Rapid synthesis of mesoporous silica by an accelerated microwave radiation method

Microwave-hydrothermal processes for the synthesis of mesoporous silica were investigated with different pathways and mixture conditions at 373 K, and the corresponding structures to the hydrothermal method were synthesized within a very short crystallization time. 2-D hexagonally ordered arrays of MCM-41 materials via the direct electrostatic assembly pathway of ST and mediated templating pathways of S⁺X^-I⁺ with CTAB were synthesized, and cubic mesophase of MCM-48 was also prepared within 2 hrs of microwave heating without adding alcohol. Nonionic surfactants with ethylene oxide (EO) moiety as structure-directing agents were used for the preparation of ordered array of hexagonal or cubic mesostructured silica via the charge matching principle of (S⁰H⁺)(X^-I⁺). Although the detailed roles of microwaves may differ for each process, microwaves accelerate the formation of multiply charged silicate oligomers, initiating mesophase assembly. Therefore, the use of microwave radiation can transfer energy uniformly and quickly, and complete the syntheses of mesostructured materials within a short time     

Effect of drying methods on removal of residual solvents from solvent-induced amorphous paclitaxel

We investigated the effect of solvents on the formation of amorphous paclitaxel and proposed an efficient strategy for the removal of residual solvents from solvent-induced amorphous paclitaxel. Amorphous paclitaxel was produced by solvent-induced method using non-polar solvents (methylene chloride, toluene, pentane, methyl t-butyl ether, chloroform, and acetonitrile/hexane (1 : 2, v/v)). The residual pentane and hexane levels easily met the International Conference on Harmonization (ICH)-specified values (5,000 and 290 ppm) by simple rotary evaporation. When the vacuum-dried sample was subjected to microwave-assisted drying, the ICH requirements for methylene chloride (600 ppm) and acetonitrile (410 ppm) were met by drying for 23 hr at 200 W and 3 hr at 200 W, respectively. However, residual toluene, methyl t-butyl ether, and chloroform concentrations did not meet the ICH-specified values (890, 5,000, and 60 ppm). The shape and size of amorphous paclitaxel particles were examined by SEM and XRD.     

Ferroelectric order in individual nanometre-scale crystals

Ferroelectricity in finite-dimensional systems continues to arouse interest, motivated by predictions of vortex polarization states and the utility of ferroelectric nanomaterials in memory devices, actuators and other applications. Critical to these areas of research are the nanoscale polarization structure and scaling limit of ferroelectric order, which are determined here in individual nanocrystals comprising a single ferroelectric domain. Maps of ferroelectric structural distortions obtained from aberration-corrected transmission electron microscopy, combined with holographic polarization imaging, indicate the persistence of a linearly ordered and monodomain polarization state at nanometre dimensions. Room-temperature polarization switching is demonstrated down to ~5?nm dimensions. Ferroelectric coherence is facilitated in part by control of particle morphology, which along with electrostatic boundary conditions is found to determine the spatial extent of cooperative ferroelectric distortions. This work points the way to multi-Tbit/in(2) memories and provides a glimpse of the structural and electrical manifestations of ferroelectricity down to its ultimate limits.     

Quenching of photocatalytic activity and enhancement of photostability of ZnO particles by polydimethysiloxane coating

ZnO particles with a size range of 50–150 nm were coated with polydimethylsiloxane (PDMS) with a thin film thickness of 3–4 nm using a simple ambient-pressure chemical vapor deposition method. Surfaces consisting of the PDMS-coated ZnO nanoparticles were found to be superhydrophobic with a water contact angle >160°. The superhydrophobicity was sustained in the presence of UV light. Photocatalytic activity and photocorrosion of ZnO were nearly completely quenched in the presence of PDMS-coating. It is suggested that our PDMS-coating can be of potential interest for the application of ZnO in UV protection agents and energy and electronic devices.     

Optimal design of an extrusion process for a hinge bracket

This study considers process design in forming a hinge bracket. A thin hinge bracket is typically produced by bending a sheet panel or welding a hollow bar into a sheet panel. However, the hinge bracket made by bending or welding does not have sufficient durability in severe operating conditions because of the stress concentration in the bended region or the low corrosion resistance of the welded region. Therefore, this study uses forming to produce the hinge bracket part of a foldable container and to ensure durability in difficult operating conditions. An extrusion process for a T-shaped hinge bracket is studied using finite element analysis. Preliminary analysis shows that a very high forging load is required to form the bracket by forging. Therefore, extrusion is considered as a candidate process. Producing the part through the extrusion process enables many brackets to be made in a single extrusion and through successive cutting of the extruded part, thereby reducing the manufacturing cost. The design focuses on reducing the extrusion load and on ensuring shape accuracy. An initial billet is designed to reduce the extrusion load and to obtain a geometrically accurate part. The extruded part is bent frequently because of uneven material flow. Thus, extrusion die geometries are designed to obtain straight parts.

     

An inference network for bidirectional approximate reasoning basedon an equality measure

An inference network is proposed as a tool for bidirectional approximate reasoning. The inference network can be designed directly from the given fuzzy data (knowledge). If a fuzzy input is given for the inference network, then the network renders a reasonable fuzzy output after performing approximate reasoning based on an equality measure. Conversely, due to the bidirectional structure, the network can yield its corresponding reasonable fuzzy input for a given fuzzy output. This property makes it possible to perform forward and backward reasoning in the knowledge base system     

Enhanced photocatalytic activity of TiO2 by polydimethylsiloxane deposition and subsequent thermal treatment at 800 °C

A thin film of polydimethylsiloxane (PDMS) was coated on TiO₂ nanoparticles (P-25, Dagussa), and surface structures of the thin films were analyzed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Furthermore, photocatalytic activity of PDMS-coated TiO₂ samples with various annealing temperatures was determined using UV irradiation. We show that the 800 °C-annealed sample of PDMS-coated TiO₂ showed a two-fold higher photocatalytic activity with respect to the bare TiO₂. The enhanced photocatalytic activity was attributed to the greater hydrophilicity of the annealed PDMS coating.     

Effectiveness of a new water-based oil spill dispersant comprised of an alkyl polyglycoside

Alkyl polyglycoside (AP) used in a water-based oil dispersant system showed maximal performance at typical concentrations. Premixtures of AP aqueous solutions and fuel oil contributed to higher performance, and therefore its physicochemical characteristics, such as rheology and conductivity, were studied and compared with effectiveness. When an AP containing an electrolyte (NaCl) is used, effectiveness and stability improve further.     

Quantitative phase imaging of nanoscale electrostatic and magnetic fields using off-axis electron holography

Off-axis electron holography in the transmission electron microscope is a powerful interferometric technique that enables electrostatic and magnetic fields to be imaged and quantified with spatial resolution often approaching the nanometer scale. Here, we demonstrate the capabilities of the technique for phase quantification at the nanoscale by briefly reviewing some of our recent studies of nanostructured materials. Examples that are described include determination of the electrostatic potential profiles associated with doped Si- and GaAs-based semiconductor devices, measurement of hole accumulation in Ge quantum dots, mapping of polarization fields in III-nitride heterostructures, and observation of the remanent states and reversal mechanisms of lithographically patterned magnetic nanorings. Some issues associated with sample preparation for doped semiconductor heterostructures are also briefly discussed.