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  Subjects -> CHEMISTRY (Total: 841 journals)
    - ANALYTICAL CHEMISTRY (50 journals)
    - CHEMISTRY (593 journals)
    - CRYSTALLOGRAPHY (21 journals)
    - ELECTROCHEMISTRY (25 journals)
    - INORGANIC CHEMISTRY (41 journals)
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    - PHYSICAL CHEMISTRY (67 journals)

CHEMISTRY (593 journals)                  1 2 3 | Last

Showing 1 - 200 of 735 Journals sorted alphabetically
2D Materials     Hybrid Journal   (Followers: 8)
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement     Hybrid Journal   (Followers: 26)
ACS Catalysis     Full-text available via subscription   (Followers: 34)
ACS Chemical Neuroscience     Full-text available via subscription   (Followers: 18)
ACS Combinatorial Science     Full-text available via subscription   (Followers: 23)
ACS Macro Letters     Full-text available via subscription   (Followers: 23)
ACS Medicinal Chemistry Letters     Full-text available via subscription   (Followers: 39)
ACS Nano     Full-text available via subscription   (Followers: 233)
ACS Photonics     Full-text available via subscription   (Followers: 11)
ACS Synthetic Biology     Full-text available via subscription   (Followers: 21)
Acta Chemica Iasi     Open Access   (Followers: 2)
Acta Chimica Sinica     Full-text available via subscription   (Followers: 1)
Acta Chimica Slovaca     Open Access   (Followers: 1)
Acta Chromatographica     Full-text available via subscription   (Followers: 9)
Acta Facultatis Medicae Naissensis     Open Access  
Acta Metallurgica Sinica (English Letters)     Hybrid Journal   (Followers: 5)
Acta Scientifica Naturalis     Open Access   (Followers: 2)
adhäsion KLEBEN & DICHTEN     Hybrid Journal   (Followers: 5)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Adsorption Science & Technology     Full-text available via subscription   (Followers: 5)
Advanced Functional Materials     Hybrid Journal   (Followers: 50)
Advanced Science Focus     Free   (Followers: 3)
Advances in Chemical Engineering and Science     Open Access   (Followers: 55)
Advances in Chemical Science     Open Access   (Followers: 13)
Advances in Chemistry     Open Access   (Followers: 14)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Enzyme Research     Open Access   (Followers: 9)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 15)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 8)
Advances in Materials Physics and Chemistry     Open Access   (Followers: 19)
Advances in Nanoparticles     Open Access   (Followers: 15)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15)
Advances in Polymer Science     Hybrid Journal   (Followers: 41)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 19)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Science and Technology     Full-text available via subscription   (Followers: 12)
African Journal of Bacteriology Research     Open Access  
African Journal of Chemical Education     Open Access   (Followers: 2)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Agrokémia és Talajtan     Full-text available via subscription   (Followers: 2)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
AMB Express     Open Access   (Followers: 1)
Ambix     Hybrid Journal   (Followers: 3)
American Journal of Biochemistry and Biotechnology     Open Access   (Followers: 68)
American Journal of Biochemistry and Molecular Biology     Open Access   (Followers: 14)
American Journal of Chemistry     Open Access   (Followers: 26)
American Journal of Plant Physiology     Open Access   (Followers: 14)
American Mineralogist     Hybrid Journal   (Followers: 14)
Analyst     Full-text available via subscription   (Followers: 40)
Angewandte Chemie     Hybrid Journal   (Followers: 224)
Angewandte Chemie International Edition     Hybrid Journal   (Followers: 213)
Annales UMCS, Chemia     Open Access   (Followers: 1)
Annals of Clinical Chemistry and Laboratory Medicine     Open Access   (Followers: 3)
Annual Reports in Computational Chemistry     Full-text available via subscription   (Followers: 3)
Annual Reports Section A (Inorganic Chemistry)     Full-text available via subscription   (Followers: 4)
Annual Reports Section B (Organic Chemistry)     Full-text available via subscription   (Followers: 8)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Annual Review of Food Science and Technology     Full-text available via subscription   (Followers: 15)
Anti-Infective Agents     Hybrid Journal   (Followers: 3)
Antiviral Chemistry and Chemotherapy     Hybrid Journal  
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7)
Applied Spectroscopy     Full-text available via subscription   (Followers: 23)
Applied Surface Science     Hybrid Journal   (Followers: 28)
Arabian Journal of Chemistry     Open Access   (Followers: 6)
ARKIVOC     Open Access   (Followers: 2)
Asian Journal of Biochemistry     Open Access   (Followers: 1)
Atomization and Sprays     Full-text available via subscription   (Followers: 4)
Australian Journal of Chemistry     Hybrid Journal   (Followers: 7)
Autophagy     Hybrid Journal   (Followers: 2)
Avances en Quimica     Open Access   (Followers: 1)
Biochemical Pharmacology     Hybrid Journal   (Followers: 10)
Biochemistry     Full-text available via subscription   (Followers: 295)
Biochemistry Insights     Open Access   (Followers: 6)
Biochemistry Research International     Open Access   (Followers: 6)
BioChip Journal     Hybrid Journal  
Bioinorganic Chemistry and Applications     Open Access   (Followers: 9)
Bioinspired Materials     Open Access   (Followers: 5)
Biointerface Research in Applied Chemistry     Open Access   (Followers: 2)
Biointerphases     Open Access   (Followers: 1)
Biology, Medicine, & Natural Product Chemistry     Open Access   (Followers: 1)
Biomacromolecules     Full-text available via subscription   (Followers: 19)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Biomedical Chromatography     Hybrid Journal   (Followers: 6)
Biomolecular NMR Assignments     Hybrid Journal   (Followers: 3)
BioNanoScience     Partially Free   (Followers: 4)
Bioorganic & Medicinal Chemistry     Hybrid Journal   (Followers: 119)
Bioorganic & Medicinal Chemistry Letters     Hybrid Journal   (Followers: 97)
Bioorganic Chemistry     Hybrid Journal   (Followers: 10)
Biopolymers     Hybrid Journal   (Followers: 18)
Biosensors     Open Access   (Followers: 2)
Biotechnic and Histochemistry     Hybrid Journal   (Followers: 1)
Bitácora Digital     Open Access  
Boletin de la Sociedad Chilena de Quimica     Open Access  
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Japan     Full-text available via subscription   (Followers: 24)
Bulletin of the Korean Chemical Society     Hybrid Journal   (Followers: 1)
C - Journal of Carbon Research     Open Access   (Followers: 3)
Cakra Kimia (Indonesian E-Journal of Applied Chemistry)     Open Access  
Canadian Association of Radiologists Journal     Full-text available via subscription   (Followers: 3)
Canadian Journal of Chemistry     Hybrid Journal   (Followers: 10)
Canadian Mineralogist     Full-text available via subscription   (Followers: 3)
Carbohydrate Research     Hybrid Journal   (Followers: 26)
Carbon     Hybrid Journal   (Followers: 66)
Catalysis for Sustainable Energy     Open Access   (Followers: 7)
Catalysis Reviews: Science and Engineering     Hybrid Journal   (Followers: 8)
Catalysis Science and Technology     Free   (Followers: 6)
Catalysis Surveys from Asia     Hybrid Journal   (Followers: 3)
Catalysts     Open Access   (Followers: 8)
Cellulose     Hybrid Journal   (Followers: 7)
Cereal Chemistry     Full-text available via subscription   (Followers: 4)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemCatChem     Hybrid Journal   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 13)
Chemical Bulletin of Kazakh National University     Open Access  
Chemical Communications     Full-text available via subscription   (Followers: 70)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Research in Chinese Universities     Hybrid Journal   (Followers: 3)
Chemical Research in Toxicology     Full-text available via subscription   (Followers: 19)
Chemical Reviews     Full-text available via subscription   (Followers: 175)
Chemical Science     Open Access   (Followers: 22)
Chemical Technology     Open Access   (Followers: 16)
Chemical Vapor Deposition     Hybrid Journal   (Followers: 5)
Chemical Week     Full-text available via subscription   (Followers: 8)
Chemie in Unserer Zeit     Hybrid Journal   (Followers: 57)
Chemie-Ingenieur-Technik (Cit)     Hybrid Journal   (Followers: 26)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Biodiversity     Hybrid Journal   (Followers: 6)
Chemistry & Biology     Full-text available via subscription   (Followers: 30)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry - A European Journal     Hybrid Journal   (Followers: 142)
Chemistry - An Asian Journal     Hybrid Journal   (Followers: 15)
Chemistry and Materials Research     Open Access   (Followers: 18)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry Education Research and Practice     Free   (Followers: 5)
Chemistry in Education     Open Access   (Followers: 9)
Chemistry International     Hybrid Journal   (Followers: 2)
Chemistry Letters     Full-text available via subscription   (Followers: 44)
Chemistry of Materials     Full-text available via subscription   (Followers: 258)
Chemistry of Natural Compounds     Hybrid Journal   (Followers: 9)
Chemistry World     Full-text available via subscription   (Followers: 22)
Chemistry-Didactics-Ecology-Metrology     Open Access   (Followers: 1)
ChemistryOpen     Open Access   (Followers: 2)
Chemkon - Chemie Konkret, Forum Fuer Unterricht Und Didaktik     Hybrid Journal  
Chemoecology     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
Chemosensors     Open Access  
ChemPhysChem     Hybrid Journal   (Followers: 9)
ChemPlusChem     Hybrid Journal   (Followers: 2)
ChemTexts     Hybrid Journal  
CHIMIA International Journal for Chemistry     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemistry     Hybrid Journal   (Followers: 6)
Chinese Journal of Polymer Science     Hybrid Journal   (Followers: 10)
Chromatographia     Hybrid Journal   (Followers: 24)
Clay Minerals     Full-text available via subscription   (Followers: 10)
Cogent Chemistry     Open Access  
Colloid and Interface Science Communications     Open Access  
Colloid and Polymer Science     Hybrid Journal   (Followers: 10)
Colloids and Surfaces B: Biointerfaces     Hybrid Journal   (Followers: 7)
Combinatorial Chemistry & High Throughput Screening     Hybrid Journal   (Followers: 4)
Combustion Science and Technology     Hybrid Journal   (Followers: 18)
Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature     Hybrid Journal   (Followers: 2)
Composite Interfaces     Hybrid Journal   (Followers: 6)
Comprehensive Chemical Kinetics     Full-text available via subscription   (Followers: 2)
Comptes Rendus Chimie     Full-text available via subscription  
Comptes Rendus Physique     Full-text available via subscription   (Followers: 1)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
Coordination Chemistry Reviews     Full-text available via subscription   (Followers: 2)
Copernican Letters     Open Access   (Followers: 1)
Critical Reviews in Biochemistry and Molecular Biology     Hybrid Journal   (Followers: 5)
Crystal Structure Theory and Applications     Open Access   (Followers: 3)
CrystEngComm     Full-text available via subscription   (Followers: 12)
Current Catalysis     Hybrid Journal   (Followers: 2)
Current Metabolomics     Hybrid Journal   (Followers: 5)
Current Opinion in Colloid & Interface Science     Hybrid Journal   (Followers: 9)
Current Research in Chemistry     Open Access   (Followers: 8)
Current Science     Open Access   (Followers: 58)
Dalton Transactions     Full-text available via subscription   (Followers: 22)
Detection     Open Access   (Followers: 2)
Developments in Geochemistry     Full-text available via subscription   (Followers: 2)
Diamond and Related Materials     Hybrid Journal   (Followers: 12)
Dislocations in Solids     Full-text available via subscription  
Doklady Chemistry     Hybrid Journal  
Drying Technology: An International Journal     Hybrid Journal   (Followers: 4)
Eclética Química     Open Access   (Followers: 1)
Ecological Chemistry and Engineering S     Open Access   (Followers: 4)
Ecotoxicology and Environmental Contamination     Open Access  
Educación Química     Open Access   (Followers: 1)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
EJNMMI Radiopharmacy and Chemistry     Open Access  
Elements     Full-text available via subscription   (Followers: 2)
Environmental Chemistry     Hybrid Journal   (Followers: 8)
Environmental Chemistry Letters     Hybrid Journal   (Followers: 4)
Environmental Science & Technology Letters     Full-text available via subscription   (Followers: 5)
Environmental Science : Nano     Partially Free   (Followers: 1)
Environmental Toxicology & Chemistry     Hybrid Journal   (Followers: 17)

