Synthesis and characterization of thiophene-based donor–acceptor type polyimide and polyazomethines for optical limiting applications

In this communication we describe the design and synthesis of four new conjugated polymers (P1–P4) based on 3,4-ditetradecyloxythiophene. The required diamine monomer was prepared by a unique catalyst-free reduction process using hydrazine hydrate. The structures of the intermediates and polymers were established by FTIR, ¹H NMR spectroscopy. Molecular weights of polymers were determined by gel permeation chromatographic (GPC) method. Their electrochemical properties were investigated by cyclic voltammetry and linear optical properties were determined by UV–Visible absorption and fluorescence emission spectroscopic techniques. Further, their nonlinear optical properties were evaluated by Z-scan technique using Nd:YAG laser. These polymers showed strong optical limiting behavior with two-photon absorption (2PA) coefficients of the order of 10^?10 m/W, which are comparable to that of good optical limiting materials reported in the literature. Also, it has been observed that the optical nonlinearity enhanced with the increase in donor–acceptor strength of the polymer backbone.     

Synthesis and characterization of magnesium–carbon compounds for hydrogen storage

Magnesium (Mg) and carbon (C) compounds were synthesized by ball-milling a mixture of Mg and different graphites with different crystallinities. The materials were characterized by X-ray diffraction, X-ray absorption spectroscopy, and X-ray total scattering techniques. Hydrogen storage properties were also investigated. In the case of the material using low-crystalline graphite, a Mg and C compound was formed as main phase, and its chemical bonding state was similar to that of magnesium carbide (Mg₂C₃). The hydrogen absorption reaction of the Mg–C compound occurred at around 400 °C under 3 MPa of hydrogen pressure to form magnesium hydride (MgH₂) and the C–H bonds in the carbon material. The hydrogenated Mg–C material desorbed about 3.7 mass% of hydrogen below 420 °C with two processes, which were the decomposition of MgH₂ and the subsequent reaction of the generated Mg and the C–H bonds. From the results, it is concluded that the Mg–C compound absorb and desorb about 3.7 mass% of hydrogen below 420 °C.     

Synthesis and characterization of Y2O3 doped Na–β″-Al2O3 solid electrolyte by double zeta process

Y₂O₃ doped Na–β″–Al₂O₃ was firstly synthesized by double zeta process with Al₂O₃, Na₂CO₃, Li₂CO₃ and Y₂O₃ as the starting materials. Effects of the Y₂O₃ content on the microstructure and mechanical and electrical properties of the Na–β″-Al₂O₃ were studied. Both the density and the bending strength of the samples can be effectively improved by doping Y₂O₃. Only a part of Y³⁺ can be diffused into the Na–β″-Al₂O₃ crystal lattice, and the rest of Y³⁺ form the solid solution with Al₂O₃ in the grain boundaries, which restrains the grain growth and accelerates the densification of samples during the sintering process. The optimal amount of doping is 0.5 wt%, the bending strength and conductivity are approximately 16% and 52% higher compared to the un-doped samples, respectively.     

Synthesis and characterization of cellulose nanowhisker-reinforced-poly(ε-caprolactone) scaffold for tissue-engineering applications

Poly(ε-caprolactone) (PCL) is a bioresorbable and biocompatible polymer with assorted medical applications. However, remarkable hydrophobicity and nonosteoconductivity have stood as a barrier to limit its applications. The present study aims to modify the bulk characteristics of PCL to develop a polymeric scaffold with adequate structural and mechanical properties to support regenerated tissues. For this purpose, functionalized bacterial cellulose nanowhiskers (BCNW-g-βCD-PCL₂₀₀₀) are synthesized. Reinforcing PCL matrix with 4 wt % of the nanowhiskers resulted in a bionanocomposite with promoted bulk properties. Compared to neat PCL, the obtained bionanocomposite shows improvements of 115 and 51% in tensile strength and Young's modulus, respectively; 20% increase in hydrophilicity; 7% increase in degradation rate; and 6% decrease in crystallinity. Gas foaming/combined particulate leaching technique is used to develop highly porous structures of 86–95% porosity with interconnected macropores of mean pore diameters of 250–420 μm. Porous scaffolds showed compression modulus values of 5.3–9.1 MPa and would have promising applications in regenerative medicine. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48481.     

