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Creep behaviors of the Zr-1.1Nb-0.05Cu (HANA-6) alloy strips with different orientations were investigated. Anisotropy was observed in the samples depending on their physical orientations due to the formation of texture in their microstructures. The creep strain rate was increased as the test stress and temperature increased. The rate was higher along the rolling-direction than in the transverse-direction irrespective of annealing conditions. However, the samples with 45˚ direction showed different behaviors depending on the annealing temperature. When strips were finally annealed at 600℃ for 10 min, the primary creep rate of the 45˚ strip was the highest among the various orientations although the saturated creep rate was the lowest. In the case of final annealing at 660℃ for 4 h, the highest creep rate occurred throughout the creep test in the 45˚ strip. It is considered that the fraction of (100) planes along the direction of creep deformation affect the creep rates.

keyword : metals, rolling, creep, tensile test, texture

Aluminosilicate inorganic polymer binder has been studied as an alternative to ordinary Portland cement due to its higher physical properties, chemical resistance and thermal resistance. This study has been carried out in an attempt to understand the hardening characteristics of aluminosilicate binder by varying the content of calcium. Samples with four different ratios of Al, Si, and Ca were synthesized in this study with the Al:Si:Ca mol ratio being 1.00:1.85~1.98:0.29~2.12. Furthermore, an alkali silicate solution was prepared with the sodium hydroxide (NaOH) and sodium silicate (NaSi). The hardening characteristics of the specimens were analyzed using XRD, SEM, and TG/DTA. In addition, compressive strength and sintering time of specimens were measured as a function of calcium content. The results showed that the specimen containing 2.12 mol% calcium offered the highest compressive strength. However, the compressive strength of the specimen containing 0.26 mol% calcium was lower relative to the other specimens. The results displayed a distinct tendency that as more calcium was added to the inorganic polymer, setting time became shorter. When calcium was added to the inorganic polymer structure, a second phase was not formed, indicating that the addition of calcium does not affect the crystalline structure.

keyword : amorphous materials, chemical synthesis, crystal structure, X-ray diffraction, aluminosilicate

This paper studies the experimental method that uses the homogeneous precipitation method to prepare mica flakes coated with anatase-type titania pearlescent pigment with urea as precipitant. The optimum technology parameters, the chemical composition, the microstructure, and the color property of resulting pigments are discussed. The coating principle of mica coated titania with various coating thickness is analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy(TEM) and tested by spectrophotometer analysis. The colored nanocrystalline pigments with different morphology and coating thickness 45-170 nm were prepared by homogeneous precipitation treatment of TiOSO4(titanum oxysulfate) aqueous solutions. Characterizations on the pigments show that the pearlescent effects of the pigments depend mainly on mica size, thickness of the metal oxide deposit, its chemical composition, and crystal structure.

keyword : titania, mica, pigments, optical property, transmission electron microscopy

Nano-powders of Ti3Al and 2(Al2O3) were synthesized from 3Ti(O2) and 5Al powders by high energy ball milling. A nanocrystalline Al2O3 reinforced composite was consolidated by pulsed current activated sintering within 2 minutes from mechanochemically synthesized powders of Al2O3 and Ti3Al. Nanocrystalline materials, have received much attention as advanced engineering materials due to their improved physical and mechanical properties. The relative density of the composite was 99.5%. The average obtained hardness and fracture toughness values were 1510 kg/mm2 and 9 MPa·m1/2, respectively.

keyword : compound, nanostructure, sintering, mechanical properties

Wire brushing, which is a typical surface preparation method for roll bonding, has recently been highlighted as a potentially effective method for surface nanocrystallization. In the present study, the microstructure evolution and hardness of the wire-brushed surface and roll-bonded interface of a 1050 aluminum sheet were investigated. Wire brushing formed protruded layers with a nanocrystalline structure and extremely high surface hardness. After roll bonding, the protruded layers remained as hard layers at the interface. Due to their hardness and brittleness the interface hard layers, can affect the interface bonding properties and also play an important role determining the mechanical properties of multi-layered clad sheets.

keyword : wire brushing, aluminum, surface nanocrystallization, protruded Layer, hard Layer, roll bonding, interface, mechanical properties

