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Synthesis and magnetic properties of size-controlled CoNi alloy nanoparticles
Journal of Alloys and Compounds 546 (2013) 229–233
Contents lists available at SciVerse ScienceDirect
Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom
Synthesis and magnetic properties of size-controlled CoNi alloy nanoparticles Wanheng Lu a, Dongbai Sun a, Hongying Yu b,⇑ a b
National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083, PR China Corrosion and Protection Center, Laboratory for Corrosion-Erosion and Surface Technology, University of Science and Technology Beijing, Beijing 100083, PR China
a r t i c l e
i n f o
Article history: Received 3 May 2012 Received in revised form 14 August 2012 Accepted 15 August 2012 Available online 28 August 2012 Keywords: CoNi alloy nanoparticles Size control Magnetic properties
a b s t r a c t CoNi alloy nanoparticles were obtained using liquid phase reduction method. The size of particles was selected as the research index, and the impacts of experimental conditions on the particle size were investigated. These experimental conditions included reaction temperature, solvent, initial concentration, and the amount of reducing agent and surface active agent. Through the orthogonal test, the optimized process parameters of preparing CoNi alloy nanoparticles by liquid-phase reduction were determined. The size of the particles prepared on the basis of the optimum technology was 60 nm. The particle size would impact the magnetic properties of CoNi nanoparticles measured by the test of hysteresis loops. The test result showed that the Hc of the CoNi alloy nanoparticles decreased and the Ms increased, with the increase of the particle size. Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction Ultrafine CoNi alloy powder has special surface magnetism and properties that are different from cobalt and nickel metal powder. Therefore, ultrafine CoNi alloy powders are widely applied in magnetic materials, catalysts, batteries and other industries [1]. Many researches on the preparation of CoNi alloy micro and nano particles have been made at home and abroad. At present, preparation methods of CoNi alloy nanoparticles mainly include machine-alloying, laser ablation method, liquid phase reduction method, vapor reduction method and electro-deposition method [2–6]. Among them, liquid phase reduction method has obtained sufficient attention due to its simple operation, easy control and low cost. During the preparation of metal nanoparticles, the reaction condition, such as the reducing power of the reducing agent, the concentration of the precursor etc., will affect the nucleation and growth of particles, and finally have an impact on the size of metal nanoparticles. The surfactant plays an integral role in the nanotechnology researches and applications. The surfactant is largely used in the field of nano-materials preparation since it can form ordered aggregates in a distributed system, such as micelles, reverse micelles, microemulsions. Meanwhile, using the surfactant to modify nano-powder can reduce the huge surface energy, which is an important method to inhibit the coalescence of nano-powders [7]. Since the physical and catalytic properties of nanoparticles are usually related with the particle size and shape, the control of ⇑ Corresponding author. Tel.: +86 01062332067. E-mail addresses: [email protected] (W. Lu), [email protected] (H. Yu). 0925-8388/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jallcom.2012.08.063
nanoparticle size and shape has become an important goal of nanoparticle preparation, and is also an important method to modulate properties of nanoparticles [8,9]. In this paper, we focused on the impacts of experimental condition on the particle size and the optimization of process for preparing CoNi alloy nanoparticles. At the same time, we also studied the impacts of particle size on the magnetic properties of the produced particles. 2. Material and methods 2.1. Chemicals Cobalt (II) sulfate heptahydrate (CoSO47H2O), Nickel (II) sulfate hexahydrate (NiSO46H2O), Sodium hydroxide (NaOH), Hydrazine hydrate (80%), Polyvinylpyrrolidone (PVP), Cetyltrimethylammonium bromide (CTAB), Sodium lauryl sulfate (SDS), Ethylene glycol were used as purchased without further purification.
2.2. Materials synthesis The divalent cobalt and nickel sulfate with the Co/Ni molar ratio of 1/1 and the surfactant were dissolved in the ethylene glycol. The solution was heated to the desired temperature in a water bath. Certain amounts of NaOH and hydrazine hydrate were dissolved in the ethylene glycol, which were added into the salt solution. And then the solution turned dark blue immediately. Being stirred and heated for 20– 30 min, the solution began to react and turned black. The CoNi alloy nanoparticles can be obtained after cooling, centrifugation, washing and drying.
