scholarly journals Sintering of alumina ceramics reinforced with a bioactive glass of 3CaO.P2O5-SiO2-MgO system

Cerâmica ◽  
2015 ◽  
Vol 61 (358) ◽  
pp. 160-167 ◽  
Author(s):  
A. W. Huang ◽  
C. Santos ◽  
R. O. Magnago ◽  
R. F. F. Silva ◽  
K. Strecker ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Relative Density ◽  
Transient Liquid Phase ◽  
Xrd Analysis ◽  
Alumina Ceramics ◽  
Crystalline Phases ◽  
Powder Mixtures ◽  
Solid State Sintering ◽  
Sintering Condition

<p>Alumina-based ceramics, Al<sub>2</sub>O<sub>3</sub>, exhibit a combination of properties which favor its use as biomaterial, specifically as structural dental prosthesis. Its most important properties as biomaterial are its elevated hardness, chemical stability and biocompatibility. Usually, Al<sub>2</sub>O<sub>3</sub> is processed by solid-state sintering at a temperature of about 1600 <sup>o</sup>C, but it is very difficult to eliminate the porosity due to its diffusional characteristics. The objective of this work was the development and characterization of sintered Al<sub>2</sub>O<sub>3</sub> ceramics, densified with a transient liquid phase formed by a bioactive 3CaO.P<sub>2</sub>O<sub>5</sub>-SiO<sub>2</sub>-MgO glass. Powder mixtures of 90 wt.% Al<sub>2</sub>O<sub>3</sub> and 10 wt.% bioglass were milled, compacted and sintered at 1200 <sup>o</sup>C to 1450 <sup>o</sup>C. Comparatively, monolithic Al<sub>2</sub>O<sub>3</sub> samples were sintered at 1600 <sup>o</sup>C/120 min. The sintered specimens were characterized by relative density, crystalline phases, microstructure and mechanical properties. The results indicate that the specimen sintered at 1450 <sup>o</sup>C/120 min present the best properties. Under this sintering condition, a relative density of 95% was reached, besides hardness higher than 9 GPa and fracture toughness of 6.2 MPa.m<sup>1/2</sup>. XRD analysis indicate alumina (αAl<sub>2</sub>O<sub>3</sub>), whitlockite (3CaO.P<sub>2</sub>O<sub>5</sub>) and diopsite [3(Ca,Mg)O.P<sub>2</sub>O<sub>5</sub>], as crystalline phases. Comparatively, monolithic sintered Al<sub>2</sub>O<sub>3</sub> samples presented 92% of relative density with 17.4 GPa and 3.8 MPa.m<sup>1/2</sup> of hardness and fracture toughness respectively.</p>

Characterization of Al2O3-Al2TiO2 Ceramic Composites: Effects of Sintering Parameters on the Properties

2018 ◽  
Vol 912 ◽  
pp. 118-123 ◽  
Author(s):  
Manuel Fellipe Rodrigues Pais Alves ◽  
Caio Marcelo Felbinger Azevedo Cossu ◽  
Roberto de Oliveira Magnago ◽  
Alfeu Saraiva Ramos ◽  
Claudinei dos Santos
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Relative Density ◽  
Ceramic Composites ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Crystalline Phases ◽  
Temperature Ranges ◽  
Distinct Temperature

This study aims to evaluate the effects of sintering parameters in crystalline phases, microstructure and mechanical properties of composites obtained through the Al2O3-TiO2 ceramic system. Cylindrical specimens, containing molar ratio of 3 Al2O3: 1 TiO2, were uniaxially pressed at 100 MPa. The applied sintering parameters were varied in five distinct temperature ranges (1300°C, 1400°C, 1500°C, 1575°C or 1600°C) for 2h and 1600°C for 10h. After sintering, samples were characterized by relative density, X-ray diffraction, scanning electron microscopy and mechanical properties (hardness and fracture toughness). After sintering the results point to a microstructure with grains near to 2.5mm, independent of the present phases and crystalline phases composed of: Al2O3 rhombohedral, TiO2 tetragonal e Al2TiO5 orthorhombic. The specimens sintered at 1600°C-10h feature densification 30% higher them the ones sintered at 1300°C-2h, reaching a density higher than 85% of theoretical density. The composite presents hardness higher than 1000HV and fracture toughness upper than 2.2MPam1/2. The better results for the mechanical properties were found in the composites sintered at 1600°C-10h, that showed a bigger relative density than all analyzed specimens, and only phases of Al2O3 and Al2TiO5 could be found, what means that all TiO2 was consumed in the sintering of the new composite.

