Temperature Solid Phase Research Articles

Oxy-fuel combustion as an alternative for increasing lime production in rotary kilns

The effect of Flue Gas Recirculation (FGR) on the decarbonation process during oxy-fuel combustion in a lime (and cement) rotary kiln is analyzed using an unsteady one-dimensional Eulerian–Lagrangian mathematical model. The model considers gas and limestone as continuous phases and the coal particles as the discrete phase. The model predicts limestone decarbonation, temperature and species distribution of gas and solid phases along the kiln. Simulation results of an air-combustion case are successfully validated with reported experimental data. This model is used to study and to compare the conventional air combustion process with oxy-fuel combustion with FGR ratios between 30% and 80% as controller parameter in this process. Changes in decarbonation process due to energy fluxes by convection and radiation with different FGRs were simulated and analyzed. Simulation results indicate a temperature increase of 20% in the gas and solid phases and a higher decarbonation rate of 40% in relation to the air-combustion case, for a given constant fuel consumption rate. However, for a given temperature, the increase of the CO2 partial pressure in the oxy-fuel case promotes a reduction of the decarbonation rate. Therefore, there is a compromise between FGR and decarbonation rate, which is analyzed in the present study. Simulation results of the decarbonation step in low FGR cases, compared to air-combustion case, shows that conversion takes place in shorter distances in the kiln, suggesting that the production rate can be increased for existing kilns in oxy-fuel kilns or, equivalently, shorter kilns can be designed for an equivalent production rate.

Numerical simulation of thermomagnetic convection of air in a porous square enclosure under a magnetic quadrupole field using LTNE models

In this paper, thermomagnetic convection of air in a two-dimensional porous square enclosure under a magnetic quadrupole field has been numerically investigated. The scalar magnetic potential method is used to calculate the magnetic field. A generalized model, which includes a Brinkman term, a Forcheimmer term and a nonlinear convective term, is used to solve the momentum equations and the energy for fluid and solid are solved with the local thermal non-equilibrium (LTNE) models. The results are presented in the form of streamlines and isotherms and local and average Nusselt numbers. Numerical results are obtained for a range of the magnetic force parameter from 0 to 100, the Darcy number from 10−5 to 10−1 and dimensionless solid-to-fluid heat transfer coefficient from 1 to 1000. The results show that the magnetic force number, Darcy number, Rayleigh number and dimensionless solid-to-fluid heat transfer coefficient have significant effect on the flow field and heat transfer in a porous square enclosure. The flow characteristics presents two cellular structures with horizontal symmetry about the middle plane of the enclosure and the Nusselt numbers are increased as the magnetic force number increases under the non-gravitational condition. The average Nusselt number respects the trend of decrease at first and then increases when the magnetic force number increases under gravitational condition. The non-equilibrium effect on fluid phase temperature and solid phase temperature gradually reduces with the increase of value of H.

Ultra-Low Temperature (~180°C) Solid-Phase Crystallization of GeSn on Insulator Triggered by Laser-Anneal Seeding