High speed copper filling into TSV (through-silicon-via) for three dimensional stacking of Si chips was investigated. For this study, a tapered via was prepared on a Si wafer by the DRIE (deep reactive ion etching) process. The via had a diameter of 37㎛at the via opening, and 32㎛at the via bottom, respectively and a depth of 70㎛. SiO2, Ti, and Au layers were coated as functional layers on the via wall. In order to increase the filling ratio of Cu into the via, a PPR (periodic pulse reverse) wave current was applied to the Si chip during electroplating, and a PR (pulse reverse) wave current was applied for comparison. After Cu filling, the cross sections of the vias was observed by FE-SEM (field emission scanning electron microscopy). The experimental results show that the tapered via was filled to 100% at -5.85 mA/cm2 for 60 min of plating by PPR wave current. The filling ratio into the tapered via by the PPR current was 2.5 times higher than that of a straight via by PR current. The tapered via by the PPR electroplating process was confirmed to be effective to fill the TSV in a short time.

keyword : electronic materials, plating, defects, scanning electron microscopy (SEM), three dimensional packaging

In this study, micro gas sensors for ammonia gas were prepared by adopting MEMS technology and using a sol-gel process. Three types of sensors were prepared via different synthesis routes starting with W sol and Ru sol mixture. This mixture was deposited on a MEMS platform and the platform was subsegueny heated to a temperature of 350℃. The topography and crystal structure of the sensing film were studied using FE-SEM and XRD. The response of the gas sensor to NH3 gas was examined at various operating temperatures and gas concentrations. The sensor response increased almost linearly with gas concentration and the best sensing response was obtained at 333℃ for 5.0 ppm NH3 for the specimen prepared by coating WO3 powders with the Ru sol mixture.

keyword : compounds, sol-gel, electrical properties, resistivity, gas sensor, tungsten oxide, ruthenium, NH3

ZnO nanotube arrays were synthesized by a two-step process: electrodeposition and selective dissolution. In the first step, ZnO nanorod arrays were grown on an Au/Si substrate by using a homemade electrodeposition system. ZnO nanorod arrays were then selectively dissolved in an etching solution composed of 0.125 M NaOH, resulting in hollow ZnO nanotube arrays. It is suggested that the formation mechanism of the ZnO nanotube arrays might be attributed to the preferred surface adsorption of hydroxide ion (OH-1) on a positive polar surface followed by selective dissolution of the metastable Zn-terminated ZnO (0001) polar surface caused by the difference in the surface energy per unit area between the ZnO nanorod and nanotube.

keyword : optoelectronic materials, chemical synthesis, microstructure, transmission electron microscopy, TEM, nanotube

ZnO nanorods were prepared by the electrodeposition route on conductive Au/Si substrates. The effects of deposition time on the microstructural evolution and optical properties of ZnO nanorods were investigated. With increasing deposition time from 1 h to 20 h, the diameter and length of the ZnO nanorods increased gradually to about 328 nm and 6.55㎛, respectively. The ZnO nanorods were dense and vertically well-aligned. The photoluminescence (PL) peaks corresponding to the near band edge of ZnO were observed. With increasing deposition time, the intensity of PL peaks increased with nanorod growth up to 4 h and then decreased. This might be due to the degradation of crystal quality caused by merging of nanorods.

keyword : semiconductors, crystal growth, microstructure, scanning electron microscopy, SEM

The current study investigates the electroplating characteristics of Sn-Cu eutectic micro-bumps electroplated on a Si chip for flip chip application. Under bump metallization (UBM) layers consisting of Cr, Cu, Ni and Au sequentially from bottom to top with the aim of achieving Sn-Cu bumps 10×10×6 ㎛in size, with 20㎛ pitch. In order to determine optimal plating parameters, the polarization curve, current density and plating time were analyzed. Experimental results showed the equilibrium potential from the Sn-Cu polarization curve is -0.465 V, which is attained when Sn-Cu electro-deposition occurred. The thickness of the electroplated bumps increased with rising current density and plating time up to 20 mA/cm2 and 30 min respectively. The near eutectic composition of the Sn-0.72wt%Cu bump was obtained by plating at 10 mA/cm2 for 20 min, and the bump size at these conditions was 10×10×6 ㎛. The shear strength of the eutectic Sn-Cu bump was 9.0 gf when the shearing tip height was 50% of the bump height.

keyword : electronic materials, plating, mechanical properties, scanning electron microscopy, SEM, bonding