• Current Photovoltaic Research
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• v.6 no.4
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• pp.91-93
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• 2018

Polythiophene-$TiO_2$ composite was synthesized with different molar ratios of thiophene and titaniumisopropoxide ($Ti(OPr)_4$) for flexible solar cell application as a flexible electrode or an active material. The $Ti(OPr)_4$ was stabilized by thiophene. The thiophene was polymerized by ferric chloride catalyst. The synthesized polythiophene exhibited strong UV-visible absorption in the range of the wavelength shorter than 500 nm. Field emission scanning electron microscope (FESEM) image of low concentration of $TiO_2$ film showed smooth surface. However, FESEM image of high concentration of $TiO_2$ film exhibited relatively rough surface. Polythiophene concentration dependent strong photoluminescence quenching of surfrhodamine-B was observed.

• Mass Spectrometry Letters
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• v.11 no.4
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• pp.90-94
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• 2020

Interest in aspects of industrialization relating to human health has increased. Accordingly, the use of labels such as 'natural foods' and 'organic ingredients' has become more widespread, and greater emphasis is being placed on improving quality of life. Water is an essential element for human life, and water quality has a significant impact on human health. However, technology that can precisely determine the substances present in water is still lacking. This study was conducted to establish a complete mass spectrometry process, from pretreatment to analysis, to measure and characterize natural organic matter (NOM) in Korean spring water samples. Salts and other matrices were removed from the samples using solid-phase extraction (SPE) with two different columns (PPL and C18). After establishing an accurate analysis method, the experimental results were evaluated based on Van Krevelen diagrams and analysis of molar O/C and H/C ratios. The method for characterizing NOM introduced herein should facilitate evaluation of water quality.

• Journal of the Korean Chemical Society
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• v.31 no.4
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• pp.315-321
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• 1987

The ligand, 2,10-dibenzyl-4,6,8-trioxo-3,9-diaza undecane dioic acid(DTDA) for the extraction of uranium was synthesized under dry nitrogen from phenylalanine and 3-oxoglutaric acid. Extraction was performed by stirring a solution of DTDA in dichloromethane for 1 hour with an aqueous solution of $UO_2(ClO_4)_2{\cdot}6H_2O$ at various pH values and at different $DTDA/UO_2{^{2+}}$ molar ratios. Extraction efficiency reaches a maximum when the pH of the aqueous phase was ca 8.0. The extraction percentage was affected by concentration of DTDA and increases with the $DTDA/UO_2{^{2+}}$ molar ratio to complete extraction with a 4 fold excess of DTDA. The high selectivity of the DTDA for uranium was ascertained by competition experiments with other cations. The bound uranyl ion was quantitatively liberated within few minutes from the organic phase by treatment with an aqueous 1M HCI solution and DTDA was recovered very satisfactorily from the organic phase. The values of the over-all formation constants of the complex between uranyl ion and DTDA were determined to be the following : ${\beta}_1=1.20{\times}10^5\;,\;{\beta}_2=1.01{\times}10^8$.

• Applied Chemistry for Engineering
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• v.27 no.4
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• pp.427-432
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• 2016

The purpose of the research was to examine the utilization of waste bittern from salt farm as a source for producing magnesium (Mg). In this work, a precipitation process for recovering Mg, where Mg is precipitated as $Mg(OH)_2$ by the addition of NaOH solution, was investigated. At the NaOH/Mg molar ratios of 2.70 : 1 to 2.75 : 1 and pH 9.5-10, > 99% of Mg could be precipitated from the bittern. The molar concentration of NaOH solution added as an alkaline reagent had no significant influence on the recovery efficiency of Mg precipitate. The particle size of Mg precipitate was strongly affected by the flow rate of caustic addition. The faster the flow rate of caustic addition, the smaller particles were formed. The Mg precipitate recovered was 100-120 g per 1 L of bittern and contained 94% $Mg(OH)_2$ after washing with water. Our results showed that the bittern can be used as a potential resource for Mg production.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.48 no.1
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• pp.75-81
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• 2016

