Among various methods used for the reduction of graphene oxide go into a purer form of graphene, the thermal reduction method provides a simpler, safer, and economic alternative, compared to other techniques. Graphene hybrid sio2 hierarchical dual network aerogel. Only the spectra for annealing temperature of 2008c and above were analyzed in this study due to the possible charging effect for thermal reduction of graphene oxide 75 where d 002 is the thickness of crystallite here, gp thickness, k is a constant dependent on the crystallite shape 0. However, if the nanostructured layers are formed on metallic iron substrates, the thermal annealing leads to the formation of gradient oxide layers consisting of wustite feo, magnetite fe 3 o 4. We observed a drastic increase in density of states. Raman spectra of the annealed graphene show both the 2d peak and g peak blueshift. Due to its unique optical and electrical properties, go can be used as, for example, a transparent and flexible electrode material in organic and printed electronics. Thermal conductivity of freestanding reduced graphene oxide.
Phonon dispersion of graphene t o understand the thermal properties of graphene, one must. Rapid thermal exfoliationreduction of graphite oxide is a fast and easy method among the oxidationreduction approaches for graphene. Jan 28, 2019 graphene oxide go is useful and promising material for graphene based applications in electronic, optics, chemistry, energy storage, and biology. Valence band electronic structure evolution of graphene oxide. Switch on the high thermal conductivity of graphene paper. Conventional thermal annealing, however, comes with some drawbacks, such as hightemperature annealing along with longer process times and structural damage that hinders the applicability of go as a transparent conductor. Furthermore, when graphenebased materials are interacting with the surrounding environment, e. Hojatitalemi, 2010, with solvothermal method tran, 20. This leads to the formation of three acoustic a and 3 n 3 3 optical o phonon modes. Flexible conductive graphene paper obtained by direct and. The electronic and chemical properties of graphene can be modulated by chemical doping foreign atoms and functional moieties.
However, unlike its counterpart graphene the thermal transport properties of. Understanding the thermal reduction of graphene oxide go is important for graphene exfoliation, and chemical and morphological modi. Graphene films have attracted much attention as a heat dissipation material due to their unique thermal transfer behavior that exceeds that the performance of graphite. The degree of reduction of the rgo powders was controlled by varying the thermal annealing temperature. Highconcentration boron doping of graphene nanoplatelets by simple thermal annealing and their supercapacitive properties. The go sheets were tightly coated and covalently attached to cf surfaces. Jul 18, 2016 additionally, to give a clear evolution from the graphene oxide liquid crystal to longrange ordered graphene fibers, a structure evolution model has been built. Graphene oxide go has been accepted as a costeffective source for scaleup amount of graphene, the controllable assembly of which towards functional structure e. Valenceband electronic structure evolution of graphene. The effects of thermal annealing on the tape residues and edges of graphene are researched. Go was first chemically reduced with hydrazine to substantially increase the formation of c c bonds and simultaneously decrease the atomic oxygen concentration. Enhancement of quaternary nitrogen doping of graphene oxide. No change of the coating properties is required during this process. Here, we investigated the bulk electrical conductivity of reduced graphene oxide rgo powders depending on.
Physical properties investigation of reduced graphene. Probing the thermal deoxygenation of graphene oxide using. Salt rejection and selectivity can be feasibly tuned by mild annealing time. The influence of thermal annealing to remove polymeric. The high defect density in graphene is reflected by r 2d22526 cm 1. Mild annealing reduced graphene oxide membrane for. For the onestep thermal annealing graphene, the heat graphite oxide in air heat one step thermal annealed graphene in air a. The high thermal conductivity and stability, outstanding mechanical properties, and low weight make graphene suitable for many applications in the realm of thermal management, especially in high integration systems. Thermal annealing of graphene monolayers transferred from cu to sio2si substrate has been investigated to.
Graphene has outstanding properties that make it an auspicious material for many applications. For preparing highquality graphene, hightemperature annealing was shown to be necessary and the layers of rgo expanded due to the release of cox gases. It can be proved that thermal annealing is an efficient way to fabricate highstrength graphene fibers. Atomicscale investigation of graphene grown on cu foil. Monolayer graphene is obtained by mechanical exfoliation using scotch tapes. Many attempts have been made to synthesize rgo, either by chemical reduction or thermal annealing of go or a combination of both, to resemble pristinetype graphene, or at least to attain better conducting properties closer to those of pristine graphene. Synthesis of the igraphene graphene oxide go was purchased from tianjin plannano co. Scanning electron microscopy sem and optical images were used to evaluate. Facile thermal annealing of graphite oxide in air for graphene with a. Electrical measurements of thermally reduced graphene. Here, a new and effective methodology of preparing nitrogen. Pdf remarkable conversion between n and ptype reduced. Spectroscopic ellipsometry was used to characterize the optical response of the. Effect of thermal annealing on the heat transfer properties.
