Effect of carbon nanotubes addition on electrochemical performance and thermal stability of Li4Ti5O12 anode in commercial LiMn2O4/Li4Ti5O12 full-cell

Li₄Ti₅O₁₂ (LTO)/carbon nanotubes (CNTs) composite material is synthesized based on a solid-state method by sand-milling, spray-drying and calcining at 850 ℃ under N₂ flow. The LTO/CNTs samples with 1 wt% and 3 wt% weight ratio of CNTs addition and the pristine LTO sample are prepared. The rate performance and the thermal stability of these samples are investigated based on LiMn₂O₄ (LMO)/LTO full-cell. The results show that theweight ratio of CNTs addition has distinct effect on LTO performances. The composite materials of LTO composited CNTs have better performance at high-rate due to the intercalation enhancement by conductive network of CNTs. At second, the overcharging temperature response of the cell's surface with 1 wt% CNTs addition is the lowest. The particle size distribution is measured and the most uniform particles are obtained with 1 wt% CNTs addition. This trend could explain that the mediumquantity of CNTs is optimal to improve the heat and mass transfer and prevent the problems of crystallite growing interference and aggregation during the calcination process.     

Investigation of the performance of bipolar transverse plate ESP in the sintering flue control

In order to improve the particle collection efficiency of the electrostatic precipitator (ESP), a transverse plate ESP with bipolar discharge electrodes is proposed. The simulations of the velocity distribution have shown that when the inlet velocity is 1 m/s, within the range of 40 mm from electrode plate, the average velocities of windward side and leeward side are less than 0.7 m/s and 0.3 m/s respectively. It is clear that the velocity near the collection electrode plate of this bipolar ESP is much lower than that of the ordinary ESP at the same inlet velocity. This low velocity can lead to higher efficiency for fine dust collection due to the less dust re-entrainment in ESP. It is also found that the average velocities are getting lower when the distance between plates electrodes are greater than 150 mm in accordance with the simulations. The voltage current characteristics of the bipolar ESP are superior to the ordinary ESP. The pressure drop of the bipolar ESP is about 30% higher than that of the ordinary one. The dust penetration of the bipolar ESP is about 54% less than that of the ordinary ESP when the sintering dust with 25.405 μm mass median diameter is used as the test particulate under the condition of the electric field from 2.1 kV/cm to 3.2 kV/cm and the velocity from 1.0 m/s to 1.5 m/s.     

回转窑多粒径颗粒流动与偏析的DEM模拟与实验研究

为明晰回转窑内颗粒的运动行为及偏析机理,以绿豆、黄豆和黑豆为颗粒介质,依次对3种装填顺序下的颗粒流动过程进行离散元模拟与实验研究,以颗粒质量分数和平均粒度为判据,对颗粒偏析进行评价。结果表明,回转窑内颗粒流动区可分为自由滚落区、渗流呆滞区以及窑壁携带区,自由滚落区颗粒流速最大,而渗流呆滞区流速最小。窑内颗粒沿轴向输运过程发生径向偏析,形成夹层结构,小颗粒受渗流作用在渗流呆滞区中心形成内核,大粒径和中等粒径颗粒集中在自由滚落区和窑壁携带区。窑内颗粒力链分布不均匀,强力链分布于近窑壁区,弱力链分布于自由滚落区和渗流呆滞区,且渗流呆滞区力链细而密集。当窑头附近不同粒径颗粒存在轴向速度差时,颗粒在轴向发生掺混,并产生径向偏析。     

A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables. Part II – Validation and localization analysis

We study the mechanical failure of cemented granular materials (e.g., sandstones) using a constitutive model based on breakage mechanics for grain crushing and damage mechanics for cement fracture. The theoretical aspects of this model are presented in Part I: Tengattini et al. (2014), A thermomechanical constitutive model for cemented granular materials with quantifiable internal variables, Part I – Theory (Journal of the Mechanics and Physics of Solids, 10.1016/j.jmps.2014.05.021). In this Part II we investigate the constitutive and structural responses of cemented granular materials through analyses of Boundary Value Problems (BVPs).The multiple failure mechanisms captured by the proposed model enable the behavior of cemented granular rocks to be well reproduced for a wide range of confining pressures. Furthermore, through comparison of the model predictions and experimental data, the micromechanical basis of the model provides improved understanding of failure mechanisms of cemented granular materials. In particular, we show that grain crushing is the predominant inelastic deformation mechanism under high pressures while cement failure is the relevant mechanism at low pressures. Over an intermediate pressure regime a mixed mode of failure mechanisms is observed. Furthermore, the micromechanical roots of the model allow the effects on localized deformation modes of various initial microstructures to be studied. The results obtained from both the constitutive responses and BVP solutions indicate that the proposed approach and model provide a promising basis for future theoretical studies on cemented granular materials.     

Le vaporeformage catalytique : application a la production embarquee d'hydrogene a partir d'hydrocarbures ou d'alcools

Catalytic steam reforming : Use for on-board hydrogen production from hydrocarbons or alcohols. To identify the challenges in the development of electrical vehicles, literature was rapidly reviewed. Research on hydrogen production processes suitable for fuel cell applications is a major challenge. Catalytic steam reforming of hydrocarbons as well as alcohol is a very promising route. The choice of ethanol and supported rhodium catalysts will be justified in the light of ethanol physico-chemical properties, reaction mechanism, cerium-based oxides characteristics and the specifications imposed by fuel cell applications.     