2.3. Characterization The morphology and the size of the nano-alloy particle were obtained using field emission scanning electron microscope (FESEM, SUPRA 55). In order to determine the average composition of the CoNi alloy nanoparticles with a good accuracy, the energy dispersive X-ray spectroscopy (EDS) analyzer of FESEM SUPRY 55 was used. The structure of the CoNi alloy nanoparticles was investigated by X-ray dif-
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W. Lu et al. / Journal of Alloys and Compounds 546 (2013) 229–233
fraction (XRD, DMAX-RB 12KW Rigaku). The magnetic properties of the CoNi alloy nanoparticles were tested by vibrating sample magnetometer (VSM, Quantum Design).
3. Results and discussion 3.1. The effects of the experimental condition on the particle size Fig. 1(a) was the particle size and reaction temperature curve. It can be seen, when the reaction temperature was 60 °C, the size of particle was maximum, while at the temperature of 80 °C, the size was minimum. When the reaction temperature changed during the 70–100 °C, the changes of the particle size were not obvious. The reaction temperature had little effect on particle size in this range, and the reducing agent hydrazine hydrate may decompose at the high temperature, so the reaction temperature of the subsequent experiments was set as 80 °C. Fig. 1(b) was the particle size and the precursor salt concentration curve, the lower the initial concentration, the smaller the sizes of the nanoparticles. The results of Fig. 1(c) and (d) indicated that it’s more favorable to the particle refinement when the molar ratio of reducing agent to metal salts was 8, and NaOH to metal salts was 4. The synthesis of nanoparticles included the processes of nucleation and growth. When the temperature was higher, it would rapidly form nuclear. The low of the initial concentration would reduce the probability of the interaction between ions and the gather of atoms. Therefore, higher temperature and lower initial salt concentration etc., would be more favorable to particle refinement.
Three different kinds of common surfactants with different concentrations were added to the preparing CoNi alloy nanoparticles. The results (Fig. 2) showed that the addition of surfactants can effectively control the size of particles. Compared with the cationic surfactant, cetyl trimethyl ammonium bromide (CTAB), and the anionic surfactant, sodium lauryl sulfate (SDS), the non-ionic surfactants polyvinylpyrrolidone (PVP) was more conducive to the refinement of particles. 3.3. The optimized process parameters of preparing CoNi alloy nanoparticles The orthogonal test was conducted to determine the optimized process parameters of preparing CoNi alloy nanoparticles by liquid-phase reduction. The research index was the size of the particles. Table 1 showed the factors and levels that were selected. The orthogonal test (L9 (34)) was designed according to Table 1. The optimal parameters of the preparing CoNi alloy nanoparticles by liquid-phase reduction were: metal salt concentration was 0.05 M, both the molar ratio of reducing agent to metal salts and the molar ratio of NaOH to metal salts were 4, the concentration of the surfactant PVP was 1 g/L. Meanwhile, the metal salt concentration had the greatest impact on the research index, the amounts of reducing agent and NaOH followed, the concentration of the surfactant has the minimal impact. The size of the particles prepared on the basis of the optimized process parameters was 60 nm. Fig. 3 was the FESEM image and the distribution of the particle size. It can be seen that the particles were spherical and distributed uniformly.
3.2. The effects of the surfactant on the particle size 3.4. Characterization of the sample The surfactant can be used as the template and the protective agent in the field of nano-materials preparation, which can effectively control the size of particles.
Fig. 4(a) showed the XRD pattern of CoNi alloy nanoparticles at the room temperature. The peaks at 2h values of 44.38°, 51.48°,
Fig. 1. The effects of experimental conditions on the particle size: (a) temperature; (b) the molar concentration of salts; (c) the molar ratio of reducing agent and salts; (d) the molar ratio of NaOH and salts.
W. Lu et al. / Journal of Alloys and Compounds 546 (2013) 229–233
231
Fig. 2. The effects of surfactants on the particle size: (a) CTAB; (b) SDS; (c) PVP.
Table 1 The factors and levels of the orthogonal test. Salts concentration (M)
Reducing agent to salts (molar ratio)
NaOH to salts (molar ratio)
PVP concentration (g/L)
0.05 0.2 0.8
4 8 16
2 4 8
1 2 4
76.45°correspond to the crystal planes of the (1 1 1), (2 0 0), (2 2 0) of face-centered cubic (FCC) nickel (JCDPS 04-0850, Ni) or cobalt (JCDPS 15-0806, Co.). Fig. 4(b) was the results of EDS. It could be found there existed two kinds of metal elements-cobalt and nickel, and a certain amount of oxygen. The presence of Co and Ni indicated that the formation of both nickel and cobalt metals with FCC structure. Based on the quantitative result of the EDS, the Co/Ni molar ratio of the products was 1.02, which was similar with the initial ratio in the salt solution. Thus the composition of cobalt and nickel in the products could be denoted as Co50Ni50.
