the present invention, the temperature of the heat treatment is 700 ℃.

The heat treatment temperature can be adjusted adaptively according to the type of the carbon source, and the heat treatment temperature of 700-750 ℃ is obtained according to the TGA curve of the tannic acid.

The inert gas is argon. In other embodiments, other inert gases may be selected as the working gas as desired.

In a preferred embodiment of the present invention, the surface cleaning of the tetrapod-like zinc oxide is further performed before the mixing of the tetrapod-like zinc oxide with the carbon source.

The surface cleaning comprises the steps of cleaning the surface of the tetrapod-like zinc oxide by using water bath ultrasound; preferably, the cleaned tetrapod-like zinc oxide is dried in an oven at 45-50 ℃ for 3-4 h.

And removing impurities on the surface of the template through surface cleaning to prevent the impurities from influencing the surface coating of the material.

A tetrapod-like zinc oxide coated with a carbon material is prepared by the above preparation method.

The tetrapod-like zinc oxide sample coated with the carbon material can be directly used as a composite cathode field emitter material. The field emission cold cathode with low opening field intensity, low threshold field intensity and high field enhancement factor is obtained by using the T-ZnO/carbon layer composite material with the tetrapod-shaped zinc oxide (T-ZnO) as the supporting layer.

A preparation method of a carbon material with a hollow tetrapod-like structure comprises the step of placing tetrapod-like zinc oxide coated with the carbon material prepared by the preparation method in acid liquor for etching.

And etching with acid liquor to obtain the hollow carbon material with the four-needle structure.

In a preferred embodiment of the present invention, the acid solution is hydrochloric acid solution, and the concentration of the hydrochloric acid solution is 1-1.2 mol/L.

In a preferred embodiment of the present invention, the etching time is 5-6 h.

In the preferred embodiment of the invention, the method further comprises washing and drying the etched solid, wherein the drying temperature is 60-80 ℃.

A carbon material having a hollow tetrapod-like structure, which is produced by the above production method.

The carbon material with a hollow four-needle-shaped structure can be used as a space filler to enhance the electrical effect of materials such as plastics, rubber and even metals due to the extremely strong field electron emission effect.

A filled mold comprising a carbon material having a hollow tetrapod-like structure.

In a preferred embodiment of the present invention, the carbon material is added in an amount of 7 to 10% by mass based on the mass of the filling mold.

The filling model also comprises AB glue, and the inventor finds that the resistance of the insulated AB glue material can reach the kiloohm level only by adding 7-10% of the carbon material with the hollow tetrapod-shaped structure into the AB glue.

Sp of carbon Material itself²And sp³The electronic structure further improves the electrical performance of the electronic structure. By adding the carbon material with the hollow four-needle structure, the electron mobility and the discharge efficiency of the carbon material are better, the conductivity is improved, and the tip discharge effect in space is better. The breakdown effect of the space with the potential difference at two ends can be easily realized only by doping with lower content.

The invention has the following beneficial effects:

the preparation method provided by the invention is simple and feasible, and the prepared tetrapod-like zinc oxide sample coated with the carbon material has wide application prospect and can be directly used as a composite cathode field emitter material. The carbon material with a hollow four-needle-shaped structure can be used as a space filler to enhance the electrical effect of materials such as plastics, rubber and even metals due to the extremely strong field electron emission effect.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a sample of the intermediate tannic acid/tetrapod zinc oxide obtained in example 1 (before carbonization);

FIG. 2 is a diagram showing a sample of tannic acid/tetrapod-like zinc oxide of FIG. 1 after carbonization;

FIG. 3 is an SEM image of the carbide product of FIG. 2 before etching;

FIG. 4 is an SEM image of FIG. 2 after etching of the carbide product;

FIG. 5 is a flow chart of the preparation;

FIG. 6 is an SEM photograph of tetrapod-like zinc oxide used in example 1;

FIG. 7 is a micrograph showing the results of the experiment in example 2;

FIG. 8 is a graph of the product of comparative example 1 after low temperature vacuum lyophilization without addition of surfactant;

FIG. 9 is a sample diagram before drying in comparative example 2;

FIG. 10 is a drawing of a sample after drying in comparative example 2;

FIG. 11 is a graph showing the carbonized product of the tetrapod-like zinc oxide sample after heat treatment at 700 ℃ in example 1;

FIG. 12 is a graph showing a carbonized product of a tetrapod-like zinc oxide sample after heat treatment at 800 ℃ in comparative example 3;

FIG. 13 is a graph showing a carbonized product of a tetrapod-like zinc oxide sample after heat treatment at 1000 ℃ in comparative example 4;

FIG. 14 is a tannic acid TGA curve;

FIG. 15 is a diagram of a tannin-coated tetrapod-like zinc oxide material before low-temperature vacuum drying in example 1;

FIG. 16 is a graph showing a sample of tannic acid/tetrapod-like zinc oxide after low-temperature vacuum drying in example 1.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The features and properties of the present invention are described in further detail below with reference to examples.

