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A dissolution method for analyzing the elemental composition of fuel debris using the sodium peroxide (Na2O2) fusion technique has been developed. Herein, two different types of simulated fuel debris (such as solid solution of (Zr,RE)O2 and molten core – concrete interaction products (MCCI)) were taken. At various temperatures, these debris samples were subsequently fused with Na2O2 in crucibles, which are made of different materials (Ni, Al2O3, Fe, and Zr). Then, the fused samples are dissolved in nitric acid. Effects of the experimental conditions on the elemental composition analysis were evaluated using inductively coupled plasma-atomic emission spectroscopy (ICP – AES), which suggested the use of a Ni crucible at 923 K as an optimum testing condition. The optimum testing condition was then applied to the demonstration tests with Three Mile Island unit-2 (TMI-2) debris in a shielded concrete cell, thereby achieving complete dissolution of the debris. The elemental composition of TMI-2 debris revealed by the proposed dissolution method has good reproducibility and has an insignificant contradiction in the mass balance of the sample. Therefore, this newly developed dissolution method can be effectively utilized in practical applications by dissolving fuel debris and analyzing its elemental composition. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Inorganic Analytical Chemistry / Zhongguo Wuji Fenxi Huaxue is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The sodium‐air battery offers a sustainable, high‐energy alternative to lithium‐ion batteries. Discharge in the cell containing glyme‐based electrolytes can lead to formation of large cubic NaO2 particles via a solution‐precipitation mechanism. While promising, high rates result in sudden death. The exact nature of the discharge product has been a matter of contention, and Na2O2 has never been directly detected in a dry glyme Na−O2 cell. If Na2O2 were to form during discharge in the Na−O2 cell it would have a detrimental impact on cell performance. Here we show that Na2O2 forms during discharge at high overpotential in the glyme‐based Na−O2 batteries. Na2O2 formation is confirmed by spectroscopic and electrochemical analysis and electron microscopy demonstrates that it results in thin insulating films at the electrode surface. The formation of these thin films results in rapid cell death during discharge, introducing an inherent chemical limitation to the Na−O2 battery. [ABSTRACT FROM AUTHOR]

BACKGROUND The main types of primary tin ore occur in skarn, porphyry, cassiterite silicate vein, cassiterite sulfide vein, quartz vein and greisen tin deposits. Tin ores are generally insoluble in hydrochloric acid, nitric acid and aqua regia, and tin ores cannot be dissolved completely when treated with sulfuric acid or hydrofluoric acid. Traditional measurement methods such as phenylfluorone-cetyltrimethyl ammonium bromide spectrophotometry and iodometry have disadvantages, such as the serious interference of the associated elements in the sample, poor stability, high detection limit and low analysis efficiency. OBJECTIVES To establish a method for the determination of tin in primary ore by Inductively Coupled Plasma-Mass Spectrometry. METHODS The sample was melted and decomposed by sodium oxide, and leached by hot water, followed by tartaric acid and hydrochloric acid acidification. 103Rh was used as the internal standard element to correct instrument signal drift, and the matrix effect was overcome by high-dilution factors. RESULTS The detection limit of the method was 0.1μg/g for tin, the precision was less than 5%, the minimum detection concentration was 0.4μg/g, and the measurement range was 12.5-12700μg/g. CONCLUSIONS The method has simple pretreatment and operation. The analysis efficiency and data quality are an improvement over traditional methods.

