Incorporation Of Cesium Research Articles

A study of refractory carbon deposits on Ni/Al2O3 catalysts for dry reforming of methane

AbstractWhen investigating carbonaceous species on a catalyst via temperature‐programmed techniques, both the nature of the carbons and the possibility of the catalytic reaction of carbonaceous species should be considered. Here we examined CH4 decomposition (carbon deposition from CH4) and the reverse Boudouard reaction (carbon elimination by CO2) on the Ni/Al2O3 catalyst using sequential temperature‐programmed experiments. Carefully considering both the location and characteristics of carbon deposits formed on the Ni/Al2O3 catalyst, we conclude that carbons located on the Al2O3 support are challenging to remove by CO2 regardless of their nature, indicating the importance of support activity in reducing carbon deposits. In this study, the incorporation of cesium (Cs) into Al2O3 shows no effect on the prevention of carbon deposition from CH4 but does show an enhancement of carbon removal via the reverse Boudouard reaction, resulting in less coke formation on the Ni/Cs doped Al2O3 catalyst than the Ni/Al2O3 catalyst by 17 % for the dry reforming of methane.

A study of the effects of a thermally evaporated nanoscale CsBr layer on the optoelectronic properties and stability of formamidinium-rich perovskite solar cells

Incorporation of cesium (Cs) into the perovskite layer has become a good strategy to boost the stability and power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, a suitable and scalable method of Cs incorporation in a perovskite film that does not cause a significant increase in the optical bandgap is needed. In this paper, we introduce a thin layer of CsBr into a formamidinium (FA)-rich mixed halide perovskite film using the thermal evaporation technique. The effects of the thickness of the CsBr layer on the microstructural, structural, and optoelectronic properties and surface chemical states of the perovskite film are then studied. The results indicate that the CsBr layer thickness is able to tune the microstructural and optoelectronic properties of the perovskite film. Planar PSCs fabricated with different thicknesses of CsBr layers in the perovskite absorber exhibited different photovoltaic performance characteristics. The CsBr-modified PSC device with a 50 nm layer of CsBr in the perovskite layer showed a better PCE of 16.19% ± 0.17%, which was about 15% higher than that of the control device, and was able to retain nearly 70% of its initial PCE value after 120 days of storage in an unencapsulated state.

δ‐CsPbI3 Intermediate Phase Growth Assisted Sequential Deposition Boosts Stable and High‐Efficiency Triple Cation Perovskite Solar Cells

AbstractCs/FA/MA triple cation perovskite films have been well developed in the antisolvent dripping method, attributable to its outstanding photovoltaic and stability performances. However, a facile and effective strategy is still lacking for fabricating high‐quality large‐grain triple cation perovskite films via sequential deposition method a, which is one of the key technologies for high efficiency perovskite solar cells. To address this issue, a δ‐CsPbI3 intermediate phase growth (CsPbI3‐IPG) assisted sequential deposition method is demonstrated for the first time. The approach not only achieves incorporation of controllable cesium into (FAPbI3)1–x(MAPbBr3)x perovskite, but also enlarges the perovskite grains, manipulates the crystallization, modulates the bandgap, and improves the stability of final perovskite films. The photovoltaic performances of the devices based on these Cs/FA/MA perovskite films with various amounts of the δ‐CsPbI3 intermediate phase are investigated systematically. Benefiting from moderate cesium incorporation and intermediate phase‐assisted grain growth, the optimized Cs/FA/MA perovskite solar cells exhibit a significantly improved power conversion efficiency and operational stability of unencapsulated devices. This facile strategy provides new insights into the compositional engineering of triple or quadruple cation perovskite materials with enlarged grains and superior stability via a sequential deposition method.

Highly efficient Zn2SnO4 perovskite solar cells through band alignment engineering.

An active absorption layer with a narrow band gap has been achieved through adjusting the halide ratio in a halide perovskite, and it had better energy alignment with the Zn2SnO4 electron transport layer. An efficiency of 19.37% can be obtained, and this has also been improved to 20.26% through the incorporation of cesium, giving a new triple cation perovskite.

