Preparation and Properties of Al2O3 Particle Dispersed 3Y-TZP Nanoceramics Doped with TiO2

2007 ◽  
Vol 336-338 ◽  
pp. 2254-2256 ◽  
Author(s):  
Bo Jun Chen ◽  
Zhao Qiang Zeng
Keyword(s):  
Grain Size ◽  
Relative Density ◽  
Reduction Method ◽  
Al2o3 Particle ◽  
Second Phase ◽  
Sintering Process ◽  
Tio2 Content ◽  
Powder Mixing ◽  
Powder Dispersion ◽  
Grain Sizes

Al2O3 particle dispersed 3Y-TZP nanoceramics doped with TiO2 was fabricated by the vacuum reduction of Ti(OH)4, Al(NO3)3 and 3Y-TZ powders at 873K for 2h and sintered in air at 1573K~1823K for 2-6h. The relation between Al2O3 and TiO2 content, sintering parameters, relative density and grain sizes were studied. Microstructural investigations revealed that, in comparison with direct powder mixing, the reduction method is more efficient in achieving a homogeneous dispersed fine alumina second phase, which results in the reduction of matrix grain size and the increase of the relative density of the 3Y-TZP ceramic. TiO2 addition facilitates the sintering process but may cause significant abnormal grain growth which can be offset by the homogeneity of the powder dispersion. A final 3Y-TZP-TiO2 ceramic matrix with grain size below 500nm dispersed with ultrafine second phase Al2O3 was obtained.

The Preparation and Properties of Alumina Ceramics through a Two-Step Pressureless Sintering Process

2018 ◽  
Vol 922 ◽  
pp. 47-54
Author(s):  
Chang Suo Yuan ◽  
Zi Jing Wang ◽  
Qiang Zhi ◽  
Ya Ming Zhang ◽  
Xu Dong Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Relative Density ◽  
High Purity ◽  
Dominant Factor ◽  
Second Phase ◽  
Pressureless Sintering ◽  
Sintering Process ◽  
Alumina Ceramics ◽  
Soaking Time

In this paper, a high-dense alumina ceramics were prepared through the two-step pressureless sintering process with high-purity alumina powder as raw materials and high-purity MgO as sintering aids. The effects of the sintering temperature in the first-step (T1) and the soaking time (t) in the second sintering step (T2) on the density, microstructure and mechanical properties of the alumina ceramics were studied. The results indicated that the relative density increased with the increase of T1 temperature whereas it increased and then decreased with the increase of MgO content. Higher T1 temperature and extended soaking time caused larger grain size, which accompanied with the Ostwald ripening of the grain and led to non-uniformity of grain size distribution. The addition of MgO was beneficial to the decrease in grain size due to pinning effect of the second phase. For samples with shorter soaking time, sintering with higher T1 temperature led to better mechanical properties because of its high density. However, for the long soaking time, all samples after sintering at different T1 temperature were fully-densified, so the grain size become to the dominant factor of strength, thus samples with lower T1 temperature exhibited better mechanical properties due to the refinement grain. Excessive addition of MgO resulted in defects, by which the strength increased firstly and then decreased slightly with the increased MgO content. For the samples with 2.5wt.% MgO, the optimum condition for the two-step pressureless sintering was T1=1450°C and T2=1400°C for 20h, and the obtained sample achieved the relative density of 96% and the strength of 507±32MPa.

The Influence of Sintering Process on the Microstructure of Submicron Alumina Fabricated by Gelcasting

2007 ◽  
Vol 336-338 ◽  
pp. 1185-1187 ◽  
Author(s):  
Long Hao Qi ◽  
Jian Shen ◽  
Wei Pan
Keyword(s):  
Grain Size ◽  
Relative Density ◽  
Raw Materials ◽  
Sintering Process ◽  
Maximal Strength ◽  
Grain Sizes ◽  
Transparent Alumina ◽  
Hip Process

Using ultra-fine alumina powders as raw materials, the submicron transparent alumina with relative density more than 99.9% was fabricated by gelcasting and then sintering-HIP process. It was found that only the samples with relative density more than 95% after presintering could obtain fully densification by post-HIP treatment. The final grain sizes increased after post-HIP treatment and were decided by either HIPing temperature or presintering temperature, depending on which one is higher. The maximal strength can reach about 650MPa when grain size is about 1 μm.

