Effect Of Molten Salt Research Articles

Effect of molten salt on re-pyrolysis behaviors of heavy bio-oil

The effects of KCl-ZnCl2 molten salt on the pyrolysis characteristics and pyrolysis products of heavy bio-oil at 400, 500 and 600 °C were studied. The results showed that molten salt increased the solid yield of heavy bio-oil pyrolysis and decreased the gas yield. Some compounds such as phenol, cresol, ethylphenol and 4-propylphenol had good enrichment effect, especially the relative concentration of cresol increased from 8.82% to 20.85% at 400 °C, while the relative concentration of phenol increased from 2.18% to 8.62% at 600 °C. During formation of char, molten salt reduced the content of carbon and increased the content of oxygen, increased the BET surface area and total pore volume of pores. Molten salt promoted formation of pore structure of the solid product and increased its average pore diameter.

The effect of molten salt on the mechanical properties and microstructure of CuNiSi alloys with reinforced Fe

In this study, CuNiSi alloys were produced using powder metallurgy in molten salt (KBr). In the Cu, Ni, and Si powder mixture, Fe was added at a rate of 2.5%, 5 and 7.5% and mechanical alloying was carried out for 4 hours at 400 rpm. Prepared powder mixtures were cold pressed under 600 MPa pressure and sintered for 3 hours at 900 ? in an argon atmosphere. Phase formation, microstructure, microhardness, electrical conductivity, and corrosion of the produced samples were analyzed in detail. Scanning electron microscope (SEM) was used to detect the changes in the microstructure of the produced samples, and an X-ray diffractogram (XRD) was used to determine the phases formed in the internal structure of the materials. In order to determine the mechanical properties of the produced samples, hardness analyzes were made with a microhardness measuring device. The electrical conductivity properties of the produced CuNiSi and CuNiSiFe alloys were determined due to the increase in the Fe ratio. Corrosion tests of the produced samples were determined by potentiodynamic polarization curves in a 3.5% NaCl solution. Fe-reinforced CuNiSi composite materials have been successfully produced in molten salt (KBr). CuNiSi alloy, the microstructure is dominated by the typical large and small particles. Fe element is homogeneously dispersed in the CuNiSi alloy instead of being separated using the Ni element. Fe particles have decreased the hardness of produced alloys. The electrical conductivity properties changed with increasing voltages depending on the increase of Fe supplementation, and as a result, the sample containing 7.5% Fe had the best electrical conductivity values. Results showed that by increasing the amount of Fe, the mechanical properties and corrosion resistance increased.

Impact of the additive manufacturing process on the high-temperature corrosion of 316L steel in the presence of NaCl–KCl–ZnCl2 molten solar salt

A comparative study of the high-temperature oxidation and corrosion resistance of wrought and additive manufacturing selective laser melting (SLM) 316L stainless steel was performed in presence of molten NaCl–KCl–ZnCl2 salt used for thermal energy storage in the new generation of concentrated solar plants. Isothermal tests at 650 and 700 °C in a dry air atmosphere were conducted to evaluate (i) the effect of the manufacturing process and (ii) the effect of molten salts on the corrosion behavior of the steel by dimensional metrology analysis, scanning electron microscopy and X-ray diffraction characterization. The manufacturing process had a significant influence on the oxidation resistance. The wrought samples had a mass gain after 48 h that was four times greater than that of SLM samples at 650 °C, and 50% greater at 700 °C. The presence of the salt primarily increased the corrosion rate of all the samples and, again, the wrought pieces suffered 13% and 6% more corrosion in terms of metal loss than the SLM ones at 650 and 700 °C, respectively. The presence of more pathways for Cr diffusion associated with a higher number of defects in the microstructure of the SLM sample, as dislocations and grain boundaries, facilitated the formation of Cr2O3 scales in the SLM sample, avoiding the intergranular attack shown in the wrought one.

