Effect of Additives on Thermal Conductivity of Si3N4 Ceramics

2021 ◽  
Vol 1036 ◽  
pp. 185-195
Author(s):  
Zi Hao Chen ◽  
Qiang Gu ◽  
Wei Kui Ma ◽  
Guo Qi Liu
Keyword(s):  
Thermal Conductivity ◽  
High Speed ◽  
Heat Dissipation ◽  
High Strength ◽  
High Thermal Conductivity ◽  
Raw Material ◽  
Β Phase ◽  
Sealing Material ◽  
Strong Current ◽  
High Oxidation Resistance

Compared with traditional ceramics, Si3N4 ceramics have the characteristics of high theoretical thermal conductivity, high thermal shock resistance, high oxidation resistance, high strength, and strong current carrying capacity. It is a potential high-speed circuit and high-power device for heat dissipation and heat dissipation. Sealing material. For applications in 5these fields, β-Si3N4 with a relatively stable structure and high thermal conductivity is an ideal material. However, β-Si3N4 powder is difficult to sinter as a raw material. Therefore, the prepared Si3N4 generally has a low density, and there are various defects in the crystal. The existence of these defects will cause interference and scattering of heat in the transfer process. Limits the application of β-Si3N4 ceramics. Studies have shown that the introduction of different additives can form a liquid phase at high temperatures, which can effectively reduce the firing temperature of the sample and increase the density. At the same time, it can also remove lattice oxygen, weaken the intercrystalline phase, and promote the α→β phase transition. Thereby improving the thermal conductivity and sintering performance of Si3N4 ceramics. Therefore, this article reviews the types of additives and their effects on the properties of Si3N4 ceramics and their mechanism. Trying to find an additive system for the preparation of high thermal conductivity Si3N4 ceramics with excellent comprehensive performance, hoping to provide help for the work and researchers engaged in the research on the thermal conductivity of Si3N4 ceramics.

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 Core-Shell Sr2CeO4@SiO2 Filled COC‑Based Composites with Low Dielectric Loss for High-Frequency Substrates

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 4006
Author(s):  
Qinlong Wang ◽  
Hao Wang ◽  
Caixia Zhang ◽  
Qilong Zhang ◽  
Hui Yang
Keyword(s):  
Thermal Conductivity ◽  
Dielectric Loss ◽  
High Frequency ◽  
High Speed ◽  
Heat Dissipation ◽  
Coefficient Of Thermal Expansion ◽  
Signal Transmission ◽  
Sol Gel ◽  
Normal Operation ◽  
Core Shell

High-frequency communication equipment urgently needs substrate materials with lower dielectric loss, better heat dissipation, and higher stability, to ensure real-time low-loss and high-speed signal transmission. The core-shell structure of Sr2CeO4@SiO2 was prepared by the sol-gel method, and the modified powders with different volume contents were introduced into the cyclic olefin copolymer (COC) to prepare hydrocarbon resin-based composites. Due to the protective effect of the SiO2 shell, the stability of the powders is significantly improved, and the moisture barrier and corrosion resistance of the composites are enhanced, which is conducive to the normal operation of electronic equipment in harsh and complex environments. When the filler content is 20 vol%, the composite has a dielectric loss of 0.0023 at 10 GHz, a dielectric constant of 3.5, a thermal conductivity of 0.9 W·m−1·K−1, a water absorption of 0.32% and a coefficient of thermal expansion of 37.7 ppm/℃. The COC/Sr2CeO4@SiO2 composites exhibit excellent dielectric properties and thermal conductivity, while maintaining good moisture resistance and dimensional stability, which shows potential application prospects in the field of high-frequency substrates.

scholarly journals Development of Thermally Conductive Polyurethane Composite by Low Filler Loading of Spherical BN/PMMA Composite Powder

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Kai-Han Su ◽  
Cherng-Yuh Su ◽  
Cheng-Ta Cho ◽  
Chung-Hsuan Lin ◽  
Guan-Fu Jhou ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Dissipation ◽  
Three Dimensional ◽  
Filler Loading ◽  
High Thermal Conductivity ◽  
Heat Diffusion ◽  
Composite Powders ◽  
Polyurethane Composite ◽  
Uniform Dispersion ◽  
Thermally Conductive

Abstract The issue of electronic heat dissipation has received much attention in recent times and has become one of the key factors in electronic components such as circuit boards. Therefore, designing of materials with good thermal conductivity is vital. In this work, a thermally conductive SBP/PU composite was prepared wherein the spherical h-BN@PMMA (SBP) composite powders were dispersed in the polyurethane (PU) matrix. The thermal conductivity of SBP was found to be significantly higher than that of the pure h-BN/PU composite at the same h-BN filler loading. The SBP/PU composite can reach a high thermal conductivity of 7.3 Wm−1 K−1 which is twice as high as that of pure h-BN/PU composite without surface treatment in the same condition. This enhancement in the property can be attributed to the uniform dispersion of SBP in the PU polymer matrix that leads to a three-dimensional continuous heat conduction thereby improving the heat diffusion of the entire composite. Hence, we provide a valuable method for preparing a 3-dimensional heat flow path in polyurethane composite, leading to a high thermal conductivity with a small amount of filler.

