• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.1
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• pp.47-56
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• 2017

In this study, the higher temperature thermal property of the fly ash-blast furnace slag system Geopolymer including alumina aggregate was investigated whether that Geopolymer will be or not useful as thermal-resistant construction materials. Under every mixing conditions, the crack on the surface of hardened body was not observed up to $800^{\circ}C$ and it corresponded with fact that level of changes was not significant before and after heating process. Residual compressive strength is most high when mixing Blast-Furnace Slag ratio is 60 wt% until temperature reaches $800^{\circ}C$. The major hydrates of hardened body of Geopolymer; amorphous halo pattern between $20{\sim}35^{\circ}$ (2theta) and mullite ($3Al_2O_3{\cdot}2SiO_2$) and quartz ($SiO_2$) was found during the experiment. Amorphous halo pattern was a aluminosilicate gel generated by geopolymeric polycondensation and it was found that the halo pattern of aluminosilicate gel was preserved up to $800^{\circ}C$. The patterns of aluminosilicate gel disappeared from $1,000^{\circ}C$ and crystal phases like gehlenite, calcium silicate, calcium aluminum oxide, microcline was observed with the increase of exposure temperature.

• Journal of the Korean Electrochemical Society
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• v.14 no.3
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• pp.184-190
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• 2011

$LiMn_2O_4$ with mesoporous hollow sphere shape was synthesized by precipitation method with silica template. The synthesized $LiMn_2O_4$ has nanosized first particle and mesoporous hollow sphere shape. Silica template was removed by chemical etching method using NaOH solution. When the concentration of NaOH solution was increased, first particle size of manganese oxide was decrease and confirmed mesoporous hollow shpere shape. X-ray diffraction(XRD) patterns revealed that the synthesized samples has spinel structure with Fd3m space group. In case the ratio of silica and maganese salt increased, the size of first particles was decreased. The tetragoanal $LiMn_2O_4$ with micron size was synthesized at ratio of silica and manganese salt over 1 : 9. The prepared samples were assembled as cathode materials of Li-ion battery with 2032 type coin cell and their electrochemical properties are examined by charge-discharge and cyclic performance. Electrochemical measurements show that the nano-size particles had lower capacity than micron-size particles. But, cyclic performance of nano-size particles had better than that of micron-size particles.

• Journal of the Korean Magnetics Society
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• v.24 no.3
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• pp.81-85
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• 2014

Nano-sized Ba-ferrite, Ni-Zn ferrite and $BaFe_{12}O_{19}/Ni_{0.5}Zn_{0.5}Fe_2O_4$ nanocomposite ferrite were prepared by sol-gel combustion method. Nanocomposite was calcined at temperature range of $600{\sim}900^{\circ}C$ for 1 h. According to the diffraction patterns, hard/soft nanocomposite was indicated to the coexistence of the magnetoplumbite structural $BaFe_{12}O_{19}$ and spinel $Ni_{0.5}Zn_{0.5}Fe_2O_4$ and agree with the standard data (JCPDS 10-0325). The particle size of nanocomposite turn out to be less than 90 nm. The nanocomposite ferrite shows a single-phase magnetization behavior, implying that the hard magnetic phase and soft magnetic phase were well exchange-coupled. The specific saturation magnetization ($M_s$) of the nanocomposite is located between hard ($BaFe_{12}O_{19}$) and soft ferrite ($Ni_{0.5}Zn_{0.5}Fe_2O_4$). The remanence (Mr) of nanocomposite ferrite is much higher than that for the individual $BaFe_{12}O_{19}$ and $Ni_{0.5}Zn_{0.5}Fe_2O_4$ ferrite. $(BH)_{max}$ is increased, generally.

• Journal of Nutrition and Health
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• v.57 no.1
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• pp.105-119
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• 2024

