CN109879270A - A kind of preparation method of lightweight ultra-wideband carbonization red bayberry absorbing material - Google Patents
A kind of preparation method of lightweight ultra-wideband carbonization red bayberry absorbing material Download PDFInfo
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- CN109879270A CN109879270A CN201910335839.3A CN201910335839A CN109879270A CN 109879270 A CN109879270 A CN 109879270A CN 201910335839 A CN201910335839 A CN 201910335839A CN 109879270 A CN109879270 A CN 109879270A
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Abstract
The invention discloses a kind of preparation methods of lightweight ultra-wideband carbonization red bayberry absorbing material, and described method includes following steps: Step 1: fresh red bayberry is cleaned, being put into freezer and freezes；Step 2: the red bayberry of freezing is put into freeze drying box, vacuumize, is freeze-dried；Step 3: the red bayberry of freeze-drying is carried out high temperature cabonization.Simple process of the invention, it is only necessary to which freeze-drying and carbonization can be realized.Absorbing material prepared by the present invention has the advantages that lightweight, density only have 0.13g/cm3；Effective suction wave in 8 ~ 40GHz frequency range may be implemented simultaneously, be that other biological material inhales wide 5 times or so of wave frequency, take into account the advantage of lightweight and ultra-wideband.Due to red bayberry chondritic special in this way, so that it has preferable wave-absorbing effect in different incidence angles, this comprehensive to reply radar, multi-angle detection is of great significance.
Description
Technical field
The invention belongs to absorbing material technical fields, are related to a kind of preparation method of lightweight ultra-wideband absorbing material.
Background technique
While science and technology rapid development, but also the electromagnetic pollution of multiple frequency ranges is got worse, influence people's lives and
Work.On the other hand, the wave frequency range that radar can detect is gradually broadening, and the national defense construction for country increases difficulty
Topic.Therefore, it is badly in need of may be implemented the material of broadband absorbing to solve the problems, such as electromagnetic pollution and national defense safety.
In recent years, absorbing material is fast-developing, wherein carbon material such as carbon nanotube, graphene, carbon fiber and its composite wood
Material etc. is due to its lightweight, chemical stability is good and excellent absorbing property and is used widely, but these carbon materials are general
Preparation process is more complex and at high cost.So in the recent period, researchers start with the biomass of carbonization as absorbing material.Biology
Material has the advantages that lightweight, at low cost.Although such as the stalk of carbonization, cotton, wood etc. all have stronger electromagnetism
Wave absorption intensity, but it effectively inhales wave frequency that wide (when reflection loss≤- 10dB, 90% or more electromagnetic wave is absorbed, so one
As think that reflection loss≤- 10dB frequency range is that effective to inhale wave frequency wide) it is relatively narrow, all in 7GHz hereinafter, being far from satisfying
The requirement of present broadband absorbing.
Summary of the invention
In order to solve above-mentioned current absorbing material complex process, it is at high cost, inhale wave frequency section it is narrow the problems such as, the present invention provides
A kind of preparation method of lightweight ultra-wideband carbonization red bayberry absorbing material.The present invention is in view of the structure of material itself is to absorbing property
There is important influence, choosing has the biomass red bayberry of multilevel structure as presoma, by freeze-drying removal red bayberry
Moisture keeps its structure simultaneously, obtains a kind of light porous carbon material by carbonization later, simple process, low in cost.
The purpose of the present invention is what is be achieved through the following technical solutions:
A kind of preparation method of lightweight ultra-wideband carbonization red bayberry absorbing material, includes the following steps:
Step 1: fresh red bayberry is cleaned, it is put into freezer and freezes.
In this step, the temperature of freezer is -5 ~ -10 DEG C, and cooling time is greater than 5h.
Step 2: the red bayberry of freezing is put into freeze drying box, vacuumize, be freeze-dried, freezing dry process can be with
The moisture inside red bayberry is removed, retains the special construction of red bayberry itself.
In this step, specific step is as follows for freeze-drying: first uniformly rising temperature from -30 ~ -20 DEG C in 168 ~ 240h
Then temperature is warming up to 20 ~ 30 DEG C from 0 DEG C in 72 ~ 120h, finally in 20 ~ 30 DEG C of 24 ~ 48h of heat preservation to 0 DEG C by temperature；
Step 3: the red bayberry of freeze-drying is carried out high temperature cabonization.
In this step, specific step is as follows for high temperature cabonization: being risen to temperature from room temperature with the heating rate of 2 ~ 4 DEG C/min
300 ~ 400 DEG C, in 300 ~ 400 DEG C of 0.5 ~ 1.5h of heat preservation；Continue to be warming up to 650 ~ 800 DEG C with the heating rate of 4 ~ 7 DEG C/min, protect
30 ~ 120min of temperature；It is naturally cooling to room temperature.
In this step, high temperature cabonization can carry out in inert gas, can also carry out in a vacuum.
Compared with the prior art, the present invention has the advantage that
1, compared to other carbon materials, red bayberry is simple and easy to get, at low cost.
2, simple process of the invention, it is only necessary to which freeze-drying and carbonization can be realized.