        1 2 3 | Last

Journal Cover Carbon
  [SJR: 2.109]   [H-I: 194]   [66 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0008-6223
   Published by Elsevier Homepage  [3044 journals]
  • C/SiO2 meta-composite: Overcoming the λ/a relationship limitation in
           metamaterials
    • Abstract: Publication date: December 2017
      Source:Carbon, Volume 125
      Author(s): Peitao Xie, Zidong Zhang, Kunpeng Liu, Lei Qian, Feng Dang, Yao Liu, Runhua Fan, Xiaolin Wang, Shixue Dou
      Metamaterials usually require that the unit size a should be comparable to the wavelength λ. Although the λ/a relationship could tell us what size of unit we need and which method we should choose for the fabrication, it limits the application of metamaterials in the kHz and MHz frequency range, as the unit size would be on the order of 102 m, making the overall size of the metamaterial too large for practical application. In this paper, we firstly demonstrate that the λ/a relationship limitation could be overcome by a new kind of composite, which we have called carbon-based ‘meta-composite’. A SiO2 matrix with periodic microstructure is fabricated by using self-assembly of SiO2 microspheres, and amorphous carbon fills in the gaps to form a three-dimensional periodic carbon network. The experimental results indicate that the carbon network will introduce tunable electromagnetic properties, which could be precisely tailored by controlling the geometric size of the carbon network. It is worth pointing out that the unit size of the periodic carbon network is on the sub-micrometre level, but the wavelength is on the order of 102 m. This means that the meta-composite overcomes the λ/a relationship limitation in the kHz and MHz frequency range, which shows great potential for the miniaturization of electronic devices.
      Graphical abstract image

      PubDate: 2017-09-20T07:09:16Z
       
  • High-ĸ dielectric oxide as an interfacial layer with enhanced
           photo-generation for Gr/Si solar cells
    • Abstract: Publication date: December 2017
      Source:Carbon, Volume 125
      Author(s): Muhammad Fahad Bhopal, Kamran Akbar, Malik Abdul Rehman, Doo won Lee, Atteq ur Rehman, Yongho Seo, Seung-Hyun Chun, Soo Hong Lee
      In recent years, graphene (Gr) based solar cells have attracted extensive interest because of their ability to produce low cost and highly efficient solar cells. Conventional Gr/Si Schottky junction based solar cells are mostly fabricated by transfer of graphene on silicon substrate. In current work the direct growth of graphene by using the Plasma Enhanced Chemical Vapor Deposition (PECVD) technique was demonstrated to make fabrication more practical on a large scale. Firstly Gr/Si Schottky junction based solar cells were fabricated, and by optimizing the growth process, power conversion efficiency (PCE) of about 3.5% was achieved. Additionally, we demonstrated a metal insulator semiconductor (MIS) structure by introducing hafnium oxide (HfO2), and an enriched efficiency of 6.68% was reached. Furthermore, the chemical doping of Gr grown on top of HfO2 passivated Si was done and the efficiency was further enhanced by 8.5%. This study also suggests that the Voc of the Gr/HfO2/Si solar cells strongly depends on the thickness of the HfO2 interfacial layer. These solar cells proved reliable as their efficiency was still consistent even after four months. The current study envisions the use of graphene based solar cells for commercial application.
      Graphical abstract image

      PubDate: 2017-09-20T07:09:16Z
       
  • Enhanced durability of carbon nanotube grafted hierarchical ceramic
           microfiber-reinforced epoxy composites
    • Abstract: Publication date: December 2017
      Source:Carbon, Volume 125
      Author(s): Ajay Krishnamurthy, Donald L. Hunston, Amanda L. Forster, Bharath Natarajan, Andrew H. Liotta, Sunny S. Wicks, Paul E. Stutzman, Brian L. Wardle, J. Alexander Liddle, Aaron M. Forster
      Carbon nanotube (CNT) hierarchical composites are increasingly identified as next-generation aerospace materials, so it is vital to evaluate their long-term structural performance under aging environments. In this work, the durability of hierarchical CNT grafted aluminoborosilicate microfiber-epoxy composites (CNT composites) are compared against aluminoborosilicate composites (baseline composites), before and after immersion in water at 25 °C (hydro) and 60 °C (hydrothermal), for extended durations (90 d and 180 d). The addition of CNTs is found to reduce water diffusivities by approximately 1.5 times. The mechanical properties (bending strength and modulus) and the damage sensing capabilities (DC conductivity) of the CNT composites remain intact regardless of exposure conditions. The baseline composites show significant loss of strength (44%) after only 15 d of hydrothermal aging. This loss of mechanical strength is attributed to fiber-polymer interfacial debonding caused by accumulation of water at elevated temperatures. In situ acoustic and DC electrical measurements of hydrothermally aged CNT composites identify extensive stress-relieving micro-cracking and crack deflections that are absent in the aged baseline composites. SEM images of the failed composite cross-sections highlight secondary matrix toughening mechanisms in the form of CNT pullouts and fractures that enhance the service life of composites.
      Graphical abstract image

      PubDate: 2017-09-20T07:09:16Z
       
  • Lateral force modulation by moiré superlattice structure: Surfing on
           periodically undulated graphene sheets
    • Abstract: Publication date: December 2017
      Source:Carbon, Volume 125
      Author(s): Jun Liu, Shuai Zhang, Qunyang Li, Xi-Qiao Feng, Zengfeng Di, Chang Ye, Yalin Dong
      It has been recently demonstrated that moiré pattern formed between graphene and supporting crystalline substrate can modulate atomic friction [1–3] which provides a novel strategy to control friction at the nanoscale. Despite the high potential of this new approach, its underlying mechanism is still unclear. Using molecular dynamics (MD) simulation, we reveal that moiré pattern induced lateral force modulation arises from geometric undulation of graphene due to its different stacking states on the substrate. As a result, a periodic offset modulation in lateral force is produced when a tip slides over graphene with varying height. Since height undulations could be induced either by weak van der Waals interactions or by stronger semi-covalent bonds in moiré superlattice structures [1,3–5], we expect the revealed mechanism to be generally applicable for explaining lateral force modulation of these two-dimensional heterostructures.
      Graphical abstract image

