Xiansong Liu

Rational Design of α-Fe2O3/Reduced Graphene Oxide Composites: Rapid Detection and Effective Removal of Organic Pollutants

α-Fe2O3/reduced graphene oxide (α-Fe2O3/rGO) composites are rationally designed and prepared to integrate organic pollutants detection and their photocatalytic degradation. Specifically, the composites are used as the substrate for surface-enhanced Raman scattering (SERS) to detect rhodamine 6G (R6G). Repeatable strong SERS signals could be obtained with R6G concentration as low as 10(-5) M. In addition, the substrate exhibits self-cleaning properties under solar irradiation. Compared with pure α-Fe2O3 and α-Fe2O3/rGO mechanical mixtures, the α-Fe2O3/rGO composites show much higher photocatalytic activity and much greater Raman enhancement factor. After 10 cycling measurements, the photodegradation rate of R6G could be maintained at 90.5%, indicating high stability of the photocatalyst. This study suggests that the α-Fe2O3/rGO composites would serve both as recyclable SERS substrate and as excellent visible light photocatalyst.

Microstructure and magnetic properties of La–Cu doped M-type strontium ferrites prepared by ceramic process

Abstract M-type hexaferrite Sr1−xLaxFe12−xCuxO19 (0≤x≤0·35) magnetic powders and magnets were prepared by the ceramic process. X-ray diffraction was used to investigate the phase compositions of magnetic powders. The single magnetoplumbite phase is obtained in magnetic powders with x from 0 to 0·35. The morphology of the magnets shows that the hexagonal structure is formed and the particles are distributed evenly. Magnetic properties of the magnets were measured by a permanent magnetic measure equipment. The remanence and maximum energy product for the magnets first increase with x from 0 to 0·20 and then, start to decrease when x continues to increase. Both the intrinsic coercivity and magnetic induction coercivity decrease linearly with the increase of x from 0 to 0·35.

A strong magneto-optical activity in rare-earth La3+ substituted M-type strontium ferrites

M-type strontium ferrites with substitution of Sr2+ by rare-earth La3+ were prepared by conventional ceramic technology. The structure, magnetic properties, and magneto-optical Kerr activity of Sr1−xLaxFe12O19 (x = 0, 0.05, 0.10, 0.15, 0.20) were investigated by x-ray diffraction (XRD), vibrating sample magnetometer (VSM), and magneto-optical ellipsometry, respectively. X-ray diffraction showed that the samples sintered at 1290 °C for 3 h were single M-type hexagonal ferrites. The magnetic properties were remarkably changed due to the valence change of Fe ions induced by the substitution of La ions. Most significantly, an important magneto-optical activity was induced in the La3+ substituted M-type strontium ferrites around 3 eV.

Structural and magnetic properties of Sr1−x La x Fe12−x (Cu0.5Co0.5) x O19 hexaferrites prepared by the solid-state reaction method

Hexaferrite Sr1−xLaxFe12−x(Cu0.5Co0.5)xO19 (0 ≤ x ≤ 0.50) magnetic powders and magnets were synthesized by the solid-state reaction method. The phase compositions of magnetic powders were investigated by X-ray diffraction. The single magnetoplumbite phase is obtained in magnetic powders with x from 0 to 0.40. At x = 0.50, CoFe2O4, and α-Fe2O3 were observed. The morphology of the materials was characterized by a field-emission scanning electron microscopy. The particles were hexagonal platelets. Magnetic properties of the materials were measured by a permanent magnetic measure equipment. The remanence of the materials increases with x from 0 to 0.50. However, the intrinsic coercivity and magnetic induction coercivity of the materials increase with x from 0 to 0.15, and decreases when x varies from 0.15 to 0.50. Accordingly, the maximum energy product of the materials first increases with x from 0 to 0.35, and then decreases when x exceeds 0.35.

Hierarchical Radial Co3O4 Microcrystal and Application in Gas Sensor

Three-dimensional (3D) hierarchical Co3O4 microcrystal with radial dendritic morphologies was prepared through hydrothermal reactions followed by subsequent annealing treatment. Structural and morphological characterizations were performed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The gas sensing properties of the as-obtained microcrystal were investigated at 110 °C, which revealed that the 3D hierarchical porous Co3O4 microcrystal exhibited high sensitivity to ammonia, as well as a short response time of 10 s. The response characteristic indicates that the sensor has a good stability and reversibility. Detections of toxic and flammable gases, such as ethanol, acetone and benzene were also carried out at a relative low temperature. The results indicate that such hierarchical Co3O4 microcrystal would be a potential material in the field of gas sensing.

