- Email: [email protected]
diamond composites
Scripta Materialia 170 (2019) 140–144
Contents lists available at ScienceDirect
Scripta Materialia journal homepage: www.elsevier.com/locate/scriptamat
High thermal conductivity in Bi-In-Sn/diamond composites Chengzong Zeng, Jun Shen ⁎, Chao He, Hui Chen State Key Laboratory of Mechanical Transmission, College of Material Science and Engineering, Chongqing University, Chongqing, 400044, China
a r t i c l e
i n f o
Article history: Received 9 May 2019 Received in revised form 1 June 2019 Accepted 5 June 2019 Available online 11 June 2019 Keywords: Bi-In-Sn Diamond Thermal conductivity Sintering
a b s t r a c t The Bi-In-Sn/diamond composites were manufactured and characterized. Nano and micro Bi-In-Sn powders coated by oxide skin were produced by slice technique. Optimized sintering pressure was 0.53 MPa at the temperature of 120 °C with air condition. The highest thermal conductivity of Bi-In-Sn/diamond composites was up to 71.4 W m−1 K−1, which is ~3 times higher than that of Bi-In-Sn. Compared to the results of simulation, the actual thermal conductivity of Bi-In-Sn/diamond composites was slightly lower, which is due to the gap generated between diamond particles in the solidification process, especially as the volume fraction of diamond particles is high. © 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Heat dissipation have become one of the most critical technological challenges in electronics. According to Moore's law, the integration density of a microprocessor chip will double every 18–24 months and is nearing its end [1]. Effective thermal management thus plays a crucial role in the performance and reliability of high power electronic devices, especially in a smaller space [2]. High thermal conductivity materials have been studied to face the emerging challenges in heat dissipation. Cubic boron arsenide with high thermal conductivity was obtained by chemical vapor deposition [3,4]. Copper matrix diamond-containing composites show great potential for superior thermal conductivity [5]. Magnesium/diamond composites with bimodal distribution of particles were manufactured to reach high thermal conductivity [6]. Recently, phase change materials (PCMs) (melting point between 25 °C and 85 °C [7]) are considered to be a good option for cooling devices that generate heat intermittently [8]. A large amount of latent heat can be absorbed/released during their melting/solidification process, while the temperature of PCMs remains nearly constant [9]. The thermal conductivity of metallic PCMs [10] is several dozen times larger than that of organic [11] and inorganic PCMs [12]. Low melting point alloy (LMPA) is the most widely used in Metallic PCMs, but its thermal conductivity is still lower than that of the hot or cold terminal. Thus, it is necessary to improve the thermal conductivity of the LPMA to satisfy the heat dissipation of higher hot devices. Diamond has the highest isotropic thermal conductivity of any bulk material (~2200 W m−1 K−1, at room temperature) [4]. In recent years, metal matrix with diamond particles composites have been studied to obtain a novel material with higher thermal conductivity [5,13]. However, LMPA diamond-containing composites have rarely been researched. ⁎ Corresponding author. E-mail address: [email protected] (J. Shen).
https://doi.org/10.1016/j.scriptamat.2019.06.010 1359-6462/© 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
In this work, the Field's metal Bi-In-Sn and diamond particles were selected to study. Most researchers add alloy elements into metal matrix [14,15] or coat alloy elements onto diamond surface [16,17] to improve wettability, which to enhance the interfacial bonding and increase the thermal conductivity of the composites. While in this study, it is observed that the composite of uncoated-diamond and BiIn-Sn have a high thermal conductivity. The composites were made under a micro pressure with a low temperature, which is simple and easy to produce. The surface of the Bi-In-Sn particles was wrapped in a membrane. Appropriate pressure must be applied to the particles, thus make the membrane to rupture (P N Pc, Fig. 1c). Larsen et al. [18] have proven that the pressure P is related to the surface tension γm of the membrane (~0.58 N m−1 [19]), the membrane will yield as the surface stress is more than surface tension, the relationship between the critical load pressure Pc and γm can be expressed as follows: P Pc ¼
πR2 γm
1 2 cosθ − R d S
where R is the radius of the disk, γm is the surface tension of the membrane, d is the height of the gap and θ is the contact angle of the particle making with the parallel disk, S is the pressed area. The thermal conductivity of Bi-In-Sn/diamond composites can be predicted with the numerical simulation [20]. The size of the 2D model is 1000 μm × 1000 μm. The geometric model of the diamond was simplified to a regular hexagon. Grid refinement near the diamond was implemented to ensure the calculation precision (Fig. 1d). The wall of left and right was set as insulation. The temperature imposed at the
C. Zeng et al. / Scripta Materialia 170 (2019) 140–144
141
Fig. 1. Schematic representation of (a) SLICE process, (b) preparation of Bi-In-Sn/Diamond composite materials, (c) and particle membrane crushing (not to scale); (d) the model of the composites with the random distribution of the diamond particles.
