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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. Rapid analysis with transversely heated graphite furnace atomic absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Zhang; Carnrick, Glen; Slavin, Walter

    1993-09-01

    A new graphite furnace instrument using a transversely heated furnace tube with a longitudinal Zeeman correction system has been specifically designed to provide more nearly stabilized temperature platform furnace (STPF) conditions than previous furnace systems. Because there are no cold ends on this furnace tube on which to condense analyte and matrix materials, the vapor phase interferences are expected to be smaller. Also, the cooldown step can be avoided, thus saving time. This instrument permits the delivery of sample into a furnace already heated. The delivery rate of the autosampler can be slowed. These opportunities make it feasible for the sample to be dry on the platform by the time the delivery is complete. Several elements of environmental significance were chosen for test: As, Pb, Se, Tl, Cd, Cu, Cr and V. In almost all of these situations, the analyte was fully recovered without using a matrix modifier or a pyrolysis step. However, As and Pb in urine and As in sediment required a modifier and pyrolysis step for accurate results. A new fast furnace protocol was developed to accommodate use of a matrix modifier and this new protocol was successful for Pb and As in these matrices. All the procedures required less than 1 min total cycle times and produced results in agreement with certified values. This is in contrast with conventional methods which require 2-3 min per firing. These results confirm that graphite furnace methods can be accomplished with a throughput greater than 60 determinations per hour, and eventually, it may be possible to increase this rate beyond 100 determinations per hour.

  5. Determination of mercury in soils and sediments by graphite furnace atomic absorption spectrometry with slurry sampling

    NASA Astrophysics Data System (ADS)

    López-García, Ignacio; Sánchez-Merlos, Mateo; Hernández-Córdoba, Manuel

    1997-12-01

    A graphite furnace atomic absorption spectrometric procedure for the determination of mercury is presented, in which the samples are suspended in a solution containing hydrofluoric and nitric acids. Silver nitrate (4% m/v) and potassium permanganate (3%) are incorporated, in the order specified, and aliquots are directly introduced into the graphite furnace. A fast heating programme with no conventional pyrolysis step is used. The detection limit for mercury in a 125 mg ml -1 suspension is 0.1 μg g -1. Calibration is performed by using aqueous standards. The reliability of the procedure is proved by analysing certified reference materials.

  6. 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...

  7. 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.

  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. 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.

  10. 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…

  11. 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

  12. 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

  13. 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.

  14. 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.).

  15. Determination of arsenic and cadmium in crude oil by direct sampling graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    de Jesus, Alexandre; Zmozinski, Ariane Vanessa; Damin, Isabel Cristina Ferreira; Silva, Márcia Messias; Vale, Maria Goreti Rodrigues

    2012-05-01

    In this work, a direct sampling graphite furnace atomic absorption spectrometry method has been developed for the determination of arsenic and cadmium in crude oil samples. The samples were weighed directly on the solid sampling platforms and introduced into the graphite tube for analysis. The chemical modifier used for both analytes was a mixture of 0.1% Pd + 0.06% Mg + 0.06% Triton X-100. Pyrolysis and atomization curves were obtained for both analytes using standards and samples. Calibration curves with aqueous standards could be used for both analytes. The limits of detection obtained were 5.1 μg kg- 1 for arsenic and 0.2 μg kg- 1 for cadmium, calculated for the maximum amount of sample that can be analyzed (8 mg and 10 mg) for arsenic and cadmium, respectively. Relative standard deviations lower than 20% were obtained. For validation purposes, a calibration curve was constructed with the SRM 1634c and aqueous standards for arsenic and the results obtained for several crude oil samples were in agreement according to paired t-test. The result obtained for the determination of arsenic in the SRM against aqueous standards was also in agreement with the certificate value. As there is no crude oil or similar reference material available with a certified value for cadmium, a digestion in an open vessel under reflux using a "cold finger" was adopted for validation purposes. The use of paired t-test showed that the results obtained by direct sampling and digestion were in agreement at a 95% confidence level. Recovery tests were carried out with inorganic and organic standards and the results were between 88% and 109%. The proposed method is simple, fast and reliable, being appropriated for routine analysis.

  16. 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

  17. Determination of trace and minor elements in alloys by atomic-absorption spectroscopy using an induction-heated graphite-well furnace as atom source-II.

    PubMed

    Ashy, M A; Headridge, J B; Sowerbutts, A

    1974-06-01

    Results are presented for the atomic-absorption spectrophotometric determination of zinc in aluminium and aluminium-silicon alloys, and aluminium, antimony and tin in steels, by means of solid samples dropped into an induction-heated graphite-well furnace to produce the atomic vapour. PMID:18961510

  18. Determination of gold in geological materials by carbon slurry sampling graphite furnace atomic absorption spectrometry.

    PubMed

    Dobrowolski, Ryszard; Kuryło, Michał; Otto, Magdalena; Mróz, Agnieszka

    2012-09-15

    A simple and cost effective preconcentration method on modified activated carbons is described for the determination of traces of gold (Au) in geological samples by carbon slurry sampling graphite furnace atomic absorption spectrometry (GFAAS). The basic parameters affecting the adsorption capacity of Au(III) ions on modified activated carbons were studied in detail and the effect of activated carbons modification has been determined by studying the initial runs of adsorption isotherms. The influence of chlorides and nitrates on adsorption ability of Au(III) ions onto the modified activated carbons for diluted aqueous solution was also studied in detail in respect to the determination of gold in solid materials after digestion steps in the analytical procedure, which usually involves the application of aqua regia. SEM-EDX and XPS studies confirmed that the surface reduction of Au(III) ions to Au(0) is the main gold adsorption mechanism on the activated carbon. Determination of gold after its preconcentration on the modified activated carbon was validated by applying certified reference materials. The experimental results are in good agreement with the certified values. The proposed method has been successfully applied for the determination of Au in real samples using aqueous standards. PMID:22967620

  19. 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

  20. Stability of low concentration calibration standards for graphite furnace atomic absorption spectrophotometry

    SciTech Connect

    Bass, D A; TenKate, L B

    1993-11-01

    Graphite furnace atomic absorption spectrophotometry (GFAAS) is used for determination of ultra-trace metals in environmentally important samples. In the generation of GFAAS calibration curves for many environmental applications, low concentration calibration standards must be prepared dally, as required by the Statement of Work (SOW) for the US Environmental Protection Agency (EPA) Contract Laboratory Program (CLP). This results in significant time and work for the analyst and significant cost to the Analytical Chemistry Laboratory (ACL) for chemicals and waste management. While EPA SW 846 is less prescriptive than the CLP SOW, ACL has been following the CLP guidelines because in-house criteria regarding the stability of GFAAS standards have not been established. A study was conducted to determine the stability of GFAAS standards for analytes commonly used in the ACL (single and mixed) as a function of time. Data were collected over nine months. The results show that GFAAS standards for Sb, Pb, Se, Ag, and TI are stable for a longer period of time than currently assumed by the CLP SOW. Reducing the frequency of preparing these standards will increase efficiency, decrease the handling of hazardous the quantity of hazardous waste generated, and decrease the quantity of hazardous substances to be ordered and stocked by the laboratory. These benefits will improve GFAAS analysis quality, reduce costs, enhance safety, and lower environmental concerns.

  1. Determination of chromium and molybdenum in medical foods by graphite furnace atomic absorption spectrophotometry.

    PubMed

    Phifer, E C

    1995-01-01

    Graphite furnace atomic absorption spectrophotometry was used to determine chromium and molybdenum in 7 medical foods from 5 manufacturers. Linear standard curves were obtained for both elements for concentrations between 5 and 25 ng/mL. Detection limits were 0.24 ng/mL for Cr and 0.67 ng/mL for Mo. Characteristic masses were 3.1 and 14.7 pg for Cr and Mo, respectively. No difference was detected between wet and dry ashing methods, and dry ashing was used to complete the study. The method was validated by assaying various National Institute of Standards and Technology standard reference materials. Analysis of these products for Cr and Mo were within certified values. One product was evaluated by this method for reproducibility (n = 5). Relative standard deviations were 6.8 and 4.8% for Cr and Mo, respectively. This product contained 0.31 +/= 0.02 micrograms Cr/g and 0.63 +/- 0.03 micrograms Mo/g. The remaining products contained 0.09-1.28 micrograms Cr/g and 0.07-2.3 micrograms Mo/g. Mean recovery values were 98 +/- 14% (n = 14) for Cr at spike levels of 0.20-1.89 micrograms/g and 102 +/- 24% (n = 10) for Mo at spike levels of 0.30-1.89 micrograms/g. PMID:8664588

  2. AN INTRALABORATORY COMPARATIVE STUDY OF HYDRIDE GENERATION AND GRAPHITE FURNACE ATOMIC ABSORPTION TECHNIQUES FOR DETERMINING ORGANIC AND INORGANIC ARSENIC IN COMPLEX WASTEWATERS

    EPA Science Inventory

    A detailed intralaboratory comparison of the determination of arsenic in complex wastewater samples by hydride generation and graphite furnace atomic absorption techniques has been conducted. Two hydride generation techniques were employed. One consisted of the use of sodium boro...

  3. 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.

  4. A versatile microcomputer interface and peripheral devices: An application in deuterium lamp background correction graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Gökmen, A.; Yalcin, S.

    1992-01-01

    A versatile interface card for Apple IIe computer and various peripheral devices are designed to control instruments which generates transient signals like in graphite furnace atomic spectrometer. The interface card consists of a multiplexed analog-to-digital converter, a digital-to-analog converter, and a timer/counter chip. The timer/counter chip with 16 built-in registers can be programmed in many modes which provides a time base for real-time measurements. A stepper motor runs under the control of timer/counter chip independent of computer. A light chopper connected to the stepper motor is controlled easily by computer. A dual high-voltage switch can modulate dc light sources under computer control. This system is applied to D2-lamp background correction graphite furnace atomic absorption spectrometer. The D2 lamp is chopped by a mechanical chopper driven by a stepper motor and a hollow cathode lamp is modulated electronically. The data acquisition program is written in machine language and synchronization between light sources and computer is provided by chopper position signal through the interrupts. A sampling rate of 16 during a signal period at 50-Hz chopping frequency is found to be the optimum value. A large number of data collected during atomization period is compressed in machine code. This saved storage space and analysis time.

  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. Determination of vanadium in soils and sediments by the slurry sampling graphite furnace atomic absorption spectrometry using permanent modifiers.

    PubMed

    Dobrowolski, Ryszard; Adamczyk, Agnieszka; Otto, Magdalena

    2013-09-15

    A new analytical procedure for vanadium (V) determination in soils and sediments by the slurry sampling graphite furnace atomic absorption spectrometry (slurry sampling GFAAS) using the mixed permanent modifiers is described. Moreover, the comparison of action of the modifiers based on the iridium (Ir) and carbide-forming elements: tungsten (W) and niobium (Nb) deposited on the graphite tubes is studied, especially in terms of their analytical utility and determination sensitivity. The mechanism of their action was investigated using an X-ray diffraction technique (XRD) and scanning electron microscopy (SEM) equipped with an energy dispersive X-ray detector (EDX). Finally, the mixture of 0.3 μg of Ir and 0.04 μg of Nb was used for the graphite tube permanent modification. The analytical procedure was optimized on the basis of the data from pyrolysis and atomization temperature curves studies. The results obtained for the four certified reference materials (marine sediments: PACS-1 and MESS-1, lake sediment: SL-1, soil: San Joaquin Soil SRM 2709), using the slurry sampling GFAAS and the standard calibration method, were in good agreement with the certified values. The detection and quantification limits and characteristic mass calculated for the proposed procedure were 0.04 µg/g, 0.16 µg/g and 11.9 pg, respectively. The precision (RSD% less than 8%) and the accuracy of vanadium determination in the soil and sediment samples were acceptable. PMID:23708618

  9. Determination of total tin in environmental biological and water samples by atomic absorption spectrometry with graphite furnace.

    PubMed

    Dogan, S; Haerdi, W

    1980-01-01

    Analysis of traces of tin using several analytical techniques (X-ray fluorescence, neutron activation, polarographic techniques and atomic absorption) have been tested. Parameters such as simplicity, rapidity, sensitivity and interferences are compared in order to choose the most useful method for practical purpose. Finally, flameless atomic absorption was chosen for the determination of total tin concentration in different natural samples. Digestion of biological samples (plant, plankton, fish, etc.) was achieved by using Lumatom (a trade organic chemical). Thus, the digested sample is directly injected into the graphite furnace. This digestion technique is suitable and rapid with a minimum of error (contamination and losses). For tin analysis in water samples, a preconcentration of tin is carried out by coprecipitation with 1, 10-phenanthroline and tetraphenyl boron. The precipitate is separated and dissolved in alcohol or in Lumatom. The sensitivity of this method is 0.1 ng absolute tin. PMID:7451013

  10. Elemental analysis of biological samples by graphite furnace, inductively coupled plasma - atomic emission spectroscopy (GF-ICP-AES)

    SciTech Connect

    Winge, R.K.; Fassel, V.A.; Grabau, F.; Zu-cheng, J.

    1984-08-01

    The large number of analyses required for monitoring environmental pollution and its ecological impacts suggests that an analytical screening method would be very useful if it could rapidly distinguish those samples containing environmentally significant concentrations of pollutants from those that do not. In the trace elemental analysis of solids the most time consuming step is often the conversion of the sample into a suitable analytical form, usually a digestion and dissolution process. We have addressed these problems by combining a graphite furnace with inductively coupled plasma-atomic emission spectroscopy. With this system solid samples of plant and animal tissue, as well as solutions, can be vaporized and introduced directly into the inductively coupled plasma. A simple standard additions technique was developed for solid samples that yielded acceptable results for a number of elements in biological samples. Powers of detection were not satisfactory for the lowest concentrations of several elements in the NBS biological SRMs and analytical uncertainties were relatively high for quantitative analyses but were generally satisfactory for screening methods. The design of the interface between the graphite furnace and the inductively coupled plasma and the pulse effect caused by the vaporization of the sample are critical factors in the GF-ICP-AES method. 31 references, 21 figures, 4 tables.

  11. 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.

  12. 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.

  13. Slurry sampling graphite furnace atomic absorption spectrometry: determination of trace metals in mineral coal.

    PubMed

    Silva, M M; Goreti, M; Vale, R; Caramão, E B

    1999-12-01

    A procedure for lead, cadmium and copper determination in coal samples based on slurry sampling using an atomic absorption spectrometer equipped with a transversely heated graphite tube atomizer is proposed. The slurries were prepared by weighing the samples directly into autosampler cups (5-30 mg) and adding a 1.5 ml aliquot of a diluent mixture of 5% v/v HNO(3), 0.05% Triton X-100 and 10% ethanol. The slurry was homogenized by manual stirring before measurement. Slurry homogenization using ultrasonic agitation was also investigated for comparison. The effect of particle size and the use of different diluent compositions on the slurry preparation were investigated. The temperature programmes were optimized on the basis of pyrolysis and atomization curves. Absorbance characteristics with and without the addition of a palladium-magnesium modifier were compared. The use of 0.05% m/v Pd and 0.03% m/v Mg was found satisfactory for stabilizing Cd and Pb. The calibration was performed with aqueous standards. In addition, a conventional acid digestion procedure was applied to verify the efficiency of the slurry sampling. Better recoveries of the analytes were obtained when the particle size was reduced to <37 mum. Several certified coal reference materials (BCR Nos. 40, 180, and 181) were analyzed, and good agreement was obtained between the results from the proposed slurry sampling method and the certificate values. PMID:18967798

  14. 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.

  15. 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…

  16. 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.

  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. PMID:26592606

  18. [Determination of aluminum in wheat flour food by microwave digestion-high resolution continuum source graphite furnace atomic absorption spectrometry].

    PubMed

    Ren, Ting; Zhao, Li-jiao; Zhong, Ru-gang

    2011-12-01

    The contents of aluminum (Al) in four kinds of wheat flour food (noodle, dumpling wrapper, twisted cruller and soda biscuit) were determined by high resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS) combined with microwave digestion. The samples were completely digested by the mixture of HNO3 and H2O2 in closed polytetrafluoroethylene (PTFE) vessels. The conditions for microwave digestion, pyrolysis temperature and atomization temperature were optimized. The optimum experimental conditions were determined as follows. The microwave digestion was performed with HNO3/H2O2 7:1 (volume ratio), microwave power 1000 W and 190 degrees C for 40 minutes. The optimum pyrolysis temperature was 1350 degrees C and the optimum atomization temperature was 2400 degrees C. Magnesium nitrate solution with the concentration of 1 g x L(-1) was used as the matrix modifier. The correlation coefficient for the standard curve was 0.9999, the relative standard deviation (RSD) was from 1.7% to 2.4%, and the recovery for the samples was from 98.16% to 102.67%. The assay method for the determination of Al in wheat flour food established in this study has referential importance for the constituent of the correlated food standards. PMID:22295801

  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. PMID:25958863

  20. 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

  1. 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. PMID:25384374

  2. Effect of magnesium acetylacetonate on the signal of organic forms of vanadium in graphite furnace atomic absorption spectrometry.

    PubMed

    Kowalewska, Zofia; Welz, Bernhard; Castilho, Ivan N B; Carasek, Eduardo

    2013-01-15

    The aim of this work was to investigate the influence of magnesium acetylacetonate (MgA) on the signal of organic forms of vanadium in xylene solution by graphite furnace atomic absorption spectrometry. MgA alone or mixed with palladium acetylacetonate (PdA) was considered as a chemical modifier. It has been found that MgA does not improve, but decreases significantly the integrated absorbance of V in the form of alkyl-aryl sulfonates, acetylacetonates, porphyrins and in lubricating oils, while its effect is negligible in the case of "dark products" from petroleum distillation, i.e., heavy oil fractions and residues. The decrease is also observed in the presence of Pd. The MgA (or MgA+PdA) effect on the integrated absorbance of V has been studied using the following variants: different ways of modifier application, various pyrolysis temperature, additional application of air ashing, preliminary pretreatment with iodine and methyltrioctylammonium chloride, application of various graphite furnace heating systems (longitudinal or transverse) and various optical and background correction systems (medium-resolution line source spectrometer with deuterium background correction or high-resolution continuum source spectrometer). The experiments indicate formation of more refractory compounds as a possible reason for the decrease of the integrated absorbance for some forms of V in the presence of MgA. The application of MgA as a chemical modifier in V determination is not recommended. Results of this work have general importance as, apart from the intentional use of MgA as a modifier, organic Mg compounds, present in petroleum products for other reason (e.g. as an additive), can influence the signal of V compounds and hence the accuracy in V determination. Generally, petroleum products with known amount of V are recommended as standards; however, lubricating oils can be inadequate for "dark products" from petroleum distillation. In the case of unknown samples it is

  3. Evaluation of four sample treatments for determination of platinum in automotive catalytic converters by graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Puig, Ana I.; Alvarado, José I.

    2006-09-01

    Conventional and microwave assisted digestion, both using aqua regia, alkaline fusion with lithium metaborate and aqueous slurries were evaluated as sample treatments for determination of Pt in automotive catalytic converters by Graphite Furnace Atomic Absorption Spectrometry (GF-AAS). Determination of platinum by GF-AAS in samples of the catalytic converter's substrates, prepared by the four methods described, indicates that the highest platinum concentration i.e. maximum Pt extraction in the range of 748 ± 15-998 ± 10 μg mL - 1 , is obtained for samples dissolved by alkaline fusion, closely followed by analysis of aqueous plus Triton X-100 slurries 708 ± 14-958 ± 10 μg mL - 1 , while neither one of the acid digestion procedures achieved total dissolution of the samples. Slurry analysis is thus shown to be a viable alternative and is recommended, based on its speed and ease of implementation. Aqueous standards calibration curves and the standard addition methods were also compared. The results showed that no appreciable matrix effects are present, regardless of the sample preparation procedure used. Precision of the measurements, expressed as percentage relative standard deviation, ranged between 2.5 to 4.9%. Accuracy of the results was assessed by recovery tests which rendered values between 98.9 and 100.9%.

  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. PMID:26978948

  6. Analysis of lead in 55 brands of dietary calcium supplements by graphite furnace atomic absorption spectrometry after microwave digestion.

    PubMed

    Kim, Meehye; Kim, Changmin; Song, Insang

    2003-02-01

    The lead (Pb) contents of calcium (Ca) supplements available in Korea were determined by graphite furnace atomic absorption spectrometry using Zeeman background correction and peak area mode. All samples were microwave-digested in concentrated HNO(3). Ammonium dihydrogen phosphate and magnesium nitrate were used as matrix modifiers. Fifty-five brands of Ca supplements were classified into seven categories based on the major composite: bone, milk, oyster/clam shell, egg shell, algae, shark cartilage and chelated. The mean Pb contents of Ca supplements were 1.1 microg g(-1) (coefficient of variation 5.7%), ranging from n.d. (not detected) to 6.7 microg g(-1). Ca supplements made of bone have the highest Pb contents (2.3 microg g(-1)) with a wide range (0.1-6.7 microg g(-1)). The results were similar to those reported in other countries. The mean daily intakes of Pb from the supplement could be about 5 microg (mean Pb concentration 1.1 microg g(-1) x mean daily intake 4.5 g) taking 2% of provisional tolerable daily intake that the FAO/WHO Joint Food Additive and Contaminants Committee has set to evaluate its safety. However, measures to prevent potentials of Pb toxicity from overtaking some Ca supplements should be considered. PMID:12623663

  7. NHEXAS PHASE I REGION 5 STUDY--STANDARD OPERATING PROCEDURE FOR THE CALIBRATION OF PERKIN ELMER (PE) MODEL 5100 ZL ATOMIC ABSORPTION SPECTROMETER: GRAPHITE FURNACE (NHX/SOP-171-005)

    EPA Science Inventory

    This procedure describes the calibration procedures and performance checks required to ensure the consistent performance of the Perkin Elmer (PE) Model 5100 zl atomic absorption spectrometer with graphite furnace unit as a whole. Separate calibration procedures were not required ...

  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 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

  11. 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.

  12. 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.

  13. Dispersive liquid-liquid microextraction combined with graphite furnace atomic absorption spectrometry: ultra trace determination of cadmium in water samples.

