• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.683-686
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• 1995

Using by the x-ray diffractometry(XRD), the thermomagnetic analysis(TMA), a scanning electron microscopy (SEM-EDX), we knew that the $(Sm_{0.5}RE_{0.5})Fe_{11}Ti$ (RE=Ce,Pr,Nd,Sm,Gd,Tb) compounds were formed to tetragonal $ThMn_{12}$-type structure having a uniaxial magnetocrystalline anisotropy with easy magnetization c-axis. The intrinsic magnetic properties of those were determined by fitting the two magnetization curves of experimental and calculation magnetization. The anisotropy constant $K_{1}$ of this compounds was in the range of $1.75\;-\;9.2\;MJ/m^{3}$ and approximately one order higher than $K_{2}$. $SmFe_{11}Ti$ had the highest anisotropy of $K_{1}\;=\;9.2\;MJ/m^{3}$, $K_{2}\;=\;0.4\;MJ/m^{3}$ and ${\mu}_{o}H_{A}=\;19.8\;T$ among the compounds, substitution of any other rare earth elements for Sm decreased magnetocrystalline anisotropy.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.792-799
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• 2019

The present study aims to investigate the fluorination of thorium oxide ($ThO_2$) by ammonium hydrogen difluoride ($NH_4HF_2$). Fluorination was performed at room temperature by mixing $ThO_2$ and $NH_4HF_2$ at different molar ratios, which was then left to react for 20 days. Next, the mixtures were analyzed using X-ray diffraction (XRD) at the intervals of 5, 10, 15, and 20 days, followed by the heating of the mixtures at $450-750^{\circ}C$ with argon gas flow. The characterization of $ThF_4$ was established using X-ray diffraction (XRD) and scanning electron microscopy-dispersion X-ray spectroscopy (SEM-EDX). In this study, ammonium thorium fluoride was synthesized through the fluorination of $ThO_2$ at room temperature. The optimum molar ratio in synthesizing ammonium thorium fluoride was 1.0:5.5 ($ThO_2:NH_4HF_2$) with 5 days reaction time. In addition, the heating of ammonium thorium fluoride at $450^{\circ}C$ was sufficient to produce $ThF_4$. Overall, this study proved that $NH_4HF_2$ is one of the fluorination agents that is capable of synthesizing $ThF_4$.

• Geomechanics and Engineering
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• v.19 no.1
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• pp.21-28
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• 2019

Use of cement in stabilizing the sulfate-bearing clay soils forms ettringite/ thaumasite in the presence of moisture leads to excessive swelling and causes damages to structures built on them. The development and use of non-traditional stabilisers such as alkali activated ground granulated blast-furnace slag (AGGBS) and enzyme for soil stabilisation is recommended because of its lower cost and the non detrimental effects on the environment. The objective of the study is to investigate the effectiveness of AGGBS and enzyme on improving the volume change properties of sulfate bearing soil as compared to ordinary Portland cement (OPC). The soil for present study has been collected from Tilda, Chhattisgarh, India and 5000 ppm of sodium sulfate has been added. Various dosages of the selected stabilizers have been used and the effect on plasticity index, differential swell index and swelling pressure has been evaluated. XRD, SEM and EDX were also done on the untreated and treated soil for identifying the mineralogical and microstructural changes. The tests results show that the AGGBS and enzyme treated soil reduces swelling and plasticity characteristics whereas OPC treated soil shows an increase in swelling behaviour. It is observed that the swell pressure of the OPC-treated sulfate bearing soil became 1.5 times higher than that of the OPC treated non-sulfate soil.

• Advances in nano research
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• v.7 no.3
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• pp.169-180
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• 2019

Plasmonic effects of gold and platinum alloy nanoparticles (Au-Pt NPs) and their comparison to size was studied. Various factors including ratios of gold and platinum salt, temperature, pH and time of addition of reducing agent were studied for their effect on particle size. The size of gold and platinum alloy nanoparticles increases with increasing concentration of Pt NPs. Temperature dependent synthesis of gold and platinum alloy nanoparticles shows decrease in size at higher temperature while at lower temperature agglomeration occurs. For pH dependent synthesis of Au-Pt nanoparticles, size was found to be increased by increase in pH from 4 to 10. Increasing the time of addition of reducing agent for synthesis of pure and gold-platinum alloy nanoparticles shows gradual increase in size as well as increase in heterogeneity of nanoparticles. The size and elemental analysis of Au-Pt nanoparticles were characterized by UV-Vis spectroscopy, XRD, SEM and EDX techniques.

• Journal of the Korean Wood Science and Technology
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• v.47 no.1
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• pp.110-123
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• 2019

This work was conducted to examine the relationship between lignin content and the durability of larch (LAR) pellets. LAR sawdust was immersed in tap water (TW), sulfuric acid (AC) and sodium hydroxide (AK) solutions, and then the immersed sawdust was used for pellet fabrication. Klason lignin (KL) content of the immersed LAR, contents of soluble lignin (SL) and monomeric sugars liberated from the immersion of LAR, and durability of LAR pellets were measured. KL content decreased as the concentration of AC and AK solutions increased, but glucose content increased with increase in AC and AK concentration. Durability of wood pellets fabricated using non-immersed LAR sawdust was the highest, followed by those made using TW-, AK- and AC-immersed sawdust. LAR pellets became more durable as the concentration of KL and SL increased, but a significant positive correlation was found only between pellet durability and KL content. Through the fluorescent microscopic observation and SEM-EDX analysis, it was verified that lignin content of non-immersed LAR pellets was higher than that of AC- and AK-immersed LAR pellets. These results suggest that lignin might contribute to an increase in inter-particle bonding in wood pellets.

