• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.527-534
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• 2023

This paper conducted a study on the application of ceramic materials for bridge bearing that can complement the durability of PTFE, a conventional bridge bearing friction material, and exhibit low coefficient of friction and friction behavior without lubricant. The ceramic material was zirconia (ZrO₂), and the friction behavior was evaluated according to the roughness coefficient. The roughness coefficient was divided into 0.8 and 0.027, and the average coefficient of friction was calculated to be 0.16 under 15 MPa surface pressure. Afterward, ceramic was made into friction material and applied to the bridge bearing, and performance comparison with PTFE bridge bearing was conducted through compression test and friction test. In the compression test, the ceramic and PTFE bridge bearing showed ideal compression behavior depending on the load. No fractures or defects were observed in the ceramic bridg bearing, but lubricant loss was observed in the PTFE bridge bearing. The average coefficient of friction of the ceramic bridge bearing analyzed through friction behavior was 0.16. The inherent material properties of the physical and chemical properties of ceramics, the excellent mechanical properties derived from the performance evaluation, and the coefficient of friction of 0.16 suggest that it can be considered as a friction material.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.5
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• pp.255-264
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• 2013

Cobalt aluminate ($CoAl_2O_4$) is a highly stable pigment with excellent resistance to light, weather, etc., which has resulted in widespread use as a ceramic pigment. Due to the unique optical characteristics, $CoAl_2O_4$ is generally used as a coloring agent to decorate porcelain products, glass, paints and plastics. Here, $CoAl_2O_4$ pigments were synthesized by polymerized complex method and solid state reaction. Then $CoAl_2O_4$ pigment were grinded using the attrition milling with 1 mm size zirconia ball for 3 hours. The attrition milling process was performed at the constant speed of 800 rpm and ball to powder weight ratio (BPR) was 100 : 1. The characteristics of synthesized pigment were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), particle size analyser (PSA) and CIE $L^*a^*b^*$. The XRD patterns of $CoAl_2O_4$ show single phase spinel structure. The particle size of $CoAl_2O_4$ measured by FE-SEM, TEM and PSA analysis was in the range of 100~200 nm. The blue color of obtained $CoAl_2O_4$ pigments could be confirmed through CIE $L^*a^*b^*$ measurement.

• The Korean Journal of Ceramics
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• v.6 no.2
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• pp.150-154
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• 2000

Mobilities of electrons ($\mu_p$) and holes ($\mu_p$) in 2, 5, and 10 mol% $TiO_2$-doped yttria stabilized zirconia (TD-YSZ) have been estimated by a non-steady state gas permeation method using models proposed by Weppner and Maruyama. Values of $\mu_n$ and $\mu_p$ were found to be closed to those in non-doped YSZ reported earlier. The concentration of electrons and holes were calculated from $\mu_n$ and $\mu_p$ values and the partial conductivities of electrons and holes measured by a dc-polarization method. The concentration of electrons at unit oxygen partial pressure increased with increasing $TiO_2$concentration, while the hole concentration was almost independent of $TiO_2$concentration.

• The Korean Journal of Ceramics
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• v.4 no.2
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• pp.141-145
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• 1998

The electrical properties of the mixed conducting yttria(8 mol%) stabilized zirconia(YSZ)-nickel oxide(NiO) composites were examined by a.c. impedance, 4-probe d.c. conductivity between 400 and $1000^{\circ}C$. The oxygen partial pressure dependence of conductivity, and electromotive force measurement of galvanic cell enabled to determine the electronic contribution to the conduction. Up to 6 vol% NiO addition, the conductivity decreased since the electronic NiO acted as an insulator in ionic matrix. However the ionic transport was dominant until NiO content reaches 26 vol%. Mixed conduction was observed between 26 and 68 vol% of NiO. The effect of composition on the electrical property was explained by the microstructure and thus by the distribution of two phases.

• The Korean Journal of Ceramics
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• v.1 no.3
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• pp.160-164
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• 1995

Mechanical and chemical tests were performed on $Zro_2 \cdot SiO_2$ glass fibers manufactured by the sol-gel method and E-glass fibers-reinforced cement composites in order to investigate the interactions between glass fibers and cement matrices. Chemical attack leads to corrosion of the glass fiber surfaces. In the corrosion reactions, the surface of $30ZrO_2 \cdot 70 SiO_2$ glass fibers developed a densified concentric layer, which consists of glass corrosion products with much higher Zr and lower Si than the fresh glass fiber. The layer of reaction product is regarded to stiffen the cement matrices and provide a useful improvement to the mechanical properties. The addition of $ZrO_2$ content increases the corrosion resistance of glass fibers in cement by forming a passivating layer on the surface of glass fibers.

• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.331-335
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• 1999

Mechanical propeties of $Y_2O_3$-containing tetragonal $ZrO_2$ polycrystals(Y-TZP) were investigated. Several additives were used to modify the hardness fracture toughness of Y-TZP. The effects of these individual additives were discussed and their interactions were also analyzed. Each additive, such as CoO, $Fe2O3, MnO_2$ was found to deteriorate the mechanical propeties of Y-TZP when it was used singly. But the fracture toughness of Y-TZP was singnificantly improved when these additives and $Al_2O_3$ were added in combination at a certain ratio.

• Analytical Science and Technology
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• v.15 no.1
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• pp.7-14
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• 2002

Laser ablation ion trap mass spectrometry (LAITMS) was developed for the analysis of metal and ceramic samples. For this study, XeCl excimer laser (308 nm) was used for ablating the samples and ITMS was used as a detector. Samples were introduced from outside of a ring electrode and this way of sample introduction was very effective for solid samples when laser ablation was employed. Helium gas was used as a buffer gas, and its effect on sensitivity and some parameters (buffer gas pressure, ion storage time, and cut-off RF voltage) were studied. The optimized conditions were $1{\times}10^{-4}$ Torr of buffer gas pressure, 100 ms of ion storage time and $1150V_{p-p}$ of cut-off RF voltage. From that results, copper (Cu) and molybdenum (Mo) metals were tested with LAITMS and the mass spectra of these pure metals were compared with the natural abundance of isotope ratio. We also examined ceramic samples ($Al_2O_3$, $ZrO_2$) and represented the result of elemental analysis.

• The Journal of Advanced Prosthodontics
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• v.10 no.2
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• pp.101-112
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• 2018

PURPOSE. The purpose of this study was to investigate the effect of various surface treatments (ST) on the shear bond strength of resin composite to three bilayer dental ceramics made by CAD/CAM and two veneering ceramics. MATERIALS AND METHODS. Three different bilayer dental ceramics and two different veneering ceramics were used (Group A: IPS e.max CAD+IPS e.max Ceram; Group B: IPS e.max ZirCAD+IPS e.max Ceram, Group C: Vita Suprinity+Vita VM11; Group D: IPS e.max Ceram; Group E: Vita VM11). All groups were divided into eight subgroups according to the ST. Then, all test specimens were repaired with a nano hybrid resin composite. Half of the test specimens were subjected to thermocycling procedure and the other half was stored in distilled water at $37^{\circ}C$. Shear bond strength tests for all test specimens were carried out with a universal testing machine. RESULTS. There were statistically significant differences among the tested surface treatments within the all tested fracture types (P<.005). HF etching showed higher bond strength values in Groups A, C, D, and E than the other tested ST. However, bonding durability of all the surface-treated groups were similar after thermocycling (P>.00125). CONCLUSION. This study revealed that HF etching for glass ceramics and sandblasting for zirconia ceramics were adequate for repair of all ceramic restorations. The effect of ceramic type exposed on the fracture area was not significant on the repair bond strength of resin composites to different ceramic types.

• Journal of the Korean Ceramic Society
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• v.42 no.12 s.283
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• pp.827-832
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• 2005

In this study, thin electrolyte layer was prepared by 8YSZ ($8mol\%$ Yttria-Stabilized Zirconia) slurry dip and sol coating onto the porous anode support in order to reduce ohmic resistance. 8YSZ polymeric sol was prepared from inorganic salt of nitrate and XRF results of xerogel powder exhibited similar results $(99.2\pm1wt\%)$ compared with standard sample (TZ-8YS, Tosoh Co.). The dense and thin YSZ film with $1{\mu}m$ thickness was synthesized by coating of 0.7M YSZ sol followed by heat-treatment at $600^{\circ}C$ for 1 h. Thin film electrolyte sintered at $1400^{\circ}C$ showed no gas leakage at the differential pressure condition of 3 atm.

• Korean Journal of Materials Research
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• v.27 no.1
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• pp.12-18
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• 2017

Transparent organic-inorganic hybrid hard coating films were prepared by the addition of $SiO_2$ or $ZrO_2$, as an inorganic filler to improve the hardness property, filler was highly dispersed in the acrylic resin. To improve the compatibility in the acrylic resin, $SiO_2$ or $ZrO_2$ is surface-modified using various silanes with variation of the modification time and silane content. Depending on the content and kind of the modified inorganic oxide, transparent modified inorganic sols were formulated in acryl resin. Then, the sols were bar coated and cured on PET films to investigate the optical and mechanical properties. The optimized film, which has a modified $ZrO_2$ content of 4 wt% markedly improved in terms of the hardness, haze, and transparency as compared to neat acrylate resin and acrylate resin containing modified $SiO_2$ content of 8 wt%. Meanwhile, the low transparency and high haze of these films slowly appeared at $SiO_2$ content above 10 wt% and $ZrO_2$ content of 5 wt%, but the hardness values were maintained at 2H and 3H, respectively, in comparison with the HB of neat acrylate resin.