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1

Synthesis and characterization of pure cubic zirconium oxide nanocrystals by decomposition of bis-aqua, tris-acetylacetonato zirconium(IV) nitrate as new precursor complex  

Microsoft Academic Search

Pure zirconium oxide (ZrO2) nanocrystals with diameters 10–30nm are fabricated from bis-aqua, tris-acetylacetonato zirconium(IV) nitrate; [Zr(acac)3(H2O)2](NO3); by thermal decomposition. The different combinations of oleylamine, or polyethyleneglycol (PEG) and triphenylphosphine, were added as surfactants to control the particle size. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, photoluminescence spectroscopy (PL), Fourier transform infrared (FT-IR)

Masoud Salavati-Niasari; Mahnaz Dadkhah; Fatemeh Davar

2009-01-01

2

Zirconium  

USGS Publications Warehouse

Zirconium is the 20th most abundant element in the Earth’s crust. It occurs in a variety of rock types and geologic environments but most often in igneous rocks in the form of zircon (ZrSiO4). Zircon is recovered as a coproduct of the mining and processing of heavy mineral sands for the titanium minerals ilmenite and rutile. The sands are formed by the weathering and erosion of rock containing zircon and titanium heavy minerals and their subsequent concentration in sedimentary systems, particularly in coastal environments. A small quantity of zirconium, less than 10 kt/a (11,000 stpy), compared with total world production of 1.4 Mt (1.5 million st) in 2012, was derived from the mineral baddeleyite (ZrO2), produced from a single source in Kovdor, Russia.

Bedinger, G. M.

2013-01-01

3

ADSORPTION AND RECOVERY OF NITRATED POLYCYCLIC AROMATIC HYDROCARBONS ON HYBRID SURFACTANT EXPANDED ZIRCONIUM-PHOSPHATE  

Microsoft Academic Search

This paper focuses on the removal of nitro substituted polycyclic aromatic hydrocarbon compounds (NPAHs) from water using low cost synthesized zirconium phosphate mesoporous materials. These materials are lamellar type incorporating n-alkyl-(n = 12 and n = 16) trimethylamonium bromide molecules with different concentrations. For comparison of their performance as adsorbents and in the recovery of NPAH, their results were compared

M. Algarra; M. V. Jiménez; F. G. Sánchez; J. Soto; J. J. Jiménez; Joaquim C. G. Esteves da Silva

2009-01-01

4

PROCESS OF RECOVERING ZIRCONIUM VALUES FROM HAFNIUM VALUES BY SOLVENT EXTRACTION WITH AN ALKYL PHOSPHATE  

DOEpatents

A process of separating hafnium nitrate from zirconium nitrate contained in a nitric acid solution by selectively. extracting the zirconium nitrate with a water-immiscible alkyl phosphate is reported.

Peppard, D.F.

1960-02-01

5

The influence of dibutyl phosphoric acid on zirconium extraction with diluted tributyl phosphate and the role of uranyl nitrate  

NASA Astrophysics Data System (ADS)

Distribution coefficients of zirconium (DZr) in the 30% TBP — aqueous HNO3 solution extraction system rise 1000 2000 times with the increase of the dibutyl phosphoric acid (HDBP) concentration from 0 to 0.01 0.08 mol/L. A solvate with the molar ratio Zr: HDBP=1 was found by IR spectroscopy and analytic methods in the initial range of HDBP concentration. In the presence of U(VI) DZr decreases with the growing U concentration, however, the ratio of Zr distribution coefficient in the presence of HDBP (DAZr) to DZr determined in its absence, RZr=DAZr/DZr, is rather high. Function of enhancement (F) was introduced for the evaluation of simultaneous influence of U and HDBP on Zr extraction. An increase of the U concentration resulted first in the decrease in FZr, and then in its increase. The rising part of the FZr curve was more noticeable at a molar excess of Zr over HDBP. The mechanism of Zr extraction by 30% TBP solution in the presence of HDBP when Zr is in excess to HDBP indicates the formation of the solvate with the ratio Zr: HDBP=1; in the presence of U(VI) the complex with the same ratio is formed by the HDBP interaction with U in the system with a great excess of both HDBP and Zr.

Blazheva, I. V.; Fedorov, Yu. S.; Zilberman, B. Ya.; Ryabkova, N. V.

2006-01-01

6

DISSOLUTION OF ZIRCONIUM AND ALLOYS THEREFOR  

DOEpatents

The dissolution of zirconium cladding in a water solution of ammonium fluoride and ammonium nitrate is described. The method finds particular utility in processing spent fuel elements for nuclear reactors. The zirconium cladding is first dissolved in a water solution of ammonium fluoride and ammonium nitrate; insoluble uranium and plutonium fiuorides formed by attack of the solvent on the fuel materiai of the fuel element are then separated from the solution, and the fuel materiai is dissolved in another solution.

Swanson, J.L.

1961-07-11

7

Corrosion of Zirconium and Zirconium Alloys.  

National Technical Information Service (NTIS)

Contents: The influence of alloying elements and heat treatment on the corrosion resistance of zirconium in water and steam; Theories on the mechanism of corrosion of zirconium and its alloys; Factors influencing hydrogen pick-up by zirconium alloys; The ...

B. G. Parfenov V. V. Gerasimov G. I. Venediktova

1969-01-01

8

Zirconium Esters  

Microsoft Academic Search

THE interesting results recorded recently by Speer1, and by Cullinane and Chard2, on the conditions for the preparation of titanium ortho-esters prompt us to mention our experience in preparing ortho-esters of zirconium. The literature contains little information on this subject. Meerwein and Bersin3 have recorded that zirconium ethoxide can be prepared by the following reactions: We find, however, that a

W. Wardlaw; D. C. Bradley

1950-01-01

9

METHOD OF IMPROVING CORROSION RESISTANCE OF ZIRCONIUM  

DOEpatents

An improved intermediate rinse for zirconium counteracts an anomalous deposit that often results in crevices and outof-the-way places when ordinary water is used to rinse away a strong fluoride etching solution designed to promote passivation of the metal. The intermediate rinse, which is used after the etching solution and before the water, is characterized by a complexing agent for fluoride ions such as aluminum or zirconium nitrates or chlorides.

Shannon, D.W.

1961-03-28

10

Zirconium oxide  

SciTech Connect

Zirconium is a more commonly occurring element than is widely recognized: it ranks as the 20th most abundant element in the Earth's crust at 220 ppm. In fact, zirconium is present in over 37 different mineral forms; examples are schists, gneiss, iron ore beds, and even granite. The two commercially most important sources of zirconium are zircon and baddeleyite. Both baddeleyite and zircon contain a small amount (about 2% by weight on an oxide basis) of hafnium. Structurally and chemically hafnia is so similar to zirconia that its presence has little effect on the properties of the zirconia. For the purpose of the article, the 98:2 ZrO{sub 2} {center dot} HfO{sub 2} will be referred to as zirconia.

Heathcote, R. (Magnesium Elektron, Ltd., Swinton, Manchester (GB))

1992-05-01

11

ZIRCONIUM-HAFNIUM SEPARATION  

Microsoft Academic Search

During 33 months of operation the purification plant at Albany, Oreg., ; processed 2,500,000 pounds of commercial zirconium tetrachloride to produce ; lowhafnium zirconium oxide and low-zirconium hafnium oxide. TMe average hafnium ; content of the zirconium oxide was about 40 ppm and the hafnium oxide contained ; less than 2% zirconium. The separate oxides were converted to sponge metal

Stickney

1959-01-01

12

Method for calcining nuclear waste solutions containing zirconium and halides  

DOEpatents

A reduction in the quantity of gelatinous solids which are formed in aqueous zirconium-fluoride nuclear reprocessing waste solutions by calcium nitrate added to suppress halide volatility during calcination of the solution while further suppressing chloride volatility is achieved by increasing the aluminum to fluoride mole ratio in the waste solution prior to adding the calcium nitrate.

Newby, Billie J. (Idaho Falls, ID)

1979-01-01

13

Separation of Zirconium and Uranium.  

National Technical Information Service (NTIS)

This invention relates to separation and recovery of zirconium from aqueous solutions containing zirconium and uranium. Separation of zirconium from uranium is, however, difficult since the uranium tends to accompany the zirconium in the solvent extractio...

H. G. Henry

1981-01-01

14

Zirconium - an Imported Mineral Commodity.  

National Technical Information Service (NTIS)

This report examines Canada's position in regard to the principal zirconium materials: zircon; fusion-cast zirconium-bearing refractory products; zirconium-bearing chemicals; and zirconium metal, master alloys, and alloys. None of these is produced in Can...

1983-01-01

15

PLUTONIUM-ZIRCONIUM ALLOYS  

Microsoft Academic Search

A series of nuclear reactor fuel alloys consisting of from about 5 to ; about 50 at.% zirconium (or higher zirconium alloys such as Zircaloy), balance ; plutonium, and having the structural composition of a plutonium are described. ; Zirconium is a satisfactory diluent because it alloys readily with plutonium and ; has desirable nuclear properties. Additional advantages are corrosion

F. W. Schonfeld; J. T. Waber

1960-01-01

16

Laser ablated zirconium plasma: A source of neutral zirconium  

Microsoft Academic Search

The authors report spectroscopic investigations of laser produced zirconium (Zr) plasma at moderate laser fluence. At low laser fluence the neutral zirconium species are observed to dominate over the higher species of zirconium. Laser induced fluorescence technique is used to study the velocity distribution of ground state neutral zirconium species. Two-dimensional time-resolved density distributions of ground state zirconium is mapped

Dheerendra Yadav; Raj K. Thareja

2010-01-01

17

Separation of Zirconium and Uranium.  

National Technical Information Service (NTIS)

Zirconium- and uranium-containing hydrocarbon-amine solutions are treated for separation of zirconium and uranium by means of a process comprising: (1) selctive stripping of zirconium with an aqueous chloride solution, and (2) scrubbing the resulting aque...

D. J. MacDonald H. G. Henry

1982-01-01

18

Investigation on Thermal Analysis of Binary Zirconium\\/Oxidant Pyrotechnic Systems  

Microsoft Academic Search

Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) have been used to examine the thermal behavior of powdered zirconium with some pyrotechnic oxidants, in relation to the behavior of the individual constituents. The results showed that decomposition temperature for pure compounds (potassium nitrate, potassium chlorate, potassium perchlorate, barium nitrate and barium peroxide) are 540, 472, 592, 745 and 600°C, respectively.

S. M. Pourmortazavi; S. G. Hosseini; S. S. Hajimirsadeghi; R. Fareghi Alamdari

2008-01-01

19

Electrowinning of zirconium from zirconium tetrachloride  

Microsoft Academic Search

The Bureau of Mines has produced ductile zirconium dendrites at 800°C in an electrolyte containing NaCl-NaF-ZrCl4. Sublimed zirconium tetrachloride was fed into NaCl containing a slight excess of NaF above that required to complex 2 pct\\u000a Zr as Na2ZrF6. The chlorine gas generated at the graphite anode during electrolysis was confined in and vented out of the cell through\\u000a a

G. M. Martinez; D. E. Couch

1972-01-01

20

Radiochemical separation of zirconium and hafnium from other radionuclides.  

PubMed

Radiozirconium and radiohafnium may be separated from all other radionuclides except scandium and protactinium by precipitation with mandelic acid from 5-10 M hydrochloric acid, using commercial zirconyl chloride as carrier. Scandium and protactinium are removed by dissolving the precipitate in sodium carbonate, then adding barium nitrate to precipitate barium carbonate which acts as a scavenger. Zirconium mandelate is finally reprecipitated and the sample weighed and counted in this form. The method was checked by analysing commercial zirconyl chloride and standard rock samples for zirconium and hafnium by neutron-activation analysis. PMID:18961201

Hahn, R B

1972-11-01

21

SEPARATING HAFNIUM FROM ZIRCONIUM  

DOEpatents

A dilute aqueous solution of zirconyl chloride which is 1N to 2N in HCl is passed through a column of a cation exchange resin in acid form thereby absorbing both zirconium and associated hafnium impurity in the mesin. The cation exchange material with the absorbate is then eluted with aqueous sulfuric acid of a O.8N to 1.2N strength. The first portion of the eluate contains the zirconium substantially free of hafnium.

Lister, B.A.J.; Duncan, J.F.

1956-08-21

22

Electroless deposition process for zirconium and zirconium alloys  

Microsoft Academic Search

A method is disclosed for preventing stress corrosion cracking or metal embrittlement of a zirconium or zirconium alloy container that is to be coated on the inside surface with a layer of a metal such as copper, a copper alloy, nickel, or iron and used for holding nuclear fuel material as a nuclear fuel element. The zirconium material is etched

Robert E. Donaghy; Anna H. Sherman

1981-01-01

23

Zirconium for superior corrosion resistance  

Microsoft Academic Search

Zirconium is a transition element located along with sister elements titanium and hafnium in Group IVB of the periodic table. It is grayish white metal, with a density somewhat less than carbon steel. Zirconium is the ninth most common metallic element in the earth`s crust, and is more abundant than zinc, lead, nickel, or even copper. Zirconium is exceptionally resistant

K. W. Bird; K. Richardson

1997-01-01

24

Electroless deposition process for zirconium and zirconium alloys  

DOEpatents

A method is disclosed for preventing stress corrosion cracking or metal embrittlement of a zirconium or zirconium alloy container that is to be coated on the inside surface with a layer of a metal such as copper, a copper alloy, nickel, or iron and used for holding nuclear fuel material as a nuclear fuel element. The zirconium material is etched in an etchant solution, desmutted mechanically or ultrasonically, oxidized to form an oxide coating on the zirconium, cleaned in an aqueous alkaline cleaning solution, activated for electroless deposition of a metal layer and contacted with an electroless metal plating solution. This method provides a boundary layer of zirconium oxide between the zirconium container and the metal layer.

Donaghy, Robert E. (Wilmington, NC); Sherman, Anna H. (Wilmington, NC)

1981-01-01

25

Electroless deposition process for zirconium and zirconium alloys  

DOEpatents

A method is disclosed for preventing stress corrosion cracking or metal embrittlement of a zirconium or zirconium alloy container that is to be coated on the inside surface with a layer of a metal such as copper, a copper alloy, nickel, or iron and used for holding nuclear fuel material as a nuclear fuel element. The zirconium material is etched in an etchant solution, desmutted mechanically or ultrasonically, oxidized to form an oxide coating on the zirconium, cleaned in an aqueous alkaline cleaning solution, activated for electroless deposition of a metal layer and contacted with an electroless metal plating solution. This method provides a boundary layer of zirconium oxide between the zirconium container and the metal layer. 1 fig.

Donaghy, R.E.; Sherman, A.H.

1981-08-18

26

Plasma arc melting of zirconium  

SciTech Connect

Zirconium, like some other refractory metals, has an undesirable sensitivity to interstitials such as oxygen. Traditionally, zirconium is processed by electron beam melting to maintain minimum interstitial contamination. Electron beam melted zirconium, however, does not respond positively to mechanical processing due to its large grain size. The authors undertook a study to determine if plasma arc melting (PAM) technology could be utilized to maintain low interstitial concentrations and improve the response of zirconium to subsequent mechanical processing. The PAM process enabled them to control and maintain low interstitial levels of oxygen and carbon, produce a more favorable grain structure, and with supplementary off-gassing, improve the response to mechanical forming.

Tubesing, P.K.; Korzekwa, D.R.; Dunn, P.S.

1997-12-31

27

Oxiconazole Nitrate  

Center for Drug Evaluation (CDER)

Text Version... Draft Guidance on Oxiconazole Nitrate This draft guidance, once finalized, will represent the Food and Drug Administration's (FDA's) current ... More results from www.fda.gov/downloads/drugs/guidancecomplianceregulatoryinformation

28

Process for purifying zirconium sponge  

SciTech Connect

This patent describes a Kroll reduction process wherein a zirconium sponge contaminated with unreacted magnesium and by-product magnesium chloride is produced as a regulus, a process for purifying the zirconium sponge. It comprises: distilling magnesium and magnesium chloride from: a regulus containing a zirconium sponge and magnesium and magnesium chloride at a temperature above about 800{degrees} C and at an absolute pressure less than about 10 mmHg in a distillation vessel to purify the zirconium sponge; condensing the magnesium and the magnesium chloride distilled from the zirconium sponge in a condenser; and then backfilling the vessel containing the zirconium sponge and the condenser containing the magnesium and the magnesium chloride with a gas; recirculating the gas between the vessel and the condenser to cool the zirconium sponge from above about 800{degrees} C to below about 300{degrees} C; and cooling the recirculating gas in the condenser containing the condensed magnesium and the condensed magnesium chloride as the gas cools the zirconium sponge to below about 300{degrees} C.

Abodishish, H.A.M.; Kimball, L.S.

1992-03-31

29

SEPARATING HAFNIUM FROM ZIRCONIUM  

DOEpatents

Substantially complete separation of zirconium from hafnium may be obtained by elution of ion exchange material, on which compounds of the elements are adsorbed, with an approximately normal solution of sulfuric acid. Preferably the acid concentration is between 0.8 N amd 1.2 N, amd should not exceed 1.5 N;. Increasing the concentration of sulfate ion in the eluting solution by addition of a soluble sulfate, such as sodium sulfate, has been found to be advantageous. The preferred ion exchange materials are sulfonated polystyrene resins such as Dowex 50,'' and are preferably arranged in a column through which the solutions are passed.

Lister, B.A.J.; Duncan, J.F.; Hutcheon, J.M.

1956-08-21

30

Synthesis, characterization and optical properties of novel N donor ligands-chelated zirconium(IV) complexes  

NASA Astrophysics Data System (ADS)

Novel zirconium complexes have been synthesized by using a mixture of zirconium nitrate, 1,2,4,5-benzen tetracarboxylic acid (H4btec), 1,10-phenanthroline(phen) and potassium thiocyanate. Monodentate coordination mode of btec acid for all complexes was investigated by FT-IR spectroscopy. The complexes were also characterized by UV-Vis, 1H NMR, CHN, ICP-AES. The reaction details and features were described and discussed. The photoluminescence emission of seven zirconium complexes was shown two series peaks: first, sharp and intense bands from 300 to 500 nm and broadened with less intensity from 650 to 750 nm for the second bands. Each of the zirconium compounds were doped in PVK:PBD blend as host. The ratio of zirconium complexes for each type were modified 8 wt.% in PVK:PBD(100:40). The electroluminescence spectra of zirconium complexes were indicated a red shift rather than PVK:PBD blend. We suggest that the electroplex occurring at PVK-Zr complex interface.

Shahroosvand, Hashem; Nasouti, Fahimeh; Mohajerani, Ezeddin; Khabbazi, Amir

2012-11-01

31

Separation of zirconium and uranium. [Patent application  

SciTech Connect

This invention relates to separation and recovery of zirconium from aqueous solutions containing zirconium and uranium. Separation of zirconium from uranium is, however, difficult since the uranium tends to accompany the zirconium in the solvent extraction and stripping steps. It is therefore desirable, and an object of the invention, to provide a simple and economical way of removing a major portion of the zirconium from the zirconium and uranium-containing strip solutions, with minimal removal of uranium. It has now been found, according to the present invention, that such a removal of zirconium may be accomplished by means of a process involving precipitation of zirconium from such zirconium and uranium-containing feed solutions by means of tartaric acid or a tartrate.

Henry, H.G.

1981-05-27

32

SEPARATION OF HAFNIUM FROM ZIRCONIUM  

DOEpatents

The separation of hafnium impurities from zirconium can be accomplished by means of organic solvent extraction. The hafnium-containing zirconium feed material is dissolved in an aqueous chloride solution and the resulting solution is contacted with an organic hexone phase, with at least one of the phases containing thiocyanate. The hafnium is extracted into the organic phase while zirconium remains in the aqueous phase. Further recovery of zirconium is effected by stripping the onganic phase with a hydrochloric acid solution and commingling the resulting strip solution with the aqueous feed solution. Hexone is recovered and recycled by means of scrubbing the onganic phase with a sulfuric acid solution to remove the hafnium, and thiocyanate is recovered and recycled by means of neutralizing the effluent streams to obtain ammonium thiocyanate.

Overholser, L.B.; Barton, C.J. Sr.; Ramsey, J.W.

1960-05-31

33

21 CFR 181.33 - Sodium nitrate and potassium nitrate.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 true Sodium nitrate and potassium nitrate. 181.33 Section 181.33 Food...Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions...

2010-01-01

34

21 CFR 181.33 - Sodium nitrate and potassium nitrate.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 false Sodium nitrate and potassium nitrate. 181.33 Section 181.33 Food...Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions...

2009-04-01

35

21 CFR 181.33 - Sodium nitrate and potassium nitrate.  

Code of Federal Regulations, 2013 CFR

... 2013-04-01 2013-04-01 false Sodium nitrate and potassium nitrate. 181.33...Prior-Sanctioned Food Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are...

2013-04-01

36

33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...  

Code of Federal Regulations, 2010 CFR

...ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo...contamination such as flammable liquids, combustible liquids,...

2010-07-01

37

33 CFR 126.28 - Ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...  

Code of Federal Regulations, 2010 CFR

...ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo nitrate...ammonium nitrate, ammonium nitrate fertilizers, fertilizer mixtures, or nitro carbo...contamination such as flammable liquids, combustible liquids,...

2009-07-01

38

ARSENATE METHOD OF IODOMETRIC DETERMINATION OF ZIRCONIUM  

Microsoft Academic Search

Experimental techniques for quantitative precipitation, filtration, ; elution, and solution of prepared zirconium arsenate precipitate in a strong acid ; are discussed. Precipitation of zirconium arsenate was carried out at the ; boiling point in a solution with 10% free sulfuric acid and using sodium arsenate ; as precipitating agent (with 40: 1 ratio to zirconium). Elutions using hot 2%

G. B Shakhtakhtinskii; A. S. Sarkisyan

1962-01-01

39

Localized Deformation of Zirconium-Liner Tube.  

National Technical Information Service (NTIS)

Zirconium-liner tube has come to be used in BWR. Zirconium liner mitigates the localized stress produced by the pellet-cladding interaction (PCI). In this study, simulating the ridging, stresses were applied to the inner surfaces of zirconium-liner tubes ...

F. Nagase M. Uchida

1988-01-01

40

Insensitive Ammonium Nitrate.  

National Technical Information Service (NTIS)

The danger of the accidental detonation of large masses of commercial ammonium nitrate during handling and storage under normal climatic conditions is reduced by replacing the ammonium nitrate with a solid solution of potassium nitrate in form III ammoniu...

C. Boyars

1978-01-01

41

Mössbauer spectroscopy of zirconium alloys  

NASA Astrophysics Data System (ADS)

Mössbauer investigations of zirconium alloys were examined. Data about the chemical state of iron atoms in the zirconium alloys of different composition has been provided. Mössbauer spectroscopy revealed that small quantities of iron in binary zirconium alloy are in the solid solution ?-Zr (up to 0.02 wt.%). Different iron atoms concentration and thermo-mechanical treatments may lead to formation the intermetallic compounds Zr3Fe, Zr2Fe, ZrFe2. Adding tin atoms does not affect the formation and shape of Mössbauer spectra of these compounds. Adding Cr and Nb atoms makes significant changes in the shape of Mössbauer spectra and leads to the formation of complex intermetallic compounds. Adding Cu and W atoms, the shape of the binary alloys spectra (Zr-Fe) remains unchanged, but a change in the temperature dependence behavior of the spectral parameters occurs and also, changes to the properties of the alloys.

Filippov, V. P.; Bateev, A. B.; Lauer, Yu. A.; Kargin, N. I.

2013-04-01

42

PROCESS OF DISSOLVING ZIRCONIUM ALLOYS  

DOEpatents

A process is described for dissolving binary zirconium-uranium alloys where the uranium content is about 2%. In prior dissolution procedures for these alloys, an oxidizing agent was added to prevent the precipitation of uranium tetrafluoride. In the present method complete dissolution is accomplished without the use of the oxidizing agent by using only the stoichiometric amount or slight excess of HF required by the zirconium. The concentration of the acid may range from 2M to 10M and the dissolution is advatageously carried out at a temperature of 80 deg C.

Shor, R.S.; Vogler, S.

1958-01-21

43

COLORIMETRIC DETERMINATION OF ZIRCONIUM WITH \\  

Microsoft Academic Search

A method of the colorimetric determination of zirconium with ; phenylfluron (2,3,7-trioxide-9-phenylcompound with its maximum light absorption ; at 535 m mu . The compound is soluble in ethanol, butanol, methyl ethyl ketone, ; isoamyl alcohol, butyl formate, and cyclohexanol. The ions which interfere with ; the determination are listed. The method can be adapted for the determination of ;

F. G. Zharovskiy; A. T. Philipenko

1957-01-01

44

Hydride Formation in Zirconium Alloys  

NASA Astrophysics Data System (ADS)

The ingress of hydrogen during corrosion in service can degrade the mechanical properties of zirconium alloy nuclear fuel cladding because of the formation of brittle hydrides. The formation of these hydrides is reviewed in light of recent synchrotron radiation experimental results and phase-field modeling computational results that provide new insight on the process.

Motta, Arthur T.; Chen, Long-Qing

2012-12-01

45

PROCESS OF PREPARING ZIRCONIUM OXYCHLORIDE  

DOEpatents

A process is given for preparing zirconyl chloride by mixing solid zirconyl chloride octahydrate and solid zirconium tetrachloride at room temperature whereby both chlorides are converted to zirconyl chloride trinydrate and hydrogen chloride is formed and volatilized by the reaction heat.

Wilhelm, H.A.; Andrews, M.L.

1960-06-28

46

Paliperidonium nitrate  

PubMed Central

In the title mol­ecular salt (systematic name: 3-{2-[4-(6-fluoro-1,2-benzoxazol-3-yl)piperidin-1-yl]eth­yl}-9-hy­droxy-2-methyl-1,6,7,8,9,9a-hexa­hydro­pyrido[1,2-a]pyrimidin-4-one nitrate), C23H29FN4O3 +·NO3 ?, the piperidine ring displays a chair conformation and its N atom is protonated; the N—H bond is in an axial orientation. The ring bearing the hy­droxy group exhibits a half-chair conformation. The hy­droxy group as well as the adjacent methyl­ene group are disordered over two sets of sites in a 0.823?(5):0.177?(5) ratio. In the crystal, O—H?N, O—H?O, N—H?O and N—H?N hydrogen bonds connect the components into a three-dimensional network.

Ge, Jingshui; Luo, Yang-Hui

2012-01-01

47

Nano-zirconium oxide and nano-silver oxide\\/cotton gauze fabrics for antimicrobial and wound healing acceleration  

Microsoft Academic Search

Nano-zirconium-oxide (nano-Zr-oxide) and nano-silver-oxide (nano-Ag-oxide) were in situ synthesized and deposited into cotton gauze fabrics by reduction of zirconium oxychloride or silver nitrate solutions, in the presence of fabric samples using sodium hydroxide-hydrogen peroxide mixture solution at pH 9.5. The resulted homogenous distribution of nano-Zr-oxide and nano-Ag-oxide inside the fabric were characterized by scanning electron microscopy coupled with energy dispersive

Mohamed Gouda

2012-01-01

48

40 CFR 721.9973 - Zirconium dichlorides (generic).  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Zirconium dichlorides (generic). 721.9973...Chemical Substances § 721.9973 Zirconium dichlorides (generic). (a) Chemical...chemical substances identified generically as zirconium dichlorides (PMNs...

2009-07-01

49

Integrated Utilization of Silicon Tetrafluoride and Zirconium Dioxide  

Microsoft Academic Search

The reaction of silicon tetrafluoride with zirconium dioxide was studied. A technological scheme was suggested for utilization of silicon tetrafluoride and reprocessing of spent zirconium dioxide to obtain zircon and zirconium tetrafluoride.

V. V. Guzeev; A. N. D'yachenko; V. N. Grishkov

2003-01-01

50

Thermophysical properties of zirconium hydride and uranium–zirconium hydride  

Microsoft Academic Search

Thermal diffusivities of ?-phase Zirconium hydrides (ZrH1.69–2.00) were measured in the temperature range from 300 to 600 K by means of a laser-flash method. The thermal diffusivity of ?-phase Zr hydrides increased with increasing hydrogen concentration and decreased with increasing temperature. The thermal diffusivities of ?-phase ZrHx with x>1.83 were larger than that of ?-phase Zr. The experimental data on

B. Tsuchiya; J. Huang; K. Konashi; M. Teshigawara; M. Yamawaki

2001-01-01

51

Process for producing zirconium based granules  

SciTech Connect

This patent describes a process for the production f amorphous zirconium based granules. It comprises: adding about 2--15 wt % of a suitable phase stabilizer to an aqueous solutio, based upon the total weight of ZrO{sub 2} in solution, to produce an aqueous solution having a pH in the range of about 4 to 7 comprising a zirconium based complex and phase stabilizer and thereafter; drying the aqueous solution comprising the zirconium based complex and the phase stabilizer at a temperature below about 180{degrees} C. for a time sufficient to evaporate the aqueous solution thereby forming amorphous zirconium based granules containing the phase stabilizer.

Jade, S.S.

1990-05-22

52

Spectrophotometric determination of zirconium with xylenol orange  

SciTech Connect

High purity hydride forming metal films are used as hydrogen isotope occluders and function as electrodes in neutron generator tubes. This use of zirconium occluder films requires reliable analytical methods for routine determination of the zirconium film weight in a production environment. In this study, a spectrophotometric method was evaluated for the determination of zirconium films. The method is based upon the formation of a highly colored zirconium complex with xylenol orange in a dilute perchloric acid medium. Dilute hydrofluoric acid is used in this procedure to selectively dissolve the zirconium film off the substrate. A perchloric acid fuming step is used to remove hydrofluoric acid from the solution. The zirconium solutions are depolymerized before complex formation by heating in 2 N perchloric acid. The zirconium complex exhibits a maximum absorbance in 0.2 to 0.3 M perchloric acid at a wavelength of 531 nanometers. Beer's law is obeyed for zirconium concentrations through 2.1 parts per million. Molybdenum, at concentrations equal to zirconium, does not interfere with the xylenol orange method.

Antepenko, R.J.

1982-05-14

53

Formation of zirconium metallic glass.  

PubMed

Bulk metallic glasses are commonly produced by the rapid cooling of liquid alloys. They have emerged over the past decade as a novel class of materials, with attractive properties and technological promise. The bulk metallic glasses so far produced contain three or more component elements. These complex compositions are necessary to frustrate the crystallization of the liquid melt on cooling, but can also lead to phase separation, which is detrimental to the thermal and mechanical properties of metallic glasses. Here we report, using X-ray diffraction measurements, the formation of a bulk metallic glass from elemental zirconium at high static pressures and low temperatures (relative to its melting temperature at atmospheric pressure). Amorphous zirconium can be recovered at ambient conditions and demonstrates a superior thermal stability compared to amorphous alloys, which could lead to new high-temperature applications of amorphous metals. PMID:15254533

Zhang, Jianzhong; Zhao, Yusheng

2004-07-15

54

Zirconium in the nuclear industry  

SciTech Connect

This book examines the properties of Zircaloy-2, Zircaloy-4, and Zr-2.5Nb with regard to their use as structural materials in nuclear reactors. Topics considered include refinement and fabrication (extractive metallurgy, zirconium and hafnium separation, electron-beam remelting, pressure tube development, cold working and heat treatments), basic metallurgical studies (etching, strain anisotropy, fuel cladding, anneal hardening, recrystallization, hydrides in zirconium alloy tubes), texture and irradiation creep (microstructure, ultrasonic velocity, in-reactor creep, fuel rods, deformation), irradiation growth (proton and neutron bombardment, high-fluence irradiation growth), corrosion (ZrO/sub 2/ films, aqueous corrosion kinetics, corrosive effects of lithium hydroxide, oxidation films, hydridation), fracture studies (stress-corrosion cracking, hydrogen cracking), and high-temperature and transient effects (cladding deformation in LOCA, high-temperature behavior of fuel rods, steam oxidation kinetics, dissolution of solid UO/sub 2/ by molten Zircaloy-4).

Franklin, D.G.; Adamson, R.B.

1984-01-01

55

Yttrium oxide stabilized zirconium oxide  

SciTech Connect

This patent describes a process comprising: (a) forming a solution by mixing yttrium hydroxide and a sufficient amount of an aqueous solution of acetic acid to dissolve the yttrium hydroxide. The solution has a concentration of yttrium ion of about 5% to about 20% by weight of the solution, (b) adding from about 80% to about 95% by weight of zirconium oxide having a particle size range from about 1 to about 5 microns to yield a Zr to Y weight ratio of from about 4:1 to about 19:1 and thereby forming a slurry, (c) spray drying the slurry to form spherical agglomerates consisting essentially of zirconium oxide and a relatively uniform distribution of yttrium acetate whereby the agglomerates have a size from about 20 to about 200 micrometers, (d) heating the agglomerates to about 600/sup 0/C to about 700/sup 0/C in a neutral or oxidizing atmosphere to convert yttrium acetate to yttrium oxide to thereby form zirconium oxide yttrium oxide agglomerates with about 5% to about 20% by weight of yttrium oxide.

Ritsko, J.E.; Houck, D.L.; Acla, H.L.R.

1987-09-22

56

Comparison of sodium zirconium phosphate and Synroc matrices for immobilization of high-level waste  

SciTech Connect

The aims of the present work were to investigate possible compatibility between sodium zirconium phosphate (NZP) and Synroc titanate phases, to prepare NZP-based waste forms by hot-pressing rather than sintering, and to investigate the incorporation in NZP of (a) Cs/Sr as simulated heat-generating nuclides; (b) simulated actinides; and (c) simulated Purex waste. The NZP samples were prepared by methods similar to those used for Synroc. The precursor NZP phase was formed from tetrabutyl zirconate Zr(OC{sub 4}H{sub 9}){sub 4}, sodium nitrate, and 85% orthophosphoric acid. Simulated waste nitrate solutions were then mixed with the liquid precursor. After stir drying of the precursor, calcination was carried out at 700{degree}C to remove nitrates and organics.

Zyryanov, V.N. [Inst. of Experimental Mineralogy, Chernogolovka (Russian Federation); Vance, E.R. [Australian Nuclear Science and Technology Organization (ANSTO), Menai (Australia). Materials Division

1996-12-31

57

Nitrate Risk Management under Uncertainty.  

National Technical Information Service (NTIS)

In many areas throughout the U.S., groundwater supplies are contaminated by nitrates. Nitrate contamination has been a subject of concern because nitrate salt can induce infant methemoglobinemia and cancer. Nitrate risk management describes the process lu...

Y. W. Lee

1991-01-01

58

Production of zirconium at Y-12  

Microsoft Academic Search

A general description is given of the permanent zirconium plant at Y-12. Equipment is described and materials of construction are listed. Photographs illustrating principal equipment and reduced construction drawings are also presented. Operating conditions and costs information are listed. Production of purified hafnium-free zirconium was begun at Y-12 in January, 1950. At the request of the Atomic Energy Commission, a

J. W. Ramsey; W. K. Whitson

1951-01-01

59

Pillaring of saponite with zirconium oligomers  

Microsoft Academic Search

The intercalation of two saponites and a montmorillonite with various zirconium oligomers, prepared from the hydrolysis of zirconyl chloride or zirconium acetate, has been studied. The structure of the intercalated clays strongly depended on the method of preparation and on the nature and crystallinity of the clays studied. In some cases, well-ordered intercalated clays (with basal spacings between 18 and

Ricardo Toranzo; Miguel Angel Vicente; Miguel Angel Bañares-Muñoz; Luis M Gand??a; Andoni Gil

1998-01-01

60

DISSOLUTION OF ZIRCONIUM-CONTAINING FUEL ELEMENTS  

DOEpatents

Uranium is recovered from spent uranium fuel elements containing or clad with zirconium. These fuel elements are placed in an anhydrous solution of hydrogen fluoride and nitrogen dioxide. Within this system uranium forms a soluble complex and zirconium forms an insoluble complex. The uranium can then be separated, treated, and removed from solution as uranium hexafluoride. (AEC)

Horn, F.L.

1961-12-12

61

Modern Methods of Separating Zirconium and Hafnium  

Microsoft Academic Search

CONTENTS I. Introduction 522 II. Methods of separating zirconium and hafnium 523 III. Future prospects in the application of the most important methods for separating zirconium and hafnium 532 Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return: Query Results Return items starting with number Query Form Database:

I. V. Vinarov

1967-01-01

62

UPS and EELS study of zirconium oxidation  

SciTech Connect

The electronic structures of metallic zirconium, zirconium oxide, and zirconium surfaces with intermediate degrees of oxidation have been studied by photoemission spectroscopy using synchrotron radiation and by electron energy loss spectroscopy. Both methods are used to analyze the same samples in one experimental cycle. Some specific features of the electronic structures that had not been detected earlier are revealed. The experimental data obtained are explained using the first-principles calculations of the electronic states of hcp metallic zirconium and cubic or monoclinic zirconia. The dielectric function and the electron-energy-loss function are calculated for comparison with the experimental data. Despite certain quantitative differences, the experimental and calculated data on the electronic structures of zirconium and its oxide are in good qualitative agreement.

Mikheeva, M. N.; Nazin, V. G., E-mail: nazin@isssph.kiae.ru; Kuznetsov, M. Yu. [Russian Research Center Kurchatov Institute (Russian Federation); Maksimov, E. G.; Vasilevskii, S. S. [Russian Academy of Sciences, Lebedev Institute of Physics (Russian Federation); Magnitskaya, M. V. [Russian Academy of Sciences, Vereshchagin Institute of High-Pressure Physics (Russian Federation)

2006-03-15

63

Zirconium oxide coating improves implant osseointegration in vivo  

Microsoft Academic Search

ObjectivesZirconium is widely used as material for prosthetic devices because of its good mechanical and chemical properties. When exposed to oxygen, zirconium becomes zirconium oxide (ZO, chemically ZrO2) which is biocompatible. ZO can be also prepared as a colloidal suspension and then used to coat surfaces. Zirconium oxide coating (ZOC) can potentially have specific biologic effects.

Vincenzo Sollazzo; Furio Pezzetti; Antonio Scarano; Adriano Piattelli; Carlo Alberto Bignozzi; Leo Massari; Giorgio Brunelli; Francesco Carinci

2008-01-01

64

Direct synthesis of Zr-SBA-15 mesoporous molecular sieves with high zirconium loading: Characterization and catalytic performance after sulfated  

Microsoft Academic Search

The Zr-SBA-15 mesoporous materials with high Zr\\/Si ratio (0–2.32) were first synthesized directly using zirconium nitrate and tetraethyl orthosilicate as precursor, displaying higher thermal stability after activated at 600°C. 29Si NMR spectra revealed the part existance of ZrO2 in the framework of SBA-15. After sulfated, the SO42-\\/Zr-SBA-15 exhibited high activity in the isomerization of n-pentane at 35°C, and the conversion

Li Fuxiang; Yu Feng; Li Yongli; Li Ruifeng; Xie Kechang

2007-01-01

65

URANIUM DECONTAMINATION WITH RESPECT TO ZIRCONIUM  

DOEpatents

A process is given for separating uranium values from a nitric acid aqueous solution containing uranyl values, zirconium values and tetravalent plutonium values. The process comprises contacting said solution with a substantially water-immiscible liquid organic solvent containing alkyl phosphate, separating an organic extract phase containing the uranium, zirconium, and tetravalent plutonium values from an aqueous raffinate, contacting said organic extract phase with an aqueous solution 2M to 7M in nitric acid and also containing an oxalate ion-containing substance, and separating a uranium- containing organic raffinate from aqueous zirconium- and plutonium-containing extract phase.

Vogler, S.; Beederman, M.

1961-05-01

66

Ion implantation of zirconium alloys with hafnium  

SciTech Connect

This patent describes a process for improving the corrosion resistance and hydrogen absorption resistance of zirconium alloy without changing the bulk properties of the alloy. The process consists the steps of ion plating a layer of approximately 300 Angstroms hafnium ions onto the surface of the zirconium alloy by sputtering, and driving the hafnium ions into the zirconium alloy by bombarding the layer with xenon ion doses of approximately 3 X 10/sup 16/ ions/cm/sup 2/ at an incident energy of about 50 keV.

Baty, D.L.; Young, W.C.; Lewis, D.E.

1989-07-18

67

Thermochemical nitrate destruction  

DOEpatents

A method is disclosed for denitrification of nitrates and nitrates present in aqueous waste streams. The method comprises the steps of (1) identifying the concentration nitrates and nitrites present in a waste stream, (2) causing formate to be present in the waste stream, (3) heating the mixture to a predetermined reaction temperature from about 200.degree. C. to about 600.degree. C., and (4) holding the mixture and accumulating products at heated and pressurized conditions for a residence time, thereby resulting in nitrogen and carbon dioxide gas, and hydroxides, and reducing the level of nitrates and nitrites to below drinking water standards.

Cox, John L. (Richland, WA); Hallen, Richard T. (Richland, WA); Lilga, Michael A. (Richland, WA)

1992-01-01

68

Joint Titrimetric Determination of Zirconium and Hafnium.  

National Technical Information Service (NTIS)

A method for the joint titrimetric determination of zirconium and hafnium, which are elements of similar chemical behaviour, is described. The disodic salt of the ethylendiaminetetracetic acid (EDTA) is used for titration, while xilenol orange serves as f...

C. Vazquez M. Botbol G. N. Bianco de Salas M. I. Cornell de Casas

1980-01-01

69

Process for producing zirconium based granules  

SciTech Connect

This patent describes a process for the production of amorphous zirconium based granules. It comprises forming a solution comprising Zr(R){sub 4} or zirconyl halide in an alcohol solvent, adding in either order an acid in an amount sufficient to acidify the solution comprising Zr(R){sub 4} or zirconyl halide to a pH in the range of about 2-5 and water in an amount sufficient to hydrolyze the Zr(R){sub 4} or zirconyl halide thereby forming a solution comprising a zirconium based complex; adding about 1-35 wt % of a suitable phase stabilizer to the resulting solution; and drying the solution comprising the zirconium based complex and phase stabilizer at a temperature below about 250{degrees} C. for a time sufficient to evaporate the solution thereby forming zirconium based granules containing the phase stabilizer.

Jada, S.S.

1991-10-01

70

Investigation of zirconium-containing aluminum alloys  

Microsoft Academic Search

A new zirconium foundry alloy increases the physicochemical properties of aluminum due to the structure becoming finer and\\u000a the formation of strengthening phases of doping elements with aluminum.

V. M. Grigor’ev

2011-01-01

71

Hafnium-Zirconium Separation by Selective Reduction.  

National Technical Information Service (NTIS)

The report discusses an investigation directed toward selective reduction methods to recover most of the hafnium from zircon as hafnium-enriched zirconium-tetrachloride. Successive contacts of batches of mixed tetrachlorides were made with a reductant reg...

J. E. Mauser

1968-01-01

72

Solid Solutions in the System Ammonium Nitrate-Potassium Nitrate  

Microsoft Academic Search

BY phase work on the system ammonium nitrate-potassium nitrate-water, Janëcke1,2 showed that below 23° C. two types of solid solution can exist: potassium nitrate dissolved in ammonium nitrate (form III) and ammonium nitrate in potassium nitrate (form II). At higher temperatures there is an increasing amount of another phase which is of a different crystalline form from any of the

R. V. Coates; J. M. Crewe

1961-01-01

73

Thermal stability of nanostructurally stabilized zirconium oxide  

Microsoft Academic Search

Nanostructurally stabilized zirconium oxide (NSZ) hard transparent films were produced without chemical stabilizers by the ion beam assisted deposition technique (IBAD). A transmission electron microscopy study of the samples produced below 150 °C revealed that these films are composed of zirconium oxide (ZrO2) nanocrystallites of diameters 7.5 ± 2.3 nm. X-ray and selected-area electron diffraction studies suggested that the as-deposited

Fereydoon Namavar; Gonghua Wang; Chin Li Cheung; Renat F. Sabirianov; Xiao Cheng Zeng; Wai-Ning Mei; Jaeil Bai; Joseph R. Brewer; Hani Haider; Kevin L. Garvin

2007-01-01

74

Penta-zirconium copper tribismuth  

PubMed Central

Penta­zirconium copper tribismuth, Zr5CuBi3, crystallizes in the hexa­gonal Hf5CuSn3 structure type. The asymmetric unit contains two Zr sites (site symmetries 3.2 and m2m), one Cu site (site symmetry 3.m) and one Bi site (site symmetry m2m). The environment of the Bi atoms is a tetra­gonal anti­prism with one added atom and a coordination number (CN) of 9. The polyhedron around the Zr1 atom is a defective cubo­octa­hedron with CN = 11. The bicapped hexa­gonal anti­prism (CN = 14) is typical for Zr2 atoms. The Cu atom is enclosed in a eight-vertex polyhedron (octa­hedron with two centered faces). The metallic type of bonding was indicated by an analysis of the inter­atomic distances and electronic structure calculation data.

Balinska, Agnieszka; Tarasiuk, Ivan; Pavlyuk, Volodymyr

2013-01-01

75

Electrochemical decomposition of complexes of zirconium or hafnium  

SciTech Connect

This patent describes an improvement in a method for separating hafnium from zirconium where a complex of zirconium and hafnium chlorides and phosphorus oxychloride is prepared from zirconium-hafnium chloride and the complex is subjected to a distillation to produce a hafnium chloride enriched stream of complex and a zirconium enriched chloride stream of complex. The improvement comprising: electrochemical breaking the zirconium or hafnium chloride complex from the distillation in a chloride or fluoride and chloride molten salt bath to produce the metal or a chloride oof zirconium or hafnium.

