Simple Molten Salt Research Articles

Exchange bias in LiNi0.5Mn1.5O4–NiO nanocomposites

Composites LiNi0.5Mn1.5O4–NiO nanosticks were prepared by a simple molten salt route of adding MnSO4 to molten LiNO3, NaNO3 and slightly excess NiSO4·6H2O. Field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) investigations revealed that one-dimensional composites LiNi0.5Mn1.5O4–NiO nanosticks were generated in a large quantity. The result of dc and ac magnetisation, as well as magnetic hysteresis measurements, shows that three different magnetic phases, i.e. ferrimagnetic, antiferromagnetic (AFM) and spin-glass-like (SGL) phases may coexist in LiNi0.5Mn1.5O4–NiO nanocomposites. Furthermore, magnetic measurements suggest that the exchange bias (EB) effect was obtained at low temperature.

ChemInform Abstract: Li9V3(P2O7)3 (PO4)2 Nanotubes Fabricated by a Simple Molten Salt Approach with Excellent Cycling Stability and Enhanced Rate Capability in Lithium‐Ion Batteries.

AbstractLarge scale preparation of Li9V3(P2O7)3 (PO4)2 nanotubes is performed by a simple molten salt route without the use of a surfactant as a template.

Large-scale synthesis of aluminium borate nanowires by a simple molten salt method

Aluminum borate nanowires were synthesized in a molten salt method at 1100°C in the air by using ammonium aluminum carbonate hydroxide (AACH) and H3BO3 as starting materials. The as-synthesized samples were examined by XRD and SEM. The results showed that Al18B4O33 nanowires with an orthorhombic structure were formed at 1100°C. A self-catalytic mechanism was proposed for the growth mechanism of the nanowires on the basis of the experimental phenomena.

One step molten salt synthesis of YVO4 nanoparticles and their photocatalytic properties under UV–Visible light

Well-crystalline YVO4 nanoparticles were successfully synthesized by a simple and convenient one-step molten salt synthesis (MSS) method in a wide temperature range of 350–600°C for only 5h. The UV–Visible absorption spectra measured by a spectrophotometer suggest that visible light absorption exists in the absorption spectra of all the samples prepared under different temperatures and the smaller the particle size, the stronger the absorption, the smaller the onset of UV absorption and the larger the blue shift. The photodegradation of RB indicates that both particle size and crystallinity have effects on the photocatalytic properties of YVO4 nanoparticles. YVO4 nanoparticles were further demonstrated to have excellent photocatalytic stability.

Morphology-Controlled Synthesis of Sodium Hexa-Titanate Nanowhiskers by Changing Evaporation Rate of NaCl–KCl Molten Salts

Na2Ti6O13 nanowhiskers with controllable morphologies were prepared via a simple molten salt evaporation method using a small quantity of NaCl–KCl as molten salt. The synthesized products were characterized by X-ray diffraction, field emission scanning electron microscope, and transmission electron microscope. The optimal growth dynamic conditions for synthesis of Na2Ti6O13 nanowhiskers were also studied and discussed. According to thermogravimetry-differential scanning calorimetry analysis, the calcination process was designed to include two stages, lower temperature for reaction and higher temperature for evaporation of molten salt. Nanowhiskers and nanorods with different diameters can be obtained under different evaporation conditions. By comparing residual amounts of NaCl–KCl on product surfaces calculated by determined kinetic equation and experimental results only using NaCl as molten salt, it was revealed that the molten salt evaporation rates could play an important role on the morphologies of Na...

Morphology-controlled synthesis, characterization, and luminescence properties of KEu(MoO4)2 microcrystals

Large-scale one-dimensional (1D) rod-like and octagonal-like KEu(MoO4)2 microcrystals were successfully synthesized by a simple, environmental friendly, and low cost molten salt method using halons (KCl or KBr) as flux. The as-prepared products were characterized by X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED) and photoluminescence (PL) spectrometry. The results show that the reaction parameters, including reaction temperature and reaction time, played important roles on the phase structures and morphologies of the final products. The possible growth process of 1D rod-like KEu(MoO4)2 was proposed based on the time-dependent shape evolution and HRTEM analysis, which followed oriented aggregation and Ostwald ripening. The results of SAED and HRTEM investigations indicated an incommensurate modulated structure in the rod-like KEu(MoO4)2, and all the reflections can be expressed as ha* + kb* + lc* + mq, where m is an integer, and modulated vector q = 0.182b* + 0.156c*. Room temperature photoluminescence spectra of KEu(MoO4)2 microcrystals reveal a strong red emission via5D0 → 7F2 transition at 615 nm, and the 1D rod-like microcrystals own the enhanced intensity compared with the octagonal-like ones.

