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Molten salt synthesis of highly ordered and nanostructured hexagonal boron nitride
摘要： Hexagonal boron nitride (h-BN) is a well-known ceramic that has wide application areas ranging from electronics to metallurgy. However, highly ordered h-BN is conventionally synthesized at high temperatures above 1800 °C. In this work, we investigated the formation of BN from boric acid (H3BO3)-ammonium chloride (NH4Cl) mixture in the sodium chloride (NaCl)-potassium chloride (KCl) eutectic salt. We report the synthesis of highly ordered and nanostructured h-BN at 1000 °C using molten salt synthesis. The effect of starting composition, synthesis temperature, and dwell time on BN formation and its structural ordering were systematically investigated. It is concluded that the molten salt plays important roles in the formation of BN and its structural ordering, which is achieved by i) decomposing the boron (B)-nitrogen (N) bearing reactants that lead to the formation of BN layers, and ii) increasing the mobility of BN layers formed. Furthermore, we propose a possible reaction mechanism that governs the BN formation from the reactant mixture in molten salts and explain the observations based on thermodynamic and kinetic considerations.
关键词： Molten salt synthesis,NaCl-KCl eutectic salt,Boron nitride,Structural ordering,High-resolution transmission electron microscopy
更新于2025-11-21 11:01:37
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Effect of Nb-doping on the structural and electrical properties of Ba0.97La0.02Ti1-xNb4x/5O3 ceramics at room temperature synthesized by molten-salt method
摘要： We, herein, report on the structural and electrical properties of Ba0,97La0.02Ti1-xNb4x/5O3 ceramics prepared by the molten-salt method. The XRD patterns of the samples at room temperature showed a single perovskite phase having a tetragonal structure with a P4/mmm space group. The electrical properties were studied by complex impedance spectroscopy in the frequency range (1–107Hz) at room temperature. The real and imaginary parts of impedance decreased with increasing Nb concentration. The complex impedance plot exhibited a single impedance semicircle for each compound, identified over the high and medium frequencies followed by a linear section, at low frequency, is explained by Warburg’s element. The study of the normalization curves of impedance and electrical modulus showed a mismatch of both peaks, which suggests the presence of short-range motion of charge carriers. The electrical conductivity decreased with increasing niobium amount and the experimental data were fitted using Jonscher’s universal power law. The exponent n is slightly superior to 1, indicating that the hopping occurs between neighboring sites.
关键词： molten-salt,conductivity,Ba0.97La0.02Ti1-xNb4x/5O3,EIS spectrum,impedance spectroscopy,Warburg element
更新于2025-09-23 15:22:29
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Formation of Si Hollow Structures as Promising Anode Materials through Reduction of Silica in AlCl <sub/>3</sub> –NaCl Molten Salt
摘要： Hollow nanostructures are attractive for energy storage and conversion, drug delivery, and catalysis applications. Although these hollow nanostructures of compounds can be generated through the processes involving the well-established Kirkendall effect or ion exchange method, a similar process for the synthesis of the pure-substance one (e.g., Si) remains elusive. Inspired by the above two methods, we introduce a continuous ultrathin carbon layer on the silica nano/microstructures (St?ber spheres, diatom frustules, sphere in sphere) as the stable reaction interface. With the layer as the diffusion mediator of the reactants, silica structures are successfully reduced into their porous silicon hollow counterparts with metal Al powder in AlCl3?NaCl molten salt. The structures are composed of silicon nanocrystallites with sizes of 15?25 nm. The formation mechanism can be explained as an etching?reduction/nucleation?growth process. When used as the anode material, the silicon hollow structure from diatom frustules delivers specific capacities of 2179, 1988, 1798, 1505, 1240, and 974 mA h g?1 at 0.5, 1, 2, 4, 6, and 8 A g?1, respectively. After being prelithiated, it retains 80% of the initial capacity after 1100 cycles at 8 A g?1. This work provides a general way to synthesize versatile silicon hollow structures for high-performance lithium ion batteries due to the existence of ample silica reactants and can be extended to the synthesis of hollow structures of other materials.
