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Sample records for graphite furnace atomic

  1. Improved graphite furnace atomizer

    DOEpatents

    Siemer, D.D.

    1983-05-18

    A graphite furnace atomizer for use in graphite furnace atomic absorption spectroscopy is described wherein the heating elements are affixed near the optical path and away from the point of sample deposition, so that when the sample is volatilized the spectroscopic temperature at the optical path is at least that of the volatilization temperature, whereby analyteconcomitant complex formation is advantageously reduced. The atomizer may be elongated along its axis to increase the distance between the optical path and the sample deposition point. Also, the atomizer may be elongated along the axis of the optical path, whereby its analytical sensitivity is greatly increased.

  2. Simultaneous multielement atomic absorption spectrometry with graphite furnace atomization

    NASA Astrophysics Data System (ADS)

    Harnly, James M.; Miller-Ihli, Nancy J.; O'Haver, Thomas C.

    The extended analytical range capability of a simultaneous multielement atomic absorption continuum source spectrometer (SIMAAC) was tested for furnace atomization with respect to the signal measurement mode (peak height and area), the atomization mode (from the wall or from a platform), and the temperature program mode (stepped or ramped atomization). These parameters were evaluated with respect to the shapes of the analytical curves, the detection limits, carry-over contamination and accuracy. Peak area measurements gave more linear calibration curves. Methods for slowing the atomization step heating rate, the use of a ramped temperature program or a platform, produced similar calibration curves and longer linear ranges than atomization with a stepped temperature program. Peak height detection limits were best using stepped atomization from the wall. Peak area detection limits for all atomization modes were similar. Carry-over contamination was worse for peak area than peak height, worse for ramped atomization than stepped atomization, and worse for atomization from a platform than from the wall. Accurate determinations (100 ± 12% for Ca, Cu, Fe, Mn, and Zn in National Bureau of Standards' Standard Reference Materials Bovine Liver 1577 and Rice Flour 1568 were obtained using peak area measurements with ramped atomization from the wall and stepped atomization from a platform. Only stepped atomization from a platform gave accurate recoveries for K. Accurate recoveries, 100 ± 10%, with precisions ranging from 1 to 36 % (standard deviation), were obtained for the determination of Al, Co, Cr, Fe, Mn, Mo, Ni. Pb, V and Zn in Acidified Waters (NBS SRM 1643 and 1643a) using stepped atomization from a platform.

  3. Direct analysis of solids by graphite furnace atomic absorption spectrometry using a second surface atomizer

    SciTech Connect

    Rettberg, T.M.; Holcombe, J.A.

    1986-06-01

    The direct graphite furnace atomic absorption spectrometric analysis of solids using the second surface atomizer has been investigated. The atomizer features a gas-cooled Ta insert within the graphite furnace onto which the analyte can be condensed, after which atomization is performed by raising the furnace to a higher temperature and shutting off the coolant gas. The analyses were conducted on standard reference material fly ash, river sediment, and citrus leaves, in addition to filter paper samples. All analyses were conducted without sample pretreatment or use of matrix modifiers. Quantitation was done by using simple aqueous standards. By use of peak heights, the recoveries varied from 81% to 127%, although several determinations were within the certified concentration range. The procedures typically gave low background absorbances and peak shapes that were relatively independent of the original sample matrix.

  4. DETERMINING BERYLLIUM IN DRINKING WATER BY GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROSCOPY

    EPA Science Inventory

    A direct graphite furnace atomic absorption spectroscopy method for the analysis of beryllium in drinking water has been derived from a method for determining beryllium in urine. Ammonium phosphomolybdate and ascorbic acid were employed as matrix modifiers. The matrix modifiers s...

  5. [Application of solid sampling graphite furnace atomic absorption spectrophotometry to mensuration of brain iron content in rats].

    PubMed

    Zhang, Nan; Sheng, Qing-hai; Shi, Zhen-hua; Zhang, Zhi-guo; Duan, Xiang-lin; Chang, Yan-zhong

    2009-04-01

    In the present study, the authors performed the solid sampling and detected the iron levels in cortex, hippocampus and striatum of rat brain by GFAAS. The authors' results showed that there are no remarkable difference between the data obtained by solid sampling graphite furnace atomic absorption and liquid sampling graphite furnace atomic absorption. Compared to liquid sampling graphite furnace atomic absorption, the sample pre-treatment stage was obviously simplified, the cost was reduced significantly, and the time was shortened significantly in the solid sampling GFAAS. This study will be beneficial to the mensuration of iron content in micro-tissue of animal by solid sampling GFASS.

  6. Analysis of lithium in deep basalt groundwaters using graphite furnace atomic absorption spectrophotometry

    SciTech Connect

    Dill, J.A.; Marcy, A.D.

    1986-05-01

    Lithium is under consideration for use as a reactive (sorptive) tracer in experiments designed to provide information regarding natural attenuation processes in a basalt-groundwater environment. In support of these activities, background lithium concentrations in samples obtained from a variety of test horizons have been determined using graphite furnace atomic absorption spectrophotometry. Significant interference was observed in these determinations and was found to be due to the presence of silicate in the samples. It was found that these problems could be circumvented through the use of alkaline silicate or synthetic groundwater matrix modifiers. This matrix effect was examined in some detail. Results obtained using the graphite furnace were compared to results obtained using inductively coupled plasma atomic emission spectroscopy.

  7. Determination of trace elements in paints by direct sampling graphite furnace atomic absorption spectrometry.

    PubMed

    Bentlin, Fabrina R S; Pozebon, Dirce; Mello, Paola A; Flores, Erico M M

    2007-10-17

    A direct sampling graphite furnace atomic absorption spectrometric (DS-GFAAS) method for the determination of Cd, Pb, Cr, Ni, Co and Cu in paints has been developed. Serigraphy, acrylic and tattoo paints were analysed. Approaches like pyrolysis and atomization temperatures, modifiers and sample mass introduced in the atomizer were studied. Quantification was performed using calibration curves measured with aqueous standard solutions pipetted onto the platform. The sample mass introduced in the graphite tube ranged from 0.02 to 8.0 mg. Palladium was used as modifier for Cd, Pb and Cu, while Mg(NO3)2 was used for Co. For Ni determination, the graphite platform was covered with carbon powder. The characteristic masses of Cd, Pb, Cr, Ni, Co and Cu were 1.4, 22.5, 7.9, 11.0, 9.6 and 12.5 pg, while the limits of detection were 0.0004, 0.001, 0.03, 0.22, 0.11 and 0.05 microg g(-1) of Cd, Pb, Cr, Ni, Co and Cu, respectively. The accuracy was determined by comparison of the results with those obtained by inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrometry (GFAAS), using liquid sampling of digests. For matrix characterization, major and minor elements (Al, Mg, Ba, Ca, Cr, Cu, Pb, Sr, Ti and Mg) were determined by inductively coupled plasma optical emission spectrometry (ICP OES).

  8. Method 200.12 - Determination of Trace Elements in Marine Waters by StabilizedTemperature Graphite Furnace Atomic Absorption

    EPA Science Inventory

    This method provides procedures for the determination of total recoverable elements by graphite furnace atomic absorption (GFAA) in marine waters, including estuarine, ocean and brines with salinities of up to 35 ppt.

  9. Simultaneous multielement graphite furnace atomic absorption measurements using a photodiode array detector

    NASA Astrophysics Data System (ADS)

    Tong, S. L.; Chin, K. S.

    1994-05-01

    A photodiode array detector multichannel analyser system has been coupled to a graphite furnace atomizer and tested for simultaneous multielement atomic absorption analysis. Multielement hollow cathode lamps are used as light sources and spectral lines are dispersed through a spectrograph with three selectable gratings. Multiple transmitted spectra are recorded to simultaneously determine the atomic absorption profiles of the analyte elements during the atomization stage. Atomic absorbance of individual elements is obtained by integrating the respective peak areas of the appropriate time-resolved atomic absorption spectra. The obtained sensitivities for Ni-Co-Fe are within the same order of magnitude as those from conventional single element determinations using photomultiplier tube detection. The system has also been applied for simultaneous multielement flame atomic absorption spectrometry (AAS) measurements and it has been demonstrated that background absorption can be readily corrected for both flame and graphite furnace AAS by a two-line method where non-atomic absorption lines can be chosen from the simultaneously recorded spectra.

  10. Determination of total tin in silicate rocks by graphite furnace atomic absorption spectrometry

    USGS Publications Warehouse

    Elsheimer, H.N.; Fries, T.L.

    1990-01-01

    A method is described for the determination of total tin in silicate rocks utilizing a graphite furnace atomic absorption spectrometer with a stabilized-temperature platform furnace and Zeeman-effect background correction. The sample is decomposed by lithium metaborate fusion (3 + 1) in graphite crucibles with the melt being dissolved in 7.5% hydrochloric acid. Tin extractions (4 + 1 or 8 + 1) are executed on portions of the acid solutions using a 4% solution of tricotylphosphine oxide in methyl isobutyl ketone (MIBK). Ascorbic acid is added as a reducing agent prior to extraction. A solution of diammonium hydrogenphosphate and magnesium nitrate is used as a matrix modifier in the graphite furnace determination. The limit of detection is > 10 pg, equivalent to > 1 ??g l-1 of tin in the MIBK solution or 0.2-0.3 ??g g-61 in the rock. The concentration range is linear between 2.5 and 500 ??g l-1 tin in solution. The precision, measured as relative standard deviation, is < 20% at the 2.5 ??g l-1 level and < 7% at the 10-30 ??g l-1 level of tin. Excellent agreement with recommended literature values was found when the method was applied to the international silicate rock standards BCR-1, PCC-1, GSP-1, AGV-1, STM-1, JGb-1 and Mica-Fe. Application was made to the determination of tin in geological core samples with total tin concentrations of the order of 1 ??g g-1 or less.

  11. Determining beryllium in drinking water by graphite furnace atomic absorption spectroscopy

    SciTech Connect

    Lytle, D.A.; Schock, M.R.; Dues, N.R.; Doerger, J.U.

    1993-01-01

    A direct graphite furnace atomic absorption spectroscopy method for the analysis of beryllium in drinking water has been derived from a method for determining beryllium in urine. Ammonium phosphomolybdate and ascorbic acid were employed as matrix modifiers. The matrix modifiers successfully eliminated common chemical interferences in drinking water samples analyzed for beryllium content, as well as interferences encountered during jar testing of beryllium removal by alum coagulation. The method proved to be a simple, accurate, and precise alternative to the method of standard additions. Method detection limit was 0.09 microgram/l, with a linear calibration range of 0 to 6 microgram/l.

  12. Determination of Copper by Graphite Furnace Atomic Absorption Spectrophotometry: A Student Exercise in Instrumental Methods of Analysis.

    ERIC Educational Resources Information Center

    Williamson, Mark A.

    1989-01-01

    Discusses a student exercise which requires the optimizing of the charring and atomization temperatures by producing a plot of absorbance versus temperature for each temperature parameter. Notes that although the graphite furnace atomic absorption spectroscopy technique has widespread industrial use, there are no published, structured experiments…

  13. Determination of ruthenium in pharmaceutical compounds by graphite furnace atomic absorption spectroscopy.

    PubMed

    Jia, Xiujuan; Wang, Tiebang; Bu, Xiaodong; Tu, Qiang; Spencer, Sandra

    2006-04-11

    A graphite furnace atomic absorption (GFAA) spectrometric method for the determination of ruthenium (Rh) in solid and liquid pharmaceutical compounds has been developed. Samples are dissolved or diluted in dimethyl sulfoxide (DMSO) without any other treatment before they were analyzed by GFAA with a carefully designed heating program to avoid pre-atomization signal loss and to achieve suitable sensitivity. Various inorganic and organic solvents were tested and compared and DMSO was found to be the most suitable. In addition, ruthenium was found to be stable in DMSO for at least 5 days. Spike recoveries ranged from 81 to 100% and the limit of quantitation (LOQ) was determined to be 0.5 microg g(-1) for solid samples or 0.005 microg ml(-1) for liquid samples based a 100-fold dilution. The same set of samples was also analyzed by ICP-MS with a different sample preparation method, and excellent agreement was achieved. PMID:16314066

  14. Liquid-phase microextraction combined with graphite furnace atomic absorption spectrometry: A review.

    PubMed

    de la Calle, Inmaculada; Pena-Pereira, Francisco; Lavilla, Isela; Bendicho, Carlos

    2016-09-14

    An overview of the combination of liquid-phase microextraction (LPME) techniques with graphite furnace atomic absorption spectrometry (GFAAS) is reported herein. The high sensitivity of GFAAS is significantly enhanced by its association with a variety of miniaturized solvent extraction approaches. LPME-GFAAS thus represents a powerful combination for determination of metals, metalloids and organometallic compounds at (ultra)trace level. Different LPME modes used with GFAAS are briefly described, and the experimental parameters that show an impact in those microextraction processes are discussed. Special attention is paid to those parameters affecting GFAAS analysis. Main issues found when coupling LPME and GFAAS, as well as those strategies reported in the literature to solve them, are summarized. Relevant applications published on the topic so far are included.

  15. Development of mixed-waste analysis capability for graphite furnace atomic absorption spectrophotometry

    SciTech Connect

    Bass, D.A.; TenKate, L.B.; Wroblewski, A.

    1995-03-01

    Graphite furnace atomic absorption spectrophotometer (GFAAS) are typically configured with ventilation to capture potentially toxic and corrosive gases emitted from the vaporization of sample aliquots. When radioactive elements are present, additional concerns (such as meeting safety guidelines and ALARA principles) must be addressed. This report describes a modification to a GFAAS that provides additional containment of vaporized sample aliquots. The modification was found to increase containment by a factor of 80, given expected operating conditions. The use of the modification allows more mixed-waste samples to be analyzed, permits higher levels of radioactive samples to be analyzed, or exposes the analyst to less airborne radioactivity. The containment apparatus was attached to a Perkin-Elmer Zeeman 5000 spectrophotometer for analysis of mixed-waste samples; however, it could also be used on other systems and in other applications where greater containment of vaporized material is desired.

  16. Liquid-phase microextraction combined with graphite furnace atomic absorption spectrometry: A review.

    PubMed

    de la Calle, Inmaculada; Pena-Pereira, Francisco; Lavilla, Isela; Bendicho, Carlos

    2016-09-14

    An overview of the combination of liquid-phase microextraction (LPME) techniques with graphite furnace atomic absorption spectrometry (GFAAS) is reported herein. The high sensitivity of GFAAS is significantly enhanced by its association with a variety of miniaturized solvent extraction approaches. LPME-GFAAS thus represents a powerful combination for determination of metals, metalloids and organometallic compounds at (ultra)trace level. Different LPME modes used with GFAAS are briefly described, and the experimental parameters that show an impact in those microextraction processes are discussed. Special attention is paid to those parameters affecting GFAAS analysis. Main issues found when coupling LPME and GFAAS, as well as those strategies reported in the literature to solve them, are summarized. Relevant applications published on the topic so far are included. PMID:27566338

  17. Direct analysis of silica by means of solid sampling graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Resano, M.; Mozas, E.; Crespo, C.; Pérez, J.; García-Ruiz, E.; Belarra, M. A.

    2012-05-01

    This paper reports on the use of solid sampling-graphite furnace atomic absorption spectrometry for the direct analysis of synthetic amorphous silica. In particular, determination of hazardous elements such As, Cd, Cr, Cu, Pb and Sb is investigated, as required by regulations of the food industry. The conclusion of the work is that, after proper optimization of the working conditions, paying particular attention to the atomization temperature and the use of proper modifiers (graphite powder, HNO3 or Pd), it is possible to develop suitable procedures that rely on the use of aqueous standard solutions to construct the calibration curves for all the elements investigated. The proposed method shows important benefits for the cost-effective analysis of such difficult samples in routine labs, permitting fast screening of those elements that are very rarely present in this type of sample, but also accurate quantification of those often found, while offering low limits of detection (always below 0.1 mg g- 1) that comply well with legal requirements, and precision levels that are fit for the purpose (approx. 6-9% R.S.D.).

  18. Determination of yttrium and rare-earth elements in rocks by graphite-furnace atomic-absorption spectrometry.

    PubMed

    Gupta, J G

    1981-01-01

    With use of synthetic solutions and several international standard reference materials a method has been developed for determining traces of Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu in rocks by electrothermal atomization in a pyrolytically-coated graphite furnace. Depending on the element, the sensitivity is of the order of 10(-9)-10(-12) g at 2500 degrees . To avoid matrix interferences the lanthanides are separated from the common elements by co-precipitation with calcium and iron as carriers. The data for Canadian reference rock SY-2 (syenite), U.S.G.S. reference rocks W-2 (diabase), DNC-1 (diabase) and BIR-1 (basalt), and South African reference rock NIM-18/69 (carbonatite) obtained by graphite-furnace atomization are compared with the values obtained by flame atomic-absorption. The results are in good agreement with literature values.

  19. Determination of yttrium and rare-earth elements in rocks by graphite-furnace atomic-absorption spectrometry.

    PubMed

    Gupta, J G

    1981-01-01

    With use of synthetic solutions and several international standard reference materials a method has been developed for determining traces of Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu in rocks by electrothermal atomization in a pyrolytically-coated graphite furnace. Depending on the element, the sensitivity is of the order of 10(-9)-10(-12) g at 2500 degrees . To avoid matrix interferences the lanthanides are separated from the common elements by co-precipitation with calcium and iron as carriers. The data for Canadian reference rock SY-2 (syenite), U.S.G.S. reference rocks W-2 (diabase), DNC-1 (diabase) and BIR-1 (basalt), and South African reference rock NIM-18/69 (carbonatite) obtained by graphite-furnace atomization are compared with the values obtained by flame atomic-absorption. The results are in good agreement with literature values. PMID:18962852

  20. Graphite furnace-atomic absorption spectrophotometric determination of palladium in soil.

    PubMed

    Patel, K S; Sharma, P C; Hoffmann, P

    2000-08-01

    A new and sensitive procedure for the graphite furnace-atomic absorption spectrophotometric (GF-AAS) determination of Pd in soil at nanogram level is described. The method is based on prior separation and enrichment of the metal as Pd(II)-SnCl3- -N-butylacetamide (BAA) complex into 1-pentanol (PN) by solvent extraction method. The value of the molar absorptivity of the complex in three solvents, i.e. ethyl acetate, 1-pentanol, chloroform, lie in the range of (0.70-2.75) x 10(4) L mol(-1) cm(-1) at lambda(max) 360-440 nm. The metal could be enriched into organic solvent, i.e. PN, up to 10-folds. The sensitivity (A = 0.0044) of the method in the term of the peak height was 0.5 ng Pd/mL of the aqueous solution at an enrichment factor (EF) of 5. Optimization of analytical variables during enrichment and GF-AAS determination of the metal are discussed. The method has been applied for the analysis of Pd to soil samples derived from roads and highways in Germany. PMID:11220609

  1. Model calculation of the characteristic mass for convective and diffusive vapor transport in graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Bencs, László; Laczai, Nikoletta; Ajtony, Zsolt

    2015-07-01

    A combination of former convective-diffusive vapor-transport models is described to extend the calculation scheme for sensitivity (characteristic mass - m0) in graphite furnace atomic absorption spectrometry (GFAAS). This approach encompasses the influence of forced convection of the internal furnace gas (mini-flow) combined with concentration diffusion of the analyte atoms on the residence time in a spatially isothermal furnace, i.e., the standard design of the transversely heated graphite atomizer (THGA). A couple of relationships for the diffusional and convectional residence times were studied and compared, including in factors accounting for the effects of the sample/platform dimension and the dosing hole. These model approaches were subsequently applied for the particular cases of Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, V and Zn analytes. For the verification of the accuracy of the calculations, the experimental m0 values were determined with the application of a standard THGA furnace, operating either under stopped, or mini-flow (50 cm3 min- 1) of the internal sheath gas during atomization. The theoretical and experimental ratios of m0(mini-flow)-to-m0(stop-flow) were closely similar for each study analyte. Likewise, the calculated m0 data gave a fairly good agreement with the corresponding experimental m0 values for stopped and mini-flow conditions, i.e., it ranged between 0.62 and 1.8 with an average of 1.05 ± 0.27. This indicates the usability of the current model calculations for checking the operation of a given GFAAS instrument and the applied methodology.

  2. Graphite furnace atomic absorption spectrophotometry--a novel method to quantify blood volume in experimental models of intracerebral hemorrhage.

    PubMed

    Kashefiolasl, Sepide; Foerch, Christian; Pfeilschifter, Waltraud

    2013-02-15

    Intracerebral hemorrhage (ICH) accounts for 10% of all strokes and has a significantly higher mortality than cerebral ischemia. For decades, ICH has been neglected by experimental stroke researchers. Recently, however, clinical trials on acute blood pressure lowering or hyperacute supplementation of coagulation factors in ICH have spurred an interest to also design and improve translational animal models of spontaneous and anticoagulant-associated ICH. Hematoma volume is a substantial outcome parameter of most experimental ICH studies. We present graphite furnace atomic absorption spectrophotometric analysis (AAS) as a suitable method to precisely quantify hematoma volumes in rodent models of ICH.

  3. Selenium concentration levels in whole blood of Belgian blood bank donors, as determined by direct graphite furnace atomic absorption spectrometry.

    PubMed

    Van Cauwenbergh, R; Robberecht, H; Deelstra, H

    1990-12-01

    Direct graphite furnace atomic absorption spectrometry after appropriate sample dilution is applied to whole blood of Belgian blood bank donors from different geographical areas. Highest values were obtained for the northern part of the country (Flanders). Different consumption habits may explain the significant difference in selenium level found for the two cultural communities (Flemish and Walloon). No sex difference was obtained in both parts of the country and no influence of age was observed for the two communities. Values obtained are compared with literature data on whole blood selenium content for other European countries.

  4. Maintenance of the slope of linearized calibration curves in Zeeman graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Yuzefovsky, Alexander I.; Lonardo, Robert F.; Zhou, Jack X.; Michel, Robert G.; Koltracht, Israel

    1996-06-01

    L'vov and co-workers developed a theoretical model and computational procedure (B.V. L'vov, L.K. Polzik and N.V. Kocharova, Spectrochim. Acta Part B, 47 (1992) 889 and B.V. L'vov, L.K. Polzik, N.V. Kocharova, Yu.A. Nemets and A.V. Novichikhin, Spectrochim. Acta Part B, 47 (1992) 1187) that linearized calibration curves in Zeeman graphite furnace atomic absorption spectrometry by taking into account the presence of stray light. The calculations of L'vov and co-workers were based on three parameters: the rollover absorbance Ar, Zeeman sensitivity ratio R, and the original background corrected peak absorbance values Az. In order to simplify the calculations, R was assumed to be unity. In the studies reported here, this simplification is shown to be unsatisfactory because the slope obtained in the upper portion of the calibration curve, after linearization, is found to be different from the slope obtained in the normal linear region. Deviations between these slopes were found to be as high as 30%. The present work also shows that the theoretical model of L'vov and co-workers does not have a mathematical solution at high values of Az. This failure of the model prevents its use at high Az values. The physical nature of this failure is still unclear, which points to the necessity for further work to understand the inadequacies of the present theory. In the present studies, calculations based on the Newton method of successive approximations (A.I. Yuzefovsky, E.G. Su, R.G. Michel, W. Slavin and J.T. McCaffrey, Spectrochim. Acta Part B, 49 (1994) 1643), allow incorporation of the experimental value of R at the rollover point R', which better linearizes the calibration curves. By use of this approach, a satisfactory result is obtained for lead ( R' = 0.67) up to the point of failure of the model at high values of Az.

  5. Determination of trace amount of cobalt in feed grains and forages by solvent extraction and graphite furnace atomic absorption spectrometry.

    PubMed

    Blanchflower, W J; Cannavan, A; Kennedy, D G

    1990-10-01

    A method is described for the determination of trace amounts of cobalt in feed grains and forages with a detection limit of 1 ng g-1. Samples are ashed in a muffle furnace and complexed with 2-nitroso-1-naphthol. Following solvent extraction, cobalt is determined using graphite furnace atomic absorption spectrometry. The assay can be carried out in a normal analytical laboratory without the need for special "clean" rooms. Reagents have been selected to keep reagent blank values at low levels, and heptan-2-one is used as extracting solvent to avoid problems with evaporation. The assay has been used for diagnostic purposes and to formulate special low cobalt diets for sheep for experimental purposes. PMID:2270874

  6. Cadmium, copper, lead, and zinc determination in precipitation: A comparison of inductively coupled plasma atomic emission spectrometry and graphite furnace atomization atomic absorption spectrometry

    USGS Publications Warehouse

    Reddy, M.M.; Benefiel, M.A.; Claassen, H.C.

    1987-01-01

    Selected trace element analysis for cadmium, copper, lead, and zinc in precipitation samples by inductively coupled plasma atomic emission Spectrometry (ICP) and by atomic absorption spectrometry with graphite furnace atomization (AAGF) have been evaluated. This task was conducted in conjunction with a longterm study of precipitation chemistry at high altitude sites located in remote areas of the southwestern United States. Coefficients of variation and recovery values were determined for a standard reference water sample for all metals examined for both techniques. At concentration levels less than 10 micrograms per liter AAGF analyses exhibited better precision and accuracy than ICP. Both methods appear to offer the potential for cost-effective analysis of trace metal ions in precipitation. ?? 1987 Springer-Verlag.

  7. Surfactant/oil/water system for the determination of selenium in eggs by graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Ieggli, C. V. S.; Bohrer, D.; Noremberg, S.; do Nascimento, P. C.; de Carvalho, L. M.; Vieira, S. L.; Reis, R. N.

    2009-06-01

    An oil-in-water formulation has been optimized to determine trace levels of selenium in whole hen eggs by graphite furnace atomic absorption spectrometry. This method is simpler and requires fewer reagents when compared with other sample pre-treatment procedures. Graphite furnace atomic absorption spectrometric (GF AAS) measurement was carried out using standard addition calibration and Pd as a modifier. The precision, expressed as relative standard deviation, was better than 5% and the limit of detection was 1 µg L - 1 . The validation of the method was performed against a standard reference material Whole Egg Powder (RM 8415), and the measured Se corresponded to 95.2% of the certified value. The method was used for the determination of the Se level in eggs from hens treated with Se dietary supplements. Inorganic and organic Se sources were added to hen feed. The Se content of eggs was higher when hens were fed with organic Se compared to the other treatments. The proposed method, including sample emulsification for subsequent Se determination by GF AAS has proved to be sensitive, reproducible, simple and economical.

  8. Atomic and molecular spectra of vapors evolved in graphite furnace. Part 7: Alkaline metal sulfates and sulfides

    NASA Astrophysics Data System (ADS)

    Lemme, M.; Katskov, D. A.; Tittarelli, P.

    2004-01-01

    Thermal behavior and vapor absorption spectra of Li, Na and K sulfates and Li, Na sulfides in graphite vaporizers for atomic absorption spectrometry are investigated using a UV spectrometer with a charge-coupled device (CCD) detector. Fifty spectra in the wavelength range 190-380 nm are collected during the vaporization of 1 μg and 10 μg of metal as sulfide and sulfate, respectively, simultaneously to the increase of vaporizer temperature from 700 to 2700 K during 10 s. The behavior of transient spectra is compared for the pyrocoated tube and filter furnace. It is found that Na and K sulfates in the pyrocoated tube evolve, first, metal bound sulfur-oxygen compounds, while Li sulfate emanates S 2 vapor. For all substances studied, the vaporization involves active interaction with graphite, suggestively with formation of graphite-metal and graphite-sulfur intercalation compounds. Those compounds retained metal and sulfur until above 2000 K. Both vapor dissociation and decomposition of intercalation compounds are accompanied by appearance in gas phase of CS molecules. In the filter furnace at high temperature the structured spectrum between 190 and 210 nm is characteristic for all sulfur containing compounds. It is suggestively attributed to C nS m ( n> m) molecule. The samples of Li and Na sulfides do not retain initial chemical composition after dissolving, sampling from solution, drying and pyrolysis at 700 K. Their vapor spectra show the presence of sodium sulfate (or sulfite) and lithium oxide in the respective dry residues. The diffuse absorption bands at 190-230 nm with maxima at 200-210 nm precede or appear together with molecular spectra. The phenomenon is suggestively assigned to the light scattering on specific molecular clusters.

  9. Determination of bismuth in environmental samples by slurry sampling graphite furnace atomic absorption spectrometry using combined chemical modifiers.

    PubMed

    Dobrowolski, Ryszard; Dobrzyńska, Joanna; Gawrońska, Barbara

    2015-01-01

    Slurry sampling graphite furnace atomic absorption spectrometry technique was applied for the determination of Bi in environmental samples. The study focused on the effect of Zr, Ti, Nb and W carbides, as permanent modifiers, on the Bi signal. Because of its highest thermal and chemical stability and ability to substantially increase Bi signal, NbC was chosen as the most effective modifier. The temperature programme applied for Bi determination was optimized based on the pyrolysis and atomization curves obtained for slurries prepared from certified reference materials (CRMs) of the soil and sediments. To overcome interferences caused by sulfur compounds, Ba(NO₃)₂ was used as a chemical modifier. Calibration was performed using the aqueous standard solutions. The analysis of the CRMs confirmed the reliability of the proposed analytical method. The characteristic mass for Bi was determined to be 16 pg with the detection limit of 50 ng/g for the optimized procedure at the 5% (w/v) slurry concentration.

  10. Determination of total tin in geological materials by electrothermal atomic-absorption spectrophotometry using a tungsten-impregnated graphite furnace

    USGS Publications Warehouse

    Zhou, L.; Chao, T.T.; Meier, A.L.

    1984-01-01

    An electrothermal atomic-absorption spectrophotometric method is described for the determination of total tin in geological materials, with use of a tungsten-impregnated graphite furnace. The sample is decomposed by fusion with lithium metaborate and the melt is dissolved in 10% hydrochloric acid. Tin is then extracted into trioctylphosphine oxide-methyl isobutyl ketone prior to atomization. Impregnation of the furnace with a sodium tungstate solution increases the sensitivity of the determination and improves the precision of the results. The limits of determination are 0.5-20 ppm of tin in the sample. Higher tin values can be determined by dilution of the extract. Replicate analyses of eighteen geological reference samples with diverse matrices gave relative standard deviations ranging from 2.0 to 10.8% with an average of 4.6%. Average tin values for reference samples were in general agreement with, but more precise than, those reported by others. Apparent recoveries of tin added to various samples ranged from 95 to 111% with an average of 102%. ?? 1984.

  11. Determination of Pb in Biological Samples by Graphite Furnace Atomic Absorption Spectrophotometry: An Exercise in Common Interferences and Fundamental Practices in Trace Element Determination

    ERIC Educational Resources Information Center

    Spudich, Thomas M.; Herrmann, Jennifer K.; Fietkau, Ronald; Edwards, Grant A.

    2004-01-01

    An experiment is conducted to ascertain trace-level Pb in samples of bovine liver or muscle by applying graphite furnace atomic absorption spectrophotometry (GFAAS). The primary objective is to display the effects of physical and spectral intrusions in determining trace elements, and project the usual methods employed to minimize accuracy errors…

  12. Direct determination of particulate elements in edible oils and fats using an ultrasonic slurry sampler with graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    van Dalen, Gerard; de Galan, Leo

    1994-12-01

    Through the use of an ultrasonic slurry mixer, graphite furnace atomic absorption spectrometry (GFAAS) can be applied for the fully automated determination of particulate iron and nickel in edible oils and fats. The unsupervised ultrasonic slurry autosampler yields the same accuracy and somewhat better precision than the much more laborious manual GFAAS method.

  13. Determination of cadmium in spring water by graphite-furnace atomic absorption spectrometry after coprecipitation with ytterbium hydroxide.

    PubMed

    Atsumi, Kousuke; Minami, Tomoharu; Ueda, Joichi

    2005-06-01

    A coprecipitation method with ytterbium hydroxide was studied for the determination of cadmium in water samples by graphite-furnace atomic absorption spectrometry. Up to 40 ng of cadmium in water samples was quantitatively coprecipitated with ytterbium hydroxide at pH 8.0-11.2. The concentration factor was 100 fold. The coprecipitated cadmium was sensitively determined without any influence of ytterbium and the calibration curve was linear from 0.1 to 4 ng/mL of cadmium. The detection limit (signal/noise = 2) was 2.9 pg/mL in 100 mL of the initial sample solution. Twenty-nine diverse ions tested did not interfere with the determination in at least a 10000-fold mass ratio to cadmium. The proposed method was successfully applied to the determination of cadmium in spring water.

  14. Pre-concentration of trace metals from sea-water for determination by graphite-furnace atomic-absorption spectrometry.

    PubMed

    Sturgeon, R E; Berman, S S; Desaulniers, A; Russell, D S

    1980-02-01

    Determination of Cd, Zn, Pb, Cu, Fe, Mn, Co, Cr and Ni in coastal sea-water by graphite-furnace atomic-absorption spectrometry after preconcentration by solvent extraction and use of a chelating ion-exchange resin is described. Following the extraction of the pyrrolidine-N-carbodithioate and oxinate complexes into methyl isobutyl ketone, the trace metals are further preconcentrated by back-extraction into 1.5M nitric acid. Preconcentration on the chelating resin is effected by a combined column and batch technique, allowing greater preconcentration factors to be obtained. Provided samples are appropriately treated to release non-labile metal species prior to preconcentration, both methods yield comparable analytical results with respect to the mean concentrations determined as well as to mean relative standard deviations. Control and treatment of the analytical blank is also described. PMID:18962623

  15. Evaluation of ammonia as diluent for serum sample preparation and determination of selenium by graphite furnace atomic absorption spectrometry*1

    NASA Astrophysics Data System (ADS)

    Hernández-Caraballo, Edwin A.; Burguera, Marcela; Burguera, José L.

    2002-12-01

    A method for the determination of total selenium in serum samples by graphite furnace atomic absorption spectrometry was evaluated. The method involved direct introduction of 1:5 diluted serum samples (1% v/v NH 4OH+0.05% w/v Triton X-100 ®) into transversely heated graphite tubes, and the use of 10 μg Pd+3 μg Mg(NO 3) 2 as chemical modifier. Optimization of the modifier mass and the atomization temperature was conducted by simultaneously varying such parameters and evaluating both the integrated absorbance and the peak height/peak area ratio. The latter allowed the selection of compromise conditions rendering good sensitivity and adequate analyte peak profiles. A characteristic mass of 49 pg and a detection limit (3s) of 6 μg 1 -1 Se, corresponding to 30 μg l -1 Se in the serum sample, were obtained. The analyte addition technique was used for calibration. The accuracy was assessed by the determination of total selenium in Seronorm™ Trace Elements Serum Batch 116 (Nycomed Pharma AS). The method was applied for the determination of total selenium in ten serum samples taken from individuals with no known physical affection. The selenium concentration ranged between 79 and 147 μg l -1, with a mean value of 114±22 μg l -1.

  16. Ultrasensitive determination of cadmium in seawater by hollow fiber supported liquid membrane extraction coupled with graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Peng, Jin-feng; Liu, Rui; Liu, Jing-fu; He, Bin; Hu, Xia-lin; Jiang, Gui-bin

    2007-05-01

    A new procedure, based on hollow fiber supported liquid membrane preconcentration coupled with graphite furnace atomic absorption spectrometry (GFAAS) detection, was developed for the determination of trace Cd in seawater samples. With 1-octanol that contained a mixture of dithizone (carrier) and oleic acid immobilized in the pores of the polypropylene hollow fiber as a liquid membrane, Cd was selectively extracted from water samples into 0.05 M HNO 3 that filled the lumen of the hollow fiber as a stripping solution. The main extraction related parameters were optimized, and the effects of salinity and some coexisting interferants were also evaluated. Under the optimum extraction conditions, an enrichment factor of 387 was obtained for a 100-mL sample solution. In combination with graphite furnace atomic absorption spectrometry, a very low detection limit (0.8 ng L - 1 ) and a relative standard deviation (2.5% at 50 ng L - 1 level) were achieved. Five seawater samples were analyzed by the proposed method without dilution, with detected Cd concentration in the range of 56.4-264.8 ng L - 1 and the relative spiked recoveries over 89%. For comparison, these samples were also analyzed by the Inductively Coupled Plasma Mass Spectrometry (ICP-MS) method after a 10-fold dilution for matrix effect elimination. Statistical analysis with a one-way ANOVA shows no significant differences (at 0.05 level) between the results obtained by the proposed and ICP-MS methods. Additionally, analysis of certified reference materials (GBW (E) 080040) shows good agreement with the certified value. These results indicate that this present method is very sensitive and reliable, and can effectively eliminate complex matrix interferences in seawater samples.

  17. Determination of silicon and aluminum in silicon carbide nanocrystals by high-resolution continuum source graphite furnace atomic absorption spectrometry.

    PubMed

    Dravecz, Gabriella; Bencs, László; Beke, Dávid; Gali, Adam

    2016-01-15

    The determination of Al contaminant and the main component Si in silicon carbide (SiC) nanocrystals with the size-distribution of 1-8nm dispersed in an aqueous solution was developed using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS-GFAAS). The vaporization/atomization processes were investigated in a transversally heated graphite atomizer by evaporating solution samples of Al and Si preserved in various media (HCl, HNO3). For Si, the best results were obtained by applying a mixture of 5µg Pd plus 5µg Mg, whereas for Al, 10µg Mg (each as nitrate solution) was dispensed with the samples, but the results obtained without modifier were found to be better. This way a maximum pyrolysis temperature of 1200°C for Si and 1300°C for Al could be used, and the optimum (compromise) atomization temperature was 2400°C for both analytes. The Si and Al contents of different sized SiC nanocrystals, dispersed in aqueous solutions, were determined against aqueous (external) calibration standards. The correlation coefficients (R values) of the calibrations were found to be 0.9963 for Si and 0.9991 for Al. The upper limit of the linear calibration range was 2mg/l Si and 0.25mg/l Al. The limit of detection was 3µg/l for Si and 0.5µg/l for Al. The characteristic mass (m0) was calculated to be 389pg Si and 6.4pg Al. The Si and Al content in the solution samples were found to be in the range of 1.0-1.7mg/l and 0.1-0.25mg/l, respectively.

  18. Determination of silicon and aluminum in silicon carbide nanocrystals by high-resolution continuum source graphite furnace atomic absorption spectrometry.

    PubMed

    Dravecz, Gabriella; Bencs, László; Beke, Dávid; Gali, Adam

    2016-01-15

    The determination of Al contaminant and the main component Si in silicon carbide (SiC) nanocrystals with the size-distribution of 1-8nm dispersed in an aqueous solution was developed using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS-GFAAS). The vaporization/atomization processes were investigated in a transversally heated graphite atomizer by evaporating solution samples of Al and Si preserved in various media (HCl, HNO3). For Si, the best results were obtained by applying a mixture of 5µg Pd plus 5µg Mg, whereas for Al, 10µg Mg (each as nitrate solution) was dispensed with the samples, but the results obtained without modifier were found to be better. This way a maximum pyrolysis temperature of 1200°C for Si and 1300°C for Al could be used, and the optimum (compromise) atomization temperature was 2400°C for both analytes. The Si and Al contents of different sized SiC nanocrystals, dispersed in aqueous solutions, were determined against aqueous (external) calibration standards. The correlation coefficients (R values) of the calibrations were found to be 0.9963 for Si and 0.9991 for Al. The upper limit of the linear calibration range was 2mg/l Si and 0.25mg/l Al. The limit of detection was 3µg/l for Si and 0.5µg/l for Al. The characteristic mass (m0) was calculated to be 389pg Si and 6.4pg Al. The Si and Al content in the solution samples were found to be in the range of 1.0-1.7mg/l and 0.1-0.25mg/l, respectively. PMID:26592606

  19. Study of the roles of chemical modifiers in determining boron using graphite furnace atomic absorption spectrometry and optimization of the temperature profile during atomization.

    PubMed

    Yamamoto, Yuhei; Shirasaki, Toshihiro; Yonetani, Akira; Imai, Shoji

    2015-01-01

    The measurement conditions for determining boron using graphite furnace-atomic absorption spectrometry (GF-AAS) were investigated. Differences in the boron absorbance profiles were found using three different commercially available GF-AAS instruments when the graphite atomizers in them were not tuned. The boron absorbances found with and without adjusting the graphite atomizers suggested that achieving an adequate absorbance for the determination of boron requires a sharp temperature profile that overshoots the target temperature during the atomization process. Chemical modifiers that could improve the boron absorbance without the need for using coating agents were tested. Calcium carbonate improved the boron absorbance but did not suppress variability in the peak height. Improvement of boron absorbance was comparatively less using iron nitrate or copper nitrate than using calcium carbonate, but variability in the peak height was clearly suppressed using iron nitrate or copper nitrate. The limit of detection was 0.0026 mg L(-1) when iron nitrate was used. It appears that iron nitrate is a useful new chemical modifier for the quick and simple determination of boron using GF-AAS.

  20. Determination of tellurium and antimony in nickel alloys by laser excited atomic fluorescence spectrometry in a graphite furnace

    NASA Astrophysics Data System (ADS)

    Liang, Zhongwen; Lonardo, Robert F.; Michel, Robert G.

    1993-01-01

    Analytical laser excited atomic fluorescence of the metalloids tellurium and antimony in an electrothermal atomizer was studied. The detection limits were 20 fg and 10 fg for tellurium and antimony respectively, equivalent to about 0.01 ng g -1 in nickel based alloys by direct solid sample analysis, for a 1 mg solid sample, or 1 ng g -1 by the dissolution method, for a 100 mg solid sample in 100 ml solution. The detection limits were three orders of magnitude better than those obtained by graphite furnace atomic absorption spectrometry. They were also comparable to, or better than, those by inductively coupled plasma mass spectrometry. The linear dynamic ranges of the calibration curves were found to be six and seven orders of magnitude for antimony and tellurium respectively. By use of aqueous calibration, tellurium was accurately determined in NIST nickel alloy Standard Reference Materials by both a solid sample method, with a relative standard deviation (RSD) of about 13%, and a dissolution method with an RSD of about 9%. Antimony in Pratt and Whitney "A" series nickel alloy standards was successfully determined by the dissolution method, with an RSD of about 7%, but by solid sampling the antimony method gave incomplete recovery. Molecular fluorescence backgrounds from nitric oxide and silicon monoxide were observed and discussed.

  1. Determination of total selenium in pharmaceutical and herbal supplements by hydride generation and graphite furnace atomic absorption spectrometry.

    PubMed

    Kazi, Tasneem G; Kolachi, Nida F; Afridi, Hassan I; Brahman, Kapil Dev; Shah, Faheem

    2014-01-01

    The total selenium (Se) was determined in herbal and pharmaceutical supplements used for liver diseases. The total Se contents were determined in different pharmaceutical and herbal supplements by hydride generation atomic absorption spectrometry (HGAAS) and graphite furnace atomic absorption spectrometry (GFAAS) after microwave-assisted acid digestion. The accuracy of the techniques was evaluated by using certified reference material and the standard addition method. The recoveries of total Se were 99.4 and 99.0% for HGAAS and GFAAS, respectively. The precision of the techniques expressed as RSD were 2.34 and 4.54% for HGAAS and GFAAS measurements, respectively. The LOD values for HGAAS and GFAAS were 0.025 and 0.052 pglg, respectively. The concentrations of Se in pharmaceutical and herbal supplements were found in the range of 19.2-53.8 and 25.0-42.5 pg/g, respectively, corresponding to 35-76% and 45-76% of the total recommended dose of Se for adults.

  2. Determination of total selenium in pharmaceutical and herbal supplements by hydride generation and graphite furnace atomic absorption spectrometry.

    PubMed

    Kazi, Tasneem G; Kolachi, Nida F; Afridi, Hassan I; Brahman, Kapil Dev; Shah, Faheem

    2014-01-01

    The total selenium (Se) was determined in herbal and pharmaceutical supplements used for liver diseases. The total Se contents were determined in different pharmaceutical and herbal supplements by hydride generation atomic absorption spectrometry (HGAAS) and graphite furnace atomic absorption spectrometry (GFAAS) after microwave-assisted acid digestion. The accuracy of the techniques was evaluated by using certified reference material and the standard addition method. The recoveries of total Se were 99.4 and 99.0% for HGAAS and GFAAS, respectively. The precision of the techniques expressed as RSD were 2.34 and 4.54% for HGAAS and GFAAS measurements, respectively. The LOD values for HGAAS and GFAAS were 0.025 and 0.052 pglg, respectively. The concentrations of Se in pharmaceutical and herbal supplements were found in the range of 19.2-53.8 and 25.0-42.5 pg/g, respectively, corresponding to 35-76% and 45-76% of the total recommended dose of Se for adults. PMID:25632445

  3. Determination of cadmium and lead in beverages after leaching from pewter cups using graphite furnace atomic absorption spectrometry.

    PubMed

    Dessuy, Morgana B; Vale, Maria Goreti R; Welz, Bernhard; Borges, Aline R; Silva, Márcia M; Martelli, Patrícia B

    2011-07-15

    Two simple methods have been developed to determine cadmium and lead in different kinds of beverages and vinegar leached from pewter cups produced in Brazil. Leaching experiments have been carried out with different solutions: beer, sugar cane spirit, red and white wine, vinegar and a 3% acetic acid solution. The solutions were kept in cups with and without solder for 24h. Lead and cadmium have been determined using graphite furnace atomic absorption spectrometry with deuterium background correction. The limits of detection were 0.05 and 1.4 μg L(-1), and the characteristic mass was 1.0 pg and 19 pg for Cd and Pb, respectively. With the developed methods it was possible to determine accurately cadmium and lead by direct analysis in these liquids and to evaluate the leaching of these metals from pewter cups. The results presented in this work show that pewter cups are not cadmium- and lead-free; this point goes against the manufacturers' declaration that their products are lead-free.

  4. Determination of cadmium and lead in beverages after leaching from pewter cups using graphite furnace atomic absorption spectrometry.

    PubMed

    Dessuy, Morgana B; Vale, Maria Goreti R; Welz, Bernhard; Borges, Aline R; Silva, Márcia M; Martelli, Patrícia B

    2011-07-15

    Two simple methods have been developed to determine cadmium and lead in different kinds of beverages and vinegar leached from pewter cups produced in Brazil. Leaching experiments have been carried out with different solutions: beer, sugar cane spirit, red and white wine, vinegar and a 3% acetic acid solution. The solutions were kept in cups with and without solder for 24h. Lead and cadmium have been determined using graphite furnace atomic absorption spectrometry with deuterium background correction. The limits of detection were 0.05 and 1.4 μg L(-1), and the characteristic mass was 1.0 pg and 19 pg for Cd and Pb, respectively. With the developed methods it was possible to determine accurately cadmium and lead by direct analysis in these liquids and to evaluate the leaching of these metals from pewter cups. The results presented in this work show that pewter cups are not cadmium- and lead-free; this point goes against the manufacturers' declaration that their products are lead-free. PMID:21645758

  5. Determination of Beryllium in Soil and Sediment by Graphite Furnace Atomic Absorption with a Microwave-Acid Digestion Method.

    PubMed

    Lin, Hai-lan; Gan, Jie; Yu, Lei; Zhu, Ri-long; Tian, Yun; Luo, Yue-ping

    2015-11-01

    A method for determination of beryllium in soils and sediments by microwave-acid digestion/graphite furnace atomic absorption (GFAA) is described. In this paper, the working conditions of the instrument are optimized, the drawing of calibration curve is expounded, the pretreatment process of soil and sediments (including microwave heating process and the selection of digestion system) is discussed, and the interference of coexisting elements is examined. The sample was pretreated by microwave digestion parameters using HNO₃/ HCl/HF mixed acid system. The method is fast and simple without matrix modifier, and has no interference by coexisting ions, and has high repeatability and reproducibility. Under the optimal experimental conditions, the limit of detection (LOD) is 0.004 9 mg · kg⁻¹ (sample quantity 0.200 0 g, sample volume 25 mL), and the limits of quantitation (LOQ) is 0.20 mg · kg⁻¹. This method is used to measure the standard samples and actual samples, whether in the laboratory, or between laboratories, has good accuracy and precision.

  6. Determination of Beryllium in Soil and Sediment by Graphite Furnace Atomic Absorption with a Microwave-Acid Digestion Method.

    PubMed

    Lin, Hai-lan; Gan, Jie; Yu, Lei; Zhu, Ri-long; Tian, Yun; Luo, Yue-ping

    2015-11-01

    A method for determination of beryllium in soils and sediments by microwave-acid digestion/graphite furnace atomic absorption (GFAA) is described. In this paper, the working conditions of the instrument are optimized, the drawing of calibration curve is expounded, the pretreatment process of soil and sediments (including microwave heating process and the selection of digestion system) is discussed, and the interference of coexisting elements is examined. The sample was pretreated by microwave digestion parameters using HNO₃/ HCl/HF mixed acid system. The method is fast and simple without matrix modifier, and has no interference by coexisting ions, and has high repeatability and reproducibility. Under the optimal experimental conditions, the limit of detection (LOD) is 0.004 9 mg · kg⁻¹ (sample quantity 0.200 0 g, sample volume 25 mL), and the limits of quantitation (LOQ) is 0.20 mg · kg⁻¹. This method is used to measure the standard samples and actual samples, whether in the laboratory, or between laboratories, has good accuracy and precision. PMID:26978948

  7. Antimony in drinking water, red blood cells, and serum: development of analytical methodology using transversely heated graphite furnace atomization-atomic absorption spectrometry.

    PubMed

    Subramanian, K S; Poon, R; Chu, I; Connor, J W

    1997-05-01

    An atomic absorption spectrometric (AAS) method has been developed for determining microg/L levels of Sb in samples of water and blood. The AAS method is based on the concept of stabilized temperature platform furnace atomization (STPF) realized through the use of a transversely heated graphite atomizer (THGA) furnace, longitudinal Zeeman-effect background correction, and matrix modification with palladium nitrate-magnesium nitrate-nitric acid. The method of standard additions is not mandatory. The detection limit (3 standard deviations of the blank) is 2.6 microg Sb/L for the water, red blood cells (RBCs), and serum samples. Data are presented on the degree of accuracy and precision. The THGA-AAS method is simple, fast, and contamination-free because the entire operation from sampling to AAS measurement is carried out in the same tube. The method has been applied to the determination of Sb in some leachate tap water samples derived from a static copper plumbing system containing Sn/Sb solders, and in small samples (0.5 ml) of RBCs and serum derived from rats given Sb-supplemented drinking water. PMID:9175512

  8. Application of wavelet transforms to determine peak shape parameters for interference detection in graphite-furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Sadler, D. A.; Littlejohn, D.; Boulo, P. R.; Soraghan, J. S.

    1998-08-01

    A procedure to quantify the shape of the absorbance-time profile, obtained during graphite furnace atomic absorption spectrometry, has been used to detect interference effects caused by the presence of a concomitant salt. The quantification of the absorption profile is achieved through the use of the Lipschitz regularity, α0, obtained from the wavelet transform of the absorbance-time profile. The temporal position of certain features and their associated values of α0 provide a unique description of the shape of the absorbance-time profile. Changes to the position or values of α0 between standard and sample atomizations may be indicative of uncorrected interference effects. A weak, but linear, dependence was found of the value of α0 upon the analyte concentration for Cr and Cu. The ability of the Lipschitz regularity to detect interference effects was illustrated for Pb, Se and Cu. For Pb, the lowest concentration of NaCl added, 0.005% m/v, changed both the values of α0 and the peak height absorbance. For Se, no change in the peak height and peak area absorbance signals was detected up to a NaCl concentration of 0.25% m/v. The values of the associated Lipschitz regularities were found to be invariant to NaCl concentration up to this value. For Cu, a concentration of 0.05% m/v NaCl reduced the peak height and peak area absorbance signals by approximately 25% and significantly altered the values of α0.

  9. Determination of manganese in diesel, gasoline and naphtha by graphite furnace atomic absorption spectrometry using microemulsion medium for sample stabilization

    NASA Astrophysics Data System (ADS)

    Brandão, Geisamanda Pedrini; de Campos, Reinaldo Calixto; de Castro, Eustáquio Vinicius Ribeiro; de Jesus, Honério Coutinho

    2008-08-01

    The determination of Mn in diesel, gasoline and naphtha samples at µg L - 1 level by graphite furnace atomic absorption spectrometry, after sample stabilization in a three-component medium (microemulsion) was investigated. Microemulsions were prepared by mixing appropriate volumes of sample, propan-1-ol and nitric acid aqueous solution, and a stable system was immediately and spontaneously formed. After multivariate optimization by central composite design the optimum microemulsion composition as well as the temperature program was defined. In this way, calibration using aqueous analytical solution was possible, since the same sensitivity was observed in the optimized microemulsion media and 0.2% v/v HNO 3. The use of modifier was not necessary. Recoveries at the 3 µg L - 1 level using both inorganic and organic Mn standards spiked solutions ranged from 98 to 107% and the limits of detection were 0.6, 0.5 and 0.3 µg L - 1 in the original diesel, gasoline and naphtha samples, respectively. The Mn characteristic mass 3.4 pg. Typical relative standard deviation ( n = 5) of 8, 6 and 7% were found for the samples prepared as microemulsions at concentration levels of 1.3, 0.8, and 1.5 µg L - 1 , respectively. The total determination cycle lasted 4 min for diesel and 3 min for gasoline and naphtha, equivalent to a sample throughput of 7 h - 1 for duplicate determinations in diesel and 10 h - 1 for duplicate determinations in gasoline and naphtha. Accuracy was also assessed by using other method of analysis (ASTM D 3831-90). No statistically significant differences were found between the results obtained with the proposed method and the reference method in the analysis of real samples.

  10. Determination of mercury in sewage sludge by direct slurry sampling graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Baralkiewicz, Danuta; Gramowska, Hanka; Kózka, Małgorzata; Kanecka, Anetta

    2005-03-01

    Ultrasonic slurry sampling electrothermal atomic absorption spectrometry (ETAAS) method was elaborated to the determination of Hg in sewage sludge samples with the use of KMnO 4+Pd modifier. The minimum sample amount required for slurry preparation with respect to sample homogeneity was evaluated by weighting masses between 3 and 30 mg directly into the autosampler cups. Validation of the proposed method was performed with the use of Certified Reference Materials of sewage sludge, CRM 007-040 and CRM 144R. Two sewage sludge samples from Poznañ (Poland) city were analysed using the present direct method and a method with sample digestion, resulting in no difference within statistical error.

  11. Determination of Chlorine in Milk via Molecular Absorption of SrCl Using High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry.

    PubMed

    Ozbek, Nil; Akman, Suleyman

    2016-07-20

    Total chlorine in milk was determined via the molecular absorption of diatomic strontium monochloride at 635.862 nm using high-resolution continuum source graphite furnace atomic absorption spectrometry. The effects of coating the graphite furnace, using different modifiers, amount of molecule-forming element, and different calibrants were investigated and optimized. Chlorine concentrations in milk samples were determined in a Zr-coated graphite furnace using 25 μg of Sr as the molecule-forming reagent and applying a pyrolysis temperature of 600 °C and a molecule-forming temperature of 2300 °C. Linearity was maintained up to 500 μg mL(-1) of Cl. The method was tested by analyzing a certified reference wastewater. The results were in the uncertainty limits of the certified value. The limit of detection of the method was 1.76 μg mL(-1). The chlorine concentrations in various cow milk samples taken from the market were found in the range of 588-1472 mg L(-1).

  12. Determination of Chlorine in Milk via Molecular Absorption of SrCl Using High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry.

    PubMed

    Ozbek, Nil; Akman, Suleyman

    2016-07-20

    Total chlorine in milk was determined via the molecular absorption of diatomic strontium monochloride at 635.862 nm using high-resolution continuum source graphite furnace atomic absorption spectrometry. The effects of coating the graphite furnace, using different modifiers, amount of molecule-forming element, and different calibrants were investigated and optimized. Chlorine concentrations in milk samples were determined in a Zr-coated graphite furnace using 25 μg of Sr as the molecule-forming reagent and applying a pyrolysis temperature of 600 °C and a molecule-forming temperature of 2300 °C. Linearity was maintained up to 500 μg mL(-1) of Cl. The method was tested by analyzing a certified reference wastewater. The results were in the uncertainty limits of the certified value. The limit of detection of the method was 1.76 μg mL(-1). The chlorine concentrations in various cow milk samples taken from the market were found in the range of 588-1472 mg L(-1). PMID:27345208

  13. Cadmium accumulation in the crayfish, Procambarus clarkii, using graphite furnace atomic absorption spectroscopy

    SciTech Connect

    Diaz-Mayans, J.; Hernandez, F.; Medina, J.; Del Ramo, J.; Torreblanca, A.

    1986-11-01

    Lake Albufera and the surrounding rice-field waters are being subject to very heavy loads of sewage and toxic industrial residues (including heavy metals and pesticides) from the many urban and wastewaters in this area. The American red crayfish Procambarus clarkii is native to the Louisiana marshes (USA). In 1978, the crayfish appeared in Lake Albufera near Valencia (Spain), and presently, without adequate sanitary controls, the crayfish is being fished commercially for human consumption. In view of this interest, it is important to have accurate information on concentrations of cadmium in natural waters and cadmium levels of tissues of freshwaters animals used as human food, as well as the accumulation rates of this metal in this animal. In the present study, the authors investigated the accumulation of cadmium in several tissues of the red crayfish, P clarkii (Girard) from Lake Albufera following cadmium exposure. Determinations of cadmium were made by flameless atomic absorption spectroscopy and the standard additions method. Digestion of samples was made by wet ashing in open flasks with concentrated HNO/sub 3/ at 80-90/sup 0/C.

  14. Direct determination of cadmium and copper in seawater using a transversely heated graphite furnace atomic absorption spectrometer with Zeeman-effect background corrector.

    PubMed

    Chan, M S; Huang, S D

    2000-02-01

    Methods for the direct determination of copper and cadmium in seawater were described using a graphite furnace atomic absorption spectrometer (GFAAS) equipped with a transversely heated graphite atomizer (THGA) and a longitudinal Zeeman effect background corrector. Ammonium nitrate was used as the chemical modifier to determine copper. The mixture of di-ammonium hydrogen phosphate and ammonium nitrate was used as the chemical modifier to determine cadmium. The matrix interference was removed completely so that a simple calibration curve method could be applied. This work is the first one with the capability of determining cadmium in unpolluted seawater directly with GFAAS using calibration curve based on simple aqueous standards. The accuracy of the methods was confirmed by analysis of three kinds of certified reference saline waters. The detection limits (LODs), with injection of a 20-mul aliquot of seawater sample, were 0.06 mug l(-1) for copper and 0.005 mug l(-1) for cadmium.

  15. Solid sampling determination of lithium and sodium additives in microsamples of yttrium oxyorthosilicate by high-resolution continuum source graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Laczai, Nikoletta; Kovács, László; Péter, Ágnes; Bencs, László

    2016-03-01

    Solid sampling high resolution continuum source graphite furnace atomic absorption spectrometry (SS-HR-CS-GFAAS) methods were developed and studied for the fast and sensitive quantitation of Li and Na additives in microsamples of cerium-doped yttrium oxyorthosilicate (Y2SiO5:Ce) scintillator materials. The methods were optimized for solid samples by studying a set of GFAAS conditions (i.e., the sample mass, sensitivity of the analytical lines, and graphite furnace heating programs). Powdered samples in the mass range of 0.099-0.422 mg were dispensed onto graphite sample insertion boats, weighed and analyzed. Pyrolysis and atomization temperatures were optimized by the use of single-element standard solutions of Li and Na (acidified with 0.144 mol/L HNO3) at the Li I 610.353 nm and Na I 285.3013 nm analytical lines. For calibration purposes, the method of standard addition with Li and Na solutions was applied. The correlation coefficients (R values) of the calibration graphs were not worse than 0.9678. The limit of detection for oxyorthosilicate samples was 20 μg/g and 80 μg/g for Li and Na, respectively. The alkaline content of the solid samples were found to be in the range of 0.89 and 8.4 mg/g, respectively. The accuracy of the results was verified by means of analyzing certified reference samples, using methods of standard (solution) addition calibration.

  16. [A Zeeman graphite furnace atomic absorption spectrometric method for the determination of trace copper and chromium in drinking water].

    PubMed

    Wang, Z

    1999-08-01

    The determination of trace copper and chromium in drinking water is described in this paper using transverse heated graphite atomizer (THGA) with the technique of Zeeman effect background correction without any other matrix modifiers. The method is fast, and simple with low detection limit which makes it possible to be used for routine analysis of drinking water.

  17. On the possibilities of high-resolution continuum source graphite furnace atomic absorption spectrometry for the simultaneous or sequential monitoring of multiple atomic lines

    NASA Astrophysics Data System (ADS)

    Resano, M.; Rello, L.; Flórez, M.; Belarra, M. A.

    2011-05-01

    This paper explores the potential of commercially available high-resolution continuum source graphite furnace atomic absorption spectrometry instrumentation for the simultaneous or sequential monitoring of various atomic lines, in an attempt to highlight the analytical advantages that can be derived from this strategy. In particular, it is demonstrated how i) the monitoring of multiplets may allow for the simple expansion of the linear range, as shown for the measurement of Ni using the triplet located in the vicinity of 234.6 nm; ii) the use of a suitable internal standard may permit improving the precision and help in correcting for matrix-effects, as proved for the monitoring of Ni in different biological samples; iii) direct and multi-element analysis of solid samples may be feasible on some occasions, either by monitoring various atomic lines that are sufficiently close (truly simultaneous monitoring, as demonstrated in the determination of Co, Fe and Ni in NIST 1566a Oyster tissue) or, alternatively, by opting for a selective and sequential atomization of the elements of interest during every single replicate. Determination of Cd and Ni in BCR 679 White cabbage is attempted using both approaches, which permits confirming that both methods can offer very similar and satisfactory results. However, it is important to stress that the second approach provides more flexibility, since analysis is no longer limited to those elements that show very close atomic lines (closer than 0.3 nm in the ultraviolet region) with a sensitivity ratio similar to the concentration ratio of the analytes in the samples investigated.

  18. Determination of cobalt in biological samples by line-source and high-resolution continuum source graphite furnace atomic absorption spectrometry using solid sampling or alkaline treatment

    NASA Astrophysics Data System (ADS)

    Ribeiro, Anderson Schwingel; Vieira, Mariana Antunes; da Silva, Alessandra Furtado; Borges, Daniel L. Gallindo; Welz, Bernhard; Heitmann, Uwe; Curtius, Adilson José

    2005-06-01

    Two procedures for the determination of Co in biological samples by graphite furnace atomic absorption spectrometry (GF AAS) were compared: solid sampling (SS) and alkaline treatment with tetramethylammonium hydroxide (TMAH) using two different instruments for the investigation: a conventional line-source (LS) atomic absorption spectrometer and a prototype high-resolution continuum source atomic absorption spectrometer. For the direct introduction of the solid samples, certified reference materials (CRM) were ground to a particle size ≤50 μm. Alkaline treatment was carried out by placing about 250 mg of the sample in polypropylene flasks, adding 2 mL of 25% m/v tetramethylammonium hydroxide and de-ionized water. Due to its unique capacity of providing a 3-D spectral plot, a high-resolution continuum source (HR-CS) graphite furnace atomic absorption spectrometry was used as a tool to evaluate potential spectral interferences, including background absorption for both sample introduction procedures, revealing that a continuous background preceded the atomic signal for pyrolysis temperatures lower than 700 °C. Molecular absorption bands with pronounced rotational fine structure appeared for atomization temperatures >1800 °C probably as a consequence of the formation of PO. After optimization had been carried out using high resolution continuum source atomic absorption spectrometry, the optimized conditions were adopted also for line-source atomic absorption spectrometry. Six biological certified reference materials were analyzed, with calibration against aqueous standards, resulting in agreement with the certified values (according to the t-test for a 95% confidence level) and in detection limits as low as 5 ng g -1.

  19. Development of a simple method for the determination of lead in lipstick using alkaline solubilization and graphite furnace atomic absorption spectrometry.

    PubMed

    Soares, Aline Rodrigues; Nascentes, Clésia Cristina

    2013-02-15

    A simple method was developed for determining the total lead content in lipstick samples by graphite furnace atomic absorption spectrometry (GFAAS) after treatment with tetramethylammonium hydroxide (TMAH). Multivariate optimization was used to establish the optimal conditions of sample preparation. The graphite furnace heating program was optimized through pyrolysis and atomization curves. An aliquot containing approximately 50mg of the sample was mixed with TMAH and heated in a water bath at 60°C for 60 min. Using Nb as the permanent modifier and Pd as the chemical modifier, the optimal temperatures were 900°C and 1800°C for pyrolysis and atomization, respectively. Under optimum conditions, the working range was from 1.73 to 50.0 μg L(-1), with detection and quantification limits of 0.20 and 0.34 μg g(-1), respectively. The precision was evaluated under conditions of repeatability and intermediate precision and showed standard deviations of 2.37%-4.61% and 4.93%-9.75%, respectively. The % recovery ranged from 96.2% to 109%, and no significant differences were found between the results obtained using the proposed method and the microwave decomposition method for real samples. Lead was detected in 21 tested lipstick samples; the lead content in these samples ranged from 0.27 to 4.54 μg g(-1).

  20. Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; determination of chromium in water by graphite furnace atomic absorption spectrophotometry

    USGS Publications Warehouse

    McLain, B.J.

    1993-01-01

    Graphite furnace atomic absorption spectrophotometry is a sensitive, precise, and accurate method for the determination of chromium in natural water samples. The detection limit for this analytical method is 0.4 microg/L with a working linear limit of 25.0 microg/L. The precision at the detection limit ranges from 20 to 57 percent relative standard deviation (RSD) with an improvement to 4.6 percent RSD for concentrations more than 3 microg/L. Accuracy of this method was determined for a variety of reference standards that was representative of the analytical range. The results were within the established standard deviations. Samples were spiked with known concentrations of chromium with recoveries ranging from 84 to 122 percent. In addition, a comparison of data between graphite furnace atomic absorption spectrophotometry and direct-current plasma atomic emission spectrometry resulted in suitable agreement between the two methods, with an average deviation of +/- 2.0 microg/L throughout the analytical range.

  1. Development of a simple method for the determination of lead in lipstick using alkaline solubilization and graphite furnace atomic absorption spectrometry.

