Stabilizing decontamination foam using surface-modified silica nanoparticles containing chemical reagent: foam stability, structures, and dispersion properties.

The stabilization of decontamination foams containing a chemical reagent is a crucial requirement for their use in the decontamination of nuclear power plants. We have investigated the effects on decontamination foam stability of adding silica nanoparticles (NPs) modified with various functional groups, namely propyl (-CH3), amine (-NH2), and thiol (-SH) groups. The surface properties of these silica NPs were characterized with ATR-FTIR, solid NMR, and TGA analyses. We also established that the agglomeration in such foams of the amine-modified silica NPs is weaker than that of the other modified silica NPs due to their thorough dispersion in the liquid film. Further, the foam containing amine-modified silica NPs was found to be stable for 60 min at a pH of 2, i.e. under decontamination conditions. The bubble structure analysis showed that this decontamination foam has a bubble count that is approximately 5-8 times higher than the foams containing NPs modified with the other functional groups, which indicates that the decontamination foam with amine-modified silica NPs has the best foam structure of the three investigated foams. The well-dispersed and smaller amine-modified silica NPs enhance the foam stability by providing a barrier between the gas bubbles and delaying their coalescence. In contrast, the thiol- and propyl-modified silica NPs form aggregates with large diameters that reduce the maximum capillary pressure of coalescence and hence decrease the foam stability.

Calcination-temperature-Dependent shape and crystal structure of TiO2 nanomaterials synthesized by hard-template method.

The shape and crystal structure of TiO2 nanomaterials synthesized by the hard-template method can be controlled by simply changing the calcination temperature. In this work, SiO2 nanoparticles were used as a hard template and TiO2 was coated onto the surface of the silica core, resulting in core-shell nanoparticles, which were then calcined at various temperatures to induce shape transformation and crystallization of the TiO2 shell. After etching of the silica cores, spherical hollow nanocapsules with anatase crystal phase were obtained by calcination at 400-1000 degrees C, while urchin-like hollow capsules and small-sized particulates were obtained at temperatures below 400 degrees C and above 1000 degrees C, respectively. The core-shell nanoparticles exhibited greatly enhanced anatase phase stability (up to approximately 1200 degrees C), which was attributable to the effect of the core material. The phase stability was found to be dependent on the shell thickness of the nanocapsules, also supporting the effect of the core material.

Fabrication of nanoporous TiO2 hollow capsules using core-shell silica nanoparticle templates.

We report on the fabrication of the nanoporous TiO2 hollow capsules using core-shell silica nanoparticle templates. The thickness of the capsules can be simply controlled by varying the amount of the TiO2 precursor. The resulting nanoporous capsules exhibited the high specific surface area and the large pore volume of 103-180 m2/g and 0.40-0.86 cm3/g, respectively. Photocatalytic activity of the TiO2 hollow capsules was also investigated and compared to that of the commercial TiO2 nanoparticles.

Superhydrophobic thin films with nanostructured surface prepared with Au nanoparticle masks.

The hydrophobicity of a perfluoropolyether bisurethane methacrylate polymer film was investigated along with the formation of nano-hairs on its surface through reactive ion etching using gold nanoparticles (Au NPs) as masks. It was found that the hydrophobicity of the polymer film was strongly dependent on the number density of the nano-hairs which was determined by that of the Au NPs. The superhydrophobic surface was obtained when the number density was higher than 250 microm(-2). The effects of surface functionalization, Au NP immobilization, and etching time on the hydrophobicity of the polymer film were also examined extensively and discussed based on the results of the contact angle measurements and the scanning electron microscopy.

Fabrication of carbon capsules with hierarchical pore structures.

Carbon capsules with hierarchical pore structures were fabricated by using core-shell silica nanoparticles as templates and phenolic resin as a carbon precursor. Carbon capsules with hierarchical pore structures were obtained via in-situ polymerization of the phenolic resin on the surface of the silica nanoparticles followed by the carbonization and removal of the silica templates. The hierarchically pored carbon capsules exhibited multimodal porosity with a high specific surface area (approximately 1834 m2/g) and a large pore volume (approximately 1.83 cm3/g).

Layer-by-layer films of dual-pore carbon capsules with designable selectivity of gas adsorption.

Stable, homogeneous ultrathin films of uniformly dimensioned dual-pore carbon capsules with mesoporous walls and macroscopic empty cores were fabricated using layer-by-layer methods based on electrostatic interaction between a polyelectrolyte and a surfactant coating of the carbon capsules. The resulting dual-porous carbon capsule films were investigated as a sensor substrate for vapors of different organic solvents. The carbon capsule films have much higher adsorption capacities than conventional electrolyte films and even than noncapsular mesoporous carbon films. The dual-pore carbon capsules have greater affinities for aromatic volatiles over their aliphatic counterparts, probably due to stronger pi-pi interactions. Additionally, the adsorption selectivity can be designed. Impregnation of additional recognition components into the carbon capsules permits further control over adsorption selectivity between aromatic and nonaromatic substances and between acids and bases in the prevailing atmosphere. Therefore, it is anticipated that the dual-pore carbon capsule films developed in this work will find application in sensing and separation applications because of their designable selectivity.

Use of pluronic F108 as a cosurfactant in a synthesis of mesoporous silica microspheres with bimodal pore size distribution.

