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Investigation on two abnormal phenomena about thermal conductivity enhancement of BN/EG nanofluids.

Li Y, Zhou J, Luo Z, Tung S, Schneider E, Wu J, Li X - Nanoscale Res Lett (2011)

Bottom Line: The thermal conductivity of boron nitride/ethylene glycol (BN/EG) nanofluids was investigated by transient hot-wire method and two abnormal phenomena was reported.The chain-like loose aggregation of nanoparticles is responsible for the abnormal increment of thermal conductivity enhancement for the BN/EG nanofluids at very low particles volume fraction.And the difference in specific surface area and aspect ratio of BN nanoparticles may be the main reasons for the abnormal difference between thermal conductivity enhancements for BN/EG nanofluids prepared with 140- and 70-nm BN nanoparticles, respectively.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an, Shanxi, 710049, China. lyj.xjtu@yahoo.com.cn.

ABSTRACT
The thermal conductivity of boron nitride/ethylene glycol (BN/EG) nanofluids was investigated by transient hot-wire method and two abnormal phenomena was reported. One is the abnormal higher thermal conductivity enhancement for BN/EG nanofluids at very low-volume fraction of particles, and the other is the thermal conductivity enhancement of BN/EG nanofluids synthesized with large BN nanoparticles (140 nm) which is higher than that synthesized with small BN nanoparticles (70 nm). The chain-like loose aggregation of nanoparticles is responsible for the abnormal increment of thermal conductivity enhancement for the BN/EG nanofluids at very low particles volume fraction. And the difference in specific surface area and aspect ratio of BN nanoparticles may be the main reasons for the abnormal difference between thermal conductivity enhancements for BN/EG nanofluids prepared with 140- and 70-nm BN nanoparticles, respectively.

No MeSH data available.


XRD patterns of the BN nanoparticles. (a) Original pattern (b) partial enlarged pattern.
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Figure 6: XRD patterns of the BN nanoparticles. (a) Original pattern (b) partial enlarged pattern.

Mentions: Figure 6a is an XRD pattern of the BN powder with different size. Figure 6b is a partial enlarged pattern of Figure 6a. From Figure 6b, we can observe that the BN powder was composed of different phases. Hexagonal BN and cubic BN are the main phases for 140-nm BN powder. The weight ratio of hexagonal BN and cubic BN is about 93:7 through qualitative analysis made by the software attached by the Rigaku D/MAX-2400 x-ray diffraction analysis. For 70-nm BN powder, hexagonal BN, rhombohedral BN, and cubic BN are the main phases and the weight ratio of these three different phases is about 62:35:3. So we can conclude that the 140-nm BN powder are mainly composed of flake-like hexagonal BN while 70-nm BN powder are composed of 62% flake-like hexagonal BN and 38% BN with different shape.


Investigation on two abnormal phenomena about thermal conductivity enhancement of BN/EG nanofluids.

Li Y, Zhou J, Luo Z, Tung S, Schneider E, Wu J, Li X - Nanoscale Res Lett (2011)

XRD patterns of the BN nanoparticles. (a) Original pattern (b) partial enlarged pattern.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211862&req=5

Figure 6: XRD patterns of the BN nanoparticles. (a) Original pattern (b) partial enlarged pattern.
Mentions: Figure 6a is an XRD pattern of the BN powder with different size. Figure 6b is a partial enlarged pattern of Figure 6a. From Figure 6b, we can observe that the BN powder was composed of different phases. Hexagonal BN and cubic BN are the main phases for 140-nm BN powder. The weight ratio of hexagonal BN and cubic BN is about 93:7 through qualitative analysis made by the software attached by the Rigaku D/MAX-2400 x-ray diffraction analysis. For 70-nm BN powder, hexagonal BN, rhombohedral BN, and cubic BN are the main phases and the weight ratio of these three different phases is about 62:35:3. So we can conclude that the 140-nm BN powder are mainly composed of flake-like hexagonal BN while 70-nm BN powder are composed of 62% flake-like hexagonal BN and 38% BN with different shape.

Bottom Line: The thermal conductivity of boron nitride/ethylene glycol (BN/EG) nanofluids was investigated by transient hot-wire method and two abnormal phenomena was reported.The chain-like loose aggregation of nanoparticles is responsible for the abnormal increment of thermal conductivity enhancement for the BN/EG nanofluids at very low particles volume fraction.And the difference in specific surface area and aspect ratio of BN nanoparticles may be the main reasons for the abnormal difference between thermal conductivity enhancements for BN/EG nanofluids prepared with 140- and 70-nm BN nanoparticles, respectively.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an, Shanxi, 710049, China. lyj.xjtu@yahoo.com.cn.

ABSTRACT
The thermal conductivity of boron nitride/ethylene glycol (BN/EG) nanofluids was investigated by transient hot-wire method and two abnormal phenomena was reported. One is the abnormal higher thermal conductivity enhancement for BN/EG nanofluids at very low-volume fraction of particles, and the other is the thermal conductivity enhancement of BN/EG nanofluids synthesized with large BN nanoparticles (140 nm) which is higher than that synthesized with small BN nanoparticles (70 nm). The chain-like loose aggregation of nanoparticles is responsible for the abnormal increment of thermal conductivity enhancement for the BN/EG nanofluids at very low particles volume fraction. And the difference in specific surface area and aspect ratio of BN nanoparticles may be the main reasons for the abnormal difference between thermal conductivity enhancements for BN/EG nanofluids prepared with 140- and 70-nm BN nanoparticles, respectively.

No MeSH data available.