The most common method for gold content determination in raw materials is fire assay. An alternative to this method is atomic absorption in a solution obtained by dissolving an initial sample in aqua regia. This study focuses on the sludge of one of the chemical plants, in which the barite concentrate (barium in sulphate form) is fused with calcium chloride at coal presence, and then leached in water. Decomposition of samples in aqua regia followed by atomic absorption analysis, as well as fire assay, showed gold content in the sludge at the level of 1-4 gram per ton. The presence of infusible and chemically resistant compounds in the sludge does not allow to the reliable determination of the gold content. Sintering with sodium peroxide for decomposition of stable compounds at 700 ° C, dissolution of sinter in acidic solution, evaporation and fire assay of residue made it possible to establish a reliable concentration of gold in the sludge - 10-20 gram per ton. It was found that a direct determination of gold in acidic sinter leach solution provides inadequate values associated with the influence of the background. [ABSTRACT FROM AUTHOR]

A novel strategy for selective recovery of chromium from ferronickel slag via microwave assisted sodium peroxide roasting followed by water leaching was proposed in this study. The experimental results showed that 94.21% of chromium was leached with 64.43% of sodium and 6.13% of silicon, while only 0.06 wt% chromium remained in the leaching residue when the mixture of ferronickel slag and sodium peroxide with the mass ratio of 1 was roasted at 600 °C for 20 min before leaching at 50 °C for 1 h with the liquid-to-solid ratio of 10 mL/g. In comparison with conventional roasting, the microwave roasting showed a much higher efficiency for recovering chromium from ferronickel slag with the recovery of chromium increased by 12.92%, resulting from the enhanced conversion of Cr 2 O 3 in the slag to NaCrO 2 and from the looser and more porous structure during the roasting process which was beneficial for subsequent water leaching. Unlabelled Image • A microwave roasting strategy was proposed for recovering Cr from ferronickel slag. • Microwave roasting promoted phase transformation of the slag during recovery of Cr. • The microwave-induced looser and more porous structure facilitated water leaching. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Inorganic Analytical Chemistry / Zhongguo Wuji Fenxi Huaxue is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

BACKGROUND: The main types of primary tin ore occur in skarn, porphyry, cassiterite silicate vein, cassiterite sulfide vein, quartz vein and greisen tin deposits. Tin ores are generally insoluble in hydrochloric acid, nitric acid and aqua regia, and tin ores cannot be dissolved completely when treated with sulfuric acid or hydrofluoric acid. Traditional measurement methods such as phenylfluorone-cetyltrimethyl ammonium bromide spectrophotometry and iodometry have disadvantages, such as the serious interference of the associated elements in the sample, poor stability, high detection limit and low analysis efficiency. OBJECTIVES:To establish a method for the determination of tin in primary ore by Inductively Coupled Plasma-Mass Spectrometry. METHODS: The sample was melted and decomposed by sodium oxide, and leached by hot water, followed by tartaric acid and hydrochloric acid acidification. 103Rh was used as the internal standard element to correct instrument signal drift, and the matrix effect was overcome by high-dilution factors. RESULTS: The detection limit of the method was 0.1μg/g for tin, the precision was less than 5%, the minimum detection concentration was 0.4μg/g, and the measurement range was 12.5-12700μg/g. CONCLUSIONS: The method has simple pretreatment and operation. The analysis efficiency and data quality are an improvement over traditional methods. [ABSTRACT FROM AUTHOR]

Recently we have highlighted the importance of hypergolic reactions in carbon materials synthesis. In an effort to expand this topic with additional new paradigms, herein we present novel preparations of carbon nanomaterials, such-like carbon nanosheets and fullerols (hydroxylated fullerenes), through spontaneous ignition of coffee-sodium peroxide (Na2O2) and C60-Na2O2 hypergolic mixtures, respectively. In these cases, coffee and fullerenes played the role of the combustible fuel, whereas sodium peroxide the role of the strong oxidizer (e.g., source of highly concentrated H2O2). The involved reactions are both thermodynamically and kinetically favoured, thus allowing rapid product formation at ambient conditions. In addition, we provide tips on how to exploit the released energy of such highly exothermic reactions in the generation of useful work.

