Search

Abstract Wet-mechanical alloying was used to synthesize NiCo 2 O 4 (Ni-Co) nanoparticles. XRD results showed that single phase nanoparticles were formed after 1 h of milling and a minimum crystallite size of ~ 3 nm was obtained for 3 h-milled sample. The 3-h-milled sample was mechanically alloyed with Vulcan (Vu) to fabricate NiCo 2 O 4 /Vulcan (Ni-Co/Vu). The Ni-Co/Vu sample was thoroughly mixed with aniline (ANI), and the mixture was then polymerized to polyaniline (PANI). The microscopic evaluations showed the change in shape of Ni-Co particles from spherical to worm-liked after the polymerization process. Their structure was evaluated using FT-IR and Raman spectroscopies. The electrochemical studies through cyclic voltammetry (CV) and chronopotentiometry (CP) showed the highest capacitance for the 3-h-milled Ni-Co, in comparison with other milled samples. The capacitance of 341 F g−1 of the 3-h-milled sample, was enhanced to 455 and 644 F g−1, upon introducing Vu and Vu/ PANI, respectively. [ABSTRACT FROM AUTHOR]

Abstract Co-Mg ferrites, Co x Mg 1 − y Fe 2 − z O 4 (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0, 0 < y < 0.34 and 0 < z < 0.67), were synthesized via a standard ceramic route, and the structural, morphological, magnetic properties and transmission parameter of the samples were studied. The thermal behavior of the ground powder was characterized using a differential thermal analysis technique (DTA). The XRD patterns proved the formation of single phase Mg-ferrite in the samples with "x" contents varying from 0.0 to 0.8. The sample with x = 1.0 showed two phases: a spinel Mg-ferrite and a secondary (Co,Mg)O phase. The lattice parameter and crystallite size of the samples increased remarkably by increasing the x content. The SEM images revealed that Co substitution in Mg ferrite at x = 0.2 causes the particle growth, but their growth was not significant until x = 0.8. For x = 1.0, a remarkable particle growth was again observed. A maximum bulk density of 4.94 g/cm3 was obtained for x = 0.8. Magnetic properties of the sintered samples showed an increase in coercive force up to 113 Oe by increasing Co substitution up to x = 1.0. Saturation magnetization reached a maximum value of ~45.40 emu/g at x = 0.8. Studying the microwave transmission behavior of the samples, using a vector network analyzer (VNA), indicated that by increasing Co, the transmission loss was reduced from ~ − 15 dB for x = 0.0 to less than − 10 dB for x = 0.8 in the frequency range of 8–12 GHz. [ABSTRACT FROM AUTHOR]

In this work, a lightweight double layered composite with excellent, mechanical and electromagnetic (EM) absorption properties was fabricated. The structure, morphology, magnetic and microwave absorption properties of prepared samples and bonding strength between the double-layer coatings were investigated. In order to prepare the composite samples, a multi-step cathodic method employed to deposite magnetite on the surface of activated carbon fibers (CFs) through the reduction of Fe (III)–Triethanolamine complex in an aqueous alkaline solution at 60–80 °C. Our results indicated that, a more homogenous and denser magnetite coating and consequently, improved EM absorption properties could be achieved by multi-step electro-deposition method on CFs comparing to single step method. Furthermore, a porous flake-like layer of magnetite was formed uniformly at 60 °C, while a dense and discontinuous layer with globular nano-particles deposited on the surface of CFs at 80 °C. [ABSTRACT FROM AUTHOR]

The curing time and temperature of a paste adhesive were found to be one of the most effective parameters in the behavior of the bonded composite-steel joints. These parameters were utilized in modeling and optimization, using response surface methodology to achieve a good joint strength and a reasonable joint elongation. The central composite second-order rotatable design has been utilized to conduct the experimental matrix planning. Analysis of variance has been employed successfully to test the adequacy, significance and meaningfulness of the developed mathematical model. Numerical analyses indicated the optimized curing temperature and time as 40 °C and 180 min, respectively. The predicted values were verified by mechanical tests, optical microscopy and scanning electron microscopy; thus the developed mathematical models can predict the responses adequately and optimize the key process parameters quickly and precisely. [ABSTRACT FROM AUTHOR]