scholarly journals The Effect of the Addition of Y2O3 on the Microstructure of Polycrystalline Alumina Ceramics

Proceedings ◽  
2018 ◽  
Vol 2 (23) ◽  
pp. 1407
Author(s):  
Serkan Abalı ◽  
Cem Uğur Karaçam
Keyword(s):  
Bending Strength ◽  
Xrd Analysis ◽  
Milling Process ◽  
Alumina Ceramics ◽  
Mechanical Behaviors ◽  
Cold Isostatic Press ◽  
Powder Mixtures ◽  
Polycrystalline Alumina ◽  
Microscope Images ◽  
Pure Al2o3

In the scope of this study, a powder mixture was prepared that contained 3 Al2O3-Y2O3 consisting of 99.99% pure Al2O3 and aluminum oxide of 65–67% and 70% by weight of 99.999% pure Y2O3 powders. After the powders were weighed on a precision scale, the milling process was carried out in a vibratory disc mill. For the granulation, 3 powder mixtures that were subject to sintering were sieved to a size of less than 106 µm in a powder sieve shaker. The powders were shaped with a cold isostatic press after this step and the 3 acquired samples were sintered for 12 h under a temperature of 1923 K. Selected physical and mechanical behaviors were taken by evaluating microhardness measurements, bending strength XRD analysis and electron microscope images of the 3 sintered samples. The changes in the Y2O3 additive and phase composition, microstructure, and mechanic properties were examined.

Spark Plasma Sintering and Characterization of WC-Co-cBN Composites

2014 ◽  
Vol 616 ◽  
pp. 194-198 ◽  
Author(s):  
Jian Feng Zhang ◽  
Rong Tu ◽  
Takashi Goto
Keyword(s):  
Fracture Toughness ◽  
Phase Transformation ◽  
Relative Density ◽  
Spark Plasma Sintering ◽  
Sintering Temperature ◽  
Moderate Pressure ◽  
Plasma Sintering ◽  
Spark Plasma

WC-Co-cBN composites were consolidated by SPS at 1373 to 1673 K under a moderate pressure of 100 MPa. The addition of cBN increased the starting and finishing temperature of shrinkage and decreased the relative density of WC-Co. The relative density of WC-(10-20 vol%) cBN composites was about 97-100% at 1573 K and decreased with increasing the sintering temperature to 1673 K due to the phase transformation of cBN to hBN. The highest hardness and fracture toughness of WC-Co-20 vol% cBN composite sintered at 1573 K were 23.2 GPa and 8.0 MP m1/2, respectively.

Synthesis and Characterization of Pb(Zr0.52Ti0.48)O3 Properties via High Planetary Mill

2017 ◽  
Vol 888 ◽  
pp. 96-102
Author(s):  
Shafiza Afzan Sharif ◽  
Julie Juliewatty Mohamed ◽  
Hasmaliza Mohamed ◽  
Zainal Arifin Ahmad ◽  
Wan Azhar Wan Yusoff
Keyword(s):  
Sintering Temperature ◽  
Xrd Analysis ◽  
High Energy ◽  
Planetary Mill ◽  
Firing Process ◽  
Material System ◽  
Sintering Process ◽  
Grain Growth Behavior ◽  
Sintering Condition

In this work, the piezoelectric material system of Pb (Zr0.52Ti0.48)O3 ceramics were synthesized by conventional solid state via high energy planetary mill reaction. This process were chosen in order to skip the calcinations and implement a single firing process which very effective to reduce the possibility of PbO loss. The effect of sintering parameters on structural behavior of pure PZT ceramic was discussed in detail. Comprehensive studies have been carried out in order get optimum parameter for sintering process, thus improved the performance of the pure PZT ceramics. Grain size properties of Pb (Zr0.52Ti0.48)O3 ceramics increased with increasing the sintering temperature and duration. However longer sintering condition (1200 °C, 3 hours) causes excessive PbO loss which leads to presence new phases in XRD analysis, promote grain growth behavior with inhomogenous microstructure and tend to have more pores.

