Invention Journal of Research Technology in Engineering & Management (IJRTEM) ISSN: 2455-3689 www.ijrtem.com Volume 1 Issue 12 ǁ September. 2017 ǁ PP 18-24
Grinding graphene characteristics after physical process 1,
Ji-Hye Kim , 2,Gwi-Nam Kim , 3,Jung-Pil Noh , 4,HyoMin Jeong , 5,Sun-Chul Huh
1,2,3,4,5,
(Department of Energy and Mechanical Engineering, Gyeongsang National University, Republic of Korea)
ABSTRACT : Graphene features higher thermal conductivity than copper. However, despite its superior property, the research on its applicable technology was limited since the van der Waals’ forces between graphene. As a solution to such problem, research on making graphene distributed evenly in solvent is being actively conducted via physical and chemical method. Because the chemical method is likely to have harmful effect on the environment, we used the environmental-friendly process that does not consume toxic chemicals, and suitable for application. In this study, ball milling process controllable a range of experiment conditions more easily and conveniently than other physical methods was conducted so as to disperse graphene evenly in solvent and improve the thermal conductivity. Therefore, the effect of milling process was confirmed in TEM image and Raman ratio, and the shearing force makes the edge of graphene piece defective. When graphene is evenly dispersed, the wide specific surface area absorbs a great deal of light, improving absorbance. We confirmed the absorbance of pristine graphene was showed below milling graphene and considerable thermal conductivity increase compared to pristine graphene.
Keywords: Ball milling, Graphene, Nano-fluid, Physical process, Thermal conductivity I. INTRODUCTION Theoretical background: Emerging as a topic of nano scientific technology in 21st century, a range of nano carbon materials including graphene, carbon nano tube and carbon nano fiber became familiar terms even to the general public and symbol of scientific technology in the future. Graphene features having wider specific surface area, 200 times higher mechanical strength than steel but as much flexibility, 100 times higher electrical conductivity than copper, more superior thermal conductivity (around 5000W/mk) than diamond, optical characteristic of transmitting 97.7% of incident-light and high stability in structural and chemical way. Graphene is also recognized as the highest potential core material that can replace the existing electronic device based on silicon as the mobility of its electron in room temperature is 100 times as high as silicon, exceeding 200,000cm2/V᛫s. Since diverse chemical functionalization of graphene is possible, the possibility of controlling its superior property was presented in a range of methodology, resulting in active research on its application across industries such as electronic device, optical device, electrically conducting composite material, sensor, clear electrode, transistor, organic solar cell, and composite material with ultra-light ᛫ high intensity. [1-5] However, despite its superior property, the research on its applicable technology was very limited since the van der Waals’ forces between graphene and its very stable chemical structure prevent graphene from being evenly distributed in solvent, making it difficult to manufacture graphene nano-fluid with uniform feature. As a solution to such problem, research on making graphene distributed evenly in solvent is being actively conducted via physical and chemical method. The chemical method is separating graphene in solution state chemically via oxidant. Graphene oxide oxidized with strong acid and oxidizer assumes strong hydrophilic property and is separated with ease via ultrasonic waves. The graphene oxide then undergoes the reduction process additionally, turning into reduction graphene with structure and property equivalent to almost original graphene though in not perfect state. The chemical method is also likely to have harmful effect on the environment in that the research on applicable fields of graphene material will increase, and is unreasonable in terms of cost, thus generating active research on environmental-friendly, inexpensive and novel stripping method than can replace the chemical method. [6-8] There is a manufacture method of directly distributing graphene via surfactant without going through oxidation process. The method, however, has no substantial effect due to the inter-layer resistance of nano-scale graphene pieces, and has fatal disadvantage that the dispersion in nano-fluid is not improved than the chemical method and others. [9] Meanwhile, the dispersed graphene in solution made by the chemical method has the advantage of being employed in various ways by forming compound with other substances. Though reduced graphene assumes less electrical property than that made by mechanical method, it is differentiated from other manufacture processes in its applicability such as solution process with low production cost, the film thin and easy for mass production, and complex formation with other substances. The recent several studies revealed that the layers of carbon allotropes are comparatively easily separated in the environment with shearing force acted, and if proper surface stabilizer is employed at this stage in order to prevent re-cohesion, carbon allotropes are separated without chemical process to the extent of at least three layers of graphene being stuck together.
| Volume 1 | Issue 12 |
www.ijrtem.com
| 18 |