[en] We demonstrate high yield fabrication of field effect transistors (FET) using chemically reduced graphene oxide (RGO) sheets. The RGO sheets suspended in water were assembled between prefabricated gold source and drain electrodes using ac dielectrophoresis. With the application of a backgate voltage, 60% of the devices showed p-type FET behavior, while the remaining 40% showed ambipolar behavior. After mild thermal annealing at 200 deg. C, all ambipolar RGO FET remained ambipolar with increased hole and electron mobility, while 60% of the p-type RGO devices were transformed to ambipolar. The maximum hole and electron mobilities of the devices were 4.0 and 1.5 cm² V^-1 s^-1 respectively. High yield assembly of chemically derived RGO FET will have significant impact in scaled up fabrication of graphene based nanoelectronic devices.

[en] Monte Carlo (MC) simulations based on the migration-coalescence model are important tools for studying the evolution of gas bubbles in materials, a subject of concern across numerous fields. The acceleration of MC simulations is always desired especially when a large simulation system is required to extract highly accurate statistics. The present work focuses on the algorithmic study. A graphics processing unit (GPU)-based implementation of an MC simulation of the migration-coalescence evolution of bubbles is described. The acceleration of simulations involves two factors. In addition to acceleration due to the parallel computing features of GPUs, algorithmic strategies are proposed to improve performance. Considering that bubbles have a finite radius and grow with time, this paper proposes generating a nearest-neighbor-list (NNL) instead of a cutoff-radius-neighbor-list. An evaluation demonstrated that an NNL strategy can improve computational efficiency and, more importantly, conserve valuable GPU memory. This paper also proposes a strategy using many small boxes in one run instead of one large box. An evaluation of this strategy shows that significant promotion of the computational efficiency for generating neighbor-lists can be achieved. Regarding the migration and coalescence process, this paper proposes a method in which a merging table is generated and CUDA atomic operations are applied to bubbles in a bi-directional procedure that handles coalescence events. This method avoids asynchronous reading and writing conflicts that may occur in the GPU implementation of the migration and coalescence process without losing numerical accuracy. The algorithms and implementations presented in this paper would be instructive to the development of simulation codes, for an example the code of object kinetic Monte Carlo, in which the defects have finite sizes. (paper)

[en] Molecular dynamics simulations were performed to study the diffusion behavior of hydrogen isotopes in single-crystal tungsten in the temperature range of 300–2000 K. The simulations show that the diffusion coefficient of H isotopes exhibits non-Arrhenius behavior, though this deviation from Arrhenius behavior is slight. Many-body and anharmonic effects of the potential surface may induce slight isotope-dependence by the activation energy; however, the dependence of the pre-factor of the diffusion coefficient on the isotope mass is diminished. The simulation results for H-atom migration near W surfaces suggest that no trap mutations occur for H atoms diffusing near either W{100} or W{111} surfaces, in contrast to the findings for He diffusion near W surfaces. Based on the H behavior obtained by our MD simulations, the time evolution of the concentration distribution of interstitial H atoms in a semi-infinite W single crystal irradiated by energetic H projectiles was calculated. The effect of H concentration on H diffusion is discussed, and the applicability of the diffusion coefficients obtained for dilute H in W is assessed. (paper)

[en] Highlights: • An experimental system for wide-range 2D RBS analysis in vacuum chamber was developed. • The system automatic control and RBS analysis in batch mode are realized. • An analysis for a test sample was provided. Rutherford backscattering spectrometry (RBS) analysis is a widely used ion beam analysis technique to obtain the concentration and/or thickness of the target. In some cases we have to utilize the large area target, for example, about 40 mm diameter target in our ${}^{12}\mathrm{C}{(\alpha ,\gamma )}^{16}\mathrm{O}$ experiment of Jinping Underground laboratory for Nuclear Astrophysics (JUNA) project, it means that we should perform wide-range two dimensional (2D) RBS analyses for tens of points in the large area target to obtain the elemental area (or 2D) depth profile distribution which is needed in the ${}^{12}\mathrm{C}{(\alpha ,\gamma )}^{16}\mathrm{O}$ experiment. In order to perform the large area target RBS analysis in vacuum chamber accurately and efficiently, an experimental system was developed in this work, which included (1) a 2D moving sample stage in vacuum chamber for precisely positioning points to be analyzed in target, (2) synchronously starting spectrum acquisition when the sample stage is located at the measurement point and saving the corresponding spectrum when the acquisition is finished by utilizing the job control script of ORTEC MAESTRO software, and (3) using the Object Linking and Embedding (OLE) automation of SIMNRA software to perform batch analysis for tens of experimental RBS spectra. The experimental system developed in this work and corresponding demonstration results were described in detail in this paper. The experimental system developed here can also be used in other research fields.

