• Journal of the Korean Society for Heat Treatment
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• v.34 no.5
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• pp.239-244
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• 2021

Following Silicon Carbide, single crystal diamond continues to attract attention as a next-generation semiconductor substrate material. In addition to excellent physical properties, large area and productivity are very important for semiconductor substrate materials. Research on the increase in area and productivity of single crystal diamonds has been carried out using various devices such as HPHT (High Pressure High Temperature) and MPECVD (Microwave Plasma Enhanced Chemical Vapor Deposition). We hit the limits of growth rate and internal defects. However, HFCVD (Hot Filament Chemical Vapor Deposition) can be replaced due to the previous problem. In this study, HFCVD confirmed the distance between the substrate and the filament, the accompanying growth rate, the surface shape, and the Raman shift of the substrate after vapor deposition according to the vapor deposition temperature change. As a result, it was confirmed that the difference in the growth rate of the single crystal substrate due to the change in the vapor deposition temperature was gained up to 5 times, and that as the vapor deposition temperature increased, a large amount of polycrystalline diamond tended to be generated on the surface.

• Resources Recycling
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• v.27 no.6
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• pp.38-43
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• 2018

In this study, using electro-refining process and methane gas reduction, we performed studying the recovery of tin with high purity from waste tin oxide had used as a electrode rod of ceramic furnace which occurred during glass production process. We recovered the crude tin of 99% purity from a methane gas reduction process and controlled a little amount of impurities. When the electrolytic refining condition was a current density of $60A/dm^2$ and the sulfuric acid concentration of 0.75 mol, 96.8% of recovered tin (99.979% of purity) were recovered during the electrolytic refining. We confirmed that toxic impurities such as Pb, Sb included in electrode rod. could be controlled.

• Advances in concrete construction
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• v.8 no.1
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• pp.65-76
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• 2019

This paper investigates the effect of recycled glass powder (RGP) on flowing properties of self-compacting mortars (SCMs) containing different ratios of fillers and superplasticizer dosages. Fly ash (FA), nano-silica (NS), micro-silica (MS), metakaolin (MK) and rice husk ash (RHA) are used as fillers and their synergistic effect with RFP is studied. The effects of fillers and high-range water reducer (HRWR) on flowing ability of mortars are primarily determined by slump flow and V-funnel flow time tests. The results showed that for composites with a higher RGP content, the mortar flowing ability increased but tended to decrease when the composites containing 10% MK or 5% RHA. However, the flowing ability of samples incorporating 5% RGP and 10% SF or 25% FA showed an opposite result that their slump flow spread decreased and then increased with increasing RGP content. For specimens with 3% NS, the influence of RGP content on flowing properties was not significant. Except RHA and MS, the fillers studied in this paper could reduce the dosage of HRWR required for achieving the same followability. Also, the mixture parameters were determined and indicated that the flowability of mixtures was also affected by the content of sand and specific surface area of cement materials. It is believed that excess fine particles provided ball-bearing effect, which could facilitate the movement of coarse particles and alleviate the interlocking action among particles. Also, it can be concluded that using fillers in conjunction with RGP as cementitious materials can reduce the material costs of SCM significantly.

• Advances in nano research
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• v.7 no.3
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• pp.209-221
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• 2019

Graphene, with impressive electronic properties, have high potential in the microelectronic field. However, graphene itself is a zero bandgap material which is not suitable for digital logic gates and its application. Thus, much focus is on graphene nanoribbons (GNRs) that are narrow strips of graphene. During GNRs fabrication process, the occurrence of defects that ultimately change electronic properties of graphene is difficult to avoid. The modelling of GNRs with defects is crucial to study the non-idealities effects. In this work, nearest-neighbor tight-binding (TB) model for GNRs is presented with three main simplifying assumptions. They are utilization of basis function, Hamiltonian operator discretization and plane wave approximation. Two major edges of GNRs, armchair-edged GNRs (AGNRs) and zigzag-edged GNRs (ZGNRs) are explored. With single vacancy (SV) defects, the components within the Hamiltonian operator are transformed due to the disappearance of tight-binding energies around the missing carbon atoms in GNRs. The size of the lattices namely width and length are varied and studied. Non-equilibrium Green's function (NEGF) formalism is employed to obtain the electronics structure namely band structure and density of states (DOS) and all simulation is implemented in MATLAB. The band structure and DOS plot are then compared between pristine and defected GNRs under varying length and width of GNRs. It is revealed that there are clear distinctions between band structure, numerical DOS and Green's function DOS of pristine and defective GNRs.

