bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of Porous 4H-SiC by Surface Anodization
Authors: Chen Yi , Shoji Satoko , Sugishita S. , Ohshima Satoru , Nishino Shigehiro
Published: March 2009

The preparation of porous 4H-SiC by electrochemical etching of SiC crystals was
investigated. The porous layer was created at the porous SiC (PSC)/SiC interface but not from the SiC/electrolyte interface. The nanopores at the adjacent region of PSC/SiC interface were bigger than those at the top region. In the visible light region, the optical reflectance from PSC exhibits interference fringes. In the Reststrahlen region, the fourier transform infrared (FTIR) reflectance of
porous 4H-SiC shows a splitting into more bands: a broad band with high reflectivity at low frequency and several sharp peaks near the LO frequency. The width and shape of FTIR spectra depended on the anodization current density. The anodization current density is a crucial parameter which determined the porosity, porosity depth profile, and the thickness of PSC layers. A pore transformation of porous structure was observed after chemical vapor deposition process.
On Current Limitations in Porous SiC Applications
Authors: Mynbaeva Marina G. , Lavrent'ev A. , Kotousova I. , Volkova A.N. , Mynbaev K. , Lebedev Alexander A.
Published: March 2009

Thermal stability of porous SiC (PSC) with nano-, micro- and double-layer porous
structure is assessed through annealing the material at T=900–1700 0C in vacuum and Ar. Changes in composition of PSC under thermal treatment are correlated with porous structure modification. Limitations in PSC technology and applications due to compositional and structure evolution at high temperatures are discussed.
Dynamical Study of Dislocations and 4H → 3C Transformation Induced by Stress in (11-20) 4H-SiC
Authors: Idrissi Hosni , Lancin Maryse , Douin Joel , Regula G. , Pichaud Bernard
Published: March 2009

4H-SiC samples were bent in compression mode at temperature ranging from 400°C to 700°C. The introduced-defects were identified by Weak Beam (WB) and High Resolution Transmission Electron Microscopy (HRTEM) techniques. They consist of double stacking faults bound by 30° Si(g) partial dislocations whose glide locally transforms the material in its cubic phase. The velocity of partial dislocations was measured after chemical etching of the sample surface. The formation and the expansion of the double stacking faults are discussed.
Intensity Ratio of the Doublet Signature of Excitons Bound to 3C-SiC Stacking Faults in a 4H-SiC Matrix
Authors: Camassel Jean , Juillaguet Sandrine
Published: March 2009

In 4H-SiC, 3C stacking fault (SF) behaves like a finite thickness type II quantum well. As a consequence, it can bind two excitons per well. We show in this work that, as the SF thickness increases, the relative intensity of the two transitions changes. This comes from a change in the wave functions overlap between the electron trapped in the well and the holes trapped neighbouring parts of the 4H-SiC matrix.
Growth of Undoped (Vanadium-Free) Semi-Insulating 6H-SiC Single Crystals
Authors: Anderson Thomas , Barrett Donovan L. , Chen J. , Emorhokpor Ejiro , Gupta A. , Hopkins R.H. , Souzis Andrew E. , Tanner C.D. , Yoganathan Murugesu , Zwieback Ilya
Published: March 2009

II-VI has developed an Advanced PVT (APVT) process for the growth of
nominally undoped (vanadium-free) semi-insulating 2” and 3” diameter 6H-SiC crystals with room temperature resistivity up to 1010 W·cm. The process utilizes high-purity SiC source and employs special measures aimed at the reduction of the impurity background. The APVT-grown material demonstrates concentrations of B and N reduced to about 2·1015cm-3. Wafer resistivity has been studied and correlated with Schottky barrier capacitance, yielding the density of deep compensating centers in 6H-SiC in the low 1015 cm-3 range for both ntype
and p-type material. The nearly equal density of deep donors and deep acceptors
ndicates that the centers responsible for the intrinsic compensation can be amphoteric. TheEPR density of spins from free carbon vacancies is about 1014 cm-3. It is also hypothesized that impurity-vacancy complexes can be present in the undoped material and participate in compensation.
Direct Experimental Comparison of the Effects of Electron Irradiation on the Charge Carrier Removal Rate in n-Type Silicon and Silicon Carbide
Authors: Kozlovski Vitalii V. , Bogdanova Elena V. , Emtsev Valentin V. , Emtsev Konstantin V. , Lebedev Alexander A. , Lomasov V.N.
Published: March 2009

A comparison study of radiation damage in n-type silicon grown by the floating zone
technique and n-type silicon carbide grown by the sublimation epitaxy technique was carried out for the first time under the same irradiation conditions. This comparison is drawn for an energy region of fast electrons at ≈ 1 MeV where Frenkel pairs as primary defects, i e the self-interstials bound to their parent vacant sites at a distance of a few lattice spacings, are produced most effectively. The removal rates of charge carriers in n-Si and n-SiC (4H and 6H) were found to be about 0.23 cm-1 and 0.015 cm-1, respectively. The possible reasons of the observed difference are briefly discussed.
Improved Resolution of Epitaxial Thin Film Doping Using FTIR Reflectance Spectroscopy
Authors: Mazzola Michael S. , Sunkari Swapna G. , Mazzola Janice , Das Hrishikesh , Melnychuck Galyna , Koshka Yaroslav , Wyatt Jeffery L. , Zhang Jie
Published: March 2009

