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Despite AlB2 is the most typical structure prototype of transition metal diborides (TMB2), studies on AlB2 thin films are scarce. Furthermore, although Al is the primary alloying element for TMB2 to improve their oxidation resistance, no such data are available for AlB2 thin films. Here, we develop AlBx thin films through non-reactive magnetron sputtering of an AlB2 compound target and investigate their microstructure, mechanical properties, thermal stability and oxidation resistance. Keeping the substrate temperature at 700 °C and increasing the Ar pressure during deposition from pAr = 0.4 to 0.8 to 1.2, Pa, the films‘ chemistry slightly varies between x = 1.99, 1.97, and to 2.27, respectively. Detailed transmission electron microscopy shows that the highly (0001)-oriented AlB2.27 thin film exhibits small platelet-like amorphous B regions next to the large columnar α-structured AlB2 crystals. In the as deposited state, this film exhibits an indentation hardness and elastic modulus of 19.2 ± 1.2 GPa and 331.8 ± 14.4 GPa, respectively. Between 850 and 900 °C, the AlB2.27 thin film starts to decompose into tetragonal (t-) AlB12, but still maintains dominant α structure up to 950 °C. At 1000 °C, the thin film is completely decomposed into t-AlB12 and hexagonal AlB10. The AlB2.27 thin film also shows exceptional oxidation-resistance with an onset temperature for the formation of oxides (α-Al2O3 and o-Al18B4O33) between 950 and 1000 °C when exposed to lab-air.

High-performance polymers like polyimides are well known for their outstanding chemical and physical properties and play an important role in high-demanding applications like automotive, aerospace, medical, etc. Polyimide thin films are especially useful in the electronics industry to protect the underlying devices from elevated temperatures, humidity, corrosive gases and high voltages. Therefore, the curing of polyimides has been studied extensively to ensure ideal material properties and new tools and methods for sample characterization are of great interest. Besides conventional techniques like Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA) or Differential Scanning Calorimetry (DSC), Laser Induced Breakdown Spectroscopy (LIBS) has been introduced recently to monitor the imidization reaction of a polyimide thin film. To obtain information about the temporal evolution of the reaction as well as optimize labor- and time-consuming sample preparation, a heating chamber for simultaneous thermal treatment and LIBS measurements (in-situ experiments) was developed and successfully used for imidization studies of self-synthesized polyimides. Besides a general introduction of the chamber design, the results of the in-situ investigation are presented: isothermal studies to gain temporal information about the imidization reaction of a single film and stepwise heating to investigate the influence of the curing temperature. Finally, LIBS depth-profiling revealed depth-resolved information about the imidization degree over the entire film thickness, illustrating one of the great advantages of the LIBS technique.

Transition metal diboride thin films are promising functional materials for their outstanding mechanical properties and thermal stability. By combining experiment and simulations, we discuss angular distribution of the sputtered species, their scattering in the gas phase, re-sputtering and potential evaporation from the grown films for the complex evolution of film compositions, as well as energetic preference for vacancy formation and competing phases as factors for governing the phase constitution. By co-sputtering from two compound targets, we developed phase-pure crystalline (Ta,Al)B2 solid solution thin films and correlate the stoichiometry changes with the evolution of their microstructure, hardness, and elastic modulus.

The continuous extraction of the rhodium inventory in supported liquid-phase (SLP) catalytic materials utilized in the hydroformylation (HyFo) of 1-butene was investigated by supercritical carbon dioxide (scCO2). Optimization of extraction efficiency involved varying parameters such as temperature (90 and 120 °C), pressure (10, 20 and 30 MPa), and the addition of methanol as a polar co-feed to the extraction medium (0–20 vol%). The results underscored the critical role of methanol in facilitating extraction, as experiments employing pure scCO2 yielded no rhodium recovery. Furthermore, extraction performance demonstrated sensitivity to temperature and pressure adjustments during the process. Notably, the use of 10 vol% methanol at 120 °C and 30 MPa achieved complete rhodium extraction from the grained SLP materials, which was identified as the optimum extraction condition. This study highlights the potential for scaling up in-situ rhodium extraction processes within HyFo production plants based on SLP catalysts, emphasizing significant implications for industrial applications.

