Experimental Characterization Techniques Research Articles

Theoretical and experimental investigation of Al3+ ion-suppressed phase-separation structures in rare-earth-doped high-phosphorus silica glasses.

Rare-earth-doped silica-based composite glasses (Re-SCGs) are widely used as high-quality laser gain media in defense, aerospace, energy, power, and medical applications. The variable regional chemical environments of Re-SCGs can induce new photoluminescence properties of rare-earth ions but can cause the selective aggregation of rare-earth ions, limiting the application of Re-SCGs in the field of high-power lasers. Here, topological engineering is proposed to adjust the degree of cross-linking of phase-separation network chains in Re-SCGs. A combination of experimental and theoretical characterization techniques suggested that the selective aggregation of rare-earth ions originates from the formation of phase-separated structures in glasses. The decomposition of nanoscale phase separation structures to the sub-nanometer scale, enabled by incorporating Al3+ ions, not only maintains the high luminescence efficiency of rare earth ions but also increases light transmittance and reduces light scattering. Furthermore, our investigation encompassed the exploration of the inhibitory mechanism of Al3+ ions on phase-separation structures, as well as their influence on the spectral characteristics of Re-SCGs. This work provides a new design concept for composite glass materials doped with rare-earth ions and could broaden their application in the field of high-power lasers.

Frictional behavior of one-dimensional materials: an experimental perspective

Experimental characterization techniques for the frictional properties of 1D materials were compiled and critically assessed. Key achievements were discussed, and future research focuses and directions were outlined.

Polysulfides in Magnesium-Sulfur Batteries.

Mg-S batteries hold great promise as a potential alternative to Li-based technologies. Their further development hinges on solving a few key challenges, including the lower capacity and poorer cycling performance when compared to Li counterparts. At the heart of the issues is the lack of knowledge on polysulfide chemical behaviors in the Mg-S battery environment. In this Review, a comprehensive overview of the current understanding of polysulfide behaviors in Mg-S batteries is provided. First, a systematic summary of experimental and computational techniques for polysulfide characterization is provided. Next, conversion pathways for Mg polysulfide species within the battery environment are discussed, highlighting the important role of polysulfide solubility in determining reaction kinetics and overall battery performance. The focus then shifts to the negative effects of polysulfide shuttling on Mg-S batteries. The authors outline various strategies for achieving an optimal balance between polysulfide solubility and shuttling, including the use of electrolyte additives, polysulfide-trapping materials, and dual-functional catalysts. Based on the current understanding, the directions for further advancing knowledge of Mg polysulfide chemistry are identified, emphasizing the integration of experiment with computation as a powerful approach to accelerate the development of Mg-S battery technology.

Experimental simulation of enhanced oil recovery on shale rocks using gas injection from material to Characterization: challenges and solutions

To assess the effect of gas injection as a technique for enhancing oil recovery (EOR) in shale rocks, extensive simulations have been carried out over the past few decades. However, the varied experimental conditions and inconsistent results have led to confusion and misinterpretation among researchers. To address this issue, we conducted a thorough literature review to examine the experimental materials, treatment methods, simulation designs, and characterization techniques used in previous studies. The experimental conditions of these studies were then carefully compared and analyzed. Based on our findings, we established a rigorous, precise, and reliable experimental workflow to minimize deviation and reduce uncertainty in simulation. Our updated description of the experimental design and operational considerations serves as a valuable resource for researchers working in this field, providing a clearer understanding of the critical role of experimental simulation in the success of EOR.