Structure, magnetic and magneto-optical properties of La-Ca-Co substituted strontium ferrites

Strontium ferrites Sr0.70-xLa0.3CaxFe11.7Co0.3O19 (x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30)，according to the formula Sr1-x-yCaxLay∙Fe12-yCoyO19, were prepared by the conventional ceramic process. The structure, morphology, optical, magnetic properties and transverse magneto-optical Kerr effect of the samples were studied by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscope (SEM) and magneto-optical ellipsometry. It is found that the samples are single phase except the samples with the largest substitution amount, x = 0.25 and x = 0.30. Doping with Ca2+, the coercivity of these material magnets is increased while their magnetization is nearly unchanged. In all cases, a strong transverse magneto-optical Kerr activity appears according to the optical and magneto-optical spectra of the samples.

Structural and magnetic properties of La-substituted strontium W-type hexagonal hexaferrites

W-type strontium hexaferrites with chemical composition of Sr1−xLaxZn2Fe16O27 (x = 0–0.25) were synthesized by traditional ceramics process. Effects of the substituted amount x of La3+ on the ferrites microstructure and magnetic properties have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and a magnetic properties test instrument. As a result, at x ≤ 0.20, all samples are single phase after the La substitution. At x = 0.25, another phase of La2O3 is present. In addition, the maximum values of the remanence (Br) and maximum energy product ((BH)max) for the magnets have been obtained at x = 0.10. The maximum value of the intrinsic coercive force (Hcj) and magnetic induction coercivity (Hcb) for the magnets has been obtained at x = 0.15.

Improvement of magnetic properties of Cr3+ substituted SrFe12O19

Abstract M type strontium hexaferrites SrFe12 − xCrxO19 (x = 0.0–0.6) were prepared by the ceramic process. The structure, morphology and magnetic properties of the samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and B–H hysteresis curve measurements. The XRD patterns show the formation of the M-type hexaferrite phase in the pre-sintered samples with non-magnetic phase, α-Fe2O3. The SEM results indicate that the Cr substitution does not obviously affect the structure of strontium ferrite. The results of magnetic mensuration, especially for the SrFe11.8Cr0.2O19 samples, reveal that rather high magnetic properties can be obtained in the sintering temperature range of 1135–1165°C.

Substitution effects of calcium to microstructures and magnetic properties of Sr0·70–xCaxLa0·30Fe11·72Cu0·28O19 hexaferrites

Abstract The hexaferrite Sr0·70–xCaxLa0·30Fe11·72Cu0·28O19 (0≤x≤0·70) magnetic powders and magnets were synthesised by the ceramic process. The phase compositions of the magnetic powders were investigated using X-ray diffraction. X-ray diffraction patterns show that the hexagonal single phase is obtained in all samples. The morphology of the magnets was investigated using a field emission scanning electron microscopy. The magnets are formed of hexagonal shaped crystals and the particles are distributed evenly. The bulk density of the magnets decreases with calcium content (x) from 0 to 0·70. Magnetic properties of the magnets were measured using a permanent magnetic measure equipment. The remanence, intrinsic coercivity, magnetic induction coercivity and maximum energy product of the magnets first increase with x from 0 to 0·20, and then decrease when x continues to increase. The magnetic properties of the magnet at x = 0·20 reach the maximum values.

Structure and magnetic analyses of hexaferrite Sr 1−x La x Fe 2 2+ Fe 16 3+ O 27 prepared via the solid-state reaction

W-type ferrite Sr1−xLaxFe22+Fe163+O27 (x = 0.00, 0.05, 0.08, 0.10, 0.13 and 0.15) powders and magnets were prepared via the solid-state reaction in nitrogen. Phase components of the powder samples were examined by X-ray diffraction (XRD). XRD results demonstrated the appearance of pure phase hexagonal crystal structure and calculate the lattice constants c and a, c/a ratio, cell volume (Vcell), X-ray density (dX-ray) and crystallite size (D) parameters according to XRD data. Scanning electron microscopy (SEM) was used to observe the morphology of the magnets. SEM analyses revealed the hexagonal morphology of the ferrites. The magnetic characteristics of magnetic powders were measured by a vibrating sample magnetometer (VSM), and the magnetic characteristics of magnets were also measured by a permanent magnetic measuring equipment. The results indicate that, the synthesized samples with a low coercive force value and a considerable saturation magnetization are best able to make optical read-out of the magnetic storage information in erasable video and audio discs.