      PubDate: 2017-09-20T07:09:16Z
       
  • Long-wavelength, multicolor, and white-light emitting carbon-based dots:
           Achievements made, challenges remaining, and applications
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Mojtaba Shamsipur, Ali Barati, Sara Karami
      The use of carbon-based dots (C-bDs), involving carbon dots, carbon quantum dots, and graphene quantum dots, as a new class of photoluminescent nanomaterials is rapidly expanding. Their many advantages including water solubility, high stability, low toxicity, ease of functionalization, and cost-efficient and simple synthetic routes have introduced them as potential alternatives to conventional semiconductor-based quantum dots. However, difficulty in preparing long-wavelength and multicolor-emitting C-bDs has caused some major disadvantages for these nanomaterials and limited their application in fields such as bioimaging and multicolor patterning. Although different emission colors from C-bDs can be observed by varying their excitation wavelength, this is not identified as real photoluminescence tuning, and in fact, preparing C-bDs with such special photoluminescence properties has proven to be a challenging task. This review summarizes to date successes in preparing long-wavelength, multicolor, and white-light-emitting C-bDs along with their potential applications. We discuss the developments in using specific precursors, synthetic methods, heteroatom doping, and post treatments such as separation and surface modification methods that have led to C-bDs with unique emission colors.
      Graphical abstract image

      PubDate: 2017-09-14T00:48:49Z
       
  • A facile and high-efficient approach to yellow emissive graphene quantum
           dots from graphene oxide
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Yan Zhao, Xiaolong Wu, Shan Sun, Liling Ma, Ling Zhang, Hengwei Lin
      A facile and high-efficient approach for the preparation of graphene quantum dots (GQDs) is reported. With the assistance of KO2 in the hydrothermal cutting graphene oxide (GO), a conversion rate of ∼35 wt% from GO to GQDs is achieved. The as-prepared GQDs display rarely observed yellow emissive photoluminescence with a respectable quantum yield of 8.9% in H2O. Moreover, the GQDs are further demonstrated to perform as a potential pH probe and bioimaging agent.
      Graphical abstract image

      PubDate: 2017-09-14T00:48:49Z
       
  • Multiwall carbon nanotubes filled with Al4C3: Spectroscopic signatures for
           electron-phonon coupling due to doping process
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): P.T. Araujo, N.M. Barbosa Neto, M.E.S. Sousa, R.S. Angélica, S. Simões, M.F.G. Vieira, M.S. Dresselhaus, M.A. Leite dos Reis
      The spectroscopic signatures related to doping mechanisms in multiwall carbon nanotubes filled with aluminum carbide (Al 4 C 3 @MWCNTs) were studied and interpreted relative to changes in their electronic and phononic structures. Unfilled MWCNTs were used as standard samples to help interpreting the filling and the doping processes. The samples were characterized via scanning electron microscopy, transmission electron microscopy, X-ray diffraction and resonant Raman spectroscopy. The electron-phonon coupling mechanisms associated to the Raman intensities, frequencies and linewidths of the G- and G'-band Raman modes were analyzed and connected to the doping mechanism in these multi-walled systems. Our results indicate that the Al4C3 particles transfer electrons to the MWCNTs. In order to shed light into the experimental findings, theoretical calculations were performed using two examples of filled and unfilled achiral MWCNTs and the results for the density of electronic states indicate that the two systems under consideration, exhibit metallic behavior, with aluminum carbide doping the carbon nanotubes, thereby supporting our experimental observations.
      Graphical abstract image

      PubDate: 2017-09-14T00:48:49Z
       
  • Synchrotron X-ray characterization of crack strain fields in polygranular
           graphite
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): S.M. Barhli, L. Saucedo-Mora, M.S.L. Jordan, A.F. Cinar, C. Reinhard, M. Mostafavi, T.J. Marrow
      The strain field of a crack in polygranular isotropic nuclear graphite, a quasi-brittle material, has been studied during stable fracture propagation. Synchrotron X-ray computed tomography and strain mapping by diffraction were combined with digital volume correlation and phase congruency image analysis to extract the full field displacements and elastic crystal strains. The measured displacement fields have been analysed using a Finite Element method to extract the elastic strain energy release rate as a J-integral. Non-linear properties described the effect of microcracking on the elastic modulus in the fracture process zone. The analysis was verified by the good agreement of the predicted and measured elastic strain fields when using the non-linear model. The intrinsic critical elastic strain energy release rate for mode I crack propagation is approximately 200 J m−2.
      Graphical abstract image

      PubDate: 2017-09-14T00:48:49Z
       
  • Optical properties of organic carbon and soot produced in an inverse
           diffusion flame
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): C. Russo, B. Apicella, J.S. Lighty, A. Ciajolo, A. Tregrossi
      The carbonaceous particulate matter (soot plus organic carbon) sampled downstream of an ethylene inverse diffusion flame (IDF) was chemically and spectroscopically analyzed in detail. In particular, the H/C ratio, the UV–Visible absorption coefficient and Raman parameters were measured and found to be representative of a highly disordered sp2-rich carbon as the early soot sampled in a premixed flame. In contrast, the optical band gap was found to be relatively low (0.7eV), closer to the optical band gap of graphite than to that of medium-sized polycyclic aromatic hydrocarbons (>2eV) which are widely considered to be soot precursors and are mostly contained in the organic carbon. The significance of the optical band gap as signature of different structural levels (nano-, micro- and macro-structure) of sp2-rich aromatic disordered carbons was critically analyzed in reference to their molecular weight/size distribution. The relevance of the optical band analysis to the study of the soot formation mechanism was also highlighted.
      Graphical abstract image

      PubDate: 2017-09-14T00:48:49Z
       
  • Pulsed laser annealing of carbon black
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Joseph P. Abrahamson, Madhu Singh, Jonathan P. Mathews, Randy L. Vander Wal
      Laser heating was used to study the rates and trajectories of carbon black during the earliest stages of annealing. A commercial carbon black, Regal 250 (R250 Cabot Corporation) was heated with a Q-switched Nd:YAG laser and a continuous wave CO2 laser. Structural transformations were observed with transmission electron microscopy. Micrographs were processed with in-house codes for the purpose of extracting distributions of fringe length, tortuosity (curvature), and number of lamellae per stack. Time-temperature-histories with nanosecond temporal resolution and temperature reproducibility within tens of degrees Celsius were determined by spectrally resolving the laser induced incandescence signal and applying multi-wavelength pyrometry. The Nd:YAG laser fluences include: 25, 50, 100, 200, 300, and 550 mJ/cm2. The maximum observed temperature ranged from 2400 °C to the C2 sublimation temperature of 4180 °C. The CO2 laser was used to collect a series of isothermal (2600 °C) heat treatments versus time (100 ms–20 s). Laser heated samples are compared against R250 annealed in a furnace at 2600 °C. The material transformation trajectory of Nd:YAG laser heated R250 was different than the traditional furnace heating. The traditional furnace annealing pathway is followed for CO2 laser heating as based upon equivalent end structures.
      Graphical abstract image

      PubDate: 2017-09-14T00:48:49Z
       
  • Carbon nanoflake-nanoparticle interface: A comparative study on structure
           and photoluminescent properties of carbon nanoflakes synthesized on
           nanostructured gold and carbon by hot filament CVD
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): B.B. Wang, X.L. Qu, M.K. Zhu, I. Levchenko, M. Keidar, X.X. Zhong, S. Xu, K. Ostrikov
      Three dimensional vertically-oriented carbon nanoflakes grown on carbon and gold nanoparticles by the hot filament chemical vapor deposition in CH4 environment demonstrate quite similar structure and composition, but drastically different room temperature photoluminescent properties. The interfacial interactions were asserted to be the main reason for the differences in the optical emission. The mechanisms of highly oriented growth, generation and enhancement of photoluminescence were investigated, and it was demonstrated that the formation of oriented nanoflakes resulted from the stress produced in the carbon layers on carbon and gold nanoparticles. Specifically, deformation of nanoparticles and difference in the expansion rates of carbon layer, gold and carbon nanoparticles are the main causes for the stress formation. The oriented growth of carbon nanoflakes is maintained by the repulsion effect between the carbon nanoflakes due to the net charge produced from the hydrocarbon radicals on the edges of carbon nanoflakes via charge transfer between H and C atoms. The photoluminescence generation of carbon nanoflakes is related to the sp 2 carbon clusters on the edges of carbon nanoflakes. Stronger green photoluminescent emission from the carbon nanoflake/gold nanoparticle system than from the carbon nanoflake/carbon nanoparticle system is the result of the intense plasmon emission from gold nanoparticles.
      Graphical abstract image

      PubDate: 2017-09-14T00:48:49Z
       
  • Fast nanostructured carbon microparticle synthesis by one-step high-flux
           plasma processing
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): D.U.B. Aussems, K. Bystrov, İ. Doğan, C. Arnas, M. Cabié, T. Neisius, M. Rasiński, E. Zoethout, P.J.L. Lipman, M.C.M. van de Sanden, T.W. Morgan
      This study demonstrates a fast one-step synthesis method for nanostructured carbon microparticles on graphite samples using high-flux plasma exposure. These structures are considered as potential candidates for energy applications such as Li-ion batteries and supercapacitors. The samples were exposed to plasmas in the linear plasma generator Pilot-PSI with an average hydrogen ion-flux of ∼1024 m−2s−1. The parameter window was mapped by varying the ion energy and flux, and surface temperature. The particle growth depended mainly on the sample gross-erosion and the resulting hydrocarbon concentration in the plasma. A minimum concentration was necessary to initiate particle formation. The surface of the sample was covered with microparticles with an average growth rate of 0.2 μm/s, which is significantly faster than most chemical methods. The particles were initially volumetrically grown in in the gas-phase by a multi-phase process and after deposition on the sample their growth proceeded. Scanning and transmission electron microscopy reveal that the core of these microparticles can be made of an agglomeration of nanoparticles, surrounded by crumpled layers of carbon nanowalls. Gas sorption analysis shows sufficient meso- and macropores for fast mass transport. In conclusion, this processing technique could be a novel synthesis route to nanostructure surfaces for electrochemical applications.
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      PubDate: 2017-09-14T00:48:49Z
       
