• Clean Technology
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• v.12 no.4
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• pp.205-210
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• 2006

In this study, polystyrene hollow microspheres were prepared via optimized purifying steps for the reuse of waste polystyrene. PS/PVA double layered hollow microspheres were prepared using the multiple emulsion ($W_1/O/W_2$) method with recycled polystyrene. The sonication treatment at the first stage of $W_1/O$ emulsion formation was very important factor of control of particle size and its distribution. When sonication was treated for 20 seconds, the average particle size and distribution were $1.35{\mu}m$ and $0.8{\mu}m{\sim}2.8{\mu}m$, respectively. The double layered hollow microspheres that have smaller and uniformed particle size distribution were manufactured when gelatin or Tween 80 was used as surfactants in the $W_2$ phase.

• Membrane Journal
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• v.20 no.4
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• pp.290-296
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• 2010

Ethylene vinyl acetate (EVA-28)/Co-Al LDH nanocomposite membranes were prepared by solution intercalation using organically modified LDH. LDH was made organophilic by the intercalation of dodecyl sulfate (DS) anion in the interlayer. The prepared membranes were characterized using XRD, FT-IR and SEM. Gas permeability of EVA/LDH nanocomposite membranes with LDH content of 1, 3, and 5 w% was studied for $O_2$ and $CO_2$ at pressure of 3, 4, and 5 bar. The permeability of $O_2$ and $CO_2$ was minimum for nanocomposite membrane with 1 wt% LDH and increased with increasing LDH content, which is presumably due to aggregation of LDH filler. The selectivity of $CO_2$ for $O_2$ showed the maximum value at 1 wt% of LDH content and decreased thereafter.

• Journal of Adhesion and Interface
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• v.12 no.4
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• pp.133-137
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• 2011

Exfoliated graphite oxide (EGO) was prepared by graphite oxide in an aqueous solution of TMAOH. The hybrid graphene/Zn-Al LDH material was fabricated by the hydrothermal reduction of the solution of EGO, $Zn(NO_3)_2{\cdot}6H_2O$, $Al(NO_3)_3{\cdot}9H_2O$, urea, and trisodium citrate. That is, metal ions were absorbed on the surface of EGO, and Zn-Al LDH material was randomly dispersed on the surface of graphene along with a reduction process of EGO to graphene by hydrothermal treatment. The composition, morphology, and thermal property of the obtained graphene-based hybrid material were studied by FE-SEM, EDX, TEM, FT-IR, XRD, TGA, and DSC.

• Membrane Journal
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• v.15 no.3
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• pp.198-205
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• 2005

Double-layered polymer films to assay the radioactive contamination were formulated using polysulfone (PSF) and cerium activated yttrium silicate (CAYS), consisting of a dense support layer and a CAYS-holding top layer prepared via the diffusion-induced phase inversion. As the vapor exposure process was omitted, the CAYS-holding layer showed a typical asymmetric structure, with CAYS being transfixed into the polymer network spread with large macropores. With the increase in vapor exposure time before immersion, morphology of the films transformed from asymmetric to sponge-like structures, with CAYS being localized in cellular structure. The border structure between the two layers reflects the phase inversion behavior of a cast solution during the coagulation. In the radioactive detection, the polymer phase in a film holding a sponge-like structure is so dense that the radionuclides, deposited on the film, could not filter through the phase, consequently resulting in the loss in the detection efficiency of the film.

• Journal of Hydrogen and New Energy
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• v.24 no.1
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• pp.36-43
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• 2013

In this paper, a three-dimensional hydrogen desorption model is applied to a thin double-layered annulus ZrCo hydride bed and validated against the temperature evolution data measured by Kang et al. The present model reasonably captures the bed temperature evolution behavior and the 90% hydrogen discharging time. In addition, the performance of thin double-layered annulus bed is evaluated by comparing with a simple cylindrical bed using hydrogen desorption model. This study provides multi-dimensional contours such as temperature and H/M atomic ratio in the metal hydride region. This numerical study provides fundamental understanding during hydrogen desorption process and indicates that efficient design of the metal hydride bed is critical to achieve rapid hydrogen discharging performance. The present three-dimensional hydrogen desorption model is a useful tool for the optimization of bed design and operating conditions.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.113-118
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• 2006

Recently, wireless LANs are often applied in home or office because of its various of convenience. Frequency rage of wireless LANs specified by IEEE 802.11b is at 2.4 GHz. The bluetooth, the microwave oven, and the PDA(Personal Digital Assistants) uses ,however, the same frequency band. So problems will be produced in these environments, such as multi-pass interference and system-to-system interference. These problems can be eliminated by using EM wave absorber. In this paper, we designed and fabricated EM wave absorber using Sendust, $Al(OH)_3$, and CPE. The double-layered EM wave absorber with thickness of 1.5 mm has absorption ability more than 10 dB at 2.4 GHz.