    PubMed

    Soares, Aline Rodrigues; Nascentes, Clésia Cristina

    2013-02-15

    A simple method was developed for determining the total lead content in lipstick samples by graphite furnace atomic absorption spectrometry (GFAAS) after treatment with tetramethylammonium hydroxide (TMAH). Multivariate optimization was used to establish the optimal conditions of sample preparation. The graphite furnace heating program was optimized through pyrolysis and atomization curves. An aliquot containing approximately 50mg of the sample was mixed with TMAH and heated in a water bath at 60°C for 60 min. Using Nb as the permanent modifier and Pd as the chemical modifier, the optimal temperatures were 900°C and 1800°C for pyrolysis and atomization, respectively. Under optimum conditions, the working range was from 1.73 to 50.0 μg L(-1), with detection and quantification limits of 0.20 and 0.34 μg g(-1), respectively. The precision was evaluated under conditions of repeatability and intermediate precision and showed standard deviations of 2.37%-4.61% and 4.93%-9.75%, respectively. The % recovery ranged from 96.2% to 109%, and no significant differences were found between the results obtained using the proposed method and the microwave decomposition method for real samples. Lead was detected in 21 tested lipstick samples; the lead content in these samples ranged from 0.27 to 4.54 μg g(-1). PMID:23598019

  2. Simultaneous and direct determination of iron and nickel in biological solid samples by high-resolution continuum source graphite furnace atomic absorption spectrometry.

    PubMed

    Gómez-Nieto, Beatriz; Gismera, Ma Jesús; Sevilla, Ma Teresa; Procopio, Jesús R

    2013-11-15

    The simultaneous and direct determination of nickel and iron in plants and lichens has been investigated using high-resolution continuum source graphite furnace atomic absorption spectrometry. The primary resonance line for nickel at 232.003 nm and the adjacent secondary line for iron at 232.036 nm have been used for this purpose. The optimization of the experimental conditions was performed using a pine needles certified reference material (SRM 1575a). The influence of pyrolysis and atomization temperatures, the amount of solid sample introduced into the graphite furnace and the use of aqueous or solid standard for calibration were studied. The spectral interferences caused by absorption of the concomitants of the solid sample were detected and corrected using a least square algorithm. Aliquots of 0.1-1mg of the solid samples were weighed onto the solid sampling platforms and analyzed directly, without addition of any reagents. The limits of detection were 25 µg kg(-1) for nickel and 0.40 mg kg(-1) for iron and the precision, expressed as the relative standard deviation, ranged from 7% to 12%. The proposed method was used to determine both metals in different bioindicator samples with successful results.

  3. Fast and direct screening of copper in micro-volumes of distilled alcoholic beverages by high-resolution continuum source graphite furnace atomic absorption spectrometry.

    PubMed

    Ajtony, Zsolt; Laczai, Nikoletta; Dravecz, Gabriella; Szoboszlai, Norbert; Marosi, Áron; Marlok, Bence; Streli, Christina; Bencs, László

    2016-12-15

    HR-CS-GFAAS methods were developed for the fast determination of Cu in domestic and commercially available Hungarian distilled alcoholic beverages (called pálinka), in order to decide if their Cu content exceeds the permissible limit, as legislated by the WHO. Some microliters of samples were directly dispensed into the atomizer. Graphite furnace heating programs, effects/amounts of the Pd modifier, alternative wavelengths (e.g., Cu I 249.2146nm), external calibration and internal standardization methods were studied. Applying a fast graphite furnace heating program without any chemical modifier, the Cu content of a sample could be quantitated within 1.5min. The detection limit of the method is 0.03mg/L. Calibration curves are linear up to 10-15mg/L Cu. Spike-recoveries ranged from 89% to 119% with an average of 100.9±8.5%. Internal calibration could be applied with the assistance of Cr, Fe, and/or Rh standards. The accuracy of the GFAAS results was verified by TXRF analyses.

  4. Fast and direct screening of copper in micro-volumes of distilled alcoholic beverages by high-resolution continuum source graphite furnace atomic absorption spectrometry.

    PubMed

    Ajtony, Zsolt; Laczai, Nikoletta; Dravecz, Gabriella; Szoboszlai, Norbert; Marosi, Áron; Marlok, Bence; Streli, Christina; Bencs, László

    2016-12-15

    HR-CS-GFAAS methods were developed for the fast determination of Cu in domestic and commercially available Hungarian distilled alcoholic beverages (called pálinka), in order to decide if their Cu content exceeds the permissible limit, as legislated by the WHO. Some microliters of samples were directly dispensed into the atomizer. Graphite furnace heating programs, effects/amounts of the Pd modifier, alternative wavelengths (e.g., Cu I 249.2146nm), external calibration and internal standardization methods were studied. Applying a fast graphite furnace heating program without any chemical modifier, the Cu content of a sample could be quantitated within 1.5min. The detection limit of the method is 0.03mg/L. Calibration curves are linear up to 10-15mg/L Cu. Spike-recoveries ranged from 89% to 119% with an average of 100.9±8.5%. Internal calibration could be applied with the assistance of Cr, Fe, and/or Rh standards. The accuracy of the GFAAS results was verified by TXRF analyses. PMID:27451250

  5. Redox speciation analysis of dissolved iron in estuarine and coastal waters with on-line solid phase extraction and graphite furnace atomic absorption spectrometry detection.

    PubMed

    Chen, Yaojin; Feng, Sichao; Huang, Yongming; Yuan, Dongxing

    2015-05-01

    An automatic on-line solid phase extraction (SPE) system employing the flow injection (FI) technique directly coupled to a graphite furnace atomic absorption spectrometer (GFAAS) was established for speciation and determination of dissolved iron in estuarine and coastal waters. Fe(II) was mixed with ferrozine solution in a sample stream to form the Fe(II)-ferrozine complex which was extracted onto a C18 SPE cartridge, eluted with eluent and detected with GFAAS. In a parallel flow channel, Fe(III) was reduced to Fe(II) with ascorbic acid and then detected in the same way as Fe(II). The home-made interface between FI-SPE and GFAAS efficiently realized the sample introduction to the furnace in a semi-automated way. Parameters of the FI-SPE system and graphite furnace program were optimized based on a univariate experimental design and an orthogonal array design. The salinity effect on the method sensitivity was investigated. The proposed method provided a detection limit of 1.38 nmol L(-1) for Fe(II) and 1.87 nmol L(-1) for Fe(II+III). With variation of the sample loading volume, a broadened determination range of 2.5-200 nmol L(-1) iron could be obtained. The proposed method was successfully applied to analyze iron species in samples collected from the Jiulongjiang Estuary, Fujian, China. With the 2-cartridge FI-SPE system developed, on-line simultaneous determination of Fe species with GFAAS was achieved for the first time.

  6. Determination of selenium in infant formula and enteral formula by dry ash graphite furnace atomic absorption spectrometry with deuterium background correction.

    PubMed

    Cook, K K

    1996-01-01

    A method was developed to determine selenium in infant formula using a graphite furnace equipped with deuterium background correction after dry ashing. The method circumvents the use of perchloric acid, 2,3-diaminonapthalene (DAN) and hydride generation without the use of Zeeman background correction. Twelve commercial infant and enteral formulas and corresponding spiked products (30-500 ng) were analyzed in triplicate for Se to evaluate this method. All test portions were digested on a hot plate after addition of magnesium nitrate-nitric acid. Following heating, digests were evaporated to dryness and placed in a 500 degrees C muffle furnace for 30 min to complete ashing. All Se was converted to Se+4 by dissolving the ash in HCl (5 + 1) and holding the solution for 20 min in a 60 degrees C water bath. Se+4 was subsequently reduced to Se(zero) with ascorbic acid and collected on a membrane filter. The membrane filters were digested in a small volume of nitric acid in a microwave oven. Following digestion, contents of the vessels were diluted and analyzed for Se by graphite furnace atomic absorption spectrometry. Selenium standards in starch or in unfortified formula containing trace levels of Se were carried through the entire process. The recovery range for Se was 85-127%, and analyzed reference materials fell within their certified range for Se. This method is as sensitive (detection limit 0.44 ng Se/g) as methods reported in the literature and may be applicable to other foods. PMID:8823924

  7. Redox speciation analysis of dissolved iron in estuarine and coastal waters with on-line solid phase extraction and graphite furnace atomic absorption spectrometry detection.

    PubMed

    Chen, Yaojin; Feng, Sichao; Huang, Yongming; Yuan, Dongxing

    2015-05-01

    An automatic on-line solid phase extraction (SPE) system employing the flow injection (FI) technique directly coupled to a graphite furnace atomic absorption spectrometer (GFAAS) was established for speciation and determination of dissolved iron in estuarine and coastal waters. Fe(II) was mixed with ferrozine solution in a sample stream to form the Fe(II)-ferrozine complex which was extracted onto a C18 SPE cartridge, eluted with eluent and detected with GFAAS. In a parallel flow channel, Fe(III) was reduced to Fe(II) with ascorbic acid and then detected in the same way as Fe(II). The home-made interface between FI-SPE and GFAAS efficiently realized the sample introduction to the furnace in a semi-automated way. Parameters of the FI-SPE system and graphite furnace program were optimized based on a univariate experimental design and an orthogonal array design. The salinity effect on the method sensitivity was investigated. The proposed method provided a detection limit of 1.38 nmol L(-1) for Fe(II) and 1.87 nmol L(-1) for Fe(II+III). With variation of the sample loading volume, a broadened determination range of 2.5-200 nmol L(-1) iron could be obtained. The proposed method was successfully applied to analyze iron species in samples collected from the Jiulongjiang Estuary, Fujian, China. With the 2-cartridge FI-SPE system developed, on-line simultaneous determination of Fe species with GFAAS was achieved for the first time. PMID:25770602

  8. Speciation of organic and inorganic selenium in selenium-enriched rice by graphite furnace atomic absorption spectrometry after cloud point extraction.

    PubMed

    Sun, Mei; Liu, Guijian; Wu, Qianghua

    2013-11-01

    A new method was developed for the determination of organic and inorganic selenium in selenium-enriched rice by graphite furnace atomic absorption spectrometry detection after cloud point extraction. Effective separation of organic and inorganic selenium in selenium-enriched rice was achieved by sequentially extracting with water and cyclohexane. Under the optimised conditions, the limit of detection (LOD) was 0.08 μg L(-1), the relative standard deviation (RSD) was 2.1% (c=10.0 μg L(-1), n=11), and the enrichment factor for selenium was 82. Recoveries of inorganic selenium in the selenium-enriched rice samples were between 90.3% and 106.0%. The proposed method was successfully applied for the determination of organic and inorganic selenium as well as total selenium in selenium-enriched rice.

  9. Influence of experimental parameters on the determination of antimony in seawater by atomic absorption spectrometry using a transversely heated graphite furnace with Zeeman-effect background correction.

    PubMed

    Cabon, Jean Yves

    2002-12-01

    Spectroscopic and electrothermal conditions for the determination of antimony in seawater using a transversely heated graphite furnace with Zeeman-effect background correction have been optimized with the use of an a priori calculation of the detection limit. The lowest limit of detection was obtained with a 2 nm spectral curvatures bandwidth and the use of an electrodeless discharge lamp; however, these experimental conditions resulted in strong premature curvature of calibration curves. Pd(NO(3))(2) can be recommended as a chemical modifier because seawater interference effects are minimized and pretreatment curves up to 1500 degrees C can be used permitting the removal of the major part of the saline matrix before atomization. Under optimized spectroscopic and electrothermal conditions the obtained limit of detection of Sb in seawater was about 0.4 microg L(-1).

  10. Trace and Essential Elements Analysis in Cymbopogon citratus (DC.) Stapf Samples by Graphite Furnace-Atomic Absorption Spectroscopy and Its Health Concern

    PubMed Central

    Anal, Jasha Momo H.

    2014-01-01

    Cymbopogon citratus (DC.) Stapf commonly known as lemon grass is used extensively as green tea and even as herbal tea ingredient across the world. Plants have the ability to uptake metals as nutrient from the soil and its environment which are so essential for their physiological and biochemical growth. Concentrations of these twelve trace elements, namely, Mg, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Mo, As, Cd, and Pb, are analysed by graphite furnace-atomic absorption spectroscopy (GF-AAS) and are compared with the permissible limits of FAO/WHO, ICMR, and NIH, USA, which are found to be within permissible limits. Toxic metals like As, Cd, and Pb, analysed are within the tolerable daily diet limit and at low concentration. PMID:25525430

  11. Induction graphitizing furnace acceptance test report

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The induction furnace was designed to provide the controlled temperature and environment required for the post-cure, carbonization and graphitization processes for the fabrication of a fibrous graphite NERVA nozzle extension. The acceptance testing required six tests and a total operating time of 298 hrs. Low temperature mode operations, 120 to 850 C, were completed in one test run. High temperature mode operations, 120 to 2750 C, were completed during five tests.

  12. Cloud point extraction for the determination of lead and cadmium in urine by graphite furnace atomic absorption spectrometry with multivariate optimization using Box Behnken design

    NASA Astrophysics Data System (ADS)

    Maranhão, Tatiane De A.; Martendal, Edmar; Borges, Daniel L. G.; Carasek, Eduardo; Welz, Bernhard; Curtius, Adilson J.

    2007-09-01

    Cloud point extraction (CPE) is proposed as a pre-concentration procedure for the determination of Pb and Cd in undigested urine by graphite furnace atomic absorption spectrometry (GF AAS). Aliquots of 0.5 mL urine were acidified with HCl and the chelating agent ammonium O,O-diethyl dithiophosphate (DDTP) was added along with the non-ionic surfactant Triton X-114 at the optimized concentrations. Phase separation was achieved by heating the mixture to 50 °C for 15 min. The surfactant-rich phase was analyzed by GF AAS, employing the optimized pyrolysis temperatures of 900 °C for Pb and 800 °C for Cd, using a graphite tube with a platform treated with 500 μg Ru as permanent modifier. The reagent concentrations for CPE (HCl, DDTP and Triton X-114) were optimized using a Box Behnken design. The response surfaces and the optimum values were very similar for aqueous solutions and for the urine samples, demonstrating that aqueous standards submitted to CPE could be used for calibration. Detection limits of 40 and 2 ng L- 1 for Pb and Cd, respectively, were obtained along with an enhancement factor of 16 for both analytes. Three control urine samples were analyzed using this approach, and good agreement was obtained at a 95% statistical confidence level between the certified and determined values. Five real samples have also been analyzed before and after spiking with Pb and Cd, resulting in recoveries ranging from 97 to 118%.

  13. Multivariate approach in the optimization procedures for the direct determination of manganese in serum samples by graphite furnace atomic absorption spectrometry.

    PubMed

    Fabrino, Henrique José Ferraz; Silveira, Josianne Nicácio; Neto, Waldomiro Borges; Goes, Alfredo Miranda; Beinner, Mark Anthony; da Silva, José Bento Borba

    2011-10-01

    A method for direct determination of manganese (Mn) in human serum by graphite furnace atomic absorption spectrometry (GFAAS) was proposed in this work. The samples were only diluted 1:4 with nitric acid 1% (v/v) and Triton(®) X-100 0.1% (v/v). The optimization of the instrumental conditions was made using multivariate approach. A factorial design (2(3)) was employed to investigate the tendency of the most intense absorbance signal. The pyrolysis and atomization temperatures and the use of modifier were available and only the parameter modifier use did not have a significant effect on the response. A Center Composed Design (CCD) presented best temperatures of 430 °C and 2568 °C for pyrolysis and atomization, respectively. The method allowed the determination of manganese with a curve varying from 0.7 to 3.3 μg/L. Recovery studies in three concentration levels (n=7 for each level) presented results from 98 ± 5 to 102 ± 7 %. The detection limit was 0.2 μg/L, the quantifying limit was 0.7 μg/L, and the characteristic mass, 1.3 ± 0.2 pg. Intra- and interassay studies showed coefficients of variation of 4.7-7.0% (n=21) and 6-8%(n=63), respectively. The method was applied for the determination of manganese in 53 samples obtaining concentrations from 3.9 to 13.7 μg/L.

  14. Evaluation of solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry for direct determination of chromium in medicinal plants

    NASA Astrophysics Data System (ADS)

    Virgilio, Alex; Nóbrega, Joaquim A.; Rêgo, Jardes F.; Neto, José A. Gomes

    2012-12-01

    A method for Cr determination in medicinal plants using direct solid sampling graphite furnace high-resolution continuum source atomic absorption spectrometry was developed. Modifiers were dispensable. Pyrolysis and atomization temperatures were 1500 °C and 2400 °C, respectively. Slopes of calibration curves (50-750 pg Cr, R2 > 0.999) using aqueous and solid standards coincides in 96%, indicated feasibility of aqueous calibration for solid sampling of medicinal plants. Accuracy was checked by analysis of four plant certified reference materials. Results were in agreement at 95% confidence level with certified and non-certified values. Ten samples of medicinal plants were analyzed and Cr contents were in the 1.3-17.7 μg g- 1 Cr range. The highest RSD (n = 5) was 15.4% for the sample Melissa officinalis containing 13.9 ± 2.1 μg g- 1 Cr. The limit of detection was 3.3 ng g- 1 Cr.

  15. Investigation of chemical modifiers for the direct determination of arsenic in fish oil using high-resolution continuum source graphite furnace atomic absorption spectrometry.

    PubMed

    Pereira, Éderson R; de Almeida, Tarcísio S; Borges, Daniel L G; Carasek, Eduardo; Welz, Bernhard; Feldmann, Jörg; Campo Menoyo, Javier Del

    2016-04-01

    High-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) has been applied for the development of a method for the determination of total As in fish oil samples using direct analysis. The method does not use any sample pretreatment, besides dilution with 1-propanole, in order to decrease the oil viscosity. The stability and sensitivity of As were evaluated using ruthenium and iridium as permanent chemical modifiers and palladium added in solution over the sample. The best results were obtained with ruthenium as the permanent modifier and palladium in solution added to samples and standard solutions. Under these conditions, aqueous standard solutions could be used for calibration for the fish oil samples diluted with 1-propanole. The pyrolysis and atomization temperatures were 1400 °C and 2300 °C, respectively, and the limit of detection and characteristic mass were 30 pg and 43 pg, respectively. Accuracy and precision of the method have been evaluated using microwave-assisted acid digestion of the samples with subsequent determination by HR-CS GF AAS and ICP-MS; the results were in agreement (95% confidence level) with those of the proposed method.

  16. Sequential determination of Cd and Cr in biomass samples and their ashes using high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis.

    PubMed

    Duarte, Alvaro T; Dessuy, Morgana B; Vale, Maria Goreti R; Welz, Bernhard; de Andrade, Jailson B

    2013-10-15

    High-resolution continuum source graphite furnace atomic absorption spectrometry, because of the use of only one radiation source for all elements, offers the possibility of sequential determination of two or more elements from the same sample aliquot if their volatilities are significantly different. Cd and Cr were determined sequentially in samples of biomass and biomass ashes employing direct solid sample analysis. The use of a chemical modifier was found to be not necessary, and calibration could be carried out using aqueous standard solutions. A pyrolysis temperature of 400°C and an atomization temperature of 1500°C were used for the determination of Cd; no losses of Cr were observed at this temperature. After the atomization of Cd the wavelength was changed and Cr atomized at 2600°C. The limits of detection (LOD) and quantification (LOQ) were 1.1 μg kg(-1) and 3.7 μg kg(-1), respectively, for Cd and 21 μg kg(-1) and 70 μg kg(-1), respectively, for Cr using the most sensitive line at 357.869 nm, or 90 μg kg(-1) and 300 μg kg(-1), respectively, using the less sensitive line at 428.972 nm. The precision, expressed as relative standard deviation was around 10%, which is typical for direct solid sample analysis. The values found for Cd in biomass samples were between <1.1 µg kg(-1) and 789 µg kg(-1), whereas those for Cr were between 7.9 mg kg(-1) and 89 mg kg(-1); the values found in the ashes were significantly lower for Cd, between <1.1 µg kg(-1) and 6.3 µg kg(-1), whereas the trend was not so clear for Cr, where the values were between 3.4 mg kg(-1) and 28 mg kg(-1).

  17. Ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction combined with graphite furnace atomic absorption spectrometric for selenium speciation in foods and beverages.

    PubMed

    Tuzen, Mustafa; Pekiner, Ozlem Zeynep

    2015-12-01

    A rapid and environmentally friendly ultrasound assisted ionic liquid dispersive liquid liquid microextraction (USA-IL-DLLME) was developed for the speciation of inorganic selenium in beverages and total selenium in food samples by using graphite furnace atomic absorption spectrometry. Some analytical parameters including pH, amount of complexing agent, extraction time, volume of ionic liquid, sample volume, etc. were optimized. Matrix effects were also investigated. Enhancement factor (EF) and limit of detection (LOD) for Se(IV) were found to be 150 and 12 ng L(-1), respectively. The relative standard deviation (RSD) was found 4.2%. The accuracy of the method was confirmed with analysis of LGC 6010 Hard drinking water and NIST SRM 1573a Tomato leaves standard reference materials. Optimized method was applied to ice tea, soda and mineral water for the speciation of Se(IV) and Se(VI) and some food samples including beer, cow's milk, red wine, mixed fruit juice, date, apple, orange, grapefruit, egg and honey for the determination of total selenium.

  18. Novel ion imprinted magnetic mesoporous silica for selective magnetic solid phase extraction of trace Cd followed by graphite furnace atomic absorption spectrometry detection

    NASA Astrophysics Data System (ADS)

    Zhao, Bingshan; He, Man; Chen, Beibei; Hu, Bin

    2015-05-01

    Determination of trace Cd in environmental, biological and food samples is of great significance to toxicological research and environmental pollution monitoring. While the direct determination of Cd in real-world samples is difficult due to its low concentration and the complex matrix. Herein, a novel Cd(II)-ion imprinted magnetic mesoporous silica (Cd(II)-II-MMS) was prepared and was employed as a selective magnetic solid-phase extraction (MSPE) material for extraction of trace Cd in real-world samples followed by graphite furnace atomic absorption spectrometry (GFAAS) detection. Under the optimized conditions, the detection limit of the proposed method was 6.1 ng L- 1 for Cd with the relative standard deviation (RSD) of 4.0% (c = 50 ng L- 1, n = 7), and the enrichment factor was 50-fold. To validate the proposed method, Certified Reference Materials of GSBZ 50009-88 environmental water, ZK018-1 lyophilized human urine and NIES10-b rice flour were analyzed and the determined values were in a good agreement with the certified values. The proposed method exhibited a robust anti-interference ability due to the good selectivity of Cd(II)-II-MMS toward Cd(II). It was successfully employed for the determination of trace Cd(II) in environmental water, human urine and rice samples with recoveries of 89.3-116%, demonstrating that the proposed method has good application potential in real world samples with complex matrix.

  19. Determination of tellurium in ores, concentrates and related materials by graphite-furnace atomic-absorption spectrometry after separations by iron collection and xanthate extraction.

    PubMed

    Donaldson, E M; Leaver, M E

    1990-02-01

    A method for determining approximately 0.01 mug/g or more of tellurium in ores, concentrates, rocks, soils and sediments is described. After sample decomposition and evaporation of the solution to incipient dryness, tellurium is separated from > 300 mug of copper by co-precipitation with hydrous ferric oxide from an ammoniacal medium and the precipitate is dissolved in 10M hydrochloric acid. Alternatively, for samples containing 300 mug of copper, the salts are dissolved in 10M hydrochloric acid. Tellurium in the resultant solutions is reduced to the quadrivalent state by heating and separated from iron, lead and various other elements by a single cyclohexane extraction of its xanthate complex from approximately 9.5M hydrochloric acid in the presence of thiosemicarbazide as a complexing agent for copper. After washing with 10M hydrochloric acid followed by water to remove residual iron, chloride and soluble salts, tellurium is stripped from the extract with 16M nitric acid and finally determined, in a 2% v/v nitric acid medium, by graphite-furnace atomic-absorption spectrometry at 214.3 nm in the presence of nickel as matrix modifier. Small amounts of gold and palladium, which are partly co-extracted as xanthates if the iron-collection step is omitted, do not interfere. Co-extraction of arsenic is avoided by volatilizing it as the bromide during the decomposition step. The method is directly applicable, without the co-precipitation step, to most rocks, soils and sediments.

  20. Determination of Lead in Water Samples Using a New Vortex-Assisted, Surfactant-Enhanced Emulsification Liquid-Liquid Microextraction Combined with Graphite Furnace Atomic Absorption Spectrometry.

    PubMed

    Peng, Guilong; He, Qiang; Lu, Ying; Mmereki, Daniel; Pan, Weiliang; Tang, Xiaohui; Zhou, Guangming; Mao, Yufeng; Su, Xaioxuan

    2016-04-01

    A low toxic solvent-based vortex-assisted surfactant-enhanced emulsification liquid-liquid microextraction (LT-VSLLME) combined with graphite furnace atomic absorption spectrometry was developed for the extraction and determination of lead (Pb) in water samples. In the LT-VSLLME method, the extraction solvent was dispersed into the aqueous samples by the assistance of vortex agitator. Meanwhile, the addition of a surfactant, which acted as an emulsifier, could enhance the speed of the mass-transfer from aqueous samples to the extraction solvent. The influences of analytical parameters, including extraction solvent type and its volume, surfactant type and its volume, pH, concentration of chelating agent, salt effect and extraction time were investigated. Under the optimized conditions, a good relative standard deviation of 3.69% at 10 ng L(-1) was obtained. The calibration graph showed a linear pattern in the ranges of 5-30 ngL(-1), with a limit of detection of 0.76 ng L(-1). The linearity was obtained by five points in the concentration range of 5-30 ngL(-1). The enrichment factor was 320. The procedure was applied to wastewater and river water, and the accuracy was assessed through the analysis of the recovery experiments. PMID:26614355

  1. Determination of macro and trace elements in multivitamin dietary supplements by high-resolution continuum source graphite furnace atomic absorption spectrometry with slurry sampling.

    PubMed

    Krawczyk, Magdalena

    2014-01-01

    In this research, three different commercially available multivitamin dietary supplements were analyzed by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS) with slurry sampling. The concentrations of Cr, Cu, Fe, Mn, and Se were determined and compared to the amounts stated by producers. The safety of multivitamin dietary supplements depends on various factors including the manufacturing process and the purity and origins of the raw ingredients. For this reason, this research determined concentrations of several toxic elements (As, Cd, and Pb). Microwave-assisted high pressure Teflon bomb digestion was used to determine total amounts of elements in samples. Samples were prepared as slurries at a concentration of 0.1% (m/v) for macro elements (Cr, Cu, Fe, Mn, and Se) and at a concentration of % (m/v) for trace elements (As, Cd, and Pb) in acidic media (3M HNO3). The influence of acid concentration, Triton X-100 addition, sonication time, and sonication power on absorbance was investigated. The accuracy of this method was validated by analyses of NRCC LUTS-1 (Lobster hepatopancreas), NRCC DORM-1 (Dogfish Muscle), NRCC DOLT-2 (Dogfish Liver), NBS SRM 1570 (Spinach Leaves) and NBS SRM 1573 (Tomato Leaves) certified reference materials. The measured elements contents in these reference materials (except NRCC DOLT-2) were in satisfactory agreement with the certified values according to the t-test for a 95% confidence level.

  2. Determination of Lead in Water Samples Using a New Vortex-Assisted, Surfactant-Enhanced Emulsification Liquid-Liquid Microextraction Combined with Graphite Furnace Atomic Absorption Spectrometry.

    PubMed

    Peng, Guilong; He, Qiang; Lu, Ying; Mmereki, Daniel; Pan, Weiliang; Tang, Xiaohui; Zhou, Guangming; Mao, Yufeng; Su, Xaioxuan

    2016-04-01

    A low toxic solvent-based vortex-assisted surfactant-enhanced emulsification liquid-liquid microextraction (LT-VSLLME) combined with graphite furnace atomic absorption spectrometry was developed for the extraction and determination of lead (Pb) in water samples. In the LT-VSLLME method, the extraction solvent was dispersed into the aqueous samples by the assistance of vortex agitator. Meanwhile, the addition of a surfactant, which acted as an emulsifier, could enhance the speed of the mass-transfer from aqueous samples to the extraction solvent. The influences of analytical parameters, including extraction solvent type and its volume, surfactant type and its volume, pH, concentration of chelating agent, salt effect and extraction time were investigated. Under the optimized conditions, a good relative standard deviation of 3.69% at 10 ng L(-1) was obtained. The calibration graph showed a linear pattern in the ranges of 5-30 ngL(-1), with a limit of detection of 0.76 ng L(-1). The linearity was obtained by five points in the concentration range of 5-30 ngL(-1). The enrichment factor was 320. The procedure was applied to wastewater and river water, and the accuracy was assessed through the analysis of the recovery experiments.

  3. Graphite furnace atomic absorption spectrometric determination of Ni and Pb in diesel and gasoline samples stabilized as microemulsion using conventional and permanent modifiers

    NASA Astrophysics Data System (ADS)

    Reyes, Mariela N. Matos; Campos, Reinaldo C.

    2005-06-01

    A procedure for the graphite furnace atomic absorption spectrometric determination of Ni and Pb in diesel and gasoline samples was developed. Sample stabilization was necessary because of evident analyte losses that occurred immediately after sampling. Excellent long-term sample stabilization was observed by mixing different organic solvents with propan-1-ol and 50% vol/vol HNO 3 at a 3.3:6.5:1 volume ratio. For Pb, efficient thermal stabilization was obtained using aqueous Pd-Mg modifier as well as for Ir as permanent modifier. The drying temperature and ramp rate influenced the sensitivity obtained for Ni, and had to be carefully optimized. Taking this into account, the same sensitivity was attained in all investigated organic media stabilized as microemulsion. Thus, calibration with microemulsions prepared with a single organic solvent was possible, using aqueous or organic stock solutions. Commercial gasoline and diesel samples were directly analyzed after stabilization as microemulsion and by comparative UOP procedures. n-Hexane microemulsions were used for calibration, and good agreement was obtained between the results using the proposed and comparative procedures. Typical coefficients of variation ( n = 6) ranged from 1% to 4%, and from 1% to 3% for Ni and Pb, respectively. Detection limits ( k = 3) in the original gasoline or diesel samples, derived from 10 blank measurements, were 4.5 and 3.6 μg l - 1 for Ni and Pb, respectively, comfortably below the values found in the analyzed samples.

  4. Solidified floating organic drop microextraction (SFODME) for simultaneous separation/preconcentration and determination of cobalt and nickel by graphite furnace atomic absorption spectrometry (GFAAS).

    PubMed

    Bidabadi, Mahboubeh Shirani; Dadfarnia, Shayessteh; Shabani, Ali Mohammad Haji

    2009-07-15

    Solidified floating organic drop microextraction (SFODME), combined with graphite furnace atomic absorption spectrometry (GFAAS) was proposed for simultaneous separation/enrichment and determination of trace amounts of nickel and cobalt in surface waters and sea water. 1-(2-Pyridylazo)-2-naphthol (PAN) was used as chelating agent. The main parameters affecting the performance of SFODME, such as pH, concentration of PAN, extraction time, stirring rate, extraction temperature, sample volume and nature of the solvent were optimized. Under the optimum experimental conditions, a good relative standard deviation for six determination of 20 ng l(-1) of Co(II) and Ni(II) were 4.6 and 3.6%, respectively. An enrichment factor of 502 and 497 and detection limits of 0.4 and 0.3 ng l(-1) for cobalt and nickel were obtained, respectively. The procedure was applied to tap water, well water, river water and sea water, and accuracy was assessed through the analysis of certified reference water or recovery experiments. PMID:19117672

  5. Separation and preconcentration of trace level of lead in one drop of blood sample by using graphite furnace atomic absorption spectrometry.

    PubMed

    Shrivas, Kamlesh; Patel, Devesh Kumar

    2010-04-15

    Drop-to-drop solvent microextraction (DDSME) assisted with ultrasonication is applied for the determination of lead in one drop (30 microL) of blood sample by using graphite furnace atomic absorption spectrometry (GF-AAS). The optimum extraction efficiency of lead was observed for 10 min extraction time at pH 5.0 with 2 microL of organic solvent that containing 0.5 M of Cyanex-302. The optimized methodology exhibited good linearity in the range of 0.3-30.0 ng mL(-1) lead with relative standard deviations (RSD) from 2.5 to 4.4%. The method is found to be simple and rapid for the analysis of lead in micro amount of blood sample with the limit of detection (LOD) of 0.08 ng mL(-1). The application of the proposed method has been successfully tested for the determination of lead in blood samples. The results showed that under the optimized experimental conditions, the method showed good sensitivity and recovery %, as well as advantages such as linearity, simplicity, low cost and high feasibility. PMID:20004520

  6. Ultrasound-assisted emulsification microextraction based on solidification floating organic drop trace amounts of manganese prior to graphite furnace atomic absorption spectrometry determination.

    PubMed

    Mohadesi, Alireza; Falahnejad, Masoumeh

    2012-01-01

    In the present study, an ultrasound-assisted emulsification microextraction based on solidification floating organic drop method is described for preconcentration of trace amounts of Mn (II). 2-(5-Bromo-2-pyridylazo)-5 diethylaminophenol was added to a solution of Mn(+2) at ph = 10.0. After this, 1-undecanol was added to the solution as an extraction solvent, and solution was stirred. Several factors influencing the microextraction efficiency, such as pH, the amount of chelating agent, nature and volume of extraction solvent, the volume of sample solution, stirring rate, and extraction time were investigated and optimized. Then sample vial was cooled by inserting into an ice bath, and the solidified was transferred into a suitable vial for immediate melting. Finally the sample was injected into a graphite furnace atomic absorption spectrometry. Under the optimum condition the linear dynamic range was 0.50-10.0 ng mL(-1) with a correlation coefficient of 0.9926, and the detection limit of 0.3 ng mL(-1) was obtained. The enrichment factor was 160. The proposed method was successfully applied for separation and determination of manganese in sea, rain, tap, and river water samples. PMID:22645504

  7. Ultrasound-assisted emulsification solidified floating organic drops microextraction of ultra trace amount of Te (IV) prior to graphite furnace atomic absorption spectrometry determination.

    PubMed

    Fathirad, Fariba; Afzali, Daryoush; Mostafavi, Ali; Ghanbarian, Maryam

    2012-01-15

    In the present study, a new, simple and efficient method for the preconcentration of ultra trace amounts of Te (IV) is developed using ultrasound-assisted emulsification solidified floating organic drops microextraction (USAE-SFODME) before graphite furnace atomic absorption spectrometry determination. In this method, tellurium is extracted into the fine droplets of 1-undecanol after chelate formation with the water soluble ligand, ammonium pyrrolidinedithiocarbamate (APDC). Several factors such as pH, chelating agent amount, type and volume of the extracting solvent, sonication and centrifuging time that influence the extraction and complex formation are optimized. Under the optimum conditions, the calibration graph is linear in the range of 0.01-0.24ngmL(-1) of tellurium in the original solution, with limit of detection of 0.003ngmL(-1). The relative standard deviation (RSD) for seven replicated determinations of tellurium ion at 0.08ngmL(-1) concentration level is calculated as 3.4%. The proposed method was successfully applied to the determination of Te (IV) in a standard soil and several water samples. PMID:22265571

  8. The study of applicability of dithiocarbamate-coated fullerene C 60 for preconcentration of palladium for graphite furnace atomic absorption spectrometric determination in environmental samples

    NASA Astrophysics Data System (ADS)

    Leśniewska, Barbara A.; Godlewska, Iwona; Godlewska—Żyłkiewicz, Beata

    2005-03-01

    The present method comprises an off-line enrichment of Pd on the fullerene, C 60, coated with ammonium pyrrolidinedithiocarbamate (APDC), followed by the elution of formed Pd-chelate with ethanol and the subsequent determination of Pd from the eluate by graphite furnace atomic absorption spectrometry. By using fullerene loaded with 0.1% APDC, the analytical system is simplified as the sample can be directly preconcentrated on the column. The following parameters affecting the preconcentration of Pd on C 60 were optimized: amount of ligand used for the coating of fullerene, sample pH, kind of eluent, sample and eluent flow rates, volume and number of fractions of eluent used. The sorption efficiency for Pd on coated fullerene was 99.2±1.1%. The best elution efficiency for Pd from the column was obtained with 0.6 ml of ethanol at a flow rate of 0.2 ml min -1. The limit of detection was 0.044 ng ml -1. The effect of sample pretreatment procedure on the preconcentration of Pd by evaluated method is discussed. The content of Pd in road dust (179.2±17.4 ng g -1) determined by proposed method was in agreement with the results obtained with a reference method. The low recovery of analyte (64%) was obtained for geological material CRM SARM-7 (platinum ore) due to the much higher concentration of interfering elements.

  9. Determination of lead in sea-water with a graphite furnace atomic absorption spectrometer and an improved automatic on-line pre-concentration system

    NASA Astrophysics Data System (ADS)

    Liu, Zhen-Shan; Huang, Shang-Da

    1995-03-01

    An improved automatic on-line pre-concentration system for graphite furnace atomic absorption spectrometry (GFAAS) for the determination of trace metals in sea-water was developed. This system was modified from a Perkin-Elmer AS-40 autosampler by mounting a silica gel C 18 microcolumn near the tip of the autosampler capillary. The pre-concentration procedure was performed by using a four-way distribution valve and controlled by a programmable controller. The pre-concentration system developed previously was improved by using a peristaltic pump to replace the reciprocating pumps, a newly designed tube bed adjuster to release the back-pressure in the pre-concentration system, and a better control program, such that on-line pre-concentration became more reliable and fully automatic. The chelating agent ammonium pyrolidinedithiocarbamate (APDC) and a miniature column packed with 5 mg of C 18 silica gel were used for pre-concentration. This system was tested by analyzing the lead content in reference standard sea-water samples. A sample volume of only 2 ml was required to determine lead in sea-water. The relative limit of detection of lead was 3.5 pg/ml.

  10. Automatic microemulsion preparation for metals determination in fuel samples using a flow-batch analyzer and graphite furnace atomic absorption spectrometry.

    PubMed

    Cunha, Francisco Antônio S; Sousa, Rafael A; Harding, David P; Cadore, Solange; Almeida, Luciano F; Araújo, Mário César U

    2012-05-21

    The principal thermodynamic advantages of using microemulsions over standard emulsions for flow metal analysis are the greatly increased analyte stability and emulsive homogeneity that improve both the ease of sample preparation, and the analytical result. In this study a piston propelled flow-batch analyzer (PFBA) for the determination of Cu, Cr and Pb in gasoline and naphtha by graphite furnace atomic absorption spectrometry (GF AAS) was explored. Investigative phase modeling for low dilution was conducted both for gasoline and naphtha microemulsions. Rheological considerations were also explored including a mathematical flow derivation to fine tune the system's operational parameters, and the GF AAS coupling. Both manual and automated procedures for microemulsion preparation were compared. The results of the paired t test at a 95% confidence level showed no significant differences between them. Further recovery test results confirmed a negligible matrix effect of the sample on the analyte absorption signals and an efficient stabilization of the samples (with metals) submitted to microemulsion treatment. The accuracy of the developed procedure was attested by good recovery percentages in the ranges of 100.0±3.5% for Pb in the naphtha samples, and 100.2±3.4% and 100.7±4.6% for Cu and Cr, respectively in gasoline samples. PMID:22541820

  11. Ionic liquid-based extraction followed by graphite-furnace atomic absorption spectrometry for the determination of trace heavy metals in high-purity iron metal.

    PubMed

    Matsumiya, Hiroaki; Kato, Tatsuya; Hiraide, Masataka

    2014-02-01

    The analysis of high-purity materials for trace impurities is an important and challenging task. The present paper describes a facile and sensitive method for the determination of trace heavy metals in high-purity iron metal. Trace heavy metals in an iron sample solution were rapidly and selectively preconcentrated by the extraction into a tiny volume of an ionic liquid [1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide] for the determination by graphite-furnace atomic absorption spectrometry (GFAAS). A nitrogen-donating neutral ligand, 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPTZ), was found to be effective in the ionic liquid-based selective extraction, allowing the nearly complete (~99.8%) elimination of the iron matrix. The combination with the optimized GFAAS was successful. The detectability reached sub-μg g(-1) levels in iron metal. The novel use of TPTZ in ionic liquid-based extraction followed by GFAAS was successfully applied to the determination of traces of Co, Ni, Cu, Cd, and Pb in certified reference materials for high-purity iron metal.

  12. Ultrasound-assisted ionic liquid dispersive liquid-liquid microextraction combined with graphite furnace atomic absorption spectrometric for selenium speciation in foods and beverages.

    PubMed

    Tuzen, Mustafa; Pekiner, Ozlem Zeynep

    2015-12-01

    A rapid and environmentally friendly ultrasound assisted ionic liquid dispersive liquid liquid microextraction (USA-IL-DLLME) was developed for the speciation of inorganic selenium in beverages and total selenium in food samples by using graphite furnace atomic absorption spectrometry. Some analytical parameters including pH, amount of complexing agent, extraction time, volume of ionic liquid, sample volume, etc. were optimized. Matrix effects were also investigated. Enhancement factor (EF) and limit of detection (LOD) for Se(IV) were found to be 150 and 12 ng L(-1), respectively. The relative standard deviation (RSD) was found 4.2%. The accuracy of the method was confirmed with analysis of LGC 6010 Hard drinking water and NIST SRM 1573a Tomato leaves standard reference materials. Optimized method was applied to ice tea, soda and mineral water for the speciation of Se(IV) and Se(VI) and some food samples including beer, cow's milk, red wine, mixed fruit juice, date, apple, orange, grapefruit, egg and honey for the determination of total selenium. PMID:26041239

  13. Graphite furnace atomic absorption spectrometric detection of vanadium in water and food samples after solid phase extraction on multiwalled carbon nanotubes.

    PubMed

    Wadhwa, Sham Kumar; Tuzen, Mustafa; Gul Kazi, Tasneem; Soylak, Mustafa

    2013-11-15

    Vanadium(V) ions as 8-hydroxyquinoline chelates were loaded on multiwalled carbon nanotubes (MWNTs) in a mini chromatographic column. Vanadium was determined by graphite furnace atomic absorption spectrometry (GFAAS). Various analytical parameters including pH of the working solutions, amounts of 8-hydroxyquinoline, eluent type, sample volume, and flow rates were investigated. The effects of matrix ions and some transition metals were also studied. The column can be reused 250 times without any loss in its sorption properties. The preconcentration factor was found as 100. Detection limit (3 s) and limit of quantification (10 s) for the vanadium in the optimal conditions were observed to be 0.012 µg L(-1) and 0.040 μg L(-1), respectively. The capacity of adsorption was 9.6 mg g(-1). Relative standard deviation (RSD) was found to be 5%. The validation of the method was confirmed by using NIST SRM 1515 Apple leaves, NIST SRM 1570a Spinach leaves and GBW 07605 Tea certified reference materials. The procedure was applied to the determination of vanadium in tap water and bottled drinking water samples. The procedure was also successfully applied to microwave digested food samples including black tea, coffee, tomato, cabbage, zucchini, apple and chicken samples.

  14. Magnetic stirrer induced dispersive ionic-liquid microextraction for the determination of vanadium in water and food samples prior to graphite furnace atomic absorption spectrometry.

    PubMed

    Naeemullah; Kazi, Tasneem Gul; Tuzen, Mustafa

    2015-04-01

    A new dispersive liquid-liquid microextraction, magnetic stirrer induced dispersive ionic-liquid microextraction (MS-IL-DLLME) was developed to quantify the trace level of vanadium in real water and food samples by graphite furnace atomic absorption spectrometry (GFAAS). In this extraction method magnetic stirrer was applied to obtained a dispersive medium of 1-butyl-3-methylimidazolium hexafluorophosphate [C4MIM][PF6] in aqueous solution of (real water samples and digested food samples) to increase phase transfer ratio, which significantly enhance the recovery of vanadium - 4-(2-pyridylazo) resorcinol (PAR) chelate. Variables having vital role on desired microextraction methods were optimised to obtain the maximum recovery of study analyte. Under the optimised experimental variables, enhancement factor (EF) and limit of detection (LOD) were achieved to be 125 and 18 ng L(-1), respectively. Validity and accuracy of the desired method was checked by analysis of certified reference materials (SLRS-4 Riverine water and NIST SRM 1515 Apple leaves). The relative standard deviation (RSD) for 10 replicate determinations at 0.5 μg L(-1) of vanadium level was found to be <5.0%. This method was successfully applied to real water and acid digested food samples.

  15. Determination of Pb and Cd in Garlic Herb (Allium sativum) Planted in Gilan and Khuzestan Provinces Using Graphite Furnace Atomic Absorption Spectrometry

    PubMed Central

    Ramezani, Zahra; Aghel, Nasrin; Amirabedin, Negar

    2012-01-01

    Background Foods are enriched with variety of chemical elements. Some of these elements are necessary for human health. These elements enter in liquid, the cells and other organs, certain amount of these elements are essential for body organs to work properly. Objectives This research was conducted to compare the level of lead and cadmium contamination in garlic species planted in Ramhormoz and Rasht and discuss about the source of this contaminations. Materials and Methods Twenty composite samples were collected from each province, Khozestan (Ramhormoz) and Gilan (Rasht). Each sample was burned according to instruction reported in AOAC. Then the white residue was dissolved in diluted nitric acid then the Pb and Cd contents were determined using graphite furnace atomic absorption spectrometer at 217 and 228.8 nm, respectively. No Pb level was detected in garlic cultured in both cities. The mean concentration of cadmium was 0.40 and 0.58 mg/kg in garlics planted in Ramhormoz and Rasht, respectively. Results Statistical analysis showed significant difference between mean concentration of cadmium in Rasht garlic and the permitted value (P < 0.001). The cadmium level in Rasht garlic is much higher than the standard level. Conclusions In order to test the reliability of the data obtained using this method, randomly selected samples were spiked with Pb and Cd standard solutions. The cadmium and lead recovery were reported 93.93 and 90.18 percent. PMID:24624152

  16. Ultrasound-assisted emulsification solidified floating organic drops microextraction of ultra trace amount of Te (IV) prior to graphite furnace atomic absorption spectrometry determination.

    PubMed

    Fathirad, Fariba; Afzali, Daryoush; Mostafavi, Ali; Ghanbarian, Maryam

    2012-01-15

    In the present study, a new, simple and efficient method for the preconcentration of ultra trace amounts of Te (IV) is developed using ultrasound-assisted emulsification solidified floating organic drops microextraction (USAE-SFODME) before graphite furnace atomic absorption spectrometry determination. In this method, tellurium is extracted into the fine droplets of 1-undecanol after chelate formation with the water soluble ligand, ammonium pyrrolidinedithiocarbamate (APDC). Several factors such as pH, chelating agent amount, type and volume of the extracting solvent, sonication and centrifuging time that influence the extraction and complex formation are optimized. Under the optimum conditions, the calibration graph is linear in the range of 0.01-0.24ngmL(-1) of tellurium in the original solution, with limit of detection of 0.003ngmL(-1). The relative standard deviation (RSD) for seven replicated determinations of tellurium ion at 0.08ngmL(-1) concentration level is calculated as 3.4%. The proposed method was successfully applied to the determination of Te (IV) in a standard soil and several water samples.

  17. One-step displacement dispersive liquid-liquid microextraction coupled with graphite furnace atomic absorption spectrometry for the selective determination of methylmercury in environmental samples.

    PubMed

    Liang, Pei; Kang, Caiyan; Mo, Yajun

    2016-01-01

    A novel method for the selective determination of methylmercury (MeHg) was developed by one-step displacement dispersive liquid-liquid microextraction (D-DLLME) coupled with graphite furnace atomic absorption spectrometry. In the proposed method, Cu(II) reacted with diethyldithiocarbamate (DDTC) to form Cu-DDTC complex, which was used as the chelating agent instead of DDTC for the dispersive liquid-liquid microextraction (DLLME) of MeHg. Because the stability of MeHg-DDTC is higher than that of Cu-DDTC, MeHg can displace Cu from the Cu-DDTC complex and be preconcentrated in a single DLLME procedure. MeHg could be extracted into the extraction solvent phase at pH 6 while Hg(II) remained in the sample solution. Potential interference from co-existing metal ions with lower DDTC complex stability was largely eliminated without the need of any masking reagent. Under the optimal conditions, the limit of detection of this method was 13.6ngL(-1) (as Hg), and an enhancement factor of 81 was achieved with a sample volume of 5.0mL. The proposed method was successfully applied for the determination of trace MeHg in some environmental samples with satisfactory results.

  18. Study of the versatility of a graphite furnace atomic absorption spectrometric method for the determination of cadmium in the environmental field.

    PubMed

    Rucandio, M Isabel; Petit-Domínguez, M Dolores

    2002-01-01

    Cadmium is a representative example of trace elements that are insidious and widespread health hazards. In contemporary environmental analysis, there is a clear trend toward its determination over a wide range of concentrations in complex matrixes. This paper describes a versatile method for the determination of Cd at various levels (0.1-500 microg/g) in several sample types, such as soils, sediments, coals, ashes, sewage sludges, animal tissues, and plants, by graphite furnace atomic absorption spectrometry with Zeeman background correction. The effect of the individual presence of about 50 elements, with an interference/analyte concentration ratio of up to 10(5), was tested; recoveries of Cd ranged from 93 to 106%. The influence of different media, such as HNO3, HCI, HF, H2SO4, HClO4, acetic acid, hydroxylammonium chloride, and ammonium acetate, in several concentrations, was also tested. From these studies it can be concluded that the analytical procedure is scarcely matrix dependent, and the results obtained for a wide diversity of reference materials are in good agreement with the certified values.

  19. Simultaneous determination of iron and nickel in fluoropolymers by solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry.

    PubMed

    Soares, Bruno M; Santos, Rafael F; Bolzan, Rodrigo C; Muller, Edson I; Primel, Ednei G; Duarte, Fabio A

    2016-11-01

    This paper reports the development of a method of simultaneous determination of iron and nickel in fluoropolymers by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) with direct solid sampling. In order to carry out simultaneous measurements, both the main resonance line of nickel (232.003nm) and the adjacent secondary line of iron (232.036nm) were monitored in the same spectral window. The proposed method was optimized with a perfluoroalkoxy (PFA) sample and was applied to the determination of iron and nickel in fluorinated ethylene propylene (FEP) and modified polytetrafluoroethylene (PTFE-TFM) samples. Pyrolysis and atomization temperatures, as well as the use of Pd and H2 (during pyrolysis) as chemical modifiers, were carefully investigated. Compromise temperatures for pyrolysis and atomization of both analytes were achieved at 800 and 2300°C, respectively, using only 0.5Lmin(-1) H2 as chemical modifier during pyrolysis. Calibration curves were performed with aqueous standards by using a single solution which contained both analytes. Limits of detection were 221 and 9.6ngg(-1) for iron and nickel, respectively. Analyte concentrations in all samples ranged from 3.53 to 12.4µgg(-1) for iron and from 37 to 78ngg(-1) for nickel, with relative standard deviation less than 19%. Accuracy was evaluated by comparing these results with those obtained by inductively coupled plasma mass spectrometry after sample digestion by microwave-induced combustion and no significant statistical difference was observed. PMID:27591638

  20. Simultaneous determination of iron and nickel in fluoropolymers by solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry.

    PubMed

    Soares, Bruno M; Santos, Rafael F; Bolzan, Rodrigo C; Muller, Edson I; Primel, Ednei G; Duarte, Fabio A

    2016-11-01

    This paper reports the development of a method of simultaneous determination of iron and nickel in fluoropolymers by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) with direct solid sampling. In order to carry out simultaneous measurements, both the main resonance line of nickel (232.003nm) and the adjacent secondary line of iron (232.036nm) were monitored in the same spectral window. The proposed method was optimized with a perfluoroalkoxy (PFA) sample and was applied to the determination of iron and nickel in fluorinated ethylene propylene (FEP) and modified polytetrafluoroethylene (PTFE-TFM) samples. Pyrolysis and atomization temperatures, as well as the use of Pd and H2 (during pyrolysis) as chemical modifiers, were carefully investigated. Compromise temperatures for pyrolysis and atomization of both analytes were achieved at 800 and 2300°C, respectively, using only 0.5Lmin(-1) H2 as chemical modifier during pyrolysis. Calibration curves were performed with aqueous standards by using a single solution which contained both analytes. Limits of detection were 221 and 9.6ngg(-1) for iron and nickel, respectively. Analyte concentrations in all samples ranged from 3.53 to 12.4µgg(-1) for iron and from 37 to 78ngg(-1) for nickel, with relative standard deviation less than 19%. Accuracy was evaluated by comparing these results with those obtained by inductively coupled plasma mass spectrometry after sample digestion by microwave-induced combustion and no significant statistical difference was observed.

  1. Influence of citric acid as chemical modifier for lead determination in dietary calcium supplement samples by graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Cezar Paz de Mattos, Julio; Medeiros Nunes, Adriane; Figueiredo Martins, Ayrton; Luiz Dressler, Valderi; Marlon de Moraes Flores, Érico

    2005-06-01

    Citric acid was used as a chemical modifier for Pb determination by graphite furnace atomic absorption spectrometry in dietary supplement samples (calcium carbonate, dolomite and oyster shell samples) and its efficiency was compared to the use of palladium. Pyrolysis and atomization curves were established without use of chemical modifier, with the addition of 20, 100 and 200 μg of citric acid, and with 3 μg of palladium. The citric acid modifier made possible the interference-free Pb determination in the presence of high concentrations of Ca and Mg nitrates. Acid sample digestion involving closed vessels (microwave-assisted and conventional heating) and acid attack using polypropylene vessels at room temperature were compared. All digestion procedures presented similar results for calcium carbonate and dolomite samples. However, for oyster shell samples accurate results were obtained only with the use of closed vessel systems. Analyte addition and matrix-matched standards were used for calibration. The characteristic mass for Pb using citric acid and palladium were 16 and 25 pg, respectively. The relative standard deviation (RSD) was always less than 5% when citric acid was used. The relative and absolute limits of detection were 0.02 μg g - 1 and 8 pg with citric acid and 0.1 μg g - 1 and 44 pg with the Pd modifier, respectively ( n = 10, 3σ). The recovery of Pb in spiked calcium supplement samples (10 μg l - 1 ) was between 98% and 105%. With the use of 100 μg of citric acid as chemical modifier, problems such as high background absorption and high RSD values were minimized in comparison to the addition of 3 μg of palladium.

  2. Direct solid sample analysis with graphite furnace atomic absorption spectrometry—a fast and reliable screening procedure for the determination of inorganic arsenic in fish and seafood.

    PubMed

    Zmozinski, Ariane V; Llorente-Mirandes, Toni; Damin, Isabel C F; López-Sánchez, José F; Vale, Maria Goreti R; Welz, Bernhard; Silva, Márcia M

    2015-03-01

    Direct solid sample analysis with graphite furnace atomic absorption spectrometry (SS-GF AAS) was investigated initially with the intention of developing a method for the determination of total As in fish and other seafood. A mixture of 0.1% Pd+0.06% Mg+0.06% Triton X-100 was used as the chemical modifier, added in solution over the solid samples, making possible the use of pyrolysis and atomization temperatures of 1200 °C and 2400 °C, respectively. The sample mass had to be limited to 0.25 mg, as the integrated absorbance did not increase further with increasing sample mass. Nevertheless, the recovery of As from several certified reference materials was of the order of 50% lower than the certified value. Strong molecular absorption due to the phosphorus monoxide molecule (PO) was observed with high-resolution continuum source AAS (HR CS AAS), which, however, did not cause any spectral interference. A microwave-assisted digestion with HNO3/H2O2 was also investigated to solve the problem; however, the results obtained for several certified reference materials were statistically not different from those found with direct SS-GF AAS. Accurate values were obtained using inductively coupled plasma mass spectrometry (ICP-MS) to analyze the digested samples, which suggested that organic As compounds are responsible for the low recoveries. HPLC-ICP-MS was used to determine the arsenobetaine (AB) concentration. Accurate results that were not different from the certified values were obtained when the AB concentration was added to the As concentration found by SS-GF AAS for most certified reference materials (CRM) and samples, suggesting that SS-GF AAS could be used as a fast screening procedure for inorganic As determination in fish and seafood.

  3. Determination of copper and mercury in phosphate fertilizers employing direct solid sampling analysis and high resolution continuum source graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    de Oliveira Souza, Sidnei; François, Luciane Luiza; Borges, Aline Rocha; Vale, Maria Goreti Rodrigues; Araujo, Rennan Geovanny Oliveira

    2015-12-01

    The present study proposes the determination of copper and mercury in phosphate fertilizers by direct solid sampling analysis (SS) employing high resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). For Cu determination, two analytical lines were used: 327.3960 nm and 249.2146 nm. Hg determination was carried out on the line 253.6521 nm and 100 μg KMnO4 was used as chemical modifier. The optimal pyrolysis temperature for Cu determination was 1300 °C. Atomization temperatures for Cu and Hg were 2400 and 1100 °C, respectively. External calibration with aqueous standard solutions was adopted for both elements. The limits of quantification (LoQs) and characteristic mass (m0) obtained for Cu determination were 0.4 μg g- 1 and 1.12 ng, respectively, on line 249.2146 nm, and 64 μg g- 1 and 25 pg on 327.3960 nm. For mercury, LoQ and m0 were 4.8 ng g- 1 and 39 pg, respectively. The accuracy of the proposed methods was confirmed by the analysis of standard reference material (SRM) of Trace Elements in Multi-Nutrient Fertilizer (SRM NIST 695). The precision expressed as relative standard deviation (RSD), was better than 8.2% for Hg and 7.7% for the Cu (n = 5), considered satisfactory for microanalysis in solid sample. Four fertilizer samples acquired in commercial establishments in the city of Salvador, Bahia, Brazil, were analyzed. The optimized analytical methods were simple, fast, accurate, precise and free of spectral interferences for the determination of Cu and Hg in phosphate fertilizer samples by SS-HR-CS GF AAS, avoiding the dissolution of the sample, the use of harmful reagents and the generation of residues.

  4. Multiple response optimization for Cu, Fe and Pb determination in naphtha by graphite furnace atomic absorption spectrometry with sample injection as detergent emulsion

    NASA Astrophysics Data System (ADS)

    Brum, Daniel M.; Lima, Claudio F.; Robaina, Nicolle F.; Fonseca, Teresa Cristina O.; Cassella, Ricardo J.

    2011-05-01

    The present paper reports the optimization for Cu, Fe and Pb determination in naphtha by graphite furnace atomic absorption spectrometry (GF AAS) employing a strategy based on the injection of the samples as detergent emulsions. The method was optimized in relation to the experimental conditions for the emulsion formation and taking into account that the three analytes (Cu, Fe and Pb) should be measured in the same emulsion. The optimization was performed in a multivariate way by employing a three-variable Doehlert design and a multiple response strategy. For this purpose, the individual responses of the three analytes were combined, yielding a global response that was employed as a dependent variable. The three factors related to the optimization process were: the concentration of HNO 3, the concentration of the emulsifier agent (Triton X-100 or Triton X-114) in aqueous solution used to emulsify the sample and the volume of solution. At optimum conditions, it was possible to obtain satisfactory results with an emulsion formed by mixing 4 mL of the samples with 1 mL of a 4.7% w/v Triton X-100 solution prepared in 10% v/v HNO 3 medium. The resulting emulsion was stable for 250 min, at least, and provided enough sensitivity to determine the three analytes in the five samples tested. A recovery test was performed to evaluate the accuracy of the optimized procedure and recovery rates, in the range of 88-105%; 94-118% and 95-120%, were verified for Cu, Fe and Pb, respectively.

  5. Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; determination of low-level silver by graphite furnace atomic absorption spectrophotometry

    USGS Publications Warehouse

    Damrau, D.L.

    1993-01-01

    Increased awareness of the quality of water in the United States has led to the development of a method for determining low levels (0.2-5.0 microg/L) of silver in water samples. Use of graphite furnace atomic absorption spectrophotometry provides a sensitive, precise, and accurate method for determining low-level silver in samples of low ionic-strength water, precipitation water, and natural water. The minimum detection limit determined for low-level silver is 0.2 microg/L. Precision data were collected on natural-water samples and SRWS (Standard Reference Water Samples). The overall percent relative standard deviation for natural-water samples with silver concentrations more than 0.2 microg/L was less than 40 percent throughout the analytical range. For the SRWS with concentrations more than 0.2 microg/L, the overall percent relative standard deviation was less than 25 percent throughout the analytical range. The accuracy of the results was determined by spiking 6 natural-water samples with different known concentrations of the silver standard. The recoveries ranged from 61 to 119 percent at the 0.5-microg/L spike level. At the 1.25-microg/L spike level, the recoveries ranged from 92 to 106 percent. For the high spike level at 3.0 microg/L, the recoveries ranged from 65 to 113 percent. The measured concentrations of silver obtained from known samples were within the Branch of Quality Assurance accepted limits of 1 1/2 standard deviations on the basis of the SRWS program for Inter-Laboratory studies.

  6. A sensitive magnetic nanoparticle-based immunoassay of phosphorylated acetylcholinesterase using protein cage templated lead phosphate for signal amplification with graphite furnace atomic absorption spectrometry detection.

    PubMed

    Liang, Pei; Kang, Caiyan; Yang, Enjian; Ge, Xiaoxiao; Du, Dan; Lin, Yuehe

    2016-04-01

    We developed a new magnetic nanoparticle sandwich-like immunoassay using protein cage nanoparticles (PCN) for signal amplification together with graphite furnace atomic absorption spectrometry (GFAAS) for the quantification of an organophosphorylated acetylcholinesterase adduct (OP-AChE), the biomarker of exposure to organophosphate pesticides (OPs) and nerve agents. OP-AChE adducts were firstly captured by titanium dioxide coated magnetic nanoparticles (TiO2-MNPs) from the sample matrixes through metal chelation with phospho-moieties, and then selectively recognized by anti-AChE antibody labeled on PCN which was packed with lead phosphate in its cavity (PCN-anti-AChE). The sandwich-like immunoreaction was performed among TiO2-MNPs, OP-AChE and PCN-anti-AChE to form a TiO2-MNP/OP-AChE/PCN-anti-AChE immunocomplex. The complex could be easily isolated from the sample solution with the help of magnet, and the released lead ions from PCN were detected by GFAAS for the quantification of OP-AChE. Greatly enhanced sensitivity was achieved because PCN increased the amount of metal ions in the cavity of each apoferritin. The proposed immunoassay yielded a linear response over a broad range of OP-AChE concentrations from 0.01 nM to 2 nM, with a detection limit of 2 pM, which has enough sensitivity for monitoring of low-dose exposure to OPs. This new method showed an acceptable stability and reproducibility and was validated with OP-AChE spiked human plasma.

  7. Sensitive magnetic nanoparticle-based immunoassay of phosphorylated acetylcholinesterase using protein cage templated lead phosphate for signal amplification with graphite furnace atomic absorption spectrometry detection

    PubMed Central

    Liang, Pei; Kang, Caiyan; Yang, Enjian; Ge, Xiaoxiao; Du, Dan; Lin, Yuehe

    2016-01-01

    We developed a new magnetic nanoparticles sandwich-like immunoassay using protein cage nanoparticles (PCN) for signal amplification together with graphite furnace atomic absorption spectrometry (GFAAS) for quantification of organophosphorylated acetylcholinesterase adduct (OP-AChE), the biomarker of exposure to organophosphate pesticides (OPs) and nerve agents. OP-AChE adducts were firstly captured by titanium dioxide coated magnetic nanoparticles (TiO2-MNPs) from the sample matrixes through metal chelation with phospho-moieties, and then selectively recognized by anti-AChE antibody labeled on PCN which was packed with lead phosphate in its cavity (PCN-anti-AChE). The sandwich-like immunoreaction was performed among TiO2-MNPs, OP-AChE and PCN-anti-AChE to form TiO2-MNPs/OP-AChE/PCN-anti-AChE immunocomplex. The complex could be easily isolated from the sample solution with the help of magnet, and the released lead ions from PCN were detected by GFAAS for the quantification of OP-AChE. Greatly enhanced sensitivity was achieved because PCN increased the amount of metal ions in the cavity of each apoferritin. The proposed immunoassay yielded a linear response over a broad OP-AChE concentrations from 0.01 nM to 2 nM, with a detection limit of 2 pM, which has enough sensitivity for monitoring of low-dose exposure to OPs. This new method showed an acceptable stability and reproducibility and was validated with OP-AChE spiked human plasma. PMID:26953358

  8. A dried urine spot test to simultaneously monitor Mo and Ti levels using solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Rello, L.; Lapeña, A. C.; Aramendía, M.; Belarra, M. A.; Resano, M.

    2013-03-01

    Home-based collection protocols for clinical specimens are actively pursued as a means of improving life quality of patients that require frequent controls, such as patients with metallic prosthesis, for whom monitoring the evolution of Mo and Ti in biological fluids may play a decisive role to detect prosthesis mal-functioning. The collection of biological fluids on clinical filter papers provides a simple way to implement these protocols. This work explores the potential of solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry for the simultaneous and direct determination of Mo and Ti in urine, after its deposition onto clinical filter paper, giving rise to a dried urine spot. The approach used for depositing the sample was found crucial to develop a quantitative method, since the filter paper acts as a chromatographic support and produces a differential distribution of the target analytes. Furthermore, the high spreading of urine onto a filter paper results in a small amount of urine per surface unit, and thus, ultimately, in lack of sensitivity. In order to circumvent these problems, the use of an alternative approach based on the use of pre-cut 17 × 19 mm filter paper pieces onto which larger amounts of sample (500 μL) can be retained by single deposition was proposed and evaluated. In this way, an approximately 12-fold increase in sensitivity and a more homogeneous distribution of the target analytes were obtained, permitting the development of a quantification strategy based on the use of matrix-matched urine samples of known analyte concentrations, which were subjected to the same procedure as the samples. Accuracy of this method, which provides LODs of 1.5 μg L- 1 for Mo and 6.5 μg L- 1 for Ti, was demonstrated after analysis of urine reference materials. Overall, the performance of the method developed is promising, being likely suitable for determination of other analytes in dried urine spots.

  9. Magnetic solid-phase extraction combined with graphite furnace atomic absorption spectrometry for speciation of Cr(III) and Cr(VI) in environmental waters.

