J Sol-Gel Sci Technol (2010) 54:147–153 DOI 10.1007/s10971-010-2169-x
ORIGINAL PAPER
Preparation of hollow silica beads via soft template calcinating route Xiangfeng Wu • Huiran Lu • Zhiqiang Wang Xinhua Xu
•
Received: 24 December 2009 / Accepted: 27 January 2010 / Published online: 12 February 2010 Ó Springer Science+Business Media, LLC 2010
Abstract Heat treated hollow silica beads have been prepared via a two-step method: the fast synthesis of mesoporous hollow silica beads via soft template method and the closing of the porosity of as prepared hollow silica beads in a vertical furnace at more than 1,000 °C. The experiment results showed that the size of the as prepared hollow silica beads was greatly affected by the size of the octylamine vesicles, which increased as the mixing rate decreased, and the optimal synthesis time was 5 min. Fourier transform-infrared spectroscopy results indicated that the soft template was incorporated in as prepared hollow silica beads. The optical photographs and the X-ray diffraction results indicated that the shell of as prepared hollow silica beads was fully densified in the high temperature furnace. In addition, the morphology observation of polypropylene/polyolyaltha olfin/heat treated hollow silica beads ternary composites indicated that this type of silica beads possessed high intensity and strength to blend with the polypropylene/polyolyaltha olfin composites. Keywords Hollow silica beads Synthesis Template method Heat treating
X. Wu H. Lu X. Xu (&) School of Materials Science and Engineering, Tianjin University, 300072 Tianjin, China e-mail:
[email protected];
[email protected] Z. Wang Shanxi Research Center of Engineering Technology for Engineering Plastics, North University of China, 030051 Taiyuan, China
1 Introduction Hollow glass beads have low specific gravity, satisfactory heat resistance, heat insulating properties, pressure resistance and impact resistance, and achieve physical propertyimproving effects in respect of size stability and mold ability, as compared with conventional filler. Accordingly, they have been attracted much attention and broadly used for the polymer composites with light-weight and highstrength, the sealing material, the synthetic wood, the reinforcing cement outer wall material, and the artificial marble [1–6]. Until now, Hollow glass beads can be produced via various methods, such as dried sol–gel granules method [7], liquid-droplet technique [8], plasma method [9], spray drying method [10], sputtering method and decomposable mandrel technique [11, 12]. However, few papers were reported to adapt soft template calcinating method to prepare heat treated hollow silica beads (HHSB) as filler for polymer. In recent years, using tetraethoxysilane (TEOS), as an inorganic framework source, and 1-alkylamine or other surfactants, as a template, to produce as prepared mesoporous hollow silica beads (AHSB) were broadly reported [13–19]. These methods adapted alkali or acid, as a hydrolysis catalyst, to initiate hydrolytic polycondensation of the TEOS. However, few papers were reported to synthesize the AHSB with the help of inorganic salt, and then to heat AHSB in a vertical furnace at more than 1,000 °C. This work has successfully prepared HHSB by adapting a two-step approach. The first step was the fast synthesis of AHSB by using a soft template method [13, 15–17] in the dilute solution of sodium chloride (NaCl). The second step was the continuous preparation of HHSB in a vertical furnace, which possessed different temperature control system in the four separated regions.