Snyder, T.S.; Stoltz, R.A.; McLaughlin, D.F.

1989-09-12

76

Nitrate reduction by metallic iron  

Microsoft Academic Search

Chemical reduction of nitrate by metallic iron (Fe0) was studied as a potential technology to remove nitrate from water. The effects of pH and the iron-to-nitrate ratio on both nitrate reduction rate and percent removal were investigated. Rate constants and the apparent reaction order with respect to nitrate were determined and a mass balance was obtained. Rapid nitrate reduction by

Chin-Pao Huang; Hung-Wen Wang; Pei-Chun Chiu

1998-01-01

77

X-ray Photoelectron Spectroscopy and Catalytic Activity of alpha-Zirconium Phosphate and Zirconium Phosphate.  

National Technical Information Service (NTIS)

X-ray photoelectron spectroscopic (XPS) analyses were performed on alpha-zirconium phosphate (ZrP) and on an organic derivative of ZrP, zirconium phosphate sulfophenylphosphonate (ZrPS). The XPS results show that the change of half of the phosphate groups...

A. Clearfield C. R. Martin C. Y. Yang D. S. Thakur J. L. Colon

1990-01-01

78

Catalysis of terpene rearrangements by zirconium phosphates and zirconium organo-substituted phosphonates  

Microsoft Academic Search

Vapour phase catalysis of the dehydration of cyclohexanol, nerol and geraniol and of the thermal rearrangement of ?-pinene by unsubstituted zirconium phosphates has been compared with similar catalysis effected by organically pillared zirconium phosphates and with catalysis by alumina. Many of the observed differences in reaction rates can be rationalised by consideration of the acidity and surface area of the

M Conceiçao Cruz Costa; Robert A. W. Johnstone; David Whittaker

1998-01-01

79

RECOVERY AND RECRYSTALLIZATION OF ZIRCONIUM AND ITS ALLOYS. PART 2. ANNEALING OF COLD-WORKED ZIRCONIUM  

Microsoft Academic Search

Hardness, x-ray diffraction, electrical resistivity, and metallography ; were used to study the annealing of coldworked zirconium at temperatures from 300 ; to 800 deg C (570 to 1470 deg F). Cold work, annealing time, temperature, and ; furnace atmosphere were chosen as variables. Recrystallization of 25 and 50 per ; cent cold-worked zirconium occurred by nucleation and growth of

Gray

1961-01-01

80

Electrochemical-metallothermic reduction of zirconium in molten salt solutions  

SciTech Connect

This patent describes a method for separating hafnium from zirconium of the type wherein a feed containing zirconium and hafnium chlorides is prepared from zirconium-hafnium chloride and the feed is introduced into a distillation column, which distillation column has a reboiler connected at the bottom and a reflux condenser connected at the top and wherein a hafnium chloride enriched stream is taken from the top of the column and a zirconium enriched chloride stream is taken from the bottom of the column. It comprises: reducing the zirconium enriched chloride stream taken from the distillation column to metal by electrochemically reducing an alkaline earth metal in a molten salt bath with the molten salt in the molten salt bath consisting essentially of a mixture of at least one alkali metal chloride and at least one alkaline earth metal chloride and zirconium chloride, with the reduced alkaline earth metal reacting with the zirconium chloride to produce zirconium metal and alkaline earth metal chloride.

McLaughlin, D.F.; Talko, F.

1990-05-08

81

ZIRCONIUM OXIDE NANOSTRUCTURES PREPARED BY ANODIC OXIDATION  

SciTech Connect

Zirconium oxide is an advanced ceramic material highly useful for structural and electrical applications because of its high strength, fracture toughness, chemical and thermal stability, and biocompatibility. If highly-ordered porous zirconium oxide membranes can be successfully formed, this will expand its real-world applications, such as further enhancing solid-oxide fuel cell technology. Recent studies have achieved various morphologies of porous zirconium oxide via anodization, but they have yet to create a porous layer where nanoholes are formed in a highly ordered array. In this study, electrochemical methods were used for zirconium oxide synthesis due to its advantages over other coating techniques, and because the thickness and morphology of the ceramic fi lms can be easily tuned by the electrochemical parameters, such as electrolyte solutions and processing conditions, such as pH, voltage, and duration. The effects of additional steps such as pre-annealing and post-annealing were also examined. Results demonstrate the formation of anodic porous zirconium oxide with diverse morphologies, such as sponge-like layers, porous arrays with nanoholes ranging from 40 to 75 nm, and nanotube layers. X-ray powder diffraction analysis indicates a cubic crystallographic structure in the zirconium oxide. It was noted that increased voltage improved the ability of the membrane to stay adhered to the zirconium substrate, whereas lower voltages caused a propensity for the oxide fi lm to fl ake off. Further studies are needed to defi ne the parameters windows that create these morphologies and to investigate other important characteristics such as ionic conductivity.

Dang, Y. Y.; Bhuiyan, M.S.; Paranthaman, M. P.

2008-01-01

82

Zirconium Oxide Nanostructures Prepared by Anodic Oxidation  

SciTech Connect

Zirconium oxide is an advanced ceramic material highly useful for structural and electrical applications because of its high strength, fracture toughness, chemical and thermal stability, and biocompatibility. If highly-ordered porous zirconium oxide membranes can be successfully formed, this will expand its real-world applications, such as further enhancing solid-oxide fuel cell technology. Recent studies have achieved various morphologies of porous zirconium oxide via anodization, but they have yet to create a porous layer where nanoholes are formed in a highly ordered array. In this study, electrochemical methods were used for zirconium oxide synthesis due to its advantages over other coating techniques, and because the thickness and morphology of the ceramic films can be easily tuned by the electrochemical parameters, such as electrolyte solutions and processing conditions, such as pH, voltage, and duration. The effects of additional steps such as pre-annealing and post-annealing were also examined. Results demonstrate the formation of anodic porous zirconium oxide with diverse morphologies, such as sponge-like layers, porous arrays with nanoholes ranging from 40 to 75 nm, and nanotube layers. X-ray powder diffraction analysis indicates a cubic crystallographic structure in the zirconium oxide. It was noted that increased voltage improved the ability of the membrane to stay adhered to the zirconium substrate, whereas lower voltages caused a propensity for the oxide film to flake off. Further studies are needed to define the parameters windows that create these morphologies and to investigate other important characteristics such as ionic conductivity.

Dang, Ying Yi [ORNL; Bhuiyan, Md S [ORNL; Paranthaman, Mariappan Parans [ORNL

2008-01-01

83

Reactions of Metal Salts and Alkali Metal Nitrates. Role of the Metal Precursors and Alkali Metal Ions in the Resulting Phase of Zirconia  

NASA Astrophysics Data System (ADS)

Zirconia powders are prepared by reaction of a zirconium precursor with an alkali metal nitrate. The major part of the reactions takes place before the melting points and then the reactions go slowly to completion at 450°C in the molten salts. The roles of the precursor and the alkali metal ion are discussed considering the reaction between two precursors, octahydrated zirconium oxychloride and zirconium tetrachloride, and two nitrates, LiNO3 and NaNO3, and some resulting physico-chemical differences. The obtained zirconia powders contain very small amounts of alkali metal ions which act as stabilizing agent. Their effect on the balance tetragonal-monoclinic ZrO2 depends upon the homogeneity of their distribution which is related to their ability to diffuse inside the bulk of particles and their polarizing power when located mainly on the surface. .

Marote, Pedro; Durand, Bernard; Deloume, Jean-Pierre

2002-01-01

84

Cloud processing of nitrate  

NASA Astrophysics Data System (ADS)

The role of clouds in the transport and transformation of tropospheric pollutants was investigated through airborne measurements made out of Cleveland, Ohio, from 21 July to 18 August 2004, as part of the International Consortium for Atmospheric Research on Transport and Transformation 2004 program. Observations of gas-phase nitrate, size-resolved particulate nitrate, cloud water nitrate, and size-distributed cloud residual nitrate are used to examine changes in the partitioning of nitrate from precloud to postcloud as a function of particle size. The [NO3-]/[SO42-] ratio was highest in the bulk cloud water and higher in the cloud droplet residuals compared with the below-cloud aerosols. Most of the nitrate entered the cloud water as HNO3, and in 30% of 43 size distributions examined, the nitrate in the cloud droplets was found in residual particle sizes smaller than those of sulfate. Simulations from a trace gas-aerosol-cloud parcel model show that this size difference results from differences in the processes by which nitrate and sulfate enter cloud water. The transfer of HNO3 to cloud droplets is governed primarily by gas-phase mass transfer to the droplets, leading to greater accumulation in the smaller, more numerous droplets with higher total surface area. In contrast, much of the sulfate in the cloud water is the result of nucleation scavenging, which distributes the sulfate mass toward slightly larger sizes. The extent of separation between nitrate and sulfate is dependent on the cloud base sulfate size distribution and the factors that govern both HNO3 and SO2 uptake, with subsequent S(IV) oxidation.

Hayden, K. L.; MacDonald, A. M.; Gong, W.; Toom-Sauntry, D.; Anlauf, K. G.; Leithead, A.; Li, S.-M.; Leaitch, W. R.; Noone, K.

2008-09-01

85

INFRARED SPECTRA OF URANYL NITRATE HYDRATES AND RUBIDIUM URANYL NITRATE  

Microsoft Academic Search

The infrared spectra of uranyl nitrate di-, tri-, and hexahydrate have ; been examined from 3700 to 700 cm⁻¹, with nitrogen of normal isotopic ; composition and enriched in N¹⁵, and most of the bands are assigned. The ; spectrum of uranyl nitrate hexahydrate is in most respects that of a typical ; ionic nitrate. The spectra of uranyl nitrate

Bryan M. Gatehouse; Alan E. Comyns

1958-01-01

86

Decomposition of Four Ammonium Nitrate Propellants.  

National Technical Information Service (NTIS)

The biodegradability of four ammonium nitrate propellants, trimethylammonium nitrate (TMAN), isopropylammonium nitrate (IPAN), triethanolammonium nitrate (TEAN), and hydroxylammonium nitrate (HAN) was assessed in batch and continuous cultures under a vari...

D. L. Kaplan D. J. Emerson P. A. Riley A. M. Kaplan

1983-01-01

87

The Chilean nitrate deposits.  

USGS Publications Warehouse

The nitrate deposits in the arid Atacama desert of northern Chile consist of saline-cemented surficial material, apparently formed in and near a playa lake that formerly covered the area. Many features of their distribution and chemical composition are unique. The author believes the principal sources of the saline constituents were the volcanic rocks of late Tertiary and Quaternary age in the Andes and that the nitrate is of organic origin. Possible sources of the nitrate, iodate, perchlorate and chromate are discussed. -J.J.Robertson

Ericksen, G. E.

1983-01-01

88

THE PRODUCTION OF DUCTILE HAFNIUM-FREE ZIRCONIUM  

Microsoft Academic Search

Current processes for the production of zirconium metal from its ores ; are reviewed, particular attention being given to methods for the removal of ; hafnium. Two main routes for the production of ductile hafniumfree zirconium are ; recommended for investigation. A synopsis of the more important chemical and ; physical properties of zirconium is given as an appendix. (auth);

W. E. Dennis; A. F. Adamson

1954-01-01

89

Processing fissile material mixtures containing zirconium and/or carbon  

DOEpatents

A method of processing spent TRIZO-coated nuclear fuel may include adding fluoride to complex zirconium present in a dissolved TRIZO-coated fuel. Complexing the zirconium with fluoride may reduce or eliminate the potential for zirconium to interfere with the extraction of uranium and/or transuranics from fission materials in the spent nuclear fuel.

Johnson, Michael Ernest; Maloney, Martin David

2013-07-02

90

Industrial applications of titanium and zirconium: Fourth volume  

SciTech Connect

This book presents industrial applications of titanium and zirconium. This book also contains information on other reactive and refractory metals, including niobium, tantalum, and hafnium. There are fourteen (14) peer-reviewed papers which target these subjects: the applications of titanium; the applications of zirconium and other reactive metals and the technology of titanium and zirconium.

Young; Durham

1986-01-01

91

ON THE MELTING AND FABRICATION OF ZIRCONIUM AND ZIRCALOY2  

Microsoft Academic Search

Experimental studies were carried out on the melting and fabrication of ; low purity reactor grade zirconium, high purity reactor grade zirconium, Zircaloy-; 2, and commercial zirconium. Sound ingots were obtained and it was recognized ; that hot workability (forging and rolling) was good. Effects of cold rolling, ; anneallng temperature, time, atmosphere, and cooling rate on the mechanical ;

Y. Kondo; S. Suzuki; M. F. Ugori

1959-01-01

92

Organo derivatives of zirconium-phosphate  

SciTech Connect

A series of alkyl and aryl diphosphonic acids in which the size of the alkyl and aryl group is systematically varied has been synthesized. The corresponding zirconium diphosphonates, mixed-component pillared zirconium phosphite/phosphate diphosphonates, mixed-component non-pillared zirconium phosphite phenyl phosphonates and their sulphonated derivatives have been prepared by various synthetic methods. An extensive study of the preparative conditions of these synthetic methods has been carried out. These compounds were characterized by X-ray diffraction, TG analysis, elemental analysis, IR spectroscopy, titration curves, surface area measurement, pore size distribution, solid state NMR and electron microscopic study. Their various possible applications were also investigated. Since the organic zirconium exchangers readily form membranes which quantitatively adsorb (Ru(bipy)/sub 3/)/sup 2 +/ (bipsy = bipsyridyl) and methyl viologen, they serve as a convenient support for photochemically induced charge transfer reactions. The charge-transfer photochemical reaction between (Ru(bipy)/sub 3/)/sup 2 +/ and (Co(NH/sub 3/)/sub 5/ Cl)/sup 2 +/ in layered film of zirconium sulphophosphonate undergoes a limited cyclic photolytic water splitting reaction was described.

Yang, C.Y.

1986-01-01

93

Stereoregular Polyvinyl Nitrate.  

National Technical Information Service (NTIS)

Isotactic polyvinyl nitrate (PVN) was prepared to investigate the effect of stereorgularity on the physical properties of PVN. The isotatic PVN had a higher softening point and was more difficult to stabilize than regular PVN. (Author)

R. A. Strecker

1980-01-01

94

Thermochemical nitrate destruction  

SciTech Connect

The thermochemical destruction of nitrate was conducted in an aqueous media. Six reducing agents (ammonia, formate, urea, glucose, methane, and hydrogen) were mixed separately with 3 wt % NO[sub 3][sup [minus

Cox, J.L.; Hallen, R.T.; Lilga, M.A. (Pacific Northwest Lab., Richland, WA (United States))

1994-03-01

95

Protein tyrosine nitration  

PubMed Central

Nitric oxide metabolism in plant cells has a relative short history. Nitration is a chemical process which consists of introducing a nitro group (-NO2) into a chemical compound. in biological systems, this process has been found in different molecules such as proteins, lipids and nucleic acids that can affect its function. This mini-review offers an overview of this process with special emphasis on protein tyrosine nitration in plants and its involvement in the process of nitrosative stress.

Chaki, Mounira; Leterrier, Marina; Barroso, Juan B

2009-01-01

96

Review of zirconium-zircaloy pyrophoricity  

SciTech Connect

Massive zirconium metal scrap can be handled, shipped, and stored with no evidence of combustion or pyrophoricity hazards. Mechanically produced fine scrap such as shavings, turnings, or powders can burn but are not pyrophoric unless the particle diameter is less than 54 ..mu..m. Powders with particle diameters less than 54 ..mu..m can be both pyrophoric and explosive. Pyrophoric powders should be collected and stored underwater or under inert gas cover to reduce the flammability hazard. Opening sealed containers of zirconium stored underwater should be attempted with caution since hydrogen may be present. The factors that influence the ignition temperature have been explored in depth and recommendations are included for the safe handling, shipping, and storage of pyrophoric or flammable zirconium. 29 refs., 5 figs., 6 tabs.

Cooper, T.D.

1984-11-01

97

Neutron Resonance Parameters for Zr-93 (Zirconium)  

NASA Astrophysics Data System (ADS)

This document is part of the Supplement containing the complete sets of data of Volume 24 `Neutron Resonance Parameters' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms'. It provides the neutron resonance parameters for the isotope Zr-93 (Zirconium).

Sukhoruchkin, S. I.; Soroko, Z. N.

98

Neutron Resonance Parameters for Zr93 (Zirconium)  

Microsoft Academic Search

This document is part of the Supplement containing the complete sets of data of Volume 24 `Neutron Resonance Parameters' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms'. It provides the neutron resonance parameters for the isotope Zr-93 (Zirconium).

S. I. Sukhoruchkin; Z. N. Soroko

2009-01-01

99

Neutronographic Texture Analysis of Zirconium Based Alloys  

Microsoft Academic Search

Neutron diffraction is a very powerful tool in texture analysis of zirconium based alloys used in nuclear technique. Textures of five samples (two rolled sheets and three tubes) were investigated by using basal pole figures, inversion pole figures, and ODF distribution function. The texture measurement was performed at diffractometer KSN2 on the Laboratory of Neutron Diffraction, Department of Solid State

M Kruželová; S Vratislav; L Kalvoda; M Dlouhá

2012-01-01

100

Minerals Yearbook, 1988: Zirconium and Hafnium.  

National Technical Information Service (NTIS)

Domestic mine production of zircon, the principal ore mineral of zirconium and hafnium, increased in 1988. Zircon was mined by two companies in Florida as a coproduct of the titanium minerals ilmenite and rutile and by one company in New Jersey from taili...

J. B. Hedrick

1988-01-01

101

[Pharmacology of nitrates].  

PubMed

Nitrates (nitroglycerin, isosorbide dinitrate and isosorbide 5-mononitrate) are drugs used in the treatment of angina pectoris and in the prevention of myocardial ischaemia. By providing nitric oxide (NO), which, in turn, increases the level of cGMP and decreases (Ca)i, they induce effects of vasodilatation and anti-platelet aggregation. In patients suffering from endothelial dysfunction, they therefore act like exogenous NO providers. At low doses, they act as venous vasodilators by decreasing the tension (preload) and volume of the ventricle, as well as myocardial oxygen requirements (MVO2). The reduction of ventricular tension and volume also indirectly increases subendocardial blood flow. In the coronary vessels, they produce epicardial vasodilatation (all the more marked the smaller the calibre of the vessels), increase collateral blood flow and, through stenoses, induce reduction of coronary tone and the excess pressure due to vasospasm. At higher doses, the vasodilator effect is exerted on arteries and, although it reduces peripheral vascular resistance (afterload) and blood pressure, it can also produce reflex tachycardia which annihilates the reduction of MVO2. Finally, nitrates exert anti-platelet aggregation effects. All these properties account for the beneficial effects of nitrates in acute or chronic coronary ischaemic syndromes, in patients suffering from left ventricular dysfunction, during the acute phase of myocardial infarction and in post-myocardial infarction ventricular remodelling. There are many pharmaceutical formulations allowing administration of nitrates via a variety of routes. However, the efficacy of repeated nitrate administration is limited by the appearance of tolerance, which can be prevented by observing short periods without nitrates (8-24 hours). The use of sustained-release formulations, with a single daily dose, ensures a maximum anti-ischaemic effect, reduces the risk of tolerance and facilitates the patient's compliance with treatment, which makes it the treatment of choice in angina patients. PMID:9452771

Tamargo Menendez, J; Delpón, E

102

Cloning and Nitrate Induction of Nitrate Reductase mRNA  

Microsoft Academic Search

Nitrate is the major source of nitrogen taken from the soil by higher plants but requires reduction to ammonia prior to incorporation into amino acids. The first enzyme in the reducing pathway is a nitrate-inducible enzyme, nitrate reductase (EC 1.6.6.1). A specific polyclonal antiserum raised against purified barley nitrate reductase has been used to immunoprecipitate in vivo labeled protein and

Chi-Lien Cheng; Julia Dewdney; Andris Kleinhofs; Howard M. Goodman

1986-01-01

103

International strategic minerals inventory summary report; zirconium  

USGS Publications Warehouse

Zircon, a zirconium silicate, is currently the most important commercial zirconium-bearing mineral. Baddeleyite, a natural form of zirconia, is less important but has some specific end uses. Both zircon and baddeleyite occur in hard-rock and placer deposits, but at present all zircon production is from placer deposits. Most baddeleyite production is from hard-rock deposits, principally as a byproduct of copper and phosphate-rock mining. World zirconium resources in identified, economically exploitable deposits are about 46 times current production rates. Of these resources, some 71 percent are in South Africa, Australia, and the United States. The principal end uses of zirconium minerals are in ceramic applications and as refractories, abrasives, and mold linings in foundries. A minor amount, mainly of zircon, is used for the production of hafnium-free zirconium metal, which is used principally for sheathing fuel elements in nuclear reactors and in the chemical-processing industry, aerospace engineering, and electronics. Australia and South Africa are the largest zircon producers and account for more than 70 percent of world output; the United States and the Soviet Union account for another 20 percent. South Africa accounts for almost all the world's production of baddeleyite, which is about 2 percent of world production of contained zirconia. Australia and South Africa are the largest exporters of zircon. Unless major new deposits are developed in countries that have not traditionally produced zircon, the pattern of world production is unlikely to change by 2020. The proportions, however, of production that come from existing producing countries may change somewhat.

Towner, R. R.

1992-01-01

104

Zirconium oxidation on the atomic scale.  

PubMed

Zirconium alloys are used in the nuclear industry as fuel rod cladding. They are chosen for this role because of their good mechanical properties and low thermal neutron absorption. Oxidation of these alloys by coolant is one of the chief limiting factors of the fuel burn-up efficiency. The aim of the present study is to understand these oxidation mechanisms. As a first step, a fundamental study of the oxidation of commercially pure zirconium has been conducted using the 3D atom probe (3DAP). The current generation of 3DAPs allows both voltage and laser pulsing, providing data sets of many millions of ions. According to the literature the only stable oxide of zirconium is ZrO(2). However, the 3DAP shows that an initial layer a few nanometres thick forms with a composition of ZrO(1-)(x) when subjected to light oxidation. This result confirms and extends the work of Wadman et al. [Colloque de Physique 50 (1989) C8 303; Journal de Physique, 11 (1988) C6 49] and Wadman and Andrén [in: C.M. Euchen, A.M. Garde (Eds.), Zirconium in the Nuclear Industry: Ninth Symposium, ASTM STP 1132, ASTM, USA, 1991, p. 461], who used 1DAP techniques, obtaining reduced data sets. Segregation of hydrogen to the metal-oxide interface and a distinct ZrH phase were observed in this study. A novel kinetics study of the room temperature oxidation of zirconium showed the ZrO layer to be non-protective over the time period investigated (up to 1h). PMID:19101084

Hudson, Daniel; Cerezo, Alfred; Smith, George D W

2008-11-12

105

40 CFR 721.10089 - Modified salicylic acid, zirconium complex (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Modified salicylic acid, zirconium complex (generic...Substances § 721.10089 Modified salicylic acid, zirconium complex (generic...identified generically as modified salicylic acid, zirconium complex (PMN...

2013-07-01

106

40 CFR 721.10089 - Modified salicylic acid, zirconium complex (generic).  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Modified salicylic acid, zirconium complex (generic). 721.10089...721.10089 Modified salicylic acid, zirconium complex (generic). (a) Chemical...generically as modified salicylic acid, zirconium complex (PMN P-00-552) is...

2009-07-01

107

40 CFR 721.10089 - Modified salicylic acid, zirconium complex (generic).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Modified salicylic acid, zirconium complex (generic). 721.10089...721.10089 Modified salicylic acid, zirconium complex (generic). (a) Chemical...generically as modified salicylic acid, zirconium complex (PMN P-00-552) is...

2010-07-01

108

40 CFR 471.90 - Applicability; description of the zirconium-hafnium forming subcategory.  

Code of Federal Regulations, 2010 CFR

...Applicability; description of the zirconium-hafnium forming subcategory. 471.90 Section...POWDERS POINT SOURCE CATEGORY Zirconium-Hafnium Forming Subcategory § 471.90 Applicability; description of the zirconium-hafnium forming subcategory. This...

2009-01-01

109

40 CFR 421.330 - Applicability: Description of the primary zirconium and hafnium subcategory.  

Code of Federal Regulations, 2010 CFR

...Description of the primary zirconium and hafnium subcategory. 421.330 Section 421...SOURCE CATEGORY Primary Zirconium and Hafnium Subcategory § 421.330 Applicability: Description of the primary zirconium and hafnium subcategory. The provisions of...

2010-07-01

110

40 CFR 471.90 - Applicability; description of the zirconium-hafnium forming subcategory.  

Code of Federal Regulations, 2011 CFR

...Applicability; description of the zirconium-hafnium forming subcategory. 471.90 Section...POWDERS POINT SOURCE CATEGORY Zirconium-Hafnium Forming Subcategory § 471.90 Applicability; description of the zirconium-hafnium forming subcategory. This...

2011-07-01

111

40 CFR 471.90 - Applicability; description of the zirconium-hafnium forming subcategory.  

Code of Federal Regulations, 2010 CFR

...Applicability; description of the zirconium-hafnium forming subcategory. 471.90 Section...POWDERS POINT SOURCE CATEGORY Zirconium-Hafnium Forming Subcategory § 471.90 Applicability; description of the zirconium-hafnium forming subcategory. This...

2010-07-01

112

40 CFR 421.330 - Applicability: Description of the primary zirconium and hafnium subcategory.  

Code of Federal Regulations, 2012 CFR

...Description of the primary zirconium and hafnium subcategory. 421.330 Section 421...SOURCE CATEGORY Primary Zirconium and Hafnium Subcategory § 421.330 Applicability: Description of the primary zirconium and hafnium subcategory. The provisions of...

2012-07-01

113

40 CFR 421.330 - Applicability: Description of the primary zirconium and hafnium subcategory.  

Code of Federal Regulations, 2010 CFR

...Description of the primary zirconium and hafnium subcategory. 421.330 Section 421...SOURCE CATEGORY Primary Zirconium and Hafnium Subcategory § 421.330 Applicability: Description of the primary zirconium and hafnium subcategory. The provisions of...

2009-07-01

114

Nitrate, bacteria and human health  

Microsoft Academic Search

Nitrate is generally considered a water pollutant and an undesirable fertilizer residue in the food chain. Research in the 1970s indicated that, by reducing nitrate to nitrite, commensal bacteria might be involved in the pathogenesis of gastric cancers and other malignancies, as nitrite can enhance the generation of carcinogenic N-nitrosamines. More recent studies indicate that the bacterial metabolism of nitrate

Eddie Weitzberg; Jeff A. Cole; Nigel Benjamin; Jon O. Lundberg

2004-01-01

115

Batch Crystallization of Uranyl Nitrate  

Microsoft Academic Search

Batch crystallization of uranyl nitrate is carried out in order to obtain fundamental data required for the development of reprocessing involving crystallization. Particular attention is paid to the development of a method for predicting the concentrations of uranium and nitric acid in the mother liquor and the amount of uranyl nitrate crystals produced. Initial concentrations of uranyl nitrate and nitric

Takahiro CHIKAZAWA; Toshiaki KIKUCHI; Atsuhiro SHIBATA; Tomozo KOYAMA; Shunji HOMMA

2008-01-01

116

Molten salt extractive distillation process for zirconium-hafnium separation  

SciTech Connect

This patent describes an improvement in a process for zirconium-hafnium separation. It utilizes an extractive distillation column with a mixture of zirconium and hafnium tetrachlorides introduced into a distillation column having a top and bottom with hafnium enriched overheads taken from the top of the column and a molten salt solvent circulated through the column to provide a liquid phase, and with molten salt solvent containing zirconium chloride being taken from the bottom of the distillation column. The improvements comprising: utilizing a molten salt solvent consisting principally of lithium chloride and at least one of sodium, potassium, magnesium and calcium chlorides; stripping of the zirconium chloride taken from the bottom of the distillation column by electrochemically reducing zirconium from the molten salt solvent; and utilizing a pressurized reflux condenser on the top of the column to add the hafnium chloride enriched overheads to the molten salt solvent previously stripped of zirconium chloride.

McLaughlin, D.F.; Stoltz, R.A.

1989-10-17

117

Nitrate reductase regulation: Effects of nitrate and light on nitrate reductase mRNA accumulation  

Microsoft Academic Search

Summary  Regulation of nitrate reductase mRNA by light and nitrate was studied in barley seedlings using a partial cDNA clone as a\\u000a probe. Nitrate reductase mRNA was detected in roots and leaves within 40 min after supplying nitrate to the roots and reached\\u000a peak accumulation at 2 h in the roots and at 12 h in the leaves. In the absence

James M. Melzer; Andris Kleinhofs; Robert L. Warner

1989-01-01

118

Anodic electrodeposition of highly oriented zirconium phosphate and polyaniline-intercalated zirconium phosphate films.  

PubMed

Films of highly oriented alpha-zirconium phosphate and polyaniline-intercalated zirconium phosphate with controllable thickness in the micrometer range were grown anodically on Pt electrodes. To optimize the electrodeposition conditions, the exfoliation of alpha-zirconium phosphate by tetrabutylammonium (TBA) salts was investigated in several nonaqueous solvents. Acetonitrile was found to be the best solvent for making crack-free, oriented films because of its high vapor pressure, low viscosity, and relatively high permittivity. With TBA salts of neutral or weakly acidic anions (TBACl, TBABr, TBAI, TBA(HSO4), or TBA(H2PO4)), full exfoliation did not occur and alpha-zirconium phosphate and/or polyaniline were deposited as rough films. With basic anions (TBAF or TBAOH), dense, adherent films were obtained. X-ray diffraction patterns of the films showed that they were highly oriented along the stacking axis. The thickness could be controlled, up to about 40 microm, by limiting the time of the electrodeposition reaction. At monomer concentrations below 1.0 x 10(-2) mol/dm3, the emeraldine form of the intercalated polymer was obtained. Electrodeposition thus provides a thick film alternative to layer-by-layer assembly for intercalation compounds of alpha-zirconium phosphate with a conducting polymer. PMID:17177412

Takei, Takahiro; Kobayashi, Yoji; Hata, Hideo; Yonesaki, Yoshinori; Kumada, Nobuhiro; Kinomura, Nobukazu; Mallouk, Thomas E

2006-12-27

119

METHOD OF MAKING DELTA ZIRCONIUM HYDRIDE MONOLITHIC MODERATOR PIECES  

DOEpatents

A method is given for preparing large, sound bodies of delta zirconium hydride. The method includes the steps of heating a zirconium body to a temperature of not less than l000 deg C, providing a hydrogen atmosphere for the zirconium body at a pressure not greater than one atmosphere, reducing the temperature slowly to 800 deg C at such a rate that cracks do not form while maintaining the hydrogen pressure substantially constant, and cooling in an atmosphere of hydrogen. (AEC)

Vetrano, J.B.

1962-01-23

120

Zirconium Bis(Amido) Catalysts for Asymmetric Intramolecular Alkene Hydroamination  

PubMed Central

In situ combination of diphosphinic amides and Zr(NMe2)4 results in the formation of chiral zirconium bis(amido) complexes. The complexes are competent catalysts for intramolecular asymmetric alkene hydroamintion, providing piperidines and pyrrolidines in up to 80% ee and high yield. This system utilizes an inexpensive zirconium precatalyst and readily prepared ligands and is the first asymmetric alkene hydroamination catalyst based upon a neutral zirconium bis(amido) complex.

Watson, Donald A.; Chiu, Melanie

2008-01-01

121

Removal of iron contaminant from zirconium chloride solution  

SciTech Connect

This patent describes a process for eliminating iron contaminant from an aqueous zirconium chloride solution that has been contaminated with FeCl{sub 3} in a plant in which zirconium and hafnium chloride solutions are separated by a main MINK solvent extraction system and the FeCl{sub 3} is normally removed from the zirconium chloride solution by a secondary MINK solvent extraction system.

Voit, D.O.

1992-01-07

122

XPS studies of zirconium complexes on polymer surfaces  

NASA Astrophysics Data System (ADS)

Four pure zirconium carboxylate complexes, [Zr(acac) 4], [Zr(acac) 3Cl], [Zr(acac) 2(crotonate) 2] and [Zr(acac) 2(benzoate) 2], hav been prepared and used as "model" surfactants on polythylene surfaces. From XPS spectra of the pure zirconium complexes and the acid-etched polymer surface, before and after treatment with ethanolic zirconium carboxylate solutions, it was concluded that the zirconium species were chemically bound or chemically reacted with the polymer surface and that [Zr(acac) 4] interacted to the greatest extent.

Palmer, D. M.; Straughan, B. P.; Treverton, J. A.

1993-06-01

123

Manufacturing process to reduce large grain growth in zirconium alloys  

DOEpatents

It is an object of the present invention to provide a procedure for desensitizing zirconium-based alloys to large grain growth (LGG) during thermal treatment above the recrystallization temperature of the alloy. It is a further object of the present invention to provide a method for treating zirconium-based alloys which have been cold-worked in the range of 2 to 8% strain to reduce large grain growth. It is another object of the present invention to provide a method for fabricating a zirconium alloy clad nuclear fuel element wherein the zirconium clad is resistant to large grain growth.

Rosecrans, P.M.

1984-08-01

124

Removal of zirconium from hydrous titanium dioxide  

NASA Astrophysics Data System (ADS)

A method was proposed for removing zirconium (Zr) from hydrous titanium dioxide (HTD) by the NaF solution. The effects of main parameters, i.e. pH values, NaF dosage, temperature and retention time, on the removal of zirconium were studied. The optimal conditions were found as the following: pH value, <5.5; molar ratio of NaF to TiO2, 0.6; retention time, 80 min; and temperature, 80°C. The removal rate of Zr under the optimized conditions was above 87.7%. The adsorption energy of the preferential absorption of hydrofluoric acid for Zr(OH)2SO4(OH2) on the (001) crystal surface of HTD was determined by theoretical calculation. The possible mechanism of the removal process was also discussed.

Ma, Xue-qin; Liu, Ya-hui; Chu, Jing-long; Li, Jie; Xue, Tian-yan; Wang, Li-na; Qi, Tao

2013-01-01

125

Thermal sprayed zirconium coatings for corrosion resistance  

SciTech Connect

Vacuum Plasma Spraying (VPS) is conducted in inert reduced pressures. This results in higher particle velocities than in atmospheric plasma spraying. Reverse arc sputter cleaning and pre-heating of the workpiece lead to elevated substrate temperatures during deposition, allowing sintering of the coating and, thus, enhanced densities and bond strengths. Inert Environment Electric Arc Spraying (IEAS) is performed in inert gas chambers, utilizing wire as the feedstock. This leads to lower gas content in the coating, since the initial gas content in wire is lower than that of the powder feedstock used in VPS. Controlled atmosphere sprayed zirconium coatings had inferior mechanical and corrosion properties when compared with bulk zirconium. The VPS coatings displayed higher bond strengths and better cavitation erosion resistance than did the IEAS coatings. The IEAS coatings had lower gas content and showed better electrochemical and corrosion behavior. The lower gas content for IEAS was due to a lower initial gas level in the wire feedstock used in this process. Also, scanning electron microscopy revealed that larger particles result in the IEAS process. Thus, a smaller surface-area-to-volume ratio is available for gas-metal reactions to occur. Improvements in mechanical and corrosion properties for the IEAS coatings were due to elevated substrate temperatures during deposition. Compressive surface stresses induced by post-spray shot-peening enhanced corrosion and cavitation resistance of IEAS coatings. Coating porosity caused failure during immersion testing. Therefore, it was concluded that controlled environment thermal spraying of zirconium is not suitable for forming corrosion resistant coatings on steel. ZrN coatings were formed by electric arc spraying using a nitrogen shroud and post-spray nitriding. Two phases; ZrN and zirconium solid solution, exist in the as-sprayed coating. Nitriding increases the proportion of ZrN.

Bamola, R.K.

1992-01-01

126

Autohydration of Nanosized Cubic Zirconium Tungstate  

PubMed Central

Nanoparticulate zirconium tungstate prepared through hydrothermal methods was found to autohydrate under ambient conditions. This results in positive thermal expansion, limiting its usefulness for controlled thermal expansion composites. TEM and BET studies provided strong evidence that the cause of autohydration is a result of structural defects present in the nanoparticles, while kinetics are governed by surface area, suggesting that processing methods can be used to minimize or overcome this problem.

2010-01-01

127

Neutronographic Texture Analysis of Zirconium Based Alloys  

NASA Astrophysics Data System (ADS)

Neutron diffraction is a very powerful tool in texture analysis of zirconium based alloys used in nuclear technique. Textures of five samples (two rolled sheets and three tubes) were investigated by using basal pole figures, inversion pole figures, and ODF distribution function. The texture measurement was performed at diffractometer KSN2 on the Laboratory of Neutron Diffraction, Department of Solid State Engineering, Faculty of Nuclear Sciences and Physical Engineering, CTU in Prague. Procedures for studying textures with thermal neutrons and procedures for obtaining texture parameters (direct and inverse pole figures, three dimensional orientation distribution function) are also described. Observed data were processed by software packages HEXAL and GSAS. Our results can be summarized as follows: i) All samples of zirconium alloys show the distribution of middle area into two maxima in basal pole figures. This is caused by alloying elements. A characteristic split of the basal pole maxima tilted from the normal direction toward the transverse direction can be observed for all samples, ii) Sheet samples prefer orientation of planes (100) and (110) perpendicular to rolling direction and orientation of planes (002) perpendicular to normal direction, iii) Basal planes of tubes are oriented parallel to tube axis, meanwhile (100) planes are oriented perpendicular to tube axis. Level of resulting texture and maxima position is different for tubes and for sheets. The obtained results are characteristic for zirconium based alloys.

Kruželová, M.; Vratislav, S.; Kalvoda, L.; Dlouhá, M.

2012-02-01

128

Fluorometric determination of zirconium in minerals  

USGS Publications Warehouse

The increasing use of zirconium in alloys and in the ceramics industry has created renewed interest in methods for its determination. It is a common constituent of many minerals, but is usually present in very small amounts. Published methods tend to be tedious, time-consuming, and uncertain as to accuracy. A new fluorometric procedure, which overcomes these objections to a large extent, is based on the blue fluorescence given by zirconium and flavonol in sulfuric acid solution. Hafnium is the only element that interferes. The sample is fused with borax glass and sodium carbonate and extracted with water. The residue is dissolved in sulfuric acid, made alkaline with sodium hydroxide to separate aluminum, and filtered. The precipitate is dissolved in sulfuric acid and electrolysed in a Melaven cell to remove iron. Flavonol is then added and the fluorescence intensity is measured with a photo-fluorometer. Analysis of seven standard mineral samples shows excellent results. The method is especially useful for minerals containing less than 0.25% zirconium oxide.

Alford, W. C.; Shapiro, L.; White, C. E.

1951-01-01

129

Sulfate, nitrate declines noted  

NASA Astrophysics Data System (ADS)

An analysis of more than 4000 samples of precipitation that were collected weekly from 1978 through 1983 at 19 sites in 13 states showed no clear pattern of changes in overall acidity, according to a recent report by the U.S. Geological Survey (USGS) of the Department of the Interior. The analysis did, however, reveal significant declines in sulfate and nitrate concentrations during that 5-year period.USGS hydrologists said that sulfate and nitrate, sometimes used as indirect indicators of the acidity of precipitation, showed widespread and substantial downward trends in the eastern United States. (All but three of the 19 stations are located east of the Mississippi River.) At the five stations in Ohio, Pennsylvania, and West Virginia, for example, sulfate concentrations declined 25% to 40% during the 5-year period. Only two of those five stations showed statistically significant trends in pH; these were decreases in acidity comparable to the decreases in sulfate.

130

Ammonium nitrate explosive systems  

DOEpatents

Novel explosives which comprise mixtures of ammonium nitrate and an ammonium salt of a nitroazole in desired ratios are disclosed. A preferred nitroazole is 3,5-dinitro-1,2,4-triazole. The explosive and physical properties of these explosives may readily be varied by the addition of other explosives and oxidizers. Certain of these mixtures have been found to act as ideal explosives.

Stinecipher, Mary M. (Los Alamos, NM); Coburn, Michael D. (Los Alamos, NM)

1981-01-01

131

Synthesis of zirconium dioxide by ultrasound assisted precipitation: effect of calcination temperature.  

PubMed

Nanostructured zirconium dioxide was synthesized from zirconyl nitrate using both conventional and ultrasound assisted precipitation in alkaline medium. The synthesized samples were calcinated at temperatures ranging from 400°C to 900°C in steps of 100°C. The ZrO(2) specimens were characterized using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The thermal characteristics of the samples were studied via Differential Scanning Calorimetry-Thermo-Gravimetry Analysis (DSC-TGA). The influence of the calcination temperature on the phase transformation process from monoclinic to tetragonal to cubic zirconia and its consequent effect on the crystallite size and % crystallinity of the synthesized ZrO(2) was studied and interpreted. It was observed that the ultrasound assisted technique helped to hasten to the phase transformation and also at some point resulted in phase stabilization of the synthesized zirconia. PMID:21458352

Prasad, Krishnamurthy; Pinjari, D V; Pandit, A B; Mhaske, S T

2011-03-06

132

COMPARISON OF MUTAGENIC ACTIVITIES OF SEVERAL PEROXYACYL NITRATES  

EPA Science Inventory

Salmonella typhimurium strain TA100 was exposed to a series of peroxyacyl nitrates including peroxyacetyl nitrate (PAN), peroxypropionyl nitrate peroxybutyryl nitrate (PBN), peroxybenzoyl nitrate (PBzN), and chlororoxyacetyl nitrate (CPAN). as phase concentrations for the individ...

133

COMPARISON OF MUTAGENIC ACTIVITIES OF SEVERAL PEROXYACL NITRATES  

EPA Science Inventory

Salmonella typhimurium, strain TA100 was exposed to a series of peroxyacyl nitrates including peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), peroxybutyryl nitrate (PBN), peroxybenzoyl nitrate (PBzN), and chloroperoxyacetyl nitrate (CPAN). as-phase concentrations for t...

134

Solubility of plutonium nitrate in uranyl nitrate hexahydrate melt  

Microsoft Academic Search

At a weight fraction below 20%, Pu(IV) nitrate is isomorphically dissolved and homogeneously distributed in the uranyl nitrate\\u000a hexahydrate phase, the solubility being independent of the HNO3 concentration in the mixed U-Pu melt up to the acid concentration of 7 M. In dissolving solid Pu(IV) nitrate in 1–6 M HNO3, Pu(IV) disproportionates to form Pu(III) and Pu(VI). With increasing HNO3

Yu. M. Kulyako; T. I. Trofimov; M. D. Samsonov; A. Yu. Shadrin; B. F. Myasoedov

2008-01-01

135

Bismuth nitrate pentahydrate-induced novel nitration of eugenol  

PubMed Central

Background Eugenol, the main constituent of clove oil possesses a number of medicinal activities. To enhance the medicinal property, structural modification is required. On the other hand, bismuth nitrate pentahydrate has been established as an excellent eco-friendly nitrating agent for several classes of organic compounds. Results Bismuth nitrate pentahydrate-induced nitration of eugenol has been investigated very thoroughly. Twenty five different conditions have been studied. The microwave-induced solvent-free reaction has been identified as the best condition. Conclusions Spectral analyses confirm that 5-nitroeugenol is the sole product in all the cases. No oxidized or isomerized product could be detected.

2011-01-01

136

SPECIFICATION OF ZIRCONIUM FOR USE IN GASLESS MIXTURES  

Microsoft Academic Search

An investigation was made to determine the relationship between the ; properties of zirconium powder and the properties of heat powders or delay ; compositions and to arrive at a suitable specification. Seventeen samples were ; examined. The data show that the important points to be specified are the total ; zirconium content, the ignition gain, the hydrogen content, the

R. E. Mcintyre; M. L. Couch

1960-01-01

137

Silver electrowinning from photographic fixing solutions using zirconium cathode  

Microsoft Academic Search

Suitable electrochemical conditions for using zirconium as a cathode in the electrochemical recovery of silver from photographic fixing solutions were studied by cyclic voltammetry. The influence of the thin, natural zirconium oxide layer was investigated. A flowing system was tested to simulate industrial electrolysis and determine the recovery efficiency, the compactness and purity of the recovered silver. The influence of

M Chatelut; E Gobert; O Vittori

2000-01-01

138

Temperature dependence of lattice parameters of alpha-zirconium.  

National Technical Information Service (NTIS)

This work presents a brief review of X-ray and thermal expansion determination of lattice parameters for (alpha)-Zirconium. Data reported by different authors cover almost all the field of existence of the hexagonal phase of Zirconium, from temperatures a...

R. A. Versaci M. Ipohorski

1991-01-01

139

Molten salt scrubbing of zirconium or hafnium tetrachloride  

SciTech Connect

This patent describes a continuous process for removing impurities of iron or aluminum chloride or both from vaporous zirconium or hafnium chloride or both. It comprises: introducing impure zirconium or hafnium chloride vapor or both into a middle portion of an absorbing column containing a molten salt phase, the molten salt phase absorbing the impurities of iron or aluminum chloride or both to produce chloride vapor stripped of zirconium or hafnium chloride; introducing sodium or potassium chloride or both into a top portion of the column; controlling the top portion of the column to between 300--375{degrees} C.; heating a bottom portion of the column to 450--550{degrees} C. To vaporize zirconium chloride or hafnium chloride or hafnium and zirconium chloride from the molten salt; withdrawing molten salt substantially free of zirconium and hafnium chloride from the bottom portion of the column; and withdrawing zirconium chloride or hafnium chloride or hafnium and zirconium chloride vapor substantially free of impurities of iron and aluminum chloride from the top of the column.

