CN1300054C - Composite microwave absorbent of Nano carbon tube, and preparation method - Google Patents

Abstract

The invention relates to a carbon nanotube composite microwave absorbent and a preparation method thereof. The method can use simple equipment to pyrolyze acetylene to prepare a microwave-absorbing carbon nanotube composite absorbent with controllable pipe diameter, which has the advantages of simple synthesis process, high purity and low The characteristics of cost, the outer diameter of the synthesized carbon nanotubes is 10-35nm. The main components of this absorbent include carbon nanotubes, Fe ₂ O ₃ and Al ₂ O ₃ , wherein carbon nanotubes account for 75-90% by mass, Fe ₂ O ₃ accounts for 5-11% by mass, and Al ₂ O ₃ The mass percentage is 1-15%, the mass percentage of amorphous carbon particles is 1-5%, and the appearance of the absorbent is black.

Description

A kind of carbon nanotube composite microwave absorber and preparation method thereof

technical field

The invention relates to a carbon nanotube composite microwave absorber and a preparation method thereof.

Background technique

According to the results reported so far, the absorbing materials mainly include: (1) conductive high polymer absorbent, (2) metal compound absorbent. (3) metal and alloy absorbent, (4) ceramic absorbent. Mainly SiC Powder, SiC fiber, aluminum silicate, etc., (5) nano wave absorbing material. The unique structure of nanomaterials has quantum size effect, small size effect and surface interface effect. The number of atoms on the surface of nano-scale superfine powder is much larger, which increases the activity of nano-materials, thereby increasing the absorption of electromagnetic waves. The nano-microwave absorbers studied at home and abroad mainly include the following types: nano-metal and alloy absorbers, nano-oxide absorbers, nano-SiC absorbers, nano-ferrite absorbers, nano-graphite absorbers, nano-metal films, insulating Dielectric film absorbent, nano conductive polymer absorbent, nano nitride absorbent, etc. The above-mentioned absorbers have the following problems: the metal powder absorber has poor oxidation resistance, which causes the anti-aging performance of the coating to decline; the amount of metal compound absorber needs to be added, which causes the coating to be too heavy; the resistivity of the ceramic absorber is low. Higher, compared with the above-mentioned absorbing materials, the advantage of carbon nanotube absorbing materials is that it is not only nanomaterials, but also that carbon nanotubes are chiral absorbing materials. The advantage of chiral materials is that there is no mirror symmetry for incident electromagnetic waves , can better realize the diffuse scattering of electromagnetic waves, and achieve the purpose of absorbing electromagnetic waves by reducing the reflection of incident electromagnetic waves. And it has low sensitivity to frequency, and it is easy to realize broadband absorption. Carbon nanotubes also have the characteristics of high strength, high modulus, light weight and good thermal stability, so they are an ideal electromagnetic wave absorbing material. Another innovation of the carbon nanotube composite microwave absorber of the present invention is that the catalyst itself is also a nano metal oxide absorber, and the carbon nanotube composite microwave absorber synthesized by the catalyst also has nano oxide absorber The advantages of electromagnetic wave absorption performance of absorbents and carbon nanotube absorbents.

Contents of the invention

The object of the present invention is to provide a carbon nanotube composite microwave absorber and a preparation method thereof.

The carbon nanotube composite microwave absorbent of the present invention is mainly composed of carbon nanotubes, containing Fe2O3, Al2O3 and amorphous carbon particles; wherein the carbon nanotubes account for 75% to 90% by mass, and Fe2O3 accounts for 5% by mass. ~11%, the mass percentage of Al2O3 is 1 ~ 15%, the mass percentage of amorphous carbon particles is 1 ~ 5%, and the outer diameter distribution of carbon nanotubes is 10 ~ 35nm.

The preparation technology of carbon nanotube composite microwave absorber has the following steps:

(1) Weigh an appropriate proportion of ferric nitrate and aluminum nitrate to dissolve in distilled water, add an appropriate amount of organic acid, stir well, add ammonia to adjust the pH value of the solution to 7, and dry the solution at 120°C. Add 95% ethanol to the solid matter obtained after complete drying, and the product obtained after ignition and combustion is used as a catalyst for preparing carbon nanotube composite microwave absorbers;

(2) Adopt horizontal tube furnace, at first feed nitrogen on the catalyzer to get rid of the air in the reaction device, then heat up, when the device temperature rises to about 873K, feed flow is the hydrogen of 50sccm, continue to heat up, when the device temperature rises When the temperature reaches 1000K, acetylene is introduced, and the flow rate of acetylene is 100 sccm. After 30 minutes of reaction, the heating is stopped, the gas is switched to nitrogen, and the temperature is lowered in a nitrogen atmosphere. The product is collected to obtain a carbon nanotube composite microwave absorber.

Detailed ways

The following is an example of preparing a carbon nanotube composite microwave absorber.

Example 1:

Weigh ferric nitrate salt and aluminum nitrate salt (nFe ⁺³ : ^nAl+3 =1:5) in an appropriate proportion and dissolve them in distilled water, add an appropriate amount of organic acid, stir well, add ammonia water to adjust the pH value of the solution to 7, Dry the solution at 120°C, add 95% ethanol igniter to the solid substance obtained after complete drying, and the product obtained after ignition and combustion is a catalyst with a Fe/Al molar ratio of 1:5. 1g of this catalyst will be housed (Fe/Al molar ratio is 1: 5) quartz boat is put into reaction chamber, pass into hydrogen again when passing through nitrogen to heat to 873K, hydrogen flow rate is 50sccm acetylene, when device temperature rises to 1000K, pass into acetylene, Adjust the acetylene flow rate to 100 sccm, stop heating after reacting at 1000 K for 0.5 h, switch the gas to nitrogen, and feed nitrogen until the device cools down to room temperature to obtain a carbon nanotube composite microwave absorber. In the composite microwave absorber, carbon nanotubes accounted for 75% by mass, Fe2O3 accounted for 5% by mass, Al2O3 accounted for 15% by mass, and amorphous carbon particles accounted for 5% by mass.