• Advances in nano research
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• v.7 no.5
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• pp.293-310
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• 2019

In this paper, thermal-buckling behavior of the functionally graded (FG) nanocomposite plates reinforced with graphene oxide powder (GOP) is studied under three types of thermal loading once the plate is supposed to be rested on a two-parameter elastic foundation. The effective material properties of the nanocomposite plate are considered to be graded continuously through the thickness according to the Halpin-Tsai micromechanical scheme. Four types of GOPs' distribution namely uniform (U), X, V and O, are considered in a comparative way in order to find out the most efficient model of GOPs' distribution for the purpose of improving the stability limit of the structure. The governing equations of the plate have been derived based on a refined higher-order shear deformation plate theory incorporated with Hamilton's principle and solved analytically via Navier's solution for a simply supported GOP reinforced (GOPR) nanocomposite plate. Some new results are obtained by applying different thermal loadings to the plate according to the GOPs' negative coefficient of thermal expansion and considering both Winkler-type and Pasternak-type foundation models. Besides, detailed parametric studies have been carried out to reveal the influences of the different types of thermal loading, weight fraction of GOP, aspect and length-to-thickness ratios, distribution type, elastic foundation constants and so on, on the critical buckling load of nanocomposite plates. Moreover, the effects of thermal loadings with various types of temperature rise are investigated comparatively according to the graphical results. It is explicitly shown that the buckling behavior of an FG nanocomposite plate is significantly influenced by these effects.

• Computers and Concrete
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• v.24 no.2
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• pp.125-135
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• 2019

Concrete pipelines are the most efficient and safe means for gas and oil transportation over a long distance. The use of nano materials and nono-engineering can be considered for enhancing concrete pipelines properties. the tests show that SiO2 nanoparticles can improve the mechanical behavior of concrete. Moreover, severe hazard for pipelines is seismic ground motion. Over the years, scientists have attempted to understand pipe behavior against earthquake most frequently via numerical modeling and simulation. Therefore, in this paper, the dynamic response of underwater nanocomposite submerged pipeline conveying fluid is studied. The structure is subjected to the dynamic loads caused by earthquake and the governing equations of the system are derived using mathematical model via Classic shell theory and Hamilton's principle. Navier-Stokes equation is employed to calculate the force due to the fluid in the pipe. As well, the effect of external fluid is modeled with an external force. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite. 1978 Tabas earthquake in Iran is considered for modelling seismic load. The dynamic displacement of the structure is extracted using differential quadrature method (DQM) and Newmark method. The effects of different parameters such as SiO2 nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios, internal and external fluid pressure and earthquake intensity are discussed on the seismic response of the structure. From results obtained in this paper, it can be found that the dynamic response of the pipe is increased in the presence of internal and external fluid. Furthermore, the use of SiO2 nanoparticles in concrete pipeline reduces the displacement of the structure during an earthquake.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.27 no.2
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• pp.55-62
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• 2021

This study aims to reduce the rancid odor generated during the fermentation process of kimchi by inserting zinc oxide (ZnO) into an inorganic porous material with a high surface area to decompose or adsorb the fermentation odor. ZnO activated by the presence of moisture exhibits decomposition of rancid odors. Mixed with Titanium dioxide (TiO₂), a photocatalyst. To manufacture the packaging liner used in this study, NaOH, ZnCl₂, and TiO₂ powder were placed in a tank with diatomite and water. The sludge obtained via a hydrothermal ultrasonication synthesis was sintered in an oven. After being pin-milled and melt-blended, the powders were mixed with linear low-density polyethylene (L-LDPE) to make a masterbatch (M/B), which was further used to manufacture liners. A gas detector (GasTiger 2000) was used to investigate the total amount of sulfur compounds during fermentation and determine the reduction rate of the odor-causing compounds. The packaging liner cross-section and surface were investigated using a scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDS) to observe the adsorption of sulfur compounds. A variety of sulfur compounds associated with the perceived unpleasant odor of kimchi were analyzed using gas chromatography-mass spectrometry (GC-MS). For the analyses, kimchi was homogenized at room temperature and divided into several sample dishes. The performance of the liner was evaluated by comparing the total area of the GC-MS signals of major off-flavor sulfur compounds during the five days of fermentation at 20℃. As a result, Nano-grade inorganic compound liners reduced the sulfur content by 67 % on average, compared to ordinary polyethylene (PE) foam liners. Afterwards SEM-EDS was used to analyze the sulfur content adsorbed by the liners. The findings of this study strongly suggest that decomposition and adsorption of the odor-generating compounds occur more effectively in the newly-developed inorganic nanocomposite liners.