Towards efficient solar hydrogen production by intercalated carbon nitride photocatalyst

The development of efficient photocatalytic material for converting solar energy to hydrogen energy as viable alternatives to fossil-fuel technologies is expected to revolutionize energy shortage and environment issues. However, to date, the low quantum yield for solar hydrogen production over photocatalysts has hindered advances in the practical applications of photocatalysis. Here, we show that a carbon nitride intercalation compound (CNIC) synthesized by a simple molten salt route is an efficient polymer photocatalyst with a high quantum yield. We found that coordinating the alkali metals into the C-N plane of carbon nitride will induce the un-uniform spatial charge distribution. The electrons are confined in the intercalated region while the holes are in the far intercalated region, which promoted efficient separation of photogenerated carriers. The donor-type alkali metal ions coordinating into the nitrogen pots of carbon nitrides increase the free carrier concentration and lead to the formation of novel nonradiative paths. This should favor improved transport of the photogenerated electron and hole and decrease the electron-hole recombination rate. As a result, the CNIC exhibits a quantum yield as high as 21.2% under 420 nm light irradiation for solar hydrogen production. Such high quantum yield opens up new opportunities for using cheap semiconducting polymers as energy transducers.

Investigations on the temperature dependent electrical and magnetic properties of NiTiO3 by molten salt synthesis

Submicron-sized NiTiO3 particles were successfully synthesized by simple molten salt method. The phase purity and crystal structure was confirmed through X-ray diffraction. The characteristics bands of NiO and TiO were identified using Fourier Transform Infra-red spectrum. The SEM and TEM images shows that the particles are lying in the range of 150–300nm and selected area electron diffraction pattern (SAED) infers the single crystalline nature of NiTiO3. The impedance spectra elucidate the grain interior conducting mechanism and semi-conducting nature of NiTiO3 at elevated temperatures. The frequency dependent conductance spectra were found to obey Jonscher's power law and a maximum value of conductivity observed was 2×10−5Scm−1 at 520°C. The magnetic susceptibility measurement infers the antiferromagnetic behavior with the Neel temperature (TN) of 14.9K. The increase in coercivity below TN reveals the coexistence of antiferromagnetic with superparamagnetic behavior. B–H curve represents the first order phase transition from antiferromagnetic to ferromagnetic transition.

Eu3+‐activated Y2MoO6: a narrow band red‐emitting phosphor with strong near‐UV absorption

Near-UV excited narrow line red-emitting phosphors, Eu(3+)-activated Y2MoO6 systems, were synthesized using a simple molten salt reaction. The structure and photoluminescence characteristics were investigated using X-ray powder diffraction, UV-Vis absorption and fluorescent spectrophotometry. The excitation spectra show strong broad-band absorptions in the near-UV to blue light regions which match the radiation of near-UV light-emitting diode chips well. Under excitation of either near-UV or blue light, intense red emission with a main peak of 611 nm is observed, ascribed to the (5)D0-(7)F2 transition of Eu(3+) ions; the optimal doping concentration is 20 mol%. The chromaticity coordinates (x = 0.65, y = 0.34) of the as-obtained phosphor are very close to the National Television Standard Committee standard values (x = 0.67, y = 0.33). All these characteristics suggest that this material is a promising red-emitting phosphor candidate for white-LEDs based on near-UV LED chips.

TiO2 nanoparticles synthesized by the molten salt method as a dual functional material for dye-sensitized solar cells

We report the simple and versatile molten salt fabrication of mesoporous anatase TiO2 nanoparticles with a high surface area of ∼200 m2 g−1, which show an impressive efficiency of ∼7.5% in dye-sensitized solar cells.

Molten salt synthesis and energy storage studies on CuCo2O4 and CuO·Co3O4

CuCo2O4 and CuO·Co3O4 compounds were prepared by a one-pot simple molten salt method (MSM) at 280 °C to 750 °C. Changes in morphology, crystal structure and electrochemical properties of CuCo2O4 as a function of preparation temperatures were investigated using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Brunauer–Emmett–Teller absorption isotherm. XRD patterns of the sample prepared at 280 °C show a crystalline cubic structure with a lattice parameter value of a = 8.131 A and a surface area value of 9.8 m2 g−1. The sample prepared at temperatures >510 °C shows the presence of CuO·Co3O4 phases. Energy storage properties are evaluated using cyclic voltammetry (CV) and galvanostatic cycling studies. CV studies show a main anodic peak at ∼2.1 V and cathodic peak at ∼1.2 V. At a current rate of 60 mA g−1 and in the voltage range of 0.005–3.0 V vs. Li, CuCo2O4 composite prepared at 510 °C shows a high and stable capacity of ∼680 (quenched) and 740 (slow cooling) mAh g−1 at the end of the 40th cycle.