关键词： carbon interface,hollow structures,silicon,molten salt,anode
更新于2025-09-23 15:21:01
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Orientation factor and piezoelectric property in textured (K,Na)NbO <sub/>3</sub> system ceramics with minimal templates
摘要： To lower the sintering temperature and decrease the weight ratio of templates required for fabricating textured (K,Na)NbO3 (KNN) system ceramics, the method of preparing platelike NaNbO3 (NN) single-crystal particles for the templates was improved. The NN crystal particles synthesized by the single-step molten salt method using a mixed salt were treated by ultrasonic vibration and subsequently screened. Using these improved templates, we developed the fabrication method for the textured KNN system ceramics by which the weight ratio of the templates required for the orientation control can be reduced to 1/10 of the conventional weight ratio. The effects of decreasing the weight ratio of templates on sintering temperature, orientation factor, and piezoelectric properties were investigated. In addition, the effects of adding Bi2O3 to KNN calcined powder were also studied to suppress abnormal grain growth, which appears in the textured samples fabricated using smaller amounts of the templates.
关键词： reactive template grain growth,molten salt synthesis,Bi2O3 addition,lead-free piezoelectric materials,ultrasonic treatment,textured ceramics
更新于2025-09-23 15:21:01
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Enhanced heat capacity of binary nitrate eutectic salt-silica nanofluid for solar energy storage
摘要： In concentrating solar power plants, the heat capacity of thermal storage media is a key factor that affects the cost of electricity generation. This work investigated the effective specific heat capacity of binary nitrate eutectic salts seeded with silica nanoparticles, using both experimental measurements and molecular dynamics simulations. The effects of the mass concentration (0–2.0 wt%) and average size (10, 20, and 30 nm) of the nanoparticles on the specific heat capacity value of nanofluids were analyzed. The results show that specific heat capacity increases when adding 10 nm silica nanoparticles up to 1.0 wt%, and then it decreases at higher concentrations. At this optimal mass concentration, the 20 nm nanoparticles displayed a maximum enhancement in the average specific heat capacity (by ~26.7%). The simulation results provided information about the different energy components in the system. The rate of potential energy change versus nanoparticle mass concentration was found to be maximized at 1.0 wt% concentration, which agrees with the experimental measurements. The potential energy components in the simulation system indicate that the change of Coulombic energy contributes the most to the variation of specific heat capacity.
关键词： Molten salt based nanofluids,Molecular dynamics simulation,Solar energy storage,Specific heat capacity
更新于2025-09-23 15:19:57
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Enhanced photocatalytic activity of potassium-doped titania photocatalyst films with nanosheet structure
摘要： Potassium-doped titania (K-doped TiO2) films had been prepared by molten-salt treatment in KNO3 for Ti-TiC coatings, containing different amount of TiC, in order to achieve enhanced activity of the films. When the amount of TiC is lower than 40%, the partial surface morphology of K-doped TiO2 films clearly shows a nanosheet structure, and the formed nanosheets could increase the accessible surface area. The results show that K-doped TiO2 with composite crystals has formed with different amount of TiC, and the relative Raman peak intensity of Ti-O-K bonding is highest for 40% TiC. Even avoiding high adsorption of K-doped TiO2 films, the films exhibit excellent and stable photocatalytic activity. With increasing the amount of TiC, the photocatalytic activity of K-doped TiO2 films first increases then decreases, reaching the highest for 40% TiC.
关键词： nanosheet,K-doped TiO2,photocatalytic activity,photocatalyst films,molten salt of KNO3
更新于2025-09-19 17:15:36
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Techno-economic optimization of molten salt solar tower plants
摘要： In this paper the results of a techno-economic analysis of improved and optimized molten salt solar tower plants (MSSTP plants) are presented. The potential improvements that were analyzed include different receiver designs, different designs of the HTF-system and plant control, increased molten salt temperatures (up to 640°C) and multi-tower systems. Detailed technological and economic models of the solar field, solar receiver and high temperature fluid system (HTF-system) were developed and used to find potential improvements compared to a reference plant based on Solar Two technology and up-to-date cost estimations. The annual yield model calculates the annual outputs and the LCOE of all variants. An improved external tubular receiver and improved HTF-system achieves a significant decrease of LCOE compared to the reference. This is caused by lower receiver cost as well as improvements of the HTF-system and plant operation strategy, significantly reducing the plant own consumption. A novel star receiver shows potential for further cost decrease. The cavity receiver concepts result in higher LCOE due to their high investment cost, despite achieving higher efficiencies. Increased molten salt temperatures seem possible with an adapted, closed loop HTF-system and achieve comparable results to the original improved system (with 565°C) under the given boundary conditions. In this analysis all multi tower systems show lower economic viability compared to single tower systems, caused by high additional cost for piping connections and higher cost of the receivers.
