scholarly journals Development of Radar Absorbing Nano Crystals under Thermal Irradiation

2008 ◽  
Vol 2 ◽  
pp. 91-104 ◽  
Author(s):  
Rahul Sharma ◽  
Ramesh Chandra Agarwala ◽  
Vijaya Agarwala
Keyword(s):  
Single Phase ◽  
Ostwald Ripening ◽  
Barium Hexaferrite ◽  
Uniform Structure ◽  
Precipitation Process ◽  
Vacuum Furnace ◽  
Morphological Transformation ◽  
Radar Absorbing Material ◽  
Wide Range ◽  
Co Precipitation

Single phase W-type barium hexaferrite nano crystals of radar absorbing material (RAM) i.e., BaMe2Fe16O27 (Me2+=Fe2+) were synthesized by a modified flux method that combines the controlled chemical co-precipitation process for nucleation and complete uniform growth during in-situ annealing with NaCl flux under vacuum furnace. Uniform structure morphological transformation of nano crystals from spherical to prism faces were noticed after annealing with increasing temperatures from 200 to 1200 oC for 4 h in vacuum. XRD results showed the single phase nanocrystals of BaFe18O27 with increasing crystallanity and size from 10 to 90 nm during annealing. FESEM and TEM were used to investigate the systematic growth processes of various morphologies of nano crystals. The effect of such systematic morphological transformation of nanocrystals was observed in dielectric, dynamic magnetic and refection loss (RL) properties in Kuband (12.4 -18.0 GHz). A significant increment from -15.23 dB to -43.65 dB with wide range of bandwidth in RL loss is noticed due to the symmetric morphological growth of single phase nano crystals of RAM during annealing. This process of crystal growth, morphology evolution and RL enhancement with respect to increasing temperature were also explained in terms of ostwald ripening and quantum size effect.

A Comparative Study on Process-Properties Correlation of Nano Radar Absorbing Heat Treated Materials

2009 ◽  
Vol 67 ◽  
pp. 39-44 ◽  
Author(s):  
Rahul Sharma ◽  
Ramesh Chandra Agarwala ◽  
Vijaya Agarwala
Keyword(s):  
Reflection Loss ◽  
Ostwald Ripening ◽  
Barium Hexaferrite ◽  
Precipitation Process ◽  
Morphological Transformation ◽  
Radar Absorbing Material ◽  
Quantum Size ◽  
Heat Treated ◽  
Absorbing Material ◽  
Co Precipitation

Single phase M-type barium hexaferrite nano radar absorbing material (NRAM) i.e., BaFe12O19 were synthesized by modified flux method that combines the controlled chemical co-precipitation process for nucleation and complete uniform growth during annealing with NaCl flux under microwave annealing (MWA) and vacuum annealing (VA). Uniform morphological transformation of nano crystals from spherical (~ 10 nm) to prism faces (~ 35 nm) were observed under TEM during annealing. The effect of such systematic nano morphological transformation of NRAM was observed on magnetic and reflection loss (RL) properties. Maximum reflection loss (RL) was improved to 37.15 dB at 16.00 GHz for MWA at 760 watt and 27.56 dB at 15.75 GHz for VA at 1200 oC with continuous increasing absorption range under −10 dB for 2 mm thick coating layer in the Ku Band (12.4-18.0 GHz).. Excellent microwave absorption properties are a consequence of accurate EM match in the nano morphological planes, a strong natural resonance, as well as multipolarization. This process of crystal growth, morphology evolution and RL enhancement with respect to the heat treatments were also explained in terms of Ostwald ripening and quantum size effect.

An investigation on the synthesis of nickel aluminate

2019 ◽  
Vol 48 (6) ◽  
pp. 487-492
Author(s):  
Liliya Frolova
Keyword(s):  
Electrical Conductivity ◽  
Single Phase ◽  
Molar Ratio ◽  
Precipitation Process ◽  
Complex Method ◽  
Nickel Aluminate ◽  
Content Type ◽  
Wide Range ◽  
Co Precipitation ◽  
Derivatographic Analysis

Purpose The purpose of this paper is to study the process of coprecipitation of polyhydroxocomplexes of nickel and aluminum from solutions of nickel (Ni) (II) sulfate and aluminum (Al) (III) sulfate with caustic soda and to study the conversion process to nickel aluminate and to check its properties. Design/methodology/approach For the thermodynamic analysis of the precipitation process, the software package MEDUSA was used. The dependences of the electrical conductivity, pH and residual concentrations as functions of the OH/Me ratio were obtained. Using X-ray phase analysis, spectroscopic analysis and derivatographic analysis, the properties of the products obtained were studied. The effects of OH/Me ratio and molar ratio cation of reagents on the physicochemical properties of the products were analyzed. Findings The paper deals with the results of theoretical and experimental research on the synthesis pigments of blue and green colors based on Ni-Al spinel. The influence of the molar ratio cation content on optical and color characterise of pigments were studied. Originality/value The original complex method of studying the processes of co-precipitation of cations in the form of hydroxides is proposed. pH precipitation of aluminum hydroxide and nickel are different. It is interesting to study their co-precipitation. The resulting single-phase product is a precursor of nickel aluminate over a wide range of cation ratios. The dependences of the electrical conductivity, pH and residual concentrations as functions of the OH/Me ratio were obtained.