Lee, E.D.; McLaughlin, D.F.

1990-04-03

140

Dissolution of Anodic Zirconium Dioxide Films in Aqueous Media  

Microsoft Academic Search

Zirconium with a low thermal neutron cross section, good corrosion resistance in high-temperature water, and high thermal conductivity is an ideal material for nuclear reactors. Its good resistance to water and steam at reactor temperatures is of the greatest interest to nuclear fuel designers. Dissolution of zirconium dioxide (ZrOâ) films in aggressive media was investigated. The extent of uniform and

A. Merati; B. Cox

1999-01-01

141

Zirconium-hafnium production in a zero liquid discharge process  

Microsoft Academic Search

This patent describes a zero liquid discharge, continuous process for separating and purifying zirconium and hafnium which substantially eliminates waste disposal problems. It comprises preparing a concentrated aqueous zirconium and hafnium-containing feed solution; loading the feed solution into a resin medium at a first point on a continuous annular chromatograph; feeding an aqueous acid eluant to the resin medium at

T. S. Snyder; E. D. Lee

1992-01-01

142

Process of precipitating zirconium or hafnium from spent pickling solutions  

SciTech Connect

This patent describes a process for regenerating a spent, fluoride-containing pickle solution used in the pickling of zirconium or hafnium metal or their alloys. It comprises adding to the spent pickle solution a sufficient amount of sodium sulfate to precipitate sodium zirconium or hafnium fluoride.

Aguilar, C.L.; Walker, R.G.

1991-12-31

143

Molten salt extractive distillation process for zirconium-hafnium separation  

Microsoft Academic Search

This patent describes an improvement in a process for zirconium-hafnium separation. It utilizes an extractive distillation column with a mixture of zirconium and hafnium tetrachlorides introduced into a distillation column having a top and bottom with hafnium enriched overheads taken from the top of the column and a molten salt solvent circulated through the column to provide a liquid phase,

D. F. McLaughlin; R. A. Stoltz

1989-01-01

144

Status report and plant proposals for zirconium purification  

Microsoft Academic Search

This report contains a summary of the latest improvements in zirconium purification as developed by the Y-12 research, pilot plant, production, and engineering groups, all of whom have been generously cooperating in this project. Four distinct plant estimates are also proposed for the construction and operation of permanent zirconium purification facilities.

1950-01-01

145

49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.  

Code of Federal Regulations, 2010 CFR

...nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 ...nitrates, and certain ammonium nitrate fertilizers. (a) Except as provided in...Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more than 70%...

2010-10-01

146

49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.  

Code of Federal Regulations, 2010 CFR

...nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 ...nitrates, and certain ammonium nitrate fertilizers. (a) Except as provided in...Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more than 70%...

2009-10-01

147

Nitrate Reductase from Monoraphidium braunii  

PubMed Central

Homogeneous nitrate reductase (EC 1.6.6.2) from Monoraphidium braunii was obtained by means of affinity chromatography in blue-Sepharose and gel filtration. After electrophoresis in polyacrylamide, gel slices containing pure nitrate reductase were disrupted and injected into previously unimmunized rabbits. The antiserum produced after several weeks was found to inhibit the different activities of nitrate reductase to a similar degree. Monospecificity of the antiserum was demonstrated by Ouchterlony double diffusion and crossed immunoelectrophoresis. The antibodies were purified by immunoabsorption to Sepharose-bound nitrate reductase. The intracellular location of nitrate reductase in green algae was examined by applying an immunocytochemical method to M. braunii cells. Ultrathin frozen sections were first treated with immunopurified anti-nitrate reductase monospecific antibodies, followed by incubation with colloidal gold-labeled goat antirabbit immunoglobulin G as a marker. The enzyme was specifically located in the pyrenoid region of the chloroplast. Images Fig. 1 Fig. 2 Fig. 4 Fig. 5

Lopez-Ruiz, Antonio; Roldan, Jose Manuel; Verbelen, Jean Pierre; Diez, Jesus

1985-01-01

148

Effects of nitrate supply on plant growth, nitrate accumulation, metabolic nitrate concentration and nitrate reductase activity in three leafy vegetables  

Microsoft Academic Search

Three leafy vegetables, rape (Brassica campestris L.), Chinese cabbage (Brassica chinensis var. Oleifera Makino et Nenoto) and spinach (Spinacia oleracea L.), were grown in plastic pots with 5kg soil per pot at five nitrate supply rates, 0.00 (N1), 0.15 (N2), 0.30 (N3), 0.45 (N4), and 0.60 (N5)gNkg?1 soil to investigate the effects of nitrate supply on plant growth, nitrate accumulation

Bao-Ming Chen; Zhao-Hui Wang; Sheng-Xiu Li; Gen-Xuan Wang; Hai-Xing Song; Xi-Na Wang

2004-01-01

149

PROCESS FOR DISSOLVING BINARY URANIUM-ZIRCONIUM OR ZIRCONIUM-BASE ALLOYS  

Microsoft Academic Search

A process of dissolving uranium-- zirconium and zircaloy alloys, e.g. ; jackets of fuel elements, with an anhydrous hydrogen fluoride containing from 10 ; to 32% by weight of hydrogen chloride at between 400 and 450 deg C., preferably ; while in contact with a fluidized inert powder, such as calcium fluoride is ; described. (AEC)

A. A. Jonke; J. J. Barghusen; N. M. Levitz

1962-01-01

150

Determination of fracture strength of ?-zirconium hydrides embedded in zirconium matrix at high temperatures  

NASA Astrophysics Data System (ADS)

The fracture strength of ?-zirconium hydrides embedded in a zirconium matrix was determined at temperatures between 25 °C and 250 °C by ring tensile tests using Zircaloy-2 tubes. Essentially all of the present hydrides in the tubes were re-oriented in the radial direction by a temperature cycling treatment and then tensile stress was applied perpendicular to the hydrides to ensure that brittle fracture would occur at the hydrides. The hydrides failed in a brittle manner below 100 °C where-as the zirconium matrix itself underwent ductile fracture without hydride cracking at temperatures above 200 °C under plane stress condition. Brittle fracture of the hydrides continued to occur at temperatures up to 250 °C under plane strain condition, suggesting that the upper limit temperature for hydride fracture, Tupper, was raised by the triaxial stress state under the plane strain condition. The apparent fracture strength of the hydrides, ?hydridef, was determined at temperatures below Tupper from the measured fracture strength of the tubes, making a correction for the compressive transformation stress in the hydrides. ?hydridef was about 710 MPa at temperatures between 25 °C and 250 °C at both plane stress and plane strain conditions. The temperature dependency was very small in this temperature range. Tupper was almost equivalent to the cross-over temperature between ?hydridef and the ultimate tensile strength (UTS), which suggests that, at temperatures above Tupper, the zirconium matrix would undergo ductile fracture before the stress in the hydride is raised above ?hydridef, since UTS is smaller than ?hydridef.

Kubo, T.; Kobayashi, Y.; Uchikoshi, H.

2013-04-01

151

PROCESS FOR DISSOLVING BINARY URANIUM-ZIRCONIUM OR ZIRCONIUM-BASE ALLOYS  

DOEpatents

A process of dissolving uranium-- zirconium and zircaloy alloys, e.g. jackets of fuel elements, with an anhydrous hydrogen fluoride containing from 10 to 32% by weight of hydrogen chloride at between 400 and 450 deg C., preferably while in contact with a fluidized inert powder, such as calcium fluoride is described. (AEC)

Jonke, A.A.; Barghusen, J.J.; Levitz, N.M.

1962-08-14

152

Zirconium-hafnium production in a zero liquid discharge process  

SciTech Connect

This patent describes a zero liquid discharge, continuous process for separating and purifying zirconium and hafnium which substantially eliminates waste disposal problems. It comprises preparing a concentrated aqueous zirconium and hafnium-containing feed solution; loading the feed solution into a resin medium at a first point on a continuous annular chromatograph; feeding an aqueous acid eluant to the resin medium at a second point angularly displaced from the first point on the chromatograph to elute the feed solution; continuously rotating the chromatograph; separately collecting a substantially pure zirconium fraction, a substantially pure hafnium fraction and at least one waste fraction at locations on the annular chromatograph angularly and longitudinally displaced from the first point; further separately processing the zirconium fraction and the hafnium fraction to produce nuclear quality zirconium metal and hafnium metal; subjecting the waste fraction to volume reduction and disposing of the waste fraction as a dry solid; and recycling the acid eluant for reuse.

Snyder, T.S.; Lee, E.D.

1992-05-12

153

Uranium-preextraction in zirconium/hafnium separations processs  

SciTech Connect

This patent describes an improvement in a process for recovering zirconium values from uranium containing zircon ore. The process comprising a fluidized bed carbochlorination of the zircon ore at 800{degrees}--1250{degrees} C., producing a relatively impure, hafnium-containing zirconium tetrachloride stream and by-product silicon tetrachloride, which silicon tetrachloride by-product is separated by differential condensation, and wherein uranium chloride is volatilized at the ore chlorinator temperature and follows as an impurity in the zirconium-hafnium tetrachloride stream, mixing the zirconium-hafnium tetrachloride with water to produce a zirconium-hafnium oxychloride solution, and removing iron impurities by liquid--liquid iron extraction with a methyl isobutyl ketone extractant.

Feuling, R.J.

1990-04-03

154

49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation...176.410 Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. (a) This...

2009-10-01

155

49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. 176.410 Section 176.410 Transportation...176.410 Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures. (a) This...

2010-10-01

156

Glycine lithium nitrate crystals  

NASA Astrophysics Data System (ADS)

Crystals of glycine lithium nitrate with non-linear optical properties have been grown in a solution by slow evaporation at room temperature. The crystal shows a good thermal stability from room temperature to 175 °C where the crystal begins to degrade. This property is desirable for future technological applications. Also, a good performance on the second harmonic generation was found, characterizing the emitted dominant wavelength by a customized indirect procedure using luminance and chromaticity measured data based on the CIE-1931 standard. Additionally, the 532 nm signal was detected by using a variant to the Kurtz and Perry method.

González-Valenzuela, R.; Hernández-Paredes, J.; Medrano-Pesqueira, T.; Esparza-Ponce, H. E.; Jesús-Castillo, S.; Rodriguez-Mijangos, R.; Terpugov, V. S.; Alvarez-Ramos, M. E.; Duarte-Möller, A.

157

Study of the Hydroxylammonium Nitrate - Isopropyl Ammonium Nitrate Reaction.  

National Technical Information Service (NTIS)

When a balanced mixture of hydroxylammonium nitrate (HAN) and isopropyl ammonium nitrate (IPAN) in aqueous solution at appropriate concentrations is ignited in a high pressure bomb the reaction goes to completion to produce H2O, CO2 and N2. Some intermedi...

J. J. Kaufman W. S. Koski

1980-01-01

158

METHOD FOR DISSOLVING ZIRCONIUM-URANIUM COMPOSITIONS  

DOEpatents

A method is descrioed for treating a zirconium-- uranium composition to form a stable solution from which uranium and other values may be extracted by contacting the composition with at least a 4 molar aqueous solution of ammonium fluoride at a temperature of about 100 deg C, adding a peroxide, in incremental amounts, to the heated solution throughout the period of dissolution until all of the uranium is converted to soluble uranyl salt, adding nitric acid to the resultant solution to form a solvent extraction feed solution to convert the uranyl salt to a solvent extractable state, and thereafter recovering the uranium and other desired values from the feed solution by solvent extraction.

Gens, T.A.

1961-07-18

159

High temperature behavior of zirconium germanates  

NASA Astrophysics Data System (ADS)

The high temperature behavior of zirconium germanates ZrGeO4 and Zr3GeO8 up to 2300 °C has been studied using the original photoemission thermal analysis technique with the comprehensive physicochemical study of solid and gaseous intermediate and final products. The two-stage process of incongruent sublimation of GeO2 was established and the phase boundary of the homogeneity range for ZrGeO4 and Zr3GeO8 were deduced from the thermal analysis, X-ray diffraction and Raman spectroscopy studies. A high tendency to sintering of the final ZrO2 product is discussed.

Utkin, A. V.; Baklanova, N. I.; Vasilyeva, I. G.

2013-05-01

160

ZIRCONIUM-TITANIUM-BERYLLIUM BRAZING ALLOY  

DOEpatents

A new and improved ternary alloy is described which is of particular utility in braze-bonding parts made of a refractory metal selected from Group IV, V, and VI of the periodic table and alloys containing said metal as a predominating alloying ingredient. The brazing alloy contains, by weight, 40 to 50 per cent zirconium, 40 to 50 per cent titanium, and the balance beryllium in amounts ranging from 1 to 20 per cent, said alloy having a melting point in the range 950 to 1400 deg C. (AEC)

Gilliland, R.G.; Patriarca, P.; Slaughter, G.M.; Williams, L.C.

1962-06-12

161

Shell model description of zirconium isotopes  

SciTech Connect

We calculate the low-lying spectra and several high-spin states of zirconium isotopes (Z=40) with neutron numbers from N=50 to N=58 using a large valence space with the {sup 78}Ni inert core, which a priori allows one to study the interplay between spherical and deformed configurations, necessary for the description of nuclides in this part of the nuclear chart. The effective interaction is derived by monopole corrections of the realistic G matrix. We reproduce essential nuclear properties, such as subshell closures in {sup 96}Zr and {sup 98}Zr. The spherical-to-deformed shape transition in {sup 100}Zr is addressed as well.

Sieja, K. [GSI-Helmholtzzentrum fuer Schwerionenforschung mbH., Planckstrasse 1, D-64-220 Darmstadt (Germany); Institut fuer Kernphysik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany); Nowacki, F. [Institute Pluridisciplinaire Hubert Curien, 23 rue du Loess, Strasbourg (France); Langanke, K. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, D-64289 Darmstadt (Germany); Frankfurt Institute for Advanced Studies, D-60438 Frankfurt am Main (Germany); Martinez-Pinedo, G. [GSI-Helmholtzzentrum fuer Schwerionenforschung mbH., Planckstrasse 1, D-64-220 Darmstadt (Germany)

2009-06-15

162

The irradiation effects on zirconium alloys  

NASA Astrophysics Data System (ADS)

Pressure tube samples were irradiated under helium atmosphere in the TRIGA Steady State Research and Material Test Reactor of the Romanian Institute for Nuclear Research (INR). These samples are made of the Zr 2.5%Nb alloy used as structural material for the CANDU Romanian power reactors. After irradiation, mechanical tests were performed in the Post Irradiation Examination Laboratory (PIEL) to study the influence of irradiation on zirconium alloys mechanical behaviour. The tensile test results were used for structural integrity assessment. Results of the tests are presented. The paper presents, also, pressure tube structural integrity assessment.

Negut, Gh.; Ancuta, M.; Radu, V.; Ionescu, S.; Stefan, V.; Uta, O.; Prisecaru, I.; Danila, N.

2007-05-01

163

Nitrates in myocardial infarction.  

PubMed

Until two decades ago nitroglycerin was contraindicated in acute myocardial infarction (MI). Studies in the canine model demonstrated that low-dose intravenous (i.v.) infusion, carefully titrated to decrease mean blood pressure by 10% but not below 80 mmHg, during early stages of acute MI produced marked reduction of left ventricular (LV) preload, improvement in regional perfusion, and limitation of infarct size and remodeling. However, more i.v. nitroglycerin to decrease blood pressure further resulted in a paradoxical J-curve effect, with hypoperfusion and increased infarct size. Clinical studies have confirmed that low-dose i.v. nitroglycerin infusion for the first 48 hours after acute MI is safe, not only for improving performance in LV failure, but also for limiting ischemic injury, infarct size, remodeling, and infarct-related complications, including deaths in-hospital and up to 1 year. Recent studies suggest that more prolonged therapy with nitrates spanning the healing phase of acute anterior Q-wave MI can further limit LV remodeling and preserve function. Preliminary results of the recently completed ISIS-4 megatrial suggest, however, that long-term nitrate in patients with suspected MI in the 1990s does not improve survival significantly. PMID:7848898

Jugdutt, B I

1994-08-01

164

Nitrate Reductase Activity Is Required for Nitrate Uptake into Fungal but Not Plant Cells  

Microsoft Academic Search

The ability to transport net nitrate was conferred upon transformant cells of the non-nitrate-assimilating yeast Pichia pastoris after the introduction of two genes, one encoding nitrate reductase and the other nitrate transport. It was observed that cells of this lower eukaryote transformed with the nitrate transporter gene alone failed to display net nitrate transport despite having the ability to produce

Shiela E. Unkles; Rongchen Wang; Ye Wang; Anthony D. M. Glass; Nigel M. Crawford; James R. Kinghorn

2004-01-01

165

Molecular Control of Nitrate Reductase and Other Enzymes Involved in Nitrate Assimilation  

Microsoft Academic Search

Nitrate acts as both a nutrient and a signal in plants. Nitrate induces gene expression of enzymes for its metabolism into amino acids but also has other effects on plant metabolism and development. Familiar nitrate-induced enzymes are nitrate and nitrite reductases, nitrate transporters, glutamine synthetase, glutamate synthase, ferredoxin and ferredoxin NADP+ reductase. Microarray analysis of nitrate-stimulated gene expression has identified

Wilbur H. Campbell

166

Catalyzed reduction of nitrate in aqueous solutions.  

National Technical Information Service (NTIS)

Sodium nitrate and other nitrate salts in wastes is a major source of difficulty for permanent disposal. Reduction of nitrate using aluminum metal has been demonstrated, but NH(sub 3), hydrazine, or organic compounds containing oxygen would be advantageou...

P. A. Haas

1994-01-01

167

Mortality of nitrate fertiliser workers  

Microsoft Academic Search

An epidemiological cohort study was conducted to investigate the mortality patterns among a group of workers engaged in the production of nitrate based fertilisers. This study was designed to test the hypothesis that individuals exposed to high concentrations of nitrates might be at increased risk of developing cancers, particularly gastric cancer. A total of 1327 male workers who had been

S Al-Dabbagh; D Forman; D Bryson; I Stratton; R Doll

1986-01-01

168

Nitration reaction modification of asphalt  

SciTech Connect

An experimental design was prepared to study the nitration reaction of asphalts at various concentrations by Fourier Transform Infrared Spectroscopy (FT-IR) and physical methods. After selection of a usable treatment level (1% by weight), the nitration reaction was performed on eight asphalts. These asphalts were evaluated by physical methods and for elastic recovery and by FT-IR.

Boucher, J.L.; Ihsiung Wang; Romine, R.A. (Southwestern Labs., Inc., Houston, TX (United States))

1990-07-01

169

TREATMENT OF AMMONIUM NITRATE SOLUTIONS  

DOEpatents

The treatment of waste solutions obtained in the processing of neutron- irradiated uranium containing fission products and ammonium nitrate is described. The object of this process is to provide a method whereby the ammonium nitrate is destroyed and removed from the solution so as to permit subsequent concentration of the solution.. In accordance with the process the residual nitrate solutions are treated with an excess of alkyl acid anhydride, such as acetic anhydride. Preferably, the residual nitrate solution is added to an excess of the acetic anhydride at such a rate that external heat is not required. The result of this operation is that the ammonium nitrate and acetic anhydride react to form N/sub 2/ O and acetic acid.

Boyer, T.W.; MacHutchin, J.G.; Yaffe, L.

1958-06-10

170

Retrospective Reactor Dosimetry with Zirconium Alloy Samples  

SciTech Connect

Retrospective measurements are routinely performed with stainless steel samples. Recent experiments have been successfully conducted using zirconium alloy samples, involving somewhat different neuron activation reactions than are normally encountered with stainless steel samples. The alloy composition consisted of nominally 1% (by weight) niobium, 1% tin, and 0.1% iron, with the balance zirconium. The activation products observed in the samples by gamma spectroscopy included Zr-95, Nb-95, Sn-113, Sb-125, Mn-54, Co-60, Nb-94, and Ta-182. The niobium was then chemically separated following ASTM procedure E1297 and the Nb-93m activities were measured by x-ray spectroscopy. The thermal neutron fluences, as determined independently by the neutron capture gamma reactions to Zr-95, Sn-113, Nb-94, and Sn/Sb-125, were in excellent agreement. The fast neutron fluences, as determined separately by the Fe-54(n,p)Mn-54 and Nb-93(n,n’)Nb-93m reactions, were also in good agreement, thus demonstrating the versatility of the retrospective dosimetry technique.

Greenwood, Lawrence R.; Foster, John P.

2009-11-01

171

Diffusion of insoluble carbon in zirconium oxides  

NASA Astrophysics Data System (ADS)

The diffusion coefficient of insoluble carbon in zirconium oxides has been obtained for the temperature range of 900-1000°C. There are no published data on the diffusion of insoluble impurities; these data are of current interest for the diffusion theory and nuclear technologies. Tracer atoms 13C have been introduced into oxides by means of ion implantation and the kinetics of their emission from the samples in the process of annealing in air has been analyzed. The measurements have been performed using the methods of nuclear microanalysis and X-ray photoelectron spectroscopy. The diffusion activation energy is 2.7 eV and the carbon diffusion coefficient is about six orders of magnitude smaller than that for oxygen self-diffusion in the same systems. This result indicates the strong anomaly of the diffusion properties of carbon in oxides. As a result, zirconium oxides cannot be used in some nuclear technologies, in particular, as a material of sources for accelerators of short-lived carbon isotopes.

Vykhodets, V. B.; Kurennykh, T. E.; Kesarev, A. G.; Kuznetsov, M. V.; Kondrat'ev, V. V.; Hülsen, C.; Koester, U.

2011-03-01

172

Mortality of nitrate fertiliser workers.  

PubMed

An epidemiological cohort study was conducted to investigate the mortality patterns among a group of workers engaged in the production of nitrate based fertilisers. This study was designed to test the hypothesis that individuals exposed to high concentrations of nitrates might be at increased risk of developing cancers, particularly gastric cancer. A total of 1327 male workers who had been employed in the production of fertilisers between 1946 and 1981 and who had been occupationally exposed to nitrates for at least one year were followed up until 1 March 1981. In total, 304 deaths were observed in this group and these were compared with expected numbers calculated from mortality rates in the northern region of England, where the factory was located. Analysis was also carried out separately for a subgroup of the cohort who had been heavily exposed to nitrates--that is, working in an environment likely to contain more than 10 mg nitrate/m3 for a year or longer. In neither the entire cohort nor the subgroup was any significant excess observed for all causes of mortality or for mortality from any of five broad categories of cause or from four specific types of cancer. A small excess of lung cancer was noted more than 20 years after first exposure in men heavily exposed for more than 10 years. That men were exposed to high concentrations of nitrate was confirmed by comparing concentrations of nitrates in the saliva of a sample of currently employed men with control men, employed at the same factory but not in fertiliser production. The men exposed to nitrate had substantially raised concentrations of nitrate in their saliva compared with both controls within the industry and with men in the general population and resident nearby. The results of this study therefore weight against the idea that exposure to nitrates in the environment leads to the formation in vivo of material amounts of carcinogens. PMID:3015194

Al-Dabbagh, S; Forman, D; Bryson, D; Stratton, I; Doll, R

1986-08-01

173

Nitrates for unstable angina.  

PubMed

The term unstable angina encompasses heterogeneous clinical syndromes. Fissuring of an atherosclerotic coronary artery plaque with superimposed platelet deposition, with or without additional thrombus formation, is invariably responsible for a prolonged episode of angina at rest, increasing frequency of angina at rest, or with minimal exertion of less than 4 weeks in duration and early postinfarction angina. Plaque progression, rather than plaque fissuring, is the most likely mechanism for progressive reduction in walking distance due to angina in patients who previously have stable angina. Coronary artery spasm is responsible for Prinzmetal's variant angina, but its exact role in other forms of unstable angina is unknown. The mainstay of treatment of unstable angina (prolonged episode of angina at rest and recent onset angina at rest, or with minimal exertion with a crescendo pattern) is aspirin, heparin, or both. Both aspirin and intravenous (i.v.) heparin or their combination reduce early mortality and the incidence of acute myocardial infarction in patients hospitalized with unstable angina. However, these agents do not promptly relieve chest pain. There are no placebo-controlled studies evaluating the usefulness of nitrates in unstable angina. In open-label studies, continuous therapy with i.v. nitroglycerin (NTG) for 24 hours or longer has been shown to relieve chest pain in patients with rest angina refractory to therapy with other antianginal agents, including long-acting nitrates. Recurrence of chest pain in patients receiving i.v. NTG is a common problem and probably represents development of pharmacologic tolerance, but this can be overridden by dose escalation; protracted tolerance during short-term use of i.v. NTG is usually not a problem.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7873468

Thadani, U; Opie, L H

1994-10-01

174

RECOVERY OF URANIUM FROM ZIRCONIUM-URANIUM NUCLEAR FUELS  

DOEpatents

An improvement was made in a process of recovering uranium from a uranium-zirconium composition which was hydrochlorinated with gsseous hydrogen chloride at a temperature of from 350 to 800 deg C resulting in volatilization of the zirconium, as zirconium tetrachloride, and the formation of a uranium containing nitric acid insoluble residue. The improvement consists of reacting the nitric acid insoluble hydrochlorination residue with gaseous carbon tetrachloride at a temperature in the range 550 to 600 deg C, and thereafter recovering the resulting uranium chloride vapors. (AEC)

Gens, T.A.

1962-07-10

175

METHOD OF PREPARING SINTERED ZIRCONIUM METAL FROM ITS HYDRIDES  

DOEpatents

The invention relates to the preparation of metal shapes from zirconium hydride by powder metallurgical techniques. The zirconium hydride powder which is to be used for this purpose can be prepared by rendering massive pieces of crystal bar zirconium friable by heat treatment in purified hydrogen. This any then be ground into powder and powder can be handled in the air without danger of it igniting. It may then be compacted in the normal manner by being piaced in a die. The compact is sintered under vacuum conditions preferably at a temperature ranging from 1200 to 1300 deg C and for periods of one to three hours.

Angier, R.P.

1958-02-11

176

Ultraviolet absorption spectrum of peroxyacetyl nitrate and peroxypropionyl nitrate. [Peroxypropionyl nitrate  

SciTech Connect

The UV absorption spectrum was measured for peroxyacetyl nitrate (PAN) and peroxypropionyl nitrate (PPN) at 298 +/- 1 K in the 200-400-nm wavelength region. From this, the absorption cross sections for PAN and PPN have been calculated. Solar photolysis rates for PAN and PPN are estimated on the basis of the measured and extrapolated cross sections. 2 tables.

Senum, G.I.; Lee, Y.N.; Gaffney, J.S.

1984-03-29

177

A Zirconium Cermet for Transuranic Isotope Storage and Burning  

SciTech Connect

Transuranic (TRU) isotopes comprise {approx} 1% of the spent nuclear fuel (SNF) inventory from commercial light water reactors and supply the majority of the late-term (>300 years) heat load produced by SNF. These isotopes also have significant potential fission energy content that could be recovered in a fast reactor or accelerator driven system. Estimates by Wigeland, et al. suggest that removal of 99.9% of TRU isotopes and 97% of cesium, strontium, and europium from SNF could increase the linear drift load (i.e. capacity) of the proposed geologic repository at Yucca Mountain, NV by an order of magnitude. In other words, the waste packing capacity in Yucca Mt. would be increased and the recovered TRU could be used in a fast reactor system for energy production. One of the goals of the Advanced Fuel Cycle Initiative (AFCI) of the U.S. Department of Energy is to develop advanced nuclear technologies to recycle spent nuclear fuel without separating pure plutonium. The UREX+ family of solvent extraction and ion exchange processes can be manipulated to isolate TRU isotopes from uranium and other short-lived isotopes while leaving the Pu intimately mixed with other minor actinides (this corresponds with the UREX+1a process). The product TRU nitrate solution can be converted into oxide microspheres via direct denitration or sol-gel processing, leaving the TRU product in a stable oxide form for further processing. In addition, nuclear-grade zirconium metal can be recovered by recycling Zircaloy from the spent fuel cladding after the fuel has been chopped and dissolved away. The Zircaloy cladding hulls may be processed via a hydride/de-hydride process to produce high purity zirconium powder.These powder products can be combined via powder metallurgy techniques to produce a stable, safe storage form for TRU waste with the possibility of converting a long term waste liability into an advanced energy resource. Previous work by McDeavitt et al. at Argonne National Laboratory analyzed the production of a (Th,U)O-2-Zr cermet fuel using a cold-drawing process. This was a multi-pass process wherein a series of reductions were performed on each individual rod with a high temperature anneal between successive reductions to relieve strain hardening. This process allowed excellent control over the finished product matrix density allowing the user to pre-select the desired density by manipulating the reduction scheme. The final cold-drawn cermet contained a large fraction of damaged oxide particles, though the cause of this damage was not investigated due to project time constraints. It is believed that the high stress profile developed during cold deformation was the primary cause of this damage. The Fuel Cycle and Materials Laboratory (FCML) at Texas A and M University is currently analyzing a hot extrusion process to fabricate the proposed cermet and provide comparison data with the previous work. Initial studies have been completed and a system redesign is near completion. This paper presents the initial findings of the initial work and describes the new system setup. (authors)

Totemeier, Aaron R.; McDeavitt, Sean M. [Fuel Cycle and Materials Laboratory, Texas A and M University, College Station, TX 77843 (United States)

2007-07-01

178

Ballistic effectiveness of superdense solid composite propellants with zirconium or zirconium hydride  

NASA Astrophysics Data System (ADS)

The ballistic effectiveness of propellants depends not only on the value of specific impulse but also on many other performances, primarily on the density. Despite the density itself does not enter the expression of the rocket velocity (W = Isp ln(Mlaunch/Mfinish) where Mlaunch and Mfinish are the rocket launch mass and its mass after the propellant is burnt, respectively), it in§uences the value Mlaunch/Mfinish of the specific rocket. If one charges the construction of fixed volume with a more dense propellant, the ratio Mlaunch/Mfinish increases and, consequently, W increases as well. In this paper, the possibility of creating solid composite propellants (SCP) with zirconium (density 6.49 g/cm3) and zirconium hydride (density 5.61 g/cm3 ) as energetic compounds instead of aluminum is considered. It was found for what kinds of engines these propellants have to be more effective than propellants based on aluminum.

Lempert, D.; Manelis, G.; Nechiporenko, G.

2011-10-01

179

Syntheses and structural characterization of zirconium-tin and zirconium-lead binary and ternary systems.  

National Technical Information Service (NTIS)

The binary zirconium-tin system was reinvestigated. The A15 phase appears to be a line phase with a Zr(sub 4)Sn composition. The Zr(sub 5)Sn(sub 3) (Mn(sub 5)Si(sub 3)-type) and Zr(sub 5)Sn(sub 4) (Ti(sub 5)Ga(sub 4)-type) compounds are line phases below ...

Y. U. Kwon

1991-01-01

180

Nitrate therapy in heart failure.  

PubMed

Nitrates are drugs of first choice in patients with acute heart failure. Acute pulmonary edema can be successfully treated with single or repeated doses of sublingual nitroglycerin. In cases of prolonged acute heart failure, e.g. in the setting of acute myocardial infarction, nitroglycerin or isosorbide dinitrate can be given by the intravenous route for up to 24 h. Patients with acute myocardial infarction usually benefit from nitrate therapy if filling pressures are high and/or left ventricular function is compromised. Nitrate therapy can be considered safe if arterial blood pressure is maintained above 95 mm Hg. With these precautions nitrates can reduce infarct size and the incidence of complications as well as improve long-term prognosis. In the chronic treatment concern has risen with regard to possible nitrate tolerance. Thus, therapy schedules allowing for nitrate-poor phases are generally recommended. Therapy schedules with constant-rate delivery of drugs achieved with patches or intravenous administration of nitrates should be used with caution. PMID:1760830

Schneider, W; Bussmann, W D; Hartmann, A; Kaltenbach, M

1991-01-01

181

Nitrate Reductase from Squash: cDNA Cloning and Nitrate Regulation  

Microsoft Academic Search

The assimilation of nitrate in plants involves the reduction of nitrate to ammonia in two steps. The first step requires nitrate reductase, a nitrate-inducible enzyme. When seedlings of squash (Cucurbita maxima L.) were treated with nitrate, both nitrate reductase activity and protein were induced in the cotyledons. Poly(A)+ RNA was prepared from cotyledons of nitrate-treated seedlings and was used to

Nigel M. Crawford; Wilbur H. Campbell; Ronald W. Davis

1986-01-01

182

Erosive Resistance of Zirconium Dioxide, Stabilized by Yttrium Oxide.  

National Technical Information Service (NTIS)

Results are presented from the study of the erosion resistance of zirconium dioxide stabilized by yttrium oxide under conditions corresponding to the function of electrodes in the channel of an open cycle type MHD generator. It is experimentally shown tha...

A. B. Ivanov A. I. Rekov I. S. Mayauskas R. I. Abraitis V. G. Gordon

1971-01-01

183

PRECIPITATION OF ZIRCONIUM AND FLUORIDE IONS FROM SOLUTIONS  

DOEpatents

A process is given for removing zirconium and fluorine ions from aqueous solutions also containing uranium(VI). The precipitation is carried out with sodium formate, and the uranium remains in solution. (AEC)

Newby, B.J.

1963-06-11

184

Extractive separation of uranium and zirconium sulfates by amines  

SciTech Connect

This paper describes an amine extraction process for zirconium and uranium separation. The behaviour of an extraction system containing uranium (VI) sulfate, zirconium (IV) sulfate, 0.2 and 0.5 M sulfuric acid (as the original aqueous phase), tertiary amine tri-n-lauryl- amine or primary amine Primene JMT in benzene (as the original organic phase) is discussed on the basis of equilibrium data. The measured dependences show that the degree of extraction of zirconium at the sulfuric acid concentration of 0.5 M and above is only slightly affected by a presence of uranium in solution. From this surprising behaviour it follows that zirconium may be employed for the displacement of uranium from the organic phase. This effect is more pronounced with the primary amine Primene JMT than with TLA. 29 refs., 4 figs., 1 tab.

Schroetterova, D.; Nekovar, P.; Mrnka, M. [Prague Inst. of Chemical Technology (Czechoslovakia)

1992-04-01

185

Chemical Tinting of Hafnium and Zirconium Carbides for Metallographic Examination.  

National Technical Information Service (NTIS)

An etchant is described that imparts color to the surface of hafnium and to zirconium carbide metallographic specimens. These colors not only provide a sharp delineation of individual grains, but also define the boundaries of eutectic colonies that contai...

R. L. Joyce K. R. Janowski J. H. Richardson

1967-01-01

186

Separation of zirconium from hafnium by solvent extraction  

SciTech Connect

Separation of zirconium and hafnium by solvent extraction with a tertiary amine from sulfuric acid solution is improved by addition of water-soluble alpha -hydroxycarboxylic acid to the aqueous phase.

Macdonald, D.J.

1980-11-04

187

SHORT SURVEY OF THE SEPARATION METHODS FOR ZIRCONIUM AND HAFNIUM  

Microsoft Academic Search

After a discussion of the essential ways to use zircondum as a ; construction material for nuclear reactors, a critical review is given of the ; most common chemical methods for separation of zirconium and hafnium. (auth);

Getoff

1958-01-01

188

Review of Anhydrous Zirconium-Hafnium Separation Techniques.  

National Technical Information Service (NTIS)

Sixteen nonaqueous techniques conceived to replace the current aqueous scheme for separating hafnium and zirconium tetrachlorides were reviewed and evaluated by the Bureau of Mines. The methods are divided into two classes: separation by fractional volati...

D. B. Hunter D. T. Rogers R. L. Skaggs

1983-01-01

189

Separation of zirconium from hafnium by solvent extraction  

Microsoft Academic Search

Separation of zirconium and hafnium by solvent extraction with a tertiary amine from sulfuric acid solution is improved by addition of water-soluble alpha -hydroxycarboxylic acid to the aqueous phase.

1980-01-01

190

Zirconium as a Structural Material for Naval Systems.  

National Technical Information Service (NTIS)

The important basic physical properties and steps in the manufacture of elemental zirconium and several of its important alloys are discussed. Once considered prohibitively expensive for structural uses, its current cost is becoming competitive with other...

W. A. Ferrando

1985-01-01

191

40 CFR 721.10152 - Oxirane, substituted silylmethyl-, hydrolysis products with alkanol zirconium(4+) salt and silica...  

Code of Federal Regulations, 2010 CFR

...silylmethyl-, hydrolysis products with alkanol zirconium(4+) salt and silica, acetates...silylmethyl-, hydrolysis products with alkanol zirconium(4+) salt and silica, acetates...hydrolysis products with alkanol zirconium(4+) salt and silica,...

2009-07-01

192

Strength of zirconium carbide composites with disperse carbon inclusions  

Microsoft Academic Search

The introduction of 0.2- to 6-µm carbon particles into zirconium carbide leads to a nonmonotonic variation of the strength, fracture toughness, and thermal fatigue resistance of the resultant zirconium carbide-carbon composites as functions of free carbon content, with maxima at about 2.5 wt. %. Coarser (50-µm) carbon particles added in larger quantities have a deleterious effect on the strength properties.

P. V. Gerasimov; V. S. Egorov; A. G. Lanin; L. B. Nezhevenko; V. A. Sokolov

1982-01-01

193

Synthesis of spherical mesostructured zirconium phosphate with acidic properties  

Microsoft Academic Search

Spherical particles of mesoporous zirconium phosphate with excellent acidic properties have been prepared using a zirconium carbonate complex, diammonium hydrogen phosphate and tetradecyltrimethylammonium bromide (TTBr) in basic medium through precipitation. EDAX analysis of the calcined product has shown the P\\/Zr ratio 1.93. High specific surface area of 299m2\\/g with narrow pore size distribution has been achieved after the removal of

A. Tarafdar; A. B. Panda; N. C. Pradhan; P. Pramanik

2006-01-01

194

Fabrication and characterization of uranium–thorium–zirconium hydrides  

Microsoft Academic Search

Two uranium–thorium–zirconium hydrides, (UTh4Zr10)H1.9 and (U4Th2Zr9)H1.5, have been fabricated and characterized. Fabrication involved arc melting of the constituent pure metals to form homogenous alloys, followed by hydriding at elevated temperatures in a hydrogen gas environment. The compounds were characterized by X-ray powder diffractometry as well as scanning and transmission electron microscopy. These methods revealed a multi-phase mixture of ?-zirconium hydride

Kurt A. Terrani; G. W. Chinthaka Silva; Charles B. Yeamans; Mehdi Balooch; Donald R. Olander

2009-01-01

195

Zirconium and hafnium with low oxygen and iron  

SciTech Connect

A high purity zirconium sponge or hafnium sponge is described consisting of 250-about 350 ppm of oxygen impurity, 50-350 ppm of iron impurity, total impurities of 500-1,000 ppm, with the remainder being zirconium or hafnium, whereby an inexpensive intermediate product is provided which can be processed for use in applications requiring high purity material, without resorting to expensive crystal bar processing.

Kwon, Y.J.

1988-02-02

196

Computer Simulation of Zirconium-Hafnium Separation by Countercurrent Extraction  

Microsoft Academic Search

In carrying out research and development on an improved method for production of reactor-grade zirconium oxide, the Bureau of Mines has prepared a computer program capable of accurately predicting the stage-by-stage performance of a multistage countercurrent solvent extraction system for separation of zirconium from hafnium using a tertiary amine extractant. The results were used to plan laboratory experiments using a

D. J. Mac Donald

1981-01-01

197

Uranium-preextraction in zirconium\\/hafnium separations processs  

Microsoft Academic Search

This patent describes an improvement in a process for recovering zirconium values from uranium containing zircon ore. The process comprising a fluidized bed carbochlorination of the zircon ore at 800°--1250° C., producing a relatively impure, hafnium-containing zirconium tetrachloride stream and by-product silicon tetrachloride, which silicon tetrachloride by-product is separated by differential condensation, and wherein uranium chloride is volatilized at the

Feuling

1990-01-01

198

Numerical simulation of irradiation hardening in Zirconium  

NASA Astrophysics Data System (ADS)

A phase field model is developed to simulate interactions between gliding dislocations and irradiation induced damage loops (i.e., vacancy and self-interstitial loops) in Zirconium. Pinning contact interactions and long-range elastic interactions are simulated, with populations of defects generated based on experimental observations of typical damage microstructures in irradiated Zr. The model is employed to simulate irradiation hardening as a function of damage loop density. We find that the stress fields of damage loops contribute significantly to their effective obstacle strength, and that the elastic interactions cause the dependence of critical resolved shear stress on damage loop number density to deviate from analytical predictions of dispersed barrier hardening. The simulation predictions of the yield strength agree well with experimental measurements for different damage loop densities.

Boyne, A.; Shen, C.; Najafabadi, R.; Wang, Y.

2013-07-01

199

Zirconium deformation behavior: insights from EBSD measurements.  

SciTech Connect

The deformation of crystal-bar zirconium was investigated as a function of strain and strain rate through electron back-scattered diffraction (EBSD) characterization. The resultant data provided spatially resolved information on microstructure and texture evolution, individual twin system activity, and subsequent strain partitioning between twinned volume and parent grains. A range of deformation conditions was represented through quasi-static compression, 4-point beam bend tests at room and cryogenic temperature, and Taylor cylinder impact experiments. Effects from the interplay between slip and twinning deformation modes on anisotropic plasticity are considered in order to address the apparent trend toward isotropy at high rates. The role of various length scales on deformation behavior will be considered, along with the implications of these length scales on the assumptions typically invoked for plasticity modeling.

Bingert, J. F. (John F.); Mason, T. A. (Thomas A.); Kaschner, G. C. (George C.); Maudlin, P. J. (Paul J.); Gray, G. T. (George T.), III

2001-01-01

200

Draft Guidance on Miconazole Nitrate  

Center for Biologics Evaluation and Research (CBER)

Text Version... Draft Guidance on Miconazole Nitrate This draft guidance, once finalized, will represent the Food and Drug Administration's (FDA's) current thinking ... More results from www.fda.gov/downloads/drugs/guidancecomplianceregulatoryinformation

201

Density of Hydroxylammonium Nitrate Solutions.  

National Technical Information Service (NTIS)

Hydroxylammonium nitrate is miscible with water in all proportions at room temperature. The densities of such salt solutions were measured using water and deuterium oxide as solvents. A second order equation is given to relate to molar concentration. Keyw...

R. A. Sasse M. A. Davies R. A. Fifer M. M. Decker A. J. Kotlar

1988-01-01

202

[Preparation and characterization of zirconium hydroxide powder for fluoride adsorption].  

PubMed

The method co-precipitation was applied to preparation the zirconium hydroxide as a type drinking-water defluoridation adsorbent. The effect of the preparation conditions on the adsorptive capacity was studied. The optimization of preparation condition for zirconium hydroxide concludes that co-precipitation time is 10 h, pH value is 7.0, drying time is 72 h, calcination temperature is below 100 degrees C. Also, the adsorbent samples were characterized. SEM measurements reveal that zirconium hydroxide powder are constructed by several small particles, with a diameter about 20-30 microm. XRD and TG/DTA measurements show that the zirconium hydroxide samples have amorphous phase and converse to tetragonal phase when calcined at 600 degrees C. Nitrogen adsorption/desorption measurements show that samples have large surface areas of 138.4 m2/g and a 2 nm average pore size distribution in the mesopore region. The performance of zirconium hydroxide regeneration process was investigated. The results show that the regeneration techniques are very suitable to restore the fluorine-removal ability for zirconium hydroxide. PMID:20825020

Yang, Shuo; Dou, Xiao-min; Liang, Wen-yan; Wang, Yi-li; Lin, Wei

2010-07-01

203

Photosynthetic nitrate assimilation in cyanobacteria.  

PubMed

Nitrate uptake and reduction to nitrite and ammonium are driven in cyanobacteria by photosynthetically generated assimilatory power, i.e., ATP and reduced ferredoxin. High-affinity nitrate and nitrite uptake takes place in different cyanobacteria through either an ABC-type transporter or a permease from the major facilitator superfamily (MFS). Nitrate reductase and nitrite reductase are ferredoxin-dependent metalloenzymes that carry as prosthetic groups a [4Fe-4S] center and Mo-bis-molybdopterin guanine dinucleotide (nitrate reductase) and [4Fe-4S] and siroheme centers (nitrite reductase). Nitrate assimilation genes are commonly found forming an operon with the structure: nir (nitrite reductase)-permease gene(s)-narB (nitrate reductase). When the cells perceive a high C to N ratio, this operon is transcribed from a complex promoter that includes binding sites for NtcA, a global nitrogen-control regulator that belongs to the CAP family of bacterial transcription factors, and NtcB, a pathway-specific regulator that belongs to the LysR family of bacterial transcription factors. Transcription is also affected by other factors such as CnaT, a putative glycosyl transferase, and the signal transduction protein P(II). The latter is also a key factor for regulation of the activity of the ABC-type nitrate/nitrite transporter, which is inhibited when the cells are incubated in the presence of ammonium or in the absence of CO(2). Notwithstanding significant advance in understanding the regulation of nitrate assimilation in cyanobacteria, further post-transcriptional regulatory mechanisms are likely to be discovered. PMID:16143847

Flores, Enrique; Frías, José E; Rubio, Luis M; Herrero, Antonia

2005-01-01

204

Analysis of nitrate in food extracts using a thermostable formate linked nitrate reductase enzyme system  

Microsoft Academic Search

A method for reduction of nitrate to nitrite for determination of nitrate is described, using a thermostable formate linked nitrate reductase enzyme system (FLNR). The reduction of nitrate to nitrite was found to be quantitative in water and in various food samples containing nitrate. The method is suggested as an alternative for the cadmium reduction method.

