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epoxy resin nanocomposite prepared by a novel method
Materials Letters 58 (2003) 176 – 178 www.elsevier.com/locate/matlet
PbS/epoxy resin nanocomposite prepared by a novel method Lijia Pan, Pingsheng He *, Gang Zou, Dazhu Chen Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026, Anhui, China Received 4 November 2002; received in revised form 28 April 2003; accepted 2 May 2003
Abstract PbS/epoxy resin nanocomposite is prepared by a novel method. The epoxy resin microemulsion is taken as a microreactor for the formation of PbS nanocrystals. After the reaction, the collected epoxy proved to be a composite with nano-PbS embedded in. The morphological observation of cured PbS/epoxy resin nanocomposite by tunnel electronic microscopy (TEM) indicates that the PbS nanocrystals are dispersed in cured epoxy resin matrix homogenously. X-ray diffraction (XRD) and TEM were used to characterize the PbS nanocrystals. D 2003 Elsevier B.V. All rights reserved. Keywords: PbS; Epoxy resin; Nanocomposite
The research of nanometer-size semiconductor particles has witnessed tremendous growth due to their unusual chemical and physical properties and wide applications in nonlinear optics [1], light emitting diodes [2], and so on. When the diameter of a cluster approaches its excitation Bohr diameter, the material will present special optical and electronic properties [1]. It offers potential application of nanometer-size semiconductor particles in the construction of novel optical and electronic devices. In recent years, inorganic-polymer composites play increasingly important roles in research and in high-tech applications. Because of the difficulty of dispersion of nanoparticles with high specific energies in resin matrix, the inorganic-resin nanocomposites may be, principally, prepared in alternative approaches, such as using inorganic clay, for example montmorillonite, with nanoscale layer structures to prepare the resin/montmorillonite nanocomposites [3 –6], organic capping of inorganic nanoparticles then mixed with the resin together [7 – 9], and synthesis nanocomposite by in situ polymerization [10 – 12], or in situ reactions by ion exchanging of resins and consequently chemical reaction [13], etc. In this research letter, we present a novel simple method to prepare the PbS/epoxy resin nanocomposite (PbS nano-
* Corresponding author. Tel.: +86-551-3601714; fax: +86-5513601714. E-mail address: [email protected] (P. He). 0167-577X/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0167-577X(03)00440-3
particles formed in epoxy/water emulsion). The product could be cured by a normal curing agent and has the mechanical strength and the optical transparence properties as that of the epoxy resin without any fillers. The PbS crystal particles in the composite proved to be in nanosize by X-ray diffraction (XRD) and tunnel electronic microscopy (TEM). The epoxy resin used is diglycidyl ether of biphenyl A, epoxy resin E51 produced by Shanghai Resin Factory. The diethylenetriamine (DEEA, Development Center of Special Chemical Agents in Huabei Region, C.R. grade) was used as the curing agent. Other chemicals: methanol, acetone, Pb(Ac)2, and Na2S are all A.R. grades and used without any further treatment. Pb(Ac)2 (0.5 g) was dissolved in 12 ml methanol, and 5 g epoxy resin E51 and 10 ml acetone were added into the solution with agitation. Then, the mixed solution was added slowly into an aqueous solution of Na2S (1 g in 75 ml) with agitation. It was found out that an emulsion was formed and the color of the emulsion turned into black quickly. The epoxy resin droplets began to precipitate because the PbS particles formed in epoxy resin matrix are heavy in density. The product was vacuum-filtered and washed several times with water, then dried in oven at 70 jC for 2 h. It is necessary to agitate the drying materials every 10 min. Finally, the homogenous black viscous liquid was obtained. The resulting ointment-like composite was cured by adding diethylenetriamine (DEEA) with the ratio of W DEEA/ WEPOXY = 13:100.
