Structural, FTIR, Optical and Dielectric Properties of Zn1-xAlxO Ceramics For Advanced Applications

We report here the structural, FTIR, optical and dielectric properties of Zn1−xAlxO with x = 00.00 < x ≤ 0.20)). The wurtzite structure is conformed to all samples and the lattice constants, crystallite diameter, porosity and average crystalline size are generally decreased. The residual stress is compressive for pure samples, but it is changed to tensile for the doped samples. Interestingly, Debye temperature and elastic modulus are increased as x increases to 0.10, followed by a decrease at x = 0.20. Two different energy gaps Egh and Egl are apparent for each sample, corresponding of two transition absorption peaks. Interestingly, the ΔE = (Egh – Egl) ~ 0.60 for all samples. Further, the residual dielectric constant is decreased by increasing x to 0.10, followed by a sharp increase at x = 0.20 while the opposite behavior for (N/m*). The dielectric constant ε′ is slightly increased as x increases to 0.025, followed by a sharp increase as x increases to 0.20, as well as the ac conductivity σ/. The conduction is electronic for x ≤ 0.025 samples, but it is changed to hole with an increase of x to 0.20. The binding energy Wm was decreased as x increases to 0.20, but there is no exact trend against x for the behaviors of minimum hopping distance Rmin and density of localized states N. In addition, the density of states at Fermi level N (EF) has an optimum value at 195 KHz for all samples. The F-factor for solar cell design is increased as x increases to 0.10, but it is almost constant at x = 0.20. The Cole-Cole plot is a straight line for x = 0.00, a semicircle arc for x = 0.025 and a complete semicircle for x ≥ 0.05. The impedance resistance of grain Z\(g) and grain boundaries Z\(gb) are gradually decreased by increasing x to 0.20. These outcomes indicate that the addition of Al to ZnO shifts the mechanical, optical, and dielectric medium to higher values, which is strongly recommended for the design of optoelectronic and solar cell instruments.

Mechanical and Dynamic Mechanical Properties of the Amino Silicone Oil Emulsion Modified Ramie Fiber Reinforced Composites

The mechanical and dynamic mechanical properties, interface adhesion and microstructures of the amino silicone oil emulsion (ASO) modified short ramie fiber reinforced polypropylene composites (RFPCs) with different fiber fractions were investigated. The RFPCs were made through a combined process of extrusion and injection molding. Mechanical property tests of the RFPCs revealed enhancements in tensile and flexural strengths with increase of the fiber fraction due to the high stiffness of the fiber filler and a better interfacial bonding from ASO treatment. The dynamic mechanical analysis (DMA) results indicated that fiber incorporation plays an important role in DMA parameters (storage modulus, loss modulus, and damping ratio) at Tg by forming an improved interfacial adhesion and providing more effective stress transfer rate and energy dissipation between matrix and fiber. The phase behavior analysis suggests all the RFPCs are a kind of heterogeneity system based on the Cole-Cole plot analysis.

Evolution of spin freezing transition and structural, magnetic phase diagram of Dy$$_{2-\textit{x}}$$La$$_\textit{x}$$Zr$$_{2}$$O$$_{7}$$ (0 $$\le$$ $$\textit{x}$$ $$\le$$ 2.0)

Dy$$_{2}$$ 2 Zr$$_{2}$$ 2 O$$_{7}$$ 7 a disordered pyrochlore system, exhibits the spin freezing behavior under the application of the magnetic field. We have performed detailed magnetic studies of Dy$$_{2-\textit{x}}$$ 2 - x La$$_\textit{x}$$ x Zr$$_{2}$$ 2 O$$_{7}$$ 7 to understand the evolution of the magnetic spin freezing in the system. Our studies suggest the stabilization of the pyrochlore phase with the substitution of non-magnetic La along with the biphasic mixture of fluorite and pyrochlore phases for the intermediate compositions. We observed that the spin freezing (T$$_{f}$$ f $$\sim$$ ∼ 17 K) at higher La compositions (1.5 $$\le$$ ≤ $$\textit{x}$$ x $$\le$$ ≤ 1.99) is similar to the field-induced spin freezing for low La compositions (0 $$\le$$ ≤ $$\textit{x}$$ x $$\le$$ ≤ 0.5) and the well-known spin ice systems Dy$$_{2}$$ 2 Ti$$_{2}$$ 2 O$$_{7}$$ 7 and Ho$$_{2}$$ 2 Ti$$_{2}$$ 2 O$$_{7}$$ 7 . The low-temperature magnetic state for higher La compositions (1.5 $$\le$$ ≤ $$\textit{x}$$ x $$\le$$ ≤ 1.99) culminates into a spin-glass like state below 6 K. Cole–Cole plot and Casimir-du Pr$$\acute{e}$$ e ´ fit shows the narrow distribution of spin relaxation time in these compounds.

