Material Characterization Techniques Research Articles

A Unique Fe-N4 Coordination System Enabling Transformation of Oxygen into Superoxide for Photocatalytic CH Activation with High Efficiency and Selectivity.

Selective oxidation of CH bonds is one of the most important reactions in organic synthesis. However, activation of the α-CH bond of ethylbenzene by use of photocatalysis-generated superoxide anions (O2 •- ) remains a challenge. Herein, the formation of individual Fe atoms on polymeric carbon nitride (CN), that activates O2 to create O2 •- for facilitating the reaction of ethylbenzene to form acetophenone, is demonstrated. By utilizing density functional theory and materials characterization techniques, it is shown that individual Fe atoms are coordinated to four N atoms of CN and the resultant low-spin Fe-N4 system (t2g 6 eg 0 ) is not only a great adsorption site for oxygen molecules, but also allows for fast transfer of electrons generated in the CN framework to adsorbed O2 , producing O2 •- . The oxidation reaction of ethylbenzene triggered by O2 •- ions turns out to have a high conversion rate of 99% as well as an acetophenone selectivity of 99%, which can be ascribed to a novel reaction pathway that is different from the conventional route involving hydroxyl radicals and the production of phenethyl alcohol. Furthermore, it possesses great potential for other CH activation reactions besides ethylbenzene oxidation.

Non-classical hydrogen storage mechanisms other than chemisorption and physisorption

The hydrogen storage mechanism of materials is usually divided into chemisorption and physisorption according to the way the material interacts with hydrogen. Chemisorption refers to the breaking of hydrogen molecules into hydrogen atoms, which are then bonded to materials through chemical bonds. Physisorption refers to the adsorption of hydrogen molecules on the surface of materials with high specific surface areas through van der Waals forces. With the development of materials science and characterization techniques, some new hydrogen storage materials are emerging, which exhibit relatively complex interactions with hydrogen. This review will focus on non-classical hydrogen storage materials and mechanisms beyond physisorption and chemisorption, including Kubas interactions, nanopump effects, non-dissociative chemisorption, and weak-confined insertion of hydrides. This review will give researchers a clear view of the diversity of hydrogen storage materials and the complexity of hydrogen storage mechanisms, which may help enrich future hydrogen storage materials.

Microstructures and mechanical properties of three medium-Mn steels processed via quenching and partitioning as well as austenite reversion heat treatments

In order to establish the processing conditions to achieve the target of tensile strength of ∼1500 MPa with minimum retained austenite (RA) fraction of 10% in hot-rolled 3–4%Mn medium Mn steels, three hot-deformed steels with the base composition of Fe-0.3C–1Si-0.5Al (concentrations in wt.%) and variable contents of Mn (3 or 4 wt%), Ni (1 or 2 wt%), Mo (0.2 or 0.4 wt%) and V (0 or 0.2 wt%) were processed using both the quenching and partitioning (QP) and austenite reverse transformation (ART) treatments. Physical simulation experiments were carried out using small cylinders in a thermomechanical simulator and the differences in the amounts, morphology and stability of RA were established by using X-ray diffraction and electron probe microanalysis, besides standard material characterization techniques. Both processes provided relatively high fractions of austenite; up to 26 vol% using the QP route and up to 49 vol% by the ART treatment under specific conditions. These amounts were comparable to those predicted for the conditions of thermodynamic equilibrium using the ThermoCalc software. The stability of RA for various conditions was estimated in terms of the average carbon contents of the RA. In QP process RA had mostly blocky-like appearance while in ART process the majority of RA was lath-like shaped. The hardness measurements revealed that the level of hardness in the QP structures was higher than that of the ART samples, possibly affected by RA fraction but more obviously as a result of martensite tempered at relatively low temperatures in the QP and at high temperatures in the ART treated structures. Preliminary tensile properties were measured on selected laboratory hot-rolled samples and results analyzed based on RA characteristics. The preliminary results indicated that the target is achievable in the laboratory scale through both the processing routes.