bottom wall and the top wall is 57 °C and 20 °C. Assuming that there is no interspace between Bi-In-Sn and diamond particles. MBD8 quality diamond particles were used in this work (Zhecheng Hongxiang Superhard Material Co., Ltd., China). Field's metal (Bi: In: Sn 32.5: 51.0: 16.5 wt%) was prepared in a salt melt (27.1 wt% Bi, 42.5 wt% In, 13.8 wt% Sn, 9.2 wt% KCl and 7.4 wt% LiCl). The purity of bismuth, indium and tin is at least 99.995%, 99.999% and 99.995% (Shenyang Jiabei Trading Co., Ltd., China). Bi-In-Sn particles were fabricated by slice technique [21]. ~15 g metal was added in polyethylene glycol solution (Fig. 1a). The solution prepared in a glass beaker was kept in an oil bath at the preset temperature (120 °C) for at least 10 min before slice. Slice procedure was applied using a homogenizer (FSH-2A) at the rate of 16,000 rpm. Total continuous shearing time lasts for 5 mins. Excess polyethylene glycol were washed out, and then the Bi-In-Sn particles were dried in a vacuum oven (BZF-30). Bi-In-Sn/diamond composites were performed using the sintering technique with a micro-pressure under a low temperature (Fig. 1b). A certain proportion of diamond particles and Bi-In-Sn particles were mixed evenly, then put into a 304 stainless steel moulds with the diameter of 12.5 mm. Prepared Bi-In-Sn/diamond composites specimens were heated in an oven (LTKC-4-10A) with air condition. Then they were cooled to room temperature in air. The sintering parameters were given in Table 1. Bi-In-Sn alloy was studied using a differential scanning calorimeter (DSC, TGA/DSC1/1100LF) and X-ray photoelectron spectroscopy (XPS, ESCALAB250Xi). The microstructures of diamond, Bi-In-Sn particles, and the Bi-In-Sn/diamond composites were characterized by field emission scanning electron microscope (SEM, Zeiss Auriga-39-60) equipped with energy dispersive X-ray spectrometer (EDS) and X-ray diffraction
Table 1 Diamond particle used in the preparation of Bi-In-Sn/diamond composites. D is the average equivalent diameter of the corresponding particle type. Vd is the volume fraction of diamond particles measured within 1% error. T is the sintering temperature and P is the sintering pressure. Code
Diamond type
D (μm)
Vd
T (°C)
P (MPa)
C1 C2 C3 C4 C5 C6 C7 C8
MBD8 120/140 MBD8 120/140 MBD8 120/140 MBD8 120/140 MBD8 35/40 MBD8 270/325 MBD8 120/140 MBD8 120/140
115 115 115 115 403 50 115 115
0.5
120
5.6 × 10−3 0.26 0.53 0.64 0.53 0.53 0.53 0.53
0.1 0.3
(XRD, Empryean) with Cu Kα radiation. The density of the composites ρc was measured by the Archimedes principle (DK-300A). The thermal diffusivity α was measured using a LFA467 MicroFlash (Netzsch) thermal analyzer at room temperature. Each sample was tested three times to reduce testing errors of experimental data. The specific heat capacity of the sample Cp was measured using the DSC. The thermal conductivity Kc was obtained from Kc = ρcαCp. The melting point of the bulk Bi-In-Sn was 59 °C (Fig. 2a), which is consistent with the result of Witusiewicz [22]. DSC result of Bi-In-Sn powders was similar to that of bulk Bi-In-Sn, that means the melting point of the Bi-In-Sn cannot be changed after the slice technique. TGA was conducted on the bulk Bi-In-Sn and Bi-In-Sn powders in air condition to confirm that the Bi-In-Sn of the composites would not be over oxidized before or after sintering (Fig. 2b). The sintering temperature in this study was 120 °C, while the weight of Bi-In-Sn powders remained constant as soon as the temperature increased to above 300 °C, so did the bulk Bi-In-Sn. Thus, all the sintering process was carried out under air condition, which greatly reduced the time and cost. The macrograph of Bi-In-Sn powders fabricated in a single process was represented in Fig. 2c. The diameter of nano spheres is almost 30–100 nm (Fig. 2d), and the diameter of microspheres is less than 30 μm (Fig. 2e). A close-up of a Bi-In-Sn microparticle was presented in Fig. 2f and analyzed by EDS. Around most of the surface of the microparticle, the elements of Bi, In and Sn are evenly distributed on the whole, which indicates that this area is composed of one phase (eutectic Bi-In-Sn). However, in some regions of the particle, there are some differences in element distribution due to the different combination of phases generated in solidification (β, BiIn2, γ), while the melting point of the Bi-In-Sn would not be affected [22]. Element of O was also found on the surface of the powder, which means the Bi-In-Sn powder was coated by an oxide film. Further, Fig. 2g displays the XPS spectra of Bi-In-Sn powders. Peaks at 156.20, 444.69, 485.11, and 531.73 eV each indicates the presence of bismuth, indium, tin, and oxygen. The O1s signal is illustrated in Fig. 2h. It shows two clear peaks at 529.4 and 531.3 eV, which indicates the presence of Bi 2O 3 /In2 O3 and SnO 2 . The results are likely due to the slight oxidation of the surface of the Bi-In-Sn powders. The oxide film on the surface of Bi-In-Sn powders could prevent further oxidation combined with the DSC results (Fig. 2b). Fig. 3a illustrates the morphology of diamond particles used in the composite fabrication. Complete crystal shape of cubo-octahedron with no cracks was observed. Combining XRD analyses (Fig. 3b), diamond (111) became the dominant feature of 35/40 mesh diamond particles, while particles of 120/140 mesh and 270/325 mesh exist (111), (220) and (311) diamond faces.
142
C. Zeng et al. / Scripta Materialia 170 (2019) 140–144
Fig. 2. (a) DSC and (b) TGA curves of the bulk Bi-In-Sn and Bi-In-Sn particles as measured at a ramping rate of 5 °C min−1; (c) The macrograph of Bi-In-Sn powders fabricated in a single process; SEM images of (d) Bi-In-Sn nanoparticles and (e) microparticles; (f) EDS map of a Bi-In-Sn microparticle; (g) XPS wide patterns and (h) O 1 s pattern of Bi-In-Sn powders.
Fig. 3. (a) SEM images of diamond particles of 35/40 mesh; (b) XRD patterns of diamond particles with different size; SEM images of Bi-In-Sn/diamond composites under different sintered pressure (c) 5.6 × 10−3 MPa, (d) 0.26 MPa, (e) 0.53 MPa, (f) 0.64 MPa; (g) Microstructure of the Bi-In-Sn/diamond composite (0.53 MPa) with its (h) EDS image; (i) SEM image of the composite with diamond particles of 35/40 mesh and (j) enlarged view.