Correlation Between Structural and Ionic Transport Properties of Lithium-ion Hybrid Gel Polymer Electrolytes Based PMMA-PLA

In this work, the investigation on hybrid gel polymer electrolytes (HGPEs) comprising polymethyl methacrylate (PMMA)-polylactic acid (PLA) incorporate with LiTFSI were carried out. The HGPEs samples were characterized for their structural, thermal and ionic conduction properties via FTIR, XRD, DSC, and EIS. FTIR analysis show the indication of the interaction between PMMA-PLA hybrid polymer and LiTFSI with the appearance of peak and changes in peak shifting at the coordinating site from polymer blend. The DSC analysis shows that the glass transition temperature (Tg) of HGPEs was decreased as the LiTFSI content increases, suggesting that the HGPEs system has good thermal stability. The ionic conductivity was calculated based on the Cole-Cole plot and the incorporation of LiTFSI with 20 wt. % into hybrid polymer matrixes revealed the maximum ionic conductivity of 1.02 х 10-3 S cm-1 at room temperature as the amorphous phase increases. The dissociation of ions and transport properties of the PMMA-PLA-LiTFSI systems was determined via dielectric response approach and it was found that number density (ɳ), mobility (μ), and diffusion coefficient (D) of mobile ions follows ionic conductivity trend.

Investigation of Mg2+ ion on Structural, Morphological, FTIR, Dielectric and AC Conductivity of PVDF-HFP Based Solid Polymer Electrolytes and Application to Electrochemical Cell

In this paper, solid polymer electrolytes comprising of Poly (vinylidene-fluoride-hexafluoropropylene) (PVDF-HFP) polymer and Mg (ClO4)2 salt were prepared by employing the solution casting technique. The fabricated polymer-salt electrolyte membranes are exposed to XRD, FTIR and SEM studies. The real and imaginary part of dielectric permittivity is illustrated with the Cole-Cole plot. Static dielectric constant \({(\epsilon }_{s})\), dynamic dielectric constant \(\left({\epsilon }_{\infty }\right)\), dielectric strength \(({\Delta }\epsilon\)), dielectric loss (tanδ) and relaxation time (τ) are determined using the Cole-Cole plot. The electrochemical properties; cell stability, cell discharge characteristics, dc and ac conductivity are analyzed. Structural studies of XRD peaks are broadened to confirm the amorphous phase of polymer matrix. Morphological studies shows the presence of interlinked micro-pores promote for ease of mobility of Mg2+ ions which attribute to enhance ionic conductivity. The static dielectric constant \({(\epsilon }_{s})\), dynamic dielectric constant \(\left({\epsilon }_{\infty }\right)\), dielectric strength \(({\Delta }\epsilon\)), dielectric loss (tanδ) reach maximum but relaxation time (τ) decreases for an optimal concentration ratio of (100:40) PVDF-HFP: Mg (ClO4)2 that reveals fast hopping of ions from one site of the polymer chain to another. The highest ionic conductivity of 7.73333x 10− 4 Scm− 1 is obtained at room temperature for [PVDF-HFP: Mg(ClO4)2] polymer-salt electrolyte. The cell discharge characteristics of OCV and SCC of Mg/ [PVDF-HFP: Mg(ClO4)2] /I + C cell are found to be 1.8 V and 120 mA respectively The electrochemical stability was observed with a constant voltage of 0.43volt in a positive cycle and 0.4 volts of negative potential which favors an electrochemical membrane for battery applications

Influence of Cr2O3 Nanoparticles on the Structural, Optical, Thermal and Electrical Properties of PEO/CMC Nanocomposites