Processing and characterization of elastomeric polycaprolactone triol–citrate coatings for biomedical applications

In this paper we describe the synthesis, processing and characterization of a novel elastic polyester coating created by carrying out catalyst-free polyesterification between biocompatible and non-toxic multifunctional reactants, namely polycaprolactone triol and citric acid. The physico-chemical and surface properties of the resulting polyester coatings and films have been investigated. This new material has been characterized by matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-ToF-MS), nuclear magnetic resonance spectroscopy (NMR), Fourier-transform infra-red spectroscopy (FTIR), water-in-air contact angle measurements, scanning electron microscopy (SEM), thermal analysis (DSC), mechanical tests and swelling experiments. The polymer structure, surface properties (morphology and chemistry), mechanical integrity and hydration of the elastomer can be controlled by simple variation of the initial citric acid concentration in the polymer formation. This feature of the novel polyester material presents a significant development in the production of advanced coatings for biomedical applications.     

Preparation by sol–gel and solid state reaction methods and properties investigation of double perovskite Sr2FeMoO6

Double perovskite Sr₂FeMoO₆ was prepared by two ways consisting in sol–gel technique and solid-state reaction method. The resulting powders from gel and mixed oxides precursors showed microstructures consisting of very fine grains (0.5–0.8 μm) and a crystalline perovskite structure. The structural and microstructural properties of the double perovskite Sr₂FeMoO₆ powders as-prepared and ceramics were compared. Tetragonal Sr₂FeMoO₆ pellets were prepared from the two powders by spark plasma sintering at: 1000, 1100 and 1200 °C and then annealing at 1200 °C, 2 h in 5%H₂/Ar. The pellets presented different magnetic characteristics. The saturation magnetization of the samples prepared by sol–gel is close to those prepared by conventional synthesis method.     

Synthesis and characterization of Sb–SnO2/kaolinites nanoparticles

In this paper, we reported the synthesis of composite conductive powders of antimony-doped tin oxide (Sb–SnO₂) coated onto kaolinite. Structure and morphology of the samples were systematically characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared (FTIR) and X-ray photoelectron spectrum (XPS). The results showed that Sb–SnO₂ nanoparticles (< 10 nm) were successfully coated as thin layers on the surface of kaolinite. The antimony-doped tin oxide/kaolinite (ATK) composites retained the flake morphology like the original kaolinite and had a resistivity of 273.2 Ω·cm. Sb–SnO₂ layers were proved to attach to the kaolinite surface via the Sn–O–Si or Sn–O–Al bonds. The growth mode of Sb–SnO₂ layers onto the kaolinite was investigated.     

Synthesis and characterization of boron doped bismuth–calcium–cobalt oxide nanoceramic powders via polymeric precursor technique

In this study, boron doped calcium stabilized bismuth cobalt oxide nanocrystalline ceramic powders were successfully prepared from aqueous boric acid containing calcium–bismuth–cobalt acetate/poly(vinyl alcohol) hybrid precursor polymer solutions. Then, obtained ceramic powders were characterized via FT-IR, XRD, and SEM techniques. According to X-ray results, fcc and bcc phases coexist in the samples of the nanocrystalline ceramic powders. fcc peaks became sharper and bcc peak decreased with increasing boron content. Structural parameters for face centered cubic structure were calculated using the Scherrer equation. Moreover, dislocation densities and microstrain values were calculated for the nanocrystalline powder samples.     

Electrodeposition and characterization of Au–Cu–Cd alloys

The electrodeposition of Au–Cu–Cd alloys from cyanide baths was investigated under different hydrodynamic conditions. Alloys obtained at different current densities were characterized from the compositional, structural and morphological points of view. Depending on the electrodeposition current density, the deposit structure displays either one or two-phase disordered solid solutions; corresponding changes in mechanical properties were observed. Morphology and roughness show a marked smoothing transition when the current density is increased over the limit for the inception of Cu codeposition. The Cd²⁺ concentration in the bath is a critical factor for control of the electrodeposition process, especially in respect to compositional stability and absence of hydrogen incorporation. Alloy composition was shown to be critically affected by hydrodynamic conditions; strict control of flow conditions is needed in order to obtain alloys of desired and reproducible composition.     

