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Strengthening and Toughening of Dental Porcelain by the Inclusion of an Yttria-Stabilized Zirconia Reinforcing Phase

Year: 2015 Volume: 9 Issue: 5 369 - 372 Pages

• Authors:
• Bruno Henriques
• Rafaela Santos
• Mihaela Buciumeanu
• Júlio Matias de Souza
• Filipe Silva
• Rubens Nascimento
• Márcio Fredel

Abstract: Dental porcelain composites reinforced and toughened by 20 wt.% tetragonal zirconia (3Y-TZP) were processed by hot pressing at 1000°C. Two types of particles were tested: yttriastabilized zirconia (ZrO2–3%Y2O3) agglomerates and pre-sintered yttria-stabilized zirconia (ZrO2–3%Y2O3) particles. The composites as well as the reinforcing particles were analyzed by the means of optical and Scanning Electron Microscopy (SEM), Energy Dispersion Spectroscopy (EDS) and X-Ray Diffraction (XRD). The mechanical properties were obtained by the transverse rupture strength test. Wear tests were also performed on the composites and monolithic porcelain. The best mechanical results were displayed by the porcelain reinforced with the pre-sintered ZrO2–3%Y2O3 agglomerates.

• Keywords:
• Composite
• dental restoration
• porcelain
• strengthening
• toughening
• wear
• zirconia.

Effects of the Sintering Process on Properties of Triaxial Electrical Porcelain from Ugandan Ceramic Minerals

Year: 2013 Volume: 7 Issue: 5 297 - 303 Pages

• Authors:
• Peter W. Olupot
• Stefan Jonsson
• Joseph K. Byaruhanga

Abstract: Porcelain specimens were fired at 6C/min to 1250C (dwell time 0.5-3h) and cooled at 6C/min to room temperature. Additionally, three different slower firing/cooling cycles were tried. Sintering profile and effects on MOR, crystalline phase content and morphology were investigated using dilatometry, 4-point bending strength, XRD and FEG-SEM respectively. Industrial-sized specimens prepared using the promising cycle were tested basing on the ANSI standards. Increasing dwell time from 1h to 3h at peak temperature of 1250C resulted in neither a significant effect on the quartz and mullite content nor MOR. Reducing the firing/cooling rate to below 6C/min, for peak temperature of 1250C (dwell time of 1h) does not result in improvement of strength of porcelain. The industrial sized specimen exhibited flashover voltages of 20.3kV (dry) and 9.3kV (wet) respectively, transverse strength of 12.5kN and bulk density of 2.27g/cm3, which are satisfactory. There was however dye penetration during porosity test. KeywordsDwell time, Microstructure, Porcelain, Strength.

• Keywords:
• Dwell time
• Microstructure
• Porcelain
• Strength.

Difference of Properties on Surface Leakage and Discharge Currents of Porcelain Insulator Material

Year: 2009 Volume: 3 Issue: 10 1831 - 1835 Pages

• Authors:
• Waluyo
• Ngapuli I. Sinisuka
• Suwarno
• Maman A. Djauhari

Abstract: This paper presents the experimental results of comparison between leakage currents and discharge currents. The leakage currents were obtained on polluted porcelain insulator. Whereas, the discharge currents were obtained on lightly artificial polluted porcelain specimen. The conducted measurements were leakage current or discharge current and applied voltage. The insulator or specimen was in a hermetically sealed chamber, and the current waveforms were analyzed using FFT. The result indicated that the leakage current (LC) on low RH condition the fifth harmonic would be visible, and followed by the seventh harmonic. The insulator had capacitive property. Otherwise, on 99% relative humidity, the fifth harmonic would also be visible, and the phase angle reached up to 12.2 degree. Whereas, on discharge current, the third harmonic would be visible, and followed by fifth harmonic. The third harmonic would increase as pressure reduced. On this condition, the specimen had a non-linear characteristics

• Keywords:
• leakage current
• discharge current
• third harmonic
• fifth harmonic
• porcelain.