Standard Reference Materials Alloys Research Articles

Preparation and Certification of Hydrogen in Titanium Alloy Standard Reference Materials

A series of three hydrogen in titanium alloy Standard Reference Materials (SRMs 2452, 2453, and 2454) was prepared with hydrogen mass fractions bracketing the hydrogen specification limit of 125 mg/kg. Commercial titanium alloy Ti6Al4V (6 pct aluminum and 4 pct vanadium) was heated under vacuum in a furnace to remove native hydrogen, then it was doped with a measured quantity of hydrogen. Prompt gamma-ray activation analysis was used to determine hydrogen in the degassed material and finished SRMs. A combination of preparation data and PGAA measurement was used to certify the hydrogen mass fraction of each. The certified hydrogen mass fractions are 62.5 mg/kg ± 1.6 mg/kg for SRM 2452, 114 mg/kg ± 5 mg/kg for SRM 2453, and 211 mg/kg ± 4 mg/kg for SRM 2454.

A selective flotation-spectrophotometric method for the determination of nickel using dimethylglyoxime

A simple and selective method for separation and preconcentration of nickel has been developed. The method is based on the flotation of a complex of Ni and dimethylglyoxime (DMG) at the aqueous solution-n-hexane interface. The complex was separated and Ni determined spectrophotometrically by DMG after addition of oxidizing agent. The quantitative flotation of the complex was possible in the pH range of 9-12. The method is simple and free from the interference of all cations and anions and has a wide linear range. The procedure was successfully applied to the determination of trace amounts of nickel in well water and waste water in coating plant. The method's accuracy was investigated by using standard reference materials alloys (NIST 864) and by spiking the samples with different amounts of Ni2+.

Selection of Discharge Gases for Analysis of Aluminum Alloys by Glow Discharge Mass Spectrometry

Analysis of aluminum (Al) alloys was carried out using helium and argon/glow discharge mass spectrometry (He/GD-MS, and Ar/GD-MS). The relative sensitivity factors RSFX, Al over the Al matrix used for GD-MS quantitative analysis were determined using six commercial Al alloy standard reference materials. The analytes comprise 15 elements containing in Al alloys: beryllium (Be), magnesium (Mg), silicon (Si), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), strontium(Sr), tin (Sn), lead (Pb), and bismuth (Bi). A glow discharge cell for disk samples was used. A 12-mm internal diameter sample mask made from Ta was employed as the part of the anode. The discharge current was 3-mA for both of discharge gas. Large dispersion was observed in several obtained RSF values, resulting from insufficient validity of certified values of some elements such as Be. Nevertheless, the dispersion in RSF values was 8% or less as RSD for most of the analytes. The Ar/glow discharge was suitable for analysis of Al alloys because the RSF-values almost were better than those obtained by measurement using the He/glow discharge. Values obtained by GD-MS for a practical Al alloy A356 well agreed with the chemical analysis result, from alloying elements like Si, minor components such as Mg and Ti, to trace elements of parts per million level. Moreover, regarding the accuracy of GD-MS analysis, minor components such as Mg, Ti, and Fe can be determined within about 2% accuracy as RSD, and trace elements below a single mass ppm within 5%, except for Cr (RSD: 24.4%), Ni (9.8%), and Sn (13.3%). We established an eco-friendly analytical method without acid-decomposition by chemical reagents.

Glow Discharge Mass Spectrometry for Cobalt Alloys Analysis

A comparison of results obtained using argon/glow discharge mass spectrometry (Ar/GD-MS) and fundamental parameter/X-ray fluorescence analysis (FP/XRF) was made by analyzing of cobalt (Co) alloys. The relative sensitivity factors (RSF) used for GD-MS quantitative analysis were determined using six commercial Co alloy standard reference materials. The analysis objects comprised 16 elements contained in Co alloys : C, Al, Si, P, S, Ti, Cr, Mn, Fe, Ni, Cu, Nb, Mo, Sn, La, and W. A glow-discharge cell for disk samples was used. A sample mask made from Ta, a part of the anode, was employed ; it had an internal diameter of 12 mm. The discharge parameters were 1 kV and 3 mA. Samples were put on a liquid sample cup with an adherent 6.3-μm-thick polypropylene film and subjected to a FP/XRF measurement. The sensitivity coefficients (Kij) of XRF for Co alloys were determined through measuring identical standard substances, such as GD-MS, and processing thereof using UQ5 software. A commercial Co alloy, Haynes188, was subjected to chemical analysis ; the GD-MS, chemical analysis, and FP/XRF results were compared. The FP/XRF results of the main components (Cr, Fe, Ni, and W) agreed well with the GD-MS and chemical analysis results. The analytical accuracy was satisfactory as 0.18% (Cr)∼0.46% (W) in RSD. However, some overestimation occurred for minor, elements such as Cu and La, at low concentrations, where RSD was 10∼17%. On the other hand, the GD-MS results agreed well with results of chemical analysis obtained from P and S at the trace impurity level, minor components, to main components. The analytical accuracy of GD-MS was shown to be within 2% as RSD for most elements, from main components, such as Cr (RSD : 1.2%), Ni (1.0%), and W (0.89%), to elements of trace impurity level, like S (4.5%), including minor components.