    PubMed

    Zeini Jahromi, Elham; Bidari, Araz; Assadi, Yaghoub; Milani Hosseini, Mohammad Reza; Jamali, Mohammad Reza

    2007-03-01

    Dispersive liquid-liquid microextraction (DLLME) technique was successfully used as a sample preparation method for graphite furnace atomic absorption spectrometry (GF AAS). In this extraction method, 500 microL methanol (disperser solvent) containing 34 microL carbon tetrachloride (extraction solvent) and 0.00010 g ammonium pyrrolidine dithiocarbamate (chelating agent) was rapidly injected by syringe into the water sample containing cadmium ions (interest analyte). Thereby, a cloudy solution formed. The cloudy state resulted from the formation of fine droplets of carbon tetrachloride, which have been dispersed, in bulk aqueous sample. At this stage, cadmium reacts with ammonium pyrrolidine dithiocarbamate, and therefore, hydrophobic complex forms which is extracted into the fine droplets of carbon tetrachloride. After centrifugation (2 min at 5000 rpm), these droplets were sedimented at the bottom of the conical test tube (25+/-1 microL). Then a 20 microL of sedimented phase containing enriched analyte was determined by GF AAS. Some effective parameters on extraction and complex formation, such as extraction and disperser solvent type and their volume, extraction time, salt effect, pH and concentration of the chelating agent have been optimized. Under the optimum conditions, the enrichment factor 125 was obtained from only 5.00 mL of water sample. The calibration graph was linear in the rage of 2-20 ng L(-1) with detection limit of 0.6 ng L(-1). The relative standard deviation (R.S.D.s) for ten replicate measurements of 20 ng L(-1) of cadmium was 3.5%. The relative recoveries of cadmium in tap, sea and rivers water samples at spiking level of 5 and 10 ng L(-1) are 108, 95, 87 and 98%, respectively. The characteristics of the proposed method have been compared with cloud point extraction (CPE), on-line liquid-liquid extraction, single drop microextraction (SDME), on-line solid phase extraction (SPE) and co-precipitation based on bibliographic data. Therefore, DLLME

  14. 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.

  15. Development of an analytical method for the determination of arsenic in gasoline samples by hydride generation-graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Becker, Emilene M.; Dessuy, Morgana B.; Boschetti, Wiliam; Vale, Maria Goreti R.; Ferreira, Sérgio L. C.; Welz, Bernhard

    2012-05-01

    The purpose of the present work was to optimize the conditions for the determination of arsenic in gasoline with hydride generation-graphite furnace atomic absorption spectrometry after acid digestion using a full two-level factorial design with center point. The arsine was generated in a batch system and collected in a graphite tube coated with 150 μg Ir as a permanent modifier. The sample volume, the pre-reduction conditions, the temperature program and modifier mass were kept fixed for all experiments. The estimated main effects were: reducing agent concentration (negative effect), acid concentration (negative effect) and trapping temperature (positive effect). It was observed that there were interactions between the variables. Moreover, the curvature was significant, indicating that the best conditions were at the center point. The optimized parameters for arsine generation were 2.7 mol L- 1 hydrochloric acid and 1.6% (w/v) sodium tetrahydroborate. The optimized conditions to collect arsine in the graphite furnace were a trapping temperature of 250 °C and a collection time of 30 s. The limit of detection was 6.4 ng L- 1 and the characteristic mass was 24 pg. Two different systems for acid digestion were used: a digester block with cold finger and a microwave oven. The concentration of arsenic found with the proposed method was compared with that obtained using a detergentless microemulsion and direct graphite furnace determination. The results showed that the factorial design is a simple tool that allowed establishing the appropriate conditions for sample preparation and also helped in evaluating the interaction between the factors investigated.

  16. 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.

  17. 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

  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. An improved impaction-graphite furnace system for the direct and near real-time determination of cadmium, chromium, lead and manganese in aerosols and cigarette smoke by simultaneous multielement atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Lee, Yong-Ill; Smith, Mark V.; Indurthy, Suneetha; Deval, Anupama; Sneddon, Joseph

    1996-01-01

    The design, operating characteristics, and preliminary evaluation of an improved impaction-graphite furnace system, based on a theoretical study of particle size collected, are presented. After direct collection, the graphite furnace from the system is inserted in an atomic absorption spectrometer for analysis by simultaneous multielement atomic absorption spectrometry. This system has the potential for the direct and near real-time (few minutes) determination of metals in aerosols. The system has been preliminarily evaluated using aqueous solutions of chromium, and has then been applied to the determination of cadmium, chromium, lead, and manganese in cigarette smoke. Results show an increase ranging from almost five (lead) to sixteen (cadmium) over background levels.

  20. Investigation of spectral interferences in the determination of lead in fertilizers and limestone samples using high-resolution continuum source graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Borges, Aline R.; Becker, Emilene M.; François, Luciane L.; de Jesus, Alexandre; Vale, Maria Goreti R.; Welz, Bernhard; Dessuy, Morgana B.; de Andrade, Jailson B.

    2014-11-01

    In the present work, spectral interferences on the determination of lead in fertilizer and limestone samples were investigated using high-resolution continuum source graphite furnace atomic absorption spectrometry at the main analytical lines: 217.001 and 283.306 nm. For these investigations, samples were introduced into the furnace as slurry together with a mixture of Pd and Mg as chemical modifier. Spectral interferences were observed for some samples at both analytical lines. In order to verify whether a wet digestion procedure would avoid these interferences, a reference method for wet digestion of fertilizers was employed as an alternative sample preparation procedure. However, the same interferences were also observed in the digested samples. In order to identify and eliminate the fine-structured background using a least-squares background correction, reference spectra were generated using the combination of different species. The use of the latter technique allowed the elimination of spectral interferences for most of the investigated samples, making possible the determination of lead in fertilizer and limestone samples free of interferences. The best results were found using a reference spectrum of NH4H2PO4 at 217.001 nm, and a mixture of H2SO4 + Ca and HNO3 + Ca at the 283.306 nm line. The accuracy of the method was evaluated using a certified reference material “Trace Elements in Multi-Nutrient Fertilizer”. Similar results were obtained using line source graphite furnace atomic absorption spectrometry with Zeeman-effect background correction, indicating that the latter technique was also capable to correct the spectral interferences, at least in part.

  1. 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

  2. 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

  3. 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

  4. 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.

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

    PubMed

    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

  6. 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

  7. NHEXAS PHASE I REGION 5 STUDY--STANDARD OPERATING PROCEDURE FOR MAINTENANCE OF PERKIN ELMER (PE) MODEL ZL5100 PC ATOMIC ABSORPTION SPECTROMETER: GRAPHITE FURNACE (NHX/SOP-171-006)

    EPA Science Inventory

    This procedure describes maintenance practices for the Perkin Elmer (PE) Model ZL5100 PC atomic absorption spectrometer with graphite furnace. It was required that the procedure be performed daily by the instrument operator during periods of analysis and recorded in the instrumen...

  8. Graphite filter atomizer in atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Katskov, Dmitri A.

    2007-09-01

    Graphite filter atomizers (GFA) for electrothermal atomic absorption spectrometry (ETAAS) show substantial advantages over commonly employed electrothermal vaporizers and atomizers, tube and platform furnaces, for direct determination of high and medium volatility elements in matrices associated with strong spectral and chemical interferences. Two factors provide lower limits of detection and shorter determination cycles with the GFA: the vaporization area in the GFA is separated from the absorption volume by a porous graphite partition; the sample is distributed over a large surface of a collector in the vaporization area. These factors convert the GFA into an efficient chemical reactor. The research concerning the GFA concept, technique and analytical methodology, carried out mainly in the author's laboratory in Russia and South Africa, is reviewed. Examples of analytical applications of the GFA in AAS for analysis of organic liquids and slurries, bio-samples and food products are given. Future prospects for the GFA are discussed in connection with analyses by fast multi-element AAS.

  9. The determination of total Se in urine and serum by graphite furnace atomic absorption spectrometry using Ir as permanent modifier and in situ oxidation for complete trimethylselenonium recovery.

    PubMed

    Grinberg, Patricia; Gonçalves, Rodrigo Araújo; de Campos, Reinaldo Calixto

    2005-12-01

    The present work evaluated the use of iridium (Ir) as permanent modifier for the determination of total selenium in urine and serum by graphite furnace atomic absorption spectrometry. Concerning urine, the presence of trimethylselenonium (TMSe(+)) was especially considered. Pyrolysis and atomization temperatures of 1,000 and 2,100 degrees C, respectively, were used. For nondigested urine and serum samples, 0.2% v/v HNO(3) and Triton X-100 were used as diluents, respectively, and the same initial platform Ir treatment was effective for up to 1,100 atomization cycles. Good precision [less than 5% relative standard deviation (RSD)] can be achieved with the proposed method. Low TMSe(+) recovery was observed for nondigested urine samples. Thus, if this species is to be considered in urine analysis, a previous external mineralization step was found to be necessary. Alternatively, an in situ oxidation treatment was developed. Detection limits of 8, 10, and 7 mug l(-1) were obtained after dilution, microwave-assisted digestion, and in situ oxidation procedures, respectively. The accuracy of the method was validated by the analysis of certified reference or commercial quality control materials and spiked samples. PMID:16267645

  10. 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. PMID:26838392

  11. 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.

  12. Determination of Cd, Cr, Cu, Pb and Zn in human semen by graphite furnace atomic absorption spectrometry after microwave sample dissolution.

    PubMed

    Alvarado, J; Moreno, R; Cristiano, A R

    1991-09-01

    Human semen samples were analyzed by graphite furnace atomic absorption spectrometry, using L'vov platforms and the method of standard additions, to determine their Cd, Cr, Cu, Pb and Zn content. The samples were analyzed directly and after conventional and microwave wet acid dissolution. Matrix modification, using magnesium and palladium nitrates and ammonium biphosphate solutions, was evaluated for the analysis of the microwave-digested samples. The best results were obtained for Cr, Cu and Zn using Pd(NO3)2, and a mixture of Mg(NO3)2 and Pd(NO3)2 solutions. The direct analysis of water-diluted semen produced inaccurate results with unacceptably high standard deviations. The results obtained for the microwave-dissolved samples showed relative standard deviation values within the range 0.63-8.4%. The analysis of spiked semen solutions showed recoveries of the added analytes ranging from 96 to 104%. The accuracy of the measurements was checked against the NIST 1,577a, bovine liver, standard reference material. Sample dissolution time was drastically reduced from 3-4 hours, using the conventional method, to approximately 8 minutes using the microwave-assisted wet acid digestion procedure. PMID:1821719

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. Ultrasound-Assisted Emulsification Microextraction Based on Solidification Floating Organic Drop Trace Amounts of Manganese Prior to Graphite Furnace Atomic Absorption Spectrometry Determination

    PubMed Central

    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

  19. 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

    2016-03-01

    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. PMID:26717807

  20. 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. PMID:24176741

  1. 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

  2. Lead and cadmium in human placentas and maternal and neonatal blood (in a heavily polluted area) measured by graphite furnace atomic absorption spectrometry.

    PubMed Central

    Baranowska, I

    1995-01-01

    OBJECTIVE--To measure the concentrations of the trace elements lead and cadmium in human placenta and in maternal and neonatal (cord) blood. To assess the influence of the strongly polluted environment on the content of metals in tissues and on the permeability of placenta to cadmium and lead. Various methods of mineralisation were tested before analysis. METHODS--Graphite furnace atomic absorption spectrometry was used for the determination of lead and cadmium. The samples for analysis were prepared by mineralisation under pressure in a Teflon bomb (HNO3, 110 degrees C), by wet ashing under normal pressure (HNO3 + H2O2 for 12 hours), and by microwave digestion in concentrated nitric acid. RESULTS--In analysed samples the following mean concentrations of cadmium and lead were found: in venous blood Pb = 72.50 ng/ml, Cd = 4.90 ng/ml; in placenta Pb = 0.50 microgram/g, Cd = 0.11 microgram/g; in cord blood Pb = 38.31 ng/ml, Cd = 1.13 ng/ml. CONCLUSION--High concentrations of lead and cadmium were found in placentas and in maternal blood whereas in neonatal blood there was an increased concentration of lead and only traces of cadmium. It is concluded that the placenta is a better barrier for cadmium than for lead. Among the examined methods of mineralisation, microwave digestion was the best. PMID:7795737

  3. 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

  4. 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

  5. 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

  6. 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

  7. Solid phase chelating extraction and separation of inorganic antimony species in pharmaceutical and water samples for graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Zih-Perényi, Katalin; Jankovics, Péter; Sugár, Éva; Lásztity, Alexandra

    2008-03-01

    A separation procedure for antimony(III) and antimony(V) was developed with the use of chelating celluloses. Sb(III) was separately pre-concentrated on imino diacetic acid-ethyl cellulose in the acidic pH range, in which the uptake of Sb(V) was negligible in the μg L - 1 concentration range. On the other hand, both Sb species Sb(V) and Sb(III) were pre-concentrated on a chloride form of 2,2'-diaminodiethylamine-cellulose. These solid phase extraction procedures were combined with graphite furnace atomic absorption spectrometry (SPE-GFAAS) for Sb detection. Pharmaceutical compounds of organic and inorganic types (ten compounds), as well as mineral water samples (twelve types) were analyzed. Detection limits of 0.18 µg L - 1 Sb(III) and 0.25 µg L - 1 Sb(V) were found in aqueous sample solutions and water samples, respectively, considering a 25-fold pre-concentration. The total Sb, mostly in the form of Sb(V), could be determined in phosphate-containing pharmaceuticals, while in phosphoric acid, Sb(III) was the dominant form. In all other types of samples the Sb content was below the detection threshold, and therefore, the potential suitability of the SPE-GFAAS method for the determination of Sb(III) species was proven by recovery tests of spiked samples. This method ensures the required detection power with regard to the allowable Sb limits established by international organizations.

  8. Ultrasound-assisted ion-pair dispersive liquid-liquid microextraction of trace amounts of lead in water samples prior to graphite furnace atomic absorption spectrometry determination.

    PubMed

    Afzali, Daryoush; Mohadesi, Ali Reza; Falahnejad, Masoumeh; Bahadori, Behnoosh

    2013-01-01

    A new ion-pair dispersive liquid-liquid microextraction method is described for separation and preconcentration of trace amounts of lead in different water samples. Graphite furnace atomic absorption spectrometry was used for determination of lead. The ion association complex between lead and iodide ions that forms is PbI4(-2)-tetradecyl-dimethylbenzylammonium, which is extracted into fine droplets of chlorobenzene. In order to reach the optimized experimental conditions, the influence of different parameters, such as concentration of KI, nature and volume of extraction solvents, pH effect, extraction time, and the period and speed of sonication and centrifugation, were optimized. The LOD was 0.08 ng/mL and the linear dynamic range was 0.20-8.0 ng/mL in initial solution with a correlation coefficient of 0.9985. Under the optimum conditions, the enrichment factor was 555.5. The proposed method was successfully applied for separation and determination of lead in sea, rain, river, and drinking water samples. PMID:23513972

  9. 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

  10. Investigation of chemical modifiers for the determination of lead in fertilizers and limestone using graphite furnace atomic absorption spectrometry with Zeeman-effect background correction and slurry sampling

    NASA Astrophysics Data System (ADS)

    Borges, Aline R.; Becker, Emilene M.; Dessuy, Morgana B.; Vale, Maria Goreti R.; Welz, Bernhard

    2014-02-01

    In this work, chemical modifiers in solution (Pd/Mg, NH4H2PO4 and NH4NO3/Pd) were compared with permanent modifiers (Ir and Ru) for the determination of lead in fertilizer and limestone samples using slurry sampling and graphite furnace atomic absorption spectrometry with Zeeman-effect background correction. The analytical line at 283.3 nm was used due to some spectral interference observed at 217.0 nm. The NH4H2PO4 was abandoned due to severe spectral interference even at the 283.3-nm line. For Pd/Mg and NH4NO3/Pd the optimum pyrolysis and atomization temperatures were 900 °C and 1900 °C, respectively. For Ru and Ir, the integrated absorbance signal was stable up to pyrolysis temperatures of 700 °C and 900 °C, respectively, and up to atomization temperature of 1700 °C. The limit of detection (LOD) was 17 ng g- 1 using Pd/Mg and 29 ng g- 1 using NH4NO3/Pd. Among the permanent modifiers investigated, the LOD was 22 ng g- 1 Pb for Ir and 10 ng g- 1 Pb for Ru. The accuracy of the method was evaluated using the certified reference material NIST SRM 695. Although Ru provided lower LOD, which can be attributed to a lower blank signal, only the modifiers in solution showed concordant values of Pb concentration for the NIST SRM 695 and the most of analyzed samples. Moreover, the Pd/Mg modifier provided the highest sensitivity and for this reason it is more suitable for the determination of Pb in fertilizers samples in slurry; besides this it presented a better signal-to-noise ratio than NH4NO3/Pd.

  11. 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. PMID:25618661

  12. 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.

  13. 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.

  14. Direct sample introduction of wines in graphite furnace atomic absorption spectrometry for the simultaneous determination of arsenic, cadmium, copper and lead content.

    PubMed

    Ajtony, Zsolt; Szoboszlai, Norbert; Suskó, Emoke Klaudia; Mezei, Pál; György, Krisztina; Bencs, László

    2008-07-30

    A multi-element graphite furnace atomic absorption spectrometry (GFAAS) method was elaborated for the simultaneous determination of As, Cd, Cu, and Pb in wine samples of various sugar contents using the transversally heated graphite atomizer (THGA) with end-capped tubes and integrated graphite platforms (IGPs). For comparative GFAAS analyses, direct injection (i.e., dispensing the sample onto the IGP) and digestion-based (i.e., adding oxidizing agents, such as HNO(3) and/or H(2)O(2) to the sample solutions) methods were optimized with the application of chemical modifiers. The mixture of 5 microg Pd (applied as nitrate) plus 3 microg Mg(NO(3))(2) chemical modifier was proven to be optimal for the present set of analytes and matrix, it allowing the optimal 600 degrees C pyrolysis and 2200 degrees C atomization temperatures, respectively. The IGP of the THGA was pre-heated at 70 degrees C to prevent the sputtering and/or foaming of sample solutions with a high organic content, dispensed together with the modifier solution, which method also improved the reproducibility of the determinations. With the digestion-based method, the recovery ranged between 87 and 122%, while with the direct injection method it was between 96 and 102% for Cd, Cu, and Pb, whereas a lower, compromise recovery of 45-85% was realized for As. The detection limits (LODs) were found to be 5.0, 0.03, 1.2, and 0.8 microg l(-1) for As, Cd, Cu, and Pb, respectively. The characteristic mass (m(0)) data were 24 pg As, 1.3 pg Cd, 13 pg Cu, and 35 pg Pb. The upper limits of the linear calibration range were 100, 2, 100, and 200 microg l(-1) for As, Cd, Cu, and Pb, respectively. The precisions were not worse than 4.8, 3.1, 3.7, and 2.3% for As, Cd, Cu, and Pb, respectively. For arsenic, a higher amount of the modifier (e.g., 20 microg Pd plus 12 microg Mg(NO(3))(2)) could be recommended to overcome the interference from the presence of sulphate and phosphate in wines. Although this method increased the

  15. 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

  16. 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.

  17. 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.

  18. 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

  19. 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. PMID:24148416

  20. Noble metals as permanent chemical modifiers for the determination of mercury in environmental reference materials using solid sampling graphite furnace atomic absorption spectrometry and calibration against aqueous standards

    NASA Astrophysics Data System (ADS)

    da Silva, Alessandra Furtado; Welz, Bernhard; Curtius, Adilson J.

    2002-12-01

    Iridium, palladium, rhodium and ruthenium, thermally deposited on the platform, were investigated as permanent modifiers for the determination of mercury in ash, sludge, marine and river sediment reference materials, ground to a particle size of 50 μm, using solid sampling graphite furnace atomic absorption spectrometry. A total mass of 250 μg of each modifier was applied using 25 injections of 20 μl of modifier solution (500 mg l -1), and executing a temperature program for modifier conditioning after each injection. The performance of palladium was found to be most consistent, taking the characteristic mass as the major criterion, resulting in an excellent correlation between the measured integrated absorbance values and the certified mercury contents. Mercury was found to be lost in part from aqueous solutions during the drying stage in the presence of all the investigated permanent modifiers, as well as in the presence of the palladium and magnesium nitrates modifier added in solution. A loss-free determination of mercury in aqueous solutions could be reached only after the addition of potassium permanganate, which finally made possible the use of aqueous standards for the direct analysis of solid samples. A characteristic mass of 55-60 pg Hg was obtained for the solid samples, using Pd as a permanent modifier, and also in aqueous solutions after the addition of permanganate. The results obtained for mercury in ash, sludge and sediment reference materials, using direct solid sapling and calibration against aqueous standards, as well as the detection limit of 0.2 mg kg -1 were satisfactory for a routine procedure.

  1. 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.

  2. 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.

  3. Extension of working range in Zeeman graphite furnace atomic absorption spectrometry by nonlinear calibration with prior correction for stray light

    NASA Astrophysics Data System (ADS)

    Lonardo, Robert F.; Yuzefovsky, Alexander I.; Zhou, Jack X.; McCaffrey, John T.; Michel, Robert G.

    1996-09-01

    The nonlinear working range of a Perkin-Elmer 4100Zl atomic absorption spectrometer was improved in three steps. Firstly, each absorbance datum within the transient profile was corrected for the presence of stray light by an algorithm originally developed by L'vov and co-workers (Spectrochim. Acta Part B, 47 (1992) 889-895 and 1187-1202), but with the incorporation of the Newton method of successive approximations (Spectrochim. Acta Part B, 49 (1994) 1643-1656. Secondly, a dip correction procedure was performed on temporal signal profiles that exhibited a dip due to rollover. In the final step, an analytically useful working curve was generated by the nonlinear calibration routine of Barnett (Spectrochim. Acta Part B, 39 (1984) 829). Goodness of fit between the resultant calibration curve and the data was measured by the method suggested by Miller-Ihli et al. (Spectrochim. Acta Part B, 39 (1984) 1603) that is based on the sum of squares of the percentage deviation (SSPD) and the root mean square (RMS) percentage deviation. For lead, silver, copper, thallium, and cadmium, the analytical nonlinear working range was increased by as much as one and a half orders of magnitude, without any significant effect on the RMS. For chromium and manganese, no significant improvement in the nonlinear working range was observed, while the RMS improved by 50%. In the case of nickel, neither the working range nor the RMS was improved.