Boosting CO2 Hydrogenation to Formate over Edge‐Sulfur Vacancies of Molybdenum Disulfide

AbstractSynthesis of formate from hydrogenation of carbon dioxide (CO2) is an atom‐economic reaction but is confronted with challenges in developing high‐performance non‐precious metal catalysts for application of the process. Herein, we report a highly durable edge‐rich molybdenum disulfide (MoS2) catalyst for CO2 hydrogenation to formate at 200 °C, which delivers a high selectivity of over 99 % with a superior turnover frequency of 780.7 h−1 surpassing those of previously reported non‐precious metal catalysts. Multiple experimental characterization techniques combined with theoretical calculations reveal that sulfur vacancies at MoS2 edges are the active sites and the selective production of formate is enabled via a completely new water‐mediated hydrogenation mechanism, in which surface OH* and H* species in dynamic equilibrium with water serve as moderate hydrogenating agents for CO2 with residual O* reduced by hydrogen. This study provides a new route for developing low‐cost high‐performance catalysts for CO2 hydrogenation to formate.

Unveiling the interactions between biomaterials and heterocyclic dyes: A sustainable approach for wastewater treatment

The present Review investigates the interactions between biomaterials and heterocyclic dyes, focusing on their potential application in sustainable wastewater treatment. Heterocyclic dyes are widely used in various industries, resulting in their widespread presence in wastewater, posing environmental challenges. This review explores the utilization of biomaterials as adsorbents for the removal of heterocyclic dyes from contaminated water sources. The interactions between biomaterials, such as cellulose, microfibrilated cellulose and lignin and different heterocyclic dyes are examined through reported experimental analysis and characterization techniques. The study evaluates the adsorption capacity, kinetics, and thermodynamics of the biomaterial-dye systems to elucidate the underlying mechanisms and optimize the treatment process. The review highlight the promising potential of biomaterial-based approaches for sustainable wastewater treatment, providing insights for the development of efficient and environmentally friendly dye removal technologies.

Polyamide–based membranes with nanoscale homogeneity and asymmetric structure for ultrafast ion separation

Polymeric membranes are the most practical separation technology for extracting target ionic species necessary for water purification and clean energy, but are limited by the multi-scale heterogeneity, and transient and dynamic free volume pores. Modulated interfacial polymerization techniques are emergent concepts for preparing polyamide composite membranes with reduced thickness and homogeneous pore structures to satisfy the requirements for efficient ion separation applications. Herein, N–Cyclic cation-assisted kinetically regulated interfacial polymerization strategy to generate polyamide nanofilm composite membranes with tuned pore network and asymmetric structures for water purification is reported. Experimental characterization techniques and molecular dynamic simulations revealed that the N-Cyclic cations control the kinetic diffusion behaviour of the amine monomers to the aqueous/organic interface conducing to the formation of nanofilm membranes with fine-tuned polyamide network structures. Meanwhile, the N–Cyclic cation–regulated IP process not only affords to decrease the thickness of the formed polyamide nanofilm selective layers but also effectively narrows the effective pore size of the membranes. These membranes with thinner, homogeneous and asymmetric polyamide network structures exhibit enhanced water permeance of 55.7–60.42 L m−2 h−1 bar−1, and showed Na2SO4 rejection of 99.59–99.66% and MgCl2 rejection of 98.94–98.96% in nanofiltration separations, thereby outperforming the permeance–selectivity performance of the state-of-the-art polyamide-based membranes. The membranes also exhibit improved forward osmosis performances. We envision that this research will provide insightful foundations for the molecular tuning and construction of the next-generation structurally modulated polyamide nanofilms for various applications in molecular separation and water purification.

Hydrothermal synthesis of nickel substituted magnesium ferrites (NixMg1-xFe2O4) and insight into the detailed structural, magnetic and electrochemical properties

A series of single-phase nickel (Ni+2) substituted magnesium Mg-spinel ferrites (NixMg1-xFe2O4) were synthesized by hydrothermal technique and investigated for morphological, structural, magnetic, and electrochemical properties. Experimental characterization techniques revealed that single-phase spinel structure was confirmed by X-ray diffraction, lattice parameter dropped with increasing Ni concentrations, nanoparticles clustered together, the nanoparticles in the SEM micrographs of different sizes are clustered together. Raman spectra showed lower wave numbers, FTIR spectrum showed that peaks move towards lower wave numbers because of nickel's substitution, and this shortens the Fe-O bond hence reduces the lattice parameter, saturation magnetization increased, coercivity decreased, specific capacitance decreased, and loop size increased. These ferrites are suitable for energy storage applications.

