The characterization and property of polystyrene compounding of α-Fe<Subscript>2</Subscript>O<Subscript>3 </Subscript>in the nano-scale

-Fe₂O₃/polystyrene composite nanoparticles were synthesized in an oil/water microemulsion. Their structure was characterized by transmission electron microscopy, X-ray diffraction and Fourier transform-infrared spectrometry. An Ubbelonde viscometer, a Gouy balance and a model 283 potentiostat/galvanostat measured the molecular weight of the composite nanoparticles and their magnetic and electrical characteristics respectively.     

Morphology-controlled synthesis of Ti-doped α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanorod arrays as an efficient photoanode for photoelectrochemical applications

Few reports have been published on the optimization of nanostructures while doping with the Ti (Ti³⁺/Ti⁴⁺) elemental. Here, Ti-doped α-Fe₂O₃ nanorod arrays prepared via the hydrothermal method with the addition of TiCl₃ as the Ti source and urea as the morphological regulator were used as photoanodes in photoelectrochemical cells. In the process of a hydrothermal reaction, Ti elemental was incorporated into α-Fe₂O₃ photoanodes using TiCl₃ as precursor and urea was used as the morphological regulator to assist α-Fe₂O₃ to form nanorod arrays. The photoelectrochemical performance of the as-prepared Ti-doped α-Fe₂O₃ nanorod array (TF1) photoanodes exhibited a remarkable photocurrent of 0.22 mA cm^?2 (275 times higher than that of the undoped α-Fe₂O₃ nanorod arrays) at 1.23 V (vs. RHE) and a 150-mV cathodic shift of photocurrent onset potential. The enhanced photoelectrochemical performance was ascribed to the synergistic effect of the one-dimensional nanoarray structure and the Ti elemental doping, which increased donor density and reduced photogenerated electron–hole recombination.     

Fast degradation of methylene blue with electrospun hierarchical α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> nanostructured fibers

The α-Fe₂O₃ fibers have been prepared by electrospinning the corresponding sol–gel precursor, then these fibers were characterized by TGA, SEM, XRD, BET and FT-IR respectively, indicating that the hierarchical α-Fe₂O₃ nanostructured fibers came into being. Photocatalytic degradation of methylene blue (MB) in water was carried out under ultraviolet (UV) light, showing that the fibers had better efficiency for removing MB than other catalysts. And several process parameters have also been studied, which showed that the removal effect of MB was influenced by the process parameters, such as the initial dye concentration, catalyst amounts, inorganic anions, and so on.     

Structure and magnetic properties of the nanocomposites γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript>

The structural features and magnetic properties of composite materials Fe₂O₃-SiO₂ consisting of γ-Fe₂O₃ nanoparticles in an amorphous porous matrix of SiO₂ were considered. The studied samples were synthesized by the sol-gel method. The structure of γ-Fe₂O₃-SiO₂ depending on the heating temperature was studied by electron microscopy, X-ray diffraction analysis, ESR and IR spectroscopy. Magnetic measurements were performed on a SQUID magnetometer in the range 2–350 K.     

Ultrathin-layer α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> deposited under hematite for solar water splitting

This work proposes a new strategy to prepare a hematite (α-Fe₂O₃) bilayer photoanode by hydrothermally depositing α-Fe₂O₃ (B) on the α-Fe₂O₃ (A) films prepared by electrochemical deposition. Compact smooth surfaced α-Fe₂O₃ (A) films were electrochemically deposited on FTO (SnO₂:F) substrates from an aqueous bath. The α-Fe₂O₃ (A), α-Fe₂O₃ (B), and α-Fe₂O₃/α-Fe₂O₃ bilayer films’ characteristics were defined by X-ray diffraction (XRD) measurements, field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray (EDX) spectroscopy. Pure crystalline α-Fe₂O₃ (B) films with a typical anisotropic-like nanoparticle formation, which exhibited nanostructured rods covering the substrate and formed the characteristic mesoporous film morphology, were hydrothermally deposited on α-Fe₂O₃ (A) films prepared by electrochemical depositing in a solution bath at 25 °C and a potential of ??0.15 V. The photocurrent measurements exhibited increased intrinsic surface states (or defects) at the α-Fe₂O₃ (A)/α-Fe₂O₃ (B) interface. The photoelectrochemical performance of the α-Fe₂O₃ (A)/α-Fe₂O₃ (B) structure was examined by chronoamperometry, which found that the α-Fe₂O₃ (A)/α-Fe₂O₃ (B) structure exhibited greater photoelectrochemical activity than the α-Fe₂O₃ (A) and α-Fe₂O₃ (B) thin films. The highest photocurrent density was obtained for the bilayer α-Fe₂O₃ (A)/α-Fe₂O₃ (B) films in 1 M NaOH electrolyte. This great photoactivity was ascribed to the highly active surface area, and to the externally applied bias that favored the transfer and separation of photogenerated charge carriers in α-Fe₂O₃ (A)/α-Fe₂O₃ (B). The improved photocurrent density was attributed to an appropriate band edge alignment of semiconductors and to enhanced light absorption by both semiconductors. The best performing samples were α-Fe₂O₃ (A)/α-Fe₂O₃ (B), which reached the maximum incident photon conversion efficiencies (IPCE) of 400 nm at the potential of 0.1 V. In this case, the IPCE values were 3-fold higher than those of the α-Fe₂O₃ (A) and α-Fe₂O₃ (B) films.     

