Experimental study on carbon corrosion of the gas diffusion layer in polymer electrolyte membrane fuel cells

Generally, the GDL of a PEM fuel cell experiences three external attacks: dissolution of water, erosion of gas flow, and corrosion of electric potential. Of these degradation factors, this study focuses on the carbon corrosion of electric potential and investigates its impact through the accelerated carbon corrosion test. This study confirms that carbon corrosion occurs at the GDL, which decreases the operating fuel cell’s performance. To discover the effects of carbon corrosion, the GDL property changes are measured through various devices, including a scanning electron microscopy, a thermo gravimetric analyzer, and a tensile stress test. Carbon corrosion causes not only loss of weight and thickness but also degradation of mechanical strength in the GDL. In addition, the GDL shows serious damage in its center.     

Experimental study of the effect of dissolution on the gas diffusion layer in polymer electrolyte membrane fuel cells

The gas diffusion layer (GDL) is important for maintaining the performance of polymer electrolyte membrane (PEM) fuel cells, as its main function is to provide the cells with a path for fuel and water. In this study, the mechanical degradation process of the GDL was investigated using a leaching test to observe the effect of water dissolution. The amount of GDL degradation was measured using various methods, such as static contact angle measurements and scanning electron microscopy. After 2000 h of testing, the GDL showed structural damage and a loss of hydrophobicity. The carbon-paper-type GDL showed weaker characteristics than the carbon-felt-type GDL after dissolution because of the structural differences, and the fuel cell performance of the leached GDL showed a greater voltage drop than that of the fresh GDL. Contrary to what is generally believed, the hydrophobicity loss of GDL was not caused by the decomposition of polytetrafluoroethylene (PTFE).     

Study on operating characteristics of fuel cell powered electric vehicle with different air feeding systems

In this paper the modeling of a fuel cell powered electric vehicle is presented. The fuel cell system consisting of a proton exchange membrane (PEM) fuel cell stack and balance of plant (BOP) was co-simulated with a commercial vehicle simulation program. The simulation program calculates the load of the fuel cell depending on the driving mode of the vehicle and also calculates the overall efficiency and each parasitic loss by applying the load in the fuel cell model that is used to estimate the performance of the entire vehicle system by calculating the acceleration performances and fuel economy of the vehicle. Two types of air feeding systems (blower type and compressor type) were modeled by using MATLAB/Simulink environment and the effect of fuel cell stack size (number of cells, cell area) on the fuel economy and performance of the fuel cell powered vehicle was investigated. Using a driving cycle of FTP-75, the required power, BOP component power loss, and system efficiency for two types of fuel cell systems were analyzed. Through this study, we could get a basic insight into the fuel cell powered electric vehicle and its characteristics.     

An experimental investigation of temperature distribution and flooding phenomena of cathode flow fields in a proton exchange membrane (PEM) fuel cell

Water management is considered to be one of the main issues to be addressed for the performance improvement of proton exchange membrane (PEM) fuel cells. In this paper, to investigate cathode flooding and its relationship with temperature distribution, an experimental study was carried out on cathode sides of an operating single PEM fuel cell. For the direct visualization of temperature fields and water transport in cathode flow channels, a transparent cell was designed and manufactured using quartz window. Liquid water transport and distribution in the flow channels were investigated experimentally. Also, the visualization of temperature distributions in the cathode channels was made by using an IR (infra-red) camera. Results indicate that the temperature rise near the exit of cathode flow channels was found. It is expected that this study can effectively contribute to get the detailed data on water transport linked with thermal management during the operation of a PEM fuel cell.     

Advanced gear-shifting and clutching strategy for a parallel-hybridvehicle

In parallel-hybrid electric vehicles (HEVs), both the electric drive and the internal combustion engine provide driving torque to the wheels either separately or together. The electric drive also can be used as a generator to recharge the batteries when the engine produces more power than is needed to propel the vehicle. As a result of the battery peak power density requirement, the vehicle needs a multispeed transmission between the electric drive and the main differential. In addition, due to the load sharing between the two independent driving sources, a clutch to separate the internal combustion engine and electric drive from the drive shaft is also required. Because the shift quality is directly related to the driving comfort of the vehicle, it is important to reduce both shift shock and time. To enhance the shift quality, we have proposed the advanced gear-shifting and clutching strategy for a parallel-hybrid drive train with an automated manual transmission (AMT). By using the electronically controlled AMT, users can achieve the optimal gear shifting, with regard to the efficiency of the hybrid drive train. Owing to the speed control of the induction machine and the diesel engine at gear shifting, the synchronization is always guaranteed and it reduces the shift shock and shortens the shift time. The dynamo-based experiments have been carried out for the purpose of proving the validity of the proposed transmission and clutch control in parallel-hybrid drive trains     

