Bulletin of Materials Science

Preparation and characterization of a low-cost, novel steam-activated bamboo charcoal (BC) and poly(methacrylate) (PMAA) bound with chitosan (CTS) to form chitosan/bamboo charcoal/poly(methacrylate) (CTS/BC/PMAA) composite beads is reported for the first time in this paper. The characteristics are revealed by techniques such as X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Brunauer Emmett Teller (BET), solution pH and pH at point of zero charge $$(\hbox {pH}_{\mathrm {pzc}})$$ . The composite beads possessed a dominant acidic surface group of 0.663 mmol $$\hbox {g}^{\mathrm {-1}}$$ , as revealed by Boehm titration method. This acidity was confirmed by its solution pH of 6.46; $$\hbox {pH}_{\mathrm {pzc}}$$ of 6.70 and increase in oxygen surface via XPS analysis. $$\hbox {N}_{\mathrm {2}}$$ adsorption–desorption isotherms at 77 K of the beads revealed high BET surface area (SA) of 681.15 $$\hbox {m}^{\mathrm {2}}\hbox {g}^{\mathrm {-1}}$$ . Langmuir model affords a SA of 773.34 $$\hbox {m}^{\mathrm {2}}\hbox {g}^{\mathrm {-1}}$$ . SEM showed the microporous nature of the composite beads. The properties of CTS/BC/PMAA composite beads were compared to CTS/BC and neat BC. Thermal stability and successful coating of 5.1 wt% of PMAA and 6.8 wt% of CTS to CTS/BC/PMAA beads were shown by DSC and TGA analyses. The composite beads showed low carbon particle released at pH 7.4 and 6.8. Furthermore, dynamic adsorption revealed that CTS/BC/PMAA composite beads can be used to capture a polar substance, such as creatinine.

Materials with small particle size are being extensively used in composites and hybrid materials. Exfoliated clay-polymer hybrids show enhanced properties. Exfoliation of clay platelets can be affected by selecting dispersing agents. In the present work, clay dispersed by natural dispersant (soap stone powder), cetyl trimethyl ammonium bromide (CTAB) dispersed clay and acid clay (amorphous clay) are taken. They are then polymerized with poly methyl methacrylate (PMMA) by solution intercalation method. The thermal stability of these different clay-PMMA hybrids have been studied and compared with that of pure PMMA by differential scanning calorimeter (DSC). The bonding of clay with PMMA has been studied by IR. Morphology of clay-PMMA hybrids has been shown by SEM and XRD which indicate partially exfoliated structure in T606-4 and intercalated structures in T606-6 and T606-2.

$${\mathrm{SrBi}}_{0.95}{\mathrm{Sm}}_{0.05}{\mathrm{Ta}}_{2-x}{\mathrm{V}}_{x}{\mathrm{O}}_{9}$$ (x = 0, 0.05, 0.1, 0.2) compounds, which have been studied through X-ray diffraction Rietveld refinement, Fourier transform infrared (FTIR), absorption and emission techniques, were prepared through the molten salt method. All samples were refined in the orthorhombic system without any secondary phase detected. The Ta–O bond strength in the compounds is revealed by FTIR and Rietveld measurements. Along with scanning electron microscopic analysis, ceramics also consist of plate-like grains that decreased with the V content increasing. The difference in absorption spectra is attributed to localized tail stats within the bandgap. According to the impedance and AC conductivity results, after introducing vanadium into the structure, the V-doped $${\mathrm{SrBi}}_{0.95}{\mathrm{Sm}}_{0.05}{\mathrm{Ta}}_{2}{\mathrm{O}}_{9}$$ ceramics exhibit higher conductivity. The reason that x = 0.1 ceramic has the smallest semicircle radius referring to a higher efficient charge carrier transfer is that this ceramic sample is mainly composed of large particles. Samarium emits orange-red colour at wavelength 599 nm, which is attributed to $${}^{4}\mathrm{G}_{\frac{5}{2}}\to { }^{6}\mathrm{H}_{\frac{7}{2}}$$ transition. Regarding photoluminescence intensity, the more vanadium ions are introduced into the lattice, the fewer emission peaks are obtained. The latter has been interpreted in terms of the inhibition of the transfer of energy from one ion to another. In essence, The red photoluminescence emission intensity of Sm $${}^{3+}$$ ions were successfully enhanced in $${\mathrm{SrBi}}_{0.95}{\mathrm{Sm}}_{0.05}{\mathrm{Ta}}_{2-x}{\mathrm{V}}_{x}{\mathrm{O}}_{9}$$ (x = 0.05).

