Molten Salt Route Research Articles

Synthesis of nano-crystalline Ti2SC by molten salt route

Synthesis of nano-crystalline Ti2SC by molten salt route

In-Situ Preparation of High-Performance CNS/Cu Composites with Molten Salt Route

Carbon nanosheets (CNSs) reinforced copper composites are obtained with a molten salt route for uniform distribution of carbon in the copper matrix. The structures and properties of the composite are thoroughly characterized and tested. The mechanical properties of the composite are greatly improved compared to pure copper. The effects of annealing temperatures and carbon contents on the mechanical properties of composites are investigated and discussed. When the annealing temperature is 800∘C, the composite has excellent comprehensive properties. Its yield strength is 283 MPa, which is 3.14 times that of pure copper, and its hardness is 78[Formula: see text]HV, which is 1.77 times of pure copper. The simple and low-cost preparation process opens up a novel route for the preparation of high-performance copper-based composites.

Piezocatalytic degradation of methylene blue, tetrabromobisphenol A and tetracycline hydrochloride using Bi4Ti3O12 with different morphologies

In this paper, we report the piezocatalytic application of morphologically different Bi4Ti3O12 nanostructures for piezocatalytic degradation of various environmental pollutants. Three types of Bi4Ti3O12 nanostructures with different morphologies, i.e. nanosheet-assembled hierarchical microrods, microplates, and nanoflake-assembled hierarchical microspheres, have been synthesized via a hydrothermal route and a molten salt route. Three typical environmental pollutants — methylene blue (MB), tetrabromobisphenol A (TBBPA) and tetracycline hydrochloride (TC) — were separately used the target pollutant to evaluate the piezocatalytic degradation performances of the as-synthesized Bi4Ti3O12 nanostructures under ultrasonic vibration. It is demonstrated that all the Bi4Ti3O12 samples exhibit a pronounced piezocatalytic degradation of these pollutants. The highest piezocatalytic degradation performance is observed for the Bi4Ti3O12 microplates. Further, the effects of pH, initial pollutant concentration, catalyst dosage and various anions on the piezocatalytic degradation of MB over the Bi4Ti3O12 microplates were investigated. A possible piezocatalytic mechanism of Bi4Ti3O12 was proposed and analyzed.

On the Reactive Molten Salt Synthesis, Solubility and Na-Ion Storage Performance of Na2Mo2O7

A systematic investigation is conducted to evaluate the effect of temperature on the structural and morphological characteristics of Na2Mo2O7 produced by a facile and low-energy-intensive molten salt route using MoS2 and NaCl as precursors. The solubility of the Na2Mo2O7 product in water is confirmed by assessing the light absorption of the dissolved substance. The solubility values change between around 0.4 to 3.0 g l−1, depending on the temperature and pH level. The Na-ion storage performance of the molten salt-produced Na2Mo2O7 is characterized by cyclic voltammetry, charge–discharge and electrochemical impedance spectroscopy tests. Nanostructuring of Na2Mo2O7 through high-energy ball milling with graphene nanosheets decreases the interface impedance, enhancing the pseudocapacitive performance of the material.

Study of Ag2O/TiO2 nanowires synthesis and characterization for heterogeneous reduction reaction catalysis of 4-nitrophenol

Ag2O/TiO2 nanowires as catalyst for reduction reaction of 4-nitrophenol has been synthesized in this study with molten-salt route and followed by the impregnation method. Analysis by characterization results show that the addition of Ag2O does not change TiO2 crystal structure and morphology, and it was found that the impregnated Ag2O has metal-support interactions with TiO2 nanowires. Size distribution of TiO2 nanowires structure along with the Ag2O is known to be within the range of nanomaterial. TiO2 nanowires has an average width of 339.706 nm, and the impregnated Ag2O has an average diameter size of 19.873 nm respectively. The catalytic test performance shows that Ag2O/TiO2 nanowires has excellent result compared to the control sample morphology of Ag2O/TiO2 anatase. It is closely correlated with the electron transfer capability of TiO2 nanowires structure and this shows that Ag2O/TiO2 nanowires is suitable for catalysis of 4-nitrophenol reduction reaction.