• Journal of the Korean Wood Science and Technology
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• v.48 no.5
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• pp.755-764
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• 2020

Due to pronounced mechanical performance and being environmental friendly, aqueous polymer isocyanate adhesive (API) has been widely applied in the production of formaldehyde-free wood products. In this study, flame retardant formaldehyde-free plywood was prepared by incorporation of flame retardants into the API adhesive. Partially phosphorylated poly (vinyl alcohol) (PPVA) which was prepared by reacting poly (vinyl alcohol) with phosphoric acid was used to replace PVA in API formula. In addition, Mg-Al layered double hydroxides (LDH) was chosen as additive flame retardant, replacing traditional filler CaCO₃ in API adhesive formula. And then, the flame retardant API adhesive with main agent (PPVA replacing PVA70wt.%, SBR emulsion 30wt.%), curing agent 10wt.% (accounts for of the main agent), and 20wt.% LDHs (accounts of the main agent) was used to prepare flame retardant plywood. The effect of application of PPVA and Mg-Al LDH on bonding strength of plywood was investigated. The flammability characteristics of the plywood were determined by cone calorimeter test (CCT). The results revealed that compared with the plywood prepared with API adhesive, the use of PPVA and LDH enhanced the flame retardancy of plywood without negatively affecting bonding strength. The CCT tests indicated that the heat release and smoke production flame retardant API plywood were lower than those of the ordinary API glued plywood. Promising developments for flame retardant API adhesive were expected in future applications of flame retardant formaldehyde-free plywood.

• Journal of the Korea Institute of Building Construction
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• v.21 no.1
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• pp.21-29
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• 2021

The objective of this study is to evaluate the effect of the application of double layered bubble sheet on the curing of slab and wall concrete placed at the job site in cold weather and to offer a feasibility of Concrete IoT Management System(CIMS), which is wireless sensor network developed by the authors, to manage early age quality of the concrete in terms of temperature, maturity and strength development. Test results indicated that the application of bubble sheet enhances the insulation performance, which results in an increase of the temperature by around 1~20. 6℃. It is found that CIMS can gather the temperature, maturity and strength development data from the sensors embedded from 30 m far from CIMS successfully. Predicted compressive strengths by CIMS had good agreement with measured ones within 2 MPa error level until 7 days. It is thought that the combination of the bubble sheet application for cold weather protection and CIMS for quality management tool in cold weather concreting contributes to shorten the time for the form removal by one day.

• Economic and Environmental Geology
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• v.56 no.1
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• pp.23-53
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• 2023

In this review paper, previous studies on layered double hydroxides (LDHs) published in the Korean Citation Index (KCI) were examined to investigate a research trend for LDHs in Korea. Since the first publication in 2002, 160 papers on LDHs have been published until January 2023. Among the 31 academic fields, top 5 fields appeared in the order of chemical engineering, chemistry, materials engineering, environmental engineering, and physics. The chemical engineering shows the highest record of published paper (71 papers) while around 10 papers have been published in the other four fields. All papers were reclassified into 15 research fields based on the industrial and academic purposes of using LDHs. The top 5 in these fields are in order of environmental purification materials, polymer catalyst materials, battery materials, pharmaceutical/medicinal materials, and basic physicochemical properties. These findings suggest that researches on the applications of LDH materials in the academic fields of chemical engineering and chemistry for the improvement of their functions such as environmental purification materials, polymer catalysts, and batteries have been being most actively conducted. The application of LDHs for cosmetic and agricultural purposes and for developing environmental sensors is still at the beginning of research. Considering a market-potential and high-efficiency-eco-friendly trend, however, it will deserve our attention as emerging application fields in the future. All reclassified papers were summarized in our tables and a supplementary file, including information on applied materials, key results, characteristics and synthesis methods of LDHs used. We expect that our findings of overall trends in LDH research in Korea can help design future researches with LDHs and suggest policies for resources and energies as well as environments efficiently.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.276-279
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• 2008

In order to measure sound transmission loss (STL) of a shipboard window of small size, a special partition is built into the test opening between two reverberation rooms and the specimen is placed in that partition. For high sound insulation, the filler wall often has multi-layered structure such as double-brick wall or buckhead structure with thick steel plate, absorptive material, and sandwich panels. This paper discusses the installation method of a multi-layered filler wall that consist of gypsum boards, lead plates, and glass wool. The experimental results of various wall structures are introduced. The comparison between the results show that the sound bridge effect plays a significant role in lowering the maximum STL of the filler wall. It is also found that the higher the sound insulation performance of the filler wall is, the more important the franking transmission through other side wall of the test facility is.