Synthesis and study of microwave absorption of la1.5sr0.5nio4 dielectric/ferroferrimagnetic nanocomposite

In recent years, the electromagnetic radiation with the frequency in range of 1-100 GHz has great application in telecommunication, medical treatment, and military. In company with that electromagnetic radiation also brings problems such as: electromagnetic interference, health diseases. Therefore, developing absorbing materials, which has able to absorb electromagnetic radiation, have paid much attention in GHz frequency. Microwave absorption materials (MAM) helps to prevent electromagnetic interference issue, reduce the cross-section reflectivity, and ensure the security of electronic systems. Radar absorption materials (RAM) worked in frequency range of 8-12 GHz is widely used in military systems for stealth technology. Generally, the study on electromagnetic absorption material mainly focuses on three ways: (1) preventing reflectivity signal, (2) enhancing the absorbability of material, and (3) extending frequency range. The increase of loss tangent and absorption efficiency can be obtained if absorbing material can observe both electric and magnetic energy. Moreover, nanotechnology provides the other ways to fabricate absorption material in nanoscale for shielding. MAM with nano-size displays the improvement of absorption ability in comparison with micro-size. Nanotechnology also helps to make the light weight and thin absorbed layer. The microwave absorption ability of material can be determined by relative permeability (r), permittivity (r), and impedance matching between environment and material. The reflection loss (RL) is used to determine the quality of MAM via the formula: RL = 20log|(Z - Z0)/(Z + Z0)|, where Z = Z0(r/r)1/2 is the impedance of material, Z0 is the impedance of air. The maximum reflection loss can be obtained via two mechanisms: (i) the impedance of material equals to impedance of air, |Z| = Z0, which is so called Z matching; (ii) the thickness of absorbing layer satisfies the phase matching or quarter-wavelength condition (d = (2n+1)c/[4f(|r||r|)1/2], n = 0, 1, 2, ). Z matching normally achieves by balancing the permeability and permittivity values, r = r. It can be obtained by fabricating a composite of dielectric and ferrite materials. Recently, there are a lot of publications on MAM based on the nanocomposite of magnetic and dielectric materials in which the RL can be obtained below -50 dB. The RL of nanocomposite is much higher than that of traditional materials such as carbon black-C and carbonyl-Fe.

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MINISTRY OF EDUCATION AND TRAINING VIET NAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY ..*****. CHU THI ANH XUAN SYNTHESIS AND STUDY OF MICROWAVE ABSORPTION OF La1.5Sr0.5NiO4 DIELECTRIC/FERRO- FERRIMAGNETIC NANOCOMPOSITE Specialized: Electronic materials Numerical code: 9.44.01.23 SUMMARY OF DOCTORAL IN MATERIALS SCIENCE Ha noi, 2018 The work is completed at: INSTITUTE OF MATERIALS SCIENCE - VIET NAM ACADEMY OF SCIENCE AND TECHNOLOGY Science supervisor: 1. Dr. Dao Nguyen Hoai Nam 2. Prof. Nguyen Xuan Phuc PhD dissertation reviewer 1: PhD dissertation reviewer 2: PhD dissertation reviewer 3: The thesis will be protected under supervisory board academy level at: Academy at .. hours.. day ..month .. 2018 People can find this thesis at: - National library - Graduate university of Science and Technology library LIST OF PROJECTS PUBLISHED Articles in the ISI directory: 1. 