Evaluation of the effect that the substitution of the ion MA by the ion Cs produces on the properties of thin films of CsxMA1-xPbI3 prepared by spin-coating

In this paper we report results concerning the effect that the substitution of the ion methylamonium (MA) by the ion cesium causes on the properties of the hybrid compound CsxMA1-xPbI3, synthesized by spin coating. It was found that this substitution occurs effectively when less than 15% of the ions of MA are replaced by cesium and that above this quantity the cesium forms another compound. Special emphasis was placed on evaluating the effect of the Cs content on the optical, structural and morphological properties of CsxMA1-xPbI3 films, through characterization performed using techniques such as diffuse reflectance, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). These studies allowed checking that the incorporation of cesium in the structure of the compound MAPbI3 induces structural disorder, as well as an increase of its energy gap Eg, from a value of 1.56 eV for samples of composition MAPbI3 to a value of 1.59 eV for samples with composition Cs0.25MA0.75PbI3. Additionally, it was found that the CsxMA1-xPbI3 films exhibits a morphology consisting of compact grain with sub-micron size, grouped in needle-shaped structures.

Triple cation mixed-halide perovskites for tunable lasers

Metal halide perovskites are recently attracting strong attention due to their potential in solar cells, LEDs, and lasers. Here, we demonstrate the broad spectral tuning of the optical gain characteristics of triple cation (containing methylammonium, formamidinium and cesium) mixed-halide perovskite thin films. We explicitly study the interrelation between amplified spontaneous emission (ASE) thresholds, the operational stability of the gain, and the material composition. The incorporation of cesium and a deficiency of lead in the precursor solutions is found to be crucial for low ASE thresholds and the improved stability of mixed-halide perovskites. We tune the photoluminescence in mixed-halide perovskites between peak wavelengths of 510 and 790 nm by exchanging the halide from iodide to bromide and chloride in small steps of 10%, while preserving the narrowband emission below a linewidth of 130 meV for all mixtures. The optical gain under ns-excitation can be tuned over a significant portion of this spectral window; we observe ASE emission in regions between 545 to 555 nm and 680 to 810 nm. This is a significant step towards perovskite lasers operating through a broad portion of the visible to near infrared spectrum.

Nonstoichiometric Adduct Approach for High-Efficiency Perovskite Solar Cells.

Since the groundbreaking report on a solid-state perovskite solar cell employing a methylammonium lead iodide-sensitized mesoporous TiO2 film and an organic hole conducting layer in 2012 by our group, the swift surge of perovskite photovoltaics opens a new paradigm in solar-cell research. As a result, ca. 1300 peer-reviewed research articles were published in 2015. In this Inorganic Chemistry Forum on Halide Perovskite, the researches with highlights of work on perovskite solar cells in my laboratory are reviewed. We have developed a size-controllable two-step spin-coating method and found that minimal nonradiative recombination in perovskite crystals could lead to high photovoltaic performance. A Lewis acid based adduct method and self-formed grain boundary process were developed for high-efficiency devices with reproducibility. A power conversion efficiency of 20.4% was achieved via grain boundary engineering based on a nonstoichiometric adduct approach. The incorporation of cesium in a formamidinium lead iodide perovskite was found to show better photostability and moisture-stability. A reduction in the dimensionality from a three-dimensitonal nanocrystal to a one-dimensional nanowire led to a hypsochromic shift of absorption and fluorescence. To enhance the charge-carrier transport and light-harvesting efficiency, a nanoarchitecture of oxide layers was proposed.

Formate Drilling and Completion Fluids: Evaluation of Potential Well-Productivity Impact, Valemon

Summary Valemon, operated by Statoil, is a high-pressure/high-temperature (HP/HT) gas/condensate field on the Norwegian Continental Shelf. Production started at the beginning of 2015 from a development consisting initially of cased-and-perforated wells. However, during early field development, the orginal concept was for a standalone-screen (SAS) lower completion. A potassium/cesium (K/Cs) formate water-based system with a density of 2.02 specific gravity (sg) was considered as a candidate drilling-and-completion fluid for the wells completed with screens, one of which could potentially be suspended in formate brine for up to 10 months before the arrival of the platform and before cleanup and the onset of production. An unknown was the possibility for any near-wellbore interaction with these fluids during extended contact and the possible detrimental impact on productivity. Computational-fluid-dynamics (CFD) modeling was performed to determine the length of time formate would be in contact with the near wellbore, demonstrating that, especially for the lower-permeability intervals, a contact time of approximately 45 days was a possibility. In light of this, a sequence of corefloods was performed that involved extended soaks in formate along with pre- and post-test analyses to identify potential damage mechanisms. Those identified included kaolinite dissolution, precipitation of barium and cesium silicate, and swelling of kaolinite because of the incorporation of potassium and cesium into the kaolinite lattice. To confirm the findings from the CFD and coreflood modeling, a field review was made of Statoil’s experiences with suspending wells for extended time in formate before cleanup and production. The field review demonstrated positive experiences in the use of formates in suspended wells with respect to productivity. Lower than expected productivity was experienced for some wells, but this could not be related conclusively to the use of formates. This paper provides an overview of lessons learned from coreflooding, CFD modeling, and actual field data on wells suspended in formate before cleanup and production.

