Glycine functionalized activated carbon derived from navel orange peel for enhancement recovery of Gd(Ⅲ)

Glycine functionalized activated carbon adsorption material (NOPAC-GLY-X) was successfully prepared by one-step thermal decomposition using agricultural waste navel orange peel as a precursor. Through batch adsorption experiments, it is found that the adsorption performance of Gd(III) on activated carbon can be significantly enhanced by glycine modification. The adsorption isotherms of the NOPACs conform to the Langmuir isotherm model, and the maximum adsorption capacity of the activated carbon sample NOPAC-Gly-60 is approximately 48.5 mg/g. The Gd(III) adsorption capacity of navel orange peel activated carbon can be doubled after glycine modification, and the adsorption efficiency of gadolinium can reach 99% at pH = 7. The physicochemical properties of the prepared adsorbents were characterized by Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), and X-ray photoelectron spectroscopy (XPS). The characterization test shows that the specific surface area of the sample increases from 1121 to 1523 m²/g, and the ratio of (N + O)/C increases from 10.8% to 30.0% by the glycine modification. After five cycles of adsorption–desorption, the adsorption capacity can still be maintained at 88% of the initial capacity. NOPAC-GLY-60 has excellent adsorption selectivity for Gd(III). With the obvious advantages of simple synthesis steps and low cost, the activated carbon modification method adopted in this study has great application value in the field of rare earth adsorption and recovery.     

Simultaneous improvement of strength and ductility by Mn addition in extruded Mg–Gd–Zn alloy

The influence of Mn content on the microstructure, tensile properties and strain-hardening behaviors of extruded Mg?1Gd?0.5Zn?xMn (x=0, 0.3 and 1, wt.%) alloy sheets was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), and electron backscatter diffraction (EBSD). The results show that the completely recrystallized grain structure and the extrusion direction (ED)-titling texture are observed in all the extruded sheets. The mean grain size and weakened ED-titling texture of the extruded sheets are gradually reduced with increasing Mn content. This is primarily associated with the formation of new fine α-Mn particles by Mn addition. Tensile properties show that the addition of Mn also leads to the improvement of yield strengths, ultimate tensile strengths and elongations of the extruded Mg?1Gd?0.5Zn?xMn sheets, which is mainly due to the fine grains and α-Mn particles. In addition, the Mg?1Gd?0.5Zn?1Mn sheet has the lowest strain-hardening exponent and the best hardening capacity among all prepared Mg?1Gd?0.5Zn?xMn sheets.     

Rapid synthesis of Gd2Zr2O7 glass-ceramics using spark plasma sintering

Glass-ceramics are possible host matrix for high level waste immobilization. The Gd₂Zr₂O₇ glass-ceramic matrix was successfully synthesized using spark plasma sintering (SPS) method in 5 minutes. The phase transition with sintering temperature was studied using X-ray diffraction, Raman and transmission electron microscopy. It revealed that samples kept a main defected fluorite phase as being sintered below 1800°C. Glass phase increased rapidly beyond 1850°C. The amorphous structure became the main body at 1900°C, with nanoscale crystal scattered in the bulk. With the increase of glass phase, the grain boundary became almost indistinguishable. The relationship between the final phase of Gd₂Zr₂O₇ with its synthetic temperature range and corresponding technology was reviewed. Gd₂Zr₂O₇ glass-ceramics could be acquired by extending the sintering temperature beyond 1850°C using SPS method.     

Synthesis route dependent structure,conductivity and dielectric properties of Ce0.8Gd0.2O1.9 oxygen ion conductor: A comparative approach

The main focus of this study is to investigate the effect of the synthesis route on structure, microstructure, and ionic transport properties of Ce_0.8Gd_0.2O_1.9 ionic conductors. Three different synthesis routes, namely citrate auto–ignition, mechanical alloying, and co–precipitation method, were employed for the synthesis of Ce_0.8Gd_0.2O_1.9 nanomaterials. The density of the composition prepared through the citrate auto–ignition method was found to be much greater than the compositions prepared by the other two methods. The dissolution of Gd³⁺ ions into ceria was highest for the samples prepared via this method. The crystallite and grain size of the samples was also found to depend on the synthesis route. On the other hand, the co–precipitation method produced finer nanomaterials in comparison with the other two methods. The sample prepared via the auto?ignition method exhibited the highest ionic conductivity, dielectric constant, and lowest association energy. The sample prepared using the co–precipitation method exhibited enhanced grain boundary conductivity due to the lesser value of grain boundary thickness and grain boundary blocking factor.     

Thermodynamic assessment of BaO–Ln2O3 (Ln = La,Pr, Eu,Gd, Er) systems

Heat capacities and enthalpies of formation of BaGd₂O₄ were determined by high-temperature differential scanning calorimetry and high-temperature oxide melt solution calorimetry, respectively. Thermodynamic stability of BaLn₂O₄ compounds increases with decreasing Ln³⁺ ionic radius. Previously reported data on BaNd₂O₄ and BaSm₂O₄ corroborate this trend. Missing data for compounds in BaO–Ln₂O₃ (Ln = La, Pr, Eu, Er) systems were estimated from established relations, thermodynamic assessment was performed, and binary phase diagrams were calculated.     

