Rheological Phase Reaction Method Research Articles

Preparation of Coated CMC-nZVI Using Rheological Phase Reaction Method and Research on Degradation of Chloroform in Water

This study reported the synthesis of nanoscale zero-valent iron (nZVI) by rheological phase reaction method in the presence of sodium (CMC). The synthesized CMC coated nZVI (CMC-nZVI) was then characterized with x-ray diffraction (XRD) and transmission electron microscope (TEM) and was tested for the removal of chloroform from simulated groundwater. The investigated parameters in the uptake experiments included different adsorbents, initial concentrations of chloroform and different water flow. The results show that:(1) the prepared CMC-nZVI has good stability and dispersibility; (2) when the concentration of chloroform is 0.1 mg/L, the dosage of CMC-Fe0 is 0.01 g, the removal rate of chloroform is 91.2%;(3)The reaction follows the first-order kinetic reaction equation, and the apparent reaction rate constant increases with decreasing the concentration of chloroform.

Synthesis and electrochemical properties of ZnMn2O4 anode for lithium-ion batteries

The precursors of ZnMn2O4 were synthesized by different methods (the rheological phase reaction method or the mixed solvothermal method). The precursors were heat-treated at a suitable temperature to obtain the expected product (ZnMn2O4). The synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The electrochemical properties of the samples were also investigated. The results show that ZnMn2O4 was synthesized successfully. The particles of ZnMn2O4 were irregular quasi-spheres with sizes of about 50 nm. The ZnMn2O4 nanoparticles synthesized through the mixed solvothermal method were clustered together to form microspheres about 1 μm in diameter. The electrochemical testing results showed that the ZnMn2O4 synthesized through the mixed solvothermal method featured higher reversible capacity and better cycling performance than the sample synthesized by the rheological phase reaction method. The ZnMn2O4 synthesized through the mixed solvothermal method could be a promising anode material for lithium ion battery application.

Characterization and electrochemical properties of Li2MoO4 modified Li4Ti5O12/C anode material for lithium-ion batteries

Li2MoO4 modified Li4Ti5O12/C anode material has been synthesized by a ball-milling assisted rheological phase reaction method. The structures, morphologies and electrochemical properties of the as-prepared materials have been analyzed by different physical and electrochemical methods. The results show that the amorphous carbon is successfully coated on the surface of Li4Ti5O12 nanoparticles with partial doping of Mo6+ into the Li4Ti5O12 structure. Electrochemical results indicate that Li2MoO4 modified Li4Ti5O12/C samples deliver improved rate capability and decreased charge transfer resistance. Among the investigated samples, the one with 5wt% Li2MoO4 sample exhibits the optimal electrochemical properties and it shows a large capacity of 167.5mAhg−1 at 1C rate, which is close to its theoretical capacity. Even at 10C, its charge capacity is up to 137.5mAhg−1 with a high capacity retention of 92.5% after 200 cycles. The excellent electrochemical properties should be attributed to the improvement of electrochemical kinetics by the synergistic employment of reducing particle size, partial Mo6+ doping and Li2MoO4/C modification.

Nd3+-doped Li3V2(PO4)3 cathode material with high rate capability for Li-ion batteries

Abstract A series of Nd 3+ -doped Li 3 Nd x V 2− x (PO 4 ) 3 ( x = 0.00, 0.02, 0.05, 0.08 or 0.1) composites are synthesized by the rheological phase reaction method. The XRD results indicate that Nd 3+ ions have been successfully merged into a lattice structure. Doped samples show good electrochemical performance in high discharge rate and long cycle. In the potential range of 3.0–4.3 V, Li 3 Nd 0.08 V 1.92 (PO 4 ) 3 exhibits an initial discharge capacity of 115.8 mAh/g at 0.2 C and retain 80.86% of capacity retention at 2 C in the 51st cycle. In addition, Li 3 Nd 0.05 V 1.95 (PO 4 ) 3 holds at 100.4 mAh/g after 80 cycles at 0.2 C with a capacity retention of 92.4%. Finally, the CV test proves that the potential polarization of Li 3 Nd 0.08 V 1.92 (PO 4 ) 3 decreased compared with the un-doped one.