  4. 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

  5. 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

  6. Hollow fiber liquid phase microextraction combined with graphite furnace atomic absorption spectrometry for the determination of methylmercury in human hair and sludge samples

    NASA Astrophysics Data System (ADS)

    Jiang, Hongmei; Hu, Bin; Chen, Beibei; Zu, Wanqing

    2008-07-01

    Two methods, based on hollow fiber liquid-liquid-liquid (three phase) microextraction (HF-LLLME) and hollow fiber liquid phase (two phase) microextraction (HF-LPME), have been developed and critically compared for the determination of methylmercury content in human hair and sludge by graphite furnace atomic absorption spectrometry (GFAAS). In HF-LPME, methylmercury was extracted into the organic phase (toluene) prior to its determination by GFAAS, while inorganic mercury remained as a free species in the sample solution. In HF-LLLME, methylmercury was first extracted into the organic phase (toluene) and then into the acceptor phase (4% thiourea in 1 mol L - 1 HCl) prior to its determination by GFAAS, while inorganic mercury remained in the sample solution. The total mercury was determined by inductively coupled plasma-mass spectrometry (ICP-MS), and the levels of inorganic mercury in both HF-LLLME and HF-LPME were obtained by subtracting methylmercury from total mercury. The factors affecting the microextraction of methylmercury, including organic solvent, extraction time, stirring rate and ionic strength, were investigated and the optimal extraction conditions were established for both HF-LLLPME and HF-LPME. With a consumption of 3.0 mL of the sample solution, the enrichment factors were 204 and 55 for HF-LLLPME and HF-LPME, respectively. The limits of detection (LODs) for methylmercury were 0.1 μg L - 1 and 0.4 μg L - 1 (as Hg) with precisions (RSDs (%), c = 5 μg L - 1 (as Hg), n = 5) of 13% and 11% for HF-LLLPME-GFAAS and HF-LPME-GFAAS, respectively. For ICP-MS determination of total mercury, a limit of detection of 39 ng L - 1 was obtained. Finally, HF-LLLME-GFAAS was applied to the determination of methylmercury content in human hair and sludge, and the recoveries for the spiked samples were in the range of 99-113%. In order to validate the method, HF-LLLME-GFAAS was also applied to the analysis of a certified reference material of NRCC DORM-2 dogfish

  7. Determination of thallium in cadmium and lead by graphite-furnace atomic-absorption spectrometry with sample vaporization from a platform.

    PubMed

    Fazakas, J; Marinescu, D M

    1983-11-01

    When the sample is vaporized from the wall of a graphite furnace it is not possible to determine thallium in cadmium and lead by AAS without matrix matching of the standards. In the case of a lead matrix and vaporization from the wall, the thallium signal is barely distinguishable from the base-line. When the sample is vaporized from a platform, and the peak area is used for measurement, pure aqueous standards may be used for instrument calibration. The peak heights and areas of the thallium signals are considerably enhanced by vaporization from a platform (peak height 1.7-fold and peak area 2.6-fold in pure aqueous solutions as compared to vaporization from the wall). The enhancement factors are larger in presence of the cadmium or lead matrix since here the reduced interference also makes a contribution. PMID:18963481

  8. 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.

  9. Low-temperature transformations of sodium sulfate and sodium selenite in the presence of pre-reduced palladium modifier in graphite furnaces for electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Volynsky, Anatoly B.; Stakheev, Alexandr Yu.; Telegina, Natalia S.; Senin, Valery G.; Kustov, Leonid M.; Wennrich, Rainer

    2001-08-01

    The low-temperature interaction (up to 550°C) of a pre-reduced palladium modifier with sodium sulfate and sodium selenite on the pyrolytic graphite platform was studied using X-ray photoelectron spectroscopy (XPS) and electron microprobe analysis. The equipment applied allowed the introduction of samples heated in an argon flow into the analytical chamber of the XPS spectrometer without contact with the air. Electron microprobe analysis showed that palladium and sulfur preferably occupy different areas on the platform surface. On the contrary, selenium from sodium selenite tends to occupy areas of the graphite surface covered with palladium. The most probable reason for this is the chemisorption of selenium (IV) on the palladium surface at the drying stage. No changes in the XPS spectra of metallic Pd and S 6+ were observed when Na 2SO 4 and Pd were heated together on the graphite platform in the range 100-550°C. The reduction of sodium selenite on the graphite surface already starts during drying. Pre-reduced palladium intensifies this process. The rate of the reduction is proportional to the amount of palladium, and in the presence of palladium at an atomic ratio of Pd/Se=7.5, the transformation of Se 4+ into Se 0 completes at 250°C.

  10. 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.

  11. Study on solid phase extraction and graphite furnace atomic absorption spectrometry for the determination of nickel, silver, cobalt, copper, cadmium and lead with MCI GEL CHP 20Y as sorbent.

    PubMed

    Yang, Guangyu; Fen, Weibo; Lei, Chun; Xiao, Weilie; Sun, Handong

    2009-02-15

    A solid phase extraction and graphite furnace atomic absorption spectrometry (GFAAS) for the determination of nickel, silver, cobalt, copper, cadmium and lead with MCI GEL CHP 20Y as sorbent was studied. Trace amounts of chromium, nickel, silver, cobalt, copper, cadmium and lead were reacted with 2-(2-quinolinil-azo)-4-methyl-1,3-dihydroxidobenzene (QAMDHB) followed by adsorption onto MCI GEL CHP 20Y solid phase extraction column, and 1.0molL(-1) HNO(3) was used as eluent. The metal ions in 300mL solution can be concentrated to 1.0mL, representing an enrichment factor of 300 was achieved. The recoveries of analytes at pH 8.0 with 1.0g of resin were greater than 95% without interference from alkaline, earth alkaline and some metal ions. When detected with graphite furnace atomic absorption spectrometry, the detection limits in the original samples were 1.4ngL(-1) for Cr(III), 1.0ngL(-1) for Ni(II), 0.85ngL(-1) for Ag(I), 1.2ngL(-1) for Co(II), 1.0ngL(-1) for Cu(II), 1.2ngL(-1) for Cd(II) and 1.3ngL(-1) for Pb(II). The validation of the procedure was performed by the analysis of the certified standard reference materials, and the presented procedure was applied to the determination of analytes in biological, water and soil samples with good results (recoveries range from 89 to 104%, and R.S.D.% lower than 3.2%. The results agreed with the standard value or reference method). PMID:18562094

  12. A micromethod for the determination of blood lead with matrix modification by graphite furnace atomic absorption utilizing a L`VOV platform

    SciTech Connect

    Sheier, D.R.

    1994-12-31

    The effect of low concentrations of lead on pre- and post-natal growth and development is a growing concern. Several hundred thousand children, most of them living in older houses, are at risk of ingesting lead-based paint as well as lead bearing soil and house dust contaminated by the deterioration of lead-based paint. The authors have developed a micromethod utilizing 40 microliters of whole blood for the determination of lead in whole blood. Platform furnace technology coupled with the use of a matrix modifier has enabled the determination of lead in whole blood using aqueous standards for creating the calibration curve. The matrix modifier is prepared with 0.2% Triton X-100, 0.5% Ammonium Phosphate Dibasic, and 0.2% Nitric Acid. The standards are prepared in 1% Nitric Acid and diluted 1:10 with matrix modifier. The aqueous standards are compared to the NIST Standard Reference Material 955a and the values are adjusted accordingly. The controls and patient samples are prepared by diluting 40 microliters of whole blood with 360 microliters of matrix modifier. The sample is dried in two steps (120{degrees} and 250{degrees} C), charred at 615{degrees} C, and atomized at 1700{degrees} C. The 283.3 nm lead line is used because the background absorbance is lower and the calibration curve more linear. Blood controls are obtained from BioRad and show the following CV`s: Level 1 (7.8 ug/dl) 12.4; Level 2 (23.1 ug/dl) 5.3; and Level 3 (54.6 ug/dl) 4.2. The sensitivity of the method is 1 ug/dl. The recovery of whole blood spiked with 10 ug/dl of lead standard is 101%. The quality control data and recovery studies indicate that this method is very good for the determination of lead in whole blood.

  13. 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

  14. Solid sampling-graphite furnace atomic absorption spectrometry for the direct determination of trace amounts of silicon in polyamide. Comparison of the performance of platinum and palladium as chemical modifiers

    NASA Astrophysics Data System (ADS)

    Resano, M.; Aramendía, M.; Volynsky, A. B.; Belarra, M. A.

    2004-04-01

    In this paper, the use of solid sampling-graphite furnace atomic absorption spectrometry for the direct determination of silicon in a polyamide sample at the 10 μg g -1 level has been investigated. The performance of Pt and Pd as chemical modifiers for the reproducible atomization of this element has been compared, both for aqueous solutions and for solid samples. According to the results obtained, it can be concluded that Pt is an interesting alternative to Pd, since it is capable of providing a similar performance with the use of lower modifier amounts (1 μg of Pt vs. 20 μg of Pd for direct analysis of the sample). The method proposed shows important benefits for the determination of such a complicated element: the use of aqueous standards for calibration, low sample consumption (a few milligrams), high sample throughput (20 min per sample), low limit of detection (0.1 μg g -1) and reduced risk of analyte losses and, especially, of contamination, while precision is fit for the purpose (approx. 6% R.S.D.).

  15. 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. PMID:24274293

  16. 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

  17. 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. PMID:26992542

  18. 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

  19. Study on the effects of nitrilotriproprionic acid and 4,5-dihydroxy-1,3-benzene disulphonate on the fractionation of beryllium in human serum using graphite furnace atomic absorption spectrometry

    PubMed Central

    Stephan, Chadi H; Fournier, Michel; Brousseau, Pauline; Sauvé, Sébastien

    2008-01-01

    Background Occupational exposure to beryllium may cause Chronic Beryllium Disease (CBD), a lung disorder initiated by an electrostatic interaction with the MHC class II human leukocyte antigen (HLA). Molecular studies have found a significant correlation between the electrostatic potential at the HLA-DP surface and disease susceptibility. CBD can therefore be treated by chelation therapy. In this work, we studied the effect of two complexing agents, nitrilotriproprionic acid (NTP) and 4,5-dihydroxy-1,3-benzene disulphonate (Tiron), on the fractionation of beryllium in human serum analysed by graphite furnace atomic absorption spectrometry (GFAAS). Results We found the average serum beryllium concentration of fourteen non-exposed individuals to be 0.53 (± 0.14) μg l-1, with 21 (± 3)% of the beryllium mass bound to the low molecular weight fraction (LMW), and 79 (± 3)% bound to the high molecular weight fraction (HMW). The addition of Tiron increased the beryllium mass in the HMW fraction, while NTP was not seen to have any influence on the fractionation of beryllium between the two fractions. NTP was, however, shown to complex 94.5% of the Be mass in the LMW fraction. The beryllium GFAAS detection limit, calculated as three times the standard deviation of 10 replicates of the lowest standard (0.05 μg L-1), was 6.0 (± 0.2) ng L-1. Conclusion The concentration of beryllium or its fractionation in human serum was not affected by sex or smoking habit. On average, three quarters of the beryllium in serum were found in the HMW fraction. Of the two ligands tested, only Tiron was effective in mobilising beryllium under physiological conditions, thus increasing the Be content in the HMW fraction. PMID:18479524

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. Preatomization separation of chromium(III) from chromium(VI) in the graphite furnace

    SciTech Connect

    Arpadjan, S.; Krivan, V.

    1986-11-01

    By means of /sup 51/Cr as a radiotracer, the behavior of Cr(III) and Cr(VI) in a graphite furnace was investigated. After the addition of a mixture of trifluoroacetylacetone, tetramethylammonium hydroxide, and 0.5 M sodium acetate (1:2:2) to a water or urine sample, Cr(III) can quantitatively be removed from a graphite tube combined with an L'vov platform or from a tungsten-impregnated graphite tube without an L'vov platform at 400/sup 0/C while Cr(VI) quantitatively remains in the furnace up to a temperature of 1200/sup 0/C.

  8. Ion bombardment glow-discharge furnaces for atomic emission spectroscopy

    SciTech Connect

    Tanguay, S.L.

    1990-01-01

    Two glow discharge plasma devices for the atomic emission analysis of aqueous samples were investigated. The devices use thermal vaporization of samples from a graphite cathode coupled with glow-discharge excitation. Furnace heating of the cathode is accomplished by the positive ion bombardment of the cathode during plasma operation. The dc plasma operates in Ar at 0.5-5.0 torr, with currents up to 250 mA. A cw, axial magnetic field of up to 1.25 kG is applied to the cylindrical-post cathode system to reduce electron losses, thereby increasing plasma excitation and ionization efficiency. At higher currents, the cathodes heat to temperatures as high as 2,500{degree}C in the case of the cylindrical-post cathode. Hollow-cathode heating temperatures are lower under comparable conditions, due to the larger cathode surface area, greater cathode mass, and lower power dissipation. The peak furnace temperature using this configuration is approximately 2100{degree}C. The role of the emission of thermionic electrons from the hot cathodes in limiting the cathode heating and in regulating the cathode temperature are considered. Sample residues of up to 50 ng of the analyte are vaporized from the cylindrical-post cathode within a few seconds of the initiation of the discharge, resulting in a transient emission intensity profile. With the hollow-cathode furnace, vaporization may take several seconds. Although a lower rate of cathode heating and a lower sample vapor residence time results in limits of detection which are one to two orders of magnitude lower than those achieved using the cylindrical-post cathode system. For the hollow cathode, limits of detection are on the order of 10 pg to 1 ng.

  9. 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.

  10. COMPUTER-ASSISTED FURNACE ATOMIC ABSORPTION SPECTROMETRIC ANALYSIS

    EPA Science Inventory

    The use of furnace atomic absorption instrumentation with a turnkey chromatography data system is described. A simple addition of relays to the furnace power supply allows for automatic start-up of A/D conversion and spectrophotometer zeroing at the proper time. Manipulations inv...

  11. Determination of mercury by furnace atomic nonthermal excitation spectrometry

    NASA Astrophysics Data System (ADS)

    Dittrich, K.; Franz, T.; Wennrich, R.

    1994-12-01

    The determination of Hg using different variants of the Furnace Atomic Nonthermal Excitation Spectrometry (FANES) is described. In the direct analysis of micro volumes of solutions, the results could be improved by working with chemical modifiers for the stabilization of Hg during the thermal pretreatment. The best results were obtained using Ir and Pd as modifiers, with absolute detection limits of 4 and 12 pg, respectively. The determination of mercury in sample volumes up to 10 ml could be achieved by coupling a cold vapour generation system and an amalgam attachment to the FANES source. A detection limit of 22 ng/l was obtained with this technique. The best results were obtained by using the cold vapour generation technique and in situ enrichment of Hg onto the modified inner surface of the graphite tube of the FANES source. Using Ir for permanent impregnation of the tube a detection limit of 0.0009 μ;g/l was found. The influence of hydride forming elements on the determination of mercury by the technique of vapour generation and in situ enrichment was studied. A reduction of the concentration of NaBH 4 to 0.002% m/v made it possible to determine traces of mercury in presence of a high excess of hydride forming elements without any depression of the Hg emission intensity. The results were validated using standard reference materials.

  12. 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.

  13. Effect of beryllium nitrate vaporization on surface temperature in the pyrocoated graphite furnace

    NASA Astrophysics Data System (ADS)

    Katskov, D. A.; Mofolo, R.; Tittarelli, P.

    1999-12-01

    The vaporization of 20-50 μg beryllium from nitrate solution was observed in graphite furnace atomizers using pyrocoated and Ta-lined tubes. A charge coupled device (CCD) spectrometer was employed to follow the evolution of absorption spectra (200-475 nm), the light scattering and emission. Molecular bands of NO and NO 2 were observed below 1000°C. Beryllium absorption at 234.9 nm was prominent in spectra above 2200°C and 1900°C, respectively, in Ta-lined and pyrocoated tubes. The evolution profile of Be atomic absorption and of some bands indicated a faster vapor release in the pyrocoated tube. Light scattering occurred only in the pyrocoated tube, increasing with the tube age. When purge gas mini flow was applied, the scattering was observed at 1900-2200°C simultaneously with Be atomic absorption and emission continuum at long wavelength. The emission continuum showed the wavelength distribution characteristic of black body radiation. The temperature increase, due to the vaporization of the sample, was estimated using Planck's equation. The maximum temperature increase reached 400°C, when the most intense Be atomic absorption, light scattering and emission was observed. According to the hypothesis proposed, the black body radiation was induced by the formation of Be carbide in the pyrographite layer. Low heat capacity across the pyrographite prevented the heat dissipation, and led to increase of surface temperature. This induced an increase of sample evaporation rate and the formation of a thermal gradient in the cross section of the tube. Both factors originated vapor supersaturation in the tube center, spatial condensation and, accordingly, light scattering. The results, together with those already obtained with Mg nitrate place limitations to the atomization theories based on the concept of isothermal equilibrium or on Arrhenius kinetic approach.

  14. Treatment of simulated INEL buried wastes using a graphite electrode DC arc furnace

    SciTech Connect

    Surma, J.E.; Lawrence, W.E.; Titus, C.H.; Wittle, J.K.; Hamilton, R.A.; Cohn, D.R.; Rhea, D.; Thomas, P.; Woskov, P.P.

    1994-08-01

    A program has been established under the auspices of the Department of Energy (DOE), Office of Technology Development (OTD), to develop the graphite electrode DC arc technology for the application of treating buried heterogenous solid wastes. A three way {open_quotes}National Laboratory-University-Industry{close_quotes} partnership was formed to develop this technology in the most timely and cost effective manner. This program is presently testing a newly fabricated pilot-scale DC arc furnace with associated diagnostics at the Plasma Fusion Center at the Massachusetts Institute of Technology. Initial testing in a smaller engineering scale furnace has established the viability of this technology for the treatment of solid heterogeneous wastes. Two diagnostic tools were developed under this program which support the evaluation of the DC arc technology. The diagnostics provide for both spatially resolved temperature measurements within the furnace and real time monitoring of the furnace metal emissions.

  15. COMPARISON BETWEEN ZEEMAN AND CONTINUUM BACKGROUND CORRECTION FOR GRAPHITE FURNACE AAS ON ENVIRONMENTAL SAMPLES

    EPA Science Inventory

    A comparison study was carried out to evaluate the two most commonly used background correction techniques in furnace atomic absorption spectroscopy, the Zeeman effect and continuum source background correction. Synthetic sample matrices were prepared consisting of the most frequ...

  16. 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.

  17. NHEXAS PHASE I ARIZONA STUDY--STANDARD OPERATING PROCEDURE FOR EXTRACTION OF METALS FROM SOIL, DUST, AIR FILTER, AND SURFACE AND DERMAL SAMPLES FOR AA (GRAPHITE FURNACE OR FLAME) OR ICP-AES ANALYSIS (BCO-L-3.1)

    EPA Science Inventory

    The purpose of this SOP is to describe the acid digestion of soil, house dust, air filter, and surface or dermal wipe samples for analysis using inductively coupled plasma atomic emissions spectrometry (ICP-AES) and/or graphite furnace atomic absorption spectrometry (GFAAS) or fl...

  18. 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.

  19. DETERMINATION OF LEAD AND CADMIUM IN FISH AND CLAM TISSUE BY ATOMIC ABSORPTION SPECTROMETRY WITH A MOLYBDENUM AND LANTHANUM TREATED PYROLYTIC GRAPHITE ATOMIZER

    EPA Science Inventory

    A molybdenum and lanthanum treated pyrolytically coated graphite tube is employed for the furnace atomic absorption spectrometric determination of lead and cadmium directly in nitric-perchloric acid tissue digests. Lanthanum tends to promote the formation of a smooth lead atomiza...

  20. 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.

  1. Fe-Si droplets associated with graphite on blast furnace coke

    NASA Astrophysics Data System (ADS)

    Gornostayev, Stanislav S.; Fabritius, Timo M. J.; Kerkkonen, Olavi; Härkki, Jouko J.

    2012-06-01

    Fe-Si droplets on the surface of blast furnace (BF) coke from 25 to 50 cm at the tuyere level are mostly composed of Fe3Si, which has various shapes (round, elongated, and irregular) and penetration degrees into the BF coke matrix. The shapes and penetration degrees may depend on the saturation of molten iron by silicon during interaction with the coke matrix. The droplets are covered by a tiny shell of carbon. Graphite observed inside the droplets can be divided into two categories: well-formed tabular crystals with relatively large size and flakes with structures similar as those in cast iron. The textures of the droplets reflect composition, interaction with the coke matrix, and cooling conditions.

  2. 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.

  3. 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.

  4. From the Cover: Revealing the hidden atom in graphite by low-temperature atomic force microscopy

    NASA Astrophysics Data System (ADS)

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

    2003-10-01

    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.

  5. 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. PMID:14504395

  6. U.S.-MEXICO BORDER PROGRAM ARIZONA BORDER STUDY--STANDARD OPERATING PROCEDURE FOR EXTRACTION OF METALS FROM SOIL, DUST, AIR FILTER, AND SURFACE AND DERMAL WIPE SAMPLES FOR AA (GRAPHITE FURNACE OR FLAME) OR ICP-AES ANALYSIS (BCO-L-3.1)

    EPA Science Inventory

    The purpose of this SOP is to describe the acid digestion of soil, house dust, air filter, and surface or dermal wipe samples for analysis using inductively coupled plasma atomic emissions spectrometry (ICP-AES) and/or graphite furnace atomic absorption spectrometry (GFAAS) or fl...

  7. 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.

  8. Conducting atomic force microscopy of alkane layers on graphite

    SciTech Connect

    Klein, D.L.; McEuen, P.L.

    1995-05-08

    We have used an atomic force microscope with a conducting tip to investigate the layering of hexadecane on graphite. Discrete jumps were observed in both the tip--sample conductance and separation as individual liquid layers are penetrated. These conductance measurements extend solvation studies to higher force scales than have been previously achieved, and can be used to determine when the tip makes contact with the substrate. The layering also enables the formation of stable tunneling junctions.