For the sake of achieving the practical application of sodium‐ion batteries, extensive efforts have been made to improve the electrochemical performance of cathode materials. A simple co‐precipitation route is successfully developed to synthesize nanowires of transition metal hydroxides through a sodium peroxide pouring process instead of the traditional sodium hydroxide dropping approach. After a subsequent annealing process, a well‐crystallized P2‐Na0.56[Ni0.1Co0.1Mn0.8]O2 layered cathode material is obtained. Owing to such an exquisite architecture, this material possesses an excellent electrochemical performance, exhibits a reversible capacity of 188 mAh g−1 at 48 mA g−1 in the voltage range of 1.5‐4.1 V with nearly 99.7 % coulombic efficiency and retains approximately 80.2 % of the initial capacity after 50 cycles. Moreover, even at an extremely high current density of 2400 mA g−1, it delivers a capacity of 134 mAh g−1 and remains at 76 mAh g−1 after 1500 cycles, which surpasses most reported layered transition metal oxide cathode materials. This strategy of providing a strong oxidizing environment during the co‐precipitation process is especially crucial for obtaining materials with excellent electrochemical performances for future energy storage application. Layer cake: A P2‐type layered transition metal oxide cathode for sodium‐ion batteries is prepared through a co‐precipitation method, using the sodium peroxide as precipitant to provide an oxidation environment, increasing the content of Mn4+. This material shows a better morphology, structure, and electrochemical performance, which reveals a reversible capacity of 134 mAh g−1 at 2400 mA g−1 and retains 76 mAh g−1 after 1500 cycles. [ABSTRACT FROM AUTHOR]

Abstract: The sodium oxygen battery is a promising metal–air battery; however, the discharge process is not well understood and the major discharge product is still under debate. The discharge products determined the theoretical specific energy and electrochemical performance of the battery. Now it is demonstrated that NaO2 spontaneously disproportionates to Na2O2, no matter whether it is dissolved in solution or stays on the surface. The behaviors of NaO2 in solution and on the surface are different. Solvents play a crucial effect on the disproportionation of dissolved NaO2 species, which is fast in low donor number (DN) solvents such as acetonitrile but sluggish in high DN solvents such as DMSO. In situ XRD results exhibited the different product growing processes in various solvents. Surface NaO2 would slowly disproportionate to Na2O2 anyway, but this process is relatively slow compared to the time span of discharge process and it does not affect the major product on discharge. [ABSTRACT FROM AUTHOR]

A protocol based on peroxide fusion has been developed for the determination of Au in metallurgical samples and ores covering a wide range of concentrations and diverse mineralogies. The quantity of Na 2 O 2 required was minimised, while maintaining lixiviant efficacy, by the use of mixed NaOH + Na 2 O 2 fluxes. The method was shown to be particularly applicable to the determination of coarsely-particulate gold. Fusion cakes were dissolved in hydrochloric acid and then extracted using methylisobutylketone to provide concentrations appropriate for quantification by graphite furnace atomic absorption spectroscopy and to minimise interferences from dissolved salts. The protocol was tested on a variety of certified reference materials and produced results in excellent agreement (at Au concentrations ranging from 0.05 to 47 μg g − 1 ) with the traditional lead fire assay method, while avoiding the health and safety issues associated with that technique. [ABSTRACT FROM AUTHOR]

The aluminum induced texturing method offers an effective light trapping scheme by random texture that is formed by U-shaped craters on the glass surface. The texture is mainly shaped by the reaction between Al and SiO 2 . However, the reaction mechanism is not totally understood. Besides, the influence of other components present in the glass such as Na 2 O, CaO, and MgO. is neglected. In this study, the evolution of Al films on soda-lime glass during annealing has been inspected by depth resolved X-ray photoelectron spectroscopy. The elemental distribution of Si, Al and O have been investigated for different annealing durations and compositional analysis has been conducted for Na, Ca and Mg in addition to Si, Al and O. According to results, a relevant evolution model for annealing process has been constructed. [ABSTRACT FROM AUTHOR]