• Korean Journal of Materials Research
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• v.31 no.8
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• pp.450-457
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• 2021

From measured thermal conductivity and modeling by simulation, this study suggests that U-factors are highly related to materials used between steel and polymer. The objective and prospective point of this study are to relate the relationship between the U-factor and the thermal conductivity of the materials used. For the characterization, EDX, SEM, a thermal conductive meter, and computer simulation utility are used to analyze the elemental, surface structural properties, and U-factor with a simulation of the used material between steel and polymer. This study set out to divide the curtain wall system that makes up the envelope into an aluminum frame section and entrance frame section and interpret their thermal performance with U-factors. Based on the U-factor thermal analysis results, the target curtain wall system is divided into fix and vent types. The glass is 24 mm double glazing (6 mm common glass +12 mm Argon +6 mm Low E). The same U-factor of 1.45 W/m²·K is applied. The interpretation results show that the U-factor and total U-value of the aluminum frame section are 1.449 and 2.343 W/m²·K, respectively. Meanwhile, those of the entrance frame section are 1.449 and 2.

• Tribology and Lubricants
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• v.37 no.5
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• pp.179-188
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• 2021

Reputed for their low friction coefficient and wear protection effect, diamond-like carbon (DLC) materials are considered amongst the most important lubricant coatings for tribological applications. In this framework, this investigation aims to elucidate the effect of a few operating parameters, such as applied stress and sliding amplitude on the friction lifetime of DLC coatings. Fretting wear tests are conducted using a 12.7 mm radius counterpart of 52100 steel balls slid against a substrate of the same material coated with a 2 ㎛ thickness DLC. Approximately, 5 to 57 N force is applied, generating a maximum Hertzian contact pressure of 430 to 662 MPa, corresponding to the applied force. The coefficient of friction (CoF) generates three regimes, first a running-in period regime, followed by a steady-state evolution regime, and finally a progressive increase of the CoF reaching the steel CoF value, as an indicator of reaching the substrate. To track the wear scenario, interrupted tests are performed with analysis combining scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), 3D profilometer and micro-Raman spectroscopy. The results show two endurance values: one characterizing the coating failure (Nc₁), and the other (Nc₂) indicating the friction failure which is situated where the CoF reaches a threshold value of μ_th = 0.3 in the third regime. The Archard energy density factor is used to determine the two endurance values (Nc₁, Nc₂). Based on this approach, a master curve is established delimitating both the coating and the friction endurances.

• Korean Journal of Metals and Materials
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• v.49 no.8
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• pp.619-627
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• 2011

The poisoning effect of Zr in aluminum alloys was investigated by analyzing the filtered cakes of aluminum alloy melt taken with the $Prefil^{(R)}$ footprinter through a variety of analytic instruments, SEM/EDX, Auger, and TEM. Experimental results indicated that the morphology and chemical composition of the aluminum alloys were not modified with the addition of Zr, which is to previous belief that Zr poisoning is caused by modification of $(Ti_{1-x}Zr_x)Al_3$. On the other hand, $TiAl_3$ surroundig $TiB_2$ particles was modified and its lattice parameter was more mismatched by increasing Zr content, leading to less nucleation rate. This is also supported by the observation that the poisoning effect is reduced when Ti is added, resulting in a lower content ratio of Zr to Ti. These results suggest that extra Ti should be added to eliminate the poisoning effect of Zr in aluminum alloys containing Zr.

• Journal of Ceramic Processing Research
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• v.19 no.6
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• pp.492-498
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• 2018

In this study, a sea shell was converted into bioceramic phases at three different sintering temperatures ($450^{\circ}C$, $850^{\circ}C$, $1000^{\circ}C$). Among the obtained bioceramic phases, a valuable ${\beta}-TCP$ was produced via mechanochemical conversion method from sea snail Turritella terebra at $1000^{\circ}C$ sintering temperature. For this reason, only the bioceramic sintered at $1000^{\circ}C$ was concentrated on and FT-IR, SEM/EDX, BET, XRD, ICP-OES analyses were carried out for the complete characterization of ${\beta}-TCP$ phase. Biodegradation test in Tris-buffer solution, bioactivity tests in simulated body fluid (SBF) and cell studies were conducted. Bioactivity test results were promising and high rate of cell viability was observed in MTT assay after 24 hours and 7 days incubation. Results demonstrated that the produced ${\beta}-TCP$ bioceramic is qualified for further consideration and experimentation with its features of pore size and ability to support bone tissue growth and cell proliferation. This study suggests an easy, economic method of nanobioceramic production.

• Korean Journal of Materials Research
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• v.30 no.12
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• pp.641-649
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• 2020

A facile microwave assisted solvothermal process is designed for fabricating SnS nanoparticles decorated on graphene nanosheet, which used as visible light driven photocatalyst. Some typical characterization techniques such as XRD, FT-IR, SEM with EDX analysis, and TEM and BET analysis are used to analyse the physical characteristics of as-prepared samples. Spherical SnS nanoparticles are uniformly dispersed on the surface of graphene nanosheet due to ammonia, which can prevent the aggregation of graphene oxide. Meanwhile, microwave radiation provides fast energy that promotes the formation of spherical SnS nanoparticles within a short time. The visible light photocatalytic activity of as-prepared SnS-GR nanocomposites is analysed through photodegradation efficiency of methylene blue with high concentration. According to the higher photocatalytic property, the as-prepared SnS-GR nanocomposites can be expected to be an efficient visible light driven photocatalyst. After five cycles for decolorization, the rate decreases from 87 % to 78 % (about 9 %). It is obvious that the photocatalytic activity of SnS-GR nanocomposite has good repeatability.