Structure of cesium loaded iron phosphate glasses: An infrared and Raman spectroscopy study

The structure of cesium loaded iron phosphate glasses (IPG) was investigated using infrared and Raman spectroscopy. The spectra of the cesium doped samples revealed a structural modification of the parent glass owing to the incorporation of cesium. The structural changes could be correlated with the variation observed in the glass transition temperature of these glasses. Increased Cs-mediated cationic cross linking appears to be the reason for the initial rise in glass transition temperature up to 21 mol% Cs 2O in IPG; while, breakdown of the phosphate network with increasing cesium content, brings down the glass transition temperature.

Optimization of 4H-SiC MOS Properties with Cesium Implantation

The effect of incorporation of cesium with implantation on the electrical characteristics of SiO2/4H-SiC interface has been evaluated using MOS capacitors. With a cesium dosage of 1012 and 3x1012 cm-2 on deposited oxide re-oxidized in steam, effective oxide charge densities of - 1.4x1012 and -7.5x1011 cm-2 respectively were extracted and a cesium implant activation percentage of 33% was estimated from flatband voltage shift. Also, corresponding interfacial state densities of 2.5x1013 and 1.8x1013 cm-2-eV-1 near the conduction band edge were extracted from High-Low frequency C-V technique, showing a decreasing Dit with increasing Cs dosage.

A study of mechanisms responsible for incorporation of cesium and radiocesium into fruitbodies of king oyster mushroom ( Pleurotus eryngii)

Ex vitro cultures of Pleurotus eryngii were carried out under controlled conditions using sterile medium composed of barley seeds. The influence of alkali and alkaline earth element salts (CsCl, KCl, NaCl, RbCl, and CaCl 2) and tetraethylammonium chloride on incorporation of cesium, potassium, sodium, rubidium and calcium, and their distribution within fruitbodies, was examined. The results show that incorporation of cesium into fruitbodies was not suppressed by Na + and Rb + or tetraethylammonium chloride. However, it was inhibited by Ca 2+ and stimulated by high concentrations of K +. The inhibition of cesium incorporation by Ca 2+, lack of influence of tetraethylammonium chloride and stimulation by high K + concentrations suggest that there may exist two pathways of passive transport of cesium in mycelium: (i) uptake mediated by a non-specific potassium channel localised in plasmalemma (similar to voltage-insensitive cation channel, VICC) followed by diffusive transport inside hyphae and (ii) extracellular transport from the medium through inter-hyphal cavities into fruitbodies. The results highlight distinctiveness of mechanisms responsible for the uptake and incorporation of cesium in mushrooms and plants.

Cesium-incorporated indium-tin-oxide films for use as a cathode with low work function for a transparent organic light-emitting device

Transparent organic light-emitting devices (TOLEDs) were successfully fabricated utilizing a novel transparent conducting cathode with low work function. Cesium-incorporated indium-tin-oxide film was deposited on the organic layers with negligible damage by simultaneous operation of RF magnetron sputtering using an ITO target and vacuum evaporation of metallic cesium. Incorporation of cesium in the ITO film was confirmed by XPS analysis. The work function (4.3 eV) determined by photoelectron spectroscopy in air (PESA) was lower than that of 0.3–0.4-eV without cesium-incorporation and stable under the atmospheric environment. The electron injection efficiency of cesium-incorporated ITO cathode in the present transparent OLED fabricated was comparable to that of the previous double-layered structure comprising of ITO cathode and an organic buffer layer (BCP) doped by evaporation of cesium [T. Uchida, S. Kaneta, M. Ichihara, M. Ohtsuka, T. Otomo, D.R. Marx, Jpn. J. Appl. Phys., 44, No. 9 (2005) L282].

Vapour phase O-alkylation of phenol over alkali promoted rare earth metal phosphates

The vapour phase synthesis of anisole by O-alkylation of phenol with methanol was investigated over lanthanum, cerium, samarium, and antimony phosphate catalysts promoted with cesium hydroxide. Among various catalysts investigated, the cesium promoted samarium phosphate provided better activity and selectivity. The effect of temperature, contact time, time-on-stream, reusability, and up-scaling of the catalyst were also studied. These studies clearly reveal that the Cs-Sm combination is the superior catalyst for selective O-alkylation of phenol with methanol. The unpromoted catalysts provided more C-alkylated side products. Incorporation of cesium suppressed the formation of side products. The X-ray diffraction analysis of various samples revealed that there is no change in the crystalline composition of the catalysts up on addition of cesium promoter. However, the surface acidity of the catalyst was observed to decrease after the incorporation of cesium promoter as revealed by the temperature programmed desorption study of anhydrous ammonia.