Orbitrap™-SIMS analysis of advanced semiconductor inorganic structures

Shrinking semiconductor device dimensions requires extensive R&D in all areas, inclusive of the materials characterization techniques and methodologies commonly used. With dimensions now being much smaller than the beam spot sizes of usual characterization methods like SIMS, RBS, etc., new concepts are needed. In this context, the application of Self-Focusing SIMS (SF-SIMS) to determine the bulk composition of structures of exceedingly small dimensions was demonstrated in the past years. However, due to the extensive use of secondary ions of higher m/z in the SF-SIMS concept, high mass resolution is often required; this is to avoid possible mass interferences that limit the SF-SIMS method to reach low detection limits and/or to unambiguously identify the ion signals. Although the mass resolving power of Time-of-Flight (ToF) analyzers of SIMS instruments is considered high (m/Δm ∼10000), it still presents a restriction for the SF-SIMS methodology on specific systems. The Orbitrap™ mass analyzer allows an increase in the mass resolution up ∼20x along with mass accuracy levels below one ppm. In this study, we demonstrate that the mass resolving power of the Orbitrap™-SIMS allows to resolve limiting mass interferences, thereby allowing accurate quantification of impurities/dopants in small finFET structures (<20 nm).

Revealing Localised Mechanochemistry of Biomaterials Using In Situ Multiscale Chemical Analysis.

The study of mechanical and chemical phenomena arising within a material that is being subjected to external stress is termed mechanochemistry (MC). Recent advances in MC have revealed the prospect not only to enable a greener route to chemical transformations but also to offer previously unobtainable opportunities in the production and screening of biomaterials. To date, the field of MC has been constrained by the inability of current characterisation techniques to provide essential localised multiscale chemically mapping information. A potential method to overcome this is secondary electron hyperspectral imaging (SEHI). SEHI is a multiscale material characterisation technique applied within a scanning electron microscope (SEM). Based on the collection of secondary electron (SE) emission spectra at low primary beam energies, SEHI is applicable to the chemical assessment of uncoated polymer surfaces. Here, we demonstrate that SEHI can provide in situ MC information using poly(glycerol sebacate)-methacrylate (PGS-M) as an example biomaterial of interest. This study brings the use of a bespoke in situ SEM holder together with the application of SEHI to provide, for the first time, enhanced biomaterial mechanochemical characterisation.

Accurate THz ellipsometry using calibration in time domain.

We report on the realisation of a customized THz time domain spectroscopic ellipsometer (THz-TDSE) based on fiber-coupled photoconductive antennas, operating in a wide range of incident angles and allowing also standard transmission spectroscopy without any optical realignment. To ensure accurate parameter extraction for a broad range of materials, we developed a fast and effective algorithm-assisted method to calibrate the setup and compensate for the nonideality in the response of the THz system. The procedure allows to minimise errors induced by imperfect response of the antennas and polarizers, imprecise setting of the impinging and receiving angles in the goniometric mechanical arms, and unavoidable mismatches in the THz beam optics. Differently from other calibration methods applied in the literature, our approach compares in time domain the ellipsometric derived electric field s- and p-polarised components at a given angle of incidence with the reconstructed ones, attained by using the complex dielectric function of a known sample. The calibrated response is determined with high precision by setting the system in transmission mode. In order to validate the technique, ellipsometric measurements have been carried out at various angle of incidences on a number of materials both in solid and liquid form, and their data compared with what obtained by conventional THz spectroscopy. Results show that THz-TDSE accompanied with an accurate calibration procedure is an effective technique for material characterization, especially in case of samples with a high absorption rate that are not easily investigated through transmission measurements.

The properties of stainless steel 17-4PH produced by a low-cost additive manufacturing technique, the Markforged MetalX™

The lower capital and running cost of the Markforged Metal X™ platform, in comparison to competing metal additive manufacturing systems, makes it a highly attractive proposition for several industries. The unusual print, then sinter, process also has the potential to avoid many of the metallurgy issues that can arise using more typical additive manufacturing, which relies on melting to bind the material. However, the mechanical properties of the material produced must be well understood. In this paper, the properties of 17-4PH stainless steel samples produced by the Metal X™ are documented following a systematic testing program, involving standard mechanical testing as well as material characterisation techniques. Significant differences were observed between the samples tested in differing orientations. This is thought to be due to the deposition process used to lay the material prior to sintering, which results in voids and surface stress concentrations that reduce the strength of the material. Heat treatments and surface machining were both found to improve the tensile properties of the material.

