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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
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The Effect of Circulat Hole Size and Distribution on Strength of Braided Composite
Lee, Gyeong-U ; Gang, Tae-Jin ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 253~258
The effect of hole size and hole-to-hole distance in the braided and laminated composite was studied in terms of tensile strength, pin bearing strength, and flexural strength of S2-glass fiber braided polyester. The tensile strength reduction with hole size was well fitted with he Whitney and Nuismer's prediction for the laminated composite. The characteristic distance was measured to be about 1.6mm for braided composite and 1.8mm for laminated one. The effect of distance between the centers of two circu lar holes on tensile strength was negligible when the distance between these two holes was larger than 4 times of the diameter of circular hole for both braided and laminated composite. The side effect was diminished when the center of hole was located 3 times farther than the diamet.er of the hole. The pin bearing strengths was decreased with the size of pin hole for both braided and laminated composite.
Effect of Processing Parameters on the Densification of Carbon/Carbon Composite by Isothermal Low-Pressure Chemical Vapor Infiltration
Park, Hui-Dong ; An, Chi-Won ; Jo, Geon ; Yun, Byeong-Il ; Kim, Gwang-Su ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 259~267
The effect of processing parameters, temperature, gas concentration, gas flow rate and pressure, were studied on the densification of carbon/carbon composites using a Robust design method in isothermal low-pressure chemical vapor infiltration with a gas system of
After one time of isothermal low-pressure chemical vapor infiltrat.ion, the bulk density of carbon/carbon composites in creased up to 1-9% and apparent porosity of the composites decreased down to 20-50%. ANOVA analysis of the experiment.al data revealed that the important parameters of isothermal lowpressure chemical vapor infiltration were temperature, gas concentration and gas flnw rate. 'There was almost no ~ f f e c t on densification by pressure and interaction between each parameters. In t, he present experimental conditions, the highest bulk density was obtained at
, concentration, 100 SCCM flow rate and 5 torr pressure.
SUPERSTRUCTURES OF Bi-Sr-Ca-Cu-O SUPERCONDUTORS
Nam, Gung-Chan ; Lee, Sang-Yun ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 268~279
The x-ray powtler pattern of single phase
has been identified and fullyindexed using a pseudotetragonal subcell with a= 5.408, c = 30.83
and an incommensurate supercellwith reciprocal lattice vector,
X$q^*$, given by
. The x -ray powder pattern of the Pb-free110K superconductor phase "
" has many lines which belong t.o an incommensuratesupercell. Using elect.ron d~ffraction pImt.ographs as a indexing guide, an indexing scheme for the powderpattern has been obtained. The unit cell has a geometrically orthorhombic subcell a=5.411, b= 5.420, c=37.29(2)
. Supercell reflections have indices that are derived from the subcell k, 1 indices by addition uf
The incommensurate con~ponent In the b dwection,
, is the same for both phases but on going from2212 to 2223 phase, the superlattic component in the c direction changes from commensurate(
Effect of Acvated Oxygen Plasma on the Crystallinity and Superconductivity of
Thin Films Prepated by Reactive Co-evaporation method
Chang, Ho-Jung ; Kim, Byoung-Chul ; Akihama, Ryozo ; Song, Jin-Tae ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 280~286
films on MgO(100)substrates were prepated by a reactive co-evaporation method, and effects of activated oxygen plasma on the crystallinity and superconductivity at substrate temperature ranging from
were investigated. The film deposited under the activated oxygen plasma at the substrate temperature of
had a single crystal phase. Whereas, when films were deposited under only oxygen gas, they were not in perfect single crystal phase but with slight polycrystalline nature. When the substrate temperature was
's were 83K and 80K for films with and without activated oxygen plasma, respectively. The critical temperature, the crystal structure and the surface morphology of as-grown films were found to be insensitive to the activated oxygen plasma which is introduced during deposition instead of oxygen gas, but the crystalline quality was improved somewhat by the introduction by the introduction of actvated oxygen plasma.
A Study on the Effents of High Temperature Heat Treatment on the Physical and Mechanical Properities of Carbon Fiber and Carbon Composites
Kim, Dong-Gyu ; Ha, Heon-Seung ; Park, In-Seo ; Im, Yeon-Su ; Yun, Byeong-Il ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 287~294
PAN-based carbon fiber roving and fabric were heat treated at the temperature of
. Using non-heat treated and heat treated fabric, greenbodies of CFRP and GFRP were manufactured in the Autoclave. After the analysis of heat treated and non-heat treated carbon fiber roving and two types of greenbodies, the variations of physical and mechanical properties of carbon fibers and greenbodies with heat treatment were studied. Observing the cross-section of carbon fiber with SEM, we knew the diameter of carbon fiber was decreased from 6.8gm to 6.4p1. The results of TGA showed that the oxidation resistence was enhanced after heat treatment. The tensile strength of carbon fiber was decreased from (3.11
MPa to (1.87
MPa, but tensile modulus was increased from (1.94
MPa to (2.02
MPa after heat treatment. The interlaminar shear strengths of CFRP and GFRP were 148.8
1.6Mpa and 82.2
1.1Mpa, respectively. Torch test showed that CFRP was abraded smoothly but GFRP was delaminated.
