Effect of In Situ Formed Spinel Phase on the Mechanical Properties of Zirconia Ceramics

2007 ◽  
Vol 345-346 ◽  
pp. 1573-1576
Author(s):  
Z. X. Yang ◽  
Jeong Bae Yoon ◽  
Kyu Hong Hwang ◽  
J.K. Lee ◽  
B.S. Jun
Keyword(s):  
Mechanical Properties ◽  
Spinel Phase ◽  
Sintering Behavior ◽  
Reaction Sintering ◽  
Stabilized Zirconia ◽  
Homogeneous Microstructure ◽  
Fine Grain ◽  
Firing Shrinkage ◽  
Spinel Mgal2o4

The reaction-sintered zirconia-alumina and zirconia-spinel ceramics having low firing shrinkage were prepared from ZrO2(Ca-PSZ)/Al and ZrO2(Baddellyite)/MgAl powder mixtures via the attrition milling and the effect of the characteristics of used raw powders was investigated. Flaky Al powders mixed with coarse Ca-PSZ powders was not effectively comminuted due to lower hardness of zirconia powders. So by using the alumina ball media or coarse Al2O3 powders rather than Al, the milling efficiency could be much more increased. When fused Ca-PSZ powder was reaction-sintered with Al at 1550 for 3 hours, the reaction-sintering and densification were somewhat difficult because the Ca-PSZ/Al powder mixture was not effectively comminuted. And the Ca ion in Ca-PSZ grains diffused into alumina grains during sintering so that the unstabilization of Ca-PSZ body was occurred which gave the cracks in the specimens. But when MgAl alloy powder was added to monoclinic zirconia, Mg and Al became to oxide at first and subsequently converted to spinel(MgAl2O4) during heating and finally unreacted MgO seemed to stabilize the zirconia. The oxides which formed at the oxidation process would have very fine grain size so that the reaction sintering was more effective to densification and homogeneous microstructure. The mechanical properties of reaction-sintered stabilized zirconia/spinel composite were better than only MgO stabilized zirconia. Sintering behavior in reaction and mechanical properties of sintered body were examined, with emphasis on the relations between spinel formation and mechanical properties.

Densification and Mechanical Properties of B4C Based Composites Sintered by Reaction Hot-Pressing

2010 ◽  
Vol 434-435 ◽  
pp. 24-27 ◽  
Author(s):  
Guo Feng Wang ◽  
Ji Hong Zhang ◽  
Chunping Zhang ◽  
Kai Feng Zhang
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Residual Stress ◽  
Thermal Properties ◽  
Sintering Temperature ◽  
Crack Deflection ◽  
Sintering Behavior ◽  
Reaction Sintering ◽  
Boron Carbide B4c

Boron carbide (B4C) possesses unique physical and thermal properties. In this paper, B4C based composites toughened by TiB2 were fabricated by in-situ reaction sintering with the original microcrystalline powders B4C, TiO2 and glucose. The influences of sintering temperature and content of TiO2 on the sintering behavior and mechanical properties were investigated. (TiB2, Al2O3)/B4C and (TiB2,SiC)/B4C composites with almost fully dense were fabricated by using additives　of Al2O3 and Si powders and sintering at 1950°C and 1900°C, the fracture toughness of composites reach to 7.09 and 6.35 MPa•m1/2 respectively. The analysis of microstructure shows that the main toughen mechanism is the crack deflection due to the existence of residual stress.

In Situ Preparation and Mechanical Properties of (ZrB2+ZrC)/Zr3[Al(Si)]4C6 Composites

2014 ◽  
Vol 602-603 ◽  
pp. 438-442
Author(s):  
Lei Yu ◽  
Jian Yang ◽  
Tai Qiu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Bending Strength ◽  
Coefficient Of Thermal Expansion ◽  
Raw Materials ◽  
Linear Increase ◽  
Fine Grain ◽  
Fine Grain Strengthening ◽  
Uniform Microstructure

Fully dense (ZrB2+ZrC)/Zr3[Al (Si)]4C6 composites with ZrB2 content varying from 0 to 15 vol.% and fixed ZrC content of 10 vol.% were successfully prepared by in situ hot-pressing in Ar atmosphere using ZrH2, Al, Si, C and B4C as raw materials. With the increase of ZrB2 content, both the bending strength and fracture toughness of the composites increase and then decrease. The synergistic action of ZrB2 and ZrC as reinforcements shows significant strengthening and toughing effect to the Zr3[Al (Si)]4C6 matrix. The composite with 10 vol.% ZrB2 shows the optimal mechanical properties: 516 MPa for bending strength and 6.52 MPa·m1/2 for fracture toughness. With the increase of ZrB2 content, the Vickers hardness of the composites shows a near-linear increase from 15.3 GPa to 16.7 GPa. The strengthening and toughening effect can be ascribed to the unique mechanical properties of ZrB2 and ZrC reinforcements, the differences in coefficient of thermal expansion and modulus between them and Zr3[Al (Si)]4C6 matrix, fine grain strengthening and uniform microstructure derived by the in situ synthesis reaction.

