Preparation of graphene from carbon by-products of thermochemical process and restacking thereof

Abstract

The present invention relates to the concept and study of preparation of graphene from carbon by-product by thermochemical process, and restacking of graphene by cutting process via ultrasonic horn sonotrode. The characteristics of prepared graphene are examined by scanning electron microscope and energy dispersive X-Ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The results appear morphological surface of the graphene is 94.1% of carbon. Moreover, it is found that the characteristic of prepared graphene have a wrinkled structure, and have two diffraction rings, which related to the crystal plane (002) and (100), and observes that dots on the diffraction ring indicates the well-arranged hexagonal structure of the graphene. In addition, the XRD confirms peaks at the (002) and (004) crystal planes with reduced intensity and broad peak, which found the d-spacing of (002) crystal is 0.3856 nm, which is a characteristic of graphene that are separated obviously. Therefore, the quality and purity of the prepared graphene can be confirmed by the results of the characteristics disclosed in this invention.

Description

[0001] PREPARATION OF GRAPHENE FROM CARBON BY-PRODUCTS OF THERMOCHEMICAL PROCESS AND RESTACKING THEREOF

[0002] Field of the invention

[0003] Chemistry, especially related to the preparation of graphene from carbon by-products of thermochemical process, and restacking of said graphene by cutting process via ultrasonic.

[0004] Background of the invention

[0005] Graphene is a material consisting of a single-layer carbon atoms arranged in a two- dimensional plane with a hexagonal structure, similar to a honeycomb or henhouse mesh. The graphene has an sp2hybridization, which bonded by strong covalent bonds, so that making graphene a thin sheet with a thickness of 0.34 nm. The graphene has outstanding properties, for examples, hardness which stronger than steel and diamonds, conductivity which is better than copper, transparency, and high flexible. The graphene also has a theoretical surface area up to 2,630 m2 / g, which is suitable for a variety of applications, for examples, high-speed logic devices, thermal and conductive composites, electrochemical sensor, transparent electrodes for displays and solar cells. However, the widespread use of graphene has not yet occurred for the reason that the difficulty in producing high quality graphene, especially in a scalable form since the performance of graphene depends on both the number of layers and the overall quality of the structure, and significantly, the cost limitation that requires high-quality graphite without metal impurities, which is expensive to synthesize and produce good quality graphene.

[0006] Biomass is waste from the agricultural production. In each year, tons of biomass from agricultural products, for examples, rice, sugarcane, com, cassava, rubber, and oil palm, which cause waste biomass of, for examples, husks, straws, cobs, barks, trunks, branches, treetops, leaves, roots, and wood slabs, that is high proportion compared with product. Moreover, the leftovers, for examples, dust from the wood processing process, which is currently being used as a biomass fuel for renewable energy production via biomass conversion, including physical, thermochemical, and biological conversion processes. It appears that the thermochemical process produce carbon by-product, which is further disposed, or applied to non-value added works.

[0007] Biomass conversion by thermochemical processes include direct combustion, pyrolysis and gasification. Each process has a difference in the use of oxygen in combustion. That is, direct combustion uses oxygen, pyrolysis process does not use oxygen, and gasification uses some oxygen. After combustion, thermal energy is generated for use to boil water to produce steam vapor to circulate in a steam turbine, or use of combustible gas to a generator to produce electricity. Moreover, char or biochar, which is a by-product of this process, is obtained and disposed by filling to the land, or producing fertilizer, or compressed charcoal, for examples.

[0008] Graphene can be prepared from graphite with high purity and low metal impurities, which therefore cause graphene high cost in production. Conventionally, graphene can be prepared by, for examples, micromechanical cleavage, chemical synthesis through oxidation of graphite, chemical vapor deposition (CVD), solvothermal synthesis, and electrolytic exfoliation. However, it was found that such processes still have scale-up limitation, expensive instrument, and non-environmental friendly processes.

