Sanghoon Ji

Plasma-Enhanced Atomic Layer Deposition of Nanoscale Yttria-Stabilized Zirconia Electrolyte for Solid Oxide Fuel Cells with Porous Substrate

Nanoscale yttria-stabilized zirconia (YSZ) electrolyte film was deposited by plasma-enhanced atomic layer deposition (PEALD) on a porous anodic aluminum oxide supporting substrate for solid oxide fuel cells. The minimum thickness of PEALD-YSZ electrolyte required for a consistently high open circuit voltage of 1.17 V at 500 °C is 70 nm, which is much thinner than the reported thickness of 180 nm using nonplasmatic ALD and is also the thinnest attainable value reported in the literatures on a porous supporting substrate. By further reducing the electrolyte thickness, the grain size reduction resulted in high surface grain boundary density at the cathode/electrolyte interface.

Fabrication of low-temperature solid oxide fuel cells with a nanothin protective layer by atomic layer deposition

Anode aluminum oxide-supported thin-film fuel cells having a sub-500-nm-thick bilayered electrolyte comprising a gadolinium-doped ceria (GDC) layer and an yttria-stabilized zirconia (YSZ) layer were fabricated and electrochemically characterized in order to investigate the effect of the YSZ protective layer. The highly dense and thin YSZ layer acted as a blockage against electron and oxygen permeation between the anode and GDC electrolyte. Dense GDC and YSZ thin films were fabricated using radio frequency sputtering and atomic layer deposition techniques, respectively. The resulting bilayered thin-film fuel cell generated a significantly higher open circuit voltage of approximately 1.07 V compared with a thin-film fuel cell with a single-layered GDC electrolyte (approximately 0.3 V).

A Mobile Robot Exploration Strategy with Low Cost Sonar and Tungsten-Halogen Structured Light

Autonomous environment mapping is an essential part of efficiently carrying out complex missions in unknown indoor environments. In this paper, a low cost mapping system composed of a web camera with structured light and sonar sensors is presented. We propose a novel exploration strategy based on the frontier concept using the low cost mapping system. Based on the complementary characteristics of a web camera with structured light and sonar sensors, two different sensors are fused to make a mobile robot explore an unknown environment with efficient mapping. Sonar sensors are used to roughly find obstacles, and the structured light vision system is used to increase the occupancy probability of obstacles or walls detected by sonar sensors. To overcome the inaccuracy of the frontier-based exploration, we propose an exploration strategy that would both define obstacles and reveal new regions using the mapping system. Since the processing cost of the vision module is high, we resolve the vision sensing placement problem to minimize the number of vision sensing in analyzing the geometry of the proposed sonar and vision probability models. Through simulations and indoor experiments, the efficiency of the proposed exploration strategy is proved and compared to other exploration strategies.

Atomic layer deposition of ultrathin blocking layer for low-temperature solid oxide fuel cell on nanoporous substrate

An ultrathin yttria-stabilized zirconia (YSZ) blocking layer deposited by atomic layer deposition (ALD) was utilized for improving the performance and reliability of low-temperature solid oxide fuel cells (SOFCs) supported by an anodic aluminum oxide substrate. Physical vapor-deposited YSZ and gadolinia-doped ceria (GDC) electrolyte layers were deposited by a sputtering method. The ultrathin ALD YSZ blocking layer was inserted between the YSZ and GDC sputtered layers. To investigate the effects of an inserted ultrathin ALD blocking layer, SOFCs with and without an ultrathin ALD blocking layer were electrochemically characterized. The open circuit voltage (1.14 V) of the ALD blocking-layered SOFC was visibly higher than that (1.05 V) of the other cell. Furthermore, the ALD blocking layer augmented the power density and improved the reproducibility.

Properties of nanostructured undoped ZrO2 thin film electrolytes by plasma enhanced atomic layer deposition for thin film solid oxide fuel cells

Nanostructured ZrO2 thin films were prepared by thermal atomic layer deposition (ALD) and by plasma-enhanced atomic layer deposition (PEALD). The effects of the deposition conditions of temperature, reactant, plasma power, and duration upon the physical and chemical properties of ZrO2 films were investigated. The ZrO2 films by PEALD were polycrystalline and had low contamination, rough surfaces, and relatively large grains. Increasing the plasma power and duration led to a clear polycrystalline structure with relatively large grains due to the additional energy imparted by the plasma. After characterization, the films were incorporated as electrolytes in thin film solid oxide fuel cells, and the performance was measured at 500 °C. Despite similar structure and cathode morphology of the cells studied, the thin film solid oxide fuel cell with the ZrO2 thin film electrolyte by the thermal ALD at 250 °C exhibited the highest power density (38 mW/cm2) because of the lowest average grain size at cathode/electro...