Room temperature Fourier Transform Infrared Reflection Spectroscopy (FTIR) was used to investigate the thickness and Free Carrier Concentration (FCC) of
heavily and lightly doped 4H and 6H-SiC epitaxial films. Multiple epitaxial layer stacks
typical of lateral devices such as the MESFET were grown on 6H-SiC semi-insulating substrates. The estimation of thickness and FCC of the n-channel epi layer is improved by studying the Longitudinal Optical Phonon Plasmon Coupled Modes (LPP). A modelbased analysis of the experimental reflectance spectra from these samples is performed using a dielectric function that accounts for the phonon-photon coupling and plasmonphoton coupling. The value of the LPP+ mode frequency estimated from the reflectance spectrum in the range 600-1200 cm-1 is observed to increase in direct correlation with the electron free-carrier concentration.
Effects of Epitaxial Layer Growth Parameters on the Defect Density and on the Electrical Characteristics of Schottky Diodes
Authors: La Via Francesco , Roccaforte Fabrizio , Di Franco Salvatore , Ruggiero Alfonso , Neri L. , Reitano Ricardo , Calcagno Lucia , Foti Gaetano , Mauceri Marco , Leone Stefano , Pistone Giuseppe , Abbondanza Giuseppe , Valente Gian Luca , Crippa Danilo
Published: March 2009

The effects of the Si/H2 ratio on the growth of the epitaxial layer and on the epitaxial
defects was studied in detail. A large increase of the growth rate has been observed with the increase of the silicon flux in the CVD reactor. Close to a Si/H2 ratio of 0.05 % silicon nucleation in the gas phase occurs producing a great amount of silicon particles that precipitate on the wafers. The epitaxial layers grown with a Si/H2 ratio of 0.03% show a low defect density and a low leakage current of the Schottky diodes realized on these wafers. For these diodes the DLTS spectra show thepresence of several peaks at 0.14, 0.75, 1.36 and 1.43 eV. For epitaxial layers grown with higher values of the Si/H2 ratio and then with an higher growth rate, the leakage current of the Schottky diodes increases considerably.
Infrared Gratings Based on SiC/Si-Heterostructures
Authors: Rockstuhl Carsten , Herzig H.P. , Förster Christian , Leycuras André , Ambacher Oliver , Pezoldt Joerg
Published: March 2009

The fabrication process and the spectral properties of gratings for the infrared wavelength region on the basis of 3C-SiC layers grown by CVD on (100) oriented Si substrates are demonstrated. The formed 3C-SiC gratings on Si support two phonon polaritons as a function of the geometrical properties excited between 10.3 and 11.4 µm. They appear as a dip in the transmission spectrum. A third minimum in the transmission spectrum is caused by the substrate – grating interaction. The obtained resonances were polarization sensitive, i.e. they appeared only under TMpolarized illumination.
Photoluminescence Study of In-Situ Rare Earth Doped PVT-Grown SiC Single Crystals
Authors: Schmitt Holger , Müller Ralf , Maier Manfred , Winnacker Albrecht , Wellmann Peter J.
Published: March 2009

Several SiC bulk crystals were grown with erbium and ytterbium as doping materials.
Erbium contents determined by secondary ion mass spectroscopy (SIMS) ranged from 1.2 · 1014 cm-3 to 1.04 · 1015 cm-3, while ytterbium contents were below SIMS detection limit. Photoluminescence (PL) investigations of the characteristic 4f-4f-transition lines revealed a reduced luminescence yield in highly nitrogen and aluminum co-doped samples. Also, samples without intentional
co-doping grown on the C-face showed less luminescence intensity than those grown on the Si-face. A stabilizing effect of erbium doping on the 4H polytype was observed.
4H-SiC Epitaxial Growth on SiC Substrates with Various Off-Angles
Authors: Saitoh Hiroaki , Kimoto Tsunenobu
Published: March 2009

Chemical vapor deposition of 4H-SiC on (0001) substrates with various off-angles from 1o to 45o has been investigated. On large-off-angled (15o-45o) substrates, very smooth surface morphology is obtained in the wide range of C/Si ratio. The micropipe dissociation during epitaxial growth is observed on 4o-45o off-angled substrates with a low C/Si ratio. The incorporation of nitrogen was dramatically suppressed by increasing C/Si ratio irrespective of substrate’s off-angle.
Investigation of Basal Plane Dislocations in the 4H-SiC Epilayers Grown on {0001} Substrates
Authors: Tsuchida Hidekazu , Miyanagi Toshiyuki , Kamata Isaho , Nakamura Tomonori , Izumi Kunikaza , Nakayama Koji , Ishii R. , Asano Katsunori , Sugawara Yoshitaka
Published: March 2009

In this paper, we investigated the density of basal plane dislocations (BPDs) in 4H-SiC epilayers grown on (0001) and (000-1). Re-polishing of the substrate surface, in-situ H2 etching and off-cut angle were found to influence the propagation of BPDs into the epilayers. The epitaxial growth on (000-1) substrates yields a relatively low density of BPDs compared to growth on (0001). The electrical characteristics of pn diodes were also investigated, and the suppressed forward
degradation and high-voltage blocking performance were obtained in the use of the (000-1) epilayers.
Thermal and Leaching Behaviors of EAF Dust-Clay Systems
Authors: Kim Jung Hwan , Lee Ki Gang , Kim Yoo Taek , Kang S.K.
Published: March 2009

