Method and device to produce pourable, directly pressable uranium dioxide powder. Verfahren und Vorrichtung zur Herstellung von rieselfaehigem, direkt verpressbarem Urandioxid-Pulver

Energy Technology Data Exchange (ETDEWEB)

Boerner, P.; Isensee, H.J.; Vietzke, H.

1978-08-17

The uranium dioxide powder is produced from uranium peroxide which is obtained by continuous precipitation of uranyl nitrate solutions. By varying the precipitation conditions, one can exactly adjust the desired properties of the UO/sub 2/ powder, there is no 'post sintering'. The individual process steps are shown in detail.

Tungsten oxide coatings deposited by plasma spray using powder and solution precursor for detection of nitrogen dioxide gas

Energy Technology Data Exchange (ETDEWEB)

Zhang, Chao, E-mail: zhangc@yzu.edu.cn [College of Mechanical Engineering, Yangzhou University, Yangzhou 225127 (China); Wang, Jie [College of Mechanical Engineering, Yangzhou University, Yangzhou 225127 (China); Geng, Xin [College of Mechanical Engineering, Yangzhou University, Yangzhou 225127 (China); College of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China)

2016-05-25

Increasing attention has been paid on preparation methods for resistive-type gas sensors based on semiconductor metal oxides. In this work, tungsten oxide (WO{sub 3}) coatings were prepared on alumina substrates and used as gas sensitive layers. The coatings were deposited by atmospheric plasma spray using powder, solution precursor, or a combination of both. Tungsten oxide powder through a powder port and ammonium tungstate aqueous solution through a liquid port were injected into plasma stream respectively or together to deposit WO{sub 3} coatings. Phase structures in the coatings were characterized by X-ray diffraction analyzer. The field-emission scanning electron microscopy images confirmed that the coatings were in microstructure, nanostructure or micro-nanostructure. The sensing properties of the sensors based on the coatings exposed to 1 ppm nitrogen dioxide gas were characterized in a home-made instrument. Sensing properties of the coatings were compared and discussed. The influences of gas humidity and working temperature on the sensor responses were further studied. - Highlights: • Porous gas sensitive coatings were deposited by plasma spray using powder and solution precursor. • Crystallized WO{sub 3} were obtained through hybrid plasma spray plus a pre-conditioned step. • Plasma power had an important influence on coating microstructure. • The particle size of atmospheric plasma-sprayed microstructured coating was stable. • Solution precursor plasma-sprayed WO{sub 3} coatings had nanostructure and showed good responses to 1 ppm NO{sub 2}.

Light extinction in metallic powder beds: Correlation with powder structure

International Nuclear Information System (INIS)

Rombouts, M.; Froyen, L.; Gusarov, A.V.; Bentefour, E.H.; Glorieux, C.

2005-01-01

A theoretical correlation between the effective extinction coefficient, the specific surface area, and the chord length distribution of powder beds is verified experimentally. The investigated powder beds consist of metallic particles of several tens of microns. The effective extinction coefficients are measured by a light-transmission technique at a wavelength of 540 nm. The powder structure is characterized by a quantitative image analysis of powder bed cross sections resulting in two-point correlation functions and chord length distributions. The specific surface area of the powders is estimated by laser-diffraction particle-size analysis and by the two-point correlation function. The theoretically predicted tendency of increasing extinction coefficient with specific surface area per unit void volume is confirmed by the experiments. However, a significant quantitative discrepancy is found for several powders. No clear correlation of the extinction coefficient with the powder material and particle size, and morphology is revealed, which is in line with the assumption of geometrical optics

Polyphenol-Retaining Decaffeinated Cocoa Powder Obtained by Supercritical Carbon Dioxide Extraction and Its Antioxidant Activity.

Science.gov (United States)

Kobori, Kinji; Maruta, Yuto; Mineo, Shigeru; Shigematsu, Toru; Hirayama, Masao

2013-10-14

Cocoa beans contain many functional ingredients such as theobromine and polyphenols, but also contain a relatively high amount of caffeine, which can negatively impact human health. It is therefore desirable to reduce caffeine levels in cocoa powder used to make chocolate or cocoa beverages while retaining functional ingredients. We have established conditions for supercritical carbon dioxide (SCCO₂) extraction that remove 80.1% of the caffeine from cocoa powder while retaining theobromine (94.1%) and polyphenols (84.7%). The antioxidant activity of the decaffeinated cocoa powder (DCP) made with this optimized SCCO₂ extraction method was 85.3% that of non-processed cocoa powder. The total procyanidin and total polyphenol concentrations of the DCPs resulting from various SCCO₂ extractions showed a significant positive correlation with oxygen radical absorbance capacity (ORAC). The correlation coefficient between total polyphenols and ORAC was higher than that between total procyanidins and ORAC; thus, the concentration of total polyphenols might be a greater factor in the antioxidant activity of DCP. These results indicate that we could remove large quantities of caffeine from conventional high-cocoa products while retaining the functional benefits of high polyphenol content. This SCCO₂ extraction method is expected to be applicable high-cocoa products, such as dark chocolate.

Polyphenol-Retaining Decaffeinated Cocoa Powder Obtained by Supercritical Carbon Dioxide Extraction and Its Antioxidant Activity

Directory of Open Access Journals (Sweden)

Kinji Kobori

2013-10-01

Full Text Available Cocoa beans contain many functional ingredients such as theobromine and polyphenols, but also contain a relatively high amount of caffeine, which can negatively impact human health. It is therefore desirable to reduce caffeine levels in cocoa powder used to make chocolate or cocoa beverages while retaining functional ingredients. We have established conditions for supercritical carbon dioxide (SCCO2 extraction that remove 80.1% of the caffeine from cocoa powder while retaining theobromine (94.1% and polyphenols (84.7%. The antioxidant activity of the decaffeinated cocoa powder (DCP made with this optimized SCCO2 extraction method was 85.3% that of non-processed cocoa powder. The total procyanidin and total polyphenol concentrations of the DCPs resulting from various SCCO2 extractions showed a significant positive correlation with oxygen radical absorbance capacity (ORAC. The correlation coefficient between total polyphenols and ORAC was higher than that between total procyanidins and ORAC; thus, the concentration of total polyphenols might be a greater factor in the antioxidant activity of DCP. These results indicate that we could remove large quantities of caffeine from conventional high-cocoa products while retaining the functional benefits of high polyphenol content. This SCCO2 extraction method is expected to be applicable high-cocoa products, such as dark chocolate.

Solving Crystal Structures from Powder Diffraction Data

DEFF Research Database (Denmark)

Christensen, A. Nørlund; Lehmann, M. S.; Nielsen, Mogens

1985-01-01

High resolution powder data from both neutron and X-ray (synchrotron) sources have been used to estimate the possibility of direct structure determination from powder data. Two known structures were resolved by direct methods with neutron and X-ray data. With synchrotron X-ray data, the measured ...

The pressure bonding ability of uranium dioxide powders in relation to the evolution of their surface properties

International Nuclear Information System (INIS)

Danroc, J.

1982-09-01

The long term storage of sinterable uranium dioxide powders generally improves their pressure bonding ability and the strength of the resulting green pellets. Evidence of the gradual evolution of the surface texture and composition of these powders during storage at room temperature and pressure has been provided by infrared spectroscopy, X-ray diffraction and thermogravimetric and microcalorimetric methods. These techniques demonstrated the existence of a thin adherent surface layer of UO 3 2H 2 0. Such a natural evolutionary process can be reproduced and substantially amplified by subjecting the powder to thermal treatments at temperatures up to 90 0 C in a moist air environment. It was shown that powder treated in this manner could be more readily compacted into strong green pellets than could raw material. The tensile strength, commonly regarded as a quality test for such pellets and measured by the brazilian method, was found to be at least twice that of normal pellets. The high density and geometric integrity of these sintered products ensures the extrapolation of these preparation techniques to the mass production of nuclear reactor fuel pellets [fr

The effect of particle structure on apparent density of electrolytic copper powder

Directory of Open Access Journals (Sweden)

K. I. POPOV

2001-12-01

Full Text Available The quantitative microstructural analysis and the sieve analysis of copper powder as well as the scanning electron microscopy analysis of the copper powders particles were performed. It was found that the structure of the copper powder particles determines the apparent density of copper powder. The powder particles from the same fractions of different powders occupy approximately the same volume, but the structure of metallic copper is very different. This causes the difference in apparent densities of copper powder obtained under different conditions. The more dendritic is the structure of powder particles the smaller is the apparent density of copper powder.

An investigation of heat exchanger fouling in dust suspension cooling systems using graphite powder and carbon dioxide gas

International Nuclear Information System (INIS)

Garton, D.A.; Hawes, R.I.; Rose, P.W.

1966-01-01

Some experiments have been performed to study the fouling of heat exchanger surfaces where heat is being transferred from a heated fluid to a cooled surface. The fluid studied was a suspension of 4-5 microns mean diameter graphite powder in carbon dioxide gas at near atmospheric pressures. The solids loading range covered was from 5 to 30 lb. graphite/lb. carbon dioxide, and gas Reynolds numbers from 6000 to 16000. Temperature gradients across the cooler of from 20 to 120 deg. C were obtained. The heat transfer ratio is correlated to show the dependence upon the solids loading ratio of the suspension, the gas Reynolds number and the temperature gradient across the cooler. The results have demonstrated that stringent precautions are necessary to ensure complete dryness of the graphite powder and the loop flow surfaces before any quantitative fouling data can be obtained, as the presence of entrained moisture will accelerate the deposition of material on the cold walls of the heat exchanger and can result in plugging. The heat transfer coefficient showed no obvious dependency upon either the gas Reynolds number or the temperature gradient across the cooler over the range investigated. The measured heat transfer coefficient was considerably lower than that obtained when the heat is transferred from a hot wall to a cooler fluid. At a solids loading of 30 lb, graphite/lb. carbon dioxide, the heat transfer coefficient was only 50% of that for heat transfer from a heated wall. At solids loadings below 7 lb/lb., the heat transfer was less than that for a gas alone. (author)

Industrial structural transformation and carbon dioxide emissions in China

International Nuclear Information System (INIS)

Zhou, Xiaoyan; Zhang, Jie; Li, Junpeng

2013-01-01

Using provincial panel data from the period 1995–2009 to analyze the relationship between the industrial structural transformation and carbon dioxide emissions in China, we find that the first-order lag of industrial structural adjustment effectively reduced the emissions; technical progress itself did not reduce the emissions, but indirectly led to decreasing emissions through the upgrading and optimization of industrial structure. Foreign direct investment and intervention by local governments reduced carbon dioxide emissions, but urbanization significantly increased the emissions. Thus, industrial structural adjustment is an important component of the development of a low-carbon economy. In the context of industrial structural transformation, an effective way to reduce a region’s carbon dioxide emissions is to promote the upgrading and optimization of industrial structure through technical progress. Tighter environmental access policies, selective utilization of foreign direct investment, and improvements in energy efficiency can help to reduce carbon dioxide emissions. - Highlights: ► Relationship between the transformation of industrial structure and CO 2 emissions in China. ► Dynamic panel data model. ► Industrial structural adjustments can effectively reduce current CO 2 emissions. ► Technical progress leads to decreasing CO 2 emissions through upgrading of industrial structure

[Ultra-Fine Pressed Powder Pellet Sample Preparation XRF Determination of Multi-Elements and Carbon Dioxide in Carbonate].

Science.gov (United States)

Li, Xiao-li; An, Shu-qing; Xu, Tie-min; Liu, Yi-bo; Zhang, Li-juan; Zeng, Jiang-ping; Wang, Na

2015-06-01

The main analysis error of pressed powder pellet of carbonate comes from particle-size effect and mineral effect. So in the article in order to eliminate the particle-size effect, the ultrafine pressed powder pellet sample preparation is used to the determination of multi-elements and carbon-dioxide in carbonate. To prepare the ultrafine powder the FRITSCH planetary Micro Mill machine and tungsten carbide media is utilized. To conquer the conglomeration during the process of grinding, the wet grinding is preferred. The surface morphology of the pellet is more smooth and neat, the Compton scatter effect is reduced with the decrease in particle size. The intensity of the spectral line is varied with the change of the particle size, generally the intensity of the spectral line is increased with the decrease in the particle size. But when the particle size of more than one component of the material is decreased, the intensity of the spectral line may increase for S, Si, Mg, or decrease for Ca, Al, Ti, K, which depend on the respective mass absorption coefficient . The change of the composition of the phase with milling is also researched. The incident depth of respective element is given from theoretical calculation. When the sample is grounded to the particle size of less than the penetration depth of all the analyte, the effect of the particle size on the intensity of the spectral line is much reduced. In the experiment, when grounded the sample to less than 8 μm(d95), the particle-size effect is much eliminated, with the correction method of theoretical α coefficient and the empirical coefficient, 14 major, minor and trace element in the carbonate can be determined accurately. And the precision of the method is much improved with RSD element, the fluorescence yield is low and the interference is serious. With the manual multi-layer crystal PX4, coarse collimator, empirical correction, X-ray spectrometer can be used to determine the carbon dioxide in the carbonate

Photoluminescence and hydrogen gas-sensing properties of titanium dioxide nanostructures synthesized by hydrothermal treatments

CSIR Research Space (South Africa)

Sikhwivhilu, LM

2012-03-01

Full Text Available Titanium dioxide (TiO2) nanostructures were synthesized by microwave-assisted and conventionally heated hydrothermal treatment of TiO2 powder. The tubular structures were converted to a rodlike shape by sintering the samples at various temperatures...

Sol-gel growth of vanadium dioxide

International Nuclear Information System (INIS)

Speck, K.R.

1990-01-01

This thesis examines the chemical reactivity of vanadium (IV) tetrakis(t-butoxide) as a precursor for the sol-gel synthesis of vanadium dioxide. Hydrolysis and condensation of the alkoxide was studied by FTIR spectroscopy. Chemical modification of the vanadium tetraalkoxide by alcohol interchange was studied using 51 V NMR and FTIR. Vanadium dioxide thin films and powders were made from vanadium tetrakis(t-butoxide) by standard sol-gel techniques. Post-deposition heating under nitrogen was necessary to transform amorphous gels into vanadium dioxide. Crystallization of films and powders was studied by FTIR, DSC, TGA, and XRD. Gel-derived vanadium dioxide films undergo a reversible semiconductor-to-metal phase transition near 68C, exhibiting characteristic resistive and spectral changes. The electrical resistance decreased by two to three orders of magnitude and the infrared transmission sharply dropped as the material was cycled through this thermally induced phase transition. The sol-gel method was also used to make doped vanadium dioxide films. Films were doped with tungsten and molybdenum ions to effectively lower the temperature at which the transition occurs

Powder Neutron Diffraction and Magnetic structures

International Nuclear Information System (INIS)

Vigneron, F.

1986-01-01

The determination of the magnetic structures of materials (ferromagnetic, antiferromagnetic, helimagnetic, .) can be achieved only by neutron diffraction. A general survey of the powder technique is given: 2-axis spectrometer and analysis of the magnetic data. For the REBe/sb13/ intermetallic compounds (RE = Rare Earth), commensurate and/or incommensurate magnetic structures are observed and discussed as a function of RE (Gd, Tb, Dy, Ho, Er)

High Resolution Powder Diffraction and Structure Determination

International Nuclear Information System (INIS)

Cox, D. E.

1999-01-01

It is clear that high-resolution synchrotrons X-ray powder diffraction is a very powerful and convenient tool for material characterization and structure determination. Most investigations to date have been carried out under ambient conditions and have focused on structure solution and refinement. The application of high-resolution techniques to increasingly complex structures will certainly represent an important part of future studies, and it has been seen how ab initio solution of structures with perhaps 100 atoms in the asymmetric unit is within the realms of possibility. However, the ease with which temperature-dependence measurements can be made combined with improvements in the technology of position-sensitive detectors will undoubtedly stimulate precise in situ structural studies of phase transitions and related phenomena. One challenge in this area will be to develop high-resolution techniques for ultra-high pressure investigations in diamond anvil cells. This will require highly focused beams and very precise collimation in front of the cell down to dimensions of 50 (micro)m or less. Anomalous scattering offers many interesting possibilities as well. As a means of enhancing scattering contrast it has applications not only to the determination of cation distribution in mixed systems such as the superconducting oxides discussed in Section 9.5.3, but also to the location of specific cations in partially occupied sites, such as the extra-framework positions in zeolites, for example. Another possible application is to provide phasing information for ab initio structure solution. Finally, the precise determination of f as a function of energy through an absorption edge can provide useful information about cation oxidation states, particularly in conjunction with XANES data. In contrast to many experiments at a synchrotron facility, powder diffraction is a relatively simple and user-friendly technique, and most of the procedures and software for data analysis

Photocatalytically active titanium dioxide nanopowders: Synthesis, photoactivity and magnetic separation

International Nuclear Information System (INIS)

Nikkanen, J-P; Heinonen, S; Saarivirta, E Huttunen; Honkanen, M; Levänen, E

2013-01-01

Two approaches were used to obtain nanocrystalline titanium dioxide (TiO 2 ) photocatalyst powders. Firstly, low-temperature synthesis method and secondly liquid flame spraying. The structural properties of the produced powders were determined with X-ray diffraction, transmission electron microscopy and nitrogen adsorption tests. The photocatalytic properties of the powders were studied with methylene blue (MB) discoloration tests. After discolorations tests, TiO 2 was coagulated with magnetite particles using FeCl 3 ·6 H 2 O at a fixed pH value. Magnetic separation of coagulated TiO 2 and magnetite was carried out by a permanent magnet. The obtained results showed that the particle size of the powders synthesized at low-temperature was very small and the specific surface area high. The phase content of the powder was also shown to depend greatly on the acidity of the synthesis solution. Powder synthesized by liquid flame spraying was mixture of anatase and rutile phases with essentially larger particle size and lower specific surface area than those of low-temperature synthesized powders. The MB discoloration test showed that photocatalytic activity depends on the phase structure as well as the specific surface area of the synthesized TiO 2 powder. The magnetic separation of TiO 2 –magnetite coagulate from solution proved to be efficient around pH:8

Structure, mechanical and corrosion properties of powdered stainless steel Kh13

International Nuclear Information System (INIS)

Radomysel'skij, I.D.; Napara-Volgina, S.G.; Orlova, L.N.; Apininskaya, L.M.

1982-01-01

Structure, mechanical and corrosion properties are studied for compact powdered stainless steel, Grade Kh13, produced from prealloyed powder and a mixture of chromium and iron powders by hot vacuum pressing (HVP) following four schemes: HVP of unsintered billets; HVP of presintered billets; HVP of unsintered billets followed by diffusion annealing; HVP of sintered billets followed by diffusion annealing. Analysis of the structure, mechanical and corrosion properties of Kh13 steel produced according to the four schemes confirmed that production of this steel by the HVP method without presintering of porous billets and diffusion annealing of compact stampings is possible only when prealloyed powder of particular composition is used as a starting material

The effect of phosphorus on the formation of tungsten dioxide: A novel morphology

International Nuclear Information System (INIS)

Hegedus, E.; Neugebauer, J.

1999-01-01

The industrial production of tungsten is based on the hydrogen reduction of tungsten oxides, ammonium paratungstate (APT) or ammonium tungsten oxide bronze (ATOB). Hydrogen reduction is applied when high purity tungsten is required and when the addition of other elements or compounds (dopants) is desired for modification of the properties of the metal powder. The first stage of the reduction is finished when WO 2 is formed and it seems that the efficient incorporation of the additives starts mainly at this reduction step. The study reported here was undertaken to investigate the effect of phosphorus dope on the morphology of the intermediate tungsten dioxide and analyze its influence on the grain size of the final tungsten metal powder. The authors observed star shaped morphology of WO 2 , a structure which has not been describe in the literature. Contrary to the well-known cauliflower shaped tungsten dioxide, these starlets are not pseudomorphic to the initial ATOB particles; they grow separately and have a great influence on the grain size of the final metal powder

Production of rare earth polishing powders in Russia

International Nuclear Information System (INIS)

Kosynkin, V.D.; Ivanov, E.N.; Kotrekhov, V.A.; Shtutza, M.G.; Grabko, A.I.

1998-01-01

Full text: Russia is a potent producer of polishing powders made of rare earth material presented as an extensive and well developed base. Considering the reserves, the facilities predisposition and the polishing agent (cerium dioxide) content the chief mineral source is loparite, apatite and monazite. The production of rare earth polishing powders is based on specially developed continuous technological processes, corrosion-proof equipment, ensuring a high and stable production quality. A special attention is paid to the radiation safety of the powders. The initial material for the rare earth polishing powders based on loparite is the fusion cake of rare earth chlorides obtained at that mineral chlorination. The technology of the polishing powder production from the REE fusion cake includes the following stages: dissolution of the REE fusion cake chlorides; - thorough cleaning of the REE fusion cake chlorides from radioactive and non-rare-earth impurities; chemical precipitation of REE carbonates, obtaining middlings with proper material and granulometric composition, thermal treatment of precipitated carbonates followed with the operations of drying and roasting; classification of roasted oxides, obtaining end products - polishing powders. The production of fluorine-containing powders includes the stage of their fluorination after the stage of carbonate precipitation. The stabilizing doping can be introduced both into the middlings during one of the technological process of powders manufacturing and into the end product. Rare earth polishing powders are manufactured in Russia by the Share Holding Company 'Chepetz Mechanical Plant' (ChMP Co.), the city of Glasov. The plant produces a number of polishing materials, such as; polishing powder Optinol, containing at least 50% by mass of cerium dioxide, used in the mass production of optical and other articles; polishing powder Optinol-10 with doping to improve the sedimentary and aggregate stability of the solid phase

Preparation and Characterization of Nano-structured Ceramic Powders Synthesized by Emulsion Combustion Method

International Nuclear Information System (INIS)

Takatori, Kazumasa; Tani, Takao; Watanabe, Naoyoshi; Kamiya, Nobuo

1999-01-01

The emulsion combustion method (ECM), a novel powder production process, was originally developed to synthesize nano-structured metal-oxide powders. Metal ions in the aqueous droplets were rapidly oxidized by the combustion of the surrounding flammable liquid. The ECM achieved a small reaction field and a short reaction period to fabricate the submicron-sized hollow ceramic particles with extremely thin wall and chemically homogeneous ceramic powder. Alumina, zirconia, zirconia-ceria solid solutions and barium titanate were synthesized by the ECM process. Alumina and zirconia powders were characterized to be metastable in crystalline phase and hollow structure. The wall thickness of alumina was about 10 nm. The zirconia-ceria powders were found to be single-phase solid solutions for a wide composition range. These powders were characterized as equiaxed-shape, submicron-sized chemically homogeneous materials. The powder formation mechanism was investigated through the synthesis of barium titanate powder with different metal sources

Uranium dioxide. Sintering test

International Nuclear Information System (INIS)

Anon.

Description of a sintering method and of the equipment devoted to uranium dioxide powder caracterization and comparison between different samples. Determination of the curve giving specific volume versus pressure and micrographic examination of a pellet at medium pressure [fr

Identification of a Herbal Powder by Deoxyribonucleic Acid Barcoding and Structural Analyses.

Science.gov (United States)

Sheth, Bhavisha P; Thaker, Vrinda S

2015-10-01

Authentic identification of plants is essential for exploiting their medicinal properties as well as to stop the adulteration and malpractices with the trade of the same. To identify a herbal powder obtained from a herbalist in the local vicinity of Rajkot, Gujarat, using deoxyribonucleic acid (DNA) barcoding and molecular tools. The DNA was extracted from a herbal powder and selected Cassia species, followed by the polymerase chain reaction (PCR) and sequencing of the rbcL barcode locus. Thereafter the sequences were subjected to National Center for Biotechnology Information (NCBI) basic local alignment search tool (BLAST) analysis, followed by the protein three-dimension structure determination of the rbcL protein from the herbal powder and Cassia species namely Cassia fistula, Cassia tora and Cassia javanica (sequences obtained in the present study), Cassia Roxburghii, and Cassia abbreviata (sequences retrieved from Genbank). Further, the multiple and pairwise structural alignment were carried out in order to identify the herbal powder. The nucleotide sequences obtained from the selected species of Cassia were submitted to Genbank (Accession No. JX141397, JX141405, JX141420). The NCBI BLAST analysis of the rbcL protein from the herbal powder showed an equal sequence similarity (with reference to different parameters like E value, maximum identity, total score, query coverage) to C. javanica and C. roxburghii. In order to solve the ambiguities of the BLAST result, a protein structural approach was implemented. The protein homology models obtained in the present study were submitted to the protein model database (PM0079748-PM0079753). The pairwise structural alignment of the herbal powder (as template) and C. javanica and C. roxburghii (as targets individually) revealed a close similarity of the herbal powder with C. javanica. A strategy as used here, incorporating the integrated use of DNA barcoding and protein structural analyses could be adopted, as a novel

Use of the CSD program package for structure determination from powder data

International Nuclear Information System (INIS)

Akselrud, L.G.; Zavalii, P.Yu.; Grin, Yu.N.; Pecharski, V.K.; Baumgartner, B.; Woelfel, E.

1993-01-01

Although Rietveld's method of full profile structure refinement of powder data is a much-used tool today, ab initio structure solution from powder data is still not a routine task. One of the reasons for this is that fully overlapped peaks usually cannot be handled by routine structure determination programs. This shortcoming is not present in the Crystal Structure Determination (CSD) package which accepts intensities from powder diagrams as well as single crystal data. In order to demonstrate the possibilities of the CSD package, powder diagrams of five substances with already known crystal structure were collected and evaluated with the CSD package. The samples were scheelite (CaWO 4 ), pentaerythritol (C(CH 2 OH) 4 ), sodium sulfite (Na 2 SO 3 ), copper sulfate pentahydrate (CuSO 4 .5H 2 O) and silver germanium phosphide (Ag 6 Ge 10 P 12 ) and showed problems typical for powder work like preferred orientation and heavy peak overlapping. For four of the samples, correct atomic positions for some atoms could be found from the automatic MULTAN solution, which were then used in subsequent least squares- and difference Fourier calculations to locate the remaining atoms. Surprisingly, the cubic Ag 6 Ge 10 P 12 posed the most problems for the structure solution although one third of the observed intensities was single-indexed and the final R-value was as low as 4%. (orig.)

Design of a Uranium Dioxide Spheroidization System

Science.gov (United States)

Cavender, Daniel P.; Mireles, Omar R.; Frendi, Abdelkader

2013-01-01

The plasma spheroidization system (PSS) is the first process in the development of tungsten-uranium dioxide (W-UO2) fuel cermets. The PSS process improves particle spherocity and surface morphology for coating by chemical vapor deposition (CVD) process. Angular fully dense particles melt in an argon-hydrogen plasma jet at between 32-36 kW, and become spherical due to surface tension. Surrogate CeO2 powder was used in place of UO2 for system and process parameter development. Particles range in size from 100 - 50 microns in diameter. Student s t-test and hypothesis testing of two proportions statistical methods were applied to characterize and compare the spherocity of pre and post process powders. Particle spherocity was determined by irregularity parameter. Processed powders show great than 800% increase in the number of spherical particles over the stock powder with the mean spherocity only mildly improved. It is recommended that powders be processed two-three times in order to reach the desired spherocity, and that process parameters be optimized for a more narrow particles size range. Keywords: spherocity, spheroidization, plasma, uranium-dioxide, cermet, nuclear, propulsion

A new powder morphology for making high-porosity nickel structures

International Nuclear Information System (INIS)

Cormier, Elena; Yang, Quan Min; Charles, Doug; Wasmund, Eric Bain; Renny, Les V.

2007-01-01

Nickel powders with a special branched chain microstructure such as CVRD Inco Limited's Type 255 trademark have been used for more than 50 years as the basis for making porous metal monoliths for applications such as the electrical backbone of nickel electrode batteries by the sinter/slurry process. The classic trade-off when making these structures is that the strength and porosity are inversely correlated. A number of adaptations to the sinter/slurry making process have been proposed to address this problem. The current approach proposes another solution, optimization of the particle microstructure. The strength and porosity relationship of battery plaques made from Type 255 trademark is compared with plaques made with the new powder and it is statistically verified that plaques made from the new powder have an improved combination of structural properties. A comparison of the rheological characteristics of metal powder slurries suggests ways that the new powder can be incorporated into existing processes. Finally, it is shown that properties such as the slurry apparent viscosity can be used as the basis for measuring and predicting the characteristics of particle microstructure that impute these benefits to the sinter/slurry process. An analysis of battery plaques made with the new powder on an industrial battery sinter/slurry production line confirms that the laboratory results are valid. (author)

Properties of 40N3M powder structural steel

International Nuclear Information System (INIS)

Moskvina, T.P.; Gulyaev, A.P.; Gulyaev, I.A.; Byakov, S.V.; Melent'ev, I.V.; Morgun, G.N.

1984-01-01

Effect of the fabrication technique of compact slabs made of the 40N3M powder structural steel on mechanical properties with determination of a cold brittleness threshold was studied. It is established that after a thermal treatment at a density close to 100% a powder steel is sufficiently close to steel, rolled of an ingot, but is second in reference to steel in its ductility and impact strength. Properties of powder steel obtained by the method of dynamic hot forming (DHF) and hot extrusion are practically equal, but the first method has definite advantages as it allows to obtain details with a definitive form. The above investigation permits to recommend an application of the 40N3M powder steel fabricated by the DHF methods. The optimum thermal treatment course is: quenching+high annealing

Structural investigations of zirconia powders obtained by hf-plasmochemical denitration

International Nuclear Information System (INIS)

Dedov, N.V.; Ivanov, Yu.F.; Dorda, F.A.; Paul', A.V.; Zav'yalov, A.V.; Koneva, N.A.; Korobtsev, V.P.; Kutyavin, E.M.; Mazin, V.I.; Matyukha, V.A.

1992-01-01

Results are presented of structural and physicochemical investigations of unstabilized and stabilized (using yttria, magnesia, calcium oxide and alumina) zirconia, obtained from nitrate solutions on pilot HF-plasmochemical equipment with an electric rating of 63 kW. The phase composition of the ultradispersed powder is shown. Morphological and grain-size analyses were carried out on the EM-125K electron diffraction microscope. specimens were prepared by applying powder to a carbon film obtained in a VUP-4 vacuum cell. The phase composition was studied by x-ray analysis on the DRON-3 diffractometer. These studies established that the main morphological constituents of the ZrO 2 powder are polycrystalline hollow spheres and fragments of films. The average sizes (diameter) of the spheres in 0.77 μ (mean square deviation σ n = 0.57μ) and for the grains in them 31 nm (σ n = 9.5 nm). There exists a certain correlation between the dimensions of the polycrystalline spheres and their grain structure - the coarser the powders, the larger the grains observed

Enhancement of antioxidant activity of C-phycocyanin of Spirulina powder treated with supercritical fluid carbon dioxide

Directory of Open Access Journals (Sweden)

Monchai Dejsungkranont

2017-10-01

Full Text Available The functionality and activity of proteins can be modified by supercritical fluid CO2 (SCFCO2. The objectives of this study were to investigate the possibility of enhanced antioxidant activity of C-phycocyanin (C-PC proteins from light-harvested Spirulina maxima powder using the SCFCO2 pretreatment and to optimize the SCFCO2 pretreatment conditions enhancing the antioxidant activity of C-PC. The Taguchi method was used to determine the optimum conditions for the SCFCO2 pretreatment. The experimental factors were the pretreatment temperature, pressure, pretreatment mode (static, dynamic and conjugated and duration. The optimal conditions of SCFCO2 pretreatment were: 60 °C, 24.13 MPa and 60 min in static batch mode. Using these pretreatment conditions, the maximum antioxidant activity of C-PC from the treated residual biomass was 410.1 μmole trolox/mg, which was 1.7-fold higher than the untreated biomass (control. The factor that most affected the antioxidant activity of C-PC was temperature (59%. A high pretreatment temperature could damage C-PC, but promoted antioxidant activity. Of note is that this work was the first to explore SCFCO2 treatment enhancing the antioxidant activity of C-PC in Spirulina sp. powder. Keywords: Antioxidant activity, C-phycocyanin, Spirulina sp., Supercritical fluid carbon dioxide pretreatment, Taguchi method

Synthesis and characterization on titanium dioxide prepared by precipitation and hydrothermal treatment

International Nuclear Information System (INIS)

Santos, Andre V.P. dos; Yoshito, Walter K.; Lazar, Dolores R.R.; Ussui, Valter

2012-01-01

Surface properties of titanium dioxide (titania) are outstanding among ceramic materials and enables uses as catalysts, photoelectrochemical devices, solar cells and others. In many of these applications, it is necessary to keep the anatase phase, that is stable only in low temperatures (<400 deg C). In the present work, the influence of hydrothermal treatment on physical characteristics and crystal structure of titania powders synthesized by precipitation was investigated. Characterizations of obtained powders were carried out by X-ray diffraction, surface area analysis by N2 gas sorption (BET) and microstructure of powders and ceramics were analyzed by scanning electron microscopy. As prepared powders were formed as cylindrical pellets by uniaxial pressing and sintered at 1500 deg C for 01 hour. Results showed that anatase phase without formation of rutile phase can be formed in hydrothermally treated samples . Rutile phase is predominant in calcined and/or sintered samples (author)

Zirconium dioxide ultrafine powders formation in ultra-high frequency discharge plasma

International Nuclear Information System (INIS)

Triotskij, V.N.; Kurkin, E.N.; Torbov, V.I.; Berestenko, V.I.; Torbova, O.D.; Gurov, S.V.; Alekseev, N.V.

1995-01-01

ZrO 2 fine powders of 30...60 nm particle size were synthesized by ZrCl 4 oxidation in a flow of oxygen microwave plasma. Oxygen flow rate and ZrCl 4 feeding rate were the defining parameters effecting on powder particles size at constant discharge power.At predominant contribution of the coalescence process into ZrO 2 powder particles formation their heterogeneous growth was shown necessary to take into account. 16 refs.; 5 figs

Structural comparison of sintering products made of "TiC + Ti" composite powders and "Ti + C" powder mixtures

Science.gov (United States)

Krinitcyn, Maksim G.; Pribytkov, Gennadii A.; Korosteleva, Elena N.; Firsina, Irina A.; Baranovskii, Anton V.

2017-12-01

In this study, powder composite materials comprised of TiC and Ti with different ratios are processed by sintering of Ti and C powder mixtures and self-propagating high-temperature synthesis (SHS) in "Ti+C" system followed by sintering. The microstructure and porosity of obtained composites are investigated and discussed. The dependence of porosity on sintering time is explained theoretically. Optimal regimes that enable to obtain the most homogeneous structure with the least porosity are described.

Control of core structure in MgB{sub 2} wire through tailoring boron powder

Energy Technology Data Exchange (ETDEWEB)

Maeda, Minoru, E-mail: maeda.minoru70@nihon-u.ac.jp [Department of Physics, College of Science and Technology, Nihon University, 1-8-14 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8308 (Japan); Uchiyama, Daisuke [Department of Physics, College of Science and Technology, Nihon University, 1-8-14 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8308 (Japan); Hossain, Md Shahriar Al; Ma, Zongqing [Institute for Superconducting and Electronic Materials, University of Wollongong, North Wollongong, New South Wales 2500 (Australia); Shahabuddin, Mohammed [Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Kim, Jung Ho, E-mail: jhk@uow.edu.au [Institute for Superconducting and Electronic Materials, University of Wollongong, North Wollongong, New South Wales 2500 (Australia)

2015-07-05

Highlights: • The typical void structure in the wire is obtained by using large-sized B powder. • In contrast, void alignment can be achieved by using fine B powder. • The sintering at lower temperatures improves the critical current density in fields. - Abstract: A common fabrication process for MgB{sub 2} wire, namely, the in situ powder-in-tube process, forms numerous voids within the wire core, and void formation cannot be completely avoided. The orientation is, however, known to be aligned more or less along the current-flow direction when ductile coarse magnesium powder is used as a precursor, and further tailoring approaches could open up the way to improving the transport critical current density. Herein, we have used boron powders with different particle sizes, in combination with the coarse magnesium powder, and evaluated their size effects on the phase composition, microstructure, and transport properties. A mixture of the coarse magnesium powder with large-sized boron powder in the wire core, after cold working and sintering, forms a granular morphology. In contrast, an aligned core appears during the reduction process for wire which is prepared by using fine boron powder. The sintering process, especially at a low temperature, where magnesium evaporation hardly occurs, yields an aligned structure, mainly consisting of MgB{sub 2} phase, along the wire direction. These findings demonstrate that the initial size of the starting materials is critical for the tailored structure.

Method of manufacturing mixed stock powders for nuclear fuel elements

International Nuclear Information System (INIS)

Hirayama, Satoshi.

1980-01-01

Purpose: To alleviate the limit of the present reactor operating conditions by uniformly mixing an additive to the main content as an uranium dioxide or mixture of the uranium dioxide with plutonium dioxide. Method: A mixed stock powder is obtained by adding an additive of at least two of aluminium oxide, beryllium oxide, calcium oxide, magnesium oxide, silicon oxide, sodium oxide, potassium oxide, phosphorus oxide, titanium oxide and iron oxide to suspension having ammonia water as dispersion medium to start the deposition of precipitation at a step of precipitating ammonium diuranate or plutionium hydroxide of a main content of uranium dioxide or mixture of uranium dioxide and plutonium dioxide and deposited precipitate is calcinated and reduced. (Yoshihara, H.)

Fabrication of TiC-TiO{sub 2} composite powders by thermal plasma oxidation of titanium carbide powder; Tanka chitan funmatsu no plasma sanka hanno ni yori seiseishita TiC-TiO{sub 2} fukugo funmatsu

Energy Technology Data Exchange (ETDEWEB)

Ishigaki, T.; Li, Y.; Haneda, H. [National institute for Research Inorganic materials, Tsukuba (Japan); Kataoka, E. [Showa Cabot Supermetals K.K., Tokyo (Japan)

2000-09-15

TiC-TiO{sub 2} composite powders were prepared by in-flight oxidation of titanium carbide powder in RF induction thermal plasmas. Original titanium carbide powder of 20 - 38 {mu}m in particle size was axially injected into the center of argon-oxygen plasma. The powders were partially spheroidized and evaporated through the plasma treatment. X-ray diffraction of plasma-treated powders showed the formation of titanium dioxides, both rutile and anatase phases. The phase content of the plasma-prepared powders strongly depended on the plasma conditions, such as the plasma generating pressure and the oxygen flow rate in plasma generating gas. Especially, the increase of oxygen flow rate in plasma gas gave rise to the increase of heat transfer from plasma to powder particles, exothermic heat of oxidation reaction and cooling rate of plasma, giving the increase of spheroidization ratio, formation ratio of titanium dioxides, and content of anatase phases. (author)

Correlation between UO2 powder and pellet quality in PHWR fuel manufacturing

International Nuclear Information System (INIS)

Glodeanu, F.; Spinzi, M.; Balan, V.

1988-01-01

Natural uranium dioxide fuel for heavy water reactors has a series of very tightly controlled quality factors: Chemical purity, density and microstructures. Although the fabrication history may consistently affect the fuel quality, the quality factor mentioned above are function mainly of the quality of the powder used as raw material. As regards the fulfilment of the requirements for very high density of the pellets, it was found that in a definite technology the raw material plays the decisive part. Except for the powder sinterability, one found other important subtile parameters, such as the degree of agglomeration and structural homogeneity. The fuel microstructure, very important for in-serive performances of the fuel, is related to a great extent to some powder characteristics (homogeneity, sinterability). This is why much stress was laid on UO 2 power quality evaluation both by standard methods and non-conventional ones (agglomeration, microscopy, X-rays). Some of the characteristics defined by product specification, such as powder sinterability, should be better defined to guarantee the final product quality. (orig.)

Structure and hardness of a hard metal alloy prepared with a WC powder synthesized at low temperature

Energy Technology Data Exchange (ETDEWEB)

Costa, F.A. da [Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil)], E-mail: francineac@yahoo.com; Medeiros, F.F.P. de [Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil); Silva, A.G.P. da [Laboratorio de Materiais Avancados, UENF, 28015-620 Campos de Goytacazes, RJ (Brazil); Gomes, U.U. [Departamento de Fisica Teorica e Experimental, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil); Filgueira, M. [Laboratorio de Materiais Avancados, UENF, 28015-620 Campos de Goytacazes, RJ (Brazil); Souza, C.P. de [Laboratorio de Termodinamica e Reatores, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil)

2008-06-25

The structure and hardness of a WC-10 wt% Co alloy prepared with an experimental WC powder are compared with those of another alloy of the same composition produced under the same conditions and prepared with a commercial WC powder. The experimental WC powder was synthesized by a gas-solid reaction between APT and methane at low temperature and the commercial WC powder was conventionally produced by a solid-solid reaction between tungsten and carbon black. WC-10 wt% Co alloys with the two powders were prepared under the same conditions of milling and sintering. The structure of the sample prepared with the experimental WC powder is homogeneous and coarse grained. The structure of the sample prepared with the commercial powder is heterogeneous. Furthermore the size and shape of the WC grains are significantly different.

Influence of antimony on the elctrochemical behaviour and the structure of the lead dioxide active mass of lead/acid batteries

Energy Technology Data Exchange (ETDEWEB)

Pavlov, D. (Central Lab. of Electrochemical Power Sources, Bulgarian Academy of Sciences, Sofia (Bulgaria)); Dakhouche, A. (Central Lab. of Electrochemical Power Sources, Bulgarian Academy of Sciences, Sofia (Bulgaria)); Rogachev, T. (Central Lab. of Electrochemical Power Sources, Bulgarian Academy of Sciences, Sofia (Bulgaria))

1993-01-29

The effect of antimony on the formation of the skeleton structure of tubular electrodes filled with lead dioxide active mass (PAM) is investigated. Antimony is added as ions to the solution, as Sb[sub 2]O[sub 3] or Sb[sub 2]O[sub 5] to PAM, or as an additive to the electrode spine alloy. The effect of antimony on the crystallinity of PAM particles and agglomerates is examined. It is established that antimony increases the capacity of tubular powder electrodes when added either to the alloy or as antimony oxide to the PAM. It accelerates the processes of formation of the PAM skeleton structure and decreases the crystallinity of PAM particles and agglomerates. These effects of antimony are explained based on the concept of a gel-crystal structure for the PAM. Antimony improves the electron conductivity of gel zones. Its effect depends on the type and valency of the antimony ions, and on the density of the PAM. (orig.)

Structure determination of modulated structures by powder X-ray diffraction and electron diffraction

Czech Academy of Sciences Publication Activity Database

Zhou, Z.Y.; Palatinus, Lukáš; Sun, J.L.

2016-01-01

Roč. 3, č. 11 (2016), s. 1351-1362 ISSN 2052-1553 Institutional support: RVO:68378271 Keywords : electron diffraction * incommensurate structure * powder diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.036, year: 2016

Conversion of metal plutonium to plutonium dioxide by pyrochemical method

Energy Technology Data Exchange (ETDEWEB)

Panov, A.V.; Subbotin, V.G. [Russian Federal Nuclear Center, ALL-Russian Science and Research Institute of Technical Physics, Snezhinsk (Russian Federation); Mashirev, V.P. [ALL-Russian Science and Research Institute of Chemical Technology, Moscow (Russian Federation)

2000-07-01

Report contains experimental results on metal plutonium of weapon origin samples conversion to plutonium dioxide by pyrochemical method. Circuits of processes are described. Their advantages and shortcomings are shown. Parameters of plutonium dioxide powders (phase and fraction compositions, poured density) manufactured by pyrochemical method in RFNC-VNIITF are shown as well. (authors)

Structure and properties of powder metallurgy constructional steel of different densities

International Nuclear Information System (INIS)

Gulyaev, A.P.; Moskvina, T.P.

1986-01-01

A specific feature of powder metallurgy steels is porosity, the degree of which depends upon the method of their production. This article establishes the influence of a small amount of porosity on the mechanical properties of powder metallurgy constructional steel. The structure of heat-treated cast and powder metallurgy steels with different porosities are shown. The results of mechanical tests of the experimental steels with different porosities are shown. With an increase in porosity the nonmetallic inclusion rating of the powder metallurgy constructional steel increases, primarily as the result of the increase in the coarse particles, which is caused by the lower degree of plastic deformation in pressing. With an increase in porosity the mechanical properties of the powder metallurgy steel become poorer: the hardness and strength properties with a porosity of more than 3-5%, the plasticity with more than 1-2%, and the toughness even with a porosity of 1%

Thermal Oxidation of Structured Silicon Dioxide

DEFF Research Database (Denmark)

Christiansen, Thomas Lehrmann; Hansen, Ole; Jensen, Jørgen Arendt

2014-01-01

The topography of thermally oxidized, structured silicon dioxide is investigated through simulations, atomic force microscopy, and a proposed analytical model. A 357 nm thick oxide is structured by removing regions of the oxide in a masked etch with either reactive ion etching or hydrofluoric acid....... Subsequent thermal oxidation is performed in both dry and wet ambients in the temperature range 950◦C to 1100◦C growing a 205 ± 12 nm thick oxide in the etched mask windows. Lifting of the original oxide near the edge of the mask in the range 6 nm to 37 nm is seen with increased lifting for increasing...

Photoreduction of carbon dioxide and water into formaldehyde and methanol on semiconductor materials

Energy Technology Data Exchange (ETDEWEB)

Aurian-Blajeni, B; Halmann, M; Manassen, J

1980-01-01

Heterogeneous photoassisted reduction of aqueous carbon dioxide was achieved using semiconductor powders, with either high-pressure Hg-lamps or sunlight as energy sources. The products were methanol, formaldehyde and methane. The reaction was carried out either as a gas-solid process, by passing carbon dioxide and water vapor over illuminated semiconductor surfaces, or as a liquid-solid reaction, by illuminating aqueous suspensions of semiconductor powders through which carbon dioxide was bubbled. Best results, under illumination by Hg-lamps, were obtained with aqueous suspensions of strontium titanate, SrTiO3, tungsten oxide, WO3, and titanium oxide, TiO2, resulting in absorbed energy conversion efficiencies of 6, 5.9 and 1.2 per cent, respectively.

Acemetacin cocrystal structures by powder X-ray diffraction

Science.gov (United States)

Bolla, Geetha

2017-01-01

Cocrystals of acemetacin drug (ACM) with nicotinamide (NAM), p-aminobenzoic acid (PABA), valerolactam (VLM) and 2-pyridone (2HP) were prepared by melt crystallization and their X-ray crystal structures determined by high-resolution powder X-ray diffraction. The powerful technique of structure determination from powder data (SDPD) provided details of molecular packing and hydrogen bonding in pharmaceutical cocrystals of acemetacin. ACM–NAM occurs in anhydrate and hydrate forms, whereas the other structures crystallized in a single crystalline form. The carboxylic acid group of ACM forms theacid–amide dimer three-point synthon R 3 2(9)R 2 2(8)R 3 2(9) with three different syn amides (VLM, 2HP and caprolactam). The conformations of the ACM molecule observed in the crystal structures differ mainly in the mutual orientation of chlorobenzene fragment and the neighboring methyl group, being anti (type I) or syn (type II). ACM hydrate, ACM—NAM, ACM–NAM-hydrate and the piperazine salt of ACM exhibit the type I conformation, whereas ACM polymorphs and other cocrystals adopt the ACM type II conformation. Hydrogen-bond interactions in all the crystal structures were quantified by calculating their molecular electrostatic potential (MEP) surfaces. Hirshfeld surface analysis of the cocrystal surfaces shows that about 50% of the contribution is due to a combination of strong and weak O⋯H, N⋯H, Cl⋯H and C⋯H interactions. The physicochemical properties of these cocrystals are under study. PMID:28512568

Acemetacin cocrystal structures by powder X-ray diffraction

Directory of Open Access Journals (Sweden)

Geetha Bolla

2017-05-01

Full Text Available Cocrystals of acemetacin drug (ACM with nicotinamide (NAM, p-aminobenzoic acid (PABA, valerolactam (VLM and 2-pyridone (2HP were prepared by melt crystallization and their X-ray crystal structures determined by high-resolution powder X-ray diffraction. The powerful technique of structure determination from powder data (SDPD provided details of molecular packing and hydrogen bonding in pharmaceutical cocrystals of acemetacin. ACM–NAM occurs in anhydrate and hydrate forms, whereas the other structures crystallized in a single crystalline form. The carboxylic acid group of ACM forms theacid–amide dimer three-point synthon R32(9R22(8R32(9 with three different syn amides (VLM, 2HP and caprolactam. The conformations of the ACM molecule observed in the crystal structures differ mainly in the mutual orientation of chlorobenzene fragment and the neighboring methyl group, being anti (type I or syn (type II. ACM hydrate, ACM—NAM, ACM–NAM-hydrate and the piperazine salt of ACM exhibit the type I conformation, whereas ACM polymorphs and other cocrystals adopt the ACM type II conformation. Hydrogen-bond interactions in all the crystal structures were quantified by calculating their molecular electrostatic potential (MEP surfaces. Hirshfeld surface analysis of the cocrystal surfaces shows that about 50% of the contribution is due to a combination of strong and weak O...H, N...H, Cl...H and C...H interactions. The physicochemical properties of these cocrystals are under study.

Structure and amphoteric properties of titanium dioxide gels

International Nuclear Information System (INIS)

Kertesz, C.

1991-01-01

Mechanisms responsible for the in-solution ion retention by titanium dioxide are studied. Mineral oxide gel formation and structure are described and various titanium dioxide gel synthesis modes are presented. A two-phase model, taking into account the porous nature of the solid and allowing for the application of the mass action law, is adopted. The oxide amphoteric properties are studied with the potentiometric titration technique. Hysteresis loops are imputed to the slowness of the acid-basic neutralization reaction. The main characteristics are determined: isoelectric point, cation and anion retention capacity. Depending on the suspension agitation, the speed limiting factor may be the diffusion in the film or the diffusion in the particle. 60 fig., 128 ref

Superficial evolution and compacting aptitude of uranium dioxide powders

International Nuclear Information System (INIS)

Danroc, J.

1982-04-01

Long term storage of UO 2 powder improves slightly shaping and solidity of compacted powder. The aim of this work is the study of material evolution and the increase of this evolution rate for application to industrial fabrication. Aging in wet air at different temperatures is examined. Evolution of texture and superficial composition is followed. Below 80 0 C UO 3 , 2H 2 O is formed at crystal surface and thermal decomposition gives different hydrates. Kinetics of the transformation is studied. Oxidohydratation in liquid phase is rapid with hydrogen peroxide. The aged or treated material is compacted and mechanical behaviour is examined. Improvement is explained by inter-layer water molecule of the superficial hydrate giving lubricant and pseudo-plastic properties [fr

PRODUCTION OF METAL CHEMICAL WELDING ADDITIVE WITH NANODISPERSED PARTICLES OF TITANIUM DIOXIDE

Directory of Open Access Journals (Sweden)

BOLDYREV Alexander Mikhaylovich

2013-12-01

Full Text Available When welding bridge structures automatic welding under a gumboil layer with metal chemical additive (MCA is widely applied in the modern bridge building. MCA consists of a chopped welding wire (granulated material, which is powdered by modifying chemical additive of titanium dioxide (TiO₂ in the cylindrical mixer «drunk cask». Chemical composition of all welding materials including welding wire, gumboil, electrodes, are strictly normalized and controlled. However, the existing technology of producing MCA doesn’t allow precise controlling of its structure under working conditions and that causes an impact on the stability of welded connections properties. Therefore the aim of this work is to develop a technology to produce stable MCA structure. The paper compares the existing and proposed manufacturing techniques of the metal chemical additive (MCA which is applied in automatic welding of butt connections for bridge structures. It is shown that production of MCA in a high-energy planetary mill provides more stable structure of the additive introduced into a welded joint. The granulometric analysis of the powder TiO₂ showed that when processing MCA in a planetary mill TiO₂ particles are crashed to nanodimensional order. This process is accompanied by crushing of granulated material too. The proposed method for production of MCA in a planetary mill provides stronger cohesion of dioxide with the granulate surface and, as a consequence, more stable MCA chemical structure. Application of MCA which has been mechanical intensified in a planetary mill, increases stability of mechanical properties, if compare with applied technology, in single-order by breaking point and almost twice by impact viscosity.

Thermal and Physical Properties of Plutonium Dioxide Produced from the Oxidation of Metal: a Data Summary

Energy Technology Data Exchange (ETDEWEB)

Wayne, David M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2014-01-13

The ARIES Program at the Los Alamos National Laboratory removes plutonium metal from decommissioned nuclear weapons, and converts it to plutonium dioxide in a specially-designed Direct Metal Oxidation furnace. The plutonium dioxide is analyzed for specific surface area, particle size distribution, and moisture content. The purpose of these analyses is to certify that the plutonium dioxide powder meets or exceeds the specifications of the end-user, and the specifications for the packaging and transport of nuclear materials. Analytical results from plutonium dioxide from ARIES development activities, from ARIES production activities, from muffle furnace oxidation of metal, and from metal that was oxidized over a lengthy time interval in air at room temperature, are presented. The processes studied produce plutonium dioxide powder with distinct differences in measured properties, indicating the significant influence of oxidation conditions on physical properties.

Cold compaction behavior of nano-structured Nd–Fe–B alloy powders prepared by different processes

International Nuclear Information System (INIS)

Liu, Xiaoya; Hu, Lianxi; Wang, Erde

2013-01-01

Graphical abstract: Relative density enhancement and nanocrystallization of Nd 2 Fe 14 B phase are two major effective means to improve magnetic properties. Since the matrix Nd 2 Fe 14 B phase in the starting Nd–Fe–B alloy can be disproportionated into a nano-structured mixture of NdH 2.7 , Fe 2 B, and α-Fe phases during mechanical milling in hydrogen. It is thus important to study the densification behavior of nanocrystalline powders to evaluate and predict the cold compactibility of powders. By comparison with the as milled as well as melt-spun Nd 16 Fe 76 B 8 alloy powders, we find that the as-disproportionated Nd 16 Fe 76 B 8 alloy powder exhibits the best cold compactibility. As evident from the illustration presented below, compaction parameters (representing the powder compactibility) have been determined by fitting density–pressure data with double logarithm compaction equation. Densification mechanisms involved during cold compaction process are clarified in our work by referring to microstructure observation of samples prepared by various methods. As a result, highly densified green magnet compact can be obtained by cold pressing of as-disproportionated NdFeB alloy powders. Highlights: ► Nano-structured disproportionated Nd–Fe–B alloy powders by mechanical milling in hydrogen. ► Highly densified green magnet compact by cold pressing of as-disproportionated Nd–Fe–B alloy powders. ► Density–pressure data fitted well by an empirical powder compaction model. ► As-disproportionated powder showed better compactibility than as milled and melt-spun counterparts. ► The effects of physical properties on powder compactibility and densification mechanisms are clarified. - Abstract: The compaction behavior of nano-structured Nd 16 Fe 76 B 8 (atomic ratio) alloy powders, which were prepared by three different processing routes including melt spinning, mechanical milling in argon, and mechanically activated disproportionation by milling in

Obtainment of TiO2 powders solar cells photo electrodes dye sensitized

International Nuclear Information System (INIS)

Forbeck, Guilherme; Folgueras, Marilena V.; Chinelatto, Adilson L.

2012-01-01

Titanium dioxide in its polymorphic anatase phase, presents interesting properties for solar cells photo electrodes dye sensitized such as the forbidden energy band, high refractive index and high constant dielectric. In this study, powders of nanometric titanium dioxide were produced with predominantly the anatase phase and high surface area. We used the sol-gel method, and titanium tetraisopropoxide as a precursor, which was hydrolyzed in nitric acid solution. The obtained powder was heated to 450 ° C, varying the time for each lot (0, 20 or 120 minutes). The powders were characterized by X-ray diffraction, atomic force microscopy and surface area analysis. For all lots nanosized crystallites predominated. It was observed that in the batch with 120min heating an increase rutile content. The TiO 2 with 20min heating showed high surface area, greater than that of TiO 2 as taken reference

The effect of electrolytes on the aggregation kinetics of titanium dioxide nanoparticle aggregates

International Nuclear Information System (INIS)

Shih Yanghsin; Zhuang Chengming; Tso Chihping; Lin Chenghan

2012-01-01

Metal oxide nanoparticles (NPs) are receiving increasing attention due to their increased industrial production and potential hazardous effect. The process of aggregation plays a key role in the fate of NPs in the environment and the resultant health risk. The aggregation of commercial titanium dioxide NP powder (25 nm) was investigated with various environmentally relevant solution chemistries containing different concentrations of monovalent (Na + , K + ) and divalent (Ca 2+ ) electrolytes. Titanium dioxide particle size increased with the increase in ion concentration. The stability of titanium dioxide also depended on the ionic composition. Titanium dioxide aggregated to a higher degree in the presence of divalent cations than monovalent ones. The attachment efficiency of NPs was constructed through aggregation kinetics data, from which the critical coagulation concentrations for the various electrolytes are determined (80, 19, and 1 meq/L for Na + , K + , and Ca 2+ , respectively). Our results suggest that titanium dioxide NP powders are relatively unstable in water and could easily be removed by adding multivalent cations so hazardous potentials decrease in aquatic environment.

Standard test methods for chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade plutonium dioxide powders and pellets

CERN Document Server

American Society for Testing and Materials. Philadelphia

2010-01-01

1.1 These test methods cover procedures for the chemical, mass spectrometric, and spectrochemical analysis of nuclear-grade plutonium dioxide powders and pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Plutonium Sample Handling 8 to 10 Plutonium by Controlled-Potential Coulometry Plutonium by Ceric Sulfate Titration Plutonium by Amperometric Titration with Iron(II) Plutonium by Diode Array Spectrophotometry Nitrogen by Distillation Spectrophotometry Using Nessler Reagent 11 to 18 Carbon (Total) by Direct Combustion–Thermal Conductivity 19 to 30 Total Chlorine and Fluorine by Pyrohydrolysis 31 to 38 Sulfur by Distillation Spectrophotometry 39 to 47 Plutonium Isotopic Analysis by Mass Spectrometry Rare Earth Elements by Spectroscopy 48 to 55 Trace Elements by Carrier–Distillation Spectroscopy 56 to 63 Impurities by ICP-AES Impurity Elements by Spark-Source Mass Spectrography 64 to 70 Moisture by the Coulomet...

Structure and morphology of dispersed lanthanum powders and compact specimens of them

International Nuclear Information System (INIS)

Strashinskaya, L.V.; Dudnik, E.M.; Kopylova, L.I.; Savvakin, G.I.

1986-01-01

In this work a comparative electron microscopic investigation was made of the structure of dispersed LaB 6 powders. Specimens were prepared from the original and shock-wavetreated LaB 6 powders by hot-pressing. The compaction was done in such a manner that the coarser grains are surrounded by finer grains and all of the grains are rounded. Dispersion of LaB 6 powder by a shock wave leads to a decrease in the residual porosity of hot pressed specimens as the result of an increase in the quantity of finer fraction (1-2 um) in the mixture, i.e., better compaction, and the coarser grains are as immersed in a dense ''matrix'' of the finer ones. To obtain compact porosity-free parts of ultradispersed powders it is necessary to have a purer original material and to adopt special methods of forming which would make it possible to realize the potential reserves of activity of these powders in sintering. Illustrations and table are shown

Structure solution from powder neutron and x-ray diffraction data: getting the best of both worlds

International Nuclear Information System (INIS)

Hunter, B.A.

