• Applied Chemistry for Engineering
• /
• v.34 no.5
• /
• pp.522-528
• /
• 2023

In this work, adhesive tapes were prepared for the dicing process in semiconductor manufacturing. Compounds with different numbers of photoreactive groups (f = 1 to 3) were synthesized and incorporated into acrylic copolymers to formulate UV-curable acrylic adhesives. Structural confirmation of the synthesized photoreactive compounds (f = 2 or 3) was performed using nuclear magnetic resonance (NMR) spectroscopy. The introduction of the photoreactive compounds into the acrylic adhesive was accomplished by urethane reactions, and the successful synthesis of the UV-curable acrylic adhesive was verified by Fourier transform infrared (FT-IR) measurements. To evaluate the performance of the adhesive, the peel strength was evaluated before and after UV irradiation using a silicon wafer as a substrate. The adhesive exhibited high peel strength (~2000 gf/25 mm) before UV exposure, which was significantly reduced (~5 gf/25 mm) after UV exposure. Interestingly, the adhesive containing multifunctional photoreactive compounds showed the most significant reduction in peel strength. In addition, surface residue measurements by field emission scanning electron microscopy (FE-SEM) showed minimal surface residue (~0.2%) after UV exposure. Overall, these results contribute to the understanding of the behavior of UV-curable acrylic adhesives and pave the way for potential applications in semiconductor manufacturing processes.

• Journal of the Korea Institute of Building Construction
• /
• v.23 no.6
• /
• pp.703-714
• /
• 2023

This research conducts a series of tests to investigate the setting retarding properties and strength development in cement pastes incorporating various types and dosages of sugar-based super retarding agents. Six such agents, including Sucrose, Sugar powder, Saccharin, Aspartame, Stevioside, and Mogroside, commercially available, were selected for evaluation. The study also examines the micro-structural properties of these cement pastes. The test mixtures were prepared using a 27.5% water-to-cement ratio and ordinary Portland cement. Micro-structural analyses were conducted using Scanning Electron Microscopy(SEM), X-Ray Diffraction(XRD), and Energy Dispersive Spectroscopy(EDS). The findings reveal that the incorporation of sucrose, sugar powder, and stevioside significantly retards the setting time. Particularly, adding 0.1% sucrose extended the setting time by approximately two-fold compared to the control(Plain) mixture. Most mixtures, barring those with sugar powder and stevioside, exhibited compressive strength comparable to the Plain mixture. Notably, with 0.2% sucrose, strength measurements were not feasible at 1 day, but at 3 days, the strength gains aligned with the Plain mixture. XRD, SEM, and EDS analyses confirmed the hydration delay(set retarding) of C3S due to sucrose, with further quantitative corroboration provided by EDS. SEM was used to verify the presence or absence of hydration products. The study concludes that sucrose, as a sugar-based retarder, offers effective set retarding capabilities and compressive strength development in concrete.

• Journal of the Korea Institute of Building Construction
• /
• v.23 no.6
• /
• pp.693-702
• /
• 2023

This research explores the potential application of Liquid Red Mud(LRM), a byproduct of industrial processes, in the construction sector. We neutralized LRM(pH 10-12) using nitric acid, aiming to understand its viability in construction applications. The study involved substituting LRM(pH 7-8) in mortar formulations, varying by cement type. We assessed the properties of these mixtures by measuring flow, setting time, and compressive strength. Additionally, X-ray Diffraction(XRD) and Scanning Electron Microscopy(SEM) analyses were conducted to examine the chemical properties. Results indicated a reduction in flow value for LRM and LN(neutralized LRM) compared to the control (Plain ) across different cement types. The setting times(initial and final) for LRM and LN were notably shorter than Plain. In compressive strength tests, LRM replaced with slag cement showed enhanced initial strength, though long-term strength gains were marginal across different cement types. SEM analysis revealed distinct voids in Plain and LN, with LRM exhibiting a fibrous microstructure. XRD patterns in SN(slag neutralized) resembled those in OR(original red mud) and ON(original neutralized), with a notable peak at a 2θ value of 22°. The study concludes that unneutralized LRM, when substituted for slag cement in mortar, yields superior initial strength compared to its neutralized counterpart.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.14 no.3
• /
• pp.163-170
• /
• 2009

