• Journal of Periodontal and Implant Science
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• v.32 no.4
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• pp.753-767
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• 2002

The purpose of this study was to evaluate histologically the effect of LiF-maleic acid added calcium aluminate(LM-CA) bone cement & CA-PMMA composite bone cement on the healing of calvarial defect in Sprague-Dawley rats. The critical size defects were surgically produced in the calvarial bone using the 8mm trephine bur. The rats were divided in three groups : In the control group, nothing was applied into the defect of each rat. LM-CA bone cement was implanted in the experimental group 1 and CA-PMMA composite bone cement was implanted in the experimental group 2. Rats were sacrificed at 2, 8 weeks after surgical procedure. The specimens were examined by histologic analysis, especially about the bone-cement interface and the response of surrounding tissue. The results are as follows; 1. In the control group, inflammatory infiltration was observed at 2 weeks. At 8 weeks, periosteum and duramater were continuously joined together in the defect area. But the center of defect area was filled up with the loose connective tissue. 2. In the experimental group 1, the bonding between implanted bone cement and the existing bone was seen, which more increased in 8 weeks than 2 weeks. Inflammatory infiltration and the dispersion of implanted bone cement particles were seen in both 2 weeks and 8 weeks. 3. In the experimental group 2, implanted bone itself had a dimensional stability and no bonding between implanted bone cement and the existing bone was seen in both 2 weeks and 8 weeks. Implanted bone cement was encapsulated by fibrous connective tissue. In addition, inflammatory infiltration was seen around implanted bone cement. On the basis of these results, when LM-CA bone cement or CA-PMMA composite bone cement was implanted in rat calvarial defect, LM-CA bone cement can be used as a bioactive bone graft material due to ability of bonding to the existing bone and CA-PMMA can be used as a graft material for augmentation of bone-volume due to dimensional stability.

• Journal of the Korean Ceramic Society
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• v.39 no.4
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• pp.413-419
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• 2002

Particulate composites of $Al_2O_3$/TiC/SiC, $Al_2O_3$/TiC and $Al_2O_3$/SiC have been fabricated by hot pressing and their R-curve behaviors and mechanical properties were investigated. $Al_2O_3$ containing 30 vol% TiC particles showed higher toughness by 8% than that for monolithic alumina and its fracture strength was increased significantly by approximately 30%. On the other hand, the addition of 30 vol% SiC of $3{\mu}m$ in $Al_2O_3$ decreased the fracture strength slightly but induced a rising R-curve behavior owing to the strong crack bridging of SiC particles. In case of $Al_2O_3$/TiC/SiC, arising R-curve behavior was also observed and the fracture toughness reached 6.6 MPa${\cdot}\sqrt{m}$ at the crack length of $1000{\mu}m$, which was lower than that of $Al_2O_3$/SiC, however, while the fracture strength was higher by about 20%. The fracture toughness seemed to be decreased as smaller TiC particles roughened the SiC interface and pullout of the SiC particles for crack bridging became less active.

• The Journal of Advanced Prosthodontics
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• v.10 no.5
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• pp.374-380
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• 2018

PURPOSE. The effect of silica-based glass-ceramic liners on the tensile bond strength between zirconia and resin-based luting agent was evaluated and compared with the effect of 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing primers. MATERIALS AND METHODS. Titanium abutments and zirconia crowns (n = 60) were fabricated, and the adhesive surfaces of the specimens were treated by airborne-particle abrasion. The specimens were divided into 5 groups based on surface treatment: a control group, 2 primer groups (MP: Monobond Plus; ZP: Z Prime Plus), and 2 liner groups (PL: P-containing Liner; PFL: P-free Liner). All specimens were cemented with self-adhesive resin-based luting agent. After 24-hour water storage and thermocycling (5,000 cycles, $5^{\circ}C/55^{\circ}C$), the tensile bond strength was measured using a universal testing machine. Failure mode analysis and elemental analysis on the bonding interface were performed. The data were analyzed using Kruskal-Wallis test, Dunn's post hoc test, and Fisher's exact test. RESULTS. The liner groups and primer groups showed significantly higher tensile bond strengths than that of the control group (P<.05). PFL showed a significantly higher tensile bond strength than the primer groups (P<.05). The percentage of mixed failure was higher in the primer groups than in the control group (P<.001), and all the specimens showed mixed failure in the liner groups (P<.001). A chemical reaction area was observed at the bonding interface between zirconia and liner. CONCLUSION. The application of liner significantly increased the tensile bond strength between zirconia and resin-based luting agent. PFL was more effective than MDP-containing primers in improving the tensile bond strength with the resin-based luting agent.

