Synthesis and Magnetic Characterization of SolGel‐Derived Submicrometer NaGd(WO4)2

NaGd(WO₄)₂ (NGW) submicrometer powder was derived by solgel method, and its magnetic properties were investigated for magnetic texturing application. The analysis of X‐ray diffraction indicates the formation of tetragonal phase. Organic liberation with respect to temperature in the samples and carbon content in the prefired powder was analyzed using FTIR results. Raman spectra confirm the tetrahedral tungstate formation and corresponding vibrations. UV‐Vis Reflectance study revealed the corresponding absorption of NGW host and gadolinium ions. The morphology and approximate size of the synthesis powder was observed with SEM micrographs. The paramagnetic nature of NGW was confirmed with EPR, and VSM analysis at room temperature and paramagnetic to antiferromagnetic phase transition was observed around 5 K. Results indicate that NGW powders can be used for magnetic texturing to grow transparent ceramic.     

Photoluminescence properties of Eu-doped WO3-Eu2(WO4)3 composites and single-phase Eu2(WO4)3 powders

The development of highly stable and efficient oxide-based red phosphors is urgently required for next-generation lighting devices. Herein, we report the micro/crystal structures and luminescent properties of single-phase Eu₂(WO₄)₃ and Eu³⁺-doped WO₃-Eu₂(WO₄)₃ composite phosphors prepared by a one-step conventional solid-state reaction method in air atmosphere. As increasing Eu contents in the mixtures of WO₃ and Eu₂O₃, the intensities of the X-ray diffraction peaks of Eu₂(WO₄)₃ increased while that of WO₃ decreased. The photoluminescence intensity of the synthesized phosphors increased with increase in the Eu content when calcined at 900 °C, while it degraded at a higher temperature. Red-emitting single-phase Eu₂(WO₄)₃ powders were successfully obtained when the WO₃ and Eu₂O₃ powders were calcined in the ratio of 3:1. The intensity of the red emission spectra of the Eu₂(WO₄)₃ phosphor was higher than those of the 6, 12, and 24 at.% Eu-added WO₃ composites at excitation wavelengths of 394 and 465 nm. On the other hand, the intensity of emission from the single-phase phosphor was lower than that of the Eu-doped WO₃-Eu₂(WO₄)₃ composites under excitation of UV light at 254 nm. Thus, we propose two prospective phosphors for application as red phosphors at various wavelengths.     

Ethanol‐Water‐Derived Sucrose‐Coated‐Al2O3 for Submicrometer AlON Powder Synthesis

Fluffy and homogenous sucrose‐coated‐γ‐Al₂O₃ structured precursor was prepared by drying ethanol‐water sucrose/Al₂O₃ suspension, in which the ethanol content of 85 vol% was optimized. Using the C/Al₂O₃ mixture pyrolyzed from such precursor with 23.2 wt% sucrose, single‐phase AlON powder was synthesized by two‐step carbothermal reduction and nitridation method at 1550°C for 2 h and 1700°C for another 1.5 h. The particle size of the AlON powder was around 0.6–1.0 μm. Compared with those synthesized by the traditional approaches with mechanical C/Al₂O₃, Al/Al₂O₃, or AlN/Al₂O₃ mixtures, the synthesis temperature was reduced about 50°C, and the AlON powder was fine and exhibited good dispersity. Such superiority of this method was attributed to that the pyrolyzed carbon film on Al₂O₃ particle greatly restrained Al₂O₃ coalescence during the thermal treatment.     

Preparation of Fe3Si‐Al2O3 Nanocomposite Powders by Mechanochemical Reaction of Fe3O4‐Si‐Al Powder Mixtures

Phase evolution and morphology of Fe₃O₄‐Si‐Al powder mixtures during ball milling from 30 min to 20 h were investigated. A 3‐h critical milling was necessary for the occurrence of mechanically activated combustion reaction. The reaction results in the formation of Fe (Si), Fe₃Si, and α‐Al₂O₃. During ball milling from 3 to 20 h, Fe (Si) and Fe₃Si were combined into disordered Fe₃Si intermetallic and Fe₃Si‐Al₂O₃ composite powder was formed. The presence of in situ formed alumina leads to a decrease in crystallite and particle sizes. The Fe₃Si‐Al₂O₃ particles after milling for 20 h had a crystalline size of 10~12 nm.     