A simple approach to strontium sodium tantalite mesocrystals with ultra-high photocatalytic properties for water splitting

A novel kind of strontium sodium tantalite (SNT) mesocrystal has been synthesized via a simple molten salt process without using any organic additives. The SNT mesocrystals are characterized as built from nanocubes (20–60 nm) via a non-classical crystallization process. The obtained 3D architectures show high crystallinity and a preferred orientation growth. Formation of SNT mesocrystals strongly depends on the weight ratio (W) of salt to starting materials. An inappropriate value of W will restrain the orientation attachment and promote the process of classic crystallization. The SNT mesocrystals exhibit an outstanding photocatalytic performance due to their nanosteps, high porosity and preferred oriented direction. Rates of hydrogen generation reach values of 27.5 and 4.89 mmol h−1 for aqueous methanol and pure water splitting, respectively. Besides, the molten salt method is suggested to be beneficial for large scale applications of catalysts due to its nontoxicity, recyclability, cheapness and high efficiency.

Synthesis and visible-light photocatalytic activity of NdVO 4 nanowires

NdVO 4 nanowires are synthesized by a simple composite molten salt method. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrum, energy dispersive spectrometry and UV–vis spectrum are used to characterize the structure, morphology and composition of the sample. The results show that the product is of tetragonal phase NdVO 4 nanowires which are connected together in bases, rooted in one center, with typical diameters of 100 nm and lengths up to 3 μm. The UV–vis spectrum shows that NdVO 4 nanowires have four strong absorption peaks from the UV to near infrared region. The photocatalytic degradation of Rhodamine B (RhB) and methyl orange under visible light irradiation using the NdVO 4 nanowires are also investigated. Excellent catalytic degradation activity of RhB observed suggests possible applications for organic pollutant treatment under visible light irradiation. The electron density states of the NdVO 4 were calculated with the Vienna ab initio simulation package. The results of these simulations were used to form a description of the observed light absorption and photodegradation properties of NdVO 4 nanowires.

Synthesis of carbon coated nanocrystalline porous α-LiFeO 2 composite and its application as anode for the lithium ion battery

In this work, we describe for the first time a high surface area nanocrystalline porous α-LiFeO 2-C composite anode material synthesized by a simple molten salt method, followed by a carbon coating process. The synthesized nanocomposite presents an interconnected porous architecture, as was confirmed by field emission scanning electron microscope observations. Transmission electron microscope investigations revealed that amorphous carbon was incorporated into the pores among the nanoparticles and that some nanoparticles were covered by a thin layer of amorphous carbon as well. Electrochemical measurements showed that the carbon played an important role, as it affected both the cycle life and the rate capability of the electrode. The α-LiFeO 2-C nanocomposite electrode delivered a higher reversible capacity and good cycle stability (540 mAh g −1 at 1 C after 200 cycles) compared to the pure α-LiFeO 2 electrode. Good electrochemical performance of the α-LiFeO 2-C nanocomposite electrode could be attributed to the porous conductive architecture among the nanoparticles, which not only has benefits in terms of decreasing the absolute volume changes and increasing the mobility of lithium ions, but also offers conductive pathways along the whole interconnected wall in the structure, which is favourable for the transport of electrons, promotes liquid electrolyte diffusion into the bulk material, and acts as a buffer zone to absorb the volume changes. Our results indicate that α-LiFeO 2-C nanocomposite could be considered as a potential anode material for lithium-ion batteries.

α-Fe 2O 3 as an anode material with capacity rise and high rate capability for lithium-ion batteries

We report a simple molten salt method to prepare nanosize α-Fe 2O 3, as well as its electrochemical performance as anode material for lithium ion batteries. The structure and morphology were confirmed by Raman spectroscopy, X-ray diffraction, and transmission electron microscopy. The as-prepared α-Fe 2O 3 is a rhombohedral phase of hematite with crystal size in the range of 20–40 nm. The electrochemical measurements were performed using the as-prepared powders as the active material for a lithium-ion cell. The nanosized α-Fe 2O 3 shows excellent cycling performance and rate capability. It also exhibits the feature of capacity increase upon cycling. The outstanding electrochemical performance of the α-Fe 2O 3 can be related to several factors, namely, the short Li + diffusion length along the porous rhombohedral structures and the nanosized nature of the materials, which decreases the traverse time for electrons and Li + ions, and reduces the volume expansion to some extent during charge/discharge reactions.