Preparation,characterization, and thermal studies of γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> and CuO dispersed polycarbonate nanocomposites

Polycarbonate with γ-Fe₂O₃ and CuO dispersions were carried out by solvent casting method to make polycarbonate-γ-Fe₂O₃ and polycarbonate-CuO composite films. These films were characterized for the molecular structure through FTIR spectroscopy and crystallinity by X-ray diffraction (XRD) measurements. The morphology of polycarbonate-γ-Fe₂O₃ was found to be different from that of polycarbonate-CuO composite films based on the scanning electron micrograph (SEM) images. The thermal traces of composites are different from that of pure polycarbonate which indicating the catalytic decomposition when compared with virgin polymer which is oxidative decomposition. An understanding of the structure, morphology, and thermal behaviour of the composite films are envisaged in the present study.     

A Green,Low-Cost and Efficient Photocatalyst: Atomic-Hydrogenated α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

The environmental-friendly hematite iron oxide (α-Fe₂O₃) has important application prospects in the photocatalysis field owing to its narrow indirect band gap. Here, we report a band gap engineering of α-Fe₂O₃ by incorporation of electrochemically-generated atomic hydrogen at moderate conditions. The ultraviolet–visible spectra show the reduction of the α-Fe₂O₃ band gap after hydrogenation and the absorption region from 200–800 nm is enhanced, especially in the visible light region. First principles calculation reveals the mixing of the new hybrid energy level with the valence band top resulting in a decrease in the band gap of α-Fe₂O₃. Further photocatalytic degradation experiments of dyes demonstrate that the photocatalytic efficiency of α-Fe₂O₃ can be greatly enhanced by the atomic hydrogen incorporation. The hydrogenated α-Fe₂O₃ can be easily recycled by magnets and has good photocatalytic stability. These findings offer possibilities for utilizing this inexpensive and earth-abundant oxide materials in the pollution controlling areas.     

Sol–gel preparation of highly transparent α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> film for the application in red color filter

α-Fe₂O₃ films as inorganic red color filter were synthesized through a simple procedure, epoxide assisted sol–gel route. The sol was prepared through reaction of FeCl₂ in boiling ethanol solution with propylene oxide. The films were formed by the dip-coating of sol on substrate, drying and the following annealing steps. The obtained α-Fe₂O₃ films were composed of homogeneous distributed α-Fe₂O₃ nanoparticles with size of 30–50 nm. The film shows strong absorption to the light below 600 nm and high transparency to the red light (87% at 630 nm). As inorganic red color filter, the optic behavior of this film is nearly as same as the organic color filter made of dye.     

Effect of MoO<Subscript>3</Subscript> additions on the thermal stability and crystallization kinetics of PbO–Sb<Subscript>2</Subscript>O<Subscript>3</Subscript>–As<Subscript>2</Subscript>O<Subscript>3</Subscript> glasses

The present paper reports on the effect of MoO₃ on the glass transition, thermal stability and crystallization kinetics for (40PbO–20Sb₂O₃–40As₂O₃)_100−x –(MoO₃) _x (x = 0, 0.25, 0.5, 0.75 and 1 mol%) glasses. Differential scanning calorimetry (DSC) results under non-isothermal conditions for the studied glasses were reported and discussed. The values of the glass transition temperature (T _g) and the peak temperature of crystallization (T _p) are found to be dependent on heating rate and MoO₃ content. From the compositional dependence and the heating rate dependence of T _g and T _p, the values of the activation energy for glass transition (E _g) and the activation energy for crystallization (E _c) were evaluated and discussed. Thermal stability for (40PbO–20Sb₂O₃–40As₂O₃)_100−x –(MoO₃) _x glasses has been evaluated using various thermal stability criteria such as ΔT, H _r , H _g and S. Moreover, in the present work, the K _r(T) criterion has been considered for the evaluation of glass stability from DSC data. The stability criteria increases with increasing MoO₃ content up to x = 0.5 mol%, and decreases beyond this limit.     