3, absorbing material prepared by the present invention has the advantages that lightweight, density only have 0.13g/cm3；It may be implemented simultaneously
Effective suction wave in 8 ~ 40GHz frequency range is that other biological material inhales wide 5 times or so of wave frequency, takes into account lightweight and ultra-wide
The advantage of frequency.
4, absorbing material prepared by the present invention has multistage oriented structure, and has the characteristics that variable density from outside to inside.
5, the chondritic special in this way due to red bayberry, so that it has in different incidence angles and preferable must inhale wave
Effect, this comprehensive to reply radar, multi-angle detection are of great significance.
Detailed description of the invention
Fig. 1 is the photo of red bayberry carbonization front and back, and a left side is before carbonization (after freeze-drying), after the right side is carbonization；
Fig. 2 is the stereoscan photograph of red bayberry different parts after carbonization；
Fig. 3 is the absorbing property test schematic diagram and test result of carbonization red bayberry, (a) arch frame method test schematic diagram, (b)-(d)
The reflection loss result of different frequency；
Fig. 4 is test sample picture.
Specific embodiment
Below with reference to embodiment, further description of the technical solution of the present invention, and however, it is not limited to this, all right
Technical solution of the present invention is modified or replaced equivalently, and without departing from the spirit and scope of the technical solution of the present invention, should all be contained
Lid is within the protection scope of the present invention.
Embodiment 1:
In the present embodiment, lightweight ultra-wideband carbonization red bayberry absorbing material is specifically to follow the steps below preparation:
(1) fresh red bayberry is cleaned, is placed in metal tray, it is -5 DEG C that it is constant, which to be then put into togerther temperature, together with metal tray
Freezer in freeze 10h.
(2) being put into togerther temperature to be reduced to the temperature inside the box by the red bayberry of freezing and metal tray is -30 DEG C of freeze-dryings
In case, vacuumize.The program of freeze-drying is set are as follows: 0 DEG C is uniformly heating to from -30 DEG C in 168h, then again in 120h from 0 DEG C
30 DEG C are uniformly heating to, is kept the temperature for 24 hours at 30 DEG C later.
(3) red bayberry after freeze-drying is put into the quartz ampoule of tube furnace, Guan Zhongyi leads directly to argon gas, and setting tube furnace is joined
Number, makes stove that temperature be risen to 350 DEG C from room temperature with the heating rate of 2 DEG C/min, in 350 DEG C of heat preservation 1h；Continue with 5 DEG C/min
Heating rate be warming up to 700 DEG C, keep the temperature 120min；Sample is taken out after being naturally cooling to room temperature.
Fig. 1 gives the photomacrograph of the present embodiment carbonization front and back red bayberry.Red bayberry after being freeze-dried as can be seen from Figure 1
The structure for preferably maintaining itself, the volume of red bayberry has apparent contraction after carbonization.
Fig. 2 is the microstructure scanning electron microscope (SEM) photograph of red bayberry different parts after carbonization.The fruit on red bayberry surface layer as can be seen from Figure 2
The column structure that meat part is made of multiple hollow tubular structures, internal caliber between tens microns to more than 100 microns,
1 microns of thickness of pipe wall；In one layer of fiber of pulp and core intermediate distribution；Kernel disappears after carbonization, leaves hollow core, Er Qieyang
The density of plum from outside to inside increases, and the porous material of this variable density is the key that realize excellent absorbing property.
In order to which in situ measurement can be carried out to the absorbing property of sample, the red bayberry of carbonization is placed on one with a thickness of 2mm's
On acrylic board (acrylic board does not have absorbing property), there is equally distributed hole for fixing spherical red bayberry on the acrylic,
It as shown in Fig. 3 a and Fig. 4, is then placed on on-gauge plate, with the absorbing property of arch frame method test red bayberry.With different antenna point
Ce Shi not be in the performance of different-waveband, and test the suction under different incidence angles (angle of transmitting antenna and receiving antenna)
Wave performance, as a result as shown in Fig. 3 b-c.It can be seen that within the scope of 8 ~ 40GHz from Fig. 3 b-c, reflection loss can reach-
10dB reaches 32GHz hereinafter, effectively inhaling wave frequency section, is 5 times of other biological matter carbon material, and it is difficult to realize inhale wave 1 ~
8GHz wave band, reflection loss also can achieve -8dB or less.In addition, can still be kept excellent when incidence angle increases to 40 °
Wave-absorbing effect.The gross density of red bayberry only has 0.13g/cm after carbonization3, achieved the purpose that lightweight ultra-wideband.
Embodiment 2:
In the present embodiment, lightweight ultra-wideband carbonization red bayberry absorbing material is specifically to follow the steps below preparation:
(1) fresh red bayberry is cleaned, is placed in metal tray, it is -10 that it is constant, which to be then put into togerther temperature, together with metal tray
DEG C freezer in freeze 6h.
