Study on influence of temperature and duration of hydrothermal treatment to properties of nano ferrite nife2o4 materials - Tran Quang Dat

Journal of Science and Technology 54 (1A) (2016) 1-8 STUDY ON INFLUENCE OF TEMPERATURE AND DURATION OF HYDROTHERMAL TREATMENT TO PROPERTIES OF NANO FERRITE NiFe2O4 MATERIALS Tran Quang Dat * , Pham Van Thin, Do Quoc Hung Le Quy Don Technical University, 236 Hoang Quoc Viet Street, Ha Noi * Email: dattqmta@gmail.com Received: 30 August 2015; Accepted for publication: 29 October 2015 ABSTRACT NiFe2O4 superparamagnetic nanoparticles have been prepared by the method of spraying - co-precipitation subsequent by hydrothermal treatment. This procedure allowed to produce efficiently nanoparticles with high performances. Different techniques such as XRD, TEM, EDX, VSM were used to investigate the morphology, structure and magnetic properties of the obtained materials. It is shown that the materials have face-centered cubic trevorite structure, and their degree of crystallinity and magnetic properties improved with increasing temperature and time of hydrothermal treatment. After 32 hours of hydrothermal treatment at 160 C, NiFe2O4 nanomaterial has particle size of about 23 nm and saturation magnetization (Ms) of 49 emu/g. Keywords: ferrite, hydrothermal, co-precipitation, NiFe2O4. 1. INTRODUCTION Hydrothermal treatment is an effective technological method for the synthesis of nanomaterials, including nano magnetic ones [1]. On the other hand, the interest in the spinel ferrites MFe2O4 (M: Ni, Mn, Zn, Cu...) for many applications greatly increased in recent years due to their unique ability to respond to the action of external magnetic fields [2]. Among the ferrites, NiFe2O4 has great advantages, namely low cost of manufacturing, abundance of resources of raw materials, stability of properties to the environment and because of that this material is widely used in particularity for absorption, extraction and catalysis [3 - 5]. There are many technological methods for the synthesis of NiFe2O4 magnetic nanoparticles, such as grinding, micro-emulsion, ultrasonic and co-precipitation..., among which, the co- precipitation method has serious advantages: it is simple and it can produce in large scale nanoparticles with very small size, from 2 nm to 15 nm [6]. Spraying-coprecipitation, thanks to flexible scale and repeatability, is a very promising technique for the preparation of uniform nanoparticles. As a result of co-precipitation process, metal hydroxides are formed, which, after dehydration converted to oxides, and the latter, - after the solid-phase reaction, - lead to the Tran Quang Dat, Pham Van Thin, Do Quoc Hung 2 formation of ferrites. Typically, the processes of dehydration and solid state reactions occur only at high temperatures (600 0 C and higher) [7]. Hydrothermal treatment, because of its specificity, allows these processes to take place even at 120 - 160 C, i.e. at significantly lower temperatures in comparison with the method of sintering. Duration of the hydrothermal treatment affects the degree of crystallinity of the formed nanoparticles: typically, the crystallinity level of the particles improves with increasing of processing time. In previous papers we used the method of spraying - co-precipitation for fabrication of a number of magnetic nanomaterials [8 - 11]. In the studies we have found that for obtaining nanoparticles of ferrite materials, treatment at high temperature (at 600 degrees Celsius and over) is always required after co-precipitation, except the only case of Fe3O4, where no special heat treatment is needed [11]. The aim of our present research is to prepare nanoparticles NiFe2O4 by the method of co-precipitation combined with hydrothermal treatment and to study the influence of technological conditions on the properties of the obtained materials. 