    PubMed

    Jiang, Hong-mei; Yang, Ting; Wang, Yan-hong; Lian, Hong-zhen; Hu, Xin

    2013-11-15

    A new approach of magnetic solid phase extraction (MSPE) coupled with graphite furnace atomic absorption spectrometry (GFAAS) has been developed for the speciation of Cr(III) and Cr(VI) using zincon-immobilized silica-coated magnetic Fe3O4 nanoparticles (Zincon-Si-MNPs) as the MSPE absorbent. Cr(III) was quantitatively reserved on the absorbent at pH 9.1 while total Cr was reserved at pH 6.5. The absorbed Cr species were eluted by using 2 mol/L HCl and detected by GFAAS. The concentration of Cr(VI) could be calculated by subtracting Cr(III) from total Cr. All the parameters affecting the separation and extraction efficiency of Cr species such as pH, extraction time, concentration and volume of eluent, sample volume and influence of co-existing ions were systematically examined and the optimized conditions were established accordingly. The detection limit (LOD) of the method was 0.016 and 0.011 ng mL(-1) for Cr(III) and Cr(VI), respectively, with the enrichment factor of 100 and 150. The precisions of this method (Relative standard deviation, RSD, n=7) for Cr(III) and Cr(VI) at 0.1 ng mL(-1) were 6.0% and 6.2%, respectively. In order to validate the proposed method, a certified reference material of environmental water was analyzed, and the result of Cr speciation was in good agreement with the certified value. This MSPE-GFAAS method has been successfully applied for the speciation of Cr(III) and Cr(VI) in lake and tap waters with the recoveries of 88-109% for the spiked samples. Moreover, the MSPE separation mechanism of Cr(III) and Cr(VI) based on their adsorption-desorption on Zincon-Si-MNPs has been explained through various spectroscopic characterization.

  10. Determination of lead, cadmium, copper, and nickel in the tonghui river of beijing, china, by cloud point extraction-high resolution continuum source graphite furnace atomic absorption spectrometry.

    PubMed

    Ren, Ting; Zhao, Li-Jiao; Sun, Bo-Si; Zhong, Ru-Gang

    2013-11-01

    Heavy metal contamination of water has become an important problem in recent years. Most hazardous heavy metals exist in environmental water in trace or ultra-trace amounts, which requires establishing highly sensitive analytical methods. In this research, quantitative analyses were performed using high-resolution continuum source graphite furnace atomic absorption spectrometry combined with cloud point extraction (CPE) to determine Pb, Cd, Cu, and Ni levels in environmental surface water. By optimizing the CPE conditions, the enrichment factors were 29 for Pb, Cd, and Cu and 25 for Ni. The limits of detection (LOD) were 0.080, 0.010, 0.035, and 0.014 μg L for Pb, Cd, Cu, and Ni, respectively. The sensitivity of the method is comparable with those reported in previous investigations using various methods and improves outcome by 2 to 3 orders of magnitude compared with the LODs of the current national standard methods of China. Our method was used to determine Pb, Cd, Cu, and Ni in 55 water samples collected from the Tonghui River, which is the principal river in the urban area of Beijing, China. The results indicated that the distributions of the four heavy metals in the Tonghui River were related with the environments. The levels of Pb and Ni exhibit increasing trends along the river from upstream to downstream possibly due to the existence of some chemical factories in the downstream area. Lead, Cd, Cu, and Ni averaged 13.9, 0.8, 46.8, and 38.5%, respectively, of the total amount of the determined heavy metals. The levels of the four heavy metals conformed to the Environmental Quality Standards for Surface Water (Grade I) of China. This work provides a reliable quantitative method to determine trace-amount heavy metals in water, which lays a foundation for establishing standards and regulations for environmental water protection.

  11. A sensitive magnetic nanoparticle-based immunoassay of phosphorylated acetylcholinesterase using protein cage templated lead phosphate for signal amplification with graphite furnace atomic absorption spectrometry detection.

    PubMed

    Liang, Pei; Kang, Caiyan; Yang, Enjian; Ge, Xiaoxiao; Du, Dan; Lin, Yuehe

    2016-04-01

    We developed a new magnetic nanoparticle sandwich-like immunoassay using protein cage nanoparticles (PCN) for signal amplification together with graphite furnace atomic absorption spectrometry (GFAAS) for the quantification of an organophosphorylated acetylcholinesterase adduct (OP-AChE), the biomarker of exposure to organophosphate pesticides (OPs) and nerve agents. OP-AChE adducts were firstly captured by titanium dioxide coated magnetic nanoparticles (TiO2-MNPs) from the sample matrixes through metal chelation with phospho-moieties, and then selectively recognized by anti-AChE antibody labeled on PCN which was packed with lead phosphate in its cavity (PCN-anti-AChE). The sandwich-like immunoreaction was performed among TiO2-MNPs, OP-AChE and PCN-anti-AChE to form a TiO2-MNP/OP-AChE/PCN-anti-AChE immunocomplex. The complex could be easily isolated from the sample solution with the help of magnet, and the released lead ions from PCN were detected by GFAAS for the quantification of OP-AChE. Greatly enhanced sensitivity was achieved because PCN increased the amount of metal ions in the cavity of each apoferritin. The proposed immunoassay yielded a linear response over a broad range of OP-AChE concentrations from 0.01 nM to 2 nM, with a detection limit of 2 pM, which has enough sensitivity for monitoring of low-dose exposure to OPs. This new method showed an acceptable stability and reproducibility and was validated with OP-AChE spiked human plasma. PMID:26953358

  12. Cloud point extraction for the determination of cadmium and lead in biological samples by graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Maranhão, Tatiane De A.; Borges, Daniel L. G.; da Veiga, Márcia A. M. S.; Curtius, Adilson J.

    2005-06-01

    The phase-separation phenomenon of non-ionic surfactants occurring in aqueous solution was used for the extraction of Cd and Pb from digested biological samples. After complexation with O,O-diethyldithiophosphate (DDTP) in hydrochloric acid medium, the analytes are quantitatively extracted to the phase rich in the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) after centrifugation. Methanol acidified with 0.1 mol L-1 HNO3 was added to the surfactant-rich phase prior to its analysis by electrothermal atomic absorption spectrometry (ET AAS). The adopted concentrations for DDTP, Triton X-114 and hydrochloric acid were all optimized. Pyrolysis and atomization temperatures were optimized using the extracts and pyrolysis temperatures of 700 °C for both elements and atomization temperatures of 1400 and 1600 °C for cadmium and lead, respectively, were used without adding any modifier, which shows that considerable analyte stabilization is provided by the medium itself. A more detailed investigation was carried out to determine which components of the extract were responsible for the high thermal stability achieved and it revealed that the amount of DDTP added and the phosphorus content of the digested samples contributed significantly to this phenomenon. Detection limits (3σB) of 6 and 40 ng g-1, along with enrichment factors of 129 and 18 for Cd and Pb, respectively, were achieved. The proposed procedure was applied to the analysis of five certified biological reference materials after microwave-assisted acid digestion in a mixture of H2O2 and HNO3. Comparison with certified values was performed for accuracy evaluation, resulting in good agreement according to the t-test for a 95% confidence level. The high efficiency of cloud point extraction to carry out the determination of the studied analytes in complex matrices was, therefore, demonstrated.

  13. Slurry sampling graphite furnace atomic absorption spectrometry: a preliminary examination of results from an international collaborative study

    NASA Astrophysics Data System (ADS)

    Miller-Ihli, N. J.

    1995-06-01

    An international collaborative study was initiated to evaluate the current state-of-the-art for solid sampling. Samples were sent to 28 laboratories and data were received from 18 collaborators, 16 of which reported slurry results. A preliminary check of performance using NIST SRM 1643c acidified water, showed that at least 13 laboratories were able to provide accurate results within ±10% of the mean certified Pb and Cr concentrations. The focus of this work was slurry analytical data reported by collaborators. Average performance by collaborators for the determination of Pb in NIST SRM 2704 Buffalo River Sediment was 103% recovery based on the mean certified reference value and was 84% recovery based on the mean certified reference value for NRCC PACS-1, a marine estuarine sediment, which was identified to collaborators as an unknown sediment. Average performance by collaborators for Cr in SRM 2704 was 96% based on the mean certified reference value and was 78% recovery based on the mean certified reference value for PACS-1. The use of secondary wavelengths and the importance of analysis of a representative subsample are highlighted. Possible problems leading to inaccurate results being reported by collaborators are discussed including the use of mini-flows, matrix modifiers, low atomization temperatures, short atomization times, and expulsion losses.

  14. Method development for the determination of cadmium in fertilizer samples using high-resolution continuum source graphite furnace atomic absorption spectrometry and slurry sampling

    NASA Astrophysics Data System (ADS)

    Borges, Aline R.; Becker, Emilene M.; Lequeux, Céline; Vale, Maria Goreti R.; Ferreira, Sergio L. C.; Welz, Bernhard

    2011-07-01

    The determination of cadmium (Cd) in fertilizers is of major interest, as this element can cause growth problems in plants, and also affect animals and humans. High-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) with charge-coupled device (CCD) array detection overcomes several of the limitations encountered with conventional line source AAS, especially the problem of accurate background measurement and correction. In this work an analytical method has been developed to determine Cd in fertilizer samples by HR-CS GF AAS using slurry sampling. Both a mixture of 10 μg Pd + 6 μg Mg in solution and 400 μg of iridium as permanent modifier have been investigated and aqueous standards were used for calibration. Pyrolysis and atomization temperatures were 600 °C and 1600 °C for the Pd-Mg modifier, and 500 °C and 1600 °C for Ir, respectively. The results obtained for Cd in the certified reference material NIST SRM 695 (Trace Elements in Multi-Nutrient Fertilizer) of 16.7 ± 1.3 μg g -1 and 16.4 ± 0.75 μg g -1 for the Pd-Mg and Ir modifier, respectively, were statistically not different from the certified value of 16.9 ± 0.2 μg g -1 on a 95% confidence level; however, the results obtained with the Ir modifier were significantly lower than those for the Pd-Mg modifier for most of the samples. The characteristic mass was 1.0 pg for the Pd-Mg modifier and 1.1 pg Cd for the Ir modifier, and the correlation coefficients (R 2) of the calibration were > 0.99. The instrumental limits of detection were 7.5 and 7.9 ng g -1, and the limits of quantification were 25 and 27 ng g -1 for Pd-Mg and Ir, respectively, based on a sample mass of 5 mg. The cadmium concentration in the investigated samples was between 0.07 and 5.5 μg g -1 Cd, and hence below the maximum value of 20 μg g -1 Cd permitted by Brazilian legislation.

  15. Simultaneous determination of cadmium, iron and tin in canned foods using high-resolution continuum source graphite furnace atomic absorption spectrometry.

    PubMed

    Leao, Danilo J; Junior, Mario M S; Brandao, Geovani C; Ferreira, Sergio L C

    2016-06-01

    A method was established to simultaneously determine cadmium, iron and tin in canned-food samples using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). The quantification step has been performed using the primary line (228.802nm) for cadmium and the adjacent secondary lines (228.725nm and 228.668nm) for iron and tin, respectively. The selected chemical modifier was an acid solution that contained a mixture of 0.1% (w/v) Pd and 0.05% (w/v) Mg. The absorbance signals were measured based on the peak area using 3 pixels for cadmium and 5 pixels for iron and tin. Under these conditions, cadmium, iron and tin have been determined in canned-food samples using the external calibration technique based on aqueous standards, where the limits of quantification were 2.10ngg(-1) for cadmium, 1.95mgkg(-1) for iron and 3.00mgkg(-1) for tin, and the characteristic masses were 1.0pg for cadmium, 0.9ng for iron and 1.1ng for tin. The precision was evaluated using two solutions of each metal ion, and the results, which were expressed as the relative standard deviation (RSD%), were 3.4-6.8%. The method accuracy for cadmium and iron was confirmed by analyzing a certified reference material of apple leaves (NIST 1515), which was supplied by NIST. However, for tin, the accuracy was confirmed by comparing the results of the proposed method and another analytical technique (inductively coupled plasma optical emission spectrometry). The proposed procedure was applied to determine cadmium, iron and tin in canned samples of peeled tomato and sardine. Eleven samples were analyzed, and the analyte concentrations were 3.57-62.9ngg(-1), 2.68-31.48mgkg(-1) and 4.06-122.0mgkg(-1) for cadmium, iron and tin, respectively. In all analyzed samples, the cadmium and tin contents were lower than the permissible maximum levels for these metals in canned foods in the Brazilian legislation.

  16. Graphene oxide-TiO2 composite solid phase extraction combined with graphite furnace atomic absorption spectrometry for the speciation of inorganic selenium in water samples.

    PubMed

    Zhang, Yanan; Chen, Beibei; Wu, Shaowei; He, Man; Hu, Bin

    2016-07-01

    In this paper, a method of graphene oxide (GO)-TiO2 composite solid phase extraction followed by graphite furnace atomic absorption spectrometry (GFAAS) detection was proposed for the speciation of inorganic selenium in environmental waters. The adsorption behavior of inorganic Se(IV) and Se(VI) on the GO-TiO2(1:1) composite was investigated. It was found that Se(IV) was quantitatively retained on the GO-TiO2 composites within a wide pH range of 0.5-10, while Se(VI) was quantitatively adsorbed on GO-TiO2(1:1) composite at pH 0.5-2, and no obvious adsorption of Se(VI) within the pH range of 4-10 was found. By selecting pH 6.0, Se(IV) could be easily determined. After reduction of Se(VI), total Se was determined by the proposed method, and Se(VI) was calculated as the difference between the total Se and Se(IV). The factors affecting the separation/preconcentration of Se(IV) and Se(VI) were studied. Under the optimum conditions, the isothermal adsorption of Se(IV) on the GO-TiO2(1:1) composite fitted Langmuir model; a linear range over 0.1-12ngmL(-1) was obtained. The limit of detection (LOD) and precision of the method for Se(IV) was 0.04ngmL(-1) and 9.4% (cSe(IV)=0.5ngmL(-1), n=7), respectively. In order to verify the accuracy of the method, a standard water sample (GSBZ50031-94) was analyzed, and the determined value was in a good agreement to the certified value. The established method was applied to inorganic Se speciation in environmental water samples and the recovery of 87.4-102% was obtained for the spiked samples.

  17. Simultaneous determination of cadmium, iron and tin in canned foods using high-resolution continuum source graphite furnace atomic absorption spectrometry.

    PubMed

    Leao, Danilo J; Junior, Mario M S; Brandao, Geovani C; Ferreira, Sergio L C

    2016-06-01

    A method was established to simultaneously determine cadmium, iron and tin in canned-food samples using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). The quantification step has been performed using the primary line (228.802nm) for cadmium and the adjacent secondary lines (228.725nm and 228.668nm) for iron and tin, respectively. The selected chemical modifier was an acid solution that contained a mixture of 0.1% (w/v) Pd and 0.05% (w/v) Mg. The absorbance signals were measured based on the peak area using 3 pixels for cadmium and 5 pixels for iron and tin. Under these conditions, cadmium, iron and tin have been determined in canned-food samples using the external calibration technique based on aqueous standards, where the limits of quantification were 2.10ngg(-1) for cadmium, 1.95mgkg(-1) for iron and 3.00mgkg(-1) for tin, and the characteristic masses were 1.0pg for cadmium, 0.9ng for iron and 1.1ng for tin. The precision was evaluated using two solutions of each metal ion, and the results, which were expressed as the relative standard deviation (RSD%), were 3.4-6.8%. The method accuracy for cadmium and iron was confirmed by analyzing a certified reference material of apple leaves (NIST 1515), which was supplied by NIST. However, for tin, the accuracy was confirmed by comparing the results of the proposed method and another analytical technique (inductively coupled plasma optical emission spectrometry). The proposed procedure was applied to determine cadmium, iron and tin in canned samples of peeled tomato and sardine. Eleven samples were analyzed, and the analyte concentrations were 3.57-62.9ngg(-1), 2.68-31.48mgkg(-1) and 4.06-122.0mgkg(-1) for cadmium, iron and tin, respectively. In all analyzed samples, the cadmium and tin contents were lower than the permissible maximum levels for these metals in canned foods in the Brazilian legislation. PMID:27130088

  18. Graphene oxide-TiO2 composite solid phase extraction combined with graphite furnace atomic absorption spectrometry for the speciation of inorganic selenium in water samples.

    PubMed

    Zhang, Yanan; Chen, Beibei; Wu, Shaowei; He, Man; Hu, Bin

    2016-07-01

    In this paper, a method of graphene oxide (GO)-TiO2 composite solid phase extraction followed by graphite furnace atomic absorption spectrometry (GFAAS) detection was proposed for the speciation of inorganic selenium in environmental waters. The adsorption behavior of inorganic Se(IV) and Se(VI) on the GO-TiO2(1:1) composite was investigated. It was found that Se(IV) was quantitatively retained on the GO-TiO2 composites within a wide pH range of 0.5-10, while Se(VI) was quantitatively adsorbed on GO-TiO2(1:1) composite at pH 0.5-2, and no obvious adsorption of Se(VI) within the pH range of 4-10 was found. By selecting pH 6.0, Se(IV) could be easily determined. After reduction of Se(VI), total Se was determined by the proposed method, and Se(VI) was calculated as the difference between the total Se and Se(IV). The factors affecting the separation/preconcentration of Se(IV) and Se(VI) were studied. Under the optimum conditions, the isothermal adsorption of Se(IV) on the GO-TiO2(1:1) composite fitted Langmuir model; a linear range over 0.1-12ngmL(-1) was obtained. The limit of detection (LOD) and precision of the method for Se(IV) was 0.04ngmL(-1) and 9.4% (cSe(IV)=0.5ngmL(-1), n=7), respectively. In order to verify the accuracy of the method, a standard water sample (GSBZ50031-94) was analyzed, and the determined value was in a good agreement to the certified value. The established method was applied to inorganic Se speciation in environmental water samples and the recovery of 87.4-102% was obtained for the spiked samples. PMID:27154702

  19. Electrochemical generation of volatile form of cadmium and its in situ trapping in a graphite furnace

    NASA Astrophysics Data System (ADS)

    Nováková, Eliška; Rychlovský, Petr; Resslerová, Tina; Hraníček, Jakub; Červený, Václav

    2016-03-01

    This publication describes the combination of flow-through electrochemical generation (EcVG) of cadmium volatile form with its in situ trapping in a graphite furnace atomizer. Three cathode materials (Pt, Pb, and Ti) and four potentially suitable electrolytes (HCl, H2SO4, HCOOH and NaCl) were tested. Automated sampling equipment for the graphite furnace atomizer with an untreated fused silica capillary was used for the introduction of the cadmium volatile form into the iridium-treated graphite furnace. The limit of detection (LOD) of the electrochemical Cd volatile form generation with in situ collection was 1.0 ng ml- 1 (concentration LOD) or 1.5 ng (absolute LOD). The efficiency of the method was estimated and discussed. The effect of selected concomitant ions was evaluated and the accuracy of the proposed method was established by determination of the Cd content in the NIST SRM 1643e certified reference material.

  20. The interference effect of more than one anion and cation in graphite furnace atomic absorption spectrometry. Part 2: Effect of sodium, magnesium, sulphate and chloride mixtures on the atomization of manganese

    NASA Astrophysics Data System (ADS)

    Akman, S.; Tekgül, H. Ince

    1999-04-01

    Although there are numerous cations and anions in real samples generally, the interference effects of a matrix consisting of one cation and one anion on the atomization of an element in graphite furnace atomic absorption spectrometry (GFAAS) have been investigated. Therefore, it would be more realistic to investigate the interference of a matrix containing more than one cation and anion. In this study, the simultaneous interference effects of sodium, magnesium, sulphate and chlorine, which are the most common and abundant ions in many samples, e.g. sea water, on the atomization of manganese in GFAAS were studied. As a first step, the individual interferences of some possible salts consisting of simple combinations of the ions studied such as sodium chloride, magnesium chloride, sodium sulphate and magnesium sulphate, were investigated. It was found that in the presence of these four ions and in their wide concentration range, sodium chloride and magnesium sulphate are the major salts formed after the drying step which were supported by X-ray diffraction (XRD) studies. Sodium chloride causes a significant depressive effect at low pyrolysis temperatures. The interference of sodium chloride originates from expulsion of the analyte with matrix and gas phase reaction between manganese and chloride ions during atomization. Magnesium sulphate does not cause any depression and in fact higher pyrolysis temperatures compared to matrix-free manganese can be applied without loss of any analyte. The depressive effect of sodium chloride on manganese markedly decreased in the presence of magnesium sulphate due to its protecting effect. The mutual interaction mechanism of these two salts and their effects on manganese have been discussed.

  1. Plumbrook Hypersonic Tunnel Facility Graphite Furnace Degradation Mechanisms

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.

    1999-01-01

    A recent rebuild revealed extensive degradation to the large graphite induction furnace in the Hypersonic Tunnel Facility (HTF). This damage to the graphite blocks and insulating felt is examined and modeled with thermochemical equilibrium codes. The primary reactions appear to be with water vapor and the nitrogen purge gas. Based on these conclusions, several changes are recommended. An inert purge gas (e.g. argon or helium) and controlling and monitoring water vapor to about 10 ppm should decrease the damage substantially.

  2. Fast emulsion-based method for simultaneous determination of Co, Cu, Pb and Se in crude oil, gasoline and diesel by graphite furnace atomic absorption spectrometry.

    PubMed

    Luz, Maciel S; Nascimento, Angerson N; Oliveira, Pedro V

    2013-10-15

    A method for the simultaneous determination of Co, Cu, Pb and Se in crude oil, gasoline and diesel samples using emulsion-based sampling and GF AAS is proposed. 400mg of sample was weighted in volumetric flask following the sequential addition of 125 µL of hexane and 7.5 mL of Triton X-100(®) (20% mv(-1)). Subsequently, the mixture was stirred in ultrasonic bath, during 30 min, before dilution to 25 mL with deionized water. Aliquots of 20 μL of reference solution or sample emulsion were co-injected into the graphite tube with 10 μL of 2 g L(-1) Pd(NO3)2. The pyrolysis and atomization temperatures were 1300°C and 2250°C, respectively. The limits of detection (n=10, 3σ) and characteristic masses were 0.02 μg g(-1) (0.32 μg L(-1)) and 18 pg for Co, 0.03 μg g(-1) (0.48 μg L(-1)) and 15 pg for Cu, 0.04 μg g(-1) (0.64 μg L(-1)) and 48 pg for Pb, and 0.11 μg g(-1) (1.76 μg L(-1)) and 47 pg for Se. The reliabilities of the proposed method for Co and Se were checked by SRM(®) 1634c Residual Oil analysis. The found values are in accordance to the SRM at 95% confidence level (Student's t-test). Each sample was spiked with 0.18 μg g(-1) of Co, Cu, Pb and Se and the recoveries varied from 92% to 116% for Co, 83% to 117% for Cu, 72% to 117% for Pb, and 82% to 122% for Se. PMID:24054610

  3. The dynamic wall and gas temperature distributions in a graphite furnace atomiser

    NASA Astrophysics Data System (ADS)

    Rademeyer, C. J.; Human, H. G. C.; Faure, P. K.

    A model is presented for calculation of the dynamic wall and gas temperature distribution of a heated graphite furnace used for analytical atomic absorption measurements. Numerical iterative procedures were used to obtain data for a furnace of specific dimensions (28 × 6 mm), as well as "shaped" variants of this bask design. Instrumental parameters such as the voltage applied and the resistivity of the graphite were measured accurately and the values used in the model so that the real situation on a commercial instrument was resembled well Results of absorbance-time measurements enabled the temperature distribution to be known at all stages of the evolution of the analyte absorbance pulse. It is shown that for shaped furnaces, the gas temperature at the centre of the furnace can be lower than that at some intermediate positions, as well as higher than the furnace wall temperature at the centre. Results for the gas temperature at tube centre agree reasonably well with that of another model put forward recently. Due to problems associated with experimental measurement of gas temperatures, such values do not compare well with the theoretically calculated ones.

  4. Chemometric evaluation of Cd, Co, Cr, Cu, Ni (inductively coupled plasma optical emission spectrometry) and Pb (graphite furnace atomic absorption spectrometry) concentrations in lipstick samples intended to be used by adults and children.

    PubMed

    Batista, Érica Ferreira; Augusto, Amanda dos Santos; Pereira-Filho, Edenir Rodrigues

    2016-04-01

    A method was developed for determining the concentrations of Cd, Co, Cr, Cu, Ni and Pb in lipstick samples intended to be used by adults and children using inductively coupled plasma optical emission spectrometry (ICP OES) and graphite furnace atomic absorption spectrometry (GF AAS) after treatment with dilute HNO3 and hot block. The combination of fractional factorial design and Desirability function was used to evaluate the ICP OES operational parameters and the regression models using Central Composite and Doehlert designs were calculated to stablish the best working condition for all analytes. Seventeen lipstick samples manufactured in different countries with different colors and brands were analyzed. Some samples contained high concentrations of toxic elements, such as Cr and Pb, which are carcinogenic and cause allergic and eczematous dermatitis. The maximum concentration detected was higher than the permissible safe limits for human use, and the samples containing these high metal concentrations were intended for use by children. Principal component analysis (PCA) was used as a chemometrics tool for exploratory analysis to observe the similarities between samples relative to the metal concentrations (a correlation between Cd and Pb was observed).

  5. Cobalt internal standard for Ni to assist the simultaneous determination of Mo and Ni in plant materials by high-resolution continuum source graphite furnace atomic absorption spectrometry employing direct solid sample analysis.

    PubMed

    de Babos, Diego Victor; Bechlin, Marcos André; Barros, Ariane Isis; Ferreira, Edilene Cristina; Gomes Neto, José Anchieta; de Oliveira, Silvana Ruella

    2016-05-15

    A new method is proposed for the simultaneous determination of Mo and Ni in plant materials by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS), employing direct solid sample analysis (DSS) and internal standardization (IS). Cobalt was used as internal standard to minimize matrix effects during Ni determinations, enabling the use of aqueous standards for calibration. Correlation coefficients for the calibration curves were typically better than 0.9937. The performance of the method was checked by analysis of six plant certified reference materials, and the results for Mo and Ni were in agreement with the certified values (95% confidence level, t-test). Analysis was made of different types of plant materials used as renewable sources of energy, including sugarcane leaves, banana tree fiber, soybean straw, coffee pods, orange bagasse, peanut hulls, and sugarcane bagasse. The concentrations found for Mo and Ni ranged from 0.08 to 0.63 ng mg(-1) and from 0.41 to 6.92 ng mg(-1), respectively. Precision (RSD) varied from 2.1% to 11% for Mo and from 3.7% to 10% for Ni. Limits of quantification of 0.055 and 0.074 ng were obtained for Mo and Ni, respectively.

  6. Determination of selenium in ores, concentrates and related materials by graphite-furnace atomic-absorption spectrometry after separation by extraction of the 4-nitro-o-phenylenediamine complex.

    PubMed

    Donaldson, E M

    1988-08-01

    A method for determining approximately 0.01 mug/g or more of selenium in ores, concentrates, rocks, soils, sediments and related materials is described. After sample decomposition selenium is reduced to selenium(IV) by heating in 4M hydrochloric acid and separated from the matrix elements by toluene extraction of its 5-nitropiazselenol complex from approximately 4.2M hydrochloric acid. After the extract has been washed with 2% nitric acid to remove residual iron, copper and chloride, the selenium in the extract is oxidized to selenium(VI) with 20% bromine solution in cyclohexane and stripped into water. This solution is evaporated to dryness in the presence of nickel, and selenium is ultimately determined in a 2% v/v nitric acid medium by graphite-furnace atomic-absorption spectrometry at 196.0 nm with the nickel functioning as matrix modifier. Common ions, including large amounts of iron, copper and lead, do not interfere. More than 1 mg of vanadium(V) and 0.25 mg each of platinum(IV), palladium(II), and gold(III) causes high results for selenium, and more than 1 mg of tungsten(VI) and 2 mg of molybdenum(VI) causes low results. Interference from chromium(VI) is eliminated by reducing it to chromium(III) with hydroxylamine hydrochloride before the formation of the selenium complex.

  7. Chemometric evaluation of Cd, Co, Cr, Cu, Ni (inductively coupled plasma optical emission spectrometry) and Pb (graphite furnace atomic absorption spectrometry) concentrations in lipstick samples intended to be used by adults and children.

    PubMed

    Batista, Érica Ferreira; Augusto, Amanda dos Santos; Pereira-Filho, Edenir Rodrigues

    2016-04-01

    A method was developed for determining the concentrations of Cd, Co, Cr, Cu, Ni and Pb in lipstick samples intended to be used by adults and children using inductively coupled plasma optical emission spectrometry (ICP OES) and graphite furnace atomic absorption spectrometry (GF AAS) after treatment with dilute HNO3 and hot block. The combination of fractional factorial design and Desirability function was used to evaluate the ICP OES operational parameters and the regression models using Central Composite and Doehlert designs were calculated to stablish the best working condition for all analytes. Seventeen lipstick samples manufactured in different countries with different colors and brands were analyzed. Some samples contained high concentrations of toxic elements, such as Cr and Pb, which are carcinogenic and cause allergic and eczematous dermatitis. The maximum concentration detected was higher than the permissible safe limits for human use, and the samples containing these high metal concentrations were intended for use by children. Principal component analysis (PCA) was used as a chemometrics tool for exploratory analysis to observe the similarities between samples relative to the metal concentrations (a correlation between Cd and Pb was observed). PMID:26838401

  8. Development of a new green non-dispersive ionic liquid microextraction method in a narrow glass column for determination of cadmium prior to couple with graphite furnace atomic absorption spectrometry.

    PubMed

    Naeemullah; Kazi, Tasneem Gul; Tuzen, Mustafa; Shah, Faheem; Afridi, Hassan Imran; Citak, Demirhan

    2014-02-17

    Easy and innovative non-dispersive ionic liquid based microextraction (NDILME) has been developed for preconcentration of trace level of cadmium (Cd) in aqueous real surface water samples prior to couple with graphite furnace atomic absorption spectrometry (GFAAS). A 200 cm long narrow glass column containing aqueous solution of standard/sample was used to increase phase transfer ratio by providing more contact area between two medium (aqueous and extractive), which drastically improve the recoveries of labile hydrophobic chelate of Cd ammonium pyrrolidinedithiocarbamate (APDC), into ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim][PF6]. Different aspect of the desire method have been investigated and optimized. Under the optimized key experimental variables, limit of detection (LOD) and enhancement factor (EF) were achieved to be 0.5 ng L(-1) and 150, respectively. Reliability of the model method was checked by relative standard deviation (%RSD), which was found to be <5%. Validity and accuracy of the developed method was checked by analysis of certified reference water samples (SLRS-4 Riverine water) using standard addition method. Application of the model method was productively performed by analysis of Cd in real surface water samples (tap and sea).

  9. Displacement-dispersive liquid-liquid microextraction based on solidification of floating organic drop of trace amounts of palladium in water and road dust samples prior to graphite furnace atomic absorption spectrometry determination.

    PubMed

    Ghanbarian, Maryam; Afzali, Daryoush; Mostafavi, Ali; Fathirad, Fariba

    2013-01-01

    A new displacement-dispersive liquid-liquid microextraction method based on the solidification of floating organic drop was developed for separation and preconcentration of Pd(ll) in road dust and aqueous samples. This method involves two steps of dispersive liquid-liquid microextraction based on solidification. In Step 1, Cu ions react with diethyldithiocarbamate (DDTC) to form Cu-DDTC complex, which is extracted by dispersive liquid-liquid microextraction based on a solidification procedure using 1-undecanol (extraction solvent) and ethanol (dispersive solvent). In Step 2, the extracted complex is first dispersed using ethanol in a sample solution containing Pd ions, then a dispersive liquid-liquid microextraction based on a solidification procedure is performed creating an organic drop. In this step, Pd(ll) replaces Cu(ll) from the pre-extracted Cu-DDTC complex and goes into the extraction solvent phase. Finally, the Pd(ll)-containing drop is introduced into a graphite furnace using a microsyringe, and Pd(ll) is determined using atomic absorption spectrometry. Several factors that influence the extraction efficiency of Pd and its subsequent determination, such as extraction and dispersive solvent type and volume, pH of sample solution, centrifugation time, and concentration of DDTC, are optimized.

  10. Preparation and characterization of magnetic nanoparticles for the on-line determination of gold, palladium, and platinum in mine samples based on flow injection micro-column preconcentration coupled with graphite furnace atomic absorption spectrometry.

    PubMed

    Ye, Juanjuan; Liu, Shuxia; Tian, Miaomiao; Li, Wanjun; Hu, Bin; Zhou, Weihong; Jia, Qiong

    2014-01-01

    A simple and highly selective procedure for on-line determination of trace levels of Au, Pd, and Pt in mine samples has been developed using flow injection-column adsorption preconcentration coupled with graphite furnace atomic absorption spectrophotometry (FI-column-GFAAS). The precious metals were adsorbed on the as-synthesized magnetic nanoparticles functionalized with 4'-aminobenzo-15-crown-5-ether packed into a micro-column and then eluted with 2% thiourea + 0.1 mol L(-1) HCl solution prior to the determination by GFAAS. The properties of the magnetic adsorbents were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). Various experimental parameters affecting the preconcentration of Au, Pd, and Pt were investigated and optimized. Under the optimal experimental conditions, the detection limits of the developed technique were 0.16 ng mL(-1) for Au, 0.28 ng mL(-1) for Pd, and 1.01 ng mL(-1) for Pt, with enrichment factors of 24.3, 13.9, and 17.8, respectively. Precisions, evaluated as repeatability of results, were 1.1%, 3.9%, and 4.4% respectively for Au, Pd, and Pt. The developed method was validated by the analysis of Au, Pd, and Pt in certified reference materials and mine samples with satisfactory results.

  11. Zincon-immobilized silica-coated magnetic Fe3O4 nanoparticles for solid-phase extraction and determination of trace lead in natural and drinking waters by graphite furnace atomic absorption spectrometry.

    PubMed

    Jiang, Hong-mei; Yan, Zhong-peng; Zhao, Yue; Hu, Xin; Lian, Hong-zhen

    2012-05-30

    A new protocol using zincon-immobilized silica-coated magnetic Fe(3)O(4) nanoparticles (Zincon-Si-MNPs) as solid-phase extraction (SPE) medium has been developed for the separation and preconcentration of trace lead in water. Various parameters such as pH, extraction time, concentration and volume of eluent, sample volume, and influence of co-existing ions have been investigated in order to establish the optimum conditions for the determination of lead in combination with graphite furnace atomic absorption spectrometry (GFAAS). The detection limit (LOD) of the proposed method for lead based on an enrichment factor of 200 was 10 ng L(-1). The relative standard deviations (RSDs, n=5) were 8.3%, 7.8% and 9.2%, respectively, at 5, 0.5 and 0.05 ng mL(-1) levels. This method has been successfully applied to the analysis of trace lead in natural and drinking water samples and the recoveries for the spiked samples were in the range of 84-104%.

  12. Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; determination of arsenic and selenium in water and sediment by graphite furnace atomic absorption spectrometry

    USGS Publications Warehouse

    Jones, Sandra R.; Garbarino, John R.

    1999-01-01

    Graphite furnace-atomic absorption spectrometry (GF-AAS) is a sensitive, precise, and accurate technique that can be used to determine arsenic and selenium in samples of water and sediment. The GF-AAS method has been developed to replace the hydride generation-atomic absorption spectrometry (HG-AAS) methods because the method detection limits are similar, bias and variability are comparable, and interferences are minimal. Advantages of the GF-AAS method include shorter sample preparation time, increased sample throughput from simultaneous multielement analysis, reduced amount of chemical waste, reduced sample volume requirements, increased linear concentration range, and the use of a more accurate digestion procedure. The linear concentration range for arsenic and selenium is 1 to 50 micrograms per liter in solution; the current method detection limit for arsenic in solution is 0.9 microgram per liter; the method detection limit for selenium in solution is 1 microgram per liter. This report describes results that were obtained using stop-flow and low-flow conditions during atomization. The bias and variability of the simultaneous determination of arsenic and selenium by GF-AAS under both conditions are supported with results from standard reference materials--water and sediment, real water samples, and spike recovery measurements. Arsenic and selenium results for all Standard Reference Water Samples analyzed were within one standard deviation of the most probable values. Long-term spike recoveries at 6.25, 25.0, 37.5 micrograms per liter in reagent-, ground-, and surface-water samples for arsenic averaged 103 plus or minus 2 percent using low-flow conditions and 104 plus or minus 4 percent using stop-flow conditions. Corresponding recoveries for selenium were 98 plus or minus 13 percent using low-flow conditions and 87 plus or minus 24 percent using stop-flow conditions. Spike recoveries at 25 micrograms per liter in 120 water samples ranged from 97 to 99 percent

  13. Determination of palladium, platinum and rhodium in used automobile catalysts and active pharmaceutical ingredients using high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis

    NASA Astrophysics Data System (ADS)

    Resano, Martín; Flórez, María del Rosario; Queralt, Ignasi; Marguí, Eva

    2015-03-01

    This work investigates the potential of high-resolution continuum source graphite furnace atomic absorption spectrometry for the direct determination of Pd, Pt and Rh in two samples of very different nature. While analysis of active pharmaceutical ingredients is straightforward and it is feasible to minimize matrix effects, to the point that calibration can be carried out against aqueous standard solutions, the analysis of used automobile catalysts is more challenging requiring the addition of a chemical modifier (NH4F·HF) to help in releasing the analytes, a more vigorous temperature program and the use of a solid standard (CRM ERM®-EB504) for calibration. However, in both cases it was possible to obtain accurate results and precision values typically better than 10% RSD in a fast and simple way, while only two determinations are needed for the three analytes, since Pt and Rh can be simultaneously monitored in both types of samples. Overall, the methods proposed seem suited for the determination of these analytes in such types of samples, offering a greener and faster alternative that circumvents the traditional problems associated with sample digestion, requiring a small amount of sample only (0.05 mg per replicate for catalysts, and a few milligrams for the pharmaceuticals) and providing sufficient sensitivity to easily comply with regulations. The LODs achieved were 6.5 μg g- 1 (Pd), 8.3 μg g- 1 (Pt) and 9.3 μg g- 1 (Rh) for catalysts, which decreased to 0.08 μg g- 1 (Pd), 0.15 μg g- 1 (Pt) and 0.10 μg g- 1 (Rh) for pharmaceuticals.

  14. Evaluation of Bi as internal standard to minimize matrix effects on the direct determination of Pb in vinegar by graphite furnace atomic absorption spectrometry using Ru permanent modifier with co-injection of Pd/Mg(NO 3) 2

    NASA Astrophysics Data System (ADS)

    de Oliveira, Silvana Ruella; Neto, José Anchieta Gomes

    2007-09-01

    Bismuth was evaluated as an internal standard for the direct determination of Pb in vinegar by graphite furnace atomic absorption spectrometry using Ru as a permanent modifier with co-injection of Pd/Mg(NO 3) 2. The correlation coefficient of the graph plotted from the normalized absorbance signals of Bi versus Pb was r = 0.989. Matrix effects were evaluated by analyzing the slope ratios between the analytical curve obtained from reference solutions prepared in 0.2% (v/v) HNO 3 and analytical curves obtained from Pb additions in red and white wine vinegar samples. The calculated ratios were around 1.04 and 1.02 for analytical curves established applying an internal standard and 1.3 and 1.5 for analytical curves without. Analytical curves in the 2.5-15 μg L - 1 Pb concentration interval were established using the ratio Pb absorbance to Bi absorbance versus analyte concentration, and typical linear correlations of r = 0.999 were obtained. The proposed method was applied for direct determination of Pb in 18 commercial vinegar samples and the Pb concentration varied from 2.6 to 31 μg L - 1 . Results were in agreement at a 95% confidence level (paired t-test) with those obtained for digested samples. Recoveries of Pb added to vinegars varied from 96 to 108% with and from 72 to 86% without an internal standard. Two water standard reference materials diluted in vinegar sample were also analyzed and results were in agreement with certified values at a 95% confidence level. The characteristic mass was 40 pg Pb and the useful lifetime of the tube was around 1600 firings. The limit of detection was 0.3 μg L - 1 and the relative standard deviation was ≤ 3.8% and ≤ 8.3% ( n = 12) for a sample containing 10 μg L - 1 Pb with and without internal standard, respectively.

  15. Speciation of As(III) and As(V) in water samples by graphite furnace atomic absorption spectrometry after solid phase extraction combined with dispersive liquid-liquid microextraction based on the solidification of floating organic drop.

    PubMed

    Shamsipur, Mojtaba; Fattahi, Nazir; Assadi, Yaghoub; Sadeghi, Marzieh; Sharafi, Kiomars

    2014-12-01

    A solid phase extraction (SPE) coupled with dispersive liquid-liquid microextraction based on the solidification of floating organic drop (DLLME-SFO) method, using diethyldithiphosphate (DDTP) as a proper chelating agent, has been developed as an ultra preconcentration technique for the determination of inorganic arsenic in water samples prior to graphite furnace atomic absorption spectrometry (GFAAS). Variables affecting the performance of both steps were thoroughly investigated. Under optimized conditions, 100mL of As(ΙΙΙ) solution was first concentrated using a solid phase sorbent. The extract was collected in 2.0 mL of acetone and 60.0 µL of 1-undecanol was added into the collecting solvent. The mixture was then injected rapidly into 5.0 mL of pure water for further DLLME-SFO. Total inorganic As(III, V) was extracted similarly after reduction of As(V) to As(III) with potassium iodide and sodium thiosulfate and As(V) concentration was calculated by difference. A mixture of Pd(NO3)2 and Mg(NO3)2 was used as a chemical modifier in GFAAS. The analytical characteristics of the method were determined. The calibration graph was linear in the rage of 10-100 ng L(-1) with detection limit of 2.5 ng L(-1). Repeatability (intra-day) and reproducibility (inter-day) of method based on seven replicate measurements of 80 ng L(-1) of As(ΙΙΙ) were 6.8% and 7.5%, respectively. The method was successfully applied to speciation of As(III), As(V) and determination of the total amount of As in water samples and in a certified reference material (NIST RSM 1643e). PMID:25159375

  16. A novel approach in dispersive liquid-liquid microextraction based on the use of an auxiliary solvent for adjustment of density UV-VIS spectrophotometric and graphite furnace atomic absorption spectrometric determination of gold based on ion pair formation.

    PubMed

    Kocúrová, Lívia; Balogh, Ioseph S; Skrlíková, Jana; Posta, József; Andruch, Vasil

    2010-10-15

    This paper presents a novel approach to dispersive liquid-liquid microextraction (DLLME), based on the use of an auxiliary solvent for the adjustment of density. The procedure utilises a solvent system consisting of a dispersive solvent, an extraction solvent and an auxiliary solvent, which allows for the use of solvents having a density lower than that of water as an extraction solvent while preserving simple phase separation by centrifugation. The suggested approach could be an alternative to procedures described in the literature in recent months and which have been devoted to solving the same problem. The efficiency of the suggested approach is demonstrated through the determination of gold based on the formation of the ion pair [Au(CN)(2)](-) anion with Astra Phloxine (R) reagent and its extraction using the DLLME procedure with subsequent UV-VIS spectrophotometric and graphite furnace atomic absorption spectrometric detection. The optimum conditions were found to be: pH 3; 0.8 mmol L(-1) K(4)[Fe(CN)(6)]; 0.12 mmol L(-1) R; dispersive solvent, methanol; extraction solvent, toluene; auxiliary solvent, tetrachloromethane. The calibration plots were linear in the ranges 0.39-4.7 mg L(-1) and 0.5-39.4 μg L(-1) for UV-VIS and GFAAS detection, respectively; thus enables the application of the developed method in two ranges differing from one from another by three orders of magnitude. The presented approach can be applied to the development of DLLME procedures for the determination of other compounds extractable by organic solvents with a density lower than that of water. PMID:20875602

  17. Speciation of As(III) and As(V) in water samples by graphite furnace atomic absorption spectrometry after solid phase extraction combined with dispersive liquid-liquid microextraction based on the solidification of floating organic drop.

    PubMed

    Shamsipur, Mojtaba; Fattahi, Nazir; Assadi, Yaghoub; Sadeghi, Marzieh; Sharafi, Kiomars

    2014-12-01

    A solid phase extraction (SPE) coupled with dispersive liquid-liquid microextraction based on the solidification of floating organic drop (DLLME-SFO) method, using diethyldithiphosphate (DDTP) as a proper chelating agent, has been developed as an ultra preconcentration technique for the determination of inorganic arsenic in water samples prior to graphite furnace atomic absorption spectrometry (GFAAS). Variables affecting the performance of both steps were thoroughly investigated. Under optimized conditions, 100mL of As(ΙΙΙ) solution was first concentrated using a solid phase sorbent. The extract was collected in 2.0 mL of acetone and 60.0 µL of 1-undecanol was added into the collecting solvent. The mixture was then injected rapidly into 5.0 mL of pure water for further DLLME-SFO. Total inorganic As(III, V) was extracted similarly after reduction of As(V) to As(III) with potassium iodide and sodium thiosulfate and As(V) concentration was calculated by difference. A mixture of Pd(NO3)2 and Mg(NO3)2 was used as a chemical modifier in GFAAS. The analytical characteristics of the method were determined. The calibration graph was linear in the rage of 10-100 ng L(-1) with detection limit of 2.5 ng L(-1). Repeatability (intra-day) and reproducibility (inter-day) of method based on seven replicate measurements of 80 ng L(-1) of As(ΙΙΙ) were 6.8% and 7.5%, respectively. The method was successfully applied to speciation of As(III), As(V) and determination of the total amount of As in water samples and in a certified reference material (NIST RSM 1643e).

  18. Determination of diphenylarsinic acid, phenylarsonic acid and inorganic arsenic in drinking water by graphite-furnace atomic-absorption spectrometry after simultaneous separation and preconcentration with solid-phase extraction disks.

    PubMed

    Hagiwara, Kenta; Inui, Tetsuo; Koike, Yuya; Nakamura, Toshihiro

    2013-01-01

    A simple method of graphite-furnace atomic-absorption spectrometry (GFAAS) after solid-phase extraction (SPE) was developed for the determination of diphenylarsinic acid (DPAA), phenylarsonic acid (PAA), and inorganic arsenic (iAs) in drinking water. This method involves the simultaneous collection of DPAA, PAA, and iAs using three stacked SPE disks, i.e., an Empore SDB-XD disk (the upper layer), an activated carbon disk (the middle layer), and a Cation-SR disk loaded with Zr and Ca (ZrCa-CED; the lower layer). A 200-mL aqueous sample was adjusted to pH 3 with nitric acid and passed through the SPE disks at a flow rate of 15 mL min(-1), to concentrate DPAA on the SDB-XD disk, PAA on the activated carbon disk, and iAs on the ZrCa-CED. The As compounds were eluted from the disks with 10 mL of ethanol containing 0.5 mol L(-1) ammonia solution for DPAA, 20 mL of 1 mol L(-1) ammonia solution for PAA, and 20 mL of 6 mol L(-1) hydrochloric acid for iAs. The eluates of DPAA, PAA, and iAs were diluted to 20, 25, and 25 mL, respectively, with deionized water, and then analyzed by GFAAS. The detection limits of As (three-times the standard deviation (n = 3) of the blank values) were 0.13 and 0.16 μg L(-1) at enrichment factors of 10 and 8, respectively, using a 200-mL water sample. Spike tests with 2 μg (10 μg L(-1)) of DPAA, PAA, and iAs in 200 mL of tap water and bottled drinking water showed good recoveries (96.1-103.8%).

  19. Optimisation of Direct Copper Determination in Human Breast Milk Without Digestion by Zeeman Graphite Furnace Atomic Absorption Spectrophotometry with Two Chemical Modifiers.

    PubMed

    Pineau, Alain; Fauconneau, Bernard; Marrauld, Annie; Lebeau, Alexandra; Hankard, Regis; Guillard, Olivier

    2015-08-01

    Milk is an important food in the human diet, and copper (Cu) in human milk is indispensable to children's normal growth and development. It is consequently important that Cu deficiency, occurring in malnourished women or in malabsorption following bariatric surgery, be prevented. The objective of this work is to provide hospital-based paediatricians with a tool enabling rapid measurement of Cu in human breast milk through a technique that biology laboratories can easily apply. Using electrothermal atomic absorption spectrophotometry with Zeeman correction, we have optimized this method with two chemical modifiers and without digestion for analytical procedure. Detection limits and quantification limits for Cu in human milk were found to be 0.077 and 0.26 μmol/L, respectively. Within-run (n = 30) and between-run (n = 15) variations in a pool of human milk samples were 1.50 and 3.62%, respectively. Average recoveries ranged from 98.67 to 100.61%. The reliability of this method was also confirmed by analysing certified reference material (10%). In breast milk samples collected from 100 lactating mothers, Cu mean (±1 SD) was 7.09 ± 1.60 μmol/L. In conclusion, with minimal preparation and quick determination, the method proposed is suitable for measurement of Cu in human breast milk.

  20. Separation and preconcentration of platinum-group metals from spent autocatalysts solutions using a hetero-polymeric S, N-containing sorbent and determination by high-resolution continuum source graphite furnace atomic absorption spectrometry.

    PubMed

    Eskina, Vasilina V; Dalnova, Olga A; Filatova, Daria G; Baranovskaya, Vasilisa B; Karpov, Yuri A

    2016-10-01

    This paper describes the potential of high-resolution continuum source graphite furnace atomic absorption spectrometry for determination of Pt, Pd and Rh after separation and concentration by original in-house developed heterochain polymer S, N-containing sorbent. The methods of sample preparation of spent ceramic-based autocatalysts were considered, two of which were used: autoclave decomposition in mixture of acids HCl:HNO3 (3:1) and high-temperature melting with K2S2O7. Both methods anyway limit the direct determination of analytes by HR CS GFAAS. Using the first method it is an incomplete digestion of spent autocatalysts samples, since the precipitate is Si, and the rhodium metal dissolves with difficulty and partially passes into solution. In contrast to the first method, the second method allow to completely transfer analytes into solution, however, the background signal produced by the chemical composition of the flux, overlaps the analytical zone. It was found, that Pt, Pd and Rh contained in the spent ceramic automotive catalysts could be effectively separated and concentrated by heterochain polymer S, N-containing sorbent, which has high sorption capacity, selectivity and resistant to dilute acids. The chosen HR CS GFAAS analysis conditions enable us to determine Pt, Pd and Rh with good metrological characteristics. The concentrations of Pt, Pd and Rh in two samples of automobile exhaust catalysts were found in range of 0.00015-0.00050; 0.170-0.189; 0.0180-0.0210wt%, respectively. The relative standard deviation obtained by HR CS GFAAS was not more than 5%. Limits of detection by HR CS GFAAS achieved were 6.2·10(-6)wt% for Pt, 1.8·10(-6)wt% for Pd, and 3.4·10(-6)wt% for Rh. Limits of determination achieved by HR CS GFAAS were 1.1·10(-5)wt% for Pt, 6.9·10(-5)wt% for Pd, and 8.3·10(-5)wt% for Rh. To control the accuracy of PGM in sorption concentrates by HR CS GFAAS method, it was appropriate to conduct an inter-method comparative experiment. The

  1. Separation and preconcentration of platinum-group metals from spent autocatalysts solutions using a hetero-polymeric S, N-containing sorbent and determination by high-resolution continuum source graphite furnace atomic absorption spectrometry.

    PubMed

    Eskina, Vasilina V; Dalnova, Olga A; Filatova, Daria G; Baranovskaya, Vasilisa B; Karpov, Yuri A

    2016-10-01

    This paper describes the potential of high-resolution continuum source graphite furnace atomic absorption spectrometry for determination of Pt, Pd and Rh after separation and concentration by original in-house developed heterochain polymer S, N-containing sorbent. The methods of sample preparation of spent ceramic-based autocatalysts were considered, two of which were used: autoclave decomposition in mixture of acids HCl:HNO3 (3:1) and high-temperature melting with K2S2O7. Both methods anyway limit the direct determination of analytes by HR CS GFAAS. Using the first method it is an incomplete digestion of spent autocatalysts samples, since the precipitate is Si, and the rhodium metal dissolves with difficulty and partially passes into solution. In contrast to the first method, the second method allow to completely transfer analytes into solution, however, the background signal produced by the chemical composition of the flux, overlaps the analytical zone. It was found, that Pt, Pd and Rh contained in the spent ceramic automotive catalysts could be effectively separated and concentrated by heterochain polymer S, N-containing sorbent, which has high sorption capacity, selectivity and resistant to dilute acids. The chosen HR CS GFAAS analysis conditions enable us to determine Pt, Pd and Rh with good metrological characteristics. The concentrations of Pt, Pd and Rh in two samples of automobile exhaust catalysts were found in range of 0.00015-0.00050; 0.170-0.189; 0.0180-0.0210wt%, respectively. The relative standard deviation obtained by HR CS GFAAS was not more than 5%. Limits of detection by HR CS GFAAS achieved were 6.2·10(-6)wt% for Pt, 1.8·10(-6)wt% for Pd, and 3.4·10(-6)wt% for Rh. Limits of determination achieved by HR CS GFAAS were 1.1·10(-5)wt% for Pt, 6.9·10(-5)wt% for Pd, and 8.3·10(-5)wt% for Rh. To control the accuracy of PGM in sorption concentrates by HR CS GFAAS method, it was appropriate to conduct an inter-method comparative experiment. The

  2. Application of Zeeman graphite furnace atomic absorption spectrometry with high-frequency modulation polarization for the direct determination of aluminum, beryllium, cadmium, chromium, mercury, manganese, nickel, lead, and thallium in human blood.

    PubMed

    Ivanenko, Natalya B; Solovyev, Nikolay D; Ivanenko, Anatoly A; Ganeev, Alexander A

    2012-10-01

    Determination of aluminum (Al), beryllium (Be), cadmium (Cd), chromium (Cr), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), and thallium (Tl) concentrations in human blood using high-frequency modulation polarization Zeeman graphite furnace atomic absorption spectrometry (GFAAS) was performed. No sample digestion was used in the current study. Blood samples were diluted with deionized water or 0.1 % (m/v) Triton X-100 solution for Tl. Dilution factors ranged from 1/5 per volume for Be and Tl to 1/20 per volume for Cd and Pb. For Tl, Cd, and Hg, noble metals (gold, platinum, rhodium, etc.) were applied as surface modifiers. To mitigate chloride interference, 2 % (m/v) solution of NH(4)NO(3) was used as matrix modifier for Tl and Ni assessment. The use of Pd(NO(3))(2) as oxidative modifier was necessary for blood Hg and Tl measurement. Validation of the methods was performed by analyzing two-level reference material Seronorm. The precision of the designed methods as relative SD was between 4 and 12 % (middle of a dynamic range) depending on the element. For additional validation, spiked blood samples were analyzed. Limits of detection (LoDs, 3σ, n = 10) for undiluted blood samples were 2.0 μg L(-1) for Al, 0.08 μg L(-1) for Be, 0.10 μg L(-1) for Cd, 2.2 μg L(-1) for Cr, 7 μg L(-1) for Hg, 0.4 μg L(-1) for Mn, 2.3 μg L(-1) for Ni, 3.4 μg L(-1) for Pb, and 0.5 μg L(-1) for Tl. The LoDs achieved allowed determination of Al, Cd, Cr, Mn, Ni, and Pb at both toxic and background levels. Be, Hg, and Tl could be reliably measured at toxic levels only. The methods developed are used for clinical diagnostics and biological monitoring of work-related exposure.

  3. Graphite electrode DC arc furnace. Innovative technology summary report

    SciTech Connect

    1999-05-01

    The Graphite Electrode DC Arc Furnace (DC Arc) is a high-temperature thermal process, which has been adapted from a commercial technology, for the treatment of mixed waste. A DC Arc Furnace heats waste to a temperature such that the waste is converted into a molten form that cools into a stable glassy and/or crystalline waste form. Hazardous organics are destroyed through combustion or pyrolysis during the process and the majority of the hazardous metals and radioactive components are incorporated in the molten phase. The DC Arc Furnace chamber temperature is approximately 593--704 C and melt temperatures are as high as 1,500 C. The DC Arc system has an air pollution control system (APCS) to remove particulate and volatiles from the offgas. The advantage of the DC Arc is that it is a single, high-temperature thermal process that minimizes the need for multiple treatment systems and for extensive sorting/segregating of large volumes of waste. The DC Arc has the potential to treat a wide range of wastes, minimize the need for sorting, reduce the final waste volumes, produce a leach resistant waste form, and destroy organic contaminants. Although the DC arc plasma furnace exhibits great promise for treating the types of mixed waste that are commonly present at many DOE sites, several data and technology deficiencies were identified by the Mixed Waste Focus Area (MWFA) regarding this thermal waste processing technique. The technology deficiencies that have been addressed by the current studies include: establishing the partitioning behavior of radionuclides, surrogates, and hazardous metals among the product streams (metal, slag, and offgas) as a function of operating parameters, including melt temperature, plenum atmosphere, organic loading, chloride concentration, and particle size; demonstrating the efficacy of waste product removal systems for slag and metal phases; determining component durability through test runs of extended duration, evaluating the effect of

  4. Heating rates in furnace atomic absorption using the L'vov platform

    USGS Publications Warehouse

    Koirtyohann, S.R.; Giddings, R.C.; Taylor, H.E.

    1984-01-01

    Heating rate profiles for the furnace tube wall, the furnace atmosphere, and a L'vov platform were established for a range of conditions in a cyclically heated graphite atomizer. The tube wall profile was made by direct observation with a recording optical pyrometer. The sodium line reversal method was used to establish the heating rate of the furnace atmosphere, and appearance temperatures for a series metals of differing volatility was used to establish platform profiles. The tube wall heating rate was nearly linear at 2240??C s- until the desired temperature was reached after which the temperature remained constant. The furnace atmosphere reached a given temperature 0.2-0.4 s later than the tube wall through most of the atomize cycle. The platform lagged the tube wall 0.5-0.8 s. Under typical operating conditions the furnace atmosphere was 100-200??C cooler than the tube wall and at nearly constant temperature when the analyte vaporized from the platform. The L'vov platform causes the cyclically heated commercial furnace to approximate the behavior of a constant temperature furnace during atomization. ?? 1984.

  5. Atomic resolution images of graphite in air

    SciTech Connect

    Grigg, D.A.; Shedd, G.M.; Griffis, D.; Russell, P.E.

    1988-12-01

    One sample used for proof of operation for atomic resolution in STM is highly oriented pyrolytic graphite (HOPG). This sample has been imaged with many different STM`s obtaining similar results. Atomic resolution images of HOPG have now been obtained using an STM designed and built at the Precision Engineering Center. This paper discusses the theoretical predictions and experimental results obtained in imaging of HOPG.

  6. Atomically resolved graphitic surfaces in air by atomic force microscopy.

    PubMed

    Wastl, Daniel S; Weymouth, Alfred J; Giessibl, Franz J

    2014-05-27

    Imaging at the atomic scale using atomic force microscopy in biocompatible environments is an ongoing challenge. We demonstrate atomic resolution of graphite and hydrogen-intercalated graphene on SiC in air. The main challenges arise from the overall surface cleanliness and the water layers which form on almost all surfaces. To further investigate the influence of the water layers, we compare data taken with a hydrophilic bulk-silicon tip to a hydrophobic bulk-sapphire tip. While atomic resolution can be achieved with both tip materials at moderate interaction forces, there are strong differences in force versus distance spectra which relate to the water layers on the tips and samples. Imaging at very low tip-sample interaction forces results in the observation of large terraces of a naturally occurring stripe structure on the hydrogen-intercalated graphene. This structure has been previously reported on graphitic surfaces that are not covered with disordered adsorbates in ambient conditions (i.e., on graphite and bilayer graphene on SiC, but not on monolayer graphene on SiC). Both these observations indicate that hydrogen-intercalated graphene is close to an ideal graphene sample in ambient environments.

  7. Atomically resolved graphitic surfaces in air by atomic force microscopy.

    PubMed

    Wastl, Daniel S; Weymouth, Alfred J; Giessibl, Franz J

    2014-05-27

    Imaging at the atomic scale using atomic force microscopy in biocompatible environments is an ongoing challenge. We demonstrate atomic resolution of graphite and hydrogen-intercalated graphene on SiC in air. The main challenges arise from the overall surface cleanliness and the water layers which form on almost all surfaces. To further investigate the influence of the water layers, we compare data taken with a hydrophilic bulk-silicon tip to a hydrophobic bulk-sapphire tip. While atomic resolution can be achieved with both tip materials at moderate interaction forces, there are strong differences in force versus distance spectra which relate to the water layers on the tips and samples. Imaging at very low tip-sample interaction forces results in the observation of large terraces of a naturally occurring stripe structure on the hydrogen-intercalated graphene. This structure has been previously reported on graphitic surfaces that are not covered with disordered adsorbates in ambient conditions (i.e., on graphite and bilayer graphene on SiC, but not on monolayer graphene on SiC). Both these observations indicate that hydrogen-intercalated graphene is close to an ideal graphene sample in ambient environments. PMID:24746062

  8. Graphitization of Coke and Its Interaction with Slag in the Hearth of a Blast Furnace

    NASA Astrophysics Data System (ADS)

    Li, Kejiang; Zhang, Jianliang; Liu, Yanxiang; Barati, Mansoor; Liu, Zhengjian; Zhong, Jianbo; Su, Buxin; Wei, Mengfang; Wang, Guangwei; Yang, Tianjun

    2016-04-01

    Coke reaction behavior in the blast furnace hearth has yet to be fully understood due to limited access to the high temperature zone. The graphitization of coke and its interaction with slag in the hearth of blast furnace were investigated with samples obtained from the center of the deadman of a blast furnace during its overhaul period. All hearth coke samples from fines to lumps were confirmed to be highly graphitized, and the graphitization of coke in the high temperature zone was convinced to start from the coke surface and lead to the formation of coke fines. It will be essential to perform further comprehensive investigations on graphite formation and its evolution in a coke as well as its multi-effect on blast furnace performance. The porous hearth cokes were found to be filled up with final slag. Further research is required about the capability of coke to fill final slag and the attack of final slag on the hearth bottom refractories since this might be a new degradation mechanism of refractories located in the hearth bottom.

  9. Improvement of precision for pipetting blood serum samples into a graphite furnace

    NASA Astrophysics Data System (ADS)

    Bohrer, D.; do Nascimento, P. C.; Binotto, R.; Borges da Costa, J. A. T.; Szlachta, T.

    2002-12-01

    Graphite furnace atomic absorption spectrometry is a well-established technique for trace metal determination in blood and serum samples. For this kind of samples, a R.S.D. of up to 10% is considered acceptable, especially for those elements, the concentrations of which do not allow high dilution. Among the reasons that contribute to an increase of the S.D. is the retention of proteins (and analyte) in the sample dispenser capillary, because proteins might be adsorbed on polymeric surfaces. In the present work, the interaction protein/polymer was studied, considering the amount of protein that could be retained by the capillary, the influence of sample dilution, time of contact and the possible co-adsorption of metals. Serum proteins were retained in the capillary, depending on the material (Tygon>silicone rubber>poly(tetrafluorethylene)); dilution did not prevent the adsorption, and only 30 s of contact were enough for the adsorption to occur. Using a column filled with PTFE powder (60 mesh), it was possible to observe that metals were co-adsorbed to a large extent. Water, diluted nitric acid or aqueous solutions of Triton X-100 were not able to promote the complete desorption of the proteins retained by the polymeric materials. Total elution was achieved with methanol, and its use as rinse solution decreased the R.S.D. ( n=10) for aluminium, manganese and chromium determination in serum to <10%.

  10. Formation mechanism of the graphite-rich protective layer in blast furnace hearths

    NASA Astrophysics Data System (ADS)

    Jiao, Ke-xin; Zhang, Jian-liang; Liu, Zheng-jian; Liu, Feng; Liang, Li-sheng

    2016-01-01

    A long campaign life of blast furnaces is heavily linked to the existence of a protective layer in their hearths. In this work, we conducted dissection studies and investigated damage in blast furnace hearths to estimate the formation mechanism of the protective layer. The results illustrate that a significant amount of graphite phase was trapped within the hearth protective layer. Furthermore, on the basis of the thermodynamic and kinetic calculations of the graphite precipitation process, a precipitation potential index related to the formation of the graphite-rich protective layer was proposed to characterize the formation ability of this layer. We determined that, under normal operating conditions, the precipitation of graphite phase from hot metal was thermodynamically possible. Among elements that exist in hot metal, C, Si, and P favor graphite precipitation, whereas Mn and Cr inhibit this process. Moreover, at the same hot-face temperature, an increase of carbon concentration in hot metal can shorten the precipitation time. Finally, the results suggest that measures such as reducing the hot-face temperature and increasing the degree of carbon saturation in hot metal are critically important to improve the precipitation potential index.

  11. Evaluation of the graphite electrode DC arc furnace for the treatment of INEL buried wastes

    SciTech Connect

    Surma, J.E.; Freeman, C.J.; Powell, T.D.; Cohn, D.R.; Smatlak, D.L.; Thomas, P.; Woskov, P.P.; Hamilton, R.A.; Titus, C.H.; Wittle, J.K.

    1993-06-01

    The past practices of DOE and its predecessor agencies in burying radioactive and hazardous wastes have left DOE with the responsibility of remediating large volumes of buried wastes and contaminated soils. The Buried Waste Integrated Demonstration (BWID), has chosen to evaluate treatment of buried wastes at the Idaho National Engineering Laboratory (INEL). Because of the characteristics of the buried wastes, the potential for using high-temperature thermal treatment technologies is being evaluated. The soil-waste mixture at INEL, when melted or vitrified, produces a glass/ceramic referred to as iron-enriched basalt (IEB). One potential problem with producing the IEB material is the high melting temperature of the waste and soil (1,400-1,600{degrees}C). One technology that has demonstrated capabilities to process high melting point materials is the plasma arc heated furnace. A three-party program was initiated and the program involved testing an engineering-scale DC arc furnace to gain preliminary operational and waste processibility information. It also included the design, fabrication, and evaluation of a second-generation, pilot-scale graphite electrode DC arc furnace. Widely ranging simulants of INEL buried waste were prepared and processed in the Mark I furnace. The tests included melting of soils with metals, sludges, combustibles, and simulated drums. Very promising results in terms of waste product quality, volume reduction, heating efficiency, and operational reliability and versatility were obtained. The results indicate that the graphite electrode DC arc technology would be very well suited for treating high melting point wastes such as those found at INEL. The graphite electrode DC arc furnace has been demonstrated to be very simple, yet effective, with excellent prospects for remote or semi-remote operation.

  12. DC graphite arc furnace, a simple system to reduce mixed waste volume

    SciTech Connect

    Wittle, J.K.; Hamilton, R.A.; Trescot, J.

    1995-12-31

    The volume of low-level radioactive waste can be reduced by the high temperature in a DC Graphite Arc Furnace. This volume reduction can take place with the additional benefit of having the solid residue being stabilized by the vitrified product produced in the process. A DC Graphite Arc Furnace is a simple system in which electricity is used to generate heat to vitrify the material and thermally decompose any organic matter in the waste stream. Examples of this type of waste are protective clothing, resins, and grit blast materials produced in the nuclear industry. The various Department of Energy (DOE) complexes produce similar low-level waste streams. Electro-Pyrolysis, Inc. and Svedala/Kennedy Van Saun are engineering and building small 50-kg batch and up to 3,000 kg/hr continuous feed DC furnaces for the remediation, pollution prevention, and decontamination and decommissioning segments of the treatment community. This process has been demonstrated under DOE sponsorship at several facilities and has been shown to produce stable waste forms from surrogate waste materials.

