AlN with high strength and high thermal conductivity based on an MCAS-Y2O3-YSZ multi-additive system

2021 ◽  
Author(s):  
Su-Hyun Baek ◽  
Hyeondeok Jeong ◽  
Sung-Soo Ryu
Keyword(s):  
Thermal Conductivity ◽  
High Strength ◽  
High Thermal Conductivity ◽  
Additive System

scholarly journals Simultaneous achievement of high thermal conductivity, high strength and formability in Mg-Zn-Ca-Zr sheet alloy

2020 ◽  
Vol 8 (9) ◽  
pp. 335-340 ◽  
Author(s):  
Z. H. Li ◽  
T. T. Sasaki ◽  
T. Shiroyama ◽  
A. Miura ◽  
K. Uchida ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Strength ◽  
High Thermal Conductivity ◽  
Sheet Alloy

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.

Graphitic Foam with High Strength and High Thermal Conductivity Doped by Tungsten

2008 ◽  
Vol 27 (4) ◽  
pp. 251-260 ◽  
Author(s):  
Yong Wang ◽  
Lingling Cao ◽  
Jin Gao ◽  
Yimin Wang
Keyword(s):  
Thermal Conductivity ◽  
High Strength ◽  
High Thermal Conductivity ◽  
Graphitic Foam

Using Regression Analysis to Optimize the Combination of Thermal Conductivity and Hardness in Compacted Graphite Iron

2010 ◽  
Vol 457 ◽  
pp. 337-342 ◽  
Author(s):  
Martin Selin
Keyword(s):  
Thermal Conductivity ◽  
Linear Regression ◽  
High Strength ◽  
Positive Influence ◽  
High Thermal Conductivity ◽  
Regression Equations ◽  
Compacted Graphite Iron ◽  
Free Electrons ◽  
Compacted Graphite ◽  
Microstructure Parameters

In cast iron there is a contradictory relationship between thermal conductivity and strength. In many applications it is desirable to optimize the material properties to obtain both sufficiently high thermal conductivity and sufficiently high strength. The aim of this paper is to investigate how various microstructure parameters and alloying elements affect thermal conductivity and hardness in compacted graphite irons. It was found that the fraction of ferrite, the fraction of cementite, nodularity and content of carbon and silicon are parameters that influence the thermal conductivity and hardness the most. Based on these five key parameters linear regression equations were created for calculation of thermal conductivity and hardness. Ferrite and carbon have a positive influence on the thermal conductivity, while silicon, cementite and nodularity have a deleterious effect. All parameters except ferrite have a positive influence on the hardness. This is because the thermal conductivity is dependent on the movement of free electrons, and therefore unfavourable growth directions and grain boundaries which impede the electron movement will reduce the thermal conductivity. Ferrite has quite high thermal conductivity, while cementite has poor thermal conductivity, due to an unfavourable crystal structure. Nodular shaped graphite has a lower thermal conductivity than compacted graphite which explains the deleterious influence of nodularity. The soft ferrite phase will reduce the hardness value, while increasing the fraction of harder graphite nodules and harder cementite phase will increase the hardness. To investigate how these five parameters affect the combination of hardness and thermal conductivity, values for hardness and thermal conductivity were calculated for all combinations of key parameters in given intervals, using two linear regression equations. From these it is possible to predict the combination of parameters which gives a particular combination of hardness and thermal conductivity in compacted graphite iron.

Thermal Conductivity Improvement by Heat-Treatment in Si3N4 Ceramics Using SiO2-MgO-Y2O3 Additive System

2007 ◽  
Vol 352 ◽  
pp. 233-238 ◽  
Author(s):  
Thanakorn Wasanapiarnpong ◽  
Shigetaka Wada ◽  
Masamitsu Imai ◽  
Toyohiko Yano
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Liquid Phase ◽  
Low Temperature ◽  
Glassy Phase ◽  
Bending Strength ◽  
High Thermal Conductivity ◽  
Full Density ◽  
Additive System ◽  
Si3n4 Ceramics

