Atomic spectrometry update: Review of advances in the analysis of metals, chemicals and materials

There has been a large increase in the number of papers published that are relevant to this review over this review period. The growth in popularity of LIBS is rapid, with applications being published for most sample types. This is undoubtedly because of its capability to analyse in situ on a production line (hence saving time and money) and its minimally destructive nature meaning that both forensic and cultural heritage samples may be analysed. It also has a standoff analysis capability meaning that hazardous materials, e.g. explosives or nuclear materials, may be analysed from a safe distance. The use of mathematical algorithms in conjunction with LIBS to enable improved accuracy has proved a popular area of research. This is especially true for ferrous and non-ferrous samples. Similarly, chemometric techniques have been used with LIBS to aid in the sorting of polymers and other materials. An increase in the number of papers in the subject area of alternative fuels was noted. This was at the expense of papers describing methods for the analysis of crude oils. For nanomaterials, previous years have seen a huge number of single particle and field flow fractionation characterisations. Although several such papers are still being published, the focus seems to be switching to applications of the nanoparticles and the mechanistic aspects of how they retain or bind with other analytes. This is the latest review covering the topic of advances in the analysis of metals, chemicals and materials. It follows on from last year's review1-6 and is part of the Atomic Spectrometry Updates series

Quantum mechanically guided design of mechanical properties and topology of metallic glasses

Metallic glasses are promising structural materials due to their unique property combinations such as high fracture toughness and high strength. For structural applications and processing, the coefficient of thermal expansion is an important design parameter. Here, it is demonstrated that predictions of the coefficient of thermal expansion for metallic glasses by density functional theory based ab initio calculations are efficient both with respect to time and resources. The coefficient of thermal expansion is predicted by an ab initio based method utilising the Debye-Grüneisen model for a Pd-based metallic glass, which exhibits a pronounced medium range order. The predicted coefficient of thermal expansion of 3.4∙10−5 K−1 at room temperature iscritically appraised by in situ synchrotron X-ray diffraction and excellent agreement is observed. Through this combined theoretical and experimental research strategy, the feasibility to predict the coefficient of thermal expansion from the ground state structure of a metallic glass until the onset of structural changes is shown. This strategy provides a method to efficiently probe a potentially vast number of metallic glass alloying combinations regardingthermal expansion. For the application of metallic glasses as structural materials, high fracture toughness is crucialto avoid catastrophic failure of the material in a brittle manner. One fingerprint for fracture toughness in metallic glasses is the fraction of hybridized bonds, which is affected by alloyingPd57.4Al23.5Y7.8M11.3 with M = Fe, Ni, Co, Cu, Os, Ir, Pt, and Au. It is shown that experimental fracture toughness data is correlated to the fraction of hybridized bonds which scale with the localized bonds at the Fermi level. Thus, the localized bonds at the Fermi level are utilized quantitatively as a measure for fracture toughness. Based on ab initio calculations, the minimum fraction of hybridized bonds was identified for Pd57.4Al23.5Y7.8Ni11.3. According to the ansatz that the crystal orbital overlap population at the Fermi level scales with fracture toughness, for Pd57.4Al23.5Y7.8Ni11.3 a value of around 95 ± 20 MPa·m0.5 is predicted quantitatively for the first time. Consistent with this prediction, in micro-mechanical beam bending experiments Pd57.4Al23.5Y7.8Ni11.3 thin films show pronounced plasticity and absence of crack growth. As the properties of metallic glasses depend on the electronic structure, which in turn is definedby chemical composition, the influence of metalloids such as B on glass transition, topology, magnetism, and bonding is investigated systematically for B concentrations x = 2 to 92 at.% inthe (Co6.8±3.9Ta)100-xBx system. From an electronic structure and coordination point of view, theB concentration range is divided into three regions: Below 39 ± 5 at.% B, the material is a metallic glass due to the dominance of metallic bonds. Above 69 ± 6 at.%, the presence of an icosahedra-like B network is observed. As the B concentration is increased above 39 ± 5 at.%,the B network evolves while the metallic coordination of the material decreases until the Bconcentration of 69 ± 9 at.% is reached. Hence, a composite is formed. It is evident that, based on the B concentration, the ratio of metallic bonding to icosahedral bonding in the compositecan be controlled. It is proposed that, by tuning the coordination in the composite region, glassy materials with defined plasticity and processability can be designed. While it is accepted that the plastic behaviour of metallic glasses is affected by their free volume content, the effect thereof on chemical bonding has not been investigated systematically. According to electronic structure analysis, the overall bond strength is not significantly affected by the free volume content. However, with increasing free volume content, the average coordination number decreases. Furthermore, the volume fraction of regions containing atoms with lower coordination number increases. As the local bonding character changes from bonding to anti-bonding with decreasing coordination number, bonding is weakened in the volume fraction of lower coordination number. During deformation, the number of strong, short-distance bonds decreases more for free volume containing samples than for samples without free volume, resulting in additional bond weakening. Thus, it is shown that the introduction of free volume causes the formation of volume fractions oflower coordination number resulting in weaker bonding and proposed that this is the electronic structure origin of the enhanced plastic behaviour reported for glasses containing free volume

