Dean Pan

Giant magnetoelectric effect in Ni–lead zirconium titanate cylindrical structure

The magnetoelectric (ME) coupling of a bilayered Ni–lead zirconate titanate composite structure synthesized by electrodeposition was studied in this paper. The ME voltage coefficient was measured in the range of 1–120kHz as the bias field is parallel to the axial. The results indicate that an electromechanical resonance appears at 59.9kHz. The bilayered cylindrical ME composite exhibits a special field dependence of ME coefficient. Either for the resonant state or the nonresonant state, above 1kOe, the ME voltage coefficient increased linearly with the strengthening of bias field, up to 30V∕cmOe at 8kOe.

Rare earth elements recycling from waste phosphor by dual hydrochloric acid dissolution

This paper is a comparative study of recycling rare earth elements from waste phosphor, which focuses on the leaching rate and the technical principle. The traditional and dual dissolution by hydrochloric acid (DHA) methods were compared. The method of dual dissolution by hydrochloric acid has been developed. The Red rare earth phosphor (Y0.95Eu0.05)2O3 in waste phosphor is dissolved during the first step of acid leaching, while the Green phosphor (Ce0.67Tb0.33MgAl11O19) and the Blue phosphor (Ba0.9Eu0.1MgAl10O17) mixed with caustic soda are obtained by alkali sintering. The excess caustic soda and NaAlO2 are removed by washing. The insoluble matter is leached by the hydrochloric acid, followed by solvent extraction and precipitation (the DHA method). In comparison, the total leaching rate of the rare earth elements was 94.6% by DHA, which is much higher than 42.08% achieved by the traditional method. The leaching rate of Y, Eu, Ce and Tb reached 94.6%, 99.05%, 71.45%, and 76.22%, respectively. DHA can decrease the consumption of chemicals and energy. The suggested DHA method is feasible for industrial applications.

Shape and size effects on layered Ni/PZT/Ni composites magnetoelectric performance

This paper presents the magnetoelectric (ME) effect in trilayered Ni/PZT/Ni composites which is related to their size and shape. The ME composites with the same interfacial areas but different geometrical shapes have different ME voltage coefficients. Longitudinal resonant modes in the rectangular and triangular trilayered ME composites were studied. One should choose optimized size, shape and working frequency of the ME composites in order to gain the maximum ME effect. This study plays a guiding role for trilayered ME composites design for real applications.

Simple model of the magnetoelectric effect in layered cylindrical composites

A simple model of the magnetoelectric (ME) effect in cylindrical layered composites is presented. The cylinder is replaced by the effective layered plate structure with effective length, Leff, thickness t and height h. In the axial coupling mode, the effective magnetic field acts along the length direction (Leff). However, in the vertical coupling mode, the effective magnetic fields act in two directions simultaneously, one along the thickness direction (normal, t) and the other along the effective height (tangential, Leff) direction, respectively. Experimental results and theoretical analysis indicated that the cylindrical layered composites ME voltage coefficient is much higher compared with that of the layered plate.

Electro-deposition current density effect on Ni/PZT layered magnetoelectric composites performance

This paper considers the magnetoelectric (ME) effect in Ni/PZT layered ME composites that is related to the preferred crystallographic orientation of electro-deposited Ni layers. The Ni electro-deposition rate increases with applied cathodic current density. High (1 0 0) texture in the Ni layer was obtained at either low or high current densities, which improves the ME composites performance. It is advantageous to increase the current density, while trying to avoid hydrogen evolution during electro-deposition to reduce the number of pinhole defects.

Peak divergence in the curve of magnetoelectric coefficient versus dc bias magnetic field at resonance region for bi-layer magnetostrictive/piezoelectric composites

Magnetoelectric (ME) coefficient dependence on the bias magnetic field at resonance frequencies for the bi-layered bonded Terfenol-D/Pb(Zr,Ti)O3 composite was investigated. The resonance frequency decreases first and then increases with the bias magnetic field (HDC), showing a “V” shape in the range of 0 ∼ 5 kOe. Below the resonance frequency, the pattern of ME coefficient dependence on the HDC shows a single peak, but splits into a double-peak pattern when the testing frequency increases into a certain region. With increasing the frequency, a divergent evolution of the HDC patterns was observed. Domain motion and ΔE effect combined with magnetostriction-piezoelectric coupling effect were employed to explain this experimental result.