  9. Tributyl phosphate as a sensitivity-enhancing solvent for organotin in carbon furnace atomic absorption spectrometry.

    PubMed

    Li, H; Gong, B; Matsumoto, K

    1996-07-01

    Tributyl phosphate (TBP) has been found to be a sensitivity-enhancing solvent for organotin compounds in graphite furnace atomic absorption spectrometry; (C(4)H(9))(2)Sn(O(2)CCH(3))(2), (C(4)H(9))(2)Sn(O(2)CC(11)H(23))(2), (C(4)H(9))(3)SnCl, and (C(4)H(9))(4)Sn all give 1 order of magnitude higher sensitivities in TBP than in toluene or ethyl acetate. The sensitivities are enhanced further 1-2 orders of magnitude in TBP, when PdCl(2)(CH(3)CN)(2) is added as a matrix modifier in the organic solvent. Among the four organotin compounds, (C(4)H(9))(2)Sn(O(2)CCH(3))(2) and (C(4)H(9))(2)Sn(O(2)CC(11)H(23))(2) give better sensitivities than (C(4)H(9))(3)SnCl and (C(4)H(9))(4)Sn in the absence of palladium in any organic solvent, which suggests that the oxygen atom in the tin compound might form tin oxides that are resistant to volatilization loss during ashing. Scanning electron microscopic, electrothermal vaporization ICPMS, and powder X-ray diffraction studies show that the final products before atomization include phosphorus-containing compounds Sn(2)P(2)O(7), SnP(2)O(7), and Pd(9)P(2), besides tin-palladium alloys, PdSn, Pd(3)Sn, Pd(2)Sn, Pd(3)Sn(2), and PdSn(3). These phosphorus-containing compounds would more efficiently stabilize tin and suppress tin vaporization loss during ashing, to give higher sensitivity. PMID:21619315

  10. 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.

  11. Catalytically active single-atom niobium in graphitic layers.

    PubMed

    Zhang, Xuefeng; Guo, Junjie; Guan, Pengfei; Liu, Chunjing; Huang, Hao; Xue, Fanghong; Dong, Xinglong; Pennycook, Stephen J; Chisholm, Matthew F

    2013-01-01

    Carbides of groups IV through VI (Ti, V and Cr groups) have long been proposed as substitutes for noble metal-based electrocatalysts in polymer electrolyte fuel cells. However, their catalytic activity has been extremely limited because of the low density and stability of catalytically active sites. Here we report the excellent performance of a niobium-carbon structure for catalysing the cathodic oxygen reduction reaction. A large number of single niobium atoms and ultra small clusters trapped in graphitic layers are directly identified using state-of-the-art aberration-corrected scanning transmission electron microscopy. This structure not only enhances the overall conductivity for accelerating the exchange of ions and electrons, but it suppresses the chemical/thermal coarsening of the active particles. Experimental results coupled with theory calculations reveal that the single niobium atoms incorporated within the graphitic layers produce a redistribution of d-band electrons and become surprisingly active for O2 adsorption and dissociation, and also exhibit high stability. PMID:23715283

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. A metallic furnace atomizer in hydride generation atomic absorption spectrometry: Determination of bismuth and selenium

    NASA Astrophysics Data System (ADS)

    Klassen, Aline; Kim, Manuela Leticia; Tudino, Mabel Beatriz; Baccan, Nivaldo; Arruda, Marco Aurélio Zezzi

    2008-08-01

    A flow injection hydride generation system with a metal furnace atomizer (Inconel 600® alloy) was employed for Bi and Se determination. The presented methods have linear ranges up to 200 and 500 μg L - 1 for Bi and Se, respectively, with good linearities ( r2 = 0.9997 and 0.9974, respectively). The limits of quantification obtained according to IUPAC recommendations were 2.3 μg L - 1 for Bi and 6 μg L - 1 for Se, and the relative standard deviations ( N = 6) based on Bi and Se analytical responses from real samples were 2.7% and 10%, respectively. Accuracy evaluations were based on certified materials such as SRM 361, SRM 363, and SRM 364 (steel alloys) for Bi, Mess-3 (marine sediment), SRM 397 (human hair), and Bio-Rad2 — 69042 (urine) for Se. Good agreements between the results were obtained at the 95% confidence level, according to the t-test.

  17. Optimization of fluorine determination via the molecular absorption of gallium mono-fluoride in a graphite furnace using a high-resolution continuum source spectrometer

    NASA Astrophysics Data System (ADS)

    Gleisner, Heike; Welz, Bernhard; Einax, Jürgen W.

    2010-09-01

    The determination of fluorine using the molecular absorption of gallium mono-fluoride (GaF) at the 211.248 nm rotational line has been optimized using a commercially available high-resolution continuum source atomic absorption spectrometer with a transversely heated graphite tube furnace. The electron excitation spectrum of GaF was generated by adding 500 μg Ga per injection into the graphite tube as molecule forming reagent. Best results were obtained by applying Zr as a permanent modifier and a mixed Pd/Zr modifier, thermally pretreated before each sample injection together with the Ga reagent at 1100 °C. The use of sodium acetate and Ru(III) nitrosyl nitrate as additional modifiers injected together with the sample further improved the performance. This way a maximum pyrolysis temperature of 550 °C could be used, and the optimum molecule forming temperature was 1550 °C. Several drinking water samples, a mineral water sample, and two certified reference materials were analyzed using the standard calibration technique; the absence of potential matrix effects was verified by measuring different dilutions and spiking with known fluorine mass. The results were in good agreement with the certified values and those measured by ion selective electrode; the recovery rate for the spiking experiments was between 97% and 106%. The results show that there was no matrix influence for that kind of samples containing relatively high concentrations of Ca, Mg and chloride, which are known to cause interference in GaF molecule absorption. The limit of detection and the characteristic mass of the method were 5.2 and 7.4 pg F, respectively, and were both about a factor of two better than recently published values.

  18. 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.

  19. 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

    2015-12-01

    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.

  20. 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.

  1. 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%).

  2. 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.

  3. 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.

  4. 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

  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. 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.

  7. 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

  8. 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

  9. Influence of reaction between silica crucible and graphite susceptor on impurities of multicrystalline silicon in a unidirectional solidification furnace

    NASA Astrophysics Data System (ADS)

    Gao, B.; Nakano, S.; Kakimoto, K.

    2011-01-01

    The influence of silica crucible reaction with graphite susceptor on carbon and oxygen impurities in multicrystalline silicon was studied by global numerical simulations. Results showed that the crucible reaction has a marked effect on carbon and oxygen impurities in the crystal. When the activity of carbon on the surface of the graphite susceptor increases, both oxygen and carbon impurities in the melt increase rapidly. Therefore, the production of high-purity multicrystalline silicon requires setting a free space between the silica crucible and the graphite susceptor or depositing a layer of SiC film on the surface of susceptor to prevent reaction between them.

  10. 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.

  11. Adsorption and recombination of hydrogen atoms on a model graphite surface. [in interstellar space

    NASA Technical Reports Server (NTRS)

    Aronowitz, S.; Chang, S.

    1985-01-01

    The adsorption and recombination of atomic hydrogen on a model graphite grain have been examined in a series of calculations in which a modified, iterative, extended Hueckel program was used. The hydrogen atom is found to be chemisorbed at a site with a zero-point binding energy of 0.7 eV and at an equilibrium distance of 2.25 A above the site. Despite a barrier of about 0.4 eV between adjacent sites, calculations suggest that at temperatures as low as 10 K, an H atom will tunnel through to adjacent sites in less than one nanosecond. However, a potential barrier to the recombination of two hydrogen atoms has been found which displays high sensitivity to the mutual arrangement of the two hydrogen atoms with respect to the graphite surface. Results show that at very low temperatures, recombinations can occur only by tunneling. Consistent with experiment, the region in which H2 begins to form exhibits a repulsive potential with respect to possible chemisorption of the incipient H2 entity.

  12. H2 recombination on interstellar grains. [due to hydrogen atom chemisorption on graphite grains

    NASA Technical Reports Server (NTRS)

    Barlow, M. J.; Silk, J.

    1976-01-01

    From a consideration of relevant theoretical and experimental data it is concluded that H atoms (but not H2 molecules) will be chemisorbed on interstellar graphite grains, with H2 formation proceeding efficiently for graphite grain temperatures less than 70 K. It is argued that graphite grains will act as the principal sites for H2 formation, with a formation rate of about 4 to the minus 17th cu cm per sec. Heating by H2 molecules formed by surface recombination is analyzed in the context of the available experimental data, and a heating rate is derived and compared with other suggested cloud heating mechanisms. It is concluded that H2 recombination will provide the largest heat source in diffuse clouds if the albedo of interstellar dust in the 912-1200 A region is high (about 0.9), whereas if the albedo in this wavelength region is lower (about 0.5), photoelectron ejection from grains will tend to predominate, and can explain observed cloud temperatures with a carbon depletion factor of approximately 2, a factor attributable to a normal interstellar abundance of graphite grains.

  13. 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.

  14. Commensurate-incommensurate transition of monolayer krypton on graphite by helium-atom scattering

    NASA Astrophysics Data System (ADS)

    Chung, S.; Kara, A.; Larese, J. Z.; Leung, W. Y.; Frankl, And D.

    1987-04-01

    The commensurate-incommensurate transition of monolayer krypton films on a graphite single-crystal substrate is observed by helium-atom diffraction for transition temperatures in the range 50-60 K. The change in lattice spacing appears continuous, with an upper limit of 0.3% on a possible jump, with no detectable hysteresis. The slightly incommensurate phase is disordered but apparently well correlated. The spatial correlation length changes in a possibly discontinuous manner. A decrease of specular and diffracted intensities while the film is still commensurate is observed. This may be due to incoherent elastic scattering from isolated defects, or possibly to increased inelastic scattering.

  15. Electronic and spectroscopic properties of early 3d metal atoms on a graphite surface

    NASA Astrophysics Data System (ADS)

    Rakotomahevitra, A.; Garreau, G.; Demangeat, C.; Parlebas, J. C.

    1995-07-01

    High-sensitivity magneto-optic Kerr effect experiments failed to detect manifestations of magnetism in epitaxial films of V on Ag(100) substrates. More recently V 3s XPS of freshly evaporated V clusters on graphite exhibited the appearance of a satellite structure which has then been interpreted by the effect of surface magnetic moments on V. It is the absence of unambiguous results on the electronic properties of early 3d supported metals that prompts us to examine the problem. Our purpose is twofold. In a first part, after a total energy calculation within a tight-binding method which yields the equilibrium position of a given adatom, we use the Hartree-Fock approximation to find out a possible magnetic solution of V (or Cr) upon graphite for a reasonable value of the exchange integral Jdd. In a second part the informations given by the density of states of the graphite surface as well as the additional states of the adsorbed atom are taken into account through a generalised impurity Anderson Hamiltonian which incorporates the various Coulomb and exchange interactions necessary to analyse the 3s XPS results.

  16. Hot tube atomic absorption spectrochemistry.

    PubMed

    Woodriff, R; Stone, R W

    1968-07-01

    A small, commercially available atomic absorption instrument is used with a heated graphite tube for the atomic absorption analysis of liquid and solid silver samples. Operating conditions of the furnace are described and a sensitivity of about 5 ng of silver is reported. PMID:20068797

  17. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

  19. 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.

  20. 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

  1. 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. PMID:26695253

  2. 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.

  3. Direct determination of bromine in plastic materials by means of solid sampling high-resolution continuum source graphite furnace molecular absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Flórez, M. R.; Resano, M.

    2013-10-01

    This work investigates the potential of high-resolution continuum source graphite furnace molecular absorption spectrometry for the direct determination of bromine in polymers, which could be interesting in view of the current regulations restricting the use of organobrominated compounds. The method developed is based on the addition of Ca (300 μg) and Pd (30 μg) to favor the formation of CaBr, which is monitored at the main molecular “lines” (rotational spectra) found in the vicinity of 625.315 nm. It was found that accurate results could be obtained for all the samples investigated (polyethylene, polypropylene and acrylonitrile butadiene styrene certified reference materials) using any of the lines studied and constructing the calibration curve with aqueous standards. Furthermore, the combined use of the main four CaBr lines available in the spectral area simultaneously monitored permits to easily expand the linear range up to 2000 ng, provides a limit of detection of 1.8 ng (1.8 μg g- 1 for a mass of 1 mg) and further improves precision to values between 3-7% RSD. Overall, the method proposed seems suited for the fast and simple control of these types of samples (approximately 10 min for sample are required), circumventing the traditional problems associated with sample digestion (e.g., losses of volatile compounds), and providing sufficient sensitivity to easily comply with regulations.

  4. Determination of sulfur in coal using direct solid sampling and high-resolution continuum source molecular absorption spectrometry of the CS molecule in a graphite furnace.

    PubMed

    Mior, Renata; Morés, Silvane; Welz, Bernhard; Carasek, Eduardo; de Andrade, Jailson B

    2013-03-15

    An analytical method has been developed for the determination of sulfur in coal using direct solid sample analysis in a graphite tube furnace and high-resolution continuum source molecular absorption spectrometry (HR-CS GF MAS). The molecular absorbance of the carbon monosulfide molecule (CS), which is formed in the vaporization stage, has been measured using the rotational line at 258.033 nm. Several chemical modifiers were tested and Ru, applied as permanent modifier was chosen, because it exhibited the best performance. The optimum pyrolysis and vaporization temperatures were found to be 500 °C and 2200 °C, respectively. Aqueous standard solutions prepared from l-cysteine were used for calibration, as the linear regression obtained for this standard was not significantly different from that for a certified coal reference material (CRM) according to a Student t-test. The results obtained for sulfur in three coal CRM and six additional samples also showed no significant difference for the two calibration techniques according to the same statistical test. The sulfur concentration in the coal samples was found between 3.5 mg g(-1) and 33.7 mg g(-1) with a typical repeatability around 10%. The limit of detection for the direct analysis of solid coal samples was better than 0.1 μg S. PMID:23598139

  5. Method development for the determination of bromine in coal using high-resolution continuum source graphite furnace molecular absorption spectrometry and direct solid sample analysis

    NASA Astrophysics Data System (ADS)

    Pereira, Éderson R.; Castilho, Ivan N. B.; Welz, Bernhard; Gois, Jefferson S.; Borges, Daniel L. G.; Carasek, Eduardo; de Andrade, Jailson B.

    2014-06-01

    This work reports a simple approach for Br determination in coal using direct solid sample analysis in a graphite tube furnace and high-resolution continuum source molecular absorption spectrometry. The molecular absorbance of the calcium mono-bromide (CaBr) molecule has been measured using the rotational line at 625.315 nm. Different chemical modifiers (zirconium, ruthenium, palladium and a mixture of palladium and magnesium nitrates) have been evaluated in order to increase the sensitivity of the CaBr absorption, and Zr showed the best overall performance. The pyrolysis and vaporization temperatures were 800 °C and 2200 °C, respectively. Accuracy and precision of the method have been evaluated using certified coal reference materials (BCR 181, BCR 182, NIST 1630a, and NIST 1632b) with good agreement (between 98 and 103%) with the informed values for Br. The detection limit was around 4 ng Br, which corresponds to about 1.5 μg g- 1 Br in coal, based on a sample mass of 3 mg. In addition, the results were in agreement with those obtained using electrothermal vaporization inductively coupled plasma mass spectrometry, based on a Student t-test at a 95% confidence level. A mechanism for the formation of the CaBr molecule is proposed, which might be considered for other diatomic molecules as well.

  6. Comparative Study of Atomic Force Imaging of DNA on Graphite and Mica Surfaces

    NASA Astrophysics Data System (ADS)

    Klinov, Dmitry; Dwir, Benjamin; Kapon, Eli; Borovok, Natalia; Molotsky, Tatiana; Kotlyar, Alexander

    2006-09-01

    Various DNA-based structures (single-, double-, triple-stranded and quadruplex-DNA) were characterized using non-contact atomic-force microscopy on two substrates: modified highly-oriented pyrolitic graphite (HOPG) and mica. Deposition on mica, a conventional substrate used in studies of bio-molecules, results in strong deformation of all above types of molecules while deposition on modified HOPG affects the morphology of DNA much less compared to mica. This is demonstrated by a larger measured height of the DNA molecules deposited on HOPG, as compared to mica, and an increased flexibility of the molecules, evidenced by a shorter molecular end-to-end distance on HOPG. The estimated heights of the triplex and the quadruplex DNA measured on HOPG are similar to the diameter of these molecules in liquid. We thus conclude that modified HOPG is a substrate more suitable than mica for AFM characterization of DNA morphology.

  7. 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.

  8. 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.

  9. Determination of chlorine in food samples via the AlCl molecule using high-resolution continuum source molecular absorption spectrometry in a graphite furnace

    NASA Astrophysics Data System (ADS)

    Fechetia, Miriam; Tognon, André Luiz; da Veiga, Márcia A. M. S.

    2012-05-01

    Determination of chlorine using the molecular absorption of aluminum mono-chloride (AlCl) at the 261.418 nm wavelength was accomplished by high-resolution continuum source molecular absorption spectrometry using a transversely heated graphite tube furnace with an integrated platform. For the analysis, 10 μL of the sample followed by 10 μL of a solution containing Al-Ag-Sr modifier, (1 g L- 1 each), were directly injected onto the platform. A spectral interference due to the use of Al-Ag-Sr as mixed modifier was easily corrected by the least-squares algorithm present in the spectrometer software. The pyrolysis and vaporization temperatures were 500 °C and 2200 °C, respectively. To evaluate the feasibility of a simple procedure for the determination of chlorine in food samples present in our daily lives, two different digestion methods were applied, namely (A) an acid digestion method using HNO3 only at room temperature, and (B) a digestion method with Ag, HNO3 and H2O2, where chlorine is precipitated as a low-solubility salt (AgCl), which is then dissolved with ammonia solution. The experimental results obtained with method B were in good agreement with the certified values and demonstrated that the proposed method is more accurate than method A. This is because the formation of silver chloride prevented analyte losses by volatilization. The limit of detection (LOD, 3σ/s) for Cl in methods A and B was 18 μg g- 1 and 9 μg g- 1, respectively, 1.7 and 3.3 times lower compared to published work using inductively coupled plasma optical emission spectrometry, and absolute LODs were 2.4 and 1.2 ng, respectively.

  10. Imaging surface nanobubbles at graphite-water interfaces with different atomic force microscopy modes

    NASA Astrophysics Data System (ADS)

    Yang, Chih-Wen; Lu, Yi-Hsien; Hwang, Ing-Shouh

    2013-05-01

    We have imaged nanobubbles on highly ordered pyrolytic graphite (HOPG) surfaces in pure water with different atomic force microscopy (AFM) modes, including the frequency-modulation, the tapping, and the PeakForce techniques. We have compared the performance of these modes in obtaining the surface profiles of nanobubbles. The frequency-modulation mode yields a larger height value than the other two modes and can provide more accurate measurement of the surface profiles of nanobubbles. Imaging with PeakForce mode shows that a nanobubble appears smaller and shorter with increasing peak force and disappears above a certain peak force, but the size returns to the original value when the peak force is reduced. This indicates that imaging with high peak forces does not cause gas removal from the nanobubbles. Based on the presented findings and previous AFM observations, the existing models for nanobubbles are reviewed and discussed. The model of gas aggregate inside nanobubbles provides a better explanation for the puzzles of the high stability and the contact angle of surface nanobubbles.

  11. 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.

  12. Probing the electronic properties of atomically thin graphitic layers with optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Mak, Kin Fai

    Since its discovery, graphene (a mono-layer of graphitic layer) has attracted tremendous attention from the physics community. Being one-atom thick, Single Layer Graphene (SLG) is an ideal model for fundamental studies of 2-Dimensional (2D) systems. One of the most interesting aspects of SLG is the resemblance of its electronic structure to an important class of particles in high energy physics, the Dirac massless Fermions, i.e., massless Fermions with 4 flavors. Such an electronic structure leads to many peculiar phenomena in fundamental physics and many desirable properties for technological applications of this new material. Therefore, a basic understanding of the electronic properties of SLG is of the greatest importance in this field. In this thesis, the electronic structure of single- and few-layer graphene is investigated with optical spectroscopic techniques. In the first part, the optical absorption spectrum of SLG is measured. In the mid/near infrared range, the absorbance is a universal constant equal to pialpha = 2.29%, a being the fine structure constant, independent of photon energies, the particular sample characteristics and all parameters describing the band structure of SLG. This reflects a fundamental fact that the charge carriers in SLG indeed behave as 2D Dirac massless Fermions at low energies. Since each Fermionic species absorbs by pialpha/4, the 4 spin-nodal flavors of Fermions in SLG gives an absorbance of pialpha. On the other hand, strong modifications of optical absorption in the visible/UV range due to many body interactions are observed. Such effects give rise to a breakdown of the universal absorbance and experimental signatures of saddle point excitons. In the second part, the electronic structure of Bi-Layer Graphene (BLG) is studied in the presence of strong applied electric fields. In contrast to SLG, the low-energy electrons in BLG are described as chiral massive Fermions. The linearly dispersing bands in SLG are replaced by

  13. SINGLE-LABORATORY EVALUATION OF SW-846 METHODS 7090/7091 DETERMINATION OF BERYLLIUM BY FLAME AND FURNACE ATOMIC ABSORPTION SPECTROPHOTOMETRY

    EPA Science Inventory

    The results of a single-laboratory study of the 'Determination of Beryllium by Flame and Furnace Atomic Absorption Spectrophotometry', are described. The study examined the application of these two powerful beryllium detection methods to the analysis of selected liquid and solid ...

  14. 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%.

  15. Improvements in cobalt determination by thermospray flame furnace atomic absorption spectrometry using an on-line derivatization strategy.

    PubMed

    Matos, Geraldo Domingues; Arruda, Marco Aurélio Zezzi

    2008-07-15

    An on-line derivatization strategy was developed for improving cobalt sensitivity using thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) as the analytical technique. This strategy involves the generation of a volatile cobalt compound, providing better sample vaporization efficiency. The effect of sodium diethyldithiocarbamate (DDTC) as complexing agent on the integrated absorbance signal was evaluated. Parameters including the pH of complex formation, complex concentration and volume, sample volume, flame gas composition and tube atomization configuration were optimized. A wide linear range (from 23 microg L(-1) to 3 mg L(-1); r(2)=0.9786) was obtained, with the best one (r(2)=0.9992) attained from 23 to 400 microg L(-1) with a sample throughput of 30 h(-1). The improvement in the detection power was 17-fold when compared to FAAS, which provides 7 microg L(-1) as the limit of detection when considered TS-FF-AAS technique. A relative standard deviation (n=10) of 4% for a cobalt solution containing 50 microg L(-1) was attained, and the accuracy of the procedure was evaluated through certified reference materials (IAEA-SL-1, lake sediment; and ISS-MURST-A1, Antarctic marine sediment). Good agreement between the results at the 95% confidence level was observed. PMID:18585309

  16. On the performance of van der Waals corrected-density functional theory in describing the atomic hydrogen physisorption on graphite

    NASA Astrophysics Data System (ADS)

    Ferullo, Ricardo M.; Domancich, Nicolás F.; Castellani, Norberto J.