Purpose: The atherogenic index of plasma (AIP) is gaining recognition as a superior predictor of coronary artery disease. This study examined the relationship between the AIP and the intake of various food groups in Korean adults, using the baseline data from the Korean Genome and Epidemiology Study-The Health Examinees (KoGES-HEXA) study. Methods: This study included 133,381 adults (46,288 men, 87,093 women) who completed the nutrition survey and biochemical tests of the KoGES-HEXA study. The AIP was calculated as the log (triglycerides/high-density lipoprotein-cholesterol) and was divided into quintiles according to sex for further analysis. Data on food group intake were obtained using the semi-quantitative food frequency questionnaire, and daily food group intake (g/d) was evaluated for each individual. The association between the food group intake and the AIP was examined using the linear regression analysis after adjusting for the confounding variables. Results: In this study population, there was a positive correlation between energy intake and the AIP in men whereas an inverse assocation was shown in women (p < 0.001). In women, a rise in the AIP significantly correlated with an increased percentage of energy intake derived from carbohydrates but decreased percentages of energy from protein and fat (p < 0.001). In men and women, the consumption of grains and kimchi/pickles increased as the AIP rose, while the intake of legumes, nuts, meat and its products, eggs, fish, and milk and dairy products decreased. Among men, individuals in the highest AIP group showed higher intake of wheat products than those in the lowest group of the AIP. In women, the AIP was inversely correlated with potatoes and beverages consumption. Conclusion: This study highlights the importance of a balanced diet, including various protein sources, milk and dairy products, legumes, and nuts, for preventing cardiovascular diseases. Further research into sex-specific dietary patterns is essential for tailoring appropriate dietary recommendations.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.433-433
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• 2012

As the requirement in patterning geometry continuously shrinks down, the termination of etch process at the exact time became crucial for the success in nano patterning technology. By virtue of real-time optical emission spectroscopy (OES), etch end point detection (EPD) technique continuously develops; however, it also faced with difficulty in low open ratio etching, typically in self aligned contact (SAC) and one cylinder contact (OCS), because of very small amount of optical emission from by-product gas species in the bulk plasma glow discharge. In developing etching process, one may observe that coupon test is being performed. It consumes costs and time for preparing the patterned sample wafers every test in priority, so the coupon wafer test instead of the whole patterned wafer is beneficial for testing and developing etch process condition. We also can observe that etch open area is varied with the number of coupons on a dummy wafer. However, this can be a misleading in OES study. If the coupon wafer test are monitored using OES, we can conjecture the endpoint by experienced method, but considering by data, the materials for residual area by being etched open area are needed to consider. In this research, we compare and analysis the OES data for coupon wafer test results for monitoring about the conditions that the areas except the patterns on the coupon wafers for real-time process monitoring. In this research, we compared two cases, first one is etching the coupon wafers attached on the carrier wafer that is covered by the photoresist, and other case is etching the coupon wafers on the chuck. For comparing the emission intensity, we chose the four chemical species (SiF2, N2, CO, CN), and for comparing the etched profile, measured by scanning electron microscope (SEM). In addition, we adopted the Dynamic Time Warping (DTW) algorithm for analyzing the chose OES data patterns, and analysis the covariance and coefficient for statistical method. After the result, coupon wafers are over-etched for without carrier wafer groups, while with carrier wafer groups are under-etched. And the CN emission intensity has significant difference compare with OES raw data. Based on these results, it necessary to reasonable analysis of the OES data to adopt the pre-data processing and algorithms, and the result will influence the reliability for relation of coupon wafer test and whole wafer test.

• Journal of the Korean Magnetics Society
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• v.15 no.5
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• pp.282-286
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• 2005

Ni-Cu-Zn ferrites were prepared by the co-precipitation and ferrite microwave absorbers on low temperature sintering were investigated in this work. The properties of its microwave absorbing and physical were analyzed into variations of Ni addition, calcination temperature, sintering temperature. From the analysis of X-ray diffraction patterns, we can see that all the particles have only a single phase spinel structure. In addition, the powders particle size distribution obtained the nano size. By increasing the Ni additive, the permeability of the powders was decreased and the loss factor increased at sintering temperature $1100^{\circ}C$. Also, we considered that it can used high frequency rage. We found that the $(Ni_{0.7}Cu_{0.2}Zn_{0.1}O)_{1.02}(Fe_{2}O_3)_{0.98}$ appeared microwave absorbing properties better than other composition.

• Korean Journal of Materials Research
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• v.15 no.10
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• pp.626-631
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• 2005

GaN-related compound semiconductors were grown on the corrugated interface substrate using a metalorganic chemical vapor deposition system to increase the optical power of white LEDs. The patterning of substrate for enhancing the extraction efficiency was processed using an inductively coupled plasma reactive ion etching system and the surface morphology of the etched sapphire wafer and that of the non-etched surface were investigated using an atomic force microscope. The structural and optical properties of GaN grown on the corrugated interface substrate were characterized by a high-resolution x-ray diffraction, transmission electron microscopy, atomic force microscope and photoluminescence. The roughness of the etched sapphire wafer was higher than that of the non-etched one. The surface of III-nitride films grown on the hemispherically patterned wafer showed the nano-sized pin-holes that were not grown partially. In this case, the leakage current of the LED chip at the reverse bias was abruptly increased. The reason is that the hemispherically patterned region doesn't have (0001) plane that is favor for GaN growth. The lateral growth of the GaN layer grown on (0001) plane located in between the patterns was enhanced by raising the growth temperature ana lowering the reactor pressure resulting in the smooth surface over the patterned region. The crystal quality of GaN on the patterned substrate was also similar with that of GaN on the conventional substrate and no defect was detected in the interface. The optical power of the LED on the patterned substrate was $14\%$ higher than that on the conventional substrate due to the increased extraction efficiency.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.393-393
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• 2012