Sodium-based catalysts (such as Na2WO4) were proposed to selectively catalyze OH radical formation from H2O and O2 at high temperatures. This reaction may proceed on molten salt state surfaces owing to the lower melting point of the used Na salts compared to the reaction temperature. This study provides direct evidence of the molten salt state of Na2WO4, which can form OH radicals, using in situ techniques including X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), laser induced fluorescence (LIF) spectrometry, and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). As a result, Na2O2 species, which were hypothesized to be responsible for the formation of OH radicals, have been identified on the outer surfaces at temperatures of ≥800 °C, and these species are useful for various gas-phase hydrocarbon reactions, including the selective transformation of methane to ethane. [ABSTRACT FROM AUTHOR]

It is an unsolved problem how to steer between sodium superoxide and sodium peroxide as discharge products in sodium-oxygen batteries. Sodium peroxide yields a higher theoretical energy density; thus, it is preferred in view of maximized energy density. Three novel approaches to form sodium peroxide are presented: First, cells loaded with sodium superoxide are further discharged in argon, with the aim of reducing sodium superoxide to peroxide. Second, carbon nanotube electrodes preloaded with sodium peroxide are utilized. Third, sodium peroxide is dissolved in the electrolyte to enhance precipitation of solid sodium peroxide. Interestingly, all approaches yield sodium superoxide as a discharge product. Thus, it might not be possible to have high energy density sodium-oxygen batteries with sodium peroxide as the discharge product. However, potential pathways for peroxide formation during discharge have been excluded to help to find the true factors that govern the competition between superoxide and peroxide formation. [ABSTRACT FROM AUTHOR]

A novel dietary fiber (MsCDF) based core of maize straw (Core) was prepared by using high boiling solvent of sodium peroxide by high pressure pretreatment (HBSHP). The composition of MsCDF, and several physicochemical properties for MsCDF related to its nutritional quality were investigated. The results revealed that the MsCDF contains high contents total dietary fiber (TDF), soluble dietary fiber (SDF), insoluble dietary fiber (IDF) and two main monosaccharaides, xylose and glucose. Meanwhile, the studies of physicochemical properties of MsCDF indicated that MsCDF performed well water-holding capacity (WHC), oil-holding capacity (OHC), Swelling, solubility (SOL), Glucose dialysis retardation index (GDRI) and adsorption capacity on cholesterol. The results of this study serve as evidence that MsCDF can be used as a functional food additive, Core can be used as a crude material to produce MsCDF and the technology of HBSHP can be used to modify the physico-chemical properties of Core. [ABSTRACT FROM AUTHOR]

Bauxite has strong chemical stability, which often contains a small amount of corundum. Therefore, samples are classified to refractory samples by the method of inductive coupled plasma-optical emission spectrometry. The routine 4 acids digestion system works well for non-corundum bearing bauxite, but cannot completely digest the high Al and corundum bearing bauxite and simultaneously determine Si. Four elements of Si, Al, Fe and Ti in bauxite were simultaneously quantified by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) after the samples were digested in a Nickel Crucible with NaOH-Na2O2 and acid treated. The melting effect, dosage of Na2O2, temperature, elementary spectral lines, coexisting ions, matrix interference and elimination of melting samples are discussed in this paper. The results show that corundum bearing bauxite samples are completely melted with 3.0 g NaOH and 1.0 g Na2O2 at 650-700℃ for 10 minutes. The standard solution prepared by national bauxite standard material is good to eliminate the matrix interferences for Si, Al, Fe and Ti measurements. The detection limits are 0.0025%-0.063%, and the precisions (RSD, n=11) are 0.15%-3.05%. The measured values of national standard materials were consistent with the certified values, and the measured values of actual samples were consistent with the values by the other methods. This method has the advantages of completely decomposing the sample, having a short digesting time, is simple for analysis procedure, rapid, accurate, has a wide range for determination content and is especially suitable for high Al or corundum bearing bauxite samples.

