KCl Matrix Research Articles

Synergistic effect mechanism of biomass ash-derived K-Ca-Si catalytic system on syngas production and reactivity characteristics of high-sulfur petroleum coke gasification

In this study, three typical biomass ash (BA) components, KCl, CaCO3 and SiO2, are selected as model compounds to construct BA-based key ternary component system for petroleum coke (PC) gasification. Gas product analysis was conducted using gas chromatography to study the influence of different catalysts on the gas product distribution, gas yield and carbon conversion of PC gasification, and clarify the synergistic effects of binary and ternary components in K-Ca-Si catalytic system. In addition, electron scanning microscopy (SEM) and Raman techniques are used to characterize the physicochemical structure of gasification semi-char to reveal the synergistic mechanism of K-Ca-Si system. The results show that the yield of different gases is ordered as H2 > CO > CO2 and the increment of H2 yield, CO yield, syngas yield and carbon conversion in K-Ca-Si catalytic system is 43.41 mmol/g, 26.67 mmol/g, 80.37 mmol/g and 0.49, compared with single PC gasification, respectively. By comparing the theoretical and actual value of gas yield and carbon conversion, it is found that there are synergistic catalytic effects for K-Ca-Si ternary catalyst, but Si will inhibit the activity of K and Ca. Coupled with SEM and Raman analysis, synergistic mechanism of ternary catalytic system can be revealed. KCl and CaCO3 reduce the graphitization degree of semi-char by reacting with carbon matrix, and CaCO3 can stimulate the pore structure development of semi-char, which accelerate reaction between KCl and carbon matrix to form intermediate active sites, thus favoring gasification reaction and exhibiting a synergistic effect. SiO2, on the other hand, will combine with KCl and CaCO3 to form inert silicates, resulting in the deactivation of KCl and CaCO3. It could be concluded that for high K-high Ca-low Si ternary catalytic system, KCl and CaCO3 would still show a synergistic effect due to higher CaCO3 content than SiO2.

Cocrystallization Enabled Spatial Self‐Confinement Approach to Synthesize Crystalline Porous Metal Oxide Nanosheets for Gas Sensing

AbstractCrystalline metal oxide nanosheets show exceptional catalytic performance owing to the large surface‐to‐volume ratio and quantum confinement effect. However, it is still a challenge to develop a facile and general method to synthesize metal oxide nanosheets. Herein, we report a cocrystallization induced spatial self‐confinement approach to synthesize metal oxide nanosheets. Taking the synthesis of SnO2 as an example, the solvent evaporation from KCl and SnCl2 solution induces the cocrystallization of KCl and K2SnCl6, and the obtained composite with encapsulated K2SnCl6 can be in situ converted into SnO2 nanosheets confined in KCl matrix, after water washing to remove KCl, porous SnO2 nanosheets can be obtained. Notably, a series of metal oxide nanosheets can be obtained through this general and efficient green route. In particular, porous CeO2/SnO2 nanosheets with improved surface O− species and abundant oxygen vacancies exhibit superior gas sensing performance to 3‐hydroxy‐2‐butanone.

Cocrystallization Enabled Spatial Self-Confinement Approach to Synthesize Crystalline Porous Metal Oxide Nanosheets for Gas Sensing.

Crystalline metal oxide nanosheets show exceptional catalytic performance owing to the large surface-to-volume ratio and quantum confinement effect. However, it is still a challenge to develop a facile and general method to synthesize metal oxide nanosheets. Herein, we report a cocrystallization induced spatial self-confinement approach to synthesize metal oxide nanosheets. Taking the synthesis of SnO2 as an example, the solvent evaporation from KCl and SnCl2 solution induces the cocrystallization of KCl and K2 SnCl6 , and the obtained composite with encapsulated K2 SnCl6 can be in situ converted into SnO2 nanosheets confined in KCl matrix, after water washing to remove KCl, porous SnO2 nanosheets can be obtained. Notably, a series of metal oxide nanosheets can be obtained through this general and efficient green route. In particular, porous CeO2 /SnO2 nanosheets with improved surface O- species and abundant oxygen vacancies exhibit superior gas sensing performance to 3-hydroxy-2-butanone.