A comparison of cesium-containing heteropolyacid and sulfated zirconia catalysts for isomerization of light alkanes

The heteropolyacid H3PW12O40 and its cesium salts CsxH3-xPW12O40 (x = 1, 2, 2.5, 3) were synthesized, characterized and tested as catalysts for hydrocarbon reactions. All samples were characterized by a variety of techniques including elemental analysis, X-ray diffraction, dinitrogen adsorption, thermal gravimetric analysis and ammonia sorption. Results from these methods confirmed that pure cesium salts were prepared without significant contamination by amorphous oxide phases. Incorporation of cesium into the heteropolyacid decreased the acidic protons available for catalysis, increased the specific surface area, and increased the thermal stability. The heteropolyacids were tested as catalysts for butane skeletal isomerization, pentane skeletal isomerization and 1-butene double bond isomerization. For comparison, the activity of sulfated zirconia, a well-studied strong acid catalyst, was also evaluated for the three probe reactions. On a per gram basis, the Cs2HPW12O40 sample was the most active heteropolyacid, presumably due to its high surface area. This sample was more active than sulfated zirconia for pentane skeletal isomerization and 1-butene double bond isomerization. However, sulfated zirconia was more effective for butane skeletal isomerization. Since the pentane and 1-butene reactions were monomolecular in nature, whereas butane isomerization was bimolecular, restrictions inside the micropores of the heteropolyacid may inhibit the formation of long chain intermediates. Interestingly, trace butenes were required to initiate butane isomerization reactions on sulfated zirconia, whereas heteropolyacids catalyzed the reaction in the absence of butenes.

Layered structures with delta-doped layers for enhancement of field emission

The electron field emission, from silicon tip arrays with layer structures on their surfaces, was investigated. The main task of the study was to enhance field emission. The n–Si–SiO2, n–Si–Cs–SiO2,n–Si–SiO2–Si*–SiO2,n–Si–Si3N4–Si*–SiO2, etc., were among the different prepared layered structures. The thicknesses of dielectric layers were 1–5 nm and they were prepared both by thermal oxidation and by chemical vapor deposition (CVD). The cesium was deposited on the cathodes with the application of cesium salt (CsCl) in solution. The outer SiO2 layer prevents cesium from evaporating during heating or reaction under exposure to gases. The thin silicon layer (Si*) was formed by CVD. The measurements of electron field emission from layered structures show sufficient enhancement of emission in the case of using the delta-doped cesium layer. The incorporation of cesium is an important way to decrease the threshold voltage of cold cathodes, and in our case the use of a SiO2 layer allows us to stabilize the emission.

Initial stages of cesium incorporation on keV-Cs+-irradiated surfaces: Positive-ion emission and work-function changes.

The gradual incorporation of cesium into elemental samples of Al, Si, Nb, and Au bombarded with 5.5-keV ${\mathrm{Cs}}^{+}$ ions was investigated by monitoring the emission of sputtered positive ${\mathrm{Cs}}^{+}$ and molecular ions and the relative work-function changes (\ensuremath{\Delta}\ensuremath{\Phi}) induced from the shifts of secondary-ion energy distributions. With increasing Cs fluence and Cs surface concentration the work function is reduced, and reaches a stationary value at about 1\ifmmode\times\else\texttimes\fi{}${10}^{16}$ ${\mathrm{Cs}}^{+}$/ ${\mathrm{cm}}^{2}$ for Si and Al, 5\ifmmode\times\else\texttimes\fi{}${10}^{15}$ ${\mathrm{Cs}}^{+}$/${\mathrm{cm}}^{2}$ for Nb, and 1.5\ifmmode\times\else\texttimes\fi{}${10}^{15}$ ${\mathrm{Cs}}^{+}$/${\mathrm{cm}}^{2}$ for Au. The corresponding \ensuremath{\Delta}\ensuremath{\Phi} shifts then amount to -1.3\ifmmode\pm\else\textpm\fi{}0.1 eV for Al and Si, -0.9 eV for Nb, and -0.4 eV for Au. This lowering of the work function reduces the ionization probability of positive ${\mathrm{Cs}}^{+}$ ions by factors of about ten (Al), seven (Si), and three (Nb). In agreement with the electron-tunneling model of secondary-ion formation, this reduced ionization is observed only when the work function falls below a limiting value which is close to the ionization potential of Cs. Computer simulations of the Cs incorporation process result in stationary Cs surface concentrations of 12 at. % for Si, 10% for Al, 5.5% for Nb, and \ensuremath{\sim}2.5% for Au. These values scale inversely with these elements' sputtering yields. \textcopyright{} 1996 The American Physical Society.

