Study of poly(vinyl alcohol)/titanium oxide composite polymer membranes and their application on alkaline direct alcohol fuel cell

The novel poly(vinyl alcohol)/titanium oxide (PVA/TiO₂) composite polymer membrane was prepared using a solution casting method. The characteristic properties of the PVA/TiO₂ composite polymer membrane were investigated by thermal gravimetric analysis (TGA), a scanning electron microscopy (SEM), a micro-Raman spectroscopy, a methanol permeability measurement and the AC impedance method. An alkaline direct alcohol (methanol, ethanol and isopropanol) fuel cell (DAFC), consisting of an air cathode based on MnO₂/C inks, an anode based on PtRu (1:1) black and a PVA/TiO₂ composite polymer membrane, was assembled and examined for the first time. The results indicate that the alkaline DAFC comprised of a cheap, non-perfluorinated PVA/TiO₂ composite polymer membrane shows an improved electrochemical performances. The maximum power densities of alkaline DAFCs with 4 M KOH + 2 M CH₃OH, 2 M C₂H₅OH and 2 M isopropanol (IPA) solutions at room temperature and ambient air are 9.25, 8.00, and 5.45 mW cm⁻², respectively. As a result, methanol shows the highest maximum power density among three alcohols. The PVA/TiO₂ composite polymer membrane with the permeability values in the order of 10⁻⁷ to 10⁻⁸ cm² s⁻¹ is a potential candidate for use on alkaline DAFCs.     

Synthesis of New Europium Complexes and Their Application in Electroluminescent Devices

Several substituted phenanthrolines (L = pyrazino[2,3‐f][1,10]phenanthroline (PyPhen), 2‐methylpyrazino[2,3‐f][1,10]phenanthroline (MPP), dipyrido[3,2‐a:2′,3′‐c]phenazine (DPPz), 11‐methyldipyrido[3,2‐a:2′,3′‐c]phenazine (MDPz), 11,12‐dimethyldipyrido[3,2‐a:2′,3′‐c]phenazine (DDPz), and benzo[i]dipyrido[3,2‐a:2,3‐c]phenazine (BDPz)) were successfully prepared and europium complexes Eu(TTA)₃L (Eu‐L) based on these ligands were synthesized from EuCl₃, 2‐thenoyltrifluoroacetone (TTA) and L in good yields. Irradiation at the absorption band between 320–390 nm of all these europium complexes, except Eu‐BDPz, in solution or in the solid state leads to the emission of a sharp red band at ～ 612 nm, a characteristic Eu³⁺ emission due to the transition ⁵D₀ → ⁷F₂. No emission from the ligands was found. The result indicates that complete energy transfer from the ligand to the center Eu³⁺ ion occurs for these europium complexes. In contrast, the photoluminescence spectrum of Eu‐BDPz exhibits a strong emission at around 550 nm from the coordinated BDPz ligand and a weak emission at 612 nm from the central europium ion. Incomplete energy transfer from the ligand to the central Eu³⁺ ion was observed for the first time. Several electroluminescent devices ( A – I ) using Eu‐PyPhen, Eu‐MPP, Eu‐DPPz, and Eu‐DDPz as dopant emitters with the device configuration: TPD or NPB (50 nm)/Eu:CBP (1.7–7 %, 30 nm)/BCP (20–30 nm)/Alq (25–35 nm) (where TPD: 4,4′‐bis[N‐(p‐tolyl)‐N‐phenylamino]biphenyl; NPB: 4,4′‐bis[1‐naphthylphenylamino]biphenyl; CBP: 4,4′‐N,N′‐dicarbazole biphenyl; BCP: 2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline; Alq: tris[8‐hydroxyquinoline]aluminum) were fabricated. Some of these devices emit saturated red light and are the only europium complex‐based devices that show a brightness of more than 1000 cd m^–2.     

