Room-temperature nonequilibrium growth of controllable ZnO nanorod arrays

In this study, controllable ZnO nanorod arrays were successfully synthesized on Si substrate at room temperature (approx. 25°C). The formation of controllable ZnO nanorod arrays has been investigated using growth media with different concentrations and molar ratios of Zn(NO3)2 to NaOH. Under such a nonequilibrium growth condition, the density and dimension of ZnO nanorod arrays were successfully adjusted through controlling the supersaturation degree, i.e., volume of growth medium. It was found that the wettability and electrowetting behaviors of ZnO nanorod arrays could be tuned through variations of nanorods density and length. Moreover, its field emission property was also optimized by changing the nanorods density and dimension

Enhanced Luminescence of Eu-Doped TiO2Nanodots

Monodisperse and spherical Eu-doped TiO2nanodots were prepared on substrate by phase-separation-induced self-assembly. The average diameters of the nanodots can be 50 and 70 nm by changing the preparation condition. The calcined nanodots consist of an amorphous TiO2matrix with Eu3+ions highly dispersed in it. The Eu-doped TiO2nanodots exhibit intense luminescence due to effective energy transfer from amorphous TiO2matrix to Eu3+ions. The luminescence intensity is about 12.5 times of that of Eu-doped TiO2film and the luminescence lifetime can be as long as 960 μs

DIELECTRIC AND FERROELECTRIC BEHAVIORS OF NOVEL PbTiO3/NiFe2O4 THIN FILMS PREPARED BY SOL–GEL METHOD

Ferroelectric/ferromagnetic (ME) biphase composite thin films with the type of (1–x)PbTiO3 (PT)–xNiFe2O4 (NFO) (x = 1–9) were successfully formed in situ by sol–gel process. The dielectric and ferroelectric behaviors of the composite thin films were investigated. The asymmetrical hysteresis loops of the composite arise from the leak current due to low resistivity of NFO. The stronger stress in the thin films due to the strong conjunction between PT and the substrate contributes to the increase (decrease) of the coercive force (the remanent polarization) with increasing the content of PT. The ME composites exhibit slight percolation effect. The high dielectric constant near the percolation threshold is attributed to the "micro-capacitors" in the composite thin films.Magnetoelectric composites, ferroelectric properties, dielectric properties, in situ combination, sol–gel method

Room-temperature nonequilibrium growth of controllable ZnO nanorod arrays

<p>Abstract</p> <p>In this study, controllable ZnO nanorod arrays were successfully synthesized on Si substrate at room temperature (approx. 25&#176;C). The formation of controllable ZnO nanorod arrays has been investigated using growth media with different concentrations and molar ratios of Zn(NO₃)₂to NaOH. Under such a nonequilibrium growth condition, the density and dimension of ZnO nanorod arrays were successfully adjusted through controlling the supersaturation degree, i.e., volume of growth medium. It was found that the wettability and electrowetting behaviors of ZnO nanorod arrays could be tuned through variations of nanorods density and length. Moreover, its field emission property was also optimized by changing the nanorods density and dimension.</p

Exchange coupling controlled ferrite with dual magnetic resonance and broad frequency bandwidth in microwave absorption

Ti-doped barium ferrite powders BaFe12−xTixO19 (x = 0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8) were synthesized by the sol–gel method. The phase structure and morphology were analyzed by x-ray diffraction (XRD) and scanning electron microscopy, respectively. The powders were also studied for their magnetic properties and microwave absorption. Results show that the Ti-doped barium ferrites (BFTO) exist in single phase and exhibit hexagonal plate-like structure. The anisotropy field Ha of the BFTO decreases almost linearly with the increase in Ti concentration, which leads to a shift of the natural resonance peak toward low frequency. Two natural resonance peaks appear, which can be assigned to the double values of the Landé factor g that are found to be ~2.0 and ~2.3 in the system and can be essentially attributed to the existence of Fe3+ ions and the exchange coupling effect between Fe3+ and Fe2+ ions, respectively. Such a dual resonance effect contributes a broad magnetic loss peak and thus a high attenuation constant, and leads to a dual reflection loss (RL) peak over the frequency range between 26.5 and 40 GHz. The high attenuation constants are between 350 and 500 at peak position. The optimal RL reaches around −45 dB and the practicable frequency bandwidth is beyond 11 GHz. This suggests that the BFTO powders could be used as microwave absorbing materials with extraordinary properties

Azimuthally Controlled Magnetic and Dielectric Properties of Multiferroic Nanocrystalline Composite by Magnetic Coupling and Charge Hopping

Multiferroic composite is an environmentally friendly material with the extraordinary multisusceptible and high storage properties. It is significant to find an effective way for designing and fabricating high-quality materials. In this context, the BTO/NZFO nanocrystalline multiferroic composite thin films with and without (100) oriented spinel ferrite were prepared by RF magnetron sputtering. The saturation magnetization, coercivity, and initial susceptibility of composite thin films with (100) oriented spinel NZFO phase are 1.05, 1.75 to 2.08, and 1.15 times as high as those of the composites without orientation, respectively. The dc conductivity and dielectric loss of the composite thin film with (100) oriented NZFO are 18 and 33.3% lower than those of composite without orientation, respectively. It is exhibited that the magnetic and dielectric properties of the BTO/NZFO multiferroic composite thin films are azimuthally controlled by distribution of the Zn/Fe–O–Ni/Fe superexchange coupling and charge hopping between Fe²⁺–Fe³⁺ pair, respectively. Obviously, controlling the arrangement of magnetic couplings and charge hopping is an effective route to fabricate the multiferroic composite with the optimal or specific magnetic and dielectric properties