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We report the results of a Versailles Project on Advanced Materials and Standards (VAMAS) interlaboratory study on the measurement of the shell thickness and chemistry of nanoparticle coatings. Peptide-coated gold particles were supplied to laboratories in two forms: a colloidal suspension in pure water and particles dried onto a silicon wafer. Participants prepared and analyzed these samples using either X-ray photoelectron spectroscopy (XPS) or low energy ion scattering (LEIS). Careful data analysis revealed some significant sources of discrepancy, particularly for XPS. Degradation during transportation, storage, or sample preparation resulted in a variability in thickness of 53%. The calculation method chosen by XPS participants contributed a variability of 67%. However, variability of 12% was achieved for the samples deposited using a single method and by choosing photoelectron peaks that were not adversely affected by instrumental transmission effects. The study identified a need for more consistency in instrumental transmission functions and relative sensitivity factors since this contributed a variability of 33%. The results from the LEIS participants were more consistent, with variability of less than 10% in thickness, and this is mostly due to a common method of data analysis. The calculation was performed using a model developed for uniform, flat films, and some participants employed a correction factor to account for the sample geometry, which appears warranted based upon a simulation of LEIS data from one of the participants and comparison to the XPS results.
Due to the extremely high specific surface area of nanoparticles and corresponding potential for adsorption, the results of surface analysis can be highly dependent on the history of the particles, particularly regarding sample preparation and storage. The sample preparation method has, therefore, the potential to have a significant influence on the results. This report describes an interlaboratory comparison (ILC) with the aim of assessing which sample preparation methods for ToF-SIMS analysis of nanoparticles provided the most intra- and interlaboratory consistency and the least amount of sample contamination. The BAM reference material BAM-P110 (TiO2 nanoparticles with a mean Feret diameter of 19 nm) was used as a sample representing typical nanoparticles. A total of 11 participants returned ToF-SIMS data,in positive and (optionally) negative polarity, using sample preparation methods of “stick-and-go” as well as optionally “drop-dry” and “spin-coat.” The results showed that the largest sources of variation within the entire data set were caused by adventitious hydrocarbon contamination or insufficient sample coverage, with the spin-coating protocol applied in this ILC showing a tendency toward insufficient sample coverage; the sample preparation method or the participant had a lesser influence on results.
Results from a study conducted between National Metrology Institutes (NMIs) for the measurements of the absolute thicknesses of ultra-thin layers of SiO2 on Si are reported. These results are from a key comparison and associated pilot study under the auspices of the Consultative Committee for Amount of Substance. ´Amount of substance´ may be expressed in many ways, and here the measurand is the thickness of the silicon oxide layers with nominal thicknesses in the range 1.5-8 nm on Si substrates, expressed as the thickness of SiO2. Separate samples were provided to each institute in containers that limited the carbonaceous contamination to approximately < 0.3 nm. The SiO2 samples were of ultra-thin on (100) and (111) orientated wafers of Si. The measurements from the laboratories which participated in the study were conducted using ellipsometry, neutron reflectivity, X-ray photoelectron spectroscopy or X-ray reflectivity, guided by the protocol developed in an earlier pilot study. A very minor correction was made in the different samples that each laboratory received. Where appropriate, method offset values attributed to the effects of contaminations, from the earlier pilot study, were subtracted. Values for the key comparison reference values (agreed best values from a Consultative Committee study) and their associated uncertainties for these samples are then made from the weighted means and the expanded weighted standard deviations of the means of these data. These results show a dramatic improvement on previous comparisons, leading to 95% uncertainties in the range 0.09-0.27 nm, equivalent to 0.4-1.0 monolayers over the 1.5-8.0 nm nominal thickness range studied. If the sample-to-sample uncertainty is reduced from its maximum estimate to the most likely value, these uncertainties reduce to 0.05-0.25 nm or ~1.4% relative standard uncertainties. The best results achieve ~1% relative standard uncertainty. It is concluded that XPS has now been made fully traceable to the SI, for ultra-thin thermal SiO2 on Si layers, by calibration using wavelength methods in an approach that may be extended to other material systems.
A pilot study for the thickness measurement of HfO2 films was performed by the Surface Analysis Working Group (SAWG) of the Consultative Committee for Amount of Substance (CCQM). The aim of this pilot study was to ensure the equivalency in the measurement capability of national metrology institutes for the thickness measurement of HfO2 films. In this pilot study, the thicknesses of six HfO2 films with nominal thickness from 1 nm to 4 nm were measured by X-ray Photoelectron Spectroscopy (XPS), X-ray Reflectometry(XRR), X-ray Fluorescence Analysis (XRF), Transmission Electron Spectroscopy (TEM), Spectroscopic Ellipsometry (SE) and Rutherford Backscattering Spectrometry (RBS). The reference thicknesses were determined by mutual calibration of a zero-offset method (Medium Energy Ion Scattering Spectroscopy (MEIS) of KRISS) and a method traceable to the length unit (the average thicknesses of three XRR data except the thinnest film). These reference thicknesses are traceable to the length unit because they are based on the traceability of XRR. For the thickness measurement by XPS, the effective attenuation length of Hf 4f electrons was determined. In the cases of XRR and TEM, the offset values were determined from a linear fitting between the reference thicknesses and the individual data by XRR and TEM. The amount of substance of HfO2, expressed as thickness of HfO2 films (in both linear and areal density units), was found to be a good subject for a CCQM key comparison.