2000-01-01

Full text: Powder diffraction methods have traditionally been used in three main areas: phase identification and quantification, lattice parameter determination and structure refinement. Until recently structure solution has been the almost exclusive domain of single crystal diffraction methods, predominantly using x-rays. The increasing use of synchrotron and neutron sources, and the unrelenting advances in computing hardware and software means that powder methods are challenging single crystal methods as a practical method for structure solution, especially when single crystal method can not be applied. It is known that structural refinements from a known starting structure using combined X-ray and neutron data sets are capable of providing highly accurate structures. Likewise, using combined x-ray and neutron powder diffraction data in the structure solution process should also be a powerful technique, although to date no one is pursuing this methodology. This paper present examples of solutions to the problem. Namely we are using high resolution powder X-ray and neutron methods to solve the structures of molecular materials and minerals, then refining the structures using both sets of data. In this way we exploit the advantages of both methods while minimising the disadvantages. We present our solution for a small amino acid structure, a metalorganic and a mineral structure

Cold compaction behavior of nano-structured Nd-Fe-B alloy powders prepared by different processes

Energy Technology Data Exchange (ETDEWEB)

Liu, Xiaoya [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Hu, Lianxi, E-mail: hulx@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Wang, Erde [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

2013-02-25

Graphical abstract: Relative density enhancement and nanocrystallization of Nd{sub 2}Fe{sub 14}B phase are two major effective means to improve magnetic properties. Since the matrix Nd{sub 2}Fe{sub 14}B phase in the starting Nd-Fe-B alloy can be disproportionated into a nano-structured mixture of NdH{sub 2.7}, Fe{sub 2}B, and {alpha}-Fe phases during mechanical milling in hydrogen. It is thus important to study the densification behavior of nanocrystalline powders to evaluate and predict the cold compactibility of powders. By comparison with the as milled as well as melt-spun Nd{sub 16}Fe{sub 76}B{sub 8} alloy powders, we find that the as-disproportionated Nd{sub 16}Fe{sub 76}B{sub 8} alloy powder exhibits the best cold compactibility. As evident from the illustration presented below, compaction parameters (representing the powder compactibility) have been determined by fitting density-pressure data with double logarithm compaction equation. Densification mechanisms involved during cold compaction process are clarified in our work by referring to microstructure observation of samples prepared by various methods. As a result, highly densified green magnet compact can be obtained by cold pressing of as-disproportionated NdFeB alloy powders. Highlights: Black-Right-Pointing-Pointer Nano-structured disproportionated Nd-Fe-B alloy powders by mechanical milling in hydrogen. Black-Right-Pointing-Pointer Highly densified green magnet compact by cold pressing of as-disproportionated Nd-Fe-B alloy powders. Black-Right-Pointing-Pointer Density-pressure data fitted well by an empirical powder compaction model. Black-Right-Pointing-Pointer As-disproportionated powder showed better compactibility than as milled and melt-spun counterparts. Black-Right-Pointing-Pointer The effects of physical properties on powder compactibility and densification mechanisms are clarified. - Abstract: The compaction behavior of nano-structured Nd{sub 16}Fe{sub 76}B{sub 8} (atomic ratio) alloy

Computational characterization of 13C NMR lineshapes of carbon dioxide in structure 1 clathrate hydrates

Energy Technology Data Exchange (ETDEWEB)

Dornan, P.; Woo, T.K. [Ottawa Univ., ON (Canada). Dept. of Chemistry

2008-07-01

Nonspherical large cages in structure one clathrates impose non-uniform motion of nonspherical guest molecules and anisotropic lineshapes in nuclear magnetic resonance (NMR) spectra of the guest. This paper presented a general method for calculating the chemical shift lineshape anisotropy of guest molecules in clathrate hydrate compounds from molecular dynamics simulations for the case of weak host, guest dipolar coupling. In order to calculate the cage chemical shielding tensors and the NMR lineshape produced by each guest molecule, the study involved the use of orientational distributions from molecular dynamics simulation along with time and powder angle averaging. The total predicted lineshape anisotropy was calculated from the superposition of the lineshapes of all guests. The approach was applied to calculate the temperature dependent 13C NMR lineshape anisotropy of carbon dioxide in structure 1 clathrates. The paper presented the computational methodology and results and discussion. It was concluded that the resulting lineshapes were in good agreement with the experimental 13C NMR spectrum at each temperature. The method provided a uniform procedure to calculate the lineshapes at different temperatures and no prior assumptions about the nature of the motion of the guest in cages was required. 37 refs., 2 tabs., 3 figs.

Development of the process for production of UO2 powder by atomization of uranyl nitrate

International Nuclear Information System (INIS)

Oliveira Lainetti, P.E. de.

1991-01-01

A method of direct conversion of uranyl nitrate hexahydrate (UNH) solution to ceramic grade uranium dioxide powders by thermal denitration in a furnace that combines atomization nozzle and a gas stirred bed is described. The main purpose of this work is to show that this alternative process is technically viable, specially if the recovery of the scrap generated in the nuclear fuel pellet production is required, without further generation of new liquid wastes. The steps for the development of the denitration unit as well as the characteristics of the final powders are described. Powder production experiments have been carried out for different atomization gas pressures and furnace upper section temperatures. Determination of impurity content, specific surface area, particle size and pore size distribution, density, U content, and O/U rate of uranium dioxide powders have been done; phase identification and morphology studies have also been performed. Sintered pellets have been studied by hydrostatic density determination and microstructure analyses. (author)

The influence of structural changes on electrical and magnetic characteristics of amorphous powder of the nixmoy alloy

Directory of Open Access Journals (Sweden)

Ribić-Zelenović Lenka

2006-01-01

Full Text Available Nickel and molybdenum alloy powder was electrodeposited on a titanium cathode from a NiSO4⋅7H2O and (NH46 Mo7O24⋅4H2O ammonium solution. The desired chemical composition, structure, size and shape of particles in the powder samples were achieved by an appropriate choice of electrolysis parameters (current density, composition and temperature of the solution, cathode material and electrolysis duration. Metal coatings form in the current density range 15 mA cm-2powders form. The chemical composition of powder samples depends on the current density of electrodeposition. The molybdenum content in the powder increases with the increase of current density (in the low current density range, while in the higher current density range the molybdenum content in the alloy decreases with the increase of the current density of deposition. Smaller sized particles form at higher current density. X-ray analysis, differential scanning calorimetric and measurements of the temperature dependence of electric resistance and magnetic permeability of the powder samples were all used to establish a predominantly amorphous structure of the powder samples formed at the current density of j≥70mA cm-2. The crystalline particle content in the powder samples increases with the decrease of the current density of deposition. Powder heating causes structural changes. The process of thermal stabilization of nickel and molybdenum amorphous powders takes place in the temperature interval from 463K to 573K and causes a decrease in electrical resistance and increase in magnetic permeability. The crystallization temperature depends on the value of current density of powder electrodeposition. Powder formed at j=180 mA cm-2 begins to crystallize at 573K, while the powder deposited at j=50 mA cm-2 begins to crystallize at 673K. Crystallization of the powder causes a decrease in electric resistivity and magnetic

Room-temperature ferromagnetism in cerium dioxide powders

Energy Technology Data Exchange (ETDEWEB)

Rakhmatullin, R. M., E-mail: rrakhmat@kpfu.ru; Pavlov, V. V.; Semashko, V. V.; Korableva, S. L. [Kazan Federal University, Institute of Physics (Russian Federation)

2015-08-15

Room-temperature ferromagnetism is detected in a CeO{sub 2} powder with a grain size of about 35 nm and a low (<0.1 at %) manganese and iron content. The ferromagnetism in a CeO{sub 2} sample with a submicron crystallite size and the same manganese and iron impurity content is lower than in the nanocrystalline sample by an order of magnitude. Apart from ferromagnetism, both samples exhibit EPR spectra of localized paramagnetic centers, the concentration of which is lower than 0.01 at %. A comparative analysis of these results shows that the F-center exchange (FCE) mechanism cannot cause ferromagnetism. This conclusion agrees with the charge-transfer ferromagnetism model proposed recently.

Standard test method for the determination of uranium by ignition and the oxygen to uranium (O/U) atomic ratio of nuclear grade uranium dioxide powders and pellets

CERN Document Server

American Society for Testing and Materials. Philadelphia

2000-01-01

1.1 This test method covers the determination of uranium and the oxygen to uranium atomic ratio in nuclear grade uranium dioxide powder and pellets. 1.2 This test method does not include provisions for preventing criticality accidents or requirements for health and safety. Observance of this test method does not relieve the user of the obligation to be aware of and conform to all international, national, or federal, state and local regulations pertaining to possessing, shipping, processing, or using source or special nuclear material. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 1.4 This test method also is applicable to UO3 and U3O8 powder.

Observation of Conducting Structures in Detonation Nanodiamond Powder by Electron Paramagnetic Resonance

Science.gov (United States)

Binh, Nguyen Thi Thanh; Dolmatov, V. Yu.; Lapchuk, N. M.

2018-01-01

We have used electron paramagnetic resonance (EPR) to study high-purity detonation nanodiamond (DND) powders at room temperature. In recording the EPR signal with g factor 2.00247 and line width 0.890 mT, with automatic frequency control locking the frequency of the microwave generator (klystron) to the frequency of the experimental cavity, we observed a change in the shape of the EPR signal from the DND powder due to formation of an anisotropic electrically conducting structure in the powder. The electrical conductivity of the DND sample is apparent in the Dysonian EPR lineshape (strongly asymmetric signal with g factor 2.00146 and line width 0.281 mT) together with an abrupt shift of the baseline at the time of resonant absorption, and in the decrease in the cavity Q due to nonresonant microwave absorption. The observed effect can be explained by transition of the DND powder from a dielectric state to a state with metallic conductivity, due to spin ordering in a preferred direction.

Studies on the structure of zirconium carbide powders subjected to vibration grinding

International Nuclear Information System (INIS)

Kravchik, A.E.; Neshpor, V.S.

1976-01-01

The present work is a study of zirconium carbide powders subjected to vibratory milling in various media. The powders were comminuted in air (dry milling), benzene, trichloroethylene, and distilled water. The milling time was 10-160 h. The chemical compositions, specific surfaces, and crystal lattice parameters of the powder in the initial condition and after milling for 100 h in the various media are given. Vibratory milling of zirconium carbide powder can be successfully performed in benzene. Comminution in benzene enables a large specific surface to be attained, with practically no chemical reaction between the medium and the milling products. In milling in trichloroethylene the latter decomposes, with the formation of hydrochloric acid which reacts with the milling products. In a study of the fine structure parameters of zirconium carbide in the , , and directions the smallest crystal lattice strains and block sizes were observed in the direction. This may be taken as evidence that under such disintegration conditions the (110) planes constitute cleavage planes. An evaluation of internal and surface energies established that the strained crystal lattice energy reaches values which must be allowed for in any subsequent uses of the powder

Ceramic UO2 powder production at Cameco Corporation

International Nuclear Information System (INIS)

Kwong, A.K.; Kuchurean, S.M.

1997-01-01

This presentation covers the various aspects of ceramic grade uranium dioxide (UO 2 ) powder production at Cameco Corporation and its use as fuel and blanket fuel for heavy-water and light-water reactors, respectively. In addition, it discusses the significant production variables that affect production and product quality. It also provides an insight into how various support groups such as Quality Assurance, Analytical Services, and Technology Development fit into the quality cycle and contribute to a successful operation. The ability of Cameco to identify, measure and control the physical and chemical properties of ceramic grade UO 2 has resulted in the production of uniform quality powder. This has meant that 100% of Cameco's ceramic grade UO 2 powder produced since mid-1989 has been accepted by the fuel manufacturers. (author)

Modeling conversion of ammonium diuranate (ADU) into uranium dioxide (UO{sub 2}) powder

Energy Technology Data Exchange (ETDEWEB)

Hung, Nguyen Trong; Thuan, Le Ba [Institute for Technology of Radioactive and Rare Elements (ITRRE), 48 Lang Ha, Dong Da, Ha Noi (Viet Nam); Khoai, Do Van [Institute for Technology of Radioactive and Rare Elements (ITRRE), 48 Lang Ha, Dong Da, Ha Noi (Viet Nam); Current Postdoctoral Fellow at Tokai Reprocessing Technology Development Center, Japan Atomic Energy Agency (JAEA), 4-33 Tokaimura, Nakagun, Ibaraki, 319-1194 (Japan); Lee, Jin-Young, E-mail: jylee@kigam.re.kr [Convergence Research Center for Development of Mineral Resources (DMR), Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, 34132 (Korea, Republic of); Jyothi, Rajesh Kumar, E-mail: rkumarphd@kigam.re.kr [Convergence Research Center for Development of Mineral Resources (DMR), Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, 34132 (Korea, Republic of)

2016-10-15

In the paper, Brandon mathematical model that describes the relationship between the essential fabrication parameters [reduction temperature (T{sub R}), calcination temperature (T{sub C}), calcination time (t{sub C}) and reduction time (t{sub R})] and specific surface area of ammonium diuranate (ADU)-derived UO{sub 2} powder products was established. The proposed models can be used to predict and control the specific surface area of UO{sub 2} powders prepared through ADU route. Suitable temperatures for conversion of ADU and ammonium uranyl carbonate (AUC) was examined with the proposed model through assessment of the sinterability of UO{sub 2} powders.

Structural and optical analysis of ZnBeMgO powder and thin films

International Nuclear Information System (INIS)

Panwar, Neeraj; Liriano, J.; Katiyar, Ram S.

2011-01-01

Research highlights: → Structural and optical studies of Zn 1-x-y Be x Mg y O (0 ≤ x ≤0.10; 0 ≤ y ≤ 0.20) powders and thin films. → Raman studies of the pure ZnO powder showed all the characteristic peaks of the wurtzite hexagonal structure and with (Be, Mg) co-doping new modes appeared which can be attributed to arise as a result of doping effect. → The XRD of the films prepared from the powders using pulsed laser deposition (PLD) technique exhibited the preferential orientation and with doping the (0 0 0 2) peak also shifts to higher 2θ values suggesting the incorporation of Be/Mg at the Zn-site. → From the UV-visible optical band gap measurement it was noticed that the band gap of the pristine ZnO film is 3.3 eV which enhanced up to 4.51 eV for Zn 0.7 Be 0.1 Mg 0.2 O film which lies in the solar blind region and is very useful for the deep UV detection. - Abstract: We here report the structural and optical studies of Zn 1-x-y Be x Mg y O (0 ≤ x ≤ 0.15; 0 ≤ y ≤ 0.20) powders and thin films. From the Rietveld refinement of the powder X-ray diffraction (XRD) patterns it was revealed that the value of 'a' lattice parameter remains almost unchanged whereas 'c' parameter reduces with Be and Mg co-doping in ZnO. The Zn-O bond length also decreases in co-doped samples. Raman studies of the pure ZnO powder showed all the characteristic peaks of the wurtzite hexagonal structure and with (Be, Mg) co-doping new modes appeared which can be attributed to arise as a result of substitution. The XRD of the films prepared from the powders using pulsed laser deposition (PLD) technique exhibited the preferential orientation and with increase in co-doping the (0 0 0 2) peak also shifts to higher 2θ values suggesting the incorporation of Be/Mg at the Zn-site. From the UV-visible optical transmittance measurement it was noticed that the band gap of the pristine ZnO film is 3.3 eV which enhanced up to 4.51 eV for Zn 0.7 Be 0.1 Mg 0.2 O film which lies in the

Influence of various manufacturing parameters on some characteristics of UO2 powders and their sintering behaviour

International Nuclear Information System (INIS)

Mintz, M.H.; Vaknin, Sh.; Kremener, A.; Hadari, Z.

1977-02-01

Various parameters in the process of manufacturing uranium dioxide are examined and their influence on the characteristics and sintering behaviour of the powders obtained established. In addition some correlations between the powder aggregates microstructure and their adhesion properties and sintering behaviour are indicated. Shrinkage during the sintering process is also discussed

Reaction mechanisms for enhancing carbon dioxide mineral sequestration

Science.gov (United States)

Jarvis, Karalee Ann

Increasing global temperature resulting from the increased release of carbon dioxide into the atmosphere is one of the greatest problems facing society. Nevertheless, coal plants remain the largest source of electrical energy and carbon dioxide gas. For this reason, researchers are searching for methods to reduce carbon dioxide emissions into the atmosphere from the combustion of coal. Mineral sequestration of carbon dioxide reacted in electrolyte solutions at 185°C and 2200 psi with olivine (magnesium silicate) has been shown to produce environmentally benign carbonates. However, to make this method feasible for industrial applications, the reaction rate needs to be increased. Two methods were employed to increase the rate of mineral sequestration: reactant composition and concentration were altered independently in various runs. The products were analyzed with complete combustion for total carbon content. Crystalline phases in the product were analyzed with Debye-Scherrer X-ray powder diffraction. To understand the reaction mechanism, single crystals of San Carlos Olivine were reacted in two solutions: (0.64 M NaHCO3/1 M NaCl) and (5.5 M KHCO3) and analyzed with scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and fluctuation electron microscopy (FEM) to study the surface morphology, atomic crystalline structure, composition and amorphous structure. From solution chemistry studies, it was found that increasing the activity of the bicarbonate ion increased the conversion rate of carbon dioxide to magnesite. The fastest conversion, 60% conversion in one hour, occurred in a solution of 5.5 M KHCO3. The reaction product particles, magnesium carbonate, significantly increased in both number density and size on the coupon when the bicarbonate ion activity was increased. During some experiments reaction vessel corrosion also altered the mineral sequestration mechanism. Nickel ions from vessel

Influence of some factors upon forces transmission during UO2 powders compaction

International Nuclear Information System (INIS)

Deju, R.; Georgeoni, P.; Turcanu, N.C.; Dobos, I.

1979-01-01

The ratio between the transmitted force to the lower punch and the force applied to the upper punch is a constant, k, on given conditions. The obtained results have shown the validity of the proposed relation between the ratio, k, on the one hand, and the inverse of mass compact, the ratio between height and diameter, the average density of the compact, on the other hand. The influence of the powder quality, powder conditioning, granulometry of the conditioned material, quality and quantity of the lubricant, over the k ratio, during the uranium dioxide powder compaction, were studied. (author)

Kinetic study of synthesis of Titanium carbide by methano thermal reduction of Titanium dioxide

International Nuclear Information System (INIS)

Alizadeh, R.; Ostrovski, O.

2011-01-01

Reduction of the Titanium dioxide, TiO 2 , by methane was investigated in this work. The thermodynamic of reaction was examined and found favorable. The reaction of titanium dioxide with methane was carried out in the temperature range 1150 d egree C to 1450 d egree C at atmospheric pressure with industrial high porosity pellets prepared from titanium dioxide powder. The evolved gas analyzing method was used for determination of the extent of reduction rate. The gas products of the reaction are mostly CO and trace amount of CO 2 and H 2 O. The synthesized product powder was characterized by X-ray diffraction for elucidating solid phase compositions. The effect of varying temperature was studied during the reduction. The conversion-time data have been interpreted by using the grain model. For first order reaction with respect to methane concentration, the activation energy of titanium dioxide reduction by methane is found to be 51.4 kcal/g mole. No detailed investigation of kinetic and mechanism of the reaction was reported in literatures.

The fabrication and visible-near-infrared optical modulation of vanadium dioxide/silicon dioxide composite photonic crystal structure

Science.gov (United States)

Liang, Jiran; Li, Peng; Song, Xiaolong; Zhou, Liwei

2017-12-01

We demonstrated a visible and near-infrared light tunable photonic nanostructure, which is composed of vanadium dioxide (VO2) thin film and silicon dioxide (SiO2) ordered nanosphere arrays. The vanadium films were sputtered on two-dimensional (2D) SiO2 sphere arrays. VO2 thin films were prepared by rapid thermal annealing (RTA) method with different oxygen flow rates. The close-packed VO2 shell formed a continuous surface, the composition of VO2 films in the structure changed when the oxygen flow rates increased. The 2D VO2/SiO2 composite photonic crystal structure exhibited transmittance trough tunability and near-infrared (NIR) transmittance modulation. When the oxygen flow rate increased from 3 slpm to 4 slpm, the largest transmittance trough can be regulated from 904 to 929 nm at low temperature, the transmittance troughs also appear blue shift when the VO2 phase changes from insulator to metal. The composite nanostructure based on VO2 films showed visible transmittance tunability, which would provide insights into the glass color changing in smart windows.

The cohesive energy of uranium dioxide and thorium dioxide

International Nuclear Information System (INIS)

Childs, B.G.

1958-08-01

Theoretical values have been calculated of the heats of formation of uranium dioxide and thorium dioxide on the assumption that the atomic binding forces in these solids are predominantly ionic in character. The good agreement found between the theoretical and observed values shows that the ionic model may, with care, be used in calculating the energies of defects in the uranium and thorium dioxide crystal structures. (author)

Point Defects in 3D and 1D Nanomaterials: The Model Case of Titanium Dioxide

International Nuclear Information System (INIS)

Knauth, Philippe

2010-01-01

Titanium dioxide is one of the most important oxides for applications in energy and environment, such as solar cells, photocatalysis, lithium-ion batteries. In recent years, new forms of titanium dioxide with unusual structure and/or morphology have been developed, including nanocrystals, nanotubes or nanowires. We have studied in detail the point defect chemistry in nanocrystalline TiO 2 powders and ceramics. There can be a change from predominant Frenkel to Schottky disorder, depending on the experimental conditions, e.g. temperature and oxygen partial pressure. We have also studied the local environment of various dopants with similar ion radius, but different ion charge (Zn 2+ , Y 3+ , Sn 4+ , Zr 4+ , Nb 5+ ) in TiO 2 nanopowders and nanoceramics by Extended X-Ray Absorption Fine Structure (EXAFS) Spectroscopy. Interfacial segregation of acceptors was demonstrated, but donors and isovalent ions do not segregate. An electrostatic 'space charge' segregation model is applied, which explains well the observed phenomena.

The analysis of powder diffraction data

International Nuclear Information System (INIS)

David, W.I.F.; Harrison, W.T.A.

1986-01-01

The paper reviews neutron powder diffraction data analysis, with emphasis on the structural aspects of powder diffraction and the future possibilities afforded by the latest generation of very high resolution neutron and x-ray powder diffractometers. Traditional x-ray powder diffraction techniques are outlined. Structural studies by powder diffraction are discussed with respect to the Rietveld method, and a case study in the Rietveld refinement method and developments of the Rietveld method are described. Finally studies using high resolution powder diffraction at the Spallation Neutron Source, ISIS at the Rutherford Appleton Laboratory are summarized. (U.K.)

Determination of crystal structures with large known fragments directly from measured X-ray powder diffraction intensities

International Nuclear Information System (INIS)

Rius, J.; Miravitlles, C.

1988-01-01

A strategy for the determination of crystal structures with large known fragments directly from measured X-ray powder diffraction intensities is presented. It is based on the automated full-symmetry Patterson search method described by Rius and Miravitlles where the Fourier coefficients of the observed Patterson function are modified to allow the use of powder diffraction intensity data. Its application to two structures, one with simulated and one with experimental data, is shown. (orig.)

Nano-powder production by electrical explosion of wires

International Nuclear Information System (INIS)

Mao Zhiguo; Zou Xiaobing; Wang Xinxin; Jiang Weihua

2010-01-01

A device for nano-powder production by electrical explosion of wires was designed and built. Eight wires housed in the discharge chamber are exploded one by one before opening the chamber for the collection of the produced nano-powder. To increase the rate of energy deposition into a wire, the electrical behavior of the discharge circuit including the exploding wire was simulated. The results showed that both reducing the circuit inductance and reducing the capacitance of the energy-storage capacitor (keeping the storage energy constant) can increase the energy deposition rate. To better understand the physical processes of the nano-powder formation by the wire vapor, a Mach-Zehnder interferometer was used to record the time evolution of the wire vapor as well as the plasma. A thermal expansion lag of the dense vapor core as well as more than one times of the vapor burst was observed for the first time. Finally, nano-powders of titanium nitride, titanium dioxide, copper oxides and zinc oxide were produced by electrical explosion of wires. (authors)

Powder-based synthesis of nanocrystalline material components for structural application. Final report

Energy Technology Data Exchange (ETDEWEB)

Ilyuschenko, A.F.; Ivashko, V.S.; Okovity, V.A. [Powder Metallurgy Research Inst., Minsk (Belarus)] [and others

1998-12-01

Hydroxiapate spray coatings and substrates for implant production as well as multilayered metal ceramic coatings from nanocrystalline materials are a subject of the investigation. The work aims at the improvement of quality of said objects. This study has investigated the processes of hydroxiapatite powder production. Sizes, shapes and relief of initial HA powder surface are analyzed using SEM and TEM. Modes of HA plasma spraying on a substrate from titanium and associated compositions of traditional and nanocrystalline structure are optimized. The quality of the sprayed samples are studied using X-ray phase analysis and metallographic analysis. The results of investigations of bioceramic coating spraying on titanium are theoretically generalized, taking into account obtained experimental data. The results of investigations of ion-beam technology are presented for spraying multilayered coatings consisting of alternating metal-ceramic layers of nanocrystalline structure.

Internal exposure to neutron-activated {sup 56}Mn dioxide powder in Wistar rats. Pt. 1. Dosimetry

Energy Technology Data Exchange (ETDEWEB)

Stepanenko, Valeriy; Kaprin, Andrey; Galkin, Vsevolod; Ivanov, Sergey; Kolyzhenkov, Timofey; Petukhov, Aleksey; Yaskova, Elena; Belukha, Irina; Khailov, Artem; Skvortsov, Valeriy; Ivannikov, Alexander; Akhmedova, Umukusum; Bogacheva, Viktoria [Medical Radiological Research Center (MRRC) named after A.F. Tsyb - National Medical Research Radiological Center of the Health Ministry of the Russian Federation, Obninsk, Kaluga Region (Russian Federation); Rakhypbekov, Tolebay; Dyussupov, Altay; Chaizhunusova, Nailya; Sayakenov, Nurlan; Uzbekov, Darkhan; Saimova, Aisulu; Shabdarbaeva, Dariya; Kairkhanova, Yankar [Semey State Medical University, Semey (Kazakhstan); Otani, Keiko; Endo, Satoru; Satoh, Kenichi; Kawano, Noriyuki; Fujimoto, Nariaki; Hoshi, Masaharu [Hiroshima University, Hiroshima (Japan); Shichijo, Kazuko; Nakashima, Masahiro; Takatsuji, Toshihiro [Nagasaki University, Nagasaki (Japan); Sakaguchi, Aya; Kato, Hiroaki; Onda, Yuichi [University of Tsukuba, Ibaraki (Japan); Toyoda, Shin [Okayama University of Science, Okayama (Japan); Sato, Hitoshi [Ibaraki Prefectural University of Health Science, Ibaraki (Japan); Skakov, Mazhin; Vurim, Alexandr; Gnyrya, Vyacheslav; Azimkhanov, Almas; Kolbayenkov, Alexander [National Nuclear Center of the Republic of Kazakhstan, Kurchatov (Kazakhstan); Zhumadilov, Kasym [Eurasian National University named after L.N. Gumilyov, Astana (Kazakhstan)

2017-03-15

There were two sources of ionizing irradiation after the atomic bombings of Hiroshima and Nagasaki: (1) initial gamma-neutron irradiation at the moment of detonation and (2) residual radioactivity. Residual radioactivity consisted of two components: radioactive fallout containing fission products, including radioactive fissile materials from nuclear device, and neutron-activated radioisotopes from materials on the ground. The dosimetry systems DS86 and DS02 were mainly devoted to the assessment of initial radiation exposure to neutrons and gamma rays, while only brief considerations were given for the estimation of doses caused by residual radiation exposure. Currently, estimation of internal exposure of atomic bomb survivors due to dispersed radioactivity and neutron-activated radioisotopes from materials on the ground is a matter of some interest, in Japan. The main neutron-activated radionuclides in soil dust were {sup 24}Na, {sup 28}Al, {sup 31}Si, {sup 32}P, {sup 38}Cl, {sup 42}K, {sup 45}Ca, {sup 46}Sc, {sup 56}Mn, {sup 59}Fe, {sup 60}Co, and {sup 134}Cs. The radionuclide {sup 56}Mn (T{sub 1/2} = 2.58 h) is known as one of the dominant beta- and gamma emitters during the first few hours after neutron irradiation of soil and other materials on ground, dispersed in the form of dust after a nuclear explosion in the atmosphere. To investigate the peculiarities of biological effects of internal exposure to {sup 56}Mn in comparison with external gamma irradiation, a dedicated experiment with Wistar rats exposed to neutron-activated {sup 56}Mn dioxide powder was performed recently by Shichijo and coworkers. The dosimetry required for this experiment is described here. Assessment of internal radiation doses was performed on the basis of measured {sup 56}Mn activity in the organs and tissues of the rats and of absorbed fractions of internal exposure to photons and electrons calculated with the MCNP-4C Monte Carlo using a mathematical rat phantom. The first results of

Experimental study on influence of carbon dioxide on porous structure and mechanical properties of shale rock

Directory of Open Access Journals (Sweden)

Danuta Miedzińska

2017-12-01

Full Text Available Shale rocks are geological formations which can be unconventional gas reservoirs. During their interaction with carbon dioxide, which can be used as a fracturing fluid in shale gas recovery process, many phenomena take place that can influence rock structure and mechanical properties. The research on changes in rock structure under super critical carbon dioxide interaction and their influence of shale properties were presented in the paper. The structural tests were carried out with the use of microscopic techniques with different resolutions of visualization. The uniaxial compression test was applied as a mechanical properties’ assessment experiment. As a result of research, some dependence was observed. The bigger decrease was in porosity after infiltration in lower zooms, the bigger increase in porosity in high zooms and mechanical properties was noticed. Keywords: geomechanics, shale rock, carbon dioxide

The fabrication and visible-near-infrared optical modulation of vanadium dioxide/silicon dioxide composite photonic crystal structure

Energy Technology Data Exchange (ETDEWEB)

Liang, Jiran; Li, Peng; Song, Xiaolong; Zhou, Liwei [Tianjin University, School of Microelectronics, Tianjin (China)

2017-12-15

We demonstrated a visible and near-infrared light tunable photonic nanostructure, which is composed of vanadium dioxide (VO{sub 2}) thin film and silicon dioxide (SiO{sub 2}) ordered nanosphere arrays. The vanadium films were sputtered on two-dimensional (2D) SiO{sub 2} sphere arrays. VO{sub 2} thin films were prepared by rapid thermal annealing (RTA) method with different oxygen flow rates. The close-packed VO{sub 2} shell formed a continuous surface, the composition of VO{sub 2} films in the structure changed when the oxygen flow rates increased. The 2D VO{sub 2}/SiO{sub 2} composite photonic crystal structure exhibited transmittance trough tunability and near-infrared (NIR) transmittance modulation. When the oxygen flow rate increased from 3 slpm to 4 slpm, the largest transmittance trough can be regulated from 904 to 929 nm at low temperature, the transmittance troughs also appear blue shift when the VO{sub 2} phase changes from insulator to metal. The composite nanostructure based on VO{sub 2} films showed visible transmittance tunability, which would provide insights into the glass color changing in smart windows. (orig.)

Effects of bioglass powders with and without mesoporous structures on fibroblast and osteoblast responses

Energy Technology Data Exchange (ETDEWEB)

Shih, Chi-Jen, E-mail: cjshih@kmu.edu.tw [Department of Fragrance and Cosmetic Science, College of Pharmacy, Kaohsiung Medical University, 100 Shi-Chuan 1st Road, Kaohsiung 80708, Taiwan (China); Lu, Pei-Shan [Department of Fragrance and Cosmetic Science, College of Pharmacy, Kaohsiung Medical University, 100 Shi-Chuan 1st Road, Kaohsiung 80708, Taiwan (China); Hsieh, Chih-Hsin [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Chen, Wen-Cheng [Advanced Medical Devices and Composites Laboratory, Department of Fiber and Composite Materials, College of Engineering, Feng Chia University, Taichung 40724, Taiwan (China); Chen, Jian-Chih [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China); Department of Orthopaedics, College of Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan (China)

2014-09-30

Highlights: • Fluorescent microscopy images show that BG-M has excellent cellular affinity. • Both the BG and BG-M substrates had positive effects on the proliferation of the osteoblastic cells. • Cells cultured on BG-M had approximately 1.4 times higher proliferation activity. - Abstract: The main objective of this study was to compare the responses of fibroblasts and osteoblasts to bioglass (BG) and bioglass-containing mesoporous structure (BG-M) powders. The BG-M powders exhibited specific surface areas approximately three times larger than those of the BG powders. The formation of a hysteresis loop also signified the presence of mesoporous structures in the BG-M samples; however, a hysteresis loop was not observed for the BG samples, resulting in 1/5 the pore volume of the BG-M samples. The viabilities of the fibroblasts and osteoblasts cultured in media containing the BG-M powders for 1, 2, and 3 days were greater than 90%. Importantly, the results of fluorescent microscopy images show that BG-M has excellent cellular affinity. Both the BG and BG-M substrates had positive effects on the proliferation of the osteoblastic cells. However, cells cultured on BG-M had approximately 1.4 times higher proliferation activity.

Effects of bioglass powders with and without mesoporous structures on fibroblast and osteoblast responses

International Nuclear Information System (INIS)

Shih, Chi-Jen; Lu, Pei-Shan; Hsieh, Chih-Hsin; Chen, Wen-Cheng; Chen, Jian-Chih

2014-01-01

Highlights: • Fluorescent microscopy images show that BG-M has excellent cellular affinity. • Both the BG and BG-M substrates had positive effects on the proliferation of the osteoblastic cells. • Cells cultured on BG-M had approximately 1.4 times higher proliferation activity. - Abstract: The main objective of this study was to compare the responses of fibroblasts and osteoblasts to bioglass (BG) and bioglass-containing mesoporous structure (BG-M) powders. The BG-M powders exhibited specific surface areas approximately three times larger than those of the BG powders. The formation of a hysteresis loop also signified the presence of mesoporous structures in the BG-M samples; however, a hysteresis loop was not observed for the BG samples, resulting in 1/5 the pore volume of the BG-M samples. The viabilities of the fibroblasts and osteoblasts cultured in media containing the BG-M powders for 1, 2, and 3 days were greater than 90%. Importantly, the results of fluorescent microscopy images show that BG-M has excellent cellular affinity. Both the BG and BG-M substrates had positive effects on the proliferation of the osteoblastic cells. However, cells cultured on BG-M had approximately 1.4 times higher proliferation activity

Structure of orthorhombic SrZrO/sub 3/ by neutron powder diffraction

Energy Technology Data Exchange (ETDEWEB)

Ahtee, A; Ahtee, M [Helsinki Univ. (Finland). Dept. of Physics; Glazer, A M [Cambridge Univ. (UK). Cavendish Lab.; Hewat, A W [Institut Max von Laue - Paul Langevin, 38 - Grenoble (France)

1976-12-15

The room-temperature structure of SrZrO/sub 3/ has been established by neutron powder-profile refinement. The space group is Pbnm and SrZrO/sub 3/ is isostructural with other perovskites, such as CaTiO/sub 3/.

Preparation and characterization of functional fabrics from bamboo charcoal/silver and titanium dioxide/silver composite powders and evaluation of their antibacterial efficacy

Energy Technology Data Exchange (ETDEWEB)

Yang, Fu-Chu, E-mail: yfc580629@yahoo.com.tw [Army Command Headquarters, MND, Taoyuan, Taiwan (China); Wu, Kuo-Hui [Department of Applied Chemistry and Materials Science, Chung Cheng Institute of Technology, NDU, No. 190, Sanyuan 1st Street, Tahsi, Taoyuan 335, Taiwan (China); Huang, Jen-Wei [Department of Physics, Chinese Military Academy, Fengshan, Kaohsiung, Taiwan (China); Horng, Deng-Nan; Liang, Chia-Feng [Department of Chemistry, Chinese Military Academy, Fengshan, Kaohsiung, Taiwan (China); Hu, Ming-Kuan [School of Pharmacy, National Defense Medical Center, Taipei, Taiwan (China)

2012-07-01

Bamboo charcoal supporting silver (BC/Ag) and titanium dioxide supporting silver (TiO{sub 2}/Ag) were prepared by activation and chemical reduction. The BC/Ag and TiO{sub 2}/Ag composites were characterized by silver particle size and distribution and antibacterial properties. The pore and surface properties were studied in terms of BET volumetric measurement with nitrogen adsorption, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The antibacterial effects of the BC/Ag and TiO{sub 2}/Ag composite powders were assessed from the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs), and an excellent antibacterial performance was discovered. Moreover, these composite powders were deposited via immersion coating onto fabrics (nonwoven and carbon fibers) to improve the antibacterial efficacy and to act as a biologically-protective material. The antibacterial activities of the fabrics supported by BC/Ag and TiO{sub 2}/Ag were studied in zone of inhibition and plate counting tests against Gram-positive Staphylococcus aureus ME/GM/TC Resistant, Bacillus subtilis, Candida albicans, Gram-negative Pseudomonas aeruginosae (CTZ and EM and GM) Res. Clin. Isol., Escherichia coli Juhl, and Klebsiella pneumoniae. The results showed that fabric-BC/Ag and fabric-TiO{sub 2}/Ag possess a strong antibacterial activity and an inhibitory effect on the growth of these bacteria and are therefore believed to have great potential for use as antibacterial fabrics.

Dihydroxycoumarin Schiff base synthesis and structure determination from powder diffraction data

Czech Academy of Sciences Publication Activity Database

Rohlíček, Jan; Ketata, I.; Ben Ayed, T.; Ben Hassen, R.

2013-01-01

Roč. 1051, NOV (2013), s. 280-284 ISSN 0022-2860 Grant - others:AV ČR(CZ) AP0701 Program:Akademická prémie - Praemium Academiae Institutional support: RVO:68378271 Keywords : powder diffraction * structure solution * Schiff base * dihydroxycoumarine Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.599, year: 2013

Morphological and structural characterization of the Zn0,9Mn0,1O powder synthesized by combustion reaction and Pechini

International Nuclear Information System (INIS)

Ribeiro, M.A.; Torquato, R.; Simoes, A.N.; Costa, A.C.F.M.; Gama, L.; Kiminami, R.H.G.A.

2009-01-01

Zinc oxide, due to the piezoelectric and electro-optical characteristics, is used in application such as, chemical sensor, varistor, transparent conductive thin film and DMS. The aim of this work is to evaluate and compare structural and morphological characteristics of nanometric powders of Zn 0,9 Mn 0,1 O prepared by chemical synthesis of combustion reaction and Pechini method. The powders were characterized by XRD, SEM and BET. The XRD data shown to both studied method the presence of ZnO phase with hexagonal structure and without second phase. The powder prepared by combustion reaction presented 9% of reduction in crystallinity and 42% of increase in surface area in comparison with the powder prepared by Pechini method. The morphological analysis of the powder showed that both method produce powders with soft agglomerates constituted by nano size particles. (author)

Influence of Process Control Agent on Characterization and Structure of Micron Chitosan Powders Prepared by Ball Milling Method

Directory of Open Access Journals (Sweden)

ZHANG Chuan-jie

2016-12-01

Full Text Available With ethyl alcohol or distilled water as process control agent (PCA, micron chitosan powder was prepared by ball milling method. The yield rate, particle size distribution, micro morphology, viscosity average molecular mass, chemical and crystal structures, and thermal properties of these different micron chitosan powders were measured. The results indicate that the yield rate of micron chitosan powders prepared with ethyl alcohol as PCA increases significantly, and improves to 94.7% from 25% while the amount of ethyl alcohol is 0.75mL/g. The particle size distribution of micron chitosan powder prepared with ethyl alcohol as PCA is concentrated, while the D50 and D90 in size are 824nm and 1629nm respectively. Chitosan do not react with ethyl alcohol used as PCA, but the viscosity average molecular mass of prepared micron chitosan powder decreases by 23%, the crystal structures are destroyed slightly, and its thermal stability is slightly weakened.

Uranium tetrafluoride production via dioxide by wet process

International Nuclear Information System (INIS)

Aquino, A.R. de.

1988-01-01

The study for the wet way obtention of uranium tetrafluoride by the reaction of hydrofluoric acid and powder uranium dioxide, is presented. From the results obtained at laboratory scale a pilot plant was planned and erected. It is presently in operation for experimental data aquisition. Time of reaction, temperature, excess of reagents and the hydrofluoric acid / uranium dioxide ratio were the main parameters studied to obtain a product with the following characteristics: - density greater than 1 g/cm 3 , conversion rate greater than 96%, and water content equal to 0,2% that allows its application to heaxafluoride convertion or to magnesiothermic process. (author) [pt

Stereological analysis of structure formation for solid WC-Co alloys in the process of carbide powder consolidation

Energy Technology Data Exchange (ETDEWEB)

Chernyavskij, K S

1986-03-01

Evolution of particle size distribution in carbide powders of different technological prehistory is studied in the process of their consolidation as a hard alloy. A successive estimate on identical preparations is used to study a structural powder->alloy transition. Temperature dependences of integral measures of the consolidated structure and characteristics of its heterogeneity are studied. It is shown that all studied structural rearrangements: formation of regular alternation of carbide and binding phases, development of particle-phase interfaces, change in size distribution - more intensely proceed in the high-temperature carbide base alloy.

Properties of raw materials and intermediate products in the production of uranium dioxide sintered tablets

International Nuclear Information System (INIS)

Landspersky, H.; Vanecek, I.; Podest, M.

1977-01-01

The properties are described of ammonium polyuranate and of powder uranium dioxide. Ammonium polyuranate, an intermediate product, is prepared by filtering the precipitate from uranyl nitrate solution precipitation, this either by an ammonia aqueous solution from a uranyl nitrate aqueous solution or by direct U 6+ precipitation from a TBP kerosene solution by aqueous concentrated ammonia. With relation to further processing, the major properties of the intermediate product include grain size, shape and appearance of crystallites, structure and thermal decomposition. These properties affect the properties of UO 2 , the following intermediate product obtained by reduction of ammonium polyuranate. Powder UO 2 is the final intermediate product; high-compacted UO 2 pellets are manufactured from it by compacting and sintering. The final product properties are affected by the following parameters: specific surface, grain size and shape, U/O ratio and compactibility. The effect of and the techniques of determining these parameters are shown. The necessity is emphasised of studying the properties of powder ammonium polyuranate because changes in its production technology affect the properties of further products. (J.P.)

The structure-property relationships of powder processed Fe-Al-Si alloys

Energy Technology Data Exchange (ETDEWEB)

Prichard, Paul D. [Iowa State Univ., Ames, IA (United States)

1998-02-23

Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic %). The powder alloys were produced with a high pressure gas atomization (HPGA) process to obtain a high fraction of metal injection molding (MIM) quality powder (D₈₄ < 32 μm). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 μm. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 μm to 104 μm. Mechanical property testing was conducted on both extruded and sintered material using a small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25 to 550 C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase α + DO₃ structure. This investigation provided a framework for understanding the effects of silicon in powder processing and mechanical property behavior of Fe-Al-Si alloys.

Method of carbon dioxide-free hydrogen production from hydrocarbon decomposition over metal salts

Science.gov (United States)

Erlebacher, Jonah; Gaskey, Bernard

2017-10-03

A process to decompose methane into carbon (graphitic powder) and hydrogen (H.sub.2 gas) without secondary production of carbon dioxide, employing a cycle in which a secondary chemical is recycled and reused, is disclosed.

Optimization of process parameters in precipitation for consistent quality UO2 powder production

International Nuclear Information System (INIS)

Tiwari, S.K.; Reddy, A.L.V.; Venkataswamy, J.; Misra, M.; Setty, D.S.; Sheela, S.; Saibaba, N.

2013-01-01

Nuclear reactor grade natural uranium dioxide powder is being produced through precipitation route, which is further processed before converting into sintered pellets used in the fabrication of PHWR fuel assemblies of 220 and 540 MWe type reactors. The process of precipitating Uranyl Nitrate Pure Solution (UNPS) is an important step in the UO 2 powder production line, where in soluble uranium is transformed into solid form of Ammonium Uranate (AU), which in turn reflects and decides the powder characteristics. Precipitation of UNPS with vapour ammonia is being carried out in semi batch process and process parameters like ammonia flow rate, temperature, concentration of UNPS and free acidity of UNPS are very critical and decides the UO 2 powder quality. Variation in these critical parameters influences powder characteristics, which in turn influences the sinterability of UO 2 powder. In order to get consistent powder quality and sinterability the critical parameter like ammonia flow rate during precipitation is studied, optimized and validated. The critical process parameters are controlled through PLC based automated on-line data acquisition systems for achieving consistent powder quality with increased recovery and production. The present paper covers optimization of process parameters and powder characteristics. (author)

Biaxially textured articles formed by powder metallurgy

Science.gov (United States)

Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

2003-08-05

A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of ternary mixtures consisting of: Ni powder, Cu powder, and Al powder, Ni powder, Cr powder, and Al powder; Ni powder, W powder and Al powder; Ni powder, V powder, and Al powder; Ni powder, Mo powder, and Al powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100} orientation texture; and further having a Curie temperature less than that of pure Ni.

Powder X-ray diffraction studies of structural and kinetic aspects of polymorphism

International Nuclear Information System (INIS)

Chan, F.C.

1999-01-01

Polymorphism is a poorly understood phenomenon that is of considerable technological interest to the pharmaceutical industry. The polymorph selected can influence the bioavailability, processing and stability of the pharmaceutical dosage form. In this study structural, kinetic and thermodynamics aspects of polymorphism and polymorphic phase transformations have been examined using powder X-ray diffraction (PXRD). The compound sulphathiazole is a well-studied model in the investigation of polymorphism and crystal growth. There are five known polymorphic forms and the structure of form V was unknown until this study. The difficulty has been that it has not been possibly to prepare crystals of appropriate size and quality for single crystal diffraction. Furthermore, structure solution from powder data for organic molecules is almost impossible. Despite the challenge the structure of sulphathiazole form V have been solved ab initio from powder data using direct methods. With 16 non-hydrogen atoms in the molecule and two molecules in the asymmetric unit, this structure represents a significant advance in terms of the complexity of an organic structure solved from PXRD data. The structural data should be invaluable for rationalizing experimental observations and the development of theoretical ideas regarding polymorphism and crystal growth. The second part of the study, has examined kinetics of polymorphic phase transformations as a function of pressure combined with temperature using real-time synchrotron PXRD. The significance of pressure arises from the fact that phase transitions can be induced in pharmaceuticals during tabletting. The phase transformation behaviour of rubidium iodide (chosen as a simple test model) has been investigated as a function of isobaric pressure at ambient and elevated temperatures. The kinetics have been characterized by using the Johnson-Melil-Avrami equation. The effect of successive cycling across the transition pressure was also

Synthesis and characterization on titanium dioxide prepared by precipitation and hydrothermal treatment; Sintese e caracterizacao de dioxido de titanio preparado por precipitacao e tratamento hidrotermico

Energy Technology Data Exchange (ETDEWEB)

Santos, Andre V.P. dos; Yoshito, Walter K.; Lazar, Dolores R.R.; Ussui, Valter, E-mail: vussui@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2012-07-01

Surface properties of titanium dioxide (titania) are outstanding among ceramic materials and enables uses as catalysts, photoelectrochemical devices, solar cells and others. In many of these applications, it is necessary to keep the anatase phase, that is stable only in low temperatures (<400 deg C). In the present work, the influence of hydrothermal treatment on physical characteristics and crystal structure of titania powders synthesized by precipitation was investigated. Characterizations of obtained powders were carried out by X-ray diffraction, surface area analysis by N2 gas sorption (BET) and microstructure of powders and ceramics were analyzed by scanning electron microscopy. As prepared powders were formed as cylindrical pellets by uniaxial pressing and sintered at 1500 deg C for 01 hour. Results showed that anatase phase without formation of rutile phase can be formed in hydrothermally treated samples . Rutile phase is predominant in calcined and/or sintered samples (author)

Crystal structure determination from powder diffraction data of the coumarin vanillin chalcone

Czech Academy of Sciences Publication Activity Database

Ghouili, A.; Rohlíček, Jan; Ayed, T.B.; Hassen, R.B.

2014-01-01

Roč. 29, č. 4 (2014), s. 361-365 ISSN 0885-7156 Grant - others:AV ČR(CZ) Praemium Academiae Institutional support: RVO:68378271 Keywords : chalcone * absorption spectra * powder diffraction * crystal structure determination * coumarin derivatives Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.636, year: 2014

Highly photocatalytic TiO_2 interconnected porous powder fabricated by sponge-templated atomic layer deposition

International Nuclear Information System (INIS)

Pan, Shengqiang; Zhao, Yuting; Huang, Gaoshan; Li, Menglin; Mei, Yongfeng; Wang, Jiao; Zheng, Lirong; Baunack, Stefan; Schmidt, Oliver G; Gemming, Thomas

2015-01-01

A titanium dioxide (TiO_2) interconnected porous structure has been fabricated by means of atomic layer deposition of TiO_2 onto a reticular sponge template. The obtained freestanding TiO_2 with large surface area can be easily taken out of the water to solve a complex separation procedure. A compact and conformal nanocoating was evidenced by morphologic characterization. A phase transition, as well as production of oxygen vacancies with increasing annealing temperature, was detected by x-ray diffraction and x-ray photoelectron spectroscopy, respectively. The photocatalytic experimental results demonstrated that the powder with appropriate annealing treatment possessed excellent photocatalytic ability due to the co-action of high surface area, oxygen vacancies and the optimal crystal structure. (paper)

Carbon dioxide capture from exhaust gases by selective adsorption on porous solids

Energy Technology Data Exchange (ETDEWEB)

Schindler, M.; Ernst, S. [Technische Univ. Kaiserslautern (Germany). Dept. of Chemistry

2007-07-01

The metal-organic frameworks Cu{sub 3}(BTC){sub 2}, MIL-53 and MIL-96 were synthesized and characterized by powder X-ray diffraction, scanning electron microscopy and nitrogenphysisorption. The adsorption isotherms for carbon dioxide at temperatures of 20, 40 and 60 C and pressures up to 1000 mbar on this new type of microporous solids were measured by a static volumetric method. For comparison, experiments with zeolite NaX (13X) were also included. High adsorption capacities for carbon dioxide were found for the adsorbents investigated in this study. The breakthrough curves for the adsorption of a mixture of nitrogen and carbon dioxide on Cu{sub 3}(BTC){sub 2} reveal a high affinity of this material for the adsorption of carbon dioxide in the presence of nitrogen. (orig.)

Characterization of ceramic powder compacts

International Nuclear Information System (INIS)

Yanai, K.; Ishimoto, S.; Kubo, T.; Ito, K.; Ishikawa, T.; Hayashi, H.

1995-01-01

UO 2 and Al 2 O 3 powder packing structures in cylindrical powder compacts are observed by scanning electron microscopy using polished cross sections of compacts fixed by low viscosity epoxy resin. Hard aggregates which are not destroyed during powder compaction are observed in some of the UO 2 powder compacts. A technique to measure local density in powder compacts is developed based on counting characteristic X-ray intensity by energy dispersive X-ray analysis (EDX). The local density of the corner portion of the powder compact fabricated by double-acting dry press is higher than that of the inner portion. ((orig.))

Structural markers of the evolution of whey protein isolate powder during aging and effects on foaming properties.

Science.gov (United States)

Norwood, E-A; Le Floch-Fouéré, C; Briard-Bion, V; Schuck, P; Croguennec, T; Jeantet, R

2016-07-01

The market for dairy powders, including high added-value products (e.g., infant formulas, protein isolates) has increased continuously over the past decade. However, the processing and storage of whey protein isolate (WPI) powders can result in changes in their structural and functional properties. It is therefore of great importance to understand the mechanisms and to identify the structural markers involved in the aging of WPI powders to control their end use properties. This study was performed to determine the effects of different storage conditions on protein lactosylations, protein denaturation in WPI, and in parallel on their foaming and interfacial properties. Six storage conditions involving different temperatures (θ) and water activities (aw) were studied for periods of up to 12mo. The results showed that for θ≤20°C, foaming properties of powders did not significantly differ from nonaged whey protein isolates (reference), regardless of the aw. On the other hand, powders presented significant levels of denaturation/aggregation and protein modification involving first protein lactosylation and then degradation of Maillard reaction products, resulting in a higher browning index compared with the reference, starting from the early stage of storage at 60°C. These changes resulted in a higher foam density and a slightly better foam stability (whisking) at 6mo. At 40°C, powders showed transitional evolution. The findings of this study will make it possible to define maximum storage durations and to recommend optimal storage conditions in accordance with WPI powder end-use properties. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

The influence of raw material, added emulsifying salt and spray drying on cheese powder structure and hydration properties

DEFF Research Database (Denmark)

Felix da Silva, Denise; Larsen, Flemming Hofmann; Hougaard, Anni Bygvrå

2017-01-01

The present work has evaluated how raw material, addition of emulsifying salts (ES) and drying technology affect particle characteristics, structure, and hydration of cheese powders. In this context the spray drying technology induced the strongest effect on morphology and swelling of cheese powder...

Standard test methods for analysis of sintered gadolinium oxide-uranium dioxide pellets

CERN Document Server

American Society for Testing and Materials. Philadelphia

2006-01-01

1.1 These test methods cover procedures for the analysis of sintered gadolinium oxide-uranium dioxide pellets to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Section Carbon (Total) by Direct CombustionThermal Conductivity Method C1408 Test Method for Carbon (Total) in Uranium Oxide Powders and Pellets By Direct Combustion-Infrared Detection Method Chlorine and Fluorine by Pyrohydrolysis Ion-Selective Electrode Method C1502 Test Method for Determination of Total Chlorine and Fluorine in Uranium Dioxide and Gadolinium Oxide Gadolinia Content by Energy-Dispersive X-Ray Spectrometry C1456 Test Method for Determination of Uranium or Gadolinium, or Both, in Gadolinium Oxide-Uranium Oxide Pellets or by X-Ray Fluorescence (XRF) Hydrogen by Inert Gas Fusion C1457 Test Method for Determination of Total Hydrogen Content of Uranium Oxide Powders and Pellets by Carrier Gas Extraction Isotopic Uranium Composition by Multiple-Filament Surface-Ioni...

Biaxially textured articles formed by powder metallurgy

Science.gov (United States)

Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

2003-07-29

A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100} orientation texture; and further having a Curie temperature less than that of pure Ni.

Technological investigation for producing UO2 powder from ADU by using rotary furnace

International Nuclear Information System (INIS)

Pham Duc Thai; Ngo Trong Hiep; Dam Van Tien; Vu Quang Chat; Nguyen Duy Lam; Ngo Xuan Hung; Ngo Quang Hien; Tran Duy Hai; Nguyen Van Sinh

2003-01-01

Uranium dioxide powder UO 2 is main material for producing UO 2 fuel ceramic pellets. The technical characteristics of UO 2 powder directly affect on mechanical and physical characteristics of UO 2 fuel ceramic pellets. Project titled 'Technological investigation for producing UO 2 powder from ADU by using rotary furnace' with the code number BO/01/03-06 for two years 2001 and 2002, on purpose to step by step perfect the technology and equipments for producing UO 2 powder, that is as nuclear fuel. This UO 2 powder may be good material for producing UO 2 fuel ceramic pellets. The results had been achieved as follows: 1. Study on the perfection of the reduction process U 3 O 8 to UO 2 in the gas mixture of 3H 2 + N 2 in inactive condition. 2. Study, design and production of active device system called rotary furnace for manufacturing UO 2 powder from ADU. 3. Study on 4 steps of technology process: drying, calcination, reduction and stabilization of UO 2 powder in the system of rotary furnace from which obtained UO 2 with technical characteristics meeting basic criteria of UO 2 fuel powder. (author)

Simple method of preparing nitrogen - doped nanosized TiO2 powders of high photocatalytic activity under visible light

International Nuclear Information System (INIS)

Nguyen Van Hung; Dang Thi Thanh Le

2014-01-01

Nitrogen-doped nanosized TiO 2 powders were prepared by a simple thermal treatment method of the mixture of titanium dioxide and urea. The prepared products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectra (UV-Vis-DRS) and Fourier transform infrared (FT-IR) spectroscopy. The results showed that the crystal structure of N-TiO 2 was a mixture of anatase and rutile phases, and the average particle size was 31 nm calculated from XRD results. The UV-vis spectra indicate an increase in absorption of visible light when compared to undoped TiO 2 . The photocatalytic activity of nitrogen-doped TiO 2 powder was evaluated by the decomposition of methylene blue under visible light irradiation. And it was found that nitrogen-doped TiO 2 powders exhibited much higher photocatalytic activity than undoped TiO 2 . Moreover, the study also showed that, the doping N atoms improve the growth of the TiO 2 crystal and phase transformation. (author)

Structure investigations of ferromagnetic Co-Ni-Al alloys obtained by powder metallurgy.

Science.gov (United States)

Maziarz, W; Dutkiewicz, J; Lityńska-Dobrzyńska, L; Santamarta, R; Cesari, E

2010-03-01

Elemental powders of Co, Ni and Al in the proper amounts to obtain Co(35)Ni(40)Al(25) and Co(40)Ni(35)Al(25) nominal compositions were ball milled in a high-energy mill for 80 h. After 40 h of milling, the formation of a Co (Ni, Al) solid solution with f.c.c. structure was verified by a change of the original lattice parameter and crystallite size. Analytical transmission electron microscopy observations and X-ray diffraction measurements of the final Co (Ni, Al) solid solution showed that the crystallite size scattered from 4 to 8 nm and lattice parameter a = 0.36086 nm. The chemical EDS point analysis of the milled powder particles allowed the calculation of the e/a ratio and revealed a high degree of chemical homogeneity of the powders. Hot pressing in vacuum of the milled powders resulted in obtaining compacts with a density of about 70% of the theoretical one. An additional heat treatment increased the density and induced the martensitic transformation in a parent phase. Selected area diffraction patterns and dark field images obtained from the heat-treated sample revealed small grains around 300 nm in diameter consisting mainly of the ordered gamma phase (gamma'), often appearing as twins, and a small amount of the L1(0) ordered martensite.

Development of nano-structured silicon carbide ceramics: from synthesis of the powder to sintered ceramics

International Nuclear Information System (INIS)

Reau, A.