Background: The color change on post-endodontic treated teeth can be overcome by intracoronal tooth bleaching using walking bleach. Some agents used in walking bleach are combination of sodium peroxide and hydrogen peroxide, and combination of sodium perborate and water. Purpose: The objective of this review is to provide information and consideration of using safe and effective bleaching agents in the field of dentistry. Reviews: On one side, the use of sodium perborate and water combination does not cause the reduction of dentin hardness, enamel decay, and root resorbtion. On the other side, the use of sodium perborate and 30% hydrogen peroxide combination indicates that it takes longer time in yielding the proper color of teeth. Conclusion: The use of sodium perborate and water combination as bleaching agents is effective and safe.

23Na MAS NMR spectra of sodium-oxygen (Na-O2) cathodes reveals a combination of degradation species: newly observed sodium fluoride (NaF) and the expected sodium carbonate (Na2CO3), as well as the desired reaction product sodium peroxide (Na2O2). The initial reaction product, sodium superoxide (NaO2), is not present in a measurable quantity in the 23Na NMR spectra of the cycled electrodes. The reactivity of solid NaO2 is probed further, and NaF is found to be formed through a reaction between the electrochemically generated NaO2 and the electrode binder, polyvinylidene fluoride (PVDF). The instability of cell components in the presence of desired electrochemical reaction products is clearly problematic and bears further investigation. [ABSTRACT FROM AUTHOR]

The data presented here refer to 60 g melts of glass of composition in wt%, 73·5 SiO2, 10·0 CaO, 16·5 Na2O, founded in platinum in an electric furnace at 1400 and 1450°C. There was no significant convection of the melt. Melts were made at 1400° C, containing all possible combinations of 0, 0·10 and 0·50% As2O3 with 0, 1·00 and 5·00% Na2O supplied as sodium peroxide. Four of these combinations were investigated in detail at 1400°C and two at 1450°C. By counting the seed remaining in 30 g slabs cast from melts founded for different times it was possible to construct graphs showing the decrease of total number (N) of seed per cm3 with time. This relation was approximately, but not exactly, exponential. The refining agents affected the number of seed present at the beginning of refining as well as the rate of refining; because of this it was concluded thatmelting and refining could not be considered as two independent processes. Measurements of seed size distributions allowed the decrease of the number of seed per cm3 (n), of given diameter (x), with time to be plotted. Most of the data were well fitted by an exponential relation between n and t. The refining agents altered the shapes of the seed size distributions and the rates at which seed disappeared. Small seed disappeared more slowly in melts containing 0·50% As2O3 and 5·0% Na2O as Na2O2 than in melts containing 0·50% As2O3 and 1·0% Na2O as Na2O2. This suggested that it was possible to supply too much oxygen for any given addition of As2O3. Raising the temperature had effects similar to some combinations of refining agents, affecting seed size distributions and rates of disappearance of seed. [ABSTRACT FROM AUTHOR]

Metal air batteries are considered as promising candidates for room-temperature batteries with high-energy densities. On discharge, atmospheric oxygen is reduced at the positive electrode which, in the ideal case, forms the discharge products in a reversible cell reaction. In Na-O 2 batteries upon discharge either sodium peroxide (Na 2 O 2 ) or sodium superoxide (NaO 2 ) is reported to be formed. So far, the charge carrier transport remains relatively unexplored but is expected to crucially determine the efficiency of such energy storage systems. Na 2 O 2 is predicted to be an electrical insulator wherein the transport presumably is determined by very slow hopping processes. Understanding the basic fundamental properties of the overall charge carrier transport, including also nanostructured forms of Na 2 O 2 , is key to developing high-energy metal oxygen batteries. The present study answers the question how overall, i.e. , total, conductivity changes when going from microcrystalline to nanocrystalline, defect-rich Na 2 O 2 . Nanocrystalline Na 2 O 2 was prepared via a top-down approach, viz by high-energy ball milling. Milling does not only shrink the average crystallite diameter but also introduces a large amount of defects which are anticipated to influence total conductivity. It turned out that even after vigorous mechanical treatment the conductivity of the sample is only increased by ca. one order of magnitude. The activation energy remains almost untouched. Thus, the increase seen might be attributed to an enhanced number of charge carriers. Low-temperature data reveals nearly constant loss relaxation behavior which has frequently explained in terms of strictly localized electrical relaxation processes. [ABSTRACT FROM AUTHOR]