Solid-phase crystallization (SPC) of amorphous-GeSn (a-GeSn) films on insulating substrates has been developed combining with laser-annealed seeding, to realize next generation thin-film devices. By this technique, we have realized crystallization of GeSn (>10%) at low temperatures (~180oC), which is applicable for flexible thin-film devices on low cost plastic substrates with low softening temperatures (~200oC). In addition, the starting point of crystallization can be controlled by seeding, which is big advantage in device designing. Introduction In order to realize next generation flexible devices, novel functional materials have to be crystallized at controlled positions on insulating substrates below the softening temperature of low cost plastic substrates (~200oC). GeSn is attracting material for this purpose, since GeSn has higher carrier mobility than Si or Ge, and moreover, GeSn shows direct band structure by introducing substitutional Sn concentration more than 8%. Under such background, we have investigated solid-phase crystallization (SPC) of GeSn [1] and realized growth of GeSn at 180oC. However, to initiate the SPC at controlled positions, the samples have to be annealed above the melting point of Sn (~232oC) to form seeding regions, which is not applicable on flexible plastic substrates. In line with this, we propose an idea to use laser-annealing (LA) to form crystal seeds. By forming seeds by LA, lateral SPC is expected at process temperature below 200°C. Moreover, by decreasing the process temperature, we can expect that GeSn crystals with high substitutional Sn concentration should be obtained. Experimental Procedure In the experiment, amorphous Ge0.8Sn0.2 layers (100 nm thickness) were deposited on quartz substrates by a molecular beam technique. The samples were irradiated with a KrF excimer laser (wavelength: 248 nm, energy: 160 mJ/cm2) with 100 pulses in 1 sec to form seed regions, followed by thermal annealing (180 - 220 oC) for lateral SPC as shown in Fig. 1. Results and Discussion Nomarski images of samples as LA and after annealing at 180oC for 48h are shown in Figs. 2(a) and 2(b), respectively. The laser annealed seed region is formed as shown in Fig. 2(a). From the seed, a bright region spreads after 180oC annealing. The Raman spectra obtained at points A, B, and C in Figs. 2(a) and 2(b) are shown in Fig. 2(c). From these spectra, we can clearly say that lateral SPC is initiated from only the seed and no spontaneous nucleation occurs. From the length of lateral SPC region, growth rates of GeSn at various annealing temperatures (180, 200, 220 oC) are evaluated. It is found that the growth rate is about 1 μm/h at 180 oC, which is nearly 106 time as large as that of Ge [2]. The activation energy of the growth rate of Ge0.8Sn0.2 was estimated to be ~1.5 eV, which was smaller than that of Ge (~2.0 eV). This is attributed to the weakening atomic bonds by Sn atoms. This is a very useful technique to realize next generation flexible thin-film devices. Substitutional Sn concentration in grown layer obtained after annealing at 180oC for 48h is evaluated by Raman measurement, which is shown in Fig. 3. Substitutional Sn concentration in SPC region shows higher value (>10%) than that of LA region (~7.5%), which is attributed to difference of non-equilibrium conditions between SPC and LA. Interestingly, substitutional Sn concentration shows very high values exceeding 15% near the growth edge. The Sn concentration decreases with increasing distance from the edge. Decrease in the Sn concentration from >15% to ~10% is attributed to the post annealing effect of grown regions. Detailed physics will be discussed at the presentation.

Experimental investigation of a radiant porous burner performance with simulated natural gas, biogas and synthesis gas fuel blends

The general performance of a porous inert media burner system in terms of radiative efficiency, fuel flexibility, pollutant formation and reliability was determined experimentally. The porous burner of choice has been previously proven of being capable to operate on conventional and alternative gaseous fuels. The present study examines its operation with virtual blends of model fuels in order to assign and evaluate synergistic effects. In this regard, the present work examines mixtures of CH4, CO, H2 and CO2 on a two-layer burner with a 10 ppi (pores per inch) SiSiC foam flame zone. The study focused on gaseous and solid phase temperature levels and pollutant formation trends over various nominal thermal loads in the lean combustion regime. The burner optimum operating range was identified and results revealed low NOx levels. For a given stoichiometry, the burner is characterized by a NOx level threshold systematically below 20 ppm, independently of the fuel, with however, distinct behaviour especially with respect to CO2 content. The opposing effects of CO and H2 addition on CH4/air combustion, aside the influence of CO2 dilution, were assessed on burner operation and radiation efficiency. The CO2 addition increased measured CO emission levels and decreased the radiation efficiency of the burner. This may also be attributed to the lower adiabatic flame temperature and burning velocity of CO2 enriched blends, as also acknowledged by supportive numerical calculations. The relative impact of thermal load on temperature, emissions and burner radiation efficiency with respect to equivalence ratio was also studied. It was identified that the specific burner design, delivers wide power flexibility at lean combustion regimes, providing, at the same time, low total pollutant emissions, i.e. less than 50 ppm and high radiation efficiency, i.e. up to 70% for low thermal loads and depending on the stoichiometry.

Tunable Electromagnetic Properties of Yttrium Iron Garnet Ceramics

Different porosity Y3Fe5O12 (YIG) ceramics (32% - 62%) were prepared from ceramic powders, which was synthesised by high temperature solid-phase reactions, and the effects of porosity on their electromagnetic properties were investigated. XRD and SEM were used to analyze the phase composition and microstructure of the porous composites. Electromagnetism properties including alternate current conductivity, permittivity and permeability of the composites were tested by HP4991 impedance analyzer (10 MHz~1 GHz). The results indicated that, the porosity and pore diameter were increasing with the addition of pore former by pressureless sintering; the real permeability and permittivity of YIG ceramic decreased when the porosity increasing, at the same time, the peaks of magnetic loss were moved to high frequency. That is to say, the electromagnetism properties of YIG ceramic composites could be adjusted by its porosity. Yttrium iron garnet ceramic can be widely used for high frequency devices due to its excellent and tunable magnetic properties.