Large mesoporous silica microspheres with bimodal pore size distributions will be very promising in a special application. Silica microspheres of 10-100 microm in size were synthesized using n-dodecylamine and polymeric surfactant as co-templating agents at room temperature. Surface area and large pore volume of the mesoporous silica microspheres were 884-1009 m2/g and 1.25-1.68 cm3/g, respectively, depending on the reaction conditions. Mesoporous silica microspheres prepared using a short-chained alkylamine surfactant and a long-chained polymeric surfactant exhibited distinct bimodal pore size distribution, that is, small (< 3 nm) and large mesopores (> 20 nm). Pluronic F108, which is a poly(ethylene glycol)-poly(propylene glycol) triblock copolymer, played an important role in the formation of the large mesopores as well as the formation of stable silica microspheres without strong aggregation between particles.

The role of Di(2-ethylhexyl)phosphoric acid as a cosurfactant on the morphology control of mesoporous silica microspheres.

Synthesis of mesoporous silica microspheres larger than 10 microm via surfactant template approach has rarely been reported. According to the previous studies, particle morphologies were highly variable, depending on the synthesis conditions and impeller design such as impeller type, size, and agitation speed. A new robust surfactant-template synthesis strategy for the stable suspension of large silica microspheres was investigated by introducing an additional cosurfactant. Di(2-ethylhexyl)phosphoric acid (HDEHP) as a cosurfactant played a key role in suspension stabilization without distorting the spherical morphology as well as in the formation of uniform pore structures. High quality of mesoporous silica microspheres was obtained and compared with the Kosuge's silica under different conditions such as stirring rate, acid concentration, the amount of solvent in a mother liquor.

Graphitized pitch-based carbons with ordered nanopores synthesized by using colloidal crystals as templates.

A highly graphitized ordered nanoporous carbon (ONC) was synthesized by using commercial mesophase pitch as carbon precursor and siliceous colloidal crystal as template. Since silica colloids of different sizes (above 6 nm) and narrow particle size distribution are commercially available, the pore size tailoring in the resulting ONCs is possible.

Fabrication of bimodal porous silicate with silicalite-1 core/mesoporous shell structures and synthesis of nonspherical carbon and silica nanocases with hollow core/mesoporous shell structures.

In this work, an attempt has been made to modify the shape and nanostructure of core-shell materials, which have been usually generated on the basis of amorphous spherical cores. Novel core-shell silicate particles, each of which consists of a silicalite-1 zeolite crystal core and mesoporous shell (ZCMS), were synthesized for the first time. The ZCMS core-shell particles are unique because they are of pseudohexagonal prismatic shape and have hierarchical porosity of both a uniform microporous core and a mesoporous shell coexisting in a particle framework. The nonspherical bimodal porous core-shell particles were then utilized as templates to fabricate a new carbon replica structure. Interestingly, the pore replication process was carried out only through the mesopores in the shell, and not through the micropores due to the narrower micropore size in the core, resulting in nonspherical carbon nanocases with a hollow core and mesoporous shell (HCMS) structure. Nonspherical silica nanocases with HCMS structure were also generated by replication using the carbon nanocases as templates, which are not possible to synthesize through other synthetic methods. Interestingly, the pseudohexagonal prismatic shape of the zeolite crystals was transferred onto the carbon and silica nanocases.

Spherical carbon capsules with hollow macroporous core and mesoporous shell structures as a highly efficient catalyst support in the direct methanol fuel cell.

Carbon capsules with hollow core and mesoporous shell (HCMS) structures were used as a support material for Pt(50)-Ru(50) catalyst, and the catalytic performance of the HCMS supported catalyst in the direct methanol fuel cell was described; the HCMS carbon supported catalysts exhibited much higher specific activity for methanol oxidation than the commonly used E-TEK catalyst by about 80%, proving that the HCMS carbon capsules are an excellent support for electrode catalysts in DMFC.

Fabrication of nanocapsules with Au particles trapped inside carbon and silica nanoporous shells.

Carbon capsules with hollow cores and mesoporous shells (HCMS) containing entrapped Au particles were prepared by template replication from solid core/mesoporous shell silica spheres with encapsulated Au particles. The resulting HCMS carbon capsules were then nanocast one step further to generate Au-trapping hollow core silica capsules with nanostructured shells.

Fabrication of macroporous SiC from templated preceramic polymers.

Macroporous SiC with a highly ordered pore array was prepared for the first time using low molecular weight SiC preceramic polymers such as polymethylsilane or polycarbosilane by utilizing sacrificial colloidal silica crystalline arrays, as a template which were subsequently etched off after pyrolysis in an argon atmosphere.

A direct template synthesis of nanoporous carbons with high mechanical stability using as-synthesized MCM-48 hosts.

A simple and efficient synthetic method for highly ordered nanoporous carbons with high mechanical and thermal stability has been performed through a direct template carbonization using as-synthesized MCM-48 hosts.

Fabrication of ordered uniform porous carbon networks and their application to a catalyst supporter.

Ordered uniform porous carbon frameworks showing interesting morphology variations were synthesized against removable colloidal silica crystalline templates through simply altering acid catalyst sites for acid-catalyzed polymerization. These highly ordered uniform porous carbons as a catalyst supporter resulted in much improved catalytic activity for methanol oxidation in a fuel cell.