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Lim, Sungil,Park, Myoung Jun,Phuntsho, Sherub,Tijing, Leonard D.,Nisola, Grace M.,Shim, Wang-Geun,Chung, Wook-Jin,Shon, Ho Kyong Elsevier 2017 Polymer Vol.110 No.-
<P><B>Abstract</B></P> <P>A novel thin-film composite (TFC) forward osmosis (FO) membrane with dual-layered substrate membrane was fabricated by a double-blade casting technique using different polysulfone (PSf) concentrations for top (15 wt%) and bottom (7 wt%) substrate layers. Graphene oxide (GO) was incorporated in the substrate layer, and the dual casting approach resulted in a membrane support with a highly porous bottom structure and a dense top skin layer on which the polyamide active layer was effectively formed. The dual-layered TFC PSf/GO membrane (TFC-PSf<SUB>d</SUB>GO) exhibited high water permeability, and ion selectivity was enhanced by the presence of well dispersed hydrophilic GO in the PSf substrate. The TFC-PSf<SUB>d</SUB>GO also exhibited the lowest specific reverse salt flux (<I>J</I> <SUB> <I>s</I> </SUB> <I>/J</I> <SUB> <I>v</I> </SUB> = 0.19 g L<SUP>-1</SUP>) and a more favorable structural parameter (S = 130 μm) compared to GO-free membranes. Using deionized water as feed solution and 1 M NaCl as draw solution (DS), TFC-PSf<SUB>d</SUB>GO had <I>J</I> <SUB> <I>v</I> </SUB> = 33.8 L m<SUP>−2</SUP> h<SUP>−1</SUP> and <I>J</I> <SUB> <I>s</I> </SUB> = 6.9 g<SUP>−2</SUP> h<SUP>−1</SUP> under AL-FS mode, and <I>J</I> <SUB> <I>v</I> </SUB> = 61.5 L m<SUP>−2</SUP>h<SUP>−1</SUP> and <I>J</I> <SUB> <I>s</I> </SUB> = 14.0 g<SUP>−2</SUP> h<SUP>−1</SUP> under AL-DS mode. The potential of TFC-PSf<SUB>d</SUB>GO for commercial application was further evaluated by fabricating it with a fabric backing support (denoted as TFC-PSf<SUB>d</SUB>GO<SUB>f</SUB>). Compared to TFC-PSf<SUB>d</SUB>GO, TFC-PSf<SUB>d</SUB>GO<SUB>f</SUB> exhibited only 14% decline in its water flux. The overall results reveal that, fabrication of TFC substrate membrane via dual-blade casting approach along with GO incorporation produced high-performance TFC FO membranes which likely reduced the internal concentration polarization effects.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The dual-layered PSf/GO membrane was developed to mitigate the ICP effect. </LI> <LI> The dual-layered PSf substrates exhibited higher porosity and water permeability. </LI> <LI> Incorporation of GO further improved hydrophilicity of membrane substrate. </LI> <LI> The dual-layered PSf/GO membrane demonstrated the best membrane performances. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Tijing, Leonard D.,Jung, Min Young,Kim, Dong-Won,Kim, Cheol Sang American Scientific Publishers 2011 Journal of Nanoscience and Nanotechnology Vol.11 No.2
<P>This paper presents an investigation on the deposition behavior of self-assembled monolayers (SAMs) and bacteria on titanium and gold surfaces using an electrochemical quartz crystal nanobalance (EQCN). The tests included alkanethiol and alkanesilane and three bacteria, namely: E. coli, P. fluorescens and K. aerogenes. The mass change with respect to immersion time was measured by EQCN. The results showed SAM formation on both titanium and gold surfaces, but SAM formation on gold was generally higher by 26-74% as compared to that of titanium. On the other hand, bacteria also adhered well on the two metal surfaces. E. coli and P. fluorescens had high affinity on gold and titanium surfaces, respectively, while K. aerogenes was more adherent to titanium. The results showed that titanium and gold are good metals for biomaterials yet at the same time, their bioinert property provide excellent condition for bacterial adhesion. Therefore, there is a need for proper surface preparation to optimize the use of titanium and gold as biomaterials.</P>
Leonard D. Tijing,Bock Choon Pak(박복춘),Byung Joon Baek(백병준),Dong Hwan Lee(이동환) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
The present study investigated the mechanism of physical water treatment through particle count analysis of the water sample with and without physical water treatment (PWT) technology. The PWT methods utilized catalytic devices and low-voltage-high-frequency device wherein water continuously recirculated through them. Concentrated hard water at 2,300-2,700 μS/㎝ electrical conductivity was utilized in the study at two different flow rates (i.e., 500 l/h, and 800 l/h). After 66 hours of operation for each test, the results showed that the total number of particles in the PWT-treated cases increased from 165-539% as compared with the no-treatment cases depending on the flow rate used. The present results provided by particle counting support the bulk precipitation hypothesis as the mechanism of PWT and electro-flocculation mechanism with the use of catalytic materials and LVHF technique.
