• Title/Summary/Keyword: $S_i3N_4$ composite

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Processing and Thermal Properties of S${i_3}{N_4}$-BN Composites (S${i_3}{N_4}$-BN복합재료의 제조 및 열적 특성)

  • Lee, O-Sang;Park, Hui-Dong;Lee, Jae-Do
    • Korean Journal of Materials Research
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    • v.3 no.4
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    • pp.381-387
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    • 1993
  • The silicon oxynitride bonded $Si_3N_4-BN$ composite has been developed based on the selective oxidation behavier of $Si_3N_4$ over BN. The silicon oxynitride phase converted to the reaction between $Si_3N_4$ and $SiO_2$ formed on $Si_3N_4$ powder surface during oxidation treatment at the sintering temperature. The developed composite has excellent high-temperature strength, thermal shock resistance, precision machinability and corrosion resistance to the molten steel. The developed composite may therefore be used as, for example, break ring materials in continuous casting of steel.

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Effects of Carbon-coated SiC Whiskers on the Mechanical Properties of SiC Whisker Reinforced Silicon Nitride Ceramic Composite (SiC 휘스커 강화 질화규소 복합재료의 기계작 성질에 미치는 카본 코팅 SiC 휘스커의 영향)

  • 배인경;이영규;조원승;최상욱;장병국;임실묵
    • Journal of the Korean Ceramic Society
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    • v.36 no.10
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    • pp.1007-1015
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    • 1999
  • The Si3N4 composites reinforced with carbon-coated SiC whiskers were fabricated by hot-pressing at 180$0^{\circ}C$ for 2 hours to examine the effects of carbon-coated whiskers on the mechanical properties of SiC whisker reinforced Si3N4 composites. The flexural strength of the Si3N4 composites and Si3N4 monolith respectively. The weak interfacial bond between carbon-coated SiC whiskers and Si3N4 matrix which enhances the crack deflection and whisker pull-out could contribute to the improvement of mechanical properties of the composites.

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Design of Composite Laminate Bicycle Wheel considering Stacking Sequence (적층각을 고려한 복합재료 라미네이트 자전거 휠의 설계)

  • Lee, Jin-Ah;Hong, Hyoung-Taek;Kang, Kyoung-Tak;Chun, Heoung-Jae
    • Composites Research
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    • v.25 no.5
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    • pp.141-146
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    • 2012
  • The strength design for the lightweight bicycle wheel made of the Carbon/Epoxy composite laminates has been discussed in this paper. For bicycle wheel design, lightness of the wheel is important. Also, it has to satisfy the required strength under specific loading cases. Two testing methods for the bicycle wheel, i.e. vertical and complex loadings, are adopted in this study. Because the strengths of composite wheel is different in relation to the stacking sequence and the number of plies, it is important to decide an appropriate stacking sequence and number of layers for the composite wheel. From the finite element analysis results, the most stable sequence orientation and number of layers are determined. The stacking sequence $[0]_{8n}$, $[90]_{8n}$, $[0/90]_{2ns}$, $[{\pm}45]_{2ns}$, $[0/{\pm}45/90]_{ns}$ (n=1,2,3,4)are performed for finite element analysis. From results, $[0/{\pm}45/90]_{3s}$ lay-up is a good selection for the composite bicycle wheel. Also, the weakest point and layer are found in this study.

Basic Characteristics of Micro-Fatigue-Cracks on the Unnotched Smooth Specimens (平활材表面 의 微小피勞균열에 관한 基礎的 特性)

  • 서창민;북천영부;결성양치
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.7 no.1
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    • pp.28-35
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    • 1983
  • Quantitative analysis have been carried out on the micro-cracks on the surface and into the depth of unnotched smooth mild steel specimen under cyclic stains by rotating bending fatigue tests. Some of the results are; (1) Cracks initiate at the early stage of fatigue life N$_{I}$/ N$_{f}$=10 to 20%, and propagate during the rest of fatigue life. (2) Coalescence of highly crowded small fatigue cracks of random distribution seems to induce the final fracture at higher stress level. (3) The curves of crack initiation and the equal crack length on the graph of stress versus number of cycles are parallel to the S-N curve. (3) The curves of crack initiation and the equal crack length on the graph of stress versus number of cycles are parallel to the S-N curve. (4) The distributions of micro-surface crack length and depth show the composite Weibull distributions which are approximated to two straight lines separated by the value of transient region between stage I and stage II crack.k.k.