Thermal behaviors of EAF dust, water-washed EAF dust, and EAF dust/heavy clay
mixtures with wet mixing process were characterized by TG/ DTA analysis. The ionic concentrations of some metal ions and anions in the supernatant from water-washing process were evaluated by ICP and IC analysis. Weight loss of water-washed EAF dust above the temperature range of 1000°C was significantly decreased because of the washing effect of chloride and sulfate compounds. The
variation of volatile ZnO and PbO contents were not detected in 20wt% D dust-80wt% clay sample. The wet mixing process not only enhanced the homogeneous mixing of EAF dust and clay particles, but also reduced the volatilization of heavy metals(Zn, Pb, etc.) at the high temperature range.
Life Cycle Improvement Assessment of Al and Mg Diecasting Processes
Authors: Kim Shae K. , Kim Young Jig
Published: March 2009

To comply with the growing demand for life cycle environmental effect, life cycle
assessment (LCA) was carried out for producing A356 aluminum alloy and AZ91D magnesium alloy diecastings. The main emphasis was placed on the improvement assessment for aluminum and magnesium diecasting processes and the comparison between the two competitive processes. The process evaluated was based on yields of finished parts relative to the metal input. This is important
both from the environmental point of view and the commercial point of view because the environmental data are sensitive to the design of cast parts and the efficiency of the diecasting operation.
Effects of Post-Weld Heat Treatment on Optimum Cathodic Protection Potential of High-Strength Steel in Marine Environment Conditions
Authors: Kim Seong Jong , Jang Seok Ki , Kim Jeong Il
Published: March 2009

The electrochemical and mechanical properties of welded high-strength steel
were investigated using the slow strain rate test method with a constant applied cathodic potential. No correlations were found with the maximum tensile strength, yield strength, stress at failure, or hydrogen embrittlement. However, the elongation, time-to-fracture, and strain-to-failure ratio decreased as the potential became more negative. These parameters were greatest when the potential was -770mV, regardless of the post-weld heat treatment conditions. The elongation and time-to-fracture increased with PWHT.
Characterization of Long-Term Oxidized Nickel Aluminide Coating by Photoluminescence Spectroscopy
Authors: Byeon Jai Won , Mu N. , Liu J. , Sohn Yong Ho
Published: March 2009

Microstructures and residual stress of long-term oxidized nickel aluminide coating on
superalloy were evaluated by photostimulated luminescence spectroscopy (PSLS). CMSX-4 superalloy coupons coated with single phase b-NiAl were oxidized in air at 788, 871, 954 and 1010°C for up to 10000 hours. The photoluminescence technique was applied for the analysis of the
phase constituents and the residual stress of the thermally grown oxide (TGO) scale formed on the^coating, together with transmission electron microscopy. According to the PSLS analysis, TGO consisted of both stable a-Al2O3 and metastable Al2O3 phases in specimens oxidized at 788°C and 871°C. At higher temperatures, the TGO scale primarily consisted of equilibrium a-Al2O3. The
compressive residual stress within TGO increased up to about 3GPa with increasing oxidation temperature and time until local spallation, after which a decrease as well as large standard deviation of residual stress was observed owing to the stress-relief associated with TGO scale spallation.
Characterization of Isothermally Oxidized ZrO2-8wt.%Y2O3 Thermal Barrier Coatings by Electrochemical Impedance Spectroscopy
Authors: Byeon Jai Won , Jayaraj B. , Sohn Yong Ho
Published: March 2009

Electrochemical impedance spectroscopy was employed to examine ZrO2-8wt.%Y2O3 (yttria stabilized zirconia, YSZ) thermal barrier coating (TBC) as a function of isothermal exposure time at 1121°C. Electrochemical impedance response (resistance and capacitance of YSZ and thermally grown oxide (TGO)) of TBC specimens was analyzed with an alternative current
equivalent circuit based on the multi-layered micro-constituents of TBC, and the impedance response was correlated with microstructural changes attributed to isothermal oxidation. The resistance of YSZ was observed to increase initially and then decrease with thermal exposure. The initial increase was related to the high temperature sintering of YSZ, and the subsequent decrease was discussed in terms of microcrack initiation and electrolyte penetration. The TGO thickness was
linearly correlated to the capacitance of TGO.
Transmission Electron Microscopy of Isothermally Oxidized EB-PVD Thermal Barrier Coating on (Ni,Pt)Al Bondcoat
Authors: Byeon Jai Won , Laxman S. , Sohn Yong Ho
Published: March 2009

The growth and microstructure of the thermally grown oxide (TGO) underneath the electron beam physical vapor deposited (EB-PVD) yttria stabilized zirconia (YSZ) topcoat were examined after short-term isothermal oxidation (1100 °C, up to 50 hours) for the as-coated and gritblasted (Ni,Pt)Al bondcoats. Microstructural analysis was carried out by a high resolution scanning
transmission electron microscope equipped with bright/dark field imaging, high angle annular dark field imaging, and nano-spot energy dispersive spectroscopy. Presence of mixed oxide zone (MOZ) and a continuous Al2O3 oxide zone (COZ) was observed on the thermal barrier coating (TBC) with the as-coated (Ni,Pt)Al bondcoat. However, on the TBC with grit-blasted bondcoat, only the continuous-columnar Al2O3 scale was observed. For the as-coated type bondcoat, numerous voids were observed near the interface between MOZ and COZ after isothermal oxidation. On the other hand, COZ showed parabolic growth without any formation of voids for the grit-blasted specimens.
Surface Coating of Reactive Layer with Inner Nano-Pores on Lantanium Gallium Based Oxide
Authors: Lee Kee Sung , Shin Tae Ho , Lee Shi Woo , Woo Sang Kuk , Yang Jae Kyo , Choa Yong Ho
Published: March 2009