2008-12-01

The materials used inside future nuclear reactors will be subjected to very high temperature and neutrons flux. Silicon carbide, in the form of SiC f /SiC nano-structured composite is potentially interesting for this type of application. It is again necessary to verify the contribution of nano-structure on the behaviour of this material under irradiation. To verify the feasibility and determine the properties of the matrix, it was envisaged to produce it by powder metallurgy from SiC nanoparticles. The objective is to obtain a fully dense nano-structured SiC ceramic without additives. For that, a parametric study of the phases of synthesis and agglomeration was carried out, the objective of which is to determine the active mechanisms and the influence of the key parameters. Thus, studying the nano-powder synthesis by laser pyrolysis allowed to produce, with high production rates, homogeneous batches of SiC nanoparticles whose size can be adjusted between 15 and 90 nm. These powders have been densified by an innovating method: Spark Plasma Sintering (SPS). The study and the optimization of the key parameters allowed the densification of silicon carbide ceramic without sintering aids while preserving the nano-structure of material. The thermal and mechanical properties of final materials were studied in order to determine the influence of the microstructure on their properties. (author)

Structural characterization of nanocrystalline cadmium sulphide powder prepared by solvent evaporation technique

Science.gov (United States)

Pandya, Samir; Tandel, Digisha; Chodavadiya, Nisarg

2018-05-01

CdS is one of the most important compounds in the II-VI group of semiconductor. There are numerous applications of CdS in the form of nanoparticles and nanocrystalline. Semiconductors nanoparticles (also known as quantum dots), belong to state of matter in the transition region between molecules and solids, have attracted a great deal of attention because of their unique electrical and optical properties, compared to bulk materials. In the field of optoelectronic, nanocrystalline form utilizes mostly in the field of catalysis and fluid technology. Considering these observations, presented work had been carried out, i.e. based on the nanocrystalline material preparation. In the present work CdS nano-crystalline powder was synthesized by a simple and cost effective chemical technique to grow cadmium sulphide (CdS) nanoparticles at 200 °C with different concentrations of cadmium. The synthesis parameters were optimized. The synthesized powder was structurally characterized by X-ray diffraction and particle size analyzer. In the XRD analysis, Micro-structural parameters such as lattice strain, dislocation density and crystallite size were analysed. The broadened diffraction peaks indicated nanocrystalline particles of the film material. In addition to that the size of the prepared particles was analyzed by particle size analyzer. The results show the average size of CdS particles ranging from 80 to 100 nm. The overall conclusion of the work can be very useful in the synthesis of nanocrystalline CdS powder.

Effect of powder geometry on densification

International Nuclear Information System (INIS)

Spasskij, M.R.; Spasskaya, I.A.; Shatalova, I.G.; Shchukin, E.D.

1979-01-01

The effect of particle shape and size composition on the processes of powder vibratory compacting is considered. Using microstress measurements in compacted structures of conglomerated and disintegrated tungsten powders as well as powder strength testing the existence of a zone of transition from a structural deformation to a plastic one has been shown. The formation of phase interparticle contacts of practically stable strength (approximately 5-6 dyn) is a characteristic feature of the zone. The width of the transition zone greatly depends upon geometrical powder properties; 55-65 % for conglomerated tungsten, 63-66 % for integrated tungsten

Structure and properties of permeable fine-fibrous materials fabricated of powders

Energy Technology Data Exchange (ETDEWEB)

Fedorchenko, I M; Kostornov, A G; Kirichenko, O V; Guzhva, N S [AN Ukrainskoj SSR, Kiev. Inst. Problem Materialovedeniya

1982-09-01

Effect of main structural characteristics of fine fibrous materials (FFM) of nickel and Ni-Cr, Ni-Mo, Ni-Cr-Mo, Ni-Fe-Cr, Ni-Fe alloys on their hydraulic and mechanical properties was studied. FFM was produced by sintering of polymer fibers filled with metal powders and converted to felts. It was shown, that the level of permeable material properties increases with reduction of filament diameter.

Structure and properties of permeable fine-fibrous materials fabricated of powders

International Nuclear Information System (INIS)

Fedorchenko, I.M.; Kostornov, A.G.; Kirichenko, O.V.; Guzhva, N.S.

1982-01-01

Effect of main structural characteristicf of fine fibrous materials (FFM) of nickel and Ni-Cr, Ni-Mo, Ni-Cr-Mo, Ni-Fe-Cr, Ni-Fe alloys on their hydraulic and mechanical properties was studied. FFM was produced by sintering of polymer fibers filled with metal powders and converted to felts. It was shown, that the level of permeable material properties increases with reduction of filament diameter

Electronic structure of the actinides and their dioxides. Application to the defect formation energy and krypton solubility in uranium dioxide

International Nuclear Information System (INIS)

Petit, T.; CEA Centre d'Etudes de Grenoble, 38

1996-01-01

Uranium dioxide is the standard nuclear fuel used in French h power plants. During irradiation, fission products such as krypton and xenon are created inside fuel pellets. So, gas release could become, at very high burnup, a limiting factor in the reactor exploitation. To study this subject, we have realised calculations using the Density Functional Theory (DFT) into the Local Density Approximation (LDA) and the Atomic Sphere Approximation (ASA). First, we have validated our approach by calculating cohesive properties of thorium, protactinium and uranium metals. The good agreement between our results and experimental values implies that 5f electrons are itinerant. Calculated lattice parameter, cohesive energy and bulk modulus for uranium and thorium dioxides are in very good agreement with experiment. We show that binding between uranium and oxygen atoms is not completely ionic but partially covalent. The question of the electrical conductivity still remains an open problem. We have been able to calculate punctual defect formation energies in uranium dioxide. Accordingly to experimental observations, we find that it is easier to create a defect in the oxygen sublattice than in the uranium sublattice. Finally, we have been able to predict a probable site of krypton atoms in nuclear fuel: the Schottky trio. Experiences of Extended X-ray Absorption Fine structure Spectroscopy (EXAFS) and X-ray Photoelectron Spectroscopy (XPS) on uranium dioxide doped by ionic implantation will help us in the comprehension of the studied phenomena and the interpretation of our calculations. (author)

Influence of the external heating type in the morphological and structural characteristics of alumina powder prepared by combustion reaction

International Nuclear Information System (INIS)

Cordeiro, V.V.; Freitas, N.L.; Viana, K.M.S.; Dias, G.; Costa, A.C.F.M.; Lira, H.L.

2009-01-01

The aim of this work is to evaluate the influence of the external heating in the morphological and structural characteristics of the alumina powder prepared by combustion reaction. It was evaluated different types of external heating: muffle oven, microwave oven and ceramic plate with electrical spiral resistance. The powders were prepared according to the propellants and explosives theory, using urea in the stoichiometric proportion (Φe = 1). During the synthesis parameters such as flame combustion time and temperature were measured. The structural and morphological characteristics of the powders were evaluate by XRD, particle size distribution, SEM and nitrogen adsorption (BET). The results showed the production of a-alumina as unique phase and formed by agglomerates with irregular plate shape of thin particles for all studied conditions. The powders prepared by electrical oven presented small particle size, with narrow agglomerates size distribution. (author)

Investigating the structural changes of uranium dioxide dependent on additives, Phase I - Uranium-oxide system from structural-phase aspect

International Nuclear Information System (INIS)

Manojlovic, Lj.

1962-12-01

Having in mind the complex structure of the system uranium-oxygen, and that experimental studies of this system lead to controversial conclusions, an extensive review and analysis of the papers published on this subject were needed. This review wold be very useful for interpreting the expected structural changes of the uranium dioxide dependent on the additives

Effect of Pressing Parameters on the Structure of Porous Materials Based on Cobalt and Nickel Powders

Science.gov (United States)

Shustov, V. S.; Rubtsov, N. M.; Alymov, M. I.; Ankudinov, A. B.; Evstratov, E. V.; Zelensky, V. A.

2018-03-01

Porous materials with a bulk porosity of more than 68% were synthesized by powder metallurgy methods from a cobalt-nickel mixture. The effect of the ratio of nickel and cobalt powders used in the synthesis of this porous material (including cases when either nickel or cobalt alone was applied) and the conditions of their compaction on structural parameters, such as open and closed porosities and pose size, was established.

Structural and electrical properties of copper-nickel-aluminum alloys obtained by conventional powder metallurgy method

International Nuclear Information System (INIS)

Monteiro, Waldemar A.; Carrio, Juan A.G.; Silveira, C.R. da; Pertile, H.K.S.

2009-01-01

This work looked for to search out systematically, in scale of laboratory, copper-nickel-aluminum alloys (Cu-Ni-Al) with conventional powder metallurgy processing, in view of the maintenance of the electric and mechanical properties with the intention of getting electric connectors of high performance or high mechanical damping. After cold uniaxial pressing (1000 kPa), sintering (780 deg C) and convenient homogenization treatments (500 deg C for different times) under vacuum (powder metallurgy), the obtained Cu-Ni-Al alloys were characterized by optical microscopy, electrical conductivity, Vickers hardness. X rays powder diffraction data were collected for the sintered samples in order to a structural and microstructural analysis. The comparative analysis is based on the sintered density, hardness, macrostructures and microstructures of the samples. (author)

High capacity carbon dioxide sorbent

Science.gov (United States)

Dietz, Steven Dean; Alptekin, Gokhan; Jayaraman, Ambalavanan

2015-09-01

The present invention provides a sorbent for the removal of carbon dioxide from gas streams, comprising: a CO.sub.2 capacity of at least 9 weight percent when measured at 22.degree. C. and 1 atmosphere; an H.sub.2O capacity of at most 15 weight percent when measured at 25.degree. C. and 1 atmosphere; and an isosteric heat of adsorption of from 5 to 8.5 kilocalories per mole of CO.sub.2. The invention also provides a carbon sorbent in a powder, a granular or a pellet form for the removal of carbon dioxide from gas streams, comprising: a carbon content of at least 90 weight percent; a nitrogen content of at least 1 weight percent; an oxygen content of at most 3 weight percent; a BET surface area from 50 to 2600 m.sup.2/g; and a DFT micropore volume from 0.04 to 0.8 cc/g.

Preparation of TiC/W core–shell structured powders by one-step activation and chemical reduction process

International Nuclear Information System (INIS)

Ding, Xiao-Yu; Luo, Lai-Ma; Huang, Li-Mei; Luo, Guang-Nan; Zhu, Xiao-Yong; Cheng, Ji-Gui; Wu, Yu-Cheng

2015-01-01

Highlights: • A novel wet chemical method was used to prepare TiC/W core–shell structure powders. • TiC nanoparticles were well-encapsulated by W shells. • TiC phase was present in the interior of tungsten grains. - Abstract: In the present study, one-step activation and chemical reduction process as a novel wet-chemical route was performed for the preparation of TiC/W core–shell structured ultra-fine powders. The XRD, FE-SEM, TEM and EDS results demonstrated that the as-synthesized powders are of high purity and uniform with a diameter of approximately 500 nm. It is also found that the TiC nanoparticles were well-encapsulated by W shells. Such a unique process suggests a new method for preparing X/W (X refers the water-insoluble nanoparticles) core–shell nanoparticles with different cores

Hydrogeologic framework of the uppermost principal aquifer systems in the Williston and Powder River structural basins, United States and Canada

Science.gov (United States)

Thamke, Joanna N.; LeCain, Gary D.; Ryter, Derek W.; Sando, Roy; Long, Andrew J.

2014-01-01

The glacial, lower Tertiary, and Upper Cretaceous aquifer systems in the Williston and Powder River structural basins within the United States and Canada are the uppermost principal aquifer systems and most accessible sources of groundwater for these energy-producing basins. The glacial aquifer system covers the northeastern part of the Williston structural basin. The lower Tertiary and Upper Cretaceous aquifer systems are present in about 91,300 square miles (mi2) of the Williston structural basin and about 25,500 mi2 of the Powder River structural basin. Directly under these aquifer systems are 800 to more than 3,000 feet (ft) of relatively impermeable marine shale that serves as a basal confining unit. The aquifer systems in the Williston structural basin have a shallow (less than 2,900 ft deep), wide, and generally symmetrical bowl shape. The aquifer systems in the Powder River structural basin have a very deep (as much as 8,500 ft deep), narrow, and asymmetrical shape.

Aluminum powder metallurgy processing

Energy Technology Data Exchange (ETDEWEB)

Flumerfelt, J.F.

1999-02-12

The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from aluminum powder. The hypothesis was tested with pure aluminum powders produced by commercial air atomization, commercial inert gas atomization, and gas atomization reaction synthesis (GARS). A comparison of the GARS aluminum powders with the commercial aluminum powders showed the former to exhibit superior powder characteristics. The powders were compared in terms of size and shape, bulk chemistry, surface oxide chemistry and structure, and oxide film thickness. Minimum explosive concentration measurements assessed the dependence of explosibility hazard on surface area, oxide film thickness, and gas atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization oxidation of aluminum powder. An Al-Ti-Y GARS alloy exposed in ambient air at different temperatures revealed the effect of reactive alloy elements on post-atomization powder oxidation. The pure aluminum powders were consolidated by two different routes, a conventional consolidation process for fabricating aerospace components with aluminum powder and a proposed alternative. The consolidation procedures were compared by evaluating the consolidated microstructures and the corresponding mechanical properties. A low temperature solid state sintering experiment demonstrated that tap densified GARS aluminum powders can form sintering necks between contacting powder particles, unlike the total resistance to sintering of commercial air atomization aluminum powder.

Solving crystal structures from powder data. I. The role of the prior information in the two-stage method

International Nuclear Information System (INIS)

Altomare, A.; Carrozzini, B.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A.G.G.; Rizzi, R.

1996-01-01

For pt.II see ibid., p.674-81, 1996. The principal limitation of the diffraction methods for crystal structure analysis from powder data is originated by the collapse of the three-dimensional reciprocal space into the one dimension of the powder diffraction pattern. The degradation of the information can make difficult even the solution of small crystal structures and can generate inefficiencies in the least-squares methods devoted to crystal structure refinement. In this paper, the current two-stage procedures, the first stage dedicated to powder-pattern decomposition and the second to direct phasing of powder data, are analysed. It is shown that in the first stage such procedures disregard a large amount of information that can become available during the process of crystal structure solution and analysis. The use of such information is essential for making direct-methods procedures more robust and for improving the accuracy of the least-squares techniques. The performances of EXTRA [Altomare, Burla, Cascarano, Giacovazzo, Guagliardi, Moliterni and Polidori (1995). J. Appl. Cryst. 28, 842-846], a program for full-pattern decomposition based on the Le Bail algorithm, and of SIRPOW.92 [Altomare, Burla, Cascarano, Giacovazzo, Guagliardi, Polidori and Camalli (1994). J. Appl. Cryst. 27, 435-436], a direct-methods program optimized for powder data, are discussed in order to offer to the reader a logical pathway for the analysis of the traditional techniques and for the proposition of a new approach. It is shown that pattern-decomposition programs based on the Le Bail algorithm are able to exploit the prior information in a more effective way than Pawley-method-based decomposition programs. (orig.)

Interaction of titanium and vanadium with carbon dioxide in heating

International Nuclear Information System (INIS)

Vlasyuk, R.Z.; Kurovskii, V.Y.; Lyapunov, A.P.; Radomysel'skii, I.D.

1986-01-01

To obtain prediction data on the change in properties of titaniumand vanadium-base powder metallurgy materials operating in a carbon dioxide atmosphere, and also to clarify the mechanism of their interaction with the gas in this work, gravimetric investigations of specimens heated at temperatures of 300-1000 C and an x-ray diffraction analysis of their surface were made and the composition of the gas in the heating chamber was studied. The results of the investigations indicate a similarity between the mechanisms of interaction of titanium and vanadium with carbon dioxide including the formation of oxides on the surface of the metal with subsequent carbidization at temperatures above 800 C. On the basis of the data obtained, it may be concluded that the operating temperature limits of titanium- or vanadium-base materials in carbon dioxide must not exceed 400 and 600 C, respectively

The preparation of uranium tetrafluoride from dioxide by aqueous way

International Nuclear Information System (INIS)

Aquino, A.R. de; Abrao, A.

1990-01-01

This paper describes the study for the wet way obtention of uranium tetrafluoride by the reaction of hydrofluoric acid and powder uranium dioxide. With the results obtained at laboratory scale a pilot plant was planned and erected. It is presently in operation for experimental data aquisition. Time of reaction, temperature, excess of reagents and the hydrofluoric acid / uranium dioxide ratio were the main parameters studied to obtain a product with the following characteristics: - density greater than 1 g/cm 3 , - conversion rate greater than 96%, -water content equal to 0,2%, that allows its application to hexafluoride convertion or to magnesiothermic process. (authOr) [pt

The effect of structural changes during sintering on the electric and magnetic traits of the Ni96.7Mo3.3 alloy nanostructured powder

Directory of Open Access Journals (Sweden)

Ribić-Zelenović L.

2009-01-01

Full Text Available Ni96.7Mo3.3 powder was electrochemically obtained. An X-ray diffraction analysis determined that the powder consisted of a 20% amorphous and 80% crystalline phase. The crystalline phase consisted of a nanocrystalline solid nickel and molybdenum solution with a face-centred cubic (FCC lattice with a high density of chaotically distributed dislocations and high microstrain value. The scanning electronic microscopy (SEM showed that two particle structures were formed: larger cauliflower-like particles and smaller dendriteshaped ones. The thermal stability of the alloy was examined by differential scanning calorimetry (DSC and by measuring the temperature dependence of the electrical resistivity and magnetic permeability. Structural powder relaxation was carried out in the temperature range of 450 K to 560 K causing considerable changes in the electrical resistivity and magnetic permeability. Upon structural relaxation, the magnetic permeability of the cooled alloy was about 80% higher than the magnetic permeability of the fresh powder. The crystallisation of the amorphous portion of the powder and crystalline grain increase occurred in the 630 K to 900 K temperature interval. Upon crystallisation of the amorphous phase and crystalline grain increase, the powder had about 50% lower magnetic permeability than the fresh powder and 3.6 times lower permeability than the powder where only structural relaxation took place.

Carbon dioxide elimination and regeneration of resources in a microwave plasma torch.

Science.gov (United States)

Uhm, Han S; Kwak, Hyoung S; Hong, Yong C

2016-04-01

Carbon dioxide gas as a working gas produces a stable plasma-torch by making use of 2.45 GHz microwaves. The temperature of the torch flame is measured by making use of optical spectroscopy and a thermocouple device. Two distinctive regions are exhibited, a bright, whitish region of a high-temperature zone and a bluish, dimmer region of a relatively low-temperature zone. The bright, whitish region is a typical torch based on plasma species where an analytical investigation indicates dissociation of a substantial fraction of carbon dioxide molecules, forming carbon monoxides and oxygen atoms. The emission profiles of the oxygen atoms and the carbon monoxide molecules confirm the theoretical predictions of carbon dioxide disintegration in the torch. Various hydrocarbon materials may be introduced into the carbon dioxide torch, regenerating new resources and reducing carbon dioxide concentration in the torch. As an example, coal powders in the carbon dioxide torch are converted into carbon monoxide according to the reaction of CO2 + C → 2CO, reducing a substantial amount of carbon dioxide concentration in the torch. In this regards, the microwave plasma torch may be one of the best ways of converting the carbon dioxides into useful new materials. Copyright © 2015 Elsevier Ltd. All rights reserved.

Comparative studies of industrial grade carbon black powders

Energy Technology Data Exchange (ETDEWEB)

Chawla, Komal, E-mail: komalchawla.rs@gmail.com; Chauhan, Alok P. S., E-mail: chauhan.alok@gmail.com, E-mail: alok.chauhan@alumni.stonybrook.edu [Department of Physics and Material Science and Engineering, Jaypee Institute of Information Technology, A-10, Sector-62, Noida-201307, UP, India. (India)

2016-05-06

Comparative studies of two dissimilar industrial grade Carbon Black (CB) powders (N375 and N405) were conducted. The structure, surface area and particle size are the three important characteristics of CB powder that determine their processability and application as filler in preparing rubber compounds. The powders were characterized for their structure using dibutyl phthalate absorption (DBPA), particle size via laser particle size analyzer and surface area by nitrogen adsorption method. The structural characterization showed that N405 had lower DBPA in comparison to N375, confirming low structure of N405 grade CB powder. It was observed from the particle size analysis that N375 was coarser than N405 grade CB. The total surface area values were determined by the BET method based on the cross sectional area of the nitrogen molecule. N375, a coarse grade CB powder with high structure, depicted less surface area as compared to N405.

Experience with a uranyl nitrate/uranium dioxide conversion pilot plant

International Nuclear Information System (INIS)

Arcuri, L.; Pietrelli, L.

1984-01-01

A plant for the precipitation of sinterable nuclear grade UO 2 powders is described in this report. The plant has been designed, built and set up by SNIA TECHINT. ENEA has been involved in the job as nuclear consultant. Main process steps are: dissolution of UO 2 powder or sintered UO 2 pellets, adjustment of uranyl nitrate solutions, precipitation of uranium peroxide by means of hydrogen peroxide, centrifugation of the precipitate, drying, calcination and reduction to uranium dioxide. The report is divided in two main section: the process description and the ''hot test'' report. Some laboratory data on precipitation of ammonium diuranate by means of NH 4 OH, are also reported

Optimization of process parameters in precipitation for consistent quality UO{sub 2} powder production

Energy Technology Data Exchange (ETDEWEB)

Tiwari, S.K.; Reddy, A.L.V.; Venkataswamy, J.; Misra, M.; Setty, D.S.; Sheela, S.; Saibaba, N., E-mail: misra@nfc.gov.in [Nuclear Fuel Complex, Hyderabad (India)

2013-07-01

Nuclear reactor grade natural uranium dioxide powder is being produced through precipitation route, which is further processed before converting into sintered pellets used in the fabrication of PHWR fuel assemblies of 220 and 540 MWe type reactors. The process of precipitating Uranyl Nitrate Pure Solution (UNPS) is an important step in the UO{sub 2} powder production line, where in soluble uranium is transformed into solid form of Ammonium Uranate (AU), which in turn reflects and decides the powder characteristics. Precipitation of UNPS with vapour ammonia is being carried out in semi batch process and process parameters like ammonia flow rate, temperature, concentration of UNPS and free acidity of UNPS are very critical and decides the UO{sub 2} powder quality. Variation in these critical parameters influences powder characteristics, which in turn influences the sinterability of UO{sub 2} powder. In order to get consistent powder quality and sinterability the critical parameter like ammonia flow rate during precipitation is studied, optimized and validated. The critical process parameters are controlled through PLC based automated on-line data acquisition systems for achieving consistent powder quality with increased recovery and production. The present paper covers optimization of process parameters and powder characteristics. (author)

Validation of molecular crystal structures from powder diffraction data with dispersion-corrected density functional theory (DFT-D)

International Nuclear Information System (INIS)

Streek, Jacco van de; Neumann, Marcus A.

2014-01-01

The accuracy of 215 experimental organic crystal structures from powder diffraction data is validated against a dispersion-corrected density functional theory method. In 2010 we energy-minimized 225 high-quality single-crystal (SX) structures with dispersion-corrected density functional theory (DFT-D) to establish a quantitative benchmark. For the current paper, 215 organic crystal structures determined from X-ray powder diffraction (XRPD) data and published in an IUCr journal were energy-minimized with DFT-D and compared to the SX benchmark. The on average slightly less accurate atomic coordinates of XRPD structures do lead to systematically higher root mean square Cartesian displacement (RMSCD) values upon energy minimization than for SX structures, but the RMSCD value is still a good indicator for the detection of structures that deserve a closer look. The upper RMSCD limit for a correct structure must be increased from 0.25 Å for SX structures to 0.35 Å for XRPD structures; the grey area must be extended from 0.30 to 0.40 Å. Based on the energy minimizations, three structures are re-refined to give more precise atomic coordinates. For six structures our calculations provide the missing positions for the H atoms, for five structures they provide corrected positions for some H atoms. Seven crystal structures showed a minor error for a non-H atom. For five structures the energy minimizations suggest a higher space-group symmetry. For the 225 SX structures, the only deviations observed upon energy minimization were three minor H-atom related issues. Preferred orientation is the most important cause of problems. A preferred-orientation correction is the only correction where the experimental data are modified to fit the model. We conclude that molecular crystal structures determined from powder diffraction data that are published in IUCr journals are of high quality, with less than 4% containing an error in a non-H atom

Determination of Ni(II) crystal structure by powder x-ray diffraction ...

African Journals Online (AJOL)

X-ray powder diffraction pattern was used to determine the length of the unit cell, “a”, the lattice structure type, and the number of atoms per unit cell of Ni(II) crystal. The “a” value was determined to be 23.66 ± 0.005 Å, particle size of 34.87 nm, volume 13.24 Å and Strain value ε = 9.8 x 10-3. The cell search on PXRD patterns ...

Development of cobalt ferrite powder preparation employing the sol-gel technique and its structural characterization

International Nuclear Information System (INIS)

Sajjia, M.; Oubaha, M.; Prescott, T.; Olabi, A.G.

2010-01-01

Research highlights: This work focuses on the sol-gel process and the effects that the initial parameters have on the final product, which is the cobalt ferrite powder, in addition to the heat treatment. Particular interest is devoted to understand how the crosslinker and the chelating agent work and affect the final product. - Abstract: This work focuses on the development of a method to make cobalt ferrite powder using the sol-gel process. A particular emphasis is devoted to the understanding of the role of the chemical parameters involved in the sol-gel technique, and of the heat treatment on the structures and morphologies of the materials obtained. Several samples of cobalt ferrite powder were obtained by varying the initial parameters of the process in addition to the heat treatment temperature. X-ray diffraction and scanning electron microscopy were used to identify the structure and morphology of samples demonstrating the influence of the initial parameters. DTA/TGA was carried out on two standard samples to identify important reaction temperatures during the heat treatment. The average size of the nano crystallites was estimated for a sample by the full width at half maximum (FWHM) of the strongest X-ray diffraction (XRD) peak. It has been found that the chelating agent and the crosslinker have a critical influence on the resultant structure, the particle size and the particle size distribution.

Structural characterisation of 1- and 2-dimensional transition metal polymers using powder neutron diffraction

International Nuclear Information System (INIS)

James, M.

1999-01-01

Powder neutron diffraction provides an alternate technique for the structural study of transition metal polymers and finds utility over standard X-ray methods in two significant ways. Firstly, due to a different instrument geometry, preferred orientation effects are removed from the system. The second advantage gained by utilising neutrons is that H atoms in the sample contribute much more to the nuclear scattering of the diffraction profile - allowing their atomic position to be accurately determined. In X-ray diffraction studies, where H atoms typically account for only ∼3-5% of the scattering from the sample, it is essentially impossible to refine their position in the molecular structure. The structures of several transition metal polymers have been determined using neutrons from the HIFAR reactor at ANSTO and the Powder Diffractometers HRPD and MRPD, along with Rietveld refinement methods. The 1-dimensional polymer dibromobis(thiazole)nickel(II) illustrated in the paper is characteristic of these types of systems which are comprised of transition metal centres bridged by halogen atoms with pendant amine side groups

Structural, optical, and magnetic properties of Fe doped In{sub 2}O{sub 3} powders

Energy Technology Data Exchange (ETDEWEB)

Krishna, N. Sai [Thin Films Laboratory, School of Advanced Sciences, VIT University, Vellore 632 014, Tamilnadu (India); Kaleemulla, S., E-mail: skaleemulla@gmail.com [Thin Films Laboratory, School of Advanced Sciences, VIT University, Vellore 632 014, Tamilnadu (India); Amarendra, G. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India); UGC-DAE-CSR, Kalpakkam Node, Kokilamedu 603 104, Tamilnadu (India); Rao, N. Madhusudhana; Krishnamoorthi, C.; Kuppan, M.; Begam, M. Rigana [Thin Films Laboratory, School of Advanced Sciences, VIT University, Vellore 632 014, Tamilnadu (India); Reddy, D. Sreekantha [Department of Physics and Sungkyunkwan Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Omkaram, I. [Department of Electronics and Radio Engineering, Kyung Hee University, Yongin-si, Gyeonggi-do 446-701 (Korea, Republic of)

2015-01-15

Highlights: • Synthesis of Fe doped In{sub 2}O{sub 3} powders using a solid state reaction. • Characterization of the samples using XRD, UV–vis-NIR, FT-IR, and VSM. • All Fe doped In{sub 2}O{sub 3} powders exhibited the cubic structure of In{sub 2}O{sub 3}. • All the Fe doped In{sub 2}O{sub 3} samples exhibited room temperature ferromagnetism. - Abstract: Iron doped indium oxide dilute magnetic semiconductor (In{sub 1−x}Fe{sub x}){sub 2}O{sub 3} (x = 0.00, 0.03, 0.05, and 0.07) powders were synthesized by standard solid state reaction method followed by vacuum annealing. The effect of Fe concentration on structural, optical, and magnetic properties of the (In{sub 1−x}Fe{sub x}){sub 2}O{sub 3} powders have been systematically studied. X-ray diffraction patterns confirmed the polycrystalline cubic structure of all the samples. An optical band gap increases from 3.12 eV to 3.16 eV while Fe concentration varying from 0.03 to 0.07. Magnetic studies reveal that virgin/undoped In{sub 2}O{sub 3} is diamagnetic. However, all the Fe-doped In{sub 2}O{sub 3} samples are ferromagnetic. The saturation magnetization (M{sub s}) of ferromagnetic (In{sub 1−x}Fe{sub x}){sub 2}O{sub 3} (x = 0.03, 0.05, and 0.07) samples increases from 11.56 memu/g to 148.64 memu/g with x = 0.03–0.07. The observed ferromagnetism in these samples was attributed to magnetic nature of the dopant (Fe) as well as defects created in the samples during vacuum annealing.

Control over Coating Structure during Electromagnetic Welding and Application of HighSpeed Steel Powder

Directory of Open Access Journals (Sweden)

L. M. Kozhuro

2004-01-01

Full Text Available The paper considers peculiar features concerning coating formation in the process of electromagnetic welding of high-speed steel powder. The paper reveals how to control coating structure that ensures the required operational properties of working surfaces of machine parts. 

Coarsening-densification transition temperature in sintering of uranium dioxide

International Nuclear Information System (INIS)

Balakrishna, Palanki; Narasimha Murty, B.; Chakraborthy, K.P.; Jayaraj, R.N.; Ganguly, C.

2001-01-01

The concept of coarsening-densification transition temperature (CDTT) has been proposed to explain the experimental observations of the study of sintering undoped uranium dioxide and niobia-doped uranium dioxide powder compacts in argon atmosphere in a laboratory tubular furnace. The general method for deducing CDTT for a given material under the prevailing conditions of sintering and the likely variables that influence the CDTT are described. Though the present work is specific in nature for uranium dioxide sintering in argon atmosphere, the concept of CDTT is fairly general and must be applicable to sintering of any material and has immense potential to offer advantages in designing and/or optimizing the profile of a sintering furnace, in the diagnosis of the fault in the process conditions of sintering, and so on. The problems of viewing the effect of heating rate only in terms of densification are brought out in the light of observing the undesirable phenomena of coring and bloating and causes were identified and remedial measures suggested

Controlled Synthesis of Manganese Dioxide Nano structures via a Facile Hydrothermal

International Nuclear Information System (INIS)

Pang, R.S.C.; Chin, S.F.; Ye, Ch. Ling

2012-01-01

Manganese dioxide nano structures with controllable morphological structures and crystalline phases were synthesized via a facile hydrothermal route at low temperatures without using any templates or surfactants. Both the aging duration and aging temperatures were the main synthesis parameters used to influence and control the rate of morphological and structural evolution of MnO 2 nano structures. MnO 2 nano structures comprise of spherical nano particulate agglomerates and highly amorphous in nature were formed at lower temperature and/or short aging duration. In contrast, MnO 2 nano structures of sea-urchin-like and nano rods-like morphologies and nanocrystalline in nature were prepared at the combined higher aging temperatures and longer aging durations. These nano structures underwent notable phase transformation from d-MnO 2 to a-MnO 2 upon prolonged hydrothermal aging duration and exhibited accelerated rate of phase transformation at higher aging temperature.

Characteristic of nanoparticles generated from different nano-powders by using different dispersion methods

International Nuclear Information System (INIS)

Tsai, Chuen-Jinn; Lin, Guan-Yu; Liu, Chun-Nan; He, Chi-En; Chen, Chun-Wan

2012-01-01

A standard rotating drum with a modified sampling train (RD), a vortex shaker (VS), and a SSPD (small-scale powder disperser) were used to investigate the emission characteristics of nano-powders, including nano-titanium dioxide (nano-TiO 2 , primary diameter: 21 nm), nano-zinc oxide (nano-ZnO, primary diameter: 30–50 nm), and nano-silicon dioxide (nano-SiO 2 , primary diameter: 10–30 nm). A TSI SMPS (scanning mobility particle sizer), a TSI APS (aerodynamic particle sizer), and a MSP MOUDI (micro-orifice uniform deposit impactor) were used to measure the number and mass distributions of generated particles. Significant differences in specific number and mass concentration or distributions were found among different methods and nano-powders with the most specific number and mass concentration and the smallest particles being generated by the most energetic SSPD, followed by VS and RD. Near uni-modal number or mass distributions were observed for the SSPD while bi-modal number or mass distributions existed for nano-powders except nano-SiO 2 which also exhibited bimodal mass distributions. The 30-min average results showed that the mass median aerodynamic diameter (MMAD) and number median diameter (NMD) of the SSPD ranged 1.1–2.1 μm and 166–261 nm, respectively, for all three nano-powders, which were smaller than those of the VS (MMAD: 3.3–6.0 μm and NMD: 156–462 nm), and the RD (MMAD: 5.2–11.2 μm and NMD: 198–479 nm). For nano-particles (electric mobility diameter < 100 nm), specific mass concentrations were nearly negligible for all three nano-powders and test methods. Specific number concentrations of nano-particles were low for the RD tester but were elevated when more energetic VS and SSPD testers were used. The quantitative size and concentration data obtained in this study is useful to elucidate the field emission and personal exposure data in the future provided that particle loss in the generation system is carefully assessed.

Investigation of Structure and Physico-Mechanical Properties of Composite Materials Based on Copper - Carbon Nanoparticles Powder Systems

Directory of Open Access Journals (Sweden)

Kovtun V.

2015-04-01

Full Text Available Physico-mechanical and structural properties of electrocontact sintered copper matrix- carbon nanoparticles composite powder materials are presented. Scanning electron microscopy revealed the influence of preliminary mechanical activation of the powder system on distribution of carbon nanoparticles in the metal matrix. Mechanical activation ensures mechanical bonding of nanoparticles to the surface of metal particles, thus giving a possibility for manufacture of a composite with high physico-mechanical properties.

Experimental study and kinetic modeling of the hydro-fluorination of uranium dioxide

International Nuclear Information System (INIS)

Pages, Simon

2014-01-01

A kinetic study of hydro-fluorination of uranium dioxide was performed between 375 and 475 C under partial pressures of HF between 42 and 720 mbar. The reaction was followed by thermogravimetry in isothermal and isobaric conditions. The kinetic data obtained coupled with a characterization of the powder before, during and after reaction by SEM, EDS, BET and XRD showed that the powder grains of UO 2 are transformed according a model of instantaneous germination, anisotropic growth and internal development. The rate limiting step of the growth process is the diffusion of HF in the UF 4 layer. A mechanism of growth of the UF 4 layer has been proposed. In the temperature and pressure range studied, the reaction is of first order with respect to HF and follows an Arrhenius law. A rate equation was determined and used to perform kinetic simulations which have shown a very good correlation with experience. Coupling of this rate equation with heat and mass transport phenomena allowed to perform simulations at the scale of a powder's agglomerate. They have shown that some structures of agglomerates influence the rate of diffusion of the gases in the porous medium and thereby influence the reaction rate. Finally kinetic simulations on powder's beds and pellets were carried out and compared with experimental rates. The experimental and simulated kinetic curves have the same paces, but improvements in the simulations are needed to accurately predict rates: the coupling between the three scales (grain, agglomerate, oven) would be a good example. (author) [fr

Fine defective structure of silicon carbide powders obtained from different starting materials

Directory of Open Access Journals (Sweden)

Tomila T.V.

2006-01-01

Full Text Available The fine defective structure of silicon carbide powders obtained from silicic acid-saccharose, aerosil-saccharose, aerosil-carbon black, and hydrated cellulose-silicic acid gel systems was investigated. The relation between IR absorption characteristics and the microstructure of SiC particles obtained from different starting materials was established. The numerical relationship between the lattice parameter a and the frequency νTO is presented.

Study of the changes of uranium dioxide properties resulting from sintering; Izucavanje procesa sinterovanja urandioksida sa gledista promene karakteristicnih osobina

Energy Technology Data Exchange (ETDEWEB)

Ristic, M M [Institute of Nuclear Sciences Vinca, Laboratorija za reaktorske materijale, Beograd (Serbia and Montenegro)

1962-12-15

Uranium dioxide powder used for studying the sintering process having grain size 63 {mu}. Sintering was performed in the temperature interval from 1000 - 1300 deg C in argon atmosphere. The O/U ratio of the used uranium dioxide was 2.07. Densities obtained by sintering under the mentioned conditions were not higher than 91% TG (theoretical density). This showed that the mentioned conditions were optimal, but the uranium dioxide obtained could be used for studying the radiation damage of fuel.

Optimization of dissolution process parameters for uranium ore concentrate powders

Energy Technology Data Exchange (ETDEWEB)

Misra, M.; Reddy, D.M.; Reddy, A.L.V.; Tiwari, S.K.; Venkataswamy, J.; Setty, D.S.; Sheela, S.; Saibaba, N. [Nuclear Fuel Complex, Hyderabad (India)

2013-07-01

Nuclear fuel complex processes Uranium Ore Concentrate (UOC) for producing uranium dioxide powder required for the fabrication of fuel assemblies for Pressurized Heavy Water Reactor (PHWR)s in India. UOC is dissolved in nitric acid and further purified by solvent extraction process for producing nuclear grade UO{sub 2} powder. Dissolution of UOC in nitric acid involves complex nitric oxide based reactions, since it is in the form of Uranium octa oxide (U{sub 3}O{sub 8}) or Uranium Dioxide (UO{sub 2}). The process kinetics of UOC dissolution is largely influenced by parameters like concentration and flow rate of nitric acid, temperature and air flow rate and found to have effect on recovery of nitric oxide as nitric acid. The plant scale dissolution of 2 MT batch in a single reactor is studied and observed excellent recovery of oxides of nitrogen (NO{sub x}) as nitric acid. The dissolution process is automated by PLC based Supervisory Control and Data Acquisition (SCADA) system for accurate control of process parameters and successfully dissolved around 200 Metric Tons of UOC. The paper covers complex chemistry involved in UOC dissolution process and also SCADA system. The solid and liquid reactions were studied along with multiple stoichiometry of nitrous oxide generated. (author)

Production of uranium dioxide

International Nuclear Information System (INIS)

Hart, J.E.; Shuck, D.L.; Lyon, W.L.

1977-01-01

A continuous, four stage fluidized bed process for converting uranium hexafluoride (UF 6 ) to ceramic-grade uranium dioxide (UO 2 ) powder suitable for use in the manufacture of fuel pellets for nuclear reactors is disclosed. The process comprises the steps of first reacting UF 6 with steam in a first fluidized bed, preferably at about 550 0 C, to form solid intermediate reaction products UO 2 F 2 , U 3 O 8 and an off-gas including hydrogen fluoride (HF). The solid intermediate reaction products are conveyed to a second fluidized bed reactor at which the mol fraction of HF is controlled at low levels in order to prevent the formation of uranium tetrafluoride (UF 4 ). The first intermediate reaction products are reacted in the second fluidized bed with steam and hydrogen at a temperature of about 630 0 C. The second intermediate reaction product including uranium dioxide (UO 2 ) is conveyed to a third fluidized bed reactor and reacted with additional steam and hydrogen at a temperature of about 650 0 C producing a reaction product consisting essentially of uranium dioxide having an oxygen-uranium ratio of about 2 and a low residual fluoride content. This product is then conveyed to a fourth fluidized bed wherein a mixture of air and preheated nitrogen is introduced in order to further reduce the fluoride content of the UO 2 and increase the oxygen-uranium ratio to about 2.25

Magnetic, hyperthermic and structural properties of zn substituted CaFe2O4 powders

Science.gov (United States)

Kheradmand, Abbas; Vahidi, Omid; Masoudpanah, S. M.

2018-03-01

In the present study, we have synthesized single phase Ca1 - x Zn x Fe2O4 powders by hydrothermal method. The cation distribution between the tetrahedral and octahedral sites in the spinel structure and the magnetic properties as a function of the zinc substitution have been investigated by X-ray diffraction (XRD), infrared spectroscopy and vibrating sample magnetometer methods. The obtained XRD pattern indicated that the synthesized particles had single phase cubic spinel structure with no impurity. The magnetic measurements showed that the saturation magnetization increased from 83 to 98 emu/g with the addition of zinc due to the decrease of inversity. The particle size observed by electron microscopy decreased from 1.38 to 0.97 µm with the increase of zinc addition. The Ca0.7Zn0.3Fe2O4 powders exhibited appropriate heating capability for hyperthermia applications with the maximum AC heating temperature of 20 °C and specific loss power of 9.29 W/g.

Optical modulation in silicon-vanadium dioxide photonic structures

Science.gov (United States)

Miller, Kevin J.; Hallman, Kent A.; Haglund, Richard F.; Weiss, Sharon M.

2017-08-01

All-optical modulators are likely to play an important role in future chip-scale information processing systems. In this work, through simulations, we investigate the potential of a recently reported vanadium dioxide (VO2) embedded silicon waveguide structure for ultrafast all-optical signal modulation. With a VO2 length of only 200 nm, finite-differencetime- domain simulations suggest broadband (200 nm) operation with a modulation greater than 12 dB and an insertion loss of less than 3 dB. Predicted performance metrics, including modulation speed, modulation depth, optical bandwidth, insertion loss, device footprint, and energy consumption of the proposed Si-VO2 all-optical modulator are benchmarked against those of current state-of-the-art all-optical modulators with in-plane optical excitation.

Validation of molecular crystal structures from powder diffraction data with dispersion-corrected density functional theory (DFT-D)

DEFF Research Database (Denmark)

van de Streek, Jacco; Neumann, Marcus A

2014-01-01

In 2010 we energy-minimized 225 high-quality single-crystal (SX) structures with dispersion-corrected density functional theory (DFT-D) to establish a quantitative benchmark. For the current paper, 215 organic crystal structures determined from X-ray powder diffraction (XRPD) data and published...

Structural evolution of Fe-50 at.% Al powders during mechanical alloying and subsequent annealing processes

International Nuclear Information System (INIS)

Haghighi, Sh. Ehtemam; Janghorban, K.; Izadi, S.

2010-01-01

Iron aluminides, despite having desirable properties like excellent corrosion resistance, present low room-temperature ductility and low strength at high temperatures. Mechanical alloying as a capable process to synthesize nanocrystalline materials is under consideration to modify these drawbacks. In this study, the microstructure of iron aluminide powders synthesized by mechanical alloying and subsequent annealing was investigated. Elemental Fe and Al powders with the same atomic percent were milled in a planetary ball mill for 15 min to 100 h. The powder milled for 80 h was annealed at temperatures of 300, 500 and 700 o C for 1 h. The alloyed powders were disordered Fe(Al) solid solutions which were transformed to FeAl intermetallic after annealing. The effect of the milling time and annealing treatment on structural parameters, such as crystallite size, lattice parameter and lattice strain was evaluated by X-ray diffraction. Typically, these values were 15 nm, 2.92 A and 3.1% for the disordered Fe(Al) solid solution milled for 80 h and were 38.5 nm, 2.896 A and 1.2% for the FeAl intermetallic annealed at 700 o C, respectively.

Structure and magnetic properties of nanocrystalline Fe75Si25 powders prepared by mechanical alloying

International Nuclear Information System (INIS)

Kalita, M.P.C.; Perumal, A.; Srinivasan, A.

2008-01-01

Nanocrystalline Fe 75 Si 25 powders were prepared by mechanical alloying in a planetary ball mill. The evolution of the microstructure and magnetic properties during the milling process were studied by X-ray diffraction, scanning electron microscope and vibrating sample magnetometer measurements. The evolution of non-equilibrium solid solution Fe (Si) during milling was accompanied by refinement of crystallite size down to 10 nm and the introduction of high density of dislocations of the order of 10 17 m -2 . During the milling process, Fe sites get substituted by Si. This structural change and the resulting disorder are reflected in the lattice parameters and average magnetic moment of the powders milled for various time periods. A progressive increase of coercivity was also observed with increasing milling time. The increase of coercivity could be attributed to the introduction of dislocations and reduction of powder particle size as a function of milling time

Relativistic band-structure calculations for electronic properties of actinide dioxides

International Nuclear Information System (INIS)

Maehira, Takahiro; Hotta, Takashi

2007-01-01

Energy band structures of actinide dioxides AnO 2 (An=Th, U, Np, and Pu) are investigated by a relativistic linear augmented-plane-wave method with the exchange-correlation potential in a local density approximation (LDA). It is found in common that the energy bands in the vicinity of the Fermi level are mainly due to the hybridization between actinide 5f and oxygen 2p electrons. By focusing on the crystalline electric field states, we point out the problem in the application of the LDA to AnO 2

Toxicity and Fate Comparison between Several Brass and Titanium Dioxide Powders

Science.gov (United States)

1993-07-01

the entire gut without showing any apparent effects . 14. UBJET TEMS1I. NUMBER OF PAGES 27 Daphnia Algae EC50 Aquatic toxicity 11T.PRICE CODE 9...levels of soluble copper and zinc in solution. 3. RESULTS The titanium dioxide ( TiO2 ) materials did not show any apparent toxic effects to daphnia up to...The extended exposure did not show any apparent toxic effects . Long term effects on aquatic org.rnisms exposed to TiO2 are not known. It is apparent

Method and device for the dry preparation of ceramic uranium dioxide nuclear fuel wastes

International Nuclear Information System (INIS)

Pirk, H.; Roepenack, H.; Goeldner, U.

1977-01-01

Reprocessing of waste, resulting from the production of ceramic sintered bodies from uranium dioxide for use as nuclear fuel, in a dry process into very finely dispersed pure U 3 O 8 powder may be improved by applying vibrating screening during oxidation. An appropriate device is described. (UWI) [de

Determination of Crystallite Size Distribution Histogram in Nanocrystalline Anatase Powders by XRD

Czech Academy of Sciences Publication Activity Database

Matěj, Z.; Matějová, Lenka; Novotný, F.; Drahokoupil, Jan; Kužel, R.

2011-01-01

Roč. 1, - (2011), s. 87-92 [European Powder Diffraction Conference EPDIC 12 /12./. Darmstadt, 27.08.2010-30.08.2010] R&D Projects: GA AV ČR KAN400720701 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z10100520 Keywords : titanium dioxide * crystallite size * crystallite size distribution Subject RIV: CA - Inorganic Chemistry http://www.oldenbourg-link.com/ toc /zkpr/current

Electrical Conductivity of Ni-YSZ Anode for SOFCs According to the Ni Powder Size Variations in Core-shell Structure

International Nuclear Information System (INIS)

Kang, Young Jin; Jung, Sung-Hun; An, Yong-Tae; Choi, Byung-Hyun; Ji, Mi-Jung

2015-01-01

Ni-YSZ (Y_2O_3-stabilized ZrO_2) core-shell structures were prepared by a high-speed mixing method, starting from Ni particles of three different average sizes of 0.2, 0.4, and 1.8 μm. The Ni-YSZ core-shell structures prepared using Ni particles of size 0.2, 0.4, and 1.8 μm exhibited dense core, porous core, and random-morphology core, respectively. Subsequently, nano structured cermet anodes were fabricated using the prepared Ni-YSZ core-shell powders. During the formation of cermet, the heat treatment of Ni-YSZ core-shell powder results in the eruption of Ni core out of the YSZ shell layers, thereby facilitating the formation of nano structured Ni-YSZ cermet. Systematic studies indicated that the morphology and electrical conductivity of the prepared Ni-YSZ core-shell powders and the cermet anode varied, depending on the initial particle size of the Ni particles. Of the different samples prepared in this study, the Ni-YSZ cermet prepared using Ni particles of size 0.4 μm showed the highest electrical conductivity at 750 ℃.

Electrical Conductivity of Ni-YSZ Anode for SOFCs According to the Ni Powder Size Variations in Core-shell Structure

Energy Technology Data Exchange (ETDEWEB)

Kang, Young Jin; Jung, Sung-Hun; An, Yong-Tae; Choi, Byung-Hyun; Ji, Mi-Jung [Korea Institute of Ceramic Engineering and Technology (KICET), Seoul (Korea, Republic of)

2015-04-15

Ni-YSZ (Y{sub 2}O{sub 3}-stabilized ZrO{sub 2}) core-shell structures were prepared by a high-speed mixing method, starting from Ni particles of three different average sizes of 0.2, 0.4, and 1.8 μm. The Ni-YSZ core-shell structures prepared using Ni particles of size 0.2, 0.4, and 1.8 μm exhibited dense core, porous core, and random-morphology core, respectively. Subsequently, nano structured cermet anodes were fabricated using the prepared Ni-YSZ core-shell powders. During the formation of cermet, the heat treatment of Ni-YSZ core-shell powder results in the eruption of Ni core out of the YSZ shell layers, thereby facilitating the formation of nano structured Ni-YSZ cermet. Systematic studies indicated that the morphology and electrical conductivity of the prepared Ni-YSZ core-shell powders and the cermet anode varied, depending on the initial particle size of the Ni particles. Of the different samples prepared in this study, the Ni-YSZ cermet prepared using Ni particles of size 0.4 μm showed the highest electrical conductivity at 750 ℃.

Synthesis, characterization and electrochemical performance of core/shell structured carbon coated silicon powders for lithium ion battery negative electrodes

Directory of Open Access Journals (Sweden)

Tuğrul Çetinkaya

2017-06-01

Full Text Available Surface of nano silicon powders were coated with amorphous carbon by pyrolysis of polyacronitrile (PAN polymer. Microstructural characterization of amorphous carbon coated silicon powders (Si-C were carried out using scanning electron microscopy (SEM and thickness of carbon coating is defined by transmission electron microscopy (TEM. Elemental analyses of Si-C powders were performed using energy dispersive X-ray spectroscopy (EDS. Structural and phase characterization of Si-C composite powders were investigated using X-ray diffractometer (XRD and Raman spectroscopy. Produced Si-C powders were prepared as an electrode on the copper current collector and electrochemical tests were carried out using CR2016 button cells at 200 mA/g constant current density. According to electrochemical test results, carbon coating process enhanced the electrochemical performance by reducing the problems stem from volume change and showed 770 mAh/g discharge capacity after 30 cycles.

Hyperfine interactions and structural features of Fe–44Co–6Mo (wt.%) nanostructured powders

International Nuclear Information System (INIS)

Moumeni, Hayet; Nemamcha, Abderrafik; Alleg, Safia; Grenèche, Jean Marc

2013-01-01

Nanocrystalline Fe–44Co–6Mo (wt.%) powders have been prepared by high-energy ball milling from elemental Fe, Co and Mo pure powders in a P7 planetary ball mill. The obtained powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Mössbauer spectrometry techniques. The influence of milling process and Mo substitution for Co in equiatomic FeCo have been examined in order to study structural evolution and formation mechanism of nanostructured Fe(CoMo) solid solution. XRD results show the formation of a BCC Fe(CoMo) solid solution (a = 0.2874 nm) where unmixed nanocrystalline Mo with a BCC structure is embedded. Disordered Fe(CoMo) solid solution is characterized by a broad hyperfine magnetic field distribution with two regions centered at B 1 = 35.0 T and B 2 = 30.7 T, respectively, attributed to disordered Fe(Co) solid solution and CoMo enriched environments. Prolonged milling and Mo addition cause the decrease of average hyperfine magnetic field while the average isomer shift remains nearly constant. - Highlights: ► BCC nanostructured Fe(CoMo) solid solution is prepared by milling of Fe, Co and Mo. ► Formation mechanism: Co diffusion into Fe lattice and Mo dissolution in Fe(Co). ► Crystallite size of Fe(CoMo) solid solution reaches 11 nm after 24 h of milling. ► Mössbauer analysis reveals 3 components: high field, enriched Co and low field

Hyperfine interactions and structural features of Fe–44Co–6Mo (wt.%) nanostructured powders

Energy Technology Data Exchange (ETDEWEB)

Moumeni, Hayet, E-mail: hmoumeni@yahoo.fr [Laboratoire de Chimie Computationnelle et Nanostructures, Département des Sciences de la Matière, Faculté des Mathématiques et de l' Informatique et des Sciences de la Matière, Université 08 Mai 1945 - Guelma, B.P. 401, Guelma 24000 (Algeria); Nemamcha, Abderrafik [Laboratoire d' Analyses Industrielles et Génie des Matériaux, Faculté des Sciences et de la Technologie, Université 08 Mai 1945 - Guelma, B.P. 401, Guelma 24000 (Algeria); Alleg, Safia [Laboratoire de Magnétisme et de Spectroscopie des Solides, Département de Physique, Faculté des Sciences, Université de Annaba, B.P. 12, Annaba 23000 (Algeria); Grenèche, Jean Marc [Laboratoire de Physique de l' Etat Condensé, UMR CNRS 6087, Institut de Recherche en Ingénierie Moléculaire et Matériaux Fonctionnels IRIM2F, FR CNRS 2575, Université du Maine, 72085 Le Mans Cedex 9 (France)

2013-02-15

Nanocrystalline Fe–44Co–6Mo (wt.%) powders have been prepared by high-energy ball milling from elemental Fe, Co and Mo pure powders in a P7 planetary ball mill. The obtained powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Mössbauer spectrometry techniques. The influence of milling process and Mo substitution for Co in equiatomic FeCo have been examined in order to study structural evolution and formation mechanism of nanostructured Fe(CoMo) solid solution. XRD results show the formation of a BCC Fe(CoMo) solid solution (a = 0.2874 nm) where unmixed nanocrystalline Mo with a BCC structure is embedded. Disordered Fe(CoMo) solid solution is characterized by a broad hyperfine magnetic field distribution with two regions centered at B{sub 1} = 35.0 T and B{sub 2} = 30.7 T, respectively, attributed to disordered Fe(Co) solid solution and CoMo enriched environments. Prolonged milling and Mo addition cause the decrease of average hyperfine magnetic field while the average isomer shift remains nearly constant. - Highlights: ► BCC nanostructured Fe(CoMo) solid solution is prepared by milling of Fe, Co and Mo. ► Formation mechanism: Co diffusion into Fe lattice and Mo dissolution in Fe(Co). ► Crystallite size of Fe(CoMo) solid solution reaches 11 nm after 24 h of milling. ► Mössbauer analysis reveals 3 components: high field, enriched Co and low field.

Carbon dioxide elimination and regeneration of resources in a microwave plasma torch

International Nuclear Information System (INIS)

Uhm, Han S.; Kwak, Hyoung S.; Hong, Yong C.

2016-01-01

Carbon dioxide gas as a working gas produces a stable plasma-torch by making use of 2.45 GHz microwaves. The temperature of the torch flame is measured by making use of optical spectroscopy and a thermocouple device. Two distinctive regions are exhibited, a bright, whitish region of a high-temperature zone and a bluish, dimmer region of a relatively low-temperature zone. The bright, whitish region is a typical torch based on plasma species where an analytical investigation indicates dissociation of a substantial fraction of carbon dioxide molecules, forming carbon monoxides and oxygen atoms. The emission profiles of the oxygen atoms and the carbon monoxide molecules confirm the theoretical predictions of carbon dioxide disintegration in the torch. Various hydrocarbon materials may be introduced into the carbon dioxide torch, regenerating new resources and reducing carbon dioxide concentration in the torch. As an example, coal powders in the carbon dioxide torch are converted into carbon monoxide according to the reaction of CO_2 + C → 2CO, reducing a substantial amount of carbon dioxide concentration in the torch. In this regards, the microwave plasma torch may be one of the best ways of converting the carbon dioxides into useful new materials. - Highlights: • Carbon dioxide gas produces a plasma-torch by making use of 2.45 GHz microwaves. • The temperature measurement of torch flame by optical spectroscopy. • Disintegration of carbon dioxide into carbon monoxide and oxygen atom. • Emission profiles of carbon monoxide confirm disintegration theory. • Conversion of carbon dioxide into carbon monoxide in the plasma torch. - This article presents carbon-dioxide plasma torch operated by microwaves and its applications to regeneration of new resources, eliminating carbon dioxide molecules.

Crystal structure refinement of α-Si3N4 using synchrotron radiation powder diffraction data: unbiased refinement strategy

International Nuclear Information System (INIS)

Toraya, H.

2000-01-01

The crystal structure of α-silicon nitride (Si 3 N 4 ) was refined by the Rietveld method using synchrotron radiation powder diffraction data (wavelength = 1.2 A) collected at station BL-4B2 in the photon factory. A refinement procedure that adopted a new weight function, w = 1/Y o e (Y o is the observed profile intensity and e ≅ 2), for the least-squares fitting [Toraya (1998). J. Appl. Cryst. 31, 333-343] was studied. The most reasonable structural parameters were obtained with e = 1.7. Crystal data of α-Si 3 N 4 : trigonal, P31c, a = 7.75193 (3), c = 5.61949 (4) A, V = 292.447 (3) A 3 , Z = 4; R p = 5.08, R wp = 6.50, R B = 3.36, R F = 2.26%. The following five factors are considered equally important for deriving accurate structural parameters from powder diffraction data: (i) sufficiently large sin θ/λ range of >0.8 A -1 ; (ii) adequate counting statistics; (iii) correct profile model; (iv) proper weighting on observations to give a uniform distribution of the mean weighted squared residuals; (v) high-angular-resolution powder diffraction data. (orig.)

Adsorption of F2C=CFCl on TiO2 nano-powder: Structures, energetics and vibrational properties from DRIFT spectroscopy and periodic quantum chemical calculations

International Nuclear Information System (INIS)

Tasinato, Nicola; Moro, Daniele; Stoppa, Paolo; Pietropolli Charmet, Andrea; Toninello, Piero; Giorgianni, Santi

2015-01-01

Graphical abstract: - Highlights: • Adsorption of F 2 C=CFCl on TiO 2 unveiled by DRIFTS and periodic DFT. • Structural, energetic and vibrational properties of F 2 C=CFCl @ anatase (1 0 1). • Binding energies (B3LYP-D2) between −17 and −46 kJ mol −1 depending on the anchor point. • Theory and experiment converge on the CF 2 moiety as the main anchor point. - Abstract: Photodegradation over titanium dioxide (TiO 2 ) is a very appealing technology for removing environmental pollutants from the air, the adsorption interaction being the first step of the whole reaction pathway. In the present work the adsorption of F 2 C=CFCl (chlorotrifluoroethene, halon 1113), a compound used by industry and detected in the atmosphere, on a commercial TiO 2 nano-powder is investigated experimentally by in situ DRIFT spectroscopy and theoretically through periodic ab initio calculations rooted in DFT. The spectra of the adsorbed molecule suggest that the anchoring to the surface mainly takes place through F atoms. Theoretically, five adsorption configurations for the molecule interacting with the anatase (1 0 1) surface are simulated at B3LYP level and for each of them, structures, binding energies and vibrational frequencies are derived. The interplay between theory and experiments shows the coexistence of different adsorption configurations, the foremost ones featuring the interaction of one F atom with a fivefold coordinated Ti 4+ of the surface. These two adsorption models, which mostly differ for the orientation of the adsorbate with respect to the surface, feature a binding energy of −45.6 and −41.0 kJ mol −1 according to dispersion corrected DFT calculations. The favorable adsorption interaction appears as an important requirement toward the application of titanium dioxide technologies for the photocatalytic degradation of halon 1113.