Phase equilibria in the Nb<Subscript>2</Subscript>O<Subscript>5</Subscript>–CdO system and the thermal stability of Cd<Subscript>2</Subscript>Nb<Subscript>2</Subscript>O<Subscript>7</Subscript> and CdNb<Subscript>2</Subscript>O<Subscript>6</Subscript>

Phase equilibria were studied in the Nb₂O₅–CdO system in the Nb₂O₅-rich region including CdNb₂O₆ and Cd₂Nb₂O₇. It was determined that CdNb₂O₆ and Cd₂Nb₂O₇ in air are stable to 1150 and 1120°C, respectively, and that, above these temperatures, there is solid-phase decomposition of niobates with CdO release in the gas phase. Along with the cadmium oxide evaporation, the Cd₂Nb₂O₇ decomposition is accompanied by the formation of cadmium metaniobate CdNb₂O₆ and the CdNb₂O₆ decomposition results in the formation of niobium oxide Nb₂O₅. No thermal events were observed in the differential thermal analysis curve for a 1: 1 CdNb₂O₆–Cd₂Nb₂O₇ mixture heated to 1100°C in air, which suggests that there are neither phase transformations in cadmium niobates, nor a eutectic within this temperature and concentration ranges. A study of the morphology of compacted samples of niobates determined specific conditions for producing dense composite ceramics, a mixture of niobates, that is suitable for using as a dielectric material.     

Specific features of the interaction of α- and γ-modifications of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> with carbonate and carbonate-chloride melts

Data on reactivities of α- and γ-Al₂O₃ finely dispersed powders in a melted carbonate eutectic (Li₂CO₃–Na₂CO₃–K₂CO₃)_eut and carbonate-chloride mixture 0.72(Li₂CO₃–Na₂CO₃–K₂CO₃)_eut–0.28NaCl were obtained. The methods of synchronous thermal and X-ray phase analyses and Raman spectroscopy confirmed that, in contrast to γ-Al₂O₃, α-Al₂O₃ does not chemically interact with the melted carbonate eutectic and carbonate-chloride mixture (Li₂CO₃–Na₂CO₃–K₂CO₃)_eut–NaCl can be recommended as a thickening agent for a carbonate fuel cell.     

Formation of solid solutions of multiferroics in the Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The sequence of phases appearance during the formation of Bi_1–xNd_xFeO₃ solid solutions in powder oxides mixtures of bismuth, neodymium, and iron has been determined. It has been shown that the closeness of the reaction mixture composition to that of the individual compound (BiFeO₃ or NdFeO₃) is essential for the realization of the series of phase transformations yielding solid solutions of multiferroics Bi_1–xNd_xFeO₃ as the final product, due to the prevalence of various interphase contacts in the starting reaction zone.     

Novel sol–gel method for preparation of high concentration ε-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/SiO<Subscript>2</Subscript> nanocomposite

ε-Fe₂O₃/SiO₂ nanocomposite was prepared by novel solgel method using single precursor for both nanoparticles and matrix. This method allows to prepare the samples free of α-Fe₂O₃ with 40% of Fe₂O₃ in SiO₂. Nanoparticles of 12 nm diameter were obtained by annealing at 1,000 °C. The samples were characterized by powder X-ray diffraction and transmission electron microscopy. Mössbauer spectroscopy identified ε-Fe₂O₃ as the only magnetically ordered phase at room temperature. Magnetic measurements revealed progressive necking of hysteresis loops measured at 300 and 2 K. In both cases the intrinsic coercivity reaches only 0.25 T. Measurements up to 14 T shows monotonous decreasing trend of saturated magnetization with increasing temperature.     