The numerical assessment of volume averaging method in heat transfer modeling of tissue-like porous media

In this paper, the heat transfer characteristics of a tissue-like capillary porous media are investigated, using the realistic and volume averaging methods. For this purpose, a cylindrical medium is introduced with counter-current vascular network, including longitudinal parallel vessel pairs and numerous interconnect capillaries. The energy equations of solid and fluids phases are derived based on one realistic and two volume averaging methods. Accordingly, the thermal behavior of this capillary porous media was modeled in three cases: constant temperature of solid phase, uniform moderate heat generation in solid phase, and local intensive heat generation in solid phase. The comparison of results for various lengths and densities of interconnect capillaries indicates the inaccuracy of volume averaging method, especially if the supply and return fluids are considered as single integrated phase. Thus, despite much anatomical dissimilarities between the present medium and real living tissues, the occurrences of such errors can be expected if the volume averaging method is used. In addition, the predicted temperature of solid phase at the end of various interstitial heating processes shows that the constant delivery of focused energy in shorter time can increase the maximum temperature of solid phase and its heat affected zone.

Role of inclusions for formation of acicular ferit in low carbonsteel weld deposits

Acicular ferit was investigated from the viewpoint of orientation relationships among acicular ferit, prior austenite, and inclusions. The Baker-Nutting orientation relationship was observed between acicular ferit and a TiO layer forming at inclusion surfaces. Meanwhile, the Kurdjumov-Sachs orientation relationship was observed between acicular ferit and prior austenite. The results indicate that acicular ferit is considered to nucleate due to a low misfit with TiO layers; however, there is still doubt. In case the TiO layer form at molten steel, its orientation would be random with austenite. Thus, acicular ferit nucleating with the Baker-Nutting orientation relationship should have no orientation relationship with austenite. In order to address the issue, the inclusion formation process was investigated by using the liquid-tin quenching technique and the thermodynamic calculation. The results reveal that TiO form not at the high temperature such as molten steel temperature but at below the solid phase temperature such as austenite or ferit temperature. As the result of orientation analysis between prior austenite and TiO, TiO is not considered to form in austenite. It can be assumed that TiO layers form in order to match interface with acicular ferit. Additionally, the Mn depleted zone were also not observed. Therefore, acicular ferit is considered to nucleate not due to the low misfit or the Mn depleted zone but due to another mechanism.

Solid Phase Synthesis and Optical Properties of CdTiO<sub>3</sub> Submicron Particles from Cd(OH)<sub>2</sub> and P25 TiO<sub>2</sub>

A simple and cost-effective low temperature (600 oC) solid phase method was proposed for the synthesis of CdTiO3 submicron particles, using Cd (OH)2 and P25 TiO2 as the starting materials. The composition and structure of the as-synthesized CdTiO3 submicron particles were characterized by X-ray diffraction and transmission electron microscopy. Besides, the optical properties of the as-synthesized CdTiO3 submicron particles were characterized by UV-vis diffuse reflection spectrum and photoluminescence spectrum.

Thermal non-equilibrium heat transfer in a porous cavity in the presence of bio-chemical heat source

This paper is concerned with thermal non-equilibrium natural convection in a square cavity filled with a porous medium in the presence of a biomass which is transported in the cavity. The biomass can consume a secondary moving substrate. The physics of the presented problem is related to the analysis of heat and mass transfer in a composting process that controlled by internal heat generation. The intensity of the bio-heat source generated in the cavity is equal to the rate of consumption of the substrate by the biomass. It is assumed that the porous medium is homogeneous and isotropic. A two-field model that represents the fluid and solid phase temperature fields separately is used for energy equation. A simplified Monod model is introduced along with the governing equations to describe the consumption of the substrate by the biomass. In other word, the transient biochemical heat source which is dependent on a solute concentration is considered in the energy equations. Investigation of the biomass activity and bio-chemical heat generation in the case of thermal non-equilibrium assumption has not been considered in the literature and they are open research topics. The effects of thermal non-equilibrium model on heat transfer, flow pattern and biomass transfer are investigated. The effective parameters which have a direct impact on the generated bio-chemical heat source are also presented. The influences of the non-dimensional parameters such as fluid-to-solid conductivity ratio on the temperature distribution are presented.