Several species of the genus Pseudo-nitzschia produce the neurotoxin domoic acid (DA) known to be responsible for amnesic shellfish poisoning. In spite of the potentially toxic effects on marine ecosystem, even the representative Pseudo-nitzschia species occurring in Korean coastal waters have not been clearly reported. Plankton samples from several outer coastal sites of Tongyeong were collected fortnightly from May to November 2008 and the presence of diatoms of the genus Pseudo-nitzschia was examined using light and scanning electron microscopy. Thirteen species were observed, including P. americana, P. brasiliana, P. caciantha, P. calliantha, P. cuspidata, P. delicatissima, P. micropora, P. multiseries, P. multistriata, P. pseudodelicatissima, P. pungens, P. subfraudulenta, and P. subpacifica. The number of Pseudo-nitzschia species observed were only four in May, which was minimum during this survey, and then gradually increased attaining maximum, twelve, in September. After September it began to decrease again and got to five in November. Of these, P. americana, P. brasiliana, P. caciantha, P. calliantha, P. micropora, and P, pseudodelicatissima are new records for the Korean coastal waters and P. calliantha, P. cuspidata, P. delicatissima, P multiseries, P. multistriata, and P. pungens have been reported as DA producers around the world, but the potential toxicity of these species was not ascertained in Tongyeong area.

• Research in Plant Disease
• /
• v.29 no.4
• /
• pp.405-413
• /
• 2023

Bacterial blight of carrot caused by Xanthomonas hortorum pv. carotae (Xhc) is one of the serious diseases of carrot, of which control measures has not been still established in the domestic farm. In this study, in order to select effective sterilizer for bacterial blight of carrots, three antibiotics such as streptomycin, oxolinic acid, kasugamycin, two copper compounds like copper hydroxide and copper sulfate basic and three rhizobacteria Burkholderia gladioli MRL408-3, Pseudomonas fluorescens TRH415-2 and Bacillus cereus KRY505-3 were selected to investigate their direct antibacterial effects using artificial media, aiming to identify effective pesticides against Xhc. Among them, treated medium with antibiotics such as streptomycin, oxolinic acid, and the antagonistic rhizobacteria MRL408-3 were formed inhibition zone. The agrochemicals and the rhizobacteria MRL408-3, which showed antibacterial effects on carrot leaves, pre-treated on the carrot leaves and then inoculated with Xhc. High control effects were shown on the carrot leaves pre-treated with both streptomycin and oxolinic acid. Scanning electron microscopy images of the carrot leaf surfaces showed that the population of bacteria decreased significantly on leaves pre-treated with streptomycin and oxolinic acid. From these results, it can be inferred that antibiotics like streptomycin and oxolinic acid exhibit superior control effects compared to other agents. This study provides valuable insights towards establishing an effective control system for bacterial blight of carrot.

• Korean Journal of Materials Research
• /
• v.34 no.6
• /
• pp.291-302
• /
• 2024

In this paper, iron ore tailings (IOT) were separated from the tailings field and used to prepare cement stabilized macadam (CSM) with porous basalt aggregate. First, the basic properties of the raw materials were studied. Porous basalt was replaced by IOT at ratios of 0, 20 %, 40 %, 60 %, 80 %, and 100 % as fine aggregate to prepare CSM, and the effects of different cement dosage (4 %, 5 %, 6 %) on CSM performance were also investigated. CSM's durability and mechanical performance with ages of 7 d, 28 d, and 90 d were studied with the unconfined compression strength test, splitting tensile strength test, compressive modulus test and freeze-thaw test, respectively. The changes in Ca²⁺ content in CSM of different ages and different IOT ratios were analyzed by the ethylene diamine tetraacetic acid (EDTA) titration method, and the micro-morphology of CSM with different ages and different IOT replaced ratio were observed by scanning electron microscopy (SEM). It was found that with the same cement dosage, the strengths of the IOT-replaced CSM were weaker than that of the porous basalt aggregate at early stage, and the strength was highest at the replaced ratio of 60 %. With a cement dosage of 4 %, the unconfined compressive strength of CSM without IOT was increased by 6.78 % at ages from 28 d to 90 d, while the splitting tensile strength increased by 7.89 %. However, once the IOT replaced ratio reached 100 %, the values increased by about 76.24 % and 17.78 %, which was better than 0 % IOT. The CSM-IOT performed better than the porous basalt CSM at 90 d age. This means IOT can replace porous basalt fine aggregate as a pavement base.

• Composites Research
• /
• v.37 no.3
• /
• pp.209-214
• /
• 2024

Graphene oxide (GO), known for its high stiffness, thermal conductivity, and electrical conductivity, is being utilized as a reinforcement in nanocomposite materials. This study evaluates the mechanical properties of epoxy nanocomposites incorporating GO and edge modified GO (E-GO), which has hydroxyl groups substituted only on its edges. GO/E-GO was uniformly dispersed in epoxy resin using ultrasonic dispersion, and mechanical properties were assessed through tensile testing. The results showed that the addition of nanoparticles increased both tensile strength and toughness. The tensile strength of the epoxy without nanoparticles was 74.4 MPa, while the highest tensile strength of 90.7 MPa was observed with 0.3 wt% E-GO. Additionally, the modulus increased from 2.55 GPa to 3.53 GPa with the addition of nanoparticles. Field emission scanning electron microscopy of the fracture surface revealed that the growth of cracks was impeded by the nanoparticles, preventing complete fracture and causing the cracks to split in multiple directions. E-GO, with surface treatment only on the edges, exhibited higher mechanical properties than GO due to its superior dispersion and surface treatment effects. These results highlight the importance of nanoparticle surface treatment in developing high-performance nanocomposite materials.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.32 no.1
• /
• pp.31-38
• /
• 2024