C. Zeng et al. / Scripta Materialia 170 (2019) 140–144
As the pressure is 5.6 × 10−3 MPa, only part of the Bi-In-Sn powders was melted and connected together, while another part of powders was not completely jointed, which surrounded the diamond particles (Fig. 3c). The most surfaces of diamond particles were not coated by Bi-In-Sn. As the pressure increased to 0.26 MPa, the Bi-In-Sn powders in quantity were joined together and a small amount of Bi-In-Sn powders existed in the composites. A majority of diamond particles were embedded in bulk Bi-In-Sn (Fig. 3d). Thus, in order to melt and join all the Bi-In-Sn powders, the sintering pressure was added to 0.53 MPa. Dense microstructures of the composites were observed (Fig. 3e). With the increase of the pressure, all of the Bi-In-Sn powders were melted and connected together, but some gaps appeared among diamond particles due to the enhancement of liquidity of Bi-In-Sn under constant sintering temperature and time (Fig. 3f), which would reduce the thermal conductance of the interface between diamond and Bi-InSn. The microstructure of the single diamond surrounded by bulk Bi-InSn prepared for the sintered pressure of 0.53 MPa was characterized in Fig. 3g, the diamond particle is dark and the Bi-In-Sn matrix is light. Note that not all surfaces of diamond were closely coated by Bi-In-Sn, some gap existed in part interface of diamond and Bi-In-Sn. Fig. 3h presents the EDS analysis, which shows the elemental distribution mappings of Bi-In-Sn/diamond composite. The Bi, In, and Sn elements were distributed uniformly around the surface of the diamond. In most studies of diamond-containing composites, the diamond particles were previously treated with different coatings or formed a new reaction layer to improve the thermal conductivity of the composites,
143
which due to the poor wettability [23–26]. However, in this work, the diamond particles were not previously coated any metal or formed new interface. Diamond particles of 35/40 mesh only have (111) face (Fig. 3b). The microstructure of the composites containing diamond particles of 35/40 mesh was presented in Fig. 3i, it is indicated that the diamond was closely surrounded by Bi-In-Sn. No gaps were found at the interface of diamond and Bi-In-Sn (Fig. 3j). Thus, it can be believed that the (111) face of the diamond was wetted well by Bi-In-Sn, which would enhance the interfacial thermal conductance and improve the thermal conductivity of the Bi-In-Sn/diamond composites. The thermal conductivity of the metal (Cu/Mg/Al)/uncoated-diamond composites was less than that of metal matrix [5,6,25]. However, it is a special case in this work. Priorly, the influence of sintering pressure was conducted to confirm the comparatively excellent pressure loaded on the prepared Bi-In-Sn/diamond composites during the sintering process (Fig. 4a). The thermal conductivity of Bi-In-Sn in this work was 18.23 W m−1 K−1 at room temperature. Higher thermal conductivity of the composites was obtained as the pressure was 0.53 MPa, followed by 0.26 MPa and 0.64 MPa. The thermal conductivity of the composites under the pressure of 0.53 MPa was ~57 W m−1 K −1, which was 3 times higher than that of bulk Bi-In-Sn. Meantime, Bi-In-Sn powders were sintered under the pressure of 0.53 MPa, which the thermal conductivity is close to that of bulk Bi-In-Sn (the difference is ~0.9 W m−1 K−1). The volume fraction of diamond particles also affected the thermal conductivity of the composites (Fig. 4b). The thermal conductivity increased with the volume fraction of diamond particles, which
Fig. 4. Measured thermal conductivity along with (a) sintering pressure (50 vol% dia., 120/140 mesh), (b) volume fracture of diamond (120/140 mesh), and (c) particle size of diamond for the Bi-In-Sn/diamond composites (50 vol% dia.); (d) comparison of thermal conductivity with other PCMs [10,12,29]; (e) temperature gradient and (f) thermal flux in Bi-In-Sn/diamond composite (50 vol% Dia.); comparison between experimental and simulated thermal conductivities as a function of diamond (g) vol% and (h) size.
144
C. Zeng et al. / Scripta Materialia 170 (2019) 140–144
was 1.87 times (10 vol% dia.), 2.37 times (30 vol% dia.) and 3.13 times (50 vol% dia.) higher than that of bulk Bi-In-Sn. Particle size of the diamond has been found mainly influenced the thermal conductivity of metal matrix diamond containing composites [27,28]. Diamond particles of 35/40 mesh, 120/140 mesh and 270/325 mesh were selected to research (Fig. 4c). It is observed that the thermal conductivity of Bi-In-Sn/diamond composites increased with the diamond size. That is due to the interface area between Bi-InSn and diamond decreased, which would reduce the thermal resistance of the composites. Composites of diamond particles with 35/ 40 mesh have the highest thermal conductivity ~ 71 W m −1 K−1, which is a remarkable increase of approximately 290%. Fig. 4d represents the thermal conductivity of metallic, inorganic and organic PCMs along with the melting point. The metallic PCMs with melting point from 40 °C to70 oC exhibited the excellent thermal conductivity. However, the thermal conductivity of them (for security use) mostly below 20 W m−1 K−1. The thermal conductivity of Bi-In-Sn can be improved 2–3 times by composite with diamond particles using micro-pressure sintering, which could face the challenges of high