Optically active nanostructures such as subwavelength moth-eye antireflective structures or surface enhanced Raman spectroscopy (SERS) active structures have been demonstrated to provide the effective suppression of unwanted reflections as in subwavelength structure (SWS) or effective enhancement of selective signals as in SERS. While various nanopatterning techniques such as photolithography, electron-beam lithography, wafer level nanoimprinting lithography, and interference lithography can be employed to fabricate these nanostructures, roll-to-roll (R2R) nanoimprinting is gaining interests due to its low cost, continuous, and scalable process. R2R nanoimprinting requires a master to produce a stamp that can be wrapped around a quartz roller for repeated nanoimprinting process. Among many possibilities, two different types of mask can be employed to fabricate optically active nanostructures. One is self-assembled Au nanoparticles on Si substrate by depositing Au film with sputtering followed by annealing process. The other is monolayer silica particles dissolved in ethanol spread on the wafer by spin-coating method. The process is optimized by considering the density of Au and silica nano particles, depth and shape of the patterns. The depth of the pattern can be controlled with dry etch process using reactive ion etching (RIE) with the mixture of SF6 and CHF3. The resultant nanostructures are characterized for their reflectance using UV-Vis-NIR spectrophotometer (Agilent technology, Cary 5000) and for surface morphology using scanning electron microscope (SEM, JEOL JSM-7100F). Once optimized, these optically active nanostructures can be used to replicate with roll-to-roll process or soft lithography for various applications including displays, solar cells, and biosensors.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3355-3360
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• 2012

To promote the photoelectric conversion efficiency of dye-sensitized solar cells (DSSCs), graphene is introduced as a working electrode with $TiO_2$ in this study, because it has great transparency and very good conductivity. XRD patterns indicate the presence of graphene and $TiO_2$ particles in graphene-linked $TiO_2$ samples. Moreover, TEM pictures also show that the nano-sized $TiO_2$ particles are highly dispersed and well-linked onto the thin layered graphene. On the basis of the UV-visible spectra, the band gaps of $TiO_2$, 1.0 wt % graphene-$TiO_2$, 5.0 wt % graphene-$TiO_2$, and 10.0 wt % graphene-$TiO_2$ are 3.16, 2.94, 2.25, and 2.11 eV, respectively. Compared to pure $TiO_2$, the energy conversion efficiency was enhanced considerably by the application of graphene-linked $TiO_2$ anode films in the DSSCs to approximately 6.05% for 0.1 wt % graphene-$TiO_2$ with N719 dye (10.0 mm film thickness and $5.0mm{\times}5.0mm$ cell area) under $100mW/cm^2$ of simulated sunlight. The quantum efficiency was the highest when 1.0 wt % of graphene was used. In impedance curves, the resistance was smallest for 1.0 wt % graphene-$TiO_2$-DSSC.

• Elastomers and Composites
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• v.43 no.4
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• pp.241-252
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• 2008

ZnAl-LDH(layered double hydroxide) modified with oleic acid(SO-ZnAl LDH) was synthesized and added to the flame retardant ABS compounds containing brominated epoxy resin(BER) and antimony trioxide(${Sb_2}{O_3}$). Flame retardant ABS compounds were manufactured by using a twin-screw co-rotating extruder and subsequently injection molded into several specimen for flame retardancy and mechanical properties. The XRD patterns of ABS nanocomposites showed no peaks. The thermal stability of ABS nanocomposites was enhanced by the addition of SO-ZnAl LDH as shown in TGA results. However, these nanocomposites showed no rating in the UL 94 vertical test at 1.6 mm thickness. Only ABS nanocomposites with additional BER more than 1.5 wt% showed UL 94 V0 rating. Notched Izod impact strength, tensile modulus, and elongation at break of flame retardant ABS nanocomposites increased with the proportion of So-ZnAl LDH whereas their melt index decreased.