Recovery of iron as a form of ferrous acetate precipitates from low-grade magnetite ore

This paper describes the recovery process of iron as a form of ferrous acetate from low-grade magnetite ore (Shinyemi Mine, Gangwon province, Korea). The magnetically separated magnetite powder was dissolved in aqueous oxalic acid solution. The dissolution fraction of magnetite concentrates was measured as a function of initial pH, reaction temperature and oxalic acid concentration. Optimum conditions for dissolution of magnetite ore were the temperature higher than 90 °C, pH 1 and oxalic acid concentration 0.5 M. Addition of aqueous H₂O₂ solution oxidized ferrous ion of iron-containing solution. And then, at pH 4, ferric hydroxide was precipitated from iron-containing solution by the addition of NaOH aqueous solution. Ferrous acetate was prepared from the reaction between ferric hydroxide and acetic acid/acetic anhydride mixture and quantitatively characterized by ICP-AES, XRD, SEM, FT-IR and XPS. Purity of ferrous acetate was found to be 91.88% with other impure elements such as Na, Ca, K, Mg and Al by ICP-AES and XPS analysis. XRD and SEM analysis showed that as-prepared ferrous acetate in the present experiments was in low crystalline state. FT-IR spectra confirmed the presence of free acetate ions and monoacetato bidentate structure in as-prepared ferrous acetate.     

Experimental investigation of liquid water droplet removal in a simulated polymer electrolyte membrane fuel cell gas channel with gas diffusion layer characteristics

Journal of Mechanical Science and Technology - Since the accumulation of liquid water droplets in gas flow channels significantly affects the performance of polymer electrolyte membrane (PEM) fuel...     

Investigation on the liquid water droplet instability in a simulated flow channel of PEM fuel cell

To investigate the characteristics of water droplets on the gas diffusion layer from both top-view and side-view of the flow channel, a rig test apparatus was designed and fabricated with prism attached plate. This experimental device was used to simulate the growth of a single liquid water droplet and its transport process with various air flow velocity and channel height. Not only dry condition but also fully humidified condition was also simulated by using a water absorbing sponge. The detachment height of the water droplet with dry and wet conditions was measured and analyzed. It was found that the droplet tends towards becoming unstable by decreased channel height, increased flow velocity or making a gas diffusion layer (GDL) dryer. Also, peculiar behavior of the water droplet in the channel was presented like attachment to hydrophilic wall or sudden breaking of droplet in case of fully hydrated condition. The simplified force balance model matches with experimental data as well.     

Mucoadhesive and pH-sensitive thiolated Eudragit microspheres for oral delivery of Pasteurella multocida antigens containing dermonecrotoxin

In this study, cysteine was conjugated to the Eudragit to have mucoadhesive and pH-sensitive properties. Pasteurella multocida dermonecrotoxin (PMT) is a major virulence factor as a causative agent of atrophic rhinitis (AR) in swine and, therefore, inactivated P. multocida was used as a candidate vaccine in the current study. PMT-loaded thiolated Eudragit microspheres (TEMS) prepared using W/O/W emulsion-solvent evaporation method were characterized to assess their efficacy in oral vaccination. PMT-loaded TEMS were observed as spherical shapes with smooth surfaces and average particle sizes were 5.2 +/- 0.55 microm. The loading efficiency of PMT in the TEMS was about 75.3%. A significantly higher percentage of PMT from PMT-loaded TEMS was released at pH 7.4 than at pH 1.5. Murine macrophage stimulated with PMT-loaded TEMS facilitated a gradual secretion of tumor necrosis factor-alpha and nitric oxide as immune stimulatory mediators in a time dependent manner, suggesting that the released PMT from PMT-loaded TEMS had immune stimulating activity of AR vaccine in vitro.     

Barrier effect of e-beam evaporated tungsten interlayer in Al/W/PtSi metallization layer

The reaction characteristic of Al/PtSi and the effectiveness of W diffusion barrier interlayer in the Al/W/PtSi metallization system are examined. Ideal I-V characteristic and low constant end resistance are obtained in PtSi/n^-Si and PtSi/n⁺Si contact system. However, Al/PtSi/n^-Si and Al/PtSi/n⁺P Si can not stand the sintering for 30 min at 350° C and 400° C, respectively. A new phase, PtAl2, is observed after sintering at 350° C for 15 min. The W diffusion barrier layer is proved to enhance the stability of Al/PtSi. Tungsten layers of 500Å and 1000Å are effective up to 450° C annealing for 1 hr and 500° C for 4 hrs, respectively. A new phase, W₁₂Al, is observed after sintering at 550° C for 15 min.