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The functionalized Janus MXene monolayers: ideal and promising materials for use in visible light-driven photocatalysis.

Coupling Co1-xS nanoparticles of rich cobalt vacancies (VCo) between layered carbon framework, the Co1-xS@N/S-C was designed to demonstrate an effective defect and structure synergistic engineering for boosted oxide electrolysis activities for zinc air batteries.

Bimetallic ZIFs-derived Co-Zn@NPC@MWCNTs nanocomposites are successfully fabricated, which possess double absorption peaks of −76.18 dB and −33.09 dB with a thickness of 3.187 mm. The composites exhibit a bandwidth of 6.56 GHz with 3.0 mm thickness.

The strong magnetic coupling effect and intensive interfacial polarization endow hierarchical core–shell Fe3O4@C composites with excellent microwave absorption performance.

In this study, silicone rubber and silicone oil were used to modify melamine sponge to obtain lipophilic and hydrophobic properties. The result showed that the modification had no effect on the intrinsic properties of sponges such as the structure and elasticity. After modification, the melamine sponge changed from hydrophilic to superhydrophobic, and the contact angle could reach 155.7°. In addition, this sponge also maintained its good oil-absorption performance and showed its excellent selective oil absorption in an oil-water mixture. Using xylene to simulate pollutants, the oil-absorption rate of the modified sponge could reach 44 g/g while the contact angle and oil-absorption rate of the sponge showed no significant changes after 20 cycles of oil-absorption experiments. The sponge showed a reliable and stable oil-absorption effect after repeated extrusion cycle experiments. The above experiments proved that the modification method and modified sponge have broad application prospects in oil-water separation.

Wet grinding is one of the most common forms of technology in powder production and preparation. Sand mill is the latest technology of wet grinding, which can effectively reduce the grinding particle size and improve the powder reactivity. LiFePO4 is one of the widely used cathode materials for lithium batteries at present, and the grinding process will affect the product performance. In this paper, parallel type and series type grinding processes were simulated by the single-cylinder system and the double cylinder system, which were studied and compared through the preparation of LiFePO4. It was discovered that the series type grinding process can not only increase the grinding efficiency but also improve the consistency of particle size distribution. LiFePO4 prepared by the series type grinding process has better rate performance and a higher discharge voltage platform. Attributing to the uniform particle size of LiFePO4, the lithium-ion diffusion coefficient was raised, which was proved by the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). To sum up, based on the results of this paper, the properties of lithium iron phosphate will be affected by the particle size distribution, which is related to the grinding process. Therefore, in order to obtain the best performance of LiFePO4, it is necessary to choose the appropriate production process. This research work provides references and the basis for the research of powder grinding production technology.

High magnetic field effects on the microstructure and magnetic properties of BaFe 12 O 19 hexaferrites synthesized hydrothermal method have been investigated. The obtained results indicate that the lattice constant decreases gradually as the magnetic field strength increases, which may be attributed to the lattice distortion resulted from the high magnetic field. Polycrystalline BaFe 12 O 19 samples prepared under magnetic field strength at zero and 5 T are single phase. It is found that application of external magnetic field during synthesis can induce orientated growth of the hexaferrite crystals along the easy magnetic axis. The magnetic properties can be effectively regulated by an application of high magnetic fields. It is observed that the BaFe 12 O 19 prepared under a 5 T magnetic field exhibits a higher room-temperature saturation magnetization (66.3 emu/g) than that of the sample (43.6 emu/g) obtained without magnetic field. The results can be explained as the enhanced crystalline, improvement of Fe 3+ ions occupancy and the oriented growth induced by the external magnetic field. The growing orientation of particles gives rise to increased coercivity due to the enhancement in shape anisotropy. It is expected that an application of magnetic field during the formation of magnetic nanoparticles could be a promising technique to modify magnetic properties with excellent performance.

