• 대한기계학회논문집A
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• 제30권11호
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• pp.1376-1383
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• 2006

Densification behavior of various metal and ceramic powders was investigated under cold compaction. The Cap model was proposed by using the parameters involved in the yield function for sintered metal powder and volumetric strain evolution under cold isostatic pressing. The parameters for ceramic powder can also be obtained from experimental data under triaxial compression. The Cap model was implemented into a finite element program (ABAQUS) to compare with experimental data for densification behavior of various metal and ceramic powders under cold compaction. The agreement between finite element calculations from the Cap model and experimental data is very good for metal and ceramic powder under cold compaction.

• 한국세라믹학회지
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• 제22권6호
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• pp.58-70
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• 1985

The bond strength of metal to ceramic sealing in Mo-Mn metallizing was investigated by examining the effects of flux composition in alumina ceramics particle size of molybdenum metal powder wet hydrogen atmosphere and temperature in metallizing. The maximum bond strength was obtained when the glass phase filled almost all the microstructural cavities around the interfacial area with few micropores. Such a favorable microstrcutre waas formed and maximum bond strength was observed between 130$0^{\circ}C$. Also the metal to ceramic bond strength was increased using finer molybdenum metal powder than coarse powder. When content of $SiO_2$ in the flux of alumina ceramics was constant metal to ceramic bond strength was improved with increasing the ratio of CaO to MgO in the flux.

• 대한치과기공학회지
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• 제27권1호
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• pp.89-95
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• 2005

In the manufacture of ceramo-metal crown, difference of fracture strength according to the metal depth has been known to be an important influence on enough intensity and internal stress to endure an occlusion-pressure as well as aesthetics of rehabilitating similar colour such as natural teeth. Depth of ceramic material could be determined by that of metal in three groups: first case of thin depth, second case of thick depth, and third case of constant depth. For the enhancement of the fracture strength between metal and ceramic materials and aesthetic satisfaction, a study on the bonding force, fracture strength, and aesthetics have been required more. In this study, therefore metal coping were made in three groups of A, B and C by using both ceramic powder of Norithe and metal of Columbium, which have been used primarily in the market. A group was made in $0.2mm\times10mm\times10mm$, B group was made in $0.4mm\times10mm\times10mm$, and, C group was made in $0.8mm\times10mm\times10mm$, respectively. The number of metal coping in each group was 10, and total sample numbers used in this study were 30 metal copings. After these metal coping tissue were in the process of build-up in 1.5mm constant depth of porcelain, firing, and glazing, the fracture strength about each metal coping tissue was investigated using oil press. It was found that the average values of durable occlusion pressure for separation of ceramic material in the porcelain fused to metal crown (PFM) in the each group showed the increasing order of A group (30 bar), B group (42 bar), and C group (44 bar), respectively. Proper depth of metal coping in the PFM was considered to be 0.4mm in the B group because this metal size showed higher durable property to the occlusion pressure and better coupling strength in the ceramo-metal crown.

• 대한치과보철학회지
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• 제45권3호
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• pp.295-302
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• 2007

Statement of problem. Fracture of the tooth-colored superstructure material is one of the main prosthetic complications in implant-supported prostheses. Purpose. The purpose of this in vitro study was to compare the fracture strength between the cement-retained implant-supported metal-ceramic crowns and the indirect composite resinveneered metal crowns under the vertical compressive load. Material and methods. Standard implants of external type (AVANA IFR 415 Pre-mount; Osstem Co., Busan, Korea) were embedded in stainless steel blocks perpendicular to their long axis. Customized abutments were fabricated using plastic UCLA abutments (Esthetic plastic cylinder; Osstem Co., Busan, Korea). Thirty standardized copings were cast with non-precious metal (Rexillium III, Pentron, Walling ford, Conn., USA). Copings were divided into two groups of 15 specimens each (n = 15). For Group I specimens, metal-ceramic crowns were fabricated. For Group II specimens, composite resin-veneered (Sinfony, 3M-ESPE, St. Paul, MN, USA) metal crowns (Sinfony-veneered crowns) were fabricated according to manufacturer's instructions. All crowns were temporary cemented and vertically loaded with an Instron universal testing machine (Instron 3366, Instron Corp., Norwood, MA, USA). The maximum load value (N) at the moment of complete failure was recorded and all data were statistically analyzed by independent sample t-test at the significance level of 0.05. The modes of failure were also investigated with visual analysis. Results. The fracture strength of Sinfony-veneered crowns ($2292.7{\pm}576.0N$) was significantly greater than that of metal-ceramic crowns ($1150.6{\pm}268.2N$) (P < 0.05). With regard to the failure mode, Sinfony-veneered crowns exhibited adhesive failure, while metal-ceramic crowns tended to fracture in a manner that resulted in combined failure. Conclusion. Sinfony-veneered crowns demonstrated a significantly higher fracture strength than that of metal-ceramic crowns in cement-retained implant-supported prostheses.

