The Experts below are selected from a list of 183 Experts worldwide ranked by ideXlab platform
Ilhan A. Aksay - One of the best experts on this subject based on the ideXlab platform.
-
Enhanced Fuel Decomposition in the Presence of Colloidal Functionalized Graphene Sheet-Supported Platinum Nanoparticles
ACS Applied Energy Materials, 2020Co-Authors: Hyung Sub Sim, Daniel M. Dabbs, Richard A. Yetter, Sungwook Hong, Adri C T Van Duin, Ilhan A. AksayAbstract:Experiments and simulations were used to demonstrate that decorating Functionalized Graphene Sheets (FGSs) with platinum nanoparticles (Pt@FGS) stabilized these particles. Addition of these particles to liquid hydrocarbon fuels was observed to significantly affect decomposition under supercritical conditions at a pressure of 4.75 MPa and temperatures from 753 to 803 K. The suspension of only 50 ppmw Pt@FGS in the fuel (equivalent to adding 10 ppmw Pt) enhanced fuel conversion rates (by up to 24%) with a major effect on specific product yields. The production of low-molecular-weight species increased in the pyrolysis products (with the hydrogen yield increasing by a factor of 12.5). ReaxFF molecular dynamics (MD) simulations supported a mechanism in which synergy between Pt and FGS catalyzed dehydrogenation during n-C12H26 pyrolysis. The highest conversion rates and greatest yields of hydrogen and low-molecular-weight species were observed for fuels containing Pt@FGS particles rather than those containing either FGSs or Pt-clusters alone. Analysis of the platinum decorated FGSs post reaction indicated no deterioration of the composite particles.
-
Functionalized Graphene Sheet as a dispersible fuel additive for catalytic decomposition of methylcyclohexane
Combustion and Flame, 2020Co-Authors: Hyung Sub Sim, Daniel M. Dabbs, Richard A. Yetter, Sungwook Hong, Adri C T Van Duin, Ilhan A. AksayAbstract:Abstract The decomposition of methylcyclohexane (MCH) containing suspended Functionalized Graphene Sheets (FGS) was studied using a high-pressure flow reactor, under supercritical conditions over the temperature range of 780 – 825 K at a constant pressure of 4.72 MPa. Experiments showed both fuel conversion rates and C1-C2 product yields were increased by 43.3% and 62.1%, respectively, with the addition of 50 ppmw of FGS at 820 K. The reaction mechanisms between hydrocarbon and FGS were computationally investigated using reactive molecular dynamics (MD) with ReaxFF force fields at the temperatures of 1700, 1800, and 1900 K. The MD simulations revealed that oxygen-containing functional groups attached to the FGS plays an important role in catalyzing the decomposition of the fuel. Heterogeneous dehydrogenation of MCH into a C7H13 radical intermediate led to formation of secondary and tertiary radicals, such as H, CH3, and C2H5, during early extents of reaction promoting additional fuel-consuming steps, including H-abstraction and hydrogenation.
-
strain induced crystallization and mechanical properties of Functionalized Graphene Sheet filled natural rubber
Journal of Polymer Science Part B, 2012Co-Authors: Bulent Ozbas, Ilhan A. Aksay, Shigeyuki Toki, Benjamin S Hsiao, Benjamin Chu, Richard A Register, Robert K Prudhomme, Douglas H. AdamsonAbstract:The effects of Functionalized Graphene Sheets (FGSs) on the mechanical properties and strain-induced crystallization of natural rubber (NR) are investigated. FGSs are predominantly single Sheets of Graphene with a lateral size of several hundreds of nanometers and a thickness of 1.5 nm. The effect of FGS and that of carbon black (CB) on the strain-induced crystallization of NR is compared by coupled tensile tests and X-ray diffraction experiments. Synchrotron X-ray scattering enables simultaneous measurements of stress and crystallization of NR in real time during sample stretching. The onset of crystallization occurs at significantly lower strains for FGS-filled NR samples compared with CB-filled NR, even at low loadings. Neat-NR exhibits strain-induced crystallization around a strain of 2.25, while incorporation of 1 and 4 wt % FGS shifts the crystallization to strains of 1.25 and 0.75, respectively. In contrast, loadings of 16 wt % CB do not significantly shift the critical strain for crystallization. Two-dimensional (2D) wide angle X-ray scattering patterns show minor polymer chain alignment during stretching, in accord with previous results for NR. Small angle X-ray scattering shows that FGS is aligned in the stretching direction, whereas CB does not show alignment or anisotropy. The mechanical properties of filled NRmore » samples are investigated using cyclic tensile and dynamic mechanical measurements above and below the glass transition of NR.« less
-
Functionalized Graphene Sheets as a versatile replacement for platinum in dye-sensitized solar cells.