Acceleration of Fe3+/Fe2+ cycle in garland-like MIL-101(Fe)/MoS2 nanosheets to promote peroxymonosulfate activation for sulfamethoxazole degradation

Iron-based molybdenum disulfide (Fe-MoS2) has emerged as a Fenton-like catalyst for the highly efficient degradation of antibiotics, but the structure–activity relationship remains elusive. Herein, garland-like MIL-101(Fe)/MoS2 nanosheets (MMS) with dual metal active sites (Fe and Mo) and rich sulfur vacancies were fabricated to directly activate peroxymonosulfate (PMS) for fast degradation of different organic pollutants (phenols, dyes and drugs), even in real water bodies. The MMS exhibited extremely fast catalytic rate constant of 0.289 min−1 in the degradation of sulfamethoxazole (SMX), which was about 36 and 29 times that of single MoS2 (0.008 min−1) and MIL-101(Fe) (0.01 min−1). Moreover, MMS with good stability and reusability could reach 92% degradation of SMX after 5 cycles. Quenching experiments and electron spin resonance (ESR) tests revealed that hydroxyl radicals (.OH) and singlet oxygen (1O2) were the dominant reactive oxygen species (ROS) for SMX degradation. The integration of experimental works, characterization techniques and density functional theory (DFT) calculations unraveled that the formation of sulfur vacancies in MMS catalyst could expose more Mo sites, improve the charge density and boost the electron transfer, which was conducive to accelerating the Fe3+/Fe2+ cycle for enhancing the activation of PMS. Finally, the C-N, N-O, S-N, C-O and C-S bonds of SMX were easily attacked by ROS to generate the nontoxic intermediates in the MMS/PMS/SMX system. This study offers a new approach to designing high-performance Fe-MoS2 catalysts for the removal of organic pollutants.

Advances on in situ TEM mechanical testing techniques: a retrospective and perspective view

Over the past few decades, in situ transmission electron microscopy (TEM) has emerged as a powerful experimental technique for materials design and characterization. It offers unparalleled dynamic details of materials deformation under mechanical stimuli, providing fundamental insights into their deformation and failure mechanisms for various materials. In this review, we summarize recent advances on in situ TEM mechanical characterization techniques, including classical tension holders, nanoindentation holders, MEMS devices, thermal bimetallic-based techniques, and nanomanipulation techniques. The advantages and limitations of in situ TEM tests are also discussed. To provide a broader perspective, the article highlights promising opportunities for in situ TEM mechanical testing studies in characterization-processing-manufacturing based on nanomanipulation, ultrafast TEM, electron beam irradiation environmental conditions, data-driven machine learning, and integrated experimental and simulation characterization. This article aims to provide a comprehensive understanding of in situ TEM-based mechanical characterization techniques to promote the development of novel materials with improved mechanical properties for various applications.

Activated g-C3N4 Photocatalyst with Defect Engineering for Efficient Reduction of CO2 in Water

The conversion and utilization of CO2 into hydrocarbon fuel using solar energy is an attractive way to reduce CO2 emissions. In the photocatalytic CO2 conversion process, a synergistic enhancement of both photoreaction and chemical reaction is quite important for promoting the conversion. Here, we present a facile method for preparing a defective and activated graphitic carbon nitride (g-C3N4) photocatalyst, which exhibits a superior CO2-to-CO production of 32.06 μmol g–1 without sacrificial agent or noble metal. This is about 9.1 times higher than that of the defect containing g-C3N4 (3.51 μmol g–1). The activated g-C3N4, in which the TiO2 species coexist, not only improved the CO production to 54.03 umol g–1 but also reduced CO2 into CH4 with 2.50 umol g–1 in 5 h. This is because the coexistence of TiO2 species in activated g-C3N4 promotes molecule and electron transfer, as observed through experimental characterization techniques. Therefore, this work provides a novel insight into the synthesis of multifunctional g-C3N4 for efficient photocatalytic CO2 reduction with H2O.

