Effect of Different Composite Additives on Thermal Conductivity of Corundum Ceramics

2012 ◽  
Vol 512-515 ◽  
pp. 500-504 ◽  
Author(s):  
Xing Yong Gu ◽  
Shao Ling Wu ◽  
Ai Hua Zhang ◽  
Ting Luo ◽  
Yun Xia Chen
Keyword(s):  
Thermal Conductivity ◽  
Flexural Strength ◽  
Sintering Temperature ◽  
Alumina Ceramic ◽  
Inorganic Materials ◽  
High Thermal Conductivity ◽  
Alumina Ceramics ◽  
Composite Ceramics ◽  
Subsequent Reaction ◽  
X Ray

To improve the thermal conductivity of alumina ceramics, different inorganic materials such as AlN, BN, Si3N4 and SiC which own high thermal conductivity were integrated with 96% alumina ceramic. The effect of addition of AlN, BN, Si3N4 and SiC on water absorption, flexural strength and thermal conductivity of the as-prepared alumina-based composite ceramics were investigated. Field emission scanning electron microscopy (FESEM) and X-ray diffractometer (XRD) were employed to characterize the microstructure and phase compositions of the composites. The results showed that sintering temperature of 96% alumina ceramic matrixes were improved in varying degree due to adding AlN, BN, SiC and Si3N4. A small quantity of Al6Si2O13 crystals were formed in the case of adding Si3N4 and SiC, which is due to the oxidation of Si3N4 and SiC into SiO2 in the air and the subsequent reaction with alumina. At appropriate firing temperature, the flexural strength of the composites with the addition of AlN is the best and higher than corundum matrixes. Meanwhile, the thermal conductivity of the composites with AlN has 110% improvement. It is obvious that AlN with high thermal conductivity is suitable for improving the thermal conductivity of corundum ceramics.

Preparation of the System of MgO-CaO-SiO2-Al2O3-Y2O3 Wear-Resistant Alumina Ceramics

2014 ◽  
Vol 941-944 ◽  
pp. 542-546 ◽  
Author(s):  
Yuan Xiong ◽  
Bo Lin Wu
Keyword(s):  
Wear Rate ◽  
Sintering Temperature ◽  
Raw Materials ◽  
Alumina Ceramic ◽  
Pressureless Sintering ◽  
Alumina Ceramics ◽  
X Ray Diffraction ◽  
Wear Resistant ◽  
X Ray ◽  
Ceramic Samples

In order to improve the wear resistance and reduce the sintering temperature of alumina ceramics, Y2O3powder added in the system of MgO-CaO-SiO2-Al2O3alumina ceramics were prepared by the technique of pressureless sintering. The properties of the ceramic samples were investigated by the measurements of bulk density, wear rate, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the wear rate of alumina ceramic contenting Y2O3 of the 0.8wt% is 0.041‰. Adding the yttrium oxide to the raw materials and then calcine them to ceramics, which can reduces the sintering temperature, promote the densification and improve wear-resistant property of alumina ceramics.

Effect of Sintering Temperature on Microstructure and Mechanical Properties of Al2O3-TiC-ZrO2 Ceramic Composites

2012 ◽  
Vol 476-478 ◽  
pp. 1031-1035
Author(s):  
Wei Min Liu ◽  
Xing Ai ◽  
Jun Zhao ◽  
Yong Hui Zhou
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Fracture Toughness ◽  
Flexural Strength ◽  
Relative Density ◽  
Sintering Temperature ◽  
Ceramic Composites ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

Al2O3-TiC-ZrO2ceramic composites (ATZ) were fabricated by hot-pressed sintering. The phases and microstructure of the composites were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The relative density and mechanical properties (flexural strength, fracture toughness and Vicker’s hardness) of the composites were tested. The results show that the microstructure of the composites was the gray core-white rim. With the increase of sintering temperature, the relative density and mechanical properties of the composites increased first and then decreased. The composite sintered at 1705°C has the highest synthetical properties, and its relative density, flexural strength, fracture toughness and Vickers hardness are 98.3%,970MPa,6.0 MPa•m1/2and 20.5GPa, respectively.

Microstructure and Properties of Spark Plasma Sintering AlN/BN Ceramics

2006 ◽  
Vol 313 ◽  
pp. 105-108 ◽  
Author(s):  
Lian Meng Zhang ◽  
Mei Juan Li ◽  
Qiang Shen ◽  
T. Li ◽  
M.Q. Yu
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Mechanical Strength ◽  
Spark Plasma Sintering ◽  
Volume Fraction ◽  
Sintering Temperature ◽  
Composite Ceramics ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Full Densification

Aluminum nitride-boron nitride (AlN/BN) composite ceramics were prepared by spark plasma sintering (SPS). The sintering behaviors of AlN/BN composites with 5~15% volume fraction of BN were studied. The influences of BN content, as well as the sintering temperature on the density, microstructure, mechanical strength, thermal conductivity and machinability of the composites were also investigated. The results showed that the full densification of AlN/BN composite ceramics could be realized by SPS technique at the temperature no higher than 1800°C for 3 minutes. The thermal conductivity of AlN/BN composites is in the range of 66~79W/mK, and AlN/BN composites can be cut or drilled by carbides or even steel tools when BN content is 15% volume fraction. The mechanical strength of AlN/BN composites is about 330MPa and is not remarkably affected by the addition of BN. The improvement of mechanical properties of AlN/BN composite ceramics is due to the fine and homogenous microstructure developed in the SPS process.