  • Control of ice growth and recrystallization by sulphur-doped oxidized
           quasi-carbon nitride quantum dots
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Guoying Bai, Dong Gao, Jianjun Wang
      Carbonaceous particles, as one of the main sources of atmospheric aerosols, have great influence on the climate change, such as ice formation, precipitation and polar ice melting. Because sulphur-containing emissions can significantly affect the chemical compositions and properties of carbonaceous particles through various aging processes, it is critical to investigate the influence of sulphur-doped carbon materials on ice formation. Here, we synthesized a sulphur-doped carbon nanomaterial–sulphur-doped oxidized quasi-carbon nitride quantum dots (S-OCNQDs), and investigated the influence of chemical structure on ice growth and recrystallization. The experimental results show that the S-OCNQDs can inhibit ice growth/recrystallization. In addition, we found that forming more hydrogen-bonds with ice contributes to enhancing the efficiency of ice growth/recrystallization inhibition and that heteroatom-doping is a promising way to regulate the ice growth/recrystallization. This work correlates the specific chemical structures of carbon nanomaterials with their performance in inhibiting ice growth/recrystallization through their density of hydrogen-bonds formed with ice. It is instructive for understanding the effect of sulphur-doping on ice formation as well as the design of efficient anti-icing materials.
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      PubDate: 2017-09-14T00:48:49Z
       
  • Impact of geometry on transport properties of armchair graphene nanoribbon
           heterojunction
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Weixiang Zhang, Cemal Basaran, Tarek Ragab
      Electron transport properties of undoped armchair Graphene Nanoribbon Heterojunction (GNRHJ) has been studied using semi-empirical extended Hückel method (EH). A two-probe configuration device utilizing armchair GNRHJ has been proposed. It is shown that a potential barrier was formed at the heterojunction interface between semiconductor and semi-metal, which resemble the conventional Schottky barrier at the interface of semiconductor/metal. Transmission spectrum was analyzed at finite bias; and current-bias voltage characteristic relations were established. Results show that the I–V characteristics of the heterojunction have rectifying nature, with its rectification ratio affected by the geometric asymmetry of the heterojunction.

      PubDate: 2017-09-14T00:48:49Z
       
  • Wood-based straightway channel structure for high performance microwave
           absorption
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Jiabin Xi, Erzhen Zhou, Yingjun Liu, Weiwei Gao, Ji Ying, Zichen Chen, Chao Gao
      Microwave absorption (MA) materials have gained wide range of applications including satellite communications, radar detections, etc. Here, for the first time we designed high-performance porous biomass-pyrolized carbon (PBPC) based on natural wood. The PBPC with orderly parallel channel structure is on the top among all MA materials, showing excellent MA performance with maximum reflection loss (RL) of −68.3 dB and absorption bandwidth (RL ≤ −10 dB) up to 7.63 GHz. Furthermore, we predict the reflection loss by calculation and point out regulation of electrical conductivity would maximize MA performance. The combination of renewability, easy mass production and simple fabrication provides PBPC practical application value, and the strategy of channel structure design followed by permittivity adjustment casts a light for accessing new high-performance MA materials.
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      PubDate: 2017-09-14T00:48:49Z
       
  • Spectroscopic investigation on graphene-copper nanocomposites with strong
           UV emission and high catalytic activity
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): R. Udayabhaskar, R.V. Mangalaraja, T. Pandiyarajan, B. Karthikeyan, Héctor D. Mansilla, David Contreras
      In this work, we described the synthesis of pure graphene sheets (≤5 layers) and graphene-copper nanocomposites by using the commercial microwave oven and l -ascorbic acid (LAA), as a cost effective and environmental friendly approach. The successful formation of composites, few layer graphene sheets (FLG) with copper nanostructures, was confirmed by the X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. The optical studies of the prepared samples exhibited band-band transition related strong UV absorption and strong UV emission alone with no visible range emission that supported the successful formation of graphene sheets with insignificant surface functional groups. The observed luminescence quenching in the composites when compared with the pure graphene sheets was discussed. Further we demonstrated the usage of these composites as a catalyst for hazardous azo dye reduction. The comparative study of the pure graphene and graphene-copper composites in the reduction of azo dye showed that the composites exhibited a rapid and higher catalytic activity than the pure graphene sheets.
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      PubDate: 2017-09-08T01:28:48Z
       
  • Graphene membranes with tuneable nanochannels by intercalating
           self-assembled porphyrin molecules for organic solvent nanofiltration
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Tiantian Gao, Liang Huang, Chun Li, Guochuang Xu, Gaoquan Shi
      Organic solvent nanofiltration (OSN) membranes with excellent and tuneable molecular separation performances are important in pharmaceutical industry. Here, we report reduced graphene oxide (rGO) membranes intercalated with self-assembled 5, 10, 15, 20-tetrakis (1-methyl-4-pyridinio) porphyrin (TMPyP) molecules for this purpose. These membranes showed strong tolerances to water and various organic solvents and their OSN performances can be easily tuned by controlling the amount of intercalated porphyrin molecules. The methanol permeance of an rGO membrane (mass loading = 44 mg m−2) was increased by 2 times upon intercalating 60% TMPyP relative to its own weight. This composite membrane also exhibited high rejection (>92%) for negatively charged organic dyes with molecular dimensions larger than 1.7 nm in methanol. As a demonstration, it was used to separate vitamin B12 from its aqueous or methanol solution, exhibiting a solvent permeance of 5.76 or 4.40 L m−2 h−1 bar−1 and a rejection of 98.4% or 91.0%.
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      PubDate: 2017-09-08T01:28:48Z
       
  • Temperature dependence of water adsorption on highly graphitized carbon
           black and highly ordered mesoporous carbon
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Toshihide Horikawa, Shiliang (Johnathan) Tan, D.D. Do, Ken-Ichiro Sotowa, J. Rafael Alcántara-Avila, D. Nicholson
      In previous work [1] we showed an unusual temperature dependence for water adsorption in porous activated carbons, and hypothesized that the pore size plays a critical role in water adsorption in mesopores. In this paper, we shed further light on water adsorption in mesopores by investigating its dependence on temperature for a highly graphitized non-porous carbon black and a highly ordered mesoporous carbon, Hex. They were chosen because of their distinctly different structures, with the former representing an open graphitic surface, while the latter having highly structured and graphitic mesopores of hexagonal shape. Analysis of the isotherms for these systems shows that adsorption proceeds by nucleation of water molecules around functional groups (FG) to form an embryo FG-water complex, which grows with increasing pressure to form a cluster. If the clusters are closer than a critical separation, they agglomerate to form a condensate, and provided that the pore size is small enough, the adsorbate fills the confined space. Interestingly, the amount adsorbed in the mesopores at 298 K is greater than that at 263 K, which is attributed to the formation of larger clusters at 298 K, facilitating the agglomeration of clusters followed by condensation in the mesopores.
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      PubDate: 2017-09-08T01:28:48Z
       
  • Reducing energy dissipation and surface effect of diamond
           nanoelectromechanical resonators by annealing in oxygen ambient
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Haihua Wu, Liwen Sang, Tokuyuki Teraji, Tiefu Li, Kongping Wu, Masataka Imura, Jianqiang You, Yasuo Koide, Meiyong Liao
      The authors report on the marked improvement of the quality factor (Q-factor) of single crystal diamond (SCD) nanoelectromechanical system (NEMS) resonators through annealing in oxygen ambient. The SCD NEMS resonators were fabricated by ion implantation assisted technique. The resonance frequency followed well the inverse power law relationship with the length of the cantilevers despite of the annealing. It was observed that there was little modification in the resonance frequency and Q-factor at 430 °C, while an obvious red-shift in the resonance frequency occurred at 500 °C. Meanwhile, a marked improvement in the Q-factor from around 3500 to 7000 was observed at 500 °C. The frequency red shift is due to the etching of diamond with a rate of 0.4–0.5 nm/h at 500 °C. The analysis of the energy dissipation discloses that the surface effect dominates the energy loss mechanism for the SCD NEMS resonator. The improvement of the Q-factor is thus attributed to the reduction of the surface defects in SCD NEMS.
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      PubDate: 2017-09-08T01:28:48Z
       
  • Activation effect of porous structure on fluorination of graphene based
           materials with large specific surface area at mild condition
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Xu Wang, Weimiao Wang, Dazhou Xu, Yang Liu, Wenchan Lai, Xiangyang Liu
      Fluorinated 2D porous graphene-based materials, FPGMs, were synthesized by using porous activated graphene material as raw material. The fluorination of PGM was activated through the introduction of meso- and micropores which generated a large number of vacancy, edges and defects. The fluorinated sample FPGM-10 with a F/C ratio of 0.67 was obtained at room temperature. Meanwhile, the temperate fluorination conditions guaranteed the porous structure from destruction, which endowed the FPGMs with large specific surface area and well-defined micro- and mesopores, among which FPGM-10 exhibited a BET SSA value of around 1100 m2/g. It was found the bare C atoms near the CF bonds with unpaired electron showed high reactivity with F2 resulting in the clustering of fluorine atoms at the edges, thus highly fluorinated edge region was formed. The thermogravimetric analysis, electrochemical measurement and computer simulation results simultaneously confirmed this structural characteristic ensured FPGMs with high chemical and thermal stability.
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      PubDate: 2017-09-08T01:28:48Z
       
