scholarly journals Effect of Different Sintering Additives on the Microstructure, Phase Compositions and Mechanical Properties of Si3N4/SiC Ceramics

2020 ◽  
Author(s):  
Ying Qin ◽  
Hailing Yang ◽  
Qinggang Li ◽  
Zhi Wang ◽  
Hao Wu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Glass Phase ◽  
Secondary Recrystallization ◽  
Pressureless Sintering ◽  
Composite Ceramics ◽  
Flexure Strength ◽  
Sic Ceramics ◽  
Liquid Phases ◽  
Sic Ceramic

Abstract Y2O3 and CeO2 were chosen as additives to investigate the effect of different additives on the microstructure, composition of phases and mechanical properties of Si3N4/SiC ceramics using pressureless sintering. Si3N4/SiC ceramic without additives had a high density, while after adding Y2O3 and CeO2, the density and flexural strength of Si3N4/SiC ceramics were significantly decreased due to the increase of porosity. The main phase compositions of samples were β-Si3N4 and SiC. Moreover, the liquid phases Y-Si-O-N and Ce-Si-O-N were observed after adding Y2O3 and CeO2 respectively. It also indicated that for Si3N4/SiC composite ceramics, the high aspect ratio β-Si3N4 overlapped with each other and closely bonded with glass phase could improve flexure strength effectively. Besides, the SiC crystal grains mainly existed in grain boundary, which could inhibit the secondary recrystallization to avoid that the decrease of flexural strength caused by the overgrowth of β-Si3N4 grains.

Si3N4/BN Composite Ceramics with Nd2O3-Al2O3-Y2O3 Ternary Additives by Pressureless Sintering

2010 ◽  
Vol 434-435 ◽  
pp. 106-108
Author(s):  
Ping Liu ◽  
Yong Feng Li ◽  
Xiang Dong Wang ◽  
Hai Yun Jin ◽  
Guan Jun Qiao
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Phase Transformation ◽  
Flexural Strength ◽  
Pressureless Sintering ◽  
Sintering Process ◽  
Composite Ceramics ◽  
Fracture Toughness Testing ◽  
Β Phase ◽  
Toughness Testing

Si3N4/BN composite ceramics with 25vol% h-BN were prepared by pressure-less sintering process with Nd2O3/Al2O3/Y2O3 as sintering additives. The effects of these ternary additives on the densification behaviors and mechanical properties were investigated. XRD and FESEM were used to investigate the α-β phase transformation and microstructure. The XRD results showed that α-Si3N4 has transformed to β-Si3N4 completely in all the samples during the pressureless sintering process. The line shrinkage increased with the Nd2O3 contents increasing, and the highest line shrinkage (7.75%) was observed when 4wt% Nd2O3 was added, then decreased. The same trends were observed in flexural strength and fracture toughness testing. The ternary additives of Y2O3-Al2O3-Nd2O3 could improve the density, strength and fracture toughness of the material effectively.

Preparation and Mechanical Properties of ReAl11O18 Ceramics

2014 ◽  
Vol 602-603 ◽  
pp. 345-348
Author(s):  
Jun Dong Zhang ◽  
Ming Hao Fang ◽  
Zhao Hui Huang ◽  
Yan Gai Liu ◽  
Xin Min ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Flexural Strength ◽  
Bulk Density ◽  
Room Temperature ◽  
Pressureless Sintering ◽  
Optimal Temperature ◽  
Flexure Strength ◽  
The Real

In this paper, plate-like ReAl11O18 (Re = La, Pr, Nd) toughened ceramics were prepared by pressureless sintering at 1650 °C for 5 h in air. The bulk densities of the sintered samples were between 4.7 to 5.3g/cm3. The mechanical properties of the ReAl11O18 ceramics were studied systematically at room temperature. The flexure strength and fracture toughness of ReAl11O18 ceramics were 97.5 to 102.7 Mpa and 3.8 to 4.2Mpa.m1/2. The results show that: The optimal temperature to synthesis ReAl11O18 ceramics was 1650 °C; The flexural strength and fracture toughness of the ReAl11O18 ceramics increase with the increasing of its bulk density.

Effect of AlF3 Content on Microstructure and Properties of Mullite/Al2O3 Composite Ceramics

2018 ◽  
Vol 922 ◽  
pp. 62-67
Author(s):  
Ke Zheng Sang ◽  
Fan Wang ◽  
De Jun Zeng ◽  
Hong Wei Li
Keyword(s):  
Fracture Toughness ◽  
Flexural Strength ◽  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Diameter Ratio ◽  
Pressureless Sintering ◽  
Composite Ceramics ◽  
Microstructure And Properties ◽  
Shock Resistance ◽  
Mullite Whiskers

To reinforce the mullite/Al2O3 composite ceramics through formation of mullite whiskers, the composite ceramics were prepared by pressureless sintering using different AlF3 content. The microstructure, porosity, fracture toughness and thermal shock resistance of the composite ceramics were investigated. The results show that the addition of AlF3 can promote the mullite whisker formations, and the whiskers with the size of 3～10μm in diameter and a length-diameter ratio of 10～15 are obtained by sintering at 1600°C with the AlF3 content of 5wt%. Fracture toughness and thermal shock resistance of the composite ceramics are improved by the formation of mullite whisker. The fracture toughness of 4.79MPa•m1/2 can be obtained, and the 95.18% flexural strength remained after thermal shock.

