Investigation of electrochemical performance of MgNiO2 prepared by sol-gel synthesis route for aqueous-based supercapacitor application

In this work, we have successfully synthesized MgNiO₂ using a sol-gel wet chemical synthesis technique named MNO - 3. Electrochemical measurements in the presence of aqueous 1 M Li₂SO₄ electrolyte indicate that MNO - 3 samples exhibit a capacitance value of about 30 F/g and an energy density of about 20 Wh/kg. Subsequently, in the experiment involving aqueous 0.5 M Na₂SO₄ electrolyte system, it has been found that the capacitance for MNO - 3 sample is about 34 F/g and the energy density is about 23 Wh/kg for MNO - 3 sample. Finally, in the presence of aqueous-based 1 M Mg(ClO₄)₂ electrolyte, MNO - 3 sample is found to exhibit a capacitance of about 26 F/g and an energy density of about 17 Wh/kg, respectively. In all three electrolyte systems, the MNO -3 sample exhibit a long cycle capacitance retention of greater than 85% for 1000 charge-discharge cycles.     

Synthesis and investigation of structural,optical, magnetic,and biocompatibility properties of nanoferrites AFeO2

Sol-gel method has been used for the synthesis of biocompatible superparamagnetic nanoferrites of AFeO₂ (A = Li, Na, K, Ca). Structural study of the nanoferrites reveals that LiFeO₂ exhibits cubic phase on the other hand NaFeO₂, KFeO₂, CaFeO₂ nanoparticles possess orthorhombic phase. Transmission electron microscopy (TEM) suggests that synthesized nanoferrites are nano-sized with spherical morphology. Optical properties confirm that nanoferrites emit and absorb light in a visible range of the electromagnetic spectrum. International Commission on Illumination (CIE) study discloses that the nanoparticles can be used to produce light of various colors. Magnetic study reveals that the nanoferrites exhibit superparamagnetic nature with high values of saturation magnetization 40.26 emu/g, 41.69 emu/g, 57.16 emu/g, and 43.66 emu/g, respectively for LiFeO_2, NaFeO₂, KFeO₂, and CaFeO₂. Biocompatibility study of the nanoferrites has been performed using Sulforhodamine B (SRB) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The reason behind the observed properties and behavior has been discussed.     

Effect of metal ions on structural,morphological and optical properties of nano-crystallite spinel cobalt-aluminate (CoAl2O4)

The bright blue nano crystallite cobalt aluminate (CoAl₂O₄) was synthesized by sol–gel method using a mixture of chelating agent of glycerol and citric acid. The effects of changing (0.05, 0.075, 0.10, 0.25, 0.50, and 0.75 mol/L) metal ion concentration on the structural, morphological and color properties of synthesized CoAl₂O₄ were characterized by using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), Nanoparticle size analyzer, Simultaneous Thermal Analyzer (STA), UV–vis absorption spectroscopy, and CIE-LAB colorimetric analysis. From the X-ray peak profile analysis, the crystallite size was measured by Debye-Scherrer (D-S) equation, and three different models presenting average crystallite sizes between 88.3 and 125.4 nm.The average lattice strain, dislocation density, lattice constant, cell volume, and zeta potential were between 0.00021 and 0.0058, (1.73 to 12.8) × 10¹⁴ (lines/m²), 8.10658 to 8.11181 Å, 533.60 to 533.81 Å³, ?56.4 to ? 63.5 mV, respectively. Using UV–vis absorption spectroscopy, the band gap was calculated from Kubelka-Munk method, and the values of band gap increasing from 1.82 to 1.84 eV, respectively. The reflectance spectra and the CIE-L*a*b* values of cobalt aluminate is also measured which confirmed the formation of blue nano crystallite cobalt aluminate.     