In the present paper, different concentrations of chromium oxide (Cr2O3) nanoparticles were incorporated within PEO/CMC polymer blend to produce nanocomposite films using the casting method. The X-ray diffraction was performed on PEO/CMC-Cr2O3 nanocomposites. The main X-ray peaks of Cr2O3 were observed and defined as cubic structure and orthorhombic shape with an average particle size of the Cr2O3 ~ 50-80 nm. The decrease of some IR bands after the addition of Cr2O3 nanoparticles was found attributed to the interactions between PEO/CMC and Cr2O3. Effect of Cr2O3 nanoparticles on optical properties such as absorbance and optical energy gap (Eg) were characterized using UV-Vis spectroscopy. The Eg was reduced after the addition of Cr2O3 nanoparticles. The AC conductivity (sac), dielectric constant (ε′), dielectric loss (ε′′) and the dielectric modulus (M′ and M′′) were calculated at frequency range 0.1 Hz-7 GHz. The increases of direct conductivity (σdc) imply that the free charge density or of the charge mobility that results. The estimated values of both ε′ and ε′′ were decreased with increases of frequency. The addition of Cr2O3 nanoparticles causes the formation of a charge-transfer complex. The Cole-Cole plot between (M′ and M′′) shows a semi-circular shape confirm discuses according to a non‐Debye method.

A New Ceramic Sr2Fe8O18: Crystal Structure and Analysis of Application on Solid Electrolytes

All-solid-state batteries have been expected to overcome the safety problem of present lithium-ion batteries including organic liquid electrolytes. The materials with high ionic conductivity are urgently needed. In this paper, we reported a new ionic crystal Sr2Fe8O18 which can be applicated on solid electrolyte. Sr2Fe8O18 is a typical p-type semiconductor and shows a layered monoclinic crystal structure. The resistivities of Sr2Fe8O18 in the temperature range of 20 ~ 145 °C were above 107 Ω•cm. The microstructure of Sr2Fe8O18 was flaky, and the size of flaks were 1 µm ~ 5 µm. The E- P curve suggested that it was a ferroelectric semiconductor and had small ferroelectric effect. The dielectric response study (Cole-Cole plot) showed that Sr2Fe8O18 had two separated relaxation time, each of which contained a group of relaxation. The ionic conductivity σ of the sample was calculated to be 0.2196 × 10− 4 S/cm. The conductive mechanism which confirmed by the results of First principle calculation at 300K is mainly sublattice vacancy cation diffusion with self-diffusion coefficient D of 1.794 × 10− 5cm2/s. Fe ion has two dimensional diffusion path (x and y axial), and Sr ion has on dimensional diffusion path (x axial). The crystal structure of Sr2Fe8O18 shows tremendous potential application on the solid electrolyte preparation.

Dirhamnolipid ester – formation of reverse wormlike micelles in a binary (primerless) system

We report new dirhamnolipid ester forming reverse wormlike micelles in nonpolar solvents without the addition of any primer. Therefore, these compounds represent a rare case of a binary system showing this gel-like behavior. In this study, the influence of the concentration of the rhamnolipid ester and the ester alkyl chain length on the rheological properties of the reverse wormlike micelles in toluene was investigated in detail. Highly viscoelastic solutions were obtained even at a relatively low concentration of less than 1 wt %. The phase transition temperatures indicate that the formation of reverse wormlike micelles is favored for dirhamnolipid esters with shorter alkyl chain lengths. Oscillatory shear measurements for the viscoelastic samples reveal that the storage modulus (G') and the loss modulus (G'') cross each other and fit the Maxwell model very well in the low-ω region. As is typical for wormlike micelle systems, the normalized Cole–Cole plot of G''/G'' max against G'/G'' max was obtained as a semicircle centered at G'/G'' max = 1. The formation of network structures was also verified by polarized light microscopy. The sample was birefringent at ambient temperature and anisotropic at an elevated temperature. Differential scanning calorimetry analysis yielded a transition enthalpy of about ΔH SG/GS = ±7.2 kJ/mol. This value corresponds to a strong dispersion energy and explains the formation of the highly viscous gels by the entanglement of wormlike micelles through the interaction of the alkyl chains.