3.5. Magnetic measurement Magnetic properties of the samples were investigated at room temperature using a VSE with an applied fields, 20kOe 6 H 6 20kOe. Fig. 5 showed the hysteresis loops for samples with different sizes. The values of the coercivity (Hc), the saturation magnetization (Ms) and the remanent magnetization (Mr) of field for all samples were listed in Table 2. It can be seen that the overall tendency of Hc was decreasing and the Ms was increasing with increasing particle size.
Fig. 3. The FESEM image of CoNi alloy nanoparticle: (a) the FESEM image; (b) the size distribution.
If the size of the nanoparticles was smaller, there would be more surface area, which will enhance the oxidation of the surface of the nanoparticles. And finally there would create a magnetically dead layer and decrease the values of Ms.
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Fig. 4. (a) The XRD pattern of the CoNi alloy nanoparticles; (b) The EDS pattern of the CoNi alloy nanoparticles.
domain particles when the size is smaller than ds. The Hc of multidomain particles decreases, while the Hc of single domain particles increases, with the increase of the particle size. The critical size ds of CoNi alloy nanoparticles is about 40 nm [11]. The particle size of the products is 60 nm, therefore, the products were the multi-domain particles, and the Hc decreased with the increase of the particle size, which was consistent with the magnetic theory. Even so, it was still easily found that the sample with the size of 425 nm didn’t follow this rule. The formation of oxide on the surface of nanoparticles could possibly cause this abnormal phenomenon. The previous researches [12,13] also showed that the oxide would affect the magnetic properties of ultrafine particles. 4. Conclusion
Fig. 5. The hysteresis loops for samples with different sizes.
Table 2 Magnetization data for CoNi alloy nanoparticles with different sizes. Particle size/nm
Hc/Oe
Ms/emu g
60 127 425 526
287 131 75 100
35.30 69.20 45.01 151.30
1
Mr/emu g
1
13.28 9.25 2.00 4.45
The optimized process parameters of preparation of CoNi alloy nanoparticles by liquid-phase reduction have been determined, and the particle size of CoNi alloy nanoparticles obtained by the optimized process parameters was 60 nm. CoNi alloy nanoparticles were FCC structure, spherical and distributed uniformly. The magnetic test shows the Hc of the CoNi alloy nanoparticles decreased and the Ms increased, with the increase of the particle size. References
According to the magnetic domain theory [10], there is a critical size ds of single domain particles: the magnetic particles are multidomain particles when the particle size is larger than ds, and single
[1] Jing Zhang, Chuanfu Zhang, Changjun Li, et al., Cemented Carbide 19 (4) (2002) 206. [2] L. Armard, B. Dumont, G. Viau, Journal of Alloys and Compounds 242 (1–2) (1996) 108–113.
W. Lu et al. / Journal of Alloys and Compounds 546 (2013) 229–233 [3] Jin Zhang, Christopher Q. Lan, Materials Letters 62 (10) (2008) 1521–1524. [4] A. Bianco, G. Gusmano, R. Montanari, et al., Thermochimica Acta. 269 (1995) 117. [5] G. Viau, F. Ravel, O. Acher, et al., Journal of Magnetism and Magnetic Materials 144 (1995) 377. [6] D. Girirdin, M. Marer, Materials Research Bulletin 25 (1) (1990) 119. [7] Dezhi Wang, Zhuangzhi Wu, Liang Xun, Hongbin Jin, Journal of Central South University (Science and Technology). 40 (3) (2009) 676. [8] Debao Wang, Caixia Song, Materials Letters (2006) 77–80.
233
[9] Xiaoming Sun, Yadong Li, Angewandte Chemie International Edition 43 (5) (2004) 597–601. [10] G.D. Tang, D.L. Hou, M. Zhang, et al., Influence of preparing condition on magnetic properties of the FeCoNi–SiO2 granular alloy solids [J], Journal of Magnetism and Magnetic Materials. 251 (1) (2002) 42–49. [11] C. Luna, M.P. Morales, C.J. Serna, et al., Nanotechnology 14 (2) (2003) 268–272. [12] Hua Li, Wei Gong, Acta Physica Sinica 40 (8) (1991) 1356–1363. [13] Jian Wu, Huaixian Lu, Youwei Du, Xuekui Gao, Tingxiang Wang, Tingxiang Wang, Acta Physica Sinica 37 (12) (1988) 2044–2047.