  • Mechanically robust and electrically conductive
           graphene-paper/glass-fibers/epoxy composites for stimuli-responsive
           sensors and Joule heating deicers
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Qiangqiang Zhang, Yikang Yu, Kaichun Yang, Baoqiang Zhang, Keren Zhao, Guoping Xiong, Xingyi Zhang
      In this article, by composing three functional constituents into a multilayered structure with well-bonded interfaces, a conductive graphene-papers (GPs)/glass-fibers (GFs) reinforced epoxy composite (GPs-GE) with outstanding mechanical robustness, high electrical conductivity and sensitive stimuli-responsive performance is highlighted. Thereinto, GPs serves as a stimuli-responsive and Joule heating chip due to its superiorities on both of mechanical and electrical properties, while GFs possessing mechanically protective and strengthening functionality. The stimuli-responsive characterizations by electrical resistance change reveal the synchronous sensing properties of GPs-GE to different stimuli inputs such as mechanical deformation, temperature fluctuation and humidity. Subsequently, Joule heating and de-icing/anti-icing properties of GPs-GE are investigated symmetrically, indicating its large heating rate, high efficiency of energy conversion and low cost. Such superior performance of GPs-GE confirms that the design of multilayer microstructure to achieve multi-functionalization paves a novel way to scale-up fabrication of advanced graphene composites, indicating promising applications as mechanically reinforcing elements, stimuli-responsive sensors and electrical Joule heating chips in intelligent engineering monitoring and icing-induced disaster prevention at low-temperature environment.
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      PubDate: 2017-09-08T01:28:48Z
       
  • Relaxation of the photoexcited electrons in chevron-type graphene
           nanoribbons: Many-body theory and nonadiabatic molecular dynamics modeling
           
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Shudong Wang, Rong Guo
      The dynamics of photoexcited electrons associated with the absorption processes of the dominant peaks in pristine and nitrogen-doped chevron-type graphene nanoribbons (CGNRs and NCGNRs) have been investigated via nonadiabatic molecular dynamics simulations. The results show that the decay time in NCGNR is shorter than in CGNR. The results rationalized by the large energy difference between LUMO and LUMO+3 in CGNR (0.61 eV) and in NCGNR (0.37 eV), the comparable coherence timescales (22 fs and 21 fs) and nonadiabatic couplings (2.97 meV and 2.48 meV) of these two systems. Furthermore, phonon influence spectra show that the modes participate in the relaxation of the photoexcited electron in CGNR reside around in 101 cm−1 while in NCGNR they are in a broad range of frequencies between 210 cm−1 to 2304 cm−1, which means there exist more additional channels for accelerating the transfer in NCGNR, rationalizing why the photoexcited electrons decay faster in NCGNR.
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      PubDate: 2017-09-08T01:28:48Z
       
  • An understanding of lattice strain, defects and disorder in nuclear
           graphite
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Ram Krishna, James Wade, Abbie N. Jones, Michael Lasithiotakis, Paul M. Mummery, Barry J. Marsden
      In this study, microstructural parameters, such as lattice dimension, micro-strain and dislocation density, of different neutron-irradiated graphite grades have been evaluated using the diffraction profiles of X-ray diffraction (XRD) and the scattering profiles of Raman spectroscopy. Using Generation-IV candidate graphite samples (grade PCEA, GrafTech), subjected to neutron irradiation at 900 °C to 6.6 and 10.2 dpa, and graphite samples of similar grain size and microstructure taken from the core of the British Experimental Pile Zero reactor, which have been irradiated at 100–120 °C to 1.60 dpa, an investigation is presented on the effect of irradiation dose and temperature on the aforementioned microstructural parameters. Using two complementary techniques in Raman spectroscopy and XRD, which produced agreeable results, the average lateral crystallite size of the two graphites tested was found to decrease with increasing exposure to fast-neutron irradiation or at lower irradiation temperatures. Conversely, dislocation densities and micro-strains were found to increase following the same changes in irradiation conditions. Supporting evidence for the microstructural information obtained is provided by direct observations made using high-resolution transmission electron microscopy. These images demonstrate the presence of irradiation-induced prismatic edge dislocations as well as features that indicate the presence of basal dislocations. They also provide supporting evidence for the progressive deterioration of the graphitic planes via damage mechanisms as proposed in the literature.
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      PubDate: 2017-09-08T01:28:48Z
       
  • Effects of nitrogen doping on the structure and performance of carbon
           coated Na3V2(PO4)3 cathodes for sodium-ion batteries
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Huang Zhang, Ivana Hasa, Daniel Buchholz, Bingsheng Qin, Stefano Passerini
      Na3V2(PO4)3 (NVP) is a promising cathode material for sodium ion batteries due to the good electrochemical performance in terms of cycling stability and rate capability. However, in order to access this performance a carbon coating is required to enhance the intrinsically poor material's conductivity. Herein, we systematically investigate the role of N-doped carbon (NC) coatings on both the structural and electrochemical properties of NVP materials. NC-coated NVP materials with various nitrogen contents have been rationally synthesized by a novel solid-state method allowing the selective N-doping of the carbon coating. In fact, the N-doping changes the disorder and graphitic character of the carbon layer, strongly impacting the electrochemical performance of the NVP/C composite materials. Results suggest that the appropriate N-doping amount of the carbon leads to highly decreased electrode polarization and excellent cycling stability at high rate, enabling the NVP materials with high energy and power efficiencies.
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      PubDate: 2017-09-08T01:28:48Z
       
  • Statistical analysis of the temperature dependence of the phonon
           properties in supported CVD graphene
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Jarosław Judek, Arkadiusz P. Gertych, Maciej Krajewski, Karolina Czerniak, Anna Łapińska, Jan Sobieski, Mariusz Zdrojek
      Existing literature reports on the dependence of phonon properties on temperature rarely use statistical analysis. The lack of uncertainty assessment, which takes into account changes in the parameter value within the sample, substantially hinders comparison among the data reported so far. Moreover, it is impossible to determine whether these results display discrepancies between themselves due to sample- and technology-dependent issues, manifestations of statistical noise, or a deeper cause that has not yet been grasped. Here, we show the distributions of the phonon properties at temperatures in the range of 300 K–500 K, which were used to calculate the temperature derivatives of the phonon energies χ. These can be used in the procedure of the extraction of graphene thermal conductivity κ but are also related to the anharmonic part of the graphene crystal lattice potential and/or nonadiabatic effects. Finally, we show that the correlation analyses revealed the existence of an unknown physical cause of differences between χ values, showing that the thermal properties of phonons in graphene are still not fully understood and further studies on the contribution of doping, stress, defects and interaction with the substrate, including its thermal expansion, are required to explain the observed parameter variability.
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      PubDate: 2017-09-02T10:18:11Z
       
  • Morphology- and dehydrogenation-controlled mechanical properties in
           diamond nanothreads
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Can Feng, Jie Xu, Zhisen Zhang, Jianyang Wu
      Recently synthesized diamond nanothreads (DNTs), collecting desired properties of both inorganic nanostructures and hydrocarbon molecular structures, are an interesting group of carbon-based materials. Using full atomistic first-principles based ReaxFF molecular dynamics (MD) simulations, a comprehensive study on tensile and bending mechanical characteristics of fifteen energy-favorable DNTs is performed. All the DNTs show unique tensile and bending mechanical properties that markedly vary with morphology and arrangement of carbon polygons. A straight DNT composed of purely carbon hexagons shows brittle fracture in the temperature range of 1–2000 K, whereas with regard to another hexagon-dominated DNT and helically coiled DNT with the largest coiled radius, a thermal-induced brittle-to-ductile transition is uncovered at 2000 K. Particularly, the coiled DNT subjected to tensile loading/unloading shows a clear mechanical hysteresis loop. Dehydrogenation does not change the morphologies and stability of DNTs, but significantly affect the tensile mechanical responses; the tensile stiffness, toughness and ductility can be enhanced by approximately 1-fold, 2-folds and 3-folds as much of their pristine counterparts, respectively, however, the failure strain is reduced at any degree of dehydrogenation. Similarly, bending stiffness also closely connects with dehydrogenation. A transition of bending stiffness in two specific dehydrogenation-free DNTs occurring at critical curvatures is detected as a consequence of local bond transformations. Moreover, bending stiffness in different bending directions can differ by around 8-folds, originating from the distinct surface morphologies. The findings provide a critical knowledge of mechanical properties of DNTs for practical applications.
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      PubDate: 2017-09-02T10:18:11Z
       
  • Nitrogen and oxygen dual-doped hollow carbon nanospheres derived from
           catechol/polyamine as sulfur hosts for advanced lithium sulfur batteries
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Yueying Peng, Yiyong Zhang, Jianxing Huang, Yunhui Wang, He Li, Bing Joe Hwang, Jinbao Zhao
      Although lithium-sulfur batteries are considered as promising high-energy-storage system owing to their high energy density, developing effective materials to host sulfur species on the cathode is still challenging. Herein, an inexpensive and effective carbon precursor, catechol and polyamine is explored to fabricate nitrogen/oxygen dual-doped hollow carbon nanospheres (DHCSs) as sulfur hosts. The group containing nitrogen and oxygen can provide stronger chemisorption for lithium polysulfides than single-doped carbon matrix, which is confirmed by X-ray photoelectron spectroscopy analysis and the theoretical calculation. As a result, the designed sulfur/DHCSs cathode delivers a stable cycling performance remained 851 mAh g−1 discharge capacity at 0.2 C with ∼0.08% capacity decay per cycle after 200 cycles, revealing its great promise for energy storage application.
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      PubDate: 2017-09-02T10:18:11Z
       
