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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Korean Journal of Materials Research
Journal Basic Information
Journal DOI :
The Materials Research Society of Korea
Editor in Chief :
Volume & Issues
Volume 4, Issue 8 - Dec 1994
Volume 4, Issue 7 - Oct 1994
Volume 4, Issue 6 - Sep 1994
Volume 4, Issue 5 - Aug 1994
Volume 4, Issue 4 - Jun 1994
Volume 4, Issue 3 - May 1994
Volume 4, Issue 2 - Apr 1994
Volume 4, Issue 1 - Feb 1994
Selecting the target year
Friction and Wear Properties of Fiber Reinforced Composite
Ju, Hyeok-Jong ; Choe, Don-Muk ; O, In-Seok ; Hong, Myeong-Ho ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 733~740
Oxidized-PAN fiber reinforced composite(OFRP), carbon fiber reinforced composite(CFRP), aramid fiber reinforced composite(AFRP), and glass fiber reinforced composite(GFRP) were fabricated with phenolic resin matrix by hot press molding. We tested the friction coefficient and wear rate varying with fiber weight fraction and observed the effect of fibers according to characteristics of individual reinforcement. When the amount of aramid fiber was 45wt%, average friction coefficient was maximum value of 0.353~0.383, where as, when the amount of pitch based carbon fiber was 45wt%, average friction coefficient was the lowest value of 0.164~0.190. The wear rate of AFRP and CFRP was low, but that of GFRP and OFRP increases drastically in the case of increasing of fiber weight fraction. Wear diagram of OFRP was unstable, but that of CFRP and AFRP was a bit stable. Through very unstable diagram of GFRP, we found that friction stability of GFRP was the lowest.
Joining of Lanthanum Chromite and Yttria Stabilized Zirconia in Sealing of Planar Solid Oxide Fuel Cell
Lee, You-Kee ; Park, Jong-Wan ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 741~749
The planar solid oxide fuel cell(SOFC) contains several ceramic materials depending on its structure and has rdfractory metal parts for manifolds, shrouds and current leads. Among ceramic materials for planar SOFC, joining of lanthanum chromite separator and yttria stabilized zirconia(YSZ) electoyte in planar SOFC stack to give strong gas tight seals is necessary for satisfactory operation and high performance. Nevertheless, for planar SOFC/sub s/, how to seal the cell stack and gas manifold remains as one of the unsolved problems. Therefore, in this study. we investigated the joining of sintered lanthanum chromite and YSZ pellets using unsintered lanthanum chromite green films as sealent. Scanning electron microscopy(SEM) and energy dispersive X-ray analysis(EDX) revealed that Ca in the sealing material diffused and dissolved into YSZ and sintered lanthanum chromite, and unsintered lanthanum chromite green films reacted with YSZ to from a new phase at the interface. Also, the densification of unsintered lanthanum chromite green films was inpeded by the Ca migration.
Crystallopraphic Growth Orientation of Polycrystalline HSG Silicon Film
Sin, Dong-Won ; Park, Chan-Ro ; Park, Chan-Gyeong ; Kim, Jong-Cheol ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 750~758
The purpose of present study is to find out the formation mechanism of hemi-spherical grained(HSG) polysilicon film. Silicon film was deposited using LPCVD. Polycrystalline silicon film was deposited at
contained crystalline HSG in the amorphous matrix phase. The crystalline HSG can be categorized into two grains : lower grains and upper grains. Lower grains are located at interface between silicon dioxide and silicon film, and upper grains are located at surface. The growth orientations of HSG were identified as (311) or (111) directions for lower grains and perferentially (110) direction for upper grains. This difference of growth orientations seems to be caused by the difference of formation mechanisms. That is, lower grain is formed by soild phase crystallization, on the other hand, upper grain is formed by surface diffusion of silicon atoms. It was thus, proposed that the formation of practical HSG polysilicon film is mainly controlled by surface diffusion of silicon atoms.
Dielectric properties of
thin film capacitor with
thin film underlayer
Kim, Jin-Seok ; Jeong, Gang-Min ; Lee, Mun-Hui ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 759~766
Our investigation aimed to reduce the leakage current of
thin film capacitor by layering SnOz thin film layer under Ta thin film, thereby supplying extra oxygen ions from the
underlayer to enhance the stoichiometry of
during the oxidation of Ta thin film. Tantalum was evaporated by e-beam or sputtered on p-Si wafers with various deposition temperatures and was oxidized by dry--oxygen at the temperatures between
. Aluminum top and bottom electrodes were formed to make Al/
p-Si/AI MIS type capacitors. LCR meter and pico-ammeter were used to measure the dielectric constants and leakage currents of the prepared thm film capacitors. XRD, AES and ESCA were employed to confirm the crystallization of the thin f~lm and the compositions of the films. Dielectric constant of
thin film capacitor with
underlayer was found to be about 200, which is about 10 times higher than that of
thin film capacitor without
underlayer. In addition, higher oxidation temperatures increased the dielectric constants and reduced the leakage current. Higher deposition temperature generally gave lower leakage current.
capacitor deposited at
and oxidized at
showed significantly lower leakage current,
V/cm, compared to the one without
underlayer. XRD showed that
thin film was crystallized above
. AES and ESCA showed that initially the
, underlayer supplied oxygen ions to oxidize the Ta layer, however, Sn also diffused into the Ta thin film layer to form a new
, ternary oxide layer after all.