• Journal of Mechanical Science and Technology
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• 제16권9호
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• pp.1078-1083
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• 2002

Ceramics are significantly used in many industrial applications due to their excellent mechanical and thermal properties such as high temperature strength, low density, high hardness, low thermal expansion, and good corrosion resistive properties, while their disadvantages are brittleness, poor formability and high manufacturing cost. To combine advantages of ceramics with those of metals, they are often used together as one composite component, which necessiates reliable joining methods between metal and ceramic. Direct brazing using an active filler metal has been found to be a reliable and simple technique, producing strong and reliable joints. In this study, the fracture characteristics of Si$_3$N$_4$ ceramic joined to ANSI 304L stainless steel with a Ti-Ag-Cu filler and a Cu (0.25-0.3 mm) interlayer are investigated as a function of strain rate and temperature. In order to evaluate a local strain a couple of strain gages are pasted at the ceramic and metal sides near joint interface. As a result the 4-point bending strength and the deflection of interlayer increased at room temperature with increasing strain rate. However bending strength decreased with temperature while deflection of interlayer was almost same. The fracture shapes were classified into three groups ; cracks grow into the metal-brazing filler line, the ceramic-brazing filler line or the ceramic inside.

• 대한치과보철학회지
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• 제45권1호
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• pp.12-20
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• 2007

Purpose: The purpose of this study was to compare the fracture strength of the zirconia monolithic all-ceramic crowns according to the thickness (0.5mm, 0.8mm, 1.1mm) and metal-ceramic crowns (1.0mm, 1.5mm) Material and method: Twelve crowns for each of 3 zirconia crown groups were fabricated using CAD/CAM system (Kavo, Germany) and twelve crowns for each of 2 metal-ceramic crown groups were made by the conventional method. All crowns were luted to the metal dies using resin cement. Half of the specimens were exposed to thermocycling ($5-55^{\circ}C$, 1 Hz) and cyclic loading (300,000 cycles, 50N). Subsequently, all crowns were mounted on the testing jig in a universal testing machine. The load was directed at the center of crown with perpendicular to the long axis of each specimen until catastrophic failure occurred. Analysis of variance and Tukey multiple comparison test (P<.05) were used for statistical analysis of all groups, and paired t-test (P<.05) was followed for statistical comparison between each groups' fracture load before and after cyclic loading. Results: 1. The fracture strength of the zirconia monolithic crowns and the metal-ceramic crown increased as thickness increased (P<.05). 2. The cyclic loading and thermocycling significantly decreased the fracture strength of the zirconia monolithic crowns (P<.05). 3. The standard deviation of fracture strength of the zirconia monolithic crowns was very low. Conclusion: The fracture strength of the zirconia monolithic crowns for the posterior area tends to be higher with thickness increased and 0.8mm or over in thickness is recommended to have similar or over the fracture strength of metal-ceramic crowns.