Thermal expansion of Pd-based metallic glasses by ab initio methods and high energy X-ray diffraction

Metallic glasses are promising structural materials due to their unique properties. For structural applications and processing the coefficient of thermal expansion is an important design parameter. Here we demonstrate that predictions of the coefficient of thermal expansion for metallic glasses by density functional theory based ab initio calculations are efficient both with respect to time and resources. The coefficient of thermal expansion is predicted by an ab initio based method utilising the Debye-Grüneisen model for a Pd-based metallic glass, which exhibits a pronounced medium range order. The predictions are critically appraised by in situ synchrotron X-ray diffraction and excellent agreement is observed. Through this combined theoretical and experimental research strategy, we show the feasibility to predict the coefficient of thermal expansion from the ground state structure of a metallic glass until the onset of structural changes. Thereby, we provide a method to efficiently probe a potentially vast number of metallic glass alloying combinations regarding thermal expansion

Effect of hybridization in PdAlY-(Ni/Au/Ir) metallic glasses thin films on electrical resistivity

Thin film metallic glasses (MGs) are promising materials for electronic applications. While the transport properties of MGs are composition dependent, the influence of hybridization on the resistivity has not been investigated systematically. We implement a correlative experimental and computational approach utilizing thin film deposition, electrical resistivity measurements, synchrotron X-ray diffraction and ab initio calculations to explore the relationship between the fraction of hybridized bonds present in PdAlY-M glasses with M=Ir,Au,Ni, where the electrical behavior is dominated by d-electrons. The strong bonds hybridization in PdAlY-Ir yields a high resistivity of 175 µΩm, while the weakly hybridized bonds in PdAlY-M MGs (M = Au, Ni) result in lower resistivities of 114 and 92 µΩm, respectively. We propose that an increase in the amount of anti-bonding states close to the Fermi level yields an increased room temperature resistivity

Thermal expansion of Pd-based metallic glasses by ab initio methods and high energy X-ray diffraction

Metallic glasses are promising structural materials due to their unique properties. For structural applications and processing the coefficient of thermal expansion is an important design parameter. Here we demonstrate that predictions of the coefficient of thermal expansion for metallic glasses by density functional theory based ab initio calculations are efficient both with respect to time and resources. The coefficient of thermal expansion is predicted by an ab initio based method utilising the Debye-Grüneisen model for a Pd-based metallic glass, which exhibits a pronounced medium range order. The predictions are critically appraised by in situ synchrotron X-ray diffraction and excellent agreement is observed. Through this combined theoretical and experimental research strategy, we show the feasibility to predict the coefficient of thermal expansion from the ground state structure of a metallic glass until the onset of structural changes. Thereby, we provide a method to efficiently probe a potentially vast number of metallic glass alloying combinations regarding thermal expansion

Improving Spatial and Elemental Associations in Analytical Field Ion Microscopy

International audienceChemically resolved atomic resolution imaging can give fundamental information about material properties. However, even today, a technique capable of such achievement is still only an ambition. Here, we take further steps in developing the analytical field ion microscopy (aFIM), which combines the atomic spatial resolution of field ion microscopy (FIM) with the time-of-flight spectrometry of atom probe tomography (APT). To improve the performance of aFIM that are limited in part by a high level of background, we implement bespoke flight path time-offlight corrections normalized by the ion flight distances traversed in electrostatic simulations modeled explicitly for an atom probe chamber. We demonstrate effective filtering in the field evaporation events upon spatially and temporally correlated multiples, increasing the mass spectrum's signal-to-background. In an analysis of pure tungsten, mass peaks pertaining to individual W isotopes can be distinguished and identified, with the signal-to-background improving by three orders of magnitude over the raw data. We also use these algorithms for the analysis of a CoTaB amorphous film to demonstrate application of aFIM beyond pure metals and binary alloys. These approaches facilitate elemental identification of the FIM-imaged surface atoms, making analytical FIM more precise and reliable