[en] We report the first fully compressed Li₄Ti₅O₁₂ electrode designed by an aqueous process. An adhesive, elastomeric, and lithium ion conductive PEG-based copolymer is used as a binder for the aqueous fabrication thick, flexible, and densely packed Li₄Ti₅O₁₂ (LTO) electrodes. Self-adherent cathode films exceeding 200 μm in thickness and withholding high active mass loadings of 28 mg/cm² deliver 4.2 mAh/cm² at C/2 rate. Structurally defect-free electrodes are fabricated by casting aqueous cathode slurries onto nickel foam, dried, and hard-calendared at 10 tons/cm². As a multifunctional material, the binder is synthesized by the copolymerization of poly(ethylene glycol) methyl ether methacrylate (PEGMA), methyl methacrylate (MMA), and isobutyl vinyl ether (IBVE) in optimal proportions. Furthermore, coordinating the binder with lithium salt is necessary for the electrode to function

[en] We herein report the dispersion of multi-walled carbon nanotubes (MWCNTs) using trifluoroacetic acid (TFA) as a co-solvent. TFA is a strong but volatile acid which is miscible with many commonly used organic solvents. Our study demonstrates that MWCNTs can be effectively purified and readily dispersed in a range of organic solvents including dimethyl formamide (DMF), tetrahydrofuran (THF), and dichloromethane when mixed with 10 vol.% trifluoroacetic acid (TFA). X-ray photoelectron spectroscopic analysis revealed that the chemical structure of the TFA-treated MWCNTs remained intact without oxidation. The dispersed carbon nanotubes in TFA/THF solution were mixed with poly(methyl methacrylate) (PMMA) to fabricate polymer nanocomposites. A good dispersion of nanotubes in solution and in polymer matrices was observed and confirmed by SEM, optical microscopy, and light transmittance study. Low percolation thresholds of electrical conductivity were observed from the fabricated MWCNT/PMMA composite films. Further enhancement in the dispersion of MWCNTs was achieved by adding a conjugated conducting polymer, poly(3-hexylthiophene) (P3HT), to the dispersion, wherein TFA also serves as a doping agent to the conducting polymer. The ternary nanocomposite MWCNT/P3HT/PMMA exhibited an extremely low percolation threshold of less than 0.006 wt% of MWCNT content. This low percolation threshold is attributed to a good dispersion of MWCNTs and enhanced conductivity of the nanocomposites by conjugated conducting polymer

[en] This session brings together 10 posters dealing with: 1 - Optimization of Microbial DNA Extraction from Tritium-Contaminated Soils - 21467 (Logan Willis, Yong Lee, John Seaman, Robin Brigmon). 2 - Fouling Reduction During Crossflow Filtration of Tank Wastes - 21469 (Hamid Ghaffari Nazarlou, Kimberly L. Jones). 3 - A Study on Modified Biochars for the Removal of TCE and PCE - 21470 (Suraj Venkat Pochampally, Padmanabhan Krishnaswamy, Ashtin Hofert, Erica Marti, Jaeyun Moon). 4 - Comparison of Biochars Obtained from Different Feedstocks for the Adsorption of TCE and PCE in Water - 21471 (Padmanabhan Krishnaswamy, Suraj Venkat Pochampally, Jaeyun Moon, Erica Marti, Christina Obra). 5 - Detecting Mercury Ions Using Silver Nanoparticle Loaded Hydrogel Nanofiber Electrodes - 21472 (David Fox, Woo Hyoung Lee, Lei Zhai, Yuen Yee Li Sip, Stephen Sarnyai, Jaehoon Hwang). 6 - Assessing VOC Plume Attenuation Pathways for Groundwater and Hyporheic Zone Microbial Attenuation Effectiveness - 21473 (Malik Williams, John Williams). 7 - Genomic Analysis of a Uranium Resistant Burkholderia sp. Strain SRS-147 Isolated from Uraniferous Soils of the Savannah River Site, USA - 21474 (Rajesh Singh Rathore, Meenakshi Agarwal, Ashish Pathak, John Seaman, Ashvini Chauhan). 8 - Characterization and Geochemical Modeling of Manganese Oxide Amendments for Remediation of Mercury-Contaminated Sediments - 21476 (Edwin Rivas Meraz, Mark Seelos). 9 - Spectro-electrochemical Analysis of Neptunium Solutions - 21478 (Nicholas Cicchetti). 10 - Analytical Functions for the Hanford 200 West Pump-and-Treat SCADA Sensor Data - 21595 (Jonas LaPier, Chris Johnson)