The effect of Pd activator and annealing temperatures on the response characteristecs of the
Jeon, Chun-Saeng ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 295~300
This paper is aimed to study the effect of Pd activator, the annealing temperature, and operating temperatures on the response characteristics of the
sensor. The resistance of device has shown minimum value when annealing temperature and operating temperature of device are
respectively in ethanol gas. And the response characteristics of the device showed the best results when lwt% Pd was added to SnOz especially in low concentration of ethanol gas.
Formation of amorphous and crystalline phase, phase sequence by solid state reaction in Co/Si multilayer thin films
Sim, Jae-Yeop ; Park, Sang-Uk ; Ji, Eung-Jun ; Gwak, Jun-Seop ; Choe, Jeong-Dong ; Baek, Hong-Gu ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 301~311
The growth of amorphous and first crystalline phase, and phase sequence by solid state reaction were examined in Co/Si multilayer thin films by DSC and XRD. The experimental results were compared with the results expected by effective driving force models, PDF and effective heat of formation models.Amorphous phase growth was not observed in Co/Si system and it was consistent with the predicted result by effective driving force. It was observed that the first crystalline phase is CoSi. According to the PDF and effective heat of formation models, the first crystalline phases were CoSi and
, respectively. The experiemental results were coincident with the PDF model considering structure factors. In case of the atomic concentration ratios of 2Co : 1Si and 1Co : 2Si, the phases sequences were
, respectively and it was analysized through the effective heat of formation model. The formations of CoSi,
in initial stage were controlled by nucleation and the activation energies for the nucleation of three phases were 1.71, 2.34 and 2.79eV.
Inprovenent of the Electrical Characteristics of Transformer Oil dissolved with
Jeon, Chung-Saeng ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 312~318
In this paper the breakdown and dielectric characteristics of purified transformer oil dissolved with
Gas are investigated with a few decade MHz frequency voltage. The results are as follows. 1) High frequency current is a approximately proportional to the square root of high frequency voltage in purified transformer oil. 2) As frequency increase breakdown voltage decrease inversely proportional to the square root of frequency and the high frequency breakdown voltage is lower about 35 percentage than that of AC 3) The breakdown voltage of high frequency has a little increase with the pressure increase of dissolved
, Air and Ar Gas. 4) As voltage freguency increases the value of the dielectric loss tangent has increased almost exponentially and the dielectric constant (
) has tended to decrease with a slope[0.6% MHz]. 5) When dissolved with
Gas, oil electrical characteristics has more increased about 25% than in Air or Ar gas with high voltage frequency.
A Study on the Preparation of Aluina & Titania Sols for Coatings
Kim, Chu-Hui ; Choe, Hyeong-Su ; Jo, Yeong-Sang ; Im, Jong-Ju ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 319~328
Aluminium and titanium precursors containing
-diketonate ligands were used for the synthesis of polymeric sols of alumina and titania by sol-gel methods. To prepare polymeric sols by solgel processing, we synthesized modified precursors having chelating organic ligands. With these precursors it was found to be possible to control both hydrolysis and polycondensation reaction rates which resulted in ultrafine particles few nms of average size. The optimum molar ratio of acid to alkoxide for alumina sol was 0.3-0.4 and that of water to alkoxide &as 1. On the other hand, the corresponding ratios for titania sol were found be 0.25-0.20 and 1 respectively. Dynamic light scattering measurements indicated that the average particle size in both sols was in the order of few nms. SEM photographs were taken to observe crack-free and smooth surfaces of coated membranes after sintering at
. Alumina coated membrane on a slide glass had about 4-4.5
, thickness and titania coated one had 2-2.5
, thickness. And according to TEM photographs, the grain size of titania was smaller than 30nm and that of alumina was in the range of few
s to 2nms. An X-ray diffraction study revealed that alumina was
phase and titania was anatase crystal.
IMPURITY SEGREGATION ON CRACKED GRAIN BOUNDARIES IN LLCC SOLDER JOINTS DURING THERMAL CYCLING
Lee, Seong-Min ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 329~333
A large number of grain boundaries were seen to crack in near-eutectic solder joints of leadless ceramic chip carriers (LLCC's) during thermal cycling at temperature ranges from -
with lhr time period. One potential explanation for this type of cracking might be the presence of embrittling species on the boundary. Although there do not appear to be any instances reported in the literature of solders being embrittled by small amounts of contaminating species, the possibility of such an occurrence exists. The potential presence of impurities located at crack surfaces was inspected using Scanning Auger Microprobe(SAM) and it was found that intergranular cracking could be accomplished by the oxidation of the grain boundary. A physical model for fatigue crack growth was introduced, in which grain boundary separation took place under oxidation facilitated by sliding.
