[en] Materials Chemistry and PhysicsVolume 213, 1 July 2018, Page 95

[en] LaCoO₃ and La_0.5Sr_0.5CoO_3−δ perovskites have been studied by in situ Co K-edge XAS. Although the partial substitution of La(III) by Sr(II) species induces an important increase in the catalytic oxidation activity and modifies the electronic state of the perovskite, no changes could be detected in the oxidation state of cobalt atoms. So, maintaining the electroneutrality of the perovskite requires the generation of oxygen vacancies in the network. The presence of these vacancies explains that the substituted perovskite is now much more reducible than the original LaCoO₃ perovskite. As detected by in situ XAS, after a consecutive reduction and oxidation treatment, the original crystalline structure of the LaCoO₃ perovskite is maintained, although in a more disordered state, which is not the case for the Sr doped perovskite. So, the La_0.5Sr_0.5CoO_3−δ perovskite submitted to the same hydrogen reduction treatment produces metallic cobalt, while as determined by in situ XAS spectroscopy the subsequent oxidation treatment yields a Co(III) oxide phase with spinel structure. Surprisingly, no Co(II) species are detected in this new spinel phase. - Highlights: • A Sr-substituted lanthanum cobalt perovskite has been prepared by spray pyrolysis. • It has been established that Co(III) cations are present in both perovskites. • LaCoO₃ is a less reducible phase than the substituted La_0.5Sr_0.5CoO_3−δ. • After reoxidation of reduced La_0.5Sr_0.5CoO_3−δ, a 100% Co(III) spinel is obtained

[en] 75 KHz plasma was used to modify track etched poly(ethylene terephthalate) membranes and deposit on them flouropolymers. Two fluorine bearing monomers were used: perflourohexane and hexafluorobenzene. The modified surfaces were analyzed by means of attenuated total reflection infra-red spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy and wettability. It was detected that hexaflourobenxene deposited to the larger extent than perflourohaxane did. The roughness of surfaces decreased when more fluoropolymer was deposited. The hydrophobic character of surface slightly disappeared during 20-days storage of hexaflourobenzene modified membrane. Perfluorohexane modified membrane did not change its character within 120 days after modification. It was expected that this phenomenon resulted from post-reactions of oxygen with radicals in polymer deposits. The obtained membranes could be used for membrane distillation of juices. - Highlights: • Plasma deposited hydrophobic layer of flouropolymers. • Deposition degree affects the surface properties. • Hydrohilization of surface due to reaction of oxygen with entrapped radicals. • Possibility to use modified porous membrane for water distillation and apple juice concentration

[en] A green method for producing pristine porous ZnO nanoparticles with narrow particle size distribution is reported. This method consists in synthesizing ZnO₂ nanopowders via a hydrothermal route using cheap and non-toxic reagents, and its subsequent thermal decomposition at low temperature under a non-protective atmosphere (air). The morphology, structural and optical properties of the obtained porous ZnO nanoparticles were studied by means of powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and nitrogen adsorption–desorption measurements. It was found that after thermal decomposition of the ZnO₂ powders, pristine ZnO nanoparticles are obtained. These particles are round-shaped with narrow size distribution. A further analysis of the obtained ZnO nanoparticles reveals that they are hierarchical self-assemblies of primary ZnO particles. The agglomeration of these primary particles at the very early stage of the thermal decomposition of ZnO₂ powders provides to the resulting ZnO nanoparticles a porous nature. The possibility of using the synthesized porous ZnO nanoparticles as photocatalysts has been evaluated on the degradation of rhodamine B dye. - Highlights: • A green synthesis method for obtaining porous ZnO nanoparticles is reported. • The obtained ZnO nanoparticles have narrow particle size distribution. • This method allows obtaining pristine ZnO nanoparticles avoiding unintentional doping. • A growth mechanism for the obtained porous ZnO nanoparticles is proposed