L. Pan et al. / Materials Letters 58 (2003) 176–178
The XRD profile of PbS/epoxy resin E51 composite was recorded on Rigaku D/max-gA rotating anode X-ray diffractometer using Cu K a line (k = 0.15418 nm) with DS = 1j, SS=(1/6)j, RS = 0.15 mm, and RSm = 0.3 mm. The tube current and voltage were 50 mA and 40 kV, respectively. Fig. 1 shows the X-ray diffraction pattern of the composites before (upper curve) and after (below curve) curing in the range of 2h = 10 –70j. These two curves are almost the same in both position and width of peaks, indicating that the morphology of PbS particles has not been changed during the curing process. This is quite important for producing nanodevices because it means the nanofeature of the composite could be retained in the forming procedure. The particle diameter can be estimated to be about 7 nm with Debby –Scherrer’s equation: Lhkl = kk/B cosh, where k is taken as 1, k as 0.1542 nm, and B is the half width of the diffraction peak. All the results mean that the product composite is a real nanocomposite in which PbS nanoparticles are dispersed in epoxy resin E51 matrix homogenously, and therefore we will call the composite as PbS/epoxy resin E51 nanocomposites. The rod of the cured nanocomposite was sliced up into super thin sheet by microtome and observed under TEM. Fig. 2 shows the TEM image of the cured PbS/epoxy resin E51 nanocomposite (JEM-100SX with the voltage of 100 kV, the sample with the thickness of 80 nm is microtomed by the ULTRACUT-E). It can directly be seen that the PbS particles are dispersed in composite homogenously without connected aggregates. The diameter of PbS particles is under 10 nm, coinciding with the results of XRD data. The resulting PbS/epoxy resin E51 nanocomposite before curing is quite stable and no phase separation is observed in the time period of 1 month, and the homogenous dispersion of PbS nanoparticles in epoxy resin will not be changed during the curing procedure.
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Fig. 2. TEM image of cured PbS/epoxy resin E51 nanocomposite.
As seen in Fig. 2, the PbS nanoparticles are dispersed homogenously in resin matrix. The PbS nanoparticles can be prevented from agglomeration due to very high viscosity of epoxy resin matrix. It is easy to understand that the PbS/epoxy resin E51 nanocomposite can be successfully prepared by the abovementioned procedure. The emulsion is formed when the acetone solution of epoxy resin E51 is added into the water with agitation, because acetone dissolves in water very easily and quickly while the epoxy resin E51 is insoluble in water. The Pb(Ac)2 in epoxy resin matrix may react with S2 at the interface of epoxy droplet and water, or the epoxy microdroplet may coat the PbS crystal that formed in the water and separate them from agglomerating. Here, the high viscosity of epoxy resin E51 plays an essential role in the in situ formation of PbS nanoparticles, and keeping the dispersion and separation of nanoparticles. Actually, the PbS nanoparticles will agglomerate when the uncured ointment-like composite is diluted by a large amount of solvent acetone.
Acknowledgements This work was financially supported by the National Natural Science Foundation of China (No. 20174038).
References
Fig. 1. X-ray diffraction pattern of PbS/epoxy resin E51 nanocomposite in the range of 2h = 10 – 70j.
[1] Y. Wang, N. Herron, J. Phys. Chem. 95 (1991) 525 – 532. [2] V.L. Colvin, M.C. Schlamp, A.P. Alivisatos, Nature 370 (1994) 354. [3] Y.S. Choi, K.H. Wang, M.Z. Xu, et al., Chem. Mater. 14 (2002) 2936 – 2939. [4] G. Zou, K. Fang, P.S. He, J. Mater. Sci. Lett. 21 (2002) 761 – 763. [5] W.B. Xu, M.L. Ge, P.S. He, J. Appl. Polym. Sci. 82 (12) (2001) 2281 – 2289. [6] W.B. Xu, S.P. Bao, P.S. He, J. Appl. Polym. Sci. 84 (4) (2002) 842 – 849. [7] G. Winiarz, L.M. Zhang, M. La, et al., Chem. Phys. 245 (1999) 417 – 428.
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L. Pan et al. / Materials Letters 58 (2003) 176–178
[8] Y. Dirix, C. Bastiaansen, W. Caseri, et al., J. Mater. Sci. 34 (1999) 3859 – 3866. [9] M.Z. Rong, M.Q. Zhang, H. Liu, et al., Polymer 40 (1999) 6169 – 6178. [10] D.D. Papakonstantinou, J. Huang, P. Lianos, J. Mater. Sci. Lett. 17 (1998) 1571 – 1573.
[11] J.M. Huang, Y. Yang, S.H. Xue, B. Yang, Appl. Phys. Lett. 70 (1997) 2335. [12] E.C. Hao, H.P. Sun, Z. Zhou, et al., Chem. Mater. 11 (1999) 3096 – 3102. [13] Y.F. Liu, L. Chen, B. Su, et al., J. Appl. Polym. Sci. 84 (2002) 1263 – 1268.
