Eco-Materials Processing & Design VI

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Authors: Min Kyu Yang, Hyu Seung Yang, Jong Ku Park, Keun Ryu, Yong Bok Lee, Jeon Kook Lee
Abstract: The self-lubricating composite films were deposited on Inconel 718 by Hollow Cathode Plasma Jet (HCPJ). These composite materials consist of chrome nickel alloy matrix and Ag, BaF2/CaF2 solid lubricants. The Cr2O3-NiCr-Ag composite thin film was crystallized and had the main peaks of Cr2O3 (012) and Ag (111). The deposition rate of 200 nm /min by HCPJ was much faster than the ordinary R.F planar magnetron sputtering. The surface roughness of coated shaft was 30 nm.
Authors: Kee Sung Lee, Tae Ho Shin, Shi Woo Lee, Sang Kuk Woo, Jae Kyo Yang, Yong Ho Choa
Abstract: A layer consisting of La0.6Sr0.4CoO3-d particles with inner nano-pores is coated on the La0.7Sr0.3Ga0.6Fe0.4O3-d oxide to improve the surface reaction resulting in high oxygen permeability. The La0.6Sr0.4CoO3-d particles with inner nano-pores are synthesized by an ultrasonic spray pyrolysis method. The permeated oxygen contents from air to helium gas were measured using gas chromatography after the synthesized particles were coated on the La0.7Sr0.3Ga0.6Fe0.4O3-d oxide by the conventional screen-printing. The results demonstrated that the reactive free surfaces of the nano-pores are an important factor in determining the oxygen permeation for application such as gas separation membrane and ceramic fuel cell.
Authors: Dong Bok Lee, Seung Wan Woo
Abstract: New ceramic composites that consist of the amorphous SiOC matrix having dispersoids of Mo4.8Si3C0.6 and some MoSi2 were synthesized, and their oxidation characteristics were investigated between 450 and 1050oC in air. The SiOC matrix was obtained by converting polymethylsiloxane via pyrolysis. The good oxidation resistance of the prepared composites originated from a thin, protective SiO2 layer formed on the surface. But the outermost oxide surface was porous, owing to the formation of the highly volatile MoO3, which was formed together with SiO2.
Authors: Dong Bok Lee, J.H. Ko
Abstract: The Ni-19at.%W coating was electodeposited to protect the stainless steel substrate, and then corroded between 500 and 700oC in Ar-0.2% SO2 atmosphere for 5 hr. The coating effectively protected the substrate from corrosion at 500oC, but failed at 700oC owing to serious corrosion. The corrosion products were mainly NiO, WO3 and NiWO4, together with some NiS, FeS, Fe2O3 and FeWO4. Detailed scale morphologies and corrosion mechanism are presented.
Authors: Young Sup Lee, C.H. Lee, Cheol Ho Lim, Dong Choul Cho, Seung Y. Shin
Abstract: A diffusion brazing of aluminium alloy A6061 was preformed using a Ag-28Cu insert to conduct eutectic brazing. Interface behaviors of the brazed joints were observed after brazing at 450-560°C. The tensile property of the brazed joints was also examined. During diffusion brazing of Al6061 alloys with Ag-28Cu insert, eutectic melts were formed by eutectic reaction between Al6061 and Ag-28Cu insert. It was found that the reaction layers composed of two phases were formed at the interface between Al6061 and Ag-28Cu insert. EPMA analysis revealed that two phases in the reaction layers consist of Ag-rich phase and Cu-rich phase. The tensile strength of the joints brazed at 560°C for 30min was 160 MPa.
Authors: Chan Won Lee, H.B Kwon, Hong Pyo Jeon, B. Koopman
Abstract: A technology for phosphate recovery was developed using waste oyster shell as a raw material in a fluidized bed reactor (FBR). Raw oyster shell that causes a major disposal problem in coastal aquaculture regions was converted to activated oyster shell (AOS) by pyrolysis under defined conditions. A prototype of precipitates collection ports was devised relating to AOS particle size and flow velocity. The optimum conditions determined were applied to wastewater for phosphate recovery with the knowledge of mass balance in the FBR system.
Authors: Dae Ho Choi, Byung Kyu Moon, Rak Joo Sung, Seung Ho Kim, Koichi Niihara
Abstract: Mechanical and thermal properties of Si3N4 ceramics with various rare-earth oxides (La2O3, CeO2, Lu2O3, Dy2O3, Sm2O3, Nd2O3, Yb2O3, and RuO2) were investigated. Flexural strength of silicon nitride with addition of 5vol% Nd2O3, CeO2, Dy2O3, and Sm2O3 showed higher value than that of silicon nitride with Lu2O3 and La2O3 added because they form denser microstructure and smaller elongated grain. Thermal conductivity of silicon nitride with an addition of 5vol% RuO2 was more enhanced than that of silicon nitride added with Nd2O3, Sm2O3, and Dy2O3 because the addition of RuO2 depressed grain growth. It is also associated with lattice oxygen governing thermal conductivity of Si3N4 when added rare-earth oxides.
Authors: Ho Sung Aum, M.C. Curiel, Daniel G. Carillo
Abstract: A high stress condition in the hip system may cause fracture of the ball head. This failure may appear after a heavy accident such as sudden fall. The aim of this investigation is to make a computer simulated model of the hip system to evaluate the regions of stress concentration as well as the pressure in the stem-ball junction. 3D Non-Linear Finite Element Analyses were performed taking into consideration a high peak load to simulate trauma conditions. Ball heads from 22 to 36 mm in diameter were modeled, and also two sizes for taper lock were simulated to report their influence on the stresses over the critical areas of the ball head. Two different materials of common ball head ceramics (Alumina and Zirconia) were considered to evaluate its relation to the stresses produced. It was found that the ball head cone’s depth has major incidence in the stress concentration surrounding the stem when an impact load is applied, and that a deeper cone may offer a more relieved loading configuration when considering stress related parameters such as Von Mises stress, contact pressure and friction stress.
Authors: Feng Lan Xu, Yu Bao Li, Jimei Han, Guo Yu Lv
Abstract: Porous scaffold containing biodegradable Ca-crosslinked alginate(ALG) and nano-hydroxyapatite(n-HA) is synthesized by the freeze-extraction and freeze-gelation methods. The prepared scaffolds were tested by scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared absorption spectra (IR), raman spectra, X-ray diffraction (XRD) and burning test. Chemical binding between inorganic n-HA and Ca-crosslinked alginate was investigated. It indicated that n-HA was interacted with Ca-crosslinked alginate. The results of SEM showed that the scaffolds exhibited open-cellular pore structures. The content of n-HA affected the porosity and pore size of the composite. The composite can be a promising scaffold material for tissue engineering.
Authors: Pham Huyen Tram, Joon Won Min, Huang Chen, Soo Wohn Lee
Abstract: Based on the strong inhibition of SiC particles on the grain growth of the Αl2O3 matrix, a mixture powder of α-Al2O3 and SiC was used as feedstock to deposit the nanocomposite coatings by plasma spraying. To determine the effect of plasma spraying gas on microstructure and mechanical properties of Al2O3–SiC nanocomposite coatings, primary Ar gas and secondary H2 gas were chosen, which have an effect on temperature and velocity of the flyingpowders at the time of impacting on substrate. The X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were used to characterize the microstructures of these coatings. Surface roughness was measured also.

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