Physical and Mechanical Properties of Mullite-Whisker Reinforced Alumina Composites

2007 ◽  
Vol 334-335 ◽  
pp. 325-328 ◽  
Author(s):  
Wei Kong Pang ◽  
Nobuo Tezuka ◽  
It Meng Low ◽  
E.G. Mehrtens ◽  
Bruno A. Latella
Keyword(s):  
Mechanical Properties ◽  
Thermal Analysis ◽  
Hot Isostatic Pressing ◽  
Physical And Mechanical Properties ◽  
Reaction Sintering ◽  
Alumina Matrix ◽  
Young’S Moduli ◽  
Solid Density ◽  
Alumina Composites

Reaction sintering and hot-isostatic-pressing (HIP) have been used for the compaction and densification of mullite-whisker-reinforced alumina composites. The effect of alumina matrix constraints on the in-situ transformation sequence in alumina-halloysite-AlF3 system was studied using differential thermal analysis. The physical and mechanical properties of the HIPed samples have been characterized in terms of bulk density, apparent solid density, porosity, Young’s moduli, flexural strength, hardness and the fracture toughness.

Milling and Sintering Behavior of the Metal-Ceramic Mixed Powders

2007 ◽  
Vol 534-536 ◽  
pp. 93-96
Author(s):  
Z. X. Yang ◽  
Sang Heum Youn ◽  
Kyu Hong Hwang ◽  
Seog Young Yoon ◽  
Jong Kook Lee ◽  
...  
Keyword(s):  
Sintering Behavior ◽  
Alumina Powder ◽  
Reaction Sintering ◽  
Alumina Ceramics ◽  
Mixed Powder ◽  
Attrition Milling ◽  
Alumina Particles ◽  
Metal Ceramic ◽  
Milling Characteristics ◽  
Firing Shrinkage

The reaction-sintered alumina ceramics with low firing shrinkage were prepared from Al/Al2O3 powder mixture by attrition milling and the effect of milling characteristics of raw powders on reaction sintering was investigated. Powder mixtures of flaky shape Al with coarse alumina was much more effectively comminuted by the attrition milling than the mixtures of globular shape Al with coarse alumina powders. Furthermore the coarse alumina was much more useful in pulverizing and grinding the ductile Al particles than fine alumina. After attrition milling and isopressing at 400MPa, the Al/Al2O3 specimen was oxidized at 1200°C for 8 hours followed by sintering at 1550°C for 3 hours. Because mixed powder of coarse alumina with flaky Al was much more effectively comminuted than the globular Al, sintered body of more than 97% theoretical density was achieved, but low contents of Al leads to relatively higher shrinkage of about 8%. As the coarse alumina particles are much more useful in cutting and reducing the ductile Al particles, the use of the coarse alumina powder was much more effective in reaction-sintering.

In Situ Fabrication of Particles Reinforced Al-Si-Al2O3 Composites by Hot Isostatic Pressing

2011 ◽  
Vol 284-286 ◽  
pp. 38-42 ◽  
Author(s):  
Ying Gao ◽  
Dei Gui Zhu ◽  
Ling Cheng ◽  
Hong Liang Sun ◽  
Qing Wang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Hot Isostatic Pressing ◽  
Reaction Sintering ◽  
Test Results ◽  
Isostatic Pressing ◽  
In Situ Reaction ◽  
Heating Up ◽  
Sintering Processes

Particles reinforced Al-xwt.%Si-Al2O3(x=10,20) composites are fabricated through in situ reaction sintering of Al and SiO2powder by hot isostatic pressing. Outgassing process and the microstructure of composites under different sintering processes are studied.XRD analysis confirms that the best hot outgassing temperature is 500°C,in situ reaction achieves completely and samples A2 and B2 have better microstructure at 550°C then heating-up to 700°C only for 1h.The microstructure analysis indicates that the reinforcement particulates distribute uniformly in the aluminum matrix.The mechanical properties test results show that the tensile strength of A2 is higher than B2. whenx=10,the Al-Si-Al2O3composites have better performance.

