scholarly journals Properties of yttria-tetragonal zirconia polycrystal (Y-TZP) materials after long-term exposure to elevated temperatures. Final report

1989 ◽  
Author(s):  
J.J. Swab
Keyword(s):  
Elevated Temperatures ◽  
Tetragonal Zirconia ◽  
Final Report ◽  
Tetragonal Zirconia Polycrystal

Laser-Assisted Milling of Zirconia with Systematically Determined Machining Conditions

2017 ◽  
Vol 11 (2) ◽  
pp. 258-269
Author(s):  
Toru Kizaki ◽  
◽  
Yusuke Ito ◽  
Naohiko Sugita ◽  
Mamoru Mitsuishi
Keyword(s):  
Fracture Toughness ◽  
Unique Feature ◽  
Elevated Temperatures ◽  
Thrust Force ◽  
Tetragonal Zirconia ◽  
Systematic Method ◽  
Processing Efficiency ◽  
Diamond Tools ◽  
Dental Restoratives ◽  
Tetragonal Zirconia Polycrystal

Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) is a promising material for dental restoratives. Although grinding or polishing with diamond tools is widely used to machine Y-TZP, the processing efficiency and cost of the process are problematic. In this study, we applied laser-assisted machining (LAM) to Y-TZP, in which non-diamond tools were used. Unlike LAM applied to other materials, decrease of the fracture toughness at elevated temperatures which is a unique feature of the Y-TZP was adopted as a key mechanism for machinability enhancement. In addition, a systematic method to determine the LAM conditions was proposed. In this study, we explain the LAM condition-determining method, which is based on numerical simulations of the temperature distribution. Secondly, the determining method was evaluated through a series of LAM experiments to obtain the appropriate LAM conditions. Using the determined conditions, LAM of Y-TZP was demonstrated to be effective; the thrust force was reduced by 51.3% and the tool wear was significantly reduced, while no cracks formed on the Y-TZP.

scholarly journals Novel Zirconia Materials in Dentistry

2017 ◽  
Vol 97 (2) ◽  
pp. 140-147 ◽  
Author(s):  
Y. Zhang ◽  
B.R. Lawn
Keyword(s):  
Tetragonal Zirconia ◽  
Glass Ceramics ◽  
Clinical Applications ◽  
Cubic Phase ◽  
Routine Laboratory ◽  
Dental Ceramics ◽  
Sintering Aid ◽  
Progressive Development ◽  
Tetragonal Zirconia Polycrystal

Zirconias, the strongest of the dental ceramics, are increasingly being fabricated in monolithic form for a range of clinical applications. Y-TZP (yttria-stabilized tetragonal zirconia polycrystal) is the most widely used variant. However, current Y-TZP ceramics on the market lack the aesthetics of competitive glass-ceramics and are therefore somewhat restricted in the anterior region. This article reviews the progressive development of currently available and next-generation zirconias, representing a concerted drive toward greater translucency while preserving adequate strength and toughness. Limitations of efforts directed toward this end are examined, such as reducing the content of light-scattering alumina sintering aid or incorporating a component of optically isotropic cubic phase into the tetragonal structure. The latest fabrication routes based on refined starting powders and dopants, with innovative sintering protocols and associated surface treatments, are described. The need to understand the several, often complex, mechanisms of long-term failure in relation to routine laboratory test data is presented as a vital step in bridging the gaps among material scientist, dental manufacturer, and clinical provider.