The effect of indium doping on structural and magnetic properties of Y-type hexaferrite Ba0.5Sr1.5Zn2(Fe1-xInx)12O22 (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.1) prepared by the solid state reaction method was investigated. The Rietveld refinement method was used to analyze the X-ray diffraction patterns. The magnetic transition temperatures associated with the proper-screw spin phase to the collinear ferrimagnetic spin phase transition can be efficiently modulated by varying indium content. The magnetic transition temperature increases to a maximum with indium content x = 0.04 and then decreases with x, suggesting the possibility that electrically controlled magnetization reversal can be can be effectively tailored by varying indium content. The saturation magnetization at room temperature was decreased as increasing indium content, which can be explained as the metal ions occupation. It is worthy to note that the coercivity of In-doped samples was decreased drastically compared that of undoped sample, which is probably resulted from the reduction in anisotropy field with substitution of In3+ for Fe3+. The In-doped hexaferrite Ba0.5Sr1.5Zn2(Fe1-xInx)12O22 may be potential candidates for application in magnetoelectric devices.

Fe3O4/carbon core/shell composites were fabricated via a two-step process. Fe3O4/phenol formaldehyde resin (PFR) core/shell composites were first obtained by hydrothermal method, and the Fe3O4/carb...

The effect of Mg substitution on structural, magnetic, and dielectric properties of Y-type hexaferrite Ba0.5Sr1.5Zn2-xMgxFe11AlO22 (x = 0, 0.4, 0.8, 1.2, 1.6, 2.0) prepared by the solid state reaction method was investigated. The X-ray diffraction patterns are analyzed by Rietveld refinement method and the hexagonal structure with R 3 − m was confirmed. The magnetic transition temperatures associated with the longitudinal conical to proper screw phase transition (T1) and proper screw to ferrimagnetic phase transition (T2) can be modulated by varying Mg content. For x ≤ 1.2 samples, the transition temperature T2 monotonically increases with increasing Mg substitution, suggesting the possibility that the helical spin order of Mg substituted Y-type hexaferrites is sustained up to higher temperatures than that of undoped samples. The saturation magnetization at room temperature increases to a maximum with Mg content x = 1.2 and then decreases with x. The variations of magnetic properties can be attributed to the difference in the preferential site for Zn and Mg and different distribution of Fe3+ ions over tetrahedral and octahedral sites. The results of magnetic field dependence of dielectric constant, i.e., magnetodielectric effect, at various temperatures imply that the doped samples show magnetically induced ferroelectricity up to 250 K. The intrinsic magnetodielectric effect is observed in all the samples. It is worthy to note that the magnetodielectric effect measured below 200 K increases with increasing Mg content, which is probably attributed to the variation of magnetic structures. The Mg-doped hexaferrites Ba0.5Sr1.5Zn2-xMgxFe11AlO22 may be potential candidates for application in magnetoelectric devices.

The microstructure and magnetic properties of Mg-doped Ba0.5Sr1.5Zn2Fe12O22 hexaferrites synthesized by the solid state method are investigated. All the undoped and doped samples show a sharp screw proper spin phase to collinear ferrimagnetic spin phase transition above room temperature, and transition temperature increases distinctly with Mg doping. It is noteworthy that all the samples exhibit another magnetic phase transition at a lower temperature T1, which is associated with the longitudinal conical to the proper screw phase transition. The transition temperature T1 can be modulated by varying Mg content, indicating that the longitudinal conical spin phase is stabilized by the Mg-substitution. The saturation magnetization at room temperature increases to a maximum with Mg content x = 0.8 and then decreases with x. The variations of magnetic properties can be ascribed to the difference in the preferential site for Zn and Mg and different distribution of Fe3+ ions over tetrahedral and octahedral sites. It is worth noting that the range for the intermediate-III phase increases significantly as x increases to 2.0, suggesting that Mg-doped samples may be display field-induced ferroelectric order at temperature close to RT and in wide magnetic-field regions. The room-temperature M-H curves at lower applied field indicate that magnetic-field-induced ferroelectric phase can be stabilized at zero magnetic field by the substitution by Mg2+ for Zn2+. The Mg-doped hexaferrites Ba0.5Sr1.5Zn2Fe12O22 may be potential candidates for applying in magnetoelectric devices.

A novel kind of microwave absorption composite in Ku-band with low cost, low density and strong absorption was prepared through Bio-template carbonization and solvothermal method. The phase structures and morphologies of the composite had been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The microwave absorption properties of carbonized kapok fibers and Fe3O4/kapok fibers were measured by vector network analysis (VNA). When the sample thickness is 1.5 mm, the Fe3O4/kapok fibers have an optimal absorption peak value of about −24.1 dB at 17.4 GHz and its effective absorption bandwidth lower than −10 dB reaches 2.4 GHz (from 15.6 to 18.0 GHz). The reflection loss results indicate that the Fe3O4/kapok fibers possess higher microwave absorption in the Ku-band. A possible mechanism of the improved microwave absorption performance of the composite was discussed.