123
148
J Sol-Gel Sci Technol (2010) 54:147–153
2 Experimental 2.1 Materials TEOS, octylamine (OA), NaCl and c-Aminopropyltriethoxysilane (KH550) were purchased from Tianjin Chemical Corporation. A commercial grade polypropylene (PP 1300), with the density of 0.90 g/cm3, was supplied by Beijing Yanshan Petrifaction Company, and a commercial grade polyolyaltha olfin (POE 8150, a metallocene catalysed copolymer of ethylene and 1-octene with 25 wt% of comonomer), with the density of 0.87 g/cm3, was provided by Dupont Dow Company. 2.2 Synthesis of AHSB AHSB were synthesized by using the TEOS and the OA in the dilute solution of NaCl. In a typical preparation, 50 ml OA and 125 ml TEOS were mixed in a 1,000 ml threeneck round-bottomed flask equipped with a mechanical stirrer (Fig. 1). 1.5 g NaCl was dissolved in 750 ml distilled water, and rapidly added to the above solution at 50 °C. After 5 min, the white precipitate was filtrated, and repeatedly washed with water and ethanol for 3 times, and then dried in a vacuum oven at 90 °C for 2 h. 2.3 Preparation of HHSB AHSB were continuously added into the top of a vertical furnace (Fig. 2) by uniform air stream, which emitted from an air compressor with adjustable varying-speed system. The furnace temperature in the four separate regions (from top to bottom) were kept at 1,300, 900, 500, 100 °C,
Fig. 2 The sketch for the equipments of HHSB formation
respectively, and the final HHSB were collected at the bottom of the furnace. 2.4 Preparation of PP/POE/HHSB ternary composites HHSB, obtained via the vertical furnace at more than 1,000 °C and treated by surface performance modifier (KH550), the PP and the POE (PP/POE/HHSB 70/20/10, by volume fraction) were mixed in a rubber mixer (Model XXS-30, mixer with screw diameter 35 mm, made in Shanghai, China) with mixing time of 10 min. The rotor speed was set at 32 rpm and the mixing temperature was set at 200 °C. The following equation was used to calculate the HHSB volume fraction, VHHSB ð%Þ ¼
WHHSB=qHHSB WPP=qPP þ WPOE=qPOE þ WHHSB=qHHSB
where V, W, and q are volume, weight, and the density of corresponding components in the subscripts, respectively. 2.5 Characterization
Fig. 1 The sketch for the device of AHSB formation
123
The morphology of the specimens was observed by a Nikon Eclipse TE2000-U phase contrast microscopy (PCM), with bright field and cross-polarization field, and the optical photographs were taken by a CCD camera. The structural identification was characterized by Philips PW1830 small-angle (SXRD) and wide-angle x-ray diffraction (WXRD). The fourier transform-infrared spectroscopy (FT-IR) spectrum was performed by using a FTIR-8400s spectrometer.
J Sol-Gel Sci Technol (2010) 54:147–153
3 Results and discussion 3.1 Effects of the reaction time on the morphology of AHSB PCM images for AHSB prepared using 600 rpm in different reaction time are given in Fig. 3. AHSB with a definite diameter of several tens of micrometers can be obtained in only 5 min, as shown in Fig. 3a. This result was similar to the reports, which prepared AHSB by adapting diluted acid or alkali as the hydrolysis catalyst [18, 20–22], indicating that the inorganic salt, NaCl, was also in favor of forming AHSB, although the reaction mechanism was still not clear. The hollow structure of AHSB is indicated by the black arrows as shown in Fig. 3c. It can also be seen in Fig. 3a–c that more and more fragments are observed as the reaction time extend, and no intact beads are found when the reaction time exceed 110 min (Fig. 3d). The possible reasons about this trend were that there were hydrogen bonding interactions between the interface of vesicles and SiO2 oligomer which formed by the hydrolysis of TEOS [23, 24]. Further crosslinking and polymerization of adjacent silica oligomer on the surface of vesicles resulted into a wormhole-like and incompact shell [25, 26]. Because of the collision of each
149
particle in the reaction system, the longer reaction time, the higher probability for AHSB to break into small pieces. Therefore, the optimal reaction time was 5 min. 3.2 Effects of the stirring rate on the morphology of OA vesicles, AHSB and HHSB PCM images for OA vesicles, AHSB and HHSB, prepared using different stirring rates in 5 min, are shown in Fig. 4. It can be clearly seen that the size of the OA vesicles, which can be obtained by easily adjusting the stirring rate (Fig. 4a–c), played a very important role on the size of AHSB (Fig. 4d–f). A high stirring rate led to small particles. AHSB with narrow particle size range have mean particle sizes about 150 lm for 300 rpm, 60 lm for 600 rpm, and 20 lm for 900 rpm. It can also been found that there are no obvious change between the size of AHSB (Fig. 4d–f) and HHSB (Fig. 4h–j). It was easily to conclude that the size of OA vesicles also played a very important role on the size of HHSB, although the shell of AHSB was densified during heating. In addition, HHSB, observed under the cross-polarization field, exhibit multiple colors and cross extinction (Fig. 4h’–j’), obviously signifying that the structure of the HHSB were hollow, asymmetrical and ideally spherulitic.