1. P.T. Tho, C.T.A. Xuan, D.M. Quang, T.N. Bach, T.D. Thanh, N.T.H. Le, D.H. Manh, N.X. Phuc, D.N.H. Nam, “Microwave absorption properties of dielectric La1.5Sr0.5NiO4 ultrafine particles”, Materials Science and Engineering B, 186 (2014), pp. 101-105. 2. 2. Chu T. A. Xuan, Pham T. Tho, Doan M. Quang, Ta N. Bach, Tran D. Thanh, Ngo T. H. Le, Do H. Manh, Nguyen X. Phuc, and Dao N. H. Nam, “Microwave Absorption in La1.5Sr0.5NiO4/CoFe2O4 Nanocomposites”, IEEE Transactions on Magnetics, Vol. 50, No 6 (2014), pp. 2502804. 3. 3. Xuan T. A. Chu, Bach N. Ta, Le T. H. Ngo, Manh H. Do, Phuc X. Nguyen, and Dao N. H. Nam, “Microwave Absorption Properties of Iron Nanoparticles Prepared by Ball-Milling”, Journal of Electronic Materials, Vol. 45, No. 5 (2016), pp. 2311-2315. 4. 4. T.N. Bach, C.T.A. Xuan, N.T.H. Le, D.H. Manh, D.N.H. Nam, “Microwave absorption properties of (100-x)La1.5Sr0.5NiO4/xNiFe2O4 nanocomposites”, Journal of Alloys and Compounds, 695 (2017), pp. 1658-1662. Articles published in domestic magazines: 5. 5. Chu Thị Anh Xuân, Phạm Trường Thọ, Đoàn Mạnh Quang, Tạ Ngọc Bách, Nguyễn Xuân Phúc, Đào Nguyên Hoài Nam, “Nghiên cứu khả năng hấp thụ sóng vi ba của các hạt nano điện môi La1,5Sr0,5NiO4”, Tạp chí Khoa học Công nghệ, 52 (3B) (2014), tr. 289-297. 6. 6. Chu Thi Anh Xuan, Ta Ngoc Bach, Tran Dang Thanh, Ngo Thi Hong Le, Do Hung Manh, Nguyen Xuan Phuc, Dao Nguyen Hoai Nam, “High- energy ball milling preparation of La0.7Sr0.3MnO3 and (Co,Ni)Fe2O4 nanoparticles for microwave absorption applications”, Vietnam Journal of Chemistry, International Edition, 54(6) (2016), pp. 704-709. 7. 7. Chu Thị Anh Xuân, Tạ Ngọc Bách, Ngô Thị Hồng Lê, Đỗ Hùng Mạnh, Nguyễn Xuân Phúc, Đào Nguyên Hoài Nam, “Chế tạo và nghiên cứu tính chất hấp thụ sóng vi ba của tố hợp hạt nano (100 - x)La1.5Sr0.5NiO4/xNiFe2O4”, Tạp chí Khoa học và Công nghệ - Đại học Thái Nguyên, 157(12/1), tr. 177-181. 8. 8. Chu Thị Anh Xuân, Tạ Ngọc Bách, Đỗ Hùng Mạnh, Ngô Thị Hồng Lê, Nguyễn Xuân Phúc, Đào Nguyên Hoài Nam, “Tính chất hấp thụ sóng điện từ của hệ hạt nano kim loại Fe trong vùng tần số vi ba”, Tạp chí Khoa học – Trường Đại học Sư phạm Hà Nội 2, Số 44 (2016), tr. 16-23. 9. 9. Ta Ngoc Bach, Chu Thi Anh Xuan, Do Hung Manh, Ngo Thi Hong Le, Nguyen Xuan Phuc and Dao Nguyen Hoai Nam, “Microwave absorption properties of La1,5Sr0,5NiO4/La0.7Sr0.3MnO3 nanocomposite with and without metal backing”, Journal of Science of HNUE - Mathematical and Physical Sci., Vol. 61(7) (2016), pp. 128-137. 1 Introduction In recent years, the electromagnetic radiation with the frequency in range of 1-100 GHz has great application in telecommunication, medical treatment, and military. In company with that electromagnetic radiation also brings problems such as: electromagnetic interference, health diseases. Therefore, developing absorbing materials, which has able to absorb electromagnetic radiation, have paid much attention in GHz frequency. Microwave absorption materials (MAM) helps to prevent electromagnetic interference issue, reduce the cross-section reflectivity, and ensure the security of electronic systems. Radar absorption materials (RAM) worked in frequency range of 8-12 GHz is widely used in military systems for stealth technology. Generally, the study on electromagnetic absorption material mainly focuses on three ways: (1) preventing reflectivity signal, (2) enhancing the absorbability of material, and (3) extending frequency range. The increase of loss tangent and absorption efficiency can be obtained if absorbing material can observe both electric and magnetic energy. Moreover, nanotechnology provides the other ways to fabricate absorption material in nanoscale for shielding. MAM with