ALTECH 2021 – Analytical Techniques for Precise Characterization of Nano Materials

ALTECH 2021 – Analytical Techniques for Precise Characterization of Nano Materials

Investigation on spray combustion characteristics of Boron-Loaded slurry fuel in a Swirl-Stabilized combustor

For many decades, liquid hydrocarbon fuels are being used to propel air-breathing engines. However, the energy content of liquid hydrocarbon fuels has reached close to its limitation. Any further improvement in energy value is quite difficult through chemical methods. Slurry fuels, which are colloidal suspensions of solid energetic particles in liquid fuel, became a potential alternative fuel. Among several solid additives, boron is considered the best choice because of its higher heating values. However, our knowledge about boron-loaded slurry fuel is very limited. Therefore, here in this study, we experimentally investigated the combustion characteristics of boron/Jet A-1 slurry fuel spray in a swirl-stabilized combustor. A particle loading of 10% by weight is considered here for the experiment. The feed boron, as well as the burnt boron samples, were characterized using standard material characterization techniques in order to understand the surface morphology, oxidation behavior, and active boron content. The combustion characteristics of slurry fuel were analyzed through spectroscopy and BO2* chemiluminescence imaging. Positive thermal contribution from boron combustion was quantified via temperature measurements at three different radial locations of the combustor exit. The spectroscopy and chemiluminescence signatures indicate that combustion of boron particles occurs downstream of the dump plane. The exit temperature of boron-laden slurry fuel measured at all three different radial locations is higher compared to neat Jet A-1. An increment of 19% in exit temperature was observed in the case of boron slurry fuel relative to neat Jet A-1. The X-ray diffractograms (XRD) and thermogravimetric analysis (TGA) show the complete oxidation of boron particles.

A Novel Non-Destructive Technique for Cultural Heritage: Depth Profiling and Elemental Analysis Underneath the Surface with Negative Muons

Scientists, curators, historians and archaeologists are always looking for new techniques for the study of archaeological artefacts, especially if they are non-destructive. With most non-destructive investigations, it is challenging to measure beneath the surface. Among the vast board of techniques used for cultural heritage studies, it is difficult to find one able to give information about the bulk and the compositional variations, along with the depth. In addition, most other techniques have self-absorption issues (i.e., only surface sensitive) and limited sensitivity to low Z atoms. In recent years, more and more interest has been growing around large-scale facility-based techniques, thanks to the possibility of adding new and different insights to the study of material in a non-destructive way. Among them, muonic X-ray spectroscopy is a very powerful technique for material characterization. By using negative muons, scientists are able to perform elemental characterization and depth profile studies. In this work, we give an overview of the technique and review the latest applications in the field of cultural heritage.

Investigation of XLPE Cable Insulation Using Electrical, Thermal and Mechanical Properties, and Aging Level Adopting Machine Learning Techniques.

Hydrothermal and chemical aging tests on a 230 kV cross-linked polyethylene (XLPE) insulation cable were carried out in the present study to evaluate the degradation and aging levels qualitatively. The samples were subjected to water aging at a temperature of 80 °C, and in an aqueous ionic solution of CuSO4 at room temperature. The diffusion coefficient results indicated that the ion migration was not at the same rate in the aging conditions. The diffusion coefficient–D–of the sample immersed in an aqueous CuSO4 solution was lower than the hydrothermally aged specimens. The hydrophobicity of aged specimens decreased considerably compared to unaged samples. The distribution of trapped charges was quantitatively characterized. The presence of shallow trap energy states were observed in unaged XLPE, whereas the deep trap sites were noticed in aged specimens. In addition, the charge trap characteristics were different for positive and negative charge deposition. Various material characterization techniques, viz. dynamic mechanical analysis (DMA), tensile, contact angle, and LIBS, were further employed on the aged and virgin specimens. The tensile behavior of the hydrothermally aged specimen was degraded due to the oxidised regions, which had formed a weak spot against the mechanical stress. Reduced glass transition temperature and increased loss tangent measurements were noticed for aged specimens over their unaged counterparts. Machine learning techniques, such as the principal component analysis (PCA) and the artificial neural network (ANN) analysis, were performed on LIBS spectral data of the samples to classify the aging mechanisms qualitatively.

Strontium based Astragalus polysaccharides promote osteoblasts differentiation and mineralization.

Bone formation and repair represent a clinical challenge. In this work, we designed and synthesized strontium Astragalus polysaccharide (APS-Sr), a novel polysaccharide compound that should have therapeutic effects on both anti-inflammation and promoting bone formation. Using material characterization techniques, including SEM, FITR, XRD, etc., we verified the successful synthesis of this compound. Moreover, we examined the potential of this compound for promoting bone repair and inhibiting inflammatory response by cell proliferation assay, ALP and Alizarin Red staining experiments and RT-qPCR. The biological experiment results showed that APS-Sr can effectively inhibit inflammatory factors, promote osteogenic differentiation and up-regulate the bone growth factors. It is therefore believed that APS-Sr should be a promising polysaccharide compound in bone-related biomedical applications.