  13. Atomic hydrogen adsorption on lithium-doped graphite surfaces

    SciTech Connect

    Allouche, Alain

    2012-01-01

    The effects of lithium doping of pristine and defective graphite surfaces on hydrogen adsorption are studied by the first-principles Plane-Wave Density Functional Theory. The surface defects are simulated by a single atomic vacancy. The DFT calculation is corrected for long-range effects through semi-empirical London terms for each constituent of the system. The lithium doping of the graphite surfaces notably reinforces hydrogen atom binding. Qualitative comparison with experimental results is given using the lithium 1s energy level shifts induced by the atomic vacancy and/or hydrogen trapping.

  14. Electrochemical selenium hydride generation with in situ trapping in graphite tube atomizers

    NASA Astrophysics Data System (ADS)

    Šíma, Jan; Rychlovský, Petr

    2003-05-01

    A manifold coupling continuous electrolytic hydride generation of volatile hydrides with atomization in graphite tube atomizers after in situ collection was used for Se(IV) determination. Laboratory-made thin-layer flow-through cells with lead wire (cell I) and granular lead (cell II) as the cathode material were used as the electrolytic generators of volatile selenium hydride. The automatic sampling equipment of the graphite atomizer, with an untreated fused silica capillary, was used both for the introduction of volatile hydride into the atomizer and for pretreatment of the graphite furnace surface with a palladium modifier. The influence of the experimental parameters on the analytical signal was studied and optimum conditions for selenium determination were found. The optimum experimental parameters for hydride generation were: catholyte (1 mol l -1 HCl)/anolyte (2 mol l -1 H 2SO 4) flow rate of 2.0 ml min -1; applied generation current of 1.2 A (cell I) and 0.8 A (cell II); and carrier gas flow rate of 40 (cell I) and 70 ml min -1 (cell II). The hydride generated was collected in the graphite tube (pre-treated with 5 μg of Pd reduced at 800 °C) at a temperature of 400 °C for 30 s. The overall efficiency of H 2Se electrochemical generation, transport and collection was 71±7% for cell I and 80±5% for cell II. The results for electrochemical generation of H 2Se (cell II) (absolute limit of detection 50 pg, 3σ criterion) were compared with the original generation of H 2Se using NaBH 4 as a reduction agent (absolute limit of detection 30 pg) and with conventional liquid sampling. The repeatability at the 1.0 ng ml -1 level was better than 2.4% (relative standard deviation) for electrochemical hydride generation and better than 2.8% for chemical hydride generation.

  15. Evaluation of quartz tubes as atomization cells for gold determination by thermospray flame furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Morzan, Ezequiel; Piano, Ornela; Stripeikis, Jorge; Tudino, Mabel

    2012-11-01

    This work describes the development of a new analytical procedure able to determine gold by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) using nickel tubes (NiT) and quartz tubes (QT) as atomization cells. Experiments involving changes in the flow injection operational parameters, reagent concentrations and sizes of the QT were performed in order to optimize sensitivity. Under the same operational conditions, it was observed that the employment of QT increases the sensitivity of gold determination when compared to the nickel tube. Since solutions of highly concentrated hydrochloric acid showed the best performance as carriers, quartz tubes were also preferred due to its greater tolerance to corrosion by mineral acids in comparison to NiT. In addition, changes in the internal diameter of the QT revealed an important improvement in sensitivity for smaller tubes. Under optimized conditions the main figures of merit showed values close to that of graphite furnace atomic absorption spectrometry with the addition of an excellent improvement of the sample throughput. They are: LOD (3 s): 0.004 μg mL- 1, sensitivity: 0.306 (μg mL- 1)- 1, RSD% (n = 10, 1 μg mL- 1): 2.5, linear range: 0.01-4 μg mL- 1 and sample throughput: 72 h- 1. This new method was employed for the determination of gold in homeopathic medicines with no need of sample digestion. Validation of the analytical results will be shown. A full discussion of the most relevant findings regarding the role of the atomization cell as a strategic key for improving sensitivity will be also provided.

  16. Revealing the hidden atom in graphite by low-temperature atomic force microscopy.

    PubMed

    Hembacher, Stefan; Giessibl, Franz J; Mannhart, Jochen; Quate, Calvin F

    2003-10-28

    Carbon, the backbone material of life on Earth, comes in three modifications: diamond, graphite, and fullerenes. Diamond develops tetrahedral sp3 bonds, forming a cubic crystal structure, whereas graphite and fullerenes are characterized by planar sp2 bonds. Polycrystalline graphite is the basis for many products of everyday life: pencils, lubricants, batteries, arc lamps, and brushes for electric motors. In crystalline form, highly oriented pyrolytic graphite is used as a diffracting element in monochromators for x-ray and neutron scattering and as a calibration standard for scanning tunneling microscopy (STM). The graphite surface is easily prepared as a clean atomically flat surface by cleavage. This feature is attractive and is used in many laboratories as the surface of choice for "seeing atoms." Despite the proverbial ease of imaging graphite by STM with atomic resolution, every second atom in the hexagonal surface unit cell remains hidden, and STM images show only a single atom in the unit cell. Here we present measurements with a low-temperature atomic force microscope with pico-Newton force sensitivity that reveal the hidden surface atom.

  17. Interaction of atomic oxygen with a graphite surface

    NASA Astrophysics Data System (ADS)

    Mateljevic, Natasa

    This project was a part of the Multi University Research Initiative (MURI) Center for Materials Chemistry in the Space Environment which seeks to develop a quantitative and predictive understanding of how materials degrade or become passivated in the space environment. This is a critical research area for the Department of Defense (DoD) and National Aeronautics and Space Administration (NASA) given the large and increasing dependence on satellites and manned spacecrafts that reside in, or pass through, the low-Earth orbit (LEO) space environment. In this work, we completed three separate projects. First, we carried out ab initio electronic structure studies of the interaction of oxygen atoms with graphite surfaces. The (O3 P) ground state of oxygen interacts weakly with the graphite surface while the excited (O1D) state interacts more strongly with a binding energy sufficient for a high coverage of oxygen to be maintained on the surface. Thus, it requires a transition from O(3P) to O(1D) in order for oxygen to strongly bind. Since graphite is a semi-metal, it requires a vanishingly small energy to remove an electron of up spin from just below the Fermi level, and replace it with a down spin electron just above the Fermi level; spin-orbit interaction is not required to switch the state of the oxygen atom. We have examined this complexity for the first time and developed guidelines for properly describing chemical reactivity on graphite surfaces. The second project is a kinetic Monte Carlo study of the erosion of graphite by energetic oxygen atoms in LEO and in the laboratory. These simulations, in conjunction with experiments by our MURI collaborators, reveal new insights about reaction pathways. Finally, we have developed a new model for accommodation of energy and momentum in collisions of gases with highly corrugated surfaces. This model promises to be valuable in simulating frictional heating and drag of objects moving through the atmosphere.

  18. Determination of phosphorus using high-resolution diphosphorus molecular absorption spectra produced in the graphite furnace

    NASA Astrophysics Data System (ADS)

    Huang, Mao Dong; Becker-Ross, Helmut; Okruss, Michael; Geisler, Sebastian; Florek, Stefan

    2016-01-01

    Molecular absorption of diphosphorus was produced in a graphite furnace and evaluated in view of its suitability for phosphorus determination. Measurements were performed with two different high-resolution continuum source absorption spectrometers. The first system is a newly in-house developed simultaneous broad-range spectrograph, which was mainly used for recording overview absorption spectra of P2 between 193 nm and 245 nm. The region covers the main part of the C 1Σu+ ← X 1Σg+ electronic transition and shows a complex structure with many vibrational bands, each consisting of a multitude of sharp rotational lines. With the help of molecular data available for P2, an assignment of the vibrational bands was possible and the rotational structure could be compared with simulated spectra. The second system is a commercial sequential continuum source spectrometer, which was used for the basic analytical measurements. The P2 rotational line at 204.205 nm was selected and systematically evaluated with regard to phosphorus determination. The conditions for P2 generation were optimized and it was found that the combination of a ZrC modified graphite tube and borate as a chemical modifier were essential for a good production of P2. Serious interferences were found in the case of nitrate and sulfuric acid, although the nitrate interference can be eliminated by a higher pyrolysis temperature. The reliability of the method was proved by analysis of certified samples. Using standard tubes, a characteristic mass of 10 ng and a limit of detection of 7 ng were found. The values could further be improved by a factor of ten using a miniaturized tube with an internal diameter of 2 mm. Compared to the conventional method based on the phosphorus absorption line at 213.618 nm, the advantages of using P2 are the gentle temperature conditions and the potential of performing a simultaneous multi-line evaluation to further improve the limit of detection.

  19. Atomic-scale structure of SiO2/Si interface formed by furnace oxidation

    NASA Astrophysics Data System (ADS)

    Miyata, Noriyuki; Watanabe, Heiji; Ichikawa, Masakazu

    1998-11-01

    SiO2/Si interfaces formed by furnace oxidation are investigated by scanning reflection electron microscopy (SREM). SREM observations reveal that the initial atomic steps on the Si(111)-7×7 and Si(001)-2×1 surfaces are preserved at the SiO2/Si interfaces and the interfacial atomic steps do not move laterally during furnace oxidation. A profile analysis of reflection high-energy electron diffraction indicates that the atomic-scale roughness at the SiO2/Si interfaces is formed by furnace oxidation. The respective SiO2/Si(111) and SiO2/Si(001) interfaces are made up of about 5- and 3-nm-diam islands. Our results indicate that the layer-by-layer oxidation caused by two-dimensional island nucleation progresses during furnace oxidation.

  20. The spectral opacity of triatomic carbon measured in a graphite tube furnace over the 280 to 600 nm wavelength range

    NASA Technical Reports Server (NTRS)

    Snow, W. L.; Wells, W. L.

    1980-01-01

    The opacity of linear triatomic carbon (C3) was measured in a graphite tube furnace from 280 to 600 nm to supplement the earlier measurements of Brewer and Engelke. The spectral cross section was estimated from the opacities using temperature profiles determined pyrometrically and a revised heat of formation delta H = 198 kcal/mole). The cross section was found to be nonnegligible over the range 300 to 500 nm and the electronic oscillator strength based on the total cross section estimate was 0.02.

  1. Laser excited analytical atomic and ionic fluorescence in flames, furnaces and inductively coupled plasmas—I. General considerations

    NASA Astrophysics Data System (ADS)

    Omenetto, N.; Human, H. G. C.

    Several important parameters for the analytical use of laser excited fluorescence spectrometry in flames, graphite furnaces and inductively coupled plasmas are discussed in some detail. These parameters include the laser characteristics such as peak power, pulse duration, spectral bandwidth and repetition rate, the choice of the excitation line, the optical arrangement and the detection system, this last one centred on the widespread use of the boxcar averager. It is shown that, if the ultimate sensitivity is the goal to be achieved, then the choice must be the electrothermal atomization. However, even for flames and inductively coupled plasmas, excellent results are possible provided that: (i) the laser system allows complete spectral coverage in the ultraviolet: (ii) saturation of the fluorescence signal can be approached over a large sample volume; and (iii) the gated detection parameters and the laser repetition frequency are optimized with respect to each other so as to reach the maximum signal-to-noise ratio.

  2. Solid sampling determination of total fluorine in baby food samples by high-resolution continuum source graphite furnace molecular absorption spectrometry.

    PubMed

    Ozbek, Nil; Akman, Suleyman

    2016-11-15

    This study describes the applicability of solid sampling technique for the determination of fluorine in various baby foods via molecular absorption of calcium monofluoride generated in a graphite furnace of high-resolution continuum source atomic absorption spectrometry. Fluorine was determined at CaF wavelength, 606.440nm in a graphite tube applying a pyrolysis temperature of 1000°C and a molecule forming temperature of 2200°C. The limit of detection and characteristic mass of the method were 0.20ng and 0.17ng of fluorine, respectively. The fluorine concentrations determined in standard reference sample (bush branches and leaves) were in good agreement with the certified values. By applying the optimized parameters, the concentration of fluorine in various baby foods were determined. The fluorine concentrations were ranged from

  3. Solid sampling determination of total fluorine in baby food samples by high-resolution continuum source graphite furnace molecular absorption spectrometry.

    PubMed

    Ozbek, Nil; Akman, Suleyman

    2016-11-15

    This study describes the applicability of solid sampling technique for the determination of fluorine in various baby foods via molecular absorption of calcium monofluoride generated in a graphite furnace of high-resolution continuum source atomic absorption spectrometry. Fluorine was determined at CaF wavelength, 606.440nm in a graphite tube applying a pyrolysis temperature of 1000°C and a molecule forming temperature of 2200°C. The limit of detection and characteristic mass of the method were 0.20ng and 0.17ng of fluorine, respectively. The fluorine concentrations determined in standard reference sample (bush branches and leaves) were in good agreement with the certified values. By applying the optimized parameters, the concentration of fluorine in various baby foods were determined. The fluorine concentrations were ranged from

  4. Determination of cadmium in the livers and kidneys of puffins by carbon furnace atomic absorption spectrometry.

    PubMed

    Ottaway, J M; Campbell, W C

    1976-01-01

    A carbon furnace atomic absorption procedure is described for the determination of cadmium in the livers and kidneys of puffins, fratercula arctica. Samples are dried and weighed and 2 to 100 mg are dissolved in sulphuric and nitric acids. These solutions are analysed directly in the carbon furnace against aqueous standards and provide accurate results in the range 0-1 to 100 micrograms/g dry weight. The method is simple and rapid and requires much less of the small total sample than would be required for flame atomic absorption. PMID:1030692

  5. Investigation of aging processes of graphite tubes modified with iridium and rhodium used for atomic spectrometry

    NASA Astrophysics Data System (ADS)

    Bulska, Ewa; Piaścik, Marek; Katskov, Dmitri; Darangwa, Nicholas; Grotti, Marco

    2007-11-01

    UV spectrometry (187-380 nm) with charge coupled device (CCD) detection was used to study the evolution of absorption spectra during the vaporization of various species in the pyrocoated graphite furnace, with electrodeposited Ir and Rh as modifiers. In order to mimic a typical matrix composition, various salts of aluminum, manganese, copper, magnesium, sodium, and lead were used in microgram amounts. Changes in spectra and vapor release rate, along with aging of the tubes in the repetitive temperature cycles, were observed. Compared to the unmodified pyrocoated tubes, the presence of Ir or Rh causes a significant reduction in the vaporization efficiency, especially for microgram amounts of copper and aluminum introduced as nitrates, and manganese introduced as a sulfate. The vaporization efficiency, for magnesium and sodium as chlorides, and for lead as a sulfate, remained unchanged. Interestingly, the aging of the tubes was accompanied by partial restoration of the spectral characteristics for unmodified tubes. For example, with unmodified pyrocoated tubes, the vaporization spectrum, appearing as a consequence of the decomposition of aluminum nitrate, consisted of Al2O bands overlapped by Al atomic lines. In the freshly modified tubes, intensities of those lines and bands were substantially reduced, and in this case, the dominance of AlO molecules was observed. The efficiency of vaporization of aluminum species increased in the aged modified tubes. The scanning electron microscopy (SEM) images of the modified surfaces for the new and aged tubes indicated that aging of the tubes is accompanied by the destruction of the pyrocoating, formation of pyrographite shells around the areas where the modifier was electrodeposited, and finally, complete substitution of the metal on the graphite surface by pyrographite debris.

  6. Transport of atomic hydrogen through graphite and its reaction with azoaromatic compounds.

    PubMed

    Ye, Jianchang; Chiu, Pei C

    2006-06-15

    Graphite is a major non-iron component in commercial iron granules that are typically used for groundwater remediation. Recent studies suggest graphite inclusions in commercial iron may serve as both adsorption and reaction sites for nitrogenous pollutants such as nitroaromatics, nitrate esters, and heterocyclic nitramines. In this study, we investigated graphite-mediated reduction of azoaromatic compounds with elemental iron in dialysis cells, where azo compounds and iron were physically separated by graphite foil. Both the nonpolar azobenzene and the water-soluble orange G were reduced to aniline, suggesting that exposed graphite in granular iron may mediate reduction of both polar and nonpolar compounds. Orange G reduction was zero-order and commenced after a long initial lag. Both the lag time and the zero-order rate constant varied with graphite thickness, consistent with the explanation that orange G reduction was limited by atomic hydrogen, which was formed via anaerobic iron corrosion and spilled over to graphite. Involvement of atomic hydrogen was confirmed by detection of deuterated aniline when iron was placed in a D2O-based buffer. Our results indicate that atomic hydrogen is mobile in graphite at room temperature, is reactive toward azoaromatic compounds, and may be consumed during transport in graphite.

  7. Simultaneous direct determination of aluminum, calcium and iron in silicon carbide and silicon nitride powders by slurry-sampling graphite furnace AAS.

    PubMed

    Minami, Hirotsugu; Yada, Masako; Yoshida, Tomomi; Zhang, Qiangbin; Inoue, Sadanobu; Atsuya, Ikuo

    2004-03-01

    A fast and accurate analytical method was established for the simultaneous direct determination of aluminum, calcium and iron in silicon carbide and silicon nitride powders by graphite furnace atomic absorption spectrometry using a slurry sampling technique and a Hitachi Model Z-9000 atomic absorption spectrometer. The slurry samples were prepared by the ultrasonication of silicon carbide or silicon nitride powders with 0.1 M nitric acid. Calibration curves were prepared by using a mixed standard solution containing aluminum, calcium, iron and 0.1 M nitric acid. The analytical results of the proposed method for aluminum, calcium and iron in silicon carbide and silicon nitride reference materials were in good agreement with the reference values. The detection limits for aluminum, calcium and iron were 0.6 microg/g, 0.15 microg/g and 2.5 microg/g, respectively, in solid samples, when 200 mg of powdered samples were suspended in 20 ml of 0.1 M nitric acid and a 10 microl portion of the slurry sample was then measured. The relative standard deviation of the determination of aluminum, calcium and iron was 5 - 33%.

  8. Energy corrugation in atomic-scale friction on graphite revisited by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Sun, Xiao-Yu; Qi, Yi-Zhou; Ouyang, Wengen; Feng, Xi-Qiao; Li, Qunyang

    2016-08-01

    Although atomic stick-slip friction has been extensively studied since its first demonstration on graphite, the physical understanding of this dissipation-dominated phenomenon is still very limited. In this work, we perform molecular dynamics (MD) simulations to study the frictional behavior of a diamond tip sliding over a graphite surface. In contrast to the common wisdom, our MD results suggest that the energy barrier associated lateral sliding (known as energy corrugation) comes not only from interaction between the tip and the top layer of graphite but also from interactions among the deformed atomic layers of graphite. Due to the competition of these two subentries, friction on graphite can be tuned by controlling the relative adhesion of different interfaces. For relatively low tip-graphite adhesion, friction behaves normally and increases with increasing normal load. However, for relatively high tip-graphite adhesion, friction increases unusually with decreasing normal load leading to an effectively negative coefficient of friction, which is consistent with the recent experimental observations on chemically modified graphite. Our results provide a new insight into the physical origins of energy corrugation in atomic scale friction.

  9. Direct determination of Cu, Mn, Pb, and Zn in beer by thermospray flame furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Nascentes, Clésia C.; Kamogawa, Marcos Y.; Fernandes, Kelly G.; Arruda, Marco A. Z.; Nogueira, Ana Rita A.; Nóbrega, Joaquim A.

    2005-06-01

    In this work, thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) was employed for Cu, Mn, Pb, and Zn determination in beer without any sample digestion. The system was optimized and calibration was based on the analyte addition technique. A sample volume of 300 μl was introduced into the hot Ni tube at a flow-rate of 0.4 ml min -1 using 0.14 mol l -1 nitric acid solution or air as carrier. Different Brazilian beers were directly analyzed after ultrasonic degasification. Results were compared with those obtained by graphite furnace atomic absorption spectrometry (GFAAS). The detection limits obtained for Cu, Mn, Pb, and Zn in aqueous solution were 2.2, 18, 1.6, and 0.9 μg l -1, respectively. The relative standard deviations varied from 2.7% to 7.3% ( n=8) for solutions containing the analytes in the 25-50 μg l -1 range. The concentration ranges obtained for analytes in beer samples were: Cu: 38.0-155 μg l -1; Mn: 110-348 μg l -1, Pb: 13.0-32.9 μg l -1, and Zn: 52.7-226 μg l -1. Results obtained by TS-FF-AAS and GFAAS were in agreement at a 95% confidence level. The proposed method is fast and simple, since sample digestion is not required and sensitivity can be improved without using expensive devices. The TS-FF-AAS presented suitable sensitivity for determination of Cu, Mn, Pb, and Zn in the quality control of a brewery.

  10. Method for processing aluminum spent potliner in a graphite electrode ARC furnace

    DOEpatents

    O'Connor, William K.; Turner, Paul C.; Addison, Gerald W.

    2002-12-24

    A method of processing spent aluminum pot liner containing carbon, cyanide compositions, fluorides and inorganic oxides. The spent aluminum pot liner is crushed iron oxide is added to form an agglomerated material. The agglomerated material is melted in an electric arc furnace having the electrodes submerged in the molten material to provide a reducing environment during the furnace operation. In the reducing environment, pot liner is oxidized while the iron oxides are reduced to produce iron and a slag substantially free of cyanide compositions and fluorides. An off-gas including carbon oxides and fluorine is treated in an air pollution control system with an afterburner and a scrubber to produce NaF, water and a gas vented to the atmosphere free of cyanide compositions, fluorine and CO.

  11. Method for processing aluminum spent potliner in a graphite electrode arc furnace

    DOEpatents

    O'Connor, William K.; Turner, Paul C.; Addison, G.W.

    2002-12-24

    A method of processing spent aluminum pot liner containing carbon, cyanide compositions, fluorides and inorganic oxides. The spend aluminum pot liner is crushed, iron oxide is added to form an agglomerated material. The agglomerated material is melted in an electric arc furnace having the electrodes submerged in the molten material to provide a reducing environment during the furnace operation. In the reducing environment, pot liner is oxidized while the iron oxides are reduced to produce iron and a slag substantially free of cyanide compositions and fluorides. An off-gas including carbon oxides and fluorine is treated in an air pollution control system with an afterburner and a scrubber to produce NaF, water and a gas vented to the atmosphere free of cyanide compositions, fluorine, and CO.

  12. Evaluation of a method for arsenic(III) and antimony(III) determination by vapour phase molecular absorption spectrometry using graphite furnace volati

    NASA Astrophysics Data System (ADS)

    Galban, J.; Marcos, E.; Lamana, J.; Castillo, J. R.

    1993-01-01

    This paper presents a procedure for determining As(III) and Sb(III) by vapour phase molecular absorption spectrometry (VPMAS). The chlorides of these elements are volatilized from aqueous solutions in a L'vov platform inside the graphite furnace of an atomic absorption spectrophotometer. Molecular absorption is measured at 205 nm for arsenic chloride and 220 nm for antimony chloride. Both species are formed in the sample drying stage. A study of the temperature program led to different results in each case. In the case of arsenic, a two-step program (one mixed drying and volatilization step, and another cleaning step) is found to be best, whereas in the case of antimony, three separate steps can be used (drying, volatilization and cleaning). In both cases, optimum volatilization was obtained with low HCl concentrations, and volatilization fell off sharply as HCl concentration increased. Under optimum generation and determination conditions, the linear response range is from 0.06 to 3.75 μg for As(III), and from 0.30 to 5.0 μg for Sb(III) with relative standard deviations of 2.1% for As(III) and 2.5% for Sb(III). The effect of other anions and cations on the arsenic analytical signal was studied, and other halides were found to interfere. The method was applied to arsenic determination in an arsenic ore.

  13. Effects of Stone-Wales and vacancy defects in atomic-scale friction on defective graphite

    SciTech Connect

    Sun, Xiao-Yu; Wu, RunNi; Xia, Re; Chu, Xi-Hua; Xu, Yuan-Jie

    2014-05-05

    Graphite is an excellent solid lubricant for surface coating, but its performance is significantly weakened by the vacancy or Stone-Wales (SW) defect. This study uses molecular dynamics simulations to explore the frictional behavior of a diamond tip sliding over a graphite which contains a single defect or stacked defects. Our results suggest that the friction on defective graphite shows a strong dependence on defect location and type. The 5-7-7-5 structure of SW defect results in an effectively negative slope of friction. For defective graphite containing a defect in the surface, adding a single vacancy in the interior layer will decrease the friction coefficients, while setting a SW defect in the interior layer may increase the friction coefficients. Our obtained results may provide useful information for understanding the atomic-scale friction properties of defective graphite.

  14. The Determination of Trace Metals in Saline Waters and Biological Tissues Using the Heated Graphite Atomizer

    NASA Technical Reports Server (NTRS)

    Segar, D. A.

    1971-01-01

    A selective, volatalization technique utilizing the heated graphite atomizer atomic absorption technique has been developed for the analysis of iron in sea water. A similar technique may be used to determine vanadium, copper, nickel and cobalt in saline waters when their concentrations are higher than those normally encountered'in unpolluted sea waters. A preliminary solvent extraction using ammonium pyrolidine dithiocarbamate and methyl iso-butyl ketone permits the determination of a number of elements including iron, copper, zinc, nickel, cobalt and lead in sea water. The heated graphite atomized technique has also been applied to the determination of a range of trace transition elements in marine plant and animal tissues.

  15. Reduction of matrix interferences in furnace atomic absorption with the L'vov Platform

    USGS Publications Warehouse

    Kaiser, M.L.; Koirtyohann, S.R.; Hinderberger, E.J.; Taylor, H.E.

    1981-01-01

    Use of a modified L'vov Platform and ammonium phosphate as a matrix modifier greatly reduced matrix interferences in a commercial Massmann-type atomic absorption furnace. Platforms were readily fabricated from furnace tubes and, once positioned in the furnace, caused no inconvenience in operation. Two volatile elements (Pb, Cd), two of intermediate volatility (Co, Cr) and two which form stable oxides (Al, Sn) were tested in natural water and selected synthetic matrices. In every case for which there was a significant matrix effect during atomization from the tube wall, the platform and platform plus modifier gave improved performance. With lead, for example, an average ratio of 0.48 ?? 0.11 was found when the slope of the standard additions plot for six different natural water samples was compared to the slope of the standard working curve in dilute acid. The average slope ratio between the natural water matrices and the dilute acid matrix was 0.94 ?? 0.03 with the L'vov Platform and 0.96 ?? 0.03 with the platform and matrix modifier. In none of the cases studied did the use of the platform or platform plus modifier cause an interference problem where none existed while atomizing from the tube wall. An additional benefit of the platform was a factor of about two improvement in peak height precision. ?? 1981.

  16. Ab initio calculations on etching of graphite and diamond surfaces by atomic hydrogen

    SciTech Connect

    Kanai, C.; Watanabe, K.; Takakuwa, Y.

    2001-06-15

    Etching of graphite and hydrogenated diamond C(100) 2{times}1 surfaces by irradiating atomic hydrogen, which is one of the key reactions to promote epitaxial diamond growth by chemical vapor deposition, has been investigated by ab initio pseudopotential calculations. We demonstrate the reaction pathways and determine the activation energies for breaking C-C bonds on the surfaces by irradiating hydrogen atoms. The activation energy for C-C bond breaking on graphite is found to be only one-half of that on the hydrogenated diamond surface. This indicates that graphite, which is a typical nondiamond phase unnecessarily generated on the diamond surface during epitaxial growth, can be selectively eliminated by atomic hydrogen, resulting in methane desorption. Our result supports the growth rate enhancement in diamond epitaxy observed in a recent experiment by gas-source molecular beam epitaxy under hydrogen beam irradiation.

  17. Fluorine determination in coal using high-resolution graphite furnace molecular absorption spectrometry and direct solid sample analysis

    NASA Astrophysics Data System (ADS)

    Machado, Patrícia M.; Morés, Silvane; Pereira, Éderson R.; Welz, Bernhard; Carasek, Eduardo; de Andrade, Jailson B.

    2015-03-01

    The absorption of the calcium mono-fluoride (CaF) molecule has been employed in this study for the determination of fluorine in coal using direct solid sample analysis and high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS). The rotational line at 606.440 nm was used for measuring the molecular absorption in the gas phase. The pyrolysis and vaporization temperatures were 700 °C and 2100 °C, respectively. Different chemical modifiers have been studied, such as Pd and Ir as permanent modifiers, and Pd and the mixed Pd/Mg modifier in solution. The limit of detection and the characteristic mass were 0.3 and 0.1 ng F, respectively. One certified reference material (CRM) of coal (NIST 1635) and four CRMs with a non-certified value for F (SARM 18, SARM 20, BCR 40, BCR 180) were used to evaluate the accuracy and precision of the method, obtaining good agreement (104%) with the certified value and with the informed values (ranging from 90 to 103%).

  18. Preservation of atomic flatness at SiO_2/Si(111) interface during furnace oxidation

    NASA Astrophysics Data System (ADS)

    Miyata, Noriyuki; Watanabe, Heiji; Ichikawa, Masakazu

    1998-03-01

    We used a scanning reflection electron microscopy (SREM) to study SiO_2/Si(111) interfaces formed by a furnace oxidation. Clean Si(111)-7x7 surfaces were slightly oxidized at 630^circC in ultrahigh-vacuum chamber (0.3 nm thick). Then SiO2 layers (2.5 - 48 nm) were grown by furnace oxidation under 1-atm O2 at 900^circC. In order to observe atomic-step images at thick-SiO_2/Si interfaces, as-grown SiO2 layers were chemically thinned by using dilute HF to less than 1 nm without exposure of the Si areas. SREM observation indicates that atomic steps on an initial Si surface are preserved at the SiO_2/Si interface and the interfacial steps do not move laterally even after 48-nm-thick oxidation. A profile analysis of reflection high-energy electron diffraction shows that the SiO_2/Si interface consists of islands which have a diameter of about 5 nm and monolayer depth. Our results indicate that the layer-by-layer oxidation caused by two-dimensional island nucleation proceeds under furnace oxidation.

  19. Internal and external atomic steps in graphite exhibit dramatically different physical and chemical properties.

    PubMed

    Lee, Hyunsoo; Lee, Han-Bo-Ram; Kwon, Sangku; Salmeron, Miquel; Park, Jeong Young

    2015-04-28

    We report on the physical and chemical properties of atomic steps on the surface of highly oriented pyrolytic graphite (HOPG) investigated using atomic force microscopy. Two types of step edges are identified: internal (formed during crystal growth) and external (formed by mechanical cleavage of bulk HOPG). The external steps exhibit higher friction than the internal steps due to the broken bonds of the exposed edge C atoms, while carbon atoms in the internal steps are not exposed. The reactivity of the atomic steps is manifested in a variety of ways, including the preferential attachment of Pt nanoparticles deposited on HOPG when using atomic layer deposition and KOH clusters formed during drop casting from aqueous solutions. These phenomena imply that only external atomic steps can be used for selective electrodeposition for nanoscale electronic devices.

  20. Real-space Wigner-Seitz Cells Imaging of Potassium on Graphite via Elastic Atomic Manipulation

    PubMed Central

    Yin, Feng; Koskinen, Pekka; Kulju, Sampo; Akola, Jaakko; Palmer, Richard E.

    2015-01-01

    Atomic manipulation in the scanning tunnelling microscopy, conventionally a tool to build nanostructures one atom at a time, is here employed to enable the atomic-scale imaging of a model low-dimensional system. Specifically, we use low-temperature STM to investigate an ultra thin film (4 atomic layers) of potassium created by epitaxial growth on a graphite substrate. The STM images display an unexpected honeycomb feature, which corresponds to a real-space visualization of the Wigner-Seitz cells of the close-packed surface K atoms. Density functional simulations indicate that this behaviour arises from the elastic, tip-induced vertical manipulation of potassium atoms during imaging, i.e. elastic atomic manipulation, and reflects the ultrasoft properties of the surface under strain. The method may be generally applicable to other soft e.g. molecular or biomolecular systems. PMID:25651973

  1. The electrical resistivity of some graphite types as used in electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Rademeyer, C. J.; Human, H. G. C.; Faure, P. K.

    This paper describes the measurement of the electrical resistivity of four types of graphite as used in electrothermal atomic absorption spectrometry (ETAAS). Results are presented for temperatures in a range between 140 and 1800°C. From 1200°C on the resistivity was found to depend linearly on temperature. The regression coefficients for the corresponding straight portions of the experimental curves are given to provide data for extrapolating the resistivity values to 2500°C and to calculate the dynamic temperature characteristics of the graphite tubes in ETAAS.

  2. Gigahertz Dielectric Polarization of Substitutional Single Niobium Atoms in Defective Graphitic Layers.

    PubMed

    Zhang, Xuefeng; Guo, Junjie; Guan, Pengfei; Qin, Gaowu; Pennycook, Stephen J

    2015-10-01

    We synthesize two Nb/C composites with an order of magnitude difference in the density of single niobium atoms substituted into defective graphitic layers. The concentration and sites of single Nb atoms are identified using aberration-corrected scanning transmission electron microscopy and density functional theory. Comparing the experimental complex permittivity spectra reveals that a representative dielectric resonance at ∼16  GHz originates from the intrinsic polarization of single Nb atom sites, which is confirmed by theoretical simulations. The single-atom dielectric resonance represents the physical limit of the electromagnetic response of condensed matter, and thus might open up a new avenue for designing electromagnetic wave absorption materials. Single-atom resonance also has important implications in understanding the correlation between the macroscopic dielectric behaviors and the atomic-scale structural origin. PMID:26551823

  3. Determination of indium in geological materials by electrothermal-atomization atomic absorption spectrometry with a tungsten-impregnated graphite furance

    USGS Publications Warehouse

    Zhou, L.; Chao, T.T.; Meier, A.L.

    1984-01-01

    The sample is fused with lithium metaborate and the melt is dissolved in 15% (v/v) hydrobromic acid. Iron(III) is reduced with ascorbic acid to avoid its coextraction with indium as the bromide into methyl isobutyl ketone. Impregnation of the graphite furnace with sodium tungstate, and the presence of lithium metaborate and ascorbic acid in the reaction medium improve the sensitivity and precision. The limits of determination are 0.025-16 mg kg-1 indium in the sample. For 22 geological reference samples containing more than 0.1 mg kg-1 indium, relative standard deviations ranged from 3.0 to 8.5% (average 5.7%). Recoveries of indium added to various samples ranged from 96.7 to 105.6% (average 100.2%). ?? 1984.

  4. Tandem focused ultrasound (TFU) combined with fast furnace analysis as an improved methodology for total mercury determination in human urine by electrothermal-atomic absorption spectrometry.

    PubMed

    Capelo, J L; Dos Reis, C D; Maduro, C; Mota, A

    2004-09-01

    A new sample preparation procedure based on tandem (that is, different diameter probe sonicators used in the same sample treatment) focused ultrasound (TFU) for mercury separation, preconcentration and back-extraction in aqueous solution from human urine has been developed. The urine is first oxidized with KMnO(4)/HCl/focused ultrasound (6mm probe). Secondly, the mercury is extracted and preconcentrated with dithizone and cyclohexane. Finally, the mercury is back-extracted and preconcentrated again with the aid of focused ultrasound (3mm probe). The procedure allows determining mercury by electrothermal atomic absorption spectrometry with fast furnace analysis and calibration against aqueous standards. Matrix modification is provided by the chemicals used in the sample treatment. The procedure is accomplished with low sample volume (8.5ml). Low volume and low concentration reagents are used. The sample treatment is rapid (less than 3min per sample) and avoids the use of organic phase in the graphite furnace. The preconcentration factor used in this work was 14. The limit of detection and the limit of quantification in urine were, respectively, 0.27 and 0.9mugl(-1). The relative standard deviation of aqueous standards (n=10) was 4% for a concentration of 100mugl(-1) and 5% for a concentration of 400mugl(-1). Recoveries from spiked urine with inorganic mercury, methyl-mercury, phenyl-mercury and diphenyl-mercury ranged from 86 to 98%.

  5. Determination of chlorine in coal via the SrCl molecule using high-resolution graphite furnace molecular absorption spectrometry and direct solid sample analysis

    NASA Astrophysics Data System (ADS)

    Pereira, Éderson R.; Rocha, Lucas M.; Cadorim, Heloisa R.; Silva, Vanessa D.; Welz, Bernhard; Carasek, Eduardo; de Andrade, Jailson B.

    2015-12-01

    In this study, the determination of chlorine in coal is described via molecular absorption of the strontium mono-chloride (SrCl) molecule at 635.862 nm using high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) and direct solid sample analysis. The pyrolysis and vaporization temperatures were optimized and the measurements are accomplished with a platform coated with zirconium as a permanent chemical modifier in order to increase the sensitivity of the gaseous SrCl molecule generated in the graphite furnace. The optimum pyrolysis and vaporization temperatures were 700 °C and 2100 °C, respectively. Under optimized conditions, the limit of detection and characteristic mass of the method were 0.85 and 0.24 ng, respectively. The accuracy of the method has been verified using four certified reference materials and one not certified reference material of coal, and the results were in good agreement with the certified or reference values.

  6. Atomic oxygen erosion of a graphite coating on a TQCM onboard the Return Flux Experiment (REFLEX)

    NASA Astrophysics Data System (ADS)

    Benner, Steve M.; Lorentson, Charles C.; Chen, Philip T. C.; Thomson, Shaun R.

    1998-10-01

    A TQCM coated with graphite was flown aboard a Spartan carrier in January 1996. During a flight of about 46 hours at an altitude of 305 km, the graphite reacted with the atomic oxygen (AO) in the environment and was eroded away. The 15-MHz TQCM's frequency dropped from 6800 to 4000 Hz in about 15 hours of exposure and was shown to be a strong function of the TQCM's orientation to the ram direction. The erosion rates for four different ram angels was measured and found to be both consistent and repeatable. The average graphite volume loss for the 61 degree and -62 degree ram angles was calculated to be about 2 X E-08 cm3/hr and for the 18 degrees and 19 degrees angles to be about 8.5 X E-08 cm3/hr, which is slightly less than previous flight data. The erosion data was then correlated with AO density numbers for the particular times and positions of the spacecraft in orbit. From this analysis, an equation was derived that shoed the carbon volume loss as a function of both atomic oxygen density and ram angle. For example, 1.59 E-07 cm3/hr would be the calculated carbon volume loss for a ram angle of 0- degrees and an AO fluence of 3.52 E+17 atoms/hr. The results of this data and analysis may lead to the development of a sensor capable of monitoring the AO fluence on a spacecraft.

  7. BOOK REVIEW: The Magic Furnace: the search for the origins of atoms

    NASA Astrophysics Data System (ADS)

    Anderson, Molly

    2000-01-01

    Science is beautiful with hindsight. Cut out the dead ends, the dull interludes and the mad theories that stayed mad and you are left with the highlights. Each amazing discovery builds on the last in a straight, undiverted road towards understanding. Even the twists of fate fit neatly into the evolving story. It is never quite as simple as that but it is immensely appealing nonetheless. This book uses the clarity of hindsight to tell one of the most amazing scientific stories of all time: the birth of atoms in the furnaces of the big bang and the stars. It draws together two seemingly separate lines of enquiry, both of which began in Ancient Greece. The Ancient Greeks looked at the skies, as we do today, and wondered what makes the sun shine. In answer, the philosopher Anaxogorus proposed that the sun was a red-hot ball of iron. Similarly, the idea of atoms was first introduced by Democritus in answer to the question: Can matter be subdivided forever? Democritus' atoms and Anaxogorus' iron sun were both theories that no-one thought could ever be proved or contested. After all, atoms are too small to see and the sun is too hot to visit. But proof comes in many guises and the existence of atoms was established by other means long before they could be `seen' with electron microscopes. The same ingenuity had to be applied to understanding the sun from the cool comfort of the Earth. Marcus Chown tells the story of these tremendous feats in a simple and entertaining way. He introduces all the principal characters of the story, blending personal anecdotes with descriptions of their work. Somehow knowing that we owe the discovery of radioactivity to a cloudy day and that of spectral lines to a roof falling on Fraunhofer's head adds to the evolving drama. Each chapter begins with a carefully chosen quote showing how great minds, from physicists to poets, have pondered these ancient questions. However, the text itself is uncluttered and scientific definitions and

  8. Atomic-Resolution Kinked Structure of an Alkylporphyrin on Highly Ordered Pyrolytic Graphite.

    PubMed

    Chin, Yiing; Panduwinata, Dwi; Sintic, Maxine; Sum, Tze Jing; Hush, Noel S; Crossley, Maxwell J; Reimers, Jeffrey R

    2011-01-20

    The atomic structure of the chains of an alkyl porphyrin (5,10,15,20-tetranonadecylporphyrin) self-assembled monolayer (SAM) at the solid/liquid interface of highly ordered pyrolytic graphite (HOPG) and 1-phenyloctane is resolved using calibrated scanning tunneling microscopy (STM), density functional theory (DFT) image simulations, and ONIOM-based geometry optimizations. While atomic structures are often readily determined for porphyrin SAMs, the determination of the structure of alkyl-chain connections has not previously been possible. A graphical calibration procedure is introduced, allowing accurate observation of SAM lattice parameters, and, of the many possible atomic structures modeled, only the lowest-energy structure obtained was found to predict the observed lattice parameters and image topography. Hydrogen atoms are shown to provide the conduit for the tunneling current through the alkyl chains.

  9. Calculation of the dynamic temperature characteristics of a heated graphite tube used in electrothermal atomic absorption measurements

    NASA Astrophysics Data System (ADS)

    Human, H. G. C.; Ferreira, N. P.; Rademeyer, C. J.; Faure, P. K.

    A method and computer program were developed for calculating the temperature of any part of a graphite furnace tube at any instant of time after onset of the heating cycle. Results for tubes of the Massman design show large differences in spatial temperature distributions during and at the end of the heating cycle when equilibrium is reached. When constant current is applied to contoured tubes, greater heating rates at the tube centres are obtained than with standard tubes.

  10. Preservation of atomic flatness at SiO2/Si(111) interfaces during thermal oxidation in a furnace

    NASA Astrophysics Data System (ADS)

    Miyata, Noriyuki; Watanabe, Heiji; Ichikawa, Masakazu

    1998-04-01

    SiO2/Si(111) interfaces formed by a furnace oxidation are studied by a scanning reflection electron microscopy (SREM). SREM observation indicates that the initial atomic steps on a Si(111) surface are preserved at the SiO2/Si interface and the interfacial steps do not move laterally even after 48-nm-thick oxidation. A profile analysis of reflection high-energy electron diffraction shows that the SiO2/Si interface consists of islands which have a diameter of about 5 nm and monolayer depth. Our results indicate that the layer-by-layer oxidation caused by two-dimensional island nucleation proceeds under furnace oxidation.

  11. Atomic friction at exposed and buried graphite step edges: Experiments and simulations

    SciTech Connect

    Ye, Zhijiang; Martini, Ashlie

    2015-06-08

    The surfaces of layered materials such as graphite exhibit step edges that affect friction. Step edges can be exposed, where the step occurs at the outmost layer, or buried, where the step is underneath another layer of material. Here, we study friction at exposed and buried step edges on graphite using an atomic force microscope (AFM) and complementary molecular dynamics simulations of the AFM tip apex. Exposed and buried steps exhibit distinct friction behavior, and the friction on either step is affected by the direction of sliding, i.e., moving up or down the step, and the bluntness of the tip. These trends are analyzing in terms of the trajectory of the AFM tip as it moves over the step, which is a convolution of the topography of the surface and the tip shape.

  12. Matrix modifiers for feedstuff selenium analysis by graphite furnace atomic absorption spectroscopy

    SciTech Connect

    Brown, T.F.; Zeringue, L.K.

    1988-01-01

    Gallium, Co, Mn, Ni, Cd, Cu, and Zn, dissolved in methanol, were evaluated for efficacy as an alternate volume matrix modifier in Se analysis of forages and concentrates. Gallium, Co, Mn, and Zn were unsuitable as modifiers. Nickel, Cd, Cu, and modifier M (Ni + Cd + Cu) were used to test recovery of Se addition (.025, .050, .100, .200, and .500 ..mu..g) in meat and bone meal, pelleted grain dust, dry milk replacer, whole soybeans, and alfalfa hay. Recovery of Se with Cu, Cd, and M had large and variable SD of means within Se concentrations across feedstuffs and within feedstuff across Se concentrations. Mean percent recoveries of Se with the Ni modifier for the five concentrations over all feedstuffs were 106.4, 102.4, 100.2, 97.5, and 97.4, respectively. Repeated analyses of these same five feedstuffs, plus National Bureau of Standards citrus leaves and corn stalk (recommended Se = .016 ..mu..g/g), gave Se concentration (means ..mu..g/g) of .423, .104, .168, .196, .624, .027, and .015, respectively. Results obtained with Cd, Cu, and M had larger SD than did results obtained with Ni. Nickel nitrate in methanol as an alternate volume matrix modifier for Se provided reliable and sensititive Se analyses for a variety of feedstuffs.

  13. The use of electron scattering for studying atomic momentum distributions: the case of graphite and diamond.

    PubMed

    Vos, M; Moreh, R; Tokési, K

    2011-07-14

    The momentum distributions of C atoms in polycrystalline diamond (produced by chemical vapor deposition) and in highly oriented pyrolitic graphite (HOPG) are studied by scattering of 40 keV electrons at 135°. By measuring the Doppler broadening of the energy of the elastically scattered electrons, we resolve a Compton profile of the motion of the C atoms. The aim of the present work is to resolve long-standing disagreements between the calculated kinetic energies of carbon atoms in HOPG and in diamond films and the measured ones, obtained both by neutron Compton scattering (NCS) and by nuclear resonance photon scattering (NRPS). The anisotropy of the momentum distribution in HOPG was measured by rotating the HOPG sample relative to the electron beam. The obtained kinetic energies for the motion component along, and perpendicular to, the graphite planes were somewhat higher than those obtained from the most recent NCS data of HOPG. Monte Carlo simulations indicate that multiple scattering adds about 2% to the obtained kinetic energies. The presence of different isotopes in carbon affects the measurement at a 1% level. After correcting for these contributions, the kinetic energies are 3%-6% larger than the most recent NCS results for HOPG, but 15%-25% smaller than the NRPS results. For diamond, the corrected direction-averaged kinetic energy is ≈ 6% larger than the calculated value. This compares favorably to the ≈25% discrepancy between theory and both the NCS and NRPS results for diamond.

  14. Adsorption of beryllium atoms and clusters both on graphene and in a bilayer of graphite investigated by DFT.

    PubMed

    Ferro, Yves; Fernandez, Nicolas; Allouche, Alain; Linsmeier, Christian

    2013-01-01

    We herein investigate the interaction of beryllium with a graphene sheet and in a bilayer of graphite by means of periodic DFT calculations. In all cases, we find the beryllium atoms to be more weakly bonded on graphene than in the bilayer. Be(2) forms both magnetic and non-magnetic structures on graphene depending on the geometrical configuration of adsorption. We find that the stability of the Be/bilayer system increases with the size of the beryllium clusters inserted into the bilayer of graphite. We also find a charge transfer from beryllium to the graphite layers. All these results are analysed in terms of electronic structure.

  15. Atomically isolated nickel species anchored on graphitized carbon for efficient hydrogen evolution electrocatalysis.

    PubMed

    Fan, Lili; Liu, Peng Fei; Yan, Xuecheng; Gu, Lin; Yang, Zhen Zhong; Yang, Hua Gui; Qiu, Shilun; Yao, Xiangdong

    2016-01-01

    Hydrogen production through electrochemical process is at the heart of key renewable energy technologies including water splitting and hydrogen fuel cells. Despite tremendous efforts, exploring cheap, efficient and durable electrocatalysts for hydrogen evolution still remains as a great challenge. Here we synthesize a nickel-carbon-based catalyst, from carbonization of metal-organic frameworks, to replace currently best-known platinum-based materials for electrocatalytic hydrogen evolution. This nickel-carbon-based catalyst can be activated to obtain isolated nickel atoms on the graphitic carbon support when applying electrochemical potential, exhibiting highly efficient hydrogen evolution performance with high exchange current density of 1.2 mA cm(-2) and impressive durability. This work may enable new opportunities for designing and tuning properties of electrocatalysts at atomic scale for large-scale water electrolysis. PMID:26861684

  16. Atomically isolated nickel species anchored on graphitized carbon for efficient hydrogen evolution electrocatalysis

    PubMed Central

    Fan, Lili; Liu, Peng Fei; Yan, Xuecheng; Gu, Lin; Yang, Zhen Zhong; Yang, Hua Gui; Qiu, Shilun; Yao, Xiangdong

    2016-01-01

    Hydrogen production through electrochemical process is at the heart of key renewable energy technologies including water splitting and hydrogen fuel cells. Despite tremendous efforts, exploring cheap, efficient and durable electrocatalysts for hydrogen evolution still remains as a great challenge. Here we synthesize a nickel–carbon-based catalyst, from carbonization of metal-organic frameworks, to replace currently best-known platinum-based materials for electrocatalytic hydrogen evolution. This nickel-carbon-based catalyst can be activated to obtain isolated nickel atoms on the graphitic carbon support when applying electrochemical potential, exhibiting highly efficient hydrogen evolution performance with high exchange current density of 1.2 mA cm−2 and impressive durability. This work may enable new opportunities for designing and tuning properties of electrocatalysts at atomic scale for large-scale water electrolysis. PMID:26861684

  17. Local Force Interactions and Image Contrast Reversal on Graphite Observed with Noncontact Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Dagdeviren, Omur; Goetzen, Jan; Altman, Eric; Schwarz, Udo

    Surface interactions of graphene-based nanostructures remain a topic of considerable interest in nanotechnology. Similarly, tip-dependent imaging contrasts have attracted attention as they allow conclusions to be made about the surface's chemical structure and local reactivity. In this talk, we present noncontact atomic force microscopy data recorded in the attractive regime on highly oriented pyrolytic graphite that reveals image contrast reversal for the first time. While larger tip-sample separations feature bright spots on atomic sites, the maximum of the tip-sample interaction flips to the hollow site positions upon further approach, which represents the contrast predominantly observed in previous studies during attractive-mode imaging. This cross over of the local chemical interaction is confirmed in force spectroscopy experiments. The results will be discussed in light of recent theoretical simulations that have predicted the occurrence of such contrast reversal for specific tip terminations.

  18. Ultraclean Radiant Furnace

    NASA Technical Reports Server (NTRS)

    Blair, David W.

    1989-01-01

    Relatively-inexpensive radiant furnace brings specimen in controlled atmosphere to temperature higher than previously attainable - nearly as high as maximum operating temperature of heating element. Heating element made of refractory material like tungsten, molybdenum, graphite, or silicon carbide, or consists of plasma or electric arcs. Furnace distributes heat fairly uniformly over surface of specimen.

  19. Exploring atomic-scale lateral forces in the attractive regime: a case study on graphite (0001)

    NASA Astrophysics Data System (ADS)

    Baykara, Mehmet Z.; Schwendemann, Todd C.; Albers, Boris J.; Pilet, Nicolas; Mönig, Harry; Altman, Eric I.; Schwarz, Udo D.

    2012-10-01

    A non-contact atomic force microscopy-based method has been used to map the static lateral forces exerted on an atomically sharp Pt/Ir probe tip by a graphite surface. With measurements carried out at low temperatures and in the attractive regime, where the atomic sharpness of the tip can be maintained over extended time periods, the method allows the quantification and directional analysis of lateral forces with piconewton and picometer resolution as a function of both the in-plane tip position and the vertical tip-sample distance, without limitations due to a finite contact area or to stick-slip-related sudden jumps of tip apex atoms. After reviewing the measurement principle, the data obtained in this case study are utilized to illustrate the unique insight that the method offers. In particular, the local lateral forces that are expected to determine frictional resistance in the attractive regime are found to depend linearly on the normal force for small tip-sample distances.

  20. Surface Modification and Chemical Sputtering of Graphite Induced by Low Energy Atomic and Molecular Deuterium Ions

    SciTech Connect

    Zhang, Hengda; Meyer, Fred W; Meyer III, Harry M; Lance, Michael J

    2008-01-01

    The surface morphology, and chemical/structural modifications induced during chemical sputtering of ATJ graphite by low-energy (<200 eV/D) deuterium atomic and molecular ions are explored by Scanning Electron Microscopy (SEM), Raman and Auger Electron Spectroscopy (AES) diagnostics. At the lowest impact energies, the ion range may become less than the probe depth of Raman and AES spectroscopy diagnostics. We show that such diagnostics are still useful probes at these energies. As demonstration, we used these surface diagnostics to confirm the characteristic changes of surface texture, increased amorphization, enhanced surface reactivity to impurity species, and increased sp{sup 3} content that low-energy deuterium ion bombardment to steady-state chemical sputtering conditions produces. To put these studies into proper context, we also present new chemical sputtering yields for methane production of ATJ graphite at room temperature by impact of D{sub 2}{sup +} in the energy range 10-250 eV/D, and by impact of D{sup +} and D{sub 3}{sup +} at 30 eV/D and 125 eV/D, obtained using a Quadrupole Mass Spectroscopy (QMS) approach. Below 100 eV/D, the methane production in ATJ graphite is larger than that in HOPG by a factor of {approx} 2. In the energy range 10-60 eV/D, the methane production yield is almost independent of energy and then decreases with increasing ion energies. The results are in good agreement with recent molecular dynamics simulations.

  1. Observation of Dislocation Behavior in Graphite by Using Ultrasonic Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Tsuji, Toshihiro; Irihama, Hiroshi; Yamanaka, Kazushi

    We verify that ultrasonic atomic force microscopy (UAFM) can detect and evaluate subsurface objects with a resolution of around 10nm. We first show that the resonance frequency of UAFM cantilever shows a measurable change due to subsurface low-elasticity layer by a finite element analysis. We then proved the ability of subsurface imaging in a highly oriented pyrolytic graphite (HOPG) specimen. We found a new type of dislocation motion. As a load was applied to the tip, apparent edge-type dislocations (Frank partial dislocations) moved to the direction of climb over distances of 47nm and returned to the original position as the load was removed. To explain this motion, we propose a possible model where the extra half-plane of the dislocation is elastically compressed to shorten its length due to the normal load applied by the tip.

  2. Determination of sulfur in crude oil using high-resolution continuum source molecular absorption spectrometry of the SnS molecule in a graphite furnace.

    PubMed

    Cadorim, Heloisa R; Pereira, Éderson R; Carasek, Eduardo; Welz, Bernhard; de Andrade, Jailson B

    2016-01-01

    An analytical method for the determination of sulfur, as the tin mono-sulfide (SnS) molecule, in crude oil using high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) has been developed. The molecular absorbance of the SnS has been measured using the wavelength at 271.624 nm and the crude oil samples were prepared as micro-emulsions due to their high viscosity. Several chemical modifiers (Ir, Pd, Ru, Zr) were tested and palladium was chosen, because it exhibited the best performance. The heating program was optimized by comparing the pyrolysis and vaporization curves obtained for an aqueous sulfur standard and a micro-emulsion of a crude oil certified reference material (CRM). The optimum pyrolysis and vaporization temperatures were found to be 600 and 2000°C, respectively. The limit of detection and the characteristic mass using micro-emulsion analysis of crude oil samples were 5.8 and 13.3 ng S. Accuracy and precision of the method has been evaluated using two crude oil CRM (NIST 2721 and NIST 2722), showing good agreement with the informed or certified values.

  3. Investigation of chemical modifiers for sulfur determination in diesel fuel samples by high-resolution continuum source graphite furnace molecular absorption spectrometry using direct analysis

    NASA Astrophysics Data System (ADS)

    Huber, Charles S.; Vale, Maria Goreti R.; Welz, Bernhard; Andrade, Jailson B.; Dessuy, Morgana B.

    2015-06-01

    High-resolution continuum source graphite furnace molecular absorption spectrometry has been applied for sulfur determination in diesel fuel. The sharp rotational lines of the carbon monosulfide molecule (formed during the vaporization step) were used to measure the absorbance. The analytical line at 258.056 nm was monitored using the sum of three pixels. Different chemical modifiers were investigated and the mixture of palladium and magnesium was used as chemical modifier in combination with iridium as permanent modifier. L-Cysteine was chosen as sulfur standard and the calibration was done against aqueous standard solutions. The proposed method was applied for the analyses of four diesel samples: two S10 samples and two S500 samples. The trueness of the method was checked with a certified reference material (CRM) of sulfur in diesel fuel (NIST 2724b). Accurate results, for samples and CRM, were achieved after a dilution with propan-1-ol. The following figures of merit were obtained: characteristic mass of 17 ± 3 ng, limit of detection and limit of quantification of 1.4 mg kg- 1 and 4.7 mg kg- 1, respectively.

  4. Study of mass attenuation coefficients and effective atomic numbers of bismuth-ground granulated blast furnace slag concretes

    NASA Astrophysics Data System (ADS)

    Kumar, Sandeep; Singh, Sukhpal

    2016-05-01

    Five samples of Bismuth-Ground granulated blast furnace slag (Bi-GGBFS) concretes were prepared using composition (0.6 cement + x Bi2O3 + (0.4-x) GGBFS, x = 0.05, 0.10, 0.15, 0.20 and 0.25) by keeping constant water (W) cement (C) ratio. Mass attenuation coefficients (μm) of these prepared samples were calculated using a computer program winXCOM at different gamma ray energies, whereas effective atomic numbers (Zeff) is calculated using mathematical formulas. The radiation shielding properties of Bi-GGBFS concrete has been compared with standard radiation shielding concretes.

  5. Observation of single-stranded DNA on mica and highly oriented pyrolytic graphite by atomic force microscopy.

    PubMed

    Adamcik, Jozef; Klinov, Dmitry V; Witz, Guillaume; Sekatskii, Sergey K; Dietler, Giovanni

    2006-10-16

    Atomic force microscopy was used to image single-stranded DNA (ssDNA) adsorbed on mica modified by Mg(2+), by 3-aminopropyltriethoxysilane or on modified highly oriented pyrolytic graphite (HOPG). ssDNA molecules on mica have compact structures with lumps, loops and super twisting, while on modified HOPG graphite ssDNA molecules adopt a conformation without secondary structures. We have shown that the immobilization of ssDNA under standard conditions on modified HOPG eliminates intramolecular base-pairing, thus this method could be important for studying certain processes involving ssDNA in more details.

  6. Spectrometer system using a modular echelle spectrograph and a laser-driven continuum source for simultaneous multi-element determination by graphite furnace absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Geisler, Sebastian; Okruss, Michael; Becker-Ross, Helmut; Huang, Mao Dong; Esser, Norbert; Florek, Stefan

    2015-05-01

    A multi-element absorption spectrometer system has been developed based on a laser-driven xenon continuum source and a modular simultaneous echelle spectrograph (MOSES), which is characterized by a minimized number of optical components resulting in high optical throughput, high transmittance and high image quality. The main feature of the new optical design is the multifunction usage of a Littrow prism, which is attached on a rotation stage. It operates as an order-sorter for the echelle grating in a double-pass mode, as a fine positioning device moving the echelle spectrum on the detector, and as a forwarder to address different optical components, e.g., echelle gratings, in the setup. Using different prisms, which are mounted back to back on the rotation stage, a multitude of different spectroscopic modes like broad-range panorama observations, specific UV-VIS and NIR studies or high resolution zoom investigations of variable spectral channels can be realized. In the UV panorama mode applied in this work, MOSES has simultaneously detectable wavelength coverage from 193 nm to 390 nm with a spectral resolution λ/Δλ of 55,000 (3-pixel criterion). In the zoom mode the latter can be further increased by a factor of about two for a selectable section of the full wavelength range. The applicability and the analytical performance of the system were tested by simultaneous element determination in a graphite furnace, using eight different elements. Compared to an instrument operating in the optimized single line mode, the achieved analytical sensitivity using the panorama mode was typically a factor of two lower. Using the zoom mode for selected elements, comparable sensitivities were obtained. The results confirm the influence of the different spectral resolutions.

  7. Direct determination of lead in wine materials by atomic absorption spectrometry using an electrothermal atomizer with a graphite filter-insert

    NASA Astrophysics Data System (ADS)

    Zacharia, A. N.; Zhuravlev, A. S.; Chebotarev, A. N.; Arabadgi, M. V.

    2013-01-01

    The operational parameters of an atomizer with a graphite filter-insert and a Pd-Mg matrix modifier are optimized for direct electrothermal atomic absorption determination of lead in some wines and associated materials. A method is proposed for eliminating interferences from mineral and organic components, as well as from nonatomic absorption, and for increasing the detection sensitivity for the element by up to a factor of two. The lower limit for determining the amount of lead in wines is 0.0025 mg/dm3. The relative standard deviation ( S r) does not exceed 10%.

  8. Solid phase microextraction capillary gas chromatography combined with furnace atomization plasma emission spectrometry for speciation of mercury in fish tissues

    NASA Astrophysics Data System (ADS)

    Grinberg, Patricia; Campos, Reinaldo C.; Mester, Zoltan; Sturgeon, Ralph E.

    2003-03-01

    The use of solid phase microextraction in conjunction with tandem gas chromatography-furnace atomization plasma emission spectrometry (SPME-GC-FAPES) was evaluated for the determination of methylmercury and inorganic mercury in fish tissue. Samples were digested with methanolic potassium hydroxide, derivatized with sodium tetraethylborate and extracted by SPME. After the SPME extraction, species were separated by GC and detected by FAPES. All experimental parameters were optimized for best separation and analytical response. A repeatability precision of typically 2% can be achieved with long-term (3 months) reproducibility precision of 4.3%. Certified Reference Materials DORM-2, DOLT-2 and TORT-2 from the National Research Council of Canada were analyzed to verify the accuracy of this technique. Detection limits of 1.5 ng g -1 for methylmercury and 0.7 ng g -1 for inorganic mercury in biological tissues were obtained.

  9. Cloud point extraction thermospray flame quartz furnace atomic absorption spectrometry for determination of ultratrace cadmium in water and urine

    NASA Astrophysics Data System (ADS)

    Wu, Peng; Zhang, Yunchang; Lv, Yi; Hou, Xiandeng

    2006-12-01

    A simple, low cost and highly sensitive method based on cloud point extraction (CPE) for separation/preconcentration and thermospray flame quartz furnace atomic absorption spectrometry was proposed for the determination of ultratrace cadmium in water and urine samples. The analytical procedure involved the formation of analyte-entrapped surfactant micelles by mixing the analyte solution with an ammonium pyrrolidinedithiocarbamate (APDC) solution and a Triton X-114 solution. When the temperature of the system was higher than the cloud point of Triton X-114, the complex of cadmium-PDC entered the surfactant-rich phase and thus separation of the analyte from the matrix was achieved. Under optimal chemical and instrumental conditions, the limit of detection was 0.04 μg/L for cadmium with a sample volume of 10 mL. The analytical results of cadmium in water and urine samples agreed well with those by ICP-MS.

  10. Electrochemical generation of mercury cold vapor and its in-situ trapping in gold-covered graphite tube atomizers

    NASA Astrophysics Data System (ADS)

    Červený, Václav; Rychlovský, Petr; Netolická, Jarmila; Šíma, Jan

    2007-03-01

    The combination of more efficient flow-through electrochemical mercury cold vapor generation with its in-situ trapping in a graphite tube atomizer is described. This coupled technique has been optimized to attain the maximum sensitivity for Hg determination and to minimize the limits of detection and determination. A laboratory constructed thin-layer flow-through cell with a platinum cathode served as the cold vapor generator. Various cathode arrangements with different active surface areas were tested. Automated sampling equipment for the graphite atomizer with an untreated fused silica capillary was used for the introduction of the mercury vapor. The inner surface of the graphite tube was covered with a gold foil placed against the sampling hole. The results attained for the electrochemical mercury cold vapor generation (an absolute limit of detection of 80 pg; peak absorbance, 3 σ criterion) were compared with the traditional vapor generation using NaBH 4 as the reducing agent (an absolute limit of detection of 124 pg; peak absorbance, 3 σ criterion). The repeatability at the 5 ng ml - 1 level was better than 4.1% (RSD) for electrochemical mercury vapor generation and better than 5.6% for the chemical cold vapor generation. The proposed method was applied to the determination the of Hg contents in a certified reference material and in spiked river water samples.

  11. [Determination of lead and cadmium in rapeseed and rapeseed meal with microwave digestion by graphite furnace atomic absorption spectrometry].

    PubMed

    He, Xiao-Min; Wang, Min; Wang, Xiao-Dong; Xue, Ai-Fang; Sheng-Qing, Li; Chen, Hao

    2007-11-01

    Comprehensive utilization of rapeseed and rapeseed meal has been increasingly emphasized, and contaminative problems of heavy metal have been attracting great attention, so it is of quite important significance to determine the contents of Pb and Cd. An effective method was developed for the rapid determination of Pb and Cd in rapeseed and rapeseed meal. Digestive dissolvent, time and pressure were discussed for sample preparation by microwave digestion technique, and the optimum condition of determination by GFAAS was studied. The determination limits were 2.172 and 0.243 microg x L(-1), and the linear arranges were 0-100 microg x L(-1) and 0-8 microg x L(-1) for Pb and Cd, respectively. The recoveries were from 80.8% to 110.7%. The RSD of determination was lower than 5.3%. The method offers traits of low detection limit, high sensitivity, speediness and exactness, and was applied to the determination of Pb and Cd in samples with satisfactory results.

  12. Determination of carbide-forming metals, chromium and barium, by graphite furnace atomic absorption spectrometry using a tungsten coil platform

    NASA Astrophysics Data System (ADS)

    Moreno Camero, Rosa; Alvarado, José

    2000-07-01

    The use of a tungsten coil as a platform has been evaluated for the determination of carbide-forming metals, Cr and Ba. The methodology developed has been used for Cr and Ba determinations in HPS CRM, Trace Metals in Drinking Water, and NIST SRM 1643b, Trace Elements in Water. Good agreement was found between the results obtained and the certified values for Cr in both reference materials and for Ba in the NIST SRM. Barium results were approximately 14% lower than the certified results for the HPS CRM. This inaccuracy was ascribed to the presence of considerable amounts of Ca in this particular material. Precision of the measurements, 3σ relative standard deviation as percentage, were 2.5 and 5.8 for Cr and Ba, respectively. Characteristic masses, in picograms, were 1.70 for Cr and 19.0 for Ba. These results compare favorably with the literature values for Cr but not for Ba.

  13. [A rapid Zeeman graphite furnace atomic absorption spectrometic method for the determination of trace lead and cadium in drinking water].

