KCl Crystals Research Articles

Production of Potassium Chloride from K-Feldspar Through Roast–Leach–Solvent Extraction Route

This work focuses on extraction of potassium from feldspar through pyro-hydrometallurgical route. Calcium chloride was used as roasting agent for feldspar. Effect of various operating variables, viz. time, roasting temperature and CaCl2 dose on extent of roasting, were thoroughly studied. Roasting 10 g of feldspar with 17 g of CaCl2 at 900 °C for 1 h resulted in 99.9% conversion of K2O to KCl. Order of feldspar roasting was found to be around 2, and activation energy requirement was 136.6 kJ/mol. Calcium and sodium were leached along with potassium from chloride-roasted K-Feldspar with water at room temperature. To generate a pure solution of potassium from the leach liquor containing K, Ca and Na, it was selectively extracted from leach liquor by using dibenzo-18-crown-6 ether as extractant and m-cresol as diluent. Loading of potassium was carried out at an A/O ratio of 2:1, while stripping was carried out in water at O/A ratio of 2:1. 99.5% pure crystals of KCl were obtained on evaporation of the strip solution. A schematic flowsheet has been provided for the preparation of pure KCl from feldspar.

Optical and luminescence studies on Tm3+-doped KCl single crystals

Thulium-doped KCl crystals have been successfully grown using Bridgman–Stockbarger technique. The crystals were characterized by optical absorption, photoluminescence (PL), thermoluminescence glow, TL emission, powder X-ray diffraction, scanning electron microscopy (SEM), laser Raman spectroscopy and electron paramagnetic resonance spectroscopy (EPR). PL spectra exhibit broadband blue emission at 468 nm for the application of light-emitting diodes. The trap parameters of the TL glow curve are calculated using Chen’s peak shape method. XRD analysis carried out on the grown crystals and lattice parameters predicted that it crystallized in cubic structure. SEM studies revealed the presence of microcrystalline structure. EPR measurements were made at X-band frequencies with 9–10 GHz field modulation at room temperature, and the g-factor value of 2.4 was calculated by using Lande formula.

Luminescence characteristics of silver and rare earth co-doped KCl single crystals grown from melt using Czochralski technique

Single crystals of KCl:Ag, KCl:Ag,Eu and KCl:Ag,Ce were grown from melt using Czochralski technique and investigated for thermally (TSL) and optically stimulated luminescence characteristics (OSL) with main focus on dosimetric applications. The XRD of crystals showed good crystalline nature with a face centered cubic KCl structure. SEM and EDAX analysis confirmed the distribution of dopants in the host lattice. Thermo luminescence (TL) emission of KCl:Ag after irradiating with 60Co gamma rays showed two TL glow peaks around 100 °C and 150 °C. An enhanced TL intensity of 3.5 times and OSL intensity of 1.5 times were observed by co-doping KCl:Ag with Ce. The result is further confirmed by taking photoluminescence and TL emission spectra of the samples. This increased TL and OSL response for KCl:Ag,Ce crystal is attributed to the formation of Vk centers formed due to the doping of Ag in KCl and the F center formed by Ce2+ on irradiation. Dose response of KCl:Ag,Ce showed linearity up to 6 Gy indicating its use in the personal dosimetry applications.

Optical activity induced by rare-earth ions in As2S3 glasses and KCl crystals

Optical transmission spectra of As2S3 glass-like plates and nanolayers, undoped and doped with Sm and Pr ions have been investigated. The spectral dependences of the refractive index and glass transmission spectra, registered in the configuration of crossed polarizers, were studied. The concentration of rare-earth ions in the matrix influences on the magnitude of refractive indices (n−, n+) of polarized light. The emission spectra of As2S3 glasses, doped with rare-earth ions (Sm and Pr) and KCl crystals doped by Sm ions have been investigated for different temperatures in the range 300–10 K. A broad luminescence band associated with recombination transitions of charge carriers from 5D0 levels to 7F0-6 levels or from 4G5/2 levels to 6H5/2…15/2 levels of samarium ions (Sm2+ and Sm3+, respectively) was registered. A number of narrow absorption bands were registered on this broad photoluminescence band, which can be attributed to self-absorption process, determined by electronic transitions between the levels (7F0-6 ⟶ 5D0 or 6H5/2…15/2 ⟶ 4G5/2) of samarium ions.