    2010-11-01

    The atomic hydrogen physisorption on graphite was studied using the hydrogen-coronene model system and the van der Waals corrected-density functional theory (DFT + vdW). The results show that H preferentially occupies the hollow site. The adsorption energy at this site is calculated as 38.1 meV, in very good agreement with the available experimental measurements on a single graphite layer (39.2 ± 0.5 meV) and with reported MP2/aug-cc-pVDZ calculations (39.7 meV). The results suggest that, in DFT simulations, dispersion corrections should be considered in order to obtain accurate distances, adsorption energies and diffusion barriers in physisorption processes such as those occurring in the cold interstellar medium.

  17. Determination of trace elements in automotive fuels by filter furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Anselmi, Anna; Tittarelli, Paolo; Katskov, Dmitri A.

    2002-03-01

    The determination of Cd, Cr, Cu, Pb and Ni was performed in gasoline and diesel fuel samples by electrothermal atomic absorption spectrometry using the Transverse Heated Filter Atomizer (THFA). Thermal conditions were experimentally defined for the investigated elements. The elements were analyzed without addition of chemical modifiers, using organometallic standards for the calibration. Forty-microliter samples were injected into the THFA. Gasoline samples were analyzed directly, while diesel fuel samples were diluted 1:4 with n-heptane. The following characteristic masses were obtained: 0.8 pg Cd, 6.4 pg Cr, 12 pg Cu, 17 pg Pb and 27 pg Ni. The limits of determination for gasoline samples were 0.13 μg/kg Cd, 0.4 μg/kg Cr, 0.9 μg/kg Cu, 1.5 μg/kg Pb and 2.5 μg/kg Ni. The corresponding limit of determination for diesel fuel samples was approximately four times higher for all elements. The element recovery was performed using the addition of organometallic compounds to gasoline and diesel fuel samples and was between 85 and 105% for all elements investigated.

  18. 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.

  19. 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.

  20. Atomically Thin Mesoporous Nanomesh of Graphitic C3N4 for High-Efficiency Photocatalytic Hydrogen Evolution.

    PubMed

    Han, Qing; Wang, Bing; Gao, Jian; Cheng, Zhihua; Zhao, Yang; Zhang, Zhipan; Qu, Liangti

    2016-02-23

    Delamination of layer materials into two-dimensional single-atom sheets has induced exceptional physical properties, including large surface area, ultrahigh intrinsic carrier mobility, pronounced changes in the energy band structure, and other properties. Here, atomically thin mesoporous nanomesh of graphitic carbon nitride (g-C3N4) is fabricated by solvothermal exfoliation of mesoporous g-C3N4 bulk made from thermal polymerization of freeze-drying assembled Dicyandiamide nanostructure precursor. With the unique structural advantages for aligned energy levels, electron transfer, light harvesting, and the richly available reaction sites, the as-prepared monolayer of mesoporous g-C3N4 nanomesh exhibits a superior photocatalytic hydrogen evolution rate of 8510 μmol h(-1) g(-1) under λ > 420 nm and an apparent quantum efficiency of 5.1% at 420 nm, the highest of all the metal-free g-C3N4 nanosheets photocatalysts. PMID:26766237

  1. Microwave plasma continuous emissions monitor for trace-metals in furnace exhaust

    NASA Astrophysics Data System (ADS)

    Woskov, P. P.; Rhee, D. Y.; Thomas, P.; Cohn, D. R.; Surma, J. E.; Titus, C. H.

    1996-10-01

    A microwave plasma continuous emissions monitor has been successfully demonstrated for sensitive (<1 ppb), real time measurements of trace metals in furnace exhaust. The instrument uses a robust, up to 1.5 kW, 2.45 GHz microwave plasma sustained in a portion of the undiluted furnace exhaust flow for atomic emission spectroscopy. The waveguide device is constructed of refractory materials compatible with high-temperature environments (≳500 °C) and is flange mountable into the inside of the furnace exhaust duct. Fused quartz fiber optics in close proximity to the plasma flame transmit the UV through visible emission (190-690 nm) to three spectrometers for simultaneous monitoring of several metals. This instrument has been used for continuous monitoring for a 49 h period with 0.5 s time resolution on a dc graphite electrode arc furnace during a soil vitrification test. Results are presented for chromium, manganese, and iron emissions during soil loading operations.

  2. DIRECT DETERMINATION OF PHOSPHORUS IN GASOLINE BY FLAMELESS ATOMIC ABSORPTION SPECTROMETRY

    EPA Science Inventory

    A new method is presented for the determination of phosphorus in gasoline using flameless atomic absorption. Lanthanum nitrate solution is inserted in a graphite furnace prior to direct addition of gasoline. The organic matrix is charred prior to atomization of the phosphorus. Th...

  3. 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.

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1992-11-01

    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.

  7. 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.

  8. 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.

  9. Morphological and spectroscopic investigation of the behavior of permanent iridium modifier deposited on pyrolytic graphite coated and zirconium treated platforms in electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Slaveykova, Vera I.; Lampugnani, Leonardo; Tsalev, Dimiter L.; Sabbatini, L.

    1997-12-01

    In order to better characterise a permanent modifier based on iridium deposited on zirconium or tungsten treated platforms of transversely heated graphite atomizer, and to gain additional information about its chemical behavior directed to an eventual further optimization, a series of experiments were carried out, both by surface techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS or ESCA) and X-ray fluorescence (XRF) and by electrothermal atomic absorption spectrometry on the iridium release from unmodified and various other modified pyrolytic graphite platforms. Special attention was paid to the influence of the amount of iridium, zirconium carbide coating of the platform surface and the presence of citric acid on the iridium vaporization during pyrolysis and atomization. The processes of iridium losses during pyrolysis and atomization and peak maximum alignment depend on the amount of the iridium deposited on the pyrolytic graphite coated platforms in the presence of nitric acid. A fractional order of release which suggests an atom vaporization from the surface or edges of the iridium islands was estimated. In the presence of citric acid, mass independence and zero order of the atom release were found. The zirconium treatment of the platform results in change of the spatial distribution of iridium and hence its vaporization. Vaporization temperatures as high as 2100°C, and first order of the process of atom generation were obtained. While it was possible to study the iridium atomization from uncoated and zirconium coated surfaces, evidencing a different order for the release process, the same was not possible for the tungsten coated platforms due to an 'overstabilization' that brought the iridium atomization temperature out of the working range of the instrument used. The different chemical behavior of tungsten and zirconium was also confirmed by XPS investigations. With tungsten, evidence of both WC and WO bonding

  10. 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

  11. U.S.-MEXICO BORDER PROGRAM ARIZONA BORDER STUDY--STANDARD OPERATING PROCEDURE FOR OPERATION, CALIBRATION, AND MAINTENANCE OF THE PERKIN-ELMER ZEEMAN/5000 SYSTEM ATOMIC ABSORPTION SPECTROPHOTOMETER (BCO-L-6.0)

    EPA Science Inventory

    The purpose of this SOP is to outline the start-up, calibration, operation, and maintenance procedures for the Perkin-Elmer 5000 atomic absorption spectrophotometer (PE 5000 AA), and the Perkin Elmer 5000 Zeeman graphite furnace atomic absorption spectrophotometer (PE 5000Z GFAA)...

  12. NHEXAS PHASE I ARIZONA STUDY--STANDARD OPERATING PROCEDURE FOR OPERATION, CALIBRATION AND MAINTENANCE OF THE PERKIN-ELMER ZEEMAN/5000 SYSTEM ATOMIC ABSORPTION SPECTROMETER (BCO-L-6.0)

    EPA Science Inventory

    The purpose of this SOP is to outline the start-up, calibration, operation, and maintenance procedures for the Perkin-Elmer 5000 atomic absorption spectrophotometer (PE 5000 AA), and the Perkin Elmer 5000 Zeeman graphite furnace atomic absorption spectrophotometer (PE 5000Z GFAA)...

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. Tube furnace

    SciTech Connect

    Foster, K.G.; Frohwein, E.J.; Taylor, R.W.; Bowen, D.W.

    1990-12-31

    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.

  18. Tube furnace

    SciTech Connect

    Foster, K.G.; Frohwein, E.J.; Taylor, R.W.; Bowen, D.W.

    1990-01-01

    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.

  19. 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.

  20. Selective determination of four arsenic species in rice and water samples by modified graphite electrode-based electrolytic hydride generation coupled with atomic fluorescence spectrometry.

    PubMed

    Yang, Xin-An; Lu, Xiao-Ping; Liu, Lin; Chi, Miao-Bin; Hu, Hui-Hui; Zhang, Wang-Bing

    2016-10-01

    This work describes a novel non-chromatographic approach for the accurate and selective determining As species by modified graphite electrode-based electrolytic hydride generation (EHG) for sample introduction coupled with atomic fluorescence spectrometry (AFS) detection. Two kinds of sulfydryl-containing modifiers, l-cysteine (Cys) and glutathione (GSH), are used to modify cathode. The EHG performance of As has been changed greatly at the modified cathode, which has never been reported. Arsenite [As(III)] on the GSH modified graphite electrode (GSH/GE)-based EHG can be selectively and quantitatively converted to AsH3 at applied current of 0.4A. As(III) and arsenate [As(V)] on the Cys modified graphite electrode (Cys/GE) EHG can be selectively and efficiently converted to arsine at applied current of 0.6A, whereas monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) do not form any or only less volatile hydrides under this condition. By changing the analytical conditions, we also have achieved the analysis of total As (tAs) and DMA. Under the optimal condition, the detection limits (3s) of As(III), iAs and tAs in aqueous solutions are 0.25μgL(-1), 0.22μgL(-1) and 0.10μgL(-1), respectively. The accuracy of the method is verified through the analysis of standard reference materials (SRM 1568a). PMID:27474289

  1. Combined dynamic scanning tunneling microscopy and frequency modulation atomic force microscopy investigations on polythiophene chains on graphite with a tuning fork sensor

    NASA Astrophysics Data System (ADS)

    Polesel-Maris, Jérôme; Lubin, Christophe; Thoyer, François; Cousty, Jacques

    2011-04-01

    Polythiophene molecules adsorbed on a highly oriented pyrolytic graphite surface were studied by combined dynamic scanning tunneling microscopy (STM) and frequency modulation atomic force microscopy (FM-AFM) with a quartz tuning fork sensor operating in Qplus mode and equipped with a Pt/Ir tip. Upon completing a careful sub-angström oscillation amplitude calibration of the probe, experiments were conducted in an ultra high vacuum at room temperature. By selecting the tip/surface distance regulation parameter, one can select the type of simultaneous information obtained in an area. For distance regulation based on the mean tunneling current, dynamic STM images together with maps of tip/surface force gradient were obtained. FM-AFM images with maps of the tunneling current were also acquired when the distance regulation was based on the frequency shift. Comparison between these images reveals interesting features. For example the tip which operates in STM mode with ultra low current (<10 pA) generates different interaction forces above molecules or graphite. Changes in energy dissipation processes as small as tens of millielectronvolts per cycle were recorded when the tip oscillates above the polymer or on the graphite surface. Hence data demonstrates that a stiff piezoelectric tuning fork of several kilonewtons/meters working as an AFM/STM probe with sub-angström amplitude can characterize weakly adsorbed molecules.

  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. 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.

  4. 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.

  5. An electrochemical flow-cell for permanent modification of graphite tube with palladium for mercury determination by electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Moreno, Ruben G. M.; de Oliveira, Elisabeth; Pedrotti, Jairo J.; Oliveira, Pedro V.

    2002-04-01

    An electrochemical procedure for palladium deposition on the inner surface of pyrolytic graphite-coated tubes for permanent chemical modification and a cold vapor generation system for the pre-concentration and determination of mercury trace levels in rain, potable, and non-potable water and lake sediment by electrothermal atomic absorption spectrometry is proposed. A tubular electrochemical flow-cell was assembled on the original geometry of the graphite tube, which operated as the working electrode. A stainless steel tube, positioned downstream from the working electrode, was used as the auxiliary electrode. The applied potential was measured against a micro Ag/AgCl (sat) reference electrode inserted in the auxiliary electrode. Palladium solution in acetate buffer (100 mmol l -1, pH=4.8), flowing at 0.5 ml min -1 for 60 min was used to perform the electrodeposition. A homemade cold vapor generation system composed of a peristaltic pump, an injector-commutator, a flow meter and a disposable polyethylene gas-liquid separator flask (approx. 4.0 ml volume) were used. Volumes of 1.0 ml of reagent (2.0% w/v NaBH 4 in 0.10 mol l -1 of NaOH) and 1.0 ml of reference or sample solution in 0.25 mol l -1 of HNO 3 were carried to the gas-liquid separator using the peristaltic pump. The mercury vapor was carried out to the modified graphite tube by argon flow (200 ml min -1), and pre-concentrated for 120 s. The characteristic mass for 1.0 ml of reference solution was 26 pg (R.S.D.=0.12%, n=5). The detection limit obtained was 93 pg ( n=20, 3δ). The reliability of the entire procedure was confirmed by addition and recovery tests and cold vapor atomic absorption spectrometry.

  6. RBS investigations of high-temperature reactions on graphite substrates

    NASA Astrophysics Data System (ADS)

    Eloi, Corinne C.; David Robertson, J.; Majidi, Vahid

    1995-05-01

    While graphite furnace atomic absorption spectrometry (GFAAS) is one of the most powerful techniques for ultratrace analysis of Pb, it is often plagued by matrix interferences. These interferences are minimized by the addition of matrix modifiers which stabilize the analyte signal through unknown mechanisms. Using RBS, the high temperature reactions of nitrate salts of Pb were studied on pyrolytically coated graphite with and without matrix modifiers. The addition of an ammonium phosphate modifier was found to stabilize Pb through the formation of a metal oxy-phosphorus compound. Moreover, the depth profiles demonstrated that the pyrolytically coated graphite was not impervious as previously thought. Pre-treatment of the surface with O 2 is also known to cause a delay in the vaporization of Pb. While a surface effect had previously been postulated, the 3.04 MeV resonance 16O(α, α) 16O elastic scattering measurements show that it proceeds through the formation of surface bound lead-oxygen species as the number of oxygen atoms chemisorbed and the number of lead atoms, present on the surface prior to vaporization, are nearly equal.

  7. L-tyrosine immobilized on multiwalled carbon nanotubes: a new substrate for thallium separation and speciation using stabilized temperature platform furnace-electrothermal atomic absorption spectrometry.

    PubMed

    Pacheco, Pablo H; Gil, Raúl A; Smichowski, Patricia; Polla, Griselda; Martinez, Luis D

    2009-12-10

    An approach for the separation and determination of inorganic thallium species is described. A new sorbent, L-tyrosine-carbon nanotubes (L-tyr-CNTs), was used and applied to the analysis of tap water samples. At pH 5.0, L-tyr was selective only towards Tl(III), while total thallium was determined directly by stabilized temperature platform furnace-electrothermal atomic absorption spectrometry (STPF-ETAAS). The Tl(III) specie, which was retained by L-tyrosine, was quantitatively eluted from the column with 10% of nitric acid. An on-line breakthrough curve was used to determine the column capacity, which resulted to be 9.00 micromol of Tl(III) g(-1) of L-tyr-CNTs with a molar ratio of 0.14 (moles of Tl bound to moles of L-tyr at pH 5). Transient peak areas revealed that Tl stripping from the column occurred instantaneously. Effects of sample flow rate, concentration and flow rate of the eluent, and interfering ions on the recovery of the analyte were systematically investigated. The detection limit for the determination of total thallium (3sigma) by STPF-ETAAS was 150 ng L(-1). The detection limit (3sigma) for Tl(III) employing the separation system was 3 ng L(-1), with an enrichment factor of 40. The precision of the method expressed as the relative standard deviation (RSD) resulted to be 3.4%. The proposed method was applied to the speciation and determination of inorganic thallium in tap water samples. The found concentrations were in the range of 0.88-0.91 microg L(-1) of Tl(III), and 3.69-3.91 microg L(-1) of total thallium. PMID:19932812

  8. Application of Dispersive Liquid-Liquid Microextraction with Graphite Furnace Atomic Absorption Spectrometry for Determination of Trace Amounts of Zinc in Water Samples

    PubMed Central

    Mazloomifar, Ali

    2013-01-01

    A selective and simple method for separation and preconcentration of zinc ions was developed by using dispersive liquid-liquid microextraction. Parameters that have an effect on the microextraction efficiency such as volume of extraction and disperser solvent, extraction time, and adding salt were investigated. Under optimum conditions, a preconcentration factor of 250 was obtained. The limit of detection (LOD) obtained under the optimal conditions was 0.09 ng mL−1. The linearity of method was obtained in range of 0.2–50 ng mL−1 with a correlation coefficient (r) of 0.9974. The relative standard deviation for 10 replicate determinations at 1.0 ng mL−1 of zinc was 2.53%. The proposed method was successfully applied to the analysis of zinc in water sample. PMID:23737791

  9. 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

  10. Online time-differential perturbed angular correlation study with an 19O beam - Residence sites of oxygen atoms in highly oriented pyrolytic graphite

    NASA Astrophysics Data System (ADS)

    Sato, W.; Ueno, H.; Watanabe, H.; Miyoshi, H.; Yoshimi, A.; Kameda, D.; Ito, T.; Shimada, K.; Kaihara, J.; Suda, S.; Kobayashi, Y.; Shinohara, A.; Ohkubo, Y.; Asahi, K.

    2008-01-01

    The online time-differential perturbed angular correlation (TDPAC) method was applied to a study of the physical states of a probe 19F, the β- decay product of 19O (t1/2 = 26.9 s), implanted in highly oriented pyrolytic graphite. The observed magnitude of the electric field gradient at the probe nucleus, ∣Vzz∣ = 2.91(17) × 1022 V m-2, suggests that the incident 19O atoms are stabilized at an interlayer position with point group C3v. Exhibiting observed TDPAC spectra having a clear sample-to-detector configuration dependence, we demonstrate the applicability of the present online method with a short-lived radioactive 19O beam.

  11. Atomic force microscopy on phase-control pulsed force mode in water: Imaging and force analysis on a rhodium-octaethylporphyrin layer on highly oriented pyrolytic graphite

    NASA Astrophysics Data System (ADS)

    Maeda, Yasushi; Yamazaki, Shin-ichi; Kohyama, Masanori

    2014-06-01

    We developed phase-control pulsed force mode (p-PFM) as the operation mode for atomic force microscopy (AFM). The p-PFM allowed us to observe soft or weakly adsorbed materials in a liquid environment using a conventional AFM apparatus, and allowed for force curve mapping (FCM) after offline data processing. We applied the p-PFM to a rhodium-octaethylporphyrin (RhOEP) layer on highly oriented pyrolytic graphite (HOPG), which is applicable to anode catalysts of fuel cells. The RhOEP/HOPG system was stably observed in water by this mode. In the p-PFM image, we found both large and small protrusions, which were not observed in the dynamic force mode, in air. The detailed force analysis suggested that these protrusions are nanobubbles located on the HOPG substrate exposed in holes or pits of the RhOEP layer.

  12. Investigation of the Transition from Local Anodic Oxidation to Electrical Breakdown During Nanoscale Atomic Force Microscopy Electric Lithography of Highly Oriented Pyrolytic Graphite.

    PubMed

    Yang, Ye; Lin, Jun

    2016-04-01

    As one of the tip-based top-down nanoscale machining methods, atomic force microscopy (AFM) electric lithography is capable of directly generating flexible nanostructures on conductive or semi-conductive sample surfaces. In this work, distinct fabrication mechanisms and mechanism transition from local anodic oxidation (LAO) to electrical breakdown (BD) in the AFM nanoscale electric lithography of the highly oriented pyrolytic graphite sample surface was studied. We provide direct evidence of the transition process mechanism through the detected current-voltage (I-V) curve. Characteristics of the fabrication results under the LAO, transition, and BD regions involving the oxide growth rate or material removal rate and AFM probe wear are analyzed in detail. These factors are of great significance for improving the machining controllability and expanding its potential applications. PMID:26847869

  13. 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

  14. Furnace afterburner

    SciTech Connect

    Angelo, J.F. II

    1987-01-13

    An afterburner is described for the exhaust effluvia of a furnace, which exhaust contains combustible material, the afterburner comprising: a. an elongated, generally cylindrical combustion chamber having an inlet for the exhaust at or adjacent one end thereof, and an outlet at or adjacent its other end, b. means operable to induce a draft through the combustion chamber from its inlet to its outlet, c. a series of air nozzles disposed to direct jets of air into the interior of the combustion chamber. Certain nozzles are arranged to direct air jets into the combustion chamber substantially tangentially thereto in a clockwise direction, and the remainder of the nozzles and arranged to direct air jets into the chamber substantially tangentially thereto in a counter-clockwise direction, whereby to induce turbulence within the chamber to intermix the air and the exhaust thoroughly, and d. means operable to deliver air to the air nozzles.

  15. Microwave plasma continuous emissions monitor for trace-metals in furnace exhaust

    SciTech Connect

    Woskov, P.P.; Rhee, D.Y.; Thomas, P.; Cohn, D.R.; Surma, J.E.; Titus, C.H.

    1996-10-01

    A microwave plasma continuous emissions monitor has been successfully demonstrated for sensitive ({lt}1 ppb), real time measurements of trace metals in furnace exhaust. The instrument uses a robust, up to 1.5 kW, 2.45 GHz microwave plasma sustained in a portion of the undiluted furnace exhaust flow for atomic emission spectroscopy. The waveguide device is constructed of refractory materials compatible with high-temperature environments ({approx_gt}500{degree}C) and is flange mountable into the inside of the furnace exhaust duct. Fused quartz fiber optics in close proximity to the plasma flame transmit the UV through visible emission (190{endash}690 nm) to three spectrometers for simultaneous monitoring of several metals. This instrument has been used for continuous monitoring for a 49 h period with 0.5 s time resolution on a dc graphite electrode arc furnace during a soil vitrification test. Results are presented for chromium, manganese, and iron emissions during soil loading operations. {copyright} {ital 1996 American Institute of Physics.}

  16. 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.

