CN112357918B - Nano-diamond prepared from plant fiber and method thereof - Google Patents

Abstract

The application discloses a nano diamond prepared by taking plant fiber as a raw material and a method thereof, and the steps are as follows: adding plant fiber raw materials into a ball mill, and performing ball milling, crushing and mixing to obtain plant fiber powder; tabletting the plant fiber powder to obtain flaky plant fiber; and (3) carrying out laser irradiation on the sheet plant fiber by using a femtosecond laser, and carbonizing the plant fiber and simultaneously carrying out carbon phase change under the action of the laser irradiation to generate the nano diamond. The method has the advantages of cheap and easily obtained raw materials, simple synthesis method, mild conditions, high efficiency, simple operation and the like. The prepared nano diamond has the granularity of less than 50nm and has higher application value in the fields of miniature super capacitors, sensors, wastewater treatment and the like.

Description

Nano-diamond prepared from plant fiber and method thereof

technical field

The invention belongs to the technical field of diamond preparation, and in particular relates to a nano-diamond prepared from plant fibers and a method thereof.

Background technique

In the past decades, carbon materials have been extensively studied due to their high thermal stability and mechanical properties. Nanodiamonds are sp ³ hybridized carbon nanoparticles, which are allotropes with graphite, graphene, carbon nanotubes, and fullerenes. Nanodiamond has attracted much attention because of its excellent mechanical and optical properties, high specific surface area, adjustable surface structure and other excellent properties. It has a wide range of applications in polishing, lubrication, biological calibration, drug delivery, quantum computing, biosensors and other fields. prospect. However, the scarcity of natural diamond reserves greatly limits its large-scale application. At present, nanodiamonds are mainly prepared by explosion, chemical vapor deposition (CVD), high temperature and high pressure grinding, plasma high pressure impact and other methods. However, these methods are harsh and require extremely high temperature and pressure environments, or expensive gaseous/chemical precursors. Therefore, it is of great significance to develop a simple, safe, effective, and green method for the preparation of nano-diamonds.

Plant fiber is the most abundant renewable resource in nature, and has the advantages of being cheap, easy to obtain, environmentally friendly, and biodegradable. Plant fibers mainly include cellulose, hemicellulose, lignin and other substances, which are important sources of raw materials for the pulp and paper industry. The data shows that in 2018, the global pulp production was about 184 million tons, and about 70 million tons of lignin was also produced, of which only about 2% of the lignin was burned to recover heat energy and replace fossil materials, which also caused plant damage. The added value of fiber products is not high.

Contents of the invention

Aiming at the deficiencies of the prior art, the object of the present invention is to provide a nano-diamond prepared from plant fibers and a method thereof. The present invention prepares the nano-diamond under normal temperature and pressure conditions through laser irradiation of a femtosecond laser. The problem of harsh preparation conditions and expensive raw materials in the prior art is overcome.

The purpose of the present invention is achieved through the following technical solutions:

A method for preparing nano-diamonds from plant fibers, the steps are as follows:

(1) adding plant fiber raw materials in a ball mill, and obtaining plant fiber powder after being pulverized and mixed by ball milling;

(2) Perform tableting treatment on the plant fiber powder to obtain flaky plant fibers; preferably, the pressure of the tableting treatment is 5-10 MPa, and the thickness of the flaky plant fibers is 0.2-2 mm. Specifically, according to actual needs, an appropriate pressure can be selected for tableting, such as 5Mpa, 7Mpa, 8Mpa or 10Mpa; the thickness of the sheet-like plant fibers can also be adjusted appropriately, for example, the thickness can be selected as 0.2mm, 0.8mm, 1mm , 1.4mm, 1.8mm or 2mm, etc.; different types of tablet presses can be selected for tableting, and the shape of the sheet-like plant fibers can be round or square.

(3) Place the plant fiber film on a computer program-controlled workbench, and use a femtosecond laser to irradiate the plant fiber film under normal temperature and pressure. Under the action of laser irradiation, the plant fiber is carbonized and the phase of carbon occurs simultaneously change to produce nanodiamonds. Further, the laser power of the femtosecond laser is 100mW-1000mW, the laser radiation time is 1-60min, and the running speed of the workbench is 1mm/s-100mm/s. Specifically, the laser power of the femtosecond laser can be 100mW, 500mW, 800mW or 1000mW, the laser radiation time is 1min, 10min, 30min, 45min or 60min, and the running speed of the workbench is 1mm/s, 30mm/s, 60mm/s , 80mm/s or 100mm/s.