Preparation of wrapped nZVI particles and their application for the degradation of trichloroethylene (TCE) in aqueous solution

Three types of wrappped nanoscale zero-valent iron (W-nZVI) with different coatings including agar, starch, and carboxyl methyl cellulose, were synthesized using a rheological phase reaction method. The structure and morphology of W-nZVI particles were characterized by scanning electron microscopy and transmission electron microscopy. Batch degradation experiments exhibited that W-nZVI dosage, initial trichloroethylene (TCE) concentration and solution pH had significant effects on TCE dechlorination. Experimental results proved that the highest dechlorination efficiency was obtained within 320 minutes for 10 mg/L of TCE at the optimal pH of 5.0 and W-nZVI dosage of 0.5 g/L. Kinetic study revealed that TCE dechlorination by W-nZVI in aqueous solution obeyed the quasi-first-order reaction kinetics. The product after the reaction could be easily separated by the permanent magnet for re-use.

Effects of Synthesis Temperature and Holding Time on the Electrochemical Properties of LiNi<sub>1/3</sub>Co<sub>1/3</sub>Mn<sub>1/3</sub>O<sub>2</sub> Cathode Material Using Rheological Phase Method

In this paper, LiNi1/3Co1/3Mn1/3O2 was prepared via a facile rheological phase reaction method. The effect of synthesis temperature and holding time on its electrochemical performance has been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV) tests and galvanostatic charge–discharge tests. The results suggest that the synthesis temperature and holding time greatly affect the electrochemical performance of the LiNi1/3Co1/3Mn1/3O2 and the optimized synthesis condition for the synthesis of LiNi1/3Co1/3Mn1/3O2 via rheological phase reaction method is 900 °C for 8 h. The obtained sample possesses a highly ordered layered structure and low cation mixing. It delivers an initial discharge capacity of 198 mAh g-1 at 0.2 C and 140 mAh g-1 at 1.0 C between 2.5 and 4.6 V, respectively.

Synthesis and Electrochemical Properties of LiFePO4/C for Lithium Ion Batteries.

LiFePO4/C was prepared through a facile rheological phase reaction method by using Fe3(PO4)2, Li3PO4 · 8H2O, and glucose as reactants. The LiFePO4/C samples were characterized by X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The electrochemical properties of the samples were investigated. The results show that the LiFePO4/C samples have single-phase olivine-type structure, and their particles feature a spherical shape. The carbon coating on the particles of LiFePO4 is about 1.8% of the LiFePO4/C by weight. The particle size was distributed from 0.2 to 1 µm. The initial discharge capacity of LiFePO4/C reached 154 mA h/g at 0.1 C. The retained discharge capacity of LiFePO4/C was 152.9 mA h g(-1) after 50 cycles. The LiFePO4/C also showed better cycling performance than that of the bare LiPeO4 at a higher charge/discharge rate (1 C). The LIFePO4/C prepared in this way could be a promising cathode material for lithium ion battery application.

Preparation of LiBOB via rheological phase method and its application to mitigate voltage fade of Li1.16[Mn0.75Ni0.25]0.84O2cathode

High-purity LiBOB, synthesizedvianovel rheological phase reaction method without further recrystallization, mitigated voltage-fade of Li-rich cathode as electrolyte additive.

Synthesis and electrochemical performance of ZnCo2O4 for lithium-ion battery application

ZnCo2O4 was synthesized through the rheological phase reaction method using zinc acetate dehydrate, cobalt (II) acetate tetrahydrate, and citric acid as raw materials. The precursors were heat-treated in a muffle furnace at 400°C or 500°C, respectively. The samples were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The electrochemical properties of the samples were investigated. The results show that ZnCo2O4 nanoparticles were synthesized successfully. The particles took on irregular quasi-spherical shapes, and the sizes of the particles were less than 100nm. The electrochemical properties showed that the ZnCo2O4 synthesized at 400°C featured better reversible capacity than that of ZnCo2O4 synthesized at 500°C, and its specific capacity was 801mAhg−1 after 100 cycles at a constant current of 100mAhg−1 in the voltage range of 0.01–3V. Hence, the ZnCo2O4 synthesized by this method could be a promising anode material for lithium ion battery application.