Single-phase La-substituted bismuth ferrite (Bi $_{\boldsymbol {1-x}}$ La $_{\boldsymbol {x}}$ FeO $_{\mathbf {3}}$ ) nanoparticles have been synthesized by thermal decomposition of a glyoxylate precursor. The crystal structure transition of BiFeO $_{\mathbf {3}}$ from the rhombohedral (R3c) to the cubic $\boldsymbol {Pm}\bar {\mathbf {3}}\boldsymbol {m}$ structure by La addition was confirmed by X-ray diffraction and infrared spectrometry methods. Furthermore, the Bi $_{\boldsymbol {1-x}}$ La $_{\boldsymbol {x}}$ FeO $_{\mathbf {3}}$ nanoparticles showed a weak ferrimagnetism behaviour, while the magnetization increased from 0.18 to 0.48 emu g $^{\mathbf {-1}}$ with La substitution. The Bi $_{\boldsymbol {1-x}}$ La $_{\boldsymbol {x}}$ FeO $_{\mathbf {3}}$ nanoparticles exhibited strong absorption in the visible region with the optical band gap calculated from Tauc’s plot in the range of 2.19–2.15 eV. Furthermore, the effects of La substitution on the photodegradation of the methylene blue (MB) under visible light were also studied. The photodegradation of MB dye was enhanced from 64 to $\sim $ 99% with increasing La substitution from $\boldsymbol {x =}$ 0 to 0.1 and then decreased to 8% for $\boldsymbol {x =}$ 0.15.

Gibbs energies of formation of CoF2 and MnF2 have been measured in the temperature range from 700 to 1100 K using Al2O3-dispersed CaF2 solid electrolyte and Ni+NiF2 as the reference electrode. The dispersed solid electrolyte has higher conductivity than pure CaF2 thus permitting accurate measurements at lower temperatures. However, to prevent reaction between Al2O3 in the solid electrolyte and NiF2 (or CoF2) at the electrode, the dispersed solid electrolyte was coated with pure CaF2, thus creating a composite structure. The free energies of formation of CoF2 and MnF2 are (± 1700) J mol−1; {fx37-1} The third law analysis gives the enthalpy of formation of solid CoF2 as ΔH° (298·15 K) = −672·69 (± 0·1) kJ mol−1, which compares with a value of −671·5 (± 4) kJ mol−1 given in Janaf tables. For solid MnF2, ΔH°(298·15 K) = − 854·97 (± 0·13) kJ mol−1, which is significantly different from a value of −803·3 kJ mol−1 given in the compilation by Barinet al.

Two different commercially available sources of alumina and silica were used to study the formation and densification behaviour of mullite prepared by solid-oxide reaction technique in a single firing. Phase analysis and densification studies were carried out on the samples sintered between 1200 and $$1600^{{\circ }}\hbox {C}$$ . Effect of addition of 1–6 wt% MgO on the sintered mullite ceramics was also studied. MgO was found to improve the density values for all the compositions till 4 wt% and with higher addition it deteriorated, mainly due to higher extent of liquid phase formation. Mullite formation was found to start below $$1200^{{\circ }}\hbox {C}$$ and constituent oxides were found even at $$1600^{{\circ }}\hbox {C}$$ ; however, addition of 4 wt% MgO was found to complete the mullite formation at $$1600^{{\circ }}\hbox {C}$$ for all the compositions. Microstructural studies showed grain growth in the compositions containing MgO and higher impurities due to formation of greater extent of liquid phase.

