• 한국세라믹학회지
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• 제51권3호
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• pp.170-176
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• 2014

Effective glass frit compositions enabled to absorb laser energy, and to seal a commercial dye-sensitized solar-cell-panel substrate were developed by using $V_2O_5$-based glasses with various amounts of $TeO_2$ substitution. The latter was intended to increase the lifetime of the solar cells. Substitution of $V_2O_5$ by $TeO_2$ provided a strong network structure for the glasses via the formation of tetrahedral pyramids in the glass, and changed the various glass properties, such as glass transition temperature ($T_g$), dilatometric softening point ($T_d$), crystallization temperature, coefficient of thermal expansion (CTE), and glass flowage without any detrimental effect on the laser absorption property of the glasses. The thermal expansion mismatch (${\Delta}{\alpha}$) between the glass frit and the substrate could be controlled within less than ${\pm}5%$ by addition of 10 wt% of ${\beta}$-eucryptite. An 810 nm diode laser was used for the sealing test. The laser sealing test revealed that the VZBT20 glass frit with 10 wt% ${\beta}$-eucryptite was successfully sealed the substrates without interfacial cracks and pores. The optimum sealing conditions were provided by a beam size of 3 mm, laser power of 40 watt, scan speed of 300 mm/s, and 200 irradiation cycles.

• 한국세라믹학회지
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• 제37권4호
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• pp.395-401
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• 2000

In this study, we chose the basic composition which indicated the best electrical properties by change of x content(0, 0.05, 0.1, 0.15, 0.2, 0.25 mol respectively) in xPb(Mn1/3Sb2/3)O3-(1-x)Pb(Zr0.52Ti0.48)O3 ceramics. And we substituted Cd2+ for Pb2+ site, then observed the sintering behavior, microstructure and electrical propertties according to the various sintering temperature. The basic composition was the 0.05PMS-0.95PZt, and it showed single perovskite phase and excellent properties. In case of Cd2+ substitution, we were able to sinter at 90$0^{\circ}C$ which was lower than conventional sintering temperature(1200~130$0^{\circ}C$). Especially, when the 2mol% substituted PMS-PZT specimens were sintered at 90$0^{\circ}C$ for 2h, we obtained the p=7.6g/㎤, kp=56%, Qm=520 and made sure of a position of Cd2+ substitution by observing lattice parameter, phase transition temperature. From this results, we could infer that because Cd2+ substituted fro A-site, low temperature sintering of Cd2+ substituted PMS-PZT without any loss of electrical properties shows its applicability for the piezoelectric ceramic transformer.

• 한국세라믹학회지
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• 제48권5호
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• pp.467-470
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• 2011

Pb(Zr,Ti)$O_3$ (PZT) based ceramics with superior piezoelectric properties have been extensively used in various domestic and industrial appliances. However, PZT ceramics causing environmental contamination and health problems need to be eventually replaced by any of Pb-free materials. $(Na_{0.53}K_{0.47})(Nb_{1-x}Ta_x)O_3$ (NKNT), one of Pb-free piezoelectric ceramics, has long been known but its properties are not fully understood and developed. In this study, dielectric and piezoelectric properties of Pb-free NKNT ceramics were studied with Ta substitution for B-site at x = 0~0.6. It was found that polymorphic phase transition (PPT) between orthorhombic and tetragonal phases was notably influenced by Ta substitution. The highest piezoelectric coefficient ($d_{33}$) of 284 pC/N was occurred at x = 0.45.

• 한국염색가공학회지
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• 제17권2호
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• pp.10-18
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• 2005

Silk fabrics mordanted with $Fe^{2+},\;Ni^{2+},\;and\;Cu^{2+}$ were dyed with the aqueous extract of Cassia tora L. seed which was known to include water soluble colorant kaempferol, one of flavonol compounds. Kaempferol can react with free radicals and chelate transition metal ions, which is thought to catalyze processes leading to the appearance of free radicals and have antioxidant activity. In relation to the coordinating and chelating mechanism of the ions with the silk protein and kaempferol, reasonable conclusions should be made on the colorant uptake and the water fastness of the fabric. The amount of the colorant on the fabric was in the order of $Fe^{2+}>Ni^{2+}>Cu^{2+}$. In case of dyeing through coordinaiton bonds between transition metal ions and silk protein and colorants, it was thought that the ions with the smaller secondary hydration shell, the higher preference to the atoms of the ligand coordinated, and the suitable bonding stability for the substitution of primarily hydrated water molecules for colorants led to the higher colorant uptake. The water fastnsess of the fabric was in the order of $Fe^{2+}>Cu^{2+}>Ni^{2+}$. It should be reasonable to choose transition metal ions with weak and strong tendency to the ionic and the coordination bond, respectively, to the carboxylate anion of the silk protein. Although further research needs to be done, the conclusions above may be generally applied to the natural dyeing through the coordination bond mechanism between transition metal ions and colorants and substrates.