Effect of TiO2 on Crystallization, Microstructure and Mechanical Properties of Glass-ceramics

The effect of TiO2 addition to the stainless steel slag glass-ceramics was studied. Different mass percentages of TiO2 were added to four samples of the parent glass made from stainless steel slag and cullet. The temperatures of nucleation and crystallization were determined by differential scanning calorimetry (DSC). According to X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, adding TiO2 refined grains and restricted the formation of the akermanite phase by capturing Ca2+ to form the perovskite phase. Diopside was the main crystal phase of the glass-ceramics. The bending strength and Vickers hardness increased with the addition of TiO2. The optimal amount of TiO2 was 7 mass%, and the highest bending strength and Vickers hardness were 144.6 MPa and 6.26 GPa, respectively.

Multi-electrode Pb(Zr,TiO)3/Ni cylindrical layered magnetoelectric composite

Multi-electrode Pb(Zr,TiO)3/Ni cylindrical layered magnetoelectric (ME) composites were made by electroplating. The electroplated Ni layers were arrayed as four arcs on the inner PZT cylinder surface. The axial ME voltage coefficient of the composites was studied. Due to the cylinder symmetry, each of the four units of the PZT/Ni cylinder showed the same ME voltage response as the whole cylindrical ME composite, or when connected in parallel. When the four units were connected in series, the ME voltage was improved about three times than the single unit. This optimization is promising for the miniaturized ME devices design.

One-step Crystallization Kinetic Parameters of the Glass-ceramics Prepared from Stainless Steel Slag and Pickling Sludge

One-step crystallization is one of the most energy conserving methods for glass-ceramics preparation. However, only a few kinetics studies focused on the glass-ceramics prepared by the one-step crystallization. The one-step crystallization kinetic parameters were studied using differential scanning calorimetry. The activation energy (Ea) and the Avrami parameter (n) were calculated as 152. 79 kJ • mol−1 and 4.39, respectively. These parameters indicate that continuous nucleation and three-dimensional crystal growth are the dominating mechanisms in the one-step crystallization process of the parent glass. The properties of the obtained glass-ceramics can be compared to the glass-ceramics prepared by the two-stage heat treatment and sintering method. This crystallization kinetics research can be used to evaluate the one-step crystallization potential of a parent glass.

Complete recovery of Eu from BaMgAl10O17:Eu2+ by alkaline fusion and its mechanism

An environmentally friendly and efficient process for recycling waste phosphors has been developed. The alkaline fusion process is used for recycling Eu from BaMgAl10O17:Eu2+ (BMA) completely. The comprehensive BMA disintegration via alkaline fusion is discussed. Relationships between the alkaline fusion temperature and various properties of the compounds have been examined by various techniques (DSC-TG, XRD, SEM and XPS) to elucidate their roles in BMA disintegration in the alkaline fusion process. X-ray diffraction analysis provides details of the phase change. Based on X-ray photoelectron spectroscopy, a scientific hypothesis of crystal structure disintegration is presented. Sodium ions would substitute the europium and barium ions in the mirror plane and magnesium ions in the spinel block successively, which results in more oxygen vacancies and interstitial sodium ions appearing. The unit cell (P63/mmc (194)) would break from the mirror plane, then changes into BaAl2O4 (P6322 (182)), and be decomposed into NaAlO2, and barium and europium ions combine with free OH− and CO2 to form BaCO3, Eu2O3 and H2O. In the end the Eu2O3 can be recycled easily by acidolysis, oxalic acid precipitation and ignition. The mechanism provides a fundamental basis for recycling REEs from waste phosphors.