Sigurður Baldursson; Jakob K. Kristjánsson

1990-01-01

205

A zirconium based nanoparticle for significantly enhanced adsorption of arsenate: Synthesis, characterization and performance.  

PubMed

In this study, a zirconium nanoparticle sorbent for significantly enhanced adsorption of arsenate (As(V)) was successfully synthesized. The characterization of the zirconium nanoparticle sorbent and its adsorption behavior for arsenate were investigated. The HRTEM micrographs showed that the sorbent was nanoscale with particle sizes ranging from 60 to 90nm. The thermal gravimetric and elemental analyses indicated that the sorbent had a molecular formula of Zr(2)(OH)(6)SO(4)·3H(2)O. The X-ray diffraction study revealed that the sorbent was amorphous. The potentiometric titration study demonstrated the surface charge density of the sorbent decreased with an increase in solution pH, and the pH of zero point charge of the sorbent was around 2.85. The kinetics study showed that most of the uptake took place in the first 6h, and the adsorption equilibrium was obtained within 12h. The optimal pH for As(V) adsorption was between 2.5 and 3.5. The Langmuir equation well described the adsorption isotherm; the maximum adsorption capacity of 256.4mg As/g was found at the optimal pH, better than most of sorbents available in the market. The presence of fluoride or nitrate did not obviously affect the adsorption of As(V) onto the sorbent; however, the existence of humic acid, phosphate or silicate in aqueous solution significantly reduced the uptake of As(V). The humic acid did not cause the reduction of the As(V). The FTIR and XPS spectroscopic analyses revealed that surface hydroxyl and sulfur-containing groups played important roles in the adsorption. PMID:21093869

Ma, Yue; Zheng, Yu-Ming; Chen, J Paul

2010-10-23

206

EXTRACTION OF URANYL NITRATE FROM AQUEOUS SOLUTIONS  

DOEpatents

An improvement in the process is described for extracting aqueous uranyl nitrate solutions with an organic solvent such as ether. It has been found that the organic phase will extract a larger quantity of uranyl nitrate if the aqueous phase contains in addition to the uranyl nitrate, a quantity of some other soluble nitrate to act as a salting out agent. Mentioned as suitable are the nitrates of lithium, calcium, zinc, bivalent copper, and trivalent iron.

Furman, N.H.; Mundy, R.J.

1957-12-10

207

Effect of nitrate pulses on the nitrate-uptake rate, synthesis of mRNA coding for nitrate reductase, and nitrate-reductase activity in the roots of barley seedlings  

Microsoft Academic Search

Using pulses of nitrate, instead of the permanent presence of external nitrate, to induce the nitrate-assimilating system in Hordeum vulgare L., we demonstrated that nitrate can be considered as a trigger or signal for the induction of nitrate uptake, the appearance of nitratereductase activity and the synthesis of mRNA coding for nitrate reductase. Nitrate pulses stimulated the initial rate of

Rudolf Tischner; Barbara Waldeck; Sham S. Goyal; William D. Rains

1993-01-01

208

Fluidized Solids Process for Recovery of Uranium from Zirconium-Type Fuel Elements.  

National Technical Information Service (NTIS)

Uranium is recovered from uranium bearing zirconium clad nuclear fuel elements. The zirconium is reacted with anhydrous hydrogen chloride. Then the uranium is contacted with gaseous fluorine. The improvement includes immersing the element in a bed of iner...

L. P. Hatch J. J. Reilly W. H. Regan

1964-01-01

209

Study of the Production of Zirconium Tetrachloride by Chlorination of Its Oxide.  

National Technical Information Service (NTIS)

This work describes the studies carried out on the production of zirconium tetrachloride by chlorianation of pure zirconium oxide with (a) carbon tetrachloride and (b) chlorine in the presence of carbon. In the process of chlorination with carbon tetrachl...

E. S. M. Seo A. Abrao

1987-01-01

210

Co-Rolled U10Mo/Zirconium-Barrier-Layer Monolithic Fuel Foil Fabrication Process.  

National Technical Information Service (NTIS)

Contents: Foil fabrication for monolithic fuel; Rolling can assembly: material preparation (Preparation of the Low Carbon Steel Canning Materials, Zirconium Foil Preparation, Attachment of Zirconium Foils to Cover Plates, Preparation of the Fuel Alloy Cou...

G. A. Moore M. C. Marshall

2010-01-01

211

Preparation of complexes of zirconium and hafnium tetrachlorides with phosphorus oxychloride  

Microsoft Academic Search

This patent describes an improvement in a method for separating hafnium tetrachloride from zirconium tetrachloride where a complex of zirconium-hafnium tetrachlorides and phosphorus oxychloride is prepared from zirconium-hafnium tetrachlorides and the complex of zirconium-hafnium tetrachlorides and phosphorus oxychloride is introduced into a distillation column, which distillation column has a reboiler connected at the bottom and a reflux condenser connected at

1989-01-01

212

Elimination of phosphate and zirconium in the high-activity fraction resulting from TRUEX partitioning of ICPP zirconium calcines  

SciTech Connect

Laboratory testing was undertaken with the aim of developing a TRUEX flowsheet that would efficiently remove actinides from solutions of dissolved zirconium calcine and minimize the glass volume produced from the ensuing high-activity fraction. A TRUEX flowsheet is recommended for testing in the 2-cm centrifugal contactor pilot-plant based on the results from this testing. These laboratory tests show that zirconium recovery in the high activity fraction is minimized by scrubbing with an optimized NHF concentration of 0.2 M. This NH4F concentration in the scrub allowed the HEDPA strip concentration to be reduced from 0.04 M to 0.004 M because HEDPA is not consumed by zirconium. Complete TRU stripping was also achieved in these laboratory tests with 0.004 M HEDPA. Data from the small-scale laboratory batch contact tests were used in the Generic TRUEX Model (GTM) to evaluate the proposed flowsheet under counter-current conditions. GTM results indicate the raffinate will meet the Class A non-TRU limit of < 10 nCi/g in six extraction stages (O/A = 1), and quantitative actinide recovery will be achieved with the 0.004 M HEDPA in six strip stages (O/A = 1). Only 6.6 % of the initial zirconium concentration is anticipated to be recovered with the actinides, indicating the four scrub stages (O/A = 3) efficiently removes zirconium from the TRUEX solvent. In addition to recommending an improved TRUEX flowsheet for testing in the 2-cm centrifugal contactor pilot-plant, this work has shown that small reductions in zirconium extraction drastically improves flowsheet performance. These small changes in zirconium extraction can be accomplished by modifying the calcine dissolution parameters. Therefore, further calcine dissolution testing followed by TRUEX testing with the resulting feed solutions is also recommended.

Brewer, K.N.; Tillotson, R.D.; Tullock, P.A. [and others

1997-07-01

213

Electrochemical studies of zirconium and hafnium in alkali chloride and alkali fluoride-chloride molten salts  

Microsoft Academic Search

The electrochemical reduction of zirconium and hafnium in alkali chloride or fluoride-chloride molten salts on platinum electrodes has been investigated by means of linear and cyclic voltammetry. It has been found that fluoride ions greatly influenced the reduction of zirconium and hafnium in fluoride-chloride melts. It has been proposed that the mechanism for reduction of zirconium and hafnium in baths

Chen Guang-Sen; Masazumi Okido; Takeo Oki

1990-01-01

214

LIQUID-LIQUID EXTRACTION OF HAFNIUM FROM ZIRCONIUM BY TRIBUTYL PHOSPHATE  

Microsoft Academic Search

ABS>The removal of hafnium from zirconium is one of a number of ; operations required to produce high purity zirconium metal for use in nuclear ; reactors. Since the metallurgical operations involved in the production of ; zirconium must use the products of hafnium-removal processes, the choice of a ; process for hafnium removal must be integrated with subsequent metallurgical

G. H. Beyer; H. C. Peterson

1951-01-01

215

Laboratory production of zirconium carbide compacts for use in inert matrix fuels  

Microsoft Academic Search

Zirconium carbide is being actively considered for use as an inert matrix material in composite nuclear fuel for gas-cooled fast reactors. ZrC can be produced either by the endothermic carbothermal reduction of zirconium dioxide or by the direct exothermic reaction of pure zirconium and graphite powder mixtures. The exothermic reaction is classified as combustion synthesis or self heating synthesis. Experiments

Gokul Vasudevamurthy; Travis W. Knight; Elwyn Roberts; Thad M. Adams

2008-01-01

216

RELATIVE DATA OF CHEMICAL EQUILIBRIA GOVERNING THE SEPARATION OF ZIRCONIUM FROM HAFNIUM. PARTS II AND III  

Microsoft Academic Search

The chemical equilibria governing the separation of zirconium from ; hafnium are considered with particular reference to the solvent. The conditions ; of separation of a mixture of tributylphosphate, diluent, and zirconium were ; studied as well as the interacUon of tributylphosphate and zirconium. The latter ; results in the formation of dibutylphosphate which has a strong complexing ; capacity

J. Hure; M. Rastoix; R. Saint-James

1961-01-01

217

Equilibrium and kinetic data of adsorption and separation for zirconium and hafnium onto MIBK extraction resin  

Microsoft Academic Search

The equilibrium and kinetics of methyl isobutyl ketone (MIBK) extraction resin for adsorption and separation of zirconium and hafnium were studied under the different conditions of acidity, initial total concentrations of zirconium and hafnium and temperature. The equilibrium data of both zirconium and hafnium are found to follow the Freundlich adsorption isotherm, and the Freundlich isotherm constants (KF) are 3.53

Zhi-gao XU; Yan-ke WU; Jian-dong ZHANG; Li ZHANG; Li-jun WANG

2010-01-01

218

Extraction chromatography of quadrivalent titanium and zirconium from succinate solution  

SciTech Connect

Liquid ion exchangers such as tri-n-octyl amine (TOA), tri-iso-octylamine (TIOA) and Aliquat 336 have been used in this laboratory for analytical separation of vanadium(V) and niobium(V), indium(III), thalium(III), thorium(IV), cerium(IV) from succinate solutions. Extension of this study has revealed that benzene solutions of TOA, TIOA and Aliquat 336 could be used for anion exchange extraction of quadrivalent titanium and zirconium from succinate solution. The metal ions from the organic phase are stripped and determined spectrophotometrically. Solvent extraction methods for titanium(IV) and zirconium(IV) have been reviewed by De et al. and Korkisch in their monographs. Diethylamine, tri-ethylamine and tributylamine have been used for extraction of titanium from thiocyanate and citrate solution. Similarly high molecular weight amines such as TOA and TIOA have been used for the extraction of zirconium from mineral acids, but systematic solvent extraction separation of titanium(IV) and zirconium(IV) is lacking. In this communication we propose a new method for selective extraction and separation of titaium(IV) and zirconium(IV) from metal ions such as Mn, Cr, Mo, V, U, La, Ta, Th and Hf. The proposed method is comparatively free from drawbacks such as pre-equilibration of phases, multiple scrubbing, multiple extraction and coextraction of a large number of cations and anions.

Shete, S.D.; Shinde, V.M.

1982-01-01

219

The organometallic chemistry of cycloheptatrienyl zirconium complexes.  

PubMed

This tutorial review summarizes the organometallic chemistry derived from the half-sandwich complex [(?(7)-C(7)H(7))ZrCl(tmeda)], which was used as an efficient and versatile starting material for the incorporation of monoanionic ligands into the cycloheptatrienyl zirconium coordination sphere by conventional salt metathesis reactions. A broad variety of ligands was employed, affording novel and previously inaccessible cycloheptatrienyl (sandwich) complexes of the type [(?(7)-C(7)H(7))Zr(Y)]; Y comprises pentadienyl, cyclopentadienyl, allyl, phospholyl, boratabenzene, imidazolin-2-iminato and amido systems. The cycloheptatrienyl ring in these systems usually acts as an "innocent spectator ligand", but reactivity can arise from the second ligand Y or the Lewis acidity of the, formally, Zr(+iv) center, which was probed in selected examples and put in perspective to related studies. The corresponding results emphasize why the use of [(?(7)-C(7)H(7))ZrCl(tmeda)] is clearly an advancement in the chemistry of the still fairly unexplored area of cycloheptatrienyl transition metal complexes. PMID:23027385

Glöckner, Andreas; Tamm, Matthias

2012-10-01

220

Dissolved zirconium in the north Pacific Ocean  

SciTech Connect

Picomolar levels of dissolved Zr in seawater were measured using an analytical technique developed with a Chelex-100 extraction/concentration step and subsequent detection by isotope-dilution inductively-coupled-plasma mass spectrometry (ID-ICP-MS). Here the authors present the first vertical profile of Zr in the oceans, from the central-North Pacific, and a horizontal surface transect across the western Pacific. Dissolved Zr ranges from 12--95 pmol/kg in the surface waters then increases linearly with depth to a maximum of 300 pmol/kg in the deep water. The vertical profile shows a strong correlation with Si in the mid-waters, with higher Zr/Si ratios in the surface and bottom waters. There is evidence of both a bottom source and a coastal source of dissolved Zr to the oceans. A comparison with dissolved Ti and Be shows similar depth dependence, but an enrichment in Zr/Ti and a depletion in Zr/Be ratios in seawater relative to average crustal materials. Zirconium appears to have a reactivity intermediate between these two elements. 24 refs., 4 figs., 1 tab.

McKelvey, B.A.; Orians, K.J. (Univ. of British Columbia, Vancouver (Canada))

1993-08-01

221

Dissolved zirconium in the North Pacific Ocean  

NASA Astrophysics Data System (ADS)

Picomolar levels of dissolved Zr in seawater were measured using an analytical technique developed with a Chelex-100 extraction/concentration step and subsequent detection by isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). Here we present the first vertical profile of Zr in the oceans, from the central-North Pacific, and a horizontal surface transect across the western Pacific. Dissolved Zr ranges from 12-95 pmol/kg in the surface waters then increases linearly with depth to a maximum of 300 pmol/kg in the deep water. The vertical profile shows a strong correlation with Si in the mid-waters, with higher Zr/Si ratios in the surface and bottom waters. There is evidence of both a bottom source and a coastal source of dissolved Zr to the oceans. A comparison with dissolved Ti and Be shows similar depth dependence, but an enrichment in Zr/Ti and a depletion in Zr/Be ratios in seawater relative to average crustal materials. Zirconium appears to have a reactivity intermediate between these two elements.

McKelvey, Brad A.; Orians, Kristin J.

1993-08-01

222

Inhibition of Ice Growth and Recrystallization by Zirconium Acetate and Zirconium Acetate Hydroxide  

PubMed Central

The control over ice crystal growth, melting, and shaping is important in a variety of fields, including cell and food preservation and ice templating for the production of composite materials. Control over ice growth remains a challenge in industry, and the demand for new cryoprotectants is high. Naturally occurring cryoprotectants, such as antifreeze proteins (AFPs), present one solution for modulating ice crystal growth; however, the production of AFPs is expensive and inefficient. These obstacles can be overcome by identifying synthetic substitutes with similar AFP properties. Zirconium acetate (ZRA) was recently found to induce the formation of hexagonal cavities in materials prepared by ice templating. Here, we continue this line of study and examine the effects of ZRA and a related compound, zirconium acetate hydroxide (ZRAH), on ice growth, shaping, and recrystallization. We found that the growth rate of ice crystals was significantly reduced in the presence of ZRA and ZRAH, and that solutions containing these compounds display a small degree of thermal hysteresis, depending on the solution pH. The compounds were found to inhibit recrystallization in a manner similar to that observed in the presence of AFPs. The favorable properties of ZRA and ZRAH suggest tremendous potential utility in industrial applications.

Mizrahy, Ortal; Bar-Dolev, Maya; Guy, Shlomit; Braslavsky, Ido

2013-01-01

223

Acetonyltriphenyl-phospho-nium nitrate.  

PubMed

Crystals of the title salt, C(21)H(20)OP(+)·NO(3) (-), are composed of acetonyltriphenyl-phospho-nium cations and nitrate anions that mainly inter-act through electrostatic forces. The P atom in the cation has a slightly distorted tetra-hedral environment, with C-P-C angles ranging from 104.79?(7) to 112.59?(6)°. The sum of O-N-O angles of the nitrate anion is 359.99°, reflecting its trigonal-planar character. C-H?O hydrogen bonds help to consolidate the crystal packing. PMID:23424568

Diop, Tidiane; Diop, Libasse; Ku?eráková, Monika; Dušek, Michal

2013-01-31

224

Process for electroless deposition of metals on zirconium materials  

DOEpatents

A process for the electroless deposition of a metal layer on an article comprised of zirconium or a zirconium alloy is disclosed. The article is activated in an aged aqueous solution comprising from about 10 to about 20 grams per liter ammonium bifluoride and from about 0.75 to about 2 grams per liter of sulfuric acid. The solution is aged by immersion of pickled zirconium in the solution for at least about 10 minutes. The loosely adhering film formed on the article in the activating step is removed and the article is contacted with an electroless plating solution containing the metal to be deposited on the article upon sufficient contact with the article.

Donaghy, Robert E. (Wilmington, NC)

1978-01-01

225

METHOD OF FABRICATING A URANIUM-ZIRCONIUM HYDRIDE REACTOR CORE  

DOEpatents

A method is described of evenly dispersing uranlum metal in a zirconium hydride moderator to produce a fuel element for nuclear reactors. According to the invention enriched uranium hydride and zirconium hydride powders of 200 mesh particle size are thoroughly admixed to form a mixture containing 0.1 to 3% by weight of U/sup 235/ hydride. The mixed powders are placed in a die and pressed at 100 tons per square inch at room temperature. The resultant compacts are heated in a vacuum to 300 deg C, whereby the uranium hydride deoomposes into uranium metal and hydrogen gas. The escaping hydrogen gas forms a porous matrix of zirconium hydride, with uramum metal evenly dispersed therethrough. The advantage of the invention is that the porosity and uranium distribution of the final fuel element can be more closely determined and controlled than was possible using prior methods of producing such fuel ele- ments.

Weeks, I.F.; Goeddel, W.V.

1960-03-22

226

Protection against oral and gastrointestinal diseases: Importance of dietary nitrate intake, oral nitrate reduction and enterosalivary nitrate circulation  

Microsoft Academic Search

Over the last 20 years, dietary nitrate has been implicated in the formation of methemoglobin and carcinogenic nitrosamines in humans. This has led to restrictions of nitrate and nitrite levels in food and drinking water. However, there is no epidemiological evidence for an increased risk of gastric and intestinal cancer in population groups with high dietary vegetable or nitrate intake.

Callum Duncan; Hong Li; Roelf Dykhuizen; Rennie Frazer; Peter Johnston; Gillian MacKnight; Lorna Smith; Kathryn Lamza; Hamish McKenzie; Les Batt; Denise Kelly; Michael Golden; Nigel Benjamin; Carlo Leifert

1997-01-01

227

Uptake, allocation and signaling of nitrate.  

PubMed

Plants need to acquire nitrogen (N) efficiently from the soil for growth. Nitrate is one of the major N sources for higher plants. Therefore, nitrate uptake and allocation are key factors in efficient N utilization. Membrane-bound transporters are required for nitrate uptake from the soil and for the inter- and intracellular movement of nitrate inside the plants. Four gene families, nitrate transporter 1/peptide transporter (NRT1/PTR), NRT2, chloride channel (CLC), and slow anion channel-associated 1 homolog 3 (SLAC1/SLAH), are involved in nitrate uptake, allocation, and storage in higher plants. Recent studies of these transporters or channels have provided new insights into the molecular mechanisms of nitrate uptake and allocation. Interestingly, several of these transporters also play versatile roles in nitrate sensing, plant development, pathogen defense, and/or stress response. PMID:22658680

Wang, Ya-Yun; Hsu, Po-Kai; Tsay, Yi-Fang

2012-05-31

228

21 CFR 172.170 - Sodium nitrate.  

Code of Federal Regulations, 2010 CFR

...ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified foods in accordance with the following prescribed conditions: (a) It is used...

2009-04-01

229

21 CFR 172.170 - Sodium nitrate.  

Code of Federal Regulations, 2010 CFR

...ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on specified foods in accordance with the following prescribed conditions: (a) It is used...

2010-01-01

230

BAM Media M101: Motility Nitrate Medium  

Center for Food Safety and Applied Nutrition (CFSAN)

... Food. ... Tryptose, 10 g. Heart infusion agar (Difco), 8 g. Potassium (or sodium) nitrate, 1 g. Glucose, 0.5 g. ... NOTE: Make sure nitrates are nitrite-free. ... More results from www.fda.gov/food/foodscienceresearch/laboratorymethods

231

21 CFR 172.160 - Potassium nitrate.  

Code of Federal Regulations, 2013 CFR

...CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing agent in the...

2013-04-01

232

Proof-of-Principle Measurements on Unirradiated Zirconium Alloys  

SciTech Connect

The ability to determine fuel assembly burnup has important non-proliferation implications since proliferation activities involve either irradiating fuel assemblies to a much lower level of burnup than is normal in commercial Light Water Reactor (LWR) practice, and/or irradiation of separate targets. Similarly, a method of determining burnup could be used to confirm declared operation for a reactor that is operating under IAEA safeguards. It is possible to determine fuel assembly burnup by measuring gamma radiation from specific fission products; however this technique is only useable after the fuel assembly has been out of the reactor for at least a year, and is not very useful after the assembly has been out of the reactor for 10 years or more. The use of isotope ratio measurements to measure the level of neutron exposure that material has received is well-known for graphite applications. The current project is an attempt to demonstrate that isotope ratio measurements can be performed on zirconium alloys used in LWR fuel assemblies. Zirconium alloys are used for structural elements of fuel assemblies and for the fuel element cladding. This report covers proof-of-principle measurements done on unirradiated zirconium alloys, these measurements show that: Titanium 48/Titanium 49 ratios can be measured in zirconium alloys using a Secondary Ionization Mass Spectrometer (SIMS) - enough Titanium was present in each of 6 samples tried to allow resolving the peaks associated with each isotope, and correction of interfering ions. The Ti 48/49 ratio measured in unirradiated zirconium alloy is, within a narrow error band, the same as that found in natural, unirradiated zirconium.

Gerlach, David C.; Mitchell, Mark R.; Reid, Bruce D.; Gesh, Christopher J.; Hurley, David E.

2007-04-18

233

A Novel Chemical Nitrate Destruction Process  

SciTech Connect

Nitrates represent one of the most significant pollutant discharged to the Baltic Sea by the Sliiamae hydrometallurgical plant. This article contains a brief overview of the existing nitrate destruction technologies followed by the description of a new process developed by the authors. The new chemical process for nitrate destruction is cost effective and simple to operate. It converts the nitrate to nitrogen gas which goes to the atmosphere.

Dziewinski, J.; Marczak, S.

1999-03-01

234

In-situ stabilization of radioactive zirconium swarf  

DOEpatents

The method for treating ignitable cutting swarf in accordance with the present invention involves collecting cutting swarf in a casting mold underwater and injecting a binder mixture comprising vinyl ester styrene into the vessel to fill void volume; and form a mixture comprising swarf and vinyl ester styrene; and curing the mixture. The method is especially useful for stabilizing the ignitable characteristics of radioactive zirconium cutting swarf, and can be used to solidify zirconium swarf, or other ignitable finely divided material, underwater. The process could also be performed out of water with other particulate wastes. 6 figs.

Hess, C.C.

1999-08-31

235

A new conducting nanocomposite -- PPy-zirconium (IV) oxide  

SciTech Connect

Pyrrole was polymerized in the presence of ultrafine zirconium (IV) oxide (ZrO{sub 2}) particles which act as a dispersant for pyrrole. Room temperature conductivities of the resulting polypyrrole-zirconium (IV) oxide nanocomposites having different ZrO{sub 2} particle concentrations were measured and were compared with that of bare polypyrrole. It was observed that the conductivities of the nanocomposites were higher than that of the polypyrrole without ZrO{sub 2} and increased with ZrO{sub 2} concentration up to a certain limit. From transmission electron microscope studies, particle size and morphology of the nanocomposites and ZrO{sub 2} particles were obtained.

Bhattacharya, A.; De, A.; Sarkar, S. [Saha Inst. of Nuclear Physics, Calcutta (India). Nuclear Chemistry Div.; Ganguly, K.M. [Nabadwip Vidyasagar Coll., Nadia (India). Dept. of Chemistry

1996-05-01

236

Stress corrosion cracking of zirconium in nitric acid  

SciTech Connect

The susceptibility of zirconium and its common alloys to stress corrosion cracking (SCC) in nitric acid was investigated by slow strain-rate and constant deflection techniques. Cracking occurred at 25/sup 0/C over a wide range of acid concentrations and electrochemical potentials. The crack velocity increased slightly with increasing temperature. The failure mode was transgranular and the morphology was similar to SCC failures of zirconium alloys in other environments. The fracture was very orientation-dependent suggesting that it occurs on a single crystallographic plane in the material. The results of the study are not consistent with a hydrogen mechanism for cracking.

Beavers, J.A.; Griess, J.C.; Boyd, W.K.

1980-01-01

237

Temperature dependence of lattice parameters of alpha-zirconium  

NASA Astrophysics Data System (ADS)

This work presents a brief review of X-ray and thermal expansion determination of lattice parameters for alpha-zirconium. Data reported by different authors cover almost all the field of existence of the hexagonal phase of Zirconium, from temperatures as low as 4.2 K up to about 1130 K, near the alpha to beta transformation temperature. Polynomial expressions based on a least squares fitting of experimental data are also presented. The expressions obtained by Goldak et al. are considered to be the most complete. The influence of impurities on the lattice parameters is also discussed.

Versaci, R. A.; Ipohorski, M.

238

In-situ stabilization of radioactive zirconium swarf  

DOEpatents

The method for treating ignitable cutting swarf in accordance with the present invention involves collecting cutting swarf in a casting mold underwater and injecting a binder mixture comprising vinyl ester styrene into the vessel to fill void volume; and form a mixture comprising swarf and vinyl ester styrene; and curing the mixture. The method is especially useful for stabilizing the ignitable characteristics of radioactive zirconium cutting swarf, and can be used to solidify zirconium swarf, or other ignitable finely divided material, underwater. The process could also be performed out of water with other particulate wastes.

Hess, Clay C.

1997-12-01

239

Constructed Marshes for Nitrate Removal  

Microsoft Academic Search

Large numbers of free water surface treatment wetlands are in use for nitrate reduction. Target applications are field runoff, river and stream improvement, and enhancement of wastewater treatment plants. In total, an extensive database now exists, in many publications and operating reports. Microcosms and mesocosms are not included here, because of lack of transferability to design. A first-order areal model

Robert H. Kadlec

2011-01-01

240

Constructed Marshes for Nitrate Removal  

Microsoft Academic Search

Large numbers of free water surface treatment wetlands are in use for nitrate reduction. Target applications are field runoff, river and stream improvement, and enhancement of wastewater treatment plants. In total, an extensive database now exists, in many publications and operating reports. Microcosms and mesocosms are not included here because of the lack of transferability to design. A first-order areal

Robert H. Kadlec

2012-01-01

241

Nitrate reduction in Aerobacter aerogenes  

Microsoft Academic Search

Mutants of Aerobacter aerogenes have been isolated, which are blocked in nitrate assimilation or which are resistant against chlorate. Chlorate resistance was always determined in the presence of cysteine, as it was found that chlorate interfered with the biosynthesis of this amino acid. All chlorate resistant mutants have lost the possibility to reduce chlorate, indicating that its reduction products are

A. H. Stouthamer

1967-01-01

242

Nitrate Therapy in Heart Failure  

Microsoft Academic Search

Nitrates are drugs of first choice in patients with acute heart failure. Acute pulmonary edema can be successfully treated with single or repeated doses of sublingual nitroglycerin. In cases of prolonged acute heart failure, e.g. in the setting of acute myocardial infarction, nitroglycerin or isosorbide dinitrate can be given by the intravenous route for up to 24 h. Patients with

Wolfgang Schneider; Wulf-Dirk Bussmann; Andreas Hartmann; Martin Kaltenbach

1991-01-01

243

4-Methyl-anilinium nitrate  

PubMed Central

The asymmetric unit of the title compound, C7H10N+·NO3 ?, consists of a 4-methyl­anilinium cation protonated at the amino group and a nitrate anion. In the crystal, anions and cations are linked through N—H?O and N—H?(O,O) hydrogen bonds, buiding a corrugated layer structure parallel to (001).

Benali-Cherif, Nourredine; Boussekine, Houda; Boutobba, Zina; Dadda, Noureddine

2009-01-01

244

SOURCE ASSESSMENT: AMMONIUM NITRATE PRODUCTION  

EPA Science Inventory

The report describes a study of air pollutants emitted by the ammonium nitrate industry. The potential environmental effect of the source was evaluated. Representative processes and an average plant were defined for the purpose of establishing a base on which to determine the emi...

245

Unusual luminescence from uranyl nitrate  

Microsoft Academic Search

Temperature-induced luminescence was observed from uranyl nitrate hexahydrate crystals. Flashes of green light were detected when the crystal was cooled with liquid nitrogen and also when the cooled crystal was allowed to return to room temperature. They mostly occurred between 77 and 100K. More and stronger flashes were observed during cooling. The intensities of these flashes and the temperatures of

R. Griffith; A. F Leung; E. Mercado; M. Morshedabbasi

2001-01-01

246

Fluorescence properties of uranyl nitrates  

Microsoft Academic Search

Fluorescence spectra of uranyl nitrate hexahydrate, trihydrate, and dihydrate at 77K were recorded. Those of the hexahydrate and trihydrate were similar but were different from that of the dihydrate. Fluorescence lifetimes of the hexahydrate, trihydrate, and dihydrate at 77K were observed to be 699, 838 and 499?s, respectively. The difference between these lifetimes was explained by considering the interaction between

A. F. Leung; L. Hayashibara; J. Spadaro

1999-01-01

247

Nitrate reductase assay using sodium nitrate for rapid detection of multidrug resistant tuberculosis.  

PubMed

We validated the nitrate reductase assay (NRA) for the detection of multidrug-resistant Mycobacterium tuberculosis (MDR-TB) using sodium nitrate (NaNO3) in replacement of potassium nitrate (KNO3) as nitrate source. NaNO3 is cheaper than KNO3 and has no restriction on use which facilitates the implementation of NRA to detect MDR-TB. PMID:24031916

Macedo, Maíra Bidart; Groll, Andrea Von; Fissette, Krista; Palomino, Juan Carlos; da Silva, Pedro Eduardo Almeida; Martin, Anandi

2012-06-01

248

Nitrate reductase assay using sodium nitrate for rapid detection of multidrug resistant tuberculosis  

PubMed Central

We validated the nitrate reductase assay (NRA) for the detection of multidrug-resistant Mycobacterium tuberculosis (MDR-TB) using sodium nitrate (NaNO3) in replacement of potassium nitrate (KNO3) as nitrate source. NaNO3 is cheaper than KNO3 and has no restriction on use which facilitates the implementation of NRA to detect MDR-TB.

Macedo, Maira Bidart; Groll, Andrea Von; Fissette, Krista; Palomino, Juan Carlos; da Silva, Pedro Eduardo Almeida; Martin, Anandi

2012-01-01

249

Nitrate reductase transcript is expressed in the primary response of maize to environmental nitrate  

Microsoft Academic Search

The nitrate induction of NADH:nitrate reductase mRNA in maize roots, scutella and leaves was investigated in the presence and absence of inhibitors of protein synthesis. In the absence of inhibitors, nitrate treatment caused a fairly rapid (2 to 3 h) increase in the level of the nitrate reductase transcript in all tissues. When cytoplasmic protein synthesis was inhibited by cycloheximide,

G. Gowri; Juana D. Kenis; Björn Ingemarsson; Margaret G. Redinbaugh; Wilbur H. Campbell

1992-01-01

250

Plasma nitrate and nitrite are increased by a high nitrate supplement, but not by high nitrate foods in older adults  

PubMed Central

Little is known about the effect of dietary nitrate on the nitrate/nitrite/NO (nitric oxide) cycle in older adults. We examined the effect of a 3-day control diet vs. high nitrate diet, with and without a high nitrate supplement (beetroot juice), on plasma nitrate and nitrite kinetics, and blood pressure using a randomized four period cross-over controlled design. We hypothesized that the high nitrate diet would show higher levels of plasma nitrate/nitrite and blood pressure compared to the control diet, which would be potentiated by the supplement. Participants were eight normotensive older men and women (5 female, 3 male, 72.5±4.7 yrs) with no overt disease or medications that affect NO metabolism. Plasma nitrate and nitrite levels and blood pressure were measured prior to and hourly for 3 hours after each meal. The mean daily changes in plasma nitrate and nitrite were significantly different from baseline for both control diet+supplement (p<0.001 and =0.017 for nitrate and nitrite, respectively) and high nitrate diet+supplement (p=0.001 and 0.002), but not for control diet (p=0.713 and 0.741) or high nitrate diet (p=0.852 and 0.500). Blood pressure decreased from the morning baseline measure to the three 2 hr post-meal follow-up time-points for all treatments, but there was no main effect for treatment. In healthy older adults, a high nitrate supplement consumed at breakfast elevated plasma nitrate and nitrite levels throughout the day. This observation may have practical utility for the timing of intake of a nitrate supplement with physical activity for older adults with vascular dysfunction.

Miller, Gary D.; Marsh, Anthony P.; Dove, Robin W.; Beavers, Daniel; Presley, Tennille; Helms, Christine; Bechtold, Erika; King, S. Bruce; Kim-Shapiro, Daniel

2012-01-01

251

21 CFR 172.160 - Potassium nitrate.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2009-04-01 true Potassium nitrate. 172.160 Section 172.160 Food...CONSUMPTION Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing agent...

2010-01-01

252

21 CFR 172.160 - Potassium nitrate.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Potassium nitrate. 172.160 Section 172.160 Food...CONSUMPTION Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing agent...

2009-04-01

253

Assessing uncertainty of nitrate variability in groundwater  

Microsoft Academic Search

Nitrate is the primary form of nitrogen in natural waters and it can easily pass through soil to groundwater. Some levels of nitrate concentration in groundwater can cause some health problems such as methemoglobinemia in infants and several cancers. Since geological structures are not homogeneous, investigation of spatial variability of nitrate concentrations in groundwater is characterized by particularly high uncertainties.

Bulent Tutmez

2009-01-01

254

High Nitrate Potential in Corn Silage  

Microsoft Academic Search

Crop conditions have turned from dry to wet in many areas and our corn silage harvest in continuing. This has raised some concerns about the potential for nitrates in corn silage. Nitrates are a possibility under these conditions and are often hard to predict when then will appear. Frequently, nitrates are most severe on drought stunted, heavily manured fields for

Greg Roth; Doug Beegle

255

Nitrate and nitrogen balances in men?4  

Microsoft Academic Search

Nitrate is a nitrogen-containing compound that is not detected by the traditional Kjeldahh method of nitrogen analysis. Nitrate balance studies were done in order to determine if nitrate production in the human body contributes to the irrationally positive nitrogen balances that have been reported in healthy adults. Seven healthy young men, confmed to a metabolic unit, received five diets for

Mindy S. Kurzer; Doris Howes Calloway

256

Nitrate removal from drinking water -- Review  

Microsoft Academic Search

Nitrate concentrations in surface water and especially in ground water have increased in Canada, the US, Europe, and other areas of the world. This trend has raised concern because nitrates cause methemoglobiinemia in infants. Several treatment processes including ion exchange, biological denitrification, chemical denitrification, reverse osmosis, electrodialysis, and catalytic denitrification can remove nitrates from water with varying degrees of efficiency,

Anoop Kapoor; T. Viraraghavan

1997-01-01

257

21 CFR 172.170 - Sodium nitrate.  

Code of Federal Regulations, 2013 CFR

...3 2013-04-01 2013-04-01 false Sodium nitrate. 172.170 Section 172.170 Food...CONSUMPTION Food Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or on...

2013-04-01

258

Measuring nitrate fluxes to assess estuarine eutrophication  

Microsoft Academic Search

Summary form only given.The availability of nitrate sensors has enabled integration of these instruments into real-time profiling buoys and, when coupled with current meters, allows for calculation of nitrate fluxes into and out of estuaries. As the United States' estuaries are increasingly experiencing eutrophication this technological development is timely. We report on the use of nitrate sensors on our profiling

J. Newton; A. Devol; W. Ruef

2009-01-01

259

Beneficial actions of nitrates in cardiovascular disease  

Microsoft Academic Search

Nitroglycerin and the long-acting nitrates have been used in cardiovascular medicine for > 100 years. Nitrates are widely utilized for the various anginal syndromes and are also used in congestive heart failure and patients with left ventricular dysfunction. The potential mechanisms for relief of myocardial ischemia with nitrates are multiple. The nitrovasodilators are a related group of drugs that result

Jonathan Abrams

1996-01-01

260

Nitration of Naphthol: A Laboratory Experiment.  

ERIC Educational Resources Information Center

|Products of nitrations, upon distillation or steam distillation, may produce dermatitis in some students. A procedure for nitration of beta-naphthol producing a relatively non-volatile product not purified by steam distillation is described. Nitration of alpha-naphthol by the same procedure yields Martius Yellow dye which dyes wool yellow or…

Mowery, Dwight F.

1982-01-01

261

SOME PHYSICAL PROPERTIES OF URANYL NITRATE SOLUTIONS  

Microsoft Academic Search

Boillng points, freezing points, and densities were measured in the ;\\u000a concentration range between uranyl nitrate hexahydrate and uranyl nitrate ;\\u000a dihydrate. The surface tension of molten uranyl nitrate hexahydrate was ;\\u000a determined to be approximately 45 dynes per square centimeter at 90 to 1OO icient ;\\u000a laborato C. (auth)

G. P. Lang; M. O. Nethaway

1958-01-01

262

Stainless steel-zirconium alloy waste forms  

SciTech Connect

An electrometallurgical treatment process has been developed by Argonne National Laboratory to convert various types of spent nuclear fuels into stable storage forms and waste forms for repository disposal. The first application of this process will be to treat spent fuel alloys from the Experimental Breeder Reactor-II. Three distinct product streams emanate from the electrorefining process: (1) refined uranium; (2) fission products and actinides extracted from the electrolyte salt that are processed into a mineral waste form; and (3) metallic wastes left behind at the completion of the electrorefining step. The third product stream (i.e., the metal waste stream) is the subject of this paper. The metal waste stream contains components of the chopped spent fuel that are unaffected by the electrorefining process because of their electrochemically ``noble`` nature; this includes the cladding hulls, noble metal fission products (NMFP), and, in specific cases, zirconium from metal fuel alloys. The selected method for the consolidation and stabilization of the metal waste stream is melting and casting into a uniform, corrosion-resistant alloy. The waste form casting process will be carried out in a controlled-atmosphere furnace at high temperatures with a molten salt flux. Spent fuels with both stainless steel and Zircaloy cladding are being evaluated for treatment; thus, stainless steel-rich and Zircaloy-rich waste forms are being developed. Although the primary disposition option for the actinides is the mineral waste form, the concept of incorporating the TRU-bearing product into the metal waste form has enough potential to warrant investigation.

McDeavitt, S.M.; Abraham, D.P.; Keiser, D.D. Jr.; Park, J.Y.

1996-07-01

263

Extraction of rare earth metal(III) nitrates with trialkylmethylammonium nitrate from multicomponent solutions containing ammonium nitrate  

SciTech Connect

A study has been made of the extraction of rare earth elements (III) (praseodymium-lutetium, yttrium) by trialkylmethylammonium nitrate in kerosine (1.10 M) from binary and multicomponent solutions containing 1.0-3.0 M of ammonium nitrate. Physicochemical and mathematical models have been proposed for the distribution of individual lanthanides (III) depending on the composition of the initial raw material and on the total REE(III) and ammonium nitrate concentrations in the aqueous phase. The optimal concentration ranges for total REE and ammonium nitrate in the aqueous phase have been found for separating complex REE concentrates by using trialkylmethylammonium nitrate in the diluent.

Pyartman, A.K.; Puzikov, E.A.; Bogatov, K.B. [St. Petersburg Technological Institute (Russian Federation)

1994-10-20

264

Preparation of complexes of zirconium and hafnium tetrachlorides with phosphorus oxychloride  

SciTech Connect

This patent describes an improvement in a method for separating hafnium tetrachloride from zirconium tetrachloride where a complex of zirconium-hafnium tetrachlorides and phosphorus oxychloride is prepared from zirconium-hafnium tetrachlorides and the complex of zirconium-hafnium tetrachlorides and phosphorus oxychloride is introduced into a distillation column, which distillation column has a reboiler connected at the bottom and a reflux condenser connected at the top and where a hafnium tetrachloride enriched stream is taken from the top of the column and a zirconium enriched tetrachloride stream is taken from the bottom of the column. The improvement comprising: prepurifying the zirconium-hafnium tetrachlorides, prior to preparation of the complex and introduction of the complex into a distillation column, to substantially eliminate iron chloride from the zirconium hafnium tetrachlorides, whereby buildup or iron chloride in the distillation column and in the reboiler is substantially eliminated and the column can be operated in a continuous, stable and efficient manner.

McLaughlin, D.F.

1989-09-12

265

THE INFRARED SPECTRA OF ANHYDROUS TRANSITION-METAL NITRATES  

Microsoft Academic Search

Infrared spectra for the anhydrous nitrates of manganese, copper, zinc, ; and mercury indicate the presence of covalent metal-nitrate bonds. The ; anhydrous nitrates of cobalt, silver, cadmium, and lead have spectra ; characteristic of the nitrate ion. Frequencies for the hydrated nitrates of ; iron, cobalt, nickel, copper, zinc, and cadmium are given for comparison. ; Hydrated thorium nitrate

C. C. Addison; B. M. Gatehouse

1960-01-01

266

Nitrate-independent expression of plant nitrate reductase in Lotus japonicus root nodules  

Microsoft Academic Search

Nitrate-independent nitrate reductase (NR) activity is generally found in legume root nodules. Therefore, the effects of nitrate on plant NR activity and mRNA were investigated in the root nodules of Lotus japonicus (L. japonicus). Both NR activity and mRNA levels in roots and root nodules were up-regulated by the addition of nitrate. In the absence of nitrate, NR activity and

Kazuhisa Kato; Yoshimichi Okamura; Koki Kanahama; Yoshinori Kanayama

2003-01-01

267

Nitrate Uptake, Nitrate Reductase Distribution and their Relation to Proton Release in Five Nodulated Grain Legumes  

Microsoft Academic Search

Nitrate uptake, nitrate reductase activity (NRA) and net proton release were compared in five grain legumes grown at 0·2 and 2 mM nitrate in nutrient solution. Nitrate treatments, imposed on 22-d-old, fully nodulated plants, lasted for 21 d. Increasing nitrate supply did not significantly influence the growth of any of the species during the treatment, but yellow lupin (Lupinus luteus)

X. H. F AN

268

Zirconium nanoparticles prepared by the reduction of zirconium oxide using the RAPET method  

PubMed Central

Summary The aim of the current work is the synthesis and characterization of metallic Zr nanoparticles. The preparation is carried out by using the RAPET method (Reaction under Autogenic Pressure at Elevated Temperatures) developed in our lab. The RAPET reaction of commercial ZrO2 with Mg powder was carried out in a closed stainless steel cell, at 750 °C. On completion of the reaction, the additionally formed MgO is removed by treatment with acid. The characterization of the product was performed by XRD, X-ray absorption spectroscopy, SEM, TEM and elemental analysis. The XRD pattern reveals that the product is composed of pure metallic zirconium, without any traces of the MgO by-product.

Eshed, Michal; Pol, Swati; Balasubramanian, Mahalingam

2011-01-01

269

Nitrate radical quantum yield from peroxyacetyl nitrate photolysis.  

PubMed

Peroxyacetyl nitrate (PAN, CH3C(O)OONO2) is a ubiquitous pollutant that is primarily destroyed by either thermal or photochemical mechanisms. We have investigated the photochemical destruction of PAN using a combination of laser pulsed photolysis and cavity ring-down spectroscopic detection of the NO3 photoproduct. We find that the nitrate radical quantum yield from the 289 nm photolysis of PAN is Phi(NO3)PAN = 0.31 +/- 0.08 (+/-2 sigma). The quantum yield is determined relative to that of dinitrogen pentoxide, which is assumed to be unity, under identical experimental conditions. The instrument design and experimental procedure are discussed as well as auxiliary experiments performed to further characterize the performance of the optical cavity and photolysis system. PMID:16833558

Flowers, Bradley A; Angerhofer, Mark E; Simpson, William R; Nakayama, Tomoki; Matsumi, Yutaka

2005-03-24

270

Phosphorus Recovery Using Zirconium-Loaded Saponified Orange Juice Residue  

NASA Astrophysics Data System (ADS)

Zirconium was immobilized to orange juice residue, to investigate the feasibility of using zirconium-loaded saponified orange juice residue (Zr-SOJR) for phosphorus recovery from secondary effluent and the extraction solution from incinerated sewage sludge ash by using H2SO4 and HCl. These had phosphorus concentrations of 68.2 mg/dm3 and 5.9 mg/dm3, respectively. The phosphorus removal rate secondary effluent increased with an increasing solid/liquid ratio in batch experiments. The adsorption capacity of Zr-SOJR was also compared with those obtained using a synthetic phosphorus solution and using zirconium-loaded ferrite. The prepared absorbent was effective for phosphorus removal and exhibited a reasonably high sorption capacity, twice that of zirconium ferrite. Secondary effluent was treated by packed column, and this reached break-through after 300 bed volumes. The results from phosphorous extraction from the ash indicate that can be treated with acid to efficiently recover phosphorous and thus can be absorbed by Zr-SOJR.

