• Journal of the Korean Ceramic Society
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• v.48 no.1
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• pp.74-79
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• 2011

The pore generation technology using GHM (Glass Hollow Microsphere) was studied in order to reduce the weights of porcelain. In this study, we verify the property of modified slurry by adding GHM. The modified slurry was prepared by adding 1.0~2.5 wt%(K1), 1.0~6.0 wt%(K37) of GHM to the slurry for porcelain. The slurry viscosity were stable inside a content range of 1.0~2.5 wt%(K1), 1.0~6.0 wt%(K37). However, the viscosity of modified slurry increased more than 3.0 wt%(K1) and 6.5 wt%(K37). The formed specimen by slip casting was fired at $1229^{\circ}C$, $1254^{\circ}C$. As the amount of GHM content increased, the weight decreased and the addition of 1.0~2.5 wt%(K1), 1.0~6.0 wt%(K37) of GHM resulted in a weight drop of 30%(K1) and 25(K37). However, when the GHM content increased, the strength decreases over 70%. This is caused by the presence of a large volume of surface defects (pores) and defects from the agglomeration of GHM.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.4
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• pp.79-83
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• 2021

In this study, hollow silica microspheres (HSM) of various sizes formed according to the concentration of surfactants using water glass as a precursor, which is advantageous for commercialization due to its lower unit cost compared to conventional silicon alkoxide (tetraethyl orthosilicate, TEOS) was synthesized. The physical properties of the silica hollow microspheres according to the concentration of surfactant were analyzed using Fourier transform infrared, contact angle measurement, Brunauer-Emmett-Teller and Barrett-Joyner-Halenda analyzers and field emission scanning electron microscopy. When porous water glass-based hollow silica spheres were prepared by adding a surfactant at an appropriate concentration, it was confirmed that excellent hollow silica spheres were formed with a specific surface area of 169 m²/g, an average particle size of 25.3 ㎛, and a standard deviation of 6.25.

• Progress in Superconductivity and Cryogenics
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• v.16 no.1
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• pp.36-41
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• 2014

Since glass microsphere has high crush strength, low density and small particle size, it becomes alternative thermal insulation material for cryogenic systems, such as storage and transportation tank for cryogenic fluids. Although many experiments have been performed to verify the effective thermal conductivity of microsphere, prediction by calculation is still inaccurate due to the complicated geometries, including wide range of powder diameter distribution and different pore sizes. The accurate effective thermal conductivity model for microsphere is discussed in this paper. There are four mechanisms which contribute to the heat transfer of the evacuated powder: gaseous conduction ($k_g$), solid conduction ($k_s$), radiation ($k_r$) and thermal contact ($k_c$). Among these components, $k_g$ and $k_s$ were calculated by Zehner and Schlunder model (1970). Other component values for $k_c$ and $k_r$, which were obtained from experimental data under high vacuum conditions were added. In this research paper, the geometry of microsphere was simplified as a homogeneous solid sphere. The calculation results were compared with previous experimental data by R. Wawryk (1988), H. S. Kim (2010) and the experiment of this paper to show good agreement within error of 46%, 4.6% and 17 % for each result.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.258-259
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• 2014

Modern concrete high safety, constructability and economy due to advantages such as buildings used for more than about 70%, but due to the low thermal performance is essential, such as installation of additional insulation is required, and therefore increase the cost of construction, as well as the construction period and condensation Symptoms such as a domestic environment, such as to inhibit the problem by generating such an improvement has been desired. In this study, we want to present the base line data for the development of improved insulation performance concrete with analyzing and evaluating the Durable Properties of the concrete combination of hollow glass microsphere and lightweight aggregate.

• Journal of Powder Materials
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• v.29 no.6
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• pp.505-510
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• 2022

The thermal shock resistance of cement composites with hollow glass microspheres (HGM) is investigated. Cement composites containing various concentrations of HGM are prepared and their properties studied. The density, thermal conductivity, and coefficient of thermal expansion of the composites decrease with increasing HGM concentration. A thermal shock test is performed by cycling between -60 and 50℃. After the thermal shock test, the compressive strength of the cement composite without HGM decreases by 28.4%, whereas the compressive strength of the cement composite with 30 wt% HGM decreases by 5.7%. This confirms that the thermal shock resistance of cement is improved by the incorporation of HGM. This effect is attributed to the reduction of the thermal conductivity and coefficient of thermal expansion of the cement composite because of the incorporation of HGM, thereby reducing the occurrence of defects due to external temperature changes.

