ABSTRACT
A thermoplastic elastomer (TPE) based nanocomposite with the same weight ratio of hybrid nanofillers composed of carbon nanotubes (CNTs) and montmorillonite nanoclay (DK4) was prepared using a melt blending technique with an internal mixer. The TPE composite was blended from polylactic acid (PLA), liquid natural rubber (LNR) as a compatibilizer and natural rubber (NR) in a volume ratio of 70:10:20, respectively. The weight ratio of CNTs and DK4 was 2.5 wt%. The prepared samples were exposed to gamma radiation at range of 0-250 kGy. After exposure to gamma radiation, the mechanical, thermo-mechanical, thermal and electrical conductivity properties of the composites were significantly higher than unirradiated TPE composites as the irradiation doses increased up to 150 kGy. Transmission electron microscopy (TEM) micrographs revealed the good distribution and interaction between the nano-fillers and the matrix in the prepared TPE hybrid nanocomposites. In summary, the findings from this work definite that gamma irradiation might be a viable treatment to improve the properties of TPE nanocomposite for electronic packaging applications.
ABSTRACT
In this study, we report a comprehensive density functional theory investigation of the structure and thermodynamic stability of FeCl2 and FeCl3 surfaces. Calculated lattice constants and heats of formation for bulk FeCl2 and FeCl3 were found to be in relatively good agreement with experimental measurements. We provide structural parameters for 15 distinct FeCl2 and FeCl3 surfaces along the three low-index orientations. The optimized geometries for all surfaces are compared with analogous bulk values. Ab initio atomistic thermodynamic calculations have been carried out to assess the relative thermodynamic stability of FeCl2 and FeCl3 surfaces under practical operating conditions of temperatures and pressures. The FeCl2 (100-Cl) surface is found to afford the most stable configuration at all experimentally accessible gas phase conditions.
ABSTRACT
This study represents a detailed DFT periodic-slab study on the interaction between atomic chlorine and the Fe(100) surface. Energetic and structural parameters are calculated for a wide range of coverages corresponding to top, bridge and hollow pure on-surface adsorptions. Calculated chemisorbed energies are found to increase gradually with the degree of coverage. Formation of iron chlorides via substitutional adsorption is predicted to be not feasible in view of the calculated chemisorption energies. This finding is in line with earlier experimental measurements with regard to the absence of chlorine diffusion into bulk Fe. Sublimation energies for FeCl2 and FeCl3 are estimated and discussed to elucidate the fate of the chlorine-iron thin layer. A stability temperature-pressure diagram is constructed for a wide range of chlorine chemical potentials to mimic real operational conditions.
ABSTRACT
Using density functional theory, we report detailed reaction path calculations for the reaction of acetone with the silicon (001) surface. We identify the key reaction intermediates of dissociative adsorption and the transition states between them. This resolves the identity of the one-dimer intermediate observed in STM experiments and its role in the formation of several two-dimer-wide end products of dissociation. Key to the understanding of the dissociation mechanism is the ambiphilic character of the two reactants, that is the simultaneous expression of electrophilic and nucleophilic reactivities in both the surface and the acetone molecule.
ABSTRACT
The ability to covalently attach organic molecules to semiconductor surfaces in a controllable and selective manner is currently receiving much attention due to the potential for creating hybrid silicon-organic molecular-electronic devices. Here we use scanning tunneling microscopy (STM) and density functional theory calculations to study the adsorption of a simple ketone [acetone; (CH(3))(2)CO] to the silicon (001) surface. We show both bias and time-dependent STM images and their agreement with total energy DFT calculations, simulated STM images, and published spectroscopic data. We investigate the stability of the resulting adsorbate structures with respect to temperature and applied STM tip bias and current. We demonstrate the ability to convert from the kinetically favored single-dimer alpha-H cleavage adsorbate structure to thermodynamically favored bridge-bonded adsorbate structures. This can be performed for the entire surface using a thermal anneal or, for individual molecules, using the highly confined electron beam of the STM tip. We propose the use of the carbonyl functional group to tether organic molecules to silicon may lead to increased stability of the adsorbates with respect to current-voltage characterization. This has important implications for the creation of robust single-molecule devices.