    PubMed

    Wu, J

    1998-02-01

    The determination of trace lead and cadium in drinking water by rapid GFAAS has been described in this paper, which is based on eliminating ashing step, shortening drying time and without chemical matrix modifier. The fast speed and simplicity makes it possible for routine analysis.

  14. Biosorption of platinum and palladium for their separation/preconcentration prior to graphite furnace atomic absorption spectrometric determination

    NASA Astrophysics Data System (ADS)

    Godlewska-Żyłkiewicz, Beata

    2003-08-01

    Inexpensive baker's yeast Saccharomyces cerevisiae and green algae Chlorella vulgaris, either free or immobilized on silica gel have been shown to selectively accumulate platinum and palladium from water samples in acidic medium (pH 1.6-1.8). Optimization of conditions of metals biosorption (sample pH, algae and yeast masses, adsorption time, temperature) was performed in batch mode. The procedure of matrix separation based on biosorption of platinum and palladium on algae C. vulgaris covalently immobilized on silica gel in flow mode was developed. The use of algae in flow procedure offers several advantages compared with its use in the batch mode. The procedure shows better reproducibility (<2%), improved efficiency of platinum retention on the column (93.3±1.6%), is less laborious and less time consuming. The best recovery of biosorbed metals from column (87.7±3.3% for platinum and 96.8±1.1 for palladium) was obtained with solution of 0.3 mol l -1 thiourea in 1 mol l -1 hydrochloric acid. The influence of thiourea on analytical signals of examined metals during GFAAS determination is discussed. The procedure has been applied for separation of noble metals from tap and waste water samples spiked with platinum and palladium.

  15. Divalent Fe Atom Coordination in Two-Dimensional Microporous Graphitic Carbon Nitride.

    PubMed

    Oh, Youngtak; Hwang, Jin Ok; Lee, Eui-Sup; Yoon, Minji; Le, Viet-Duc; Kim, Yong-Hyun; Kim, Dong Ha; Kim, Sang Ouk

    2016-09-28

    Graphitic carbon nitride (g-C3N4) is a rising two-dimensional material possessing intrinsic semiconducting property with unique geometric configuration featuring superimposed heterocyclic sp(2) carbon and nitrogen network, nonplanar layer chain structure, and alternating buckling. The inherent porous structure of heptazine-based g-C3N4 features electron-rich sp(2) nitrogen, which can be exploited as a stable transition metal coordination site. Multiple metal-functionalized g-C3N4 systems have been reported for versatile applications, but local coordination as well as its electronic structure variation upon incoming metal species is not well understood. Here we present detailed bond coordination of divalent iron (Fe(2+)) through micropore sites of graphitic carbon nitride and provide both experimental and computational evidence supporting the aforementioned proposition. In addition, the utilization of electronic structure variation is demonstrated through comparative photocatalytic activities of pristine and Fe-g-C3N4.

  16. Untergrundstörungen durch organische Lösungsmittel in der Atomabsorptionsspektrometrie mit Graphitöfen

    NASA Astrophysics Data System (ADS)

    Gücer, S.; Massmann, H.

    In atomic absorption spectrometry with graphite furnaces, marked background interferences may occur during the atomization step, when organic solvents are used. Aromatic molecules can sorb to the graphite, partly very firmly, so that they appear in the absorption volume only during the atomizing step, even after preceding interim heating to 800°C. The undissociated molecules show characteristic vibrational spectra in which bands with relative sharp edges can be observed. No rotational structure is recognizable. Reliable background measurements may prove problematic if not entirely impossible in some wavelength regions.

  17. Steady-State and Transient Hydrocarbon Production in Graphite by Low Energy Impact of Atomic and Molecular Deuterium Projectiles

    SciTech Connect

    Meyer, Fred W; Zhang, Hengda

    2009-01-01

    We report measurements of steady-state yields of methyl, methane and heavier hydrocarbons for deuterium atomic and molecular ions incident on ATJ graphite, HOPG, and a-C:D thin films in the energy range 10-200 eV/D. The yields were determined using a QMS technique in conjunction with calibrated hydrocarbon leaks. We have also studied transient hydrocarbon production and hydrogen (deuterium) re-emission for 80 and 150 eV/D D+, D{sub 2}{sup +}, and D{sub 3}{sup +} projectiles incident on ATJ graphite surfaces pre-loaded to steady state by 20 eV/D beams of the corresponding species. Immediately after starting the higher-energy beams, transient hydrocarbon and D2 re-emission yields significantly larger than steady-state values were observed, which exponentially decayed as a function of beam fluence. The initial yield values were related to the starting hydrocarbon and deuterium densities in the prepared sample, while the exponential decay constants provided information on the hydrocarbon kinetic release and hydrogen (deuterium) detrapping cross-sections.

  18. Direct and rapid analysis of ambient air and exhaled air via electrostatic precipitation of aerosols in an atomizer furnace and Zeeman spectrometry.

    PubMed

    Ivanenko, A A; Ivanenko, N B; Kuzmenkov, M A; Jakovleva, E M; Skudra, A; Slyadnev, M N; Ganeev, A A

    2005-02-01

    Techniques that allow the elements present in the air to be determined in a simple and rapid manner are very attractive. Direct aerosol sampling techniques avoid the need to pretreat the filter via wet digestion in order to remove any sources of contamination, and they decrease the precipitation time significantly. Analyzers based on this technique can also determine the concentrations of elements in the air automatically in situ. This paper is concerned with the development of a novel analytical system that is based on electrostatically precipitating aerosols from the air into a graphite furnace. The equipment includes a Zeeman spectrometer with high frequency modulation polarization (MGA-915), and an electrostatic precipitation system incorporated into the analyzer. The high sensitivity of the system developed here means that it can be used to determine element concentrations in the air exhaled by humans, as well as those in ambient air.

  19. Brazing graphite to graphite

    DOEpatents

    Peterson, George R.

    1976-01-01

    Graphite is joined to graphite by employing both fine molybdenum powder as the brazing material and an annealing step that together produce a virtually metal-free joint exhibiting properties similar to those found in the parent graphite. Molybdenum powder is placed between the faying surfaces of two graphite parts and melted to form molybdenum carbide. The joint area is thereafter subjected to an annealing operation which diffuses the carbide away from the joint and into the graphite parts. Graphite dissolved by the dispersed molybdenum carbide precipitates into the joint area, replacing the molybdenum carbide to provide a joint of virtually graphite.

  20. Unraveling the nanostructure of supramolecular assemblies of hydrogen-bonded rosettes on graphite: An atomic force microscopy study

    PubMed Central

    Schönherr, Holger; Paraschiv, Vasile; Zapotoczny, Szczepan; Crego-Calama, Mercedes; Timmerman, Peter; Frank, Curtis W.; Vancso, G. Julius; Reinhoudt, David N.

    2002-01-01

    The self-organization of multicomponent tetrarosette assemblies into ordered nanostructures on graphite surfaces has been studied by atomic force microscopy (AFM). Real-space information on the level of individual molecules allowed us to analyze the underlying structure in unprecedented detail. In highly ordered nanorod domains, tetrarosettes 13⋅(DEB)12 arrange in the form of parallel rows with a spacing of 4.6 ± 0.1 nm. High resolution AFM revealed the internal packing of the tetrarosette assemblies in these rows, which can be described by an oblique lattice with a = 2.5 ± 0.3 nm, b = 5.0 ± 0.1 nm, and γ = 122 ± 3°. The results, together with recent improvements in synthetic approaches, contribute to the development of a general strategy to develop H-bonding-based nanostructures with molecular precision. PMID:11929980

  1. First-principles study of ternary graphite compounds cointercalated with alkali atoms (Li, Na, and K) and alkylamines towards alkali ion battery applications

    NASA Astrophysics Data System (ADS)

    Ri, Gum-Chol; Yu, Chol-Jun; Kim, Jin-Song; Hong, Song-Nam; Jong, Un-Gi; Ri, Mun-Hyok

    2016-08-01

    First-principles calculations were carried out to investigate the structural, energetic, and electronic properties of ternary graphite compounds cointercalated with alkali atoms (AM = Li, Na, and K) and normal alkylamine molecules (nCx; x = 1, 2, 3, 4), denoted as AM-nCx-GICs. From the optimization of the orthorhombic unit cells for the crystalline compounds, it was found that, with the increase in the atomic number of alkali atoms, the layer separations decrease in contrast to AM-GICs, while the bond lengths between alkali atoms and graphene layer, and nitrogen atom of alkylamine increase. The calculated formation energies and interlayer binding energies of AM-nC3-GICs indicate that the compounds is increasingly stabilized from Li to K, and the energy barriers for migration of alkali atoms suggest that alkali cation with larger ionic radius diffuses more smoothly in graphite, being similar to AM-GICs. Through the analysis of electronic properties, it was established that more extent of electronic charge is transferred from more electropositive alkali atom to the carbon ring of graphene layer, and the hybridization of valence electron orbitals between alkylamine molecules and graphene layer is occurred.

  2. Leveling coatings for reducing the atomic oxygen defect density in protected graphite fiber epoxy composites

    NASA Technical Reports Server (NTRS)

    Jaworske, D. A.; Degroh, Kim K.; Podojil, G.; Mccollum, T.; Anzic, J.

    1992-01-01

    Pinholes or other defect sites in a protective oxide coating provide pathways for atomic oxygen in low Earth orbit to reach underlying material. One concept of enhancing the lifetime of materials in low Earth orbit is to apply a leveling coating to the material prior to applying any reflective and protective coatings. Using a surface tension leveling coating concept, a low viscosity epoxy was applied to the surface of several composite coupons. A protective layer of 1000 A of SiO2 was deposited on top of the leveling coating, and the coupons were exposed to an atomic oxygen environment in a plasma asher. Pinhole populations per unit area were estimated by counting the number of undercut sites observed by scanning electron microscopy. Defect density values of 180,000 defects/sq cm were reduced to about 1000 defects/sq cm as a result of the applied leveling coating. These improvements occur at a mass penalty of about 2.5 mg/sq cm.

  3. Leveling coatings for reducing the atomic oxygen defect density in protected graphite fiber epoxy composites

    NASA Technical Reports Server (NTRS)

    Jaworske, D. A.; Degroh, K. K.; Podojil, G.; Mccollum, T.; Anzic, J.

    1992-01-01

    Pinholes or other defect sites in a protective oxide coating provide pathways for atomic oxygen in low Earth orbit to reach underlying material. One concept for enhancing the lifetime of materials in low Earth orbits is to apply a leveling coating to the material prior to applying any reflective and protective coatings. Using a surface tension leveling coating concept, a low viscosity epoxy was applied to the surface of several composite coupons. A protective layer of 1000 A of SiO2 was deposited on top of the leveling coating, and the coupons were exposed to an atomic oxygen environment in a plasma asher. Pinhole populations per unit area were estimated by counting the number of undercut sites observed by scanning electron microscopy. Defect density values of 180,000 defects/sq cm were reduced to about 1000 defects/sq cm as a result of the applied leveling coating. These improvements occur at a mass penalty of about 2.5 mg/sq cm.

  4. Probing the adsorption of weak acids on graphite using amplitude modulation-frequency modulation atomic force microscopy.

    PubMed

    Moustafa, Ahmed M A; Huang, Jun; McPhedran, Kerry N; Zeng, Hongbo; El-Din, Mohamed Gamal

    2015-03-17

    Recent thermodynamics calculations and adsorption isotherms showed that the adsorption of a self-assembled layer (SAL) of ionized weak acids to carbon was attributed to the negatively charged hydrogen bonding (-CAHB), yet the direct visualization and characterization of this adsorption behavior have not been reported. Here, an amplitude modulation-frequency modulation atomic force microscopy (AM-FM AFM) technique was applied to discriminate the adsorption of decanoic acids (DA) on highly ordered pyrolytic graphite (HOPG). Thermodynamics calculations revealed that the adsorption of SAL was driven by the formation of -CAHB with negatively charged functional groups of HOPG. Multilayer adsorption could occur over the adsorbed ionized SAL, leading to the development of aggregates. AM-FM AFM imaging showed that the adsorption of the DA molecules forming aggregates occurred only for the HOPG-functionalized steps, while DA molecules were found to adsorb over the entire functionalized HOPG surface after water-plasma treatment, as evident from the frequency shifts identified in AFM images. PMID:25710305

  5. Probing the adsorption of weak acids on graphite using amplitude modulation-frequency modulation atomic force microscopy.

    PubMed

    Moustafa, Ahmed M A; Huang, Jun; McPhedran, Kerry N; Zeng, Hongbo; El-Din, Mohamed Gamal

    2015-03-17

    Recent thermodynamics calculations and adsorption isotherms showed that the adsorption of a self-assembled layer (SAL) of ionized weak acids to carbon was attributed to the negatively charged hydrogen bonding (-CAHB), yet the direct visualization and characterization of this adsorption behavior have not been reported. Here, an amplitude modulation-frequency modulation atomic force microscopy (AM-FM AFM) technique was applied to discriminate the adsorption of decanoic acids (DA) on highly ordered pyrolytic graphite (HOPG). Thermodynamics calculations revealed that the adsorption of SAL was driven by the formation of -CAHB with negatively charged functional groups of HOPG. Multilayer adsorption could occur over the adsorbed ionized SAL, leading to the development of aggregates. AM-FM AFM imaging showed that the adsorption of the DA molecules forming aggregates occurred only for the HOPG-functionalized steps, while DA molecules were found to adsorb over the entire functionalized HOPG surface after water-plasma treatment, as evident from the frequency shifts identified in AFM images.

  6. Ultramicro analysis for copper, cadmium, and zinc in human liver tissue by use of atomic absorption spectrophotometry and the heated graphite tube atomizer.

    PubMed

    Evenson, M A; Anderson, C T

    1975-04-01

    We describe a method of analysis for copper, cadmium, and zinc in a 15-mg (wet weight) sample of human liver by atomic absorption spectrophotometry. The sample is digested with nitric acid (1.0 mol/liter), evaporated, and dilute HNO3 (10 mmol/liter) added. The reconstituted acid mixture is injected into the graphite tube atomizer for analysis of Cu and Cd and aspirated into the air--acetylene flame for measurement of Zn. The absorbance for each metal is suppressed with increasing pH. NaNO3, KNO3, KCl, and NaCl (e.g.) quench the Cd absorbance in acid solutions that contain no protein, but not in the presence of protein. Metal ions added to the predigestion human liver sample at 10 percent and 100 percent of the intrinsic metal concentrations were, respectively, 93 percent and 90 percent accounted for analytically in the case of Cu, 98 percent and 102 percent for Zn, and 101 percent and 93 percent for Cd. Analysis of a National Bureau of Standards' Bovine Liver Standard Reference Material yielded results corresponding to 99 percent (Cu), 112 percent (Zn), and 91 percent (Cd) of the mean expected concentrations of these metals. The between-run coefficient of variation for the bovine liver material was 6 percent for Cu, 9 percent for Zn, and 10 percent for Cd. For 16 histologically normal samples of human liver, the mean values were: Cu, 26; Zn, 293; and Cd, 6.0 nanograms of metal per milligram dry weight, in agreement with values published previously. The method can be easily and reliably applied to small samples of liver obtained by closed-needle biopsy.

  7. Ultrafast probing of the x-ray-induced lattice and electron dynamics in graphite at atomic-resolution

    SciTech Connect

    Hau-Riege, S

    2010-10-07

    We used LCLS pulses to excite thin-film and bulk graphite with various different microstructures, and probed the ultrafast ion and electron dynamics through Bragg and x-ray Thomson scattering (XRTS). We pioneered XRTS at LCLS, making this technique viable for other users. We demonstrated for the first time that the LCLS can be used to characterize warm-dense-matter through Bragg and x-ray Thomson scattering. The warm-dense-matter conditions were created using the LCLS beam. Representative examples of the results are shown in the Figure above. In our experiment, we utilized simultaneously both Bragg and two Thomson spectrometers. The Bragg measurements as a function of x-ray fluence and pulse length allows us to characterize the onset of atomic motion at 2 keV with the highest resolution to date. The Bragg detector was positioned in back-reflection, providing us access to scattering data with large scattering vectors (nearly 4{pi}/{lambda}). We found a clear difference between the atomic dynamics for 70 and 300 fs pulses, and we are currently in the process of comparing these results to our models. The outcome of this comparison will have important consequences for ultrafast diffractive imaging, for which it is still not clear if atomic resolution can truly be achieved. The backward x-ray Thomson scattering data suggests that the average graphite temperature and ionization was 10 eV and 1.0, respectively, which agrees with our models. In the forward scattering data, we observed an inelastic feature in the Thomson spectrum that our models currently do not reproduce, so there is food for thought. We are in the process of writing these results up. Depending on if we can combine the Bragg and Thomson data or not, we plan to publish them in a single paper (e.g. Nature or Science) or as two separate papers (e.g. two Phys. Rev. Lett.). We will present the first analysis of the results at the APS Plasma Meeting in November 2010. We had a fantastic experience performing our

  8. Integration of point-contact microscopy and atomic force microscopy: application to characterization of graphite/Pt(111)

    SciTech Connect

    Enachescu, M.; Schleef, D.; Ogletree, D.F.; Salmeron, M.

    1999-08-19

    The electrical current through the point-contact junction of an AFM tip is used to image the surfaces of bulk graphite (HOPG) and the surface of a graphitized carbon monolayer on Pt(111) under ultra-high vacuum (UHV) conditions. Lattice-resolved images are obtained simultaneously in topography, lateral friction, and contact current channels. Lattice resolution in current maps persisted up to 0.9 mA and pressures of up to 5 GPa. In both bulk graphite and the case of graphitized carbon monolayer on Pt(111), the current images show only one maximum per unit cell. In addition, the contact current images of the graphite monolayer reveal local conductivity variations. The authors observed local conductivity variations in the form of Moire superstructures resulting from high order commensurability with the Pt lattice.

  9. Integration of point-contact microscopy and atomic-force microscopy: Application to characterization of graphite/Pt(111)

    SciTech Connect

    Enachescu, M.; Schleef, D.; Ogletree, D. F.; Salmeron, M.

    1999-12-15

    The electrical current through the point-contact junction of an AFM tip is used to image the surfaces of bulk graphite (HOPG) and the surface of a graphitized carbon monolayer on Pt(111) under ultra-high-vacuum (UHV) conditions. Lattice-resolved images are obtained simultaneously in topography, lateral friction, and contact current channels. Lattice resolution in current maps persisted up to 0.9 mA and pressures of up to 5 GPa. In both bulk graphite and the case of graphitized carbon monolayer on Pt(111), the current images show only one maximum per unit cell. In addition, the contact current images of the graphite monolayer reveal local conductivity variations. We observed local conductivity variations in the form of moire superstructures resulting from high order commensurability with the Pt lattice. (c) 1999 The American Physical Society.

  10. Determination of nanogram amounts of bismuth in rocks by atomic absorption spectrometry with electrothermal atomization

    USGS Publications Warehouse

    Kane, J.S.

    1979-01-01

    Bismuth concentrations as low as 10 ng g-1 in 100-mg samples of geological materials can be determined by atomic absorption spectrometry with electrothermal atomization. After HF-HClO4 decomposition of the sample, bismuth is extracted as the iodide into methyl isobutyl ketone and is then stripped with ethylenediaminetetraacetic acid into the aqueous phase. Aliquots of this solution are pipetted into the graphite furnace and dried, charred, and atomized in an automated sequence. Atomic absorbance at the Bi 223.1-nm line provides a measure of the amount of bismuth present. Results are presented for 14 U.S. Geological Survey standard rocks. ?? 1979.

  11. 3-Dimensional atomic scale structure of the ionic liquid-graphite interface elucidated by AM-AFM and quantum chemical simulations.

    PubMed

    Page, Alister J; Elbourne, Aaron; Stefanovic, Ryan; Addicoat, Matthew A; Warr, Gregory G; Voïtchovsky, Kislon; Atkin, Rob

    2014-07-21

    In situ amplitude modulated atomic force microscopy (AM-AFM) and quantum chemical simulations are used to resolve the structure of the highly ordered pyrolytic graphite (HOPG)-bulk propylammonium nitrate (PAN) interface with resolution comparable with that achieved for frozen ionic liquid (IL) monolayers using STM. This is the first time that (a) molecular resolution images of bulk IL-solid interfaces have been achieved, (b) the lateral structure of the IL graphite interface has been imaged for any IL, (c) AM-AFM has elucidated molecular level structure immersed in a viscous liquid and (d) it has been demonstrated that the IL structure at solid surfaces is a consequence of both thermodynamic and kinetic effects. The lateral structure of the PAN-graphite interface is highly ordered and consists of remarkably well-defined domains of a rhomboidal superstructure composed of propylammonium cations preferentially aligned along two of the three directions in the underlying graphite lattice. The nanostructure is primarily determined by the cation. Van der Waals interactions between the propylammonium chains and the surface mean that the cation is enriched in the surface layer, and is much less mobile than the anion. The presence of a heterogeneous lateral structure at an ionic liquid-solid interface has wide ranging ramifications for ionic liquid applications, including lubrication, capacitive charge storage and electrodeposition.

  12. Se atoms and Se6 molecules as guests in Se-carbons - prepared by reduction of a SeCl4-graphite precursor

    NASA Astrophysics Data System (ADS)

    Walter, J.; Shioyama, H.

    2000-01-01

    A SeCl4 -graphite intercalation compound precursor was reduced by a solution of lithium diphenylide in tetrahydrofuran at room temperature. X-ray diffraction measurements gave two distinguishable stages. One stage represented a Se-atom intercalation the other represented an intercalation of Se6 molecules. The in-plane diffraction patterns were estimated by selected-area electron diffraction, the existence of two different guest species (atoms and molecules) could be proved. The Se6 -molecule phase shows an incommensurate lattice with regard to the host lattice, but they are in the same orientation. The lattice parameter of intercalated Se6 is a Se 6-guest = 1158+/-36 pm, c Se 6-guest = 483+/-38 pm, which fits with the lattice parameter of non-intercalated Se6 molecules. Se atom domains show a 2 × agraphite superlattice with respect to the host lattice, which is a commensurate superstructure. Raman scattering data showed the occurrence of an acceptor-type graphite intercalation compound. Three different types of spectra could be obtained, two kinds of spectra consists of doublets at 1588 cm-1 and 1608 cm-1 , with different intensity ratios. These two kinds of spectra are certainly attributed to Se-atom domains, with different stages. A third type of spectrum show bands at higher wavenumbers (1646 cm-1 and 1653 cm-1 ). These bands are probably correlated to Se6 -molecule domains. They represent maybe very early stages of nanoparticle formation.

  13. Flameless atomic-absorption determination of gold in geological materials

    USGS Publications Warehouse

    Meier, A.L.

    1980-01-01

    Gold in geologic material is dissolved using a solution of hydrobromic acid and bromine, extracted with methyl isobutyl ketone, and determined using an atomic-absorption spectrophotometer equipped with a graphite furnace atomizer. A comparison of results obtained by this flameless atomic-absorption method on U.S. Geological Survey reference rocks and geochemical samples with reported values and with results obtained by flame atomic-absorption shows that reasonable accuracy is achieved with improved precision. The sensitivity, accuracy, and precision of the method allows acquisition of data on the distribution of gold at or below its crustal abundance. ?? 1980.

  14. Thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) — a simple method for trace element determination with microsamples in the μg/l concentration range

    NASA Astrophysics Data System (ADS)

    Gáspár, Attila; Berndt, Harald

    2000-06-01

    A new flame method of atomic absorption spectrometry has been developed. The liquid sample to be analyzed is transported through a very hot, simple metal capillary tip acting as a flame-heated thermospray into a glowing atomization tube (flame furnace) which is positioned into the air/acetylene flame of a standard flame-AAS burner head. Both the complete introduction of the whole sample and the extended residence time inside the absorption volume result in an improvement of detection limits from 14 to 67 for five investigated elements. The detection limits determined using 10-μl samples amount to 0.19 ng/ml (Cd), 1.3 ng/ml (Cu), 5.2 ng/ml (Tl), 13 ng/ml (Pb) and 21 ng/ml (Hg). A relative standard deviation of 1.4-3.4% ( N=12, 10 μl) was achieved. Sample volumes between 2.5 μl and 200 μl have been investigated. In the case of 10 μl the sampling frequency was three per minute. The method can also be considered as a simple, effective interface between HPLC or FIA techniques and flame AAS. The determinations can be easily automated.

  15. Radial furnace shows promise for growing straight boron carbide whiskers

    NASA Technical Reports Server (NTRS)

    Feingold, E.

    1967-01-01

    Radial furnace, with a long graphite vaporization tube, maintains a uniform thermal gradient, favoring the growth of straight boron carbide whiskers. This concept seems to offer potential for both the quality and yield of whiskers.

  16. A fast and accurate method for the determination of total and soluble fluorine in toothpaste using high-resolution graphite furnace molecular absorption spectrometry and its comparison with established techniques.

    PubMed

    Gleisner, Heike; Einax, Jürgen W; Morés, Silvane; Welz, Bernhard; Carasek, Eduardo

    2011-04-01

    A fast and reliable method has been developed for the determination of total and soluble fluorine in toothpaste, important quality control parameters in dentifrices. The method is based on the molecular absorption of gallium mono-fluoride, GaF, using a commercially available high-resolution continuum source atomic absorption spectrometer. Transversely heated platform tubes with zirconium as permanent chemical modifier were used throughout. Before each sample injection, a palladium and zirconium modifier solution and a gallium reagent were deposited onto the graphite platform and thermally pretreated to transform them into their active forms. The samples were only diluted and introduced directly into the graphite tube together with additional gallium reagent. Under these conditions the fluoride was stable up to a pyrolysis temperature of 550 °C, and the optimum vaporization (molecule formation) temperature was 1550 °C. The GaF molecular absorption was measured at 211.248 nm, and the limits of detection and quantification were 5.2 pg and 17 pg, respectively, corresponding to a limit of quantification of about 30 μg g(-1) (ppm) F in the original toothpaste. The proposed method was used for the determination of total and soluble fluorine content in toothpaste samples from different manufactures. The samples contained different ionic fluoride species and sodium monofluorophosphate (MFP) with covalently bonded fluorine. The results for total fluorine were compared with those obtained with a modified conventional headspace gas chromatographic procedure. Accuracy and precision of the two procedures were comparable, but the proposed procedure was much less labor-intensive, and about five times faster than the latter one.

  17. A fast and accurate method for the determination of total and soluble fluorine in toothpaste using high-resolution graphite furnace molecular absorption spectrometry and its comparison with established techniques.

    PubMed

    Gleisner, Heike; Einax, Jürgen W; Morés, Silvane; Welz, Bernhard; Carasek, Eduardo

    2011-04-01

    A fast and reliable method has been developed for the determination of total and soluble fluorine in toothpaste, important quality control parameters in dentifrices. The method is based on the molecular absorption of gallium mono-fluoride, GaF, using a commercially available high-resolution continuum source atomic absorption spectrometer. Transversely heated platform tubes with zirconium as permanent chemical modifier were used throughout. Before each sample injection, a palladium and zirconium modifier solution and a gallium reagent were deposited onto the graphite platform and thermally pretreated to transform them into their active forms. The samples were only diluted and introduced directly into the graphite tube together with additional gallium reagent. Under these conditions the fluoride was stable up to a pyrolysis temperature of 550 °C, and the optimum vaporization (molecule formation) temperature was 1550 °C. The GaF molecular absorption was measured at 211.248 nm, and the limits of detection and quantification were 5.2 pg and 17 pg, respectively, corresponding to a limit of quantification of about 30 μg g(-1) (ppm) F in the original toothpaste. The proposed method was used for the determination of total and soluble fluorine content in toothpaste samples from different manufactures. The samples contained different ionic fluoride species and sodium monofluorophosphate (MFP) with covalently bonded fluorine. The results for total fluorine were compared with those obtained with a modified conventional headspace gas chromatographic procedure. Accuracy and precision of the two procedures were comparable, but the proposed procedure was much less labor-intensive, and about five times faster than the latter one. PMID:21215545

  18. Determination of cadmium and lead at low levels by using preconcentration at fullerene coupled to thermospray flame furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Pereira, M. G.; Pereira-Filho, E. R.; Berndt, H.; Arruda, M. A. Z.

    2004-04-01

    A new and sensitive method for Cd and Pb determinations, based on the coupling of thermospray flame furnace atomic absorption spectrometry and a preconcentrator system, was developed. The procedure comprised the chelating of Cd and Pb with ammonium pyrrolidinedithiocarbamate with posterior adsorption of the chelates on a mixture (40 mg) of C 60 and C 70 at a flow rate of 2.0 ml min -1. These chelates were eluted from the adsorbent by passing a continuous flow of ethanol (80% v/v) at 0.9 ml min -1 to a nickel tube placed in an air/acetylene flame. After sample introduction into the tube by using a ceramic capillary (0.5 mm i.d.), the analytical signals were registered as peak height. Under these conditions, improvement factors in detectability of 675 and 200 were obtained for Cd and Pb, respectively, when compared to conventional flame atomic absorption spectrometry. Spiked samples (mineral and tap waters) and drinking water containing natural concentrations of Cd were employed for evaluating accuracy by comparing the results obtained from the proposed methodology with those using electrothermal atomic absorption spectrometry. In addition, certified reference materials (rye grass, CRM 281 and pig kidney, CRM 186) were also adopted for the accuracy tests. Due to the good linearity ranges for Cd (0.5-5.0 μg l -1) and Pb (10-250 μg l -1), samples with different concentrations could be analyzed. Detection limits of 0.1 and 2.4 μg l -1 were obtained for Cd and Pb, respectively, and RSD values <4.5% were observed ( n=10). Finally, a sample throughput of 24 determinations per hour was possible.

  19. Tube furnace

    DOEpatents

    Foster, Kenneth G.; Frohwein, Eugene J.; Taylor, Robert W.; Bowen, David W.

    1991-01-01

    A vermiculite insulated tube furnace is heated by a helically-wound resistance wire positioned within a helical groove on the surface of a ceramic cylinder, that in turn is surroundingly disposed about a doubly slotted stainless steel cylindrical liner. For uniform heating, the pitch of the helix is of shorter length over the two end portions of the ceramic cylinder. The furnace is of large volume, provides uniform temperature, offers an extremely precise programmed heating capability, features very rapid cool-down, and has a modest electrical power requirement.

  20. Optimization of a hydride generation metallic furnace atomic absorption spectrometry (HG-MF-AAS) method for tin determination: analytical and morphological parameters of a metallic atomizer.

    PubMed

    Moretto Galazzi, Rodrigo; Arruda, Marco Aurélio Zezzi

    2013-12-15

    The present work describes a metallic tube as hydride atomizer for atomic absorption spectrometry. Its performance is evaluated through tin determination, and the accuracy of the method assessed through the analysis of sediment and water samples. Some chemical parameters (referring to the generation of the hydride) such as acid, NaOH and THB concentrations, as well as physical parameters (referring to the transport of the hydride) such as carrier, acetylene, air flow-rates, flame composition, coil length, tube hole area, among others, are evaluated for optimization of the method. Scanning electron microscopy is used for evaluating morphological parameters in both new and used (after 150 h) tube atomizers. The method presents linear Sn concentration from 50 to 1000 µg L(-1) (r>0.9995; n=3) and the analytical frequency of ca. 40 h(-1). The limit of detection (LOD) is 7.1 µg L(-1) and the precision, expressed as RSD is less than 4% (200 µg L(-1); n=10). The accuracy is evaluated through reference materials, and the results are similar at 95% confidence level according to the t-test.

  1. Furnace assembly

    DOEpatents

    Panayotou, N.F.; Green, D.R.; Price, L.S.

    A method of and apparatus for heating test specimens to desired elevated temperatures for irradiation by a high energy neutron source. A furnace assembly is provided for heating two separate groups of specimens to substantially different, elevated, isothermal temperatures in a high vacuum environment while positioning the two specimen groups symmetrically at equivalent neutron irradiating positions.

  2. Furnace assembly

    DOEpatents

    Panayotou, Nicholas F.; Green, Donald R.; Price, Larry S.

    1985-01-01

    A method of and apparatus for heating test specimens to desired elevated temperatures for irradiation by a high energy neutron source. A furnace assembly is provided for heating two separate groups of specimens to substantially different, elevated, isothermal temperatures in a high vacuum environment while positioning the two specimen groups symmetrically at equivalent neutron irradiating positions.

  3. Single Atom (Pd/Pt) Supported on Graphitic Carbon Nitride as an Efficient Photocatalyst for Visible-Light Reduction of Carbon Dioxide.

    PubMed

    Gao, Guoping; Jiao, Yan; Waclawik, Eric R; Du, Aijun

    2016-05-18

    Reducing carbon dioxide to hydrocarbon fuel with solar energy is significant for high-density solar energy storage and carbon balance. In this work, single atoms of palladium and platinum supported on graphitic carbon nitride (g-C3N4), i.e., Pd/g-C3N4 and Pt/g-C3N4, respectively, acting as photocatalysts for CO2 reduction were investigated by density functional theory calculations for the first time. During CO2 reduction, the individual metal atoms function as the active sites, while g-C3N4 provides the source of hydrogen (H*) from the hydrogen evolution reaction. The complete, as-designed photocatalysts exhibit excellent activity in CO2 reduction. HCOOH is the preferred product of CO2 reduction on the Pd/g-C3N4 catalyst with a rate-determining barrier of 0.66 eV, while the Pt/g-C3N4 catalyst prefers to reduce CO2 to CH4 with a rate-determining barrier of 1.16 eV. In addition, deposition of atom catalysts on g-C3N4 significantly enhances the visible-light absorption, rendering them ideal for visible-light reduction of CO2. Our findings open a new avenue of CO2 reduction for renewable energy supply. PMID:27116595

  4. Single Atom (Pd/Pt) Supported on Graphitic Carbon Nitride as an Efficient Photocatalyst for Visible-Light Reduction of Carbon Dioxide.

    PubMed

    Gao, Guoping; Jiao, Yan; Waclawik, Eric R; Du, Aijun

    2016-05-18

    Reducing carbon dioxide to hydrocarbon fuel with solar energy is significant for high-density solar energy storage and carbon balance. In this work, single atoms of palladium and platinum supported on graphitic carbon nitride (g-C3N4), i.e., Pd/g-C3N4 and Pt/g-C3N4, respectively, acting as photocatalysts for CO2 reduction were investigated by density functional theory calculations for the first time. During CO2 reduction, the individual metal atoms function as the active sites, while g-C3N4 provides the source of hydrogen (H*) from the hydrogen evolution reaction. The complete, as-designed photocatalysts exhibit excellent activity in CO2 reduction. HCOOH is the preferred product of CO2 reduction on the Pd/g-C3N4 catalyst with a rate-determining barrier of 0.66 eV, while the Pt/g-C3N4 catalyst prefers to reduce CO2 to CH4 with a rate-determining barrier of 1.16 eV. In addition, deposition of atom catalysts on g-C3N4 significantly enhances the visible-light absorption, rendering them ideal for visible-light reduction of CO2. Our findings open a new avenue of CO2 reduction for renewable energy supply.

  5. Structural state of expanded graphite prepared from intercalation compounds

    SciTech Connect

    Teplykh, A. E. Bogdanov, S. G.; Dorofeev, Yu. A.; Pirogov, A. N.; Skryabin, Yu. N.; Makotchenko, V. G.; Nazarov, A. S.; Fedorov, V. E.

    2006-12-15

    The structural state of nanocrystalline samples of expanded graphite is investigated using X-ray diffraction and neutron diffraction analyses. The expanded graphite samples are prepared by a rapid thermal decomposition of intercalation compounds of oxidized graphite based on fluorinated graphite, graphite oxide, and graphite aminofluoride. It is established that the main phase of expanded graphite belongs to the hexagonal crystal system (space group P6{sub 3}/mmc) and that carbon atoms in the structure occupy the 2b and 2c positions. The unit cell parameters and the unit cell volume in the structure of expanded graphite samples are larger than those in the structure of massive graphite.

  6. Intercalated graphite electrical conductors

    NASA Technical Reports Server (NTRS)

    Banks, B. A.

    1983-01-01

    For years NASA has wanted to reduce the weight of spacecraft and aircraft. Experiments are conducted to find a lightweight synthetic metal to replace copper. The subject of this paper, intercalated graphite, is such a material. Intercalated graphite is made by heating petroleum or coal to remove the hydrogen and to form more covalent bonds, thus increasing the molecular weight. The coal or petroleum eventually turns to pitch, which can then be drawn into a fiber. With continued heating the pitch-based fiber releases hydrogen and forms a carbon fiber. The carbon fiber, if heated sufficiently, becomes more organized in parallel layers of hexagonally arranged carbon atoms in the form of graphite. A conductor of intercalated graphite is potentially useful for spacecraft or aircraft applications because of its low weight.

  7. Determination of chromium in Mentha piperita L. and soil by graphite furnace atomic absorption spectrometry after sequential extraction and microwave-assisted acid digestion to assess potential bioavailability.

    PubMed

    Razić, Slavica; Dogo, Svetlana

    2010-01-01

    Analysis of chromium in Mentha piperita and the soil where it is cultivated was done. The capacity of soil for chromium immobilization and the capacity of M. piperita L., to control its uptake were analyzed by spiking the soil with standard solutions of Cr(III). For each concentration three acidity levels: natural, one unit below and one above its natural acidity (pH(2)=6, pH(1)=5 and pH(3)=7) were tested. Three-stage sequential extraction was performed (I stage: 1M ammonium-acetate, II stage: 0.1M hydroxylamine-chlorohydrate and III stage: 0.2/0.2M oxalic acid/ammonium-oxalate mixture). The chromium content in the extracts was obtained after the measurements by GFAAS. The results (expressed in mgL(-1)), at pH(1), pH(2) and pH(3), respectively, were as follows: I stage: 4.64-10.93, 0.79-5.78 and 0.26-5.26; II stage: 1.14-15.99, 0.76-20.31 and 0.67-20.64; III stage: 0.67-20.64, 19.17-100.76 and 19.17-116.05. A high potential of the soil for chromium immobilization was observed. In parallel, soil and plant samples were prepared by microwave-assisted acid digestion for total chromium determination. By analysis of SRMs (NIST SRM 2711 - Montana II Soil, NIST SRM 8433 - Corn Bran and NIST SRM 1547 - Peach Leaves) good recoveries (72.7-115.3%) were obtained. Additionally, iron and manganese oxides and hydroxides were recognized as matrix components of special importance for mobility of chromium species within a soil structures so, the determination of Mn and Fe was done too.

  8. Characterization of arsenic (V) and arsenic (III) in water samples using ammonium molybdate and estimation by graphite furnace atomic absorption spectroscopy.

    PubMed

    Sounderajan, Suvarna; Udas, A C; Venkataramani, B

    2007-10-01

    Arsenic (V) is known to form heteropolyacid with ammonium molybdate in acidic aqueous solutions, which can be quantitatively extracted into certain organic solvents. In the present work, 12-molybdoarsenic acid extracted in butan-1-ol is used for quantification of As (V). Total arsenic is estimated by converting arsenic (III) to arsenic (V) by digesting samples with concentrated nitric acid before extraction. Concentration of As (III) in the sample solutions could be calculated by the difference in total arsenic and arsenic (V). The characterization of arsenic was carried out by GFAAS using Pd as modifier. Optimization of the experimental conditions and instrumental parameters was investigated in detail. Recoveries of (90-110%) were obtained in the spiked samples. The detection limit was 0.2 microg l(-1). The proposed method was successfully applied for the determination of trace amount of arsenic (III) and arsenic (V) in process water samples. PMID:17761387

  9. Crystal Furnace

    NASA Technical Reports Server (NTRS)

    1985-01-01

    A "melt recharging" technique which eliminates the cooldown and heating periods in a crystal "growing" crucible, resulted from a Jet Propulsion Laboratory (JPL)/Kayex Corporation program. Previously, the cost of growing the silicon solar cells had been very high. The JPL/Kayex system improved productivity by serially growing crystals from the same crucible using a melt recharger which made it possible to add raw silicon to an operating crucible. An isolation value, developed by Kayex, allowed the hopper to be lowered into the crucible without disturbing the inert gas atmosphere. The resulting product, a CG6000 crystal growing furnace, has become the company's major product.

  10. Radiation heat transfer within an optical fiber draw tower furnace

    SciTech Connect

    Issa, J.; Jaluria, Y.; Polymeropoulos, C.E.; Yin, Z.

    1995-12-31

    Study of the thermal transport and material flow processes associated with the drawing of optical fiber in a graphite draw furnace requires modeling of the heat transfer from the furnace wall. Previous work has shown that accurate knowledge of the furnace heater element axial temperature distribution is essential for proper modeling of the radiative transfer process. The present work is aimed at providing this information, as well as generating a set of data for the study of radiation exchange in the furnace cavity. The experimental procedure involved measuring the centerline temperature distribution in graphite and fused silica rods inserted into an optical fiber draw tower furnace. The temperature measurements were then used along with a model for radiative-convective heat transfer in the furnace in order to obtain the furnace temperature profile. This is an inverse problem since the centerline temperature in the rod is known whereas the furnace thermal conditions are not. The results obtained showed that the furnace temperature distribution was independent of rod material and size. The shape of the computed temperature distributions suggest that they can be well represented by a Gaussian function.

  11. GRAPHITE EXTRUSIONS

    DOEpatents

    Benziger, T.M.

    1959-01-20

    A new lubricant for graphite extrusion is described. In the past, graphite extrusion mixtures have bcen composed of coke or carbon black, together with a carbonaceous binder such as coal tar pitch, and a lubricant such as petrolatum or a colloidal suspension of graphite in glycerin or oil. Sinee sueh a lubricant is not soluble in, or compatible with the biiider liquid, such mixtures were difficult to extrude, and thc formed pieees lacked strength. This patent teaches tbe use of fatty acids as graphite extrusion lubricants and definite improvemcnts are realized thereby since the fatty acids are soluble in the binder liquid.

  12. Diagnostics for a waste processing plasma arc furnace (invited) (abstract)a)

    NASA Astrophysics Data System (ADS)

    Woskov, P. P.

    1995-01-01

    Maintaining the quality of our environment has become an important goal of society. As part of this goal new technologies are being sought to clean up hazardous waste sites and to treat ongoing waste streams. A 1 MW pilot scale dc graphite electrode plasma arc furnace (Mark II) has been constructed at MIT under a joint program among Pacific Northwest Laboratory (PNL), MIT, and Electro-Pyrolysis, Inc. (EPI)c) for the remediation of buried wastes in the DOE complex. A key part of this program is the development of new and improved diagnostics to study, monitor, and control the entire waste remediation process for the optimization of this technology and to safeguard the environment. Continuous, real time diagnostics are needed for a variety of the waste process parameters. These parameters include internal furnace temperatures, slag fill levels, trace metals content in the off-gas stream, off-gas molecular content, feed and slag characterization, and off-gas particulate size, density, and velocity distributions. Diagnostics are currently being tested at MIT for the first three parameters. An active millimeter-wave radiometer with a novel, rotatable graphite waveguide/mirror antenna system has been implemented on Mark II for the measurement of surface emission and emissivity which can be used to determine internal furnace temperatures and fill levels. A microwave torch plasma is being evaluated for use as a excitation source in the furnace off-gas stream for continuous atomic emission spectroscopy of trace metals. These diagnostics should find applicability not only to waste remediation, but also to other high temperature processes such as incinerators, power plants, and steel plants.

  13. Modified Claus furnace

    SciTech Connect

    Reed, R.L.

    1986-03-11

    A Claus thermal conversion furnace is described comprising a primary furnace chamber, a burner in the primary furnace chamber, an oxidant containing gas supply inlet connected to the burner, a hydrogen sulfide containing gas supply conduit connected to the burner, an outlet extending from the furnace, a secondary reaction chamber in heat but not gas exchange relationship with the primary furnace chamber, the secondary reaction chamber extending through the length of the primary furnace chamber to a point in the outlet extending from the furnace, a hydrogen sulfide decomposing catalyst in the secondary reaction chamber, a hydrogen sulfide containing gas supply conduit connected to the secondary reaction chamber.

  14. Graphite Gamma Scan Results

    SciTech Connect

    Mark W. Drigert

    2014-04-01

    This report documents the measurement and data analysis of the radio isotopic content for a series of graphite specimens irradiated in the first Advanced Graphite Creep (AGC) experiment, AGC-1. This is the first of a series of six capsules planned as part of the AGC experiment to fully characterize the neutron irradiation effects and radiation creep behavior of current nuclear graphites. The AGC-1 capsule was irradiated in the Advanced Test Reactor (ATR) at INL at approximately 700 degrees C and to a peak dose of 7 dpa (displacements per atom). Details of the irradiation conditions and other characterization measurements performed on specimens in the AGC-1 capsule can be found in “AGC-1 Specimen Post Irradiation Data Report” ORNL/TM 2013/242. Two specimens from six different graphite types are analyzed here. Each specimen is 12.7 mm in diameter by 25.4 mm long. The isotope with the highest activity was 60Co. Graphite type NBG-18 had the highest content of 60Co with an activity of 142.89 µCi at a measurement distance of 47 cm.

  15. Effectiveness of the statistical potential in the description of fermions in a worm-algorithm path-integral Monte Carlo simulation of 3He atoms placed on a 4He layer adsorbed on graphite.

    PubMed

    Ghassib, Humam B; Sakhel, Asaad R; Obeidat, Omar; Al-Oqali, Amer; Sakhel, Roger R

    2012-01-01

    We demonstrate the effectiveness of a statistical potential (SP) in the description of fermions in a worm-algorithm path-integral Monte Carlo simulation of a few 3He atoms floating on a 4He layer adsorbed on graphite. The SP in this work yields successful results, as manifested by the clusterization of 3He, and by the observation that the 3He atoms float on the surface of 4He. We display the positions of the particles in 3D coordinate space, which reveal clusterization of the 3He component. The correlation functions are also presented, which give further evidence for the clusterization.

  16. Designing modern furnace cooling systems

    NASA Astrophysics Data System (ADS)

    Merry, J.; Sarvinis, J.; Voermann, N.

    2000-02-01

    An integrated multidisciplinary approach to furnace design that considers the interdependence between furnace cooling elements and other furnace systems, such as binding, cooling water, and instrumentation, is necessary to achieve maximum furnace production and a long refractory life. The retrofit of the BHP Hartley electric furnace and the Kidd Creek copper converting furnace are successful examples of an integrated approach to furnace cooling design.

  17. Spent graphite fuel element processing

    SciTech Connect

    Holder, N.D.; Olsen, C.W.

    1981-07-01

    The Department of Energy currently sponsors two programs to demonstrate the processing of spent graphite fuel elements. General Atomic in San Diego operates a cold pilot plant to demonstrate the processing of both US and German high-temperature reactor fuel. Exxon Nuclear Idaho Company is demonstrating the processing of spent graphite fuel elements from Rover reactors operated for the Nuclear Rocket Propulsion Program. This work is done at Idaho National Engineering Laboratory, where a hot facility is being constructed to complete processing of the Rover fuel. This paper focuses on the graphite combustion process common to both programs.

  18. Graphite Formation in Cast Iron

    NASA Technical Reports Server (NTRS)

    Stefanescu, D. M.

    1985-01-01

    In the first phase of the project it was proven that by changing the ratio between the thermal gradient and the growth rate for commercial cast iron samples solidifying in a Bridgman type furnace, it is possible to produce all types of graphite structures, from flake to spheroidal, and all types of matrices, from ferritic to white at a certain given level of cerium. KC-135 flight experiments have shown that in a low-gravity environment, no flotation occurs even in spheroidal graphite cast irons with carbon equivalent as high as 5%, while extensive graphite flotation occurred in both flake and spheroidal graphite cast irons, in high carbon samples solidified in a high gravity environment. This opens the way for production of iron-carbon composite materials, with high carbon content (e.g., 10%) in a low gravity environment. By using KC-135 flights, the influence of some basic elements on the solidification of cast iron will be studied. The mechanism of flake to spheroidal graphite transition will be studied, by using quenching experiments at both low and one gravity for different G/R ratios.

  19. The effect of heating power on impurity formation and transport during the holding phase in a Bridgman furnace for directional solidification of multi-crystalline silicon

    NASA Astrophysics Data System (ADS)

    Ellingsen, Kjerstin; Lindholm, Dag; M`Hamdi, Mohammed

    2016-06-01

    Oxygen and carbon are the most common impurities in multi-crystalline silicon. The general mechanism for formation and transport of O and C in the solidification furnace is as follows: oxygen from the silica crucible comes into the melt and combines with a silicon atom and evaporates at the gas/melt interface in the form of silicon oxide (SiO). Argon inert gas, injected into the furnace chamber, carries the SiO to the hot graphite fixtures, where it reacts with carbon to form carbon monoxide (CO) and silicon carbide (SiC). CO is carried by the gas to the melt free surface, where it dissociates into carbon and oxygen. Finally, during solidification oxygen and carbon are incorporated into the crystal. A global furnace model accounting for heat transfer, melt flow, gas flow and impurity transport has been applied to investigate the oxygen and carbon formation and transport in a vertical Bridgman furnace during the holding phase when the furnace is at its hottest. A case study is performed to investigate the effect of the applied heating power on the carbon and oxygen concentrations in the melt prior to solidification.

  20. Graphite Revisited

    NASA Astrophysics Data System (ADS)

    Draine, B. T.

    2016-11-01

    Laboratory measurements are used to constrain the dielectric tensor for graphite, from microwave to X-ray frequencies. The dielectric tensor is strongly anisotropic even at X-ray energies. The discrete dipole approximation is employed for accurate calculations of absorption and scattering by single-crystal graphite spheres and spheroids. For randomly oriented single-crystal grains, the so-called 1/3{--}2/3 approximation for calculating absorption and scattering cross sections is exact in the limit a/λ \\to 0 and provides better than ∼10% accuracy in the optical and UV even when a/λ is not small, but becomes increasingly inaccurate at infrared wavelengths, with errors as large as ∼40% at λ =10 μ {{m}}. For turbostratic graphite grains, the Bruggeman and Maxwell Garnett treatments yield similar cross sections in the optical and ultraviolet, but diverge in the infrared, with predicted cross sections differing by over an order of magnitude in the far-infrared. It is argued that the Maxwell Garnett estimate is likely to be more realistic, and is recommended. The out-of-plane lattice resonance of graphite near 11.5 μm may be observable in absorption with the MIRI spectrograph on James Webb Space Telescope. Aligned graphite grains, if present in the interstellar medium, could produce polarized X-ray absorption and polarized X-ray scattering near the carbon K edge.

  1. Molecular absorption spectrometry in flames and furnaces: a review.

    PubMed

    Butcher, David J

    2013-12-01

    Molecular absorption spectrometry (MAS), originally developed in the 1970s, is a technique to determine non-metals in flames and graphite furnaces by monitoring the absorbance of diatomic molecules. Early studies employed low resolution instruments designed for line source atomic absorption, which provided a limited choice of analytical wavelengths, insufficient spectral resolution, and spectral interferences. However, the development of high-resolution continuum source atomic absorption spectrometry (HR-CS AAS) instrumentation has allowed the analysis of challenging samples for non-metals as well as some difficult elements to determine by AAS, such as aluminum and phosphorus. In this review, theory and analytical considerations for MAS are discussed. The principles and limitations of low resolution MAS are described, along with its applications. HR-CS AAS instrumentation is reviewed, emphasizing performance characteristics most relevant for MAS. Applications of flame and HR-CS GFMAS are reviewed, highlighting the most significant work to date. The paper concludes with an evaluation of the enhanced analytical capabilities provided by HR-CS MAS.

  2. Heat treatment furnace

    SciTech Connect

    Seals, Roland D; Parrott, Jeffrey G; DeMint, Paul D; Finney, Kevin R; Blue, Charles T

    2014-10-21

    A furnace heats through both infrared radiation and convective air utilizing an infrared/purge gas design that enables improved temperature control to enable more uniform treatment of workpieces. The furnace utilizes lamps, the electrical end connections of which are located in an enclosure outside the furnace chamber, with the lamps extending into the furnace chamber through openings in the wall of the chamber. The enclosure is purged with gas, which gas flows from the enclosure into the furnace chamber via the openings in the wall of the chamber so that the gas flows above and around the lamps and is heated to form a convective mechanism in heating parts.

  3. Reaction rates of graphite with ozone measured by etch decoration

    NASA Technical Reports Server (NTRS)

    Hennig, G. R.; Montet, G. L.

    1968-01-01

    Etch-decoration technique of detecting vacancies in graphite has been used to determine the reaction rates of graphite with ozone in the directions parallel and perpendicular to the layer planes. It consists essentially of peeling single atom layers off graphite crystals without affecting the remainder of the crystal.

  4. Applications Of Graphite Fluoride Fibers In Outer Space

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheng; Long, Martin; Dever, Therese

    1993-01-01

    Report characterizes graphite fluoride fibers made from commercially available graphitized carbon fibers and discusses some potential applications of graphite fluoride fibers in outer space. Applications include heat-sinking printed-circuit boards, solar concentrators, and absorption of radar waves. Other applications based on exploitation of increased resistance to degradation by atomic oxygen, present in low orbits around Earth.

  5. Benchmarking thermal neutron scattering in graphite

    NASA Astrophysics Data System (ADS)

    Zhou, Tong

    A Slowing-Down-Time experiment was designed and performed at the Oak Ridge National Laboratory (ORNL) by using the Oak Ridge Electron Linear Accelerator (ORELA) as a neutron source to study the neutron thermalization in graphite at room and higher temperatures. The MCNP5 code was utilized to simulate the detector responses and help optimize the experimental design including the size of the graphite assembly, furnace, shielding system and detector position. To facilitate such analysis, MCNP5 version 1.30 was modified to enable perturbation calculation using point detector type tallies. By using the modified MCNP5 code, the sensitivity of the experimental models to the graphite total thermal neutron cross-sections was studied to optimize the design of the experiment. Measurements of slowing-down-time spectrum in graphite were performed at room temperature for a 70x70x70 cm graphite pile by using a Li-6 scintillator and a U-235 fission counter at different locations. The measurements were directly compared to Monte Carlo simulations that use different graphite thermal neutron scattering cross-section libraries. Simulations based on the ENDF/B-VI graphite library were found to have a 30%-40% disagreement with the measurements. In addition to the graphite SDT experiment, which provided the data in the energy region above the graphite Bragg-cutoff energy, transmission experiments were performed for different types of graphite samples using the NIST 8.9 A beam (located at NG-6) to investigating the energy region below the Bragg-cutoff energy. Measurements confirmed that reactor grade graphite, which is a two phase material (crystalline graphite and binder (amorphous-like) carbon), has different thermal neutron scattering cross section from pyrolytic graphite (crystalline graphite). The experiments presented in this work compliment each other and provide an experimental data set which can be used to benchmark graphite thermal neutron scattering cross section libraries that

  6. Evaluation of lining/cooling systems for blast furnace bosh and stack

    SciTech Connect

    Tijhuis, G.J.

    1996-08-01

    Different blast furnace linings and cooling systems are used throughout the world. Most furnaces have either a stave or plate cooling system. Some furnaces have an externally cooled shell using panel cooling. Refractories applied include alumina, silicon carbide, carbon, graphite and semi-graphite. The performance of a lining/cooling system does not only depend on the design, but also on the type of furnace operation, burden composition, etc. To compare one lining/cooling system with another requires that all these factors are taken into account. A refractory lining and/or cooling system may fail due to several mechanisms. The attack mechanism may be related to temperature, stress, chemical reactions, abrasion or a combination of these factors. Hoogovens` experience with modern blast furnace operations indicates that failure due to temperature fluctuations is the most important factor. The behavior of lining/cooling systems under several conditions has been discussed. High temperatures and severe temperature fluctuations are particularly important.

  7. Laser excited analytical atomic and ionic fluorescence in flames, furnaces and inductively coupled plasmas—II. Fluorescence characteristics and detection limits for fourteen elements

    NASA Astrophysics Data System (ADS)

    Human, H. G. C.; Omenetto, N.; Cavalli, P.; Rossi, G.

    An account is given of the analytical characteristics of the elements Al, B, Ba, Ga, Mo, Pb, Si, Sn, Ti, Tl, V, Y, Zr and U in atomic and ionic fluorescence spectrometry using an excimer (XeCl) pumped pulsed dye laser as excitation source. The inductively coupled argon plasma was mainly used as atom/ion reservoir. The detection limits were found to be in the range 0.4-20 ng ml -1, improving "standard" tabulated ICP emission values by factors between 1 and 66. The separated air-acetylene flame and the carbon rod were also used as atom reservoir for a few volatile elements, the practical detection limit for lead with the latter being 6 × 10 -15g. The advantages and disadvantages of such an analytical system are discussed, one of the main advantages being certainly the high spectral selectivity of the technique.

  8. Structural change of graphite during electron irradiation

    SciTech Connect

    Koike, J. . Dept. of Mechanical Engineering); Pedraza, D.F. )

    1992-01-01

    Highly oriented pyrolytic graphite was irradiated at room temperature with 300-keV electrons. High resolution transmission electron microscopy and electron energy loss spectroscopy were employed to study the structure of electron-irradiated graphite. Results consistently indicated absence of long-range order periodicity in the basal plane, and loose retention of the c-axis periodicity. Structure was modeled based on a mixture of sixfold and non-sixfold atom rings. Formation of non-sixfold atom rings was related to the observed buckling and discontinuity of the original graphite basal plane.

  9. Structural change of graphite during electron irradiation

    SciTech Connect

    Koike, J.; Pedraza, D.F.

    1992-12-31

    Highly oriented pyrolytic graphite was irradiated at room temperature with 300-keV electrons. High resolution transmission electron microscopy and electron energy loss spectroscopy were employed to study the structure of electron-irradiated graphite. Results consistently indicated absence of long-range order periodicity in the basal plane, and loose retention of the c-axis periodicity. Structure was modeled based on a mixture of sixfold and non-sixfold atom rings. Formation of non-sixfold atom rings was related to the observed buckling and discontinuity of the original graphite basal plane.

  10. Thermally exfoliated graphite oxide

    NASA Technical Reports Server (NTRS)

    Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Abdala, Ahmed (Inventor)

    2011-01-01

    A modified graphite oxide material contains a thermally exfoliated graphite oxide with a surface area of from about 300 sq m/g to 2600 sq m/g, wherein the thermally exfoliated graphite oxide displays no signature of the original graphite and/or graphite oxide, as determined by X-ray diffraction.

  11. Electromelt furnace evaluation

    SciTech Connect

    Reimann, G.A.; Welch, J.M.

    1981-09-01

    An electromelt furnace was designed, built, and operated at the Idaho National Engineering Laboratory to demonstrate the suitability of this equipment for large-scale processing of radioactive wastes in iron-enriched basalt. Several typical waste compositions were melted and cast. The furnace was disassembled and the components evaluated. Calcines and fluorides attacked the furnace lining, unoxidized metals accumulated under the slag, and electrode attrition was high.

  12. Determination of selected elements in whole coal and in coal ash from the eight argonne premium coal samples by atomic absorption spectrometry, atomic emission spectrometry, and ion-selective electrode

    USGS Publications Warehouse

    Doughten, M.W.; Gillison, J.R.

    1990-01-01

    Methods for the determination of 24 elements in whole coal and coal ash by inductively coupled argon plasma-atomic emission spectrometry, flame, graphite furnace, and cold vapor atomic absorption spectrometry, and by ion-selective electrode are described. Coal ashes were analyzed in triplicate to determine the precision of the methods. Results of the analyses of NBS Standard Reference Materials 1633, 1633a, 1632a, and 1635 are reported. Accuracy of the methods is determined by comparison of the analysis of standard reference materials to their certified values as well as other values in the literature.

  13. EXTERIOR VIEW, BLAST FURNACE NO. 3 (JANE FURNACE) CENTER, NO. ...

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

    EXTERIOR VIEW, BLAST FURNACE NO. 3 (JANE FURNACE) CENTER, NO. 3 CAST HOUSE TO THE LEFT, WEST ORE BRIDGE TO THE RIGHT. - Pittsburgh Steel Company, Monessen Works, Blast Furnace No. 3, Donner Avenue, Monessen, Westmoreland County, PA

  14. [The electric furnace of Henri Moissan at one hundred years: connection with the electric furnace, the solar furnace, the plasma furnace?].

    PubMed

    Royère, C

    1999-03-01

    The trace of Henri Moissan's pioneer work 100 years ago is clearly evidenced by an overview of achievements in high temperature devices; 1987: "Le four électrique" by Henri Moissan; 1948-1952: "High temperature heating in a cavity rotary kiln using focusing of solar radiation" by Félix Trombe; 1962: "The cavity rotary kiln using focused solar radiation jointly with a plasma gun" by Marc Foëx; 1970: "The rotary kiln with two plasma guns and arc transfer" by Marc Foëx; 1984: "The plasma furnace" by Electricité de France (EDF) at Renardières; 1997: "The plasma furnace" by the Atomic Energy Center (CEA) at Cadarache, the VULCANO program. The first part of this contribution is devoted to Henri Moissan. Re-reading his early book on the electric furnace, especially the first chapter and the sections on silica, carbon vapor and experiments performed in casting molten metal--the conclusions are outstanding--provides modern readers with an amazing insight into future developments. The last two parts are devoted to Félix Trombe and Marc Foëx, tracing the evolution of high temperature cavity processus leading to the solar furnace and the present day plasma furnace at the CEA. Focus is placed on research conducted by the French National Center for Scientific Research (CNRS) with the solar and plasma furnaces at Odeillo. The relationships with Henri Moissan's early work are amazing, offering a well deserved homage to this pioneer researcher.

  15. Bridged graphite oxide materials

    NASA Technical Reports Server (NTRS)

    Herrera-Alonso, Margarita (Inventor); McAllister, Michael J. (Inventor); Aksay, Ilhan A. (Inventor); Prud'homme, Robert K. (Inventor)

    2010-01-01

    Bridged graphite oxide material comprising graphite sheets bridged by at least one diamine bridging group. The bridged graphite oxide material may be incorporated in polymer composites or used in adsorption media.

  16. A thin-walled metallic hollow cathode as an atomizer for Zeeman atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Ganeyev, A. A.; Sholupov, S. E.

    1998-03-01

    A new kind of glow discharge atomizer, a thin-walled metallic hollow cathode (TMHC) combined with Zeeman atomic absorption spectrometry using high frequency modulated light polarization (ZAAS-HFM), is studied. A theoretically suggested, and experimentally confirmed, model of the atom confinement in the TMHC yields the appearance of the diffusion traps for atoms at both ends of the cathode, which increases the residence time of the analyte atoms in the analysis volume. The high atomization efficiency in the glow discharge atomizer (caused by the ionic-thermal mechanism of sputtering) and the high selectivity of ZAAS-HFM are demonstrated in the analysis of complex matrix samples such as whole blood and urine. The analytical system TMHC + ZAAS-HFM is characterized by low detection limits, which are comparable to those of graphite furnace atomic absorption spectrometry (GFAAS). Owing to its rather low average power consumption (30-50 W) the TMHC can be used in a portable and mobile spectrometer, and is therefore suitable for the in situ analysis of various sample materials.

  17. Advanced steel reheat furnace

    SciTech Connect

    Moyeda, D.; Sheldon, M.; Koppang, R.; Lanyi, M.; Li, X.; Eleazer, B.

    1997-10-01

    Energy and Environmental Research Corp. (EER) under a contract from the Department of Energy is pursuing the development and demonstration of an Advanced Steel Reheating Furnace. This paper reports the results of Phase 1, Research, which has evaluated an advanced furnace concept incorporating two proven and commercialized technologies previously applied to other high temperature combustion applications: EER`s gas reburn technology (GR) for post combustion NOx control; and Air Product`s oxy-fuel enrichment air (OEA) for improved flame heat transfer in the heating zones of the furnace. The combined technologies feature greater production throughput with associated furnace efficiency improvements; lowered NOx emissions; and better control over the furnace atmosphere, whether oxidizing or reducing, leading to better control over surface finish.

  18. Ferric chloride graphite intercalation compounds prepared from graphite fluoride

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh

    1994-01-01

    The reaction between graphite fluoride and ferric chloride was observed in the temperature range of 300 to 400 C. The graphite fluorides used for this reaction have an sp3 electronic structure and are electrical insulators. They can be made by fluorinating either carbon fibers or powder having various degrees of graphitization. Reaction is fast and spontaneous and can occur in the presence of air. The ferric chloride does not have to be predried. The products have an sp2 electronic structure and are electrical conductors. They contain first stage FeCl3 intercalated graphite. Some of the products contain FeCl2*2H2O, others contain FeF3 in concentrations that depend on the intercalation condition. The graphite intercalated compounds (GIC) deintercalated slowly in air at room temperature, but deintercalated quickly and completely at 370 C. Deintercalation is accompanied by the disappearing of iron halides and the formation of rust (hematite) distributed unevenly on the fiber surface. When heated to 400 C in pure N2 (99.99 vol %), this new GIC deintercalates without losing its molecular structure. However, when the compounds are heated to 800 C in quartz tube, they lost most of its halogen atoms and formed iron oxides (other than hematite), distributed evenly in or on the fiber. This iron-oxide-covered fiber may be useful in making carbon-fiber/ceramic-matrix composites with strong bonding at the fiber-ceramic interface.

  19. General view of blast furnace plant, with blast furnace "A" ...

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

    General view of blast furnace plant, with blast furnace "A" (built in 1907) to the left; in the foreground is the turbo-blower and blast furnace gas-powered electric generating station (built in 1919), looking northwest - Bethlehem Steel Corporation, South Bethlehem Works, Blast Furnace "A", Along Lehigh River, North of Fourth Street, West of Minsi Trail Bridge, Bethlehem, Northampton County, PA

  20. INTERIOR VIEW SHOWING FURNACE KEEPER OBSERVING FURNACE THROUGH BLUE GLASS ...

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

    INTERIOR VIEW SHOWING FURNACE KEEPER OBSERVING FURNACE THROUGH BLUE GLASS EVERY TWENTY MINUTES TO DETERMINE SIZE AND TEXTURE OF BATCH AND OTHER VARIABLES. FAN IN FRONT COOLS WORKERS AS THEY CONDUCT REPAIRS. FURNACE TEMPERATURE AT 1572 DEGREES FAHRENHEIT. - Chambers-McKee Window Glass Company, Furnace No. 2, Clay Avenue Extension, Jeannette, Westmoreland County, PA

  1. Preparation of graphitic articles

    DOEpatents

    Phillips, Jonathan; Nemer, Martin; Weigle, John C.

