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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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Using near infrared measurements to evaluate NaCl and KCl in water
摘要： Spectral differences between aqueous solutions of NaCl and KCl have received minimal attention in previous research due to strong similarities between the two salts and the lack of motivation to differentiate between them. Correlations between salinity and absorbance have been developed previously with varying degrees of linearity but have not been tested to saturation. This work will demonstrate that correlating spectral measurements and the concentration of NaCl and KCl in water can be extended up to the saturation point of both salts and that solutions of these salts with unknown concentrations can be distinguished. Spectral data for samples of NaCl and KCl in single-salt solutions were collected up to saturation and correlations were developed for differentiating between solutions of the two species. These correlations were able to correctly identify the solution type for all solutions in the test set and estimate their concentrations with an average error of 0.9%.
关键词： spectroscopy,salinity,KCl,NaCl,water,absorbance
更新于2025-09-23 15:22:29
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Detecting Laser-Volatilized Salts with a Miniature 100-GHz Spectrometer
摘要： Rotational transitions are unique identi?ers of molecular species, including isotopologues. This article describes the rotational detections of two laser-volatilized salts, NaCl and KCl, made with a miniature Fourier transform millimeter-wave (FTmmW) cavity spectrometer that could one day be used to measure solid composition in the ?eld or in space. The two salts are relevant targets for icy moons in the outer solar system, and in principle, other molecular solids could be analyzed with the FTmmW instrument. By coupling the spectrometer to a collisionally cooling laser ablation source, (a) we demonstrate that the FTmmW instrument is sensitive enough to detect ablation products, and (b) we use the small size of the FTmmW cavity to measure ablation product signal along the carrier gas beam. We ?nd that for 532 nm nanosecond pulses, ablated molecules are widely dispersed in the carrier-gas jet. In addition to the miniature spectrometer results, we present several complementary measurements intended to characterize the laser ablation process. For pulse energies between 10 and 30 mJ, the ablation product yield increases linearly, reaching approximately 1012 salt molecules per 30 mJ pulse. Using mass spectrometry, we observe Li+, Na+, and K+ in the plumes of ablated NaCl, KCl, and LiCl, which implies dissociation of the volatilized material. We do not observe salt ions (e.g., NaCl+). However, with 800 nm femtosecond laser pulses, the triatomic ion clusters Li2Cl+, Na2Cl+, and K2Cl+ are produced. Finally, we observe incomplete volatilization with the nanosecond pulses: some of the ejecta are liquid droplets. The insights about ablation plume physics gleaned from these experiments should guide future implementations of the laser-volatilization technique.
关键词： KCl,Fourier transform millimeter-wave,FTmmW,rotational transitions,NaCl,mass spectrometry,outer solar system,icy moons,laser-volatilized salts,laser ablation
更新于2025-09-23 15:19:57
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2D alloying molybdenum tin-disulfide monolayers with fast photoresponse
摘要： Elemental alloying in monolayer, two-dimensional (2D) transition metal dichalcogenides (TMDs) promises unprecedented ability to modulate their electronic structure leading to the unique optoelectronic properties. MoS2 monolayer based photodetectors typically exhibit a high photoresponsivity but suffer from a low response time. Here we develop a new approach for Sn alloying in MoS2 monolayers based on the synergy of the customized chemical vapor deposition (CVD) and the effects of common salt (NaCl) to produce high-quality and large-size Mo1-xSnxS2 (x<0.5) alloy monolayers. The composition difference results in different growth behaviors; Mo dominated alloys (x<0.5) exhibit uniform and large size (up to 100 μm) triangular monolayers, while Sn dominated alloys (x>0.5) present multilayer grains. The Mo1-xSnxS2 (x<0.5) based photodetectors and phototransistors exhibit a maximum responsitivity of 12 mA/W and a minimum response time of 20 ms, which is faster than most reported MoS2 based photodetectors. This work offers new perspectives for precision 2D alloy engineering to improve the optoelectronic performance of TMD-based photodetectors.
关键词： photodetector,Mo1-xSnxS2 monolayer,chemical vapor depostion,NaCl,response time
更新于2025-09-16 10:30:52
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Controllable Synthesis of Crystalline ReS <sub/>2(1?</sub><i> <sub/>x</sub></i> <sub/>)</sub> Se <sub/>2</sub><i> <sub/>x</sub></i> Monolayers on Amorphous SiO <sub/>2</sub> /Si Substrates with Fast Photoresponse
摘要： Re-based transition metal dichalcogenides (TMDs) and alloys have many unusual features such as in-plane anisotropic optical, electrical, and phonon properties and thus receive increasing research interest. However, the distorted 1T structure and the weaker interlayer coupling easily cause anisotropic growth and out-of-plane growth, making it particularly challenging to produce Re-based TMD and alloy monolayers on amorphous SiO2/Si substrates. Here, a reliable method is developed for the synthesis of high-quality and large-size ReS2(1?x)Se2x monolayer crystals on SiO2/Si substrates by NaCl-assisted, confined-space chemical vapor deposition. The synergy of salt assistance with the confined reaction space facilitates the formation of intermediate metal oxychlorides and creates a relatively stable growth environment, finally leading to the successful synthesis of ReS2(1?x)Se2x monolayer crystals on SiO2/Si substrates. The as-grown ReS2(1?x)Se2x monolayer alloys exhibit continuously variable composition, high crystal quality, and uniform distribution of Re, S, and Se elements. Furthermore, the ReS2(1?x)Se2x based photodetectors display good photoresponse to visible and near-infrared light with a fast response of less than 15 ms. The salt-assisted, confined-space chemical vapor deposition provides a reliable way for the synthesis of large-scale low-lattice symmetry 2D materials on amorphous SiO2/Si substrates and opens up new prospects for Re-based TMDs and alloys in optoelectronic devices.
关键词： ReS2(1?x)Se2x monolayers,NaCl,chemical vapor deposition,confined-space,photoresponse
更新于2025-09-12 10:27:22
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The Sommerfeld ground-wave limit for a molecule adsorbed at a surface
摘要： Using a mid-infrared emission spectrometer based on a superconducting nanowire single-photon detector (SNSPD), we observe the dynamics of vibrational energy pooling of CO adsorbed at the surface of a NaCl crystal. After exciting a majority of the CO molecules to their first vibrationally excited state (v = 1), we observe infrared emission from states up to v = 27. Kinetic Monte Carlo simulations show that vibrational energy collects in a few CO molecules at the expense of those up to eight lattice sites away by selective excitation of NaCl’s transverse phonons. The vibrating CO molecules behave like classical oscillating dipoles, losing their energy to NaCl lattice-vibrations via the electromagnetic near-field. This is analogous to Sommerfeld’s description of the Earth’s influence on radio transmission by ground waves.
关键词： vibrational energy pooling,NaCl crystal,superconducting nanowire single-photon detector,electromagnetic near-field,Kinetic Monte Carlo simulations,Sommerfeld ground-wave limit,CO adsorbed
更新于2025-09-04 15:30:14