ACS applied materials & interfaces, 2012Co-Authors: Joseph D. Roy-mayhew, Gerrit Boschloo, Anders Hagfeldt, Ilhan A. AksayAbstract:Several techniques for fabricating Functionalized Graphene Sheet (FGS) electrodes were tested for catalytic performance in dye-sensitized solar cells (DSSCs). By using ethyl cellulose as a sacrificial binder, and partially thermolyzing it, we were able to create electrodes which exhibited lower effective charge transfer resistance (
-
local voltage drop in a single Functionalized Graphene Sheet characterized by kelvin probe force microscopy
Nano Letters, 2011Co-Authors: Christian Punckt, Ilhan A. Aksay, W Mertin, G BacherAbstract:We studied the local voltage drop in Functionalized Graphene Sheets of subμm size under external bias conditions by Kelvin probe force microscopy. Using this noninvasive experimental approach, we measured ohmic current–voltage characteristics and an intrinsic conductivity of about 3.7 × 105 S/m corresponding to a Sheet resistance of 2.7 kΩ/sq under ambient conditions for Graphene produced via thermal reduction of graphite oxide. The contact resistivity between Functionalized Graphene and metal electrode was found to be <6.3 × 10–7 Ωcm2.
Kattimuttathu I. Suresh - One of the best experts on this subject based on the ideXlab platform.
-
surface initiated atom transfer radical polymerization si atrp from Graphene oxide effect of Functionalized Graphene Sheet fgs on the synthesis and material properties of pmma nanocomposites
Macromolecular Materials and Engineering, 2016Co-Authors: Nutenki Rajender, Kattimuttathu I. SureshAbstract:The effect of Functionalized Graphene Sheets (FGS) on the synthesis and materials properties of PMMA nanocomposites has been studied. The esterified GO was used to perform the surface initiated atom transfer radical polymerization (SI-ATRP) of MMA and the effects of ligand type, ligand:CuBr ratio and supported initiator concentration on the synthesis and properties of hybrid nanocomposites are studied at 95 °C. The nanocomposites prepared via SI-ATRP showed improved damping and film formation as compared to the peroxide polymerized composite from acrylated GO. The nanocomposites showed higher thermal stability, rheological and mechanical properties that varied with the FGS initiator content. The water contact angle of PMMA increases from 69° to 82° in the nanocomposite prepared with 2.33 wt% FGS content.
-
Surface‐Initiated Atom Transfer Radical Polymerization (SI‐ATRP) From Graphene Oxide: Effect of Functionalized Graphene Sheet (FGS) on the Synthesis and Material Properties of PMMA Nanocomposites
Macromolecular Materials and Engineering, 2015Co-Authors: Nutenki Rajender, Kattimuttathu I. SureshAbstract:The effect of Functionalized Graphene Sheets (FGS) on the synthesis and materials properties of PMMA nanocomposites has been studied. The esterified GO was used to perform the surface initiated atom transfer radical polymerization (SI-ATRP) of MMA and the effects of ligand type, ligand:CuBr ratio and supported initiator concentration on the synthesis and properties of hybrid nanocomposites are studied at 95 °C. The nanocomposites prepared via SI-ATRP showed improved damping and film formation as compared to the peroxide polymerized composite from acrylated GO. The nanocomposites showed higher thermal stability, rheological and mechanical properties that varied with the FGS initiator content. The water contact angle of PMMA increases from 69° to 82° in the nanocomposite prepared with 2.33 wt% FGS content.
Joseph D. Roy-mayhew - One of the best experts on this subject based on the ideXlab platform.
-
Functionalized Graphene Sheets as a versatile replacement for platinum in dye-sensitized solar cells.