关键词： receiver designs,HTF-system,molten salt solar tower plants,plant control,techno-economic analysis,increased molten salt temperatures,multi-tower systems
更新于2025-09-16 10:30:52
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Electrodeposition of crystalline silicon films from silicon dioxide for low-cost photovoltaic applications
摘要： Crystalline-silicon solar cells have dominated the photovoltaics market for the past several decades. One of the long standing challenges is the large contribution of silicon wafer cost to the overall module cost. Here, we demonstrate a simple process for making high-purity solar-grade silicon films directly from silicon dioxide via a one-step electrodeposition process in molten salt for possible photovoltaic applications. High-purity silicon films can be deposited with tunable film thickness and doping type by varying the electrodeposition conditions. These electrodeposited silicon films show about 40 to 50% of photocurrent density of a commercial silicon wafer by photoelectrochemical measurements and the highest power conversion efficiency is 3.1% as a solar cell. Compared to the conventional manufacturing process for solar grade silicon wafer production, this approach greatly reduces the capital cost and energy consumption, providing a promising strategy for low-cost silicon solar cells production.
关键词： crystalline-silicon solar cells,molten salt,silicon dioxide,photovoltaic applications,electrodeposition
更新于2025-09-12 10:27:22
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Antibacterial and photocatalytic activity of anatase phase Ag-doped TiO2 nanoparticles
摘要： A simple and new solid-state molten-salt method to synthesise silver (Ag)-doped titanium dioxide (TiO2) nanoparticles for solar light-induced photocatalytic applications is examined. Ag-doped TiO2 nanoparticles with varied Ag content ranging from 3 to 10% were synthesised by a single-step molten-salt synthesis method. The effect of Ag content on the antibacterial and photocatalytic activity of nanoparticles was tested. The prepared nanoparticles were studied by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectrometry, ultraviolet–visible (UV–vis) diffusive re?ectance spectrometer (UV–vis DRS) and powder X-ray diffraction. The SEM image of nanoparticles clearly showed the presence of agglomerated spherical particles. The EDX analysis of the particles con?rmed successful doping of particles in the presence of the Ag in the particles. The doping of Ag in TiO2 produced TiO2 pure anatase phase. According to UV–vis DRS results, increasing Ag-doped content in the Ag-doped TiO2 resulted in a higher visible absorption capability of the materials. Ag doping also improved the antibacterial and photocatalytic activity of TiO2 nanoparticles. The maximum photocatalytic activity under light irradiation was observed for 5% Ag-doped TiO2.
关键词： antibacterial activity,anatase phase,photocatalytic activity,molten-salt method,Ag-doped TiO2
更新于2025-09-09 09:28:46
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Recent advances in the chemical strengthening of glass
摘要： Since its development in the early 1960s till recently, applications of the glass chemical strengthening technology were limited mostly to aircraft cockpit windshields, photocopier transparencies, and hard disks. The interest has been renewed by a need to have stronger and lighter glass products, led mostly by display cover in personal mobile electronic devices, such as cell phones, and glass packaging for safe delivery of medicines in pharmaceutical applications. In this paper, I suggest that the science of the compressive stress development is nearly completely understood. The so-called “dilation anomaly” is resolved. Newer technologies are being developed, for example, thin float-produced flat glasses can be strengthened with reduced warp. Molten salt bath maintenance techniques to avoid discarding of degraded salt have been developed to some extent. In addition to more and more pharmaceutical businesses looking to strengthen the glass packaging to avoid costly recalls, interest is also high in break-resistant automobile and locomotive transparencies. Other miscellaneous topics where the use of chemically strengthened glass could bring value-added premium are also mentioned.
关键词： molten salt bath,pharmaceutical packaging,chemical strengthening,compressive stress,glass,automobile transparencies,dilation anomaly
更新于2025-09-09 09:28:46