Towards understanding the hole making performance and chip formation mechanism of thermoplastic carbon fibre/polyetherketoneketone composite

Here, we report the first study on the hole making performance of thermoplastic carbon fibre/polyetherketoneketone (CF/PEKK) composite. Different hole making methods (conventional drilling vs. helical milling) have been compared and the effect of different feed rates has been investigated. The effect of thermal-mechanical interaction on the resulting hole damage has been elucidated for the first time for carbon fibre reinforced thermoplastics (CFRTPs) hole making. In the material science dimension, advanced material characterization techniques have been deployed to reveal the material removal mechanisms at microscopic scale and unveil the underlying material structural change at a molecular level. Results show that the delamination damage of CF/PEKK is a result of the thermal-mechanical interaction. For conventional drilling, the high machining temperature (at low feed rate <0.1 mm/rev) has a stronger influence on the delamination damage and the delamination starts to show stronger dependence on the thrust force at high feed rate >0.1 mm/rev. In contrast, helical milling generates a much higher machining temperature which plays a more predominant role in the associated delamination damage. Microstructural analysis shows that all the hole surfaces feature matrix smearing, as a result of combined in-plane shear stress and high machining temperature. Conventional drilling leads to more severe hole wall microstructural damage (matrix loss and surface cavity) as compared to helical milling. Finally, thermal analysis reveals that the hole making process has led to significantly increased crystallinity in the PEKK matrix as a result of the strain-induced crystallization under the combined effect of shear stress and high temperature. • Hole making performance of CF/PEKK is investigated for the first time. • A comparative study on conventional drilling and helical milling is reported. • The role of thermo-mechanical interaction is elucidated for CF/PEKK hole making. • Chip morphology and the associated material removal mechanism are revealed. • Shear-induced crystallization caused by hole making is reported for the first time.

A physics-based model for crystal orientation dictionary indexing by directional reflectance microscopy

Directional reflectance microscopy (DRM) is a new optical technique that enables grain orientation mapping in crystalline solids by capturing and analyzing light reflectance signals generated by chemically etched surfaces. Currently, orientation indexing by DRM relies on fitting the optical signals to identify user-defined features that carry orientation information. This approach is inevitably error-prone and material-dependent. These shortcomings hinder the adoption of DRM as a universal characterization method in materials science. We propose a new indexing method to improve the robustness and versatility of DRM. Our method relies on building a dictionary of all possible reflectance signals generated by a metal, which we simulate using a physics-based forward model that takes crystal orientation as input. We then compare each measured reflectance signal acquired by DRM to all the entries in the dictionary in search of the best match, and thus the correct crystal orientation. We demonstrate our dictionary indexing DRM (DI-DRM) approach on nickel and aluminum polycrystals, which produce markedly different optical reflectance signals. We find that DI-DRM yields measurements with improved accuracy compared to those enabled by fitting the optical signal on both materials and across all crystal orientations considered. We also show that the measurement error (∼3°) is mildly sensitive to experimental variability, including noise, measurement settings, and sample surface preparation. DI-DRM represents a considerable step forward towards the implementation of DRM as a streamline materials characterization technique.

Detailed Characterization of a Fully Additive Covalent Bonded PCB Manufacturing Process (SBU-CBM Method)

To bridge the technology gap between IC-level and board-level fabrications, a fully additive selective metallization has already been demonstrated in the literature. In this article, the surface characterization of each step involved in the fabrication process is outlined with bulk metallization of the surface. This production technique has used polyurethane as epoxy resin and proprietary grafting chemistry to functionalize the surface with covalent bonds on an FR-4 base substrate. The surface was then metalized using an electroless copper (Cu) bath. This sequential growth of layers on top of each other using an actinic laser beam and palladium (Pd) ions to deposit Cu is analyzed. State-of-the-art material characterization techniques were employed to investigate process mechanism at the interfaces. Density functional theory calculations were performed to validate the experimental evidence of covalent bonding of the layers. This manufacturing approach is capable of adding metallic layers in a selective manner to the printed circuit boards at considerably lower temperatures. A complete analysis of the process using bulk deposition of the materials is illustrated in this work.