• Journal of Korean Society on Water Environment
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• v.27 no.1
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• pp.98-103
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• 2011

Photocatalysis using UV light and catalysts is an attractive low temperature and non-energy- intensive method for remediation of a wide range of chemical contaminants like chloroform (CF). Recently development of environmental friendly and sustainable catalytic systems is needed before such catalysts can be routinely applied to large-scale remediation or drinking water treatment. Titanium dioxide is a candidate material, since it is stable, highly reactive, and inexpensive. Diatoms are photosynthetic, single-celled algae that make a microscale silica shell with nano scale features. These diatoms have an ability to biologically fabricate $TiO_2$ nanoparticles into this shell in a process that parallels nanoscale silica mineralization. We cultivated diatoms, metabolically deposited titanium into the shell by using a two-stage photobioreactor and used this biogenic $TiO_2$ to this study. In this study we evaluated how effectively biogenic $TiO_2$ nanoparticles transform CF compared with chemically-synthesized $TiO_2$ nanoparticlesthe and effect of pretreatment of diatom-produced $TiO_2$ nanoparticles on photocatalytic transformation of CF. The rate of CF transformation by diatom-$TiO_2$ particles is a factor of 3 slower than chemically-synthesized one and chloride ion production was also co-related with CF transformation, and 79~91% of CF mineralization was observed in two $TiO_2$ particles. And the period of sonication and mass transfer due to particle size, evaluated by difference of oxygen tention does not affect on the CF transformation. Based on the XRD analysis we conclude that slower CF transformation by diatom-$TiO_2$ might be due to incomplete annealing to the anatase form.

• Applied Chemistry for Engineering
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• v.22 no.2
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• pp.230-234
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• 2011

In this work, the primary material for a single layered hardmask which can afford a spin-on process was prepared by the minture of organic and inorganic sources. The preparation of hybrid polymer was attempted by esterification from silanol terminated siloxane compounds and acetonide-2,2-bis(methoxy)propionic acid. The optical, thermal and morphological properties of the test hardmask film was examined in terms of cross-linking agent and additives. In addition, the etch rate of hardmask film and photo resist layer were compared. The hybrid polymer prepared from organic and inorganic materials was found to be useful for hardmask film to form the nano-patterns.

• Journal of the Korean Physical Society
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• v.73 no.12
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• pp.1863-1866
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• 2018

The sodium-iron phosphate maricite-$NaFe_{0.9}Mn_{0.1}PO_4$ was synthesized using the ball mill method. The crystal structure and magnetic properties of the prepared materials were studied using X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and $M{\ddot{o}}ssbauer$ spectroscopy. Structural refinement of maricite-$NaFe_{0.9}Mn_{0.1}PO_4$ was analyzed using the FullProf program. From the XRD patterns, the crystal structure of maricite-$NaFe_{0.9}Mn_{0.1}PO_4$ was found to be orthorhombic with the space group Pmnb. The lattice parameters of maricite-$NaFe_{0.9}Mn_{0.1}PO_4$ are as follows: $a_0=6.866{\AA}$, $b_0=8.988{\AA}$, $c_0=5.047{\AA}$, and $V=311.544{\AA}^3$. Maricite-$NaFePO_4$ has an edge-sharing structure that consists of $FeO_6$ octahedral. Under an applied field of 100 Oe, the temperature dependences of zero-field-cooled (ZFC) and field-cooled (FC) curves were measured from 4.2 to 295 K. $M{\ddot{o}}ssbauer$ spectra were also recorded at various temperatures ranging from 4.2 to 295 K. We thus confirmed that the $N{\acute{e}}el$ temperature of $NaFe_{0.9}Mn_{0.1}PO_4$ ($T_N=14K$) was lower than that of maricite-$NaFePO_4$ ($T_N=15K$).