Enhanced Densification and Grain-Size Refinement in Cation-Doped Tetragonal Zirconia

2010 ◽  
Vol 62 ◽  
pp. 227-231
Author(s):  
Keijiro Hiraga ◽  
Hidehiro Yoshida ◽  
Koji Morita ◽  
Byung Nam Kim
Keyword(s):  
Grain Size ◽  
Relative Density ◽  
Grain Growth ◽  
Sintering Temperature ◽  
Initial Density ◽  
Tetragonal Zirconia ◽  
The Other ◽  
Size Refinement ◽  
Grain Sizes ◽  
Materials Used

In tetragonal zirconia, possibility is investigated of densification with finer grain sizes under the combination of doping and sintering in air. The materials used are CIP'ed compacts of 3-mol%-yttria-stabilized tetragonal zirconia (3Y-TZP) doped with a small amount of cations. For a given sintering temperature and initial density of the compacts, while the doped cations enhances densification in the latest stage of sintering, the effect is different in grain growth during densification: a doped cation tended to enhance grain growth, whereas the other cations tended to suppress grain growth. As a result, the doping of the latter cations brings about a grain size finer than that of the undoped 3Y-TZP for a given relative density.

Preparation and Characterization of Fe Doped Bi2Ga4O9 Ceramics

2014 ◽  
Vol 552 ◽  
pp. 283-285
Author(s):  
Huan Huan Chen ◽  
Xiao Yan Zhang ◽  
Xi Wei Qi ◽  
Zhao Jie Zhou ◽  
Gui Fang Sun
Keyword(s):  
Grain Size ◽  
Solid Phase ◽  
Sem Analysis ◽  
Phase Method ◽  
Second Phase ◽  
Doping Content ◽  
Fe Doping ◽  
Sintering Process ◽  
Solid Phase Method

A series of Fe-doped Bi2(FexGa1-x)4O9 (x=0.1,0.2,0.3,0.4,0.5) ceramics were synthesized by solid-phase method with sintering process. The influences of Fe doping content on phase, morphology, dielectric properties are discussed. XRD results show that there is no second phase in Fe-doped Bi2(FexGa1-x)4O9 ceramics. The SEM analysis indicates the grain size of as-prepared doped samples are relatively uniform and estimated to be about 1–4μm. The permittivity of as-prepared doped samples increases and the dielectric loss decrease compared to pure Bi2Ga4O9 ceramics.

Preparation of Barium Titanate Grain-Oriented Ceramics and their Piezoelectric Properties

2010 ◽  
Vol 445 ◽  
pp. 3-6 ◽  
Author(s):  
Rintaro Mori ◽  
Petr Pulpan ◽  
Hiroshi Hayashi ◽  
Yoshitaka Nagamori ◽  
Yuichi Yamamoto ◽  
...  
Keyword(s):  
Grain Size ◽  
Barium Titanate ◽  
Relative Density ◽  
Grain Growth ◽  
Piezoelectric Properties ◽  
Templated Grain Growth ◽  
Grain Sizes ◽  
Degree Of Orientation ◽  
High Degree ◽  
The Relationship

Barium titanate (BaTiO3, BT) grain-oriented ceramics along [110] direction were prepared by a templated grain growth (TGG) method. The [110] oriented BT platelike particles (t-BT) were used as template particles. BT grain-oriented ceramics with higher relative density (Drel) over 95 %, high degree of orientation along [110] direction (F110) over 80 % and grain sizes around 30 µm were successfully prepared using only the template particles. The relationship between microstructures and piezoelectric constant (d33) was investigated. The higher F110 was, the higher Drel and the smaller grain size were required for enhancement of the piezoelectric properties.

Mechanical Properties of ZrB2-Based Ceramics Reinforced by Nano-SiC Whiskers

2007 ◽  
Vol 353-358 ◽  
pp. 1564-1567 ◽  
Author(s):  
Hai Long Wang ◽  
Chang An Wang ◽  
Rui Zhang ◽  
Xing Hu ◽  
Dai Ning Fang
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Relative Density ◽  
Hot Pressing ◽  
Bending Strength ◽  
Sintering Process ◽  
Homogeneous Microstructure ◽  
Sic Whiskers ◽  
Xrd Techniques

In this paper, ZrB2-based ceramics containing up to 15 vol% nano-SiC whiskers were prepared by hot pressing at 1950°C under 20MPa pressure in flow argon. SEM and XRD techniques were used to characterize the sintered compacts. A fine and homogeneous microstructure was observed. The relative density of ZrB2-based ceramic containing 10vol% SiC whiskers reached to 97.7%. The bending strength and fracture toughness of the composite were 550 MPa and 8.08 MPa·m1/2 respectively, while those of the monolithic ZrB2 ceramic (0 vol% SiC whiskers added) were 424 MPa and 4.52 MPa·m1/2 respectively. The grain size of the ZrB2-based ceramics was reduced greatly by the addition of nano-SiC whiskers during the sintering process.