Structural, Thermal and Magnetic Analysis of Co2FeO4 Spinel Oxide Synthesized by Co-Precipitation Process

2014 ◽  
Vol 895 ◽  
pp. 287-290 ◽  
Author(s):  
Pradeep Reddy ◽  
Yesu Raja ◽  
M. Ashok
Keyword(s):  
Crystallite Size ◽  
Single Phase ◽  
Annealing Temperature ◽  
Precipitation Process ◽  
Spinel Oxide ◽  
Nano Powder ◽  
Magnetic Analysis ◽  
Phase Compound ◽  
Different Temperatures ◽  
Co Precipitation

Co2FeO4spinel oxide nano powder was synthesized by co-precipitation process. Samples were annealed at different temperatures of 500, 800 and 900oC and the phase purity were also analyzed. As-prepared sample has two spinel phases and on annealing at 900οC single phase compound formed. The crystallite size of as-prepared is found to be 11.9 nm. The crystallite size increased with increase in annealing temperature to a maximum of 17.4 nm for 900 °C. Samples were subjected to necessary characterization for finding thermal, magnetic and optical band gap.

Synthesis and Properties of Superparamagnetic Fe3O4 Nanoparticles by Co-Precipitation Process

2013 ◽  
Vol 377 ◽  
pp. 173-179 ◽  
Author(s):  
Chan Yin ◽  
Xiao Yi Wei ◽  
Ji Hua Li ◽  
Fei Wang
Keyword(s):  
Particle Size ◽  
Saturation Magnetization ◽  
Single Phase ◽  
Average Particle Size ◽  
Particle Surface ◽  
Anhydrous Ethanol ◽  
Precipitation Process ◽  
Average Particle ◽  
Agglomeration Of Nanoparticles ◽  
Co Precipitation

Superparamagnetic Fe3O4nanoparticle with single phase has been synthesized successfully by a co-precipitation process. On the other hand, the effect of additive anhydrous ethanol in synthesis procedure was investigated for the magnetic properties of nanoparticles in this paper. The structure properties of synthetic Fe3O4particle were measured through XRD, FT-IR and TG-DSC devices. The characteristic peaks of Fe3O4have been observed to testify Fe3O4with single phase. The particle size and shape were observed by SEM and TEM measurements. The addition of anhydrous ethanol could enhance the dispersion of Fe3O4nanoparticles and restrain the agglomeration of nanoparticles. Therefore, the average particle size was about 18.2 nm, smaller than that of Fe3O4particles prepared without anhydrous ethanol of 24.3 nm. Correspondingly, the saturation magnetization (Ms) of Fe3O4prepared with and without anhydrous ethanol was determined to be 53.28 emu/g and 65.28 emu/g, respectively, lower than bulk magnetite particles of 90 emu/g. That is because, synthetic Fe3O4with smaller particle size obtains the higher surface curvature, which could enhance the disordered crystal orientation on the particle surface, so the saturation magnetization was decreased.

Synthesis and Characterization of RADAR Absorbing BaFe12O19/ZnFe2O4 Magnetic Nanocomposite

2015 ◽  
Vol 830-831 ◽  
pp. 452-455 ◽  
Author(s):  
Sachin Tyagi ◽  
Amandeep Singh ◽  
Ashok Kumar Paul ◽  
R.C. Agarwala ◽  
Vijaya Agarwala
Keyword(s):  
Sodium Hydroxide Solution ◽  
Hysteresis Loops ◽  
Barium Hexaferrite ◽  
Barium Chloride ◽  
Nitrogen Atmosphere ◽  
Magnetic Composite ◽  
Morphological Transformation ◽  
Plate Shape ◽  
Co Precipitation ◽  
Chloride Salts

Magnetic composite comprising zinc ferrite and barium hexaferrite; BaFe12O19/ZnFe2O4 nanoparticles having super paramagnetic nature were synthesized by co-precipitation of iron, zinc and barium chloride salts using 7.5 M sodium hydroxide solution. The resulting precursors were heat treated (HT) at 800 and 1200°C for 4 h in nitrogen atmosphere. The hysteresis loops showed an increase in saturation magnetization from 1.040 to 52.938 emu/g with increasing heat treatment (HT) temperatures. The ‘as synthesized’ particles have size in the range of 20–22 nm with spherical and needle shapes. Further, these spherical and needle shaped nanoparticles tend to change their morphology to hexagonal plate shape with increase in HT temperatures. The effect of such a systematic morphological transformation of nanoparticles on microwave absorption properties were estimated in X band (8.2–12.2 GHz). The maximum reflection loss of the composite reaches-23.12 dB (more than 99% power attenuation) at 10.46 GHz which make it a potential material in the area of stealth technology.