Thermomechanical characterization of phase transformation surfaces for thin SMA wires

The phase transformation of thermal shape memory alloys (SMAs) can be described by surfaces in a temperature-stress-strain space. A novel experimental technique for the thermomechanical characterization of thin SMA wires allows to scan these surfaces with high resolution. Each experimental run uses a sequence of experimental conditions to traverse the phase transformation surfaces on a different path from “full martensite” to “full austenite” and vice versa. At all times, stress and strain are kept within the limits specified for the use of the SMA wire in actuators. The wire is heated externally through a silicon oil bath, which ensures a controlled and homogeneous temperature of the specimen. The experimental setup is designed to minimize the impact of the large oil temperature variations on measurement results. Experimental results are shown for both mechanical contraction and electrical resistance, each of which forms consistent surfaces for the phase transformation. Measurements for external heating in the oil bath are compared to electrical heating in air.

Surfactant Layers on Gold Nanorods.

ConspectusGold nanorods (Au NRs) are an exceptionally promising tool in nanotechnology due to three key factors: (i) their strong interaction with electromagnetic radiation, stemming from their plasmonic nature, (ii) the ease with which the resonance frequency of their longitudinal plasmon mode can be tuned from the visible to the near-infrared region of the electromagnetic spectrum based on their aspect ratio, and (iii) their simple and cost-effective preparation through seed-mediated chemical growth. In this synthetic method, surfactants play a critical role in controlling the size, shape, and colloidal stability of Au NRs. For example, surfactants can stabilize specific crystallographic facets during the formation of Au NRs, leading to the formation of NRs with specific morphologies.The process of surfactant adsorption onto the NR surface may result in various assemblies of surfactant molecules, such as spherical micelles, elongated micelles, or bilayers. Again, the assembly mode is critical toward determining the further availability of the Au NR surface to the surrounding medium. Despite its importance and a great deal of research effort, the interaction between Au NPs and surfactants remains insufficiently understood, because the assembly process is influenced by numerous factors, including the chemical nature of the surfactant, the surface morphology of Au NPs, and solution parameters. Therefore, gaining a more comprehensive understanding of these interactions is essential to unlock the full potential of the seed-mediated growth method and the applications of plasmonic NPs. A plethora of characterization techniques have been applied to reach such an understanding, but many open questions remain.In this Account, we review the current knowledge on the interactions between surfactants and Au NRs. We briefly introduce the state-of-the-art methods for synthesizing Au NRs and highlight the crucial role of cationic surfactants during this process. The self-assembly and organization of surfactants on the Au NR surface is then discussed to better understand their role in seed-mediated growth. Subsequently, we provide examples and elucidate how chemical additives can be used to modulate micellar assemblies, in turn allowing for a finer control over the growth of Au NRs, including chiral NRs. Next, we review the main experimental characterization and computational modeling techniques that have been applied to shed light on the arrangement of surfactants on Au NRs and summarize the advantages and disadvantages for each technique. The Account ends with a "Conclusions and Outlook" section, outlining promising future research directions and developments that we consider are still required, mostly related to the application of electron microscopy in liquid and in 3D. Finally, we remark on the potential of exploiting machine learning techniques to predict synthetic routes for NPs with predefined structures and properties.

Calculation of Tissue Oxygenation via an Inverse Boundary Problem for Transcutaneous Oxygenation Wearable Applications.

In this article, we present a toolset to fully leverage a previously developed transcutaneous oxygenation monitor (TCOM) wearable technology to accurately measure skin oxygenation values. We describe numerical models and experimental characterization techniques that allow for the extraction of precise tissue oxygenation measurements. The numerical model is based on an inverse boundary problem of the parabolic equation with Dirichlet boundary conditions. To validate this model and characterize the diffusion of oxygen through the oxygen sensing materials, we designed a series of control/calibration experiments modeled after the device's clinical application using oxygenation values in the physiological range expected for healthy tissue. Our results demonstrate that it is possible to obtain accurate tissue pO2 measurements without the need for long equilibration times with a small wearable device.