Example 1

This example provides a method for preparing a carbon material having a hollow tetrapod-like structure.

The method comprises the following steps of:

(1) selecting the tetrapod-like zinc oxide (purchased from Shanghai New Material science and technology Co., Ltd., nanometer HB-PZ-F001 tetrapod-like zinc oxide whisker sample) with a relatively complete structure as a template, cleaning the surface of the tetrapod-like zinc oxide by water bath ultrasound, and drying in an oven at 50 ℃ for 4h to obtain the tetrapod-like zinc oxide material with a clean surface.

(2) Preparing 5ml of tannic acid (tannic acid) solution of 200mg/ml (20 ℃) as a carbon source, and putting 2g of the tetrapod-shaped zinc oxide obtained in the step (1) and 1ml of a surfactant (liquid detergent) in the tannic acid solution for 2min (stirring) to form a tannic acid/tetrapod-shaped zinc oxide suspension.

(3) And (3) rapidly filtering the tannic acid/zinc oxide suspension in the step (2) by using a suction filtration mode (0.45um filter paper) to obtain the tannic acid-coated tetrapod-shaped zinc oxide material, which is shown in fig. 15.

(4) And (3) drying the tannic acid/tetrapod-like zinc oxide sample in the step (3) by using a low-temperature vacuum drying technology (30 ℃, the vacuum degree is 80Pa, and the low-temperature vacuum drying time is 3h), so as to obtain the tannic acid/tetrapod-like zinc oxide sample which is complete in structure and independent from each other (the macroscopic expression is shown in figures 1 and 16: loose yellow small particles).

(5) And (4) placing the tannic acid/tetrapod-like zinc oxide sample dried in the step (4) into a tube furnace, and carrying out heat treatment at 700 ℃ for 3h in an argon atmosphere to obtain a tetrapod-like zinc oxide sample coated by a carbon layer. The carbonization products of the tetrapod-like zinc oxide samples coated with the carbon layer are shown in fig. 2 and 11.

SEM images of the carbon/tetrapod zinc oxide sample before etching are shown with reference to A, B, C and D in fig. 3, and A, B, C and D in fig. 3 are enlarged views, respectively. It can be seen from the figure that a carbon shell with a relatively compact structure is attached to the surface layer of the tetrapod-like zinc oxide. The carbon coating rate of the whole sample is relatively high, the thickness of the carbon layer is relatively moderate, and the carbon layer is tightly attached to the surface of the tetrapod-shaped zinc oxide to form a carbon shell with a tetrapod-shaped structure.

(6) The carbon material with the hollow tetrapod-like structure can be obtained by placing a tetrapod-like zinc oxide sample coated with the carbon layer in a 1mol/L hydrochloric acid solution for 5h (stirring), then repeatedly washing with deionized water until the pH of the solution is 7, and drying in an oven (60 ℃).

SEM images of the etched carbon/tetrapod zinc oxide samples are shown with reference to A, B, C and D in fig. 4. The A, B, C, D diagram in fig. 4 is the tetrapod-like carbon shell after being etched with hydrochloric acid, and as can be seen from the surface profile of the a diagram, the etching process does not collapse the tetrapod-like carbon structure, and the B, C, D diagram can prove that the tetrapod-like zinc oxide has been completely etched.

The preparation steps of this example are shown in fig. 5, and the SEM image of the tetrapod-like zinc oxide used in this example is shown in fig. 6.

Example 2

5mL of 200mg/mL of a tannic acid solution selected from the group of the tannic acid solutions of example 1 was mixed with 2g of tetrapod-like zinc oxide. And carrying out microscopic observation for 0min, 30min and 60min after mixing respectively.

Referring to fig. 7, it can be seen from fig. 7 that the four-needle structure was seriously damaged at 30min and 60min after the mixing. This is because, in the mixing of the tetrapod-like zinc oxide with the tannic acid solution, since the tannic acid solution exhibits weak acidity, the time for mixing the two should be strictly controlled during the mixing process to prevent excessive corrosion of the needle structure of the tetrapod-like zinc oxide.

Compared with the example 1, the difference is that the carbon source selection in the step (2) is different, and the rest steps are the same.

Example 3

In this example, the carbon source was chlorogenic acid, and the rest of the steps were the same.

Example 4

In this example, the carbon source was gallic acid, and the rest steps were the same.

Example 5

In this example, the carbon source was ellagic acid, and the rest of the procedure was the same.

Example 6

In this example, the carbon source was (-) -epigallocatechin gallate, and the rest steps were the same.

Example 7

The difference from example 1 is that the solid-liquid separation method and the drying method in steps (3) and (4) are different, and the other steps are the same.

In this embodiment, the solid-liquid separation mode and the drying mode are air drying, and the air speed is controlled during the air drying, and the sample is continuously vibrated.

Comparative example 1

Compared with the example 1, the difference lies in that no surfactant is added in the step (2), the rest steps are the same, the product obtained after low-temperature vacuum freeze-drying is shown in figure 8, and figure 1 is the product obtained after low-temperature vacuum freeze-drying after the surfactant is added in the example 1.