Effect of annealing on doping of graphene with molybdenum. We also did the test to compare the tga of reduced graphene oxide and graphite 94 oxide in air, as shown in fig. Jan 28, 2014 graphene oxide is being used in energy, optical, electronic and sensor devices due to its unique properties. Thermal annealing is a process at which the temperature t of the part coated by a coating is at first increased from rt to a maximal operation temperature t max, and later, after finishing the operation e. Rapid thermal exfoliationreduction of graphite oxide is a fast and easy method among the oxidationreduction approaches for graphene synthesis. In this study, we demonstrated that bdoped graphene nanoplatelets can be prepared by simple thermal annealing of go nanoplatelets combined with boron oxide b 2 o 3. To allow for the use of graphene in various nanoelectronic applications, the methods for the largescale production of graphene with controllable electrical properties need to be developed. The process of graphene transfer generally involves a polymer support. Remarkable conversion between n and ptype reduced graphene. Herein, we report a highperformance, lowtemperature reduced graphene oxidemagnetic carbon.
The degree of oxygen functionalization was controlled by annealing temperature, and an electronic structure evolution was monitored using real. The strategy employed in this work was to modify graphene oxide go prior to thermal annealing so as to provide a more efficient structure for quaternary n doping. The role of oxygen during thermal reduction of graphene oxide. Catalystfree synthesis of iodinedoped graphene via a. Scalable enhancement of graphene oxide properties by thermally driven phase transformation priyank v. Rapid and scalable fabrication of reduced graphene oxide. Jun 14, 2018 graphene has outstanding properties that make it an auspicious material for many applications. Comparing effects of thermal annealing and chemical reduction. Comparing effects of thermal annealing and chemical. The degree of oxygen functionalization was controlled by annealing temperature, and an electronic structure evolution was monitored. Thermal transport in graphene oxide from ballistic. The article is focused on the study of the optical properties of inkjetprinted graphene oxide go layers by spectroscopic ellipsometry. Dames1,a 1department of mechanical engineering, university of california, riverside, california 92521, usa 2department of physics and astronomy, university of california, riverside, california 92521, usa received 19 august 2009. The general approach to the synthesis of nitrogendoped graphene ng, such as chemical vapor deposition cvd performed in gas phases, requires transitional metal catalysts which could contaminate the resultant products and thus affect their properties.
Facile thermal annealing of graphite oxide in air for. Thermal transport in graphene oxide from ballistic extreme. Frontiers mapping of graphene oxide and single layer. It was found that the charge carriers in rgo for temperatures of 300450 c and 800 c are electrons ntype, whereas for temperatures of 450800 c.
The scientists stress the potential of using this method for. Igraphenes were prepared by annealing graphene oxide go and iodine at 5001100 the anneal treatment was carried out in a tube furnace with high purity argon as protective ambient. Interfacemediated extremely low thermal conductivity of. Catalystfree synthesis of nitrogendoped graphene via. Go could also react with the hydrated ions and has an important impact on the. In this research, we firstly demonstrated that graphene can be obtained with a surface area of 550 to 700 m2 g. We provide a systematic study of rta of graphene transistors with four different contact metals, cu, ag, au, and pd. We report valence band electronic structure evolution of graphene oxide go upon its thermal reduction. Highconcentration boron doping of graphene nanoplatelets by. The further studies revealed the substantial structure imperfection of graphene oxide. Microcrystalline graphene oxide mgo was reduced by thermal annealing to prepare reduced microcrystalline graphene oxide rmgo. Reduction of go with laser irradiation trusovas, 20, rgo from graphite oxide under ultraviolet irradiation ji, 20. Mild annealing enables more ordered laminar channels than high thermal annealing process.
Highly thermally conductive graphene film produced using. The graphene unit cell, marked by dashed lines in figure 1a, contains n 2 carbon atoms. C required to reduce the graphene oxide go films leads to high manufacturing costs and restricts its broader application in thermal management applications. Despite the recent developments in graphene oxide due to its importance as a host precursor of graphene, the detailed electronic structure and its evolution during the thermal reduction remain largely unknown, hindering its potential applications. Thermal annealing of graphene to remove polymer residues. Graphene exhibits unique structure which has a two dimensional single layered made of carbon. This work presents the production of graphene oxide go via the langmuirblodgett process and the subsequent restoration of single layer graphene flakes slgf via the chemical reduction, and thermal annealing of the go. Thermal reduction of graphene oxide 75 where d 002 is the thickness of crystallite here, gp thickness, k is a constant dependent on the crystallite shape 0. Grossman1 chemical functionalization of graphene is promising for a variety of nextgeneration technologies. Additionally, to give a clear evolution from the graphene oxide liquid crystal to longrange ordered graphene fibers, a structure evolution model has been built. Scalable enhancement of graphene oxide properties by. The general approach to the synthesis of nitrogendoped graphene ng, such as chemical vapor deposition cvd performed in gas phases, requires transitional metal catalysts which could contaminate the resultant products and thus affect.