General molten-salt route to three-dimensional porous transition metal nitrides as sensitive and stable Raman substrates

Transition metal nitrides have been widely studied due to their high electrical conductivity and excellent chemical stability. However, their preparation traditionally requires harsh conditions because of the ultrahigh activation energy barrier they need to cross in nucleation. Herein, we report three-dimensional porous VN, MoN, WN, and TiN with high surface area and porosity that are prepared by a general and mild molten-salt route. Trace water is found to be a key factor for the formation of these porous transition metal nitrides. The porous transition metal nitrides show hydrophobic surface and can adsorb a series of organic compounds with high capacity. Among them, the porous VN shows strong surface plasmon resonance, high conductivity, and a remarkable photothermal conversion efficiency. As a new type of corrosion- and radiation-resistant surface-enhanced Raman scattering substrate, the porous VN exhibits an ultrasensitive detection limit of 10−11 M for polychlorophenol.

Molten salt synthesis of carbon-doped boron nitride nanosheets with enhanced adsorption performance

Owing to their large specific areas, high thermal stability and chemical inertness, two-dimensional boron carbon nitride nanosheets (BCNNs) have captured much attention in recent years in the field of adsorption of pollutants. The formation of BCNNs via incorporating carbon into boron nitride (BN) can effectively improve the photoelectric and adsorption properties of the latter. In this work, carbon-doped BN (BCN) nanosheets were prepared at 1100 °C via a molten salt route using boric acid, melamine and glucose as the main starting materials. The effects of molten salt type and carbon doping level on the formation of BCN were investigated, and their isothermal adsorption properties in a methylene blue (MB) aqueous solution were evaluated based on the Langmuir and Freundlich models. The results indicated that using molten LiCl-KCl as a liquid medium was more favorable than NaCl-KCl to the formation of BCNNs. As-prepared BC0.4N sample possessed a sheet-like structure of about 10 nm thick and a specific surface area as high as 484 m2 g−1. Moreover, the adsorption test of MB demonstrated a high adsorption capacity of 249.04 mg g−1, which was about 14 times higher than that in the case of the pristine BN, and the kinetic rate constant value in the case of using BC0.4N is about ten times as high as that of BN following a pseudo-second-order model, suggesting that the as-formed BC0.4N nanosheets could be potentially used as a value-added effective adsorbent for future wastewater remediation.

HF‐free molten salt route for synthesis of highly efficient and water‐resistant K2SiF6:Mn4+ for warm white LED

AbstractIt has been one of the hot issues to prepare the red‐emitting Mn4+‐doped fluoride phosphors with highly efficient and waterproofness for warm white‐light‐emitting diodes (WLEDs) by the green and environmentally friendly method. Herein, we design a novel green molten salt route to synthesize K2SiF6:Mn4+ red powder using molten NH4HF2 salt instead of HF liquor as the reaction medium. The results show that KMnO4 and MnF2 could produce Mn4+ in NH4HF2 molten salt through a reduction reaction, and the resulting Mn4+‐doped K2SiF6 exhibited a bright red emission peaked at 632 nm under blue light excitation. The luminescence intensity of the as‐obtained product after immersing into water for 24 hours maintain nearly 100% of that before soaking and emission peak shape remains unchanged. The thermal stability of the sample was evaluated by temperature‐dependent luminescence spectral intensity during heating and cooling. Furthermore, a warm white‐light‐emitting diodes (WLEDs) with an excellent color rendering index (Ra = 87.1), lower correlated color temperature (CCT = 3536K), and high luminous efficacy (116.99 lm·W−1) was fabricated based on blue chip and K2SiF6:Mn4+ and commercial yellow phosphor (Y3Al5O12:Ce3+).

Molten salt synthesis of hierarchically porous carbon for the efficient adsorptive removal of sodium diclofenac from aqueous effluents

Pharmaceutical and personal care products (PPCPs) are emerging organic pollutants (EOPs) that pose a serious peril to both aquatic biota and mankind's health. The development of novel adsorbent materials for the effectual treatment of PPCPs-included wastewater has become one of the foremost research issues in the environmental research area. In this work, a hierarchical carbon material (GHPC), produced through the simple and effective molten salt route adopting glucose and the eutectic mixture (KCl/ZnCl2) as the carbon precursor and the pore generator, respectively, was applied in adsorption of sodium diclofenac, as a representative of organic contaminants of emerging concern, from aqueous solution. GHPC manifested superior adsorption performance towards DFC, which was believed to stem from its high surface area and total pore volume, hierarchically porous texture, and the presence of plentiful available functional groups. Langmuir adsorption isotherm, and the pseudo-second-order kinetics were found to be appropriate to represent the adsorption equilibrium and kinetics, respectively. Hydrogen bonding interaction was thought to be the main mechanism underlying DFC (as H-bond donor) adsorption onto GHPC (as H-bond acceptor). The impacts of the co-existing cations and anions on the adsorptive removal of DFC were additionally scrutinized. Finally, GHPC demonstrated good reusability properties that qualify it for the practical remediation of PPCPs-included wastewater.

