Woo-Su Kim

Pitting resistance of TiN deposited on Inconel 600 by plasma-assisted chemical vapor deposition

Abstract TiN films were deposited on Inconel 600 by PACVD using the gaseous mixture of TiCl4, N2, H2, and Ar in order to increase the pitting resistance of Inconel 600. The pitting resistance was examined using a potentiodynamic polarization technique with a chloride solution. The effect of chloride concentration in the electrolyte on the pitting potential was also investigated. Inconel 600 coated with TiN film shows a superior pitting resistance to that without TiN film in condition that the thickness of the film is greater than a certain critical value. As the deposition temperature as well as the RF power increases, the residual Cl concentration in the film decreases, resulting in the improvement of the pitting resistance. However, the TiN films deposited at too high RF powers, even though the Cl concentration in TiN film is very small, show inferior pitting resistance, which is due to the formation of the network type microvoids structure.

Pitting resistance and mechanism of TiN-coated Inconel 600 in 100°C NaCl solution

TiN films were deposited on Inconel 600 by PACVD method using a gaseous mixture of TiCl4, N2, H2 and Ar, and their pitting resistance and mechanism in 100°C NaCl solution were investigated. Anodic polarization measurement of TiN-coated Inconel 600 was compared with that of bare Inconel 600. TiN-coated Inconel 600 has a higher Enp and a lower pit depth than bare Inconel 600. It also shows a smaller pit aspect ratio due to the concentration of the corrosion in the Inconel 600 contacted with the TiN film. When the Inconel 600 has a rough surface, Enp decreases and the pit density increases to a great extent. However, Ecorr, pit depth and pit aspect ratio are not affected.

A Frequency-Selecting Technique for Mobile Handset Antennas Based on Capacitance Switching

This paper introduces a mobile switchable antenna for long term evolution (LTE) of the 4th generation (4G), applicable to all mobile service bands. The validity of this antenna is assessed by design, realization, and measurement. A new frequency-selecting method is used in the proposed antenna, based on capacitance switching among four states. Due to the limited antenna space in existing terminals, it is quite di-cult to cover the entire low band with a single antenna. To overcome this di-culty, three single- pole double-throw (SPDT) switches, one 74HC04, and four capacitors are used. The resulting antenna covers the LTE (698{798MHz) and GSM (824{960MHz) bands in the low-band characteristic by realizing four capacitance states and at the same time covers the DCS (1710{1880 MHz)/PCS (1850{1990MHz)/WCDMA (1920{2170MHz) bands in the high-band characteristic. The antenna provides a gain of i1:04{6.00dBi, a radiation e-ciency of 32.73{74.99%, and omnidirectional characteristics in the H-plane. Because of this outstanding performance, it is expected that the new frequency - selecting technique will be applied in 4G mobile communication terminals.

Dual-Band Wi-Fi Antenna With a Ground Stub for Bandwidth Enhancement

Design of a compact modified inverted-L antenna with a ground stub is proposed for Wi-Fi applications. With the ground stub structure, the impedance bandwidth for 2.45-GHz band enhances from 13.1% to 15.7%, and the impedance bandwidth for 5.2/5.8-GHz bands improves from 10.1% to 19.9%. The performances of the antenna with optimized parameters are characterized in terms of reflection coefficient, gain, and radiation pattern measurements in an anechoic chamber. The measured result satisfies Wi-Fi frequency specifications.

A study on pitting corrosion of TiN-coated Inconel 600 by immersion test in high temperature chloride solutions

Abstract Pitting corrosion of TiN-coated Inconel 600 was studied in chloride solution at 200 °C. Stoichiometric polycrystalline TiN films were coated by the plasma-assisted chemical vapor deposition (PACVD) method at 500 °C. The TiN-coated and bare Inconel samples were immersed in aerated CuCl 2 solution at 200 °C. The density, maximum depth, growth behavior and shape of the pits were determined at various chloride concentrations and immersion times. The TiN-coated Inconel showed superior pitting resistance to that of the bare Inconel at low CuCl 2 concentration, but the TiN film could not improve the pitting resistance of the Inconel substrate at high CuCl 2 concentration.

A Low-Profile WLAN Antenna with Inductor and Tuning Stub for Broadband Impedance Matching

This paper presents a low-profile multiband antenna suitable for wireless local area networks (WLANs), using a chip inductor and tuning stub for broadband impedance matching. The proposed antenna is compact and covers three bands: 2.4-GHz (2.400–2.484 GHz), 5.2-GHz (5.150–5.350 GHz), and 5.8-GHz (5.725–5.825 GHz). The measured 10-dB bandwidths are 12.0% (2.28–2.57 GHz) in the lower band for 2.4-GHz WLANs and 39.1% (4.81–7.15 GHz) in the upper band for 5 GHz-WLANs. The measured peak gain of the antenna is between 2.7 and 4.39 dBi and the radiation patterns are omnidirectional.

Low-Profile Dual-Wideband MIMO Antenna with Low ECC for LTE and Wi-Fi Applications

This paper presents a low-profile dual-wideband multiple input multiple output (MIMO) antenna with low envelop correlation coefficient (ECC) for long-term evolution (LTE) and wireless fidelity (Wi-Fi) applications. The antenna covers LTE band 7 and Wi-Fi as well as wireless broadband (Wibro) and Worldwide Interoperability for Microwave Access (WiMax) (except for the 3.5-GHz band). To aid with integration of a practical mobile terminal, the MIMO antenna elements are placed at appropriate locations by analyzing the surface current distribution and without using any additional isolation techniques. The measured bandwidths with reflection coefficients of 20 dB in the operating frequency ranges of both LTE band 7 and Wi-Fi. Additionally, the calculated ECC is in the range , which is considerably lower than the required for MIMO applications. The measured radiation patterns are appropriate for mobile terminals, and omnidirectional radiation patterns are obtained.

EIRP Characterization of Electrically Large Wireless Equipment with Integrated Signal Generator in a Compact Environment

We describe a measurement technique to characterize the equivalent isotropically radiated power (EIRP) of electrically large wireless equipment in a compact environment. A modified phase-measurement method was proposed and, thus, the separation of the signal generator and radiating element was not required during the measurement. A Fresnel-to-far-field transformation was used for the fast measurement time in a compact anechoic chamber. An experimental verification of the method was carried out in a compact anechoic chamber, where the source-detector separation was approximately 1/5 of the far-field distance. The measured magnitude and phase pattern exhibited only a small error. The EIRP obtained using a Fresnel-to-far-field transformation was compared with a reference value, and the error was within 0.5 dB.