Polycrystalline CoFe 2 O 4 thin films were deposited on Si (100) substrates by chemical solution deposition with and without magnetic annealing. Magnetic field directions were applied parallel and perpendicular to the film surface during the magnetic annealing process. The variations of strain, microstructure and magnetic anisotropy of the films caused by the magnetic annealing are investigated. The results show that the film densification is promoted and grain morphology is changed by the magnetic annealing, which can be attributed to the promoting effect of magnetization force on the grain growing and grain boundary diffusing. Magnetic measurements indicate the enhancement of anisotropy and saturation magnetizations of the polycrystalline CoFe 2 O 4 after magnetic annealing. Furthermore, the rotation of easy axis along the field direction, the increased occupation of Co 2+ ions at B sites and the additional strain induced by the magnetic field are considered as the main reasons of the increased magnetic anisotropy.

In this study, we have successfully synthesized porous CoO–Co@RGO composites using GO and Co-based metal-organic frameworks (MOFs) as precursors. Due to particular structures and advantageous characteristics, the synthesized porous CoO–Co@RGO composites exhibit outstanding electromagnetic (EM) wave absorbing properties with a filler loading of 10[Formula: see text]wt.% in wax matrix. The maximum reflection loss (RL) of the prepared porous CoO–Co@RGO was [Formula: see text][Formula: see text]dB with 2.1[Formula: see text]mm thickness, and the effective absorption bandwidth as wide as 6.24[Formula: see text]GHz (11.76–18[Formula: see text]GHz), which covers the full Ku-band. Remarkably, the achieved all values of[Formula: see text]RL were under [Formula: see text][Formula: see text]dB with 1.0–5.0[Formula: see text]mm thickness, the corresponding to bandwidth range can be tuned to 13.84[Formula: see text]GHz (4.16–18[Formula: see text]GHz). The superior absorbing performance is attributed to suitable magnetic loss, high dielectric loss and large attenuation mainly caused by conduction loss and polarization relaxation.

Manganese oxide nanowires have been prepared through the thermal decomposition of manganese oxalate hydrate precursor. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry-differential thermal analysis (TG-DTA) and high-resolution transmission electron microscopy (HRTEM). The microwave absorption property of the manganese oxide nanowires was measured by vector network analysis (VNA). The excellent microwave absorption property of manganese oxide nanowires was achieved due to the relatively high dielectric loss tangent. The RL value for Mn2O3 nanowires less than −10 dB is obtained in the 5.0–18 GHz with absorber thickness of 2.0–5.0 mm. The minimum RL value is −21.0 dB. For Mn3O4 nanowires, the RL value less than −10 dB is obtained in the 7.8–18.0 GHz with absorber thickness of 2.5–5.0 mm. The minimum RL value is −21.2 dB at 7.7 GHz (H band). The effective absorption bandwidth exceeding −10 dB reaches 4.4 GHz (from 6.0 to 10.4 GHz). A pos...

M-type hexaferrites BaFe 12−2 x (NiTi) x O 19 ( x =0, 0.05, 0.1, 0.3, 0.5, 0.7, and 0.9) were synthesized by the solvothermal method. X-ray diffraction (XRD) analysis reveals that the samples are of pure-phase with the space group of p 6 3 / mmc . As the Ni–Ti substitution level increases from x =0 to 0.9, the results of field-emission scanning electronic microscopy indicate that the particles are agglomerated and the mean particle size decreases. With the increase in substitution concentration x , the saturation magnetization increases first, and then declines slowly, whereas the coercivity decreases gradually. The variation of magnetic properties can be explained by the effects of Ni–Ti substitution. The results above indicate that our samples have positive effects on high density perpendicular recording.

