Photonic crystals in biology

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Poster Session, Tuesday, June 15 Theme A1 - B702 Synthesis and Characterization of ZnO Nano Powde rs Used in Rubber Technology 1 *, Ali Murat Soydan 2 and Cem Bulent Ustundag 3 1 Kocaeli University, Faculty of Engineering, Department of Metallurgical and M aterials Engineering, Kocaeli 41380, Turkey 2 Gebze Institute of Technology, Faculty of Engineering, Department of Materials Science and Engineering, Gebze/Kocaeli 41400, Turkey 3 Yildiz Technical University, Vocational School Ceramic Department, Maslak/Istanbul 34398, Turkey Abstract-In this study synthesis and characterization of nano sized ZnO powders, which are commonly used in various industrial applications especially used in tire industry, were done. Zn(NO 3 ) 2 , NH 3 and NaOH were used as raw starting materials. Nano sized Z nO powders were produced by applying chemical (precipitation) and thermal processes to raw materials. Contrary to the product morphology of American and French techniques known at the literature, it is observed that the obtained powders were in spherical structure with considerably high specific surface area (~39 m 2 /g) and nano particle size distribution (5–300 nm). ZnO usage in tire manufacturing technology as an activator for tire vulcanization, as a direct accelerator and hardening filler at “neoprene” and “Thiokol” type synthetic rubber processing, is really important [1]. Especially it’s usage as a reinforcement material for the resistance of the tires against shearing and tearing becomes really essential at high speed tires [2]. For this types of applications, homogeneous ZnO distribution at the structure and complete wetting to prevent the porosity formation is required [2]. Because of the stick/needle like structure of ZnO manufactured by American and French techniques, it is really hard to obtain complete wetting and consequently %100 reinforcement at tire manufacturing [2]. For this reason spherical ZnO powders are desired. ZnO; has various areas of usage such as varistor, gas sensors, catalysts and pigments. And also added to glass structure as a stabilizer in order to increase the chemical stability. By the way ZnO helps to set the properties such as chemical resistance, index of refraction and dielectric constant of the glass[3]. At all these kinds of applications chemical composition (impurity), morphology (spherical powder structure), micro structural properties, particle size and distribution (powders with high specific surface area) of the ZnO is really important. These powder properties strongly depends on the manufacturing process and process parameter [3, 4]. There are 3 commonly used technique in ZnO manufacturing: a) American Process, b) French Process and c) Wet (chemical) Process. At American technique the manufactured ZnO powders are in needle structure [5]. After a controlled grinding process, specific surface area of the powder is known to be around 1-2 m 2 /g [5]. By the way ZnO manufactured by French technique has a complex structure. Zn is obtained by the burning of the metal [5]. After a controlled grinding process, specific surface area of the powder is found to be around 4-5 m 2 /g [5]. ZnO manufactured by different chemical techniques is highly pure and depending on the process control high quality powders with high specific surface area around 4-75 m 2 /g can be obtained [5]. In this study nanocrystalline ZnO powders were produced by using chemical techniques. Precipitation and Sol-gel methods are widely used as chemical processes in literature [6]. Despite the fact that powders manufactured with sol-gel method exhibits better powder characteristics and better performance especially at ceramic applications, it’s high unit costs makes precipitation, which is simple and carry lower costs, more favorable. Product characteristics at ZnO production with the precipitation method from Zn(NO3) 2 , ZnCl 2 and ZnSO 4 solutions can be controlled by chancing the process parameters (temperature, catalyst type, feeding amount, speed and contact surface ) [6-9]. But at both 2 methods, due to the draying treatment at production stage powder size becomes massive and the agglomerates are hard. Consequently a grinding operation must be applied to the powders before forming, in order to use at composite material manufacturing or etc. At grinding process undesired manufacturing results like high costs and impurities can come across. In this study precipitation technique is modified and applied to a different system. By combining methods such as precipitation and spray pyrolysis, nano sized ZnO powders with high purity and high quality were obtained. Manufacturing of ZnO powders with desired powders characteristics such as spherical structure, controlled grain size and high wetting ability can be obtained and the formation of agglomerates can be eliminated with changing parameters like the fluid environment of Spray Pyrolysis machine, working pressure and temperature. Thermal, physical and micro structural characterizations were done by using Differential Thermal Analysis (DTA), Thermogravometric Analysis (TG), X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), BET and Nanosizer apparatus. The requirement for a grinding operation at the spherical agglomerates could be eliminated by the nano sized manufactured ZnO powders with nano crystalline structure. Powders are μm sized, spherical soft agglomerates, which can be easily broken and disperse at forming operations. This work was supported by TUBITAK; project No. 108M 124. *Corresponding author: oyildiz@kocaeli.edu.tr [1] – orisi ve 15-16 Eylül 1997 – Ankara [2] US Patent, Application No. 20050027054 “Rubber composition containing nanoscaled zinc oxide particles”, Goodyear Tire & Rubber Co., February 2005 [3] -Seramik Malzemeler, Metalurji [4] E. Sokullu; http://www.teknointel.com; Lastik Sanayiinde ZnO'in Rolü [5] Th. Guilmin, BPRI Latex, 2003 [6] C.-H. Lu, C.-H. Yeh, Materials Letters, 33 (1997) 129–132 [7] M. Castellano, E. Matijevic, Chem. Materials, 1 (1989) 78 [8] T. Tsuchida, S. Kitajima, Chemistry Letters, 19 (1990) 1769. [9] D. Chen, X. Jiao, G. Cheng, Solid State Communications, 113 (2000) 363–366 [10] S. Sahoo, M. Maiti, A. Ganguly, J.J. George, A.K. Bhowmick, Journal of Applied Polymer Science, 105 (2007) 2407–2415 [11] S. Sahoo, A.K. Bhowmick, Journal of Applied Polymer Science, 106 (2007) 3077–3083. 6th Nanoscience and Nanotechnology Conference, zmir, 2010 246
Poster Session, Tuesday, June 15 Theme A1 - B702 A rapid synthesis and charac terization of nano-crystalline CoCr 2 O 4 Figen Kurtulus 1 and Gulsah Celik 2 * 1 Balikesir University, Faculty of Science, Chemistry Department, Balikesir 10145, Turkey 2 Balikesir University, Science Institute, Balikesir 10145, Turkey Abstract- Nanocrystalline cobalt chromite (CoCr 2 O 4 ) was synthesized by rapid microwave method using Cr(NO 3 ) 3·9H 2 O and Co(NO 3 ) 2·6H 2 O raw materials with molar ratio 1:2. The synthesized product was characterization by powder X-ray diffraction and Fourier Transform Infrared Spectroscopy. Nanocrystalline CoCr 2 O 4 (ICDD Card no:78-0711) crystallizes in the face-centered cubic system, space group Fd 3 m (227), with cell parametres a = 8.334 Å and V = 578.97 Å 3 . The cristalline grain size of CoCr 2 O 4 was calculated as 83,5 nm by Debye Scherrer Formula. In recent years, spinel-type oxides based on 3d transitation metals have been the subject of increasing fundamental and applied research because of their catalytic properties [1,2]. Spinels are represented by the Formula AB 2 O 4 , in which A ions are generally divalent cations occupying tetrahedral sites and B ions are trivalent cations in octahedral sites; this is the structure of most chromites [3]. On the other hand, magmetism of small particles has generated increasing interest due to their