Effect of magnetic ion substitution on the structure and temperature-dependent magnetic properties of strontium hexaferrite

ABSTRACT Rare earth substituted strontium hexaferrite powders were synthesised through a molten salt route at 900°C for 5 h. The influence of rare-earth magnetic ion substitution on microstructural features, morphology and temperature-dependent magnetic properties was investigated. The lattice parameter ratio of less than 3.98 proves that all the substituted samples primarily present the hexaferrite phase. Fourier transform infrared peaks also confirmed the presence of a metal-oxygen bond. A 66% increase in magnetic saturation, 38% increase in coercivity and a more than two-time increase in remanence for the samarium doped sample are seen as the highest magnetic measurements compared to pure SrFe12O19 at room temperature. There were also differences in the temperature-dependent magnetic properties of strontium ferrites. As temperature decreased from 300 K, saturation magnetisation and remanence value were found to increase. This will perhaps be a promising material for magnetic field sensor application.

Sustainable production of nano α-Fe2O3/N-doped biochar hybrid nanosheets for supercapacitors

Nano α-Fe2O3/N-doped biochar nanosheets were successfully fabricated from biomass waste through a facile, scalable and environmentally friendly molten salt route.

Germanium and iron double-substituted ZnGa2O4 solid-solution photocatalysts with modulated band structure for boosting photocatalytic CO2 reduction with H2O

The conversion of CO2 into renewable fuels by artificial photosynthesis is an attractive solution for storing solar energy in the form of chemical fuel. Herein, we presented a general molten-salt route to synthesize spinel germanium and iron double-substituted ZnGa2O4 solid solutions. Introducing ZnFe2O4 and Zn2GeO4 into ZnGa2O4 can effectively expand the light-harvesting wavelength range to improve the ability of photocatalyst in CO2 reduction and H2O oxidation. The solid solutions provide a larger effective mass of holes compared with electrons through the introduction of Fe3d, Ge4s and Ge4p orbitals according to DFT analysis. This leads to a great difference in the mobility between the electrons and holes to lessen the electron–hole recombination rate, and enhance the conversion of CO2 and H2O in kinetics. This approach is developed to achieving smaller bandgap values and a closer bracketing of the CO2/reduced-H2O/oxidized redox couples to drive the overall conversion of CO2 and H2O.

A simple and recyclable molten-salt route to prepare superthin biocarbon sheets based on the high water-absorbent agaric for efficient lithium storage

Due to its sustainability, biomass materials shows great potential in replacing mineral carbon source to fabricate high-energy electrode materials, and efficient routes have been explored to synthesize and regulate biomass-derived carbonaceous materials with rational structures to enable their applications. Herein, a simple and recyclable molten-salt route is used to synthesize porous ultrathin biocarbon nanosheets from biomass (agaric). Due to the excellent adsorption ability of agaric for molten-salt ions, the interior and exterior of the agaric was fully exposed to the molten-salts, the fluidity and thermal motion of the high-temperature ionic solution promoted the complete exfoliation of biomass. The obtained superthin porous 2D carbon nanosheets provided more active sites and shortened the diffusion distance for lithium ion insertion/deinsertion, and formed a continuous conducting network for electron transport. Consequently, when used as the anodic material for lithium storage, the electrode displayed a higher specific capacity (∼795 mAh g−1 at 0.1 A g−1), outstanding rate performance (∼382 and ∼331 mAh g−1 at 5 and 10 A g−1), and superior cyclic stability (no capacity decay after 1000 cycles at 1 A g−1). Therefore, the preparation of sustainable biocarbon materials by the recyclable, molten-salt-assisted method described in this paper will enable the practical application of such materials in various energy storage devices.

Towards Blue Long-Lasting Luminescence of Eu/Nd-Doped Calcium-Aluminate Nanostructured Platelets via the Molten Salt Route.