PbS/epoxy resin nanocomposite prepared by a novel method Lijia Pan, Pingsheng He *, Gang Zou, Dazhu Chen Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026, Anhui, China Received 4 November 2002; received in revised form 28 April 2003; accepted 2 May 2003
Abstract PbS/epoxy resin nanocomposite is prepared by a novel method. The epoxy resin microemulsion is taken as a microreactor for the formation of PbS nanocrystals. After the reaction, the collected epoxy proved to be a composite with nano-PbS embedded in. The morphological observation of cured PbS/epoxy resin nanocomposite by tunnel electronic microscopy (TEM) indicates that the PbS nanocrystals are dispersed in cured epoxy resin matrix homogenously. X-ray diffraction (XRD) and TEM were used to characterize the PbS nanocrystals. D 2003 Elsevier B.V. All rights reserved. Keywords: PbS; Epoxy resin; Nanocomposite
The research of nanometer-size semiconductor particles has witnessed tremendous growth due to their unusual chemical and physical properties and wide applications in nonlinear optics [1], light emitting diodes [2], and so on. When the diameter of a cluster approaches its excitation Bohr diameter, the material will present special optical and electronic properties [1]. It offers potential application of nanometer-size semiconductor particles in the construction of novel optical and electronic devices. In recent years, inorganic-polymer composites play increasingly important roles in research and in high-tech applications. Because of the difficulty of dispersion of nanoparticles with high specific energies in resin matrix, the inorganic-resin nanocomposites may be, principally, prepared in alternative approaches, such as using inorganic clay, for example montmorillonite, with nanoscale layer structures to prepare the resin/montmorillonite nanocomposites [3 –6], organic capping of inorganic nanoparticles then mixed with the resin together [7 – 9], and synthesis nanocomposite by in situ polymerization [10 – 12], or in situ reactions by ion exchanging of resins and consequently chemical reaction [13], etc. In this research letter, we present a novel simple method to prepare the PbS/epoxy resin nanocomposite (PbS nano-
* Corresponding author. Tel.: +86-551-3601714; fax: +86-5513601714. E-mail address: [email protected] (P. He). 0167-577X/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0167-577X(03)00440-3
particles formed in epoxy/water emulsion). The product could be cured by a normal curing agent and has the mechanical strength and the optical transparence properties as that of the epoxy resin without any fillers. The PbS crystal particles in the composite proved to be in nanosize by X-ray diffraction (XRD) and tunnel electronic microscopy (TEM). The epoxy resin used is diglycidyl ether of biphenyl A, epoxy resin E51 produced by Shanghai Resin Factory. The diethylenetriamine (DEEA, Development Center of Special Chemical Agents in Huabei Region, C.R. grade) was used as the curing agent. Other chemicals: methanol, acetone, Pb(Ac)2, and Na2S are all A.R. grades and used without any further treatment. Pb(Ac)2 (0.5 g) was dissolved in 12 ml methanol, and 5 g epoxy resin E51 and 10 ml acetone were added into the solution with agitation. Then, the mixed solution was added slowly into an aqueous solution of Na2S (1 g in 75 ml) with agitation. It was found out that an emulsion was formed and the color of the emulsion turned into black quickly. The epoxy resin droplets began to precipitate because the PbS particles formed in epoxy resin matrix are heavy in density. The product was vacuum-filtered and washed several times with water, then dried in oven at 70 jC for 2 h. It is necessary to agitate the drying materials every 10 min. Finally, the homogenous black viscous liquid was obtained. The resulting ointment-like composite was cured by adding diethylenetriamine (DEEA) with the ratio of W DEEA/ WEPOXY = 13:100.
