• Advances in nano research
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• 제16권1호
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• pp.53-69
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• 2024

Advancements in the technology of building materials has led to diverse applications of nanomaterials with the aim to monitor concrete structures. While there are myriad instances of the use of nanoparticles in building materials, the production of smart nano cement-composites is often expensive. Thereupon, this research aims to discover a sustainable nanomaterial from tyre waste using the pyrolysis process as part of the green manufacturing circle. Here, Nano Structure Tyre-Char (NSTC) is introduced as a zero-dimension carbon-based nanoparticle. The NSTC particles were characterized using various standard characterization techniques. Several salient results for the NSTC particles were obtained using microscopic and spectroscopic techniques. The size of the particles as well as that of the agglomerates were reduced significantly using the milling process and the results were validated through a scanning electron microscope. The crystallite size and crystallinity were found to be ~35nm and 10.42%, respectively. The direct bandgap value of 5.93eV and good optical conductivity at 786 nm were obtained from the ultra violet visible spectroscopy measurements. The thermal analysis reveals the presence of a substantial amount of carbon, the rate of maximum weight loss, and the two stages of phase transformation. The FT-Raman confirms the presence of carboxyl groups and a ID/IG ratio of 0.83. Water contact angle around 140° on the surface implies the highly hydrophobic nature of the material and its low surface energy. This characteristic process assists to obtain a sustainable nanomaterial from waste tyres, contributing to the development of a smart building material.

• Structural Engineering and Mechanics
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• 제53권3호
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• pp.497-517
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• 2015

In this study, nonlocal nonlinear buckling analysis of embedded polymeric temperature-dependent microplates resting on an elastic matrix as orthotropic temperature-dependent elastomeric medium is investigated. The microplate is reinforced by single-walled carbon nanotubes (SWCNTs) in which the equivalent material properties nanocomposite are estimated based on the rule of mixture. For the carbon-nanotube reinforced composite (CNTRC) plate, both cases of uniform distribution (UD) and functionally graded (FG) distribution patterns of SWCNT reinforcements are considered. The small size effects of microplate are considered based on Eringen's nonlocal theory. Based on orthotropic Mindlin plate theory along with von K$\acute{a}$rm$\acute{a}$n geometric nonlinearity and Hamilton's principle, the governing equations are derived. Generalized differential quadrature method (GDQM) is applied for obtaining the buckling load of system. The effects of different parameters such as nonlocal parameters, volume fractions of SWCNTs, distribution type of SWCNTs in polymer, elastomeric medium, aspect ratio, boundary condition, orientation of foundation orthtotropy direction and temperature are considered on the nonlinear buckling of the microplate. Results indicate that CNT distribution close to top and bottom are more efficient than those distributed nearby the mid-plane for increasing the buckling load.

• Advances in materials Research
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• 제7권1호
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• pp.17-28
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• 2018

Niobium is a candidate base for new alloys devoted to applications at especially elevated temperatures. Elaborating and shaping niobium-based alloys by conventional foundry may lead to mechanically interesting microstructures. In this work a series of charges constituted of pure elements were subjected to high frequency induction melting in cold crucible to try obtaining cast highly refractory Nb-xCr and Nb-xCr-0.4 wt.%Calloys(x=27, 34 and 37 wt.%). Melting and solidification were successfully achieved. The as-cast microstructures of the obtained alloys were characterized by electron microscopy and X-ray diffraction and their hardness were specified by Vickers macro-indentation. The obtained as-cast microstructures are composed of a body centered cubic (bcc) niobium dendritic matrix and of an interdendritic eutectic compound involving the bcc Nb phase and a $NbCr_2$ Laves phase. The obtained alloys are hard to cut and particularly brittle at room temperature. Hardness is of a high level (higher than 600Hv) and is directly driven by the chromium content or the amount of {bcc Nb - $NbCr_2$} eutectic compound. Adding 0.4 wt.% of carbon did not lead to carbides but tends to increase hardness.

• 한국물환경학회지
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• 제37권5호
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• pp.355-362
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• 2021

This study investigated the fate of dissolved organic matter (DOM) in a water reclamation facility (WRF) in Korea. The WRF consists of coagulation, sedimentation, microfiltration, and reverse osmosis (RO) components. The production capacity of WRF is 90,000 m³/day. The reclaimed water is reused as industrial water. We also characterized DOM in raw, processed, and finished waters based on analysis of dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm (UVA₂₅₄), fluorescence excitation emission matrix (FEEM), and DOC fractions via liquid chromatography-organic carbon detection (LC-OCD). Based on the results of DOC, UVA₂₅₄, and FEEM analyses, neither the coagulation/sedimentation nor the microfiltration at the WRF effectively removed DOM. The RO process removed more than 94% of DOM. The raw water (i.e., secondary treated effluent obtained from a wastewater treatment plant) exhibited tryptophan-like peaks, which are a promising marker of wastewater, in the FEEM analysis. Coagulation and microfiltration failed to eliminate the wastewater marker, whereas RO completely removed it. The raw water also carried high levels (89.4%) of hydrophilic and low-molecular weight substances, which are difficult to remove via coagulation-sedimentation or microfiltration. Humic substance was a major component of the hydrophilic fractions. Based on the LC-OCD analysis, RO effectively removed the humic and polymeric materials from DOM.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.7-12
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• 2003