Exciton-like luminescence of KCl matrix under thermoelastic, local and uniaxial deformation

The radiative relaxation of exciton-like formations in KCl-Na single crystal has been studied by experimental methods of luminescent spectroscopy. The amplifying effect of the radiation intensity with a maximum at 2.8 eV up to 500 times as compared to pure KCl has been detected in KCl-Na. The luminescence efficiency of an exciton-like formation increases with rise in: sodium ions concentration ( 10 ÷ 1000 ppm), thermal exposure ( 500◦C ÷ 600◦C ) and the degree of uniaxial deformation along <100> and <110> crystallographic directions. Previously, such a scale of the luminescence enhancement effect has not been registered in KCl matrix at room temperature. At high sodium concentrations (1000 ppm) in KCl-Na crystals, the additional intense emission with a maximum at 3.1 eV has also been revealed, which is typical for pair sodium ions. It is interpreted that the exciton-like formation in the sodium field with the maximum quantum yield of luminescence is formed by recombination assembly of electron-hole pairs due to the mobility of unrelaxed holes.

Mechanisms of radiation defect formation in KCl crystals under the influence of local and plastic deformation

This work proposes an original approach to the study of trihalide centers in a KCl matrix in the field of local and plastic deformation. Local lattice deformation is carried out by purposeful doping of the KCl crystal with light homologous cations, as well as bivalent impurities, which create dipole strontium complexes to maintain the electroneutrality of the lattice. Plastic deformation, which creates paired vacancy defects in the lattice, divacancies and vacancy quartets, is realized at room temperature within the degree of relative uniaxial deformation of 3–5%. After subsequent cooling down to 80 K the deformed crystal was additionally irradiated with X-rays. The absorption spectra of the crystals subjected to two types of deformation and additional isodose irradiation by X-rays were recorded in a special cryostat at 80 K. The spectral characteristics and formation efficiency of V-type centers, lithium- and strontium-containing centers in the field of pre-irradiation dipole complexes have been considered.

ZnO-doped KCl single crystal with enhanced UV emission lines

The embedded bulk KCl single crystal with the ZnO nanocrystal was grown using Czochralski technique. Various structural and optical analyses were employed to characterize the grown sample. X-ray diffraction confirmed the diffusion of ZnO NCs in the KCl bulk lattice. The crystal structure and the lattice parameters were estimated for both ZnO NCs and KCl matrix by Rietveld analysis. The bond formation of KCl:ZnO was demonstrated by Fourier transform infrared (FTIR) spectroscopy. FE-SEM was carried out for the morphological study of ZnO NCs and estimation of particle size distributions. Energy-dispersive X-ray (EDX) analysis was used to investigate the elemental composition of the prepared sample. The experimental results confirmed the improvement in optical properties of KCl single crystal was found when it was doped by ZnO. The second derivative of absorption spectrum confirmed the band gap of 6.06 eV for KCl single crystal. In PL spectrum, several intense UV light emission peaks at 297 and 360 nm were observed in which the emission peaks of KCl:ZnO samples were very sharp in comparison with the pure KCl single crystal. It seems that the UV peaks at 297 and 360 nm emission lines of ZnO-doped KCl crystals originated from electron capturing from F center.

Development of a simple spectrophotometric method to estimate uranium concentration in LiCl–KCl matrix

A fast, precise and simple spectrophotometric method was developed for the estimation of uranium in LiCl–KCl salt matrix using phosphoric acid as a complexing agent. The 421 nm absorbance peak of uranium was found to be spectral interference free and area of this peak was used for the quantitative analysis. Linearity over 100–7000 ppm with a detection limit of 25 ppm of uranium in 10% LiCl–KCl matrix was obtained by this method. The present method was successfully applied for the quantitative estimation of uranium in synthetic salt mixtures and the results were found to be more accurate than the values measured by ICP-OES.