    2010-05-11

    Graphitic structures have been prepared by exposing templates (metal, metal-coated ceramic, graphite, for example) to a gaseous mixture that includes hydrocarbons and oxygen. When the template is metal, subsequent acid treatment removes the metal to yield monoliths, hollow graphitic structures, and other products. The shapes of the coated and hollow graphitic structures mimic the shapes of the templates.

  2. General purpose rocket furnace

    NASA Technical Reports Server (NTRS)

    Aldrich, B. R.; Whitt, W. D. (Inventor)

    1979-01-01

    A multipurpose furnace for space vehicles used for material processing experiments in an outer space environment is described. The furnace contains three separate cavities designed to process samples of the widest possible range of materials and thermal requirements. Each cavity contains three heating elements capable of independent function under the direction of an automatic and programmable control system. A heat removable mechanism is also provided for each cavity which operates in conjunction with the control system for establishing an isothermally heated cavity or a wide range of thermal gradients and cool down rates. A monitoring system compatible with the rocket telemetry provides furnace performance and sample growth rate data throughout the processing cycle.

  3. Continuous ring furnaces

    SciTech Connect

    De Stefani, G.; Genevois, J.L.; Paolo, P.

    1981-01-06

    A smoke conducting apparatus for use particularly with continuous ring furnaces (e.g., Hoffman furnaces) wherein each furnace chamber is connected to the smoke channel, the latter being a metal pipe inclined slightly from horizontal and provided with one or more traps along the length of its bottom surface, each trap containing a removable receptacle, and heating means being disposed along the bottom of the channel to fluidize tarry deposits of combustion products so that such deposits will flow by gravity into the removable receptacle.

  4. High Temperature Transparent Furnace Development

    NASA Technical Reports Server (NTRS)

    Bates, Stephen C.

    1997-01-01

    This report describes the use of novel techniques for heat containment that could be used to build a high temperature transparent furnace. The primary objective of the work was to experimentally demonstrate transparent furnace operation at 1200 C. Secondary objectives were to understand furnace operation and furnace component specification to enable the design and construction of a low power prototype furnace for delivery to NASA in a follow-up project. The basic approach of the research was to couple high temperature component design with simple concept demonstration experiments that modify a commercially available transparent furnace rated at lower temperature. A detailed energy balance of the operating transparent furnace was performed, calculating heat losses through the furnace components as a result of conduction, radiation, and convection. The transparent furnace shells and furnace components were redesigned to permit furnace operation at at least 1200 C. Techniques were developed that are expected to lead to significantly improved heat containment compared with current transparent furnaces. The design of a thermal profile in a multizone high temperature transparent furnace design was also addressed. Experiments were performed to verify the energy balance analysis, to demonstrate some of the major furnace improvement techniques developed, and to demonstrate the overall feasibility of a high temperature transparent furnace. The important objective of the research was achieved: to demonstrate the feasibility of operating a transparent furnace at 1200 C.

  5. Space station furnace facility

    NASA Astrophysics Data System (ADS)

    Cobb, Sharon D.; Lehoczky, Sandor L.

    1996-07-01

    The Space Shuttle Furnace Facility (SSFF) is the modular, multi-user scientific instrumentation for conducting materials research in the reduced gravity environment of the International Space Station. The facility is divided into the Core System and two Instrument Racks. The core system provides the common electrical and mechanical support equipment required to operate experiment modules (EMs). The EMs are investigator unique furnaces or apparatus designed to accomplish specific science investigations. Investigations are peer selected every two years from proposals submitted in response to National Aeronautics and Space Administration Research Announcements. The SSFF Core systems are designed to accommodate an envelope of eight types of experiment modules. The first two modules to be developed for the first instrument rack include a high temperature gradient furnace with quench, and a low temperature gradient furnace. A new EM is planned to be developed every two years.

  6. Paired Straight Hearth Furnace

    SciTech Connect

    2009-04-01

    This factsheet describes a research project whose goals are to design, develop, and evaluate the scalability and commercial feasibility of the PSH Paired Straight Hearth Furnace alternative ironmaking process.

  7. Adsorption of lead over graphite oxide.

    PubMed

    Olanipekun, Opeyemi; Oyefusi, Adebola; Neelgund, Gururaj M; Oki, Aderemi

    2014-01-24

    The adsorption efficiency and kinetics of removal of lead in presence of graphite oxide (GO) was determined using the Atomic Absorption Spectrophotometer (AAS). The GO was prepared by the chemical oxidation of graphite and characterized using FTIR, SEM, TGA and XRD. The adsorption efficiency of GO for the solution containing 50, 100 and 150 ppm of Pb(2+) was found to be 98%, 91% and 71% respectively. The adsorption ability of GO was found to be higher than graphite. Therefore, the oxidation of activated carbon in removal of heavy metals may be a viable option to reduce pollution in portable water.

  8. High temperature furnace

    DOEpatents

    Borkowski, Casimer J.

    1976-08-03

    A high temperature furnace for use above 2000.degree.C is provided that features fast initial heating and low power consumption at the operating temperature. The cathode is initially heated by joule heating followed by electron emission heating at the operating temperature. The cathode is designed for routine large temperature excursions without being subjected to high thermal stresses. A further characteristic of the device is the elimination of any ceramic components from the high temperature zone of the furnace.

  9. Structure and functionality of bromine doped graphite.

    PubMed

    Hamdan, Rashid; Kemper, A F; Cao, Chao; Cheng, H P

    2013-04-28

    First-principles calculations are used to study the enhanced in-plane conductivity observed experimentally in Br-doped graphite, and to study the effect of external stress on the structure and functionality of such systems. The model used in the numerical calculations is that of stage two doped graphite. The band structure near the Fermi surface of the doped systems with different bromine concentrations is compared to that of pure graphite, and the charge transfer between carbon and bromine atoms is analyzed to understand the conductivity change along different high symmetry directions. Our calculations show that, for large interlayer separation between doped graphite layers, bromine is stable in the molecular form (Br2). However, with increased compression (decreased layer-layer separation) Br2 molecules tend to dissociate. While in both forms, bromine is an electron acceptor. The charge exchange between the graphite layers and Br atoms is higher than that with Br2 molecules. Electron transfer to the Br atoms increases the number of hole carriers in the graphite sheets, resulting in an increase of conductivity. PMID:23635160

  10. Structure and functionality of bromine doped graphite

    SciTech Connect

    Hamdan, Rashid; Kemper, A. F.; Cao Chao; Cheng, H. P.

    2013-04-28

    First-principles calculations are used to study the enhanced in-plane conductivity observed experimentally in Br-doped graphite, and to study the effect of external stress on the structure and functionality of such systems. The model used in the numerical calculations is that of stage two doped graphite. The band structure near the Fermi surface of the doped systems with different bromine concentrations is compared to that of pure graphite, and the charge transfer between carbon and bromine atoms is analyzed to understand the conductivity change along different high symmetry directions. Our calculations show that, for large interlayer separation between doped graphite layers, bromine is stable in the molecular form (Br{sub 2}). However, with increased compression (decreased layer-layer separation) Br{sub 2} molecules tend to dissociate. While in both forms, bromine is an electron acceptor. The charge exchange between the graphite layers and Br atoms is higher than that with Br{sub 2} molecules. Electron transfer to the Br atoms increases the number of hole carriers in the graphite sheets, resulting in an increase of conductivity.

  11. Structure and functionality of bromine doped graphite.

    PubMed

    Hamdan, Rashid; Kemper, A F; Cao, Chao; Cheng, H P

    2013-04-28

    First-principles calculations are used to study the enhanced in-plane conductivity observed experimentally in Br-doped graphite, and to study the effect of external stress on the structure and functionality of such systems. The model used in the numerical calculations is that of stage two doped graphite. The band structure near the Fermi surface of the doped systems with different bromine concentrations is compared to that of pure graphite, and the charge transfer between carbon and bromine atoms is analyzed to understand the conductivity change along different high symmetry directions. Our calculations show that, for large interlayer separation between doped graphite layers, bromine is stable in the molecular form (Br2). However, with increased compression (decreased layer-layer separation) Br2 molecules tend to dissociate. While in both forms, bromine is an electron acceptor. The charge exchange between the graphite layers and Br atoms is higher than that with Br2 molecules. Electron transfer to the Br atoms increases the number of hole carriers in the graphite sheets, resulting in an increase of conductivity.

  12. Precise determination of the absolute isotopic abundance ratio and the atomic weight of chlorine in three international reference materials by the positive thermal ionization mass spectrometer-Cs2Cl+-graphite method.

    PubMed

    Wei, Hai-Zhen; Jiang, Shao-Yong; Xiao, Ying-Kai; Wang, Jun; Lu, Hai; Wu, Bin; Wu, He-Pin; Li, Qing; Luo, Chong-Guang

    2012-12-01

    Because the variation in chlorine isotopic abundances of naturally occurring chlorine bearing substances is significant, the IUPAC Inorganic Chemistry Division, Commission on Isotopic Abundances and Atomic Weights (CIAAW-IUPAC) decided that the uncertainty of atomic weight of chlorine (A(r)(Cl)) should be increased so that the implied range was related to terrestrial variability in 1999 (Coplen, T. B. Atomic weights of the elements 1999 (IUPAC Technical Report), Pure Appl. Chem.2001, 73(4), 667-683; and then, it emphasized that the standard atomic weights of ten elements including chlorine were not constants of nature but depend upon the physical, chemical, and nuclear history of the materials in 2009 (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396). According to the agreement by CIAAW that an atomic weight could be defined for one specified sample of terrestrial origin (Wieser, M. E.; Coplen, T. B. Pure Appl. Chem.2011, 83(2), 359-396), the absolute isotope ratios and atomic weight of chlorine in standard reference materials (NIST 975, NIST 975a, ISL 354) were accurately determined using the high-precision positive thermal ionization mass spectrometer (PTIMS)-Cs(2)Cl(+)-graphite method. After eliminating the weighing error caused from evaporation by designing a special weighing container and accurately determining the chlorine contents in two highly enriched Na(37)Cl and Na(35)Cl salts by the current constant coulometric titration, one series of gravimetric synthetic mixtures prepared from two highly enriched Na(37)Cl and Na(35)Cl salts was used to calibrate two thermal ionization mass spectrometers in two individual laboratories. The correction factors (i.e., K(37/35) = R(37/35meas)/R(37/35calc)) were obtained from five cycles of iterative calculations on the basis of calculated and determined R((37)Cl/(35)Cl) values in gravimetric synthetic mixtures. The absolute R((37)Cl/(35)Cl) ratios for NIST SRM 975, NIST 975a, and ISL 354 by the precise

  13. A rapid method for the determination of Pb, Cu and Sn in dried tomato sauces with solid sampling electrothermal atomic absorption spectrometry.

    PubMed

    Baysal, Asli; Ozcan, Mustafa; Akman, Suleyman

    2011-06-01

    In this work, lead, copper and tin were determined in tomato sauces by solid sampling graphite furnace atomic absorption spectrometry (SS-GFAAS) and the results were compared with those obtained after sample digestion. The tomato sauce samples were dried at 90 °C for 12 h and directly introduced into the graphite furnace by means of solid auto sampler. Alternatively the dried samples were digested with concentrated HNO(3) (65%) and pipetted into the graphite furnace. After the optimization of the experimental parameters, the average lead, copper and tin concentrations found by the solid sampling and digestion methods in 10 different kinds of tomato sauce samples were not significantly different at 95% confidence level. For solid sampling technique, the limits of detection (LOD) for Cu, Sn and Pb were 10.4, 3.2 and 0.4 ng/g, respectively. Whereas for digestion method, for Cu, Sn and Pb were 6.7, 2.7 and 0.3 ng/g, respectively. The proposed solid sampling technique was fast, simple, the risks of contamination and analyte loss were low.

  14. Laser-excited atomic fluorescence spectrometry in a pressure-controlled electrothermal atomizer.

    PubMed

    Lonardo, R F; Yuzefovsky, A I; Irwin, R L; Michel, R G

    1996-02-01

    A theoretical model was developed to describe the loss of analyte atoms in graphite furnaces during atomization. The model was based on two functions, one that described the supply of analyte by vaporization, and another that described the removal of the analyte by diffusion. Variation in working pressure was shown to affect the competition between these two processes. Optimal atomization efficiency was predicted to occur at a pressure where the supply of the analyte was maximized, and gas phase interactions between the analyte and matrix were minimized. Experiments to test the model included the direct determination of phosphorus and tellurium in nickel alloys and of cobalt in glass. In all cases, reduction in working pressure from atmospheric pressure to 7 Pa decreased sensitivity by 2 orders of magnitude, but improved temporal peak shape. For the atomization of tellurium directly from a solid nickel alloy, and the atomization of cobalt from an aqueous solution, no change in sensitivity was observed as the working pressure was reduced from atmospheric pressure to approximately 70 kPa. If a reduction in working pressure affected only the diffusion of the analyte, poorer sensitivity should have been obtained. Only a commensurate increase in analyte vaporization could account for maintained sensitivity at lower working pressures. Overall, analyte vaporization was not dramatically improved at reduced working pressures, and maximum atomization efficiency was found to occur near atmospheric pressure. PMID:8712359

  15. High gradient directional solidification furnace

    NASA Technical Reports Server (NTRS)

    Aldrich, B. R.; Whitt, W. D. (Inventor)

    1985-01-01

    A high gradient directional solidification furnace is disclosed which includes eight thermal zones throughout the length of the furnace. In the hot end of the furnace, furnace elements provide desired temperatures. These elements include Nichrome wire received in a grooved tube which is encapsulated y an outer alumina core. A booster heater is provided in the hot end of the furnace which includes toroidal tungsten/rhenium wire which has a capacity to put heat quickly into the furnace. An adiabatic zone is provided by an insulation barrier to separate the hot end of the furnace from the cold end. The old end of the furnace is defined by additional heating elements. A heat transfer plate provides a means by which heat may be extracted from the furnace and conducted away through liquid cooled jackets. By varying the input of heat via the booster heater and output of heat via the heat transfer plate, a desired thermal gradient profile may be provided.

  16. Better VPS Fabrication of Crucibles and Furnace Cartridges

    NASA Technical Reports Server (NTRS)

    Holmes, Richard R.; Zimmerman, Frank R.; O'Dell, J. Scott; McKechnie, Timothy N.

    2003-01-01

    An experimental investigation has shown that by (1) vacuum plasma spraying (VPS) of suitable refractory metal alloys on graphite mandrels, and then (2) heat-treating the VPS alloy deposits under suitable conditions, it is possible to fabricate improved crucibles and furnace cartridges that could be used at maximum temperatures between 1,400 and 1,600 C and that could withstand chemical attack by the materials to be heated in the crucibles and cartridges. Taken by itself, the basic concept of fabricating furnace cartridges by VPS of refractory materials onto graphite mandrels is not new; taken by itself, the basic concept of heat treatment of VPS deposits for use as other than furnace cartridges is also not new; however, prior to this investigation, experimental crucibles and furnace cartridges fabricated by VPS had not been heat treated and had been found to be relatively weak and brittle. Accordingly, the investigation was directed toward determining whether certain combinations of (1) refractory alloy compositions, (2) VPS parameters, and (3) heat-treatment parameters could result in VPS-fabricated components with increased ductility.

  17. Chapter 20: Graphite

    SciTech Connect

    Burchell, Timothy D

    2012-01-01

    Graphite is truly a unique material. Its structure, from the nano- to the millimeter scale give it remarkable properties that lead to numerous and diverse applications. Graphite bond anisotropy, with strong in-plane covalent bonds and weak van der Waals type bonding between the planes, gives graphite its unique combination of properties. Easy shear of the crystal, facilitated by weak interplaner bonds allows graphite to be used as a dry lubricant, and is responsible for the substances name! The word graphite is derived from the Greek to write because of graphites ability to mark writing surfaces. Moreover, synthetic graphite contains within its structure, porosity spanning many orders of magnitude in size. The thermal closure of these pores profoundly affects the properties for example, graphite strength increases with temperature to temperatures in excess of 2200 C. Consequently, graphite is utilized in many high temperature applications. The basic physical properties of graphite are reviewed here. Graphite applications include metallurgical; (aluminum and steel production), single crystal silicon production, and metal casting; electrical (motor brushes and commutators); mechanical (seals, bearings and bushings); and nuclear applications, (see Chapter 91, Nuclear Graphite). Here we discuss the structure, manufacture, properties, and applications of Graphite.

  18. Monitoring lining and hearth conditions at Inland`s No. 7 blast furnace

    SciTech Connect

    Quisenberry, P.; Grant, M.; Carter, W.

    1997-12-31

    The paper describes: furnace statistics; mini-reline undertaken in November, 1993; the stack condition; throat gunning; stabilizing the graphite bricks; the hearth condition; reactions to temperature excursions; future instrumentation; and hot blast system areas of concern. The present data from monitoring systems and inspections indicate that the furnace should be able to operate well beyond the expectation for the 1993 mini-reline (3--5 years) with: (1) consistent, high quality raw materials; (2) instrumentation, diagnostic, remedial, and preventative techniques developed; and (3) stopping quickly any water leaks into the furnace. The longevity of this campaign has undoubtedly been a result of this monitoring program.

  19. ZPR-3 Assembly 12 : A cylindrical assembly of highly enriched uranium, depleted uranium and graphite with an average {sup 235}U enrichment of 21 atom %.

    SciTech Connect

    Lell, R. M.; McKnight, R. D.; Perel, R. L.; Wagschal, J. J.; Nuclear Engineering Division; Racah Inst. of Physics

    2010-09-30

    Over a period of 30 years, more than a hundred Zero Power Reactor (ZPR) critical assemblies were constructed at Argonne National Laboratory. The ZPR facilities, ZPR-3, ZPR-6, ZPR-9 and ZPPR, were all fast critical assembly facilities. The ZPR critical assemblies were constructed to support fast reactor development, but data from some of these assemblies are also well suited for nuclear data validation and to form the basis for criticality safety benchmarks. A number of the Argonne ZPR/ZPPR critical assemblies have been evaluated as ICSBEP and IRPhEP benchmarks. Of the three classes of ZPR assemblies, engineering mockups, engineering benchmarks and physics benchmarks, the last group tends to be most useful for criticality safety. Because physics benchmarks were designed to test fast reactor physics data and methods, they were as simple as possible in geometry and composition. The principal fissile species was {sup 235}U or {sup 239}Pu. Fuel enrichments ranged from 9% to 95%. Often there were only one or two main core diluent materials, such as aluminum, graphite, iron, sodium or stainless steel. The cores were reflected (and insulated from room return effects) by one or two layers of materials such as depleted uranium, lead or stainless steel. Despite their more complex nature, a small number of assemblies from the other two classes would make useful criticality safety benchmarks because they have features related to criticality safety issues, such as reflection by soil-like material. ZPR-3 Assembly 12 (ZPR-3/12) was designed as a fast reactor physics benchmark experiment with an average core {sup 235}U enrichment of approximately 21 at.%. Approximately 68.9% of the total fissions in this assembly occur above 100 keV, approximately 31.1% occur below 100 keV, and essentially none below 0.625 eV - thus the classification as a 'fast' assembly. This assembly is Fast Reactor Benchmark No. 9 in the Cross Section Evaluation Working Group (CSEWG) Benchmark Specifications

  20. Looking Northwest at Furnace Control Panels and Gas Control Furnace ...

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

    Looking Northwest at Furnace Control Panels and Gas Control Furnace in Red Room Within Recycle Recovery Building - Hematite Fuel Fabrication Facility, Recycle Recovery Building, 3300 State Road P, Festus, Jefferson County, MO

  1. Low-energy electron diffraction study of potassium adsorbed on single-crystal graphite and highly oriented pyrolytic graphite

    SciTech Connect

    Ferralis, N.; Diehl, R.D.; Pussi, K.; Lindroos, M.; Finberg, S.E.; Smerdon, J.; McGrath, R.

    2004-12-15

    Potassium adsorption on graphite has been a model system for the understanding of the interaction of alkali metals with surfaces. The geometries of the (2x2) structure of potassium on both single-crystal graphite (SCG) and highly oriented pyrolytic graphite (HOPG) were investigated for various preparation conditions for graphite temperatures between 55 and 140 K. In all cases, the geometry was found to consist of K atoms in the hollow sites on top of the surface. The K-graphite average perpendicular spacing is 2.79{+-}0.03 A , corresponding to an average C-K distance of 3.13{+-}0.03 A , and the spacing between graphite planes is consistent with the bulk spacing of 3.35 A. No evidence was observed for a sublayer of potassium. The results of dynamical LEED studies for the clean SCG and HOPG surfaces indicate that the surface structures of both are consistent with the truncated bulk structure of graphite.

  2. Graphite Technology Development Plan

    SciTech Connect

    W. Windes; T. Burchell; M.Carroll

    2010-10-01

    The Next Generation Nuclear Plant (NGNP) will be a helium-cooled High Temperature Gas Reactor (HTGR) with a large graphite core. Graphite physically contains the fuel and comprises the majority of the core volume. Graphite has been used effectively as a structural and moderator material in both research and commercial high-temperature gas-cooled reactors. This development has resulted in graphite being established as a viable structural material for HTGRs. While the general characteristics necessary for producing nuclear grade graphite are understood, historical “nuclear” grades no longer exist. New grades must be fabricated, characterized, and irradiated to demonstrate that current grades of graphite exhibit acceptable non-irradiated and irradiated properties upon which the thermomechanical design of the structural graphite in NGNP is based. This Technology Development Plan outlines the research and development (R&D) activities and associated rationale necessary to qualify nuclear grade graphite for use within the NGNP reactor.

  3. CHARGING SIDE OF #130 ELECTRIC FURNACE CO. REHEAT FURNACE IN ...

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

    CHARGING SIDE OF #130 ELECTRIC FURNACE CO. REHEAT FURNACE IN REROLL BAY. CAKES FROM THE CASTING SHOP ARE BROUGHT UP TO ROLLING TEMPERATURE IN ONE OF TWO (#130 AND 146) GAS-FIRED FURNACES. A RADIO-CONTROLLED OVERHEAD CRANE TRANSFERS CAKES FROM FLATCARS TO THE ROLLER LINE LEADING INTO THE FURNACE. CAKES ARE HEATED AT 900-1000 DEGREES FAHRENHEIT FOR THREE TO FOUR HOURS. RATED FURNACE CAPACITY IS 100,000 LBS.\\HOUR. - American Brass Foundry, 70 Sayre Street, Buffalo, Erie County, NY

  4. Investigations on Freon-assisted atomization of refractory analytes (Cr, Mo, Ti, V) in multielement electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Heinrich, Hans-Joachim; Matschat, Ralf

    2007-08-01

    Premixed 1% Freon in argon inner gas of various composition (CCl 2F 2, CHClF 2, CHF 3) was applied to graphite furnace atomizer to minimize unfavorable effects of carbide formation, such as signal tailing and memory effects in the simultaneous determination of Cr, Mo, Ti and V refractory analytes by electrothermal atomic absorption spectrometry using a multielement atomic absorption spectrometer. The effect of these gaseous additives was investigated when applied separately in atomization, pyrolysis and clean-out steps. The halogenation effects were analytically useful only under the precondition of using Ar-H 2 outer gas to the furnace to all heating steps, and also using this gas in the pre-atomization (drying, pyrolysis) steps. Optimum analytical performance was obtained when mixtures of 1% Freon in argon were applied just before and during the atomization step at a flow rate of 50 mL min - 1 and 2% hydrogen was used as purge gas. Using optimum conditions, signal tailings and carry-over contamination were reduced effectively and good precision (relative standard deviation below 1%) could be attained. Applying 1% CHClF 2 and an atomization temperature of 2550 °C, the characteristic masses obtained for simple aqueous solutions were 8.8 pg for Cr, 17 pg for Mo, 160 pg for Ti, and 74 pg for V. The limits of detection were 0.05, 0.2, 2.3 and 0.5 μg L - 1 for Cr, Mo, Ti and V, respectively. The developed method was applied to the analysis of digests of advanced ceramics. The accuracy of the procedure was confirmed by analyzing the certified reference material ERM-ED 102 (Boron Carbide Powder) and a silicon nitride powder distributed in the inter-laboratory comparison CCQM-P74.

  5. Simultaneous separation/preconcentration of ultra trace heavy metals in industrial wastewaters by dispersive liquid-liquid microextraction based on solidification of floating organic drop prior to determination by graphite furnace atomic absorption spectrometry.

    PubMed

    Mirzaei, Mohammad; Behzadi, Mansoureh; Abadi, Nasrin Mahmoud; Beizaei, Alieh

    2011-02-28

    In the present work, an efficient microextraction method was applied to separation and preconcentration of Ni(II), Co(II), Pb(II) and Cr(III). This method is dispersive liquid-liquid microextraction based on solidification of floating organic drop, which overcomes the most important problems of each aforementioned technique. The influences of analytical parameters, including pH, extraction solvent volume, disperser solvent type and its volume, concentration of chelating agent, salt effect and extraction time on the quantitative recoveries of nickel, cobalt, lead and chromium ions were investigated. Under the optimized conditions, the limits of detection were 0.2 ng L(-1) for Cr and 1.3 ng L(-1) for Co, Ni and Pb, with a preconcentration factor of 800 times. The relative standard deviations of 6.2% at 6.0 ng L(-1) of Cr and 7.2% at 10 ng L(-1) of Co, Ni and Pb were obtained (n=7). The proposed method was successfully applied for the analysis of ultra trace metals in water and wastewater samples. PMID:21232852

  6. Thermal neutron scattering in graphite

    NASA Astrophysics Data System (ADS)

    Al-Qasir, Iyad Ibrahim

    Generation IV Very High Temperature Reactor (VHTR) concepts, are graphite moderated and gas cooled thermal spectrum reactors. The characteristics of the low energy (E < 1 eV) neutron spectrum in these reactors will be dictated by the process of neutron slowing-down and thermalization in the graphite moderator. The ability to accurately predict this process in these reactors can have significant neutronic and safety implications. In reactor design calculations, thermal neutron scattering cross section libraries are needed for the prediction of the thermal neutron environment in the core. Currently used libraries (ENDF/B-VII) are a product of the 1960s and remain based on many physical approximations. In addition, these libraries show noticeable discrepancies with experimental data. In this work, investigation of thermal neutron scattering in graphite as a function of temperature was performed. The fundamental input for the calculation of thermal neutron scattering cross sections, i.e., the phonon frequency distribution and/or the dispersion relations, was generated using a modern approach that is based on quantum mechanical electronic structure (ab initio) simulations combined with a lattice dynamics direct method supercell approach. The calculations were performed using the VASP and PHONON codes. The VASP calculations used the local density approximation, and the projector augmented-wave pseudopotential. A supercell of 144 atoms was used; and the integration over the Brillouin zone was confined to a 3x3x4 k-mesh generated by the Monkhorst-Pack scheme. A plane-wave basis set with an energy cutoff of 500 eV was applied. The corresponding dispersion relations, heat capacity, and phonon frequency distribution show excellent agreement with experimental data. Despite the use of the above techniques to produce more accurate input data, the examination of the results indicated persistence of the inconsistencies between calculations and measurements at neutron energies

  7. Friction and wear of metals in contact with pyrolytic graphite

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.; Brainard, W. A.

    1975-01-01

    Sliding friction experiments were conducted with gold, iron, and tantalum single crystals sliding on prismatic and basal orientations of pyrolytic graphite in various environments, including vacuum, oxygen, water vapor, nitrogen, and hydrogen bromide. Surfaces were examined in the clean state and with various adsorbates present on the graphite surfaces. Auger and LEED spectroscopy, SEM, and EDXA were used to characterize the graphite surfaces. Results indicate that the prismatic and basal orientations do not contain nor do they chemisorb oxygen, water vapor, acetylene, or hydrogen bromide. All three metals exhibited higher friction on the prismatic than on the basal orientation and these metals transferred to the atomically clean prismatic orientation of pyrolytic graphite. No metal transfer to the graphite was observed in the presence of adsorbates at 760 torr. Ion bombardment of the graphite surface with nitrogen ions resulted in the adherence of nitrogen to the surface.

  8. Mercury in dumped blast furnace sludge.

    PubMed

    Földi, Corinna; Dohrmann, Reiner; Mansfeldt, Tim

    2014-03-01

    Blast furnace sludge (BFS) is a waste generated in the production of pig iron and was dumped in sedimentation ponds. Sixty-five samples from seven BFS locations in Europe were investigated regarding the toxic element mercury (Hg) for the first time. The charge material of the blast furnace operations revealed Hg contents from 0.015 to 0.097mgkg(-1). In comparison, the Hg content of BFS varied between 0.006 and 20.8mgkg(-1) with a median of 1.63mgkg(-1), which indicates enrichment with Hg. For one site with a larger sample set (n=31), Hg showed a stronger correlation with the total non-calcareous carbon (C) including coke and graphite (r=0.695; n=31; p<0.001). It can be assumed that these C-rich compounds are hosting phases for Hg. The solubility of Hg was rather low and did not exceed 0.43% of total Hg. The correlation between the total Hg concentration and total amount of NH4NO3-soluble Hg was relatively poor (r=0.496; n=27; p=0.008) indicating varying hazard potentials of the different BFS. Finally, BFS is a mercury-containing waste and dumped BFS should be regarded as potentially mercury-contaminated sites.

  9. Synthesis of soluble graphite and graphene.

    PubMed

    Kelly, K F; Billups, W E

    2013-01-15

    Because of graphene's anticipated applications in electronics and its thermal, mechanical, and optical properties, many scientists and engineers are interested in this material. Graphene is an isolated layer of the π-stacked hexagonal allotrope of carbon known as graphite. The interlayer cohesive energy of graphite, or exfoliation energy, that results from van der Waals attractions over the interlayer spacing distance of 3.34 Å (61 meV/C atom) is many times weaker than the intralayer covalent bonding. Since graphene itself does not occur naturally, scientists and engineers are still learning how to isolate and manipulate individual layers of graphene. Some researchers have relied on the physical separation of the sheets, a process that can sometimes be as simple as peeling of sheets from crystalline graphite using Scotch tape. Other researchers have taken an ensemble approach, where they exploit the chemical conversion of graphite to the individual layers. The typical intermediary state is graphite oxide, which is often produced using strong oxidants under acidic conditions. Structurally, researchers hypothesize that acidic functional groups functionalize the oxidized material at the edges and a network of epoxy groups cover the sp(2)-bonded carbon network. The exfoliated material formed under these conditions can be used to form dispersions that are usually unstable. However, more importantly, irreversible defects form in the basal plane during oxidation and remain even after reduction of graphite oxide back to graphene-like material. As part of our interest in the dissolution of carbon nanomaterials, we have explored the derivatization of graphite following the same procedures that preserve the sp(2) bonding and the associated unique physical and electronic properties in the chemical processing of single-walled carbon nanotubes. In this Account, we describe efficient routes to exfoliate graphite either into graphitic nanoparticles or into graphene without

  10. Synthesis of soluble graphite and graphene.

    PubMed

    Kelly, K F; Billups, W E

    2013-01-15

    Because of graphene's anticipated applications in electronics and its thermal, mechanical, and optical properties, many scientists and engineers are interested in this material. Graphene is an isolated layer of the π-stacked hexagonal allotrope of carbon known as graphite. The interlayer cohesive energy of graphite, or exfoliation energy, that results from van der Waals attractions over the interlayer spacing distance of 3.34 Å (61 meV/C atom) is many times weaker than the intralayer covalent bonding. Since graphene itself does not occur naturally, scientists and engineers are still learning how to isolate and manipulate individual layers of graphene. Some researchers have relied on the physical separation of the sheets, a process that can sometimes be as simple as peeling of sheets from crystalline graphite using Scotch tape. Other researchers have taken an ensemble approach, where they exploit the chemical conversion of graphite to the individual layers. The typical intermediary state is graphite oxide, which is often produced using strong oxidants under acidic conditions. Structurally, researchers hypothesize that acidic functional groups functionalize the oxidized material at the edges and a network of epoxy groups cover the sp(2)-bonded carbon network. The exfoliated material formed under these conditions can be used to form dispersions that are usually unstable. However, more importantly, irreversible defects form in the basal plane during oxidation and remain even after reduction of graphite oxide back to graphene-like material. As part of our interest in the dissolution of carbon nanomaterials, we have explored the derivatization of graphite following the same procedures that preserve the sp(2) bonding and the associated unique physical and electronic properties in the chemical processing of single-walled carbon nanotubes. In this Account, we describe efficient routes to exfoliate graphite either into graphitic nanoparticles or into graphene without

  11. Blast furnace stove control

    SciTech Connect

    Muske, K.R.; Hansen, G.A.; Howse, J.W.; Cagliostro, D.J.; Chaubal, P.C.

    1998-12-31

    This paper outlines the process model and model-based control techniques implemented on the hot blast stoves for the No. 7 Blast Furnace at the Inland Steel facility in East Chicago, Indiana. A detailed heat transfer model of the stoves is developed. It is then used as part of a predictive control scheme to determine the minimum amount of fuel necessary to achieve the blast air requirements. The controller also considers maximum and minimum temperature constraints within the stove.

  12. Producing graphite with desired properties

    NASA Technical Reports Server (NTRS)

    Dickinson, J. M.; Imprescia, R. J.; Reiswig, R. D.; Smith, M. C.

    1971-01-01

    Isotropic or anisotropic graphite is synthesized with precise control of particle size, distribution, and shape. The isotropic graphites are nearly perfectly isotropic, with thermal expansion coefficients two or three times those of ordinary graphites. The anisotropic graphites approach the anisotropy of pyrolytic graphite.

  13. High Efficiency Furnace

    SciTech Connect

    Hwang, K. S.; Koestler, D. J.

    1985-08-27

    Disclosed is a dwelling furnace having at least one clam-shell type primary heat exchanger in parallel orientation with a secondary heat exchanger, both the primary and secondary heat exchangers being vertically oriented relative to a furnace housing and parallel to the flow of air to be heated. The primary heat exchanger has a combustion chamber in the lower end thereof, and the lower end of the secondary heat exchanger exhausts into a tertiary heat exchanger oriented approximately perpendicular to the primary and secondary heat exchangers and horizontally relative to the housing, below the combustion chambers of the primary heat exchangers and below the exhaust outlet of the secondary heat exchanger. The tertiary heat exchanger includes a plurality of condensation tubes for retrieving the latent heat of condensation of the combustion gases. The furnace further comprises an induced draft blower for drawing combustion gases through the heat exchangers and inducting sufficient air to the combustion chamber of the primary heat exchanger for efficient combustion.

  14. High efficiency furnace

    SciTech Connect

    Hwang, K. S.; Koestler, D. J.

    1985-12-31

    Disclosed is a dwelling furnace having at least one clam-shell type primary heat exchanger in parallel orientation with a secondary heat exchanger, both the primary and secondary heat exchangers being vertically oriented relative to a furnace housing and parallel to the flow of air to be heated. The primary heat exchanger has a combustion chamber in the lower end thereof, and the lower end of the secondary heat exchanger exhausts into a tertiary heat exchanger oriented approximately perpendicular to the primary and secondary heat exchangers and horizontally relative to the housing, below the combustion chambers of the primary heat exchangers and below the exhaust outlet of the secondary heat exchanger. The tertiary heat exchanger includes a plurality of condensation tubes for retrieving the latent heat of condensation of the combustion gases. The furnace further comprises an induced draft blower for drawing combustion gases through the heat exchangers and inducting sufficient air to the combustion chamber of the primary heat exchanger for efficient combustion.

  15. Preparation of Ceramic-Bonded Carbon Block for Blast Furnace

    NASA Astrophysics Data System (ADS)

    Li, Yiwei; Li, Yawei; Sang, Shaobai; Chen, Xilai; Zhao, Lei; Li, Yuanbing; Li, Shujing

    2014-01-01

    Traditional carbon blocks for blast furnaces are mainly produced with electrically calcined anthracite owing to its good hot metal corrosion resistance. However, this kind of material shows low thermal conductivity and does not meet the demands for cooling of the hearth and the bottom of blast furnaces. In this article, a new kind of a high-performance carbon block has been prepared via ceramic-bonded carbon (CBC) technology in a coke bed at 1673 K (1400 °C) using artificial graphite aggregate, alumina, metallic aluminum, and silicon powders as starting materials. The results showed that artificial graphite aggregates were strongly bonded by the three-dimensional network of ceramic phases in carbon blocks. In this case, the good resistance of the CBC blocks against erosion/corrosion by the hot metal is provided by the ceramic matrix and the high thermal conductivity by the graphite aggregates. The microstructure of this carbon block resembles that of CBC composites with a mean pore size of less than 0.1 μm, and up to 90 pct of the porosity shows a pore size <1 μm. Its thermal conductivity is higher than 30 W · m-1 · K-1 [293 K (20 °C)]. Meanwhile, its hot metal corrosion resistance is better than that of traditional carbon blocks.

  16. Determination of trace amounts of molybdenum in plant tissue by solvent extraction-atomic-absorption and direct-current plasma emission spectrometry.

    PubMed

    Lajunen, L H; Kubin, A

    1986-03-01

    Methods are presented for determination of molybdenum in plant tissue by flame and graphite-furnace atomic-absorption spectrometry and direct-current argon-plasma emission spectrometry. The samples are digested in HNO(3)-H(2)SO(4)-HC1O(4) mixture, and Mo is separated and concentrated by chelation and extraction. Three organic solvents (methyl isobutyl ketone, di-isobutyl ketone and isoamyl alcohol) and two ligands (8-hydroxyquinoline and toluene-3,4-dithiol) were studied. The procedure were tested on pine needle and birch leaf samples. PMID:18964076

  17. Oxidation Resistant Graphite Studies

    SciTech Connect

    W. Windes; R. Smith

    2014-07-01

    The Very High Temperature Reactor (VHTR) Graphite Research and Development Program is investigating doped nuclear graphite grades exhibiting oxidation resistance. During a oxygen ingress accident the oxidation rates of the high temperature graphite core region would be extremely high resulting in significant structural damage to the core. Reducing the oxidation rate of the graphite core material would reduce the structural effects and keep the core integrity intact during any air-ingress accident. Oxidation testing of graphite doped with oxidation resistant material is being conducted to determine the extent of oxidation rate reduction. Nuclear grade graphite doped with varying levels of Boron-Carbide (B4C) was oxidized in air at nominal 740°C at 10/90% (air/He) and 100% air. The oxidation rates of the boronated and unboronated graphite grade were compared. With increasing boron-carbide content (up to 6 vol%) the oxidation rate was observed to have a 20 fold reduction from unboronated graphite. Visual inspection and uniformity of oxidation across the surface of the specimens were conducted. Future work to determine the remaining mechanical strength as well as graphite grades with SiC doped material are discussed.

  18. Experimental Observations and Numerical Prediction of Induction Heating in a Graphite Test Article

    SciTech Connect

    Jankowski, Todd A; Johnson, Debra P; Jurney, James D; Freer, Jerry E; Dougherty, Lisa M; Stout, Stephen A

    2009-01-01

    The induction heating coils used in the plutonium casting furnaces at the Los Alamos National Laboratory are studied here. A cylindrical graphite test article has been built, instrumented with thermocouples, and heated in the induction coil that is normally used to preheat the molds during casting operations. Preliminary results of experiments aimed at understanding the induction heating process in the mold portion of the furnaces are reported. The experiments have been modeled in COMSOL Multiphysics and the numerical and experimental results are compared to one another. These comparisons provide insight into the heating process and provide a benchmark for COMSOL calculations of induction heating in the mold portion of the plutonium casting furnaces.

  19. Hyperthermal oxidation of graphite and diamond.

    PubMed

    Paci, Jeffrey T; Minton, Timothy K; Schatz, George C

    2012-11-20

    Carbon materials have mechanical, electrical, optical, and tribological properties that make them attractive for use in a wide range of applications. Two properties that make them attractive, their hardness and inertness in many chemical environments, also make them difficult to process into useful forms. The use of atomic oxygen and other forms of oxidation has become a popular option for processing of these materials (etching, erosion, chemical functionalization, etc.). This Account provides an overview of the use of theory to describe the mechanisms of oxidation of diamond and graphite using hyperthermal (few electronvolts) oxygen atoms. The theoretical studies involve the use of Born-Oppenheimer molecular dynamics calculations in which on-the-fly electronic structure calculations have been performed using either density functional theory or density-functional-tight-binding semiempirical methods to simulate collisions of atomic oxygen with diamond or graphite. Comparisons with molecular-beam scattering on surfaces provide indirect verification of the results. Graphite surfaces become oxidized when exposed to hyperthermal atomic oxygen, and the calculations have revealed the mechanisms for formation of both CO and CO(2). These species arise when epoxide groups form and diffuse to holes on the surface where carbonyls are already present. CO and CO(2) form when these carbonyl groups dissociate from the surface, resulting in larger holes. We also discuss mechanisms for forming holes in graphite surfaces that were previously hole-free. For diamond, the (111) and (100) surfaces are oxidized by the oxygen atoms, forming mostly oxy radicals and ketones on the respective surfaces. The oxy-covered (111) surface can then react with hyperthermal oxygen to give gaseous CO(2), or it can become graphitized leading to carbon removal as with graphite. The (100) surface is largely unreactive to hyperthermal atomic oxygen, undergoing large amounts of inelastic scattering and

  20. Carbon-free induction furnace

    DOEpatents

    Holcombe, Cressie E.; Masters, David R.; Pfeiler, William A.

    1985-01-01

    An induction furnace for melting and casting highly pure metals and alloys such as uranium and uranium alloys in such a manner as to minimize contamination of the melt by carbon derived from the materials and the environment within the furnace. The subject furnace is constructed of carbon free materials and is housed within a conventional vacuum chamber. The furnace comprises a ceramic oxide crucible for holding the charge of metal or alloy. The heating of the crucible is achieved by a plasma-sprayed tungsten susceptor surrounding the crucible which, in turn, is heated by an RF induction coil separated from the susceptor by a cylinder of inorganic insulation. The furnace of the present invention is capable of being rapidly cycled from ambient temperatures to about 1650.degree. C. for effectively melting uranium and uranium alloys without the attendant carbon contamination problems previously encountered when using carbon-bearing furnace materials.

  1. Non-carbon induction furnace

    DOEpatents

    Holcombe, C.E.; Masters, D.R.; Pfeiler, W.A.

    1984-01-06

    The present invention is directed to an induction furnace for melting and casting highly pure metals and alloys such as uranium and uranium alloys in such a manner as to minimize contamination of the melt by carbon derived from the materials and the environment within the furnace. The subject furnace is constructed of non-carbon materials and is housed within a conventional vacuum chamber. The furnace comprises a ceramic oxide crucible for holding the charge of metal or alloys. The heating of the crucible is achieved by a plasma-sprayed tungsten susceptor surrounding the crucible which, in turn, is heated by an rf induction coil separated from the susceptor by a cylinder of inorganic insulation. The furnace of the present invention is capable of being rapidly cycled from ambient temperatures to about 1650/sup 0/C for effectively melting uranium and uranium alloys without the attendant carbon contamination problems previously encountered when using carbon-bearing furnace materials.

  2. Separate vaporisation of boric acid and inorganic boron from tungsten sample cuvette-tungsten boat furnace followed by the detection of boron species by inductively coupled plasma mass spectrometry and atomic emission spectrometry (ICP-MS and ICP-AES).

    PubMed

    Kataoka, Hiroko; Okamoto, Yasuaki; Tsukahara, Satoshi; Fujiwara, Terufumi; Ito, Kazuaki

    2008-03-10

    Utilising extremely different vaporisation properties of boron compounds, the determination procedures of volatile boric acid and total boron using tungsten boat furnace (TBF) ICP-MS and TBF-ICP-AES have been investigated. For the determination of volatile boric acid by TBF-ICP-MS, tetramethylammonium hydroxide (TMAH, Me(4)NOH) was used as a chemical modifier to retain it during drying and ashing stages. As for the total boron, not only non-volatile inorganic boron such as boron nitride (BN), boron carbide (B(4)C), etc. but also boric acid (B(OH)(3)) was decomposed by a furnace-fusion digestion with NaOH to produce sodium salt of boron, a suitable species for the electrothermal vaporisation (ETV) procedure. The proposed method was applied to the analysis of various standard reference materials. The analytical results for various biological and steel samples are described.

  3. HIGH TEMPERATURE MICROSCOPE AND FURNACE

    DOEpatents

    Olson, D.M.

    1961-01-31

    A high-temperature microscope is offered. It has a reflecting optic situated above a molten specimen in a furnace and reflecting the image of the same downward through an inert optic member in the floor of the furnace, a plurality of spaced reflecting plane mirrors defining a reflecting path around the furnace, a standard microscope supported in the path of and forming the end terminus of the light path.

  4. Determination of ytterbium in animal faeces by tungsten coil electrothermal atomic absorption spectrometry.

    PubMed

    Lima, E C; Krug, F J; Nóbrega, J A; Nogueira, A R

    1998-11-01

    A method for ytterbium determination in animal faeces by tungsten coil electrothermal atomic absorption spectrometry (TCAAS) was developed. Faeces were dry-ashed in a muffle furnace, the ashes were treated with hydrochloric acid, and 10 mul of sample solution were delivered into 150-W tungsten coil atomizer. A matrix-matching procedure employing a 66-s heating program proved to be efficient for obtaining accurate results. Characteristic mass and detection limit were 7.1 pg and 0.35 mug g(-1) Yb, respectively. The tungsten coil atomizer lifetime exceeded 300 firings with digested solutions and R.S.D. of measurements was 1.9% after ten consecutive injections of 10.0 mug l(-1) Yb. Accuracy of the proposed method was assessed by employing a graphite furnace atomic absorption spectrometric procedure. Application of the paired t-test did not reveal any significant difference for ytterbium contents determined by both methods at 95% confidence level. It was demonstrated that the proposed procedure can successfully be used for evaluation of kinetic passage rate of feed through digestive tract of animals. PMID:18967363

  5. Implement proper furnace safety interlocks

    SciTech Connect

    Thomas, C.D.; Schoenmaker, G.J.W.

    1996-07-01

    Cracking furnaces are among some of the most complex operations in chemical process industries (CPI) plants. Consider, for example, the cracking furnaces in ethylene plants. Furnace explosions can occur during the light-off process or from accumulations of unburned fuel, incomplete combustion, or introduction of flammable products into the combustion spaces of the furnace. Over half of all furnace explosions occur during the initial light-off process for the furnace. The deficiencies that cause these events can be grouped into three broad categories: (1) human error; (2) incorrect or incomplete safety controls and equipment arrangement; and (3) equipment malfunction. This article presents a safety system that helps address all three of these categories for light-off events. No system is totally foolproof, but the use of a safety system, along with strict operating discipline, will reduce the number of furnace events encountered over the lifetime of the equipment. (Note that the controls typically referred to as ``combustion control,`` which include process temperature control, fuel-gas control, oxygen trim/draft control, and the like, are not part of the control described here.) Note also that although this system was developed for cracking furnaces in ethylene plants, it is equally applicable to other types of radiant-wall multiple-burner furnaces. It can be used for both new installations and retrofit situations. This safety system is not applicable to boilers or other devices with only one or two burners.

  6. Multi-zone furnace system

    SciTech Connect

    Orbeck, G.A.

    1986-05-06

    A multi-zone furnace is described which consists of: a furnace chamber having at least one heat zone and at least one zone adjacent to the heat zone and disposed along the length of the furnace chamber; the heat zone having a hearth at a level different from the hearth level of the adjacent zone; a walking beam conveyor disposed in the furnace chamber and operative in a short stroke mode to convey a product along the hearth of the heat zone, and in a long stroke mode to convey a product from the heat zone to the adjacent zone.

  7. Determination of arsenic in ores, concentrates and related materials by continuous hydride-generation atomic-absorption spectrometry after separation by xanthate extraction.

    PubMed

    Donaldson, E M; Leaver, M E

    1988-04-01

    A recent graphite-furnace atomic-absorption method for determining approximately 0.2 mug/g or more of arsenic in ores, concentrates, rocks, soils and sediments, after separation from matrix elements by cyclohexane extraction of arsenic(III) xanthate from approximately 8-10M hydrochloric acid, has been modified to include an alternative hydride-generation atomic-absorption finish. After the extract has been washed with 10M hydrochloric acid-2% thiourea solution to remove co-extracted copper and residual iron, arsenic(III) in the extract is oxidized to arsenic(V) with bromine solution in carbon tetrachloride and stripped into water. Following the removal of bromine by evaporation of the solution, arsenic is reduced to arsenic(III) with potassium iodide in approximately 4M hydrochloric acid and ultimately determined to hydride-generation atomic-absorption spectrometry at 193.7 nm, with sodium borohydride as reductant. Interference from gold, platinum and palladium, which are partly co-extracted as xanthates under the proposed conditions, is eliminated by complexing them with thiosemicarbazide before the iodide reduction step. The detection limits for ores and related materials is approximately 0.1 mug of arsenic per g. Results obtained by this method are compared with those obtained previously by the graphite-furnace method.

  8. Method for producing dustless graphite spheres from waste graphite fines

    DOEpatents

    Pappano, Peter J; Rogers, Michael R

    2012-05-08

    A method for producing graphite spheres from graphite fines by charging a quantity of spherical media into a rotatable cylindrical overcoater, charging a quantity of graphite fines into the overcoater thereby forming a first mixture of spherical media and graphite fines, rotating the overcoater at a speed such that the first mixture climbs the wall of the overcoater before rolling back down to the bottom thereby forming a second mixture of spherical media, graphite fines, and graphite spheres, removing the second mixture from the overcoater, sieving the second mixture to separate graphite spheres, charging the first mixture back into the overcoater, charging an additional quantity of graphite fines into the overcoater, adjusting processing parameters like overcoater dimensions, graphite fines charge, overcoater rotation speed, overcoater angle of rotation, and overcoater time of rotation, before repeating the steps until graphite fines are converted to graphite spheres.

  9. Coating method for graphite

    DOEpatents

    Banker, John G.; Holcombe, Jr., Cressie E.

    1977-01-01

    A method of limiting carbon contamination from graphite ware used in induction melting of uranium alloys is provided comprising coating the graphite surface with a suspension of Y.sub.2 O.sub.3 particles in water containing about 1.5 to 4% by weight sodium carboxymethylcellulose.

  10. Coating method for graphite

    DOEpatents

    Banker, J.G.; Holcombe, C.E. Jr.

    1975-11-06

    A method of limiting carbon contamination from graphite ware used in induction melting of uranium alloys is provided. The graphite surface is coated with a suspension of Y/sub 2/O/sub 3/ particles in water containing about 1.5 to 4 percent by weight sodium carboxymethylcellulose.

  11. Exothermic furnace module

    NASA Technical Reports Server (NTRS)

    Poorman, R. M. (Inventor)

    1982-01-01

    An exothermic furnace module is disclosed for processing materials in space which includes an insulated casing and a sample support, carried within the casing which supports a sample container. An exothermic heat source includes a plurality of segments of exothermic material stacked one upon another to produce a desired temperature profile when ignited. The exothermic material segments are constructed in the form of an annular element having a recess opening which defines an open central core throughout the vertical axis of the stacked exothermic material. The sample container is arranged within the core of the stacked exothermic heating material.

  12. Radiantly heated furnace

    SciTech Connect

    Pargeter, J.K.

    1987-06-30

    This patent describes a travelling hearth furnace comprising at least one impermeable hearth member adapted to travel generally horizontally along a path from a first locus to a second locus, means to cause the hearth member to travel along the path. Means directs radiant hat toward the upper surface of the hearth member. Means at the first locus positions a thin layer of objects on the upper surface of the hearth member. Means at the second locus removes objects from the hearth member. Means, positioned intermediate the first locus and the second locus, positions additional objects on the thin layer of objects on the upper surface of the hearth member.

  13. Water gas furnace

    SciTech Connect

    Gallaro, C.

    1985-12-03

    A water gas furnace comprising an outer container to provide a housing in which coke is placed into its lower part. A water container is placed within the housing. The coke is ignited and heats the water in the container converting it into steam. The steam is ejected into the coke, which together with air, produces water gas. Preferably, pumice stones are placed above the coke. The water gas is accepted into the pores of the pumice stones, where the heated pumice stones ignite the water gas, producing heat. The heat is extracted by a heat exchanger provided about the housing.

  14. Magnetically Damped Furnace (MDF)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The Magnetically Damped Furnace (MDF) breadboard is being developed in response to NASA's mission and goals to advance the scientific knowledge of microgravity research, materials science, and related technologies. The objective of the MDF is to dampen the fluid flows due to density gradients and surface tension gradients in conductive melts by introducing a magnetic field during the sample processing. The MDF breadboard will serve as a proof of concept that the MDF performance requirements can be attained within the International Space Station resource constraints.

  15. Novel laser atomic fluorescence spectrometer for environmental and biomedical analyses of heavy metals

    NASA Astrophysics Data System (ADS)

    Dergachev, Alex Y.; Mirov, Sergey B.; Pitt, Robert E.; Parmer, Keith D.

    1997-05-01

    We report on the development of a novel experimental set-up using laser atomic fluorescence for detection and concentration measurements of heavy metal atoms for environmental and biomedical analyses. This spectrometer is based on the application of tunable LiF:F2+** and LiF:F2- color center and alexandrite lasers with nonlinear converters for narrowband excitation of atomic fluorescence and the use of gated multichannel CCD detectors for fluorescence measurements. A standard graphite furnace module was used for sample atomization. The laser sources used provide narrowband selective laser excitation continuously tunable in the 200 - 400 nm range and are therefore suitable for resonant excitation of atomic transitions in practically all known heavy metal atoms. In the first experiments, water samples containing Cu, Pb and Fe impurities were studied and detection levels of less than 1 ppb were observed. Comparison of the results of atomic laser fluorescence analysis and traditional atomic absorption spectrometry showed good qualitative agreement between these two methods. It is projected that full optimization of our experimental set up will allow for improved detection levels of several orders of magnitude. Possible optimization and simplification of the spectrometer are discussed in the context of developing a portable instrument for field use.

  16. [Determination of Al, Be, Cd, Co, Cr, Mn, Ni, Pb, Se and Tl in whole blood by atomic absorption spectrometry without preliminary sample digestion].

    PubMed

    Ivanenko, N B; Ivanenko, A A; Solov'ev, N D; Navolotskiĭ, D V; Pavlova, O V; Ganeev, A A

    2014-01-01

    Methods of whole blood trace element determination by Graphite furnace atomic absorption spectrometry (in the variant of Zeeman's modulation polarization spectrometry) have been proposed. They do not require preliminary sample digestion. Furnace programs, modifiers and blood dilution factors were optimized. Seronorm™ human whole blood reference materials were used for validation. Dynamic ranges (for undiluted blood samples) were: Al 8 ¸ 210 мg/L; Be 0.3 ¸ 50 мg/L; Cd 0.2 ¸ 75 мg/L; Сo 5 ¸ 350 мg/L; Cr 10 ¸ 100 мg/L; Mn 6 ¸ 250 мg/L; Ni 10 ¸ 350 мg/L; Pb 3 ¸ 240 мg/L; Se 10 ¸ 500 мg/L; Tl 2 ¸ 600 мg/L. Precision (RSD) for the middle of dynamic range ranged from 5% for Mn to 11 for Se.

  17. Cupola Furnace Computer Process Model

    SciTech Connect

    Seymour Katz

    2004-12-31

    The cupola furnace generates more than 50% of the liquid iron used to produce the 9+ million tons of castings annually. The cupola converts iron and steel into cast iron. The main advantages of the cupola furnace are lower energy costs than those of competing furnaces (electric) and the ability to melt less expensive metallic scrap than the competing furnaces. However the chemical and physical processes that take place in the cupola furnace are highly complex making it difficult to operate the furnace in optimal fashion. The results are low energy efficiency and poor recovery of important and expensive alloy elements due to oxidation. Between 1990 and 2004 under the auspices of the Department of Energy, the American Foundry Society and General Motors Corp. a computer simulation of the cupola furnace was developed that accurately describes the complex behavior of the furnace. When provided with the furnace input conditions the model provides accurate values of the output conditions in a matter of seconds. It also provides key diagnostics. Using clues from the diagnostics a trained specialist can infer changes in the operation that will move the system toward higher efficiency. Repeating the process in an iterative fashion leads to near optimum operating conditions with just a few iterations. More advanced uses of the program have been examined. The program is currently being combined with an ''Expert System'' to permit optimization in real time. The program has been combined with ''neural network'' programs to affect very easy scanning of a wide range of furnace operation. Rudimentary efforts were successfully made to operate the furnace using a computer. References to these more advanced systems will be found in the ''Cupola Handbook''. Chapter 27, American Foundry Society, Des Plaines, IL (1999).

  18. Electrostatic Manipulation of Graphene On Graphite

    NASA Astrophysics Data System (ADS)

    Untiedt, Carlos; Rubio-Verdu, Carmen; Saenz-Arce, Giovanni; Martinez-Asencio, Jesús; Milan, David C.; Moaied, Mohamed; Palacios, Juan J.; Caturla, Maria Jose

    2015-03-01

    Here we report the use of a Scanning Tunneling Microscope (STM) under ambient and vacuum conditions to study the controlled exfoliation of the last layer of a graphite surface when an electrostatic force is applied from a STM tip. In this work we have focused on the study of two parameters: the applied voltage needed to compensate the graphite interlayer attractive force and the one needed to break atomic bonds to produce folded structures. Additionally, we have studied the influence of edge structure in the breaking geometry. Independently of the edge orientation the graphite layer is found to tear through the zig-zag direction and the lifled layer shows a zig-zag folding direction. Molecular Dinamics simulations and DFT calculations have been performed to understand our results, showing a strong correlation with the experiments. Comunidad Valenciana through Prometeo project.

  19. Two chamber reaction furnace

    DOEpatents

    Blaugher, R.D.

    1998-05-05

    A vertical two chamber reaction furnace is described. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 C and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.

  20. Two chamber reaction furnace

    DOEpatents

    Blaugher, Richard D.

    1998-05-05

    A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. C. to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product.

  1. Torrefied biomasses in a drop tube furnace to evaluate their utility in blast furnaces.

    PubMed

    Chen, Wei-Hsin; Du, Shan-Wen; Tsai, Chien-Hsiung; Wang, Zhen-Yu

    2012-05-01

    Torrefaction and burning characteristics of bamboo, oil palm, rice husk, bagasse, and Madagascar almond were studied and compared with a high-volatile bituminous coal using a drop tube furnace to evaluate the potential of biomass consumed in blast furnaces. Torrefaction at 250 and 300°C for 1h duration was carried out. Analysis using the ash tracer method indicated that the extent of atomic carbon reduction in the biomasses was less than that of atomic hydrogen and oxygen. Torrefaction also lowered the sulfur content in bamboo and oil palm over 33%. An examination of the R-factor and burnout of the samples suggests that more volatiles were released and a higher burnout was achieved with raw and torrefied biomasses at 250°C than at 300°C; however, torrefaction at 300°C is a feasible operating condition to transform biomass into a solid fuel resembling a high-volatile bituminous coal used for blast furnaces. PMID:22386202

  2. Torrefied biomasses in a drop tube furnace to evaluate their utility in blast furnaces.

    PubMed

    Chen, Wei-Hsin; Du, Shan-Wen; Tsai, Chien-Hsiung; Wang, Zhen-Yu

    2012-05-01

    Torrefaction and burning characteristics of bamboo, oil palm, rice husk, bagasse, and Madagascar almond were studied and compared with a high-volatile bituminous coal using a drop tube furnace to evaluate the potential of biomass consumed in blast furnaces. Torrefaction at 250 and 300°C for 1h duration was carried out. Analysis using the ash tracer method indicated that the extent of atomic carbon reduction in the biomasses was less than that of atomic hydrogen and oxygen. Torrefaction also lowered the sulfur content in bamboo and oil palm over 33%. An examination of the R-factor and burnout of the samples suggests that more volatiles were released and a higher burnout was achieved with raw and torrefied biomasses at 250°C than at 300°C; however, torrefaction at 300°C is a feasible operating condition to transform biomass into a solid fuel resembling a high-volatile bituminous coal used for blast furnaces.

  3. Blast furnace injection symposium: Proceedings

    SciTech Connect

    1996-12-31

    These proceedings contain 14 papers related to blast furnace injection issues. Topics include coal quality, coal grinding, natural gas injection, stable operation of the blast furnace, oxygen enrichment, coal conveying, and performance at several steel companies. All papers have been processed separately for inclusion on the data base.

  4. NEW METHOD OF GRAPHITE PREPARATION

    DOEpatents

    Stoddard, S.D.; Harper, W.T.

    1961-08-29

    BS>A method is described for producing graphite objects comprising mixing coal tar pitch, carbon black, and a material selected from the class comprising raw coke, calcined coke, and graphite flour. The mixture is placed in a graphite mold, pressurized to at least 1200 psi, and baked and graphitized by heating to about 2500 deg C while maintaining such pressure. (AEC)

  5. High pressure furnace

    DOEpatents

    Morris, D.E.

    1993-09-14

    A high temperature high pressure furnace has a hybrid partially externally heated construction. A metallic vessel fabricated from an alloy having a composition of at least 45% nickel, 15% chrome, and 10% tungsten is utilized (the preferred alloy including 55% nickel, 22% chrome, 14% tungsten, 2% molybdenum, 3% iron (maximum) and 5% cobalt (maximum)). The disclosed alloy is fabricated into 11/4 or 2 inch, 32 mm or 50 mm bar stock and has a length of about 22 inches, 56 cm. This bar stock has an aperture formed therein to define a closed high temperature, high pressure oxygen chamber. The opposite and closed end of the vessel is provided with a small blind aperture into which a thermocouple can be inserted. The closed end of the vessel is inserted into an oven, preferably heated by standard nickel chrome electrical elements and having a heavily insulated exterior. 19 figures.

  6. High pressure furnace

    DOEpatents

    Morris, Donald E.

    1993-01-01

    A high temperature high pressure furnace has a hybrid partially externally heated construction. A metallic vessel fabricated from an alloy having a composition of at least 45% nickel, 15% chrome, and 10% tungsten is utilized (the preferred alloy including 55% nickel, 22% chrome, 14% tungsten, 2% molybdenum, 3% iron (maximum) and 5% cobalt (maximum). The disclosed alloy is fabricated into 11/4 or 2 inch, 32 mm or 50 mm bar stock and has a length of about 22 inches, 56 cm. This bar stock has an aperture formed therein to define a closed high temperature, high pressure oxygen chamber. The opposite and closed end of the vessel is provided with a small blind aperture into which a thermocouple can be inserted. The closed end of the vessel is inserted into an oven, preferably heated by standard nickel chrome electrical elements and having a heavily insulated exterior.

  7. High pressure oxygen furnace

    DOEpatents

    Morris, D.E.

    1992-07-14

    A high temperature high pressure oxygen furnace having a hybrid partially externally heated construction is disclosed. A metallic bar fabricated from an alloy having a composition of at least 45% nickel, 15% chrome, and 10% tungsten is utilized, the preferred alloy including 55% nickel, 22% chrome, 14% tungsten, 2% molybdenum, 3% iron (maximum) and 5% cobalt (maximum). The disclosed alloy is fabricated into 11/4 inch bar stock and has a length of about 17 inches. This bar stock is gun drilled for over 16 inches of its length with 0.400 inch aperture to define a closed high temperature, high pressure oxygen chamber. The opposite and closed end of the bar is provided with a small support aperture into which both a support and a thermocouple can be inserted. The closed end of the gun drilled bar is inserted into an oven, preferably heated by standard nickel chrome electrical elements and having a heavily insulated exterior. 5 figs.

  8. High pressure oxygen furnace

    DOEpatents

    Morris, Donald E.

    1992-01-01

    A high temperature high pressure oxygen furnace having a hybrid partially externally heated construction is disclosed. A metallic bar fabricated from an alloy having a composition of at least 45% nickel, 15% chrome, and 10% tungsten is utilized (the preferred alloy including 55% nickel, 22% chrome, 14% tungsten, 2% molybdenum, 3% iron (maximum) and 5% cobalt (maximum). The disclosed alloy is fabricated into 11/4 inch bar stock and has a length of about 17 inches. This bar stock is gun drilled for over 16 inches of its length with 0.400 inch aperture to define a closed high temperature, high pressure oxygen chamber. The opposite and closed end of the bar is provided with a small support aperture into which both a support and a thermocouple can be inserted. The closed end of the gun drilled bar is inserted into an oven, preferably heated by standard nickel chrome electrical elements and having a heavily insulated exterior.

  9. Graphite fluoride fibers and their applications in the space industry

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Chen; Long, Martin; Dever, Therese

    1990-01-01

    Characterization and potential space applications of graphite fluoride fibers from commercially available graphitized carbon fibers are presented. Graphite fluoride fibers with fluorine to carbon ratios of 0.65 and 0.68 were found to have electrical resistivity values of 10(exp 4) and 10(exp 11) Ohms-cm, respectively, and thermal conductivity values of 24 and 5 W/m-K, respectively. At this fluorine content range, the fibers have tensile strength of 0.25 + or - 0.10 GPa (36 + or - 14 ksi), Young's modulus of 170 + or - 30 GPa (25 + or - 5 Msi). The coefficient of thermal expansion value of a sample with fluorine to carbon ratio of 0.61 was found to be 7 ppm/C. These properties change and approach the graphite value as the fluorine content approach 0. Electrically insulative graphite fluoride fiber is at least five times more thermally conductive than fiberglass. Therefore, it can be used as a heat sinking printed circuit board material for low temperature, long life power electronics in spacecraft. Also, partially fluorinated fiber with tailor-made physical properties to meet the requirements of certain engineering design can be produced. For example, a partially fluorinated fiber could have a predetermined CTE value in -1.5 to 7 ppm/C range and would be suitable for use in solar concentrators in solar dynamic power systems. It could also have a predetermined electrical resistivity value suitable for use as a low observable material. Experimental data indicate that slightly fluorinated graphite fibers are more durable in the atomic oxygen environment than pristine graphite. Therefore, fluorination of graphite used in the construction of spacecraft that would be exposed to the low Earth orbit atomic oxygen may protect defect sites in atomic oxygen protective coatings and therefore decrease the rate of degradation of graphite.

  10. Graphite Technology Development Plan

    SciTech Connect

    W. Windes; T. Burchell; R. Bratton

    2007-09-01

    This technology development plan is designed to provide a clear understanding of the research and development direction necessary for the qualification of nuclear grade graphite for use within the Next Generation Nuclear Plant (NGNP) reactor. The NGNP will be a helium gas cooled Very High Temperature Reactor (VHTR) with a large graphite core. Graphite physically contains the fuel and comprises the majority of the core volume. Considerable effort will be required to ensure that the graphite performance is not compromised during operation. Based upon the perceived requirements the major data needs are outlined and justified from the perspective of reactor design, reatcor performance, or the reactor safety case. The path forward for technology development can then be easily determined for each data need. How the data will be obtained and the inter-relationships between the experimental and modeling activities will define the technology development for graphite R&D. Finally, the variables affecting this R&D program are discussed from a general perspective. Factors that can significantly affect the R&D program such as funding, schedules, available resources, multiple reactor designs, and graphite acquisition are analyzed.

