Search

The bi-pyramidal shape of LiNi0.8Co0.1Mn0.1O2/C was achieved via a sol-gel technique aided by agar. The agar-assisted procedure resulted in bi-pyramidal-shaped particles with less agglomeration and less cation mixing. The resulting sample had a high specific discharge capacity of 182 mAh/g at 0.1 C. The capacity retention rate for LiNi0.8Co0.1Mn0.1O2/C was observed to be 78% after 50 cycles at 0.3 C. However, the pristine LiNi0.8Co0.1Mn0.1O2 sample made without agar, on the other hand, showed a low specific discharge capacity of 171 mAh/g at 0.1 C. The retention rate of without carbon-coated LiNi0.8Co0.1Mn0.1O2 sample was just 67% after 50 cycles at 0.3 C. The agar-assisted procedure yielded a low charge transfer resistance of 20 Ω due to the presence of a carbon coating on the surface of LiNi0.8Co0.1Mn0.1O2/C particles. The diffusion coefficient of lithium ions measured during the charging and discharging processes for LiNi0.8Co0.1Mn0.1O2/C was 3.80 × 10−10 cm2/s and 1.45 × 10−10 cm2/s, respectively. The increased cell efficiency was ascribed to the sample's reduced cell polarization as a result of improved cation ordering and the addition of agar to create carbon coating. An agar-assisted sol-gel synthesis is a viable approach for producing LiNi0.8Co0.1Mn0.1O2 cathode material for high-performance lithium-ion batteries in recent studies. Highlights: LiNi0.8Co0.1Mn0.1O2/C was prepared by a biopolymer agar-assisted sol-gel process. The sample delivered a high specific discharge capacity of 182 mAh/g at 0.1C. DLi+ was observed to be 1.45× 10-10 cm2/s for discharge process. The present approach was the potential to synthesize LiNi0.8Co0.1Mn0.1O2 for LIBs. [ABSTRACT FROM AUTHOR]

TiNb2O7 microspheres are prepared via a microwave‐assisted solvothermal method. The microwave irradiation lowers the compound formation temperature to 600°C, and highly crystalline TiNb2O7 powders are obtained upon calcination at 800°C. Morphological analysis of the sample shows uniformly distributed microspheres with a particle size of around 1 μm. The Li+‐ion diffusion coefficient calculated from the electrochemical impedance result is around 1.21 × 10−13 cm2 s−1, which is 1.5 times higher than the sample obtained from the conventional solvothermal method. The TiNb2O7 sample derived from microwave yields a high discharge capacity of 299 mA h g−1 at 0.1 C, whereas the sample synthesized via the conventional solvothermal process yields only 278 mA h g−1 at 0.1 C. Excellent rate capabilities such as 220 mA h g−1 at 5 C and 180 mA h g−1 at 10 C are also observed for the microwave‐assisted solvothermal sample. Moreover, the sample exhibits a large capacity retention of 95.5% after 100 discharge–charge cycles at 5 C. These results reveal the appropriateness of the microwave‐assisted solvothermal process to prepare TiNb2O7 powders with superior properties for battery applications. [ABSTRACT FROM AUTHOR]

TiNb2O7 materials were synthesized via a microwave‐assisted microemulsion technique and a conventional solid‐state reaction route. Microwave‐assisted microemulsion process produced TiNb2O7 powders with small particle sizes (50–100 nm) and increased surface area (22.4 m2/g) in comparison to the samples synthesized from solid‐state method. Micelles in the microemulsion acted as nano‐reactors and confined the grain growth of TiNb2O7. The microwave‐assisted microemulsion‐derived TiNb2O7 powders presented a high discharge capacity of 333.2 mAh/g at 0.1C. The materials also delivered 94.8% retention at 5C after 100 cycles. The solid‐state derived samples only processed the 283.2‐mAh/g discharge capacity at 0.1C with 83.2% retention at 5C after 100 cycles. The amended capacity and cyclability of microwave‐assisted microemulsion‐derived TiNb2O7 resulted from the augmented Li+ diffusion and the diminished charge transfer resistance. It was also found that the microwave‐assisted microemulsion‐derived TiNb2O7 delivered 208 mAh/g discharge capacity at 10C, which was higher than solid‐state derived samples (92 mAh/g). The improved capacity was owing to the enhancement in pseudocapacitive contribution. Present research indicated that the microwave‐assisted microemulsion method effectively enhanced the electrochemical performance of TiNb2O7 powders. [ABSTRACT FROM AUTHOR]

