[0042] Example 1
[0043] The isopropyl alcohol aqueous solution is used as the stripping liquid, graphite is used as the raw material, and the low-layer graphene material is prepared by coupling of high gravity.
[0044] Among them: the specific gravity of the stripping liquid is between 0.955 and 0.956 g/ml, and it starts to freeze below -8°C, and the stripping liquid can completely wet the graphite flakes.
[0045] This embodiment adopts Figure 5 The shown high-gravity coupling preparation of two-dimensional nanomaterials is realized by the device, which includes a cooling circulation system composed of a refrigerating circulation pump 7 and a tubular heat exchanger 8, a high-gravity circulation stripping system, and a high-gravity circulation concentration system. The gravity circulation stripping system includes a high-gravity coupling machine 11 connected with the first metering tank 10, the first magnetic pump 9 and the cooling circulation system through a pipeline; the high-gravity circulation concentration system includes a second metering tank 13 through a pipeline, The second magnetic pump 14 and the high-gravity coupling machine II 12 communicated with the conductivity meter 15.
[0046] Such as figure 1 As shown, both the high gravity coupling machine I and the high gravity coupling machine I have a streamlined structure of a turntable 18 and a power generating motor 16. The turntable includes a high gravity separation unit 5 located inside and a high gravity mixing unit 6 located outside. The high gravity separation unit is a U-shaped tube formed by the double-sided symmetrical rotating impeller 1 and the upper cover plate 19 and the lower cover plate 20; the high gravity mixing unit is a groove formed on the upper cover plate 19 and the lower cover plate 20. The secondary rotating flow channel 3 formed by the groove (see figure 2 ), the center of the bottom of the U-shaped tube of the high-gravity coupling machine I and the high-gravity coupling machine II is provided with a slurry inlet 22, and the bottom two sides of the U-shaped tube are provided with a concentrated slurry discharge communicating with the secondary rotating flow channel. Port 2, where the dilute solution outlet 4 is provided on both sides of the open end of the IU tube of the high gravity coupling machine, and the stripping liquid outlet 4 is provided on both sides of the open end of the IU tube of the high gravity coupling machine. The flow section of the secondary rotating flow channel of the high-gravity coupling machine I is a circular section with a diameter of 2.5 mm and a radial length of 60 mm; the flow section corresponding to the high-gravity coupling machine II is a circular section with a diameter of 2.0 mm and the radial length is 30 mm; the separation unit includes a double-sided symmetrical rotating impeller and a supergravity separation chamber; image 3 As shown, there are 12 impellers on the front and back sides of the double-sided symmetric impeller, and a feed liquid inlet 21 is provided between adjacent impellers, a total of 12 impellers.
[0047] In the process of preparing graphene, the rotational speeds of the high-gravity coupling machines I and II are 4500 rpm and 5500 rpm, respectively, and the maximum high-gravity field levels within one rotation of the two separation units are 3170 g and 4733 g, respectively (g is Normal gravitational field acceleration), the device can achieve such as Figure 4 The synchronization of the three cycles shown is performed efficiently.
[0048] (1) Such as Figure 5 As shown, the step of starting the refrigeration cycle: disperse the flake graphite material in the dispersion to obtain graphite slurry, pour the slurry into the first metering tank 10, turn on the refrigeration cycle pump 7 and the first magnetic pump 9 to make the slurry in the tube There is a circulating cooling flow between the heat exchanger 8 and the first metering tank 10, so that the temperature of the slurry drops to -2°C, and the concentration of the low-temperature graphene slurry is controlled at 3.0 g/L.
[0049] (2) Such as Figure 4 As shown, start the three loop steps:
[0050] This step includes two small cycles, namely the cyclic stripping of the graphite slurry and the cyclic concentration of the graphene slurry, and one large cycle, the cycle between the stripping liquid and the graphene solution, and the three cycles are performed simultaneously.
[0051] In the cyclic peeling process, there is a peeling balance between graphite and graphene. The graphite slurry circulates between the first metering tank 10, the tubular heat exchanger 8 and the high gravity coupling machine I 11, and the graphite slurry enters the high gravity The low-concentration graphene solution and the high-concentration graphene slurry are first separated in the coupling machine I 11, and the flow rates of the two are similar. The separated low-concentration graphene solution flows into the high-gravity coupling machine II 12 for cyclic concentration.