Fig. 3 PCM images for AHSB prepared using 600 rpm in different reaction time a 5 min, b 40 min, c 75 min, d 110 min
123
150
J Sol-Gel Sci Technol (2010) 54:147–153
Fig. 4 PCM images for OA vesicles (a–c), AHSB (d–f) and HHSB (h–j, h’–j’), prepared using different stirring rates in 5 min, (a), (d), (h), (h’): 300 rpm; (b), (e), (i), (i’): 600 rpm; (c), (f), (j), (j’): 900 rpm, where the images (h’–j’) were observed under the cross-polarization field
3.3 FT-IR analysis Figure 5a and b show the FT-IR spectra of AHSB and the corresponding HHSB, respectively. A strong adsorption peak, especially for HHSB, is clearly seen at 3,442 cm-1 wavelength, which is assigned to the stretching modes of O–H bands [27]. In all samples, the band at 1,078 cm-1 wavelength is clearly visible, which is attributed to the asymmetric stretching vibrations of Si–O–Si band. The absorption peaks at 798 cm-1 are due to the symmetric stretching vibrations of Si–O–Si band. In addition to these peaks, the peaks at 1,643 and 968 cm-1 are indicative of
123
the existence of surface Si–OH groups [28]. On the other hand, it can be seen in Fig. 5a that there are two bands at 2,931 and 2,860 cm-1, which ascribed to C–H stretching modes of the hydrocarbon chain of OA, and two small bands at 1,548 and 1,469 cm-1, which due to the deformation vibration of –CH2– and –CH3 of the incorporated OA [29]. It should be noted that the peaks, related to 2,931, 2,860, 1,548 and 1,469 cm-1, disappeared after heating, indicating the complete removal of OA after high temperature treatment [26]. Hence, it could be easily concluded that the soft template of the OA was incorporated into AHSB during the formation of them.
J Sol-Gel Sci Technol (2010) 54:147–153
151
100
Transmittance/%
80
(b) 60
(a) 40
20
3442
2931 2860
798
1643 1548 1469
968 1078
0 4000
3500
3000
2500
2000
1500
1000
500
Wavenumber/cm-1 Fig. 5 FT-IR spectrums for AHSB (a) and HHSB (b)
3.4 XRD analysis
furnace at more than 1,000 °C, exhibit a pattern with no diffraction peak (Fig. 6b’), indicating that the shell were densefied, and the nanopores were padded. The results were also in accord with the Fig. 7c. It can be clearly seen in Fig. 7a that AHSB partly sink and partly float at the top presenting poor hydrophilicity, while HHSB, obtained via the muffle at 500 °C, sink in the water completely (Fig. 7b). However, HHSB, obtained via the vertical furnace at more than 1,000 °C, completely float on the water (Fig. 7c), and present excellent hydrophilicity due to much more O–H bands in the surface of the shell (as shown in Fig. 5). The possible reasons about this phenomenon were that part of AHSB were coated by excess OA and floated on the water, while the HHSB, obtained at 500 °C via the muffle, sunk in the water due to the full removal of the OA, as illustrated in Fig. 8. However, when the HHSB were heated at more than 1,000 °C via the vertical furnace, the shell of AHSB was fully densified. Therefore, they can float on the water.
WXRD and SXRD for HHSB, obtained via a muffle at 500 °C, and HHSB, obtained via the vertical furnace at more than 1,000 °C, are shown in Fig. 6. It can be clearly seen that only one broad diffraction peak for all the specimens can be observed in Fig. 6a and b, obviously demonstrating that HHSB, regardless of heat treated ways, were amorphous structure. It can also be seen in the inset that a diffraction peak could be clearly observed in the spectrum of HHSB, obtained via a muffle at 500 °C (Fig. 6a’). This result obviously demonstrated that this type of HHSB, heated at a low temperature, were mesoporous materials [30], and the nanopores were randomly distributed in the shell [31]. However, HHSB, obtained via the vertical
800
100000 80000
Intensity/cps
700
Intensity/cps
600
60000
a' b'
40000 20000
500 0
2
4
6
8
10
2 θ /degree
400
Fig. 7 Optical photographs for AHSB and HHSB, dispersing in the water for 24 h, (a) AHSB, obtained before the heating, (b) HHSB, obtained via the muffle at 500 °C, (c) HHSB, obtained via the vertical furnace at more than 1,000 °C
300
(a)
200
(b)
100 0 10
20
30
40
50
60
70
2θ /degree Fig. 6 WXRD spectrums for HHSB (a), obtained via a muffle at 500 °C, and HHSB (b), obtained via the vertical furnace at more than 1,000 °C (the inset shows the corresponding SXRD spectrums for HHSB (a’) and HHSB (b’), respectively.)