L. Pan et al. / Materials Letters 58 (2003) 176–178
The XRD profile of PbS/epoxy resin E51 composite was recorded on Rigaku D/max-gA rotating anode X-ray diffractometer using Cu K a line (k = 0.15418 nm) with DS = 1j, SS=(1/6)j, RS = 0.15 mm, and RSm = 0.3 mm. The tube current and voltage were 50 mA and 40 kV, respectively. Fig. 1 shows the X-ray diffraction pattern of the composites before (upper curve) and after (below curve) curing in the range of 2h = 10 –70j. These two curves are almost the same in both position and width of peaks, indicating that the morphology of PbS particles has not been changed during the curing process. This is quite important for producing nanodevices because it means the nanofeature of the composite could be retained in the forming procedure. The particle diameter can be estimated to be about 7 nm with Debby –Scherrer’s equation: Lhkl = kk/B cosh, where k is taken as 1, k as 0.1542 nm, and B is the half width of the diffraction peak. All the results mean that the product composite is a real nanocomposite in which PbS nanoparticles are dispersed in epoxy resin E51 matrix homogenously, and therefore we will call the composite as PbS/epoxy resin E51 nanocomposites. The rod of the cured nanocomposite was sliced up into super thin sheet by microtome and observed under TEM. Fig. 2 shows the TEM image of the cured PbS/epoxy resin E51 nanocomposite (JEM-100SX with the voltage of 100 kV, the sample with the thickness of 80 nm is microtomed by the ULTRACUT-E). It can directly be seen that the PbS particles are dispersed in composite homogenously without connected aggregates. The diameter of PbS particles is under 10 nm, coinciding with the results of XRD data. The resulting PbS/epoxy resin E51 nanocomposite before curing is quite stable and no phase separation is observed in the time period of 1 month, and the homogenous dispersion of PbS nanoparticles in epoxy resin will not be changed during the curing procedure.
177
Fig. 2. TEM image of cured PbS/epoxy resin E51 nanocomposite.
As seen in Fig. 2, the PbS nanoparticles are dispersed homogenously in resin matrix. The PbS nanoparticles can be prevented from agglomeration due to very high viscosity of epoxy resin matrix. It is easy to understand that the PbS/epoxy resin E51 nanocomposite can be successfully prepared by the abovementioned procedure. The emulsion is formed when the acetone solution of epoxy resin E51 is added into the water with agitation, because acetone dissolves in water very easily and quickly while the epoxy resin E51 is insoluble in water. The Pb(Ac)2 in epoxy resin matrix may react with S2 at the interface of epoxy droplet and water, or the epoxy microdroplet may coat the PbS crystal that formed in the water and separate them from agglomerating. Here, the high viscosity of epoxy resin E51 plays an essential role in the in situ formation of PbS nanoparticles, and keeping the dispersion and separation of nanoparticles. Actually, the PbS nanoparticles will agglomerate when the uncured ointment-like composite is diluted by a large amount of solvent acetone.
Acknowledgements This work was financially supported by the National Natural Science Foundation of China (No. 20174038).
References
Fig. 1. X-ray diffraction pattern of PbS/epoxy resin E51 nanocomposite in the range of 2h = 10 – 70j.
[1] Y. Wang, N. Herron, J. Phys. Chem. 95 (1991) 525 – 532. [2] V.L. Colvin, M.C. Schlamp, A.P. Alivisatos, Nature 370 (1994) 354. [3] Y.S. Choi, K.H. Wang, M.Z. Xu, et al., Chem. Mater. 14 (2002) 2936 – 2939. [4] G. Zou, K. Fang, P.S. He, J. Mater. Sci. Lett. 21 (2002) 761 – 763. [5] W.B. Xu, M.L. Ge, P.S. He, J. Appl. Polym. Sci. 82 (12) (2001) 2281 – 2289. [6] W.B. Xu, S.P. Bao, P.S. He, J. Appl. Polym. Sci. 84 (4) (2002) 842 – 849. [7] G. Winiarz, L.M. Zhang, M. La, et al., Chem. Phys. 245 (1999) 417 – 428.
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L. Pan et al. / Materials Letters 58 (2003) 176–178
[8] Y. Dirix, C. Bastiaansen, W. Caseri, et al., J. Mater. Sci. 34 (1999) 3859 – 3866. [9] M.Z. Rong, M.Q. Zhang, H. Liu, et al., Polymer 40 (1999) 6169 – 6178. [10] D.D. Papakonstantinou, J. Huang, P. Lianos, J. Mater. Sci. Lett. 17 (1998) 1571 – 1573.
[11] J.M. Huang, Y. Yang, S.H. Xue, B. Yang, Appl. Phys. Lett. 70 (1997) 2335. [12] E.C. Hao, H.P. Sun, Z. Zhou, et al., Chem. Mater. 11 (1999) 3096 – 3102. [13] Y.F. Liu, L. Chen, B. Su, et al., J. Appl. Polym. Sci. 84 (2002) 1263 – 1268.