2. EXPERIMENTAL NiFe2O4 nanoparticles were prepared by method of spraying-coprecipitation combined with hydrothermal treatment. The process consists of two stages: co-precipitation and hydrothermal treatment. At the first stage, for co-precipitation to be carried out, we have used a specially designed unit, which consists of two receptacles that can withstand high pressure, and a reaction vessel, where a precipitate is formed. In the first pressure vessel was a mixture of aqueous solutions of 0.1 mol/l NiCl2, and 0.2 mol/l FeCl3. The other pressure vessel contained 0.8 mol/l solution of NaOH. A compressed air flow was piped into the two vessels so that the liquid comes out in the mist form at the nozzles. Co-precipitation process occurred in the reaction vessel, containing 10 -4 mol/l NaOH to keep the reaction medium at constant pH = 10. Precipitation was collected, filtered and washed until the pH reached 7 ÷ 8. Thereafter, at the second stage, the collected precipitate is subjected to hydrothermal treatment in a special reactor which is capable of withstanding high temperature and pressure. The temperature of the hydrothermal treatment is in the range 120 - 160 degrees Celsius and the processing time ranges from 4 to 32 hours. Due to high vapor pressure inside the reactor, it seems difficult to perform the heat treatment at higher temperatures. The temperature of the hydrothermal treatment chosen by other authors for fabrication of ferrite nanomaterials, is also located in this interval [12, 13]. The morphologies, size and crystal structures of the NiFe2O4 nanoparticles were characterised using transmission electron microscopy (TEM, JEM - 100 CX), X-ray diffraction (XRD, Bruker D5 with CuKα1 radiation λ = 1.54056 Å) and energy dispersive X-ray spectroscopy (EDX). The specific surface area was determined by Brunauer - Emmett - Teller (BET) method. Magnetic measurements were performed with a vibrating sample magnetometer (VSM, DMS 880), at room temperature. 3. RESULTS AND DISSCUSION 3.1. Morphology and microstructure of NiFe2O4 materials TEM images of materials obtained at different stages of our experiments NiFe2O4 аre shown in Figure 1. Figure 1 (a) shows TEM image of slurry obtained immediately after co- precipitation. It is obvious that at this stage, no particles are formed, and crystallization has not occurred yet. It is in good agreement with the X-ray diffraction pattern of the same sample, Study on effects of temperature and hydrothermal time to properties of nano ferrite NiFe2O4 3 shown in Figure 3. After the hydrothermal treatment, however, crystallization occurred and the nanoparticles were formed, as evidenced by Figures 1 (b), 1 (c) and 1 (d). The figures also suggest that the obtained nanoparticles are relatively uniform and their sizes are in the range of 15 - 25 nanometers. Looking more closely at these pictures, we see that the shape and size of nanoparticles do not vary significantly with increasing temperature of the hydrothermal treatment. Perhaps this is due to the fact that the treatment temperature is still relatively low, therefore thermal energy is insufficient to excite intensive lattice vibrations, which are necessary to combine small particles into larger. Figure 1. TEM images of NiFe2O4 samples (a) after spray; hydrothermal process (b) at 120 C for 32 h; (c) at 140 C for 32 h; (d) at 160 C for 32 h. Figure 2. EDX spectrum of the NiFe2O4 sample with hydrothermal process at 160 C for 32 h. EDX spectrum of the sample treated at temperature 160 C for 32 h is shown in Figure 2. It can be seen in this figure that the material contains three main elements Ni, Fe and O with atomic percentage of 13.65%, 26.52% and 59.83%, respectively. This indicates good (a) (b) (c) (d) Tran Quang Dat, Pham Van Thin, Do Quoc Hung 4 stoichiometric composition of the obtained NiFe2O4 material. Consequently, 32 h is considered as the optimum hydrothermal time to produce material with the high crystallinity level. The BET specific surface area of NiFe2O4 sample after treatment at 160 C for 32 h is found to be 75.2 m 2 /g. Figure 3. XRD pattern of the amorphous mixture. Figure 4. XRD patterns of NiFe2O4 particles obtained at different hydrothermal temperatures for 32 h. XRD pattern of the slurry collected after spaying is shown in Figure 3. This is a typical pattern for amorphous materials, there is almost