heat dissipation in electronics. The temperature contours with gradients over the Bi-In-Sn/diamond composite microstructure for diamond volume fraction of 50% was plotted in Fig. 4e. Based on given material properties for Bi-In-Sn and diamond particles, the thermal conductance can be determined by the temperature distribution and thermal gradient. Fig. 4f presents the heat flux density with vectors in the composites, which show that the heat flux transfers among the Bi-In-Sn matrix and diamond particles, and especially concentrates in the diamond particles. Most of the heat flux traverse the diamond regions. The thermal conductivity of the composites can be calculated using the results of the temperature gradient and heat flux. These values are compared with experimental results in Fig. 4g and (h). All the error percentage was less than 1%. The thermal conductivity shows a polynomial function with the volume fraction of diamond particles. With the increase of the diamond volume fraction, the difference between simulation results and experimental results becomes larger, which due to the quantity of micro voids or gaps increased with the volume fraction of diamond particles under the same sintering pressure in the experimental process. Fig. 4h shows the difference of simulation results and experimental results varied with the size of diamond particles. It shows that the relationship between thermal conductivity and diamond size is linear. And some experimental results can reach more than 76% of the simulation results. This means the 2D modeling of metal matrix diamond containing diamond particles can be used to calculate or predict the thermal conductivity of its composites. In summary, Bi-In-Sn particles coated by an oxide layer are fabricated using liquid phase separation. The optimized pressure to break the oxide skin of the Bi-In-Sn was 0.53 MPa at the temperature of 120 °C with air condition. Better thermal conductance was observed at the Bi-In-Sn/diamond interface, especially with the diamond face of (111). The thermal
conductivity of the Bi-In-Sn/diamond composites increased with the volume fraction and the size of diamond particles. The highest thermal conductivity of Bi-In-Sn/diamond composites was over 71 W m−1 K−1, which is ~3 times higher than that of the bulk Bi-In-Sn. The experimental results were slightly lower than simulation results, which is due to the gap generated between diamond particles in the solidification process, especially when the volume fraction of diamond particles is high. Acknowledgement This research is supported by a Fundamental Research Funds for the Central Universities of China (Grant No. 2018CDGFCL0003) and an Industry Joint Technology Innovation Project of Suzhou of China in 2017. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]
[17] [18] [19] [20] [21] [22] [23] [24] [25] [26]
M.M. Waldrop, Nature 530 (7589) (2016) 144–147. S.M.S. Murshed, C.A.N.D. Castro, Renew. Sust. Energ. Rev. 78 (2017) 821–833. J.S. Kang, M. Li, H. Wu, H. Nguyen, Y. Hu, Science 361 (6402) (2018) 575–578. S. Li, Q. Zheng, Y. Lv, X. Liu, X. Wang, P.Y. Huang, D.G. Cahill, B. Lv, Science 361 (6402) (2018) 579–581. G. Bai, N. Li, X. Wang, J. Wang, M.J. Kim, H. Zhang, J. Alloy. Compd. 735 (2018) 1648–1653. J.M. Molina-Jordá, Acta Mater. 96 (2015) 101–110. X.H. Yang, J. Liu, Advances in Liquid Metal Science and Technology in Chip Cooling and Thermal Management, Elsevier2018. Y. Wu, T. Yong, Z. Li, X. Ding, Y. Wei, X. Zhao, B. Yu, Appl. Therm. Eng. 108 (2016) 192–203. X.H. Yang, J. Liu, Int. J. Heat Mass Transf. 127 (2018) 457–468. H. Ge, H. Li, S. Mei, J. Liu, Renew. Sust. Energ. Rev. 21 (2013) 331–346. G.G.D. Han, H. Li, J.C. Grossman, Nat. Commun. 8(1) (2017) 1446. M.M. Kenisarin, Renew. Sust. Energ. Rev. 14 (3) (2010) 955–970. J.M. Molina-Jordá, Compos. Pt. A-Appl. Sci. Manuf. 105 (2018) 265–273. J. Li, H. Zhang, L. Wang, Z. Che, Y. Zhang, J. Wang, M.J. Kim, X. Wang, Compos. Pt. AAppl. Sci. Manuf. 91 (2016) 189–194. J. Li, X. Wang, Q. Yi, Z. Yang, Z. He, H. Zhang, Scr. Mater. 109 (2015) 72–75. Q.L. Che, J.J. Zhang, X.K. Chen, Y.Q. Ji, Y.W. Li, L.X. Wang, S.Z. Cao, L. Guo, Z. Wang, S.W. Wang, Z.K. Zhang, Y.G. Jiang, Mater. Sci. Semicond. Process. 33 (2015) 67–75. A.M. Abyzov, M.J. Kruszewski, Ł. Ciupiński, M. Mazurkiewicz, A. Michalski, K.J. Kurzydłowski, Mater. Des. 76 (2015) 97–109. R.J. Larsen, M.D. Dickey, G.M. Whitesides, D.A. Weitz, J. Rheol. 53 (6) (2009) 1305–1326. E.E.M. Noor, N.M. Sharif, C.K. Yew, T. Ariga, A.B. Ismail, Z. Hussain, J. Alloy. Compd. 507 (1) (2010) 290–296. M. Zain-ul-abdein, K. Raza, F.A. Khalid, T. Mabrouki, Mater. Des. 86 (2015) 248–258. S. Cinar, I.D. Tevis, J. Chen, M. Thuo, Sci. Rep. 6 (2016). V.T. Witusiewicz, U. Hecht, B. Böttger, S. Rex, J. Alloy. Compd. 428 (1) (2007) 115–124. C.-Y. Chung, M.-T. Lee, M.-Y. Tsai, C.-H. Chu, S.-J. Lin, Appl. Therm. Eng. 69 (1) (2014) 208–213. S. Ren, X. Shen, C. Guo, N. Liu, J. Zang, X. He, X. Qu, Compos. Sci. Technol. 71 (13) (2011) 1550–1555. C. Xue, J.K. Yu, X.M. Zhu, Mater. Des. 32 (8) (2011) 4225–4229. Y. Zhang, H.L. Zhang, J.H. Wu, X.T. Wang, Scr. Mater. 65 (12) (2011) 1097–1100.
[27] L. Chen, S. Chen, Y. Hou, Carbon 148 (2019) 249–257. [28] H.J. Cho, Y.-J. Kim, U. Erb, Compos. Pt. B-Eng. 155 (2018) 197–203. [29] A.S. Fleischer, Thermal Energy Storage Using Phase Change Materials: Fundamentals and Applications, Springer 2015.