nano-size displays the improvement of absorption ability in comparison with micro-size. Nanotechnology also helps to make the light weight and thin absorbed layer. The microwave absorption ability of material can be determined by relative permeability (r), permittivity (r), and impedance matching between environment and material. The reflection loss (RL) is used to determine the quality of MAM via the formula: RL = 20log|(Z - Z0)/(Z + Z0)|, where Z = Z0(r/r)1/2 is the impedance of material, Z0 is the impedance of air. The maximum reflection loss can be obtained via two mechanisms: (i) the impedance of material equals to impedance of air, |Z| = Z0, which is so called Z matching; (ii) the thickness of absorbing layer satisfies the phase matching or quarter-wavelength condition (d = (2n+1)c/[4f(|r||r|)1/2], n = 0, 1, 2, ). Z matching normally achieves by balancing the permeability and permittivity values, r = r. It can be obtained by fabricating a composite of dielectric and ferrite materials. Recently, there are a lot of publications on MAM based on the nanocomposite of magnetic and dielectric materials in which the RL can be obtained below -50 dB. The RL of nanocomposite is much higher than that of traditional materials such as carbon black-C and carbonyl-Fe. If traditional materials provide the RL below -15 dB, the nanocomposite of ferrite and carbon give very deep RL below -50 dB. For 2 instance, a composite of Fe3O4/GCs shows RL around -52 dB at 8.76 GHz, or a composite of BaFe9Mn0.75Co0.75Ti1.5O19/ MWCNTs displays RL ~ -56 dB at 17 GHz. It has been reported that a composite of C/CoFe- CoFe2O4/paraffin is an excellent absorbing material with deep RL below - 71.73 dB at 4.78 GHz. The other core-shell composite Fe/HCNTs and core- shell Co-C in paraffin show the RL about – 50 dB and 62.12 dB at 7.41 GHz and 11.85 dB, respectively. In Vietnam, the study on electromagnetic absorbing material started from 2011 by several group in military. They show ability of nanocomposite of BiFeO3-CoFe2O4 (RL ~ -35.5 dB at 10.2 GHz) in X band. The other nanocomposite Mn0.5Zn0.5Fe2O4 in resin and nano-ferrite Ba-Co have been also studied by them. Besides, the studies on electromagnetic absorption of metamaterial and metamaterial cloaking by a group of Assoc. Profs. Vu Dinh Lam also show prominent results. According to above reason, we propose a project “Synthesis and study of microwave absorption of La1.5Sr0.5NiO4 dielectric/ferro-ferrimagnetic nanocomposite”. This proposal is used to replace the previous name “Synthesis and study of microwave absorption of ferro- ferrimagnetic/dielectric nanocomposite”. We hope that our results contribute to the knowledge on electromagnetic absorbing material and develop the shielding and preventing EMI for electronic device. This dissertation includes four chapter: Chapter 1. Microwave absorption phenomena and materials. Chapter 2. Experimental. Chapter 3. Microwave absorption properties of dielectric La1.5Sr0.5NiO4 nanoparticles Chapter 4. Synthesis and microwave absorption properties of iron nanoparticle. Chapter 5. Synthesis and microwave absorption properties of nanocomposite of dielectric with ferrite and ferromagnetic materials. The main theme of dissertation: - Synthesis nanoparticle and nanocomposite of dielectric, ferrites, ferromagnetic, metal. - Synthesis nanoparticle and nanocomposite of dielectric, ferrites, ferromagnetic, metal. Studying the synthesis process and properties of materials. - Studying the microwave absorption properties and absorption mechanism of ferromagnetic-dielectric nanocomposite. 