For an improved mechanistic understanding of the e. Nanocomposites a lot of research works have been reported on graphene or rgo andor go. Mild annealing enables more ordered laminar channels than high thermal annealing process. Graphene oxide go was employed as the sizing agent for continuous carbon fiber cf tows by an electrophoretic deposition and subsequent thermal annealing. 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. 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. Graphene oxide go has been accepted as a costeffective source for scaleup amount of graphene, the controllable assembly of which towards functional structure e. Graphene has outstanding properties that make it an auspicious material for many applications. Here, we investigated the bulk electrical conductivity of reduced graphene oxide rgo powders depending on the applied pressure and additional thermal annealing. The role of oxygen during thermal reduction of graphene oxide. Highconcentration boron doping of graphene nanoplatelets by simple thermal annealing and their supercapacitive properties.
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. Comparing effects of thermal annealing and chemical reduction. No change of the coating properties is required during this process. Doping nanoparticles doping nanoparticles onto graphene or go has been done for the following works brenner, 2012. Thermal transport in graphene oxide from ballistic extreme. We report valence band electronic structure evolution of graphene oxide go upon its thermal reduction. The process of graphene transfer generally involves a polymer support.
Thermal contact resistance between graphene and silicon dioxide z. Investigation of the thermal stability of the carbon. Spectroscopic ellipsometry was used to characterize the optical response of the. Effect of thermal annealing on the electrochemical capacitive. Catalystfree synthesis of iodinedoped graphene via a. Mechanical and thermal properties of graphene oxide filled. Thermal reduction methods in combination with ultrasonic or laser irradiation go can be reduced by microwaves in combination with thermal reduction chen, 2010. However, unlike its counterpart graphene the thermal transport properties of. 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. 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. The high defect density in graphene is reflected by r 2d22526 cm 1.
Nitrogen doping significantly improves the electrochemical properties of graphene. Scanning electron microscopy sem and optical images were used to evaluate. Rapid thermal exfoliationreduction of graphite oxide is a fast and easy method among the oxidationreduction approaches for graphene. Graphene oxide is being used in energy, optical, electronic and sensor devices due to its unique properties.
Furthermore, when graphene based materials are interacting with the surrounding environment, e. Hojatitalemi, 2010, with solvothermal method tran, 20. Graphene hybrid sio2 hierarchical dual network aerogel. It is found that the hightemperature annealing dramatically increases the inplane thermal conductivity, k, of the. 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. Degree of oxygen functionalization was controlled by annealing temperatures, and an electronic structure evolution was monitored using realtime ultraviolet photoelectron spectroscopy.
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. Mild annealing reduced graphene oxide membrane for nanofiltration. We observed a drastic increase in density of states. Highlightsmild thermal annealing was proved effective for preparing rgo nanofiltration membrane.
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 conductivity of freestanding reduced graphene oxide. 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. Go owns rich functionalized oxygen groups, which guarantees excellent water dispersibility. Catalystfree synthesis of nitrogendoped graphene via. 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. Remarkable conversion between n and ptype reduced graphene oxide on varying the thermal annealing temperature article pdf available in chemistry of materials 2721. Physical properties investigation of reduced graphene. Rapid and scalable fabrication of reduced graphene oxide. Jan 28, 2014 graphene oxide is being used in energy, optical, electronic and sensor devices due to its unique properties.
We provide a systematic study of rta of graphene transistors with four different contact metals, cu, ag, au, and pd. 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. Understanding the thermal reduction of graphene oxide go is important for graphene exfoliation, and chemical and morphological modi. High temperature reduction process increases thermal. Electrophoretic deposition epd is believed to be an effective and versatile approach for this purpose. Thermal annealing an overview sciencedirect topics. Thermal annealing of graphene monolayers transferred from cu to sio2si substrate has been investigated to remove polymethyl. Phonon dispersion of graphene t o understand the thermal properties of graphene, one must. Highly thermally conductive graphene film produced using. Enhancement of quaternary nitrogen doping of graphene oxide.
Remarkable conversion between n and ptype reduced graphene oxide on varying the thermal annealing temperature. Scalable enhancement of graphene oxide properties by. Probing the thermal deoxygenation of graphene oxide using. 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. 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. In this process, the role of trapped water and the evolution of oxygen during annealingarestillnotwellunderstood. Effect of low oxygen annealing on photoelectrochemical. Remarkable conversion between n and ptype reduced graphene. The scientists stress the potential of using this method for. Mild annealing reduced graphene oxide membrane for. Switch on the high thermal conductivity of graphene paper. The electrical conductivity of graphene powders is critical for their uses in fabricating highperformance devices or materials.
Jun 14, 2018 graphene has outstanding properties that make it an auspicious material for many applications. Microcrystalline graphene oxide mgo was reduced by thermal annealing to prepare reduced microcrystalline graphene oxide rmgo. Valence band electronic structure evolution of graphene oxide. Effect of thermal annealing on the heat transfer properties. 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. Additionally, to give a clear evolution from the graphene oxide liquid crystal to longrange ordered graphene fibers, a structure evolution model has been built.