Monodisperse porous Ni 0.5 Zn 0.5 Fe 2 O 4 nanospheres have been successfully synthesized by the solvothermal method. The diameter of the nanospheres can be tuned by controlling the reactant concentration. Lower reactant concentration is favoured for the synthesis of mesoporous Ni 0.5 Zn 0.5 Fe 2 O 4 nanospheres with higher surface area. The electrochemical results show that mesoporous Ni 0.5 Zn 0.5 Fe 2 O 4 nanospheres exhibit high reversible specific capacity (1110 mAh g −1 ) for Li storage and high capacity retention, with 700 mAh g −1 retained up to 50 cycles. The excellent electrochemical properties could be attributed to the large surface area and mesoporous structure. The results suggest that Ni 0.5 Zn 0.5 Fe 2 O 4 could be a promising high capacity anode material for lithium ion batteries.

Cu2O/CuO composite thin films were synthesized by a facile hydrothermal method on Cu foils. Surface morphology, chemical composition, microstructure and wettability were investigated by scanning electron microscope, X-ray photoelectron spectroscopy, X-ray diffractometer and water contact angle apparatus. The results indicate that the Sample 2 is composed of many regular Cu2O octahedrons, tiny nanovillus and a small amount of spheric particles. The other samples were composed mainly of flower-like microparticles and regular Cu2O octahedrons. The content of copper (II) increases firstly and then decreases and the maximal value of content of copper (II) has been observed in the Sample 2. The Sample 2 displayed superhydrophobic property owing to its hierarchical porous micro/nanostructured surface.

The chemical solution deposition was used to synthesize La0.7Sr0.3MnO3 (LSMO) films. Effects of external magnetic-field (Hext=5 kOe) annealing on microstructure and magnetic properties were investigated. Under the effect of external magnetic field, FE-SEM images indicate that the mean grain size of LSMO film increases. X-ray diffraction results show that all the LSMO films are single-phase rhombohedral structure with a space group of R 3 ¯ C . The coercivity (Hc) of the magnetic-field annealing LSMO film decreases slightly. The values of Curie temperature (TC) and saturation magnetization (Ms) are obviously enhanced, which can be explained by the influence of the magnetic texture and enlarged grain size.

Crystal structure, surface morphology, surface chemical composition and photocurrent response curves of the thin films were investigated by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical workstation. The results show that the composite thin films are composed of CuO and Cu2O phase. The relative content of copper (I) oxide on the composite thin films increases with the increase of solution concentration. Leaf-like CuO particles have been observed on the thin film grown in the 0.5 mol/L solution. Some regular octahedral and truncated octahedral Cu2O particles have been observed on the surface of thin films grown in the 0.6 and 0.8 mol/L solution, respectively. The best photocurrent response and the fastest growth and decay have been observed in the thin film grown in 0.6 mol/L solution.

Magnesium doped zinc oxide (MgxZn1−xO) thin films were synthesized on silicon substrate through sol–gel process. Mg0.15Zn0.85O thin films were annealed at 500–800 °C and ZnO, Mg0.1Zn0.9O, Mg0.05Zn0.95O thin films were annealed at 600 °C for 60 min, respectively. The results show that all the samples are of a hexagonal wurtzite structure of ZnO. The surface morphology is strongly dependent on mean grain size and surface fluctuation. Fourier transform infrared spectra reveal that the vibration peak at 420 cm−1 is of the intrinsic lattice absorption of ZnO. The peak at 1083 cm−1 belongs to Si O Si asymmetric stretching vibration. Photoluminescence spectra show that the ultraviolet emission (365–400 nm) and the broad visible emission (469–569 nm) are observed. In particular, Mg0.05Zn0.95O thin film annealed at 600 °C exhibits the highest photocatalytic activity, degrading MO by almost 85.8% after 180 min illumination. The photocatalytic activity of the thin film is a synergistic effect defined by grain size, roughness factor, oxygen defects and amorphous MgO.

The planar anisotropy ball milling carbonyl-iron/Fe3O4 composites (BMCI/Fe3O4) have been synthesised via ball milling technique and hydrothermal method. The constituents, phase, and morphology have been characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electromagnetic wave absorption properties are measured by vector network analysis (VNA). The results indicate that BMCI/Fe3O4 composites synthesised in the pH values of 12 and 13 have absorption peak values of about −33·5 dB at 3·9 GHz and −28·2 dB at 4·2 GHz respectively, when the volume fraction of BMCI/Fe3O4 composites is only 20% and the matching thickness is 3·0 mm. A layer of ferromagnetic Fe3O4 crystals on the surface of BMCI has an obvious effect on the electromagnetic wave absorption properties of composites. A possible mechanism of the improved electromagnetic wave absorption properties of the composite has also been discussed.