Effects of Polarization Treatment on Mechanical Properties of Al2O3/LiTaO3 Composite Ceramics

2007 ◽  
Vol 353-358 ◽  
pp. 1314-1317
Author(s):  
You Feng Zhang ◽  
Qing Chang Meng ◽  
De Chang Jia ◽  
Yu Zhou
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Domain Switching ◽  
Composite Ceramic ◽  
Polarization Direction ◽  
Composite Ceramics ◽  
Pressing Method ◽  
Width Direction ◽  
Different Temperatures ◽  
Polarization Temperature

The Al2O3/LiTaO3 (ALT) composite ceramics were fabricated by hot pressing method and polarization treated at different temperatures along height and width directions. Effects of polarization treatment on mechanical properties of the ALT composite ceramic were investigated. Flexural strength decreased with the increase of polarization temperature. Meanwhile, the flexural strength of samples polarized in height direction is higher than that polarized in width direction. The composite ceramic fractures intragranularly, and many rupture steps in polarization direction were observed on fractographs of the composite ceramics. Domain switching in LiTaO3 particles increased the resistance of crack propagation and improved the mechanical properties of the polarized ALT composite ceramics.

Mechanical Properties and Machinability of Si3N4/hBN Composites Prepared by Pressureless Sintering

2006 ◽  
Vol 510-511 ◽  
pp. 1014-1017 ◽  
Author(s):  
Won Seung Cho ◽  
Ki Ju Lee ◽  
Myeong Woo Cho ◽  
Jae Hyung Lee ◽  
Woon Suk Hwang
Keyword(s):  
Mechanical Properties ◽  
Flexural Strength ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Ceramic Composites ◽  
Pressureless Sintering ◽  
Si3n4 Ceramic ◽  
Cutting Resistance ◽  
Axis Parallel ◽  
Si3n4 Ceramics

The effects of hBN content on microstructure, mechanical properties, and machinability of the pressureless-sintered Si3N4 ceramics were investigated. Flexural strength, Young’s modulus, and hardness decreased with increasing h-BN content. The mechanical properties are decreased mainly because of increased porosity of composite, and the much lower Young's modulus of BN compared to that of Si3N4. Pressureless-sintered Si3N4/hBN composites exhibit strong texture of BN grains oriented with the c-axis parallel to the cold-pressing direction. Cutting resistance of Si3N4 ceramic composites with more than 10 vol% hBN decreased with increasing hBN content, demonstrating a good machinability of the composites. The residual pores can be attributed to improved machinability of pessureless-sintered Si3N4-BN composite.

Mechanical Properties of Machinable Zirconia Dental Composites

2007 ◽  
Vol 336-338 ◽  
pp. 1587-1589
Author(s):  
Wen Xu Li ◽  
Hua Zhao ◽  
Ying Song ◽  
Bin Su ◽  
Fu Ping Wang
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Calcium Phosphate ◽  
Flexural Strength ◽  
Dental Composite ◽  
The Other ◽  
Dental Composites ◽  
Composite Ceramics ◽  
Cad Cam ◽  
The Common

Ca3(PO4)2/ZrO2 dental composite ceramics using for CAD/CAM system were prepared and the effects of weak phases on microstructures and mechanical properties were studied. The results showed that intergranular spreads happened with the increasing Ca3(PO4)2 contents due to the discontinuity of weak interfaces between Zirconia and Calcium phosphate in matrix. So the flexural strength and hardness of the Ca3(PO4)2/ZrO2 composite ceramics were decreased effectively, which improved the machinability of the composites. On the other hand, strong interfaces between Zirconias increased the integrality of the ceramic structures. ZrO2 composite Ceramics with 15% Ca3(PO4)2 were sintered at 1350°C. The flexural strength is 300.44MPa, fracture toughness is 4.36 MPam1/2, and hardness is 6.69 GPa. The cutting exponent of the Ca3(PO4)2/ZrO2 composite ceramics is obviously lower than that of the common commercial Vita Mark II and Dicor MGC ceramics, which shows good mechanical properties and machinability.

Microstructure and properties of pressureless sintered ZrC-based materials

2008 ◽  
Vol 23 (7) ◽  
pp. 1882-1889 ◽  
Author(s):  
Laura Silvestroni ◽  
Diletta Sciti
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Flexural Strength ◽  
Room Temperature ◽  
Pressureless Sintering ◽  
Secondary Phases ◽  
Sintering Aid ◽  
Mean Particle Size ◽  
Dense Bodies ◽  
Similar Materials

ZrC-based composites were produced by pressureless sintering thanks to the addition of MoSi2 as sintering aid. After preliminary tests, a baseline ZrC material and two mixed ZrC–HfC and ZrC–ZrB2 composites with 20 vol% MoSi2 were densified at 1900 to 1950 °C reaching final relative densities of 96%–98%. Mean particle size of the dense bodies ranged from 5 to 9 μm. Secondary phases were found to form during sintering, such as SiC and Zr–Mo–Si-based compounds. Room-temperature mechanical properties were in the range of the values reported in the literature for similar materials densified by pressure-assisted techniques. The flexural strength was tested at room temperature, 1200 and 1500 °C.