Effects of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> on the crystallization and structure of CaO–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> glass ceramics

Radiation-induced degradation of the weakly and strongly 4-vinylpyridine basic ion exchange resins by gamma radiolysis was investigated in the presence of air and liquid water. This study is focused on evaluating the radiolytic gases (H₂, CO, CO₂ and CH₄) and liquid products (water-solute TOC and NH₄ ⁺). The weakly basic resin yielded lower amounts of H₂ and CO and higher amounts of CO₂ than those of the strongly basic resin. Moreover, the strong basic resin tended to yield greater amounts of NH₄ ⁺. Resins were characterized by the FTIR spectroscopy technique and the results showed that the resins structures are relatively stable.     

Structural and Temperature Dependent Electrical Conductivity Properties of Dy<Subscript>2</Subscript>O<Subscript>3</Subscript>–Sm<Subscript>2</Subscript>O<Subscript>3</Subscript> CO-Doped Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>

In the present work, Dy₂O₃ and Sm₂O₃ double-doped Bi₂O₃-based materials are synthesized by exploiting the solid-state synthesis method. The structural and temperature dependent electrical properties of these ternary ceramic samples, which are candidate materials for solid oxide fuel cell (SOFCs) electrolyte, are determined by means of a powder X-ray diffractometer (XRD), the four point-probe method (FPPM), and the thermal-gravimetry/differential thermal analysis (TG/DTA). As a result of the XRD measurements, the fluorite-type fcc δ-phase with a stable structure is obtained for higher values of the dopant oxide material, which are the samples with the maximum content of fixed 20% Dy₂O₃ and 15% and 20% Sm₂O₃. The samples with the stable δ-phase structure have higher conductivities. The highest electrical conductivity is found for the (Bi₂O₃)0.6(Dy₂O₃)_0.2(Sm₂O₃)_0.2 sample, which was 2.5×10^–2 (Ohm cm)^–1 at 750 °C. The activation energies are also calculated from the Arrhenius charts, which were determined from the FPPM measurements. The lowest activation energy is found as 0.85 eV for the sample with the highest electrical conductivity.     

Synthesis and properties of γ-Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> solid solutions

The textural and structural properties of mixed oxides Ga₂O₃–Al₂O₃, obtained via impregnating γ-Al₂O₃ with a solution of Ga(NO₃)₃ and subsequent heat treatment, are studied. According to the results from X-ray powder diffraction, gallium ions are incorporated into the structure of aluminum oxide to form a solid solution of spinel-type γ-Ga₂O₃–Al₂O₃ up to a Ga₂O₃ content of 50 wt % of the total weight of the sample, accompanied by a reduction in the specific surface area, volume, and average pore diameter. It is concluded that when the Ga₂O₃ content exceeds 50 wt %, the β-Ga₂O₃ phase is observed along with γ-Ga₂O₃–Al₂O₃ solid solution. ⁷¹Ga and ²⁷Al NMR spectroscopy shows that gallium replaces aluminum atoms from the tetrahedral position to the octahedral coordination in the structure of γ-Ga₂O₃–Al₂O₃.     

Thermal and Magnetic Properties of Maghemite γ-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> Synthesized by a Precursor Method

Low-dimension ferromagnetic maghemite γ-Fe₂O₃ was synthesized through a precursor route, using basic iron formate Fe(OH)(HCOO)₂ as a precursor. Conditions of formation of γ-Fe₂O₃ and the temperature range of its existence on heating in air were determined. The saturation magnetization of γ-Fe₂O₃ produced through heating the precursor at 350°C 57.5 (T = 4.2 K) and 43.8 emu/g (T = 300 K).     

Pd/Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts for the selective liquid-phase hydrogenation of acetylene to ethylene

The structure of Ga₂O₃–Al₂O₃ supports and Pd/Ga₂O₃–Al₂O₃ catalysts and the performance of these catalysts in liquid-phase acetylene hydrogenation have been investigated. The deposition of Ga(NO₃)₃ onto Al₂O₃ by impregnation followed by calcination of the impregnated support at 600°C yields γ-Ga₂O₃–Al₂O₃ solid solutions containing up to 50 wt % Ga₂O₃. X-ray diffraction characterization of model palladium catalysts and their temperature-programmed reduction with hydrogen have demonstrated that, while palladium in Pd/Ga₂O₃ is in the form of a Pd₂Ga alloy, in the Pd/γ-Ga₂O₃–Al₂O₃ catalyst there is no direct interaction between PdО and Ga₂O₃ particles and palladium is in the monometallic state. The introduction of 10–20 wt % gallium oxide into Al₂O₃ lowers the activity of the supported palladium catalyst relative to that of the initial Pd/Al₂O₃ but increases the ethylene yield by enhancing the ethylene formation selectivity.