Step by step resolving the formation of dendritic crystal in solution: an observation against the classical model of one-by-one addition

During crystallization, one-by-one addition of atomic species or nucleation-generated nanoparticles is widely considered to be the fundamental mode to construct advanced morphologies. However, due to a lack of approaches with high resolution and real-time tracing ability, the correctness of this conventional concept has never been verified in a complicated crystallization process, even including the simplest species--the formation of dendritic crystals. In this work, we successfully resolved the growth mechanism of dendritic KCl crystals in a thin water film by terminating the continuous crystallization at different stages. The results were quite against the conventional concept. For example, one-by-one aggregation of individual ions was unable to directly form a dendritic morphology, and nucleation-generated nanoparticles had been prearranged into dendritic configuration before they could attach one another. In summary, the crystallization was precisely self-controlled to follow several specific steps rather than the simple addition of building blocks.

Strategies To Control Product Characteristics in Simultaneous Crystallization of NaCl and KCl from Aqueous Solution: Seeding with KCl

To meet contemporary industry needs, saline wastewater treatment with zero liquid discharge goals is gaining increasing attention. In this context, evaporative crystallization has been applied to s...

Growth and Optical Characterization of Europium and Cerium Doped KCl Single Crystals by Czochralski Method for Dosimetric Applications

Rare-earth-doped alkali halide single crystals KCl:Eu, KCl:Ce, and KCl:Eu,Ce were grown from melt using the Czochralski technique, and optical characterization was carried out with the prime focus on dosimetric applications. The grown crystals were investigated using XRD analysis, PL analysis, TSL measurements, and OSL measurements. The XRD of the crystals matched well with ICDD patterns (00-041-1476), and diffraction peaks can be assigned to the KCl structure, indicating that all the crystals have the same structure as KCl. The enhanced intensity of TSL and OSL was observed for co-doping of (Eu, Ce) in KCl crystals as compared to single doping. The appearance of a single glow peak in KCl:Eu,Ce at 230°C compared to single-doped KCl:Ce crystals suggested the use of the material in TL dosimetry. The intensity of OSL also showed a two-fold increase compared to single-doped crystals, suggesting its use in OSL dosimetry. PL studies showed a very high enhancement of intensity in Eu2+ emissions, reaching a maximum of about 421 nm in the (Eu2+, Ce3+) co-doped crystal compared to single-doped crystals. This justifies the occurrence of energy transfer from Ce3+ to Eu2+ in the KCl host lattice. These results showed that KCl:Eu,Ce acts as a potential TL and OSL dosimeter due to its high sensitivity to ionizing radiation.

Формирование наночастиц натрия и калия при локальном электронном облучении щелочно-галоидных кристаллов

It is shown experimentally that during local electron irradiation of NaCl, KCl and KBr crystals by electrons with energy 50 keV spherical metal nanoparticles of sodium and potassium with plasmon resonances in visible spectral region are formed. Optical density spectra of crystals after electron irradiation are presented. By computer simulation the possibility of solid or liquid state of nanoparticles is studied, as well as interference effects, which appear in the irradiated zone of crystals.

Effect of variation in concentration of water and plant part used on physicochemical properties of Yavakṣāra

Introduction: Kṣāra Kalpanā (Ayurvedic alkali formulation) mainly deals with extraction of alkaline material from herb, animals and minerals. Kṣāra preparation mainly has variation in the concentration of Water used for extraction. Objective: To assess the effect of variation in concentration of water and plant part used on the physicochemical parameters of Yavakṣāra (YK). Materials and Methods: YK was prepared by using whole plant with seeds and without seeds. Further these batches were divided depend upon of 4, 6 and 8 times of concentration of water used for extraction. YK was analyzed by using the XRD, AAS-ICP and FTIR. Results: All samples contain Halite crystals of NaCl and Sylvine crystals of KCl. Halite and Sylvine crystals generally formed due to evaporation which is main step in the preparation of Kṣāra Kalpanā. Crystal size of NaCl and KCl is near to nanoparticles (in the range between 90 to 135 nm). YK contains other elements like Fe, Mg and Ca in small amount with slight variance in quantity in different batches. FTIR shows presence of same functional group (C-H of (Alkyl) amines) in all samples of YK. Absences (Pb, As) or traces (Hg) of heavy metal indicate care taken during harvesting and manufacturing. Conclusion: Slight variation is seen in the elements, their concentration and functional group in different batches of YK. Variation in the concentration of water alters the frequency of filtration and affect the period of sedimentation. A batch prepared with less concentration of water (4 times) and without seeds seems to be cost effective.