3 - Finding new material for better absorption performance (RL ~ -40 dB - -60 dB). The object of thesis: - Ferromagnetic and ferrites nanoparticle with large µ and Ms, such as La0.3Sr0.7MnO3, CoFe2O4, NiFe2O4, and Fe. - Colossal dielectric material La1.5Sr0.5NiO4. - Nanocomposite of ferro-ferrite and dielectric materials. The methodology: This dissertation follows the experimental method. According to the experimental data, we analyse the absorption properties of materials and compare with other reports. Firstly, we synthesize material in nanoscale by high energy ball milling method combined with annealing in furnace at suitable temperature. The crystal structure, morphology, and particle size have been analyzed by X-ray diffraction, scanning electron microscope. The vibrating sample magnetometer (VSM) is used for investigation magentic properties of material. Lastly, the measurement of the reflection and transmission of microwave is done in frequency 4 – 18 GHz by free space method at room temperature. The reflection loss can be calculated by transmission line and NRW method. The experimental results is explained for the absorption properties of material. The results of dissertation:  The platelet of nanocomposite material with paraffin have been synthesized.  The large absorption ability of La1.5Sr0.5NiO4/paraffin has been reported for the first time in frequency 4 – 18 GHz. The RL reaches -36.7 dB, and the absorption efficiency closes to 99.98%  The enhancement of resonance phase matching is observed for measuring absorption properties by reflection metal-back method.  The contrary behavior on the shifting of resonance peak of La1.5Sr0.5NiO4/NiFe2O4 and La1.5Sr0.5NiO4/La0.7Sr0.3MnO3 are observed. As NFO and LSMO concentration increases, the absorption peak related to impedance matching tends to high-frequency shift for LSNO/NFO and low- frequency shift for LSNO/LSMO. This different behavior is believed origin from different absorption mechanisms. The composite of LSNO/NFO follows the ferromagnetic resonance of NFO nanoparticle, while LSNO/LSMO relates to the ferromagnetic relaxation of LSMO nanoparticle. In the process of working and writing this thesis, although the author has tried hard but still can not avoid the errors. I wishes to receive the comments, the reviewer of the scientists as well as the people interested in the topic. 4 Chapter 1. Microwave absorption phenomena and materials This chapter presents the researchs and developments of microwave absorption materials. Some basic knowledge relates to the interaction between electromagnetic waves and materials, major absorption mechanisms occurring in absorbers, such as: electromagnetic loss in conductors, dielectric loss and magnetic losses have been presented to support discussions and explain experimental results in the following chapters. This chapter also introduces some of the typical microwave absorption structures and materials, such as resonant absorption layer (Salisbury, Dallenbach), broadband absorption multilayer (Jaumann), inhomogeneous absorber, hybrid microwave absorption materials, magnetic absorbers or metamaterial perfect absorber and some of the specific materials related to the object of thesis (the dielectric material with colossal permittivity-La1.5Sr0.5NiO4, ferrite materials Ni(Co)Fe2O4 and ferromagnetic materials Fe, La0.7Sr0.3MnO3) based on the analysis of previous researched results. This is important for discussing the researched results of thesis. Chapter 2. Experimental This chapter presents solid state reaction method combined with a high- energy ball milling technique