Porous Silicon Nitride Microwave Transparent Material with Compounded Component Pore Former

2010 ◽  
Vol 105-106 ◽  
pp. 612-615
Author(s):  
Fang Gao ◽  
Chong Hai Wang ◽  
Ling Li ◽  
Da Qian Chen ◽  
Ping Zhai ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Silicon Nitride ◽  
Porous Silicon ◽  
Bending Strength ◽  
High Strength ◽  
Green Body ◽  
Pore Former ◽  
Transparent Materials ◽  
Gas Pressure Sintering ◽  
Different Content

It is an effective way to decrease dielectric constant of microwave transparent materials by improving porosity rate. Network -Si3N4 porous transparent materials were prepared by gas pressure sintering (GPS) with Y2O3 additions. Porosity rate of silicon nitride using pore former with different content starch, polytetrafluoroethylene (PTEE) powder respectively and their compounded component were discussed in this paper. It is concluded that porosity rate can be improved by all the three, starch is most favorable to improve porosity but great volume rebound after cold iso-static pressing were happened and easily lead to crack of green body. Method of pore-making by step on principle of pore formers discharging in different temperature range used to get high strength and porosity green body. Series of porous silicon nitride microwave transparent materials were prepared with porosity rate from 48% to 67%, bending strength from 162MPa to 59MPa and dielectric constant from 3.41 to 2.37.

Si3N4-BN-SiO2 Based Microwave-Transparent Materials

2008 ◽  
Vol 368-372 ◽  
pp. 913-916 ◽  
Author(s):  
Wei Ru Zhang ◽  
Chong Hai Wang ◽  
Ling Li ◽  
Jian Liu ◽  
Wen Chen
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Technological Parameter ◽  
Bending Strength ◽  
Raw Materials ◽  
Gas Pressure ◽  
Loss Angle ◽  
Transparent Materials ◽  
Gas Pressure Sintering ◽  
N Wave

The Si-B-O-N microwave-transparent materials were prepared by gas pressure sintering (GPS).The effect of BN and nano-SiO2 contents on the mechanical and dielectric properties of the composites was studied. The microstructural characteristic and reinforced mechanism of the composites were also investigated. The results showed that a series of Si-B-O-N wave-transparent materials could be obtained by controlling the contents of raw materials and technological parameter. The bending strength of composites is from 74.7MPa to 174.83MPa, the dielectric constant is from 3.5 to 4.2 and the tangent of loss angle is from 0.5×10-3 to 4.5×10-3.

scholarly journals BN Nanoparticles/Si3N4Wave-Transparent Composites with High Strength and Low Dielectric Constant

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Dongliang Zhao ◽  
Yujun Zhang ◽  
Hongyu Gong ◽  
Baoxin Zhu ◽  
Xiaoyu Zhang
Keyword(s):  
Mechanical Properties ◽  
Dielectric Constant ◽  
Volume Content ◽  
Bending Strength ◽  
High Strength ◽  
Low Dielectric Constant ◽  
Low Dielectric ◽  
Transparent Composites ◽  
Gas Pressure Sintering ◽  
Dielectric And Mechanical Properties

Si3N4wave-transparent composites with different volume content of BN nanoparticles (BNnp/Si3N4) were prepared by gas pressure sintering at 1800°C in N2atmosphere. The effects of BN nanoparticles on the dielectric and mechanical properties of BNnp/Si3N4composites were investigated. The results showed that the addition of the BN nanoparticles improved the dielectric properties of BNnp/Si3N4composites effectively and decreased the mechanical properties. When the volume content of BN nanoparticles was 10%, the dielectric constant and dielectric loss tangent were 4.31 and 0.006, respectively, and the bending strength and fracture toughness still reached 198.9 MPa and 3.36 MPa·m1/2. The high mechanical properties of BNnp/Si3N4composites with 10% BN nanoparticles were attributed to homogeneously dispersed BN nanoparticles which were embedded in the pores formed by the rod-likeβ-Si3N4.

High-strength porous silicon nitride fabricated by the sinter-forging technique

2001 ◽  
Vol 16 (1) ◽  
pp. 32-34 ◽  
Author(s):  
Naoki Kondo ◽  
Yoshikazu Suzuki ◽  
Tatsuki Ohji
Keyword(s):  
Silicon Nitride ◽  
Porous Silicon ◽  
Relative Density ◽  
Elevated Temperatures ◽  
Bending Strength ◽  
High Strength ◽  
Uniaxial Pressure ◽  
Specific Density ◽  
Sinter Forging

Porous silicon nitride with aligned fibrous grains was fabricated by sinter-forging technique, where uniaxial pressure was applied to achieve a specific density after soaking at elevated temperatures. Fibrous silicon nitride grains were formed during the soaking, and the grains were aligned by the subsequent forging. As the result, a specimen with strongly aligned fibrous silicon nitride grains was successfully fabricated. The specimen with a relative density of 76% exhibited high bending strength of 778 MPa.