As a preferred technical solution, in step (1), the plant fiber raw material is lignin or a mixture of lignin and cellulose. When lignin is used alone as a raw material to prepare nano-diamonds, because lignin is mainly aromatic structure, strong hydrophobicity, and there is no connection site between lignin molecules, it cannot be made into a film by a film-forming method, so tableting is used. The method is used to press it into a sheet, which is convenient for subsequent laser irradiation. When using a mixture of lignin and cellulose as raw materials to prepare nano-diamonds, since the cellulose molecules contain a large number of hydrogen-containing groups such as hydroxyl groups, and the lignin molecules contain oxygen-containing groups such as carbonyl groups, the lignin and cellulose There is a certain hydrogen bond between them, that is, cellulose can act like a binder to strengthen the cohesion between lignin molecules, so that the stability of the prepared sheet material is better, which is conducive to subsequent laser irradiation steps are carried out. In addition, after laser irradiation, cellulose can generate CO, H ₂ , CO ₂ and other decomposition gases, among which CO, H ₂ and other gases have reducing properties, have a catalytic effect on the reduction of carbon, and can promote the formation of diamonds.

Further preferably, the lignin is at least one of nano lignin, softwood lignin, broadleaf lignin, herbaceous lignin, alkaline lignin, and sodium lignosulfonate; the cellulose is Nanocellulose or pulp.

Further preferably, the method of mechanical crushing treatment is ball milling treatment, the rotating speed of the ball mill during the ball milling treatment is 200-400r/min, and the time of ball milling is 10-30h. During specific implementation, the rotating speed of the ball mill can be 200r/min, 250r/min, 300r/min, 360r/min or 400r/min, and the time of ball milling can be 10h, 15h, 18h, 25h or 30h.

Another object of the present invention is to provide the nano-diamond prepared by the method described above.

Compared with prior art, the beneficial effect of the present invention is:

In the present invention, after the plant fiber is made into a sheet-like plant fiber, the plant fiber is carbonized and the phase transition of carbon occurs through the laser irradiation effect of a femtosecond laser to generate nano-diamond. The method has the advantages of cheap and easy-to-obtain raw materials, simple synthesis method, mild conditions, high efficiency, simple operation and the like. The prepared nano-diamond has a particle size within 50nm and has high application value in the fields of micro-supercapacitors, sensors, wastewater treatment and the like.

Description of drawings

Fig. 1 is the transmission electron microscope picture of nano-diamond in embodiment 1.

FIG. 2 is a high-resolution transmission electron microscope image of nanodiamonds in Example 1.

3 is a transmission electron microscope image of nanodiamonds in Example 2.

FIG. 4 is a high-resolution transmission electron microscope image of nanodiamonds in Example 2.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments and accompanying drawings. It should be noted that the following examples are illustrative and not intended to limit the scope of the present invention. After reading the content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope of protection defined in the present application.

It should be noted that the various raw materials and reagents used in the following examples are all commercially available products, and will not be described in detail here.

Example 1

Put the pine lignin into a ball mill for 18 hours, set the speed of the ball mill to 360r/min, rest for 0.5h every 1 hour of work, and take it out after the ball milling to obtain lignin powder. Take 0.08 g of lignin powder and put it into a tablet press, and press with a pressure of 10 MPa to obtain disc-shaped lignin with a diameter of 13 mm and a thickness of about 1.0 mm. The disc-shaped lignin is placed on the XY workbench controlled by a computer program, and the femtosecond laser is used for laser radiation at normal temperature and pressure, and the irradiated lignin is transformed into nano-diamonds. Among them, the laser wavelength of the femtosecond laser is 1030nm, the laser frequency is 120kHz, and the pulse time is 150fs; the radiation conditions are laser power 1000mW, radiation time 30min, and the working speed of the workbench is 4mm/s.

Utilize transmission electron microscope to analyze the microstructure of nano-diamond, result as shown in Figure 1 and Figure 2, wherein: Fig. 1 is the transmission electron microscope figure of the nano-diamond of preparation, can find out the crystal grain of the nano-diamond that the present invention makes by Fig. 1 The size is relatively uniform, all below 50nm. Fig. 2 is a high-resolution transmission electron microscope image of nano-diamond. It can be seen from Fig. 2 that there are obvious nano-diamond lattice fringes, and the interplanar spacing is calculated to be 0.269nm, which corresponds to the (200) orientation of nano-diamond. Combining Fig. 1 and Fig. 2, it shows that the nano-diamond is effectively prepared by this method.