Example 2:

Weigh ferric nitrate salt and aluminum nitrate salt (nFe ⁺³ : ^nAl+3 =1:2) in an appropriate proportion and dissolve them in distilled water, add an appropriate amount of organic acid, stir well, add ammonia water to adjust the pH value of the solution to 7, Dry the solution at 120°C, add 95% ethanol igniter to the solid matter obtained after complete drying, and the product obtained after ignition and combustion is a catalyst with a Fe/Al molar ratio of 1:2. (Fe/Al molar ratio is 1: 2) quartz boat is put into reaction chamber, feeds hydrogen again when feeding nitrogen to heat to 873K, hydrogen flow rate is 50sccm acetylene, when device temperature rises to 1000K, feeds acetylene, Adjust the acetylene flow rate to 100 sccm, stop heating after reacting at 1000 K for 0.5 h, switch the gas to nitrogen, and feed nitrogen until the device cools down to room temperature to obtain a carbon nanotube composite microwave absorber. In the composite microwave absorber, carbon nanotubes accounted for 76% by mass, Fe2O3 accounted for 8% by mass, Al2O3 accounted for 12% by mass, and amorphous carbon particles accounted for 4% by mass.

Example 3:

Weigh an appropriate proportion of ferric nitrate and aluminum nitrate (nFe ⁺³ : ^nAl+3 =1:1) to dissolve in distilled water, add an appropriate amount of organic acid, stir well, add ammonia to adjust the pH of the solution to 7, Dry the solution at 120° C., add 95% ethanol as a igniter to the solid substance obtained after complete drying, and the product obtained after ignition and combustion is a catalyst with a Fe/Al molar ratio of 1:1. Put the quartz boat equipped with 1g of this catalyst (Fe/Al molar ratio is 1:1) into the reaction chamber, pass through nitrogen gas and heat to 873K, then pass into hydrogen gas, the flow rate of hydrogen gas is 50 sccm acetylene, when the temperature of the device rises to 1000K At this time, feed acetylene, adjust the flow rate of acetylene to 100 sccm, stop heating after reacting at 1000 K for 0.5 h, switch the gas to nitrogen, feed nitrogen until the device is cooled to room temperature, and obtain a carbon nanotube composite microwave absorber. In the composite microwave absorber, carbon nanotubes accounted for 80% by mass, Fe2O3 accounted for 11% by mass, Al2O3 accounted for 6% by mass, and amorphous carbon particles accounted for 3% by mass.

Example 4:

Weigh ferric nitrate salt and aluminum nitrate salt (nFe ⁺³ : ^nAl+3 =2:1) in an appropriate proportion and dissolve them in distilled water, add an appropriate amount of organic acid, stir well, add ammonia water to adjust the pH value of the solution to 7, Dry the solution at 120°C, add 95% ethanol igniter to the solid matter obtained after complete drying, and the product obtained after ignition and combustion is a catalyst with a Fe/Al molar ratio of 2.:1. Will contain 1.0g The quartz boat of the catalyst (Fe/Al molar ratio is 2:1) is put into the reaction chamber, and then hydrogen is passed into when the nitrogen gas is heated to 873K. The hydrogen flow rate is 50 sccm acetylene. For acetylene, adjust the acetylene flow rate to 100 sccm, stop heating after reacting at 1000K for 0.5h, switch the gas to nitrogen, and feed nitrogen until the device cools down to room temperature to obtain a carbon nanotube composite microwave absorber. In the composite microwave absorber, carbon nanotubes accounted for 82% by mass, Fe2O3 accounted for 11% by mass, Al2O3 accounted for 5% by mass, and amorphous carbon particles accounted for 2% by mass.

Example 5:

Weigh ferric nitrate salt and aluminum nitrate salt (nFe ⁺³ : ^nAl+3 =5:1) in an appropriate proportion and dissolve them in distilled water, add an appropriate amount of organic acid, stir well, add ammonia water to adjust the pH value of the solution to 7, Dry the solution at 120° C., add 95% ethanol as a igniter to the solid substance obtained after complete drying, and the product obtained after ignition and combustion is a catalyst with a Fe/Al molar ratio of 39:1. The quartz boat that 1.0g this catalyst (Fe/Al molar ratio is 5: 1) is housed is put into reaction chamber, feeds hydrogen again when feeding nitrogen and heating to 873K, hydrogen flow is 50sccm acetylene, when device temperature rises to At 1000K, feed acetylene, adjust the flow rate of acetylene to 100 sccm, stop heating after reacting at 1000K for 0.5h, switch the gas to nitrogen, feed nitrogen until the device is cooled to room temperature, and obtain a carbon nanotube composite microwave absorber. In the composite microwave absorber, carbon nanotubes accounted for 90% by mass, Fe2O3 accounted for 8% by mass, Al2O3 accounted for 1% by mass, and amorphous carbon particles accounted for 1% by mass.

Claims (1)

1. carbon nanotube composite microwave absorption agent is characterized in that: described carbon nanotube composite microwave absorption agent is to be main component with the carbon nanotube, contains Fe ₂O ₃, Al ₂O ₃With the decolorizing carbon particle; Wherein to account for mass percent be 75～90% to carbon nanotube, Fe ₂O ₃Accounting for mass percent is 5～11%, Al ₂O ₃Shared mass percent is 1～15%, and the shared mass percent of decolorizing carbon particle is 1～5%, and the carbon nanotube external diameter is distributed as 10～35nm.