Research on the Insulation Materials with Sugar Filter Mud as Pore-Forming Agent and Jilin Clay as Aggregate

2013 ◽  
Vol 361-363 ◽  
pp. 682-685
Author(s):  
Chao Qian ◽  
Wen Yuan Gao ◽  
Chun Yuan Luo ◽  
Li Dong Tuo ◽  
Hai Yuan Li ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electron Microscope ◽  
Flexural Strength ◽  
Scanning Electron Microscope ◽  
Elemental Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Insulation Materials ◽  
Filter Mud ◽  
Scanning Electron

Insulation materials with flexural strength 5.238 MPa and porosity 39.24% obtained at 1050 °C for 0.5 h show that its bulk density of the materials decreased down to 1.252 g/cm3using clay as aggregate. Due to change the amount of sugar filter mud, the porosity arises from 37.07% to 39.24% and the thermal conductivity decreases from 0.086 to 0.052 W·m-1·K-1. The clay and wastes were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and chemical elemental analysis. The main crystalline phases of sample observed by XRD are quartz, mullite and anorthite. The insulation materials were manufactured from clay and the optimal proportion of wastes.

scholarly journals Improvement in mechanical properties in AlN-h-BN composites with high thermal conductivity

2021 ◽  
Author(s):  
Zetan Liu ◽  
Shiqiang Zhao ◽  
Tian Yang ◽  
Ji Zhou
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Hexagonal Boron Nitride ◽  
Relative Dielectric Constant ◽  
High Strength ◽  
Secondary Phase ◽  
High Thermal Conductivity ◽  
Raw Material ◽  
Composite Ceramics ◽  
Powder Particles

AbstractIt is possible to improve the machinability of aluminum nitride-hexagonal boron nitride (AlN-h-BN) ceramics while maintaining high strength and high thermal conductivity. The composite ceramics with 0–30 wt% BN as secondary phase were prepared by hot pressed sintering, using yttrium oxide (Y2O3) as sintering aid. The phase composition, density, microstructure, mechanical properties, thermal conductivity, and dielectric properties were investigated. The sintering additives were favorable to purify the grain boundaries and improve densification, reacting with oxide impurities on the surface of raw material powder particles. The optimum BN content improved the flexural strength and fracture toughness of composite ceramics with 475 MPa and 4.86 MPa·m1/2, respectively. With increasing the amount of BN, the thermal conductivity and hardness of composites gradually decreased, but the minimum value of thermal conductivity was still 85.6 W·m−1·K−1. The relative dielectric constant and dielectric loss tangent of the samples ranged from 6.8 to 8.3 and from 2.4 × 10−3 to 6.4 × 10−3, respectively, in 22–26 GHz.

scholarly journals High-thermally conductive AlN-based microwave attenuating composite ceramics with spherical graphite as attenuating agent

2020 ◽  
Author(s):  
Xia Fang ◽  
Lei Jiang ◽  
Limei Pan ◽  
Shuang Yin ◽  
Tai Qiu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Three Dimensional ◽  
High Thermal Conductivity ◽  
Composite Ceramics ◽  
Dielectric Constant And Loss ◽  
Spherical Graphite ◽  
Thermally Conductive ◽  
Absorption Performance ◽  
Hot Pressing Sintering ◽  
Addition Amount

Abstract High-thermally conductive AlN-based microwave attenuating composite ceramics with spherical graphite (SG) as the attenuating agent were fabricated through hot-pressing sintering. The SG maintains its three-dimensional morphology within the sintered bodies, which considerably impedes the sintering of the composites to some extent but slightly influences on the growth of AlN grains. The addition of SG reduces the strength of the composites, but provides a moderate toughening effect at the optimal addition amount (3.8 MPa·m1/2 at 4 wt% SG). Benefiting from the low anisotropy, high thermal conductivity, and the three-dimensional morphology of SG, the composites exhibit a relatively higher thermal conductivity (76.82 W·m-1·k-1 at 10 wt% SG) compared with composites added with non-spherical attenuating agent. The dielectric constant and loss (8.2–12.4 GHz) increase remarkably as the amount of SG added increases up to 8 wt%, revealing that the incorporation of SG improves the dielectric property of the composite. The composite with 7 wt% SG exhibits the best absorption performance with a minimum reflection loss of -14 dB at 12.4 GHz and an effective absorbing bandwidth of 0.87 GHz. The excellent overall properties of the SG/AlN microwave attenuating composites render them as a promising material for various applications. Moreover, SG has a great potential as an attenuating agent for microwave attenuating composites due to its strong attenuation upon integration, high thermal conductivity, and low anisotropy.