no diffraction peaks and at the same time the background line is very wide and located at a rather high level. XRD patterns of samples obtained after the hydrothermal treatment at different temperatures are shown in Figure 4. Unlike the previous sample, in this case, we see clear diffraction peaks, moreover, the higher the temperature, the sharper the peaks. This means that during the hydrothermal processing occurs crystallization. Based on these data it can also be concluded that the materials have face-centered cubic trevorite structure and the peaks in the XRD patterns correspond to the (111), (220), (311), (400), (422), (511) and (440) crystal planes, respectively. Table 1. Lattice constant and crystallite size of the NiFe2O4 samples. Sample Lattice constant (A 0 ) Crystallite size (nm) NiFe2O4 – 4h 8.3207 17.50 NiFe2O4 – 8h 8.3307 20.86 NiFe2O4 – 16h 8.3350 22.69 NiFe2O4 – 24h 8.3363 22.80 NiFe2O4 – 32h 8.3387 22.92 The value of crystallite size of the NiFe2O4 nanoparticles was evaluated using Scherrer formula d = k / .cos , where k is equal 0.94, is the X-ray wavelength, is the peak full width half maxima (FWHM) and is the diffraction peak position. Results obtained by calculation with (311) peak indicate that the crystallite size of the samples treated at 120 C, 140 C and 160 C is 21.40, 21.56, 22.92 nm, respectively. This result is in good agreement with the previous analysis of the TEM images. Thus, we can say that in our experimental conditions 160 C is an optimum temperature for the hydrothermal processing. 50 100 150 20 30 40 50 60 70 80 2 (degree) I n t e n s it y ( a .u ) 10 20 30 40 50 60 70 0 400 800 1200 (c)-160 0 C (b)-140 0 C In te n s it y ( a .u ) 2 (degree) (a)-120 0 C (4 4 0 ) (5 1 1 ) (4 2 2 ) (4 0 0 ) (3 1 1 ) (2 2 0 ) (1 1 1 ) Study on effects of temperature and hydrothermal time to properties of nano ferrite NiFe2O4 5 Now consider the influence of the duration of heat treatment on the structure and particle size of the materials. Curves (a), (b), (c), (d) and (e) in Figure 5 represent XRD patterns of the samples treated at 160 0 C with treatment duration of 4, 8, 16, 24 and 32 hours, respectively. We see that at the duration of 4 hours on XRD pattern appear a small number of peaks, and they are wide, not clear (Figure 5 (a)). This indicates that in this case the crystallinity is low and the crystallite size is small. By increasing the duration of the hydrothermal treatment, the number of peaks becomes greater, and they have more clearly defined shape (Figures 5 (b), (c), (d), (e)). This means that with increasing duration of treatment improves the crystalline structure of the samples and their crystallite size increases. This conclusion is confirmed by Table 1, wherein the crystallite size is determined by the method described above, and the lattice constant is calculated according to the highest (311) peaks by the following formula: Tendency to increase crystallite size, which is observed in the table, can be explained by the diffusion of oxides into the ferrite spinel lattice, leading to the formation of larger crystals. 3.2. Magnetization measurement of NiFe2O4 materials Room temperature magnetic hysteresis loops of NiFe2O4 nanomaterials, prepared during 32 hours at hydrothermal temperatures of 120 0 C, 140 0 C, 160 0 C were investigated and are shown in Figure 6. It is evidenced that all samples are typically superparamagnetic with remanences (Mr) and coercive forces (Hc) being near to zero. Meanwhile, when the hydrothermal temperature increased, the magnetic properties were markedly improved: the saturated magnetization increased from 41 emu/g to 49 emu/g, when the temperature increases from 120 C to 160 C. Good magnetic properties are very important for applications of nanoparticles for environmental treatment, as it allows to recollect the distributed particles and to disperse them again in environment by using an external magnetic field [14]. To study the effect of hydrothermal annealing time to the properties of the materials, we have measured the magnetization curves and magnetic hysteresis loops of the samples. According