The effect of sodium polymethacrylate on the rheology of the positive paste and performance of the lead-acid battery

Due to its rheological properties, positive lead-acid battery paste can be difficult to spread on lead current collectors accurately and efficiently under industry machinery and setting. Sodium polymethacrylate dispersant was studied as an effective positive paste additive that could lower the yield stress of the paste without affecting paste density and battery performance. Under a four-blade vane rheometer setup, stress growth and oscillatory amplitude strain sweep experiments evaluated the rheological properties of positive paste with the addition of varying amounts of sodium polymethacrylate. Further, the electrochemical effects of sodium polymethacrylate were also evaluated in 2V batteries by testing positive active material utilization and cycle life.     

Molecular weight control of poly(ethylene terephthalate) in extrusion process

A control strategy is developed to control molecular weight of recycled poly(ethylene terephthalate), PET, to overcome its degradation through an extrusion process. To obtain dynamic model of a twin screw extruder, steady‐state, and unsteady‐state experiments were performed. Discrete convolution models between inputs and outputs were obtained. Process inputs were considered as screw speed (SS), feed rate, and barrel temperatures and the output was viscosity average molecular weight (M_v) of the extrudate. SS and molecular weight of the product were chosen as the manipulated, controlled variable pair by considering singular value decomposition (SVD) technique. Model based PID controller and model predictive controller were used in the designed control scheme. By the simulation studies, both controllers were found to be successful for set‐point tracking, disturbance rejection cases; and were proven to be robust under modeling errors. POLYM. ENG. SCI., 54:459–465, 2014. © 2013 Society of Plastics Engineers     

Free radical polymerization of ethyl methacrylate and ethyl α-hydroxy methacrylate: A computational approach to the propagation kinetics

The propagation kinetics of ethyl methacrylate (EMA) and ethyl α-hydroxy methacrylate (EHMA) has been subject to a computational study to understand their free radical polymerization (FRP) behavior in bulk and in solution using Density Functional Theory (DFT). The propagation of EHMA is studied in ethanol and toluene to assess the effect of hydrogen-bonding solvents on FRP of monomers with α-hydroxy functionality. Although EMA and EHMA resemble each other in structure, EHMA propagates faster in bulk due to the presence of intermolecular hydrogen-bonds, which tend to facilitate the approach of the propagating species. This falls in contrast with the experimentally observed lower propagation rates of EHMA in ethanol compared to toluene. Calculations show that the 2.28 rate acceleration in toluene is governed by the ratio of the pre-exponential factors, which reflect the entropies of activation, in both media. The polar protic solvent ethanol has a disruptive effect via hydrogen-bonding on the 6-membered ring shape of EHMA monomers thus decreasing the entropy of activation of the reaction. In the case of toluene, there are no special interactions with the hydrophobic solvent, the entropy of activation is higher than in ethanol.     

Effect of various pore formers on the microstructural development of tape-cast porous ceramics

Various types of pore formers have been used for the fabrication of ceramics with controlled porosity. This study addresses a detailed and systematic comparison of different pore formers (e.g. graphite, polymethyl methacrylate, sucrose and polystyrene) with distinct features such as size, distribution and morphology of particles and decomposition/oxidation behavior. Investigations also involve their effect on the rheological properties of the slurries and the microstructural development of laminated porous ceramic tapes.Morphological features of the pore former particles were characterized using laser diffraction, B.E.T. surface area measurement and scanning electron microscopy (SEM) techniques as their thermal decomposition/oxidation behavior were determined by thermogravimetric analysis (TGA) and differential thermal analysis (DTA) methods. Tape compositions were developed and optimized in order to incorporate identical volumetric loadings of the materials in the tape formulations with different pore formers for a reliable comparison of their pore forming characteristics. Porous yttria stabilized zirconia (YSZ) ceramics were fabricated without macroscopic defects (e.g. cracks, warpage and delamination) by developing heating profiles based on the identified thermal properties of the pore formers. Characterization of the sintered porous ceramics by SEM and mercury intrusion porosimetry techniques revealed novel relationships between the physical properties of the utilized pore formers, processing parameters and final pore structures.     

A review on selected heterogeneous photocatalysts for hydrogen production

In this study, visible light‐driven heterogeneous photocatalysts for hydrogen production are comparatively assessed based on technical, environmental, and cost criteria. The photocatalysis systems are compared with respect to their (i) rate of hydrogen generation per gram; (ii) rate of hydrogen generation per m² of the specific surface area; and (iii) the band gap energy. The photocatalysis systems are also compared and discussed in terms of flammability, reactivity, and their impact on living systems' health. Furthermore, the costs of the required components of the photocatalysis systems are ranked. In addition to individual photocatalyst comparison, seven photocatalyst groups are ranked and compared. The results show that TiO₂‐C‐362 and Ag_0.03Mn_0.40Cd_0.60S show the highest in terms of µmol/h‐g_cat and µmol/h‐m²_cat, respectively, and TiO₂‐C‐362 has the highest overall rankings. The Zn/In/S‐based photocatalyst groups show the highest hydrogen production rate in terms of µmol/h‐gcat and µmol/h‐m²_cat. Overall, Cd/S/Zn has the highest rankings when cost and health and environmental impact criteria are taken into account. Copyright © 2014 John Wiley & Sons, Ltd.     

Crystallographic analysis of the martensitic phase transformation associated with bcc to orthorhombic TaO<Subscript>y</Subscript>

Crystallographic parameters associated with the martensitic phase transformation from bcc to orthorhombic structure is derived by using the rigorous infinitesimal deformation approach, which predicts crystallographic parameters such as habit plane, orientation relationship between austenite and martensite, rotation matrix and total shape deformation matrix etc., from a knowledge of only the crystal structures of the austenite and martensite phase. The obtained numerical values of orientation relationships observed in TaO_y plates in the present study are compared with the predictions of the phenomenological crystallographic theory and experimental values.