The oxidation of TaFeCo thin films according to the depositio conditions
Mun, Jeong-Tak ; Kim, Myeong-Han ; Lee, Dong-Cheol ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 767~774
The TbFeCo thin films were prepared by the magnetron sputtering system to investigate the effect of the base pressure, film thickness and pre sputtering on the oxidation of the films by analyzing the change of matneto optical properties and by AES depth profile. The films prepared by the facing targets sputtering system represented almost constant magneto optical properties independent of the base pressure resulting from the short flight distance of the sputtered particles. Also, the thin TbFeCo films represented better perpendicular anisotropy as the films thickness increased with pre sputtering. However, it was still needed a deposition rate higher than a certain critical deposition rate to obtain a perfect perpendicular anisotropy even at a very high film thickness.
on Sintering and Microstructure of Magnesia-Zirconia Composites
Lee, Yun-Bok ; Kim, In-Sul ; Jang, Yun-Sik ; Park, Hong-Chae ; O, Gi-Dong ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 775~782
addition on sintering behavior and microstructure of MgO-
composites was studied.
containing 3mol%Y203 was existed as a c-
phase due to the formation of solubility of MgO,
for 2h. All the compositions employed exhibited a similar shrinkage behavior with an end-point shrinkage between 8.58 and 11.00%. The additlon of
promoted densification and the bulk density of specimen containing 1.67wt%
(98% TD) when
for 2h. The amount of solubilities of MgO and TiOz in
were 5.ti7wt% and 2.62wt%,respectively. They were partially segregated near
grain boundary in the form of Ti-compounds during cooling. This segregation resulted in the formation microcracks which decreased the bending strength.
Deposition of ZnO Thin Films by RF Magnetron Sputtering and Charcaterization of the ZnO thin film SAW filter
Lee, Yong-Ui ; Yang, Hyeong-Guk ; Kim, Yeong-Jin ; Han, Jeong-In ; Kim, Hyeong-Jun ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 783~791
Piezoelectric ZnO thin films were deposited on 7059 glass substrate by rf magnetron sputtering. The effects of deposition parameter, such as rf power, gas pressure and
/Ar gas ratio, on the crystallinity and electrical properties of the deposited ZnO thin films were studied. It was found that the deposition rate was higher than the previously reported values. ZnO films were suitable for SAW filter since a standard deviation of XRD (002) peak rocking curve was less than
. ZnO thin films, which were deposited at
/Ar ratio larger than 25%, showed high resistance. SAW filter was fabricated using ZnO film, of which thickness was 0.25 of the wavelength of the propatating surface acoustic wave. The measured frequency response was consistent with the calculated one. The SAW filter had center frequency 39.08 MHz, phase velocity 2501 m/sec and insertion loss 29 dB.
Force Fields and Elastic Properties of Syndiotactic Isoregic Poly(viny1 fluoride) Crystal
Geo, G ; Lee, Jeong-Gu ; Hong, Jin-Hu ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 792~797
Force fields of syndiotactic isoregic PVF crystal have been extracted by optimizing a structure of 2,4,6-trifluoroheptane with ab initio Quantum mechanical method with 6-31G * * basis set, and applied to calculate the structure parameters and elastic constants of the material. The cell parameters turned out to be 5.205
, of a axis(chain axis), 8.457
, of b axis and 4.621
of c axis. These parameters are in fair agreement with those of the atactic X-ray structure(5.04
, and 4.95
,respectively). The young's modulus of defect free syndiotactic PVF crystal was computed to be 267 GPa comparable to those of polyvinilidene fluoride(277-293 GPa) and polyethylene(264-337 GPa) crystals. Bulk modulus value obtained at optimum geometry is more than twice greater than that obtained at experimental geometry due to large difference of elastic compliance constant (especially Sgj element) at these two different geometries.