In this study, vinyl waste, which is the cause of environmental pollution, is recycled via an electrospinning method and applied as a separator that can be employed for energy storage devices. In detail, vinyl wastes are dissolved in a solution containing p-xylene and cyclohexanone, followed by electrospinning to obtain a vinyl waste-derived separator(VWS), and then the hydrophilic functional groups on the surface of VWS are introduced using a plasma treatment to improve wettability. Scanning electron microscopy analysis have verified that the shape and thickness of as-spun VWS vary depending on the concentration of vinyl waste. The surface hydrophility of VWS is modified by plasma treatment with applied powers ranging from 80 to 120W. The lowest contact angle is observed when the 100W power is applied to VWS(VWS-100W). In electrochemical analysis, the VWS-100W-based supercapacitor device shows the highest specific capacitance of 57.9 F g^-1. This is ascribed to the high porosity achieved by electrospinning as well as the introduction of hydrophilic functional groups by the oxygen plasma treatment. In conclusion, vinyl waste is successfully recycled into separators for energy storage devices, suggesting a new way to reduce environmental pollution.

• Journal of Life Science
• /
• v.34 no.8
• /
• pp.576-587
• /
• 2024

In this study, diverse bacterial strains were isolated from fermented foods to screen those with antibacterial activity. Among them, one strain, identified as Bacillus vallismortis MCBL 1012 through 16S rRNA gene sequence analysis, was selected for its bacteriocin production. The culture supernatant of B. vallismortis MCBL 1012 showed antibacterial activity, mainly against Gram-positive bacteria. Scanning electron microscopy (SEM) revealed that bacteriocin treatment led to cellular content leakages in Listeria monocytogenes KCCM 40307, Enterococcus faecium KCCM 12118, and Streptococcus mutans KCTC 3065. PCR analysis confirmed B. vallismortis MCBL 1012 harbored subtilosin A gene (sbo A). Antibacterial activity was decreased by proteolytic enzymes like proteinase K, subtilisin A, and α-chymotrypsin. The bacteriocin demonstrated stability at 40℃ and 60℃ for 120 min, and up to 80℃ for 60 min, with rapid activity loss at 100℃. It retained full antibacterial activity within a pH range of 4.0 to 8.0 and was not affected by up to 100% organic solvents like ethanol, methanol, acetonitrile, and tetrahydrofuran. Nevertheless, activity decreased with more than 40% isopropanol and 80% acetone. Most tested inorganic salts and detergents had no effect on antibacterial activity except, CuSO₄ and NiSO₄ at specified concentrations. The bacteriocin exerted its antibacterial effect through bactericidal action against L. monocytogenes KCCM 40307. The bacteriocin was purified by ammonium sulfate precipitation, DEAE anion exchange chromatography, and RP-HPLC. The purification resulted in a final yield of 0.03% and a 283.7-fold increase in specific activity. MALDI-TOF MS analysis determined the exact molecular weight of purified bacteriocin to be 3,326.1 Da.

• Journal of Mushroom
• /
• v.22 no.3
• /
• pp.92-101
• /
• 2024

Hair dyeing, hair perming, and daily hair dryer use can substantially damage hair. Consequently, the demand for products containing natural ingredients for the care of damaged hair is growing. Although polyphenols with antioxidant effects are often used for hair conditioning, few studies have focused on hair conditioning, and the potential of Sparassis latifolia mushroom extract for hair improvement has not been evaluated to date. In this study, the antioxidant activity of and polyphenol content in hot water, 70% and 100% ethanol (EtOH), n-hexane, ethyl acetate (EtOAc), and water extracts of S. latifolia were analyzed. A hair treatment containing S. latifolia extract was prepared, and its effect on damaged hair was evaluated. The highest antioxidant activity was observed in the hot water and EtOAc extracts. Moreover, polyphenol analysis using high-performance liquid chromatography and liquid chromatography-mass spectroscopy confirmed that the EtOAc fraction has relatively high contents of specific polyphenols beneficial for hair. Based on these results, a hair treatment containing S. latifolia extract was applied to damaged hair, and hair improvement was evaluated using hair thickness, tensile strength, and scanning electron microscopy. The hair treatment containing 70% EtOH extract effectively improved hair condition. We postulate that this improvement was caused by the high hydrophobic polyphenol content in the 70% EtOH extract.