  11. Graphite design handbook

    SciTech Connect

    Ho, F.H.

    1988-09-01

    The objectives of the Graphite Design Handbook (GDH) are to provide and maintain a single source of graphite properties and phenomenological model of mechanical behavior to be used for design of MHTGR graphite components of the Reactor System, namely, core support, permanent side reflector, hexagonal reflector elements, and prismatic fuel elements; to provide a single source of data and material models for use in MHTGR graphite component design, performance, and safety analyses; to present properties and equations representing material models in a form which can be directly used by the designer or analyst without the need for interpretation and is compatible with analytical methods and structural criteria used in the MHTGR project, and to control the properties and material models used in the MHTGR design and analysis to proper Quality Assurance standards and project requirements. The reference graphite in the reactor internal components is the nuclear grade 2020. There are two subgrades of interest, the cylinder nuclear grade and the large rectangular nuclear grade. The large rectangular nuclear grade is molded in large rectangular blocks. It is the reference material for the permanent side reflector and the central column support structure. The cylindrical nuclear grade is isostatically pressed and is intended for use as the core support component. This report gives the design properties for both H-451 and 2020 graphite as they apply to their respective criteria. The properties are presented in a form for design, performance, and safety calculations that define or validate the component design. 103 refs., 20 figs., 19 tabs.

  12. Fast heating induced impulse halogenation of refractory sample components in electrothermal atomic absorption spectrometry by direct injection of a liquid halogenating agent.

    PubMed

    György, Krisztina; Ajtony, Zsolt; Van Meel, Katleen; Van Grieken, René; Czitrovszky, Aladár; Bencs, László

    2011-09-15

    A novel electrothermal atomic absorption spectrometry (ETAAS) method was developed for the halogenation of refractory sample components (Er, Nd and Nb) of lithium niobate (LiNbO(3)) and bismuth tellurite (Bi(2)TeO(5)) optical single crystals to overcome memory effects and carry-over. For this purpose, the cleaning step of a regular graphite furnace heating program was replaced with a halogenation cycle. In this cycle, after the graphite tube cooled to room temperature, a 20 μL aliquot of liquid carbon tetrachloride (CCl(4)) was dispensed with a conventional autosampler into the graphite tube. The CCl(4) was partially dried at 80°C under the mini-flow (40 cm(3) min(-1)) condition of the Ar internal furnace gas (IFG), then the residue was decomposed (pyrolyzed) by fast furnace heating at 1900-2100°C under interrupted flow of the IFG. This step was followed by a clean-out stage at 2100°C under the maximum flow of the IFG. The advantage of the present method is that it does not require any alteration to the graphite furnace gas supply system in contrast to most of the formerly introduced halogenation techniques. The effectiveness of the halogenation method was verified with the determination of Er and Nd dopants in the optical crystals. In these analyses, a sensitivity decrease was observed, which was likely due to the enhanced deterioration of the graphite tube surface. Therefore, the application of mathematical correction (resloping) of the calibration was also required. The calibration curves were linear up to 1.5 and 10 μmol L(-1) for Er and Nd, respectively. Characteristic masses of 18 and 241 pg and the limit of detection (LOD) values of 0.017 and 0.27 μmol L(-1) were found for Er and Nd, respectively. These LOD data correspond to 0.68 μmol mol(-1) Er and 11 μmol mol(-1) Nd in solid bismuth tellurite samples. The analytical results were compared with those obtained by a conventional ETAAS method and validated with X-ray fluorescence spectrometry analysis.

  13. Gas exhaust nozzle for ARC furnaces

    SciTech Connect

    Buhler, K.

    1984-10-09

    Arc furnace has a furnace shell, a furnace lid with lid ring and a lid lifting and swivelling means as well as a lid opening in the furnace lid for exhausting the flue gas from the interior of the furnace and a flue gas exhaust nozzle for removing the flue gases above the lid opening, the nozzle being supported on the furnace lid ring. By means of this design feature as well as a guide arrangement and a locking means the flue gas exhaust nozzle can be completely integrated into the operating steps of the arc furnace in a simple and economical fashion.

  14. Rebuilding of Rautaruukki blast furnaces

    SciTech Connect

    Kallo, S.; Pisilae, E.; Ojala, K.

    1997-12-31

    Rautaruukki Oy Raahe Steel rebuilt its blast furnaces in 1995 (BF1) and 1996 (BF2) after 10 year campaigns and production of 9,747 THM/m{sup 3} (303 NTHM/ft{sup 3}) and 9,535 THM/m{sup 3} (297 NTHM/ft{sup 3}), respectively. At the end of the campaigns, damaged cooling system and shell cracks were increasingly disturbing the availability of furnaces. The goal for rebuilding was to improve the cooling systems and refractory quality in order to attain a 15 year campaign. The furnaces were slightly enlarged to meet the future production demand. The blast furnace control rooms and operations were centralized and the automation and instrumentation level was considerably improved in order to improve the operation efficiency and to reduce manpower requirements. Investments in direct slag granulation and improved casthouse dedusting improved environmental protection. The paper describes the rebuilding.

  15. Glass Furnace Model Version 2

    2003-05-06

    GFM2.0 is a derivative of the GFM code with substantially altered and enhanced capabilities. Like its predecessor, it is a fully three-dimensional, furnace simulation model that provides a more accurate representation of the entire furnace, and specifically, the glass melting process, by coupling the combustion space directly to the glass batch and glass melt via rigorous radiation heat transport models for both the combustion space and the glass melt. No assumptions are made with regardmore » to interfacial parameters of heat, flux, temperature distribution, and batch coverage as must be done using other applicable codes available. These critical parameters are calculated. GFM2.0 contains a processor structured to facilitate use of the code, including the entry of teh furnace geometry and operating conditions, the execution of the program, and display of the computational results. Furnace simulations can therefore be created in a straightforward manner.« less

  16. Improved Blackbody Temperature Sensors for a Vacuum Furnace

    NASA Technical Reports Server (NTRS)

    Farmer, Jeff; Coppens, Chris; O'Dell, J. Scott; McKechnie, Timothy N.; Schofield, Elizabeth

    2009-01-01

    Some improvements have been made in the design and fabrication of blackbody sensors (BBSs) used to measure the temperature of a heater core in a vacuum furnace. Each BBS consists of a ring of thermally conductive, high-melting-temperature material with two tantalum-sheathed thermocouples attached at diametrically opposite points. The name "blackbody sensor" reflects the basic principle of operation. Heat is transferred between the ring and the furnace heater core primarily by blackbody radiation, heat is conducted through the ring to the thermocouples, and the temperature of the ring (and, hence, the temperature of the heater core) is measured by use of the thermocouples. Two main requirements have guided the development of these BBSs: (1) The rings should have as high an emissivity as possible in order to maximize the heat-transfer rate and thereby maximize temperature-monitoring performance and (2) the thermocouples must be joined to the rings in such a way as to ensure long-term, reliable intimate thermal contact. The problem of fabricating a BBS to satisfy these requirements is complicated by an application-specific prohibition against overheating and thereby damaging nearby instrumentation leads through the use of conventional furnace brazing or any other technique that involves heating the entire BBS and its surroundings. The problem is further complicated by another application-specific prohibition against damaging the thin tantalum thermocouple sheaths through the use of conventional welding to join the thermocouples to the ring. The first BBS rings were made of graphite. The tantalum-sheathed thermocouples were attached to the graphite rings by use of high-temperature graphite cements. The ring/thermocouple bonds thus formed were found to be weak and unreliable, and so graphite rings and graphite cements were abandoned. Now, each BBS ring is made from one of two materials: either tantalum or a molybdenum/titanium/zirconium alloy. The tantalum

  17. Variable frequency microwave furnace system

    DOEpatents

    Bible, D.W.; Lauf, R.J.

    1994-06-14

    A variable frequency microwave furnace system designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity for testing or other selected applications. The variable frequency microwave furnace system includes a microwave signal generator or microwave voltage-controlled oscillator for generating a low-power microwave signal for input to the microwave furnace. A first amplifier may be provided to amplify the magnitude of the signal output from the microwave signal generator or the microwave voltage-controlled oscillator. A second amplifier is provided for processing the signal output by the first amplifier. The second amplifier outputs the microwave signal input to the furnace cavity. In the preferred embodiment, the second amplifier is a traveling-wave tube (TWT). A power supply is provided for operation of the second amplifier. A directional coupler is provided for detecting the direction of a signal and further directing the signal depending on the detected direction. A first power meter is provided for measuring the power delivered to the microwave furnace. A second power meter detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load. 5 figs.

  18. Variable frequency microwave furnace system

    DOEpatents

    Bible, Don W.; Lauf, Robert J.

    1994-01-01

    A variable frequency microwave furnace system (10) designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity (34) for testing or other selected applications. The variable frequency microwave furnace system (10) includes a microwave signal generator (12) or microwave voltage-controlled oscillator (14) for generating a low-power microwave signal for input to the microwave furnace. A first amplifier (18) may be provided to amplify the magnitude of the signal output from the microwave signal generator (12) or the microwave voltage-controlled oscillator (14). A second amplifier (20) is provided for processing the signal output by the first amplifier (18). The second amplifier (20) outputs the microwave signal input to the furnace cavity (34). In the preferred embodiment, the second amplifier (20) is a traveling-wave tube (TWT). A power supply (22) is provided for operation of the second amplifier (20). A directional coupler (24) is provided for detecting the direction of a signal and further directing the signal depending on the detected direction. A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load (28).

  19. Fossil fuel furnace reactor

    DOEpatents

    Parkinson, William J.

    1987-01-01

    A fossil fuel furnace reactor is provided for simulating a continuous processing plant with a batch reactor. An internal reaction vessel contains a batch of shale oil, with the vessel having a relatively thin wall thickness for a heat transfer rate effective to simulate a process temperature history in the selected continuous processing plant. A heater jacket is disposed about the reactor vessel and defines a number of independent controllable temperature zones axially spaced along the reaction vessel. Each temperature zone can be energized to simulate a time-temperature history of process material through the continuous plant. A pressure vessel contains both the heater jacket and the reaction vessel at an operating pressure functionally selected to simulate the continuous processing plant. The process yield from the oil shale may be used as feedback information to software simulating operation of the continuous plant to provide operating parameters, i.e., temperature profiles, ambient atmosphere, operating pressure, material feed rates, etc., for simulation in the batch reactor.

  20. Recompressed exfoliated graphite articles

    DOEpatents

    Zhamu, Aruna; Shi, Jinjun; Guo, Jiusheng; Jang, Bor Z

    2013-08-06

    This invention provides an electrically conductive, less anisotropic, recompressed exfoliated graphite article comprising a mixture of (a) expanded or exfoliated graphite flakes; and (b) particles of non-expandable graphite or carbon, wherein the non-expandable graphite or carbon particles are in the amount of between about 3% and about 70% by weight based on the total weight of the particles and the expanded graphite flakes combined; wherein the mixture is compressed to form the article having an apparent bulk density of from about 0.1 g/cm.sup.3 to about 2.0 g/cm.sup.3. The article exhibits a thickness-direction conductivity typically greater than 50 S/cm, more typically greater than 100 S/cm, and most typically greater than 200 S/cm. The article, when used in a thin foil or sheet form, can be a useful component in a sheet molding compound plate used as a fuel cell separator or flow field plate. The article may also be used as a current collector for a battery, supercapacitor, or any other electrochemical cell.

  1. Graphene-like nanosheets synthesized by natural flaky graphite in Shandong, China

    NASA Astrophysics Data System (ADS)

    Xiu-Yun, Chuan

    2013-02-01

    Natural flaky graphite in Shandong, China was purified by H2O2, a new patent method to produce graphite without sulfur and used as precursor to prepare exfoliated graphite through microwave irradiated expansion with some chemicals (such as hydrogen peroxide, nitric acid, and acetic acid). With the centrifugation process, graphene was synthesized by using an efficient and simple method under ultrasonic and microwave irradiation at the room temperature. Natural graphite and exfoliated graphite were characterized by X-ray diffraction and scanning electronic microscopy, and the resultant graphene was investigated and confirmed by atomic force microscopy, Raman micro-spectrometer, etc. Natural graphite in Shandong, China, consisted of mainly hexagonal (2H) and a little rhombohedral structure (3R), was beneficial for the synthesis of graphene. Graphene-like nanosheets about 1 to 3 nm, around three to five carbon layers can be synthesized efficiently by microwave and ultrasonic irradiation with natural graphite.

  2. Interaction of boron with graphite: A van der Waals density functional study

    NASA Astrophysics Data System (ADS)

    Liu, Juan; Wang, Chen; Liang, Tongxiang; Lai, Wensheng

    2016-08-01

    Boron doping has been widely investigated to improve oxidation resistance of graphite. In this work the interaction of boron with graphite is investigated by a van der Waals density-functional approach (vdW-DF). The traditional density-functional theory (DFT) is well accounted for the binding in boron-substituted graphite. However, to investigate the boron atom on graphite surface and the interstitial impurities require use of a description of graphite interlayer binding. Traditional DFT cannot describe the vdW physics, for instance, GGA calculations show no relevant binding between graphite sheets. LDA shows some binding, but they fail to provide an accurate account of vdW forces. In this paper, we compare the calculation results of graphite lattice constant and cohesive energy by several functionals, it shows that vdW-DF such as two optimized functionals optB88-vdW and optB86b-vdW give much improved results than traditional DFT. The vdW-DF approach is then applied to study the interaction of boron with graphite. Boron adsorption, substitution, and intercalation are discussed in terms of structural parameters and electronic structures. When adsorbing on graphite surface, boron behaves as π electron acceptor. The π electron approaches boron atom because of more electropositive of boron than carbon. For substitution situation, the hole introduced by boron mainly concentrates on boron and the nearest three carbon atoms. The B-doped graphite system with the hole has less ability to offer electrons to oxygen, ultimately resulted in the inhibition of carbon oxidation. For interstitial doping, vdW-DFs show more accurate formation energy than LDA. PBE functional cannot describe the interstitial boron in graphite reasonably because of the ignoring binding of graphite sheets. The investigation of electron structures of boron doped graphite will play an important role in understanding the oxidation mechanism in further study.

  3. Graphite formation in the Hiroshima fire storm

    SciTech Connect

    Fields, D.E.; Crenshaw, M.; Yalcintas, M.G.; Strehlow, R.A. ); Cole, L.L. )

    1991-01-01

    In order to investigate what might be the composition and optical properties of particles that could lead to a nuclear winter, a search has been made for particles that had been generated in urban fire storms. Deposits containing small amounts of graphite have been found on an artifact from the Hiroshima fire storm. The fire storm was initiated on August 6, 1945, by the atomic bomb detonation. The particles were rained out of the atmosphere in the black rain that commenced following the urban fire storm. Initial studies using electron microscopy have revealed that the particles consist of a mixture of clay and amorphous sooty carbon. Scanning electron photomicrographs have suggested the presence of graphite. Its presence has been confirmed using laser Raman spectroscopy (LRS), surface ionization mass spectroscopy (SIMS), and electron scattering for chemical analysis (ESCA). Significant amounts of the sooty material consist of clay, and the graphite is probably present as short-range ordered structure in sooty microspheres. The results of this study are presented with a discussion of conditions that may lead to graphite formation.

  4. Irradiation Creep in Graphite

    SciTech Connect

    Ubic, Rick; Butt, Darryl; Windes, William

    2014-03-13

    An understanding of the underlying mechanisms of irradiation creep in graphite material is required to correctly interpret experimental data, explain micromechanical modeling results, and predict whole-core behavior. This project will focus on experimental microscopic data to demonstrate the mechanism of irradiation creep. High-resolution transmission electron microscopy should be able to image both the dislocations in graphite and the irradiation-induced interstitial clusters that pin those dislocations. The team will first prepare and characterize nanoscale samples of virgin nuclear graphite in a transmission electron microscope. Additional samples will be irradiated to varying degrees at the Advanced Test Reactor (ATR) facility and similarly characterized. Researchers will record microstructures and crystal defects and suggest a mechanism for irradiation creep based on the results. In addition, the purchase of a tensile holder for a transmission electron microscope will allow, for the first time, in situ observation of creep behavior on the microstructure and crystallographic defects.

  5. Coatings for graphite fibers

    NASA Technical Reports Server (NTRS)

    Galasso, F. S.; Scola, D. A.; Veltri, R. D.

    1980-01-01

    Graphite fibers released from composites during burning or an explosion caused shorting of electrical and electronic equipment. Silicon carbide, silica, silicon nitride and boron nitride were coated on graphite fibers to increase their electrical resistances. Resistances as high as three orders of magnitude higher than uncoated fiber were attained without any significant degradation of the substrate fiber. An organo-silicone approach to produce coated fibers with high electrical resistance was also used. Celion 6000 graphite fibers were coated with an organo-silicone compound, followed by hydrolysis and pyrolysis of the coating to a silica-like material. The shear and flexural strengths of composites made from high electrically resistant fibers were considerably lower than the shear and flexural strengths of composites made from the lower electrically resistant fibers. The lower shear strengths of the composites indicated that the coatings on these fibers were weaker than the coating on the fibers which were pyrolyzed at higher temperature.

  6. Cesium diffusion in graphite

    SciTech Connect

    Evans, R.B. III; Davis, W. Jr.; Sutton, A.L. Jr.

    1980-05-01

    Experiments on diffusion of /sup 137/Cs in five types of graphite were performed. The document provides a completion of the report that was started and includes a presentation of all of the diffusion data, previously unpublished. Except for data on mass transfer of /sup 137/Cs in the Hawker-Siddeley graphite, analyses of experimental results were initiated but not completed. The mass transfer process of cesium in HS-1-1 graphite at 600 to 1000/sup 0/C in a helium atmosphere is essentially pure diffusion wherein values of (E/epsilon) and ..delta..E of the equation D/epsilon = (D/epsilon)/sub 0/ exp (-..delta..E/RT) are about 4 x 10/sup -2/ cm/sup 2//s and 30 kcal/mole, respectively.

  7. Hydration and dewetting near graphite-CH(3) and graphite-COOH plates.

    PubMed

    Li, Jingyuan; Liu, Ting; Li, Xin; Ye, Lei; Chen, Huajun; Fang, Haiping; Wu, Zhaohui; Zhou, Ruhong

    2005-07-21

    The dynamics of water near the nanoscale hydrophobic (graphite-CH(3)) and hydrophilic (graphite-COOH) plates has been studied in detail with molecular dynamics simulations in this paper. It is shown that these designed surfaces (by growing a layer of methyl or carboxyl groups on top of graphite) can have a significant impact on the neighboring water dynamics, with the hydrophilic carboxyl surface having even more profound effects. The water hydrogen bond lifetime is much longer near both types of surfaces than that in the bulk, while on the other hand the water diffusion constant is much smaller than that in the bulk. The difference in the diffusion constant can be as large as a factor of 8 and the difference in the hydrogen bond lifetime can be as large as a factor of 2, depending on the distance from the surface. Furthermore, the water molecules in the first solvation shell of surface atoms show a strong bias in hydroxyl group orientation near the surface, confirming some of the previous findings. Finally, the possible water dewetting transition between two graphite-CH(3) plates and the effect of the strength of the solute-solvent attractions on the water drying transition are investigated. The relationship among the dewetting transition critical distance, van der Waals potential well depth, and water contact angle on the graphite-CH(3) surface is also analyzed on the basis of a simple macroscopic theory, which can be used to predict the dewetting transition critical distance.

  8. EAST (FRONT) AND NORTH SIDE OF DOUBLE FURNACE AND NORTH ...

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

    EAST (FRONT) AND NORTH SIDE OF DOUBLE FURNACE AND NORTH SIDE OF SINGLE FURNACE, SOUTHWEST. - Tannehill Furnace, 12632 Confederate Parkway, Tannehill Historical State Park, Bucksville, Tuscaloosa County, AL

  9. Role of hydrogen in blast furnaces to improve productivity and decrease coke consumption

    SciTech Connect

    Agarwal, J.C.; Brown, F.C.; Chin, D.L.; Stevens, G.; Clark, R.; Smith, D.

    1995-12-01

    The hydrogen contained in blast furnace gases exerts a variety of physical, thermochemical, and kinetic effects as the gases pass through the various zones. The hydrogen is derived from two sources: (1) the dissociation of moisture in the blast air (ambient and injected with hot blast), and (2) the release from partial combustion of supplemental fuels (including moisture in atomizing water, steam, or transport air, if any). With each atom of oxygen (or carbon), the molar amounts of hydrogen released are more than six times higher for natural gas than for coal, and two times higher for natural gas than for oil. Injection of natural gas in a blast furnace is not a new process. Small amounts of natural gas--about 50--80 lb or 1,100--1,700 SCF/ton of hot metal--have been injected in many of the North American blast furnaces since the early 1960s, with excellent operating results. What is new, however, is a batter understanding of how natural gas reacts in the blast furnace and how natural gas and appropriate quantities of oxygen can be used to increase the driving rate or combustion rate of carbon (coke) in the blast furnace without causing hanging furnace and operating problems. The paper discusses the factors limiting blast furnace productivity and how H{sub 2} and O{sub 2} can increase productivity.

  10. Fundamental properties of an ICP with a graphite torch injector

    SciTech Connect

    Clemons, P.S.; Houk, R.S.; Praphairakisit, N.

    1996-09-01

    A hollow graphite torch injector can be used to constrict the analyte zone in an ICP. From a practical standpoint, oxide levels can be reduced to 0.01% for the signal ratio LaO{sup +}/La{sup +} and analyte signals increased by factors of three to fifteen, depending on the element. This paper reports recent measurements of background mass spectra, temperature and electron density in the plasma flowing into the sampler using a graphite torch injector. The graphite injector improves BEC values for most analytes that suffer interference from prominent polyatomic ions like ArO{sup +}, ClO{sup +}, and ArCl{sup +}. One notable exception is ArC{sup +}, which is substantially worse because of the high level of carbon injected into the plasma. Carbon evaporation rates of 1x10{sup 17} to 5x10{sup 17} atoms/s have been measured, the actual values depending on the grade of graphite used. This is sufficient carbon for C{sup +} to become a major background ion and for formation of CO to help reduce the level of O atoms in the plasma. Charge transfer reactions from C{sup +} to neutral As and Se help enhance the sensitivity for these important elements. Doubly charged ions are somewhat more abundant with the graphite injector than with a conventional torch, because a hotter region of the plasma is sampled with the graphite injector.

  11. Graphite-based photovoltaic cells

    DOEpatents

    Lagally, Max; Liu, Feng

    2010-12-28

    The present invention uses lithographically patterned graphite stacks as the basic building elements of an efficient and economical photovoltaic cell. The basic design of the graphite-based photovoltaic cells includes a plurality of spatially separated graphite stacks, each comprising a plurality of vertically stacked, semiconducting graphene sheets (carbon nanoribbons) bridging electrically conductive contacts.

  12. The adsorption of aromatic acids onto the graphite basal surface

    NASA Astrophysics Data System (ADS)

    Martin, David S.

    2003-06-01

    The adsorption of benzoic acid, toluic acid, and salicylic acid from solution onto the graphite basal surface has been studied using atomic force microscopy (AFM). A systematic study of these three related planar aromatic acids is conducted in order to observe the influence of the functional side-group upon adsorption. It is found that upon adsorption all three acids orient with the benzene ring parallel to the graphite surface. On the graphite terraces, the benzoic acid decoration follows a Stranski-Krastanov growth mode whereas toluic acid follows Volmer-Weber growth. Salicylic acid forms a fibrous aggregate network. In addition to the terraces, graphite steps and near-surface bulk defects are found to be important sites for adsorption. The AFM tip is used to create irreversible nanoscale modifications of adsorbate structures.

  13. Coatings for Graphite Fibers

    NASA Technical Reports Server (NTRS)

    Galasso, F. S.; Scola, D. A.; Veltri, R. D.

    1980-01-01

    Several approaches for applying high resistance coatings continuously to graphite yarn were investigated. Two of the most promising approaches involved (1) chemically vapor depositing (CVD) SiC coatings on the surface of the fiber followed by oxidation, and (2) drawing the graphite yarn through an organo-silicone solution followed by heat treatments. In both methods, coated fibers were obtained which exhibited increased electrical resistances over untreated fibers and which were not degraded. This work was conducted in a previous program. In this program, the continuous CVD SiC coating process used on HTS fiber was extended to the coating of HMS, Celion 6000, Celion 12000 and T-300 graphite fiber. Electrical resistances three order of magnitude greater than the uncoated fiber were measured with no significant degradation of the fiber strength. Graphite fibers coated with CVD Si3N4 and BN had resistances greater than 10(exp 6) ohm/cm. Lower pyrolysis temperatures were used in preparing the silica-like coatings also resulting in resistances as high as three orders of magnitude higher than the uncoated fiber. The epoxy matrix composites prepared using these coated fibers had low shear strengths indicating that the coatings were weak.

  14. Structural graphitic carbon foams

    SciTech Connect

    Kearns, K.M.; Anderson, H.J.

    1998-12-31

    Graphitic carbon foams are a unique material form with very high structural and thermal properties at a light weight. A process has been developed to produce microcellular, open-celled graphitic foams. The process includes heating a mesophase pitch preform above the pitch melting temperature in a pressurized reactor. At the appropriate time, the pressure is released, the gas nucleates bubbles, and these bubbles grow forming the pitch into the foam structure. The resultant foamed pitch is then stabilized in an oxygen environment. At this point a rigid structure exists with some mechanical integrity. The foam is then carbonized to 800 C followed by a graphitization to 2700 C. The shear action from the growing bubbles aligns the graphitic planes along the foam struts to provide the ideal structure for good mechanical properties. Some of these properties have been characterized for some of the foam materials. It is known that variations of the blowing temperature, blowing pressure and saturation time result in foams of variously sized with mostly open pores; however, the mechanism of bubble nucleation is not known. Therefore foams were blown with various gases to begin to determine the nucleation method. These gases are comprised of a variety of molecular weights as well as a range of various solubility levels. By examining the resultant structures of the foam, differences were noted to develop an explanation of the foaming mechanism.

  15. Graphite technology development plan

    SciTech Connect

    1986-07-01

    This document presents the plan for the graphite technology development required to support the design of the 350 MW(t) Modular HTGR within the US National Gas-Cooled Reactor Program. Besides descriptions of the required technology development, cost estimates, and schedules, the plan also includes the associated design functions and design requirements.

  16. GRAPHITE BONDING METHOD

    DOEpatents

    King, L.D.P.

    1964-02-25

    A process for bonding or joining graphite members together in which a thin platinum foil is placed between the members, heated in an inert atmosphere to a temperature of 1800 deg C, and then cooled to room temperature is described. (AEC)

  17. (Irradiation creep of graphite)

    SciTech Connect

    Kennedy, C.R.

    1990-12-21

    The traveler attended the Conference, International Symposium on Carbon, to present an invited paper, Irradiation Creep of Graphite,'' and chair one of the technical sessions. There were many papers of particular interest to ORNL and HTGR technology presented by the Japanese since they do not have a particular technology embargo and are quite open in describing their work and results. In particular, a paper describing the failure of Minor's law to predict the fatigue life of graphite was presented. Although the conference had an international flavor, it was dominated by the Japanese. This was primarily a result of geography; however, the work presented by the Japanese illustrated an internal program that is very comprehensive. This conference, a result of this program, was better than all other carbon conferences attended by the traveler. This conference emphasizes the need for US participation in international conferences in order to stay abreast of the rapidly expanding HTGR and graphite technology throughout the world. The United States is no longer a leader in some emerging technologies. The traveler was surprised by the Japanese position in their HTGR development. Their reactor is licensed and the major problem in their graphite program is how to eliminate it with the least perturbation now that most of the work has been done.

  18. Deconstructing graphite: graphenide solutions.

    PubMed

    Pénicaud, Alain; Drummond, Carlos

    2013-01-15

    Growing interest in graphene over past few years has prompted researchers to find new routes for producing this material other than mechanical exfoliation or growth from silicon carbide. Chemical vapor deposition on metallic substrates now allows researchers to produce continuous graphene films over large areas. In parallel, researchers will need liquid, large scale, formulations of graphene to produce functional graphene materials that take advantage of graphene's mechanical, electrical, and barrier properties. In this Account, we describe methods for creating graphene solutions from graphite. Graphite provides a cheap source of carbon, but graphite is insoluble. With extensive sonication, it can be dispersed in organic solvents or water with adequate additives. Nevertheless, this process usually creates cracks and defects in the graphite. On the other hand, graphite intercalation compounds (GICs) provide a means to dissolve rather than disperse graphite. GICS can be obtained through the reaction of alkali metals with graphite. These compounds are a source of graphenide salts and also serve as an excellent electronic model of graphene due to the decoupling between graphene layers. The graphenide macroions, negatively charged graphene sheets, form supple two-dimensional polyelectrolytes that spontaneously dissolve in some organic solvents. The entropic gain from the dissolution of counterions and the increased degrees of freedom of graphene in solution drives this process. Notably, we can obtain graphenide solutions in easily processable solvents with low boiling points such as tetrahydrofuran or cyclopentylmethylether. We performed a statistical analysis of high resolution transmission electronic micrographs of graphene sheets deposited on grids from GICs solution to show that the dissolved material has been fully exfoliated. The thickness distribution peaks with single layers and includes a few double- or triple-layer objects. Light scattering analysis of the

  19. The characterization of fluorinated graphite

    SciTech Connect

    Hagaman, E.W.; Gakh, A.A.; Annis, B.K.

    1995-12-31

    The characterization of solid fossil fuels by chemical and spectroscopic methods requires extensive modelling in less complex systems for chemical proof of principle and technique development. In previous work coal was fluorinated with dilute, elemental fluorine under conditions that were expected to lead to materials that contain only fluoromethine moieties. The solid state, cross polarization/magic angle spinning (CP/MAS) {sup 13}C NMR spectra of the fluorinated coal are complex, indicating more chemical modification than originally anticipated. Our goal in the coal derivatization was to sequentially increase the severity of the fluorination and observe by {sup 19}F and {sup 13}C NMR the type and concentration of fluorine functional groups created in the coal milieu. This requires the ability to discriminate between C, CF, CF{sub 2}, and CF, moieties in the coal matrix. The task can be accomplished by implementing the spectral editing technique of Wu and Zilm which distinguishes different kinds of carbon resonances, especially CH and CH{sub 2} resonances. These experiments utilize cross polarization (CP) and polarization inversion (PI) to effect the discrimination. Our version of this experiment is a triple resonance experiment that incorporates {sup 19}F-{sup 13}C CP, PI, and simultaneous {sup 1}H and {sup 19}F dipolar decoupling. In order to evaluate the elemental fluorine chemistry in a matrix simpler than coal, fluorinated graphite was prepared. X-ray photoelectron spectroscopy (XPS) was used to characterize the surface species, i.e., count CF, CF{sub 2} and CF{sub 3} species. These well-characterized samples are the models we will use to test the NIVIR editing experiments. The XPS and atomic force microscopy (AFM) data on the first fluorinated graphites we have prepared are reported in this paper.

  20. Towards graphene iodide: iodination of graphite oxide

    NASA Astrophysics Data System (ADS)

    Šimek, Petr; Klímová, Kateřina; Sedmidubský, David; Jankovský, Ondřej; Pumera, Martin; Sofer, Zdeněk

    2014-11-01

    Halogenated graphene derivatives are interesting owing to their outstanding physical and chemical properties. In this paper, we present various methods for the synthesis of iodinated graphene derivatives by the iodination of graphite oxides prepared according to either the Hummers or Hofmann method. Both graphite oxides were iodinated by iodine or hydroiodic acid under reflux or in an autoclave at elevated temperatures (240 °C) and pressures (over 100 bar). The influence of both graphite oxide precursors on the properties of resulting iodinated graphenes was investigated by various techniques, including SEM, SEM-EDS, high-resolution XPS, FTIR, STA, and Raman spectroscopy. Electrical resistivity was measured by a standard four point technique. In addition, the electrochemical properties were investigated by cyclic voltammetry. Although the iodinated graphenes were structurally similar, they had remarkably different concentrations of iodine. The most highly iodinated graphenes (iodine concentration above 30 wt%) exhibited relatively high C/O ratios, confirming high degrees of reduction. Iodine is incorporated in the form of covalent bonds to carbon atoms or as polyiodide anions non-covalently bonded through the charge transfer reaction with the graphene framework. Iodinated graphenes with such properties could be used as the starting material for further chemical modifications or as flame-retardant additives.Halogenated graphene derivatives are interesting owing to their outstanding physical and chemical properties. In this paper, we present various methods for the synthesis of iodinated graphene derivatives by the iodination of graphite oxides prepared according to either the Hummers or Hofmann method. Both graphite oxides were iodinated by iodine or hydroiodic acid under reflux or in an autoclave at elevated temperatures (240 °C) and pressures (over 100 bar). The influence of both graphite oxide precursors on the properties of resulting iodinated graphenes was

  1. Feeder apparatus for melting furnaces, particularly for plasma melting furnaces

    SciTech Connect

    Primke, K.; Papsdorf, P.; Pohle, G.; Trautmann, K.P.

    1984-08-28

    The invention comprises a charging apparatus for melting furnaces, especially for plasma melting furnaces, for the continuous melting of preferably prepared aluminum scrap material. With the help of the proposed solution a controlled and regulated supply of the scrap material along with the prevention of a direct application of the plasma arc or other energy sources directly to the material to be melted, can be accomplished with the simultaneous pre-warming and cleaning of the material to be melted, wherein the metal loss resulting from burning is minimized, the contents of the contaminants within the metallic smelt is reduced and, in addition, an effective environmental protection can be accomplished. This is attained by the provision of an axially movable shaft arranged vertically or tilted in the opening of the furnace and having on the charging side a charging funnel with an exhaust ring nozzle. The shaft is guided in a guiding bushing provided with sliding strips, which is welded to the outer wall of the furnace. For the supply of the combustion air as well as for the production of the axial oscillations, the upper portion of the shaft and below the charging funnel, a compressed air piping and a mechanical shaker is arranged. The regulation of the charging height is performed by means of a mechanical sensor or a mirror system which is arranged in the shaft or outer of the charging apparatus.

  2. Automated, High Temperature Furnace for Glovebox Operation

    SciTech Connect

    Neikirk, K.

    2001-01-03

    The Plutonium Immobilization Project (PIP), to be located at the Savannah River Site SRS, is a combined development and testing effort by Lawrence Livermore National Laboratory (LLNL), Westinghouse Savannah River Company (WSRC), Pacific Northwest National Laboratory (PNNL), Argonne National Laboratory (ANL), and the Australian National Science and Technology Organization (ANSTO). The Plutonium Immobilization process involves the disposition of excess plutonium by incorporation into ceramic pucks. As part of the immobilization process, furnaces are needed for sintering the ceramic pucks. The furnace being developed for puck sintering is an automated, bottom loaded furnace with insulating package and resistance heating elements located within a nuclear glovebox. Other furnaces types considered for the application include retort furnaces and pusher furnaces. This paper, in part, will discuss the furnace technologies considered and furnace technology selected to support reliable puck sintering in a glovebox environment.

  3. Calculation of 3s photoemission spectra of vanadium on graphite

    SciTech Connect

    Krueger, P.; Taguchi, M.; Parlebas, J.C.; Kotani, A.

    1997-06-01

    A few years ago, a satellite structure in the vanadium 3s x-ray photoemission spectroscopy (XPS) spectrum of V clusters upon graphite was observed and attributed to the presence of magnetic moments on the V surface. Here, we present calculations of these spectra using a cluster model that takes into account intra-atomic d-d and d{endash}core electron correlation and hybridization between V d and graphite {pi} states. When the V-graphite distance is increased from 1.5 to 2.0 {Angstrom} the system undergoes a low-to-high spin transition, which is clearly evidenced in the evolution of the XPS line shape. Although direct comparison with experiment is difficult, our study suggests that the observed satellite is due to core hole screening rather than a magnetic moment on the V atom. {copyright} {ital 1997} {ital The American Physical Society}

  4. Electrostatic Levitation Furnace for the ISS

    NASA Technical Reports Server (NTRS)

    Murakami, Keiji; Koshikawa, Naokiyo; Shibasaki, Kohichi; Ishikawa, Takehiko; Okada, Junpei; Takada, Tetsuya; Arai, Tatsuya; Fujino, Naoki; Yamaura, Yukiko

    2012-01-01

    JAXA (Japan Aerospace Exploration Agency) has just started the development of Electrostatic Levitation Furnace to be launched in 2014 for the ISS. This furnace can control the sample position with electrostatic force and heat it above 2000 degree Celsius using semiconductor laser from four different directions. The announcement of Opportunity will be issued soon for this furnace. In this paper, we will show the specifications of this furnace and also the development schedule

  5. Hopewell Furnace National Historic Site. Teacher's Guide.

    ERIC Educational Resources Information Center

    National Park Service (Dept. of Interior), Washington, DC.

    This teacher's guide contains activities to use in conjunction with a site visit to the Hopewell Furnace National Historic Site (Elverson, Pennsylvania). The guide provides diagrams of the furnace, a cold-blast smelting operation, and the furnace operation. It presents a timeline of iron production from ancient times through contemporary times.…

  6. 10 CFR 429.18 - Residential furnaces.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 3 2014-01-01 2014-01-01 false Residential furnaces. 429.18 Section 429.18 Energy... COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.18 Residential furnaces. (a) Sampling plan for selection of units for testing. (1) The requirements of § 429.11 are applicable to residential furnaces;...

  7. 10 CFR 429.18 - Residential furnaces.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 3 2012-01-01 2012-01-01 false Residential furnaces. 429.18 Section 429.18 Energy... COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.18 Residential furnaces. (a) Sampling plan for selection of units for testing. (1) The requirements of § 429.11 are applicable to residential furnaces;...

  8. Design and construction of a compact vacuum furnace for scientific research

    NASA Astrophysics Data System (ADS)

    Lee, Chin C.; Wang, David T.; Choi, Won S.

    2006-12-01

    The design, construction, and measurement of a compact vacuum furnace are reported. This type of furnace has many scientific applications in material processing and growth research. One example is the fluxless bonding process, where elevated temperature is needed to melt the solder and vacuum environment is required to inhibit solder oxidation. The primary objective of the furnace design is to keep the vacuum enclosure cool using only natural convection while allowing the heating platform to reach high temperature. This characteristic is necessary to enable us to seal the vacuum chamber using O-rings. To achieve this, the platform was designed to be thermally isolated from the chamber enclosure. Heat losses from the platform by conduction, convection, and radiation were analyzed. The dominating loss was found to be caused by the blackbody radiation, which can thus be used to estimate the relationship between platform temperature and the drive power needed. With a graphite platform of 75×75×25mm3, only 270W of power is needed to drive the platform to 400°C. At this temperature, the temperature of the furnace enclosure is below 55°C, allowing O-rings to be used to seal the vacuum chamber. Using a mechanical pump, the furnace can be pumped down to 40mTorr, which is low enough for our fluxless bonding processes. With a temperature controller, the platform temperature can be controlled within 1%. The heat-up time to 400°C is only 7min.

  9. Crystal growth and furnace analysis

    NASA Technical Reports Server (NTRS)

    Dakhoul, Youssef M.

    1986-01-01

    A thermal analysis of Hg/Cd/Te solidification in a Bridgman cell is made using Continuum's VAST code. The energy equation is solved in an axisymmetric, quasi-steady domain for both the molten and solid alloy regions. Alloy composition is calculated by a simplified one-dimensional model to estimate its effect on melt thermal conductivity and, consequently, on the temperature field within the cell. Solidification is assumed to occur at a fixed temperature of 979 K. Simplified boundary conditions are included to model both the radiant and conductive heat exchange between the furnace walls and the alloy. Calculations are performed to show how the steady-state isotherms are affected by: the hot and cold furnace temperatures, boundary condition parameters, and the growth rate which affects the calculated alloy's composition. The Advanced Automatic Directional Solidification Furnace (AADSF), developed by NASA, is also thermally analyzed using the CINDA code. The objective is to determine the performance and the overall power requirements for different furnace designs.

  10. Acoustical Measurement Of Furnace Temperatures

    NASA Technical Reports Server (NTRS)

    Parthasarathy, Shakkottai; Venkateshan, Shakkottai P.

    1989-01-01

    Simple probes withstand severe conditions, yet give spatially-resolved temperature readings. Prototype acoustical system developed to measure temperatures from ambient to 1,800 degree F in such structures as large industrial lime kilns and recovery-boiler furnaces. Pulses of sound reflected from obstructions in sensing tube. Speed of sound and temperature in each segment deduced from travel times of pulses.

  11. Arc furnace steelmaking - an excerpt

    SciTech Connect

    Fitzgerald, F.

    1982-01-01

    According to the author, the arc furnace, with its small capital investment and economic plant size, seems destined to grow. The article reviews technical developments against a breakdown of costs and highlights new developments which have recently come to the fore. Energy considerations are covered.

  12. Training Guidelines: Glass Furnace Operators.

    ERIC Educational Resources Information Center

    Ceramics, Glass, and Mineral Products Industry Training Board, Harrow (England).

    Technological development in the glass industry is constantly directed towards producing high quality glass at low operating costs. Particularly, changes have taken place in melting methods which mean that the modern furnace operator has greater responsibilities than any of his predecessors. The complexity of control systems, melting rates, tank…

  13. Graphite polyhedral crystals.

    PubMed

    Gogotsi, Y; Libera, J A; Kalashnikov, N; Yoshimura, M

    2000-10-13

    Polyhedral nano- and microstructures with shapes of faceted needles, rods, rings, barrels, and double-tipped pyramids, which we call graphite polyhedral crystals (GPCs), have been discovered. They were found in pores of glassy carbon. They have nanotube cores and graphite faces, and they can exhibit unusual sevenfold, ninefold, or more complex axial symmetry. Although some are giant radially extended nanotubes, Raman spectroscopy and transmission electron microscopy suggest GPCs have a degree of perfection higher than in multiwall nanotubes of similar size. The crystals are up to 1 micrometer in cross section and 5 micrometers in length, and they can probably be grown in much larger sizes. Preliminary results suggest a high electrical conductivity, strength, and chemical stability of GPC.

  14. Self-assembly of 50 bp poly(dA)·poly(dT) DNA on highly oriented pyrolytic graphite via atomic force microscopy observation and molecular dynamics simulation.

    PubMed

    Doi, Kentaro; Takeuchi, Hiroshi; Nii, Ryosuke; Akamatsu, Shingo; Kakizaki, Toshiya; Kawano, Satoyuki

    2013-08-28

    This study has investigated the formation patterns resulting from the self-assembly of deoxyribonucleic acid (DNA) on highly oriented pyrolytic graphite (HOPG), using both experimental and molecular dynamics approaches. Under optimized conditions based on pretreatment of HOPG surface and specific solution concentrations, DNA is found to self-assemble to form various patterned networks. The associated self-assembly mechanism is elucidated using coarse-grained molecular dynamics simulations and fractal dimension analysis. The results of this work demonstrate an effective technique allowing the formation of arrays of negatively charged biomacromolecules on negatively charged HOPG surfaces.

  15. Characterization of nitrogen species incorporated into graphite using low energy nitrogen ion sputtering.

    PubMed

    Kiuchi, Hisao; Kondo, Takahiro; Sakurai, Masataka; Guo, Donghui; Nakamura, Junji; Niwa, Hideharu; Miyawaki, Jun; Kawai, Maki; Oshima, Masaharu; Harada, Yoshihisa

    2016-01-01

    The electronic structures of nitrogen species incorporated into highly oriented pyrolytic graphite (HOPG), prepared by low energy (200 eV) nitrogen ion sputtering and subsequent annealing at 1000 K, were investigated by X-ray photoelectron spectroscopy (XPS), angle-dependent X-ray absorption spectroscopy (XAS), and Raman spectroscopy. An additional peak was observed at higher binding energy of 401.9 eV than 400.9 eV for graphitic1 N (graphitic N in the basal plane) in N 1s XPS, where graphitic2 N (graphitic N in the zigzag edge and/or vacancy sites) has been theoretically expected to appear. N 1s XPS showed that graphitic1 N and graphitic2 N were preferably incorporated under low nitrogen content doping conditions (8 × 10(13) ions cm(-2)), while pyridinic N and graphitic1 N were dominantly observed under high nitrogen content doping conditions. In addition, angle-dependent N 1s XAS showed that the graphitic N and pyridinic N atoms were incorporated into the basal plane of HOPG and thus were highly oriented. Furthermore, Raman spectroscopy revealed that low energy sputtering resulted in almost no fraction of the disturbed graphite surface layers under the lowest nitrogen doping condition. The suitable nitrogen doping condition was discovered for realizing the well-controlled nitrogen doped HOPG. The electrochemical properties for the oxygen reduction reaction of these samples in acidic solution were examined and discussed.

  16. Blast furnace repairs, relines and modernizations

    SciTech Connect

    Carpenter, J.A.; Swanson, D.E; Chango, R.F. . Burns Harbor Div.)

    1994-09-01

    Bethlehem Steel's Burns Harbor Div. operates two 89,000-cu ft blast furnaces, D and C, built in 1969 and 1972. These furnaces have been in the forefront of blast furnace performance since they were blown-in. To maintain a credible operation throughout the past 25 years their performance has been improved continuously. Production was increased approximately 3%/year while fuel rate decreased 1%/year. This presentation summarizes the early repairs, relines and improvements that have sustained and enhanced the furnace's performance. The fourth reline of both furnaces will be discussed in detail. As part of the 1991 reline of D furnace its lines were improved and modern penstocks installed. The bosh, tuyere jacket, hearth jacket and both cast floors were replaced. The furnace now has a larger hearth making it easier to control and, liquid level is no longer a problem when pulling the wind to shut down. The new cast floor with its increased trough length has much improved separation of slag from iron and lowered refractory consumption. Since the cast floors on D furnace were changed, there has been a reduction in accidents and absenteeism. This may be related to the change in work practices on the new cast floors. The 1994 reline of C furnace incorporates those improvements made on D furnace in 1991. In addition, C furnace will have high-density cooling which is expected to double its campaign from 6 to 12 years, without interim repairs.

  17. METHOD OF FABRICATING A GRAPHITE MODERATED REACTOR

    DOEpatents

    Kratz, H.R.

    1963-05-01

    S>A nuclear reactor formed of spaced bodies of uranium and graphite blocks is improved by diffusing helium through the graphite blocks in order to replace the air in the pores of the graphite with helium. The helium-impregnated graphite conducts heat better, and absorbs neutrons less, than the original air- impregnated graphite. (AEC)

  18. CMB-13 research on carbon and graphite

    NASA Technical Reports Server (NTRS)

    Smith, M. C.

    1972-01-01

    Preliminary results of the research on carbon and graphite accomplished during this report period are presented. Included are: particle characteristics of Santa Maria fillers, compositions and density data for hot-molded Santa Maria graphites, properties of hot-molded Santa Maria graphites, and properties of hot-molded anisotropic graphites. Ablation-resistant graphites are also discussed.

  19. Graphite fiber reinforced thermoplastic resins

    NASA Technical Reports Server (NTRS)

    Navak, R. C.

    1977-01-01

    The results of a program designed to optimize the fabrication procedures for graphite thermoplastic composites are described. The properties of the composites as a function of temperature were measured and graphite thermoplastic fan exit guide vanes were fabricated and tested. Three thermoplastics were included in the investigation: polysulfone, polyethersulfone, and polyarylsulfone. Type HMS graphite was used as the reinforcement. Bending fatigue tests of HMS graphite/polyethersulfone demonstrated a gradual shear failure mode which resulted in a loss of stiffness in the specimens. Preliminary curves were generated to show the loss in stiffness as a function of stress and number of cycles. Fan exit guide vanes of HMS graphite polyethersulfone were satisfactorily fabricated in the final phase of the program. These were found to have stiffness and better fatigue behavior than graphite epoxy vanes which were formerly bill of material.

  20. Direct current, closed furnace silicon technology

    SciTech Connect

    Dosaj, V.D.; May, J.B.; Arvidson, A.N.

    1994-05-01

    The dc closed furnace technology for smelting silicon offers technical operating challenges, as well as, economic opportunities for off-gas recovery, reduced electrode consumption, reduced reductant oxidation losses, reduced energy consumption, and improved silicon recovery. The 10 mva dc closed furnace is located in East Selkirk, Manitoba. Construction of this pilot plant was started in September 1990. Following successful commissioning of the furnace in 1992, a number of smelting tests have been conducted aimed at optimization of the furnace operation and the raw material mix. The operation of a closed furnace is significantly different from an open furnace operation. The major difference being in the mechanical movement of the mix, off-gas recovery, and inability to observe the process. These differences made data collection and analysis critical in making operating decisions. This closed furnace was operated by computer control (state of the art in the smelling industry).

  1. Energy of Cohesion, Compressibility, and the Potential Energy Functions of the Graphite System

    NASA Technical Reports Server (NTRS)

    Girifalco, L. A.; Lad, R. A.

    1956-01-01

    The lattice summations of the potential energy of importance in the graphite system have been computed by direct summation assuming a Lennard-Jones 6-12 potential between carbon atoms. From these summations, potential energy curves were constructed for interactions between a carbon atom and a graphite monolayer, between a carbon atom and a graphite surface, between a graphite monolayer and a semi-infinite graphite crystal and between two graphite semi-infinite crystals. Using these curves, the equilibrium distance between two isolated physically interacting carbon atoms was found to be 2.70 a, where a is the carbon-carbon distance in a graphite sheet. The distance between a surface plane and the rest of the crystal was found to be 1.7% greater than the interlayer spacing. Theoretical values of the energy of cohesion and the compressibility were calculated from the potential curve for the interaction between two semi-infinite crystals. They were (delta)E(sub c) = -330 ergs/sq cm and beta =3.18x10(exp -12)sq cm/dyne, respectively. These compared favorably with the experimental values of (delta)E(sub c) = -260 ergs/sq cm and beta = 2.97 X 10(exp -2) sq cm/dyne.

  2. Studying disorder in graphite-based systems by Raman spectroscopy.

    PubMed

    Pimenta, M A; Dresselhaus, G; Dresselhaus, M S; Cançado, L G; Jorio, A; Saito, R

    2007-03-21

    Raman spectroscopy has historically played an important role in the structural characterization of graphitic materials, in particular providing valuable information about defects, stacking of the graphene layers and the finite sizes of the crystallites parallel and perpendicular to the hexagonal axis. Here we review the defect-induced Raman spectra of graphitic materials from both experimental and theoretical standpoints and we present recent Raman results on nanographites and graphenes. The disorder-induced D and D' Raman features, as well as the G'-band (the overtone of the D-band which is always observed in defect-free samples), are discussed in terms of the double-resonance (DR) Raman process, involving phonons within the interior of the 1st Brillouin zone of graphite and defects. In this review, experimental results for the D, D' and G' bands obtained with different laser lines, and in samples with different crystallite sizes and different types of defects are presented and discussed. We also present recent advances that made possible the development of Raman scattering as a tool for very accurate structural analysis of nano-graphite, with the establishment of an empirical formula for the in- and out-of-plane crystalline size and even fancier Raman-based information, such as for the atomic structure at graphite edges, and the identification of single versus multi-graphene layers. Once established, this knowledge provides a powerful machinery to understand newer forms of sp(2) carbon materials, such as the recently developed pitch-based graphitic foams. Results for the calculated Raman intensity of the disorder-induced D-band in graphitic materials as a function of both the excitation laser energy (E(laser)) and the in-plane size (L(a)) of nano-graphites are presented and compared with experimental results. The status of this research area is assessed, and opportunities for future work are identified.

  3. Heat exchanger using graphite foam

    DOEpatents

    Campagna, Michael Joseph; Callas, James John

    2012-09-25

    A heat exchanger is disclosed. The heat exchanger may have an inlet configured to receive a first fluid and an outlet configured to discharge the first fluid. The heat exchanger may further have at least one passageway configured to conduct the first fluid from the inlet to the outlet. The at least one passageway may be composed of a graphite foam and a layer of graphite material on the exterior of the graphite foam. The layer of graphite material may form at least a partial barrier between the first fluid and a second fluid external to the at least one passageway.

  4. Furnace for treating industrial wastes

    SciTech Connect

    Nakamura, T.D.

    1982-08-31

    A furnace for treating sewage sludge, ash from municipal incinerators or other industrial wastes by melting the waste with a high-temperature bed formed from a combustible carbonaceous material for the reuse of the resulting molten product, for example, as aggregate. A gas for combustion is supplied to the bed at an intermediate portion between its upper and lower portions while causing the resulting combustion gas to flow through the bed dividedly upward and downward.

  5. Graphitic packing removal tool

    SciTech Connect

    Meyers, K.E.; Kolsun, G.J.

    1996-12-31

    Graphitic packing removal tools are described for removal of the seal rings in one piece from valves and pumps. The packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal.

  6. Graphitic packing removal tool

    DOEpatents

    Meyers, K.E.; Kolsun, G.J.

    1997-11-11

    Graphitic packing removal tools for removal of the seal rings in one piece are disclosed. The packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal. 5 figs.

  7. Graphitic packing removal tool

    DOEpatents

    Meyers, Kurt Edward; Kolsun, George J.

    1997-01-01

    Graphitic packing removal tools for removal of the seal rings in one piece. he packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal.

  8. High temperature furnace modeling and performance verifications

    NASA Technical Reports Server (NTRS)

    Smith, James E., Jr.

    1992-01-01

    Analytical, numerical, and experimental studies were performed on two classes of high temperature materials processing sources for their potential use as directional solidification furnaces. The research concentrated on a commercially available high temperature furnace using a zirconia ceramic tube as the heating element and an Arc Furnace based on a tube welder. The first objective was to assemble the zirconia furnace and construct parts needed to successfully perform experiments. The 2nd objective was to evaluate the zirconia furnace performance as a directional solidification furnace element. The 3rd objective was to establish a data base on materials used in the furnace construction, with particular emphasis on emissivities, transmissivities, and absorptivities as functions of wavelength and temperature. A 1-D and 2-D spectral radiation heat transfer model was developed for comparison with standard modeling techniques, and were used to predict wall and crucible temperatures. The 4th objective addressed the development of a SINDA model for the Arc Furnace and was used to design sample holders and to estimate cooling media temperatures for the steady state operation of the furnace. And, the 5th objective addressed the initial performance evaluation of the Arc Furnace and associated equipment for directional solidification. Results of these objectives are presented.

  9. Automated, High Temperature Furnace for Glovebox Operation

    SciTech Connect

    Neikirk, K.

    2001-01-26

    The U.S. Department of Energy will immobilize excess plutonium in the proposed Plutonium Immobilization Plant (PIP) at the Savannah River Site (SRS) as part of a two track approach for the disposition of weapons usable plutonium. As such, the Department of Energy is funding a development and testing effort for the PIP. This effort is being performed jointly by Lawrence Livermore National Laboratory (LLNL), Westinghouse Savannah River Company (WSRC), Pacific Northwest National Laboratory (PNNL), and Argonne National Laboratory (ANL). The Plutonium Immobilization process involves the disposition of excess plutonium by incorporation into ceramic pucks. As part of the immobilization process, furnaces are needed for sintering the ceramic pucks. The furnace being developed for puck sintering is an automated, bottom loaded furnace with insulting package and resistance heating elements located within a nuclear glovebox. Other furnaces considered for the application include retort furnaces and pusher furnaces. This paper, in part, will discuss the furnace technologies considered and furnace technology selected to support reliable puck sintering in a glovebox environment. Due to the radiation levels and contamination associated with the plutonium material, the sintering process will be fully automated and contained within nuclear material gloveboxes. As such, the furnace currently under development incorporates water and air cooling to minimize heat load to the glovebox. This paper will describe the furnace equipment and systems needed to employ a fully automated puck sintering process within nuclear gloveboxes as part of the Plutonium Immobilization Plant.

  10. REFRACTORY COATING FOR GRAPHITE MOLDS

    DOEpatents

    Stoddard, S.D.

    1958-06-24

    Refractory coating for graphite molds used in the casting of uranium is described. The coating is an alumino-silicate refractory composition which may be used as a mold surface in solid form or as a coating applied to the graphite mold. The composition consists of a mixture of ball clay, kaolin, alumina cement, alumina, water, sodium silicate, and sodium carbonate.

  11. Cryotribology of diamond and graphite

    SciTech Connect

    Iwasa, Yukikazu; Ashaboglu, A.F.; Rabinowicz, E.R.

    1996-12-31

    An experimental study was carried out on the tribological behavior of materials of interest in cryogenic applications, focusing on diamond and graphite. Both natural diamond (referred in the text as diamond) and chemical-vapor-deposition (CVD) diamond (CVD-diamond) were used. The experiment was carried out using a pin-on-disk tribometer capable of operating at cryogenic temperatures, from 4.2 to 293 K. Two basic scenarios of testing were used: (1) frictional coefficient ({mu}) vs velocity (v) characteristics at constant temperatures; (2) {mu} vs temperature (T) behavior at fixed sliding speeds. For diamond/CVD-diamond, graphite/CVD-diamond, stainless steel/CVD-diamond pairs, {mu}`s are virtually velocity independent. For each of diamond/graphite, alumina/graphite, and graphite/graphite pairs, the {partial_derivative}{mu}/{partial_derivative}v characteristic is favorable, i.e., positive. For diamond/CVD-diamond and graphite/CVD-diamond pairs, {mu}`s are nearly temperature independent between in the range 77 - 293 K. Each {mu} vs T plot for pin materials sliding on graphite disks has a peak at a temperature in the range 100 - 200 K.

  12. Examining graphite reinforcement in composites

    NASA Technical Reports Server (NTRS)

    Sanders, R. E.; Yates, C. I.

    1980-01-01

    Structure of graphite layers in composite parts can be checked by pyrolizing epoxy portion of composite samples. After 2-3 hours in nitrogen atmosphere at 540 C, only graphite fibers remain. These can be separated and checked for proper number, thickness, and orientation.

  13. Multiaxial graphite test specimen

    SciTech Connect

    1988-09-01

    A multiaxial test program is to be conducted by Oak Ridge National Laboratory (ORNL) on the core component graphite. The objectives of the tests are to obtain failure data under uniaxial and biaxial states of stress in order to construct a failure surface in a two-dimensional stress space. These data will be used in verifying the accuracy of the maximum stress failure theory being proposed for use in designing the core graphite components. Tubular specimens are proposed to be used and are either loaded axially and/or subjected to internal pressure. This report includes a study on three specimen configurations. The conclusions of that study indicate that an elliptical transition geometry procedures the smallest discontinuity effects. Several loading combustions were studied using the elliptical transition specimen. The primary purpose is to establish the location of the highest stress state and its relation to the gage section for all of the loading conditions. The tension/internal pres sure loading condition (1:1) indicated that the high stress area is just outside the gage section but still should be acceptable. 5 refs., 18 figs.

  14. Atomic Oxygen Fluence Monitor

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.

    2011-01-01

    This innovation enables a means for actively measuring atomic oxygen fluence (accumulated atoms of atomic oxygen per area) that has impinged upon spacecraft surfaces. Telemetered data from the device provides spacecraft designers, researchers, and mission managers with real-time measurement of atomic oxygen fluence, which is useful for prediction of the durability of spacecraft materials and components. The innovation is a compact fluence measuring device that allows in-space measurement and transmittance of measured atomic oxygen fluence as a function of time based on atomic oxygen erosion yields (the erosion yield of a material is the volume of material that is oxidized per incident oxygen atom) of materials that have been measured in low Earth orbit. It has a linear electrical response to atomic oxygen fluence, and is capable of measuring high atomic oxygen fluences (up to >10(exp 22) atoms/sq cm), which are representative of multi-year low-Earth orbital missions (such as the International Space Station). The durability or remaining structural lifetime of solar arrays that consist of polymer blankets on which the solar cells are attached can be predicted if one knows the atomic oxygen fluence that the solar array blanket has been exposed to. In addition, numerous organizations that launch space experiments into low-Earth orbit want to know the accumulated atomic oxygen fluence that their materials or components have been exposed to. The device is based on the erosion yield of pyrolytic graphite. It uses two 12deg inclined wedges of graphite that are over a grit-blasted fused silica window covering a photodiode. As the wedges erode, a greater area of solar illumination reaches the photodiode. A reference photodiode is also used that receives unobstructed solar illumination and is oriented in the same direction as the pyrolytic graphite covered photodiode. The short-circuit current from the photodiodes is measured and either sent to an onboard data logger, or

  15. Synthesis of carbon nanotubes by laser ablation in graphite substrate of industrial arc electrodes

    NASA Astrophysics Data System (ADS)

    Guerrero, A.; Puerta, J.; Gomez, F.; Blanco, F.

    2008-10-01

    In this work, an inexpensive and simple technique for the synthesis of carbon nanotubes (CNTs) by using graphite as the target for IR laser radiation is presented. This graphite material is obtained from the recycled graphite electrode core of an electric arc furnace. The experiment was carried out in a reaction chamber in an argon atmosphere at a low pressure. For laser ablation, a Lumonics TEA CO2 laser beam (7 J; 0.05-50 μs pulse length) was used in multimode operation. Products were collected on free mica sheets. The substrates were characterized by scanning electron microscopy (SEM) and the products were characterized (collected as powder) by transmission electron microscopy (TEM). They showed significant amounts of high-quality dense filaments (CNTs) that were morphologically not aligned.

  16. Baseline Graphite Characterization: First Billet

    SciTech Connect

    Mark C. Carroll; Joe Lords; David Rohrbaugh

    2010-09-01

    The Next Generation Nuclear Plant Project Graphite Research and Development program is currently establishing the safe operating envelope of graphite core components for a very high temperature reactor design. To meet this goal, the program is generating the extensive amount of quantitative data necessary for predicting the behavior and operating performance of the available nuclear graphite grades. In order determine the in-service behavior of the graphite for the latest proposed designs, two main programs are underway. The first, the Advanced Graphite Creep (AGC) program, is a set of experiments that are designed to evaluate the irradiated properties and behavior of nuclear grade graphite over a large spectrum of temperatures, neutron fluences, and compressive loads. Despite the aggressive experimental matrix that comprises the set of AGC test runs, a limited amount of data can be generated based upon the availability of space within the Advanced Test Reactor and the geometric constraints placed on the AGC specimens that will be inserted. In order to supplement the AGC data set, the Baseline Graphite Characterization program will endeavor to provide supplemental data that will characterize the inherent property variability in nuclear-grade graphite without the testing constraints of the AGC program. This variability in properties is a natural artifact of graphite due to the geologic raw materials that are utilized in its production. This variability will be quantified not only within a single billet of as-produced graphite, but also from billets within a single lot, billets from different lots of the same grade, and across different billets of the numerous grades of nuclear graphite that are presently available. The thorough understanding of this variability will provide added detail to the irradiated property data, and provide a more thorough understanding of the behavior of graphite that will be used in reactor design and licensing. This report covers the

  17. Automatic furnace downloading to SUPREM format

    NASA Astrophysics Data System (ADS)

    Fallon, Martin; Findlater, Keith; McGinty, Jim; Rankin, N.; Yarr, A.

    1999-04-01

    Technology CAD (TCAD) is a commonly used tool in process development and analysis. The task of creating the process in the required format for the TCAD deck is non-trivial and often prone to error due to the detailed nature of the furnace processing. Ensuring that the simulation deck is matched to the actual furnace process is also a key area. There is a difference between what is programmed into the furnace and what the wafers actually see. This work presents a method of automatic download of the actual furnace parameters to a format directly readable by the process simulator SUPREM, and examines the consequences of the furnace variability inherent in batch processing. The three furnace zones can be seen to interact and product best-worst case simulations to aid in the prediction of manufacturability.

  18. Role of nuclear grade graphite in controlling oxidation in modular HTGRs

    SciTech Connect

    Windes, Willaim; Strydom, G.; Kane, J.; Smith, R.

    2014-11-01

    The passively safe High Temperature Gas-cooled Reactor (HTGR) design is one of the primary concepts considered for Generation IV and Small Modular Reactor (SMR) programs. The helium cooled, nuclear grade graphite moderated core achieves extremely high operating temperatures allowing either industrial process heat or electricity generation at high efficiencies. In addition to their neutron moderating properties, nuclear grade graphite core components provide excellent high temperature stability, thermal conductivity, and chemical compatibility with the high temperature nuclear fuel form. Graphite has been continuously used in nuclear reactors since the 1940’s and has performed remarkably well over a wide range of core environments and operating conditions. Graphite moderated, gas-cooled reactor designs have been safely used for research and power production purposes in multiple countries since the inception of nuclear energy development. However, graphite is a carbonaceous material, and this has generated a persistent concern that the graphite components could actually burn during either normal or accident conditions [ , ]. The common assumption is that graphite, since it is ostensibly similar to charcoal and coal, will burn in a similar manner. While charcoal and coal may have the appearance of graphite, the internal microstructure and impurities within these carbonaceous materials are very different. Volatile species and trapped moisture provide a source of oxygen within coal and charcoal allowing them to burn. The fabrication process used to produce nuclear grade graphite eliminates these oxidation enhancing impurities, creating a dense, highly ordered form of carbon possessing high thermal diffusivity and strongly (covalently) bonded atoms.

  19. Kinetics of Chronic Oxidation of NBG-17 Nuclear Graphite by Water Vapor

    SciTech Connect

    Contescu, Cristian I; Burchell, Timothy D; Mee, Robert

    2015-05-01

    This report presents the results of kinetic measurements during accelerated oxidation tests of NBG-17 nuclear graphite by low concentration of water vapor and hydrogen in ultra-high purity helium. The objective is to determine the parameters in the Langmuir-Hinshelwood (L-H) equation describing the oxidation kinetics of nuclear graphite in the helium coolant of high temperature gas-cooled reactors (HTGR). Although the helium coolant chemistry is strictly controlled during normal operating conditions, trace amounts of moisture (predictably < 0.2 ppm) cannot be avoided. Prolonged exposure of graphite components to water vapor at high temperature will cause very slow (chronic) oxidation over the lifetime of graphite components. This behavior must be understood and predicted for the design and safe operation of gas-cooled nuclear reactors. The results reported here show that, in general, oxidation by water of graphite NBG-17 obeys the L-H mechanism, previously documented for other graphite grades. However, the characteristic kinetic parameters that best describe oxidation rates measured for graphite NBG-17 are different than those reported previously for grades H-451 (General Atomics, 1978) and PCEA (ORNL, 2013). In some specific conditions, certain deviations from the generally accepted L-H model were observed for graphite NBG-17. This graphite is manufactured in Germany by SGL Carbon Group and is a possible candidate for the fuel elements and reflector blocks of HTGR.

