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Dielectric properties of Bi-substituted LDHs synthesized by co-precipitation and sol-gel methods

Abstract

Magnesium-aluminum-bismuth layered double hydroxides (Mg3Al1−xBix; LDHs) were prepared using both coprecipitation and sol-gel methods. For the preparation of Mg/Al/Bi LDH by the co-precipitation method, the appropriate amounts of dissolved starting materials (Al(NO3)3 · 9H2O, Mg(NO3)2 · 6H2O and Bi(NO3)3 · 5H2O) were mixed with a solution of NaHCO3:NaOH. In the sol-gel processing, the precursor Mg–Al–Bi–O gels were synthesized using the same starting materials and ethylene glycol as complexing agent. The mixed-metal oxides obtained by subsequent heating of Mg–Al–Bi–O gels at 650 °C were reconstructed to Mg3Al1−xBix LDHs in water at 80 °C. All the synthesized products were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and dielectric measurements.

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Dynamic magnetoelastic properties of TbxHo0.9−xNd0.1(Fe0.8Co0.2)1.93/epoxy composites

Abstract

TbxHo0.9−xNd0.1(Fe0.8Co0.2)1.93/epoxy (0 ⩽ x ⩽ 0.40) composites are fabricated in the presence of a magnetic field. The structural and dynamic magnetoelastic properties are investigated as a function of both magnetic bias field Hbias and frequency f at room temperature. The composites are formed as textured orientation structure of 1–3 type with 〈1 0 0〉 preferred orientation for x ⩽ 0.10 and 〈1 1 1〉-orientation for x ⩾ 0.25. The composites generally possess insignificant eddy-current losses for frequency up to 50 kHz, and their dynamic magnetoelastic properties depend greatly on Hbias. The elastic modulus (E3 H and E3 B) shows a maximum negative ΔE effect, along with a maximum d33, at a relatively low Hbias ~ 80 kA/m, contributed by the maximum motion of non-180° domain-wall. The 1–3 type composite for x ⩾ 0.25 shows an enhanced magnetoelastic effect in comparison with 0 to 3 type one, which can be principally ascribed to its easy magnetization direction (EMD) towards 〈1 1 1〉 axis and the formation of 〈1 1 1〉-texture-oriented structure in the composite. These attractive dynamic magnetoelastic properties, e.g., the low magnetic anisotropy and d33 , max as high as 2.0 nm/A at a low Hbias ~ 80 kA/m, along with the light rare-earth Nd element existing in insulating polymer matrix, would make it a promising magnetostrictive material system.

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Effect of addition of Cu on the properties of eutectic Sn-Bi solder alloy

Abstract

The present work reports the effect of Cu addition on the melting point, hardness and electrical resistivity of Sn-57 wt.% Bi eutectic solder alloy. Both binary eutectic Sn-57 wt.% Bi and ternary Sn-(57-x)Bi-xCu (x = 0.1, 0.3, 0.5, 0.7 and 1 wt.%) alloys containing various amounts of Cu were developed by melting casting route. The microstructure of the various solder alloys was analyzed using an optical microscope and a SEM. The variation in melting point, hardness and electrical resistivity of the Sn-Bi eutectic solder alloys with the addition of Cu was determined. The melting point of the eutectic Sn-Bi solder alloy was found to decrease up to the addition of 0.7 wt.% Cu. However, further addition of Cu led to an increase in the melting point of the alloy. Addition of Cu led to an increase in the hardness of the eutectic Sn-Bi solder alloy whereas the electrical resistivity of this alloy was found to increase up to the addition of 0.7 wt.% of Cu beyond which a decrease in the electrical resistivity was observed. A change in the microstructure of the solder alloy was observed when it was reheated above the melting temperature.

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The effects of deposition potential on the optical, morphological and mechanical properties of DLC films produced by electrochemical deposition technique at low voltages

Abstract

Diamond-like carbon (DLC) films were electrochemically deposited onto indium tin oxide (ITO) substrates using acetic acid and deionized water as electrolyte at low deposition voltages (2.4 V and 60 V). The transmittance of the films was investigated by UV spectrometry. Transmittance measurements versus wavelength revealed that the films transmit 86 % to 89 % light in visible region and band gap of the films varies between 3.87 eV and 3.89 eV. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used for structural characterization to evaluate surface morphology of the DLC films. The grain size and the surface roughness increased for the films prepared at higher deposition potential, while their measured average height decreased. The mechanical properties (hardness H and elastic modulus Er) were determined from load-displacement curves which were obtained by using nanoindentation method. Hardness and elastic modulus of the films increased as the deposition voltage of the films increased from 2.4 V to 60 V.