[en] As a part of serial work about tuning the selective location of carbon nanotubes (CNTs) in immiscible polymer blends, this work reports the effects of component polarity and viscosity ratio between components on the selective location of CNTs and the resultant electrical resistivity of the nanocomposites. To achieve the research aim, maleic anhydride (MA) was grafted onto poly(L-lactide) (PLLA) main chain through a reactive compounding processing. After that, different contents of CNTs were incorporated into blends of high density polyethylene (HDPE) and PLLA (or PLLA-g-MA). The morphologies of the ternary nanocomposites and the selective location of CNTs in the nanocomposites were characterized using scanning electron microscope (SEM) and transmission electron microscope (TEM). The microstructure of nanocomposites and the dispersion of CNTs were further proved by rheological measurement. Finally, the electrical resistivity of nanocomposites containing different CNT contents was measured. The results showed that through increasing the polarity of PLLA and decreasing the melt viscosity, CNTs were kinetically trapped at the blend interface region. Consequently, largely decreased percolation threshold was achieved for the PLLA-g-MA/HDPE/CNT nanocomposites. The morphological changes as well as the rheological properties were also comparatively analyzed. - Highlights: • PLLA/HDPE/CNT and PLLA-g-MA/HDPE/CNT composites were prepared. • Different selective location states of CNTs were achieved in different composites. • Selectively located CNTs at the interface resulted in lower percolation threshold

[en] A complete thermodynamic description of the Cu–Ni–Y ternary system has been obtained using the CALPHAD (CALculation of PHAse Diagram) approach. Ternary solubility of the third element in the binary compounds in the Cu–Ni–Y system is described using sublattice model within the compound energy formalism (CEF) to take into account the recently reported experimental solubility ranges. The modified quasi-chemical model (MQM) has been used to describe the liquid phase in order to account for the presence of short range ordering properly. To study the melting behavior of the Cu–Ni–Y alloys and to verify the consistency of the thermodynamic model with experimental results, 10 key samples were prepared and the phase transformation temperatures were measured using differential scanning calorimeter (DSC). The microstructural characterization and crystallographic analysis of the alloys were carried out using scanning electron microscopy (SEM) coupled with WDS analysis and X-ray diffraction (XRD). Several vertical sections, liquidus projection and isothermal section at 973 K have been calculated and found to be in good agreement with the current experimental data as well as with the literature. - Highlights: • Thermodynamic modeling of the Cu–Ni–Y system has been performed. • Ternary solubilities of the binary compounds have been reproduced. • Modified quasi-chemical model is used to model the liquid phase. • DSC experiments are performed on selected key alloys. • The calculations are consistent with the experimental results

[en] The TiC–ZrC binary compound of nanostructured powders was synthesised by combination of sol–gel and carbothermal reduction. The polymeric precursor of the blend was produced by sol–gel process from titanium tetrabutoxide, zirconium tetrabutoxide and benzene-1.4-diol; then carbothermally reduced to the TiC–ZrC blend at 1600 °C in an inert environment. The chemical reactions occurring in the system were monitored by infrared spectrometry. Stable alkoxide solution was obtained by adding acetylacetone to avoid premature gelation of the metal alkoxide mixture. A solid solution of ZrTiC_2 was produced by spark plasma sintering at temperature of 2000 °C. - Highlights: • A polymeric precursor of TiC–ZrC blend was synthesised by sol–gel process. • The polymeric precursor synthesis was studied by infrared spectroscopy. • TiC–ZrC powder blend was carbothermally reduced from polymeric precursor. • TiC–ZrC powder blend was sintered to ZrTiC_2 solid solution by spark plasma sintering. • Sintered ZrTiC_2 have good mechanical properties

[en] Solid silicon oxycarbide (SiCO) ceramic microspheres and rigid porous siloxane microspheres were obtained in a two step process. First, polysiloxane microspheres with a large number of Si–OH groups in their bulk and on their surface were synthesized from polyhydromethylsiloxane (PHMS) using a recently developed process. The process included a combination of three reactions of Si–H groups of PHMS occurring in aqueous emulsion and catalyzed by the same Karstedt Pt(0) complex: (i) hydrosilylation of 1,3-divinyltetramethyldisiloxane (DVTMDS), (ii) hydrolysis, (iii) dehydrogenocondensation involving the SiOH groups formed during the hydrolysis. DVTMDS was grafted on PHMS prior to emulsification. Microspheres had a loose structure and were able to absorb a significant amount of organic solvents. In the second step the microspheres were subjected to pyrolysis with heating in the argon atmosphere at following temperatures: 400, 700 and 1000 °C. These heated at 400 °C had micro and mezopores, while those heated at 700 and 1000 °C gave spherical solid SiCO ceramic particles. Polysiloxane microspheres and microspheres obtained by pyrolysis of the former were analyzed by "2"9Si and "1"3C MAS NMR, FTIR, SEM, and N_2 gas adsorption. - Highlights: • Thermal properties of cross-linked polysiloxane microspheres are studied. • New route to solid silicon oxycarbide microspheres is worked out. • New method of preparation of mezoporous siloxane microspheres is shown. • Role of silanol side groups on polysiloxane in its ceramization is explained