The pH and electrical conductivity are important properties of nanofluids that have not been widely studied, especially with regard to temperature and ultrasonication energy. To study the factors that affect the pH and electrical conductivity of magnesium oxide–ethylene glycol (MgO–EG) nanofluid, the effects of temperature, volume fraction, particle size and ultrasonication energy were investigated. Two different sizes of MgO were dispersed in EG base fluid up to the volume fraction of 3%, and the pH and electrical conductivity were monitored between the temperatures of 20 and 70∘C. Characterization by transmission electron microscopy and size analyses revealed the morphology and sizes of the nanoparticle samples. The pH values dropped consistently with the increase of temperature, while electrical conductivity value increased with the increase of temperature. The experimental result showed that the increase in the MgO volume fraction increased both the pH and electrical conductivity values of the MgO–EG nanofluid. There was no recognizable influence of ultrasonication energy density on the pH and electrical conductivity of the nanofluid; therefore, it was concluded that temperature, volume fraction and particle size are the predominant factors affecting both the pH and electrical conductivity of MgO–EG nanofluid within the present experimental conditions.

The Sutton–Chen potential was used to simulate the process of solidification of Ni nanoparticles at temperatures ranging from 1000 to 100 K in the cooling process. The number of atoms per particle ranged from 500 to 4000. The results show an expected increase in solidification temperature with size. Analysis of the first-neighbour interatomic distance as a function of temperature showed exponential behaviour up to the phase transition. A reduction in the interatomic distance was observed at small sizes below the established lattice parameter. Characterization of the surface as a function of the number of first neighbours allowed interpretation and quantification of the surface planes as a function of particle size at low temperatures.

In this study, photodegradation of the non-biodegradable azo dye acid orange 7 (AO7) was selected as modal target in aqueous solution using graphene–TiO 2 (GR–TiO2) hybrid nanocomposite, was well investigated and elucidated. The crystal phase, special surface area, microscopic analysis of the GR–TiO2 and also, chemical state of the photocatalysts were studied by powdered X-ray diffraction (PXRD), Raman spectrum, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution scanning electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), Brunauere Emmette Teller (BET) method and photoluminescence spectroscopy (PL). During photocatalysis, the GR–TiO2 nanocomposite improved photocatalytic performance compared with that of pure TiO 2 towards AO7 organic azo-dye degradation. The reusability test of photocatalytic activity was also examined. A conceivable reaction mechanism was suggested and nattered on the basis of tentative effects. Therefore, the GR–TiO2 nanomaterial can be widely used as a photocatalyst for treating the organic dye contaminant in the field of environmental protection.

The temperature- and frequency-dependent relaxation processes in films of a polymeric blend comprising a polyvinyl alcohol (PVA)/polyvinyl acetate (PVAc) co-polymer blended with polyvinyl pyrrolidone (PVP) in equal proportion by weight, and doped with an inorganic metallic salt, cadmium chloride $$(\hbox {CdCl}_{2})$$ , at 0.0 wt% and 10.2 wt% doping levels (DLs), have been studied using dielectric relaxation spectroscopy (DRS). The frequency response of dielectric parameters for these samples has been studied with variation in temperature, from 303 up to 373 K, at different fixed frequencies (from 12 Hz up to 200 kHz). Study of Cole–Cole plots reveals a decrease in bulk resistivity of the samples with increase in temperature, which is attributed to thermally induced increase in the mobility of polymer chains. A 10-fold increase in bulk conductivity is observed for doped films with a DL of 10.2 wt%, when compared with the bulk conductivity of the un-doped (0.0 wt% DL) sample. The temperature dependence of dielectric parameters at different frequencies has been studied and the activation energy has been calculated. The relaxation time is found to be of the order of a few milliseconds, which implies that electrical conduction in $$\hbox {CdCl}_{2}$$ -doped PVA/PVAc–PVP blend films is predominantly due to the migration of ions. The variation of AC conductivity with frequency is in agreement with Jonscher’s universal power law. AC conductivity of the sample is found to increase significantly with an increase in temperature of the sample. Frequency-dependent dielectric properties of $$\hbox {CdCl}_{2}$$ -doped PVA/PVAc–PVP blend films, for various DLs, are also studied at room temperature.