Enhancing low-temperature energy harvesting by lead-free ferroelectric Ba(Zr0.1Ti0.9)O3

The energy-harvesting ability of the lead-free ferroelectric Ba(Zr,Ti)O₃ was investigated and greatly enhanced using the Kim novel electrothermodynamic cycle for low-temperature application. Ba(Zr,Ti)O₃ was synthesized with a Zr:Ti ratio of 10:90 (BZT10) by hot-press sintering, which exhibited a mix relaxor-ferroelectric behavior. For power generation using the Kim cycle with low and high temperatures of T_L = 25°C, T_H = 120°C, the most optimized temperature pattern occurred for a heating time of 12.5 s and a cooling time of 22.5 s. Under these conditions, the electric field increased during the novel isodisplacement process, and the displacement variation in the isoelectric step reached the highest value and maximized the BZT10 cycle loop area. Applying these conditions while lowering T_L to 20°C, an energy density N_D = 504 mJ/cm³ was achieved. This value is the highest obtained energy density in a practical test for lead-free ferroelectric bulk material in the BaTiO₃ family.     

Water‐soluble/dispersible carbazole‐containing random and block copolymers by nitroxide‐mediated radical polymerisation

A series of carbazole‐containing water‐dispersible poly(acrylic acid)‐b‐(9‐(4‐vinylbenzyl)‐9H‐carbazole) block copolymers (poly(AA)‐b‐poly(VBK)) and water‐soluble poly(methacrylic acid‐ran‐(9‐(4‐vinylbenzyl)‐9H‐carbazole)) (poly(MAA‐ran‐VBK)) random copolymers were synthesised in a controlled manner (i.e. low polydispersities $(\overline {M_{{\rm w}} } /\overline {M_{n} } < 1.3)$ by nitroxide‐mediated polymerisation (NMP) using an SG1‐based alkoxyamine initiator, BlocBuilder. Poly(AA)‐b‐poly(VBK) block copolymers were most easily accessed by using poly(AA) in its protected form as the macroinitiator for the 9‐(4‐vinylbenzyl)‐9H‐carbazole (VBK) block. Controlled polymerisation of MAA was accomplished using an excess of 10 mol.% SG1 relative to BlocBuilder with VBK as controlling co‐monomer (initial molar feed content f_VBK,0 = 0.03–0.20) in dimethylformamide at 80°C. Poly(MAA‐ran‐VBK) copolymers with a final VBK molar composition of F_VBK < 0.30 resulted in water‐soluble copolymers. In addition, as macroinitiators, poly(MAA‐ran‐VBK)s were sufficiently pseudo‐living to reinitiate a second batch of monomer (90 mol.% methyl methacrylate with styrene) in organic solvent and by ab initio, surfactant‐free emulsion polymerisation. In both cases, low polydispersity, amphiphilic block copolymers resulted $(\overline {M_{{\rm w}} } /\overline {M_{{\rm n}} } < 1.3)$ . © 2012 Canadian Society for Chemical Engineering     

A brief review of environmentally benign antifouling and foul-release coatings for marine applications

Antifouling coatings for ship hulls are a very important topic in coating research. They are essential with respect to fuel consumption of ships: without antifouling coating, biological species start to adhere to the ship’s exterior, leading to a gradual increase in fuel consumption. To date, the working principle of most of the paint systems applied is based on slow release of toxins in time (self-polishing coatings). In this article, we discuss the environmental impact of marine antifouling coatings based on quantitative data available from literature. In addition, we critically review hydrophilic antifouling and hydrophobic foul-release coatings as toxin-free alternatives and discuss their potential for replacing self-polishing coatings.     

The effect of NO2 on the activity of fresh and aged zeolite catalysts in the NH3-SCR reaction

The activity of fresh and hydrothermally aged zeolite-based catalysts in the NH₃-selective catalytic reduction (SCR) reaction with excess of oxygen were studied. In addition, the effect of NO₂ in the gas feed as well as the acidity of the catalysts for the SCR activity was investigated. The studied catalysts were hydrogen, copper, iron and silver ion exchanged ZSM-5, mordenite, beta, ferrierite, and Y-zeolites. The investigation verifies that the zeolite-based catalysts are very promising for the ammonia SCR reaction. Especially, the activity at low and high temperatures was higher than the activity of commercial vanadia-based catalysts. From the studied catalysts, Fe-beta was the most potential one. The presence of NO₂ in the inlet flow enhanced significantly the catalytic activity of fresh and hydrothermally aged zeolite catalysts. This suggests that the oxidation of NO to NO₂ is probably the rate-determining step for the SCR reaction.     

