Narrow Results

The rGO/TiO₂ nanocomposite was synthesized using graphene oxide and butyl titanate as raw materials in a hydrothermal process. Various samples were produced by varying the duration of the hydrothermal treatment. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used to examine the nucleation and growth processes of anatase in the hydrothermal process from the thermodynamics and kinetics perspectives. The structural evolution of titanium dioxide/reduced graphene oxide with hydrothermal time was analyzed. The crystallite size as well as the particle size of the TiO₂, rGO and TiO₂/rGO decreases with increase in the hydrothermal reaction time.

Multilayer dielectric capacitors were fabricated from nanocomposite precursor comprised of BaTiO₃@TiO₂ core–shell nanosized particles and poly(vinylidene fluoride–hexafluoropropylene) (P(VDF–HFP)) polymer matrix (20 vol%). The multilayer capacitors showed very high discharge speed and high discharged energy density of around 2.5 J/cm³ at its breakdown field (~ 166 MV/m). The energy density of the nanocomposite multilayer capacitors was substantially higher than the energy density of commercially used power capacitors. Low cost, flexible structure, high discharge rate and energy density suggest that the nanocomposite multilayer capacitors are promising for energy storage applications in many power devices and systems.

Due to their excellent electrical insulation properties and processability, polymer materials are used in many electrical products. It is widely believed that space charge plays an important role for the electric field distribution, conduction, ageing, and electric breakdown of polymeric insulation. This paper reviews measurements and characteristics of space charge behavior which mainly determined by the pulsed electro-acoustic (PEA) measurement technique. Particular interests are the effects of the applied voltage, the electrodes, temperature, humidity, microstructure, additives, and filler materials on accumulation, distribution, transport, and the decay of space charge in polymeric materials. This review paper is to provide an overview on various space charge effects under different conditions, and also to summarize the information for polymeric materials with suppressed space charge and improved electrical behavior.

The development of advanced dielectric film materials with high energy storage performance is of critical significance for pulsed power capacitor applications. Nevertheless, the low discharged energy density ($U_e$) of current dielectric film material restricts their further application. In this work, core-shell structured SrTiO₃@SiO₂ nanowires (ST@SiO₂ NWs) fillers are fabricated based on interface engineering for high $U_e$. The optimized SiO₂ insulating layer could effectively confine the mobility of space charge carriers in the interfacial zone between ST NWs and thick SiO₂ insulating layer, thus reducing the interfacial polarization between the interface of nanofillers/polymer, which could be used to optimize the electric field strength and electric displacement of the corresponding nanocomposite. As a result, this nanocomposite film simultaneously exhibits enhanced maximum applied electric field ($E_{max}$) and ($D_{max}$-$P_r$) values, thus releasing an ultrahigh discharged energy density of 14.7J/cm³ at 390MV/m, which is 99% higher than that of the conventional ST/P(VDF-CTFE) (without SiO₂ coating) nanocomposite, and it is almost 2.5 times that of pure P(VDF-CTFE). This work demonstrates the superiority of the core-shell structured paraelectric nanowire in enhancing the energy storage performance of dielectric film capacitors, which is expected to guide the design of advanced energy-storage nanocomposites.

SnO₂–ZnO thin films consisting of nanoscale crystallites were obtained on glass and silicon substrates by solid-phase low-temperature pyrolysis. The synthesized materials were studied by XRD and SEM methods, electrophysical and optical properties were evaluated, as well as the band gap was calculated. It was shown that regardless of the phase composition all films were optically transparent in the visible range (310–1000 nm). The nanocrystallites’ minimum size, the highest activation energy of the conductivity and the smallest band gap calculated for indirect transitions were shown for a thin film 50SnO₂–50ZnO. It was assumed that the band gap decreasing might be attributed to the existence of surface electric fields with a strength higher than 4 × 10⁵ V/cm.

Flexible dielectric materials with environmental-friendly, low-cost and high-energy density characteristics are in increasing demand as the world steps into the new Industrial 4.0 era. In this work, an elastomeric nanocomposite was developed by incorporating two components: cellulose nanofibrils (CNFs) and recycled alum sludge, as the reinforcement phase and to improve the dielectric properties, in a bio-elastomer matrix. CNF and alum sludge were produced by processing waste materials that would otherwise be disposed to landfills. A biodegradable elastomer polydimethylsiloxane was used as the matrix and the nanocomposites were processed by casting the materials in Petri dishes. Nanocellulose extraction and heat treatment of alum sludge were conducted and characterized using various techniques including scanning electron microscopy (SEM), thermogravimetric analysis/derivative thermogravimetric (TGA/DTG) and X-ray diffraction (XRD) analysis. When preparing the nanocomposite samples, various amount of alum sludge was added to examine their impact on the mechanical, thermal and electrical properties. Results have shown that it could be a sustainable practice of reusing such wastes in preparing flexible, lightweight and miniature dielectric materials that can be used for energy storage applications.