USING LOW-VOLTAGE-HIGH-FREQUENCY ELECTRIC FIELD TO MITIGATE MINERAL FOULING IN A HEAT EXCHANGER
Leonard D. Tijing,Bock Choon Pak,Byung Joon Baek,Dong Hwan Lee,Young I. Cho 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
This paper presents an investigative study on the efficacy of a new physical water treatment (PWT) technology using an oscillating electric field to mitigate mineral fouling in heat exchangers. Parallel graphite electrode plates immersed in water were used to generate the electric field directly in water. Artificial hard water at 500 ppm hardness was used in all fouling tests. The inlet temperatures were maintained at 23.5±0.5℃ and 85±0.5℃ for cold and hot water sides, respectively. The results at a cold water-side velocity of 0.3 ㎧ showed a 16-60% drop in fouling resistances from the baseline test depending on the frequency of the electric field for the PWT-treated cases.
Kang, Seung-Ji,Tijing, Leonard D.,Hwang, Bo-sang,Jiang, Zhe,Kim, Hak Yong,Kim, Cheol Sang Elsevier 2013 Ceramics international Vol.39 No.6
<P><B>Abstract</B></P> <P>In this paper, we report the effect of the incorporation of titanium dioxide (TiO<SUB>2</SUB>) nanoparticles (NPs) on the photocatalytic properties of a tourmaline NP/nylon-6 composite mat prepared by one-step electrospinning process. Several characterization techniques were utilized to check the successful incorporation of NPs in/on the nanofibers. Both TiO<SUB>2</SUB> and tourmaline NPs were confirmed to be incorporated on the surface of the nylon-6 nanofibers or fully embedded in the fibers through SEM and TEM observations. The fiber diameter showed increasing size trend in the order of nylon-6<tourmaline/nylon-6<TiO<SUB>2</SUB>-tourmaline/nylon-6. The incorporation of both TiO<SUB>2</SUB> and tourmaline NPS on/in nylon-6 nanofibers has resulted to increased photocatalytic degradation of organic pollutant. The successful immobilization on nylon-6 nanofibers through simple electrospinning of tourmaline possessing unique properties, and photocatalytic TiO<SUB>2</SUB> showed synergistic effect in the degradation of organic pollutants, which could have potential application in water treatment applications.</P>
A study on heat transfer enhancement using straight and twisted internal fin inserts
Leonard D. Tijing,Bock Choon Pak(박복춘),Byung Joon Baek(백병준),Young I. Cho(조영일) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The present study investigated the effect of internal aluminum fins with a star shape cross section on the heat transfer enhancement and pressure drop in a counterflow heat exchanger. A concentric tube heat exchanger was used with water as the working fluid. The heat transfer rate increased by 12-51% over the plain tube value, depending on the internal fin configuration used. However, the pressure drop also increased substantially by an average of 286-338%. The results showed that a straight fin configuration is good enough to produce a heat transfer increase in a counterflow heat exchanger. Twisted fin configurations did not further increase the heat transfer rate.