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.
Oxidation of SiOC Composite Having Dispersoids of Mo4.8Si3C0.6 and MoSi2
Authors: Lee Dong Bok , Woo Seung Wan
Published: March 2009

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.
Corrosion of Ni-W Coatings in SO2 Atmosphere between 500 and 700 °C
Authors: Lee Dong Bok , Ko J.H.
Published: March 2009

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.
A Rainwater Harvesting Technology by Roof Coating Using TiO2
Authors: Kim Ree Ho , Lee Sang Ho , Lee Jung Hun , Kim Young Min
Published: March 2009

Rainwater utilization has great potentials for recovering hydrological cycles, for buffering extreme run-off situations in the watercourses, and for reducing the costs for water supply in urban area. However, little information is available on the water qualities and runoff properties of collected rainwater, which is critical for efficient design and maintenance strategies of rainwater harvesting facilities. In this study, characteristics of rainwater collected in a rainwater harvesting system were
examined in terms of pollutant concentrations. Based on these results, TiO2 photocatalysts were applied on the roof surface as a novel coating material to improve the quality of collected rainwater. The analysis of rainwater samples shows that the contamination by turbidity, conductivity, and color occurs during the catchment process, which may result in troubles for further use. The roof coating
technique developed in this study appeared to be effective in increasing the wash-off of pollutants and improving the water quality in roof runoff because of its increased hydrophililicy as well as photocatalytic reactivity. Further research is required on trace pollutants such as endocrine disruptors to estimate and minimize health risk in rainwater harvesting.
Structure and Photoluminescence Properties of ZnO:Al/Porous Silicon Thin Films
Authors: Park Hyun Ah , Prabakar K. , Yoo Yeon Chul , Hwang Sun Keun , Lee Chong Mu
Published: March 2009

Al doped ZnO (AZO) films were deposited on porous silicon (PS) substrates by a reactive rf-cosputtering process from two targets of ZnO and Al. The effect of ZnO target rf-sputtering power on the structural and photoluminescence (PL) properties of AZO/PS heterojunctions were studied. Strong monochromatic blue emission located at 2.78 eV was observed for the AZO films
deposited at 150 W. Freshly prepared PS showed an emission band in the green spectral region. We show that deposition of AZO on PS does not degrade the skeleton of the PS and enhance the PL intensity. The PL band shifted to the high energy for AZO films deposited on PS and the intensity became stable.
Sintering Effects of ZnO Nanopowders Synthesized by Solution–Combustion Method
Authors: Park Sung , Lee Jae Chun , Seo Jung Uk , Lee Ju Hyeon
Published: March 2009

ZnO nanopowders with an average grain size of 30nm were prepared by a solution
combustion method with various sintering temperatures (100-1000o C). The optical properties of the ZnO nanopowders were investigated in the temperature range of 14-150K in air. Based on the results of XRD, Photoluminescence, and excitation spectra, the ZnO powders showed wurtzite single phase with UV-blue light emitting. Deep level defects such as oxygen vacancies and Zn interstitials were
not observed from the ZnO powders sintered up to 700 o C. However, these defects were observed as the sintering temperature was increased up to 900 o C. This seems to be due to the generation of oxygen vacancies and zinc interstitials. Furthermore, the blue light intensity was doubled when the synthesized ZnO powders were sintered at 700 o C. This might be very useful for high efficiency
photocatalysts and the blue light emitting phosphors of displays such as field emission displays and plasma display panels.
Probabilistic Assessment for Failure Probability of Pipe Lines by Extreme Value Distribution
Authors: Lee S.H. , Choe Byung Hak , Kim Young Pyo , Kim Woo Sik , Ko Y.T. , Lee Je Hyun , Paik Ung Yu
Published: March 2009

This study presents a probabilistic methodology for estimation of the remaining life of
pressurized pipelines containing active corrosion defects. A reliability assessment was carried out using extreme value distribution of the corroded defects instead of the already published failure pressure model like NG18 or ASME B31G. The failure probability of pipelines depends on the number of corroded defects, and it was calculated directly as the area exceeded a defined LV(Limited Value of corrosion depth). The remaining life of pressurized pipelines can also be estimated by the PDF of extreme value distribution as calculating the exceeded area with a defined
failure probability.
Optimum Shear Height for Evaluation of Pb-Free Solder Ball Shear Strength
Authors: Kim Jong Woong , Park Sun Kyu , Jung Seung Boo
Published: March 2009

Ball shear test was investigated in terms of the effects of important test parameter, i.e., shear height, with an experimental and non-linear finite element analysis for evaluating the solder joint integrity of area array packages. The substrate was a common SMD type with solder bond pad openings of 460 ㎛ in diameter. It was observed that increasing the shear height, at a fixed shear speed, has the effect of decreasing the shear force. The high shear height could cause some bad effects on the test results such as unexpected high standard deviation values or shear tip sliding from the solder ball surface. The low shear height conditions were favorable for screening the type of brittle interfacial fractures or the degraded layers in the interfaces.
An Approach to Legal and Technical Norms to Manage Hazardous Materials and Wastes in Latin America
Authors: Grüber Nélida , Gerdler Sibrahim , Rodriguez Josefina , Lira-Olivares Joaquín
Published: March 2009

