Higher permittivity of Ni-doped lead zirconate titanate,Pb[(Zr0.52Ti0.48)(1-x) Nix]O3, ceramics

The paper reports highest obtained dielectric constant for Ni-doped Lead Zirconate Titanate [PZT, Pb(Zr_0.52Ti_0.48)O₃] ceramics. The Ni-doped PZT ceramic pellets were prepared via conventional solid-state reaction method with Ni content chosen in the range 0–20?at%. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were employed to investigate the crystal structure of the prepared ceramics. The X-ray diffraction analysis indicated that the ceramic pellets had crystallized into tetragonal perovskite structure. A minute displacement of XRD peaks was detected in the diffraction spectra of Ni-doped PZT ceramic samples which when examined by size-strain plot (SSP) method revealed presence of homogenous strain that decreased with increase in concentration of Ni. In FTIR the maximum absorption at 597?cm^?1, 608?cm^?1, 611?cm^?1, 605 and 613?cm^?1 for Ni?=?0, 5, 10, 15 and 20?at%, respectively, confirmed the formation of perovskite structure in all the compositions and the slight shift suggests decrease in cell size on doping. The values of dielectric constant (ε′) & tanδ as a function of frequency and temperature were measured for the prepared ceramics and it revealed highest ever reported dielectric constant for Ni - doped PZT with Ni?=?5?at%. The dielectric variation with temperature exhibited a diffused type ferroelectric–paraelectric phase transition for the doped samples. Also, the maximum dielectric constant value (ε′_max) decreased while the phase transition temperature increased with increase in doping concentration of Ni. The estimated activation energy of different compositions was found to increase from 0.057 to 0.068?eV for x?=?0.00 to x?=?0.20 in ferroelectric phase. The piezoelectric, ferroelectric and magnetic properties were also investigated.     

Ba0.95La0.05Fe0.8Ni0.2O3−δ perovskite as efficient cathode electrocatalysts for proton-conducting solid oxide fuel cells

The key issue that limits the electrochemical performance of proton-conducting solid oxide fuel cells (H⁺-SOFCs) is the sluggish kinetics of the oxygen reduction reaction (ORR) of cathode at intermediate and low temperatures. Herein, oxygen vacancy engineering is conducted on cobalt-free Ba_0.95La_0.05FeO_3?δ (BLF) by nickel substitution, which is confirmed by density functional theory computations. Nickel-substituted BLF material (Ba_0.95La_0.05Fe_1?xNi_xO_3?δ (x = 0, 0.1, 0.2, 0.3)) can promote the generation of oxygen vacancies and improve catalytic activity, which is found to be in line with the experimental results of XPS. The phase structure, microstructure, and electrochemical performance of Ba_0.95La_0.05Fe_0.8Ni_0.2O_3?δ (BLFNi0.2) are well-investigated. The single cells with the BLFNi0.2-BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3?δ (BCZYYb) composite cathode achieve low polarization resistance (R_p) of 0.099 Ω cm² and a peak power density of 631 mW cm^?2 at 700 °C while maintaining good durability for 120 h with no observable degradation. The results demonstrate that Ni-doped BLF is a promising cobalt-free cathode material for H⁺-SOFCs.     

镍镁掺杂LiFePO4的电子结构

采用基于密度泛函理论的第一性原理研究锂离子电池正极材料LiFePO4掺杂Ni和Mg的电子结构。结果表明:Ni氧化物的电子结构和能量性质受d轨道中电子影响,用于掺杂改性时,结构稳定,带隙降低使电子电导率增加,充放电速率提高;Mg掺杂改性时,当掺杂在Li位时,带隙和总能均降低,同时Li离子的扩散运动也提高,有利于改性,而在Fe位掺杂时,费米面附近Fe-d轨道中电子影响能带,使带隙增加,不利于电子电导,键的布居分析也表明Li—O共价性增强,不利于离子扩散,即不利于改性。因此,通过掺杂可对LiFePO4的微观结构产生影响,从而影响其电化学性能,但这种微观结构主要受d轨道中电子运动对费米面附近能带的影响,而与掺杂离子的化合价和半径无关。     

Efficient multimetallic catalytic systems for the selective hydrogenation of nitric acid

New multimetallic catalytic systems for the selective hydrogenation of nitric acid to hydroxylamine were developed by investigating the promoter effect of one or more additional metals from Group 8 to 11 on Pd/C (combined with GeO₂). Among various multimetallic catalytic systems investigated here, Pd + Ni/C, Pd + Ni + Fe/C, and Pd + Au + Fe/C (combined with GeO₂) were found to be particularly effective systems, which provided much higher catalytic activity as well as higher selectivity than those of not only the non-doped Pd/C system but also the Pd + Fe/C system developed recently.     