Improved photocatalytic activity of Bi4TaO8Cl by Gd3+ doping

Bi₄TaO₈Cl and Bi₄TaO₈Cl:Gd³⁺ photocatalysts were synthesized by the solvothermal technique. The phase, microstructure, optical properties, and photocatalytic activities were investigated. Both Bi₄TaO₈Cl and Bi₄TaO₈Cl:Gd³⁺ have the singly orthorhombic phase and the flower-like hierarchical structure. The Bi₄TaO₈Cl:Gd³⁺ has higher photocatalytic activity of MB than that of Bi₄TaO₈Cl under visible light irradiation. The higher photocatalytic activity of Bi₄TaO₈Cl:Gd³⁺ is induced by its lower band gap energy, the higher efficiency charge separation, and transfer process, as well as the photogenerated charge carriers with a longer time, which are confirmed by the longer absorption band edge, lower emission intensity, and higher photocurrent under visible light irradiation. The trapping experiments and electron spin resonance results suggest that ˙O₂⁻ is the predominant active species for the photocatalysis of MB by Bi₄TaO₈Cl and Bi₄TaO₈Cl:Gd³⁺ under visible light irradiation.     

Fabrication of gadolinium zirconate films by laser CVD

In the present work, Gadolinium zirconate (GZ) films were prepared by laser CVD (LCVD) method. The influence of preparation conditions, involving preheating temperature (T_pre) and laser output power density (P_l) on morphology, microstructure, substrate temperature (T_sub) and deposition rate was thoroughly investigated. An extended formation region of GZ films, based on T_pre and P_l values, was observed at a pressure of about 0.9 kPa. Laser irradiation mainly plays a photolytic role when P_l <?0.40?W/mm² and pyrolytic role when P_l ≥?0.40?W/mm² at GZ films deposition. The maximum deposition rate was up to 307?µm/h. Gd₂O₃-ZrO₂ films phase diagram including three zones can be obtained under an optimized condition of T_pre =?1173?K, P_l =?0.80?W/mm² and P_tot =?0.9 kPa. Pure GZ films with 0.19?≤?Gd/Zr?≤?1.72 can be observed at one of the three zones. In addition, Gd₂O₃ and ZrO₂ can stabilize each other to their cubic phases, offering a stable structure.     

Improvement of flux pinning in GdBa2Cu3O7−δ thin film by nanoscale ferromagnetic La0.67Sr0.33MnO3 pretreatment of substrate surface

The present paper presents the effects of ferromagnetic La_0.67Sr_0.33MnO₃ (LSMO) nanoparticles on the pinning characteristics of an epitaxial GdBa₂Cu₃O_7?δ ((Gd) BCO) film deposited on top. LSMO nanoparticles with the size between 10 and 20 nm were obtained on a (001) STO substrate by RF sputtering method. The analyses of magnetic measurements revealed that the presence of a complex vortex pinning mechanism within the (Gd) BCO film deposited on the undecorated substrate. With respect to a reference (Gd) BCO film, two additional pinning effects in LSMO decorated (Gd) BCO film were observed. One is the effect of the threading dislocations due to LSMO nanoparticles, and the other one is the LSMO nanoparticles itself. Like other nanosized particles, the LSMO nanoparticles on substrate will induce threading dislocations passing through the (Gd) BCO film. These threading dislocations serve as correlated pinning centers along the c-axis, which lead to the improvement of flux pinning properties in LSMO decorated (Gd) BCO film. According to the ferromagnetic property of LSMO material, a magnetic pinning mechanism was proposed to explain the significant increase of Jc and Fp values. The flux pinning abilities of LSMO nanoparticles were evaluated. The enhanced pinning characteristics in the high field region and high temperature together with the movement of H _Fpmax (the corresponding field of F_pmax) also suggest a magnetic pinning mechanism for LSMO nanoparticles existed in LSMO decorated (Gd) BCO film.     

Relation of normal load with test temperature at mild–severe wear transition state for Mg–Gd–Y–Zr alloy

The wear behavior and mild–severe (M–S) wear transition of Mg–10Gd–1.5Y–0.4Zr alloy were investigated within a temperature range of 20–200 °C. The morphologies and compositions of worn surfaces were examined to identify the wear mechanisms using scanning electron microscope and energy dispersive X-ray spectrometer. The microstructure and hardness in the subsurfaces were analyzed to reveal the M–S wear transition mechanism. Under a constant loads of 20, 35 and 40 N, each wear rate–test temperature curve presented a turning point which corresponded to the M–S wear transition. In mild wear, the surface material was plastically deformed and hence was strain- hardened, whereas in severe wear, the surface material was dynamically recrystallized and consequently was softened. It has been found that the critical temperature for M–S wear transition decreases with increasing the normal load, and the normal load exhibits an almost linear relationship with critical temperature for M–S wear transition. This work reveals that the M–S wear transition of the studied alloy conforms to the surface DRX temperature criterion.