Contents lists available at ScienceDirect
Scripta Materialia journal homepage: www.elsevier.com/locate/scriptamat
High thermal conductivity in Bi-In-Sn/diamond composites Chengzong Zeng, Jun Shen ⁎, Chao He, Hui Chen State Key Laboratory of Mechanical Transmission, College of Material Science and Engineering, Chongqing University, Chongqing, 400044, China
a r t i c l e
i n f o
Article history: Received 9 May 2019 Received in revised form 1 June 2019 Accepted 5 June 2019 Available online 11 June 2019 Keywords: Bi-In-Sn Diamond Thermal conductivity Sintering
a b s t r a c t The Bi-In-Sn/diamond composites were manufactured and characterized. Nano and micro Bi-In-Sn powders coated by oxide skin were produced by slice technique. Optimized sintering pressure was 0.53 MPa at the temperature of 120 °C with air condition. The highest thermal conductivity of Bi-In-Sn/diamond composites was up to 71.4 W m−1 K−1, which is ~3 times higher than that of Bi-In-Sn. Compared to the results of simulation, the actual thermal conductivity of Bi-In-Sn/diamond composites was slightly lower, which is due to the gap generated between diamond particles in the solidification process, especially as the volume fraction of diamond particles is high. © 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Heat dissipation have become one of the most critical technological challenges in electronics. According to Moore's law, the integration density of a microprocessor chip will double every 18–24 months and is nearing its end [1]. Effective thermal management thus plays a crucial role in the performance and reliability of high power electronic devices, especially in a smaller space [2]. High thermal conductivity materials have been studied to face the emerging challenges in heat dissipation. Cubic boron arsenide with high thermal conductivity was obtained by chemical vapor deposition [3,4]. Copper matrix diamond-containing composites show great potential for superior thermal conductivity [5]. Magnesium/diamond composites with bimodal distribution of particles were manufactured to reach high thermal conductivity [6]. Recently, phase change materials (PCMs) (melting point between 25 °C and 85 °C [7]) are considered to be a good option for cooling devices that generate heat intermittently [8]. A large amount of latent heat can be absorbed/released during their melting/solidification process, while the temperature of PCMs remains nearly constant [9]. The thermal conductivity of metallic PCMs [10] is several dozen times larger than that of organic [11] and inorganic PCMs [12]. Low melting point alloy (LMPA) is the most widely used in Metallic PCMs, but its thermal conductivity is still lower than that of the hot or cold terminal. Thus, it is necessary to improve the thermal conductivity of the LPMA to satisfy the heat dissipation of higher hot devices. Diamond has the highest isotropic thermal conductivity of any bulk material (~2200 W m−1 K−1, at room temperature) [4]. In recent years, metal matrix with diamond particles composites have been studied to obtain a novel material with higher thermal conductivity [5,13]. However, LMPA diamond-containing composites have rarely been researched. ⁎ Corresponding author. E-mail address: [email protected] (J. Shen).
https://doi.org/10.1016/j.scriptamat.2019.06.010 1359-6462/© 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
In this work, the Field's metal Bi-In-Sn and diamond particles were selected to study. Most researchers add alloy elements into metal matrix [14,15] or coat alloy elements onto diamond surface [16,17] to improve wettability, which to enhance the interfacial bonding and increase the thermal conductivity of the composites. While in this study, it is observed that the composite of uncoated-diamond and BiIn-Sn have a high thermal conductivity. The composites were made under a micro pressure with a low temperature, which is simple and easy to produce. The surface of the Bi-In-Sn particles was wrapped in a membrane. Appropriate pressure must be applied to the particles, thus make the membrane to rupture (P N Pc, Fig. 1c). Larsen et al. [18] have proven that the pressure P is related to the surface tension γm of the membrane (~0.58 N m−1 [19]), the membrane will yield as the surface stress is more than surface tension, the relationship between the critical load pressure Pc and γm can be expressed as follows: P Pc ¼
πR2 γm
1 2 cosθ − R d S
where R is the radius of the disk, γm is the surface tension of the membrane, d is the height of the gap and θ is the contact angle of the particle making with the parallel disk, S is the pressed area. The thermal conductivity of Bi-In-Sn/diamond composites can be predicted with the numerical simulation [20]. The size of the 2D model is 1000 μm × 1000 μm. The geometric model of the diamond was simplified to a regular hexagon. Grid refinement near the diamond was implemented to ensure the calculation precision (Fig. 1d). The wall of left and right was set as insulation. The temperature imposed at the
C. Zeng et al. / Scripta Materialia 170 (2019) 140–144
141
Fig. 1. Schematic representation of (a) SLICE process, (b) preparation of Bi-In-Sn/Diamond composite materials, (c) and particle membrane crushing (not to scale); (d) the model of the composites with the random distribution of the diamond particles.