Carbon dioxide sensor

Science.gov (United States)

Dutta, Prabir K [Worthington, OH; Lee, Inhee [Columbus, OH; Akbar, Sheikh A [Hilliard, OH

2011-11-15

The present invention generally relates to carbon dioxide (CO.sub.2) sensors. In one embodiment, the present invention relates to a carbon dioxide (CO.sub.2) sensor that incorporates lithium phosphate (Li.sub.3PO.sub.4) as an electrolyte and sensing electrode comprising a combination of lithium carbonate (Li.sub.2CO.sub.3) and barium carbonate (BaCO.sub.3). In another embodiment, the present invention relates to a carbon dioxide (CO.sub.2) sensor has a reduced sensitivity to humidity due to a sensing electrode with a layered structure of lithium carbonate and barium carbonate. In still another embodiment, the present invention relates to a method of producing carbon dioxide (CO.sub.2) sensors having lithium phosphate (Li.sub.3PO.sub.4) as an electrolyte and sensing electrode comprising a combination of lithium carbonate (Li.sub.2CO.sub.3) and barium carbonate (BaCO.sub.3).

Fast and Straightforward Synthesis of Luminescent Titanium(IV Dioxide Quantum Dots

Directory of Open Access Journals (Sweden)

Václav Štengl

2017-01-01

Full Text Available The nucleus of titania was prepared by reaction of solution titanium oxosulphate with hydrazine hydrate. These titania nuclei were used for titania quantum dots synthesis by a simple and fast method. The prepared titanium(IV dioxide quantum dots were characterized by measurement of X-ray powder diffraction (XRD, X-ray photoelectron spectroscopy (XPS, atomic force microscopy (AFM, high-resolution electron microscopy (HRTEM, and selected area electron diffraction (SAED. The optical properties were determined by photoluminescence (PL spectra. The prepared titanium(IV dioxide quantum dots have the narrow range of UV excitation (365–400 nm and also a close range of emission maxima (450–500 nm.

MULTILAYER COMPOSITE PLASMA COATINGS ON SCREEN PROTECTION ELEMENTS BASED ON ZIRCONIUM DIOXIDE

Directory of Open Access Journals (Sweden)

V. A. Okovity

2017-01-01

Full Text Available The paper contains results of investigations pertaining to an influence of plasma jet parameters (current, spraying distance, consumption of plasma formation gas (nitrogen, fractional composition of initial powder and degree of cooling with compressed air on anti-meteoric coating characteristics. Optimum modes (arc current 600 A; spray distance of 110 mm; consumption of plasma formation gas (nitrogen – 50 l/min; fractional composition of zirconium dioxide powder <50 μm; compressed air consumption for cooling – 1 m3/min; p = 4 bar make it possible to obtain anti-meteoric coatings based on zirconium dioxide with material utilization rate of 62 %, total ceramic layer porosity of 6 %. After exposure of compression plasma flows on a coating in the nitrogen atmosphere a cubic modification of zirconium oxide is considered as the main phase being present in the coating. The lattice parameter of cubic zirconium oxide modification is equal to 0.5174 nm. Taking into consideration usage of nitrogen as plasma formation substance its interaction with zirconium coating atoms occurs and zirconium nitride (ZrN is formed with a cubic crystal lattice (lattice parameter 0.4580 nm. Melting of pre-surface layer takes place and a depth of the melted layer is about 8 μm according to the results of a scanning electron microscopy. Pre-surface layer being crystallized after exposure to compression plasma flows is characterized by a homogeneous distribution of ele-ments and absence of pores formed in the process of coating formation. The coating structure is represented by a set of lar- ge (5–7 μm and small (1–2 μm zirconium oxide particles sintered against each other. Melting of coating surface layer and speed crystallization occur after the impact of compression plasma flows on the formed coating. Cracking of the surface layer arises due to origination of internal mechanical stresses in the crystallized part. While using a scanning electron microscopy a

Impact strength of sintered astaloy CrM powders

International Nuclear Information System (INIS)

Kazior, J.; Ploszczak, J.; Nykiel, M.; Pieczonka, T.

2003-01-01

In this paper results of a series of impact tests on sintered Astaloy CrM powders alloys modified by boron are presented and discussed. Boron in different forms, i.e. as elemental boron powder, boron carbide B 4 C powder or mixture of boron and carbon elemental powders, was used in different weight percentage to activate sintering of Astaloy CrM powder and to increase hardenability, with aim of increasing impact strength in view of structural applications. (author)

Three dimensional reduced graphene hydrogels with tunable pore sizes using thiourea dioxide for electrode materials in supercapacitors

International Nuclear Information System (INIS)

Xing, Ling-Bao; Zhang, Jing-Li; Zhang, Juan; Hou, Shu-Fen; Zhou, Jin; Si, Weijiang; Cui, Hongyou; Zhuo, Shuping

2015-01-01

Graphical abstract: Three-dimensional porous reduced graphene hydrogels with tunable pore size distribution are prepared by using thiourea dioxide in GO suspension with ammonia. - Highlights: • Three-dimensional reduced graphene hydrogels (RGHs) were prepared. • Thiourea dioxide was used as reducing agent with ammonia. • RGHs showed tunable pore size distribution by thiourea dioxide. • RGHs exhibited relatively good electrochemical properties in supercapacitor. - Abstract: In present work, we demonstrate a rapid and easy approach to fabricate three-dimensional (3D) reduced graphene hydrogels (RGHs) by using thiourea dioxide as reducing agents in an aqueous solution of graphene oxide (GO) with ammonia. The transformation of GO suspension to the hydrogels can be confirmed by X-ray powder diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. The hierarchical porosity, structure and surface chemical properties can be demonstrated by N 2 sorption experiments, scanning electron microscopy and X-ray photoelectron spectroscopy. With adding different amounts of thiourea dioxide, the obtained RGHs behave different degree of reduction, controlled specific surface area and pore size distribution, and unlike performances in supercapacitors. Benefiting from well-defined and cross-linked 3D porous network architectures, the supercapacitors based on the RGHs in KOH electrolyte exhibited a high specific capacitance of 258.6, 167.3 and 198.3 F g −1 at 0.1 A g −1 for RGHs-1, RGHs-2 and RGHs-5, respectively. Furthermore, this capacitance also showed good electrochemical stability and a high degree of reversibility in the repetitive charge/discharge cycling test

Aqueous Synthesis of Technetium-Doped Titanium Dioxide by Direct Oxidation of Titanium Powder, a Precursor for Ceramic Nuclear Waste Forms

Energy Technology Data Exchange (ETDEWEB)

Lukens, Wayne W. [Chemical; Saslow, Sarah A. [Earth

2017-11-17

Technetium-99 (Tc) is a problematic fission product that complicates the long-term disposal of nuclear waste due to its long half-life, high fission yield, and the environmental mobility of pertechnetate, its stable form in aerobic environments. One approach to preventing Tc contamination is through incorporation into durable waste forms based on weathering-resistant minerals such as rutile (titanium dioxide). Here, the incorporation of technetium into titanium dioxide by means of simple, aqueous chemistry is presented. X-ray absorption fine structure spectroscopy and diffuse reflectance spectroscopy indicate that Tc(IV) replaces Ti(IV) within the structure. Rather than being incorporated as isolated Tc(IV) ions, Tc is present as pairs of edge-sharing Tc(IV) octahedra similar to molecular Tc(IV) complexes such as [(H2EDTA)TcIV](u-O)2. Technetium-doped TiO2 was suspended in deionized water under aerobic conditions, and the Tc leached under these conditions was followed for 8 months. The normalized release rate of Tc (LRTc) from the TiO2 particles is low (3×10-6 g m-2 d-1), which illustrates the potential utility of TiO2 as waste form. However, the small size of the as-prepared TiO2 nanoparticles results in estimated retention of Tc for 104 years, which is only a fraction of the half-life of Tc (2×10-5 years).

The application of the zeolyte powder for the construction of the dense composite membranes for the carbon-dioxide separation

Directory of Open Access Journals (Sweden)

Nedeljković Dragutin M.

2015-01-01

Full Text Available The main task of the work is to construct the polymeric membrane that could be used for the waste gases treatment. For this purpose, membrane must have high permeability for the carbon dioxide and low permeability of the other gases commonly present in waste gases (hydrogen, oxygen, nitrogen and methane. The constructed membranes were of a dense type, based on a solubility/diffusivity mechanism. In order to enchase the permeability of carbon dioxide, four different zeolytes were added, and in order to improve mechanical stability two different additives were tested. Three zeolytes were with the 3-dimensional pores (ZSM5; Faujasite Linde type A and one was with the 1-dimensional pores (Linde type L. As an additive, n-tetradecyldimethylamonium bromide - n-C14TMABr was tested. The aim of an additive was to provide good wetting of a highly electrically charged zeolyte particle by the hydrophobic polymer chains. The other examined additive was dimethylaminopyridine (DMAP which should improve the solubility of carbon dioxide due to its alkali properties. The best results in carbon dioxide/hydrogen selectivity and permeability were obtained with the membrane constructed with PEBAX 1657 and surface treated zeolyte. The obtained permeability of carbon dioxide was 128 Barrer, and the carbon dioxide/hydrogen selectivity was 9.7.

Structural and morphological characterization of TiO2-ZrO2 powders obtained by the polymeric precursors method

International Nuclear Information System (INIS)

Ribeiro, M.A.; Gama, L.; Bispo, A.; Neiva, L.S.; Bernardi, M.I.B.; Kiminami, R.H.G.A.

2010-01-01

This work aims to characterize the structure and morphology of TiO 2 -ZrO 2 powders obtained by polymeric precursor method. For this we studied the following compositions: 0.25, 0.5 and 0.75 moles of Zr and calcined at 800 deg C for one hour. The powders obtained were characterized by XRD, SEM and nitrogen adsorption (BET). The analysis of X-ray diffraction showed that the powders had a phase of TiO 2 in the anatase form and a tetragonal phase of ZrO 2 . The crystallite size was between 8, 13 and 11 nm respectively. The analysis of scanning electron microscopy showed the growth of ZrO 2 nanoparticles and that these comprise spherical agglomerates of less than 100 nm. Particle size determined by the BET ranging 28.1-29.5 nm, showing thereby the character of nanosized powders. (author)

Development of materials science by Ab initio powder diffraction analysis

International Nuclear Information System (INIS)

Fujii, Kotaro

2015-01-01

Crystal structure is most important information to understand properties and behavior of target materials. Technique to analyze unknown crystal structures from powder diffraction data (ab initio powder diffraction analysis) enables us to reveal crystal structures of target materials even we cannot obtain a single crystal. In the present article, three examples are introduced to show the power of this technique in the field of materials sciences. The first example is dehydration/hydration of the pharmaceutically relevant material erythrocycin A. In this example, crystal structures of two anhydrous phases were determined from synchrotron X-ray powder diffraction data and their different dehydration/hydration properties were understood from the crystal structures. In the second example, a crystal structure of a three dimensional metal-organic-framework prepared by a mechanochemical reaction was determined from laboratory X-ray powder diffraction data and the reaction scheme has been revealed. In the third example, a crystal structure of a novel oxide-ion conductor of a new structure family was determined from synchrotron X-ray and neutron powder diffraction data which gave an important information to understand the mechanism of the oxide-ion conduction. (author)

Energy efficiency opportunities within the powder coating industry

Energy Technology Data Exchange (ETDEWEB)

Osbeck, Sofie; Bergek, Charlotte; Klaessbo, Anders (Swerea IVF AB, Moelndal (Sweden)), e-mail: anders.klassbo@swerea.se; Thollander, Patrik; Rohdin, Patrik (Dept. of Management and Engineering, Linkoeping Univeristy, Linkoeping (Sweden)); Harvey, Simon (Dept. of Energy and Environment, Chalmers Univ. of Technology, Goeteborg (Sweden))

2011-06-15

A new challenge to reduce energy usage has emerged in Swedish industry because of increasing energy costs. Energy usage in the Swedish powder coating industry is about 525 GWh annually. This industry has a long and successful record of working towards reduced environmental impact. However, they have not given priority to energy saving investments. Electricity and LPG, for which end-user prices are predicted to increase by as much as 50 - 60% by 2020, are the main energy carriers used in the plants. This paper presents the results of two detailed industrial energy audits conducted with the aim of quantifying the energy efficiency potential for the Swedish powder coating industry. Energy auditing and pinch analysis methods were used to identify possible energy housekeeping measures and heat exchanging opportunities. The biggest users of energy within the plants are the cure oven, drying oven and pre-treatment units. The energy use reduction by the housekeeping measures is 8 - 19% and by thermal heat recovery an additional 8 - 13%. These measures result in an average energy cost saving of 25% and reduction of carbon dioxide emissions of 30%. The results indicate that the powder coating industry has a total energy efficiency potential of at least 20%

Solid-state structural properties of 2,4,6-trimethoxybenzene derivatives, determined directly from powder X-ray diffraction data in conjunction with other techniques

International Nuclear Information System (INIS)

Pan Zhigang; Xu Mingcan; Cheung, Eugene Y.; Platts, James A.; Harris, Kenneth D.M.; Constable, Edwin C.; Housecroft, Catherine E.

2006-01-01

Structural properties of 2,4,6-trimethoxybenzaldehyde, 2,4,6-trimethoxybenzyl alcohol and 2,4,6-trimethoxyacetophenone have been determined directly from powder X-ray diffraction data, using the direct-space Genetic Algorithm (GA) technique for structure solution followed by Rietveld refinement. Structural similarities and contrasts within this family of materials are elucidated. The work illustrates the value of utilizing information from other sources, including spectroscopic data and computational techniques, as a means of augmenting the structural knowledge established from the powder X-ray diffraction data

Production and properties of boride powders

International Nuclear Information System (INIS)

Klinskaya, N.A.; Koroleva, E.B.; Petrunichev, V.A.

1990-01-01

Results of plasma metallization of boride powders 40-80 μ diam. are presented. Peculiarities of changes of granulometric powder composition and of metallic cover on refractory cores were investigated. There are shown size- and compositional cores effects on metallization level of poders and on cover structure

Advances in food powder agglomeration engineering.

Science.gov (United States)

Cuq, B; Gaiani, C; Turchiuli, C; Galet, L; Scher, J; Jeantet, R; Mandato, S; Petit, J; Murrieta-Pazos, I; Barkouti, A; Schuck, P; Rondet, E; Delalonde, M; Dumoulin, E; Delaplace, G; Ruiz, T

2013-01-01

Food powders are used in everyday life in many ways and offer technological solutions to the problem of food production. The natural origin of food powders, diversity in their chemical composition, variability of the raw materials, heterogeneity of the native structures, and physicochemical reactivity under hydrothermal stresses contribute to the complexity in their behavior. Food powder agglomeration has recently been considered according to a multiscale approach, which is followed in the chapter layout: (i) at the particle scale, by a presentation of particle properties and surface reactivity in connection with the agglomeration mechanisms, (ii) at the mechanisms scale, by describing the structuration dynamics of agglomerates, (iii) at the process scale, by a presentation of agglomeration technologies and sensors and by studying the stress transmission mode in the powder bed, and finally (iv) by an integration of the acquired knowledge, thanks to a dimensional analysis carried out at each scale. Copyright © 2013 Elsevier Inc. All rights reserved.

Thermal and structural study of guava (Psidium guajava L powders obtained by two dehydration methods

Directory of Open Access Journals (Sweden)

Coralia Osorio

2011-01-01

Full Text Available Two food products (powders were obtained by hot-air drying or lyophilisation methods on the whole guava fruits. The powders were characterised by sensory and thermal analyses (TGA-DSC, infrared spectroscopy (IR, X-ray diffraction (XRD and scanning electron microscopy (SEM. Thermal, morphological and structural characterisations showed a similar behaviour for the two solids. TGA-DSC and IR showed the presence of pectin as the main constituent of solids. A semi-crystalline profile was evidenced by XRD, and lamellar/spherical morphologies were observed by SEM. Sensory analyses revealed an aroma highly related to guava. These value-added food products are an alternative to process guava and avoid loss during postharvest handling.

Determination of carbon content of UO2, (U, Gd)O2 and (U, Pu)O2 powders and sintered pellets - Combustion in a high-frequency induction furnace -Infrared absorption spectrometry

International Nuclear Information System (INIS)

2008-01-01

This International Standard describes a method for determining the carbon content in UO 2 , (U,Gd)O 2 and (U,Pu)O 2 powder and sintered pellets by combustion in an induction furnace and infrared absorption spectroscopy measurement. It is applicable for determining 10 μg/g to 500 μg/g of carbon in UO 2 , (U,Gd)O 2 and (U,Pu)O 2 powder and pellets. The sample is heated to a temperature above 1500 deg. C in an induction furnace, under pure oxygen atmosphere, to convert any carbon compounds to carbon dioxide gas. The resulting carbon dioxide gas is filtered and dried before measurement using infrared spectroscopy to measure the carbon dioxide signal at 2350 cm -1 . The result is converted into the carbon content of the material analysed

Magneto-structural transformations in Ni{sub 50}Mn{sub 37.5}Sn{sub 12.5−x}In{sub x} Heusler powders

Energy Technology Data Exchange (ETDEWEB)

Maziarz, Wojciech; Wójcik, Anna; Czaja, Paweł [Instituite of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta Str, 30-059 Kraków (Poland); Żywczak, Antoni [AGH University of Science and Technology, Academic Centre for Materials and Nanotechnology, Mickiewicza 30, 30-059 Kraków (Poland); Jan Dutkiewicz [Instituite of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta Str, 30-059 Kraków (Poland); Hawełek, Łukasz [Institute of Non-Ferrous Metals, ul. Sowinskiego 5, 44-100 Gliwice (Poland); Cesari, Eduard [Department de Física, Universitat de les Illes Balears, Ctra. de Valldemossa, km 7.5, Palma de Mallorca E-07122 (Spain)

2016-08-15

The effect of ball milling and subsequently annealing of melt spun ribbons on magneto-structural transformations in Ni{sub 50}Mn{sub 37.5}Sn{sub 12.5−x}In{sub x} (x=0, 2, 4, 6) ribbons is presented. Short time vibration milling allows to obtain chemically homogenous powders of angular particle shapes and size within 10–50 μm. Milling does not change the characteristic temperatures of martensitic transformation in comparison to the melt spun ribbons. The effect of In substitution for Sn on martensitic transformation has a complex mechanism, associated with electron density change. Substitution of Sn by In in both milled and annealed powders leads to decrease of Curie temperature of austenite and increase of martensitic transformation temperature, stabilizing martensitic phase. The coexistence of magnetic transformation of austenite and martensitic transformation at low magnetic field was observed. The intermartensitic transformation of 4O martensite to L1{sub 0} martensite was observed during cooling at low magnetic field and this was confirmed by TEM microstructure observations. The annealing process of as-milled powders leads to the change of their martensitic structure due to relaxation of internal stresses associated with anisotropic columnar grain microstructure formed during melt spinning process. The level of stresses introduced during milling of ribbons has no significant influence on martensitic transformation. The annealing process of as milled powders leads to enhancement of their magnetic properties, decrease of Curie temperature of austenite, and marginal change of temperature of martenisitic transformation. - Highlights: • Vibration milling of ribbons allows to obtain angular powders of size 10–50 μm. • Vibration milling improves chemical homogeneity of alloys. • Indium addition changes the magneto-structural transformations in Ni–Mn–Sn–In alloys. • Complex character of magneto-structural transformations is visible. • Multistep

Sinteractive thoria powders derived through gel-combustion and oxalate deagglomeration - a comparison

International Nuclear Information System (INIS)

Ananthasivan, K.; Balakrishnan, S.; Anthonysamy, S.; Ganesan, V.; Vasudeva Rao, P.R.

2011-01-01

Thorium dioxide finds extensive application in the nuclear industry. Pellets of thoria are used in PHWRs for flux flattening and in FBRs as a blanket material. The development of advanced methods for the synthesis and sintering of thoria is relevant to these applications. This paper attempts to compare the properties of sinteractive nanocrystalline thoria (pure and doped with Ca 2+ and Mg 2+ ) synthesized in our laboratory through two different techniques, viz. gel-combustion and oxalate de-agglomeration. In all the investigations cited above the precursors obtained by using both the procedures were calcined in air at 1073 K. The thoria powders thus obtained were characterised for their specific surface area (SSA), X-ray crystallite size (XCS), bulk density, particle size distribution and residual carbon content. These powders were pelletised and sintered at 1473, 1673, and 1873 K. The sinterability of these powders was compared by measuring the density of the sintered pellets. A matrix density as high as 96.8 % TD (gel combustion) or 98.6 % TD (de-agglomeration) could be obtained at 1873 K, with the powders doped with 0.5 mole % calcia. (author)

Standard test methods for chemical and mass spectrometric analysis of nuclear-grade gadolinium oxide (Gd2O3) powder

CERN Document Server

American Society for Testing and Materials. Philadelphia

2006-01-01

1.1 These test methods cover procedures for the chemical and mass spectrometric analysis of nuclear-grade gadolinium oxide powders to determine compliance with specifications. 1.2 The analytical procedures appear in the following order: Sections Carbon by Direct CombustionThermal Conductivity C1408 Test Method for Carbon (Total) in Uranium Oxide Powders and Pellets By Direct Combustion-Infrared Detection Method Total Chlorine and Fluorine by Pyrohydrolysis Ion Selective Electrode C1502 Test Method for Determination of Total Chlorine and Fluorine in Uranium Dioxide and Gadolinium Oxide Loss of Weight on Ignition 7-13 Sulfur by CombustionIodometric Titration Impurity Elements by a Spark-Source Mass Spectrographic C761 Test Methods for Chemical, Mass Spectrometric, Spectrochemical,Nuclear, and Radiochemical Analysis of Uranium Hexafluoride C1287 Test Method for Determination of Impurities In Uranium Dioxide By Inductively Coupled Plasma Mass Spectrometry Gadolinium Content in Gadolinium Oxid...

Various continuum approaches for studying shock wave structure in carbon dioxide

Science.gov (United States)

Alekseev, I. V.; Kosareva, A. A.; Kustova, E. V.; Nagnibeda, E. A.

2018-05-01

Shock wave structure in carbon dioxide is studied using different continuum models within the framework of one-temperature thermal equilibrium flow description. Navier-Stokes and Euler equations as well as commonly used Rankine-Hugoniot equations with different specific heat ratios are used to find the gas-dynamic parameters behind the shock wave. The accuracy of the Rankine-Hugoniot relations in polyatomic gases is assessed, and it is shown that they give a considerable error in the predicted values of fluid-dynamic variables. The effect of bulk viscosity on the shock wave structure in CO2 is evaluated. Taking into account bulk viscosity yields a significant increase in the shock wave width; for the complete model, the shock wave thickness varies non-monotonically with the Mach number.

Fe-based nanocrystalline powder cores with ultra-low core loss

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiangyue, E-mail: wangxiangyue1986@163.com [China Iron and Steel Research Institute Group, Beijing 100081 (China); Center of Advanced Technology and Materials Co., Ltd., Beijing 100081 (China); Lu, Zhichao; Lu, Caowei; Li, Deren [China Iron and Steel Research Institute Group, Beijing 100081 (China); Center of Advanced Technology and Materials Co., Ltd., Beijing 100081 (China)

2013-12-15

Melt-spun amorphous Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 15.5}B{sub 7} alloy strip was crushed to make flake-shaped fine powders. The passivated powders by phosphoric acid were mixed with organic and inorganic binder, followed by cold compaction to form toroid-shaped bonded powder-metallurgical magnets. The powder cores were heat-treated to crystallize the amorphous structure and to control the nano-grain structure. Well-coated phosphate-oxide insulation layer on the powder surface decreased the the core loss with the insulation of each powder. FeCuNbSiB nanocrystalline alloy powder core prepared from the powder having phosphate-oxide layer exhibits a stable permeability up to high frequency range over 2 MHz. Especially, the core loss could be reduced remarkably. At the other hand, the softened inorganic binder in the annealing process could effectively improve the intensity of powder cores. - Highlights: • Fe-based nanocrystalline powder cores were prepared with low core loss. • Well-coated phosphate-oxide insulation layer on the powder surface decreased the core loss. • Fe-based nanocrystalline powder cores exhibited a stable permeability up to high frequency range over 2 MHz. • The softened inorganic binder in the annealing process could effectively improve the intensity of powder cores.

Methane explosion suppression characteristics based on the NaHCO3/red-mud composite powders with core-shell structure.

Science.gov (United States)

Wang, Yan; Cheng, Yi-Shen; Yu, Ming-Gao; Li, Yao; Cao, Jian-Liang; Zheng, Li-Gang; Yi, Hong-Wei

2017-08-05

The NaHCO 3 /red-mud (RM) composite powders were successfully prepared by the solvent-anti-solvent method for methane explosion suppression. The RM was used as a carrier, and the NaHCO 3 was used as a loaded inhibitor. The NaHCO 3 /RM composite powders showed a special core-shell structure and excellent endothermic performance. The suppression properties of NaHCO 3 /RM composite for 9.5% CH 4 explosion were tested in a 20L spherical explosion vessel and a 5L Perspex duct. The results showed that the NaHCO 3 /RM composite powders displayed a much better suppression property than the pure RM or NaHCO 3 powders. The loading amount of NaHCO 3 has an intensive influence on the inhibition property of NaHCO 3 /RM composite powders. The best loaded content of NaHCO 3 is 35%. It exhibited significant inhibitory effect that the explosion max-pressure declined 44.9%, the max-pressure rise rate declined 96.3% and the pressure peak time delayed 366.7%, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

Structural studies of carbon nanotubes by powder x-ray diffraction at SPring-8 and KEK PF

CERN Document Server

Maniwa, Y; Fujiwara, A

2003-01-01

Powder X-ray diffraction (XRD) studies on carbon nanotubes (CNTs) using synchrotron radiation are reported. In spite of the observed broad XRD peak profiles of two-dimensional triangular (hexagonal) lattice of single-wall carbon nanotubes (SWNTs), it was shown that useful structural information, such as the tube diameter and its distribution, can be deduced from detailed analysis of the characteristic XRD patterns. In particular, powder-XRD measurements were performed to study the phase transition of encapsulated materials inside SWNTs. In the C sub 7 sub 0 -one dimensional (1D) crystals formed inside SWNTs, importance of one-dimensionality in the C sub 7 sub 0 -molecular dynamics was suggested. It was also shown that water inside SWNTs undergoes a phase transition from liquid to an ice-nanotube structure below -38degC. Conversion process from SWNT to double-wall carbon nanotube (DWNT) was also studied by XRD.

Size-dependent magnetic and structural properties of CoCrFeO4 nano-powder prepared by solution self-combustion

Science.gov (United States)

Sijo, A. K.; Dutta, Dimple P.

2018-04-01

The study reports the tuning of magnetic and structural properties of nano-sized CoCrFeO4 via post-annealing treatment. CoCrFeO4 nano-powder has been prepared by solution self-combustion method. The structural and magnetic properties have been studied over a range of annealing temperatures (300-900 °C). The formation of the phase pure CoCrFeO4 spinel has been confirmed from powder XRD analysis. The crystallite size is observed to increase with an increase in annealing temperature. On annealing, the value of magnetic parameters-remanence, coercivity and saturation magnetization have enhanced. All the samples exhibit irreversibility at low-temperature measurements.

IMPEDANCE SPECTROSCOPY OF POLYCRYSTALLINE TIN DIOXIDE FILMS

Directory of Open Access Journals (Sweden)

D. V. Adamchuck

2016-01-01

Full Text Available The aim of this work is the analysis of the influence of annealing in an inert atmosphere on the electrical properties and structure of non-stoichiometric tin dioxide films by means of impedance spectroscopy method. Non-stoichiometric tin dioxide films were fabricated by two-step oxidation of metallic tin deposited on the polycrystalline Al2O3 substrates by DC magnetron sputtering. In order to modify the structure and stoichiometric composition, the films were subjected to the high temperature annealing in argon atmosphere in temperature range 300–800 °С. AC-conductivity measurements of the films in the frequency range 20 Hz – 2 MHz were carried out. Variation in the frequency dependencies of the real and imaginary parts of the impedance of tin dioxide films was found to occur as a result of high-temperature annealing. Equivalent circuits for describing the properties of films with various structure and stoichiometric composition were proposed. Possibility of conductivity variation of the polycrystalline tin dioxide films as a result of аnnealing in an inert atmosphere was demonstrated by utilizing impedance spectroscopy. Annealing induces the recrystallization of the films, changing in their stoichiometry as well as increase of the sizes of SnO2 crystallites. Variation of electrical conductivity and structure of tin dioxide films as a result of annealing in inert atmosphere was confirmed by X-ray diffraction analysis. Analysis of the impedance diagrams of tin dioxide films was found to be a powerful tool to study their electrical properties. 

Brandon mathematical model describing the effect of calcination and reduction parameters on specific surface area of UO{sub 2} powders

Energy Technology Data Exchange (ETDEWEB)

Hung, Nguyen Trong; Thuan, Le Ba [Institute for Technology of Radioactive and Rare Elements (ITRRE), 48 Lang Ha, Dong Da, Ha Noi (Viet Nam); Van Khoai, Do [Micro-Emission Ltd., 1-1 Asahidai, Nomi, Ishikawa, 923-1211 (Japan); Lee, Jin-Young, E-mail: jinlee@kigam.re.kr [Convergence Research Center for Development of Mineral Resources (DMR), Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, 305-350 (Korea, Republic of); Jyothi, Rajesh Kumar, E-mail: rkumarphd@kigam.re.kr [Convergence Research Center for Development of Mineral Resources (DMR), Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, 305-350 (Korea, Republic of)

2016-06-15

Uranium dioxide (UO{sub 2}) powder has been widely used to prepare fuel pellets for commercial light water nuclear reactors. Among typical characteristics of the powder, specific surface area (SSA) is one of the most important parameter that determines the sintering ability of UO{sub 2} powder. This paper built up a mathematical model describing the effect of the fabrication parameters on SSA of UO{sub 2} powders. To the best of our knowledge, the Brandon model is used for the first time to describe the relationship between the essential fabrication parameters [reduction temperature (T{sub R}), calcination temperature (T{sub C}), calcination time (t{sub C}) and reduction time (t{sub R})] and SSA of the obtained UO{sub 2} powder product. The proposed model was tested with Wilcoxon's rank sum test, showing a good agreement with the experimental parameters. The proposed model can be used to predict and control the SSA of UO{sub 2} powder.

Study of carbon dioxide adsorption on a Cu-nitroprusside polymorph

International Nuclear Information System (INIS)

Roque-Malherbe, R.; Lozano, C.; Polanco, R.; Marquez, F.; Lugo, F.; Hernandez-Maldonado, A.; Primera-Pedrozo, J.N.

2011-01-01

A careful structural characterization was carried out to unequivocally determine the structure of the synthesized material. The TGA, DRIFTS and a Pawley fitting of the XRD powder profiles indicate that the hydrated and in situ dehydrated polymorph crystallizes in the orthorhombic space group Pnma. Meanwhile, the CO 2 isosteric heat of adsorption appears to be independent of loading with an average value of 30 kJ/mol. This translates to a physisorption type interaction, where the adsorption energy corresponding to wall and lateral interactions are mutually compensated to produce, an apparently, homogeneous adsorption energy. The somewhat high adsorption energy is probably due to the confinement of the CO 2 molecules in the nitroprusside pores. Statistical Physics and the Dubinin theory for pore volume filling allowed model the CO 2 equilibrium adsorption process in Cu-nitroprusside. A DRIFTS test for the adsorbed CO 2 displayed a peak at about 2338 cm -1 that was assigned to a contribution due to physical adsorption of the molecule. Another peak found at 2362 cm -1 evidenced that this molecule interacts with the Cu 2+ , which appears to act as an electron accepting Lewis acid site. The aim of the present paper is to report a Pnma stable Cu-nitroprusside polymorph obtained by the precipitation method that can adsorb carbon dioxide. -- Graphical abstract: The adsorption space of a very well characterized Cu-nitroprusside polymorph, applying carbon dioxide as probe molecule, was studied. Display Omitted Highlights: → Accurate information about the geometry of the adsorption space was provided. → Truthful data about the interactions within the adsorption space was presented. → The structure of the tested Cu-NP polymorph was established. → Was evidenced adsorbed CO 2 molecules in the form of weakly bonded adducts. → Is proposed that adsorbed molecules could change the Cu-NP magnetic properties.

Contact-Free Support Structures for Part Overhangs in Powder-Bed Metal Additive Manufacturing

Directory of Open Access Journals (Sweden)

Kenneth Cooper

2017-12-01

Full Text Available This study investigates the feasibility of a novel concept, contact-free support structures, for part overhangs in powder-bed metal additive manufacturing. The intent is to develop alternative support designs that require no or little post-processing, and yet, maintain effectiveness in minimizing overhang distortions. The idea is to build, simultaneously during part fabrications, a heat sink (called “heat support”, underneath an overhang to alter adverse thermal behaviors. Thermomechanical modeling and simulations using finite element analysis were applied to numerically research the heat support effect on overhang distortions. Experimentally, a powder-bed electron beam additive manufacturing system was utilized to fabricate heat support designs and examine their functions. The results prove the concept and demonstrate the effectiveness of contact-free heat supports. Moreover, the method was tested with different heat support parameters and applied to various overhang geometries. It is concluded that the heat support proposed has the potential to be implemented in industrial applications.

Structural and magnetic properties of turmeric functionalized CoFe2O4 nanocomposite powder

International Nuclear Information System (INIS)

Mehran, E; Farjami Shayesteh, S; Sheykhan, M

2016-01-01

The structural and magnetic properties of the synthesized pure and functionalized CoFe 2 O 4 magnetic nanoparticles (NPs) are studied by analyzing the results from the x-ray diffraction (XRD), transmission electron microscopy (TEM), FT–IR spectroscopy, thermogravimetry (TG), and vibrating sample magnetometer (VSM). To extract the structure and lattice parameters from the XRD analysis results, we first apply the pseudo-Voigt model function to the experimental data obtained from XRD analysis and then the Rietveld algorithm is used in order to optimize the model function to estimate the true intensity values. Our simulated intensities are in good agreement with the experimental peaks, therefore, all structural parameters such as crystallite size and lattice constant are achieved through this simulation. Magnetic analysis reveals that the synthesized functionalized NPs have a saturation magnetization almost equal to that of pure nanoparticles (PNPs). It is also found that the presence of the turmeric causes a small reduction in coercivity of the functionalized NPs in comparison with PNP. Our TGA and FTIR results show that the turmeric is bonded very well to the surface of the NPs. So it can be inferred that a nancomposite (NC) powder of turmeric and nanoparticles is produced. As an application, the anti-arsenic characteristic of turmeric makes the synthesized functionalized NPs or NC powder a good candidate for arsenic removal from polluted industrial waste water. (paper)

Layered surface structure of gas-atomized high Nb-containing TiAl powder and its impact on laser energy absorption for selective laser melting

Science.gov (United States)

Zhou, Y. H.; Lin, S. F.; Hou, Y. H.; Wang, D. W.; Zhou, P.; Han, P. L.; Li, Y. L.; Yan, M.

2018-05-01

Ti45Al8Nb alloy (in at.%) is designed to be an important high-temperature material. However, its fabrication through laser-based additive manufacturing is difficult to achieve. We present here that a good understanding of the surface structure of raw material (i.e. Ti45Al8Nb powder) is important for optimizing its process by selective laser melting (SLM). Detailed X-ray photoelectron spectroscopy (XPS) depth profiling and transmission electron microscopy (TEM) analyses were conducted to determine the surface structure of Ti45Al8Nb powder. An envelope structure (∼54.0 nm in thickness) was revealed for the powder, consisting of TiO2 + Nb2O5 (as the outer surface layer)/Al2O3 + Nb2O5 (as the intermediate layer)/Al2O3 (as the inner surface layer)/Ti45Al8Nb (as the matrix). During SLM, this layered surface structure interacted with the incident laser beam and improved the laser absorptivity of Ti45Al8Nb powder by ∼32.21%. SLM experiments demonstrate that the relative density of the as-printed parts can be realized to a high degree (∼98.70%), which confirms good laser energy absorption. Such layered surface structure with appropriate phase constitution is essential for promoting SLM of the Ti45Al8Nb alloy.

Retraction Note to: Ultra-High Strength and Ductile Lamellar-Structured Powder Metallurgy Binary Ti-Ta Alloys

Science.gov (United States)

Liu, Yong; Xu, Shenghang; Wang, Xin; Li, Kaiyang; Liu, Bin; Wu, Hong; Tang, Huiping

2018-05-01

The editors and authors have retracted the article, "Ultra-High Strength and Ductile Lamellar-Structured Powder Metallurgy Binary Ti-Ta Alloys" by Yong Liu, Shenghang Xu, Xin Wang, Kaiyang Li, Bin Liu, Hong Wu, and Huiping Tang (https://doi.org/10.1007/s11837-015-1801-1).

A kinetic study of the reaction of water vapor and carbon dioxide on uranium

International Nuclear Information System (INIS)

Santon, J.P.

1964-09-01

The kinetic study of the reaction of water vapour and carbon dioxide with uranium has been performed by thermogravimetric methods at temperatures between 160 and 410 deg G in the first case, 350 and 1050 deg C in the second: Three sorts of uranium specimens were used: uranium powder, thin evaporated films, and small spheres obtained from a plasma furnace. The experimental results led in the case of water vapour, to a linear rate of reaction controlled by diffusion at the lower temperatures, and by a surface reaction at the upper ones. In the case of carbon dioxide, a parabolic law has been found, controlled by diffusional processes. (author) [fr

Conformational analysis of an acyclic tetrapeptide: ab-initio structure determination from X-ray powder diffraction, Hirshfeld surface analysis and electronic structure.

Science.gov (United States)

Das, Uday; Naskar, Jishu; Mukherjee, Alok Kumar

2015-12-01

A terminally protected acyclic tetrapeptide has been synthesized, and the crystal structure of its hydrated form, Boc-Tyr-Aib-Tyr-Ile-OMe·2H2O (1), has been determined directly from powder X-ray diffraction data. The backbone conformation of tetrapeptide (1) exhibiting two consecutive β-turns is stabilized by two 4 → 1 intramolecular N-H · · · O hydrogen bonds. In the crystalline state, the tetrapeptide molecules are assembled through water-mediated O-H · · · O hydrogen bonds to form two-dimensional molecular sheets, which are further linked by intermolecular C-H · · · O hydrogen bonds into a three-dimensional supramolecular framework. The molecular electrostatic potential (MEP) surface of (1) has been used to supplement the crystallographic observations. The nature of intermolecular interactions in (1) has been analyzed quantitatively through the Hirshfeld surface and two-dimensional fingerprint plot. The DFT optimized molecular geometry of (1) agrees closely with that obtained from the X-ray structure analysis. The present structure analysis of Boc-Tyr-Aib-Tyr-Ile-OMe·2H2 O (1) represents a case where ab-initio crystal structure of an acyclic tetrapeptide with considerable molecular flexibility has been accomplished from laboratory X-ray powder diffraction data. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.

Pressure/temperature fluid cell apparatus for the neutron powder diffractometer instrument: Probing atomic structure in situ

Energy Technology Data Exchange (ETDEWEB)

Wang, Hsiu-Wen; Fanelli, Victor R.; Reiche, Helmut M.; Larson, Eric; Taylor, Mark A.; Siewenie, Joan [Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Xu, Hongwu [Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Zhu, Jinlong [High Pressure Science and Engineering Center, Department of Physics and Astronomy, The University of Nevada, Las Vegas, Nevada 89154, USA and National Lab for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Page, Katharine, E-mail: pagekl@ornl.gov [Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

2014-12-15

This contribution describes a new local structure compatible gas/liquid cell apparatus for probing disordered materials at high pressures and variable temperatures in the Neutron Powder Diffraction instrument at the Lujan Neutron Scattering Center, Los Alamos National Laboratory. The new sample environment offers choices for sample canister thickness and canister material type. Finite element modeling is utilized to establish maximum allowable working pressures of 414 MPa at 15 K and 121 MPa at 600 K. High quality atomic pair distribution function data extraction and modeling have been demonstrated for a calibration standard (Si powder) and for supercritical and subcritical CO{sub 2} measurements. The new sample environment was designed to specifically target experimental studies of the local atomic structures involved in geologic CO{sub 2} sequestration, but will be equally applicable to a wide variety of energy applications, including sorption of fluids on nano/meso-porous solids, clathrate hydrate formation, catalysis, carbon capture, and H{sub 2} and natural gas uptake/storage.

Preparation and characterization of phase-pure anatase and rutile TiO2 powder by new chemistry route

International Nuclear Information System (INIS)

Pereira, E. A.; Montanhera, M.A.; Paula, F.R.; Spada, E.R.

2014-01-01

Titanium dioxide (TiO 2 ) is used in a wire range applications such as photocatalysis and sensor device. In this work is shown a new and effective method for the preparation of TiO 2 nanocrystalline in the crystallographic forms, anatase and rutile. The method involves dissolving the TiOSO 4 powder in H 2 O 2 solution and thermal treatment of amorphous precipitate. The technique of X-ray diffraction was used to follow the structure evolution of amorphous precipitate. Pure anatase structure and rutile are obtained at 600 deg C and 1000 deg C with a grain size estimated 24 and 55 nm respectively. TiO 2 nanoparticles is a promising alternative of the low cost whose potential for solar cells deserve a careful evaluation, especially in hybrid solar cells that employs TiO 2 as electron acceptor and as transport channels. (author)

1-(2-furoyl)-3,3-(diphenyl)thiourea: spectroscopic characterization and structural study from X-ray powder diffraction using simulated annealing

Energy Technology Data Exchange (ETDEWEB)

Estevez H, O.; Duque, J. [Universidad de La Habana, Instituto de Ciencia y Tecnologia de Materiales, 10400 La Habana (Cuba); Rodriguez H, J. [UNAM, Instituto de Investigaciones en Materiales, 04510 Mexico D. F. (Mexico); Yee M, H., E-mail: oestevezh@yahoo.com [Instituto Politecnico Nacional, Escuela Superior de Fisica y Matematicas, 07738 Mexico D. F. (Mexico)

2015-07-01

1-Furoyl-3,3-diphenylthiourea (FDFT) was synthesized, and characterized by Ftir, {sup 1}H and {sup 13}C NMR and ab initio X-ray powder structure analysis. FDFT crystallizes in the monoclinic space group P2{sub 1} with a = 12.691(1), b = 6.026(2), c = 11.861(1) A, β = 117.95(2) and V = 801.5(3) A{sup 3}. The crystal structure has been determined from laboratory X-ray powder diffraction data using direct space global optimization strategy (simulated annealing) followed by the Rietveld refinement. The thiourea group makes a dihedral angle of 73.8(6) with the furoyl group. In the crystal structure, molecules are linked by van der Waals interactions, forming one-dimensional chains along the a axis. (Author)

Sol-gel synthesis and structure of La2O3–CoO–SiO2 powders

Directory of Open Access Journals (Sweden)

Lachezar Radev

2008-12-01

Full Text Available LaCoO3 powders are studied because they exhibit interesting electrical, magnetic and catalytic properties. In this paper, new synthesized La2O3-CoO-SiO2 powders with different quantity of silica were prepared via solgel method in aqua media, starting from metal nitrates with different chelating agents. The relation between the reaction in solution, crystallization pathway and morphology were discussed. In LaCoO3-SiO2 powders, depending on the content of SiO2 and the treatment temperature (700–1100°C, different crystalline phases (LaCoO3, Co2SiO4 and La9.31(SiO46O2 were observed with the crystallite sizes ranging from 50 to 100 nm. It was proved that chemical composition and nature of used additives has influence on the phase formation and structure of obtained nanomaterials.

Effects of anticaking agents and relative humidity on the physical and chemical stability of powdered vitamin C.

Science.gov (United States)

Lipasek, Rebecca A; Taylor, Lynne S; Mauer, Lisa J

2011-09-01

Vitamin C is an essential nutrient that is widely used by the food industry in the powder form for both its nutritional and functional properties. However, vitamin C is deliquescent, and deliquescence has been linked to physical and chemical instabilities. Anticaking agents are often added to powder systems to delay or prevent caking, but little is known about their effect on the chemical stability of powders. In this study, various anticaking agents (calcium phosphate, calcium silicate, calcium stearate, corn starch, and silicon dioxide) were combined with sodium ascorbate at 2% and 50% w/w ratios and stored at various relative humidities (23%, 43%, 64%, 75%, 85%, and 98% RHs). Chemical and physical stability and moisture sorption were monitored over time. Additionally, saturated solution samples were stored at various pHs to determine the effect of surface pH and dissolution on the vitamin degradation rate. Storage RH, time, and anticaking agent type and ratio all significantly affected (P vitamin C stability. Silicon dioxide and calcium silicate (50% w/w) and calcium stearate (at both ratios) were the only anticaking agents to improve the physical stability of powdered sodium ascorbate while none of the anticaking agents improved its chemical stability. However, corn starch and calcium stearate had the least adverse effect on chemical stability. Dissolution rate and pH were also important factors affecting the chemical and physical stability of the powders. Therefore, monitoring storage environmental conditions and anticaking agent usage are important for understanding the stability of vitamin C. Anticaking agent type and ratio significantly affected the physical and chemical stability of vitamin C over time and over a range of RHs. No anticaking agent improved the chemical stability of the vitamin, and most caused an increase in chemical degradation even if physical stability was improved. It is possible that anticaking agents would greatly affect other

Dispersion-strengthened Aluminium Products Manufactured by Powder Blending

DEFF Research Database (Denmark)

Hansen, Niels

1969-01-01

Detailed experiments carried out to examine relationship between microstructure and mechanical properties of powder-blended aluminum products are reported; their results as well as structural studies by transmission electron microscopy and tensile-and creep- testing, are given; as dispersed phase......, various oxide powders were selected on criterion that during manufacturing no reaction must taken place between metal and oxide phase; strength of powder-blended aluminum products increases and elongation decreases with decreasing particle size of aluminum powder and with increasing concentration of oxide...

Preparation of Heat Treated Titanium Dioxide (TiO2) Nanoparticles for Water Purification

Science.gov (United States)

Araoyinbo, A. O.; Abdullah, M. M. A. B.; Rahmat, A.; Azmi, A. I.; Vizureanu, P.; Rahim, W. M. F. Wan Abd

2018-06-01

Photocatalysis using the semiconductor titanium dioxide (TiO2) has proven to be a successful technology for waste water purification. The photocatalytic treatment is an alternative method for the removal of soluble organic compounds in waste water. In this research, titanium dioxide nanoparticles were synthesized by sol-gel method using titanium tetraisopropoxide (TTIP) as a precursor. The sol was dried in the oven at 120°C after aging for 24 hours. The dried powder was then calcined at 400°C and 700°C with a heating rate of 10°C/min. The phase transformation of the heat treated titanium dioxide nanoparticles were characterized by X-Ray Diffraction (XRD, and the surface morphology by Scanning Electron Microscopy (SEM). The photocatalytic activity of the heat treated titanium dioxide nanoparticles in the degradation of methyl orange (MO) dye under ultraviolet (UV) light irradiation has been studied. At calcination temperature of 400°C, only anatase phase was observed, as the calcination temperature increases to 700°C, the rutile phase was present. The SEM images show the irregular shape of titanium dioxide particles and the agglomeration which tends to be more significant at calcined temperature of 700°C. Degradation of methyl orange by 5 mg heat treated titanium dioxide nanoparticles gives the highest percentage of degradation after irradiation by UV lamp for 4 hours.

Obtainment of TiO{sub 2} powders solar cells photo electrodes dye sensitized; Obtencao de pos de TiO{sub 2} para fotoeletrodos de celulas solares sensibilizados por corante

Energy Technology Data Exchange (ETDEWEB)

Forbeck, Guilherme; Folgueras, Marilena V., E-mail: guilhermeforbeck@hotmail.com [Universidade do Estado de Santa Catarina (PGCE/UDESC), SC (Brazil). Programa de Pos Graduacao em Ciencia e Engenharia de Materiais; Chinelatto, Adilson L. [Universidade Estadual de Ponta Grossa (UEPG), PR (Brazil). Programa de Mestrado em Engenharia e Ciencia dos Materiais

2012-07-01

Titanium dioxide in its polymorphic anatase phase, presents interesting properties for solar cells photo electrodes dye sensitized such as the forbidden energy band, high refractive index and high constant dielectric. In this study, powders of nanometric titanium dioxide were produced with predominantly the anatase phase and high surface area. We used the sol-gel method, and titanium tetraisopropoxide as a precursor, which was hydrolyzed in nitric acid solution. The obtained powder was heated to 450 ° C, varying the time for each lot (0, 20 or 120 minutes). The powders were characterized by X-ray diffraction, atomic force microscopy and surface area analysis. For all lots nanosized crystallites predominated. It was observed that in the batch with 120min heating an increase rutile content. The TiO{sub 2} with 20min heating showed high surface area, greater than that of TiO{sub 2} as taken reference.

Shock diffraction in alumina powder

International Nuclear Information System (INIS)

Venz, G.; Killen, P.D.; Page, N.W.

1996-01-01

In order to produce complex shaped components by dynamic compaction of ceramic powders detailed knowledge of their response under shock loading conditions is required. This work attempts to provide data on release effects and shock attenuation in 1 μm and 5 μm α-alumina powders which were compacted to between 85 % and 95 % of the solid phase density by the impact of high velocity steel projectiles. As in previous work, the powder was loaded into large cylindrical dies with horizontal marker layers of a contrasting coloured powder to provide a record of powder displacement in the recovered specimens. After recovery and infiltration with a thermosetting resin the specimens were sectioned and polished to reveal the structure formed by the passage of the projectile and shock wave. Results indicate that the shock pressures generated were of the order of 0.5 to 1.4 GPa and higher, with shock velocities and sound speeds in the ranges 650 to 800 m/s and 350 to 400 m/s respectively

Nuclear energy - Determination of chlorine and fluorine in uranium dioxide powder and sintered pellets

International Nuclear Information System (INIS)

2008-01-01

This International Standard describes a method for determining the chlorine and fluorine concentrations in uranium dioxide and in sintered fuel pellets by pyrohydrolysis of samples, followed either by liquid ion-exchange chromatography or by selective electrode measurement of chlorine and fluorine ions. Many ion-exchange chromatography systems and ion-selective electrode measurement systems are available

Nanograin formation in milled MoO3 powders

International Nuclear Information System (INIS)

Guerrero-Paz, J; Dorantes-Rosales, H; Aguilar-Martínez, J A; Garibay-Febles, V

2013-01-01

Powder of Molybdenum trioxide was milled for different times in horizontal ball mills. Such powder was characterized by TEM and XRD. Powder was rapidly de-agglomerated and fragmented up to attain nanoplates of two types, amorphous and crystalline. Finally, cold-welding of nanoplates occurred permitting some relaxation process to obtain a more stable energized structure consisting of equiaxial crystalline nanograins after 16 hours of milling.

Structural Properties of Nanoparticles TiO2/PVA Polymeric Films

Directory of Open Access Journals (Sweden)

Samara A. Madhloom

2018-04-01

Full Text Available In this research, X-ray diffraction of the powder (PVA polymer, titanium dioxide with two parti-cle sizes and (TiO2 (15.7 nm/PVA and TiO2 (45.7 nm/PVA films have been studied,the amount of polymer is (0.5 g and (0.01g from each particle sizes of nanoparticles will be used. Casting method is used to prepare homogeneous films on glass petri dishes. All parameters ac-counted for the X-ray diffraction; full width half maximum (FWHM, Miller indices (hkl, size of crystalline (D, Specific Surface Area (S and Dislocation Density (δ. The nature of the structural of materials and films will be investigated. The XRD pattern of PVA polymer has semi-crystalline nature and the titanium dioxide with two particle sizes have crystalline structure; ana-tase type. While the mixture between these materials led to appearing some crystalline peaks into XRD pattern of PVA polymer

Powder preparation and compaction behaviour of fine-grained Y-TZP

NARCIS (Netherlands)

Groot Zevert, W.F.M.; Winnubst, Aloysius J.A.; Theunissen, G.S.A.M.; Burggraaf, A.J.

1990-01-01

Two wet chemical preparation methods are described for yttria-doped tetragonal zirconia powders. Both methods yield powders with an extremely small crystallite size (8 nm) and a narrow size distribution. The agglomerate and aggregate structure of these powders have been investigated by several

Structural and magnetic properties of turmeric functionalized CoFe2O4 nanocomposite powder

Science.gov (United States)

Mehran, E.; Farjami Shayesteh, S.; Sheykhan, M.

2016-10-01

The structural and magnetic properties of the synthesized pure and functionalized CoFe2O4 magnetic nanoparticles (NPs) are studied by analyzing the results from the x-ray diffraction (XRD), transmission electron microscopy (TEM), FT-IR spectroscopy, thermogravimetry (TG), and vibrating sample magnetometer (VSM). To extract the structure and lattice parameters from the XRD analysis results, we first apply the pseudo-Voigt model function to the experimental data obtained from XRD analysis and then the Rietveld algorithm is used in order to optimize the model function to estimate the true intensity values. Our simulated intensities are in good agreement with the experimental peaks, therefore, all structural parameters such as crystallite size and lattice constant are achieved through this simulation. Magnetic analysis reveals that the synthesized functionalized NPs have a saturation magnetization almost equal to that of pure nanoparticles (PNPs). It is also found that the presence of the turmeric causes a small reduction in coercivity of the functionalized NPs in comparison with PNP. Our TGA and FTIR results show that the turmeric is bonded very well to the surface of the NPs. So it can be inferred that a nancomposite (NC) powder of turmeric and nanoparticles is produced. As an application, the anti-arsenic characteristic of turmeric makes the synthesized functionalized NPs or NC powder a good candidate for arsenic removal from polluted industrial waste water. Project supported by the University of Guilan and the Iran Nanotechnology Initiative Council.

Development and directions of powder diffraction on proteins

Energy Technology Data Exchange (ETDEWEB)

Von Dreele, R B; Besnard, C; Basso, S; Camus, F; Pattison, P; Schiltz, M; Wright, J P; Margiolaki, R; Fitch, A N; Fox, G C; Prugoveeki, S; Beckers, D; Helliwell, J R; Helliwell, M; Jones, R H; Roberts, M A; Miura, K; Kahn, R; Giacovazzo, C; Altomare, A; Caliandro, R; Camalli, M; Cuocci, C; Moliterni, A G.G.; Rizzi, R; Hinrichsen, B; Kern, A; Coelho, A A; Degen, T; Kokkinidis, M; Fadouloglou, V; Gazi, A; Panopoulos, N; Pinotsis, N; Wilmanns, M; Norrman, M; Schluckebier, G; Prugoveeki, B; Dilovic, J; Matkovic-Calogovic, D; Bill, David; Markvardsen, A; Grosse-Kunstleve, R; Rius, J; Glykos Nicholas, M; Murshudov, G N

2007-07-01

X-ray diffraction is one of the most important method for obtaining information about the structure of proteins and thereby for gaining insight into fundamental biological and biochemical mechanisms. This seminar was dedicated to X-ray powder diffraction and was organized around 6 sessions: 1) what can powder diffraction do for proteins?, 2) adapting experimentally to proteins, 3) interpreting powder data, 4) the world of protein crystallography, 5) advancing methods for powder data analysis, and 6) transferable methods from single crystals. This document gathers the abstracts of the 23 papers presented. (A.C.)

Development and directions of powder diffraction on proteins

International Nuclear Information System (INIS)

Von Dreele, R.B.; Besnard, C.; Basso, S.; Camus, F.; Pattison, P.; Schiltz, M.; Wright, J.P.; Margiolaki, R.; Fitch, A.N.; Fox, G.C.; Prugoveeki, S.; Beckers, D.; Helliwell, J.R.; Helliwell, M.; Jones, R.H.; Roberts, M.A.; Miura, K.; Kahn, R.; Giacovazzo, C.; Altomare, A.; Caliandro, R.; Camalli, M.; Cuocci, C.; Moliterni, A.G.G.; Rizzi, R.; Hinrichsen, B.; Kern, A.; Coelho, A.A.; Degen, T.; Kokkinidis, M.; Fadouloglou, V.; Gazi, A.; Panopoulos, N.; Pinotsis, N.; Wilmanns, M.; Norrman, M.; Schluckebier, G.; Prugoveeki, B.; Dilovic, J.; Matkovic-Calogovic, D.; Bill, David; Markvardsen, A.; Grosse-Kunstleve, R.; Rius, J.; Glykos Nicholas, M.; Murshudov, G.N.

2007-01-01

X-ray diffraction is one of the most important method for obtaining information about the structure of proteins and thereby for gaining insight into fundamental biological and biochemical mechanisms. This seminar was dedicated to X-ray powder diffraction and was organized around 6 sessions: 1) what can powder diffraction do for proteins?, 2) adapting experimentally to proteins, 3) interpreting powder data, 4) the world of protein crystallography, 5) advancing methods for powder data analysis, and 6) transferable methods from single crystals. This document gathers the abstracts of the 23 papers presented. (A.C.)

Characteristics of Inconel Powders for Powder-Bed Additive Manufacturing

Directory of Open Access Journals (Sweden)

Quy Bau Nguyen

2017-10-01

Full Text Available In this study, the flow characteristics and behaviors of virgin and recycled Inconel powder for powder-bed additive manufacturing (AM were studied using different powder characterization techniques. The results revealed that the particle size distribution (PSD for the selective laser melting (SLM process is typically in the range from 15 μm to 63 μm. The flow rate of virgin Inconel powder is around 28 s·(50 g−1. In addition, the packing density was found to be 60%. The rheological test results indicate that the virgin powder has reasonably good flowability compared with the recycled powder. The inter-relation between the powder characteristics is discussed herein. A propeller was successfully printed using the powder. The results suggest that Inconel powder is suitable for AM and can be a good reference for researchers who attempt to produce AM powders.

Simvastatin: structure solution of two new low-temperature phases from synchrotron powder diffraction and ss-NMR

Czech Academy of Sciences Publication Activity Database

Hušák, M.; Kratochvíl, B.; Jegorov, A.; Brus, Jiří; Maixner, J.; Rohlíček, J.