Feasibility study for quantification of lanthanides in LiF–KCl salt by laser induced breakdown spectroscopy

Quantitative analysis of Pr, Nd, Ce, La and Sm were carried out simultaneously in LiF–KCl matrix using laser induced breakdown spectroscopic technique. Two non-interfering analytical emission lines have been identified for each lanthanide and using the internal standard method, the calibration curve is constructed from 0.3 to 5% for Pr, Nd, Ce and La and from 0.3 to 3% for Sm. Both the emission lines showed good regression coefficient (R 2) ranging from 0.9953 to 0.9996. The analytical capability of this method is studied through the correlation uncertainty of measured values with its known value in synthetic samples containing all the lanthanides in equal amount (0.5, 1 and 2%). Low value of correlation uncertainty (less than 10%) confirms that LIBS has a great potential for quantitative analysis of lanthanides in LiF–KCl matrix.

Synthesis of CsPbCl3‐Mn Nanocrystals via Cation Exchange

AbstractMn doped caesium lead halide perovskite (CsPbCl3‐Mn) nanocrystals are obtained from CsPbBr3 nanocrystals via ion exchange with MnCl2. The doping of Mn and the activity in energy acceptance in different stages of ion exchange are proved using photoluminescence (PL) lifetime measurement and inductively coupled plasma mass spectrometry measurements. During the ion exchange, ultrasonic treatment and cold flow (in a KCl matrix) are used to assist Mn incorporation. The resulting CsPbCl3‐Mn@KCl shows excellent PL properties and stability. Finally, the CsPbCl3‐Mn@KCl tablet is applied to the production of a light emitting diode prototype.

Synthesis of carbon supported ordered tetragonal pseudo-ternary Pt2M′M″ (M = Fe, Co, Ni) nanoparticles and their activity for oxygen reduction reaction

Alloying Pt with 3d transition metals has attracted much attention due to their reduced Pt content and reports of enhanced electrocatalytic activity for proton exchange membrane fuel cell applications. However, synthesizing ordered nanocrystalline intermetallics in the sub-10 nm range can be challenging. Here, we report on the co-reduction synthesis of ordered ternary Pt-base transition metal intermetallics with particle sizes in the regime of 3–5 nm. Since differences in the activity of PtM (M = Fe, Co, Ni) for oxygen reduction reaction (ORR) have been reported, we explored their combinations: Pt2FeCo, Pt2FeNi, and Pt2CoNi. These ternary intermetallic nanoparticles crystallized in P4/mmm space group upon annealing in a protective KCl matrix. The electrocatalysts were prepared by dispersing these intermetallics onto a carbon support using ethylene glycol and various sonication techniques. A combination of analytical techniques including powder X-ray diffraction, thermogravimetric analysis, electron microscopy and electrochemical methods have been used in this study. The oxygen reduction reaction activity and stability of the catalysts were tested in 0.1 M HClO4 and 0.1 M H2SO4 using cyclic voltammetry and rotating disk electrode voltammetry. The correlations between the composition, structure, morphology and activity of the intermetallics have been established and are discussed.

Infrared and Raman spectra of [Re(CN)5NO]3- complex isolated in KCl matrix

We report here the infrared and Raman spectra of [Re(CN)5NO]3- complex as guest diluted in the KCl crystal lattice. According to the chemical analysis, the anion concentration in the KCl host matrix is in excess of 2% (in mole). The solid state Raman spectrum of this complex is reported for the first time. The information obtained from the relative intensities of infrared and Raman bands affords a reexamination of vibration mode assignments. The observed bands splitting may be explained by the interactions of the guest complex with the host lattice, including the ways in which the K+ vacancies are distributed around [Re(CN)5NO]3- to achieve lattice charge neutrality.

TH-C-19A-12: Two-Dimensional High Spatial-Resolution Dosimeter Using Europium Doped Potassium Chloride