and proper post-milling thermal annealing processes, allows preparing large amounts of high quality nanopowders required for microwave tranmission/reflection measurements. Structure analysis techniques, elemental determination and magnetic properties measurements of materials have been effectively exploited to assess the quality of the product. Some of electromagnetic parameters techniques of absorbers also introduce. By using free-space transmission techniques, microwave transimission and reflection measurements in the air are carried out in the frequency range of 4-18 GHz. This is the most suitable measurement method for investigating the microwave absorption capability of MAMs that are coated from a mixture of nanoparticles with paraffin on thin plates of mica. The devices, which used in the experimental measurements of this thesis, are modern and high accuracy. Finally, the impedance (Z) and the reflection loss (RL), which are characterized for both weak reflection and high absorption of MAMs, are calculated via the KaleidaGraph data processing software based on transmission line theory and NRW algorithm. 5 Chapter 3: Microwave absorption properties of dielectric La1.5Sr0.5NiO4 nanoparticles 3.1. Characteristics of dielectric La1.5Sr0.5NiO4 nanoparticles 3.1.1. Crystal structure and particle size Figure 3.1. X-ray diffraction pattern of the LSNO powder at 300 K. Figure 3.2. SEM image of the LSNO powder. X-ray diffraction data (Fig. 3.1) indicates that La1,5Sr0,5NiO4 particles are single phase of a tetragonal (F4K2Ni-perovskite-type, I4/mmm(139) space group). The nano particle size is about 50 nm. The SEM images (Fig. 3.2) indicates that the particle size is significantly larger than that obtained from the XRD technique, ranging from 100 nm to 300 nm. 3.1.2. Magnetic properties Figure. 3.3 shows the magnetization loop, M(μ0H), of LSNO nanoparticles. The result indicates very small magnetic moments with no hysteresis. This proves that the LSNO fabricated nanoparticles exhibit paramagnet- like behavior at room temperature. 3.2. Microwave absorption capability of La1,5Sr0,5NiO4 nanoparticles at different layers thicknesses The characteristic parameters of La1,5Sr0,5NiO4/paraffin samples with 40/60 vol. percentage, respectively, and different thicknesses, d = 1.5; 2.0; 3.0 and 3.5 mm are summarized in Table 3.1. The RL(f) and |Z|(f) curves are presented in Figures 3.4 (a)-(d). 30 40 50 60 70 80 (0 0 4 ) (1 0 3 ) (1 1 0 ) (1 1 2 ) (1 0 5 ) (1 1 4 ) (2 0 0 ) (2 1 1 ) (1 1 6 ) (2 0 4 /1 0 7 ) (0 0 8 /2 1 3 ) (2 0 6 ) (1 1 8 ) (2 2 0 ) (3 0 1 ) ( 2 2 4 ) (3 0 3 /2 0 8 ) (3 1 0 ) La1,5Sr0,5NiO4 Figure 3.3. Magnetic loop, M(H), of the LSNO material at room temperature. -0.2 -0.1 0 0.1 0.2 -1 10 4 -5000 0 5000 1 10 4 H (Oe) M ( e m u /g ) La1,5Sr0,5NiO4 6 Figure 3.4. RL(f) and Z(f) curves of the LSNO/paraffin layers: (a) d = 1.5 mm; (b) d = 2.0 mm; d = 3.0 mm và d = 3.5 mm. Table 3.1. The microwave absorption characteristics for the paraffin- mixed La1,5Sr0,5NiO4 particle layers with different thicknesses. d (mm) 1.0 1.5 2.0 3.0 3.5 fr (GHz) - 14.7 12.18 9.7 8.2 fz1 (GHz) - 14.3 12.22 9.7 - fz2 (GHz) - 13.2 - 9.2 - fp (GHz) (n=1) 4.18 13.9 12.7 10.9 10.4 |Z”|(fz1)(Ω) - 209.5 34.6 18.5 - |Z”|(fz2)(Ω) - 317.2 - 242 - RL(fr)(dB) - -24.5 -28.2 -36.7 -9.9 The RL(f) curves of d = 1,5; 2,0 và 3,0 mm samples in fig. 3.4a-c exhibit a deep minimum peak in RL at fr that is close to the fz1 frequency (Tab. 3.1), where the impedance matching condition (|Z| ≈ Z0 = 377 Ω) is satisfied. This suggests that the strong microwave absorption at the minimum absorption notch