Synthesis of MCM-41 stabilized NZVI and its use in removal of Cr(VI) from aqueous solution

In this study, MCM-41 stabilized nano zero-valent iron (M-NZVI) is synthesized using the rheological phase reaction method. Characterization with transmission electron microscopy validates the hypothesis that the introduction of MCM-41 leads to a decrease in aggregation of iron nanoparticles. X-ray diffraction confirms the existence of Fe0 and the strong antioxidant activity of Fe0 nanoparticles. Batch Cr(VI) reduction experiments exhibit that solution pH, M-NZVI dosage, and reaction time have significant effects on Cr(VI) removal. A high removal efficiency of Cr(VI) (84.5%) is obtained within 60 min for 100 mg/L of Cr(VI) solution at an initial pH of 6.0 and M-NZVI dosage of 0.5 g/L at 35 °C. The Cr(VI) removal rates follow modified pseudo-first-order kinetic equations. The observed removal rate constant was 0.0168/min for the M-NZVI dosage of 1.0 g/L. Our study suggests that the introduction of an innocuous stabilizer such as MCM-41 can significantly improve the performance of Fe0 nanoparticles for environmental remediation applications.

Structure and electrochemical behaviors of spherical Li1+xNi0.5Mn0.5O2+δ synthesized by rheological phase reaction method

Spherical layered Li1+xNi0.5Mn0.5O2+δ (x=0, 0.1 and 0.2) materials are synthesized by rheological phase reaction method. X-ray diffraction patterns reveal that the prepared materials have the α-NaFeO2 structure with R-3m space group. The materials with different lithium contents show distinct differences in structure, particle morphology, electrochemical property and safety characteristics. When x=0.1 and 0.2, excess lithium resides in the transition metal layer to form Li2MnO3-like structure. With lithium content increasing from 1.0 to 1.2, the initial discharge capacity and Coulombic efficiency are decreased, while capacity maintenance is improved. Mn ions are electrochemically activated in the charge–discharge process and has a contribution to the capacity when cycling in a voltage window of 2.5–4.5V for x=0.2, leading to a high discharge capacity of near 200mAhg−1 and the excellent cycling performance (with no capacity decay after 100 cycles) at 20mAg−1. Electrochemical impedance spectroscopy shows that the appropriate excess of lithium can decrease charge transfer resistance obviously in the initial several cycles. The differential scanning calorimetric indicates that the generated heat of Li1+xNi0.5Mn0.5O2+δ is increased with the increase of x.

Effect of process medium on the synthesis of carbon coated lithium vanadium phosphate composite using rheological phase reaction method

Li3V2(PO4)3/C composites (LVP/C) are synthesized by rheological phase reaction (RPR) method using alginic acid (HAlg) as the carbon source. Different process media are applied in the synthetic process to assess the possible effects on LVP/C composite. And the whole synthetic route is discussed in detail with qualitative and instrumental analysis, in terms of ball-milling process, rheology phase reaction process and thermogravimetric analysis of precursors. The much different morphological properties of as-prepared LVP/C composites demonstrate that process medium indeed has some effects on the synthetic process, especially on the refinement and dispersion of particles. According to these investigations, ethylene glycol (EG) is revealed more proper for preparing LVP/C using this method attributed to its moderate viscosity, surface activity and synergistic effects with HAlg. The corresponding LVP/C composite shows nanoscaled particles with smooth surfaces and uniform size distribution. Besides, LVP-EG sample exhibits excellent electrochemical performances under different voltage windows as well. Between 3.0 and 4.3 V, when charge/discharge at 20/50 C, the composite exhibits relatively high capacity and stable cycling performance for 300 cycles. Within 3.0–4.8 V, it can cycle for 200 times at a high rate of 20 C without obvious capacity fading. The outstanding performances can be attributed to the enhanced electronic/ionic conductivities of LVP/C benefitting from the influences of EG and HAlg via the RPR method.