Synthesis,characterization and charge transport properties of Pr–Ni Co-doped SrFe2O4 spinel for high frequency devices applications

Ferrites are materials of interest due to their broad applications in high technological devices and a lot of research has been focused to synthesize new ferrites. In this regard, an effort has been devoted to synthesize spinel Pr–Ni co-substituted strontium ferrites with a nominal formula of Sr_1-xPr_xFe_2-yNi_yO₄ (0.0 ≤ x ≤ 0.1, 0.0 ≤ y ≤ 1.0). The cubic structure of pure and Pr–Ni co-substituted strontium ferrite samples calcinated at 1073 K for 3 h has been confirmed through X-ray diffraction (XRD). Average sizes of crystallites (18–25 nm) have been estimated from XRD analysis and nanometer particle sizes of synthesized ferrites have been further verified by scanning electron microscopy (SEM). SEM results have also shown that particles are mostly agglomerated and all the samples possess porosity. It has been observed that at 298 K, the values of resistivity (ρ) increase, while that of AC conductivity, dielectric loss, and dielectric constants decrease with increasing amounts of Pr³⁺ and Ni²⁺ ions. The values of dielectric parameters initially decrease with frequency and later become constant and can be explained on the basis of dielectric polarization. Electrochemical impedance spectroscopy (EIS) studies show that the charge transport phenomenon in ferrite materials is mainly controlled via grain boundaries. Overall, synthesized ferrite materials own enhanced resistivity values in the range of 1.38 × 10⁹–1.94 × 10⁹ Ω cm and minimum dielectric losses, which makes them suitable candidates for high frequency devices applications.     

Interfacial characterization of YSZ-to-steel joints with Ag–Cu–Pd interlayers for solid oxide fuel cell applications

Yttria-stabilized zirconia (YSZ)/stainless steel joints made using two commercial silver-based interlayers containing palladium (58Ag–32Cu–10Pd and 65Ag–20Cu–15Pd), were systematically analyzed for the microstructures of the interlayer matrices, interlayer–steel interface, and interlayer–YSZ interface using scanning electron microscopy (SEM) and transmission electron microscopy coupled with energy dispersive spectroscopy (TEM/EDS). In the interlayer matrix, a face-centered cubic (FCC) Cu-rich phase formed in the vicinity of the YSZ and dissolved a significant amount of Zr from the ZrO₂ and minor amounts of Fe and Cr from the steel. The Cu-rich phase in the interlayer matrix in the vicinity of the steel substrate was the ordered phase Cu₃Pd with antiphase boundaries (APBs) and the L1₂ crystal structure. Silver particles precipitated within the Cu₃Pd phase in 58Ag–32Cu–10Pd; a Fe(Cr) needle-like phase, instead of Ag particles, precipitated within the Cu₃Pd phase in 65Ag–20Cu–15Pd. Although no reaction products at the interlayer–steel interface were found, dislocations appeared within the Ag- and Cu-rich phases. At the interlayer–YSZ interface, two reaction products, SiO₂ (impurity in YSZ) and Ti₃O₅ (from the reaction of YSZ with Ti impurities in the steel) were observed. Diffusion and chemical reactions led to the compositional changes and interface reconstruction, thereby yielding metallurgically sound YSZ/steel joints.     

Synthesis of ZnS–Mn nano-luminescent pigment for ink applications

In the present study, ZnS–Mn nano-luminescent pigments were synthesized, using co-precipitation method. Polyvinylpyrrolidine (PVP) surface modifier and Mn dopant concentrations were considered as affecting parameters. The luminescent ink was loaded with two different concentrations of pigments. The obtained ink was silk-screened on different types of fabrics mainly treated cotton, cotton and nylon. Structure, microstructure, luminescent properties of nano-pigments, inks and fabrics and also rheological properties of the inks were investigated. The results showed that the ceramic ink prepared with nano-luminescent pigment had high photoluminescence (PL) intensity. Moreover, the optimum concentrations of Mn and PVP for obtaining maximum PL intensity were found as 2 and 5 wt%, respectively. SEM images of fabrics indicated that nanoparticles were loaded, nonuniformly, on the fibers. The treated linen and nylon fabrics showed maximum and minimum PL intensity, respectively, due to ink penetration depth in the fabrics. Furthermore, washing fastness estimated for all fabrics was in the proper range.     