To reach the main text of this paper, click on Final Report.
The final report has been peer-reviewed and approved for publication by the CCQM.
Our ability to produce and transform engineered materials over the past 150 years is responsible for our high standards of living today, especially in the developed economies. Yet, we must carefully think of the effects our addiction to creating and using materials at this fast rate will have on the future generations. The way we currently make and use materials detrimentally affects the planet Earth, creating many severe environmental problems. It affects the next generations by putting in danger the future of economy, energy, and climate. We are at the point where something must drastically change, and it must change NOW. We must create more sustainable materials alternatives using natural raw materials and inspiration from Nature while making sure not to deplete important resources, i.e. in competition with the food chain supply. We must use less materials, eliminate the use of toxic materials and create a circular materials economy where reuse and recycle are priorities. We must develop sustainable methods for materials recycling and encourage design for disassembly. We must look across the whole materials life cycle from raw resources till end of life and apply thorough life cycle assessments based on reliable and relevant data to quantify sustainability.
ICP-MS has played a key role in inorganic chemical metrology for 25 years, from the 1993 CIPM feasibility study which led to establishment of the CCQM. Since that time, the Inorganic Analysis Working Group of the CCQM has organised 56 international comparisons involving measurements by ICP-MS and, in a recent comparison, 16 different national institutes submitted their results using the technique. Metrological applications of ICP-MS currently address an enormous range of measurements using a wide variety of instrumentation, calibration strategies and methodologies. This review provides an overview of the ICP-MS field with an emphasis on developments which are of particular relevance to chemical metrology.
Examples from CCQM comparisons and the services available from the participants are used to illustrate how the capability and scope of ICP-MS methods have expanded far beyond the expectations of 1993. This is due in part to the research and development Programmes of the national institutes which participate in the CCQM. They have played a key role in advancing new instrumentation and applications for elemental analysis, isotope dilution mass spectrometry, determination of isotopic ratio or composition, and speciation of organometallic compounds. These developments are continuing today, as demonstrated by work in new fields such as heteroatom quantitation of proteins, characterisation and counting of nanoparticles using spICP-MS, and LA-ICP-MS analysis of solid materials.
An international comparison study on the accurate determination of the molar mass M(Si) of silicon artificially enriched in 28Si (x(28Si) > 0.9999 mol mol−1) has been completed. The measurements were part of the high level CCQM-P160 pilot study assessing the ability of National Metrology Institutes (NMIs) and Designated Institutes (DIs) to make such measurements at the lowest possible levels of measurement uncertainty and to identify possible difficulties when measuring this kind of sample. This study supports the molar mass measurements critical to disseminating the silicon route to realizing the new definitions for the kilogram and the mole. Measurements were also made by one external research institute and an external company. The different institutes were free to choose their experimental (mass spectrometric) set-ups and equipment, thereby enabling also the comparison of different techniques. The investigated material was a chemically pure, polycrystalline silicon material. The subsequent modified single crystalline secondary product of this material was intended for the production of silicon which was used for two additional spheres in the context of the redetermination of the Avogadro constant NA, required for the revision of the International System of Units (SI) via fundamental constants which came into force from May 2019. The CCQM pilot study was organized by Physikalisch-Technische Bundesanstalt (PTB). Aqueous silicon solutions were shipped to all participating institutions. The data analysis as well as the uncertainty modelling and calculation of the results was predefined. The participants were provided with an uncertainty budget as a GUM Workbench® file as well as a free software license for the duration of the comparison. The agreement of the values of the molar mass (M(Si) = 27.976 942 577 g mol−1) was excellent with ten out of 11 results reported within the range of relative uncertainty of 1 × 10−8 required
for the revision of the SI.