bottom wall and the top wall is 57 °C and 20 °C. Assuming that there is no interspace between Bi-In-Sn and diamond particles. MBD8 quality diamond particles were used in this work (Zhecheng Hongxiang Superhard Material Co., Ltd., China). Field's metal (Bi: In: Sn 32.5: 51.0: 16.5 wt%) was prepared in a salt melt (27.1 wt% Bi, 42.5 wt% In, 13.8 wt% Sn, 9.2 wt% KCl and 7.4 wt% LiCl). The purity of bismuth, indium and tin is at least 99.995%, 99.999% and 99.995% (Shenyang Jiabei Trading Co., Ltd., China). Bi-In-Sn particles were fabricated by slice technique [21]. ~15 g metal was added in polyethylene glycol solution (Fig. 1a). The solution prepared in a glass beaker was kept in an oil bath at the preset temperature (120 °C) for at least 10 min before slice. Slice procedure was applied using a homogenizer (FSH-2A) at the rate of 16,000 rpm. Total continuous shearing time lasts for 5 mins. Excess polyethylene glycol were washed out, and then the Bi-In-Sn particles were dried in a vacuum oven (BZF-30). Bi-In-Sn/diamond composites were performed using the sintering technique with a micro-pressure under a low temperature (Fig. 1b). A certain proportion of diamond particles and Bi-In-Sn particles were mixed evenly, then put into a 304 stainless steel moulds with the diameter of 12.5 mm. Prepared Bi-In-Sn/diamond composites specimens were heated in an oven (LTKC-4-10A) with air condition. Then they were cooled to room temperature in air. The sintering parameters were given in Table 1. Bi-In-Sn alloy was studied using a differential scanning calorimeter (DSC, TGA/DSC1/1100LF) and X-ray photoelectron spectroscopy (XPS, ESCALAB250Xi). The microstructures of diamond, Bi-In-Sn particles, and the Bi-In-Sn/diamond composites were characterized by field emission scanning electron microscope (SEM, Zeiss Auriga-39-60) equipped with energy dispersive X-ray spectrometer (EDS) and X-ray diffraction
Table 1 Diamond particle used in the preparation of Bi-In-Sn/diamond composites. D is the average equivalent diameter of the corresponding particle type. Vd is the volume fraction of diamond particles measured within 1% error. T is the sintering temperature and P is the sintering pressure. Code
Diamond type
D (μm)
Vd
T (°C)
P (MPa)
C1 C2 C3 C4 C5 C6 C7 C8
MBD8 120/140 MBD8 120/140 MBD8 120/140 MBD8 120/140 MBD8 35/40 MBD8 270/325 MBD8 120/140 MBD8 120/140
115 115 115 115 403 50 115 115
0.5
120
5.6 × 10−3 0.26 0.53 0.64 0.53 0.53 0.53 0.53
0.1 0.3
(XRD, Empryean) with Cu Kα radiation. The density of the composites ρc was measured by the Archimedes principle (DK-300A). The thermal diffusivity α was measured using a LFA467 MicroFlash (Netzsch) thermal analyzer at room temperature. Each sample was tested three times to reduce testing errors of experimental data. The specific heat capacity of the sample Cp was measured using the DSC. The thermal conductivity Kc was obtained from Kc = ρcαCp. The melting point of the bulk Bi-In-Sn was 59 °C (Fig. 2a), which is consistent with the result of Witusiewicz [22]. DSC result of Bi-In-Sn powders was similar to that of bulk Bi-In-Sn, that means the melting point of the Bi-In-Sn cannot be changed after the slice technique. TGA was conducted on the bulk Bi-In-Sn and Bi-In-Sn powders in air condition to confirm that the Bi-In-Sn of the composites would not be over oxidized before or after sintering (Fig. 2b). The sintering temperature in this study was 120 °C, while the weight of Bi-In-Sn powders remained constant as soon as the temperature increased to above 300 °C, so did the bulk Bi-In-Sn. Thus, all the sintering process was carried out under air condition, which greatly reduced the time and cost. The macrograph of Bi-In-Sn powders fabricated in a single process was represented in Fig. 2c. The diameter of nano spheres is almost 30–100 nm (Fig. 2d), and the diameter of microspheres is less than 30 μm (Fig. 2e). A close-up of a Bi-In-Sn microparticle was presented in Fig. 2f and analyzed by EDS. Around most of the surface of the microparticle, the elements of Bi, In and Sn are evenly distributed on the whole, which indicates that this area is composed of one phase (eutectic Bi-In-Sn). However, in some regions of the particle, there are some differences in element distribution due to the different combination of phases generated in solidification (β, BiIn2, γ), while the melting point of the Bi-In-Sn would not be affected [22]. Element of O was also found on the surface of the powder, which means the Bi-In-Sn powder was coated by an oxide film. Further, Fig. 2g displays the XPS spectra of Bi-In-Sn powders. Peaks at 156.20, 444.69, 485.11, and 531.73 eV each indicates the presence of bismuth, indium, tin, and oxygen. The O1s signal is illustrated in Fig. 2h. It shows two clear peaks at 529.4 and 531.3 eV, which indicates the presence of Bi 2O 3 /In2 O3 and SnO 2 . The results are likely due to the slight oxidation of the surface of the Bi-In-Sn powders. The oxide film on the surface of Bi-In-Sn powders could prevent further oxidation combined with the DSC results (Fig. 2b). Fig. 3a illustrates the morphology of diamond particles used in the composite fabrication. Complete crystal shape of cubo-octahedron with no cracks was observed. Combining XRD analyses (Fig. 3b), diamond (111) became the dominant feature of 35/40 mesh diamond particles, while particles of 120/140 mesh and 270/325 mesh exist (111), (220) and (311) diamond faces.
142
C. Zeng et al. / Scripta Materialia 170 (2019) 140–144
Fig. 2. (a) DSC and (b) TGA curves of the bulk Bi-In-Sn and Bi-In-Sn particles as measured at a ramping rate of 5 °C min−1; (c) The macrograph of Bi-In-Sn powders fabricated in a single process; SEM images of (d) Bi-In-Sn nanoparticles and (e) microparticles; (f) EDS map of a Bi-In-Sn microparticle; (g) XPS wide patterns and (h) O 1 s pattern of Bi-In-Sn powders.
Fig. 3. (a) SEM images of diamond particles of 35/40 mesh; (b) XRD patterns of diamond particles with different size; SEM images of Bi-In-Sn/diamond composites under different sintered pressure (c) 5.6 × 10−3 MPa, (d) 0.26 MPa, (e) 0.53 MPa, (f) 0.64 MPa; (g) Microstructure of the Bi-In-Sn/diamond composite (0.53 MPa) with its (h) EDS image; (i) SEM image of the composite with diamond particles of 35/40 mesh and (j) enlarged view.