Corrosion characterization of the 6061 Al–Mg–Si alloy in synthetic acid rain using neutron tomography

Neutron tomography has gained increasing importance as an imaging technique for materials characterization. In general, neutron beams are able to show microstructure features of hydrogenous materials, even enfolded with thick metal layers. In the present paper, neutron tomography and observation of cross section images were successfully applied to investigate the corrosion features of the 6061 Al–Mg–Si alloy. The results showed good agreement between neutron 3D tomography and the cross section images obtained in the high attenuation areas of the samples, whereas significant differences in depth of corrosion penetration were obtained between the results from Neutron Tomography and 3D optical profilometry.

Production of powders for metal additive manufacturing applications using surface grinding

Metal powders for additive manufacturing (AM) applications are commonly produced using atomization techniques, which are known to be expensive, capital intensive and highly inflexible. In this work, we explore an alternative route for producing metal powders by the use of surface grinding. We demonstrate the production of nearly monodisperse AISI 52100 steel powders for AM applications. The formation of these powder particles is analyzed using material characterization techniques. We then evaluate the usability of the produced powders for metal AM using a custom-built directed energy deposition setup. Post-process analysis of laser-assisted deposition tracks shows that our powders perform just as well as conventional gas-atomized powders, resulting in void and inclusion-free metallurgical bonding.

Enhanced Capacitive Deionization Exploiting Novel Functionalized Graphene Oxide Electrodes

AbstractIn this study, a novel functionalized graphene oxide (fGO) is proposed for application in water desalination. The fGO is obtained with a simple and scalable method. Pristine GO is functionalized with (2‐(acryloyloxy)ethyl)trimethylammonium through a two‐step functionalization. Then, it is mixed with activated carbon and coated onto a metallic current collector. Material characterization techniques such as electron microscopy, thermal analyses, and infrared spectroscopy are employed to study the physical and chemical structures of the proposed materials. This process provides a porous electrode useful for capacitive deionization (CDI). The desalination performance is compared to the performance of bare activated carbons, showing a remarkable improvement. The final device reaches a value of around 17 mg g‐1 of salt removal, with a charge efficiency of 98%. The findings from this study lay the groundwork for future research, contributing in increasing the existing knowledge on materials for CDI.

Can oxygen vacancies in ceria surfaces be measured by O1s photoemission spectroscopy?

X-ray photoemission spectroscopy is a standard technique for materials characterization and the O 1s binding energy is commonly measured for oxides. Here we use density functional theory calculations to investigate how the O 1s binding energy in CeO2(111) is influenced by the presence of oxygen vacancies. The case with point vacancies in CeO2(111) is compared to complete reduction to Ce2O3. Reduction of CeO2 by oxygen vacancies is found to have a minor effect on the O 1s binding energy. The O 1s binding energy is instead clearly changed when the character of the chemical bond for the considered oxygen atom is modified by, for example, the formation of OH-groups or carbonates.

Soft-Tissue Material Properties and Mechanogenetics during Cardiovascular Development.

During embryonic development, changes in the cardiovascular microstructure and material properties are essential for an integrated biomechanical understanding. This knowledge also enables realistic predictive computational tools, specifically targeting the formation of congenital heart defects. Material characterization of cardiovascular embryonic tissue at consequent embryonic stages is critical to understand growth, remodeling, and hemodynamic functions. Two biomechanical loading modes, which are wall shear stress and blood pressure, are associated with distinct molecular pathways and govern vascular morphology through microstructural remodeling. Dynamic embryonic tissues have complex signaling networks integrated with mechanical factors such as stress, strain, and stiffness. While the multiscale interplay between the mechanical loading modes and microstructural changes has been studied in animal models, mechanical characterization of early embryonic cardiovascular tissue is challenging due to the miniature sample sizes and active/passive vascular components. Accordingly, this comparative review focuses on the embryonic material characterization of developing cardiovascular systems and attempts to classify it for different species and embryonic timepoints. Key cardiovascular components including the great vessels, ventricles, heart valves, and the umbilical cord arteries are covered. A state-of-the-art review of experimental techniques for embryonic material characterization is provided along with the two novel methods developed to measure the residual and von Mises stress distributions in avian embryonic vessels noninvasively, for the first time in the literature. As attempted in this review, the compilation of embryonic mechanical properties will also contribute to our understanding of the mature cardiovascular system and possibly lead to new microstructural and genetic interventions to correct abnormal development.