Although Na-O2 batteries have a low overpotential and good capacity retention, degradation reactions of glyme-based electrolytes are the primary reason for inefficiency in cell performance. The discharge capacity is accounted for through analysis of the side-products. Although sodium superoxide is the primary product (90 % theoretical), quantitative and qualitative evaluation of the side-products (using 1H NMR, iodometric titration, and on-line mass spectrometry) shows the presence of sodium acetate (∼3.5 %), and three-fold less sodium formate, methoxy (oxo)acetic anhydride, and sodium carbonate. Our reaction mechanism proposes two paths for their formation. Because the side-products are not fully removed during oxidation, they accumulate on the cathode upon cycling. Resting the cell at open circuit potential during discharge results in consumption of the superoxide through the reaction with diglyme, which greatly increases the fraction of side products, as also confirmed by ex situ reaction studies. These findings have implications in the search for more stable electrolytes. [ABSTRACT FROM AUTHOR]

Sodium peroxide (Na 2 O 2 ) fusion coupled to Inductively Coupled Plasma Tandem Mass Spectrometry (ICP-MS/MS) measurements was used to rapidly screen quartz-rich geological samples for rare earth element (REE) content. The method accuracy was checked with a geological reference material and Instrumental Neutron Activation Analysis (INAA) measurements. The used mass-mode combinations presented accurate results (only exception being 157 Gd in He gas mode) with recovery of the geological reference material QLO-1 between 80% and 98% (lower values for Lu, Nd and Sm) and in general comparable to INAA measurements. Low limits of detection for all elements were achieved, generally below 10 pg g −1 , as well as measurement repeatability below 15%. Overall, the Na 2 O 2 /ICP-MS/MS method proved to be a suitable lab-based method to quickly and accurately screen rock samples originating from quartz-rich geological areas for rare earth element content; particularly useful if checking commercial viability. [ABSTRACT FROM AUTHOR]

The primary dischargeproduct in sodium–air batteries hasbeen reported in some experiments to be sodium peroxide, Na2O2, while in others sodium superoxide, NaO2, is observed. Importantly, cells that discharge to NaO2exhibit low charging overpotentials, while those that dischargeto Na2O2do not. These differences could arisefrom a higher conductivity within the superoxide; however, this explanationremains speculative given that charge transport in superoxides isrelatively unexplored. Here, density functional and quasi-particleGW methods are used to comparatively assess the conductivities ofNa–O2discharge phases by calculating the concentrationsand mobilities of intrinsic charge carriers in Na2O2and NaO2. Both compounds are predicted to be electricalinsulators, with bandgaps in excess of 5 eV. In the case of sodiumperoxide, the transport properties are similar to those reported previouslyfor lithium peroxide, suggesting low bulk conductivity. Transportin the superoxide has some features in common with the peroxide butalso differs in important ways. Similar to Na2O2, NaO2is predicted to be a poor electrical conductor,wherein transport is limited by sluggish charge hopping between O2dimers. Different from Na2O2, in NaO2this transport is mediated by a combination of electron andhole polarons. An additional distinguishing feature of the superoxideis its ionic conductivity, which is 10 orders of magnitude largerthan the electronic component. The ionic component is comprised primarilyof p-type contributions from (surprisingly mobile) oxygen dimer vacancies,and from n-type contributions from negative sodium vacancies. In thecontext of sodium–air batteries, the low electronic conductivityafforded by NaO2suggests that enhanced bulk transportwithin this phase is unlikely to account for the low overpotentialsassociated with its decomposition. Rather, the enhanced efficiencyof NaO2-based cells should be attributed to other factors,such as a reduced tendency for electrolyte decomposition. [ABSTRACT FROM AUTHOR]