Dielectric and Magnetic Properties of BaTiO3-LaMnO3 Composites

  • Kim, N.G.;Koo, Y.S.;Jung, J.H.
    • Journal of Magnetics
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    • v.11 no.4
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    • pp.164-166
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    • 2006
  • We have investigated the dielectric and magnetic properties of ferroelectric-antiferromagnetic $BaTiO_{3}-LaMnO_{3}$ composite with changing relative mole percents. Due to high sintering temperature, i.e. $1150^{\circ}C$, the Ba ion in $BaTiO_{3}$ seems to diffuse into $LaMnO_{3}$; resulting in $BaTiO_{3}-(La,Ba)MnO_{3}$ ferroelectric-ferromagnetic composite. At room temperature, $0.9BaTiO_{3}-0.1LaMnO_{3}$ composite exhibits considerable magnetization (${\sim}0.7\;emu/g\;at\;2000\;Oe$) and low coercive field (${\sim}5\;Oe$). Also it exhibits high dielectric constant (${\sim}560$) and low loss (${\sim}0.08$) at 10 kHz. This result may imply that $BaTiO_{3}-LaMnO_{3}$ could be suitable for a low leakage multiferroic composite.

Nano-Ruthenium Oxide Polymeric Composite pH Electrodes (나노 Ruthenium Oxide 고분자 복합재료 pH전극)

  • Park, Jongman
    • Journal of the Korean Chemical Society
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    • v.62 no.4
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    • pp.269-274
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    • 2018
  • Surface renewable nano-$RuO_2$/poly(methyl methacrylate) polymeric composite pH electrodes were prepared. The composite electrode with 53 wt% of nano-$RuO_2$ showed similar good response characteristics to nano-$IrO_2$ composite electrode reported earlier. It showed response slope of -58.7 mV/pH, response time of <1 s, surface renewability of $-57.0{\pm}0.3mV/pH$ (n=5) and long time stability for a month as well as low interferences but high interferences by electrochemically active species like $I^-$ and $Fe(CN){_6}^{3-}$. However, the response slope and time became worse at higher pH than 9 compared to those of nano-$IrO_2$ composite electrodes possibly due to the difference of physical properties resulting from higher content of nano-$RuO_2$ in polymeric composite matrix.

Development of fiber reinforced self-compacting concrete (FRSCC): Towards an efficient utilization of quaternary composite binders and fibers

  • Fediuk, Roman;Mosaberpanah, Mohammad A.;Lesovik, Valery
    • Advances in concrete construction
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    • v.9 no.4
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    • pp.387-395
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    • 2020
  • This study has been carried out in two-phases to develop Fiber Reinforced Self-Compacting Concrete (FRSCC) performance. In the first phase, the composition of the quaternary composite binder compromised CEM I 42.5N (58-70%), Rice Husk Ash (25-37%), quartz sand (2.5-7.5%) and limestone crushing waste (2.5-7.5%) were optimized. And in the second phase, the effect of two fiber types (steel brass-plated and basalt) was investigated on the SCC optimized with the optimum CB as disperse reinforcement at 6 different ratios of 1, 1.2, 1.4, 1.6, 1.8, and 2.0% by weight of mix for each type. In this study, the theoretical principles of the synthesis of self-compacting dispersion-reinforced concrete have been developed which consists of optimizing structure-formation processes through the use of a mineral modifier, together with ground crushed cement in a vario-planetary mill to a specific surface area of 550 m2 / kg. The amorphous silica in the modifier composition intensifies the binding of calcium hydroxide formed during the hydration of C3S, helps reduce the basicity of the cement-composite, while reducing the growth of portlandite crystals. Limestone particles contribute to the formation of calcium hydrocarbonate and, together with fine ground quartz sand; act as microfiller, clogging the pores of the cement. Furthermore, the results revealed that the effect of fiber addition improves the mechanical properties of FRSCC. It was found that the steel fiber performed better than basalt fiber on tensile strength and modulus of elasticity; however, both fibers have the same performance on the first crack strength and sample destruction of FRSCC. It also illustrates that there will be an optimum percentage of fiber addition.

X-ray/gamma radiation shielding properties of Aluminium-Bariume-Zinc Oxide nanoparticles synthesized via low temperature solution combustion method

