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Crosslinkable nanoparticle-filled poly(4-methyl-2-pentyne) [PMP] membranes were cast from carbon tetrachloride solutions containing PMP, hydrophobic fumed silica, and 4,4¡¯-(hexafluoroisopropylidene)diphenyl azide [HFBAA]. The composite membranes were crosslinked by UV irradiation at room temperature. Low levels of the bis azide were effective in rendering the membranes insoluble in cyclohexane and carbon tetrachloride, both good solvents for PMP. The process is simple and effective, and thus PMP can be easily converted to mechanically stable membranes. Compared to the pure PMP membrane, the permeability of the crosslinked membrane is initially reduced for all tested gases due to the crosslinking. By adding nanoparticles, the permeability is again increased, crosslinking is successful in maintaining the permeability and selectivity of PMP over time.
This paper presents a radionuclide migration model that incorporates bentonite extrusion. The model consists of two parts: one for movement of water and bentonite in a planar fracture and the other for radionuclide transport by taking into account advection, diffusion, and sorption with moving bentonite particles. Numerical results indicate that strongly sorbing radionuclides are contained completely within the region of bentonite extrusion. This observation suggests importance of the region in the vicinity of buffer/rock interface in terms of impact on radionuclide release to surrounding host rock.
The reported electromagnetic properties of carbon nanotubes (CNT) make them a promising material for nanoelectronic applications [1,2]. Addition of CNT has recently been shown to enhance mechanical properties of phenolic-resin polymers . We are attempting to control the electrical transport behavior of phenolic-based polymers doped with CNT as a function of the different nanopowder concentration added to the polymer. In that regard, we developed a technique to obtain a material with homogenous dispersion of nanopowders, an important factor that influences the transport behavior. The chemical structure characterization was also evaluated using optical techniques.
The BMIM+NO3-/Ag metal nanocomposite membranes were utilized for separation of propylene/propane mixtures. The selectivity of propylene/propane and the mixed gas permeance increased to 10 and 1.3 GPU, respectively. It is anticipated that the interactions between NO3- of BMIM+NO3- and the surface of silver nanoparticles causes the Ag surface to be partially positively charged, resulting in the reversible complexation with propylene and consequently facilitated propylene transport. The surface positive charge was confirmed from the increase in the binding energy of the d5/2 orbital of the silver nanoparticles by x-ray photoelectron spectroscopy. It increased from 368.26 for the neat silver nanoparticles to 368.47 eV for BMIM+NO3-/Ag metal composite. The positively charged surface of silver nanoparticles can be utilized as a new durable olefin carrier for facilitated transport.
The covalent grafting of low-molecular weight poly(ethylene glycol) (PEG) onto high surface silica nanoparticles (Cab-O-Sil EH5) has been accomplished by a multi-step reaction. Reaction involved PEG attachment by epoxide-terminated ring opening of a sylilation agent previously grafted. A maximum grafting density of 0.42 PEG per nm2 has been determined by thermogravimetric analysis (TGA). Differential scanning (DSC) calorimetry confirmed the modification of silica after reaction. Infra-Red (IR) analysis and Carbon-13 Magic Angle Spinning Nuclear Magnetic Resonance (13C MAS NMR) confirmed PEG fixation and opening of the epoxide ring.
Silicon Carbide (SiC) nanofibers were synthesized from SiC powder dispersed in polyethylene oxide (PEO) solution in Chloroform using the electrospinning technique. The as-spun fibers were then annealed at 1000ËC to 7 hours. The average diameter of the annealed fibers is 500 nm while the length of the annealed fibers is about 50 Âµm. The fibers were characterized using scanning electron microscope (SEM), X-ray diffraction (XRD) and Cathodoluminescence (CL). PL spectra from the annealed SiC fibers show a broad emission in the red-infrared spectral regime. The main peak is centered at 774 nm while the shoulder on the left is at 740 nm
Surface coating of carbon nanotubes and carbon nanofibers can significantly improve their properties such as electrical, thermal, magnetic, acoustic, vibration, catalytic, optical properties. This paper presents a novel method to coat carbon nanotubes and carbon nanofibers by using as-prepared carbon nanopaper sheets. The carbon nanopaper sheet consisted of randomly oriented single-walled nanotubes and vapor grown carbon nanofibers, which formed into a highly uniform non-woven material. This flexible and lightweight material was coated with nickel by laser pulse deposition. The effects of deposition parameters on the morphology of the nanotubes and nanofibers will be studied using scanning electron microscopy. The electrical conductivities of carbon nanopaper sheets associated with deposition parameters will be characterized using four-point probe method. The deposition parameters will be optimized to achieve a highly conductive carbon nanopaper sheet.
Glassy Polymeric Carbon (GPC) is a material widely used because of its high temperature properties, inertness and biocompatibility . GPC samples were prepared from a phenolic resin, cured in a careful process at 100 ºC and pyrolyzed to 1000 ºC. In this work, we have introduced 3wt%, 10wt%, and 20 wt% of Carbon Nano Tubes (CNT) in the precursor resin to study the evolution of the electrical conductivities of the nanocomposite as a function of the CNT concentration.
Glassy polymeric carbon (GPC) has a unique graphite micro-fibril structure that attributes singular properties to the material. The addition of nanoparticles in the GPC matrix to improve its properties has been the focus of recent studies for spacecraft coating applications. We report the effects of Al2O3 nanoparticles dispersed in GPC on the electrical properties. The fabrication process to produce homogenous samples and the electrical measurements are fully described. In addition, the chemical structure characterization was evaluated using Raman spectroscopy.
We report a new experimental method for the characterization of the electromechanical properties of polyelectrolyte gels (PG). PGs have been studied extensively, but with limited success, as mechanical actuators. However, they are also promising as potentially biocompatible mechanical sensors. In order to integrate them into actual devices, their electromechanical transduction properties need to be characterized in a reproducible manner.
We have therefore developed a technique to measure the mechanically induced change in electrostatic potential in PGs. The polyelectrolyte gel is subjected to a well-defined pressure gradient by placing a thin, flat sample on a substrate with integrated concentric Platinum electrodes and indenting it with a spherical indenter. The potential values at the electrodes are measured using a MOSFET operational amplifier circuit with an input impedance of 1014 Ù and an effective dynamic range better than 16 bit. This method can be directly used to quantify electromechanical coupling in polyelectrolyte gels.