Growth of pure and BFO doped KCl crystals by Czochralski technique and fabrication of microstrip patch antenna for GHz applications

Large sized pure and 0.1 mol% BiFeO3 (BFO) doped KCl single crystals were grown by Czochralski technique. Structural parameters were confirmed by powder XRD and single crystal XRD. EDX analysis was used to determine the elemental composition of BFO and KCl crystal. Photoluminescence confirmed that BFO acts as defect quenching agent for KCl single crystal which improved its optical transparency. Doping of BFO in KCl single crystal increased its hardness as measured by a Vicker’s microhardness test. The effect of BFO on dielectric constant and dielectric loss of KCl crystal, at various temperature and frequencies was studied. The low dielectric constant viz. 4.5 and 5.8 for pure and BFO doped KCl was helpful in designing and fabricating patch antenna in GHz frequency. As a result of BFO doping, the resonant frequency of microstrip patch antenna can be tuned at 5.40 GHz from 6.01 GHz for the KCl single crystal.

Features of the action of an uniaxial deformation on the radiative annihilation of excitons in KBr crystal

To study the effect of uniaxial deformation by 〈100〉 and 〈110〉 directions on the radiative annihilation of self-trapped excitons (STE), the experiments were carried out with KI, KCl and KBr crystals. At deformation by 〈110〉 direction, the band with a maximum at 2.95 eV with a large relative Stokes shift (SR = 0.56) in KBr crystal, characteristic for STE with a strongly asymmetric configuration, was detected. In crystals KI and KCl at deformation by 〈110〉 direction and in KBr crystal by 〈100〉 direction, no additional bands were detected besides to intrinsic σ-, π-luminescence. The appearance of an exciton with a strongly asymmetric configuration in KBr crystal is explained on the basis of the ratio of the radii of the anion and the cation, and also on the basis of the energy of excitons with different configurations on the surface of the adiabatic potential for the KI, KBr, and KCl crystals. For KBr crystal the ratio is 1.9, which is greater than in KI. The energy of the configuration transformations in KBr crystal is the smallest.

X-ray-induced colouring kinetics of (Ba2+, Eu2+)-doubly doped KCl single crystals: influence of the different aggregation–precipitation states of the doping ions

ABSTRACTThe effects of different aggregation–precipitation states of the doping Ba2+-ion on the X-ray-induced generation of F-centres in KCl:Ba2+(675 ppm):Eu2+(27 ppm) single crystals was investigated by optical absorption spectrophotometry. Such states were induced to occur in a controlled manner by subjecting the crystals to suitable thermal treatments. During these treatments, the aggregation–precipitation kinetics of the doping Ba2+-ions was monitored, by optical fluorescence spectrophotometry, utilising the doping Eu2+-ion as an optical probe. As dissolved into the host matrix as forming part of impurity–vacancy (I–V) dipole complexes and small aggregates, divalent barium increases the initial F-colouring rate and F-centre solubility limit by impressive factors of 2 ± 1 and 3 ± 1, respectively, in relation to those of a non-doped crystal. As a constituent of incipient metastable BaCl2-type second-phase precipitates, divalent barium reduces the initial F-colouring rate and F-centre concentration at which the second colouring stage begins by factors of 0.6 ± 0.1 and 0.8 ± 0.1, respectively, in relation to those of the crystal containing barium I–V dipole complexes and small aggregates. As forming part of stable BaCl2 second-phase precipitates and large metastable BaCl2-type second-phase precipitates, divalent barium modifies such a rate and concentration by factors of 1.4 ± 0.1 and 0.7 ± 0.1, respectively, in relation to those of the crystal containing incipient metastable BaCl2-type second-phase precipitates. Also, the doping with divalent barium disrupts the equilibrium between the generation and extinction of F-centres that exists characteristically during the F-curve second colouring stage in a non-doped KCl crystal so that such a rate increases as the aggregation–precipitation phenomena occur within the host matrix. This rate is 0.08 ± (0.08, 0.07), 0.10 ± 0.06 and 0.22 ± (0.05, 0.08) cm–1/h for crystals containing the divalent barium in the form of I–V dipole complexes and small aggregates, incipient precipitates of the metastable BaCl2-type second phase, and large precipitates of both the metastable BaCl2-type second phase and the stable BaCl2 second phase, respectively. The structural mechanisms that are behind the observed effects are discussed.

