• Bulletin of the Korean Chemical Society
• /
• v.16 no.11
• /
• pp.1109-1112
• /
• 1995

Bis(silyl)alkylbenzenes such as bis(1-sila-sec-butyl)benzene (1) and 2-phenyl-1,3-disilapropane (2) were prepared in high yields by reduction of the corresponding chlorosilanes with LiAlH4. The dehydropolymerization of 1 and 2 was carried out with group 4 metallocene complexes generated in situ from Cp2MCl2/Red-Al and Cp2MCl2/n-BuLi (M=Ti, Hf), producing two phases of polymers. The TGA residue yields of the insoluble polymers were in the range of 64-74%. The molecular weights of the soluble polymers produced ranged from 700 to 5000 (Mw vs polystyrene) and from 500 to 900 (Mn vs polystyrene). The dehydropolymerization of 1 and 2 seemed to initially produce a low-molecular-weight polymer, which then underwent an extensive cross-linking reaction of backbone Si-H bonds, leading to an insoluble polymer.

• Transactions on Electrical and Electronic Materials
• /
• v.12 no.5
• /
• pp.222-225
• /
• 2011

Lead zirconate titanate (PZT) films were fabricated on Pt/Ti/$SiO_2$/Si substrate by the sol-gel method using a sol containing poly(N-vinylpyrrolidone) (PVP). PVP in alkoxide solutions can suppress the condensation reaction in gel films during heat treatment, and increase the viscosity of alkoxide solutions. Single-phase PZT films as thick as 1 ${\mu}m$ were deposited by repetitive coating with successive third-step heat treatments at 150$^{\circ}C$, 350$^{\circ}C$ and 650$^{\circ}C$. After heat treatment, the films were crack free, and optically transparent. As a result, we demonstrated a PZT film with a PVP molar ratio of 0.5, which has a permittivity of 734, a dielectric loss of 0.042, a $P_r$ of 40.5 ${\mu}C/cm^2$ and an $E_c$ of 156 kV/cm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.3
• /
• pp.248-252
• /
• 2005

The effects of electric field strength and mechanical compressive stress on the displacement of multilayered ceramic actuator, stacked alternatively 0.2 (PbM $n_{1}$3/N $b_{2}$3/ $O_3$)-0.8(PbZ $r_{0.475}$ $Ti_{0.525}$ $O_3$) ceramic thin films and 70Ag-30Pd electrodes were investigated. Because the actuators were designed to stack ceramic layer and electrode layer alternatively, the ceramic-electrode interfaces may act as a resistance to motion of domain wall. so the polarization and strain were affected by the amount of 180$^{\circ}$domain, electric field strength and mechanical compressive stress. Consequently, the change of polarization, displacement with respect to field strength, and mechanical compressive stress were likely to be caused by readiness of the domain wall movement around the ceramic-electrode interfaces.ces.

• 한국초전도학회:학술대회논문집
• /
• v.9
• /
• pp.91-94
• /
• 1999

A new type of high-T$_c$ superconducting Josephson junctions has been prepared by Ar ion beam etching and electron beam lithography. YBa$_2Cu_3O_{7-x}$ (YBCO) films deposited on (001) SrTiO$_3$ single crystal substrate by pulsed laser deposition were patterned by Ar ion milling with photolithography. The narrow slit with a electroresist mask, about 1000 ${\AA}$ wide, was constructed over a 3 ${\sim}$ 5 ${\mu}$m bridge of a 1200-${\AA}$-thick YBCO film by electron beam lithography. The slit was then etched by the Ar ion beam to form a damaged 600-${\AA}$-thick YBCO. Thus prepared structure forms an S-N-S (YBCO - damaged YBCO - YBCO) type Josephson junctions. Those junctions exhibit RSI-like I-V characteristics at 77 K. The properties of the Josephson junctions such as I$_c$ R$_N$, and J$_c$ were characterized.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.28 no.3
• /
• pp.165-169
• /
• 2015

In this paper, in order to develop the composition ceramics with the excellent dielectric properties, $Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_{0.09}(Zr_{0.5}Ti_{0.5})_{0.88}O_3$ ceramics were fabricated by the conventional solid-state method. The effects of ZnO addition on their microstructure and piezoelectric properties were systematically investigated. The rhombohedral-tetragonal phase coexistence has been found in the ceramics without ZnO content and then with further increasing ZnO content, specimens exhibited tetragonal phase. The optimized ZnO content formed liquid phase and aided the grain growth of specimens. When 0.4 wt% ZnO was added, the optimal physical properties ($d_{33}=422pC/N$, $d_{31}=161pC/N$, ${\varepsilon}_r=1,905$, $k_p=0.55$, $Q_m=160$) were obtained.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.115-115
• /
• 2011

Nano hybrid superlattices consisting of organic and inorganic components have great potential for creation of new types of functional material by utilizing the wide variety of properties which differ from their constituents. They provide the opportunity for developing new materials with new useful properties. Herein, we fabricated new type of organic-inorganic nano hybrid superlattice thin films by a sequential, self-limiting surface chemistry process known as molecular layer depostion (MLD) combined with atomic layer deposition (ALD). An organic layer was formed at $150^{\circ}C$ using MLD with repeated sequintial adsorption of Hydroquinone and Titanium tetrachloride. A $TiO_2$ inorganic nanolayer was deposited at the same temperature using ALD with alternating surface-saturating reactions of Titanium tetrachloride and water. Using UV-Vis spectroscopy, we confirmed visible light absorption by LMCT. And FTIR spectroscopy and XPS were employed to determine the chemical composition. Ellipsometry and TEM analysis were also used to confirm linear growth of the film versus number of MLD cycles at all same temperature. In addition, p-n junction diodes domonstrated in this study suggest that the film can be suitable for n-type semiconductors.