Fabrication and Properties of Pressureless Sintered Si3N4/BN Composite Ceramics with La2O3-Al2O3-Y2O3 as Sintering Additives

2009 ◽  
Vol 620-622 ◽  
pp. 761-764
Author(s):  
Yong Feng Li ◽  
Ping Liu ◽  
Guan Jun Qiao ◽  
Jian Feng Yang ◽  
Hai Yun Jin ◽  
...  
Keyword(s):  
Flexural Strength ◽  
Room Temperature ◽  
Weight Ratio ◽  
Pressureless Sintering ◽  
Sintering Process ◽  
Composite Ceramics ◽  
Sintering Additives ◽  
Xrd Patterns ◽  
Room Temperature Strength

With commercial α-Si3N4 and h-BN powders as starting materials, La2O3, Al2O3, Y2O3 as sintering additives, Si3N4/BN composite ceramics with 25vol% h-BN were fabricated by pressureless sintering. Various amounts of La2O3 (0, 2, 4, 8, 15wt%) were added, with constant Y2O3/Al2O3 weight ratio and additives (Y2O3/Al2O3/La2O3) amount. The densification behaviors, α-βtransformation and room-temperature strength of Si3N4/BN composite were investigated. The porosity of samples decreased with La2O3 content increasing, and the lowest porosity of 20.83% was observed for samples containing 4wt% La2O3, then leaded to an increase. The flexural strength of all the specimens increased with the addition up to 4wt% and changed greatly thereafter. The highest room-temperature flexural strength, 272.4MPa, was obtained when 4wt% La2O3 was added. Results of XRD patterns revealed that β-Si3N4 and h-BN existed in all the specimens. No α-Si3N4 was detected, implying thatα- toβ-Si3N4 transformation has been completed during the pressureless sintering process. These results show that the La2O3-Al2O3-Y2O3 system can act as effective sintering additives for pressureless sintered Si3N4/BN composite.

Influence of Hot Pressing Temperature and SiC Content on the Microstructure and Mechanical Properties of ZrB2-SiC

2010 ◽  
Vol 434-435 ◽  
pp. 189-192
Author(s):  
Yong Zhang ◽  
Ping Hu ◽  
Xing Hong Zhang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Flexural Strength ◽  
Hot Pressing ◽  
Volume Percent ◽  
Pressing Temperature ◽  
Sic Ceramics ◽  
Opposite Trend ◽  
Microstructure And Mechanical Properties ◽  
Dense Ceramic

The influence of hot pressing temperature and SiC content on the microstructure and mechanical properties of ZrB2-SiC ceramics was investigated. ZrB2 containing 20 volume percent SiC were prepared by hot pressing at 1850, 1900 and 1950°C for 60 min. Fully dense ceramic was obtained after hot pressing at temperature of 1950°C. In addition, the materials with SiC content of 0, 10vol.%, 15 vol.%, 20 vol.% and 30 vol.% hot pressed at 1950°C were also investigated. Results showed that the grain size of the ZrB2 significantly reduced on adding 10vol.% SiC and then decreased slightly with further increasing SiC content, whereas the grain size of SiC exhibited a opposite trend. The flexural strength of ZrB2-SiC ceramics remarkedly increased on adding 10vol.% SiC due to the significant decrease of ZrB2 particle size and then slightly increased with increasing SiC content up to 20vol.%. However, further increasing SiC content led to a reduction of the flexural strength.

Microstructure and Mechanical Properties of Hot-Pressed and Pressureless Sintered WC-Al2O3 Ceramic Composites

1993 ◽  
Vol 327 ◽  
Author(s):  
Hidehiro Endo ◽  
Masanori Ueki
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Flexural Strength ◽  
Hot Pressing ◽  
Composite System ◽  
Ceramic Composites ◽  
Pressureless Sintering ◽  
Sintering Aid ◽  
Al2o3 Ceramic ◽  
Remarkable Improvement

AbstractFully densified WC-A12O3 composites were successfully consolidated by both hot-pressing and pressureless sintering. The optimum hot-pressing condition for the composites was 1700°C for 2h under a pressure of 40MPa. A remarkable improvement in mechanical properties was achieved in the composite system, especially in WC-30 and -70vol%A12O3, compared to the monolithic WC and A12O3 ceramics. The addition of MgO as a sintering aid had a great effect on the properties of the composites. WC-30vol%A12O3 composite with 1.Owt% MgO addition exhibited flexural strength higher than 1000MPa up to 1200°C, fracture toughness; KIC≥7MPa√m, and hardness; HV ≥2450. In pressureless sintering with the addition of MgO as a sintering aid and subsequent HIP treatment, the WC-30vol%A12O3 composite exhibited the flexural strength higher than 900MPa up to 1200°C.

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