Contents lists available at SciVerse ScienceDirect
Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom
Synthesis and magnetic properties of size-controlled CoNi alloy nanoparticles Wanheng Lu a, Dongbai Sun a, Hongying Yu b,⇑ a b
National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083, PR China Corrosion and Protection Center, Laboratory for Corrosion-Erosion and Surface Technology, University of Science and Technology Beijing, Beijing 100083, PR China
a r t i c l e
i n f o
Article history: Received 3 May 2012 Received in revised form 14 August 2012 Accepted 15 August 2012 Available online 28 August 2012 Keywords: CoNi alloy nanoparticles Size control Magnetic properties
a b s t r a c t CoNi alloy nanoparticles were obtained using liquid phase reduction method. The size of particles was selected as the research index, and the impacts of experimental conditions on the particle size were investigated. These experimental conditions included reaction temperature, solvent, initial concentration, and the amount of reducing agent and surface active agent. Through the orthogonal test, the optimized process parameters of preparing CoNi alloy nanoparticles by liquid-phase reduction were determined. The size of the particles prepared on the basis of the optimum technology was 60 nm. The particle size would impact the magnetic properties of CoNi nanoparticles measured by the test of hysteresis loops. The test result showed that the Hc of the CoNi alloy nanoparticles decreased and the Ms increased, with the increase of the particle size. Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction Ultrafine CoNi alloy powder has special surface magnetism and properties that are different from cobalt and nickel metal powder. Therefore, ultrafine CoNi alloy powders are widely applied in magnetic materials, catalysts, batteries and other industries [1]. Many researches on the preparation of CoNi alloy micro and nano particles have been made at home and abroad. At present, preparation methods of CoNi alloy nanoparticles mainly include machine-alloying, laser ablation method, liquid phase reduction method, vapor reduction method and electro-deposition method [2–6]. Among them, liquid phase reduction method has obtained sufficient attention due to its simple operation, easy control and low cost. During the preparation of metal nanoparticles, the reaction condition, such as the reducing power of the reducing agent, the concentration of the precursor etc., will affect the nucleation and growth of particles, and finally have an impact on the size of metal nanoparticles. The surfactant plays an integral role in the nanotechnology researches and applications. The surfactant is largely used in the field of nano-materials preparation since it can form ordered aggregates in a distributed system, such as micelles, reverse micelles, microemulsions. Meanwhile, using the surfactant to modify nano-powder can reduce the huge surface energy, which is an important method to inhibit the coalescence of nano-powders [7]. Since the physical and catalytic properties of nanoparticles are usually related with the particle size and shape, the control of ⇑ Corresponding author. Tel.: +86 01062332067. E-mail addresses: [email protected] (W. Lu), [email protected] (H. Yu). 0925-8388/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jallcom.2012.08.063
nanoparticle size and shape has become an important goal of nanoparticle preparation, and is also an important method to modulate properties of nanoparticles [8,9]. In this paper, we focused on the impacts of experimental condition on the particle size and the optimization of process for preparing CoNi alloy nanoparticles. At the same time, we also studied the impacts of particle size on the magnetic properties of the produced particles. 2. Material and methods 2.1. Chemicals Cobalt (II) sulfate heptahydrate (CoSO47H2O), Nickel (II) sulfate hexahydrate (NiSO46H2O), Sodium hydroxide (NaOH), Hydrazine hydrate (80%), Polyvinylpyrrolidone (PVP), Cetyltrimethylammonium bromide (CTAB), Sodium lauryl sulfate (SDS), Ethylene glycol were used as purchased without further purification.
2.2. Materials synthesis The divalent cobalt and nickel sulfate with the Co/Ni molar ratio of 1/1 and the surfactant were dissolved in the ethylene glycol. The solution was heated to the desired temperature in a water bath. Certain amounts of NaOH and hydrazine hydrate were dissolved in the ethylene glycol, which were added into the salt solution. And then the solution turned dark blue immediately. Being stirred and heated for 20– 30 min, the solution began to react and turned black. The CoNi alloy nanoparticles can be obtained after cooling, centrifugation, washing and drying.
2.3. Characterization The morphology and the size of the nano-alloy particle were obtained using field emission scanning electron microscope (FESEM, SUPRA 55). In order to determine the average composition of the CoNi alloy nanoparticles with a good accuracy, the energy dispersive X-ray spectroscopy (EDS) analyzer of FESEM SUPRY 55 was used. The structure of the CoNi alloy nanoparticles was investigated by X-ray dif-
230
W. Lu et al. / Journal of Alloys and Compounds 546 (2013) 229–233
fraction (XRD, DMAX-RB 12KW Rigaku). The magnetic properties of the CoNi alloy nanoparticles were tested by vibrating sample magnetometer (VSM, Quantum Design).