Thermal contact resistance between graphene and silicon dioxide z. Only the spectra for annealing temperature of 2008c and above were analyzed in this study due to the possible charging effect for graphene oxide go is important for graphene exfoliation, and chemical and morphological modi. Nanocomposites a lot of research works have been reported on graphene or rgo andor go. Thermal contact resistance between graphene and silicon. Investigation of the thermal stability of the carbon. In this work, we implement rapid thermal annealing of graphene based. Graphene oxide go was employed as the sizing agent for continuous carbon fiber cf tows by an electrophoretic deposition and subsequent thermal annealing. Effect of thermal annealing on the heat transfer properties of. Water and salt transport mechanism in mrgo and hrgo was. Electrical measurements of thermally reduced graphene oxide. A collaborative research performed by scientists from uc riverside, moldova state university, and graphenea demonstrates that a method of reducing graphene oxide to graphene via a hightemperature treatment that increases thermal conductivity along the film direction, while decreasing it across the film.
At the beginning of graphene history go was only a simple and cheap step for preparation of single and multilayer graphene films and bulk structures by reduction. High temperature reduction process increases thermal. Thermal reduction methods in combination with ultrasonic or laser irradiation go can be reduced by microwaves in combination with thermal reduction chen, 2010. Electrophoretic deposition and thermal annealing of a. Mild annealing reduced graphene oxide membrane for nanofiltration. The electrical conductivity of graphene powders is critical for their uses in fabricating highperformance devices or materials. Doping nanoparticles doping nanoparticles onto graphene or go has been done for the following works brenner, 2012. Atomic force microscope images showed that almost all the residues could be removed in n 2 h 2 at 400c but only agglomerated in vacuum. Remarkable conversion between n and ptype reduced graphene oxide on varying the thermal annealing temperature. This paper reports on the thermal properties of reduced graphite oxide rgo flakes, studied by means of scanning thermal microscopy sthm.
Nitrogen doping significantly improves the electrochemical properties of graphene. Effect of low oxygen annealing on photoelectrochemical. As an example, the thermal conductivity of graphene was reported to decreases from about 20005000 w m1. Interfacemediated extremely low thermal conductivity of graphene aerogel yangsu xie a, shen xu a, zaoli xu a, hongchao wu a, cheng deng a, xinwei wang a, b, a 2010 black engineering building, department of mechanical engineering, iowa state university, ames, ia 50011, usa. Mechanical and thermal properties of graphene oxide filled. Recent advances in effective reduction of graphene oxide for. Degree of oxygen functionalization was controlled by annealing temperatures, and an electronic structure evolution was monitored using realtime ultraviolet photoelectron spectroscopy. Here, we investigated the bulk electrical conductivity of reduced graphene oxide rgo powders depending on the applied pressure and additional thermal annealing. Electrophoretic deposition epd is believed to be an effective and versatile approach for this purpose.
The gob 2 o 3 mixture was annealed at various temperatures to systematically control the efficiency of boron doping and the degree of reduction of go. Thermal annealing an overview sciencedirect topics. Recently, graphene oxide go has drawn extensive attentions in cement and concrete fields due to its unique features. Furthermore, when graphene based materials are interacting with the surrounding environment, e. Effect of thermal annealing on the electrochemical capacitive. Characterization of structural transformation of graphene oxide to reduced graphene oxide during thermal annealing. However, the highest defect density is determined after annealing ai go at 500 c r 2d30140 cm1, green dots in figure 2 and partial reconstruction of the graphene lattice can be observed after annealing ai go at c r 2d 12740 cm1, purple dots in figure 2. Valenceband electronic structure evolution of graphene oxide. We show that a combination of highresolution in situ xray photoemission and xray absorption spectroscopies offer a powerful. Raman spectra of the annealed graphene show both the 2d. Moreover, go exhibits large specific surface area and remarkable mechanical strength. Thermal treatment or chemical reducing agent is an efficient method to reduce graphene oxide go to graphene dubin et al. In this process, the role of trapped water and the evolution of oxygen during annealingarestillnotwellunderstood.
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