Defect Chemistry of Ca and Nb doped
Jeong, Jae-Ho ; Han, Yeong-Ho ; Park, Sun-Ja ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 798~807
The increase in the resistance of
with addition of Ca is attributed to the formation ofthe acceptor impurity by
" which substitutes Ti4+. However, some authors suggested that
can not substitute
because of its larger ionic radius. In this work, the existence of acceptor by Ca hasbeen studied through the high temperature equilibrium electrical conductivity of
codoped with Caand Nb, where Ba/(Ti+Ca+Nb) was kept equal to unity. It was measured at
, and the oxygenpartial pressure was controlled between
~ 1 atm. Changing the amount of added Ca and Nbresulted in the compensation effect between donor and acceptor, i.e., Nb was compensated by the acceptor.And through the defect chemical interpretation of the measured data, it was concluded that Ti canbe substitued with Ca. The existence of such acceptor was reaffirmated by ICTS(Isotherma1 CapacitanceTransient Spectroscopy) measurements.oscopy) measurements.
Preparation of p-Doped Polypyrrole and its Composition Latex and study on its Electrical Properties
Han, Yu-Dong ; Kim, Jung-Hyeon ; Kim, Jung-In ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 808~816
The work present here shows the technique to produce p-Doped polypyrrole particles by semibatch dispersion polymerization using steric-stabilizer. Monomer-starved polymerization process was successful to increase the particle size up to 50 nm in case of polyvinylalcohol (PVA) stabilizer, and up to 95 nm in case of methylcellulose stabilizer. The particle size and the bulk conductivity changed with the feed rates of monomer, the concentrations of initiator (dopant) and the type, molecular weight, concentrations of steric-stabilizer.
potential of Noncircular Fiber as Reinforcing Material l. C-type carbon fiber
Boh, Shim-Hwan ; Rhee Bo sung ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 817~822
The reinforcing effect of C-shape carbon fiber was investigated as comparing to typical round-shape fiber with similar properties. The results show that C-shape fiber reinforced materials have better in almost all aspects of mechanical properties, or 218% in flexural strength, 223% flexural modulus, 157% interlamina shear strength, 227% impact strength, 184% transverse flexural strength and so on. Also in damping characteristics considerably concerned with fatigue life, friction/wear coefficient of a material, C-CF/EP had about 185% greater. In this research, we present the potential of non-circular fiber reinforcing materials by C-shape carbon fiber.
Mechanical Properties of Diglycidy1 Ether of Bisphenol A/4, 4'-Methylene Dianiline/Malononitrile/Hydroquinone system
Jeong, Seon-Gyeong ; Lee, Jae-Yeong ; Choe, Hyeong-Gi ; Sim, Mi-Ja ; Kim, Sang-Uk ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 823~827
The mechanical properties of diglycidyl ether of bisphenol A(DGEBA)/4,4- methylene dianiline(MDA) system with the addition of malononitrile(MN) and hydroquinone(HQ) were investigated. The specimens which were prepared by curing at
for lhr after curing at
for 1.5hr were tested. The effects of MN as a chain extender and HQ, a reaction accelerator on the mechanical properties were investigated. With the increase of MN and HQ contents, impact property improved significantly but tensile property decreased.
High temperature deformation characteristics
Kim, Byeong-Cheol ; Jang, Ho-Jeong ; Song, Jin-Tae ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 828~836
In order to investigate the high temperature deformation characteristics in YBaiCu307-, oxide superconductor, the compression test was performed at temperatures from
at initial strain rate between
. As the temperature increased and the initial strain rate decreased, the flow stress decreased. The strain rate sensitivity exponent measured as 0.41-0.46, supporting occurence of a superplastic deformation. The activation energy for superplastic deformation was calculated as 500-580KJ/mol, which decreased with increasing Ag content. Microstructure of the superplastically-deformed specimens showed that a grain growth occurred during deformation, and it appeared to be considerable when Ag content increased, but most grains still remained equiaxed after deformation. In this study, the deformation mechanism of YBCO superconductor was the grain boundary sliding with the diffusional accommodation and the contribution of the gram boundary sliding to the total strain was estimated to be 65%.
A Study on Extrusion Forces in Hot Extursion of Al-Si Alloys
Jo, Hyeong-Ho ;
Korean Journal of Materials Research, volume 4, issue 7, 1994, Pages 837~844
To investigate that the theoretical formulas for extrusion forces are applicable to the manufacturing plant, the maximum extrusion forces were calculated from Siebel's and Geleji's formulas and also measured using 550 ton extrusion press. Parameters such as flow stress,
, angle of dead metal zone,
were obtained experimentally in order to calculate the maximum extrusion forces by the the theoretical formulas, and it was showed that the results were reliable as the deformation efficient factor,
was determined to be less than 0.5. The maximum extrusion forces calculated from Siebel's formula and Geleji's formula for the angle of dead metal zone,
were approached to the experimental results. However, it was found that Siebel's formula is more useful to apply to the manufacturing plant.