• 한국자기학회지
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• 제18권2호
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• pp.75-78
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• 2008

$AB_2X_4$((A, B)=Transition Metal, X=O, S, Se) 물질에서의 8면체 자리의 이온 거동과 4면체 자리 이온과의 상호작용에 대하여 많은 연구가 이루어지고 있다. 본 연구에서는 4면체 자리에 비자성 이온인 Zn 이온을 치환함에 따른 자기구조의 변화를 관측하여 8면체 자리의 자기구조를 분석하고자 하였다. Cr이온의 일부를 Fe로 치환한 $[Co_{0.9}Zn_{0.1}]_A[Cr_{1.98}{^{57}Fe_{0.02}}]_BO_4$의 닐온도($T_N$는 90K로 $CoCr_{1.98}{^{57}Fe_{0.02}}O_4$ 비하여 감소하였다. 4.2 K에서의 초미세자기장값의 분석결과, 초미세자기장값의 작은 차이를 보이는 잘 분리된 2-set 형태로 나타났으며, $CoCr_{1.98}{^{57}Fe_{0.02}}O_4$의 초미세자기장값은 488, 478 kOe 인데 반하여, $Co_{0.9}Zn_{0.1}Cr_{1.98}{^{57}Fe_{0.02}}O_4$의 초미세자기장값은 $B_1=486$, $B_2=468$ kOe으로 나타났다. Zn 이온의 치환에 따라서 초미세자기장값의 변화를 알 수 있었다. 이러한 결과로 인하여, Zn 이온이 x=0.1 치환된 물질의 경우, 스핀재정렬온도($T_S$)가 18K으로 감소함을 알 수 있다.

• 한국자기학회지
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• 제18권1호
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• pp.39-42
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• 2008

[ $AB_2X_4$ ]((A, B)=Transition Metal, X=O, S, Se) 물질에서의 8면체 자리의 이온 거동과 4면체 자리 이온과의 상호작용에 대하여 많은 연구가 이루어지고 있다. 본 연구에서는 4면체 자리에 비자성 이온인 Zn 이온을 치환함에 따른 자기구조의 변화를 관측하여 8면체 자리의 자기구조를 분석하고자 하였다. Cr이온의 일부를 Fe로 치환한 $[Co_{0.9}Zn_{0.1}]_A[Cr_{1.98}{^{57}Fe_{0.02}}]_BO_4$의 닐온도($T_N$는 90K로 $CoCr_{1.98}{^{57}Fe_{0.02}}O_4$ 비하여 감소하였다. 4.2 K에서의 초미세자기장값의 분석결과, 초미세자기장값의 작은 차이를 보이는 잘 분리된 2-set 형태로 나타났으며, $CoCr_{1.98}{^{57}Fe_{0.02}}O_4$의 초미세자기장값은 488, 478 kOe 인데 반하여, $Co_{0.9}Zn_{0.1}Cr_{1.98}{^{57}Fe_{0.02}}O_4$의 초미세자기장값은 $B_1=486$, $B_2=468$ kOe으로 나타났다. Zn 이온의 치환에 따라서 초미세자기장값의 변화를 알 수 있었다. 이러한 결과로 인하여, Zn 이온이 x=0.1 치환된 물질의 경우, 스핀재정렬온도($T_S$)가 18K으로 감소함을 알 수 있다.

• Bulletin of the Korean Chemical Society
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• 제33권2호
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• pp.663-669
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• 2012

The nucleophilic substitution reactions of dibutyl chlorophosphate (3) with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) are investigated kinetically in acetonitrile at $55.0^{\circ}C$. The obtained deuterium kinetic isotope effects (DKIEs; kH/kD) are secondary inverse ($k_H/k_D$ = 0.86-0.97) with the strongly basic anilines while primary normal ($k_H/k_D$ = 1.04-1.10) with the weakly basic anilines. The DKIEs, steric effects of the two ligands, activation parameters, cross-interaction constants, variation trends of the kH/kD values with X, and mechanism are discussed for the anilinolyses of the nine ($R_1O$)($R_2O$)P(=O)Cl-type chlorophosphates. A concerted mechanism is proposed with a backside nucleophilic attack transition state for the strongly basic anilines and with a frontside attack involving a hydrogen-bonded four-center-type transition state for the weakly basic anilines on the basis of the magnitudes, secondary inverse and primary normal, and variation trends of the $k_H/k_D$ values with X.