3. Results and discussion 3.1. The effects of the experimental condition on the particle size Fig. 1(a) was the particle size and reaction temperature curve. It can be seen, when the reaction temperature was 60 °C, the size of particle was maximum, while at the temperature of 80 °C, the size was minimum. When the reaction temperature changed during the 70–100 °C, the changes of the particle size were not obvious. The reaction temperature had little effect on particle size in this range, and the reducing agent hydrazine hydrate may decompose at the high temperature, so the reaction temperature of the subsequent experiments was set as 80 °C. Fig. 1(b) was the particle size and the precursor salt concentration curve, the lower the initial concentration, the smaller the sizes of the nanoparticles. The results of Fig. 1(c) and (d) indicated that it’s more favorable to the particle refinement when the molar ratio of reducing agent to metal salts was 8, and NaOH to metal salts was 4. The synthesis of nanoparticles included the processes of nucleation and growth. When the temperature was higher, it would rapidly form nuclear. The low of the initial concentration would reduce the probability of the interaction between ions and the gather of atoms. Therefore, higher temperature and lower initial salt concentration etc., would be more favorable to particle refinement.
Three different kinds of common surfactants with different concentrations were added to the preparing CoNi alloy nanoparticles. The results (Fig. 2) showed that the addition of surfactants can effectively control the size of particles. Compared with the cationic surfactant, cetyl trimethyl ammonium bromide (CTAB), and the anionic surfactant, sodium lauryl sulfate (SDS), the non-ionic surfactants polyvinylpyrrolidone (PVP) was more conducive to the refinement of particles. 3.3. The optimized process parameters of preparing CoNi alloy nanoparticles The orthogonal test was conducted to determine the optimized process parameters of preparing CoNi alloy nanoparticles by liquid-phase reduction. The research index was the size of the particles. Table 1 showed the factors and levels that were selected. The orthogonal test (L9 (34)) was designed according to Table 1. The optimal parameters of the preparing CoNi alloy nanoparticles by liquid-phase reduction were: metal salt concentration was 0.05 M, both the molar ratio of reducing agent to metal salts and the molar ratio of NaOH to metal salts were 4, the concentration of the surfactant PVP was 1 g/L. Meanwhile, the metal salt concentration had the greatest impact on the research index, the amounts of reducing agent and NaOH followed, the concentration of the surfactant has the minimal impact. The size of the particles prepared on the basis of the optimized process parameters was 60 nm. Fig. 3 was the FESEM image and the distribution of the particle size. It can be seen that the particles were spherical and distributed uniformly.
3.2. The effects of the surfactant on the particle size 3.4. Characterization of the sample The surfactant can be used as the template and the protective agent in the field of nano-materials preparation, which can effectively control the size of particles.
Fig. 4(a) showed the XRD pattern of CoNi alloy nanoparticles at the room temperature. The peaks at 2h values of 44.38°, 51.48°,
Fig. 1. The effects of experimental conditions on the particle size: (a) temperature; (b) the molar concentration of salts; (c) the molar ratio of reducing agent and salts; (d) the molar ratio of NaOH and salts.
W. Lu et al. / Journal of Alloys and Compounds 546 (2013) 229–233
231
Fig. 2. The effects of surfactants on the particle size: (a) CTAB; (b) SDS; (c) PVP.
Table 1 The factors and levels of the orthogonal test. Salts concentration (M)
Reducing agent to salts (molar ratio)
NaOH to salts (molar ratio)
PVP concentration (g/L)
0.05 0.2 0.8
4 8 16
2 4 8
1 2 4
76.45°correspond to the crystal planes of the (1 1 1), (2 0 0), (2 2 0) of face-centered cubic (FCC) nickel (JCDPS 04-0850, Ni) or cobalt (JCDPS 15-0806, Co.). Fig. 4(b) was the results of EDS. It could be found there existed two kinds of metal elements-cobalt and nickel, and a certain amount of oxygen. The presence of Co and Ni indicated that the formation of both nickel and cobalt metals with FCC structure. Based on the quantitative result of the EDS, the Co/Ni molar ratio of the products was 1.02, which was similar with the initial ratio in the salt solution. Thus the composition of cobalt and nickel in the products could be denoted as Co50Ni50.