Variabilité de la relation entre les pertes de césium et de sol par érosion hydrique

The relationship between 134Cs loss and soil erosion was investigated on two sites with different soil textures. Three successive applications of 3700 Bq m −2 were incorporated at two different depths. After each one of these applications, soil and cesium losses were measured following two simulated rainfalls. 134Cs losses increased with soil losses. A logarithmic relationship was developed between these two parameters. However, this relationship fluctuates depending on soil texture and soil tillage. 134Cs losses and sediment radioactivity were higher under shallow tillage than under deeper incorporation of cesium. The sediments coming from the light textured soil showed a greater enrichment in clay and organic matter, resulting in a higher activity in 134Cs. The addition of cesium with time increased the radioactivity of sediments and the specific losses of 134Cs. The relationship between cesium loss and soil erosion is therefore variable and may be influenced by numerous factors. Consequently, this variability should be considered when estimating soil movements from 137Cs data under field conditions.

Combined PIXE/RBS study on the incorporation and depth distribution of cesium in cuticles of pear leaves subject to cation exchange in a cscl solution

Enzymatically isolated cuticles of pear leaves were analysed by PIXE and RBS after storage in either a buffer solution containing CsCl or a reference solution without CsCl. Comparison of the composition of the samples passed through the different solutions showed that the potassium present in the reference sample can be replaced almost fully be cesium. RBS measurements revealed a strongly nonuniform cesium distribution with a peak at that side of the cuticle which was originally facing the interior of the leaf. A rough estimate of the depth scale as well as of the variation in thickness of the cuticle was obtained by analysing standards of cuticles and Mylar foils onto which a thin film of gold was vapour deposited. A close similarity between the depth distributions of Cs and (K + Cl) is evident from the RBS data. The study shows that combined PIXE/RBS measurements are required for a reasonably complete characterization of the cuticle composition.

Incorporation of Cesium by Hydrating Calcium Aluminosilicates

The leach behavior of cesium from a series of cement‐based waste forms has been modeled in terms of pore solution concentration and phase formation data. Cement‐based Materials enriched in alumina and silica, and compositionally related glasses, were hydrated in the presence of cesium hydroxide to gauge the degree of partitioning of cesium by the developing hydrates. The compositions of the pore solutions extracted from the cement‐based waste forms were compared both pore solution and leachates, the retention of cesium was found to be directly related to the bulk composition of the waste form; the degree of partitioning of cesium by the hydrated phases increased as more alumina and/or silica were added to the formulation, suggesting that cesium‐containing phases were forming. Additionally, the leachate concentration of cesium for any given composition was also found to be related to the pore solution concentration. This observation led to the development of a leaching model for cement‐based waste forms in which the concentration of cesium in the leachate could be described in terms of pore solution concentration, diffusion, dissolution, and development of cesium host phases. Using this model, effective diffusion coefficients for cesium were calculated to be ∼2 × 10−7 cm2· s−1. Pollucite and cesium‐substituted herschelite were identified as two of the hydration products of the studied glasses. The ability of these zeolites to strongly partition cesium suggests that small quantities of zeolitic phases may also be forming in the cement‐based waste forms, thus explaining their compositionally related leach behavior.

Kinetics of choline uptake in neuroblastoma clones

The uptake of choline has been investigated in an inactive clone (N 18) and in a cholinergic clone (S 21) of mouse neuroblastoma C1300. Choline uptake was linear with time and a saturation plateau appeared at about 120 min for clone N 18 and at 40 min for clone S 21. Sodium substitution inhibited the incorporation of choline, sucrose and cesium being more inhibitory than lithium. Potassium ferricyanide and ouabain inhibited the uptake in both clones. Two mechanisms, which differ for their affinity towards choline, have been revealed, with different substrate concentrations. Clone S 21 showed a high affinity component with an apparent K m which was much lower (1.1 × 10 −7 M) than the one presented by clone N 18(2.6 × 10 −6 M).