Rare earth-rich compounds RE9TMg4 (RE = Y,Dy-Tm,Lu; T = Ru,Rh, Os,Ir) with an ordered Co2Al5-type structure

The rare earth-rich intermetallic phases RE₉TMg₄ (RE = Y, Dy-Tm, Lu; T = Ru, Rh, Os, Ir) were synthesized by induction melting of the elements using sealed niobium ampoules as crucible material. The melted samples were additionally annealed in muffle furnaces and subsequently characterized by X-ray powder diffraction. The RE₉TMg₄ compounds adopt an ordered Co₂Al₅ type structure, space group P6₃/mmc. Four structures were refined from single-crystal X-ray diffractometer data: a = 953.71(5), c = 968.41(5) pm, wR2 = 0.00273, 603 F² values, 21 parameters for Tm_8.76RuMg_4.24; a = 958.37(5), c = 975.66(5), wR2 = 0.00384, 661 F² values, 20 parameters for Dy₉OsMg₄; a = 943.70(5), c = 967.91(5) pm, wR2 = 0.00430, 592 F² values, 21 parameters for Tm_8.74OsMg_4.26; a = 968.09(5), c = 978.25(5) pm, wR2 = 0.0439, 623 F² values, 21 parameters for Y_9.18IrMg_3.82. The compounds are prone to small homogeneity ranges (RE/Mg mixing). The transition metal atoms have tricapped trigonal prismatic rare earth coordination. These T@RE₉ units (TP) are condensed with empty RE₆ octahedra (O) via common triangular faces forming infinite strands with a sequence –TP–O–O–. These strands show the motif of hexagonal rod packing and they are separated by chains of edge- and corner-sharing tetrahedra. The magnesium substructures in the hexagonal Laves phase YMg₂ and the prototype Y₉CoMg₄ are structurally closely related. Charge transfer trends, electronic band structures and bonding properties were studied within DFT. The resulting picture is that cobalt brings covalent character by reducing the overall charge transfer and modifies the Laves phase YMg₂ by providing larger localization in the density of states. The Y–Co bonding in Y₉CoMg₄ prevails while weakening the Y–Mg bonds. The investigations of the magnetic properties of selected RE₉TMg₄ compounds revealed Pauli paramagnetic behavior for Y₉CoMg₄, Y₉OsMg₄ and Y₉IrMg₄. A ferromagnetic ground state with Curie temperatures of 46.0 and 47.6 K was observed for Dy₉RuMg₄ and Dy₉OsMg₄, respectively. Ho₉RuMg₄, Ho₉OsMg₄ and Tm₉OsMg₄ reveal antiferromagnetic ordering with Neél temperatures below 20 K.     

Equation of state of the hard-disk fluid on a sphere from Percus–Yevick equation

The Percus–Yevick equation is solved numerically for hard disks on a sphere. The effect of curvature of the hosting surface is calculated, and an empirical correction to the equation of state is proposed.     

Atomistic simulation of kink structure on edge dislocation in bcc iron

Based on the general theory of dislocation and kink, we have constructed the three kink models corresponding to the 1/2 （111）{011} and 1/2 （111）{112} edge dislocations （EDs） in bcc Fe using the molecular dynamics method. We found that the geometric structure of a kink depends on the type of ED and the structural energies of the atom sites in the dislocation core region, as well as the geometric symmetry of the dislocation core and the characteristic of the stacking sequence of atomic plane along the dislocation line. The formation energies and widths of the kinks on the 1/2 （111）{011} and 1/2 （111）{112} EDs are calculated, the formation energies are 0.05eV and 0.04eV, and widths are 6.02b and 6.51b, respectively （b is the magnitude of the Burgers vector）. The small formation energies indicate that the formation of kink in the edge dislocation is very easy in bcc Fe.     

Characterization of the globular oxide inclusion ratings in steel using laser-induced breakdown spectroscopy

Grade assessment of steel is generally performed via the metallographic method, which is timeconsuming and is not able to provide the elemental distribution information. In this paper, we present a method to measure the globular oxide inclusion ratings in steel using laser-induced breakdown spectroscopy (LIBS). The measurement is performed in two basic steps: steel samples are polished using metallographic sand paper and the Al₂O₃ inclusion number and size distribution in a marked area are observed using scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDS) for further LIBS scanning analysis. The threshold intensity that distinguishes soluble aluminum and insoluble aluminum inclusions is determined using LIBS combined with the SEM/EDS statistical data. Carbon steel (the sample number is S9256) and bearing steel (the sample number is GCr15) are analyzed in scanning mode, and the number of Al₂O₃ inclusions in different size ranges is obtained from the statistical information derived from the Al₂O₃ size calibration curve. According to heavy and thin series for globular oxide inclusions grade assessment, the method we propose is comparable to the traditional metallographic method in terms of accuracy; however, the process is simplified and the measurement speed is significantly improved.     

Magnetic properties of Ni/NiO nanocomposites synthesized by one step solution combustion method

Ni/NiO nanocomposites were synthesized using solution combustion method and characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX) and carbon, hydrogen, nitrogen (CHN) analyser. The Ni or NiO content in Ni/NiO nanocomposites vary with the quantity of HNO₃ used for the synthesis. Magnetic coercivity (H_c) of Ni/NiO nanocomposites is found to be 413 Oe which can be used in magnetic applications. A feeble exchange bias of 7 Oe is seen from the NiO rich Ni/NiO.