Novel sulfonated diblock copolymers containing cross-linkable moieties were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization for proton exchange membranes (PEMs) in proton exchange membrane fuel cells (PEMFCs). The copolymers were synthesized using allyl acrylate (AA), and sulfonated styrene ethyl ester (ESS) as monomers and pentaerythritol 3-mercapto propionic ester (PMPE) as the cross-linker. The chemical structures of the diblock copolymers were analyzed by using ¹H NMR spectroscopy. Membranes were obtained through cross-linking with a thiol–ene reaction via via copolymer heat curing. TGA was employed to characterize the thermal properties of the cross-linked membranes. Gel permeation chromatography (GPC) was employed to measure the molecular weight, and scanning electron microscopy (SEM) was employed to elucidate the morphological changes in the membranes with an increase in the of cross-linking degree. The liquid uptake was significantly suppressed by the cross-linked network. The decrease in the proton conductivity may have been caused by the enhanced barrier properties of the membranes due to the introduction of more cross-linkers duing the membrane formation. These decreases in the liquid uptake and proton conductivity were probably due to the increased cross-linking degree, leading to a relatively tortuous pathway for water and methanol transport. The water uptakes were higher than the methanol uptakes for all the studied membranes, which lead to increased water selectivities. The proposed B2 membrane showed advantageous mechanical properties, better proton conductivityin water or methanol, and significantly higher liquid uptake compared to those of recast Nafion^®.

The present work investigates the first flow regime transition, namely, the onset of flow separation from the surface of a submerged body, for power-law fluids (shear-thinning and shear-thickening fluids) for a range of axisymmetric shapes. In particular, the geometries considered here include spheroids, hemisphere, spherical caps, cones, conical caps, frustum of cones and disks in two orientations with respect to the direction of the flow. Broadly, this transition occurs at progressively lower Reynolds numbers for objects with reduced degree of streamlining, or in the presence of geometric singularities (corners) and a high level of curvature, even in Newtonian fluids. The role of body shape is further accentuated for power-law fluids due to the variation in the fluid viscosity along the surface, as well as its spatial variation. For shear-thinning fluids (n<1), the critical Reynolds number exhibits a peak somewhere around n~0.4–0.5 for each shape studied here, and this is attributed to the interaction between the non-linear viscous and inertial forces prevailing in the flow field. For shear-thickening fluids, it progressively decreases with the increasing value of power-law index.

Branched flocculants are more efficient at improving flocculation rates than linear flocculants, but the reason is not well understood. The adsorption of linear polymers is known to increase the hydrodynamic radius of particles for effective collisions between particles and subsequently improve flocculation rate. To reveal such an effect with branched polymers, we measured the thickness of the adsorbed polyelectrolyte layer and their electrophoretic mobility as a function of time for polyelectrolytes with different degrees of branching. The results show that all polyelectrolytes adsorbed on the particles undergo a relaxation effect, where the thickness of the adsorbed layer continuously decreases as a function of time. The branched polymers exhibited a thick layer regardless of ionic strength due to branching points that disturbed smooth reconformation when adsorbed to the particles. However, linear polymers consistently showed a thinner layer thickness than branched polymers because of their flexible structure, which was prone to relaxation effects. The most significant layer thickness was observed at low ionic strength, and the electrophoretic mobility confirmed that adsorption was kinetically controlled. The thick adsorbed layer of branched polymers explains the commonly observed trend, where branched polymers show better flocculating abilities than linear polymers.

The Czochralski (CZ) process, a well-established monocrystalline silicon ingot production process, is a nonlinear, time-varying batch process. In the semiconductor industry, it is desirable to improve the control method and manufacture higher-quality 300-mm-diameter silicon ingots at a lower cost. The authors developed a nonlinear model predictive control method based on the gray-box (GB) model of the CZ process and successive linearization. This study proposes a method for updating the prediction model, to handle a plant-model mismatch. The proposed method constructs several GB models beforehand and selects a proper model based on the moving horizon estimation. This method was applied to the GB model-based predictive control, and its disturbance rejection performance was compared with that of the conventional control method without a model update. The obtained control simulation results demonstrated that the sums of the integral absolute errors of the controlled variables using the proposed method were smaller than those using the conventional method in 128/180 simulations.

The effect of an internal fuel reforming unit on the power generation efficiency of a thin-film solid oxide fuel cell (SOFC) system, was evaluated via process simulation. Here, the internal reforming reaction of the fuel on thin anode was unlikely to proceed. The efficiency of the system equipped with an internal fuel reforming unit was found to significantly increase at approximately 600°C compared to that without the unit. In the system with an internal fuel reforming unit, high efficiency was maintained even at low steam to carbon ratios (S/C). It was also found that the difference in fuel concentration between the inlet and outlet of the cell decreased by installing an internal fuel reforming unit inside SOFC and lowering the temperature of the external reformer. Installing an internal fuel reforming unit can be effective for thin-film SOFC systems to operate at temperatures less than 800°C.