  17. Determination of Chromium(III), Chromium(VI), and Chromium(III) acetylacetonate in water by ion-exchange disk extraction/metal furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Kamakura, Nao; Inui, Tetsuo; Kitano, Masaru; Nakamura, Toshihiro

    A new method for the separate determination of Chromium(III) (Cr(III)), Chromium(VI) (Cr(VI)), and Cr(III) acetylacetonate (Cr(acac)3) in water was developed using a cation-exchange extraction disk (CED) and an anion-exchange extraction disk (AED) combined with metal furnace atomic absorption spectrometry (MFAAS). A 100-mL water sample was adjusted to pH 5.6 and passed through the CED placed on the AED. Cr(acac)3 and Cr(III) were adsorbed on the CED, and Cr(VI) was adsorbed on the AED. The adsorbed Cr(acac)3 was eluted with 50 mL of carbon tetrachloride, followed by the elution of Cr(III) with 50 mL of 3 mol L- 1 nitric acid. Cr(VI) was eluted with 50 mL of 3 mol L- 1 nitric acid. The chemical species of Cr eluted from the CED with carbon tetrachloride was identified as Cr(acac)3 using infrared spectroscopy. The eluate of Cr(acac)3 was diluted to 100 mL with carbon tetrachloride, and those of Cr(III) and Cr(VI) were diluted to 100 mL with deionized water. All of the solutions were subsequently analyzed by MFAAS. The calibration curve for the Cr(acac)3 aqueous solutions exhibited good linearity in the range of 0.1 to 1 ng. The detection limit of Cr, which corresponded to three times the standard deviation (n = 10) of the blank values, was 20 pg. The recovery test for Cr(III), Cr(VI), and Cr(acac)3 exhibited desirable results (96.0%-107%) when 5 μg of each species (50 μg L- 1) was added to 100 mL water samples (i.e., tap water, rainwater, and bottled drinking water). In a humic acid solution, Cr(acac)3 was quantitatively recovered (103%), but Cr(III) and Cr(VI) exhibited poor recoveries (i.e., 84.8% and 78.4%, respectively).

  18. 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.

  19. 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.

  20. 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.

  1. Graphite-Fiber-Reinforced Glass-Matrix Composite

    NASA Technical Reports Server (NTRS)

    Prewo, K. M.; Dicus, D. L.

    1982-01-01

    G/GI structural composite material made of graphite fibers embedded in borosilicate glass exhibit excellent strength, fracture toughness, and dimensional stability at elevated temperatures. It is made by passing graphite-fiber yarn through slurry containing suspension of fine glass particles in carrier liquid and winding on drum to produce prepegged uniaxial tape. After drying, tapes are cut into appropriate lengths and laid up in graphite die in desired stacking scheme. Stack is consolidated by hot pressing in furnace.

  2. 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.

  3. Blast furnace on-line simulation model

    NASA Astrophysics Data System (ADS)

    Saxén, Henrik

    1990-10-01

    A mathematical model of the ironmaking blast furnace (BF) is presented. The model describes the steady-state operation of the furnace in one spatial dimension using real process data sampled at the steelworks. The measurement data are reconciled by an interface routine which yields boundary conditions obeying the conservation laws of atoms and energy. The simulation model, which provides a picture of the internal conditions of the BF, can be used to evaluate the current state of the process and to predict the effect of operating actions on the performance of the furnace.

  4. 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.

  5. 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.

  6. 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.

  7. Heat treatment furnace

    DOEpatents

    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.

  8. 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

  9. 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.

  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. 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.

  12. 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.

  13. 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

  14. 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

  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. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Space Station Furnace Facility

    SciTech Connect

    Cobb, S.D.; Lehoczky, S.L.

    1996-12-31

    The Space Station Furnace Facility (SSFF) is the modular, multi-user scientific instrumentation for conducting materials research in the reduced gravity ({approximately}10{sup {minus}6} g) environment of the International Space Station (ISS). The facility is divided into the Core System and two Instrument Racks (IRs). 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 (NASA) 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 (HGFQ), and a Low Temperature Gradient Furnace (LGF). A new EM is planned to be developed every two years.

  1. 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.

  2. Programmable Multizone Furnace

    NASA Technical Reports Server (NTRS)

    Ting, Edmund Y.; Larson, David J., Jr.

    1990-01-01

    Moving thermal gradients created without mechanical motion. Furnace having multiple, individually programmable heating zones developed for use in experiments on directional solidification. Holds rod specimen and generates thermal gradients moving along specimen. Elimination of translation mechanism makes furnace more compact and reduces vibrations, which disturb experiment. Availability of different temperature profiles through programming makes it versatile tool for research at low thermal gradients traveling at moderate speeds.

  3. 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.

  4. Ferrix Chloride-Graphite Intercalation Compounds Prepared From Graphite Flouride

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh

    1995-01-01

    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 sp(sup 3) 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 sp(sup 2) electronic structure and are electrical conductors. They contain first-stage FeCl3 intercalated graphite. Some of the products contain FeCl2 (center dot) 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 disappearance 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 exposed to 800 C N2, in a quartz tube, they lost most of their halogen atoms and formed iron oxides (other than hematite), distributed evenly in or on the fiber.

  5. Atomic absorption determination of traces of cadmium in urine after electrodeposition onto a tungsten wire.

    PubMed

    Zhang, G; Li, J; Fu, D; Hao, D; Xiang, P

    1993-03-01

    A three-coil tungsten wire is used as electrode for the preconcentration of cadmium, which is then placed in a graphite tube for atomization and atomic absorption measurement. The heating parameters of the graphite furnace are optimized using the Modified and Weighted Centroid Simplex Method (MWCS), and computer program for automatic calculation. Sulphuric acid is selected as the supporting electrolyte for electrodeposition. The linear range of the calibration graph is 0.00-0.55 ng/ml. The detection limit is 0.01 ng/ml. For 0.1 ng/ml cadmium the coefficient of variation is 3.35% for ten parallel determinations. No interference occurs in the presence of more than 20 coexisting ions. Traces of cadmium in urine of normal people and in river water and the recoveries for cadmium are determined. The results are satisfactory. PMID:18965645

  6. Characterization of the structure of PM-16E furnace black

    SciTech Connect

    Varlakov, V.P.; Fialkov, A.S.; Smirnov, B.N.

    1982-01-01

    An investigation of the structure of PM-16E furnace black in the initial and graphitized states has been carried out with the aid of phase-contact electron microscopy with direct resolution of the carbon layers (002). A two-stage mechanism of the formation of furnace black has been confirmed. In the first stage there is a free-radical mechanism of the formation of the particles of carbon black. In the second stage the orientated deposition of pyrolysis products takes place on the particles and their aggregates in the form of planar carbon layers. The structure of graphitized carbon black is represented in the form of a hollow polyhedron the faces of which consist of packets of continuous closed carbon layers.

  7. 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.

  8. 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.

  9. 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.

  10. Oscillator strengths of ultraviolet Ni I lines from hook-method and absorption measurements in a furnace

    NASA Technical Reports Server (NTRS)

    Huber, M. C. E.; Sandeman, R. J.

    1980-01-01

    Measurements of the oscillator strengths of the ultraviolet lines of neutral nickel obtained by the use of the combined hook and absorption technique are reported. A total of 221 transitions in the range 1964-4094 A was measured for nickel atoms from a high-temperature graphite furnace (2000-2500 K) using a continuum background source, a Mach-Zehnder interferometer and a 3-m Czerny-Turner spectrograph. Hook and absorption measurements are presented, and radiative lifetimes are derived from log gf values. Comparison of the present values with previous results indicates only those of Bell et al. (1966) and Lennard et al. (1975) to consistently agree with the data presented, although the reliability laser-excitation technique of lifetime measurement is supported over that of Hanle methods.

  11. 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

  12. 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.

  13. Adsorption of lead over Graphite Oxide

    PubMed Central

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

    2014-01-01

    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 Pb2+ 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. PMID:24152870

  14. Monte Carlo simulation of electrothermal atomization on a desktop personal computer

    NASA Astrophysics Data System (ADS)

    Histen, Timothy E.; Güell, Oscar A.; Chavez, Iris A.; Holcombea, James A.

    1996-07-01

    Monte Carlo simulations have been applied to electrothermal atomization (ETA) using a tubular atomizer (e.g. graphite furnace) because of the complexity in the geometry, heating, molecular interactions, etc. The intense computational time needed to accurately model ETA often limited its effective implementation to the use of supercomputers. However, with the advent of more powerful desktop processors, this is no longer the case. A C-based program has been developed and can be used under Windows TM or DOS. With this program, basic parameters such as furnace dimensions, sample placement, furnace heating and kinetic parameters such as activation energies for desorption and adsorption can be varied to show the absorbance profile dependence on these parameters. Even data such as time-dependent spatial distribution of analyte inside the furnace can be collected. The DOS version also permits input of external temperaturetime data to permit comparison of simulated profiles with experimentally obtained absorbance data. The run-time versions are provided along with the source code. This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by a diskette with a program (PC format), data files and text files.

  15. Radiation-Induced Transformation of Graphite to Diamond

    SciTech Connect

    Zaiser, M.; Banhart, F.

    1997-11-01

    It is demonstrated theoretically that particle irradiation may lead to a destabilization of graphitic structures with respect to low-pressure growth of diamond. This is due to the large difference in the cross sections for irradiation-induced displacements of carbon atoms in diamond and graphite. A nonequilibrium phase diagram is calculated that shows the stability of graphite and diamond as a function of the displacement rate of atoms. The theoretical results are related to the experimentally observed transformation of spherical graphitic onions to diamond under electron irradiation. {copyright} {ital 1997} {ital The American Physical Society}

  16. 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.

  17. 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

  18. 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.

  19. 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

  20. 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.

  1. New possibilities of Consteel furnaces

    NASA Astrophysics Data System (ADS)

    Tuluevskii, Yu. N.; Zinurov, I. Yu.; Shver, V. G.

    2012-06-01

    The disadvantages of Consteel electric furnaces, which are mainly caused by the low efficiency of heating of a charged metal scrap by effluent furnace gases, are considered. A new concept of an electric-arc furnace with scrap heating on a conveyer by powerful burners, which provide fast scrap heating to 800°C, is proposed. As follows from calculations, the capacity of such a furnace increases substantially, the specific electric power consumption decreases, and the emission of toxic substances into the atmosphere decreases as compared to the existing Consteel furnaces.

  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. 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

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. Blast Furnace Granulated Coal Injection

    SciTech Connect

    1998-09-30

    Production levels on each furnace exceeded 7000 NTHM/day during July. The combined production of 14,326 was a result of lower coke rates and below average delay rates on both furnaces, The combined production was at its highest level since September 1997. In August, the combined productivity declined to less than 13,500 NTHM/day. Although D furnace maintained a production rate in excess of 7000 NTHM/day, C furnace was lower because of a castfloor breakout and subsequent five day repair from August 26-30. Despite the lower productivity in August, injected coal and furnace coke rates were very good during the month. During September, the operation was difficult as a result of higher delays on both furnaces. The combined average monthly delay rate was considerably above the twenty-month average of 113 minutes per day and the combined average monthly production was less than 14,000 NTHM/day. Higher furnace coke rates at lower coal injection levels also contributed to the decrease. Additionally, the coke rate on both furnaces was increased substantially and the injected coal rate was decreased in preparation for the high volatile Colorado coal trial that started on September 28. The furnace process results for this quarter are shown in Tables 1A and 1B. In addition, the last twelve months of injected coal and coke rates for each furnace are shown in Figures 1 and 2.

  10. 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

  11. 3D-graphite structure

    SciTech Connect

    Belenkov, E. A. Ali-Pasha, V. A.

    2011-01-15

    The structure of clusters of some new carbon 3D-graphite phases have been calculated using the molecular-mechanics methods. It is established that 3D-graphite polytypes {alpha}{sub 1,1}, {alpha}{sub 1,3}, {alpha}{sub 1,5}, {alpha}{sub 2,1}, {alpha}{sub 2,3}, {alpha}{sub 3,1}, {beta}{sub 1,2}, {beta}{sub 1,4}, {beta}{sub 1,6}, {beta}{sub 2,1}, and {beta}{sub 3,2} consist of sp{sup 2}-hybridized atoms, have hexagonal unit cells, and differ in regards to the structure of layers and order of their alternation. A possible way to experimentally synthesize new carbon phases is proposed: the polymerization and carbonization of hydrocarbon molecules.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. [Determination of trace barium in environmental samples by electric-heated AAS with lanthanum-coated graphite tube].

    PubMed

    Han, Hua-yun; Lin, Lin; Chen, Ke; Wang, Feng

    2002-02-01

    In this paper a new method was established for determination of trace barium in environmental samples by graphite furnace atomic absorption spectrometry. In the presence of matrix modifier magnesium nitrate, the matrix inference was eliminated efficiently. To avoid producing barium carbide, the graphite tubes were coated differently with lanthanum, zirconium, tungsten, molybdenum, and tantalum. Results showed that the tube with lanthanum was the best. The atomization temperature was diminished. The sensitivity was improved, and the tube with lanthanum gave the longest service life. So we used the tube to determine trace barium. The trace barium in Geodchemical Standard Reference Sample Soil-1 (GSS-1) was determined by the new method, the test results showed that the method was reliability and accurate. The method has been used for the determination of trace barium in environmental samples and in water of Yellow River. The detection limit for Ba was 2.1 x 10(-12) g and the relative standard deviation(RSD) was 5.4% for 15 ng.mL-1 Ba. PMID:12940053

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Monitoring of Pd in airborne particulates by solid sampling high-resolution continuum source electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Atilgan, Semin; Akman, Suleyman; Baysal, Asli; Bakircioglu, Yasemin; Szigeti, Tamás; Óvári, Mihály; Záray, Gyula

    2012-04-01

    An analytical method has been developed for determination of palladium in PM2.5 fractions of urban airborne particulate matter by solid sampling high-resolution continuum source electrothermal atomic absorption spectrometry. For the optimization of the experimental conditions, a road dust certified reference material (BCR-723) was used. The influence of pyrolysis and atomization temperatures, the amount of sample introduced into the graphite furnace and the addition of acids, surfactants and modifiers on the analytical signal of Pd were investigated. The limit of detection, calculated based on three times the standard deviations of analytical signals obtained during the atomization of 10 blank filter pieces, was 0.07 pg/m3. Since the amount of solid certified reference material introduced into the graphite furnace was about 50-2000 times lower than those required in order to obtain the certified value, the precision was relatively poor. This analytical method was applied for investigation of urban airborne particulate matter collected onto quartz fiber filters by high-volume aerosol samplers in the city center of Istanbul (Turkey) and Budapest (Hungary). The measured Pd concentrations changed in the range of 0.22-0.64 and 0.25-0.86 pg/m3 in Istanbul and Budapest, respectively.

  5. Radiation Effects in Graphite

    SciTech Connect

    Burchell, Timothy D

    2012-01-01

    The requirements for a solid moderator are reviewed and the reasons that graphite has become the solid moderator of choice discussed. The manufacture and properties of some currently available near-isotropic and isotropic grades are described. The major features of a graphite moderated reactors are briefly outlined. Displacement damage and the induced structural and dimensional changes in graphite are described. Recent characterization work on nano-carbons and oriented pyrolytic graphites that have shed new light on graphite defect structures are reviewed, and the effect of irradiation temperature on the defect structures is highlighted. Changes in the physical properties of nuclear graphite caused by neutron irradiation are reported. Finally, the importance of irradiation induced creep is presented, along with current models and their deficiencies.

  6. 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).

  7. 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.

  8. Fuel stoker and furnace

    SciTech Connect

    Schafer, T.L.; Schafer, G.L.; Swett, H.D.

    1984-02-14

    A furnace having a primary heat exchange unit also providing a combustion chamber, a secondary heat exchange unit connected by an upper crossover conduit to the primary heat exchange unit, and a tertiary heat exchange unit connected by a lower V-shaped crossover conduit to the secondary heat exchange unit. A third crossover conduit connects the V-shaped crossover conduit with the primary heat exchange unit. Vibrating means are provided between the secondary and tertiary heat exchange units to vibrate the walls thereof and dislodge clinging fly ash so that it falls into the V-shaped crossover conduit for removal by the screw conveyor. A burner assembly of a furnace includes a combustion air housing carrying a circular, stationary grate with an annular valley for carrying fuel during combustion. A central opening is connected to a fuel conveyor for introduction of fuel to the grate through the lower portion of the housing. Combustion air introduction conduits on the housing are remote from the fuel introduction passages and introduce air under pressure at the lower portion of the grate. An agitator and discharge ring is provided on the grate and is rotated on the grate by a suitable drive sprocket mechanism to agitate the fuel for more complete burning thereof and to remove burned ash. A horizontal burner plate is supported by a plurality of legs connected to the agitator and discharge ring over the grate to promote more complete combustion of the fuel.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Modelling of furnaces and combustors

    SciTech Connect

    Kahil, E.E.

    1985-01-01

    This book presents an account of the art of modelling for heat transfer and fluid flows in furnaces and combustors. After describing the different types of furnace flows, the author deals with the conservation equations. The different turbulence modelling assumptions, the more complicated problem of turbulent combustion modelling, and various types of turbulent flames are also described and reviewed, with appropriate models being assigned.

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. Challenges in Melt Furnace Tests

    NASA Astrophysics Data System (ADS)

    Belt, Cynthia

    2014-09-01

    Measurement is a critical part of running a cast house. Key performance indicators such as energy intensity, production (or melt rate), downtime (or OEE), and melt loss must all be understood and monitored on a weekly or monthly basis. Continuous process variables such as bath temperature, flue temperature, and furnace pressure should be used to control the furnace systems along with storing the values in databases for later analysis. While using measurement to track furnace performance over time is important, there is also a time and place for short-term tests.

  6. Mercury in dumped blast furnace sludge

    NASA Astrophysics Data System (ADS)

    Földi, Corinna

    2014-05-01

    Blast furnace sludge (BFS) is a waste generated in the production of pig iron and was dumped in sedimentation ponds. As these wastes often contain high contents of zinc, lead, cadmium, and arsenic, significant hazards to environmental surroundings may arise from former BFS 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 (coke, iron ores, and additives such as olivine, bauxite, ilmenite and gravels) revealed Hg contents from 0.015 to 0.093 mg kg-1. In comparison, the Hg content of BFS varied between 0.006 and 20.8 mg kg-1 with a median of 1.63 mg kg-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. Consequently, BFS is a mercury-containing waste and dumped BFS should be regarded as potentially mercury-contaminated sites.

  7. 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

  8. Role of Nuclear Grade Graphite in Oxidation in Modular HTGRs

    SciTech Connect

    Willaim Windes; G. Strydom; J. Kane; R. Smith

    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.

  9. Glass Furnace Model Version 2

    Energy Science and Technology Software Center (ESTSC)

    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

  10. Laser nanoablation of graphite

    NASA Astrophysics Data System (ADS)

    Frolov, V. D.; Pivovarov, P. A.; Zavedeeev, E. V.; Komlenok, M. S.; Kononenko, V. V.; Konov, V. I.

    2014-01-01

    Experimental data on laser ablation of highly oriented pyrolitic graphite by nanosecond pulsed UV ( nm) and green ( nm) lasers are presented. It was found that below graphite vaporization threshold 1 J/cm, the nanoablation regime can be realized with material removal rates as low as 10 nm/pulse. The difference between physical (vaporization) and physical-chemical (heating + oxidation) ablation regimes is discussed. Special attention is paid to the influence of laser fluence and pulse number on ablation kinetics. Possibility of laser-induced graphite surface nanostructuring has been demonstrated. Combination of tightly focused laser beam and sharp tip of scanning probe microscope was applied to improve material nanoablation.

  11. 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.

  12. 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)

  13. 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.

  14. 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).

  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. 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. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. On crucible effects during the growth of cadmium zinc telluride in an electrodynamic gradient freeze furnace

    NASA Astrophysics Data System (ADS)

    Gasperino, David; Bliss, Mary; Jones, Kelly; Lynn, Kelvin; Derby, Jeffrey J.

    2009-04-01

    The CrysMAS code of the Crystal Growth Laboratory, Fraunhofer IISB, is applied to reveal conditions occurring in electrodynamic gradient freeze furnaces during the growth of cadmium zinc telluride crystals. Of particular interest are heat transfer and growth conditions associated with crucibles of different design, one constructed of graphite and the other of pyrolytic boron nitride (PBN). Under identical furnace set-point schedules, the two systems exhibit very different behaviors. Specifically, the temperature field through the cone region of the PBN crucible displays much steeper axial thermal profiles and promotes convex solid-liquid interface shapes (rather than the concave shapes computed for the graphite crucible). Both systems exhibit a concave interface during growth through the cylindrical part of the crucible. However, the axial thermal profile through the graphite-crucible charge is considerably more offset from the set-point profile of the furnace due to significant axial heat flows through the crucible walls. These factors argue in favor of the PBN crucible; however, comparatively larger radial gradients in the PBN system could lead to higher dislocation levels.

  3. On crucible effects during the growth of cadmium zinc telluride in an electrodynamic gradient freeze furnace

    SciTech Connect

    Gasperino, David; Bliss, Mary; Jones, Kelly A.; Lynn, Kelvin G.; Derby, Jeffrey

    2009-01-04

    The CrysMAS code of the Crystal Growth Laboratory, Fraunhofer IISB, is applied to reveal conditions occurring in electrodynamic gradient freeze furnaces during the growth of cadmium zinc telluride crystals. Of particular interest are heat transfer and growth conditions associated with crucibles of different design, one constructed of graphite and the other of pyrolytic boron nitride (PBN). Under identical furnace set-point schedules, the PBN system exhibits very different heat transfer through the cone region of the crucible, resulting in steeper axial thermal profiles and convex solid-interface shapes (rather than the concave shapes computed for the graphite crucible). Both systems exhibit a concave interface during growth through the cylindrical part of the crucible; however, the axial thermal profile through the contents of the graphite crucible is considerably more offset from the set-point profile of the furnace due to the large axial flows of heat through the crucible walls. These conditions argue for advantage to the PBN system; however, comparatively larger radial gradients in the PBN system could lead to higher dislocation levels.

  4. 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.