[0009] This present invention represents a process for preparing graphene from carbon materials which are by-products of thermochemical process, purification, and restacking of said graphene respectively by cutting process via ultrasonic horn sonotrode in order to obtain high quality and pure graphene.

[0010] Summary of the invention

[0011] This invention relates to the preparation of graphene by thermochemical process and the restacking of said graphene by cutting process via ultrasonic horn sonotrode, and show the results of characteristics of the prepared graphene by scanning electron microscope and energy dispersive X-Ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), and X- ray diffraction (XRD) with the following processes and steps of the preparation.

[0012] - Preparation of graphene from carbon by-products of thermochemical processes, including direct combustion, pyrolysis and gasification.

[0013] - Purification and restacking of graphene by cutting process via ultrasonic horn sonotrode.

[0014] - Characterization of graphene using SEM-EDS, TEM, and XRD.

[0015] Various purposes and features of the present invention will become clearer when considered together with the accompanying drawings and the best detailed description of the invention which will be described below.

[0016] Brief description of the drawings

[0017] Figure 1 illustrates a process flow diagram of the preparation of graphene from carbon by-products of the thermochemical process. Figure 2 illustrates the SEM images of a) the carbon by-product prepared by the thermochemical process and b) the prepared graphene.

[0018] Figure 3 illustrates the SEM images and element analysis via X-ray of a) the carbon byproduct prepared by the thermochemical process and b) the prepared graphene.

[0019] Figure 4 illustrates the TEM images of a) the prepared graphene, and b) the results of selected area electron diffraction (SAED) analysis.

[0020] Figure 5 illustrates the X-ray diffraction patterns of a) the carbon by-product prepared by the thermochemical process and the prepared graphene, and b) the X-ray diffraction patterns of the prepared graphene at high magnification.

[0021] Detailed description of the invention

[0022] This description of this invention will be made by illustrating the invention and referring to it by means of drawings and photographs to illustrate and clarify the description, and identical parts in these drawings will be represented by the same reference numbers. This is without any limitation and the scope of the invention will be in accordance with the appended claims.

[0023] Figure 1 illustrates the process flow diagram of the graphene preparation process which shows the carbon by-product of the thermochemical process, through a purification process to remove organic substances and impurities by using the leaching process, in combination with high-speed centrifugation selection. Then, the drying process is performed, and continue to the characterization process via SEM-EDS. After obtained the carbon without organic substances and impurities, the carbon is dispersed in dispersive medium in order to separate and restack by cutting process via ultrasonic horn sonotrode, using specific property of eddy current in the reactor to produce multi-batch reaction. The reactor is oftentimes used in biology, physics, and chemistry in order to produce the reaction to special environments in mixing, extraction, crystallization, separation, and cultivation. However, it does not currently appear the report that the reactor is used in the graphene preparation, so that the fluid is subject to uncertainty and produces double vortexes that flow in the direction of the normal rotation of the shaft, while it flow in the opposite direction at the same time, that called Taylor vortex. When the carbon byproduct is introduced into the reactor, and when the reactor is working, the above-mentioned eddy current causes shearing stress on carbon by-product. Because the shear stress exerts a force in the opposite direction along the side of the carbon by-product, this allows each layer of carbon to be easily peeled. Meanwhile the peeling of the carbon layer can be executed by using the reactor as described above. Each layer of carbon is peeled by shear forces inside the reactor. Therefore, we can use a device to control for accelerating the speed of the rotation of the reactor, and peeling off the carbon into sheets in order to produce graphene. The obtained graphene can be applied for the various applications, for examples, nanoscale of electrical and electronic devices, nanosensors, optoelectronic devices, and high performance composites. After that, the product is filtered in order to separate the graphene from the medium, and then dried, and reduced in particle size (by grinding), respectively, in order to obtain the graphene.