Behavior of 3mol% yttria-stabilized tetragonal zirconia polycrystal film prepared by slurry spin coating

2009 ◽  
Vol 186 (1) ◽  
pp. 128-132 ◽  
Author(s):  
Kongfa Chen ◽  
Yanting Tian ◽  
Zhe Lü ◽  
Na Ai ◽  
Xiqiang Huang ◽  
...  
Keyword(s):  
Spin Coating ◽  
Tetragonal Zirconia ◽  
Tetragonal Zirconia Polycrystal

scholarly journals CO Detection Investigation at High Temperature by SiC MISFET Metal/Oxide Gas Sensors

Proceedings ◽  
2021 ◽  
Vol 56 (1) ◽  
pp. 41
Author(s):  
Lida Khajavizadeh ◽  
Anita Lloyd Spetz ◽  
Mike Andersson
Keyword(s):  
High Temperature ◽  
Gas Sensors ◽  
Elevated Temperatures ◽  
Long Term Stability ◽  
Stability Performance ◽  
Catalytic Metal ◽  
Co Detection ◽  
Effect Transistor ◽  
Metal Oxide Gas Sensors

In order to investigate the necessary device improvements for high-temperature CO sensing with SiC metal insulator semiconductor field effect transistor (MISFET)-based chemical gas sensors, devices employing, as the gas-sensitive gate contact, a film of co-deposited Pt/Al2O3 instead of the commonly used catalytic metal-based contacts were fabricated and characterized for CO detection at elevated temperatures and different CO and O2 levels. It can be concluded that the sensing mechanism at elevated temperatures correlates with oxygen removal from the sensor surface rather than the surface CO coverage as observed at lower temperatures. The long-term stability performance was also shown to be improved compared to that of previously studied devices.

Transformation behavior of yttria stabilized tetragonal zirconia polycrystal–TiB2 composites

2001 ◽  
Vol 16 (7) ◽  
pp. 2158-2169 ◽  
Author(s):  
B. Basu ◽  
J. Vleugels ◽  
O. Van Der Biest
Keyword(s):  
Thermal Expansion ◽  
Phase Transformation ◽  
Low Temperature ◽  
Tetragonal Zirconia ◽  
Mechanical Analysis ◽  
Transformation Behavior ◽  
Thermal Expansion Data ◽  
Thermally Induced ◽  
First Time ◽  
Tetragonal Zirconia Polycrystal

The objective of the present article is to study the influence of TiB2 addition on the transformation behavior of yttria stabilized tetragonal zirconia polycrystals (Y-TZP). A range of TZP(Y)–TiB2 composites with different zirconia starting powder grades and TiB2 phase contents (up to 50 vol%) were processed by the hot-pressing route. Thermal expansion data, as obtained by thermo-mechanical analysis were used to assess the ZrO2 phase transformation in the composites. The thermal expansion hysteresis of the transformable ceramics provides information concerning the transformation behavior in the temperature range of the martensitic transformation and the low-temperature degradation. Furthermore, the transformation behavior and susceptibility to low-temperature degradation during thermal cycling were characterized in terms of the overall amount and distribution of the yttria stabilizer, zirconia grain size, possible dissolution of TiB2 phase, and the amount of residual stress generated in the Y-TZP matrix due to the addition of titanium diboride particles. For the first time, it is demonstrated in the present work that the thermally induced phase transformation of tetragonal zirconia in the Y-TZP composites can be controlled by the intentional addition of the monoclinic zirconia particles into the 3Y-TZP matrix.

1 Final Report on the Safety Assessment of Isostearyl Neopentanoate

1985 ◽  
Vol 4 (3) ◽  
pp. 1-22 ◽  
Keyword(s):  
Test Data ◽  
Clinical Studies ◽  
Safety Assessment ◽  
Final Report ◽  
Cosmetic Products ◽  
Short And Long Term ◽  
Cosmetic Formulation

Isostearyl Neopentanoate, the ester of Isostearyl Alcohol and Neopentanoic Acid, is used in cosmetic products as an emollient at concentrations up to 50 percent. The undiluted ingredient at doses up to 4 ml/kg was shown to be relatively non-toxic in short-and long-term feeding studies. Test data from animal and clinical studies indicate the undiluted ingredient is neither an irritant nor a sensitizer. A cosmetic formulation containing 16 percent Isostearyl Neopentanoate produced no phototoxicity and no photoallergenicity. Mutagenicity, carcinogenicity, and teratogenicity data were not available. Isostearyl Neopentanoate was not considered to be a significant comedogenic agent. On the basis of available data, it is concluded that this ingredient is safe as a cosmetic ingredient in its present practices of use.