ACS applied materials & interfaces, 2012Co-Authors: Joseph D. Roy-mayhew, Gerrit Boschloo, Anders Hagfeldt, Ilhan A. AksayAbstract:Several techniques for fabricating Functionalized Graphene Sheet (FGS) electrodes were tested for catalytic performance in dye-sensitized solar cells (DSSCs). By using ethyl cellulose as a sacrificial binder, and partially thermolyzing it, we were able to create electrodes which exhibited lower effective charge transfer resistance (
-
Functionalized Graphene as a catalytic counter electrode in dye-sensitized solar cells
ACS Nano, 2010Co-Authors: Joseph D. Roy-mayhew, David J. Bozym, Christian Punckt, Ilhan A. AksayAbstract:When applied on the counter electrode of a dye-sensitized solar cell, Functionalized Graphene Sheets with oxygen-containing sites perform comparably to platinum (conversion efficiencies of 5.0 and 5.5%, respectively, at 100 mW cm(-2) AM1.5G simulated light). To interpret the catalytic activity of Functionalized Graphene Sheets toward the reduction of triiodide, we propose a new electrochemical impedance spectroscopy equivalent circuit that matches the observed spectra features to the appropriate phenomena. Using cyclic voltammetry, we also show that tuning our material by increasing the amount of oxygen-containing functional groups can improve its apparent catalytic activity. Furthermore, we demonstrate that a Functionalized Graphene Sheet based ink can serve as a catalytic, flexible, electrically conductive counter electrode material.
Cheol Min Shin - One of the best experts on this subject based on the ideXlab platform.
-
Functionalized Graphene Sheet polyurethane nanocomposites effect of particle size on physical properties
Macromolecular Research, 2011Co-Authors: Jin Taek Choi, Han Mo Jeong, Cheol Min Shin, Kwang Sun Ryu, Hyungil Lee, Jung Ho Kim, Dong Hoon Kim, Byung-kyu KimAbstract:Nanocomposites of thermoplastic polyurethane (TPU), which were prepared using two types of Functionalized Graphene Sheets (FGS) of similar thickness but different sizes were examined. The percolation threshold of the nanocomposite was reduced, evidently by increasing the particle size of the FGS. This means that the FGS with a mean particle size of 8.3 μm had a percolation threshold at 0.39 wt% in the nanocomposite of TPU, whereas it was 1.41 wt% when the FGS size was 2.4 μm. The FGS enhanced the modulus of TPU through a reinforcing effect but both the tensile strength and elongation at break were reduced as the FGS content was increased. These effects of FGS on the tensile properties were more evident with a larger particle size of FGS. The morphology and thermal properties of the nanocomposites were also examined.
-
Functionalized Graphene Sheet polyurethane nanocomposites effect of particle size on the physical properties
International Forum on Strategic Technology, 2010Co-Authors: Jin Taek Choi, Han Mo Jeong, Cheol Min Shin, Kwang Sun Ryu, Hyungil Lee, Jung Ho KimAbstract:The percolation threshold in the nanocomposite of Functionalized Graphene Sheet (FGS) and thermoplastic polyurethane (TPU) reduced effectively by increasing the particle size of FGS. That is the FGS with average size of 8.3 µm has the percolation threshold at 0.4 wt% in the nanocomposite of TPU, whereas it was more than 1.4 wt% when the FGS size was 2.4 µm. The effect of FGS size on mechanical and other properties were also examined.
-
Functionalized Graphene Sheet/polyurethane nanocomposites: Effect of particle size on the physical properties
International Forum on Strategic Technology 2010, 2010Co-Authors: Jin Taek Choi, Han Mo Jeong, Cheol Min ShinAbstract:The percolation threshold in the nanocomposite of Functionalized Graphene Sheet (FGS) and thermoplastic polyurethane (TPU) reduced effectively by increasing the particle size of FGS. That is the FGS with average size of 8.3 μm has the percolation threshold at 0.4 wt% in the nanocomposite of TPU, whereas it was more than 1.4 wt% when the FGS size was 2.4 μm. The effect of FGS size on mechanical and other properties were also examined.