This study was conducted to investigate the effects of deep eutectic solvent (DES) treatment on BCTMP fibers and handsheets properties. DES was prepared using lactic acid and betaine (LB), and the molar ratio of these two components mixtures was controlled to 2:1 (LB 2:1) and 5:1 (LB 5:1). As results, 2% of BCTMP pulp (o.d. weight) was extracted when it was treated by LB 5:1 at $50^{\circ}C$ for 12 hours, stirring constantly at 120 rpm. In contrast, lignin was not extracted when BCTMP was mildly treated by the LB DES mixed with 50% of distilled water at the reacting condition of temperature $60^{\circ}C$ for 2 hours using water bath. These results indicate that conditioned water content and adequate reaction time are needed to achieve effective extraction of lignin. It was also found that stiffening of cellulose fiber due to the mild treatment of LB DES to BCTMP fiber leads to the increase of paper bulk without the loss of strength.

• Economic and Environmental Geology
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• v.28 no.3
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• pp.231-241
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• 1995

It is well known that hydroxyapatite [$Ca_{10}(PO_4)_6(OH)_2$] have an exchangeability for various heavy metal ions in aqueous solution. To evalute the feasibility of employing the synthetic hydroxyapatites as an eliminatable exchanger for environmentally noxious caions in waste water, the adsorption properties, the removal capacities and the selectivity of the apatites for various cations were investigated in more detailed. The heavy metal cations have been exchanged in calcium part of hydroxyapatite. The order of the degree of amount exchanged of the investigated cations is $Pb^{2+}>Cd^{2+}>Zn^{2+}>Ba^{2+}$. The molar ratios between released $Cd^{2+}$ ions and remeved divalent metal cations in the reacted solution with hydroxyapatite are roughly close to an integer 1.0, suggesting that an ion-exchange reaction could have played a major role in the removal of heavy metals rather then an adsorption effect. The exchangeability of the hydroxyapatite powder of Ca/P molar ratio 1.67, which have specipic surface area of $104.5m^2g^{-1}$, appeared to be better then $237.6{\mu}g$ per g for $Pb^{2+}$ ions. The removal capacity of the heavy metal ions varies directly as particle size of hydroxyapatites. All evidences obtained indicate that the synthesized hydroxyapatite powders by precipitation reaction method can be employed as an effective cation exchanger for eliminating noxious ions in waste water even in some improvemental.

• Journal of Powder Materials
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• v.11 no.6 s.47
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• pp.477-485
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• 2004

Monodispersed flaky silver powder was obtained by controlling the ratios of $H_{2}O_{2}/NH_{3}$ and Agin in a mixed solution of ethylene glycol and ammonia with an addition of PVP. The effects of $NH_{3}/Ag,\; H_{2}O_{2}/Ag\;and\;H_{2}PtCl_{6}/Ag$ on its morphology and size were investigated. In $H_{2}O_{2}-NH_{3}-AgNO_{3}\;system,\;NH_{3}/Ag$ molar ratio was found to be an important reaction factor for the nucleation and crystal growth of Ag powder. The synthesis of flaky powder was optimized at over 6 of $NH_{3}/Ag \;and\;5\;of\;H_{2}O_{2}/Ag\;under\;1.0{\times}10^{-3}\;of\;Pt/Ag.\;Moreover,\;as\;the\; NH_{3}/Ag$ molar ratio increased, the size of precipitates was increased regardless of the amount of Pt. In the absence of $H_{2}PtCI$, the morphology and size of reduced Ag powder were found to be irregular in shape $2-4{\mu}m$ in diameter. However, homogenized fine Ag powder was obtained due to heterogeneous nucleation when $H_{2}PtCI$ used as a cat-alyst, and flaky one was synthesized with the addition of Pt over $1.0{\times}10^{-3}$ of Pt/Ag.

