Damping analysis of nonwoven natural fibre-reinforced polypropylene composites used in automotive interior parts

The aim of this work is to evaluate the dynamic properties of nonwoven flax, hemp, kenaf and glass fibre-reinforced polypropylene (PP) composites. Also, the influence of some parameters, such as the type of reinforcement, the fibre/matrix weight ratio, the fibre orientation and the porosity content, on the damping behaviour of these nonwoven composites is investigated. To this end, a free flexural vibrations analysis was conducted to experimentally identify their natural frequencies and their associated loss factors. The obtained results show that the nonwoven composites reinforced by natural fibres present higher loss factors compared with those of the glass-PP composite. These interesting damping properties make these nonwoven composites very attractive for automotive applications where the dissipation of vibrations is highly requested.     

Spinel–rocksalt transition as a key cathode reaction toward high-energy-density magnesium rechargeable batteries

Mg-metal-anode rechargeable battery (MRB) has been a promising candidate for next-generation batteries with high energy densities and high safety. The lack of high-performance cathode materials, however, retards the development of MRBs. In recent years, it has been revealed that various spinel oxides can accommodate a large amount of Mg, exhibiting relatively high potentials (2–3 V vs. Mg²⁺/Mg) and high capacities (～150 mAh g^?1) accompanied by the coherent structural transformation into the rocksalt structure. This review summarizes the recent progress in the development of such spinel–rocksalt transition materials from the viewpoints of the reaction mechanisms, design guidelines of spinel oxides (for tailoring the redox potential, volume change, and cyclability), and challenges to construct full-cell MRBs.     

富含吡啶氮-钴活性位点的三维多级大/介孔石墨烯作为高效可逆氧电催化剂用于可充电锌-空气电池

随着能源危机的日益严峻,能源的储存和转换越来越受到人们的重视.目前人们加以开发和利用的清洁能源主要包括太阳能、风能、氢能、地热能以及电化学能等.其中,燃料电池和金属-空气电池等作为电化学器件为电化学能的开发及可持续利用提供了条件.特别是金属-空气电池以电极电位较负的金属如镁、铝、锌、铁等作负极,以空气中的氧或纯氧作正极...     

Bio-silica incorporated barium ferrite composites: Evaluation of structure,morphology, magnetic and microwave absorption traits

A series of bio-silica incorporated barium-ferrite-composites with the composition of (x)Bio-SiO₂:(80-x)γ-Fe₂O₃:(20)BaO, where x = 0, 1, 2, and 3 wt% were prepared using the modified solid-state reaction method. The influence of different bio-silica (extricated from sintered rice husk) contents on the surface morphologies, structures, and magnetic characteristics of these composites were assessed. The relative complex permittivity and permeability were resolved using the Nicholson-Ross-Weir strategy in the frequency range of 8–13 GHz. Meanwhile, the reflection loss was estimated through the transmission/reflection line theory to assess the MW absorption properties of the composites. Incorporation of the bio-silica in the barium ferrite composites generated a new hexagonal phase (Ba₃Fe₃₂O₅₁) and a tetragonal phase (BaFeSi₄O₁₀) which led to a decrease in the saturation magnetization and significant shift in the MW frequency absorption peak positions.     

Characterization of superparamagnetic Mg x Zn1−x Fe2O4 powders

Structural and magnetic properties of Mg _x Zn_1−x Fe₂O₄ powders have been studied with respect to the application for thermal cancer therapy (magnetic hyperthermia). Mg _x Zn_1−x Fe₂O₄ (x=0.1–0.5) powders with particle sizes between 5 and 8 nm were produced by citrate method. The X-ray diffraction patterns of the samples correspond to a spinel phase. The lattice constant and the volume of the elementary cell increase when x changes from 0.1 to 0.5. The FTIR-spectra ascertain the spinel phase formation. The Mossbauer studies reveal the presence of extremely small particles, which undergo superparamagnetic relaxation at room temperature. The core-shell model has been applied to explain quadruple doublets. The quadruple splitting at “shells” is bigger than those at “cores” whereas the isomer shifts remain close. Magnetic studies confirm the presence of extremely small particles that behave as superparamagnetic ones.      

以酚醛树脂为碳源原位合成富锂层状相/尖晶石/碳核壳结构正极材料及其电化学性能

通过酚醛树酯包覆和碳热反应在富锂正极材料表面原位构建碳和尖晶石双壳保护结构, 对这种核壳结构的正极材料进行了结构和形貌表征, 并研究了其电化学性能. 研究发现, 尖晶石相为材料提供了三维锂离子迁移通道, 碳包覆层显著提高了正极材料的电子电导率, 两种效应的共同作用极大降低了材料的电化学阻抗, 提升了材料的放电比容量, 这种多壳层结构正极材料还具有优异的倍率性能, 在5C倍率下放电比容量可达到135.1 mA·h/g.     

温和条件下元素对M~(2+)/Fe~(2+)/Fe~(3+)-LDHs转化成尖晶石铁氧体过程的影响(英文)

研究了二价金属离子在温和条件下(低于100℃,暴露于空气中)从水滑石M2+/Fe2+/Fe3+-LDHs(M=Co,Ni,Mn,Zn)转化成尖晶石铁氧体的过程中所起的作用。结果表明,该转化过程不仅与晶化温度有关,还与M2+在元素周期表中所处的位置有关。当这些二价金属离子处于同一周期并且相邻较近时,M2+的半径越大,水滑石微晶向尖晶石铁氧体的转化就越容易。此外,Fe2+在转化过程中起着至关重要的作用,如果没有Fe2+的参与,在此条件下的转化将无法进行。     

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.     

铁酸铜负极材料的微波合成和电化学性能

以十六烷基三甲基溴化铵(CTAB)为模板,硝酸铁和硝酸铜为起始物,采用一步微波法,再经过简单的热处理制备了CuFe₂O₄负极材料,采用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶红外光谱(FT-IR)等测试技术表征材料的结构和形貌。 电化学测试表明,在100 mA/g电流密度,0.01~3.0 V电压条件下,材料的首周嵌脱锂比容量分别为1202.2和873.2 mA·h/g,循环50周后,嵌锂比容量仍保持在近650 mA·h/g,显示出优异的电化学性能。     

Hardware components wastes pyrolysis: energy recovery and liquid fraction valorisation

Pyrolysis of hardware components wastes consisting mainly in computers and television components was performed under nitrogen. The degradation products were separated in three fractions, solid, liquid and gaseous. Analyses of the three phases were carried out using gas chromatography (GC), mass spectrometry (MS), thermal analysis and infrared spectroscopy. The energetic content of the gas phase and the economic value of the liquid phase were also determined. The gas fraction produced was rich in light hydrocarbons and hydrogen. Consequently, its calorific value was high and widely sufficient to make the pyrolysis process self-sustained. The main products of the liquid phase were phenol and isopropylphenol (ca. 50–80 wt.%). The presence of Br-based compounds, deriving from the flame retardant employed in hardware components, were also detected. A controlled combustion of the solid phase permitted to obtain the glass fibres unaltered, which can be recycled.