-
Morphological and physical properties of a thermoplastic polyurethane reinforced with Functionalized Graphene Sheet
Polymer International, 2009Co-Authors: Duc Anh Nguyen, Yu Rok Lee, Anjanapura V Raghu, Han Mo Jeong, Cheol Min Shin, Byung-kyu KimAbstract:BACKGROUND: Functionalized Graphene Sheet (FGS) was recently introduced as a new nano-sized conductive filler, but little work has yet examined the possibility of using FGS as a nanofiller in the preparation of polymer nanocomposites. in particular, there are currently no published papers that evaluate polyurethane/FGS nanocomposites. The purpose of this study was to prepare a polyurethane/FGS nanocomposite and examine the morphological and physical properties of the material. RESULTS: A cast nanocomposite film was prepared from a mixture of thermoplastic polyurethane (TPU) solution and FGS suspended in methyl ethyl ketone. The FGS dispersed on the nanoscale throughout the TPU matrix and effectively enhanced the conductivity. A nanocomposite containing 2 parts of FGS per 100 parts of TPU had an electrical conductivity of 10(-4) S cm(-1), a 107 times increase over that of pristine TPU. The dynamic mechanical properties showed that the FGS efficiently reinforced the TPU matrix, particularly in the temperature region above the soft segment melt. CONCLUSION: Our results show that FGS has a high affinity for TPU, and it could therefore be used effectively in the preparation of TPU/FGS nanocomposites without any further chemical surface treatment. This indicates that FGS is an effective and convenient new material that could be used for the modification of polyurethane. It could also be used in place of other nano-sized conductive fillers, such as carbon nanotubes. (C) 2009 Society of Chemical Industry
-
preparation and physical properties of waterborne polyurethane Functionalized Graphene Sheet nanocomposites
Macromolecular Chemistry and Physics, 2008Co-Authors: Anjanapura V Raghu, Yu Rok Lee, Han Mo Jeong, Cheol Min ShinAbstract:A nanocomposite of waterborne polyurethane (WPU) was prepared with Functionalized Graphene Sheets (FGSs) which are a new type of nano-sized conductive filler. The FGS were finely dispersed in a polymer matrix to improve the conductivity of the WPU. Conductivity of about 105 times that of pristine WPU was attained using two parts FGS per 100 parts of the matrix polymer. The FGS reduced the hard segment crystallinity of the WPU, which lowered the modulus of the WPU at room temperature. This modulus reduction became more evident in the temperature region above the glass transition temperature of the hard segment.
Han Mo Jeong - One of the best experts on this subject based on the ideXlab platform.
-
physical properties of Functionalized Graphene Sheet poly ethylene co vinyl acetate composites
Polymer-korea, 2014Co-Authors: Kisuk Lee, Jeong Ho Kim, Han Mo JeongAbstract:The physical properties of Functionalized Graphene Sheet (FGS)/poly(ethylene-co-vinyl acetate) (EVA) was examined with various kinds of EVA, having vinyl acetate (VA) contents in the range of 0 to 40 wt%. The compatibility between FGS and EVA was enhanced as the polar VA content of EVA increased. Thus, the dispersion of FGS in EVA became finer, and the decrease of surface resistivity and the increase of tensile modulus by the added FGS became more effective when the VA content of EVA was high. When the VA content was low, the elongation at break was reduced drastically by added FGS due to the poor adhesion of FGS/EVA interface. The crystallization of EVA was generally retarded by the interaction with dispersed FGS. However, when both the VA content of EVA and the added amount of FGS were low, the crystallization of EVA was enhanced, probably due to the predominant nucleating effect by FGS.
-
Functionalized Graphene Sheet polyurethane nanocomposites effect of particle size on physical properties
Macromolecular Research, 2011Co-Authors: Jin Taek Choi, Han Mo Jeong, Cheol Min Shin, Kwang Sun Ryu, Hyungil Lee, Jung Ho Kim, Dong Hoon Kim, Byung-kyu KimAbstract:Nanocomposites of thermoplastic polyurethane (TPU), which were prepared using two types of Functionalized Graphene Sheets (FGS) of similar thickness but different sizes were examined. The percolation threshold of the nanocomposite was reduced, evidently by increasing the particle size of the FGS. This means that the FGS with a mean particle size of 8.3 μm had a percolation threshold at 0.39 wt% in the nanocomposite of TPU, whereas it was 1.41 wt% when the FGS size was 2.4 μm. The FGS enhanced the modulus of TPU through a reinforcing effect but both the tensile strength and elongation at break were reduced as the FGS content was increased. These effects of FGS on the tensile properties were more evident with a larger particle size of FGS. The morphology and thermal properties of the nanocomposites were also examined.