[en] Lead titanate and strontium hexaferrite multiferroic composite with general formula (x)PbTiO_3 – (1 − x)SrFe_1_2O_1_9 (where x = 0.10, 0.20, 0.30 and 0.50) was prepared using solid state sintering method. Lead titanate and strontium hexaferrite phase formation was identified using X-ray diffraction technique, thus establishing diphase system without any secondary phase. Calculation of lattice parameter shows that the composite prefers hexagonal structure. The morphology of the formation of composite was seen through scanning electron microscopic technique. The morphological investigations show that the composites are dense, have fewer pores and ferroelectric grains are homogenously distributed in the ferrite matrix. The ferroelectric and ferromagnetic grains are identified on the basis of energy dispersive spectroscopy (EDS) studies. The magnetic behavior of the composites at room temperature display magnetic hysteresis loop, indicating that the composites are ferromagnetic. The value of saturation magnetization decreases with increase in ferroelectric content from x = 0.10 to 0.30, whereas for x = 0.50 it shows an increase. The magneto-capacitance shows a decrease in its value due to magnetostriction. - Highlights: • Composite multiferroic xPbTiO_3 – (1 − x) SrFe_1_2O_1_9 nanoparticles were prepared by solid state reaction method. • Magnetic hysteresis loop indicates the composite to be ferromagnetic. • Magneto dielectric values decreases due to magnetostriction. • Nanoparticle composite shows a strong magnetoelectric coupling for x = 0.30

[en] Tunable modifications of physical and optical properties of metallic nanoparticles (NPs) embedded rare earth (RE) doped inorganic binary glasses are the key issue. Series of glass with composition (69-x)P_2O_5–30ZnO–1Er_2O_3–(x)Fe_3O_4, where 0 ≤ x ≤ 2 mol% containing Fe_3O_4 NPs are prepared by melt quenching method and characterized using XRD, UV–Vis–NIR, PL, TEM and vibrating sample magnetometer (VSM) techniques. The Fe_3O_4 NPs concentration dependent density, molar volume, structural, magnetic and optical properties are determined. The XRD pattern confirms the amorphous nature of all samples. The glass density is found increase and molar volume decrease with the increase of NPs concentration. The TEM micrographs reveal the presence of spherical NPs of average diameter ∼26 nm with homogenous distribution. The UV–Vis–NIR absorption spectra exhibit ten absorption bands centered at 376, 406, 448, 486, 522, 546, 652, 798, 976 and 1534 nm corresponding to the absorption from "4I_1_5_/_2 ground state to various excited states of Er"3"+ ions. The optical band gap energy for direct (4.47–3.64 eV) and indirect (4.27–3.53 eV) transitions and Urbach energy (0.65–0.15 eV) are found to decrease with the increase of Fe_3O_4 contents. The decrease in band gap energy is ascribed to the creation of non bridging oxygen (NBO) ions in the glass network. The emission spectra at 478 nm excitations display two prominent peaks centered at 532 and 634 nm originate from "4S_3_/_2 → "4I_1_5_/_2 and "4F_9_/_2 → "4I_1_5_/_2 transitions, respectively. Furthermore, increasing NPs concentration dependent luminescence quenching is attributed to the energy transfer from the erbium ion to NPs. These glasses displaying ferrimagnetic behavior in the concentration range of 1.5–2 mol% of NPs verify the presence of iron oxide or ferrite in the glass sample are useful for magneto-optic devices. - Highlights: • Erbium-doped zinc phosphate glass embedded with Fe_3O_4 nanoparticles were prepared. • Fe_3O_4 NPs were observed with average size of 26–31 nm. • The quench of emission was discussed by energy transfer from Fe_3O_4 to Er"3"+ ions. • Influence of magnetic nanoparticles in structure, optical and magnetic properties