Water and salt transport mechanism in mrgo and hrgo was. As an example, the thermal conductivity of graphene was reported to decreases from about 20005000 w m1. 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. Recent advances in effective reduction of graphene oxide for.
Thermal annealing of graphene to remove polymer residues. Recently, graphene oxide go has drawn extensive attentions in cement and concrete fields due to its unique features. For preparing highquality graphene, hightemperature annealing was shown to be necessary and the layers of rgo expanded due to the release of cox gases. 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. Here, we report the results of a fundamental study on the remarkable conversion between n and ptype reduced graphene oxide rgo with changes in the thermal annealing temperature. The further studies revealed the substantial structure imperfection of graphene oxide. In this work, we implement rapid thermal annealing of graphene based. This leads to the formation of three acoustic a and 3 n 3 3 optical o phonon modes. Facile thermal annealing of graphite oxide in air for. 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. Monolayer graphene is obtained by mechanical exfoliation using scotch tapes.
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. Here, a new and effective methodology of preparing nitrogen. The degree of reduction of the rgo powders was controlled by varying the thermal annealing temperature. It is possible only in the case when t max is smaller than the. Despite being applied as graphene precursor, go along with other carbon nanostructures have been labeled. Here, we investigated the bulk electrical conductivity of reduced graphene oxide rgo powders depending on. The degree of oxygen functionalization was controlled by annealing temperature, and an electronic structure evolution was monitored. Thermal annealing of graphene monolayers transferred from cu to sio2si substrate has been investigated to. The degree of oxygen functionalization was controlled by annealing temperature, and an electronic structure evolution was monitored using real. 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. Rapid thermal exfoliationreduction of graphite oxide is a fast and easy method among the oxidationreduction approaches for graphene synthesis. Graphene exhibits unique structure which has a two dimensional single layered made of carbon. C required to reduce the graphene oxide go films leads to high manufacturing costs and restricts its broader application in thermal management applications.
Go could also react with the hydrated ions and has an important impact on the. Go was first chemically reduced with hydrazine to substantially increase the formation of c c bonds and simultaneously decrease the atomic oxygen concentration. The influence of thermal annealing to remove polymeric. Herein, we report a highperformance, lowtemperature reduced graphene oxidemagnetic carbon. Electrical measurements of thermally reduced graphene oxide. Improved performance of graphene in heat dissipation when. Characterization of structural transformation of graphene oxide to reduced graphene oxide during thermal annealing. Grossman1 chemical functionalization of graphene is promising for a variety of nextgeneration technologies. Comparing effects of thermal annealing and chemical. Effect of annealing on doping of graphene with molybdenum.
For the onestep thermal annealing graphene, the heat graphite oxide in air heat one step thermal annealed graphene in air a. 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. 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. In this research, we firstly demonstrated that graphene can be obtained with a surface area of 550 to 700 m2 g. This paper reports on the thermal properties of reduced graphite oxide rgo flakes, studied by means of scanning thermal microscopy sthm. Electrical measurements of thermally reduced graphene. Interfacemediated extremely low thermal conductivity of. Valenceband electronic structure evolution of graphene oxide. Jan 28, 2019 graphene oxide go is useful and promising material for graphene based applications in electronic, optics, chemistry, energy storage, and biology. Facile thermal annealing of graphite oxide in air for graphene with a. Atomicscale investigation of graphene grown on cu foil.
Thermal treatment or chemical reducing agent is an efficient method to reduce graphene oxide go to graphene dubin et al. The electronic and chemical properties of graphene can be modulated by chemical doping foreign atoms and functional moieties. 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. The effects of thermal annealing on the tape residues and edges of graphene are researched. Bardhan1,2, sefaattin tongay3, junqiao wu3,angelam. The article is focused on the study of the optical properties of inkjetprinted graphene oxide go layers by spectroscopic ellipsometry. Frontiers mapping of graphene oxide and single layer. Electrophoretic deposition and thermal annealing of a. Raman spectra of the annealed graphene show both the 2d peak and g peak blueshift. 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. We also did the test to compare the tga of reduced graphene oxide and graphite 94 oxide in air, as shown in fig.
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. Reduction of go with laser irradiation trusovas, 20, rgo from graphite oxide under ultraviolet irradiation ji, 20. The graphene unit cell, marked by dashed lines in figure 1a, contains n 2 carbon atoms. Pdf remarkable conversion between n and ptype reduced. Raman spectra of the annealed graphene show both the 2d. Flexible conductive graphene paper obtained by direct and. 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. Thermal contact resistance between graphene and silicon. Valenceband electronic structure evolution of graphene. Highconcentration boron doping of graphene nanoplatelets by.
Scalable enhancement of graphene oxide properties by thermally driven phase transformation priyank v. Thermal transport in graphene oxide from ballistic. We show that a combination of highresolution in situ xray photoemission and xray absorption spectroscopies offer a powerful. Salt rejection and selectivity can be feasibly tuned by mild annealing time. Moreover, go exhibits large specific surface area and remarkable mechanical strength. It can be proved that thermal annealing is an efficient way to fabricate highstrength graphene fibers.
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