would be attributed to a resonance caused by impedance matching (Z- matching). However, the resonance could also be caused by a phase -25 -20 -15 -10 -5 0 0 0.5 1 1.5 2 12 13 14 15 16 17 18 RL |Z| R L ( d B ) |Z | (× 1 0 3 ) f (GHz) 377  d = 1,5 mm fz1fz2 a) -40 -30 -20 -10 0 0.2 0.4 0.6 0.8 1 1.2 8 9 10 11 12 RL |Z| R L ( d B ) |Z | (× 1 0 3  ) f (GHz) 377  fz1fz2 d = 3,0 mmc) -30 -25 -20 -15 -10 -5 0 0.3 0.4 0.5 0.6 0.7 0.8 0.9 12 12.5 13 13.5 14 RL |Z| R L ( d B ) |Z | (× 1 0 3  ) f (GHz) 377 fz1 d = 2,0 mmb) -10 -8 -6 -4 -2 0 0 1 2 3 4 4 6 8 10 12 RL |Z| R L ( d B ) |Z | (× 1 0 3 ) f (GHz) d = 3,5 mm 377  d) 7 matching at fp frequency if the phases of the reflected waves from the two sample’s surfaces differ by π: 𝑓𝑝 = (2𝑛 + 1)𝑐/(4𝑑√|𝜀𝑅|. |𝜇𝑅|); n = 0, 1, 2, ... (3.1) It is difficult to determine conclusively which mechanism is responsible for the deep negative RL at fr since both fz1 and fp values are quite close to the fr value. With increasing thickness from 1.5 mm to 3.0 mm, the resonance shifts to lower frequencies while the notch in RL, respectively, becomes deeper (Fig. 3.6). The resonance mechanic that is observed in this samples at minimum absorption peaks is the impedance mathching. The strong absorption is obtained only at fz1 while there is no observable anomaly (except for the t = 1.5 mm sample) in the RL(f) curve at fz2 frequency. The large values of |Z”| (the mismatch at the Z- matching condition) may explain the absence of resonant absorption at the fz2 frequencies. When the thickness is increased to 3.5 mm (Fig. 3.4(d)), the microwave absorption is strongly suppressed. No absorption notch could be observed at the fp frequencies for all samples (Tab. 3.1). We hope that using a metal backing plate will be drastically reduced the minimum values of RL or can be broadened the resonance frequency region by combining the Z-matching and phase- matching. 8 Chapter 4. Synthesis and microwave absorption properties of iron nanopaticles 4.1. The effect of fabricated conditions on the crystal structure, particle size and magnetic properties of Iron metal nanomaterials The analysis of crystal structure of Fe samples prepared for 1 to 20 hours (Fig. 4.1) show the appearance of diffraction lines corresponding to the body-centered cubic structure for α-Fe. The average particle size for all samples are listed in Table 4.1. The magnetization curve, M(H), at room temperature of Fe-10h sample (see the inset of Fig. 4.2) shows a high satutation moment Ms and small coercivity Hc. The satutation magnetization of Fe powder decreased sharply after milling for 10 hours and then decreased slowly for longer milling time (Tab. 4.1; Fig. 4.2). Figure 4.2. The dependence of Ms on milling time and the M(H) cuver of Fe-10h sample. Figure 4.3. The variability of Ms (Fe- 10h) following presered in air. Table 4.1. The average particle size D and the satutation magnetization Ms at 10 kOe magnetic field of Fe powder after from 1h to 20h milling. Samples Fe-1h Fe-3h Fe-5h Fe-10h Fe-15h Fe-20h D (nm) 76 42 28 21 20 19 MS (emu/g) 217 209 204 200 197 194 0 50 100 150 200 250 1 3 5 7 9 11 13 15 17 19 Ms M S ( e m u /g ) t (h) -200 -100 0 100 200 -1 10 4 -5000 0 5000 1 10 4 Fe-10h M ( e m u /g ) H (Oe) 0 0.3 0.6 0.9 1.2 0 120 240 360 480 600 720 M S (t)/M S (0) M S (t )/ M S (0 ) t (h) 0 1 2 3 4 5 6 7 8 24h 72h 168h 240h 480h 720h keV O | Fe Fe Fe | (b) Figure 4.1. X-ray diffraction (XRD) of iron samples after from 1-20h milling. 30 40 50 60 70 80 Fe-20h Fe-15h Fe-10h Fe-5h Fe-3h Fe-1h (011) (002) (112) 9 Table 4.2. The
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