Thermal and fire risk analysis of typical insulation material in a high elevation area: Influence of sidewalls, dimension and pressure

Small-scaled experiments and modeling are performed to investigate the downward flame spread over extruded polystyrene (XPS) slabs at different widths with and without sidewalls in a city (Lhasa, China) at high elevation. This study provides an understanding of the thermal characteristics and fire risk of XPS under the influence of various factors. It is found that the flame pulsation is more significant for wider samples. The average flame height (H) rises as the width increases. Compared to the results obtained without sidewalls, the flame pulsation is less considerable and H is higher for samples with sidewalls. When sidewalls are present, the average maximum flame temperature (Tmax) increases with the rise of sample width, and it is lower than that without sidewalls. Tmax in the combustion zone besides the sidewalls is larger than that in the middle zone, while the reverse is true for samples without sidewall. The solid-phase temperature curve is comprised of three stages. The temperature growth rate is low during the melting stage. The duration of the melting stage without sidewalls is longer than that with sidewalls. This duration at a low elevation is shorter than that at the high elevation. The shorter duration of the melting stage corresponds to the higher temperature at which the melting stage occurs. A three dimensional downward flame spread model taking into account the effects of sample width, thickness, ambient pressure and sidewall is established. The predicted trends of Vf using the model agree well with the experimental results. The model could also predict XPS fire hazard. The thermal and risk analysis of XPS provides a guidance to fire safety design of energy saving system of buildings.

CFD Simulation of a Bubbling Fluidized Bed Gasifier Using a Bubble-Based Drag Model

Wood gasification in a fluidized bed reactor is regards as a promising technique to efficiently exploit the energy from biomass, which has attracted great attention. To further understand complex fluid mechanics and thermal behaviors of wood during the gasification process, a multiphase reactive model is presented, and a computational fluid dynamics (CFD) simulation of wood gasification in a bubbling fluidized bed gasifier is implemented. To account for the impact of bubble-structure on the gas–solid interaction, a revised bubble-based energy minimization multiscale (EMMS) drag model is developed and incorporated into a two-fluid model. Flow behaviors and reactive characteristics in a bubbling fluidized bed gasifier are analyzed. Profiles of temperature and concentration of gas and solid phase are also obtained. By comparisons of the outlet gas species concentrations, the prediction by a revised bubble-based EMMS drag model agrees better with experimental results than that by the conventional drag model.

Al-doped Li2ZnTi3O8 as an effective anode material for lithium-ion batteries with good rate capabilities

Al-doped Li2ZnTi3O8 in the form of Li2ZnTi3−xAlxO8 (0⩽x⩽0.2) compounds are successfully synthesized by a simple and facile high temperature solid-phase reaction. The characteristics of Li2ZnTi3−xAlxO8 are examined by X-ray diffraction, scanning electronic microscopy, transmission electron microscopy and laser particle size analyzer, while the electrochemical performances including galvanostatic charge–discharge testing, cyclic voltammetry, and electrochemical impedance spectroscopy were also investigated. It is shown from the structure analysis that Li2ZnTi3−xAlxO8 (x=0, 0.05, 0.1) has the pure phase structure, but impurity peak of LiAlO2 can be detected when x>0.1. In the voltage range of 0.05–3.0V, Li2ZnTi2.9Al0.1O8 electrode presents the largest initial discharge capacity of 223.1mAhg−1 at 0.1Ag−1. Moreover, the discharge capacities of Li2ZnTi2.9Al0.1O8 after 100 cycles are 173.2, 136.7, 108.6, and 61.4mAhg−1 at 0.5, 1.0, 2.0, and 3.0Ag−1, respectively, which obviously higher than those of un-doped sample. The electrode reaction reversibility and electronic conductivity of pure Li2ZnTi3O8 are enhanced after doping Al (x=0.1). The results revealed that doping Al should be an effective way to improve the cycling performance.