Preparing Fe[sub 3]O[sub 4] Nanoparticles from Fe[sup 2+] Ions Source by Co-precipitation Process in Various pH

2011 ◽  
Author(s):  
Darminto ◽  
Machida N. Cholishoh ◽  
Feby A. Perdana ◽  
Malik A. Baqiya ◽  
Mashuri ◽  
...  
Keyword(s):  
Precipitation Process ◽  
Co Precipitation

Preparation and Properties of Fe3O4/PMMA Nanocomposite Films

2009 ◽  
Vol 79-82 ◽  
pp. 505-508
Author(s):  
Li Li ◽  
H. Zhao ◽  
Wei Wang ◽  
F.F. Nie
Keyword(s):  
Fe3o4 Nanoparticles ◽  
Chemical Structure ◽  
Silane Coupling Agent ◽  
Blood Compatibility ◽  
Nanocomposite Films ◽  
Precipitation Process ◽  
Silane Coupling ◽  
Magnetic Fe3o4 Nanoparticles ◽  
Co Precipitation ◽  
Magnetic Fe3o4

The magnetic Fe3O4 nanoparticles had been synthesized by co-precipitation process and surface treatment by silane coupling agent (KH570). The magnetic Fe3O4/PMMA nanocomposite films were prepared by blend method, and the chemical structure, mechanical properties, surface morphology and the biocompatibility of the nanocomposite films were studied in this work. The magnetic Fe3O4 nanoparticles were well dispersed in the Fe3O4/PMMA nanocomposite films. The strength of the nanocomposite films, as well as the strain, decreased first and then increased with the increasing of the nanoparticles. The hemolytic ratio indicated that the nanocomposite films had a better blood compatibility.

Novel Fe3O4/HNT@rGO composite via a facile co-precipitation method for the removal of contaminants from aqueous system

RSC Advances ◽  
2016 ◽  
Vol 6 (54) ◽  
pp. 49228-49235 ◽  
Author(s):  
Chengwei Gao ◽  
Baojun Li ◽  
Ning Chen ◽  
Jie Ding ◽  
Qiang Cai ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Water Treatment ◽  
Potential Application ◽  
High Performance ◽  
Aqueous System ◽  
Precipitation Method ◽  
Precipitation Process ◽  
System P ◽  
Removal Of Contaminants ◽  
Co Precipitation

Fe3O4/HNT@rGO composite (FHGC) was fabricated via a facile co-precipitation process, followed by heat treatment. For RhB and As5+removal, the high performance and easy separation of FHGC highlight its potential application in water treatment.

Effect of the Dispersion of Nanosized Carbides (NbC - TaC) in the Sintered Microstructure of the Stainless Steel 316L

2008 ◽  
Vol 591-593 ◽  
pp. 294-298
Author(s):  
Uilame Umbelino Gomes ◽  
L.A. Oliveira ◽  
S.R.S. Soares ◽  
M. Furukava ◽  
C.P. Souza
Keyword(s):  
Stainless Steel ◽  
Automotive Industry ◽  
Sintering Temperature ◽  
Vacuum Furnace ◽  
Nanosized Particles ◽  
Stainless Steel 316L ◽  
Wide Range ◽  
Sintered Stainless Steel ◽  
20 Nm ◽  
Hardness Values

Sintered stainless steel has a wide range of applications mainly in the automotive industry. Properties such as wear resistance, density and hardness can be improved by addition of nanosized particles of refractory carbides. The present study compares the behavior of the sintering and hardness of stainless steel samples reinforced with NbC or TaC (particles size less than 20 nm) synthesized at UFRN. The main aim of this work was to identify the effect of the particle size and dispersion of different refractory carbides in the hardness and sintered microstructure. The samples were sintered in a vacuum furnace. The heating rate, sintering temperature and times were 20°C/min, 1290°C and 30, 60 min respectively. We have been able to produce compacts with a relative density among 95.0%. The hardness values obtained were 140 HV for the reinforced sample and 76 HV for the sample without reinforcement.

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