2010-01-01

Roč. 21, č. 3 (2010), s. 511-518 ISSN 1040-0400 R&D Projects: GA AV ČR IAA400500602; GA MŠk 2B08021 Institutional research plan: CEZ:AV0Z40500505 Keywords : crystal structure * simvastatin * powder diffraction Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.727, year: 2010

Titanium dioxide modified with various amines used as sorbents of carbon dioxide

International Nuclear Information System (INIS)

Kapica-Kozar, Joanna; Pirog, Ewa; Kusiak-Nejman, Ewelina; Wrobel, Rafal J.; Gesikiewicz-Puchalska, Andzelika; Morawski, Antoni W.; Narkiewicz, Urszula; Michalkiewicz, Beata

2017-01-01

In this study, titanium dioxide was modified with various amines through hydrothermal treatment for adsorption of CO_2. The carbon dioxide adsorption performance of the prepared samples was measured using an STA 449 C thermo-balance (Netzsch Company, Germany). The morphological structures, functional groups and elemental compositions of the unmodified and amine-modified titanium dioxide sorbents were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR/DR) and scanning electron microscopy (SEM), respectively. The results showed that modification of TiO_2 with amines through hydrothermal treatment is a simple method to prepare CO_2 sorbents with high adsorption capacities. Moreover, the results revealed that TEPA-modified titanium dioxide shoved the highest adsorption capacity, enabling an increase in CO_2 uptake from 0.45 mmol CO_2 g"-"1 in the case of raw TiO_2 to 1.63 mmol CO_2 g"-"1. This result could be indirectly related to the fact that TEPA has the highest amino group content among the three amines used in our research. Additionally, durability tests performed by cyclic adsorption-desorption revealed that TEPA modified titanium dioxide also possesses excellent stability, despite a slight decrease in adsorption capacity over time. (authors)

Investigation of structural and optical properties of CaTiO3 powders doped with Mg2+ and Eu3+ ions

International Nuclear Information System (INIS)

Oliveira, Larissa H.; Savioli, Julia; Moura, Ana P. de; Nogueira, Içamira C.; Li, Maximo S.; Longo, Elson; Varela, José A.; Rosa, Ieda L.V.

2015-01-01

In this work, CaTiO 3 powders doped with Mg 2+ ions and CaTiO 3 powders co-doped with Mg 2+ and Eu 3+ ions were prepared by the polymeric precursor method (PPM). These powders were characterized by different characterization techniques to study the influence of Mg 2+ doping as well as Mg 2+ and Eu 3+ co-doping in structural and optical properties of CaTiO 3 perovskite-type structure. The Rietveld refinement and Micro-Raman analyses suggested the substitution Mg 2+ and Eu 3+ ions in the A-site of CaTiO 3 perovskite. The influence of Mg 2+ doping can be detected by the displacement of calcium and oxygen atomic positions when compared to the non-doped CaTiO 3 powder. When Eu 3+ ions are added to the A-site of this perovskite the excess of positive charge can be compensated by the formation of calcium vacancies. Luminescence data showed that Ca 1-x Mg x TiO 3 and Ca 1x Mg x/2 Eu 2y/3 TiO 3 powders are potential materials for fabrication of lighting devices based on near-UV and blue LED using an excitation wavelength of 397 and/or 450 nm. - Highlights: • CaTiO 3 co-doped with Mg 2+ and Eu 3+ were obtained by the Polymeric Precursor Method. • Incorporation of Mg 2+ and Eu 3+ ions in the CaTiO 3 lattice. • Enhancement of the Eu 3+ photoluminescence

The Crystal Structure of the Malaria Pigment Hemozoin as Elucidated by X-ray Powder Diffraction

DEFF Research Database (Denmark)

Straasø, Tine

survival. Successful inhibition of hemozoin crystallization will lead to parasitic death and thus break the cycle. The aim of this thesis is to elucidate the structure of hemozoin by means of X-ray diffraction techniques. Knowledge of the structure will help facilitate intelligent drug design in the future....... As part of the project an all-in-vacuum powder diffractometer was developed, which provides data with a minimum background level and an improved signal-to-noise ratio. Moreover, the diffractometer is designed with the particular purpose of decreasing the number of parameters to be fitted. Installation...

CVD carbon powders modified by ball milling

Directory of Open Access Journals (Sweden)

Kazmierczak Tomasz

2015-09-01

Full Text Available Carbon powders produced using a plasma assisted chemical vapor deposition (CVD methods are an interesting subject of research. One of the most interesting methods of synthesizing these powders is using radio frequency plasma. This method, originally used in deposition of carbon films containing different sp2/sp3 ratios, also makes possible to produce carbon structures in the form of powder. Results of research related to the mechanical modification of these powders have been presented. The powders were modified using a planetary ball mill with varying parameters, such as milling speed, time, ball/powder mass ratio and additional liquids. Changes in morphology and particle sizes were measured using scanning electron microscopy and dynamic light scattering. Phase composition was analyzed using Raman spectroscopy. The influence of individual parameters on the modification outcome was estimated using statistical method. The research proved that the size of obtained powders is mostly influenced by the milling speed and the amount of balls. Powders tend to form conglomerates sized up to hundreds of micrometers. Additionally, it is possible to obtain nanopowders with the size around 100 nm. Furthermore, application of additional liquid, i.e. water in the process reduces the graphitization of the powder, which takes place during dry milling.

Structure and Mechanical Properties of Powdered Quasicrystalline Al94Fe3Cr3 Alloy Consolidated by Quasi-Hydrostatic Compression

Directory of Open Access Journals (Sweden)

Alexandra I. Yurkova

2017-10-01

Full Text Available Background. Quasicrystalline Al-based alloys belong to the class of the state-of-the-art metal materials for the application in light engineering constructions, primarily in aviation and the motor transport industry. These materials are commonly made in the form of powders, which is due to the high productivity of powder metallurgy methods. Therefore, the powder consolidation methods are of great importance in the production of products, which is associated with certain difficulties, and consequently, they should be chosen considering not only the quasicrystals’ propensity to brittle fracture but also the metastable nature of the quasicrystalline phases. Certain possibilities in this direction are provided by the quasi-hydrostatic compression method, which can provide a non-trivial combination of strength and ductility properties of materials. Objective. The aim of the paper is to investigate the effect of high pressure under quasi-hydrostatic compression on the formation of structure, phase composition and mechanical properties of the quasicrystalline Al94Fe3Cr3 alloy. Methods. 40 μm Al94Fe3Cr3 alloy quasicrystalline powder was fabricated by water-atomisation technique. Consolidation of quasicrystalline powder was performed by quasi-hydrostatic compression technique in high-pressure cells at room temperature at a pressure of 2.5, 4, and 6 hPa. Structure, phase composition and mechanical characteristics of Al94Fe3Cr3 alloy were performed by scanning electron microscopy (SEM, X-ray diffraction andmicromechanical tests. Results. Using the phase X-ray analysis and SEM, the content of the quasicrystalline icosahedral phase (i-phase in the Al94Fe3Cr3 alloy structure was completely preserved after its consolidation at different pressures (2.5, 4, and 6 hPa under quasi-hydrostatic compression at room temperature. Despite the high pressure applied in the consolidation process, the morphology of quasicrystalline phase particles located in the a

Synthesis, Structure, and Luminescent Properties of Europium-Doped Hydroxyapatite Nanocrystalline Powders

Directory of Open Access Journals (Sweden)

Carmen Steluta Ciobanu

2012-01-01

Full Text Available The luminescent europium-doped hydroxyapatite (Eu:HAp, Ca10−xEux(PO46(OH2 with 0≤x≤0.2 nanocrystalline powders was synthesized by coprecipitation. The structural, morphological, and textural properties were well characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The vibrational studies were performed by Fourier transform infrared, Raman, and photoluminescence spectroscopies. The X-ray diffraction analysis revealed that hydroxyapatite is the unique crystalline constituent of all the samples, indicating that Eu has been successfully inserted into the HAp lattice. Eu doping inhibits HAp crystallization, leading to a decrease of the average crystallite size from around 20 nm in the undoped sample to around 7 nm in the sample with the highest Eu concentration. Furthermore, the samples show the characteristic 5D0→7F0 transition observed at 578 nm related to Eu3+ ions distributed on Ca2+ sites of the apatitic structure.

Synthesis, Structure, and Luminescent Properties of Europium-Doped Hydroxyapatite Nanocrystalline Powders

International Nuclear Information System (INIS)

Ciobanu, C.S.; Iconaru, S.L.; Predoi, D.; Massuyeau, F.; Constantin, L.V.; Costescu, A.

2012-01-01

The luminescent europium-doped hydroxyapatite (Eu:HAp, Ca 10-x Eu x (PO 4 ) 6 (OH) 2 ) with 0>x>0.2 nanocrystalline powders was synthesized by coprecipitation. The structural, morphological, and textural properties were well characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The vibrational studies were performed by Fourier transform infrared, Raman, and photoluminescence spectroscopies. The X-ray diffraction analysis revealed that hydroxyapatite is the unique crystalline constituent of all the samples, indicating that Eu has been successfully inserted into the HAp lattice. Eu doping inhibits HAp crystallization, leading to a decrease of the average crystallite size from around 20 nm in the undoped sample to around 7 nm in the sample with the highest Eu concentration. Furthermore, the samples show the characteristic 5 D 0 → 7 F 0 transition observed at 578 nm related to Eu 3+ ions distributed on Ca 2+ sites of the apatitic structure

Formation, structure and magnetism of the metastable defect fluorite phases AVO3.5+x (A=In, Sc)

International Nuclear Information System (INIS)

Shafi, Shahid P.; Lundgren, Rylan J.; Cranswick, Lachlan M.D.; Bieringer, Mario

2007-01-01

We report the preparation and stability of ScVO 3.5+x and the novel phase InVO 3.5+x . AVO 3.5+x (A=Sc, In) defect fluorite structures are formed as metastable intermediates during the topotactic oxidation of AVO 3 bixbyites. The oxidation pathway has been studied in detail by means of thermogravimetric/differential thermal analysis and in-situ powder X-ray diffraction. The oxidation of the bixbyite phase follows a topotactic pathway at temperatures between 300 and 400 deg. C in air/carbon dioxide. The range of accessible oxygen stoichiometries for the AVO 3.5+x structures following this pathway are 0.00≤x≤0.22. Rietveld refinements against powder X-ray and neutron data revealed that InVO 3.54 and ScVO 3.70 crystallize in the defect fluorite structure in space group Fm-3 m (227) with a=4.9863(5) and 4.9697(3)A, respectively with A 3+ /V 4+ disorder on the (4a) cation site. Powder neutron diffraction experiments indicate clustering of oxide defects in all samples. Bulk magnetic measurements showed the presence of V 4+ and the absence of magnetic ordering at low temperatures. Powder neutron diffraction experiments confirmed the absence of a long range ordered magnetic ground state. - Graphical abstract: Topotactic oxidation of AVO 3 bixbyite to AVO 3.5 defect fluorite structure followed by in-situ powder X-ray diffraction. The upper structural diagram shows a six coordinated (A/V)-O 6 fragment in bixbyite, the lower structure illustrates the same seven-fold coordinated (A/V)-O 7 cubic environment in the defect fluorite structure

The precursors effects on biomimetic hydroxyapatite ceramic powders.

Science.gov (United States)

Yoruç, Afife Binnaz Hazar; Aydınoğlu, Aysu

2017-06-01

In this study, effects of the starting material on chemical, physical, and biological properties of biomimetic hydroxyapatite ceramic powders (BHA) were investigated. Characterization and chemical analysis of BHA powders were performed by using XRD, FT-IR, and ICP-AES. Microstructural features such as size and morphology of the resulting BHA powders were characterized by using BET, nano particle sizer, pycnometer, and SEM. Additionally, biological properties of the BHA ceramic powders were also investigated by using water-soluble tetrazolium salts test (WST-1). According to the chemical analysis of BHA ceramic powders, chemical structures of ceramics which are prepared under different conditions and by using different starting materials show differences. Ceramic powders which are produced at 80°C are mainly composed of hydroxyapatite, dental hydroxyapatite (contain Na and Mg elements in addition to Ca), and calcium phosphate sulfide. However, these structures are altered at high temperatures such as 900°C depending on the features of starting materials and form various calcium phosphate ceramics and/or their mixtures such as Na-Mg-hydroxyapatite, hydroxyapatite, Mg-Whitlockit, and chloroapatite. In vitro cytotoxicity studies showed that amorphous ceramics produced at 80°C and ceramics containing chloroapatite structure as main or secondary phases were found to be extremely cytotoxic. Furthermore, cell culture studies showed that highly crystalline pure hydroxyapatite structures were extremely cytotoxic due to their high crystallinity values. Consequently, the current study indicates that the selection of starting materials which can be used in the production of calcium phosphate ceramics is very important. It is possible to produce calcium phosphate ceramics which have sufficient biocompatibility at physiological pH values and by using appropriate starting materials. Copyright © 2017 Elsevier B.V. All rights reserved.

The effect of process control agent on the structure and magnetic properties of nanocrystalline mechanically alloyed Fe–45% Ni powders

Energy Technology Data Exchange (ETDEWEB)

Gheisari, Kh., E-mail: khgheisari@scu.ac.ir [Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University, Ahvaz (Iran, Islamic Republic of); Javadpour, S. [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of)

2013-10-15

In this study, nanocrystalline Fe-45 wt% Ni alloy powders were prepared by mechanical alloying via high-energy ball milling. The effect of adding stearic acid as a process control agent (PCA) on the particle size, structure and magnetic properties of Fe-45 wt% Ni alloy powders have been studied by X-ray diffraction, scanning electron microscope and vibrating sample magnetometer measurements. The results show that the addition of 1 wt% PCA causes fine uniform spherical powder particles of the fcc γ-(Fe, Ni) phase to be formed after 48 h milling time. It is also found that crystallite size, lattice strain and content of γ-(Fe, Ni) phase are three of the most important variables that are significantly affected by PCA content and can influence the magnetic properties. - Highlights: • Different amount of stearic acid as a PCA was used during milling. • Particle size and crystallite size decrease with increasing PCA content. • The addition of 1 wt% PCA leads to a good combination of structure and magnetic properties.

The effect of process control agent on the structure and magnetic properties of nanocrystalline mechanically alloyed Fe–45% Ni powders

International Nuclear Information System (INIS)

Gheisari, Kh.; Javadpour, S.

2013-01-01

In this study, nanocrystalline Fe-45 wt% Ni alloy powders were prepared by mechanical alloying via high-energy ball milling. The effect of adding stearic acid as a process control agent (PCA) on the particle size, structure and magnetic properties of Fe-45 wt% Ni alloy powders have been studied by X-ray diffraction, scanning electron microscope and vibrating sample magnetometer measurements. The results show that the addition of 1 wt% PCA causes fine uniform spherical powder particles of the fcc γ-(Fe, Ni) phase to be formed after 48 h milling time. It is also found that crystallite size, lattice strain and content of γ-(Fe, Ni) phase are three of the most important variables that are significantly affected by PCA content and can influence the magnetic properties. - Highlights: • Different amount of stearic acid as a PCA was used during milling. • Particle size and crystallite size decrease with increasing PCA content. • The addition of 1 wt% PCA leads to a good combination of structure and magnetic properties

Nanostructured Polypyrrole Powder: A Structural and Morphological Characterization

Directory of Open Access Journals (Sweden)

Edgar A. Sanches

2015-01-01

Full Text Available Polypyrrole (PPY powder was chemically synthesized using ferric chloride (FeCl3 and characterized by X-ray diffraction (XRD, Le Bail Method, Fourier Transform Infrared Spectrometry (FTIR, and Scanning Electron Microscopy (SEM. XRD pattern showed a broad scattering of a semicrystalline structure composed of main broad peaks centered at 2θ = 11.4°, 22.1°, and 43.3°. Crystallinity percentage was estimated by the ratio between the sums of the peak areas to the area of amorphous broad halo due to the amorphous phase and showed that PPY has around 20 (1%. FTIR analysis allowed assigning characteristic absorption bands in the structure of PPY. SEM showed micrometric particles of varying sizes with morphologies similar to cauliflower. Crystal data (monoclinic, space group P 21/c, a=7.1499 (2 Å, b=13.9470 (2 Å, c=17.3316 (2 Å, α=90 Å, β=61.5640 (2 Å and γ=90 Å were obtained using the FullProf package program under the conditions of the method proposed by Le Bail. Molecular relaxation was performed using the density functional theory (DFT and suggests that tetramer polymer chains are arranged along the “c” direction. Average crystallite size was found in the range of 20 (1 Å. A value of 9.33 × 10−9 S/cm was found for PPY conductivity.

Geohydrology and potential effects of coal mining in 12 coal-lease areas, Powder River structural basin, northeastern Wyoming. Water Resources Investigation

International Nuclear Information System (INIS)

Fogg, J.L.; Martin, M.W.; Daddow, P.B.

1991-01-01

The purpose of the report is to describe the geohydrology of 12 coal-lease areas in the Powder River structural basin in relation to the mining proposed for each area. The description of the geohydrology of each of the lease areas focuses on the shallow ground-water system and includes identification of recharge and discharge areas, directions of ground-water movement, and potential effects of mining. The shallow ground-water system in the Powder River structural basin is not well defined because of the discontinuous nature of the aquifers in the basin. Understanding the ground-water hydrology of these 12 coal-lease areas will improve understanding of the shallow ground-water system in the basin. The first part of the report is a description of the general geohydrology of the Wyoming part of the Powder River structural basin. The second part of the report is a general discussion of the effects of coal mining on ground-water hydrology. The third part of the report contains site-specific discussions of the ground-water hydrology and potential effects of mining for each of the 12 coal-lease areas

In situ X-ray powder diffraction, synthesis, and magnetic properties of InVO 3

Science.gov (United States)

Lundgren, Rylan J.; Cranswick, Lachlan M. D.; Bieringer, Mario

2006-12-01

We report the first synthesis and high-temperature in situ X-ray diffraction study of InVO 3. Polycrystalline InVO 3 has been prepared via reduction of InVO 4 using a carbon monoxide/carbon dioxide buffer gas. InVO 3 crystallizes in the bixbyite structure in space group Ia-3 (206) with a=9.80636(31) Å with In 3+/V 3+ disorder on the (8 b) and (24 d) cation sites. In situ powder X-ray diffraction experiments and thermal gravimetric analysis in a CO/CO 2 buffer gas revealed the existence of the metastable phase InVO 3. Bulk samples with 98.5(2)% purity were prepared using low-temperature reduction methods. The preparative methods limited the crystallinity of this new phase to approximately 225(50) Å. Magnetic susceptibility and neutron diffraction experiments suggest a spin-glass ground state for InVO 3.

Effects of thickness on the nanocrystalline structure and semiconductor-metal transition characteristics of vanadium dioxide thin films

International Nuclear Information System (INIS)

Luo, Zhenfei; Zhou, Xun; Yan, Dawei; Wang, Du; Li, Zeyu; Yang, Cunbang; Jiang, Yadong

2014-01-01

Nanocrystalline vanadium dioxide (VO 2 ) thin films were grown on glass substrates by using reactive direct current magnetron sputtering and in situ thermal treatments at low preparation temperatures (≤ 350 °C). The VO 2 thin films were characterized by grazing-incidence X-ray diffraction, field emission scanning electron microscope, transmission electron microscopy and spectroscopic ellipsometry (SE). The semiconductor-metal transition (SMT) characteristics of the films were investigated by four-point probe resistivity measurements and infrared spectrometer equipped with heating pads. The testing results showed that the crystal structure, morphology, grain size and semiconductor-metal transition temperature (T SMT ) significantly changed as the film thickness decreased. Multilayer structures were observed in the particles of thinner films whose average particle size is much larger than the film thickness and average VO 2 grain size. A competition mechanism between the suppression effect of decreased thickness and coalescence of nanograins was proposed to understand the film growth and the formation of multilayer structure. The value of T SMT was found to decrease as average VO 2 grain size became smaller, and SE results showed that small nanograin size significantly affected the electronic structure of VO 2 film. - Highlights: • Nanocrystalline vanadium dioxide thin films were prepared. • Multilayer structures were observed in the films with large particles. • The transition temperature of the film is correlated with its electronic structure

SEU blending project, concept to commercial operation, Part 3: production of powder for demonstration irradiation fuel bundles

International Nuclear Information System (INIS)

Ioffe, M.S.; Bhattacharjee, S.; Oliver, A.J.; Ozberk, E.

2005-01-01

The processes for production of Slightly Enriched Uranium (SEU) dioxide powder and Blended Dysprosium and Uranium (BDU) oxide powder that were developed at laboratory scale at Cameco Technology Development (CTD), were implemented and further optimized to supply to Zircatec Precision Industries (ZPI) the quantities required for manufacturing twenty six Low Void Reactivity (LVRF) CANFLEX fuel bundles. The production of this new fuel was a challenge for CTD and involved significant amount of work to prepare and review documentation, develop and approve new analytical procedures, and go through numerous internal reviews and audits by Bruce Power, CNSC and third parties independent consultants that verified the process and product quality. The audits were conducted by Quality Assurance specialists as well as by Human Factor Engineering experts with the objective to systematically address the role of human errors in the manufacturing of New Fuel and confirm whether or not a credible basis had been established for preventing human errors. The project team successfully passed through these audits. The project management structure that was established during the SEU and BDU blending process development, which included a cross-functional project team from several departments within Cameco, maintained its functionality when Cameco Technology Development was producing the powder for manufacturing Demonstration Irradiation fuel bundles. Special emphasis was placed on the consistency of operating steps and product quality certification, independent quality surveillance, materials segregation protocol, enhanced safety requirements, and accurate uranium accountability. (author)

Validation of molecular crystal structures from powder diffraction data with dispersion-corrected density functional theory (DFT-D).

Science.gov (United States)

van de Streek, Jacco; Neumann, Marcus A

2014-12-01

In 2010 we energy-minimized 225 high-quality single-crystal (SX) structures with dispersion-corrected density functional theory (DFT-D) to establish a quantitative benchmark. For the current paper, 215 organic crystal structures determined from X-ray powder diffraction (XRPD) data and published in an IUCr journal were energy-minimized with DFT-D and compared to the SX benchmark. The on average slightly less accurate atomic coordinates of XRPD structures do lead to systematically higher root mean square Cartesian displacement (RMSCD) values upon energy minimization than for SX structures, but the RMSCD value is still a good indicator for the detection of structures that deserve a closer look. The upper RMSCD limit for a correct structure must be increased from 0.25 Å for SX structures to 0.35 Å for XRPD structures; the grey area must be extended from 0.30 to 0.40 Å. Based on the energy minimizations, three structures are re-refined to give more precise atomic coordinates. For six structures our calculations provide the missing positions for the H atoms, for five structures they provide corrected positions for some H atoms. Seven crystal structures showed a minor error for a non-H atom. For five structures the energy minimizations suggest a higher space-group symmetry. For the 225 SX structures, the only deviations observed upon energy minimization were three minor H-atom related issues. Preferred orientation is the most important cause of problems. A preferred-orientation correction is the only correction where the experimental data are modified to fit the model. We conclude that molecular crystal structures determined from powder diffraction data that are published in IUCr journals are of high quality, with less than 4% containing an error in a non-H atom.

Characterization of Ni ferrites powders prepared by plasma arc discharge process

Energy Technology Data Exchange (ETDEWEB)

Safari, A. [Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University, Ahvaz (Iran, Islamic Republic of); Gheisari, Kh., E-mail: khgheisari@scu.ac.ir [Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University, Ahvaz (Iran, Islamic Republic of); Farbod, M. [Physics Department, Shahid Chamran University, Ahvaz (Iran, Islamic Republic of)

2017-01-01

The aim of this work was to synthesize a single-phase spinel structure from a mixture of zinc, iron and nickel powders by plasma arc discharge method. A mixture of zinc, iron and nickel powders with the appropriate molar ratio was prepared and formed into a cylindrical shape. The synthesis process was performed in air, oxygen and argon atmospheres with the applied arc current of 400 A and pressure of 1 atm. After establishing an arc between the electrodes, the produced powders were collected and their structure and magnetic properties were examined by XRD and VSM, respectively. ZnO as an impurity was appeared in the as-produced powders owing to the high reactivity of zinc atoms, preventing the formation of Ni–Zn ferrite. A pure spinel structure with the highest saturation magnetization (43.8 emu/g) was observed as zinc powders removed completely from the initial mixture. Morphological evaluations using field emission scanning electron microscopy showed that the mean size of fabricated nanoparticles was in the range 100–200 nm and was dependent on the production conditions. - Highlights: • Nanocrystalline Ni ferrite powders are prepared by plasma arc discharge process. • The mean particle size of the as-synthesized ceramic powders is about 100 nm. • The highest saturation magnetization is observed as zinc powders removed completely from the initial mixture.

Methods of improving the production structure and quality of clay powders

Energy Technology Data Exchange (ETDEWEB)

Ryabchenko, V I; Lityayeva, Z A

1981-01-01

Results are generalized of scientific research work in relation to the quality of argillaceous raw material and powders made of it to prepare drilling fluids. The output of the solution of definite effective viscosity is adopted as the criterion for the quality of clay powders. Recommendations are made for the use of jet grinding of clays and the technology of plasticizing.

Synthesis of Uranium nitride powders using metal uranium powders

International Nuclear Information System (INIS)

Yang, Jae Ho; Kim, Dong Joo; Oh, Jang Soo; Rhee, Young Woo; Kim, Jong Hun; Kim, Keon Sik

2012-01-01

Uranium nitride (UN) is a potential fuel material for advanced nuclear reactors because of their high fuel density, high thermal conductivity, high melting temperature, and considerable breeding capability in LWRs. Uranium nitride powders can be fabricated by a carbothermic reduction of the oxide powders, or the nitriding of metal uranium. The carbothermic reduction has an advantage in the production of fine powders. However it has many drawbacks such as an inevitable engagement of impurities, process burden, and difficulties in reusing of expensive N 15 gas. Manufacturing concerns issued in the carbothermic reduction process can be solved by changing the starting materials from oxide powder to metals. However, in nitriding process of metal, it is difficult to obtain fine nitride powders because metal uranium is usually fabricated in the form of bulk ingots. In this study, a simple reaction method was tested to fabricate uranium nitride powders directly from uranium metal powders. We fabricated uranium metal spherical powder and flake using a centrifugal atomization method. The nitride powders were obtained by thermal treating those metal particles under nitrogen containing gas. We investigated the phase and morphology evolutions of powders during the nitriding process. A phase analysis of nitride powders was also a part of the present work

The structure and mechanical properties of parts elaborated by direct laser deposition 316L stainless steel powder obtained in various ways

Science.gov (United States)

Loginova, I. S.; Solonin, A. N.; Prosviryakov, A. S.; Adisa, S. B.; Khalil, A. M.; Bykovskiy, D. P.; Petrovskiy, V. N.

2017-12-01

In this work the morphology, the size and the chemical composition of the powders of steel 316L received by the two methods was studied: fusion dispersion by a gas stream and reduction of metal chlorides with the subsequent plasma atomization of the received powder particles. The powder particles received by the first method have a spherical shape (aspect ratio 1,0-1,2) with an average size of 77 μm and are characterized by the absence of internal porosity. Particles of the powder received by the second method also have a spherical shape and faultless structure, however, their chemical composition may vary in different particles. The average size of particles is 32 μm. Though the obtained powders had different properties, the experimental samples received by DLD technology demonstrated by equally high durability (Ultimate strength is 623±5 and of 623±18 MPa respectively) and plasticity (38 and 41% respectively). It is established that mechanical properties of DLD samples increase for 7-10% after treatment of the surface.

Structural study on the gas adsorption phenomena in porous coordination polymers by synchrotron powder diffraction method

International Nuclear Information System (INIS)

Kubota, Yoshiki

2017-01-01

In situ synchrotron powder diffraction measurement of gas adsorption and crystal structure analysis for porous coordination polymers (PCPs) were performed. From the obtained accurate crystal structure in both atomic and charge density levels, not only the position and orientation of adsorbed gas molecules but also the interaction between the adsorbed gas molecule and host framework were found. The information enables us to understand the mechanism of gas adsorption phenomena and functions of PCPs. It will give us the guiding principles for the novel functional materials design. (author)

Structural study of Sr{sub 2}CuO{sub 3+delta} by neutron powder diffraction

Energy Technology Data Exchange (ETDEWEB)

Shimakawa, Y. [NEC Corp., Tsukuba (Japan). Fundamental Research Labs.; Jorgensen, J.D.; Mitchell, J.F.; Hunter, B.A. [Argonne National Lab., IL (United States); Shaked, S. [Israel Atomic Energy Commission, Beersheba (Israel). Nuclear Research Center-Negev][Ben-Gurion Univ. of the Negev, Beersheba (Israel). Dept. of Physics; Hinks, D.G.; Hitterman, R.L. [Argonne National Lab., IL (United States); Hiroi, Z.; Takano, M. [Kyoto Univ., Uji (Japan). Inst. for Chemical Research

1996-11-01

Average crystal structures of superconducting Sr{sub 2}CuO{sub 3+{delta}} synthesized at ambient pressure from a hydroxometallate precursor were refined from neutron powder diffraction data. A simplified model was used to fit the modulated superstructures. Both compounds have an oxygen deficient La{sub 2}CuO{sub 4}-type tetragonal T structure with O vacancies located in the CuO{sub 2} planes, not in the Sr{sub 2}O{sub 2} layers. This raises important questions about the superconductivity in Sr{sub 2}CuO{sub 3+{delta}} reported to be a 70 K superconductor.

The influence of powder composition and sintering temperature on transformation kinetics, structure and mechanical properties of hot-pressed silicon nitride

International Nuclear Information System (INIS)

Knoch, H.; Ziegler, G.

1977-01-01

The strength at room temperature of hot-pressed silicon nitride is strongly dependent on the structure which in turn depends on powder composition and process parameters. Connections between production conditions (MgO content, pressing temperature, pressing time), structure (α/β content and morphology), and the properties at room temperature are discussed. The growth of oblong β grains - as a direct result of phase transition from α- to β-Si 3 N 4 - results in microstructural meshing and thus in a higher strength. Optimum mechanical properties are achieved after full phase transformation and with a microstructure as fine as possible. The direct connection between strength and transformed β fraction indicates a possible way for a relatively fast determination of optimum properties for a given initial powder. (orig.) [de

Improving accuracy of overhanging structures for selective laser melting through reliability characterization of single track formation on thick powder beds

DEFF Research Database (Denmark)

Mohanty, Sankhya; Hattel, Jesper Henri

2016-01-01

Repeatability and reproducibility of parts produced by selective laser melting is a standing issue, and coupled with a lack of standardized quality control presents a major hindrance towards maturing of selective laser melting as an industrial scale process. Consequently, numerical process...... modelling has been adopted towards improving the predictability of the outputs from the selective laser melting process. Establishing the reliability of the process, however, is still a challenge, especially in components having overhanging structures.In this paper, a systematic approach towards...... establishing reliability of overhanging structure production by selective laser melting has been adopted. A calibrated, fast, multiscale thermal model is used to simulate the single track formation on a thick powder bed. Single tracks are manufactured on a thick powder bed using same processing parameters...

Luminescent properties of Al2O3: Tb powders

International Nuclear Information System (INIS)

Esparza G, A.E.; Garcia, M.; Falcony, C.; Azorin N, J.

2000-01-01

In this work the photo luminescent and cathode luminescent characteristics of aluminium oxide (Al 2 O 3 ) powders impurified with terbium (Tb) were studied for their use in dosimetry. The optical, structural, morphological characteristics of the powders as function of variation in the impurity concentration and the annealing temperature will be presented. As regards the optical properties of powders (photoluminescence and cathode luminescence) it was observed a characteristic emission associated with radiative transitions between electron energy levels of terbium, the spectra associated with this emission consists of several peaks associated with such transitions. In the structural and morphological characterization (X-ray diffraction and scanning electron microscopy) it was appreciated that in accordance the annealing temperature of powders is augmented it is evident the apparition of certain crystalline phases. The results show that this is a promissory material for radiation dosimetry. (Author)

Micro-powder injection moulding of tungsten

International Nuclear Information System (INIS)

Zeep, B.

2007-12-01

For He-cooled Divertors as integral components of future fusion power plants, about 300000 complex shaped tungsten components are to be fabricated. Tungsten is the favoured material because of its excellent properties (high melting point, high hardness, high sputtering resistance, high thermal conductivity). However, the material's properties cause major problems for large scale production of complex shaped components. Due to the resistance of tungsten to mechanical machining, new fabrication technologies have to be developed. Powder injection moulding as a well established shaping technology for a large scale production of complex or even micro structured parts might be a suitable method to produce tungsten components for fusion applications but is not yet commercially available. The present thesis is dealing with the development of a powder injection moulding process for micro structured tungsten components. To develop a suitable feedstock, the powder particle properties, the binder formulation and the solid load were optimised. To meet the requirements for a replication of micro patterned cavities, a special target was to define the smallest powder particle size applicable for micro-powder injection moulding. To investigate the injection moulding performance of the developed feedstocks, experiments were successfully carried out applying diverse cavities with structural details in micro dimension. For debinding of the green bodies, a combination of solvent debinding and thermal debinding has been adopted for injection moulded tungsten components. To develop a suitable debinding strategy, a variation of the solvent debinding time, the heating rate and the binder formulation was performed. For investigating the thermal consolidation behaviour of tungsten components, sinter experiments were carried out applying tungsten powders suitable for micro-powder injection moulding. First mechanical tests of the sintered samples showed promising material properties such as a

Carbon materials-functionalized tin dioxide nanoparticles toward robust, high-performance nitrogen dioxide gas sensor.

Science.gov (United States)

Zhang, Rui; Liu, Xiupeng; Zhou, Tingting; Wang, Lili; Zhang, Tong

2018-08-15

Carbon (C) materials, which process excellent electrical conductivity and high carrier mobility, are promising sensing materials as active units for gas sensors. However, structural agglomeration caused by chemical processes results in a small resistance change and low sensing response. To address the above issues, structure-derived carbon-coated tin dioxide (SnO 2 ) nanoparticles having distinct core-shell morphology with a 3D net-like structure and highly uniform size are prepared by careful synthesis and fine structural design. The optimum carbon-coated SnO 2 nanoparticles (SnO 2 /C)-based gas sensor exhibits a low working temperature, excellent selectivity and fast response-recovery properties. In addition, the SnO 2 /C-based gas sensor can maintain a sensitivity to nitrogen dioxide (NO 2 ) of 3 after being cycled 4 times at 140 °C for, suggesting its good long-term stability. The structural integrity, good synergistic properties, and high gas-sensing performance of SnO 2 /C render it a promising sensing material for advanced gas sensors. Copyright © 2018 Elsevier Inc. All rights reserved.

Effects of thickness on the nanocrystalline structure and semiconductor-metal transition characteristics of vanadium dioxide thin films

Energy Technology Data Exchange (ETDEWEB)

Luo, Zhenfei, E-mail: zhfluo8@yahoo.com [Terahertz Research Center, China Academy of Engineering Physics, Mianyang Sichuan 621900 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang Sichuan 621900 (China); Zhou, Xun, E-mail: zx_zky@yahoo.com [Terahertz Research Center, China Academy of Engineering Physics, Mianyang Sichuan 621900 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang Sichuan 621900 (China); Yan, Dawei [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang Sichuan 621900 (China); Wang, Du; Li, Zeyu [Terahertz Research Center, China Academy of Engineering Physics, Mianyang Sichuan 621900 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang Sichuan 621900 (China); Yang, Cunbang [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang Sichuan 621900 (China); Jiang, Yadong [State Key Laboratory of Electronic Thin Films and Integrated Devices, School of Optoelectronic Information, University of Electronic Science and Technology of China (UESTC), Chengdu 610054 (China)

2014-01-01

Nanocrystalline vanadium dioxide (VO{sub 2}) thin films were grown on glass substrates by using reactive direct current magnetron sputtering and in situ thermal treatments at low preparation temperatures (≤ 350 °C). The VO{sub 2} thin films were characterized by grazing-incidence X-ray diffraction, field emission scanning electron microscope, transmission electron microscopy and spectroscopic ellipsometry (SE). The semiconductor-metal transition (SMT) characteristics of the films were investigated by four-point probe resistivity measurements and infrared spectrometer equipped with heating pads. The testing results showed that the crystal structure, morphology, grain size and semiconductor-metal transition temperature (T{sub SMT}) significantly changed as the film thickness decreased. Multilayer structures were observed in the particles of thinner films whose average particle size is much larger than the film thickness and average VO{sub 2} grain size. A competition mechanism between the suppression effect of decreased thickness and coalescence of nanograins was proposed to understand the film growth and the formation of multilayer structure. The value of T{sub SMT} was found to decrease as average VO{sub 2} grain size became smaller, and SE results showed that small nanograin size significantly affected the electronic structure of VO{sub 2} film. - Highlights: • Nanocrystalline vanadium dioxide thin films were prepared. • Multilayer structures were observed in the films with large particles. • The transition temperature of the film is correlated with its electronic structure.

Effects of Lignosulfonate Structure on the Surface Activity and Wettability to a Hydrophobic Powder

Directory of Open Access Journals (Sweden)

Yuanyuan Ge

2014-10-01

Full Text Available The wettability of a solid material is very important in many applications, such as food, agrochemical formulations, and cosmetics. Wettability can be improved by adding surface active agents, especially biocompatible surfactants derived from biomass. In this work, the surface activity (ability to lower the surface tension of an aqueous solution and wettability toward a hydrophobic powder by a series of sodium lignosulfonates (NaLS synthesized with different degree of sulfonation (QS and weight-average molecular weights (Mw were investigated by measuring the surface tension and contact angle. The results demonstrated NaLS with a larger Mw or lower QS had higher surface activity. Conversely, the wettability of the NaLS aqueous solution toward difenoconazole powder showed a reverse trend, i.e., NaLS with a smaller Mw or higher Qs improved the wettability to difenoconazole. The surface activity and wettability was controlled by the varying densities of the NaLS molecules at the water to air interface or the solid/liquid interface, which was dependent on the molecular structure of NaLS.

Powder processing and spheroidizing with thermal inductively coupled plasma

International Nuclear Information System (INIS)

Nutsch, G.; Linke, P.; Zakharian, S.; Dzur, B.; Weiss, K.-H.

2001-01-01

Processing of advanced powder materials for the spraying industry is one of the most promising applications of the thermal RF inductively coupled plasma. By selecting the feedstock carefully and adjusting the RF plasma parameters, unique materials with high quality can be achieved. Powders injected in the hot plasma core emerge with modified shapes, morphology, crystal structure and chemical composition. Ceramic oxide powders such as Al 2 O 3 , ZrO 2 , SiO 2 are spheroidized with a high spheroidization rate. By using the RF induction plasma spheroidizing process tungsten melt carbide powders are obtained with a high spheroidization rate at high feeding rates by densification of agglomerated powders consisting of di-tungsten carbide and monocarbide with a definite composition. This kind of ball-like powders is particularly suited for wear resistant applications. (author)

Emerging Applications Using Magnesium Alloy Powders: A Feasibility Study

Science.gov (United States)

Tandon, Rajiv; Madan, Deepak

The use of powder metallurgy offers a potential processing route based on tailored compositions and unique microstructures to achieve high performance in magnesium alloys. This paper highlights recent advances in the production, qualification, and characterization of gas atomized AZ91E, WE43 and Elektron21 alloy powders. Transmission electron microscopy (TEM) was used to understand the bulk and surface structure of the atomized powder. The potential for using these magnesium alloy powders for emerging applications involves establishing compatibility with viable consolidation processes such as cold spray, laser assisted deposition, forging and extrusion. This study summarizes the preliminary results for various ongoing investigations using WE43 powder as an example. Results show that powder metallurgy processed WE43 results in comparable properties to those obtained from cast and wrought and offers potential for improvement.

Computer simulation of model cohesive powders: Plastic consolidation, structural changes and elasticity under isotropic loads

OpenAIRE

Gilabert, Francisco; Roux, Jean-Noël; Castellanos, Antonio

2008-01-01

International audience; The quasistatic behavior of a simple 2D model of a cohesive powder under isotropic loads is investigated by Discrete Element simulations. The loose packing states, as studied in a previous paper, undergo important structural changes under growing confining pressure P, while solid fraction \\Phi irreversibly increases by large amounts. The system state goes through three stages, with different forms of the plastic consolidation curve \\Phi(P*), under growing reduced press...

Adsorption of F{sub 2}C=CFCl on TiO{sub 2} nano-powder: Structures, energetics and vibrational properties from DRIFT spectroscopy and periodic quantum chemical calculations

Energy Technology Data Exchange (ETDEWEB)

Tasinato, Nicola, E-mail: tasinato@unive.it; Moro, Daniele; Stoppa, Paolo; Pietropolli Charmet, Andrea; Toninello, Piero; Giorgianni, Santi

2015-10-30

Graphical abstract: - Highlights: • Adsorption of F{sub 2}C=CFCl on TiO{sub 2} unveiled by DRIFTS and periodic DFT. • Structural, energetic and vibrational properties of F{sub 2}C=CFCl @ anatase (1 0 1). • Binding energies (B3LYP-D2) between −17 and −46 kJ mol{sup −1} depending on the anchor point. • Theory and experiment converge on the CF{sub 2} moiety as the main anchor point. - Abstract: Photodegradation over titanium dioxide (TiO{sub 2}) is a very appealing technology for removing environmental pollutants from the air, the adsorption interaction being the first step of the whole reaction pathway. In the present work the adsorption of F{sub 2}C=CFCl (chlorotrifluoroethene, halon 1113), a compound used by industry and detected in the atmosphere, on a commercial TiO{sub 2} nano-powder is investigated experimentally by in situ DRIFT spectroscopy and theoretically through periodic ab initio calculations rooted in DFT. The spectra of the adsorbed molecule suggest that the anchoring to the surface mainly takes place through F atoms. Theoretically, five adsorption configurations for the molecule interacting with the anatase (1 0 1) surface are simulated at B3LYP level and for each of them, structures, binding energies and vibrational frequencies are derived. The interplay between theory and experiments shows the coexistence of different adsorption configurations, the foremost ones featuring the interaction of one F atom with a fivefold coordinated Ti{sup 4+} of the surface. These two adsorption models, which mostly differ for the orientation of the adsorbate with respect to the surface, feature a binding energy of −45.6 and −41.0 kJ mol{sup −1} according to dispersion corrected DFT calculations. The favorable adsorption interaction appears as an important requirement toward the application of titanium dioxide technologies for the photocatalytic degradation of halon 1113.

Structural evolution of Ni-20Cr alloy during ball milling of elemental powders

International Nuclear Information System (INIS)

Lopez B, I.; Trapaga M, L. G.; Martinez F, E.; Zoz, H.

2011-01-01

The ball milling (B M) of blended Ni and Cr elemental powders was carried out in a Simoloyer performing on high-energy scale mode at maximum production to obtain a nano structured Ni-20Cr alloy. The phase transformations and structural changes occurring during mechanical alloying were investigated by X-ray diffraction (XRD) and optical microscopy (Om). A gradual solid solubility of Cr and the subsequent formation of crystalline metastable solid solutions described in terms of the Avrami-Ero fe ev kinetics model were calculated. The XRD analysis of the structure indicates that cumulative lattice strain contributes to the driving force for solid solution between Ni and Cr during B M. Microstructure evolution has shown, additionally to the lamellar length refinement commonly observed, the folding of lamellae in the final processing stage. Om observations revealed that the lamellar spacing of Ni rich zones reaches a steady value near 500 nm and almost disappears after 30 h of milling. (Author)

Structural evolution of Ni-20Cr alloy during ball milling of elemental powders

Energy Technology Data Exchange (ETDEWEB)

Lopez B, I.; Trapaga M, L. G. [IPN, Centro de Investigacion y de Estudios Avanzados, Unidad Queretaro, Libramiento Norponiente No. 2000, Juriquilla, 76230 Queretaro (Mexico); Martinez F, E. [Centro de Investigacion e Innovacion Tecnologica, Cerrada de Cecati s/n, Col. Santa Catarina Azcapotzalco, 02250 Mexico D. F. (Mexico); Zoz, H., E-mail: israelbaez@gmail.co [Zoz GmbH, D-57482, Wenden (Germany)

2011-07-01

The ball milling (B M) of blended Ni and Cr elemental powders was carried out in a Simoloyer performing on high-energy scale mode at maximum production to obtain a nano structured Ni-20Cr alloy. The phase transformations and structural changes occurring during mechanical alloying were investigated by X-ray diffraction (XRD) and optical microscopy (Om). A gradual solid solubility of Cr and the subsequent formation of crystalline metastable solid solutions described in terms of the Avrami-Ero fe ev kinetics model were calculated. The XRD analysis of the structure indicates that cumulative lattice strain contributes to the driving force for solid solution between Ni and Cr during B M. Microstructure evolution has shown, additionally to the lamellar length refinement commonly observed, the folding of lamellae in the final processing stage. Om observations revealed that the lamellar spacing of Ni rich zones reaches a steady value near 500 nm and almost disappears after 30 h of milling. (Author)

Characterization of Ni ferrites powders prepared by plasma arc discharge process

Science.gov (United States)

Safari, A.; Gheisari, Kh.; Farbod, M.

2017-01-01

The aim of this work was to synthesize a single-phase spinel structure from a mixture of zinc, iron and nickel powders by plasma arc discharge method. A mixture of zinc, iron and nickel powders with the appropriate molar ratio was prepared and formed into a cylindrical shape. The synthesis process was performed in air, oxygen and argon atmospheres with the applied arc current of 400 A and pressure of 1 atm. After establishing an arc between the electrodes, the produced powders were collected and their structure and magnetic properties were examined by XRD and VSM, respectively. ZnO as an impurity was appeared in the as-produced powders owing to the high reactivity of zinc atoms, preventing the formation of Ni-Zn ferrite. A pure spinel structure with the highest saturation magnetization (43.8 emu/g) was observed as zinc powders removed completely from the initial mixture. Morphological evaluations using field emission scanning electron microscopy showed that the mean size of fabricated nanoparticles was in the range 100-200 nm and was dependent on the production conditions.

Self-powdering and nonlinear optical domain structures in ferroelastic β'-Gd2(MoO4)3 crystals formed in glass

International Nuclear Information System (INIS)

Tsukada, Y.; Honma, T.; Komatsu, T.

2009-01-01

Ferroelastic β'-Gd 2 (MoO 4 ) 3 , (GMO), crystals are formed through the crystallization of 21.25Gd 2 O 3 -63.75MoO 3 -15B 2 O 3 glass (mol%), and two scientific curious phenomena are observed. (1) GMO crystals formed in the crystallization break into small pieces with a triangular prism or pyramid shape having a length of 50-500 μm spontaneously during the crystallizations in the inside of an electric furnace, not during the cooling in air after the crystallization. This phenomenon is called 'self-powdering phenomenon during crystallization' in this paper. (2) Each self-powdered GMO crystal grain shows a periodic domain structure with different refractive indices, and a spatially periodic second harmonic generation (SHG) depending on the domain structure is observed. It is proposed from polarized micro-Raman scattering spectra and the azimuthal dependence of second harmonic intensities that GMO crystals are oriented in each crystal grain and the orientation of (MoO 4 ) 2- tetrahedra in GMO crystals changes periodically due to spontaneous strains in ferroelastic GMO crystals. - Graphical abstract: This figure shows the polarized optical photograph at room temperature for a particle (piece) obtained by a heat treatment of the glass at 590 deg. C for 2 h in an electric furnace in air. This particle was obtained through the self-powdering behavior in the crystallization of glass. The periodic domain structure is observed. Ferroelastic β'-Gd 2 (MoO 4 ) 3 crystals are formed in the particle, and second harmonic generations are detected, depending on the domain structure.

Correlation between morphology and magnetic properties of electrochemically produced cobalt powder particles

Directory of Open Access Journals (Sweden)

Maksimović Vesna M.

2015-01-01

Full Text Available Cobalt 3D powder particles were successfully prepared by the galvanostatic electrodeposition. Electrodeposited cobalt powder were characterized by X-ray diffraction (XRD, scanning electron microscope (SEM, Energy Dispersive Spectroscopy (EDS analysis and SQUID magnetometry. It has been shown that morphology, structure and magnetic properties of cobalt particles are closely associated and can be easily controlled by adjusting process parameters of electrodeposition. Morphology of cobalt powder particles is strongly affected by hydrogen evolution reaction as a parallel reaction to cobalt electrodeposition. Depending on the applied current density, the two types of powder particles were formed: dendrites at lower and spongy-like particles at higher current densities. Morphologies and structures of powder particles are correlated with their magnetic properties, and compared with those of the bulk cobalt. In comparison with the properties of bulk cobalt, the obtained 3D structures exhibited a decreased saturation magnetization (MS, but an enhanced coercivity (HC which is explained by their peculiar morphology. [Projekat Ministarstva nauke Republike Srbije, br. III 45012

Strength Improvement of Clay Soil by Using Stone Powder

OpenAIRE

Ahmed Sameer Abdulrasool

2015-01-01

Soil stabilization with stone powder is a good solution for the construction of subgrade for road way and railway lines, especially under the platforms and mostly in transition zones between embankments and rigid structures, where the mechanical properties of supporting soils are very influential. Stone powder often has a unique composition which justifies the need for research to study the feasibility of using this stone powder type for ground improvement applications. This paper presents re...

Hierarchically structured nanoporous carbon tubes for high pressure carbon dioxide adsorption

Directory of Open Access Journals (Sweden)

Julia Patzsch

2017-05-01

Full Text Available Mesoscopic, nanoporous carbon tubes were synthesized by a combination of the Stoeber process and the use of electrospun macrosized polystyrene fibres as structure directing templates. The obtained carbon tubes have a macroporous nature characterized by a thick wall structure and a high specific surface area of approximately 500 m²/g resulting from their micro- and mesopores. The micropore regime of the carbon tubes is composed of turbostratic graphitic areas observed in the microstructure. The employed templating process was also used for the synthesis of silicon carbide tubes. The characterization of all porous materials was performed by nitrogen adsorption at 77 K, Raman spectroscopy, infrared spectroscopy, thermal gravimetric analysis (TGA, scanning electron microscopy (SEM as well as transmission electron microscopy (TEM. The adsorption of carbon dioxide on the carbon tubes at 25 °C at pressures of up to 30 bar was studied using a volumetric method. At 26 bar, an adsorption capacity of 4.9 mmol/g was observed. This is comparable to the adsorption capacity of molecular sieves and vertically aligned carbon nanotubes. The high pressure adsorption process of CO2 was found to irreversibly change the microporous structure of the carbon tubes.

Multipole electron-density modelling of synchrotron powder diffraction data: the case of diamond

DEFF Research Database (Denmark)

Svendsen, H.; Overgaard, J.; Busselez, R.

2010-01-01

between experiment and theory, and the study therefore demonstrates that synchrotron powder diffraction can indeed provide accurate structure-factor values based on data measured in minutes with limited sample preparation. Thus, potential systematic errors such as extinction and twinning commonly......Accurate structure factors are extracted from synchrotron powder diffraction data measured on crystalline diamond based on a novel multipole model division of overlapping reflection intensities. The approach limits the spherical-atom bias in structure factors extracted from overlapping powder data...

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)

Fine crystalline powders. Analysis of scientific and technical literature

International Nuclear Information System (INIS)

Denisenko, Eh.T.; Kulik, O.P.; Eremina, T.V.

1983-01-01

The state of development and studies of fine crystalline powders for recent five years is reviewed in the paper. Based on data available in literature, the most significant methods for fine metal and alloy powder production are considered and physicochemical properties of ultrafine particles are discussed from the standpoint of their interrelation with promising techniques for powder production. It is stated that the most important feature of ultrafine powder production technique at the present stage is a transition from the stage of data accumulation to that of controlled production of ultrafine structures of various metals and alloys under controllable conditions

Radiation effects in high-disperse metal media and their application in powder metallurgy

International Nuclear Information System (INIS)

Zaykin, Y.A.; Aliyev, B.A.

2002-01-01

Experimental and theoretical results showing up effects of metal powder radiation processing, such as powder grinding, chemical refinement, and changes in powder particle surface state, are discussed. It is shown that preliminary irradiation of metal powders leads to profound structural alterations at all further stages of their processing by conventional methods of powder metallurgy and eventually effects the properties of the resulting product

Carbon dioxide absorbent and method of using the same

Science.gov (United States)

Perry, Robert James; O'Brien, Michael Joseph

2014-06-10

In accordance with one aspect, the present invention provides a composition which contains the amino-siloxane structures I, or III, as described herein. The composition is useful for the capture of carbon dioxide from process streams. In addition, the present invention provides methods of preparing the amino-siloxane composition. Another aspect of the present invention provides methods for reducing the amount of carbon dioxide in a process stream employing the amino-siloxane compositions of the invention, as species which react with carbon dioxide to form an adduct with carbon dioxide.

Carbon dioxide absorbent and method of using the same

Energy Technology Data Exchange (ETDEWEB)

Perry, Robert James; O' Brien, Michael Joseph

2015-12-29

In accordance with one aspect, the present invention provides a composition which contains the amino-siloxane structures I, or III, as described herein. The composition is useful for the capture of carbon dioxide from process streams. In addition, the present invention provides methods of preparing the amino-siloxane composition. Another aspect of the present invention provides methods for reducing the amount of carbon dioxide in a process stream employing the amino-siloxane compositions of the invention, as species which react with carbon dioxide to form an adduct with carbon dioxide.

Standard specification for blended uranium oxides with 235U content of less than 5 % for direct hydrogen reduction to nuclear grade uranium dioxide

CERN Document Server

American Society for Testing and Materials. Philadelphia

2001-01-01

1.1 This specification covers blended uranium trioxide (UO3), U3O8, or mixtures of the two, powders that are intended for conversion into a sinterable uranium dioxide (UO2) powder by means of a direct reduction process. The UO2 powder product of the reduction process must meet the requirements of Specification C 753 and be suitable for subsequent UO2 pellet fabrication by pressing and sintering methods. This specification applies to uranium oxides with a 235U enrichment less than 5 %. 1.2 This specification includes chemical, physical, and test method requirements for uranium oxide powders as they relate to the suitability of the powder for storage, transportation, and direct reduction to UO2 powder. This specification is applicable to uranium oxide powders for such use from any source. 1.3 The scope of this specification does not comprehensively cover all provisions for preventing criticality accidents, for health and safety, or for shipping. Observance of this specification does not relieve the user of th...

Study of process parameters for reducing ammonium uranyl carbonate to uranium dioxide in fluidized bed furnace

International Nuclear Information System (INIS)

Leitao Junior, C.B.

1992-01-01

This work consists of studying the process parameters of AUC (ammonium uranyl carbonate) to U O 2 (uranium dioxide) reduction, with good physical and chemical characteristics, in fluidized bed. Initially, it was performed U O 2 cold fluidization experiments with an acrylic column. Afterward, it was done AUC to U O 2 reduction experiments, in which the process parameters influence in the granulometry, specific surface area, porosity and fluoride amount on the U O 2 powder produced were studied. As a last step, it was done compacting and sintering tests of U O 2 pellets in order to appreciate the U O 2 powder performance, obtained by fluidized bed, in the fuel pellets fabrication. (author)

Structure of zirconium dioxide based porous glasses

Czech Academy of Sciences Publication Activity Database

Gubanova, N. N.; Kopitsa, G. P.; Ezdakova, K. V.; Baranchikov, A. Y.; Angelov, Borislav; Feoktystov, A.; Pipich, V.; Ryukhtin, Vasyl; Ivanov, V. K.

2014-01-01

Roč. 8, č. 5 (2014), s. 967-975 ISSN 1027-4510 R&D Projects: GA ČR GAP208/10/1600; GA MŠk(XE) LM2011019; GA ČR GB14-36566G Institutional support: RVO:61389013 ; RVO:61389005 Keywords : zirconium dioxide * porous glasse * nanoparticles Subject RIV: CF - Physical ; Theoretical Chemistry; BG - Nuclear, Atomic and Molecular Physics, Colliders (UJF-V) Impact factor: 0.359, year: 2012

Report of the Carbon Dioxide Committee II

International Nuclear Information System (INIS)

1994-01-01

The Carbon Dioxide Committee was given the task of preparing a suggestion of the acts aimed at reducing the greenhouse gas emissions and increasing the sinks of carbon in Finland. Emissions of all greenhouse gases were in 1990 80 million tons. calculated as carbon dioxide. The carbon dioxide emissions were about 58 million tons of the total. The increase of forest resources binds carbon from the atmosphere and reduces thereby net emissions of Finland at present by nearly 30 million tons of carbon dioxide. Carbon dioxide emissions will grow during the next decades, unless strong measures to control them will not be taken. As a result of the Commissions examination, acts will be needed both in the production of energy and in its consumption. Emissions can be reduced by replacing fossil fuels with nuclear energy, bioenergy and other renewable energy sources. Saving of energy and improvement of energy efficiency will limit carbon dioxide emissions. The Commission has made suggestions both to change the structure of energy production and to control the consumption of energy. (orig.)

Barium strontium titanate powders prepared by spray pyrolysis

International Nuclear Information System (INIS)

Brankovic, G.; Brankovic, Z.; Goes, M.S.; Paiva-Santos, C.O.; Cilense, M.; Varela, J.A.; Longo, E.

2005-01-01

Ultasonic spray pyrolysis (SP) has been investigated for the production of the barium strontium titanate (BST) powders from the polymeric precursors. The processing parameters, such as flux of aerosol and temperature profile inside the furnace, were optimized to obtain single phase BST. The powders were characterized by the methods of X-ray diffraction analysis, SEM, EDS and TEM. The obtained powders were submicronic, consisting of spherical, polycrystalline particles, with internal nanocrystalline structure. Crystallite size of 10 nm, calculated using Rietveld refinement, is in a good agreement with results of HRTEM

Time resolved fluorescence of cow and goat milk powder

Science.gov (United States)

Brandao, Mariana P.; de Carvalho dos Anjos, Virgílio; Bell., Maria José V.

2017-01-01

Milk powder is an international dairy commodity. Goat and cow milk powders are significant sources of nutrients and the investigation of the authenticity and classification of milk powder is particularly important. The use of time-resolved fluorescence techniques to distinguish chemical composition and structure modifications could assist develop a portable and non-destructive methodology to perform milk powder classification and determine composition. This study goal is to differentiate milk powder samples from cows and goats using fluorescence lifetimes. The samples were excited at 315 nm and the fluorescence intensity decay registered at 468 nm. We observed fluorescence lifetimes of 1.5 ± 0.3, 6.4 ± 0.4 and 18.7 ± 2.5 ns for goat milk powder; and 1.7 ± 0.3, 6.9 ± 0.2 and 29.9 ± 1.6 ns for cow's milk powder. We discriminate goat and cow powder milk by analysis of variance using Fisher's method. In addition, we employed quadratic discriminant analysis to differentiate the milk samples with accuracy of 100%. Our results suggest that time-resolved fluorescence can provide a new method to the analysis of powder milk and its composition.

Modern trends in x-ray powder diffraction

International Nuclear Information System (INIS)

Goebel, H.E.; Snyder, R.L.