  • Metal-free nitrogen-doped carbon nanoribbons as highly efficient
           electrocatalysts for oxygen reduction reaction
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Jinzhen Huang, Jiecai Han, Tangling Gao, Xinghong Zhang, Jiajie Li, Zhenjiang Li, Ping Xu, Bo Song
      Nitrogen-abundant compounds are generally regarded as perfect precursors toward in situ synthesis of nitrogen-doped carbon materials. In this study, we demonstrate a facile one-pot procedure to synthesize polyaniline-coated melamine fiber (PANI@MF) as the precursor, in which melamine fiber (MF) acts as both scaffold and nitrogen source. After high-temperature pyrolysis, wrinkled nitrogen-doped carbon nanoribbons (NCNRs) with high specific surface area (701 cm2 g−1) and cumulative pore volume (3.13 cm3 g−1) are fabricated for electrocatalytic oxygen reduction reaction (ORR). The NCNR catalyst exhibits comparative onset potential, half-wave potential, and limiting current to those of commercial Pt/C (20 wt%, E-TEK) in alkaline media, mainly due to its high specific surface area and sufficient active sites induced by synthetic effect between nitrogen atom and carbon framework. Moreover, NCNR catalyst shows enhanced stability and high tolerance to methanol crossover effect. This study is expected to broaden new horizon to the design and fabrication of new metal-free carbon-based electrocatalyst for ORR.
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      PubDate: 2017-09-02T10:18:11Z
       
  • The influence of strain on the elastic constants of graphene
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): G. López-Polín, M. Jaafar, F. Guinea, R. Roldán, C. Gómez-Navarro, J. Gómez-Herrero
      Recent advances in the understanding of graphene elasticity have shown that suspended graphene does not behave as a conventional thin plate but has a more complex behavior where flexural modes play a significant role. Among other effects, out-of-plane thermal fluctuations modify the in-plane elastic properties. Here we report indentation experiments on graphene subjected to strain. This strain is achieved by applying pressure difference across suspended graphene drumheads. Our indentation curves show an increased mechanical response at strains larger than 0.3%. Finite element simulations of the indentation curves on pressurized membranes show that this observation can be ascribed to a twofold increase of the in-plane elastic modulus and the Poisson ratio. Based in the thermodynamic theory of elastic membranes, this increase is attributed to the suppression of out-of-plane fluctuations by strain. This result reinforces the idea that suspended graphene behaves as a fluctuating membrane and points out that a careful analysis should be done when analyzing indentation curves on atomic thick materials.
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      PubDate: 2017-09-02T10:18:11Z
       
  • Ultrafast electron dynamics in twisted graphene by femtosecond
           photoemission electron microscopy
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Keiki Fukumoto, Mohamed Boutchich, Hakim Arezki, Ken Sakurai, Daniela Di Felice, Yannick J. Dappe, Ken Onda, Shin-ya Koshihara
      Twisted multilayer graphene (tMLG) present electronic properties that depend on the relative misalignment and interaction between layers. These interactions affect the band structures and the carrier dynamics upon photonic excitation. These structures are being under scrutiny and recent work high-lighted the strong potential they offer for optoelectronic devices. However, the ultrafast carrier dynamics is still at an early stage, often due to the instrumental limitations. Here, we investigated the carrier dynamics by femtosecond photoemission electron microscopy of chemical vapor deposited (CVD) twisted graphene super lattices presenting different interlayer rotation angles. The photo-generated carrier lifetimes in these selected regions show a longer lifetime compared to monolayer graphene (1 ML). This observation is assigned to the presence of band gap and sub bands in the trilayer graphene and has been supported by DFT calculations.
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      PubDate: 2017-09-02T10:18:11Z
       
  • Chemical environment dominated Fermi level pinning of a graphene gas
           sensor
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Guiming Cao, Xiaorong Liu, Weihua Liu, Quanfu Li, Xin Li, Xiaoli Wang
      The time evolution of the Fermi level of the graphene channel during a gas sensing process is systematically investigated. A Fermi level converging behavior at negative back-gate voltage and a Fermi level pinning behavior at positive back-gate voltage are observed during NH3 gas sensing process for an originally p-type doped graphene channel. The experimental results confirm that the original p-type doping level has a significant effect on the energy level where the Fermi level converges (CFL). An empirical model is proposed for the Fermi level converging and pinning behavior: the up-shift of Fermi level suppresses the electron injection from NH3 to graphene while it enhances the electron extraction from graphene to the original p-type doping agent such as H2O. At positive back-gate voltage, the significantly suppressed electron injection from the freshly absorbed NH3 is complemented by the electron extraction from graphene to the original p-type doping agent. That is why a graphene channel shows no response to NH3 when the Fermi level is pushed above CFL even though it is still significantly below the donor level of NH3. The results in this report reveal a general interplay behavior between the freshly introduced testing gas and the original dopant of the graphene.
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      PubDate: 2017-09-02T10:18:11Z
       
  • Mesoporous activated carbon materials with ultrahigh mesopore volume and
           effective specific surface area for high performance supercapacitors
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Yanhong Lu, Suling Zhang, Jiameng Yin, Congcong Bai, Junhao Zhang, Yingxue Li, Yang Yang, Zhen Ge, Miao Zhang, Lei Wei, Maixia Ma, Yanfeng Ma, Yongsheng Chen
      High specific surface area (SSA), especially effective specific surface area (E-SSA) of the active electrode materials is required for high performance supercapacitors. In this work, such materials (e.g. AC-KOH) were obtained using a scalable industrial method from biomass waste material, with controlling the pore size distribution and mesopores as the major contribution. Thus, an electrode material, with ultrahigh mesopore volume of 1.85 cm3 g−1, E-SSA up to 1771 m2 g−1 for organic electrolyte ion (TEA+) and taking 55% of the total SSA of 3237 m2 g−1 with an excellent conductivity of 33 S m−1, was obtained. With these outstanding properties, the materials demonstrate excellent double-layer capacitance with remarkable rate performance and good cycling stability. The material delivers capacitance up to 222, 202 and 188 F g−1 at current density of 1 A g−1 in aqueous, organic and ionic liquid electrolyte system, respectively. Meanwhile, it exhibits a high energy density of 80 W h kg−1 in ionic liquid electrolyte at a power density of 870 W kg−1. Furthermore, these materials can be produced in large scale from various biomass materials, and thus could be an excellent choice of the high performance materials required in the increasing important supercapacitor industry.
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      PubDate: 2017-09-02T10:18:11Z
       
  • Highly enhanced stability and efficiency for atmospheric ammonia
           photocatalysis by hot electrons from a graphene composite catalyst with
           Al2O3
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Yang Yang, Tengfei Zhang, Zhen Ge, Yanhong Lu, Huicong Chang, Peishuang Xiao, Ruiqi Zhao, Yanfeng Ma, Yongsheng Chen
      Stable and cost-effective catalysts for efficient ammonia synthesis under mild conditions particularly at ambient pressure and temperature have been pursued widely and intensively. Recently we have reported a method using a composite catalyst with nano iron oxide hosted in a three-dimensional cross-linked graphene template material, Fe@3DGraphene. With this catalyst, a light driven and efficient ammonia synthesis from N2 and H2 directly at ambient pressure was achieved, where graphene works as an electron reservoir under light illumination. But, the catalytic activity dropped over time due to the aggregation of the Fe2O3 particles. Here we report the new version of this catalyst, a nano Al2O3 modified Fe@3DGraphene catalyst (FeAl@3DGraphene) through a simple solvothermal method, where nano Al2O3 serves as a barrier among nano Fe2O3 to efficiently prevent the aggregation of the Fe2O3 particles. The optimized ammonia synthesis rate of 430 μg gcat −1 h−1 was achieved and kept steady for a 60-h test which was enhanced to more than twice of the previous catalyst without Al2O3 structural promoter.
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      PubDate: 2017-09-02T10:18:11Z
       
  • Carbon nanomaterials for flexible lithium ion batteries
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Ye Zhang, Yiding Jiao, Meng Liao, Bingjie Wang, Huisheng Peng
      With the rapid progress of wearable electronics, it is highly desirable to develop flexible power supplies, and significant progress has been thus made in making a variety of flexible batteries. Here the recent advances of flexible lithium ion batteries based on carbon nanomaterials have been carefully discussed from the viewpoint of material synthesis, structure design and property optimization. The remaining challenges and promising directions are highlighted to provide the clues for the future study in this booming field at end.
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      PubDate: 2017-09-02T10:18:11Z
       