• Ceramist
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• v.21 no.4
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• pp.378-387
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• 2018

The optimal fabrication conditions for $Gd_{0.1}Ce_{0.9}O_{2-{\delta}}$(GDC) buffer layer and $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-{\delta}}$ (LSCF) cathode on 1mol% $CeO_2-10mol%\;Sc_2O_3$ stabilized $ZrO_2$ (CeScSZ) electrolyte were investigated for application of IT-SOFCs. GDC buffer layer was used in order to prevent undesired chemical reactions between LSCF and CeScSZ. These experiments were carried out with $5{\times}5cm^2$ anode supported unit cells to investigate the tendencies of electrochemical performance, Microstructure development and interface reaction between LSCF/GDC/CeScSZ along with the variations of GDC buffer layer thickness, sintering temperatures of GDC and LSCF were checked, respectively. Electrochemical performance was analyzed by DC current-voltage measurement and AC impedance spectroscopy. Microstructure and interface reaction were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Although the interfacial reaction between these materials could not be perfectly inhibited, We found that the cell, in which $6{\mu}m$ GDC interlayer sintered at $1200^{\circ}C$ and LSCF sintered at $1000^{\circ}C$ were applied, showed good interfacial adhesions and effective suppression of Sr, thereby resulting in fairly good performance with power density of $0.71W/cm^2$ at $800^{\circ}C$ and 0.7V.

• The Korean Journal of Ceramics
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• v.6 no.2
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• pp.138-142
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• 2000

Thin film $LiNbO_3$MFS (metal-ferroelectric-semiconductor) capacitor showed improved characteristics such as low interface trap density, low interaction with Si substrate, and large remanent polarization. This paper reports ferroelectric $LiNbO_3$thin films grown directly on p-type Si (100) substrates by 13.56 MHz RF magnetron sputtering system for FRAM (ferroelectric random access memory) applications. RTA (rapid thermal anneal) treatment was performed for as-deposited films in an oxygen atmosphere at $600^{\circ}C$ for 60sec. We learned from X-ray diffraction that the RTA treated films were changed from amorphous to poly-crystalline $LiNbO_3$which exhibited (012), (015), (022), and (023) plane. Low temperature film growth and post RTA treatments improved the leakage current of $LiNbO_3$films while keeping other properties almost as same as high substrate temperature grown samples. The leakage current density of $LiNbO_3$films decreased from $10^{-5}$ to $10^{-7}$A/$\textrm{cm}^2$ after RTA treatment. Breakdown electric field of the films exhibited higher than 500 kV/cm. C-V curves showed the clockwise hysteresis which represents ferroelectric switching characteristics. Calculated dielectric constant of thin film $LiNbO_3$illustrated as high as 27.9. From ferroelectric measurement, the remanent polarization and coercive field were achieved as 1.37 $\muC/\textrm{cm}^2$ and 170 kV/cm, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.949-955
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• 2009

In this study, we investigated the effects of Cr dopant (1.0 at% $Cr_2O_3$ sintered at $1000^{\circ}C$ for 1 h in air) on the bulk trap (i.e. defect) and interface state levels of ZnO using dielectric functions ($Z^*$, $M^*$, $Y^*$, $\varepsilon^*$, and $tan{\delta}$), admittance spectroscopy (AS), and impedance-modulus spectroscopy (IS & MS). For the identification of the bulk trap levels, we examine the zero-biased admittance spectroscopy and dielectric functions as a function of frequency and temperature. Impedance and electric modulus spectroscopy is a powerful technique to characterize grain boundaries of electronic ceramic materials as well. As a result, three kinds of bulk defect trap levels were found below the conduction band edge of ZnO in 1.0 at% Cr-doped ZnO (Cr-ZnO) as 0.11 eV, 0.21 eV, and 0.31 eV. The overlapped defect levels ($Zn^{..}_i$ and $V^{\cdot}_0$) in admittance spectra were successfully separated by the combination of dielectric function such as $M^*$, $\varepsilon^*$, and $tan{\delta}$. In Cr-ZnO, the interfacial state level was about 1.17 eV by IS and MS. Also we measured the resistance ($R_{gb}$) and capacitance ($C_{gb}$) of grain boundaries with temperature using impedance-modulus spectroscopy. It have discussed about the stability and homogeneity of grain boundaries using distribution parameter ($\alpha$) simulated with the Z"-logf plots with temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.941-948
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• 2009