Harada, Hiroyuki; Kondo, Mitsunori; Biswas, Biplob K.; Ohura, Seichirou; Inoue, Katsutoshi; Ishikawa, Susumu; Kawakita, Hidetaka; Ohto, Keisuke

271

Ion beam mixing of chromium or zirconium films with sapphire.  

National Technical Information Service (NTIS)

Ion beam mixing of thin metallic films deposited on sapphire substrates was studied for chromium or zirconium films deposited on single crystalline (alpha)-Al(sub 2)0(sub 3) substrates. Evidence for the influence of equilibrium thermodynamic factors was s...

C. J. McHargue D. L. Joslin C. W. White M. F. daSilva E. Alves

1995-01-01

272

Physical and mechanical properties of chromium zirconium nitride thin films  

Microsoft Academic Search

This paper reports on the physical, chemical, mechanical, and tribological properties of reactively sputtered chromium zirconium nitride deposited on Si (111) substrates using Cr and Zr targets. These films were grown using a fixed power to the Zr target (70 W), a fixed flow of nitrogen (1.5 sccm), but with a variable power to the Cr target (0–13 W). The

S. M. Aouadi; T. Maeruf; R. D. Twesten; D. M. Mihut; S. L. Rohde

2006-01-01

273

Wood surface protection with some titanium, zirconium and manganese compounds  

Microsoft Academic Search

Thin radiata pine veneers were treated with a range of titanium, zirconium and manganese compounds and exposed to natural weathering. Veneer weight and tensile strength losses were used to assess the protective efficacy of the compounds. The oxidative manganese compounds potassium permanganate and manganic acetate restricted both weight and tensile strength loss of treated wood veneers during weathering. FTIR internal

K. J. Schmalzl; P. D. Evans

2003-01-01

274

Evidence for an ideal transparent anodic oxide film on zirconium  

Microsoft Academic Search

The properties of a transparent oxide formed on zirconium by anodic oxidation in carbonate buffer are described. The transparent oxide has all the properties of an ideal valve-metal oxide. The film grows via a high field conduction mechanism. The potential and film thickness both increase linearly with time under constant-current growth conditions to well over 100 V with no sign

J. L. Ord; D. J. De Smet

1995-01-01

275

Extraction of Zirconium from Zircon (A New Process).  

National Technical Information Service (NTIS)

A new process has been used for the extraction of zirconium from zircon. Caustic fritting was done in the presence of magnesium hydroxide carbonate and magnesium oxide. These additives decrease the amount of nitric acid soluble silica less than 1000 ppm. ...

K. A. Shahid D. Saeed S. Jan A. Masood J. Akhtar

1985-01-01

276

THE DETERMINATION OF MAGNESIUM IN ZIRCONIUM USING ION EXCHANGE CHROMATOGRAPHY  

Microsoft Academic Search

The method is based upon the ability of zirconium to form an easily ; soluble oxalate complex compound which is not adsorbed by a cation exchanger ; (catfonite). The magnesium in the solution is, however, adsorbed by the ; cationite and can then be eluted with hydrochloric acid. An ion exchange resin ; with SOâH as the active group was

S. V. Yelinson; M. S. Limonik

1958-01-01

277

Electrochemical Deoxidation of Solid Zirconium Dioxide in Molten Calcium Chloride  

NASA Astrophysics Data System (ADS)

The reduction of zirconium dioxide pellets by electro-deoxidation in molten calcium chloride-calcium oxide (900 °C) has been studied. In this technique, the solid oxide is cathodically polarized against a graphite counter electrode under a constant applied potential. Unlike other metal oxides that have been reduced by this technique, only a small area around the cathodic current-collector wire was reduced to zirconium metal with zirconia pellets sintered at ~1100 °C; the rest of the sample was largely calcium zirconate. Pellets sintered above 1200 °C showed better reduction near the cathode wire and the reduction extended to the entire surface of the pellet with the passage of time. However, reduction of the inner core was found to be increasingly difficult, because the surface metal layer thickened on continuous electro-deoxidation. An analysis of the experimental results showed that the poor electrical conductivity of the intermediate compound, CaZrO3 and its blocky morphology inhibited the electro-deoxidation process. The increase in the sintering temperature of the pellet made it better conducting. However, the pores formed in the thick zirconium metal layer in such samples were too small for an ideal contact between the inner core and the molten electrolyte and hence the reduction of the inner core remained incomplete. Within the scope of this study, it is concluded that preforms with good grain growth and porosity are necessary for the electro-deoxidation of solid zirconium oxide.

Mohandas, K. S.; Fray, D. J.

2009-10-01

278

40 CFR 721.10602 - Lead niobium titanium zirconium oxide.  

Code of Federal Regulations, 2013 CFR

...zirconium oxide (PMN P-11-270; CAS No. 61461-40-3); Calcium cobalt lead titanium tungsten oxide (PMN P-11-271; CAS No. 1262279-31-1); Calcium cobalt lead strontium titanium tungsten oxide (PMN P-11-272; CAS...

2013-07-01

279

40 CFR 721.10601 - Lanthanum lead titanium zirconium oxide.  

Code of Federal Regulations, 2013 CFR

...zirconium oxide (PMN P-11-270; CAS No. 61461-40-3); Calcium cobalt lead titanium tungsten oxide (PMN P-11-271; CAS No. 1262279-31-1); Calcium cobalt lead strontium titanium tungsten oxide (PMN P-11-272; CAS...

2013-07-01

280

40 CFR 721.10598 - Lead strontium titanium zirconium oxide.  

Code of Federal Regulations, 2013 CFR

...zirconium oxide (PMN P-11-270; CAS No. 61461-40-3); Calcium cobalt lead titanium tungsten oxide (PMN P-11-271; CAS No. 1262279-31-1); Calcium cobalt lead strontium titanium tungsten oxide (PMN P-11-272; CAS...

2013-07-01

281

Relative isotopic abundances of zirconium in S-type stars  

Microsoft Academic Search

The relative abundances of the six stable or nearly stable isotopes of zirconium were measured for three S stars, R Cyg, V Cnc, and R Gem. The method of analysis is described with the abundances determined by comparing the observed stellar profile of intensity vs wavelength with synthetic spectra calculated by the Minnaert interpolation scheme for a single slab LTE

A. C. Zook

1978-01-01

282

Surface characterization of anodized zirconium for biomedical applications  

NASA Astrophysics Data System (ADS)

Mechanical properties and corrosion resistance of zirconium make this material suitable for biomedical implants. Its good in vivo performance is mainly due to the presence of a protective oxide layer that minimizes corrosion rate, diminishes the amount of metallic ions released to the biological media and facilitates the osseointegration process. Since the implant surface is the region in contact with living tissues, the characteristics of the surface film are of great interest. Surface modification is a route to enhance both biocompatibility and corrosion resistance of permanent implant materials. Anodizing is presented as an interesting process to modify metal surfaces with good reproducibility and independence of the geometry. In this work the surface of zirconium before and after anodizing in 1 mol/L phosphoric acid solution at a fixed potential between 3 and 30 V, was characterized by means of several surface techniques. It was found that during anodization the surface oxide grows with an inhomogeneous coverage on zirconium surface, modifying the topography. The incorporation of P from the electrolyte to the surface oxide during the anodizing process changes the surface chemistry. After 30 days of immersion in Simulated Body Fluid (SBF) solution, Ca-P rich compounds were present on anodized zirconium.

Sanchez, A. Gomez; Schreiner, W.; Duffó, G.; Ceré, S.

2011-05-01

283

The Ion-Exchange Separation of Zirconium and Hafnium  

Microsoft Academic Search

In the course of a rather cursory examination of the elution of tetra-positive ions from the cation exchange resin Dowex 50 with hydrochloric acid solutions, the authors have discovered a very effective method of separating zirconium from hafnimu. In view of the great labor involved in preparing even reasonably pure hafnium compounds by existing methods, they feel that this procedure

Glenn T. Seaborg

1948-01-01

284

Zirconium and hafnium in meteorites by activation analysis  

Microsoft Academic Search

Zirconium and hafnium have been determined in 28 chondrites and 7 achondritea by the use of thermal and 14 MeV neutron activation analyses. The distribution pattern of these elements in the three major classes of chondrites showed that the order of atomic abundances for both elements relative to silicon (Si = 10 6 atoms) was: carbonaceous chondrites > ordinary chondrites

W. D. Ehmann; T. V. Rebagay

1970-01-01

285

CRYSTAL STRUCTURES OF TITANIUM, ZIRCONIUM, AND HAFNIUM AT HIGH PRESSURES  

Microsoft Academic Search

At high pressures, as determined by x-ray analysis, titanium and ; zirconium metal have a distorted, bodycentered-cubic structure. This phase ; persists on pressure release. The normal hexagonal close-packed structures are ; recovered when the metals are heated. An electronic shift must occur in the ; transition. Hafnium metal showed no such transition. (auth);

J. C. Jamieson

1963-01-01

286

The undercooling and nucleation of zirconium by bulk containerless processing  

Microsoft Academic Search

The undercooling and nucleation kinetics of pure zirconium have been measured using several bulk containerless processing techniques. The experiments reported herein are the first in which distributions of undercoolings were obtained by direct temperature measurement of bulk samples. The results for the nucleation kinetics as determined from the undercooling distributions are also the first such measurements of their kind. The

Craig William Morton

1998-01-01

287

Mineral resource of the month: zirconium and hafnium  

USGS Publications Warehouse

Zirconium and hafnium are corrosion-resistant metals that are grouped in the same family as titanium on the periodic table. The two elements commonly occur in oxide and silicate minerals and have significant economic importance in everything from ink, ceramics and golf shoes to nuclear fuel rods.

Gambogi, Joseph

2007-01-01

288

Zirconium-hafnium separation: Mixer-settler studies. Final report  

Microsoft Academic Search

Use of the mixer-settler apparatus as a rapid means of determining improved conditions for plant operation is described including the experimental details. The preparation of highly purified samples of both zirconium oxide and hafnium oxide is discussed. This document is concerned almost entirely with explorations of small scale continuous systems. Another document dealing with this general problem using small scale

F. B. Waldrop; W. T. Ward; W. M. Leaders

1950-01-01

289

Separation of zirconium and hafnium using hollow fibers  

Microsoft Academic Search

A supported liquid membrane system using hollow fiber membranes as supports (HFSLM) has been studied for the separation of zirconium and hafnium, which are typical metal pairs with extreme similarity in chemistry. Tri-n-octylamine (TNOA) and trioctylmethyl ammonium chloride (Aliquat 336) were used as carriers. The effect on the transport and separation of Zr and Hf of HCl concentrations in the

X. J. Yang; A. G. Fane; C. Pin

2002-01-01

290

Separation of zirconium and hafnium using hollow fibres  

Microsoft Academic Search

A novel extraction chromatography system using hollow fibre membranes as supports is reported for separation of zirconium and hafnium. The effects of flow rate and flow mode, stationary phase concentration loaded on the hollow fibre membranes and fibre length on the separation were investigated. The separation performance of hollow fibre membrane chromatography can be analysed from existing theories of conventional

X. J Yang; A. G Fane; C Pin

2002-01-01

291

Screw dislocation in zirconium: An ab initio study  

NASA Astrophysics Data System (ADS)

Plasticity in zirconium is controlled by 1/3<12¯10> screw dislocations gliding in the prism planes of the hexagonal close-packed structure. This prismatic and not basal glide is observed for a given set of transition metals like zirconium and is known to be related to the number of valence electrons in the d band. We use ab initio calculations based on the density functional theory to study the core structure of screw dislocations in zirconium. Dislocations are found to dissociate in the prism plane in two partial dislocations, each with a pure screw character. Ab initio calculations also show that the dissociation in the basal plane is unstable. We calculate then the Peierls barrier for a screw dislocation gliding in the prism plane and obtain a small barrier. The Peierls stress deduced from this barrier is lower than 21 MPa, which is in agreement with experimental data. The ability of an empirical potential relying on the embedded atom method (EAM) to model dislocations in zirconium is also tested against these ab initio calculations.

Clouet, Emmanuel

2012-10-01

292

[Induced activity of nitrate reductase by nitrate and cloning of nitrate reductase gene].  

PubMed

Excessive nitrate accumulated in plants affects vegetable quality severely and excessive nitrate ingestion would do harm to human health. Assimilatory NADH: nitrate reductase (NR, EC 1.6.6.1), a complex Mo-pterin-, cytochrome b(557)- and FAD-containing protein, catalyzes the regulated and rate-limiting step in the utilization of inorganic nitrogen by higher plants. Enhancing the activity of NR is conducive to reduce the concentration of nitrate in plants. The experiments were conducted to investigate the activity of nitrate reductase in different plant tissues and the relationship between external inducing solution concentration and NR activity (NRA) in plant leaves. Six plant seedlings growing in solution culture were deprived of an external nitrogen (N) supply for 2 weeks. On selected days, three of six plant seedlings were exposed to 50mmol/L NO3- for 0, 2, 5, 8, 11h, and four of the six plant seedlings were exposed to 0, 10, 30, 50mmol/L NO3- for 2h. The NRA was determined in vivo at 538nm using spectrophotometer. The results showed that NRA increased when those plant seedlings were induced by nitrate solution. The change trends of NRA in roots and in leaves of cole, pea and tomato were different during treating time. The NRA in cole leaves was higher than that in its root and in other two plants and increased along with inducing time, but the NRA in bea and tomato was highest when the treating time was 8h and 2h, respectively. The highest NRA in leaves of three kinds of Chinese cabbages and tomato was induced by different concentrations of KNO3 solution. In tomato leaves, the highest NRA was induced by 10 - 30mmol/L KNO3 solution. In three Chinese cabbages, Brassica chinensis L. cv. AJH, XBC and KR-605, the highest NRA was induced by 10, 30, 10mmol/L KNO3 solution, respectively. The results indicated that the response manners of NRA in plants to external nitrate solutions were different. According to these results, the level of NR mRNA in plants could be enhanced by nitrate inducement. The total RNA was isolated from tomato leaves and root which induced by 30mmol/L KNO3 solution for 2h, and NR cDNA was obtained by RT-PCR using the specific primers. The fragments of PCR products were cloned and sequenced. There are 2736 base pairs in the whole cDNA fragment. The deduced protein sequence contains 911 amino acids. The NR gene can be fused to the CaMV 35S promoter, then introduced to higher plants, such as vegetables. It is hoped to decrease drastically the nitrate content of the transgenic plants. PMID:15969098

Wang, Li-Qun; Wang, Yong; Dong, Ying; Wang, Wen-Bing

2003-09-01

293

Enzyme inactivation by peroxyacetyl nitrate  

Microsoft Academic Search

Isocitric dehydrogenase (NADP linked), G-6-P dehydrogenase, and malic dehydrogenase were inactivated by peroxyacetyl nitrate. The enzymes could be protected in some cases; isocitric dehydrogenase by isocitrate and NAPD, the former being more effective, and G-6-P dehydrogenase by NADP but not by G-6-P. Malic dehydrogenase was not significantly protected either by substrate or coenzyme. Inhibition of these three enzymes by cadmium

J MUDD

1963-01-01

294

Photochemical reduction of uranyl nitrate  

SciTech Connect

The photochemical reduction of uranyl nitrate solutions to tetravalent uranium was investigated as a means of producing uranium dioxide feed for the saltless direct oxide reduction (SDOR) process. At high uranium concentrations, reoxidation of U{sup +4} occurs rapidly. The kinetics of the nitric oxidation of tetravalent uranium depend on the concentrations of hydrogen ion, nitrate ion, nitrous acid, and tetravalent uranium in the same manner as was reported elsewhere for the nitrate oxidation of PU{sup +3}. Reaction rate data were successfully correlated with a mechanism in which nitrogen dioxide is the reactive intermediate. Addition of a nitrous acid scavenger suppresses the reoxidation reaction. An immersion reactor employing a mercury vapor lamp gave reduction times fast enough for routine production usage. Precipitation techniques for conversion of aqueous U(NO{sub 3}){sub 4} to hydrous UO{sub 2} were evaluated. Prolonged dewatering times tended to make the process time consuming. Use of 3- to 4-M aqueous NaOH gave the best dewatering times observed. Reoxidation of the UO{sub 2} by water of hydration was encountered, which required the drying process to be carried out under a reducing atmosphere.

Duerksen, W.K.

1993-10-20

295

Removal of Zirconium in Electrometallurgical Treatment of Experimental Breeder Reactor II Spent Fuel  

SciTech Connect

During electrorefining of irradiated, binary U-Zr Experimental Breeder Reactor II fuel, a portion of zirconium is found to dissolve along with uranium. It accumulates in the cadmium pool both as dissolved zirconium and as a zirconium-cadmium intermetallic precipitate. Two electrochemical methods of removing zirconium from the electrorefiner have been evaluated. The first is a three-step method consisting of chemical oxidation of zirconium by CdCl{sub 2} addition, depletion of zirconium from the cadmium pool by electrotransport, and drawdown of zirconium from the LiCl-KCl eutectic salt by using a different electrorefiner configuration. A transport model is employed to determine the cell operating conditions for growing pure zirconium deposits and the throughput rate. The second method eliminates the chemical oxidation step and permits codeposition of uranium and zirconium onto the solid cathode. The transport model is used to assess the level of uranium impurity in the cathode product; an additional step is proposed to reoxidize uranium in the deposit. The two methods are compared from the standpoints of throughput, deposit composition, deposit adherence to a solid cathode mandrel, and the underlying uncertainties. A brief review is given of the related past laboratory work on removal of zirconium from the electrorefiner.

Ahluwalia, Rajesh K.; Hua, Thanh Q.; Geyer, Howard K. [Argonne National Laboratory (United States)

2001-01-15

296

The mechanism of gas-phase dehydration of cyclohexanol and the methylcyclohexanols catalysed by zirconium phosphate and zirconium phosphite  

Microsoft Academic Search

By means of deuterium labelling experiments, the mechanism of the gas-phase dehydration of cyclohexanol over a solid zirconium phosphate catalyst has been shown to involve a carbocation with a long lifetime. Product distribution studies have been used to show that the corresponding dehydrations of the 4-methylcyclohexanols also proceed through a carbocation mechanism, but have shown that the 2-methylcyclohexanols react partly

M. Conceiçao Cruz Costa; Lisa F. Hodson; Robert A. W. Johnstone; Jun-Yao Liu; David Whittaker

1999-01-01

297

Zirconium and Hafnium Separation, Part 3. Ligand?Enhanced Separation of Zirconium and Hafnium from Aqueous Solution using Nanofiltration  

Microsoft Academic Search

Membrane filtration equipment was used to evaluate zirconium and hafnium separation efficiency by a membrane separation process. High rejection of Zr and Hf species in aqueous solution were obtained with nanofiltration and ultrafiltration membranes. This high rejection could be explained by the formation of high molecular weight polynuclear species. Enhanced transportation across the nanofiltration and ultrafiltration membranes was observed when

L. Poriel; F. Chitry; M. Lemaire

2006-01-01

298

THE SEPARATION OF ZIRCONIUM FROM HAFNIUM. II. FRACTIONAL DISTILLATION OF THE ADDITION COMPOUNDS FORMED BY PHOSPHORUS OXYCHLORIDE WITH THE TETRACHLORIDES OF HAFNIUM AND ZIRCONIUM  

Microsoft Academic Search

The preparation of the addition compounds formed by phoshorus ; oxychloride with hafnium and zirconium tetrachlorides is described. Partial ; separation of the addition compounds is effected in a specially constructed ; apparatus which is sultable for the fractionation of highmelting and high-boiling ; compounds. Zirconium oxide, containing less than 0.1% by weight of hafnium ; oxide, is recovered by

F. Hudswell; K. L. Wilkinson; L. J. Wyatt; J. S. Nairn

1950-01-01

299

Investigation of methods for producing reactor-grade zirconium oxide from a zirconium-bearing chloride-sulfate strip liquor solution. Report of investigations/1984  

SciTech Connect

The Bureau of Mines investigated two alternative methods for treating a zirconium-bearing chloride-sulfate strip liquor to obtain reactor-grade ZrO2. One method involves neutralization with NH3 and the other hydrothermal precipitation. The strip liquor was derived from zircon sand by a Bureau of Mines method for separating zirconium and hafnium via solvent extraction with a tertiary amine. Neutralization with NH3 to precipitate hydrous zirconium oxide required 0.9 to 1.1 g NH3 per gram of zirconium. The NH3 can be recovered for recycle. ZrO2 that met reactor-grade specifications was produced by precipitation with NH3. Hydrothermal precipitation of ZrO2 from strip liquor required that the solution be maintained at 260C and 680 psi for 10 min and in a noncorrodible pressure vessel. In bench-scale experiments both methods gave zirconium recoveries greater than 99 pct.

MacDonald, D.J.; Defilippi, C.E.; Henry, H.G.

1984-02-01

300

Syntheses and structural characterization of zirconium-tin and zirconium-lead binary and ternary systems  

SciTech Connect

The binary zirconium-tin system was reinvestigated. The A15 phase appears to be a line phase with a Zr{sub 4}Sn composition. The Zr{sub 5}Sn{sub 3} (Mn{sub 5}Si{sub 3}-type) and Zr{sub 5}Sn{sub 4} (Ti{sub 5}Ga{sub 4}-type) compounds are line phases below 1000{degree}C, the latter being a self-interstitial phase of the former. ZrSn{sub 2} is the tin-richest phase. There is an one-phase region between these phases with partial self-interstitials at high temperatures. The zirconium-lead system behaves similarly: there are an A15 phase with a Zr{sub {approximately}5.8}Pb composition, Zr{sub 5}Pb{sub 3} (Mn{sub 5}Si{sub 3}-type) and Zr{sub 5}Pb{sub 4} (Ti{sub 5}Ga{sub 4-type}) compounds, and a high temperature solid solution between Zr{sub 5}Pb{sub >3.5} and Zr{sub 5}Pb{sub 4} from below 1000{degree}C; however, the ZrSn{sub 2} analogue is not formed. The Mn{sub 5}Si{sub 3}-type phases in these systems can accommodate third elements interstitially to form stoichiometric compounds Zr{sub 5}Sn{sub 3}Z (Z = B, C, N, O, Al, Si, P, S, Cu, Zn, Ga, Ge, and As and Se) and Zr{sub 5}Pb{sub 3}Z (Z = Al, Si, P, S, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Ag, Cd, In, Sn, Sb and Te) as well as their self-interstitial derivatives. The systems Zr-Sn-T, T = Fe, Co and Ni, did not produce stoichiometric interstitial phases Zr{sub 5}Sn{sub 3}T. Instead, the interstitial phases for these elements are formed only with excess tin that partially occupies the interstitial site together with a T element. Reducing the amount of tin in these systems yields two new phases; Zr{sub 5}Sn{sub 2+x}Fe{sub 1-x} (0 {le} {times} {le} 0.28) (W{sub 5}Si{sub 3}-type) and Zr{sub 6}Sn{sub 2}Fe (Zr{sub 6}Al{sub 2}Co-type) as characterized by X-ray single crystal analyses. A cobalt analogue for the latter was also synthesized.

Kwon, Y.U.

1991-01-28

301

Method of purifying zirconium tetrachloride and hafnium tetrachloride in a vapor stream  

SciTech Connect

This patent describes a method of purifying zirconium tetrachloride and hafnium tetrachloride in a vapor stream from a sand chlorinator in which the silicon and metals present in sand fed to the chlorinator are converted to chlorides at temperatures over about 800{degrees} C. It comprises cooling a vapor stream from a sand chlorinator, the vapor stream containing principally silicon tetrachloride, zirconium tetrachloride, and hafnium tetrachloride contaminated with ferric chloride, to a temperature of from about 335{degrees} C to about 600{degrees} C; flowing the vapor stream through a gaseous diffusion separative barrier to produce a silicon tetrachloride-containing vapor stream concentrated in zirconium tetrachloride and hafnium tetrachloride and a silicon tetrachloride-containing vapor stream depleted in zirconium tetrachloride and hafnium tetrachloride; adsorbing the ferric chloride in the separative barrier; and recovering the silicon tetrachloride stream concentrated in zirconium tetrachloride and hafnium tetrachloride separately from the silicon tetrachloride stream depleted in zirconium tetrachloride and hafnium tetrachloride.

Snyder, T.S.; Stolz, R.A.

1992-04-07

302

Physiological aspects of ammonium and nitrate fertilization  

Microsoft Academic Search

Various physiological effects of ammonium, nitrate and mixed ammonium?nitrate nutrition of plants have been studied in this laboratory during the last years. Some of the characteristic distinctions observed between plants growing on these nitrogen sources are described and discussed. Biomass production of ammonium?grown plants increased with K concentration in the nutrient medium between 0.1 to 3 mM , while nitrate?fed

S. H. Lips; E. O. Leidi; M. Silberbush; M. I. M. Soares; O. E. M. Lewis

1990-01-01

303

Chemical removal of nitrate from water  

Microsoft Academic Search

HIGH levels of nitrate in ground water can pose a serious health risk. Reduction of nitrate to nitrite in the gut may cause methemoglobinaemia1both in newborn infants and in adults deficient in glucose-phosphate dehydrogenase2. Under abnormal circumstances, reduction to nitrite can also occur in the stomach to form N-nitrosamines, a postulated cause of stomach cancer3. Nitrate outflow onto shallow continental

Andrew P. Murphy

1991-01-01

304

Minol IV, A New Explosive Composition Containing Ammonium Nitrate-Potassium Nitrate Solid Solution. Part I.  

National Technical Information Service (NTIS)

Minol II (40% ammonium nitrate, 20% aluminum) is useful as an explosive fill for bombs, because its use substitutes cheap, and abundant, ammonium nitrate (AN) for more expensive, and sometimes scarce, TNT. However, Minol II exhibits poor dimensional stabi...

A. L. Bertram C. Boyars J. R. Holden

1973-01-01

305

Mammalian Nitrate Biosynthesis: Incorporation of 15NH3 into Nitrate is Enhanced by Endotoxin Treatment  

NASA Astrophysics Data System (ADS)

Incorporation of an oral dose of [15N]ammonium acetate into urinary [15N]nitrate has been demonstrated in the rat. Investigation of the regulation of nitrate synthesis has shown that Escherichia coli lipopolysaccharide potently stimulates urinary nitrate excretion (9-fold increase). It was further shown that the enhanced rate of nitrate excretion by lipopolysaccharide was due not to a reduction in nitrate metabolic loss but rather to an increased rate of synthesis. This conclusion was based on finding a proportionally increased incorporation of [15N]ammonium into nitrate nitrogen with lipopolysaccharide treatment. Nitrate biosynthesis was also increased by intraperitoneal injection of carrageenan and subcutaneous injection of turpentine. It is proposed that the pathway of nitrate biosynthesis may be the result of oxidation of reduced nitrogen compounds by oxygen radicals generated by an activated reticuloendothelial system.

Wagner, David A.; Young, Vernon R.; Tannenbaum, Steven R.

1983-07-01

306

The reproducibility of the conversion of nitrate to nitrite in human saliva after a nitrate load.  

PubMed

We investigated the reproducibility of the inter- and intra-individual variations in the conversion of nitrate to nitrite in saliva. Saliva samples were collected from 20 volunteers just before and at regular intervals after a nitrate load on four non-consecutive days within a period of 2 months. On three occasions beetroot juice was the nitrate source and on one occasion a nitrate solution was given. Despite large day-to-day variations it was possible to discriminate between subjects with a consistently high or low nitrate conversion after a nitrate load. Neither saliva sampling before a nitrate load nor single saliva samples are sufficient to obtain clear information about individual capacities for nitrate-nitrite conversion. PMID:3366416

Bos, P M; Van den Brandt, P A; Wedel, M; Ockhuizen, T

1988-02-01

307

Microstructural investigations on zirconium oxide–carbon nanotube composites synthesized by hydrothermal crystallization  

Microsoft Academic Search

Zirconium oxide (ZrO2)\\/carbon nanotube composites were prepared by hydrothermal crystallization at 200 °C for 8 h of zirconium hydroxide [(Zr(OH)4nH2O; n=8–16] in the presence of carbon nanotubes. The hydrothermal crystallization of zirconium oxide, under autoclave conditions, occurred on the walls of the tubes. The process yielded a homogeneous composite powder consisting of microcrystalline ZrO2 and multi-walled nanotubes, hence representing an

F Lupo; R Kamalakaran; C Scheu; N Grobert; M Rühle

2004-01-01

308

Behavior of atomic reactor zirconium cladding fuel rod tubes under extreme operating conditions  

Microsoft Academic Search

The effect of zirconium alloy strength on stress corrosion cracking for cladding tubes prepared from these materials is studied.\\u000a Structure-phase transformations and the nature of failure during high-temperature oxidation, i.e. simulation of critical situations\\u000a with loss of heat carrier (LOCA) for zirconium cladding tubes, are studied. Areas are analyzed for improving zirconium cladding\\u000a tubes for fuel rods intended for a

S. A. Nikulin; V. G. Khanzhin; A. B. Rozhnov; V. A. Belov

2009-01-01

309

Nuclear-grade zirconium prepared by combining combustion synthesis with molten-salt electrorefining technique  

Microsoft Academic Search

Zirconium has a low absorption cross-section for neutrons, which makes it an ideal material for use in nuclear reactor applications. However, hafnium typically contained in zirconium causes it to be far less useful for nuclear reactor materials because of its high neutron-absorbing properties. In the present study, a novel effective method has been developed for the production of hafnium-free zirconium.

Hui Li; Hayk H. Nersisyan; Kyung-Tae Park; Sung-Bin Park; Jeong-Guk Kim; Jeong-Min Lee; Jong-Hyeon Lee

2011-01-01

310

Flame propagation characteristics and flame structures of zirconium particle cloud in a small-scale chamber  

Microsoft Academic Search

Flame propagating through zirconium particle cloud in a small-scale vertical rectangle chamber was investigated experimentally.\\u000a In the experiments, the zirconium quoted 99% purity was used and the diameter of particles was distributed 1–22 ?m. The zirconium\\u000a dust was dispersed into the chamber by air flow and ignited by an electrode spark. A high-speed video camera was used to record\\u000a the

YiBin Ding; JinHua Sun; XueChao He; QiuHong Wang; Yi Yin; Yao Xu; XianFeng Chen

2010-01-01

311

High cycle fatigue properties and microstructure of zirconium and zircaloy-4 under reversal bending  

Microsoft Academic Search

Fatigue lifetime curves of a commercial-purity zirconium and zircaloy-4 were measured under reversal bending. Scanning electron microscopic examination on surfaces of fatigued specimens shows that zirconium displays planar slip, whereas zircaloy-4 displays wavy slip. Fracture surface analysis shows that many fatigue striations with a considerable number of micro-cracks are the primary characters in zirconium and zircaloy-4. Fatigue crack generally nucleates

Xiao Lin; Gu Haicheng

1998-01-01

312

Stoichiometric relation for extraction of zirconium and hafnium from acidic chloride solutions with Versatic Acid 10  

Microsoft Academic Search

The stoichiometric relation for the extraction of zirconium and hafnium from acidic chloride solutions was investigated with Versatic Acid 10. Extraction runs were carried out batchwise at ambient temperature in the pH range from 1.4 to 2.3 for zirconium and from 2.3 to 2.9 for hafnium. The results showed that zirconium was extracted in the form of ZrO2+ rather than

Hwa Young Lee; Sung Gyu Kim; Jong Kee Oh

2004-01-01

313

Safety in the Chemical Laboratory: Nitric Acid, Nitrates, and Nitro Compounds.  

ERIC Educational Resources Information Center

|Discussed are the potential hazards associated with nitric acid, inorganic and organic nitrate salts, alkyl nitrates, acyl nitrates, aliphatic nitro compounds, aromatic nitro compounds, and nitration reactions. (CW)|

Bretherick, Leslie

1989-01-01

314

Anharmonic effects in ammonium nitrate and hydroxylammonium nitrate clusters.  

PubMed

The covalent and ionic clusters of ammonium nitrate and hydroxyl ammonium nitrate are characterized using density functional theory and second-order vibrational perturbation theory. The most stable structures are covalent acid-base pairs for the monomers and ionic acid-base pairs for the dimers. The hydrogen-bonding distances are greater in the ionic dimers than in the covalent monomers, and the stretching frequencies are significantly different in the covalent and ionic clusters. The anharmonicity of the potential energy surfaces is found to influence the geometries, frequencies, and nuclear magnetic shielding constants for these systems. The inclusion of anharmonic effects significantly decreases many of the calculated vibrational frequencies in these clusters and improves the agreement of the calculated frequencies with the experimental data available for the isolated neutral species. The calculations of nuclear magnetic shielding constants for all nuclei in these clusters illustrate that quantitatively accurate predictions of nuclear magnetic shieldings for comparison to experimental data require the inclusion of anharmonic effects. These calculations of geometries, frequencies, and shielding constants provide insight into the significance of anharmonic effects in ionic materials and provide data that will be useful for the parametrization of molecular mechanical force fields for ionic liquids. Anharmonic effects will be particularly important for the study of proton transfer reactions in ionic materials. PMID:17474693

Kumarasiri, Malika; Swalina, Chet; Hammes-Schiffer, Sharon

2007-05-10

315

Groundwater nitrate contamination: Factors and indicators  

PubMed Central

Identifying significant determinants of groundwater nitrate contamination is critical in order to define sensible agri-environmental indicators that support the design, enforcement, and monitoring of regulatory policies. We use data from approximately 1200 Austrian municipalities to provide a detailed statistical analysis of (1) the factors influencing groundwater nitrate contamination and (2) the predictive capacity of the Gross Nitrogen Balance, one of the most commonly used agri-environmental indicators. We find that the percentage of cropland in a given region correlates positively with nitrate concentration in groundwater. Additionally, environmental characteristics such as temperature and precipitation are important co-factors. Higher average temperatures result in lower nitrate contamination of groundwater, possibly due to increased evapotranspiration. Higher average precipitation dilutes nitrates in the soil, further reducing groundwater nitrate concentration. Finally, we assess whether the Gross Nitrogen Balance is a valid predictor of groundwater nitrate contamination. Our regression analysis reveals that the Gross Nitrogen Balance is a statistically significant predictor for nitrate contamination. We also show that its predictive power can be improved if we account for average regional precipitation. The Gross Nitrogen Balance predicts nitrate contamination in groundwater more precisely in regions with higher average precipitation.

Wick, Katharina; Heumesser, Christine; Schmid, Erwin

2012-01-01

316

Microbial degradation of glycerol nitrates.  

PubMed Central

The fate of glycerol trinitrate when exposed to microbial attack has been investigated. Contrary to some earlier reports, this compound was readily biodegraded by employing batch or continuous techniques under a variety of cultural conditions. Breakdown of glycerol trinitrate took place stepwise via the dinitrate and mononitrate isomers, with each succeeding step proceeding at a slower rate. After a residence time of 8 to 15 h, none of the glycerol nitrates could be detected in the effluent from a continuous-culture apparatus (chemostat) supplied with an influent containing 30 mg of glycerol trinitrate per liter.

Wendt, T M; Cornell, J H; Kaplan, A M

1978-01-01

317

Effect of Carbon Dioxide on Nitrate Accumulation and Nitrate Reductase Induction in Corn Seedlings 1  

PubMed Central

Exposure of the leaf canopy of corn seedlings (Zea mays L.) to atmospheric CO2 levels ranging from 100 to 800 ?l/l decreased nitrate accumulation and nitrate reductase activity. Plants pretreated with CO2 in the dark and maintained in an atmosphere containing 100 ?l/l CO2 accumulated 7-fold more nitrate and had 2-fold more nitrate reductase activity than plants exposed to 600 ?l/l CO2, after 5 hours of illumination. Induction of nitrate reductase activity in leaves of intact corn seedlings was related to nitrate content. Changes in soluble protein were related to in vitro nitrate reductase activity suggesting that in vitro nitrate reductase activity was a measure of in situ nitrate reduction. In longer experiments, levels of nitrate reductase and accumulation of reduced N supported the concept that less nitrate was being absorbed, translocated, and assimilated when CO2 was high. Plants exposed to increasing CO2 levels for 3 to 4 hours in the light had increased concentrations of malate and decreased concentrations of nitrate in the leaf tissue. Malate and nitrate concentrations in the leaf tissue of seven of eight corn genotypes grown under comparable and normal (300 ?l/l CO2) environments, were negatively correlated. Exposure of roots to increasing concentrations of potassium carbonate with or without potassium sulfate caused a progressive increase in malate concentrations in the roots. When these roots were subsequently transferred to a nitrate medium, the accumulation of nitrate was inversely related to the initial malate concentrations. These data suggest that the concentration of malate in the tissue seem to be related to the accumulation of nitrate.

Purvis, A. C.; Peters, D. B.; Hageman, R. H.

1974-01-01

318

Nitrates  

MedlinePLUS

... Outside the U.S., call 1-832-355-6536.) Texas Heart Institute Heart Information Center Through this community outreach program, staff members of the Texas Heart Institute (THI) provide educational information related to ...

319

SEPARATION OF PLUTONIUM IONS FROM SOLUTION BY ADSORPTION ON ZIRCONIUM PYROPHOSPHATE  

DOEpatents

A method is given for separating plutonium in its reduced, phosphate- insoluble state from other substances. It involves contacting a solution containing the plutonium with granular zirconium pyrophosphate.

Stoughton, R.W.

1961-01-31

320

Radioactivity in zirconium oxide powders used in industrial applications  

SciTech Connect

Recent work involving the decommissioning of a former ceramic manufacturing facility licensed by the Nuclear Regulatory Commission for activities involving depleted uranium oxide has uncovered the presence of unexpected high levels of natural radioactivity in non-licensed zirconium oxide powders also used in the same facility. A comparison between the levels of source material found in samples of this material and the current regulatory guidance for licensed activities and decommissioning has been conducted. It has been determined that the radioactivity in the zirconium oxide is of a high enough magnitude to raise health physics concerns in the areas of licensing and regulatory compliance, decontamination criteria, and worker health and safety. An examination of these areas has been conducted and the implications associated with our findings are presented.

Lischinsky, J.; Vigliani, M.A.; Allard, D.J. (Applied Consultants, Inc., Woburn, MA (USA))

1991-06-01

321

Corrosion behavior of stainless steel-zirconium alloy waste forms.  

SciTech Connect

Stainless steel-zirconium (SS-Zr) alloys are being considered as waste forms for the disposal of metallic waste generated during the electrometallurgical treatment of spent nuclear fuel. The baseline waste form for spent fuels from the EBR-II reactor is a stainless steel-15 wt.% zirconium (SS-15Zr) alloy. This article briefly reviews the microstructure of various SS-Zr waste form alloys and presents results of immersion corrosion and electrochemical corrosion tests performed on these alloys. The electrochemical tests show that the corrosion behavior of SS-Zr alloys is comparable to those of other alloys being considered for the Yucca Mountain geologic repository. The immersion tests demonstrate that the SS-Zr alloys are resistant to selective leaching of fission product elements and, hence, suitable as candidates for high-level nuclear waste forms.

Abraham, D. P.

1999-01-13

322

Corrosion testing of stainless steel-zirconium metal waste form.  

SciTech Connect

Stainless steel-zirconium (SS-Zr) alloys are being considered as waste forms for the disposition of metallic waste generated during the electrometallurgical treatment of spent nuclear fuel. The waste forms contain irradiated cladding hulls, components of the alloy fuel, noble metal fission products, and actinide elements. The baseline waste form is a stainless steel-15 wt% zirconium (SS-15Zr) alloy. This article presents microstructure and some of the corrosion studies being conducted on the waste form alloys. Electrochemical corrosion, immersion corrosion, and vapor hydration tests have been performed on various alloy compositions to evaluate corrosion behavior and resistance to selective leaching of simulated fission products. The SS-Zr waste forms are successful at the immobilization and retention of fission products and show potential for acceptance as high-level nuclear waste forms.

Abraham, D. P.

1998-12-14

323

Modelling zirconium hydrides using the special quasirandom structure approach.  

PubMed

The study of the structure and properties of zirconium hydrides is important for understanding the embrittlement of zirconium alloys used as cladding in light water nuclear reactors. Simulation of the defect processes is complicated due to the random distribution of the hydrogen atoms. We propose the use of the special quasirandom structure approach as a computationally efficient way to describe this random distribution. We have generated six special quasirandom structure cells based on face centered cubic and face centered tetragonal unit cells to describe ZrH(2-x) (x = 0.25-0.5). Using density functional theory calculations we investigate the mechanical properties, stability, and electronic structure of the alloys. PMID:23588997

Wang, H; Chroneos, A; Jiang, C; Schwingenschlögl, U

2013-04-15

324

Stress corrosion cracking of zirconium used in the reprocessing plant  

SciTech Connect

We investigated stress corrosion cracking (SCC) of zirconium by constant load test and the small-scale mock-up test simulated the fuel dissolve. These tests operated in the simulated solution, which substituted non-radioactive elements, i.e. V with radioactive elements such as Pu and Np. From the results of constant load test, the cracks were not observed on 150 MPa after 908 hours in approximately 3 % strain. However a lot of cracks caused by SCC were observed over 20 % strain under high tensile stress in the simulated solution and the heat-transfer condition having more corrosive circumstance and noble potential accelerated the susceptibility of SCC. The cracking behavior would be caused by the creep phenomena. The small-scale mock-up test had been operated for about 50000 hours during 7 year. From the results, zirconium showed excellent corrosion resistance and no SCC was observed during these long-term operations. (authors)

Kato, Chiaki; Motooka, Takafumi; Yamamoto, Masahiro [Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan)

2007-07-01

325

Voltammetric determination of zirconium(IV) and hafnium(IV)  

SciTech Connect

Zirconium (IV) and hafnium (IV) do not form coordination compounds with 8-mercaptoquinoline and its alkyl derivatives. For determination of these elements in various samples, the most appropriate reagent appears to be 2-carboxy-8-mercaptoquinoline. A new metal-oxygen bond is formed in the complexes with 2-carboxy-8-mercaptoquinoline, in contrast to the complexes with its alkyl derivatives. Moreover, this reagent a reveals the properties of a bi- and tridentate ligand. From the data of redox potentiometry, zirconium (IV) and hafnium (IV) form the complexes of composition 1:2 and 1:3 with 2-carboxy-8-mercaptoquinoline; which were isolated in the form of red crystals. The aim of this work is to develop procedures for the direct voltammetric determination of Zr(IV) and Hf(IV) in the form of their complexes with 2-carboxy-8-mercaptoquinoline in aqueous solutions and extracts using a stationary mercury film electrode (SMFE) in dimethylformamide (DMFA) and dichloroethane (DCE).

Shaidarova, L.G.; Ulakhovich, N.A.; Fedorova, I.K. [Kazan State Univ., Tatarstan (Russian Federation)] [and others

1994-08-01

326

Charge-optimized many-body (COMB) potential for zirconium  

NASA Astrophysics Data System (ADS)

An interatomic potential for zirconium is developed within the charge-optimized many-body (COMB) formalism. The potential correctly predicts the hexagonal close-packed (HCP) structure as the ground state with cohesive energy, lattice parameters, and elastic constants matching experiment well. The most stable interstitial position is the basal octahedral followed by basal split, in agreement with recent first principles calculations. Stacking fault energies within the prism and basal planes satisfactorily match first principles calculations. A tensile test using nanocrystalline zirconium exhibits both prismatic {101¯0}<112¯0> slip and pyramidal {112¯2}<112¯3¯> slip, showing the model is capable of reproducing the mechanical deformation modes observed in experiments.

Noordhoek, Mark J.; Liang, Tao; Lu, Zizhe; Shan, Tzu-Ray; Sinnott, Susan B.; Phillpot, Simon R.

2013-10-01

327

Process for producing high purity zirconium and hafnium  

SciTech Connect

An improved process is described for producing zirconium or hafnium. The process is of the type wherein a tetrachloride of zirconium or hafnium is reduced by magnesium and the resulting metal is subjected to a distillation treatment. The improvement comprises: introducing magnesium chloride into a combination reduction-distillation vessel. An inner liner with at least one bottom drain opening with the drain opening providing fluid communication between the vessel and the liner. The magnesium chloride is added in a quantity to fill the vessel and the inner liner to a level above the liner bottom drain opening, whereby the magnesium chloride provides a seal which prevents magnesium in the inner liner from flowing out of the inner liner.

Kwon, Y.J.

1987-05-26

328

Preparation and ion-exchange properties of zirconium sulphosphosphonates  

SciTech Connect

A number of layered zirconium phosphite arylphosphonate and zirconium phosphate arylphosphonate mixed derivatives were prepared. These compounds were readily sulfonated in fuming sulfuric acid and the resultant sulfonates behaved as strong-acid ion exchangers. In the case where the aryl group bridged across layers, a non-swelling exchanger resulted, and these solids showed ion exclusion towards large complexes. They also exhibited the selectivity sequences lithium + greater than sodium + less than potassium + and magnesium + greater than calcium + less than barium +. In the exchanger in which the layers were not connected, large degrees of swelling to the point of colloid formation, were observed. As a consequence, the rates of exchange were very high. The non-crosslinked exchanger showed increased selectivity was remarkable and may stem from a combination of favorable electrostatic and steric factors.

Yang, C.Y.; Clearfield, A.

