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Multiferroic composites with ferromagnetic and ferroelectric properties can be used in nanobiomedicine and multifunctional drug load owing to their strong magnetoelectric performance at room temperature. In this study, cobalt ferrite (CFO) and barium titanate (BTO) nanocomposites are synthesized by chemical co-precipitation method, the fraction of CFO with respect to the BTO is 20, 40, and 60 wt% (hereafter abbreviation as C20, C40, and C60). In this way, CFO as the growth site of BTO grains, forms a structure that BTO grains coated CFO grains. With the addition of CFO, the crystalline size of BTO in nanocomposites become smaller than pure BTO, particles size of nanocomposites is between 48 and 60 nm, lower than pure BTO. Smaller particle size of nanocomposites lead to higher dielectric constant in nanocomposites. The magnetization (M) versus field (H) loops reveal the ferromagnetic nature of CFO–BTO nanocomposites. All nanocomposite samples present outstanding ME effect with high αME value of exceeding 41 mV Oe−1 all samples, reaching 44.13 mV Oe−1 of C20. [ABSTRACT FROM AUTHOR]

XRD (X-ray diffraction) pattern analysis can estimate approximate preparation condition values based on nanomaterials formation; however, these initial values can be further refined without additional experiments by combining DSC (Differential Scanning Calorimetry) curves with thermodynamic equations to track crystallinity and crystallization rate of nanomaterials, which effectively improves the speed of preparation scheme. In this study, XRD pattern analysis from the comparative experimental results revealed that the optimum preparing solvothermal conditions on the IATO (tin-doped indium oxide) are at 200 °C for 24 h with 20 vol% 1-butanol; however, these conditions can be further optimized as 160 °C for 20 h with 5 vol% 1-butanol by simulating the growth process of nanomaterials in accordance to combine DSC curves with thermodynamic equations. [ABSTRACT FROM AUTHOR]

Magnetic metals are vital microwave absorbing materials, while they face the problems of a large density and relatively narrow absorption band in practical microwave absorption applications. The combination of magnetic metals with carbon materials can effectively ameliorate the electromagnetic (EM) parameters to resolve these the problems to a certain extent. In this study, we successfully fabricated the N-doped Co/graphite C (Co/NC) composites via directly calcining a dry mixture of Co powders and melamine in an Ar atmosphere. This method is simple and low cost. The effects of the variation in the phase composition and morphology on EM parameters and the microwave absorbing property were investigated. The graphite C content in Co/NC was relatively larger than Co content. Thus, the contribution of the dielectric loss to EM energy dissipation was more than that of the magnetic loss. Compared to pure Co, the Co/NC composites exhibit superior EM wave absorbency and are easier to realize strong absorption and lightweight. A minimum reflection loss of − 41.45 dB was obtained at 3.84 GHz. The effective absorbing bandwidth (EABW, RL ≤ − 10 dB) reached 14.80 GHz (3.20−18.00 GHz) at a coating thickness d of 1.54−5.00 mm. The maximum EABW was as large as 5.50 GHz at only 1.54 mm thick. The main reasons for the enhanced EM wave absorption performance of Co/NC were the well impedance matching and strong attenuation capability (interfacial and dipolar polarization, conduction loss, magnetic loss, and microwave multiple scattering and reflections on rough surfaces). Our study can provide a simple guideline for preparing other light carbon-based magnetic metal composites. The Co/NC composites with melamine as C and N source more favor for realization of strong absorption and lightweight compared to Co. [ABSTRACT FROM AUTHOR]

In this work, CoFe2O4/CoFe particles were prepared by two steps methods of ethylene glycol solvothermal and hydrogen reduction. The structure and morphology of the samples were characterized by X-ray diffraction and field-emission scanning electron microscopy. The samples were mixed with paraffin wax at a mass ratio of 3:1 to prepare rings with an inner diameter of 3.04 mm and an outer of 7 mm, and its electromagnetic parameters were measured by a network vector analyzer. The results show that the dielectric loss and magnetic loss of the composites can be improved after high temperature hydrogen reduction. The optimal reflection loss of −52.14 dB can be achieved at 12.34 GHz in a thickness of only 1.7 mm, when CoFe2O4 was annealed at 500°C for three hours, and the obtained particles can reach less than −20 dB in all C, X, and Ku bands. In all the samples annealing under 500–700°C, the maximum absorption bandwidth over 5.0 GHz can be observed. By comparing the impedance matching properties of CoFe2O4 precursor and CoFe2O4/CoFe composites, it is found that the tunability of the electromagnetic property in composite structure contributes to the excellent electromagnetic wave absorbing performances. [ABSTRACT FROM AUTHOR]