Preparation of phosphate promoted Na2WO4/Al2O3 catalyst and its application for oxidative desulfurization

Phosphate promoted Na₂WO₄/Al₂O₃ catalyst with 10 wt.% tungsten was prepared by simple impregnation method. Analytical characterization results showed that tungstate and phosphate were uniformly dispersed in alumina matrix and its structural properties were preserved. The effect of phosphate as promoter in catalyst activity was studied using dibenzothiophine (DBT) as model oil and the results reveal that it plays an important role in oxidation activity of Na₂WO₄/Al₂O₃ catalyst, in addition, the catalytic activity of Na₂WO₄/Al₂O₃ was increased gradually with increasing phosphorus contents up to 2.5 wt.%. The catalyst was recycled and the results show that no significant decrease in catalyst activity was observed even after five recycled runs. We also applied our catalyst in oxidative desulfurization (ODS) of FCC diesel oil (with sulfur contents 4100 ppm), and more than 92% of sulfur was removed from diesel oil under mild reaction conditions.     

In situ characterization of LiY(WO4)2 nanotubes for electrochemical energy storage

Here, LiY(WO₄)₂ nanotubes are prepared via a feasible electrospinning technique. This new anode material shows excellent electrochemical properties. The capacity loss of LiY(WO₄)₂ nanotubes is as low as 6.9% after 156 cycles, while bulk LiY(WO₄)₂ presents the capacity loss higher than 55.0%. Even after 600 long-life cycles, the capacity loss of the nanotubes is only 9%. It can be seen that the hollow structure with a rough surface and a porous morphology contributes to the improvement of electrochemical performance. Furthermore, online X-ray diffraction (XRD) method is firstly applied to understand the lithium ions insertion/extraction mechanism of LiY(WO₄)₂ nanotubes. It can be concluded that it is an asymmetrical two-phase reaction. A phase transformation from LiY(WO₄)₂ to Li₃Y(WO₄)₂ can be obviously seen from the in situ XRD during discharge process. While Li₂Y(WO₄)₂ appears as an intermediate phase with a reverse charge reaction. In addition, in situ XRD also demonstrates that LiY(WO₄)₂ nanotubes have surprised electrochemical reversibility. All the above results indicate that LiY(WO₄)₂ nanotubes can be expected to be anode candidate for rechargeable lithium ion batteries (LIBs).     

LiTi2（PO4）3表面包覆LiNi0.05Mn1.95O4及其性质

采用湿化学法在LiNi0.05Mn1.95O4表面包覆锂离子导体LiTi2(PO4)3。采用X射线衍射、扫描电子显微镜、恒电流充放电、电位阶跃、交流阻抗技术对合成产物进行物相、形貌和电化学分析。结果表明:LiTi2(PO4)3包覆LiNi0.05Mn1.95O4与未包覆LiNi0.05Mn1.95O4具有相似的X射线衍射结果,LiNi0.05Mn1.95O4包覆LiTi2(PO4)3前后的锂离子扩散系数变化不大,但包覆LiTi2(PO4)3后的LiNi0.05Mn1.95O4颗粒边界和轮廓变得模糊。LiTi2(PO4)3包覆LiNi0.05Mn1.95O4的比容量略低于未包覆LiNi0.05Mn1.95O4,且随着LiTi2(PO4)3包覆量的增加而减小,但包覆LiTi2(PO4)3后的LiNi0.05Mn1.95O4循环性能得到了大幅提高。     

Crystallization Kinetics of Superionic Conductive Al(B,La)‐ Incorporated LiTi2(PO4)3 Glass‐Ceramics

