Hybrid ion-exchange membrane-electrode for advanced catalysis and desalination processes

This PhD Thesis aimed at developing novel hybrid polymer-metal composite materials for desalination and catalytic applications. The stability and electrical conductivity of the metal phase combined with the reactivity of the polymeric phase allowed for the development of novel electro-desalination and electro-catalytic processes in both water and alcoholic solutions.<br /

Electro-catalytic biodiesel production from canola oil in methanolic and ethanolic solutions with low-cost stainless steel and hybrid ion-exchange resin grafted electrodes

Biodiesel is a growing alternative to petroleum fuels and is produced by the catalyzed transesterification of fats in presence of an alcohol base. Transesterification processes using homogeneous catalysts are considered to be among the most efficient methods but rely on the feedstock quality and low water content in order to avoid undesirable saponification reactions. In this work, the electro-catalytic conversion of canola oil to biodiesel in a 1% aqueous methanolic and ethanolic reaction mixture was performed without the addition of external catalyst or cosolvent. An inexpensive stainless steel (SS) electrode and a hybrid SS electrode coated with an ion-exchange resin catalyst were used as cathode materials while the anode was composed of a plain carbon paper. The cell voltages were varied from 10 to 40 V and the reaction temperature maintained at 20 or 40&deg;C. The canola oil conversion rates were found to be superior at 40&deg;C without saponification reactions for cell voltages below 30 V. The conversion rates were as high as 87% for the hybrid electrode and 81% for the plain SS electrode. This work could inspire new process development for the conversion of high water content feedstock for the production of second-generation biodiesel

Preparation of porous stainless steel hollow-fibers through multi-modal particle size sintering towards pore engineering

The sintering of metal powders is an efficient and versatile technique to fabricate porous metal elements such as filters, diffusers, and membranes. Neck formation between particles is, however, critical to tune the porosity and optimize mass transfer in order to minimize the densification process. In this work, macro-porous stainless steel (SS) hollow-fibers (HFs) were fabricated by the extrusion and sintering of a dope comprised, for the first time, of a bimodal mixture of SS powders. The SS particles of different sizes and shapes were mixed to increase the neck formation between the particles and control the densification process of the structure during sintering. The sintered HFs from particles of two different sizes were shown to be more mechanically stable at lower sintering temperature due to the increased neck area of the small particles sintered to the large ones. In addition, the sintered HFs made from particles of 10 and 44 &mu;m showed a smaller average pore size (&lt;1 &mu;m) as compared to the micron-size pores of sintered HFs made from particles of 10 &mu;m only and those of 10 and 20 &mu;m. The novel HFs could be used in a range of applications, from filtration modules to electrochemical membrane reactors

Ultrasound-assisted fabrication of metal nano-porous shells across polymer beads and their catalytic activity for reduction of 4-nitrophenol

Metal nano-porous architectures are a novel class of nanomaterials which has been applied in the fields of catalysis, sensing and gas storage because of their high surface-to-volume ratio, high mechanical strength and long-range ordered architectures. A commonly-used synthetic strategies to achieve architectures with high precision and diverse porosity design is the seed-and-growth method. In this work, using a dual-frequency sequential sonication approach, we have demonstrated a sonochemical-assisted one-pot seeding with a successive shell growth synthetic strategy for mesoporous metal deposition via a gold (Au) nanoparticle and poly(styrene) beads system. A uniform coating of gold nanoparticle seeds with dense surface coverage was formed by first employing 300 kHz ultrasound irradiation while the nano-porous shell growth was then performed under 1 MHz ultrasonic frequency. The precise control over the process conditions and parameters allowed for the design of well-defined shell thicknesses and surface roughness and area. The catalytic property of the MNMs was evaluated for the degradation of 4-nitrophenol and a high catalytic activity was achieved for the most porous gold structures, suggesting synergistic effects between the architecture of the nanomaterials and their surface reactivity

Gallium-based liquid metal particles for therapeutics

Gallium (Ga) and Ga-based liquid metal (LM) alloys offer low toxicity, excellent electrical and thermal conductivities, and fluidity at or near room temperature. Ga-based LM particles (LMPs) synthesized from these LMs exhibit both fluidic and metallic properties and are suitable for versatile functionalization in therapeutics. Functionalized Ga-based LMPs can be actuated using physical or chemical stimuli for drug delivery, cancer treatment, bioimaging, and biosensing. However, many of the fundamentals of their unique characteristics for therapeutics remain underexplored. We present the most recent advances in Ga-based LMPs in therapeutics based on the underlying mechanisms of their design and implementation. We also highlight some future biotechnological opportunities for Ga-based LMPs based on their extraordinary advantages.</p

Applications of liquid metals in nanotechnology

Post-transition liquid metals (LMs) offer new opportunities for accessing exciting dynamics for nanomaterials. As entities with free electrons and ions as well as fluidity, LM-based nanomaterials are fundamentally different from their solid counterparts. The low melting points of most post-transition metals (less than 330 °C) allow for the formation of nanodroplets from bulk metal melts under mild mechanical and chemical conditions. At the nanoscale, these liquid state nanodroplets simultaneously offer high electrical and thermal conductivities, tunable reactivities and useful physicochemical properties. They also offer specific alloying and dealloying conditions for the formation of multi-elemental liquid based nanoalloys or the synthesis of engineered solid nanomaterials. To date, while only a few nanosized LM materials have been investigated, extraordinary properties have been observed for such systems. Multi-elemental nanoalloys have shown controllable homogeneous or heterogeneous core and surface compositions with interfacial ordering at the nanoscale. The interactions and synergies of nanosized LMs with polymeric, inorganic and bio-materials have also resulted in new compounds. This review highlights recent progress and future directions for the synthesis and applications of post-transition LMs and their alloys. The review presents the unique properties of these LM nanodroplets for developing functional materials for electronics, sensors, catalysts, energy systems, and nanomedicine and biomedical applications, as well as other functional systems engineered at the nanoscale.</p

Graphene based room temperature flexible nanocomposites from permanently cross-linked networks

Abstract Graphene based room temperature flexible nanocomposites were prepared using epoxy thermosets for the first time. Flexible behavior was induced into the epoxy thermosets by introducing charge transfer complexes between functional groups within cross linked epoxy and room temperature ionic liquid ions. The graphene nanoplatelets were found to be highly dispersed in the epoxy matrix due to ionic liquid cation–π interactions. It was observed that incorporation of small amounts of graphene into the epoxy matrix significantly enhanced the mechanical properties of the epoxy. In particular, a 0.6 wt% addition increased the tensile strength and Young’s modulus by 125% and 21% respectively. The electrical resistance of nanocomposites was found to be increased with graphene loading indicating the level of self-organization between the ILs and the graphene sheets in the matrix of the composite. The graphene nanocomposites were flexible and behave like ductile thermoplastics at room temperature. This study demonstrates the use of ionic liquid as a compatible agent to induce flexibility in inherently brittle thermoset materials and improve the dispersion of graphene to create high performance nanocomposite materials