Fig. 8 The schematic illustration for the formation of AHSB and HHSB
123
152
J Sol-Gel Sci Technol (2010) 54:147–153
Fig. 9 PCM images for PP/POE (70/20) (a) and PP/POE/HHSB (70/20/10) (b)
3.5 Morphology observation of PP/POE/HHSB ternary composites Figure 9 shows the images for PP/POE (70/20) and PP/POE/HHSB (70/20/10). It could be seen that there are nothing in Fig. 9a, however, when PP/POE blends is filled with 10 vol% of HHSB, the particles are homogeneously dispersed in the composites, and few fragments of HHSB are found (Fig. 9b), indicating that this type of HHSB possess high intensity and strong to mix with the PP/POE composites.
4 Conclusions We have developed a two-step method for the preparation of HHSB with narrow particle size range. The experiment results showed that the size of AHSB was greatly affected by the size of the OA vesicles, which increased as the mixing rate decreased, about 150 lm for 300 rpm, 60 lm for 600 rpm, and 20 lm for 900 rpm. In addition, the wall thickness and the broken rate of AHSB increased as the reaction time extended, and no intact AHSB particles were obtained when the reaction time exceeded 110 min, and the optimal reaction time was 5 min. FT-IR results indicated that the soft template was incorporated into AHSB during the formation of them, and completely removed after high temperature treatments. The optical photographs and the XRD results indicated that the shell of HHSB were fully densified after heat treating in the vertical furnace at more than 1,000 °C. In addition, the morphology observation of PP/POE/HHSB ternary composites indicated that HHSB, obtained via this technology, possessed high intensity and strength to blend with the PP/POE composites. Acknowledgments The authors gratefully acknowledge the financial support of National Natural Science Foundation of China (No. 02490220).
123
References 1. Liang JZ (2002) Tensile and impact properties of hollow glass bead-filled PVC composites. Macromol Mater Eng 287:588–591 2. Kohli DK, Khardekar RK, Singh R, Gupta PK (2008) Glass micro-container based hydrogen storage scheme. Int J Hydrogen Energy 33:417–422 3. Zhao HG, Liu YZ, Wen JH, Yu DL, Wen XS (2007) Dynamics and sound attenuation in viscoelastic polymer containing hollow glass microspheres. J Appl Phys 101:123518.1–123518.3 4. Li GL, Yang XL, Bai F (2007) A facile route to poly(divinylbenzene) hollow microspheres with pyridyl group on the interior surface. Polymer 48:3074–3081 5. Koopman M, Chawla KK, Carlisle KB (2006) Microstructural failure modes in three-phase glass syntactic foams. J Mater Sci 41:4009–4014 6. Geleil AS, Hall MM, Shelby JE (2006) Hollow glass microspheres for use in radiation shielding. J Non-Cryst Solids 352:620–625 7. Schmitt ML, Shelby JE, Hall MM (2006) Preparation of hollow glass microspheres from sol-gel derived glass for application in hydrogen gas storage. J Non-Cryst Solids 352:626–631 8. Qiu LH, Fu YB, Tang YJ, Wei Y, Zheng YM, Shi T, Yao SJ (2002) Hollow glass microsphere production for laser directdriven fusion targets on Shen Guang II. Sci China Ser A 45: 371–377 9. Bica I (2000) Formation of glass microspheres with rotating electrical arc. Mater Sci Eng B 77:210–212 10. Bartenev GM, Sanditov DS (1982) The strength and some mechanical and thermal characteristics of high-strength glasses. J Cryst Solids 48:405–411 11. Nikroo A, Steinman DA (1999) Thin sputtered glass as a permeation barrier for plasma polymer shells. Fusion Technol 35: 212–215 12. Hoppe ML (2000) Large glass shells from GDP shells. Fusion Technol 38:42–45 13. Kosuge K, Murakami T, Kikukawa N, Takemori M (2003) Direct synthesis of porous pure and thiol-functional silica spheres through the S?X-I? assembly pathway. Chem Mater 15: 3184–3189 14. Bore MT, Rathod SB, Ward TL, Datye AK (2003) Hexagonal mesostructure in powders produced by evaporation-induced selfassembly of aerosols from aqueous tetraethoxysilane solutions. Langmuir 19:256–264 15. Shimura N, Ogawa M (2005) Growth of nanoporous silica spherical particles by the Stober method combined with
J Sol-Gel Sci Technol (2010) 54:147–153
16.