The nucleation mechanism of copper nanopowder on copper electrode in copper sulfate solutions with (or without) fluorocarbon-polysorbate surfactant (FPS) were investigated via linear sweep voltammetry (LSV), cyclic voltammetry (CV), and chronoamperometry (CA) techniques. These electrochemical experiments combining with morphological analysis conducted via field emission scanning electron microscopy (FE-SEM) to characterize the relatively complex electrocrystallization which occurs in FPS electrolyte system. Such electrodeposition in FPS electrolyte system with pH 0.5, 2.5, 3.5, or 4.5 first proceeds according to Scharifker–Hills (SH) instantaneous nucleation with three-dimensional growth before its behavior deviates from the theoretical model at longer nucleation times. The additives (FPS) does not change the nucleation mechanism, but H+ concentration have a greatly influence on nucleation mechanism. In the FPS electrolyte system, decreasing pH leads to a decrease in size of the powder particles and a change in their shape. Consequently, at the pH of 0.5, the copper nanopowder is the smallest, and it exhibits good dispersion and nearly spherical morphology. At pH of 0.5, the particle size of copper powder prepared by the FPS electrolyte system was 30–60 nm smaller than that by the copper sulfate solution. [ABSTRACT FROM AUTHOR]

In this paper, NdFeO3 nanoparticles were synthesized by the co-precipitation method. The particle size of NdFeO3 nanoparticles was controlled by changing the NaOH concentration in the co-precipitation method, mainly because NaOH concentration could control grain growth. The samples were characterized by X-ray diffraction (XRD) and filed-emission scanning electron microscopy (FE-SEM). They were found that with the change of NaOH concentration, the lattice parameters and cell volume of NdFeO3 nanoparticles changed little, but the average particle size ranged from ~ 100 to ~ 142 nm. And the influence of particle size on electrical properties of samples was also explored. The results showed that the dielectric constant of the sample increased with the decrease of the average particle size, and the dielectric loss decreases. When the average particle size was ~ 100 nm and the frequency was 103 Hz, the dielectric constant (ε′) was at most (~ 1.4 × 104) at room temperature, indicating that it had potential applications in dielectric capacitors. In addition, the conduction mechanism of NdFeO3 nanoparticle was studied by frequency dependence of AC conductivity. The effect of the grain and grain boundaries of NdFeO3 nanoparticles on the electrical properties of material was observed in complex impedance spectroscopy. The grain boundary resistance played a leading role in the resistance of the material, and the values of resistance increased with the decrease of the particle size. [ABSTRACT FROM AUTHOR]

For a single nano-optical material, it is difficult to possess high transmittance and adequately filter ultraviolet (UV) and infrared radiation (IR) simultaneously. Consequently, hybrid nano-optical materials comprising components of appropriate proportions for superimposing serviceable optical property are required. The design, optimization and processing of new composite blends with an aim to creating defect free thin films is far from a trivial endeavor. In this report, optimum composition and optical properties of hybrid nano-optical material has been determined and improved by crossover matching experiments and ball milling, respectively. Film preparation has been optimized to reduce defects expressed as cracks, tiny bubbles, strips, groove points, corrugation, and formation of acicular fibers by regulating proportion of polyvinyl butyral colloid and dry film processes. Two ameliorative processing conditions are exemplified where the resultant composite films possessed 86% maximum transmittance in the visible range and 90% and 50% blocking rate with respect to the IR and UV bands. [ABSTRACT FROM AUTHOR]

Broadband and lightweight microwave absorbers have gained considerable research interest in overcoming electromagnetic interference pollution. Here, mixture of two phase (fcc and hcp) metallic cobalt powders with broadband absorption was synthesized through solvothermal method using ethylene glycol as the reducing agent. The effect of NaOH content on the structure and morphology of the prepared Co powders is investigated by X-ray diffraction and field-emission scanning electron microscopy. Ring samples of 7.00/3.04 mm of out/inner diameter were prepared with paraffin for microwave absorption testing by vector network analyzer. It was observed that the increase of NaOH content caused a relative higher generation of hcp-Co phase and formation of irregular microspheres. The reflection loss (RL) peak and effective absorbing bandwidth (EABW, RL ≤ − 10 dB) shifted towards lower frequency when the sample thickness increased from 1.00 to 3.00 mm with EABW covering almost all the C, X and Ku bands (4–18 GHz). The bi-phase Co prepared in a low base solution exhibited enhanced microwave absorption properties. The width of largest EABW has reached 6.33 GHz covering partial Ku band and almost all the X band with optimal RL of − 56.95 dB at a sample thickness of only 1.85 mm, which is superior to EABW of Co crystals reported earlier. We proposed that such a wide EABW is due to the fact of Z values closed to 1.0 (0.8 ≤ |Z| ≤ 1.2) at almost the whole frequency range. This indicates that the prepared bi-phase Co powders are excellent microwave absorbers with large bandwidth, have good prospects. [ABSTRACT FROM AUTHOR]

In this work, different compositions of lanthanum hexaboride (LaB) and tin-doped indium oxide (ITO) nanoparticles were doped into poly(vinylbutyral) (PVB) matrix to prepare PVB/LaB-ITO nanocomposite (PLINC) films by a solution casting method. X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis (TGA) and ultraviolet-visible-near infrared spectroscopy (UV-vis-NIR) were employed to characterize the PLINCs. The TGA and UV-vis-NIR results reveal that the nanocomposite films possessed outstanding thermal stability. The temperature where 5 % weight loss of the PVB matrix was improved after the addition of LaB and ITO particles and the property for blocking near infrared light was also enhanced as compared with the case of pure PVB film. [ABSTRACT FROM AUTHOR]