1987-01-01

329

Effect of nitrate and incubation conditions on the production of catalase and nitrate reductase by staphylococci  

Microsoft Academic Search

The objective of this work was to study the production of catalase and nitrate reductase by staphylococci in order to understand their role in lipid oxidation during sausage manufacturing. Catalase and nitrate reductase were measured in resting cells and supernatants of staphylococci grown in different conditions. All staphylococci (except S. warneri) synthetized nitrate reductase. In static condition, the synthesis was

R Talon; D Walter; S Chartier; C Barrière; M. C Montel

1999-01-01

330

The thermal effect of reactions of nitration of phenylmethylcarbinol, its nitrate, and p-nitrophenylmethylcarbinol  

Microsoft Academic Search

To determine the thermal effect both of the summary reaction of nitration of phenylmethylcarb inol and of its individual steps - nitration at the hydroxy group and in the benzene ring - we used phenylmethylcarbinol [4], phenylmethylcarb inoI nitrate [5], and p-nitrophenylcar binol [6], prepared by the well known methods, with constants corresponding to the literature data. EXPERIMENTAL PROCEDURE The

S. G. Barashkov; P. M. Kochergin; N. V. Marchenko; G. A. Karpov

1972-01-01

331

Rapid colorimetric determination of nitrate in plant tissue by nitration of salicylic acid  

Microsoft Academic Search

An analysis is described for the rapid determination of nitrate?N in plant extracts. The complex formed by nitration of salicylic acid under highly acidic conditions absorbs maximally at 410 nm in basic (pH>12) solutions. Absorbance of the chromophore is directly proportional to the amount of nitrate?N present. Ammonium, nitrite, and chloride ions do not interfere.

D. A. Cataldo; M. Maroon; L. E. Schrader; V. L. Youngs

1975-01-01

332

Nitrate anion templated assembly of a [2]rotaxane for selective nitrate recognition in aqueous solvent mixtures.  

PubMed

The first nitrate anion templated assembly of an interlocked molecular architecture is demonstrated through the preparation of a [2]rotaxane. Removal of the discrete nitrate anion template from the [2]rotaxane reveals an interlocked host system capable of strong and selective recognition of nitrate, in aqueous-organic solvent mixtures, over a range of more basic mono-charged oxoanions. PMID:23949001

Langton, Matthew J; Duckworth, Lucy C; Beer, Paul D

2013-10-01

333

NADH: nitrate reductase and NAD(P)H: nitrate reductase activities in mustard seedlings  

Microsoft Academic Search

Mustard (Brassica juncea L. Czern and Coss cv. Pusa Jai Kisan) seedlings were grown for 10 days in nutrient solutions containing different concentrations of nitrate (10, 20, 30, 40 and 50 mM). Nitrate reductase activity was determined in the presence of either NADH or NADPH as electron donor. NADH- and NADPH-supported nitrate reductase activity varied significantly in the seedlings grown

Altaf Ahmad; M. Z. Abdin

1999-01-01

334

46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.  

Code of Federal Regulations, 2012 CFR

...more than 70 percent of ammonium nitrate and a maximum of 0.4 percent combustible material; (2) Ammonium nitrate with calcium carbonate and/or dolomite, containing more than 80 percent but less than 90 percent of ammonium nitrate and a maximum...

2012-10-01

335

46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.  

Code of Federal Regulations, 2011 CFR

...more than 70 percent of ammonium nitrate and a maximum of 0.4 percent combustible material; (2) Ammonium nitrate with calcium carbonate and/or dolomite, containing more than 80 percent but less than 90 percent of ammonium nitrate and a maximum...

2011-10-01

336

Removal of Nitrate from Groundwater by Cyanobacteria: Quantitative Assessment of Factors Influencing Nitrate Uptake  

PubMed Central

The feasibility of biologically removing nitrate from groundwater was tested by using cyanobacterial cultures in batch mode under laboratory conditions. Results demonstrated that nitrate-contaminated groundwater, when supplemented with phosphate and some trace elements, can be used as growth medium supporting vigorous growth of several strains of cyanobacteria. As cyanobacteria grew, nitrate was removed from the water. Of three species tested, Synechococcus sp. strain PCC 7942 displayed the highest nitrate uptake rate, but all species showed rapid removal of nitrate from groundwater. The nitrate uptake rate increased proportionally with increasing light intensity up to 100 ?mol of photons m?2 s?1, which parallels photosynthetic activity. The nitrate uptake rate was affected by inoculum size (i.e., cell density), fixed-nitrogen level in the cells in the inoculum, and aeration rate, with vigorously aerated, nitrate-sufficient cells in mid-logarithmic phase having the highest long-term nitrate uptake rate. Average nitrate uptake rates up to 0.05 mM NO3? h?1 could be achieved at a culture optical density at 730 nm of 0.5 to 1.0 over a 2-day culture period. This result compares favorably with those reported for nitrate removal by other cyanobacteria and algae, and therefore effective nitrate removal from groundwater using this organism could be anticipated on large-scale operations.

Hu, Qiang; Westerhoff, Paul; Vermaas, Wim

2000-01-01

337

Sorption of europium on zirconium oxide from aqueous solutions  

Microsoft Academic Search

Sorption of europium on zirconium oxide has been studies as a function of shaking time, concentration and nature of electrolyte. The effect of initial europium concentration and the amount of adsorbent has been investigated in the range from 6.6·10–10 to 6.6·10–8 mol·dm–3 and between 10 to 200 mg of the oxide. Maximum sorption (>99.8%) from pH 10 buffer and low

S. M. Hasany; M. H. Chaudhary

1994-01-01

338

Reaction of graphite and pyrographite with titanium and zirconium nitrides  

Microsoft Academic Search

1.A study was made of the reaction of titanium and zirconium nitrides with graphite and pyrographite in a vacuum (0.1 N\\/m2) over the temperature range 1673–2473°K at contact periods from 1 to 5 h.2.It was established that the reaction yields carbide phases which change to a MeC-MeN solid solution in an intermediate zone at the nitride interface.3.It is shown that

A. L. Burykina; T. M. Evtushok

1969-01-01

339

Atomic Mass and Nuclear Binding Energy for Zr-85 (Zirconium)  

NASA Astrophysics Data System (ADS)

This document is part of the Supplement containing the complete sets of data of Subvolume A `Nuclei with Z = 1 - 54' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms'. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Zr-85 (Zirconium, atomic number Z = 40, mass number A = 85).

Sukhoruchkin, S. I.; Soroko, Z. N.

340

Atomic Mass and Nuclear Binding Energy for Zr-93 (Zirconium)  

NASA Astrophysics Data System (ADS)

This document is part of the Supplement containing the complete sets of data of Subvolume A `Nuclei with Z = 1 - 54' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms'. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Zr-93 (Zirconium, atomic number Z = 40, mass number A = 93).

Sukhoruchkin, S. I.; Soroko, Z. N.

341

A theoretical and experimental study of hydrides in zirconium alloys  

Microsoft Academic Search

A method developed for computing the critical length and thickness of hydride plates formed in delayed hydride cracking (DHC)\\u000a in zirconium alloys is considered. The model is based on analyzing the distribution of tensile stresses in the plane of a\\u000a sharp normal tensile crack. The characteristics of hydrides formed due to DHC in reactor tubes produced from alloy Zr-2.5%\\u000a Nb

A. A. Shmakov; D. Yan; R. L. Eadie

2006-01-01

342

Calculation of the vibrational frequencies and structure of zirconium tetrahydroborate  

Microsoft Academic Search

The normal mode frequencies and corresponding vibrational assignments of zirconium tetrahydroborate (Zr(BH4)4) in T symmetry are examined theoretically using the Gaussian98 set of quantum chemistry codes. All normal modes were successfully assigned to one of the six types of motion (B?H stretch, Zr?B stretch, B?Zr?B bend, H?B?H bend, BH4 wag, and BH4 twist) predicted by a group theoretical analysis. By

James O Jensen

2003-01-01

343

Thermal diffusivity measurement of uranium–thorium–zirconium hydride  

Microsoft Academic Search

The uranium–thorium mixed zirconium hydrides of UTh4Zr10Hx (x=20, 24, 27) have been successfully fabricated without large crack by means of a Sieverts apparatus. The scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses show that UTh4Zr10Hx consist of ?-U, ThZr2Hx, and (?, ?)-ZrHx. The thermal diffusivity measurements of UTh4Zr10Hx have been performed over the temperature ranges to around 773 K

B Tsuchiya; J Huang; K Konashi; W Saiki; T Onoue; M Yamawaki

2000-01-01

344

Pressureless Sintering of Zirconium Diboride: Particle Size and Additive Effects  

Microsoft Academic Search

Zirconium diboride (ZrB2) was densified by pressureless sinte- ring using o4-wt% boron carbide and\\/or carbon as sintering aids. As-received ZrB2 with an average particle size of B2 lm could be sintered to B100% density at 19001C using a combi- nation of boron carbide and carbon to react with and remove the surface oxide impurities. Even though particle size reduction in-

William G. Fahrenholtz; Gregory E. Hilmas; Shi C. Zhang; Sumin Zhu

2008-01-01

345

Powder metallurgical fabrication of zirconium matrix cermet nuclear fuels  

Microsoft Academic Search

Two powder metallurgical fabrication methods for a zirconium-based cermet nuclear dispersion fuel with oxide microspheres\\u000a have been demonstrated. A multi-pass, cold-drawing process is shown to have excellent capability to control the final matrix\\u000a density, though it requires several high-temperature anneals during fabrication to relieve strain hardening and increase matrix–particle\\u000a bonding. Severe oxide particle damage was observed in the cold-drawn fuel

Aaron R. Totemeier; Sean M. McDeavitt

2009-01-01

346

Zirconium umbelliferonephosphate – A luminescent organic–inorganic hybrid nanomaterial  

Microsoft Academic Search

Zirconium umbelliferonephosphate (ZrO(UFP)) is prepared by nucleation in the ionic liquid [MeBu3N][NTf2]. According to electron microscopy the resulting nanoparticles exhibit mean particle diameters of about 50 nm. The organic–inorganic hybrid material ZrO(UFP) shows blue emission upon UV-excitation. Luminescence originates from the organic dye and is highly intense due to the molar amount of luminescent centers per nanoparticle. The as-prepared material turns

Marcus Roming; Claus Feldmann

2011-01-01

347

Raman spectra of zirconium oxychloride crystalline hydrate and solutions  

Microsoft Academic Search

Raman spectra of zirconium oxychloride crystalline hydrate and its deuteroanalogs in the 50-4000 cm⁻¹ region have been obtained and examined. They have been compared with the spectra of solutions. In the region of nu\\/sub Zr-O\\/ vibrations the Raman spectrum of the solution has been resolved into its components with the aid of a computer. Spectral properties of the nu\\/sub Zr-OH\\/

G. V. Kozhevnikova; L. A. Myund; K. A. Burkov

1988-01-01

348

Stable supported lipid bilayers on zirconium phosphonate surfaces.  

PubMed

Supported lipid bilayers that can fully represent biological cell membranes are attractive biomimetic models for biophysical and biomedical applications. In this study, we develop a new approach to engineering stable supported lipid membranes and demonstrate their utility for the study of protein-membrane interactions. This system uses a zirconium phosphonate monolayer to modify a substrate and generate a reactive surface that tethers the lipid membrane via a highly covalent bond between surface zirconium ions and divalent phosphate groups in the lipid assembly, for example, from phosphatidic acid. An advantage of the approach is that the zirconium phosphonate modifier can be applied to nearly any surface, allowing the same methods to be used on glass, gold, silicon, or plastic supports. The lipid bilayers are formed by vesicle fusion, either directly on the zirconated surface to form symmetric bilayers or following deposition of a Langmuir-Blodgett lipid layer to generate asymmetric bilayers. The membrane formation was studied by surface plasmon resonance enhanced ellipsometry (SPREE) as the phosphatidic acid composition was varied. We found that 10% of phosphatidic acid generates supported lipid bilayers stable to dehydration. The two-dimensional fluidity of these systems was characterized by fluorescence recovery after photobleaching (FRAP) measurements. Uniform, mobile supported lipid bilayers with lipid diffusion coefficients of approximately 4 mum(2)/s were obtained. SPREE was also used to measure kinetic parameters of the binding of melittin, a bee venom peptide, to asymmetric lipid bilayers with different electrostatic properties. The results are comparable to those obtained by other research groups, confirming that the model membranes behave as expected. Overall, the results of this study prove that supported lipid bilayers on zirconium phosphonate inorganic surfaces make up an attractive biomimetic system that is highly stable, can be used with multiple substrates, and does not require any biomolecule synthetic modifications. PMID:19711922

Fabre, Roxane M; Talham, Daniel R

2009-11-01

349

Wear Analysis in THA Utilizing Oxidized Zirconium and Crosslinked Polyethylene  

Microsoft Academic Search

Oxidized zirconium, a material with a ceramic surface on a metal substrate, and highly cross-linked polyethylene are two materials\\u000a developed to reduce wear. We measured in vivo femoral head penetration in patients with these advanced bearings. We hypothesized\\u000a the linear wear rates would be lower than those published for cobalt-chrome and standard polyethylene. We retrospectively\\u000a reviewed a select series of

Kevin L. Garvin; Curtis W. Hartman; Jimmi Mangla MBBS; Nathan Murdoch; John M. Martell

2009-01-01

350

The abundances of zirconium and hafnium in the solar system  

Microsoft Academic Search

The concentrations of zirconium and hafnium have been determined in the Orgueil, Murchison, Allende, Bruderheim, and Alais meteorites by radiochemical neutron activation analysis. The mean Zr\\/Hf weight ratio in the first four of these meteorites is 31.3 (plus or minus 2.2), indicating no major fractionation of Zr from Hf. Alais contains anomalously high amounts of many refractory lithophile elements, including

R. Ganapathy; G. M. Papia; LAWRENCE GROSSMAN

1976-01-01

351

Synthesis, formation and characterization of zirconium titanate (ZT) powders  

Microsoft Academic Search

Zirconium titanate (ZrTiO4) powders have been prepared and characterised by differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) techniques. The effect of calcination temperature, dwell time and heating\\/cooling rates on phase formation, morphology and particle size distribution of the powders are examined. The calcination temperature and dwell time have been found to have

S. Ananta; R. Tipakontitikul; T. Tunkasiri

2003-01-01

352

Separation of zirconium--hafnium by nitride precipitation  

Microsoft Academic Search

A method is described for the separation of a light reactive metal (e.g., zirconium) from a heavy reactive metal (e.g., hafnium) by forming insoluble nitrides of the metals in a molten metal solvent (e.g., copper) inert to nitrogen and having a suitable density for the light metal nitride to form a separate phase in the upper portion of the solvent

R. N. Anderson; N. A. Parlee

1977-01-01

353

Electrochemical separation of zirconium from hafnium using chloraluminate melts  

Microsoft Academic Search

This paper reports on the electroreduction of Hf(IV) in chloraluminate melts of similar compositions and on the electrochemical separation of zirconium from hafnium using low-melting chloraluminate melts. Results indicated that the addition of HfClâ to AlClâ-NaCl melts (ranging in composition from 50.3 to 52 mol % AlClâ) resulted in a poorly defined voltammetric reduction wave that occurs at potentials somewhat

M. Katabua; P. Rolland; G. Mamantov; L. Hulett

1982-01-01

354

Computer simulation of zirconium-hafnium separation by countercurrent extraction  

Microsoft Academic Search

In carrying out research and development on an improved method for production of reactor-grade zirconium oxide, the Bureau of Mines has prepared a computer program capable of accurately predicting the stage-by-stage performance of a multistage countercurrent solvent extraction system for extractant. The results were used to plan laboratory experiments using a multistage countercurrent mixer-settler unit. The number of extractor stages,

1981-01-01

355

Continuous ion exchange separation of zirconium and hafnium  

SciTech Connect

A pressurized continuous annular chromatograph (CAC) has been developed for truly continuous ion exchange preparative separations. This device utilizes a slowly rotating annular bed of sorbent material, fixed multiple feed points, and fixed withdrawal locations. Most of our investigations have been performed with a 28-cm-diam by 60-cm-long CAC, but a larger model has recently been designed and constructed. A detailed study has been made of the separation of copper, nickel, and cobalt components from a simulated carbonate leach liquor of the Caron process for recovering nickel and cobalt from laterite ores. Recent studies have investigated the ion exchange separation of zirconium and hafnium from a sulfate feed solution. Nuclear reactor-grade zirconium, containing < 0.01 wt % hafnium, and hafnium, containing < 1% zirconium, have been continuously prepared using cation exchange resin in the pressurized CAC. This device, because of its continuous feed and product withdrawal, its adaptability to largescale operations, and its ability to separate many components, is expected to make chromatography a more competitive process in the industrial sector.

Begovich, J.M.; Sisson, W.G.

1981-01-01

356

Review of the oxidation rate of zirconium alloys.  

SciTech Connect

The oxidation of zirconium alloys is one of the most studied processes in the nuclear industry. The purpose of this report is to provide in a concise form a review of the oxidation process of zirconium alloys in the moderate temperature regime. In the initial ''pre-transition'' phase, the surface oxide is dense and protective. After the oxide layer has grown to a thickness of 2 to 3 {micro}m's, the oxidation process enters the ''post-transition'' phase where the density of the layer decreases and becomes less protective. A compilation of relevant data suggests a single expression can be used to describe the post-transition oxidation rate of most zirconium alloys during exposure to oxygen, air, or water vapor. That expression is: Oxidation Rate = 13.9 g/(cm{sup 2}-s-atm{sup -1/6}) exp(-1.47 eV/kT) x P{sup 1/6} (atm{sup 1/6}).

Causey, Rion A. (Sandia National Laboratories, Livermore, CA); Cowgill, Donald F. (Sandia National Laboratories, Livermore, CA); Nilson, Robert H. (Sandia National Laboratories, Livermore, CA)

2005-11-01

357

Nitrite and Nitrate in Cancer  

Microsoft Academic Search

\\u000a \\u000a \\u000a \\u000a \\u000a \\u000a • \\u000a \\u000a \\u000a \\u000a Studies in animal models established the feasibility of sodium nitrite contributing to gastric carcinogenesis primarily via\\u000a conversion to nitrosamines.\\u000a \\u000a \\u000a \\u000a \\u000a \\u000a • \\u000a \\u000a \\u000a \\u000a Most animal studies did not corroborate this assumption.\\u000a \\u000a \\u000a \\u000a \\u000a • \\u000a \\u000a \\u000a \\u000a Exposure of humans to nitrates is primarily from vegetables.\\u000a \\u000a \\u000a \\u000a \\u000a • \\u000a \\u000a \\u000a \\u000a Since a fraction of nitrate is reduced to nitrite by oral bacteria, the largest source of nitrite exposure is also

David M. Klurfeld

358

Dietary nitrate and O? consumption during exercise.  

PubMed

Recent studies have investigated the influence of dietary nitrate supplementation on the physiological responses to exercise. Specifically, it has been reported that enhancing nitric oxide (NO) bioavailability through supplementation of the diet with nitrate salts or nitrate-rich beetroot juice reduces the O(2) cost of exercise and improves exercise performance. The lower O(2) cost for a given sub-maximal work rate following nitrate ingestion indicates that muscle efficiency is enhanced either as a consequence of a reduced energy cost of contraction or enhanced mitochondrial efficiency. The positive effects of nitrate supplementation on the O(2) cost of sub-maximal exercise can be manifested acutely (i.e. 2.5 h following ingestion) and maintained for at least 15 days if supplementation is continued. Most recently, the influence of dietary nitrate supplementation on time trial performance in competitive cyclists has been investigated. Studies have shown a 1-2% reduction in the time to complete time trial distances between 4 and 16 km. The dose of nitrate that has been shown to improve exercise efficiency can readily be achieved through the consumption of 0.5 litre of beetroot juice or an equivalent high-nitrate foodstuff. Following a 5- to 6-mmol bolus of nitrate, plasma [nitrite] typically peaks within 2-3 h and remains elevated for a further 6-9 h before declining towards baseline. Therefore, consuming nitrate approximately 3 h prior to competition or training is recommended if athletes wish to explore the ergogenic potential of nitrate supplementation. PMID:23075552

Jones, Andrew M; Bailey, Stephen J; Vanhatalo, Anni

2012-10-15

359

Nitrate uptake, nitrate reductase distribution and their relation to proton release in five nodulated grain legumes.  

PubMed

Nitrate uptake, nitrate reductase activity (NRA) and net proton release were compared in five grain legumes grown at 0.2 and 2 mM nitrate in nutrient solution. Nitrate treatments, imposed on 22-d-old, fully nodulated plants, lasted for 21 d. Increasing nitrate supply did not significantly influence the growth of any of the species during the treatment, but yellow lupin (Lupinus luteus) had a higher growth rate than the other species examined. At 0.2 mM nitrate supply, nitrate uptake rates ranged from 0.6 to 1.5 mg N g(-1) d(-1) in the order: yellow lupin > field pea (Pisum sativum) > chickpea (Cicer arietinum) > narrow-leafed lupin (L angustifolius) > white lupin (L albus). At 2 mM nitrate supply, nitrate uptake ranged from 1.7 to 8.2 mg N g(-1) d(-1) in the order: field pea > chickpea > white lupin > yellow lupin > narrow-leafed lupin. Nitrate reductase activity increased with increased nitrate supply, with the majority of NRA being present in shoots. Field pea and chickpea had much higher shoot NRA than the three lupin species. When 0.2 mM nitrate was supplied, narrow-leafed lupinreleased the most H+ per unit root biomass per day, followed by yellow lupin, white lupin, field pea and chickpea. At 2 mM nitrate, narrow-leafed lupin and yellow lupin showed net proton release, whereas the other species, especially field pea, showed net OH- release. Irrespective of legume species and nitrate supply, proton release was negatively correlated with nitrate uptake and NRA in shoots, but not with NRA in roots. PMID:12234143

Fan, X H; Tang, C; Rengel, Z

2002-09-01

360

9 CFR 319.2 - Products and nitrates and nitrites.  

Code of Federal Regulations, 2013 CFR

...false Products and nitrates and nitrites. 319...and Animal Products FOOD SAFETY AND INSPECTION...319.2 Products and nitrates and nitrites. Any...there is a standard in this part and to which nitrate or nitrite is...

2013-01-01

361

78 FR 32690 - Certain Ammonium Nitrate From Ukraine  

Federal Register 2010, 2011, 2012, 2013

...Review)] Certain Ammonium Nitrate From Ukraine Determination On the basis of the record...order on certain ammonium nitrate from Ukraine would be likely to lead to continuation...entitled Certain Ammonium Nitrate from Ukraine: Investigation No....

2013-05-31

362

70. INTERIOR VIEW OF AMMONIUM NITRATE HOUSE, LOOKING AT AMMONIUM ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

70. INTERIOR VIEW OF AMMONIUM NITRATE HOUSE, LOOKING AT AMMONIUM NITRATE IN STORAGE. APRIL 18, 1919. - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

363

46 CFR 148.227 - Calcium nitrate fertilizers.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Calcium nitrate fertilizers. 148.227...Certain Materials § 148.227 Calcium nitrate fertilizers. This part does not apply to commercial grades of calcium nitrate fertilizers consisting...

2011-10-01

364

46 CFR 148.227 - Calcium nitrate fertilizers.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Calcium nitrate fertilizers. 148.227...Certain Materials § 148.227 Calcium nitrate fertilizers. This part does not apply to commercial grades of calcium nitrate fertilizers consisting...

2012-10-01

365

NITRATE IN GROUNDWATER ASSOCIATED WITH AGRICULTURAL SYSTEMS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Data from the U.S.G.S. NAWQA program confirm hypotheses about the hydrologic and agricultural factors useful for defining spatial trends in groundwater vulnerability to nitrate contamination. Unconfined aquifers are most vulnerable to nitrate contamination with unconsolidated aquifers more vulnerabl...

366

NITRATE CONTAMINATION OF GROUND WATER (GW-761)  

EPA Science Inventory

The occurrence of nitrate and related compounds in ground water is discussed from the perspectives of its natural as well as anthropogenic origins. A brief explanation of the nitrogen cycle touches on the production as well as utilization of ammonia, nitrite, nitrate, and nitrog...

367

Sources of nitrate to ground water  

Microsoft Academic Search

There are a multitude of sources of nitrate to ground waters. Nitrogen undergoes a complex series of biochemical, chemical, and physical reactions in soils and waters, and thus the source of nitrate in ground waters is often difficult or impossible to ascertain with any degree of certainty. However, highly contaminated ground waters often have local sources that can be controlled.

Dennis Keeney; Robert A. Olson

1986-01-01

368

Electrophilic Nitration of Alkanes with Nitronium Hexafluorophosphate  

NASA Astrophysics Data System (ADS)

Nitration of alkanes such as methane, ethane, propane, n-butane, isobutane, neopentane, and cyclohexane was carried out with nitronium hexafluorophosphate in methylene chloride or nitroethane solution. Nitration of methane, albeit in poor yield, required protolytic activation of the nitronium ion. The results indicate direct electrophilic insertion of NO2+ into C-H and C-C ? -bonds.

Olah, George A.; Ramaiah, Pichika; Surya Prakash, G. K.

1997-10-01

369

High Dose Potassium-Nitrate Chemical Dosimeter.  

National Technical Information Service (NTIS)

This dosimeter is used to control 10 kGY-order doses (1 Mrad). Nitrate suffers a radiolitic reduction phenomena, which is related to the given dose. The method to use potassium nitrate as dosimeter is described, as well as effects of the temperature of ir...

E. M. Dorda de Cancio S. S. Munoz

1982-01-01

370

THERMAL DECOMPOSITION OF URANYL NITRATE HEXAHYDRATE  

Microsoft Academic Search

The thermal decomposition of uranyl nitrate hexahydrate was studied in ; the temperature range of 250to 400 deg C at atmospheric and at <0.1 mm pressure. ; The intermediate and final products of the decomposition were determined. The ; decomposition follows a zero-order reaction until less than half of the uranyl ; nitrate remains. The remaining portion of the decomposition

Ondrejcin

1963-01-01

371

HEALTH EFFECTS OF NITRATES IN WATER  

EPA Science Inventory

A multi faceted study of the health effects of nitrate in drinking water using epidemiological and toxicological techniques is reported. The results of the epidemiological studies indicate that infants consuming appreciable amounts of water high in nitrates in the form of powdere...

372

The influence of Glyceria maxima and nitrate input on the composition and nitrate metabolism of the dissimilatory nitrate-reducing bacterial community  

Microsoft Academic Search

The influence of nitrate addition and the presence of Glyceria maxima (reed sweetgrass) on the composition and nitrate metabolism of the dissimilatory nitrate-reducing bacterial community was investigated. Anoxic freshwater sediment was incubated in pots with or without G. maxima and with or without addition of nitrate. After incubation the sediments were sampled. Dilution series of these sediment samples were incubated

Nijburg W. J; H. J. Laanbroek

1997-01-01

373

Methemoglobinemia: nitrate toxicity in rural America  

SciTech Connect

Nitrates are frequently found in vegetables and ground water. Nitrate levels in ground water have increased over the past two decades because of the heightened use of nitrogenous fertilizers. Following ingestion, nitrates are converted to nitrites by fecal organisms. Nitrites are absorbed and form methemoglobin, which interferes with the oxygen-carrying capacity of hemoglobin. Infants are particularly susceptible to nitrate poisoning because fetal hemoglobin is more readily oxidized to methemoglobin. In infants, the most common source of nitrate exposure is well water, which is mixed with infant formula. Affected infants may present with asymptomatic cyanosis, which can progress to dyspnea and lethargy or coma. Blood methemoglobin concentrations are elevated. Treatment consists of the administration of oxygen and intravenous and oral methylene blue.24 references.

Kross, B.C.; Ayebo, A.D.; Fuortes, L.J. (University of Iowa College of Medicine, Iowa City (United States))

1992-07-01

374

Nitrate removal from drinking water -- Review  

SciTech Connect

Nitrate concentrations in surface water and especially in ground water have increased in Canada, the US, Europe, and other areas of the world. This trend has raised concern because nitrates cause methemoglobiinemia in infants. Several treatment processes including ion exchange, biological denitrification, chemical denitrification, reverse osmosis, electrodialysis, and catalytic denitrification can remove nitrates from water with varying degrees of efficiency, cost, and ease of operation. Available technical data, experience, and economics indicate that ion exchange and biological denitrification are more acceptable for nitrate removal than reverse osmosis. Ion exchange is more viable for ground water while biological denitrification is the preferred alternative for surface water. This paper reviews the developments in the field of nitrate removal processes.

Kapoor, A.; Viraraghavan, T. [Univ. of Regina, Saskatchewan (Canada)

1997-04-01

375

Analysis of C2-C4 peroxyacyl nitrates and C1-C5 alkyl nitrates with a non-polar capillary column.  

PubMed

Analysis of peroxyacetyl nitrate (PAN), peroxypropionyl nitrate, peroxy-n-butyryl nitrate, and peroxyisobutyryl nitrate (PiBN) with a non-polar capillary column indicated PAN not to coelute with PiBN. Isopropyl nitrate coeluted with PAN, n-butyl nitrate with PiBN and ethyl nitrate with chloroform, at oven temperature 30 degrees C. In addition methyl nitrate, n-propyl nitrate, 2-butyl nitrate, 2-methyl-2-butyl nitrate, 3-pentyl nitrate and 2-pentyl nitrate were studied. Their response factors in the electron-capture detector were also determined. Tetrachloroethylene, carbon tetrachloride and chloroform whose vapors occur in the atmosphere were also examined. PMID:11358259

Glavas, S

2001-04-27

376

Pseudo-constitutivity of nitrate-responsive genes in nitrate reductase mutants.  

PubMed

In fungi, transcriptional activation of genes involved in NO3(-) assimilation requires the presence of an inducer (nitrate or nitrite) and low intracellular concentrations of the pathway products ammonium or glutamine. In Aspergillus nidulans, the two transcription factors NirA and AreA act synergistically to mediate nitrate/nitrite induction and nitrogen metabolite derepression, respectively. In all studied fungi and in plants, mutants lacking nitrate reductase (NR) activity express nitrate-metabolizing enzymes constitutively without the addition of inducer molecules. Based on their work in A. nidulans, Cove and Pateman proposed an "autoregulation control" model for the synthesis of nitrate metabolizing enzymes in which the functional nitrate reductase molecule would act as co-repressor in the absence and as co-inducer in the presence of nitrate. However, NR mutants could simply show "pseudo-constitutivity" due to induction by nitrate which accumulates over time in NR-deficient strains. Here we examined this possibility using strains which lack flavohemoglobins (fhbs), and are thus unable to generate nitrate internally, in combination with nitrate transporter mutations (nrtA, nrtB) and a GFP-labeled NirA protein. Using different combinations of genotypes we demonstrate that nitrate transporters are functional also in NR null mutants and show that the constitutive phenotype of NR mutants is not due to nitrate accumulation from intracellular sources but depends on the activity of nitrate transporters. However, these transporters are not required for nitrate signaling because addition of external nitrate (10 mM) leads to standard induction of nitrate assimilatory genes in the nitrate transporter double mutants. We finally show that NR does not regulate NirA localization and activity, and thus the autoregulation model, in which NR would act as a co-repressor of NirA in the absence of nitrate, is unlikely to be correct. Results from this study instead suggest that transporter-mediated NO?? accumulation in NR deficient mutants, originating from traces of nitrate in the media, is responsible for the constitutive expression of NirA-regulated genes, and the associated phenotype is thus termed "pseudo-constitutive". PMID:23454548

Schinko, Thorsten; Gallmetzer, Andreas; Amillis, Sotiris; Strauss, Joseph

2013-02-27

377

Pseudo-constitutivity of nitrate-responsive genes in nitrate reductase mutants  

PubMed Central

In fungi, transcriptional activation of genes involved in NO3- assimilation requires the presence of an inducer (nitrate or nitrite) and low intracellular concentrations of the pathway products ammonium or glutamine. In Aspergillus nidulans, the two transcription factors NirA and AreA act synergistically to mediate nitrate/nitrite induction and nitrogen metabolite derepression, respectively. In all studied fungi and in plants, mutants lacking nitrate reductase (NR) activity express nitrate-metabolizing enzymes constitutively without the addition of inducer molecules. Based on their work in A. nidulans, Cove and Pateman proposed an “autoregulation control” model for the synthesis of nitrate metabolizing enzymes in which the functional nitrate reductase molecule would act as co-repressor in the absence and as co-inducer in the presence of nitrate. However, NR mutants could simply show “pseudo-constitutivity” due to induction by nitrate which accumulates over time in NR-deficient strains. Here we examined this possibility using strains which lack flavohemoglobins (fhbs), and are thus unable to generate nitrate internally, in combination with nitrate transporter mutations (nrtA, nrtB) and a GFP-labeled NirA protein. Using different combinations of genotypes we demonstrate that nitrate transporters are functional also in NR null mutants and show that the constitutive phenotype of NR mutants is not due to nitrate accumulation from intracellular sources but depends on the activity of nitrate transporters. However, these transporters are not required for nitrate signaling because addition of external nitrate (10 mM) leads to standard induction of nitrate assimilatory genes in the nitrate transporter double mutants. We finally show that NR does not regulate NirA localization and activity, and thus the autoregulation model, in which NR would act as a co-repressor of NirA in the absence of nitrate, is unlikely to be correct. Results from this study instead suggest that transporter-mediated NO3- accumulation in NR deficient mutants, originating from traces of nitrate in the media, is responsible for the constitutive expression of NirA-regulated genes, and the associated phenotype is thus termed “pseudo-constitutive”.

Schinko, Thorsten; Gallmetzer, Andreas; Amillis, Sotiris; Strauss, Joseph

2013-01-01

378

PREPARATION OF DIBASIC ALUMINUM NITRATE  

DOEpatents

A method is given for the preparation and recovery of basic aluminum nltrates having an OH: Al ratio of at least two, comprising two steps. First, metallic aluminum is dissolved in aqueous Al(NO/sub 3/)/sub 3/, in the presence of a small quantity of elemental or ionic mercury, to increase its Al: NO/sub 3/ ratio into the range 1 to 1.2. The resulting aqueous solution is then added to an excess of a special organic solvent, typically a mixture of five parts methanol and six parts diethyl ether, whereupon the basic aluminum nitrate, e.g. Al/sub 6/(OH)/sub 13/-(NO/sub 3/)/sub 5/, recoverably precipitates.

Gresky, A.T.; Nurmi, E.O.; Foster, D.L.; Wischow, R.P.; Savolainen, J.E.

1960-04-01

379

Zirconium oxides formed by hydrolytic condensation of alkoxides and parameters that affect their morphology  

Microsoft Academic Search

When zirconium oxides are formed via hydrolytic condensation of zirconium alkoxides, the particle size and morphology of the resultant zirconia is strongly affected by certain parameters during the condensation. These parameters include: the type of alkyl group in the alkoxide, water\\/alkoxide ratio, molecular separation of species, and the reaction temperature. The particle size and the morphology in turn affect the

Bulent E. Yoldas

1986-01-01

380

Corrosion Cracking of Zirconium Cladding Tubes (A Review). I. Methods of Study and Mechanisms of Fracture  

Microsoft Academic Search

Methods of study and criteria of evaluation of stress corrosion cracking (SCC) of zirconium alloys are generalized as applied to cladding tubes of nuclear reactors. Mechanisms of SCC in zirconium cladding tubes in iodine-bearing media (iodine vapors, solution of iodine in methanol, etc.) are described. Metallographic and fracture features of damage in these media are analyzed. Data on cracking rates

S. A. Nikulin; A. B. Rozhnov

2005-01-01

381

On the evolution of morphology of zirconium sponge during reduction and distillation  

Microsoft Academic Search

High purity zirconium metal is produced by magnesio-thermic reduction of zirconium tetrachloride followed by vacuum distillation. The reduction process is carried out in a batch giving metal sponge and magnesium chloride in the reduced mass. The sponge is purified to using by vacuum distillation. The morphology of the sponge formed during the reduction and its influence on further processing has

K. Kapoor; C. Padmaprabu; D. Nandi

2008-01-01

382

Lithium aluminate/zirconium material useful in the production of tritium  

DOEpatents

A composition is described useful in the production of tritium in a nuclear reactor. Lithium aluminate particles are dispersed in a matrix of zirconium. Tritium produced by the reactor of neutrons with the lithium are absorbed by the zirconium, thereby decreasing gas pressure within capsules carrying the material.

Cawley, W.E.; Trapp, T.J.

1984-10-09

383

ELECTROCHEMICAL BEHAVIOR OF ZINC-ZIRCONIUM ALLOYS IN THE PRESENCE OF FUSED CHLORIDES  

Microsoft Academic Search

The electrochemical behavior of zinc-zirconium alloys was studied by ; determinating the electromotive force of galvanic cells which comprise an alloy ; electrode, a pure metal electrode (zinc or zirconium), and an electrolyte made up ; of a eutectic mixture of potassium chloride and lithium chloride. When the ; galvanic chain comprises an alloy electrode and a pure zinc electrcde,

C. Decroly; R. Vaghar

1961-01-01

384

Rheological study of the gelation kinetics of the scleroglucan—zirconium system  

Microsoft Academic Search

The formation kinetics of scleroglucan-zirconium gels was studied using rheological measurements. It was possible to determine such kinetics by following the change in solution elastic modulus as a function of time. Gelation kinetics was found to increase vs. polymer concentration according to a power law function. In contrast, when zirconium concentration was increased, gelation kinetics was found to increase, reaching

Abdelaziz Omari

1995-01-01

385

Microprobe study of the surface of a zeolite-containing zirconium-silicate catalyst  

SciTech Connect

X-ray microprobe techniques have been used to study the chemical and phase compositions of a zeolite-containing zirconium-silicate catalyst synthesized by introducing crystallites of the zeolite into the hydrosol and hydrogel of the zirconium silicate. It is shown that dispersion of the zeolite crystallites occurs in this process.

Mel'nikov, V.B.; Chukin, G.D.; Nefedov, B.K.

1987-02-01

386

Ultrasonic Estimation of Hydride Degradation of Zirconium Pressure Tubes of RBMK Fuel Channel  

Microsoft Academic Search

Fuel channels of nuclear reactors, which are major structural elements of a reactor core, have to meet strict requirements in terms of operational reliability. The middle part of the fuel channel, located in a graphite stack, is a tube made of a zirconium-2.5% niobium alloy. However, zirconium alloys can pick up hydrogen during operation as a consequence of corrosion reaction

Rymantas KAZYS; Reimondas SLITERIS; Liudas MAZEIKA; Algirdas VOLEISIS

387

Inorganic ion-exchangers for the removal of zirconium, hafnium and niobium radioisotopes from aqueous solutions  

Microsoft Academic Search

Studies were made on the uptake of zirconium, hafnium and niobium isotopes onto zeolites and amorphous zirconium phosphate. Ion exchange capacities and distribution coefficients were determined and the influence of pH examined. Kinetic experiments were made to determine the rates of uptake of the radioisotopes on the exchangers and to measure the leaching of isotopes from preloaded exchangers by synthetic

A. Dyer; F. H. Kadhim

1989-01-01

388

SEPARATION OF ZIRCONIUM AND HAFNIUM USING ANIONEXCHANGE RESINS. PART II. INFLUENCE OF PHYSICAL FACTORS  

Microsoft Academic Search

The influence of some factors on the differential elution of hafnium and ; zirconium on Amberlite IRA 400 anionexchange resin was investigated to ascertain ; the optimum conditions for the separation of hafnium from zirconium. The data ; obtained from experiments on 200 mg mixed oxide were successfully applied to 5 g ; mixed oxide loads on Amberlite IRA 400

K. S. Rajan; J. Gupta

1957-01-01

389

SEPARATION OP ZIRCONIUM \\/IV\\/ FROM HAFNIUM \\/IV\\/ ON VARIOUS TYPES OF SELECTIVE ION-EXCHANGERS  

Microsoft Academic Search

Results of the studies on separation of hefnium \\/IV\\/ from zirconium \\/IV\\/ by frontal analysis on chelating ion-exchangers of different types have been presented. The phosphonic ion-exchanger Duolite ES-63 proved to be the best in zirconium sulphate purification from hafnium \\/IV\\/ among the examined chelating ion-exchangers.

Z. HUBICKI

1988-01-01

390

THE NITROPHOS EXTRACTION PROCESS FOR THE SEPARATION OF ZIRCONIUM AND HAFNIUM  

Microsoft Academic Search

The several possible processes for separating zirconium and hafnium are ; reviewed briefly and the reasons for selecting the Nitrophos liquid-liquid ; extraction process, by means of a nitric acid-tributyl phosphate system, are ; given. The laboratory and pilot plant experiments are described and the data ; presented. Under the conditions studied, reactor-grade zirconium can be prepared ; in a

W. H. Keller; I. S. Zonis

1959-01-01

391

Reactions of powders of zirconium and niobium carbides in their homogeneity ranges with some acids  

Microsoft Academic Search

In the work described below a study was made of the reactions of zirconium and niobium carbides in their homogeneity ranges with some mineral acids. It was considered of great interest also to investigate the gaseous products of acid decomposition of the carbides. Experiments were carried out, using hydrochloric, sulfuric, and nitric acids as reactants, on powders of the zirconium

V. P. Kopylova; V. I. Kornilova; T. N. Nazarchuk; V. B. Fedorus

1980-01-01

392

Room temperature reaction between uranyl nitrate hexahydrate and rubidium nitrate and polymerisation during denitration of rubidium uranyl nitrate at elevated temperatures  

Microsoft Academic Search

The interaction between uranyl nitrate hexahydrate (UNH) and rubidium nitrate in solid state at elevated temperatures has been studied for several compositions using simultaneous thermal analysis techniques (TG–DTA–EGA), X-ray diffraction and IR spectral measurements. The formation of rubidium uranyl nitrate has been observed in rubidium nitrate rich mixtures even at ambient temperature during mixing of the two nitrates in solid

Bhupesh B. Kalekar; K. V. Rajagopalan; P. V. Ravindran

2010-01-01

393

Preparation and properties of uniform mixed and coated colloidal particles. Part 5. Zirconium compounds  

SciTech Connect

Colloidal dispersions of uniform spherical particles by zirconium basic sulphate and zirconium oxy-basic carbonate were prepared by ageing zirconium sulphate solutions at elevated temperatures in the presence of urea. Different chemical compositions of the above products resulted when the ageing temperature was altered. Depending on the nature of the original solids, calcination at 800 C resulted in the formation of tetragonal or monoclinic zirconia. Under certain conditions a mixed phase, including cubic zirconia, has also been identified. The particle morphology was retained during these transformations. Coprecipitation in mixed solutions of zirconium and yttrium salts aged at 80 C yielded composite spherical particles of basic carbonate with a zirconium to yttrium ratio of the solid similar to that used in the initial solution.

Alken, B.; Hsu, W.P.; Matijevic, E.

1990-01-01

394

Preparation of complexes of zirconium and hafnium tetrachlorides with phosphorus oxychloride  

SciTech Connect

This patent describes an improvement in a method for separating hafnium chloride from zirconium chloride using a distillation column, with a hafnium chloride enriched vapor stream taken from the top of the column and a zirconium enriched chloride stream taken from the bottom of the column. The improvement comprising: purifying the zirconium-hafnium chloride in a molten salt purification vessel prior to or after introduction into the distillation column to substantially eliminate iron chloride from the zirconium-hafnium chloride by at least periodically removing iron chloride from the molten salt purification vessel by electrochemically plating iron onto an electrode in the molten salt purification vessel. The molten salt in the molten salt purification vessel consisting essentially of a mixture of chlorides selected from the group consisting of alkali metals, alkaline earth metals, zirconium, hafnium, aluminum, manganese, and zinc.

Snyder, T.S.; Stoltz, R.A.

1989-09-12

395

Determination of zirconium and hafnium in the presence of one another  

SciTech Connect

The prospective uses of zirconium and hafnium in present day technology are important and varied; these metals find their greatest use in nuclear power engineering. Because of the well-known difference between zirconium and hafnium in the absorption of thermal neutrons, it is very important to obtain pure zirconium with minimum hafnium content and vice versa. The separation of these elements that are so similar in chemical properties is exceedingly complicated. There are difficulties in the analytical monitoring of the separation processes, and in the determination of the elements in the presence of one another in various materials, viz. zirconium against a hafnium background and vice versa. In the present review they describe the present state of the problem of zirconium and hafnium determination in presence of one another, and they note the advances and the unsolved problems in this field of analytical chemistry.

Serbinovich, V.V.; Antonovich, V.P.; Pshetakovskaya, N.A.

1986-12-20

396

Fused salt process for purifying zirconium and/or hafnium tetrachlorides  

SciTech Connect

This patent describes a fused salt process for continuously purifying zirconium and/or hafnium tetrachloride dissolved in a molten bath in a vessel. It comprises: maintaining a mass of a suitable mixture of salts, including zirconium and/or hafnium tetrachloride; heating the mixture of salts to a temperature at or immediately below the vaporization temperature of the zirconium and/or hafnium tetrachloride at which temperature the mixture of salts is fused to form a molten, tetrachloride-dissolving bath; continuously introducing into the dissolving bath a zirconium and/or hafnium tetrachloride powder; heating a portion of the dissolving bath in situ to a temperature higher than the vaporization temperature of the zirconium and/or hafnium tetrachloride so as to vaporize the tetrachloride; internally circulating the dissolving bath whereby the portion of the dissolving bath at the high temperature circulate with the bath at the lower temperature.

Lee, E.D.