Leonard D. Tijing,Woorim Choi,Zhe Jiang,Altangerel Amarjargal,Chan-Hee Park,Hem Raj Pant,Ik-Tae Im,김철생 한국물리학회 2013 Current Applied Physics Vol.13 No.7
Composite nanofibrous mat composed of neat polyurethane (PU) and multiwalled carbon nanotubes/polyurethane (MWNT/PU) nanofibers have been fabricated by one-step angled two-nozzle electrospinning. The morphological, thermal, and mechanical properties of the electrospun nanofibers were evaluated. The diameters of electrospun neat PU and composite nanofibers ranged from 239 to 1058 nm. The two-nozzle electrospun (MWNT/PU)/PU composite nanofibers showed curly, and randomly-oriented fibers with interfiber bonding, and were generally bigger in size than single-nozzle electrospun nanofibers. The tensile strength of the neat PU composite nanofiber mat obtained from two-nozzle electrospinning was 25% higher than that obtained from neat PU single-nozzle electrospinning. The incorporation of MWNTs in the composite nanofiber increased the tensile strength by as much as 64%without reducing elongation, made the composite nanofiber more thermally stable, and improved the melting zone. The present results showed that side-by-side angled two-nozzle electrospinning can improve the quality of the electrospun nanofibers that could have potential application in different fields such as filtration, protective clothing and tissue engineering.
Leonard D. Tijing,Altangerel Amarjargal,Zhe Jiang,Michael Tom G. Ruelo,Chan-Hee Park,Hem Raj Pant,김동원,Dong Hwan Lee,김철생 한국물리학회 2013 Current Applied Physics Vol.13 No.1
In this study, tourmaline (TM) nanoparticles (NPs) were incorporated in a polyurethane (PU) matrix by electrospinning and silver (Ag) nanoparticles in the form of wire-like structure were further decorated on the TM/PU nanofibrous mat by photoreduction under ultraviolet light irradiation. The incorporation of TM NPs has increased the conductivity of the solution, thus forming thinner fiber diameters compared to neat PU, but with improved tensile strength. Wire-like, agglomerated Ag NPs were decorated on the TM/ PU matrix, and exhibited high bactericidal activity depending on the Ag content. The present antibacterial Ag/TM/PU hybrid mat has potential application in water treatment.
Subagia, I.D.G. Ary,Jiang, Zhe,Tijing, Leonard D.,Kim, Yonjig,Kim, Cheol Sang,Lim, Jae Kyoo,Shon, Ho Kyong THE KOREAN FIBER SOCIETY 2014 FIBERS AND POLYMERS Vol.15 No.6
In this study, we report the fabrication and evaluation of a hybrid multi-scale basalt fiber/epoxy composite laminate reinforced with layers of electrospun carbon nanotube/polyurethane (CNT/PU) nanofibers. Electrospun polyurethane mats containing 1, 3 and 5 wt% carbon nanotubes (CNTs) were interleaved between layers of basalt fibers laminated with epoxy through vacuum-assisted resin transfer molding (VARTM) process. The strength and stiffness of composites for each configuration were tested by tensile and flexural tests, and SEM analysis was conducted to observe the morphology of the composites. The results showed increase in tensile strength (4-13 %) and tensile modulus (6-20 %), and also increase in flexural strength (6.5-17.3 %) and stiffness of the hybrid composites with the increase of CNT content in PU nanofibers. The use of surfactant to disperse CNTs in the electrospun PU reinforcement resulted to the highest increase in both tensile and flexural properties, which is attributed to the homogeneous dispersion of CNTs in the PU nanofibers and the high surface area of the nanofibers themselves. Here, the use of multi-scale reinforcement fillers with good and homogeneous dispersion for epoxy-based laminates showed increased mechanical performance of the hybrid composite laminates.