scholarly journals Effect of Al2O3 Sandblasting Particle Size on the Surface Topography and Residual Compressive Stresses of Three Different Dental Zirconia Grades

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 610
Author(s):  
Hee-Kyung Kim ◽  
Byungmin Ahn
Keyword(s):  
Particle Size ◽  
Residual Stresses ◽  
Surface Topography ◽  
Tetragonal Zirconia ◽  
Peak Shift ◽  
Confocal Laser ◽  
Compressive Stresses ◽  
Surface Topographies ◽  
Altered Surface ◽  
Tetragonal Zirconia Polycrystal

This study investigated the effect of sandblasting particle size on the surface topography and compressive stresses of conventional zirconia (3 mol% yttria-stabilized tetragonal zirconia polycrystal; 3Y-TZP) and two highly translucent zirconia (4 or 5 mol% partially stabilized zirconia; 4Y-PSZ or 5Y-PSZ). Plate-shaped zirconia specimens (14.0 × 14.0 × 1.0 mm3, n = 60 for each grade) were sandblasted using different Al2O3 sizes (25, 50, 90, 110, and 125 μm) under 0.2 MPa for 10 s/cm2 at a 10 mm distance and a 90° angle. The surface topography was characterized using a 3-D confocal laser microscopy and inspected with a scanning electron microscope. To assess residual stresses, the tetragonal peak shift at 147 cm−1 was traced using micro-Raman spectroscopy. Al2O3 sandblasting altered surface topographies (p < 0.05), although highly translucent zirconia showed more pronounced changes compared to conventional zirconia. 5Y-PSZ abraded with 110 μm sand showed the highest Sa value (0.76 ± 0.12 μm). Larger particle induced more compressive stresses for 3Y-TZP (p < 0.05), while only 25 μm sand induced residual stresses for 5Y-PSZ. Al2O3 sandblasting with 110 μm sand for 3Y-TZP, 90 μm sand for 4Y-PSZ, and 25 μm sand for 5Y-PSZ were considered as the recommended blasting conditions.

Technology Focus: Wellbore Tubulars (July 2021)

2021 ◽  
Vol 73 (07) ◽  
pp. 50-50
Author(s):  
Robello Samuel
Keyword(s):  
Geothermal Energy ◽  
Elevated Temperatures ◽  
Clean Energy ◽  
Well Integrity ◽  
The Future ◽  
Geothermal Wells ◽  
Abandoned Wells ◽  
Thermal Simulations ◽  
Technology Focus

How we think about the future of the pipe industry must evolve. How must tubular design and manufacturing change as we transition to clean energy? Geothermal energy is an area that needs attention and, further, needs very specific attention on tubulars. Tubulars are an important component in the construction of geothermal wells, and we must align our requirements for geothermal energy. Some of the main challenges encountered in geothermal wells are corrosion and scaling. Moreover, temperature becomes a major consideration for tubulars, even more so with the temperature excursion during geothermal production. Perhaps the critical aspect in the design of the geothermal wells involves casing selection and design. Beyond manufacturing casing pipes to withstand these problems, considering the manufacturing of other components, such as connections, float collars, and float shoes, also is essential. Thermal expansion and thermal excursion of casings are well-integrity concerns; thus, casing design is important for long-term sustainability of geothermal wells. Apart from thermal simulations, guidelines and software are needed to undergird the designs to withstand not only temperature excursions but also thermomechanical and thermochemical loadings. Engineered nonmetallic casings also provide an alternative solution because they provide the desired strength and corrosion resistance in addition to meeting the goals of sustainability. Undoubtedly, the future of the tubular industry is going to be revitalized. The question now is how we can retrofit existing abandoned wells for this purpose. Recommended additional reading at OnePetro: www.onepetro.org. SPE 199570 - Special Considerations for Well-Tubular Design at Elevated Temperatures by Gang Tao, C-FER Technologies, et al.

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