The present study aims at the examination of the effects of 1 mol% NiO addition on the reaction, microstructure development, resultant electrical properties, and especially the bulk trap and interface state levels of $ZnO-Bi_2O_3-Sb_2O_3$ (Sb/Bi=0.5, 1.0, and 2.0) systems (ZBS). The samples were prepared by conventional ceramic process, and characterized by density, XRD, SEM, I-V, impedance and modulus spectroscopy (IS & MS) measurement. The sintering and electrical properties of Ni-doped ZBS (ZBSN) systems were controlled by Sb/Bi ratio. Pyrochlore ($Zn_2Bi_3Sb_3O_{14}$) was decomposed more than $100^{\circ}C$ lowered in ZBS (Sb/Bi=1.0) by Ni doping. The reproduction of pyrochlore was suppressed by the addition of Ni in ZBS. Between two polymorphs of $Zn_7Sb_2O_{12}$ spinel ($\alpha$ and $\beta$), microstructure of ZBSN (Sb/Bi=0.5) composed of a-spinel was more homogeneous than $Sb/Bi{\geq}1.0$ composed of $\beta$-spinel phase. In ZBSN, the varistor characteristics were not improved drastically (non-linear coefficient $\alpha\;=\;6{\sim}11$) and independent on microstructure according to Sb/Bi ratio. Doping of Ni to ZBS seemed to form ${V_0}^{\cdot}$ (0.33 eV) as dominant bulk defect. From IS & MS, especially the grain boundaries of Sb/Bi=0.5 systems were divided into two types, i.e. sensitive to oxygen and thus electrically active one and electrically inactive intergranular one with temperature.

• Korean Journal of Materials Research
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• v.20 no.9
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• pp.467-471
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• 2010

Composites of ceramic powders and an elastomer-based matrix were prepared by mixing $CaCO_3$ powders with polyethylene and polypropylene elastomers, and their mechanical and sound insulation properties were measured. $CaCO_3$ powders with 0.7 ${\mu}m$ and 35 ${\mu}m$ particle size were added to elastomers up to 80 wt%. Scanning electron microscopy photographs showed uniform distribution of the $CaCO_3$ powders in the matrix. While density and surface hardness increased, melt index, tensile strength and elongation of the composites decreased as the amount of added $CaCO_3$ powders increased. As more $CaCO_3$ powders were added sound transmission loss of the composites increased owing to the increase of density. Addition of 0.7 ${\mu}m$ sized $CaCO_3$ powders resulted in a slightly higher transmission loss than the addition of 35 ${\mu}m$ sized powders because of the increased interface area between the elastomer matrix and the $CaCO_3$ powders. Composites with a polyethylene matrix showed higher transmission loss than those with a polypropylene matrix because the tensile strength and hardness of the polyethylene-based composites were low and their elongation was high.

• The Korean Journal of Ceramics
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• v.3 no.4
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• pp.274-278
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• 1997

(Ba, Sr) TiO$_3$(BST) thin films were prepared on RuO$_2$/Si substrates by rf magnetron sputtering and annealing was followed at temperatures ranging from 550 to 80$0^{\circ}C$ in $N_2$or $O_2$atmosphere. The effects of annealing conditions on the properties of BST film deposited on RuO$_2$bottom electrodes were investigated. It was found that the crystallinity. surface roughness, and grain size of BST films vary with the annealing temperature but they are not dependent upon the annealing atmosphere. The flat region in the current-voltage (I-V) curves of BST capacitors shortened with increasing annealing temperature under both atmospheres. This is believed to be due to the lowering of potential barrier caused by unstable interface and the increase of charge The shortening of the flat region by $O_2$annealing was more severe than that by $N_2$-annealing. As a result, there was no flat region when the films were annealed at 700 and 80$0^{\circ}C$ in $O_2$atmosphere. The dielectric properties of BST films were improved by annealing in either atmosphere. however, a degradation with frequency was observed when the films were annealed at relatively high temperature under $O_2$atmosphere.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.8
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• pp.738-748
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• 2008

In this study, it has been investigated on the changing behavior of electrical properties in $ZnO-Bi_2O_3-Sb_2O_3$ (Sb/Bi=2.0, 1.0 and 0.5) ceramics. The samples were prepared by conventional ceramic process, and then characterized by I-V, C-V curve plots, impedance and modulus spectroscopy (IS & MS) measurement. The electrical properties of ZBS systems were strongly dependent on Sb/Bi. In ZBS systems, the varistor characteristics were deteriorated noticeably with increasing Sb/Bi and the donor density and interface state density were increased with increasing Sb/Bi. On the other hand, we observed that the grain boundary reacted actively with the ambient oxygen according to Sb/Bi ratio. Especially the grain boundaries of Sb/Bi=0.5 systems were divided into two types, i.e. sensitive to oxygen and thus electrically active one and electrically inactive intergranular one with temperature. Besides, the increased pyrochlore and $\beta$-spinel phase with Sb/Bi ratio caused the distributional inhomogeneity in the grain boundary barrier height and the temperature instability. To the contrary, the grain boundary layer was relatively homogeneous and more stable to temperature change and kept the system highly nonlinear at high Bi-rich phase contents.