• Title, Summary, Keyword: $SiO_2$ Nano Colloid

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Wear Characteristics According of Heat Treatment of Si3N4 with Different Amounts of SiO2 Nano-Colloid (SiO2 나노 콜로이드 량이 다른 Si3N4의 열처리에 따른 마모 특성)

  • Ahn, Seok Hwan;Nam, Ki Woo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.10
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    • pp.1117-1123
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    • 2014
  • This study sintered $Si_3N_4$ with different amounts of $SiO_2$ nano-colloid. The surface of a mirror-polished specimen was coated with $SiO_2$ nano-colloid, and cracks were healed when the specimen was treated at a temperature of 1273 K for 1 h in air. Wear specimen experiments were conducted after heat treatments for 10 min at 1073, 1273, and 1573 K. The heat-treated surface that was coated with the $SiO_2$ nano-colloid was slightly rougher than the noncoated surface. The oxidation state of the surface according to the heat treatment temperature showed no correlation with the surface roughness. Moreover, the friction coefficient, wear loss, and bending strength were not related to the surface roughness. $Si_3N_4$ exhibited an abrasive wear behavior when SKD11 was used as an opponent material. The friction coefficient was proportional to the wear loss, and the bending strength was inversely proportional to the friction coefficient and wear loss. The friction coefficient and wear loss increased with increasing amounts of the $SiO_2$ nanocolloid. In addition, the friction coefficient was slightly increased by increasing the heat treatment temperature.

Preparation of silica-coated gadolinium compound particle colloid solution and its application in imaging

  • Kobayashi, Yoshio;Morimoto, Hikaru;Nakagawa, Tomohiko;Gonda, Kohsuke;Ohuchi, Noriaki
    • Advances in nano research
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    • v.1 no.3
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    • pp.159-169
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    • 2013
  • A preparation method for gadolinium compound (GdC) nanoparticles coated with silica ($GdC/SiO_2$) is proposed. GdC nanoparticles were prepared with a homogeneous precipitation method at $80^{\circ}C$ using $1.0{\times}10^{-3}$ M $Gd(NO_3)_3$, 0.5 M urea and $0-3.0{\times}10^{-4}$ M ethylenediarinnetetraacetic acid disodium salt dihydrate (ETDA) in water. As a result of preparation at various EDTA concentrations, GdC nanoparticles with a size as small as $40.5{\pm}6.2$ nm, which were colloidally stable, were prepared at an EDTA concentration of $2.0{\times}10^{-4}$ M. Silica-coating of the GdC nanoparticles was performed by a St$\ddot{o}$ber method at $35^{\circ}C$ using $1.0-10.0{\times}10^{-3}$ M tetraethylorthosilicate (TEOS), 11 M $H_2O$ and $1.5{\times}10^{-3}$ M NaOH in ethanol in the presence of $1.0{\times}10^{-3}$ M GdC nanoparticles. Performance of preparation at various TEOS concentrations resulted in production of $GdC/SiO_2$ particles with an average size of $106.1{\pm}11.2$ nm at a TEOS concentration of $5.0{\times}10^{-3}$ M. The gadolinium (Gd) concentration of $1.0{\times}10^{-3}$ M in the as-prepared $GdC/SiO_2$ particle colloid solution was increased up to a Gd concentration of 0.2 M by concentrating with centrifugation. The core-shell structure of $GdC/SiO_2$ particles was undamaged, and the colloid solution was still colloidally stable, even after the concentrating process. The concentrated $GdC/SiO_2$ colloid solution showed images of X-ray and magnetic resonance with contrast as high as commercial Gd complex contrast agents.

Nano-Sized Mullite(3Al2O3.42SiO2) Colloids Fabricated by Spray Combustion Synthesis (SCS) Technique (분무연소합성(SCS)법에 의한 나노크기 물라이트(3Al2O3.42SiO2) 콜로이드 제조)

  • Lee, Sang-Jin;Jun, Byung-Sei
    • Journal of the Korean Ceramic Society
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    • v.41 no.4
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    • pp.297-301
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    • 2004
  • Nano-sized mullite (3Al$_2$O$_3$$.$2SiO$_2$) colloids were prepared by use of the spray combustion method. For combustion reaction, Al(NO$_3$)$_3$$.$9$H_2O$, and CH$_{6}$N$_4$O were used as an oxidizer and a fuel respectively, and then colloidal silica was also added as 2SiO$_2$source for mullite. The temperature of the reaction chamber was kept at 80$0^{\circ}C$ to initiate the ignition of droplets of the mixed precursors. For preventing droplet coagulation, the droplet number concentration was reduced using the metal screen filter, and the residence time of aerosol was kept at 2.5 seconds for laminar flow. The synthesized colloidal particles had an uniform spherical shape with 130 nanometer size and the crystalline phase showed the mullite with stoichiometry in the observations of XRD and TEM.