For the purpose of developing high‐performance glass‐ceramic superionic conductor, the controllable precipitation of LiTi₂(PO₄)₃‐like superionic conducting phase in the Li₂O–TiO₂–P₂O₅ glass system was studied. Al with B or La co‐incorporated LiTi₂(PO₄)₃‐based glass‐ceramics were prepared by the crystallization of the corresponding original glasses. Compared with the sole Al‐incorporated LiTi₂(PO₄)₃‐based glass‐ceramics, the ionic conductivity shows an increase for the boron co‐incorporated one and a decrease for the lanthanum co‐incorporated one. Through the further in‐depth analysis based on the methods of DSC and X‐ray diffractive technique, this opposite change in ion conductivity was ascribed to the alterations of crystallization mechanism together with quantity of crystal phases within the glass‐ceramics.. The boron addition promoted the precipitation of LiTi₂(PO₄)₃ phase and restrained the precipitation of second phase. The highest ionic conductivity 1.3 × 10^?3 S/cm at 25°C was obtained through the heat treatment of B and Al co‐incorporated glassy samples at 900°C for 12 h. These inorganic solid electrolytes have a potential application in lithium batteries or other electrochemical ionic devices.     

Toward Facile Preparation and Design of Mulberry-Shaped Poly(2-methylaniline)-Ce2(WO4)3@CNT Nanocomposite and Its Application for Electrochemical Cd2+ Ion Detection for Environment Remediation

Novel hybrid material was prepared by adding slurries of poly(N-methylaniline) and cerium tungstate [Ce₂(WO₄)₃] into a conical flask contained dispersed carbon nanotubes. It was characterized by scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Electrical conductivity of poly(N-methylaniline)-Ce₂(WO₄)₃@carbon nanotube samples was determined using four-probe method. The thin layer of poly(N-methylaniline)-Ce₂(WO₄)₃@carbon nanotube was fabricated onto glassy carbon electrode for a selective Cd²⁺ ion sensor. The calibration plot is linear (r²?=?0.9917) over the large Cd²⁺ concentration ranges (1.0?nM–1.0?mM). The sensitivity, detection limit is ～5.138?µA?µM^?1?cm^?2 and ～0.11?nM (signal-to-noise ratio, at a SNR of 3), respectively.     

Controllable Preparation of Al2O3‐MgO·Al2O3‐CaO·6Al2O3 (AMC) Composite with Improved Slag Penetration Resistance

Compact Al₂O₃‐MgO·Al₂O₃‐CaO·6Al₂O₃ (AMC) composite was obtained by melting technology using industrial alumina, light‐burned magnesia, and quick lime as raw materials based on the Al₂O₃‐MgO‐CaO ternary phase diagram. The results show that the phases of MgO·Al₂O₃ and Al₂O₃ are formed as the main framework with plate‐like CaO·6Al₂O₃ crystals mainly discontinuously embedded in MgO·Al₂O₃. The bulk density of AMC composite is up to 3.42 g/cm³, equivalent to 90.5% of the theoretical density. The synthesized compact AMC composite in the work also exhibits better slag penetration resistance than the castable based on tabular corundum due to the formation of liquid phase.     

Al_2(SO_4)_3-NH_3·H_2O法大孔拟薄水铝石的制备及其应用

在Al3+浓度0.6 mol·L-1、反应温度60℃和p H=9条件下,研究了硫酸铝滴定氨水(酸滴碱法)、氨水滴定硫酸铝(碱滴酸法)、p H摆动法和并流法成胶方式对共沉淀法制得的拟薄水铝石物化性能的影响。采用X射线衍射、N2吸附-脱附和扫描电镜等对拟薄水铝石进行表征。结果表明,成胶方式对拟薄水铝石物理性能影响显著,采用并流法成胶方式制得的拟薄水铝石比表面积374 m2·g-1,孔容0.89 cm3·g-1,孔径6.4 nm且分布集中,结晶度高,纯度好,能够满足加氢催化剂载体所用拟薄水铝石的物化性能要求。以并流法成胶方式得到的拟薄水铝石制备的Pd/Al2O3催化剂用于裂解汽油双烯烃选择加氢时表现出优异的加氢性能。     

Preparation and properties of novel Tb3Sc2Al3O12 (TSAG) magneto-optical transparent ceramic