When the wind turbine is used in cold regions, the mechanical properties and dimension stability of the blade will be changed. The proposal of this paper is to test the durability of the blade for wind turbine. It is necessary to select the most comfortable materials and fabrication processes for more stable wind turbine blade in cold regions. To select the most comfortable materials and processes, the static strength has to know through the tensile static tests at the severe condition as cold regions. First, the tensile static specimens made by RIM (Resin injection molding) process & vacuum bagging process with reinforcement materials and resin. Tensile static tests were carried out on three laminate lay-ups (carbon prepreg, carbon fiber dry fabric and glass fiber dry fabric) at different test temperature($24^{\circ}$, $-30^{\circ}$), determining properties such as the mechanical strength, stiffness and strain to failure. At different test temperature, in order to test the tensile strengths of these specimens used the low temperature chamber. Next, the results of this test were compared with each other. Finally, the most comfortable materials and fabrication processes can select based on these results. The results show the changes in the static behavior of three laminate lay-ups at different test temperatures. At low temperatures, the static strengths are higher than the ones at room temperature.

• Journal of the Korean Physical Society
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• 제73권10호
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• pp.1437-1443
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• 2018

In this work, $SnO_2$ modified with reduced graphene oxide (rGO) and carbon nanotubes (CNTs) separately and combined sensitized by using the co-precipitation method and their sensing behavior toward ethanol vapor at room temperature were investigated. An interdigitated electrode (IDE) gold substrate is very expensive compared to a fluorine doped tin oxide (FTO) substrate; hence, we used the latter to reduce the fabrication cost. The structure and the morphology of the studied materials were characterized by using differential thermal analyses (DTA) and thermogravimetric analysis (TGA), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller surface area and Barrett-Joyner-Halenda (BJH) pore size measurements. The studied composites were subjected to ethanol in its gas phase at concentrations from 10 to 200 ppm. The present composites showed high-performance sensitivity for many reasons: the incorporation of $SnO_2$ and CNTs which prevents the agglomeration of rGO sheets, the formation of a 3D mesopourus structure and an increase in the surface area. The decoration with rGO and CNTs led to more active sites, such as vacancies, which increased the adsorption of ethanol gas. In addition, the mesopore structure and the nano size of the $SnO_2$ particles allowed an efficient diffusion of gases to the active sites. Based on these results, the present composites should be considered as efficient and low-cost sensors for alcohol.

• 한국표면공학회지
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• 제57권4호
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• pp.265-273
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• 2024

An amperometric sensor for measuring indole-3-acetic acid (IAA) was studied based on a screen-printed carbon electrode (SPCE) coated with a reduced graphene oxide composite electrocatalyst. The PEI-GO dispersion is uniformly formed through a nucleophilic substitution reaction between the active amine group of Polyethyleneimine (PEI) and the epoxide group exposed on the surface of graphene oxide. And The 3-dimensional PEI-rGO AG (Polyethyleneimine-reduced graphene oxide aerogel) complex was easily prepared through simple heat treatment of the combined PEI-GO dispersion. The proposed composite catalyst electrode, PEI-rGO AG/SPCE, showed a two linear relationship in the low and high concentrations in IAA detection, and the linear equation was I_pa = 0.2883C + 0.0883 (R²=0.9230) at low concentration and Ipa = 0.00464C + 0.6623 (R²=0.9894) at high concentration was proposed, and the detection limit was calculated to be 203.5nM±33.2nM. These results showed the applicability of the PEI-rGO AG composite catalyst as an electrode material for electrocatalysts for the detection of IAA.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.16.2-16.2
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• 2011