  • Elemental mercury reaction chemistry on brominated petroleum cokes
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Yi Xiao, Deepak Pudasainee, Rajender Gupta, Zhenghe Xu, Yongfa Diao
      Activated carbon injection is a proven technology to capture mercury from flue gases. Due to the high cost and environmental concerns related to its disposal, high efficiency and low-cost sorbents have been studied to replace activated carbon. In this study, the petroleum coke obtained from two Canadian petroleum refineries, with high inherent sulfur content and impregnated with bromine, was compared to investigate elemental mercury capture mechanisms. These carbon-based sorbents showed excellent mercury removal efficiency at 100 and 200 °C. Elemental analysis, Brunauer–Emmett–Teller surface area, pore volume and thermogravimetric analysis were used to characterize the sorbents. X-ray photoelectron spectroscopy was used to examine the significant changes in chemistry and oxidation states of Br, S and Hg on the sorbent surface. More active mercury binding sites were created on brominated petroleum cokes after the chemical-mechanical bromination process. The inherent thiophene and organic sulfide in petroleum coke played a dominant role in mercury capture.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Crystalline hydrogenation of graphene by scanning tunneling microscope
           tip-induced field dissociation of H2
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): S.J. Tjung, S.M. Hollen, G.A. Gambrel, N.M. Santagata, E. Johnston-Halperin, J.A. Gupta
      We have developed a novel method for crystalline hydrogenation of graphene on the nanoscale. Molecular hydrogen was physisorbed at 5 K onto pristine graphene islands grown on Cu(111) in ultrahigh vacuum. Field emission local to the tip of a scanning tunneling microscope dissociates H2 and results in hydrogenated graphene. At lower coverage, isolated point defects are found on the graphene and are attributed to chemisorbed H on top and bottom surfaces. Repeated H2 exposure and field emission yielded patches and then complete coverage of a crystalline √3 × √3 R30° phase, as well as less densely packed 3 × 3 and 4 × 4 structures. The hydrogenation can be reversed by imaging with higher bias voltage.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • High-quality graphene synthesis on amorphous SiC through a rapid thermal
           treatment
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Dong Han, Xu Wang, Yunbiao Zhao, Yi Chen, Meixiong Tang, Ziqiang Zhao
      Synthesizing high-quality graphene by catalytic transformation from amorphous silicon carbide (a-SiC) through a rapid thermal treatment (RTT) method is reported. SiO2/Si substrates are coated by a-SiC films followed by Cu and Ni films deposited sequentially. The samples are then thermally annealed by RTT for the synthesis of high-quality graphene in only 3 min. The synergistic effect of Cu and Ni catalyst is observed. We conjecture that the inserted copper film acts not only as a catalyst or substrate for graphene growth but also as a barrier for carbon diffusion to facilitate the synthesis of monolayer graphene, while the nickel film acts as another catalyst and forms Cu-Ni alloy to lower the catalytic temperature. In this paper, we present a simple and time-saving way in preparation of high-quality graphene and put forward a brief theoretical model for the growth of graphene.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Efficient removal of dimethyl phthalate with activated iron-doped carbon
           aerogel through an integrated adsorption and electro-Fenton oxidation
           process
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Hongying Zhao, Qingning Wang, Ying Chen, Qingling Tian, Guohua Zhao
      A promising activated iron-doped carbon aerogel (AFeC) possessing high adsorption capacity and “self-cleaning” ability via generated OH radicals was fabricated and applied to remove dimethyl phthalate (DMP). Around 90% of the DMP (50 ppm) was first adsorbed on the surface of a DMP-imprinted AFeC electrode and then further catalytically oxidized by surface OH produced via an electro-Fenton reaction. DMP removal of 98% can be achieved in 150 min in the heterogeneous electro-Fenton process. The addition of Fe0 favoured the generation of graphene sheets of amorphous carbon and then provided strong π-π interaction with aromatic pollutants. In addition to iron, a DMP molecular template was also introduced to AFeC to create special molecular imprinting affinity for DMP. The CO2-N2 activation treatment increased the porosity and enriched the hydroxyl and quinone groups (C-O and C=O). The high DMP adsorption capacity of the DMP-imprinted AFeC electrode can be ascribed to the following mechanism: (i) electrostatic interaction; (ii) hydrophobic interaction; (iii) π-π electron-donor-acceptor interactions; (iv) molecular imprinting affinity between template molecules and imprinted sites. Thus, this carbon-based material is promising to be potentially applied in the removal of DMP containing wastewater through integrated adsorption and degradation.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Stability of edge magnetism in functionalized zigzag graphene nanoribbons
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Prashant P. Shinde, Oliver Gröning, Shiyong Wang, Pascal Ruffieux, Carlo A. Pignedoli, Roman Fasel, Daniele Passerone
      Graphene nanoribbons are attractive candidates for future technological applications due to exceptional electronic and magnetic properties. We investigate the stability of edge magnetism in zigzag graphene nanoribbons with indene-type functionalized edges, recently synthesised on Au(111) in our laboratory. Using density functional theory (DFT) calculations, we show that the functionalized nanoribbons preserve most electronic properties of the pristine ribbon, with band modifications making edge magnetism sensitive or unstable to environmental influences. The tendency towards such instability already emerges when the system is investigated with a simple mean field Hubbard model where the on-site Coulomb repulsion can be parametrically tuned. It becomes fully evident in DFT calculations when the mostly dispersive interactions between the nanoribbon and the metal substrate are modeled using different van der Waals correction schemes. One of such schemes gives results in agreement with spectroscopy experiments in which the highest occupied and lowest unoccupied states locate on the unmodified and modified zigzag edge sections, respectively. When a different dispersion correction approach is considered, theory predicts, despite a very similar adsorption geometry, an inversion of occupied/unoccupied states and a 60% reduction in absolute magnetization. Such sensitivity with respect to small perturbations is discussed.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Preparation of water-soluble graphene nanoplatelets and highly conductive
           films
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Xuezhu Xu, Jian Zhou, Jacques Jestin, Veronica Colombo, Gilles Lubineau
      This paper tackles the challenge of preparation stable, highly concentrated aqueous graphene dispersions. Despite tremendous recent interest, there has been limited success in developing a method that ensures the total dispersion of non-oxidized, defect-free graphene nanosheets in water. This study successfully demonstrates that few-layer graphene nanoplatelets (GNPs) can form highly concentrated aqueous colloidal solutions after they have been pretreated in a low-concentration inorganic sodium-hypochlorite and sodium-bromide salted aqueous solvent. This method retains the graphitic structure as evidenced by nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Vacuum-filtrated freestanding films demonstrate an electrical conductivity as high as 3000 S m−1. This dispersion technique is believed to be applicable not only for GNPs, but also for dispersing other types of graphitic materials, including fullerenes, single/double/multi-walled carbon nanotubes, graphene nanoribbons and etc.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Effect of sonication and hydrogen peroxide oxidation of carbon nanotube
           modifiers on the microstructure of pitch-derived activated carbon foam
           discs
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Shuai Gao, Byron S. Villacorta, Lei Ge, Thomas E. Rufford, Zhonghua Zhu
      We used carbon nanotubes (CNTs) as modifying particles and potassium hydroxide as a porogen to prepare mesoporous pitch-derived activated carbon discs (ACD) with high surface areas. The parameters investigated in this study included the concentration of CNTs (1%, 2%, 3.5% and 5%), the dispersion of the CNTs in the pitch using a 750 W sonic probe, the oxidation of the CNTs with H2O2, and the aspect ratio of the CNTs. The highest surface area ACD was obtained with 2% oxidized CNTs dispersed in the pitch with the ultrasonic probe (ACD-2%-SO, SBET = 2089 m2 g−1). The ACDs prepared with the sonic probe and with 2 wt% or more of raw and oxidized CNTs exhibited larger mesopore volumes than those ACDs prepared with 1 wt% CNTs. A series of quench tests performed during the foaming process by withdrawal of the carbon from the tube furnace at 673 K, 773 K and 873 K revealed that mesopores in ACD develop at temperatures ranging from 773 K to 873 K, whereas micropores formed between 873 K and 1073 K. The adsorption capacities of N2 and CO2 on ACD-2%-SO were measured with a gravimetric apparatus at 298 K and 303 K at pressures up to 4000 kPa. The uptake of CO2 on ACD-2%-SO at a temperature of 298 K was 3.33 mol/kg at 100 kPa and 11.51 mol/kg at 3496 kPa.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Molecular simulation aided nanoporous carbon design for highly efficient
           low-concentrated formaldehyde capture
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Piotr Kowalczyk, Jin Miyawaki, Yuki Azuma, Seong-Ho Yoon, Koji Nakabayashi, Piotr A. Gauden, Sylwester Furmaniak, Artur P. Terzyk, Marek Wisniewski, Jerzy Włoch, Katsumi Kaneko, Alexander V. Neimark
      Although recent experimental studies have demonstrated that doping of nanoporous carbons with nitrogen is an effective strategy for highly diluted formaldehyde capture, the impact of carbon surface chemistry and the pore size on formaldehyde capture at ∼ppm concentrations is still poorly understood and controversial. This work presents a combined theoretical and experimental study on dynamic formaldehyde adsorption on pure and oxidized nanocarbons. We find using Monte Carlo simulations and confirm experimentally that cooperative effects of pore size and oxygen surface chemistry have profound impacts on the breakthrough time of formaldehyde. Molecular modeling of formaldehyde adsorption on pure and oxidized model nanoporous carbons at ∼ppm pressures reveals that high adsorption of formaldehyde ppm concentrations in narrow ultramicropores <6 Å decorated with phenolic and carboxylic groups is correlated with long formaldehyde breakthrough times measured in the columns packed with specially prepared oxidized activated carbon fiber adsorbents with the pore size of ∼5 Å.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Multiscale characterization of 13C-enriched fine-grained graphitic
           materials for chemical and electrochemical applications
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): V.O. Koroteev, W. Münchgesang, Yu.V. Shubin, Yu.N. Palyanov, P.E. Plyusnin, D.A. Smirnov, K.A. Kovalenko, M. Bobnar, R. Gumeniuk, E. Brendler, D.C. Meyer, L.G. Bulusheva, A.V. Okotrub, A. Vyalikh