SnO2‐coated TiNb2O7 powders were synthesized via the solution coating method in the present research. The SnO2 layers with a thickness of 3–5 nm were homogeneously coated on the surface of TiNb2O7 particles. TiNb2O7 coated with SnO2 of 5 mol% with high Li+ diffusion coefficient delivered the discharge capacity of 319.5 mAh/g, which was 6.6% higher than that of the non‐coated samples. The enhancement of capacity for the coated TiNb2O7 was owing to the low charge‐transfer resistance of 17.5 Ω in contrary to the non‐coated TiNb2O7 (27.8 Ω). SnO2‐coated TiNb2O7 possessed an improved capacity retention of 85.2% at 5 C after 100 cycles, superior to the non‐coated TiNb2O7 (79.8%). On the other hand, the excessive amounts of SnO2 coating led to the reduction in the capacity of the prepared samples. The excessive amounts of SnO2 layers suppressed the Li+ diffusion and increased the charge‐transfer resistance. The obtained results in this study indicated that coating of TiNb2O7 with appropriate amounts of SnO2 significantly improved the electrochemical performance of TiNb2O7. [ABSTRACT FROM AUTHOR]

The discharge capacities and rate capability of TiNb2O7 powders were enhanced through the additional postreduction treatment. X‐ray photoelectron spectroscopy and electron paramagnetic resonance results confirmed the formation of oxygen vacancies in TiNb2O7 powders after a reduction treatment. The appearance of oxygen vacancies in TiNb2O7 powders formed the impurity level in the forbidden gap and decreased the bandgap values of TiNb2O7. Compared with the pristine TiNb2O7 powders, when TiNb2O7 powders were reduced at 400°C for 40 min, the charge transfer resistance of prepared samples was reduced from 43.67 to 19.35 Ω, and the pseudocapacitive contribution of TiNb2O7 was increased from 44% to 59%. In addition, the discharge capacities at 0.1 and 20 C of prepared batteries were increased by 10.84% and 105.85%, respectively. On the other hand, increasing the temperature in the reduction treatment caused the formation of Ti4+/Ti3+ and Nb5+/Nb4+ pairs and decreased the amounts of available redox couples, thereby deteriorating the electrochemical performance of prepared batteries. The results in the present study revealed that the discharge capacities and rate capability of TiNb2O7 powders were enhanced through a postreduction treatment. [ABSTRACT FROM AUTHOR]

Abstract: Thermoluminescence (TL) measurements were carried out on europium (Eu) doped magnesium pyrophosphate (Mg2P2O7) nanopowders using gamma irradiation in the dose range of 0.1 to 3 kGy. The powder samples were successfully synthesized by chemical co‐precipitation synthesis route. The formation and crystallinity of the compound was confirmed by powder X‐ray diffraction (PXRD) pattern. The estimated particle size was found to be in nanometer scale by using Debye Scherer's formula. A scanning electron microscopy (SEM) study was carried out for the morphological characteristics of as synthesized Mg2P2O7:Eu phosphor. Photoluminescence (PL) study was carried out to confirm the presence of the rare‐earth ion and its valence state. The TL analysis of synthesized samples were performed after the irradiation of Mg2P2O7:Eu with cobalt‐60 (60Co) gamma rays. The high and low intensity peaks of TL glow curve appeared at around 400 K, 450 K, 500 K and 596 K respectively. The appreciable shift in peak positions has been observed for different concentrations of Eu ion. The trapping parameters, namely activation energy (E), order of kinetics (b) and frequency factor (s) have been determined using thermal cleaning process, peak shape (Chen's) method and glow curve deconvolution (GCD) functions. [ABSTRACT FROM AUTHOR]

The present paper reports on the γ-ray and C6+ ion beam induced effect on the structural and luminescence properties of Eu doped LiNaSO4 phosphors synthesized via wet the chemical method. The material was irradiated by 60Co and 137Cs γ-rays and 75 MeV C6+ ions in a fluence range varying from 2 × 1010 to 1 × 1012 ion per cm2. The ion induced modified properties were investigated using X-ray diffraction (XRD), micro-Raman spectroscopy, photoluminescence (PL), thermoluminescence (TL) and electron paramagnetic resonance (EPR) studies. The XRD and micro-Raman results confirm the loss of crystallinity and elongation of the lattice parameters after ion beam irradiation. The presence of both divalent as well as trivalent states of Eu ions at multiple sites of LiNaSO4 is observed by PL study. Irradiation of the LiNaSO4:Eu phosphor with a C6+ ion beam modifies the population of the valence state of the doped rare earth Eu ion and enhances the TL sensitivity of this phosphor. The nature of the prominent TL glow curve is identical for both γ-ray and C6+ ion beam irradiated materials while additional deep trap levels appear in the latter due to the formation of several types of cation and anion vacancy. The electron paramagnetic resonance (EPR) technique also supports the presence of the Eu ion at multiple sites and provides information regarding several types of radical produced after γ-ray and C6+ ion irradiation. Finally, a mechanism is presented for the thermally stimulated luminescence phenomenon on the basis of our observed results from the PL, TL and EPR studies. The reason behind ion beam irradiation induced modification of the TL properties and enhancement of luminescence intensity is also explained in this report. [ABSTRACT FROM AUTHOR]