The Effect of Grain Boundaries and Second-Phase Particles on Hydride Precipitation in Zirconium Alloys

MRS Advances ◽  
2018 ◽  
Vol 3 (31) ◽  
pp. 1749-1754 ◽  
Author(s):  
Said El Chamaa ◽  
Mitesh Patel ◽  
Catrin M. Davies ◽  
Mark R. Wenman
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Zirconium Alloys ◽  
Second Phase ◽  
Distribution Profile ◽  
Grain Sizes ◽  
Hydride Precipitation ◽  
Nucleation Sites ◽  
Wide Range ◽  
Pure Zirconium

ABSTRACTUnderstanding the precipitation of brittle hydride phases is crucial in establishing a failure criterion for various zirconium alloy nuclear fuel cladding. Accordingly, it is important to quantify the sensitivity of hydride precipitation to the component microstructure. This experimental investigation focuses on two microstructural characteristics and their role as hydride nucleation sites: The grain size and the alloy chemical composition. Samples of commercially pure zirconium (Zr-702) and Zircaloy-4, each with a wide range of grain sizes, were hydrided to 100 ppm and micrographs of the hydride distribution were optically analyzed for inter-granular and intra-granular precipitate sites. For most grain sizes, it was found that a significantly lower fraction of the precipitated hydrides nucleated at grain boundaries in Zircaloy-4 than in Zr-702, suggesting that a higher SPP content encourages the formation of intra-granular hydrides. Moreover, this effect became more prominent as the grain size increased; large-grain specimens contained a higher fraction of intra-granular hydrides than small-grain specimens of both Zr-702 and Zircaloy-4, highlighting the potency of grain boundaries as nucleation sites and how SPPs can influence the hydride distribution profile.

Structure of second phases in TiAl alloys containing Cr and B

1991 ◽  
Vol 49 ◽  
pp. 576-577
Author(s):  
Ernest L. Hall ◽  
Shyh-Chin Huang
Keyword(s):  
Grain Size ◽  
Second Phase ◽  
Structure And Properties ◽  
Tial Alloys ◽  
Second Phases ◽  
Interstitial Elements

Addition of interstitial elements to γ-TiAl alloys is currently being explored as a method for improving the properties of these alloys. Previous work in which a number of interstitial elements were studied showed that boron was particularly effective in refining the grain size in castings, and led to enhanced strength while maintaining reasonable ductility. Other investigators have shown that B in γ-TiAl alloys tends to promote the formation of TiB2 as a second phase. In this study, the microstructure of Bcontaining TiAl alloys was examined in detail in order to describe the mechanism by which B alters the structure and properties of these alloys.

scholarly journals Improvement of mechanical properties of HfB2-based composites by incorporating in situ SiC reinforcement through pressureless sintering

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Ghadami ◽  
E. Taheri-Nassaj ◽  
H. R. Baharvandi ◽  
F. Ghadami
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Relative Density ◽  
Pressureless Sintering ◽  
Sintering Process ◽  
Vacuum Atmosphere ◽  
Sic Reinforcement ◽  
Microstructural Studies ◽  
Composite Samples

AbstractHfB2, Si, and activated carbon powders were selected to fabricate 0–30 vol% SiC reinforced HfB2-based composite. Pressureless sintering process was performed at 2050 °C for 4 h under a vacuum atmosphere. Microstructural studies revealed that in situ SiC reinforcement was formed and distributed in the composite according to the following reaction: Si + C = SiC. A maximum relative density of 98% was measured for the 20 vol% SiC containing HfB2 composite. Mechanical investigations showed that the hardness and the fracture toughness of these composites were increased and reached up to 21.2 GPa for HfB2-30 vol% SiC and 4.9 MPa.m1/2 for HfB2-20 vol% SiC, respectively. Results showed that alpha-SiC reinforcements were created jagged, irregular, and elongated in shape which were in situ formed between HfB2 grains and filled the porosities. Formation of alpha-SiC contributed to improving the relative density and mechanical properties of the composite samples. By increasing SiC content, an enhanced trend of thermal conductivity was observed as well as a reduced trend for electrical conductivity.

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