INTERGRANULAR FAILURE ASSOCIATED WITH BOUNDARY SLIDING IN Pb-SN EUTECTIC SOLDERS USED FOR MICROELECTRONICS APPLICATIONS
Lee, Seong-Min ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 334~338
This report details the microscopic aspects of grain boundary cracking in Pb-Sn eutecticduring displacement-controlled mechanical tests performed over a range of low frequency (
/s)and moderate strain range (0.2 - 1 %) where is the most technologically relevant to solder jointssubjected to thermal cycling. It is shown that intergranular cracking begins with the appearance ofcrack-like features (CLF's), which can be seen due in part because they are associated with grainboundary sliding, and is able to be described by certain stages of isolated crack growth. In the initialstages CLF's are not ture cracks but instead what I shall call "proto-cracks" where grain boundarysliding begins to damage the gram boundary at the surface. At some point during the initiation stagesonce proto-cracks become ture cracks, they develop into isolated cracks and the growth of isolatedcracks is eventually accomplished by coalescence, resulting in 5 stages of cracking.ing in 5 stages of cracking.
Study on the ablation structures of Carbon/Phenolic composites used PAN based carbon fiber
Im, Yeon-Su ; Kim, Dong-Gyu ; Park, In-Seo ; Yun, Byeong-Il ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 339~348
The study has been conducted to know ablation microstructures and characteristics in carbon /phenolic composites. Ablation properties depend on mole fraction of
gas which were produced by reaction between propellant and oxidizer. However, the results of this study shown that the ablation also depended on weaving structure, density of fabric, and tow size of carbon fiber. 3K 8HS fabric showed superior ablation resistance to others, 3K twill and 12K 8HS fabric structures.
Dislication Loop Models for Plastic Deformation of the AI-5.5 at.%Mg alloy
An, Seong-Uk ; Jeong, Seung-Bu ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 349~356
For the deformation, life time prediction and improvement of the life time in high temperature materials it's very important to know the mechanism of deformation. For these mechanisms the dislocation loop models of Orlova et al. and Mills et al. are used often now. But they show controversial differencies, even if they have unertaken similar experimental tests with the same alloy of A1-5.5at.% Mg. In this work also the similiar tests of them have done under the same temperature of 573 K ; (1) The specimen was deformed by
= 30MPa and
=0.03. (2) Direct after creep deformation of
= 30MPa and
= 0.03 the stress reduction tests to 15, 10 and OMPa have been performed. (3) To study the loop models dislocation structure and dislocation density ( p ) have been observed.
Analysis of Irradiation Growth Behavior for the Zircaloy-4 Cladding used in the KOFA Fuel
Kim, Gi-Hang ; Lee, Chan-Bok ; Kim, Gyu-Tae ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 357~363
The irradiation growth of the Zircaloy-4 cladding in the KOFA fuel loaded in the Kori-2 nuclear plant was measured to evaluate the irradiation growth behavior and to be compared with that of the Siemens cladding having different manufacturing process. Due to the partial recrystallization by final heat treatment, the KOFA Zircaloy-4 cladding showed a two step irradiation growth behavior such as the growth saturation and the accerlation which is typical of the fully annealed Zircaloy cladding. The difference in the measured irradiation growth rate between the KOFA and the Siemens cladding could be explained by the difference in the cladding texture which depends on the manufacturing process. From the measured irradiation growth data of Kori-2 KOFA fuel, a two-step irradiation growth model of the KOFA Zircaloy-4 cladding was derived, the accuracy of which can be more clearly verified as the measured data of the irradiation growth are accumulated in the future.
Effect of Molybdenum Addition on the Mechanical Properties of Direct-Quenched Low-Carbon Non-Treated Steels
Ju, Eun-Seok ; An, Byeong-Gyu ; Lee, Gyeong-Seop ;
Korean Journal of Materials Research, volume 4, issue 3, 1994, Pages 364~375
The microstructure of medium-carbon non-heat treated steels by air-cooling shows ferritepearlite structure. Compared to the conventional Q/T steels, the strength of these steels containing V, Nb and Ti are similar to Q/T steels. However, their toughness are inferior. In this study, the mechanical properties and microstructures of low-carbon Mo bearing steels produced by direct-quenching process were investigated. Especially, the effect of Mo on the direct-quenched steels was examined. The direct-quenched steels containing Mo were found to have higher strength and toughness. Mo seemed to be effective in producing the fine structure and dense precipitates because of decreasing transformation temperature. The best results were 1211 MPa in UTS and 127.5 J in toughness in the oil quenched 0.15C+O.llV+ 0.035Nb+ 1.81Mo steel. Compared to 0.4% C microalloyed steels, this results showed that UTS increased by 45% and toughness by 2 times.