C. Zeng et al. / Scripta Materialia 170 (2019) 140–144
As the pressure is 5.6 × 10−3 MPa, only part of the Bi-In-Sn powders was melted and connected together, while another part of powders was not completely jointed, which surrounded the diamond particles (Fig. 3c). The most surfaces of diamond particles were not coated by Bi-In-Sn. As the pressure increased to 0.26 MPa, the Bi-In-Sn powders in quantity were joined together and a small amount of Bi-In-Sn powders existed in the composites. A majority of diamond particles were embedded in bulk Bi-In-Sn (Fig. 3d). Thus, in order to melt and join all the Bi-In-Sn powders, the sintering pressure was added to 0.53 MPa. Dense microstructures of the composites were observed (Fig. 3e). With the increase of the pressure, all of the Bi-In-Sn powders were melted and connected together, but some gaps appeared among diamond particles due to the enhancement of liquidity of Bi-In-Sn under constant sintering temperature and time (Fig. 3f), which would reduce the thermal conductance of the interface between diamond and Bi-InSn. The microstructure of the single diamond surrounded by bulk Bi-InSn prepared for the sintered pressure of 0.53 MPa was characterized in Fig. 3g, the diamond particle is dark and the Bi-In-Sn matrix is light. Note that not all surfaces of diamond were closely coated by Bi-In-Sn, some gap existed in part interface of diamond and Bi-In-Sn. Fig. 3h presents the EDS analysis, which shows the elemental distribution mappings of Bi-In-Sn/diamond composite. The Bi, In, and Sn elements were distributed uniformly around the surface of the diamond. In most studies of diamond-containing composites, the diamond particles were previously treated with different coatings or formed a new reaction layer to improve the thermal conductivity of the composites,
143
which due to the poor wettability [23–26]. However, in this work, the diamond particles were not previously coated any metal or formed new interface. Diamond particles of 35/40 mesh only have (111) face (Fig. 3b). The microstructure of the composites containing diamond particles of 35/40 mesh was presented in Fig. 3i, it is indicated that the diamond was closely surrounded by Bi-In-Sn. No gaps were found at the interface of diamond and Bi-In-Sn (Fig. 3j). Thus, it can be believed that the (111) face of the diamond was wetted well by Bi-In-Sn, which would enhance the interfacial thermal conductance and improve the thermal conductivity of the Bi-In-Sn/diamond composites. The thermal conductivity of the metal (Cu/Mg/Al)/uncoated-diamond composites was less than that of metal matrix [5,6,25]. However, it is a special case in this work. Priorly, the influence of sintering pressure was conducted to confirm the comparatively excellent pressure loaded on the prepared Bi-In-Sn/diamond composites during the sintering process (Fig. 4a). The thermal conductivity of Bi-In-Sn in this work was 18.23 W m−1 K−1 at room temperature. Higher thermal conductivity of the composites was obtained as the pressure was 0.53 MPa, followed by 0.26 MPa and 0.64 MPa. The thermal conductivity of the composites under the pressure of 0.53 MPa was ~57 W m−1 K −1, which was 3 times higher than that of bulk Bi-In-Sn. Meantime, Bi-In-Sn powders were sintered under the pressure of 0.53 MPa, which the thermal conductivity is close to that of bulk Bi-In-Sn (the difference is ~0.9 W m−1 K−1). The volume fraction of diamond particles also affected the thermal conductivity of the composites (Fig. 4b). The thermal conductivity increased with the volume fraction of diamond particles, which
Fig. 4. Measured thermal conductivity along with (a) sintering pressure (50 vol% dia., 120/140 mesh), (b) volume fracture of diamond (120/140 mesh), and (c) particle size of diamond for the Bi-In-Sn/diamond composites (50 vol% dia.); (d) comparison of thermal conductivity with other PCMs [10,12,29]; (e) temperature gradient and (f) thermal flux in Bi-In-Sn/diamond composite (50 vol% Dia.); comparison between experimental and simulated thermal conductivities as a function of diamond (g) vol% and (h) size.
144
C. Zeng et al. / Scripta Materialia 170 (2019) 140–144
was 1.87 times (10 vol% dia.), 2.37 times (30 vol% dia.) and 3.13 times (50 vol% dia.) higher than that of bulk Bi-In-Sn. Particle size of the diamond has been found mainly influenced the thermal conductivity of metal matrix diamond containing composites [27,28]. Diamond particles of 35/40 mesh, 120/140 mesh and 270/325 mesh were selected to research (Fig. 4c). It is observed that the thermal conductivity of Bi-In-Sn/diamond composites increased with the diamond size. That is due to the interface area between Bi-InSn and diamond decreased, which would reduce the thermal resistance of the composites. Composites of diamond particles with 35/ 40 mesh have the highest thermal conductivity ~ 71 W m −1 K−1, which is a remarkable increase of approximately 290%. Fig. 4d represents the thermal conductivity of metallic, inorganic and organic PCMs along with the melting point. The metallic PCMs with melting point from 40 °C to70 oC exhibited the excellent thermal conductivity. However, the thermal conductivity of them (for security use) mostly below 20 W m−1 K−1. The thermal conductivity of Bi-In-Sn can be improved 2–3 times by composite with diamond particles using micro-pressure sintering, which could face the challenges of