Purpose: Recent research has shown that KCl:Eu2+ has great potential for use in megavoltage radiation therapy dosimetry because this material exhibits excellent storage performance and is reusable due to strong radiation hardness. This work reports our attempts to fabricate 2D KCl:Eu2+ storage phosphor films (SPFs) using both a physical vapor deposition (PVD) method and a tape casting method. Methods: A thin layer of KCl:Eu2+ was deposited on a substrate of borosilicate glass (e.g., laboratory slides) with a PVD system. For tape casting, a homogenous suspension containing storage phosphor particles, liquid vehicle and polymer binder was formed and subsequently cast by doctor-blade onto a polyethylene terephthalate substrate to form a 150 μm thick SPF. Results: X ray diffraction analysis showed that a 10 μm thick PVD sample was composed of highly crystalline KCl. No additional phases were observed, suggesting that the europium activator had completed been incorporated into the KCl matrix. Photostimulated luminescence and photoluminescence spectra suggested that F (Cl−) centers were the electron storage centers post x ray irradiation and that Eu2+ cations acted as luminescence centers in the photostimulation process. The 150 μm thick casted KCl:Eu2+ SPF showed sub-millimeter spatial resolution. Monte Carlo simulations further demonstrated that the admixture of 20% KCl:Eu2+ and 80% low Z polymer binder exhibited almost no energy dependence in a 6 MV beam. KCl:Eu2+ pellet samples showed a large dynamic range from 0.01 cGy to 60 Gy dose-to-water, and saturated at approximately 500 Gy as a Result of its intrinsic high radiation hardness. Conclusions: This discovery research provides strong evidence that KCl:Eu2+ based SPF with associated readout apparatus could Result in a novel electronic film system that has all the desirable features associated with classic radiographic film and, importantly, water equivalence and the capability of permanent identification of each detector. This work was supported in part by NIH Grant No. R01CA148853. The authors would like to thank Paul Leblans (AGFA Healthcare, Belgium) for many helpful discussions on this topic.

Two-dimensional high spatial-resolution dosimeter using europium doped potassium chloride: a feasibility study

Recent research has shown that KCl:Eu2+ has great potential for use in megavoltage radiation therapy dosimetry because this material exhibits excellent storage performance and is reusable due to strong radiation hardness. This work reports the authors’ attempts to fabricate 2D KCl:Eu2+ storage phosphor films (SPFs) using both a physical vapor deposition (PVD) method and a tape casting method. X-ray diffraction analysis showed that a 10 µm thick PVD sample was composed of highly crystalline KCl. No additional phases were observed, suggesting that the europium activator had been completely incorporated into the KCl matrix. Photostimulated luminescence and photoluminescence spectra suggested that F (Cl−) centers were the electron storage centers post x-ray irradiation and that Eu2+ cations acted as luminescence centers in the photostimulation process. The 150 µm thick casted KCl:Eu2+ SPF showed sub-millimeter spatial-resolution. Monte Carlo simulations further demonstrated that the admixture of 20% KCl:Eu2+ and 80% low Z polymer binder exhibited almost no energy-dependence in a 6 MV beam. KCl:Eu2+ pellet samples showed a large dynamic range from 0.01 cGy to 60 Gy dose-to-water, and saturated at approximately 500 Gy as a result of KCl's intrinsic high radiation hardness. Taken together, this work provides strong evidence that KCl:Eu2+-based SPF with associated readout apparatus could result in a novel electronic film system that has all the desirable features associated with classic radiographic film and, importantly, water equivalence and the capability of permanent identification of each detector.

Coalescence in the Thermal Annealing of Nanoparticles: An in Situ STEM Study of the Growth Mechanisms of Ordered Pt–Fe Nanoparticles in a KCl Matrix

Thermal annealing is essential for achieving ultrasmall size ferromagnetic properties in next-generation high performance nanocomposite magnetic materials. However, during the annealing process, growth and agglomeration of nanoparticles normally occurs, which destroys the narrow size distributions. Thus, the materials become less suitable for application in high-density magnetic recording. The mechanism of nanoparticle growth and sintering has been difficult to determine because of the lack of suitable in situ tools to probe subnanometer changes at the local level. Here we report a study using high-resolution scanning transmission electron microscopy (STEM) coupled with an in situ thermal annealing stage of surfactant-free, monodispersed superparamagnetic PtFe (cubic) alloy nanoparticles (≈2 nm in diameter) stabilized in or on a KCl matrix. Ex situ experiments confirmed that annealing produces PtFe (tetragonal) ordered intermetallic nanoparticles with a mean diameter of 5 nm, and the in situ study revealed that the mechanism of nanoparticle growth is dominated by particle–particle coalescence, although Ostwald ripening is also implicated in a few regions. In addition, to determine the time dependent evolution of the size distribution of an ensemble of over 400 nanoparticles, analysis of the in situ data also allows tracking of individual nanoparticles, distinguishing coalescence from Ostwald ripening, nanoparticle by nanoparticle. This approach has provided valuable insights into changes in crystal structure and sintering that occur during the thermal annealing of Pt–Fe nanoparticles.