Modification of DLC films by Ni ions implantation

Enhanced diamond-like carbon (DLC) multilayer films were produced by a method of alternating the magnetic filtered vacuum cathode arc deposition and the metal vapor vacuum arc (MEVVA) implantation of Ni⁺ ions. The microstructure and mechanical properties of these multilayer films were studied by XPS, Raman, SEM, AFM, XRD, nano-intender and internal stress measurement. The results reveal that with the increasing dose of implanted Ni⁺ ions, the sp³ contents are declining and reduction of the nanohardness and release of the internal stress are observed.     

镍掺杂碳气凝胶的脉冲电沉积法制备及表征

利用脉冲电沉积法成功制备了金属镍掺杂碳气凝胶。通过XRD、SEM EDS和TEM测试方法证实脉冲电沉积法成功地在碳气凝胶结构中还原出了金属镍，SEM图谱表明生成的金属镍粒子均匀分布于碳气凝胶结构中。利用ICP-AES仪测试了掺杂金属碳气凝胶中金属的含量。N2吸附数据分析表明，掺入金属镍后，碳气凝胶的比表面积、总孔体积、介孔体积和微孔体积均减小，说明还原生成的金属镍颗粒填充了部分碳气凝胶的介孔和微孔。     

纳米Ni-TiO2光催化剂的制备及其性能研究

采用溶胶-凝胶法制备了过渡金属Ni掺杂纳米TiO2光催化剂(Ni-TiO2),采用XRD、纳米粒度、UVVis和PL对其进行了表征和分析,并以亚甲基蓝(MB)作为目标降解物,研究了Ni掺杂量以及热处理温度对NiTiO2性能的影响。结果表明:当pH=2.5、n(Ni)∶n(Ti)=1%、热处理温度为500℃时制备的样品在普通日光灯下、5h内对MB的光催化降解率达到92.54%,明显优于Degussa P25在相同条件下的降解率(50.69%)。     

Ni掺杂对介孔硅结构和性能的影响

用直接水热合成法(DHT)、模板剂离子置换法(TIE)及焙烧后的介孔MCM-41后处理法(PS)合成了N i掺杂的纳米介孔MCM-41。研究了用这3种方法进行N i掺杂对纳米介孔材料形貌、结构和性能的影响。TEM和XRD结果表明,采用后处理法将N i引入,不影响纳米介孔颗粒的分散性和形貌,并且PS20〔PS法合成,n(S i)/n(N i)=20〕中没有N i的氧化物形成。随着N i的引入,PS20的比表面由MCM-41的757 m2/g下降为545m2/g,孔径和孔容分别由3.2 nm和0.75 cm3/g增大为4.3 nm和0.86 cm3/g。     

Ultra-Highly Active Ni-Doped MOF-5 Heterogeneous Catalysts for Ethylene Dimerization

Here, an ultra-highly active Ni-MOF-5 catalyst with high Ni loading for ethylene dimerization is reported. The Ni-MOF-5 catalysts are synthesized by a facile one-pot co-precipitation method at room temperature, where Ni²⁺ replaces Zn²⁺ in MOF-5. Unlike Zn²⁺ with tetrahedral coordination in MOF-5, Ni²⁺ is coordinated with extra solvent molecules except for four-oxygen from the framework. After removing coordinated solvent molecules, Ni-MOF-5 achieves an ethylene turnover frequency of 352 000 h⁻¹, corresponding to 9040 g of product per gram of catalyst per hour, at 35 °C and 50 bar, far exceeding the activities of all reported heterogeneous catalysts. The high Ni loading and full exposure structure account for the excellent catalytic performance. Isotope labeling experiments reveal that the catalytic process follows the Cossee–Arlman mechanism, rationalizing the high activity and selectivity of the catalyst. These results demonstrate that Ni-MOF-5 catalysts are very promising for industrial catalytic ethylene dimerization.     

固相烧结辅助高温球磨合成LiNi_xMn_(2-x)O_4

以氢氧化锂、硝酸镍、二氧化锰为原料,用固相烧结辅助高温球磨方法,合成了具有Ni掺杂的LiMn_2O_4正极材料。研究了Ni在不同掺杂量时对材料的相结构、形貌和充放电性能的影响,并与未掺杂Ni的LiMn_2O_4进行对比。结果表明,掺Ni后材料的放电比容量随着掺杂量的增大逐渐减小,而材料的容量保持率相比未掺杂时略有提高;当掺杂量x=0.05时,所得产物的充放电性能最佳,首次放电容量达到122.9mAh/g,充放电容量保持率在40次循环后为97.48%。