Silicon nitride (Si3N4) ceramics have been interested for electrical substrate applications, because the ceramics can be made highly mechanical strength, fracture toughness, electrical resistivity and high thermal conductivity. Generally, relatively large amount of additives are required to obtain dense Si3N4 ceramics. During sintering, additives react with SiO2 including surface oxide of Si3N4 raw powder to form a liquid phase. Most of liquid phase changed into glassy phase during cooling down. In this study, Si3N4 ceramics were fabricated by gas pressure sintering. Yttrium oxide (Y2O3), silica (SiO2), and magnesia (MgO) were used for liquid-phase-enhanced sintering process. Dense materials were sintered by this process, but their thermal conductivities were not so high (30-40 W/m·K). Therefore, post-sintering heat-treatment process was performed to reduce the excess amount of glassy phase. An additive system (3 mass% SiO2 with 3 mass% MgO and 1-5 mass% Y2O3) was selected as the sintering aid. These ceramics could be sintered to almost full density at relatively low temperature as 1650oC for 2 h under 0.1 MPa-N2 without packing powder. The resulting materials have high bending strength, about 1 GPa, when 5mass% of Y2O3 was added. Based on the creation of low temperature pressureless sintering without packing powder, a novel two-step sintering (once firing) was proposed. The two-step sintering conducted by sintered at 1650oC under 0.1 MPa-N2 for 2 h for densification in the first step. Followed by heated up to and kept at 1950oC for 8 h under 1.0 MPa-N2 in the second step. The Si3N4 ceramics could be fabricated with relatively high thermal conductivity of 90 W/m·K. Mass loss, microstructure, mechanical properties, oxygen content and chemical composition were discussed.

Carbon Foam with High Strength and High Thermal Conductivity Doped by Nano-Titanium

2008 ◽  
Vol 47-50 ◽  
pp. 566-569
Author(s):  
Yong Wang ◽  
Ling Ling Cao ◽  
Yi Min Wang
Keyword(s):  
Thermal Conductivity ◽  
Cell Walls ◽  
High Strength ◽  
Carbon Foam ◽  
High Thermal Conductivity ◽  
Mesophase Pitch ◽  
Test Results ◽  
Titanium Concentration ◽  
Titanium Particle ◽  
Scanning Electron

A carbon foam with high strength and high thermal conductivity was prepared through the incorporation of nano-titanium particle into mesophase pitch precursor. Results show that titanium act as catalysts to accelerate the graphitization of carbon, promote more perfect and larger crystallites and enhance the conductive and mechanical properties. Test results reveal that titanium doped carbon foam (TDCF) has excellent compressive strength and high thermal conductivity, with highest values reaching 29.6 MPa and 117.8 Wm-1 K-1 for a titanium concentration of 12 wt% in the precursor materials. More compact struts and cell walls stacked by more uniform were observed by scanning electron microscope in carbon foam. Correlation between the content of dopant and the properties and microstructure of TDCF was discussed.

High Strength and High Thermal Conductivity Carbon Foam Reinforced with Graphite Nanoparticles

2007 ◽  
Vol 26 (5) ◽  
pp. 305-312 ◽  
Author(s):  
Yong Wang ◽  
Zhi Xu ◽  
Qingqing An ◽  
Yimin Wang
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
High Pressure ◽  
Coal Tar ◽  
High Strength ◽  
Carbon Foam ◽  
High Thermal Conductivity ◽  
Mesophase Pitch ◽  
High Pressure And Temperature ◽  
Graphite Nanoparticles

A novel carbon foam with high strength and high thermal conductivity was prepared through the incorporation of graphite nanoparticles into coal tar based mesophase pitch precursor. Carbon foam was obtained after carbonization and graphitication of pitch foam formed by the pyrolysis of coal tar based mesophase pitch mixed with graphite nanoparticles in a high pressure and temperature chamber. The foam had possessed high strength and exceptional high thermal conductivity. SEM observation showed that less micro cracking appeared on the cell wall of foam by the addition of graphite nanoparticles. The test of thermal conductivity and mechanical properties shows that the thermal conductivity of modified carbon foam could reach 195 W/m.K. The mechanical properties were improved markedly, and compressive strength was increased from 2 MPa to 18.8 MPa when the additive amount of graphite nanoparticles was 8%.

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