to Figure 7, the magnetization of the samples increases as hydrothermal time increases. The observed magnetizations at 1 kOe were 18.1, 23, 37.2, 41.5, 45.9 emu/g corresponding to the samples treated during 4 h, 8 h, 16 h, 24 h and 32 h, respectively. If compared with the saturated magnetization of the corresponding samples (Figure 8), these values range from 88.2% to 93.7%. Figure 8 shows the hysteresis measured in high magnetic fields up to 15 kOe for these samples. It is seen that the magnetic properties of the samples seriously improve with increasing time of heat treatment, namely the saturated magnetization increases 2 2 2 2 2 1 h k l d a Figure 5. XRD patterns of NiFe2O4 particles obtained with different hydrothermal times, at 160 0 C. 10 20 30 40 50 60 70 0 300 600 900 1200 1500 (e)-32h (d)-24h (c)-16h (b)-8h (4 4 0 ) (5 1 1 ) (4 2 2 ) (4 0 0 )( 3 1 1 ) (2 2 0 ) In te n s it y ( a .u ) 2 (degree) (1 1 1 ) (a)-4h Tran Quang Dat, Pham Van Thin, Do Quoc Hung 6 from 22 to 49 emu/g (Figure 9). It is remarkable that the value of 49 emu/g obtained for the nanomaterial with 32 hours of hydrothermal treatment is only slightly inferior to the saturated magnetization of the bulk NiFe2O4 material (52 emu/g [15]) and it is significantly higher in comparison with the similar value reported by other authors [12, 13, 16, 17]. In our opinion, such an improvement of the magnetic properties of nanoparticles can be associated with the amelioration of their structure, namely when the processing time increases the thickness of the shell-layer decreases, while the cores expands, and this ultimately leads to increasing of saturated magnetization [18]. Based on the experimental results described above, we come to the final conclusion that, hydrothermal treatment at 160 C for 32 hours is the optimal technological condition for preparation of nickel ferrite magnetic nanoparticles. Figure 6. Room temperature hysteresis loops of NiFe2O4 samples obtained at different hydrothermal temperatures for 32 h. Figure 7. Room temperature magnetization curves in weak magnetic field of NiFe2O4 samples obtained with different hydrothermal times, at 160 C. Figure 8. Room temperature magnetic hysteresis loops of NiFe2O4 samples with different hydrothermal times, at 160 C. Figure 9. Room temperature saturated magnetization of NiFe2O4 samples with different hydrothermal times, at 160 C. 4. CONCLUSION NiFe2O4 nanomaterials have been prepared by the method of spraying - co-precipitation subsequent by hydrothermal treatment. It is shown, that the properties of the materials depend on temperature and duration of treatment. The obtained results showed that NiFe2O4 materials have -15 -10 -5 0 5 10 15 -60 -40 -20 0 20 40 60 (a) (b) M ( e m u /g ) H (kOe) (a) 120 o C (b) 140 o C (c) 160 o C (c) 0 500 1000 0 10 20 30 40 50 (e)-32h (d)-24h (c)-16h (b)-8h M ( e m u /g ) H (Oe) (a)-4h -15 -10 -5 0 5 10 15 -60 -40 -20 0 20 40 60 (a) (b) (c) (d) M ( e m u /g ) H (kOe) (e)-32h (d)-24h (c)-16h (b)-8h (a)-4h (e) 0 8 16 24 32 20 30 40 50 M s ( e m u /g ) Time (h) Study on effects of temperature and hydrothermal time to properties of nano ferrite NiFe2O4 7 face-centered cubic trevorite structure, their degree of crystallinity, particle size and magnetic properties improve with temperature and duration of hydrothermal processing. After 32 hours hydrothermal treatment at 160 C, NiFe2O4 nanomaterial has particle size of about 23 nm and saturation magnetization (Ms) of about 49 emu/g. High magnetic performances of materials have great significance for the prospective application of this material, especially in such fields as electronics engineering and environmental remediation. REFERENCES 1. Byrapa K. and Adschiri T. - Hydrothermal technology for nanotechnology, Progress in crystal Growth and Characterization of Materials 53 (2) (2007) 117 - 166. 2. Li L., Li G., Smith R. L. and Inomata H. - Microstructural evolution and magnetic properties of NiFe2O4 nanocrystals dispersed in amorphous silica, Mater. Chem. 12 (12) (2000) 3705 - 3714. 