Synthesis and magnetic properties of single-crystalline Na2- x Mn8O16 nanorods

The synthesis of single-crystalline hollandite-type manganese oxides Na2-xMn8O16 nanorods by a simple molten salt method is reported for the first time. The nanorods were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and a superconducting quantum interference device magnetometer. The magnetic measurements indicated that the nanorods showed spin glass behavior and exchange bias effect at low temperatures. The low-temperature magnetic behaviors can be explained by the uncompensated spins on the surface of the nanorods.

MgFeSiO4 prepared via a molten salt method as a new cathode material for rechargeable magnesium batteries

Well-crystallized MgFeSiO4 microparticles were synthesized at different temperatures by a simple molten salt method using KCl flux. As a new cathode for rechargeable magnesium batteries, the material shows a reversible Mg2+ intercalation-deintercalation process. In 0.25 mol/L Mg(AlCl2EtBu)2/THF electrolyte, MgFeSiO4 synthesized at 900°C can deliver a 125.1 mAh/g initial discharge capacity and a 91.4% capacity retention on the 20th cycle at a rate of 0.1C (about 15.6 mA/g). The results show that MgFeSiO4 could be a good host for Mg2+ intercalation, and a potential cathode material for high-energy rechargeable magnesium batteries.

K2Mo4O13 nanobelts: synthesis and properties

This Letter describes a simple molten salt approach to the synthesis of K 2 Mo 4 O 13 nanobelts with lengths of several tens of micrometres. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrum and energy dispersive spectroscopy are used to characterise the structure, morphology and composition of the sample. The UV-visible spectrum shows that the bandgap of the K 2 Mo 4 O 13 nanobelts is 3.6 eV. Photoluminescence measurement shows a strong and broad emission peak of 355 nm for the K 2 Mo 4 O 13 nanobelts. Electrochemical tests show good performance of the material in cycling stability as cathode material for Li-ion batteries.

Nanocrystalline porous α-LiFeO2–C composite—an environmentally friendly cathode for the lithium-ion battery

A novel nanocrystalline porous α-LiFeO2–C composite with a high surface area of around 115 m2 g−1 has been synthesized by a simple molten salt method, followed by a carbon coating process. The structure and morphology were confirmed by X-ray diffraction, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). FE-SEM observations demonstrated that the morphology consists of α-LiFeO2–C nanoclusters composed of very tiny nanoparticles joined together by a porous architecture. TEM investigations revealed that amorphous carbon was incorporated into the pores among the nanoparticles and that some nanoparticles were covered by a thin layer of carbon as well. Electrochemical measurements showed that the α-LiFeO2–C nanocomposite delivered a significantly higher reversible capacity and excellent cycle stability (230 mA h g−1 at 0.5 C after 100 cycles). Even at the high rate of 3 C, the electrode showed more than 50% of the capacity at low rate (0.1 C). The excellent electrochemical performance of the α-LiFeO2–C nanocomposite electrode can be attributed to the porous conductive architecture among the nanoparticles, which not only has benefits in terms of decreasing the absolute volume changes and increasing the mobility of lithium ions, but also offers conductive pathways along the whole interconnected wall in the structure, which is favourable for the transport of electrons, promotes liquid electrolyte diffusion into the bulk materials, and acts as a buffer zone to absorb the volume changes.

Molten salt synthesis, characterization and luminescence of ZnWO 4:Eu 3+ nanophosphors

ZnWO 4:Eu 3+ red nanophosphors have been synthesized by a simple, environmentally friendly and low cost molten salt method using LiNO 3, NaNO 3 and KNO 3 as flux. We investigate the influences of the variety and amount of molten salt flux on photoluminescence properties of these phosphors. The products belong to the nanoparticle with particle size of around 50 nm. The PL intensity of the ZnWO 4:Eu 3+ using NaNO 3 molten flux is stronger than that of the samples using KNO 3 molten flux, revealing that the remaining impurity molten salt produces the defects within ZnWO 4 host to be favorable for the luminescence of Eu 3+.