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.

Influence of YAG-Based Composite Sintering Aids on Gas Pressure Sintered BNw/Si3N4 Composites

2015 ◽  
Vol 655 ◽  
pp. 53-57
Author(s):  
Xian Li Wang ◽  
Hong Yu Gong ◽  
Yu Jun Zhang ◽  
Song Wei Che
Keyword(s):  
Dielectric Properties ◽  
Bending Strength ◽  
Mechanical Performance ◽  
Raw Materials ◽  
Gas Pressure ◽  
Apparent Porosity ◽  
Sintering Process ◽  
Sintering Aids ◽  
Liquid Phases ◽  
Gas Pressure Sintering

BNw/Si3N4composites were fabricated by gas pressure sintering process using α-Si3N4powder and self-made BN whisker as principal raw materials. The effects of different sintering additives such as YAG, MgO+YAG and RE2O3+YAG(RE=La, Sm, Dy) on the apparent porosity, microstructure, phase composition, mechanical performance and dielectric properties of the composites were analysed. The results revealed that composite sintering aids at certain ratio (MgO/RE2O3:YAG=1:5) was more conducive to ceramic densification than single YAG additive. The BNw/Si3N4sintered with La2O3+YAG acquired the highest density and the maximum bending strength (272.46 MPa) and fracture toughness(4.9 MPa·m1/2). It was speculated that ceramic densification process was related to formation of different eutectic liquid phases with different viscosity. Additionally, when the apparent porosity of BNw/Si3N4composites was 20% or less, dielectric properties of the material were mainly influenced by the porosity and the value of the permittivity and dielectric loss decreased with the increase of ceramic porosity.

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.

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.

Effect of Al2O3 and MgO Additives on Dielectric Properties of BaZrxTi1-xO3-Based Ceramics

2014 ◽  
Vol 602-603 ◽  
pp. 714-718
Author(s):  
Hong Jun Feng ◽  
Hui Ming Ji ◽  
Xiao Lei Li ◽  
Jian Wang ◽  
Da Hao Wang
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Raw Materials ◽  
Bias Field ◽  
Phase Shifters ◽  
Sem Images ◽  
Solid State Method ◽  
Tunable Capacitors ◽  
Lcr Meter

BaZrxTi1-xO3-based (BZT) ceramics with Al2O3 and MgO addtives were prepared by the conventional solid state method with BaCO3, ZrO2, TiO2, Al2O3 and MgO as raw materials and B2O3 and Li2CO3 as sintering additive. The morphologies were analysized by scanning electron microscopy (SEM). The dielectric constant and dielectric loss of ceramics were measured by LCR meter. The temperature dependences of dielectric constant were measured by high-low temperature incubator tank and LCR meter at 1 MHz and a temperature range-55 to 125 °C. The tunabilities were tested by C-T-V converter and LCR meter at 1 MHz at room temperature. The results show that with the increase of Zr/Ti, BZT ceramic dielectric constant increases, the loss increases, the Curie temperature moves to a lower temperature, and dielectric bias field coordination is relatively lower. The SEM images show that the grain size reaches about 1-2 μm when the sintering temperature is 1100 °C, and the addition of Al2O3 and MgO promote the grain growth and densification of the composite ceramics. The Curie peaks are broadened and depressed with the addition of Al2O3 and MgO. The tunability is improved to 9.59% under a DC electric field of 7.0 kV/cm after the addition of Al2O3. The dielectric constant and dielectric loss of BaZr0.25Ti0.75O3-30wt%Al2O3 and BaZr0.25Ti0.75O3-30wt%MgO are 586, 0.011 and 486, 0.003, respectively. The optimistic dielectric properties make it a promising candidate for the application of tunable capacitors and phase shifters.

scholarly journals Effects of additional amount of carbon micro-coils on the dielectric properties of its composite sheet

2014 ◽  
Vol 38 (1) ◽  
pp. 39-47
Author(s):  
Meherun Nessa
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Relative Dielectric Constant ◽  
Loss Angle ◽  
Composite Sheet ◽  
Dielectric Parameters ◽  
Dielectric Loss Angle ◽  
Additional Amount ◽  
Academy Of Sciences