二价与四价金属离子等摩尔共掺杂的锂离子电池正极材料LiMn1.9Mg0.05Ti0.05O4的制备与表征

以氢氧化锂、乙酸锰、硝酸镁和钛酸丁酯为原料, 以柠檬酸为螯合剂, 采用溶胶-凝胶法制备了二价镁离子与四价钛离子等摩尔共掺杂的尖晶石型锂离子电池正极材料LiMn_1.9Mg_0.05Ti_0.05O₄. 采用热重分析(TGA), X射线衍射(XRD), 扫描电子显微镜(SEM), 透射电子显微镜(TEM)和电化学性能测试(包括循环伏安(CV)和电化学交流阻抗谱(EIS)测试)对所得样品的结构、形貌及电化学性能进行了表征. 结果表明: 780℃下煅烧12 h 得到了颗粒均匀细小的尖晶石型结构的LiMn_1.9Mg_0.05Ti_0.05O₄材料, 该材料具有良好的电化学性能, 在室温下以0.5C倍率充放电, 在4.35-3.30 V电位范围内放电比容量达到126.8 mAh·g^-1, 循环50 次后放电比容量仍为118.5mAh·g^-1, 容量保持率为93.5%. 在55℃高温下循环30次后的放电比容量为111.9 mAh·g^-1, 容量保持率达到91.9%, 远远高于未掺杂的LiMn₂O₄的容量保存率. 二价镁离子与四价钛离子等摩尔共掺杂LiMn₂O₄, 改善了尖晶石锰酸锂的电子导电和离子导电性能, 使其倍率性能和高温性能都得到了明显的提高.     

三元掺杂改性锂离子电池正极材料Li3V2(PO4)3

Li₃V₂(PO₄)₃ and its triple-cation-doped counterpart Li_2.85Na_0.15V_1.9Al_0.1(PO₄)_2.9F_0.1 were prepared by a conventional sol-gel method. The effect of Na-Al-F co-doping on the physicochemical properties, especially the electrochemical performance of Li₃V₂(PO₄)₃, were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), Raman spectroscopy, scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), galvanostatic charge/discharge, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). It was found that combined with surface coating from residual carbon, this triple-cation co-doping stabilizes the crystalline structure of Li₃V₂(PO₄)₃, suppresses secondary particle agglomeration, and improves the electric conductivity. Moreover, reversible deinsertion/insertion of the third lithium ion at deeper charge/discharge is enabled by such doping. As a consequence, the practical electrochemical performance of Li₃V₂(PO₄)₃ is significantly improved. The specific capacity of the doped material at a low rate of 1/9C is 172 mAh·g^-1 and it maintains 115 mAh·g^-1 at a rate of 14C, while the specific capacities of the undoped sample at 1/9C and 6C are only 141 and 98 mAh·g^-1, respectively. After 300 cycles at 1C rate, the doped material has a capacity of 118 mAh·g^-1, which is 32.6% higher than that of the undoped counterpart. It is also noteworthy that the multiplateau discharge curve of Li₃V₂(PO₄)₃ transforms to a slope-like curve, indicating the possibility of a different lithium intercalation mechanism after this co-doping.     

介孔Fe-Cu复合金属氧化物纳米粉催化剂催化低温CO氧化

以环氧丙烷为凝胶剂,采用简便低廉的无表面活性剂的溶胶-凝胶法制备了一系列不同Cu/Fe摩尔比的高比表面积介孔Fe-Cu复合氧化物纳米粉末。运用微反应器-色谱体系考察了它们在低温CO氧化反应中的催化性能。采用X射线衍射、N2吸附-脱附、热重-差热分析、程序升温还原、傅里叶变换红外光谱和透射电镜对所制样品进行了表征。结果表明,这些介孔Fe-Cu复合氧化物催化剂具有纳米晶结构、窄的孔径分布和高的比表面积,在低温CO氧化反应中表现出高的活性和稳定性。 CuO的添加影响了Fe2O3的结构和催化性能。当CuO含量为15 mol%时,催化剂具有最高的比表面积和催化活性,在低温CO氧化反应中表现出较高的催化稳定性。     