Synthesis and characterization of microporous silica–alumina membranes

The development of microporous ceramic thin layers is of prime interest for sensors or gas separation membranes working at high temperature. Microporous silica membranes can be easily prepared by the sol–gel process. However the microporosity of pure silica is rapidly modified by steam at high temperature. One way to improve hydrothermal stability is to use mixed-oxide membranes. In this work, microporous silica–alumina membranes were prepared by a simple and robust sol–gel method. Tetraethoxysilane was mixed with an acidic alumina hydrosol. Urea was added for preparing the alumina hydrosol, for controlling the mixed-oxide network polycondensation and also as porogen agent. FTIR and ²⁷Al NMR spectroscopic analyses showed that for Si/Al molar ratios up to 6/1, homogeneous mixed oxides were obtained with a random distribution of Al and Si atoms in the oxide lattice based on tetrahedral units. The derived supported layers were crack-free as demonstrated by scanning electron microscopy (SEM) observations. Their microporosity was investigated using ellipsoporosimetry (EP) with films supported on flat dense substrates. He, N₂ and CO₂ permeance measurements were performed for membranes deposited on porous tubular substrates. The measured values of He/N₂ and He/CO₂ ideal selectivities are in agreement with the microporous nature of the prepared layers.     

Synthesis and characterization of novel Ti3SiC2–cBN composites

In this paper, synthesis of novel super hard and high performance composites of titanium silicon carbide–cubic boron nitride (Ti₃SiC₂–cBN) was evaluated at three different conditions: (a) high pressure synthesis at ~ 4.5 GPa, (b) hot pressing at ~ 35 MPa, and (c) sintering under ambient pressure (0.1 MPa) in a tube furnace. From the analysis of experimental results, the authors report that the novel Ti₃SiC₂–cBN composites can be successfully fabricated at 1050 °C under a pressure of ~ 4.5 GPa from the mixture of Ti₃SiC₂ powders and cBN powders. The subsequent analysis of the microstructure and hardness studies indicates that these composites are promising candidates for super hard materials.     

Synthesis and characterization of chlorapatite–ZnO composite nanopowders

The influence of zinc oxide content on the formation of chlorapatite-based composite nanopowders in the mechanically alloyed CaO–CaCl₂–P₂O₅–ZnO system was studied. To mechanosynthesize composite nanopowders, different amounts of hydrothermally synthesized zinc oxide nanoparticles (0–10 wt%) were mixed with ingredients and then were mechanically activated for 5 h. Results showed that in the absence of zinc oxide, high crystalline chlorapatite nanopowder was obtained after 5 h of milling. In the presence of 4 and 7 wt% zinc oxide, the main product of milling for 5 h was chlorapatite–zinc oxide composite nanopowder. On increasing the zinc oxide content to 10 wt%, composite nanopowder was not formed due to improper stoichiometric ratio of the reactants. The crystallite size, lattice strain, volume fraction of grain boundary, and crystallinity degree of the samples fluctuated significantly during the milling process. In the presence of 7 wt% zinc oxide, the crystallite size and crystallinity degree reached 51±2 nm and 79±2%, respectively. During annealing at 900 °C for 1 h, the crystallization of composite nanopowder occurred and as a result the crystallinity degree rose sharply to 96±3%. In addition, the crystallite size increased to 77±2 nm after annealing at 900 °C. According to SEM and TEM images, the composite nanopowder was composed of both ellipse-like and polygonal particles with a mean size of about 98 nm.     

Synthesis and characterizations of BNT–BT and BNT–BT–KNN ceramics for actuator and energy storage applications

Dielectric and ferroelectric properties of 0.93Bi_0.5Na_0.5TiO₃–0.07BaTiO₃ (BNT–BT) and 0.93Bi_0.5Na_0.5TiO₃–0.06BaTiO₃–0.01K_0.5Na_0.5NbO₃ (BNT–BT–KNN) ceramics were studied in detail. An XRD analysis confirmed the single perovskite phase formation in both the samples. Room temperature (RT) dielectric constant (ε_r) ~1020 and 1370, respectively at 1 kHz frequency were obtained in the BNT–BT and BNT–BT–KNN ceramics. Temperature dependent dielectric and the polarization vs. electric field (P–E) studies confirmed the coexistence of ferroelectric (FE) and anti-ferroelectric (AFE) phases in the BNT–BT and BNT–BT–KNN ceramics. Substitution of KNN into the BNT–BT system decreased the remnant polarization, coercive field and the maximum strain percentage. The energy storage density values ~0.485 J/cm³ and 0.598 J/cm³ were obtained in the BNT–BT and BNT–BT–KNN ceramics, respectively. High induced strain% in the BNT–BT ceramics and the high energy storage density in the BNT–BT–KNN ceramics suggested about the usefulness of these systems for the actuator and the energy storage applications, respectively.     