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Growth, solvent effect, optical and electrical properties of sodium 4-hydroxybenzenesulfonate dihydrate

Abstract

Single crystal of sodium 4-hydroxybenzenesulfonate dihydrate (Na-4-HBS) was grown from an aqueous solution by slow evaporation method. Powder X-ray diffraction study was carried out to identify the lattice parameters of the crystal. FT-IR spectral analysis confirmed the existence of various functional groups in the compound. The optical transmittance, cut-off wavelength and band gap energy were estimated from the UV-Vis studies. Photoluminescence studies revealed the transition mechanism by optical excitation. The variation of dielectric properties and AC conductivity of the grown crystal with frequency was studied at different temperatures. Measurements of mechanical properties of Na-4-HBS were carried out to find the hardness of the material. The laser induced surface damage threshold and relative second harmonic generation nonlinear optical properties of the grown crystal were studied using Q-switched Nd:YAG laser.

Open access
Influence of Bi on dielectric properties of GaAs1−xBix alloys

Abstract

Pure GaAs and GaAs1−xBix alloys with different Bi ratios (1 %, 2.5 %, 3.5 %) fitted with silver contacts were measured with a dielectric spectroscopy device. Dielectric characterization was performed at room temperature in the frequency range of 0.1 Hz to 1 MHz. GaAs exhibits three relaxation regions corresponding to space-charge, dipolar and ionic polarizations in sequence with increasing frequency while GaAs1−xBix samples show only a broad dipolar polarization in the same frequency range. This result proves the filling of the lattice with Bi through making a new bonding reducing the influence of ionic polarization. This finding supports the previous results concerning optical properties of GaAs1−xBix, presented in the literature.

Open access
An Influence of Factors of Flow Condition, Particle and Material Properties on Slurry Erosion Resistance

Abstract

The degradation of materials due to slurry erosion is the serious problem which occurs in the power industries. The paper presents actual knowledge about an influence of individual factors connected with flow conditions, particles and material properties on the slurry erosion resistance. Among the factors connected with operating conditions, an influence of impact angle, and velocity of impact, particle concertation and liquid temperature have been described. In case of the factors connected with solid particle properties, an influence of the size, shape and hardness have been discussed. In the part devoted to the impact of material properties, due to different types of materials, the issues of resistance to erosion of slurries related to the properties of steel, ceramics and polymers are discussed separately. In the paper has been shown that a change of any of mentioned factors causes a change in the erosion rate due to the synergistic effects that accompany to slurry degradation.

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The Influence of Pulsating Tensile Stress on Residual Magnetic Field of P91 Steel Samples

ABSTRACT

Measurements of Residual Magnetic Field RMF (the tangential component parallel to the load direction) were taken on the surface of P91 steel plate samples (X10CrMoVNb9-1) subjected to periodic pulsating tensile cyclic loads with the use of flux-gate and magneto impedance sensors, and preliminary measurement results are compiled and analyzed. The study investigates how the microstructure and load cycle parameters affect the RMF changes due to stress variations. Each combination of parameters: microstructure and load cycle corresponds to the characteristic variability pattern of magnetization and its maximum and minimum values.

Open access
Luminescent properties of a novel reddish-orange phosphor Eu-activated KLaSiO4

Abstract

A novel reddish-orange emitting phosphor Eu-activated KLaSiO4 was synthesized by the conventional solid-state reaction at 1200 °C. The luminescence properties of KLaSiO4:Eu phosphor were investigated, and the critical concentration of the activator ion (Eu3+) was established as 0.02 mol per formula unit. Chromaticity coordinates of a typical KLa0.98SiO4:0.02Eu phosphor were x = 0.614 and y = 0.385. The phosphor exhibited reddish-orange luminescence with dominating emission at 612 nm, corresponding to 5D07F2 of Eu3+. Furthermore, the phosphor was characterized by excellent thermal stability, implying its potential use in white light emitting diodes.

Open access
Mixed structure Zn(S,O) nanoparticles: synthesis and characterization

Abstract

In the present work, mixed structure Zn(S,O) nanoparticles have been synthesized using solution based chemical coprecipitation technique. Two different zinc sources (Zn(CH3COO)2·2H2O and ZnSO4·7H2O) and one sulfur source (CSNH2NH2) have been used as primary chemical precursors for the synthesis of the nanoparticles in the presence and absence of a capping agent (EDTA). The structural, morphological, compositional and optical properties of the nanoparticles have been analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transmission infra-red (FT-IR) and UV-Visible (UV-Vis) spectroscopy. XRD revealed the formation of mixed phases of c-ZnS, h-ZnS and h-ZnO in the synthesized nanoparticles. The surface morphology was analyzed from SEM micrographs which showed noticeable changes due to the effect of EDTA. EDX analysis confirmed the presence of zinc, sulfur and oxygen in Zn(S,O) nanoparticles. FT-IR spectra identified the presence of characteristic absorption peaks of ZnS and ZnO along with other functional group elements. The optical band gap values were found to vary from 4.16 eV to 4.40 eV for Zn(S,O) nanoparticles which are higher in comparison to the band gap values of bulk ZnS and ZnO. These higher band gap values may be attributed to the mixed structure of Zn(S,O) nanoparticles.

Open access