The morphology and dielectric properties of carbon micro-coils (CMC) composite sheet wereexamined. Frequency dependence of dielectric parameters; dielectric loss angle (?), dielectric losstangent (tan?) and relative dielectric constant ( ?r) were measured on single and double-helixcomposite sheet. It was found that these parameters of CMC/polysilicone composites extensivelychanged with the additional amount of CMC with polysilicone resine. It was also observed that thehigher additional amount (wt%) of CMC is appropriate for high response. DOI: http://dx.doi.org/10.3329/jbas.v38i1.20210 Journal of Bangladesh Academy of Sciences, Vol. 38, No. 1, 39-47, 2014

scholarly journals Studying the Effect of Titania Additions on some properties of Porcelain

2018 ◽  
Vol 28 (2) ◽  
pp. 169
Author(s):  
Abbas K. Saadon
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Titanium Oxide ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Raw Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Manufacturing Method

The paper presents the production of porcelain for the ceramic by inexpensive natural raw materi-als, the principal raw materials of porcelain composition was selected consisting of 50% kaolin, 25% feldspar, 25% silica, the sample synthesized were characterize by X-ray diffraction (XRD) technique, than study the effect additives at different concentration form titanium oxide (𝑇𝑖𝑂2 )at (2, 5, 10, 15, 20) wt% on some physical and dielectric properties of porcelain. The samples are prepared by the conventional manufacturing method. The physical and dielectric properties of porcelain show that change considerably with the sub-stituent sample. It was found that the increase of the titanium oxide (𝑇𝑖𝑂2 ) additives of all our sample produce increasing in dielectric constant and bulk density, while decreasing with open porosity and dielectric loss tangent.

Defects Analysis of Large Size Silicon Nitride Balls Sintered by Gas Pressure Sintering

2010 ◽  
Vol 434-435 ◽  
pp. 61-63
Author(s):  
Feng Sun ◽  
Wei Ru Zhang ◽  
Ting Yan Tian ◽  
Xiang Hong Teng ◽  
Min Chao Ru ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Silicon Nitride ◽  
Temperature Gradient ◽  
Raw Materials ◽  
Gas Pressure ◽  
Sintering Process ◽  
The Core ◽  
Large Size ◽  
Defects Analysis ◽  
Gas Pressure Sintering

The sections of Φ55mm silicon nitride balls, sintered by gas pressure sintering were analyzed. The results show that temperature gradient during of the sintering process from the surface to the core of large size silicon nitride balls occurred because of the lower thermal conductivity of Si3N4. With the diameter increasing, the temperature gradient was more visible. The impurity of raw materials, such as free Si, free C and other metal oxides, like the SiO2 could produce gas, such as SiO, CO and so on, during the sintering process through the thermodynamic analysis. The producing gas exhausted more difficultly with the diameter of silicon nitride balls increasing. These factors were the most important to the defects of large size silicon nitride balls during the sintering process and made cracks and crescent on the surface of balls.

Dielectric Properties of Mg-Doped CaCu3Ti4O12 Measured at High Frequencies

2014 ◽  
Vol 895 ◽  
pp. 190-193
Author(s):  
Mohd Fariz Ab Rahman ◽  
Sabar Derita Hutagalung ◽  
Julie Juliewatty Mohamed ◽  
Mohd Fadzil Ain
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Solid State ◽  
Dielectric Loss ◽  
Solid State Reaction ◽  
Single Phase ◽  
Raw Materials ◽  
Sintering Process ◽  
High Frequencies ◽  
Mg Doped

Mg-doped CaCu3Ti4O12 (CCTO) systems were prepared by solid state reaction using raw materials of CaCO3, CuO, TiO2 and MgO. The samples were calcined at 900°C for 12 hours and sintered at 1030°C for 10 hours. Single phase CCTO formed after sintering process. It was found that dielectric constant and dielectric loss of CCTO improved by MgO dopant.

scholarly journals Dielectric properties of bionano-composites modified by fish scales

2021 ◽  
Vol 9 (2) ◽  
pp. 043-046
Author(s):  
Gojayev EM ◽  
Salimova VV
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Fish Scales ◽  
Loss Angle ◽  
Dielectric Loss Angle ◽  
Temperature Dependences ◽  
Volumetric Content

The presented work presents the results of studying the temperature dependences of the dielectric constant and the tangent of the dielectric loss angle of biocomposites modified with fish scales. It was found that with an increase in the volumetric content of the bio-filler, the dielectric constant of the biocomposites increases, and the tangent of the dielectric loss angle decreases. By varying the volumetric content of the bio-filler, it is possible to control the properties of biocomposites in the desired direction.

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