  5. Floor furnace burns to children.

    PubMed

    Berger, L R; Kalishman, S

    1983-01-01

    Three children with grid-like second-degree burns of their extremities from contact with floor furnace registers prompted an examination of this thermal hazard. Average temperature of the gratings was 294 degrees F (146 degrees C), with a range of 180 degrees to 375 degrees F (82.2 degrees to 191 degrees C). All of the furnaces tested were positioned at the entrance to bedrooms and had so little clearance that it was impossible to walk around them without contact with their surface. Infants and toddlers are at particular risk: 1 or 2 seconds of exposure would be expected to produce a serious burn. Suggestions for preventing burns from floor furnaces include turning them off when young children are at home; installing barrier gates to prevent children from coming in contact with the registers; and developing a surface coating or replacement grate with less hazardous thermal properties. PMID:6848984

  6. Interpretation of Scanning Tunneling Microscopy Images of Graphite.

    NASA Astrophysics Data System (ADS)

    Mizes, Howard Albert

    This dissertation analyzes scanning tunneling microscopy (STM) images of graphite. Graphite is an important substrate for molecular imaging and nanometer lithography. Because it is a layered structure with a simple unit cell, its electronic structure can be described simply using tight binding theory. More interestingly, the charge density at the Fermi level, which is the quantity that the STM probes, is well approximated by the six leading Fourier components. The effect of multiple atomic tips on the STM images of graphite can be predicted using the three sine wave description. Both the varying asymmetry between the two inequivalent atoms, and the loss of three fold symmetry observed in experimental images, can be attributed to differing tip configurations. The existence of multiple atomic tips is directly confirmed by the observation of moire patterns occurring near grain boundaries. Physisorbed and intercalated atoms and molecules will produce weak perturbations in the electronic structure of the graphite. These perturbations can be measured with the STM as localized changes in the tunneling current, and appear as bright areas in STM gray-scale images. The dependence of the brightness with scanning height is calculated and can be used as a measure to help identify the atom or molecule. Chemisorbed atoms and molecules will produce a stronger long-range perturbation in the electronic structure of the graphite. It is shown that any strong perturbation should give rise to oscillations in the Fermi level charge density with a wavelength surd{3} times that of the graphite lattice. The intensity of the oscillations and their symmetry about the defect is shown to be a probe of the geometry of the bonding to the surface. Predicted images that arise from multiple tips, along with those arising from physisorbed and chemisorbed atoms, are compared with available experiments.

  7. 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.

  8. 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.

  9. Interlayer interactions in graphites

    PubMed Central

    Chen, Xiaobin; Tian, Fuyang; Persson, Clas; Duan, Wenhui; Chen, Nan-xian

    2013-01-01

    Based on ab initio calculations of both the ABC- and AB-stacked graphites, interlayer potentials (i.e., graphene-graphene interaction) are obtained as a function of the interlayer spacing using a modified Möbius inversion method, and are used to calculate basic physical properties of graphite. Excellent consistency is observed between the calculated and experimental phonon dispersions of AB-stacked graphite, showing the validity of the interlayer potentials. More importantly, layer-related properties for nonideal structures (e.g., the exfoliation energy, cleave energy, stacking fault energy, surface energy, etc.) can be easily predicted from the interlayer potentials, which promise to be extremely efficient and helpful in studying van der Waals structures. PMID:24192753

  10. 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.

  11. Interlayer interactions in graphites

    NASA Astrophysics Data System (ADS)

    Chen, Xiaobin; Tian, Fuyang; Persson, Clas; Duan, Wenhui; Chen, Nan-Xian

    2013-11-01

    Based on ab initio calculations of both the ABC- and AB-stacked graphites, interlayer potentials (i.e., graphene-graphene interaction) are obtained as a function of the interlayer spacing using a modified Möbius inversion method, and are used to calculate basic physical properties of graphite. Excellent consistency is observed between the calculated and experimental phonon dispersions of AB-stacked graphite, showing the validity of the interlayer potentials. More importantly, layer-related properties for nonideal structures (e.g., the exfoliation energy, cleave energy, stacking fault energy, surface energy, etc.) can be easily predicted from the interlayer potentials, which promise to be extremely efficient and helpful in studying van der Waals structures.

  12. Lightweight graphite/polyimide panels

    NASA Technical Reports Server (NTRS)

    Poesch, J. G.; Merlette, J. B.

    1973-01-01

    Panels are constructed of honeycombed polyimide/graphite core covered with thin face sheet of same material. Fabrication is based on extension of thin-gage graphite technology and modification of glass filament polyimide honeycomb techniques.

  13. Strength of modified carbon-graphite composites

    SciTech Connect

    Bolotina, K.S.; Shchugorev, V.N.

    1995-01-01

    Composite materials are being more and more widely used in the nontraditional power generation fields, particularly in powerplants using the ecologically clean energy sources (solar, wind, and tidal plants). The less expensive composites are preferred. Requirements of a functional nature are usually imposed on the composites: high (or low) thermal conductivity and high electroconductive (or electroinsulative) properties. At the same time, many powerplant components act as load-carrying structures and require analysis of their mechnical reliability and service life. Because of the considerable intrinsic mass (for large structures) and the wind, snow, and wave loads with long periods of operation, the mechnical analysis is a critical part of the design process. Various modification techniques are used to obtain materials with the required combination of mechanical, thermophysical, and electrical properties on the basis of the inexpensive composites. These techniques include modification of the properties of the binders by selecting the curing technique and introducing additives to the binder, and also the use of composites containing a quite high percentage of modifiers - metallic powders, ferromagnetics, ferroelectrics, and so on. The authors have studied the influence of the modifiers on the mechanical properties of the carbon-graphite composites that are created on the basis of powdered carbon-graphites and phenolformaldehyde resins. Such composites are already used in the heat engineering field. The carbon-graphite materials are obtained from a mixture of pulverized coke and coal tar with subsequent pressing into rod or blocks, which are sintered at 1200{degrees}C in air-free furnaces.

  14. 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

  15. 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.

  16. 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.

  17. 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…

  18. 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;...

  19. 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.…

  20. 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;...

  1. 10 CFR 429.18 - Residential furnaces.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 3 2013-01-01 2013-01-01 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;...

  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-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.

  4. (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.

  5. 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)

  6. Graphite criteria peer review

    SciTech Connect

    1986-09-01

    This report documents a review of the stress criteria proposed for the graphite components of the modular high temperature gas-cooled reactor (MHTGR) core. The review was conducted by a panel of six independent consultants, chosen for their expertise over a range of relevant disciplines.

  7. 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.

  8. 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.

  9. 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.

  10. Lamellar nanostructures of silicon heterogeneously solidified on graphite sheets

    NASA Astrophysics Data System (ADS)

    Li, Y. F.; Yu, H. Q.; Li, H.; Liew, K. M.; Liu, X. F.

    2010-04-01

    Molecular dynamics simulations are performed to examine the heterogeneous solidification of silicon on foreign graphite sheets (GSs). It clearly indicates that silicon atoms are concentrated to form hierarchical nanostructures composed of equidistant nanolayers. Graphite plate induces strong ordered liquid silicon layers near the surfaces of GSs. This study suggests ordered liquid layers should be the early form of the solid crystal, which determine the subsequent nucleation. The confined nanospace between two GSs favors the solidification and results in the decrease in the distance between layers. GSs make silicon atoms solidify into an hcp crystal rather than fcc structure.

  11. 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.

  12. Intercalating oleylamines in graphite oxide.

    PubMed

    Yang, Kaikun; Liang, Si; Zou, Lianfeng; Huang, Liwei; Park, Cheol; Zhu, Lisheng; Fang, Jiye; Fu, Qiang; Wang, Howard

    2012-02-01

    Graphite oxide has been synthesized from raw graphite particles and been treated with various mass amounts of oleylamine as intercalants to form intercalation compounds. X-ray diffraction patterns reveal that the inter-sheet distances strongly depend on the graphite oxide to oleylamine mass ratios. The equilibrium-like behavior implies diffusion-dominated oleylamine adsorption on graphite oxide in solution and excluded volume intercalations among oleylamine-adsorbed graphite oxide during restacking. The intercalation compounds are soluble in organic solvents, and their applications in the fabrication of transparent and conductive coatings have been demonstrated. PMID:22229856

  13. 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.

  14. The transformation of graphitic onions to diamond under electron irradiation

    SciTech Connect

    Banhart, F.

    1997-04-01

    Diamond crystals nucleate in the centers of spherical concentric-shell graphitic particles where high pressure prevails under electron irradiation at specimen temperatures above 900 K. The diamond crystals grow under further irradiation until the graphitic particles have wholly transformed to diamond. Hence, the conversion of the graphitic structure to diamond starts at high pressure and proceeds at decreasing, possibly even at zero, pressure. The experiment is carried out in a transmission electron microscope which enables us to monitor this phase transformation {ital in situ} on an atomic scale. It is shown that the graphite/diamond system under electron irradiation is highly dissipative. This suggests that the phase transformation at low pressure occurs via self-organization under nonequilibrium conditions. {copyright} {ital 1997 American Institute of Physics.}

  15. 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.

  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. 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).

  18. 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

  19. Graphite Polyhedral Crystals

    NASA Astrophysics Data System (ADS)

    Gogotsi, Yury; Libera, Joseph A.; Kalashnikov, Nikolay; Yoshimura, Masahiro

    2000-10-01

    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.

  20. 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}

  1. Probing the helium-graphite interaction

    NASA Astrophysics Data System (ADS)

    Cole, Milton W.; Frankl, D. R.; Goodstein, David L.

    1981-04-01

    Two separate lines of investigation have recently converged to produce a highly detailed picture of the behavior of helium atoms physisorbed on graphite basal plane surfaces. Atomic beam scattering experiments on single crystals have yielded accurate values for the binding energies of several states for both 4He and 3He, as well as matrix elements of the largest Fourier component of the periodic part of the interaction potential. From these data, a complete three-dimensional description of the potential has been constructed, and the energy band structure of a helium atom moving in this potential calculated. At the same time, accurate thermodynamic measurements were made on submonolayer helium films adsorbed on Grafoil. The binding energy and low-coverage specific heat deduced from these measurements are in excellent agreement with those calculated from the band structures.

  2. 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.

  3. 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.

  4. 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)

  5. 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.

  6. 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.

  7. Energy aspects of a lead blast furnace

    NASA Astrophysics Data System (ADS)

    Cowperthwaite, Janice E.; Dugdale, Peter J.; Landry, Christian J. F.; R. Morris, David; Steward, Frank R.; Wilson, Timothy C. W.

    1980-06-01

    The energy effects accompanying the processing of the feed material to a lead blast furnace are considered in terms of a reversible model. Relative to this model the efficiencies of operating furnaces are found to be in the range 18 to 35 pct. The effects of the effluent gas CO2/CO ratio and temperature and oxygen enrichment of the blast air in the thermodynamic efficiency are quantified. Improvements in efficiency achieved in industrial furnaces as a result of oxygen enrichment of the blast air are substantially greater than those predicted. Mass and enthalpy balances on an industrial lead blast furnace are presented from which it is estimated that approximately 9 pct of the carbon charged to the furnace is lost due to the solution loss reaction in the upper regions of the furnace.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Heat exchanger using graphite foam

    SciTech Connect

    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.

  13. Graphite patterning in a controlled gas environment

    NASA Astrophysics Data System (ADS)

    Park, Joonkyu; Kim, K. B.; Park, Jun-Young; Choi, T.; Seo, Yongho

    2011-08-01

    Although a number of methods using scanning probe lithography to pattern graphene have already been introduced, the fabrication of real devices still faces limitations. We report graphite patterning using scanning probe lithography with control of the gas environment. Patterning processes using scanning probe lithography of graphite or graphene are normally performed in air because water molecules forming the meniscus between the tip and the sample mediate the etching reaction. This water meniscus, however, may prevent uniform patterning due to its strong surface tension or large contact angle on surfaces. To investigate this side effect of water, our experiment was performed in a chamber where the gas environment was controlled with methyl alcohol, oxygen or isopropanol gases. We found that methyl alcohol facilitates graphite etching, and a line width as narrow as 3 nm was achieved as methyl alcohol also contains an oxygen atom which gives rise to the required oxidation. Due to its low surface tension and highly adsorptive behavior, methyl alcohol has advantages for a narrow line width and high speed etching conditions.

  14. Nitrogen-promoted formation of graphite-like aggregations in SiC during neutron irradiation

    SciTech Connect

    Wang, P. F.; Ruan, Y. F.; Huang, L.; Zhu, W.

    2012-03-15

    The undoped and nitrogen-doped SiC bulk crystals irradiated with two neutron fluences were investigated by using confocal micro-Raman spectroscopy to analyze the effect of nitrogen impurity on irradiation damage. We found that the nitrogen impurity can promote the segregation of carbon atoms into graphite during heavy neutron irradiation, demonstrated by the presence of typical D and G graphite bands. Further experimental analysis indicated that the graphite-like aggregations uniformly distribute in SiC and possess much inferior thermal stability to crystalline graphite. The nucleation, namely generation of stable sp{sup 2} C=C configuration induced by nitrogen atoms, and growth during neutron irradiation can account for the formation of graphite-like aggregations.

  15. From Graphite to Graphene via Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Qi, Dejun

    The primary objective of this dissertation is to study both graphene on graphite and pristine freestanding grapheme using scanning tunneling microscopy (STM) and density functional theory (DFT) simulation technique. In the experiment part, good quality tungsten metalic tips for experiment were fabricated using our newly developed tip making setup. Then a series of measurements using a technique called electrostatic-manipulation scanning tunneling microscopy (EM-STM) of our own development were performed on a highly oriented pyrolytic graphite (HOPG) surface. The electrostatic interaction between the STM tip and the sample can be tuned to produce both reversible and irreversible large-scale movement of the graphite surface. Under this influence, atomic-resolution STM images reveal that a continuous electronic transition between two distinct patterns can be systematically controlled. DFT calculations reveal that this transition can be related to vertical displacements of the top layer of graphite relative to the bulk. Evidence for horizontal shifts in the top layer of graphite is also presented. Excellent agreement is found between experimental STM images and those simulated using DFT. In addition, the EM-STM technique was also used to controllably and reversibly pull freestanding graphene membranes up to 35 nm from their equilibrium height. Atomic-scale corrugation amplitudes 20 times larger than the STM electronic corrugation for graphene on a substrate were observed. The freestanding graphene membrane responds to a local attractive force created at the STM tip as a highly conductive yet flexible grounding plane with an elastic restoring force.

  16. Condensing furnaces: Lessons from a utility

    SciTech Connect

    Beers, J.

    1994-11-01

    for the last several years about 90% of the new natural gas furnaces installed in Wisconsin have been condensing furnaces and a number of lessons have been learned. If you avoid the common mistakes, condensing furnaces typically can deliver heating savings of 20-35 % assuming the old furnace was in the 60% AFUE range. This article describes the common mistakes and how to avoid them: outside air needed 100%; benefits of sealed combustion; follow the installation manual scrupulously; how to avoid potential problems; tips on venting.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Purification and preparation of graphite oxide from natural graphite

    NASA Astrophysics Data System (ADS)

    Panatarani, C.; Muthahhari, N.; Rianto, Anton; Joni, I. Made

    2016-03-01

    Graphite oxide has attracted much interest as a possible route for preparation of natural graphite in the large-scale production and manipulation of graphene as a material with extraordinary electronic properties. Graphite oxide was prepared by modified Hummers method from purified natural graphite sample from West Kalimantan. We demonstrated that natural graphite is well-purified by acid leaching method. The purified graphite was proceed for intercalating process by modifying Hummers method. The modification is on the reaction time and temperature of the intercalation process. The materials used in the intercalating process are H2SO4 and KMNO4. The purified natural graphite is analyzed by carbon content based on Loss on Ignition test. The thermo gravimetricanalysis and the Fouriertransform infrared spectroscopy are performed to investigate the oxidation results of the obtained GO which is indicated by the existence of functional groups. In addition, the X-ray diffraction and energy dispersive X-ray spectroscopy are also applied to characterize respectively for the crystal structure and elemental analysis. The results confirmed that natural graphite samples with 68% carbon content was purified into 97.68 % carbon content. While the intercalation process formed a formation of functional groups in the obtained GO. The results show that the temperature and reaction times have improved the efficiency of the oxidation process. It is concluded that these method could be considered as an important route for large-scale production of graphene.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Ionic Graphitization of Ultrathin Films of Ionic Compounds.

    PubMed

    Kvashnin, A G; Pashkin, E Y; Yakobson, B I; Sorokin, P B

    2016-07-21

    On the basis of ab initio density functional calculations, we performed a comprehensive investigation of the general graphitization tendency in rocksalt-type structures. In this paper, we determine the critical slab thickness for a range of ionic cubic crystal systems, below which a spontaneous conversion from a cubic to a layered graphitic-like structure occurs. This conversion is driven by surface energy reduction. Using only fundamental parameters of the compounds such as the Allen electronegativity and ionic radius of the metal atom, we also develop an analytical relation to estimate the critical number of layers. PMID:27333810

  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. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  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. 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

  20. 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

  1. 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

  2. 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

  3. Electronic structure of graphite oxide

    NASA Astrophysics Data System (ADS)

    Jeong, Hae Kyung; Yang, Cheolsoo; Kim, Bong Soo; Kim, Ki-Jeong

    2011-03-01

    We have investigated the electronic structure of graphite oxide by photoelectron spectroscopy at the Pohang Accelerator Laboratory, Korea. The typical sp 2 hybridization states found in graphite were also seen in graphite oxide. However, the π state disappeared near the Fermi level because of bonding between the π and oxygen-related states originating from graphite oxide, indicating electron transfer from graphite to oxygen and resulting in a downward shift of the highest occupied molecular orbital (HOMO) state to higher binding energies. The band gap opening increased to about 1.8 eV, and additional oxygen-related peaks were observed at 8.5 and 27 eV. This research was supported by the Basic Science Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Education, Science and Technology (2010-0004592), and partly by the MEST (2009-0087138). Experiments at the PLS were supported in part by POSTECH and MEST.

  4. 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.

  5. 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.

  6. 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).

  7. 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.

  8. Developmental testing of a programmable multizone furnace

    NASA Technical Reports Server (NTRS)

    Ting, E. Y.; Larson, D. J., Jr.

    1986-01-01

    A multizone furnace was evaluated for its potential utilization for process experimentation on board the Space Shuttle. A temperature gradient can be created through the use of a series of connected temperature zones and can be translated by the coordinated sequencing of zone temperatures. The Bridgman-Stockbarger thermal configuration for directional solidification was implemented so that neither the sample nor furnace was translated. The thermal behavior of the furnace was measured and characterized. Limitations due to both thermal and electronic (computer) factors are identified. The results indicate that the multizone design is limited to low temperature gradients because of the indirect furnace-to-sample thermal coupling needed to blend the discrete thermal zones. The multizone furnace design inherently consumes more power than a similar (two temperature) conventional Bridgman type directional solidification furnace because every zone must be capable of the high cooling rates needed to produce the maximum desired temperature drop. Typical achievable static temperature gradients for the furnace tested were between 6 and 75 C/in. The maximum gradient velocity was approximately 10 in./hr. Several aspects of the tested system could be improved, but the dependence of the multizone design on high heat loss will limit Space Shuttle applications in the form tested unless additional power is available. The multizone furnace offers great flexibility but requires a high level of operator understanding for full advantage to be obtained.

  9. Refractory of Furnaces to Reduce Environmental Impact

    NASA Astrophysics Data System (ADS)

    Hanzawa, Shigeru

    2011-10-01

    The energy load of furnaces used in the manufacturing process of ceramics is quite large. Most of the environmental impact of ceramics manufacturing is due to the CO2 produced from this high energy load. To improve this situation, R&D has focused on furnace systems and techniques of control in order to reduce energy load. Since furnaces are comprised of refractory, consideration of their mechanical and thermal characteristics is important. Herein are described several refractory types which were chosen through comparison of the characteristics which contribute to heat capacity reduction, heat insulating reinforcement and high emissivity, thereby improving thermal radiation heat transfer efficiency to the ceramic articles. One selected refractory material which will reduce the environmental impact of a furnace, chosen considering low heat capacity and high emissivity characteristics, is SiC. In this study, thermal radiation heat transfer efficiency improvement and its effect on ceramic articles in the furnace and oxidation behaviour were investigated at 1700K. A high density SiC refractory, built into the furnace at construction, has relatively high oxidation durability and has the ability to reduce environmental impact-CO2 by 10 percent by decreasing the furnace's energy load. However, new oxidation prevention techniques for SiC will be necessary for long-term use in industrial furnaces, because passive to active oxidation transition behaviour of commercial SiC refractory is coming to close ideal.

  10. ANALYSIS OF EMISSIONS FROM RESIDENTIAL OIL FURNACES

    EPA Science Inventory

    The paper gives results of a series of emission tests on a residential oil furnace to determine emissions from two types of burners. umber of analyses were performed on the emissions, including total mass, filterable particulate, total oil furnaces tested by the EPA in Roanoke, V...

  11. 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).

  12. Quantum modelling of hydrogen chemisorption on graphene and graphite

    SciTech Connect

    Karlický, František; Lepetit, Bruno Lemoine, Didier

    2014-03-28

    The chemisorption of hydrogen on graphene or graphite is studied within a quantum formalism involving a subsystem coupled to a phonon bath. The subsystem includes the hydrogen atom approaching the surface perpendicularly right on top of a carbon atom which puckers out of the surface. The bath includes the acoustic and optical phonon modes vibrating perpendicularly to the surface. Couplings between subsystem and bath are obtained with a periodic density functional theory calculation. Trapping probabilities are obtained as a function of the hydrogen atom kinetic energy. These results are discussed in the light of the experimental hydrogenation studies performed on graphite by Zecho et al. [J. Chem. Phys. 117, 8486 (2002)] and on graphene by Haberer et al. [Adv. Mater. 23, 4497 (2011)].

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. GENERAL VIEW OF EAST (FRONT) OF DOUBLE FURNACE FROM ACROSS ...

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

    GENERAL VIEW OF EAST (FRONT) OF DOUBLE FURNACE FROM ACROSS THE CREEK, LOOKING SOUTHWEST. - Tannehill Furnace, 12632 Confederate Parkway, Tannehill Historical State Park, Bucksville, Tuscaloosa County, AL

  18. Soft X-Ray Absorption Spectroscopy of High-Abrasion-Furnace Carbon Black

    NASA Astrophysics Data System (ADS)

    Muramatsu, Yasuji; Harada, Ryusuke; Gullikson, Eric M.

    2007-02-01

    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 π* and σ* 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 π* peak. The lower-energy peak, denoted as the "pre-peak", in the subtracted spectra and the π*/σ* 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 π*/σ* ratio reflect the local graphitic structure of carbon black.