Example 2

Since the purchased nanocellulose is a nano-lignin dispersion with a concentration of 3%, take 100g of the above-mentioned nano-lignin dispersion (that is, the dry weight of the nano-cellulose is 3g), then mix it with 7g pine lignin and add Put the ball mill into the ball mill tank for 18 hours, set the speed of the ball mill to 360r/min, rest for 0.5 hours every 1 hour of work, take it out after the ball mill is finished, put it in a freeze dryer at -40°C for 72 hours, and obtain a cellulose/lignin compound things. Add 0.08 g of the cellulose/lignin composite into a tablet press, and press with a pressure of 10 MPa to obtain a disk-shaped cellulose/lignin composite with a diameter of 13 mm and a thickness of about 0.9 mm. The disc-shaped cellulose/lignin composite is placed on an XY workbench controlled by a computer program, and a femtosecond laser is used for laser radiation at normal temperature and pressure, and the raw material after radiation is transformed into nano-diamonds. Among them, the laser wavelength of the femtosecond laser is 1030nm, the laser frequency is 120kHz, and the pulse time is 150fs; the radiation conditions are laser power 700mW, radiation time 30min, and the working speed of the workbench is 5mm/s.

Utilize transmission electron microscope to analyze the microstructure of nano-diamond, result as shown in Figure 3 and Figure 4, wherein: Fig. 3 is the transmission electron microscope figure of the nano-diamond of preparation, can find out the crystal grain of the nano-diamond that the present invention makes by Fig. 1 The size is relatively uniform, all below 50nm. Figure 4 is a high-resolution transmission electron microscope image of nano-diamond. It can be seen from Figure 4 that there are obvious nano-diamond lattice fringes. The calculated interplanar spacing is 0.27nm and 0.31nm, corresponding to (200) and (111) of nano-diamond respectively. )orientation. Combining Fig. 3 and Fig. 4, it shows that the nano-diamond is effectively prepared by this method. And compared with Example 1, after adding cellulose to pine lignin, the laser power required for preparing nanodiamonds is lower, which can reduce energy consumption.

Example 3

Take 30g of pulp and tear it into sheets, add 1500mL of deionized water and soak for 6h. The soaked pulp and deionized water were added to a deflaker for 5 minutes, and the deflagged liquid was repeatedly filtered 3 times, and the deflagged pulp was prepared into a cellulose dispersion with a concentration of 3 wt.%. Put the cellulose dispersion with a dry weight of 7g and 3g of eucalyptus lignin into a ball mill for 18 hours, set the speed of the ball mill to 360r/min, and rest for 0.5h every 1 hour of work. After the ball milling, take out the mixture and place it at -40 ℃ for 72 hours in a freeze dryer to obtain a cellulose/lignin composite. Take 0.08 g of the cellulose/lignin composite and put it into a tablet press, and press at a pressure of 10 MPa to obtain a disk-shaped cellulose/lignin composite with a diameter of 13 mm and a thickness of about 0.9 mm. The disc-shaped cellulose/lignin composite is placed on an XY workbench controlled by a computer program, and a femtosecond laser is used for laser radiation at normal temperature and pressure, and the raw material after radiation is transformed into nano-diamonds. Among them, the laser wavelength of the femtosecond laser is 1030nm, the laser frequency is 120kHz, and the pulse time is 150fs; the radiation conditions are laser power 150mW, radiation time 60min, and the working speed of the workbench is 90mm/s.

Example 4

Take 30g of pulp and tear it into sheets, add 1500mL of deionized water and soak for 6h. The soaked pulp and deionized water were added to a de-flaker for 5 minutes, and the de-flatter was repeatedly filtered three times, and the obtained de-flaker was prepared into a cellulose dispersion with a concentration of 3 wt.%. Put the cellulose dispersion with a dry weight of 5g and 5g of pine lignin into a ball mill for 18 hours, set the speed of the ball mill to 360r/min, rest for 0.5h every 1 hour of work, take out the mixture after ball milling, and place it at -40°C Freeze drier for 72 hours to obtain cellulose/lignin composite. Add 0.08 g of the cellulose/lignin composite into a tablet press, and press with a pressure of 10 MPa to obtain a disk-shaped cellulose/lignin composite with a diameter of 13 mm and a thickness of about 0.9 mm. The disc-shaped cellulose/lignin composite is placed on an XY workbench controlled by a computer program, and a femtosecond laser is used for laser radiation at normal temperature and pressure, and the raw material after radiation is transformed into nano-diamonds. Among them, the laser wavelength of the femtosecond laser is 1030nm, the laser frequency is 120kHz, and the pulse time is 150fs; the radiation conditions are laser power 450mW, radiation time 35min, and the working speed of the workbench is 30mm/s.