Calcia-alumina binary compounds doped with rare earths and some transition metals cations show persistent luminescence from the visible to the infrared range. Specifically, the blue light can be obtained through the Eu2+ activator center in a potential host, such as dodecacalcium hepta-aluminate (Ca12Al14O33) and monocalcium aluminate (CaAl2O4). By doping with Nd3+, the persistent luminescence can be substantially prolonged; for this reason, the Eu/Nd pair is a potential choice for developing long-lasting blue luminescence. Herein, the phase evolution of the calcia-alumina system via molten salt synthesis is reported as a function of the synthesis temperature and the atmospheric environment. The fraction of CaAl2O4 phase increases when the temperature is higher. Synthesized microparticles of platelet-type morphology represent isolated nanostructured ceramic pieces. Under visible light, the particles are white. This indicates that the followed process solves the dark-gray coloring of phosphor when is synthesized in a reduced atmosphere at high temperature. As regards the synthesis mechanism, which is assisted by the molten flux, the dissolution−diffusion transport process is promoted at the surface of the alumina microparticles. In fact, the emission intensity can be modulated through the phase of the Eu-doped calcium-aluminate discrete platelets synthesized. Consequently, the photoluminescence intensity depends also on the oxidation state of the Eu ion. X-ray absorption near-edge structure and photoluminescence measurements corroborate the Eu reduction and the grain coarsening with the enhancement of the blue emission. The doped phosphors with Eu/Nd show a broad and strong absorption in the region of 320–400 nm and a broad emission band at around 440 nm when they are excited in this absorption range. From a broader perspective, our findings prove that the Ca12Al14O33 and CaAl2O4 phases open new opportunities for research into the design of blue long-lasting emitters for a wide range of fields from ceramic to optoelectronic materials.

One-step synthesis of novel K+ and cyano groups decorated triazine-/heptazine-based g-C3N4 tubular homojunctions for boosting photocatalytic H2 evolution

Constructing homojunctions with different morphologies, exposing facets, crystal phases or semiconductor types in a photocatalyst is an essential approach to boost the photoactivity. Herein, the g-C3N4 phase homojunctions decorated with cyano groups and K+ were designed and successfully synthesized via only adjusting the reaction temperatures within a facile one-step molten salt route. Such unique junctions were constructed through the overgrowth of triazine-based g-C3N4 nanoparticles embedded in the surface and inner wall of heptazine-based g-C3N4 hollow tubes. Benefited from the multiple advantages of high specific surface area, unique tubular structure, enhanced visible light absorption, and fast charge transfer and separation, the triazine-/heptazine-based g-C3N4 homojunctions drastically enhanced the photocatalytic hydrogen production performance, achieving a 2 and 12-fold improvement than the pristine g-C3N4 microtube and bulk g-C3N4, respectively. This study provides an in-depth insight into the design and fabrication of other g-C3N4-based photocatalysts for more efficient solar energy conversion applications.

The Effect of Melt Ultrasound Treatment on the Microstructure and Age Hardenability of Al-4 Wt Pct Cu/TiC Composite

In the present work, Al-4 wt pct Cu/TiC composite was synthesized by the molten salt route that contains submicron-sized TiC particles in the Al-4 wt pct Cu matrix. The concentration of the TiC particle in the base alloy is 7.5 wt pct. Melt ultrasound treatment was done by remelting the as-cast composite at 1023 K (750 °C) in a view to refine the size of TiC particles to nanoscale and distribute them evenly in the matrix. The microstructure and age hardenability of the untreated and ultrasound-treated composites were investigated. The TiC particles accelerate the precipitation kinetics of CuAl2 phase in Al-4 wt pct Cu alloy. In the present study, the hardness obtained for untreated Al-4 wt pct Cu/TiC composite is 120 VHN within 5 hours of peak aging time, which is higher than the hardness of the monolithic Al-4 wt pct Cu, which is 104 VHN at 35 hours of peak aging time. Melt ultrasound treatment of Al-4 wt pct Cu/TiC composite shows no significant effect on the distribution and refinement of TiC particles in the matrix. However, it partially disintegrates the TiC into Al3Ti and Al4C3 particles. The ultrasound-treated composite showed an improved hardness of about 132 VHN at 5 hours of peak aging, in comparison to that of the untreated composite, by forming denser and homogeneous CuAl2 precipitates.

Molten salt synthesis of nano structured pyrochlore lanthanum zirconate: a potential material for high temperature applications