Ag/Yb掺杂对Ca_3Co_(3.9)Cu_(0.1)O_(9-δ)热电性能的影响

采用溶胶凝胶及冷压方法,通过在Ca_3Co_(3.9)Cu_(0.1)O_(9-δ)体系中引入不同量的Ag~+或Yb~(3+)离子来调控体系的热电性能,制备了可在300~880 K下稳定存在且热电性能优良的陶瓷材料Ca_(3-x)Ag_xCo_(3.9)Cu_(0.1)O_(9-δ)(x=0.1,0.15,0.2,0.3)和Ca_(3-y)Yb_yCo_(3.9)Cu_(0.1)O_(9-δ)(y=0.05,0.1,0.2,0.3).通过X射线衍射(XRD)和扫描电子显微镜(SEM)等测试手段对产物进行了表征,结果显示所制备的样品纯度较高,晶粒均匀,晶粒间较致密.适量的Ag~+,Yb~(3+)离子取代Ca~(2+)离子固溶到晶体中使制备的双掺杂材料晶胞体积发生了变化,但并未引起晶体对称结构的变化.电阻率和Seebeck系数的表征结果说明双掺杂优化了载流子的浓度,随着温度的升高电阻率不断减小,Seebeck系数不断增大.经过计算可知Seebeck系数的增大还有电子有效质量的贡献.热导率表征结果显示双掺杂体系的热导率随着温度的升高而减小,其中声子热导依然起主要作用,这与单掺杂体系的结果一致.随着温度的升高,双掺杂样品Ca_(2.7)Ag_(0.3)Co_(3.9)Cu_(0.1)O_(9-δ)在880 K下ZT值达到最大,为0.2.     

Electrochemical and surface characterization of mild steel with corrosion resistant zirconia network fabricated by aqueous sol-gel technique

Zirconia (ZrO₂) coating was developed on mild steel surface through an aqueous sol-gel route followed by heat treatment. The coating quality was optimized by varying dipping time, curing time, and drying temperature. ZrO₂ coating was competent to prevent a substantial corrosion loss in 0.5 ​M–2 ​M hydrochloric acid with more than 90% efficiency. The morphology of coated surface has revealed the formation of a fine ZrO₂ network on the metal surface at optimum conditions. This network is found to be effective to control steel deterioration in hydrochloric acid and the same appeared to be either cracked or irregular for less efficient formulations.     

Magnetic and dielectric response of M-type barium hexaferrite

Barium hexaferrite (BaFe₁₂O₁₉) is a promising candidate for ceramics, microwave devices and numerous applications. Barium hexaferrite was synthesised via the sol-gel auto-combustion technique using glycine fuel. The X-ray diffraction technique confirmed the hexagonal structure of the particles with space group P63/mmc. The morphological analysis was performed using the field-emission scanning microscope, and the images displayed the plate-like particle formation. Transmission electron microscopy was employed to determine the average particle size of the sample, which was estimated to be 155.93 nm. The magnetic studies were taken through the vibrating sample magnetometer (VSM) at 300 K, with which the saturation magnetization (M_s), coercivity (H_c), squareness ratio (M_r/M_s), and energy product (BH_max) was calculated, and the particles were validated to be in single domain arrangement. The dielectric properties were investigated through the LCR meter. Koop and Maxwell-Wagner's model was used to interpret charge conduction and the occurrence of relaxations in the system.     

Synthesis and characterization of TENORM-free nano zirconia from zircon sand

To avoid radiation exposure in the use of nano zirconia in the ceramics and dentistry industries, a Technologically Enhanced Natural Radioactive Materials (TENORM)-free nano zirconia was required. The purpose of this research was to obtain an environmentally friendly TENORM-free nano zirconia prototype. TENORM-free nano zirconia synthesis consists of processing zircon sand into sodium zirconate, leaching of sodium zirconate to form zirconyl chloride solution, separation of impurities (silica, ThO₂, U₃O₈, etc.), crystallization of zirconyl chloride, zirconyl-oxalate sol-gel formation, and calcination. The quality test of nano zirconia products was characterized by XRD, FT-IR, SEM, and Surveymeter, while the composition test was carried out by the XRF method. The results of this research obtained an environmentally friendly TENORM-free nano zirconia prototype, that has the chemical compound of ZrO₂, the crystal size was 15.09 nm, the average particle size was 91.33 nm, free of radiation exposure, and its composition includes ZrO₂: 96.599%, HfO₂: 2.899%, and CaO: 0.303%. This synthesis can process zircon sand containing TENORM (ThO₂: 0.070% and U₃O₈: 0.047%) into TENORM-free nano zirconia and increase the added value by increasing the zirconia content from 40.493% to 96.599%.