• 대한치과보철학회지
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• 제27권1호
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• pp.123-141
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• 1989

The purpose of this study was to investigate the tendency of color change of ceramic, and its mechanism un der the influence of Pd-Ag alloy. The specimens were made by firing porcelain on tile metal plates cast with Au-Pt alloy, Pd-Cu alloy and Pd-Ag alloy. In the case of Pd-Ag alloy, specimens were fired under three different conditions as follows, 1) without protection, 2) protection with ceramic metal conditioner, 3) protection with carbon block. For the specimens of element analysis, a barrier was constructed with platinum foil between metal plate and ceramic. Color change was measured with colorimeter and elemental changes in ceramic were calculated with DC argon plasma emission spectrophotometer. The results were as follows : 1. Color change of ceramic by Pd-Ag alloy was negligible in hue, but decreased in value and increased in chroma (yellow discoloration). 2. Color change of ceramic by Pd-Ag alloy was appeared through vapor transport mechanism. 3. As the protection method for the color change of ceramic by Pd-Ag alloy, application of ceramic metal conditioner was superior to utilization of carbon block.

• 대한치과기공학회지
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• 제30권2호
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• pp.87-92
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• 2008

Purpose: In this study, we tried to compare marginal accuracy when produce ceramic crown using all ceramic materials and existent metal-ceramic system. Material and methods: All-ceramic systems were E-max (Ivoclar/Vivadent, Lichtenstein), Lava(3M, U.S.A.) and Wol-ceram(Teamziereis, Germany). Metal-ceramic system(PFG) was composed of Au-Pt alloy (Metalor, Switzerlandand) and overlying ceramic(D-sign, Ivoclar/Vivadent, Lichtenstein). We fabricated metal master die with upper diameter of 7.95mm, bottom diameter of 9.00mm, height of 5.00mm, and taper of $6^{\circ}$. All ceramic system used 0.5mm thickness ceramic coping, while metalceramic system used 0.3 thickness metal coping. By adding dentin and enamel ceramics on each coping, a crown with a proximal thickness of 1.0 mm and occlusal thickness of 2.0mm was fabricated. Pressure of 2kg was applied for 10 seconds on each crown with static load compressor. Before and after cementation, we measured the marginal gap at 4 points of each crown using optical microscope. The data was analyzed using a Student's t test and repeated-measures of analyses of variance(ANOVA) followed by a Bonferroni test. A p value<0.05 was considered significant. Results: As experiment results, marginal accuracy of wol-ceram and Lava is no good when compared with marginal accuracy of PFG. But marginal accuracy of E.max is good when compared with PFG. This result showed not significant. The marginal accuracy of E.max is good when compared with marginal accuracy of wol-ceram and Lava. Conclusion: The marginal accuracy of E.max is very good when compared with marginal accuracy of another group.

• 대한치과보철학회지
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• 제38권4호
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• pp.461-471
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• 2000

This study evaluated the effect of degassing on the ceramic bond strength of two Ni-Cr alloys under varying holding time at the upper limit temperature and atmospheric conditions. Metal specimens were divided into 5 groups for each alloy according to degassing conditions prior to porcelain application no degassing, degassing under vacuum without hold, degassing under vacuum with hold for 5 min. and 10 min. respectively at the upper limit temperature and degassing in air. Total number of metal ceramic specimens was eighty and each group had eight specimens. The ceramic bond strength was measured by four-point flexural test using Instron and the fractured surface was examined under SEM. The results obtained were as follows. 1. Degassing in air improved the ceramic bond strength of Ni-Cr alloys. 2. In degassing under vacuum, hold at the upper limit temperature was advantageous to the ceramic bonding of Ni-Cr alloys. 3. After ceramic metal bond test, metal surfaces were partially covered with the thin porcelain layer, and the cohesive failures in porcelain were predominant in groups showing higher ceramic bond strength.

• 한국세라믹학회지
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• 제49권1호
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• pp.90-94
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• 2012

This study has been focused on properties of mirror surface grinding technology by ELID(Electrolytic In-process Dressing) for metal matrix ceramic composites using in high precision mirror for optics. The experimental studies have been carried out to get mirror surface by grinding for composites, Al-SiC, Al-graphite and Mg-SiC. Grinding process is carried out with varying abrasive mesh type, depth of cut and feed rate using diamond wheel. The machining result of the surface roughness and condition of ground surface, have been analyzed by use of surface roughness tester and SEM measurement system. ELID grinding technology could be applied successfully for the mirror-surface manufacturing processes in spite of ductility of metal matrix material. As the results of experiments, surface roughness of Al-SiC(45 wt%) has been the most superior in these experimental work-pieces as 0.021 ${\mu}m$ Ra.