      13C-enriched fine-grained graphitic material has been studied towards its potential for chemical and electrochemical applications. The structural and morphological modification of the material as results of pressure-assisted thermal treatment and gaseous BrF3 and/or Br2 room-temperature treatments has been investigated using a combination of the characterization tools: electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron and near edge X-ray absorption fine structure spectroscopy, solid state nuclear magnetic resonance (NMR) spectroscopy and magnetic susceptibility measurements. It has been found that the starting material represents graphitized carbon with oxygen containing defects. The evidence of distorted sp2 hybridization of carbon was found in the Raman and the 13C NMR spectra. Under high pressure and temperature, some initially open graphitic edges are coupled that causes decreasing specific surface area and mean in-plane size of crystallites, and, generally, a higher degree of disorder. The Br2 treatment improves the material structure due to removal of tiny graphitic flakes and oxygenated carbon groups. The use of BrF3 results, in addition, in partial fluorination of graphitic material. Electrochemical characteristics along with a high degree of 13C isotope enrichment enable the application of these graphitic materials in operando studies using methods sensitive to 13C isotope, such as NMR.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Synthesis and characterization of graphite-encapsulated iron nanoparticles
           from ball milling-assisted low-pressure chemical vapor deposition
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Duygu Ağaoğulları, Steven J. Madsen, Burcu Ögüt, Ai Leen Koh, Robert Sinclair
      Graphite-encapsulated Fe nanoparticles were synthesized using a combined method of high-energy ball milling and low-pressure chemical vapor deposition (LPCVD). Fe2O3 and graphite powders were milled to increase their surface areas and obtain a more homogeneous distribution. LPCVD was performed at a pressure of ∼0.57 Torr in a tube furnace under a CH4/H2 atmosphere at 1050 °C for 1 and 3 h. As-synthesized samples were purified in a 2 M HF solution. Characterization was performed using X-ray diffractometry (XRD), scanning and transmission electron microscopy (SEM and TEM) and alternating gradient magnetometry (AGM). XRD revealed the presence of body centered cubic (BCC) and face centered cubic (FCC) Fe phases without residual iron oxides. SEM confirmed the powders were better mixed and smaller after ball milling compared to mortar and pestle milled powders. High resolution TEM showed all nanoparticles had at least four and on average 16 graphitic layers, around an Fe core ranging from 20 to 300 nm. Magnetic measurements indicated that nanoparticles exhibit soft ferromagnetic behavior with low saturation magnetization (17–21 emu/g) and coercivity (110 Oe). A chemical stability test performed in a 2 M HCl solution showed that graphitic shells did not degrade, nor was there evidence of core dissolution or shell discontinuity.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Molecularly dispersed nickel-containing species on the carbon nitride
           network as electrocatalysts for the oxygen evolution reaction
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Saerom Ohn, Seung Yeon Kim, Seon Kyu Mun, Junghoon Oh, Young Jin Sa, Sunghee Park, Sang Hoon Joo, Seong Jung Kwon, Sungjin Park
      Hybrid materials containing single atoms or molecule-based active species immobilized on nanomaterials have been suggested as new, efficient catalytic systems for various reactions. In this study, novel hybrid materials consisting of molecularly dispersed Ni-based species on a graphitic carbon nitride (g-C3N4) framework are prepared, and their excellent electrocatalytic performance for the oxygen evolution reaction (OER) is discussed. Extensive chemical and structural characterizations confirm that the Ni-based species are attached and well-dispersed on the C3N4 network without agglomeration. In addition, results obtained from electrochemical characterization suggest that Ni-containing molecular entities dispersed on the C3N4 network are active species for the OER.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Enhanced intervalley scattering of aluminum oxide-deposited graphene
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Muhammad Zahir Iqbal, Salma Siddique, Adil Rehman
      In this article, we report the weak localization effect of aluminum oxide (Al2O3)-deposited graphene field effect transistor. Initially, the resistivity tunability of graphene and Al2O3-deposited graphene devices were studied by applying gate voltages. Furthermore, the magnetotransport properties were investigated as a function of gate voltages and temperatures. It was observed that the phase coherence and intervalley scattering rates are enhanced with the deposition of Al2O3 on graphene film compared to uncovered graphene. Most transistor device fabrication processes use an oxide layer for top gate. Therefore, it would be interesting to explore the effect of an oxide capping layer on the magnetotransport properties of graphene.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Thickness-dependent magnetotransport: from multilayer graphene to
           few-layer graphene
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): H. Li, Y.J. Zeng, X.J. Hu, H.H. Zhang, S.C. Ruan, M.J. Van Bael, C. Van Haesendonck
      We present a comparative study of magetoresistance (MR) behaviors in few-layer graphene (FLG) and multilayer graphene (MLG) with various thicknesses. A maximum MR as large as 9500% is observed in a ∼23 nm sample @ 2.5 K, with a non-saturating linear characteristic up to 7 T. MR decreases with increasing temperature and is proportional to the average mobility <μ> in ∼23 nm and ∼12 nm thick samples. In a thinner sample with thickness of ∼1.6 nm, the maximum MR value is only 68% @ 7 T @ 280 K, which is two orders of magnitude smaller than those in the thicker samples. We attribute the MR mechanism of the FLG to mobility fluctuations Δ μ . Both the above situations follow the classical Parish and Littlewood model. Through comparison we unveil that both changes in the band structure resulting from a different sample thickness and the disorder induced by sample preparation and graphene/substrate interface are responsible for the MR behavior in the thickness variation. Our results indicate that MR tuning can be realized by precise thickness control in multilayer graphene.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Variation of the optical properties of soot as a function of particle mass
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Ramin Dastanpour, Ali Momenimovahed, Kevin Thomson, Jason Olfert, Steven Rogak
      Light absorption and scattering properties of combustion-generated soot particles are important to measurement methods and are used as the inputs for climate models. For decades, mass-specific absorption cross section (MAC) of soot has been assumed to be independent of its size and mass. Here we investigate the size-dependent optical properties of particles produced by a single source. Soot particles were produced by combustion of CH4, and CH4 - N2 mixtures, within a laminar inverted diffusion flame. Extinction and scattering coefficients of mass-classified particles were measured by a Cavity Attenuated Phase Shift Single Scattering Albedo Spectrometer. Primary particle diameter and morphology of particles were characterized by transmission electron microscopy. Graphitization level of the size-classified particles was also investigated by Raman spectroscopy. Here, for the first time we observed that MAC and graphitization level of the soot particles increase with the particle mass. MAC number increases from approximately 4.5 to 8.5 (m2g−1) with the particle mass increasing from 0.05 fg to 8 fg. The soot aggregate size is correlated with primary particle size, which may reflect the inhomogeneity of the combustion environment that could affect the optical properties of soot.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Bacterial cellulose derived carbon nanofiber aerogel with lithium
           polysulfide catholyte for lithium–sulfur batteries
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): Shiqi Li, Juliusz Warzywoda, Shu Wang, Guofeng Ren, Zhaoyang Fan
      Highly insulating nature of sulfur species and the shuttling effects caused by soluble lithium polysulfides have been blamed for hindering the development of lithium–sulfur (Li–S) batteries. A variety of carbonaceous materials have been investigated to ameliorate these problems by providing a conductive matrix with physical trapping and chemical binding capabilities, but inevitably resulted in typically low sulfur content in the cathode and hence low gross specific energy when considering all the active and inactive masses. A highly conductive and crosslinked matrix with superior trapping and binding capability to sulfur species but a very low mass density is essential. Herein, crosslinked carbon nanofiber aerogel (CNFA) with extremely low density, attained from pyrolysis of bacterial cellulose (BC) aerogel, was studied for sulfur cathodes. With its unique combination of several merits, in particular the capability of strong absorption of catholyte, CNFA based sulfur electrodes exhibit outstanding performance. With 75% sulfur content of the gross cathode mass, cells demonstrated an initial capacity of 1360 mA h g−1 at 0.2 C, and exhibited excellent cycling stability with 76% of the initial capacity retained after 200 cycles.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
  • Magneto-electronic properties and carrier mobility in phagraphene
           nanoribbons: A theoretical prediction
    • Abstract: Publication date: November 2017
      Source:Carbon, Volume 124
      Author(s): P.F. Yuan, Z.Q. Fan, Z.H. Zhang
      To explore the quantum confinement and edge state effects for phagraphene, a recently proposed new 2D material, we here consider to cut it along a certain direction, and six kinds of the nanoribbons with special A-, B- and C-type edge structures are achieved. Their structural stability with H passivation is verified by the calculated binding energy, phonon dispersion and molecular dynamics simulation. The nanoribbons with two A-type edge structures are nonmagnetic semiconductors with a periodically altered band-gap versus the width. While those with B-type and/or C-type edge structure for two edges are spin-degenerate/spin-splitting semiconductors in the antiferromagnetic ground state. Particularly, nanoribbons with A-type edge structure for one edge while with B-type or C-type edge structure for other edge only hold the ferromagnetic ground state and present the bipolar magnetic semiconducting nature. The further studies reveal that the nanoribbon is an excellent magnetoelectric material and its half-metallicity can be realized by the application of an electric field. More interestingly, the carrier mobility for the nanoribbon with two A-type edge structures is very high and strikingly size-dependent, from ∼103 to 106 cm2/V.S. This means that width control is a possible routine to effectively regulate the mobility of nanoribbons.
      Graphical abstract image

      PubDate: 2017-09-02T10:18:11Z
       
 
 
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