• Advances in materials Research
• /
• v.4 no.3
• /
• pp.133-144
• /
• 2015

The aim of this investigation is to prepare geopolymer resin by alkali activation of ceramic waste (AACW) with different sodium hydroxide (NaOH) and liquid sodium silicate (LSS) concentrations. In order to prepare geopolymer cement, AACW was replaced by 10 and 30 % by weight (wt.,) of concrete waste (CoW) as well as 10 and 30 wt., % ground granulated blast-furnace slag (GGBFS). The results showed that, the compressive strength of AACW increases with the increase of activator content up to 15:15 wt., % NaOH: LSS. All AACW hardened specimens activated by 3:3 (MC6), 6:6 (MC12), 12:12 (MC24) and 15:15 wt., % (MC30) NaOH: LSS destroyed when cured in water for 24h. The MC18 mix showed higher resistivity to water curing. The results also showed that, the replacement of AACW containing 9:9 wt., % NaOH: LSS (MC18) by 10 (MCCo10) and 30 (MCCo30) wt., % CoWdecreased the compressive strength at all ages of curing. In contrast, the MCCo10 mix showed the lower chemically combined water content compared to MC18 mix. The MCCo30 mix showed the higher chemically combined water content compared to MC18 and MCCo10 mixes. The compressive strength and chemically combined water of all AACWmixes containing GGBFS (MCS10 and MCS30) were higher than those of AACWwith no GGBFS (MC18). As the amount of GGBFS content increases the chemically combined water increases. The x-ray diffraction (XRD) proved that as the amount of CoWcontent increases, the degree of crystallinity increases. Conversely, the replacement of AACW by GGBFS leads to increase the amorphiticity character. The infrared spectroscopy (FTIR) confirms the higher reactivity of GGBFS compared to CoW as a result of successive hydration products formation, enhancing the compaction of microstructure as observed in scanning electron microscopy (SEM).

• Korean Journal of Materials Research
• /
• v.3 no.3
• /
• pp.215-222
• /
• 1993

Malononitrile(MN) as a reactive additive was added to Diglycidyl ether of bisphenol A (DGEBA)/Methylene dianiline (MDA) system in order to modify a thermosetting epoxy resin. Cure ki. netics and cure mechanism of this modified system were investigated by using DSC(differential scanning calorimetry) and FT-IR(fourier transform infrared spectrometry). Cure kinetics gave an information that the DGEBA/MDA system modified with MN should cure at over $110^{\circ}C$ after curing at about $80^{\circ}C$ for the complete curing. The activation energy of the first cure was nearly constant and that of the second cure was increased as the MN content was increased. Cure mechanism for the system was investigated with the samples cured every $30^{\circ}C$, from $80^{\circ}C$ to $170^{\circ}C$, for Ihr. It was known that the cure reactions of the epoxy-diamine system were composed of PA -E, SA - E and E-OH reactions. Beside these three reactions, in the DGEBA/MDA/MN system PA-CN and CN-OH reaction was found.

• Fashion & Textile Research Journal
• /
• v.24 no.2
• /
• pp.260-266
• /
• 2022

Cellulose fiber is a material used in various fields. It is the most used type of fiber because of its excellent hygroscopicity and dyeability. Recently, as natural fiber materials have been highlighted due to the influence of eco-friendliness and well-being, bamboo fiber has become a commonly used eco-friendly fiber. Cellulose fibers are part of the -OH hydroxyl group, which means they are more chemically reactive than synthetic fibers. In this study, the cationization properties of bamboo-cotton blended fabrics cationized using CHPTAC (3-chloro-2-hydroxypropyl trimethyl ammonium chloride) in the PDC (padding-drying-curing) method were investigated. Various characteristics according to cationization were studied through elemental analysis, FT-IR (fourier-transform infrared spectroscopy) analysis, X-ray diffraction analysis, TGA (thermogravimetric) analysis, and SEM (scanning electron microscope) analysis. The nitrogen content of the cationized bamboo-cotton blended fabric increased with an increase in the concentration of the cationizing agent CHPTAC, and it was seen to be highly bound to cellulose molecules. As a result of the FT-IR analysis, both 100% pure cotton fabrics and CHPTAC-0 and CHPTAC-150 fabrics were seen to be typical cellulose. As a result of the X-ray diffraction analysis, both 100% pure cotton fabrics and CHPTAC-0 and CHPTAC-150 fabrics showed typical cellulose I structures. As a result of the X-ray diffraction analysis, both 100% pure cotton fabrics and CHPTAC-0 and CHPTAC-150 fabrics showed typical cellulose I structures. As the cationization progressed, micropores appeared on the surface of the blended fabric.