Example 5

Put the nanocellulose dispersion with a dry weight of 6g and a concentration of 3wt.% and 4g of eucalyptus lignin into a ball mill for 12 hours, set the speed of the ball mill to 360r/min, rest for 0.5h every 1 hour of work, and take it out after the ball mill. , placed in a freeze dryer at -40°C for 72 hours to obtain a cellulose/lignin composite. Add 0.08 g of the cellulose/lignin composite into a tablet press, and press with a pressure of 10 MPa to obtain a disk-shaped cellulose/lignin composite with a diameter of 13 mm and a thickness of about 0.9 mm. The disc-shaped cellulose/lignin composite is placed on an XY workbench controlled by a computer program, and a femtosecond laser is used for laser radiation at normal temperature and pressure, and the raw material after radiation is transformed into nano-diamonds. Among them, the laser wavelength of the femtosecond laser is 1030nm, the laser frequency is 120kHz, and the pulse time is 150fs; the radiation conditions are laser power 300mW, radiation time 30min, and the working speed of the workbench is 60mm/s.

Example 6

Put the nanocellulose dispersion with a dry weight of 2g and a concentration of 3wt.% and 8g of eucalyptus lignin into the ball mill for 12 hours, set the speed of the ball mill to 360r/min, and rest for 0.5h every 1 hour of work, and take it out after the ball mill. , placed in a freeze dryer at -40°C for 72 hours to obtain a cellulose/lignin composite. Add 0.08 g of the cellulose/lignin composite into a tablet press, and press with a pressure of 10 MPa to obtain a disk-shaped cellulose/lignin composite with a diameter of 13 mm and a thickness of about 0.9 mm. The disc-shaped cellulose/lignin composite is placed on an XY workbench controlled by a computer program, and a femtosecond laser is used for laser radiation at normal temperature and pressure, and the raw material after radiation is transformed into nano-diamonds. Among them, the laser wavelength of the femtosecond laser is 1030nm, the laser frequency is 120kHz, and the pulse time is 150fs; the radiation conditions are laser power 900mW, radiation time 30min, and the working speed of the workbench is 10mm/s.

Claims (6)

1. a method for preparing nano-diamond with plant fiber as raw material, is characterized in that: the steps are as follows: (1) adding plant fiber raw materials into a ball mill, and obtaining plant fiber powder after being pulverized and mixed by ball milling; the plant fiber raw materials are a mixture of lignin and cellulose; (2) tableting the plant fiber powder to obtain sheet-like plant fibers; (3) Using a femtosecond laser to irradiate sheet-shaped plant fibers with laser at normal temperature and pressure, under the action of laser irradiation, the plant fibers undergo carbonization and carbon phase transition occurs at the same time to generate nano-diamonds; the laser of the femtosecond laser The power is 100mW~1000mW, and the laser radiation time is 1~60min. 2. The method according to claim 1, characterized in that: the lignin is at least one of nano lignin, broad-leaved wood lignin, herbaceous lignin, alkaline lignin, sodium lignosulfonate; The cellulose is nanocellulose or pulp. 3. The method according to claim 1, characterized in that: in step (1), the rotational speed of the ball mill during the ball milling treatment is 200-400 r/min, and the ball milling time is 10-30 hours. 4. The method according to claim 1, characterized in that in step (2), the pressure of the tableting process is 5-10 MPa, and the thickness of the sheet-like plant fibers is 0.2-2 mm. 5. The method according to claim 1, characterized in that: in step (3), the method of using a femtosecond laser to irradiate the plant fiber membrane with laser light is: placing the plant fiber membrane on a workbench controlled by a computer program. 6. The method according to claim 5, characterized in that: the running speed of the workbench is 1 mm/s˜100 mm/s.