high heat dissipation in electronics. The temperature contours with gradients over the Bi-In-Sn/diamond composite microstructure for diamond volume fraction of 50% was plotted in Fig. 4e. Based on given material properties for Bi-In-Sn and diamond particles, the thermal conductance can be determined by the temperature distribution and thermal gradient. Fig. 4f presents the heat flux density with vectors in the composites, which show that the heat flux transfers among the Bi-In-Sn matrix and diamond particles, and especially concentrates in the diamond particles. Most of the heat flux traverse the diamond regions. The thermal conductivity of the composites can be calculated using the results of the temperature gradient and heat flux. These values are compared with experimental results in Fig. 4g and (h). All the error percentage was less than 1%. The thermal conductivity shows a polynomial function with the volume fraction of diamond particles. With the increase of the diamond volume fraction, the difference between simulation results and experimental results becomes larger, which due to the quantity of micro voids or gaps increased with the volume fraction of diamond particles under the same sintering pressure in the experimental process. Fig. 4h shows the difference of simulation results and experimental results varied with the size of diamond particles. It shows that the relationship between thermal conductivity and diamond size is linear. And some experimental results can reach more than 76% of the simulation results. This means the 2D modeling of metal matrix diamond containing diamond particles can be used to calculate or predict the thermal conductivity of its composites. In summary, Bi-In-Sn particles coated by an oxide layer are fabricated using liquid phase separation. The optimized pressure to break the oxide skin of the Bi-In-Sn was 0.53 MPa at the temperature of 120 °C with air condition. Better thermal conductance was observed at the Bi-In-Sn/diamond interface, especially with the diamond face of (111). The thermal
conductivity of the Bi-In-Sn/diamond composites increased with the volume fraction and the size of diamond particles. The highest thermal conductivity of Bi-In-Sn/diamond composites was over 71 W m−1 K−1, which is ~3 times higher than that of the bulk Bi-In-Sn. The experimental results were slightly lower than simulation results, which is due to the gap generated between diamond particles in the solidification process, especially when the volume fraction of diamond particles is high. Acknowledgement This research is supported by a Fundamental Research Funds for the Central Universities of China (Grant No. 2018CDGFCL0003) and an Industry Joint Technology Innovation Project of Suzhou of China in 2017. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]
[17] [18] [19] [20] [21] [22] [23] [24] [25] [26]
M.M. Waldrop, Nature 530 (7589) (2016) 144–147. S.M.S. Murshed, C.A.N.D. Castro, Renew. Sust. Energ. Rev. 78 (2017) 821–833. J.S. Kang, M. Li, H. Wu, H. Nguyen, Y. Hu, Science 361 (6402) (2018) 575–578. S. Li, Q. Zheng, Y. Lv, X. Liu, X. Wang, P.Y. Huang, D.G. Cahill, B. Lv, Science 361 (6402) (2018) 579–581. G. Bai, N. Li, X. Wang, J. Wang, M.J. Kim, H. Zhang, J. Alloy. Compd. 735 (2018) 1648–1653. J.M. Molina-Jordá, Acta Mater. 96 (2015) 101–110. X.H. Yang, J. Liu, Advances in Liquid Metal Science and Technology in Chip Cooling and Thermal Management, Elsevier2018. Y. Wu, T. Yong, Z. Li, X. Ding, Y. Wei, X. Zhao, B. Yu, Appl. Therm. Eng. 108 (2016) 192–203. X.H. Yang, J. Liu, Int. J. Heat Mass Transf. 127 (2018) 457–468. H. Ge, H. Li, S. Mei, J. Liu, Renew. Sust. Energ. Rev. 21 (2013) 331–346. G.G.D. Han, H. Li, J.C. Grossman, Nat. Commun. 8(1) (2017) 1446. M.M. Kenisarin, Renew. Sust. Energ. Rev. 14 (3) (2010) 955–970. J.M. Molina-Jordá, Compos. Pt. A-Appl. Sci. Manuf. 105 (2018) 265–273. J. Li, H. Zhang, L. Wang, Z. Che, Y. Zhang, J. Wang, M.J. Kim, X. Wang, Compos. Pt. AAppl. Sci. Manuf. 91 (2016) 189–194. J. Li, X. Wang, Q. Yi, Z. Yang, Z. He, H. Zhang, Scr. Mater. 109 (2015) 72–75. Q.L. Che, J.J. Zhang, X.K. Chen, Y.Q. Ji, Y.W. Li, L.X. Wang, S.Z. Cao, L. Guo, Z. Wang, S.W. Wang, Z.K. Zhang, Y.G. Jiang, Mater. Sci. Semicond. Process. 33 (2015) 67–75. A.M. Abyzov, M.J. Kruszewski, Ł. Ciupiński, M. Mazurkiewicz, A. Michalski, K.J. Kurzydłowski, Mater. Des. 76 (2015) 97–109. R.J. Larsen, M.D. Dickey, G.M. Whitesides, D.A. Weitz, J. Rheol. 53 (6) (2009) 1305–1326. E.E.M. Noor, N.M. Sharif, C.K. Yew, T. Ariga, A.B. Ismail, Z. Hussain, J. Alloy. Compd. 507 (1) (2010) 290–296. M. Zain-ul-abdein, K. Raza, F.A. Khalid, T. Mabrouki, Mater. Des. 86 (2015) 248–258. S. Cinar, I.D. Tevis, J. Chen, M. Thuo, Sci. Rep. 6 (2016). V.T. Witusiewicz, U. Hecht, B. Böttger, S. Rex, J. Alloy. Compd. 428 (1) (2007) 115–124. C.-Y. Chung, M.-T. Lee, M.-Y. Tsai, C.-H. Chu, S.-J. Lin, Appl. Therm. Eng. 69 (1) (2014) 208–213. S. Ren, X. Shen, C. Guo, N. Liu, J. Zang, X. He, X. Qu, Compos. Sci. Technol. 71 (13) (2011) 1550–1555. C. Xue, J.K. Yu, X.M. Zhu, Mater. Des. 32 (8) (2011) 4225–4229. Y. Zhang, H.L. Zhang, J.H. Wu, X.T. Wang, Scr. Mater. 65 (12) (2011) 1097–1100.
[27] L. Chen, S. Chen, Y. Hou, Carbon 148 (2019) 249–257. [28] H.J. Cho, Y.-J. Kim, U. Erb, Compos. Pt. B-Eng. 155 (2018) 197–203. [29] A.S. Fleischer, Thermal Energy Storage Using Phase Change Materials: Fundamentals and Applications, Springer 2015.