Peripheral shear strength of biaxially tensioned reinforced concrete wall elements

The results of a series of tests on biaxially tensioned, orthogonally reinforced concrete panels subjected to punching shear are presented and discussed. Contrary to existing U.S. code provisions, the punching shear capacity is not reduced significantly as the biaxial tension level is increased to as much as 0.8f_y in the reinforcement. A design equation is proposed that gives 4√f′_c shear stress for zero biaxial tension and a linear decrease to 3.1√f′_c as the tension is increased to 0.9f_y.The size of the loading pad under the punching force and the shear span have little effect on the strength but the pattern of the failure crack does change with these geometric variables. The splitting crack tends to connect the edge of the loading pad and the supports.More testing is recommended to evaluate a few additional variables, such as the use of inserts which receive the punching force.     

A direct borohydride fuel cell based on poly(vinyl alcohol)/hydroxyapatite composite polymer electrolyte membrane

A new poly(vinyl alcohol)/hydroxyapatite (PVA/HAP) composite polymer membrane was synthesized using a solution casting method. Alkaline direct borohydride fuel cells (DBFCs), consisting of an air cathode based on MnO₂/C inks on Ni-foam, anodes based on PtRu black and Au catalysts on Ni-foam, and the PVA/HAP composite polymer membrane, were assembled and investigated for the first time. It was demonstrated that the alkaline direct borohydride fuel cell comprised of this low-cost PVA/HAP composite polymer membrane showed good electrochemical performance. As a result, the maximum power density of the alkaline DBFC based on the PtRu anode (45 mW cm⁻²) proved higher than that of the DBFC based on the Au anode (33 mW cm⁻²) in a 4 M KOH + 1 M KBH₄ solution at ambient conditions. This novel PVA/HAP composite polymer electrolyte membrane with high ionic conductivity at the order of 10⁻² S cm⁻¹ has great potential for alkaline DBFC applications.     

Study of polystyrene/titanium dioxide nanocomposites via melt compounding for optical applications

This article presents the study of melt compounding of polystyrene (PS) with various types of titanium dioxide (TiO₂) nanoparticles and surfactants, using a corotating twin screw extruder with multiple screw element configurations. It was found that a properly designed high shear screw configuration and the copolymer of silicone, ethylene oxide, and propylene oxide‐based surfactant produced the greatest degree of nanoparticle dispersion in PS/TiO₂ nanocomposites, whereas a silane‐based surfactant and silicon dioxide (SiO₂) or aluminum oxide (Al₂O₃) coated TiO₂ nanoparticles yielded nanocomposites with the least photocatalytic degradation effects and the best retention of tensile and impact properties. POLYM. COMPOS., 28:241–250, 2007. © 2007 Society of Plastic Engineers     

Highly transparent polyimide/nanocrystalline-titania hybrid optical materials for antireflective applications

This study prepared polyimide/titania hybrid thin films of, poly(3,3′,4,4′-Benzophenone tetra carboxylic dianhydride)–(4,4-Diaminodiphenyl Ether)/nanocrystalline titania (BTDA-ODA/TiO₂), with a high refractive index. FTIR analysis confirmed the formation of a polyimide and titania matrix. TGA and DSC analysis gauged the decomposition temperature in the range of 455–532 °C, indicating that the addition of titania could increase the glass transition temperature of hybrid films. XRD results indicate the formation of nanocrystalline titania domains of approximately 8–11 nm in the hybrid films. AFM, SEM, TEM, and XRD results show the formation of well-dispersed nanocrystalline titania. The refractive index was measured by ellipsometry, demonstrating an increase in the refractive index of the prepared hybrid thin films from 1.657 to 1.958, when the titania content was increased from 0 to 90 wt.%. UV–vis analysis gauged the cutoff wavelength in the range of 288–357 nm. The prepared polyimide/titania hybrid thin films were used to develop a three layer antireflective (AR) coating on a glass substrate. The average reflectance of the AR was 0.5% for the PT20/PT90/F-siloxane layer and 0.6% for the PT20/PT90/porous silica. Transparency at 550 nm exceeded 90% for both AR coatings.     