Effect of molten salts on the structure, morphology and electrical conductivity of PET-derived carbon nanostructures

The effective disposal and/or utilization of polyethylene terephthalate ((C10H8O4)n, PET) waste plastics are currently global problems that need to be addressed urgently. The current research examines the molten salt-based thermal treatment of PET waste, as a new approach to tackle this challenge. The effect of various molten salts, comprising KCl, MgCl2, ZnCl2, NaCl, KF and NaF on the structural and morphological evolution of PET upon heating in air to 1300 °C is investigated. PET is transformed into carbon materials with different characteristics, including graphene-like nanosheets and porous nanostructures, with different electrical conductivity values, depending on the type of salt employed. The melting and evaporation points, as well as the cation size of the salt, are found to have a significant influence on the morphology and the crystallization level of the carbon products, based on which the characteristics of PET-derived carbons are regulated. Accordingly, the crystallinity and graphitization degree of the carbon materials obtained in NaF, KF and NaCl are found to be considerably greater than those obtained in ZnCl2, MgCl2 and KCl. The possible mechanism involved in the conversion of PET into carbon nanostructures in the molten salt environment is discussed. The results obtained provide insights into molten salt conversion of PET into carbon materials with different properties for various applications.

Numerical study of the dynamic characteristics of a single-layer graphite core in a thorium molten salt reactor

A reactor core in a thorium molten salt reactor uses graphite as a moderator and reflector. The graphite core is a multi-layered arrangement of graphite bricks that are loosely connected to each other using a system of keys and dowels. Consequently, the graphite core is a type of discrete stack structure with highly nonlinear dynamic behavior. Hence, it is important to investigate the dynamic characteristics of the graphite core. In this study, a three-dimensional single-layer graphite core model, which is a part of the thorium molten salt reactor side reflector structure, was analyzed using the explicit method in ABAQUS 2016 to study the core dynamic behavior when subjected to different excitations. The design parameters, such as the diameter of the dowel, the gap between key and keyway and the bypass flow gap between two adjacent bricks, were also considered in this model. To reduce excessive demands on available computational resources considering the effect of molten salt, the spring–dashpot model was applied to model the interaction forces between the molten salt and graphite bricks. Numerical simulation results show that the effect of molten salt is a reduction in the peak maximal principal stress, and a larger gap between two bricks is beneficial to maintain the integrity of the graphite core under earthquake loading. The results obtained by the simulation can be used as a reference for future designs of a molten salt graphite core.

Effect of Molten Salts on Synthesis and Upconversion Luminescence of Ytterbium and Thulium-Doped Alkaline Yttrium Fluorides

Upconversion luminescence materials have recently received attentions because of theirs light conversion ability from infrared into visible and ultraviolet light. In this work, alkaline yttrium fluoride doped by ytterbium and thulium (AYF4: 20%Yb3+, 0.5%Tm3+) were synthesized by molten salt method at 400 °C for 2 hours with different eutectic molten salts, i.e. NaNO3-KNO3, NaNO3-LiNO3, KNO3-LiNO3, and NaNO3-KNO3-LiNO3. Pure hexagonal NaYF4 microrods were successfully synthesized using eutectic NaNO3-KNO3 molten salt. Under 980 nm laser diode excitation, upconversion luminescence in both visible and ultraviolet region was clearly observed. On the other hand, for the use of other eutectic molten salts containing LiNO3, the mixed phases of tetragonal LiYF4 and orthorhombic Y6O5F8 were obtained. These powders emitted only visible light with 10 times lower intensity than the hexagonal NaYF4 microrods synthesized using NaNO3-KNO3.