(2) being put into togerther temperature to be reduced to the temperature inside the box by the red bayberry of freezing and metal tray is -20 DEG C of freeze-dryings
In case, vacuumize.The program of freeze-drying is set are as follows: 0 DEG C is uniformly heating to from -20 DEG C in 240h, then again in 72h from 0 DEG C
20 DEG C are uniformly heating to, later in 20 DEG C of heat preservation 48h.
(3) red bayberry after freeze-drying is put into the quartz ampoule of tube furnace, Guan Zhongyi leads directly to argon gas, and setting tube furnace is joined
Number, makes stove that temperature be risen to 300 DEG C from room temperature with the heating rate of 4 DEG C/min, in 300 DEG C of heat preservation 1.5h；Continue with 4 DEG C/
The heating rate of min is warming up to 800 DEG C, keeps the temperature 30min；Sample is taken out after being naturally cooling to room temperature.
The different parts structure and embodiment 1 of red bayberry are identical after carbonization, gross density 0.12g/cm3, survey in aforementioned manners
The absorbing property of examination carbonization red bayberry, the results showed that Effective frequency width of absorption 31GHz.
Embodiment 3:
In the present embodiment, lightweight ultra-wideband carbonization red bayberry absorbing material is specifically to follow the steps below preparation:
(1) fresh red bayberry is cleaned, is placed in metal tray, it is -8 DEG C that it is constant, which to be then put into togerther temperature, together with metal tray
Freezer in freeze 8h.
(2) being put into togerther temperature to be reduced to the temperature inside the box by the red bayberry of freezing and metal tray is -25 DEG C of freeze-dryings
In case, vacuumize.The program of freeze-drying is set are as follows: 0 DEG C is uniformly heating to from -25 DEG C in 200h, then again in 100h from 0 DEG C
25 DEG C are uniformly heating to, later in 25 DEG C of heat preservation 36h.
(3) red bayberry after freeze-drying is put into vacuum sintering furnace, is vacuumized, after vacuum degree reaches 10Pa, started to warm up,
Temperature is risen to 400 DEG C from room temperature with the heating rate of 3 DEG C/min, in 400 DEG C of heat preservation 0.5h；Continue with the heating of 7 DEG C/min
Rate is warming up to 650 DEG C, keeps the temperature 60min；Sample is taken out after being naturally cooling to room temperature, whole process all keeps vacuum environment.
Red bayberry gross density is 0.13g/cm after carbonization3, the absorbing property of carbonization red bayberry is tested in aforementioned manners, the results showed that
Effective frequency width of absorption is 28GHz.
Claims (5)
1. a kind of preparation method of lightweight ultra-wideband carbonization red bayberry absorbing material, it is characterised in that the method includes walking as follows
It is rapid:
Step 1: fresh red bayberry is cleaned, it is put into freezer and freezes；
Step 2: the red bayberry of freezing is put into freeze drying box, vacuumize, is freeze-dried；
Step 3: the red bayberry of freeze-drying is carried out high temperature cabonization.
2. the preparation method of lightweight ultra-wideband carbonization red bayberry absorbing material according to claim 1, it is characterised in that described
Cryogenic temperature is -5 ~ -10 DEG C, and the time is greater than 5h.
3. the preparation method of lightweight ultra-wideband carbonization red bayberry absorbing material according to claim 1, it is characterised in that described
Specific step is as follows for freeze-drying: temperature is first uniformly heating to 0 DEG C from -30 ~ -20 DEG C in 168 ~ 240h, then 72 ~
Temperature is warming up to 20 ~ 30 DEG C from 0 DEG C in 120h, finally in 20 ~ 30 DEG C of 24 ~ 48h of heat preservation.
4. the preparation method of lightweight ultra-wideband carbonization red bayberry absorbing material according to claim 1, it is characterised in that described
Specific step is as follows for high temperature cabonization: temperature is risen to 300 ~ 400 DEG C from room temperature with the heating rate of 2 ~ 4 DEG C/min, 300 ~
400 DEG C of 0.5 ~ 1.5h of heat preservation；Continue to be warming up to 650 ~ 800 DEG C with the heating rate of 4 ~ 7 DEG C/min, keeps the temperature 30 ~ 120min；It is natural
It is cooled to room temperature.
5. the preparation method of lightweight ultra-wideband carbonization red bayberry absorbing material according to claim 1, it is characterised in that described
High temperature cabonization carries out in inert gas or vacuum.
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| CN111961441A (en) * | 2020-08-26 | 2020-11-20 | 浙江理工大学桐乡研究院有限公司 | Preparation method of wave-absorbing material based on mulberry silk biomass charcoal |
| CN112299391A (en) * | 2020-10-15 | 2021-02-02 | 南京师范大学 | Water chestnut derived oxygen-doped carbon material and preparation method and application thereof |
| CN113122184A (en) * | 2021-05-11 | 2021-07-16 | 盐城工学院 | Preparation method of biomass porous carbon wave-absorbing material |
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| CN112299391A (en) * | 2020-10-15 | 2021-02-02 | 南京师范大学 | Water chestnut derived oxygen-doped carbon material and preparation method and application thereof |
| CN113122184A (en) * | 2021-05-11 | 2021-07-16 | 盐城工学院 | Preparation method of biomass porous carbon wave-absorbing material |
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