• Clean Technology
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• v.28 no.2
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• pp.154-162
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• 2022

Microstructured Al@Al₂O₃ and Al@Ni-Al LDH (LDH = layered double hydroxide) core-shell metal-ceramic composites are prepared by hydrothermal reactions of aluminum (Al) metal substrates. Controlled hydrothermal reactions of Al metal substrates induce the hydrothermal dissolution of Al ions at the Al-substrate/solution interface and reconstruction as porous metal-hydroxides on the Al substrate, thereby constructing unique metal-ceramic core-shell composite structures. The morphology, composition, and crystal structure of the core-shell composites are affected largely by the ions in the hydrothermal solution; therefore, the critical physicochemical and surface properties of these unique metal-ceramic core-shell microstructures can be modulated effectively by varying the solution composition. A Ni/Al@Al₂O₃ catalyst with highly dispersed catalytic Ni nanoparticles on an Al@Al₂O₃ core-shell substrate was prepared by a controlled reduction of an Al@Ni-Al LDH core-shell prepared by hydrothermal reactions of Al in nickel nitrate solution. The reduction of Al@Ni-Al LDH leads to the exolution of Ni ions from the LDH shell, thereby constructing the Ni nanoparticles dispersed on the Al@Al₂O₃. The catalytic properties of the Ni/Al@Al₂O₃ catalyst were investigated for CO₂ methanation reactions. The Ni/Al@Al₂O₃ catalyst exhibited 2 times greater CO₂ conversion than a Ni/Al₂O₃ catalyst prepared by conventional incipient wetness impregnation and showed high structural stability. These results demonstrate the high effectiveness of the design and synthesis methods for the metal-ceramic composite catalysts derived by hydrothermal reactions of Al metal substrates.

• Ceramist
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• v.9 no.6
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• pp.49-55
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• 2006

Intra-type alumina-based nanocomposites, in which second-phase nanoparticles are embedded within alumina grains, use dislocation activities to enhance strength and fracture toughness. The dislocations are generated around the nanoparticles by residual stresses during cooling process. In this paper, first, we explain strengthening and toughening mechanisms of alumina-based nanocomposites based on dislocation activities. Second, we propose a soaking method to construct the intra-type nanostructure and fabricate alumina/nickel and alumina/silver nanocomposites. The nanocomposites are then annealed in order to enhance the fracture toughness of the materials. Finally, we discuss the relation between the strength, fracture toughness, and critical frontal process zone size of the materials.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.149-149
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• 2016

Ceramic is widely known material due to its outstanding mechanical property. Besides, Zirconia(ZrO2) has a low thermal conductivity so it is advantage in a heat insulation. Because of these superior properties, ZrO2 is attracted to many fields using ultra high temperature for example vehicle engines, aerospace industry, turbine, nuclear system and so on. However brittle fracture is a disadvantage of the ZrO2. In order to overcome this problem, we can make the ceramic materials to the forms of ceramic nanoparticles, ceramic nanowhiskers and these forms can be used to an agent of composite materials. In this work, we selected Au catalyzed Vapor-Liquid-Solid mechanism to synthesize ZrO2 nanowhiskers. The ZrO2 whiskers are grown through Hot-wall Chemical Vapor Deposition(Hot wall CVD) using ZrCl4 as a powder source and Au film as a catalyst. This Hot wall CVD method is known to comparatively cost effective. The synthesis condition is a temperature of $1100^{\circ}C$, a pressure of 760torr(1atm) and carrier gas(Ar) flow of 500sccm. To observe the morphology of ZrO2 scanning electron microscopy is used and to identify the crystal structure x-ray diffraction is used.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.2
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• pp.91-97
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• 2018

Indium hydroxide powder was prepared by precipitation method. The reaction temperature ($150{\sim}250^{\circ}C$) and the holding time at each reaction temperature (1~72 h) were used as experimental variables. The particle size, microstructure and crystal phase of each prepared powder were observed through X-ray diffraction (XRD), Transmission electron microscope (FE-TEM) and BET. In this study, we investigated the phase and microstructural change induced by heat treatment of indium hydroxide nanoparticles at various temperatures for different holding times.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.476-479
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• 2013

$CoSb_3$ with its high electrical conductivity, Seebeck coefficient and rather low thermal conductivity is quite a promising material for thermoelectric conversion applications. A potentially high figure of merit (ZT) can be achieved by a nanostructure evolution of thermoelectric materials. In this work, $CoSb_3$ nanoparticles were synthesized through a thermal decomposition method in cooperation with a hot injection technique. Nano-sized $CoSb_3$ particles were obtained through the thermal decomposition reaction between the pre-heated cobalt-oleate at $320^{\circ}C$ and the injected antimony oleate with room temperature. The results showed that the particle size was increased with increasing synthesis temperature and the crystallinity of particles was improved with temperature but the decomposition of $CoSb_3$ was observed at $320^{\circ}C$. The $CoSb_3$ particles synthesized at $300^{\circ}C$ showed a high purity and an homogeneous shape with average particle size of 26 nm.