Hot corrosion behavior of YSZ, Gd2Zr2O7 and YSZ/Gd2Zr2O7 thermal barrier coatings exposed to molten sulfate and vanadate salt

Thermal barrier coatings (TBCs) are mostly used in critical components of aircraft gas turbine engines. Hot corrosion is among the main deteriorating factors in TBCs which results from the effect of molten salt on the coating–gas interface. This type of corrosion is observed as a result of contamination accumulated during combustion processes. Fuels used in aviation industry generally contain impurities such as vanadium oxide (V2O5) and sodium sulfate (Na2SO4). These impurities damage turbines’ inlet at elevated temperatures because of chemical reaction. Yttria stabilized zirconia (YSZ) is a conventional top coating material for TBCs while Gd2Zr2O7 is a new promising top coating material for TBCs. In this study, CoNiCrAlY metallic bond coat was deposited on Inconel 718 nickel based superalloy substrate material with a thickness about 100μm using cold gas dynamic spray (CGDS) method. Production of TBCs were done with deposition of YSZ, Gd2Zr2O7, YSZ/Gd2Zr2O7 ceramic top coating materials using EB-PVD method, having a total thickness of 300μm. Hot corrosion behavior of YSZ, Gd2Zr2O7, YSZ/Gd2Zr2O7 TBC systems were exposed to 45wt.% Na2SO4 and 55wt.% V2O5 molten salt mixtures at 1000°C temperature. TBC samples were investigated and compared using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis and X-ray diffractometer (XRD). The hot corrosion failure mechanisms of YSZ, Gd2Zr2O7 and YSZ/Gd2Zr2O7 TBCs in the molten salts were evaluated.

Effect of Molten NaCl on the Synthesis of Ti<sub>3</sub>SiC<sub>2</sub> Powders

Free Ti/Si/C powder mixtures with or without molten salt were heated under vacuum with various schedules. The effect of molten salt during synthesis on the morphology and phase composition of Ti3SiC2 powders were investigated. The combustion powders were analyzed by DSC, XRD, SEM and EDS. The results indicated that the existence of molten salt could promote the reaction process and decrease the synthesis temperature. The Ti3SiC2 powders obtained by molten salt method were uniform and well dispersive. The content of Ti3SiC2 phase was influenced by salt/powders ratio and molding pressure. The appropriate salt/powders ratio and pre-press pressure were 1:1and 100 MPa, respectively.

The effect of molten salt on oxygen removal from titanium and its alloys using calcium

The sensitivity of titanium to increasing oxygen content and the high cost of reducing oxygen content in titanium have prevented its broader applications. Here we report a low-temperature de-oxygenation process, which can remove oxygen from titanium powders to less than 1000 ppm from original oxygen levels of over 20,000 ppm. The effect of molten salt on de-oxygenation was investigated in this study. The calcium halide-bearing molten salt facilitates the dissolution of solid calcium and creates a metal-molten solution condition by forming intermediate Ca+ ions and finally Ca2+ ions and electrons (e (-)). The molten salt enables the de-oxygenation of Ti at temperatures lower than the melting point of calcium. It will be shown that the de-oxygenation temperature can be as low as 873 K (600 A degrees C).

Molten salt synthesis and growth mechanism of WC platelet powders

Plate-like tungsten carbide powders have been prepared from oxides by molten salt synthesis at temperatures higher than 1200°C for 2h. The phase evolution of the reaction products and the growth mechanism of WC platelets are investigated. It was found that the phase evolution, with the presence of sodium chloride as a solvent, was quite different from the traditional carbothermal reduction process. Sodium tungsten bronzes, MχWO3, were generated as intermediate phases with a variable value of χ. The formation of platelets with a high aspect ratio has been discussed based on the effect of molten salt. Besides, the size distribution of the as-prepared powder showed a bimodal pattern, which is explained with the 2-Dimension nucleation of angular grains.