Study of the Application of Gel Electrolyte in the Reference Electrode of $Cu/CuSO_4$

  • Lin, Cunguo;Xu, Likun;Liu, Yang
    • Corrosion Science and Technology
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    • v.7 no.3
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    • pp.179-181
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    • 2008
  • With nano-$SiO_2$ and sulphate acid, a kind of colloid electrolyte is synthesized by sol-gel method. It is placed outside the reference electrode as a layer of gel electrolyte so as to decrease the leaching of $Cu^{2+}$ and increase the life of the reference electrode. The performance of the gel electrode in simulating soil solution is measured as follows: the potential of the electrodes ranging from 60 mV to 80 mV (vs. SCE) with potential variation no more than $\pm10mV$, enough resistance to polarization. The $Cu^{2+}$ effusion rate of the reference electrode without gel electrolyte is 3 times that with colloid electrolyte, which means that gel electrolyte can extend the life of the reference electrode significantly.

A Study on the Zeta Potential Measurement and the Stability Analysis of Nano Fluids using a Particle Image Processing System (입자 영상 처리 시스템을 이용한 콜로이드 입자의 제타포텐셜 측정 및 나노유체 분산 특성 연구)

  • Lee, J.K.;Kim, S.C.;Kim, H.J.;Lee, C.G.;Ju, C.H.;Lee, L.C.
    • Journal of ILASS-Korea
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    • v.8 no.1
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    • pp.16-22
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    • 2003
  • Zeta potential measurements of colloid particles suspended in a liquid are performed by a Zeta Meter developed. There are many applications of colloid stability in spray technology, paints, wastewater treatment, and pharmaceuticalse. Zeta potentials of charged particles are obtained by measuring the electrophoretic velocities of the particles using video enhanced microscopy and image analysis program. The values of zeta potential of polystyrene latex(PSL), $silica(SiO_2)$M, polyvinylidence difluoride(PVDF), silicon nitride, and alumina particles in deionized (DI) water were measured to be -40.5, -31.9, -25.2, -15.1 and -10.1mV, respectively. The particles having high zeta potential less than -20 mV are stable in DI water, because the double layers of them have strong repulsive forces mutually, and the particles having low zeta potential over -20mV are unstable due to Van Der Waals forces. Silica(>20nm), PSL, aluminum and PVDF particles were found to be stable that would remain separate and well disperse, while silicon nitride and alumina particles were found to be unstable that would gradually agglomerate in DI water.

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Tribology of Si3N4 Ceramics Depending on Amount of Added SiO2 Nanocolloid (SiO2 나노 콜로이드 첨가량에 따른 질화규소의 트라이볼러지)

  • Nam, Ki-Woo;Chung, Young-Kyu;Hwang, Seok-Hwan;Kim, Jong-Soon;Moon, Chang-Kwon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.3
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    • pp.267-272
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    • 2011
  • We analyzed the wear characterization of $Si_3N_4$ ceramics according to the amount of added $SiO_2$ nanocolloid. The test specimen was prepared by hot-press sintering at 35 MPa and 2123 K in an $N_2$ gas atmosphere for 1 h. A wear test was performed with a block-on-ring tester, and the test conditions were as follows: (1) the ring with a diameter of 35 mm had a rotational speed of 50 rpm; (2) the load was 9.8 N; and (3) the temperature was $25^{\circ}C$. The test results show that $Si_3N_4$ ceramics have a friction coefficient of about 1.0 and a wear loss of about 0.02 mm. Of the specimens used this study, the test specimen with 1.3 wt% of added $SiO_2$ nanocolloid has the best wear resistance because it has the lowest friction coefficient and the smallest wear loss. This specimen also has the highest Vickers hardness and bending strength. In this study, the friction coefficient is inversely proportional to the hardness and bending strength.

Characterization of Crack Healing of Si3N4 Ceramic Structures According to Crack Length and Coating Methods (균열 길이와 코팅방법에 따른 Si3N4의 균열 치유 특성)

  • Nam, Ki-Woo;Moon, Chang-Kwon;Park, Sang-Hyun;Eun, Kyung-Ki;Kim, Jong-Soon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.11
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    • pp.1715-1720
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    • 2010
  • In this study, we analyzed the crack-healing characteristics of specimens; different crack lengths and coating methods of $Si_3N_4$ ceramic structures with long cracks were analyzed. Cracks with lengths of about $100-500\;{\mu}m$ were obtained using a Vickers indenter for a load of 24.5-98 N. In the case of a crack obtained by applying a load of 24.5 N, the crack-healed specimen with $SiO_2$ nanocolloid coating exhibited the highest bending strength, which was higher than that of a smooth specimen by 140%, but the bending strength of a crack-healed specimen that had a $SiO_2$ nanocolloid coating and originally had multiple cracks was lower than that of a smooth specimen. However, when compared to the cracked specimens, the bending strength of most specimens with multiple cracks increased slightly. On the basis of these results, the crack-healing characteristics of $Si_3N_4$ ceramic structures with multiple indentations were studied for different coating methods. The most effective coating method for long-crack specimens was hydrostatic pressure coating.