-
The Properties of Functionalized Graphene Sheet/Poly( ethyl methacrylate) Nanocomposites: The Effects of Preparation Method
Macromolecular Research, 2011Co-Authors: Hyungil Lee, Han Mo Jeong, Byung-kyu KimAbstract:Poly(ethyl methacrylate) (PEMA) nanocomposites reinforced with a Functionalized Graphene Sheet (FGS) were prepared by two different methods; a physical mixing method and an in situ method. The results from thermogravimetric analysis and Fourier transform infrared spectroscopy suggested the possibility that PEMA molecules could be grafted on FGS, when ethyl methacrylate (EMA) was polymerized in the presence of FGS by an in situ method with a radical initiator, 2,2′-azobisisobutyronitrile. The enhanced interaction between FGS and matrix PEMA observed from tensile storage modulus and rheological properties also demonstrated the possibility of the graft reaction. However, the differences in morphology and conductivity between the nanocomposites prepared by different preparation methods were marginal. That is, in both nanocomposites prepared by two different methods, FGS dispersed finely in the PEMA matrix to effectively make a conductive channel; 3 wt% FGS improved the conductivity by approximately 107-fold compared to that of pristine PEMA. Open image in new window
-
the properties of Functionalized Graphene Sheet poly ethyl methacrylate nanocomposites the effects of preparation method
Macromolecular Research, 2011Co-Authors: Hyungil Lee, Han Mo Jeong, Byung-kyu KimAbstract:Poly(ethyl methacrylate) (PEMA) nanocomposites reinforced with a Functionalized Graphene Sheet (FGS) were prepared by two different methods; a physical mixing method and an in situ method. The results from thermogravimetric analysis and Fourier transform infrared spectroscopy suggested the possibility that PEMA molecules could be grafted on FGS, when ethyl methacrylate (EMA) was polymerized in the presence of FGS by an in situ method with a radical initiator, 2,2′-azobisisobutyronitrile. The enhanced interaction between FGS and matrix PEMA observed from tensile storage modulus and rheological properties also demonstrated the possibility of the graft reaction. However, the differences in morphology and conductivity between the nanocomposites prepared by different preparation methods were marginal. That is, in both nanocomposites prepared by two different methods, FGS dispersed finely in the PEMA matrix to effectively make a conductive channel; 3 wt% FGS improved the conductivity by approximately 107-fold compared to that of pristine PEMA. Open image in new window
-
Functionalized Graphene Sheet / Polyurethane Nanocomposites
Physics and Applications of Graphene - Experiments, 2011Co-Authors: Hyungil Lee, Han Mo JeongAbstract:One of an integral aspect of polymer nanotechnology is precise synthesis of polymer nanocomposites. [1-6] Small insertion of nanosized inorganic compounds usually improves the properties of polymers in a great deal, which makes many of the most important application areas possible depending on the inorganic material present in polymers. [7] Specially, polymer composites which contain electrically conducting inorganic fillers, such as natural graphite, carbon black and metal powders, have been extensively investigated in the past few decades for their potential applications in antistatic coatings, electromagnetic shielding and corrosion-resistant coatings, etc. [8-10] Sometimes, in order to obtain an electrical conductivity of 10−4 S cm−1 required for commercial uses, these composites often contain as much as 15 wt% filler, which in turn causes deterioration of mechanical properties and poor processability. It is, therefore, important to use a small amount of filler to retain the stretchability or transparency of a matrix polymer. Graphene is essentially an isolated atomic plane of graphite, which is composed of a single layer Sheet of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice with large specific surface area. [11,12] Single-layer Graphene Sheet have been of great interest for their unique properties, including not only excellent mechanical properties but thermal conductivity and stiffness. Given these unique properties, Graphene has been considered as an ideal reinforcing agent for high strength polymer composites. [13,14] In addition, the elusive two-dimensional structure of Graphene has a number of unusual electronic and robust transport properties that may be useful in the electronics or in the related regions. [15-17] The properties of polymer nanocomposites depend strongly on how well inorganic fillers are dispersed in the polymer matrix. A great deal of nanocomposite research using carbon nanotubes (CNT) as nanosize conductive fillers has focused on finding better methods for dispersing nanotubes into polymers since pristine carbon nanotubes have poor compatibility with most organic solvents and polymers. For this reason, additional surface treatment is necessary for CNT based nanocomposites to allow better compatibility. [18] Though surface modification via acid modification and polymer grafting improves solubility of CNT in solvents and polymers somehow, the extent of disentanglement of the CNT bundles into polymers is low, and severe sonication often leads to disruption of the CNT. In case of Graphene, during the synthesis of Graphene from graphite oxide (GO)[19] some epoxide and hydroxyl groups remain, which greatly facilitate dispersion. [20] There