The present work provides a comparative study on the interface and adhesion properties of surface modified single glass fibers embedded in an acrylate matrix. To facilitate a covalent bonding at the fibermatrix interface, the fibers are functionalized with selected organosilanes that comprise either passive (unsaturated C¼C bonds of methacrylate moieties) or photoactive functionalities (photocleavable bis(acyl)phosphane oxide groups). Immobilization of the functional silanes is carried out by a classic silanization reaction involving a condensation reaction across the surface hydroxyl groups of the inorganic glass fibers. The change of the physico-chemical properties of the fibers due to desizing and subsequent surface modification is monitored by X-ray photoelectron spectroscopy and zeta potential measurements. In addition, scanning electron microscopy is used to follow the changes in surface morphology. After the modification step, the desized and modified single fibers are embedded in a photocurable acrylate resin formulation. By performing single fiber pull-out tests, maximum pull-out force, friction strength and apparent interfacial shear strength are determined as a function of the coupled silanes. The results reveal that the attached organosilanes lead to a significant increase in adhesion strength, whilst the performance of the photo-cleavable organosilane is superior to the passive methacryl-functional derivative.
Following the reviews of atomic-weight determinations and other cognate data in 2015, 2017, 2019 and 2021, the IUPAC (International Union of Pure and Applied Chemistry) Commission on Isotopic Abundances and Atomic Weights (CIAAW) reports changes of standard atomic weights. The symbol Ar(E) was selected for standard atomic weight of an element to distinguish it from the atomic weight of an element E in a specific substance P, designated Ar(E, P). The CIAAW has changed the values of the standard atomic weights of five elements based on recent determinations of terrestrial isotopic abundances:
Ar (argon): from 39.948 ± 0.001 to [39.792, 39.963]
Hf (hafnium): from 178.49 ± 0.02 to 178.486 ± 0.006
Ir (iridium): from 192.217 ± 0.003 to 192.217 ± 0.002
Pb (lead): from 207.2 ± 0.1 to [206.14, 207.94]
Yb (ytterbium): from 173.054 ± 0.005 to 173.045 ± 0.010
The standard atomic weight of argon and lead have changed to an interval to reflect that the natural variation in isotopic composition exceeds the measurement uncertainty of Ar(Ar) and Ar(Pb) in a specific substance. The standard atomic weights and/or the uncertainties of fourteen elements have been changed based on the Atomic Mass Evaluations 2016 and 2020 accomplished under the auspices of the International Union of Pure and Applied Physics (IUPAP). Ar of Ho, Tb, Tm and Y were changed in 2017 and again updated in 2021:
Al (aluminium), 2017: from 26.981 5385 ± 0.000 0007 to 26.981 5384 ± 0.000 0003
Au (gold), 2017: from 196.966 569 ± 0.000 005 to 196.966 570 ± 0.000 004
Co (cobalt), 2017: from 58.933 194 ± 0.000 004 to 58.933 194 ± 0.000 003
F (fluorine), 2021: from 18.998 403 163 ± 0.000 000 006 to 18.998 403 162 ± 0.000 000 005
(Ho (holmium), 2017: from 164.930 33 ± 0.000 02 to 164.930 328 ± 0.000 007)
Ho (holmium), 2021: from 164.930 328 ± 0.000 007 to 164.930 329 ± 0.000 005
Mn (manganese), 2017: from 54.938 044 ± 0.000 003 to 54.938 043 ± 0.000 002
Nb (niobium), 2017: from 92.906 37 ± 0.000 02 to 92.906 37 ± 0.000 01
Pa (protactinium), 2017: from 231.035 88 ± 0.000 02 to 231.035 88 ± 0.000 01
Pr (praseodymium), 2017: from 140.907 66 ± 0.000 02 to 140.907 66 ± 0.000 01
Rh (rhodium), 2017: from 102.905 50 ± 0.000 02 to 102.905 49 ± 0.000 02
Sc (scandium), 2021: from 44.955 908 ± 0.000 005 to 44.955 907 ± 0.000 004
(Tb (terbium), 2017: from 158.925 35 ± 0.000 02 to 158.925 354 ± 0.000 008)
Tb (terbium), 2021: from 158.925 354 ± 0.000 008 to 158.925 354 ± 0.000 007
(Tm (thulium), 2017: from 168.934 22 ± 0.000 02 to 168.934 218 ± 0.000 006)
Tm (thulium), 2021: from 168.934 218 ± 0.000 006 to 168.934 219 ± 0.000 005
(Y (yttrium), 2017: from 88.905 84 ± 0.000 02 to 88.905 84 ± 0.000 01)
Y (yttrium), 2021: from 88.905 84 ± 0.000 01 to 88.905 838 ± 0.000 002
A strain-based automated operational modal analysis algorithm is proposed to track the long-term dynamic behavior of a horizontal wind turbine under operational conditions.
This algorithm is firstly validated by a scaled wind turbine model, and then it is applied to the dynamic strain responses recorded from a 5 MW wind turbine system. We observed variations in the fundamental frequency and 1f, 3f excitation frequencies due to the mass imbalance of the blades and aerodynamic excitation by the tower dam or tower wake. Inspection of the Campbell diagram revealed that the adverse resonance phenomenon and Sommerfeld effect causing excessive vibrations of the wind tower.