1991-04-23

397

Effect of Sulfur and Zirconium on the Machinability and Mechanical Properties of AISI 1045 Steels  

NASA Astrophysics Data System (ADS)

The effects of small increases of sulfur and addition of zirconium in conjunction with sulfur on the machinability and mechanical properties of laboratory-produced AISI 1045 steels have been investigated. Machinability was measured in terms of cutting energy per unit volume of metal machined. With increasing sulfur, there is a linear increase in sulfide volume fraction and improvement in machinability. Ductility parameters such as tensile reduction in area and impact shelf energy, however, significantly decrease with sulfur, particularly in the transverse direction. Addition of zirconium causes formation of manganese-zirconium sulfides and increased globularity. Although further improvement in machinability by zirconium addition is not evident, there is a significant improvement in transverse impact properties by zirconium addition for steels containing high sulfur. The study suggests that an optimum combination of higher sulfur for improved machinability and zironium for better impact properties yields a steel with acceptable machining and ductility criteria.

Bhattacharya, Debanshu

1981-06-01

398

Inhibition of nitrate tolerance without reducing vascular response during eccentric dosing of nitrates.  

PubMed

It has been reported that the nitrate tolerance related to continuous dosing of nitrates reduces drug efficacy, and therefore eccentric dosing of nitrates is recommended. In this study, we investigated the appearance of nitrate tolerance related to continuous dosing of nitrates and prevention of nitrate tolerance during eccentric dosing by comparing the grade of coronary dilatation after sublingual nitroglycerin. Of 26 patients with ischemic heart disease who underwent elective cardiac catheterization, 8 patients were continuously administered nitrates, 8 patients were eccentrically administered nitrates, and 10 patients were not treated. We compared the coronary response to sublingual nitroglycerin among the 3 groups. In a coronary vessel without significant stenosis, the coronary vessel area, coronary lumen area, and mean coronary blood flow velocity after sublingual nitroglycerin were measured using intravascular ultrasound (IVUS). In the continuous dosing group, the maximal rate of change in the vessel area after sublingual nitroglycerin was 105 +/- 1 (mean +/- SEM) %, significantly lower than those in the untreated group and the eccentric dosing group (114 +/- 2%, 114 +/- 2%) (p < 0.01, respectively). In conclusion, eccentric dosing of nitrates inhibited the appearance of nitrate tolerance without reducing vascular response. PMID:17283867

Morii, Hideki; Naito, Norikatsu; Nakano, Kazue; Kanamasa, Ken

2006-10-01

399

NITRATE REDUCTION AND ASSIMILATION IN CHLORELLA  

PubMed Central

1. Nitrate reduction and assimilation have been studied in Chlorella pyrenoidosa under growth conditions by observing effects on the CO2/O2 gas exchange quotient. 2. During assimilation of glucose in the dark, nitrate reduction is noted as an increase in the R.Q. to about 1.6 caused by an increased rate of carbon dioxide production. 3. During photosynthesis at low light intensity nitrate reduction is evidenced by a reduction in the CO2O2 quotient to about 0.7 caused by a decreased rate of carbon dioxide uptake. 4. Chlorella will assimilate nitrogen from either nitrate or ammonia. When both sources are supplied, only ammonia is utilized and no nitrate reduction occurs. It is inferred that under the usual conditions of growth nitrate is reduced only at a rate required for subsequent cellular syntheses. The effect of nitrate reduction on the CO2O2 quotient therefore provides a measure of the relative rate of nitrogen assimilation. 5. Over-all photosynthetic metabolism may be described from elementary analysis of the cells since excretory products are negligible. The gas exchange predicted in this way is in good agreement with the observed CO2/O2 quotients.

Cramer, Marian; Myers, Jack

1948-01-01

400

Photodegradation of Paracetamol in Nitrate Solution  

SciTech Connect

The photodegradation of paracetamol in nitrate solution under simulated solar irradiation has been investigated. The degradation rates were compared by varying environmental parameters including concentrations of nitrate ion, humic substance and pH values. The quantifications of paracetamol were conducted by HPLC method. The results demonstrate that the photodegradation of paracetamol followed first-order kinetics. The photoproducts and intermediates of paracetamol in the presence of nitrate ions were identified by extensive GC-MS method. The photodegradation pathways involving. OH radicals as reactive species were proposed.

Meng Cui; Qu Ruijuan; Liang Jinyan; Yang Xi [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093 (China)

2010-11-24

401

Circular autowave pacemakers in thin-layered zirconium oxyhydrate  

NASA Astrophysics Data System (ADS)

The periodic nature of the rheological property variation of zirconium oxyhydrate is determined by the microheterogeneous variability of the precipitate structure which changes with time. This effect is interpreted as the autowave manifestation of polymer-peptization processes in forming gel matrix. The work considers new experimental and theoretical approaches to the formation of discrete features of the oxyhydrate gel system structure, which interpret the processes of self-organization of such compounds. The effect of the quantization of circular pacemaker diameters in forming oxyhydrate gels of heavy metals far from the equilibrium state is found experimentally and described mathematically.

Sukharev, Yu. I.; Markov, B. A.; Antonenko, I. V.

2002-04-01

402

Rapid and cost-effective method for synthesizing zirconium silicides  

Microsoft Academic Search

An experimental study on the preparation of zirconium silicides was conducted using ZrSiO4–Mg, ZrSiO4–SiO2–Mg and ZrSiO4–ZrO2–Mg powder mixtures by the combustion synthesis (CS) technique. Test specimens having different composition ratios including Zr:Si=1:2, 1:1, 5:4, 5:3, 2:1, and 3:1 were employed in this study. Temperature profiles relative to all the starting compositions were measured using thermocouples, and the values of the

Il-Je Cho; Kyung-Tae Park; Sang-Ki Lee; Hayk H. Nersisyan; Yong-Soo Kim; Jong-Hyeon Lee

2010-01-01

403

METHOD FOR ANNEALING AND ROLLING ZIRCONIUM-BASE ALLOYS  

DOEpatents

A fabrication procedure is presented for alpha-stabilized zirconium-base alloys, and in particular Zircaloy-2. The alloy is initially worked at a temperature outside the alpha-plus-beta range (810 to 970 deg ), held at a temperature above 970 deg C for 30 minutes and cooled rapidly. The alloy is then cold-worked to reduce the size at least 20% and annealed at a temperature from 700 to 810 deg C. This procedure serves both to prevent the formation of stringers and to provide a randomly oriented crystal structure.

Picklesimer, M.L.

1959-07-14

404

Identification and characterization of a new zirconium hydride.  

PubMed

Zirconium alloys are currently used in nuclear power plants where they are susceptible to hydrogen pick-up. Hydride precipitation may occur when the hydrogen solubility limit is reached. Various Zr hydride phases, gamma, delta and epsilon have been identified since the 1950s. Combining electron precession microdiffraction, electron energy loss spectroscopy and ab initio electronic calculations, a new Zr hydride named zeta has been identified and characterized. It belongs to the trigonal crystal system with space group P3 m1 and it is fully coherent with the alphaZr matrix. PMID:19094018

Zhao, Z; Morniroli, J-P; Legris, A; Ambard, A; Khin, Y; Legras, L; Blat-Yrieix, M

2008-12-01

405

Pion induced interactions in tantalum, europium, antimony and zirconium  

NASA Astrophysics Data System (ADS)

Interaction of 80 and 100 MeV ?+ with targets of tantalum, europium, antimony and zirconium have been studied using muscovite mica and CR-39 solid state nuclear track detectors. These studies yielded information regarding the binary and ternary fission cross-sections. Emission of heavy and light reaction products has also been studied. The results indicate that besides the emission of heavy charged particles like fission fragments, a large fraction of light charged particles such as alpha particles and protons are emitted. The angular distributions of both fission fragments and light reaction products have been found to be slightly peaked in the direction of the incidence beam.

Khan, Hameed A.; Khan, Naeem A.; Peterson, R. J.

1990-10-01

406

Plate-shaped transformation products in zirconium-base alloys  

SciTech Connect

Plate-shaped products resulting from martensitic, diffusional, and mixed mode transformations in zirconium-base alloys are compared in the present study. These alloys are particularly suitable for the comparison in view of the fact that the lattice correspondence between the parent {beta} (bcc) and the product {alpha} (hcp) or {gamma}-hydride (fct) phases are remarkably similar for different types of transformations. Crystallographic features such as orientation relations, habit planes, and interface structures associated with these transformations have been compared, with a view toward examining whether the transformation mechanisms have characteristic imprints on these experimental observables.

Banerjee, S.; Dey, G.K.; Srivastava, D. [Bhabba Atomic Research Center, Mumbai (India). Materials Science Div.; Ranganathan, S. [Indian Inst. of Science, Bangalore (India)

1997-11-01

407

Adsorption of phosphate from aqueous solution by hydrous zirconium oxide.  

PubMed

Synthetic ZrO2 x nH2O was used for phosphate removal from aqueous solution. The optimum adsorbent dose obtained for phosphate adsorption on to hydrous zirconium oxide was 0.1 g. The kinetic process was described very well by a pseudo-second-order rate model. The phosphate adsorption tended to increase with the decrease in pH. The adsorption capacity increased from 61 to 66 mg g(-1) when the temperature was increased from 298 to 338 K. A phosphate desorption of approximately 74% was obtained using water at pH 12. PMID:22856308

Rodrigues, Liana Alvares; Maschio, Leandro José; Coppio, Luciana de Simone Cividanes; Thim, Gilmar Patrocínio; da Silva, Maria Lúcia Caetano Pinto

2012-06-01

408

Structure and thermal stability of mesostructured zirconium oxophosphates  

Microsoft Academic Search

Highly ordered mesoporous zirconium oxophosphates (designated as ZOP) with hexagonal P63\\/mmc and cubic Fm3¯m symmetries were firstly prepared by using gemini cationic surfactants as templates. It has been found that the thermal stability was elevated with the structure curvature order: cubic Ia3¯d2D-hexagonalp6mmcubicFm3¯m, hexagonal P63\\/mmc and cubic Pm3¯n. The ZOP mesoporous materials with cubic Fm3¯m and hexagonal P63\\/mmc structures were stable

Yifeng Zhang; Yongsheng Li; Yasuhiro Sakamoto; Osamu Terasaki; Shunai Che

2007-01-01

409

Minerals yearbook, 1991: Zirconium and hafnium. Annual report  

SciTech Connect

Mr. Templeton is a physical scientist with the Branch of Industrial Minerals. He has covered zirconium and hafnium for about 4 years. Domestic survey data were prepared by the Section of Metals Data. World production data are provided by country specialists in the Division of International Minerals, and the data were compiled by Mr. Harold D. Willis. Data in the report are collected from an assortment of sources. U.S. mine production of zircon sand is obtained by directly surveying the three producing mines, all of which responded.

Templeton, D.A.

1993-03-01

410

High efficiency removal of phosphate from water by zirconium sulfate-surfactant micelle mesostructure immobilized on polymer matrix.  

PubMed

A zirconium sulfate-surfactant micelle mesostructure (ZS) was synthesized to investigate its capacity for phosphate removal from water. Its phosphate adsorption kinetics, the effect of pH and interfering anions, adsorption isotherm, desorption capacity, and reusability were investigated. The adsorption isotherms could be described by the Langmuir model. The ZS was an effective adsorbent for phosphate with a very high adsorption capacity (114 mg P/g ZS). The phosphate adsorption capacity increased with decrease in pH. Although the adsorption of nitrate, chloride and acetate ions was negligible, bicarbonate ions were found to be possible interfering anions. The adsorbed phosphate was desorbed effectively using NaOH solution. Since breakage of ZS particles resulted when using NaOH, ZS was immobilized on a polymer matrix and a 50-cycle adsorption-desorption test was carried out to determine the ZS-immobilized polymer (P-ZS) reusability. The P-ZS retained its functionality and adsorption and desorption capacity over 50 cycles without loss of original capacity. A phosphate solution containing about 10 mg P/L was treated in a column packed with P-ZS. The phosphate could be adsorbed completely onto P-ZS up to 1020 bed volumes. These results indicate clearly that ZS is a highly effective adsorbent for phosphate and enables the removal of phosphate from water. PMID:23726694

Pitakteeratham, Niti; Hafuka, Akira; Satoh, Hisashi; Watanabe, Yoshimasa

2013-04-23

411

Nitrate stimulation of indigenous nitrate-reducing, sulfide-oxidising bacterial community in wastewater anaerobic biofilms  

Microsoft Academic Search

The role of the nitrate-reducing, sulfide-oxidising bacteria (NR-SOB) in the nitrate-mediated inhibition of sulfide net production by anaerobic wastewater biofilms was analyzed in two experimental bioreactors, continuously fed with the primary effluent of a wastewater treatment plant, one used as control (BRC) and the other one supplemented with nitrate (BRN). This study integrated information from H2S and pH microelectrodes, RNA-based

Juan Garcia-de-Lomas; Alfonso Corzo; M. Carmen Portillo; Juan M. Gonzalez; Jose A. Andrades; Cesáreo Saiz-Jimenez; Emilio Garcia-Robledo

2007-01-01

412

STUDIES OF JOINT SOLUBILITY OF URANYL NITRATE AND NITRATES OF ALKALI EARTH METALS IN WATER  

Microsoft Academic Search

Isothermic solubility was studied in ternary systems Hâ O, 25, and ; 50 d . The eutectoid point for this system was not found. Three ; solubiliiy curves corresponding to the solubility of tetrahydrate of strontium ; nitrate, anhydrous strontium nitrate, and hexahydrate of uranyl nitrate ; (transition points at 37.33% UOâ(NOâ)â, 13.18% Sr(NOâ)\\/; sub 2\\/, and 5 UOâ(NOâ)â, 4.78%

M. A. Yakimov; N. F. Nosova; V. A. Grishin

1958-01-01

413

Nitrate removal and denitrification affected by soil characteristics in nitrate treatment wetlands  

Microsoft Academic Search

Several small-scale surface flow constructed wetlands unplanted and planted (monoculture) with various macrophytes (Phragmites australis, Typha orientalis, Pennisetum purpureum, Ipomoea aquatica, and Pistia stratiotes) were established to continuously receive nitrate-contaminated groundwater. Soil characteristics and their effects on nitrate removal and soil denitrification were investigated. The results showed that planted wetland cells exhibited significantly higher (P < 0.05) nitrate removal efficiencies

Ying-Feng Lin; Shuh-Ren Jing; Der-Yuan Lee; Yih-Feng Chang; Kai-Chung Shih

2007-01-01

414

The need for reference materials when monitoring nitrate intake  

Microsoft Academic Search

Whether dietary exposure to nitrate metabolites is detrimental or beneficial to human health has long been a matter of controversy. In spite of no consistent epidemiological evidence, nitrate metabolites are associated with the formation of carcinogenic-nitrosamines and gastric cancer. Furthermore, recent studies demonstrate that ingested nitrate plays a role in host defence against gastrointestinal pathogenic bacteria. Analytical values of nitrate

Isabel Castanheira; Luisa Oliveira; Ana Valente; Paula Alvito; Helena S. Costa; Anton Alink

2004-01-01

415

Rapid abiotic transformation of nitrate in an acid forest soil  

Microsoft Academic Search

Nitrate immobilization into organic matter is thought to require catalysis by the enzymes of soil microorganisms. However, recent studies suggest that nitrate added to soil is immobilized rapidly and this process may include abiotic pathways. We amended living and sterilized soil with 15N-labeled nitrate and nitrite to investigate biotic and abiotic immobiliz- ation. We report rapid transformation of nitrate in

DAVID BRYAN DAIL; RIC A. DAVIDSON; JON CHOROVER

2001-01-01

416

The influence of ammonium on nitrate reduction in wheat seedlings  

Microsoft Academic Search

Ammonium markedly inhibited nitrate absorption by nitrogenstarved wheat seedlings but did not decrease the proportion of absorbed nitrate that was reduced. Seedlings high in nitrate (absorbed prior to the experimental periods) reduced similar amounts of this nitrate regardless of whether or not ammonium was present and being absorbed during the period of measurement. Ammonium or products of ammonium assimilation did

P. L. Minotti; Doris Craig Williams; W. A. Jackson

1969-01-01

417

76 FR 46907 - Ammonium Nitrate Security Program  

Federal Register 2010, 2011, 2012, 2013

...Department of Homeland Security/NPPD'' in the subject line...by the minimal security benefit gained...ammonium nitrate in their products...recreational centers, schools, and other entities...while gaps in security of the...

2011-08-03

418

Qualitative Determination of Nitrate with Triphenylbenzylphosphonium Chloride.  

ERIC Educational Resources Information Center

|Discusses two procedures for the identification of nitrate, the standard test ("Brown Ring" test) and a new procedure using triphenylbenzylphosphonium chloride (TPBPC). Effectiveness of both procedures is compared, with the TPBPC test proving to be more sensitive and accurate. (JM)|

Berry, Donna A.; Cole, Jerry J.

1984-01-01

419

Nitrate Leaching From Intensive Forest Management on ...  

Treesearch

... Forest Management on Abandonded Agricultural Land: Fifth-Year Results ... quality impacts of maximizing plantation growth on abandoned agricultural land, ... Soil moisture nitrate was significantly higher in the plots with vegetation control.

420

Thermal Decomposition of Nitrated Tributyl Phosphate.  

National Technical Information Service (NTIS)

Contact between tributyl phosphate and aqueous solutions of nitric acid and/or heavy metal nitrate salts at elevated temperatures can lead to exothermic reactions of explosive violence. Even though such operations have been routinely performed safely for ...

D. F. Paddleford Y. Hou E. K. Barefield D. W. Tedder S. I. Abdel-Khalik

1995-01-01

421

Thermal Characteristics of Concentrated Hydroxylammonium Nitrate Solutions.  

National Technical Information Service (NTIS)

The thermal response of concentrated hydroxylammonium nitrate solutions has been studied where solutions have been brought to boiling, with only a small degree of decomposition being noted over protracted time periods. Boiling points were related to molar...

R. A. Sasse

1988-01-01

422

Analysis of Hydroxylammonium Nitrate Based Liquid Propellants.  

National Technical Information Service (NTIS)

Chemical analysis of hydroxlammonium nitrate (HAN) based liquid propellants have matured over the past twenty years, and various techniques have been offered to meet particular requirements at particular times. This has resulted in a plethora of technolog...

R. Sasse

1990-01-01

423

Global distribution of peroxyacetyl nitrate.  

PubMed

Nitrogen oxides (NOx) have a central role in the chemistry of the atmosphere, especially in key processes relating to ozone, hydroxyl-radical (OH) and acid formation. High reactivity of NOx (lifetime of 0.5-2 days) precludes hemispheric-scale transport and it has been proposed that non-methane hydrocarbons present in the troposphere can transform NOx into its organic forms principally as peroxyacetyl nitrate (PAN). PAN is highly stable in the colder regions of the middle and upper troposphere and can provide a mechanism for NOx storage and transport. Once transported, PAN and its homologues can easily release free NOx in warmer atmospheric conditions. PAN is probably ubiquitous and its concentrations could exceed those of NOx in clean tropospheric conditions. Here we present the first view of the global distribution of PAN based on extensive shipboard and aircraft measurements. PAN is more abundant in the Northern than in the Southern Hemisphere and in the continental than in the marine troposphere. In contrast to its behaviour in polluted atmospheres, PAN mixing ratios in winter greatly exceed those in summer. These measurements provide a basis for assessing the significance of PAN as a reservoir of NOx and for extending and validating reactive nitrogen chemistry theory in the troposphere. PMID:3713843

Singh, H B; Salas, L J; Viezee, W

424

Peroxyacetyl nitrate in eastern Scotland.  

PubMed

Peroxyacetyl nitrate (PAN) concentrations in air were sampled hourly from 1994 to 1998 at a rural site 15 km south-west of Edinburgh, in eastern Scotland. Annual average concentrations were between 0.1 and 0.15 nl l(-1), with episodes up to 3 nl l(-1) in long-range transported polluted air. PAN concentrations were approximately log-normally distributed. The concentrations measured are the result of a balance between photochemical production rates and removal by thermal decomposition and dry deposition. In general, there was a poor correlation between PAN and ozone concentrations at this rural site except during episodes of photochemical pollution, when the PAN/O(3) volume ratio exceeded 0.01. The PAN/NO(x) volume ratio had a median value of 0.015 but ranged up to 0.25. There was a pronounced seasonal maximum in PAN concentrations in late spring, and a strong diurnal cycle only in April-June, with a maximum at 1700 h. Individual episodes, with concentrations up to 3 nl l(-1), could be traced over distances of ca. 1000 km, with rapid changes in concentration as the prevailing winds advected polluted air masses across the site. PMID:15626392

McFadyen, G G; Cape, J N

2005-01-20

425

Nitrate inhibition of legume nodule growth and activity. II. Short term studies with high nitrate supply  

SciTech Connect

Soybean plants (Glycine max (L.) Merr) were grown in sand culture with 2 millimolar nitrate for 37 days and then supplied with 15 millimolar nitrate for 7 days. Control plants received 2 millimolar nitrate and 13 millimolar chloride and, after the 7-day treatment period, all plants were supplied with nil nitrate. The temporary treatment with high nitrate inhibited nitrogenase (acetylene reduction) activity by 80% whether or not Rhizobium japonicum bacteroids had nitrate reductase (NR) activity. The pattern of nitrite accumulation in nodules formed by NR/sup +/ rhizobia was inversely related to the decrease and recovery of nitrogenase activity. However, nitrite concentration in nodules formed by NR/sup -/ rhizobia appeared to be too low to explain the inhibition of nitrogenase. Nodules on plants treated with 15 millimolar nitrate contained higher concentrations of amino N and, especially, ureide N than control nodules and, after withdrawal of nitrate, reduced N content of treated and control nodules returned to similar levels. The accumulation of N/sub 2/ fixation products in nodules in response to high nitrate treatment was observed with three R. japonicum strains, two NR/sup +/ and one NR/sup -/.

Streeter, J.G.

1985-02-01

426

The photochemistry of aqueous nitrate ion revisited  

Microsoft Academic Search

Aqueous nitrate solutions were photolysed at 254 nm in the absence of oxidizable additives, in the presence of methanol or propan-2-ol and oxygen and in the presence of cyclopentane under anaerobic conditions. The main nitrogen-containing products are nitrite and peroxynitrite. The quantum yields depend on the pH, nitrate concentration, nature of the additive and the light intensity. The intrinsic nitrite

Gertraud Mark; Hans-Gert Korth; Heinz-Peter Schuchmann; Clemens von Sonntag

1996-01-01

427

Electrophilic nitration of alkanes with nitronium hexafluorophosphate  

PubMed Central

Nitration of alkanes such as methane, ethane, propane, n-butane, isobutane, neopentane, and cyclohexane was carried out with nitronium hexafluorophosphate in methylene chloride or nitroethane solution. Nitration of methane, albeit in poor yield, required protolytic activation of the nitronium ion. The results indicate direct electrophilic insertion of NO2+ into C 000000000000 000000000000 000000000000 000000000000 111111111111 000000000000 000000000000 000000000000 000000000000 H and CC ?-bonds.

Olah, George A.; Ramaiah, Pichika; Prakash, G. K. Surya

1997-01-01

428

Nitrate pollution of groundwater in northern China  

Microsoft Academic Search

Since the 1980s, nitrogen fertiliser consumption in China has increased substantially. High nitrogen application rates may increase the potential groundwater N-pollution. These effects were investigated in 14 cities and counties in northern China. The Merckoquant-nitrate-test strip was used to measure the nitrate concentration in water. Information on well depth, groundwater level, crop rotation, yield and fertiliser application was obtained.The results

W. L. Zhang; Z. X. Tian; N. Zhang; X. Q. Li

1996-01-01

429

Synthesis of a new energetic nitrate ester  

SciTech Connect

Nitrate esters have been known as useful energetic materials since the discovery of nitroglycerin by Ascanio Sobrero in 1846. The development of methods to increase the safety and utility of nitroglycerin by Alfred Nobel led to the revolutionary improvement in the utility of nitroglycerin in explosive applications in the form of dynamite. Since then, many nitrate esters have been prepared and incorporated into military applications such as double-based propellants, detonators and as energetic plasticizers. Nitrate esters have also been shown to have vasodilatory effects in humans and thus have been studied and used for treatments of ailments such as angina. The mechanism of the biological response towards nitrate esters has been elucidated recently. Interestingly, many of the nitrate esters used for military purposes are liquids (ethylene glycol dinitrate, propylene glycol dinitrate, etc). Pentaerythritol tetranitrate (PETN) is one of the only solid nitrate esters, besides nitrocellulose, that is used in any application. Unfortunately, PETN melting point is above 100 {sup o}C, and thus must be pressed as a solid for detonator applications. A more practical material would be a melt-castable explosive, for potential simplification of manufacturing processes. Herein we describe the synthesis of a new energetic nitrate ester (1) that is a solid at ambient temperatures, has a melting point of 85-86 {sup o}C and has the highest density of any known nitrate ester composed only of carbon, hydrogen, nitrogen and oxygen. We also describe the chemical, thermal and sensitivity properties of 1 as well as some preliminary explosive performance data.

Chavez, David E [Los Alamos National Laboratory

2008-01-01

430

Low-level nitrate waste process development  

SciTech Connect

Chemical methods of denitrification of simulated low-level nitrate wastes were investigated on a laboratory scale. Various reducing agents and catalysts were tested in evaporation and drying experiments to determine denitrification efficiency, NO/sub x/ off-gas generation, and future process applicability. A peer review was conducted to gain input on processing needs and preferences from actual nitrate waste generators. Experimental results are discussed and conclusions presented. 10 tables.

Meile, L.J.; Johnson, A.J.

1984-01-01

431

Thermal decomposition of uranyl nitrate hexahydrate  

Microsoft Academic Search

TG-DTA-EGA studies have shown that anhydrous uranyl nitrate cannot be obtained by thermal decomposition of uranyl nitrate\\u000a hexahydrate. Hydrolysis and polymerization of the salt during dehydration resulted in hydroxynitrates which decomposed in\\u000a multiple steps with the evolution of oxides of nitrogen and water. The extent of hydrolysis dependend on the sample size,\\u000a heating rate and nature of sample containment. Large

K. V. Rajagopalan; P. V. Ravindran; T. P. Radhakrishnan

1995-01-01

432

Field compatible calibration procedure for peroxyacetyl nitrate  

Microsoft Academic Search

A field compatible calibration procedure for generating ppb levels of peroxyacetyl nitrate is presented. The procedure is based upon the condensed-phase synthesis of peroxyacetyl nitrate (PAN) in octane solution. These solutions show PAN loss of <4% month⁻¹ when stored at -20°C. The dilute PAN solutions are injected directly into known volumes of air in Tedlar bags to obtain ppb gas-phase

Michael W. Holdren; Chester W. Spicer

1984-01-01

433

Peroxyacetyl nitrate and peroxypropionyl nitrate during SCOS 97-NARSTO.  

PubMed

Peroxyacyl nitrates [RC(O)OONO2] play an important role in urban air quality and tropospheric chemistry. They also receive attention as mutagens, phytotoxins, and possible air quality indicators of changes in vehicle fuel composition. Ambient concentrations of PAN (R = CH3) and PPN (R = C2H5) have been measured during summer 1997 at two southern California locations, Azusa (July 14-October 16) and Simi Valley (June 18-October 16). The highest concentrations were 4.8 ppb for PAN and 0.72 ppb for PPN in Azusa and 3.0 ppb for PAN and 0.28 ppb for PPN in Simi Valley. Ambient levels of PAN and PPN during summer 1997 were lower than those measured in the last three studies carried out in southern California in the summers of 1990, 1991, and 1993. Average PPN/PAN concentration ratios were about the same in Azusa (0.142+/-0.025, n = 132) and in Simi Valley (0.135+/-0.028, n = 138). The PPN/PAN ratio measured in Azusa was the same as that measured at that location in 1993 prior to the introduction in 1996 of California Phase 2 reformulated gasoline. Diurnal variations of PAN and PPN generally followed those of ozone with respect to time of day but not with respect to amplitude. The PAN/ozone ratio was lower in Simi Valley than in Azusa, and daytime minima were recorded at both locations. The amount of PAN lost by thermal decomposition accounted for large fractions of the amount of PAN formed (measured + decomposed) during daytime hours at both locations. The amount of PAN lost by thermal decomposition was higher in Azusa and was up to ca. 8.5 ppb, i.e., 4-5 times more than that measured, when afternoon temperatures were ca. 40 degrees C. PMID:11686360

Grosjean, E; Grosjean, D; Woodhouse, L F

2001-10-15

434

Analysis of uranium-zirconium-carbon-oxygen quaternary system for applications in advanced zirconium carbide coated TRISO particles  

NASA Astrophysics Data System (ADS)

The implementation of ZrC for use in oxide TRISO particles for Very High Temperature Reactor (VHTR) conditions to prevent kernel overpressurization and kernel migration has been proposed by several researchers. Analysis is performed incorporating first-principles thermodynamics along with out-of-pile experimental work. UO2+x-U4O9 powders are created and used for in-vacuo thermogravimetric testing with both carbon and zirconium carbide powders to evaluate the efficiency of ZrC for usage as an oxygen getter in oxide TRISO fuels.

Degange, Jonathan Lee

435

Groundwater nitrate pollution in intensively farmed regions  

NASA Astrophysics Data System (ADS)

Intensified agricultural practices that have developed during the past century have helped improve food security for many people but have also added to nitrate pollution in water supply. Balancing the water needs for agriculture with the need for clean groundwater for drinking requires understanding factors such as the routes by which nitrate enters the water supply and how long nitrate remains in the water. The Thames River catchment provides a good study example because the water quality in the river, which supplies drinking water to millions of people, has been monitored for the past 140 years, and the region has undergone significant agricultural development over the past century. Howden et al. studied nitrate transport from agricultural land to water in the Thames basin using a simple model that considers an estimate of the amount of nitrate that could leach the groundwater based on land use practices along with an algorithm that determines the route nitrate would take to reach surface water or groundwater from agricultural areas.

Balcerak, Ernie

2011-12-01

436

Nitration of Hsp90 induces cell death.  

PubMed

Oxidative stress is a widely recognized cause of cell death associated with neurodegeneration, inflammation, and aging. Tyrosine nitration in these conditions has been reported extensively, but whether tyrosine nitration is a marker or plays a role in the cell-death processes was unknown. Here, we show that nitration of a single tyrosine residue on a small proportion of 90-kDa heat-shock protein (Hsp90), is sufficient to induce motor neuron death by the P2X7 receptor-dependent activation of the Fas pathway. Nitrotyrosine at position 33 or 56 stimulates a toxic gain of function that turns Hsp90 into a toxic protein. Using an antibody that recognizes the nitrated Hsp90, we found immunoreactivity in motor neurons of patients with amyotrophic lateral sclerosis, in an animal model of amyotrophic lateral sclerosis, and after experimental spinal cord injury. Our findings reveal that cell death can be triggered by nitration of a single protein and highlight nitrated Hsp90 as a potential target for the development of effective therapies for a large number of pathologies. PMID:23487751

Franco, Maria Clara; Ye, Yaozu; Refakis, Christian A; Feldman, Jessica L; Stokes, Audrey L; Basso, Manuela; Melero Fernández de Mera, Raquel M; Sparrow, Nicklaus A; Calingasan, Noel Y; Kiaei, Mahmoud; Rhoads, Timothy W; Ma, Thong C; Grumet, Martin; Barnes, Stephen; Beal, M Flint; Beckman, Joseph S; Mehl, Ryan; Estévez, Alvaro G

2013-03-04

437

Process for decomposing nitrates in aqueous solution  

DOEpatents

This invention is a process for decomposing ammonium nitrate and/or selected metal nitrates in an aqueous solution at an elevated temperature and pressure. Where the compound to be decomposed is a metal nitrate (e.g., a nuclear-fuel metal nitrate), a hydroxylated organic reducing agent therefor is provided in the solution. In accordance with the invention, an effective proportion of both nitromethane and nitric acid is incorporated in the solution to accelerate decomposition of the ammonium nitrate and/or selected metal nitrate. As a result, decomposition can be effected at significantly lower temperatures and pressures, permitting the use of system components composed of off-the-shelf materials, such as stainless steel, rather than more costly materials of construction. Preferably, the process is conducted on a continuous basis. Fluid can be automatically vented from the reaction zone as required to maintain the operating temperature at a moderate value--e.g., at a value in the range of from about 130.degree.-200.degree. C.

Haas, Paul A. (Knoxville, TN)

1980-01-01

438

Characterization of Atmospheric Organic Nitrates in Particles  

NASA Astrophysics Data System (ADS)

Aerosols in the atmosphere significantly affect climate, human health and visibility. Knowledge of aerosol composition is necessary to understand and then predict the specific impacts of aerosols in the atmosphere. It is known that organic nitrates are present in particles, but there is limited knowledge of the individual compounds and quantity. This is in part due to the lack of a wide variety of proven analytical techniques for particulate organic nitrates. In this study, several known organic nitrates, as well as those present in complex mixtures formed from oxidation of "Ñ-pinene, were studied using a variety of techniques. These include Fourier Transform infrared spectroscopy (FTIR) of samples collected by impaction on ZnSe discs. Samples were also collected on quartz fiber filters and the extracts analyzed by electrospray mass spectrometry (ESI- MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS), HPLC-UV, LC-MS and GC-MS. In addition, real-time analysis was provided by SPLAT-II and aerosol mass spectrometry (AMS). FTIR analysis of particles collected on ZnSe discs provides information on the ratio of organic nitrate to total organic content, while the analysis of filter extracts allows identification of specific organic nitrates. These are compared to the particle mass spectrometry data and the implications for detecting and measuring particulate organic nitrate in air is discussed.

Bruns, E. A.; Alexander, M. L.; Perraud, V.; Yu, Y.; Ezell, M.; Johnson, S. N.; Zellenyuk, A.; Imre, D.; Finlayson-Pitts, B. J.

2008-12-01

439

The fate of atmospheric organic nitrates  

NASA Astrophysics Data System (ADS)

Isoprene (2-methyl-1,3-butadiene) is the dominant biogenic volatile organic compound emitted into the atmosphere at 500-750 Tg yr -1. Isoprene is emitted by plants and readily reacts with hydroxyl radicals (OH), ozone (O3), and NO3 in the atmosphere. The products of these include hydroxy nitrates (isoprene nitrates) and NO 2, which can go on to form ozone or be recycled back into the NO/NO 2 cycle. However, when isoprene nitrates are produced instead of NO 2, the NOx (NO + NO2) is sequestered, the chain is terminated, and ozone is not formed. These isoprene nitrates and other organic nitrogen compounds, such as PAN (peroxyacetyl nitrate, RC(O)OONO 2) and organic nitrates (RONO2) can deposit and impact the natural nitrogen cycle. In forest environments, nitrogen that is deposited and retained can increase photosynthesis and growth, especially in N-limited environments. These nitrogen compounds can directly affect global climate change by reacting to form ozone and indirectly by providing nitrogen to the biosphere causing an increase in carbon sequestration. Vegetation can act as an important sink for atmospheric pollutants, such as CO2 and oxidized nitrogen, because they have many highly reactive surfaces available for deposition, making the atmosphere and biosphere important factors in global climate change.

Lockwood, Amanda L.

440

Cobalt cluster effects in zirconium promoted Co/SiO{sub 2} Fischer-Tropsch catalysts  

SciTech Connect

The effect of zirconium addition to the catalyst formulation of Co/SiO{sub 2} Fischer-Tropsch catalysts was investigated. With increasing zirconium content the strong interaction between silica and cobalt is reduced and a somewhat weaker cobalt-zirconium interaction is observed. Therefore the degree of reduction of catalysts, which were reduced at 400 C for 16 h, increases strongly. The cobalt crystallite size increases with increasing zirconium content, leading to smaller cobalt metal surface areas for the freshly reduced catalyst. Cobalt particles can be found in clusters on the silica support. The size of cobalt clusters decreases and thus the number of cobalt particles within a cluster decreases with increasing zirconium content. At steady-state conditions the CO-conversion of the promoted catalyst in the Fischer-Tropsch synthesis increases with increasing zirconium content. The C{sub 5+}-selectivity and the secondary hydrogenation activity pass a maximum with increasing zirconium content. The observed changes in activity and selectivity are explained in terms of an increase in the amount of metallic cobalt available under reaction conditions, leading to an increased activity, and a decrease in the cobalt cluster size, which diminishes the probability for secondary reactions. Furthermore, it was concluded that secondary double bond isomerization can be catalyzed to some extent by zirconia.

Feller, A.; Claeys, M.; Steen, E. van [Univ. of Cape Town, Rondebosch (South Africa). Dept. of Chemical Engineering

1999-07-01

441

Unusual regulatory nitrate reductase activity in cotyledons of Brassica napus seedlings: enhancement of nitrate reductase activity by ammonium supply  

Microsoft Academic Search

The effect of supplying either nitrate or ammonium on nitrate reductase activity (NRA) was investigated in Brassica napus seedlings. In roots, nitrate reductase activity (NRA) increased as a function of nitrate con- tent in tissues and decreased when ammonium was the sole nitrogen source. Conversely, in the shoots (comprising the cotyledons and hypocotyl), NRA was shown to be independent of

Olivier Leleu; Christophe Vuylsteker

2004-01-01

442

Nitrate reductase from yeast: cultivation, partial purification and characterization  

Microsoft Academic Search

Several yeast strains were assayed for occurence of nitrate reductase after growth in a defined medium with nitrate as the sole nitrogen source, Candida boidinii DSM 70026, showing the highest specific activity, was further investigated. The procedures for yeast fermentation and nitrate reductase purfication are described in detail. Nitrate reductase from this yeast was characterized as NAD(P)H: nitrate oxidoreductase (E.C.1.6.6.2).

Reiner Gromes; Harry Schwartz; Martin Heinrich; Walther Johannssen

1991-01-01

443

Sulfide enhances methanogenesis in nitrate-containing methanogenic cultures  

Microsoft Academic Search

The effects of sulfide on nitrate reduction and methanogenesis using butyrate as a carbon source were investigated in a mixed mesophilic, methanogenic culture. In the sulfide-free medium, 25–75mgl?1 nitrate markedly inhibited the efficiencies of acetogenesis and methanogenesis processes. Adding 25mg-Sl?1 increased methane production in nitrate-amended medium. Low sulfide levels shifted the nitrate reduction pathway from denitrification to dissimilatory nitrate reduction

Biing-Teo Wong; Duu-Jong Lee

2011-01-01

444

Green strength of zirconium sponge and uranium dioxide powder compacts  

SciTech Connect

Zirconium metal sponge is compacted into rectangular or cylindrical shapes using hydraulic presses. These shapes are stacked and electron beam welded to form a long electrode suitable for vacuum arc melting and casting into solid ingots. The compact electrodes should be sufficiently strong to prevent breakage in handling as well as during vacuum arc melting. Usually, the welds are strong and the electrode strength is limited by the green strength of the compacts, which constitute the electrode. Green strength is also required in uranium dioxide (UO{sub 2}) powder compacts, to withstand stresses during de-tensioning after compaction as well as during ejection from the die and for subsequent handling by man and machine. The strengths of zirconium sponge and UO{sub 2} powder compacts have been determined by bending and crushing respectively, and Weibul moduli evaluated. The green density of coarse sponge compact was found to be larger than that from finer sponge. The green density of compacts from lightly attrited UO{sub 2} powder was higher than that from unattrited category, accompanied by an improvement in UO{sub 2} green crushing strength. The factors governing green strength have been examined in the light of published literature and experimental evidence. The methodology and results provide a basis for quality control in metal sponge and ceramic powder compaction in the manufacture of nuclear fuel.

Balakrishna, Palanki [Nuclear Fuel Complex, Hyderabad 500 062 (India)], E-mail: bpalanki@rediffmail.com; Murty, B. Narasimha; Sahoo, P.K.; Gopalakrishna, T. [Nuclear Fuel Complex, Hyderabad 500 062 (India)

2008-07-15

445

Characterization of SAES St198 zirconium-iron-tin alloy  

SciTech Connect

A waste minimization program to develop a non-oxidative stripper system based on metallic getters is being conducted. Initial development is being performed using a Zr-Fe-Sn intermetallic alloy getter procured as Stl98 from SAES Gefters/USA., Inc. This memorandum describes characterizations of physical and compositional properties of SAES Stl98. SAES Stl98 getter was supplied as very durable, cylindrical pellets made by compaction of. granules of Zr-Fe-Sn alloy up to 150 [mu]m in size. Pellet density was 5.2 g/mL corresponding to 24.8% open porosity and very little closed porosity. Bulk composition of Stl98 was 73.6 weight percent (w/o) Zr, 23.3 w/o Fe and 1.2 w/o Sn. Stl98 consists of Zr[sub 2]Fe primary phase along with four secondary phases (ZrFe[sub 2], Zr[sub 5]FeSn, [alpha]-zirconium, and [eta]-Zr[sub 4]Fe[sub 2]O[sub 0.6]). Hydriding characteristics of Stl98 are expected to differ slightly from those of Zr[sub 2]Fe because [alpha]-zirconium and, possibly, Zr[sub 5]FeSn also react with hydrogen.

Mosley, W.C.

1992-10-13

446

MOCVD of zirconium oxide thin films: Synthesis and characterization  

NASA Astrophysics Data System (ADS)

The synthesis of thin films of zirconia often produces tetragonal or cubic phases, which are stable at high temperatures, but that can be transformed into the monoclinic form by cooling. In the present study, we report the deposition of thin zirconium dioxide films by metalorganic chemical vapor deposition using zirconium (IV)-acetylacetonate as precursor. Colorless, porous, homogeneous and well adherent ZrO 2 thin films in the cubic phase were obtained within the temperature range going from 873 to 973 K. The deposits presented a preferential orientation towards the (1 1 1) and (2 2 0) planes as the substrate temperature was increased, and a crystal size ranging between 20 and 25 nm. The kinetics is believed to result from film growth involving the deposition and aggregation of nanosized primary particles produced during the CVD process. A mismatch between the experimental results obtained here and the thermodynamic prediction was found, which can be associated with the intrinsic nature of the nanostructured materials, which present a high density of interfaces.

Torres-Huerta, A. M.; Domínguez-Crespo, M. A.; Ramírez-Meneses, E.; Vargas-García, J. R.

2009-02-01

447

Field assessment of the dynamics of particulate nitrate vaporization using differential TEOM ® and automated nitrate monitors  

NASA Astrophysics Data System (ADS)

In this study, we report a comparison of the results from the differential tapered element oscillating microbalance (TEOM) and a semi-continuous nitrate monitor in an attempt to obtain insights into the dynamics of volatilization from the heated TEOM filter. Measurements were conducted in Claremont, California, a city downwind of Los Angeles and a region of high nitrate concentrations. Field results are compared with that obtained in the laboratory for sampling of pure ammonium nitrate aerosol, and with the vaporization losses predicted by theory. The primary hypothesis that we are testing is that the nitric acid and ammonia gas volatilization from particle-bound ammonium nitrate loaded on the TEOM's fiber filter occurs over time scales that are longer than the 5-min cycle time for the system. This is important to the use of the Differential TEOM, which utilizes the vaporization measured during alternate 5-min periods as a reference baseline value for its particle mass measurements. Our experiments showed that under ambient conditions, the mass lost from the Differential TEOM tracks well the ambient particulate nitrate concentration. The saturation ratio for nitrate vapor immediately downstream of the filter, calculated at the filter temperature assuming all volatilized mass is ammonium nitrate, ranged from 0.05 to 0.2. By comparison, for laboratory collection of ammonium nitrate aerosol the vaporization reached a maximum value corresponding to a saturation of nitrate vapor downstream of the heated filter. This difference is due to the relatively higher particle concentrations used for the laboratory experiments. For the ambient measurements, the particulate nitrate concentrations were consistently lower than the equilibrium vapor concentration at the TEOM filter temperature. In both cases, the nitrate vaporization is driven by the temperature of the TEOM filter and independent of the pressure drop across the filter.

Hering, Susanne; Fine, Philip M.; Sioutas, Constantinos; Jaques, Peter A.; Ambs, Jeffrey L.; Hogrefe, Olga; Demerjian, Kenneth L.

448

Zirconium complexes with lactic acid in the solution and solid states  

NASA Astrophysics Data System (ADS)

Lactic acid complexes of zirconium are used in a great number of industrial applications. Among these is their use as crosslinking agents for hydraulic fracturing fluids used in secondary oil recovery operations. Because of a poor understanding of zirconium lactate complex chemistry and crosslinking reactions, however, the design of superior fluid systems is often not guided by sound chemical principles and leads to empirical guesswork. Zirconium lactate solutions were characterized using Fourier transform infrared (FT-IR) spectroscopy, 1H, 13C, and 17O nuclear magnetic resonance (NMR) spectroscopy, and potentiometry. The results indicate that lactic acid is coordinated bidentate to zirconium via the alcohol and carboxylate groups. The average number of lactate ligands per zirconium ion is approximately 2 and is demonstrated to be relatively constant from pH 4--9. The lability of the lactate complexes increases as the pH is decreased. The NMR data reveal that there are both large and small complex molecules present in solution, with the size of the complex depending on the extent of zirconium hydrolysis. Large complexes consist of lactic acid coordinated to polynuclear zirconium hydroxy ions. The molecular size of these complexes is sufficient to hinder their tumbling in solution and cause broadening of the measured NMR signals. Small complexes involve lactic acid coordinated to hydroxylated species containing fewer zirconium ions, such that the rotational motion in solution is sufficiently rapid to result in narrow NMR signals. Zirconium lactate complexes were precipitated from solution and analyzed in the solid state using FT-IR spectroscopy, 13C magic angle spinning (MAS) NMR spectroscopy, elemental analysis, thermal gravitational analysis, and x-ray diffraction. Two distinct types of crystalline compounds were synthesized with four lactate ligands per zirconium ion. The coordination of lactic acid to zirconium is different in the two compounds, with one showing evidence of at least two distinct lactate environments. This investigation has shown that the method of preparing a zirconium lactate solution can significantly affect the nature of the aqueous complex. A new preparation technique that produces solutions with significantly different properties than those available commercially has been demonstrated.