Graphene has attracted significant attention due to its unique characteristics and promising nanoelectronic device applications. For practical device applications, it is essential to synthesize high-quality and large-area graphene films. Graphene has been synthesized by eloborated mechanical exfoliation of highly oriented pyrolytic graphite, chemical reduction of exfoliated grahene oxide, thermal decomposition of silicon carbide, and chemical vapor deposition (CVD) on metal substrates such as Ni, Cu, Ru etc. The CVD has advantages over some of other methods in terms of mass production on large-areas substrates and it can be easily separated from the metal substrate and transferred to other desired substrates. Especially, plasma-enhanced CVD (PECVD) can be very efficient to synthesize high-quality graphene. Little information is available on the synthesis of graphene by PECVD even though PECVD has been demonstrated to be successful in synthesizing various carbon nanostructures such as carbon nanotubes and nanosheets. In this study, we synthesized graphene on $Ni/SiO_2/Si$ and Cu plate substrates with CH4 diluted in $Ar/H_2$ (10%) by using an inductively-coupled PECVD (ICPCVD). High-quality graphene was synthesized at as low as $700^{\circ}C$ with 600 W of plasma power while graphene layer was not formed without plasma. The growth rate of graphene was so fast that graphene films fully covered on substrate surface just for few seconds $CH_4$ gas supply. The transferred graphene films on glass substrates has a transmittance at 550 nm is higher 94%, indicating 1~3 monolayers of graphene were formed. FETs based on the grapheme films transferred to $Si/SiO_2$ substrates revealed a p-type. We will further discuss the synthesis of graphene and doped graphene by ICPVCD and their characteristics.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.62-62
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• 1999

Carbon based materials have many attractive properties such as a wide band gap, a low electron affinity, and a high chemical and mechanical stability. Therefore, researches on the carbon-based materials as field emitters have been drawn extensively to enhance the field emission properties. Especially, diamond gives high current density, high current stability high thermal conductivity durable for high temperature operation, and low field emission behaviors, Among these properties understanding the origin of low field emission is a key factor for the application of diamond to a filed emitter and the verification of the emission site and its distribution of diamond is helpful to clarify the origin of low field emission from diamond There have been many investigations on the origin of low field emission behavior of diamond crystal or chemical vapor deposition (CVD) diamond films that is intentionally doped or not. However, the origin of the low field emission behavior and the consequent field emission mechanism is still not converged and those may be different between diamond crystal and CVD diamond films as well as the diamond that is doped or not. In addition, there have been no systematic studies on the dependence of nondiamond carbon on the spatial distribution of emission sites and its uniformity. Thus, clarifying a possible mechanism for the low field emission covering the diamond with various properties might be indeed a difficult work. On the other hand, it is believed that electron emission mechanisms of diamond are closely related to the emission sites and its distributions. In this context, it will be helpful to compare the spatial distribution of emission sites and field emission properties of the diamond films prepared by systematic variations of structural property. In this study, we have focused on an understanding of the field emission variations of structural property. In this study, we have focused on an understanding of the field emission mechanism for the CVD grown undoped polycrystalline diamond films with significantly different structural properties. The structural properties of the films were systematically modified by varying the CH4/H2 ratio and/or applying positive substrate bias examined. It was confirmed from the present study that the field emission characteristics are strongly dependent on the nondiamond carbon contents of the undoped polycrystalline diamond films, and a possible field emission mechanism for the undoped polycrystalline diamond films is suggested.

• Korean Chemical Engineering Research
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• 제57권4호
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• pp.539-546
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• 2019

지구온난화가 국제 문제로 언급되면서 온실가스 저감에 관한 연구가 꾸준히 진행되고 있다. 지구온난화의 가속화를 막기 위해 지구온난화의 주된 원인으로 언급되는 이산화탄소 저감에 관한 기술 개발의 중요성이 증가하게 되었고 이로 인해 이산화탄소 포집, 저장 및 재이용기술(CCUS, Carbon Capture, Utilization and Storage)의 발전을 요구하고 있다. 다양한 이산화탄소 포집, 저장 및 재이용기술 중에서 광물탄산화 기술의 경우에는 적은 에너지를 통해 많은 이산화탄소를 고부가가치 물질로 전환할 수 있다. 기존 연구에서는 고형 폐기물에서 이온을 용출해 사용해왔으며 이는 처리 과정이 복잡하다. 하지만 해수를 사용하게 되면 고농도의 금속 양이온이 해수 속에 용해되어 있어 고형 폐기물을 이용할 때보다 공정이 단순하다. 이 연구는 해수담수화 농축수를 금속양이온공급원으로써 사용하기 위한 기초연구로, 3 M 모노에탄올아민(Monoethanolamine, MEA)을 흡수제로 사용하여 이산화탄소를 우선적으로 포집하였다. 또한 해수농축수를 모사하기 위해, 해수모사파우더를 사용하여 다양한 농도의 해수농축수를 제조하였다. 해수농축수와 포집된 이산화탄소 용액을 반응시켜 탄산염을 생성하였으며 이를 XRD (X-ray Diffraction), SEM (Scanning Electron Microscopy), TGA (Thermalgravimetric Analysis)를 통해 탄산염의 생성 경향 및 흡수제의 재이용 가능성을 파악하였다.