Effect of CO2 Exposure on the Chemical Stability and Mechanical Properties of BaZrO3‐Ceramics

The reactivity of BaZrO₃ with CO₂ has been addressed as one of the major challenges with BaZrO₃‐based electrolytes in protonic ceramic fuel cells. Here, we present a study of the effect of CO₂ exposure on BaZrO₃‐materials at elevated temperatures. Dense BaZr_1?xY_xO_3?x/2 (x = 0, 0.05, 0.1, 0.2) and BaCe_0.2Zr_0.7Y_0.1O_2.95 ceramics were prepared by sintering of powder prepared by spray pyrolysis. The Vickers indentation method was used to determine the hardness and estimate the fracture toughness of pristine materials as well as the corresponding materials exposed to CO₂. Formation of BaCO₃ on the surface of exposed ceramics was confirmed by X‐ray diffraction and electron microcopy. The reaction resulted in formation of Ba‐deficient perovskite at the exposed surface. The reaction with CO₂ was most pronounced at 650°C compared to the other temperatures applied in the study. The reactivity was also shown to depend on the Y‐content and the grain size and was most pronounced for BaZr_0.9Y_0.1O_2.95. The reaction with CO₂ was observed to have a profound effect on the fracture toughness of the ceramics, demonstrating a depression of the mechanical stability of the materials. The results are discussed with respect to the chemical and mechanical stability of BaZrO₃ materials, with particular emphasis on the composition and grain size.     

Effect of filler concentration on electrical conductivity andultralow-frequency dielectric properties

The effect of filler concentration on the dielectric properties in the ultralow-frequency region and on the electrical conductivity was studied for ethylene propylene rubber. First, we investigated the relation between the electrical conductivity and filler concentration: as the volume fraction of fillers q_a increased, the conductivity decreased in the low filler concentration region but increased abruptly in the high filler concentration region. The decrease and increase in conductivity can be explained with the action of carrier traps at the interface between EPR and fillers and with the formation of highly conductive paths of filler across the sample, respectively. Secondly, we studied the dielectric properties in the ultralow-frequency region which was obtained from the discharge current. As q_a increased, the relaxation time decreased in the low filler concentration region and then rose in the high filler concentration region. The polarization in the high filler concentration region can be explained by two-layer interfacial polarization between filler and rubber     

Very high characteristic temperature and constant differentialquantum efficiency 1.3-μm GaInAsP-InP strained-layer quantum-welllasers by use of temperature dependent reflectivity (TDR) mirror

A very high characteristic temperature T₀ of 150 K (25-70°C) or 450 K (25-50°C) and an almost constant differential quantum efficiency operation in the temperature range of 25-70°C were achieved in 1.3-μm GaInAsP-InP strained-layer quantum-well (SL-QW) lasers by use of a novel temperature dependent reflectivity (TDR) mirror composed of multiple quarter-lambda thickness α-Si-SiOx dielectric films with quarter-lambda shift in the vicinity of center portion, The mechanism of high T₀ and constant differential quantum efficiency were explained using the structural parameters, transparent current density and gain coefficient of a SL-QW laser that are derived experimentally. The effect of TDR mirror was confirmed by measuring the temperature dependence of net gain of a SL-QW laser with TDR mirror. It was found that less temperature dependent net gain due to the decrease of mirror loss with temperature played an important role for improving the temperature characteristics of threshold current. Almost constant differential quantum efficiency over a wide temperature range is attributed to the increase of the facet reflectivity with temperature     

Reduced secretion of triacylglycerol in CaCo-2 cells transfected with intestinal fatty acid-binding protein

The fatty acid-binding proteins are hypothesized to be involved in cellular fatty acid transport and trafficking. We established CaCo-2 cells stably transfected with intestinal fatty acid-binding protein (I-FABP) and examined how the expression of this protein may influence fatty acid metabolism. I-FABP expression was detectable in I-FABP-transfected cells, whereas parent CaCo-2 cells as well as mock-transfected cells failed to express detectable levels of I-FABP mRNA or protein at any stage of differentiation. For studies of lipid metabolism, cells were incubated with [¹⁴C]oleic acid in taurocholate micelles containing monoolein, and distribution of labeled fatty acid in cellular and secreted lipids was examined. In one transfected cell clone, expressing the highest level of I-FABP, labeled cellular triacylglycerol increased approximately twofold as compared to control cells. The level of intracellular triacylglycerol in two other I-FABP-transfected clones resembled that of control cells. However, secretion of triacylglycerol was markedly reduced in all the I-FABP-expressing cell lines. Our data suggest that increased expression of I-FABP leads to reduced triacylglycerol secretion in intestinal cells.     

Activation of Pozzolanic Reaction of Hydrated Portland Cement Fly Ash Pastes in Sulfate Solution

The activation of the pozzolanic reaction of fly ash in portland cement paste immersed in sulfate solution has been studied. Mixtures of two Spanish fly ashes (ASTM class F) with 0%, 15%, and 35% replacement of portland cement by fly ash were immersed in Na₂SO₄ solution, of 2880 ppm SO₄²⁻ concentration, for a period of 90 days. The resistance of the different mixtures to the sulfate attack was evaluated using the Koch-Steinegger test. The results showed that all of the mixtures were sulfate resistant, despite the high Al₂O₃ content of the fly ash. The diffusion of SO₄²⁻ and Na⁺ ions through the pore solution activated the pozzolanic reactivity of the fly ashes, causing microstructural changes, which were characterized by X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM). As a result, the flexural strength of the mixtures increased, principally for the fly ash of a lower particle size and 35% of addition.