Development and Characterization of the Al2O3-YAG Ceramic Composites

2014 ◽  
Vol 798-799 ◽  
pp. 383-388 ◽  
Author(s):  
Eduardo Sousa Lima ◽  
A.P.O. Santos ◽  
L.M. Itaboray ◽  
C. Santos ◽  
R.F. Cabral
Keyword(s):  
Relative Density ◽  
Microstructural Characterization ◽  
Ceramic Composites ◽  
Oxide Ceramic ◽  
X Ray Diffraction ◽  
Powder Mixtures ◽  
X Ray ◽  
Resistance To Oxidation ◽  
Oxidation And Corrosion

YAG (Y3Al5O12) and Al2O3 ceramics have high resistance to oxidation and corrosion in harsh environments and high temperatures, which turns into a quite attractive material as compared to other ceramics. Thus, lately oxide ceramic YAG has been extensively used as reinforcement phase to Al2O3 in order to obtain a composite with improved mechanical properties. This research focused on the development of sintered Al2O3-Y2O3 powder mixtures for the production of Al2O3-YAG composite. Powder mixtures composed of 63.65:36.35wt.% and 80.00:20.00wt.% of Al2O3 and Y2O3, respectively, were milled by planetary milling for 2h. The compositions were compacted by cold uniaxial pressing, at 70 MPa, for 30s. The two mixtures were sintered at 1500 and 1600°C for 3h. The samples were evaluated for relative density, shrinkage, weight loss, and X-Ray Diffraction (XRD). Scanning Electron Microscopy (SEM) was used for microstructural characterization. The X-Ray Diffraction showed the presence of Al2O3 and Y3Al5O12 as crystalline phases in both compositions. Samples composed by 80:20wt.% of Al2O3/Y2O3 powder sintered at 16000C-3h presented the higher relative density ranging around 86% of theoretical density.

Effect of Al2O3 Addition on the Mechanical Properties of Biocompatible ZrO2-Al2O3 Composites

2006 ◽  
Vol 530-531 ◽  
pp. 575-580 ◽  
Author(s):  
Claudinei dos Santos ◽  
L.H.P. Teixeira ◽  
Kurt Strecker ◽  
Carlos Nelson Elias
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Phase Composition ◽  
Relative Density ◽  
Room Temperature ◽  
Ceramic Composites ◽  
Linear Increase ◽  
Powder Mixtures ◽  
Al2o3 Ceramic ◽  
Sintering Conditions

In this work, the effects of alumina additions on the properties of the ZrO2-Al2O3 ceramic composites were investigated. Samples of ZrO2 with Al2O3 additions varying between 0 and 30wt-% were prepared. The powder mixtures were milled, compacted by uniaxial cold pressing and sintered at 16000C, in air, for 2 hours. The sintered samples were characterized by their relative density, phase composition and microstructure. As mechanical properties at room temperature, their Vickers hardness and fracture toughness were determined: In all sintering conditions and Al2O3 amounts, the samples presented relative density higher that 99%. The Al2O3 addition produces a linear increase of the hardness, reaching values between 1350 and 1610 HV for the addition of 0 and 30% of alumina, respectively. The fracture toughness was near to 8 MPam1/2 in all conditions. The phase composition, microstructure and relative density were correlated in order to interpret the mechanical properties obtained.

scholarly journals Densification and Mechanical Properties of Alumina Ceramics via Two-Step Sintering With Different Holding Times

2021 ◽  
Vol 6 (4) ◽  
pp. 299-304
Author(s):  
Anis Syufina Mohammad Saufi ◽  
Ramesh Singh ◽  
K. Y. Sara Lee ◽  
Tao Wu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Relative Density ◽  
Grain Growth ◽  
Vickers Hardness ◽  
Holding Time ◽  
Alumina Ceramics ◽  
Conventional Sintering ◽  
Viable Approach

The densification and mechanical properties of alumina ceramics were investigated via two-step sintering (TSS) with different holding time. The alumina ceramics were sintered at 1450 °C for 1 min during the first stage, followed by sintering at 1350 °C with different holding times (2-24h). Conventional sintering (CS) was also performed on the alumina ceramics at 1450 °C for 2 h for comparison purpose. It was found that dense alumina with a relative density above 98% could be attained when TSS with a holding time of more than 12 h. The samples exhibited Vickers hardness between 5-8 GPa and fracture toughness of about 6 MPa.m1/2. In contrast, conventional sintered alumina yielded low relative density (85%), large grain size (2 μm), low Vickers hardness (4.23 GPa) and fracture toughness (4.73 MPa.m1/2). This study revealed that TSS is a viable approach in aiding densification, suppressing grain growth, and improving the mechanical properties of alumina ceramics.