Assessment of high precision, high accuracy Inductively Coupled Plasma-Optical Emission Spectroscopy to obtain concentration uncertainties less than 0.2% with variable matrix concentrations

The ability to obtain high precision, high accuracy measurements in samples with complex matrices using High Performance Inductively Coupled Plasma-Optical Emission Spectroscopy (HP-ICP-OES) was investigated. The Common Analyte Internal Standard (CAIS) procedure was incorporated into the High Performance Inductively Coupled Plasma-Optical Emission Spectroscopy method to correct for matrix-induced changes in emission intensity ratios. Matrix matching and standard addition approaches to minimize matrix-induced errors when using High Performance Inductively Coupled Plasma-Optical Emission Spectroscopy were also assessed. The High Performance Inductively Coupled Plasma-Optical Emission Spectroscopy method was tested with synthetic solutions in a variety of matrices, alloy standard reference materials and geological reference materials.

Direct solid sample analysis in a moderate-power argon microwave-induced plasma with spark generation

A spark–Ar microwave-induced plasma (MIP) atomic emission spectrometry system has been developed for the direct analysis of solid samples. Particles of the sample are generated with a spark and swept into a moderate-power Ar MIP connected to a sequential spectrometer. Low-Alloy Steel and Aluminium Alloy Standard Reference Materials were analysed by the proposed system and the detection limits for most elements of interest were around 10 µg g–1 or less, which are comparable to a spark–Ar inductively coupled plasma (ICP) system. Precisions were in the range 3–11%, which are 2–3 times higher than those of the spark–ICP system. Hence spark–MIP AES is a viable alternative technique to spark–ICP-AES.

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

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

Determination of thallium and lead in nickel-based alloys by direct solid sampling with graphite furnace laser-excited atomic fluorescence

The direct analysis of solid nickel-based alloys was investigated using laser-excited atomic fluorescence spectrometry with an electrothermal atomiser (ETA-LEAFS) and a Perkin-Elmer cup solid sampling accessory. Advantages of direct solid sampling include high sensitivity and reduced risk of sample contamination as no dissolution step is used. Using the front-surface illumination approach for ETA-LEAFS, it has proved possible to apply modern graphite furnace solid sampling technology directly to LEAFS. The advantages of ETA-LEAFS include a long linear dynamic range (5–7 orders of magnitude) and limits of detection that can be 1–4 orders of magnitude better than electrothermal atomic absorption spectrometry (ETAAS). High temperature nickel-based alloy standard reference materials were accurately analysed for low and sub-µg g–1 concentrations of the trace metals thallium and lead, using aqueous calibration. These analyses were carried out on single alloy chips weighing between 0.5 and 2 mg with typical analytical relative standard deviations of 7–20%. The use of an internal gas flow, during atomisation, has been reported in the solid sampling ETAAS literature as a means of reducing the sensitivity of the ETAAS method, a necessity due to the short linear dynamic range of ETAAS. The long linear dynamic range of LEAFS allowed the elimination of the use of an internal gas flow through the furnace for the determination of lead. The analyte backgrounds for thallium and lead in nickel-based alloy solid samples using ETA-LEAFS and ETAAS were compared. The analyte backgrounds for solid sampling by ETA-LEAFS were significantly lower than those for solid sampling by ETAAS.

Direct solid sampling of nickel based alloys by graphite furnace atomic absorption spectrometry with aqueous calibration

The direct analysis of solid nickel based alloy samples was investigated using graphite furnace atomic absorption spectrometry (GFAAS) with Zeeman background correction and a Perkin-Elmer solid sampling cup accessory. Advantages of direct solid sampling include high sensitivity and reduced risk of sample contamination since no dissolution step is used. Using aqueous standards and STPF technology with Zeeman background correction, it has proved possible to analyze small chips of nickel based alloy directly. High temperature alloy standard reference materials (SRM's) were accurately analyzed for low and sub ppm concentrations of the trace metals thallium, bismuth, tellurium, selenium and lead in the alloys. Analyses were done on single alloy chips weighing between 0.5 and 4 mg with typical analytical RSD's of 6–14%.

Robotic preparation of metal samples for analysis by plasma emission spectrometry

A method utilizing a laboratory robotic system to automate sample preparation for the chemical analysis of metals was developed. Anticipated elemental concentration values for samples are entered into the robotic system, and the system determines the needed sample weights and calibration solution concentrations. The robot then weighs, dissolves, and dilutes the samples and prepares calibration solutions prior to multi-elemental analyses by inductively-coupled plasma — atomic-emission spectrometry. Zinc-base alloy standard reference materials were used to evaluate this method. For a batch of ten samples, operator times compared with a similar manual method were reduced by about 5-fold. Precision and accuracy data for samples prepared by robotic and manual methods were equivalent.

The Determination of Selenium and Tellurium in Stainless Steel, White Cast Iron, and Nickel Base Alloy Standard Reference Materials by Isotope Dilution Spark Source Mass Spectrometry

Procedures using stable isotope dilution spark source mass spectrometry were developed for the simultaneous determination of selenium and tellurium in stainless steels, white cast irons, and nickel based alloys. The selenium and tellurium were reduced using hypophosphorous acid except in the nickel based alloy where electrodeposition onto gold was also used for tellurium. A gold carrier was used to scavenge the selenium and tellurium efficiently during reduction. The samples were homogenized with gold and introduced into the mass spectrometer as electrodes. The concentrations calculated from the general isotope dilution equation ranged from 0.14 μg/g for selenium to 353 μg/g for tellurium. The materials tested were ten different Standard Reference Materials available from the NBS.