Multicomponent exciton gas in cuprous oxide: cooling behaviour and the role of Auger decay

Science.gov (United States)

Semkat, D.; Sobkowiak, S.; Schöne, F.; Stolz, H.; Koch, Th; Fehske, H.

2017-10-01

In this paper we present a hydrodynamic model to describe the dynamics of para- and orthoexcitons in cuprous oxide at ultralow temperatures inside a stress induced potential trap. We take into account the finite lifetime of the excitons, the excitation process and exciton-phonon as well as exciton-exciton interaction. Furthermore, we model the two-body loss mechanism assuming an Auger-like effect and compare it to an alternative explanation which relies on the formation of biexcitons. We discuss in detail the influence on the numerical results and compare the predictions to experimental data.

Cuprous oxide nanoparticles selectively induce apoptosis of tumor cells

Directory of Open Access Journals (Sweden)

Wang Y

2012-05-01

Full Text Available Ye Wang,1,2,* Xiao-Yuan Zi,1,* Juan Su,1 Hong-Xia Zhang,1 Xin-Rong Zhang,3 Hai-Ying Zhu,1 Jian-Xiu Li,1 Meng Yin,3 Feng Yang,3 Yi-Ping Hu,11Department of Cell Biology, 2School of Clinical Medicine, 3Department of Pharmaceuticals, Second Military Medical University, Shanghai, People's Republic of China*Authors contributed equally.Abstract: In the rapid development of nanoscience and nanotechnology, many researchers have discovered that metal oxide nanoparticles have very useful pharmacological effects. Cuprous oxide nanoparticles (CONPs can selectively induce apoptosis and suppress the proliferation of tumor cells, showing great potential as a clinical cancer therapy. Treatment with CONPs caused a G1/G0 cell cycle arrest in tumor cells. Furthermore, CONPs enclosed in vesicles entered, or were taken up by mitochondria, which damaged their membranes, thereby inducing apoptosis. CONPs can also produce reactive oxygen species (ROS and initiate lipid peroxidation of the liposomal membrane, thereby regulating many signaling pathways and influencing the vital movements of cells. Our results demonstrate that CONPs have selective cytotoxicity towards tumor cells, and indicate that CONPs might be a potential nanomedicine for cancer therapy.Keywords: nanomedicine, selective cytotoxicity, apoptosis, cell cycle arrest, mitochondrion-targeted nanomaterials

A Cuprous Oxide Thin Film Non-Enzymatic Glucose Sensor Using Differential Pulse Voltammetry and Other Voltammetry Methods and a Comparison to Different Thin Film Electrodes on the Detection of Glucose in an Alkaline Solution

Directory of Open Access Journals (Sweden)

Yifan Dai

2018-01-01

Full Text Available A cuprous oxide (Cu2O thin layer served as the base for a non-enzymatic glucose sensor in an alkaline medium, 0.1 NaOH solution, with a linear range of 50–200 mg/dL using differential pulse voltammetry (DPV measurement. An X-ray photoelectron spectroscopy (XPS study confirmed the formation of the cuprous oxide layer on the thin gold film sensor prototype. Quantitative detection of glucose in both phosphate-buffered saline (PBS and undiluted human serum was carried out. Neither ascorbic acid nor uric acid, even at a relatively high concentration level (100 mg/dL in serum, interfered with the glucose detection, demonstrating the excellent selectivity of this non-enzymatic cuprous oxide thin layer-based glucose sensor. Chronoamperometry and single potential amperometric voltammetry were used to verify the measurements obtained by DPV, and the positive results validated that the detection of glucose in a 0.1 M NaOH alkaline medium by DPV measurement was effective. Nickel, platinum, and copper are commonly used metals for non-enzymatic glucose detection. The performance of these metal-based sensors for glucose detection using DPV were also evaluated. The cuprous oxide (Cu2O thin layer-based sensor showed the best sensitivity for glucose detection among the sensors evaluated.

Preparing cuprous oxide nanomaterials by electrochemical method for non-enzymatic glucose biosensor

Science.gov (United States)

Nguyen, Thu-Thuy; Huy, Bui The; Hwang, Seo-Young; Vuong, Nguyen Minh; Pham, Quoc-Thai; Nghia, Nguyen Ngoc; Kirtland, Aaron; Lee, Yong-Ill

2018-05-01

Cuprous oxide (Cu2O) nanostructure has been synthesized using an electrochemical method with a two-electrode system. Cu foils were used as electrodes and NH2(OH) was utilized as the reducing agent. The effects of pH and applied voltages on the morphology of the product were investigated. The morphology and optical properties of Cu2O particles were characterized using scanning electron microscopy, x-ray diffraction, and diffuse reflectance spectra. The synthesized Cu2O nanostructures that formed in the vicinity of the anode at 2 V and pH = 11 showed high uniform distribution, small size, and good electrochemical sensing. These Cu2O nanoparticles were coated on an Indium tin oxide substrate and applied to detect non-enzyme glucose as excellent biosensors. The non-enzyme glucose biosensors exhibited good performance with high response, good selectivity, wide linear detection range, and a low detection limit at 0.4 μM. Synthesized Cu2O nanostructures are potential materials for a non-enzyme glucose biosensor.

Preparation of 3D nanoporous copper-supported cuprous oxide for high-performance lithium ion battery anodes.

Science.gov (United States)

Liu, Dequan; Yang, Zhibo; Wang, Peng; Li, Fei; Wang, Desheng; He, Deyan

2013-03-07

Three-dimensional (3D) nanoporous architectures can provide efficient and rapid pathways for Li-ion and electron transport as well as short solid-state diffusion lengths in lithium ion batteries (LIBs). In this work, 3D nanoporous copper-supported cuprous oxide was successfully fabricated by low-cost selective etching of an electron-beam melted Cu(50)Al(50) alloy and subsequent in situ thermal oxidation. The architecture was used as an anode in lithium ion batteries. In the first cycle, the sample delivered an extremely high lithium storage capacity of about 2.35 mA h cm(-2). A high reversible capacity of 1.45 mA h cm(-2) was achieved after 120 cycles. This work develops a promising approach to building reliable 3D nanostructured electrodes for high-performance lithium ion batteries.

Controlling the Optical and Magnetic Properties of Nanostructured Cuprous Oxide Synthesized from Waste Electric Cables

Science.gov (United States)

Abdelbasir, S. M.; El-Sheikh, S. M.; Rashad, M. M.; Rayan, D. A.

2018-03-01

Cuprous oxide Cu2O nanopowders were purposefully synthesised from waste electric cables (WECs) via a simple precipitation route at room temperature using lactose as a reducing agent. In this regard, dimethyl sulfoxide (DMSO) was first applied as an organic solvent for the dissolution of the cable insulating materials. Several parameters were investigated during dissolution of WECs such as dissolution temperature, time and solid/liquid ratio to determine the dissolution percentage of the insulating materials in DMSO. The morphology and the optical properties of the formed Cu2O particles were investigated using X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy and UV-visible-near IR spectrophotometer. XRD data confirmed the presence of single crystalline phase of Cu2O nanoparticles. FE-SEM and TEM images revealed spherical, cubic and octahedral shapes with the various particle sizes ranged from 16 to 57 nm depending on the synthesis conditions. A possible mechanism explaining the Cu2O nanostructures formation was proposed. The band gap energies of the Cu2O nanostructures were estimated and the values were located between 1.5 and 2.08 eV. Photoluminescence spectroscopy analysis clearly showed a noticeably blue-shifted emission for the synthesized samples compared to spectrum of the bulk. Eventually, magnetic properties of the synthesized nanoparticles have been measured by vibrating sample magnetometer and the attained results implied that the synthesized particles are weakly ferromagnetic in nature at normal temperature.

Facile synthesis of cuprous oxide nanowires decorated graphene oxide nanosheets nanocomposites and its application in label-free electrochemical immunosensor.

Science.gov (United States)

Wang, Huan; Zhang, Yong; Wang, Yulan; Ma, Hongmin; Du, Bin; Wei, Qin

2017-01-15

In this work, the assembly between one-dimensional (1D) nanomaterials and two-dimensional (2D) nanomaterials was achieved by a simple method. Cuprous oxide nanowires decorated graphene oxide nanosheets (Cu 2 O@GO) nanocomposites were synthesized for the first time by a simple electrostatic self-assembly process. The nanostructure was well confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM) images. Taking advantages of good electrocatalytic activity and high specific surface area of Cu 2 O@GO nanocomposites, a label-free electrochemical immunosensor was developed by employing Cu 2 O@GO as signal amplification platform for the quantitative detection of alpha fetoprotein (AFP). In addition, toluidine blue (TB) was used as the electron transfer mediator to provide the electrochemical signal, which was adsorbed on graphene oxide nanosheets (GO NSs) by electrostatic attraction. The detection mechanism was based on the monitoring of the electrochemical current response change of TB by the square wave voltammetry (SWV) when immunoreaction occurred on the surface of electrode. Under optimal conditions, the proposed immunosensor displayed a high sensitivity and a low detection limit. This designed method may provide an effective method in the clinical diagnosis of AFP and other tumor markers. Copyright © 2016 Elsevier B.V. All rights reserved.

Stability of sputter deposited cuprous oxide (Cu2O) subjected to ageing conditions for photovoltaic applications

Science.gov (United States)

Camacho-Espinosa, E.; Rimmaudo, I.; Riech, I.; Mis-Fernández, R.; Peña, J. L.

2018-02-01

Among various metal oxide p-type semiconductors, cuprous oxide (Cu2O) stands out as a nontoxic and abundant material, which also makes it a suitable candidate as a low-cost absorber for photovoltaic applications. However, the chemical stability of the absorber layer is critical for the solar cell lifetime, in particular, for Cu-based materials, concerning to its oxidation state changes. In this paper, we addressed the Cu2O stability depositing films of 170 nm by reactive radio frequency magnetron sputtering and subsequently ageing them in conditions similar to the typical accelerated life test for the solar module, in a period of time from one to five weeks. The stability of the optical, electrical, and structural properties of the Cu2O thin films was investigated using UV-VIS-near infrared transmittance, 4-probes electrical resistance characterization, high precision profilometry, X-ray photoelectron spectroscopy, and grazing incidence X-ray diffraction. Finally, we demonstrated that the aging tests affected only the surface of the films, while the bulk remained unaltered, making Cu2O a promising candidate for production of stable devices, including solar cells.

Cathodoluminescence and ion implantation of cadmium sulphide/cuprous sulphide solar cells

Energy Technology Data Exchange (ETDEWEB)

Glew, R W; Bryant, F J

1975-10-01

By the use of implantation with copper ions or oxygen ions of 50 keV energy, changes in the cathodoluminescence emission spectrum from cadmium sulfide/cuprous sulfide thin film manufactured solar cells have been correlated with changes in the phases of the cuprous sulfide layer. Thus, monitoring the relative intensities of cathodoluminescence emission bands affords a method of assessing the cuprous sulfide layer and possibly predicting the performance of the cells.

Reduced graphene oxide–cuprous oxide composite via facial deposition for photocatalytic dye-degradation

Energy Technology Data Exchange (ETDEWEB)

Wang, MingYan, E-mail: mingyanlyg@hotmail.com [Department of Chemical Engineering, Huaihai Institute of Technology, Lianyungang 222005 (China); Intelligent Polymer Research Institute, ARC Centre of Excellence for Electromaterials Science, Australian Institute of Innovative Materials, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522 (Australia); Huang, JunRao; Tong, ZhiWei [Department of Chemical Engineering, Huaihai Institute of Technology, Lianyungang 222005 (China); Li, WeiHua [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522 (Australia); Chen, Jun, E-mail: junc@uow.edu.au [Intelligent Polymer Research Institute, ARC Centre of Excellence for Electromaterials Science, Australian Institute of Innovative Materials, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522 (Australia)

2013-08-15

Highlights: •Cubic Cu{sub 2}O were effectively loaded on n-propylamine (PA) intercalated graphene oxide. •The addition of PA on the carbon sheets supports the stable structure of the composites. •Cu{sub 2}O/PA/rGO showed superior adsorption capacity and photocatalytic activity. -- Abstract: Cubic Cu{sub 2}O nanoparticles have been successfully synthesized on n-propylamine (PA) intercalated graphene oxide (GO) with uniform distribution followed with a subsequent hydrazine hydrate reduction process to generate Cu{sub 2}O/PA/rGO composite. For comparison, Cu{sub 2}O conjugated reduced graphene oxide (Cu{sub 2}O/rGO) composite was also synthesized using the same method. The as-prepared Cu{sub 2}O/PA/rGO and Cu{sub 2}O/rGO nanocomposites are characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) spectroscopy, infrared spectroscopy (IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface area analysis, and Electrochemical impedance spectra (EIS) measurements. UV/vis diffuse reflectance spectroscopy was employed to estimate band gap energies of cuprous oxide composites. The results show that the intercalation of PA into the layered GO increases the surface area of the composites and provides an efficient strategy to load Cu{sub 2}O due to the large and uniform distribution of active sites for anchoring copper ions. The surface area of the Cu{sub 2}O/PA/rGO (123 m{sup 2}/g) nanocomposite was found to be almost 2.5 times higher than that of Cu{sub 2}O/rGO (55.7 m{sup 2}/g). The as-prepared Cu{sub 2}O/PA/rGO show significant improvement on both adsorption capacity and photocatalytic activity towards organic pigment pollution compared with Cu{sub 2}O/rGO under identical performance conditions.

Preparation of silver-cuprous oxide/stearic acid composite coating with superhydrophobicity on copper substrate and evaluation of its friction-reducing and anticorrosion abilities

Energy Technology Data Exchange (ETDEWEB)

Li, Peipei [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China); Chen, Xinhua [College of Chemistry and Chemical Engineering, Xuchang University, Xuchang 461000 (China); Yang, Guangbin; Yu, Laigui [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China); Zhang, Pingyu, E-mail: pingyu@henu.edu.cn [Key Laboratory of Ministry of Education for Special Functional Materials, Henan University, Kaifeng 475004 (China)

2014-01-15

A simple two-step solution immersion process was combined with surface-modification by stearic acid to prepare superhydrophobic coatings on copper substrates so as to reduce friction coefficient, increase wear resistance and improve the anticorrosion ability of copper. Briefly, cuprous oxide (Cu{sub 2}O) crystal coating with uniform and compact tetrahedron structure was firstly created by immersing copper substrate in 2 mol L{sup −1} NaOH solution. As-obtained Cu{sub 2}O coating was then immersed in 0.33 mmol L{sup −1} AgNO{sub 3} solution to incorporate silver nanoparticles, followed by modification with stearic acid (denoted as SA) coating to achieve hydrophobicity. The surface morphology and chemical composition of silver-cuprous oxide/stearic acid (denoted as Ag-Cu{sub 2}O/SA) composite coating were investigated using a scanning electron microscope and an X-ray photoelectron spectroscope (XPS); and its phase structure was examined with an X-ray diffractometer (XRD). Moreover, the contact angle of water on as-prepared Ag-Cu{sub 2}O/SA composite coating was measured, and its friction-reducing and anticorrosion abilities were evaluated. It was found that as-prepared Ag-Cu{sub 2}O/SA composite coating has a water contact angle of as high as 152.4{sup o} and can provide effective friction-reducing, wear protection and anticorrosion protection for copper substrate, showing great potential for surface-modification of copper.

Effect of cuprous oxide with different sizes on thermal and combustion behaviors of unsaturated polyester resin.

Science.gov (United States)

Hou, Yanbei; Hu, Weizhao; Gui, Zhou; Hu, Yuan

2017-07-15

Cuprous oxide (Cu 2 O) as an effective catalyst has been applied to enhance the fire safety of unsaturated polyester resin (UPR), but the particle size influence on combustion behaviors has not been previously reported. Herein, the UPR/Cu 2 O composites (metal oxide particles with average particle-size of 10, 100, and 200nm) were successfully synthesized by thermosetting process. The effects of Cu 2 O with different sizes on thermostability and combustion behaviors of UPR were characterized by TGA, MCC, TG-IR, FTIR, and SSTF. The results revel that the addition of Cu 2 O contributes to sufficient decomposition of oxygen-containing compounds, which is beneficial to the release of nontoxic compounds. The smallest-sized Cu 2 O performs the excellent catalytic decomposition effect and promotes the complete combustion of UPR, which benefits the enhancement of fire safety. While the other additives retard pyrolysis process and yield more char residue, and thus the flame retardancy of UPR composites was improved. Therefore, catalysis plays a major role for smaller-sized particles during thermal decomposition of matrix, while flame retarded effect became gradual distinctly for the larger-sized additives. Copyright © 2017 Elsevier B.V. All rights reserved.

One-step synthesis and properties of monolithic photoluminescent ruby colored cuprous oxide antimony oxide glass nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Som, Tirtha [Glass Science and Technology Section, Glass Division, Central Glass and Ceramic Research Institute, Council of Scientific and Industrial Research (CSIR, India), 196, Raja S.C. Mullick Road, Kolkata 700032 (India); Karmakar, Basudeb, E-mail: basudebk@cgcri.res.in [Glass Science and Technology Section, Glass Division, Central Glass and Ceramic Research Institute, Council of Scientific and Industrial Research (CSIR, India), 196, Raja S.C. Mullick Road, Kolkata 700032 (India)

2011-04-14

Research highlights: > Single-step synthesis of Cu{sub 2}O, Cu{sub y}Sb{sub 2-x}(O,OH){sub 6-7} (y {<=} 2, x {<=} 1) and Cu nanocrystals co-doped novel antimony oxide glass hybrid nanocomposites. > Yellow and orange colored nanocomposites shows size-controlled band gap shift of Cu{sub 2}O. > Red nanocomposite exhibits surface plasmon resonance band due to metallic Cu. > They exhibit broad deep-red photoluminescence emission under various UV excitation wavelengths. - Abstract: Cuprous oxide (Cu{sub 2}O) antimony glass (K{sub 2}O-B{sub 2}O{sub 3}-Sb{sub 2}O{sub 3}) monolithic nanocomposites having brilliant yellow to ruby red color have been synthesized by a single-step melt-quench technique involving in situ thermochemical reduction of Cu{sup 2+} (CuO) by the reducing glass matrix without using any external reducing agent. The X-ray diffraction (XRD), infrared transmission and reflection spectra, and selected area electron diffraction analysis support the reduction of Cu{sup 2+} to Cu{sup +} with the formation of Cu{sub 2}O nanoclusters along with Cu{sub y}Sb{sub 2-x}(O,OH){sub 6-7} (y {<=} 2, x {<=} 1) nanocrystalline phases while Cu{sup 0} nanoclusters are formed at very high Cu concentration. The UV-vis spectra of the yellow and orange colored nanocomposites show size-controlled band gap shift of the semiconductor (Cu{sub 2}O) nanocrystallites embedded in the glasses while the red nanocomposite exhibits surface plasmon resonance band at 529 nm due to metallic Cu. Transmission electron microscopic image advocates the formation of nanocystallites (5-42 nm). Photoluminescence emission studies show broad red emission band around 626 nm under various excitation wavelengths from 210 to 270 nm.

Carbon-layer-protected cuprous oxide nanowire arrays for efficient water reduction

KAUST Repository

Zhang, Zhonghai

2013-02-26

In this work, we propose a solution-based carbon precursor coating and subsequent carbonization strategy to form a thin protective carbon layer on unstable semiconductor nanostructures as a solution to the commonly occurring photocorrosion problem of many semiconductors. A proof-of-concept is provided by using glucose as the carbon precursor to form a protective carbon coating onto cuprous oxide (Cu2O) nanowire arrays which were synthesized from copper mesh. The carbon-layer-protected Cu2O nanowire arrays exhibited remarkably improved photostability as well as considerably enhanced photocurrent density. The Cu2O nanowire arrays coated with a carbon layer of 20 nm thickness were found to give an optimal water splitting performance, producing a photocurrent density of -3.95 mA cm-2 and an optimal photocathode efficiency of 0.56% under illumination of AM 1.5G (100 mW cm-2). This is the highest value ever reported for a Cu 2O-based electrode coated with a metal/co-catalyst-free protective layer. The photostability, measured as the percentage of the photocurrent density at the end of 20 min measurement period relative to that at the beginning of the measurement, improved from 12.6% on the bare, nonprotected Cu2O nanowire arrays to 80.7% on the continuous carbon coating protected ones, more than a 6-fold increase. We believe that the facile strategy presented in this work is a general approach that can address the stability issue of many nonstable photoelectrodes and thus has the potential to make a meaningful contribution in the general field of energy conversion. © 2013 American Chemical Society.

21 CFR 184.1265 - Cuprous iodide.

Science.gov (United States)

2010-04-01

... the following specific limitations: Category of food Maximum treatment level in food Functional use... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Cuprous iodide. 184.1265 Section 184.1265 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN...

Cytotoxicity of cuprous oxide nanoparticles to fish blood cells: hemolysis and internalization

Energy Technology Data Exchange (ETDEWEB)

Chen Liqiang, E-mail: chenlq@ynu.edu.cn; Kang Bin [Yunnan University, Asian International Rivers Center, Yunnan Key Laboratory of International Rivers and Trans-boundary Eco-security (China); Ling Jian [Yunnan University, College of Chemistry and Chemical Engineering (China)

2013-03-15

Cuprous oxide nanoparticles (Cu{sub 2}O NPs) possess unique physical and chemical properties which are employed in a broad variety of applications. However, little is known about the adverse effects of Cu{sub 2}O NPs on organisms. In the current study, in vitro cytotoxicity of Cu{sub 2}O NPs (ca. 60 nm in diameter) to the blood cells of freshwater fish Carassius auratus was evaluated. A concentration-dependent hemolytic activity of Cu{sub 2}O NPs to red blood cells (RBCs) and the phagocytosis of Cu{sub 2}O NPs by leukocytes were revealed. The results showed that dosages of Cu{sub 2}O NPs greater than 40 {mu}g/mL were toxic to blood cells, and could cause serious membrane damage to RBCs. The EC{sub 50} value of Cu{sub 2}O NPs as obtained from RBCs and whole blood exposure was 26 and 63 {mu}g/mL, respectively. The generation of reactive oxygen species and the direct interaction between Cu{sub 2}O NPs and the cell membrane were suggested as the possible mechanism for cytotoxicity, and the intrinsic hemolytic active of Cu{sub 2}O NPs was the main contributor to the toxicity rather than solubilized copper ions. The adsorption of plasma proteins on the surfaces of Cu{sub 2}O NPs led to their aggregation in whole blood, and aggregate formation can significantly alleviate the hemolytic effect and subsequently mediate the phagocytosis of Cu{sub 2}O NPs by leukocytes.

When do oxide precipitates form during consolidation of oxide dispersion strengthened steels?

Energy Technology Data Exchange (ETDEWEB)

Deschamps, A., E-mail: alexis.deschamps@grenoble-inp.fr [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France); De Geuser, F. [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France); Malaplate, J.; Sornin, D. [DEN, DANS, DMN, Service de Recherches Métallurgiques Appliquées, CEA, Université Paris-Saclay, 91191 Gif-Sur-Yvette (France)

2016-12-15

The processing of oxide dispersion strengthened (ODS) steels involves ball milling, where the oxide forming species are driven in solid solution. Precipitation of the nanometre-scale oxides occurs during subsequent annealing and consolidation. This paper reports in-situ Small-Angle X-ray Scattering measurements of the formation of these precipitates during heating of cold-compressed as-milled powders. Clusters are already initially present, and precipitation starts at 300 °C. The maximum precipitate density is achieved at 600 °C, followed by very slow coarsening at higher temperature. These results open the way to understand the coupled evolution of precipitation and crystalline defects during heating and consolidation of ODS steels.

Exciton-polaritons in cuprous oxide: Theory and comparison with experiment

Science.gov (United States)

Schweiner, Frank; Ertl, Jan; Main, Jörg; Wunner, Günter; Uihlein, Christoph

2017-12-01

The observation of giant Rydberg excitons in cuprous oxide (Cu2O ) up to a principal quantum number of n =25 by T. Kazimierczuk et al. [Nature (London) 514, 343 (2014), 10.1038/nature13832] inevitably raises the question whether these quasiparticles must be described within a multipolariton framework since excitons and photons are always coupled in the solid. In this paper we present the theory of exciton-polaritons in Cu2O . To this end we extend the Hamiltonian which includes the complete valence-band structure, the exchange interaction, and the central-cell corrections effects, and which has been recently deduced by F. Schweiner et al. [Phys. Rev. B 95, 195201 (2017), 10.1103/PhysRevB.95.195201], for finite values of the exciton momentum ℏ K . We derive formulas to calculate not only dipole but also quadrupole oscillator strengths when using the complete basis of F. Schweiner et al., which has recently been proven as a powerful tool to calculate exciton spectra. Very complex polariton spectra for the three orientations of K along the axes [001 ] , [110 ] , and [111 ] of high symmetry are obtained and a strong mixing of exciton states is reported. The main focus is on the 1 S ortho-exciton-polariton, for which pronounced polariton effects have been measured in experiments. We set up a 5 ×5 matrix model, which accounts for both the polariton effect and the K -dependent splitting, and which allows treating the anisotropic polariton dispersion for any direction of K . We especially discuss the dispersions for K being oriented in the planes perpendicular to [1 1 ¯0 ] and [111 ] , for which experimental transmission spectra have been measured. Furthermore, we compare our results with experimental values of the K -dependent splitting, the group velocity, and the oscillator strengths of this exciton-polariton. The results are in good agreement. This proves the validity of the 5 ×5 matrix model as a useful theoretical model for further investigations on the 1 S

Electrochemical behaviour of cuprous complexes of dithia-alkanedicarboxylic acids

NARCIS (Netherlands)

Pieterse, M.M.J.; Janssen, L.J.J.

1972-01-01

The composition and electrochemical behaviour of the cuprous complexes of dithia-alkanedicarboxylic acids viz., 2,5-dithiahexane-1,6-dicarboxylic acid (I); 3,6 dithiaoctane-1,8-dicarboxylic acid (II); 4,7-dithiadecane-1,10-dicarboxylic acid (III) and 2,2,

Cuprous sulfide as a film insulation for superconductors

International Nuclear Information System (INIS)

Wagner, G.R.; Uphoff, J.H.; Vecchio, P.D.

1982-01-01

The LCP test coil utilizes a conductor of forced-flow design having 486 strands of multifilametary Nb 3 Sn compacted in a stainless steel sheath. The impetus for the work reported here stemmed from the need for some form of insulation for those strands to prevent sintering during reaction and to reduce ac losses. The work reported here experimented with cuprous sulfide coatings at various coating rates and thicknesses. Two solenoids that were wound with cuprous sulfide-coated wires and heat-treated at 700 degrees C were found to demonstrate that the film is effective in providing turn-to-turn insulation for less than about 0.5V between turns. The sulfide layer provided a metal-semiconductor junction which became conducting at roughly 0.5V. Repeated cycling of the coil voltage in excess of that value produced no damage to the sulfide layer. The junction provided self-protection for the coil as long as the upper allowable current density in the sulfide was not exceeded. No training was apparent up to 6.4 T

Cuprous halides semiconductors as a new means for highly efficient light-emitting diodes

Science.gov (United States)

Ahn, Doyeol; Park, Seoung-Hwan

2016-01-01

In group-III nitrides in use for white light-emitting diodes (LEDs), optical gain, measure of luminous efficiency, is very low owing to the built-in electrostatic fields, low exciton binding energy, and high-density misfit dislocations due to lattice-mismatched substrates. Cuprous halides I-VII semiconductors, on the other hand, have negligible built-in field, large exciton binding energies and close lattice matched to silicon substrates. Recent experimental studies have shown that the luminescence of I-VII CuCl grown on Si is three orders larger than that of GaN at room temperature. Here we report yet unexplored potential of cuprous halides systems by investigating the optical gain of CuCl/CuI quantum wells. It is found that the optical gain and the luminescence are much larger than that of group III-nitrides due to large exciton binding energy and vanishing electrostatic fields. We expect that these findings will open up the way toward highly efficient cuprous halides based LEDs compatible to Si technology. PMID:26880097

Multilayer core-shell structured composite paper electrode consisting of copper, cuprous oxide and graphite assembled on cellulose fibers for asymmetric supercapacitors

Science.gov (United States)

Wan, Caichao; Jiao, Yue; Li, Jian

2017-09-01

An easily-operated and inexpensive strategy (pencil-drawing-electrodeposition-electro-oxidation) is proposed to synthesize a novel class of multilayer core-shell structured composite paper electrode, which consists of copper, cuprous oxide and graphite assembled on cellulose fibers. This interesting electrode structure plays a pivotal role in providing more active sites for electrochemical reactions, facilitating ion and electron transport and shorting their diffusion pathways. This electrode demonstrates excellent electrochemical properties with a high specific capacitance of 601 F g-1 at 2 A g-1 and retains 83% of this capacitance when operated at an ultrahigh current density of 100 A g-1. In addition, a high energy density of 13.4 W h kg-1 at the power density of 0.40 kW kg-1 and a favorable cycling stability (95.3%, 8000 cycles) were achieved for this electrode. When this electrode was assembled into an asymmetric supercapacitor with carbon paper as negative electrode, the device displays remarkable electrochemical performances with a large areal capacitances (122 mF cm-2 at 1 mA cm-2), high areal energy density (10.8 μW h cm-2 at 402.5 μW cm-2) and outstanding cycling stability (91.5%, 5000 cycles). These results unveil the potential of this composite electrode as a high-performance electrode material for supercapacitors.

Electrochemical synthesis and characterization of copper (I oxide

Directory of Open Access Journals (Sweden)

Bugarinović Sanja J.

2009-01-01

Full Text Available The quest and need for clean and economical energy sources have increased interest in the development of thin film cells technologies. Electrochemical deposition is an attractive method for synthesis of thin films. It offers the advantages of low synthesis temperature, low cost and high purity. Copper (I oxide or cuprous oxide is an oxide semiconductor which is used as the anodic material in the form of thin film in lithium batteries and solar cells. The cathodic process of synthesis of cuprous oxide thin film is carried out in a potentiostatic mode from the organic electrolyte. The process parameters are chosen in that way to accomplish maximum difference between the potentials at which Cu2O and CuO are obtained. The electrochemical characterization was carried out by cyclic voltammetry. The electrodeposition techniques are particularly well suited for the deposition of single elements but it is also possible to carry out simultaneous depositions of several elements and syntheses of well-defined alternating layers of metals and oxides with thicknesses down to a few nm. Nanomaterials exhibit novel physical properties and play an important role in fundamental research. In addition, cuprous oxide is commonly used as a pigment, a fungicide, and an antifouling agent for marine paints. It is insoluble in water and organic solvents. This work presents the examinations of the influence of bath, temperature, pH and current density on the characteristics of electrochemically synthesized cuprous oxide. In the 'classic' process of synthesis, which is carried out under galvanostatic conditions on the anode, the grain size of the powder decreases with the increase in current density while the grain colour becomes lighter. The best commercial quality of the Cu2O (grain size, colour, content of choride was obtained at the temperature of 80°C, concentration of NaCl of 3 mol/dm3 and current density of 400 A/m2.

Band offsets of n-type electron-selective contacts on cuprous oxide (Cu{sub 2}O) for photovoltaics

Energy Technology Data Exchange (ETDEWEB)

Brandt, Riley E., E-mail: rbrandt@alum.mit.edu, E-mail: buonassisi@mit.edu; Lee, Yun Seog; Buonassisi, Tonio, E-mail: rbrandt@alum.mit.edu, E-mail: buonassisi@mit.edu [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Young, Matthew; Dameron, Arrelaine; Teeter, Glenn [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Park, Helen Hejin; Chua, Danny; Gordon, Roy G. [Harvard University, Cambridge, Massachusetts 02139 (United States)

2014-12-29

The development of cuprous oxide (Cu{sub 2}O) photovoltaics (PVs) is limited by low device open-circuit voltages. A strong contributing factor to this underperformance is the conduction-band offset between Cu{sub 2}O and its n-type heterojunction partner or electron-selective contact. In the present work, a broad range of possible n-type materials is surveyed, including ZnO, ZnS, Zn(O,S), (Mg,Zn)O, TiO{sub 2}, CdS, and Ga{sub 2}O{sub 3}. Band offsets are determined through X-ray photoelectron spectroscopy and optical bandgap measurements. A majority of these materials is identified as having a negative conduction-band offset with respect to Cu{sub 2}O; the detrimental impact of this on open-circuit voltage (V{sub OC}) is evaluated through 1-D device simulation. These results suggest that doping density of the n-type material is important as well, and that a poorly optimized heterojunction can easily mask changes in bulk minority carrier lifetime. Promising heterojunction candidates identified here include Zn(O,S) with [S]/[Zn] ratios >70%, and Ga{sub 2}O{sub 3}, which both demonstrate slightly positive conduction-band offsets and high V{sub OC} potential. This experimental protocol and modeling may be generalized to evaluate the efficiency potential of candidate heterojunction partners for other PV absorbers, and the materials identified herein may be promising for other absorbers with low electron affinities.

Comparison of Poly Aluminum Chloride and Chlorinated Cuprous for Chemical Oxygen Demand and Color Removal from Kashan Textile Industries Company Wastewater

Directory of Open Access Journals (Sweden)

Hoseindoost Gh.1 MSPH,

2016-08-01

Full Text Available Aims Textile wastewaters are the most important health and environmental problems in Kashan. This research was aimed to compare the poly aluminum chloride and chlorinated cuprous efficiency for removal of Chemical Oxygen Demand (COD and color from Kashan Textile Industries Company wastewater. Materials & Methods This experimental bench scale study in a batch system was conducted on 20 composed wastewater samples collected from Kashan Textile Industries Company raw wastewater. During 5 months, in the beginning of every week a day was selected randomly and in the day a composed sample was taken and studied. PAC at the doses of 10, 20, 30, 40 and 50mg.l-1 and chlorinated cuprous at the doses of 100, 200, 300, 400 and 500mg.l-1 were applied. The optimum pH also optimum concentration of PAC and chlorinated cuprous were determined using Jar test. The data was analyzed by SPSS 16 using descriptive statistics and Fisher Exact test. Findings The average concentration of COD in the raw textile wastewater was 2801.56±1398.29mg.l-1. The average COD concentration has been decreased to 1125.47±797.55mg.l-1. There was a significant difference between the effects of these two coagulants efficiency (p<0.05. The average COD removal efficiency for chlorinated cuprous and PAC was 58.52% and 72.56%, respectively. Also, the average color removal efficiency by chlorinated cuprous and PAC were 17.23 and 64.45%, respectively. Conclusion PAC is more efficient than chlorinated cuprous for both COD and color removal from KTIC wastewater.

Oxidation behaviour of zirconium alloys and their precipitates – A mechanistic study

International Nuclear Information System (INIS)

Proff, C.; Abolhassani, S.; Lemaignan, C.

2013-01-01

The precipitate oxidation behaviour of binary zirconium alloys containing 1 wt.% Fe, Ni, Cr or 0.6 wt.% Nb was characterised in TEM on FIB prepared transverse sections of the oxide and reported in previous studies [1,2]. In the present study the following alloys: Zr1%Cu, Zr0.5%Cu0.5%Mo and pure Zr are analysed to add to the available information. In all cases, the observed precipitate oxidation behaviour in the oxide close to the metal-oxide interface could be described either with delayed oxidation with respect to the matrix or simultaneous oxidation as the surrounding zirconium matrix. Attempt was made to explain these observations, with different parameters such as precipitate size and structure, composition and thermodynamic properties. It was concluded that the thermodynamics with the new approach presented could explain most precisely their behaviour, considering the precipitate stoichiometry and the free energy of oxidation of the constituting elements. The surface topography of the oxidised materials, as well as the microstructure of the oxide presenting microcracks have been examined. A systematic presence of microcracks above the precipitates exhibiting delayed oxidation has been found; the height of these crack calculated using the Pilling–Bedworth ratios of different phases present, can explain their origin. The protrusions at the surface in the case of materials containing large precipitates can be unambiguously correlated to the presence of these latter, and the height can be correlated to the Pilling–Bedworth ratios of the phases present as well as the diffusion of the alloying elements to the surface and their subsequent oxidation. This latter behaviour was much more considerable in the case of Fe and Cu with Fe showing systematically diffusion to the outer surface.

Preparation and Characterization of Hydrous Zirconium Oxide Formed by Homogeneous Precipitation

Directory of Open Access Journals (Sweden)

Silva G.L.J.P. da

2002-01-01

Full Text Available This paper reports on the preparation, characterization and study of the ion exchange behavior of hydrous zirconium oxides formed by homogeneous precipitation from zirconium oxychloride. The precipitants used were obtained by thermal decomposition of urea, sodium nitrite or ammonium carbonate. Seven compounds were prepared and characterized by thermal analysis, X-ray diffractometry and by surface area measurements. Amorphous forms were obtained in each case, a result that agrees with those obtained by conventional gel precipitation methodology. All these materials present surface area values of >148 m².g-1, determined after heat treatment at 50 °C. The ion exchange behavior of each hydrous zirconium oxide prepared was studied using K+ as the exchanged species and the results compared with those obtained for hydrous zirconium oxide originally precipitated by the sol gel method.

Precipitation of plutonium from acidic solutions using magnesium oxide

International Nuclear Information System (INIS)

Jones, S.A.

1994-01-01

Plutonium (IV) is only marginally soluble in alkaline solution. Precipitation of plutonium using sodium or potassium hydroxide to neutralize acidic solutions produces a gelatinous solid that is difficult to filter and an endpoint that is difficult to control. If the pH of the solution is too high, additional species precipitate producing an increased volume of solids separated. The use of magnesium oxide as a reagent has advantages. It is added as a solid (volume of liquid waste produced is minimized), the pH is self-limiting (pH does not exceed about 8.5), and the solids precipitated are more granular (larger particle size) than those produced using KOH or NaOH. Following precipitation, the raffinate is expected to meet criteria for disposal to tank farms. The solid will be heated in a furnace to dry it and convert any hydroxide salts to the oxide form. The material will be cooled in a desiccator. The material is expected to meet vault storage criteria

Precipitation of Zinc Oxide Nanoparticles in Bicontinuous Microemulsions

Directory of Open Access Journals (Sweden)

Liliana E. Romo

2011-01-01

Full Text Available Zinc oxide nanoparticles were obtained directly, avoiding the calcination step, by precipitation at 70°C in bicontinuous microemulsions stabilized with a mixture of surfactants sodium bis (2-ethylhexyl sulfosuccinate/sodium dodecyl sulfate (2/1, wt./wt. containing 0.7 M zinc nitrate aqueous solution. Two concentrations of aqueous solution of precipitating agent sodium hydroxide were used under different dosing times on microemulsion. Characterization by X-ray diffraction and electron microscopy allowed us to identify particles with an acicular rod-like morphology and a hexagonal wurtzite crystal structure as small as 8.5 and 30 nm in average diameter and length, respectively. Productivities much higher than those typical in the preparation of zinc oxide nanoparticles via reverse microemulsions were obtained. Particle size was the same at the two studied sodium hydroxide concentrations, while it increases as dosing time of the precipitant agent increases. It is believed that the surfactant film on the microemulsion channels restricts the particle diameter growth.

A novel reducing graphene/polyaniline/cuprous oxide composite hydrogel with unexpected photocatalytic activity for the degradation of Congo red

International Nuclear Information System (INIS)

Miao, Jie; Xie, Anjian; Li, Shikuo; Huang, Fangzhi; Cao, Juan; Shen, Yuhua

2016-01-01

Graphical abstract: Excellent photocatalytic activity of the RGO/PANI/Cu_2O composite hydrogel for CR degradation under UV–vis light irradiation. - Highlights: • The RGO/PANI/Cu_2O composite hydrogel was first synthesized via a facile method. • Photocatalytic performance was studied under UV–vis light. • The ternary composite hydrogel shows unexpected photocatalytic activity. • A possible photocatalysis mechanism was illustrated. - Abstract: In this work, a novel reducing graphene/polyaniline/cuprous oxide (RGO/PANI/Cu_2O) composite hydrogel with a 3D porous network has been successfully prepared via a one-pot method in the presence of cubic Cu_2O nanoparticles. The as-synthesized ternary composites hydrogel shows unexpected photocatalytic activity such that Congo red (CR) degradation efficiency can reaches 97.91% in 20 min under UV–vis light irradiation, which is much higher than that of either the single component (Cu_2O nanoparticles), or two component systems (RGO/Cu_2O composite hydrogel and PANI/Cu_2O nanocomposites). Furthermore, the ternary composite hydrogel exhibits high stability and do not show any significant loss after five recycles. Such outstanding photocatalytic activity of the RGO/PANI/Cu_2O composite hydrogel was ascribed to the high absorption ability of the product for CR and the synergic effect among RGO, PANI and Cu_2O in photocatalytic process. The product of this work would provide a new sight for the construction of UV–vis light responsive photocatalyst with high performance.

Evolution of zirconium-based precipitates during oxidation and irradiation of Zr alloys (impact on the oxidation kinetics of Zr alloys)

International Nuclear Information System (INIS)

Pecheur, Dominique

1993-01-01

As the oxidation of the zircaloy sheath is one of the factors which limit the lifetime of nuclear fuel rods, this research thesis aims at a better knowledge of the involved oxidation mechanisms and to improve the oxidation resistance in order to increase rod lifetime. Oxidation test performed in autoclave to study zirconium alloy oxidation without irradiation showed that oxidation kinetics is significantly higher under irradiation. This difference is attributed to a different evolution of the sheath material under irradiation. Thus, this research focused on the role of precipitates in the oxidation process of zirconium alloys, and on the impact of their amorphization on this oxidation. After a detailed description of the context and of the various implemented experimental means, the author presents the results obtained on a reference material on the one hand, and on a material irradiated by ions or neutrons on the other hand. More particularly, the author studied in these both cases the introduction of precipitates in the oxide layer by transmission electronic microscopy, and oxidation kinetics obtained in autoclave on these two types of material. He reports the analysis of the introduction of precipitates in the oxide layer formed on the reference material. He proposes interpretations for the evolutions of structure and of chemical compositions of precipitates in the oxide layer. These observations are then correlated with oxidation kinetics in these alloys. Finally, the author discusses results of oxidation tests obtained on materials irradiated by ions and by neutrons [fr

Optimization of thorium oxalate precipitation conditions relative to thorium oxide sinterability

International Nuclear Information System (INIS)

White, G.D.; Bray, L.A.; Hart, P.E.

1980-01-01

The effect of thorium oxalate precipitation conditions on derived oxide sinterability was investigated with the objective of producing ThO 2 powder that could be sintered to high density without premilling. Precipitation conditions examined were temperature, digestion time and agitation method which were employed in a two-level factorial experimental design to delineate their effects. The two levels for each of the factors, respectively, were 10 0 C and 70 0 C, 15 min and 360 min, and mechanical stirrer and a homogenizer that imparted both mechanical and ultrasonic agitation. The ThO 2 derived from each of the precipitation trials was characterized with respect to morphology, surface area, and crystallite size as well as sinterability. Only precipitation temperature had a significant effect upon all the properties of the derived oxide powders

A model for the formation of lattice defects at silicon oxide precipitates in silicon

International Nuclear Information System (INIS)

Vanhellemont, J.; Gryse, O. de; Clauws, P.

2003-01-01

The critical size of silicon oxide precipitates and the formation of lattice defects by the precipitates are discussed. An expression is derived allowing estimation of self-interstitial emission by spherical precipitates as well as strain build-up during precipitate growth. The predictions are compared with published experimental data. A model for stacking fault nucleation at oxide precipitates is developed based on strain and self-interstitial accumulation during the thermal history of the wafer. During a low-temperature treatment high levels of strain develop. During subsequent high-temperature treatment, excess strain energy in the precipitate is released by self-interstitial emission leading to favourable conditions for stacking fault nucleation

Precipitation of plutonium from acidic solutions using magnesium oxide

International Nuclear Information System (INIS)

Jones, S.A.

1994-01-01

Magnesium oxide will be used as a neutralizing agent for acidic plutonium-containing solutions. It is expected that as the magnesium oxide dissolves, the pH of the solution will rise, and plutonium will precipitate. The resulting solid will be tested for suitability to storage. The liquid is expected to contain plutonium levels that meet disposal limit requirements

Synthesis and characterization of zinc oxide thin films prepared by ...

African Journals Online (AJOL)

Zinc oxide thin films were prepared with ammonia/ammonium chloride buffer as the reaction moderating agent in the chemical bath deposition technique. An observable color change during the reaction due to variations in the reactants concentration indicated the existence of the cupric (CuO) and cuprous (Cu2O) oxides ...

A novel reducing graphene/polyaniline/cuprous oxide composite hydrogel with unexpected photocatalytic activity for the degradation of Congo red

Energy Technology Data Exchange (ETDEWEB)

Miao, Jie; Xie, Anjian; Li, Shikuo; Huang, Fangzhi; Cao, Juan; Shen, Yuhua, E-mail: yhshen@ahu.edu.cn

2016-01-01

Graphical abstract: Excellent photocatalytic activity of the RGO/PANI/Cu{sub 2}O composite hydrogel for CR degradation under UV–vis light irradiation. - Highlights: • The RGO/PANI/Cu{sub 2}O composite hydrogel was first synthesized via a facile method. • Photocatalytic performance was studied under UV–vis light. • The ternary composite hydrogel shows unexpected photocatalytic activity. • A possible photocatalysis mechanism was illustrated. - Abstract: In this work, a novel reducing graphene/polyaniline/cuprous oxide (RGO/PANI/Cu{sub 2}O) composite hydrogel with a 3D porous network has been successfully prepared via a one-pot method in the presence of cubic Cu{sub 2}O nanoparticles. The as-synthesized ternary composites hydrogel shows unexpected photocatalytic activity such that Congo red (CR) degradation efficiency can reaches 97.91% in 20 min under UV–vis light irradiation, which is much higher than that of either the single component (Cu{sub 2}O nanoparticles), or two component systems (RGO/Cu{sub 2}O composite hydrogel and PANI/Cu{sub 2}O nanocomposites). Furthermore, the ternary composite hydrogel exhibits high stability and do not show any significant loss after five recycles. Such outstanding photocatalytic activity of the RGO/PANI/Cu{sub 2}O composite hydrogel was ascribed to the high absorption ability of the product for CR and the synergic effect among RGO, PANI and Cu{sub 2}O in photocatalytic process. The product of this work would provide a new sight for the construction of UV–vis light responsive photocatalyst with high performance.

Effect of calcium oxide on the efficiency of ferrous ion oxidation and total iron precipitation during ferrous ion oxidation in simulated acid mine drainage treatment with inoculation of Acidithiobacillus ferrooxidans.

Science.gov (United States)

Liu, Fenwu; Zhou, Jun; Jin, Tongjun; Zhang, Shasha; Liu, Lanlan

2016-01-01

Calcium oxide was added into ferrous ion oxidation system in the presence of Acidithiobacillus ferrooxidans at concentrations of 0-4.00 g/L. The pH, ferrous ion oxidation efficiency, total iron precipitation efficiency, and phase of the solid minerals harvested from different treatments were investigated during the ferrous ion oxidation process. In control check (CK) system, pH of the solution decreased from 2.81 to 2.25 when ferrous ions achieved complete oxidation after 72 h of Acidithiobacillus ferrooxidans incubation without the addition of calcium oxide, and total iron precipitation efficiency reached 20.2%. Efficiency of ferrous ion oxidation and total iron precipitation was significantly improved when the amount of calcium oxide added was ≤1.33 g/L, and the minerals harvested from systems were mainly a mixture of jarosite and schwertmannite. For example, the ferrous ion oxidation efficiency reached 100% at 60 h and total iron precipitation efficiency was increased to 32.1% at 72 h when 1.33 g/L of calcium oxide was added. However, ferrous ion oxidation and total iron precipitation for jarosite and schwertmannite formation were inhibited if the amount of calcium oxide added was above 2.67 g/L, and large amounts of calcium sulfate dihydrate were generated in systems.

Optimization Recovery of Yttrium Oxide in Precipitation, Extraction, and Stripping Process

Science.gov (United States)

Perwira, N. I.; Basuki, K. T.; Biyantoro, D.; Effendy, N.

2018-04-01

Yttrium oxide can be used as a dopant control rod of nuclear reactors in YSH material and superconductors. Yttrium oxide is obtained in the Xenotime mineral derived from byproduct of tin mining PT Timah Bangka which contain rare earth elements (REE) dominant Y, Dy, and Gd whose content respectively about 29.53%, 7.76%, and 2.58%. Both usage in the field of nuclear and non-nuclear science and technology is need to pure from the impurities. The presence of impurities in the yttrium oxide may affect the characteristic of the material and the efficiency of its use. Thus it needs to be separated by precipitation and extraction-stripping and calcination in the making of the oxide. However, to obtain higher levels of Yttrium oxide, it is necessary to determine the optimum conditions for its separation. The purpose of this research was to determine the optimum pH of precipitation, determine acid media and concentration optimum in extraction and stripping process and determine the efficiency of the separation of Y from REE concentrate. This research was conducted with pH variation in the precipitation process that pHs were 4 - 8, the difference of acid media for the extraction process, i.e., HNO3, HCl and H2SO4 with each concentration of 0,5 M; 1 M; 1,5 M; and 2 M and for stripping process were HNO3, HCl, and H2SO4 with each concentration of 1 M; 2M; and 3 M. Based on the result, the optimum pH of precipitation process was 6,5, the optimumacid media was HNO3 0,5 M, and for stripping process media was HNO3 3 M. The efficiency of precipitation process at pH 6,5 was 69,53 %, extraction process was 96.39% and stripping process was 4,50%. The separation process from precipitation to extraction had increased the purity and the highest efficiency recovery of Y was in the extraction process and obtained Y2O3 purer compared to the feed with the Y2O3 content of 92.87%.

Optical investigations on indium oxide nano-particles prepared through precipitation method

International Nuclear Information System (INIS)

Seetha, M.; Bharathi, S.; Dhayal Raj, A.; Mangalaraj, D.; Nataraj, D.

2009-01-01

Visible light emitting indium oxide nanoparticles were synthesized by precipitation method. Sodium hydroxide dissolved in ethanol was used as a precipitating agent to obtain indium hydroxide precipitates. Precipitates, thus formed were calcined at 600 deg. C for 1 h to obtain indium oxide nanoparticles. The structure of the particles as determined from the X-Ray diffraction pattern was found to be body centered cubic. The phase transformation of the prepared nanoparticles was analyzed using thermogravimetry. Surface morphology of the prepared nanoparticles was analyzed using high resolution-scanning electron microscopy and transmission electron microscopy. The results of the analysis show cube-like aggregates of size around 50 nm. It was found that the nanoparticles have a strong emission at 427 nm and a weak emission at 530 nm. These emissions were due to the presence of singly ionized oxygen vacancies and the nature of the defect was confirmed through Electron paramagnetic resonance analysis.

Low temperature (< 100 °C) deposited P-type cuprous oxide thin films: Importance of controlled oxygen and deposition energy

International Nuclear Information System (INIS)

Li, Flora M.; Waddingham, Rob; Milne, William I.; Flewitt, Andrew J.; Speakman, Stuart; Dutson, James; Wakeham, Steve; Thwaites, Mike

2011-01-01

With the emergence of transparent electronics, there has been considerable advancement in n-type transparent semiconducting oxide (TSO) materials, such as ZnO, InGaZnO, and InSnO. Comparatively, the availability of p-type TSO materials is more scarce and the available materials are less mature. The development of p-type semiconductors is one of the key technologies needed to push transparent electronics and systems to the next frontier, particularly for implementing p–n junctions for solar cells and p-type transistors for complementary logic/circuits applications. Cuprous oxide (Cu 2 O) is one of the most promising candidates for p-type TSO materials. This paper reports the deposition of Cu 2 O thin films without substrate heating using a high deposition rate reactive sputtering technique, called high target utilisation sputtering (HiTUS). This technique allows independent control of the remote plasma density and the ion energy, thus providing finer control of the film properties and microstructure as well as reducing film stress. The effect of deposition parameters, including oxygen flow rate, plasma power and target power, on the properties of Cu 2 O films are reported. It is known from previously published work that the formation of pure Cu 2 O film is often difficult, due to the more ready formation or co-formation of cupric oxide (CuO). From our investigation, we established two key concurrent criteria needed for attaining Cu 2 O thin films (as opposed to CuO or mixed phase CuO/Cu 2 O films). First, the oxygen flow rate must be kept low to avoid over-oxidation of Cu 2 O to CuO and to ensure a non-oxidised/non-poisoned metallic copper target in the reactive sputtering environment. Secondly, the energy of the sputtered copper species must be kept low as higher reaction energy tends to favour the formation of CuO. The unique design of the HiTUS system enables the provision of a high density of low energy sputtered copper radicals/ions, and when combined with a

Precipitation of iron (III) using magnesium oxide in fluidized bed

International Nuclear Information System (INIS)

Esteban-Bocardo, P. A.; Ferreira-Rocha, S. D.

2006-01-01

A process for iron (III) removal by hydroxide precipitation from and acid synthetic inorganic effluent using magnesium oxide as an alternative precipitant agent in a fluidized bed was developed. An acid synthetic inorganic effluent containing 100 and 200 mg/l of ferric ions (pH=1.0) was continuously fed up to the acrylic column (30 cm high and 2 cm diameter) during 180 minutes. Magnesium oxide pulp (3% v/v) was injected at the beginning of the experiment in order to allow the iron hydroxides precipitation. The concentration and pH profiles agreed in their curves, while the pH profile rose,the concentration profile decreased and a high percentage of iron removal /higher to 99%) was reached. Extremely low iron concentrations have been reached, thus permitting to attend to the environmental standard of 10.0 mg/l for discharge of effluent containing ferric ions established by the law DN 10/86 of COPAM (Conselho de Politica Ambiental do Estado de Minas Gerais-Brazil). (Author)

Current Status and Future Prospects of Copper Oxide Heterojunction Solar Cells

OpenAIRE

Terence K. S. Wong; Siarhei Zhuk; Saeid Masudy-Panah; Goutam K. Dalapati

2016-01-01

The current state of thin film heterojunction solar cells based on cuprous oxide (Cu2O), cupric oxide (CuO) and copper (III) oxide (Cu4O3) is reviewed. These p-type semiconducting oxides prepared by Cu oxidation, sputtering or electrochemical deposition are non-toxic, sustainable photovoltaic materials with application potential for solar electricity. However, defects at the copper oxide heterojunction and film quality are still major constraining factors for achieving high power conversion e...

Characterization of manganese oxide precipitates from Appalachian coal mine drainage treatment systems

International Nuclear Information System (INIS)

Tan Hui; Zhang Gengxin; Heaney, Peter J.; Webb, Samuel M.; Burgos, William D.

2010-01-01

The removal of Mn(II) from coal mine drainage (CMD) by chemical addition/active treatment can significantly increase treatment costs. Passive treatment for Mn removal involves promotion of biological oxidative precipitation of manganese oxides (MnO x ). Manganese(II) removal was studied in three passive treatment systems in western Pennsylvania that differed based on their influent Mn(II) concentrations (20-150 mg/L), system construction (±inoculation with patented Mn(II)-oxidizing bacteria), and bed materials (limestone vs. sandstone). Manganese(II) removal occurred at pH values as low as 5.0 and temperatures as low as 2 deg. C, but was enhanced at circumneutral pH and warmer temperatures. Trace metals such as Zn, Ni and Co were removed effectively, in most cases preferentially, into the MnO x precipitates. Based on synchrotron radiation X-ray diffraction and Mn K-edge extended X-ray absorption fine structure spectroscopy, the predominant Mn oxides at all sites were poorly crystalline hexagonal birnessite, triclinic birnessite and todorokite. The surface morphology of the MnO x precipitates from all sites was coarse and 'sponge-like' composed of nm-sized lathes and thin sheets. Based on scanning electron microscopy (SEM), MnO x precipitates were found in close proximity to both prokaryotic and eukaryotic organisms. The greatest removal efficiency of Mn(II) occurred at the one site with a higher pH in the bed and a higher influent total organic C (TOC) concentration (provided by an upstream wetland). Biological oxidation of Mn(II) driven by heterotrophic activity was most likely the predominant Mn removal mechanism in these systems. Influent water chemistry and Mn(II) oxidation kinetics affected the relative distribution of MnO x mineral assemblages in CMD treatment systems.

Nano Copper Oxide-Modified Carbon Cloth as Cathode for a Two-Chamber Microbial Fuel Cell.

Science.gov (United States)

Dong, Feng; Zhang, Peng; Li, Kexun; Liu, Xianhua; Zhang, Pingping

2016-12-09

In this work, Cu₂O nanoparticles were deposited on a carbon cloth cathode using a facile electrochemical method. The morphology of the modified cathode, which was characterized by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) tests, showed that the porosity and specific surface area of the cathode improved with longer deposition times. X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) results showed that cupric oxide and cuprous oxide coexisted on the carbon cloth, which improved the electrochemical activity of cathode. The cathode with a deposition time of 100 s showed the best performance, with a power density twice that of bare carbon cloth. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) results revealed that moderate deposition of nano copper oxide on carbon cloth could dramatically reduce the charge transfer resistance, which contributed to the enhanced electrochemical performance. The mediation mechanism of copper oxide nanocatalyst was illustrated by the fact that the recycled conversion between cupric oxide and cuprous oxide accelerated the electron transfer efficiency on the cathode.

Zirconium oxide crystal phase: The role of the pH and time to attain the final pH for precipitation of the hydrous oxide

International Nuclear Information System (INIS)

Srinivasan, R.; Harris, M.B.; Simpson, S.F.; De Angelis, R.J.; Davis, B.H.

1988-01-01

Precipitated hydrous zirconium oxide can be calcined to produce either a monoclinic or tetragonal product. It has been observed that the time taken to attain the final pH of the solution in contact with the precipitate plays a dominant role in determining the crystal structure of the zirconium oxide after calcination at 500 0 C. The dependence of crystal structure on the rate of precipitation is observed only in the pH range 7--11. Rapid precipitation in this pH range yields predominately monoclinic zirconia, whereas slow (8 h) precipitation produces the tetragonal phase. At pH of approximately 13.0, only the tetragonal phase is formed from both slowly and rapidly precipitated hydrous oxide. The present results, together with earlier results, show that both the pH of the supernatant liquid and the time taken to attain this pH play dominant roles in determining the crystal structure of zirconia that is formed after calcination of the hydrous oxide. The factors that determine the crystal phase are therefore imparted in a mechanism of precipitation that depends upon the pH, and it is inferred that it is the hydroxyl concentration that is the dominant factor

Production of crystalline refractory metal oxides containing colloidal metal precipitates and useful as solar-effective absorbers

Science.gov (United States)

Narayan, Jagdish; Chen, Yok

1983-01-01

This invention is a new process for producing refractory crystalline oxides having improved or unusual properties. The process comprises the steps of forming a doped-metal crystal of the oxide; exposing the doped crystal in a bomb to a reducing atmosphere at superatmospheric pressure and a temperature effecting precipitation of the dopant metal in the crystal lattice of the oxide but insufficient to effect net diffusion of the metal out of the lattice; and then cooling the crystal. Preferably, the cooling step is effected by quenching. The process forms colloidal precipitates of the metal in the oxide lattice. The process may be used, for example, to produce thermally stable black MgO crystalline bodies containing magnetic colloidal precipitates consisting of about 99% Ni. The Ni-containing bodies are solar-selective absorbers, having a room-temperature absorptivity of about 0.96 over virtually all of the solar-energy spectrum and exhibiting an absorption edge in the region of 2 .mu.m. The process parameters can be varied to control the average size of the precipitates. The process can produce a black MgO crystalline body containing colloidal Ni precipitates, some of which have the face-centered-cubic structure and others of which have the body-centered cubic structure. The products of the process are metal-precipitate-containing refractory crystalline oxides which have improved or unique optical, mechanical, magnetic, and/or electronic properties.

Formation and Thermal Stability of Large Precipitates and Oxides in Titanium and Niobium Microalloyed Steel

Institute of Scientific and Technical Information of China (English)

ZHUO Xiao-jun; WOO Dae-hee; WANG Xin-hua; LEE Hae-geon

2008-01-01

As-cast CC slabs of microalloyed steels are prone to surface and sub-surface cracking. Precipitation phenomena in-itiated during solidification reduce ductility at high temperature. The unidirectional solidification unit is employed to sim-ulate the solidification process during continuous casting. Precipitation behavior and thermal stability are systemati-cally investigated. Samples of adding titanium and niobium to steels have been examined using field emission scanning electron microscope (FE-SEM), electron probe X-ray microanalyzer (EPMA), and transmission electron microscope (TEM). It has been found that the addition of titanium and niobium to high-strength low-alloyed (HSLA) steel resuited in undesirable large precipitation in the steels, i. e. , precipitation of large precipitates with various morphologies. The composition of the large precipitates has been determined. The effect of cooling rate on (Ti, Nb)(C, N) precipitate formation is investigated. With increasing the cooling rate, titanium-rich (Ti,Nb)(C, N) precipitates are transformed to niobium-rich (Ti,Nb)(C,N) precipitates. The thermal stability of these large precipitates and oxides have been assessed by carrying out various heat treatments such as holding and quenching from temperature at 800 and 1 200 ℃. It has been found that titanium-rich (Ti,Nb)(C,N) precipitate is stable at about 1 200 ℃ and niobi-um-rich (Ti,Nb)(C,N) precipitate is stable at about 800 ℃. After reheating at 1 200 ℃ for 1 h, (Ca, Mn)S and TiN are precipitated from Ca-Al oxide. However, during reheating at 800 ℃ for 1 h, Ca-Al-Ti oxide in specimens was stable. The thermodynamic calculation of simulating the thermal process is employed. The calculation results are in good agreement with the experimental results.

Marine Bacillus spores as catalysts for oxidative precipitation and sorption of metals.

Science.gov (United States)

Francis, C A; Tebo, B M

1999-08-01

The oxidation of soluble manganese(II) to insoluble Mn(III,IV) oxide precipitates plays an important role in the environment. These Mn oxides are known to oxidize numerous organic and inorganic compounds, scavenge a variety of other metals on their highly charged surfaces, and serve as electron acceptors for anaerobic respiration. Although the oxidation of Mn(II) in most environments is believed to be bacterially-mediated, the underlying mechanisms of catalysis are not well understood. In recent years, however, the application of molecular biological approaches has provided new insights into these mechanisms. Genes involved in Mn oxidation were first identified in our model organism, the marine Bacillus sp. strain SG-1, and subsequently have been identified in two other phylogenetically distinct organisms, Leptothrix discophora and Pseudomonas putida. In all three cases, enzymes related to multicopper oxidases appear to be involved, suggesting that copper may play a universal role in Mn(II) oxidation. In addition to catalyzing an environmentally important process, organisms capable of Mn(II) oxidation are potential candidates for the removal, detoxification, and recovery of metals from the environment. The Mn(II)-oxidizing spores of the marine Bacillus sp. strain SG-1 show particular promise, due to their inherent physically tough nature and unique capacity to bind and oxidatively precipitate metals without having to sustain growth.