[0052] The high-concentration graphite slurry continues to flow through the secondary rotating flow channel in the high-gravity coupling machine I 11 to exfoliate new graphene, and then return to the first metering tank 10, where it is coupled with the high-gravity coupling machine. The stripping liquid flowing out of machine II 12 is mixed and diluted to close to the original concentration, and then continuously cyclic stripping. The stripping balance of the material liquid is updated twice every week of circulation. As the graphite concentration will continue to decrease, new high-concentration graphite slurry needs to be supplemented. The feeding method can choose continuous feeding or intermittent feeding.
[0053] At the same time, the cyclic concentration process is also in rapid progress. The graphene slurry is cyclically concentrated between the second metering tank 13, the liquid flow meter, the conductivity meter 15 and the high gravity coupling machine II 12. With the adsorption balance between the monodisperse graphene and the graphene soft aggregates, the flow rate and conductivity of the slurry are monitored simultaneously. After the graphene slurry enters the high gravity coupling machine II 12, the first separation is close to colorless and transparent. The high-concentration graphene slurry flows back into the cyclic stripping process, and the high-concentration graphene slurry flows into the secondary rotating flow channel of the high gravity coupling machine II to be dispersed into small graphene clusters. These graphene clusters After the clusters are uniformly mixed with the low-concentration graphene solution, they are merged into the second metering tank 10 together. During this process, the dispersed graphene clusters quickly adsorb free graphene, so that the free graphene concentration in the graphene slurry is fast Reduce, and then continue to circulate and concentrate. The adsorption balance of the feed solution is updated twice per cycle. In order to stabilize the concentration of the graphene slurry, some high-concentration graphene slurry (graphene content about 1 g/L) needs to be discharged and discharged The method can choose continuous discharge or intermittent discharge.
[0054] Such as figure 1 As shown, during the preparation process, the concentrated slurry outlet 2 of the high-gravity coupling machine I flows out of the thick graphite slurry, and the graphite slurry enters from the slurry inlet 22 in the center of the bottom of the U-shaped tube, and exits from the dilute solution. The dilute graphene solution flows out of the feed port 4. The concentrated slurry outlet 2 at the bottom of the U-shaped tube of the high gravity coupling machine II flows out of the concentrated graphene fine slurry, and the graphene fine slurry enters from the slurry inlet 22 on the top of the U-shaped tube, and it exits from the stripping liquid. The graphene peeling liquid flows out from the material port 4. In the process of preparing graphene, the rotational speeds of the high-gravity coupling machines I and II are 4500 rpm and 5500 rpm, respectively. At this rotational speed, the highest supergravity field levels inside the separation unit of the two are 3170 g and 4733 g (g is the normal gravity field). Acceleration).
[0055] In the high-gravity coupling machine I, the flow rates of the concentrated graphite slurry and the graphene solution are similar; the axial average linear velocity of the concentrated graphite slurry is 50m/s. During the peeling process, the temperature is controlled at -2 to -4°C; during the concentration process, the temperature is controlled at 2 to 4°C.
[0056] Characterize the few-layer graphene obtained by exfoliation in this example:
[0057] Image 6 with Figure 7 It is a SEM electron micrograph of graphene.
[0058] Figure 8 AFM photo of graphene exfoliated by high gravity coupling method, Picture 9 Is the corresponding graphene sheet thickness curve, from Picture 9 It can be seen that the thickness of the graphene nanosheet is less than 1 nm, and the theoretical thickness of a single layer of graphene is 0.34 nm. If the number of graphene layers in the graphene layer spacing is calculated as two layers. Characterization by atomic force microscopy can prove that few-layer graphene (mostly double-layer or triple-layer graphene) with a lateral size greater than 2 μm can be obtained by the high-gravity coupling method.
[0059] Picture 10 It is a graphene XRD comparison chart of graphite raw material, ultrasonic peeling and high-gravity coupling peeling. It can be seen from the figure that the (004) plane of graphite almost disappears at 55 degrees, indicating that it has a vertical stacking dimension. The order structure is disrupted, which proves that the multi-layer graphite is exfoliated into few or single-layer graphene. The XRD results of the graphene exfoliated by the ultrasonic method and the high-gravity coupling method are consistent.