Development and Characterization of Al2O3-ZrO2 Composites Using ZrO2(Y2O3)-Recycled as Raw Material

2018 ◽  
Vol 912 ◽  
pp. 124-129
Author(s):  
Caio Marcelo Felbinger Azevedo Cossu ◽  
Manuel Fellipe Rodrigues Pais Alves ◽  
Luiz Cláudio Lemos de Assis ◽  
Roberto de Oliveira Magnago ◽  
José Vitor Candido de Souza ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Relative Density ◽  
Raw Materials ◽  
Ceramic Composites ◽  
Raw Material ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dental Prostheses ◽  
Scanning Electron

The objective of this work was the development of Al2O3-ZrO2 ceramic composites using recycled-source of ZrO2(Y2O3). Al2O3 powder was mixed with different proportions of ZrO2(Y2O3) arising from pre-sintered blocks used in dental prostheses manufacturing. The mixtures containing 3wt% to 15wt% ZrO2(Y2O3) were uniaxially pressed at 80MPa and sintered at 1600°C-2h. Raw materials and sintered samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), relative density, hardness and fracture toughness. The results of X-ray diffraction showed α-Al2O3 and tetragonal-ZrO2 as crystalline phases after sintering. Furthermore, the relative density in all compositions was higher than 95%. The samples presented Vickers hardness and fracture toughness higher than 1300HV and 3.5MPa. m1/2, respectively.

Effect of Si2N2O content on the microstructure, properties, and erosion of silicon nitride–Si2N2O in situ composites

2002 ◽  
Vol 17 (9) ◽  
pp. 2275-2280 ◽  
Author(s):  
Dong-Soo Park ◽  
Hyun-Ju Choi ◽  
Byung-Dong Han ◽  
Hai-Doo Kim ◽  
Dae-Soon Lim
Keyword(s):  
Fracture Toughness ◽  
Silicon Nitride ◽  
Hot Pressing ◽  
Xrd Analysis ◽  
Transgranular Fracture ◽  
X Ray Diffraction ◽  
Powder Mixtures ◽  
X Ray ◽  
Pressing Powder

Silicon nitride–Si2N2O in situ composites were prepared by hot pressing powder mixtures of α–Si3N4, 6 wt% Y2O3, 1 wt% Al2O3, and 0–12 wt% SiO2. X-ray diffraction (XRD) analysis indicated that the volume percents of Si2N2O were 0, 13, 31, and 54 for the composites prepared with 0, 4, 8, and 12 wt% SiO2, respectively. XRD results also indicated that both silicon nitride grains and Si2N2O grains were laid down perpendicular to hot pressing direction. As the volume percent of Si2N2O increased, the width and the amount of elongated silicon nitride grains decreased, but the fracture toughness increased. Young's modulus of the in situ composites decreased as the Si2N2O content was increased. The erosion rate decreased as the Si2N2O content was increased, in part, due to both the increased fracture toughness and the reduced grain size. Erosion of the composites occurred primarily due to the grain dislodgment. The sample without Si2N2O experienced micro-chipping due to transgranular fracture.

scholarly journals Mechanical Characterization of Zirconia Ceramic Composite

2018 ◽  
Vol 152 ◽  
pp. 02006
Author(s):  
Kelvin Chew Wai Jin ◽  
Kam Dickson ◽  
Ramesh Singh
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Relative Density ◽  
Vickers Hardness ◽  
Zirconia Ceramic ◽  
Body Parts ◽  
Steel Increase ◽  
Stainless Steel 316 ◽  
Zirconia Implants

In this day and age, zirconia ceramics are used widely in the medical field as biomaterials for the replacement of damaged body parts. This is because zirconia is one of the closest replacements for bone tissue. However, there were a few cases regarding the failure of zirconia ceramic hip transplants. To overcome this issue, composite materials are being studied as they are able to combine different properties which are not present in a material. This study of Y-TZP/stainless steel 316 composite is carried out with the idea of providing a solution for failure of zirconia implants and also an improvement in biomaterials which will benefit the biomedical world. The study aims to determine the effects on how the increasing of stainless-steel content in the composite will affect the relative density, Vickers hardness, fracture toughness and ageing resistance of the Y-TZP/stainless steel 316 composite. To carry out the research, the composite samples were prepared by mixing the powder of each samples according to their determined content with ethanol. After the powders were mixed, the powders were then pressed, followed by undergoing a Cold Isostatic Press process (CIP) and then it underwent sintering at its determined temperature. After sintering, the samples underwent grinding and polishing before being ready for testing. The outcomes of the research showed that as the sintering temperature and the content of stainless-steel increase in the composite, the fracture toughness and ageing resistance improved while the Vickers hardness and relative density decreased.

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