• 산업기술연구
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• 제28권A호
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• pp.19-22
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• 2008

In recent years, much attention has been paid to "Photocatalytic oxidation" as an alternative technique, where the pollutants are degraded by UV-irradiation in the presence of a semiconductor suspension such as titanium dioxide. $TiO_2$ is the most often used photocatalyst due to its considerable photocatalytic activity, high stability, non-environmental impact and low cost. 1n this research, the photocatalytic degradation of humic acid, acetaldehyde and methylene blue in $UV/TiO_2$ systems has been stydied. The effect of calcination temperature for manufacturing of $TiO_2$ photocatalysts and type of photocatalysts on photodegradation has been investigated. Photocatalysts with various metal ions(Mn, Fe, Cu and Pt) loading are tested to evaluate the effects of metal ions impurities on photodegradation. The photodegradation efficiency with $Pt-TiO_2$ or $Fe-TiO_2$ or $Cu-TiO_2$ is higher than Degussa P-25 powder. However, the photodegradation efficiency with $Mn-TiO_2$ is lower than Degussa P-25 powder. The photocatalytic properties of the nanocrystals were strongly dependent upon the crystallinity, particle size, standard reduction potential of various transition metal and electronegativity of various transition metal. As a result photocatalysts with various metal ion loading evaluated the effect of photodegradation.

• Bulletin of the Korean Chemical Society
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• 제32권6호
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• pp.1997-2002
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• 2011

The nucleophilic substitution reactions of dicyclohexyl phosphinic chloride [3; $cHex_2$P(=O)Cl] with substituted anilines ($XC_6H_4NH_2$) and deuterated anilines ($XC_6H_4ND_2$) are investigated kinetically in acetonitrile at 60.0 $^{\circ}C$. The anilinolysis rate is too slow to be rationalized by the stereoelectronic effects. The rate is contrary to expectations for the electronic influence of the two ligands and exhibits exceptionally great negative deviation from the Taft's eq. The deuterium kinetic isotope effects (DKIEs) involving deuterated anilines invariably change from primary normal ($k_H/k_D$ > 1; max $k_H/k_D$ = 1.10 with X = 4-MeO) with the strongly basic anilines (X = 4-MeO, 4-Me, 3-Me) to secondary inverse ($k_H/k_D$ < 1; min $k_H/k_D$ = 0.673 with X = 3-Cl) with the weakly basic anilines (X = H, 4-F, 4-Cl, 3-Cl). A concerted $S_N2$ mechanism is proposed on the basis of both secondary inverse and primary normal DKIEs. The obtained DKIEs imply that the fraction of a frontside attack increases as the aniline becomes more basic. A hydrogen-bonded, four-center-type transition state is suggested for a frontside attack, while the trigonal bipyramidal pentacoordinate transition state is suggested for a backside attack.

• E2M - 전기 전자와 첨단 소재
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• 제7권1호
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• pp.32-41
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• 1994

In this study, the TSC spectroscopy has been applied to investigate the influence of structural change due to a process of curing reaction on the electrical properties of epoxy composites cured with acid-anhydride. Five TSC peaks appeared in -160-250[.deg.C]: in the low temperature region below glass transition temperature(T$\_$g/), three relaxation mode peaks due to action of side chains, substitution group or terminal groups have been observed, a peak associated with T$\_$g/, appeared in 110[.deg. C] and p peak due to ionic space charges located in 150[.deg.C]. Each peak was separated into elementary peaks by the partial polarization procedure, and the distribution of activation energy and relaxation time were analized to clearify the origin of each peak. Also, overaboundantly added hardener separated a .betha. peak near 10[.deg. C] into two peaks of .betha.$\_$1/(10.deg. C) and .betha.$\_$2/(20.deg. C) according to increasement of forming field, and the separated hardener was oxidated thermally with increasing surrounding temperatures. The expansion of the free volume need in molecular motion and the reduction of the structural packing density through thermal oxidation process increased TSC between .alpha. peak and .betha. peak and decreased T$\_$g/.