Microwave Dielectric Property of Porous Silicon Nitride Ceramics

2007 ◽  
Vol 336-338 ◽  
pp. 307-309 ◽  
Author(s):  
Jun Qi Li ◽  
Fa Luo ◽  
Dong Mei Zhu ◽  
Wan Cheng Zhou
Keyword(s):  
Dielectric Constant ◽  
Silicon Nitride ◽  
Dielectric Property ◽  
Porous Silicon ◽  
Microwave Dielectric Property ◽  
Volume Fraction ◽  
Silicon Powder ◽  
Dense Matrix ◽  
Microwave Dielectric ◽  
Nitride Ceramics

This paper presents the microwave dielectric property of porous silicon nitride ceramics at a frequency of 9360 MHz, which were fabricated by the nitridation of silicon powder. The porous ceramics with different volume fraction of porosity from 18.6% to 56.2% were produced by adding different amount of the pore-forming agent into the initial silicon powder. Microstructural analysis revealed a dense matrix containing large pores and cavities with needle-shaped and flaky β-Si3N4 grains distributing in it. The results showed that the dielectric constant of the ceramics reduces with the porosity increases. With the addition of α-Si3N4 powder in the raw silicon powder, the nitridation rate is raised, and the dielectric constant and the dielectric loss of the ceramics decrease notablely.

Study on Hole-Sealing Coating of Porous Silicon Nitride Surface

2013 ◽  
Vol 537 ◽  
pp. 20-23
Author(s):  
Qi Hong Wei ◽  
Chong Hai Wang ◽  
Ling Li ◽  
Hong Sheng Wang ◽  
Jian Liu ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Silicon Nitride ◽  
Porous Silicon ◽  
Water Absorption ◽  
Bending Strength ◽  
Sol Gel ◽  
Universal Testing ◽  
Before And After ◽  
Scanning Electron ◽  
Sealing Coating

Hole-sealing coating was fabricated on the porous silicon nitridesubstrate by sol-gel method, with Li2O-Al2O3-SiO2 as the basic materials and other additives were added. The morphology of the coating was tested by scanning electron microscope(SEM). The density,water absorption and porosity of porous silicon nitride before and after coating were tested by Archimedes method.The bending strength was tested by universal testing machine．The results indicated that the water absorption of porous silicon nitride was decreaced by 93.73% to 96.74%, the bending strength of porous silicon nitride was increaced by 8.21％ to 15.56％.

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.

Effect of β–Si3N4 seed crystal on the microstructure and mechanical properties of sintered reaction-bonded silicon nitride

1999 ◽  
Vol 14 (1) ◽  
pp. 178-184 ◽  
Author(s):  
Soo Young Lee ◽  
K. Amoako-Appiagyei ◽  
Hai Doo Kim
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Silicon Nitride ◽  
High Strength ◽  
Considerable Improvement ◽  
Seed Crystal ◽  
Bimodal Microstructure ◽  
Seed Crystals ◽  
Before And After ◽  
Gas Pressure Sintering

β–Si3N4 seed crystal has been synthesized from α–Si3N4 powder. Reaction-bonded Si3N4/SiC composite has been fabricated with β–Si3N4 seed crystals. The nitridation behavior and the changes in mechanical properties resulting from the addition of seed crystals were studied before and after gas pressure sintering. Addition of seeds showed a considerable improvement in the nitridation, resulting in increase in fracture strength of the composite. Highly nitrided reaction-bonded Si3N4 (RBSN) as a result of the addition of seed crystals gave rise to high strength of composite after postsintering. Fracture toughness of the seeded Si3N4 was also improved up to 35% compared to the baseline Si3N4. Micrographs showed that the seeded Si3N4 developed a bimodal microstructure which resulted in an improvement in fracture toughness.

Porous Silicon Nitride Prepared by Cold Isostatic Pressure

2011 ◽  
Vol 412 ◽  
pp. 179-182
Author(s):  
Fang Gao ◽  
Jian Liu ◽  
Chong Hai Wang
Keyword(s):  
Silicon Nitride ◽  
Porous Silicon ◽  
Bending Strength ◽  
Cold Isostatic Pressing ◽  
Performance Parameter ◽  
Isostatic Pressing ◽  
Complex Shapes ◽  
Cold Isostatic Pressure

Porous silicon nitride with pore forming agent of starch were prepared by cold isostatic pressing, forming problem of complex shapes were solved by methods of carbonization of starch and decreasing forming pressure. Products of porous silicon nitride had the performance parameter with density 1.5g/cm3, porosity over 55%, bending strength over 100 MPa.

Sign in / Sign up

Export Citation Format

Share Document