• Journal of Surface Science and Engineering
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• v.44 no.3
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• pp.95-104
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• 2011

Ti based nanocomposite films including V, Si and Nb (Ti-Me-N, Me=V, Si and Nb) were fabricated by hybrid physical vapor deposition (PVD) method consisting of unbalanced magnetron (UBM) sputtering and arc ion plating (AIP). The pure Ti target was used for arc ion plating and other metal targets (V, Si and Nb) were used for sputtering process at a gas mixture of Ar/$N_2$ atmosphere. Mostly all of the films were grown with textured TiN (111) plane except the Si doped Ti-Si-N film which has strong (200) peak. The microhardness of each film was measured using the nanoindentation method. The minimum value of removal rate ($0.5{\times}10^{-15}\;m^2/N$) was found at Nb doped Ti-Nb-N film which was composed of Ti-N and Nb-N nanoparticles with small amount of amorphous phases.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.2
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• pp.144-150
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• 2013

Hybrid ceramic membrane (HCM) processes that combined ozonation with a ceramic membrane (CM) or a reactive ceramic membrane (RM), an iron oxide nanoparticles (IONs) incorporated-CM were investigated for membrane fouling control. Alumina disc type microfiltration and ultrafiltration membranes doped with IONs by sintering method were tested under varying mass fraction of IONs. Scanning electron microscope (SEM) images showed that IONs were well-doped on the CM surface and doped IONs were approximately 50 nm in size. Change in the pure water permeability of RM was negligible compared to that of CM. These results indicate that IONs incorporation onto CM had little effect on CM performance in terms of the flux. Natural organic matter (NOM) fouling and fouling recovery patterns during HCM processes confirmed that the RM-ozonation process enhanced the destruction of NOM and reduced the extent of fouling more than the CM-ozonation process by hydroxyl radical formation in the presence of IONs on RM. In addition, analyses of NOM in the feed water and the permeate showed that the efficiency of membrane fouling control results from the NOM degradation during HCM processes; leading to removal and transformation of relatively high contents of aromatic, high molecular weight and hydrophobic NOM fractions.

• Composites Research
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• v.37 no.3
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• pp.209-214
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• 2024

Graphene oxide (GO), known for its high stiffness, thermal conductivity, and electrical conductivity, is being utilized as a reinforcement in nanocomposite materials. This study evaluates the mechanical properties of epoxy nanocomposites incorporating GO and edge modified GO (E-GO), which has hydroxyl groups substituted only on its edges. GO/E-GO was uniformly dispersed in epoxy resin using ultrasonic dispersion, and mechanical properties were assessed through tensile testing. The results showed that the addition of nanoparticles increased both tensile strength and toughness. The tensile strength of the epoxy without nanoparticles was 74.4 MPa, while the highest tensile strength of 90.7 MPa was observed with 0.3 wt% E-GO. Additionally, the modulus increased from 2.55 GPa to 3.53 GPa with the addition of nanoparticles. Field emission scanning electron microscopy of the fracture surface revealed that the growth of cracks was impeded by the nanoparticles, preventing complete fracture and causing the cracks to split in multiple directions. E-GO, with surface treatment only on the edges, exhibited higher mechanical properties than GO due to its superior dispersion and surface treatment effects. These results highlight the importance of nanoparticle surface treatment in developing high-performance nanocomposite materials.

• CELLMED
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• v.6 no.4
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• pp.23.1-23.6
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• 2016

With the rapid developments in nanotechnology, an increasing number of nanomaterials have been applied in various aspects of our lives. Recently, pharmaceutical nanotechnology with numerous advantages has growingly attracted the attention of many researchers. Zinc oxide nanoparticles (ZnO-NPs) are nanomaterials that are widely used in many fields including diagnostics, therapeutics, drug-delivery systems, electronics, cosmetics, sunscreens, coatings, ceramic products, paints, and food additives, due to their magnetic, catalytic, semiconducting, anti-cancer, anti-bacterial, anti-inflammatory, ultraviolet-protective, and binding properties. The present review focused on the recent research works concerning role of ZnO-NP on inflammation. Several studies have reported that ZnO-NP induces inflammatory reaction through the generation of reactive oxygen species by oxidative stress and production of inflammatory cytokines by activation of nuclear factor-${\kappa}B$ ($NF-{\kappa}B$). Meanwhile, other researchers reported that ZnO-NP exhibits an anti-inflammatory effect by inhibiting the up-regulation of inflammatory cytokines and the activation of $NF-{\kappa}B$, caspase-1, $I{\kappa}B$ $kinase{\beta}$, receptor interacting protein2, and extracellular signal-regulated kinase. Previous studies reported that size and shape of nanoparticles, surfactants used for nanoparticles protection, medium, and experimental conditions can also affect cellular signal pathway. This review indicated that the anti-inflammatory effectiveness of ZnO-NP was determined by the nanoparticle size as well as various experimental conditions. Therefore, the author suggests that pharmaceutical therapy with the ZnO-NP is one of the possible strategies to overcome the inflammatory reactions. However, further studies should be performed to maximize the anti-inflammatory effect of ZnO-NP to apply as a potential agent in biomedical applications.

• Journal of the Korean Ceramic Society
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• v.49 no.4
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• pp.352-362
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• 2012

This paper explores the use of a variety of carbon nanoparticles to impart electrical, thermal conductivity, good frictional properties to silicon nitride matrices. We used the highly promising types of carbon as carbon nanotubes, exfoliated graphene and carbon black nanograins. A high-efficiency attritor mill has also been used for proper dispersion of second phases in the matrix. The sintered silicon nitride composites retained the mechanical robustness of the original systems. Bending strength as high as 700 MPa was maintained and an electrical conductivity of 10 S/m was achieved in the case of 3 wt% multiwall carbon nanotube addition. Electrically conductive silicon nitride ceramics were realized by using carbon nanophases. Examples of these systems, methods of fabrication, electrical percolation, mechanical, thermal and tribological properties are discussed.