1985-01-01

The revival of interest in X-ray powder diffraction, being quoted as a metamorphosis from the 'ugly duckling' to a 'beautiful swan', can be attributed to a number of modern developments in instrumentation and evaluation software. They result in faster data collection, improved accuracy and resolution, and better detectability of minor phases. The ease of data evaluation on small computers coupled direct to the instrument allows convenient execution of previously tedious and time-consuming off-line tasks like qualitative and quantitative analysis, characterization of microcrystalline properties, indexing, and lattice-constant refinements, as well as structure refinements or even exploration of new crystal structures. Powder diffraction has also progressed from an isolated analytical laboratory method to an in situ technique for analysing solid-state reactions or for the on-stream control of industrial processes. The paper surveys these developments and their real and potential applications, and tries to emphasize new trends that are regarded as important steps for the further progress of X-ray powder diffraction

Production of titanium alloy powders by vacuum fusion-centrifugation

International Nuclear Information System (INIS)

Decours, Jacques; Devillard, Jacques; Sainfort, G.

1975-01-01

This work presents a method of preparing powdered TA6V and TA6Z5D alloys by fusion-centrifugation under electron bombardment. An industrial capacity apparatus for the production of metallic powders is described and the characteristics of the powders obtained are presented. Solid parts were shaped by sintering and drawing at temperatures between 850 and 1100 deg C. The structure and mechanical properties of the cold densified products before and after heat treatment are compared [fr

Synthesis of battery grade reduced silver powder

International Nuclear Information System (INIS)

Qadeer, R.; Hameed, M.; Ikram, S.; Munir, A.

2002-01-01

Process for production of battery grade reduced silver powder, an active positive material for zinc-silver oxide batteries, having specific characteristics has been optimized and the synthesized reduced silver powder was characterized. Results reveal that the values of bulk density (1.25 0.1 g/cm3) and activity (73.27 %) of synthesized reduced silver powder lies within the recommended range for use as battery material. It has purity ≥ 98% and contains Fe and Cu as traces in the concentration range of 30 5 ppm and 15 7 ppm respectively. Others determined values of surface and pores parameters are: surface area 2.6 .4 m2/g: pore volume 3.10 cm3/g: pore diameter 0.043 mu m and porosity 20%. XRD studies reveal that reduced silver powder has a cubic structure. (author)

Electron-beam deposition of vanadium dioxide thin films

Energy Technology Data Exchange (ETDEWEB)

Marvel, R.E.; Appavoo, K. [Vanderbilt University, Interdisciplinary Materials Science Program, Nashville, TN (United States); Choi, B.K. [Vanderbilt University, Department of Electrical Engineering and Computer Science, Nashville, TN (United States); Nag, J. [Vanderbilt University, Department of Physics and Astronomy, Nashville, TN (United States); Haglund, R.F. [Vanderbilt University, Interdisciplinary Materials Science Program, Nashville, TN (United States); Vanderbilt University, Institute for Nanoscale Science and Engineering, Nashville, TN (United States); Vanderbilt University, Department of Physics and Astronomy, Nashville, TN (United States)

2013-06-15

Developing a reliable and efficient fabrication method for phase-transition thin-film technology is critical for electronic and photonic applications. We demonstrate a novel method for fabricating polycrystalline, switchable vanadium dioxide thin films on glass and silicon substrates and show that the optical switching contrast is not strongly affected by post-processing annealing times. The method relies on electron-beam evaporation of a nominally stoichiometric powder, followed by fast annealing. As a result of the short annealing procedure we demonstrate that films deposited on silicon substrates appear to be smoother, in comparison to pulsed laser deposition and sputtering. However, optical performance of e-beam evaporated film on silicon is affected by annealing time, in contrast to glass. (orig.)

Effects of phosphorus-doping on energy band-gap, structural, surface, and photocatalytic characteristics of emulsion-based sol-gel derived TiO{sub 2} nano-powder

Energy Technology Data Exchange (ETDEWEB)

Ganesh, Ibram, E-mail: ibramganesh@arci.res.in

2017-08-31

Highlights: • Reported a novel route to synthesize high specific surface area P-doped TiO{sub 2} nano-powder photocatalysts. • Established methylene blue dye-sensitization mechanism of TiO{sub 2} photocatalyst. • Established the effects of methylene blue adsorption on the surface, structural and photocatalytic activity of P-doped TiO{sub 2}. • Established true quantum efficiency determination method for TiO{sub 2} photocatalysis. - Abstract: Different amounts of phosphorus (P)-doped TiO{sub 2} (PDT) nano-powders (P = 0–10 wt.%) were synthesized by following a new emulsion-based sol-gel (EBSG) route and calcined at 400 °C–800 °C for 6 h. These calcined PDT powders were then thoroughly characterized by means of XRD, XPS, SEM, FT-IR, FT-Raman, DRS, BET surface area, zeta-potential, cyclic-voltammetry and photocatalytic evaluation using methylene blue (MB) as a model-pollutant and established the effects of phosphorous doping on structural, surface, band-gap energy, and photocatalytic characteristics of TiO{sub 2} nano-powder formed in EBSG route. The characterization results suggest that the EBSG derived TiO{sub 2} nano-powder after calcination at 400 °C for 6 h is in the form of anatase phase when it was doped with <8 wt.% P, and it is in the amorphous state when doped with >8 wt.% P. Furthermore, these EBSG derived PDT powders own high negative zeta-potentials, high specific surface areas (up to >250 m{sup 2}/g), and suitable band-gap energies (<3.34 eV). Surprisingly, these PDT powders exhibit very high MB adsorption (up to 50%) from its aqueous 0.01 mM, 0.02 mM and 0.03 mM solutions during 30 min stirring in the dark, whereas, the commercial Degussa P-25 TiO{sub 2} nano-powder shows no adsorption. Among various photocatalysts investigated in this study, the 1 wt.% P-doped TiO{sub 2} nano-powder formed in EBSG route exhibited the highest photocatalytic activity for MB degradation reaction.

Microstructure of rapidly solidified Nb-based pre-alloyed powders for additive manufacturing

Energy Technology Data Exchange (ETDEWEB)

Guo, Yueling; Jia, Lina, E-mail: jialina@buaa.edu.cn; Kong, Bin; Zhang, Shengnan; Zhang, Fengxiang; Zhang, Hu

2017-07-01

Highlights: • Sphere shaped Nb-37Ti-13Cr-2Al-1Si pre-alloyed powders were prepared by PREP. • An oxide layer with a thickness of 9.39 nm was generated on the powder surface. • The main phases of the pre-alloyed powders were Nbss and Cr{sub 2}Nb. • SDAS increased and microhardness decreased with the increase of powder size. • Microstructure of powders evolved into large grains from dendrite structures after HT. - Abstract: For powder-based additive manufacturing, sphere-shaped Nb-37Ti-13Cr-2Al-1Si pre-alloyed powders were prepared by plasma rotating electrode processing (PREP). The microstructure, surface oxidation and microhardness of the pre-alloyed powders were systematically investigated. Results showed that the main phases were Nb solid solution (Nbss) and Cr{sub 2}Nb. The Cr{sub 2}Nb phases were further determined using transmission electron microscopy (TEM). Fine dendrite structures were observed in the as-fabricated pre-alloyed powders, which transformed to large grains after heat treatment (HT) at 1450 °C for 3 h. With the increase of powder size, the secondary dendrite arm spacing (SDAS) increased and the microhardness (HV) decreased. A clean powder surface free of oxide particles was obtained by PREP and an oxide layer with 9.39 nm in thickness was generated on the powder surface. Compared with Cr- and Nb-oxides, more Ti-oxides were formed on outmost powder surface with a higher content of Ti (up to 47.86 at.%). The differences upon the microstructure and microhardness of the pre-alloyed powders with different sizes were discussed.

Laser stereolithography by multilayer cladding of metal powders

Science.gov (United States)

Jendrzejewski, Rafal; Rabczuk, Grazyna T.; Zaremba, R.; Sliwinski, Gerard

1998-07-01

3D-structures obtained by means of laser cladding of the metal alloy powders: bronze B10 and stellite 6 and the process parameters are studied experimentally. The structures are made trace-on-trace by remelting of the metal powder injected into the focusing region of the 1.2 kW CO2 laser beam. For the powder and sample feeding rates of 8-22 g/min and 0.4-1.2 m/min, respectively, and the applied beam intensities not exceeding 2 X 105 W cm-2 the process is stable and regular traces connected via fusion zones are produced for each material. The thickness of these zones does not exceed several per cent of the layer height. The process results in the efficient formation of multilayer structures. From their geometry the effect of energy coupling and interaction parameters are deduced. Moreover, the microanalysis by means of SEM- and optical photographs of samples produced under different experimental conditions confirms the expected mechanical properties, low porosity and highly homogenous structure of the multilayers. In addition to the known material stellite 6 the bronze B10 is originally proposed for a rapid prototyping.

The effect of plutonium dioxide water surface coverage on the generation of hydrogen and oxygen

Energy Technology Data Exchange (ETDEWEB)

Veirs, Douglas K. [Los Alamos National Laboratory; Berg, John M. [Los Alamos National Laboratory; Crowder, Mark L. [Savannah River National Laboratory

2012-06-20

The conditions for the production of oxygen during radiolysis of water adsorbed onto plutonium dioxide powder are discussed. Studies in the literature investigating the radiolysis of water show that both oxygen and hydrogen can be generated from water adsorbed on high-purity plutonium dioxide powder. These studies indicate that there is a threshold in the amount of water below which oxygen is not generated. The threshold is associated with the number of monolayers of adsorbed water and is shown to occur at approximately two monolayers of molecularly adsorbed water. Material in equilibrium with 50% relative humidity (RH) will be at the threshold for oxygen generation. Using two monolayers of molecularly adsorbed water as the threshold for oxygen production, the total pressure under various conditions is calculated assuming stoichiometric production of hydrogen and oxygen. The specific surface area of the oxide has a strong effect on the final partial pressure. The specific surface areas resulting in the highest pressures within a 3013 container are evaluated. The potential for oxygen generation is mitigated by reduced relative humidity, and hence moisture adsorption, at the oxide surface which occurs if the oxide is warmer than the ambient air. The potential for oxygen generation approaches zero as the temperature difference between the ambient air and the material approaches 6 C.

Spark-plasma sintering and mechanical property of mechanically alloyed NiAl powder compact and ball-milled (Ni+Al) mixed powder compact

International Nuclear Information System (INIS)

Kim, J.S.; Jang, Y.I.; Kwon, Y.S.; Kim, Y.D.; Ahn, I.S.

2001-01-01

Mechanically-alloyed NiAl powder and (Ni+Al) powder mixture prepared by ball-milling were sintered by spark-plasma sintering (SPS) process. Densification behavior and mechanical property were determined from the experimental results and analysis such as changes in linear shrinkage, shrinkage rate, microstructure, and phase during sintering process, Vicker's hardness and transverse rupture strength tests. Densification mechanisms for MA-NiAl powder compact and (Ni+Al) powder mixture were different from each other. While the former showed a rapid increase in densification rate only at higher temperature region of 800-900 o C, the latter revealed firstly a rapid increase in densification rate even at low temperature of 300 o C and a subsequent increase up to 500 o C. Densities of both powder compact (MA and mixture) sintered at 1150 o C for 5 min were 98 and above 99 %, respectively. Sintered bodies were composed mainly of NiAl phase with Ni 3 Al as secondary phase for both powders. Sintered body of MA-NiAl powder showed a very fine grain structure. Crystallite size determined by XRD result and the Sherrer's equation was approximately 80 nm. Vicker's hardness for the sintered bodies of (Ni+Al) powder mixture and MA-NiAl powder were 410±12 H v and 555±10 H v , respectively, whereas TRS values 1097±48 MPa and 1393±75 MPa. (author)

Fundamentals of powder x-ray diffraction practice

International Nuclear Information System (INIS)

Raftery, T.

2002-01-01

Full text: The goal of powder Xray diffraction is to gain information about a specimen or sample. Key aspects of this goal are 1. the sample selection, preparation and presentation; 2. the data collection process and conditions; 3. the interaction between these and the interpretation of the data. The 'ideal' powder (or polycrystalline) xray diffraction sample is fine grained, randomly orientated, homogenous and representative. There exists standard sample selection and preparation techniques for powders - sometimes however, the required information must be gained by alternate sample selection and preparation techniques. While there are few variables in the data collection process, there are some significant ones such as matching diffractometer resolution and intensity to the data collection goal whether that is phase identity, quantitative analysis or structure refinement, etc. There are also options of optical arrangement (Bragg-Brintano versus parallel beam versus Debye-Scherrer). One important aspect of the collection process is the assessment of the data quality. Powder xray diffraction has many applications from the straight-forward confirmation of phase identity and purity to structural analysis. Some of these applications will be considered and the interaction between the goal of the application and aspects of sample selection. Copyright (2002) Australian X-ray Analytical Association Inc

The thermal behaviour and structural stability of nesquehonite, MgCO3.3H2O, evaluated by in situ laboratory parallel-beam X-ray powder diffraction: New constraints on CO2 sequestration within minerals.

Science.gov (United States)

Ballirano, Paolo; De Vito, Caterina; Ferrini, Vincenzo; Mignardi, Silvano

2010-06-15

In order to gauge the appropriateness of CO(2) reaction with Mg chloride solutions as a process for storing carbon dioxide, the thermal behaviour and structural stability of its solid product, nesquehonite (MgCO(3).3H(2)O), were investigated in situ using real-time laboratory parallel-beam X-ray powder diffraction. The results suggest that the nesquehonite structure remains substantially unaffected up to 373 K, with the exception of a markedly anisotropic thermal expansion acting mainly along the c axis. In the 371-390 K range, the loss of one water molecule results in the nucleation of a phase of probable composition MgCO(3).2H(2)O, which is characterized by significant structural disorder. At higher temperatures (423-483 K), both magnesite and MgO.2MgCO(3) coexist. Finally, at 603 K, periclase nucleation starts and the disappearance of carbonate phases is completed at 683 K. Consequently, the structural stability of nesquehonite at high temperatures suggests that it will remain stable under the temperature conditions that prevail at the Earth's surface. These results will help (a) to set constraints on the temperature conditions under which nesquehonite may be safely stored and (b) to develop CO(2) sequestration via the synthesis of nesquehonite for industrial application. Copyright 2010 Elsevier B.V. All rights reserved.

New Strategies for Powder Compaction in Powder-based Rapid Prototyping Techniques

OpenAIRE

Budding, A.; Vaneker, T.H.J.

2013-01-01

In powder-based rapid prototyping techniques, powder compaction is used to create thin layers of fine powder that are locally bonded. By stacking these layers of locally bonded material, an object is made. The compaction of thin layers of powder mater ials is of interest for a wide range of applications, but this study solely focuses on the application for powder -based three-dimensional printing (e.g. SLS, 3DP). This research is primarily interested in powder compaction for creating membrane...

Reducing metal alloy powder costs for use in powder bed fusion additive manufacturing: Improving the economics for production

Science.gov (United States)

Medina, Fransisco

AM. Alternative powders can be made by blending or re-spheroidizing HDH and CPTi powders. Machine modifications were performed to allow the testing and manufacturing with these low cost alternative powders. A comparison was made between alternative powders and gas atomized powders. Powders were compared in terms of morphology and at the microstructural level. Flowability of different powder blends was also measured. Finally, a comparison of parts fabricated from the multiple powder blends and gas atomized powder was made. It has been demonstrated that powder blending can produce fully dense parts in the Arcam system by utilizing the double melt technique or HIPing the built pars. The double melt technique increased the density of the sample part and modified the microstructure into finer martensitic grains. The HIP process can make a part fully dense regardless of what percentage of HDH powder blending is used. The HIP process yielded the same microstructure, regardless of the grain structure it started with. This research allows for the reduction of costs using titanium powders in the EBM system, but can also be implemented with more costly elements and alloys using other metal AM technologies. This includes niobium, tantalum, and nickel-based superalloys for use in various industries.

The use of gamma irradiation in preparation of polybutadiene rubber nanopowder; Its effect on particle size, morphology and crosslink structure of the powder

Energy Technology Data Exchange (ETDEWEB)

Rezaei Abadchi, Majid; Jalali-Arani, Azam, E-mail: ajalali@aut.ac.ir

2014-02-01

Highlights: • Vulcanized rubber powders were prepared by spray drying of irradiated rubber latexes. • Influence of absorbed dose on powder structure and characteristics was investigated. • The size of rubber latex particles did not changed by irradiation. • Crosslink density increased by increasing dose and 98% gel was obtained at 150 kGy. • T{sub g} of rubber powder increased with increasing the irradiation dose. -- Abstract: The aim of this work was the preparation and characterization of polybutadiene rubber (BR) powder by irradiating of rubber lattices using {sup 60}Co radiation and spray-drying of them at the appropriate condition. The influences of absorbed dose on the volume swelling ratio, molecular weight between crosslinks, gel fraction, and glass transition temperature of obtained powder were studied. Morphology, size and size distribution of rubber particles were examined by using scanning electron microscopy (SEM) and laser particle size analyzer (LPSA) technique, respectively. Results obtained by LPSA revealed that radiation has no effect on particle size of rubber latex but after drying, adherence properties of rubber particle causes increase in particle size of rubber powder, as shown in SEM photograph. Fourier transform infrared spectroscopy of rubber powders confirmed that with increasing the irradiation dose, characteristic peak corresponds to the >C=C< double bands decreased. Also Charlesby–Pinner equation was used to evaluate radiation yield.

The use of gamma irradiation in preparation of polybutadiene rubber nanopowder; Its effect on particle size, morphology and crosslink structure of the powder

International Nuclear Information System (INIS)

Rezaei Abadchi, Majid; Jalali-Arani, Azam

2014-01-01

Highlights: • Vulcanized rubber powders were prepared by spray drying of irradiated rubber latexes. • Influence of absorbed dose on powder structure and characteristics was investigated. • The size of rubber latex particles did not changed by irradiation. • Crosslink density increased by increasing dose and 98% gel was obtained at 150 kGy. • T g of rubber powder increased with increasing the irradiation dose. -- Abstract: The aim of this work was the preparation and characterization of polybutadiene rubber (BR) powder by irradiating of rubber lattices using 60 Co radiation and spray-drying of them at the appropriate condition. The influences of absorbed dose on the volume swelling ratio, molecular weight between crosslinks, gel fraction, and glass transition temperature of obtained powder were studied. Morphology, size and size distribution of rubber particles were examined by using scanning electron microscopy (SEM) and laser particle size analyzer (LPSA) technique, respectively. Results obtained by LPSA revealed that radiation has no effect on particle size of rubber latex but after drying, adherence properties of rubber particle causes increase in particle size of rubber powder, as shown in SEM photograph. Fourier transform infrared spectroscopy of rubber powders confirmed that with increasing the irradiation dose, characteristic peak corresponds to the >C=C< double bands decreased. Also Charlesby–Pinner equation was used to evaluate radiation yield

Rietveld refinement of magnetic structures from pulsed-neutron-source powder-diffraction data

International Nuclear Information System (INIS)

Robinson, R.A.; Lawson, A.C.; Larson, A.C.; Von Dreele, R.B.; Goldstone, J.A.

1994-01-01

The General Structure Analysis System, GSAS, has recently been modified to include magnetic neutron- scattering cross-sections. Low-temperature diffraction data have been taken on the hexagonal noncollinear antiferromagnet UPdSn on both the HIPD and the NPD powder diffractometers ail LANSCE. The low-resolution data reveal that the magnetic structure has orthorhombic symmetry (magnetic space group P c m'c2 1 ) between 25K and 40K, and monoclinic symmetry (magnetic space group PC 1121 ) below 25K. The high-resolution data reveal that there are structural distortions with corresponding symmetry changes in each of these phases, to give chemical space groups Cmc2 1 and P2 1 , respectively, while the paramagnetic phase above 40K has space group P6 3 mc. Using GSAS, we have refined data sets from both diffractometers simultaneously, including both magnetic and structural cross-sections. Magnetoelastic coefficients for the distortions have been extracted and we have determined the sign of the coupling between the structural monoclinicity and the magnetic monoclinicity. The magnetic results from Rietveld refinement are in good agreement with model fitting to the integrated intensities of seven independent magnetic reflections and these, in turn, agree with measurements made on the same sample using the constant-wavelength reactor technique. Our results therefore validate, to some level, both the technique of using spallation sources for complicated magnetic structures and the specifics of the GSAS Rietveld code

Optical properties of titanium di-oxide thin films prepared by dip coating method

Science.gov (United States)

Biswas, Sayari; Rahman, Kazi Hasibur; Kar, Asit Kumar

2018-05-01

Titanium dioxide (TiO2) thin films were prepared by sol-gel dip coating method on ITO coated glass substrate. The sol was synthesized by hydrothermal method at 90°C. The sol was then used to make TiO2 films by dip coating. After dip coating the rest of the sol was dried at 100°C to make TiO2 powder. Thin films were made by varying the number of dipping cycles and were annealed at 500°C. XRD study was carried out for powder samples that confirms the formation of anatase phase. Transmission spectra of thin films show sharp rise in the violet-ultraviolet transition region and a maximum transmittance of ˜60%. Band gap of the prepared films varies from 3.15 eV to 3.22 eV.

Structure-Activity Relationships for Rates of Aromatic Amine Oxidation by Manganese Dioxide.

Science.gov (United States)

Salter-Blanc, Alexandra J; Bylaska, Eric J; Lyon, Molly A; Ness, Stuart C; Tratnyek, Paul G

2016-05-17

New energetic compounds are designed to minimize their potential environmental impacts, which includes their transformation and the fate and effects of their transformation products. The nitro groups of energetic compounds are readily reduced to amines, and the resulting aromatic amines are subject to oxidation and coupling reactions. Manganese dioxide (MnO2) is a common environmental oxidant and model system for kinetic studies of aromatic amine oxidation. In this study, a training set of new and previously reported kinetic data for the oxidation of model and energetic-derived aromatic amines was assembled and subjected to correlation analysis against descriptor variables that ranged from general purpose [Hammett σ constants (σ(-)), pKas of the amines, and energies of the highest occupied molecular orbital (EHOMO)] to specific for the likely rate-limiting step [one-electron oxidation potentials (Eox)]. The selection of calculated descriptors (pKa, EHOMO, and Eox) was based on validation with experimental data. All of the correlations gave satisfactory quantitative structure-activity relationships (QSARs), but they improved with the specificity of the descriptor. The scope of correlation analysis was extended beyond MnO2 to include literature data on aromatic amine oxidation by other environmentally relevant oxidants (ozone, chlorine dioxide, and phosphate and carbonate radicals) by correlating relative rate constants (normalized to 4-chloroaniline) to EHOMO (calculated with a modest level of theory).

Investigation of high burnup structures in uranium dioxide applying cellular automata: algorithms and codes

International Nuclear Information System (INIS)

Akishina, E.P.; Kostenko, B.F.; Ivanov, V.V.

2003-01-01

A new method of research in spatial structures that result from uranium dioxide burning in nuclear reactors of modern atomic plants is suggested. The method is based on the presentation of images of the mentioned structures in the form of the working field of a cellular automaton (CA). First, it has allowed one to extract some important quantitative characteristics of the structures directly from the micrographs of the uranium fuel surface. Secondly, the CA has been found out to allow one to formulate easily the dynamics of the evolution of the studied structures in terms of such micrograph elements as spots, spots' boundaries, cracks, etc. Relation has been found between the dynamics and some exactly solvable models of the theory of cellular automata, in particular, the Ising model and the vote model. This investigation gives a detailed description of some CA algorithms which allow one to perform the fuel surface image processing and to model its evolution caused by burnup or chemical etching. (author)

Preparation and Crystal Structures of Some AIVB2IIO4 Compounds: Powder X-Ray Diffraction and Rietveld Analysis

Directory of Open Access Journals (Sweden)

K. Jeyadheepan

2014-01-01

Full Text Available The AIVB2IIO4 compounds such as cadmium tin oxide (Cd2SnO4 or CTO and zinc tin oxide (Zn2SnO4 or ZTO are synthesized by solid state reaction of the subsequent binary oxides. The synthesized powders were analyzed through the powder X-ray diffraction (PXRD. Cell search done on the PXRD patterns shows that the Cd2SnO4 crystallizes in orthorhombic structure with space group Pbam and the cell parameters as a=5.568(2 Å, b=9.894(3 Å, and c=3.193(1 Å and the Zn2SnO4 crystallizes as cubic with the space group Fd3 -m and with the cell parameter a=8.660(2 Å. Rietveld refinement was done on the PXRD patterns to get the crystal structure of the Cd2SnO4 and Zn2SnO4 and to define the site deficiency of atoms which causes the electrical properties of the materials.

Corrosion-resistant powder-metallurgy stainless steel powders and compacts therefrom

International Nuclear Information System (INIS)

Klar, E.; Ro, D.H.; Whitman, C.I.

1980-01-01

Disclosed is a process for improving the corrosion resistance of a stainless steel powder or compact thereof wherein the powder is produced by atomizing a melt of metals in an oxidizing environment whereby the resulting stainless steel powder is surface-enriched in silicon oxides. The process comprises adding an effective proportion of modifier metal to the melt prior to the atomization, the modifier metal selected from the group consisting of tin, aluminum, lead, zinc, magnesium, rare earth metals and like metals capable of enrichment about the surface of the resulting atomized stainless steel powder and effective under reductive sintering conditions in the depletion of the silicon oxides about the surface; and sintering the resulting atomized powder or a compact thereof under reducing conditions, the sintered powder or compact thereof being depleted in the silicon oxides and the corrosion resistance of the powder or compact thereof being improved thereby

Plasma preparation and low-temperature sintering of spherical TiC-Fe composite powder

Institute of Scientific and Technical Information of China (English)

Jian-jun Wang; Jun-jie Hao; Zhi-meng Guo; Song Wang

2015-01-01

A spherical Fe matrix composite powder containing a high volume fraction (82vol%) of fine TiC reinforcement was produced us-ing a novel process combining in situ synthesis and plasma techniques. The composite powder exhibited good sphericity and a dense struc-ture, and the fine sub-micron TiC particles were homogeneously distributed in theα-Fe matrix. A TiC–Fe cermet was prepared from the as-prepared spherical composite powder using powder metallurgy at a low sintering temperature;the product exhibited a hardness of HRA 88.5 and a flexural strength of 1360 MPa. The grain size of the fine-grained TiC and special surface structure of the spherical powder played the key roles in the fabrication process.

Syntheses and crystal structure determination by X-ray powder diffraction of new compounds of Benzovesamicol

International Nuclear Information System (INIS)

Rukiah, M.; Assaad, Th.

2012-06-01

The compound 2,2,2-Trifluoro-N-(1a,2,7,7 a-tetra-hydronaphtho[2,3-b]oxiren-3-yl)- acetamide, C 1 2H 1 0F 3 NO 2 , an important precursor in the preparation of benzovesamicol analogues for the diagnosis of Alzheimers disease, was prepared by the epoxidation of 5,8-dihydronaphthalene-1-amine using 3-chloroperoxybenzoic acid. The structure was determined by X-ray powder diffraction, multinuclear NMR spectroscopy and FT-IR spectroscopy. A pair of molecules form intermolecular N- H...O hydrogen bonds, involving the amino and oxirene groups, to produce a dimer.The two racemic compounds (2RS,3RS)-5-amino-3-(4-phenylpiperazin-1-yl)-1,2,3,4 tetrahydronaphthalene-2-ol, C 2 0H 2 5N 3 O, (I) and (2RS,3RS)-5-amino-3-[4-(3- methoxyphenyl)piperazin-1-yl]-1,2,3,4-tetrahydronaphthalene-2-ol, C 2 1H 2 7N 3 O 2 , (II) important benzovesamicol analogues for the diagnosis of Alzheimer's disease, have been synthesized and characterized by FT-IR, and 1 H and 13 C NMR spectroscopic analyses. The crystal structures were analyses using powder diffraction as no suitable single crystal were obtained. The two compounds are racemic mixtures of enantiomers which crystallize in the monoclinic system in a centrosymmetric space group (P21/c). Crystallography, in particular powder X-ray diffraction, was pivotal in revealing that the enantio-resolution did not succeed. In two compounds, the piperazine ring has a chair conformation, while the cyclohexene ring assumes a half-chair conformation. In (I) the crystal packing is mediated by weak contacts, principally by complementary intermolecular N--H...O hydrogen bonds that connect successive molecules into a chain. Further stabilization is provided by weak C--H...N contacts and by a weak intermolecular C--H...π interaction. While in (II), the crystal packing is dominated by intermolecular O--H...N hydrogen bonding which links molecules along the c direction. (authors)

Carbon dioxide absorbent and method of using the same

Science.gov (United States)

Perry, Robert James [Niskayuna, NY; Lewis, Larry Neil [Scotia, NY; O'Brien, Michael Joseph [Clifton Park, NY; Soloveichik, Grigorii Lev [Latham, NY; Kniajanski, Sergei [Clifton Park, NY; Lam, Tunchiao Hubert [Clifton Park, NY; Lee, Julia Lam [Niskayuna, NY; Rubinsztajn, Malgorzata Iwona [Ballston Spa, NY

2011-10-04

In accordance with one aspect, the present invention provides an amino-siloxane composition comprising at least one of structures I, II, III, IV or V said compositions being useful for the capture of carbon dioxide from gas streams such as power plant flue gases. In addition, the present invention provides methods of preparing the amino-siloxane compositions are provided. Also provided are methods for reducing the amount of carbon dioxide in a process stream employing the amino-siloxane compositions of the invention as species which react with carbon dioxide to form an adduct with carbon dioxide. The reaction of the amino-siloxane compositions provided by the present invention with carbon dioxide is reversible and thus, the method provides for multicycle use of said compositions.

Fabrication of Cu-Ag core-shell bimetallic superfine powders by eco-friendly reagents and structures characterization

International Nuclear Information System (INIS)

Zhao Jun; Zhang Dongming; Zhao Jie

2011-01-01

Superfine bimetallic Cu-Ag core-shell powders were synthesized by reduction of copper sulfate pentahydrate and silver nitrate with eco-friendly ascorbic acid as a reducing agent and cyclodextrins as a protective agent in an aqueous system. The influence of Ag/Cu ratio on coatings was investigated. Ag was homogeneously distributed on the surface of Cu particles at a mole ratio of Ag/Cu=1. FE-SEM showed an uniformity of Ag coatings on Cu particles. Antioxidation of Cu particles was improved by increasing Ag/Cu ratio. TEM-EDX and UV-vis spectra also revealed that Cu cores were covered by Ag nanoshells on the whole. The surface composition analysis by XPS indicated that only small parts of Cu atoms in the surface were oxidized. It was noted that the hindrance of cyclodextrins chemisorbed on particles plays an important role in forming high quality and good dispersity Cu-Ag (Cu-Ag) core-shell powders. - Graphical abstract: Mechanism of fabricating Cu-Ag particles with good dispersibility using β-CDs as a protective agent was studied because of its special structure. Highlights: → Green supramolecular β-CD used as a protective agent and ascorbic acid(Vc) as a reducing agent to fabricate Cu-Ag powders. → Particles are monodisperse and the diameter is close to nanoscale(100-150 nm). → Resistance of Cu particles to oxidation was higher. → Formation mechanism explained.

Neutron powder diffraction and theory-aided structure refinement of rubidium and cesium ureate

Energy Technology Data Exchange (ETDEWEB)

Sterri, Kjersti B.; Deringer, Volker L.; Houben, Andreas; Jacobs, Philipp [RWTH Aachen Univ. (Germany). Inst. of Inorganic Chemistry; Kumar, Chogondahalli M.N. [Forschungszentrum Juelich GmbH, Juelich Centre for Neutron Science (JCNS), Outstation at SNS, Oak Ridge National Laboratory, Oak Ridge, TN (United States); Oak Ridge National Laboratory, TN (United States). Chemical and Engineering Materials Div.; Dronskowski, Richard [RWTH Aachen Univ. (Germany). Inst. of Inorganic Chemistry; RWTH Aachen Univ. (Germany). Juelich-Aachen Research Alliance (JARA-HPC)

2016-08-01

Urea (CN{sub 2}H{sub 4}O) is a fundamental biomolecule whose derivatives are abundant throughout chemistry. Among the latter, rubidium ureate (RbCN{sub 2}H{sub 3}O) and its cesium analog (CsCN{sub 2}H{sub 3}O) have been described only very recently and form the first structurally characterized salts of deprotonated urea. Here, we report on a neutron diffraction study on the aforementioned alkaline-metal ureates, which affords the positions for all hydrogen atoms (including full anisotropic displacement tensors) and thus allows us to gain fundamental insights into the hydrogen-bonding networks in the title compounds. The structure refinements of the experimental neutron data proceeded successfully using starting parameters from ab initio simulations of atomic positions and anisotropic displacement parameters. Such joint experimental-theoretical refinement procedures promise significant practical potential in cases where complex solids (organic, organometallic, framework materials) are studied by powder diffraction.

Gamma Radiation Dosimetry Using Tellurium Dioxide Thin Film Structures

Directory of Open Access Journals (Sweden)

Olga Korostynska

2002-08-01

Full Text Available Thin films of Tellurium dioxide (TeO2 were investigated for γ-radiation dosimetry purposes. Samples were fabricated using thin film vapour deposition technique. Thin films of TeO2 were exposed to a 60Co γ-radiation source at a dose rate of 6 Gy/min at room temperature. Absorption spectra for TeO2 films were recorded and the values of the optical band gap and energies of the localized states for as-deposited and γ-irradiated samples were calculated. It was found that the optical band gap values were decreased as the radiation dose was increased. Samples with electrical contacts having a planar structure showed a linear increase in current values with the increase in radiation dose up to a certain dose level. The observed changes in both the optical and the electrical properties suggest that TeO2 thin film may be considered as an effective material for room temperature real time γ-radiation dosimetry.

Spiral chain structure of high pressure selenium-II' and sulfur-II from powder x-ray diffraction

International Nuclear Information System (INIS)

Fujihisa, Hiroshi; Yamawaki, Hiroshi; Sakashita, Mami; Yamada, Takahiro; Honda, Kazumasa; Akahama, Yuichi; Kawamura, Haruki; Le Bihan, Tristan

2004-01-01

The structure of high pressure phases, selenium-II ' (Se-II ' ) and sulfur-II (S-II), for α-Se 8 (monoclinic Se-I) and α-S 8 (orthorhombic S-I) was studied by powder x-ray diffraction experiments. Se-II ' and S-II were found to be isostructural and to belong to the tetragonal space group I4 1 /acd, which is made up of 16 atoms in the unit cell. The structure consisted of unique spiral chains with both 4 1 and 4 3 screws. The results confirmed that the structure sequence of the pressure-induced phase transitions for the group VIb elements depended on the initial molecular form. The chemical bonds of the phases are also discussed from the interatomic distances that were obtained

Hydrothermal synthesis of tungsten doped tin dioxide nanocrystals

Science.gov (United States)

Zhou, Cailong; Li, Yufeng; Chen, Yiwen; Lin, Jing

2018-01-01

Tungsten doped tin dioxide (WTO) nanocrystals were synthesized through a one-step hydrothermal method. The structure, composition and morphology of WTO nanocrystals were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy, UV-vis diffuse reflectance spectra, zeta potential analysis and high-resolution transmission electron microscopy. Results show that the as-prepared WTO nanocrystals were rutile-type structure with the size near 13 nm. Compared with the undoped tin dioxide nanocrystals, the WTO nanocrystals possessed better dispersity in ethanol phase and formed transparent sol.

Structural and magnetic properties of Co50Ni50 powder mixtures

International Nuclear Information System (INIS)

Loudjani, N.; Bensebaa, N.; Dekhil, L.; Alleg, S.; Sunol, J.J.

2011-01-01

In the present work, morphological, structural, thermal and magnetic properties of nanocrystalline Co 50 Ni 50 alloy prepared by high energy planetary ball milling have been studied by means of scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry. The coercivity and the saturation magnetization of alloyed powders were measured at room temperature by a vibration sample magnetization. Morphological observations indicated a narrow distribution in the particle and homogeneous shape form with mean average particle size around 130 μm 2 . The results show that an allotropic Co transformation hcp→fcc occurs within the three first hours of milling and contrary to what expected, the Rietveld refinement method reveals the formation of two fcc solid solutions (SS): fcc Co(Ni) and Ni(Co) beside a small amount of the undissolved Co hcp. Thermal measurement, as a function of milling time was carried out to confirm the existence of the hcp phase and to estimate its amount. Magnetic measurement indicated that the 48 h milled powders with a steady state particles size have the highest saturation (105.3 emu/g) and the lowest coercivity (34.5 Oe). - Highlights: → By using the Rietveld refinement method we found that Co 50 Ni 50 alloy, milled for 48 h, contains two fcc solid solutions: fcc Co(Ni) and Ni(Co), beside a small amount of the undissolved Co hcp. DSC measurement as a function of milling time was carried out to confirm the existence of the hcp phase and to estimate its amount. → By means of imageJ we found the area distribution and not just the diameter distribution. → The coercivity is strongly related to the particles size distribution.

The most essential tendencies in development of powder metallurgy

International Nuclear Information System (INIS)

Fedorchenko, I.M.

1989-01-01

A progress in the sphere of creation and application of new types of powder materials is characterized. The materials are as follows: structural, tribotechnical, composite, reinforced, precipitation-hardened, refractory, tool, materials based on light metals and others. A number of important problems whose solution will promote a further development of powder metallurgy are formulated

Fat properties during homogenization, spray-drying, and storage affect the physical properties of dairy powders.

Science.gov (United States)

Vignolles, M L; Lopez, C; Madec, M N; Ehrhardt, J J; Méjean, S; Schuck, P; Jeantet, R

2009-01-01

Changes in fat properties were studied before, during, and after the drying process (including during storage) to determine the consequences on powder physical properties. Several methods were combined to characterize changes in fat structure and thermal properties as well as the physical properties of powders. Emulsion droplet size and droplet aggregation depended on the homogenizing pressures and were also affected by spray atomization. Aggregation was usually greater after spray atomization, resulting in greater viscosities. These processes did not have the same consequences on the stability of fat in the powders. The quantification of free fat is a pertinent indicator of fat instability in the powders. Confocal laser scanning microscopy permitted the characterization of the structure of fat in situ in the powders. Powders from unhomogenized emulsions showed greater free fat content. Surface fat was always overrepresented, regardless of the composition and process parameters. Differential scanning calorimetry melting experiments showed that fat was partially crystallized in situ in the powders stored at 20 degrees C, and that it was unstable on a molecular scale. Thermal profiles were also related to the supramolecular structure of fat in the powder particle matrix. Powder physical properties depended on both composition and process conditions. The free fat content seemed to have a greater influence than surface fat on powder physical properties, except for wettability. This study clearly showed that an understanding of fat behavior is essential for controlling and improving the physical properties of fat-filled dairy powders and their overall quality.

Thermodynamic and transport properties of uranium dioxide and related phases

International Nuclear Information System (INIS)

1965-01-01

The high melting point of uranium dioxide and its stability under irradiation have led to its use as a fuel in a variety of types of nuclear reactors. A wide range of chemical and physical studies has been stimulated by this circumstances and by the complex nature of the uranium dioxide phase itself. The boundaries of this phase widen as the temperature is increased; at 2000 deg. K a single, homogeneous phase exists from U 2.27 to a hypostoichiometric (UO 2-x ) composition, depending on the oxygen potential of the surroundings. Since there is often an incentive to operate a reactor at the maximum practicable heat rating and, therefore, maximum thermal gradient in the fuel, the determination of the physical properties of the UO 2-x phase becomes a matter of great technological importance. In addition a complex sequence of U-O phases may be formed during the preparation of powder feed material or during the sintering process; these affect the microstructure and properties of the final product and have also received much attention. 184 refs, 33 figs, 15 tabs

Synthesis of alumina powders by precipitation method and solvothermal treatment

International Nuclear Information System (INIS)

Politchuk, J.O.; Lima, N.B.; Lazar, D.R.R.; Ussui, V.; Yoshito, W.K.

2012-01-01

The improvement of alumina powders synthesis processes has been focused on the preparation of ceramic powders with well defined crystalline structure and with high specific surface area and nanometric particle size without formation of hard agglomerates. For this purpose the precipitation step should be studied and and also the temperature of alumina crystallization should be reduced. The aim of this study was to obtain alumina powders by hydroxide precipitation with ammonia in the presence of cationic surfactant, followed by solvothermal treatment and calcination. The powders were characterized by TG/DTA, X-ray diffraction, surface area measurements by gas adsorption (BET) and scanning electron microscopy. The results showed that powders produced by solvothermal treatment without surfactant have higher crystallinity. However the presence of CTAB enhances 240% the specific surface area compared with powders produced without this reagent (author)

Structural and Optical Properties of ZnO Thin Film Prepared by Oxidation of Zn Metal Powders

International Nuclear Information System (INIS)

Hassan, N.K.; Hashim, M.R.

2013-01-01

High quality ZnO nano structures have been fabricated at room temperature by a simple vacuum thermal evaporator from metallic Zn powders (99.999 % purity) on a silicon (100) substrate. The Zn thin films were then transferred into a thermal tube furnace for oxidation at 700 degree Celsius for different time durations. Time was found to be a critical factor in the synthesis. This was followed by characterization of their morphological, structural and optical properties. The morphology of the grown ZnO nano structures exhibited several large grains, which increased gradually with increasing oxidation time. The crystallinity of the grown nano structures was investigated using X-ray diffraction, revealing that the synthesized ZnO was in hexagonal wurtzite phase. The photoluminescence (PL) spectra of the fabricated ZnO nano structures showed high intensity peak in the UV region due to near-band-edge (NBE) emission in which the structures oxidized for 30 min showing highest intensity. (author)

Microwave assisted growth of nanorods vanadium dioxide VO2 (R): structural and electrical properties

Science.gov (United States)

Derkaoui, I.; Khenfouch, M.; Mothudi, B. M.; Moloi, S. J.; Zorkani, I.; Jorio, A.; Maaza, M.

2018-03-01

Nanostructured metal oxides have attracted a lot of attention recently owning to their unique structural advantages and demonstrated promising chemical and physical properties for various applications. In this study, we report the structural and electrical properties of vanadium dioxide VO2 (R) prepared via a single reaction microwave (SRC) synthesis. Our results are revealing that the components of VO2 (R) films have a rod-like shape with a uniform size distribution. The nanorods with very smooth and flat surfaces have a typical length of up to 2μm and a width of about several nanometers. The structural investigations reveal the high crystallinity of VO2 (R) ensuring good electrical contact and showing a high conductivity as a function of temperature. This synthesis method provides a new simple route to fabricate one-dimensional nanostructured metal oxides which is suitable for a large field of applications especially for smart windows.

Three-dimensional ordered titanium dioxide-zirconium dioxide film-based microfluidic device for efficient on-chip phosphopeptide enrichment.

Science.gov (United States)

Zhao, De; He, Zhongyuan; Wang, Gang; Wang, Hongzhi; Zhang, Qinghong; Li, Yaogang

2016-09-15

Microfluidic technology plays a significant role in separating biomolecules, because of its miniaturization, integration, and automation. Introducing micro/nanostructured functional materials can improve the properties of microfluidic devices, and extend their application. Inverse opal has a three-dimensional ordered net-like structure. It possesses a large surface area and exhibits good mass transport, making it a good candidate for bio-separation. This study exploits inverse opal titanium dioxide-zirconium dioxide films for on-chip phosphopeptide enrichment. Titanium dioxide-zirconium dioxide inverse opal film-based microfluidic devices were constructed from templates of 270-, 340-, and 370-nm-diameter poly(methylmethacrylate) spheres. The phosphopeptide enrichments of these devices were determined by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. The device constructed from the 270-nm-diameter sphere template exhibited good comprehensive phosphopeptide enrichment, and was the best among these three devices. Because the size of opal template used in construction was the smallest, the inverse opal film therefore had the smallest pore sizes and the largest surface area. Enrichment by this device was also better than those of similar devices based on nanoparticle films and single component films. The titanium dioxide-zirconium dioxide inverse opal film-based device provides a promising approach for the efficient separation of various biomolecules. Copyright © 2016 Elsevier Inc. All rights reserved.

Neutron Powder Diffraction and Constrained Refinement

DEFF Research Database (Denmark)

Pawley, G. S.; Mackenzie, Gordon A.; Dietrich, O. W.

1977-01-01

The first use of a new program, EDINP, is reported. This program allows the constrained refinement of molecules in a crystal structure with neutron diffraction powder data. The structures of p-C6F4Br2 and p-C6F4I2 are determined by packing considerations and then refined with EDINP. Refinement is...

Aluminum powder size and microstructure effects on properties of boron nitride reinforced aluminum matrix composites fabricated by semi-solid powder metallurgy

International Nuclear Information System (INIS)

Chen, Cunguang; Guo, Leichen; Luo, Ji; Hao, Junjie; Guo, Zhimeng; Volinsky, Alex A.

2015-01-01

Al matrix composite reinforced by hexagonal boron nitride (h-BN) with nearly full densification was successfully fabricated by the semi-solid powder metallurgy technique. The h-BN/Al composites were synthesized with elemental pure Al powder size of d_5_0=35, 12 and 2 μm. The powder morphology and the structural characteristics of the composites were analyzed using X-ray diffraction, scanning and transmission electron microscopy. The density, Brinell hardness and compressive behavior of the samples were characterized. Density measurement of the Al composites revealed that the composite densification can be effectively promoted by plenty of embedded liquid phase under pressure. Composites prepared using Al powder with varying granularity showed different grain characteristics, and in situ recrystallization occurred inside the original grains with 35 μm Al powder. A sharp interface consisting of Al/Al_2O_3/h-BN was present in the composites. Both the compressive strength and the fracture strain of the investigated composites increased with the decrease of the Al powder size, along with the Brinell hardness. The composite with 2 μm Al powder exhibited the highest relative density (99.3%), Brinell harness (HB 128), compressive strength (763 MPa) and fracture strain (0.299).

The production of sinterable uranium dioxide from ammonium diuranate

International Nuclear Information System (INIS)

Fane, A.G.; Le Page, A.H.

1975-02-01

The development of a 0.13 m diameter pulsed fluidised bed reactor for the continuous production of sinterable uranium dioxide from ammonium diuranate is described. Calcination-reduction at 670 to 680 0 C produced powders with surface areas of 4 to 6 m 2 g -1 giving pellet densities in excess of 10.6 g cm -3 . Sinterability was relatively insensitive to changes in operating conditions, provided the availability of hydrogen was adequate, for gas flow rates in the range 0.95 to 1.4 l S -1 , pulse frequencies of 0.5 and 0.75 Hz and mean residence times of the solids from 0.6 to 1.4 hours. Sinterability was shown to be improved either by use of higher input concentrations, or by use of a secondary flow of hydrogen (about 5 per cent of input) fed into the powder collection system and flowing countercurrent to the UO 2 product. The maximum throughput of 17 kg UO 2 h -1 (0.6 hours mean residence time) required only 120 per cent of the stoichiometric requirement at an input concentration of 50 vol.per cent with secondary hydrogen flow. Results are given for studies of the kinetics of reduction of calcined ammonia diuranate in hydrogen and the residence time distribution of solids in a pulsed fluidised bed. Estimates based on these data suggested that the overall conversion of ammonium diuranate to uranium dioxide in the continuously operated pulsed fluidised bed reactor was in excess of 99 per cent. Continuous stabilisation of the UO 2 product was demonstrated at 12 kg h -1 or UO 2 , in a 0.15 m diameter glass stabiliser, using 10 vol.per cent air in nitrogen and a temperature of about 50 0 C. (author)

New Strategies for Powder Compaction in Powder-based Rapid Prototyping Techniques

NARCIS (Netherlands)

Budding, A.; Vaneker, Thomas H.J.

2013-01-01

In powder-based rapid prototyping techniques, powder compaction is used to create thin layers of fine powder that are locally bonded. By stacking these layers of locally bonded material, an object is made. The compaction of thin layers of powder mater ials is of interest for a wide range of

Strength Improvement of Clay Soil by Using Stone Powder

Directory of Open Access Journals (Sweden)

Ahmed Sameer Abdulrasool

2015-05-01

Full Text Available Soil stabilization with stone powder is a good solution for the construction of subgrade for road way and railway lines, especially under the platforms and mostly in transition zones between embankments and rigid structures, where the mechanical properties of supporting soils are very influential. Stone powder often has a unique composition which justifies the need for research to study the feasibility of using this stone powder type for ground improvement applications. This paper presents results from a comprehensive laboratory study carried out to investigate the feasibility of using stone powder for improvement of engineering properties of clays. The stone powder contains bassanite (CaSO4. ½ H2O, and Calcite (CaCO3. Three percentages are used for stone powder (1%, 3% and 5% by dry weight of clay. Several tests are made to investigate the soil behavior after adding the stone powder (Atterberg limits, Standard Proctor density, Grain size distribution, Specific gravity, Unconfined Compressive test, and California bearing ratio test. Unconfined Compressive tests conducted at different curing. The samples are tested under both soaked and unsoaked condition. Chemical tests and X-ray diffraction analyses are also carried out. Stone powder reacts with clay producing decreasing in plasticity and The curves of grain size distribution are shifted to the coarse side as the stone powder percentage increase; the soil becomes more granular, and also with higher strength.

Characterization of Metal Powders Used for Additive Manufacturing.

Science.gov (United States)

Slotwinski, J A; Garboczi, E J; Stutzman, P E; Ferraris, C F; Watson, S S; Peltz, M A

2014-01-01

Additive manufacturing (AM) techniques can produce complex, high-value metal parts, with potential applications as critical parts, such as those found in aerospace components. The production of AM parts with consistent and predictable properties requires input materials (e.g., metal powders) with known and repeatable characteristics, which in turn requires standardized measurement methods for powder properties. First, based on our previous work, we assess the applicability of current standardized methods for powder characterization for metal AM powders. Then we present the results of systematic studies carried out on two different powder materials used for additive manufacturing: stainless steel and cobalt-chrome. The characterization of these powders is important in NIST efforts to develop appropriate measurements and standards for additive materials and to document the property of powders used in a NIST-led additive manufacturing material round robin. An extensive array of characterization techniques was applied to these two powders, in both virgin and recycled states. The physical techniques included laser diffraction particle size analysis, X-ray computed tomography for size and shape analysis, and optical and scanning electron microscopy. Techniques sensitive to structure and chemistry, including X-ray diffraction, energy dispersive analytical X-ray analysis using the X-rays generated during scanning electron microscopy, and X-Ray photoelectron spectroscopy were also employed. The results of these analyses show how virgin powder changes after being exposed to and recycled from one or more Direct Metal Laser Sintering (DMLS) additive manufacturing build cycles. In addition, these findings can give insight into the actual additive manufacturing process.

Characterization of Metal Powders Used for Additive Manufacturing

Science.gov (United States)

Slotwinski, JA; Garboczi, EJ; Stutzman, PE; Ferraris, CF; Watson, SS; Peltz, MA

2014-01-01

Additive manufacturing (AM) techniques1 can produce complex, high-value metal parts, with potential applications as critical parts, such as those found in aerospace components. The production of AM parts with consistent and predictable properties requires input materials (e.g., metal powders) with known and repeatable characteristics, which in turn requires standardized measurement methods for powder properties. First, based on our previous work, we assess the applicability of current standardized methods for powder characterization for metal AM powders. Then we present the results of systematic studies carried out on two different powder materials used for additive manufacturing: stainless steel and cobalt-chrome. The characterization of these powders is important in NIST efforts to develop appropriate measurements and standards for additive materials and to document the property of powders used in a NIST-led additive manufacturing material round robin. An extensive array of characterization techniques was applied to these two powders, in both virgin and recycled states. The physical techniques included laser diffraction particle size analysis, X-ray computed tomography for size and shape analysis, and optical and scanning electron microscopy. Techniques sensitive to structure and chemistry, including X-ray diffraction, energy dispersive analytical X-ray analysis using the X-rays generated during scanning electron microscopy, and X-Ray photoelectron spectroscopy were also employed. The results of these analyses show how virgin powder changes after being exposed to and recycled from one or more Direct Metal Laser Sintering (DMLS) additive manufacturing build cycles. In addition, these findings can give insight into the actual additive manufacturing process. PMID:26601040

More bad news about carbon dioxide emissions

International Nuclear Information System (INIS)

Stonehouse, D.

2000-01-01

The affect that increased carbon dioxide concentrations has on plants and animals was discussed. Most research focuses on the impacts that carbon dioxide concentrations has on climatic change. Recent studies, however, have shown that elevated levels of carbon dioxide in the atmosphere caused by burning fossils fuels changes the chemical structure of plants and could lead to significant disruptions in ecological food chains. High carbon dioxide levels cause plants to speed up photosynthesis, take in the gas, and use the carbon to produce more fibre and starch while giving off oxygen as a byproduct. As plants produce more carbon, their levels of nitrogen diminish making them less nutritious for the insects and animals that feed on them. This has serious implications for farmers, as pests would have to eat more of their crops to survive. In addition, farmers would have to supplement livestock with nutrients

Three-dimensional electron diffraction as a complementary technique to powder X-ray diffraction for phase identification and structure solution of powders

Directory of Open Access Journals (Sweden)

Yifeng Yun

2015-03-01

Full Text Available Phase identification and structure determination are important and widely used techniques in chemistry, physics and materials science. Recently, two methods for automated three-dimensional electron diffraction (ED data collection, namely automated diffraction tomography (ADT and rotation electron diffraction (RED, have been developed. Compared with X-ray diffraction (XRD and two-dimensional zonal ED, three-dimensional ED methods have many advantages in identifying phases and determining unknown structures. Almost complete three-dimensional ED data can be collected using the ADT and RED methods. Since each ED pattern is usually measured off the zone axes by three-dimensional ED methods, dynamic effects are much reduced compared with zonal ED patterns. Data collection is easy and fast, and can start at any arbitrary orientation of the crystal, which facilitates automation. Three-dimensional ED is a powerful technique for structure identification and structure solution from individual nano- or micron-sized particles, while powder X-ray diffraction (PXRD provides information from all phases present in a sample. ED suffers from dynamic scattering, while PXRD data are kinematic. Three-dimensional ED methods and PXRD are complementary and their combinations are promising for studying multiphase samples and complicated crystal structures. Here, two three-dimensional ED methods, ADT and RED, are described. Examples are given of combinations of three-dimensional ED methods and PXRD for phase identification and structure determination over a large number of different materials, from Ni–Se–O–Cl crystals, zeolites, germanates, metal–organic frameworks and organic compounds to intermetallics with modulated structures. It is shown that three-dimensional ED is now as feasible as X-ray diffraction for phase identification and structure solution, but still needs further development in order to be as accurate as X-ray diffraction. It is expected that three

Three-dimensional electron diffraction as a complementary technique to powder X-ray diffraction for phase identification and structure solution of powders.

Science.gov (United States)

Yun, Yifeng; Zou, Xiaodong; Hovmöller, Sven; Wan, Wei

2015-03-01

Phase identification and structure determination are important and widely used techniques in chemistry, physics and materials science. Recently, two methods for automated three-dimensional electron diffraction (ED) data collection, namely automated diffraction tomography (ADT) and rotation electron diffraction (RED), have been developed. Compared with X-ray diffraction (XRD) and two-dimensional zonal ED, three-dimensional ED methods have many advantages in identifying phases and determining unknown structures. Almost complete three-dimensional ED data can be collected using the ADT and RED methods. Since each ED pattern is usually measured off the zone axes by three-dimensional ED methods, dynamic effects are much reduced compared with zonal ED patterns. Data collection is easy and fast, and can start at any arbitrary orientation of the crystal, which facilitates automation. Three-dimensional ED is a powerful technique for structure identification and structure solution from individual nano- or micron-sized particles, while powder X-ray diffraction (PXRD) provides information from all phases present in a sample. ED suffers from dynamic scattering, while PXRD data are kinematic. Three-dimensional ED methods and PXRD are complementary and their combinations are promising for studying multiphase samples and complicated crystal structures. Here, two three-dimensional ED methods, ADT and RED, are described. Examples are given of combinations of three-dimensional ED methods and PXRD for phase identification and structure determination over a large number of different materials, from Ni-Se-O-Cl crystals, zeolites, germanates, metal-organic frameworks and organic compounds to intermetallics with modulated structures. It is shown that three-dimensional ED is now as feasible as X-ray diffraction for phase identification and structure solution, but still needs further development in order to be as accurate as X-ray diffraction. It is expected that three-dimensional ED methods

Structure-Activity Relationships for Rates of Aromatic Amine Oxidation by Manganese Dioxide

International Nuclear Information System (INIS)

Salter-Blanc, Alexandra J.; Lyon, Molly A.; Science University, Portland, OR; Ness, Stuart C.; Science University, Portland, OR; Tratnyek, Paul G.; Science University, Portland, OR

2016-01-01

New energetic compounds are designed to minimize their potential environmental impacts, which includes their transformation and the fate and effects of their transformation products. The nitro groups of energetic compounds are readily reduced to amines, and the resulting aromatic amines are subject to oxidation and coupling reactions. Manganese dioxide (MnO 2 ) is a common environmental oxidant and model system for kinetic studies of aromatic amine oxidation. Here in this study, a training set of new and previously reported kinetic data for the oxidation of model and energetic-derived aromatic amines was assembled and subjected to correlation analysis against descriptor variables that ranged from general purpose [Hammett σ constants (σ − ), pK a s of the amines, and energies of the highest occupied molecular orbital (E HOMO )] to specific for the likely rate-limiting step [one-electron oxidation potentials (E ox )]. The selection of calculated descriptors (pK a ), E HOMO , and E ox ) was based on validation with experimental data. All of the correlations gave satisfactory quantitative structure-activity relationships (QSARs), but they improved with the specificity of the descriptor. The scope of correlation analysis was extended beyond MnO 2 to include literature data on aromatic amine oxidation by other environmentally relevant oxidants (ozone, chlorine dioxide, and phosphate and carbonate radicals) by correlating relative rate constants (normalized to 4-chloroaniline) to E HOMO (calculated with a modest level of theory).

The magnetic properties of powdered and compacted microcrystalline permalloy

International Nuclear Information System (INIS)

Kollar, P.; Oleksakova, D.; Fuezer, J.; Kovac, J.; Roth, S.; Polanski, K.