Dy3+ doped β-Ca2P2O7 phosphor has been synthesized using wet chemical method. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis confirmed the formation of β-Ca2P2O7:Dy nano-phosphors. However, photoluminescence (PL) study was carried out to confirm the presence of dopant ion in the host matrix of β-Ca2P2O7:Dy material. Thermoluminescence (TL) glow curves of β-Ca2P2O7 were recorded for different concentrations of Dy3+ after exposure to various fluences of C6+ ion beam (75 meV). TL sensitivity of β-Ca2P2O7:Dy3+ (0.1 mol%) phosphor was 3.79 times more than commercially available CaSO4:Dy3+. TRIM code based on the Monte Carlo simulation was used to calculate the absorbed doses, ion range and main energy loss. Glow curve de-convolution (GCD) method was used to determine the number of TL peaks and their trapping parameters. The wide linear response of β-Ca2P2O7 nanoparticles along with high stability of TL glow curve makes this nanomaterial a good candidate for C6+ ion beam dosimetry. [ABSTRACT FROM AUTHOR]

Thermoluminescence (TL) measurements were carried out on europium (Eu) doped magnesium pyrophosphate (Mg 2 P 2 O 7 ) nanopowders using gamma irradiation in the dose range of 0.1 to 3 kGy. The powder samples were successfully synthesized by chemical co-precipitation synthesis route. The formation and crystallinity of the compound was confirmed by powder X-ray diffraction (PXRD) pattern. The estimated particle size was found to be in nanometer scale by using Debye Scherer's formula. A scanning electron microscopy (SEM) study was carried out for the morphological characteristics of as synthesized Mg 2 P 2 O 7 :Eu phosphor. Photoluminescence (PL) study was carried out to confirm the presence of the rare-earth ion and its valence state. The TL analysis of synthesized samples were performed after the irradiation of Mg 2 P 2 O 7 :Eu with cobalt-60 ( 60 Co) gamma rays. The high and low intensity peaks of TL glow curve appeared at around 400 K, 450 K, 500 K and 596 K respectively. The appreciable shift in peak positions has been observed for different concentrations of Eu ion. The trapping parameters, namely activation energy (E), order of kinetics (b) and frequency factor (s) have been determined using thermal cleaning process, peak shape (Chen's) method and glow curve deconvolution (GCD) functions., (Copyright © 2018 John Wiley & Sons, Ltd.)

The present paper reports on the γ-ray and C 6+ ion beam induced effect on the structural and luminescence properties of Eu doped LiNaSO 4 phosphors synthesized via wet the chemical method. The material was irradiated by 60 Co and 137 Cs γ-rays and 75 MeV C 6+ ions in a fluence range varying from 2 × 10 10 to 1 × 10 12 ion per cm 2 . The ion induced modified properties were investigated using X-ray diffraction (XRD), micro-Raman spectroscopy, photoluminescence (PL), thermoluminescence (TL) and electron paramagnetic resonance (EPR) studies. The XRD and micro-Raman results confirm the loss of crystallinity and elongation of the lattice parameters after ion beam irradiation. The presence of both divalent as well as trivalent states of Eu ions at multiple sites of LiNaSO 4 is observed by PL study. Irradiation of the LiNaSO 4 :Eu phosphor with a C 6+ ion beam modifies the population of the valence state of the doped rare earth Eu ion and enhances the TL sensitivity of this phosphor. The nature of the prominent TL glow curve is identical for both γ-ray and C 6+ ion beam irradiated materials while additional deep trap levels appear in the latter due to the formation of several types of cation and anion vacancy. The electron paramagnetic resonance (EPR) technique also supports the presence of the Eu ion at multiple sites and provides information regarding several types of radical produced after γ-ray and C 6+ ion irradiation. Finally, a mechanism is presented for the thermally stimulated luminescence phenomenon on the basis of our observed results from the PL, TL and EPR studies. The reason behind ion beam irradiation induced modification of the TL properties and enhancement of luminescence intensity is also explained in this report.