New charged aggregate mathematical models to predict the behavior, structural parameters, and geometrical features of microemulsions

Experimental characterization techniques can provide qualitative and quantitative information on the behavior and properties of microemulsion systems. However, they suffer from several inherent drawbacks that often restrict their application to research settings rather than routine practice in various industries. Also, the majority of theoretical studies on microemulsion systems have focused on nonionic surfactants and suffer from restrictive assumptions and limitations that can be violated under realistic conditions. Therefore, their practical applications to real-world problems such as surfactant-based enhanced oil recovery (EOR) processes require the exercise of extreme caution. This work is intended to fill existing research gaps and solve industrial challenges by developing new mathematical models for predicting micelle size besides other structural and geometrical parameters in ionic surfactant-induced oil-in-water (O/W) and water-in-oil (W/O) microemulsions. The main purpose of the present study is to derive novel models that are not only fitting-free, objective, independent of iterative algorithms and experimental data, and inclusive of intermicellar interactions, but also applicable to complex systems containing real crude oil, experiencing compositional changes, and under any thermodynamic conditions. First, a recently proposed surface charging model for dispersions of charged particles in electrolyte solutions is combined with the DLVO theory of colloidal interactions to develop a thermodynamic model for the structural description of O/W microemulsions. Then, upon coupling a surface charging model for non-electrolyte dispersions of charged aqueous cavities with the DLVO theory, another thermodynamic model is developed for W/O microemulsions. Next, the developed mathematical models are supplemented with an auxiliary material balance equation and an equilibrium condition to calculate the radius of micelles in each type of systems. After determining the radii of oil- and water-swollen micelles using the new models, other geometrical and structural parameters such as solubilized phase-to-surfactant molar ratio, aggregation number, the volumes of microemulsion and excess phases, intermicellar distance, and periodicity are readily calculated in an explicit manner using the derived relationships. Afterwards, some reliable complementary tools are discussed for calculations of the associated physical parameters to avoid the need for experimental measurements, thereby making the models more practical and operational. Finally, the validity of the developed models is verified using literature experimental data.

Molecular Pathways for Polymer Degradation during Conventional Processing, Additive Manufacturing, and Mechanical Recycling.

The assessment of the extent of degradation of polymer molecules during processing via conventional (e.g., extrusion and injection molding) and emerging (e.g., additive manufacturing; AM) techniques is important for both the final polymer material performance with respect to technical specifications and the material circularity. In this contribution, the most relevant (thermal, thermo-mechanical, thermal-oxidative, hydrolysis) degradation mechanisms of polymer materials during processing are discussed, addressing conventional extrusion-based manufacturing, including mechanical recycling, and AM. An overview is given of the most important experimental characterization techniques, and it is explained how these can be connected with modeling tools. Case studies are incorporated, dealing with polyesters, styrene-based materials, and polyolefins, as well as the typical AM polymers. Guidelines are formulated in view of a better molecular scale driven degradation control.

Effects of clay activation and amine chain length on silica–palygorskite heterostructure properties

