JOURNAL OF ADVANCED MATERIALS AND TECHNOLOGIES
Year:2020 | Volume:9 | Issue:1 |Papers Count:8

In this study, the effect of excess lithium content on lithiated cathode in lithium ion battery and nonstoichiometric state has been investigated. For this purpose, the precursor was compounded with co-precipitation synthesized Ni0. 3Mn0. 5Co0. 2 and subsequently lithiated with different amounts of LiOH to investigate the effect of excess lithium content on the Lix (Ni0. 3Mn0. 5Co0. 2) O2 cathode. The results of ICP, XRD and SEM analysis showed that the samples were well synthesized and the compositions were layered and the particle size in the samples was less than 10 microns. The results of battery charge-discharge tests for all three samples at 0. 5-5C showed that the sample of Li1. 5 (Ni0. 3Mn0. 5Co0. 2) O2 had the best electrochemical performance; such that at 1C discharge rate its capacity 200mAh/g and after 30 cycles, its capacity reached 138mAh/g at 5C discharge rate. The impedance analysis (EIS) revealed that the sample of Li1. 5 (Ni0. 3Mn0. 5Co0. 2) O2 had the lowest internal resistance. Finally, it can be concluded that increasing the amount of excess lithium has the optimum value for improving the battery performance, so that in non-stoichiometric mode, the increase of lithium up to Li1. 5 is associated with improved performance and above this level will result in reduced battery performance.

In this study, using ultrasound waves in a two-step method, molybdenum disulfide nanosheets were prepared from its bulk and then, deposited by a simple and binder free electrophoretic method at times of 20, 60, 120 and 180 min on carbon cloth as a three-dimensional conductive substrate. In order to control hydrophilicity, hydrophobic carbon cloth was activated electrochemically at 300 and 800 s and optimum activation time was selected. The electrochemical measurements showed that by increasing the deposition time and increasing the amount of molybdenum disulfide nanosheets as an electrocatalyst material on the activated carbon cloth, the hydrogen evolution overpotential decreased. The deposited electrode at time of 180 min reached to current density of-10 mA/cm2 at potential of-0. 210 V (vs RHE) and showed relatively good stability after 900 cycles. Based on the obtained results, the deposition of molybdenum disulfide nanosheets on the activated carbon cloth by electrophoretic method offers a threedimensional and binder free structure for the hydrogen evolution reaction.

In this study, titanium aluminium carbonitride (TiAlCN) ceramic coatings with different amount of Al were deposited at 350 ° C on H13 hot work tool steel substrates, using pulsed-DC plasma assisted chemical vapor deposition method. Energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), glancing incidence X-ray diffraction method (GIXRD), transmission electron microscopy (TEM), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM) and SEM and atomic force microscopy (AFM) were applied for characterizing of the coatings. Microhardness test utilized for evaluating of microhardness of the coatings. The coatings showed a nanostructure consisted of fcc-TiAlN and hcp-AlN nanocrystalline grains and an amorphous carbon phase. Increasing the amount of Al from ~10 to ~42 at. % led to a decrease of the surface roughness of the coating from 151± 49 to 88± 27 nm, due to the creation of more nuclei of AlN. Coating with the less amount of Al (~10 at. %) presented the highest microhardness of about 3840 HV0. 01, due to the less amount of chloride impurity and hcp-AlN phase.

In this research, the effects of various molar amounts of Tl2O3 addition (x= 0, 0. 1, 0. 25, 0. 5, and 1. 0) on microstructure and electrical properties of high-voltage SnO2 varistors were investigated. According to XRD and FE-SEM results, the presence of Tl2O3 was detected as secondary phase in samples which their x values are higher than 0. 25. By Tl2O3 addition from 0 to 1%, the grain size decreased from 4 μ m to 2. 3 μ m which it is resulted from a grain growth suppression induced by secondary phase based on Zener mechanism. The best non-Ohmic properties with the nonlinear coefficient of 15. 1 and the leakage current density of 95 μ A/cm2 were observed in samples doped with 0. 5% Tl2O3. Furthermore, the breakdown electric field of this sample was 532 V/mm. Further addition of Tl2O3 had no considerable effect on nonlinearity of samples, but it increased the breakdown electric field of samples through the reduction in grain size.