• Journal of the Korea Institute of Building Construction
• /
• v.24 no.3
• /
• pp.285-295
• /
• 2024

This study investigated the impact of accelerated carbonation on Ordinary Portland Cement(OPC) paste that had undergone steam curing at 500℃·hr. Two carbonation environments were examined: atmospheric carbonation(1atm, 20% CO₂) and pressurized carbonation(5atm, 99% CO₂). Chemical analysis using X-ray diffraction(XRD) and Fourier-Transform Infrared spectroscopy(FT-IR) were conducted, along with physical characterization via scanning electron microscopy(SEM) and compressive strength testing. Results indicated that atmospheric carbonation with 20% CO₂ concentration significantly densified the internal microstructure of the OPC paste, leading to enhanced compressive strength. Conversely, pressurized carbonation at 5atm with 99% CO₂ concentration resulted in rapid densification of the surface structure, which hindered CO₂ diffusion into the sample. This limited the extent of carbonation and prevented the improvement of physical properties.

• Journal of the Korean Vacuum Society
• /
• v.15 no.2
• /
• pp.216-222
• /
• 2006

In this paper, we investigated the effect of hydrogen-plasma (H-plasma) treatment on the electrical and optical properties of a quantum dot infrared photodetector (QDIP) with a 5-stacked InAs dots in an InGaAs/GaAs well structure and $Al_{0.3}Ga_{0.7}As/GaAs$ SL (superlattice) current blocking layer. It has been observed that H-plasma treatment didn't affect the band structure of QDIP. It has been also observed that the H-plasma treatment on the QDIP not only enhance the electrical property of QDIP by curing the defect channels in $Al_{0.3}Ga_{0.7}As/GaAs$ SL but also introduce defects in QDIP structure. The H-plasma treatment for 10 min with 20 W of RF power provided the lowest dark current, which made it possible to measure the photo-current (PC) of QDIP whose PC was not detectable without the H-plasma treatment due to the high dark current.

• The Journal of Advanced Prosthodontics
• /
• v.10 no.4
• /
• pp.291-299
• /
• 2018

PURPOSE. To assess the degree of conversion (DC) and light irradiance delivered to light-cured and dual-cured cements by application of different light sources through various types of monolithic computer-aided design and computer-aided manufacturing (CAD/CAM) materials. MATERIALS AND METHODS. RelyX Ultimate Clicker light-cured and dual-cured resin cement specimens with 1.5-mm thicknesses (n=300, 10/group), were placed under four types of crystalline core structure (Vita Enamic, Vita Suprinity, GC Ceresmart, Degudent Prettau Anterior). The specimens were irradiated for 40 seconds with an LED Soft-Start or pulse-delay unit or 20 seconds with a QTH unit. DC ratios were determined by using Fourier transform infrared spectroscopy (FTIR) after curing the specimen at 1 day and 1 month. The data were analyzed using the Mann-Whitney U test (for paired comparison) and the Kruskal-Wallis H test (for multiple comparison), with a significance level of P<.05. RESULTS. DC values were the highest for RelyX Ultimate Clicker light-cure specimens polymerized with the LED Soft-Start unit. The combination of the Vita Suprinity disc and RelyX Ultimate Clicker dual-cure resin cement yielded significantly higher values at both timepoints with all light units (all, P<.05). CONCLUSION. Within the limitations of this study, we conclude that the DC of RelyX Ultimate Clicker dual-cure resin cement was improved significantly by the use of Vita Suprinity and the LED Soft-Start light unit. We strongly recommend the combined use of an LED light unit and dual-cure luting cement for monolithic ceramic restorations.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.30 no.1
• /
• pp.1-6
• /
• 1985