17.
18.
19.
20.
21.
22.
supramolecular templating approach. Bull Chem Soc Jpn 78: 1154–1159 Cheng X, Liu SQ, Lu LC, Sui X, Meynen V, Cool P, Vansant EF, Jiang J (2007) Fast fabrication of hollow silica spheres with thermally stable nanoporous shells. Micropor Mesopor Mat 98:41–46 Li L, Tsung CK, Ming T, Sun ZH, Ni WH, Shi QH, Stucky GD, Wang JF (2008) Multifunctional mesostructured silica microspheres from an ultrasonic aerosol spray. Adv Funct Mater 18:2956–2962 Zheng TH, Pang JB, Tan G, He J, McPherson GL, Lu Y, John VT, Zhan J (2007) Surfactant templating effects on the encapsulation of iron oxide nanoparticles within silica microspheres. Langmuir 23:5143–5147 Ji XL, Hu Q, Hampsey JE, Qiu X, Gao L, He J, Lu Y (2006) Synthesis and characterization of functionalized mesoporous silica by aerosol-assisted self-assembly. Chem Mater 18:2265–2274 Kosuge K, Singh PS (2001) Mesoporous silica spheres via l-alkylamine templating route. Micropor Mesopor Mat 44:139– 145 Vasiliev PO, Shen Z, Hodgkins RP, Bergstrom L (2006) Meso/ macroporous, mechanically stable silica monoliths of complex shape by controlled fusion of mesoporous spherical particles. Chem Mater 18:4933–4938 Rao GVR, Lopez GP, Bravo J, Pham H, Datye AK, Xu H, Ward TL (2002) Monodisperse mesoporous silica microspheres formed by evaporation-induced self assembly of surfactant templates in aerosols. Adv Mater 14:13010–13014
153 23. Wang YD, Ma CL, Sun XD, Li HD (2002) Neutral templating route to mesoporous structured TiO2. Mater Lett 54:359–363 24. Pan CL, Zhang WX, Wang YL, Zhou Z, Jiang DZ, Wu SJ, Wu TH (2003) Synthesis of mesoporous titanium phosphate with high surface area using long-chain alkylamine. Mater Lett 57: 3815–3819 25. Pauly TR, Pinnavaia TJ (2001) Pore size modification of mesoporous HMS molecular sieve silicas with wormhole framework structures. Chem Mater 13:987–993 26. Zhao L, Yu JG, Cheng B, Yu C (2005) A novel approach for the synthesis of monodispersed porous silica microspheres with high surface area. J Non-Cryst Solids 351:3593–3599 27. Zhao XS, Lu GQ (1998) Modification of MCM-41 by surface silylation with trimethylchlorosilane and adsorption study. J Phys Chem B 102:1556–1561 28. Yu JG, Yu JC, Zhao XJ (2002) The effect of SiO2 addition on the grain size and photocatalytic activity of TiO2 thin films. J Sol Gel Sci Technol 24:95–103 29. Wang YD, Ma CL, Sun XD, Li HD (2003) Synthesis and characterization of amorphous TiO2 with wormhole-like framework mesostructure. J Non-Cryst Solids 319:109–116 30. Bagshaw SA, Prouzet E, Pinnavaia TJ (1995) Templating of mesoporous molecular sieves by nonionic polyethylene oxide surfactants. Science 269:1242–1244 31. Liu S, Rao JC, Sui X, Cool P, Vansant EF, Tendeloo GV, Cheng X (2008) Preparation of hollow silica spheres with different mesostructures. J Non-Cryst Solids 354:826–830
123