  20. Furnace for Tensile Testing of Flexible Ceramics

    NASA Technical Reports Server (NTRS)

    Smith, M.; Estrella, C. A.; Katvala, V. W.

    1986-01-01

    Ceramic cloth and thread tested quickly at temperatures up to 1,250 degree C. Tensile strengths of ceramic cloths and threads measured conveniently in new furnace at specified temperatures up to 1,250 degree C, using ordinary mechanical tester. Samples heated along part of their lengths in furnace slots. Interchangeable furnace chambers and matching heating elements sized to match size of tested ceramic material.

  1. Ferrosilicon smelting in a direct current furnace

    DOEpatents

    Dosaj, V.D.; May, J.B.

    1992-12-29

    The present invention is a process for smelting ferrosilicon alloy. The process comprises adding a carbon source and tailings comprising oxides of silicon and iron to a substantially closed furnace. Heat is supplied to the furnace by striking a direct current arc between a cathode electrode and an anode functional hearth. In a preferred embodiment of the present invention, the cathode electrode is hollow and feed to the substantially closed furnace is through the hollow electrode. 1 figure.

  2. Ferrosilicon smelting in a direct current furnace

    DOEpatents

    Dosaj, Vishu D.; May, James B.

    1992-12-29

    The present invention is a process for smelting ferrosilicon alloy. The process comprises adding a carbon source and tailings comprising oxides of silicon and iron to a substantially closed furnace. Heat is supplied to the furnace by striking a direct current arc between a cathode electrode and an anode functional hearth. In a preferred embodiment of the present invention, the cathode electrode is hollow and feed to the substantially closed furnace is through the hollow electrode.

  3. Crystal growth furnace with trap doors

    DOEpatents

    Sachs, Emanual M.; Mackintosh, Brian H.

    1982-06-15

    An improved furnace is provided for growing crystalline bodies from a melt. The improved furnace is characterized by a door assembly which is remotely controlled and is arranged so as to selectively shut off or permit communication between an access port in the furnace enclosure and a hot zone within that enclosure. The invention is especially adapted to facilitate use of crystal growing cartridges of the type disclosed in U.S. Pat. No. 4,118,197.

  4. Crystal growth furnace with trap doors

    NASA Technical Reports Server (NTRS)

    Sachs, Emanual M. (Inventor); Mackintosh, Brian H. (Inventor)

    1982-01-01

    An improved furnace is provided for growing crystalline bodies from a melt. The improved furnace is characterized by a door assembly which is remotely controlled and is arranged so as to selectively shut off or permit communication between an access port in the furnace enclosure and a hot zone within that enclosure. The invention is especially adapted to facilitate use of crystal growing cartridges of the type disclosed in U.S. Pat. No. 4,118,197.

  5. Effect of helium implantation on SiC and graphite

    NASA Astrophysics Data System (ADS)

    Guo, Hong-Yan; Ge, Chang-Chun; Xia, Min; Guo, Li-Ping; Chen, Ji-Hong; Yan, Qing-Zhi

    2015-03-01

    Effects of helium implantation on silicon carbide (SiC) and graphite were studied to reveal the possibility of SiC replacing graphite as plasma facing materials. Pressureless sintered SiC and graphite SMF-800 were implanted with He+ ions of 20 keV and 100 keV at different temperatures and different fluences. The He+ irradiation induced microstructure changes were studied by field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). Project supported by the ITER-National Magnetic Confinement Fusion Program, China (Grant Nos. 2010GB109000, 2011GB108009, and 2014GB123000) and the National Natural Science Foundation of China (Grant No. 11075119).

  6. Structure of a peptide adsorbed on graphene and graphite.

    PubMed

    Katoch, Jyoti; Kim, Sang Nyon; Kuang, Zhifeng; Farmer, Barry L; Naik, Rajesh R; Tatulian, Suren A; Ishigami, Masa

    2012-05-01

    Noncovalent functionalization of graphene using peptides is a promising method for producing novel sensors with high sensitivity and selectivity. Here we perform atomic force microscopy, Raman spectroscopy, infrared spectroscopy, and molecular dynamics simulations to investigate peptide-binding behavior to graphene and graphite. We studied a dodecamer peptide identified with phage display to possess affinity for graphite. Optical spectroscopy reveals that the peptide forms secondary structures both in powder form and in an aqueous medium. The dominant structure in the powder form is α-helix, which undergoes a transition to a distorted helical structure in aqueous solution. The peptide forms a complex reticular structure upon adsorption on graphene and graphite, having a helical conformation different from α-helix due to its interaction with the surface. Our observation is consistent with our molecular dynamics calculations, and our study paves the way for rational functionalization of graphene using biomolecules with defined structures and, therefore, functionalities.

  7. Metastable Frenkel Pair Defect in Graphite: Source of Wigner Energy?

    NASA Astrophysics Data System (ADS)

    Ewels, C. P.; Telling, R. H.; El-Barbary, A. A.; Heggie, M. I.; Briddon, P. R.

    2003-07-01

    The atomic processes associated with energy storage and release in irradiated graphite have long been subject to untested speculation. We examine structures and recombination routes for interstitial-vacancy (I-V) pairs in graphite. Interaction results in the formation of a new metastable defect (an intimate I-V pair) or a Stone-Wales defect. The intimate I-V pair, although 2.9eV more stable than its isolated constituents, still has a formation energy of 10.8eV. The barrier to recombination to perfect graphite is calculated to be 1.3eV, consistent with the experimental first Wigner energy release peak at 1.38eV. We expect similar defects to form in carbon nanostructures such as nanotubes, nested fullerenes, and onions under irradiation.

  8. Structural and electronic properties of graphite and graphite intercalation compounds MC[sub 8] (M = K, Rb, Cs) governing their scanning tunneling microscopy images

    SciTech Connect

    Whangbo, M.H.; Liang, W.; Ren, J. ); Magonov, S.N.; Wawkuschewski, A. )

    1994-08-04

    Several puzzling observations in the scanning tunneling microscopy (STM) and atomic force microscopy (AFM) studies of highly oriented pyrolytic graphite (HOPG) and its intercalation compounds MC[sub 8] (M = K, Rb, Cs) were investigated on the basis of atom-atom potential and Coulombic interaction energy calculations. The charge or spin density wave state of a graphite monolayer is found inconsistent with an identical peak registry of the HOPG STM images obtained at plus and minus bias voltages. Simultaneous STM/AFM measurements of HOPG show the STM and AFM images to have an identical peak registry, which implies that the local hardness of the surface monolayer is larger at the B-site than at the A-site. We confirm this implication by estimating the local hardness in the surface monolayer of a graphite bilayer in terms of atom-atom potential calculations. The essential characteristics of the Moire STM images of HOPG are correctly predicted by the local hardness map obtained for the surface monolayer of a graphite bilayer in terms of atom-atom potential calculations. This supports the notion that the tip-force-induced topography change in the surface monolayer is generally responsible for Moire STM patterns in layered materials. 29 refs., 5 figs., 2 tabs.

  9. Atomization of a liquid by a spray nozzle

    NASA Technical Reports Server (NTRS)

    Kutateladze, S. S. (Editor)

    1980-01-01

    The theory of atomization by mechanical and pneumatic (or vapor) spray nozzles is discussed. Basic design recommendations resulting from generalization of the material and confirmed by experiments are given. Sprayers which are widely used in the furnaces of stationary steam boilers, the combustion chambers of gas turbines, and industrial furnaces are examined.

  10. Measurement of airflow in residential furnaces

    SciTech Connect

    Biermayer, Peter J.; Lutz, James; Lekov, Alex

    2004-01-24

    In order to have a standard for furnaces that includes electricity consumption or for the efficiency of furnace blowers to be determined, it is necessary to determine the airflow of a furnace or furnace blower. This study focused on airflow testing, in order to determine if an existing test method for measuring blower airflow could be used to measure the airflow of a furnace, under conditions seen in actual installations and to collect data and insights into the operating characteristics of various types of furnace blowers, to use in the analysis of the electricity consumption of furnaces. Results of the measured airflow on furnaces with three types of blower and motor combinations are presented in the report. These included: (1) a forward-curved blower wheel with a typical permanent split capacitor (PSC) motor, (2) a forward-curved blower wheel with an electronically-commutated motor (ECM), and (3) a prototype blower, consisting of a backward-inclined blower wheel matched to an ECM motor prototype, which is being developed as an energy-saving alternative to conventional furnace blowers. The testing provided data on power consumption, static and total pressure, and blower speed.

  11. Thermal evaporation furnace with improved configuration for growing nanostructured inorganic materials.

    PubMed

    Joanni, E; Savu, R; Valadares, L; Cilense, M; Zaghete, M A

    2011-06-01

    A tubular furnace specifically designed for growing nanostructured materials is presented in this work. The configuration allows an accurate control of evaporation temperature, substrate temperature, total pressure, oxygen partial pressure, volumetric flow and source-substrate distance, with the possibility of performing both downstream and upstream depositions. In order to illustrate the versatility of the equipment, the furnace was used for growing semiconducting oxide nanostructures under different deposition conditions. Highly crystalline indium oxide nanowires with different morphologies were synthesized by evaporating mixtures of indium oxide and graphite powders with different mass ratios at temperatures between 900 °C and 1050 °C. The nanostructured layers were deposited onto oxidized silicon substrates with patterned gold catalyst in the temperature range from 600 °C to 900 °C. Gas sensors based on these nanowires exhibited enhanced sensitivity towards oxygen, with good response and recovery times. PMID:21721724

  12. VAPOR SHIELD FOR INDUCTION FURNACE

    DOEpatents

    Reese, S.L.; Samoriga, S.A.

    1958-03-11

    This patent relates to a water-cooled vapor shield for an inductlon furnace that will condense metallic vapors arising from the crucible and thus prevent their condensation on or near the induction coils, thereby eliminating possible corrosion or shorting out of the coils. This is accomplished by placing, about the top, of the crucible a disk, apron, and cooling jacket that separates the area of the coils from the interior of the cruclbIe and provides a cooled surface upon whlch the vapors may condense.

  13. Method for wetting a boron alloy to graphite

    DOEpatents

    Storms, E.K.

    1987-08-21

    A method is provided for wetting a graphite substrate and spreading a a boron alloy over the substrate. The wetted substrate may be in the form of a needle for an effective ion emission source. The method may also be used to wet a graphite substrate for subsequent joining with another graphite substrate or other metal, or to form a protective coating over a graphite substrate. A noneutectic alloy of boron is formed with a metal selected from the group consisting of nickel (Ni), palladium (Pd), and platinum (Pt) with excess boron, i.e., and atomic percentage of boron effective to precipitate boron at a wetting temperature of less than the liquid-phase boundary temperature of the alloy. The alloy is applied to the substrate and the graphite substrate is then heated to the wetting temperature and maintained at the wetting temperature for a time effective for the alloy to wet and spread over the substrate. The excess boron is evenly dispersed in the alloy and is readily available to promote the wetting and spreading action of the alloy. 1 fig.

  14. Silicon smelting in a closed furnace

    SciTech Connect

    Dosaj, V.; Brumels, M.D.; Haines, C.M.; May, J.B. )

    1991-01-01

    Dow Corning has been working towards the advancement of silicon smelting in a closed furnace over the past four years. A 200 kVA closed furnace pilot plant unit was built to investigate the operating parameters for smelting silicon. The single electrode furnace is operated under totally sealed conditions. The feed from the feed hoppers is fed through air locks to the furnace. The off-gas from the furnace, consisting of by-product CO as well as volatiles from the feeds, pass through a venturi scrubber, where water is introduced to scrub out the fume from the furnace and cool the gas. The mixed scrubber water and off-gas pass into a centrifugal mist eliminator where the water and fume disengage from the gas. The fume slurry is passed through bag filters where the fume is separated from the water. The clean off-gas from the furnace was evaluated for its calorific value and evaluated for conversion to useful products. A number of silicon smelting tests were conducted during this program. Various levels of charcoal and coal mixtures were evaluated to determine the optimum mix. A low volatile coal was preferred over typical Blue Gem coal. The coal amount in the mix was maximized without compromising the smelting performance. A raw material mix consisting of 30% charcoal and 70% low volatile coal was determined to be an optimum mix for closed furnace operation. Silicon recoveries in the low nineties were demonstrated using this mix. Four quartz sources were also evaluated in the closed furnace. The closed furnace operation for silicon smelting was identified to offer significant advantages over an open furnace from the standpoint of reduced carbon oxidation losses, electrode consumption, electrical energy consumption and silicon yield improvement. Other advantages in addition to process off-gas recovery included improved safety from reduced heat and fume exposure, and improved pollution control to the environment. 1 ref.

  15. Silicon smelting in a closed furnace

    SciTech Connect

    Dosaj, V.; Brumels, M.D.; Haines, C.M.; May, J.B.

    1991-12-31

    Dow Corning has been working towards the advancement of silicon smelting in a closed furnace over the past four years. A 200 kVA closed furnace pilot plant unit was built to investigate the operating parameters for smelting silicon. The single electrode furnace is operated under totally sealed conditions. The feed from the feed hoppers is fed through air locks to the furnace. The off-gas from the furnace, consisting of by-product CO as well as volatiles from the feeds, pass through a venturi scrubber, where water is introduced to scrub out the fume from the furnace and cool the gas. The mixed scrubber water and off-gas pass into a centrifugal mist eliminator where the water and fume disengage from the gas. The fume slurry is passed through bag filters where the fume is separated from the water. The clean off-gas from the furnace was evaluated for its calorific value and evaluated for conversion to useful products. A number of silicon smelting tests were conducted during this program. Various levels of charcoal and coal mixtures were evaluated to determine the optimum mix. A low volatile coal was preferred over typical Blue Gem coal. The coal amount in the mix was maximized without compromising the smelting performance. A raw material mix consisting of 30% charcoal and 70% low volatile coal was determined to be an optimum mix for closed furnace operation. Silicon recoveries in the low nineties were demonstrated using this mix. Four quartz sources were also evaluated in the closed furnace. The closed furnace operation for silicon smelting was identified to offer significant advantages over an open furnace from the standpoint of reduced carbon oxidation losses, electrode consumption, electrical energy consumption and silicon yield improvement. Other advantages in addition to process off-gas recovery included improved safety from reduced heat and fume exposure, and improved pollution control to the environment. 1 ref.

  16. Looking southeast at blast furnaces no. 5 and no. 6 ...

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

    Looking southeast at blast furnaces no. 5 and no. 6 with blast furnace trestle and Gondola Railroad cars in foreground. - U.S. Steel Edgar Thomson Works, Blast Furnace Plant, Along Monongahela River, Braddock, Allegheny County, PA

  17. 3. VIEW OF DUQUESNE'S RAIL LINES AND BLAST FURNACE PLANT ...

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

    3. VIEW OF DUQUESNE'S RAIL LINES AND BLAST FURNACE PLANT LOOKING NORTH. DOROTHY SIX IS THE CLOSEST FURNACE IN THE PHOTOGRAPH. (Jet Lowe) - U.S. Steel Duquesne Works, Blast Furnace Plant, Along Monongahela River, Duquesne, Allegheny County, PA

  18. 56. LOOKING NORTH AT DOROTHY SIX BLAST FURNACE WITH CAST ...

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

    56. LOOKING NORTH AT DOROTHY SIX BLAST FURNACE WITH CAST HOUSE IN FOREGROUND AND DUSTCATCHER AT RIGHT OF FURNACE (Jet Lowe) - U.S. Steel Duquesne Works, Blast Furnace Plant, Along Monongahela River, Duquesne, Allegheny County, PA

  19. Looking southwest at blast furnaces no. 5 and no. 6 ...

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

    Looking southwest at blast furnaces no. 5 and no. 6 with blast furnace trestle and Gondola Railroad cars in foreground. - U.S. Steel Edgar Thomson Works, Blast Furnace Plant, Along Monongahela River, Braddock, Allegheny County, PA

  20. INTERIOR VIEW LOOKING WEST, CAST HOUSE OF BLAST FURNACE NO. ...

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

    INTERIOR VIEW LOOKING WEST, CAST HOUSE OF BLAST FURNACE NO. 1 AND BLAST FURNACE NO. 2. - Pittsburgh Steel Company, Monessen Works, Blast Furnace No. 1 & No. 2, Donner Avenue, Monessen, Westmoreland County, PA

  1. 19. Inside the cast house at Furnace A. Molten iron ...

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

    19. Inside the cast house at Furnace A. Molten iron flowed into eight ladles. The furnace was cast (or tapped) six times each day. - Central Furnaces, 2650 Broadway, east bank of Cuyahoga River, Cleveland, Cuyahoga County, OH

  2. 41. Casting floor, "B" furnace, pour in progress; mudgun is ...

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

    41. Casting floor, "B" furnace, pour in progress; mudgun is to right of furnace; photo taken from furnace operator's booth. Looking south/southwest - Rouge Steel Company, 3001 Miller Road, Dearborn, MI

  3. INTERIOR VIEW OF FURNACE NO. 2, DRAWING ROOM, SHOWING A ...

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

    INTERIOR VIEW OF FURNACE NO. 2, DRAWING ROOM, SHOWING A FLOOR INDICATING FOURCAULT DRAWING MACHINE AND FURNACE. - Chambers-McKee Window Glass Company, Furnace No. 2, Clay Avenue Extension, Jeannette, Westmoreland County, PA

  4. 50. Taken from highline; "B" furnace slag pots, pipe is ...

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

    50. Taken from high-line; "B" furnace slag pots, pipe is main blast furnace gas line from "C" furnace dust catcher; levy, slag hauler, removing slag. Looking east - Rouge Steel Company, 3001 Miller Road, Dearborn, MI

  5. 2. EXTERIOR VIEW LOOKING SOUTHEAST AT ELECTRIC FURNACE BUILDING AND ...

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

    2. EXTERIOR VIEW LOOKING SOUTHEAST AT ELECTRIC FURNACE BUILDING AND ELECTRIC FURNACE OFFICE & CHEMICAL LABORATORY BUILDING. INGOT MOLDS IN RIGHT FOREGROUND. - U.S. Steel Duquesne Works, Electric Furnace Steelmaking Plant, Along Monongahela River, Duquesne, Allegheny County, PA

  6. Soft X-Ray Absorption Spectroscopy of High-Abrasion-Furnace Carbon Black

    SciTech Connect

    Muramatsu, Yasuji; Harada, Ryusuke; Gullikson, Eric M.

    2007-02-02

    The soft x-ray absorption spectra of high-abrasion-furnace carbon black were measured to obtain local-structure/chemical-states information of the primary particles and/or crystallites. The soft x-ray absorption spectral features of carbon black represent broader {pi}* and {sigma}* peak structures compared to highly oriented pyrolytic graphite (HOPG). The subtracted spectra between the carbon black and HOPG, (carbon black) - (HOPG), show double-peak structures on both sides of the {pi}* peak. The lower-energy peak, denoted as the 'pre-peak', in the subtracted spectra and the {pi}*/{sigma}* peak intensity ratio in the absorption spectra clearly depend on the specific surface area by nitrogen adsorption (NSA). Therefore, it is concluded that the pre-peak intensity and the {pi}*/{sigma}* ratio reflect the local graphitic structure of carbon black.

  7. Density of intercalated graphite fibers

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Slabe, Melissa E.

    1990-01-01

    The density of Amoco P-55, P-75, P-100, and P-120 pitch-based graphite fibers and their intercalation compounds with bromine, iodine monochloride, and copper (II) chloride have been measured using a density gradient column. The distribution of densities within a fiber type is found to be a sensitive indicator of the quality of the intercalation reaction. In all cases the density was found to increase, indicating that the mass added to the graphite is dominant over fiber expansion. Density increases are small (less than 10 percent) giving credence to a model of the intercalated graphite fibers which have regions which are intercalated and regions which are not.

  8. Density of intercalated graphite fibers

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Slabe, Melissa E.

    1989-01-01

    The density of Amoco P-55, P-75, P-100, and P-120 pitch-based graphite fibers and their intercalation compounds with bromine, iodine monochloride, and copper (II) chloride have been measured using a density gradient column. The distribution of densities within a fiber type is found to be a sensitive indicator of the quality of the intercalation reaction. In all cases the density was found to increase, indicating that the mass added to the graphite is dominant over fiber expansion. Density increases are small (less than 10 percent) giving credence to a model of the intercalated graphite fibers which have regions which are intercalated and regions which are not.

  9. Furnace

    SciTech Connect

    Lindstrom, O.

    1983-12-20

    An improved process of the type wherein a fuel is first pyrolyzed in a chamber and the resulting volatiles and non-volatiles are then transferred to a combustion region for burning, the improvement comprising temporarily storing at least a portion of the volatiles in an enclosure spaced from the chamber and the combustion region when volatiles production exceeds the volatiles incineration capability of the combustion region. Apparatus for carrying out the method of the invention is also disclosed.

  10. METHOD OF OBTAINING UNIFORM COATINGS ON GRAPHITE

    DOEpatents

    Campbell, I.E.

    1961-04-01

    A method is given for obtaining uniform carbide coatings on graphite bodies. According to the invention a metallic halide in vapor form is passed over the graphite body under such conditions of temperature and pressure that the halide reacts with the graphite to form a coating of the metal carbide on the surface of the graphite.

  11. Method of Obtaining Uniform Coatings on Graphite

    DOEpatents

    Campbell, I. E.

    1961-04-01

    A method is given for obtaining uniform carbide coatings on graphite bodies. According to the invention a metallic halide in vapor form is passed over the graphite body under such conditions of temperature and pressure that the halide reacts with the graphite to form a coating of the metal carbide on the surface of the graphite.

  12. Mineral resource of the month: graphite

    USGS Publications Warehouse

    ,

    2008-01-01

    The article presents facts about graphite ideal for industrial applications. Among the characteristics of graphite are its metallic luster, softness, perfect basal cleavage and electrical conductivity. Batteries, brake linings and powdered metals are some of the products that make use of graphite. It attributes the potential applications for graphite in high-technology fields to innovations in thermal technology and acid-leaching techniques.

  13. Radiocarbon from Pile Graphite; Chemical Methods for Its Concentrations

    DOE R&D Accomplishments Database

    Arnold, J. R.; Libby, W. F.

    1946-10-10

    Samples of pile graphite, irradiated in a test-hole at Hanford for 15 months, have been assayed for radioactive C{sup 14} yielding 0.38 ± 0.04 microcuries per gram. At this level of activity, the pile graphite contains very valuable amounts of C{sup14}. The relation between the above assay and the probable average assay of pile graphite is discussed, and it is concluded that the latter is almost certainly above 0.3 microcuries/gram. Controlled oxidation of this graphite, either with oxygen at ~750ºC, or with chromic acid "cleaning solution" at room temperature, yields early fractions which are highly enriched in C{sup 14}. Concentrations of 5-fold with oxygen, and 50-fold with CrO{sub 3}, have been observed. The relation between the observed enrichment and the Wigner effect is discussed, and a mechanism accounting for the observations put forward. According to this, about 25% of the stable carbon atoms in the lattice have been displaced by Wigner effect, a large fraction of which have healed by migrating to crystal edges. All the C{sup 14} atoms have been displaced, and the same fraction of these migrate to the edges. The enrichment then results from surface oxidation, in the oxygen case. Predictions are made on the basis of this hypothesis. A technique of counting radioactive CO{sub 2} in the gas phase is described.

  14. Structural, chemical, and isotopic microanalytical investigations of graphite from supernovae

    NASA Astrophysics Data System (ADS)

    Croat, T. Kevin; Bernatowicz, Thomas; Amari, Sachiko; Messenger, Scott; Stadermann, Frank J.

    2003-12-01

    We report the results of coordinated ion microprobe and transmission electron microscope (TEM) studies of presolar graphites from the KE3 separate (1.65-1.72 g/cm 3) of the Murchison CM2 meteorite. Isotopic analysis of individual graphites (1-12 μm) with the ion microprobe shows many to have large 18O excesses combined with large silicon isotopic anomalies, indicative of a supernova (SN) origin. Transmission electron microscopy (TEM) of ultramicrotome slices of these SN graphites revealed a high abundance (25-2400 ppm) of internal titanium carbides (TiCs), with a single graphite in some cases containing hundreds of TiCs. Isotopic compositions of individual TiCs by nanoscale resolution secondary ion mass spectrometry (NanoSIMS) confirmed their presolar origin. In addition to TiCs, composite TiC/Fe grains (TiCs with attached iron-nickel subgrains) and solitary kamacite internal grains were found. In the composite grains, the attached iron phase (kamacite [0-24 at. % Ni] or taenite [up to 60 at. % Ni]) was epitaxially grown onto one or more TiC faces. In contrast to the denser Murchison KFC1 graphites, no Zr-Ti-Mo carbides were observed. The average TiC diameters were quite variable among the SN graphites, from 30 to 232 nm, and were generally independent of the host graphite size. TiC grain morphologies ranged from euhedral to anhedral, with the grain surfaces exhibiting variable degrees of corrosion, and sometimes partially amorphous rims (3 to 15 nm thick). Partially amorphous rims of similar thickness were also observed on some solitary kamacite grains. We speculate that the rims on the internal grains are most plausibly the result of atom bombardment caused by drift of grains with respect to the ambient gas, requiring relative outflow speeds ˜100 km/s (i.e., a few percent of the SN mass outflow speed). Energy dispersive X-ray spectrometry (EDXS) of TiCs revealed significant V in solid solution, with an average V/Ti ratio over all TiCs of ˜83% of the solar

  15. Spray nozzles reduce furnace emissions

    SciTech Connect

    Not Available

    1993-10-01

    When the US Environmental Protection Agency (EPA) told an Illinois wood pallet manufacturer to reduce emissions of heavy smoke from its twice-weekly incineration of old pallets, the company didn't find many options. The company applied spray nozzles to enhance the efficiency of the furnaces, and scrub the smoke and gas, removing toxins and particulates before they could reach the furnace chimney and be emitted into the atmosphere. Three types of spray nozzles were installed in the incinerator. Six UniJet air blow-off nozzles, fed by a compressed air line, were installed in the fire box. These nozzles target a flat spray of pressured air to intensify the heat of the fire. As a result, the pallets burn more efficiently and completely. Eight standard FullJet nozzles also were installed in the fire box. Since the smoke concentration is heaviest in this area, the nozzles provide the large drops and the heavy spray distribution needed to clean carbon particulates from the smoke.

  16. Vertical two chamber reaction furnace

    DOEpatents

    Blaugher, Richard D.

    1999-03-16

    A vertical two chamber reaction furnace. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium-copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700.degree. and 800.degree. C.) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800.degree. to 950.degree. C. to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product.

  17. Vertical two chamber reaction furnace

    DOEpatents

    Blaugher, R.D.

    1999-03-16

    A vertical two chamber reaction furnace is disclosed. The furnace comprises a lower chamber having an independently operable first heating means for heating the lower chamber and a gas inlet means for admitting a gas to create an ambient atmosphere, and an upper chamber disposed above the lower chamber and having an independently operable second heating means for heating the upper chamber. Disposed between the lower chamber and the upper chamber is a vapor permeable diffusion partition. The upper chamber has a conveyor means for conveying a reactant there through. Of particular importance is the thallinating of long-length thallium-barium-calcium copper oxide (TBCCO) or barium-calcium-copper oxide (BCCO) precursor tapes or wires conveyed through the upper chamber to thereby effectuate the deposition of vaporized thallium (being so vaporized as the first reactant in the lower chamber at a temperature between about 700 and 800 C) on TBCCO or BCCO tape or wire (the second reactant) at its simultaneous annealing temperature in the upper chamber of about 800 to 950 C to thereby replace thallium oxide lost from TBCCO tape or wire because of the high annealing temperature or to deposit thallium on BCCO tape or wire. Continuously moving the tape or wire provides a single-step process that effectuates production of long-length TBCCO superconducting product. 2 figs.

  18. Crystal growth furnace safety system validation

    NASA Technical Reports Server (NTRS)

    Mackowski, D. W.; Hartfield, R.; Bhavnani, S. H.; Belcher, V. M.

    1994-01-01

    The findings are reported regarding the safe operation of the NASA crystal growth furnace (CGF) and potential methods for detecting containment failures of the furnace. The main conclusions are summarized by ampoule leak detection, cartridge leak detection, and detection of hazardous species in the experiment apparatus container (EAC).

  19. Existing and prospective blast-furnace conditions

    SciTech Connect

    I.G. Tovarovskii; V.I. Bol'shakov; V.P. Lyalyuk; A.E. Merkulov; D. V. Pinchuk

    2009-07-15

    Blast-furnace conditions are investigated by means of a multizone model. The expected performance of prospective technologies is assessed, as well as the trends in blast-furnace processes. The model permits the identification of means of overcoming practical difficulties.

  20. Blast furnace injection developments in British Steel

    SciTech Connect

    Jukes, M.H.

    1996-12-31

    British Steel has four integrated steel works, i.e., Llanwern, Port Talbot, Scunthorpe, Teesside, with a total of ten blast furnaces, nine of which are currently operating. The furnaces range in size from the 14 meters (45 feet 11 inches) hearth diameter Redcar No. 1 furnace at Teesside (a single furnace works) to the 8.33 meters (27 feet 4 inches) hearth Queen Mary and Queen Bess furnaces at Schunthorpe, with a total of four furnaces at that works. All have injection systems installed, those at Scunthorpe being equipped with granular coal injection and all others currently working with oil injection. The driving force behind the development of blast furnace injection has been as a means for introducing reducing agents (British Steel now refers to coke plus hydrocarbon injectants as total reductants) into the process as a part substitute/supplement for top charged coke and the technology is still being developed and used for that purpose. By utilizing practical experience and observing the work of others, British Steel has been assessing blast furnace injection technology experimentally for purposes other than the introduction of reducing agents.

  1. Thermal Imaging Control of Furnaces and Combustors

    SciTech Connect

    David M. Rue; Serguei Zelepouga; Ishwar K. Puri

    2003-02-28

    The object if this project is to demonstrate and bring to commercial readiness a near-infrared thermal imaging control system for high temperature furnaces and combustors. The thermal imaging control system, including hardware, signal processing, and control software, is designed to be rugged, self-calibrating, easy to install, and relatively transparent to the furnace operator.

  2. Tubular furnace for performance of gas reactions

    SciTech Connect

    Bruck, H.

    1984-04-03

    There is described a furnace for the performance of gas reactions in a ceramic assembly of tubes in which the heating chambers, the recuperators and the flue gas-branch channel are arranged in a compact, energy saving type of construction. The furnace is especially suited for the production of hydrocyanic acid according to the BMA process (hydrocyanic acid-methane-ammonia process).

  3. Enhancement of oxidation resistance of graphite foams by polymer derived-silicon carbide coating for concentrated solar power applications

    DOE PAGES

    Kim, T.; Singh, D.; Singh, M.

    2015-05-01

    Graphite foam with extremely high thermal conductivity has been investigated to enhance heat transfer of latent heat thermal energy storage (LHTES) systems. However, the use of graphite foam for elevated temperature applications (>600 °C) is limited due to poor oxidation resistance of graphite. In the present study, oxidation resistance of graphite foam coated with silicon carbide (SiC) was investigated. A pre-ceramic polymer derived coating (PDC) method was used to form a SiC coating on the graphite foams. Post coating deposition, the samples were analyzed by scanning electron microscopy and energy dispersive spectroscopy. The oxidation resistance of PDC-SiC coating was quantifiedmore » by measuring the weight of the samples at several measuring points. The experiments were conducted under static argon atmosphere in a furnace. After the experiments, oxidation rates (%/hour) were calculated to predict the lifetime of the graphite foams. The experimental results showed that the PDC-SiC coating could prevent the oxidation of graphite foam under static argon atmosphere up to 900 °C.« less

  4. Enhancement of oxidation resistance of graphite foams by polymer derived-silicon carbide coating for concentrated solar power applications

    SciTech Connect

    Kim, T.; Singh, D.; Singh, M.

    2015-05-01

    Graphite foam with extremely high thermal conductivity has been investigated to enhance heat transfer of latent heat thermal energy storage (LHTES) systems. However, the use of graphite foam for elevated temperature applications (>600 °C) is limited due to poor oxidation resistance of graphite. In the present study, oxidation resistance of graphite foam coated with silicon carbide (SiC) was investigated. A pre-ceramic polymer derived coating (PDC) method was used to form a SiC coating on the graphite foams. Post coating deposition, the samples were analyzed by scanning electron microscopy and energy dispersive spectroscopy. The oxidation resistance of PDC-SiC coating was quantified by measuring the weight of the samples at several measuring points. The experiments were conducted under static argon atmosphere in a furnace. After the experiments, oxidation rates (%/hour) were calculated to predict the lifetime of the graphite foams. The experimental results showed that the PDC-SiC coating could prevent the oxidation of graphite foam under static argon atmosphere up to 900 °C.

  5. High temperature furnace modeling and performance verifications

    NASA Technical Reports Server (NTRS)

    Smith, James E., Jr.

    1988-01-01

    Analytical, numerical and experimental studies were performed on two classes of high temperature materials processing furnaces. The research concentrates on a commercially available high temperature furnace using zirconia as the heating element and an arc furnace based on a ST International tube welder. The zirconia furnace was delivered and work is progressing on schedule. The work on the arc furnace was initially stalled due to the unavailability of the NASA prototype, which is actively being tested aboard the KC-135 experimental aircraft. A proposal was written and funded to purchase an additional arc welder to alleviate this problem. The ST International weld head and power supply were received and testing will begin in early November. The first 6 months of the grant are covered.

  6. A multi-zone muffle furnace design

    NASA Technical Reports Server (NTRS)

    Rowe, Neil D.; Kisel, Martin

    1993-01-01

    A Multi-Zone Muffle-Tube Furnace was designed, built, and tested for the purpose of providing an in-house experience base with tubular furnaces for materials processing in microgravity. As such, it must not only provide the desired temperatures and controlled thermal gradients at several discrete zones along its length but must also be capable of sustaining the rigors of a Space Shuttle launch. The furnace is insulated to minimize radial and axial heat losses. It is contained in a water-cooled enclosure for purposes of dissipating un-wanted residual heat, keeping the outer surfaces of the furnace at a 'touch-safe' temperature, and providing a rugged housing. This report describes the salient features of the furnace, testing procedures and results, and concluding remarks evaluating the overall design.

  7. Precision control of high temperature furnaces

    SciTech Connect

    Pollock, G.G.

    1994-12-31

    It is an object of the present invention to provide precision control of high temperature furnaces. It is another object of the present invention to combine the power of two power supplies of greatly differing output capacities in a single furnace. This invention combines two power supplies to control a furnace. A main power supply heats the furnace in the traditional manner, while the power from the auxiliary supply is introduced as a current flow through charged particles existing due to ionized gas or thermionic emission. The main power supply provides the bulk heating power and the auxiliary supply provides a precise and fast power source such that the precision of the total power delivered to the furnace is improved. Further, this invention comprises a means for high speed measurement of temperature of the process by the method of measuring the amount of current flow in a deliberately induced charged particle current.

  8. Optical cavity furnace for semiconductor wafer processing

    DOEpatents

    Sopori, Bhushan L.

    2014-08-05

    An optical cavity furnace 10 having multiple optical energy sources 12 associated with an optical cavity 18 of the furnace. The multiple optical energy sources 12 may be lamps or other devices suitable for producing an appropriate level of optical energy. The optical cavity furnace 10 may also include one or more reflectors 14 and one or more walls 16 associated with the optical energy sources 12 such that the reflectors 14 and walls 16 define the optical cavity 18. The walls 16 may have any desired configuration or shape to enhance operation of the furnace as an optical cavity 18. The optical energy sources 12 may be positioned at any location with respect to the reflectors 14 and walls defining the optical cavity. The optical cavity furnace 10 may further include a semiconductor wafer transport system 22 for transporting one or more semiconductor wafers 20 through the optical cavity.

  9. Graphite for the nuclear industry

    SciTech Connect

    Burchell, T.D.; Fuller, E.L.; Romanoski, G.R.; Strizak, J.P.

    1991-01-01

    Graphite finds applications in both fission and fusion reactors. Fission reactors harness the energy liberated when heavy elements, such as uranium or plutonium, fragment or fission''. Reactors of this type have existed for nearly 50 years. The first nuclear fission reactor, Chicago Pile No. 1, was constructed of graphite under a football stand at Stagg Field, University of Chicago. Fusion energy devices will produce power by utilizing the energy produced when isotopes of the element hydrogen are fused together to form helium, the same reaction that powers our sun. The role of graphite is very different in these two reactor systems. Here we summarize the function of the graphite in fission and fusion reactors, detailing the reasons for their selection and discussing some of the challenges associated with their application in nuclear fission and fusion reactors. 10 refs., 15 figs., 1 tab.

  10. CALANDRIA TYPE SODIUM GRAPHITE REACTOR

    DOEpatents

    Peterson, R.M.; Mahlmeister, J.E.; Vaughn, N.E.; Sanders, W.J.; Williams, A.C.

    1964-02-11

    A sodium graphite power reactor in which the unclad graphite moderator and fuel elements are contained within a core tank is described. The core tank is submersed in sodium within the reactor vessel. Extending longitudinally through the core thnk are process tubes with fuel elements positioned therein. A bellows sealing means allows axial expansion and construction of the tubes. Within the core tank, a leakage plenum is located below the graphite, and above the graphite is a gas space. A vent line regulates the gas pressure in the space, and another line removes sodium from the plenum. The sodium coolant flows from the lower reactor vessel through the annular space between the fuel elements and process tubes and out into the reactor vessel space above the core tank. From there, the heated coolant is drawn off through an outlet line and sent to the heat exchange. (AEC)

  11. Graphite-reinforced bone cement

    NASA Technical Reports Server (NTRS)

    Knoell, A. C.

    1976-01-01

    Chopped graphite fibers added to surgical bone cement form bonding agent with mechanical properties closely matched to those of bone. Curing reaction produces less heat, resulting in reduced traumatization of body tissues. Stiffness is increased without affecting flexural strength.

  12. Intercalated hybrid graphite fiber composite

    NASA Technical Reports Server (NTRS)

    Gaier, James R. (Inventor)

    1993-01-01

    The invention is directed to a highly conductive lightweight hybrid material and methods of producing the same. The hybrid composite is obtained by weaving strands of a high strength carbon or graphite fiber into a fabric-like structure, depositing a layer of carbon onto the structure, heat treating the structure to graphitize the carbon layer, and intercalating the graphitic carbon layer structure. A laminate composite material useful for protection against lightning strikes comprises at least one layer of the hybrid material over at least one layer of high strength carbon or graphite fibers. The composite material of the present invention is compatible with matrix compounds, has a coefficient of thermal expansion which is the same as underlying fiber layers, and is resistant to galvanic corrosion in addition to being highly conductive. These materials are useful in the aerospace industry, in particular as lightning strike protection for airplanes.

  13. Single layer nano graphene platelets derived from graphite nanofibres

    NASA Astrophysics Data System (ADS)

    Huang, Kai; Delport, Géraud; Orcin-Chaix, Lucile; Drummond, Carlos; Lauret, Jean-Sebastien; Penicaud, Alain

    2016-04-01

    Solutions of calibrated nanographenides (negatively charged nanographenes) are obtained by dissolution of graphite nanofibre intercalation compounds (GNFICs). Deposits show homogeneous unfolded nanographene platelets of 1 to 2 layers thickness and 10 nm lateral size, evidenced by atomic force microscopy and Raman spectroscopy. Upon oxidation, nanographenide solutions exhibit strong photoluminescence.Solutions of calibrated nanographenides (negatively charged nanographenes) are obtained by dissolution of graphite nanofibre intercalation compounds (GNFICs). Deposits show homogeneous unfolded nanographene platelets of 1 to 2 layers thickness and 10 nm lateral size, evidenced by atomic force microscopy and Raman spectroscopy. Upon oxidation, nanographenide solutions exhibit strong photoluminescence. Electronic supplementary information (ESI) available: Raman, SEM, TEM and XPS characterization of the raw nanofibres, detailed XPS spectra analysis of deposits from GNFIC/THF and GNFIC/NMP solutions, Raman and AFM characterization of fresh and aged solutions of nanofibres obtained from 3 different suppliers. See DOI: 10.1039/c6nr01512c

  14. Irradiation Induced Creep of Graphite

    SciTech Connect

    Burchell, Timothy D; Murty, Prof K.L.; Eapen, Dr. Jacob

    2010-01-01

    The current status of graphite irradiation induced creep strain prediction is reviewed and the major creep models are described. The ability of the models to quantitatively predict the irradiation induced creep strain of graphite is reported. Potential mechanisms of in-crystal creep are reviewed as are mechanisms of pore generation under stress. The case for further experimental work is made and the need for improved creep models across multi-scales is highlighted.

  15. BUNDLE - A Novel Furnace for Performing Controlled Directional Solidification Experiments in a Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Carrasquillo, Edgar J.; Griffin, Mark R.; Hammond, Monica S.; Johnson, Martin L.; Grugel, R. N.

    2001-01-01

    NASA Marshall Space Flight Center has developed a novel directional solidification furnace prototype for processing metals and alloys experiments in a microgravity environment. The BUNDLE (Bridgman Unidirectional Dendrite in Liquid Experiment) furnace is intended to accommodate the science requirements of Flight Definition Principle Investigators studying cellular/dendritic growth in aluminum and lead alloys at processing temperatures up to 1200 C. The furnace implements a number of innovative features to achieve high thermal gradients and quench rates in a low-power, light-weight design. These include a pyrolytic boron nitride/graphite composite heating element surrounded by layers of self-supporting refractory metal shielding, and a graphite fiber enhanced cold zone allowing high levels of heat extraction from the sample crucible. Novel to the BUNDLE design is an in-situ helium gas quench capability that ensures rapid freezing of the solidifying region (mushy zone) of the metal sample within the furnace without sample disturbance prior to quenching; this is a stringent requirement for subsequent analysis and understanding of microstructural development. The experiment hardware concept features multiple furnaces that may be "bundled" together so many samples, currently up to eight, can be processed at one time. The design of BUNDLE is flexible enough to be implemented on the Shuttle and Space Station in a number of locations (SpaceHab, Express Rack, MPESS, ISPR, etc). BUNDLE prototype furnaces have directionally solidified and quenched 1cm diameter lead - 5.8 weight percent antimony and aluminum - 4 weight percent copper alloys. Quenching of the mushy zone, as recorded by in-situ thermocouples, occurred on the order of 0.5 seconds or less, a rate within the PI's requirements. Subsequent metallographic examination revealed the solidified microstructure to be, as expected, unidirectional. Both the dendrite tips and the eutectic reaction were planar in nature

  16. BUNDLE: A Novel Furnace for Performing Controlled Directional Solidification Experiments in a Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Carrasquillo, Edgar J.; Griffin, Mark R.; Hammond, Monica S.; Johnson, Martin L.; Grugel, R. N.

    2000-01-01

    NASA Marshall Space Flight Center has developed a novel directional solidification furnace prototype for processing metals and alloys experiments in a microgravity environment. The BUNDLE (Bridgman Unidirectional Dendrite in Liquid Experiment) furnace is intended to accommodate the science requirements of Flight Definition Principle Investigators studying cellular/dendritic growth in aluminum and lead alloys at processing temperatures up to 1200 C. The furnace implements a number of innovative features to achieve high thermal gradients and quench rates in a low-power, light-weight design. These include a pyrolytic boron nitride/graphite composite heating element surrounded by layers of self-supporting refractory metal shielding, and a graphite fiber enhanced cold zone allowing high levels of heat extraction from the sample crucible. Novel to the BUNDLE design is an in-situ helium gas quench capability that ensures rapid freezing of the solidifying region (mushy zone) of the metal sample within the furnace without sample disturbance prior to quenching; this is a stringent requirement for subsequent analysis and understanding of microstructural development. The experiment hardware concept features multiple furnaces that may be "bundled" together so many samples, currently up to eight, can be processed at one time. The design of BUNDLE is flexible enough to be implemented on the Shuttle and Space Station in a number of locations (SpaceHab, Express Rack, MPESS, ISPR, etc). BUNDLE prototype furnaces have directionally solidified and quenched 1cm diameter lead - 5.8 weight percent antimony and aluminum - 4 weight percent copper alloys. Quenching of the mushy zone, as recorded by in-situ thermocouples, occurred on the order of 0.5 seconds or less, a rate within the PI's requirements. Subsequent metallographic examination revealed the solidified microstructure to be, as expected, unidirectional. Both the dendrite tips and the eutectic reaction were planar in nature

  17. Micromechanical properties of intercalated compounds of graphite oxide with dodecahydro- closо-dodecaboric acid

    NASA Astrophysics Data System (ADS)

    Karpenko, A. A.; Saldin, V. I.

    2016-08-01

    The micromechanical properties (Young's modulus, deformation, and adhesion) of the intercalated compound of graphite oxide with dodecahydro- closo-dodecaboric acid were studied by atomic force microscopy, transmission electron microscopy, and Raman spectroscopy and compared with the same characteristics of the starting graphite oxide. The significant difference in the micromechanical properties of the materials under study is dictated by differences in the topography and properties of their film surface, which, in turn, can be determined by their chemical composition. The introduction of dodecahydro- closo-dodecaboric acid in the interplanar space of graphite oxide affects the structuring of the latter. A considerable increase in the adhesion of the intercalated compound relative to that of oxide graphite is explained by high adhesive properties of the introduced acid, the Young's modulus of graphite oxide being higher than that of the intercalated compound. This was attributed to the high hydrophilicity of dodecahydro- closo-dodecaboric acid and the difficulty of water removal from the interplanar space; water plasticizes the material, which becomes softer than graphite oxide. The difference in the structure of the coating of the intercalated compounds and the starting graphite oxide was found to be also reflected by their Raman spectra, namely, by the increased intensity of the D line with the preserved position of the G line, which points to the impurity nature of the intercalate and the unchanged hexagonal lattice of graphite.

  18. Micromechanical properties of intercalated compounds of graphite oxide with dodecahydro- closo-dodecaboric acid

    NASA Astrophysics Data System (ADS)

    Karpenko, A. A.; Saldin, V. I.

    2016-08-01

    The micromechanical properties (Young's modulus, deformation, and adhesion) of the intercalated compound of graphite oxide with dodecahydro- closo-dodecaboric acid were studied by atomic force microscopy, transmission electron microscopy, and Raman spectroscopy and compared with the same characteristics of the starting graphite oxide. The significant difference in the micromechanical properties of the materials under study is dictated by differences in the topography and properties of their film surface, which, in turn, can be determined by their chemical composition. The introduction of dodecahydro- closo-dodecaboric acid in the interplanar space of graphite oxide affects the structuring of the latter. A considerable increase in the adhesion of the intercalated compound relative to that of oxide graphite is explained by high adhesive properties of the introduced acid, the Young's modulus of graphite oxide being higher than that of the intercalated compound. This was attributed to the high hydrophilicity of dodecahydro- closo-dodecaboric acid and the difficulty of water removal from the interplanar space; water plasticizes the material, which becomes softer than graphite oxide. The difference in the structure of the coating of the intercalated compounds and the starting graphite oxide was found to be also reflected by their Raman spectra, namely, by the increased intensity of the D line with the preserved position of the G line, which points to the impurity nature of the intercalate and the unchanged hexagonal lattice of graphite.

  19. Growth of Ferrite Needles in Compacted Graphite Cast Iron

    NASA Astrophysics Data System (ADS)

    Durán, G. A.; Perez, T.; Gregorutti, R. W.; Mercader, R. C.; Desimoni, J.

    2005-04-01

    The austempering kinetics transformation of compacted graphite cast irons austempered at 623K is studied. The length (l) and the number per unit volume (N) of ferrite needles were followed by Scanning Electron Microscopy (SEM), while Mössbauer spectroscopy (MS) was used to determine the austenite relative areas. The SEM results are compared with theoretical calculations available in the literature and indicate that the diffusion of C atoms in austenite controls the transformation, confirming the indirect MS determinations.

  20. Growth of Ferrite Needles in Compacted Graphite Cast Iron

    SciTech Connect

    Duran, G.A.; Mercader, R.C.; Desimoni, J.; Perez, T.; Gregorutti, R.W.

    2005-04-26

    The austempering kinetics transformation of compacted graphite cast irons austempered at 623K is studied. The length (l) and the number per unit volume (N) of ferrite needles were followed by Scanning Electron Microscopy (SEM), while Moessbauer spectroscopy (MS) was used to determine the austenite relative areas. The SEM results are compared with theoretical calculations available in the literature and indicate that the diffusion of C atoms in austenite controls the transformation, confirming the indirect MS determinations.

  1. Reconstruction of low-index graphite surfaces

    NASA Astrophysics Data System (ADS)

    Thinius, Sascha; Islam, Mazharul M.; Bredow, Thomas

    2016-07-01

    The low-index graphite surfaces (10 1 -0), (10 1 -1), (11 2 -0) and (11 2 - 1) have been studied by density functional theory (DFT) including van-der-Waals (vdW) corrections. Different from the (0001) surface which has been extensively investigated both experimentally and theoretically, there is no comprehensive study on the (10 1 -0)- (10 1 -1)-, (11 2 -0)- and (11 2 - 1)-surfaces available, although they are of relevance for Li insertion processes, e.g. in Li-ion batteries. In this study the structure and stability of all non-(0001) low-index surfaces were calculated with RPBE-D3 and converged slab models. In all cases reconstruction involving bond formation between unsaturated carbon atoms of two neighboring graphene sheets reduces the surface energy dramatically. Two possible reconstruction patterns have been considered. The first possibility leads to formation of oblong nanotubes. Alternatively, the graphene sheets form bonds to different neighboring sheets at the upper and lower sides and sinusoidal structures are formed. Both structure types have similar stabilities. Based on the calculated surface energies the Gibbs-Wulff theorem was applied to construct the macroscopic shape of graphite single crystals.

  2. LEO degradation of graphite and carbon-based composites aboard Space Shuttle Flight STS-46

    SciTech Connect

    Spady, B.R.; Synowicki, R.A.; Hale, J.S.; Devries, M.J.; Woollam, J.A.; Moore, A.W.; Lake, M. |

    1995-02-01

    Six different types of carbon and carbon-boron nitride composites were exposed to low Earth orbit aboard Space Shuttle flight STS-46. The samples received a nominal atomic oxygen fluence of 2.2 x 10(exp 20) atoms/sq cm in 42 hours of exposure. Pyrolytic graphite and highly oriented pyrolytic graphite showed significant degradation, and the measured erosion yield was within a factor of two of published values. The erosion yield of pyrolytic boron nitride was found to be 2.6 x 10(exp 26) cu cm/atom in plasma asher exposure, over 42 times lower than that of pyrolytic graphite. This low erosion yield makes graphite plus boron nitride mixtures quite resistant to low Earth orbit exposure. Evidence suggests that the graphitic component was preferentially etched, leaving the surface boron nitride rich. Degradation resistance increases with boron nitride composition. Carbon fiber/carbon composites degraded in low Earth orbit, and the carbon pitch binder was found to etch more easily than the graphite fibers which have much higher degradation resistance.

  3. LEO degradation of graphite and carbon-based composites aboard Space Shuttle Flight STS-46

    NASA Technical Reports Server (NTRS)

    Spady, Blaine R.; Synowicki, R. A.; Hale, Jeffrey S.; Devries, M. J.; Woollam, John A.; Moore, Arthur W.; Lake, Max

    1995-01-01

    Six different types of carbon and carbon-boron nitride composites were exposed to low Earth orbit aboard Space Shuttle flight STS-46. The samples received a nominal atomic oxygen fluence of 2.2 x 10(exp 20) atoms/sq cm in 42 hours of exposure. Pyrolytic graphite and highly oriented pyrolytic graphite showed significant degradation, and the measured erosion yield was within a factor of two of published values. The erosion yield of pyrolytic boron nitride was found to be 2.6 x 10(exp 26) cu cm/atom in plasma asher exposure, over 42 times lower than that of pyrolytic graphite. This low erosion yield makes graphite plus boron nitride mixtures quite resistant to low Earth orbit exposure. Evidence suggests that the graphitic component was preferentially etched, leaving the surface boron nitride rich. Degradation resistance increases with boron nitride composition. Carbon fiber/carbon composites degraded in low Earth orbit, and the carbon pitch binder was found to etch more easily than the graphite fibers which have much higher degradation resistance.

  4. Nuclear techniques for the inspection of blast furnaces

    SciTech Connect

    Schweitzer, J. S.; Lanza, R. C.

    1999-06-10

    Carbon hearth wall failures in blast furnaces create safety risks and require a large expense to repair. To avoid failures they are replaced early, incurring costs in wasted hearth wall use. Two non-invasive measurements provide realtime analysis of wall integrity. The two major failure modes are erosion of carbon thickness and iron-filled cracks in the bricks. Measurements of backscattered gamma-ray spectra and thermal neutron decay rate can identify both phenomena. Gamma-ray spectra from a compact Linac beam primarily respond to average carbon thickness. Neutron decay time, using a pulsed neutron source, is sensitive to iron in the carbon volume. Each measurement is sensitive to the other failure made, but the combination permits each phenomenon to be resolved. These techniques can detect a high atomic number and thermal neutron absorption cross section material behind one of low atomic number and thermal neutron absorption cross section.

  5. Structural, chemical, and isotopic microanalytical investigations of graphite from supernovae

    NASA Astrophysics Data System (ADS)

    Croat, T. Kevin; Bernatowicz, Thomas; Amari, Sachiko; Messenger, Scott; Stadermann, Frank J.

    2003-12-01

    We report the results of coordinated ion microprobe and transmission electron microscope (TEM) studies of presolar graphites from the KE3 separate (1.65-1.72 g/cm 3) of the Murchison CM2 meteorite. Isotopic analysis of individual graphites (1-12 μm) with the ion microprobe shows many to have large 18O excesses combined with large silicon isotopic anomalies, indicative of a supernova (SN) origin. Transmission electron microscopy (TEM) of ultramicrotome slices of these SN graphites revealed a high abundance (25-2400 ppm) of internal titanium carbides (TiCs), with a single graphite in some cases containing hundreds of TiCs. Isotopic compositions of individual TiCs by nanoscale resolution secondary ion mass spectrometry (NanoSIMS) confirmed their presolar origin. In addition to TiCs, composite TiC/Fe grains (TiCs with attached iron-nickel subgrains) and solitary kamacite internal grains were found. In the composite grains, the attached iron phase (kamacite [0-24 at. % Ni] or taenite [up to 60 at. % Ni]) was epitaxially grown onto one or more TiC faces. In contrast to the denser Murchison KFC1 graphites, no Zr-Ti-Mo carbides were observed. The average TiC diameters were quite variable among the SN graphites, from 30 to 232 nm, and were generally independent of the host graphite size. TiC grain morphologies ranged from euhedral to anhedral, with the grain surfaces exhibiting variable degrees of corrosion, and sometimes partially amorphous rims (3 to 15 nm thick). Partially amorphous rims of similar thickness were also observed on some solitary kamacite grains. We speculate that the rims on the internal grains are most plausibly the result of atom bombardment caused by drift of grains with respect to the ambient gas, requiring relative outflow speeds ˜100 km/s (i.e., a few percent of the SN mass outflow speed). Energy dispersive X-ray spectrometry (EDXS) of TiCs revealed significant V in solid solution, with an average V/Ti ratio over all TiCs of ˜83% of the solar

  6. Blow-down and blow-in of Inland`s No. 7 blast furnace

    SciTech Connect

    Ricketts, J.; Quisenberry, P.; Carter, W.

    1995-12-01

    After extensive and detailed planning, a mini-reline of the 13.7 meter No. 7 Blast Furnace was executed in November 1993. The furnace lining had 18 million metric tons of production and the bosh, belly and lower stack lining were being maintained through a scheduled grouting practice. The mini-reline was planned for 33 days and the reline work included (a) replacing the bosh, belly and lower stack alumina lining with graphite brick, (b) gunning the middle and upper stack, (c) rebuilding the furnace top, stove burners and tapholes and (d) minor repairs to other auxiliary equipment. During this 33 day reline period the two 8 meter furnaces could only produce 40% of the normal production requirement, therefore the blow-down, quench, salamander tap and blow-in activities were critical to meeting the planned schedule. The planning of these activities was started in the spring of 1993 and included review of Inland`s past blow-down and blow-in performance as well as bench marking the performance of other large blast furnaces in North America, Japan and Europe. The development of the 1993 procedures focused on opportunities to accelerate the blow-down, quench, salamander tap and blow-in as well as having a clean hearth and stack which could also save time during the demolition phase of the reline. Any time that could be saved in these activities directly translated to an early start-up and more plantwide production. This paper will cover the successful planning and implementation of these activities which resulted in a 2 day reduction in the reline schedule, an accelerated production curve and an earlier than planned use of PCI during blow-in.

  7. Acoustic characteristics of electric arc furnaces

    NASA Astrophysics Data System (ADS)

    Cherednichenko, V. S.; Bikeev, R. A.; Cherednichenko, A. V.; Ognev, A. M.

    2016-06-01

    A mathematical model is constructed to describe the appearance and development of the noise characteristics of superpower electric arc furnaces. The noise formation is shown to be related to the pulsation of the axial plasma flows in arc discharges because of the electrodynamic pressure oscillations caused by the interaction of the self-magnetic field with the current passing in an arc. The pressure in the arc axis changes at a frequency of 100 Hz at the maximum operating pressure of 66 kPa for an arc current of 80 kA. The main ac arc sound frequencies are multiples of 100 Hz, which is supported in the practice of operation of electric arc furnaces. The sound intensity in the furnace laboratory reaches 160 dB and is decreased to 115-120 dB in the working furnace area due to shielding by the furnace jacket, the molten metal, and the molten slag. The appropriateness of increasing the hermetic sealing of electric furnaces and creating furnaces operating at low currents and high transformer voltages is corroborated.

  8. Highly Conducting Graphite Epoxy Composite Demonstrated

    NASA Technical Reports Server (NTRS)

    Gaier, James R.

    1999-01-01

    Weight savings as high as 80 percent could be achieved if graphite polymer composites could replace aluminum in structures such as electromagnetic interference shielding covers and grounding planes. This could result in significant cost savings, especially for the mobile electronics found in spacecraft, aircraft, automobiles, and hand-held consumer electronics. However, such composites had not yet been fabricated with conductivity sufficient to enable these applications. To address this lack, a partnership of the NASA Lewis Research Center, Manchester College, and Applied Sciences, Inc., fabricated nonmetallic composites with unprecedented electrical conductivity. For these composites, heat-treated, vapor-grown graphite fibers were selected which have a resistivity of about 80 mW-cm, more than 20 times more conductive than typical carbon fibers. These fibers were then intercalated with iodine bromide (IBr). Intercalation is the insertion of guest atoms or molecules between the carbon planes of the graphite fibers. Since the carbon planes are not highly distorted in the process, intercalation has little effect on mechanical and thermal properties. Intercalation does, however, lower the carbon fiber resistivity to less than 10 mW-cm, which is comparable to that of metal fibers. Scaleup of the reaction was required since the initial intercalation experiments would be carried out on 20-mg quantities of fibers, and tens of grams of intercalated fibers would be needed to fabricate even small demonstration composites. The reaction was first optimized through a time and temperature study that yielded fibers with a resistivity of 8.7 2 mW-cm when exposed to IBr vapor at 114 C for 24 hours. Stability studies indicated that the intercalated fibers rapidly lost their conductivity when exposed to temperatures as low as 40 C in air. They were not, however, susceptible to degradation by water vapor in the manner of most graphite intercalation compounds. The 1000-fold scaleup

  9. Horizontal tapping furnace and method of operation

    SciTech Connect

    Wunsche, E.R.

    1987-07-14

    A metallurgical furnace is described including: a furnace floor and a furnace wall means extending generally upwardly about the floor, the furnace having a vertical axis and a horizontal axis, means mounting the furnace for pivotal tilting movement about the horizontal axis between a non-tilted, normal upright position, and a tilted discharge position with the furnace tilted less than 15/sup 0/ to the vertical axis; a hearth zone defined between the floor and wall means adapted to house a bath of liquid metal of predetermined volume, the hearth zone having an upper end defining a predetermined upper level for the bath and for a layer of liquid slag floating on the upper level, when the furnace is in a non-tilted, normal upright position; the hearth zone having a lower end adjacent the floor, a tapping passage extending through the wall means from a liquid metal discharge outlet at an outer end into the lower end of the hearth zone, at an inner end, the discharge outlet being defined by an outwardly facing passage wall and the passage at the outer end; the tapping passage disposed generally parallel to the horizontal axis and vertically below the predetermined upper level, when the furnace is in the non-tilted, normal, upright position; a discharge outlet closure having a closure surface and pivotally mounted externally of the passage for pivotal to and for movement towards and away from the furnace wall means between a first position. The closure surface engages the passage wall at the outer end to fully close the discharge outlet, and a second position spaced apart from the passage wall.

  10. Contamination of furnace-drawn silica fibers.

    PubMed

    Kaiser, P

    1977-03-01

    Contamination originating in an electric resistance furnace was found to increase substantially the losses of unclad and plastic-clad silica fibers. In contrast, the losses of doped silica fibers with sufficient cladding thickness were unaffected by impure drawing conditions. Operating the furnace without muffle tube and protecting the preform with a pure, inert gas injected via a counter-flow resulted in practically contamination-free operation and unclad-fiber losses as low as 3 dB/km. The removal of the muffle tube significantly simplified the furnace operation and reduced the cycling time from many hours to a few minutes. PMID:20168565

  11. Uranium casting furnace automatic temperature control development

    SciTech Connect

    Lind, R.F.

    1992-05-31

    Development of an automatic molten uranium temperature control system for use on batch-type induction casting furnaces is described. Implementation of a two-color optical pyrometer, development of an optical scanner for the pyrometer, determination of furnace thermal dynamics, and design of control systems are addressed. The optical scanning system is shown to greatly improve pyrometer measurement repeatability, particularly where heavy floating slag accumulations cause surface temperature gradients. Thermal dynamics of the furnaces were determined by applying least-squares system identification techniques to actual production data. A unity feedback control system utilizing a proportional-integral-derivative compensator is designed by using frequency-domain techniques. 14 refs.

  12. X-Ray Difraction Pattern of Graphite Oxide

    NASA Astrophysics Data System (ADS)

    Mu, Shi-Jia; Su, Yu-Chang; Xiao, Li-Hua; Liu, Si-Dong; Hu, Te; Tang, Hong-Bo

    2013-09-01

    X-ray diffraction patterns of graphite oxide (GO) are theoretically simulated as a function of the displacements of carbon atoms using the Debye—Waller factor in terms of the Warren—Bodenstein equation. The results demonstrate that GO has the turbostratically stacked structure. The high order (00l) peaks gradually disappear with the increase in atomic thermal vibrations along c-axis while the (hk0) ones weaken for the vibrations along a-axis. When the displacement deviation ua = 0.015 nm and uc = 0.100 nm the computed result is consistent with the experimental measurements.

  13. Fluorine interaction with defects on graphite surface by a first-principles study

    NASA Astrophysics Data System (ADS)

    Wang, Song; Xuezhi, Ke; Zhang, Wei; Gong, Wenbin; Huai, Ping; Zhang, Wenqing; Zhu, Zhiyuan

    2014-02-01

    The interaction between fluorine atom and graphite surface has been investigated in the framework of density functional theory. Due to the consideration of molten salt reactor system, only carbon adatoms and vacancies are chemical reactive for fluorine atoms. Fluorine adsorption on carbon adatom will enhance the mobility of carbon adatom. Carbon adatom can also be removed easily from graphite surface in form of CF2 molecule, explaining the formation mechanism of CF2 molecule in previous experiment. For the interaction between fluorine and vacancy, we find that fluorine atoms which adsorb at vacancy can hardly escape. Both pristine surface and vacancy are impossible for fluorine to penetrate due to the high penetration barrier. We believe our result is helpful to understand the compatibility between graphite and fluorine molten salt in molten salt reactor system.

  14. 21. Photocopy of ca. 1951 view (when furnaces were still ...

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

    21. Photocopy of ca. 1951 view (when furnaces were still in blast) looking north at central furnace complex with railroad cars of furnace charging materials in foreground and No. 2 Furnace at left. Photo marked on back 'David W. Corson from A. Devaney, N.Y.' - Sloss-Sheffield Steel & Iron, First Avenue North Viaduct at Thirty-second Street, Birmingham, Jefferson County, AL

  15. 46 CFR 164.009-11 - Furnace apparatus.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 6 2013-10-01 2013-10-01 false Furnace apparatus. 164.009-11 Section 164.009-11...: SPECIFICATIONS AND APPROVAL MATERIALS Noncombustible Materials for Merchant Vessels § 164.009-11 Furnace apparatus. (a) The test furnace apparatus consists of a furnace tube, stabilizer, draft shield,...

  16. 46 CFR 164.009-13 - Furnace calibration.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 6 2011-10-01 2011-10-01 false Furnace calibration. 164.009-13 Section 164.009-13...: SPECIFICATIONS AND APPROVAL MATERIALS Noncombustible Materials for Merchant Vessels § 164.009-13 Furnace calibration. A calibration is performed on each new furnace and on each existing furnace as often as...

  17. 46 CFR 164.009-13 - Furnace calibration.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 6 2013-10-01 2013-10-01 false Furnace calibration. 164.009-13 Section 164.009-13...: SPECIFICATIONS AND APPROVAL MATERIALS Noncombustible Materials for Merchant Vessels § 164.009-13 Furnace calibration. A calibration is performed on each new furnace and on each existing furnace as often as...

  18. 46 CFR 164.009-13 - Furnace calibration.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 6 2014-10-01 2014-10-01 false Furnace calibration. 164.009-13 Section 164.009-13...: SPECIFICATIONS AND APPROVAL MATERIALS Noncombustible Materials for Merchant Vessels § 164.009-13 Furnace calibration. A calibration is performed on each new furnace and on each existing furnace as often as...

  19. 46 CFR 164.009-11 - Furnace apparatus.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 6 2014-10-01 2014-10-01 false Furnace apparatus. 164.009-11 Section 164.009-11...: SPECIFICATIONS AND APPROVAL MATERIALS Noncombustible Materials for Merchant Vessels § 164.009-11 Furnace apparatus. (a) The test furnace apparatus consists of a furnace tube, stabilizer, draft shield,...

  20. 46 CFR 164.009-11 - Furnace apparatus.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 6 2012-10-01 2012-10-01 false Furnace apparatus. 164.009-11 Section 164.009-11...: SPECIFICATIONS AND APPROVAL MATERIALS Noncombustible Materials for Merchant Vessels § 164.009-11 Furnace apparatus. (a) The test furnace apparatus consists of a furnace tube, stabilizer, draft shield,...