Novel Tb₃Sc₂Al₃O₁₂ (TSAG) magneto-optical transparent ceramic was fabricated by vacuum sintering. The phase composition, microstructure, optical quality, thermal properties, and magneto-optical properties of TSAG ceramic were measured. It is shown that the increase in holding time has an effect on the grain size of TSAG ceramic. It is noted that TSAG35 ceramic presents the highest transmittance, corresponding to 81.5 % at the wavelength of 1064 nm. The thermal properties of TSAG ceramic are close to or superior to that of the reported TSAG and TGG crystals. The Verdet constant of TSAG ceramic is comparable to that of reported TSAG crystal, and 1.2 times that of TGG crystal. The results indicate that the novel TSAG ceramic is comparable to TSAG crystal in terms of magneto-optical properties and superior to TGG crystal, making it a candidate material for magneto-optical materials to be used in high-power lasers.     

Fe(2‐EHA)3/Al(i‐Bu)3/hydrogen phosphite catalyst for preparing syndiotactic 1,2‐polybutadiene

Polymerizing 1,3‐butadiene into syndiotactic 1,2‐polybutadiene with an iron(III) catalyst system has been investigated. Activity of the catalyst was affected by the type of cocatalyst alkylaluminum and the phosphorus compound as an electron donor, molar ratio of catalyst components, and their aging sequence and aging time of the catalyst. The microstructure and configuration of the polymer was decided by the catalyst components, the higher [Al]/[Fe] molar ratio tending to yield syndiotactic 1,2‐polybutadiene, while the higher [P]/[Fe] molar ratio favors the formation of amorphous 1,2‐polybutadiene. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4265–4269, 2006     

Ion transport studies in PEO:NH4ClO4 polymer electrolyte and its composite with Al2O3

Composition, temperature and humidity dependence of ionic conductivity in polyethylene oxide (PEO):NH₄ClO₄ polymer electrolyte composite obtained by the dispersal of Al₂O₃ is reported. The dispersal of Al₂O₃ introduces significant changes in the conductivity vs. composition isotherm. The conductivity of the composite peaks at two concentrations of Al₂O₃ is ~2 × 10^?5 S cm^?1. For studying ion dynamics, motional narrowing of ¹H NMR line with temperature is also reported. In PEO:NH₄ClO₄ (without dispersed Al₂O₃), two ¹H frequency-shifted NMR lines are seen (one of these have been assigned to the ¹H belonging to –CH₂–CH₂– chain of the polymer and the other to NH₄ ⁺ complexed with the chain). For the (PEO:NH₄ClO₄) + Al₂O₃ composites, however, one additional narrow peak is also seen at temperatures higher than 40 °C. This has been interpreted in terms of some hopping H⁺ ions getting loosely bonded to Al₂O₃, forming Al(OH)₃, which possibly releases an additional mobile protonic species (OH^?).     

In situ synthesis of Al2O3‐supported ZnCr2O4 nanoparticles for application as an activated photocatalyst

Zincochromite nanoparticles (NPs) were precipitated on surfaces of the as‐prepared Al₂O₃ micron‐sized particles by a heterogeneous precipitation technique using urea as a homogeneous precipitation agent. This procedure leads to decrease the pore diameter and increase the pore volume and specific surface area (a_s), realizing the potential access to ZnCr₂O₄ catalytic sites. Although the obtained band gap energy (E_g) of Al₂O₃‐ZnCr₂O₄ composite is about 2.3 eV (more than ZnCr₂O₄), the absorbance is enhanced about 1.5 orders of magnitude. These characteristics make it an effective photocatalyst of inorganic dyes from an aqueous media. Dye removal performance of the nanocomposite powder is higher than that of pure ZnCr₂O₄, which is attributed to an increase in the photocatalytic sites and the absorbance intensity. It was believed that the surface area created from Al₂O₃ support realized the potential access to ZnCr₂O₄ catalytic sites. To confirm these assertions, X‐ray diffractometry (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and N₂ adsorption‐desorption analysis were applied.     