A Surfactant-Free Strategy for Synthesizing and Processing Intermetallic Platinum-Based Nanoparticle Catalysts

Using Pt(3)Fe nanoparticles as an example, a surfactant-free Np-KCl matrix method (Np stands for nanoparticle) is developed for the synthesis of nanoparticles with controlled size and structure. In this method, the Np-KCl assembly is formed in a one-pot reduction in THF at room temperature. KCl is an insoluble byproduct of the reaction and serves as a matrix that traps the nanoparticles to avoid particle agglomeration and to control the coalescence of nanoparticles during thermal annealing up to 600 °C. By varying the molar ratio of metal precursors and KCl, as well as the time and temperature of annealing, the final particle sizes and crystalline order can be independently controlled. After thermal processing, nanoparticles were released from the KCl matrix and transferred in an ethylene glycol-water solution to support materials forming a uniform Np-support assembly. A detailed study of the synthesis of ordered intermetallic Pt(3)Fe nanoparticles with an average diameter of 4 nm, using this Np-KCl method, is provided as an example of a generally applicable method. This surfactant-free strategy has been extended to the synthesis of other bi- and trimetallic nanoparticles of Pt-transition metals.

Preparation, characterization and ionic conductivity studies of ZrO 2 dispersed mixed halide matrix (KCl) 0.9–(NaCl) 0.1

Composite electrolytes in the system [(KCl) 0.9:(NaCl) 0.1] 1− y :(ZrO 2) y were prepared and their ionic conductivities were studied. In our previous study on the mixed halide system (KCl) 1− x :(NaCl) x , maximum conductivity (∼50 times that of the base KCl matrix) was found when x=0.1. The matrix (KCl) 0.9:(NaCl) 0.1 was dispersed with different concentration of ZrO 2 (powder) for the preparation of composites and their conductivities were determined. The maximum conductivity was developed for the composite having composition y=0.5. The matrices were prepared by melt-quench technique and the dispersion of ZrO 2 was carried out in liquid medium. The conductivity measurements of the composites were carried out by impedance spectroscopy technique. The composite [(KCl) 0.9:(NaCl) 0.1] 0.5:(ZrO 2) 0.5 was characterized by X-ray diffraction (XRD) analysis, differential thermal analysis (DTA), thermogravimetric analysis (TG) and scanning electron microscopy (SEM). The conductivity of the composite [(KCl) 0.9:(NaCl) 0.1] 0.5:(ZrO 2) 0.5 as a function of temperature was also studied. The conductivity increase in the composite could be attributed to enhancement of defect concentration in the space charge region created at the interface between the host halide and the dispersoid.

Determination of phthalate esters from food-contacted materials by on-line microdialysis and liquid chromatography

Phthalates (endocrine disrupters) released from food-contacted plastics into aqueous solution during microwave conditioning were measured with microdialysis enrichment on-lined high-performance liquid chromatography. The released phthalates in aqueous solution were diffused through a cellular dialysis membrane into the perfusion stream and thus enriched prior to HPLC analysis. Conditions for obtaining optimum enrichment such as the hollow dialysis fiber, flow-rate and polarity modifier in perfusion stream, pH, added-salt and stirring rate in sample solution, as well as chromatographic conditions were investigated. Experimental results indicated that microdialysis enrichment with a 20-cm polysulfone hollow dialysis fiber and heptane as the perfusate at 0.10-μL/min flow-rate to collect phthalates from aqueous sample in 0.5 M KCl matrix (optional pH) at 250 rpm stirring offered the optimum enriched efficiency. The dimethyl phthalate (DMP), diethyl phthalate (DEP) and dibutyl phthalate (DBP) were well separated within 16 min by a C-18 column and eluted gradient from 40 to 90% aqueous acetonitrile (at pH 6.0) and 1.0 to 1.5 mL/min flow-rate. Detection was carried out with an UV detector at 225 nm. The enrichment factors were 14, 140 and 201 (at 0.10-μL/min perfusate flow-rate) for DMP, DEP and DBP, respectively, with less than 4% RSD. The proposed method provided a very simple, fast and eco-friendly enriched procedure to determine the extent of phthalates migration from disposable plastic materials into drinking soup.