  • K.V. Sathish;K.N. Sridhar;L. Seenappa;H.C. Manjunatha;Y.S. Vidya;B. Chinnappa Reddy;S. Manjunatha;A.N. Santhosh;R. Munirathnam;Alfred Cecil Raj;P.S. Damodara Gupta;B.M. Sankarshan
    • Nuclear Engineering and Technology
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    • v.55 no.5
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    • pp.1519-1526
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    • 2023
  • For the first time Aluminium-BariumeZinc oxide nanocomposite (ZABONC) was synthesized by solution combustion method where calcination was carried out at low temperatures (600℃) to study the electromagnetic (EM) (X/γ) radiation shielding properties. Further for characterization purpose standard techniques like PXRD, SEM, UV-VISIBLE, FTIR were used to find phase purity, functional groups, surface morphology, and to do structural analysis and energy band gap determination. The PXRD pattern shows (hkl) planes corresponding to spinel cubic phase of ZnAl2O4, cubic Ba(NO3)2, α and γ phase of Al2O3 which clearly confirms the formation of complex nano composite. From SEM histogram mean size of nano particles was calculated and is in the order of 17 nm. Wood and Tauc's relation direct energy band gap calculation gives energy gap of 2.9 eV. In addition, EM (X/γ) shielding properties were measured and compared with the theoretical ones using standard procedures (NaI (Tl) detector and multi channel analyzer MCA). For energy above 356 keV the measured shielding parameters agree well with the theory, while below this value slight deviation is observed, due to the influence of atomic/crystallite size of the ZABONC. Hence synthesized ZABONC can be used as a shielding material in EM (X/γ) radiation shielding.

Bone regeneration and graft material resorption in extraction sockets grafted with bioactive silica-calcium phosphate composite (SCPC) versus non-grafted sockets: clinical, radiographic, and histological findings

  • Adel-Khattab, Doaa;Afifi, Nermeen S.;el Sadat, Shaimaa M. Abu;Aboul-Fotouh, Mona N.;Tarek, Karim;Horowitz, Robert A.
    • Journal of Periodontal and Implant Science
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    • v.50 no.6
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    • pp.418-434
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    • 2020
  • Purpose: The purpose of the present study was to evaluate the effect of silica-calcium phosphate composite (SCPC) granules on bone regeneration in extraction sockets. Methods: Ten patients were selected for a split-model study. In each patient, bone healing in SCPC-grafted and control ungrafted sockets was analyzed through clinical, radiographic, histomorphometric, and immunohistochemical assessments 6 months postoperatively. Results: A radiographic assessment using cone-beam computed tomography showed minimal ridge dimension changes in SCPC-grafted sockets, with 0.39 mm and 1.79 mm decreases in height and width, respectively. Core bone biopsy samples were obtained 6 months post-extraction during implant placement and analyzed. The average percent areas occupied by mature bone, woven bone, and remnant particles in the SCPC-grafted sockets were 41.3%±12%, 20.1%±9.5%, and 5.3%±4.4%, respectively. The percent areas of mature bone and woven bone formed in the control ungrafted sockets at the same time point were 31%±14% and 24.1%±9.4%, respectively. Histochemical and immunohistochemical analyses showed dense mineralized bundles of type I collagen with high osteopontin expression intensity in the grafted sockets. The newly formed bone was well vascularized, with numerous active osteoblasts, Haversian systems, and osteocytes indicating maturation. In contrast, the new bone in the control ungrafted sockets was immature, rich in type III collagen, and had a low osteocyte density. Conclusions: The resorption of SCPC granules in 6 months was coordinated with better new bone formation than was observed in untreated sockets. SCPC is a resorbable bone graft material that enhances bone formation and maturation through its stimulatory effect on bone cell function.

Prediction of Optimal Extraction Conditions in Microwave-Assisted Process for Antioxidant-Related Components from Thymus quinquecostatus (Microwave-Assisted Process에 의한 섬백리향의 항산화 관련 성분의 최적 추출조건 예측)

  • Kwon Young-ju;Noh Jung-eun;Lee Jung-eun;Lee Sung-Ho;Choi Yong-Hee;Kwon Joong-Ho
    • Food Science and Preservation
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    • v.12 no.4
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    • pp.344-349
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    • 2005
  • Microwave-assisted process (MAP) was applied to extract antioxidant-related components from Thymus quinquecostatus var. japonica Hara. Microwave power(2,450 MHz, $0{\sim}160$ W) and extraction time($1{\sim}5\;min$) were used as independent variables($X_i$) for central composite design to yield 10 different extraction conditions. Response surface methodology was applied to predict optimum extraction conditions for dependent variables of extracts, such as total yield, total phenolics, flavonoid, and electron donation ability depending on different powers and extraction times of MAP. Determination coefficients($R^2$) of regression equations for dependent variables were higher than 0.93 excluding that of total phenolics, and microwave power was predicted more influential than extraction time in MAP (p<0.05). The optimal extraction time for each dependent variable was ranged from 3.36 to 4.97 min, but microwave power showed wide ranges depending on variables. The superimposed contour maps for maximized dependent variables illustrated extraction conditions of 64 to 100 W in microwave power and 2.9 to 4.0 min in extraction time.