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 High thermal conductivity in soft elastomers with elongated liquid metal inclusions

2017 ◽  
Vol 114 (9) ◽  
pp. 2143-2148 ◽  
Author(s):  
Michael D. Bartlett ◽  
Navid Kazem ◽  
Matthew J. Powell-Palm ◽  
Xiaonan Huang ◽  
Wenhuan Sun ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Liquid Metal ◽  
Heat Dissipation ◽  
Dielectric Materials ◽  
Phonon Transport ◽  
High Thermal Conductivity ◽  
Stretchable Electronics ◽  
Mechanical Stiffness ◽  
Mechanical Coupling ◽  
Thermally Conductive

Soft dielectric materials typically exhibit poor heat transfer properties due to the dynamics of phonon transport, which constrain thermal conductivity (k) to decrease monotonically with decreasing elastic modulus (E). This thermal−mechanical trade-off is limiting for wearable computing, soft robotics, and other emerging applications that require materials with both high thermal conductivity and low mechanical stiffness. Here, we overcome this constraint with an electrically insulating composite that exhibits an unprecedented combination of metal-like thermal conductivity, an elastic compliance similar to soft biological tissue (Young’s modulus < 100 kPa), and the capability to undergo extreme deformations (>600% strain). By incorporating liquid metal (LM) microdroplets into a soft elastomer, we achieve a ∼25× increase in thermal conductivity (4.7 ± 0.2 W⋅m−1⋅K−1) over the base polymer (0.20 ± 0.01 W⋅m−1·K−1) under stress-free conditions and a ∼50× increase (9.8 ± 0.8 W⋅m−1·K−1) when strained. This exceptional combination of thermal and mechanical properties is enabled by a unique thermal−mechanical coupling that exploits the deformability of the LM inclusions to create thermally conductive pathways in situ. Moreover, these materials offer possibilities for passive heat exchange in stretchable electronics and bioinspired robotics, which we demonstrate through the rapid heat dissipation of an elastomer-mounted extreme high-power LED lamp and a swimming soft robot.

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

Hydrophobic Dielectric Sealing Material Enabled Highly Reliable Electrical Connectors for Downhole Data and Power Transmission Application

2021 ◽  
Author(s):  
Hua Xia ◽  
Nelson Settles ◽  
David DeWire
Keyword(s):  
Safety Factor ◽  
Power Transmission ◽  
High Strength ◽  
Mixed Phase ◽  
Insulation Resistance ◽  
Β Phase ◽  
Electrical Connector ◽  
Sealing Material ◽  
Sealing Materials ◽  
Electrical Connectors

Abstract A high-strength dielectric sealing material has been developed for sealing electrical connectors, feedthroughs, bulkheads, and interconnectors. X-ray diffraction analyses have identified that the microstructures of the sealing material could be of amorphous and α-phase mixed morphology, α+β mixed phase, and β-phase dominated tetrahedral microstructure, which primarily depend upon the material processing temperature. The electrical insulation resistance of the β-phase dominated sealing material have nearly two times higher than that of α+β mixed phase sealing material. Both β-phase dominated and α+β mixed phase sealing materials have shown water repelling properties, while amorphous glass phase has shown hydrophilic properties. If a 5,000MΩ insulation resistance is also regarded as baseline for a downhole electrical connector, the maximum operation temperature of α+β mixed phase sealing materials is around 240°C while that of the β-phase dominated sealing material can be up to 300°C. Furthermore, a thermo-mechanical modeling has been developed to quantify if a designed electrical connector has sufficient reliability in the hostile wellbore or downhole environments. The temperature- and pressure-dependent seal compression have suggested that the temperature-related safety factor should be chosen in the range from 2.0 to 5.0 while the pressure-related safety factor should be chosen in the range from 1.5 to 2.0 to ensure 10-20 years electrical connector downhole operating reliability. The qualification tests from prototyped electrical connectors, under 260°C/32,000PSI simulated water-fluid based conditions, have demonstrated that such high-strength sealing material sealed electrical connector could be integrated with logging while drilling (LWD) or/and measurement while drilling (MWD) tools for providing long-term reliable signal, data, and electrical power transmission services, regardless of a water-based or moisture-rich wellbore or/and downhole environment.

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