Demkowicz, Paul Andrew

449

Histopathological and microanalytical study of zirconium dioxide and barium sulphate in bone cement.  

PubMed Central

AIMS: To report the appearances of zirconium dioxide and barium sulphate in interface membranes, synovium, and other tissues around joint prostheses. METHODS: Histological sections from 23 specimens were reviewed by light microscopy and polarisation. Scanning electron microscopy and x ray microanalysis were performed on routinely processed paraffin wax sections. RESULTS: Polyethylene, metals, and polymethylmethacrylate cement debris were easily recognisable. Almost all the cement remnants contained either zirconium dioxide or barium sulphate, confirmed by microanalysis. The contrast media had characteristic light microscopic appearances. Zirconium was identified in macrophages away from cement remnants. CONCLUSION: The presence of radiographic contrast media in tissues around prosthetic joints is common but not widely recognised. Images

Keen, C. E.; Philip, G.; Brady, K.; Spencer, J. D.; Levison, D. A.

1992-01-01

450

Synthesis of aliphatic nitrate esters by reaction of metal nitrates with phosphate esters  

Microsoft Academic Search

A safe and simple method of synthesizing short-chain alkyl nitrates is described. This method, which should be of general utility, was found to be useful in preparing compounds for studies to determine the fate of organic materials in nuclear fuel reprocessing operations. Nitrate esters of short-chain alkyl alcohols can be conveniently obtained by distilling mixtures of the appropriate trialkyl phosphate

W. H. Baldwin; W. E. Clark; W. B. Howerton

1979-01-01

451

Properties and Thermal Decomposition of the Double Salts of Uranyl Nitrate-Ammonium Nitrate.  

National Technical Information Service (NTIS)

The formation of ammonium nitrate-uranyl nitrate double salts has important effects on the thermal denitration process for the preparation of UO(sub 3) and on the physical properties of the resulting product. Analyses were performed, and properties and de...

K. J. Notz P. A. Haas

1989-01-01

452

COMPARATIVE KINETIC STUDIES OF NITRATE-LIMITED GROWTH AND NITRATE UPTAKE IN PHYTOPLANKTON IN CONTINUOUS CULTURE  

EPA Science Inventory

A comparative kinetic study of nitrate-limited growth and nitrate uptake was carried out in chemostat cultures of Ankistrodesmus falcatus, Asterionella formosa, Fragilaria crotonensis. In each species growth rate (microgram) was related to total cell nitrogen or cell quota (q) by...

453

Simultaneous online measurement of sulfide and nitrate in sewers for nitrate dosage optimisation.  

PubMed

A new method for the simultaneous online measurement of sulfide and nitrate in wastewater is developed. A UV-VIS spectrometer was used. The sensor was calibrated by means of simultaneous online and offline measurements of sulfide and nitrate in batch tests carried out on a laboratory-scale sewer system. The developed calibration algorithm was successfully validated for both sulfide and nitrate measurement, with confidence limits of 2.7 mg S/L for total dissolved sulfide, and 7.5 mg N/L for nitrate. The online measurement of sulfide and nitrate enabled detailed evaluation of seven nitrate dosing strategies in the laboratory-scale sewer system, providing strong support to process optimisation. The dosage optimisation revealed that nitrate should be added at a location close to the point of sulfide control rather than at the beginning of a rising main, at a rate proportional to the expected hydraulic retention time (HRT) of the wastewater in the sewer section between the point of nitrate addition and the point where sulfide control is desired. PMID:20150701

Gutierrez, Oriol; Sutherland-Stacey, Luke; Yuan, Zhiguo

2010-01-01

454

The influence of Glyceria maxima and nitrate input on the composition and nitrate metabolism of the dissimilatory nitrate-reducing bacterial community  

Microsoft Academic Search

The influence of nitrate addition and the presence of Glyceria maxima (reed sweetgrass) on the composition and nitrate\\u000ametabolism of the dissimilatory nitrate-reducing bacterial community was investigated. Anoxic freshwater sediment was\\u000aincubated in pots with or without G. maxima and with or without addition of nitrate. After incubation the sediments were\\u000asampled. Dilution series of these sediment samples were incubated

J. W. Nijburg; H. J. Laanbroek

1997-01-01

455

The effect of nitrate and plant size on nitrate uptake and in vitro nitrate reductase activity in strawberry ( Fragaria × ananassa cv. Selva)  

Microsoft Academic Search

Nitrogen plays a major role in the growth and yield of strawberry. For optimizing nitrogen fertilizer application, it is necessary to understand the response of strawberry to nitrogen supply. The objective of this study was to determine the effect of nitrate supply and plant size on strawberry nitrate uptake and nitrate reductase activity (NRA). Strawberry plants cv. Selva were grown

Toktam Sadat Taghavi; Mesbah Babalar

2007-01-01

456

Microbial reduction of chromate in the presence of nitrate by three nitrate respiring organisms.  

PubMed

A major challenge for the bioremediation of toxic metals is the co-occurrence of nitrate, as it can inhibit metal transformation. Geobacter metallireducens, Desulfovibrio desulfuricans, and Sulfurospirillum barnesii are three soil bacteria that can reduce chromate [Cr(VI)] and nitrate, and may be beneficial for developing bioremediation strategies. All three organisms respire through dissimilatory nitrate reduction to ammonia (DNRA), employing different nitrate reductases but similar nitrite reductase (Nrf). G. metallireducens reduces nitrate to nitrite via the membrane bound nitrate reductase (Nar), while S. barnesii and D. desulfuricans strain 27774 have slightly different forms of periplasmic nitrate reductase (Nap). We investigated the effect of DNRA growth in the presence of Cr(VI) in these three organisms and the ability of each to reduce Cr(VI) to Cr(III), and found that each organisms responded differently. Growth of G. metallireducens on nitrate was completely inhibited by Cr(VI). Cultures of D. desulfuricans on nitrate media was initially delayed (48?h) in the presence of Cr(VI), but ultimately reached comparable cell yields to the non-treated control. This prolonged lag phase accompanied the transformation of Cr(VI) to Cr(III). Viable G. metallireducens cells could reduce Cr(VI), whereas Cr(VI) reduction by D. desulfuricans during growth, was mediated by a filterable and heat stable extracellular metabolite. S. barnesii growth on nitrate was not affected by Cr(VI), and Cr(VI) was reduced to Cr(III). However, Cr(VI) reduction activity in S. barnesii, was detected in both the cell free spent medium and cells, indicating both extracellular and cell associated mechanisms. Taken together, these results have demonstrated that Cr(VI) affects DNRA in the three organisms differently, and that each have a unique mechanism for Cr(VI) reduction. PMID:23251135

Chovanec, Peter; Sparacino-Watkins, Courtney; Zhang, Ning; Basu, Partha; Stolz, John F

2012-12-17

457

Dynamic microbial response of sulfidogenic wastewater biofilm to nitrate.  

PubMed

Nitrate is one of the chemicals often added to wastewater to control hydrogen sulfide production by sulfate-reducing bacteria (SRB). While the effect of nitrate in various SRB pure cultures is well documented, the effect observed in mixed microbial communities is not consistent. This study investigates the response of mixed SRB communities to nitrate, by examining the changes in activity and community composition of sulfidogenic wastewater biofilm over a 10-day period with 10 mmol L(-1) nitrate exposure. Biofilms were enriched in SRB belonging to the Desulfobacter, Desulfobulbus, Desulfomicrobium, and Desulfovibrio genera. Nitrate exposure decreased dsrB transcription within 4 h, and sulfate consumption within 10 days, but it did not fully eliminate sulfide production in the biofilms. The effect of nitrate on SRB was genus specific; Desulfobacter and Desulfobulbus disappeared while Desulfovibrio and Desulfomicrobium persisted in the biofilms. Nitrate exposure also led to the rapid proliferation of nitrate-reducing bacteria within the biofilms, and increased the biofilm thickness. Nitrate consumption began within 2 h of nitrate exposure and gradually increased in rate over time. Transcription of the nitrate reductase napA, and the diversity of nitrate reductase genes narG and napA also increased concurrently. Our results demonstrate that some SRB, presumably those able to tolerate or detoxify nitrite, will persist in sulfidogenic wastewater biofilms despite continuous exposure to high levels of nitrate. Nitrate is therefore unlikely to provide lasting hydrogen sulfide suppression in wastewater biofilms harboring Desulfovibrio or Desulfomicrobium populations. PMID:21611797

Mohanakrishnan, Janani; Kofoed, Michael Vedel Wegener; Barr, Jeremy; Yuan, Zhiguo; Schramm, Andreas; Meyer, Rikke Louise

2011-05-25

458

Vulnerability of streams to legacy nitrate sources.  

PubMed

The influence of hydrogeologic setting on the susceptibility of streams to legacy nitrate was examined at seven study sites having a wide range of base flow index (BFI) values. BFI is the ratio of base flow to total streamflow volume. The portion of annual stream nitrate loads from base flow was strongly correlated with BFI. Furthermore, dissolved oxygen concentrations in streambed pore water were significantly higher in high BFI watersheds than in low BFI watersheds suggesting that geochemical conditions favor nitrate transport through the bed when BFI is high. Results from a groundwater-surface water interaction study at a high BFI watershed indicate that decades old nitrate-laden water is discharging to this stream. These findings indicate that high nitrate levels in this stream may be sustained for decades to come regardless of current practices. It is hypothesized that a first approximation of stream vulnerability to legacy nutrients may be made by geospatial analysis of watersheds with high nitrogen inputs and a strong connection to groundwater (e.g., high BFI). PMID:23530900

Tesoriero, Anthony J; Duff, John H; Saad, David A; Spahr, Norman E; Wolock, David M

2013-03-26

459

Proteomic approaches to analyze protein tyrosine nitration.  

PubMed

Abstract Significance: The conversion of protein-bound Tyr residues to 3-nitrotyrosine (3NY) can occur during nitrative stress and has been correlated to aging and many disease states. Proteomic analysis of this post-translational modification, using mass spectrometry-based techniques, is crucial for understanding its potential role in pathological and physiological processes. Recent Advances: To overcome some of the disadvantages inherent to well-established nitroproteomic methods using anti-3NY antibodies and gel-based separations, methods involving multidimensional chromatography, precursor ion scanning, and/or chemical derivatization have emerged for both identification and quantitation of protein nitration sites. A few of these methods have successfully detected endogenous 3NY modifications from biological samples. Critical Issues: While model systems often show promising results, identification of endogenous 3NY modifications remains largely elusive. The frequently low abundance of nitrated proteins in vivo, even under inflammatory conditions, is especially challenging, and sample loss due to derivatization and cleaning may become significant. Future Directions: Continued efforts to avoid interference from non-nitrated peptides without sacrificing recovery of nitrated peptides are needed. Quantitative methods are emerging and are crucial for identifying endogenous modifications that may have significant biological impacts. Antioxid. Redox Signal. 19, 1247-1256. PMID:23157221

Feeney, Maria B; Schöneich, Christian

2013-01-03

460

Light-dependent nitration of bacteriorhodopsin  

SciTech Connect

Purple membranes were treated with tetranitromethane to modify tyrosine residues of bacteriorhodopsin. At pH 8.0, nitration is shown to be affected by illumination during the modification. Amino acid analysis revealed about 0.7 residues nitrated if reaction was in the dark while about 2.0 tyrosines were modified if illumination greater than 540 nm was provided. Tryptophan was unaffected under both conditions. Light-dependent nitration caused a blue shift of the absorbance maximum of bacteriorhodopsin from 568 to 530 nm while no chromophore shift was observed for the dark-modified preparation. Both preparations show an absorption band at 360 nm indicative of the presence of nitrotyrosines. Reduction by dithionite eliminated the pH-dependent changes associated with the 360-nm nitrotyrosine band. Circular dichroism spectra indicate that interactions between neighboring chromophores are altered concomitant with the blue shift of the absorbance maximum by nitration. These studies show that light is required for the nitration of the tyrosine residue is probably responsible for the blue shift of the absorbance maximum. The intrinsic fluorescence and photocycle kinetics of the tyrosine-modified preparation and reduction of nitrotyrosine by dithionite were studied. In dark modification, only pH-dependent dithionite-reducible nitrotyrosines were produced. It is concluded that surface tyrosines probably do not directly participate in the proton-translocation events coupled to the photocycle of bacteriorhodopsin.

Lam, E.; Seltzer, S.; Katsura, T.; Packer, L.

1983-11-01

461

Nitrate Reductase Activity in Maize (Zea mays L.) Leaves  

PubMed Central

Experiments were conducted to determine whether the nitrate flux to the leaves or the nitrate content of the leaves regulated the nitrate reductase activity (NRA) in leaves of intact maize (Zea mays L.) seedlings having low water potentials (?w) when other environmental and endogenous factors were constant. In seedlings that were desiccated slowly, the nitrate flux, leaf nitrate content, and NRA decreased as ?w decreased. The decrease in nitrate flux was caused by a decrease in both the rate of transpiration and the rate of nitrate delivery to the transpiration stream. Upon rewatering, the recovery in NRA was correlated with the nitrate flux but not the leaf nitrate content. Recovery depended on protein synthesis, since recovery could be prevented in excised leaves if an inhibitor of protein synthesis was present. However, it also depended on a high nitrate flux, since recovery could be prevented if there was no nitrate flux, despite a relatively high, constant leaf nitrate content, a high ?w, and the absence of an inhibitor of protein synthesis. The synthesis of NRA could be increased at low ?w if seedlings were desiccated in the presence of additional nitrate, which increased the nitrate flux to the leaves. Since the decrease in NRA at low ?w could be relieved by increasing the nitrate flux and recovery also depended on nitrate flux, the inhibition of NRA at low ?3 was not controlled by a direct effect of ?w on protein synthesis nor by alterations in the leaf nitrate content, but rather by a decrease in the nitrate flux that in turn regulated the synthesis of the enzyme.

Shaner, Dale L.; Boyer, John S.

1976-01-01

462

Titrimetric Determination of Thiocyanate in Solutions of the Hafnium-Zirconium Separation Process.  

National Technical Information Service (NTIS)

The control of the thiocyanate concentration is necessary during the process of separating hafnium from zirconium by the hexone-thiocyanate method. Said control is carried out by titrimetric determination of thiocyanate in aqueous and organic solutions co...

C. Vazquez M. Botbol M. H. Hernandez

1980-01-01

463

21 CFR 700.16 - Use of aerosol cosmetic products containing zirconium.  

Code of Federal Regulations, 2010 CFR

... 2009-04-01 false Use of aerosol cosmetic products containing zirconium. 700.16...HEALTH AND HUMAN SERVICES (CONTINUED) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.16 Use of aerosol...

2009-04-01

464

21 CFR 700.16 - Use of aerosol cosmetic products containing zirconium.  

Code of Federal Regulations, 2010 CFR

... 2010-04-01 false Use of aerosol cosmetic products containing zirconium. 700.16...HEALTH AND HUMAN SERVICES (CONTINUED) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.16 Use of aerosol...

2010-04-01

465

21 CFR 700.16 - Use of aerosol cosmetic products containing zirconium.  

Code of Federal Regulations, 2013 CFR

... 2013-04-01 false Use of aerosol cosmetic products containing zirconium. 700.16...HEALTH AND HUMAN SERVICES (CONTINUED) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.16 Use of aerosol...

2013-04-01

466

21 CFR 700.16 - Use of aerosol cosmetic products containing zirconium.  

Code of Federal Regulations, 2011 CFR

... 2010-04-01 true Use of aerosol cosmetic products containing zirconium. 700.16...HEALTH AND HUMAN SERVICES (CONTINUED) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.16 Use of aerosol...

2011-04-01

467

Electrical conductivity and viscosity of melts of products of the reaction of zirconium with potassium halides  

SciTech Connect

The authors report results of a study of the electrical conductivity and viscosity of melts of products of the reaction of zirconium with potassium chloride and fluoride in binary and ternary mixtures composed of these substances.

Trifonov, K.I.; Zagidulin, S.M.; Katyshev, S.F.; Desyatnik, V.N.

1986-12-20

468

Thermally Activated Deformation of Alpha-Zirconium and Alpha-Zircaloy (LWBR/Lsbr Development Program).  

National Technical Information Service (NTIS)

The dislocation mechanism associated with the deformation dynamics of alpha-zirconium and Zircaloy at low temperatures (below 600F) was evaluated from data available in the literature using the thermal activation analysis and Fleischer's model for solute ...

J. Hull H. Conrad

1967-01-01

469

Stabilization of high-temperature phases of zirconium and hafnium dioxides by carbon and boron  

SciTech Connect

Previous papers have shown that the cubic form of ZrO/sub 2/ and tetragonal HfO/sub 2/ are stabilized by films being doped with carbon and boron during production by the pyrolysis of zirconium and hafnium acetylacetonates and zirconium borohydride correspondingly. With reference to ZrO/sub 2/, the authors estimate the changes in the effective charges in the presence of carbon required to produce the stabilization effect. The effective charges on Zr and O in zirconium dioxide are + or - 1.68 and -0.84, while the ionic radii are 0.82 and 1.4 A, correspondingly. The well-known stabilization mechanisms for zirconium and hafnium dioxides may in some cases be accompanied by stabilization by interstitial impurities such as carbon or boron.

Vodzinskii, V.Y.

1986-06-01

470

Cation-exchange separation of hafnium and zirconium from accompanying ions.  

PubMed

Hafnium and zirconium are not retained on the strongly acidic cation-exchange resin Dowex 50 from a mixture consisting of methanol and 12M nitric acid (19:1) which is 0.1M in trioctylphosphine oxide. On the other hand most other elements investigated are strongly adsorbed on the resin from this medium so that they are readily separated from hafnium and zirconium. These elements include titanium, rare earths, alkali metals, alkaline earth metals, iron, cobalt, manganese and zinc. This separation technique has been found to be suitable for the separation of tracer and milligram amounts of hafnium and zirconium from accompanying metal ions. If in place of methanol other organic solvents such as acetone, tetrahydrofuran and methyl glycol are used the selectivity of the separation of zirconium and hafnium from the other elements is decreased. The same effect is observed when hydrochloric acid is used in the mixtures instead of nitric acid. PMID:18960465

Korkisch, J; Orlandini, K A

1969-01-01

471

Anomalous Phenomena in Zirconium, Hafnium, and Titanium Salt Solutions, Studied by Capillary Isotachophoresis  

Microsoft Academic Search

Capillary isotachophoresis was used to separate mixtures of solutions containing zirconium, hafnium, titanium, and aluminum salts with various anions. Anomalous phenomena occurring in separation of mixtures in solutions with medium and high concentrations are described and analyzed.

O. V. Oshurkova; A. I. Gorshkov; V. P. Nesterov

2001-01-01

472

Zirconium and hafnium tetrachloride separation by extractive distillation with molten zinc chloride lead chloride solvent  

SciTech Connect

In an extractive distillation method for separating hafniuim tetrachloride from zirconium tetrachloride of the type wherein a mixture of zirconium and hafnium tetrachlorides is introduced into an extractive distillation column, which extractive distillation column has a reboiler connected at the bottom and a reflux condenser connected at the top and wherein a molten salt solvent is circulated into the reflux condenser and through the column to provide a liquid phase, and wherein molten salt solvent containing zirconium tetrachloride is taken from the reboiler and run through a stripper to remove zirconium tetrachloride product from the molten salt solvent and the stripped molten salt solvent is returned to the reflux condenser and hafnium tetrachloride enriched vapor is taken as product from the reflux condenser, the improvement is described comprising: the molten salt having a composition of at least 30 mole percent zinc chloride and at least 10 mole percent of lead chloride.

McLaughlin, D.F.; Stoltz, R.A.

1988-04-12

473

Plasma nitrate and nitrite are increased by a high-nitrate supplement but not by high-nitrate foods in older adults.  

PubMed

Little is known about the effect of dietary nitrate on the nitrate/nitrite/nitric oxide cycle in older adults. We examined the effect of a 3-day control diet vs high-nitrate diet, with and without a high-nitrate supplement (beetroot juice), on plasma nitrate and nitrite kinetics and blood pressure using a randomized 4-period crossover controlled design. We hypothesized that the high-nitrate diet would show higher levels of plasma nitrate/nitrite and lower blood pressure compared with the control diet, which would be potentiated by the supplement. Participants were 8 normotensive older men and women (5 female, 3 male, 72.5 ± 4.7 years old) with no overt disease or medications that affect nitric oxide metabolism. Plasma nitrate and nitrite levels and blood pressure were measured before and hourly for 3 hours after each meal. The mean daily changes in plasma nitrate and nitrite were significantly different from baseline for both control diet + supplement (P < .001 and P = .017 for nitrate and nitrite, respectively) and high-nitrate diet + supplement (P = .001 and P = .002), but not for control diet (P = .713 and P = .741) or high-nitrate diet (P = .852 and P = .500). Blood pressure decreased from the morning baseline measure to the three 2-hour postmeal follow-up time points for all treatments, but there was no main effect for treatment. In healthy older adults, a high-nitrate supplement consumed at breakfast elevated plasma nitrate and nitrite levels throughout the day. This observation may have practical utility for the timing of intake of a nitrate supplement with physical activity for older adults with vascular dysfunction. PMID:22464802

Miller, Gary D; Marsh, Anthony P; Dove, Robin W; Beavers, Daniel; Presley, Tennille; Helms, Christine; Bechtold, Erika; King, S Bruce; Kim-Shapiro, Daniel

2012-03-01

474

Nitrate removal for small public water systems. Technical report  

SciTech Connect

This Handbook for Nitrate Removal has been prepared to aid water utility owners, engineers, operators, and municipal managers in understanding and dealing with excessive nitrate levels in their water supply. It is intended to be used for defining the problem, developing or evaluating proposed solutions, and explaining to water consumers why nitrates are controlled and what the approximate costs of control will be. This handbook is designed as a technical guide to nitrate removal for those smaller size systems that have decided that nitrate control is desirable. This document contains no regulatory policy and does not obligate systems to use any treatment or nontreatment technique to reduce nitrate concentrations.

Not Available

1983-06-01

475

Solvent Extraction Separation of Zirconium (iv) With Anberlite LA - 1 From Citrate Solutions  

Microsoft Academic Search

Zirconium was quantitatively extracted with 8 × 10 M of Amberlite LA-1 or LA-2 xylene from 0.001 M citric acid at pH 3.5 and it was stripped from the organic phase with 2 M hydrochloric acid and was determined spectrophotometrically at 665 nm as its complex with arsenazo III. Zirconium was separated from binary as well as tertiary mixtures by

C. P. Vibhute; S. M. Khopkar

1983-01-01

476

Reaction of zirconium fluoride monohydrate and ammonium bifluoride; Its effect on fluoride glass preparation and quality  

SciTech Connect

The products obtained from the room-temperature reaction of ammonium bifluoride and zirconium fluoride monohydrate are ammonium heptafluorozirconate ((NH/sub 4/)/sub 3/ZrF/sub 7/), liquid water, and hydrogen fluoride. This paper discusses ammonium bifluoride and zirconium fluoride monohydrate reacted prior to glass batching, producing dry ammonium heptafluorozirconate which was used to prepare a high-quality ZBLAN fluoride glass.

Ewing, K.J.; Sanghera, J.S.; Miklos, R.E.; Sachon, M.G.; Pietersen, L.; Hart, P.; Aggarwal, I. (Naval Research Lab., Washington, DC (USA). Optical Sciences Div.)

1989-08-01

477

Interfacial and microstructural properties of zirconium oxide thin films prepared directly on silicon  

Microsoft Academic Search

Zirconium oxide thin films were deposited directly on Si by ultra high vacuum electron beam evaporation (UHV-EBE) and rapid thermal annealed (RTA) in O2 ambient at different temperatures ranging from 300 to 800°C. X-ray photoelectron spectroscopy (XPS) revealed zirconium is in the fully oxidized state of Zr4+. X-ray diffraction (XRD) results showed that as-deposited thin films were amorphous. When the

N. L Zhang; Z. T Song; Q Wan; Q. W Shen; C. L Lin

2002-01-01

478

Self-organized high-aspect-ratio nanoporous zirconium oxides prepared by electrochemical anodization  

Microsoft Academic Search

The preparation of self-organized high-aspect-ratio nanoporous zirconium oxides by the Electrochemical anodization was analyzed. The self-organized pore formation on Ti under optimized electrochemical conditions was achieved to grow Ti nanotubes with aspect ratio of more than 20. The electrochemical fabrication of highly ordered porous zirconium oxide layers of nanotubular shape with high aspect ratio was also reported. Result shows that

Hiroaki Tsuchiya; Irina Sieber; Patrik Schmuki

2005-01-01

479

Synthesis and characterization of novel aramid-zirconium oxide micro-composites  

Microsoft Academic Search

New micro-composites containing different proportions of zirconium oxide in aromatic polyamide have been prepared via a sol-gel process. Poly(phenyleneterephthalamide) chains with carbonyl chloride end groups were synthesized by reacting a mixture of p- and m-phenylene diamines with terephthaloyl chloride. The chain ends were endcapped with aminophenyltrimethoxysilane. Appropriate amount of zirconium propoxide solution (82.3 wt.%) in propanol was mixed in the

H. U. Rehman; M. I. Sarwar; Z. Ahmad; H. Krug; H. Schmidt

1997-01-01

480

THE ''CLEAN-UP'' PROCESS: A CHEMICAL CHOP PROCESS. (I. Application to Zirconium-Clad Fuel)  

Microsoft Academic Search

We present here a new head-end process for zirconium-clad fuel. Essentially, this consists of an electrochemical pre-treatment of the oxide-protected zirconium-canning, followed by chemical attack, based on the 'Zirflex' decanning concept. Such a pre-treatment may be carried out either on the whole can surface or on local peripheral bands. The first leads to a faster 'Zirflex' decanning operation; the second

R. Kroebel; E. Lopez-Menchero; J. M. Pivato

1968-01-01

481

Trace determination of iron, cobalt, nickel and copper in zirconium fluoride by substoichiometric radioactivation analysis  

Microsoft Academic Search

Trace amounts of transition elements (Fe, Co, Ni and Cu) in zirconium fluoride and NBS SRM's were determined by substoichiometric radioactivation analysis. The contents of impurities in sublimed sample were less than those of high-purity material and of reagent grade. The detection limits of these elements in zirconium fluoride were 10 ng\\/g for iron, 0.01 ng\\/g for cobalt, 1 ng\\/g

K. Kobayashi; T. Shigematsu

1987-01-01

482

Thermal analysis studies on the zirconium\\/nickel alloy-potassium perchlorate-nitrocellulose pyrotechnic system  

Microsoft Academic Search

The zirconium\\/nickel alloy-potassium perchlorate-nitrocellulose pyrotechnic system has been studied using differential scanning calorimetry, simultaneous TG-DTA-mass spectrometry and chemical analysis using ion-specific electrodes. Quantitative measurements on the solid state reaction, in the region of 400°C, between zirconium\\/nickel alloy and potassium perchlorate have shown that a major component of the solid state reaction may be represented by the equation 9Zr + 14Ni

B. Berger; E. L. Charsley; J. J. Rooney; S. B. Warrington

1995-01-01

483

AN EVALUATION OF THE PROPERTIES AND BEHAVIOR OF ZIRCONIUM-URANIUM ALLOYS  

Microsoft Academic Search

Data from a survey of the literature and other available information on ;\\u000a zirconium--uranium alloys have been reviewed for the purpose of obtaining a ;\\u000a coherent picture of current knowledge about the properties and behavior of ;\\u000a zirconium--uranium alloys. The results of the survey were used to revise and ;\\u000a extend the presentation of material gathered earlier in a similar

A. A. ed

1959-01-01

484

Mechanical response of zirconium—II. Experimental and finite element analysis of bent beams  

Microsoft Academic Search

In a companion paper [Acta mater. 2001, 49(15), 3085–3096] we develop a polycrystal constitutive law that incorporates the deformation mechanisms operating in high purity zirconium (Zr) at liquid nitrogen (LN) and room temperature (RT). In this paper we present results of 4-point bending tests performed on beams of highly textured zirconium. These tests have been performed at LN and RT,

G. C. Kaschner; J. F. Bingert; C. Liu; M. L. Lovato; P. J. Maudlin; M. G. Stout; C. N. Tomé

2001-01-01

485

The separation of zirconium and hafnium in a molten salt-molten zinc system  

Microsoft Academic Search

The commercial separation of zirconium and hafniumvia aqueous\\/organic extraction procedures is both difficult and expensive. The principal objective of the present work was to\\u000a study an alternative procedure involving the oxidation-reduction equilibria of zir-conium and hafnium between a molten salt\\u000a phase and molten zincvia the displacement reaction: Zr(IV)molten salt + Hfmolten zink ? Hf(IV)molten salt + Zrmolten zink The reaction

Joseph A. Megy; Harry Freund

1979-01-01

486

Co-Rolled U10Mo/Zirconium-Barrier-Layer Monolithic Fuel Foil Fabrication Process  

SciTech Connect

Integral to the current UMo fuel foil processing scheme being developed at Idaho National Laboratory (INL) is the incorporation of a zirconium barrier layer for the purpose of controlling UMo-Al interdiffusion at the fuel-meat/cladding interface. A hot “co-rolling” process is employed to establish a ~25-µm-thick zirconium barrier layer on each face of the ~0.3-mm-thick U10Mo fuel foil.

G. A. Moore; M. C. Marshall

2010-01-01

487

Enthalpies of solution of titanium, zirconium, and hafnium in liquid copper  

Microsoft Academic Search

Standard enthalpies of solution of titanium, zirconium, and hafnium in liquid copper were measured directly by high temperature calorimetry at 1873 K. Solution of solid metals was accompanied with exothermic effects approaching the values ?15.0 ± 3.9 kJ mol?1 for titanium, ?44.4 ± 6.6 kJ mol?1 for zirconium, and ?36.8 ± 5.4 kJ mol?1 for hafnium at infinite dilution.Concentration dependence

M. A. Turchanin; I. V. Nikolaenko

1996-01-01

488

Method to predict relative hydriding within a group of zirconium alloys under nuclear irradiation  

Microsoft Academic Search

An out-of-reactor method for screening to predict relative in-reactor hydriding behavior of zirconium-bsed materials is disclosed. Samples of zirconium-based materials having different composition and\\/or fabrication are autoclaved in a relatively concentrated (0.3 to 1.0M) aqueous lithium hydroxide solution at constant temperatures within the water reactor coolant temperature range (280.degree. to 316.degree. C.). Samples tested by this out-of-reactor procedure, when compared

Johnson Jr. A. Burtron; Ira S. Levy; Dennis J. Trimble; Donald D. Lanning; Franna S. Gerber

1990-01-01

489

Actinide partitioning studies using dihexyl-N,N-diethycarbamolymehtyl phosphonate and dissolved zirconium calcine  

SciTech Connect

A baseline flowsheet capable of partitioning the transuranic (TRU) elements from dissolved zirconium calcines has been developed. The goal of the TRU partitioning process is to remove the TRUs from solutions of dissolved zirconium calcines to below the 10 CFR 61.55 Class A waste limit of 10 nCi/g. Extraction, scrub, strip, and wash distribution coefficients for several elements, including the actinides, were measured in the laboratory by performing equal volume batch contacts. A solvent containing diheyl-N, N- diethylcarbamoylmethyl phosphonate (CMP), tributylphosphate (TBP), and a branched chain hydrocarbon as the diluent were used to develop this process. A non-radioactive zirconium pilot-plant calcine was spiked with the TRUs, U, Tc, or a radioactive isotope of zirconium to simulate the behavior of these elements in actual dissolved zirconium calcine feed. Distribution coefficient data obtained from laboratory testing were used to recommend: (1) solvent composition, (2) scrub solutions capable of selectively removing extracted zirconium while minimizing actinide recycle, (3) optimized strip solutions which quantitatively recover extracted actinides, and (4) feed adjustments necessary for flowsheet efficiency. Laboratory distribution coefficients were used in conjunction with the Generic TRUEX Model (GTM) to develop and recommend a flowsheet for testing in the 5.5-cm Centrifugal Contractor Mockup. GTM results indicate that the recommended flowsheet should remove the actinides from dissolved zirconium calcine feed to below the Class A waste limit of 10 nCi/g. Less than 0.01 wt% of the extracted zirconium will report to the high- activity waste (HAW) fraction using the 0.05 M H{sub 2}C{sub 2}O{sub 4} in 3.0 M HNO{sub 3} scrub, and greater than 99% of the extracted actinides are recovered with 0.001 M HEDPA.

Brewer, K.N.; Herbst, R.S.; Law, J.D.; Garn, T.G.; Tillotson, R.D.; Todd, T.A.

1996-01-01

490

Features of Preparing Nano-Size Powders of Tetragonal Zirconium Dioxide Stabilized with Yttrium  

Microsoft Academic Search

The effect of wet chemical synthesis parameters on the properties of nano-powders of zirconium dioxide stabilized with yttrium is studied. Features of nano-powder synthesis by the oxalate, hydroxide and thermal hydrolysis of a sol methods are determined. Nano-size zirconium dioxide powder stabilized with 3 mole% yttrium is prepared by hydrothermal coprecipitation from a sol of metal chlorides and urea followed

O. O. Vasylkiv; Y. Sakka; V. V. Skorokhod

2005-01-01

491

Reversed phase chromatographic separation of zirconium, niobium and hafnium tracers with HDEHP  

Microsoft Academic Search

Effective separation of the congeneric pair of elements, zirconium and hafnium and also niobium which was in admixtures with zirconium as daughter in its isotopic form were achieved through reversed phase column and paper extraction chromatographic procedures using di-(2-ethylhexyl)phosphoric acid (HDEHP) as the liquid exchanger. In reversed phase column chromatographic separation, the tracers,95Zr,95Nb and175,181Hf, were extracted by HDEHP impregnated on

N. R. Das; Susanta Lahiri

1992-01-01

492

Simple spectrophotometric method for determination of zirconium or hafnium in selected molybdenum-base alloys.  

PubMed

A simple analytical procedure is described for determining zirconium or hafnium in molybdenum-base alloys by formation of the Arsenazo III complex of zirconium or hafnium in 9 M hydrochloric acid medium. The absorbance is measured at 670 nm. Molybdenum (10 mg), titanium (1 mg), and rhenium (10 mg) have no adverse effect. No prior separation is needed. The relative standard deviation is 1.3-2.7%. PMID:18961121

Dupraw, W A

1972-06-01

493

XUV spectra of laser-produced zirconium plasmas  

NASA Astrophysics Data System (ADS)

XUV spectra of laser-produced zirconium plasmas in the 20 to 65 Å wavelength range, where 3d-4p and 3d-4f transitions dominate the observed emission, were studied experimentally and theoretically. Atomic structure calculations were performed with the Cowan and flexible atomic codes. Spectator satellite transitions, especially 3dn-14s-3dn-24s4f, where the 4s electron acts as a ‘real’ spectator, in Mn-, Fe-, Co-, Ni- and Cu-like ions have been found to play an important role. The resulting emission causes arrays resulting from 3dn-3dn4f transitions to broaden and must be included in spectral simulations in order to reproduce the overall spectral profile.

Li, Bowen; Higashiguchi, Takeshi; Otsuka, Takamitsu; Jiang, Weihua; Endo, Akira; Dunne, Padraig; O'Sullivan, Gerry

2012-12-01

494

Improved tribology of tool steel by zirconium ion implantation  

SciTech Connect

AISI D3 tool steel was ion implanted with zirconium and the improvement in surface tribological properties investigated. The Zr ion implantation was done using a metal vapor vacuum arc broad-beam ion source, with a mean ion energy of 130 keV and at doses of 3.6 x 10(sup 16), 5 x 10(sup 16) and 1 x 10(sup 17) ions/cm2. Wear, friction and hardness of the implanted samples were measured and compared to the performance of unimplanted steel. The wear resistance was increased by about a factor of two, the friction remained about the same or was possibly increased by a small amount, and the hardness was improved by a factor of five or more by the ion implantation. We also investigated the effect on the Zr implantation profile of the multi-component energy distribution of the ion beam used here.

Akbas, N.; Oztarhan, A.; Monteiro, O.R.; Brown, I.G.

2001-02-01

495

Computer simulation of zirconium-hafnium separation by countercurrent extraction  

SciTech Connect

In carrying out research and development on an improved method for production of reactor-grade zirconium oxide, the Bureau of Mines has prepared a computer program capable of accurately predicting the stage-by-stage performance of a multistage countercurrent solvent extraction system for extractant. The results were used to plan laboratory experiments using a multistage countercurrent mixer-settler unit. The number of extractor stages, number of scrubber stages, feed solution concentrations, scrubber solution concentration, feed flow, scrubber flow, and organic-phase flow are the significant variables. The computer simulation indicates the effects of changes in the pertinent variables and makes it possible to locate the best combination of variables without a prohibitively large number of time-consuming experiments. 7 figures, 3 tables.

MacDonald, D.J.

1981-01-01

496

Zirconium Copper - a New Material for Use at Low Temperatures?  

SciTech Connect

Cryogenic instruments usually require components with high thermal conductivity. Pure (non alloyed) copper offers very high conductivity, but is soft and not thus always suitable structurally. High conductivity beryllium copper (BeCu) alloys are a common choice when copper is unsuitable since they offer a good compromise between hardness and thermal conductivity. These alloys contain a small (<1%) amount of beryllium (along with a few percent of nickel or cobalt), with strength being obtained by precipitation hardening. An alternative precipitation hardened copper alloy is C15000 zirconium copper (ZrCu), which contains < 0.2% zirconium with the remainder being copper. This material does not seem to be generally used in cryogenic systems, though hardness and strength are comparable to BeCu. Moreover, the lower impurity content suggests that the thermal conductivity should be higher than for BeCu. I present residual resistivity measurements suggesting that ZrCu does indeed possess considerably higher conductivity than BeCu (19 Wm-1K-1 at 1 K compared to approximately 2 Wm-1K-1), and should therefore be a very useful material. A method is given for extrapolating the low temperature thermal conductivity values to temperatures up to 300 K; good agreement is seen with room temperature data-sheet values. This extrapolation method is shown to also be applicable to BeCu and thus presumably other dilute copper alloys, and is used to give recommended values for coin silver and various BeCu alloy types, including C17510 and C17200.

Woodcraft, Adam L. [School of Physics and Astronomy, Cardiff University, Cardiff, 5 The Parade, Cardiff, CF24 3YB (United Kingdom)

2006-09-07

497

Ion beam mixing of chromium or zirconium films with sapphire  

SciTech Connect

Ion beam mixing of thin metallic films deposited on sapphire substrates was studied for chromium or zirconium films deposited on single crystalline {alpha}-Al{sub 2}0{sub 3} substrates. Evidence for the influence of equilibrium thermodynamic factors was sought by comparing the effects of bombarding with oxygen ions (300 and 1073 K) with those of neon ions (300 K). Thermodynamic calculations indicate that mixing might occur for Zr/sapphire at 1073 K but not at 300 K. Chromium/sapphire should not be mixed at either temperature. The implantation energy placed the peak oxygen concentration at the metal/sapphire interface in an attempt to maintain an equilibrium ratio of cations/anions and promote a radiation-induced chemical reaction across the interface. Rutherford backscattering-ion channeling measurements indicated that the widths of ``mixed`` regions were consistent with those predicted from ballistic considerations. Other experiments employed a heavier ion (krypton) as the mixing ion (300 K) in order to increase the mixing efficiency. Rutherford backscattering-ion channeling and x-ray photoelectron spectroscopy were used to determine the extent and nature of any interface modification. XPS results indicated that only metallic chromium (Cr{sup 0}) was present near the interface before and after irradiation with Kr at 300 K. Zirconium exhibited only the metallic state (Zr{sup 0}) in the as-deposited film but was present as both Zr{sup 0} and Zr{sup 4{plus}} after irradiation. Some metallic aluminum (AI{sup O}) was detected near the Zr/sapphire interface, suggesting that a local chemical reaction between Zr and the sapphire occurred during bombardment. No long-range material transport was detected for any experimental condition examined; the width of the ``mixed` region in each case was consistent with that expected for ballistic effects.

McHargue, C.J. [Tennessee Univ., Knoxville, TN (United States); Joslin, D.L.; White, C.W. [Oak Ridge National Lab., TN (United States); daSilva, M.F.; Alves, E. [National Inst. for Industrial Technology and Engineering, Sacavem (Portugal); Soares, J.C. [Lisbon Univ. (Portugal)

1995-12-31

498

Spectrophotometric determination of zirconium and hafnium with 4-(2-pyridylazo)resorcinol  

SciTech Connect

Reaction behavior of zirconium and hafnium with 4-(2-pyridylazo)resorcinol is established under various conditions. Optimum conditions for a very sensitive spectrophotometric procedure are outlined for the determination of zirconium and hafnium. Zirconium and hafnium react quantitatively with the reagent in alkaline pH from 8 to 9.2 and 8 to 9.8, respectively, to form 1:2 water-soluble complexes. The molar absorptivity for zirconium and hafnium is 66,000 and 77,400, respectively. The order of addition of the reagent, metal ion, and buffer solution is evaluated. It is concluded that both zirconium and hafnium solutions must be maintained at higher acidities to react quantitatively with the reagent. A number of foreign ions are tested for their interference and the use of masking agents and selective extractive agents is outlined. The relative standard deviations are +/-0.5% and +/-0.7 for the determination of 30 ..mu..g of zirconium and 40 ..mu..g of hafnium, respectively. 3 figures, 3 tables.

Kalyanaraman, S.; Fukasawa, T.

1983-12-01

499

Halide Ion Enhancement of Nitrate Ion Photolysis  

NASA Astrophysics Data System (ADS)

Nitrate ion photochemistry is an important source of NOx in the polar regions. It is uncertain whether coexisting ions such as halides play a role in nitrate photochemistry. The effect of halides on NO3 photolysis was investigated using photolysis experiments in 230 L Teflon chambers that contain deliquesced aerosols of NaBr:NaNO3, KBr:KNO3 and ternary mixtures of NaCl:NaBr:NaNO3. Gas phase NO2 and gaseous halogen products were measured as a function of photolysis time using long path FTIR, NOx chemiluminescence and API-MS (atmospheric pressure ionization mass spectrometry). Experiments were conducted with NO3- held at a constant 0.5 M and with the amount of total halide concentration varying from 0.25 M to 4 M. Studies on NaBr:NaNO3 mixtures suggest that as the bromide ion to nitrate ion ratio increases, there is an enhancement in the rate of production of NO2 in the nitrate-bromide mixtures over that formed in the photolysis of NaNO3. Molecular dynamic (MD) simulations provide molecular level insight into the ions near the air-water interface in the aqueous halide-nitrate mixtures. These studies suggest that the presence of sodium halides at the air-water interface may encourage some nitrate ions to approach the top layers of water, allowing for more efficient escape of photoproducts than is seen in the absence of halides. Experiments on mixtures of KBr:KNO3 are being conducted to determine potential cation effects. In addition, ternary mixtures of NaCl:NaBr:NaNO3 are being examined to determine the effects of mixtures of halides on production of NO2 and gaseous halogen products. The implications of this photochemistry for tropospheric chemistry will be discussed.

Richards, N. K.; Wingen, L. M.; Callahan, K. M.; Tobias, D. J.; Finlayson-Pitts, B. J.

2009-12-01

500

Electrolytic removal of nitrate from crop residues.  

PubMed

The Controlled Ecological Life Support System (CELSS) resource recovery system, which is a waste-processing system,uses aerobic and anaerobic bioreactors to recover plants nutrients and secondary foods from the inedible biomass. Crop residues contain a significant amount of nitrate. There are actually two major problems concerning nitrate: 1) both CELSS biomass production and resource recovery consume large quantities of nitric acid, and 2) nitrate causes a variety of problems in both aerobic and anaerobic bioreactors. The nitrate anion causes several problems in the resource recovery system in such a way that removal prior to the process is highly desirable. The technique proposed to remove nitrate from potato inedible biomass leachate and to satisfy the nitric acid demand was a four-compartment electrolytic cell. In order to establish the electrolytic cell performance variables, experiments were carried out using potato crop residue aqueous leachate as the diluate solution. The variables studied were the potato biomass leachate composition and electrical properties, preparation of compartment solutions to be compatible with the electrolytic system, limiting current density, nutrients removal rates as a function of current density, fluid hydrodynamic conditions, applied voltage, and process operating time during batch recirculation operation. Results indicated that the limiting current density (maximum operating current density) was directly proportional to the solution electrical conductivity an a power function of the linear fluid velocity in the range between 0.083 and 0.403 m/s. During the electrolytic cell once-through operation, the nitrate, potassium, and other nutrient removal rates were proportional to the current density and were inversely proportional to fluid velocity. The removal of monovalent ions was found to be higher than divalent ones. Under batch recirculation operation at constant applied voltage of 4.5 and 8.5 V, it was found that the nutrient removal rates were independent of applied voltage, but were proportional to the ions concentration and operating time. PMID:11676458

Colon, G; Sager, J C

2001-01-01