In this study, pure aluminum powder as a composite substrate was mixed with5, 10 and 15 wt. % of silicon nitride particles and constant wt% of carbon nanotube. The specimens were sintered at 400 ° C with 5 holding time by SPS. Also, the samples were prepared by uniaxial press at 250 MPa pressure and sintered at 600, 700 and 800 ° C in microwave for one minute. The results show that by adding 15% silicon nitride particles with and without carbon nanotubes to the composites the flexural strengths of the composites with microwave sintering at 700 ° C increases to 179 MPa and 212 MPa, respectively. Also, the strength of the SPS sintered samples at 400 ° C with 15 wt. % of silicon nitride without carbon nanotubes and with carbon nanotubes are 249 and 285 MPa, respectively. The SPS samples exhibit a more homogeneous microstructure and is relatively denser than the samples which were microwave sintered due to the pressure and temperature that applied simultaneously in SPS.

The removal efficiency of methyl orange using two kinds of magnetic photocatalysts containing ZnO in the presence and absence of graphene oxide is investigated. Meanwhile, the kinetic of removal reaction of methyl orange, the effect of operational parameters such as irradiation time and weight fraction of photocatalysts based on statistical method and Duncan’ s multiple range test are studied. The removal efficiency of methyl orange using both of the applied photocatalysts is affected by irradiation time and weight fraction of photocatalyst. So that the enhancement of these two parameters leads to the increment of removal efficiency of methyl orange. The results show that the kinetic reaction is pseudo first order. The rate of reaction using photocatalyst containing graphen oxide is higher than that of without it. The results of statistical analysis based on Duncan’ s multiple range test reveals that both of the studied parameters have significant influence on the removal efficiency of methyl orange.

In this study, manganese oxide nanoparticle synthesis by thermal decomposition process of organometallic compounds. for synthesis of MnO nanoparticles was used as an organometallic manganese acetylacetonate precursor. Impact of 2 and 20 ◦ C/min Heating rates, surfactants like oleic acid, oleylamine and dibenzyl ether solvents and octadecene on size and morphology of nanoparticles were considered. The results of MnO nanoparticles synthesis indicated that the best situation to access smallest size and uniform morphology is about 20 ◦ C/min heating rate, dibenzyl ether and oleic acid surfactant.

In this study, LiNi0. 5Co0. 2Mn0. 3O2 cathode material was synthesized by solid-state reaction. Li2CO3, NiO, Co3O4, and MnO2 were used as starting materials. In order to study the influence of heat treatment temperature on synthesis of cathode, three heat treatment temperatures including 800, 850 and 900 􀔨 were selected. X-ray diffraction and scanning electron microscope equipped with EDX were utilized for sample characterization. The efficiency of produced batteries was evaluated by charge-discharge tests. XRD results showed no impurity in the powders which synthesized in 800 􀔨 and 850 􀔨 , however in 900 􀔨 the impurity was detected. The intensity ratio of I003/I104 was used as a standard for degree of cation mixing. This parameter was 1. 34 for the sample synthesized in 850 􀔨 . SEM analyzes reveal that samples which synthesized in 800 􀔨 and 850 􀔨 have homogeneous morphology with the average particles size of 0. 5 and 0. 7μ m. However, the sample which synthesizes in 900 􀔨 does not have homogeneous morphology and its average particle size was 1. 5μ m. The charge-discharge test in a voltage range of 2. 5-4. 3 V and current rate 0. 1C showed that the sample which synthesized in 850 􀔨 had a discharge capacity of 147. 15mAh/g. Also, this sample could save 88. 4% of its capacity after 30 cycles.