Zinc oxide (ZnO) thin films with different ethylene glycol monomethyl ether (EGME) ratio were prepared on Si substrates using a two-step process. The results show that they possess a polycrystalline hexagonal wurtzite crystal structure. The topography of the ZnO thin films evolves from nanoparticles to hexagonal nanorods with the decrease of EGME content. The photoluminescence spectra consist of a near-band-edge emission and two visible emissions. The optical band gap energy decreases first and then increases with the increase of EGME ratio in mixed solvent, the broadening of the optical band gap can be explained by Moss–Burstein effect. The wetting behavior of all the samples can switch from hydrophobicity to hydrophilicity through UV illumination. The degradation efficiency of the thin films increases with decreasing EGME content, photocatalytic reaction mechanism of the ZnO thin films is discussed in detail.

The urchin-like structure of Fe/α-Fe2O3 composite has been prepared by a simple thermal oxidation method. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The microwave absorption property of the Fe/α-Fe2O3 composite was measured by vector network analysis (VNA). The excellent microwave absorption property of Fe/α-Fe2O3 composite was achieved due to the relatively low permittivity and unique isotropic antenna-like morphology. When the matching thickness is 2.5 mm, the optimal reflection loss of Fe/α-Fe2O3 reaches about −41.2 dB at 5.2 GHz. A possible mechanism of the improved microwave absorption properties of the composites was discussed.

Mg0.05Zn0.95O thin films were prepared on silicon substrates by a sol–gel dip-coating technique. Microstructure, surface topography and optical properties of the thin films were characterized by X-ray diffraction, atom force microscopy, Fourier transform infrared spectrophotometer and fluorescence spectrometer. The results show that the thin film annealed at 700 °C has the largest average grain size and exhibits the best c-axis preferred orientation. As annealing temperature increases to 800 °C, the grain along c-axis has been suppressed. Roughness factor and average particle size increase with the increase of annealing temperature. The IR absorption peak appearing at about 416 cm−1 is assigned to hexagonal wurtzite ZnO. The thin film annealed at 700 °C has the maximum oxygen vacancy, which can be inferred from the green emission intensity. Photocatalytic results show that the thin film annealed at 700 °C exhibits remarkable photocatalytic activity, which may be attributed to the larger grain size, roughness factor and concentration of oxygen vacancy. Enhanced photocatalytic activity of Mg0.05Zn0.95O thin films after a cycle may be attributed to the increase of surface oxygen vacancy and photocorrosion of amorphous MgO on the surface of thin film under UV irradiation.

ZnO thin films were synthesized via hydrothermal method on silicon substrate at various solution concentrations. The thin films were characterized by X-ray diffraction, field-emission scanning electron microscope and UV–Vis spectrophotometer. The results show that the thin films are polycrystalline with wurtzite hexagonal structure. The T c values of (101) surface of the thin film increase from 0.929 to 1.840 at first, and then decrease to 0.779 with increasing solution concentration. The preferential orientation along the (101) crystal surface can be controlled by changing the solution concentration. Solution concentration has a significant effect on surface morphology of the thin films. The optical band gap of the thin films decreases, when the solution concentration of zinc nitrate hexahydrate increases from 0.01 to 0.06 mol/L and then increases when the solution concentration of zinc nitrate hexahydrate further increases to 0.08 mol/L. Photocatalytic activity of the thin films on degradation of methyl orange under UV light irradiation was studied in detail. The ZnO thin film with many cracks prepared from 0.01 mol/L shows the higher photocatalytic activity but the tower-like ZnO thin film prepared from 0.08 mol/L reveals the lower photocatalytic activity. Therefore, the photocatalytic activity of the thin films are mainly relate to surface morphology and crystallographic orientation.