As can be seen from fig. 8 and fig. 1, when no surfactant is added, more agglomeration occurs during the low-temperature drying process; when the surfactant is added, the phenomenon of more agglomeration cannot occur in the low-temperature drying process, and the integral performance is looser.

Comparative example 2

The difference from example 1 is that the drying method in step (4) is different, and the rest of the steps are the same.

In the embodiment, the drying mode is direct drying, the sample graph before drying is shown in figure 9, the sample graph after drying is shown in figure 10, the drying temperature is 60 ℃, and the drying time is 2 h.

Comparative example 3

The difference from example 1 is that the heat treatment temperature in step (5) is different, and the rest of the steps are the same.

In this example, the heat treatment temperature was 800 ℃ and the carbonized product of the tetrapod-like zinc oxide sample coated with the carbon layer was as shown in FIG. 12.

Comparative example 4

In this example, the heat treatment temperature was 1000 ℃ and the carbonized product of the tetrapod-like zinc oxide sample coated with the carbon layer was as shown in FIG. 13.

As can be seen from a comparison of fig. 11, fig. 12 and fig. 13, the color of the carbonized product of the tetrapod-like zinc oxide sample is lightened by the heat treatment temperature of the present invention, and it is analyzed that amorphous carbon is attached to the surface of the tetrapod-like zinc oxide and is more easily blown away by the airflow at a higher temperature, so that the color of the carbonized product is lightened and the amount of carbon attached is reduced.

Tannic acid belongs to antioxidant materials, but is oxidized at high temperature, and the color is gradually deepened.

Figure 14 is a TGA plot of tannic acid.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of tetrapod-like zinc oxide coated with a carbon material is characterized by comprising the following steps: taking the tetrapod-like zinc oxide as a template, carrying out solid-liquid separation on a mixed suspension of the tetrapod-like zinc oxide and a carbon source, drying, and carbonizing and sintering the dried material to obtain the tetrapod-like zinc oxide coated with a carbon material; the mixed suspension also contains a foaming agent or a surfactant.

2. The method according to claim 1, wherein the carbon source is tannic acid, chlorogenic acid, gallic acid, ellagic acid, or (-) -epigallocatechin gallate.

3. The preparation method according to claim 1, wherein the solid-liquid separation is suction filtration or air drying, and the drying is vacuum drying, air drying or freeze drying;

preferably, the vacuum drying is low-temperature vacuum drying, the low-temperature vacuum drying is vacuum drying at 30-50 ℃, the vacuum degree is less than or equal to 100Pa, and the low-temperature vacuum drying time is preferably 2-3 h.

4. The preparation method according to claim 3, wherein the addition mass ratio of the tetrapod-like zinc oxide to the carbon source is 1-4: 1;

preferably, the adding mass ratio of the tetrapod-like zinc oxide to the carbon source is 2: 1;

preferably, the tetrapod-like zinc oxide is prepared by a high-temperature gas-phase oxidation method;

preferably, the whisker length of the tetrapod-like zinc oxide is 10-100 μm;

preferably, the mixing time of the tetrapod-like zinc oxide and the carbon source is 1-15 min;

preferably, the mixing time of the tetrapod-like zinc oxide and the carbon source is 2-3 min.

5. The method according to claim 4, wherein the carbonization sintering is carried out by placing the dried material in a tube furnace and performing heat treatment in an inert gas atmosphere;

preferably, the temperature of the heat treatment is 700-750 ℃; more preferably, the temperature of the heat treatment is 700 ℃; preferably, the time of the heat treatment is 2.5-3 h;

preferably, the inert gas is argon.

6. The method of claim 1, wherein the step of surface cleaning the tetrapod-like zinc oxide before mixing the tetrapod-like zinc oxide with the carbon source;

preferably, the surface cleaning comprises cleaning the surface of the tetrapod-like zinc oxide by using water bath ultrasound; preferably, the cleaned tetrapod-like zinc oxide is dried in an oven at 45-50 ℃ for 3-4 h.

7. Tetrapod-like zinc oxide coated with a carbon material, which is produced by the production method according to any one of claims 1 to 6.

8. A method for producing a carbon material having a hollow tetrapod-like structure, comprising etching tetrapod-like zinc oxide coated with a carbon material obtained by the production method according to any one of claims 1 to 6 in an acid solution;

preferably, the acid solution is a hydrochloric acid solution, and the concentration of the hydrochloric acid solution is 1-1.2 mol/L;

preferably, the etching time is 5-6 h;

preferably, the method further comprises washing and drying the etched solid, wherein the drying temperature is 60-80 ℃.

9. A carbon material having a hollow tetrapod-like structure, which is produced by the production method according to claim 8.

10. A filled mold comprising the carbon material having a hollow tetrapod-like structure according to claim 9;

preferably, the mass of the carbon material added is 7-10% of the mass of the filling mold.