Thermal performance analysis of porous medium solar receiver with quartz window to minimize heat flux gradient

Exposure under concentrated solar radiation increases the temperature of volumetric receiver which can cause high thermal stress and damage the receiver. The Plano-convex quartz window is introduced with the aim to minimize heat flux gradient of porous medium receiver. Thermal performance of porous medium receiver with quartz window is numerically studied while the fluid inlet is located at the side wall which would be more practicable. The Monte Carlo ray tracing (MCRT) method is used to calculate the radiative heat transfer in the solar collector system with quartz window, and the local thermal non-equilibrium (LTNE) model with the consideration of radiative heat transfer in the porous medium receiver is used to calculate the fluid phase and solid phase temperature distribution of the porous medium receiver. The numerical results indicated that the pressure distribution and temperature distribution for the condition of fluid inlet located at the side wall is different from that for the condition of fluid inlet located at the front surface.

Experimentation and Simulation of the Combustion of Biomass Briquettes in Southern China

The thermogravimetry (TG) of typical biomass briquettes used as fuel in southern China was analysed to investigate the influences of fuel grain size and heating rate on combustion. The results suggested that grain size and heating rate exerted little influence on combustion. In accordance with the data and the TG results obtained from the fuel, a biomass grate incinerator process was numerically simulated using fluid dynamics-based incinerator code (FLIC) software to obtain the solid phase temperature distribution of the fuel along the bed length, the spatial temperature distribution of flue gas, and the underlying variation laws of the primary components. A comparison of the mass-loss curves from the numerical simulation to the TG analysis demonstrated that the two curves exhibited consistently staged variations, including dehydration and drying, fast pyrolysis and combustion of volatiles, and the burnout of residual carbon. The specific characteristics of the fuel obtained from these tests improved the accuracy of the numerical simulation, while the variations in temperature and components obtained were conducive to optimising the combustion process of a biomass incinerator.

Analytical solutions to a fractional generalized two phase Lame-Clapeyron-Stefan problem

Purpose – The mathematical model of a two-phase Lamé-Clapeyron-Stefan problem for a semi-infinite material with a density jump is considered. The purpose of this paper is to study the analytical solutions of the models and show the performance of several parameters. Design/methodology/approach – To describe the heat conduction, the Caputo type time fractional heat conduction equation is used and a convective term is included since the changes in density give rise to motion of the liquid phase. The similarity variables are used to simplify the models. Findings – The analytical solutions describing the changes of temperature in both liquid and solid phases are obtained. For the solid phase, the solution is given in the Wright function form. While for the liquid phase, since the appearance of the advection term, an approximate solution in series form is given. Based on the solutions, the performance of the parameters is discussed in detail. Originality/value – From the point of view of mathematics, the moving boundary problems are nonlinear, so barely any analytical solutions for these problems can be obtained. Furthermore, there are many applications in which a material undergoes phase change, such as in melting, freezing, casting and cryosurgery.

Temperature dependency of thermal conductivity of solid phases for fatty acids

Thermal conductivity variations with temperature of solid phases for lauric acid (LA), myristic acid (MA), pivalic acid (PA), and stearic acid (SA) have been measured with radial heat-flow method. Temperature dependencies of the thermal conductivity for same organic materials have been obtained by linear regression analysis. From graphs of thermal conductivity versus temperature, the thermal conductivity of solid phase at their melting temperature and temperature coefficients of thermal conductivity for LA, MA, PA, and SA have been found to be 0.37, 0.39, 0.23, and 0.35 W K−1 m−1 and 0.00935, 0.00446, 0.01095, and 0.00295 K−1, respectively. The ratios of thermal conductivity of liquid phase to thermal conductivity of solid phase for LA, MA, PA, and SA have also been measured to be 0.52, 0.48, 0.25, and 0.59, respectively, with a Bridgman-type directional solidification apparatus.