This experiment was designed to determine the effect of light quality on the appearance of photobleaching leaves during the cure of Burley Tobacco. The harvested and browned tobacco leaves were exposed to sunlight in pipe houses covered with 8 kinds of color vinyls (white, red, black, yellow, purple, orange, blue, green), and exposed to ultraviolet rays(20W x 3) and infrared rays (150W x 2) in curing chamber (1.2 x 1.2 x 1.2m). Photobleaching occured more at lower position leaf and after the leaves being browned when the curing was done in sunlight under a transparent vinyl. But photobleaching leaves were 5-6% of total cured leaves in sunlight under all kinds of color vinyl houses. It seems that photobleaching mainly induced by ultrabiolet rays of sunlight, and humidity too influenced. Yellow, orange and purple vinyl were durable and effective as shading material of color vinyls. since white and red vinyl tore easily in two monthes in strong sunlight and under black and blue vinyl houses curing period was longer than others.

• Composites Research
• /
• v.15 no.2
• /
• pp.40-47
• /
• 2002

The di-functional epoxy resins, i.e., diglycidylether of bisphenol A(DGEBA) and diglycidylethere of bisphenol F(DGEBF) were initiated by cationic catalyst, i.e., benzylquinoxalinium hexafluoroantimonate(BQH) using electron-beam(EB) technique. And the effect of structure of DGEBA and DGEBF on thermal stabilities and cure behaviors was investigated. According to the experimental results, the decomposed activation energy based on Horowitz-Metzger method was higher in the case of DGEBA, but intergral procedural decomposition temperature(IPDT) of DGEBA was lower than DGEBF. This could be interpreted in terms of high crosslink density resulted from hydroxyl bond of DGEBF backbone. It was confirmed in increasing the hydroxyl band at $7000\;cm^{-1}$ and $5235\;cm^{-1}$ using near-infrared spectroscopy(NIRS).

• Transactions of the Society of Information Storage Systems
• /
• v.1 no.2
• /
• pp.182-187
• /
• 2005

A large area micro mirror is an optical element that functions as changing an optical path by reflection in integrated optical system. We fabricated the large area silicon mirror by anisotropic etching using MEMS for implementation of integrated optical pickup. In this work, we report the optimum conditions to better fabricate and design, greatly improve mirror surface quality. To obtain mirror surface of $45^{\circ},\;9.74^{\circ}$ off-axis silicon wafer from (100) plane was used in etching condition of $80^{\circ}C$ with 40wt.% KOH solution. After wet etching, polishing process by MR fluid was applied to mirror surface for reduction of roughness. In the next step, after polymer coating on the polished Si wafer, the Si mirror was fabricated by UV curing using a trapezoid bar-type way structure. Finally, we obtained peak to valley roughness about 50 nm in large area of $mm^2$ and it is applicable to optical pickup using blu-ray wavelength as well as infrared wavelength.

• Advances in nano research
• /
• v.4 no.4
• /
• pp.281-294
• /
• 2016

The advantages of nano-scale materials (size 1-99 nm in at least in one dimension) could be realized with their potential applications in diversified avenues. Herein, we report for the first time on the successful synthesis of homogeneous epoxy coatings containing phytogenic silver nanoparticles (Ag) on PVC and glass substrates by room-temperature curing of fully mixed epoxy slurry diluted by acetone. Alstonia scholaris bark extract was used to reduce and stabilize the silver ions. The surface morphology and mechanical properties of these coatings were characterized using the techniques like, UV-Vis (UV-Visible) spectrophotometry, X-ray diffraction (XRD), Fourier transform infrared spectrophotometry (FT-IR), Epifluorescence microscopy and scanning electron microscopy (SEM). The effect of incorporating Ag nanoparticles on the biofilm (scale) resistant epoxy-coated PVC was investigated by total viable counts ($CFU/cm^2$) from epoxy coating from (Initial) $1^{st}$ day to $25^{th}$ days. The phytogenic Ag nanoparticles were found to be significantly improving the microstructure of the coating matrix and thus enhanced the anti-biofilm performance of the epoxy coating. In addition, the antimicrobial mechanism of Ag nanoparticles played an important role in improving the anti-biofilm performance of these epoxy coatings.