Carbonyls iron powders (CIPs)/Fe3O4 composites have been prepared by a simple hydrothermal method through controlling the pH value of the reaction system. The obtained products were characterized by X-ray diffraction (XRD), Raman spectrum, scanning electron microscopy (SEM), superconducting quantum interference device magnetometer (SQUID), thermogravimetry–differential thermal analysis (TG–DTA), etc. The microwave absorption properties of the CIP/Fe3O4 composites were measured by vector network analysis (VNA). A wide region of microwave absorption was achieved due to the high permeability of CIP/Fe3O4 composites (pH = 13). When the matching thickness is 2 mm, the reflection loss of the sample exceeding −10 dB was obtained at the frequency range of 8.7–15.0 GHz, with an optimal reflection loss of about −38.1 dB at 11.5 GHz. A possible mechanism of the improved microwave absorption properties of the composites was discussed.

Hollow glass microspheres/Fe3O4 (HGMs/Fe3O4) composites with low density were successfully synthesized by solvothermal method at 160 °C. The morphology, composition, and microstructure of the samples were characterized by scanning electron microscopy and X-ray diffraction, respectively. The results show that the HGMs/Fe3O4 composites exhibit compact and continuous Fe3O4 particles coating on the surface of HGMs. The complex permeability and permittivity of HGMs/Fe3O4 composites obtained at 160 °C for different reaction times were measured in the frequency range of 1–18 GHz by vector network analysis. The microwave absorption properties were well-elucidated by the traditional coaxial line method. The as-prepared HGMs/Fe3O4 composites show excellent microwave absorption properties. When the thicknesses of these HGMs/Fe3O4 composites are more than 1.5 mm, they all exhibit strong absorption peaks (lower than −10 dB). A possible mechanism of the improved microwave absorption properties was discussed.

ZnO thin films were grown on silicon substrates using a hydrothermal method. The XRD patterns show that all of the peaks can be attributed to the wurtzite structures of ZnO. The TC value of (002) plane and average crystal size increase first and then decrease with the increase of solution concentration. SEM and AFM results show that many dense hexagonal cylinder particles have been observed on the surface of the thin films, which grown at 0.08 and 0.10 mol/L. The surface roughness of the thin films deposited at 0.06, 0.08, 0.10, and 0.12 mol/L are 24.5, 38.3, 32.0, and 39.4 nm, respectively. Surface wettability results show that the preferential orientation along c-axis and surface roughness contribute significantly to the hydrophobicity. The reversible switching between hydrophobicity and hydrophilicity is related to the synergy of the transition of wetting model, surface crystal structure, and surface roughness.

Ni0.5Zn0.5Fe2O4particles with different particle sizes have been synthesized by sol-gel method. X-ray diffraction results show that all the samples are pure cubic spinel structure with their sizes ranging from 9 to 96 nm. The lattice constant significantly decreases with further increasing annealing temperature. The magnetic measurements show superparamagnetic nature below the particle size of 30 nm, while others show ferrimagnetic nature above the corresponding blocking temperature. The blocking temperature increases with the increase in particle size, which can be explained by Stoner-Wohlfarth theory. The saturation magnetization increases as the particle size increases, which can be explained by the cation redistribution on tetrahedral A and octahedral B sites and the domain wall motion. The variation of coercivity as a function of particle size is based on the domain structure.

Ni1−xZnxFe2O4 (0⩽x⩽1, in steps of 0.1) nanocrystallines were synthesized by sol-gel route. The doping effects of zinc on structural, magnetic and microwave absorption properties were investigated in detail. X-ray diffraction (XRD) results show that all the samples are single-phase spinel structure. The magnetic and microwave absorption properties are strongly dependent on the zinc content, which can be understood in terms of the cations redistribution in spinel tetrahedral and octahedral sites with the increase of zinc content. The magnetic measurement shows the antiferromagnetic nature of the samples for x=0.9 and x=1.0. The saturation magnetization reaches the maximum of 3.35 μB/f.u. at x=0.5. The optimal reflection loss (RL) of −29.6 dB is found at 6.5 GHz for an absorber thickness of 5 mm. The RL values exceeding −10 dB are obtained for the absorber in the range of 3.9–8.9 GHz. These Ni1−xZnxFe2O4 nanocrystallines may be attractive candidates for electromagnetic wave absorption materials.

