Performance improvement by metal deposition at the cathode active site in solid oxide fuel cells

In this study, the performance improvement of the SOFC single cell and its underlying mechanism was investigated. Furthermore, an application of the identified electrochemical mechanism is proposed and tested experimentally. The deposition of Platinum (Pt) at electrochemically active sites for the oxygen reduction reaction is determined to be responsible for the improved performance. Pt migration from a current collector to the cathode active sites originates from the oxygen partial pressure difference between current collector and triple phase boundary, and the electrochemical reduction reaction. It is supported by the confirmation of Pt particles at the cathode active sites by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and calculations of the thermodynamic equilibrium partial pressure values. In addition, correlation of the initial performance change and the quantities of Pt deposition are investigated. This selective Pt deposition mechanism at the active sites is applied to the LSCF cathode, as well.     

Synthesis of polystyrene/polythiophene core/shell nanoparticles by dual initiation

Polystyrene/polythiophene (PSt/PTh) core/shell nanoparticles were successfully synthesized via a one-pot Fe³⁺-catalyzed oxidative and soap-free emulsion polymerization process. A small amount of sodium styrene sulfonate (NaSS) was used to maintain the colloidal stability of the PSt/PTh nanoparticles. Hydrogen peroxide (H₂O₂) and a trace of iron chloride (FeCl₃) were used to carry out the free-radical polymerization of styrene and the oxidative polymerization of thiophene. The dual initiation characteristics of H₂O₂/FeCl₃ in the PSt/PTh core/shell nanoparticle formation were investigated by observing the time-evolution of the particle morphology. In addition, photoluminescent property, particle size distribution, core/shell morphology and the formation mechanism of the PSt/PTh nanoparticles were studied by spectrofluorophotometery, dynamic light scattering (DLS), in-situ IR, zeta-potential, and time-evolution field-emission scanning electron microscope (FE-SEM) analyses.     

Thermosensitivity control of polyethlyenimine by simple acylation

Branched polyethylenimine (b-PEI), an amine-rich polymer, can obtain thermosensitivity by a simple acylation reaction. The resulting N-acylated b-PEI derivatives showed a similar lower critical solution temperature (LCST) transition as their linear correspondent, poly(N-alkyloxazoline). Three acyl groups (propionyl, and isobutyryl, and n-butyryl) were introduced and resulted in LCSTs ranging from 10 °C to 90 °C depending on the structure and environment. The hydrophobicity of N-acylated b-PEI can be controlled by varying the acyl group and degree of acylation. Because the LCST transition is determined by the delicate balance between the hydrophobicity and hydrophilicity of the polymers, an increase of the hydrophobicity in N-acylated b-PEI lowers the transition temperature. Also, N-acylated b-PEI contains tertiary amines as well as unacylated primary or secondary amines which can be protonated during acidification from a pH of 7.4 to a pH of 5.5. The LCST transition was observed at elevated temperatures due to the increase of hydrophilicity by the protonation in the acidic environment. The LCST was also influenced by the salt concentration. A decrease of the LCST was observed as the NaCl concentration increased, probably due to the dominance of the salting-out effect. The very simple introduction of thermosensitivity into pre-existing polymers can be easily applied for the development of various dual or multiple signal-sensitive polymer systems.     

A study of operation strategy of cooling module with dynamic fuel cell system model for transportation application

A fuel cell system model with detailed cooling module model was developed to evaluate the control algorithms of cooling module which is used for the thermal management of a proton exchange membrane fuel cell (PEMFC) system. The system model is composed of a dynamic fuel cell stack model and a detailed dynamic cooling module model. To extend modeling flexibility, the fuel cell stack model utilizes analytic approach to capture the transient behavior of the stack temperature corresponding to the change of the coolant temperature and the flow rate during load follow-up. The cooling module model integrated model of fan, water pump, coolant passage, and electric motors so that the model is capable of investigation of operating strategy of pump and fan.The fuel cell system model is applied to the investigation of the control logics of the cooling module. Since, it is necessary for the control of cooling module to define the reference conditions such as coolant temperature and fuel cell stack temperature, this study presents such thermal management criteria. Finally, two control algorithms were compared, a conventional control algorithm and a feedback control algorithm. As a consequence, the feedback control algorithm was found to be more suitable for the cooling module of the PEMFC stack, as they consume less parasitic power while producing more stack power compared to a conventionally controlled cooling module.     

Feature‐Based Relation Classification Using Quantified Relatedness Information

Feature selection is very important for feature‐based relation classification tasks. While most of the existing works on feature selection rely on linguistic information acquired using parsers, this letter proposes new features, including probabilistic and semantic relatedness features, to manifest the relatedness between patterns and certain relation types in an explicit way. The impact of each feature set is evaluated using both a chisquare estimator and a performance evaluation. The experiments show that the impact of relatedness features is superior to existing well‐known linguistic features, and the contribution of relatedness features cannot be substituted using other normally used linguistic feature sets.     

Effects of Two-stage Heat Treatment on Delayed Coke and Study of Their Surface Texture Characteristics

In the present study, surface texture features and chemical properties of two types of cokes, made from coal tar by either 1-stage heat treatment or 2-stage heat treatment, were researched. The relationship between surface texture characteristics and the chemical properties was identified through molecular weight distribution, insolubility of coal tar, weight loss with temperature increase, coking yield, and polarized light microscope analysis. Rapidly cleared anisotropy texture in cokes was observed in accordance with the coking temperature rise. Quinoline insolubility and toluene insolubility of coal tar increased with a corresponding increases in coking temperature. In particular, the cokes produced by the 2-stage heat treatment (2S-C) showed surface structure of needle cokes at a temperature approximately 50°C lower than the 1-stage heat treatment (1S-C). Additionally, the coking yield of 2S-C increased by approximately 14% in comparison with 1S-C.     

Thermomechanical properties of alumina-filled plasticized polylactic acid: Effect of alumina loading percentage

Polylactic acid (PLA) is one of the most widely studied renewable and biodegradable polyesters and is expected to replace petrochemical-based synthetic polymers. In this study, we investigated the effect of the alumina volume fraction on the thermal and mechanical properties of polyethylene glycol (PEG)-plasticized PLA. The alumina particles were treated with maleic acid to improve their interaction with the PLA matrix. The field-emission scanning electron microscopy results revealed that the addition of alumina eliminated voids, leading to improved interfacial interactions between the PLA and alumina particles. The thermal conductivity of the neat PLA increased from 0.278 to 0.66?wm^?1 k^?1 with the addition of 30% alumina, which accounts for 137% increase. The tensile strength and Young's modulus of the neat PLA dropped by 52% and 56%, respectively, on the addition of 15% PEG plasticizer. However, the elongation at break increased from 5.4% to 207%, which was associated with a drop on the glass transition temperature values. The dynamic mechanical analysis results showed a drop in the storage modulus and height of the tan δ peak, revealing the increased flexibility of the composite after the inclusion of the plasticizer. The addition of 30% alumina exhibited a 41.6% increase on the stiffness of the PEG-blended PLA.