Effects of solid fission products forming dissolved oxide (Nd) and metallic precipitate (Ru) on the thermal conductivity of uranium base oxide fuel

International Nuclear Information System (INIS)

Kim, Dong-Joo; Yang, Jae-Ho; Kim, Jong-Hun; Rhee, Young-Woo; Kang, Ki-Won; Kim, Keon-Sik; Song, Kun-Woo

2007-01-01

The effects of solid fission products on the thermal conductivity of uranium base oxide nuclear fuel were experimentally investigated. Neodymium (Nd) and ruthenium (Ru) were added to represent the physical states of solid fission products such as 'dissolved oxide' and 'metallic precipitate', respectively. Thermal conductivity was determined on the basis of the thermal diffusivity, density and specific heat values. The effects of the additives on the thermal conductivity were quantified in the form of the thermal resistivity equation - the reciprocal of the phonon conduction equation - which was determined from the measured data. It is concluded that the thermal conductivity of the irradiated nuclear fuel is affected by both the 'dissolved oxide' and the 'metallic precipitate', however, the effects are in the opposite direction and the 'dissolved oxide' influences the thermal conductivity more significantly than that of the 'metallic precipitate'

The development of latent fingerprints by zinc oxide and tin oxide nanoparticles prepared by precipitation technique

Science.gov (United States)

Luthra, Deepali; Kumar, Sacheen

2018-05-01

Fingerprints are the very important evidence at the crime scene which must be developed clearly with shortest duration of time to solve the case. Metal oxide nanoparticles could be the mean to develop the latent fingerprints. Zinc oxide and Tin Oxide Nanoparticles were prepared by using chemical precipitation technique which were dried and characterized by X-ray diffraction, UV-Visible spectroscopy and FTIR. The size of zinc oxide crystallite was found to be 14.75 nm with minimum reflectance at 360 nm whereas tin oxide have the size of 90 nm and reflectance at minimum level 321 nm. By using these powdered samples on glass, plastic and glossy cardboard, latent fingerprints were developed. Zinc oxide was found to be better candidate than tin oxide for the fingerprint development on all the three types of substrates.

Microwave—enhanced Mannich Condensation of Terminal Alkynes,Primary Amines with Paraformaldehyde on cuprous Iodide Doped Alumina under Solvent Free Conditions

Institute of Scientific and Technical Information of China (English)

王磊; 李品华

2003-01-01

A microwave-enhanced,solventless Mannich condensation of terminal alkynes,primary amines with paraformaldehyde on cuprous iodide doped alumina has been investigated.The structures of products depend on the ratio of alkyne to amine and paraformaldehyde.

The effect of energetic electron precipitation on the nitric oxide density in the lower thermosphere

International Nuclear Information System (INIS)

Saetre, Camilla

2006-12-01

The objective of this thesis has been the study of the chemical effects of the electron precipitation in the upper atmosphere, and mainly the increase of thermospheric nitric oxide (NO). NO plays an important role in the temperature balance for the mesosphere and thermosphere.In this project auroral electron precipitation data, derived from the Polar Ionospheric X-ray Imaging Experiment (PIXIE) and the Ultraviolet Imager (UVI) on board the Polar satellite, have been used together with NO density measurements from the Student Nitric Oxide Explorer (SNOE)

Pitting corrosion of copper. An equilibrium - mass transport study

Energy Technology Data Exchange (ETDEWEB)

Taxen, C

1996-11-01

A mathematical model for the propagation of corrosion pits on copper is described. The model is used to predict the potentials below which copper is immune to pitting. The criteria used for immunity against pitting is that the volume of the cuprous oxide formed at the site of the metal oxidation at the bottom of a corrosion pit must be smaller than the volume of the oxidised metal. Equal volumes would give a complete coverage of the metal in a pit by adherent cuprous oxide and propagation would not be possible. For potentials where copper is not immune to pitting an estimate of the maximum growth rate is given. The model uses equilibrium data and diffusion coefficients and calculates the stationary concentration profiles from the bulk water outside a corrosion pit to the site of the metal dissolution at the bottom a corrosion pit. Precipitation of oxides as well as of basic salts of copper is considered. A total of 26 aqueous species are considered in waters with compositions ranging from those of tap waters to that of sea water. Calculations are made for the temperatures 25 deg C and 75 deg C. 38 refs, 60 figs, 17 tabs

Electrochemical preparation of uniform CuO/Cu2O heterojunction on β-cyclodextrin-modified carbon fibers

KAUST Repository

Chen, Fang-Ping

2016-01-18

Abstract: In this work, a uniform heterojunction of cupric oxide/cuprous oxide was decorated on the surface of carbon fibers by electrochemical method (CuO/Cu2O/CDs/CFs). Methyl-β-cyclodextrin was first grafted on the surface of carbon fibers (CDs/CFs). Cubic cuprous oxide was electrodeposited on the surface of (Cu2O/CDs/CFs) in 0.1 M KNO3, the cuprous oxide was then partly anodized to cupric oxide to form a heterojunction of cupric oxide/cuprous oxide with a burr shape (CuO/Cu2O/CDs/CFs). The obtained materials were characterized by field emission scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and electrochemical techniques. The potential application in pollution treatment was further investigated, and the prepared CuO/Cu2O/CDs/CFs could be a promising adsorbent/photocatalyst toward the uptake and degradation of 2, 6-dichlorophenol (2, 6-DCP). Graphical Abstract: [Figure not available: see fulltext.] © 2016 Springer Science+Business Media Dordrecht

Biogenic precipitation of manganese oxides and enrichment of heavy metals at acidic soil pH

Science.gov (United States)

Mayanna, Sathish; Peacock, Caroline L.; Schäffner, Franziska; Grawunder, Anja; Merten, Dirk; Kothe, Erika; Büchel, Georg

2014-05-01

The precipitation of biogenic Mn oxides at acidic pH is rarely reported and poorly understood, compared to biogenic Mn oxide precipitation at near neutral conditions. Here we identified and investigated the precipitation of biogenic Mn oxides in acidic soil, and studied their role in the retention of heavy metals, at the former uranium mining site of Ronneburg, Germany. The site is characterized by acidic pH, low carbon content and high heavy metal loads including rare earth elements. Specifically, the Mn oxides were present in layers identified by detailed soil profiling and within these layers pH varied from 4.7 to 5.1, Eh varied from 640 to 660 mV and there were enriched total metal contents for Ba, Ni, Co, Cd and Zn in addition to high Mn levels. Using electron microprobe analysis, synchrotron X-ray diffraction and X-ray absorption spectroscopy, we identified poorly crystalline birnessite (δ-MnO2) as the dominant Mn oxide in the Mn layers, present as coatings covering and cementing quartz grains. With geochemical modelling we found that the environmental conditions at the site were not favourable for chemical oxidation of Mn(II), and thus we performed 16S rDNA sequencing to isolate the bacterial strains present in the Mn layers. Bacterial phyla present in the Mn layers belonged to Firmicutes, Actinobacteria and Proteobacteria, and from these phyla we isolated six strains of Mn(II) oxidizing bacteria and confirmed their ability to oxidise Mn(II) in the laboratory. The biogenic Mn oxide layers act as a sink for metals and the bioavailability of these metals was much lower in the Mn layers than in adjacent layers, reflecting their preferential sorption to the biogenic Mn oxide. In this presentation we will report our findings, concluding that the formation of natural biogenic poorly crystalline birnessite can occur at acidic pH, resulting in the formation of a biogeochemical barrier which, in turn, can control the mobility and bioavailability of heavy metals in

Structure and Reactivity of Zeolite- and Carbon-Supported Catalysts for the Oxidative Carbonylation of Alcohols

OpenAIRE

Briggs, Daniel Neal

2010-01-01

AbstractStructure and Reactivity of Zeolite- and Carbon-Supported Catalysts for the Oxidative Carbonylation of AlcoholsbyDaniel Neal BriggsDoctor of Philosophy in Chemical EngineeringUniversity of California, BerkeleyProfessor Alexis T. Bell, Chair The oxidative carbonylation of alcohols to produce dialkyl carbonates is a process that takes place commercially in a slurry of cuprous chloride in the appropriate alcohol. While this process is chemically efficient, it incurs costs in terms of ene...

The formation of magnetic carboxymethyl-dextrane-coated iron-oxide nanoparticles using precipitation from an aqueous solution

International Nuclear Information System (INIS)

Makovec, Darko; Gyergyek, Sašo; Primc, Darinka; Plantan, Ivan

2015-01-01

The formation of spinel iron-oxide nanoparticles during the co-precipitation of Fe 3+ /Fe 2+ ions from an aqueous solution in the presence of carboxymethyldextrane (CMD) was studied. To follow the formation of the nanoparticles, a mixture of the Fe ions, CMD and ammonia was heated to different temperatures, while the samples were taken, quenched in liquid nitrogen, freeze-dried and characterized using transmission electron microscopy (TEM), X-ray diffractometry (XRD) and magnetometry. The CMD plays a role in the reactions of the Fe ions' precipitation by partially immobilizing the Fe 3+ ions into a complex. At room temperature, the amorphous material is precipitated. Then, above approximately 30 °C, the spinel nanoparticles form inside the amorphous matrix, and at approximately 40 °C the matrix decomposes into the suspension of carboxymethyl-dextrane-coated iron-oxide nanoparticles. The CMD bonded to the nanoparticles' surfaces hinders the mass transport and thus prevents their growth. - Highlights: • The carboxymethyl-dextrane coated iron-oxide nanoparticles were synthesized. • The carboxymethyl-dextrane significantly modifies formation of the spinel nanoparticles. • The spinel nanoparticles are formed inside the amorphous matrix. • At approximately 40 °C the matrix decomposes into the suspension of carboxymethyl-dextrane-coated iron-oxide nanoparticles

The formation of magnetic carboxymethyl-dextrane-coated iron-oxide nanoparticles using precipitation from an aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Makovec, Darko [Department for Materials Synthesis, Jožef Stefan Institute, Jamova ulica 39, SI-1000 Ljubljana (Slovenia); Gyergyek, Sašo, E-mail: saso.gyergyek@ijs.si [Department for Materials Synthesis, Jožef Stefan Institute, Jamova ulica 39, SI-1000 Ljubljana (Slovenia); Primc, Darinka [Department for Materials Synthesis, Jožef Stefan Institute, Jamova ulica 39, SI-1000 Ljubljana (Slovenia); Plantan, Ivan [Lek Pharmaceuticals d.d., Mengeš (Slovenia)

2015-03-01

The formation of spinel iron-oxide nanoparticles during the co-precipitation of Fe{sup 3+}/Fe{sup 2+} ions from an aqueous solution in the presence of carboxymethyldextrane (CMD) was studied. To follow the formation of the nanoparticles, a mixture of the Fe ions, CMD and ammonia was heated to different temperatures, while the samples were taken, quenched in liquid nitrogen, freeze-dried and characterized using transmission electron microscopy (TEM), X-ray diffractometry (XRD) and magnetometry. The CMD plays a role in the reactions of the Fe ions' precipitation by partially immobilizing the Fe{sup 3+} ions into a complex. At room temperature, the amorphous material is precipitated. Then, above approximately 30 °C, the spinel nanoparticles form inside the amorphous matrix, and at approximately 40 °C the matrix decomposes into the suspension of carboxymethyl-dextrane-coated iron-oxide nanoparticles. The CMD bonded to the nanoparticles' surfaces hinders the mass transport and thus prevents their growth. - Highlights: • The carboxymethyl-dextrane coated iron-oxide nanoparticles were synthesized. • The carboxymethyl-dextrane significantly modifies formation of the spinel nanoparticles. • The spinel nanoparticles are formed inside the amorphous matrix. • At approximately 40 °C the matrix decomposes into the suspension of carboxymethyl-dextrane-coated iron-oxide nanoparticles.

Precipitation of plutonium (III) oxalate and calcination to plutonium oxide

International Nuclear Information System (INIS)

Esteban, A.; Orosco, E.H.; Cassaniti, P.; Greco, L.; Adelfang, P.

1989-01-01

The plutonium based fuel fabrication requires the conversion of the plutonium nitrate solution from nuclear fuel reprocessing into pure PuO2. The conversion method based on the precipitation of plutonium (III) oxalate and subsequent calcination has been studied in detail. In this procedure, plutonium (III) oxalate is precipitated, at room temperature, by the slow addition of 1M oxalic acid to the feed solution, containing from 5-100 g/l of plutonium in 1M nitric acid. Before precipitation, the plutonium is adjusted to trivalent state by addition of 1M ascorbic acid in the presence of an oxidation inhibitor such as hydrazine. Finally, the precipitate is calcinated at 700 deg C to obtain PuO2. A flowsheet is proposed in this paper including: a) A study about the conditions to adjust the plutonium valence. b) Solubility data of plutonium (III) oxalate and measurements of plutonium losses to the filtrate and wash solution. c) Characterization of the obtained products. Plutonium (III) oxalate has several potential advantages over similar conversion processes. These include: 1) Formation of small particle sizes powder with good pellets fabrication characteristics. 2) The process is rather insensitive to most process variables, except nitric acid concentration. 3) Ambient temperature operations. 4) The losses of plutonium to the filtrate are less than in other conversion processes. (Author) [es

Nickel oxide/hydroxide nanoplatelets synthesized by chemical precipitation for electrochemical capacitors

International Nuclear Information System (INIS)

Wu, M.-S.; Hsieh, H.-H.

2008-01-01

Nickel hydroxide powder prepared by directly chemical precipitation method at room temperature has a nanoplatelet-like morphology and could be converted into nickel oxide at annealing temperature higher than 300 deg. C, confirmed by the thermal gravimetric analysis and X-ray diffraction. Annealing temperature influences significantly both the electrical conductivity and the specific surface area of nickel oxide/hydroxide powder, and consequently determines the capacitor behavior. Electrochemical capacitive behavior of the synthesized nickel hydroxide/oxide film is investigated by cyclic voltammetry and electrochemical impedance spectroscope methods. After 300 deg. C annealing, the highest specific capacitance of 108 F g -1 is obtained at scan rate of 10 mV s -1 . When annealing temperature is lower than 300 deg. C, the electrical conductivity of nickel hydroxide dominates primarily the capacitive behavior. When annealing temperature is higher than 300 deg. C, both electrical conductivity and specific surface area of the nickel oxide dominate the capacitive behavior

Nano Copper Oxide-Modified Carbon Cloth as Cathode for a Two-Chamber Microbial Fuel Cell

OpenAIRE

Dong, Feng; Zhang, Peng; Li, Kexun; Liu, Xianhua; Zhang, Pingping

2016-01-01

In this work, Cu2O nanoparticles were deposited on a carbon cloth cathode using a facile electrochemical method. The morphology of the modified cathode, which was characterized by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) tests, showed that the porosity and specific surface area of the cathode improved with longer deposition times. X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) results showed that cupric oxide and cuprous oxide coexisted on the ca...

Synthesis and crystal kinetics of cerium oxide nanocrystallites prepared by co-precipitation process

International Nuclear Information System (INIS)

Shih, C.J.; Chen, Y.J.; Hon, M.H.

2010-01-01

Cerium oxide nanocrystallites were synthesized at a relatively low temperature using cerium nitrate as starting materials in a water solution by a co-precipitation process. Effect of calcination temperature on the crystallite growth of cerium oxide nano-powders was investigated by X-ray diffraction, transmission electron microscopy and electron diffraction. The crystallization temperature of the cerium oxide powders was estimated to be about 273 K by XRD analysis. When calcined from 473 to 1273 K, the crystallization of the face-centered cubic phase was observed by XRD. The crystallite size of the cerium oxide increased from 10.0 to 43.8 nm with calcining temperature increasing from 673 to 1273 K. The activation energy for growth of cerium oxide nanoparticles was found to be 16.0 kJ mol -1 .

Synthesis and crystal kinetics of cerium oxide nanocrystallites prepared by co-precipitation process

Energy Technology Data Exchange (ETDEWEB)

Shih, C.J., E-mail: cjshih@kmu.edu.tw [Department of Fragrance and Cosmetics Science, Kaohsiung Medical University, 100 Shi-Chuan 1st Road, Kaohsiung 807, Taiwan (China); Chen, Y.J. [Institute of Biomedical Sciences, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Hon, M.H. [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)

2010-05-15

Cerium oxide nanocrystallites were synthesized at a relatively low temperature using cerium nitrate as starting materials in a water solution by a co-precipitation process. Effect of calcination temperature on the crystallite growth of cerium oxide nano-powders was investigated by X-ray diffraction, transmission electron microscopy and electron diffraction. The crystallization temperature of the cerium oxide powders was estimated to be about 273 K by XRD analysis. When calcined from 473 to 1273 K, the crystallization of the face-centered cubic phase was observed by XRD. The crystallite size of the cerium oxide increased from 10.0 to 43.8 nm with calcining temperature increasing from 673 to 1273 K. The activation energy for growth of cerium oxide nanoparticles was found to be 16.0 kJ mol{sup -1}.

PRECIPITATION OF PROTACTINIUM

Science.gov (United States)

Moore, R.L.

1958-07-15

An lmprovement in the separation of protactinium from aqueous nitric acid solutions is described. 1t covers the use of lead dioxide and tin dioxide as carrier precipitates for the protactinium. In carrying out the process, divalent lead or divalent tin is addcd to the solution and oxidized, causing formation of a carrier precipitate of lead dioxide or stannic oxide, respectively.

Thermodynamic properties of copper compounds with oxygen and hydrogen from first principles

Energy Technology Data Exchange (ETDEWEB)

Korzhavyi, P.A.; Johansson, B. (Applied Materials Physics, Dept. of Materials Science and Engineering, Royal Inst. of Technology, Stockholm (Sweden))

2010-02-15

We employ quantum-mechanical calculations (based on density functional theory and linear response theory) in order to test the mechanical and chemical stability of several solid-state configurations of Cu1+, Cu2+, O2-, H1-, and H1+ ions. We begin our analysis with cuprous oxide (Cu{sub 2}O, cuprite structure), cupric oxide (CuO, tenorite structure), and cuprous hydride (CuH, wurtzite and sphalerite structures) whose thermodynamic properties have been studied experimentally. In our calculations, all these compounds are found to be mechanically stable configurations. Their formation energies calculated at T = 0 K (including the energy of zero-point and thermal motion of the ions) and at room temperature are in good agreement with existing thermodynamic data. A search for other possible solid-state conformations of copper, hydrogen, and oxygen ions is then performed. Several candidate structures for solid phases of cuprous oxy-hydride (Cu{sub 4}H{sub 2}O) and cupric hydride (CuH{sub 2}) have been considered but found to be dynamically unstable. Cuprous oxy-hydride is found to be energetically unstable with respect to decomposition onto cuprous oxide and cuprous hydride. Metastability of cuprous hydroxide (CuOH) is established in our calculations. The free energy of CuOH is calculated to be some 50 kJ/mol higher than the average of the free energies of Cu{sub 2}O and water. Thus, cuprite Cu{sub 2}O is the most stable of the examined Cu(I) compounds

Thermodynamic properties of copper compounds with oxygen and hydrogen from first principles

International Nuclear Information System (INIS)

Korzhavyi, P.A.; Johansson, B.

2010-02-01

We employ quantum-mechanical calculations (based on density functional theory and linear response theory) in order to test the mechanical and chemical stability of several solid-state configurations of Cu 1+ , Cu 2+ , O 2- , H 1- , and H 1+ ions. We begin our analysis with cuprous oxide (Cu 2 O, cuprite structure), cupric oxide (CuO, tenorite structure), and cuprous hydride (CuH, wurtzite and sphalerite structures) whose thermodynamic properties have been studied experimentally. In our calculations, all these compounds are found to be mechanically stable configurations. Their formation energies calculated at T = 0 K (including the energy of zero-point and thermal motion of the ions) and at room temperature are in good agreement with existing thermodynamic data. A search for other possible solid-state conformations of copper, hydrogen, and oxygen ions is then performed. Several candidate structures for solid phases of cuprous oxy-hydride (Cu 4 H 2 O) and cupric hydride (CuH 2 ) have been considered but found to be dynamically unstable. Cuprous oxy-hydride is found to be energetically unstable with respect to decomposition onto cuprous oxide and cuprous hydride. Metastability of cuprous hydroxide (CuOH) is established in our calculations. The free energy of CuOH is calculated to be some 50 kJ/mol higher than the average of the free energies of Cu 2 O and water. Thus, cuprite Cu 2 O is the most stable of the examined Cu(I) compounds

Room temperature inorganic polycondensation of oxide (Cu2O and ZnO) nanoparticles and thin films preparation by the dip-coating technique

International Nuclear Information System (INIS)

Salek, G.; Tenailleau, C.; Dufour, P.; Guillemet-Fritsch, S.

2015-01-01

Oxide thin solid films were prepared by dip-coating into colloidal dispersions of oxide nanoparticles stabilized at room temperature without the use of chelating or complex organic dispersing agents. Crystalline oxide nanoparticles were obtained by inorganic polycondensation and characterized by X-ray diffraction and field emission gun scanning electron microscopy. Water and ethanol synthesis and solution stabilization of oxide nanoparticle method was optimized to prepare two different structural and compositional materials, namely Cu 2 O and ZnO. The influence of hydrodynamic parameters over the particle shape and size is discussed. Spherical and rod shape nanoparticles were formed for Cu 2 O and ZnO, respectively. Isoelectric point values of 7.5 and 8.2 were determined for cuprous and zinc oxides, respectively, after zeta potential measurements. A shear thinning and thixotropic behavior was observed in both colloidal sols after peptization at pH ~ 6 with dilute nitric acid. Every colloidal dispersion stabilized in a low cost and environmentally friendly azeotrope solution composed of 96 vol.% of ethanol with water was used for the thin film preparation by the dip-coating technique. Optical properties of the light absorber cuprous oxide and transparent zinc oxide thin solid films were characterized by means of transmittance and reflectance measurements (300–1100 nm). - Highlights: • Room temperature inorganic polycondensation of crystalline oxides • Water and ethanol synthesis and solution stabilization of oxide nanoparticles • Low cost method for thin solid film preparation

Production of mixed oxide fuel for fast reactor irradiation test by co-precipitation

International Nuclear Information System (INIS)

Todokoro, Akio; Masuda, Sumio; Naruki, Kaoru; Kaya, Akira; Koizumi, Masumichi

1974-01-01

Studies were made on the production of homogeneous mixed oxide by co-precipitation. Experiments were made on the effects of the addition rate of ammonia water, precipitation temperature, aging time of co-precipitate, and pH value. Plutonium refined by anion exchange was mixed with solution of uranium. The concentration of free acid in the mixed solution was adjusted to 1.5-2.0 M, and the total volume of the solution was made 3.01. The weight of Pu and U in the solution was 100g. The solution was kept at a definite temperature while being stirred. Concentrated ammonia solution was added to the solution at a definite rate. The precipitate thus formed was filtrated after aging, then dried for 24 hours at 100 +- 2 0 C. Dried co-precipitate was calcinated for 1 hr at 550 0 C. The reduction for 4 hours at 800 0 C gave the mixed powder of PuO 2 and UO 2 . After pressing, the powder was sintered for 2 hours at 1700 0 C. The shrinkage ratio decreased as the activity and tap density of the original powder increased. The activity determined by specific surface area increased as the rate of ammonia water addition increased, and as the precipitation temperature rose. Tap density was independent of the rate of addition of ammonia water. The activity of the powder increased and the tap density decreased as the aging time of precipitate increased. (Fukutomi, T.)

Room temperature inorganic polycondensation of oxide (Cu{sub 2}O and ZnO) nanoparticles and thin films preparation by the dip-coating technique

Energy Technology Data Exchange (ETDEWEB)

Salek, G.; Tenailleau, C., E-mail: tenailleau@chimie.ups-tlse.fr; Dufour, P.; Guillemet-Fritsch, S.

2015-08-31

Oxide thin solid films were prepared by dip-coating into colloidal dispersions of oxide nanoparticles stabilized at room temperature without the use of chelating or complex organic dispersing agents. Crystalline oxide nanoparticles were obtained by inorganic polycondensation and characterized by X-ray diffraction and field emission gun scanning electron microscopy. Water and ethanol synthesis and solution stabilization of oxide nanoparticle method was optimized to prepare two different structural and compositional materials, namely Cu{sub 2}O and ZnO. The influence of hydrodynamic parameters over the particle shape and size is discussed. Spherical and rod shape nanoparticles were formed for Cu{sub 2}O and ZnO, respectively. Isoelectric point values of 7.5 and 8.2 were determined for cuprous and zinc oxides, respectively, after zeta potential measurements. A shear thinning and thixotropic behavior was observed in both colloidal sols after peptization at pH ~ 6 with dilute nitric acid. Every colloidal dispersion stabilized in a low cost and environmentally friendly azeotrope solution composed of 96 vol.% of ethanol with water was used for the thin film preparation by the dip-coating technique. Optical properties of the light absorber cuprous oxide and transparent zinc oxide thin solid films were characterized by means of transmittance and reflectance measurements (300–1100 nm). - Highlights: • Room temperature inorganic polycondensation of crystalline oxides • Water and ethanol synthesis and solution stabilization of oxide nanoparticles • Low cost method for thin solid film preparation.

The role of oxide structure on copper wire to the rubber adhesion

Science.gov (United States)

Su, Yea-Yang; Shemenski, Robert M.

2000-07-01

Most metals have an oxide layer on the surface. However, the structure of the oxide varies with the matrix composition, and depends upon the environmental conditions. A bronze coating, nominal composition of 98.5% Cu and balance of Sn, is applied to steel wire for reinforcing pneumatic tire beads and to provide adhesion to rubber. This work studied the influence of copper oxides on the bronze coating on adhesion during vulcanization. To emphasize the oxide structures, electrolytic tough pitch (ETP) copper wire was used instead of the traditional bronze-coated tire bead wire. Experimental results confirmed the hypothesis that cuprous oxide (Cu 2O) could significantly improve bonding between copper wire and rubber, and demonstrated that the interaction between rubber and oxide layer on wire is an electrochemical reaction.

Iron oxide and hydroxide precipitation from ferrous solutions and its relevance to Martian surface mineralogy

International Nuclear Information System (INIS)

Posey-Dowty, J.; Moskowitz, B.; Crerar, D.; Hargraves, R.; Tanenbaum, L.

1986-01-01

Experiments were performed to examine if the ubiquitousness of a weak magnetic component in all Martian surface fines tested with the Viking Landers can be attributed to ferric iron precipitation in aqueous solution under oxidizing conditions at neutral pH. Ferrous solutions were mixed in deionized water and various minerals were added to separate liquid samples. The iron-bearing additives included hematite, goethite, magnetite, maghemite, lepidocrocite and potassium bromide blank at varying concentrations. IR spectroscopic scans were made to identify any precipitates resulting from bubbling oxygen throughout the solutions; the magnetic properties of the precipitates were also examined. The data indicated that the lepidocrocite may have been preferentially precipitated, then aged to maghemite. The process would account for the presumed thin residue of maghemite on the present Martian surface, long after abundant liquid water on the Martian surface vanished. 40 references

Iron oxide and hydroxide precipitation from ferrous solutions and its relevance to Martian surface mineralogy

Science.gov (United States)

Posey-Dowty, J.; Moskowitz, B.; Crerar, D.; Hargraves, R.; Tanenbaum, L.

1986-01-01

Experiments were performed to examine if the ubiquitousness of a weak magnetic component in all Martian surface fines tested with the Viking Landers can be attributed to ferric iron precipitation in aqueous solution under oxidizing conditions at neutral pH. Ferrous solutions were mixed in deionized water and various minerals were added to separate liquid samples. The iron-bearing additives included hematite, goethite, magnetite, maghemite, lepidocrocite and potassium bromide blank at varying concentrations. IR spectroscopic scans were made to identify any precipitates resulting from bubbling oxygen throughout the solutions; the magnetic properties of the precipitates were also examined. The data indicated that the lepidocrocite may have been preferentially precipitated, then aged to maghemite. The process would account for the presumed thin residue of maghemite on the present Martian surface, long after abundant liquid water on the Martian surface vanished.

Continuous precipitation of mineral products: influence of mixing conditions on the co-precipitation of cerium-zirconium mixed oxides

International Nuclear Information System (INIS)

Di Patrizio, Nicolas

2015-01-01

An automated experimental set-up with rapid mixers is used to study the influence of mixing conditions on the co-precipitation of cerium-zirconium mixed oxides. The intensity of mixing is controlled by the inlet flow rates of the reacting solutions. An engulfment model is used to estimate a mixing time from the measurement of a segregation index by the Villermaux-Dushman reaction system. Three geometries of Hartridge Roughton mixers are compared. Mixing performance is better when a separate mixing chamber upstream of a narrower outlet pipe is present. A better mixing decreases the maximal reducibility temperature of the material and increases the crystal strains of the particles calcined at 1100 C. This is probably due to a better homogenization of the particles content. The important incorporation of nitrates in the particle at the outlet of the mixers shows precipitation occurs while the mixing process is not finished. This experimental result was confirmed by numerical simulation and an estimation of sur-saturations during the mixing process. (author)

Formation and decomposition of some rare earth (RE = La, Ce, Pr) hydroxides and oxides by homogeneous precipitation

International Nuclear Information System (INIS)

Ozawa, Masakuni; Onoe, Ryota; Kato, Hajime

2006-01-01

Formation and thermal decomposition of rare earth (RE = La, Ce, Pr) hydroxides and oxides by homogeneous precipitation using hexamethylenetetramine. The precipitatates were examined using thermal gravimetry and differential thermal analysis, infrared spectrometry and X-ray diffraction. The as-precipitated powders from the present process were La(OH) 3 , CeO 2 , Pr(OH) 3 . In the case of Ce, a cubic fluorite phase of cerium dioxide was directly obtained. The lanthanum trihydroxide decomposed to oxides via three steps. Two-step dehydration decomposition behavior at 340 and 500 o C was observed as La(OH) 3 → LaOOH + H 2 O and 2LaOOH → La 2 O 3 + H 2 O. The activation energy (ΔH) for dehydration was 240 and 244 kJ/mol, respectively. The additional decomposition of carbonate-containing species was observed at 670 o C with ΔH of 390 kJ/mol. Pr(OH) 3 did not show additional TGA profile of carbonate decomposition. Since no carbonate species form in solution during the HMT precipitation (hydrolysis of this molecule), the difference between La and Pr depends on the strength of basicity in the reaction with CO 2 after precipitation

Improving the performance of solar still by using nanofluids and providing vacuum

International Nuclear Information System (INIS)

Kabeel, A.E.; Omara, Z.M.; Essa, F.A.

2014-01-01

Highlights: • Modified solar still integrated with an external condenser and used nanofluids were studied. • The results obtained that using cuprous oxide increased the distilled productivity by 133.64%. • Using the aluminum oxide–water nanofluid increased the distillate productivity of the modified still by 125.0%. - Abstract: The experimental modifications were carried out into the conventional solar still, considerably increasing the distillate water productivity. The effects of using different types of nanomaterials on the performance of solar still were studied. The investigated solid nanoparticles are the cuprous and aluminum oxides. The performance was investigated at different weight fraction concentrations of nanoparticles in the basin water with and without providing vacuum. These additions and modifications greatly improve the evaporation and condensation rates and hence the distillate yield was augmented. The research was conducted for range of concentrations starting from 0.02% to 0.2% with a step of 0.02%. The maxima productivity was obtained for using the cuprous oxide nanoparticles with a concentration of 0.2% with operating the vacuum fan. The results obtained that using cuprous oxide nanoparticles increased the distilled productivity by 133.64% and 93.87% with and without the fan respectively. On the other hand, using aluminum oxide nanoparticles enhanced the distillate by 125.0% and 88.97% with and without the fan respectively as compared to the conventional still. The estimated cost of 1.0 l of distillate are approximately 0.035$, 0.045$ when using the cuprous oxide nanomaterial with and without the fan and, as well as the aluminum oxide nanoparticles, 0.038$ and 0.051$ respectively, and for the conventional still is 0.048$

Hysteresis losses in iron oxide nanoparticles prepared by glass crystallization or wet chemical precipitation

International Nuclear Information System (INIS)

Mueller, Robert; Dutz, Silvio; Hergt, Rudolf; Schmidt, Christopher; Steinmetz, Hanna; Zeisberger, Matthias; Gawalek, Wolfgang

2007-01-01

Ferrofluids were prepared from glass crystallized as well as wet precipitated iron oxide particles. Comparing hysteresis losses versus applied field amplitude from particles in immobilized state (powder) and in fluid state (ferrofluid) shows in some cases anomalous large losses at low magnetic fields. The influence of texture on the losses was investigated

Formation and decomposition of some rare earth (RE = La, Ce, Pr) hydroxides and oxides by homogeneous precipitation

Energy Technology Data Exchange (ETDEWEB)

Ozawa, Masakuni [Ceramics Research Laboratory, Nagoya Institute of Technology, Tajimi, 507-0071 Gifu (Japan)]. E-mail: ozawa@crl.nitech.ac.jp; Onoe, Ryota [Ceramics Research Laboratory, Nagoya Institute of Technology, Tajimi, 507-0071 Gifu (Japan); Kato, Hajime [Ceramics Research Laboratory, Nagoya Institute of Technology, Tajimi, 507-0071 Gifu (Japan)

2006-02-09

Formation and thermal decomposition of rare earth (RE = La, Ce, Pr) hydroxides and oxides by homogeneous precipitation using hexamethylenetetramine. The precipitatates were examined using thermal gravimetry and differential thermal analysis, infrared spectrometry and X-ray diffraction. The as-precipitated powders from the present process were La(OH){sub 3}, CeO{sub 2}, Pr(OH){sub 3}. In the case of Ce, a cubic fluorite phase of cerium dioxide was directly obtained. The lanthanum trihydroxide decomposed to oxides via three steps. Two-step dehydration decomposition behavior at 340 and 500 {sup o}C was observed as La(OH){sub 3} {sup {yields}} LaOOH + H{sub 2}O and 2LaOOH {sup {yields}} La{sub 2}O{sub 3} + H{sub 2}O. The activation energy ({delta}H) for dehydration was 240 and 244 kJ/mol, respectively. The additional decomposition of carbonate-containing species was observed at 670 {sup o}C with {delta}H of 390 kJ/mol. Pr(OH){sub 3} did not show additional TGA profile of carbonate decomposition. Since no carbonate species form in solution during the HMT precipitation (hydrolysis of this molecule), the difference between La and Pr depends on the strength of basicity in the reaction with CO{sub 2} after precipitation.

Structure of short-range-ordered iron(III)-precipitates formed by iron(II) oxidation in water containing phosphate, silicate, and calcium

Science.gov (United States)

Voegelin, A.; Frommer, J.; Vantelon, D.; Kaegi, R.; Hug, S. J.

2009-04-01

The oxidation of Fe(II) in water leads to the formation of Fe(III)-precipitates that strongly affect the fate of nutrients and contaminants in natural and engineered systems. Examples include the cycling of As in rice fields irrigated with As-rich groundwater or the treatment of drinking water for As removal. Knowledge of the types of Fe(III)-precipitates forming in such systems is essential for the quantitative modeling of nutrient and contaminant dynamics and for the optimization of water purification techniques on the basis of a mechanistic understanding of the relevant biogeochemical processes. In this study, we investigated the local coordination of Fe, P, and Ca in Fe(III)-precipitates formed by aeration of synthetic Fe(II)-containing groundwater with variable composition (pH 7, 2-30 mg/L Fe(II), 2-20 mg/L phosphate-P, 2-20 mg/L silicate-Si, 8 mM Na-bicarbonate or 2.5 mM Ca-&1.5 mM Mg-bicarbonate). After 4 hours of oxidation, Fe(III)-precipitates were collected on 0.2 µm nylon filters and dried. The precipitates were analyzed by Fe K-edge EXAFS (XAS beamline, ANKA, Germany) and by P and Ca K-edge XANES spectroscopy (LUCIA beamline, SLS, Switzerland). The Fe K-edge EXAFS spectra indicated that local Fe coordination in the precipitates systematically shifted with water composition. As long as water contained P, mainly short-range-ordered Fe(III)-phosphate formed (with molar P/Fe ~0.5). In the absence of P, Fe(III) precipitated as hydrous ferric oxide at high Si/Fe>0.5, as ferrihydrite at intermediate Si/Fe, and mainly as lepidocrocite at Si/Fe<0.2. Analysis of the EXAFS by shell-fitting indicated that Fe(III)-phosphates mainly contained mono- or oligomeric (edge- or corner-sharing) Fe and that the linkage between neighboring Fe(III)-octahedra changed from predominantly edge-sharing in Si-rich hydrous ferric oxide to edge- and corner-sharing in ferrihydrite. Electron microscopic data showed that changes in local precipitate structure were systematically

Precipitation of uranium oxide by reduction in alkaline solution; Precipitation d'oxyde d'uranium par reduction en milieu alcalin

Energy Technology Data Exchange (ETDEWEB)

Pottier, P; Claus, J [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1964-07-01

In the first part of the report the authors study the reaction mechanism for this reduction which makes it possible to precipitate a hydrated uranium oxide from alkaline uranyl carbonate solutions. The research into the effects of different variables on numerous cycles are then summarized. Optical, X-ray and thermogravimetric examinations then make it possible to predict the properties of this oxide. In the second part the authors carry out calculations for the continuous operation of single cells and cells in series. These calculations give the data required for the construction of 2 cells having capacities of 0.3 and 10 litres. Results obtained from the continuous operation of this latter cell lead to certain conclusions concerning the applicability of this method to the hydrometallurgy of uranium. (authors) [French] Dans une premiere partie, les auteurs etudient le mecanisme de reaction de cette reduction qui permet la precipitation d'un oxyde d'uranium hydrate dans les solutions d'uranyle-carbonates alcalins. Les etudes de diverses variables sur de nombreux cycles sont ensuite resumees. Puis des examens optiques, aux rayons X et par thermogravimetrie, permettent de proposer une hypothese sur les proprietes de l'oxyde obtenu. Dans la deuxieme partie, les auteurs developpent un calcul prevoyant la marche continue de cellules uniques et en cascades. De ces calculs on tire les elements permettant la realisation de deux cellules de 0,3 et 10 litres. Des resultats de marche continue sur cette derniere cellule, on peut conclure a l'applicabilite de cette methode a l'hydrometallurgie de l'uranium. (auteurs)

Electrical bistability and charge-transport mechanisms in cuprous sulfide nanosphere-poly(N-vinylcarbazole) composite films

International Nuclear Information System (INIS)

Tang Aiwei; Teng Feng; Liu Jie; Wang Yichao; Peng Hongshang; Hou Yanbing; Wang Yongsheng

2011-01-01

In this study, electrically bistable devices were fabricated by incorporating cuprous sulfide (Cu 2 S) nanospheres with mean size less than 10 nm into a poly(N-vinylcarbazole) (PVK) matrix. A remarkable electrical bistability was clearly observed in the current–voltage curves of the devices due to an electric-field-induced charge transfer between the dodecanethiol-capped Cu 2 S nanospheres and PVK. The maximum ON/OFF current ratio reached up to value as large as 10 4 , which was dependent on the mass ratios of Cu 2 S nanospheres to PVK, the amplitude of the scanning voltages, and the film thickness. The charge-transport mechanisms of the electrically bistable devices were described on the basis of the experimental results using different theoretical models of organic electronics.

Preparation of Cu{sub 2}O nanoparticles in cupric chloride solutions with a simple mechanochemical approach

Energy Technology Data Exchange (ETDEWEB)

Chen, D., E-mail: ma97chen@hotamil.co [School of Materials Science and Engineering, Hunan University, Changsha, 410082 (China); Graduate School of Energy Science, Kyoto University, 606-8501, Kyoto (Japan); Ni, S. [School of Materials Science and Engineering, Hunan University, Changsha, 410082 (China); Fang, J.J. [College of Electromechanical Engineering, North China University of Technology, Beijing, 100041 (China); Xiao, T. [School of Materials Science and Engineering, Hunan University, Changsha, 410082 (China)

2010-08-15

The cuprous oxide (Cu{sub 2}O) nanoparticles with diameter of 50-150 nm are prepared by high-energy ball milling in the various CuCl{sub 2} solutions with different [Cl{sup -}] concentration. The as-synthesized products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Finally, the effects of [Cl{sup -}] concentrations on the formation of cuprous oxide and reaction mechanism are discussed.

Biogenic uraninite precipitation and its reoxidation by iron(III) (hydr)oxides: A reaction modeling approach

Science.gov (United States)

Spycher, Nicolas F.; Issarangkun, Montarat; Stewart, Brandy D.; Sevinç Şengör, S.; Belding, Eileen; Ginn, Tim R.; Peyton, Brent M.; Sani, Rajesh K.

2011-08-01

One option for immobilizing uranium present in subsurface contaminated groundwater is in situ bioremediation, whereby dissimilatory metal-reducing bacteria and/or sulfate-reducing bacteria are stimulated to catalyze the reduction of soluble U(VI) and precipitate it as uraninite (UO 2). This is typically accomplished by amending groundwater with an organic electron donor. It has been shown, however, that once the electron donor is entirely consumed, Fe(III) (hydr)oxides can reoxidize biogenically produced UO 2, thus potentially impeding cleanup efforts. On the basis of published experiments showing that such reoxidation takes place even under highly reducing conditions (e.g., sulfate-reducing conditions), thermodynamic and kinetic constraints affecting this reoxidation are examined using multicomponent biogeochemical simulations, with particular focus on the role of sulfide and Fe(II) in solution. The solubility of UO 2 and Fe(III) (hydr)oxides are presented, and the effect of nanoscale particle size on stability is discussed. Thermodynamically, sulfide is preferentially oxidized by Fe(III) (hydr)oxides, compared to biogenic UO 2, and for this reason the relative rates of sulfide and UO 2 oxidation play a key role on whether or not UO 2 reoxidizes. The amount of Fe(II) in solution is another important factor, with the precipitation of Fe(II) minerals lowering the Fe +2 activity in solution and increasing the potential for both sulfide and UO 2 reoxidation. The greater (and unintuitive) UO 2 reoxidation by hematite compared to ferrihydrite previously reported in some experiments can be explained by the exhaustion of this mineral from reaction with sulfide. Simulations also confirm previous studies suggesting that carbonate produced by the degradation of organic electron donors used for bioreduction may significantly increase the potential for UO 2 reoxidation through formation of uranyl carbonate aqueous complexes.

Literature review on the properties of cuprous oxide Cu2O and the process of copper oxidation

International Nuclear Information System (INIS)

Korzhavyi, P. A.; Johansson, B.

2011-10-01

The purpose of the present review is to provide a reference guide to the most recent data on the properties of copper(I) oxide as well as on the atomic processes involved in the initial stages of oxidation of copper. The data on the structure of surfaces, as obtained from atomic-resolution microscopy studies (for example, STM) or from first-principles calculations, are reviewed. Information of this kind may be useful for understanding the atomic mechanisms of corrosion and stress-corrosion cracking of copper

Tailoring oxides of copper-Cu_2O and CuO nanoparticles and evaluation of organic dyes degradation

International Nuclear Information System (INIS)

Raghav, Ragini; Aggarwal, Priyanka; Srivastava, Sudha

2016-01-01

We report a simple one-pot colloidal synthesis strategy tailoring cuprous or cupric nano-oxides in pure state. NaOH provided alkaline conditions (pH 12.5 -13) for nano-oxides formation, while its concentration regulated the oxidation state of the nano-oxides. The morphological, structural and optical properties of synthesized Cu_2O and CuO nanoparticles were studied by transmission electron microscopy (TEM), X-Ray diffraction (XRD) and UV-vis spectroscopy. Dye degradation capability of CuO and Cu2O nanoparticles was evaluated using four organic dyes - Malachite green, Methylene blue, Methyl orange and Methyl red. The results demonstrate effective degradation of all four dyes employing with almost comparable activity both Cu_2O and CuO nanoparticles.

Oxidative precipitation of ruthenium oxide for supercapacitors: Enhanced capacitive performances by adding cetyltrimethylammonium bromide

Science.gov (United States)

Chen, I.-Li; Wei, Yu-Chen; Chen, Tsan-Yao; Hu, Chi-Chang; Lin, Tsang-Lang

2014-12-01

Thermally stable and porous RuO2·xH2O with superior rate-retention capability is prepared by the H2O2-oxidative precipitation method modified with the cetyltrimethylammonium bromide (CTAB) template. The specific capacitance and rate-retention of RuO2·xH2O are considerably enhanced by the CTAB modification and annealing at 200 °C because of extremely localized crystallization and pore opening of slightly sintered RuO2·xH2O nanoparticles trapped with CTAB. This unique structure, confirmed by the X-ray absorption spectroscopic (XAS), Raman spectroscopic, and transmission electron microscopic (TEM) analyses, favors the utilization of RuO2·xH2O nanocrystals and increases the electrolyte accessibility in comparing with RuO2·xH2O without CTAB modification. The preferential orientation growth along the {101} facet of RuO2 nanocrystals in some local regions is acquired by the CTAB modification and annealing in air at temperatures ≥350 °C. Such preferential orientation growth of RuO2 crystallites is attributable to the oxidation of trapped surfactants during the thermal annealing process, which adsorb on the high surface energy planes of RuO2.

Leaching behavior and chemical stability of copper butyl xanthate complex under acidic conditions.

Science.gov (United States)

Chang, Yi Kuo; Chang, Juu En; Chiang, Li Choung

2003-08-01

Although xanthate addition can be used for treating copper-containing wastewater, a better understanding of the leaching toxicity and the stability characteristics of the copper xanthate complexes formed is essential. This work was undertaken to evaluate the leaching behavior of copper xanthate complex precipitates by means of toxicity characteristics leaching procedure (TCLP) and semi-dynamic leaching test (SDLT) using 1 N acetic acid solution as the leachant. Also, the chemical stability of the copper xanthate complex during extraction has been examined with the studying of variation of chemical structure using UV-vis, Fourier transform infrared and X-ray photoelectron spectroscopies (XPS). Both TCLP and SDLT results showed that a negligible amount of copper ion was leached out from the copper xanthate complex precipitate, indicating that the complex exhibited a high degree of copper leaching stability under acidic conditions. Nevertheless, chemical structure of the copper xanthate complex precipitate varied during the leaching tests. XPS data suggested that the copper xanthate complex initially contained both cupric and cuprous xanthate, but the unstable cupric xanthate change to the cuprous form after acid extraction, indicating the cuprous xanthate to be the final stabilizing structure. Despite that, the changes of chemical structure did not induce the rapid leaching of copper from the copper xanthate complex.

Two-stage precipitation of neptunium (IV) oxalate

International Nuclear Information System (INIS)

Luerkens, D.W.

1983-07-01

Neptunium (IV) oxalate was precipitated using a two-stage precipitation system. A series of precipitation experiments was used to identify the significant process variables affecting precipitate characteristics. Process variables tested were input concentrations, solubility conditions in the first stage precipitator, precipitation temperatures, and residence time in the first stage precipitator. A procedure has been demonstrated that produces neptunium (IV) oxalate particles that filter well and readily calcine to the oxide

Synthesis of cerium oxide (CeO{sub 2}) nanoparticles using simple CO-precipitation method

Energy Technology Data Exchange (ETDEWEB)

Farahmandjou, M.; Zarinkamar, M.; Firoozabadi, T. P., E-mail: farahamndjou@iauvaramin.ac.ir [Islamis Azad University, Varamin-Phisva Branch, Department of Physics, Varamin (Iran, Islamic Republic of)

2016-11-01

Synthesis of cerium oxide (CeO{sub 2}) nanoparticles was studied by new and simple co-precipitation method. The cerium oxide nanoparticles were synthesized using cerium nitrate and potassium carbonate precursors. Their physicochemical properties were characterized by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (Sem), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (Ftir) and UV-Vis spectrophotometer. XRD pattern showed the cubic structure of the cerium oxide nanoparticles. The average particle size of CeO{sub 2} was around 20 nm as estimated by XRD technique and direct HRTEM observations. The surface morphological studies from Sem and Tem depicted spherical particles with formation of clusters. The sharp peaks in Ftir spectrum determined the existence of CeO{sub 2} stretching mode and the absorbance peak of UV-Vis spectrum showed the bandgap energy of 3.26 eV. (Author)

Fabrication of Cu2 O-based Materials for Lithium-Ion Batteries.

Science.gov (United States)

Zhang, Li; Li, Qinyuan; Xue, Huaiguo; Pang, Huan

2018-05-25

The improvement of the performance of advanced batteries has played a key role in the energy research community since its inception. Therefore, it is necessary to explore high-performance materials for applications in advanced batteries. Among the variety of materials applied in batteries, much research has been dedicated to examine cuprous oxide materials as working electrodes in lithium cells to check their suitability as anodes for Li-ion cells and this has revealed great working capacities because of their specific characteristics (polymorphic forms, controllable structure, high cycling capacity, etc.). Thus, cuprous oxide and its composites will be fully introduced in this Review for their applications in advanced batteries. It is believed that, in the future, both the study and the impact of cuprous oxide and its composites will be much more profound and lasting. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-rate reduction of copper oxide using atmospheric-pressure inductively coupled plasma microjets

International Nuclear Information System (INIS)

Tajima, Satomi; Tsuchiya, Shouichi; Matsumori, Masashi; Nakatsuka, Shigeki; Ichiki, Takanori

2011-01-01

Reduction of copper oxide was performed using an atmospheric-pressure inductively coupled plasma (AP-ICP) microjet while varying the input power P between 15 and 50 W. Cuprous oxide (Cu 2 O) and cupric oxide (CuO) were formed on the sputtered Cu surface by thermal annealing. Dynamic behavior of the microplasma jet, optical emission from H atoms, the substrate temperature, chemical bonding states of the treated surface, and the thickness of the reduced Cu layer were measured to study the fundamental reduction process. Surface composition and the thickness of the reduced Cu layer changed significantly with P. Rapid reduction of CuO and Cu 2 O was achieved at a rate of 493 nm/min at P = 50 W since high-density H atoms were produced by the AP-ICP microjet.

High-rate reduction of copper oxide using atmospheric-pressure inductively coupled plasma microjets

Energy Technology Data Exchange (ETDEWEB)

Tajima, Satomi; Tsuchiya, Shouichi [Department of Bioengineering, Graduate School of Engineering, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, 113-8656 (Japan); Matsumori, Masashi; Nakatsuka, Shigeki [Panasonic Factory Solutions Co., Ltd., 2-7 Matsuba-cho, Kadoma-city, Osaka, 571-8502 (Japan); Ichiki, Takanori, E-mail: ichiki@sogo.t.u-tokyo.ac.jp [Department of Bioengineering, Graduate School of Engineering, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, 113-8656 (Japan); Institute of Engineering Innovation, Graduate School of Engineering, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-8656 (Japan)

2011-08-01

Reduction of copper oxide was performed using an atmospheric-pressure inductively coupled plasma (AP-ICP) microjet while varying the input power P between 15 and 50 W. Cuprous oxide (Cu{sub 2}O) and cupric oxide (CuO) were formed on the sputtered Cu surface by thermal annealing. Dynamic behavior of the microplasma jet, optical emission from H atoms, the substrate temperature, chemical bonding states of the treated surface, and the thickness of the reduced Cu layer were measured to study the fundamental reduction process. Surface composition and the thickness of the reduced Cu layer changed significantly with P. Rapid reduction of CuO and Cu{sub 2}O was achieved at a rate of 493 nm/min at P = 50 W since high-density H atoms were produced by the AP-ICP microjet.

A modular continuous flow reactor system for the selective bio-oxidation of iron and precipitation of schwertmannite from mine-impacted waters.

Science.gov (United States)

Hedrich, Sabrina; Johnson, D Barrie

2012-02-01

A novel modular bioremediation system which facilitates the selective removal of soluble iron from extremely acidic (pH ∼2) metal-rich wastewaters by ferrous iron oxidation and selective precipitation of the ferric iron produced is described. In the first of the three modules, rapid ferrous iron oxidation was mediated by the recently-characterized iron-oxidizing autotrophic acidophile, "Ferrovum myxofaciens", which grew as long "streamers" within the reactor. Over 90% of the iron present in influent test liquors containing 280mg/L iron was oxidized at a dilution rate of 0.41h(-1), in a proton-consuming reaction. The ferric iron-rich solutions produced were pumped into a second reactor where controlled addition of sodium hydroxide caused the water pH to increase to 3.5 and ferric iron to precipitate as the mineral schwertmannite. Addition of a flocculating agent promoted rapid aggregation and settling of the fine-grain schwertmannite particles. A third passive module (a packed-bed bioreactor, also inoculated with "Fv. myxofaciens") acted as a polishing reactor, lowering soluble iron concentrations in the processed water to iron from a synthetic acidic (pH 2.1) mine water that contained soluble aluminum, copper, manganese and zinc in addition to iron. Schwertmannite was again produced, with little or no co-precipitation of other metals. Copyright © 2011 Elsevier Ltd. All rights reserved.

Preparation of Au/Y2O3 and Au/NiO catalysts by co-precipitation and their oxidation activities

International Nuclear Information System (INIS)

Sreethawong, Thammanoon; Sitthiwechvijit, Norsit; Rattanachatchai, Apiwat; Ouraipryvan, Piya; Schwank, Johannes W.; Chavadej, Sumaeth

2011-01-01

Research highlights: → The catalytic activity of Au catalysts supported on Y 2 O 3 and NiO prepared by co-precipitation was investigated for CO and methanol oxidation. → The phase transformation of yttrium support greatly affected the CO oxidation activity. → The Au/Y 2 O 3 exhibited the same activity as Au/NiO for the methanol oxidation while the Au/NiO gave higher activity for CO oxidation. - Abstract: The objective of this work was to investigate the catalytic activity of gold catalysts supported on two metal oxides, yttrium oxide and nickel oxide, prepared by co-precipitation for CO and methanol oxidation reactions. The TGA and XRD results confirmed that yttrium hydroxide (Y(OH) 3 ) was formed at calcination temperature below 300 deg. C. When it was calcined at 400 deg. C, the Y(OH) 3 was transformed to yttrium oxide hydroxide (YOOH). Finally, when calcination temperature was raised to 600 deg. C, the YOOH was completely transformed to yttrium oxide (Y 2 O 3 ). Interestingly, the gold loaded on YOOH calcined at 400 deg. C and gold loaded on Y 2 O 3 calcined at 500 deg. C comparatively showed the highest catalytic activity for complete CO oxidation at a reaction temperature of 300 deg. C. The 0.12% Au/Y 2 O 3 catalyst calcined at 500 deg. C was employed for both CO and methanol oxidation studies. For complete CO oxidation, the reaction temperatures of Au/Y 2 O 3 and Au/NiO catalysts were 325 deg. C and 250 deg. C, respectively. The light-off temperatures of Au/Y 2 O 3 and Au/NiO catalysts for methanol oxidation were 210 deg. C and 205 deg. C, respectively. Conclusively, the Au/Y 2 O 3 clearly exhibited the same activity as that of Au/NiO for methanol oxidation while the Au/NiO gave higher activity for CO oxidation.

Studying Impact of Different Precipitating Agents on Crystal Structure, Morphology and Photocatalytic Activity of Bismuth Oxide

Directory of Open Access Journals (Sweden)

Yayuk Astuti

2017-10-01

How to Cite: Astuti, Y., Arnelli, Pardoyo, Fauziyah, A., Nurhayati, S., Wulansari, A.D., Andianingrum, R., Widiyandari, H., Bhaduri, G.A. (2017. Studying Impact of Different Precipitating Agents on Crystal Structure, Morphology and Photocatalytic Activity of Bismuth Oxide. Bulletin of Chemical Reaction Engineering & Catalysis, 12 (3: 478-484 (doi:10.9767/bcrec.12.3.1144.478-484

Synthesis of composite nanoparticles using co-precipitation of a magnetic iron-oxide shell onto core nanoparticles

International Nuclear Information System (INIS)

Primc, Darinka; Belec, Blaž; Makovec, Darko

2016-01-01

Composite nanoparticles can be synthesized by coating a shell made of one material onto core nanoparticles made of another material. Here we report on a novel method for coating a magnetic iron oxide onto the surface of core nanoparticles in an aqueous suspension. The method is based on the heterogeneous nucleation of an initial product of Fe"3"+/Fe"2"+ co-precipitation on the core nanoparticles. The close control of the supersaturation of the precipitating species required for an exclusively heterogeneous nucleation and the growth of the shell were achieved by immobilizing the reactive Fe"3"+ ions in a nitrate complex with urea ([Fe((CO(NH_2)_2)_6](NO_3)_3) and by using solid Mg(OH)_2 as the precipitating reagent. The slow thermal decomposition of the complex at 60 °C homogeneously releases the reactive Fe"3"+ ions into the suspension of the core nanoparticles. The key stage of the process is the thermal hydrolysis of the released Fe"3"+ ions prior to the addition of Mg(OH)_2. The thermal hydrolysis results in the formation of γ-FeOOH, exclusively at the surfaces of the core nanoparticles. After the addition of the solid hydroxide Mg(OH)_2, the pH increases and at pH ~ 5.7 the Fe"2"+ precipitates and reacts with the γ-FeOOH to form magnetic iron oxide with a spinel structure (spinel ferrite) at the surfaces of the core nanoparticles. The proposed low-temperature method for the synthesis of composite nanoparticles is capable of forming well-defined interfaces between the two components, important for the coupling of the different properties. The procedure is environmentally friendly, inexpensive, and appropriate for scaling up to mass production.Graphical abstract

Precipitation of iron (III) using magnesium oxide in fluidized bed; Precipitacion de hierro (III) utilizando oxido de magnesio en lecho fluidizado

Energy Technology Data Exchange (ETDEWEB)

Esteban-Bocardo, P. A.; Ferreira-Rocha, S. D.

2006-07-01

A process for iron (III) removal by hydroxide precipitation from and acid synthetic inorganic effluent using magnesium oxide as an alternative precipitant agent in a fluidized bed was developed. An acid synthetic inorganic effluent containing 100 and 200 mg/l of ferric ions (pH=1.0) was continuously fed up to the acrylic column (30 cm high and 2 cm diameter) during 180 minutes. Magnesium oxide pulp (3% v/v) was injected at the beginning of the experiment in order to allow the iron hydroxides precipitation. The concentration and pH profiles agreed in their curves, while the pH profile rose,the concentration profile decreased and a high percentage of iron removal (higher to 99%) was reached. Extremely low iron concentrations have been reached, thus permitting to attend to the environmental standard of 10.0 mg/l for discharge of effluent containing ferric ions established by the law DN 10/86 of COPAM (Conselho de Politica Ambiental do Estado de Minas Gerais-Brazil). (Author)

Theory of enhanced second-harmonic generation by the quadrupole-dipole hybrid exciton

International Nuclear Information System (INIS)

Roslyak, Oleksiy; Birman, Joseph L

2008-01-01

We report calculated substantial enhancement of the second-harmonic generation (SHG) in cuprous oxide crystals, resonantly hybridized with an appropriate organic material (DCM2:CA:PS 'solid state solvent'). The quadrupole origin of the inorganic part of the quadrupole-dipole hybrid provides inversion symmetry breaking and the organic part contributes to the oscillator strength of the hybrid. We show that the enhancement of the SHG, compared to the bulk cuprous oxide crystal, is proportional to the ratio of the DCM2 dipole moment and the effective dipole moment of the quadrupole transitions in the cuprous oxide. It is also inversely proportional to the line-width of the hybrid and bulk excitons. The enhancement may be regulated by adjusting the organic blend (mutual concentration of the DCM2 and CA part of the solvent) and pumping conditions (varying the angle of incidence in the case of optical pumping or populating the minimum of the lower branch of the hybrid in the case of electrical pumping)

To postpone the precipitation of manganese oxides in the degradation of tetrachloroethylene by controlling the permanganate concentration.

Science.gov (United States)

Yang, Weiwei; Qiu, Zhaofu; Zhao, Zhexuan; Lu, Shuguang; Sui, Qian; Gu, Xiaogang

2017-01-01

Controlled-release permanganate (CRP) is a relatively new technology used to treat contaminated groundwater. This study tested the encapsulation of permanganate using stearic acid to realize controlled-release properties. Batch experiments were conducted to investigate the performance of manganese oxides (MnO 2 ) in the reaction between CRP and the contaminant of interest: tetrachloroethylene (PCE). The results showed that higher ionic strengths (I = 0.1 mol/L) cause earlier precipitation of MnO 2 colloids. Using CRP to degrade PCE could decrease the amount of MnO 2 colloids produced and postpone precipitation compared to raw potassium permanganate (KMnO 4 ) under high ionic strength conditions by controlling the KMnO 4 concentration in the solution. The amount of MnO 2 colloids produced and the time of precipitation depended more on the CRP grain size than on the CRP mass ratio. Controlling the KMnO 4 concentration used in the reaction could control the formation of MnO 2 precipitates in the premise of guarantee the removal rate of PCE.

A detailed study on the transition from the blocked to the superparamagnetic state of reduction-precipitated iron oxide nanoparticles

International Nuclear Information System (INIS)

Witte, K.; Bodnar, W.; Mix, T.; Schell, N.; Fulda, G.; Woodcock, T.G.; Burkel, E.

2016-01-01

Magnetic iron oxide nanoparticles were prepared by salt-assisted solid-state chemical precipitation method with alternating fractions of the ferric iron content. The physical properties of the precipitated nanoparticles mainly consisting of magnetite were investigated by means of transmission electron microscopy, high energy X-ray diffraction, vibrating sample magnetometry and Mössbauer spectroscopy. With particle sizes ranging from 16.3 nm to 2.1 nm, a gradual transition from the blocked state to the superparamagnetic state was observed. The transition was described as a dependence of the ferric iron content used during the precipitation. Composition, mean particle size, coercivity, saturation polarisation, as well as hyperfine interaction parameters and their evolution were studied systematically over the whole series of iron oxide nanoparticles. - Highlights: • Study of superparamagnetic transition of magnetite varying ferric iron content. • Coercivity is mainly influenced by the particle size. • Saturation polarisation influenced by the goethite content and the particle size. • Number of vacancies tend to increase with increasing ferric iron content. • Fe 3 O 4 B-sites are stronger effected by the reduction of particle size than A-sites.

Tin-antimony oxide oxidation catalysts

Energy Technology Data Exchange (ETDEWEB)

Berry, Frank J. [Open University, Department of Chemistry (United Kingdom)

1998-12-15

Tin-antimony oxide catalysts for the selective oxidation of hydrocarbons have been made by precipitation techniques. The dehydration of the amorphous dried precipitate by calcination at increasingly higher temperatures induces the crystallisation of a rutile-related tin dioxide-type phase and the segregation of antimony oxides which volatilise at elevated temperatures. The rutile-related tin dioxide-type phase contains antimony(V) in the bulk and antimony(III) in the surface. Specific catalytic activity for the oxidative dehydrogenation of butene to butadiene is associated with materials with large concentrations of antimony(III) in the surface.

Literature review on the properties of cuprous oxide Cu{sub 2}O and the process of copper oxidation

Energy Technology Data Exchange (ETDEWEB)

Korzhavyi, P. A.; Johansson, B. (Department of Materials Science and Engineering, Royal Institute of Technology, Stockholm (Sweden))

2011-10-15

The purpose of the present review is to provide a reference guide to the most recent data on the properties of copper(I) oxide as well as on the atomic processes involved in the initial stages of oxidation of copper. The data on the structure of surfaces, as obtained from atomic-resolution microscopy studies (for example, STM) or from first-principles calculations, are reviewed. Information of this kind may be useful for understanding the atomic mechanisms of corrosion and stress-corrosion cracking of copper

A study of selective precipitation techniques used to recover refined iron oxide pigments for the production of paint from a synthetic acid mine drainage solution

International Nuclear Information System (INIS)

Ryan, M.J.; Kney, A.D.; Carley, T.L.

2017-01-01

New resource recovery methods of acid mine drainage (AMD) treatment aim to reduce waste by extracting iron contaminants in usable forms, specifically iron oxides as industrial inorganic pigments, which can be marketed and sold to subsidize treatment costs. In this study, iron oxide pigments of varying colors and properties were recovered from a synthetic AMD solution through a stepwise selective precipitation process using oxidation, pH adjustment, and filtration. Chemical and physical design variables within the process, such as alkaline addition rate, reaction temperature, drying duration, and target pH, were altered and observed for their effects on iron oxide morphology as a means of reducing—or even eliminating—the need for refining after synthesis. Resulting iron oxide pigment powders were analyzed with X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), and visually evaluated for color and coating ability. Drying duration resulted in increased redness in paint streaks and enhanced crystallinity, as amorphous phases of iron oxide transformed into hematite. Alkaline addition rate showed no effect on the crystallinity of the powders and no consistent effect on color. Conversely, increasing reaction temperature darkened the color of pigments and increased surface area of pigment particles (thus improving coating ability) without changing the crystallinity of the samples. Iron oxides precipitated at pH 3 displayed the highest purity and possessed a distinct yellow color suggestive of jarosite, while other paint streaks darkened in color as trace metal impurities increased. The choice to use lower pH for higher quality iron oxides comes with the compromise of reduced iron recovery efficiency. Manganese and nickel did not begin to precipitate out of solution up to pH 7 and thus require increased pH neutralization in the field if natural AMD is found to contain those metals. All pigments developed in this study were found to be adequate for use as

Separation of pure Cerium oxides from rare earth compounds. Homogeneous precipitation using Urea-Hydrogen Peroxide

International Nuclear Information System (INIS)

Umeda, K.; Abrao, E.

1975-01-01

The obtainment of ceric oxide (CeO 2 ) of purity higher than 97% by application of homogeneous precipitation technique is described. The selective separation of cerium was reached by hydrolysis of urea in the presence of hydrogen peroxide, using a rare earths concentrate named rare earths chloride, a natural mixture of all lanthanides provenient from the industrialization of monazite. The best conditions for the preparation of CeO 2 of 94% purity are: 35-70g R 2 O 3 /1 and pH2,0 hydrolysis temperature: 88-90 0 C, urea/R 2 O 3 ratio: 4, H 2 O 2 /Ce 2 O 3 ratio: 1,5-5,0 and hydrolysis duration: 4 hours. A leaching procedure of the precipitate with 0,25-0,75M NHO 3 leads to a product of 97-99,5% CeO 2

Inorganic precursor peroxides for antifouling coatings

DEFF Research Database (Denmark)

Olsen, S.M.; Pedersen, L.T.; Hermann, M.H.

2009-01-01

Modern antifouling coatings are generally based on cuprous oxide (Cu2O) and organic biocides as active ingredients. Cu2O is prone to bioaccumulation, and should therefore be replaced by more environmentally benign compounds when technically possible. However, cuprous oxide does not only provide...... antifouling properties, it is also a vital ingredient for the antifouling coating to obtain its polishing and leaching mechanism. In this paper, peroxides of strontium, calcium, magnesium, and zinc are tested as pigments in antifouling coatings. The peroxides react with seawater to create hydrogen peroxide...... matrix provides antifouling properties exceeding those of a similar coating based entirely on zinc oxide....

Fe hydroxyphosphate precipitation and Fe(II) oxidation kinetics upon aeration of Fe(II) and phosphate-containing synthetic and natural solutions

NARCIS (Netherlands)

Grift, B. van der; Behrends, T.; Osté, L.A.; Schot, P.P.; Wassen, M.J.; Griffioen, J.

2016-01-01

Exfiltration of anoxic Fe-rich groundwater into surface water and the concomitant oxidative precipitation of Fe are important processes controlling the transport of phosphate (PO4) from agricultural areas to aquatic systems. Here, we explored the relationship between solution composition, reaction

Fe hydroxyphosphate precipitation and Fe(II) oxidation kinetics upon aeration of Fe(II) and phosphate-containing synthetic and natural solutions

NARCIS (Netherlands)

van der Grift, B.; Behrends, T.; Osté, L.A.; Schot, P.P.; Wassen, M.J.; Griffioen, J.

2016-01-01

Abstract Exfiltration of anoxic Fe-rich groundwater into surface water and the concomitant oxidative precipitation of Fe are important processes controlling the transport of phosphate (PO4) from agricultural areas to aquatic systems. Here, we explored the relationship between solution composition,

Microstructural aspects of the oxidation of zirconium alloys

International Nuclear Information System (INIS)

Proff, Ch.

2011-01-01

This thesis is focused on the microstructural characterisation of precipitates in the oxide of binary zirconium alloys (1 wt.% Fe, Cr or Ni or 0.6 wt.% Nb) under different oxidation conditions at 415 C. The samples were oxidised in autoclave in air and steam and in an environmental scanning electron microscope in water vapour. The microstructural evolution of the precipitates during oxidation was characterised using electron microscopy. The findings from the analysis are the following: -Two types of oxidation behaviour are observed for precipitates. -Pilling Bedworth ratio of precipitates is higher than that of the zirconium matrix. -Formation of pure iron oxide crystals on the surface for iron bearing precipitates close to or at the surface. From these observations it is concluded that the precipitate oxidation behaviour can be correlated to precipitate composition and oxidation tendency of the elements in the precipitates. Iron exhibits clearly different behaviour. (author)

In-cloud oxidation of SO2 as deduced from trace elements in aerosol and precipitation

International Nuclear Information System (INIS)

Heaton, R.; Rahn, K.A.

1985-01-01

During the past year, the authors have developed and begun to apply a sampling and analytical technique for precipitation which can measure nearly as many elements (30-40) as in the parent aerosol. Rain is collected in a polyethylene bag mounted directly under a simple polyethylene funnel. Typically, up to 500 ml are accumulated; sampling begins only after the rain has started. Snow is scooped into the same kind of bag during or shortly after the event; up to 500 ml are accumulated by repeated sampling and melting in the laboratory. The bags are sealed, frozen overnight, then opened and freeze-dried until all the ice has disappeared. The bag and its contents are then analyzed by instrumental neutron activation at the Rhode Island Nuclear Science Center. Sulfate is determined from a small aliquot of the precipitation removed before it is frozen. For comparison, aerosol samples taken before, during, and after the event are analyzed similarly. The principal goal of this research is to develop procedures for applying the University of Rhode Island's regional elemental tracer system, originally to use the patter of trace elements in precipitation to determine the fraction of the sulfate which has been produced by in-cloud oxidation of SO 2 , as opposed to direct scavenging of sulfate from aerosol

Towards deriving Ni-rich cathode and oxide-based anode materials from hydroxides by sharing a facile co-precipitation method.

Science.gov (United States)

Qiu, Haifa; Du, Tengfei; Wu, Junfeng; Wang, Yonglong; Liu, Jian; Ye, Shihai; Liu, Sheng

2018-05-22

Although intensive studies have been conducted on layered transition metal oxide(TMO)-based cathode materials and metal oxide-based anode materials for Li-ion batteries, their precursors generally follow different or even complex synthesis routes. To share one route for preparing precursors of the cathode and anode materials, herein, we demonstrate a facile co-precipitation method to fabricate Ni-rich hydroxide precursors of Ni0.8Co0.1Mn0.1(OH)2. Ni-rich layered oxide of LiNi0.8Co0.1Mn0.1O2 is obtained by lithiation of the precursor in air. An NiO-based anode material is prepared by calcining the precursor or multi-walled carbon nanotubes (MWCNTs) incorporated precursors. The pre-addition of ammonia solution can simplify the co-precipitation procedures and the use of an air atmosphere can also make the heat treatment facile. LiNi0.8Co0.1Mn0.1O2 as the cathode material delivers a reversible capacity of 194 mA h g-1 at 40 mA g-1 and a notable cycling retention of 88.8% after 100 cycles at 200 mA g-1. This noticeable performance of the cathode arises from a decent particle morphology and high crystallinity of the layered oxides. As the anode material, the MWCNTs-incorporated oxides deliver a much higher reversible capacity of 811.1 mA h g-1 after 200 cycles compared to the pristine oxides without MWCNTs. The improvement on electrochemical performance can be attributed to synergistic effects from MWCNTs incorporation, including reinforced electronic conductivity, rich meso-pores and an alleviated volume effect. This facile and sharing method may offer an integrated and economical approach for commercial production of Ni-rich electrode materials for Li-ion batteries.

Cuprous oxide thin films prepared by thermal oxidation of copper layer. Morphological and optical properties

Energy Technology Data Exchange (ETDEWEB)

Karapetyan, Artak, E-mail: karapetyan@cinam.univ-mrs.fr [Aix Marseille Université, CINaM, 13288, Marseille (France); Institute for Physical Research of NAS of Armenia, Ashtarak-2 0203 (Armenia); Reymers, Anna [Russian-Armenian (Slavonic) University, H.Emin st.123, Yerevan 375051 (Armenia); Giorgio, Suzanne; Fauquet, Carole [Aix Marseille Université, CINaM, 13288, Marseille (France); Sajti, Laszlo [Laser Zentrum Hannover e.V. Hollerithallee 8, 30419 Hannover (Germany); Nitsche, Serge [Aix Marseille Université, CINaM, 13288, Marseille (France); Nersesyan, Manuk; Gevorgyan, Vladimir [Russian-Armenian (Slavonic) University, H.Emin st.123, Yerevan 375051 (Armenia); Marine, Wladimir [Aix Marseille Université, CINaM, 13288, Marseille (France)

2015-03-15

Structural and optical characterization of crystalline Cu{sub 2}O thin films obtained by thermal oxidation of Cu films at two different temperatures 800 °C and 900 °C are investigated in this work. X-ray diffraction measurements indicate that synthesized films consist of single Cu{sub 2}O phase without any interstitial phase and show a nano-grain structure. Scanning Electron Microscopy observations indicate that the Cu{sub 2}O films have a micro-scale roughness whereas High Resolution Transmission Electron Microscopy highlights that the nanocrystalline structure is formed by superposition of nearly spherical nanocrystals smaller than 30 nm. Photoluminescence spectra of these films exhibit at room temperature two well-resolved emission peaks at 1.34 eV due to defects energy levels and at 1.97 eV due to phonon-assisted recombination of the 1s orthoexciton in both film series. Emission characteristics depending on the laser power is deeply investigated to determine the origin of recorded emissions. Time-integrated spectra of the 1s orthoexciton emission reveals the presence of oxygen defects below the conduction band edge under non-resonant two-photon excitation using a wide range of excitations wavelengths. Optical absorption coefficients at room temperature are obtained from an accurate analysis of their transmission and reflection spectra, whereas the optical band gap energy is estimated at about 2.11 eV. Results obtained are of high relevance especially for potential applications in semiconductor devices such as solar cells, optical sources and detectors. - Highlights: • Nanostructured Cu{sub 2}O thin films were synthesized by thermal oxidation of Cu films. • The PL spectra of nanostructured thin films revealed two well-resolved emission peaks. • The PL properties were investigated under a broad range of experimental conditions. • Inter-band transition in the infrared range has been associated to V{sub Cu} and V{sub O} vacancies. • Absorption

Microstructural Study on Oxygen Permeated Arc Beads

Directory of Open Access Journals (Sweden)

Kuan-Heng Liu

2015-01-01

Full Text Available We simulated short circuit of loaded copper wire at ambient atmosphere and successfully identified various phases of the arc bead. A cuprous oxide flake was formed on the surface of the arc bead in the rapid solidification process, and there were two microstructural constituents, namely, Cu-κ eutectic structure and solutal dendrites. Due to the arc bead formed at atmosphere during the local equilibrium solidification process, the phase of arc bead has segregated to the cuprous oxide flake, Cu-κ eutectic, and Cu phase solutal dendrites, which are the fingerprints of the arc bead permeated by oxygen.

Mercury (II) reduction and co-precipitation of metallic mercury on hydrous ferric oxide in contaminated groundwater.

Science.gov (United States)

Richard, Jan-Helge; Bischoff, Cornelia; Ahrens, Christian G M; Biester, Harald

2016-01-01

Mercury (Hg) speciation and sorption analyses in contaminated aquifers are useful for understanding transformation, retention, and mobility of Hg in groundwater. In most aquifers hydrous ferric oxides (HFOs) are among the most important sorbents for trace metals; however, their role in sorption or mobilization of Hg in aquifers has been rarely analyzed. In this study, we investigated Hg chemistry and Hg sorption to HFO under changing redox conditions in a highly HgCl2-contaminated aquifer (up to 870μgL(-1) Hg). Results from aqueous and solid phase Hg measurements were compared to modeled (PHREEQC) data. Speciation analyses of dissolved mercury indicated that Hg(II) forms were reduced to Hg(0) under anoxic conditions, and adsorbed to or co-precipitated with HFO. Solid phase Hg thermo-desorption measurements revealed that between 55 and 93% of Hg bound to HFO was elemental Hg (Hg(0)). Hg concentrations in precipitates reached more than 4 weight %, up to 7000 times higher than predicted by geochemical models that do not consider unspecific sorption to and co-precipitation of elemental Hg with HFO. The observed process of Hg(II) reduction and Hg(0) formation, and its retention and co-precipitation by HFO is thought to be crucial in HgCl2-contaminated aquifers with variable redox-conditions regarding the related decrease in Hg solubility (factor of ~10(6)), and retention of Hg in the aquifer. Copyright © 2015 Elsevier B.V. All rights reserved.

Coprecipitation of arsenate with metal oxides. 3. Nature, mineralogy, and reactivity of iron(III)-aluminum precipitates.

Science.gov (United States)

Violante, Antonio; Pigna, Massimo; Del Gaudio, Stefania; Cozzolino, Vincenza; Banerjee, Dipanjan

2009-03-01

Coprecipitation involving arsenic with aluminum or iron has been studied because this technique is considered particularly efficient for removal of this toxic element from polluted waters. Coprecipitation of arsenic with mixed iron-aluminum solutions has received scant attention. In this work we studied (i)the mineralogy, surface properties, and chemical composition of mixed iron-aluminum oxides formed at initial Fe/Al molar ratio of 1.0 in the absence or presence of arsenate [As/ Fe+Al molar ratio (R) of 0, 0.01, or 0.1] and at pH 4.0, 7.0, and 10.0 and aged for 30 and 210 days at 50 degrees C and (ii) the removal of arsenate from the coprecipitates after addition of phosphate. The amounts of short-range ordered precipitates (ferrihydrite, aluminous ferrihydrite and/or poorly crystalline boehmite) were greater than those found in iron and aluminum systems (studied in previous works), due to the capacity of both aluminum and arsenate to retard or inhibitthe transformation of the initially formed precipitates into well-crystallized oxides (gibbsite, bayerite, and hematite). As a consequence, the surface areas of the iron-aluminum oxides formed in the absence or presence of arsenate were usually much larger than those of aluminum or iron oxides formed under the same conditions. Arsenate was found to be associated mainly into short-range ordered materials. Chemical composition of all samples was affected by pH, initial R, and aging. Phosphate sorption was facilitated by the presence of short-range ordered materials, mainly those richer in aluminum, but was inhibited by arsenate present in the samples. The quantities of arsenate replaced by phosphate, expressed as percentages of its total amount present in the samples, were particularly low, ranging from 10% to 26%. A comparison of the desorption of arsenate by phosphate from aluminum-arsenate and iron-arsenate (studied in previous works) and iron-aluminum-arsenate coprecipitates evidenced that phosphate has a greater

Synthesis and performance of cerium oxide as anode materials for lithium ion batteries by a chemical precipitation method

International Nuclear Information System (INIS)

Liu, Haowen; Le, Qi

2016-01-01

In this present work, chemical precipitation method was employed for preparing cerium oxide. XRD, SEM, TEM, TGA/DTA and BET were used to investigate the structure, shape and formation mechanism, respectively. No impurities were detected. It was found that alcohol had obvious effection on the growth of the final sample. The shape of the precursor was retained after calcined at 500 °C. This result led to the possibility of an easy scale up to a commercial process. EIS and charge–discharge tests were carried out by using the as-prepared CeO_2 as an anode material for lithium ion batteries. Specially, the initial discharge specific capacity of the rhombus CeO_2 was about 529 mAh g"−"1 and stabilized reversibly at about 374 mAh g"−"1 after 50 cycles. It showed a promising usage as anode materials in lithium ion battery. - Highlights: • Chemical precipitation method was employed for the synthesis of cerium oxide. • Alcohol has obvious effection on the growth of the final sample. • The rhombus CeO_2 showed the better electrochemical properties as anode of lithium ion batteries.

Synthesis and performance of cerium oxide as anode materials for lithium ion batteries by a chemical precipitation method

Energy Technology Data Exchange (ETDEWEB)

Liu, Haowen, E-mail: liuhwchem@hotmail.com; Le, Qi

2016-06-05

In this present work, chemical precipitation method was employed for preparing cerium oxide. XRD, SEM, TEM, TGA/DTA and BET were used to investigate the structure, shape and formation mechanism, respectively. No impurities were detected. It was found that alcohol had obvious effection on the growth of the final sample. The shape of the precursor was retained after calcined at 500 °C. This result led to the possibility of an easy scale up to a commercial process. EIS and charge–discharge tests were carried out by using the as-prepared CeO{sub 2} as an anode material for lithium ion batteries. Specially, the initial discharge specific capacity of the rhombus CeO{sub 2} was about 529 mAh g{sup −1} and stabilized reversibly at about 374 mAh g{sup −1} after 50 cycles. It showed a promising usage as anode materials in lithium ion battery. - Highlights: • Chemical precipitation method was employed for the synthesis of cerium oxide. • Alcohol has obvious effection on the growth of the final sample. • The rhombus CeO{sub 2} showed the better electrochemical properties as anode of lithium ion batteries.

Ammonia-Oxidizing Archaea Are More Resistant Than Denitrifiers to Seasonal Precipitation Changes in an Acidic Subtropical Forest Soil

Directory of Open Access Journals (Sweden)

Jie Chen

2017-07-01

Full Text Available Seasonal precipitation changes are increasingly severe in subtropical areas. However, the responses of soil nitrogen (N cycle and its associated functional microorganisms to such precipitation changes remain unclear. In this study, two projected precipitation patterns were manipulated: intensifying the dry-season drought (DD and extending the dry-season duration (ED but increasing the wet-season storms following the DD and ED treatment period. The effects of these two contrasting precipitation patterns on soil net N transformation rates and functional gene abundances were quantitatively assessed through a resistance index. Results showed that the resistance index of functional microbial abundance (-0.03 ± 0.08 was much lower than that of the net N transformation rate (0.55 ± 0.02 throughout the experiment, indicating that microbial abundance was more responsive to precipitation changes compared with the N transformation rate. Spring drought under the ED treatment significantly increased the abundances of both nitrifying (amoA and denitrifying genes (nirK, nirS, and nosZ, while changes in these gene abundances overlapped largely with control treatment during droughts in the dry season. Interestingly, the resistance index of the ammonia-oxidizing archaea (AOA amoA abundance was significantly higher than that of the denitrifying gene abundances, suggesting that AOA were more resistant to the precipitation changes. This was attributed to the stronger environmental adaptability and higher resource utilization efficiency of the AOA community, as indicated by the lack of correlations between AOA gene abundance and environmental factors [i.e., soil water content, ammonium (NH4+ and dissolved organic carbon concentrations] during the experiment.

Effect of calcination temperature on the crystallite growth of cerium oxide nano-powders prepared by the co-precipitation process

Energy Technology Data Exchange (ETDEWEB)

Chen, Jian-Chih [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Chen, Wen-Cheng [School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Tien, Yin-Chun [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Shih, Chi-Jen, E-mail: cjshih@kmu.edu.t [Department of Fragrance and Cosmetics Science, Kaohsiung Medical University, 100 Shi-Chuan1st Road, Kaohsiung 80708, Taiwan (China)

2010-04-30

Cerium oxide nanocrystallites were synthesized by a co-precipitation process at a relatively low temperature, using cerium (III) nitrate as the starting material in a water solution with pH in the range of 8-9. The effect of calcination temperature on the crystallite growth of cerium oxide nano-powders was investigated by X-ray diffraction, transmission electron microscopy and electron diffraction. The crystallization temperature of the cerium oxide powders was estimated to be about 273 K, by XRD analysis. When calcined at temperatures from 473 to 1273 K, face-centered cubic phase crystallization was observed by XRD. The crystallite size of the cerium oxide increased from 12.0 to 48 nm as the calcining temperature increased from 473 to 1273 K, in the pH range 8-9. The activation energy for the growth of cerium oxide nanoparticles was found to have very low values of 17.5 kJ/mol for pH = 8 and 16.0 kJ/mol for pH = 9.

Final Report for DOE grant no. DE-FG02-04ER63883: Can soil genomics predict the impact of precipitation on nitrous oxide flux from soil

Energy Technology Data Exchange (ETDEWEB)

Egbert Schwartz

2008-12-15

Nitrous oxide is a potent greenhouse gas that is released by microorganisms in soil. However, the production of nitrous oxide in soil is highly variable and difficult to predict. Future climate change may have large impacts on nitrous oxide release through alteration of precipitation patterns. We analyzed DNA extracted from soil in order to uncover relationships between microbial processes, abundance of particular DNA sequences and net nitrous oxide fluxes from soil. Denitrification, a microbial process in which nitrate is used as an electron acceptor, correlated with nitrous oxide flux from soil. The abundance of ammonia oxidizing archaea correlated positively, but weakly, with nitrous oxide production in soil. The abundance of bacterial genes in soil was negatively correlated with gross nitrogen mineralization rates and nitrous oxide release from soil. We suggest that the most important control over nitrous oxide production in soil is the growth and death of microorganisms. When organisms are growing nitrogen is incorporated into their biomass and nitrous oxide flux is low. In contrast, when microorganisms die, due to predation or infection by viruses, inorganic nitrogen is released into the soil resulting in nitrous oxide release. Higher rates of precipitation increase access to microorganisms by predators or viruses through filling large soil pores with water and therefore can lead to large releases of nitrous oxide from soil. We developed a new technique, stable isotope probing with 18O-water, to study growth and mortality of microorganisms in soil.

Assessing potential impacts of phosphate precipitation on nitrous oxide emissions and the carbon footprint of wastewater treatment plants.

Science.gov (United States)

Kosse, Pascal; Lübken, Manfred; Schmidt, Torsten C; Lange, Ruben-Laurids; Wichern, Marc

2018-02-15

Metal salts are widely used for the precipitation of phosphorus during wastewater treatment transforming soluble orthophosphate to an insoluble salt. In practice, more complex reactions are taking place including a reduction of the chemical solubility of dissolved greenhouse gases, such as nitrous oxide, present in the wastewater stream. In this respect, it was postulated that phosphorous precipitation will lead to artificial N 2 O stripping and hence to an increased carbon footprint of wastewater treatment plants. From lab-scale experiments utilizing N 2 O-saturated synthetic sewage solutions, it was evidenced that metal salt addition leads to N 2 O stripping with 20.8 g N 2 O per liter for a FeCl 2 -based precipitant to 26.4 g N 2 O per liter for a Al n (OH) m Cl3 n-m -based precipitant. Taking this maximum potential stripping effect into account for a carbon footprint analysis, a potential contribution of 16.11 kg CO 2,eq ·PE -1 ·a -1 was calculated in a case study, where FeCl 3 was considered. With respect to the defined system boundary conditions, the overall on-site and off-site CO 2 emissions were raised by 34% from 46.87 kg CO 2,eq ·PE -1 ·a -1 to 62.97 kg CO 2,eq ·PE -1 ·a -1 through CO 2,eq coming from phosphorous precipitation.

Particle precipitation in connection with KOH etching of silicon

DEFF Research Database (Denmark)

Nielsen, Christian Bergenstof; Christensen, Carsten; Pedersen, Casper

2004-01-01

This paper considers the precipitation of iron oxide particles in connection with the KOH etching of cavities in silicon wafers. The findings presented in this paper suggest that the source to the particles is the KOH pellets used for making the etching solution. Experiments show that the precipi......This paper considers the precipitation of iron oxide particles in connection with the KOH etching of cavities in silicon wafers. The findings presented in this paper suggest that the source to the particles is the KOH pellets used for making the etching solution. Experiments show...... that the precipitation is independent of KOH etching time, but that the amount of deposited material varies with dopant type and dopant concentration. The experiments also suggest that the precipitation occurs when the silicon wafers are removed from the KOH etching solution and not during the etching procedure. When...... not removed, the iron oxide particles cause etch pits on the Si surface when later processed and exposed to phosphoric acid. It has been found that the particles can be removed in an HCl solution, but not completely in an H2SO4- H2O2 solution. The paper discusses the involved precipitation mechanism in terms...

Arsenic removal from acidic solutions with biogenic ferric precipitates.

Science.gov (United States)

Ahoranta, Sarita H; Kokko, Marika E; Papirio, Stefano; Özkaya, Bestamin; Puhakka, Jaakko A

2016-04-05

Treatment of acidic solution containing 5g/L of Fe(II) and 10mg/L of As(III) was studied in a system consisting of a biological fluidized-bed reactor (FBR) for iron oxidation, and a gravity settler for iron precipitation and separation of the ferric precipitates. At pH 3.0 and FBR retention time of 5.7h, 96-98% of the added Fe(II) precipitated (99.1% of which was jarosite). The highest iron oxidation and precipitation rates were 1070 and 28mg/L/h, respectively, and were achieved at pH 3.0. Subsequently, the effect of pH on arsenic removal through sorption and/or co-precipitation was examined by gradually decreasing solution pH from 3.0 to 1.6 (feed pH). At pH 3.0, 2.4 and 1.6, the highest arsenic removal efficiencies obtained were 99.5%, 80.1% and 7.1%, respectively. As the system had ferric precipitates in excess, decreased arsenic removal was likely due to reduced co-precipitation at pHremoves iron and arsenic from acidic solutions, indicating potential for mining wastewater treatment. Copyright © 2015 Elsevier B.V. All rights reserved.

Precipitates and boundaries interaction in ferritic ODS steels

Energy Technology Data Exchange (ETDEWEB)

Sallez, Nicolas, E-mail: nicolas.sallez@simap.grenoble-inp.fr [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France); Hatzoglou, Constantinos [Groupe de Physique des Matériaux, Université et INSA de Rouen, UMR CNRS 6634, Normandie Université (France); Delabrouille, Fredéric [EDF–EDF R& D, Les Renardières, 77818 Moret-sur-Loing (France); Sornin, Denis; Chaffron, Laurent [CEA, DEN, Service de Recherches Métallurgiques Appliqué, 91191 Gif-sur-Yvette (France); Blat-Yrieix, Martine [EDF–EDF R& D, Les Renardières, 77818 Moret-sur-Loing (France); Radiguet, Bertrand; Pareige, Philippe [Groupe de Physique des Matériaux, Université et INSA de Rouen, UMR CNRS 6634, Normandie Université (France); Donnadieu, Patricia; Bréchet, Yves [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France)

2016-04-15

In the course of a recrystallization study of Oxide Dispersion Strengthened (ODS) ferritic steels during extrusion, particular interest was paid to the (GB) Grain Boundaries interaction with precipitates. Complementary and corresponding characterization experiments using Transmission Electron Microscopy (TEM), Energy Dispersive X-ray spectroscopy (EDX) and Atom Probe Tomography (APT) have been carried out on a voluntarily interrupted extrusion or extruded samples. Microscopic observations of Precipitate Free Zones (PFZ) and precipitates alignments suggest precipitate interaction with migrating GB involving dissolution and Oswald ripening of the precipitates. This is consistent with the local chemical information gathered by EDX and APT. This original mechanism for ODS steels is similar to what had been proposed in the late 80s for similar observation made on Ti alloys reinforced by nanosized yttrium oxides: An interaction mechanism between grain boundaries and precipitates involving a diffusion controlled process of precipitates dissolution at grain boundaries. It is believed that this mechanism can be of primary importance to explain the mechanical behaviour of such steels. - Highlights: • To study the microstructural evolution of a ferritic ODS steel during its extrusion, observations have been carried on samples resulting from a voluntarily interrupted extrusion and extruded materials. • A highly heterogeneous precipitate population have been observed. Nanosized coherent precipitates (2–5 nm) on both sides of the grain boundaries despite grain boundary migration after precipitation due to further thermo-mechanical processing as well as coarse precipitates (10–40 nm) alignments are observed on the grain boundaries and within the grains, parallel to the grain boundaries. • Asymmetrical PFZs can be observed around precipitates alignments and grain boundaries. Using TEM with EDX and APT we have been able to ensure that the PFZs are chemically depleted. �

Current Status and Future Prospects of Copper Oxide Heterojunction Solar Cells.

Science.gov (United States)

Wong, Terence K S; Zhuk, Siarhei; Masudy-Panah, Saeid; Dalapati, Goutam K

2016-04-07

The current state of thin film heterojunction solar cells based on cuprous oxide (Cu₂O), cupric oxide (CuO) and copper (III) oxide (Cu₄O₃) is reviewed. These p-type semiconducting oxides prepared by Cu oxidation, sputtering or electrochemical deposition are non-toxic, sustainable photovoltaic materials with application potential for solar electricity. However, defects at the copper oxide heterojunction and film quality are still major constraining factors for achieving high power conversion efficiency, η. Amongst the Cu₂O heterojunction devices, a maximum η of 6.1% has been obtained by using pulsed laser deposition (PLD) of Al x Ga 1- x O onto thermal Cu₂O doped with Na. The performance of CuO/n-Si heterojunction solar cells formed by magnetron sputtering of CuO is presently limited by both native oxide and Cu rich copper oxide layers at the heterointerface. These interfacial layers can be reduced by using a two-step sputtering process. A high η of 2.88% for CuO heterojunction solar cells has been achieved by incorporation of mixed phase CuO/Cu₂O nanopowder. CuO/Cu₂O heterojunction solar cells fabricated by electrodeposition and electrochemical doping has a maximum efficiency of 0.64% after surface defect passivation and annealing. Finally, early stage study of Cu₄O₃/GaN deposited on sapphire substrate has shown a photovoltaic effect and an η of ~10 -2 %.

Siderophore-mediated oxidation of Ce and fractionation of HREE by Mn (hydr)oxide-coprecipitation and sorption on MnO2: Experimental evidence for negative Ce-anomalies in abiogenic manganese precipitates

Science.gov (United States)

Krämer, Dennis; Tepe, Nathalie; Bau, Michael

2014-05-01

We conducted experiments with Rare Earths and Yttrium (REY), where the REY were sorbed on synthetic manganese dioxide as well as on coprecipitating manganese (hydr)oxide in the presence and absence of the siderophore desferrioxamine-B (DFOB). Siderophores are a group of globally abundant biogenic complexing agents which are excreted by plants and bacteria to enhance the bioavailability of Fe in oxic environments. The model siderophore used in this study, DFOB, is a hydroxamate siderophore occurring in almost all environmental settings with concentrations in the nanomolar to millimolar range and is one of the most thoroughly studied siderophores. In the absence of siderophores and other organic ligands, trivalent Ce is usually surface-oxidized to tetravalent Ce during sorption onto manganese (hydr)oxides. Such Mn precipitates, therefore, often show positive Ce anomalies, whereas the ambient solutions exhibit negative Ce anomalies (Ohta and Kawabe, 2001). In marked contrast, however, REY sorption in the presence of DFOB produces negative Ce anomalies in the Mn precipitates and a distinct and characteristic positive Ce anomaly in the residual siderophore-bearing solution. Furthermore, the heavy REY with ionic radii larger than the radius of Sm are also almost completely prevented from sorption onto the Mn solid phases. Sorption of REY onto Mn (hydr)oxides in the presence of DFOB creates a distinct and pronounced fractionation of Ce and the heavy REY from the light and middle REY. Apart from Ce, which is oxidized in solution by the siderophore, the distribution of the other REY mimics the stability constants for multi-dentate complexes of REY with DFOB, as determined by Christenson & Schijf (2011). Heavier REY are forming stronger complexes (and are hence better "protected" from sorption) than light REY, excluding Ce. Preferential partitioning of Ce into the liquid phase during the precipitation of Mn (hydr)oxides has only rarely been described for natural Mn (hydr)oxides

Red Plague Control Plan (RPCP)

Science.gov (United States)

Cooke, Robert W.

2010-01-01

SCOPE: Prescribes the minimum requirements for the control of cuprous / cupric oxide corrosion (a.k.a. Red Plague) of silver-coated copper wire, cable, and harness assemblies. PURPOSE: Targeted for applications where exposure to assembly processes, environmental conditions, and contamination may promote the development of cuprous / cupric oxide corrosion (a.k.a. Red Plague) in silver-coated copper wire, cable, and harness assemblies. Does not exclude any alternate or contractor-proprietary documents or processes that meet or exceed the baseline of requirements established by this document. Use of alternate or contractor-proprietary documents or processes shall require review and prior approval of the procuring NASA activity.

Nanocrystalline Ce 1- xY xO 2- x/2 (0≤ x≤0.35) Oxides via Carbonate Precipitation: Synthesis and Characterization

Science.gov (United States)

Li, Ji-Guang; Ikegami, Takayasu; Wang, Yarong; Mori, Toshiyuki

2002-10-01

A novel carbonate (co)precipitation method, employing nitrates as the starting salts and ammonium carbonate as the precipitant, has been used to synthesize nanocrystalline CeO 2 and Ce 1- xY xO 2- x/2 ( x≤0.35) solid-solutions. The resultant powders are characterized by elemental analysis, differential thermal analysis/thermogravimetry (DTA/TG), X-ray diffractometry (XRD), Brunauer-Emmett-Teller (BET) analysis, and high-resolution scanning electron microscopy (HRSEM). Due to the direct formation of carbonate solid-solutions during precipitation, Ce 1- xY xO 2- x/2 solid-solution oxides are formed directly during calcination at a very low temperature of ˜300°C for 2 h. The thus-produced oxide nanopowders are essentially non-agglomerated, as revealed by BET in conjunction with XRD analysis. The solubility of YO 1.5 in CeO 2 is determined via XRD to be somewhere in the range from 27 to 35 mol%, from which a Y 2O 3-related type-C phase appears in the final product. Y 3+-doping promotes the formation of spherical nanoparticles, retards thermal decomposition of the precursors, and suppresses significantly crystallite coarsening of the oxides during calcination. The activation energy for crystallite coarsening increases gradually from 68.7 kJ mol -1 for pure CeO 2 to 138.6 kJ mol -1 for CeO 2 doped with 35 mol% YO 1.5. The dopant effects on crystallite coarsening is elaborated from the view point of solid-state chemistry.

Photocatalytic degradation of methylene blue dye by zinc oxide nanoparticles obtained from precipitation and sol-gel methods.

Science.gov (United States)

Balcha, Abebe; Yadav, Om Prakash; Dey, Tania

2016-12-01

Zinc oxide (ZnO) nanoparticles were synthesized by precipitation and sol-gel methods. The aim of this study was to understand how different synthetic methods can affect the photocatalytic activity of ZnO nanoparticles. As-synthesized ZnO nanoparticles were characterized by X-ray diffraction (XRD) and UV-Visible spectroscopic techniques. XRD patterns of ZnO powders synthesized by precipitation and sol-gel methods revealed their hexagonal wurtzite structure with crystallite sizes of 30 and 28 nm, respectively. Their photocatalytic activities were evaluated by photocatalytic degradation of methylene blue, a common water pollutant, under UV radiation. The effects of operational parameters such as photocatalyst load and initial concentration of the dye on photocatalytic degradation of methylene blue were investigated. While the degradation of dye decreased over the studied dye concentration range of 20 to 100 mg/L, an optimum photocatalyst load of 250 mg/L was needed to achieve dye degradation as high as 81 and 92.5 % for ZnO prepared by precipitation and sol-gel methods, respectively. Assuming pseudo first-order reaction kinetics, this corresponded to rate constants of 8.4 × 10 -3 and 12.4 × 10 -3  min -1 , respectively. Hence, sol-gel method is preferred over precipitation method in order to achieve higher photocatalytic activity of ZnO nanostructures. Photocatalytic activity is further augmented by better choice of capping ligand for colloidal stabilization, starch being more effective than polyethylene glycol (PEG).

Superior Photocatalytic Performance of CeO₂ Nanoparticles and Reduced Graphene Oxide Nanocomposite Prepared by Low Cost Co-Precipitation Method.

Science.gov (United States)

Jayanthi, Mani; Lavanya, Thirugnanam; Saradha, Nagarajan Anbil; Satheesh, Kaveri; Chenthamarai, SriRangarajan; Jayavel, Ramasamy

2018-05-01

In this article, cerium oxide nanoparticles (CeO2 NPs) and reduced graphene oxide nanocomposite have been fabricated through simple, easy and cost effective co-precipitation method. The structural, optical and morphological characterization provides the evidence of successful synthesis of CeO2 NPs and nanocomposite. X-ray photoelectron spectroscopic characterization provides useful information about the concentrations and proportions of Ce3+ and Ce4+ ions in nanoparticles as well as in nanocomposite. These studies provide an insight to understand enhanced photocatalytic activity of nanocomposite. The nanocomposite produces 81% photocatalytic degradation of methyl orange compared to only 45% degradation by CeO2 NPs alone.

Evaluation of the structure and microstructure of NixMg1-xO oxides obtained by co-precipitation

International Nuclear Information System (INIS)

Martinez L, G.; Kryshtab, T.; Hesiquio G, M.; Kryvko, A.

2013-01-01

Ni x Mg 1-x O oxides were prepared by thermal treatment at temperatures of 400, 600 and 800 C from a hydrotalcite-like precursor obtained by co-precipitation at constant ph. The oxides obtained were characterized by X-ray diffraction methods. From the obtained results we concluded that the oxides calcined at temperatures of 400, and 600 C are unstable that means that there exists the effect of memory and with a time they return to the precursor. Presence of Ni in Mg oxide provides stability of the compounds thermally treated at 800 C. In order to analyze the structure and microstructure, the reflections 111, 200 and 220 were used. The positions of the maxima of the diffraction peaks are shifted with respect to the simulated ones for Mg O and Ni O. This result reveals that in solid solutions studied compressive strains or vacation are present. The parameters of the microstructure (coherent domain size and micro deformations) were evaluated. The coherent domain size was found to be in the range of 8 - 10 nm and the presence of residual strains of micro deformation can be associated with the existence of extended defects. (Author)

Arsenic removal from acidic solutions with biogenic ferric precipitates

Energy Technology Data Exchange (ETDEWEB)

Ahoranta, Sarita H., E-mail: sarita.ahoranta@tut.fi [Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere (Finland); Kokko, Marika E., E-mail: marika.kokko@tut.fi [Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere (Finland); Papirio, Stefano, E-mail: stefano.papirio@unicas.it [Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere (Finland); Özkaya, Bestamin, E-mail: bozkaya@yildiz.edu.tr [Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere (Finland); Department of Environmental Engineering, Yildiz Technical University, Davutpasa Campus 34220, Esenler, Istanbul (Turkey); Puhakka, Jaakko A., E-mail: jaakko.puhakka@tut.fi [Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere (Finland)

2016-04-05

Highlights: • Continuous and rapid arsenic removal with biogenic jarosite was achieved at pH 3.0. • Arsenic removal was inefficient below pH 2.4 due to reduced Fe–As co-precipitation. • As(V) had better sorption characteristics than As(III). • Biogenic jarosite adsorbed arsenic more effectively than synthetic jarosite. - Abstract: Treatment of acidic solution containing 5 g/L of Fe(II) and 10 mg/L of As(III) was studied in a system consisting of a biological fluidized-bed reactor (FBR) for iron oxidation, and a gravity settler for iron precipitation and separation of the ferric precipitates. At pH 3.0 and FBR retention time of 5.7 h, 96–98% of the added Fe(II) precipitated (99.1% of which was jarosite). The highest iron oxidation and precipitation rates were 1070 and 28 mg/L/h, respectively, and were achieved at pH 3.0. Subsequently, the effect of pH on arsenic removal through sorption and/or co-precipitation was examined by gradually decreasing solution pH from 3.0 to 1.6 (feed pH). At pH 3.0, 2.4 and 1.6, the highest arsenic removal efficiencies obtained were 99.5%, 80.1% and 7.1%, respectively. As the system had ferric precipitates in excess, decreased arsenic removal was likely due to reduced co-precipitation at pH < 2.4. As(III) was partially oxidized to As(V) in the system. In shake flask experiments, As(V) sorbed onto jarosite better than As(III). Moreover, the sorption capacity of biogenic jarosite was significantly higher than that of synthetic jarosite. The developed bioprocess simultaneously and efficiently removes iron and arsenic from acidic solutions, indicating potential for mining wastewater treatment.

Effects of sputtering power on properties of copper oxides thin films deposited on glass substrates

Energy Technology Data Exchange (ETDEWEB)

Ooi, P. K.; Ng, S. S.; Abdullah, M. J. [Nano-Optoelectronics Research and Technology Laboratory, School of Physics, Universiti Sains Malaysia, 11800 Penang (Malaysia)

2015-04-24

Copper oxides are deposited by radio frequency sputtering using copper target in the mixture of argon and oxygen gasses. The structural and optical properties of the copper oxides deposited at different sputtering powers have been investigated. All the films are single phase polycrystalline. At low RF power (100 W), the film is monoclinic structure of cupric oxide (CuO). Meanwhile, the films are cubic structure of cuprous oxide (Cu2O) at higher RF power. Field emission scanning electron microscopy images show the films have different morphologies with small grain size and consist of a lot of voids. The analysis of energy dispersive X-ray spectroscopy shows that the ratio of Cu to O is increased as the RF power increased. From the ultraviolet–visible spectroscopy, the films have a broad absorption edge in the range of 300–500 nm. The band gap of the films grown at RF power of 100 W, and 120 W and above, were 1.18 eV and 2.16 eV, respectively.

Method of producing homogeneous mixed metal oxides and metal-metal oxide mixtures

International Nuclear Information System (INIS)

Quinby, T.C.

1980-01-01

A method for preparing particulate metal or metal oxide of controlled partile size comprises contacting an an aqueous solution containing dissolved metal values with excess urea at a temperature sufficient to cause urea to react with water to provide a molten urea solution containing the metal values; heating the molten urea solution to cause the metal values to precipitate, forming a mixture containing precipitated metal values; heating the mixture containing precipitated metal values to evaporate volatile material leaving a dry powder containing said metal values. The dry powder can be calcined to provide particulate metal oxide or reduced to provide particulate metal. Oxide mixtures are provided when the aqueous solution contains values of more than one metal. Homogeneousmetal-metal oxide mistures for preparing cermets can be prepared by selectively reducing at least one of the metal oxides. (auth)

Simulation of effects of redox and precipitation on diffusion of uranium solution species in backfill

International Nuclear Information System (INIS)

Carnahan, C.L.

1987-12-01

This investigation addresses the problem of prediction of the rate of migration of redox-sensitive solution species within packing and backfill materials under conditions of variable oxidation potential. Effects of changes of oxidation potential and precipitation of stable uranium compounds during diffusion of uranium from a region of high oxidation potential into a region of low oxidation potential were simulated numerically. Questions of particular interest addressed in the investigation were the existence of a moving ''redox front'' and the influence of precipitation-dissolution processes on uranium migration. The simulations showed that no expanding redox fronts existed at any simulated time up to 3.2 x 10 5 years (10 13 s). In simulations where precipitation of stable solids was not allowed, variations of oxidation potential did not affect total uranium concentrations in solution. Concentration profiles could be predicted simply by diffusion of the (constant) source concentrations. In simulations where precipitation of stable solids was allowed, uraninite and calcium uranate accumulated at the source-transport domain interface, while coffinite penetrated further into the transport domain. Total uranium concentrations in regions of precipitation were determined by solubilities of the precipitated solids, and were six to seven orders of magnitude lower than those in the simulations without precipitation, throughout the domain of transport. 14 refs., 7 figs., 2 tabs

Corrosion resistance and calcium–phosphorus precipitation of micro-arc oxidized magnesium for biomedical applications

Energy Technology Data Exchange (ETDEWEB)

Zhao, Lichen; Cui, Chunxiang, E-mail: hutcui@hebut.edu.cn; Wang, Xin; Liu, Shuangjin; Bu, Shaojing; Wang, Qingzhou; Qi, Yumin

2015-03-01

Highlights: • Hydroxyapatite (HA) powders were added to the electrolyte. • The HA powders have participated in the formation reactions of MAO coating. • The growth efficiency of MAO coating was greatly enhanced owing to the HA addition. • The specimen anodized in the HA-containing electrolyte has a better corrosion resistance. • The specimen anodized in the HA-containing electrolyte can more efficiently induce Ca–P precipitation. - Abstract: To improve the corrosion resistance of magnesium, micro-arc oxidation (MAO) coatings were prepared on magnesium substrates in an aqueous solution with and without hydroxyapatite (HA) powders addition. The micrographs of scanning electron microscopy (SEM), the energy dispersive spectrometer (EDS) spectra, and X-ray diffraction (XRD) analysis show that the HA powders added into the electrolyte have participated in the formation reactions of MAO coating and the growth efficiency of MAO coating is greatly enhanced. Potentiodynamic polarization tests and immersion tests in simulated body fluid (SBF) confirm that the specimen anodized in the HA-containing electrolyte has a better corrosion resistance than the specimen anodized in the HA-free electrolyte. Immersion tests also indicate that the specimen anodized in the HA-containing electrolyte can more efficiently induce Ca–P precipitation compared with the specimen anodized in the HA-free electrolyte.

Fabrication of cuprous chloride films on copper substrate by chemical bath deposition

Energy Technology Data Exchange (ETDEWEB)

Lin, Yu-Ting; Ci, Ji-Wei; Tu, Wei-Chen [Department of Electronic Engineering, College of Electrical Engineering and Computer Science, Chung Yuan Christian University, Chung-Li 32023, Taiwan (China); Uen, Wu-Yih, E-mail: uenwuyih@ms37.hinet.net [Department of Electronic Engineering, College of Electrical Engineering and Computer Science, Chung Yuan Christian University, Chung-Li 32023, Taiwan (China); Lan, Shan-Ming [Department of Electronic Engineering, College of Electrical Engineering and Computer Science, Chung Yuan Christian University, Chung-Li 32023, Taiwan (China); Yang, Tsun-Neng; Shen, Chin-Chang; Wu, Chih-Hung [Institute of Nuclear Energy Research, P.O. Box 3-11, Lungtan 32500, Taiwan (China)

2015-09-30

Polycrystalline CuCl films were fabricated by chemical bath deposition (CBD) on a Cu substrate at a low solution temperature of 90 °C. Continuous CuCl films were prepared using the copper (II) chloride (CuCl{sub 2}) compound as the precursor for both the Cu{sup 2+} and Cl{sup −} sources, together with repeated HCl dip treatments. An HCl dip pretreatment of the substrate favored the nucleation of CuCl crystallites. Further, interrupting the film deposition and including an HCl dip treatment of the film growth surface facilitated the deposition of a full-coverage CuCl film. A dual beam (FIB/SEM) system with energy dispersive spectrometry facilities attached revealed a homogeneous CuCl layer with a flat-top surface and an average thickness of about 1 μm. Both the excitonic and biexcitonic emission lines were well-resolved in the 6.4 K photoluminescence spectra. In particular, the free exciton emission line was observable at room temperature, indicating the good quality of the CuCl films prepared by CBD. - Highlights: • Cuprous chloride (CuCl) was prepared on Cu substrate by chemical bath deposition. • HCl dip treatments facilitated the deposition of a full-coverage CuCl film. • A homogeneous elemental distribution was recognized for the deposited CuCl layer. • Excitonic and biexcitonic photoluminescence lines of CuCl films were well-resolved. • The free exciton emission line of CuCl films was observable at room temperature.

Characterisation of Suspension Precipitated Nanocrystalline Hydroxyapatite Powders

International Nuclear Information System (INIS)

Mallik, P K; Swain, P.K.; Patnaik, S.C

2016-01-01

Hydroxyapatite (HA) is a well-known biomaterial for coating on femoral implants, filling of dental cavity and scaffold for tissue replacement. Hydroxyapatite possess limited load bearing capacity due to their brittleness. In this paper, the synthesis of nanocrystalline hydroxyapatite powders was prepared by dissolving calcium oxide in phosphoric acid, followed by addition of ammonia liquor in a beaker. The prepared solution was stirred by using magnetic stirrer operated at temperature of 80°C for an hour. This leads to the formation of hydroxyapatite precipitate. The precipitate was dried in oven for overnight at 100°C. The dried agglomerated precipitate was calcined at 800°C in conventional furnace for an hour. The influence of calcium oxide concentration and pH on the resulting precipitates was studied using BET, XRD and SEM. As result, a well-defined sub-rounded morphology of powders size of ∼41 nm was obtained with a salt concentration of 0.02 M. Finally, it can be concluded that small changes in the reaction conditions led to large changes in final size, shape and degree of aggregation of the hydroxyapatite particles. (paper)

Effect of solid fission products forming dissolved oxide(Nd) and metallic precipitate(Ru) on the thermophysical properties of MOX fuel

International Nuclear Information System (INIS)

Kim, Dong Joo

2006-02-01

This study experimentally investigated the effect of solid fission products on the thermophysical properties of the mixed oxide fuel and evaluated them on the basis of the analytical theory. Neodymium and ruthenium were selected for the experiments to represent the physical states of the solid fission product as a 'dissolved oxide' and 'metallic precipitate', respectively. The state of the additives, crystal structures, lattice parameters, and theoretical densities were investigated with X-ray diffraction (XRD). Thermal diffusivities and thermal expansion rates were measured with laser flash method and dilatometry, respectively. The thermal expansion data were then fitted to obtain an correlation equation of the density variation as a function of the temperature. The specific heat capacity values were determined using the Neumann-Kopp's rule. The thermal expansion of the 'Nd.added' sample linearly increased with the concentration of the neodymium, which is primarily due to the fact that the melting point of Nd 2 O 3 is lower than that of UO 2 . On the other hand, the thermal expansion of the 'Ru.added' sample hardly changed with increasing ruthenium content. Thermal conductivities of the simulated MOX fuel were determined on the basis of the thermal diffusivities, density variation, and specific heat values measured in this study. The effect of additives on the thermal conductivity of the samples was quantified in the form of the thermal resistance equation, the reciprocal of the phonon conduction equation, which was determined from measured data. For 'dissolved oxide' sample in the UO 2 matrix, the effect is mainly attributed to the increase of lattice point defects caused by U 4+ , Ce 4+ , Nd 3+ and O 2- ions, which play the role of phonon scattering centers, that is, mean free path of phonon scattering decreases with the point defects, thus increase the thermal resistance. Also, the mass difference between the host (U) and the substituted atom (Ce and/or Nd) can

Helix-sense-selective co-precipitation for preparing optically active helical polymer nanoparticles/graphene oxide hybrid nanocomposites.

Science.gov (United States)

Huang, Huajun; Li, Weifei; Shi, Yan; Deng, Jianping

2017-05-25

Constructing optically active helical polymer based nanomaterials without using expensive and limited chirally helical polymers has become an extremely attractive research topic in both chemical and materials science. In this study, we prepared a series of optically active helical polymer nanoparticles/graphene oxide (OAHPNs/GO) hybrid nanocomposites through an unprecedented strategy-the co-precipitation of optically inactive helical polymers and chirally modified GO. This approach is named helix-sense-selective co-precipitation (HSSCP), in which the chirally modified GO acted as a chiral source for inducing and further stabilizing the predominantly one-handed helicity in the optically inactive helical polymers. SEM and TEM images show quite similar morphologies of all the obtained OAHPNs/GO nanocomposites; specifically, the chirally modified GO sheets were uniformly decorated with spherical polymer nanoparticles. Circular dichroism (CD) and UV-vis absorption spectra confirmed the preferentially induced helicity in the helical polymers and the optical activity of the nanocomposites. The established HSSCP strategy is thus proven to be widely applicable and is expected to produce numerous functional OAHPNs/GO nanocomposites and even the analogues.

Activation of persulfate/copper by hydroxylamine via accelerating the cupric/cuprous redox couple.

Science.gov (United States)

Zhou, Peng; Zhang, Jing; Liang, Juan; Zhang, Yongli; Liu, Ya; Liu, Bei

2016-01-01

Cuprous copper [Cu(I)] reacts with sodium persulfate (PDS) to generate sulfate radical SO4(-)•, but it has been seldom investigated owing to its instability and difficulty in dissolving it. This study proposes a new method to regenerate Cu(I) from cupric copper [Cu(II)] by addition of hydroxylamine (HA) to induce the continuous production of radicals through active PDS, and investigates the resulting enhanced methyl orange (MO) degradation efficiency and mechanism in the new system. HA accelerated the degradation of MO markedly in the pH range from 6.0 to 8.0 in the HA/Cu(II)/PDS process. Both SO4(-)• and hydroxyl radicals (•OH) were considered as the primary reactive radicals in the process. The MO degradation in the HA/Cu(II)/PDS process can be divided into three stages: the fast stage, the transitory stage, and the low stage. MO degradation was enhanced with increased dosage of PDS. Although high dosage of HA could accelerate the transformation of the Cu(II)/Cu(I) cycle to produce more reactive radicals, excess HA can quench the reactive radicals. This study indicates that through a copper-redox cycling mechanism by HA, the production of SO4(-)• and •OH can be strongly enhanced, and the effective pH range can be expanded to neutral conditions.

Arsenic precipitation from metallurgical effluents

International Nuclear Information System (INIS)

Navarro, P.; Vargas, C.; Araya, E.; Martin, I.; Alguacil, F. J.

2004-01-01

In the mining-metallurgical companies different liquid effluents are produced, which can contain a series of dissolved elements that are considered dangerous from an environmental point of view. One of these elements is the arsenic, especially in the state of oxidation +5 that can be precipitated as calcium or iron arsenate. To fulfil the environmental requests it should have in solution a content of arsenic lower than 0,5 mg/l and the obtained solid product should be very stable under the condition in which it will be stored. this work looks for the best conditions of arsenic precipitation, until achieving contents in solution lower than such mentioned concentration. Also, the stability of the precipitates was studied. (Author) 7 refs

Structural and optical studies of Mg doped nanoparticles of chromium oxide (Cr2O3) synthesized by co-precipitation method

Science.gov (United States)

Singh, Jarnail; Verma, Vikram; Kumar, Ravi

2018-04-01

We present here the synthesization, structural and optical studies of Mg doped nanoparticles of Chromium oxide (Cr2O3) prepared using co-precipitation method. These samples were characterized using powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Raman spectroscopy and UV-Vis spectroscopy techniques. We have demonstrated that there is negligible change in optical band gap with the Mg doping. The prepared Cr2O3 nanoparticles are spherical in shape, but they are transformed into platelets when doped with Mg. The XRD studies reveal that the Mg doping in Cr2O3 doesn't affect the structure of Chromium oxide (Cr2O3).

Current Status and Future Prospects of Copper Oxide Heterojunction Solar Cells

Directory of Open Access Journals (Sweden)

Terence K. S. Wong

2016-04-01

Full Text Available The current state of thin film heterojunction solar cells based on cuprous oxide (Cu2O, cupric oxide (CuO and copper (III oxide (Cu4O3 is reviewed. These p-type semiconducting oxides prepared by Cu oxidation, sputtering or electrochemical deposition are non-toxic, sustainable photovoltaic materials with application potential for solar electricity. However, defects at the copper oxide heterojunction and film quality are still major constraining factors for achieving high power conversion efficiency, η. Amongst the Cu2O heterojunction devices, a maximum η of 6.1% has been obtained by using pulsed laser deposition (PLD of AlxGa1−xO onto thermal Cu2O doped with Na. The performance of CuO/n-Si heterojunction solar cells formed by magnetron sputtering of CuO is presently limited by both native oxide and Cu rich copper oxide layers at the heterointerface. These interfacial layers can be reduced by using a two-step sputtering process. A high η of 2.88% for CuO heterojunction solar cells has been achieved by incorporation of mixed phase CuO/Cu2O nanopowder. CuO/Cu2O heterojunction solar cells fabricated by electrodeposition and electrochemical doping has a maximum efficiency of 0.64% after surface defect passivation and annealing. Finally, early stage study of Cu4O3/GaN deposited on sapphire substrate has shown a photovoltaic effect and an η of ~10−2%.

Current Status and Future Prospects of Copper Oxide Heterojunction Solar Cells

Science.gov (United States)

Wong, Terence K. S.; Zhuk, Siarhei; Masudy-Panah, Saeid; Dalapati, Goutam K.

2016-01-01

The current state of thin film heterojunction solar cells based on cuprous oxide (Cu2O), cupric oxide (CuO) and copper (III) oxide (Cu4O3) is reviewed. These p-type semiconducting oxides prepared by Cu oxidation, sputtering or electrochemical deposition are non-toxic, sustainable photovoltaic materials with application potential for solar electricity. However, defects at the copper oxide heterojunction and film quality are still major constraining factors for achieving high power conversion efficiency, η. Amongst the Cu2O heterojunction devices, a maximum η of 6.1% has been obtained by using pulsed laser deposition (PLD) of AlxGa1−xO onto thermal Cu2O doped with Na. The performance of CuO/n-Si heterojunction solar cells formed by magnetron sputtering of CuO is presently limited by both native oxide and Cu rich copper oxide layers at the heterointerface. These interfacial layers can be reduced by using a two-step sputtering process. A high η of 2.88% for CuO heterojunction solar cells has been achieved by incorporation of mixed phase CuO/Cu2O nanopowder. CuO/Cu2O heterojunction solar cells fabricated by electrodeposition and electrochemical doping has a maximum efficiency of 0.64% after surface defect passivation and annealing. Finally, early stage study of Cu4O3/GaN deposited on sapphire substrate has shown a photovoltaic effect and an η of ~10−2%. PMID:28773398

Precipitation of ammonium diuranate : a study

International Nuclear Information System (INIS)

Krishnamoorthy, T.S.; Mahadevan, N.; Sankar Das, M.

1991-01-01

The precipitation of ammonium diuranate (ADU) forms the first step in the production of UO 2 fuel for reactors, and hence the quality and consistency of the ADU precipitate is very important in industrial operations. An investigation, on the precipitation of ADU, was carried out under conditions similar to those in industrial production, to evaluate the effect of various variables on the consistency and the quality of ADU. The variables studied were concentration of uranium and ammonia, pH, temperature and form of ammonia (gas or solution). The properties studied were the settling rate of the precipitates, surface area of the ADUs and calcined oxides and compositional characteristics of the ADUs. Multifactorial experiments and ruggedness tests were applied to identify the parameters to which the precipitation process is most vulnerable, so that such parameters may be controlled effectively. Besides, the effect and the importance of equilibrium conditions during the precipitation process, on the quality of the final ADU, was also established. The paper presents the results of these studies. (author). 6 refs., 3 figs., 7 tabs

Experimental and theoretical study of heterogeneous iron precipitation in silicon

OpenAIRE

Haarahiltunen, Antti; Väinölä, Hele; Anttila, O.; Yli-Koski, Marko

2007-01-01

Heterogeneous iron precipitation in silicon was studied experimentally by measuring the gettering efficiency of oxide precipitate density of 1×10exp10cm−3. The wafers were contaminated with varying iron concentrations, and the gettering efficiency was studied using isothermal annealing in the temperature range from 300 to 780°C. It was found that iron precipitation obeys the so called s-curve behavior: if iron precipitation occurs, nearly all iron is gettered. For example, after 30 min anneal...

Fast high-temperature consolidation of Oxide-Dispersion Strengthened (ODS) steels: process, microstructure, precipitation, properties

International Nuclear Information System (INIS)

Boulnat, Xavier

2014-01-01

This work aims to lighten the understanding of the behavior of a class of metallic materials called Oxide-Dispersion Strengthened (ODS) ferritic steels. ODS steels are produced by powder metallurgy with various steps including atomization, mechanical alloying and high-temperature consolidation. The consolidation involves the formation of nanoparticles in the steel and various evolutions of the microstructure of the material that are not fully understood. In this thesis, a novel consolidation technique assisted by electric field called 'Spark Plasma Sintering' (SPS) or 'Field-Assisted Sintering Technique' (FAST) was assessed. Excellent mechanical properties were obtained by SPS, comparable to those of conventional hot isostatic pressed (HIP) materials but with much shorter processing time. Also, a broad range of microstructures and thus of tensile strength and ductility were obtained by performing SPS on either milled or atomized powder at different temperatures. However, SPS consolidation failed to avoid heterogeneous microstructure composed of ultrafine-grained regions surrounded by micron grains despite of the rapid consolidation kinetics. A multi-scale characterization allowed to understand and model the evolution of this complex microstructure. An analytical evaluation of the contributing mechanisms can explain the appearance of the complex grain structure and its thermal stability during further heat treatments. Inhomogeneous distribution of plastic deformation in the powder is argued to be the major cause of heterogeneous recrystallization and further grain growth during hot consolidation. Even if increasing the solute content of yttrium, titanium and oxygen does not impede abnormal growth, it permits to control the fraction and the size of the retained ultrafine grains, which is a key-factor to tailor the mechanical properties. Since precipitation through grain boundary pinning plays a significant role on grain growth, a careful

The characterisation of precipitated magnetites

International Nuclear Information System (INIS)

Rush, D.F.; Segal, D.L.

1982-06-01

Methods are described for the preparation of magnetite by precipitation from aqueous solutions of iron(II) and iron(III) salts. The magnetites have been characterised by transmission electron microscopy, chemical analysis and X-ray diffraction. Transmission Moessbauer spectroscopy has also been used to characterise precipitated magnetites and a comparison of the spectra has been made with those obtained from nickel ferrite and hydrated ferric oxides. The hydrothermal stability of magnetite at 573 K has also been investigated. This work is relevant to corrosion processes that can occur in the water coolant circuits of nuclear reactors. (author)

Titanium-iridium oxide layer coating to suppress photocorrosion during photocatalytic water splitting

Energy Technology Data Exchange (ETDEWEB)

Kwon, Yongwoo; Lee, Hyunjoo [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Kwon, Yongwoo; Lee, Hyunjoo [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

2015-12-15

Photocatalysts with a small band gap energy have received a great deal of interest due their high solar conversion efficiencies. Cuprous oxide (Cu{sub 2}O) has attracted attention because of its small bandgap energy, a direct bandgap structure, its suitable band structure for water splitting, high absorption coefficient, non-toxicity, and its large abundance. However, it has poor stability due to the fickle oxidation states of copper. To enhance the stability and the production rate of hydrogen and oxygen, a TiIrOX overlayer was successfully formed on the Cu{sub 2}O under various synthesis conditions. The composition and oxidation state of the Ir species in the overlayer were optimized through the control of the Ir precursor and the amount of water. The Ir/Ti precursor molar ratio was linearly related to the surface Ir/Ti molar ratio. The addition of water converted the Ir precursor to IrO{sub 2}. The thickness of the overlayer was controlled by differing the synthesis times of the coating. Then, the largest amounts of hydrogen and oxygen were produced through the optimization of the TiIrOX overlayer with a higher IrO{sub 2} fraction and a thicker overlayer.

Antisolvent Precipitation for the Synthesis of Monodisperse Mesoporous Niobium Oxide Spheres as Highly Effective Solid Acid Catalysts

KAUST Repository

Li, Cheng Chao; Dou, Jian; Chen, Luwei; Lin, Jianyi; Zeng, Hua Chun

2012-01-01

We have developed a low-cost reaction protocol to synthesize mesoporous Nb 2O 5-based solid acid catalysts with external shape control. In the synthesis, monodisperse glycolated niobium oxide spheres (GNOS) were prepared by means of a simple antisolvent precipitation approach and subsequently converted to mesoporous niobium oxide spheres (MNOS) with a large surface area of 312m 2g -1 by means of the hydrothermal treatment. The antisolvent acetone used to obtain GNOS was recovered through distillation at high purity. The obtained mesoporous MNOS were functionalized further with sulfate anions at different temperatures or incorporated with tungstophosphoric acid to obtain recyclable solid acid catalysts. These MNOS-based catalysts showed excellent performance in a wide range of acid-catalyzed reactions, such as Friedel-Crafts alkylation, esterification, and hydrolysis of acetates. As they are monodisperse spheres with diameters in the submicrometer range, the catalysts can be easily separated and reused. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Antisolvent Precipitation for the Synthesis of Monodisperse Mesoporous Niobium Oxide Spheres as Highly Effective Solid Acid Catalysts

KAUST Repository

Li, Cheng Chao

2012-03-20

We have developed a low-cost reaction protocol to synthesize mesoporous Nb 2O 5-based solid acid catalysts with external shape control. In the synthesis, monodisperse glycolated niobium oxide spheres (GNOS) were prepared by means of a simple antisolvent precipitation approach and subsequently converted to mesoporous niobium oxide spheres (MNOS) with a large surface area of 312m 2g -1 by means of the hydrothermal treatment. The antisolvent acetone used to obtain GNOS was recovered through distillation at high purity. The obtained mesoporous MNOS were functionalized further with sulfate anions at different temperatures or incorporated with tungstophosphoric acid to obtain recyclable solid acid catalysts. These MNOS-based catalysts showed excellent performance in a wide range of acid-catalyzed reactions, such as Friedel-Crafts alkylation, esterification, and hydrolysis of acetates. As they are monodisperse spheres with diameters in the submicrometer range, the catalysts can be easily separated and reused. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Review of Fabrication Methods, Physical Properties, and Applications of Nanostructured Copper Oxides Formed via Electrochemical Oxidation

Directory of Open Access Journals (Sweden)

Wojciech J. Stepniowski

2018-05-01

Full Text Available Typically, anodic oxidation of metals results in the formation of hexagonally arranged nanoporous or nanotubular oxide, with a specific oxidation state of the transition metal. Recently, the majority of transition metals have been anodized; however, the formation of copper oxides by electrochemical oxidation is yet unexplored and offers numerous, unique properties and applications. Nanowires formed by copper electrochemical oxidation are crystalline and composed of cuprous (CuO or cupric oxide (Cu2O, bringing varied physical and chemical properties to the nanostructured morphology and different band gaps: 1.44 and 2.22 eV, respectively. According to its Pourbaix (potential-pH diagram, the passivity of copper occurs at ambient and alkaline pH. In order to grow oxide nanostructures on copper, alkaline electrolytes like NaOH and KOH are used. To date, no systemic study has yet been reported on the influence of the operating conditions, such as the type of electrolyte, its temperature, and applied potential, on the morphology of the grown nanostructures. However, the numerous reports gathered in this paper will provide a certain view on the matter. After passivation, the formed nanostructures can be also post-treated. Post-treatments employ calcinations or chemical reactions, including the chemical reduction of the grown oxides. Nanostructures made of CuO or Cu2O have a broad range of potential applications. On one hand, with the use of surface morphology, the wetting contact angle is tuned. On the other hand, the chemical composition (pure Cu2O and high surface area make such materials attractive for renewable energy harvesting, including water splitting. While compared to other fabrication techniques, self-organized anodization is a facile, easy to scale-up, time-efficient approach, providing high-aspect ratio one-dimensional (1D nanostructures. Despite these advantages, there are still numerous challenges that have to be faced, including the

Millimeter- and submillimeter-wave spectrum and molecular constants of cuprous iodide

International Nuclear Information System (INIS)

Manson, E.L.; De Lucia, F.C.; Gordy, W.

1975-01-01

Monomeric cuprous iodide (CuI) in the vapor state has been produced as an intermediate product of the reaction of copper with iodine vapor at 1100 degreeK in a quasi-free-space microwave absorption cell. Rotational transitions of 63 Cu 127 I and 65 Cu 127 I were measured for J as high as 87→88 and for ν as high as 11. Hyperfine splittings due to 127 I were observed, and eqQ ( 127 I) =-935(15) MHz was derived. Analysis of the rotational frequencies yields the following Dunham and equilibrium coefficients for 63 Cu 127 I: Y 01 =2197.10172(98) MHz, Y 11 =-8.51120(66) MHz, Y 21 =0.00934(14) MHz, Y 31 =-0.0375(88) kHz, Y 02 =-0.67269(10) kHz, Y 12 =0.031(34) Hz, Y 03 =-0.00006858(10) Hz, B/sube/=2197.102(2) MHz, ω/sube/=264.897(18) cm -1 , ω/sube/chi/sube/=0.715(2) cm -1 , r/sube/=2.33831686(104) A; for 65 Cu 127 I: Y 01 =2151.89989(94) MHz, Y 11 =-8.24990(66) MHz, Y 21 =0.00896(14) MHz, Y 31 =-0.0356(88) kHz, Y 02 =-0.64530(10) kHz, Y 12 =0.030(34) Hz, Y 03 =-0.00006443(10) Hz, B/sube/=2151.900(2) MHz, ω/sube/=262.157(18) cm -1 , ω/sube/chi/sube/=0.700(2) cm -1 , r/sube/=2.33831664(102) A. The Dunham potential constants for CuI are a 0 =239 366(34) cm -1 , a 1 =-3.33365(36), a 2 =7.391(16), and a 3 =-13.20(18)

Effect of microalloying on precipitate evolution in ferritic welds and implications for toughness

International Nuclear Information System (INIS)

Narayanan, Badri K.; Kovarik, L.; Sarosi, Peter M.; Quintana, Marie A.; Mills, M.J.

2010-01-01

Ferritic weld metal deposited with a self-shielded arc-welding process has intentional additions of aluminum, magnesium, titanium and zirconium. This results in a complex precipitation process that has been characterized with a combination of electron microscopy techniques. This work indicates that the formation of a spinel oxide is critical for the nucleation of nitrides of zirconium and titanium and prevents the agglomeration of aluminum rich oxides and the formation of large aluminum nitrides. High-resolution transmission electron microscopy has been used to characterize the core/shell structure of the precipitates with microalloying additions. Thermodynamic modeling of the precipitate formation during solidification is consistent with the microstructural observations. The evolution of precipitate formation is critical to limit large inclusions and improve weld metal toughness.

New electrochemiluminescence catalyst: Cu2O semiconductor crystal and the enhanced activity of octahedra synthesized by iodide ions coordination

DEFF Research Database (Denmark)

Zhang, Ling; Qi, Liming; Gao, Wenyue

2017-01-01

Cuprous oxide (Cu2O) crystals are usually used as the photocatalysts of water splittings and carbon monoxide oxidations. Herein, we report the new catalytic properties of Cu2O to the electrochemilumenescence (ECL) reactions of luminol and oxygen. Adjusting the shape of Cu2O microcrystals from cub...

Scavenging ratios, wet deposition, and in-cloud oxidation: An application to the oxides of sulphur and nitrogen

International Nuclear Information System (INIS)

Barrie, L.A.

1985-01-01

With special regard to the class of substances in precipitation that potentially originate from both gaseous and particulate precursors, the process of precipitation scavenging is discussed. A model relating daily average ground level scavenging ratios (W) to nucleation scavenging and in-cloud chemical transformation is introduced and is used as guidance in the regression analysis of 3 years of SO 4 = and NO 3 - scavenging-ratio observations made at six locations in eastern Canada. It was found that W of SO 4 = -, NO 3 = -, and SO 4 = -bearing particles is inversely proportional to the one-third power of the precipitation amount in the event. The best regression model explained 41% of the variance in log W for SO 4 = . It included the effects of location, precipitation amount, precipitation type, and in-cloud SO 2 oxidation. The last effect accounted for 50% of the variance explained. The analysis predicts that, on average, in-cloud SO 2 oxidation accounts for 42--79% of the SO 4 = observed in rain and with the exception of one site, less than 20% of the SO 4 = observed in snow. These results are consistent with a mechanism of SO 2 oxidation involving photochemically produced H 2 O 2 . A similar analysis for NO 3 - supports the hypothesis that throughout the year much of the NO 3 - in precipitation originates from in-cloud NO 2 oxidation. It suggests that, depending on location, oxidation of 0.5--1.2 ppbv of NO 2 is sufficient to explain observations. One possible mechanism of oxidation is the reaction with O 3 to form NO 3 and hence soluble N 2 O 5

Estimating Hull Coating Thickness Distributions Using the EM Algorithm

National Research Council Canada - National Science Library

Corriere, Michael

2000-01-01

The underwater hull coating system on surface ships is comprised anti-corrosive (AC) and anti-fouling (AF) paint The AF layers are designed to wear away, continuously leaching cuprous oxide to inhibit marine growth...

Pretreatment of algae-laden and manganese-containing waters by oxidation-assisted coagulation: Effects of oxidation on algal cell viability and manganese precipitation.

Science.gov (United States)

Lin, Jr-Lin; Hua, Lap-Cuong; Wu, Yuting; Huang, Chihpin

2016-02-01

Preoxidation is manipulated to improve performance of algae and soluble manganese (Mn) removal by coagulation-sedimentation for water treatment plants (WTPs) when large amount of soluble Mn presents in algae-laden waters. This study aimed to investigate the effects of preoxidation on the performance of coagulation-sedimentation for the simultaneous removal of algae and soluble Mn, including ionic and complexed Mn. NaOCl, ClO2, and KMnO4 were used to pretreat such algae-laden and Mn containing waters. The variation of algal cell viability, residual cell counts, and concentrations of Mn species prior to and after coagulation-sedimentation step were investigated. Results show that NaOCl dosing was effective in reducing the viability of algae, but precipitated little Mn. ClO2 dosing had a strongest ability to lower algae viability and oxidize ionic and complexed soluble Mn, where KMnO4 dosing oxidized ionic and complexed Mn instead of reducing the viability of cells. Preoxidation by NaOCl only improved the algae removal by sedimentation, whereas most of soluble Mn still remained. On the other hand, ClO2 preoxidation substantially improved the performance of coagulation-sedimentation for simultaneous removal of algae and soluble Mn. Furthermore, KMnO4 preoxidation did improve the removal of algae by sedimentation, but left significant residual Mn in the supernatant. Images from FlowCAM showed changes in aspect ratio (AR) and transparency of algae-Mn flocs during oxidation-assisted coagulation, and indicates that an effective oxidation can improve the removal of most compact algae-Mn flocs by sedimentation. It suggests that an effective preoxidation for reducing algal cell viability and the concentration of soluble Mn is a crucial step for upgrading the performance of coagulation-sedimentation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Electroless deposition and electrical characterization of N- Cu 2 O ...

African Journals Online (AJOL)

This work describes the preparation of n-Cu2O layer by the electroless methods of boiling and immersion of copper plates in 0.001M CuSO4Electron Microscopy (SEM) have been used to characterize the oxide films deposited. XRD studies show, for the first time, that cuprous oxide (Cu2O) and cupric oxide (CuO) were ...

Application of ferrous-chromate and idometric titration for the determination of copper oxidation states in the superconductor YBa2Cu3Oy

International Nuclear Information System (INIS)

Oku, Masaoki; Kimura, Jin; Hosoya, Minoru; Takada, Kunio; Hirokawa, Kichinosuke

1988-01-01

Oxidation-reduction titration methods, Fe 2+ -Cr 2 O 7 2- and I - -S 2 O 3 2- , were applied to the determination of the oxidation state of copper in the superconductor YBa 2 Cu 3 O y and related compounds. The former method presented problems in the sample dissolution and titration steps. The dissolution of the sample in low concentrations of Fe 2+ -phosphoric acid and Fe 2+ -perchloric acid takes place in two steps, the oxidation of Fe 2+ to Fe 3+ and the liberation of oxygen gas, when the liberation results in low analytical values for Cu 3+ . In addition the coexistence of cuprous ion and acids induces the oxidation of ferrous ion by dissolved oxygen and air. The problems were resolved by dissolution in 0.1 mol/l Fe 2+ -phosphoric acid and titration in an argon atmosphere. The latter method gave good results by controlling the amounts of potassium chloride, the concentration of acetic acid, and by elimination of the dissolved oxygen in acetic acid solution. The results of the two titration methods coincided with each other. (orig.)

Novel p-n heterojunction copper phosphide/cuprous oxide photocathode for solar hydrogen production.

Science.gov (United States)

Chen, Ying-Chu; Chen, Zhong-Bo; Hsu, Yu-Kuei

2018-08-01

A Copper phosphide (Cu 3 P) micro-rod (MR) array, with coverage by an n-Cu 2 O thin layer by electrodeposition as a photocathode, has been directly fabricated on copper foil via simple electro-oxidation and phosphidation for photoelectrochemical (PEC) hydrogen production. The morphology, structure, and composition of the Cu 3 P/Cu 2 O heterostructure are systematically analyzed using a scanning electron microscope (SEM), X-ray diffraction and X-ray photoelectron spectra. The PEC measurements corroborate that the p-Cu 3 P/n-Cu 2 O heterostructural photocathode illustrates efficient charge separation and low charge transfer resistance to achieve the highest photocurrent of 430 μA cm -2 that is greater than other transition metal phosphide materials. In addition, a detailed energy diagram of the p-Cu 3 P/n-Cu 2 O heterostructure was investigated using Mott-Schottky analysis. Our study paves the way to explore phosphide-based materials in a new class for solar energy applications. Copyright © 2018 Elsevier Inc. All rights reserved.

Binary Oxide p-n Heterojunction Piezoelectric Nanogenerators with an Electrochemically Deposited High p-Type Cu2O Layer.

Science.gov (United States)

Baek, Seung Ki; Kwak, Sung Soo; Kim, Joo Sung; Kim, Sang Woo; Cho, Hyung Koun

2016-08-31

The high performance of ZnO-based piezoelectric nanogenerators (NGs) has been limited due to the potential screening from intrinsic electron carriers in ZnO. We have demonstrated a novel approach to greatly improve piezoelectric power generation by electrodepositing a high-quality p-type Cu2O layer between the piezoelectric semiconducting film and the metal electrode. The p-n heterojunction using only oxides suppresses the screening effect by forming an intrinsic depletion region, and thus sufficiently enhances the piezoelectric potential, compared to the pristine ZnO piezoelectric NG. Interestingly, a Sb-doped Cu2O layer has high mobility and low surface trap states. Thus, this doped layer is an attractive p-type material to significantly improve piezoelectric performance. Our results revealed that p-n junction NGs consisting of Au/ZnO/Cu2O/indium tin oxide with a Cu2O:Sb (cuprous oxide with a small amount of antimony) layer of sufficient thickness (3 μm) exhibit an extraordinarily high piezoelectric potential of 0.9 V and a maximum output current density of 3.1 μA/cm(2).

Memristive Properties of Thin Film Cuprous Oxide

Science.gov (United States)

2011-03-01

changes in the force sensed by the piezo electric crystal. ..................... 9 2. Schematic of the principles of Scanning Tunneling Microscopy (STM...developed the concept of the memristor in the 1970s. The three fundamental two-terminal elements in circuits, namely resistors , conductors, and...off the backside of the cantilever and changes in the force sensed by the piezo electric crystal. The AFM is a powerful tool for studying

Simultaneous stripping recovery of ammonia-nitrogen and precipitation of manganese from electrolytic manganese residue by air under calcium oxide assist.

Science.gov (United States)

Chen, Hongliang; Liu, Renlong; Shu, Jiancheng; Li, Wensheng

2015-01-01

Leaching tests of electrolytic manganese residue (EMR) indicated that high contents of soluble manganese and ammonia-nitrogen posed a high environmental risk. This work reports the results of simultaneous stripping recovery of ammonia-nitrogen and precipitation of manganese by air under calcium oxide assist. The ammonia-nitrogen stripping rate increased with the dosage of CaO, the air flow rate and the temperature of EMR slurry. Stripped ammonia-nitrogen was absorbed by a solution of sulfuric acid and formed soluble (NH4)2SO4 and (NH4)3H(SO4)3. The major parameters that effected soluble manganese precipitation were the dosage of added CaO and the slurry temperature. Considering these two aspects, the efficient operation conditions should be conducted with 8 wt.% added CaO, 60°C, 800 mL min(-1) air flow rate and 60-min reaction time. Under these conditions 99.99% of the soluble manganese was precipitated as Mn3O4, which was confirmed by XRD and SEM-EDS analyses. In addition, the stripping rate of ammonia-nitrogen was 99.73%. Leaching tests showed the leached toxic substances concentrations of the treated EMR met the integrated wastewater discharge standard of China (GB8978-1996).

Participation of the Pennsylvania State University in the MAP3S precipitation chemistry network

International Nuclear Information System (INIS)

Lamb, D.; de Pena, R.G.

1991-04-01

The Meteorology Department of the Pennsylvania State University collected precipitation in central Pennsylvania for more than 14 years on behalf of the Multistate Atmospheric Power Production Pollution Study (MAP3S). The MAP3S protocol, based on the sampling of precipitation from individual meteorological events over a long period of time, has allowed both for the development of a chemical climatology of precipitation in the eastern region of the United States and for a vastly improved understanding of the atmospheric processes responsible for wet acidic deposition. The precipitation chemistry data from the Penn State MAP3S site provide evidence of links to the anthropogenic emissions of sulfur dioxide and oxidant precursors. There is now little doubt that the free acidity in the precipitation of the region is due to the presence of unneutralized sulfate in the aqueous phase. In the absence of significant sources of this sulfur species and in view of supplemental enrichment studies, it is concluded that the sulfate enters cloud and rain water primarily through the aqueous-phase oxidation of sulfur dioxide emitted into the air within the geographical region of deposition. Within the source region the local abundances of sulfur dioxide often exceed those of the oxidants, so the depositions of sulfate and free acidity tend to be modulated by the availability of the strong oxidants. As a consequence, the deposition of sulfate exhibits a very strong seasonal dependence and little response to changes in the emissions of sulfur dioxide

Preparation of cerium oxide for lens polishing powder

International Nuclear Information System (INIS)

Injarean, Uthaiwan; Rodthongkom, Chouvana; Pichestapong, Pipat; Changkrurng, Kalaya

2003-10-01

Cerium is an element of rare earth group which is called lanthanide series. It is found in the ores like monazite and xenotime which are the tailings of tin mines in the south of Thailand. Cerium is used mostly as lens polishing powder besides the applications in other industries. In this study, cerium extracted from monazite ore breakdown by alkaline process was used for the preparation of lens polishing powder. Cerium hydroxide cake from the process was dissolved by hydrochloric acid and precipitated with oxalic acid. The oxalate precipitate then was calcined to oxide powder and its particle size was measured. Precipitation conditions being studied are concentration of feed cerium chloride solution, concentration of oxalic acid used for the precipitation, concentration of sulfuric acid used as precipitation control reagent and the precipitation temperature. It was found that the appropriate precipitation conditions yielded the fine oxide powder with particle size about 12μm. The oxide powder can be ground to the size of 1-3 μm which is suitable for making lens polishing powder

Synthesis and purification of oxide nanoparticle dispersions by modified emulsion precipitation.

Science.gov (United States)

Shi, Jingyu; Verweij, Henk

2005-06-07

ZrO2 and Fe2O3 precursor nanoparticles are synthesized, well-dispersed in decane, via a modified emulsion precipitation (MEP) method. This method starts with preparing two thermostable water-in-oil (w/o) emulsions with nonylphenol tetra(ethylene glycol) ether (Arkopal-40) as the main surfactant, didodecyldimethylammonium bromide (DiDAB) as the cosurfactant, decane as the continuous oil phase, and either a metal salt solution or a hexamethylenetetramine (HMTA) precipitation agent solution as the dispersed water phase. After mixing of the two emulsions, individual precursor particles are formed by precipitation in the confinement of the aqueous solution droplets. Excess water is removed by azeotropic distillation, and steric stabilization of the particles in the remaining oil medium is achieved with poly(octadecyl methacrylate) (PODMA), initially present dissolved in the oil phase. A purification process is conducted to remove the precipitation reaction byproduct and excess surfactants from the nanoparticle dispersions. Transmission electron microscopy (TEM) characterization shows that the ZrO2 and Fe2O3 precursor nanoparticles are both non-agglomerated, spherical, and have a narrow particle size distribution, centered at 4 nm in diameter. The precipitation from the dispersion of byproduct NH4Cl after water removal, and insoluble surfactant DiDAB after dilution with pure decane, is confirmed by X-ray diffraction (XRD). NMR results show that most of the oil-soluble surfactant Arkopal-40 can be removed from the dispersion by a 3x repeated dead-end pressure filtration process. It is shown that, after purification, the nanoparticle dispersions can be used for the preparation of homogeneous nanostructured coatings. The purification procedure as discussed provides guidelines for up-scaling the process and reuse of emulsifiers.

Aquifer Thermal Energy Storage as an ecosystem service for Brussels, Belgium: investigating iron (hydr)oxide precipitation with reactive transport modeling

Science.gov (United States)

Anibas, Christian; Possemiers, Mathias; Huysmans, Marijke

2016-04-01

In an evolving energy system it is important that urbanized areas contribute to their own energy demands. To reduce greenhouse gas emissions sustainable energy systems with a high efficiency are required, e.g. using urban aquifers as an ecosystem service. Here the potential of seasonal aquifer thermal energy storage and recovery (ATES) for the Brussels-Capital Region, Belgium is investigated. An important shallow geologic formation in the Brussels Capital Region is the Brussels Sand formation, a 20-60 m thick phreatic aquifer. The Brussels Sand Formation is known for its potential for ATES systems, but also for its varying redox and hydraulic conditions. Important limiting factors for ATES systems in the Brussels Sand Formation therefore are the hydraulic conductivity and the geochemical composition of the groundwater. Near the redox boundary iron hydroxide precipitation can negatively influence ATES well performance due to clogging. The interactions between physical processes (e.g. particle transport and clogging in the wider proximity of the ATES well) and chemical processes (e.g. influence of the operation temperatures on precipitation processes) during ATES operation are complex but not well understood. Therefore we constructed numerical groundwater flow models in MODFLOW to estimate maximum pumping and injection rates of different hydraulic conditions and competing water uses in the Brussels Sand Formation. In further steps the thermal potential for ATES was quantified using MT3DMS and the reactive transport model PHT3D was applied to assess the effects of operating ATES systems near the redox boundary. Results show that initial mixing plays an important role in the development of iron(hydr)oxide precipitation around the ATES wells, with the highest concentrations around the cold wells. This behavior is enhanced by the temperature effect; temperature differences of ΔT≈10°C already influence the iron (hydr)oxide concentration. The initial injection into the

Iron oxides as a cause of GPR reflections

NARCIS (Netherlands)

van Dam, R.L.; Schlager, W.; Dekkers, M.; Huisman, J.A.

2002-01-01

Iron oxides frequently occur as secondary precipitates in both modern and ancient sediments and may form bands or irregular patterns. We show from time-domain reflectometry (TDR) field studies that goethite iron-oxide precipitates significantly lower the electromagnetic wave velocity of sediments.

High Catalysis Activity of Cu₂O Microcrystals to the Electrochemiluminesence of Luminol and H₂O₂

DEFF Research Database (Denmark)

Zhang, Ling; Xu, Guobao; Zhang, Jingdong

Cuprous oxide (Cu2O) is a classical p-type semiconductor with a direct band gap of 2.17 eV, which is wildly used for solar energy conversion, CO oxidation, and photo catalytic water splitting for the low cost and environmental friendliness. For the energy band positions are favorable to the hydro......Cuprous oxide (Cu2O) is a classical p-type semiconductor with a direct band gap of 2.17 eV, which is wildly used for solar energy conversion, CO oxidation, and photo catalytic water splitting for the low cost and environmental friendliness. For the energy band positions are favorable...... to the hydrogen evolution and oxygen evolution potentials, Cu2O materials also catalyze the reduction of hydrogen peroxide (H2O2), which is an critical molecule in the bodies’ metabolism processes or the industrial catalysis reactions. To improve detection sensitivity of H2O2, people have composed Cu2O materials...... that Cu2O semiconductor microcrystal possess the good catalytic performance to this ECL reaction, which is important to develop the high-efficient and lowcost biosensors....

A model for the biological precipitation of Precambrian iron-formation

Science.gov (United States)

Laberge, G. L.

1986-01-01

A biological model for the precipitation of Precambrian iron formations is presented. Assuming an oxygen deficient atmosphere and water column to allow sufficient Fe solubility, it is proposed that local oxidizing environments, produced biologically, led to precipitation of iron formations. It is further suggested that spheroidal structures about 30 mm in diameter, which are widespread in low grade cherty rion formations, are relict forms of the organic walled microfossil Eosphaera tylerii. The presence of these structures suggests that the organism may have had a siliceous test, which allowed sufficient rigidity for accumulation and preservation. The model involves precipitation of ferric hydrates by oxidation of iron in the photic zone by a variety of photosynthetic organisms. Silica may have formed in the frustules of silica secreting organisms, including Eosphaera tylerii. Iron formates formed, therefore, by a sediment rain of biologically produced ferric hydrates and silica and other organic material. Siderite and hematite formed diagenetically on basin floors, and subsequent metamorphism produced magnetite and iron silicates.

Oxidative Precipitation of Manganese from Acid Mine Drainage by Potassium Permanganate

Directory of Open Access Journals (Sweden)

Regeane M. Freitas

2013-01-01

Full Text Available Although oxidative precipitation by potassium permanganate is a widely recognised process for manganese removal, research dealing with highly contaminated acid mine drainage (AMD has yet to be performed. The present study investigated the efficiency of KMnO4 in removing manganese from AMD effluents. Samples of AMD that originated from inactive uranium mine in Brazil were chemically characterised and treated by KMnO4 at pH 3.0, 5.0, and 7.0. Analyses by Raman spectroscopy and geochemical modelling using PHREEQC code were employed to assess solid phases. Results indicated that the manganese was rapidly oxidised by KMnO4 in a process enhanced at higher pH. The greatest removal, that is, 99%, occurred at pH 7.0, when treated waters presented manganese levels as low as 1.0 mg/L, the limit established by the Brazilian legislation. Birnessite (MnO2, hausmannite (Mn3O4, and manganite (MnOOH were detected by Raman spectroscopy. These phases were consistently identified by the geochemical model, which also predicted phases containing iron, uranium, manganese, and aluminium during the correction of the pH as well as bixbyite (Mn2O3, nsutite (MnO2, pyrolusite (MnO2, and fluorite (CaF2 following the KMnO4 addition.

Investigation of the precipitation of Na2SO4 in supercritical water

DEFF Research Database (Denmark)

Voisin, T.; Erriguible, A.; Philippot, G.

2017-01-01

solubility in sub-and supercritical water is determined on a wide temperature range using a continuous set-up. Crystallite sizes formed after precipitation are measured with in situ synchrotron wide angle X-ray scattering (WAXS). Combining these experimental results, a numerical modeling of the precipitation......SuperCritical Water Oxidation process (SCWO) is a promising technology for treating toxic and/or complex chemical wastes with very good efficiency. Above its critical point (374 degrees C, 22.1 MPa), water exhibits particular properties and organic compounds can be easily dissolved and degraded...... with the addition of oxidizing agents. But these interesting properties imply a main drawback regarding inorganic compounds. Highly soluble at ambient temperature in water, these inorganics (such as salts) are no longer soluble in supercritical water and precipitate into solids, creating plugs in SCWO processes...

DWPF integrated cold runs revised technical bases for precipitate hydrolysis

International Nuclear Information System (INIS)

Landon, L.F.

1992-01-01

The report defines new precipitate hydrolysis process operating parameters for DWPF Chemical runs assuming the precipitate feed simulants to be processed reflect the decision to implement a final wash of the tetraphenylborate slurry before transfer to DWPF (i.e. the Late Wash Facility). Control of the nitrite content of the tetraphenylborate slurry to 0.01M or less has eliminated the need for hydroxylamine nitrate (HAN) during hydrolysis. Consequently, the oxidant nitrous oxide will not be generated. However, nitric oxide (NO) is expected to be generated (reaction of formic acid with nitrite) and some fraction of the NO can be expected to be oxidized to nitrogen dioxide. The rate of NO generation with low nitrite feed has not been quantified at this time nor is the extent to which the NO is oxidized to NO 2 known. A mass spectrometer is being installed in the Precipitate Hydrolysis Experimental Facility (PHEF) which will enable the NO generation rate to be defined as well as the extent to which the NO is oxidized to NO 2 . There is some undocumented data available for C 6 H 6 /NO and C 6 H 6 /NO 2 with N 2 as the diluent but no similar data for CO 2 . Development of test data in the required time frame is not possible. However, MOC's will be estimated for benzene/NO/NO 2 /CO 2 gas mixtures (the MOC is expected to be approximately 60% less than for the HAN process). Once these data are obtained, and NO/NO 2 concentration profiles are obtained from PHEF hydrolysis process demonstrations, a flammability control strategy for the DWPF Salt Processing Cell will be developed. Implementation of the HAN process purge strategy upon startup of the SPC with the late wash process would be conservative

Effect of zinc oxide nanoparticles synthesized by a precipitation

Indian Academy of Sciences (India)

ZnO nanoparticles were synthesized by a precipitation method in aqueous media from zinc nitrate hexahydrate and sodium hydroxide. The synthesized ZnO nanoparticles exhibited a crystalline structure with hexagonal structure of the wurtzite. The morphology of the synthesized ZnO nanoparticles presented a spherical ...

Biomediated Precipitation of Calcium Carbonate in a Slightly Acidic Hot Spring

Science.gov (United States)

Jiang, L.

2015-12-01

A slightly acidic hot spring named "Female Tower" (T=73.5 °C, pH=6.64) is located in the Jifei Geothermal Field, Yunnan Province, Southwest China. The precipitates in the hot spring are composed of large amounts of calcite, aragonite, and sulfur. Scanning electron microscopy (SEM) analyses revealed that the microbial mats were formed of various coccoid, rod-shaped, and filamentous microbes. Transmission electron microscopy (TEM) showed that the intracellular sulfur granules were commonly associated with these microbes. A culture-independent molecular phylogenetic analysis demonstrated that the majority of the bacteria in the spring were sulfur-oxidizing bacteria. In the spring water, H2S concentration was up to 60 ppm, while SO42- concentration was only about 10 ppm. We speculated that H2S might be utilized by sulfur-oxidizing bacteria in this hot spring water, leading to the intracellular formation of sulfur granules. In the meantime, this reaction increased the pH in the micron-scale microdomains, which fostered the precipitation of calcium carbonate in the microbial mats. The results of this study indicated that the sulfur-oxidizing bacteria could play an important role in calcium carbonate precipitation in slightly acidic hot spring environments.

Fabrication of zinc oxide-cuprous oxide photovoltaic cell for teaching ...

African Journals Online (AJOL)

The light related current - voltage characteristics of the fabricated cell and its open circuit voltage for different illumination levels were comparable to those of conventional solar cells. This indicates that it is possible to produce a functional photovoltaic cell through local improvisation that can be used to stimulate the interest ...

Liquid Phase Plasma Synthesis of Iron Oxide/Carbon Composite as Dielectric Material for Capacitor

Directory of Open Access Journals (Sweden)

Heon Lee

2014-01-01

Full Text Available Iron oxide/carbon composite was synthesized using a liquid phase plasma process to be used as the electrode of supercapacitor. Spherical iron oxide nanoparticles with the size of 5~10 nm were dispersed uniformly on carbon powder surface. The specific capacitance of the composite increased with increasing quantity of iron oxide precipitate on the carbon powder up to a certain quantity. When the quantity of the iron oxide precipitate exceeds the threshold, however, the specific capacitance was rather reduced by the addition of precipitate. The iron oxide/carbon composite containing an optimum quantity (0.33 atomic % of iron oxide precipitate exhibited the smallest resistance and the largest initial resistance slope.

Sonochemical preparation of magnetite nanoparticles by reverse precipitation method

OpenAIRE

Shuto, Tatsuya; Nakagoe, Osamu; Tanabe, Shuji

2008-01-01

Magnetic iron oxide nanoparticles were successfully prepared by reverse precipitation method with the assistance of ultrasound. Obtained nanoparticles were identified as magnetite (Fe_3O_4) by XRD measurement. It was found that obtained magnetite nanoparticles have small sizes (about 10.7 ±2.9 nm in diameter) and spherical shape by TEM observations. In reverse precipitation method, the dropping conditions of aqueous FeSO_4 solution affect on the sizes and uniformity of the products.

Induced and catalysed mineral precipitation in the deep biosphere

Science.gov (United States)

Meister, Patrick

2017-04-01

Authigenic and early diagenetic minerals provide archives of past (bio)geochemical processes. In particular, isotopic signatures preserved in the diagenetic phases have been shown to document drastic changes of subsurface microbial activity (the deep biosphere) over geological time periods (Contreras et al., 2013; Meister, 2015). Geochemical and isotopic signatures in authigenic minerals may also document surface conditions and past climate. Nevertheless, such use of authigenic mineral phases as (bio)geochemical archives is often hampered by the insufficient understanding of mineral precipitation mechanisms. Accordingly the time, place and rate of mineral precipitation are often not well constrained. Also, element partitioning and isotopic fractionation may be modified as a result of the precipitation mechanism. Early diagenetic dolomite and quartz from drilled sequences in the Pacific were compared with adjacent porewater compositions and isotope signatures to gain fundamental insight into the factors controlling mineral precipitation. The formation of dolomite in carbonate-free organic carbon-rich ocean margin sediments (e.g. Peru Margin; Ocean Drilling Program, ODP, Site 1229; Meister et al., 2007) relies on the alkalinity-increase driven by anaerobic oxidation of methane and, perhaps, by alteration of clay minerals. In contrast, quartz is often significantly oversaturated in marine porewaters as the dissolved silica concentration is buffered by more soluble opal-A. For example, quartz does not form throughout a 400 metre thick sedimentary sequence in the Eastern Equatorial Pacific (ODP Site 1226; Meister et al., 2014) because it is kinetically inhibited. This behaviour can be explained by Ostwald's step rule, which suggests that the metastable phase forms faster. However, hard-lithified quartz readily forms where silica concentration drops sharply below opal-saturation. This violation of Ostwald's step rule must be driven by an auxiliary process, such as the

Effect of cuprous halide interlayers on the device performance of ZnPc/C60 organic solar cells

International Nuclear Information System (INIS)

Lee, Jinho; Park, Dasom; Heo, Ilsu; Yim, Sanggyu

2014-01-01

Highlights: • Effect of CuX interlayers on subsequently deposited films and devices was studied. • CuI is the most effective for the performance of ZnPc/C 60 -based solar cells. • Results were related to the molecular geometry of ZnPc and HOMO level of interlayers. - Abstract: The effect of various cuprous halide (CuX) interlayers introduced between a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) layer and zinc phthalocyanine (ZnPc) layer on the physical properties of the ZnPc thin films and device performances of ZnPc/C 60 -based small-molecule organic solar cells was studied. Strong substrate–molecule interaction between the CuX and ZnPc partly converted surface-perpendicular stacking geometry of ZnPc molecules into surface-parallel one. This flat-lying geometry led to an enhancement in electronic absorption and charge transport within the ZnPc films. As a result, the overall power conversion efficiency of the cell with CuI interlayer increased by ∼37%. In the case of the cells with CuBr and CuCl interlayer, however, the enhancement in device performances was limited because of the reduced conversion of the molecular geometry and increased energy barrier for hole extraction due to the low highest occupied molecular orbital level of the interlayer

The effect of heat on DNA degradation by the 1, 10-phenanthroline-cuprous ion complex

International Nuclear Information System (INIS)

Nagle, W.A.; Henle, K.J.; Willingham, W.M.; Sorenson, J.R.J.; McClellan, J.L.; Moss, A.J.

1987-01-01

The 1, 10-phenanthroline-cuprous ion complex (OP)/sub 2/Cu/sup +/ exhibits artificial DNase activity which closely parallels micrococcal nuclease. Using cell-free systems and in situ generated (OP)/sub 2/Cu/sup +/, other studies have shown a requirement for a reducing agent as well as O/sub 2/ or H/sub 2/O/sub 2/ to degrade DNA to acid-soluble fragments. The authors investigated the influence of hyperthermia on the degradation of V79 cell DNA using the (OP)/sub 2/Cu/sup +/-ascorbate system. The (OP)/sub 2/Cu/sup +/ complex was synthesized and characterized prior to cell treatment. Cells were prelabeled with /sup 3/H-TdR (control) or /sup 14/C-TdR (treated) and exposed 10 minutes at 45 0 C, followed by a 30 minute incubation with lμM (OP)/sub 2/Cu/sup +/ and 10μM as corbate in balanced salts solution. Cellular DNA was assayed using the alkaline elution technique. Heated cells incubated with lμM (OP)/sub 2/Cu/sup +/ or 10μM ascorbate exhibited a 300 rad equivalent increase in strand breaks over the unheated control. Incubation of cells with either lμM (OP)/sub 2/Cu/sup +/ or 10μM ascorbate alone did not induce strand breaks. These results suggests that heating initially increases the susceptibility of DNA to attack by the (OP)/sub 2/Cu/sup +/-ascorbate system

Iron biomineralization by anaerobic neutrophilic iron-oxidizing bacteria

DEFF Research Database (Denmark)

Miot, Jennyfer; Benzerara, Karim; Morin, Guillaume

2009-01-01

Minerals formed by bio-oxidation of ferrous iron (Fe(II)) at neutral pH, their association with bacterial ultrastructures as well as their impact on the metabolism of iron-oxidizing bacteria remain poorly understood. Here, we investigated iron biomineralization by the anaerobic nitrate-dependent ......Minerals formed by bio-oxidation of ferrous iron (Fe(II)) at neutral pH, their association with bacterial ultrastructures as well as their impact on the metabolism of iron-oxidizing bacteria remain poorly understood. Here, we investigated iron biomineralization by the anaerobic nitrate...... precipitation in the periplasm (in a few tens of minutes), followed by the formation of surface-bound globules. Moreover, we frequently observed an asymmetric mineral thickening at the cell poles. In parallel, the evolution of iron oxidation was quantified by STXM: iron both contained in the bacteria...... and in the extracellular precipitates reached complete oxidation within 6 days. While a progressive oxidation of Fe in the bacteria and in the medium could be observed, spatial redox (oxido-reduction state) heterogeneities were detected at the cell poles and in the extracellular precipitates after 1 day. All...

Fabrication of visible light-triggered photocatalytic materials from the coupling of n-type zinc oxide and p-type copper oxide

Science.gov (United States)

Gorospe, A. B.; Herrera, M. U.

2017-04-01

Coupling of copper oxide (CuO) and zinc oxide (ZnO) was done by chemical precipitation method. In this method, copper sulfate pentahydrate and zinc sulfate heptahydrate salt precursors were separately dissolved in distilled water; then were mixed together. The copper sulfate-zinc sulfate solution was then combined with a sodium hydroxide solution. The precipitates were collected and washed in distilled water and ethanol several times, then filtered and dried. The dried sample was grounded, and then undergone heat treatment. After heating, the sample was grounded again. Zinc oxide powder and copper oxide powder were also fabricated using chemical precipitation method. X-Ray Diffraction measurements of the coupled CuO/ZnO powder showed the presence of CuO and ZnO in the fabricated sample. Furthermore, other peaks shown by XRD were also identified corresponding to copper, copper (II) oxide, copper sulfate and zinc sulfate. Results of the photocatalytic activity investigation show that the sample exhibited superior photocatalytic degradation of methyl orange under visible light illumination compared to copper oxide powder and zinc oxide powder. This may be attributed to the lower energy gap at the copper oxide-zinc oxide interface, compared to zinc oxide, allowing visible light to trigger its photocatalytic activity.

Simultaneous precipitation of carbonato complexes of uranium and plutonium with cationic surfactants

International Nuclear Information System (INIS)

Heckmann, K.; Strnad, J.; Huber, K.

1992-01-01

The proposed method allows to separate Uranium, Thorium and Cerium from carbonate solutions and the further processing of these metals to mixed oxides. The separation can be divided into three steps: 1. Precipitation of the metals with a 10-fold surplus of carbonate and a 5-fold surplus of a cationic surfactant. 2. Thermal decomposition of the precipitates in air at 600 C. 3. Reduction of U(VI) to U(IV) with CO at 500 C. Mixed oxides in any ratio are formed in this way. This is possible due to the coprecipitation of both metals. Comparing the standard potentials it is clear that Ce(IV) is more easily reduced that Pu(IV). Therefore, the chance on the formation of U/Pu mixed oxides by this method is quite good. (orig.) [de

Recent changes in the oxidized to reduced nitrogen ratio in atmospheric precipitation

Science.gov (United States)

Kurzyca, Iwona; Frankowski, Marcin

2017-10-01

In this study, the characteristics of precipitation in terms of various nitrogen forms (NO3-, NO2-, NH4+, Norganic, Ntotal) is presented. The samples were collected in the areas of different anthropogenic pressure (urban area vs. ecologically protected woodland area, ∼30 km distant from each other; Wielkopolska region, Poland). Based on the Nox and Nred emission profiles (Nox/Nred ratio), temporal and spatial comparison was carried out. For both sites, during a decade of observation, more than 60% of samples had higher contribution of N-NH4+ than N-NO3-, the amount of N-NO2- was negligible, and organic nitrogen amounted to 30% of total nitrogen content which varied up to 16 mg/l. The precipitation events w ith high concentration of nitrogen species were investigated in terms of possible local and remote sources of nitrogen (synoptic meteorology), to indicate the areas which can act as potential sources of N-compounds. Based on the chemometric analysis, it was found that Nred implies Nox and vice versa, due to interactions between them in the atmosphere. Taking into account the analysis of precipitation occurring simultaneously in both locations (about 50% of all rainfall episodes), it was observed that such factor as anthropogenic pressure differentiates but does not determine the chemical composition of precipitation in the investigated areas (urban vs. woodland area; distance of ∼30 km). Thermodynamics of the atmosphere had a significant impact on concentrations of N-NO3- and N-NH4+ in precipitation, as well as the circulation of air masses and remote N sources responsible for transboundary inflow of pollutants.

Flux pinning by precipitates in the Bi-Sr-Ca-Cu-O system

International Nuclear Information System (INIS)

Shi, D.

1992-01-01

This patent describes a method for forming a ceramic oxide superconductor. It comprises heating a ceramic oxide to a temperature above its melting point to form a liquid; introducing calcium or copper into the ceramic oxide liquid to the extent that the ceramic oxide is supersaturated with calcium or copper; quenching the ceramic oxide liquid so as to convert the ceramic oxide to a glass supersaturated with calcium or copper; and annealing the calcium or copper and the ceramic oxide in forming grains in the ceramic oxide and a precipitate of the calcium or copper within the grains of the ceramic oxide so as to form superconducting phases in the ceramic oxide

Effect of cuprous halide interlayers on the device performance of ZnPc/C{sub 60} organic solar cells

Energy Technology Data Exchange (ETDEWEB)

Lee, Jinho; Park, Dasom; Heo, Ilsu; Yim, Sanggyu, E-mail: sgyim@kookmin.ac.kr

2014-10-15

Highlights: • Effect of CuX interlayers on subsequently deposited films and devices was studied. • CuI is the most effective for the performance of ZnPc/C{sub 60}-based solar cells. • Results were related to the molecular geometry of ZnPc and HOMO level of interlayers. - Abstract: The effect of various cuprous halide (CuX) interlayers introduced between a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) layer and zinc phthalocyanine (ZnPc) layer on the physical properties of the ZnPc thin films and device performances of ZnPc/C{sub 60}-based small-molecule organic solar cells was studied. Strong substrate–molecule interaction between the CuX and ZnPc partly converted surface-perpendicular stacking geometry of ZnPc molecules into surface-parallel one. This flat-lying geometry led to an enhancement in electronic absorption and charge transport within the ZnPc films. As a result, the overall power conversion efficiency of the cell with CuI interlayer increased by ∼37%. In the case of the cells with CuBr and CuCl interlayer, however, the enhancement in device performances was limited because of the reduced conversion of the molecular geometry and increased energy barrier for hole extraction due to the low highest occupied molecular orbital level of the interlayer.

Oxidation films morphology

International Nuclear Information System (INIS)

Paidassi, J.

1960-01-01

After studying the oxidation of several pure polyvalent metals (Fe, Cu, Mn, Ni, U) and of their oxides at high temperature and atmospheric pressure, the author suggests how to modify the usual representation of the oxide film (a piling of different oxide layers, homogeneous on a micrographic scale with a equi-axial crystallisation, free of mechanical tensions, with flat boundary surfaces) to have it nearer to reality. In this first part, the author exposes the study of the real micrographic structure of the oxidation film and gives examples of precipitation in the oxides during the cooling of the oxidised sample. (author) [fr

Copper-doped silica cuprous sulfate: A highly efficient heterogeneous nano-catalyst for one-pot three-component synthesis of 1-H-2-substituted benzimidazoles from 2-bromoanilines, aldehydes, and [bmim]N3

Directory of Open Access Journals (Sweden)

Somayeh Behrouz

2018-03-01

Full Text Available A facile and highly efficient one-pot three-component synthesis of 1-H-2-substituted benzimidazole derivatives from readily available substrates catalyzed by copper-doped silica cuprous sulfate (CDSCS is described. In this method, treatment of diverse 2-bromoanilines, aldehydes, and [bmim]N3 in DMF at 110 °C in the presence of CDSCS as a highly efficient heterogeneous nano-catalyst affords the corresponding 1-H-2-substituted benzimidazoles in good to excellent yields. The CDSCS is an inexpensive and stable nano-catalyst that could be simply prepared, recovered and reused for many consecutive reaction runs without significant loss of its activity.

Precipitation of metal nitrides from chloride melts

International Nuclear Information System (INIS)

Slater, S.A.; Miller, W.E.; Willit, J.L.

1996-01-01

Precipitation of actinides, lanthanides, and fission products as nitrides from molten chloride melts is being investigated for use as a final cleanup step in treating radioactive salt wastes generated by electrometallurgical processing of spent nuclear fuel. The radioactive components (eg, fission products) need to be removed to reduce the volume of high-level waste that requires disposal. To extract the fission products from the salt, a nitride precipitation process is being developed. The salt waste is first contacted with a molten metal; after equilibrium is reached, a nitride is added to the metal phase. The insoluble nitrides can be recovered and converted to a borosilicate glass after air oxidation. For a bench-scale experimental setup, a crucible was designed to contact the salt and metal phases. Solubility tests were performed with candidate nitrides and metal nitrides for which there are no solubility data. Experiments were performed to assess feasibility of precipitation of metal nitrides from chloride melts

Fe2+ oxidation rate drastically affect the formation and phase of secondary iron hydroxysulfate mineral occurred in acid mine drainage

International Nuclear Information System (INIS)

Huang Shan; Zhou Lixiang

2012-01-01

During the processes of secondary iron hydroxysulfate mineral formation, Fe 2+ ion was oxidized by the following three methods: (1) biooxidation treatment by Acidithiobacillus ferrooxidans (A. ferrooxidans); (2) rapid abiotic oxidation of Fe 2+ with H 2 O 2 (rapid oxidation treatment); (3) slow abiotic oxidation of Fe 2+ with H 2 O 2 (slow oxidation treatment). X-ray diffraction (XRD) patterns, element composition, precipitate weight and total Fe removal efficiency were analyzed. The XRD patterns and element composition of precipitates synthesized through the biooxidation and the slow oxidation treatments well coincide with those of potassium jarosite, while precipitates formed at the initial stage of incubation in the rapid oxidation treatment showed a similar XRD pattern to schwertmannite. With the ongoing incubation, XRD patterns and element composition of the precipitates that occurred in the rapid oxidation treatment were gradually close to those in the biooxidation and the slow oxidation treatments. Due to the inhibition of A. ferrooxidans itself and its extracellular polymeric substances (EPS) in aggregation of precipitates, the amount of precipitates and soluble Fe removal efficiency were lower in the biooxidation treatment than in the slow oxidation treatment. Therefore, it is concluded that Fe 2+ oxidation rate can greatly affect the mineral phase of precipitates, and slow oxidation of Fe 2+ is helpful in improving jarosite formation. - Highlights: ► Slow oxidation of Fe 2+ is helpful in jarosite formation. ► The already-formed schwertmannite can be gradually transformed to jarosite. ► Precipitates formation can be inhibited probably by EPS from A. ferrooxidans.

In-situ formation of complex oxide precipitates during processing of oxide dispersion strengthened ferritic steels

International Nuclear Information System (INIS)

Jayasankar, K.; Pandey, Abhishek; Mishra, B.K.; Das, Siddhartha

2016-01-01

Highlights: • Use of dual drive planetary ball mill for Bench scale (>1 kg) production. • X-ray diffraction and TEM were used to study transformations during sintering. • HIPped and rolled samples with nearly 99% density successfully produced. - Abstract: In fusion and fission reactor material development, ODS alloys are the most suitable candidate materials due to its high temperature creep properties and irradiation resistance properties. This paper describes the preparation of oxide dispersion strengthened alloy powder in large quantity (>1 kg batch) in dual drive planetary ball mill using pre-alloyed ferrtic steel powder with nano sized Y_2O_3. The consolidation of the powders was carried out in hot isostatic press (HIP) followed by hot rolling. 99% of the theoretical density was achieved by this method. The vickers hardness values of pressed and rolled samples were in the range of 380 ± 2HV and 719 ± 2HV, respectively. Samples were further investigated using X-ray diffraction particle size analyzer and electron microscope. Initial increase in particle size with milling was observed showing flattening of the particle. It was found that 5 h of milling time is sufficient to reduce the particle size to achieve the desired size. Transmission electron microscopy analysis of milled ODS steel powder revealed a uniform distribution of combustion synthesized nano-Y_2O_3 in ferritic steel matrix after a milling time of 5 h. Preliminary results demonstrated suitability of dual drive planetary ball mill for mass production of alloy within a short time due to various kinds of forces acting at a time during milling process. Fine monoclinic Y_2Si_2O_7 precipitates were also observed in the steel. This study explains the particle characteristics of nano Y_2O_3 dispersed ODS powder and formation of nano clusters in ODS ferritic alloy.

In situ precipitation and sorption of arsenic from groundwater: Laboratory and ex situ field tests

International Nuclear Information System (INIS)

Whang, J.M.; Adu-Wusu, K.; Frampton, W.H.; Staib, J.G.

1997-01-01

Permeable, reactive walls may provide long term, low-maintenance prevention of off-site migration of contaminated groundwater. Laboratory and ex situ field tests conducted on several arsenic-contaminated groundwaters indicate that both precipitation and sorption can remove arsenic to levels of less than 10 ppb. Precipitation has been induced by adjusting pH, adding selected cations, and/or reducing the oxidation-reduction potential. Adjusting pH or adding cations was most effective when there were high levels of other ionic species with which arsenic could coprecipitate. Reducing the oxidation-reduction potential was effective on a variety of groundwaters. Humate was an effective sorbent at low pH; aluminum and iron materials were effective over a large range of conditions. Long term performance of precipitation systems can be limited by formation of precipitate on reactive surfaces. Long term sorption can be reduced by competing ions, such as phosphate. Laboratory and ex situ field tests indicate that reactive walls may have lifetimes of decades or more

The influence of deformation, annealing and recrystallisation on oxide nanofeatures in oxide dispersion strengthened steel

Energy Technology Data Exchange (ETDEWEB)

Dawson, Karl, E-mail: k.dawson@liverpool.ac.uk; Tatlock, Gordon J.

2017-04-01

This work demonstrates that Y-Ti oxide nanofeatures, observed in as-extruded oxide dispersion strengthened steel, are structurally modified by cold forging. A 950 °C heat treatment promoted restructuring of the deformed particles and partial recrystallisation of the cold forged alloy. Transmission electron microscopy revealed that cuboid shaped nanofeatures were deformed during forging, which resulted in high number densities of lens shaped yttrium-titanium oxide particles. Annealing the forged alloy promoted partial recrystallisation of the ferritic matrix. Particle morphology reverted from lens shaped, as witnessed in the deformed material, to cuboid shaped oxide nanofeatures, identical to those observed in as-extruded material. Precipitation distributions evaluated in both recrystallised and recovering grains were indistinguishable from those first measured in the as-extruded alloy. TEM images revealed a widespread orientation relationship between the oxide precipitates and the recrystallised grains; registration with the ferrite lattice was omnipresent in both recovering and recrystallised grains.

Carbon nanotube—cuprous oxide composite based pressure sensors

International Nuclear Information System (INIS)

Karimov, Kh. S.; Chani, Muhammad Tariq Saeed; Khalid, Fazal Ahmad; Khan, Adam; Khan, Rahim

2012-01-01

In this paper, we present the design, the fabrication, and the experimental results of carbon nanotube (CNT) and Cu 2 O composite based pressure sensors. The pressed tablets of the CNT—Cu 2 O composite are fabricated at a pressure of 353 MPa. The diameters of the multiwalled nanotubes (MWNTs) are between 10 nm and 30 nm. The sizes of the Cu 2 O micro particles are in the range of 3–4 μm. The average diameter and the average thickness of the pressed tablets are 10 mm and 4.0 mm, respectively. In order to make low resistance electric contacts, the two sides of the pressed tablet are covered by silver pastes. The direct current resistance of the pressure sensor decreases by 3.3 times as the pressure increases up to 37 kN/m 2 . The simulation result of the resistance—pressure relationship is in good agreement with the experimental result within a variation of ±2%. (condensed matter: structural, mechanical, and thermal properties)

Picosecond nonlinear optical properties of cuprous oxide with ...

Indian Academy of Sciences (India)

2014-02-08

Feb 8, 2014 ... with a direct band gap of 2.17 eV and can be used in solar cells, ... various important applications in the field of material research. ... of isopropanol dispersed with Cu2O powder on carbon-coated copper grid to determine.

Dependence of precipitation of trace elements on pH in standard water

Science.gov (United States)

Verma, Shivcharan; Mohanty, Biraja P.; Singh, K. P.; Behera, B. R.; Kumar, Ashok

2018-04-01

The present work aimed to study the dependence of precipitation of trace elements on the pH of solution. A standard solution was prepared by using ultrapure deionized water (18.2 MΩ/cm) as the solvent and 11 water-soluble salts having different elements as solutes. Five samples of different pH values (2 acidic, 2 basic, and 1 neutral) were prepared from this standard solution. Sodium-diethyldithiocarbamate was used as the chelating agent to precipitate the metal ions present in these samples of different pH values. The targets were prepared by collecting these precipitates on mixed cellulose esters filter of 0.4 μm pore size by vacuum filtration. Elemental analysis of these targets was performed by particle-induced X-ray emission (PIXE) using 2.7 MeV protons from the single Dee variable energy cyclotron at Panjab University, Chandigarh, India. PIXE data were analyzed using GUPIXWIN software. For most of the elements, except Hg with oxidation state +2, such as Co, Ni, Zn, Ba, and Cd, a general trend of enhancement in precipitation was observed with the increase in pH. However, for other elements such as V, As, Mo, Ag, and Bi, which have oxidation state other than +2, no definite pattern was observed. Precipitation of Ba and As using this method was negligible at all five pH values. From these results, it can be concluded that the precipitation and recovery of elements depend strongly on the pH of the water sample.

Self-aligned nanocrystalline ZnO hexagons by facile solid-state and co-precipitation route

International Nuclear Information System (INIS)

Thorat, J. H.; Kanade, K. G.; Nikam, L. K.; Chaudhari, P. D.; Panmand, R. P.; Kale, B. B.

2012-01-01

In this study, we report the synthesis of well-aligned nanocrystalline hexagonal zinc oxide (ZnO) nanoparticles by facile solid-state and co-precipitation method. The co-precipitation reactions were performed using aqueous and ethylene glycol (EG) medium using zinc acetate and adipic acid to obtain zinc adipate and further decomposition at 450 °C to confer nanocrystalline ZnO hexagons. XRD shows the hexagonal wurtzite structure of the ZnO. Thermal study reveals complete formation of ZnO at 430 °C in case of solid-state method, whereas in case of co-precipitation method complete formation was observed at 400 °C. Field emission scanning electron microscope shows spherical morphology for ZnO synthesized by solid-state method. The aqueous-mediated ZnO by co-precipitation method shows rod-like morphology. These rods are formed via self assembling of spherical nanoparticles, however, uniformly dispersed spherical crystallites were seen in EG-mediated ZnO. Transmission electron microscope (TEM) investigations clearly show well aligned and highly crystalline transparent and thin hexagonal ZnO. The particle size was measured using TEM and was observed to be 50–60 nm in case of solid-state method and aqueous-mediated co-precipitation method, while 25–50 nm in case of EG-mediated co-precipitation method. UV absorption spectra showed sharp absorption peaks with a blue shift for EG-mediated ZnO, which demonstrate the mono-dispersed lower particle size. The band gap of the ZnO was observed to be 3.4 eV which is higher than the bulk, implies nanocrystalline nature of the ZnO. The photoluminescence studies clearly indicate the strong violet and weak blue emission in ZnO nanoparticles which is quite unique. The process investigated may be useful to synthesize other oxide semiconductors and transition metal oxides.

Self-aligned nanocrystalline ZnO hexagons by facile solid-state and co-precipitation route

Energy Technology Data Exchange (ETDEWEB)

Thorat, J. H. [Mahatma Phule College, Department of Chemistry (India); Kanade, K. G. [Annasaheb Awate College (India); Nikam, L. K. [B.G. College (India); Chaudhari, P. D.; Panmand, R. P.; Kale, B. B., E-mail: kbbb1@yahoo.com [Center for Materials for Electronics Technology (C-MET) (India)

2012-02-15

In this study, we report the synthesis of well-aligned nanocrystalline hexagonal zinc oxide (ZnO) nanoparticles by facile solid-state and co-precipitation method. The co-precipitation reactions were performed using aqueous and ethylene glycol (EG) medium using zinc acetate and adipic acid to obtain zinc adipate and further decomposition at 450 Degree-Sign C to confer nanocrystalline ZnO hexagons. XRD shows the hexagonal wurtzite structure of the ZnO. Thermal study reveals complete formation of ZnO at 430 Degree-Sign C in case of solid-state method, whereas in case of co-precipitation method complete formation was observed at 400 Degree-Sign C. Field emission scanning electron microscope shows spherical morphology for ZnO synthesized by solid-state method. The aqueous-mediated ZnO by co-precipitation method shows rod-like morphology. These rods are formed via self assembling of spherical nanoparticles, however, uniformly dispersed spherical crystallites were seen in EG-mediated ZnO. Transmission electron microscope (TEM) investigations clearly show well aligned and highly crystalline transparent and thin hexagonal ZnO. The particle size was measured using TEM and was observed to be 50-60 nm in case of solid-state method and aqueous-mediated co-precipitation method, while 25-50 nm in case of EG-mediated co-precipitation method. UV absorption spectra showed sharp absorption peaks with a blue shift for EG-mediated ZnO, which demonstrate the mono-dispersed lower particle size. The band gap of the ZnO was observed to be 3.4 eV which is higher than the bulk, implies nanocrystalline nature of the ZnO. The photoluminescence studies clearly indicate the strong violet and weak blue emission in ZnO nanoparticles which is quite unique. The process investigated may be useful to synthesize other oxide semiconductors and transition metal oxides.

Augmentation of a solar still distillate yield via absorber plate coated with black nanoparticles

Directory of Open Access Journals (Sweden)

A.E. Kabeel

2017-12-01

Full Text Available Effects of utilizing nanomaterial on the solar still productivity investigated experimentally. Cuprous oxides (CuO chosen as a nanoparticles material. The nanoparticles added to the black paint of the solar still walls to enhance the solar still performance. Experiments conducted with cuprous oxide nanoparticles weight concentrations ranged from 10% to 40%. It is found that adding nanoparticles to paint increase heat transfer rate and saline water temperature. Solar still productivity of the proposed system is higher than that for the conventional still. Results acquired that utilizing CuO nanoparticles boosted the distillate by 16% and 25% as compared to the conventional solar still (CSS at weight fraction concentration of 10% and 40%, respectively. Payback period of the distillation system for the modified still using CuO nanomaterials is about 96 days, at weight fraction 10%, which is considerable as compared by 89 days for CSS. Keywords: Nanomaterial, Solar still, Distillation, Nanoparticle

Recovery of iron oxide from coal fly ash

Science.gov (United States)

Dobbins, Michael S.; Murtha, Marlyn J.

1983-05-31

A high quality iron oxide concentrate, suitable as a feed for blast and electric reduction furnaces is recovered from pulverized coal fly ash. The magnetic portion of the fly ash is separated and treated with a hot strong alkali solution which dissolves most of the silica and alumina in the fly ash, leaving a solid residue and forming a precipitate which is an acid soluble salt of aluminosilicate hydrate. The residue and precipitate are then treated with a strong mineral acid to dissolve the precipitate leaving a solid residue containing at least 90 weight percent iron oxide.

PREPARATION OF METAL OXIDE POWDERS FROM METAL LOADED VERSATIC ACID

OpenAIRE

KAKIHATA, Takayuki; USAMI, Kensuke; YAMAMOTO, Hideki; SHIBATA, Junji

1998-01-01

A production process for metal oxide powders was developed using a solvent extraction method. Versatic Acid 10 and D2EHPA solutions containing copper, zinc and nickel were used for a precipitation-stripping process, where oxalic acid was added to the solution as a precipitation reagent.Copper, zinc and nickel oxalates were easily formed in an aqueous phase, and 99.9% of precipitation was obtained for each metal during this process. These metal oxalates were easily converted to metal oxides by...

Zirconia powders production by precipitation: state-of-art review

International Nuclear Information System (INIS)

Oliveira, Ana Paula Almeida de; Torem, Mauricio Leonardo

1994-01-01

The important role played by zirconia in advanced ceramics can be attributed to its excellent wear and corrosion resistance and refractory character. The polymorphic nature of zirconia made the controlled addition of stabilizing oxides or the constraining effect of a dense ceramics matrix necessary to maintain high parameters had a significant influence on powder properties and on compacted powder behaviour in sintering. Particle shape and size, purity and crystalline structure were specially influenced by precipitation parameters. Therefore, this work presented a review of the state of the art in zirconia powder production and in the recent research on precipitation of that powder. (author)

One-pot synthesis of Cu{sub 2}O octahedron particles and their catalytic application

Energy Technology Data Exchange (ETDEWEB)

Li, Biao; Li, Dan; Mu, Lei; Yang, Sung Ik [Dept. of Applied Chemistry, Kyung Hee University, Yongin (Korea, Republic of)

2017-04-15

We report a facile one-step synthesis method of cuprous oxide (Cu{sub 2}O) hollow octahedrons with controllable size Cu{sub 2}O exhibited a great catalytic activity for the reduction of methylene blue by N{sub 2}H{sub 4} as well as NABH{sub 4}.

Photoelectrocatalytic removal of color from water using TiO 2 and ...

African Journals Online (AJOL)

... a pseudo first order model and the apparent rate constant may depend on several factors such as, the nature and concentration of the organic compound, radiant flux, the solution pH and the presence of other organic substances. KEY WORDS: Photoelectrocatalysis, Titanium dioxide, Cuprous oxide, Composite thin film, ...

Synthesis and functionalisation of metal and metal oxide nanoparticles for theranostics

OpenAIRE

Mundell, VJ

2013-01-01

Metal and metal oxide nanoparticles including calcium oxide, gold, and superparamagnetic iron oxide nanoparticles (SPIOs) were synthesised using a range of techniques including reduction, co-precipitation and spinning disc technology. SPIOs were primarily synthesised via a co-precipitation method using iron (II) chloride, iron (III) chloride and ammonia; a spinning disc reactor and gaseous ammonia were trialled successfully for scale up, producing spherical particles of 10-40 nm in diameter a...

Pitting corrosion of copper. An equilibrium - mass transport study

International Nuclear Information System (INIS)

Taxen, C.

2002-08-01

A mathematical model for the propagation of corrosion pits is described and used to calculate the potentials below which copper is immune to pitting. The model uses equilibrium data and diffusion coefficients and calculates the stationary concentration profiles of 26 aqueous species from the bulk water outside a corrosion pit to the site of the metal dissolution. Precipitation of oxides and salts of copper is considered. Studied conditions include water compositions from tap waters to seawater at the temperatures 25 deg C and 75 deg C. Carbonate and sulphate are aggressive towards copper because of complex formation with divalent copper. Carbonate is less aggressive in a corrosion pit than outside at the pH of the bulk. Carbonate carries acidity out from the pit, favours oxide formation and may prevent the initiation of acidic corrosion pits. The concentration profiles are used to estimate the maximum propagation rates for a corrosion pit. A high potential is found to be the most important factor for the rate of propagation. The levels of potential copper can sustain, as corrosion potentials are discussed in terms of the stability of cuprous oxide as a cathode material for oxygen reduction relative to non-conducting cupric phases

Pitting corrosion of copper. An equilibrium - mass transport study

Energy Technology Data Exchange (ETDEWEB)

Taxen, C. [Swedish Corrosion Inst., Stockholm (Sweden)

2002-08-01

A mathematical model for the propagation of corrosion pits is described and used to calculate the potentials below which copper is immune to pitting. The model uses equilibrium data and diffusion coefficients and calculates the stationary concentration profiles of 26 aqueous species from the bulk water outside a corrosion pit to the site of the metal dissolution. Precipitation of oxides and salts of copper is considered. Studied conditions include water compositions from tap waters to seawater at the temperatures 25 deg C and 75 deg C. Carbonate and sulphate are aggressive towards copper because of complex formation with divalent copper. Carbonate is less aggressive in a corrosion pit than outside at the pH of the bulk. Carbonate carries acidity out from the pit, favours oxide formation and may prevent the initiation of acidic corrosion pits. The concentration profiles are used to estimate the maximum propagation rates for a corrosion pit. A high potential is found to be the most important factor for the rate of propagation. The levels of potential copper can sustain, as corrosion potentials are discussed in terms of the stability of cuprous oxide as a cathode material for oxygen reduction relative to non-conducting cupric phases.

Microbially-Mediated Precipitation of Calcium Carbonate Nanoparticles.

Science.gov (United States)

Kang, Ser Ku; Roh, Yul

2016-02-01

The objective of this study was to investigate the biomineralization of carbonate minerals using microorganisms (Wu Do-1) enriched from rhodoliths. A 16S rRNA sequence analysis showed that Wu Do-1 mainly contained Proteus mirabilis. The pH decreased from 6.5 to 5.3 over the first 4 days of incubation due to microbial oxidation of organic acids, after which it increased to 7.8 over the remaining incubation period. XRD analysis showed that the precipitates were Mg-rich cal- cite (MgxCa(1-x)CO3), whereas no precipitates were formed without the addition of Wu Do-1 in D-1 medium. SEM-EDS analyses showed that the Mg-rich calcite had a rhombohedron shape and consisted of Ca, Si and Mg with an extracelluar polymeric substance (EPS). In addition, TEM-EDS analyses revealed they were hexagon in shape, 500-700 nm in size, and composed of Ca, Mg, C, and O. These results indicated that Wu Do-1 induced precipitation of Mg-rich calcite on the cell walls and EPS via the accumulation of Ca and/or Mg ions. Therefore, microbial precipitation of carbonate nanoparticles may play an important role in metal and carbon biogeochemistry, as well as in carbon sequestration in natural environments.

Mn3O4 precipitates in Ag and Cu studied with HRTEM : orientation relations and tetragonal twinning

NARCIS (Netherlands)

Kooi, B.J.; de Hosson, J.T.M.; Sarton, LAJ; Zeedijk, HB

1997-01-01

Internal oxidation of Ag-3at.%Mn resulted in Mn3O4 precipitates and of Cu-1at.%Mn gave rise to MnO and a minor amount of Mn3O4 precipitates. In Cu Mn3O4 transformed out of MnO, whereas in Ag Mn3O4 developed directly. Predominantly, precipitates with parallel topotaxy and an octahedron shape due to 8

Mechanical behavior and strengthening mechanisms in ultrafine grain precipitation-strengthened aluminum alloy

International Nuclear Information System (INIS)

Ma, Kaka; Wen, Haiming; Hu, Tao; Topping, Troy D.; Isheim, Dieter; Seidman, David N.; Lavernia, Enrique J.; Schoenung, Julie M.

2014-01-01

To provide insight into the relationships between precipitation phenomena, grain size and mechanical behavior in a complex precipitation-strengthened alloy system, Al 7075 alloy, a commonly used aluminum alloy, was selected as a model system in the present study. Ultrafine-grained (UFG) bulk materials were fabricated through cryomilling, degassing, hot isostatic pressing and extrusion, followed by a subsequent heat treatment. The mechanical behavior and microstructure of the materials were analyzed and compared directly to the coarse-grained (CG) counterpart. Three-dimensional atom-probe tomography was utilized to investigate the intermetallic precipitates and oxide dispersoids formed in the as-extruded UFG material. UFG 7075 exhibits higher strength than the CG 7075 alloy for each equivalent condition. After a T6 temper, the yield strength (YS) and ultimate tensile strength (UTS) of UFG 7075 achieved 734 and 774 MPa, respectively, which are ∼120 MPa higher than those of the CG equivalent. The strength of as-extruded UFG 7075 (YS: 583 MPa, UTS: 631 MPa) is even higher than that of commercial 7075-T6. More importantly, the strengthening mechanisms in each material were established quantitatively for the first time for this complex precipitation-strengthened system, accounting for grain-boundary, dislocation, solid-solution, precipitation and oxide dispersoid strengthening contributions. Grain-boundary strengthening was the predominant mechanism in as-extruded UFG 7075, contributing a strength increment estimated to be 242 MPa, whereas Orowan precipitation strengthening was predominant in the as-extruded CG 7075 (∼102 MPa) and in the T6-tempered materials, and was estimated to contribute 472 and 414 MPa for CG-T6 and UFG-T6, respectively

Recovery of Am-Cm from high-activity waste concentrate by in-canyon-tank precipitation as oxalates

International Nuclear Information System (INIS)

Gray, L.W.; Burney, G.A.; Wilson, T.W.; McKibben, J.M.

1980-01-01

Savannah River Laboratory and Savannah River Plant have been separating actinides for more than 25 years. Work continues to upgrade processes and to initiate new processes. This report summarizes work on a precipitation process to separate kg amounts of Am and Cm from hundreds of kilograms of NaNO 3 and Al(NO 3 ) 3 . The developed process includes formic acid denitration of the Am-Cm bearing streams for acid adjustment; oxalate precipitation of the Am-Cm; and Mn +2 catalyzed oxidation of oxalate in both the decanted supernate and the precipitated actinides. The new process generates one fourth the radioactive waste as the solvent extraction process which it replaced, and produces a cleaner feed solution for downstream processing to separate the Am and Cm before conversion to their respective oxides

Precipitation Polymerization of Methyl Methacrylate by AGET ATRP%MMA的电子活化再生原子转移自由基沉淀聚合

Institute of Scientific and Technical Information of China (English)

张守成; 陈永平

2013-01-01

Precipitation polymerization of methyl methacrylate (MMA) by AGET ATRP, with cuprous chloride (CuCl2 · 2H2O)/ascorbic acid/PMDETA(C9 H23 N3) as catalyst, and initiated by ethyl bromoacetate in ethanol solution, was carried out. Molecular weight and molecular weight distribution were characterized by GPC. The results show that MMA can be rapidly polymerized with high monomer conversioa PMMA with relative narrow molecular weight distribution can be synthesized. Precipitation polymerization of methyl methacrylate (MMA) by AGET ATRP possesses characteristics of controlled/" living" radical polymerization.%以乙醇为溶剂,氯化铜(CuCl2·2H2O)为催化剂,抗坏血酸为还原剂,溴乙酸乙酯为引发剂,PMDETA为配体,进行了甲基丙烯酸甲酯(MMA)的电子活化再生原子转移自由基(AGET ATRP)沉淀聚合,通过GPC和称重法对聚合物进行表征.结果表明,在这种催化体系中甲基丙烯酸甲酯的转化速率较快,甲基丙烯酸甲酯的AGETATRP沉淀聚合得到了较好的实现,获得了分子量分布较窄的聚合物,并且沉淀聚合实现了产物与催化剂的分离.

Correlations between TD annihilation and oxygen precipitation in Czochralski-grown silicon

International Nuclear Information System (INIS)

Reiche, M.

1989-01-01

Results of two-stage annealing experiments are presented including preannealing at T o C (TD formation) and a second annealing step at T=550 to 850 o C in order to study the annihilation of TD's and their influence on the oxygen precipitation. The investigations show that (1) TD's cannot act as nuclei for oxide precipitates and that (2) their annihilation, connected with the increased formation of Si I induced defects (RLD's), proves TD's to consist also of self-interstitials. (author) 11 refs., 4 figs

Nanoparticular metal oxide/anatase catalysts

DEFF Research Database (Denmark)

2010-01-01

The present invention concerns a method of preparation of nanoparticular metal oxide catalysts having a narrow particle size distribution. In particular, the invention concerns preparation of nanoparticular metal oxide catalyst precursors comprising combustible crystallization seeds upon which...... the catalyst metai oxide is co-precipitated with the carrier metal oxide, which crystallization seeds are removed by combustion in a final calcining step. The present invention also concerns processes wherein the nanoparticular metal oxide catalysts of the invention are used, such as SCR (deNOx) reactions...

Infrared absorption study of ammonium uranates and uranium oxide powders formed during their thermal decomposition

International Nuclear Information System (INIS)

Rofail, N.H.; ELfekey, S.A.

1992-01-01

Ammonium uranates (AU) were precipitated from a nuclear-pure uranyl nitrate solution using different precipitating agents. IR spectra of the obtained uranates and oxides formed during their thermal decomposition have been studied. The results indicated that the precipitating agent, mode of stirring, washing and calcining temperature are important factors for a specific oxide formation.4 FIG., 3 TAB

Development of a methodology for the separation of europium and samarium from a mixture of rare earth oxides by electroreduction/ precipitation

International Nuclear Information System (INIS)

Chepcanoff, Vera

2006-01-01

The rare earths (RE) were first used in 1903, when Welsbach developed a lighter that is still used today. Nowadays, the RE are employed in many different fields, as in the production of super-alloys , as catalysts for petroleum industry, in the manufacture of non-ferrous alloys, color television tubes, x-ray screens, special glasses, ceramics, computer industries, nuclear medicine, lasers, pigments, etc., moving, in the last decade , a market of US$ 2 billions per year. Due to their similar properties, the RE elements are very difficult to separate, requiring complex processes, what make the products very expensive. Elements like Eu and Sm, which contents in the minerals are low (0.05% and 2.0%, respectively, in monazite) are extremely expensive, but their field of application justifies the research for looking for other processes, more simple and/or more effective. Trivalent state is a characteristic of all RE, but some of them presents oxidation state +2, like Ce, Eu, Sm and Yb. In the case of Eu and Sm, the focus of the present work, the divalent state is achieved by electro-reduction in the potentials -0.65 and -1.55 (SCE), respectively. This makes possible the separation of these elements from the other rare earths and from each other. Thus, making use of this characteristic, a process for the individual separation of Eu and Sm in (NH 4 ) 2 SO 4 solution by electro-reduction/precipitation is proposed, where Sm is first separated from the solution as sulfate, and Eu, that remains in the solution, is precipitated after the decrease of temperature and potential applied. The process developed from a synthetic Eu and Sm solution was applied to a mixture of semi-heavy RE oxide, produced at IPEN-CNEN/SP, obtaining the separation of Sm. This product was analyzed by spectrophotometry, showing high purity. (author)

Study of interaction of uranium, plutonium and rare earth fluorides with some metal oxides in fluoric salt melts

International Nuclear Information System (INIS)

Gorbunov, V.F.; Novoselov, G.P.; Ulanov, S.A.

1976-01-01

Interaction of plutonium, uranium, and rare-earth elements (REE) fluorides with aluminium and calcium oxides in melts of eutectic mixture LiF-NaF has been studied at 800 deg C by X-ray diffraction method. It has been shown that tetravalent uranium and plutonium are coprecipitated by oxides as a solid solution UO 2 -PuO 2 . Trivalent plutonium in fluorides melts in not precipitated in the presence of tetravalent uranium which can be used for their separation. REE are precipitated from a salt melt by calcium oxide and are not precipitated by aluminium oxide. Thus, aluminium oxide in a selective precipitator for uranium and plutonium in presence of REE. Addition of aluminium fluoride retains trivalent plutonium and REE in a salt melt in presence of Ca and Al oxides. The mechanism of interacting plutonium and REE trifluorides with metal oxides in fluoride melts has been considered

Precipitation of metallic chromium during rapid cooling of Cr2O3 slags

Directory of Open Access Journals (Sweden)

J. Burja

2017-01-01

Full Text Available The slag systems of CaO-SiO2- Cr2O3 and Al2O3-CaO-MgO-SiO2- Cr2O3 were analyzed. These slag systems occur in the production of stainless steel and are important from the process metallurgy point of view. Synthetic slag samples with different chromium oxide content were prepared and melted. The melted slag samples where then rapidly cooled on large steel plates, so that the high temperature microstructure was preserved. The samples were analyzed by scanning electron microscopy (SEM and X-ray diffraction (XRD. The precipitation of different chromium oxide phases was studied, but most importantly the precipitation of metallic chromium was observed. These findings help us interpret industrial slag samples.

Arsenic precipitation from metallurgical effluents; Precipitacion de arsenico desde efluentes metalurgicos

Energy Technology Data Exchange (ETDEWEB)

Navarro, P.; Vargas, C.; Araya, E.; Martin, I.; Alguacil, F. J.

2004-07-01

In the mining-metallurgical companies different liquid effluents are produced, which can contain a series of dissolved elements that are considered dangerous from an environmental point of view. One of these elements is the arsenic, especially in the state of oxidation +5 that can be precipitated as calcium or iron arsenate. To fulfil the environmental requests it should have in solution a content of arsenic lower than 0,5 mg/l and the obtained solid product should be very stable under the condition in which it will be stored. this work looks for the best conditions of arsenic precipitation, until achieving contents in solution lower than such mentioned concentration. Also, the stability of the precipitates was studied. (Author) 7 refs.

Coprecipitation mechanisms and products in manganese oxidation in the presence of cadmium

Science.gov (United States)

Hem, J.D.; Lind, Carol J.

1991-01-01

Manganese oxidation products were precipitated in an aerated open-aqueous system where a continuous influx of mixed Mn2+ and Cd2+ solution was supplied and pH was maintained with an automated pH-stat adding dilute NaOH. X-ray diffraction and electron diffraction identified the solids produced as mixtures of Cd2Mn34+O8, Mn2+2Mn4+3O8, MnO2 (ramsdellite), and CdCO3. Mean oxidation numbers of the total precipitated Mn as great as 3.6 were reached during titrations. During subsequent aging in solution, oxidation numbers between 3.8 and 3.9 were reached in some precipitates in less than 40 days. Conditional oxidation rate constants calculated from a crystal-growth equation applied to titration data showed the overall precipitation rate, without considering manganese oxidation state in the precipitate, was increased by a factor of ~4 to ~7 when the mole ratio (Cd/Mn + Cd) of cadmium in the feed solution was 0.40 compared with rate constants for hausmannite (Mn2+Mn23+O4 precipitation under similar conditions but without accessory metals. Kinetic experiments were made to test effects of various Cd/Mn + Cd mole ratios and rates of addition of the feed solution, different temperatures from 5.0 to 35??C, and pH from 8.0 to 9.0. Oxidation rates were slower when the Cd mole ratio was less than 0.40. The rate increased by a factor of ~10 when pH was raised one-half unit. The effect of temperature on the rate constants was also substantial, but the meaning of this is uncertain because the rate of formation of Mn4+ oxide in the absence of Cd or other accessory metals was too slow to be measurable in titration experiments. The increased rate of Mn4+ oxide formation in the presence of Cd2+ can be ascribed to the formation of a labile adsorbed intermediate, CdMn2O4 Int, an analog of hausmannite, formed on precipitate surfaces at the beginning of the oxidation process. The increased lability of this structure, resulting from coordination-chemical behavior of Cd2+ during the titration

Precipitation and measurements of precipitation

NARCIS (Netherlands)

Schmidt, F.H.; Bruin, H.A.R. de; Attmannspacher, W.; Harrold, T.W.; Kraijenhoff van de Leur, D.A.

1977-01-01

In Western Europe, precipitation is normal phenomenon; it is of importance to all aspects of society, particularly to agriculture, in cattle breeding and, of course, it is a subject of hydrological research. Precipitation is an essential part in the hydrological cycle. How disastrous local

Oxidation kinetics and auger microprobe analysis of some oxidized zirconium alloys

International Nuclear Information System (INIS)

Ploc, R.A.

1989-01-01

Oxidation kinetics at 300 o C in dry oxygen of 0.5 wt% binary alloys of iron, nickel, and chromium in zirconium were determined for several surface preparations. Further, chemical profiles of the oxides as they existed on the matrix and on the precipitates were obtained by sputtering and Auger electron analysis. The appearance of 'breakaway' oxidation was controlled by the surface finish of the alloy, a variable that could be used to eliminate the phenomenon for all alloys except the Zr/Ni binary, which required β-quenching to accomplish the same purpose. (author)

Method of producing homogeneous mixed metal oxides and metal--metal oxide mixtures

International Nuclear Information System (INIS)

Quinby, T.C.

1978-01-01

Metal powders, metal oxide powders, and mixtures thereof of controlled particle size are provided by reacting an aqueous solution containing dissolved metal values with excess urea. Upon heating, urea reacts with water from the solution to leave a molten urea solution containing the metal values. The molten urea solution is heated to above about 180 0 C, whereupon metal values precipitate homogeneously as a powder. The powder is reduced to metal or calcined to form oxide particles. One or more metal oxides in a mixture can be selectively reduced to produce metal particles or a mixture of metal and metal oxide particles

The adsorption of chelating reagents on oxide minerals

International Nuclear Information System (INIS)

Bryson, M.A.W.

1984-06-01

This work constitutes a fundamental study of the interaction between chelating reagents and oxide minerals. The adsorption mechanisms have been elucidated for most of the systems generated by the oxides of copper(II) or iron(III) and chelating reagents octyl hydroxamate, N-phenylbenzohydroxamate, salicylaldoxime, 5-nitro-salicylaldoxime or 8-hydroxyquinoline. In order to better understand the adsorption process associated with copper(II) oxide, the oxide was recrystallized to produce a coarser material with a more uniform surface. This allowed the oxide surface to be viewed under the scanning electron microscope. A detailed investigation of the effect of the system variables; pH, conditioning period, concentration, temperature, surface area and dispersing reagent on the rate of precipitation of the copper chelate species of general form, Cu(chel) 2 , was made. In addition the chemical nature of the adsorbed species and the structural form of the precipitates were determined with the aid of infra-red spectroscopy and the scanning electron microscope. On the basis of these results a model has been formulated for the adsorption processes. The precipitation process was examined in more detail by the study of the adsorption of chelate on copper metal. Contact angle measurements of air bubbles on copper metal conditioned with chelate were related to the adsorption results in an attempt to isolate the optimum conditions for flotation of oxide minerals

Synthesis of CuO-NiO core-shell nanoparticles by homogeneous precipitation method

International Nuclear Information System (INIS)

Bayal, Nisha; Jeevanandam, P.

2012-01-01

Highlights: ► CuO-NiO core-shell nanoparticles have been synthesized using a simple homogeneous precipitation method for the first time. ► Mechanism of the formation of core-shell nanoparticles has been investigated. ► The synthesis route may be extended for the synthesis of other mixed metal oxide core-shell nanoparticles. - Abstract: Core-shell CuO–NiO mixed metal oxide nanoparticles in which CuO is the core and NiO is the shell have been successfully synthesized using homogeneous precipitation method. This is a simple synthetic method which produces first a layered double hydroxide precursor with core-shell morphology which on calcination at 350 °C yields the mixed metal oxide nanoparticles with the retention of core-shell morphology. The CuO–NiO mixed metal oxide precursor and the core-shell nanoparticles were characterized by powder X-ray diffraction, FT-IR spectroscopy, thermal gravimetric analysis, elemental analysis, scanning electron microscopy, transmission electron microscopy, and diffuse reflectance spectroscopy. The chemical reactivity of the core-shell nanoparticles was tested using catalytic reduction of 4-nitrophenol with NaBH 4 . The possible growth mechanism of the particles with core-shell morphology has also been investigated.

Powder of a copper oxide superconductor precursor, fabrication process and use for the preparation of superconducting oxide

International Nuclear Information System (INIS)

Dehaudt, P.

1990-01-01

The precursor powder comprises at least a copper compound (hydroxide, oxide and hydroxynitrates), at least a rare earth and/or yttrium compound (nitrates, hydroxides and hydroxynitrates) or bismuth oxide and at least an alkaline earth nitrate. It can be prepared by atomization drying of a suspension a copper precipitate or coprecipitate and other elements of the superconducting oxide in solution [fr

Inhibition of bacterial oxidation of ferrous iron by lead nitrate in sulfate-rich systems.

Science.gov (United States)

Wang, Hongmei; Gong, Linfeng; Cravotta, Charles A; Yang, Xiaofen; Tuovinen, Olli H; Dong, Hailiang; Fu, Xiang

2013-01-15

Inhibition of bacterial oxidation of ferrous iron (Fe(II)) by Pb(NO(3))(2) was investigated with a mixed culture of Acidithiobacillus ferrooxidans. The culture was incubated at 30 °C in ferrous-sulfate medium amended with 0-24.2 mM Pb(II) added as Pb(NO(3))(2). Anglesite (PbSO(4)) precipitated immediately upon Pb addition and was the only solid phase detected in the abiotic controls. Both anglesite and jarosite (KFe(3)(SO(4))(2)(OH)(6)) were detected in inoculated cultures. Precipitation of anglesite maintained dissolved Pb concentrations at 16.9-17.6 μM regardless of the concentrations of Pb(NO(3))(2) added. Fe(II) oxidation was suppressed by 24.2 mM Pb(NO(3))(2) addition even when anglesite was removed before inoculation. Experiments with 0-48 mM KNO(3) demonstrated that bacterial Fe(II) oxidation decreased as nitrate concentration increased. Therefore, inhibition of Fe(II) oxidation at 24.2 mM Pb(NO(3))(2) addition resulted from nitrate toxicity instead of Pb addition. Geochemical modeling that considered the initial precipitation of anglesite to equilibrium followed by progressive oxidation of Fe(II) and the precipitation of jarosite and an amorphous iron hydroxide phase, without allowing plumbojarosite to precipitate were consistent with the experimental time-series data on Fe(II) oxidation under biotic conditions. Anglesite precipitation in mine tailings and other sulfate-rich systems maintains dissolved Pb concentrations below the toxicity threshold of A. ferrooxidans. Copyright © 2012 Elsevier B.V. All rights reserved.

Homogeneous Precipitation Synthesis and Magnetic Properties of Cobalt Ferrite Nanoparticles

Directory of Open Access Journals (Sweden)

Zhigang Liu

2008-01-01

Full Text Available Magnetic nanoparticles (NPs of cobalt ferrite have been synthesized via a homogeneous precipitation route using hexamethylenetetramine (HMT as the precipitant. The particle size, crystal structure, and magnetic properties of the synthesized particles were investigated by X-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer. The NPs are of cubic inverse spinel structure and nearly spherical shape. With the increase of oxidation time from 30 to 180 minutes in the reaction solution at 90∘C, the average particle size increases from ~30 nm to ~45 nm. The as-synthesized NPs ~30 nm in size show higher Ms (61.5 emu/g and moderate Hc (945 Oe and Mr/Ms (0.45 value compared with the materials synthesized by coprecipitation method using NaOH as precipitate at high pH value.

Uranium (III) precipitation in molten chloride by wet argon sparging

Energy Technology Data Exchange (ETDEWEB)

Vigier, Jean-François, E-mail: jean-francois.vigier@ec.europa.eu [CEA, Nuclear Energy Division, Radiochemistry & Processes Department, F-30207 Bagnols sur Cèze (France); Unité de Catalyse et de Chimie du Solide, UCCS UMR CNRS 8181, Univ. Lille Nord de France, ENSCL-USTL, B.P. 90108, 59652 Villeneuve d' Ascq Cedex (France); Laplace, Annabelle [CEA, Nuclear Energy Division, Radiochemistry & Processes Department, F-30207 Bagnols sur Cèze (France); Renard, Catherine [Unité de Catalyse et de Chimie du Solide, UCCS UMR CNRS 8181, Univ. Lille Nord de France, ENSCL-USTL, B.P. 90108, 59652 Villeneuve d' Ascq Cedex (France); Miguirditchian, Manuel [CEA, Nuclear Energy Division, Radiochemistry & Processes Department, F-30207 Bagnols sur Cèze (France); Abraham, Francis [Unité de Catalyse et de Chimie du Solide, UCCS UMR CNRS 8181, Univ. Lille Nord de France, ENSCL-USTL, B.P. 90108, 59652 Villeneuve d' Ascq Cedex (France)

2016-06-15

In the context of pyrochemical processes for nuclear fuel treatment, the precipitation of uranium (III) in molten salt LiCl-CaCl{sub 2} (30–70 mol%) at 705 °C is studied. First, this molten chloride is characterized with the determination of the water dissociation constant. With a value of 10{sup −4.0}, the salt has oxoacid properties. Then, the uranium (III) precipitation using wet argon sparging is studied. The salt is prepared using UCl{sub 3} precursor. At the end of the precipitation, the salt is totally free of solubilized uranium. The main part is converted into UO{sub 2} powder but some uranium is lost during the process due to the volatility of uranium chloride. The main impurity of the resulting powder is calcium. The consequences of oxidative and reductive conditions on precipitation are studied. Finally, coprecipitation of uranium (III) and neodymium (III) is studied, showing a higher sensitivity of uranium (III) than neodymium (III) to precipitation. - Highlights: • Precipitation of Uranium (III) is quantitative in molten salt LiCl-CaCl{sub 2} (30–70 mol%). • The salt is oxoacid with a water dissociation constant of 10{sup −4.0} at 705 °C. • Volatility of uranium chloride is strongly reduced in reductive conditions. • Coprecipitation of U(III) and Nd(III) leads to a consecutive precipitation of the two elements.

Biofilm Inhibition by Novel Natural Product- and Biocide-Containing Coatings Using High-Throughput Screening

Directory of Open Access Journals (Sweden)

Maria Salta

2018-05-01

Full Text Available The use of natural products (NPs as possible alternative biocidal compounds for use in antifouling coatings has been the focus of research over the past decades. Despite the importance of this field, the efficacy of a given NP against biofilm (mainly bacteria and diatoms formation is tested with the NP being in solution, while almost no studies test the effect of an NP once incorporated into a coating system. The development of a novel bioassay to assess the activity of NP-containing and biocide-containing coatings against marine biofilm formation has been achieved using a high-throughput microplate reader and highly sensitive confocal laser scanning microscopy (CLSM, as well as nucleic acid staining. Juglone, an isolated NP that has previously shown efficacy against bacterial attachment, was incorporated into a simple coating matrix. Biofilm formation over 48 h was assessed and compared against coatings containing the NP and the commonly used booster biocide, cuprous oxide. Leaching of the NP from the coating was quantified at two time points, 24 h and 48 h, showing evidence of both juglone and cuprous oxide being released. Results from the microplate reader showed that the NP coatings exhibited antifouling efficacy, significantly inhibiting biofilm formation when compared to the control coatings, while NP coatings and the cuprous oxide coatings performed equally well. CLSM results and COMSTAT analysis on biofilm 3D morphology showed comparable results when the NP coatings were tested against the controls, with higher biofilm biovolume and maximum thickness being found on the controls. This new method proved to be repeatable and insightful and we believe it is applicable in antifouling and other numerous applications where interactions between biofilm formation and surfaces is of interest.

Nano-size metallic oxide particle synthesis in Fe-Cr alloys by ion implantation

Science.gov (United States)

Zheng, C.; Gentils, A.; Ribis, J.; Borodin, V. A.; Delauche, L.; Arnal, B.

2017-10-01

Oxide Dispersion Strengthened (ODS) steels reinforced with metal oxide nanoparticles are advanced structural materials for nuclear and thermonuclear reactors. The understanding of the mechanisms involved in the precipitation of nano-oxides can help in improving mechanical properties of ODS steels, with a strong impact for their commercialization. A perfect tool to study these mechanisms is ion implantation, where various precipitate synthesis parameters are under control. In the framework of this approach, high-purity Fe-10Cr alloy samples were consecutively implanted with Al and O ions at room temperature and demonstrated a number of unexpected features. For example, oxide particles of a few nm in diameter could be identified in the samples already after ion implantation at room temperature. This is very unusual for ion beam synthesis, which commonly requires post-implantation high-temperature annealing to launch precipitation. The observed particles were composed of aluminium and oxygen, but additionally contained one of the matrix elements (chromium). The crystal structure of aluminium oxide compound corresponds to non-equilibrium cubic γ-Al2O3 phase rather than to more common corundum. The obtained experimental results together with the existing literature data give insight into the physical mechanisms involved in the precipitation of nano-oxides in ODS alloys.

The Contribution of Extreme Precipitation to the Total Precipitation in China

Institute of Scientific and Technical Information of China (English)

SUN Jian-Qi

2012-01-01

Using daily precipitation data from weather stations in China, the variations in the contribution of extreme precipitation to the total precipitation are analyzed. It is found that extreme precipitation accounts for approximately one third of the total precipitation based on the overall mean for China. Over the past half century, extreme precipitation has played a dominant role in the year-to-year variability of the total precipitation. On the decadal time scale, the extreme precipitation makes different contributions to the wetting and drying regions of China. The wetting trends of particular regions are mainly attributed to increases in extreme precipitation; in contrast, the drying trends of other regions are mainly due to decreases in non-extreme precipitation.

Formation of iron (hydr)oxides during the abiotic oxidation of Fe(II) in the presence of arsenate.

Science.gov (United States)

Song, Jia; Jia, Shao-Yi; Yu, Bo; Wu, Song-Hai; Han, Xu

2015-08-30

Abiotic oxidation of Fe(II) is a common pathway in the formation of Fe (hydr)oxides under natural conditions, however, little is known regarding the presence of arsenate on this process. In hence, the effect of arsenate on the precipitation of Fe (hydr)oxides during the oxidation of Fe(II) is investigated. Formation of arsenic-containing Fe (hydr)oxides is constrained by pH and molar ratios of As:Fe during the oxidation Fe(II). At pH 6.0, arsenate inhibits the formation of lepidocrocite and goethite, while favors the formation of ferric arsenate with the increasing As:Fe ratio. At pH 7.0, arsenate promotes the formation of hollow-structured Fe (hydr)oxides containing arsenate, as the As:Fe ratio reaches 0.07. Arsenate effectively inhibits the formation of magnetite at pH 8.0 even at As:Fe ratio of 0.01, while favors the formation of lepidocrocite and green rust, which can be latterly degenerated and replaced by ferric arsenate with the increasing As:Fe ratio. This study indicates that arsenate and low pH value favor the slow growth of dense-structured Fe (hydr)oxides like spherical ferric arsenate. With the rapid oxidation rate of Fe(II) at high pH, ferric (hydr)oxides prefer to precipitate in the formation of loose-structured Fe (hydr)oxides like lepidocrocite and green rust. Copyright © 2015 Elsevier B.V. All rights reserved.

The role of magnetic iron oxide nanoparticles in the bacterially induced calcium carbonate precipitation.

Science.gov (United States)

Seifan, Mostafa; Ebrahiminezhad, Alireza; Ghasemi, Younes; Samani, Ali Khajeh; Berenjian, Aydin

2018-04-01

Recently, magnetic iron oxide nanoparticles (IONs) have been used to control and modify the characteristics of concrete and mortar. Concrete is one of the most used materials in the world; however, it is susceptible to cracking. Over recent years, a sustainable biotechnological approach has emerged as an alternative approach to conventional techniques to heal the concrete cracks by the incorporation of bacterial cells and nutrients into the concrete matrix. Once cracking occurs, CaCO 3 is induced and the crack is healed. Considering the positive effects of IONs on the concrete properties, the effect of these nanoparticles on bacterial growth and CaCO 3 biosynthesis needs to be evaluated for their possible application in bio self-healing concrete. In the present work, IONs were successfully synthesized and characterized using various techniques. The presence of IONs showed a significant effect on both bacterial growth and CaCO 3 precipitation. The highest bacterial growth was observed in the presence of 150 μg/mL IONs. The highest concentration of induced CaCO 3 (34.54 g/L) was achieved when the bacterial cells were immobilized with 300 μg/mL of IONs. This study provides new data and supports the possibility of using IONs as a new tool in designing the next generation of bio self-healing concrete.

Impact of Precipitants on the Structure and Properties of Fe-Co-Ce Composite Catalysts

Directory of Open Access Journals (Sweden)

Yongli Zhang

2016-01-01

Full Text Available Fe-Co-Ce composite catalysts were prepared by coprecipitation method using CO(NH22, NaOH, NH4HCO3, and NH3·H2O as precipitant agents. The effects of the precipitant agents on the physicochemical properties of the Fe-Co-Ce based catalysts were investigated by SEM, TEM, BET, TG-DTA, and XRD. It was found that the precipitant agents remarkably influenced the morphology and particle size of the catalysts and affected the COD removal efficiency, decolorization rate, and pH of methyl orange for catalytic wet air oxidation (CWAO. The specific surface area of the Fe-Co-Ce composite catalysts successively decreased in the order of NH3·H2O, NH4HCO3, NaOH, and CO(NH22, which correlated to an increasing particle size that increased for each catalyst. For the CWAO of a methyl orange aqueous solutions, the effects of precipitant agents NH3·H2O and NaOH were superior to those of CO(NH22 and NH4HCO3. The catalyst prepared using NH3·H2O as the precipitant agent was mostly composed of Fe2O3, CoO, and CeO2. The COD removal efficiency of methyl orange aqueous solution for NH3·H2O reached 92.9% in the catalytic wet air oxidation. Such a catalytic property was maintained for six runs.

Microscopic Mechanisms of Dissolution-Precipitation at the Water-Manganese Mineral Interfaces

Science.gov (United States)

Jun, Y.; Martin, S. T.

2006-12-01

The fate and transport of metal contaminants in water are often affected by the manganese redox cycling and the accompanying dissolution and precipitation reactions. Direct microscopic observations of such dynamic reactions, however, are sparse. In this work, microscopic mechanisms of simultaneous dissolution and precipitation of manganese minerals is studied by atomic force microscope (AFM) at circumneutral pH. The effects of the substrate surface morphology, the substrate atomic structure, and the aqueous concentration of Mn2+ on the formation of Mn oxide islands are investigated. Under oxic conditions, Mn2+(aq) dissolved from MnCO3 surface is reacted with O2(aq) at circumneutral pH to form Mn oxide islands on the (10-14) surface of MnCO3. The Mn oxide islands grow heteroepitaxially. On terraces, rhombohedral islands form with 90° rotation relative to crystallographic axis of the underlying substrate, and with z-directional self-limitation. Comparison studies done with MgCO3 and CaCO3 show that the former also promotes heteroepitaxial growth whereas the latter does not. This difference is explained by the relative bond length mismatch between the structures of the carbonate substrates and the atomic structures of Mn oxide islands. A free energy model is also employed to explain why the heights of the Mn oxide islands self limit. Our results provide an improved understanding for the development of predictive models both of exchange across the sediment-water interfaces and the fate and transport of contaminants in aqueous environments.

Ultra thin buried oxide layers formed by low dose Simox process

Energy Technology Data Exchange (ETDEWEB)

Aspar, B.; Pudda, C.; Papon, A.M. [CEA Centre d`Etudes de Grenoble, 38 (France). Lab. d`Electronique et d`Instrumentation; Auberton Herve, A.J.; Lamure, J.M. [SOITEC, 38 - Grenoble (France)

1994-12-31

Oxygen low dose implantation is studied for two implantation energies. For 190 keV, a continuous buried oxide layer is obtained with a high dislocation density in the top silicon layer due to SiO{sub 2} precipitates. For 120 keV, this silicon layer is free of SiO{sub 2} precipitate and has a low dislocation density. Low density of pin-holes is observed in the buried oxide. The influence of silicon islands in the buried oxide on the breakdown electric fields is discussed. (authors). 6 refs., 5 figs.

Ultra thin buried oxide layers formed by low dose Simox process

International Nuclear Information System (INIS)

Aspar, B.; Pudda, C.; Papon, A.M.

1994-01-01

Oxygen low dose implantation is studied for two implantation energies. For 190 keV, a continuous buried oxide layer is obtained with a high dislocation density in the top silicon layer due to SiO 2 precipitates. For 120 keV, this silicon layer is free of SiO 2 precipitate and has a low dislocation density. Low density of pin-holes is observed in the buried oxide. The influence of silicon islands in the buried oxide on the breakdown electric fields is discussed. (authors). 6 refs., 5 figs

Effect of precipitation route on the properties of antimony trioxide

International Nuclear Information System (INIS)

Abdullah, Abdul Halim; Noor, Nor Hayati Mohd; Ramli, Irmawati; Hashim, Mansor

2008-01-01

Antimony trioxide was prepared, using antimony potassium tartarate as starting material, via forward and reverse precipitation technique. The characteristics of the resulting antimony oxides were determined by BET surface area method, differential thermogravimetry analysis (DTG), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and SEM. The DTG curves for all uncalcined samples showed only a single endothermic peak which indicated that the sample is antimony trioxide. Unlike forward precipitation technique which resulted in a single antimony trioxide phase which is senarmontite, reverse precipitation technique produced antimony trioxide with both senarmontite and valentinite phase. Upon calcinations at 723 K, a small amount of Sb 2 O 4 with cervantite phase was formed at the expense of Sb 2 O 3 senarmontite phase as detected from the XRD pattern and infrared spectrum of RSb. The effect of preparation route on the properties of the antimony trioxide produced was clearly demonstrated

One-step synthesis and characterizations of cerium oxide nanoparticles in an ambient temperature via Co-precipitation method

Science.gov (United States)

Pujar, Malatesh S.; Hunagund, Shirajahammad M.; Desai, Vani R.; Patil, Shivaprasadgouda; Sidarai, Ashok H.

2018-04-01

We report the simple Co-precipitation method for the synthesis of Cerium oxide (CeO2) nanoparticles (NPs) in an ambient temperature. We have taken the Cerium (III) nitrate hexahydrate (Ce(NO3)3.6H2O) and Sodium hydroxide (NaOH) as the precursors. The obtained NPs were analyzed using the UV-Vis spectrophotometer, Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The obtained results signify that UV-Vis spectrum exhibited a well-defined absorption peak at 274 nm and the estimated energy gap (Eg) is 4.05 eV. The FT-IR analysis provides the supporting evidence for the presence of bonding of O-H, nitrates, alcohols and O-Ce-O vibrations. The XRD result reveals that the synthesized CeO2 NPs was crystallite with cubic phase structure and the estimated average crystallite size of CeO2 NPs using Scherer's and W-H method was significantly different due to their assumptions. Further, it is purposed to study their photocatalytic biological activities.

Interfacial Precipitation of Phosphate on Hematite and Goethite

Directory of Open Access Journals (Sweden)

Lijun Wang

2018-05-01

Full Text Available Adsorption and subsequent precipitation of dissolved phosphates on iron oxides, such as hematite and goethite, is of considerable importance in predicting the bioavailability of phosphates. We used in situ atomic force microscopy (AFM to image the kinetic processes of phosphate-bearing solutions interacting with hematite or goethite surfaces. The nucleation of nanoparticles (1.0–4.0 nm in height of iron phosphate (Fe(III-P phases, possibly an amorphous phase at the initial stages, was observed during the dissolution of both hematite and goethite at the earliest crystallization stages. This was followed by a subsequent aggregation stage where larger particles and layered precipitates are formed under different pH values, ionic strengths, and organic additives. Kinetic analysis of the surface nucleation of Fe-P phases in 50 mM NH4H2PO4 at pH 4.5 showed the nucleation rate was greater on goethite than hematite. Enhanced goethite and hematite dissolution in the presence of 10 mM AlCl3 resulted in a rapid increase in Fe-P nucleation rates. A low concentration of citrate promoted the nucleation, whereas nucleation was inhibited at higher concentrations of citrate. By modeling using PHREEQC, calculated saturation indices (SI showed that the three Fe(III-P phases of cacoxenite, tinticite, and strengite may be supersaturated in the reacted solutions. Cacoxenite is predicted to be more thermodynamically favorable in all the phosphate solutions if equilibrium is reached with respect to hematite or goethite, although possibly only amorphous precipitates were observed at the earliest stages. These direct observations at the nanoscale may improve our understanding of phosphate immobilization in iron oxide-rich acid soils.

Casting technology for ODS steels - the internal oxidation approach

Science.gov (United States)

Miran, S.; Franke, P.; Möslang, A.; Seifert, H. J.

2017-07-01

The formation of stainless ODS steel by internal oxidation of as-cast steel has been investigated. An alloy (Fe-16Cr-0.2Al-0.05Y, wt.%) was embedded in a (VO/V2O3) powder mixture serving as an oxygen activity buffer and heat treated at 1450 °C for 20 h. After this procedure no oxide scale was present on the surface of the sample but a zone of internal oxidation with a depth of about 2000 μm was formed in its interior. The precipitates within this zone consisted of two types of oxides. Discrete aluminium oxide particles with a size of a few micrometres were formed in outer regions of the specimen. Finer aluminium-yttrium oxides with a size of some hundred nanometres were mainly precipitated in inner regions of the sample. The results can be considered as a promising step towards an alternative production route for ODS steels.

Salts-based size-selective precipitation: toward mass precipitation of aqueous nanoparticles.

Science.gov (United States)

Wang, Chun-Lei; Fang, Min; Xu, Shu-Hong; Cui, Yi-Ping

2010-01-19

Purification is a necessary step before the application of nanocrystals (NCs), since the excess matter in nanoparticles solution usually causes a disadvantage to their subsequent coupling or assembling with other materials. In this work, a novel salts-based precipitation technique is originally developed for the precipitation and size-selective precipitation of aqueous NCs. Simply by addition of salts, NCs can be precipitated from the solution. After decantation of the supernatant solution, the precipitates can be dispersed in water again. By means of adjusting the addition amount of salt, size-selective precipitation of aqueous NCs can be achieved. Namely, the NCs with large size are precipitated preferentially, leaving small NCs in solution. Compared with the traditional nonsolvents-based precipitation technique, the current one is simpler and more rapid due to the avoidance of condensation and heating manipulations used in the traditional precipitation process. Moreover, the salts-based precipitation technique was generally available for the precipitation of aqueous nanoparticles, no matter if there were semiconductor NCs or metal nanoparticles. Simultaneously, the cost of the current method is also much lower than that of the traditional nonsolvents-based precipitation technique, making it applicable for mass purification of aqueous NCs.

Characteristics of oxide scale formed on Cu-bearing austenitic stainless steel during early stages of high temperature oxidation

Energy Technology Data Exchange (ETDEWEB)

Swaminathan, Srinivasan, E-mail: swaminathan@kist.re.kr [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 136 791 (Korea, Republic of); Krishna, Nanda Gopala [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Kim, Dong-Ik, E-mail: dongikkim@kist.re.kr [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 136 791 (Korea, Republic of)

2015-10-30

Highlights: • Initial oxidation characteristics of Cu-bearing austenitic stainless steel at 650 °C were studied. • Strong segregation and oxidation of Mn and Nb were found in the entire oxide scale. • Surface coverage by metallic Cu-rich precipitates increases with exposure time. • Chemical heterogeneity of oxide scale revealed initial oxidation to be non-selective. • Fe-Cr and Mn-Cr mixed oxides were realized along with binary oxides of Fe, Cr and Mn. - Abstract: Oxide scale evolution on Cu-bearing austenitic stainless steel 304H at 650 °C, in ambient air, for exposure times 100, 300, 500 and 1000 h, has been investigated. Surface morphology and chemistry of the oxide scale grown were examined using SEM/EDX and XPS. The oxidation kinetics was determined by measuring the weight change using an electronic balance. At the initial stage, up to 500 h of exposure time, the oxidation rate was rapid due to surface reactions governed primarily by oxygen ingress, and then, dropped to a low rate after prolonged oxidation for 1000 h. The diffusion of reactants through the initially formed oxide scale limits the oxidation rate at longer times, thus, the progress of reaction followed the parabolic kinetics. The formed oxide scale was enriched significantly with segregation and subsequent oxidation of Nb, and finely dispersed metallic Cu particles. Within the time frame of oxidation, the oxide scale was mainly composed of mixed oxides such as FeCr{sub 2}O{sub 4} and MnCr{sub 2}O{sub 4} along with the binary oxides of Fe, Cr and Mn. Moreover, the precipitation fraction of Cu-rich particles on the oxide scale increased markedly with increase of exposure times. The chemical heterogeneity of oxide scale suggests that the oxidation occurred in a non-selective manner.

Improvement in structural and electrical properties of cuprous oxide ...

Indian Academy of Sciences (India)

Administrator

walled carbon nanotubes ... heat transfer applications, electrochemical supercapaci- tors and gas sensor ... They have observed that the thermal expansion coefficient decreased ... many times with ethanol and then with distilled water and dried in ...

The Global Precipitation Climatology Project (GPCP) Combined Precipitation Dataset

Science.gov (United States)

Huffman, George J.; Adler, Robert F.; Arkin, Philip; Chang, Alfred; Ferraro, Ralph; Gruber, Arnold; Janowiak, John; McNab, Alan; Rudolf, Bruno; Schneider, Udo

1997-01-01

The Global Precipitation Climatology Project (GPCP) has released the GPCP Version 1 Combined Precipitation Data Set, a global, monthly precipitation dataset covering the period July 1987 through December 1995. The primary product in the dataset is a merged analysis incorporating precipitation estimates from low-orbit-satellite microwave data, geosynchronous-orbit -satellite infrared data, and rain gauge observations. The dataset also contains the individual input fields, a combination of the microwave and infrared satellite estimates, and error estimates for each field. The data are provided on 2.5 deg x 2.5 deg latitude-longitude global grids. Preliminary analyses show general agreement with prior studies of global precipitation and extends prior studies of El Nino-Southern Oscillation precipitation patterns. At the regional scale there are systematic differences with standard climatologies.

Chlorination of bromide-containing waters: Enhanced bromate formation in the presence ofsynthetic metal oxides and deposits formed indrinking water distribution systems

KAUST Repository

Liu, Chao; von Gunten, Urs; Croue, Jean-Philippe

2013-01-01

Bromate formation from the reaction between chlorine and bromide in homogeneous solution is a slow process. The present study investigated metal oxides enhanced bromate formation during chlorination of bromide-containing waters. Selected metal oxides enhanced the decay of hypobromous acid (HOBr), a requisite intermediate during the oxidation of bromide to bromate, via (i) disproportionation to bromate in the presence of nickel oxide (NiO) and cupric oxide (CuO), (ii) oxidation of a metal to a higher valence state in the presence of cuprous oxide (Cu2O) and (iii) oxygen formation by NiO and CuO. Goethite (α-FeOOH) did not enhance either of these pathways. Non-charged species of metal oxides seem to be responsible for the catalytic disproportionation which shows its highest rate in the pH range near the pKa of HOBr. Due to the ability to catalyze HOBr disproportionation, bromate was formed during chlorination of bromide-containing waters in the presence of CuO and NiO, whereas no bromate was detected in the presence of Cu2O and α-FeOOH for analogous conditions. The inhibition ability of coexisting anions on bromate formation at pH 8.6 follows the sequence of phosphate>>sulfate>bicarbonate/carbonate. A black deposit in a water pipe harvested from a drinking water distribution system exerted significant residual oxidant decay and bromate formation during chlorination of bromide-containing waters. Energy dispersive spectroscopy (EDS) analyses showed that the black deposit contained copper (14%, atomic percentage) and nickel (1.8%, atomic percentage). Cupric oxide was further confirmed by X-ray diffraction (XRD). These results indicate that bromate formation may be of concern during chlorination of bromide-containing waters in distribution systems containing CuO and/or NiO. © 2013 Elsevier Ltd.

Chlorination of bromide-containing waters: Enhanced bromate formation in the presence ofsynthetic metal oxides and deposits formed indrinking water distribution systems

KAUST Repository

Liu, Chao

2013-09-01

Bromate formation from the reaction between chlorine and bromide in homogeneous solution is a slow process. The present study investigated metal oxides enhanced bromate formation during chlorination of bromide-containing waters. Selected metal oxides enhanced the decay of hypobromous acid (HOBr), a requisite intermediate during the oxidation of bromide to bromate, via (i) disproportionation to bromate in the presence of nickel oxide (NiO) and cupric oxide (CuO), (ii) oxidation of a metal to a higher valence state in the presence of cuprous oxide (Cu2O) and (iii) oxygen formation by NiO and CuO. Goethite (α-FeOOH) did not enhance either of these pathways. Non-charged species of metal oxides seem to be responsible for the catalytic disproportionation which shows its highest rate in the pH range near the pKa of HOBr. Due to the ability to catalyze HOBr disproportionation, bromate was formed during chlorination of bromide-containing waters in the presence of CuO and NiO, whereas no bromate was detected in the presence of Cu2O and α-FeOOH for analogous conditions. The inhibition ability of coexisting anions on bromate formation at pH 8.6 follows the sequence of phosphate>>sulfate>bicarbonate/carbonate. A black deposit in a water pipe harvested from a drinking water distribution system exerted significant residual oxidant decay and bromate formation during chlorination of bromide-containing waters. Energy dispersive spectroscopy (EDS) analyses showed that the black deposit contained copper (14%, atomic percentage) and nickel (1.8%, atomic percentage). Cupric oxide was further confirmed by X-ray diffraction (XRD). These results indicate that bromate formation may be of concern during chlorination of bromide-containing waters in distribution systems containing CuO and/or NiO. © 2013 Elsevier Ltd.

Adsorption of arsenic by iron rich precipitates from two coal mine drainage sites on the West Coast of New Zealand

International Nuclear Information System (INIS)

Rait, R.; Trumm, D.; Pope, J.; Craw, D.; Newman, N.; MacKenzie, H.

2010-01-01

Dissolved As can be strongly adsorbed to fine grained Fe(III) minerals such as hydroxides, oxyhydroxides and hydroxysulphates. Therefore precipitates that form during neutralisation or treatment of acid mine drainage have potential to be useful for treatment of As-contaminated water because acid mine drainage is often Fe rich. We tested the adsorption properties of Fe(III) rich precipitates from two West Coast coal mines with As-contaminated water from an historic gold ore processing site near Reefton. Precipitates were collected from distinctly different settings, an active acid mine drainage treatment plant at Stockton mine and the neutralisation/oxidation zone of acid mine drainage discharge at the abandoned Blackball Coal Mine. The two mine sites produce precipitates with different compositions and mineralogy. Arsenic adsorption onto precipitates from each site was determined in batch and column tests under laboratory conditions. Batch experiments indicate As adsorption occurs rapidly during the first 5 h and reaches equilibrium after 24 h. At equilibrium, and for a dosing ratio of 50 g of precipitate per litre of water, As concentrations decreased from 99 mg/L to 0.0080 mg/L with precipitates from Stockton and to 0.0017 mg/L with precipitates from Blackball. Arsenic adsorption capacity is up to 12 mg/g on precipitates from Stockton sludge and 74 mg/g on precipitates from Blackball. The Blackball precipitate adsorbs more As than precipitates from Stockton which is probably due to the higher Fe oxide content but pH and surface structure could also play a role. The column experiment confirmed that adsorption of As from a continuous waste stream onto these precipitates is possible, and that passive remediation using this waste product mixed with gravel to enhance permeability could be a viable approach at As-contaminated mine sites. (author). 56 refs., 10 figs., 6 tabs.

Oxygen Storage Capacity and Oxygen Mobility of Co-Mn-Mg-Al Mixed Oxides and Their Relation in the VOC Oxidation Reaction

Directory of Open Access Journals (Sweden)

María Haidy Castaño

2015-05-01

Full Text Available Co-Mn-Mg-Al oxides were synthesized using auto-combustion and co-precipitation techniques. Constant ratios were maintained with (Co + Mn + Mg/Al equal to 3.0, (Co + Mn/Mg equal to 1.0 and Co/Mn equal to 0.5. The chemical and structural composition, redox properties, oxygen storage capacity and oxygen mobility were analyzed using X-ray fluorescence (XRF, X-ray diffraction (XRD, Raman spectroscopy, scanning electron microscopy (SEM, temperature-programmed reduction of hydrogen (H2-TPR, oxygen storage capacity (OSC, oxygen storage complete capacity (OSCC and isotopic exchange, respectively. The catalytic behavior of the oxides was evaluated in the total oxidation of a mixture of 250 ppm toluene and 250 ppm 2-propanol. The synthesis methodology affected the crystallite size, redox properties, OSC and oxide oxygen mobility, which determined the catalytic behavior. The co-precipitation method got the most active oxide in the oxidation of the volatile organic compound (VOC mixture because of the improved mobility of oxygen and ability to favor redox processes in the material structure.

Solubility and precipitation of Fe on reduced TiO{sub 2}(001)

Energy Technology Data Exchange (ETDEWEB)

Busiakiewicz, Adam, E-mail: adambus@uni.lodz.pl

2014-01-01

The solubility of Fe in reduced rutile TiO{sub 2} crystals and the followed precipitation on the (001) surface have been studied using X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM) in ultra-high vacuum. The first step includes dissolving Fe in reduced TiO{sub 2} at 1073 K by the means of thermal diffusion and as a result the saturated solid solution is formed. Then, it undergoes fast cooling which leads to obtaining a supersaturated solid solution. When this supersaturated crystal is annealed at low temperatures of about 500 K, Fe starts to precipitate on the (001) surface forming spherical Fe-containing nanoparticles. The fast migration of Fe cations to the surface and their precipitation at relatively low temperatures are caused by high diffusion anisotropy and the reduction of the TiO{sub 2}. At about 900 K, the size of nanoparticles increases and they are transformed into nanocrystals with clearly visible facets. Simultaneously, the number of the nanocrystals substantially decreases. The partial oxidation of Fe is also observed around 900 K, which is related to strong metal support interaction between Fe and reduced TiO{sub 2}(001). The XPS and STM results suggest that the nanocrystals are mostly composed of mixed Fe/Ti oxides like FeTiO{sub 3} of ilmenite structure. Above 973 K, the nanocrystals disappear which is explained by the restored solubility of Fe cations in the reduced TiO{sub 2}. The process of the nanoparticle precipitation at lower temperatures is repeatable and the precipitation and disappearance of Fe-containing nanocrystals on TiO{sub 2}(001) are also a fully reversible phenomenon easily controlled by annealing temperature. - Highlights: • The supersaturated solid solution of Fe in TiO{sub 2}(001) is obtained at 1073 K. • Fe precipitates forming nanoparticles above 500 K and nanocrystals above 900 K. • Nanocrystals are ascribed to formation of FeTiO{sub 3} compound.

Electrochemically modified crystal orientation, surface morphology and optical properties using CTAB on Cu2O thin films

Directory of Open Access Journals (Sweden)

Karupanan Periyanan Ganesan

Full Text Available Cuprous oxide (Cu2O thin films with different crystal orientations were electrochemically deposited in the presence of various molar concentrations of cetyl trimethyl ammonium bromide (CTAB on fluorine doped tin oxide (FTO glass substrate using standard three electrodes system. X-ray diffraction (XRD studies reveal cubic structure of Cu2O with (111 plane orientation, after addition of CTAB in deposition solution, the orientation of crystal changes from (111 into (200 plane. Scanning electron microscope (SEM images explored significant variation on morphology of Cu2O thin films deposited with addition of CTAB compared to without addition of CTAB. Photoluminescence (PL spectra illustrate that the emission peak around at 650 nm is attributed to near band edge emission, and the film prepared at the 3 mM of CTAB exhibits much higher intensity than that of the all other films. UV–Visible spectra show optical absorption in the range of 480–610 nm and the highest transparency of Cu2O film prepared at the concentration of 3 mM CTAB. The optical band gap is increased in the range between 2.16 and 2.45 eV with increasing the CTAB concentrations. Keywords: Cuprous oxide, Crystal orientation, Electrodeposition and cubic structure

Charging effects and surface potential variations of Cu-based nanowires

Energy Technology Data Exchange (ETDEWEB)

Nunes, D., E-mail: daniela.gomes@fct.unl.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Calmeiro, T.R.; Nandy, S.; Pinto, J.V.; Pimentel, A.; Barquinha, P. [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Carvalho, P.A. [SINTEF Materials and Chemistry, PB 124 Blindern, NO-0314, Oslo (Norway); CeFEMA, Instituto Superior Técnico, Universidade de Lisboa, 1049-001, Lisboa (Portugal); Walmsley, J.C. [SINTEF Materials and Chemistry, Materials and Nanotechnology, Høgskoleringen 5, 7034 Trondheim (Norway); Fortunato, E., E-mail: emf@fct.unl.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Martins, R., E-mail: rm@uninova.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal)

2016-02-29

The present work reports charging effects and surface potential variations in pure copper, cuprous oxide and cupric oxide nanowires observed by electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KPFM). The copper nanowires were produced by wet synthesis, oxidation into cuprous oxide nanowires was achieved through microwave irradiation and cupric oxide nanowires were obtained via furnace annealing in atmospheric conditions. Structural characterization of the nanowires was carried out by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. During the EFM experiments the electrostatic field of the positive probe charged negatively the Cu-based nanowires, which in turn polarized the SiO{sub 2} dielectric substrate. Both the probe/nanowire capacitance as well as the substrate polarization increased with the applied bias. Cu{sub 2}O and CuO nanowires behaved distinctively during the EFM measurements in accordance with their band gap energies. The work functions (WF) of the Cu-based nanowires, obtained by KPFM measurements, yielded WF{sub CuO} > WF{sub Cu} > WF{sub Cu{sub 2O}}. - Highlights: • Charge distribution study in Cu, Cu{sub 2}O and CuO nanowires through electrostatic force microscopy • Structural/surface defect role on the charge distribution along the Cu nanowires • Determination of the nanowire work functions by Kelvin probe force microscopy • Three types of nanowires give a broad idea of charge behavior on Cu based-nanowires.

A glassy carbon electrode modified with porous Cu_2O nanospheres on reduced graphene oxide support for simultaneous sensing of uric acid and dopamine with high selectivity over ascorbic acid

International Nuclear Information System (INIS)

Mei, Li-Ping; Feng, Jiu-Ju; Wu, Liang; Chen, Jian-Rong; Shen, Liguo; Wang, Ai-Jun; Xie, Yunlong

2016-01-01

Porous cuprous oxide nanospheres were deposited on reduced graphene oxide (pCu_2O NS-rGO) by a solvothermal approach that uses hexadecyltrimethylammonium bromide as the capping agent and L-glutamic acid as the reducing agent. The nanomaterial was characterized by transmission electron microscopy, Raman spectroscopy, thermogravimetry, and electrochemical methods. A glassy carbon electrode was modified with pCu_2O NS-rGO, and the respective electrode displays a well expressed oxidation peak for dopamine (DA) located at 160 mV (vs. SCE). It also gives a strong peak for uric acid (UA) which is separated from the DA peak by 130 mV (vs. SCE). No signals can be detected for ascorbic acid (AA) in concentrations up to 2.0 mM. The findings are exploited in a method for simultaneous determination of UA and DA. The linear ranges are from 1.0 to 138 μM for UA, and from 0.05 to 109 μM for DA even in the presence of relatively high concentrations of AA. The detection limits are 112 nM for UA and 15 nM for DA (at an S/N ratio of 3). (author)

Plasticity of oxide dispersion strengthened ferritic alloys

International Nuclear Information System (INIS)

Zakine, C.; Prioul, C.; Alamo, A.; Francois, D.

1993-01-01

Two 13%Cr oxide dispersion strengthened (ODS) ferritic alloys, DT and DY, exhibiting different oxide particle size distribution and a χ phase precipitation were studied. Their tensile properties have been tested from 20 to 700 C. Experimental observations during room temperature tensile tests performed in a scanning electronic microscope have shown that the main damage mechanism consists in microcracking of the χ phase precipitates on grain boundaries. These alloys are high tensile and creep resistant between 500 and 700 C. Their strongly stress-sensitive creep behaviour can be described by usual creep laws and incorporating a threshold stress below which the creep rate is negligible. (orig.)

On the Precipitation and Precipitation Change in Alaska

Directory of Open Access Journals (Sweden)

Gerd Wendler

2017-12-01

Full Text Available Alaska observes very large differences in precipitation throughout the state; southeast Alaska experiences consistently wet conditions, while northern Arctic Alaska observes very dry conditions. The maximum mean annual precipitation of 5727 mm is observed in the southeastern panhandle at Little Port Arthur, while the minimum of 92 mm occurs on the North Slope at Kuparuk. Besides explaining these large differences due to geographic and orographic location, we discuss the changes in precipitation with time. Analyzing the 18 first-order National Weather Service stations, we found that the total average precipitation in the state increased by 17% over the last 67 years. The observed changes in precipitation are furthermore discussed as a function of the observed temperature increase of 2.1 °C, the mean temperature change of the 18 stations over the same period. This observed warming of Alaska is about three times the magnitude of the mean global warming and allows the air to hold more water vapor. Furthermore, we discuss the effect of the Pacific Decadal Oscillation (PDO, which has a strong influence on both the temperature and precipitation in Alaska.

Zinc-oxide-based sorbents and processes for preparing and using same

Science.gov (United States)

Gangwal, Santosh Kumar; Turk, Brian Scott; Gupta, Raghubir Prasael

2010-03-23

Zinc oxide-based sorbents, and processes for preparing and using them are provided. The sorbents are preferably used to remove one or more reduced sulfur species from gas streams. The sorbents comprise an active zinc component, optionally in combination with one or more promoter components and/or one or more substantially inert components. The active zinc component is a two phase material, consisting essentially of a zinc oxide (ZnO) phase and a zinc aluminate (ZnAl.sub.2O.sub.4) phase. Each of the two phases is characterized by a relatively small crystallite size of typically less than about 500 Angstroms. Preferably the sorbents are prepared by converting a precursor mixture, comprising a precipitated zinc oxide precursor and a precipitated aluminum oxide precursor, to the two-phase, active zinc oxide containing component.

New insight into nanoparticle precipitation by electron beams in borosilicate glasses

Science.gov (United States)

Sabri, M. M.; Möbus, G.

2017-06-01

Nanoprecipitation in different oxide glasses by means of electron irradiation in transmission electron microscopy (TEM) has been compared in this study. Upon irradiation, groups or patterns of nanoparticles with various morphologies and sizes were formed in borosilicate glasses, loaded with zinc, copper, and silver. The study successfully includes loading ranges for the target metal from doping level (1%) over medium level (20%) to majority phase (60%). It is found that particle patterning resolution is affected by parallel processes of amorphous phase separation, glass ablation, and delocalised precipitation. In addition, via an in-situ study, it is confirmed that by heating alone without irradiation, no precipitate nanoparticles form.

New insight into nanoparticle precipitation by electron beams in borosilicate glasses

Energy Technology Data Exchange (ETDEWEB)

Sabri, M.M.; Moebus, G. [University of Sheffield, Department of Materials Science and Engineering (United Kingdom)

2017-06-15

Nanoprecipitation in different oxide glasses by means of electron irradiation in transmission electron microscopy (TEM) has been compared in this study. Upon irradiation, groups or patterns of nanoparticles with various morphologies and sizes were formed in borosilicate glasses, loaded with zinc, copper, and silver. The study successfully includes loading ranges for the target metal from doping level (1%) over medium level (20%) to majority phase (60%). It is found that particle patterning resolution is affected by parallel processes of amorphous phase separation, glass ablation, and delocalised precipitation. In addition, via an in-situ study, it is confirmed that by heating alone without irradiation, no precipitate nanoparticles form. (orig.)

Optimization of precipitation conditions of thorium oxalate precipitate

International Nuclear Information System (INIS)

Pazukhin, Eh.M.; Smirnova, E.A.; Krivokhatskij, A.S.; Pazukhina, Yu.L.; Kiselev, P.P.

1986-01-01

Thorium precipitation in the form of difficultly soluble oxalate has been investigated. The equation binding the concentration of metal with the nitric acid in the initial solution and quantity of a precipitator necessary for minimization of desired product losses is derived. The graphical solution of this equation for a case, when the oxalic acid with 0.78 mol/l concentration is the precipitator, is presented

Electronic properties and morphology of copper oxide/n-type silicon heterostructures

Science.gov (United States)

Lindberg, P. F.; Gorantla, S. M.; Gunnæs, A. E.; Svensson, B. G.; Monakhov, E. V.

2017-08-01

Silicon-based tandem heterojunction solar cells utilizing cuprous oxide (Cu2O) as the top absorber layer show promise for high-efficiency conversion and low production cost. In the present study, single phase Cu2O films have been realized on n-type Si substrates by reactive magnetron sputtering at 400 °C. The obtained Cu2O/Si heterostructures have subsequently been heat treated at temperatures in the 400-700 °C range in Ar flow and extensively characterized by x-ray diffraction (XRD) measurements, transmission electron microscopy (TEM) imaging and electrical techniques. The Cu2O/Si heterojunction exhibits a current rectification of ~5 orders of magnitude between forward and reverse bias voltages. High resolution cross-sectional TEM-images show the presence of a ~2 nm thick interfacial SiO2 layer between Cu2O and the Si substrate. Heat treatments below 550 °C result in gradual improvement of crystallinity, indicated by XRD. At and above 550 °C, partial phase transition to cupric oxide (CuO) occurs followed by a complete transition at 700 °C. No increase or decrease of the SiO2 layer is observed after the heat treatment at 550 °C. Finally, a thin Cu-silicide layer (Cu3Si) emerges below the SiO2 layer upon annealing at 550 °C. This silicide layer influences the lateral current and voltage distributions, as evidenced by an increasing effective area of the heterojunction diodes.

The Observation of TGSCC Nucleation in α-Brass/NH3 System

International Nuclear Information System (INIS)

Kim, Joung Soo

1991-01-01

Transgranular stress corrosion cracking (TGSCC) of α-brass in cuprous ammoniacal solution was investigated to illustrate the nucleation (initiation) mechanism of TGSCC. The cuprous ammoniacal solution used tin this study is at equilibrium with Cu, which means no formation of oxide film on the specimen surface and no general corrosion occurring. TGSCC nucleation was observed to occur by localized preferential anodic corrosion along slip traces formed on the specimen surface during straining in solution. The orientation of crack surfaces formed by the nucleation and the propagation of TGSCC were different from each other: the former is {111} and the latter {110}. This represents that both events do not occur by the same mechanism. The observation of TGSCC nucleation in this investigation also shows that the thin film technique using TEM is not appropriate for a study on the propagation mechanism of TGSCC

LITERATURE REVIEW FOR OXALATE OXIDATION PROCESSES AND PLUTONIUM OXALATE SOLUBILITY

Energy Technology Data Exchange (ETDEWEB)

Nash, C.

2012-02-03

A literature review of oxalate oxidation processes finds that manganese(II)-catalyzed nitric acid oxidation of oxalate in precipitate filtrate is a viable and well-documented process. The process has been operated on the large scale at Savannah River in the past, including oxidation of 20 tons of oxalic acid in F-Canyon. Research data under a variety of conditions show the process to be robust. This process is recommended for oxalate destruction in H-Canyon in the upcoming program to produce feed for the MOX facility. Prevention of plutonium oxalate precipitation in filtrate can be achieved by concentrated nitric acid/ferric nitrate sequestration of oxalate. Organic complexants do not appear practical to sequester plutonium. Testing is proposed to confirm the literature and calculation findings of this review at projected operating conditions for the upcoming campaign. H Canyon plans to commence conversion of plutonium metal to low-fired plutonium oxide in 2012 for eventual use in the Mixed Oxide Fuel (MOX) Facility. The flowsheet includes sequential operations of metal dissolution, ion exchange, elution, oxalate precipitation, filtration, and calcination. All processes beyond dissolution will occur in HB-Line. The filtration step produces an aqueous filtrate that may have as much as 4 M nitric acid and 0.15 M oxalate. The oxalate needs to be removed from the stream to prevent possible downstream precipitation of residual plutonium when the solution is processed in H Canyon. In addition, sending the oxalate to the waste tank farm is undesirable. This report addresses the processing options for destroying the oxalate in existing H Canyon equipment.

Characterization and comparison of iron oxyhydroxide precipitates from biotic and abiotic groundwater treatments

DEFF Research Database (Denmark)

Arturi, Katarzyna R.; Bender Koch, Christian; Søgaard, Erik G.

2017-01-01

Removal of iron is an important step in groundwater treatment for drinking water production. It is performed to prevent organoleptic issues and clogging in water supply systems. Iron can be eliminated with a purely physico-chemical (abiotic) method or biotically with the help of iron......-oxidizing bacteria (FeOB). Each of the purification methods requires different operating conditions and results in formation of iron oxyhydroxide (FeOOH) precipitates. Knowledge about the differences in composition and properties of the biotic and abiotic precipitates is desirable from a technical, but also...

Ammonia release method for depositing metal oxides

Energy Technology Data Exchange (ETDEWEB)

Silver, G.L.; Martin, F.S.

1993-12-31

A method of depositing metal oxides on substrates which is indifferent to the electrochemical properties of the substrates and which comprises forming ammine complexes containing metal ions and thereafter effecting removal of ammonia from the ammine complexes so as to permit slow precipitation and deposition of metal oxide on the substrates.

Optimisation of parameters for co-precipitation of uranium and plutonium - results of simulation studies

International Nuclear Information System (INIS)

Pandey, N.K.; Velvandan, P.V.; Murugesan, S.; Ahmed, M.K.; Koganti, S.B.

1999-01-01

Preparation of plutonium oxide from plutonium nitrate solution generally proceeds via oxalate precipitation route. In a nuclear fuel reprocessing scheme this step succeeds the partitioning step (separation of uranium and plutonium). Results of present studies confirm that it is possible to avoid partitioning step and recover plutonium and uranium as co-precipitated product. This also helps in minimising the risk of proliferation of fissile material. In this procedure, the solubility of uranium oxalate in nitric acid is effectively used. Co-precipitation parameters are optimised with simulated solutions of uranium nitrate and thorium nitrate (in place of plutonium). On the basis of obtained results a reconversion flow-sheet is designed and reported here. (author)

Synthesis of Monodisperse Iron Oxide Nanoparticles without Surfactants

Directory of Open Access Journals (Sweden)

Xiao-Chen Yang

2014-01-01

Full Text Available Monodisperse iron oxide nanoparticles could be successfully synthesized with two kinds of precipitants through a precipitation method. As-prepared nanoparticles in the size around 10 nm with regular spherical-like shape were achieved by adjusting pH values. NaOH and NH3·H2O were used as two precipitants for comparison. The average size of nanoparticles with NH3·H2O precipitant got smaller and represented better dispersibility, while nanoparticles with NaOH precipitant represented better magnetic property. This work provided a simple method without using any organic solvents, organic metal salts, or surfactants which could easily obtain monodisperse nanoparticles with tunable morphology.

Oxidación de Cu2O a CuO en Aire a Altas Temperaturas Oxidación de óxico cuproso a óxido cúprico en Aire a Altas Temperaturas

Directory of Open Access Journals (Sweden)

Torstein A. Utigard

2012-02-01

Full Text Available

Small Cu2O cylinders were oxidized in a TGA apparatus in air from 850 to 1000 ºC. The activation energy for the oxidation kinetics of the cuprous oxide in the temperature range mentioned above was alsoestimated. Cuprous oxide oxidizes according to the cubic law; such kinetic law is explained in terms of the defect concentration within the Cu2O crystal structure.

Chlorination of bromide-containing waters: enhanced bromate formation in the presence of synthetic metal oxides and deposits formed in drinking water distribution systems.

Science.gov (United States)

Liu, Chao; von Gunten, Urs; Croué, Jean-Philippe

2013-09-15

Bromate formation from the reaction between chlorine and bromide in homogeneous solution is a slow process. The present study investigated metal oxides enhanced bromate formation during chlorination of bromide-containing waters. Selected metal oxides enhanced the decay of hypobromous acid (HOBr), a requisite intermediate during the oxidation of bromide to bromate, via (i) disproportionation to bromate in the presence of nickel oxide (NiO) and cupric oxide (CuO), (ii) oxidation of a metal to a higher valence state in the presence of cuprous oxide (Cu2O) and (iii) oxygen formation by NiO and CuO. Goethite (α-FeOOH) did not enhance either of these pathways. Non-charged species of metal oxides seem to be responsible for the catalytic disproportionation which shows its highest rate in the pH range near the pKa of HOBr. Due to the ability to catalyze HOBr disproportionation, bromate was formed during chlorination of bromide-containing waters in the presence of CuO and NiO, whereas no bromate was detected in the presence of Cu2O and α-FeOOH for analogous conditions. The inhibition ability of coexisting anions on bromate formation at pH 8.6 follows the sequence of phosphate > sulfate > bicarbonate/carbonate. A black deposit in a water pipe harvested from a drinking water distribution system exerted significant residual oxidant decay and bromate formation during chlorination of bromide-containing waters. Energy dispersive spectroscopy (EDS) analyses showed that the black deposit contained copper (14%, atomic percentage) and nickel (1.8%, atomic percentage). Cupric oxide was further confirmed by X-ray diffraction (XRD). These results indicate that bromate formation may be of concern during chlorination of bromide-containing waters in distribution systems containing CuO and/or NiO. Copyright © 2013 Elsevier Ltd. All rights reserved.

Process for recovery of plutonium from fabrication residues of mixed fuels consisting of uranium oxide and plutonium oxide

International Nuclear Information System (INIS)

Heremanns, R.H.; Vandersteene, J.J.

1983-01-01

The invention concerns a process for recovery of plutonium from fabrication residues of mixed fuels consisting of uranium oxide and plutonium oxide in the form of PuO 2 . Mixed fuels consisting of uranium oxide and plutonium oxide are being used more and more. The plants which prepare these mixed fuels have around 5% of the total mass of fuels as fabrication residue, either as waste or scrap. In view of the high cost of plutonium, it has been attempted to recover this plutonium from the fabrication residues by a process having a purchase price lower than the price of plutonium. The problem is essentially to separate the plutonium, the uranium and the impurities. The residues are fluorinated, the UF 6 and PuF 6 obtained are separated by selective absorption of the PuF 6 on NaF at a temperature of at least 400 0 C, the complex obtained by this absorption is dissolved in nitric acid solution, the plutonium is precipitated in the form of plutonium oxalate by adding oxalic acid, and the precipitated plutonium oxalate is calcined

Bacteria attenuation by iron electrocoagulation governed by interactions between bacterial phosphate groups and Fe(III) precipitates.

Science.gov (United States)

Delaire, Caroline; van Genuchten, Case M; Amrose, Susan E; Gadgil, Ashok J

2016-10-15

Iron electrocoagulation (Fe-EC) is a low-cost process in which Fe(II) generated from an Fe(0) anode reacts with dissolved O2 to form (1) Fe(III) precipitates with an affinity for bacterial cell walls and (2) bactericidal reactive oxidants. Previous work suggests that Fe-EC is a promising treatment option for groundwater containing arsenic and bacterial contamination. However, the mechanisms of bacteria attenuation and the impact of major groundwater ions are not well understood. In this work, using the model indicator Escherichia coli (E. coli), we show that physical removal via enmeshment in EC precipitate flocs is the primary process of bacteria attenuation in the presence of HCO3(-), which significantly inhibits inactivation, possibly due to a reduction in the lifetime of reactive oxidants. We demonstrate that the adhesion of EC precipitates to cell walls, which results in bacteria encapsulation in flocs, is driven primarily by interactions between EC precipitates and phosphate functional groups on bacteria surfaces. In single solute electrolytes, both P (0.4 mM) and Ca/Mg (1-13 mM) inhibited the adhesion of EC precipitates to bacterial cell walls, whereas Si (0.4 mM) and ionic strength (2-200 mM) did not impact E. coli attenuation. Interestingly, P (0.4 mM) did not affect E. coli attenuation in electrolytes containing Ca/Mg, consistent with bivalent cation bridging between bacterial phosphate groups and inorganic P sorbed to EC precipitates. Finally, we found that EC precipitate adhesion is largely independent of cell wall composition, consistent with comparable densities of phosphate functional groups on Gram-positive and Gram-negative cells. Our results are critical to predict the performance of Fe-EC to eliminate bacterial contaminants from waters with diverse chemical compositions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Strengthening of metallic alloys with nanometer-size oxide dispersions

Science.gov (United States)

Flinn, John E.; Kelly, Thomas F.

1999-01-01

Austenitic stainless steels and nickel-base alloys containing, by wt. %, 0.1 to 3.0% V, 0.01 to 0.08% C, 0.01 to 0.5% N, 0.05% max. each of Al and Ti, and 0.005 to 0.10% O, are strengthened and ductility retained by atomization of a metal melt under cover of an inert gas with added oxygen to form approximately 8 nanometer-size hollow oxides within the alloy grains and, when the alloy is aged, strengthened by precipitation of carbides and nitrides nucleated by the hollow oxides. Added strengthening is achieved by nitrogen solid solution strengthening and by the effect of solid oxides precipitated along and pinning grain boundaries to provide temperature-stabilization and refinement of the alloy grains.

Strengthening of metallic alloys with nanometer-size oxide dispersions

Science.gov (United States)

Flinn, J.E.; Kelly, T.F.

1999-06-01

Austenitic stainless steels and nickel-base alloys containing, by wt. %, 0.1 to 3.0% V, 0.01 to 0.08% C, 0.01 to 0.5% N, 0.05% max. each of Al and Ti, and 0.005 to 0.10% O, are strengthened and ductility retained by atomization of a metal melt under cover of an inert gas with added oxygen to form approximately 8 nanometer-size hollow oxides within the alloy grains and, when the alloy is aged, strengthened by precipitation of carbides and nitrides nucleated by the hollow oxides. Added strengthening is achieved by nitrogen solid solution strengthening and by the effect of solid oxides precipitated along and pinning grain boundaries to provide temperature-stabilization and refinement of the alloy grains. 20 figs.

Biotechnological aspects of anaerobic oxidation of methane coupled to sulfate reduction

NARCIS (Netherlands)

Meulepas, R.J.W.

2009-01-01

Sulfate reduction (SR) can be used for the removal and recovery of metals and oxidized sulfur compounds from waste streams. Sulfate-reducing bacteria reduce oxidized sulfur compounds to sulfide. Subsequently, sulfide can precipitate dissolved metals or can be oxidized to elemental sulfur. Both metal

TEM study of internal oxidation in an ODS-Eurofer alloy

International Nuclear Information System (INIS)

Klimenkov, M.; Lindau, R.; Moeslang, A.

2009-01-01

Analytical TEM investigations of samples from an oxide dispersion-strengthened Eurofer batch show the formation of new type of precipitates of Fe-Cr-V-O composition and a size of 40-250 nm. Structural HRTEM analysis reveals that the precipitates consist of (Mn,Fe)(Cr,V) 2 O 4 manganese chromium oxide of spinel structure. In some cases, the inclusions order along lines that can reach more than ten micrometers in length. Such lines of large particles might have a negative influence on the mechanical properties of the steel, as was observed. It is assumed that they form by internal oxidation during hot isostatic pressing due to the high oxygen content of the mechanically alloyed powder.

Precipitation of ammonium from concentrated industrial wastes as struvite: a search for the optimal reagents.

Science.gov (United States)

Borojovich, Eitan J C; Münster, Meshulam; Rafailov, Gennady; Porat, Ze'ev

2010-07-01

Precipitation of struvite (MgNH4PO4) is a known process for purification of wastewater from high concentrations of ammonium. The optimal conditions for precipitation are basic pH (around 9) and sufficient concentrations of magnesium and phosphate ions. In this work, we accomplished efficient precipitation of ammonium from concentrated industrial waste stream by using magnesium oxide (MgO) both as a source of magnesium ions and as a base. Best results were obtained with technical-grade MgO, which provided 99% removal of ammonium. Moreover, ammonium removal occurred already at pH 7, and the residual ammonium concentration (50 mg/L) remained constant upon addition of more MgO without rising again, as occurs with sodium hydroxide (NaOH). This process may have two other advantages; it also can be relevant for the problem of uncontrolled precipitation of struvite in the supernatant of anaerobic sludge treatment plants, and the precipitate can be used as a fertilizer.

Development of hierarchically porous cobalt oxide for enhanced photo-oxidation of indoor pollutants

Energy Technology Data Exchange (ETDEWEB)

Cheng, J. P., E-mail: chengjp@zju.edu.cn [Zhejiang University, State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering (China); Shereef, Anas; Gray, Kimberly A., E-mail: k-gray@northwestern.edu [Northwestern University, Center for Catalysis and Surface Science (United States); Wu, Jinsong [Northwestern University, Department of Materials Science and Engineering (United States)

2015-03-15

Porous cobalt oxide was successfully prepared by precipitation of cobalt hydroxide followed by low temperature thermal decomposition. The morphologies of the resultant oxides remained as the corresponding hydroxides, although the morphology of cobalt hydroxides was greatly influenced by the precursor salts. The cobalt oxides with average crystal size less than 20 nm were characterized by X-ray diffraction, scanning electron microscope, BET surface area, and XPS analysis. The photocatalytic activities of the various cobalt oxides morphologies were investigated by comparing the photo-degradation of acetaldehyde under simulated solar illumination. Relative to their low order structures and reference titania samples, the hierarchical nanostructures of cobalt oxide showed excellent abilities to rapidly degrade acetaldehyde, a model air pollutant. This was attributed to the unique nature of these hierarchical cobalt oxide nanoassemblies, which contained many catalytically active reaction sites and open pores.

Calcium phosphate bioceramics prepared from wet chemically precipitated powders

Directory of Open Access Journals (Sweden)

Kristine Salma

2010-03-01

Full Text Available In this work calcium phosphates were synthesized by modified wet chemical precipitation route. Contrary to the conventional chemical precipitation route calcium hydroxide was homogenized with planetary mill. Milling calcium oxide and water in planetary ball mill as a first step of synthesis provides a highly dispersed calcium hydroxide suspension. The aim of this work was to study the influence of main processing parameters of wet chemical precipitation synthesis product and to control the morphology, phase and functional group composition and, consequently, thermal stability and microstructure of calcium phosphate bioceramics after thermal treatment. The results showed that it is possible to obtain calcium phosphates with different and reproducible phase compositions after thermal processing (hydroxyapatite [HAp], β-tricalcium phosphate [β-TCP] and HAp/β-TCP by modified wet-chemical precipitation route. The β-TCP phase content in sintered bioceramics samples is found to be highly dependent on the changes in technological parameters and it can be controlled with ending pH, synthesis temperature and thermal treatment. Pure, crystalline and highly thermally stable (up to 1300°C HAp bioceramics with homogenous grainy microstructure, grain size up to 200–250 nm and high open porosity can be successfully obtained by powder synthesized at elevated synthesis temperature of 70°C and stabilizing ending pH at 9.

Experimental study of the oxide film structural phase state in the E635 and E110 alloys

International Nuclear Information System (INIS)

Shevyakov, A. Yu.; Shishov, V. N.; Novikov, V. V.

2013-01-01

The microstructure, phase and element compositions of oxide films of E110 (Zr-1%Nb) and E635 (Zr-1%Nb-0,35%Fe-1,2%Sn) alloys after autoclave tests in pure water had been studied by the method of transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDS). TEM investigations of oxide film structure were carried on different oxide layers according to their thickness (near interface of “metal-oxide”, in central part of the oxide film and near outer surface) and in cross-section. The results of the tests show that oxide films of the alloys have different microstructure (grain size, fraction of tetragonal phase, content of defects, etc) and the phase compositions. The crystal structure of oxide films is mainly monoclinic, however, at the “metal-oxide” interface there are a significant fraction of the tetragonal phase. Researching of oxides on different stages of oxidation allow us to determine the kinetics of the second phase precipitate structure change: a) in E635 alloy at early oxidation stages of the amorphization process of the Laves phase precipitates begins with decreasing the content of iron and niobium; b) in E110 alloy the amorphization process of β-Nb precipitates begins at a later stage of oxidation. The influence of changes of the crystal structure and the chemical composition of the second phase precipitates on protective properties of the oxides had been determined. Researching of alloying element redistribution in E635 alloy oxide film shows that iron and niobium are concentrated in pores. Increased porosity of the E635 alloy oxide films at a later oxidation stage, in comparison with the E110 alloy, shows the influence of change composition and subsequent dissolution of the Laves phase particles on the pore formation in the oxide. (authors)

Improved daily precipitation nitrate and ammonium concentration models for the Chesapeake Bay Watershed

International Nuclear Information System (INIS)

Grimm, J.W.; Lynch, J.A.

2005-01-01

Daily precipitation nitrate and ammonium concentration models were developed for the Chesapeake Bay Watershed (USA) using a linear least-squares regression approach and precipitation chemistry data from 29 National Atmospheric Deposition Program/National Trends Network (NADP/NTN) sites. Only weekly samples that comprised a single precipitation event were used in model development. The most significant variables in both ammonium and nitrate models included: precipitation volume, the number of days since the last event, a measure of seasonality, latitude, and the proportion of land within 8 km covered by forest or devoted to industry and transportation. Additional variables included in the nitrate model were the proportion of land within 0.8 km covered by water and/or forest. Local and regional ammonia and nitrogen oxide emissions were not as well correlated as land cover. Modeled concentrations compared very well with event chemistry data collected at six NADP/AirMoN sites within the Chesapeake Bay Watershed. Wet deposition estimates were also consistent with observed deposition at selected sites. Accurately describing the spatial distribution of precipitation volume throughout the watershed is important in providing critical estimates of wet-fall deposition of ammonium and nitrate. - A linear least-squares regression approach was used to develop daily precipitation nitrate and ammonium concentration models for the Chesapeake Bay Watershed

Preventing Precipitation in the ISS Urine Processor

Science.gov (United States)

Muirhead, Dean; Carter, Layne; Williamson, Jill; Chambers, Antja

2017-01-01

The ISS Urine Processor Assembly (UPA) was initially designed to achieve 85% recovery of water from pretreated urine on ISS. Pretreated urine is comprised of crew urine treated with flush water, an oxidant (chromium trioxide), and an inorganic acid (sulfuric acid) to control microbial growth and inhibit precipitation. Unfortunately, initial operation of the UPA on ISS resulted in the precipitation of calcium sulfate at 85% recovery. This occurred because the calcium concentration in the crew urine was elevated in microgravity due to bone loss. The higher calcium concentration precipitated with sulfate from the pretreatment acid, resulting in a failure of the UPA due to the accumulation of solids in the Distillation Assembly. Since this failure, the UPA has been limited to a reduced recovery of water from urine to prevent calcium sulfate from reaching the solubility limit. NASA personnel have worked to identify a solution that would allow the UPA to return to a nominal recovery rate of 85%. This effort has culminated with the development of a pretreatment based on phosphoric acid instead of sulfuric acid. By eliminating the sulfate associated with the pretreatment, the brine can be concentrated to a much higher concentration before calcium sulfate reach the solubility limit. This paper summarizes the development of this pretreatment and the testing performed to verify its implementation on ISS.

The influence of surfactant on the synthesis of gamma ferric oxide: implications on phase composition and magnetic properties

International Nuclear Information System (INIS)

Narasimhan, B.R.V.; Prabhakar, S.; Manohar, P.; Gnanam, F.D.

2002-01-01

It has already been established that ferrous carbonate precipitated from the reaction of ferrous sulphate and sodium carbonate, on direct thermal decomposition yields gamma ferric oxide. The present work describes the effect of sodium lauryl sulphate (Sodium dodecyl sulphate) on the synthesis of gamma ferric oxide when it is introduced during the precipitation of ferrous carbonate. Since ferrous carbonate undergoes rapid oxidation on standing in air, the extent of oxidation in presence of sodium lauryl sulphate is also studied using oxidation-reduction potential measurements. The ferric oxide powders are characterized for phase analysis (XRD), magnetic properties (VSM) and particle size analysis. (author)

Recovery of yttrium from fluorescent powder of cathode ray tube, CRT: Zn removal by sulphide precipitation

International Nuclear Information System (INIS)

Innocenzi, Valentina; De Michelis, Ida; Ferella, Francesco; Beolchini, Francesca; Kopacek, Bernd; Vegliò, Francesco

2013-01-01

Highlights: • Treatment of fluorescent powder of CRT waste. • Factorial experimental designs to study acid leaching of fluorescent powder and the purification of leach liquors. • Recover of yttrium by precipitation using oxalic acid. • Suitable flowsheet to recover yttrium from fluorescent powder. - Abstract: This work is focused on the recovery of yttrium and zinc from fluorescent powder of cathode ray tube (CRT). Metals are extracted by sulphuric acid in the presence of hydrogen peroxide. Leaching tests are carried out according to a 2 2 full factorial plan and the highest extraction yields for yttrium and zinc equal to 100% are observed under the following conditions: 3 M of sulphuric acid, 10% v/v of H 2 O 2 concentrated solution at 30% v/v, 10% w/w pulp density, 70 °C and 3 h of reaction. Two series of precipitation tests for zinc are carried out: a 2 2 full factorial design and a completely randomized factorial design. In these series the factors investigated are pH of solution during the precipitation and the amount of sodium sulphide added to precipitate zinc sulphide. The data of these tests are used to describe two empirical mathematical models for zinc and yttrium precipitation yields by regression analysis. The highest precipitation yields for zinc are obtained under the following conditions: pH equal to 2–2.5% and 10–12% v/v of Na 2 S concentrated solution at 10% w/v. In these conditions the coprecipitation of yttrium is of 15–20%. Finally further yttrium precipitation experiments by oxalic acid on the residual solutions, after removing of zinc, show that yttrium could be recovered and calcined to obtain the final product as yttrium oxide. The achieved results allow to propose a CRT recycling process based on leaching of fluorescent powder from cathode ray tube and recovery of yttrium oxide after removing of zinc by precipitation. The final recovery of yttrium is 75–80%

Recovery of yttrium from fluorescent powder of cathode ray tube, CRT: Zn removal by sulphide precipitation

Energy Technology Data Exchange (ETDEWEB)

Innocenzi, Valentina, E-mail: valentina.innocenzi1@univaq.it [Department of Industrial Engineering and Information and Economy, University of L’Aquila, Via Giovanni Gronchi n.18, Nucleo Ind.le di Pile, 67100 L’Aquila (Italy); De Michelis, Ida; Ferella, Francesco [Department of Industrial Engineering and Information and Economy, University of L’Aquila, Via Giovanni Gronchi n.18, Nucleo Ind.le di Pile, 67100 L’Aquila (Italy); Beolchini, Francesca [Department of Marine Sciences, Polytechnic Institute of Marche, Via Brecce Bianche, 60131 Ancona (Italy); Kopacek, Bernd [SAT, Austrian Society for Systems Engineering and Automation, Gurkasse 43/2, A-1140 Vienna (Austria); Vegliò, Francesco [Department of Industrial Engineering and Information and Economy, University of L’Aquila, Via Giovanni Gronchi n.18, Nucleo Ind.le di Pile, 67100 L’Aquila (Italy)

2013-11-15

Highlights: • Treatment of fluorescent powder of CRT waste. • Factorial experimental designs to study acid leaching of fluorescent powder and the purification of leach liquors. • Recover of yttrium by precipitation using oxalic acid. • Suitable flowsheet to recover yttrium from fluorescent powder. - Abstract: This work is focused on the recovery of yttrium and zinc from fluorescent powder of cathode ray tube (CRT). Metals are extracted by sulphuric acid in the presence of hydrogen peroxide. Leaching tests are carried out according to a 2{sup 2} full factorial plan and the highest extraction yields for yttrium and zinc equal to 100% are observed under the following conditions: 3 M of sulphuric acid, 10% v/v of H{sub 2}O{sub 2} concentrated solution at 30% v/v, 10% w/w pulp density, 70 °C and 3 h of reaction. Two series of precipitation tests for zinc are carried out: a 2{sup 2} full factorial design and a completely randomized factorial design. In these series the factors investigated are pH of solution during the precipitation and the amount of sodium sulphide added to precipitate zinc sulphide. The data of these tests are used to describe two empirical mathematical models for zinc and yttrium precipitation yields by regression analysis. The highest precipitation yields for zinc are obtained under the following conditions: pH equal to 2–2.5% and 10–12% v/v of Na{sub 2}S concentrated solution at 10% w/v. In these conditions the coprecipitation of yttrium is of 15–20%. Finally further yttrium precipitation experiments by oxalic acid on the residual solutions, after removing of zinc, show that yttrium could be recovered and calcined to obtain the final product as yttrium oxide. The achieved results allow to propose a CRT recycling process based on leaching of fluorescent powder from cathode ray tube and recovery of yttrium oxide after removing of zinc by precipitation. The final recovery of yttrium is 75–80%.

Analysis of ADU structure obtained under different precipitation conditions

International Nuclear Information System (INIS)

Ramella, Jose L.; Esteban, Adolfo; Mendez De Leo, Lucia P.; Sassone, Ariel; Novara, Oscar E.; Boero, Norma L.; Leyva, Ana G.

1999-01-01

ADU is the nominal name for ammonium poly uranate. It is a very complex compound of polymeric structure, which may have, according to precipitation conditions, different chemical composition and crystallographic structure. ADU is used as uranium oxide precursor in the manufacture of fuel elements. In former papers it was proved that if ultrasound is applied during precipitation and digestion the characteristics of the final product (U 3 O 8 UO 2 ) improve. By studying ADU thermal decomposition obtained by ultrasonic application, it was intended to obtain its composition. Therefore, differential thermal gravimetric and differential thermal analyses were performed. Samples were taken from special points and analyzed by X-ray diffraction, infra-red spectroscopy and scanning. An experiment was also designed to identify the products released during heating. Results and conclusions obtained are presented in this work. (author)

PROCESS USING POTASSIUM LANTHANUM SULFATE FOR FORMING A CARRIER PRECIPITATE FOR PLUTONIUM VALUES

Science.gov (United States)

Angerman, A.A.

1958-10-21

A process is presented for recovering plutonium values in an oxidation state not greater than +4 from fluoride-soluble fission products. The process consists of adding to an aqueous acidic solution of such plutonium values a crystalline potassium lanthanum sulfate precipitate which carries the plutonium values from the solution.

Improved daily precipitation nitrate and ammonium concentration models for the Chesapeake Bay Watershed.

Science.gov (United States)

Grimm, J W; Lynch, J A

2005-06-01

Daily precipitation nitrate and ammonium concentration models were developed for the Chesapeake Bay Watershed (USA) using a linear least-squares regression approach and precipitation chemistry data from 29 National Atmospheric Deposition Program/National Trends Network (NADP/NTN) sites. Only weekly samples that comprised a single precipitation event were used in model development. The most significant variables in both ammonium and nitrate models included: precipitation volume, the number of days since the last event, a measure of seasonality, latitude, and the proportion of land within 8km covered by forest or devoted to industry and transportation. Additional variables included in the nitrate model were the proportion of land within 0.8km covered by water and/or forest. Local and regional ammonia and nitrogen oxide emissions were not as well correlated as land cover. Modeled concentrations compared very well with event chemistry data collected at six NADP/AirMoN sites within the Chesapeake Bay Watershed. Wet deposition estimates were also consistent with observed deposition at selected sites. Accurately describing the spatial distribution of precipitation volume throughout the watershed is important in providing critical estimates of wet-fall deposition of ammonium and nitrate.

Properties of Extreme Precipitation and Their Uncertainties in 3-year GPM Precipitation Radar Data

Science.gov (United States)

Liu, N.; Liu, C.

2017-12-01

Extreme high precipitation rates are often related to flash floods and have devastating impacts on human society and the environments. To better understand these rare events, 3-year Precipitation Features (PFs) are defined by grouping the contiguous areas with nonzero near-surface precipitation derived using Global Precipitation Measurement (GPM) Ku band Precipitation Radar (KuPR). The properties of PFs with extreme precipitation rates greater than 20, 50, 100 mm/hr, such as the geographical distribution, volumetric precipitation contribution, seasonal and diurnal variations, are examined. In addition to the large seasonal and regional variations, the rare extreme precipitation rates often have a larger contribution to the local total precipitation. Extreme precipitation rates occur more often over land than over ocean. The challenges in the retrieval of extreme precipitation might be from the attenuation correction and large uncertainties in the Z-R relationships from near-surface radar reflectivity to precipitation rates. These potential uncertainties are examined by using collocated ground based radar reflectivity and precipitation retrievals.

Simulations of monthly mean nitrate concentrations in precipitation over East Asia

International Nuclear Information System (INIS)

Junling An; Xinjin Cheng; Ueda, Hiromasa; Kajino, Mizuo

2002-01-01

Monthly mean nitrate concentrations in precipitation over East Asia (10-55 o N, 75-155 o E) in April, July, September, and December of 1999 were simulated by using a regional air quality Eulerian model (RAQM) with meteorological fields four times per day taken from National Centers for Environmental Prediction. The distribution of the nitrate concentration in precipitation depends significantly on the emission patterns of nitrogen oxides (NO x =NO+NO 2 ) and volatile organic compound (VOC) and seasonal precipitation variability. The downward trend is also revealed, particularly on July and December. Highest concentrations are found in the industrialized regions, i.e., the coastal area of the Mainland of China, the Bay of the Huanghai Sea and the Bohai Sea, Korea, and Southern Japan. Long-range transport may cause elevated concentrations in remote areas downwind of the industrialized regions under favorable meteorological conditions, e.g., low precipitation. Comparison of observation and simulations indicates that the RAQM model reasonably predicts synoptic-scale changes in different months (seasons) and simulated nitrate levels in 4 months fit observed data with the discrepancy within a factor of 2. Exclusion of liquid chemistry within clouds is feasible for regional (1 o x1 o ) and long-term (monthly) nitrate simulations. The uncertainty originates mainly from that of the emission data and modeled precipitation amounts and initial and boundary conditions. (author)

Precipitation kinetics of a continuous precipitator, with application to the precipitation of ammonium polyuranate

International Nuclear Information System (INIS)

Hoyt, R.C.

1978-04-01

A mathematical model describing the kinetics of continuous precipitation was developed which accounts for crystal nucleation, crystal growth, primary coagulation, and secondary coagulation. Population density distributions, average particle sizes, dominant particle sizes, and suspension density fractions of the crystallites, primary agglomerates, and secondary agglomerates leaving the continuous precipitator can be determined. This kinetic model was applied to the continuous precipitation of ammonium polyuranate, which consists of: (1) elementary crystals, (2) clusters or primary coagulated particles, and (3) agglomerates or secondary coagulated particles. The crystallites are thin, submicron, hexagonal platelets. The clusters had an upper size limit of about 7 μ in diameter and contained numerous small voids (less than 0.3 μm) due to the packing of the crystallites. The agglomerates had an upper size limit of about 40 μm in diameter and contained large voids (approximately 1 μm). The particle size distribution and particle structure of the ammonium polyuranate precipitate can be controlled through proper regulation of the precipitation conditions. The ratio of clusters to agglomerates can be best controlled through the uranium concentration, and the cohesiveness or internal bonding strength of the particles can be controlled with the ammonium to uranium reacting feed mole ratio. These two conditions, in conjunction with the residence time, will determine the nucleation rates, growth rates, and size distributions of the particles leaving the continuous precipitator. With proper control of these physical particle characteristics, the use of pore formers, ball-milling, and powder blending can probably be eliminated from the nuclear fuel fabrication process, substantially reducing the cost

Precipitation kinetics of a continuous precipitator, with application to the precipitation of ammonium polyuranate

Energy Technology Data Exchange (ETDEWEB)

Hoyt, R.C.

1978-04-01

A mathematical model describing the kinetics of continuous precipitation was developed which accounts for crystal nucleation, crystal growth, primary coagulation, and secondary coagulation. Population density distributions, average particle sizes, dominant particle sizes, and suspension density fractions of the crystallites, primary agglomerates, and secondary agglomerates leaving the continuous precipitator can be determined. This kinetic model was applied to the continuous precipitation of ammonium polyuranate, which consists of: (1) elementary crystals, (2) clusters or primary coagulated particles, and (3) agglomerates or secondary coagulated particles. The crystallites are thin, submicron, hexagonal platelets. The clusters had an upper size limit of about 7 ..mu.. in diameter and contained numerous small voids (less than 0.3 ..mu..m) due to the packing of the crystallites. The agglomerates had an upper size limit of about 40 ..mu..m in diameter and contained large voids (approximately 1 ..mu..m). The particle size distribution and particle structure of the ammonium polyuranate precipitate can be controlled through proper regulation of the precipitation conditions. The ratio of clusters to agglomerates can be best controlled through the uranium concentration, and the cohesiveness or internal bonding strength of the particles can be controlled with the ammonium to uranium reacting feed mole ratio. These two conditions, in conjunction with the residence time, will determine the nucleation rates, growth rates, and size distributions of the particles leaving the continuous precipitator. With proper control of these physical particle characteristics, the use of pore formers, ball-milling, and powder blending can probably be eliminated from the nuclear fuel fabrication process, substantially reducing the cost.

Constraints on superoxide mediated formation of manganese oxides

Directory of Open Access Journals (Sweden)

Deric R. Learman

2013-09-01

Full Text Available Manganese (Mn oxides are among the most reactive sorbents and oxidants within the environment, where they play a central role in the cycling of nutrients, metals, and carbon. Recent discoveries have identified superoxide (O2- (both of biogenic and abiogenic origin as an effective oxidant of Mn(II leading to the formation of Mn oxides. Here we examined the conditions under which abiotically produced superoxide led to oxidative precipitation of Mn and the solid-phases produced. Oxidized Mn, as both aqueous Mn(III and Mn(III/IV oxides, was only observed in the presence of active catalase, indicating that hydrogen peroxide, a product of the reaction of O2- with Mn(II, inhibits the oxidation process presumably through the reduction of Mn(III. Citrate and pyrophosphate increased the yield of oxidized Mn but decreased the amount of Mn oxide produced via formation of Mn(III-ligand complexes. While complexing ligands played a role in stabilizing Mn(III, they did not eliminate the inhibition of net Mn(III formation by H2O2. The Mn oxides precipitated were highly disordered colloidal hexagonal birnessite, similar to those produced by biotically generated superoxide. Yet, in contrast to the large particulate Mn oxides formed by biogenic superoxide, abiotic Mn oxides did not ripen to larger, more crystalline phases. This suggests that the deposition of crystalline Mn oxides within the environment requires a biological, or at least organic, influence. This work provides the first direct evidence that, under conditions relevant to natural waters, oxidation of Mn(II by superoxide can occur and lead to formation of Mn oxides. For organisms that oxidize Mn(II by producing superoxide, these findings may also point to other microbially mediated processes, in particular enzymatic hydrogen peroxide degradation and/or production of organic ligand metabolites, that allow for Mn oxide formation.

Poly(ethylene oxide) functionalization

Science.gov (United States)

Pratt, Russell Clayton

2014-04-08

A simple procedure is provided by which the hydroxyl termini of poly(ethylene oxide) can be appended with functional groups to a useful extent by reaction and precipitation. The polymer is dissolved in warmed toluene, treated with an excess of organic base and somewhat less of an excess of a reactive acylating reagent, reacted for several hours, then precipitated in isopropanol so that the product can be isolated as a solid, and salt byproducts are washed away. This procedure enables functionalization of the polymer while not requiring laborious purification steps such as solvent-solvent extraction or dialysis to remove undesirable side products.

Pinning performance of (Nd,Eu,Gd)-123 superconductors: Comparison of melt-textured pellet and single crystal

Czech Academy of Sciences Publication Activity Database

Jirsa, Miloš; Rameš, Michal; Jurek, Karel; Muralidhar, M.; Das, P.; Koblischka, M.R.; Wolf, T.

2008-01-01

Roč. 151, č. 1 (2008), s. 25-30 ISSN 0921-5107 R&D Projects: GA ČR GA202/05/0173; GA MŠk 1P05ME728 Institutional research plan: CEZ:AV0Z10100520 Keywords : high-temperature superconductors * cuprous oxides * superconductivity perovskites, * (Nd,Eu,Gd)BaCuO * ternary compounds * melt-textured materials Subject RIV: BM - Solid Matter Physics ; Magnetism

Asymmetric synthesis of a functionalized tricyclo[6.2.0.0 ]decane ring ...

Indian Academy of Sciences (India)

reaction mixture was again brought to −78. ◦. C and to ... cuprous triflate (10 mg) was added to the reaction mix- ture. .... propionic acid (0.2 mL) and xylene (5 mL) was heated in a sealed tube at ..... ous HCl was extracted with diethyl ether (2×3 mL). Removal of .... nesium bromide and DMP oxidation of the resulting carbinol.

Facile synthesis of flower like copper oxide and their application to hydrogen peroxide and nitrite sensing

Directory of Open Access Journals (Sweden)

Zhang Li

2011-12-01

Full Text Available Abstract Background The detection of hydrogen peroxide (H2O2 and nitrite ion (NO2- is of great important in various fields including clinic, food, pharmaceutical and environmental analyses. Compared with many methods that have been developed for the determination of them, the electrochemical detection method has attracted much attention. In recent years, with the development of nanotechnology, many kinds of micro/nano-scale materials have been used in the construction of electrochemical biosensors because of their unique and particular properties. Among these catalysts, copper oxide (CuO, as a well known p-type semiconductor, has gained increasing attention not only for its unique properties but also for its applications in many fields such as gas sensors, photocatalyst and electrochemistry sensors. Continuing our previous investigations on transition-metal oxide including cuprous oxide and α-Fe2O3 modified electrode, in the present paper we examine the electrochemical and electrocatalytical behavior of flower like copper oxide modified glass carbon electrodes (CuO/GCE. Results Flower like copper oxide (CuO composed of many nanoflake was synthesized by a simple hydrothermal reaction and characterized using field-emission scanning electron microscopy (FE-SEM and X-ray diffraction (XRD. CuO modified glass carbon electrode (CuO/GCE was fabricated and characterized electrochemically. A highly sensitive method for the rapid amperometric detection of hydrogen peroxide (H2O2 and nitrite (NO2- was reported. Conclusions Due to the large specific surface area and inner characteristic of the flower like CuO, the resulting electrode show excellent electrocatalytic reduction for H2O2 and oxidation of NO2-. Its sensitivity, low detection limit, fast response time and simplicity are satisfactory. Furthermore, this synthetic approach can also be applied for the synthesis of other inorganic oxides with improved performances and they can also be extended to

Effect of copper oxide electrocatalyst on CO2 reduction using Co3O4 as anode

Directory of Open Access Journals (Sweden)

V.S.K. Yadav

2016-09-01

Full Text Available The reduction of carbon dioxide (CO2 to products electrochemically (RCPE in 0.5 M NaHCO3 and Na2CO3 liquid phase electrolyte solutions was investigated. Cobalt oxide (Co3O4 as anode and cuprous oxide (Cu2O as the cathode were considered, respectively. The impacts of applied potential with time of reaction during reduction of CO2 to products were studied. The anode and cathode were prepared by depositing electrocatalysts on the graphite plate. Ultra-fast liquid chromatography (UFLC was used to analyze the products obtained from the reduction of CO2. The feasible way of reduction by applying voltages with current densities was clearly correlated. The results illustrate the capability of electrocatalyst successfully to remove atmospheric CO2 in the form of valuable chemicals. Maximum Faradaic efficiency of ethanol was 98.1% at 2 V and for formic acid (36.6% at 1.5 V was observed in NaHCO3. On the other hand, in Na2CO3 electrolyte solution maximum efficiency for ethanol was 55.21% at 1.5 V and 25.1% for formic acid at 2 V. In both electrolytes other end products like methanol, propanol, formaldehyde and acetic acid were formed at various applied voltage and output current densities.

Linking Mn(II)-oxidizing bacteria to natural attenuation at a former U mining site

Science.gov (United States)

Akob, D.; Bohu, T.; Beyer, A.; Schäffner, F.; Händel, M.; Johnson, C.; Merten, D.; Büchel, G.; Totsche, K.; Küsel, K.

2012-04-01

Uranium mining near Ronneburg, Germany resulted in widespread environmental contamination with acid mine drainage (AMD) and high concentrations of heavy metals and radionuclides. Despite physical remediation of the area, groundwater is still a source of heavy metal contaminants, e.g., Cd, Ni, Co, Cu and Zn, to nearby ecosystems. However, natural attenuation of heavy metals is occurring in Mn oxide rich soils and sediments ranging in pH from 5 to 7. While microorganisms readily oxidize Mn(II) and precipitate Mn oxides at pH ~7 under oxic conditions, few studies describe Mn(II)-oxidizing bacteria (MOB) at pH ~5 and/or in the presence of heavy metals. In this study we (1) isolated MOB from the contaminated Ronneburg area at pH 5.5 and 7 and (2) evaluated the biological formation of Mn oxides. We isolated nine MOB strains at pH 7 (members of the Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes phyla) and a single isolate at pH 5.5 (Oxalobacteraceae isolate AB_14, within the β-Proteobacteria). LA-ICP-MS showed that all isolates accumulated Mn and Fe in their biomass. However, the Oxalobacteraceae isolate AB_14 oxidizes more Mn without additional Fe in the medium. Preliminary FTIR analysis indicated that all isolates formed precipitates, which showed absorption bands that were characteristic for birnessite. High resolution TEM showed variable morphology of precipitates and EDS confirmed the presence of Mn oxides. Isolate AB_14 was not surrounded with precipitates whereas our Actinobacteria isolate AB_18 was encrusted with Mn oxides. Electron diffraction is currently being used to confirm the presence of birnessite and other Mn oxide phases. This, the first known report of any organism capable of Mn oxidation at low pH, demonstrated that MOB can be involved in the natural attenuation of both moderately acidic and neutral pH soils and sediments via the formation of biogenic Mn oxides. Future work will fully evaluate the minerals formed in this process as well

Size dependence of photocatalytic oxidation reactions of Rh nanoparticles dispersed on (Ga1-xZnx)(N1-xOx) support

NARCIS (Netherlands)

Zhang, Y.; Ligthart, D.A.J.M.; Liu, P.; Gao, L.; Verhoeven, M.W.G.M.; Hensen, E.J.M.

2014-01-01

Mixed Ga–Zn oxynitrides were synthesized using coprecipitation, wet-precipitation, and solid-solution methods. The oxynitrides were used as supports for Rh nanoparticle catalysts in photocatalytic water splitting, CO oxidation, and H2 oxidation. Mixed Ga–Zn oxynitrides produced by wet precipitation

Phototrophic Fe(II-oxidation in the chemocline of a ferruginous meromictic lake

Directory of Open Access Journals (Sweden)

Xavier Alexis eWalter

2014-12-01

Full Text Available Precambrian Banded Iron Formation (BIF deposition was conventionally attributed to the precipitation of iron-oxides resulting from the abiotic reaction of ferrous iron (Fe(II with photosynthetically-produced oxygen. Earliest traces of oxygen date from 2.7 Ga, thus raising questions as to what may have caused BIF precipitation before oxygenic photosynthesis evolved. The discovery of anoxygenic phototrophic bacteria thriving through the oxidation of Fe(II has provided support for a biological origin for some BIFs, but despite reports suggesting that anoxygenic phototrophs may oxidize Fe(II in the environment, a model ecosystem of an ancient ocean where they are demonstrably active was lacking. Here we show that anoxygenic phototrophic bacteria contribute to Fe(II oxidation in the water column of the ferruginous sulfate-poor, meromictic lake La Cruz (Spain. We observed in-situ photoferrotrophic activity through stimulation of phototrophic carbon uptake in the presence of Fe(II, and determined light-dependent Fe(II-oxidation by the natural chemocline microbiota. Moreover, a photoferrotrophic bacterium most closely related to Chlorobium ferrooxidans was enriched from the ferruginous water column. Our study for the first time demonstrates a direct link between anoxygenic photoferrotrophy and the anoxic precipitation of Fe(III-oxides in a ferruginous water column, providing a plausible mechanism for the bacterial origin of BIF’s before the advent of free oxygen.

Ceria powders by homogeneous precipitation technique

International Nuclear Information System (INIS)

Ramanathan, S.; Roy, S.K.

2003-01-01

Formation of precursors for ceria by two homogeneous precipitation reactions - (cerium chloride + urea at 95 degC - called reaction A and cerium chloride + hexamethylenetetramine at 85 degC - called reaction B) - has been studied. The variation of size of the colloidal particles formed and the zeta potential of the suspensions with progress of reactions exhibited similar trends for both the precipitation processes. Particle size increased from 100 to 300 nm with increasing temperature and extent of reaction. The zeta potential was found to decrease with increasing extent of precipitation in the pH range of 5 to 7. Filtration and drying led to agglomeration of the fine particles in case of the precursor from reaction B. The as-formed precursors were crystalline - a basic carbonate in case of reaction A and hydrous oxide in case of reaction B. It was found that nano-crystalline ceria powders (average crystallite size -10 nm) formed above 400 degC from both these precursors. The agglomerate size (D50) of the precursors and ceria powders formed after calcination at 600 degC varied from 0.7 to 3 μm. Increasing calcination temperature up to 800 degC, increased the crystallite size (50 nm). The zeta potential variation with pH and concentration of an anionic dispersant (Calgon) for the ceria powders formed was studied to determine the ideal conditions for suspension stability. It was found to be maximum (i.e., the suspensions stable) in the pH range of 3 to 4 or Calgon concentration of 0.01 to 0.1 weight percent. (author)

STRUCTURAL, PHOTO-FUNCTIONAL AND SEMICONDUCTOR PROPERTIES OF COPPER OXIDE THIN FILMS PREPARED BY DC REACTIVE METHOD UNDER VARIOUS THICKNESSES Anmar H. Shukur

Directory of Open Access Journals (Sweden)

Anmar H. Shukur

2018-01-01

Full Text Available Cuprous oxide (Cu2O has been formed on glass substrates by dc reactive magnetron sputtering method, whereas pure target of the solid copper was sputtered with a mixture of plasma for argon gas and oxygen gas was used to form these films. Under vacuum chamber pressure of 1.2×10-5 Pa, thin film thickness was changed from 100 nm to 300 nm while other deposition parameters were fixed. The influence of changing the thickness of thin films on the electrical and the optical properties was investigated in this study. X-ray photoelectron spectroscopy (XPS, X-ray Diffractions system XRD, Atomic Force Microscopy (AFM, hall effect measurement system, UV–VIS spectrophotometer were employed to determine the characteristic of the deposited thin films. Thin film of 200 nm has observed low resistivity of 60.63 Ω cm and direct band gap of 2.5eV. This study has demonstrated that the thickness has direct influence on electrical and optical properties.

A problem in gravimetric method for the determination of rare earth elements as oxide after the fluoride separation

International Nuclear Information System (INIS)

Takada, Kunio

1979-01-01

For the gravimetric determination of lanthanum, it was precipitated as fluoride and converted to oxide by igniting (ca. 930 0 C) in a town gas flame. However, the oxidation of lanthanum fluoride by ignition was incomplete, the major part of the precipitate being converted to oxyfluoride (LaOF) and a mixture of oxide and oxyfluoride resulted. Therefore, analytical results were generally (5 -- 7)% higher than theoretically expected. The lanthanum fluoride became converted into the oxide by repeating ignition (ca. 1070 0 C) three times, each for (30 -- 40)min. However, the weight was lower than that of the corresponding sesquioxide, La 2 O 3 . Except for ytterbium and lutetium, gravimetric results as oxides for the other rare earth elements (Y, Pr, Nd, Sm, Eu and Gd) were higher than theoretical values. Therefore, the precipitation of the rare earth elements as fluoride and the subsequent determination as oxide by ignition of the fluoride could not be recommended as the gravimetric method for the rare earths. In order to obtain accurate results for major to minor amounts of the rare earth elements, an EDTA titration at pH 6 should be used after the dissolution of fluoride in acid, if the fluoride precipitation separation is involved. (author)

Long-term sustainability of microbial-induced CaCO3 precipitation in aqueous media.

Science.gov (United States)

Gat, Daniella; Ronen, Zeev; Tsesarsky, Michael

2017-10-01

Microbially induced CaCO 3 precipitation (MICP) via urea hydrolysis is an emerging technique for soil amelioration, building materials rehabilitation and pollutants sequestration amongst other various environmental applications. The successful application of MICP requires the sustainability of the precipitated CaCO 3 ; to which the fate of ammonia, the main by-product of ureolysis, is potentially significante. Ammonia volatilization and biological ammonia oxidation both induce a pH decrease, which, in turn, might cause CaCO 3 dissolution. To examine the potential effect of accumulated ammonia on precipitated CaCO 3 , we conducted a long-term MICP batch experiment, using environmental enrichment cultures of ureolytic bacteria. Here we show that CaCO 3 precipitation was completed within 15-27 days, along with a rise in ammonium concentration. Following completion of ureolysis and precipitation, ammonium concentrations decreased, leading to a pH decrease. About 30 days after precipitation was completed, as much as 30% CaCO 3 dissolution, was observed. A two-step model, describing urea hydrolysis followed by the removal of ammonia from the precipitation solution, predicted CaCO 3 dissolution due to ammonia volatilization. We suggest that ureolytic MICP might result in ammonia volatilization, leading to significant CaCO 3 dissolution. These results provide basic insights into the sustainability of ureolytic MICP and should further encourage removal of the accumulated ammonia from the treated site. Copyright © 2017 Elsevier Ltd. All rights reserved.

Uranium (III)-Plutonium (III) co-precipitation in molten chloride

Science.gov (United States)

Vigier, Jean-François; Laplace, Annabelle; Renard, Catherine; Miguirditchian, Manuel; Abraham, Francis

2018-02-01

Co-management of the actinides in an integrated closed fuel cycle by a pyrochemical process is studied at the laboratory scale in France in the CEA-ATALANTE facility. In this context the co-precipitation of U(III) and Pu(III) by wet argon sparging in LiCl-CaCl2 (30-70 mol%) molten salt at 705 °C is studied. Pu(III) is prepared in situ in the molten salt by carbochlorination of PuO2 and U(III) is then introduced as UCl3 after chlorine purge by argon to avoid any oxidation of uranium up to U(VI) by Cl2. The oxide conversion yield through wet argon sparging is quantitative. However, the preferential oxidation of U(III) in comparison to Pu(III) is responsible for a successive conversion of the two actinides, giving a mixture of UO2 and PuO2 oxides. Surprisingly, the conversion of sole Pu(III) in the same conditions leads to a mixture of PuO2 and PuOCl, characteristic of a partial oxidation of Pu(III) to Pu(IV). This is in contrast with coconversion of U(III)-Pu(III) mixtures but in agreement with the conversion of Ce(III).

Analysis of surface contaminants on beryllium and aluminum windows

International Nuclear Information System (INIS)

Gmur, N.F.

1987-06-01

An effort has been made to document the types of contamination which form on beryllium window surfaces due to interaction with a synchrotron radiation beam. Beryllium windows contaminated in a variety of ways (exposure to water and air) exhibited surface powders, gels, crystals and liquid droplets. These contaminants were analyzed by electron diffraction, electron energy loss spectroscopy, energy dispersive x-ray spectroscopy and wet chemical methods. Materials found on window surfaces include beryllium oxide, amorphous carbon, cuprous oxide, metallic copper and nitric acid. Aluminum window surface contaminants were also examined

Photoluminescent properties of Y2O3:Eu3+ phosphors prepared via urea precipitation in non-aqueous solution

International Nuclear Information System (INIS)

Sun, Y.; Qi, L.; Lee, M.; Lee, B.I.; Samuels, W.D.; Exarhos, G.J.

2004-01-01

Europium-doped yttrium oxide phosphors were obtained by firing precursors prepared by urea precipitation in ethanol and ethylenediamine. The precipitation in non-aqueous solution was carried out in an autoclave at 150 deg. C to allow the decomposition of urea. The photoluminescent intensities of the phosphors prepared in ethanol and ethylenediamine increased by about 30% compared to that of the phosphor prepared by the conventional urea homogeneous precipitation in aqueous solution. Amorphous carbonates and amorphous hydroxides/carbonates mixtures were identified as precursors from ethanol and ethylenediamine, respectively. The morphology and particle size were studied by SEM and dynamic laser scattering method

Parametric study on co-precipitation of U/Th in MOX fuel of AHWR

International Nuclear Information System (INIS)

Tiwari, S.K.; Swaroopa Lakshmi, Y.; Nath, Baidurjya; Setty, D.S.; Kalyana Krishnan, G.; Saibaba, N.

2015-01-01

During manufacturing of Mixed Oxide Fuel (MOX) pellets for Advance Heavy Water Reactor (AHWR-LEU), around 30% rejected MOX pellets are generated in every cycle. These rejected MOX pellets are dissolved in nitric acid for recovery of U/Th. The recovered U/Th is recycled for production of MOX pellets. MOX pellets of varying compositions are used in AHWR fuel. Dissolution of MOX pellets in nitric acid is a challenging task because of its low surface area and longer dissolution times. High normal nitric acid is used in order to increase rate of dissolution, which in turn results in generation of high free acidity solution which influences the precipitation characteristics of Uranium (VI) by oxalic acid. Oxalic acid precipitation helps in generation of nitric acid which can be used for dissolution there by effectively facilitating nil effluent generation. Precipitation by oxalic acid unlike ammonia has advantage of zero liquid effluent discharge by complete recycle of oxalate filtrate to dissolution section. In the present work, the effect of various parameters like free acidity, residence time, concentration of oxalic acid, initial concentration of uranium and thorium etc. on the precipitation of U(VI) and Th(IV) in nitrate media by oxalic acid was carried out. The precipitated powder was subjected to various morphological evaluations like particle size etc. Study of various parameters on the co-precipitation of uranium and thorium by oxalic acid was carried out. It was observed that complete precipitation (> 99.9%) of thorium as oxalate does not depend on free acidity range (1- 6 N). Excess oxalic acid is not required for complete precipitation of thorium oxalate. The precipitation of uranyl oxalate varies with initial free acidity of solution. Uranyl oxalate precipitation does not take place at and above 5 N of free acidity

Synthesis and Characterization of Anatase TiO_2 Powder using a Homogeneous Precipitation Method

International Nuclear Information System (INIS)

Choi, Soon Ok; Cho, Jee Hee; Lim, Sung Hwan; Chung, Eun Young

2011-01-01

This paper studies the experimental method that uses the homogeneous precipitation method to prepare mica flakes coated with anatase-type titania pearlescent pigment with urea as precipitant. The optimum technology parameters, the chemical composition, the microstructure, and the color property of resulting pigments are discussed. The coating principle of mica coated titania with various coating thickness is analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy(TEM) and tested by spectrophotometer analysis. The colored nanocrystalline pigments with different morphology and coating thickness 45-170 nm were prepared by homogeneous precipitation treatment of TiOSO_4(titanum oxysulfate) aqueous solutions. Characterizations on the pigments show that the pearlescent effects of the pigments depend mainly on mica size, thickness of the metal oxide deposit, its chemical composition, and crystal structure.

Methods of producing adsorption media including a metal oxide

Science.gov (United States)

Mann, Nicholas R; Tranter, Troy J

2014-03-04

Methods of producing a metal oxide are disclosed. The method comprises dissolving a metal salt in a reaction solvent to form a metal salt/reaction solvent solution. The metal salt is converted to a metal oxide and a caustic solution is added to the metal oxide/reaction solvent solution to adjust the pH of the metal oxide/reaction solvent solution to less than approximately 7.0. The metal oxide is precipitated and recovered. A method of producing adsorption media including the metal oxide is also disclosed, as is a precursor of an active component including particles of a metal oxide.

Acidic precipitation. Volume 3: Sources, deposition, and canopy interactions. Advances in environmental science

Energy Technology Data Exchange (ETDEWEB)

Lindberg, S.E.; Page, A.L.; Norton, S.A. (eds.)

1990-01-01

As has been the case with many environmental issues of the twentieth century, acidic precipitation has its origin in emissions to the atmosphere of numerous compounds from both natural and man-made sources. This volume emphasizes the atmospheric aspects of acidic precipitation and all that this term has come to include (e.g. toxic gases such as ozone, trace metals, aluminum, and oxides of nitrogen). It progresses from emissions of the precursors of acidic precipitation to their eventual deposition on environmental surfaces. The chapters describe the sources of acidic and basic airborne substances, their interactions in the atmosphere and with rain droplets, and their reactions with other airborne constituents such as aluminum and other metals. Also discussed are the use of metals as tracers of sources of the precursors of acidic precipitation and as tracers of historical deposition rates, the processes controlling the removal of airborne material as dry deposition and deposition interactions with the forest canopy, and past and future trends in atmospheric emissions and options for their abatement.

ANALYSIS ON THE BEHAVIOR OF PRECIPITATES IN ULTRA-THIN HOT STRIP OF PLAIN LOW CARBON STEEL PRODUCED BY COMPACT STRIP PRODUCTION

Institute of Scientific and Technical Information of China (English)

H. Yu; Y.L. Kang; H.B. Dong; D.L. Liu; J. Fu

2002-01-01

This paper investigated the mechanism of precipitation and its influence upon prop-erties of ultra-thin hot strips of low carbon steel produced by CSP techniques usingexperiment and thermodynamics theory. The experimental results show that thereare lots of fine and dispersive precipitates in microstructures. By analysis, most ofaluminum nitrides are in grains, while coexisted precipitates of MnS are along grainboundaries. Coexisted precipitates compose cation-vacancy type oxides such as Al2O3in the core, while MnS is at the fringe of surface. The precipitation behavior of AlNand MnS in the hot strip is studied by thermodynamic calculation. At last, implica-tions between strengthening effect and techniques are analyzed using obtained solubilityproducts.

Climate change and precipitation: Detecting changes Climate change and precipitation: Detecting changes

International Nuclear Information System (INIS)

Van Boxel, John H

2001-01-01

Precipitation is one of the most, if not the most important climate parameter In most studies on climate change the emphasis is on temperature and sea level rise. Often too little attention is given to precipitation. For a large part this is due to the large spatial en temporal variability of precipitation, which makes the detection of changes difficult. This paper describes methods to detect changes in precipitation. In order to arrive at statistically significant changes one must use long time series and spatial averages containing the information from several stations. In the Netherlands the average yearly precipitation increased by 11% during the 20th century .In the temperate latitudes on the Northern Hemisphere (40-60QN) the average increase was about 7% over the 20th century and the globally averaged precipitation increased by about 3%. During the 20th century 38% of the land surface of the earth became wetter, 42% experienced little change (less than 5% change) and 20% became dryer. More important than the average precipitation is the occurrence of extremes. In the Netherlands there is a tendency to more extreme precipitations, whereas the occurrence of relatively dry months has not changed. Also in many other countries increases in heavy precipitation events are observed. All climate models predict a further increase of mean global precipitation if the carbon dioxide concentration doubles. Nevertheless some areas get dryer, others have little change and consequently there are also areas where the increase is much more than the global average. On a regional scale however there are large differences between the models. Climate models do not yet provide adequate information on changes in extreme precipitations

Precipitous Birth

Directory of Open Access Journals (Sweden)

Jennifer Yee

2017-09-01

Full Text Available Audience: This scenario was developed to educate emergency medicine residents on the management of a precipitous birth in the emergency department (ED. The case is also appropriate for teaching of medical students and advanced practice providers, as well as reviewing the principles of crisis resource management, teamwork, and communication. Introduction: Patients with precipitous birth require providers to manage two patients simultaneously with limited time and resources. Crisis resource management skills will be tested once baby is delivered, and the neonate will require assessment for potential neonatal resuscitation. Objectives: At the conclusion of the simulation session, learners will be able to manage women who have precipitous deliveries, as well as perform neonatal assessment and management. Method: This session was conducted using high-fidelity simulation, followed by a debriefing session and lecture on precipitous birth management and neonatal evaluation.

Heterogeneous Catalysts for VOC Oxidation from Red Mud and Bagasse Ash Carbon

Science.gov (United States)

Pande, Gaurav

A range of VOC oxidation catalysts have been prepared in this study from agricultural and industrial waste as the starting point. The aim is to prepare catalysts with non-noble metal oxides as the active catalytic component (iron in red mud). The same active component was also supported on activated carbon obtained from unburned carbon in bagasse ash. Red mud which is an aluminum industry waste and rich in different phases of iron as oxide and hydroxide is used as the source for the catalytically active species. It is our aim to enhance the catalytic performance of red mud which though high in iron concentration has a low surface area and may not have the properties of an ideal catalyst by itself. In one of the attempts to enhance the catalytic performance, we have tried to leach red mud for which we have explored a range of leaching acids for effecting the leaching most efficiently and then precipitated the iron from the leachate as its hydroxide by precipitating with alkali solution followed by drying and calcination to give high surface area metal oxide material. Extensive surface characterization and VOC oxidation catalytic testing were performed for these solids. In a step to further enhance the catalytic activity towards oxidation, copper was introduced by taking another industrial waste from the copper tubing industry viz. the pickling acid. Copper has a more favourable redox potential making it catalytically more effective than iron. To make the mixed metal oxide, red mud leachate was mixed with the pickling acid in a pre-decided ratio before precipitating with alkali solution followed by drying and calcination as was done with the red mud leachate. The results from these experiments are encouraging. The temperature programmed reduction (TPR) of the solids show that the precipitate of red mud leachates show hydrogen uptake peak at a lower temperature than for just the calcined red mud. This could be due to the greatly enhanced surface area of the prepared

Precipitation isoscapes for New Zealand: enhanced temporal detail using precipitation-weighted daily climatology.

Science.gov (United States)

Baisden, W Troy; Keller, Elizabeth D; Van Hale, Robert; Frew, Russell D; Wassenaar, Leonard I

2016-01-01

Predictive understanding of precipitation δ(2)H and δ(18)O in New Zealand faces unique challenges, including high spatial variability in precipitation amounts, alternation between subtropical and sub-Antarctic precipitation sources, and a compressed latitudinal range of 34 to 47 °S. To map the precipitation isotope ratios across New Zealand, three years of integrated monthly precipitation samples were acquired from >50 stations. Conventional mean-annual precipitation δ(2)H and δ(18)O maps were produced by regressions using geographic and annual climate variables. Incomplete data and short-term variation in climate and precipitation sources limited the utility of this approach. We overcome these difficulties by calculating precipitation-weighted monthly climate parameters using national 5-km-gridded daily climate data. This data plus geographic variables were regressed to predict δ(2)H, δ(18)O, and d-excess at all sites. The procedure yields statistically-valid predictions of the isotope composition of precipitation (long-term average root mean square error (RMSE) for δ(18)O = 0.6 ‰; δ(2)H = 5.5 ‰); and monthly RMSE δ(18)O = 1.9 ‰, δ(2)H = 16 ‰. This approach has substantial benefits for studies that require the isotope composition of precipitation during specific time intervals, and may be further improved by comparison to daily and event-based precipitation samples as well as the use of back-trajectory calculations.

Cerium oxalate precipitation

International Nuclear Information System (INIS)

Chang, T.P.

1987-02-01

Cerium, a nonradioactive, common stand-in for plutonium in development work, has been used to simulate several plutonium precipitation processes at the Savannah River Laboratory. There are similarities between the plutonium trifluoride and the cerium oxalate precipitations in particle size and extent of plating, but not particle morphology. The equilibrium solubility, precipitation kinetics, particle size, extent of plating, and dissolution characteristics of cerium oxalate have been investigated. Interpretations of particle size and plating based on precipitation kinetics (i.e., nucleation and crystal growth) are presented. 16 refs., 7 figs., 6 tabs

Thulium oxide fuel characterization study: Part 3, Procedures

International Nuclear Information System (INIS)

Nelson, C.A.; Anderson, R.W.; Talbot, M.; Bierds, W.

1970-06-01

Procedures are presented for the following: Tm 2 O 3 -Yb 2 O 3 pseudo - binary phase diagram tests; compatibility tests; thulium-170 oxide dose rate measurements; preparation of Tm 2 O 3 wafers; SRL thulium and/or ytterbium oxide powder reprocessing for sintering; cold pressing and sintering thulium oxide wafers; preparation of thulium and/or ytterbium oxide powder via precipitation with oxalic acid, ammonium oxalate, urea and methyl oxalate; determination of the total surface area of rare earth oxide powders; determining oxygen in thulia - thulia/ytterbia for the purpose of determining metal-to-oxygen ratios; and determination of the impact resistance to fines generation of sintered rare earth oxide

Variability of Fe isotope compositions of hydrothermal sulfides and oxidation products at mid-ocean ridges

Science.gov (United States)

Li, Xiaohu; Wang, Jianqiang; Chu, Fengyou; Wang, Hao; Li, Zhenggang; Yu, Xing; Bi, Dongwei; He, Yongsheng

2018-04-01

Significant Fe isotopic fractionation occurs during the precipitation and oxidative weathering of modern seafloor hydrothermal sulfides, which has an important impact on the cycling of Fe isotopes in the ocean. This study reports the Fe-isotope compositions of whole-rock sulfides and single-mineral pyrite collected from hydrothermal fields at the South Mid-Atlantic Ridge (SMAR) and the East Pacific Rise (EPR) and discusses the impacts of precipitation and late-stage oxidative weathering of sulfide minerals on Fe isotopic fractionation. The results show large variation in the Fe-isotope compositions of the sulfides from the different hydrothermal fields on the mid-oceanic ridges, indicating that relatively significant isotope fractionation occurs during the sulfide precipitation and oxidative weathering processes. The Fe-isotope compositions of the sulfides from the study area at the SMAR vary across a relatively small range, with an average value of 0.01‰. This Fe-isotope composition is similar to the Fe-isotope composition of mid-oceanic ridge basalt, which suggests that Fe was mainly leached from basalt. In contrast, the Fe-isotope composition of the sulfides from the study area at the EPR are significantly enriched in light Fe isotopes (average value - 1.63‰), mainly due to the kinetic fractionation during the rapid precipitation process of hydrothermal sulfide. In addition, the pyrite from different hydrothermal fields is enriched in light Fe isotopes, which is consistent with the phenomenon in which light Fe isotopes are preferentially enriched during the precipitation of pyrite. The red oxides have the heaviest Fe-isotope compositions (up to 0.80‰), indicating that heavy Fe isotopes are preferentially enriched in the oxidation product during the late-stage oxidation process. The data obtained from this study and previous studies show a significant difference between the Fe-isotope compositions of the sulfides from the SMAR and EPR. The relatively heavy

Defect engineering of the electronic transport through cuprous oxide interlayers

KAUST Repository

Fadlallah, Mohamed M.

2016-06-03

The electronic transport through Au–(Cu2O)n–Au junctions is investigated using first-principles calculations and the nonequilibrium Green’s function method. The effect of varying the thickness (i.e., n) is studied as well as that of point defects and anion substitution. For all Cu2O thicknesses the conductance is more enhanced by bulk-like (in contrast to near-interface) defects, with the exception of O vacancies and Cl substitutional defects. A similar transmission behavior results from Cu deficiency and N substitution, as well as from Cl substitution and N interstitials for thick Cu2O junctions. In agreement with recent experimental observations, it is found that N and Cl doping enhances the conductance. A Frenkel defect, i.e., a superposition of an O interstitial and O substitutional defect, leads to a remarkably high conductance. From the analysis of the defect formation energies, Cu vacancies are found to be particularly stable, in agreement with earlier experimental and theoretical work.

Defect engineering of the electronic transport through cuprous oxide interlayers

KAUST Repository

Fadlallah, Mohamed M.; Eckern, Ulrich; Schwingenschlö gl, Udo

2016-01-01

The electronic transport through Au–(Cu2O)n–Au junctions is investigated using first-principles calculations and the nonequilibrium Green’s function method. The effect of varying the thickness (i.e., n) is studied as well as that of point defects

Radioactive mineral spring precipitates, their analytical and statistical data and the uranium connection

Science.gov (United States)

Cadigan, R.A.; Felmlee, J.K.

1982-01-01

Major radioactive mineral springs are probably related to deep zones of active metamorphism in areas of orogenic tectonism. The most common precipitate is travertine, a chemically precipitated rock composed chiefly of calcium carbonate, but also containing other minerals. The mineral springs are surface manifestations of hydrothermal conduit systems which extend downward many kilometers to hot source rocks. Conduits are kept open by fluid pressure exerted by carbon dioxide-charged waters rising to the surface propelled by heat and gas (CO2 and steam) pressure. On reaching the surface, the dissolved carbon dioxide is released from solution, and calcium carbonate is precipitated. Springs also contain sulfur species (for example, H2S and HS-), and radon, helium and methane as entrained or dissolved gases. The HS- ion can react to form hydrogen sulfide gas, sulfate salts, and native sulfur. Chemical salts and native sulfur precipitate at the surface. The sulfur may partly oxidize to produce detectable sulfur dioxide gas. Radioactivity is due to the presence of radium-226, radon-222, radium-228, and radon-220, and other daughter products of uranium-238 and thorium-232. Uranium and thorium are not present in economically significant amounts in most radioactive spring precipitates. Most radium is coprecipitated at the surface with barite. Barite (barium sulfate) forms in the barium-containing spring water as a product of the oxidation of sulfur species to sulfate ions. The relatively insoluble barium sulfate precipitates and removes much of the radium from solution. Radium coprecipitates to a lesser extent with manganese-barium- and iron-oxy hydroxides. R-mode factor analysis of abundances of elements suggests that 65 percent of the variance of the different elements is affected by seven factors interpreted as follows: (1) Silica and silicate contamination and precipitation; (2) Carbonate travertine precipitation; (3) Radium coprecipitation; (4) Evaporite precipitation

High resolution SEM characterization of nano-precipitates in ODS steels.

Science.gov (United States)

Jóźwik, Iwona; Strojny-Nędza, Agata; Chmielewski, Marcin; Pietrzak, Katarzyna; Kurpaska, Łukasz; Nosewicz, Szymon

2018-05-01

The performance of the present-day scanning electron microscopy (SEM) extends far beyond delivering electronic images of the surface topography. Oxide dispersion strengthened (ODS) steel is on of the most promising materials for the future nuclear fusion reactor because of its good radiation resistance, and higher operation temperature up to 750°C. The microstructure of ODS should not exceed tens of nm, therefore there is a strong need in a fast and reliable technique for their characterization. In this work, the results of low-kV SEM characterization of nanoprecipitates formed in the ODS matrix are presented. Application of highly sensitive photo-diode BSE detector in SEM imaging allowed for the registration of single nm-sized precipitates in the vicinity of the ODS alloys. The composition of the precipitates has been confirmed by TEM-EDS. © 2018 Wiley Periodicals, Inc.

Liberation of Adsorbed and Co-Precipitated Arsenic from Jarosite, Schwertmannite, Ferrihydrite, and Goethite in Seawater

Directory of Open Access Journals (Sweden)

Rodrigo Alarcón

2014-07-01

Full Text Available Sea level rise is able to change the geochemical conditions in coastal systems. In these environments, transport of contaminants can be controlled by the stability and adsorption capacity of iron oxides. The behavior of adsorbed and co-precipitated arsenic in jarosite, schwertmannite, ferrihydrite, and goethite in sea water (common secondary minerals in coastal tailings was investigated. The aim of the investigation was to establish As retention and transport under a marine flood scenario, which may occur due to climate change. Natural and synthetic minerals with co-precipitated and adsorbed As were contacted with seawater for 25 days. During this period As, Fe, Cl, SO4, and pH levels were constantly measured. The larger retention capability of samples with co-precipitated As, in relation with adsorbed As samples, reflects the different kinetics between diffusion, dissolution, and surface exchange processes. Ferrihydrite and schwertmannite showed good results in retaining arsenic, although schwertmannite holding capacity was enhanced due its buffering capacity, which prevented reductive dissolution throughout the experiment. Arsenic desorption from goethite could be understood in terms of ion exchange between oxides and electrolytes, due to the charge difference generated by a low point-of-zero-charge and the change in stability of surface complexes between synthesis conditions and natural media.

Supercapacitors Based on Nickel Oxide/Carbon Materials Composites

OpenAIRE

Lota, Katarzyna; Sierczynska, Agnieszka; Lota, Grzegorz

2011-01-01

In the thesis, the properties of nickel oxide/active carbon composites as the electrode materials for supercapacitors are discussed. Composites with a different proportion of nickel oxide/carbon materials were prepared. A nickel oxide/carbon composite was prepared by chemically precipitating nickel hydroxide on an active carbon and heating the hydroxide at 300 ∘C in the air. Phase compositions of the products were characterized using X-ray diffractometry (XRD). The morphology of the composite...

Metal insulator semiconductor solar cell devices based on a Cu2O substrate utilizing h-BN as an insulating and passivating layer

International Nuclear Information System (INIS)

Ergen, Onur; Gibb, Ashley; Vazquez-Mena, Oscar; Zettl, Alex; Regan, William Raymond

2015-01-01

We demonstrate cuprous oxide (Cu 2 O) based metal insulator semiconductor Schottky (MIS-Schottky) solar cells with efficiency exceeding 3%. A unique direct growth technique is employed in the fabrication, and hexagonal boron nitride (h-BN) serves simultaneously as a passivation and insulation layer on the active Cu 2 O layer. The devices are the most efficient of any Cu 2 O based MIS-Schottky solar cells reported to date

Preparation of a sinterable beryllium oxide through decomposition of beryllium hydroxide (1963)

International Nuclear Information System (INIS)

Bernier, M.

1963-01-01

In the course of the present study, we have attempted to precise the factors which among the ones effective in the course of the preparation of the beryllium hydroxide and oxide and during the sintering have an influence on the final result: the density and homogeneity of the sintered body. Of the several varieties of hydroxides precipitated from a sulfate solution the β-hydroxide only is always contaminated with beryllium sulfate and cannot be purified even by thorough washing. We noticed that those varieties of the hydroxide (gel, α, β) have different decomposition rates; this behaviour is used to identify and even to dose the different species in (α, β) mixtures. The various hydroxides transmit to the resulting oxides the shape they had when precipitated. Accordingly the history of the oxide is revealed by its behaviour during its fabrication and sintering. By comparing the results of the sintering operation with the various measurements performed on the oxide powders we are led to the conclusion that an oxide obtained from beryllium hydroxide is sinterable under vacuum if the following conditions are fulfilled: the particle size must lie between 0.1 and 0.2 μ and the BeSO 4 content of the powder must be less than 0.25 per cent wt (expressed as SO 3 /BeO). The best fitting is obtained with the oxide issued from an α-hydroxide precipitated as very small aggregates and with a low sulfur-content. We have observed that this is also the case for the oxide obtained by direct calcination of beryllium sulfate. (author) [fr

The influence of precipitation temperature on the properties of ceria–zirconia solid solution composites

International Nuclear Information System (INIS)

Cui, Yajuan; Fang, Ruimei; Shang, Hongyan; Shi, Zhonghua; Gong, Maochu; Chen, Yaoqiang

2015-01-01

Highlights: • The crystallite size of precipitate increases as the precipitation temperature rises. • The stack of large crystallite can form nanoparticles with big pore size. • Big pore sizes are advantageous to improve the thermal stability. • Phase segregation is restricted in CZ solid solution precipitated at 70 °C. • The reducibility and OSC of the solid solution precipitated at 70 °C are improved. - Abstract: The ceria–zirconia composites (CZ) with a Ce/Zr mass ratio of 1/1 were synthesized by a back-titration method, in which the influence of precipitation temperature on the properties of ceria–zirconia precipitates was investigated. The resulting precipitation and mixed oxides at different precipitation temperatures were then characterized by a range of techniques, including textural properties, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), H 2 -temperature programmed reduction (H 2 -TPR) as well as oxygen storage capacity (OSC) measurement. The results revealed that ceria–zirconia composites were formed as solid solution and such structure is favored of thermostability and texture properties. In particular, the composite CZ-70 synthesized at 70 °C exhibited prominent thermostability with a surface area of 32 m 2 /g as well as a pore volume of 0.15 cc/g after aging treatment at 1000 °C for 5 h. And this was found to be associated with the wider pore size distribution which maybe owed to the formation of large crystal at the primary stage of precipitation. Additionally, the composite CZ-70 showed excellent reduction property and OSC benefiting from stable texture and structure

Contribution to the Chemical and Technological Study of Ammonium Diuranate Precipitation

International Nuclear Information System (INIS)

Vuillemey, R.

1962-01-01

The present work is designed to study the relationship between the conditions for precipitation by ammonia and the properties of ammonium diuranate obtained either from uranyl nitrate solution or from gaseous uranium hexafluoride. In each case the optimum processes are defined leading on the one hand to uranate which can afterwards be treated in a reduction- fluorination oven to give uranium tetrafluoride, and on the other hand to a uranate suitable for the production of a sinterable uranium oxide. In particular it is shown that the treatment of uranyl nitrate solutions by stoichiometric quantities of ammonia leads to the complete precipitation of the uranium leaving less than 1 mg/litre of uranium in the solution, whereas the treatment of uranium hexafluoride necessitates the use of at least 8 times the stoichiometric quantity. (author) [fr

Separation of aromatic precipitates from simulated high level radioactive waste by hydrolysis, evaporation and liquid-liquid extraction

International Nuclear Information System (INIS)

Young, S.R.; Shah, H.B.; Carter, J.T.

1991-01-01

The Defense Waste Processing Facility (DWPF) at the SRS will be the United States' first facility to process High Level radioactive Waste (HLW) into a borosilicate glass matrix. The removal of aromatic precipitates by hydrolysis, evaporation and liquid-liquid extraction will be a key step in the processing of the HLW. This step, titled the Precipitate Hydrolysis Process, has been demonstrated by the Savannah River Laboratory with the Precipitate Hydrolysis Experimental Facility (PHEF). The mission of the PHEF is to demonstrate processing of simulated high level radioactive waste which contains tetraphenylborate precipitates and nitrite. Reduction of nitrite by hydroxylamine nitrate and hydrolysis of the tetraphenylborate by formic acid is discussed. Gaseous production, which is primarily benzene, nitrous oxide and carbon dioxide, has been quantified. Production of high-boiling organic compounds and the accumulation of these organic compounds within the process are addressed

The influence of green microstructure and sintering parameters on precipitation process during copper-nickel-zinc ferrites sintering

International Nuclear Information System (INIS)

Barba, A.; Clausell, C.; Jarque, J. C.; Monzo, M.

2014-01-01

Microstructural changes that occur during heat treatment of copper-nickel-zinc ferrites have been studied. The process of precipitation of the two types of crystals that occur during the sintering process has been analyzed. It is found that this process depends on dry relative density of the press specimens and on the following sintering parameters: sintering temperature, sintering time and cooling rate of the thermal cycle. Crystal precipitates characterization have been done by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). These techniques have allowed to determine the nature of these crystals, which in this case correspond to zinc and copper oxides. It has been used two chemical reactions to explain the bulk precipitation and subsequent re-dissolution of these crystal precipitates during sintering. (Author)

Synthesis of iron oxide nanoparticles under oxidizing environment and their stabilization in aqueous and non-aqueous media

International Nuclear Information System (INIS)

Maity, D.; Agrawal, D.C.

2007-01-01

Synthesis of magnetite (Fe 3 O 4 ) nanoparticles under oxidizing environment by precipitation from aqueous media is not straightforward because Fe 2+ gets oxidized to Fe 3+ and thus the ratio of Fe 3+ :Fe 2+ =2:1 is not maintained during the precipitation. A molar ratio of Fe 3+ :Fe 2+ smaller than 2:1 has been used by many to compensate for the oxidation of Fe 2+ during the preparation. In this work, we have prepared iron oxide nanoparticles in air environment by the precipitation technique using initial molar ratios Fe 3+ :Fe 2+ ≤2:1. The phases of the resulting powders have been determined by several techniques. It is found that the particles consist mainly of maghemite with little or no magnetite phase. The particles have been suspended in non-aqueous and aqueous media by coating the particles with a single layer and a bilayer of oleic acid, respectively. The particle sizes, morphology and the magnetic properties of the particles and the ferrofulids prepared from these particles are reported. The average particle sizes obtained from the TEM micrographs are 14, 10 and 9 nm for the water, kerosene and dodecane-based ferrofluids, respectively, indicating a better dispersion in the non-aqueous media. The specific saturation magnetization (σ s ) value of the oleic-acid-coated particles (∼53 emu/g) is found to be lower than that for the uncoated particles (∼63 emu/g). Magnetization σ s of the dodecane-based ferrofluid is found to be 10.1 emu/g for a volume fraction of particles φ=0.019. Zero coercivity and zero remanance on the magnetization curves indicate that the particles are superparamagnetic (SPM) in nature

Precipitation behavior and effect of new precipitated β phase in AZ80 magnesium alloy

Institute of Scientific and Technical Information of China (English)

TANG Wei; HAN En-hou; XU Yong-bo; LIU Lu

2006-01-01

Granular precipitate that was a new kind of β-Mg17Al12 phase found in aged AZ80 wrought Mg alloy at all aging temperature was studied. The structure and precipitation behavior of this granular β-Mg17Al12 precipitate were studied by environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM). The effect of the granular precipitate on mechanical properties of AZ80 alloy was also studied. The new precipitate that was granular and nucleated both on grain boundaries (GBs) and twin boundaries, has the same crystal structure and lattice parameter as those of the continuous or discontinuous precipitated β-Mg17Al12. And the nucleation and growth of the granular precipitate are faster than those of the other two precipitates at higher temperatures (above 583 K), but are suppressed at lower temperatures (below 423 K). At lower temperatures, the discontinuous β-Mg17Al12 precipitates firstly and the granular β-Mg17Al12 precipitates after aged more than 40 h. The crack is easily nucleated on the phase boundaries of granular phase and matrix because of the weak binding force. As a result, the strength and ductility of AZ80 Mg alloy are decreased by the granular β-Mg17Al12 precipitate.

Novel approach to growth of precipitate-free, high-quality oxide thin films suitable for device applications

International Nuclear Information System (INIS)

Endo, K.; Badica, P.; Sato, H.; Akoh, H.

2006-01-01

To eliminate precipitates-segregates that can easily occur on the thin film surfaces of the multicomponent materials for electronics, a new approach is proposed, consisting of the following aspects: first, on the substrates, artificial steps of predefined height and width are produced, and second, films are grown on such substrates. The width of the step is taken equal to the 'double of the migration length' of the atomic species depositing on the substrate. In these conditions, precipitates migrate and gather at the step edges where the free energy is lowest and the resulting totally precipitate-free surface of the film on the step is suitable for device applications or integration purposes. The method has several other important advantages and they are discussed in the text. Using this new approach we present successful fabrication of a mesa structure showing intrinsic Josephson effect. We have used thin films of Bi-2212/Bi-2223 superstructure grown by MOCVD on (001) SrTiO 3 single crystal substrates with artificial steps of about 20 μm width

Prediction of ferric iron precipitation in bioleaching process using partial least squares and artificial neural network

Directory of Open Access Journals (Sweden)

Golmohammadi Hassan

2013-01-01

Full Text Available A quantitative structure-property relationship (QSPR study based on partial least squares (PLS and artificial neural network (ANN was developed for the prediction of ferric iron precipitation in bioleaching process. The leaching temperature, initial pH, oxidation/reduction potential (ORP, ferrous concentration and particle size of ore were used as inputs to the network. The output of the model was ferric iron precipitation. The optimal condition of the neural network was obtained by adjusting various parameters by trial-and-error. After optimization and training of the network according to back-propagation algorithm, a 5-5-1 neural network was generated for prediction of ferric iron precipitation. The root mean square error for the neural network calculated ferric iron precipitation for training, prediction and validation set are 32.860, 40.739 and 35.890, respectively, which are smaller than those obtained by PLS model (180.972, 165.047 and 149.950, respectively. Results obtained reveal the reliability and good predictivity of neural network model for the prediction of ferric iron precipitation in bioleaching process.

IN-SITU CHEMICAL STABILIZATION OF METALS AND RADIONUCLIDES THROUGH ENHANCED ANAEROBIC REDUCTIVE PRECIPITATION

Energy Technology Data Exchange (ETDEWEB)

Christopher C. Lutes; Angela Frizzell, PG; Todd A. Thornton; James M. Harrington

2003-08-01

The objective of this NETL sponsored bench-scale study was to demonstrate the efficacy of enhanced anaerobic reductive precipitation (EARP) technology for precipitating uranium using samples from contaminated groundwater at the Fernald Closure Project (FCP) in Cincinnati, Ohio. EARP enhances the natural biological reactions in the groundwater through addition of food grade substrates (typically molasses) to drive the oxidative-reductive potential of the groundwater to a lower, more reduced state, thereby precipitating uranium from solution. In order for this in-situ technology to be successful in the long term, the precipitated uranium must not be re-dissolved at an unacceptable rate once groundwater geochemical conditions return to their pretreatment, aerobic state. The approach for this study is based on the premise that redissolution of precipitated uranium will be slowed by several mechanisms including the presence of iron sulfide precipitates and coatings, and sorption onto fresh iron oxides. A bench-scale study of the technology was performed using columns packed with site soil and subjected to a continuous flow of uranium-contaminated site groundwater (476 {micro}g/L). The ''treated'' column received a steady stream of dilute food grade molasses injected into the contaminated influent. Upon attainment of a consistently reducing environment and demonstrated removal of uranium, an iron sulfate amendment was added along with the molasses in the influent solution. After a month long period of iron addition, the treatments were halted, and uncontaminated, aerobic, unamended water was introduced to the treated column to assess rebound of uranium concentrations. In the first two months of treatment, the uranium concentration in the treated column decreased to the clean-up level (30 {micro}g/L) or below, and remained there for the remainder of the treatment period. A brief period of resolubilization of uranium was observed as the treated column

Asymmetric responses of primary productivity to precipitation extremes: A synthesis of grassland precipitation manipulation experiments.

Science.gov (United States)

Wilcox, Kevin R; Shi, Zheng; Gherardi, Laureano A; Lemoine, Nathan P; Koerner, Sally E; Hoover, David L; Bork, Edward; Byrne, Kerry M; Cahill, James; Collins, Scott L; Evans, Sarah; Gilgen, Anna K; Holub, Petr; Jiang, Lifen; Knapp, Alan K; LeCain, Daniel; Liang, Junyi; Garcia-Palacios, Pablo; Peñuelas, Josep; Pockman, William T; Smith, Melinda D; Sun, Shanghua; White, Shannon R; Yahdjian, Laura; Zhu, Kai; Luo, Yiqi

2017-10-01

Climatic changes are altering Earth's hydrological cycle, resulting in altered precipitation amounts, increased interannual variability of precipitation, and more frequent extreme precipitation events. These trends will likely continue into the future, having substantial impacts on net primary productivity (NPP) and associated ecosystem services such as food production and carbon sequestration. Frequently, experimental manipulations of precipitation have linked altered precipitation regimes to changes in NPP. Yet, findings have been diverse and substantial uncertainty still surrounds generalities describing patterns of ecosystem sensitivity to altered precipitation. Additionally, we do not know whether previously observed correlations between NPP and precipitation remain accurate when precipitation changes become extreme. We synthesized results from 83 case studies of experimental precipitation manipulations in grasslands worldwide. We used meta-analytical techniques to search for generalities and asymmetries of aboveground NPP (ANPP) and belowground NPP (BNPP) responses to both the direction and magnitude of precipitation change. Sensitivity (i.e., productivity response standardized by the amount of precipitation change) of BNPP was similar under precipitation additions and reductions, but ANPP was more sensitive to precipitation additions than reductions; this was especially evident in drier ecosystems. Additionally, overall relationships between the magnitude of productivity responses and the magnitude of precipitation change were saturating in form. The saturating form of this relationship was likely driven by ANPP responses to very extreme precipitation increases, although there were limited studies imposing extreme precipitation change, and there was considerable variation among experiments. This highlights the importance of incorporating gradients of manipulations, ranging from extreme drought to extreme precipitation increases into future climate change

Literature review for oxalate oxidation processes and plutonium oxalate solubility

Energy Technology Data Exchange (ETDEWEB)

Nash, C. A. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2015-10-01

A literature review of oxalate oxidation processes finds that manganese(II)-catalyzed nitric acid oxidation of oxalate in precipitate filtrate is a viable and well-documented process. The process has been operated on the large scale at Savannah River in the past, including oxidation of 20 tons of oxalic acid in F-Canyon. Research data under a variety of conditions show the process to be robust. This process is recommended for oxalate destruction in H-Canyon in the upcoming program to produce feed for the MOX facility. Prevention of plutonium oxalate precipitation in filtrate can be achieved by concentrated nitric acid/ferric nitrate sequestration of oxalate. Organic complexants do not appear practical to sequester plutonium. Testing is proposed to confirm the literature and calculation findings of this review at projected operating conditions for the upcoming campaign.

Endolithic microbial communities in carbonate precipitates from serpentinite-hosted hyperalkaline springs of the Voltri Massif (Ligurian Alps, Northern Italy).

Science.gov (United States)

Quéméneur, Marianne; Palvadeau, Alexandra; Postec, Anne; Monnin, Christophe; Chavagnac, Valérie; Ollivier, Bernard; Erauso, Gaël

2015-09-01

The Voltri Massif is an ophiolitic complex located in the Ligurian Alps close to the city of Genova (Northern Italy) where several springs discharge high pH (up to 11.7), low salinity waters produced by the active serpentinization of the ultramafic basement. Mixing of these hyperalkaline waters with the river waters along with the uptake of atmospheric carbon dioxide forms brownish carbonate precipitates covering the bedrock at the springs. Diverse archaeal and bacterial communities were detected in these carbonate precipitates using 454 pyrosequencing analyses of 16S ribosomal RNA (rRNA) genes. Archaeal communities were dominated by members of potential methane-producing and/or methane-oxidizing Methanobacteriales and Methanosarcinales (Euryarchaeota) together with ammonia-oxidizing Nitrososphaerales (Thaumarchaeota) similar to those found in other serpentinization-driven submarine and terrestrial ecosystems. Bacterial communities consisted of members of the Proteobacteria, Actinobacteria, Planctomycetes, Bacteroidetes, Chloroflexi, and Verrucomicrobia phyla, altogether accounting for 92.2% of total retrieved bacterial 16S rRNA gene sequences. Amongst Bacteria, potential chemolithotrophy was mainly associated with Alpha- and Betaproteobacteria classes, including nitrogen-fixing, methane-oxidizing or hydrogen-oxidizing representatives of the genera Azospirillum, Methylosinus, and Hydrogenophaga/'Serpentinomonas', respectively. Besides, potential chemoorganotrophy was attributed mainly to representatives of Actinobacteria and Planctomycetales phyla. The reported 16S rRNA gene data strongly suggested that hydrogen, methane, and nitrogen-based chemolithotrophy can sustain growth of the microbial communities inhabiting the carbonate precipitates in the hyperalkaline springs of the Voltri Massif, similarly to what was previously observed in other serpentinite-hosted ecosystems.

Plasticity of alloys strengthened with nano-precipitation

International Nuclear Information System (INIS)

Praud, M.

2012-01-01

As part of the development of the new generation of nuclear power plant, especially sodium-cooled fast reactors (SFR), oxide dispersion strengthened (ODS) steels are considered as potential candidates for cladding materials. Their main advantages are their excellent dimensional stability under irradiation, thanks to their body centered cubic structure, and their high thermal creep resistance due to the nano-particles. The aim of this work is to understand the plasticity of such materials through a multiscale approach. First, the microstructure of 9% and 14% Cr ODS steels has been finely characterized. Then, their mechanical behavior has been studied through tensile tests and creep tests. In addition, in situ Transmission Electron Microscopy straining experiments have been carried out to observe the dynamic behavior at a finer scale. This work emphasizes an evolution of the deformation and damage mechanisms with temperature. At room temperature, a mechanism with a strong intragranular contribution is noticed. At high temperature, an increase in the intergranular component has been pointed out. Consequently, it leads to more severe damage. Finally, the hardening role of the precipitates on the mechanical properties and the plasticity has been evaluated thanks to a 'model' material, without precipitate. (author) [fr

Preparation of (U, Gd)O2 by inverse co-precipitation in nitric solutions. Study of homogeneity and process optimization

International Nuclear Information System (INIS)

Marchi, Daniel E.; Menghini, Jorge E.; Trimarco, Viviana G.

1999-01-01

The inverse co-precipitation method has been used at the laboratory level to produce uranium - gadolinium mixed oxides. The formation of a mixed phase in the precipitates has been determined as well as the occurrence of only one phase in the sintered pellets, corresponding to a gadolinium - uranium solution. Moreover, a modification in the calcination-reduction stage was introduced that allows the elimination of the fissures previously detected in the sintered pellets

Interannual variation of annual precipitation and urban effect on precipitation in the Beijing region

Institute of Scientific and Technical Information of China (English)

无

2007-01-01

The large scale character of the interannual variation of precipitation and the urban effect on local annual precipitation anomaly are investigated in this paper based on the 1960-2000 annual precipitation observations at 20 stations in the Beijing region. The results show that: the annual precipitation in the Beijing region possesses the large scale variation character with the linear trend of - 1.197/10 yr, which corresponds to a total reduction of 27.82 mm in annual precipitation in the 41 years; the local annual precipitation anomalies (percent of the normal 1960-2000) show a positive center near the urban area, i.e. urban precipitation island (UPI), whose intensity increases with the linear trend of 0. 6621%/10 yr, opposite to the interannual trend of large scale precipitation over the Beijing region; changes in the UPI are also associated with the intensity of synoptic processes of precipitation, and when the synoptic processes are strong (wet years), the intensity of UPI strengthens, while the synoptic processes are weak (dry years), and the UPI disappears in the Beijing region.

DISCHARGE OXIDE STORAGE CAPACITY AND VOLTAGE LOSS IN LI-AIR BATTERY

International Nuclear Information System (INIS)

Wang, Yun; Wang, Zhe; Yuan, Hao; Li, Tianqi

2015-01-01

Air cathodes, where oxygen reacts with Li ions and electrons with discharge oxide stored in their pore structure, are often considered as the most challenging component in nonaqueous Lithium-air batteries. In non-aqueous electrolytes, discharge oxides are usually insoluble and hence precipitate at local reaction site, raising the oxygen transport resistance in the pore network. Due to their low electric conductivity, their presence causes electrode passivation. This study aims to investigate the air cathode’s performance through analytically obtaining oxygen profiles, modeling electrode passivation, evaluating the transport polarization raised by discharge oxide precipitate, and developing analytical formulas for insoluble Li oxides storage capacity. The variations of cathode quantities, including oxygen content and temperature, are evaluated and related to a single dimensionless parameter — the Damköhler Number (Da). An approximate model is developed to predict discharge voltage loss, along with validation against two sets of experimental data. Air cathode properties, including tortuosity, surface coverage factor and the Da number, and their effects on the cathode’s capacity of storing Li oxides are formulated and discussed.

A preliminary study on coloring mechanism of Jun copper red glaze

International Nuclear Information System (INIS)

Tian Shibing; Liu Yuzhen; Zhang Maolin; Wang Lihua; Wang Cangsui; Xie Yaning

2009-01-01

The origin of a red color glazes decorated on the ancient Jun porcelain has been attributed to the presence of combined copper clusters and cuprous oxide, or cuprous oxide alone. For better understanding of the color-forming mechanism, X-ray absorption at the Cu-edge by the red area of a Jun porcelain shard was carried out. By comparing the XANFS spectra of the sample with metal copper and cubic Cu 2 O, we found that the spectra of the red layer of sample were similar to the spectrum combination of 37% Cu 2 O and 63% metal copper,while the spectra from surface of the red spot mainly resembled that of cubic Cu 2 O. The EXAFS results showed that monovalence copper cations were isolated in the glaze matrix, and copper atoms were formed to metallic copper clusters or mutimers dominantly distributed in the inner layer. These can be responsible to the optical properties of the red decoration with the presence of colloidal composition containing copper particles and the Cu + ions. In conclusion, a preliminary non-destructive elemental analysis using synchrotron radiation-induce X-ray fluorescence (SR-XRF) is demonstrated, and mechanism about the formation of the complicated structures is discussed. (authors)

Uptake of seed-applied copper by maize and the effects on seed vigor

Directory of Open Access Journals (Sweden)

Marcos Altomani Neves Dias

2015-01-01

Full Text Available Seed treatment is a low-cost and efficacious method to deliver a diversity of compounds to field crops. This study evaluated the uptake of seed-applied Cu by maize and the effect on seed vigor. The treatments were composed of a control (untreated seeds and five dosages of Cu: 0.11, 0.22, 0.44, 0.88 and 1.76 mg Cu seed–1, applied as cuprous oxide and copper oxychloride formulations. Seedling emergence and the speed of seedling emergence were determined in three periods: 1, 60 and 120 days after Cu application. Evaluations of root and shoot dry mass, Cu tissue concentration and efficiencies of Cu uptake and incorporation were conducted with two-leaf stage maize plants. Seed-applied Cu reduces the speed of maize seedling emergence, while the final emergence percentage is not affected. Shoot dry mass tends to increase with the application of Cu, while there is no interference on root dry mass within the dosages tested. Cu tissue concentration of both roots and shoots increases as higher dosages of Cu are applied to seeds, with higher accumulation in roots. Cuprous oxide promotes higher uptake of Cu by maize roots compared to copper oxychloride.

Dynamic process model of a plutonium oxalate precipitator. Final report

Energy Technology Data Exchange (ETDEWEB)

Miller, C.L.; Hammelman, J.E.; Borgonovi, G.M.

1977-11-01

In support of LLL material safeguards program, a dynamic process model was developed which simulates the performance of a plutonium (IV) oxalate precipitator. The plutonium oxalate precipitator is a component in the plutonium oxalate process for making plutonium oxide powder from plutonium nitrate. The model is based on state-of-the-art crystallization descriptive equations, the parameters of which are quantified through the use of batch experimental data. The dynamic model predicts performance very similar to general Hanford oxalate process experience. The utilization of such a process model in an actual plant operation could promote both process control and material safeguards control by serving as a baseline predictor which could give early warning of process upsets or material diversion. The model has been incorporated into a FORTRAN computer program and is also compatible with the DYNSYS 2 computer code which is being used at LLL for process modeling efforts.

Dynamic process model of a plutonium oxalate precipitator. Final report

International Nuclear Information System (INIS)

Miller, C.L.; Hammelman, J.E.; Borgonovi, G.M.

1977-11-01

In support of LLL material safeguards program, a dynamic process model was developed which simulates the performance of a plutonium (IV) oxalate precipitator. The plutonium oxalate precipitator is a component in the plutonium oxalate process for making plutonium oxide powder from plutonium nitrate. The model is based on state-of-the-art crystallization descriptive equations, the parameters of which are quantified through the use of batch experimental data. The dynamic model predicts performance very similar to general Hanford oxalate process experience. The utilization of such a process model in an actual plant operation could promote both process control and material safeguards control by serving as a baseline predictor which could give early warning of process upsets or material diversion. The model has been incorporated into a FORTRAN computer program and is also compatible with the DYNSYS 2 computer code which is being used at LLL for process modeling efforts

Ytterbia doped nickel–manganese mixed oxide catalysts for liquid phase oxidation of benzyl alcohol

Directory of Open Access Journals (Sweden)

S.S.P. Sultana

2017-11-01

Full Text Available Nickel–manganese mixed oxides doped with 1, 3, 5 mol% ytterbia have been prepared by co-precipitation method and used in the catalytic oxidation of benzyl alcohol. Catalytic activity of these oxides calcined at 400 °C and 500 °C was studied for selective oxidation of benzyl alcohol to the corresponding aldehyde using molecular oxygen as an oxidizing agent. The results showed that thermally stable 5 mol% ytterbia doped nickel–manganese oxide [Yb2O3-(5%-Ni6MnO8] exhibited highest catalytic performance when it was calcined at 400 °C. A 100% conversion of the benzyl alcohol was achieved with >99% selectivity to benzaldehyde within a reaction period of 5 h at 100 °C. The mixed oxide prepared has been characterized by scanning election microscopy (SEM and energy dispersive X-ray analysis (EDXA, X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FT-IR, thermogravimetric analysis (TGA, Brunauer–Emmett–Teller (BET and temperature programed reduction (H2-TPR.

Investigation of carrier oil stabilized iron oxide nanoparticles and its ...

African Journals Online (AJOL)

Iron oxide nanoparticles were synthesized by co-precipitation method. The polyunsaturated carrier oil (flaxseed oil) is used as a stabilizing agent for iron oxide nanoparticles. Kirby Bauer method was used to investigate the antibiotic sensitivity of carrier oil stabilized and uncoated SPIONs at 10 and 20 μg/L on Gram-positive ...

Precipitation of Oriented Rutile and Ilmenite Needles in Garnet, Northeastern Connecticut, USA: Evidence for Extreme Metamorphic Conditions?

Science.gov (United States)

Ague, J. J.; Eckert, J. O.

2011-12-01

We report the discovery of oriented needles of rutile and, less commonly, ilmenite in the cores of garnets from northeastern CT, USA. The rocks preserve granulite facies mineral assemblages, form part of the Merrimack Synclinorium, and underwent metamorphism and deformation during the Acadian orogeny. The needles appear identical to those reported from a number of extreme P-T environments worldwide, including UHP metamorphic rocks, high-P granulites, and garnet peridotites. The needles are predominantly oriented along directions in garnet. The long axes of the rutile needles commonly do not go extinct parallel to the cross hairs under cross-polarized light (e.g., Griffin et al., 1971). This anomalous extinction indicates that the needles do not preserve a specific crystallographic relationship with their garnet hosts (e.g., Hwang et al., 2007). The needles range from a few hundred nm to a few um in diameter, and can be mm-scale in length. Micrometer-scale plates of rutile, srilankite and crichtonite have also been observed in some garnets together with the Fe-Ti oxide needles. Several origins for the needles have been proposed in the literature; we investigate the hypothesis that they precipitated in situ from originally Ti-rich garnet. Chemical profiles across garnets indicate that some retain Ti zoning, with elevated-Ti concentrations in the cores dropping to low values in the rims. For these zoned garnets, high-resolution, 2-D chemical mapping using the JEOL JXA-8530F field emission gun electron microprobe at Yale University reveals that the needles are surrounded by well-defined Ti-depletion halos. Chemical profiles also document strong depletions of Cr (which is present in both rutile and ilmenite) directly adjacent to needles. The observed Ti-depletions demonstrate that the needles precipitated from Ti-bearing garnet, probably during cooling and/or decompression associated with exhumation. The rutile precipitates must be largely incoherent with respect to the

Complex electrical monitoring of biopolymer and iron mineral precipitation for microbial enhanced hydrocarbon recovery

Science.gov (United States)

Wu, Y.; Hubbard, C. G.; Dong, W.; Hubbard, S. S.

2011-12-01

experiment and is correlated with the accumulation of dextran in the column. The changes of the electrical signals are interpreted to be due to surface masking of sand grains by dextran that reduces polarizable surface area of the sand grains. A second experiment was conducted to evaluate the sensitivity of electrical geophysical methods to iron mineral precipitation as an alternative plugging mechanism. Although anaerobic iron oxidation coupled with nitrate reduction is the targeted process, aerobic experiments were first conducted as a simplified case without biologically related effects. In this experiment, iron minerals were precipitated through oxidation of ferrous iron by oxygen. Changes in geophysical signals as well as hydraulic permeability across the column were measured. Quantification of iron mineral precipitation was carried out through mass balance and the precipitate morphology and mineralogy were analyzed with optical and electron microscopy and XRD at the end of the experiments. Correlation between geophysical signature and iron mineral precipitation was established and will be used to guide the next experiment, which will focus on microbial facilitated iron oxidation coupled with nitrate reduction under anaerobic conditions.

Thermally induced transformations of iron oxide stabilised APC residues from waste incineration

DEFF Research Database (Denmark)

Sørensen, Mette Abildgaard; Koch, C.B.

2001-01-01

Air pollution control (APC) facilities at waste incinerator plants produce large quantities of solid residues rich in salts and heavy metals. Heavy metals are readily released to water from the residues and it has, therefore, been found suitable to apply a rapid co-precipitation/adsorption process...... as a means to immobilize the toxic elements. In the 'Ferrox process', this immobilization is based on co-precipitation with an Fe(III) oxide formed by oxidation of Fe(II) by air in an aqueous slurry with the APC residue at alkaline pH. In this work we have undertaken a Mossbauer spectroscopy study of the Fe...

Selective carbon monoxide oxidation over Ag-based composite oxides

Energy Technology Data Exchange (ETDEWEB)

Guldur, C. [Gazi University, Ankara (Turkey). Chemical Engineering Department; Balikci, F. [Gazi University, Ankara (Turkey). Institute of Science and Technology, Environmental Science Department

2002-02-01

We report our results of the synthesis of 1 : 1 molar ratio of the silver cobalt and silver manganese composite oxide catalysts to remove carbon monoxide from hydrogen-rich fuels by the catalytic oxidation reaction. Catalysts were synthesized by the co-precipitation method. XRD, BET, TGA, catalytic activity and catalyst deactivation studies were used to identify active catalysts. Both CO oxidation and selective CO oxidation were carried out in a microreactor using a reaction gas mixture of 1 vol% CO in air and another gas mixture was prepared by mixing 1 vol% CO, 2 vol% O{sub 2}, 84 vol% H{sub 2}, the balance being He. 15 vol% CO{sub 2} was added to the reactant gas mixture in order to determine the effect of CO{sub 2}, reaction gases were passed through the humidifier to determine the effect of the water vapor on the oxidation reaction. It was demonstrated that metal oxide base was decomposed to the metallic phase and surface areas of the catalysts were decreased when the calcination temperature increased from 200{sup o}C to 500{sup o}C. Ag/Co composite oxide catalyst calcined at 200{sup o}C gave good activity at low temperatures and 90% of CO conversion at 180{sup o}C was obtained for the selective CO oxidation reaction. The addition of the impurities (CO{sub 2} or H{sub 2}O) decreased the activity of catalyst for selective CO oxidation in order to get highly rich hydrogen fuels. (author)

Oxidation films morphology; Sur la morphologie des pellicules d'oxydation

Energy Technology Data Exchange (ETDEWEB)

Paidassi, J [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

1960-07-01

After studying the oxidation of several pure polyvalent metals (Fe, Cu, Mn, Ni, U) and of their oxides at high temperature and atmospheric pressure, the author suggests how to modify the usual representation of the oxide film (a piling of different oxide layers, homogeneous on a micrographic scale with a equi-axial crystallisation, free of mechanical tensions, with flat boundary surfaces) to have it nearer to reality. In this first part, the author exposes the study of the real micrographic structure of the oxidation film and gives examples of precipitation in the oxides during the cooling of the oxidised sample. (author) [French] En se basant sur les etudes qu'il a faites sur l'oxydation aux temperatures elevees et a la pression atmospherique de quelques metaux purs a valences multiples (Fe, Cu, Mn, Ni, U), et de leurs oxydes, l'auteur suggere comment le schema qui representerait la pellicule comme etant une superposition de diverses couches d'oxydes, homogenes micrographiquement, a cristallisations equiaxes, depourvues de tensions mecaniques et separees par des interfaces plans, doit etre modifie pour s'ajuster a la realite. Dans cette premiere partie, l'auteur etudie la structure micrographique reelle des pellicules d'oxydation et donne des exemples de precipitation dans les oxydes au cours du refroidissement des echantillons oxydes. (auteur)

Metal insulator semiconductor solar cell devices based on a Cu{sub 2}O substrate utilizing h-BN as an insulating and passivating layer

Energy Technology Data Exchange (ETDEWEB)

Ergen, Onur; Gibb, Ashley; Vazquez-Mena, Oscar; Zettl, Alex, E-mail: azettl@berkeley.edu [Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Kavli Energy Nanosciences Institute at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Regan, William Raymond [Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2015-03-09

We demonstrate cuprous oxide (Cu{sub 2}O) based metal insulator semiconductor Schottky (MIS-Schottky) solar cells with efficiency exceeding 3%. A unique direct growth technique is employed in the fabrication, and hexagonal boron nitride (h-BN) serves simultaneously as a passivation and insulation layer on the active Cu{sub 2}O layer. The devices are the most efficient of any Cu{sub 2}O based MIS-Schottky solar cells reported to date.

Zinc oxide nanoparticles for water disinfection

Directory of Open Access Journals (Sweden)

Emelita Asuncion S. Dimapilis

2018-03-01

Full Text Available The world faces a growing challenge for adequate clean water due to threats coming from increasing demand and decreasing supply. Although there are existing technologies for water disinfection, their limitations, particularly the formation of disinfection-by-products, have led to researches on alternative methods. Zinc oxide, an essential chemical in the rubber and pharmaceutical industries, has attracted interest as antimicrobial agent. In nanoscale, zinc oxide has shown antimicrobial properties which make its potential great for various applications. This review discusses the synthesis of zinc oxide with focus on precipitation method, its antimicrobial property and the factors affecting it, disinfection mechanisms, and the potential application to water disinfection.

Effective Assimilation of Global Precipitation

Science.gov (United States)

Lien, G.; Kalnay, E.; Miyoshi, T.; Huffman, G. J.

2012-12-01

Assimilating precipitation observations by modifying the moisture and sometimes temperature profiles has been shown successful in forcing the model precipitation to be close to the observed precipitation, but only while the assimilation is taking place. After the forecast start, the model tends to "forget" the assimilation changes and lose their extra skill after few forecast hours. This suggests that this approach is not an efficient way to modify the potential vorticity field, since this is the variable that the model would remember. In this study, the ensemble Kalman filter (EnKF) method is used to effectively change the potential vorticity field by allowing ensemble members with better precipitation to receive higher weights. In addition to using an EnKF, two other changes in the precipitation assimilation process are proposed to solve the problems related to the highly non-Gaussian nature of the precipitation variable: a) transform precipitation into a Gaussian distribution based on its climatological distribution, and b) only assimilate precipitation at the location where some ensemble members have positive precipitation. The idea is first tested by the observing system simulation experiments (OSSEs) using SPEEDY, a simplified but realistic general circulation model. When the global precipitation is assimilated in addition to conventional rawinsonde observations, both the analyses and the medium range forecasts are significantly improved as compared to only having rawinsonde observations. The improvement is much reduced when only modifying the moisture field with the same approach, which shows the importance of the error covariance between precipitation and all other model variables. The effect of precipitation assimilation is larger in the Southern Hemisphere than that in the Northern Hemisphere because the Northern Hemisphere analyses are already accurate as a result of denser rawinsonde stations. Assimilation of precipitation using a more comprehensive

Precipitation in partially stabilized zirconia

International Nuclear Information System (INIS)

Bansal, G.K.

1975-01-01

Transmission electron microscopy was used to study the substructure of partially stabilized ZrO 2 (PSZ) samples, i.e., 2-phase systems containing both cubic and monoclinic modifications of zirconia, after various heat treatments. Monoclinic ZrO 2 exists as (1) isolated grains within the polycrystalline aggregate (a grain- boundary phase) and (2) small plate-like particles within cubic grains. These intragranular precipitates are believed to contribute to the useful properties of PSZ via a form of precipitation hardening. These precipitates initially form as tetragonal ZrO 2 , with a habit plane parallel to the brace 100 brace matrix planes. The orientation relations between the tetragonal precipitates and the cubic matrix are brace 100 brace/sub matrix/ 2 parallel brace 100 brace /sub precipitate/ or (001)/sub precipitate/ and broken bracket 100 broken bracket/sub matrix/ 2 parallel broken bracket 100 broken bracket/sub precipitate/ or [001]/sub precipitate/. (U.S.)

Formation of iron oxides from acid mine drainage and magnetic separation of the heavy metals adsorbed iron oxides

Energy Technology Data Exchange (ETDEWEB)

Kwon, Hee Won; Kim, Jeong Jin; Kim, Young Hun [Andong National University, Andong (Korea, Republic of); Ha, Dong Woo [Korea Electrotechnology Research Institute, Changwon (Korea, Republic of)

2016-03-15

There are a few thousand abandoned metal mines in South Korea. The abandoned mines cause several environmental problems including releasing acid mine drainage (AMD), which contain a very high acidity and heavy metal ions such as Fe, Cu, Cd, Pb, and As. Iron oxides can be formed from the AMD by increasing the solution pH and inducing precipitation. Current study focused on the formation of iron oxide in an AMD and used the oxide for adsorption of heavy metals. The heavy metal adsorbed iron oxide was separated with a superconducting magnet. The duration of iron oxide formation affected on the type of mineral and the degree of magnetization. The removal rate of heavy metal by the adsorption process with the formed iron oxide was highly dependent on the type of iron oxide and the solution pH. A high gradient magnetic separation (HGMS) system successfully separated the iron oxide and harmful heavy metals.

Evaluation of the suspening property of Grewia gum in zinc oxide ...

African Journals Online (AJOL)

The suspending property of grewia gum in zinc oxide suspension was evaluated. The gum was extracted by maceration, filtration, precipitation and drying techniques. It was used at 0.3 to 1% w/v as a suspending agent for zinc oxide. Sodiumcarboxymethylcellulose (SCMC) and tragacanth were used as basis for ...

Obtaining ZnO nanocrystalline through methods of combustion and precipitation

International Nuclear Information System (INIS)

Garcia, A.P.; Guaglianoni, W.C.; Cunha, M.A.; Basegio, T.M.; Bergmann, C.P.

2012-01-01

Zinc oxide is important technological applications in rubber and industrial paints. The chemical properties and microstructure of ZnO powder depends on the synthesis method employed. In this work, it was obtained nanosized ZnO using different synthesis processes, such as solution combustion and precipitation, varying the concentrations of reactants and the working temperature. The obtained powders were characterized by SEM, BET, XRD, crystallite size determination and thermal analysis (TGA and DTA). It was possible to obtain nanosized ZnO with the methods used. (author)

Oxidation and Precipitation of Sulfide in Sewer Networks

DEFF Research Database (Denmark)

Nielsen, A. H.

risks and corrosion of concrete and metals. Most of the problems relate to the buildup of hydrogen sulfide in the atmosphere of sewer networks. In this respect, the processes of the sulfur cycle are of fundamental importance in ultimately determining the extent of such problems. This study focused...... calibrated and validated against field data. In the extension to the WATS model, sulfur transformations were described by six processes: 1. Sulfide production taking place in the biofilm and sediments covering the permanently wetted sewer walls; 2. Biological sulfide oxidation in the permanently wetted...... to the sewer atmosphere, potentially resulting in concrete corrosion. The extended WATS model represents a major improvement over previously developed models for prediction of sulfide buildup in sewer networks. Compared to such models, the major processes governing sulfide buildup in sewer networks...

Synthesis and Characterization of Perovskite Type La1-xSrxAlO3-sigma(0<=X<=0.3) by Co-Precipitation Method

International Nuclear Information System (INIS)

Mahmoud, O.; Abderezak, G.

2015-01-01

This work shows the electrochemical activity of O/sub 2/ evolution reaction in KOH of perovskite type- aluminate oxide (La/sub 1-x/Sr/sub x/AlO/sub 3-sigma/ with x = 0, 0.1, 0.2, 0.3). La/sub 1-x/Sr/sub x/AlO/sub 3-sigma/ (0precipitation method. The white precipitates were then washed in distilled water by centrifugation, and calcined at 1000/degree C/ for 6h, the pure phase was characterized by X-ray diffraction (XRD), thermal gravimetric analysis and differential thermal (TG/DSC), Fourier transform infrared spectroscopy (FTIR), specific surface area (BET). The MEB micrographs are shown of the spherical grains and uniform agglomeration of the grains. The oxide powders were used as the films to form a support on Ni/oxides. Oxygen evolution on each oxide catalyst was signed in the cyclic voltammetry with +- 15 V range and the electrochemical impedance in the equivalent of 100 kHz. The results point out the electrode activity and stability of the x = 0.3 composition. (author)

Correlative Microscopy of Alpha Prime Precipitation in Neutron-Irradiated Fe-Cr-Al Alloys

Energy Technology Data Exchange (ETDEWEB)

Briggs, Samuel A. [Univ. of Wisconsin, Madison, WI (United States)

2016-12-01

Fe-Cr-Al alloys are currently being considered for accident tolerant light water reactor fuel cladding applications due to their superior high temperature oxidation and corrosion resistance compared to Zr-based alloys. This work represents the current state-of-the-art on both techniques for analysis of α' precipitate microstructures and the processes and mechanisms governing its formation in neutron-irradiated Fe-Cr-Al alloys.

Precipitation of {gamma}' phase in {delta}-precipitated Alloy 718 during deformation at elevated temperatures

Energy Technology Data Exchange (ETDEWEB)

Nalawade, S.A. [Structural Metallurgy Section, Mechanical Metallurgy Section, Bhabha Atomic Research Centre, Mumbai 400085 (India); Sundararaman, M., E-mail: msraman@barc.gov.in [Structural Metallurgy Section, Mechanical Metallurgy Section, Bhabha Atomic Research Centre, Mumbai 400085 (India); Singh, J.B.; Verma, A.; Kishore, R. [Structural Metallurgy Section, Mechanical Metallurgy Section, Bhabha Atomic Research Centre, Mumbai 400085 (India)

2010-05-15

Alloy 718 samples aged to precipitate only {delta} particles (with maximum volume fraction) when tensile deformed to fracture at elevated temperatures revealed precipitation of {gamma}' and {gamma}'' phases. The {gamma}' precipitation was found to precede the {gamma}'' phase precipitation unlike in the case of specimens subjected to standard ageing treatment where both the {gamma}' and the {gamma}'' phases precipitate simultaneously. This sequence is explained on the basis of the relative concentration of Al, Ti and Nb in the matrix of {delta} precipitated Alloy 718 microstructure. The precipitation sequence was consistent with the Cozar and Pineau's model that predicts such sequences on the basis of (Al + Ti) to Nb atom ratios.

Enhanced chlorine dioxide decay in the presence of metal oxides: Relevance to drinking water distribution systems

KAUST Repository

Liu, Chao; von Gunten, Urs; Croue, Jean-Philippe

2013-01-01

Chlorine dioxide (ClO2) decay in the presence of typical metal oxides occurring in distribution systems was investigated. Metal oxides generally enhanced ClO2 decay in a second-order process via three pathways: (1) catalytic disproportionation with equimolar formation of chlorite and chlorate, (2) reaction to chlorite and oxygen, and (3) oxidation of a metal in a reduced form (e.g., cuprous oxide) to a higher oxidation state. Cupric oxide (CuO) and nickel oxide (NiO) showed significantly stronger abilities than goethite (α-FeOOH) to catalyze the ClO2 disproportionation (pathway 1), which predominated at higher initial ClO2 concentrations (56-81 μM). At lower initial ClO2 concentrations (13-31 μM), pathway 2 also contributed. The CuO-enhanced ClO2 decay is a base-assisted reaction with a third-order rate constant of 1.5 × 10 6 M-2 s-1 in the presence of 0.1 g L -1 CuO at 21 ± 1 C, which is 4-5 orders of magnitude higher than in the absence of CuO. The presence of natural organic matter (NOM) significantly enhanced the formation of chlorite and decreased the ClO 2 disproportionation in the CuO-ClO2 system, probably because of a higher reactivity of CuO-activated ClO2 with NOM. Furthermore, a kinetic model was developed to simulate CuO-enhanced ClO 2 decay at various pH values. Model simulations that agree well with the experimental data include a pre-equilibrium step with the rapid formation of a complex, namely, CuO-activated Cl2O4. The reaction of this complex with OH- is the rate-limiting and pH-dependent step for the overall reaction, producing chlorite and an intermediate that further forms chlorate and oxygen in parallel. These novel findings suggest that the possible ClO2 loss and the formation of chlorite/chlorate should be carefully considered in drinking water distribution systems containing copper pipes. © 2013 American Chemical Society.

Enhanced chlorine dioxide decay in the presence of metal oxides: Relevance to drinking water distribution systems

KAUST Repository

Liu, Chao

2013-07-19

Chlorine dioxide (ClO2) decay in the presence of typical metal oxides occurring in distribution systems was investigated. Metal oxides generally enhanced ClO2 decay in a second-order process via three pathways: (1) catalytic disproportionation with equimolar formation of chlorite and chlorate, (2) reaction to chlorite and oxygen, and (3) oxidation of a metal in a reduced form (e.g., cuprous oxide) to a higher oxidation state. Cupric oxide (CuO) and nickel oxide (NiO) showed significantly stronger abilities than goethite (α-FeOOH) to catalyze the ClO2 disproportionation (pathway 1), which predominated at higher initial ClO2 concentrations (56-81 μM). At lower initial ClO2 concentrations (13-31 μM), pathway 2 also contributed. The CuO-enhanced ClO2 decay is a base-assisted reaction with a third-order rate constant of 1.5 × 10 6 M-2 s-1 in the presence of 0.1 g L -1 CuO at 21 ± 1 C, which is 4-5 orders of magnitude higher than in the absence of CuO. The presence of natural organic matter (NOM) significantly enhanced the formation of chlorite and decreased the ClO 2 disproportionation in the CuO-ClO2 system, probably because of a higher reactivity of CuO-activated ClO2 with NOM. Furthermore, a kinetic model was developed to simulate CuO-enhanced ClO 2 decay at various pH values. Model simulations that agree well with the experimental data include a pre-equilibrium step with the rapid formation of a complex, namely, CuO-activated Cl2O4. The reaction of this complex with OH- is the rate-limiting and pH-dependent step for the overall reaction, producing chlorite and an intermediate that further forms chlorate and oxygen in parallel. These novel findings suggest that the possible ClO2 loss and the formation of chlorite/chlorate should be carefully considered in drinking water distribution systems containing copper pipes. © 2013 American Chemical Society.

Synthesis of well-dispersed magnetic CoFe2O4 nanoparticles in cellulose aerogels via a facile oxidative co-precipitation method.

Science.gov (United States)

Wan, Caichao; Li, Jian

2015-12-10

With the increasing emphasis on green chemistry, it is becoming more important to develop environmentally friendly matrix materials for the synthesis of nanocomposites. Cellulose aerogels with hierarchical micro/nano-scale three-dimensional network beneficial to control and guide the growth of nanoparticles, are suitable as a class of ideal green nanoparticles hosts to fabricate multifunctional nanocomposites. Herein, a facile oxidative co-precipitation method was carried out to disperse CoFe2O4 nanoparticles in the cellulose aerogels matrixes, and the cellulose aerogels were prepared from the native wheat straw based on a green NaOH/polyethylene glycol solution. The mean diameter of the well-dispersed CoFe2O4 nanoparticles in the hybrid aerogels is 98.5 nm. Besides, the hybrid aerogels exhibit strong magnetic responsiveness, which could be flexibly actuated by a small magnet. And this feature also makes this class of magnetic aerogels possibly useful as recyclable adsorbents and some magnetic devices. Meanwhile, the mild green preparation method could also be extended to fabricate other miscellaneous cellulose-based nanocomposites. Copyright © 2015 Elsevier Ltd. All rights reserved.

Few multiyear precipitation-reduction experiments find a shift in the productivity-precipitation relationship.

Science.gov (United States)

Estiarte, Marc; Vicca, Sara; Peñuelas, Josep; Bahn, Michael; Beier, Claus; Emmett, Bridget A; Fay, Philip A; Hanson, Paul J; Hasibeder, Roland; Kigel, Jaime; Kröel-Dulay, Gyorgy; Larsen, Klaus Steenberg; Lellei-Kovács, Eszter; Limousin, Jean-Marc; Ogaya, Romà; Ourcival, Jean-Marc; Reinsch, Sabine; Sala, Osvaldo E; Schmidt, Inger Kappel; Sternberg, Marcelo; Tielbörger, Katja; Tietema, Albert; Janssens, Ivan A

2016-07-01

Well-defined productivity-precipitation relationships of ecosystems are needed as benchmarks for the validation of land models used for future projections. The productivity-precipitation relationship may be studied in two ways: the spatial approach relates differences in productivity to those in precipitation among sites along a precipitation gradient (the spatial fit, with a steeper slope); the temporal approach relates interannual productivity changes to variation in precipitation within sites (the temporal fits, with flatter slopes). Precipitation-reduction experiments in natural ecosystems represent a complement to the fits, because they can reduce precipitation below the natural range and are thus well suited to study potential effects of climate drying. Here, we analyse the effects of dry treatments in eleven multiyear precipitation-manipulation experiments, focusing on changes in the temporal fit. We expected that structural changes in the dry treatments would occur in some experiments, thereby reducing the intercept of the temporal fit and displacing the productivity-precipitation relationship downward the spatial fit. The majority of experiments (72%) showed that dry treatments did not alter the temporal fit. This implies that current temporal fits are to be preferred over the spatial fit to benchmark land-model projections of productivity under future climate within the precipitation ranges covered by the experiments. Moreover, in two experiments, the intercept of the temporal fit unexpectedly increased due to mechanisms that reduced either water loss or nutrient loss. The expected decrease of the intercept was observed in only one experiment, and only when distinguishing between the late and the early phases of the experiment. This implies that we currently do not know at which precipitation-reduction level or at which experimental duration structural changes will start to alter ecosystem productivity. Our study highlights the need for experiments with

DISSOLUTION OF LANTHANUM FLUORIDE PRECIPITATES

Science.gov (United States)

Fries, B.A.

1959-11-10

A plutonium separatory ore concentration procedure involving the use of a fluoride type of carrier is presented. An improvement is given in the derivation step in the process for plutonium recovery by carrier precipitation of plutonium values from solution with a lanthanum fluoride carrier precipitate and subsequent derivation from the resulting plutonium bearing carrier precipitate of an aqueous acidic plutonium-containing solution. The carrier precipitate is contacted with a concentrated aqueous solution of potassium carbonate to effect dissolution therein of at least a part of the precipitate, including the plutonium values. Any remaining precipitate is separated from the resulting solution and dissolves in an aqueous solution containing at least 20% by weight of potassium carbonate. The reacting solutions are combined, and an alkali metal hydroxide added to a concentration of at least 2N to precipitate lanthanum hydroxide concomitantly carrying plutonium values.

Similarities and Improvements of GPM Dual-Frequency Precipitation Radar (DPR upon TRMM Precipitation Radar (PR in Global Precipitation Rate Estimation, Type Classification and Vertical Profiling

Directory of Open Access Journals (Sweden)

Jinyu Gao

2017-11-01

Full Text Available Spaceborne precipitation radars are powerful tools used to acquire adequate and high-quality precipitation estimates with high spatial resolution for a variety of applications in hydrological research. The Global Precipitation Measurement (GPM mission, which deployed the first spaceborne Ka- and Ku-dual frequency radar (DPR, was launched in February 2014 as the upgraded successor of the Tropical Rainfall Measuring Mission (TRMM. This study matches the swath data of TRMM PR and GPM DPR Level 2 products during their overlapping periods at the global scale to investigate their similarities and DPR’s improvements concerning precipitation amount estimation and type classification of GPM DPR over TRMM PR. Results show that PR and DPR agree very well with each other in the global distribution of precipitation, while DPR improves the detectability of precipitation events significantly, particularly for light precipitation. The occurrences of total precipitation and the light precipitation (rain rates < 1 mm/h detected by GPM DPR are ~1.7 and ~2.53 times more than that of PR. With regard to type classification, the dual-frequency (Ka/Ku and single frequency (Ku methods performed similarly. In both inner (the central 25 beams and outer swaths (1–12 beams and 38–49 beams of DPR, the results are consistent. GPM DPR improves precipitation type classification remarkably, reducing the misclassification of clouds and noise signals as precipitation type “other” from 10.14% of TRMM PR to 0.5%. Generally, GPM DPR exhibits the same type division for around 82.89% (71.02% of stratiform (convective precipitation events recognized by TRMM PR. With regard to the freezing level height and bright band (BB height, both radars correspond with each other very well, contributing to the consistency in stratiform precipitation classification. Both heights show clear latitudinal dependence. Results in this study shall contribute to future development of spaceborne

Characterisation of a complex thin walled structure fabricated by selective laser melting using a ferritic oxide dispersion strengthened steel

Energy Technology Data Exchange (ETDEWEB)

Boegelein, Thomas, E-mail: t.boegelein@liv.ac.uk; Louvis, Eleftherios; Dawson, Karl; Tatlock, Gordon J.; Jones, Andy R.

2016-02-15

Oxide dispersion strengthened (ODS) alloys exhibit superior mechanical and physical properties due to the presence of nanoscopic Y(Al, Ti) oxide precipitates, but their manufacturing process is complex. The present study is aimed at further investigation of the application of an alternative, Additive Manufacturing (AM) technique, Selective Laser Melting (SLM), to the production of consolidated ODS alloy components. Mechanically alloyed PM2000 (ODS-FeCrAl) powders have been consolidated and a fine dispersion of Y-containing precipitates were observed in an as built thin-walled component, but these particles were typically poly-crystalline and contained a variety of elements including O, Al, Ti, Cr and Fe. Application of post-build heat treatments resulted in the modification of particle structures and compositions; in the annealed condition most precipitates were transformed to single crystal yttrium aluminium oxides. During the annealing treatment, precipitate distributions homogenised and localised variations in number density were diminished. The resulting volume fractions of those precipitates were 25–40% lower than have been reported in conventionally processed PM2000, which was attributed to Y-rich slag-like surface features and inclusions formed during SLM. - Highlights: • A wall structure was grown from ODS steel powder using selective laser melting. • A fine dispersion of nano-precipitates was apparent in as-build material. • Precipitates were multi-phased containing several elements, e.g. O, Ti, Al, Fe, Cr, Y. • Post-build annealing changed those into typically single-crystalline Y–Al–O. • The anneal also reduced and stabilised the volume fraction of precipitates to ~ 0.006.

Two-stage precipitation of plutonium trifluoride

International Nuclear Information System (INIS)

Luerkens, D.W.

1984-04-01

Plutonium trifluoride was precipitated using a two-stage precipitation system. A series of precipitation experiments identified the significant process variables affecting precipitate characteristics. A mathematical precipitation model was developed which was based on the formation of plutonium fluoride complexes. The precipitation model relates all process variables, in a single equation, to a single parameter that can be used to control particle characteristics

STRONTIUM PRECIPITATION

Science.gov (United States)

McKenzie, T.R.

1960-09-13

A process is given for improving the precipitation of strontium from an aqueous phosphoric-acid-containing solution with nickel or cobalt ferrocyanide by simultaneously precipitating strontium or calcium phosphate. This is accomplished by adding to the ferrocyanide-containing solution calcium or strontium nitrate in a quantity to yield a concentration of from 0.004 to 0.03 and adjusting the pH of the solution to a value of above 8.

Actinide removal from molten salts by chemical oxidation and salt distillation

Energy Technology Data Exchange (ETDEWEB)

McNeese, J.A.; Garcia, E.; Dole, V.R. [Los Alamos National Laboratory, NM (United States)] [and others

1995-10-01

Actinide removal from molten salts can be accomplished by a two step process where the actinide is first oxidized to the oxide using a chemical oxidant such as calcium carbonate or sodium carbonate. After the actinide is precipitated as an oxide the molten salt is distilled away from the actinide oxides leaving a oxide powder heel and an actinide free distilled salt that can be recycled back into the processing stream. This paper discusses the chemistry of the oxidation process and the physical conditions required to accomplish a salt distillation. Possible application of an analogous process sequence for a proposed accelerator driven transmutation molten salt process is also discussed.

Actinide removal from molten salts by chemical oxidation and salt distillation

International Nuclear Information System (INIS)

McNeese, James A.; Garcia, Eduardo; Dole, Vonda R.; Griego, Walter J.

1995-01-01

Actinide removal from molten salts can be accomplished by a two step process where the actinide is first oxidized to the oxide using a chemical oxidant such as calcium carbonate or sodium carbonate. After the actinide is precipitated as an oxide the molten salt is distilled away from the actinide oxides leaving a oxide powder heel and an actinide free distilled salt that can be recycled back into the processing stream. This paper discusses the chemistry of the oxidation process and the physical conditions required to accomplish a salt distillation. Possible application of an analogous process sequence for a proposed accelerator driven transmutation molten salt process is also discussed

Separation and purification of uranium product from thorium in thorex process by precipitation technique

International Nuclear Information System (INIS)

Ramanujam, A.; Dhami, P.S.; Gopalakrishnan, V.; Mukherjee, A.; Dhumwad, R.K.

1989-01-01

A sequential precipitation technique is reported for the separation of uranium and thorium present in the uranium product stream of a single cycle 5 per cent TBP Thorex Process. It involves the precipitation of thorium as oxalate in 1M HNO 3 medium at 60-70degC and after filtration, precipitation of uranium as ammonium diuranate at 80-90degC from the oxalate supernatant. This technique has several advantages over the ion-exchange process normally used for treating these products. In order to meet the varying feed conditions, this method has been tested for feeds containing 10 g/1 uranium and 1-50 g/1 thorium in 1-6M HNO 3 . Various parameters like feed acidities, uranium and thorium concentrations, excess oxalic acid concentrations in the oxalate supernatant, precipitation temperatures, precipitate wash volumes etc. have been optimised to obtain more than 99 per cent recovery of thorium and uranium as their oxides with less than 50 ppm uranium losses to ammonium diuranate filtrate. The distribution patterns of different fission products and stainless steel corrosion products during various steps of this procedure have also been studied. For simulating the actual Thorex plant scale operation, experiments have been conducted with 25g and 100g lots of uranium per batch. (author). 6 tabs., 8 figs., 22 refs

Global Precipitation Measurement (GPM) Mission: Precipitation Processing System (PPS) GPM Mission Gridded Text Products Provide Surface Precipitation Retrievals

Science.gov (United States)

Stocker, Erich Franz; Kelley, O.; Kummerow, C.; Huffman, G.; Olson, W.; Kwiatkowski, J.

2015-01-01

In February 2015, the Global Precipitation Measurement (GPM) mission core satellite will complete its first year in space. The core satellite carries a conically scanning microwave imager called the GPM Microwave Imager (GMI), which also has 166 GHz and 183 GHz frequency channels. The GPM core satellite also carries a dual frequency radar (DPR) which operates at Ku frequency, similar to the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar, and a new Ka frequency. The precipitation processing system (PPS) is producing swath-based instantaneous precipitation retrievals from GMI, both radars including a dual-frequency product, and a combined GMIDPR precipitation retrieval. These level 2 products are written in the HDF5 format and have many additional parameters beyond surface precipitation that are organized into appropriate groups. While these retrieval algorithms were developed prior to launch and are not optimal, these algorithms are producing very creditable retrievals. It is appropriate for a wide group of users to have access to the GPM retrievals. However, for researchers requiring only surface precipitation, these L2 swath products can appear to be very intimidating and they certainly do contain many more variables than the average researcher needs. Some researchers desire only surface retrievals stored in a simple easily accessible format. In response, PPS has begun to produce gridded text based products that contain just the most widely used variables for each instrument (surface rainfall rate, fraction liquid, fraction convective) in a single line for each grid box that contains one or more observations.This paper will describe the gridded data products that are being produced and provide an overview of their content. Currently two types of gridded products are being produced: (1) surface precipitation retrievals from the core satellite instruments GMI, DPR, and combined GMIDPR (2) surface precipitation retrievals for the partner constellation

Calcium Oxide Supported on Monoclinic Zirconia as a Highly Active Solid Base Catalyst

NARCIS (Netherlands)

Frey, A.M.; Haasterecht, van T.; Jong, de K.P.; Bitter, J.H.

2013-01-01

Calcium oxide supported on ZrO2 is a highly active catalyst for base-catalyzed reactions such as aldol-type reactions and transesterification reactions. The role of key parameters during preparation, that is, impregnation versus precipitation, heat treatment, and metal oxide loading on the basicity

DNAPL remediation with in situ chemical oxidation using potassium permanganate - Part I. Mineralogy of Mn oxide and its dissolution in organic acids

Science.gov (United States)

Li, X. David; Schwartz, Franklin W.

2004-01-01

Previous studies on in situ chemical oxidation of trichloroethylene (TCE) with potassium permanganate indicated that the solid reaction product, Mn oxide, could reduce the permeability of the porous medium and impact the success of dense non-aqueous phase liquid (DNAPL) removal. In order to address the issue of permeability reduction caused by precipitation, this study investigated the mineralogy of Mn oxides and the possibilities of removing the solid precipitates by dissolution. The solid reaction product from the oxidation of TCE by permanganate is semi-amorphous potassium-rich birnessite, which has a layered mineral structure with an interlayer spacing of 7.3 Å. The chemical formula is K 0.854Mn 1.786O 4·1.55H 2O. It has a relatively small specific surface area at 23.6±0.82 m 2/g. Its point of zero charge (pzc) was measured as 3.7±0.4. This birnessite is a relatively active species and could participate in various reactions with existing organic and inorganic matter. The dissolution kinetics of Mn oxide was evaluated in batch experiments using solutions of citric acid, oxalic acid, and ethylenediaminetetraacetic acid (EDTA). Initial dissolution rates were determined to be 0.126 mM/m 2/h for citric acid, 1.35 mM/m 2/h for oxalic acid, and 5.176 mM/m 2/h for EDTA. These rates compare with 0.0025 mM/m 2/h for nitric acid at pH=2. Organic acids dissolve Mn oxide quickly. Reaction rates increase with acid concentration, as tested with citric acid. The dissolution mechanism likely involves proton and ligand-promoted dissolution and reductive dissolution. Citric and oxalic acid can induce ligand-promoted dissolution, while EDTA can induce ligand-promoted and reductive dissolutions. At low pH, proton-promoted dissolution seems to occur with all the acids tested, but this process is not dominant. Reductive dissolution appears to be the most effective process in dissolving the solid, followed by ligand-promoted dissolution. These experiments indicate the significant

Preparation and characterization of sugar cane bagasse fiber modified with nanoparticles of zirconium oxide

International Nuclear Information System (INIS)

Carvalho, K.C.C. de; Mulinari, D.R.; Voorwald, H.C.J.; Cioffi, M.O.H.

2010-01-01

The sugar cane bagasse fiber are renewable materials and have great application potential when used as reinforcement in a polymer matrix to give rise to composite materials and as supports for adsorption of heavy metals. This paper therefore describes the preparation and characterization of bleached and hydrated zirconium oxide modified sugar cane bagasse fiber by conventional precipitation method. Through the technique of electron microscopy we observed the presence of oxide nanoparticles on the fiber surface, proving the efficiency of the conventional precipitation method. With the X-ray diffraction analysis it was determined a decrease of 6.2% in the crystallinity index of modified fibers when compared to the bleached fibers showing the deposition of amorphous zirconium oxide on the fiber surface. (author)

Probability of occurrence of monthly and seasonal winter precipitation over Northwest India based on antecedent-monthly precipitation

Science.gov (United States)

Nageswararao, M. M.; Mohanty, U. C.; Dimri, A. P.; Osuri, Krishna K.

2018-05-01

Winter (December, January, and February (DJF)) precipitation over northwest India (NWI) is mainly associated with the eastward moving mid-latitude synoptic systems, western disturbances (WDs), embedded within the subtropical westerly jet (SWJ), and is crucial for Rabi (DJF) crops. In this study, the role of winter precipitation at seasonal and monthly scale over NWI and its nine meteorological subdivisions has been analyzed. High-resolution (0.25° × 0.25°) gridded precipitation data set of India Meteorological Department (IMD) for the period of 1901-2013 is used. Results indicated that the seasonal precipitation over NWI is below (above) the long-term mean in most of the years, when precipitation in any of the month (December/January/February) is in deficit (excess). The contribution of December precipitation (15-20%) to the seasonal (DJF) precipitation is lesser than January (35-40%) and February (35-50%) over all the subdivisions. December (0.60), January (0.57), and February (0.69) precipitation is in-phase (correlation) with the corresponding winter season precipitation. However, January precipitation is not in-phase with the corresponding December (0.083) and February (-0.03) precipitation, while December is in-phase with the February (0.21). When monthly precipitation (December or January or December-January or February) at subdivision level over NWI is excess (deficit); then, the probability of occurrence of seasonal excess (deficit) precipitation is high (almost nil). When antecedent-monthly precipitation is a deficit or excess, the probability of monthly (January or February or January + February) precipitation to be a normal category is >60% over all the subdivisions. This study concludes that the December precipitation is a good indicator to estimate the performance of January, February, January-February, and the seasonal (DJF) precipitation.

An Improved Plutonium Trifluoride Precipitation Flowsheet

Energy Technology Data Exchange (ETDEWEB)

Harmon, H.D.

2001-06-26

This report discusses results of the plutonium trifluoride two-stage precipitation study. A series of precipitation experiments was used to identify the significant process variables affecting precipitation performance. A mathematical model of the precipitation process was developed which is based on the formation of plutonium fluoride complexes. The precipitation model relates all process variables, in a single equation, to a single parameter which can be used to control the performance of the plutonium trifluoride precipitation process. Recommendations have been made which will optimize the FB-Line plutonium trifluoride precipitation process.

An Improved Plutonium Trifluoride Precipitation Flowsheet

International Nuclear Information System (INIS)

Harmon, H.D.

2001-01-01

This report discusses results of the plutonium trifluoride two-stage precipitation study. A series of precipitation experiments was used to identify the significant process variables affecting precipitation performance. A mathematical model of the precipitation process was developed which is based on the formation of plutonium fluoride complexes. The precipitation model relates all process variables, in a single equation, to a single parameter which can be used to control the performance of the plutonium trifluoride precipitation process. Recommendations have been made which will optimize the FB-Line plutonium trifluoride precipitation process

TCA precipitation.

Science.gov (United States)

Koontz, Laura

2014-01-01

Trichloroacetic acid (TCA) precipitation of proteins is commonly used to concentrate protein samples or remove contaminants, including salts and detergents, prior to downstream applications such as SDS-PAGE or 2D-gels. TCA precipitation denatures the protein, so it should not be used if the protein must remain in its folded state (e.g., if you want to measure a biochemical activity of the protein). © 2014 Elsevier Inc. All rights reserved.

Bacteria attenuation by iron electrocoagulation governed by interactions between bacterial phosphate groups and Fe(III) precipitates

NARCIS (Netherlands)

Delaire, Caroline; van Genuchten, Case M.; Amrose, Susan E.; Gadgil, Ashok J.

2016-01-01

Iron electrocoagulation (Fe-EC) is a low-cost process in which Fe(II) generated from an Fe(0) anode reacts with dissolved O2 to form (1) Fe(III) precipitates with an affinity for bacterial cell walls and (2) bactericidal reactive oxidants. Previous work suggests that Fe-EC is a promising treatment

The Effect of the Concentration of Oxidant, Cr(VI), on the Iron Oxidation in Saline Water

Science.gov (United States)

Ahn, H.; Jo, H. Y.; Ryu, J. H.; Koh, Y. K.

2014-12-01

Deep geological disposal is currently considered as the most appropriate method to isolate high level radioactive wastes (HLRWs) from the ecosystem. If groundwater seeps into underground disposal facilities, water molecules can be dissociated to radicals or peroxides, which can oxidize metal canisters and HLRWs. The oxidized radionuclides with a high solubility can be dissolved in the groundwater. Some dissolved radionuclides can act as oxidants. The continuous radiolysis of water molecules, which results from continuous seepage of groundwater, can enable the continuous production of the radioactive oxidants, resulting in an increase in concentration of oxidants. In this study, the effect of oxidant concentration on iron oxidation in the presence of salt was evaluated. Zero valent iron (ZVI) particles were reacted with Cr(VI) solutions with initial Cr(VI) concentrations ranged from 50 to 300 mg/L in reactors. The initial pH and NaCl concentration were fixed at 3 and 0.5 M, respectively. An increase in the initial Cr(VI) concentration caused an increase in the rate and extend of H2 gas production. The decrement of Cr(VI) was increased as the initial Cr(VI) concentration was increased. The penetration of H+ ions in the presence Cl- ions through the passive film on the ZVI particles caused the reaction between H+ ions and ZVI particles, producing H2 gas and Fe2+ ions. The passive film was damaged during the reaction due to the eruption of H2 gas or peptization by Cl- ions. The Fe2+ ions were reacted with Cr(VI) ions in the solution, producing Fe(III)-Cr(III) (oxy)hydroxides on the passive film of ZVI particles or in the solution as colloidal particles. The Fe(III)-Cr(III) (oxy)hydroxides tends to be precipitated as colloidal particles at a high Cr(VI) concentration and precipitated on the passive film at a low Cr(VI) concentration. The passive film was repaired or thickened by additional formation of Fe(III)-Cr(III) (oxy)hydroxides at a lower Cr(VI) concentration.

Effects of Tributyltin Antifouling Paint Leachates on Pearl Harbor Organisms. Site-Specific Flowthrough Bioassay Tests.

Science.gov (United States)

1985-12-01

painted with a commercial ablative co-polymer coating containing tributyltin and cuprous oxide toxicants were "aged" for 4 months in flowing seawater...a 2-month recovery phase after removing the panels. Mean measured tributyltin ( TBT ) concentrations in leachate treatments were 0.04, 0.1. 0.5. 1 8...facility of Naval Ocean Systems Center (NOSC) at Mokapu. Oahu. Hawaii. In those experiments, exposure to 0.5 to 1.8 #g/L tributyltin ( TBT ) resulted in

Study of nitric oxide catalytic oxidation on manganese oxides-loaded activated carbon at low temperature

Energy Technology Data Exchange (ETDEWEB)

You, Fu-Tian [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); University of Chinese Academy of Sciences, Beijing (China); Yu, Guang-Wei, E-mail: gwyu@iue.ac.cn [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); Wang, Yin, E-mail: yinwang@iue.ac.cn [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); Xing, Zhen-Jiao [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); Liu, Xue-Jiao; Li, Jie [Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen (China); University of Chinese Academy of Sciences, Beijing (China)

2017-08-15

Highlights: • Loading manganese oxides on activated carbon effectively promotes NO oxidation. • NO adsorption-desorption on activated carbon is fundamental to NO oxidation. • A high Mn{sup 4+}/Mn{sup 3+} ratio contributes to NO oxidation by promoting lattice O transfer. - Abstract: Nitric oxide (NO) is an air pollutant that is difficult to remove at low concentration and low temperature. Manganese oxides (MnO{sub x})-loaded activated carbon (MLAC) was prepared by a co-precipitation method and studied as a new catalyst for NO oxidation at low temperature. Characterization of MLAC included X-ray diffraction (XRD), scanning electron microscopy (SEM), N{sub 2} adsorption/desorption and X-ray photoelectron spectroscopy (XPS). Activity tests demonstrated the influence of the amount of MnO{sub x} and the test conditions on the reaction. MLAC with 7.5 wt.% MnO{sub x} (MLAC003) exhibits the highest NO conversion (38.7%) at 1000 ppm NO, 20 vol.% O{sub 2}, room temperature and GHSV ca. 16000 h{sup −1}. The NO conversion of MLAC003 was elevated by 26% compared with that of activated carbon. The results of the MLAC003 activity test under different test conditions demonstrated that NO conversion is also influenced by inlet NO concentration, inlet O{sub 2} concentration, reaction temperature and GHSV. The NO adsorption-desorption process in micropores of activated carbon is fundamental to NO oxidation, which can be controlled by pore structure and reaction temperature. The activity elevation caused by MnO{sub x} loading is assumed to be related to Mn{sup 4+}/Mn{sup 3+} ratio. Finally, a mechanism of NO catalytic oxidation on MLAC based on NO adsorption-desorption and MnO{sub x} lattice O transfer is proposed.

High temperature oxidation test of oxide dispersion strengthened (ODS) steel claddings

International Nuclear Information System (INIS)

Narita, Takeshi; Ukai, Shigeharu; Kaito, Takeji; Ohtsuka, Satoshi; Matsuda, Yasushi

2006-07-01

In a feasibility study of ODS steel cladding, its high temperature oxidation resistance was evaluated. Although addition of Cr is effective for preventing high temperature oxidation, excessively higher amount of Cr leads to embrittlement due to the Cr-rich α' precipitate formation. In the ODS steel developed by the Japan Atomic Energy Agency (JAEA), the Cr content is controlled in 9Cr-ODS martensite and 12Cr-ODS ferrite. In this study, high temperature oxidation test was conducted for ODS steels, and their results were compared with that of conventional austenitic stainless steel and ferritic-martensitic stainless steel. Following results were obtained in this study. (1) 9Cr-ODS martensitic and 12Cr-ODS ferritic steel have superior high temperature oxidation resistance compared to 11mass%Cr PNC-FMS and even 17mass% SUS430 and equivalent to austenitic PNC316. (2) The superior oxidation resistance of ODS steel was attributed to earlier formation of the protective alpha-Cr 2 O 3 layer at the matrix and inner oxide scale interface. The grain size of ODS steel is finer than that of PNC-FMS, so the superior oxidation resistance of ODS steel can be attributed to the enhanced Cr-supplying rate throughout the accelerated grain boundary diffusion. Finely dispersed Y 2 O 3 oxide particles in the ODS steel matrix may also stabilized the adherence between the protective alpha-Cr 2 O 3 layer and the matrix. (author)

Radar-Derived Quantitative Precipitation Estimation Based on Precipitation Classification

Directory of Open Access Journals (Sweden)

Lili Yang

2016-01-01

Full Text Available A method for improving radar-derived quantitative precipitation estimation is proposed. Tropical vertical profiles of reflectivity (VPRs are first determined from multiple VPRs. Upon identifying a tropical VPR, the event can be further classified as either tropical-stratiform or tropical-convective rainfall by a fuzzy logic (FL algorithm. Based on the precipitation-type fields, the reflectivity values are converted into rainfall rate using a Z-R relationship. In order to evaluate the performance of this rainfall classification scheme, three experiments were conducted using three months of data and two study cases. In Experiment I, the Weather Surveillance Radar-1988 Doppler (WSR-88D default Z-R relationship was applied. In Experiment II, the precipitation regime was separated into convective and stratiform rainfall using the FL algorithm, and corresponding Z-R relationships were used. In Experiment III, the precipitation regime was separated into convective, stratiform, and tropical rainfall, and the corresponding Z-R relationships were applied. The results show that the rainfall rates obtained from all three experiments match closely with the gauge observations, although Experiment II could solve the underestimation, when compared to Experiment I. Experiment III significantly reduced this underestimation and generated the most accurate radar estimates of rain rate among the three experiments.

Photoluminescence study on amino functionalized dysprosium oxide-zinc oxide composite bifunctional nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Joseph, Aswathy; Praveen, G.L; Abha, K.; Lekha, G.M [Department of Chemistry, University of Kerala, Kariavattom, Kerala 695581 (India); George, Sony, E-mail: emailtosony@gmail.com [Department of Chemistry, University of Kerala, Kariavattom, Kerala 695581 (India)

2012-08-15

An organic dispersion of 9-15 nm size stable dysprosium oxide incorporated zinc oxide nanocomposites exhibiting luminescence in the visible region has been synthesised by a wet chemical precipitation technique at room temperature. Tetraethoxysilane TEOS [(C{sub 2}H{sub 5}O){sub 4}Si], (3-aminopropyl) trimethoxysilane (APTS) and a 1:1 mixture of TEOS-APTS have been used as capping agents to control the particle size as well as to achieve uniform dispersion of composite nanoparticles in methanol medium. X-ray diffractometer (XRD) analysis reveals the formation phase of amino-functionalised colloidal dysprosium oxide incorporated ZnO composite nanoparticles to be of zincite structure. The Transmission Electron Microscopy (TEM) images show that the particles are spheroids in shape, having average crystalline sizes ranging from 9 to 15 nm. The photoluminescence (PL) observed in these composites has been attributed to the presence of near band edge excitonic emission and existence of defect centres. The time correlated single photon counting studies of the composite nanoparticles exhibited three decay pathways. The enhanced PL emission intensity of solid state fluorescence spectra of samples is attributed to the absence of vibrational relaxation process. - Highlights: Black-Right-Pointing-Pointer Nano-composites are synthesised using a one step wet chemical precipitation method. Black-Right-Pointing-Pointer A significant fluorescence life time of 8.25 ns is obtained for the nano-composite. Black-Right-Pointing-Pointer Nano-composite particles exhibited pale yellow fluorescence rather than blue. Black-Right-Pointing-Pointer Vibrational cascade free enhanced fluorescence is obtained for the dry sample.

Precipitation Sedimentation and Advection in GFS

Science.gov (United States)

Sun, R.; Tallapragada, V.

2016-12-01

Zhao and Carr microphysics scheme as implemented in the NCEP Global Forecasting System (GFS) predicts only the total cloud condensate (cloud water or ice). The precipitation generated in the column fall to the ground instantly. This mean precipitation sedimentation and advection are not considered. As resolution increases the lack of the two physical processes creates problems. The slowly falling precipitation (snow) falls to the wrong surface grid box, which may have led to the observed spotty-precipitation pattern. To solve the problem two prognositic variables, snow and rain, are added. Addition of the two precipitation variable allows their advection. The corresponding sedimentation process are also added. In this study we examine the effect of precipitation advection and sedimentation on the precipitation pattern, associated precipitation skills and clouds.

Violet emission from Fe doped ZnO nanoparticles synthesized by precipitation method

Energy Technology Data Exchange (ETDEWEB)

Kanchana, S., E-mail: skanchana09@gmail.com [PG & Research Department of Physics, Urumu Dhanalaksmi College, Tiruchirapalli 620019 (India); Chithra, M. Jay [Nanomaterials Research Laboratory, Department of Physics, Government Arts College, Karur 639005 (India); Ernest, Suhashini [PG & Research Department of Physics, Urumu Dhanalaksmi College, Tiruchirapalli 620019 (India); Pushpanathan, K. [Nanomaterials Research Laboratory, Department of Physics, Government Arts College, Karur 639005 (India)

2016-08-15

In this article we have reported the synthesis of Fe doped zinc oxide nanoparticles by the chemical precipitation method. The structural, compositional and optical properties have been examined by powder X-ray diffractometer, scanning electron microscope, transmission electron microscope, ultraviolet–visible and spectrophotometer. X-ray diffraction analysis confirmed the crystallites are in nanometer size and the sample contains polycrystals with hexagonal wurtzite structure. The average crystallite size has been found to increase from 25 nm to 36 nm with increase in Fe concentration. Scanning electron microscope result also confirmed the nanosize of the particles. Ultraviolet–visible spectrum of Fe doped zinc oxide shows a red shift with respect to undoped zinc oxide. The band gap of the samples was calculated from ultraviolet–visible spectrum and it is narrow from 3.30 eV to 3.23 eV with increasing Fe dopant upto 6%. The stretching bonds in Zn– Fe–O have been observed in FTIR spectra.

In situ co-precipitation preparation of a superparamagnetic graphene oxide/Fe3O4 nanocomposite as an adsorbent for wastewater purification: synthesis, characterization, kinetics, and isotherm studies.

Science.gov (United States)

Pu, Shengyan; Xue, Shengyang; Yang, Zeng; Hou, Yaqi; Zhu, Rongxin; Chu, Wei

2018-04-13

A superparamagnetic graphene oxide (GO)/Fe 3 O 4 nanocomposite (MGO) was prepared by a facile in situ co-precipitation strategy, resulting in a prospective material for the application of graphene oxide in wastewater treatment. MGO was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The prepared adsorbent showed a high adsorption efficiency relevant to the purification of dye-contaminated wastewater and could be readily magnetically separated. The maximum adsorption capacity was ca. 546.45 mg g -1 for the common cationic dye methylene blue (MB) and ca. 628.93 mg g -1 for the anionic dye Congo red (CR). The adsorption processes fit the pseudo-second-order kinetic model well, which revealed that these processes may involve the chemical interaction between adsorbate and adsorbent. The thermodynamic parameters indicated that the adsorption reaction was an endothermic and spontaneous process. Furthermore, the prepared magnetic adsorbent had a wide effective pH range from 5 to 11 and showed good stability after five reuse cycles. The synthetic MGO showed great potential as a promising adsorbent for organic contaminant removal in wastewater treatment.

Relative importance of precipitation frequency and intensity in inter-annual variation of precipitation in Singapore during 1980-2013

Science.gov (United States)

Li, Xin; Babovic, Vladan

2017-04-01

Observed studies on inter-annual variation of precipitation provide insight into the response of precipitation to anthropogenic climate change and natural climate variability. Inter-annual variation of precipitation results from the concurrent variations of precipitation frequency and intensity, understanding of the relative importance of frequency and intensity in the variability of precipitation can help fathom its changing properties. Investigation of the long-term changes of precipitation schemes has been extensively carried out in many regions across the world, however, detailed studies of the relative importance of precipitation frequency and intensity in inter-annual variation of precipitation are still limited, especially in the tropics. Therefore, this study presents a comprehensive framework to investigate the inter-annual variation of precipitation and the dominance of precipitation frequency and intensity in a tropical urban city-state, Singapore, based on long-term (1980-2013) daily precipitation series from 22 rain gauges. First, an iterative Mann-Kendall trend test method is applied to detect long-term trends in precipitation total, frequency and intensity at both annual and seasonal time scales. Then, the relative importance of precipitation frequency and intensity in inducing the inter-annual variation of wet-day precipitation total is analyzed using a dominance analysis method based on linear regression. The results show statistically significant upward trends in wet-day precipitation total, frequency and intensity at annual time scale, however, these trends are not evident during the monsoon seasons. The inter-annual variation of wet-day precipitation is mainly dominated by precipitation intensity for most of the stations at annual time scale and during the Northeast monsoon season. However, during the Southwest monsoon season, the inter-annual variation of wet-day precipitation is mainly dominated by precipitation frequency. These results have

Study of the mechanisms controlling the oxide growth under irradiation: characterization of irradiated zircaloy-4 and Zr-1 Nb-O oxide scales

International Nuclear Information System (INIS)

Bossis, Ph.; Thomazet, J.; Lefebvre, F.

2002-01-01

In PWRs, the Zr-1Nb-O alloy shows a marked enhancement in corrosion resistance in comparison with Zircaloy-4. The aim of this work is to analyze the reasons for these different behaviors and to determine the respective nature of the oxide growth controlling mechanisms under irradiation. Samples taken from Zircaloy-4 irradiated 1, 2, and 4 cycles and Zr-1Nb-O irradiated 1 and 3 cycles have been systematically characterized by optical microscopy, SEM coupled with image analysis, hydride distribution, and XRD. Specific TEM characterizations have been performed on the Zr-1Nb-O samples. A XPS analysis of a nonirradiated sample is also reported. It has been shown that under irradiation the slow oxidation kinetics of the Zr-1Nb-O alloy is associated with very regular metal-oxide interface and oxide layer. On the contrary, the accelerated oxidation kinetics of Zircaloy-4 is associated with highly perturbed metal-oxide interface and oxide layer. On both irradiated alloys, cracks are observed to initiate preferentially above the delayed parts of the oxidation front. Hydrogen intake during water oxidation in PWR environment is found to be much lower on the Zr-1Nb-O alloy than on Zircaloy-4. More β-ZrO 2 is found on the oxide layer formed on Zircaloy-4 than on Zr-1NbO after oxidation in PWR. Classical irradiation-induced microstructural evolution is observed in the Zr-1Nb-O metallic alloy after 3 cycles, i.e., a fine β-Nb precipitation. β-Nb precipitates are observed to undergo a delayed oxidation associated with a crystalline to amorphous transformation. After water oxidation in autoclave, a pronounced Nb segregation is detected on the oxide surface of a Zr-1Nb-O sample. These results suggest that the oxidation kinetics of Zircaloy-4 is controlled essentially by oxygen diffusion through the inner barrier layer, which is significantly accelerated under irradiation. The oxidation kinetics of Zr-1Nb-O is controlled by both oxygen diffusion through the inner barrier and by

Synthesis of YAG nanopowder by the co-precipitation method: Influence of pH and study of the reaction mechanisms

Science.gov (United States)

Marlot, Caroline; Barraud, Elodie; Le Gallet, Sophie; Eichhorn, Marc; Bernard, Frédéric

2012-07-01

YAG nanopowders with an average grain size of 30 nm have been successfully synthesized by the co-precipitation method using nitrates with precipitant of ammonium hydrogen carbonate. The influence of precipitation conditions such as pH, aging time and calcination temperature on the formation of secondary phases has been studied. The accurate control of pH value at every stage of precipitation process is crucial to avoid the presence of YAM (Yttrium Aluminium Monoclinic, Y4Al2O9) and yttrium oxide (Y2O3) after calcination. The reaction mechanisms have been investigated using different techniques such as infrared spectroscopy, x-ray diffraction and thermal analyses. The YAG phase is formed around 1050 °C passing through an intermediate phase called YAP (Yttrium Aluminium Perovskite, YAlO3). Local chemical heterogeneities are responsible for the deviation of the Y:Al ratio and the formation of YAP during heat treatment.

Facile synthesis of ceria nanoparticles by precipitation route for UV blockers

International Nuclear Information System (INIS)

Anupriya, K.; Vivek, E.; Subramanian, B.

2014-01-01

Highlights: • Homogenous precipitation was employed to prepare ceria nanoparticles. • An increase in the specific surface area was observed. • TEM showed particle sizes of 4 nm. • Material showed UV shielding effect. -- Abstract: Homogeneous ceria (CeO 2 ) nano particles of approximately 4 nm have been successfully synthesized via a simple precipitation route by employing the mixed solvent method. X-ray diffraction analysis revealed the precipitate particles to be of highly crystalline nature with face centered cubic structure along (1 1 1) (2 0 0) (2 2 0) (3 1 1) (4 0 0) (3 3 1) (4 2 2) (5 1 1) planes. Cerium oxide nanoparticles exhibits enhanced specific surface area of about 139.116 m 2 /g. The mono-dispersed spherical shape morphology of approximately 4 nm particles was confirmed using TEM analysis and its chemical composition by SEM–EDS analysis. Surface morphology reveals the smooth surface with an average roughness of 14.9 nm with the help of AFM. Raman studies show a characteristic peak at 464 cm −1 . The UV absorption edge was found at 314 nm i.e. In the Ultra Violet region suggesting that the material has a good absorption of UV light. Also, it shows an excellent transparency in the visible region

Facile synthesis of ceria nanoparticles by precipitation route for UV blockers

Energy Technology Data Exchange (ETDEWEB)

Anupriya, K.; Vivek, E.; Subramanian, B., E-mail: subramanianb3@gmail.com

2014-03-25

Highlights: • Homogenous precipitation was employed to prepare ceria nanoparticles. • An increase in the specific surface area was observed. • TEM showed particle sizes of 4 nm. • Material showed UV shielding effect. -- Abstract: Homogeneous ceria (CeO{sub 2}) nano particles of approximately 4 nm have been successfully synthesized via a simple precipitation route by employing the mixed solvent method. X-ray diffraction analysis revealed the precipitate particles to be of highly crystalline nature with face centered cubic structure along (1 1 1) (2 0 0) (2 2 0) (3 1 1) (4 0 0) (3 3 1) (4 2 2) (5 1 1) planes. Cerium oxide nanoparticles exhibits enhanced specific surface area of about 139.116 m{sup 2}/g. The mono-dispersed spherical shape morphology of approximately 4 nm particles was confirmed using TEM analysis and its chemical composition by SEM–EDS analysis. Surface morphology reveals the smooth surface with an average roughness of 14.9 nm with the help of AFM. Raman studies show a characteristic peak at 464 cm{sup −1}. The UV absorption edge was found at 314 nm i.e. In the Ultra Violet region suggesting that the material has a good absorption of UV light. Also, it shows an excellent transparency in the visible region.

Fabrication of oxide layer on zirconium by micro-arc oxidation: Structural and antimicrobial characteristics

International Nuclear Information System (INIS)

Fidan, S.; Muhaffel, F.; Riool, M.; Cempura, G.; Boer, L. de; Zaat, S.A.J.; Filemonowicz, A. Czyrska -; Cimenoglu, H.

2017-01-01

The aim of this study was to cover the surfaces of zirconium (Zr) with an antimicrobial layer for biomedical applications. For this purpose, the micro-arc oxidation (MAO) process was employed in a sodium silicate and sodium hydroxide containing base electrolyte with and without addition of silver acetate (AgC 2 H 3 O 2 ). In general, synthesized MAO layers were composed of zirconium oxide (ZrO 2 ) and zircon (ZrSiO 4 ). Addition of AgC 2 H 3 O 2 into the base electrolyte caused homogenous precipitation of silver-containing particles in the MAO layer, which exhibited excellent antibacterial efficiency against methicillin-resistant Staphylococcus aureus (MRSA) as compared to the untreated and MAO-treated Zr. - Highlights: • Micro-arc oxidation process was applied on zirconium in an electrolyte containing silver acetate. • Silver incorporated in the oxide layer in the form of nanoparticles. • 0.45 wt.% silver incorporation provided excellent antibacterial activity.

Fabrication of oxide layer on zirconium by micro-arc oxidation: Structural and antimicrobial characteristics

Energy Technology Data Exchange (ETDEWEB)

Fidan, S.; Muhaffel, F. [Department of Metallurgical and Materials Engineering, Istanbul Technical University, Sariyer, 34469 Istanbul (Turkey); Riool, M. [Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105, AZ, Amsterdam (Netherlands); Cempura, G. [International Centre of Electron Microscopy for Materials Science, AGH University of Science and Technology, PL, 30-059 Kraków (Poland); Boer, L. de; Zaat, S.A.J. [Department of Medical Microbiology, Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105, AZ, Amsterdam (Netherlands); Filemonowicz, A. Czyrska - [International Centre of Electron Microscopy for Materials Science, AGH University of Science and Technology, PL, 30-059 Kraków (Poland); Cimenoglu, H., E-mail: cimenogluh@itu.edu.tr [Department of Metallurgical and Materials Engineering, Istanbul Technical University, Sariyer, 34469 Istanbul (Turkey)

2017-02-01

The aim of this study was to cover the surfaces of zirconium (Zr) with an antimicrobial layer for biomedical applications. For this purpose, the micro-arc oxidation (MAO) process was employed in a sodium silicate and sodium hydroxide containing base electrolyte with and without addition of silver acetate (AgC{sub 2}H{sub 3}O{sub 2}). In general, synthesized MAO layers were composed of zirconium oxide (ZrO{sub 2}) and zircon (ZrSiO{sub 4}). Addition of AgC{sub 2}H{sub 3}O{sub 2} into the base electrolyte caused homogenous precipitation of silver-containing particles in the MAO layer, which exhibited excellent antibacterial efficiency against methicillin-resistant Staphylococcus aureus (MRSA) as compared to the untreated and MAO-treated Zr. - Highlights: • Micro-arc oxidation process was applied on zirconium in an electrolyte containing silver acetate. • Silver incorporated in the oxide layer in the form of nanoparticles. • 0.45 wt.% silver incorporation provided excellent antibacterial activity.

Selective removal of Cs and Re by precipitation in a Na2CO3-H2O2 solution

International Nuclear Information System (INIS)

Eil-Hee Lee; Jae-Gwan Lim; Dong-Yong Chung; Han-Beom Yang; Kwang-Wook Kim

2010-01-01

The removal of Cs and Re (as a surrogate for Tc) by selective precipitation from the simulated fission products which were co-dissolved with uranium during the oxidative dissolution of spent fuel in a Na 2 CO 3 -H 2 O 2 solution was investigated in this study. The precipitations of Cs and Re were examined by introducing sodium tetraphenylborate (NaTPB) and tetraphenylohosponium chloride (TPPCl), respectively. The precipitation of Cs by NaTPB and that of Re by TPPCl each took place within 5 min, and an increase in temperature up to 50 deg C and a stirring speed up to 1000 rpm hardly affected their precipitation rates. The most important factor in the precipitation with NaTPB and TPPCl was found to be a pH of the solution after precipitation. Since Mo tends to co-precipitate with Cs or Re at a lower pH, an effective precipitation with NaTPB and TPPCl was done at pH of above 9 without the co-precipitation of Mo. More than 99% of Cs and Re were precipitated when the initial concentration ratio of NaTPB to Cs was above 1 and when that of TPPCl to Re was above 1. The precipitation of Cs and Re was never affected by the concentration of Na 2 CO 3 and H 2 O 2 , even though they were raised up to 1.5 and 1.0 M, respectively. Precipitation yields of Cs and Re in a Na 2 CO 3 -H 2 O 2 solution were found to be dependent on the concentration ratios of [NaTBP]/[Cs] and [TPPCl]/[Re]. (author)

Effect of morphology and solvent on two-photon absorption of nano zinc oxide

Energy Technology Data Exchange (ETDEWEB)

Kavitha, M.K. [Department of Chemistry, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695547, Kerala (India); Haripadmam, P.C.; Gopinath, Pramod; Krishnan, Bindu [Department of Physics, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695547, Kerala (India); John, Honey, E-mail: honey@iist.ac.in [Department of Chemistry, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695547, Kerala (India)

2013-05-15

Highlights: ► ZnO nanospheres and triangular structures synthesis by novel precipitation technique. ► The effect of precursor concentration on the size and shape of nano ZnO. ► Open aperture Z-scan measurements of the ZnO nanoparticle dispersions. ► Nanospheres exhibit higher two photon absorption coefficient than triangular nanostructures. ► Nanospheres dispersed in water exhibit higher two photon absorption coefficient than its dispersion in 2-propanol. - Abstract: In this paper, we report the effect of morphology and solvent on the two-photon absorption of nano zinc oxide. Zinc oxide nanoparticles in two different morphologies like nanospheres and triangular nanostructures are synthesized by novel precipitation technique and their two-photon absorption coefficient is measured using open aperture Z-scan technique. Experimental results show that the zinc oxide nanospheres exhibit higher two-photon absorption coefficient than the zinc oxide triangular nanostructures. The zinc oxide nanospheres dispersed in water exhibit higher two-photon absorption coefficient than that of its dispersion in 2-propanol. The zinc oxide nanospheres dispersed in water shows a decrease in two-photon absorption coefficient with an increase in on-axis irradiance. The result confirms the dependence of shape and solvent on the two-photon absorption of nano zinc oxide.

Centrifugal precipitation chromatography

Science.gov (United States)

Ito, Yoichiro; Lin, Qi

2009-01-01

Centrifugal precipitation chromatography separates analytes according their solubility in ammonium sulfate (AS) solution and other precipitants. The separation column is made from a pair of long spiral channels partitioned with a semipermeable membrane. In a typical separation, concentrated ammonium sulfate is eluted through one channel while water is eluted through the other channel in the opposite direction. The countercurrent process forms an exponential AS concentration gradient through the water channel. Consequently, protein samples injected into the water channel is subjected to a steadily increasing AS concentration and at the critical AS concentration they are precipitated and deposited in the channel bed by the centrifugal force. Then the chromatographic separation is started by gradually reducing the AS concentration in the AS channel which lowers the AS gradient concentration in the water channel. This results in dissolution of deposited proteins which are again precipitated at an advanced critical point as they move through the channel. Consequently, proteins repeat precipitation and dissolution through a long channel and finally eluted out from the column in the order of their solubility in the AS solution. The present method has been successfully applied to a number of analytes including human serum proteins, recombinant ketosteroid isomerase, carotenoid cleavage enzymes, plasmid DNA, polysaccharide, polymerized pigments, PEG-protein conjugates, etc. The method is capable to single out the target species of proteins by affinity ligand or immunoaffinity separation. PMID:19541553

Fundamental study on the salt distillation from the mixtures of rare earth precipitates and LiCl-KCl eutectic salt

International Nuclear Information System (INIS)

Yang, H. C.; Eun, H. C.; Cho, Y. Z.; Lee, H. S.; Kim, I. T.

2008-01-01

An electrorefining process of spent nuclear fuel generates waste salt containing some radioactive metal chlorides. The most effective method to reduce salt waste volume is to separate radioactive metals from non-radioactive salts. A promising approach is to change radioactive metal chlorides into salt-insoluble oxides by an oxygen sparging. Following this, salt distillation process is available to effectively separate the precipitated particulate metal oxides from salt. This study investigated the distillation rates of LiCl-KCl eutectic salt under different vacuums at elevated temperatures. The first part study investigated distillation rates of eutectic salt under different vacuums at high temperatures by using thermo-gravimetric furnace system. In the second part, we tested the removal of eutectic salt from the RE precipitates by using the laboratory vacuum distillation furnace system. Investigated variables were the temperature of mixture, the degree of vacuum and the time

Studies on gadolinium precipitation in moderator system of nuclear reactor

International Nuclear Information System (INIS)

Joshi, Akhilesh C.; Rajesh, Puspalata; Rufus, A.L.; Velmurugan, S.

2015-01-01

Gadolinium is used in the moderator system of many Pressurised Heavy Water Reactors (PHWRs) for start-up, shut-down and reactivity control during operation. It is very much essential to maintain gadolinium concentration in the system as desired. It has been reported that gadolinium gets precipitated in as oxalate in carbonated water under the influence of γ-radiation. Hence, studies were carried out to investigate the effect of dose, presence of other metal ions and metal surfaces on the precipitation of gadolinium. The results showed that the amount of carboxylic acids viz., formic acid and oxalic acid, formed due to radiolysis is dependent on the dose and that the curve passes though a maxima. Gadolinium is added in higher concentration in Advanced Heavy Water Reactor. So, experiments with high concentration of gadolinium were also carried out. Ultra pure water saturated with high purity CO 2 containing gadolinium and desired ion/surface was irradiated with γ-radiation from 60 Co source at 25°C to doses ranging from 2.5-16.6 Mrad. At lower doses, formation of carboxylic acids takes place but as the dose increases, decomposition of these acids starts and hence the concentration Vs dose passes through a maximum. It was found that precipitation of gadolinium as oxalate occurred at lower doses. At higher doses, it was seen that pH of the solution decreases and hence solubility of gadolinium oxalate increases. It was also observed that the amount of gadolinium precipitated varied linearly with the initial concentration of gadolinium varying from 2 ppm to 20 ppm. While for gadolinium concentration from 20 ppm to 400 ppm, gadolinium in particulate form was observed. The amount of carboxylic acids formed depends on the nature of cations present in solution. It was found that the amount of oxalic acid formed in the case of gadolinium was more than that formed in the case of sodium. Presence of metal oxides such as ZrO 2 formed over zircoloy surfaces was found to

The Version 2 Global Precipitation Climatology Project (GPCP) Monthly Precipitation Analysis (1979-Present)

Science.gov (United States)

Adler, Robert F.; Huffman, George J.; Chang, Alfred; Ferraro, Ralph; Xie, Ping-Ping; Janowiak, John; Rudolf, Bruno; Schneider, Udo; Curtis, Scott; Bolvin, David

2003-01-01

The Global Precipitation Climatology Project (GPCP) Version 2 Monthly Precipitation Analysis is described. This globally complete, monthly analysis of surface precipitation at 2.5 degrees x 2.5 degrees latitude-longitude resolution is available from January 1979 to the present. It is a merged analysis that incorporates precipitation estimates from low-orbit-satellite microwave data, geosynchronous-orbit-satellite infrared data, and rain gauge observations. The merging approach utilizes the higher accuracy of the low-orbit microwave observations to calibrate, or adjust, the more frequent geosynchronous infrared observations. The data set is extended back into the premicrowave era (before 1987) by using infrared-only observations calibrated to the microwave-based analysis of the later years. The combined satellite-based product is adjusted by the raingauge analysis. This monthly analysis is the foundation for the GPCP suite of products including those at finer temporal resolution, satellite estimate, and error estimates for each field. The 23-year GPCP climatology is characterized, along with time and space variations of precipitation.

Peculiarities in film growth of ferroelectric complex oxides in ion-plasma sputtering

International Nuclear Information System (INIS)

Mukhortov, V.M.; Golovko, Yu.I.; Mukhortov, Vl.M.; Dudkevich, V.P.

1981-01-01

Experimental investigation into the process of complex oxide film growth (using BaTiO 3 and (Ba,Sr)TiO 3 as an example) during ion-plasma sputtering has been carried out. It is shown that neutral excited atoms are knocked out of a ceramic target during its ion bombardment. Removing from the target they loss energy at the expence of collisions and at some distance hsub(cr) the oxidation reaction (BaO, TiO, TiO 2 , SrO) becomes possible. So the ''construction'' material comes in either in the form of atoms or in the form of molecules of simple oxides depending on a distance between cathode and substrate. Two mechanisms of synthesis and crystallization distinguished with dependences of growth rate, elementary cell parameters and other structure characteristics on precipitation temperature correspond to two precipitation mechanisms. Part of re-evaporation and reduction processes is discussed [ru

Satellite-Based Precipitation Datasets

Science.gov (United States)

Munchak, S. J.; Huffman, G. J.

2017-12-01

Of the possible sources of precipitation data, those based on satellites provide the greatest spatial coverage. There is a wide selection of datasets, algorithms, and versions from which to choose, which can be confusing to non-specialists wishing to use the data. The International Precipitation Working Group (IPWG) maintains tables of the major publicly available, long-term, quasi-global precipitation data sets (http://www.isac.cnr.it/ ipwg/data/datasets.html), and this talk briefly reviews the various categories. As examples, NASA provides two sets of quasi-global precipitation data sets: the older Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) and current Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (GPM) mission (IMERG). Both provide near-real-time and post-real-time products that are uniformly gridded in space and time. The TMPA products are 3-hourly 0.25°x0.25° on the latitude band 50°N-S for about 16 years, while the IMERG products are half-hourly 0.1°x0.1° on 60°N-S for over 3 years (with plans to go to 16+ years in Spring 2018). In addition to the precipitation estimates, each data set provides fields of other variables, such as the satellite sensor providing estimates and estimated random error. The discussion concludes with advice about determining suitability for use, the necessity of being clear about product names and versions, and the need for continued support for satellite- and surface-based observation.

Formation of jarosite during Fe{sup 2+} oxidation by Acidithiobacillus ferrooxidans

Energy Technology Data Exchange (ETDEWEB)

Daoud, J.; Karamanev, D. [University of Western Ontario, London, ON (Canada). Dept. of Chemical & Biochemical Engineering

2006-07-15

Jarosite precipitation is a very important phenomenon that is observed in many bacterial cultures. In many applications involving Acidithiobacillus ferrooxidans, like coal desulphurization and bioleaching, it is crucial to minimize jarosite formation in order to increase efficiency. The formation of jarosite during the oxidation of ferrous iron by free suspended cells of A. ferrooxidans was studied. The process was studied as a function of time, pH and temperature. The main parameter affecting the jarosite formation was pH. Several experiments yielded results showing oxidation rates as high as 0.181-0.194 g/L h, with low jarosite precipitation of 0.0125-0.0209 g at conditions of pH 1.6-1.7 with an operating temperature of 35{sup o} C.

Stable isotope analyses of precipitation nitrogen sources in Guiyang, southwestern China.

Science.gov (United States)

Liu, Xue-Yan; Xiao, Hong-Wei; Xiao, Hua-Yun; Song, Wei; Sun, Xin-Chao; Zheng, Xu-Dong; Liu, Cong-Qiang; Koba, Keisuke

2017-11-01

To constrain sources of anthropogenic nitrogen (N) deposition is critical for effective reduction of reactive N emissions and better evaluation of N deposition effects. This study measured δ 15 N signatures of nitrate (NO 3 - ), ammonium (NH 4 + ) and total dissolved N (TDN) in precipitation at Guiyang, southwestern China and estimated contributions of dominant N sources using a Bayesian isotope mixing model. For NO 3 - , the contribution of non-fossil N oxides (NO x , mainly from biomass burning (24 ± 12%) and microbial N cycle (26 ± 5%)) equals that of fossil NO x , to which vehicle exhausts (31 ± 19%) contributed more than coal combustion (19 ± 9%). For NH 4 + , ammonia (NH 3 ) from volatilization sources (mainly animal wastes (22 ± 12%) and fertilizers (22 ± 10%)) contributed less than NH 3 from combustion sources (mainly biomass burning (17 ± 8%), vehicle exhausts (19 ± 11%) and coal combustions (19 ± 12%)). Dissolved organic N (DON) accounted for 41% in precipitation TDN deposition during the study period. Precipitation DON had higher δ 15 N values in cooler months (13.1‰) than in warmer months (-7.0‰), indicating the dominance of primary and secondary ON sources, respectively. These results newly underscored the importance of non-fossil NO x , fossil NH 3 and organic N in precipitation N inputs of urban environments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Processing of tetraphenylborate precipitates in the Savannah River Site Defense Waste Processing Facility

International Nuclear Information System (INIS)

Eibling, R.E.

1990-01-01

The Savannah River Site has generated 77 million gallons of high level radioactive waste since the early 1950's. By 1987, evaporation had reduced the concentration of the waste inventory to 35 million gallons. Currently, the wastes reside in large underground tanks as a soluble fraction stored, crystallized salts, and an insoluble fraction, sludge, which consists of hydrated transition metal oxides. The bulk of the radionuclides, 67 percent, are in the sludge while the crystallized salts and supernate are composed of the nitrates, nitrites, sulfates and hydroxides of sodium, potassium, and cesium. The principal radionuclide in the soluble waste is 137 Cs with traces of 90 Sr. The transformation of the high level wastes into a borosilicate glass suitable for permanent disposal is the goal of the Defense Waste Processing Facility (DWPF). To minimize the volume of glass produced, the soluble fraction of the waste is treated with sodium tetraphenylborate and sodium titanate in the waste tanks to precipitate the radioactive cesium ion and absorb the radioactive strontium ion. The precipitate is washed in the waste tanks and is then pumped to the DWPF. The precipitate, as received, is incompatible with the vitrification process because of the high aromatic carbon content and requires further chemical treatment. Within the DWPF, the precipitate is processed in the Salt Processing Cell to remove the aromatic carbon as benzene. The precipitate hydrolysis process hydrolyzes the tetraphenylborate anion to produce borate anion and benzene. The benzene is removed by distillation, decontaminated and transferred out of the DWPF for disposal

C isotope fractionation during heterotrophic activity driven carbonate precipitation

Science.gov (United States)

Balci, Nurgul; Demirel, Cansu

2016-04-01

Stable carbon isotopic fractionation during carbonate precipitation induced by environmentally enriched heterotrophic halophilic microorganims was experimentally investigated under various salinity (% 4.5, %8, %15) conditions at 30 °C. Halophilic heterotrophic microorganims were enriched from a hypersaline Lake Acigöl located in SW Turkey (Balci et al.,2015) and later used for the precipitation experiments (solid and liquid medium). The carbonate precipitates had relatively high δ13C values (-4.3 to -16.9 ‰) compared to the δ13C values of the organic compounds that ranged from -27.5 to -25.4 ‰. At salinity of 4.5 % δ13C values of carbonate ranged from -4.9 ‰ to -10.9 ‰ with a 13C-enrichment factor of +20 to +16 ‰ higher than the δ13C values of the associated DOC (-27.5) . At salinity 8 % δ13C values of carbonate ranged from -16.3 ‰ to -11.7 ‰ with a 13C-enrichment factor of+11.3 to+15.9 ‰ higher than the δ13C values of the associated DOC. The respected values for 15 % salinity ranged from -12.3 ‰ to -9.7 ‰ with a 13C-enrichment factor of +15.2 to+16.8 ‰ higher than the δ13C values of the associated DOC. The carbonate precipitates produced in the solid medium are more enriched in 13C relative to liquid culture experiments. These results suggest that the carbon in the solid was derived from both the bacterial oxidation of organic compounds in the medium and from the atmospheric CO2. A solid medium used in the experiments may have suppressed convective and advective mass transport favouring diffusion-controlled system. This determination suggests that the rate and equilibration of CO2 exchange with the atmosphere is the major control on C isotope composition of carbonate minerals precipitated in the experiments. Key words: Lake Acıgöl, halophilic bacteria, carbonate biomineralization, C isotopes References Nurgul Balci, Meryem Menekşe, Nevin Gül Karagüler, M. Şeref Sönmez,Patrick Meister 2015.Reproducing authigenic carbonate