• Journal of Integrative Natural Science
• /
• v.5 no.2
• /
• pp.79-83
• /
• 2012

Trialkyltin n-$Bu_3SnH$, an endocrine disruptor, was slowly converted by the catalytic action of group 4 $Cp_2MCl_2$/Red-Al (M = Ti, Zr, Hf) to produce two phases of products: one is an insoluble cross-linked solid, polystannane in 7-23% yield as minor product via redistribution/dehydrocoupling combination process, and the other is an oil, hexabutyldistannane in 69-90% yield as major product via simple dehydrocoupling process. Redistribution/dehydrocoupling process first produced a low-molecular-weight oligostannane possessing partial backbone Sn-H bonds which then underwent an extensive cross-linking reaction of backbone Sn-H bonds, leading to an insoluble polystannane. This is the first exciting example of redistribution/dehydrocoupling of a tertiary hydrostannane catalyzed by early transition metallocenes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.30 no.4
• /
• pp.218-222
• /
• 2017

In this paper, in order to develop excellent composition ceramics for a piezoelectric energy- harvesting device, we synthesized $0.99(Na_{0.52}\;K_{0.443}\;Li_{0.037})(Nb_{0.883}\;Sb_{0.08}\;Ta_{0.037})O_3$ + $0.01(Sr_{0.95}Ca_{0.05})TiO_3$ + $0.3\;wt%\;Bi_2O_3\;+\;0.3\;wt%\;Fe_2O_3\;+\;0.3\;wt%\;CuO$ (abbreviated as NKN-SCT) ceramics with different sintering times, using the ordinary solid-state reaction method. The effect of sintering time on the microstructure and piezoelectric properties was investigated. The ceramics with the sintering time of 7 h have the optimum values of the piezoelectric constant ($d_{33}$), piezoelectric voltage constant ($g_{33}$), planar piezoelectric coupling coefficient (kp), mechanical quality factor (Qm), and dielectric constant (${\varepsilon}r$): $d_{33}=314[pC/N]$, $g_{33}=20.07[10^{-3}mV/N]$, kp = 0.442, Qm = 93, ${\varepsilon}r=1,768$, all being suitable for a piezoelectric energy-harvesting device.

• Journal of the Korean Ceramic Society
• /
• v.39 no.9
• /
• pp.846-850
• /
• 2002

A PMN-PT-BT/Ag composite was prepared by surface modification with MgO sol with hoping to suppress silver's migration during sintering. The mixture of PbO, $N_2O_5,\;TiO_2\;with\;Mg(NO_3)_2$ instead of MgO was ball milled, the solvent was removed and then the dried powders were calcined at 950$^{\circ}C$/1h. The calcined powder were treated with 3.0 mol% $Ag_2O$ and 1.0 wt% MgO sol and calcined at 550$^{\circ}C$/1h. The dielectrics sintered at 1000$^{\circ}C$/4h under a flowing oxygen showed the density of 7.84g/$cm^3$, the room temperature dielectric constant of 18400, the dielectric loss of 2.4%, the specific resistivity of $0.24{\times}10^{12}{\Omega}{\cdot}cm$. It also showed the bending strength of $120.7{\pm}11.26$ MPa and the fracture toughness of $0.87{\pm}0.002\;MPam^{1/2}$ which were comparable to commercial PZT. The microstructure sonsisted of grains of ∼4${\mu}m$. SEM and SIMS analysis showed that Ag grew as ∼1${\mu}m$ and excess MgO as ∼0.5${\mu}m$.

• Restorative Dentistry and Endodontics
• /
• v.27 no.6
• /
• pp.577-586
• /
• 2002

The purpose of this in vitro study was to compare the effects of root canal cleanness following two Ni-Ti rotary instruments with different rake angle. Thirty-six sound, extracted human premolars with single root were randomly divided into three groups. The used rotary instruments were HEROShaper (Group 1, Micro-Mega, Besancon, France, n=12) and ProFile (Group 2, Maillefer, Ballaigues, Switzerland, n=12). Control group (n=12) was only extirpated with barbed broach (Mani, Matsutani Seisakusho Co., Japan) Group 1 & 2 teeth were prepared to a #40/.04 taper at the apex followed by 1 mm using crown-down technique. After canal preparation and frequent irrigation with 5.25% sodium hypochlorite, the roots split longitudinally into a bucco-lingual direction. Root halves were cross-sectioned in apical third portion again. All root specimens were processed for SEM investigation and photographed. Separate evaluations by one endodontist were undertaken for smear layer on prepared walls with a five score-index for each using reference photograph in root halves. The penetration depth of smear layer into dentinal tubules was also estimated in the other halves. Following results were obtained: 1. Smear layer was observed on all the prepared walls with two experimental groups except control group. 2. Smear layer characteristics in two experimental groups; 1) HEROShaper group showed snowy, dusty appearance and were shown open dentinal tubuli on the prepared walls of almost specimens, and the thickness of smear layer covering onto dentinal surfaces was within 1-2 ${\mu}m$ in a few specimens. 2) ProFile group showed shiny, burnished appearance and complete root canal wall covered by a homogenous smear layer with no open dentinal tubuli in all specimens. The penetration of smear layer into dentinal tubules was found in all specimens and the thickness was at 2-4 ${\mu}m$ in all specimens. These results demonstrated that a completely clean root canal could not be achieved regardless of positive or negative rake angle, which is in accordance with the majority of previous studies on root canal cleanliness In conclusion, through irrigation with antibacterial solutions or chelating agents is recommended to remove the smear layer on prepared canal wall in spite of Ni-Ti instrumentation.