2007-01-01

The aim of this work is to investigate the magnetic properties of powdered and compacted microcrystalline Ni-Fe (81 wt% of Ni) permalloy. It was found by investigating the influence of mechanical milling on the magnetic properties of powder samples prepared by milling of the ribbon that the alloy remains a solid solution with stable structure during the whole milling process. With decreasing particle size the rotation of magnetization vector gradually becomes dominant magnetization process and thus coercivity increases. After compaction of the powder by uniaxial hot pressing the magnetic contact between powder particles is recreated and for resulting bulk the displacement of the domain walls becomes dominant magnetization process with coercivity of 11 A/m (comparable with the coercivity of conventional permalloy)

Uniting Electron Crystallography and Powder Diffraction

CERN Document Server

Shankland, Kenneth; Meshi, Louisa; Avilov, Anatoly; David, William

2012-01-01

The polycrystalline and nanocrystalline states play an increasingly important role in exploiting the properties of materials, encompassing applications as diverse as pharmaceuticals, catalysts, solar cells and energy storage. A knowledge of the three-dimensional atomic and molecular structure of materials is essential for understanding and controlling their properties, yet traditional single-crystal X-ray diffraction methods lose their power when only polycrystalline and nanocrystalline samples are available. It is here that powder diffraction and single-crystal electron diffraction techniques take over, substantially extending the range of applicability of the crystallographic principles of structure determination.  This volume, a collection of teaching contributions presented at the Crystallographic Course in Erice in 2011, clearly describes the fundamentals and the state-of-the-art of powder diffraction and electron diffraction methods in materials characterisation, encompassing a diverse range of discipl...

Processing of tungsten csrap into powders by electroerosion dispersion

International Nuclear Information System (INIS)

Fominskij, L.P.; Myuller, A.S.; Levchuk, M.V.; Tarabrina, V.P.

1985-01-01

A powder produced by electroerosion dispersion in water from tungsten chips and rod cuttings is studied for its properties and structure. Powder particles are mainly of spherical shape, their predominant size is 2-4 μm. A fraction of -63 μm comprises a basic mass of the powder (up to 80%), an ultrafine (to 40 μm) phase of WO which is isolated by decantation comprises about 3.5% of its mass. The powder particles are low oxidized, have a fine-grain microstructure and consist of tungsten with admixture of β-W (to 30%). A fraction of total oxygen mass in the mixture of fractio s 0.74%. The powder containing less than 0.25% of oxygen is produced by decantation of the oxide phase. The product purity is determined exclusively by the purity of the raw material. Prior to producing articles it is recommended to anneal the powder either in the inert atmosphere or in the reduced medium at 750 deg C for β-W to transfer into common tungsten

Resolution of the crystal structure of the deficient perovskite LaNiO2.5 from neutron powder diffraction data

International Nuclear Information System (INIS)

Alonso, J.A.; Martinez-Lope, M.J.

1996-01-01

The oxygen-deficient perovskite LaNiO 2.5 has been prepared by controlled reduction of LaNiO 3 with Zr metal. The XRD pattern could be indexed in a monoclinic unit-cell with dimensions a 0 xa 0 xa 0 (a 0 : lattice parameter of the ideal cubic perovskite). The indexing of the neutron powder diffraction pattern needed a doubled cell to account for the superstructure reflections originated by the oxygen vacancy ordering and the tilting of the Ni coordination polyhedra. The structure was solved and refined from the neutron powder data. The oxygen vacancies are ordered in such a way that square planar NiO 4 and NiO 6 octahedra alternate in the ab plane along the [110] direction. Both kinds of Ni polyhedra are fairly distorted and tilted in order to optimize the La-O distances, giving rise to a highly strained structure of metastable character. In fact, the compound readily takes oxygen, above 175 C in air, to give the much more stable LaNiO 3 perovskite. (orig.)

Certification of a plutonium dioxide reference material for elemental analyses (EC-NRM 210)

International Nuclear Information System (INIS)

Le Duigou, Y.

1990-01-01

A new EC plutonium reference material is made available in the form of 5g samples of plutonium dioxide powder. Before weighing the material must be calcined at 1 250 0 C for two hours. The plutonium content (880.26 ± 0.44) g.kg -1 has been derived from plutonium measurements performed by three different laboratories each applying a different oxydo-reductive method. The results of the plutonium measurement, the statistical evaluation of the uncertainty of the plutonium content together with information on the impurities present in the material are given in the report

Combined Approach for the Structural Characterization of Alkali Fluoroscandates: Solid-State NMR, Powder X-ray Diffraction, and Density Functional Theory Calculations.

Science.gov (United States)

Rakhmatullin, Aydar; Polovov, Ilya B; Maltsev, Dmitry; Allix, Mathieu; Volkovich, Vladimir; Chukin, Andrey V; Boča, Miroslav; Bessada, Catherine

2018-02-05

The structures of several fluoroscandate compounds are presented here using a characterization approach combining powder X-ray diffraction and solid-state NMR. The structure of K 5 Sc 3 F 14 was fully determined from Rietveld refinement performed on powder X-ray diffraction data. Moreover, the local structures of NaScF 4 , Li 3 ScF 6 , KSc 2 F 7 , and Na 3 ScF 6 compounds were studied in detail from solid-state 19 F and 45 Sc NMR experiments. The 45 Sc chemical shift ranges for six- and seven-coordinated scandium environments were defined. The 19 F chemical shift ranges for bridging and terminal fluorine atoms were also determined. First-principles calculations of the 19 F and 45 Sc NMR parameters were carried out using plane-wave basis sets and periodic boundary conditions (CASTEP), and the results were compared with the experimental data. A good agreement between the calculated shielding constants and experimental chemical shifts was obtained. This demonstrates the good potential of computational methods in spectroscopic assignments of solid-state 45 Sc NMR spectroscopy.

Quality of clay-powders of industrial assortment

Energy Technology Data Exchange (ETDEWEB)

Lityayeva, Z A; Dzetl, B G; Goncharenko, N N; Naurova, I V; Rybchenko, V I; Voyevodin, L I

1979-01-01

Nomenclature was developed for the quality indicators of clay powders which took into consideration the foreign experience, and it is suggested that a suspension of clay powders be viewed as the simplest type of drilling. In this case the technique of preparing the suspensions approaches the maximum to that used in the recommended standard (TU-39-043-074). The output of solution is determined with standardized effective viscosity /eta/ ef =/sup 20/ /SUP cP/ on a series domestic rotary viscosimeter VSN-3 with gradient of shear velocity EPSILON=666 sec/sup -1/; with EPSILON=1022 sec /sup -1//eta/ /SUB ef/ = 15 cP. This makes it possible to obtain data comparable to the foreign standards regarding the output of the fluid from the powders. According to the suggested technique, the clay powder is dispersed for 20-30 minutes in water or saturated solution of NaC1 in a mixing unit ''Voronezh2'' with rotation frequency of 9000 rpm, is left to rest and is again dispersed for 15 minutes. Then the dynamic shear stress (P /SUB k2/ ), plastic viscosity (/eta/ /SUB ef/ ), coefficients of coagulation (K /SUB c/ ) and thyxotropic (K /SUB T/ ) structure-formation are defined. Measurements are made on the instrument FLR-1 of water output with 0.7 (B) or 0.1 (B) MPa. According to this technique, a comparison was made of the domestic powders of industrial assortment with the powder ''Aquagel'' widely used abroad. It was established that only the modified concrete powders with correct selection of reagents can compete with the foreign.

Crystal structure solution of hydrides containing natEu from neutron powder diffraction data

International Nuclear Information System (INIS)

Kohlmann, H.

1999-01-01

Complete text of publication follows. The location of hydrogen in crystal structures of metal hydrides usually requires neutron diffraction data. Some elements, however, show excessively high absorption cross sections, σ a , for neutrons, thus making this technique seemingly impractical. Therefore no complete, refined crystal structure data of europium hydrides (σ a ( nat Eu) = .4530 barns at λ = 179.8 pm [1]) have been reported so far. It is shown that the absorption can be reduced to a value reasonable for neutron diffraction experiments by taking advantage of the wavelength dependence of σ a combined with the use of annular samples at advanced diffractometers. Neutron powder diffraction data on several nat Eu containing deuterides suitable for the ab initio crystal structure solution and refinement have been taken at D20 and D4 (ILL, Grenoble). The crystal chemistry of these europium hydrides, among them the two new compounds EuMg 2 H 6 and EuMgH 4 [2], is discussed. (author) [1] V.F. Sears, Neutron News 1992, 3, 26-37.; [2] H. Kohlmann, F. Gingl, T. Hansen, K. Yvon, Angew. Chem. Int. Ed. Eng. 1999, 38, accepted

Application of Powder Diffraction Methods to the Analysis of the Atomic Structure of Nanocrystals: The Concept of the Apparent Lattice Parameter (ALP)

Science.gov (United States)

Palosz, B.; Grzanka, E.; Gierlotka, S.; Stelmakh, S.; Pielaszek, R.; Bismayer, U.; Weber, H.-P.; Palosz, W.; Curreri, Peter A. (Technical Monitor)

2002-01-01

The applicability of standard methods of elaboration of powder diffraction data for determination of the structure of nano-size crystallites is analysed. Based on our theoretical calculations of powder diffraction data we show, that the assumption of the infinite crystal lattice for nanocrystals smaller than 20 nm in size is not justified. Application of conventional tools developed for elaboration of powder diffraction data, like the Rietveld method, may lead to erroneous interpretation of the experimental results. An alternate evaluation of diffraction data of nanoparticles, based on the so-called 'apparent lattice parameter' (alp) is introduced. We assume a model of nanocrystal having a grain core with well-defined crystal structure, surrounded by a surface shell with the atomic structure similar to that of the core but being under a strain (compressive or tensile). The two structural components, the core and the shell, form essentially a composite crystal with interfering, inseparable diffraction properties. Because the structure of such a nanocrystal is not uniform, it defies the basic definitions of an unambiguous crystallographic phase. Consequently, a set of lattice parameters used for characterization of simple crystal phases is insufficient for a proper description of the complex structure of nanocrystals. We developed a method of evaluation of powder diffraction data of nanocrystals, which refers to a core-shell model and is based on the 'apparent lattice parameter' methodology. For a given diffraction pattem, the alp values are calculated for every individual Bragg reflection. For nanocrystals the alp values depend on the diffraction vector Q. By modeling different a0tomic structures of nanocrystals and calculating theoretically corresponding diffraction patterns using the Debye functions we showed, that alp-Q plots show characteristic shapes which can be used for evaluation of the atomic structure of the core-shell system. We show, that using a simple

Chemical compositions of spherical titanium powders prepared by RF induction plasma

International Nuclear Information System (INIS)

Gu Zhongtao; Jin Yuping; Ye Gaoying

2012-01-01

Spherical titanium powders were prepared by RF induction plasma technology. The particle size is essentially un- changed, while the particle size distribution is relatively narrow after spheroidization processing. X-ray diffraction (XRD) random testing of the spherical titanium powders shows no structure and phase changes. The content of O, H, N and C decreases, while the content of Ti increases slightly. It indicates that spheroidization with RF plasma can enhance powder purity. (authors)

Crystal structures of new cuprates containing CO3 analyzed by the Rietveld method of neutron powder diffraction

International Nuclear Information System (INIS)

Miyazaki, Y.; Yamane, H.; Kajitani, T.; Hiraga, K.; Hirai, T.; Morii, Y.; Funahashi, S.

1993-01-01

New compounds containing CO 3 groups, Sr 2 CuO 2 (CO 3 ), (C 0.4 Cu 0.6 )Sr 2 (Y 0.86 Sr 0.14 )Cu 2 O 7 and (C 0.35 Cu 0.65 )Sr 2 (Y 0.73 Ce 0.27 ) 2 Cu 2 O 9 , were prepared as stable phases at 1273-1303 K in a flowing gas of O 2 -CO 2 . The crystal structures of these compounds were refined by means of the Rietveld analysis for neutron powder diffraction data collected using a high resolution powder diffractometer (HRPD) in the JRR-3M reactor hall of the Japan Atomic Energy Research Institute (JAERI). Positions of CO 3 groups were satisfactorily determined. The distances of C-O bonds in the CO 3 groups were around 1.3A and the O-C-O angles were almost equal to the ideal bond angle of 120deg. (author)

Effect of composition and heat treatment on the phase formation of mechanically alloyed Cr-B and Mo-B powders

International Nuclear Information System (INIS)

Wu, H M; Hu, C J; Pai, K Y

2009-01-01

Blended elemental Cr-B and Mo-B powders in atomic ratio of 67:33, 50:50, and 20:80 were subjected to mechanical alloying up to 60 h and subsequent heat treatment to investigate effect of composition and heat treatment on the phase formation of Cr-B and Mo-B powders. It was studied by X-ray diffraction and differential thermal analysis. Mechanical alloying these powder mixtures for 60 h leads essentially to a amorphous structure except for the Mo 20 B 80 powder, which creates a partially amorphous MoB 4 structure. Annealing at lower temperatures relieves the strains cumulative in the milled powders and creates no new phase. The structures obtained after annealing the milled powders at higher temperature vary and depend on the overall composition of the powder mixtures. Annealing the milled Mo-B powders having greater Mo content ends up with a dissociation reaction at higher temperature.

Rietveld analysis, powder diffraction and cement

International Nuclear Information System (INIS)

Peterson, V.

2002-01-01

Full text: Phase quantification of cement is essential in its industrial use, however many methods are inaccurate and/or time consuming. Powder diffraction is one of the more accurate techniques used for quantitative phase analysis of cement. There has been an increase in the use of Rietveld refinement and powder diffraction for the analysis and phase quantification of cement and its components in recent years. The complex nature of cement components, existence of solid solutions, polymorphic variation of phases and overlapping phase peaks in diffraction patterns makes phase quantification of cements by powder diffraction difficult. The main phase in cement is alite, a solid solution of tricalcium silicate. Tricalcium silicate has been found to exist in seven modifications in three crystal systems, including triclinic, monoclinic, and rhombohedral structures. Hence, phase quantification of cements using Rietveld methods usually involves the simultaneous modelling of several tricalcium silicate structures to fit the complex alite phase. An industry ordinary Portland cement, industry and standard clinker, and a synthetic tricalcium silicate were characterised using neutron, laboratory x-ray and synchrotron powder diffraction. Diffraction patterns were analysed using full-profile Rietveld refinement. This enabled comparison of x-ray, neutron and synchrotron data for phase quantification of the cement and examination of the tricalcium silicate. Excellent Rietveld fits were achieved, however the results showed that the quantitative phase analysis results differed for some phases in the same clinker sample between various data sources. This presentation will give a short introduction about cement components including polymorphism, followed by the presentation of some problems in phase quantification of cements and the role of Rietveld refinement in solving these problems. Copyright (2002) Australian X-ray Analytical Association Inc

Influence of the peroxide group on the surface of titanium dioxide synthesized by the OPM route

International Nuclear Information System (INIS)

Santos, Estela Melare Ribeiro dos; Kubo, Andressa Mayumi; Gorup, Luiz Fernando; Francatto, Patricia; Souza Neto, Francisco Nunes de; Leite, Edson Roberto; Longo, Elson; Camargo, Emerson Rodrigues

2016-01-01

Full text: In the context of nanotechnology, there is a growing demand for environmentally sustainable solutions and technological innovations that are linked to reducing energy consumption and minimizing waste generation during the synthesis process. The Oxidant Peroxide Method for titanium dioxide synthesis (TiO 2 -OPM) is based on the oxidation of titanium ions to obtain nanometric powders that are highly reactive particles with controlled morphology. This method is easy and advantageous because it uses reagents of low toxicity, without the necessity to operate in inert atmosphere and at high temperatures. In this work, we obtained nanometric powders of TiO 2 -OPM from metallic titanium (TiO 2 -Met), and titanium isopropoxide (TiO 2 -Iso). Separately, the precursors reacts with hydrogen peroxide in ammoniacal medium in order to compare their reactivity by quantifying the peroxo groups on the surface. Scanning electronic microscopy (SEM) images showed nanoparticles of 10nm of both materials. X-ray diffraction (XRD) patterns showed typical structures of crystalline materials with mixture of anatase and rutile phase of titanium dioxide. Raman spectroscopy also cooperated with the XRD patterns showing vibrational modes of the mixture of phases (anatase and rutile) in both materials. Thermogravimetric analysis (TGA) showed that the two materials lost mass, in which in the first stage (80 - 125 deg C) occurred 24% of loss and in the second stage (235-265 deg C) is between 10% - 13%, and is related to the elimination of peroxo groups at the surface due to thermal treatment. Differential scanning calorimetry (DSC) revealed peaks related to exothermic decomposition of the peroxo groups (200 - 250 deg C) that coincided with peak rates of mass loss in the TGA. And the redox titration showed that the surface of the TiO 2 -Met had peroxo groups in 8.6 % w/w and 10.1 % w/w for TiO 2 -Iso, resulting in an increase of peroxo groups on the surface, making the TiO 2 -Iso route

Influence of the peroxide group on the surface of titanium dioxide synthesized by the OPM route

Energy Technology Data Exchange (ETDEWEB)

Santos, Estela Melare Ribeiro dos; Kubo, Andressa Mayumi; Gorup, Luiz Fernando; Francatto, Patricia; Souza Neto, Francisco Nunes de; Leite, Edson Roberto; Longo, Elson; Camargo, Emerson Rodrigues, E-mail: estelamelare@yahoo.com.br [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil)

2016-07-01

Full text: In the context of nanotechnology, there is a growing demand for environmentally sustainable solutions and technological innovations that are linked to reducing energy consumption and minimizing waste generation during the synthesis process. The Oxidant Peroxide Method for titanium dioxide synthesis (TiO{sub 2}-OPM) is based on the oxidation of titanium ions to obtain nanometric powders that are highly reactive particles with controlled morphology. This method is easy and advantageous because it uses reagents of low toxicity, without the necessity to operate in inert atmosphere and at high temperatures. In this work, we obtained nanometric powders of TiO{sub 2}-OPM from metallic titanium (TiO{sub 2}-Met), and titanium isopropoxide (TiO{sub 2}-Iso). Separately, the precursors reacts with hydrogen peroxide in ammoniacal medium in order to compare their reactivity by quantifying the peroxo groups on the surface. Scanning electronic microscopy (SEM) images showed nanoparticles of 10nm of both materials. X-ray diffraction (XRD) patterns showed typical structures of crystalline materials with mixture of anatase and rutile phase of titanium dioxide. Raman spectroscopy also cooperated with the XRD patterns showing vibrational modes of the mixture of phases (anatase and rutile) in both materials. Thermogravimetric analysis (TGA) showed that the two materials lost mass, in which in the first stage (80 - 125 deg C) occurred 24% of loss and in the second stage (235-265 deg C) is between 10% - 13%, and is related to the elimination of peroxo groups at the surface due to thermal treatment. Differential scanning calorimetry (DSC) revealed peaks related to exothermic decomposition of the peroxo groups (200 - 250 deg C) that coincided with peak rates of mass loss in the TGA. And the redox titration showed that the surface of the TiO{sub 2}-Met had peroxo groups in 8.6 % w/w and 10.1 % w/w for TiO{sub 2}-Iso, resulting in an increase of peroxo groups on the surface, making

Development and characterization of nifedipine-amino methacrylate copolymer solid dispersion powders with various adsorbents

Directory of Open Access Journals (Sweden)

Yotsanan Weerapol

2017-07-01

Full Text Available Solid dispersions of nifedipine (NDP, a poorly water-soluble drug, and amino methacrylate copolymer (AMCP with aid of adsorbent, that is, fumed silica, talcum, calcium carbonate, titanium dioxide, and mesoporous silica from rice husks (SRH, were prepared by solvent method. The physicochemical properties of solid dispersions, compared to their physical mixtures, were determined using powder X-ray diffractometry (PXRD and differential scanning calorimetry (DSC. The surface morphology of the prepared solid dispersions was examined by scanning electron microscopy (SEM. The dissolution of NDP from solid dispersions was compared to NDP powders. The effect of adsorbent type on NDP dissolution was also examined. The dissolution of NDP increased with the ratio of NDP:AMCP:adsorbent of 1:4:1 when compared to the other formulations. As indicated from PXRD patterns, DSC thermograms and SEM images, NDP was molecularly dispersed within polymer carrier or in an amorphous form, which confirmed the better dissolution of solid dispersions. Solid dispersions containing SRH provided the highest NDP dissolution, due to a porous nature of SRH, allowing dissolved drug to fill in the pores and consequently dissolve in the medium. The results suggested that solid dispersions containing adsorbents (SRH in particular demonstrated improved dissolution of poorly water-soluble drug when compared to NDP powder.

Powder preparation technics for SnO2 with submycrometrics particles

International Nuclear Information System (INIS)

Hiratsuka, R.S.; Pulcinelli, S.H.; Santilli, C.V.; Masetto, S.R.

1989-01-01

Preparation of SnO 2 fine powders is a pointer research because of this application as gas detecting sensors. This work shows basicaly two powder preparation methods: i) from metalic tin oxidation with nitric acid, ii) from SnCl 4 hydrolysis in aquous solution of amonia hydroxides. It was analysed the concentration of nitric acid and the pH of precipitation influency of the structural and morphologic characteristics of the obtained powders. The materials were characterized by X-ray diffraction, infra-red spectroscopy and specific surface area [pt

In-house characterization of protein powder

DEFF Research Database (Denmark)

Hartmann, Christian Grundahl; Harris, Pernille; Ståhl, Kenny

2011-01-01

. For safe identification of the crystal form the experimental patterns have to be compared with patterns calculated from known crystal structures. Very good agreement with Protein Data Bank data was obtained after including corrections for background, unit cell parameters, disordered bulk......Collecting protein powder diffraction data on standard in-house powder diffractometers requires careful handling of the samples. Specially designed sample holders combined with optimized collimation were found to be the key factors in improving the data quality and reducing the data collection time......-solvent, and geometric factors. The data collection and correction procedures were demonstrated by the identification of three different crystal forms of insulin....

Determination of the structure factors of a LiF powder sample by the energy dispersive x-ray diffraction

International Nuclear Information System (INIS)

Uno, R.; Ahtee, A.; Paakkari, T.

1977-01-01

The structure factors of a LiF powder sample were determined by energy dispersive x-ray diffraction in the range 9 to 25 keV, with the use of a Si(Li) solid state detector, following the method applied on GaP. Since the absorption coefficient of LiF is small at high energy, a fraction of the incident x-rays penetrates through the sample and does not contribute to the diffraction. This effect was taken into account in the determination of the structure factors. Then the structure factors generally agree, within the limit of 5 % error, with those obtained by the usual angle dispersive method, if the penetrated part of the incident beam is less than 40 %. (author)

Structural study of CaMn_1_−_xMo_xO_3 (0.08 ≤ x ≤ 0.12) system by neutron powder diffraction

International Nuclear Information System (INIS)

Supelano, G.I.; Parra Vargas, C.A.; Barón-González, A.J.; Sarmiento Santos, A.; Frontera, C.

2016-01-01

Neutron powder diffraction experiments and magnetic measurements in polycrystalline CaMn_1_−_xMo_xO_3 (x = 0.08, 0.10, 0.12) point towards a possible charge and orbital order in this system. The analysis of structural and magnetic data show that the samples present structural phase transformation from Pnma to P2_1/m space group and the system has a C-type antiferromagnetic configuration at low temperature. A detailed analysis of the bond distances signals a small Jahn-Teller distortion of only one (x = 0.08) or of the two Mn ions (x = 0.10, 0.12). We identify the partially occupied e_g orbitals and this explains the C-type magnetic structure. - Highlights: • CaMn_1_−_xMo_xO_3 (x = 0.08, 0.10, 0.12) is investigated by neutron powder diffraction. • Analysis of individual Mn-O distances demonstrates the apparition of orbital order. • By symmetry analysis, we find that the low temperature magnetic structure is C-type. • Magnetic interactions foreseen by the orbital order explain the magnetic structure.

Spherical rhenium metal powder

International Nuclear Information System (INIS)

Leonhardt, T.; Moore, N.; Hamister, M.

2001-01-01

The development of a high-density, spherical rhenium powder (SReP) possessing excellent flow characteristics has enabled the use of advanced processing techniques for the manufacture of rhenium components. The techniques that were investigated were vacuum plasma spraying (VPS), direct-hot isostatic pressing (D-HIP), and various other traditional powder metallurgy processing methods of forming rhenium powder into near-net shaped components. The principal disadvantages of standard rhenium metal powder (RMP) for advanced consolidation applications include: poor flow characteristics; high oxygen content; and low and varying packing densities. SReP will lower costs, reduce processing times, and improve yields when manufacturing powder metallurgy rhenium components. The results of the powder characterization of spherical rhenium powder and the consolidation of the SReP are further discussed. (author)

Measurement of loose powder density

International Nuclear Information System (INIS)

Akhtar, S.; Ali, A.; Haider, A.; Farooque, M.

2011-01-01

Powder metallurgy is a conventional technique for making engineering articles from powders. Main objective is to produce final products with the highest possible uniform density, which depends on the initial loose powder characteristics. Producing, handling, characterizing and compacting materials in loose powder form are part of the manufacturing processes. Density of loose metallic or ceramic powder is an important parameter for die design. Loose powder density is required for calculating the exact mass of powder to fill the die cavity for producing intended green density of the powder compact. To fulfill this requirement of powder metallurgical processing, a loose powder density meter as per ASTM standards is designed and fabricated for measurement of density. The density of free flowing metallic powders can be determined using Hall flow meter funnel and density cup of 25 cm/sup 3/ volume. Density of metal powders like cobalt, manganese, spherical bronze and pure iron is measured and results are obtained with 99.9% accuracy. (author)

The influence of the long time milling on the structure and magnetic properties of the Fe-Cu-Nb-Si-B powder

International Nuclear Information System (INIS)

Fechova, E.; Kollar, P.; Fuezer, J.; Kovac, J.; Petrovic, P.; Kavecansky, V.

2004-01-01

We have studied the influence of milling on the structure and magnetic properties of Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 powder prepared in a vibratory micro-mill as a function of long milling time. Three powder samples have been prepared and investigated (the first one was prepared by the milling of amorphous ribbon, the second one by milling of the same ribbon in a partially nanocrystallized state and the third one by milling of pure elements). Structural analysis shows the decrease of the grain size with the increasing time of milling. The coercivity of the samples prepared from pure elements increases almost linearly up to 1700 h of milling while further milling leads to the saturation at 25 kA/m (at the milling time of 3500 h). The coercivity of the samples milled from ribbons increases to its maximum of 8 kA/m for the milling time of 800 h and then decreases

The (2 × 2) tunnels structured manganese dioxide nanorods with α phase for lithium air batteries

Science.gov (United States)

Ghouri, Zafar Khan; Zahoor, Awan; Barakat, Nasser A. M.; Alsoufi, Mohammad S.; Bawazeer, Tahani M.; Mohamed, Ahmed F.; Kim, Hak Yong

2016-02-01

The (2 × 2) tunnels structured manganese dioxide nanorods with α phase (α-MnO2) are synthesized via simplistic hydrothermal method at low temperature. The obtained tunnels structured α-MnO2 nanorods are characterized by, Transmission electron microscopy, Scanning electron microscopy, and X-ray diffraction techniques. The oxygen reduction reaction (ORR) activity was studied by cyclic voltammetry and rotating ring-disc electrode voltammetry techniques in alkaline media. Moreover; the highly electrocatalytic tunnels structured α-MnO2 nanorods were then also applied as cathode in rechargeable Li-O2 cells. The Li-O2 cells exhibited initial discharge capacity as high as ∼4000 mAh/g with the tunnels structured α-MnO2 nanorods which was double the original capacity of the cells without any catalyst. Also we obtained 100% round trip efficiency upon cycling with limited capacity for more than 50 cycles.

Functional coordination polymers and MOFs from reactions of the lanthanides and barium with azole ligands. Synthesis and characterization with a focus on structure determination from X-ray powder diffraction data

International Nuclear Information System (INIS)

Rybak, Jens-Christoph

2012-01-01

This thesis deals with the synthesis and characterization of coordination polymers and MOFs of the lanthanides and barium with different azolic N-heterocycles. A total of 18 new organic-inorganic hybrid materials, as well as a series of co-doped compounds is presented. Besides the structural characterization of these materials from X-ray diffraction powder data, the focus of the investigations is on the thermal and photoluminescence spectroscopic properties. The lanthanides La - Lu, except Eu and Pm, can be reacted with 1H-1,2,3-triazole to give the series of the isotypic dense 3D-MOFs 3 ∞ [Ln(Tz * ) 3 ]. Investigation of the photoluminescence properties of these compounds reveals a broad range of different luminescence phenomena, including the first observation of an intrinsic inner-filter effect of the Ln 3+ -ions. The structure of this isotypic series of compounds was solved and refined from X-ray powder diffraction data. A 2D-polymorph of these compounds 2 ∞ [Ln(Tz * ) 3 ], is observed for Ln = Sm, Tb and was characterized by single crystal data. The reaction of Eu with 1H-benzotriazole yields the 1D-coordination polymer 1 ∞ [Eu(Btz) 2 (BtzH) 2 ], which is the first example of a divalent rare earth benzotriazolate. Analysis of the thermal properties reveals the transformation to the 3D-MOF 3 ∞ [Eu(Btz) 2 ] at higher temperatures. The structure of this material was also solved from X-ray powder diffraction data. Investigation of the photoluminescence properties of the co-doped compounds 3 ∞ [Ba 1-x Eu x (Im) 2 ], which were obtained from reaction of the salt-like hydrides BaH 2 and EuH 2 with imidazole, show that the synthesis of luminescent MOF materials by co-doping of non-luminescent networks with luminescence centers is possible. The structure of these materials was solved from X-ray powder diffraction data of the undoped compound 3 ∞ [BaEu(Im) 2 ]. Structural characterization of materials from X-ray powder diffraction data is an important aspect

Feasibility study for application of the marine coral powder as a novel adsorbent for Volatile Organic Hydrocarbons

Directory of Open Access Journals (Sweden)

Alireza Mashkoori

2015-06-01

Full Text Available The marine coral has a porous outer surface and it has served in the processes such as water treatment systems, removal of carbon dioxide and adsorption of arsenic. Based on the need for cheap and efficient adsorbents, in sampling, the aim of this study, comparison of the efficiency of marine coral powder and activated charcoal in adsorption of volatile organic hydrocarbons was considered. In this experimental research, a certain concentrations of 8 volatile organic hydrocarbons: (para-Xylene, Chloroform, Carbon tetrachloride, tert-Butanol, Pyridine, Acetone, Ethyl acetate and Diethyl ether was injected into dynamic atmospheric chamber in the NTP (Normal Temperature and Pressure conditions. Air sampling was performed with the tube containing marine coral powder as well as the tube of activated charcoal, based on the standard method of NIOSH (National Institute of Occupational Safety and Health and in the same laboratory conditions. Then samples were injected into the gas Chromatograph apparatus and analytical comparison has been done between the amount of adsorption of hydrocarbons by activated charcoal and coral powder-test and Mann-Whitney were done with SPSS V.20.Findings showed that there was a significant difference between the amount of adsorption of Para-Xylene, carbon tetrachloride, tert-Butanol, Pyridine, acetone and Ethyl acetate hydrocarbons by activated charcoal and coral powder (P<0.05(. The amount of hydrocarbons adsorption by activated charcoal was, more than coral powder significantly (P<0.001. Based on the present research, in sampling of used hydrocarbons, the marine coral powder was less efficient than the activated charcoal, and it is recommended that more works be designed about other techniques such as coating of the marine coral powder in order to the improvement of adsorption capacity for volatile organic hydrocarbons.

Phase transition of Ni-Mn-Ga alloy powders prepared by vibration ball milling

International Nuclear Information System (INIS)

Tian, B.; Chen, F.; Tong, Y.X.; Li, L.; Zheng, Y.F.; Liu, Y.; Li, Q.Z.

2011-01-01

Research highlights: → The vibration ball milling with a high milling energy introduces the atomic disorder and large lattice distortion in the alloy during milling and makes the formation of disordered fcc structure phase in the alloy. → The transition temperature and activation energy for disordered fcc → disordered bcc are ∼320 o C and 209 ± 8 kJ/mol, respectively. → The alloy powders annealed at 800 o C for 1 h show a one-stage martensitic transformation with quite lower latent heat compared to the bulk alloy. - Abstract: This study investigated the phase transformation of the flaky shaped Ni-Mn-Ga powder particles with thickness around 1 μm prepared by vibration ball milling and post-annealing. The SEM, XRD, DSC and ac magnetic susceptibility measurement techniques were used to characterize the Ni-Mn-Ga powders. The structural transition of Heusler → disordered fcc occurred in the powders prepared by vibration ball milling (high milling energy) for 4 h, which was different from the structural transition of Heusler → disordered fct of the powders fabricated by planetary ball milling (low milling energy) for 4 h. The two different structures after ball milling should be due to the larger lattice distortion occurred in the vibration ball milling process than in the planetary ball milling process. The structural transition of disordered fcc → disordered bcc took place at ∼320 o C during heating the as-milled Ni-Mn-Ga powders, which was attributed to the elimination of lattice distortion caused by ball milling. The activation energy for this transition was 209 ± 8 kJ/mol. The Ni-Mn-Ga powder annealed at 800 o C mainly contained Heusler austenite phase at room temperature and showed a low volume of martensitic transformation upon cooling. The inhibition of martensitic transformation might be attributed to the reduction of grain size in the annealed Ni-Mn-Ga particles.

Development of semiindustrial technology for electrolytic powder production

International Nuclear Information System (INIS)

Suchkov, A.B.; Kovalev, B.F.; Zhbanov, A.M.; Rabinovich, E.M.; Sozina, A.L.

1978-01-01

The technology of the production of Fe, Mn, Cr, W pure metal powders by electrolysis of industrial waste in molten chloride-fluoride media with the addition of lower chlorides of refining metal was tested in laboratory and then in industrial electrolysers (2kA). The cathode deposit was subjected to hydrometallurgical treatment. Approximate technological parameters of electrorefining are presented. A high-temperature (700-1000 deg C) hydrogen annealing was applied to increase the quality and to change physicochemical and technological characteristics of electrolytic powders. The data on the chemical composition of Mowders are presented, testifying to their high purity. It is shown that electrolytic powders are not uniform in granulometric composition (from 1 to 100 μm), their particles being characterized mainly by the dendrite structure

Nonvolatile RRAM cells from polymeric composites embedding recycled SiC powders.

Science.gov (United States)

De Girolamo Del Mauro, Anna; Nenna, Giuseppe; Miscioscia, Riccardo; Freda, Cesare; Portofino, Sabrina; Galvagno, Sergio; Minarini, Carla

2014-10-21

Silicon carbide powders have been synthesized from tires utilizing a patented recycling process. Dynamic light scattering, Raman spectroscopy, SEM microscopy, and X-ray diffraction have been carried out to gather knowledge about powders and the final composite structure. The obtained powder has been proven to induce resistive switching in a PMMA polymer-based composite device. Memory effect has been detected in two-terminal devices having coplanar contacts and quantified by read-write-erase measurements in terms of level separation and persistence.

Effect of calcination temperature on the photocatalytic activity of TiO2 powders prepared by co-precipitation of TiCl3

International Nuclear Information System (INIS)

Yudoyono, Gatut; Ichzan, Nur; Zharvan, Vicran; Daniyati, Rizqa; Santoso, Hadi; Indarto, Bachtera; Pramono, Yono Hadi; Zainuri, Mochamad; Darminto

2016-01-01

The adsorption of basic dye methylene blue (MB) onto titanium dioxide (titania) powder that were prepared by coprecipitation method of TiCl 3 and NH 4 OH as iniatial material with different calcination temperature was studied to examine the photocatalytic activity. Synthesis process carried out by the solution pH was adjusted to be 8. Effect of calcination temperature on the titania powder were characterized with Differential Scanning Calorimetry/Thermogravimetry (DSC/TG), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM). The result of TG and XRD showed that the NH 4 Cl decomposed between 235-372°C. The XRD result showed that the anatase TiO 2 only contained a single phase when the calcination temperature of the precursor at 800°C, and over which it began to grow rutile phase. The influence of synthesis condition on the photocatalytic activity of TiO 2 powder was determined by the photodegradation of MB dye under UV light.

Fundamentals of powder metallurgy

International Nuclear Information System (INIS)

Khan, I.H.; Qureshi, K.A.; Minhas, J.I.

1988-01-01

This book is being presented to introduce the fundamentals of technology of powder metallurgy. An attempt has been made to present an overall view of powder metallurgy technology in the first chapter, whereas chapter 2 to 8 deal with the production of metal powders. The basic commercial methods of powder production are briefly described with illustrations. Chapter 9 to 12 describes briefly metal powder characteristics and principles of testing, mixing, blending, conditioning, compaction and sintering. (orig./A.B.)

Structural and thermal behaviour of carious and sound powders of human tooth enamel and dentine

International Nuclear Information System (INIS)

Tiznado-Orozco, Gaby E; Garcia-Garcia, R; Reyes-Gasga, J

2009-01-01

Powder from carious human tooth enamel and dentine were structurally, chemically and thermally analysed and compared against those from sound (healthy) teeth. Structural and chemical analyses were performed using x-ray diffraction, energy-dispersive x-ray spectroscopy and transmission electron microscopy. Thermal analysis was carried out by thermogravimetric analysis, Fourier transform infrared spectroscopy and x-ray diffraction. Results demonstrate partially dissolved crystals of hydroxyapatite (HAP) with substitutions of Na, Mg, Cl and C, and a greater weight loss in carious dentine as compared with carious enamel. A greater amount of thermal decomposition is observed in carious dentine as compared with sound dentine, with major variations in the a-axis of the HAP unit cell than in the c-axis. Variations in shape and intensity of the OH - , CO 3 2- and PO 4 3- FTIR bands were also found.

Production of a Powder Metallurgical Hot Work Tool Steel with Harmonic Structure by Mechanical Milling and Spark Plasma Sintering

Science.gov (United States)

Deirmina, Faraz; Pellizzari, Massimo; Federici, Matteo

2017-04-01

Commercial AISI-H13 gas atomized powders (AT) were mechanically milled (MM) to refine both the particle size and the microstructure. Different volume fractions of coarser grained (CG) AT powders were mixed with the ultra-fine grained (UFG) MM and consolidated by spark plasma sintering to obtain bulks showing a harmonic structure ( i.e. a 3D interconnected network of UFG areas surrounding the CG atomized particles). The low sintering temperature, 1373.15 K (1100 °C) and the short sintering time (30 minutes) made it possible to obtain near full density samples while preserving the refined microstructure induced by MM. A combination of high hardness and significantly improved fracture toughness is achieved by the samples containing 50 to 80 vol pct MM, essentially showing harmonic structure. The design allows to easily achieve specific application oriented properties by varying the MM volume fraction in the initial mixture. Hardness is governed by the fine-grained MM matrix and improved toughening is due to (1) deviatory effect of AT particles and (2) energy dissipation as a result of the decohesion in MM regions or AT and MM interface.

The crystal structures and powder diffraction patterns of the uranium tellurides

Energy Technology Data Exchange (ETDEWEB)

Snyder, R.L. (State Univ. of New York, Alfred, NY (USA). Inst. of Ceramic Superconductivity); Nichols, M.C.; Boehme, D.R. (Sandia National Labs., Livermore, CA (USA))

1990-10-03

A critical review of all of the reported structures and powder diffraction patterns in the uranium telluride system has been undertaken. Structures that are correct: Cubic -- UTe: no experimental pattern exists. Retain calculated 15--865. Cubic --U{sub 3}Te{sub 4}: retain the poor quality 12--610 but adopt the pattern calculated here. Cubic U{sub 2}Te{sub 3}: no experimental pattern exists. Adopt pattern calculated here. Orthorhombic UTe{sub 2}: Adopt the new pattern of Boehme et al. Monoclinic {alpha}UTe{sub 3} Adopt the new pattern of Boehme et al. Monoclinic {alpha}UTe{sub 3} Adopt the new pattern of Boehme et al. Orthorhombic {beta}UTe{sub 3}: Adopt pattern calculated here. Orthorhombic UTe{sub 5}: Adopt the new pattern of Boehme et al. Structures in need of refinement: Orthorhombic U{sub 2}Te{sub 3}:Adopt pattern calculated here over 34--807. Hexagonal U{sub 7}Te{sub 12}: Adopt pattern calculated here but retain 24--1368. Orthorhombic UTe{sub 1.78}: Adopt pattern calculated here and retain our modified 21--1404 reported for U{sub 4}Te{sub 7}. Orthorhombic UTe{sub 2.5}: Adopt pattern calculated here. Orthorhombic UTe{sub 3.4}: Accept recent pattern of Boehme et al. Phases for which no structures or reliable patterns exist: Orthorhombic U{sub 3}Te{sub 4}: no published pattern. Tetragonal U{sub 3}Te{sub 5}: three patterns 21--1407, 34--766 and 34--896 exit but all are of very poor quality. Phases which probably do not exist: Tetragonal UTe{sub 1.78}, Tetragonal UTe{sub 2}, Cubic UTe{sub 2} U{sub 3}Te{sub 7}(21--1402), U{sub 3}Te{sub 8}(21--1406).

The effect of reduced oxygen content powder on the impact toughness of 316 steel powder joined to 316 steel by low temperature HIP

International Nuclear Information System (INIS)

Lind, Anders; Sundstroem, Johan; Peacock, Alan

2005-01-01

During the manufacture of the blanket modules, 316L steel powder is simultaneously consolidated and joined to tubes and blocks of 316L materials by hot isostatic pressing (HIP). The high processing temperature can detrimentally increase the grain size of the water-cooling tubes in the structure and the blocks reducing their strength. It is well known [L. Arnberg, A. Karlsson, Influence of powder surface oxidation on some properties of a HIPed martensitic chromium steel, Int. J. Powder Metall. 24 (2) (1988) 107-112] that surface oxides on the powder particles negatively influence the impact toughness of material and joints consolidated in this way. At a high HIP temperature, the oxides are at least partly transformed, thereby improving the impact toughness [L. Nyborg, I. Olefjord, Surface analysis of PM martensitic steel before and after consolidation. Part 2. Surface analysis of compacted material, Powder Metall. 31 (1) (1988) 40-44]. In order to get acceptable mechanical properties of materials produced at a low HIP temperature, the oxygen content on the powder surfaces needs to be reduced. In order to study the effect of reducing the powder oxygen content, it was reduced and the results were compared to those of specimens with ordinary oxygen content. The effect on the impact toughness and the tensile strength of low temperature (1020 and 1060 deg. C) HIP joints between steel blocks and powder consolidated material with low and ordinary oxygen content was measured

Comparative study about hydrogen sorption in sponge and powder titanium

International Nuclear Information System (INIS)

Vasut, Felicia; Preda, Anisoara; Zamfirache, Marius; Ducu, Catalin; Malinovschi, Viorel

2005-01-01

Currently, hydrogen may be stored as a compressed gas or a cryogenic liquid. Neither method appears to be practical for many applications in which hydrogen use would otherwise be attractive. For example, gaseous storage of stationary fuel is not feasible because of the large volume or weight of the storage vessels. Liquid hydrogen could be use extensively but the liquefaction process is relatively expensive. The hydrogen can be stored for a long term with a high separation factor, as a solid metal hydride. Using hydride-forming metals and intermetallic compounds, for example, recovery, purification and storage of heavy isotopes in tritium containing system, can solve many problems arising in the nuclear-fuel cycle. The paper presents a comparative study about hydrogen sorption on two titanium structures: powder and sponge. Also, it is presented the characterization, by X-Ray diffraction, of two structures, before and after sorption process. From our results, one can conclude that sorption method is efficient for both samples. Kinetic curves indicates that sorption rate for titanium powder is lower than for sponge titanium. This is the effect of reaction surface, which is larger for powder titanium. Sorption capacity for hydrogen is lower in powder titanium for identical experimental conditions. The difference between storage capacities could be explained by activation temperature, which was lower for titanium powder than for sponge. (authors)

Structure analysis of K3H(SO4)2 by neutron powder diffraction

International Nuclear Information System (INIS)

Murakami, Satoshi; Kuroiwa, Yoshihiro; Noda, Yukio; Nakai, Yusuke; Kamiyama, Takashi; Asano, Hajime.

1993-01-01

Neutron powder diffraction experiments of K 3 H(SO 4 ) 2 were carried out at KENS-HRP station in order to obtain the positional parameters of hydrogen nuclei. The data was taken at six different temperatures from room temperature to 20K. Even though K 3 H(SO 4 ) 2 contained a hydrogen atom, the structural analysis was successfully performed by using a program RIETAN. Concerning the hydrogen position, four different models give almost the same R-factor so that the state of the hydrogen nucleus is not uniquely determined. The result based on the assumption that a hydrogen nucleus occupies two sites shows that the distance of split hydrogen nuclei is shorter than the distance of hydrogen electron clouds. This result suggests that a large polarizability exists in a hydrogen atom. (author)

Internal friction in uranium dioxide

International Nuclear Information System (INIS)

Paulin Filho, Pedro Iris

1979-01-01

The uranium dioxide inelastic properties were studied measuring internal friction at low frequencies (of the order of 1 Hz). The work was developed in the 160 to 400 deg C temperature range. The effect of stoichiometry variation was studied oxidizing the sample with consequent change of the defect structure originally present in the non-stoichiometric uranium dioxide. The presence of a wide and irregular peak due to oxidation was observed at low temperatures. Activation energy calculations indicated the occurrence of various relaxation processes and assuming the existence of a peak between - 80 and - 70 deg C , the absolute value obtained for the activation energy (0,54 eV) is consistent with the observed values determined at medium and high frequencies for the stress induced reorientation of defects. The microstructure effect on the inelastic properties was studied for stoichiometric uranium dioxide, by varying grain size and porosity. These parameters have influence on the high temperature measurements of internal friction. The internal friction variation for temperatures higher than 340 deg C is thought to be due to grain boundary relaxation phenomena. (author)

Preparation of soft-agglomerated nano-sized ceramic powders by sol-gel combustion process

International Nuclear Information System (INIS)

Feng, Q.; Ma, X.H.; Yan, Q.Z.; Ge, C.C.

2009-01-01

The soft-agglomerated Gd 2 BaCuO 5 (Gd211) nano-powders were synthesized by sol-gel combustion process with binary ligand and the special pretreatment on gel. The mechanism of the formation of weakly agglomerated structure was studied in detail. The results showed that network structure in gelation process was found to be a decisive factor for preventing agglomeration of colloidal particles. The removal of free water, coordinated water, and most of hydroxyl groups during pretreatment further inhibited the formation of hydrogen bonds between adjacent particles. The soft-agglomeration of the particles was confirmed by isolated particles in calcined Gd211 powders and in green compact, a narrow monomodal pore size distribution of the green compact and the low agglomeration coefficient of the calcined Gd211 powder. Extension this process to synthesis of BaCeO 3 , BaTiO 3 and Ce 0.8 Sm 0.2 O 1.9 powders, also led to weakly agglomerated nano-powders. It suggests that this method represents a powerful and facile method for the creation of doped and multi-component nano-sized ceramic powders.

In situ effects of titanium dioxide nanoparticles on community structure of freshwater benthic macroinvertebrates.

Science.gov (United States)

Jovanović, Boris; Milošević, Djuradj; Piperac, Milica Stojković; Savić, Ana

2016-06-01

For the first time in the current literature, the effect of titanium dioxide (TiO2) nanoparticles on the community structure of macroinvertebrates has been investigated in situ. Macroinvertebrates were exposed for 100 days to an environmentally relevant concentration of TiO2 nanoparticles, 25 mg kg(-1) in sediment. Czekanowski's index was 0.61, meaning 39% of the macroinvertebrate community structure was affected by the TiO2 treatment. Non-metric multidimensional scaling (NMDS) visualized the qualitative and quantitative variability of macroinvertebrates at the community level among all samples. A distance-based permutational multivariate analysis of variance (PERMANOVA) revealed the significant effect of TiO2 on the macroinvertebrate community structure. The indicator value analysis showed that the relative frequency and abundance of Planorbarius corneus and Radix labiata were significantly lower in the TiO2 treatment than in the control. Meanwhile, Ceratopogonidae, showed a significantly higher relative frequency and abundance in the TiO2 treatment than in the control. Copyright © 2016 Elsevier Ltd. All rights reserved.

Laboratory Study on the Fatigue Resistance of Asphaltic Concrete Containing Titanium Dioxide

Directory of Open Access Journals (Sweden)

Buhari Rosnawati

2018-01-01

Full Text Available This study aims to evaluate the fatigue performance of modified asphalt mixture using Indirect Tensile Fatigue Test. Titanium Dioxide (TiO2 powder in a form of rutile was used for producing asphalt concrete with lower mixing and compaction temperature compared to conventional hot mix asphalt without reducing its physical and mechanical also resistance to fatigue. The characteristic of the asphalt and modified asphalt was evaluated using penetration test, softening test and rotational viscosity test. Titanium dioxide of 2%, 4%, 6%, 8% and 10% by weight of asphalt has been incorporated into unaged 80/100 asphalt mix in order to improvise its performance and to fulfill the objectives of this experimental study. As a result, TiO2 as an additive is potential to decrease the penetration and increasing the softening point of the asphalt. In terms of fatigue performance testing, addition TiO2 additive does help in improving the fatigue properties as it shows greater result than the control asphalt. In conclusion, TiO2 is great in improving fatigue properties.

Laboratory Study on the Fatigue Resistance of Asphaltic Concrete Containing Titanium Dioxide

Science.gov (United States)

Buhari, Rosnawati; Ezree Abdullah, Mohd; Khairul Ahmad, Mohd; Azhar Tajudin, Saiful; Khatijah Abu Bakar, Siti

2018-03-01

This study aims to evaluate the fatigue performance of modified asphalt mixture using Indirect Tensile Fatigue Test. Titanium Dioxide (TiO2) powder in a form of rutile was used for producing asphalt concrete with lower mixing and compaction temperature compared to conventional hot mix asphalt without reducing its physical and mechanical also resistance to fatigue. The characteristic of the asphalt and modified asphalt was evaluated using penetration test, softening test and rotational viscosity test. Titanium dioxide of 2%, 4%, 6%, 8% and 10% by weight of asphalt has been incorporated into unaged 80/100 asphalt mix in order to improvise its performance and to fulfill the objectives of this experimental study. As a result, TiO2 as an additive is potential to decrease the penetration and increasing the softening point of the asphalt. In terms of fatigue performance testing, addition TiO2 additive does help in improving the fatigue properties as it shows greater result than the control asphalt. In conclusion, TiO2 is great in improving fatigue properties.

Synthesis and characterization of lead zirconate titanate powders obtained by the oxidant peroxo method

International Nuclear Information System (INIS)

Camargo, Emerson R.; Leite, Edson R.; Longo, Elson

2009-01-01

Lead zirconate titanate (PbZr 1-x Ti x O 3 ) was synthesized by the 'oxidant peroxo method (OPM)' with 'x' between 0.25 and 0.50. Titanium metal was dissolved into a hydrogen peroxide/ammonia aqueous solution, followed by the addition of lead and zirconium nitrate solution. The amorphous precipitated precursor obtained was crystallized by heat treatment between 400 and 1000 deg. C. Images of transmission microscopy showed spherical particles with average diameter between 20 and 60 nm, and the presence of necks between particles treated at 700 deg. C. All of the unpressed powders were characterized by X-ray diffractometry and FT-Raman spectroscopy. Powder samples with 'x' up to 0.35 showed rhombohedral structure when treated at temperatures higher than 500 deg. C, and tetragonal structure when 'x' was higher than 0.40. Analysis of XRD and Raman spectroscopy of the precursor powders showed amorphous-like structures, however powders treated at 400 deg. C showed a structure identified as an intermediate pyrochlore phase, independently of the Zr and Ti mole ratio

Comparison between powder and slices diffraction methods in teeth samples

Energy Technology Data Exchange (ETDEWEB)

Colaco, Marcos V.; Barroso, Regina C. [Universidade do Estado do Rio de Janeiro (IF/UERJ), RJ (Brazil). Inst. de Fisica. Dept. de Fisica Aplicada; Porto, Isabel M. [Universidade Estadual de Campinas (FOP/UNICAMP), Piracicaba, SP (Brazil). Fac. de Odontologia. Dept. de Morfologia; Gerlach, Raquel F. [Universidade de Sao Paulo (FORP/USP), Rieirao Preto, SP (Brazil). Fac. de Odontologia. Dept. de Morfologia, Estomatologia e Fisiologia; Costa, Fanny N. [Coordenacao dos Programas de Pos-Graduacao de Engenharia (LIN/COPPE/UFRJ), RJ (Brazil). Lab. de Instrumentacao Nuclear

2011-07-01

Propose different methods to obtain crystallographic information about biological materials are important since powder method is a nondestructive method. Slices are an approximation of what would be an in vivo analysis. Effects of samples preparation cause differences in scattering profiles compared with powder method. The main inorganic component of bones and teeth is a calcium phosphate mineral whose structure closely resembles hydroxyapatite (HAp). The hexagonal symmetry, however, seems to work well with the powder diffraction data, and the crystal structure of HAp is usually described in space group P63/m. Were analyzed ten third molar teeth. Five teeth were separated in enamel, detin and circumpulpal detin powder and five in slices. All the scattering profile measurements were carried out at the X-ray diffraction beamline (XRD1) at the National Synchrotron Light Laboratory - LNLS, Campinas, Brazil. The LNLS synchrotron light source is composed of a 1.37 GeV electron storage ring, delivering approximately 4x10{sup -1}0 photons/s at 8 keV. A double-crystal Si(111) pre-monochromator, upstream of the beamline, was used to select a small energy bandwidth at 11 keV . Scattering signatures were obtained at intervals of 0.04 deg for angles from 24 deg to 52 deg. The human enamel experimental crystallite size obtained in this work were 30(3)nm (112 reflection) and 30(3)nm (300 reflection). These values were obtained from measurements of powdered enamel. When comparing the slice obtained 58(8)nm (112 reflection) and 37(7)nm (300 reflection) enamel diffraction patterns with those generated by the powder specimens, a few differences emerge. This work shows differences between powder and slices methods, separating characteristics of sample of the method's influence. (author)

Comparison between powder and slices diffraction methods in teeth samples

International Nuclear Information System (INIS)

Colaco, Marcos V.; Barroso, Regina C.; Porto, Isabel M.; Gerlach, Raquel F.; Costa, Fanny N.

2011-01-01

Propose different methods to obtain crystallographic information about biological materials are important since powder method is a nondestructive method. Slices are an approximation of what would be an in vivo analysis. Effects of samples preparation cause differences in scattering profiles compared with powder method. The main inorganic component of bones and teeth is a calcium phosphate mineral whose structure closely resembles hydroxyapatite (HAp). The hexagonal symmetry, however, seems to work well with the powder diffraction data, and the crystal structure of HAp is usually described in space group P63/m. Were analyzed ten third molar teeth. Five teeth were separated in enamel, detin and circumpulpal detin powder and five in slices. All the scattering profile measurements were carried out at the X-ray diffraction beamline (XRD1) at the National Synchrotron Light Laboratory - LNLS, Campinas, Brazil. The LNLS synchrotron light source is composed of a 1.37 GeV electron storage ring, delivering approximately 4x10 -1 0 photons/s at 8 keV. A double-crystal Si(111) pre-monochromator, upstream of the beamline, was used to select a small energy bandwidth at 11 keV . Scattering signatures were obtained at intervals of 0.04 deg for angles from 24 deg to 52 deg. The human enamel experimental crystallite size obtained in this work were 30(3)nm (112 reflection) and 30(3)nm (300 reflection). These values were obtained from measurements of powdered enamel. When comparing the slice obtained 58(8)nm (112 reflection) and 37(7)nm (300 reflection) enamel diffraction patterns with those generated by the powder specimens, a few differences emerge. This work shows differences between powder and slices methods, separating characteristics of sample of the method's influence. (author)

Electronic structure of the actinides and their dioxides. Application to the defect formation energy and krypton solubility in uranium dioxide; Etude de la structure electronique des actinides et de leurs dioxydes. Application aux defauts ponctuels et aux gaz de fission dans le dioxyde d`uranium

Energy Technology Data Exchange (ETDEWEB)

Petit, T. [CEA Centre d`Etudes Nucleaires de Grenoble, 38 (France)]|[CEA Centre d`Etudes de Grenoble, 38 (France). Dept. de Thermohydraulique et de Physique

1996-09-28

Uranium dioxide is the standard nuclear fuel used in French h power plants. During irradiation, fission products such as krypton and xenon are created inside fuel pellets. So, gas release could become, at very high burnup, a limiting factor in the reactor exploitation. To study this subject, we have realised calculations using the Density Functional Theory (DFT) into the Local Density Approximation (LDA) and the Atomic Sphere Approximation (ASA). First, we have validated our approach by calculating cohesive properties of thorium, protactinium and uranium metals. The good agreement between our results and experimental values implies that 5f electrons are itinerant. Calculated lattice parameter, cohesive energy and bulk modulus for uranium and thorium dioxides are in very good agreement with experiment. We show that binding between uranium and oxygen atoms is not completely ionic but partially covalent. The question of the electrical conductivity still remains an open problem. We have been able to calculate punctual defect formation energies in uranium dioxide. Accordingly to experimental observations, we find that it is easier to create a defect in the oxygen sublattice than in the uranium sublattice. Finally, we have been able to predict a probable site of krypton atoms in nuclear fuel: the Schottky trio. Experiences of Extended X-ray Absorption Fine structure Spectroscopy (EXAFS) and X-ray Photoelectron Spectroscopy (XPS) on uranium dioxide doped by ionic implantation will help us in the comprehension of the studied phenomena and the interpretation of our calculations. (author). 256 refs.

One-Step Hydrothermal-Electrochemical Route to Carbon-Stabilized Anatase Powders

Science.gov (United States)

Tao, Ying; Yi, Danqing; Zhu, Baojun

2013-04-01

Black carbon-stabilized anatase particles were prepared by a simple one-step hydrothermal-electrochemical method using glucose and titanium citrate as the carbon and titanium source, respectively. Morphological, chemical, structural, and electrochemical characterizations of these powders were carried out by Raman spectroscopy, Fourier-transform infrared spectroscopy, x-ray diffraction, scanning electron microscopy, and cyclic voltammetry. It was revealed that 200-nm carbon/anatase TiO2 was homogeneously dispersed, and the powders exhibited excellent cyclic performance at high current rates of 0.05 V/s. The powders are interesting potential materials that could be used as anodes for lithium-ion batteries.

Extraction of Uranium Using Nitrogen Dioxide and Carbon Dioxide for Spent Fuel Reprocessing

Energy Technology Data Exchange (ETDEWEB)

Kayo Sawada; Daisuke Hirabayashi; Youichi Enokida [EcoTopia Science Institute, Nagoya University, Nagoya, 464-8603 (Japan)

2008-07-01

For the reprocessing of spent nuclear fuels, a new method to extract actinides from spent fuel using highly compressed gases, nitrogen dioxide and carbon dioxide was proposed. Uranium extraction from broken pieces, whose average grain size was 5 mm, of uranium dioxide pellet with nitrogen dioxide and carbon dioxide was demonstrated in the present study. (authors)

Low pressure powder injection moulding of stainless steel powders

Energy Technology Data Exchange (ETDEWEB)

Zampieron, J.V.; Soares, J.P.; Mathias, F.; Rossi, J.L. [Powder Processing Center CCP, Inst. de Pesquisas Energeticas e Nucleares, Sao Paulo, SP (Brazil); Filho, F.A. [IPEN, Inst. de Pesquisas Energeticas e Nucleares, Cidade Univ., Sao Paulo, SP (Brazil)

2001-07-01

Low-pressure powder injection moulding was used to obtain AISI 316L stainless steel parts. A rheological study was undertaken using gas-atomised powders and binders. The binders used were based on carnauba wax, paraffin, low density polyethylene and microcrystalline wax. The metal powders were characterised in terms of morphology, particle size distribution and specific surface area. These results were correlated to the rheological behaviour. The mixture was injected in the shape of square bar specimens to evaluate the performance of the injection process in the green state, and after sintering. The parameters such as injection pressure, viscosity and temperature were analysed for process optimisation. The binders were thermally removed in low vacuum with the assistance of alumina powders. Debinding and sintering were performed in a single step. This procedure shortened considerably the debinding and sintering time. (orig.)