Local recurrence based performance prediction and prognostics in the nonlinear and nonstationary systems

This paper presents a local recurrence modeling approach for state and performance predictions in complex nonlinear and nonstationary systems. Nonstationarity is treated as the switching force between different stationary systems, which is shown as a series of finite time detours of system dynamics from the vicinity of a nonlinear attractor. Recurrence patterns are used to partition the system trajectory into multiple near-stationary segments. Consequently, piecewise eigen analysis of ensembles in each near-stationary segment can capture both nonlinear stochastic dynamics and nonstationarity. The experimental studies using simulated and real-world datasets demonstrate significant prediction performance improvements in comparison with other alternative methods.     

Constructing intelligent model for acceptability evaluation of a product

In the highly competitive marketplace, consumer acceptability has become an important factor in the product design process. However, manufacturers and designers often misunderstand what consumers really want. Thus, acceptability evaluation and prediction is important in product development. This study developed an intelligent model to solve consumer acceptability problem in an attempt to evaluate consumer acceptability with better performance. The model adopted three well-known feature ranking methods to rank features of importance. In addition, it employed the Bayesian Network (BN), Radial Basis Function (RBF) Networks, Support Vector Machine–Sequential Minimal Optimization (SVM–SMO) and their ensembles to build prediction models. In this study, we also focus on the use of non- parametric statistical test for the comparison algorithms performance in classification. To demonstrate applicability of the proposed model, we adopted a real case, car evaluation, to show that the consumer acceptability problem can be easily evaluated and predicted using the proposed model. The results show that the model can improve the performance of consumer acceptability problems and can be easily extended to other industries.     

Preparation of thermoplastic polyurethane/graphene oxide composite scaffolds by thermally induced phase separation

In this study, biomedical thermoplastic polyurethane/graphene oxide (TPU/GO) composite scaffolds were successfully prepared using the thermally induced phase separation (TIPS) technique. The microstructure, morphology, and thermal and mechanical properties of the scaffolds were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and compression tests. Furthermore, NIH 3T3 fibroblast cell viability on the porous scaffolds was investigated via live/dead fluorescent staining and SEM observation. FTIR and Raman results verified the presence of GO in the composites. SEM images showed that the average pore diameter of the composite scaffolds decreased as the amount of GO increased. Additionally, the surface of the specimens became rougher due to the embedded GO. The compressive modulus of composite specimens was increased by nearly 200% and 300% with the addition of 5% and 10% GO, respectively, as compared with pristine TPU. 3T3 fibroblast culture results showed that GO had no apparent cytotoxicity. However, high loading levels of GO may delay cell proliferation on the specimens. POLYM. COMPOS., 35:1408–1417, 2014. © 2013 Society of Plastics Engineers     

Microcellular poly(hydroxybutyrate‐co‐hydroxyvalerate)‐hyperbranched polymer–nanoclay nanocomposites

The effects of incorporating hyperbranched polymers (HBPs) and different nanoclays [Cloisite® 30B and halloysite nanotubes (HNT)] on the mechanical, morphological, and thermal properties of solid and microcellular poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) were investigated. According to the X‐ray diffraction (XRD) and transmission electron microscopy (TEM) analyses, Cloisite 30B exhibited a combination of exfoliation and heterogeneous intercalation structure for both solid and microcellular PHBV–12% HBP–2% Cloisite 30B nanocomposites. TEM images indicated that HNTs were uniformly dispersed throughout the PHBV matrix. The addition of 2% nanoclays improved the thermal stability of the resulting nanocomposites. The addition of HBP+poly(maleic anhydride‐alt‐1‐octadecene) (PA), Cloisite 30B, and HNT reduced the average cell size and increased the cell density of the microcellular components. The addition of (HBP+PA), Cloisite 30B, and HNT also increased the degree of crystallinity for both solid and microcellular components in comparison with neat PHBV. Also, with the addition of 12% (HBP+PA), the area under the tan‐δ curve, specific toughness, and strain‐at‐break of the PHBV–HBP nanocomposite increased significantly for both solid and microcellular specimens, whereas the storage modulus, specific Young's modulus, and specific tensile strength decreased. The addition of 2% nanoclays into the PHBV–HBP nanocomposites improved the storage modulus, specific Young's modulus, and specific tensile strength of the PHBV–HBP–nanoclay‐based nanocomposites, but they were still lower than those of the neat PHBV. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers