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D.-H. Kim, T.-J. Kim and S.-G. Lim

Abstract

In this study, mechanical properties and microstructures of extruded aluminum matrix composites were investigated. The composite materials were manufactured by two step methods: powder metallurgy (mixture of aluminum powder and carbon fiber using a turbular mixer, pressing of mixed aluminum powder and carbon fiber using a cold isostatic pressing) and hot extrusion of pressed aluminum powder and carbon fiber. For the mixing of Al powder and carbon fibers, aluminum powder was used as a powder with an average particle size of 30 micrometer and the addition of the carbon fibers was 50% of volume. In order to make mixing easier, it was mixed under an optimal condition of turbular mixer with a rotational speed of 60 rpm and time of 1800s. The process of the hot-extrusion was heated at 450°C for 1 hour. Then, it was hot-extruded with a condition of extrusion ratio of 19 and ram speed of 2 mm/s. The microstructural analysis of extruded aluminum matrix composites bars and semi-solid casted alloys were carried out with the optical microscope, scanning electron microscope and X-ray diffraction. Its mechanical properties were evaluated by Vickers hardness and tensile test.

Open access

D. H. Kim, A. Kinmond, S. Gilani, S. Giridharan and A. Jegannathen

Abstract

INTRODUCTION: The aim of this study is to assess the efficacy and toxicity of maintenance pemetrexed following induction treatment with cisplatin and pemetrexed for patients with advanced non-small cell lung cancer.

PATIENTS AND METHODS: Eligible patients following four cycles of intravenous pemetrexed (Alimpta©; 500 mg/m2) and intravenous cisplatin (75 mg/m2) were given 21-day cycles of maintenance pemetrexed (500 mg/m2) until disease progression, unacceptable adverse event or death. From a total 80 patients receiving palliative induction chemotherapy, 17 subsequently received maintenance pemetrexed.

RESULTS: The mean number of maintenance cycles completed was 5.9 (range 1-20; median 3.0). The mean progression-free survival (PFS) was 5.2 months (range: 2-15; median: 2.0) and the 1-year PFS was 17%. Treatment was discontinued due to disease progression (71%), adverse event (21%) and death from study disease (7%). Grade 3-4 laboratory and non-laboratory adverse events were seen in 11.8 and 17.6% of patients, respectively. Anaemia was the most common adverse event (71% of all patients; 65% grade 1-2; 5.9% grade 3-4). The most common reason for withdrawal due to adverse event was declining renal function. There was a statistically significant correlation between worsening performance status and reducing number of maintenance cycles completed (Spearman’s rank; R = −0.511, p = 0.036).

DISCUSSION: The median PFS was lower than in previous studies with a higher than previously reported frequency of adverse events. Clinicians must monitor renal function and full blood counts vigilantly, especially in patients with performance status greater than 0.

Open access

D.H. Shim, S.S. Jung, H.S. Kim, H. Cho, J.K. Kim, T.G. Kim and S.J. Yoon

Abstract

Zirconia matrix ZrO2/CNT composite materials reinforced with multiwall carbon nanotubes were fabricated using a spark plasma sintering technique. The effects of the amount of CNTs addition, sintering temperature and sintering pressure on the properties of the resulting ZrO2/CNT composites were examined. 0 to 9 vol. % CNTs were dispersed in zirconia powder, and the resulting mixture was sintered. The electrical conductivity, hardness, flexural strength, and density were measured to characterize the composites. The friction and wear properties of the composites were also tested. The flexural strength and friction coefficient of the composites were improved with up to 6 vol.% of CNT addition and the flexural strength showed a close relationship with the relative density of the composite. The electrical conductivity increased with increasing proportion of the CNTs, but the efficiency was reduced at more than 6 vol.% CNTs.

Open access

E.-H. Lee, K.-M. Kim, W.-Y. Maeng and D.-H. Hur

Abstract

After preparing aqueous suspensions from magnetite particles with a poly-acrylic acid, we investigated the effects of several experimental parameters. We characterized the stability of the suspensions using visual inspection, sedimentation, adsorption, and thermal stability of the dispersant. The dispersion stability is affected by the solution pH, the concentrations of magnetite particles, the molecular weight, the concentration of the dispersants, and the temperature. The stability of the suspensions increased as the concentration of the dispersant and the temperature increased. In terms of the molecular weights of the dispersant, the suspensions with dispersant of low-molecular weight (1800) were more stable than those of high-molecular weight (250000) at room temperature. However, at high temperature the suspensions with high-molecular weight showed stability. The adsorption efficiency of the dispersant was very low. The dispersant of high-molecular weight showed a higher thermal integrity than that of low-molecular weight. From this work, we obtained the optimum conditions for stable aqueous suspensions of magnetite particles.

Open access

D.-J. Kim, K.M. Kim, J.H. Shin, Y.M. Cheong, E.H. Lee, G.G. Lee, S.W. Kim, H.P. Kim, M.J. Choi, Y.S. Lim and S.S. Hwang

Abstract

Fast water flow facilitates ferrous ion transport leading to flow accelerated corrosion (FAC) of carbon steel and the possibility of a large accident through a failure of a secondary pipe in a nuclear power plant. Ion transport is directly linked to oxide properties such as the thickness, chemical composition and porosity. This work deals with a precise observation of the cross section of the corroded specimen focusing on an oxide passivity and its thickness using SEM (scanning electron microscope) and TEM (transmission electron microscope) as well as an apparent weight loss and a surface observation for the specimens corroded using a rotating cylindrical electrode autoclave system in pure water of pH 7 at 150°C having dissolved oxygen below 1 ppb within a flow rate range of 0 to 10 m/s. The Cr content in steel was changed from 0.02 to 2.4 wt%. Increasing the Cr content in the alloy, the FAC rate and oxide thickness decreased. The oxide porosity tends to decrease with the Cr content and immersion time owing to the development of Cr containing oxide. The oxidation behavior is not changed with the immersion time.

Open access

J.-H. Lee, D.-O. Kim and K. Lee

Abstract

The hot deformation behavior of a heavy micro-alloyed high-strength low-alloy (HSLA) steel plate was studied by performing compression tests at elevated temperatures. The hot compression tests were carried out at temperatures from 923 K to 1,223 K with strain rates of 0.002 s−1 and 1.0 s−1. A long plateau region appeared for the 0.002 s−1 strain rate, and this was found to be an effect of the balancing between softening and hardening during deformation. For the 1.0 s−1 strain rate, the flow stress gradually increased after the yield point. The temperature and the strain rate-dependent parameters, such as the strain hardening coefficient (n), strength constant (K), and activation energy (Q), obtained from the flow stress curves were applied to the power law of plastic deformation. The constitutive model for flow stress can be expressed as σ = (39.8 ln (Z) – 716.6) · ε (−0.00955ln(Z) + 0.4930) for the 1.0 s−1 strain rate and σ = (19.9ln (Z) – 592.3) · ε (−0.00212ln(Z) + 0.1540) for the 0.002 s−1 strain rate.

Open access

B. Swain, D. Han, G.-H. Kim, M.-S. Kong and B. Ahn

Abstract

MA956 (Fe-Cr-Al) alloy powder was high-energy ball milled with various amount of yttria contents (1,2,3, and 4 wt.%) to fabricate an oxide dispersion strengthened alloy. The milled powders were then consolidated using hot press sintering at 1150°C. The surface morphology and crystal structure of MA956 powder during the high-energy milling depending on the yttria contents was investigated using particle size analysis, X-ray diffraction, and scanning electron microscopy. The microstructural analysis of sintered alloy was performed using transmission electron microscopy and energy dispersive spectroscopy to evaluate the dispersion behavior of yttrium oxide. The results showed that, as yttria contents increased, the oxide particles became finer and are uniformly distributed during the high-energy milling. However, after the sintering, the oxide particles were coarsened with more than 3 wt.% of yttria addition.

Open access

H.P. Kim, M.J. Choi, S.W. Kim, D.J. Kim, Y.S. Lim and S.S. Hwang

Abstract

Effects of grain boundary morphologies on stress corrosion cracking (SCC) of Alloy 600 have been studied in 40% NaOH at 315°C using C-ring specimens. The configuration of the grain boundary and the intergranular carbide density were controlled by heat treatment. SCC tests were performed at +150 mV above the corrosion potential. The specimen with a serrated grain boundary showed higher SCC resistance than that with a straight grain boundary. This appears to be caused by the fact that the specimen with the serrated grain boundary has longer SCC path. SCC resistance also increased with intergranular carbide density probably due to enhanced relaxation of stress at intergranular carbide.

Open access

M.-W. Lee, D.R. Dhakal, T.H. Kim, S.R. Lee, H.J. Kim and T.S. Jang

Abstract

Micostructural change and corresponding effect on coercivity of a NdFeB sintered magnet mixed with small amount of DyMn powder was investigated. In the sintered magnet mixed with the DyMn alloy-powder Dy-rich shell was formed at outer layer of the main grains, while Mn was mostly concentrated at Nd-rich triple junction phase (TJP), lowering melting temperature of the Nd-rich phase that eventually improved the microstructural characteristics of the gain boundary phase. The coercivity of a magnet increased more than 3.5 kOe by the mixing of the DyMn alloy-powder.

Open access

S.M. Shin, D.J. Shin, G.J. Jung, Y.H. Kim and J.P. Wang

Abstract

This study was focused on recycling process newly proposed to recover electrodic powder enriched in nickel (Ni) and rare earth elements (La and Ce) from spent nickel-metal hydride batteries (NiMH). In addition, this new process was designed to prevent explosion of batteries during thermal treatment under inert atmosphere. Spent nickel metal hydride batteries were heated over range of 300°C to 600°C for 2 hours and each component was completely separated inside reactor after experiment. Electrodic powder was successfully recovered from bulk components containing several pieces of metals through sieving operation. The electrodic powder obtained was examined by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) and image of the powder was taken by scanning electron microscopy (SEM). It was finally found that nickel and rare earth elements were mainly recovered to about 45 wt.% and 12 wt.% in electrodic powder, respectively.