[0024] Figure 2 illustrates the characteristic result by the SEM of a) the carbon by-product prepared by the thermochemical process and b) the prepared graphene. The result shows that the carbon by-product of the thermochemical process have a morphology that is grouped as graphite with organic substances and impurities, while the graphene have a morphology as a thin sheet that is stacked in layers, and spread throughout without organic substances or impurities.

[0025] Figure 3 illustrates the characteristic result by the SEM images and element analysis via X-ray of a) the carbon by-product prepared by the thermochemical process and b) the prepared graphene. From the result, it appears that the carbon by-product of the thermochemical process has a morphological surface at 68.9% of carbon, and has organic substances and impurities, including 31.1% of oxygen, calcium, magnesium, phosphorus, potassium, silicon, and aluminium. Meanwhile, the morphological surface of the graphene includes 94.1% of carbon, and 5.9% of organic substances and impurities, which shows the quality and purity of the prepared graphene.

[0026] Figure 4 illustrates the characteristic result by the TEM images of a) the prepared graphene, and b) the results of selected area electron diffraction (SAED) analysis. The results shows that the prepared graphene have a wrinkled structure caused by the thermochemical process and the presence of oxygen groups in the structure. In addition, the analysis of the electron diffraction patterns also shows the characteristics of two diffraction rings, which related to the crystal plane (002) and (100), and observes that dots on the diffraction ring indicates the well-arranged hexagonal structure of the graphene.

[0027] Figure 5 illustrates the characteristic result by the X-ray diffraction patterns of a) the carbon by-product prepared by the thermochemical process and the prepared graphene, and b) the X-ray diffraction patterns of the prepared graphene at high magnification. The results shows that carbon by-product from thermochemical process appears peaks at 2 theta of 26.38° and 54.54°, respectively, which indicate the characteristic (002) and (004) crystalline planes of graphite. Moreover, it appears that the d-spacing of (002) crystal is 0.3375 nm, which is approximately to the theoretical d-spacing of graphite of 0.3340 nm. The degree of graphitization is calculated to be 75.58 %, while the prepared graphene appears X-ray diffraction peaks at the (002) and (004) crystal planes with reduced intensity and broad peak, which found the d-spacing of (002) crystal is 0.3856 nm, which is a characteristic of graphene that are separated obviously. Although the present invention has been described in detailed description by means of the attached drawings, it is understood that modifications or alterations by a person who skilled in the art and science, within the scope and purpose of the invention, can be made. The scope of the present invention shall be in accordance with the embodiment of the invention as stated in the appended claims, including aspects of the invention, although it is not specifically stated in the claims, have a utility and produce results similar to those of the invention as stated in the claims.

[0028] Best mode for carrying out the invention

[0029] Best mode or preferred embodiment of the invention is as provided in the description of the invention.

Claims

CLAIMS1. A graphene prepared from carbon by-products of direct combustion thermochemical processes.

2. A graphene prepared from carbon by-products of pyrolysis thermochemical process.

3. A graphene prepared from carbon by-products of gasification thermochemical process.

4. The graphene prepared from carbon by at least two thermochemical processes as claimed in any one of claims 1 to 3.

5. The graphene as claimed in any one of claims 1 to 4, having restacking from cutting process via ultrasonic horn sonotrode.

6. The graphene as claimed in claim 5, wherein the dispersion medium is water and deionized water.

7. The graphene as claimed in claim 5, wherein the dispersion medium is a polar aprotic organic solvent.

8. The graphene as claimed in claim 5, wherein the dispersion medium is an organic solvent having a neutral in acid-base property.

9. The graphene as claimed in claim 5, wherein the dispersive medium is thermoplastic polymer, which selected from polystyrene, polyethylene, polypropylene, polyvinyl chloride, nylon, polyamide, polyacrylonitrile, or the combination thereof.

10. The graphene as claimed in claim 5, wherein the dispersive medium is thermosetting polymer, which selected from polyurethane resin, phenolic resin, urea formaldehyde resin, melamine formaldehyde resin, polyester resin, epoxy resin, or the combination thereof.

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