The Basel Convention (1989) and Rio Summit (1992) were two major instances to tackle with the main issues on Hazardous Waste. The first one is the mechanism to control the illegal traffic of hazardous waste, and to promote an Environmental Sound Management for the overall waste cycle. On the other hand, Rio Summit launched a renewed interest on regulatory environmental instruments for pollution prevention, control and mitigation of environmental damages generated by industrial activities. Among them, one of the major challenges is related to the hazardous waste management. In Latin America, as well as in the rest of the world, the theme has been considered mainly through the environmental regulations, pushing the enterprises to look for different solutions to face the high costs involved in the production processes. In this paper, a comparative assessment was made of the hazardous waste management in four Latin American oil-producing countries. The specific environmental regulations adopted are reviewed, to show the status of present environmental policies and legal measures to promote reuse, recycle, recovering and reduction of hazardous materials and wastes. Coincidential provisions are reported, as well as the differences in the legal approach, which is a clear signal of the efforts made in environmental regulations, trying to control and prevent the pollution generated by industries.
Ferroelectric Properties of Lead-Free (Bi,La)4Ti3O12 Thin Film Deposited on MTP Cell Structure for High Density FeRAM Device
Authors: Cho K.W. , Kim N.K. , Oh S.H. , Choi E.S. , Sun H.J. , Yeom S.J. , Lee K.N. , Lee Seoung Soo , Hong Suk Kyoung , Choi S.K. , Hong Tae Whan , Kim Il Ho , Lee J.I. , Ur Soon Chul , Lee Young Geun , Ryu Sung Lim , Kweon Soon Young
Published: March 2009

Ferroelectric properties of Pb-free (Bi,La)4Ti3O12 (BLT) films were optimized on a newly developed MTP cell structure. BLT films were coated on Pt/IrOx/Ir bottom electrode using sol-gel solutions. The composition of the optimized BLT film was about Bi3.25La0.75Ti3.0O12, which was analyzed by ICP-MS method. The switchable polarization obtained in a 100nm-thick BLT film was about 20 uC/cm2 at the 3 V applied voltage, and the optimized BLT film showed little fatigue loss
about 10% up to 1×1011 cycles. The imprint properties of the BLT film were also characterized at 25 °C and 90 °C operating temperature after 125 °C data storage. Regardless of operating temperature, switchable polarization of BLT had a sufficiently large margin for device operation up to 10 years.
Interfacial Reaction and Shear Strength of Pb-Free Sn-3.5Ag/Ni BGA Solder Joints during Reflow
Authors: Yoon Jeong Won , Kim Sang Won , Jung Seung Boo
Published: March 2009

The interfacial reaction between eutectic Sn-3.5wt.%Ag solder and Ni substrate resulted in the formation of Ni3Sn4 intermetallic compound (IMC) layer. After formation of the Ni3Sn4 IMC, its grain coarsened and faceted continuously in a prolonged reflow reaction. The thickness of the IMC layer increased with reflow time. On the other hand, the brittleness of the joints increased with increasing reflow time, and the fracture occurred at the interface. The deterioration of the shear strength was found to be predominantly caused by the formation of the thick Ni3Sn4 IMC layer.
Effect of Ternary Alloying Elements on Microstructure and Mechanical Property of Nb-Si Based Refractory Intermetallic Alloy
Authors: Kim Won Yong , Kim Han Sol , Kim Shae K. , Ra Tae Yeub , Kim Mok Soon
Published: March 2009

Microstructure and mechanical property at room temperature and at 1773 K of Nb-Si based refractory intermetallic alloys were investigated in terms of compression and fracture toughness test. Mo and V were chosen as ternary alloying elements because of their high melting points, atomic sizes smaller than Nb. Both ternary alloying elements were found to have a significant role in modifying
the microstructure from dispersed structure to eutectic-like structure in Nb solid solution/Nb5Si3 intermetallic composites. The 0.2% offset yield strength at room temperature increased with increasing content of ternary elements in Nb solid solution and volume fraction of Nb5Si3. At 1773 K, Mo addition has a positive role in increasing the yield strength. On the other hand, V addition has a role in decreasing the yield strength. The fracture toughness of ternary alloys was superior to binary
alloys. Details will be discussed in correlation with ternary alloying, volume fraction of constituent phase, and the microstructure.
Characteristic of the Residual Strength Rate by Variation of Impact Velocities for the Leaf Spring in Ankle Foot Orthosis
Authors: Kim Cheol Woong , Oh Dong Joon
Published: March 2009

Ankle Foot Orthosis (A.F.O) should endure the uncountable repeating impact and fatigue loadings owing to the gait characteristics. This study investigates the impact deflection and relationship between the absorbed energy and the residual strength rate using the glass/epoxy and the aramid/epoxy for the leaf spring in A.F.O. In conclusion, an equation was suggested to evaluate the absorbed energy and the residual strength rate by the different impact velocities. When the
glass/epoxy and the aramid/epoxy was selected for the leaf spring in A.F.O, it was reasonable to use the glass/epoxy of the cross-ply for the parts subject to the large impact and the aramid/epoxy of the woven type for the parts to require the high elastic energy such as the large deformation.
The Preparation of Rutile TiO2 Nanopowders, Phase Transformation and Their Photocatalysed Properties
Authors: Sun Jing , Gao Lian
Published: March 2009