Molten salt synthesis of nanocrystalline pyrochlore lanthanum zirconate (La2Zr2O7) powders with NaCl–KCl alone as reaction aid was prepared in the present investigation with low synthesis temperature for the first time. The structural and morphological data of the synthesized lanthanum zirconate powder was characterized using XRD, FESEM—EDS and TEM. Functional group identification was carried out using FT-Ir and simultaneous themal analysis on the starting material was also carried out characterized by thermogravimetric analysis and differential thermal analysis. Simultaneous thermal analysis of the starting materials was carried out and the results show the suitability of the molten salt synthesis below 900 °C. The XRD pattern reveal the existence of pyrochlore structure La2Zr2O7 matches with the standard ICDD pattern. The average crystallite size was measured to be 34.66 nm by Debye Scherer formula and 35.53 nm using WH plot. The particle size measured using the particle size analyser, scanning electron microscope and transmission electron microscope shows in the order of 40–50 nm and the powders are seen clearly without agglomerations. Energy dispersive spectrum results show the clear presence of La–Zr–O without any other inclusions and confirms the results obtained through x-ray photo emission spectroscopy. SAED pattern obtained through TEM shows the polycrystalline nature of the synthesised nano La2Zr2O7. The structural functional group evolution was examined using FT-Ir confirms the formation of La–Zr–O chemical bonds. The results confirms that nano crystalline pyrocholore La2Zr2O7 can be successfully synthesised using relatively low temperature molten salt route at 850 °C with the aid of anhydrous NaCl–KCl eutectic salt mixture alone as reaction aid and anhydrous La2O3 and ZrO2 as precursors.

Tunable dielectric properties of niobium (Nb) doped CaCu3Ti4O12 nanocubes synthesized via facile molten salt route

Doping induced tuning of dielectric constant of nanomaterials has huge technological importance, but its realization is limited by lack of synthetic protocols for uniform dielectric nanostructures, with controlled doping. Here, nanocubes of niobium doped calcium copper titanate (Nb-doped CCTO) is realized through molten salt route and the effect of Nb doping on tunability of dielectric behavior is reported. Particular focus is to minimize the significant dielectric loss which is practical concern of CCTO based giant dielectric materials. The structural and compositional properties of as synthesized powders and sintered pellets are analyzed by X-ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. XRD analysis carried out on the samples confirmed single phase formation and indicated overall increase in lattice constant. The surface morphology of the molten salt derived product shows nanocubes with size in the range of 250–280 nm. Energy dispersive X-ray spectroscopy pattern confirmed the presence of Nb in doped samples. The dielectric response of sintered CaCu3Ti4−xNbxO12 samples studied by precision LCR meter suggest that although Nb substitution in CCTO reduces the dielectric constant but dielectric loss had lower values than those of undoped CCTO.

Photocatalytic performance of carbon nitride intercalation compound

The carbon nitride intercalation compound photocatalyst was synthesized by a simple molten salt route. The photocatalyst was characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and Fourier transform infrared (FT-IR) spectroscopy. The photocatalytic oxidation ability of the carbon nitride intercalation compound photocatalyst was evaluated by the photocatalytic activity in photo-oxidation of MO. The as-prepared photocatalyst exhibits an improved photocatalytic activity due to the increased surface area.

Microstructures, magnetic, and dielectric properties of Ba‐doped BiFeO3 nanoparticles synthesized via molten salt route

AbstractAs the paradigm of magnetoelectric multiferroic materials, BiFeO3 (BFO) has potential applications in spintronics, memory devices, sensors, and actuators. However, its large leakage current and small magnetism at room temperature restrict its practical applications. It is demonstrated that the substitutions of Bi by alkali earth elements at A‐site of BFO can significantly reduce the leakage current and enhance the remanent magnetization of BFO. In this work, Ba‐doped BFO nanoparticles Bi1‐xBaxFeO3 (x = 0, 0.05, 0.10, 0.15 and 0.20) were synthesized via molten salt route. X‐ray diffraction patterns revealed that with increasing the Ba‐doped content the formation of the impurity phase was depressed and the rhombohedral distortions of these nanoparticles were suppressed, as confirmed by Raman spectra. X‐ray photoelectron spectroscopy measurements reveal that the Fe element in the nanoparticles exists in the dual valence states of Fe3+ and Fe2+, and two kinds of oxygen atoms (lattice oxygen atoms and the adsorbed oxygen atoms) exist in the nanoparticles. With increasing the Ba‐doped content, the content ratios of Fe3+ to Fe2+ ions were generally increased, whereas the oxygen vacancy concentrations were decreased. The average particle sizes of the Ba‐doped BFO nanoparticles were decreased as compared with that of nondoped BFO nanoparticles. In contrast, the room temperature magnetization of the Ba‐doped BFO nanoparticles was greatly enhanced by Ba‐substitution, as confirmed by the M‐H loops. At room temperature, the remanent magnetization and coercive field of the Bi0.8Ba0.2FeO3 nanoparticles were 0.51 emu/g and 1130 Oe, respectively. Furthermore, the leakage current density was reduced by one order of magnitude at x = 0.2 and the dielectric properties are also improved by Ba‐substitution. The improvements on the remanent magnetization, leakage current density as well as dielectric properties of the Ba‐doped BFO nanoparticles make them promising candidates for spintronics and dielectric energy storages.