3.5. Magnetic measurement Magnetic properties of the samples were investigated at room temperature using a VSE with an applied fields, 20kOe 6 H 6 20kOe. Fig. 5 showed the hysteresis loops for samples with different sizes. The values of the coercivity (Hc), the saturation magnetization (Ms) and the remanent magnetization (Mr) of field for all samples were listed in Table 2. It can be seen that the overall tendency of Hc was decreasing and the Ms was increasing with increasing particle size.
Fig. 3. The FESEM image of CoNi alloy nanoparticle: (a) the FESEM image; (b) the size distribution.
If the size of the nanoparticles was smaller, there would be more surface area, which will enhance the oxidation of the surface of the nanoparticles. And finally there would create a magnetically dead layer and decrease the values of Ms.
232
W. Lu et al. / Journal of Alloys and Compounds 546 (2013) 229–233
Fig. 4. (a) The XRD pattern of the CoNi alloy nanoparticles; (b) The EDS pattern of the CoNi alloy nanoparticles.
domain particles when the size is smaller than ds. The Hc of multidomain particles decreases, while the Hc of single domain particles increases, with the increase of the particle size. The critical size ds of CoNi alloy nanoparticles is about 40 nm [11]. The particle size of the products is 60 nm, therefore, the products were the multi-domain particles, and the Hc decreased with the increase of the particle size, which was consistent with the magnetic theory. Even so, it was still easily found that the sample with the size of 425 nm didn’t follow this rule. The formation of oxide on the surface of nanoparticles could possibly cause this abnormal phenomenon. The previous researches [12,13] also showed that the oxide would affect the magnetic properties of ultrafine particles. 4. Conclusion
Fig. 5. The hysteresis loops for samples with different sizes.
Table 2 Magnetization data for CoNi alloy nanoparticles with different sizes. Particle size/nm
Hc/Oe
Ms/emu g
60 127 425 526
287 131 75 100
35.30 69.20 45.01 151.30
1
Mr/emu g
1
13.28 9.25 2.00 4.45
The optimized process parameters of preparation of CoNi alloy nanoparticles by liquid-phase reduction have been determined, and the particle size of CoNi alloy nanoparticles obtained by the optimized process parameters was 60 nm. CoNi alloy nanoparticles were FCC structure, spherical and distributed uniformly. The magnetic test shows the Hc of the CoNi alloy nanoparticles decreased and the Ms increased, with the increase of the particle size. References
According to the magnetic domain theory [10], there is a critical size ds of single domain particles: the magnetic particles are multidomain particles when the particle size is larger than ds, and single
[1] Jing Zhang, Chuanfu Zhang, Changjun Li, et al., Cemented Carbide 19 (4) (2002) 206. [2] L. Armard, B. Dumont, G. Viau, Journal of Alloys and Compounds 242 (1–2) (1996) 108–113.
W. Lu et al. / Journal of Alloys and Compounds 546 (2013) 229–233 [3] Jin Zhang, Christopher Q. Lan, Materials Letters 62 (10) (2008) 1521–1524. [4] A. Bianco, G. Gusmano, R. Montanari, et al., Thermochimica Acta. 269 (1995) 117. [5] G. Viau, F. Ravel, O. Acher, et al., Journal of Magnetism and Magnetic Materials 144 (1995) 377. [6] D. Girirdin, M. Marer, Materials Research Bulletin 25 (1) (1990) 119. [7] Dezhi Wang, Zhuangzhi Wu, Liang Xun, Hongbin Jin, Journal of Central South University (Science and Technology). 40 (3) (2009) 676. [8] Debao Wang, Caixia Song, Materials Letters (2006) 77–80.
233
[9] Xiaoming Sun, Yadong Li, Angewandte Chemie International Edition 43 (5) (2004) 597–601. [10] G.D. Tang, D.L. Hou, M. Zhang, et al., Influence of preparing condition on magnetic properties of the FeCoNi–SiO2 granular alloy solids [J], Journal of Magnetism and Magnetic Materials. 251 (1) (2002) 42–49. [11] C. Luna, M.P. Morales, C.J. Serna, et al., Nanotechnology 14 (2) (2003) 268–272. [12] Hua Li, Wei Gong, Acta Physica Sinica 40 (8) (1991) 1356–1363. [13] Jian Wu, Huaixian Lu, Youwei Du, Xuekui Gao, Tingxiang Wang, Tingxiang Wang, Acta Physica Sinica 37 (12) (1988) 2044–2047.