Batteries based on the cell reaction between alkali metals and oxygen are highly attractive for energy storage due to their superior theoretical energy density. However, despite continuous progress, fundamental challenges in the further development of these cell systems remain. Understanding the oxygen electrode reaction and improving cycle life, while at the same time maximizing the practical energy density, are some of the most important issues that need to be addressed. Here, the product formation in aprotic sodium-oxygen cells is studied and it is shown how cycle life and practical capacities can be improved. Different cell reactions (leading to either NaO2 or Na2O2 as discharge products) have recently been reported. To understand whether the carbon structure or the local current density has any influence on the product stoichiometry or the cell performance, several carbon materials with a broad range in properties are tested. Phase-pure NaO2 is always found as a discharge product, but capacities range from 300 to values as high as 4000 mAh g(C)−1 depending on the type of carbon. More importantly, the cycle life of Na/O2 cells can be largely improved by shallow cycling, steadily yielding capacities of 1666 mAh g(C)−1 for at least 60 cycles using a Ketjen black carbon electrode. [ABSTRACT FROM AUTHOR]

The thermodynamic stability of materialscan depend on particlesize due to the competition between surface and bulk energy. In thisLetter, we show that, while sodium peroxide (Na2O2) is the stable bulk phase of Na in an oxygen environment at standardconditions, sodium superoxide (NaO2) is considerably morestable at the nanoscale. As a consequence, the superoxide requiresa much lower nucleation energy than the peroxide, explaining why itcan be observed as the discharge product in some Na–O2batteries. As the superoxide can be recharged (decomposed) at muchlower overpotentials than the peroxide, these findings are importantto create highly reversible Na–O2batteries. Wederive the specific electrochemical conditions to nucleate and retainNa-superoxides and comment on the importance of considering the nanophasethermodynamics when optimizing an electrochemical system. [ABSTRACT FROM AUTHOR]

Various compositions of oxo derivatives of iron reacting with sodium peroxide have been studied by Mössbauer spectroscopy. We have examined several mathematical models of the measured spectra. The results obtained are inconsistent with hypotheses made previously that such conditions may lead to the formation of compounds of iron in oxidation states above (6+). We demonstrate that a large excess of an alkali peroxide leads, most likely, to the formation of at least two iron(V) derivatives in tetrahedral coordination. In their Mössbauer spectra, they have isomer shifts of −0.45 and −0.51 mm/s and unusually large quadrupole splittings: 1.32 and 1.94 mm/s (at room temperature). [ABSTRACT FROM AUTHOR]

Highlights: [•] Interaction of O2 species with Na metal is studied. [•] Electrostatic interaction affects the binding process and complex geometries. [•] Na+/0·O2 complex has the strongest binding energy and shortest Na---O bond length. [•] Na·(O2)1–4 complexes have stronger binding energies than Na+·(O2)1–4 complexes. [•] Na·(O2)1–4 complexes have different geometries than those of Na ion complexes. [ABSTRACT FROM AUTHOR]

Using a linear combination of atomic orbitals within the CRYSTAL09 software code, the oscillation frequencies of the atoms of lithium, sodium, and potassium peroxides are calculated. In a quasiharmonic approximation of the Debye model, the thermodynamic potentials, entropy, thermal capacity, and the coefficient of thermal expansion are calculated, and their dependence on pressure and temperature is investigated. Using sodium peroxide as an example, the critical point for the sublimation process is found. [ABSTRACT FROM AUTHOR]

Zircon is an accessory mineral, which occurs at low concentrations in a wide variety of rocks and is a host for hafnium, rare-earth elements (REE) and radio active elements like uranium and thorium. The presence of uranium in zircon has led to its increased use in the age determination of rocks. Zirconium is also considered as a strategic, hi-tech element because of its various applications, especially in the manufacturing, nuclear and aerospace industries. Analysis of zircon constitutes one of the tough tasks in analytical chemistry as it is a highly resistant mineral and it is extremely difficult to achieve its complete decomposition. In the present work, inductively coupled plasma mass spectrometry has been applied to the determination of hafnium, REE, uranium and thorium in zircon samples using two different sample dissolution procedures, one employing sodium peroxide fusion and another using a fusion mixture of KHF and NaF in 3:1 ratio. Some selected zircon samples originating from different places on the eastern coast of India have been analysed by both the methods and values obtained by both methods were found to be in good agreement with each other. Though a number of international zircon reference materials are available, certified or even proposed values are available only for a very few elements in them. Two zircon reference materials have also been analysed by both methods and usable values have been proposed in this paper. The values obtained by both methods were found to compare well with each other and as well with those reported in literature. The % RSD for all the estimated elements varied from 1.0 to 12.0% at different concentration levels. [ABSTRACT FROM AUTHOR]

In this article, Fe3O4 nanoparticles (2.2 -12.1 nm) were prepared by partial oxidation of Fe2+ ion using sodium peroxide as oxidizing agent in the presence of ammonium hydroxide and ammonium oleate as precipitating reagent and capping agent, respectively. The synthesized products were characterized by XRD, LLS, EDX, TEM, FTIR and chemical analysis. The main effective factors on the formation of smaller average particle size of Fe3O4 nanoparticles were optimized using the L8 Taguchi experimental design. The magnetic behavior of Fe3O4 nanoparticles was determined using vibrating sample magnetometer (VSM) at 300 K. [ABSTRACT FROM PUBLISHER]

Sample digestion is a critical stage in the process of chemical analysis of geological materials by ICP-MS. We present a new HF/HNO3 procedure to dissolve silicate rock samples using a high pressure asher system. The formation of insoluble AlF3 was the major obstacle in achieving full recoveries. This was overcome by setting an appropriate digestion temperature and adding Mg to the samples before digestion. Sodium peroxide sintering was also investigated and the inclusion of a heating step to the alkaline sinter solution improved the recoveries of thirteen elements other than the lanthanides. The results of these procedures were compared with data sets generated by common acid decomposition techniques. Forty-one trace elements were determined using an ICP-QMS equipped with a collision cell. Under optimum conditions of gas flow and kinetic energy discrimination, polyatomic interferences were eliminated or attenuated. The measurement bias obtained for eight reference materials (BCR-2, BHVO-2, BIR-1, BRP-1, OU-6, GSP-2, GSR-1 and RGM-1) and intermediate precision (RSD) were generally better than ± 5%. The expanded measurement uncertainties estimated for two certified reference materials were mostly between 7 and 15%. New data sets for the reference materials are provided, including constituents with previously unavailable values and also for the USGS candidate reference material G-3. [ABSTRACT FROM AUTHOR]

Plutonium oxide (PuO2) calcined at >900 °C resists dissolution in nitric acid (HNO3)-potassium fluoride (KF) solutions commonly used for their dissolution. The Savannah River National Laboratory (SRNL) has developed an alternate method for large samples of PuO2-bearing materials using sodium peroxide (Na2O2) fusion as a pretreatment. The products of the reaction between Na2O2and PuO2have been reported in the literature. As part of the SRNL development effort, additional data about the reaction between Na2O2and PuO2were required. Also needed were data concerning the reaction of Na2O2with other components that may be present in the feed materials. Sodium peroxide was reacted with aluminum metal (Al), beryllium metal (Be), graphite, potassium chloride (KCl), magnesium chloride (MgCl2), and calcium chloride (CaCl2). The paper reports and discusses the reaction products of these and related compounds with Na2O2. [ABSTRACT FROM AUTHOR]

Three Cucurbit[7]uril-controlled chemiluminescent on/off switches based on the lucigenin motif have been synthesized. Light emission is triggered upon addition of sodium peroxide, interrupted or dimmed in the presence of Cucurbit[7]uril, and restored upon injection of a competitive guest. The process, which can be mimicked by a simple resistor-capacitor circuit, is rationalized by examining the role of the macrocyclic host on the network of equilibria involved in the chemiluminescent process. [ABSTRACT FROM AUTHOR]