Rutile TiO2 nanoparticles have been synthesized by direct hydrolysis method using TiCl3, TiCl4 as starting materials, yielding two different morphologies. The hydrolysis of TiCl3 resulted in needlelike rutile titania with the specific surface area of 74.5m2/g, while round particles about 200~400 nm with small acicular at edge, with specific area as high as 175m2/g, were obtained using TiCl4 as starting materials. The precipitates from TiCl4 hydrolysis could be changed into anatase phase without filtering and separation by varying pH of the system. The phenomenon was explained from the viewpoint of structure. The photocatalysed properties of rutile powders were compared with those of anatase of the same specific surface area. Rutile powders with initial crystalline size of 7 nm were found to have higher photocatalysed activity in the phenol degradation reaction than that which
anatase has. The high activity of the as prepared lab-made rutile was attributed to the abundance of hydroxy groups in powders, which was proved by TG data, making the degradation reaction have more active sites. The agglomeration form of the rutile powder makes it easy for separation and reuse.
The Solidification Microstructure and Carbide Formation Behaviors in the Cobalt-Based Superalloy ECY768
Authors: Lee J.S. , Lee Je Hyun , Choi Baig Gyu , Jo Chang Yong , Paik Ung Yu , Gang S.G.
Published: March 2009

Co-base superalloys have been applied in the stationary compoents of gas turbine owing to their excellent high temperaure properties. The stationary Co-base alloy components are generally manufactured by casting. Solidification behavior of the alloy is an important factor in the selection of casting parameters. In the present study, solidification microstructure and carbide formation behaviors were studied by directional solidification. Directional solidification experiments were carried out at the solidification rates of 0.5 ~ 150µm/s with the Co-base superalloy ECY768. Between
the dendrites just below the final freezing temperature, MC carbide and M23C6 carbide were found. It was identified that the script or blocky carbides were Ta or W-rich MC carbide, and the lamellar carbides were Cr-rich M23C6 eutectic carbides. The solid/liquid interface morphology clearly showed that freezing of the Cr-rich eutectic carbide occurred just after the script type MC carbide.
Utilization of Waste Plastics as a Fuel in the Fluidized Bed Calciner for Cement Kiln Process
Authors: Kwon Woo Teck , Bae Seong Youl
Published: March 2009

The reutilization of waste plastics as a fuel in the cement kiln precalciner process was investigated. For uniform feeding into the fluidized bed calciner, waste plastics were prepared to form of pellet type by shredding, melting, pressing, cutting and screening. We examine the property of combustion for different pellet size using the Computational Fluid Dynamic analysis program to minimize a risk and to optimize condition of an actual proof plant. Based on the results from the computational fluid dynamic analysis, the waste plastic for the industrial scale experiment were
used as 20mm, 50mm and 100mm in size. The experimental result of an actual proof plant showed comparatively good correlation with the computational fluid dynamic analysis.
Synthesis and Characterization of Clay Brick Using Coal Wastes
Authors: Yoo Jung Whan , Jung Jin Ho , Kim Hyung Tae
Published: March 2009

Utilizing coal waste byproducts formed during mine development or use is
important in solving environmental problems and recycling of waste materials. In this study, specimens prepared by mixing coal waste of 10, 20, 30, 40, and 50 % into clay brick have been investigated in terms of water absorption and compressive strength according to coal waste amounts and calcination temperature. As coal waste content increased water absorption increased and compressive strength decreased. When up to 30% coal waste was mixed into clay at 1300 oC, specimens satisfied 1st-class brick of Korea Standard requirements (water absorption 10%>, compressive strength 210 kgf/cm2<).
Die-Casting Capabilities of Heat Resistant Mg-Al-Ca Alloys
Authors: Kim Jeong Min , Park Bong Koo , Jun Joong Hwan , Kim Ki Tae , Jung Woon Jae
Published: March 2009

Various amounts of Ca were added to AZ91D magnesium alloy, and their effects on the die-casting abilities were investigated. It was observed that fluidity as die filling ability tends to decrease by Ca additions except for about 2%Ca. This reduction of fluidity by Ca was more significant at high superheats probably due to the high affinity between Ca and oxygen. Contrary to expectation, hot cracking resistance was found to increase by Ca additions. High Ca alloys showed some die-sticking tendency. However, the tendency was not observed below 2%Ca.
Formation of AlN in the N Added 18Cr Ferritic Stainless Steels
Authors: Kim H.C. , Lee Je Hyun , Heon Y.G. , Jo Chang Yong , Kim Jae Won , Kim Sung Gab
Published: March 2009

Al addition is known to enhance corrosion resistance and high temperature properties in ferritic and austenitic stainless steels. Due to the addition of Al, formation and characteristic of nitride were studied in Al added 18Cr stainless steels. The phase diagram and segregation were estimated with addition of Al in 18Cr stainless steels by the Thermo-calc program. Formation
behavior of the AlN phase was studied by observing the solid/liquid interface through directional solidification and the phase characterization was performed by XRD in the extracted precipitates from the matrix. It was confirmed that the AlN phase formed at the cell boundary from the liquid in 3 and 5 wt.% Al added 18Cr stainless steels.
Synthesis and Characterization of Nanosized ZnxMn1-xFe2O4 Powders by Glycothermal Process
Authors: Bae Dong Sik , Kim Eun Jung , Park Sang Whan , Han Kyong Sop
Published: March 2009

Nanosized ZnxMn1-xFe2O4 powders were prepared in ethylene glycol solution
under mild temperature and pressure conditions by precipitation from metal nitrates.
The average size and distribution of the synthesized ZnxMn1-xFe2O4 powders were 10- 20 ㎚ and narrow, respectively. The magnetic property of the synthesized ZnxMn1- xFe2O4 powder was of superparamagnetic character at room temperature.
Substrate Bias Effects on the Structure of the Film by a Hybrid PVD and Plasma-Based Ion Implantation Process
Authors: Chun S.Y. , Lee Sang Jin
Published: March 2009