Synthesis and electrochemical properties of spinel LiMn1.95M(x)O(4-y)F(y) for lithium ion batteries.

Spinel phase LiMn1.95M(x)O(4-y)F(y) (M = Co and Y) were prepared by a rheological phase reaction method. The samples were characterized by X-ray diffraction, scanning electron microscopy, AC impedance, and galvanostatic charge/discharge profile measurement. These results showed that the LiMn1.95M(x)O(4-y)F(y) had better cycling performance than pure LiMn2O4. Among all the doped samples, the LiMn1.95Co0.03Y0.02O3.96F0.04 sample showed the best cycling performance, the initial discharge capacitiy is 129 mAh/g, and the discharge capacity of 124 mAh/g at a rate of 0.5 C after 50 cycles. The loss of its capacity was only 3.4%. The possible reasons for the outstanding electrochemical properties of LiMn1.95Co0.03Y0.02O3.96F0.04 are also discussed.

Synthesis and Electrochemical Properties of LiNi1/3Co1/3Mn1/3O2 Cathode Material

LiNi1/3Co1/3Mn1/3O2 layer-structured compound was synthesized by the rheological phase reaction method. The structure and morphology of samples were characterized by x-ray diffraction and scanning electron microscopy. The particle size was distributed from 100 nm to 400 nm, depending on the synthesis temperature. The electrochemical properties of the samples were examined using a battery testing system. The results showed that the discharge specific capacities of the samples were strongly impacted by the synthesis temperature. The LiNi1/3Co1/3Mn1/3O2 synthesized at 850°C had a high initial discharge specific capacity (about 181 mA h/g at 0.1 C) and better electrochemical cycling performance compared to the other samples. (After 50 cycles, the discharge capacity was maintained at 170 mA h/g.) The reasons why the sample synthesized at 850°C showed outstanding electrochemical properties are also discussed.

Synthesis and characterization of coated zero-valent iron nanoparticles and their application for the removal of aqueous Pb2+ ions

Three types of coated nanoscale zero-valent iron (C-nZVI) with different coatings, agar, starch, and carboxyl methyl cellulose, were synthesized using a rheological phase reaction method. The structure and morphology of C-nZVI particles were characterized by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. Batch tests of Pb(II) removal showed that the sample dosage, initial pH, initial Pb(II) concentration, and reaction time have significant effects on Pb(II) removal efficiency. Experimental results proved that an optimized pH value of 5, Pb(II) concentration of 100 mg/L, and C-nZVI dosage of 1 g/L are beneficial to Pb(II) removal. Kinetic study revealed that Pb(II) removal by C-nZVI in aqueous solution complies with quasi-first-order reaction kinetics, and the reaction rate constant of Pb(II) removal using W-nZVI is 6–27 higher than using unwrapped nZVI.

Rheological phase synthesis and characterization of Li3V2(PO4)3/C composites as cathode materials for lithium ion batteries

Li3V2(PO4)3/C composites as cathode materials for lithium ion batteries were successfully synthesized through the rheological phase reaction method using LiOH·H2O, V2O5, NH4H2PO4, and C6H8O7·H2O as raw materials. The as-prepared powders were characterized by means of powder X-ray diffraction (XRD), scan electron microscope (SEM), and transmission electron microscope (TEM). The electrochemical properties of Li3V2(PO4)3/C composites were examined by the galvanostatic charge/discharge, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicate that the sintering temperatures have a significant effect on the crystal structure, morphology, and electrochemical performances of Li3V2(PO4)3/C composites. XRD reveals that Li3V2(PO4)3/C composites are well crystallized single phase, where Li3V2(PO4)3/C composite synthesized at 800°C for 8h displays the maximum cell volume and uniformly distributed particles. It can be seen from TEM that there is a carbon layer of about 200-500nm thick on the particle surface. The apparent DLi+ calculated from CV is in the order of magnitude of 10−7 cm2 s−1. Electrochemical tests show that Li3V2(PO4)3/C composite synthesized at 800°C for 8h exhibits excellent cycling performance of 129.149 mAh g−1 after 60 cycles at the current of 15mAg−1 and a superior rate capability of 112.101 mAh g−1 after 60 cycles at the current of 90mAg−1.