  19. Hypervelocity impacts into graphite

    NASA Astrophysics Data System (ADS)

    Latunde-Dada, S.; Cheesman, C.; Day, D.; Harrison, W.; Price, S.

    2011-03-01

    Studies have been conducted into the characterisation of the behaviour of commercial graphite (brittle) when subjected to hypervelocity impacts by a range of projectiles. The experiments were conducted with a two-stage gas gun capable of launching projectiles of differing density and strength to speeds of about 6kms-1 at right angles into target plates. The damage caused is quantified by measurements of the crater depth and diameters. From the experimental data collected, scaling laws were derived which correlate the crater dimensions to the velocity and the density of the projectile. It was found that for moderate projectile densities the crater dimensions obey the '2/3 power law' which applies to ductile materials.

  20. Metastable Frenkel pair defect in graphite: source of Wigner energy?

    PubMed

    Ewels, C P; Telling, R H; El-Barbary, A A; Heggie, M I; Briddon, P R

    2003-07-11

    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 2.9 eV more stable than its isolated constituents, still has a formation energy of 10.8 eV. The barrier to recombination to perfect graphite is calculated to be 1.3 eV, consistent with the experimental first Wigner energy release peak at 1.38 eV. We expect similar defects to form in carbon nanostructures such as nanotubes, nested fullerenes, and onions under irradiation. PMID:12906489

  1. van der Waals Heteroepitaxy of Germanene Islands on Graphite.

    PubMed

    Persichetti, Luca; Jardali, Fatme; Vach, Holger; Sgarlata, Anna; Berbezier, Isabelle; Crescenzi, Maurizio De; Balzarotti, Adalberto

    2016-08-18

    We fabricated flat, two-dimensional germanium sheets showing a honeycomb lattice that matches that of germanene by depositing submonolayers of Ge on graphite at room temperature and subsequent annealing to 350 °C. Scanning tunneling microscopy shows that the germanene islands have a small buckling with no atomic reconstruction and does not give any hints for alloy formation and hybridization with the substrate. Our density functional theory calculations of the structural properties agree well with our experimental findings and indicate that the germanene sheet interacts only weakly with the substrate underneath. Our band structure calculations confirm that the Dirac cone of free-standing germanene is preserved for layers supported on graphite. The germanene islands show a small but characteristic charge transfer with the graphite substrate which is predicted by our ab initio simulations in excellent agreement with scanning tunneling spectroscopy measurements. PMID:27487453

  2. 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.

  3. 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.

  4. Optical properties of graphite oxide and reduced graphite oxide

    NASA Astrophysics Data System (ADS)

    Jung, Eilho; Lee, Seokbae; Roh, Seulki; Hwang, Eunhee; Lee, Junghyun; Lee, Hyoyoung; Hwang, Jungseek

    2014-07-01

    We studied the optical properties of a graphite oxide and a reduced graphite oxide by using the optical spectroscopic technique. The graphite oxide does not show a finite dc conductivity and has several characteristic absorption modes in the mid-infrared region, caused by an epoxide functional group and hydroxyl and carboxyl moieties in the mid-infrared range. The reduced graphite oxide shows a Drude-like response in the far-infrared region and the estimated dc conductivity and electric mobility are around 200 Ω-1cm-1 and ˜100 cm2V-1s-1, respectively. We found that the optical conductivity cannot be fitted with a simple Drude model, which indicates that the charge carriers are correlated. We applied an extended Drude model and obtained the optical scattering rate and the optical effective mass. We found that the optical effective mass can carry information of both the enhanced mass by correlation and the electronic band structure.

  5. Graphitized needle cokes and natural graphites for lithium intercalation

    SciTech Connect

    Tran, T.D.; Spellman, L.M.; Pekala, R.W.; Goldberger, W.M.; Kinoshita, K.

    1996-05-10

    This paper examined effects of heat treatment and milling (before or after heat treatment) on the (electrochemical) intercalating ability of needle petroleum coke; natural graphite particles are included for comparison. 1 tab, 4 figs, 7 refs.

  6. 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

  7. 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

  8. Atomization of a liquid by a spray nozzle

    NASA Astrophysics Data System (ADS)

    Kutateladze, S. S.

    1980-02-01

    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.

  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. Reheat furnace upgrade results in production increase

    SciTech Connect

    Burns, A.H.; Fuhrman, F.L.

    1997-02-01

    This project is a unique example of the technique of high-intensity convective heating for generating significant material preheating that can be used to increase furnace production rate. The mathematical model predicted a production increase of 17%. The furnace has demonstrated a 22% higher sustained production rate. Oxidation rates have been gradually reduced and will be improved further by the installation of level 2 controls. The burner systems have proved to be reliable in a harsh operating environment. There has been a small improvement in the specific fuel consumption. In the case of a top-fired reheat furnace, convective pre-heating installed at the charge end of the furnace will result in a significant increase in production rate. The static thermal model developed for this project is a reliable tool for the prediction of performance of the modified furnace. The use of the high-velocity burners in the mixing zone was an effective substitute for the customary baffle wall. The installation had the benefit of preventing over-pressurization of the furnace discharge doors and enabled the operator to achieve a considerable improvement in pressure control. In addition, the removal of the baffle wall eliminated the shadowing effect where the incoming load is shaded from radiation from the heating zone. Additional turbulence in the mixing zone also had a significant impact by increasing the amount of heat removed from flue gas before it is vented from the furnace.

  11. 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.

  12. Mineral resource of the month: graphite

    USGS Publications Warehouse

    U.S. Geological Survey

    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. 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.

  14. 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.

  15. Multipurpose electroslag remelting furnace for modern energy and heavy engineering industry

    NASA Astrophysics Data System (ADS)

    Dub, A. V.; Dub, V. S.; Kriger, Yu. N.; Levkov, L. Ya.; Shurygin, D. A.; Kissel'man, M. A.; Nekhamin, C. M.; Chernyak, A. I.; Bessonov, A. V.; Kamantsev, S. V.; Sokolov, S. O.

    2012-12-01

    In 2011, a unique complex based on a multipurpose unit-type electroslag remelting (ESR) furnace is created to meet the demand for large high-quality solid and hollow billets for the products of power, atomic, petrochemical, and heavy machine engineering. This complex has modern low-frequency power supplies with a new control level that ensure a high homogeneity and quality of the billets and an increase in the engineering-and-economical performance of the production. A unique pilot ESR furnace is erected to adjust technological conditions and the main control system elements.

  16. 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.

  17. Method development for the determination of fluorine in water samples via the molecular absorption of strontium monofluoride formed in an electrothermal atomizer

    NASA Astrophysics Data System (ADS)

    Ozbek, Nil; Akman, Suleyman

    The presence of fluorine (F) was detected via the rotational molecular absorption line of diatomic strontium-monofluoride (SrF) generated in the gas phase at 651.187 nm using high-resolution continuum source electrothermal atomic absorption spectrometry. Upon the addition of excess strontium (Sr) as the nitrate, the fluorine in the sample was converted to SrF in the gas phase of a graphite furnace. The effects on the accuracy, precision and sensitivity of variables such as the SrF wavelength, graphite furnace program, amount of Sr, coating of the graphite tube and platform with Zr and Ir and the use of a modifier were investigated and optimized. It was determined that there was no need to use a modifier or to cover the platform/tubes with Zr or Ir. Fluorine concentrations in various water samples (certified waste water, tap water, drinking water and mineral water) were determined using 20 μg of Sr as the molecule-forming reagent and applying a maximum pyrolysis temperature of 800 °C and a molecule-forming temperature of 2200 °C with a heating rate of 2000 °C s- 1. Good linearity was maintained up to 0.1 μg of F. The accuracy and precision of the method were tested by analyzing certified reference wastewater. The results were in good agreement with certified values, and the precision was satisfactory (RSD < 10%). The limit of detection and the characteristic mass for the method were 0.36 ng and 0.55 ng, respectively. Finally, the fluorine concentrations in several drinking water and mineral water samples taken from the market were determined. The results were in good agreement with the values supplied by the producers. No significant differences were found between the results from the linear calibration and standard addition techniques. The method was determined to be simple, fast, accurate and sensitive.

  18. 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

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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)

  6. A novel nanoporous graphitic composite.

    PubMed

    Wang, Zheng-Ming; Hoshinoo, Kumiko; Xue, M; Kanoh, Hirofumi; Ooi, Kenta

    2002-08-21

    A novel nanoporous composite containing micrographitic carbon layers is synthesized by preliminarily expanding the interlayer of an oxidized product of graphite using surfactant, followed by Si bridging/pillaring, and carbonization. PMID:12211211

  7. 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.

  8. Simultaneous growth of diamond and nanostructured graphite thin films by hot-filament chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Ali, M.; Ürgen, M.

    2012-01-01

    Diamond and graphite films on silicon wafer were simultaneously synthesized at 850 °C without any additional catalyst. The synthesis was achieved in hot-filament chemical vapor deposition reactor by changing distance among filaments in traditional gas mixture. The inter-wire distance for diamond and graphite deposition was kept 5 and 15 mm, whereas kept constant from the substrate. The Raman spectroscopic analyses show that film deposited at 5 mm is good quality diamond and at 15 mm is nanostructured graphite and respective growths confirm by scanning auger electron microscopy. The scanning electron microscope results exhibit that black soot graphite is composed of needle-like nanostructures, whereas diamond with pyramidal featured structure. Transformation of diamond into graphite mainly attributes lacking in atomic hydrogen. The present study develops new trend in the field of carbon based coatings, where single substrate incorporate dual application can be utilized.

  9. 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.

  10. 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.

  11. Enhancement of oxidation resistance of graphite foams by polymer derived-silicon carbide coating for concentrated solar power applications

    DOE PAGESBeta

    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

  12. 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.

  13. Electronic applications of flexible graphite

    NASA Astrophysics Data System (ADS)

    Luo, Xiangcheng; Chugh, Randy; Biller, Brian C.; Hoi, Yie Meng; Chung, D. D. L.

    2002-05-01

    Flexible graphite is effective for electronic applications, specifically electromagnetic interference (EMI) gasketing, resistive heating, thermoelectric-energy generation, and heat dissipation. It is comparable to or better than conductive-filled silicone materials for EMI gasketing. The shielding effectiveness reaches 125 dB. Flexible graphite as a heating element provides temperatures up to 980°C, response half-time down to 4 sec, and heat output at 60 sec up to 5600 J. The through-thickness, absolute thermoelectric power of flexible graphite is -2.6 µV/°C. Flexible graphite is effective as a thermal-interface material if the thickness is low (0.13 mm), the density is low (1.1 g/cm3), and the contact pressure is high (11.1 MPa). These applications make use of the flexibility and compliance of flexible graphite, in addition to its electronic and thermal behavior. Compliance is particularly important for the use of flexible graphite as interface materials, whether the interface is electrom agnetic, thermoelectric, or thermal.

  14. 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...

  15. 46 CFR 164.009-13 - Furnace calibration.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 6 2012-10-01 2012-10-01 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...

  16. 46 CFR 164.009-13 - Furnace calibration.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 6 2010-10-01 2010-10-01 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 164.009-11 - Furnace apparatus.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 6 2010-10-01 2010-10-01 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,...

  18. 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...

  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. 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

  1. 20. Detail, Furnace A, shows the drill used to tap ...

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

    20. Detail, Furnace A, shows the drill used to tap the furnace (at center left) and the 'mud gun' used to close it up with a clay plug (at lower right). Metal chute at center (next to drill) was used to clean out furnace prior to its abandonment. - Central Furnaces, 2650 Broadway, east bank of Cuyahoga River, Cleveland, Cuyahoga County, OH

  2. 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,...

  3. 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,...

  4. 46 CFR 164.009-11 - Furnace apparatus.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 6 2011-10-01 2011-10-01 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,...

  5. 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...

  6. Toxic-Waste Disposal by Drain-in-Furnace Technique

    NASA Technical Reports Server (NTRS)

    Compton, L. E.; Stephens, J. B.; Moynihan, P. I.; Houseman, J.; Kalvinskas, J. J.

    1986-01-01

    Compact furnace moved from site to site. Toxic industrial waste destroyed using furnace concept developed for disposal of toxic munitions. Toxic waste drained into furnace where incinerated immediately. In furnace toxic agent rapidly drained and destroyed in small combustion chamber between upper and lower layers of hot ceramic balls

  7. Structural ceramics containing electric arc furnace dust.

    PubMed

    Stathopoulos, V N; Papandreou, A; Kanellopoulou, D; Stournaras, C J

    2013-11-15

    In the present work the stabilization of electric arc furnace dust EAFD waste in structural clay ceramics was investigated. EAFD was collected over eleven production days. The collected waste was characterized for its chemical composition by Flame Atomic Absorption Spectroscopy. By powder XRD the crystal structure was studied while the fineness of the material was determined by a laser particle size analyzer. The environmental characterization was carried out by testing the dust according to EN12457 standard. Zn, Pb and Cd were leaching from the sample in significant amounts. The objective of this study is to investigate the stabilization properties of EAFD/clay ceramic structures and the potential of EAFD utilization into structural ceramics production (blocks). Mixtures of clay with 2.5% and 5% EAFD content were studied by TG/DTA, XRD, SEM, EN12457 standard leaching and mechanical properties as a function of firing temperature at 850, 900 and 950 °C. All laboratory facilities maintained 20 ± 1 °C. Consequently, a pilot-scale experiment was conducted with an addition of 2.5% and 5% EAFD to the extrusion mixture for the production of blocks. During blocks manufacturing, the firing step reached 950 °C in a tunnel kiln. Laboratory heating/cooling gradients were similar to pilot scale production firing. The as produced blocks were then subjected to quality control tests, i.e. dimensions according to EN772-17, water absorbance according to EN772-6, and compressive strength according to EN772-1 standard, in laboratory facilities certified under EN17025. The data obtained showed that the incorporation of EAFD resulted in an increase of mechanical strength. Moreover, leaching tests performed according to the Europeans standards on the EAFD-block samples showed that the quantities of heavy metals leached from crushed blocks were within the regulatory limits. Thus the EAFD-blocks can be regarded as material of no environmental concern. PMID:24012962

  8. Ultra-violet and resonant laser ablation coupled with microwave induced plasma atomic emission spectrometry and determination of tin in nickel based alloys by electrothermal atomizer atomic absorption and laser excited atomic fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Yang, Xiaodong

    Chapter 1 reviews laser ablation in analytical atomic spectrometry. Laser ablation is categorized into two functions: one is used as a sample introduction method, the other function is used as a microprobe analysis method. Both fundamental and applicational aspects are reviewed with the citations of related papers. This chapter also serves as an introduction to the work which is described in chapter 2 and chapter 3 as laser ablation is a relatively new research area for the research group. In chapter 2, instrumentation for excimer (308nm) laser ablation of samples was coupled with a microwave induced plasma (MLP), and evaluated for its potential as an approach to solid sampling for atomic emission spectrometry. Operating parameters were optimized, and the effects of laser repetition rate and number of laser shots on the emission signal were investigated. The UV excimer laser removed more material than would be expected of an infrared laser of similar energy. The chromium detection limit in the solid steel sample was estimated to be about 500 mug/g. In chapter 3, a wavelength tunable optical parametric oscillator (OPO) laser was used to ablate a steel sample into the same apparatus described in chapter 2. The emission signal for the elements was selectively enhanced when the ablation wavelength was tuned to be in resonance with any atomic transition of that element. This was the first report of the observation of resonant ablation by use of optical detection, as prior reports of resonant ablation have used mass spectrometric detectors. Chapter 4 reviews the publications in laser excited atomic fluorescence spectrometry in recent eight years. The focus of the review is on recent development on new instruments and applications of this technique. Chapter 5 studies the determination of tin in nickel-based alloys with laser excited atomic fluorescence in a graphite furnace. Zeeman electrothermal atomizer atomic absorption spectrometry and inductively coupled plasma mass

  9. Multiple hearth furnace for reducing iron oxide

    DOEpatents

    Brandon, Mark M.; True, Bradford G.

    2012-03-13

    A multiple moving hearth furnace (10) having a furnace housing (11) with at least two moving hearths (20) positioned laterally within the furnace housing, the hearths moving in opposite directions and each moving hearth (20) capable of being charged with at least one layer of iron oxide and carbon bearing material at one end, and being capable of discharging reduced material at the other end. A heat insulating partition (92) is positioned between adjacent moving hearths of at least portions of the conversion zones (13), and is capable of communicating gases between the atmospheres of the conversion zones of adjacent moving hearths. A drying/preheat zone (12), a conversion zone (13), and optionally a cooling zone (15) are sequentially positioned along each moving hearth (30) in the furnace housing (11).

  10. Laboratory arc furnace features interchangeable hearths

    NASA Technical Reports Server (NTRS)

    Armstrong, J. L.; Kruger, O. L.

    1967-01-01

    Laboratory arc furnace using rapidly interchangeable hearths gains considerable versatility in casting so that buttons or special shaped castings can be produced. It features a sight glass for observation.

  11. Onboard photo: Crystal Growth Furnace experiment

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Space Shuttle Columbia (STS-50) astronaut Bornie Dunbar wears protective goggles to assemble a zeolite sample cartridge for the Crystal Growth Furnace (CGF) in the United States Microgravity Laboratory-1 (USML-1) science module.

  12. Chamberless residential warm air furnace design

    SciTech Connect

    Godfree, J.

    1996-07-01

    This brief paper is an introduction to the concept of designing residential warm air furnaces without combustion chambers. This is possible since some small burners do not require the thermal support of a combustion chamber to complete the combustion process.

  13. Advanced Automated Directional Solidification Furnace (AADSF)

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The Advanced Automated Directional Solidification Furnace (AADSF) with the Experimental Apparatus Container (EAC) attached flew during the USMP-2 mission. This assembly consists of a furnace module, a muffle tube assembly and a translation mechanism which are enclosed in the EAC. During USMP-2, the AADSF was used to study the growth of mercury cadmium telluride crystals in microgravity by directional solidification, a process commonly used on earth to process metals and grow crystals. The furnace is tubular and has three independently controlled temperature zone . The sample travels from the hot zone of the furnace (1600 degrees F) where the material solidifies as it cools. The solidification region, known as the solid/liquid interface, moves from one end of the sample to the other at a controlled rate, thus the term directional solidification.

  14. Redesigned Electron-Beam Furnace Boosts Productivity

    NASA Technical Reports Server (NTRS)

    Williams, Gary A.

    1995-01-01

    Redesigned electron-beam furnace features carousel of greater capacity so more experiments conducted per loading, and time spent on reloading and vacuum pump-down reduced. Common mounting plate for electron source and carousel simplifies installation and reduces vibration.

  15. 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

  16. 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.

  17. Solar Convective Furnace for Metals Processing

    NASA Astrophysics Data System (ADS)

    Patidar, Deepesh; Tiwari, Sheetanshu; Sharma, Piyush; Pardeshi, Ravindra; Chandra, Laltu; Shekhar, Rajiv

    2015-11-01

    Metals processing operations, primarily soaking, heat treatment, and melting of metals are energy-intensive processes using fossil fuels, either directly or indirectly as electricity, to operate furnaces at high temperatures. Use of concentrated solar energy as a source of heat could be a viable "green" option for industrial heat treatment furnaces. This paper introduces the concept of a solar convective furnace which utilizes hot air generated by an open volumetric air receiver (OVAR)-based solar tower technology. The potential for heating air above 1000°C exists. Air temperatures of 700°C have already been achieved in a 1.5-MWe volumetric air receiver demonstration plant. Efforts to retrofit an industrial aluminium soaking furnace for integration with a solar tower system are briefly described. The design and performance of an OVAR has been discussed. A strategy for designing a 1/15th-scale model of an industrial aluminium soaking furnace has been presented. Preliminary flow and thermal simulation results suggest the presence of recirculating flow in existing furnaces that could possibly result in non-uniform heating of the slabs. The multifarious uses of concentrated solar energy, for example in smelting, metals processing, and even fuel production, should enable it to overcome its cost disadvantage with respect to solar photovoltaics.

  18. 1. GENERAL VIEW OF BLAST FURNACE PLANT, KNOWN AS THE ...

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

    1. GENERAL VIEW OF BLAST FURNACE PLANT, KNOWN AS THE CARRIE FURNACES, FROM THE TOP OF WATER TOWER. CARRIE FURNACES No. 6 AND No. 7 ARE ON THE LEFT, AND FURNACES No. 3 AND No. 4 ARE ON THE RIGHT. THE TOWN OF RANKIN IS IN THE BACKGROUND. Jet Lowe, Photographer, 1989. - U.S. Steel Homestead Works, Blast Furnace Plant, Along Monongahela River, Homestead, Allegheny County, PA

  19. Molecular dynamics evidences of the full graphitization of a nanodiamond annealed at 1500 K

    NASA Astrophysics Data System (ADS)

    Leyssale, J.-M.; Vignoles, G. L.

    2008-03-01

    The annealing of a small nanodiamond cluster at 1500 K is studied by molecular dynamics. The transformation of the particle in an almost fully graphitized carbon onion is observed. The remaining 17% of sp 3 atoms are delocalized on the whole particle, both under the form of isolated point defects and of small diamond-like clusters separating large graphite-like domains. It is also shown, that the Berendsen thermostat, previously used to fix temperature in such simulations, transfers kinetic energy from internal to global motions of the cluster. This can lead to severe artifacts like the freezing of the graphitization process.

  20. FINGERPRINTING INORGANIC ARSENIC AND ORGANOARSENIC COMPOUNDS IN IN SITU OIL SHALE RETORT AND PROCESS VOTERS USING A LIQUID CHROMATOGRAPH COUPLED WITH AN ATOMIC ABSORPTION SPECTROMETER AS A DETECTOR

    SciTech Connect

    Fish, Richard H.; Brinckman, Frederick E.; Jewett, Kenneth L.

    1981-07-01

    Inorganic arsenic and organoarsenic compounds were speciated in seven oil shale retort and process waters, including samples from simulated, true and modified in situ processes, using a high performance liquid chromatograph automatically coupled to a graphite furnace atomic absorption detector. The molecular forms of arsenic at ppm levels (({micro}g/mL) in these waters are identified for the first time, and shown to include arsenate, methylarsonic acid and phenylarsonic acid. An arsenic-specific fingerprint chromatogram of each retort or process water studied has significant impliestions regarding those arsenical species found and those marginally detected, such as dimethylarsinic acid and the suspected carcinogen arsenite. The method demonstrated suggests future means for quantifying environmental impacts of bioactive organometal species involved in oil shale retorting technology.