Optical studies on the conversion from Ag+ to Ag− centers by the electrolytic coloration in NaCl and KCl crystals

We have investigated optical spectra of uncolored and electrolytically-colored NaCl:Ag+ and KCl:Ag+ crystals at low temperatures. In the uncolored crystals, the several absorption bands due to the 4d10 → 4d95s transitions in Ag+ ions are observed in the energy region below the absorption edge of the host crystals. When the uncolored crystals are electrolytically colored, the absorption bands due to the Ag+ centers decrease and the C absorption band due to Ag− centers appears with the compensation for the decrease of the absorption bands due to the Ag+ centers. The fact implies that the conversion from the Ag+ to Ag− centers occurs through the electrolytic coloration. In the crystals with the Ag+ concentration below about 1018 cm−3, the conversion efficiency from the Ag+ to Ag− centers reached more than 60%. The conversion processes from the Ag+ to Ag− centers are discussed.

Simultaneous Crystallization of NaCl and KCl from Aqueous Solution: Elementary Phenomena and Product Characterization

The main elementary processes were identified during simultaneous crystallization of NaCl and KCl from aqueous solutions by the batchwise evaporative method using NaCl seeds. In the early stages of the batch operation, when only NaCl crystallizes, the main elementary processes are molecular crystal growth, agglomeration, and secondary nucleation. When the eutonic condition is exceeded, a KCl primary nucleation event takes place in solution. Subsequently, part of the resulting KCl particles agglomerate with the NaCl particles. Besides, epitaxial growth of KCl upon NaCl crystals takes place. Consequently, the product is comprised of mixed composition polycrystalline particles and single crystals of each salt. The elementary phenomena just described were sensitive to crystallization conditions such as evaporation rate, seed size, and seed content, suggesting the possibility of controlling the morphological features of the particulate product as well as the chemical composition of its size fractions. Such kno...

MoS0.5Se1.5 Embedded in 2D Porous Carbon Sheets Boost Lithium Storage Performance as an Anode Material

AbstractA promising anode material is developed for Li‐ion batteries consisting of MoS0.5Se1.5 particles uniformly embedded in 2D porous carbon sheets (denoted as MoS0.5Se1.5/C sheets). The formation of MoS0.5Se1.5/C sheets depends on a facile and cost‐effective potassium chloride (KCl)‐assisted strategy. The micrometer‐level KCl crystals are selected as the solid template because they are more easily precipitated than metal precursors and carbon source during recrystallization, which drives the simultaneous formation of carbon sheets and MoS0.5Se1.5 particles on KCl surface after pyrolysis; while makes a tighter integration between MoS0.5Se1.5 and carbon sheets. As an anode for Li‐ion batteries, the MoS0.5Se1.5/C sheets show more excellent Li storage properties compared to that of S‐free MoSe2/C sheets, including excellent cyclic stability and high rate capacity. Specifically, 494.8 mA h g−1 at a current density of 100 mA g−1 still is maintained for MoS0.5Se1.5/C sheets after 200 cycles, which is much higher than that of MoSe2/C sheets (173.5 mA h g−1). The significantly enhanced performance of MoS0.5Se1.5/C sheets can be attributed to the synergistic combination of MoS0.5Se1.5 phase and porous carbon sheets, which provides an effective conductive matrix and buffer spaces for Li‐ion/electronic transfer and MoS0.5Se1.5 expansion, during the charge–discharge.

High-Performance Photodetectors Based on Solution-Processed Epitaxial Grown Hybrid Halide Perovskites.