• Nutritional Sciences
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• v.1 no.1
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• pp.8-15
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• 1998

In order to independently examine the effects of long-chain saturated fatty acids and dietary cholesterol levels on plasma and hepatic cholesterol concentrations, six different diets were fed to male Mongolian gerbils (14 gerbils pes grcup) for an 8-week period. Purified diets contained 36% energy as fat (each saturated fatty acid tested comprised about 20% of the total fat energy) and 0.06% (w/w) cholesterol, corresponding to typical human consumption patterns in Western diets. Fat blends were formulated with natural fat sources. To determine the effects of different saturated fatty acids on plasma and liver cholesterol levels, four of the six diets contained constant levels of all nutrients except for the amounts of lauric acid (12 0), myristic acid (14 : 0), palmitic acid (16 0), and stearic acid (18 : 0). Dietary cholesterol effects were tested using 16 : 0-enriched diets containing 0, 0.006, and 0.06% (w/w) cholesterol. None of the plasma lipids were influenced by fatty acid treatment, including triglycerides, plasma total-, VLDL+LDL-, and HDL-cholesterol. However, hepatic esterified cholesterol concentrations were increased in the palmitic and stearic arid diet groups compared to the lauric and myristic acid diet group. The molar ratios of hepatic EC/FC were the highest in the palmitic acid diet (12.2 $\pm$0.6) and the lowest in the myristic acid diet (6.4$\pm$0.2). Dietary cholesterol significantly (p<0.001) increased the plasma total cholesterol which was due to the increase of both HDL-and VLDL+LDL-cholesterol. In the absence of dietary cholesterol and compared to other species, the gerbil exhibited a high molar ratio of hepatic EC/FC, which was funker elevated by dietary cholesterol feeding (0.06%). The results from this study indicate that hepatic cholesterol concentrations are sensitive to both low levels of dietary cholesterol and saturated fatty acid chain length and also, that plasma cholesterol concentrations are sensitive to low levels of dietary cholesterol .

• The Journal of Advanced Prosthodontics
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• v.5 no.3
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• pp.319-325
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• 2013

PURPOSE. The objective of this study was to determine the effect of the color of a background substructure on the overall color of a zirconia-based all-ceramic crown. MATERIALS AND METHODS. Twenty one posterior zirconia crowns were made for twenty subjects. Seven premolar crowns and six molar crowns were cemented onto abutments with metal post and core in the first and second group. In the third group, eight molar crowns were cemented onto abutments with a prefabricated post and composite core build-up. The color measurements of all-ceramic crowns were made before try-in, before and after cementation. A repeated measure ANOVA was used for a statistical analysis of a color change of all-ceramic crowns at ${\alpha}$=.05. Twenty four zirconia specimens, with different core thicknesses (0.4-1 mm) were also prepared to obtain the contrast ratio of zirconia materials after veneering. RESULTS. $L^*$, $a^*$, and $b^*$ values of all-ceramic crowns cemented either on a metal cast post and core or on a prefabricated post did not show significant changes (P>.05). However, the slight color changes of zirconia crowns were detected and represented by ${\Delta}E{^*}_{ab}$ values, ranging from 1.2 to 3.1. The contrast ratios of zirconia specimens were 0.92-0.95 after veneering. CONCLUSION. No significant differences were observed between the $L^*$, $a^*$, and $b^*$ values of zirconia crowns cemented either on a metal cast post and core or a prefabricated post and composite core. However, the color of a background substructure could affect the overall color of posterior zirconia restorations with clinically recommended core thickness according to ${\Delta}E{^*}_{ab}$ values.

• Journal of the Korean Ceramic Society
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• v.54 no.1
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• pp.23-27
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• 2017

A series of $CeO_2-TiO_2$ composite samples with different Ce/Ti molar ratios were prepared by the paper template. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to confirm a face-centered cubic lattice of $CeO_2$ with Ce/Ti =8:2 or 9:1 and a two phase mixture of anatase titania and face-centered cubic ceria with Ce/Ti = 7 : 3. The field emission scanning electron microscopy (FESEM) results suggest that the products are micron braid structures consisting of fibers with diameters in a range of $1-6{\mu}m$ and lengths of several hundred micrometers. $N_2$ absorption-desorption testing shows that the composite at Ce/Ti molar fraction of 8 : 2 has the largest BET surface area (about $81m^2{\cdot}g^{-1}$). Compared to the pure $CeO_2$ sample, the composites show superior catalytic activity for $H_2$ reduction and CO oxidation. For the micron braid structure $CeO_2-TiO_2$ composite (Ce/Ti = 8 : 2), due to the high surface area and the solid solution with appropriate $Ti^{4+}$ incorporation, the CO conversion at about $280^{\circ}C$ was above 50% and at $400^{\circ}C$ was 100%.