Effect of Sm2O3 Additives on the Rod-Like β-Si3N4 Crystal of Porous Silicon Nitride Fabricated by Reaction-Bonded

2010 ◽  
Vol 105-106 ◽  
pp. 42-45
Author(s):  
Jian She Yue ◽  
Hong Jie Wang
Keyword(s):  
Silicon Nitride ◽  
Porous Silicon ◽  
Aspect Ratio ◽  
Flexural Strength ◽  
High Aspect Ratio ◽  
Liquid State ◽  
Theory Testing ◽  
Strength Testing ◽  
Xrd Diffraction ◽  
Crystal Content

Sm2O3 and MgO as a sintering additives to fabricated porous silicon nitride by reaction-bonded. The phase of as-produced silicon nitride characterized by XRD-diffraction. The microstructure of product was investigated by SEM. The samples were machined into test bar for flexural strength testing. Using Archimedes theory testing the porosity of porous silicon nitride. MgO have restrain effect on the growth of rod-like silicon nitride, because of produce a restrain layer which is MgO reacted with SiO2 on the surface of silicon., the microstructure of crystal is particle like, the maximum flexural strength is 48MPa with porosity of 35%. Sm2O3 can assistant the growth of high aspect ratio Si3N4 crystal at beginning temperature of 1300°C for it’s low melt point and low viscidity in liquid state, the as-product’s morphology is rod-like and the flexural strength is as high as 300 MPa when the porosity is 30%, high than the sample that of low rod-like crystal content.

Fabrication of High-Porosity Silicon Nitride Ceramics with Excellent Mechanical Properties

2011 ◽  
Vol 284-286 ◽  
pp. 1339-1342
Author(s):  
Shao Yun Shan ◽  
Qing Ming Jia ◽  
Ya Ming Wang ◽  
Jin Hui Peng
Keyword(s):  
Mechanical Properties ◽  
Silicon Nitride ◽  
Porous Silicon ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Strength ◽  
High Porosity ◽  
Microstructure And Mechanical Properties ◽  
Nitride Ceramics ◽  
Sintering Conditions

High-porosity silicon nitride ceramics with excellent mechanical properties were fabricated by the carbothermal reduction of SiO2. The influences of sintering conditions on microstructure and mechanical properties were studied. The results showed that microstructure and mechanical properties of porous silicon nitride ceramics were dependent mostly on the sintering conditions. The sintered porous silicon nitride ceramics exhibited the formation of fibrous microstructure with submicrometer-sized, high-aspect ratio b-Si3N4 grains, and uniform pore structure. Porous Si3N4 ceramics with a porosity of about 70%, and a flexural strength of about 70 MPa were obtained by sintering at 1750°C, with lower rate of temperature rise and no retaining time. The high strength was attributed to fine, high-aspect ratio b-Si3N4 grains and uniform pores between grains.

Effects of Sintering Additives on the Microstructure and Mechanical Properties of Silicon Nitride Ceramics by GPS

2010 ◽  
Vol 105-106 ◽  
pp. 27-30 ◽  
Author(s):  
Wei Ru Zhang ◽  
Feng Sun ◽  
Ting Yan Tian ◽  
Xiang Hong Teng ◽  
Min Chao Ru ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Phase Transformation ◽  
Silicon Nitride ◽  
Porous Silicon ◽  
Flexural Strength ◽  
Relative Density ◽  
Sintering Additives ◽  
Microstructure And Mechanical Properties ◽  
Nitride Ceramics

Silicon nitride ceramics were prepared by gas pressure sintering (GPS) with different sintering additives, including La2O3, Sm2O3 and Al2O3. Effect of sintering additives on the phase-transformation, microstructure and mechanical properties of porous silicon nitride ceramics was investigated. The results show that the reaction of sintering additives each other and with SiO2 had key effects on the phase-transformation, grain growing and grain boundaries. With 9MPa N2 atmosphere pressure, holding 1h at 1850°C, adding 10wt% one of the La2O3, Sm2O3, Al2O3, porous silicon nitride was prepared and the relative density was 78%, 72%, 85% respectively. The flexural strength was less than 500MPa, and the fracture toughness was less than 4.8MPam1/2. Dropping compounds sintering additives, such as La2O3+Al2O3, Sm2O3+Al2O3 effectively improves the sintering and mechanical properties. The relative density was 99.2% and 98.7% with 10wt% compounds sintering additives. The grain ratio of length to diameter was up to 1:8. The flexural strength was more than 900MPa, and the fracture toughness was more than 8.9MPam1/2.