This paper descirbes the characteristics of gold films prepared by a hybrid plasma based an ion implantation/deposition (PBIID) system. The surface morphology and structure of the film were affected by the voltage applied to the target. With increasing negative voltage, the surface became thinner with a lesser number of nuclei. The grain structure varied from the continuous film at 0 kV to the channel at -1 kV, and further to the islands (mounds) at -5 kV. The ions in the sheath are believed to play an important role in the deposition of the film.
Development of Strip Casting Process for Electrolytic Tough Pitch Copper
Authors: Kim Shae K. , Cho Hoon , Lee Jin Kyu , Kim Won Yong , Jo Hyung Ho
Published: March 2009

The aim of this study is to report results of initial trials involving the strip casting process for ETPC (Electrolytic Tough Pitch Copper) and to investigate the effect of process parameters on the chemistry, microstructure evolution and mechanical properties of ETPC. A vertical twin roll strip caster used in this research was designed for manufacturing high-purity and/or reactive metal strips with a system for controlled atmosphere ranging from 103 to 10-3torr. It is expected that oxygen
content can be reduced as low as 0.001wt% in as-cast strip.
Compressive Properties of Open Cell Aluminum Foams
Authors: Hur Bo Young , Park Bu Keoun , Kim Sang Youl , Bae Hoon
Published: March 2009

The uniaxial compressive test results of several aluminum foams are compared with
aluminum alloy and ppi (pore per inch) of open cell foam. The compressive stress-strain curve of aluminum alloy foams exhibits universal three deformation regions: an initial linear elastic response, and then extended plateau region with a nearly constant flow stress, a final densification as collapsed cells are compacted together. The lower the foam densities are, the longer the plateau region is, but lower densities also imply lower yield stress.
Effect of Operating Temperature on Characteristics of Single-Walled Carbon Nanotubes Gas Sensor
Authors: Nguyen Hong Quang , Van Trinh Mai , Huh Jeung Soo
Published: March 2009

The effect of operating temperature on characteristics of single-walled carbon nanotubes (SWNT) based gas sensor was investigated. SWNT-based sensor was fabricated from SWNT powder (Iljin Nanotech, Korea) by screen-printing method. SWNT powder (30 mg, AP grade) was dispersed into 0.78 gram a-terpineol (Aldrich) by ultrasonic vibration for 1 hour then stirred
manually for 1 hour to increase adhesion. From this condensed solution, a thick film of SWNT was printed onto alumina substrates. The film then was sintered at 300oC for 2 hours to remove residual impurities. Upon exposure to some gases such as nitrogen, ammonia or nitric oxide, resistance of the sensor dramatically changes due to gas adsorption. In our experiments, SWNT-based sensor was employed to detect NH3 gas in N2 ambience. After saturated of N2, the sensor exposes to NH3 with various concentrations (from 5 ppm to 100 ppm, diluted by N2 as carrier gas). This sensor exhibits a fast response, high sensitivity but slow recovery at room temperature. By heating at high temperature and increasing the flow-rate of carrier gas, NH3 gas desorbs easily and recovery of the sensor improved. The heating also influenced the characteristics of sensors such as response and
reproducibility. Other special changes in electric property of SWNT-based sensor caused by heating are also discussed.
Thermal Stability and Mechanical Properties of Hydrogenated Zr-Ni-Nb-Co Amorphous Alloy
Authors: Jayalakshmi S. , Fleury Eric , Kim Yu Chan , Kim Ki Bae
Published: March 2009

Zr50Ni27Nb18Co5 amorphous ribbons were hydrogenated using an electrochemical method. Under a current density of 30 mA/cm2, the thermal stability of the amorphous phase was found to increase with the charging time. Hardness and fracture strength were found to be independent of charging time, indicating that the Zr-Ni-Nb-Co amorphous alloys preserved its mechanical integrity.
Microwave Dielectric Properties of LTCC Materials Consisting of BaO-TiO2-SiO2-Al2O3 Glass - BaNd2Ti5O14 Ceramic Composites
Authors: Kim Yu Jin , Hwang Seong Jin , Kim Hyung Sun
Published: March 2009

The desirable characteristics of the microwave materials include excellent dielectric
constant εr, low dielectric loss (high quality factor, Q*f0 value), and small temperature coefficient (~0ppm/°C) of resonant frequency (Tf). The advantages of using a glass-ceramic include shape stability during the sintering stage, improved dielectric properties, mechanical strength, and controlled thermal expansivity. In the present study, glass-ceramic compositions consisting of a glass
system (BaO-TiO2-SiO2-Al2O3) and a ceramic filer (BaNd2Ti5O14) were prepared. The glass and glass-ceramic compositions were evaluated for sintering behavior such as shrinkage, densities, thermal properties, and microstructures. In addition, the microwave dielectric properties (≈ 15~20 for εr, > 6000 GHz for Q*f0) were determined by a network analyzer at 6-8 GHz. These results suggest
that the compositions can be a candidate for LTCC dielectric materials.
Synthesis of Calcium Carbonate Particles Modified by Coating with Nickel Precursor
Authors: Kim Kyung Nam , Kim Yong Do
Published: March 2009