One-Dimensional Dynamic Modeling of a Single-Stage Downward-Firing Entrained-Flow Coal Gasifier

In the current paper, a one-dimensional partial differential equation (PDE)-based dynamic model and its simulation results are presented for a single-stage down-fired entrained-flow gasifier. The gasifier model comprises mass, momentum, and energy balances for the gas and solid phases. The initial gasification processes of water evaporation and coal devolatilization and the key heterogeneous and homogeneous chemical reactions have also been modeled. The resulting coupled system of PDEs and algebraic equations is solved using the well-known method of lines in Aspen Custom Modeler. In addition to the dynamic gasifier model, efficient control strategies that can satisfactorily perform both servo and disturbance rejection functions have been developed for the entrained-flow gasifier. The dynamic variations of key gasifier output variables in response to the disturbances commonly encountered in industrial operation are presented. Output variables of interest include gas and solid phase temperatures, synthesis gas compositions, and carbon conversion, while disturbances include ramp and step changes in input variables such as coal flow rate, oxygen-to-coal ratio, and water-to-coal ratio among others. Feedstock switchovers have also been studied by simulating transitions from one coal type to another. The gasifier model results are also compared to the dynamic data available in the literature.

Facile synthesis of LiAl0.1Mn1.9O4 as cathode material for lithium ion batteries: towards rate and cycling capabilities at an elevated temperature

To improve the cycling performance of spinel LiMn2O4, Al-doped LiMn2O4, LiAl0.1Mn1.9O4, is synthesized using Mn1.9Al0.1O3 precursor and LiOH·H2O via a low temperature solid-phase reaction. The Mn1.9Al0.1O3 precursor, prepared from the electrolytic manganese dioxide (EMD) and Al(OH)3, is composed of spherical particles with an average diameter of 300nm, and has a large interspace. Energy dispersive spectrometer (EDS) indicates the Al element is well distributed in Mn1.9Al0.1O3 and LiAl0.1Mn1.9O4. The scanning electron microscopy (SEM) and transmission electron microscope (TEM) images show that the LiAl0.1Mn1.9O4 sample has a high crystallinity with sizes ranging from 300 to 500nm. Electrochemical properties of LiAl0.1Mn1.9O4 are studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge. The results show that LiAl0.1Mn1.9O4 possesses better rate and cycling capabilities than LiMn2O4 at both 25°C and 55°C. At a rate of 5C, the capacity retention ratio of the LiMn1.9Al0.1O4 electrode after 100 cycles is about 95% at 25°C and about 90% at 55°C.

Thermodynamic interpretation of reactive processes in Ni–Al nanolayers from atomistic simulations

Metals that can form intermetallic compounds by exothermic reactions constitute a class of reactive materials with multiple applications. Ni–Al laminates of thin alternating layers are being considered as model nanometric metallic multilayers for studying various reaction processes. However, the reaction kinetics at short timescales after mixing are not entirely understood. In this work, we calculate the free energies of Ni–Al alloys as a function of composition and temperature for different solid phases using thermodynamic integration based on state-of-the-art interatomic potentials. We use this information to interpret molecular dynamics (MD) simulations of bilayer systems at 800 K and zero pressure, both in isothermal and isenthalpic conditions. We find that a disordered phase always forms upon mixing as a precursor to a more stable nano crystalline B2 phase. We construe the reactions observed in terms of thermodynamic trajectories governed by the state variables computed. Simulated times of up to 30 ns were achieved, which provides a window to phenomena not previously observed in MD simulations. Our results provide insight into the early experimental reaction timescales and suggest that the path (segregated reactants) → (disordered phase) → (B2 structure) is always realized irrespective of the imposed boundary conditions.

Electrochemical performance of solid sphere spinel LiMn2O4 with high tap density synthesized by porous spherical Mn3O4

Solid sphere spinel LiMn2O4 materials are synthesized from porous spherical Mn3O4 particles with LiOH·H2O via a high temperature solid-phase reaction. Porous spherical Mn3O4 particles, composed of aggregated crystallites, can be obtained from as-prepared spherical β-MnOOH. The solid sphere spinel LiMn2O4 particles have a high tap-density of 2.67 g·cm−3 and are well-distributed with sizes ranging from 7-9μm. The as-prepared β-MnOOH, Mn3O4 and LiMn2O4 are characterized by X-ray diffraction and scanning electron microscopy. As cathode materials, solid sphere spinel LiMn2O4, exhibits excellent cycling performance and rate capability for lithium-ion batteries. The initial discharge capacities are 127.1, 118.1, 106.3 and 87 mAh·g−1 at 0.2, 1, 5 and 10C, respectively. At 5C the discharge capacity retention rate can be maintained at 95% after 200 cycles. Cyclic voltammetry and electrochemical impedance spectroscopy confirm the excellent electrochemical performances of the synthesized solid sphere spinel LiMn2O4 materials.