Hybrid organic-inorganic halide perovskites (HOIPs) have recently attracted tremendous attention because of their excellent semiconducting and optoelectronic properties, which exist despite their morphology and crystallinity being far inferior to those of more mature semiconductors, such as silicon and III-V compound semiconductors. Heteroepitaxy can provide a route to achieving high-performance HOIP devices when high crystalline quality and smooth morphology are required, but work on heteroepitaxial HOIPs has not previously been reported. Here, we demonstrate epitaxial growth of methylammonium lead iodide (MAPbI3) on single crystal KCl substrates with smooth morphology and the highest carrier recombination lifetime (∼213 ns) yet reported for nonsingle crystalline MAPbI3. Experimental Raman spectra agree well with theoretical calculations, presenting in particular a sharp peak at 290 cm-1 for the torsional mode of the organic cations, a marker of orientational order and typically lacking in previous reports. Photodetectors were fabricated showing excellent performance, confirming the high quality of the epitaxial MAPbI3 thin films. This work provides a new strategy to enhance the performance of all HOIPs-based devices.

Crystallization and separation of KCl from carnallite ore: Process development, simulation, and economic feasibility

Given an increasing demand for potassium in Brazil, the mining and use of carnallite is becoming increasingly important, because the current source of potassium (sylvinite) is being depleted and there is a risk of shortages. Based on theoretical and practical data available in the literature, this work describes the development, simulation, and economic feasibility of a process for dissolution and crystallization of potassium chloride from carnallite ore. Positive results were obtained following application of the Hoffman diagram and determination of the corresponding equation. The proposed process provided over 85% potassium chloride crystallization, demonstrating its superior performance, compared to existing procedures.

Experimental investigation on the mechanical behaviours of a low-clay shale under water-based fluids

The interactions between drilling/fracking fluids and shale formations have great effect on shale gas exploitation. Previous studies have shown that water/brine saturation will cause clay-rich shale swelling and strength decreasing. However, little research has been done to investigate such effect on resource shales which mainly have low clay contents. This paper presents an experimental study of the impact of water-based fluids on the mechanical properties of a low-clay shale. Uniaxial compressive strength (UCS) tests were performed on shale samples soaked in NaCl, KCl and CaCl2 solutions with saline concentrations of 0%, 10%, 20% and 25.4%. The crack propagation and the failure mechanism of the shale samples were recorded using acoustic emission (AE) sensors in combination with Digital Image Correlation (DIC) technique. Scanning electron microscopy (SEM) analysis was used to understand the micro scale variation of shale samples after soaking in saline solutions. According to the experimental results, water-saturated samples have the highest swelling increasing and the largest strength reduction. The swelling potential and UCS values decrease with increased saline concentration. Potassium ions have a significant effect on shale strength enhancement when compared to sodium ions and calcium ions. The failure pattern of the samples is mainly splitting breakage. NaCl and CaCl2 saturated samples present more axial fractures than the KCl saturated samples when failure occurs. The SEM results show that crystals of NaCl, KCl and CaCl2 were observed on the surface, and the amount of crystals increases with increasing saline concentrations. The AE results also show that saline saturation could increase the cumulative AE energy.

Laser-induced time resolved luminescence of natural sylvite KCl

Natural sylvite samples have been studied by laser-induced time-resolved luminescence techniques. The specific combinations of luminescence and excitation spectra together with luminescence decay times enabled their interpretation as Pb2+ and O2- emission centers. Such conclusions have been supported by luminescence study of artificial KCl crystals, activated by the corresponding emission centers.

Spectrally resolved thermoluminescence of pure potassium chloride crystals

Alkali halides are wide band gap dielectric materials, which are very important for luminescence dosimetry. Nevertheless, only some of them were studied comprehensively. Potassium chloride (KCl) is alkali halide material, which shows pronounced thermoluminescence (TL) and optically stimulated luminescence (OSL). The material occurs also in natural mineral form as sylvite (or sylvine). This paper presents results of spectrally resolved thermoluminescence (SR-TL) measurements of pure KCl crystals in temperature range 300–550K for various doses of beta irradiation. Four emission bands were found relating to different recombination centers in this material. TL curves relating to these centers have different shape. It indicates that recombination centers are not filled concurrently.