CaCO3 powders were prepared by the homogeneous precipitation method using CaCl2, urea as the starting materials. Uniform CaCO3(calcite, aragonite, vaterite) powders were obtained by various conditions. The surfaces of CaCO3 powders were modified by coating them with a lithium precursor using two different precipitation techniques: homogeneous decomposition of precipitating
agents(urea, NaHCO3, NH4HCO3) and forced hydrolysis in pure water. Selecting the Ni(NO3)26H2O and urea(or NaHCO3, NH4HCO3) as Ni-source and precipitating agent respectively, the NiO could be uniformly coated on the CaCO3 powder in the aqueous system. The coating NiO layer dominated the
surface properties of the coated lime powders. Calcination of these nickel hydroxide crystals in air at 500°C transformed them into NiO.
Effect of Solvent Extraction on Removal of Heavy Metal Ions Using Lignocellulosic Fiber
Authors: Lee Beom Goo , Lee Hyun Jong , Shin Dae Yong
Published: March 2009

Kenaf bast, which is lignocellulosic fiber and environment friendly natural material, was tested for its ability to remove copper, nickel and zinc ions from aqueous solutions. The fiber was analyzed for xylose, lignin content, weight loss and dry volume, and extracted with diethyl ether, ethyl alcohol, hot water, or 1% sodium hydroxide to change physical and chemical characteristics of keanf bast. Diethyl ether and ethyl alcohol are organic solvents, which extract only extractives in the cell wall. The weight losses are less than 4.1%, the dry volumes increase up to 0.68 cm3/g, and the changes of lignin content are less than 0.6%. The differences of the heavy metal ions removal capacities are less than 0.05 mg/g, compared to those of control. Hot water and 1% sodium hydroxide remove cell wall components as well as extractives in the cell wall. In addition, during the extraction process the cell wall is swollen by the delamination of cell wall layers, xylose and lignin are exposed.
The weight losses increases up to 24.0%, the dry volumes increase up to 1.20 cm3/g, and the changes of lignin content are less than 0.6%. The difference of the heavy metal ions removal capacities of kenaf bast increase up to 0.14 mg/g, and are much higher than those of diethyl ether and ethyl alcohol. The above results show that to increase the heavy metal ions removal capacities, the extraction
chemicals may swell the cell wall more than water does and remove the cell wall components as well as extractives to change cell wall chemistry and architecture.
Hydriding/Dehydriding Behavior of Mg-Ni Systems
Authors: Hong Tae Whan , Kim Il Ho , Ur Soon Chul , Lee Young Geun , Kim Young Jun
Published: March 2009

To fabricate high efficiency, light-weight hydrogen storage materials in an economical
way, a hydrogen induced mechanical alloying (HIMA) and an advanced melting/casting process were employed in a Mg-Ni hydride alloy system. The hydrogenation properties of the synthesized or/and cast specimen were evaluated with an automatic PCI (pressure-composition-isotherm) apparatus and TGA (thermo-gravimetric analysis). To produce Mg2NiHx intermetallics in an
economical way, especially, Mg and Ni chips were mechanically alloyed under 2 MPa of hydrogen atmosphere by planetary ball milling. Adopting 66:1 BCR (ball to chips mass ratio) for HIMA process, fully hydrogenated alloys were obtained after 96 hrs of milling, resulting intotal hydrogen content of 2.25 mass%. The dehydriding temperature was found to be 453∼493 K. The composite phase obtained after 96 hrs of HIMA appeared to be composed of nanocrystalline and amorphous
phases, of which structure was believed to enhance hydriding and dehydriding kinetics. The condition of BCR seemed to affect strongly the synthesis of the Mg2NiHx. In addition, the minimized Ni content specimens in Mg-Ni hydrides were successfully manufactured by Rotation- Cylinder method (RCM) without any heat treatments.
Electrical and Electrochemical Properties of Poly(P-Phenylene)-Based Carbon for Lithium Rechargeable Batteries
Authors: Kim Ju-Seung , Kim Jong Uk , Kong Mingzhe , Gu Hal Bon
Published: March 2009

Magnesium and Magnesium alloys have been studied as one of the good lightweight
hydrogen storage materials, but the materials have strong difficulties in the fabrication process of mass production until now. The Rotation-Cylinder Method (RCM) has been developed to fabricate magnesium-based composites with moderate rotation under normal atmosphere. In this study, the Mg-TiNi hydrogen storage composites materials were manufactured by RCM and evaluated their
hydrogenation properties by a Sieverts-type automatic pressure-composition-isotherm (PCI) apparatus at 523, 573 and 623K. The hydrogenation properties of Mg-TiNi composites depended on the behavior of TiNi reinforcements. The formation of Mg hydride, MgH2, on 4h milling samples of Mg-10mass% TiNi intermetallics hinted to the catalytic behavior of TiNi reinforcements. In addition,
the dehydriding profile at 573K revealed the two steps of plateau pressure, which were affected by the existence of multi hydride phases.
Thermoelectric Properties of Co1-xNbxSb3 Prepared by Induction Melting
Authors: Park J.B. , You S.-W. , Cho K.W. , Lee J.I. , Ur Soon Chul , Kim Il Ho
Published: March 2009

Induction melting was attempted to prepare the undoped and Nb-doped CoSb3 compounds, and their thermoelectric properties were investigated. Single phase d-CoSb3 was successfully obtained by induction melting and subsequent annealing at 400°C for 2 hours in vacuum. The positive signs of Seebeck coefficients for all the specimens revealed that Nb atoms acted as p-type dopants by substituting Co atoms. Electrical conductivity decreased and then increased withincreasing temperature, indicating mixed behaviors of metallic and semiconducting conductions. Electrical conductivity increased by Nb doping, and it was saturated at high temperature. Maximum value of the thermoelectric power factor was shifted to higher temperature with the increasing amount of Nb doping, mainly originated from the Seebeck coefficient variation.