The determination of mineral dust and elemental carbon in snow samples is of great interest, since both compounds are known to be light-absorbing snow impurities. Different analytical methods have to be used to quantify both compounds. The occurrence of mineral dust, which contains hematite, leads to a bias in the quantification of elemental carbon and organic carbon via thermal–optical analysis. Here we present an approach which utilizes this interference to determine the concentration of iron via thermal–optical analysis using a Lab OC / EC Aerosol Analyzer (Sunset Laboratory Inc.) and the EUSAAR2 protocol. For this, the temperature dependency of the transmittance signal determined during the calibration phase, i.e., when all carbonaceous compounds are already removed, is evaluated. Converting the transmittance signal into an attenuation, a linear relationship between this attenuation and the iron loading is obtained for loadings ranging from 10 to 100 µg Fe cm−2. Furthermore, evaluation of the transmittance signal during the calibration phase allows to identify samples which need to be re-evaluated, since the analysis of elemental carbon and organic carbon is biased by constituents of mineral dust. The method, which was initially designed for snow samples, can also be used to evaluate particulate matter samples collected within the same high alpine environment. When applying the method to a new set of samples it is crucial to check whether the composition of iron compounds and the sample matrix remain comparable. If other sources than mineral dust determine the iron concentration in particulate matter, these samples cannot be evaluated with thermal–optical analysis. This is shown exemplarily with data from particulate matter samples collected in a railway tunnel.

Nanoparticles are used in various fields, such as material manufacturing, catalysis and medicine, due to their unique physical and chemical properties. Accurate characterization of nanoparticles is essential for manufacturing purposes as well as for assessing their impact on the environment and human health. To achieve this, single particle inductively coupled plasma mass spectrometry (sp-ICP-MS) has become an essential analytical technique for nanoparticle analysis. It can also be used with laser ablation as a sampling method to overcome challenges related to introducing nanoparticles in liquid suspension. Similar to conventional sp-ICP-MS, laser ablation sp-ICP-MS requires standards for signal calibration, which is challenging as the availability of standard reference materials is limited for all different kinds of nanoparticles. In this work, nanoparticles embedded in polymer thin films are analyzed using laser ablation sp-ICP-MS, whereby the laser is used to sample and transport the intact particles to the plasma. For creating a calibration for mass and size investigations, defined amounts of the element of interest were introduced into the ICP-MS by quantitatively ablating polymer thin film spiked with a defined amount of liquid element standard with different laser spot sizes. The method was developed and optimized using gold nanoparticles with certified sizes that were analyzed using a quadrupole-ICP-MS in single-element mode. The nanoparticles were sized using the proposed calibration approach with a deviation of ≤2.5% from the certified diameter value. Using the calibration approach, a limit of detection for gold of 3 × 10−7 ng was calculated, which translates to a particle size of approximately 15.5 nm, comparable to values in the literature for liquid-suspension-based approaches. Multi-element nanoparticles in the form of gadolinium-doped cerium oxide (GDC) nanoparticles with two elements of interest were analyzed using an ICP-TOFMS utilizing the thin-film-based calibration approach. Comparative measurements of the material confirmed the investigated sizes and composition of the particles. This developed alternative approach circumvents the need for certified particulate standard materials by using in-house-produced spiked polymer thin films as storage-stable calibration standards. Moreover, changing the laser spot size makes it straightforward to alter the number of particles introduced into the ICP-MS. [ABSTRACT FROM AUTHOR]

This work introduces a novel semi-automatic approach to identify elemental lines in spectra obtained via laser-induced breakdown spectroscopy (LIBS). The algorithm is based on unique spectral fingerprints of individual elements that are configured into comb-like filters. The element-specific filters are then correlated with measured spectra for semi-supervised qualitative analysis of samples. Spectral variations are accommodated by adjusting the micro-parameters of the comb filter. This step ensures accurate results despite minor deviations from the instrument's ideal calibration due to instrumental fluctuations, e.g., drift in spectral calibration or line broadening. Additionally, the algorithm can autonomously detect spectral interference regions, aiding the analyst in verifying spectral lines where such interference may occur. The paper presents a comprehensive overview of the algorithm and discusses the main concepts, parameters, optimization steps, and limitations using Echelle spectra of two standard reference materials with different complexity: borosilicate glass (NIST 1411) and low-alloyed steel (SUS1R). Furthermore, the transferability of the approach to different scenarios and real-life applications is demonstrated using a single-channel Czerny–Turner spectrum of an amalgam filling extracted from a hyperspectral image of a human tooth. A demo of the algorithm is publicly available for non-commercial purposes. [ABSTRACT FROM AUTHOR]