Preparations and characterizations of Ca doped Ni–Mg–Mn nanocrystalline ferrites for switching field high-frequency applications

Ca-doped Ni–Mg–Mn spinel ferrites with compositions of Ni_0·5Mg_0·3Mn_0.2Ca_xFe_2-xO₄ (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) were prepared via sol-gel auto-ignition technique. TGA/DTA, FTIR, XRD, FESEM, and VSM were employed to evaluate the thermal, spectral, structural, morphological, and magnetic features of Ca-doped Ni–Mg–Mn spinel ferrites. TGA/DTA curves show the weight loss in the sample. This weight loss was attributed to the oxidation and decomposition of the sample contents at a temperature of 500 °C. XRD reveals a single-phase structure of the Ni–Mg–Mn nano ferrites. A single-phase orthorhombic structure was confirmed for Ca-doped Ni–Mg–Mn ferrites. Structural parameters such as lattice parameter, ‘da’, ‘db’, ‘dc’, and ‘dv’ were evaluated using unit cell software. The absorption peaks at 427 to 538 cm^?1 confirmed the spinel structure, which was evaluated using FTIR. FESEM analyses showed that the agglomerations increased with the doping of Ca in Ni–Mg–Mn ferrites. Remanence, Y–K angles, saturation, coercive force, magnetic squareness, magnetic moment, and anisotropy constant were determined for Ca-doped Ni–Mg–Mn spinel ferrite samples. It is noticed that saturation increases from 29.157 to 51.322 emu/g, whereas remanence increased from 5.34 to 9.40 emu/g, respectively. The permeability, anisotropy constant, and magnetic moments were also found to increase with Ca doping. However, the Y–K angles increased with Ca concentration in Ni–Mg–Mn nano ferrites. In addition, the switching field distribution (SFD) and high-frequency response of all the Ca-doped Ni–Mg–Mn samples were also evaluated. Ca-doped Ni–Mg–Mn samples are suggested to be suitable for switching, filters, inductors, and microwave absorption applications because of the superparamagnetic nature of the prepared spinel ferrites.     

Synthesis and characterization of epoxy–silicone–polythiophene interpenetrating polymer network for corrosion protection of steel

Polymer alloys, particularly interpenetrating polymer networks (IPNs) exhibit excellent coating properties. Often combination of polymers result in IPNs with controlled morphologies and synergistic behavior. In this study, corrosion-resistant IPNs were prepared from immiscible resins (epoxy, silicone and thiophene) using a cross-linking agent and a catalyst. GPC, FTIR, NMR, TG, DTA and SEM studies used to fix the best performing IPN. Surface morphology studies using SEM confirm the incorporation of silicone and polythiophene in to the epoxy polymer to form homogeneously micro structured IPN. The heat-resistance of the IPN was determined as per ASTM 2485. The improved corrosion resistance of the IPN was evaluated by AC impedance measurements.     

Synthesis and characterization of V–C60/TiO2 photocatalysts designed for degradation of methylene blue

C₆₀/TiO₂ and V–C₆₀/TiO₂ composite photocatalysts were prepared with titanium (IV) n-butoxide (TNB) by a sol–gel method. Fullerene had absorptive and semiconducting properties, and vanadium could enhance the photogenerated electron transfer. The V–C₆₀/TiO₂ composite shows a good photo-degradation activity. XRD patterns of the composites showed that the C₆₀/TiO₂ composite contained a mixture of anatase and rutile phase forms while the V–C₆₀/TiO₂ composite contained a typical single and clear anatase phase. The surface properties seen by SEM and FE-SEM present a characterization of the texture on C₆₀/TiO₂ and V–C₆₀/TiO₂ composites and showed a homogenous composition in the particles for the titanium sources used. The EDX spectra for the elemental identification showed the presence of C and Ti with strong V peaks for the V–C₆₀/TiO₂ composite. From the photocatalytic results, the excellent activity of the C₆₀/TiO₂ and V–C₆₀/TiO₂ composites for degradation of methylene blue under UV irradiation could be attributed to both the effects between photocatalysis of the supported TiO₂ and charge transfer of the fullerene, and the introduction of vanadium to enhance the photogenerated electrons transfer.