Synthesis of agar-stabilized nanoscale zero-valent iron particles and removal study of hexavalent chromium

In this study, agar-stabilized nanoscale zero-valent iron (A-nZVI) was synthesized using a rheological phase reaction method. The structure and morphology of A-nZVI particles were investigated by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and Fourier-transform infrared spectrometry. Batch removal experiments showed that the pH value of solution, hexavalent chromium [Cr(VI)]/A-nZVI mass ratio and reaction time have significant effects on the removal of Cr(VI). A 100 % removal of Cr(VI) was achieved when applying 50 mg L−1 of Cr(VI) at the optimal pH value of 3 and the Cr(VI)/A-nZVI molar ratio of 0.025 with the reaction time of 2 h at room temperature. The removal rates of Cr(VI) were fitted to the modified pseudo-first-order kinetic equations with respect to Cr(VI) concentrations.

Preparation of Ni0.9Mn2.1–xMgxO4 (0 ≤x≤0.3) negative temperature coefficient ceramic materials by a rheological phase reaction method

Negative temperature coefficient (NTC) thermistors based on Ni0.9Mn2.1−xMgxO4 (0≤x≤0.3) materials with different compositions were synthesized by a rheological phase reaction with ultrasound radiation (RPR-UR) method. It was found that the as-prepared powder crystallized well with spinel structure. It presented a microstructure of well-packed grains. The resistivity, B25/50 constant and activation energy with a wide range of values were obtained. And it can be adjusted to desired values for industrial applications by controlling the MgO content. All the results suggest that the RPR-UR method is a promising technique for the preparation of Ni0.9Mn2.1−xMgxO4 NTC ceramic materials.

Enhanced electrochemical performance of LiFePO4 coated with Li0.34La0.51TiO2.94 by rheological phase reaction method

Abstract Li0.34La0.51TiO2.94 (LLTO), as a high ionically conductive material, has been coated on the surface of olivine-type LiFePO4 by rheological phase reaction method. The structure and electrochemical properties of the prepared cathode were investigated. The XRD results indicate that the LLTO coating does not affect the structure of LiFePO4 and the LLTO-coated LiFePO4 cathode material still has olivine structure. The electrochemical measurements of LLTO-coated LiFePO4 show that the rate performance of LiFePO4 is greatly improved by the surface treatment. At the room temperature, LLTO-coated LiFePO4 exhibits high discharge capacity of 109.9 mAh g−1 at 10 C, whereas the uncoated LiFePO4 has the discharge capacity less than 80 mAh g−1 at the same rate. Besides, LLTO-coated LiFePO4 also shows better cycle stability and low-temperature performance than that of uncoated LiFePO4.

Rheological phase synthesis of Er-doped LiV3O8 as electroactive material for a cathode of secondary lithium storage

Er-doped LiV3O8 as cathode material for secondary lithium batteries was prepared through a rheological phase reaction method. The as-prepared materials were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), and galvanostatic discharge/charge measurements. The results indicate that Er doped phase preserves the layered structure of the pristine LiV3O8 and has an enlarged interlayer spacing. Compared to LiV3O8 sample, Er-doped LiV3O8 sample displays more uniform particles and large surface area. The electrochemical test shows that Er doping does not change the process of Li+ insertion/deinsertion. Er-doped LiV3O8 electrode exhibits an initial discharge capacity of 294.2 mAh g−1 and maintains a stable capacity of 220.7 mAh g−1 after 50 cycles, indicating a greatly improved good cycleability comparing with the undoped one.