• The Korean Journal of Nuclear Medicine Technology
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• v.23 no.1
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• pp.50-53
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• 2019

Purpose Yttrium-90 (Y-90) is high-energy beta emitters ($E{\beta}$, max = 2.28 MeV) with the mean penetration depth of 2.5 mm in tissue. Radioactive microspheres containing Y-90 is widely used for the transarterial radioembolization of hepatocellular carcinoma. However, bremsstrahlung radiation from Y-90 can cause the external radiation exposure to medical staff who handle the Y-90 microspheres. In this study, shielding device for Y-90 microspheres was developed to minimize the external radiation exposure. Materials and Methods Y-90 microsphere shielding device was made from 6 mm thicknesses of tungsten including the lead glass window. Radiation shielding ability of Y-90 microsphere shielding device was evaluated using 4 GBq of $SIR-Spheres^{(R)}$ Y-90 microspheres. The bremsstrahlung radiation was measured using radiation survey meter. Results The mean radiation dose of Y-90 microspheres in acrylic shield was $261.7{\pm}2.3{\mu}Sv/h$ (n=5) at 10 cm away from the shield. With the additional tungsten shielding device, it was $23.7{\pm}1.3{\mu}Sv/h$ (n=5). Thus, the bremsstrahlung radiation dose was decreased by 90.9%. At 50 cm away from the shield, bremsstrahlung radiation was reduced by 89.2% after using tungsten shielding device. Conclusion During the preparation and radioembolization of Y-90 microsphere, medical staff are exposed to external radiation. In this study, we demonstrated that the use of tungsten shielding device devices significantly reduced the amount of bremsstrahlung radiation. Y-90 microsphere tungsten shielding device can be highly effective in reducing the bremsstrahlung radiation.

• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.99-113
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• 2017

The effects of different lightweight functional fillers on the properties of cement-based composites are investigated in this study. The fillers include fly ash cenospheres (FACs) and glass micro-spheres (GMS15 and GMS38) in various proportions. The developed composites were tested for compressive, flexural and tensile strengths at 10 and 28-day ages. The results indicated that both FACs and GMS38 are excellent candidates for producing strong lightweight composites. However, incorporation of GMS15 resulted in much lower specific strength values (only up to $13.64kPa/kg\;m^3$) due to its thinner shell thickness and lower isostatic crushing strength value (2.07 MPa). Microstructural analyses further revealed that GMS38 and GMS15 were better suited for thermal insulating applications. However, higher weight fraction of the fillers in composites leads to increased porosity which might be detrimental to their strength development.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.4
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• pp.449-455
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• 2022

Concrete is the most widely used construction material. The heavy self-weight of concrete may offer an advantage when developing high compressive strength and good dimensional stability. However, it is limited in the construction of super-long bridges or very high skyscrapers owing to the substantially increased self-weight of the structure. For developing lightweight concrete, various lightweight aggregates have typically been utilized. However, due to the porous characteristics of lightweight aggregates, the strength at the composite level is generally decreased. To overcome this intrinsic limitation, this study aims to develop a construction material that satisfies both lightweight and high strength requirements. The developed cementitious composite was manufactured based on a high volume usage of hollow glass microspheres in a matrix with a low water-to-cement ratio. Regardless of the tested hollow glass microspheres from among four different types, compressive strength outcomes of more than 60 MPa and 80 MPa with a density of 1.7 g/cm³ were experimentally confirmed under ambient and high-temperature curing, respectively.

• Journal of the Semiconductor & Display Technology
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• v.22 no.3
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• pp.28-35
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• 2023

Moiré patterns emerge due to the interference between the non-emission area of the LED screen and the grid line in an image sensor of a video recording device when taking a video in the presence of the LED screen. To reduce the moiré intensity, we have fabricated an anti-moiré filter using hollow glass microspheres (HGMs) by slot-die coating. The LED screen has a large non-emission area because of a large pitch (distance between LED chips), causing more severe moiré phenomenon, compared with a display panel having a very narrow black matrix (BM). It is shown that HGMs diffuse light in such a way that the periodicity of the screen is broken and thus the moiré intensity weakens. To quantitatively analyze its moiré suppression capability, we have calculated the spatial frequencies of the moiré fringes using fast Fourier transform. It is addressed that the moiré phenomenon is suppressed and thus the amplitude of each discrete spatial frequency term is reduced as the HGM concentration is increased. Using the filter with the HGM concentration of 9 wt%, the moiré fringes appeared depending sensitively on the distance between the LED screen and the camera are almost completely removed and the visibility of a nature image is enhanced at a sacrifice of luminance.

• Membrane Journal
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• v.14 no.3
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• pp.218-229
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• 2004

We prepared monodispersed calcium alginate microspheres by controlling various conditions of emulsification procedure using a lab-scale batch type membrane emulsification system equipped with SPG (Shirasu porous glass) tubular membranes. We determined the effects of process parameters of membrane emulsification (ratio of dispersed phase to continuous phase, alginate concentration, emulsifier concentration, type and concentration of stabilizer, transmembrane pressure, concentration of crosslinking agent, stirring speed and membrane pore size) on the mean size and size distribution of alginate microspheres. The increase of the ratio of dispersed phase to continuous phase, transmembrane pressure and alginate concentration led to the increase in the mean size of alginate microspheres. On the contrary, the increase in emulsifier concentration, stirring speed of the continuous phase and concentration of the crosslinking agent caused the reduction of the mean size of microspheres. Through controlling these parameters, monodisperse alginate microspheres with about $6{\mu}{\textrm{m}}$ of the mean size and 1.1 of the size distribution value were finally prepared in case of the using SPC membrane with the pore size of $2.9{\mu}{\textrm{m}}$.