The particles of TiO₂ core/ SnO₂ shell nanocomposite were prepared by hydrolysis of SnCl₄.5H₂O in the presence of titania nanoparticle after drying and calcinations treatments. TiO₂ particle were produced from titanium isopropoxide sol by hydrothermal processing. X-ray diffraction (XRD), Fourier transformed infrared (FTIR), and transmission electron microscopy (TEM) were used to characterize the TiO₂/ SnO₂ core shell nanocomposites. The obtained results from XRD show that the SnO₂ nanoparticles coated on TiO₂ yields diffraction peaks correspond to the crystalline SnO₂ phase. Also, TEM results show that the nanocomposite particles have a spherical morphology and a narrow size distribution. The thickness of SnO₂ shell on the surface of TiO₂ particles were about 8 nm. Moreover, the results obtained from EDX analysis show that the core-shell structured nanocomposites have crystalline structure.

In this paper, carbon nanotube (CNT)- polyaniline (PANI) nanocomposites were developed from in situ polymerization of aniline. The CNT can be prepared by either acid treatment of CNTs suspension by grafting functional groups to CNTs surface. In this study, CNT and acid treatment CNT was used for preparation of nanocomposite. The PANI-CNT nanocomposite was characterized by FTIR, SEM. CNT can be prepared by either acid treatment of CNTs suspension to make them ionized or by grafting functional groups to CNTs surface. In addition, the electrochemical measurements such as cyclic voltametric (CV) curves showed that the conductivity of the obtained nanocomposite increased. Therefore, the supercapacitors behavior of polyaniline improves with adding CNT especially with acid treatment CNT.

In this study Al₂O₃-SiC nanocomposites have been fabricated by mixing of alumina and silicon carbide nano powders, followed by hot pressing at 1700°C. The mechanical properties and fracture mode of Al₂O₃-SiC nanocomposites containing different volume fractions (5, 10 and 15%) of nano scale SiC particles were investigated and compared with those of alumina. Al₂O₃-SiC powders were prepared by planetary milling in isopropanol. Fracture mode of specimens was investigated by means of scanning electron microscopy. Nanocomposites were tougher than alumina when they were hot pressed at the same temperature, and the values of nanocomposite's flexural strength and hardness were higher than those of alumina. Flexural strength, hardness and fracture toughness of the nanocomposites increase by increasing the volume percent of SiC up to 10% and then decrease slightly. The Scanning electron microscopy observations showed that fracture mode changes from intergranular for alumina to transgranular for nanocomposites. Finally X-ray diffraction analysis couldn't detect any chemical reactions between Al₂O₃ and SiC particles.

Small amount of MgO in the range of ppm and distribution of SiC particles in Al₂O₃-10vol%SiC nanocomposite has an obvious effect on improving of density and mechanical properties such as hardness of sintered nanocomposite. Improving of these properties continues to 1000 ppm of MgO, but decreases above this amount. Transgranularly fractured alumina grains were observed on the fracture surface of this kind of nanocomposites. The effects of such a small amount of MgO on the sintering and microstructural development of Al₂O₃-10vol%SiC nanocomposite may be explained using the arguments which have been documented for the beneficial effects of a small amount of MgO in alumina ceramics. In Al₂O₃-10vol%SiC nanocomposite, Al₂O₃ particles were coated by nano scale SiC particles which inhibited the abnormal grain growth of Al₂O₃.

An efficient strategy of soil-conditioner application was offered by incorporating a high molecular weight organic polymer (polyacrylic acid; PAA) into a soil-friendly inorganic material (layered double hydroxide; LDH). The prepared materials were characterized by different spectroscopic techniques to confirm the formed nanocomposite structure. The SEM images captured the morphological ability of PAA-LDH nanocomposites to absorb and keep water molecules during soil-water application. The IR analysis indicated an electrostatic grafting process between PAA units and LDH moieties. The platform of PAA-LDH nanocomposite formulation stabilized the soil aggregates and improved the water-stability.

The hollow silica/cobalt ferrite (CoFe₂O₄) magnetic microsphere with amino-groups were successfully prepared via several steps, including preparing the chelating copolymer microparticles as template by soap-free emulsion polymerization, manufacturing the hollow cobalt ferrite magnetic microsphere by in-situ chemical co-precipitation following calcinations, and surface modifying of the hollow magnetic microsphere by 3-aminopropyltrime- thoxysilane via the sol-gel method. The average diameter of polymer microspheres was ca. 200 nm from transmission electron microscope (TEM) measurement. The structure of the hollow magnetic microsphere was characterized by using TEM and scanning electron microscope (SEM). The spinel-type lattice of CoFe₂O₄ shell layer was identified by using XRD measurement. The diameter of CoFe₂O₄ crystalline grains ranged from 54.1 nm to 8.5 nm which was estimated by Scherrer's equation. Additionally, the hollow silica/cobalt ferrite microsphere possesses superparamagnetic property after VSM measurement. The result of BET measurement reveals the hollow magnetic microsphere which has large surface areas (123.4m²/g). After glutaraldehyde modified, the maximum value of BSA immobilization capacity of the hollow magnetic microsphere was 33.8 mg/g at pH 5.0 buffer solution. For microwave absorption, when the hollow magnetic microsphere was compounded within epoxy resin, the maximum reflection loss of epoxy resins could reach -35dB at 5.4 GHz with 1.9 mm thickness.