Improved Energy Storage Properties of Fine‐Crystalline BaTiO3 Ceramics by Coating Powders with Al2O3 and SiO2

The multilayer structure of capacitor demands for fine grain size of dielectric ceramics in devices, because the thinner layer which needs ceramics with fine grain size is helpful in enlarging the capacitance. In this paper, the aqueous chemical coating method was utilized to modify the BaTiO₃ particles. The fine‐crystalline BaTiO₃ ceramics with an average grain size below 200 nm without abnormal grain growth by co‐coating Al₂O₃ and SiO₂ has been prepared. The phase composition, microstructures of coated particles and ceramics, and dielectric properties were investigated. For samples containing 3 wt% of Al₂O₃ and 1 wt% of SiO₂, the energy storage density is 0.725 J/cm³ and the efficiency of the ceramic samples can keep above 80%. The breakdown strength was improved to about 190 kV/cm.     

Yb3+:Na5Bi(WO4)2(MoO4)2多晶料的制备与性能表征

采用高温固相反应合成了混酸盐多晶材料Yb3+:Na5Bi(WO4)2(MoO4)2.利用X射线衍射仪(XRD)、同步热分析仪(DSC-TG)、红外光谱仪和荧光光谱仪等分析测试技术,对多晶材料Yb3+:Na5Bi(WO4)2(MoO4)2的结构与光谱性能进行了研究,研究发现:新相属于四方晶系,空间群为I41/a(88),熔点约为930 ℃,吸收带宽为83 nm,发射中心波长为1006 nm,发射带宽为50 nm,荧光寿命为589.03 μs.     

Solvothermal Conversion of Nanofiber to Nanorod‐Like Mesoporous γ‐Al2O3 Powders,and Study Their Adsorption Efficiency for Congo Red

Mesoporous γ‐Al₂O₃ powders with nanofiber and nanorod‐like structures were synthesized using boehmite sols in the presence of triblock copolymer, P123 in ethanol by solvothermal process at different temparatures (100°C–165°C) followed by calcination at 400°C–1000°C. The powders were characterized by low‐ and wide‐angle X‐ray diffraction (XRD), N₂ adsorption–desorption, and transmission electron microscopy (TEM). The adsorption efficiency of the powders with Congo red (CR) was studied by UV–vis spectroscopy. The γ‐Al₂O₃ phase became stable up to 1000°C. The nanorods obtained at 165°C had narrower pore size distribution (PSD) than nanofibers synthesized at 100°C, the former showed higher CR adsorption efficiency. The stepwise growth mechanism of nanofibers to nanorods conversion with increase in solvothermal temperatures was illustrated.     

Comparison of Large‐Scale Production Methods of Fe2O3/Al2O3 Oxygen Carriers for Chemical‐Looping Combustion

Oxygen carrier (OC) particles for chemical‐looping combustion (CLC) may be produced in large scale by a number of methods such as freeze granulation, spray drying, impregnation, and mechanical mixing methods. To select the most appropriate technology for large‐scale preparation, the four preparation methods were adopted to prepare Fe₂O₃/Al₂O₃ OCs and compared with each other in terms of productivity, preparation period, physical and chemical characterization, and reactivity in CLC of lignite. Freeze granulation and spray drying methods were found to be more suitable for large‐scale production of OCs for CLC. The results of the comparative studies may provide guidelines for selecting appropriate methods for preparing OCs on industrial scale.     

The Distortion‐Adjusted Change of Thermal Expansion Behavior of Cubic Magnetic Semiconductor (Sc1−xMx)F3 (M = Al,Fe)

For the study of negative thermal expansion (NTE) compounds, it is critical to effectively control the thermal expansion. In this letter, a chemical approach has been taken to control the thermal expansion behavior in ScF₃ which has a strong NTE. Owing to the difference of radius of substituting ions, local distortion inevitably emerges in the lattice matrix, which is verified by pair distribution function analysis of high‐resolution synchrotron X‐ray scattering. It is a valuable clue that the thermal expansion behaviors in the ScF₃ based systems and other trifluorides are correlated closely to structural distortion of metal‐F‐metal linkages. In addition, the introduction of 3d transition‐metal enables its semiconductor and ferromagnetic characteristics. This study provides important reference opinion for the control of thermal expansion and introduction of multifunctionalization for those NTE compounds with open framework structure.