Luminescent characteristics of pure and Ce doped K2LaCl5 phase in KCl host

AbstractThe formation of Ce3+ doped K2LaCl5 microphase has been revealed for the KCl–LaCl3–CeCl3 system. Luminescent characteristics of pure and Ce3+ doped K2LaCl5 microcrystals, embedded in KCl matrix, are studied in comparison with those of bulk K2LaCl5:Ce(0.1%) crystal. For both the micro‐ and bulk K2LaCl5:Ce crystals the bands peaked at 344 and 373 nm are attributed to Ce3+ emission revealing a 24 ns time constant for the main decay component upon the excitation within the Ce3+ f–d absorption range. The method elaborated for the synthesis of the activated K2LaCl5 microphase in the KCl–LaCl3–CeCl3 system provides the possibility of producing large‐size homogeneous scintillation elements possessing efficient emission of rare earth doped A2LaX5 micro‐ and nano‐phases embedded in AX matrices (A = Cs, K, Rb; X = F, Cl, Br, I). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electronic states of AgCl nanocrystals embedded in crystalline KCl studied by95−GHzoptically detected magnetic resonance spectroscopy

The properties of shallow electron centers (SEC), self-trapped holes (STH), and self-trapped excitons (STE) are investigated in nanocrystals of AgCl embedded in a crystalline KCl matrix. Time-resolved photoluminescence (PL) measurements reveal a behavior different from that in bulk AgCl: an inhomogeneous distribution of the properties of the recombination centers is revealed by the spectral dependence of the decay rates. In time scales from nano- to microseconds, slower rates are systematically observed at the low-energy side of the emission range. In high-frequency $(95\phantom{\rule{0.3em}{0ex}}\mathrm{GHz})$ optically detected magnetic resonance (ODMR) measurements, the transitions of SEC and STH centers are only observed in the extreme-low energy tail of the PL emission and they exhibit a broad and asymmetric $g$-value distribution (width $\ensuremath{\delta}g\ensuremath{\approx}0.07$), ranging up from the respective bulk $g$-values. A complex behavior of the ODMR spectrum in the STE region is revealed, showing different spectra at $1.8\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and at higher temperature, and, different from the bulk AgCl case, exhibiting a strong dependence upon variation of the detection photon energy. Analysis of the measurements at $4.6\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ yields a zero field splitting in the STE triplet state in good agreement with the bulk value, while the $g$-values are slightly increased relative to bulk, which is ascribed to the nanocrystal environment.

Total soluble nitrogen in forest soils as determined by persulfate oxidation and by high temperature catalytic oxidation

Abstract Speedy and reliable measurements of soil soluble nitrogen (N) are critical for estimating N fluxes in forest ecosystems. The high temperature catalytic oxidation (HTCO) method was assessed and compared with persulfate oxidation (PO) to measure total soluble N in water, hot water, 2 m KCl, and 0.5 m K2SO4 extracts of 24 forest soils collected from south-east Queensland. All salt extracts were diluted 5-fold before measurement by the HTCO method to minimise the effects of salt precipitation on the surface of the Pt/Al2O3 catalysts that may impair oxidation efficiency. Drifts of sensitivity of signals in diluted KCl (0.4 m), K2SO4 (0.1 m), and water matrixes by the HTCO method were minor, with <2% in KCl matrix and <3% in K2SO4 and water matrices. Nitrogen recoveries from most standard N-containing compounds (5 mg/L) analysed by the HTCO method in all the matrices tested were >94%. The values of total soluble N in all extracts of soils obtained by both the PO and the HTCO methods were highly correlated. However, the HTCO method generally gave greater values than the PO method, particularly with high concentrations of N. We consider the HTCO method to be a simple, automated, rapid, quantitative, and reliable method for determining total soluble N in both water extracts and diluted salt extracts of forest soils.