Zn1−xCuxO nanorods with different Cu concentrations are prepared by a hydrothermal method. Bent and aggregated nanorods are obtained, which is attributed to centripetal surface tension of the evaporation and coagulation processes of the water film on the ZnO nanorods. The broad visible band consists of one violet, three blue, and one green emission. The violet emission is due to the transition of electrons from zinc interstitial (Zni) levels to the valance band. The three blue emissions may be attributed to the transition from extended Zni levels, which are slightly below the simple Zni level, to the valance band. The change of the green emission may be the result of competition between oxygen vacancies (VO) and zinc vacancies (VZn).

Multiwalled carbon nanotubes (MWCNTs)/Fe3O4 nanocomposites were synthesized via a simple low temperature solution method. The phase structures and morphologies of the composite were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the Fe3O4 spheres of about 150 nm were linked with MWCNTs. The microwave absorption properties of the MWCNTs/Fe3O4 nanocomposites were measured by vector network analysis (VNA). A wide region of microwave absorption was achieved due to dual magnetic and dielectric losses. When the matching thickness is 2 mm, the reflection loss (RL) of the sample exceeding −10 dB was obtained at the frequency range of 9.9–12.4 GHz, with an optimal RL of −29.8 dB at 11.04 GHz. A possible mechanism of the improved microwave absorption properties of the composites was discussed.

The crystal structure and morphology of ZnO, grown on silicon substrate by two-step method, were measured by X-ray diffraction and field emission scanning electron microscopy. The results reveal that the sample is mainly composed of ZnO nanorods and preferentially oriented in the c-axis direction. The photoluminescence properties of the ZnO nanorods were investigated over the temperatures from 10 K to 297 K. There exist three emission bands in near band-edge, green–yellow–orange–red and near-infrared, respectively. Donor bound exciton (D0X) and its phonon replicas emission peaks were observed in low temperature photoluminescence (PL). The D0X and its phonon replicas peak intensity decreased with the increase of temperature and disappeared when the temperature increased up to 87 K. The decay in the D0X and its phonon replicas emission peak intensity stemmed from the thermal dissociation of D0X to free exciton. Temperature-dependent second-order diffraction of the near band-edge emissions were investigated in detail.

La0.6Sr0.4MnO3 particles were prepared using the sol-gel method with an external magnetic field (Hext = 4 kOe) and without an external magnetic field. Structural and magnetic properties were systematically investigated. X-ray powder diffraction results show that both samples are single-phase. The results of field-emission scanning electronic microscopy show that the mean particle size of the sample synthesized under Hext = 4 kOe are slightly larger than that of the sample without an external magnetic field. The enhanced magnetic properties are attributed to the less disordered defects induced by an external magnetic field.

Zinc oxide thin films were deposited on silicon substrates via hydrothermal method. Microstructures, surface topographies and optical properties of ZnO thin films were systematically investigated by X-ray diffraction, atomic force microscopy and fluorescence spectrophotometer. The mean grain size and surface roughness of the thin films decrease first and then increase with increasing the concentration of zinc nitrate hexahydrate. The photoluminescence spectra of ZnO thin films, excited by the 240, 320, 360, 380 and 400 nm excitation wavelength, were investigated in detail. Based on our analysis, it can be noted that mechanisms of the ultraviolet, violet and blue emissions are attributed to the transitions from the localized levels below the conduction band, zinc vacancy, interstitial zinc and extended interstitial zinc levels to the valance band, respectively. Blue–violet emissions of ZnO have great potential in light emitting and biological fluorescence labeling applications.

M-type barium hexaferrites Ba1−xCexFe12−xCoxO19 ( 0.0 ≤ x ≤ 0.3 ) have been synthesized by a simple chemical coprecipitation method. X-ray diffraction (XRD) studies indicate that the samples are of single phase, with space group P 6 3 / m m c . The results of field-emission scanning electronic microscopy (FE-SEM) show that the grains are regular hexagonal platelets with sizes from 0.5 to 1.5 μ m . It is observed that the value of the coercivity field ( H c ) increases at low substitution ( x ≤ 0.1 ), reaches a maximum at x = 0.1 , and then decreases at x ≥ 0.1 , while the value of saturation magnetization ( M s ) decreases monotonically with increasing x . The variations of magnetic properties can be tentatively attributed to the effects of Ce–Co substitution. The results above indicate that our samples might be promising candidates for permanent magnets and perpendicular recording media materials in the future.