Surface engineering of nanoporous substrate for solid oxide fuel cells with atomic layer-deposited electrolyte

Summary Solid oxide fuel cells with atomic layer-deposited thin film electrolytes supported on anodic aluminum oxide (AAO) are electrochemically characterized with varying thickness of bottom electrode catalyst (BEC); BECs which are 0.5 and 4 times thicker than the size of AAO pores are tested. The thicker BEC ensures far more active mass transport on the BEC side and resultantly the thicker BEC cell generates ≈11 times higher peak power density than the thinner BEC cell at 500 °C.

A KNOWLEDGE BASE FOR DYNAMIC PATH PLANNING OF MULTI-AGENTS

Abstract A fuzzy rule base is proposed to navigate multi-agents from initial positions to target positions in unknown environments. The proposed fuzzy rule base determines the highest priority of nine possible heading directions. The fuzzy rule base has been developed employing genetic algorithms as an approach to dynamic path planning of autonomous multi-agents in unknown environments. Paths which satisfy some optimization criteria with respect to moving distance, smoothness, and clearance of obstacles was obtained from the fuzzy rule base. The fuzzy rule base was obtained from off-line navigation with precise sensor modeling and applied to various simulated on-line navigation. The performance of the fuzzy rule base in different unknown environments is acceptable and shown in simulation results.

Experimental Study of Performance of PEMFC Operated in Dead-End Mode

Portable fuel cells are commonly operated in the dead-end mode because of such as high fuel utilization. However, the performance of such systems deteriorates continuously with an increase in the amount of by-products such as water vapor and nitrogen. In this study, to verify the effect of water vapor on Proton Exchange Membrane Fuel Cells (PEMFCs), constant-load experiments were carried out for a current density of 600 mA/cm2 and a voltage of 0.4 V, respectively. The performance of the cell was more stable under constant voltage conditions than under constant current density conditions. Condensed water accumulated in the anode channel near the cell outlet. The experimental results show how the relative humidity (RH = 0.15, 0.4 and 0.75) of air at the cathode side affect the performance of PEMFCs with dead-end anode. At RH values higher than 0.15, the mean power density increased by up to 51% and the mean purge duration decreased by up to 25% compared to the corresponding initial values.

Development of an Open Architecture Controller for a Commercial AUV

AUVs are essential to reduce the difficulty in building up flexible exploring and working systems in the water. However it is hard to integrate sub-modules or control algorithms into an AUV because AUV makers have developed control architectures and communication protocols of their own. So we develop an open architecture for AUV controller that integrates ready-made sub-modules to a reconfigurable and fault tolerant AUV. And we apply this open architecture to the cruising AUV.

Experimentation and modelling of nanostructured nickel cermet anodes for submicron SOFCs fuelled indirectly by industrial waste carbon

Nickel-Samaria Doped Ceria (Ni-SDC) cermet anodic thin films of about 500 nm were prepared on Scandia Stabilized Zirconia (ScSZ) electrolyte supports via reactive radio frequency (RF) sputtering. Anode deposition was done at room temperature, and the background sputtering gas was a reactive mixture of Ar : O2/80 : 20. The oxide conducting fuel cell configuration was completed by screen printing of lanthanum strontium manganite (LSM/YSZ) cathodes on the other side of the ScSZ supports. High resolution transmission electron microscopy (HR-TEM) of the cermet anode revealed an arranged nanostructure, with patterned ceria enclosing the nickel molecules in porous media. These highly ordered anodes were tested under (i) H2 and (ii) a product fuel of CO2 electro-reduced via industrial waste carbon (IWC). IWC fuel performance matched the H2 fuel performance in terms of peak power density and longevity, with an added lower fuel cost advantage. HR-TEM and scanning electron microscope (SEM) 2D images were utilized to simulate the reaction kinetics of the nanostructured porous thin film cermet anode. The reported high electrochemical performance was proved to result from the high density of triple-phase boundaries, arranged nanostructure and high contiguity of the special design of the nano-anodes. Experimental and simulation results were coherent with each other, especially for IWC operated SOFCs working at or above 700 °C.