Hot corrosion behavior and mechanical properties degradation of a Ni–Cr–W-based superalloy

The effect of molten salts on the mechanical properties of a Ni–20Cr–18W (wt%)-based superalloy was investigated in this work. The hot corrosion characteristics and the microstructural evolution during the hot corrosion process were analyzed. The corrosion scale forms on the surface of the substrate, and its thickness increases gradually during the process. The element of S invades the substrate. The corrosion products mainly include NiO, Ni3S2 and Cr2O3. The hot corrosion in molten salt makes the specimens rough and flawed. The serration grain boundaries are observed in the hot corroded specimens. The tensile strength and elongation of the original alloy are ~1023 MPa and ~15 %, respectively. After corroded for 5 h, the tensile strength and elongation of the specimen decrease to ~771 MPa and ~7 % and diminish to ~814 MPa and ~9 % for the specimen corroded for 10 h. The hot corrosion process deteriorates the mechanical properties of the alloys. And the tensile strength and elongation of the specimen corroded for 20 h sharply decrease to ~539 MPa and ~3 %, respectively. The nonmonotonic variation of the mechanical properties of the specimen occurs for the specimens corroded for 10 h, which is related to the competition between the depredation of the molten salts and the strengthening process by carbides and the serrated grain boundaries. The corrosion characteristics and microstructural evolution of a Ni–20Cr–18W-based superalloy were investigated during the hot corrosion process. It is found that the attack of molten salts makes the tensile strength of the specimens deteriorate significantly. The nonmonotonic variation of mechanical properties is related to the competition between the destruction of molten salts and the strengthening process during the hot corrosion process.

Novel approach to Zr powder production by smooth ZrCl4 bubbling through molten salt

A reduction process using ZrCl4 bubbles as a reactant was investigated to produce zirconium metals. ZrCl4 vapor was bubbled through the lance in the bath, in which Mg melt and MgCl2 salt were separated. Zr powder was formed by a reduction of ZrCl4 bubbles in magnesium layer. However, the lance was clogged by the aggregate of zirconium occurred during ZrCl4 vapor injecting leading to interruption of ZrCl4 supply into the bath. This phenomenon could be caused by the presence of magnesium at the lance tip, which passes through MgCl2 salt during bubbling, and then zirconium was formed in the forms of intermetallic compounds with aluminum. In this study, the effect of molten salt on the troubled phenomena was investigated and it was verified that CaCl2 with relatively low Weber number meaning relatively high surface tension as molten salt is effective in inhibiting the lance clogging phenomena. Then, a few micrometer-sized Zr powder with the high purity of 91.6 wt% was obtained smoothly without the formation of intermetallic compound.

Facile fabrication of perovskite single-crystalline LaMnO 3 nanocubes via a salt-assisted solution combustion process

The perovskite single-crystalline LaMnO 3 nanocubes have been fabricated through a facile salt-assisted solution combustion process, using ethylene glycol as a fuel and corresponding nitrates as oxidants. The effects of the fuel-to-oxidant molar ratio and the fraction of added NaCl on the phase and microstructure of the products were investigated by X-ray diffraction, transmission electron microscopy and selected area electron diffraction. The possible mechanism about the effect of molten salt on morphological evolution of the as-prepared LaMnO 3 particles in salt-assisted solution combustion synthesis was also discussed.

Influence of Molten Salt on Luminescent Intensity and Particle Size of Y 2 O 3 :Eu 3+ Phosphor

The Y-Eu oxalate precursor was prepared with a homogeneous precipitation method. And the additives, Na 2CO 3, S, NaCl or their combination, were introduced into the precursor to prepare Y 2O 3:Eu 3+ red phosphors at 1000 ~ 1300 °C for 2 h. The effect of molten salts on particle size and luminescent intensity was studied. The experimental results showed that the complex molten salt (Na 2CO 3 + S + NaCl) was conductive to enhance the luminescent intensity of Y 2O 3:Eu 3+. The emission intensity of the phosphor prepared with these additives at 1300 °C was about 45% higher than that of the one prepared without molten salt, and about 11% higher than that of the corresponding commercial phosphor. Meanwhile, the particle size of Y 2O 3:Eu 3+ phosphor was controlled effectively with the molten salt.