Fabrication and Microstructure of Electrically Conductive AlN with High Thermal Conductivity

2011 ◽  
Vol 484 ◽  
pp. 57-60
Author(s):  
Takafumi Kusunose ◽  
Tohru Sekino ◽  
Koiichi Niihara
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Rare Earth ◽  
Sintering Temperature ◽  
Rare Earth Oxide ◽  
High Thermal Conductivity ◽  
Boundary Phase ◽  
Sudden Increase ◽  
Electrically Conductive ◽  
Electrical Conductivities

The electrically conductive AlN with high thermal conductivity were successfully fabricated by sintering AlN with a composite additive of 1wt.% Y2O3 and 4wt.% CeO2 in carbon-reduced atmosphere at over 1600 °C. The sudden increase in electrical conductivity is thought to be caused by transition of grain boundary phase from rare-earth oxide to rare-earth oxycarbide. Their electrical conductivities and thermal conductivities increased with increasing sintering temperature. Additionally, sintering temperature influenced the resultant microstructures.

Preparation and Thermal Properties of Pressureless Sintered AIN/SiC Composites

2015 ◽  
Vol 655 ◽  
pp. 78-81
Author(s):  
Shu He Ai ◽  
Yu Jun Zhang ◽  
Hong Yu Gong ◽  
Qi Song Li
Keyword(s):  
Thermal Conductivity ◽  
Mechanical Property ◽  
Thermal Properties ◽  
Flexural Strength ◽  
Relative Density ◽  
Sintering Temperature ◽  
Pressureless Sintering ◽  
Temperature Range ◽  
Sic Composites

AlN/SiC composites with 5 wt.% Y2O3addition were fabricated by pressureless sintering at 1700-1950 oC. The influences of sintering temperature and SiC content on the relative density, mechanical property and thermal conductivity were studied. With sintering temperature increasing from 1700 oC to 1750 oC, the relative density increased significantly to about 98.0%, without evident changes from 1750 oC to 1900 oC, and then decreased slightly at 1950 oC. As SiC content increased, the flexural strength of composites sintered at 1750 oC increased firstly, and then decreased, obtaining a maximum flexural strength of 337 MPa at 20 wt.% SiC content. Meanwhile, the thermal conductivity decreased from 60 W/(m∙K) to 40 W/(m∙K) with SiC content increasing from 0 wt.% to 30 wt.%. Moreover, in the sintering temperature range from 1750 oC to 1950 oC, the thermal conductivity increased from 45 W/(m∙K) to 55 W/(m∙K) for AlN-10 wt.% SiC composites, but decreased from 40 W/(m∙K) to 36 W/(m∙K) for AlN-30 wt.% SiC composites.

Preparation and Research of High-Temperature Foam Ceramic

2013 ◽  
Vol 357-360 ◽  
pp. 1353-1357
Author(s):  
Xiao Li Ji ◽  
Zhuo Chen
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
High Temperature ◽  
Sintering Temperature ◽  
X Ray Diffraction ◽  
Micro Structure ◽  
Foaming Agent ◽  
X Ray ◽  
Foam Ceramic ◽  
Scanning Electron

High-temperature foam ceramics were produced from sludge, Zhongxiang porcelain sand, shale and sand, with addition of SiC 0.15%~0.40% as foaming agent, respectively, sintered at 1130°C~1160°C. The phase composition and micro structure of sintered samples were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and density, compressive strength and thermal conductivity were evaluated. The results showed that the main phase of amorphous phase plagioclase in sintered samples and interior of samples with a large number of uniformly distributed closed pores, rose sintering temperature and increased SiC addition leading to pores size enlarged and density, compressive strength and thermal conductivity diminished.

Effect of Stoichiometry and Sintering Temperature on the Mechanical Properties of Zinc Ferrite (ZnxFe3-xO4)

2016 ◽  
Vol 857 ◽  
pp. 126-130
Author(s):  
S.S. Aqzna ◽  
Cheow Keat Yeoh ◽  
A.G. Supri ◽  
T.N. Atiqah ◽  
H.K. Amali ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Zinc Oxide ◽  
Iron Oxide ◽  
Thermal Resistance ◽  
Zinc Ferrite ◽  
Sintering Temperature ◽  
Hardness Testing ◽  
X Ray Diffraction ◽  
X Ray

The composites sample of Zinc Ferrite (ZnxFe3-xO4) were prepared by mixing zinc oxide (ZnO) and iron oxide (Fe2O3) via different stoichiometry (ratio) with ZnxFe3-xO4, for x= 0,0.2,0.4,0.6,0.8 and sintering temperature at 1000 °C, 1100 °C,1200 °C for six hours. The phase compositions of the synthesized Zinc Ferrite (ZF) were verified using X-ray Diffraction (XRD), hardness testing using hardness Vickers, density and thermal conductivity for composite was studied. The result shows the sample with ratio 0.8 and 1200 oC sintering temperature gives the highest value of thermal conductivity with 9.7614 W/m2K and the lowest thermal resistance with 0.1024 m2K / W.

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