The Factors Affecting Colloidal Processing of 8YSCZ Ceramics

2007 ◽  
Vol 280-283 ◽  
pp. 729-734 ◽  
Author(s):  
Süleyman Tekeli ◽  
Metin Gürü
Keyword(s):  
Mechanical Properties ◽  
Fine Particles ◽  
Ceramic Powder ◽  
Processing Parameters ◽  
Solid Content ◽  
Colloidal Processing ◽  
Homogeneous Microstructure ◽  
Factors Affecting ◽  
Fine Grain ◽  
Cast Specimen

To achieve improvements in the mechanical properties, fine grain size, homogeneous microstructure and high density are desirable. The poor dispersion of the powders produce difficulties in the densification and the presence of agglomerates is responsible for poor mechanical properties. Slurry casting is an important colloidal processing method for the ceramic industry and helps to prevent the agglomeration of fine particles. In the present study, the effect of processing parameters, namely solid content, dispersing agent concentration, slurry viscosity and milling time on slurry casting of 8YSCZ ceramics were investigated and optimum values were determined. The results showed that ceramic powder used was castable under limited conditions. The effect of shaping processon sintering behaviour and microstructure was also investigated for slurry-cast and die-pressed specimens. The results showed that specimen processed by slurry-casting had a faster sintering rate and lower sintering temperatures, compared to die-pressed specimen. The reason for better sintering was due to the homogeneous dispersion of the powder and elimination of agglomerates in slurry-cast specimen.

scholarly journals Properties of 2 mol% Yttria Stabilized Zirconia–Alumina–Cerium Hexaaluminate Composites

Ceramics ◽  
2020 ◽  
Vol 3 (2) ◽  
pp. 190-198 ◽  
Author(s):  
Frank Kern
Keyword(s):  
Bending Strength ◽  
Tetragonal Zirconia ◽  
High Strength ◽  
Yttria Stabilized Zirconia ◽  
Reaction Sintering ◽  
Stabilized Zirconia ◽  
Standard Material ◽  
The Matrix ◽  
Second Phases

Yttria stabilized zirconia (Y-TZP) has become a standard material in a variety of biomedical and mechanical engineering applications due to its high strength and toughness. In order to obtain improved properties in terms of strength, hardness and low temperature degradation resistance second phases, typically alumina are added. In this study an alumina toughened zirconia recipe with 20 vol% alumina in a 2Y-TZP matrix was modified by progressive substitution of alumina by up to 10 vol% cerium hexaaluminate (CA6). Samples were produced by hot pressing. The cerium hexaaluminate was synthesized in situ by reduction of tetravalent ceria and reaction sintering with alumina at 1450 °C. The materials reach attractive 4-point bending strength values of greater than 1170–1390 MPa at a fracture resistance of 6.4–7 MPa√m. Vickers hardness is slightly reduced from 1405 HV10 to 1380 HV10 with increasing CA6 fraction. Results show that substitution of alumina by low amounts CA6 does not lead to drastic changes in the mechanical properties. Hardness is slightly reduced while strength reaches a flat maximum at 4 vol% CA6 substitution. The toughness slightly declines with CA6 addition which is caused by reduced transformability of the tetragonal zirconia phase despite a slight coarsening of the matrix observed upon CA6 addition.

Reaction sintering and mechanical properties of B4C with addition of ZrO2

2000 ◽  
Vol 15 (11) ◽  
pp. 2431-2436 ◽  
Author(s):  
Hae-Won Kim ◽  
Young-Hag Koh ◽  
Hyoun-Ee Kim
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Flexural Strength ◽  
Elevated Temperatures ◽  
Applied Pressure ◽  
Sintering Behavior ◽  
Reaction Sintering ◽  
Densification Behavior ◽  
High Relative Density ◽  
Full Densification

The effect of ZrO2 addition on sintering behavior and mechanical properties of both hot-pressed and pressureless-sintered B4C was investigated. The addition of ZrO2 improved the densification behavior of B4C remarkably via a reaction with the B4C to form ZrB2 at elevated temperatures. When B4C was densified at 2000 °C by hot pressing, only a small amount (approximately 2.5 vol%) of ZrO2 was necessary to achieve a full densification. Excellent mechanical properties (hardness, elastic modulus, flexural strength, and fracture toughness) were observed in those specimens. As the amount of ZrO2 was increased further, the mechanical properties were reduced, except for the fracture toughness, apparently due to the formation of too much ZrB2 in the specimen. Without the applied pressure, larger amounts of ZrO2 should be added to obtain a body with high relative density. When the B4C was sintered at 2175 °C with addition of 10 vol% ZrO2, the specimen has a density higher than 95% of the theoretical, and hardness and flexural strength of 25 GPa and 400 MPa, respectively.

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