unique magnetic properties as well as their technological applications [4-7]. CoCr 2 O 4 , has been widely used as dye, catalyst and substrate for film growth [8]. However, few articles have reported the synthesis and magnetic of CoCr 2 O 4 nanocrystallites [9]. Synthesis of nanocrystalline cobalt chromite by different route like co-precipitation method, thermolysis of polymer-metal complex precursor at a high temperature for a long time or at low temperature for a relatively short time have been attempted in the literature [9,10]. The goal of this study is to synthesis nanocrystalline Co Cr 2 O 4 by an alternatie and relatively new microwave asisted method and investigate its structural properties A rapid synthesis route of nanocrystalline CoCr 2 O 4 is as follows: Cr(NO 3 ) 3·9H 2 O and Co(NO 3 ) 2·6H 2 O were grounded in a agate mortar in a 1:2 molar ratio, and transfer into a porcelain crucible in powder form and subjected to microwave treatment in a domestic microwave oven (2.45 GHz, 750 W). The final product was homogenized. Structural properties of the material was determined by XRD (PANanalytical X’Pert PRO). Fig. 1. shows the XRD pattern of synthesized product. Comparison of the XRD pattern with the Standard ICDD result in corresponds to CoCr 2 O 4 (ICDD Cart no:78- 0711). The broad XRD lines indicate that the product is in the range of nanosize. Few characteristic peaks of impurities, indicating other forms of cobalt oxide (ICDD Cart no:72-1474), CoO, were detected. KT-MD29-2030 + + + + * + 20 30 40 50 60 70 2 theta(degree) Figure 1. XRD pattern of CoCr 2 O 4 FT-IR analysis performed for p repared sample and spectra are presented in Fig. 2. Two significant peaks are observed in the range of 400-650 cm for the sample; the vibration frequency at 648,31 cm -1 is characteristic Co-Ostretching modes in tetrahedral sites, whereas vibration + + + CoCr 2O 4 * CoO * + + * + 551,32 cm -1 corresponds to the Cr-O in an octahedral environment. The absorption band observed at ~ 1650 cm -1 prove the presence of absorbed water on the surface of the nanocrystals. %T 1652 Figure 2. FT-IR spectrum of CoCr 2 O 4 In summary, Co Cr 2 O 4 nanoparticles were successfully prepared by a rapid microwave method. Nanocrystalline CoCr 2 O 4 (ICDD Card no:78-0711) crystallizes in the facecentered cubic system, space group Fd3 m (227), with cell parametres a = 8.334 Å and V = 578.97 Å 3 . Average particle size was calculated from XRD pattern by Debye Scherrer Formula [11]. Scherrer demonstrated in 1918 that the size of a diffracting crystallite is directly related to the width of the X-ray diffraction peaks arising from its crystalline structure. For crystallite sizes less than about 100 nm, this size-induced peak-broadening effect may be measured accurately enough to deduce an average grain size in the sample. The grain size (D) of the CoCr 2 O 4 was calculated as 83,5 nm. The result shows that the crystalline grain size of the CoCr 2 O 4 has in the range of nano extension. *Corresponding author : 0Tgulsahcelik@bau.edu.tr [1] R. Sundararajan, V. Srinivasan, Appl. Catal. 73, 165 (1991). [2] Y. Liang, R. Tong, W. Xiaolai, J. Dong, S. Jishuan, Appl. Catal. B 45, 85 (2003). [3] N. Russo, D. Fino, G. Saracco, V. Specchia, Catal. Today 119, 228 (2006). [5] V.F. Puntes, K.M. Krishnan, A.P. Alivisatos, Science 291, 2115 (2001). [6]Phys. Rev. B 51, 2995 (1995). [7] H.L. Huang, J.J. Lu, Appl. Phys. Lett. 75, 710 (1999). [8] G. Hu, Y. Suzuki, Phys. Rev. Lett. 89, 276601 (2002). [9] L. Shandong, Z. Guoxia, B. Hong, H. Zhigao, L. Heng, G. Rongquan, D. Youwei, J. Magn. Magn. Mater. 305, 448 (2006). [10] S.D. Li, H. Bi, Z.J. Tian, F. Xu, B.X. Gu, M. Lu, Y.W. Du, J. Magn. Magn. Mater. 281, 11 (2004). [11] B.D. Cullity, Elements of X- ray diffraction, 2nd Edition, AddisonWesley, Reading, MA (1978). cm -1 648 551 6th Nanoscience and Nanotechnology Conference, zmir, 2010 247
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