Integrated Sagnac optical gyroscope sensor using ultra-low loss high aspect ratio silicon nitride waveguide coil

2017 ◽  
Author(s):  
Sarat Gundavarapu ◽  
Michael Belt ◽  
Taran Huffman ◽  
Minh A. Tran ◽  
Tin Komljenovic ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Low Loss ◽  
Optical Gyroscope ◽  
Gyroscope Sensor

Preparation of Low Dielectric Constant Porous Silicon Nitride Ceramics for Radome Application

2018 ◽  
Vol 281 ◽  
pp. 610-615
Author(s):  
Ling Li ◽  
Bao Xin Zhu ◽  
Hong Sheng Wang ◽  
Jie Zhang
Keyword(s):  
Dielectric Constant ◽  
Silicon Nitride ◽  
Porous Silicon ◽  
Flexural Strength ◽  
Dielectric Material ◽  
Core Layer ◽  
Low Dielectric Constant ◽  
Low Dielectric ◽  
Dielectric Constant And Loss ◽  
Nitride Ceramics

The porous silicon nitride ceramics with low dielectric constant and high flexural strength were obtained by adding pore-forming agent through partial sintering technique. The effects of pore-forming agent amount on the properties of porous silicon nitride ceramics were investigated. Microstructure was analyzed by means of scanning electron microscopy. The results show that the porous structure is formed by the overlap of pillar β-Si3N4 with high length diameter ratio. The porosity of samples rises with the increase of pore-forming agent content, which leads to the decrease of the dielectric constant and loss, but the decrease of flexural strength. When the pore-forming agent of PMMA with mass fraction of 20% was added, the volume density, porosity, dielectric constant and loss of porous silicon nitride ceramics were 1.17g/cm3, 66.5%, 2.33 and 0.8×10-3 respectively, with higher flexural strength of 75MPa which is satisfactory as low dielectric material for core layer of broadband radome.

Laser drilling with a top-hat beam of micro-scale high aspect ratio holes in silicon nitride

2020 ◽  
Vol 281 ◽  
pp. 116636 ◽  
Author(s):  
Vahid Nasrollahi ◽  
Pavel Penchev ◽  
Afif Batal ◽  
Hoang Le ◽  
Stefan Dimov ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Laser Drilling ◽  
Micro Scale

Microstructure and Strength of Oxidation-Bonded Porous Silicon Nitride Ceramics

2007 ◽  
Vol 353-358 ◽  
pp. 503-506
Author(s):  
Shu Qiang Ding ◽  
Yu Ping Zeng ◽  
Dong Liang Jiang
Keyword(s):  
Silicon Nitride ◽  
Porous Silicon ◽  
Flexural Strength ◽  
Amorphous Silica ◽  
Fracture Mechanism ◽  
Bonding Process ◽  
Nitride Ceramics ◽  
Porous Si3n4 ◽  
Si3n4 Ceramics ◽  
Porous Si3n4 Ceramics

An oxidation bonding process was developed to fabricate oxidation-bonded porous silicon nitride (Si3N4) ceramics from α-Si3N4 powder in air at 1100-1400oC. Si3N4 particles are bonded by the oxidation-derived silica (SiO2) and the pores derive from the stack of Si3N4 particles and the release of N2 and SiO gas during the sintering. The microstructure of oxidation-bonded porous Si3N4 ceramics was observed. Moreover, the fracture mechanism was analyzed. Effects of the bonding phases and pores on the flexural strength were investigated. Oxidation-bonded porous Si3N4 ceramics with high flexural strength was obtained by restraining the crystallization of amorphous silica and forming the well-developed necks between Si3N4 particles.

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