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Due to the reduced thickness of thin films formed via atomic layer deposition, analyzing their true mechanical properties is difficult. To overcome this drawback, tensile tests on free-standing alumina thin films floating on water were conducted to measure their mechanical properties. Tensile tests on alumina thin films formed at different deposition temperatures were also conducted; the results indicated that higher Young's modulus and the strength were obtained from thin films formed at higher deposition temperatures. Factors responsible for the variations in mechanical properties were investigated through analyses of the structure, density, and composition of the films.

Aerogels have the lowest thermal conductivity (

This study evaluates the performance and stability of Pt cathodes, which are treated by infiltrating cerium oxide (CeOx) onto their surfaces, in polymer electrolyte membrane fuel cells. The concentration of CeOx on the surface of Pt is adjusted by varying the concentration of the cerium precursor in the infiltration solution. The peak power density of the cell using the Pt cathode featuring the optimal amount of infiltrated CeOx is as high as 400 mW cm−2 at 70 °C, which is approximately 40% higher than that of the cell using the untreated Pt cathode under identical test conditions. Electrochemical impedance analysis confirms that this increase in peak power density is clearly attributed to the decrease in cathodic polarization impedance, which implies that the CeOx deposited on the surface of Pt enhances the catalytic performance of Pt. The infiltration of CeOx on the surface of Pt is also confirmed to be truly effective for improving the stability of Pt. Accelerated degradation tests demonstrate that the degradation rates of the cells using CeOx-Pt cathodes are significantly lower than that of the cell using the untreated Pt cathode because of the preservation of electrochemically active sites, as revealed by cyclic voltammetry.

The semiconductor etching process, which is the most important part of the semiconductor manufacturing process, requires higher sophistication as 10 nm semiconductors are mass produced. Etching methods utilizing plasma are getting increasingly popular with the miniaturization of the etching process. As the process performance depends on the state of the plasma variables, such as electron density, it is essential to measure and control these variables in real time. Moreover, to control the plasma-based system, the sensitive and time-varying characteristics of plasma should be considered. This paper proposes a self-tuning adaptive model predictive controller that can effectively perform electron density control. As a first step, an integral squared error-based Bayesian optimization is used to tune the model predictive controller, and its performance is verified on a drift-free Ar plasma system. The self-tuning adaptive model predictive controller is constructed by combining a recursive model parameter estimator with a model predictive controller. The recursive model parameter estimator is designed using a recursive least squares algorithm with Kalman filter interpretation. The effectiveness of the proposed controller is verified through control simulations and a set-point tracking experiment on the electron density with artificial drift in real time. The experimental results show that the performance of the proposed controller is 21% better than that of the conventional model predictive controller. We expect that this result will make a significant contribution to control processes utilizing plasma.

Recently, atomic layer deposition (ALD) has drawn much attention as a suitable tool for fabrication and engineering of high performance fuel cell catalysts and electrodes. Intrinsic merits of ALD enable synthesis of conformal and uniform film even at a sub-nm scale with excellent stoichiometry control and reproducibility. Leveraging the unique characteristics, ALD has proven its promising potential as a solution to achieve two major challenges of solid oxide fuel cell research: sluggish kinetics at low operational temperatures and long-term stability. In this review, recent efforts to address the challenges by the use of ALD-based functionalization of surfaces and interfaces of cell components are discussed.

In this study, wind-battery hybrid power systems are designed, evaluated, and optimized for regular supply of electrical power at a designated minimum load level with no shortage. Our simulation uses lead-acid batteries and vanadium redox flow batteries (VRBs) for storage, and utilizes hourly wind speed data measured in 2012 at Mt. Taegi in South Korea. Twenty Vestas V80 wind turbines, each rated at 2 MW, are used as power generators, on the basis of an actual wind turbine project recently installed at Mt. Taegi. Sale to the main grid of electricity generated in excess of the minimum load offset the initial capital costs for installation of the wind turbines and batteries. Results show that the optimized wind-VRB hybrid system can supply more than 9 MW of regular electrical power at no cost. Even higher levels of production are profitable with sale of the wind-generated electricity directly to a demand site at a price greater than the price of sales to the main grid. A reduction in the VRB electrolyte costs and an increase in carbon taxes can also increase profitability.

In this study, the performance of the cathode catalyst of polymer electrolyte membrane fuel cells is improved by the atomic layer deposition (ALD) of a protective layer. An atomic layer-scale zirconia protective layer is coated on the platinum catalyst for surface treatment. The results indicate that a very thin layer deposition with two ALD cycles or less is required to minimize the deterioration of the activity of the catalyst. Further, it is also confirmed that the catalyst aggregation can be effectively suppressed by its encapsulation with the protective layer through several ALD cycles from the analysis of the electrochemical surface area by cyclic voltammetry and the change in the catalyst particle size. According to the results, even two ALD cycles, which provide less than one atom layer, has decreased the deterioration rate to one-fourth of that of the untreated catalyst, with a minor decrease in the fuel cell power. In addition, the I–V data and impedance spectroscopy confirms that the overall stability of the membrane electrode assembly is improved by the ALD treatment. Thus, the ALD of a protective layer is considered to be a very promising strategy to improve the stability and performance of fuel cell catalysts.

With the advent of more than Moore’s law era, control of plasma etch process is expected to become inevitable. Given that highly complex plasma is a medium of etch processes, plasma parameters are key factors to be controlled. In addition, highly interactive plasma characteristics require multivariate control schemes. In this paper, we design a multi-loop controller which controls effective plasma parameters in Ar plasma conditions. The effective plasma parameters obtained by optical emission spectroscopy are paired with plasma reactor instrumental variables through relative gain array and singular value decomposition. Each single input-single output (SISO) system based on the pairing result shows successful disturbance rejection performance but interactions between SISO controllers occur. In order to handle the interactions, 2 × 2 multiple input-multiple output (MIMO) controllers with and without decouplers are simulated to track set point change. Based on the simulations, a MIMO controller with decouplers is implemented in a capacitively coupled plasma reactor and show feasible control performance without interaction. Hopefully, the results introduced in this paper contribute to making progress in plasma parameter control.

This study reports on protonic ceramic fuel cells (PCFCs) that exhibit enhanced performance after the addition of palladium (Pd) interlayers at the cathode–electrode interface. The Pd interlayer is deposited by sputtering on the BaZr0.2Ce0.6Y0.1Yb0.1O3-δ (BZCYYb) electrolyte surface, followed by the inkjet printing of PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) and sintering. The proposed method successfully has produced a Pd layer that was well integrated between the BZCYYb and PBSCF layers, with no undesired reactions or phase formation. The Pd layer is diffused along the inner surface of the porous PBSCF cathode with the desired gradient composition. In our experiment, the fuel cell power is enhanced by up to 60% compared to the untreated PCFCs. In the former, the peak power density of the optimal cell is 420 mW cm−2, while that of the untreated sample is 260 mW cm−2 at 500 °C. The long-term stability of the Pd interlayer is confirmed during cell operation. The impedance analysis has revealed that the presence of the Pd significantly enhances the current collection and reduces the polarization impedance at the cathode–electrolyte interface, especially at low temperatures. These results indicate that the proposed method is promising for the fabrication of high-performance and robust PCFCs.