3. Chun J., Seo S. W., Jung G. Y. and Lee J. W. - Easy access to efficient magnetically recyclable separation of histidine-tagged proteins using superparamagnetic nickel ferrite nanoparticle clusters, Mater. Chem. 21 (18) (2011) 6713 - 6717. 4. Patil M. R. and Shrivastava V. S. - Adsorption of malachite green by polyaniline–nickel ferrite magnetic nanocomposite: an isotherm and kinetic study, Appl. Nanosci. 5 (2015) 809 - 816. 5. Hong D., Yamada Y., Nagatomi T., Takai Y. and Fukuzumi S. - Catalysis of nickel ferrite for photocatalytic water oxidation using [Ru(bpy)3] 2+ and S2O8 2– , J. Am. Chem. Soc. 134 (48) (2012) 19572 - 19575. 6. Massart R. and Cabuil V. - Synthesis of colloidal magnetite in alkaline medium: yield and particle size control, J. Chem. Phys. 84 (7-8) (1987) 967 - 973. 7. Fang J., Shama N., Le D. T., Shin E. Y., O’Connor C. J., Stokes K. L., Caruntu G., Wiley J. B., Spinu L. and Tang J. - Ultrafine NiFe2O4 powder fabricated from reverse microemulsion process, J. Appl. Phys. 93 (10) (2003) 7483 - 7485. 8. Dat T. Q., Vi L. D. and Hung D. Q. - Uranium removal activity of Cu0.5Ni0.5Fe2O4 superparamagnetic nano particles prepared by large scale method, Journal of Science and Technology 52 (3A) (2014) 66 - 73. 9. Dat T. Q. and Hung D. Q. - Large scale method to synthesize Zn0.5Ni0.5Fe2O4 nanoparticles with high magnetization, VNU Journal of science: Mathermatics - Physics 27 (3) (2011) 160 - 164. 10. Thanh N. K., Hung D. Q. and Dat T. Q. - Systhesis of Cu0.5Ni0.5Fe2O4 ferrite nanoparticles and study of several their properties, J. Sci. Tech. 50 (1A) (2012) 44 – 49 (in Vietnamese). 11. Hung D. Q., Dat T. Q. and Thanh N. K. - Synthesis and study on properties of Fe3O4 nanoparticles by the spraying - co-precipitation method, J. Chem. 48 (5A) (2010) 94 – 97 (in Vietnamese). 12. Huo J. and Wei M. - Characterization and magnetic properties of nanocrystalline nickel ferrite synthesized by hydrothermal method, Mater. Lett. 63 (2009) 1183 - 1184. 13. Nejati K. and Zabihi R. - Preparation and magnetic properties of nano size nickel ferrite particles using hydrothermal method, Chem. Cent. J. 6 (23) (2012) 1 - 6. Tran Quang Dat, Pham Van Thin, Do Quoc Hung 8 14. Bhalara P. D., Punetha D. and Balasubramanian K. - A review of potential remediation techniques for uranium (VI) ion retrieval from contaminated aqueous environment, J. Env. Chem. Eng. 2 (3) (2014) 1621 - 1634. 15. Smit J. and Wijin H. P. – Ferrites, Philips Technical Library, Eindhoven, The Netherlands, 1959, 157. 16. Wang D., Zhou J., Zhou X., Ke X., Chen C., Wang Y., Liu Y. and Ren L. - Facile ultrafast microwave synthesis of monodisperse MFe2O4 (M= Fe, Mn, Co, Ni) superparamagnetic nanocrystals, Mater. Lett. 136 (2014) 401 - 403. 17. Thakura S., Raia R. and Sharmab S. - Structural characterization and magnetic study of NiFexO4 synthesized by co-precipitation method, Mater. Lett. 139 (2015) 368 - 372. 18. Thanh N. K., Duong N. P., Hung D. Q., Anh L. N., Tu D. H., Loan T. T. và Hien T. D. - Crystallization and magnetic behavior of CuFe2O4 nanoparticles synthesized by spray co- precipitation method, J. Sci. Tech. 52 (3A) (2014) 38 – 44 (in Vietnamese). TÓM TẮT NGHIÊN CỨU ẢNH HƯỞNG CỦA NHIỆT ĐỘ VÀ THỜI GIAN THỦY NHIỆT ĐẾN TÍNH CHẤT CỦA VẬT LIỆU NANO FERRITE NiFe2O4 Trần Quang Đạt *, Phạm Văn Thìn, Đỗ Quốc Hùng Đại học Kỹ thuật Lê Quý Đôn, 236 Hoàng Quốc Việt, Hà Nội. * Email: dattqmta@gmail.com Hạt nano siêu thuận từ NiFe2O4 đã được tổng hợp bằng phương pháp phun sương đồng kết tủa, kết hợp với ủ thủy nhiệt. Đây là phương pháp có khả năng chế tạo được bột nano với chất lượng và năng suất cao. Quá trình tổng hợp mẫu, khảo sát sự hình thành tinh thể ferrite cho thấy sự phụ thuộc của tính chất vật liệu vào nhiệt độ và thời gian thủy nhiệt. Các kỹ thuật khác nhau như XRD, TEM, EDX, BET, VSM được sử dụng để phân tích hình thái, cấu trúc, tính chất từ của hệ vật liệu. Kết quả cho thấy, vật liệu NiFe2O4 có cấu trúc lập phương tâm mặt trevorite, mức độ kết tinh, kích thước hạt, từ độ tăng dần với nhiệt độ và thời gian thủy nhiệt. Sau 32 h thủy nhiệt và ở 160 0C, vật liệu NiFe2O4 có kích thước hạt cỡ 23 nm, từ độ bão hòa đạt 49 emu/g. Từ khóa: ferrite, thủy nhiệt, đồng kết tủa, NiFe2O4.