Synthesis and structural property of Si nanosheets connected to Si nanowires using MnCl{sub 2}/Si powder source

Energy Technology Data Exchange (ETDEWEB)

Meng, Erchao [Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johuku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Ueki, Akiko [Toyota Central R& D Labs., Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Meng, Xiang [Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johuku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Suzuki, Hiroaki [Graduate School of Engineering, Shizuoka University, 3-5-1 Johuku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Itahara, Hiroshi [Toyota Central R& D Labs., Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Tatsuoka, Hirokazu, E-mail: tatsuoka.hirokazu@shizuoka.ac.jp [Graduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johuku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan)

2016-08-15

Graphical abstract: Si nanosheets connected to Si nanowires synthesized using a MnCl{sub 2}/Si powder source with an Au catalyst avoid the use of air-sensitive SiH{sub 4} or SiCl{sub 4}. It was evident from these structural features of the nanosheets (leaf blade) with nanowires (petiole) that the nanosheets were formed by the twin-plane reentrant-edge mechanism. The feature of the observed lattice fringes of the Si(111) nanosheets was clearly explained by the interference with the extra diffraction spots that arose due to the reciprocal lattice streaking effect. - Highlights: • New Si nanosheets connected to Si nanowires were synthesized using MnCl{sub 2}/Si powders. • The synthesis method has benefits in terms of avoiding air sensitive SiH{sub 4} or SiCl{sub 4}. • Structural property and electron diffraction of the Si nanosheets were clarified. • Odd lattice fringes of the Si nanosheets observed by HRTEM were clearly explained. - Abstract: Si nanosheets connected to Si nanowires were synthesized using a MnCl{sub 2}/Si powder source with an Au catalyst. The synthesis method has benefits in terms of avoiding conventionally used air-sensitive SiH{sub 4} or SiCl{sub 4}. The existence of the Si nanosheets connected to the Si<111> nanowires, like sprouts or leaves with petioles, was observed, and the surface of the nanosheets was Si{111}. The nanosheets were grown in the growth direction of <211> perpendicular to that of the Si nanowires. It was evident from these structural features of the nanosheets that the nanosheets were formed by the twin-plane reentrant-edge mechanism. The feature of the observed lattice fringes, which do not appear for Si bulk crystals, of the Si(111) nanosheets obtained by high resolution transmission electron microscopy was clearly explained due to the extra diffraction spots that arose by the reciprocal lattice streaking effect.

Physico-chemical properties and solubility behaviour of multi-substituted hydroxyapatite powders containing silicon

International Nuclear Information System (INIS)

Sprio, S.; Tampieri, A.; Landi, E.; Sandri, M.; Martorana, S.; Celotti, G.; Logroscino, G.

2008-01-01

Hydroxyapatite powders characterized by ionic substitutions both in anionic and cationic sites were successfully prepared by synthesis in aqueous medium. The process parameters were set up to allow the simultaneous substitution of the foreign ions, namely carbonate, magnesium and silicon in the crystallographic site of calcium and phosphorus, keeping in count the competition which arises between atoms destined to occupy the same crystallographic site. The chemico-physical properties of the powders were investigated through several analytical techniques, i.e. X-ray diffraction, infrared spectroscopy, atomic emission spectroscopy and thermo-gravimetric analysis. The results show that the utilization of sodium hydrogen-carbonate as a reactant allows the entering of carbonate into the HA structure, mainly in phosphate position, while sodium is eliminated during the process of the powder washing. The entering of silicon in the HA structure progressively reduces its crystallinity, as also carbonate ions do. Silicate and carbonate ions can enter simultaneously into the HA structure, in biological-like amounts, although they compete for the occupation of the phosphate site; the powder crystallinity is strongly reduced as the content of the two substituting ions increases, so that a limit molar concentration exists where the apatite structure collapses and an amorphous phase forms with the simultaneous formation of crystalline calcium carbonate. Solubility tests, carried out at physiological conditions, reveal an increased calcium release in the HA powders containing silicon compared to the silicon-free HA; the solubility behaviour of the multi-substituted HA powders at physiological conditions makes these materials promising as bioactive bone scaffold, as they are able to continuously supply ions which are essential for the process of bone reconstruction

Effect of process control agent on the porous structure and mechanical properties of a biomedical Ti-Sn-Nb alloy produced by powder metallurgy.

Science.gov (United States)

Nouri, A; Hodgson, P D; Wen, C E

2010-04-01

The influence of different amounts and types of process control agent (PCA), i.e., stearic acid and ethylene bis-stearamide, on the porous structure and mechanical properties of a biomedical Ti-16Sn-4Nb (wt.%) alloy was investigated. Alloy synthesis was performed on elemental metal powders using high-energy ball milling for 5h. Results indicated that varying the PCA content during ball milling led to a drastic change in morphology and particle-size distribution of the ball-milled powders. Porous titanium alloy samples sintered from the powders ball milled with the addition of various amounts of PCA also revealed different pore morphology and porosity. The Vickers hardness of the sintered titanium alloy samples exhibited a considerable increase with increasing PCA content. Moreover, the addition of larger amounts of PCA in the powder mixture resulted in a significant increase in the elastic modulus and peak stress for the sintered porous titanium alloy samples under compression. It should also be mentioned that the addition of PCA introduced contamination (mainly carbon and oxygen) into the sintered porous product. Crown Copyright 2009. Published by Elsevier Ltd. All rights reserved.

Structural, microstructural and Mössbauer studies of nanocrystalline Fe100-x Alx powders elaborated by mechanical alloying

Directory of Open Access Journals (Sweden)

Akkouche K.

2012-06-01

Full Text Available Nanocrystalline Fe100-xAlx powders (x= 25, 30, 34 and 40 at % were prepared by the mechanical alloying process using a vario-planetary high-energy ball mill for a milling time of 35 h. The formation and physical properties of the alloys were investigated as a function of Al content by means of X-ray diffraction, scanning electron microscopy (SEM, energy dispersive X-ray and Mössbauer spectroscopy. For all Fe100-xAlx samples, the complete formation of bcc phase was observed after 35 h of milling. As Al content increases, the lattice parameter increases, whereas the grain size decreases from 106 to 12 nm. The powder particle morphology for different compositions was observed by SEM. The Mössbauer spectra were adjusted with a singlet line and a sextet containing two components. The singlet was attributed to the formation of paramagnetic A2 disordered structure rich with Al. About the sextet, the first component indicated the formation of Fe clusters/ Fe-rich phases; however, the second component is characteristic of disordered ferromagnetic phase.

Foundations of powder metallurgy

International Nuclear Information System (INIS)

Libenson, G.A.

1987-01-01

Consideration is being given to physicochemical foundations and technology of metal powders, moulding and sintering of bars, made of them or their mixtures with nonmetal powders. Data on he design of basic equipment used in the processes of powder metallurgy and its servicing are presented. General requirements of safety engineering when fabricating metal powders and products of them are mentioned

Dispersion of carbon nanotubes in hydroxyapatite powder by in situ chemical vapor deposition

International Nuclear Information System (INIS)

Li Haipeng; Wang Lihui; Liang, Chunyong; Wang Zhifeng; Zhao Weimin

2010-01-01

In the present work, we use chemical vapor deposition of methane to disperse carbon nanotubes (CNTs) within hydroxyapatite (HA) powder. The effect of different catalytic metal particles (Fe, Ni or Co) on the morphological and structural development of the powder and dispersion of CNTs in HA powder was investigated. The results show that the technique is effective in dispersing the nanotubes within HA powder, which simultaneously protects the nanotubes from damage. The results can have important and promising speculations for the processing of CNT-reinforced HA-matrix composites in general.

Structural, Morphological and Optical Characterization of Eu3+ and Nd3+ Co-Doped Tio2 Nano Particles by Sol Gel Method

Directory of Open Access Journals (Sweden)

P. Sanjay

2017-06-01

Full Text Available Semiconductor nano crystals have been widely studied for their fundamental properties. The Eu3+ and Nd3+ doped titanium dioxide nano powder was successfully synthesized by sol-gel method. The morphological and structural properties of as-prepared samples were characterized by X-ray diffraction (XRD, High Resolution Transmission Electron Microscope (HRTEM. The Powder X- ray diffraction is carried out in order to examine the phase formation and substitution of Eu3+ and Nd3+ doped in TiO2 matrix. The UV-Vis spectral analysis was carried out between 200 nm and 1200 nm. The band gap of the Eu3+ and Nd3+ doped Tio2 nanoparticles was calculated. The functional groups of the synthesized compound have been identified by FTIR spectral analysis. The strong PL intensity confirms a blue shift.

High resolution Transmission Electron Microscopy characterization of a milled oxide dispersion strengthened steel powder

Energy Technology Data Exchange (ETDEWEB)

Loyer-Prost, M., E-mail: marie.loyer-prost@cea.fr [DEN-Service de Recherches de Métallurgie Physique, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette (France); Merot, J.-S. [Laboratoire d’Etudes des Microstructures – UMR 104, CNRS/ONERA, BP72-29, Avenue de la Division Leclerc, 92 322, Châtillon (France); Ribis, J. [DEN-Service de Recherches de Métallurgie Appliquée, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette (France); Le Bouar, Y. [Laboratoire d’Etudes des Microstructures – UMR 104, CNRS/ONERA, BP72-29, Avenue de la Division Leclerc, 92 322, Châtillon (France); Chaffron, L. [DEN-Service de Recherches de Métallurgie Appliquée, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette (France); Legendre, F. [DEN-Service de la Corrosion et du Comportement des Matériaux dans leur Environnement, CEA, Université Paris-Saclay, F-91191, Gif-sur-Yvette (France)

2016-10-15

Oxide Dispersion Strengthened (ODS) steels are promising materials for generation IV fuel claddings as their dense nano-oxide dispersion provides good creep and irradiation resistance. Even if they have been studied for years, the formation mechanism of these nano-oxides is still unclear. Here we report for the first time a High Resolution Transmission Electron Microscopy and Energy Filtered Transmission Electron Microscopy characterization of an ODS milled powder. It provides clear evidence of the presence of small crystalline nanoclusters (NCs) enriched in titanium directly after milling. Small NCs (<5 nm) have a crystalline structure and seem partly coherent with the matrix. They have an interplanar spacing close to the (011) {sub bcc} iron structure. They coexist with larger crystalline spherical precipitates of 15–20 nm in size. Their crystalline structure may be metastable as they are not consistent with any Y-Ti-O or Ti-O structure. Such detailed observations in the as-milled grain powder confirm a mechanism of Y, Ti, O dissolution in the ferritic matrix followed by a NC precipitation during the mechanical alloying process of ODS materials. - Highlights: • We observed an ODS ball-milled powder by high resolution transmission microscopy. • The ODS ball-milled powder exhibits a lamellar microstructure. • Small crystalline nanoclusters were detected in the milled ODS powder. • The nanoclusters in the ODS milled powder are enriched in titanium. • Larger NCs of 15–20 nm in size are, at least, partly coherent with the matrix.

Properties of nano-structured Ni/YSZ anodes fabricated from plasma sprayable NiO/YSZ powder prepared by single step solution combustion method

Energy Technology Data Exchange (ETDEWEB)

Prakash, B. Shri; Balaji, N.; Kumar, S. Senthil; Aruna, S.T., E-mail: staruna194@gmail.com

2016-12-15

Highlights: • Preparation of plasma grade NiO/YSZ powder in single step. • Fabrication of nano-structured Ni/YSZ coating. • Conductivity of 600 S/cm at 800 °C. - Abstract: NiO/YSZ anode coatings are fabricated by atmospheric plasma spraying at different plasma powers from plasma grade NiO/YSZ powders that are prepared in a single step by solution combustion method. The process adopted is devoid of multi-steps that are generally involved in conventional spray drying or fusing and crushing methods. Density of the coating increased and porosity decreased with increase in the plasma power of deposition. An ideal nano-structured Ni/YSZ anode encompassing nano YSZ particles, nano Ni particles and nano pores is achieved on reducing the coating deposited at lower plasma powers. The coating exhibit porosities in the range of 27%, sufficient for anode functional layers. Electronic conductivity of the coatings is in the range of 600 S/cm at 800 °C.

Structural modeling and intermolecular correlation of liquid chlorine dioxide

International Nuclear Information System (INIS)

Ogata, Norio; Hironori, Shimakura; Kawakita, Yukinobu; Ohara, Yukoji; Kohara, Shinji; Takeda, Shinichi

2009-01-01

Chlorine dioxide (ClO 2 ) is water-soluble yellow gas at room temperature. It has long been used as a disinfectant of tap water and various commodities owing to its strong oxidizing activity against various microbial proteins. The oxidizing activity is believed to be due to the presence of unpaired electron in its molecular orbital. Despite wealth of physicochemical studies of gaseous ClO 2 , little is known about liquid ClO 2 , especially about fine molecular structure and intermolecular interactions of liquid ClO 2 . The purpose of this study is to elucidate the fine structure and intermolecular orientations of ClO 2 molecules in its liquid state using a high-energy X-ray diffraction technique. The measurements of liquid ClO 2 were carried out at -50 to 0 degree Celsius using a two-axis diffractometer installed at the BL04B2 beamline in the third-generation synchrotron radiation facility SPring-8 (Hyogo, Japan). The incident X-ray beamline was 113.4 keV in energy and 0.1093 Armstrong in wavelength from a Si(111) monochromator with the third harmonic reflection. Liquid ClO 2 held in a quartz capillary tube was placed in a temperature-controlled vacuum chamber. We obtained a structure factor S(Q) to a range of Q = 0.3-30 Amstrong -1 and a pair distribution function g(r) upon Fourier transform of the S(Q). The total g(r) showed peaks at 1.46, 2.08, 2.48, 3.16 and 4.24 Armstrong. From intramolecular bond lengths of 1.46 Armstrong for Cl-O and 2.48 Armstrong for O-O, O-Cl-O bond angle was estimated to be 116.1 degrees. Peaks at 3.16 and 4.24 Armstrong in the total g(r) strongly indicate presence of specific intermolecular orientations of ClO 2 molecules that are distinct from those observed as a dimer in the solid phase ClO 2 . This view was further supported by molecular simulation using a reverse Monte Carlo method (RMC). (author)

Syntheses and characterizations of LiFePO4 powders

OpenAIRE

Jugović, Dragana; Kuzmanović, Maja; Mitrić, Miodrag; Cvjetićanin, Nikola; Uskoković, Dragan

2011-01-01

The olivine type compositions LiMPO4 (M = Fe, Mn, Co) are among the most attractive materials for the positive electrode of lithium-ion battery. The benefits of using LiFePO4 are excellent cycle life, high structural stability, low cost and environmental friendliness. Here will be presented our efforts to obtain LiFePO4 powders through several synthesis methods. The differences in phase purity, microstructure, morphology, and electrochemical performances of synthesized powders were investigat...

Use of whey powder and skim milk powder for the production of fermented cream

Directory of Open Access Journals (Sweden)

Ceren AKAL

2016-01-01

Full Text Available Abstract This study is about the production of fermented cream samples having 18% fat by addition of starter cultures. In order to partialy increase non-fat solid content of fermented cream samples, skim milk powder and demineralized whey powder in two different rates (50% and 70% were used. Samples were analyzed for changes in their biochemical and physicochemical properties (total solid, ash, fat, titratable acidity, pH value, total nitrogen, viscosity, tyrosine, acid number, peroxide and diacetyl values during 29-day of storage period. Samples tested consisted of 7 different groups; control group (without adding any powder, skim milk powder, 50% demineralized whey powder and 70% demineralized whey powder samples were in two different addition rate (2% and 4%. Also samples were analyzed for sensory properties. According to the results obtained, the addition of milk powder products affected titratable acidity and tyrosine values of fermented cream samples. Although powder addition and/or storage period didn’t cause significant variations in total solid, ash, fat, pH value, viscosity, acid number, peroxide, tyrosine and diacetyl values; sensory properties of fermented cream samples were influenced by both powder addition and storage period. Fermented cream containing 2% skim milk powder gets the top score of sensory evaluation among the samples.

Vibrational spectra, powder X-ray diffractions and physical properties of cyanide complexes with 1-ethylimidazole

Science.gov (United States)

Kürkçüoğlu, Güneş Süheyla; Kiraz, Fulya Çetinkaya; Sayın, Elvan

2015-10-01

The heteronuclear tetracyanonickelate(II) complexes of the type [M(etim)Ni(CN)4]n (hereafter, abbreviated as M-Ni-etim, M = Mn(II), Fe(II) or Co(II); etim = 1-ethylimidazole, C5H8N2) were prepared in powder form and characterized by FT-IR and Raman spectroscopy, powder X-ray diffraction (PXRD), thermal (TG; DTG and DTA), and elemental analysis techniques. The structures of these complexes were elucidated using vibrational spectra and powder X-ray diffraction patterns with the peak assignment to provide a better understanding of the structures. It is shown that the spectra are consistent with a proposed crystal structure for these compounds derived from powder X-ray diffraction measurements. Vibrational spectra of the complexes were presented and discussed with respect to the internal modes of both the etim and the cyanide ligands. The C, H and N analyses were carried out for all the complexes. Thermal behaviors of these complexes were followed using TG, DTG and DTA curves in the temperature range 30-700 °C in the static air atmosphere. The FT-IR, Raman spectra, thermal and powder X-ray analyses revealed no significant differences between the single crystal and powder forms. Additionally, electrical and magnetic properties of the complexes were investigated. The FT-IR and Raman spectroscopy, PXRD, thermal and elemental analyses results propose that these complexes are similar in structure to the Hofmann-type complexes.

Effects of Carbonization Parameters of Moso-Bamboo-Based Porous Charcoal on Capturing Carbon Dioxide

Directory of Open Access Journals (Sweden)

Pei-Hsing Huang

2014-01-01

Full Text Available This study experimentally analyzed the carbon dioxide adsorption capacity of Moso-bamboo- (Phyllostachys edulis- based porous charcoal. The porous charcoal was prepared at various carbonization temperatures and ground into powders with 60, 100, and 170 meshes, respectively. In order to understand the adsorption characteristics of porous charcoal, its fundamental properties, namely, charcoal yield, ash content, pH value, Brunauer-Emmett-Teller (BET surface area, iodine number, pore volume, and powder size, were analyzed. The results show that when the carbonization temperature was increased, the charcoal yield decreased and the pH value increased. Moreover, the bamboo carbonized at a temperature of 1000°C for 2 h had the highest iodine sorption value and BET surface area. In the experiments, charcoal powders prepared at various carbonization temperatures were used to adsorb 1.854% CO2 for 120 h. The results show that the bamboo charcoal carbonized at 1000°C and ground with a 170 mesh had the best adsorption capacity, significantly decreasing the CO2 concentration to 0.836%. At room temperature and atmospheric pressure, the Moso-bamboo-based porous charcoal exhibited much better CO2 adsorption capacity compared to that of commercially available 350-mesh activated carbon.

21 CFR 520.1696a - Buffered penicillin powder, penicillin powder with buffered aqueous diluent.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Buffered penicillin powder, penicillin powder with... FORM NEW ANIMAL DRUGS § 520.1696a Buffered penicillin powder, penicillin powder with buffered aqueous diluent. (a) Specifications. When reconstituted, each milliliter contains penicillin G procaine equivalent...

Porous Nb-Ti based alloy produced from plasma spheroidized powder

Directory of Open Access Journals (Sweden)

Qijun Li

Full Text Available Spherical Nb-Ti based alloy powder was prepared by the combination of plasma spheroidization and mechanical alloying. Phase constituents, microstructure and surface state of the powder, and pore characteristics of the resulting porous alloy were investigated. The results show that the undissolved W and V in the mechanically alloyed powder is fully alloyed after spheroidization, and single β phase is achieved. Particle size of the spheroidized powder is in the range of 20–110 μm. With the decrease of particle size, a transformation from typical dendrite solidification structure to fine cell microstructure occurs. The surface of the spheroidized powder is coated by a layer of oxides consisting mainly of TiO2 and Nb2O5. Probabilities of sinter-neck formation and particle coalescence increases with increasing sintering temperature. Porous skeleton with relatively homogeneous pore distribution and open pore channel is formed after vacuum sintering at 1700 °C, and the porosity is 32%. The sintering kinetic analysis indicates that grain boundary diffusion is the primary mass transport mechanism during sintering process. Keywords: Powder metallurgy, Nb-Ti based alloy, Porous material, Mechanical alloying, Plasma spheroidizing, Solidification microstructure

Unraveling the nature of electric field- and stress- induced structural transformations in soft PZT by a new powder poling technique.

Science.gov (United States)

Kalyani, Ajay Kumar; V, Lalitha K; James, Ajit R; Fitch, Andy; Ranjan, Rajeev

2015-02-25

A 'powder-poling' technique was developed to study electric field induced structural transformations in ferroelectrics exhibiting a morphotropic phase boundary (MPB). The technique was employed on soft PZT exhibiting a large longitudinal piezoelectric response (d(33) ∼ 650 pC N(-1)). It was found that electric poling brings about a considerable degree of irreversible tetragonal to monoclinic transformation. The same transformation was achieved after subjecting the specimen to mechanical stress, which suggests an equivalence of stress and electric field with regard to the structural mechanism in MPB compositions. The electric field induced structural transformation was also found to be accompanied by a decrease in the spatial coherence of polarization.

Synthesis of yttria powders by electrospray pyrolysis

International Nuclear Information System (INIS)

Rulison, A.J.; Flagan, R.C.

1994-01-01

Electrospray atomization of high-concentration (∼400 g/L) chemical precursor solutions was applied to the synthesis of yttria powders. Conditions were found which led to high-quality powders, composed of dense, spheroidal, submicrometer, and nanocrystalline oxide particles. The precursor solutions were hydrated yttrium nitrates dissolved in n-propyl alcohol at concentrations ranging from 44.1 to 455 g/L. Electrospray atomization produced submicrometer precursor droplets which were dispersed in air and carried through an electric furnace for thermal decomposition at 500 C for several seconds residence time. X-ray powder diffraction patterns indicated the expected cubic phase. Transmission electron micrographs showed that the particle structure varied with solution composition, ranging from hollow, inflated spheres for 6-hydrated nitrates to dense spheroids for 5-hydrated nitrates. The use of 6-hydrated nitrates in the solutions appeared to form particle surfaces which were impermeable to alcohol vapor evolved during thermal decomposition, leading to hollow, inflated spheres

On the possibility of reprocessing of fuel elements of dispersion type with copper matrix by pyrochemical methods

International Nuclear Information System (INIS)

Vasin, B.D.; Ivanov, V.A.; Shchetinskij, A.V.; Vavilov, S.K.; Savochkin, Yu.P.; Bychkov, A.V.; Kormilitsyn, M.V.

2005-01-01

A consideration is given to pyrochemical processes suitable for separation of uranium dioxide from structural materials when reprocessing cermet type fuel elements. The estimation of the possibility to apply liquid antimony and bismuth, potassium and copper chlorides melts is made. The specimens compacted of copper and uranium dioxide powders in a stainless steel can are used as simulators of fuel element sections. It is concluded that the dissolution of structural materials in molten salts at the stage of uranium dioxide concentration is the process of choice for reprocessing of dispersion type fuel elements [ru

Ultrasonic hot powder compaction of Ti-6Al-4V.

Science.gov (United States)

Abedini, Rezvan; Abdullah, Amir; Alizadeh, Yunes

2017-07-01

Power ultrasonic has been recently employed in a wide variety of manufacturing processes among which ultrasonic assisted powder compaction is a promising powder materials processing technique with significant industrial applications. The products manufactured by the powder metallurgy commonly consist of residual porosities, material impurities, structural non-homogeneities and residual stress. In this paper, it is aimed to apply power ultrasonic to the hot consolidation process of Ti-6Al-4V titanium alloy powder in order to improve mechanical properties. To do this, the effects of ultrasonic power and process temperature and pressure were considered and then deeply studied through a series of experiments. It was shown that the addition of ultrasonic vibration leads to a significant improvement in the consolidation performance and the mechanical strength of the fabricated specimens. Copyright © 2017 Elsevier B.V. All rights reserved.

High-energy ball milling of powder B-C mixtures

International Nuclear Information System (INIS)

Ramos, Alfeu S.; Taguchi, Simone P.; Ramos, Erika C.T.; Arantes, Vera L.; Ribeiro, Sebastiao

2006-01-01

The present work reports on the preparation of B-10 at.% C and B-18 at.% C powders by high-energy ball milling and further heat treatment. The milling process was carried out in a planetary ball mill. Following the milling process, powder samples were heat-treated at 1200 deg. C for 4 h using inert atmosphere. The milled and heat-treated B-10C and B-18C powders were characterized by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. A reduction on the intensity of B and C peaks was noticed after milling for 2 h, probably due the fine powder particle sizes because the pronounced fracture mechanism during ball milling of brittle starting components. The XRD patterns of B-10C and B-18C powders milled for 6 h indicated the presence of other peaks, suggesting that a metastable structure could have been formed. After milling for 90 h, these unknown peaks were still present. A large amount of B 4 C was formed after heat treatment at 1200 deg. C for 4 h beside these unknown peaks

Synthesis and characterization of lead zirconate titanate powders obtained by the oxidant peroxo method

Energy Technology Data Exchange (ETDEWEB)

Camargo, Emerson R. [LIEC-Laboratorio Interdisciplinar de Eletroquimica e Ceramica, Department of Chemistry, UFSCar-Federal University of Sao Carlos, Rod. Washington Luis km 235, CP 676, Sao Carlos SP, 13565-905 (Brazil)], E-mail: camargo@ufscar.br; Leite, Edson R. [LIEC-Laboratorio Interdisciplinar de Eletroquimica e Ceramica, Department of Chemistry, UFSCar-Federal University of Sao Carlos, Rod. Washington Luis km 235, CP 676, Sao Carlos SP, 13565-905 (Brazil)], E-mail: derl@power.ufscar.br; Longo, Elson [Department of Biochemistry, Chemistry Institute of Araraquara, UNESP, Sao Paulo State University Rua Francisco Degni, CP 355 Araraquara SP, 14801-907 Brazil (Brazil)], E-mail: elson@iq.unesp.br

2009-02-05

Lead zirconate titanate (PbZr{sub 1-x}Ti{sub x}O{sub 3}) was synthesized by the 'oxidant peroxo method (OPM)' with 'x' between 0.25 and 0.50. Titanium metal was dissolved into a hydrogen peroxide/ammonia aqueous solution, followed by the addition of lead and zirconium nitrate solution. The amorphous precipitated precursor obtained was crystallized by heat treatment between 400 and 1000 deg. C. Images of transmission microscopy showed spherical particles with average diameter between 20 and 60 nm, and the presence of necks between particles treated at 700 deg. C. All of the unpressed powders were characterized by X-ray diffractometry and FT-Raman spectroscopy. Powder samples with 'x' up to 0.35 showed rhombohedral structure when treated at temperatures higher than 500 deg. C, and tetragonal structure when 'x' was higher than 0.40. Analysis of XRD and Raman spectroscopy of the precursor powders showed amorphous-like structures, however powders treated at 400 deg. C showed a structure identified as an intermediate pyrochlore phase, independently of the Zr and Ti mole ratio.

The effect of reduced oxygen content powder on the impact toughness of 316 steel powder joined to 316 steel by low temperature HIP

International Nuclear Information System (INIS)

Lind, Anders; Sundstroem, Johan

2004-11-01

During the manufacture of the blanket modules, 316L steel powder is simultaneously consolidated and joined to tubes and blocks of 316L materials by Hot Isostatic Pressing (HIP). The high processing temperature can detrimentally increase the grain size of the water cooling tubes in the structure and the blocks reducing their strength. It is well known that surface oxides on the powder particles negatively influence the impact toughness of material and joints consolidated in this way. By increasing the consolidation temperature the metallurgical bonding is improved, due to a redistribution of oxygen within the oxide layer towards more discrete oxide particles. In order to get acceptable mechanical properties of materials produced at a low HIP temperature the oxygen content on the powder surfaces needs to be reduced. The aim of this new techniques to reduce the oxygen content of the metal powder. The influence on Charpy impact energy and tensile strength were demonstrated

Thermal conductivity model for powdered materials under vacuum based on experimental studies

Directory of Open Access Journals (Sweden)

N. Sakatani

2017-01-01

Full Text Available The thermal conductivity of powdered media is characteristically very low in vacuum, and is effectively dependent on many parameters of their constituent particles and packing structure. Understanding of the heat transfer mechanism within powder layers in vacuum and theoretical modeling of their thermal conductivity are of great importance for several scientific and engineering problems. In this paper, we report the results of systematic thermal conductivity measurements of powdered media of varied particle size, porosity, and temperature under vacuum using glass beads as a model material. Based on the obtained experimental data, we investigated the heat transfer mechanism in powdered media in detail, and constructed a new theoretical thermal conductivity model for the vacuum condition. This model enables an absolute thermal conductivity to be calculated for a powder with the input of a set of powder parameters including particle size, porosity, temperature, and compressional stress or gravity, and vice versa. Our model is expected to be a competent tool for several scientific and engineering fields of study related to powders, such as the thermal infrared observation of air-less planetary bodies, thermal evolution of planetesimals, and performance of thermal insulators and heat storage powders.

Resolution of crystal structures by X-ray and neutrons powder diffraction using global optimisation methods; Resolution des structures cristallines par diffraction des rayons X et neutrons sur poudres en utilisant les methodes d'optimisation globale

Energy Technology Data Exchange (ETDEWEB)

Palin, L

2005-03-15

We have shown in this work that X-ray diffraction on powder is a powerful tool to analyze crystal structure. The purpose of this thesis is the resolution of crystal structures by X-ray and neutrons diffraction on powder using global optimisation methods. We have studied 3 different topics. The first one is the order-disorder phenomena observed in some globular organic molecular solids. The second is the opiate family of neuropeptides. These neurotransmitters regulate sensory functions including pain and control of respiration in the central nervous system. The aim of our study was to try to determine the crystal structure of Leu-enkephalin and some of its sub-fragments. The determination of the crystal structures has been done performing Monte Carlo simulations. The third one is the location of benzene in a sodium-X zeolite. The zeolite framework was already known and the benzene has been localized by simulated annealing and by the use of maximum entropy maps.

An analysis of un-dissolved powders of instant powdered soup by using ultrasonographic image

Science.gov (United States)

Kawaai, Yukinori; Kato, Kunihito; Yamamoto, Kazuhiko; Kasamatsu, Chinatsu

2008-11-01

Nowadays, there are many instant powdered soups around us. When we make instant powdered soup, sometimes we cannot dissolve powders perfectly. Food manufacturers want to improve this problem in order to make better products. Therefore, they have to measure the state and volume of un-dissolved powders. Earlier methods for analyzing removed the un-dissolved powders from the container, the state of the un-dissolved power was changed. Our research using ultrasonographic image can measure the state of un-dissolved powders with no change by taking cross sections of the soup. We then make 3D soup model from these cross sections of soup. Therefore we can observe the inside of soup that we do not have ever seen. We construct accurate 3D model. We can visualize the state and volume of un-dissolved powders with analyzing the 3D soup models.

Combined effect of sulfur dioxide and carbon dioxide gases on mold fungi

Energy Technology Data Exchange (ETDEWEB)

Kochurova, A.I.; Karpova, T.N.

1974-01-01

Sulfur dioxide at 0.08% killed Penicillium expansum, Stemphylium macrosporium, and Botrytis cinerea within 24 hours. At 0.2%, it killed P. citrinum, Alternaria tenuis, and Fusarium moniliforme. Sulfur dioxide (at 0.04%) and Sulfur dioxide-carbon dioxide mixtures (at 0.02 and 5% respectively) completely suppressed the growth of P. citrinum, P. expansum, P. rubrum, A. tenuis, S. macrosporium, B. cinerea, and F. moniliforme in laboratory experiments. 1 table.

Muon transfer to sulphur dioxide

International Nuclear Information System (INIS)

Mulhauser, F.; Schneuwly, H.

1993-01-01

A systematic study of muon capture and muon transfer has been performed in seven different H 2 + SO 2 gas mixtures. From the single-exponential time structure of the muonic sulphur x-rays, one determines the lifetime of the μp atoms under the given experimental conditions. The reduced muon transfer rates to the sulphur dioxide molecule, deduced from these lifetimes, all agree well with each other. The muonic oxygen time spectra show an additional structure as if μp atoms of another kind were present. Comparable time structures are observed in a D 2 + SO 2 mixture. (author)

Fabrication of uranium dioxide of different granulation from uranyl nitrate by ammonia diuranate; Dobijanje urandioksida razlicitih granulacija iz uranilnitrata preko amonijumdiuranata

Energy Technology Data Exchange (ETDEWEB)

Vojnovic, J; Stamenkovic, I [Institute of Nuclear Sciences Boris Kidric, Laboratorija za termotehniku reaktora, Vinca, Beograd (Serbia and Montenegro)

1961-12-15

Uranium dioxide is most frequently produced by reduction of higher oxides (UO{sub 3}, U{sub 3}O{sub 8}) or reduction of uranium salts (uranium diuranate, uranium peroxide, uranyl oxalate). Reduction is most frequently done in hydrogen or carbon monoxide atmosphere under temperatures from 500 - 1700 deg C. One of the most frequently methods for producing uranium oxide is certainly reduction of ammonia diuranate by hydrogen (ADU method). Properties of uranium dioxide obtained by ADU method depend on properties of the initial substance. Investigations shown in this report are concerned with determining the properties of UO{sub 2} powders for determining the connection between their properties and conditions of fabrication and reduction of ADU and U{sub 3}O{sub 8}.

Titanium dioxide. An effective additive for minimisation of alkali vaporisation; Titandioxidadditiv. En effektiv tillsats foer att minska alkalifoeraangning

Energy Technology Data Exchange (ETDEWEB)

Wiinikka, Henrik; Groenberg, Carola; Oehrman, Olov

2008-10-15

} could be found in the bottom ash. Probably, potassium is also bound in an amorphous phase containing K, Ti, Si, and O. Titanium dioxide additive could either be pure titanium dioxide that is introduced to the fuel or co-firing of a potassium rich fuel with waste wood that contains titanium dioxide. Titanium dioxide (titanium white) is the most common pigment in white colour. During 1998 about 20 000 ton titanium dioxide was used as white pigment in Sweden, however not only as wood colour. An estimation of the amount of titanium containing waste wood showed that about 124 ton pure titanium is released during demolition of buildings in Sweden each year. The price for pure titanium dioxide powder varies between 17-20 SEK/kg (1 SEK approx 0.13 USD) dependent on the quality of the powder. The price for titanium dioxide additive depends on the potassium content in the fuel and optimal mixing ratio of titanium dioxide additive.

Fabrication by powder metallurgy of the niobium based alloy Nb-1-Zr

International Nuclear Information System (INIS)

Marty, M.; Delaunay, C.; Walder, A.

1989-01-01

The Nb-1Zr alloy has been produced by the powder metallurgy technique. Production of powders was performed by centrifugal atomization with the rotating electrode process (REP) under an inert atmosphere of argon-helium. Alloy powders were characterized by granulometric spectra, oxygen content and the various types of structures which were found. After consolidation by extrusion, materials were evaluated by tensile test under vacuum at ambient temperature, 750 and 900 0 C and compared with the same alloy elaborated by ingot metallurgy. 8 refs., 9 figs. (Author)

Mineral carbonation of gaseous carbon dioxide using a clay-hosted cation exchange reaction.

Science.gov (United States)

Kang, Il-Mo; Roh, Ki-Min

2013-01-01

The mineral carbonation method is still a challenge in practical application owing to: (1) slow reaction kinetics, (2) high reaction temperature, and (3) continuous mineral consumption. These constraints stem from the mode of supplying alkaline earth metals through mineral acidification and dissolution. Here, we attempt to mineralize gaseous carbon dioxide into calcium carbonate, using a cation exchange reaction of vermiculite (a species of expandable clay minerals). The mineralization is operated by draining NaCI solution through vermiculite powders and continuously dropping into the pool of NaOH solution with CO2 gas injected. The mineralization temperature is regulated here at 293 and 333 K for 15 min. As a result of characterization, using an X-ray powder diffractometer and a scanning electron microscopy, two types of pure CaCO3 polymorphs (vaterite and calcite) are identified as main reaction products. Their abundance and morphology are heavily dependent on the mineralization temperature. Noticeably, spindle-shaped vaterite, which is quite different from a typical vaterite morphology (polycrystalline spherulite), forms predominantly at 333 K (approximately 98 wt%).

Porous Nb-Ti based alloy produced from plasma spheroidized powder

Science.gov (United States)

Li, Qijun; Zhang, Lin; Wei, Dongbin; Ren, Shubin; Qu, Xuanhui

Spherical Nb-Ti based alloy powder was prepared by the combination of plasma spheroidization and mechanical alloying. Phase constituents, microstructure and surface state of the powder, and pore characteristics of the resulting porous alloy were investigated. The results show that the undissolved W and V in the mechanically alloyed powder is fully alloyed after spheroidization, and single β phase is achieved. Particle size of the spheroidized powder is in the range of 20-110 μm. With the decrease of particle size, a transformation from typical dendrite solidification structure to fine cell microstructure occurs. The surface of the spheroidized powder is coated by a layer of oxides consisting mainly of TiO2 and Nb2O5. Probabilities of sinter-neck formation and particle coalescence increases with increasing sintering temperature. Porous skeleton with relatively homogeneous pore distribution and open pore channel is formed after vacuum sintering at 1700 °C, and the porosity is 32%. The sintering kinetic analysis indicates that grain boundary diffusion is the primary mass transport mechanism during sintering process.

Polarized neutron powder diffraction studies of antiferromagnetic order in bulk and nanoparticle NiO

DEFF Research Database (Denmark)

Brok, Erik; Lefmann, Kim; Deen, Pascale P.

2015-01-01

surface contribution to the magnetic anisotropy. Here we explore the potential use of polarized neutron diffraction to reveal the magnetic structure in NiO bulk and nanoparticle powders by applying the XYZ-polarization analysis method. Our investigations address in particular the spin orientation in bulk....... The results show that polarization analyzed neutron powder diffraction is a viable method to investigate magnetic order in powders of antiferromagnetic nanoparticles.......In many materials it remains a challenge to reveal the nature of magnetic correlations, including antiferromagnetism and spin disorder. Revealing the spin structure in magnetic nanoparticles is further complicated by the large incoherent neutron scattering cross section from water adsorbed...

Operation whey powder

International Nuclear Information System (INIS)

Brunner, E.

1987-01-01

The odyssey of the contaminated whey powder finally has come to an end, and the 5000 tonnes of whey now are designated for decontamination by means of an ion exchange technique. The article throws light upon the political and economic reasons that sent the whey powder off on a chaotic journey. It is worth mentioning in this context that the natural radioactivity of inorganic fertilizers is much higher than that of the whey powder in question. (HP) [de

Study on application of zirconium dioxide for upgrading quality of pouring cups used in continuous steel casting technology

International Nuclear Information System (INIS)

Pham Ba Kien; Vu Thanh Quang and Ngo Van Tuyen

2004-01-01

This theme studies on technology of zirconium oxide powder stabilized by calcium and testing production of steel pouring cup made of the stabilized dioxide zirconium ceramic. As a product of the theme, the steel pouring cup has had the following main characteristics: heat resistance > 1700 o C, density of 4.7 g/cm 3 , apparent sponge degree of 1.63%, compressibility of 3300 kg/cm 2 . The quality of the cup has been tested and highly evaluated during the actual production. (author)

Carbon dioxide as chemical feedstock

National Research Council Canada - National Science Library

Aresta, M

2010-01-01

... Dioxide as an Inert Solvent for Chemical Syntheses 15 Alessandro Galia and Giuseppe Filardo Introduction 15 Dense Carbon Dioxide as Solvent Medium for Chemical Processes 15 Enzymatic Catalysis in Dense Carbon Dioxide 18 Other Reactions in Dense Carbon Dioxide 19 Polymer Synthesis in Supercritical Carbon Dioxide 20 Chain Polymerizations: Synt...

Densification behavior of aluminum alloy powder mixed with zirconia powder inclusion under cold compaction

International Nuclear Information System (INIS)

Ryu, Hyun Seok; Lee, Sung Chul; Kim, Ki Tae

2002-01-01

Densification behavior of composite powders was investigated during cold compaction. Experimental data were obtained for aluminum alloy powder mixed with zirconia powder inclusion under triaxial compression. The cap model with constraint factors was implemented into a finite element program(ABAQUS) to simulate compaction responses of composite powders during cold compaction. Finite element results were compared with experimental data for densification behavior of composite powders under cold isostatic pressing and die compaction. The agreements between experimental data and finite element calculations from the cap model with constraint factors were good

Nuclear fuel powder transfer device

International Nuclear Information System (INIS)

Komono, Akira

1998-01-01

A pair of parallel rails are laid between a receiving portion to a molding portion of a nuclear fuel powder transfer device. The rails are disposed to the upper portion of a plurality of parallel support columns at the same height. A powder container is disposed while being tilted in the inside of the vessel main body of a transfer device, and rotational shafts equipped with wheels are secured to right and left external walls. A nuclear powder to be mixed, together with additives, is supplied to the powder container of the transfer device. The transfer device engaged with the rails on the receiving side is transferred toward the molding portion. The wheels are rotated along the rails, and the rotational shafts, the vessel main body and the powder container are rotated. The nuclear powder in the tilted powder container disposed is rotated right and left and up and down by the rotation, and the powder is mixed satisfactory when it reaches the molding portion. (I.N.)

Innovative technologies for powder metallurgy-based disk superalloys: Progress and proposal

Science.gov (United States)

Chong-Lin, Jia; Chang-Chun, Ge; Qing-Zhi, Yan

2016-02-01

Powder metallurgy (PM) superalloys are an important class of high temperature structural materials, key to the rotating components of aero engines. In the purview of the present challenges associated with PM superalloys, two novel approaches namely, powder preparation and the innovative spray-forming technique (for making turbine disk) are proposed and studied. Subsequently, advanced technologies like electrode-induction-melting gas atomization (EIGA), and spark-plasma discharge spheroidization (SPDS) are introduced, for ceramic-free superalloy powders. Presently, new processing routes are sought after for preparing finer and cleaner raw powders for disk superalloys. The progress of research in spray-formed PM superalloys is first summarized in detail. The spray-formed superalloy disks specifically exhibit excellent mechanical properties. This paper reviews the recent progress in innovative technologies for PM superalloys, with an emphasis on new ideas and approaches, central to the innovation driving techniques like powder processing and spray forming. Project supported by the National Natural Science Foundation of China (Grant Nos. 50974016 and 50071014).

Diffraction. Powder, amorphous, liquid

International Nuclear Information System (INIS)

Sosnowska, I.M.

1999-01-01

Neutron powder diffraction is a unique tool to observe all possible diffraction effects appearing in crystal. High-resolution neutron diffractometers have to be used in this study. Analysis of the magnetic structure of polycrystalline materials requires the use of high-resolution neutron diffraction in the range of large interplanar distances. As distinguished from the double axis diffractometers (DAS), which show high resolution only at small interplanar distances, TOF (time-of-flight) diffractometry offers the best resolution at large interplanar distances. (K.A.)

Direct dynamic synthesis of nanodispersed phases of titanium oxides upon sputtering of electrodischarge titanium plasma into an air atmosphere

Science.gov (United States)

Sivkov, A. A.; Gerasimov, D. Yu.; Nikitin, D. S.

2017-01-01

Experimental investigations of the possibility of directly synthesizing nanodispersed crystalline phases of titanium dioxides with rutile and anatase structures in a hypervelocity jet of electroerosion plasma generated by a coaxial magnetoplasma accelerator with titanium electrodes are presented. A powder product containing nanosized polymorphic phases of titanium dioxide with a spherical shape of particles has been manufactured.

Preparation of tris(8-hydroxyquinolinato)aluminum thin films by sputtering deposition using powder and pressed powder targets

Science.gov (United States)

Kawasaki, Hiroharu; Ohshima, Tamiko; Yagyu, Yoshihito; Ihara, Takeshi; Tanaka, Rei; Suda, Yoshiaki

2017-06-01

Tris(8-hydroxyquinolinato)aluminum (Alq3) thin films, for use in organic electroluminescence displays, were prepared by a sputtering deposition method using powder and pressed powder targets. Experimental results suggest that Alq3 thin films can be prepared using powder and pressed powder targets, although the films were amorphous. The surface color of the target after deposition became dark brown, and the Fourier transform infrared spectroscopy spectrum changed when using a pressed powder target. The deposition rate of the film using a powder target was higher than that using a pressed powder target. That may be because the electron and ion densities of the plasma generated using the powder target are higher than those when using pressed powder targets under the same deposition conditions. The properties of a thin film prepared using a powder target were almost the same as those of a film prepared using a pressed powder target.

Structure and characteristics of functional powder composite materials obtained by spark plasma sintering

Science.gov (United States)

Oglezneva, S. A.; Kachenyuk, M. N.; Kulmeteva, V. B.; Ogleznev, N. B.

2017-07-01

The article describes the results of spark plasma sintering of ceramic materials based on titanium carbide, titanium carbosilicide, ceramic composite materials based on zirconium oxide, strengthened by carbon nanostructures and composite materials of electrotechnical purpose based on copper with addition of carbon structures and titanium carbosilicide. The research shows that the spark plasma sintering can achieve relative density of the material up to 98%. The effect of sintering temperature on the phase composition, density and porosity of the final product has been studied. It was found that with addition of carbon nanostructures the relative density and hardness decrease, but the fracture strength of ZrO2 increases up to times 2. The relative erosion resistance of the electrodes made of composite copper-based powder materials, obtained by spark plasma sintering during electroerosion treatment of tool steel exceeds that parameter of pure copper up to times 15.

Single-step laser deposition of functionally graded coating by dual ‘wire powder’ or ‘powder powder’ feeding—A comparative study

Science.gov (United States)

Syed, Waheed Ul Haq; Pinkerton, Andrew J.; Liu, Zhu; Li, Lin

2007-07-01

The creation of iron-copper (Fe-Cu) alloys has practical application in improving the surface heat conduction and corrosion resistance of, for example, conformal cooling channels in steel moulds, but is difficult to achieve because the elements have got low inter-solubility and are prone to solidification cracking. Previous work by these authors has reported a method to produce a graded iron-nickel-copper coating in a single-step by direct diode laser deposition (DLD) of nickel wire and copper powder as a combined feedstock. This work investigates whether dual powder feeds can be used in that process to afford greater geometric flexibility and compares attributes of the 'nickel wire and copper powder' and 'nickel powder and copper powder' processes for deposition on a H13 tool steel substrate. In wire-powder deposition, a higher temperature developed in the melt pool causing a clad with a smooth gradient structure. The nickel powder in powder-powder deposition did not impart much heat into the melt pool so the melt pool solidified with sharp composition boundaries due to single metal melting in some parts. In wire-powder experiments, a graded structure was obtained by varying the flow rates of wire and powder. However, a graded structure was not realised in powder-powder experiments by varying either the feed or the directions. Reasons for the differences and flow patterns in the melt pools and their effect on final part properties of parts produced are discussed.

Influence of Ultrafine 2CaO·SiO₂ Powder on Hydration Properties of Reactive Powder Concrete.

Science.gov (United States)

Sun, Hongfang; Li, Zishanshan; Memon, Shazim Ali; Zhang, Qiwu; Wang, Yaocheng; Liu, Bing; Xu, Weiting; Xing, Feng

2015-09-17

In this research, we assessed the influence of an ultrafine 2CaO·SiO₂ powder on the hydration properties of a reactive powder concrete system. The ultrafine powder was manufactured through chemical combustion method. The morphology of ultrafine powder and the development of hydration products in the cement paste prepared with ultrafine powder were investigated by scanning electron microscopy (SEM), mineralogical composition were determined by X-ray diffraction, while the heat release characteristics up to the age of 3 days were investigated by calorimetry. Moreover, the properties of cementitious system in fresh and hardened state (setting time, drying shrinkage, and compressive strength) with 5% ordinary Portland cement replaced by ultrafine powder were evaluated. From SEM micrographs, the particle size of ultrafine powder was found to be up to several hundred nanometers. The hydration product started formulating at the age of 3 days due to slow reacting nature of belitic 2CaO·SiO₂. The initial and final setting times were prolonged and no significant difference in drying shrinkage was observed when 5% ordinary Portland cement was replaced by ultrafine powder. Moreover, in comparison to control reactive powder concrete, the reactive powder concrete containing ultrafine powder showed improvement in compressive strength at and above 7 days of testing. Based on above, it can be concluded that the manufactured ultrafine 2CaO·SiO₂ powder has the potential to improve the performance of a reactive powder cementitious system.

Energetics of intrinsic point defects in uranium dioxide from electronic-structure calculations

International Nuclear Information System (INIS)

Nerikar, Pankaj; Watanabe, Taku; Tulenko, James S.; Phillpot, Simon R.; Sinnott, Susan B.

2009-01-01

The stability range of intrinsic point defects in uranium dioxide is determined as a function of temperature, oxygen partial pressure, and non-stoichiometry. The computational approach integrates high accuracy ab initio electronic-structure calculations and thermodynamic analysis supported by experimental data. In particular, the density functional theory calculations are performed at the level of the spin polarized, generalized gradient approximation and includes the Hubbard U term; as a result they predict the correct anti-ferromagnetic insulating ground state of uranium oxide. The thermodynamic calculations enable the effects of system temperature and partial pressure of oxygen on defect formation energy to be determined. The predicted equilibrium properties and defect formation energies for neutral defect complexes match trends in the experimental literature quite well. In contrast, the predicted values for charged complexes are lower than the measured values. The calculations predict that the formation of oxygen interstitials becomes increasingly difficult as higher temperatures and reducing conditions are approached

Application of laser in powder metallurgy

International Nuclear Information System (INIS)

Tolochko, N.K.

1995-01-01

Modern status of works in the field of laser application in powder metallurgy (powders preparation, sintering, coatings formation, powder materials processing) is considered. The attention is paid to the new promising direction in powder products shape-formation technology - laser layer-by-layer selective powders sintering and bulk sintering of packaged layered profiles produced by laser cutting of powder-based sheet blanks. 67 refs

Process for sequestering carbon dioxide and sulfur dioxide

Science.gov (United States)

Maroto-Valer, M Mercedes [State College, PA; Zhang, Yinzhi [State College, PA; Kuchta, Matthew E [State College, PA; Andresen, John M [State College, PA; Fauth, Dan J [Pittsburgh, PA

2009-10-20

A process for sequestering carbon dioxide, which includes reacting a silicate based material with an acid to form a suspension, and combining the suspension with carbon dioxide to create active carbonation of the silicate-based material, and thereafter producing a metal salt, silica and regenerating the acid in the liquid phase of the suspension.

Validation of missed space-group symmetry in X-ray powder diffraction structures with dispersion-corrected density functional theory.

Science.gov (United States)

Hempler, Daniela; Schmidt, Martin U; van de Streek, Jacco

2017-08-01

More than 600 molecular crystal structures with correct, incorrect and uncertain space-group symmetry were energy-minimized with dispersion-corrected density functional theory (DFT-D, PBE-D3). For the purpose of determining the correct space-group symmetry the required tolerance on the atomic coordinates of all non-H atoms is established to be 0.2 Å. For 98.5% of 200 molecular crystal structures published with missed symmetry, the correct space group is identified; there are no false positives. Very small, very symmetrical molecules can end up in artificially high space groups upon energy minimization, although this is easily detected through visual inspection. If the space group of a crystal structure determined from powder diffraction data is ambiguous, energy minimization with DFT-D provides a fast and reliable method to select the correct space group.

Unit-cell refinement from powder diffraction scans

International Nuclear Information System (INIS)

Pawley, G.S.

1981-01-01

A procedure for the refinement of the crystal unit cell from a powder diffraction scan is presented. In this procedure knowledge of the crystal structure is not required, and at the end of the refinement a list of indexed intensities is produced. This list may well be usable as the starting point for the application of direct methods. The problems of least-squares ill-conditioning due to overlapping reflections are overcome by constraints. An example using decafluorocyclohexene, C 6 F 10 , shows the quality of fit obtained in a case which may even be a false minimum. The method should become more relevant as powder scans of improved resolution become available, through the use of pulsed neutron sources. (Auth.)

In situ hydrogen loading on zirconium powder

Energy Technology Data Exchange (ETDEWEB)

Maimaitiyili, Tuerdi, E-mail: tuerdi.maimaitiyili@mah.se; Blomqvist, Jakob [Malmö University, Östra Varvsgatan 11 A, Malmö, Skane 20506 (Sweden); Steuwer, Axel [Lund University, Ole Römers väg, Lund, Skane 22100 (Sweden); Nelson Mandela Metropolitan University, Gardham Avenue, Port Elizabeth 6031 (South Africa); Bjerkén, Christina [Malmö University, Östra Varvsgatan 11 A, Malmö, Skane 20506 (Sweden); Zanellato, Olivier [Ensam - Cnam - CNRS, 151 Boulevard de l’Hôpital, Paris 75013 (France); Blackmur, Matthew S. [Materials Performance Centre, School of Materials, The University of Manchester, Manchester M1 7HS (United Kingdom); Andrieux, Jérôme [European Synchrotron Radiation Facility, 6 rue J Horowitz, Grenoble 38043 (France); Université de Lyon, 43 Bd du 11 novembre 1918, Lyon 69100 (France); Ribeiro, Fabienne [Institut de Radioprotection et Sûreté Nucléaire, IRSN, BP 3, 13115 Saint-Paul Lez Durance (France)

2015-06-26

Commercial-grade Zr powder loaded with hydrogen in situ and phase transformations between various Zr and ZrH{sub x} phases have been monitored in real time. For the first time, various hydride phases in a zirconium–hydrogen system have been prepared in a high-energy synchrotron X-ray radiation beamline and their transformation behaviour has been studied in situ. First, the formation and dissolution of hydrides in commercially pure zirconium powder were monitored in real time during hydrogenation and dehydrogenation, then whole pattern crystal structure analysis such as Rietveld and Pawley refinements were performed. All commonly reported low-pressure phases presented in the Zr–H phase diagram are obtained from a single experimental arrangement.

In situ hydrogen loading on zirconium powder

International Nuclear Information System (INIS)

Maimaitiyili, Tuerdi; Blomqvist, Jakob; Steuwer, Axel; Bjerkén, Christina; Zanellato, Olivier; Blackmur, Matthew S.; Andrieux, Jérôme; Ribeiro, Fabienne

2015-01-01

Commercial-grade Zr powder loaded with hydrogen in situ and phase transformations between various Zr and ZrH x phases have been monitored in real time. For the first time, various hydride phases in a zirconium–hydrogen system have been prepared in a high-energy synchrotron X-ray radiation beamline and their transformation behaviour has been studied in situ. First, the formation and dissolution of hydrides in commercially pure zirconium powder were monitored in real time during hydrogenation and dehydrogenation, then whole pattern crystal structure analysis such as Rietveld and Pawley refinements were performed. All commonly reported low-pressure phases presented in the Zr–H phase diagram are obtained from a single experimental arrangement

STRUCTURE, PHASE COMPOSITION AND PROPERTIES OF GAS-THERMAL COVERINGS OF MECHANICALLY ALLOYED THERMOREACTING COMPOSITE POWDERS OF NICKEL-ALUMINIUM SYSTEM

Directory of Open Access Journals (Sweden)

F. G. Lovshenko

2015-01-01

Full Text Available The presented results show that coverings from mechanically alloyed thermoreacting powders of system «nickel–aluminum» are nonequilibrium multiphase systems which basis represents solid solution of aluminum in nickel. It has the microcrystalline type of structure which is characterized by an advanced surface of borders of the grains and subgrains stabilized by nanodimensional inclusions of oxides and alyuminid. These coverings surpass by 1,2–1,6 times analogs in durability, hardness and wear resistance.

Influence of Rubber Powders on Foaming Behavior and Mechanical Properties of Foamed Polypropylene Composites

Directory of Open Access Journals (Sweden)

HE Yue

2017-02-01

Full Text Available Polypropylene/rubber powders composites with different kinds of rubber powders were foamed by injection molding machine equipped with volume-adjustable cavity. The effect of dispersity of rubber powders and crystallization behavior of composites on the foaming behavior and mechanical properties was investigated. The results show that the addition of rubber powders can improve the cell structure of foamed PP with fine and uniform cell distribution. And cell density and size of PP/PP-MAH/NBR foams are 7.64×106cell/cm3 and 29.78μm respectively, which are the best among these foams. Combining cell structures with mechanical properties, notch impact strength of PP/PP-MAH/CNBR composites increases approximately by 2.2 times while tensile strength is reduced just by 26% compared with those of the pure PP. This indicates that PP/PP-MAH/CNBR composites are ideal foamed materials.

Structure and mechanical properties of parts obtained by selective laser melting of metal powder based on intermetallic compounds Ni3Al

Science.gov (United States)

Smelov, V. G.; Sotov, A. V.; Agapovichev, A. V.; Nosova, E. A.

2018-03-01

The structure and mechanical properties of samples are obtained from metal powder based on intermetallic compound by selective laser melting. The chemical analysis of the raw material and static tensile test of specimens were made. Change in the samples’ structure and mechanical properties after homogenization during four and twenty-four hours were investigated. A small-sized combustion chamber of a gas turbine engine was performed by the selective laser melting method. The print combustion chamber was subjected to the gas-dynamic test in a certain temperature and time range.

Effect of cooling rate on microstructure and deformation behavior of Ti-based metallic glassy/crystalline powders

Energy Technology Data Exchange (ETDEWEB)

Wang, D.J. [State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001 (China); School of Mechanical and Mining Engineering, University of Queensland, Brisbane, QLD 4072 (Australia); Huang, Y.J. [State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001 (China); Shen, J., E-mail: junshen@hit.edu.cn [State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001 (China); Wu, Y.Q.; Huang, H. [School of Mechanical and Mining Engineering, University of Queensland, Brisbane, QLD 4072 (Australia); Zou, J., E-mail: j.zou@uq.edu.au [School of Mechanical and Mining Engineering, University of Queensland, Brisbane, QLD 4072 (Australia); Centre for Microscopy and Microanalysis, University of Queensland, Brisbane, QLD 4072 (Australia)