AbstractVarious approaches have been used for the preparation of heterostructured materials based on clay minerals, with numerous potential applications offered by the resulting functional materials. In this study, a fibrous clay mineral (palygorskite) and a tetraethyl orthosilicate reagent were used to obtain silica–palygorskite heterostructures. The aim was to highlight the influence of two factors during the preparation process: the effect of acid activation pre-treatment of the palygorskite with HCl and the effect of varying the length of the amine chains used – dodecylamine and butylamine – on the formation and development of silica nanoparticles on the surface of the palygorskite fibres. The silica–palygorskite heterostructures were obtained after the removal of the organic templates by calcination at 500°C. The textural and structural properties of the silica–palygorskite heterostructured samples were determined using various experimental characterization techniques, such as X-ray diffraction, transmission electron microscopy, gas adsorption and Fourier-transform infrared spectroscopy. The experimental variables targeted in this study appeared to have a significant effect on the textural properties of the silica–palygorskite heterostructure obtained. The great specific surface area and the mesoporous, microporous and ultramicroporous volumes as determined using nitrogen and/or carbon dioxide gas adsorption confirm the benefit of combining the acid activation pre-treatment of the fibrous clay mineral with the use of a long-chain amine co-surfactant (dodecylamine). The resulting silica–palygorskite heterostucture has a great specific surface area (628 m2 g–1) and a well-developed total pore network (VN2 = 0.24 cm3 g–1; Vultra (CO2) = 0.18 cm3 g–1). This material will be tested for the removal of volatile organic compounds at low concentrations.

Simulating Electron Energy-Loss Spectroscopy and Cathodoluminescence for Particles in Arbitrary Host Medium Using the Discrete Dipole Approximation

Electron energy-loss spectroscopy (EELS) and cathodoluminescence (CL) are widely used experimental techniques for characterization of nanoparticles. The discrete dipole approximation (DDA) is a numerically exact method for simulating interaction of electromagnetic waves with particles of arbitrary shape and internal structure. In this work we extend the DDA to simulate EELS and CL for particles embedded into arbitrary (even absorbing) unbounded host medium. The latter includes the case of the dense medium, supporting the Cherenkov radiation of the electron, which has never been considered in EELS simulations before. We build a rigorous theoretical framework based on the volume-integral equation, final expressions from which are implemented in the open-source software package ADDA. This implementation agrees with both the Lorenz-Mie theory and the boundary-element method for spheres in vacuum and moderately dense host medium. And it successfully reproduces the published experiments for particles encapsulated in finite substrates. The latter is shown for both moderately dense and Cherenkov cases - a gold nanorod in $\text{SiO}_{\text{2}}$ and a silver sphere in $\text{SiN}_{\text{x}}$ respectively.

Effect of Flow Distributor Configuration on the Hydrodynamics in a Multipurpose Flow Electrochemical Reactor: Numerical Analysis and Experimental Characterization Employing Digital Image Treatment

Electrochemical reactors with a flat parallel plate electrode configuration and diverse flow channel designs have been extensively used in the study of different electrochemical processes at lab and bench scales, and they have been scaled up for some electrosynthesis and energy-storage processes at semipilot and industrial levels. Progress in the electrochemical process applications demands the use of different computer and experimental-assisted techniques to design novel electrochemical reactors. The objective of this work is to evaluate the hydrodynamic performance of different electrochemical reactor designs and quantify their effect on velocity magnitude through numerical and experimental studies using computational techniques like computational fluid dynamics (CFD) and digital image treatment. For local velocity magnitude measurements, a digital imaging treatment, based on the use of an optical flow algorithm, to try the validation of velocity profiles obtained by CFD is implemented. This experimental technique determined reliably that the problems associated with the use of the empty channel in the flow pattern are mainly associated with high velocities and recirculation zones, which are not detected by CFD simulations in the first instance. Also, the findings associated with the velocity behavior using this proposed technique agreed with those obtained by the traditional experimental flow characterization technique like residence time distribution, nevertheless, further work will be needed to refine the measurements and perform its comparison with other most employed velocimetry techniques.

Structural ensemble refinement with cryo-EM

Cryo-electron microscopy (cryo-EM) is a state-of-the-art experimental technique for structural characterization of biomolecules at near-atomic resolution. In Cryo-EM, thousands to millions of noisy, randomly-oriented 2D images of the biomolecule of interest are obtained, and these images are typically used to reconstruct 3D density volumes of the biomolecule. This reconstruction process is challenging due to the low signal-to-noise ratio of the images, and also heterogeneity in the structural ensemble of the biomolecule. To resolve this problem, we propose a framework that introduces a prior set of conformations obtained, for example from molecular simulations, to retrieve the structural ensemble captured by the cryo-EM images.